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+publicationDate,title,abstract,id
+2022-09-09,Magnetization dynamics and reversal of two-dimensional magnets,"Micromagnetics simulation based on the classical Landau-Lifshitz-Gilbert
+(LLG) equation has long been a powerful method for modeling magnetization
+dynamics and reversal of three-dimensional (3D) magnets. For two-dimensional
+(2D) magnets, the magnetization reversal always accompanies the collapse of the
+magnetization even at low temperatures due to intrinsic strong spin
+fluctuation. We propose a micromagnetic theory that explicitly takes into
+account the rapid demagnetization and remagnetization dynamics of 2D magnets
+during magnetization reversal. We apply the theory to a single-domain magnet to
+illustrate fundamental differences in magnetization trajectories and reversal
+times for 2D and 3D magnets.",2209.04483v1
+2016-08-16,Power Spectral Density of Magnetization Dynamics Driven by a Jump-Noise Process,"Random magnetization dynamics driven by a jump-noise process is reduced to
+stochastic magnetic energy dynamics on specific graphs using an averaging
+technique. An approach to analyzing stochastic energy dynamics on graphs is
+presented and applied to the calculation of power spectral density of random
+magnetization dynamics. An eigenvalue technique for computing the power
+spectral density under specific cases is also presented and illustrated by
+numerical results.",1608.04733v1
+2024-01-19,Modelling and dynamics of pendulum systems subjected to a nonstationary magnetic field,"The prepared doctoral dissertation focuses on studying dynamics of systems
+composed of magnetic pendulums subjected to a non-stationary magnetic field. A
+magnetic pendulum is a physical pendulum with a magnet attached to its end and
+is placed in an external magnetic field. The non-stationary external magnetic
+field is generated by an electric coil placed under the pendulum and powered by
+a time-varying current signal. The presented research mainly concerns the
+oscillations in one potential well of a single magnetic pendulum, as well as
+the control of the energy flow between two torsionally coupled magnetic
+pendulums.",2401.10594v1
+2024-03-20,Molecular Dynamics Simulations of Microscopic Structural Transition and Macroscopic Mechanical Properties of Magnetic Gels,"Magnetic gels with embedded micro/nano-sized magnetic particles in
+crosslinked polymer networks can be actuated by external magnetic fields, with
+changes in their internal microscopic structures and macroscopic mechanical
+properties. We investigate the responses of such magnetic gels to an external
+magnetic field, by means of coarse-grained molecular dynamics simulations. We
+find that the dynamics of magnetic particles are determined by the interplay of
+between magnetic dipole-dipole interactions, polymer elasticity and thermal
+fluctuations. The corresponding microscopic structures formed by the magnetic
+particles such as elongated chains can be controlled by the external magnetic
+field. Furthermore, the magnetic gels can exhibit reinforced macroscopic
+mechanical properties, where the elastic modulus increases algebraically with
+the magnetic moments of the particles in the form of
+$\propto(m-m_{\mathrm{c}})^{2}$ when magnetic chains are formed. This
+simulation work can not only serve as a tool for studying the microscopic and
+the macroscopic responses of the magnetic gels, but also facilitate future
+fabrications and practical controls of magnetic composites with desired
+physical properties.",2403.13481v1
+2020-09-24,Magnetic winding: what is it and what is it good for?,"Magnetic winding is a fundamental topological quantity that underpins
+magnetic helicity and measures the entanglement of magnetic field lines. Like
+magnetic helicity, magnetic winding is also an invariant of ideal
+magnetohydrodynamics. In this article we give a detailed description of what
+magnetic winding describes, how to calculate it and how to interpret it in
+relation to helicity. We show how magnetic winding provides a clear topological
+description of magnetic fields (open or closed) and we give examples to show
+how magnetic winding and helicity can behave differently, thus revealing
+different and imporant information about the underlying magnetic field.",2009.11708v1
+2014-03-13,Monte Carlo simulated dynamical magnetization of single-chain magnets,"Here, a dynamical Monte-Carlo (DMC) method is used to study
+temperature-dependent dynamical magnetization of famous Mn2Ni system as typical
+example of single-chain magnets with strong magnetic anisotropy. Simulated
+magnetization curves are in good agreement with experimental results under
+typical temperatures and sweeping rates, and simulated coercive fields as
+functions of temperature are also consistent with experimental curves. Further
+analysis indicates that the magnetization reversal is determined by both
+thermal-activated effects and quantum spin tunnelings. These can help explore
+basic properties and applications of such important magnetic systems.",1403.3188v2
+2023-09-22,Electric control of optically-induced magnetization dynamics in a van der Waals ferromagnetic semiconductor,"Electric control of magnetization dynamics in two-dimensional (2D) magnetic
+materials is an essential step for the development of novel spintronic
+nanodevices. Electrostatic gating has been shown to greatly affect the static
+magnetic properties of some van der Waals magnets, but the control over their
+magnetization dynamics is still largely unexplored. Here we show that the
+optically-induced magnetization dynamics in the van der Waals ferromagnet
+Cr$_2$Ge$_2$Te$_6$ can be effectively controlled by electrostatic gates, with a
+one order of magnitude change in the precession amplitude and over 10% change
+in the internal effective field. In contrast to the purely thermally-induced
+mechanisms previously reported for 2D magnets, we find that coherent
+opto-magnetic phenomena play a major role in the excitation of magnetization
+dynamics in Cr$_2$Ge$_2$Te$_6$. Our work sets the first steps towards electric
+control over the magnetization dynamics in 2D ferromagnetic semiconductors,
+demonstrating their potential for applications in ultrafast opto-magnonic
+devices.",2309.12776v1
+2010-06-21,Dynamics of magnetic charges in artificial spin ice,"Artificial spin ice has been recently implemented in two-dimensional arrays
+of mesoscopic magnetic wires. We propose a theoretical model of magnetization
+dynamics in artificial spin ice under the action of an applied magnetic field.
+Magnetization reversal is mediated by domain walls carrying two units of
+magnetic charge. They are emitted by lattice junctions when the the local field
+exceeds a critical value $H_c$ required to pull apart magnetic charges of
+opposite sign. Positive feedback from Coulomb interactions between magnetic
+charges induces avalanches in magnetization reversal.",1006.4075v2
+2024-02-05,Bifurcation to complex dynamics in largely modulated voltage-controlled parametric oscillator,"An experimental demonstration of a parametric oscillation of a magnetization
+in a ferromagnet was performed recently by applying a microwave voltage,
+indicating the potential to be applied in a switching method in non-volatile
+memories. In the previous works, the modulation of a perpendicular magnetic
+anisotropy field produced by the microwave voltage was small compared with an
+external magnetic field pointing in an in-plane direction. A recent trend is,
+however, opposite, where an efficiency of the voltage controlled magnetic
+anisotropy (VCMA) effect is increased significantly by material research and
+thus, the modulated magnetic anisotropy field can be larger than the external
+magnetic field. Here, we solved the Landau-Lifshitz-Gilbert equation
+numerically and investigated the magnetization dynamics driven under a wide
+range of the microwave VCMA effect. We evaluated bifurcation diagrams, which
+summarize local maxima of the magnetization dynamics. For low modulation
+amplitudes, the local maximum is a single point because the dynamics is the
+periodic parametric oscillation. The bifurcation diagrams show distributions of
+the local maxima when the microwave magnetic anisotropy field becomes larger
+than the external magnetic field. The appearance of this broadened distribution
+indicates complex dynamics such as chaotic and transient-chaotic behaviors,
+which were confirmed from an analysis of temporal dynamics.",2402.02742v1
+2014-12-17,Revealing the role of orbital magnetism in ultrafast laser-induced demagnetization in multisublattice metallic magnets by terahertz spectroscopy,"Simultaneous detection of THz emission and transient magneto-optical response
+is employed to study ultrafast laser-induced magnetization dynamics in
+multisublattice magnets NdFeCo and GdFeCo amorphous alloys with in-plane
+magnetic anisotropy. A satisfactory quantitative agreement between the dynamics
+revealed with the help of these two techniques is obtained for GdFeCo. For
+NdFeCo the THz emission reveals faster dynamics than the magneto-optical
+response. This indicates that in addition to spin dynamics of Fe ultrafast
+laser excitation triggers faster magnetization dynamics of Nd.",1412.5396v1
+2006-05-18,Small-scale magnetic buoyancy and magnetic pumping effects in a turbulent convection,"We determine the nonlinear drift velocities of the mean magnetic field and
+nonlinear turbulent magnetic diffusion in a turbulent convection. We show that
+the nonlinear drift velocities are caused by the three kinds of the
+inhomogeneities, i.e., inhomogeneous turbulence; the nonuniform fluid density
+and the nonuniform turbulent heat flux. The inhomogeneous turbulence results in
+the well-known turbulent diamagnetic and paramagnetic velocities. The nonlinear
+drift velocities of the mean magnetic field cause the small-scale magnetic
+buoyancy and magnetic pumping effects in the turbulent convection. These
+phenomena are different from the large-scale magnetic buoyancy and magnetic
+pumping effects which are due to the effect of the mean magnetic field on the
+large-scale density stratified fluid flow. The small-scale magnetic buoyancy
+and magnetic pumping can be stronger than these large-scale effects when the
+mean magnetic field is smaller than the equipartition field. We discuss the
+small-scale magnetic buoyancy and magnetic pumping effects in the context of
+the solar and stellar turbulent convection. We demonstrate also that the
+nonlinear turbulent magnetic diffusion in the turbulent convection is
+anisotropic even for a weak mean magnetic field. In particular, it is enhanced
+in the radial direction. The magnetic fluctuations due to the small-scale
+dynamo increase the turbulent magnetic diffusion of the toroidal component of
+the mean magnetic field, while they do not affect the turbulent magnetic
+diffusion of the poloidal field.",0605444v1
+2015-02-27,RC-circuit-like dynamic characteristic of the magnetic domain wall in ferromagnetic nanowires,"We have investigated dynamic behaviors of the magnetic domain wall under
+perpendicular magnetic field pulses in ferromagnetic nanowires using
+micromagnetic simulations. It has been found that the perpendicular magnetic
+field pulse can trigger the magnetic domain wall motion, where all the field
+torques are kept to be on the plane of nanowire strip. The magnetic domain wall
+speed faster than several hundreds meters per second is predicted without the
+Walker breakdown for the perpendicular magnetic driving field stronger than
+$200~\mathrm{mT}$. Interestingly, the dynamic behavior of the moving magnetic
+domain wall driven by perpendicular magnetic field pulses is explained by
+charging- and discharging-like behaviors of an electrical RC-circuit model,
+where the charging and the discharging of ""magnetic charges"" on the nanowire
+planes are considered. The concept of the RC-model-like dynamic characteristic
+of the magnetic domain wall might be promising for spintronic functional device
+applications based on the magnetic domain wall motion.",1502.07807v1
+2022-04-26,Slow spin dynamics and quantum tunneling of magnetization in the dipolar antiferromagnet DyScO$_3$,"We present a comprehensive study of static and dynamic magnetic properties in
+the Ising-like dipolar antiferromagnet (AFM) DyScO$_3$\ by means of DC and AC
+magnetization measurements supported by classical Monte-Carlo calculations. Our
+AC-susceptibility data show that the magnetic dynamics exhibit a clear
+crossover from an Arrhenius-like regime to quantum tunneling of magnetization
+(QTM) at $T^* = 10$ K. Below $T_{\mathrm{N}} = 3.2$ K DyScO$_3$ orders in an
+antiferromagnetic $GxAy$-type magnetic structure and the magnetization dynamics
+slow down to the minute timescale. The low-temperature magnetization curves
+exhibit complex hysteretic behavior, which depends strongly on the magnetic
+field sweep rate. We demonstrate that the low-field anomalies on the
+magnetization curve are related to the metamagnetic transition, while the
+hysteresis at higher fields is induced by a strong magnetocaloric effect. Our
+theoretical calculations, which take into account dipolar interaction between
+Dy$^{3+}$ moments, reproduce essential features of the magnetic behavior of
+DyScO$_3$. We demonstrate that DyScO$_3$ represents a rare example of inorganic
+compound, which exhibits QTM at a single-ion level and magnetic order due to
+classical dipolar interaction.",2204.12398v1
+2013-02-08,Investigation on the critical dynamics of real magnetics models by computational physics methods,"The critical dynamics of classical 3D Heisenberg model and complex model of
+the real antiferromagnetic Cr2O3 is investigated with use of the method of
+molecular dynamics. The dynamic critical exponent z are determined for these
+models on the basis of the theory dynamic finite-size scaling.",1302.1964v1
+2022-06-12,Exchange-enhancement of the ultrafast magnetic order dynamics in antiferromagnets,"We theoretically demonstrate that the ultrafast magnetic order dynamics in
+antiferromagnets is exchange-enhanced in comparison to their ferromagnetic
+counterparts. We provide an equation of motion for the magnetic order dynamics
+validated by computer simulations using atomistic spin dynamics methods. The
+exchange of angular momentum between sublattices speeds up the dynamics in
+antiferromagnets, a process absent in ferromagnets.",2206.05783v1
+2018-07-24,Asymptotic Dynamics of Magnetic Micro-Swimmers,"Micro-swimmers put into motion by a rotating magnetic field have provided
+interesting challenges both in engineering and in mathematical modelling. We
+study here the dynamics of a permanent-magnetic rigid body submitted to a
+spatially-uniform steadily-rotating magnetic field in Stokes flow. This system
+depends on two external parameters: the Ma- son number, which is proportional
+to the angular speed of the magnetic field and inversely proportional to the
+magnitude of the field, and the conical angle between the magnetic field and
+its axis of rotation. This work focuses on asymptotic dynamics in the limits of
+low and high Mason number, and in the limit of low conical angle. Analytical
+solutions are provided in these three regimes. In the limit of low Mason
+number, the dynamical system admits a periodic solution in which the magnetic
+moment of the swimmer tends to align with the magnetic field. In the limit of
+large Mason number, the magnetic moment tends to align with the average
+magnetic field, which is parallel to the axis of rotation. Asymptotic dynamics
+in the limit of low conical angle allow to bridge these two regimes. Finally,
+we use numerical methods to compare these analytical predictions with numerical
+solutions.",1807.09059v1
+2016-01-23,Nonlinear magnetization dynamics of antiferromagnetic spin resonance induced by intense terahertz magnetic field,"We report on the nonlinear magnetization dynamics of a HoFeO3 crystal induced
+by a strong terahertz magnetic field resonantly enhanced with a split ring
+resonator and measured with magneto-optical Kerr effect microscopy. The
+terahertz magnetic field induces a large change (~40%) in the spontaneous
+magnetization. The frequency of the antiferromagnetic resonance decreases in
+proportion to the square of the magnetization change. A modified
+Landau-Lifshitz-Gilbert equation with a phenomenological nonlinear damping term
+quantitatively reproduced the nonlinear dynamics.",1601.06213v1
+2023-07-04,Phonon-induced magnetization dynamics in Co-doped iron garnets,"The developing field of strain-induced magnetization dynamics offers a
+promising path toward efficiently controlling spins and phase transitions.
+Understanding the underlying mechanisms is crucial in finding the optimal
+parameters supporting the phononic switching of magnetization. Here, we present
+an experimental and numerical study of time-resolved magnetization dynamics
+driven by the resonant excitation of an optical phonon mode in iron garnets.
+Upon pumping the latter with an infrared pulse obtained from a free-electron
+laser, we observe spatially-varying magnetization precession, with its phase
+depending on the direction of an external magnetic field. Our micromagnetic
+simulations effectively describe the magnetization precession and switching in
+terms of laser-induced changes in the crystal's magneto-elastic energy.",2307.01907v1
+2013-02-14,Atomistic Coupling between Magnetization and Lattice Dynamics from First Principles,"We formulate a new scheme to study the combined magnetization and lattice
+dynamics in magnets, so-called magnetoelastics. The coupling between
+magnetization and lattice are considered through an expansion of
+electron-phonon coupling, while the magnetization is coupled to electrons
+through sd-like interaction. We show the that the time-scale of the
+magnetization dynamics due to coupling between magnetic degrees of freedom and
+electronic degrees of freedom can be transferred to lattice degrees of freedom
+and therefore can give rise to lattice dynamics on the same time-scale. This
+opens a new route to understand and treat ultrafast lattice dynamics induced by
+magnetization dynamics. We also show that all the parameters necessary to
+simulate this coupled lattice and magnetization dynamics can be obtained from
+first-principles.",1302.3333v2
+2015-07-22,Spin-current emission governed by nonlinear spin dynamics,"Coupling between conduction electrons and localized magnetization is
+responsible for a variety of phenomena in spintronic devices. This coupling
+enables to generate spin currents from dynamical magnetization. Due to the
+nonlinearity of magnetization dynamics, the spin-current emission through the
+dynamical spin-exchange coupling offers a route for nonlinear generation of
+spin currents. Here, we demonstrate spin-current emission governed by nonlinear
+magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current
+emission from the magnetic insulator is probed by the inverse spin Hall effect,
+which demonstrates nontrivial temperature and excitation power dependences of
+the voltage generation. The experimental results reveal that nonlinear
+magnetization dynamics and enhanced spin-current emission due to magnon
+scatterings are triggered by decreasing temperature. This result illustrates
+the crucial role of the nonlinear magnon interactions in the spin-current
+emission driven by dynamical magnetization, or nonequilibrium magnons, from
+magnetic insulators.",1507.06081v1
+2023-08-25,Coexistence of non-trivial van der Waals magnetic orders enable field-free spin-orbit torque switching at room temperature,"The discovery of van der Waals (vdW) materials exhibiting non-trivial and
+tunable magnetic interactions at room temperature can give rise to exotic
+magnetic states, which are not readily attainable with conventional materials.
+Such vdW magnets can provide a unique platform for studying new magnetic
+phenomena and realising magnetization dynamics for energy-efficient and
+non-volatile spintronic memory and logic technologies. Recent developments in
+vdW magnets have revealed their potential to enable spin-orbit torque (SOT)
+induced magnetization dynamics. However, the deterministic and field-free SOT
+switching of vdW magnets at room temperature has been lacking, prohibiting
+their potential applications. Here, we demonstrate magnetic field-free and
+deterministic SOT switching of a vdW magnet (Co0.5Fe0.5)5GeTe2 (CFGT) at room
+temperature, capitalizing on its non-trivial intrinsic magnetic ordering. We
+discover a coexistence of ferromagnetic and antiferromagnetic orders in CFGT at
+room temperature, inducing an intrinsic exchange bias and canted perpendicular
+magnetism. The resulting canted perpendicular magnetization of CFGT introduces
+symmetry breaking, facilitating successful magnetic field-free magnetization
+switching in the CFGT/Pt heterostructure devices. Furthermore, the SOT-induced
+magnetization dynamics and their efficiency are evaluated using 2nd harmonic
+Hall measurements. This advancement opens new avenues for investigating tunable
+magnetic phenomena in vdW material heterostructures and realizing field-free
+SOT-based spintronic technologies.",2308.13408v1
+2009-07-23,Dynamic switching of magnetization in driven magnetic molecules,"We study the magnetization dynamics of a molecular magnet driven by static
+and variable magnetic fields within a semiclassical treatment. The underling
+analyzes is valid in a regime, when the energy is definitely lower than the
+anisotropy barrier, but still a substantial number of states are excited. We
+find the phase space to contain a separatrix line. Solutions far from it are
+oscillatory whereas the separatrix solution is of a soliton type. States near
+the separatrix are extremely sensitive to small perturbations, a fact which we
+utilize for dynamically induced magnetization switching.",0907.4105v1
+2004-09-25,Nano-mechanical magnetization reversal,"The dynamics of the ferromagnetic order parameter in thin magnetic films is
+strongly affected by the magnetomechanical coupling at certain resonance
+frequencies. By solving the equation of motion of the coupled mechanical and
+magnetic degrees of freedom we show that the magnetic-field induced
+magnetization switching can be strongly accelerated by the lattice and
+illustrate the possibility of magnetization reversal by mechanical actuation.",0409681v1
+2008-05-18,Effect of spin diffusion on spin torque in magnetic nanopillars,"We present systematic magnetoelectronic measurements of magnetic nanopillars
+with different structures of polarizing magnetic layers. The magnetic reversal
+at small magnetic field, the onset of magnetic dynamics at larger field, and
+the magnetoresistance exhibit a significant dependence on the type of the
+polarizing layer. We performed detailed quantitative modeling showing that the
+differences can be explained by the effects of spin-dependent electron
+diffusion.",0805.2706v1
+2016-08-19,Vesicles in magnetic fields,"Liposome vesicles tend to align with an applied magnetic field. This is due
+to the directional magnetic susceptibility difference of the lipids which form
+the membrane of these vesicles. In this work a model of liposome vesicles
+exposed to magnetic field is presented. Starting from the base energy of a
+lipid membrane in a magnetic field, the force applied to the surrounding fluids
+is derived. This force is then used to investigate the dynamics of vesicle in
+the presence of magnetic fields.",1608.05587v1
+2004-12-09,"On ""Pulsar dynamics: magnetic dipole model revisited""","Comments on the article ""Pulsar dynamics: magnetic dipole model revisited"".",0412218v1
+1992-10-04,On the quantisation of SU(2) magnetic monopole dynamics,"We argue that there is no consistent quantisation of the two BPS SU(2)
+magnetic monopole dynamical system compatible with the correspondence
+principle.",9210019v1
+2019-12-29,Synchronized excitation of magnetization dynamics via spin waves in Bi-YIG thin film by slot line waveguide,"We have studied magnetization dynamics of a single Bi-YIG thin film by means
+of the high frequency power response induced by a slot line waveguide. Multiple
+absorption peaks that correspond to excitement states in magnetization dynamics
+appeared without the ferromagnetic resonance (FMR) condition. The peaks were
+strongly influenced by a waveguide line width and a distance between the lines.
+Micromagnetics simulation reveals that each line induces a local magnetization
+dynamics oscillation and generates spin waves. The spin wave that propagates
+from one of the lines interferences with the other side of local magnetization
+dynamics oscillation around the other line, resulting in an amplification of
+the oscillation when they are in synchronization with each other. This
+amplification occurs at both sides of the lines by the interference. Thus, the
+possible mechanism of the excitation in the magnetization dynamics oscillation
+is the synchronization of mutual magnetization dynamics oscillation via spin
+waves. This technique resonantly excites the local magnetization dynamics
+without the FMR condition, which is applicable as a highly coherent spin waves
+source.",1912.12663v1
+2017-01-16,Dynamics of magnetic nano particles in a viscous fluid driven by rotating magnetic fields,"The rotational dynamics of magnetic nano particles in rotating magnetic
+fields in the presence of thermal noise is studied both theoretically and by
+performing numerical calculations. Kinetic equations for the dynamics of
+particles with uniaxial magnetic anisotropy are studied and the phase lag
+between the rotating magnetic moment and the driving field is obtained. It is
+shown that for large enough anisotropy energy the magnetic moment is locked to
+the anisotropy axis so that the particle behaves like a rotating magnetic
+dipole. The corresponding rigid dipole model is analyzed both numerically by
+solving the appropriate Fokker-Planck equation and analytically by applying an
+effective field method. In the special case of a rotating magnetic field
+applied analytic results are obtained in perfect agreement with numerical
+results based on the Fokker-Planck equation. The analytic formulas derived are
+not restricted to small magnetic fields or low frequencies and are therefore
+important for applications. The illustrative numerical calculations presented
+are performed for magnetic parameters typical for iron oxide.",1702.04673v1
+2019-01-10,Ultrafast magnetization dynamics in uniaxial ferrimagnets with compensation point. GdFeCo,"We derive an effective Lagrangian in the quasi-antiferromagnetic
+approximation that allows to describe the magnetization dynamics for uniaxial
+f-d (rare-earth - transition metal) ferrimagnet near the magnetization
+compensation point in the presence of external magnetic field. We perform
+calculations for the parameters of GdFeCo, a metallic ferrimagnet with
+compensation point that is one of the most promising materials in ultrafast
+magnetism. Using the developed approach, we find the torque that acts on the
+magnetization due to ultrafast demagnetization pulse that can be caused either
+by ultrashort laser or electrical current pulse. We show that the torque is
+non-zero only in the non-collinear magnetic phase that can be acquired by
+applying external magnetic field to the material. The coherent response of
+magnetization dynamics amplitude and its timescale exhibits critical behavior
+near certain values of the magnetic field corresponding to a spin-flop like
+phase transition. Understanding the underlying mechanisms for these effects
+opens the way to efficient control of the amplitude and the timescales of the
+spin dynamics, which is one of the central problems in the field of ultrafast
+magnetism.",1901.03072v2
+1997-08-06,Symmetry and Dynamics of A Magnetic Oscillator,"We consider a permanent magnetic dipole in an oscillating magnetic field.
+This magnetic oscillator has two dynamical symmetries. With increasing the
+amplitude $A$ of the magnetic field, dynamical behaviors associated with the
+symmetries are investigated. For small $A$, there exist symmetric states with
+respect to one of the two symmetries. However, such symmetric states lose their
+symmetries via symmetry-breaking pitchfork bifurcations and then the
+symmetry-broken states exhibit period-doubling transitions to chaos.
+Consequently, small chaotic attractors with broken symmetries appear. However,
+as $A$ is further increased they merge into a large symmetric chaotic attractor
+via symmetry-restoring attractor-merging crisis.",9708005v1
+2020-01-08,Non-equilibrium spin dynamics in the temperature and magnetic field dependence of magnetization curves of ferrimagnetic Co$_{1.75}$Fe$_{1.25}$O$_4$ and its composite with BaTiO$_3$,"A comparative study of the non-equilibrium magnetic phenomena (magnetic
+blocking, memory, exchange bias and aging effect) has been presented for
+ferrimagnetic Co$_{1.75}$Fe$_{1.25}$O$_4$ (CFO) and its composite with
+non-magnetic BaTiO$_3$ (BTO). Synchrotron X-Ray diffraction patterns have
+confirmed coexistence of CFO and BTO structures in composite, but magnetic spin
+dynamics have been remarkably modified. The blocking phenomenon of
+ferrimagnetic domains below the room temperature has been studied by different
+modes of (zero field cooled and field cooled) magnetic measurements in
+collaboration with magnetic fields ON and OFF modes and time dependent
+magnetization. The applications of unconventional protocols during time
+dependent magnetization measurement at different stages of the temperature and
+field dependence of the magnetization curves have been useful to reveal the
+non-equilibrium dynamics of magnetic spin order. The applying of off-field
+relaxation experiments has made possible to tune the magnetic state and
+coercivity of the systems. The role of interfacial coupling between magnetic
+and non-magnetic particles has been understood on different magnetic phenomena
+(meta-stable magnetic state, exchange bias and memory effect) by comparing the
+experimental results of Co$_{1.75}$Fe$_{1.25}$O$_4$ spinel oxide and its
+composite with BaTiO$_3$ particles.",2001.02602v2
+2023-05-16,Non-periodic input-driven magnetization dynamics in voltage-controlled parametric oscillator,"Input-driven dynamical systems have attracted attention because their
+dynamics can be used as resources for brain-inspired computing. The recent
+achievement of human-voice recognition by spintronic oscillator also utilizes
+an input-driven magnetization dynamics. Here, we investigate an excitation of
+input-driven chaos in magnetization dynamics by voltage controlled magnetic
+anisotropy effect. The study focuses on the parametric magnetization
+oscillation induced by a microwave voltage and investigates the effect of
+random-pulse input on the oscillation behavior. Solving the
+Landau-Lifshitz-Gilbert equation, temporal dynamics of the magnetization and
+its statistical character are evaluated. In a weak perturbation limit, the
+temporal dynamics of the magnetization are mainly determined by the input
+signal, which is classified as input-driven synchronization. In a large
+perturbation limit, on the other hand, chaotic dynamics are observed, where the
+dynamical response is sensitive to the initial state. The existence of chaos is
+also identified by the evaluation of the Lyapunov exponent.",2305.09151v1
+2004-12-27,Magnetization suppression of Type-II Superconductors by external alternating magnetic field,"The effect of suppression of static magnetization of an anisotropic hard
+superconductor by alternating magnetic field is analyzed theoretically. The
+magnetic moment suppression dynamics is described with respect to the
+magnetization loop of the superconductor. It is found that in some cases the
+magnetic moment varies nonmonotonically with the growth in amplitude
+$\mathrm{h}$ of the alternating field. Effect of transition, induced by
+$\mathrm{\mathbf{h}}(t)$, of superconductor form paramagnetic into the
+diamagnetic state is considered. The amplitude of alternating magnetic field
+$\mathrm{h}_{c}(\delta,\vartheta)$ for which the complete suppression of the
+magnetization occurs is calculated as the function of anisotropy parameter
+$\delta$ and it orientation angle $\vartheta$ with respect to the
+crystallographic axes of the sample.",0412695v1
+2015-06-05,On the magnetization process of ferromagnetic materials,"The present article concludes that a ferromagnetic sample could be considered
+like a paramagnetic system where the role of magnetic moments plays magnetic
+domains. Based on this conclusion and taking into account presence of an
+anisotropic field the formula which describes magnetization dependence on the
+external magnetic field is derived. Expressions for a remanent magnetization
+and a coercive force are presented. The new parameter to characterize a
+magnetic stiffness of a material is introduced. A physical expression for a
+dynamic magnetic susceptibility as a function of material's characteristics,
+external magnetic field, and a temperature is given.",1506.01805v3
+2020-09-14,Voltage-driven Magnetization Switching via Dirac Magnetic Anisotropy and Spin--orbit Torque in Topological-insulator-based Magnetic Heterostructures,"Electric-field control of magnetization dynamics is fundamentally and
+technologically important for future spintronic devices. Here, based on
+electric-field control of both magnetic anisotropy and spin--orbit torque, two
+distinct methods are presented for switching the magnetization in topological
+insulator (TI)/magnetic-TI hybrid systems. The magnetic anisotropy energy in
+magnetic TIs is formulated analytically as a function of the Fermi energy, and
+it is confirmed that the out-of-plane magnetization is always favored for the
+partially occupied surface band. Also proposed is a transistor-like device with
+the functionality of a nonvolatile magnetic memory that uses voltage-driven
+writing and the (quantum) anomalous Hall effect for readout. For the
+magnetization reversal, by using parameters of Cr-doped
+Bi_{1-x}Sb_{x})_{2}Te_{3}, the estimated source-drain current density and gate
+voltage are of the orders of $10^4$--$10^5$~A/cm$^2$ and 0.1~V, respectively,
+below 20~K and the writing requires no external magnetic field. Also discussed
+is the possibility of magnetization switching by the proposed method in
+TI/ferromagnetic-insulator bilayers with the magnetic proximity effect.",2009.06187v1
+2016-12-12,Symbolic Dynamics of Magnetic Bumps,"For n convex magnetic bumps in the plane, whose boundary has a curvature
+somewhat smaller than the absolute value of the constant magnetic field inside
+the bump, we construct a complete symbolic dynamics of a classical particle
+moving with speed one.",1612.03670v1
+2021-01-12,Modeling of Thermal Magnetic Fluctuations in Nanoparticle Enhanced Magnetic Resonance Detection,"We present a systematic numerical modeling investigation of magnetization
+dynamics and thermal magnetic moment fluctuations of single magnetic domain
+nanoparticles in a configuration applicable to enhancing inductive magnetic
+resonance detection signal to noise ratio (SNR). Previous proposals for
+oriented anisotropic single magnetic domain nanoparticle amplification of
+magnetic flux in MRI coil focused only on the coil pick-up voltage signal
+enhancement. Here we extend the analysis to the numerical evaluation of the SNR
+by modeling the inherent thermal magnetic noise introduced into the detection
+coil by the insertion of such anisotropic nanoparticle-filled coil core. We
+utilize the Landau-Lifshitz-Gilbert equation under the Stoner-Wohlfarth single
+magnetic domain (macrospin) assumption to simulate the magnetization dynamics
+in such nanoparticles due to AC drive field as well as thermal noise. These
+simulations are used to evaluate the nanoparticle configurations and shape
+effects on enhancing SNR. Finally, we explore the effect of narrow band
+filtering of the broadband magnetic moment thermal fluctuation noise on the
+SNR. Our results provide the impetus for relatively simple modifications to
+existing MRI systems for achieving enhanced detection SNR in scanners with
+modest polarizing magnetic fields.",2101.04649v1
+2021-12-02,Heisenberg representation of nonthermal ultrafast laser excitation of magnetic precessions,"We derive the Heisenberg representation of the ultrafast inverse Faraday
+effect that provides the time evolution of magnetic vectors of a magnetic
+system during its interaction with a laser pulse. We obtain a time-dependent
+effective magnetic operator acting in the Hilbert space of the total angular
+momentum that describes a process of nonthermal excitation of magnetic
+precessions in an electronic system by a circularly polarized laser pulse. The
+magnetic operator separates the effect of the laser pulse on the magnetic
+system from other magnetic interactions. The effective magnetic operator
+provides the equations of motion of magnetic vectors during the excitation by
+the laser. We show that magnetization dynamics calculated with these equations
+is equivalent to magnetization dynamics calculated with the time-dependent
+Schr\""odinger equation, which takes into account the interaction of an
+electronic system with the electric field of light. We model and compare
+laser-induced precessions of magnetic sublattices of an easy-plane and an
+easy-axis antiferromagnetic systems. Using these models, we show how the
+ultrafast inverse Faraday effect induces a net magnetic moment in
+antiferromagnets and demonstrate that a crystal field environment and the
+exchange interaction play essential roles for laser-induced magnetization
+dynamics even during the action of a pump pulse. Using our approach, we show
+that light-induced precessions can start even during the action of the pump
+pulse with a duration several tens times shorter than the period of induced
+precessions and affect the position of magnetic vectors after the action of the
+pump pulse.",2112.01350v1
+2007-01-17,Projected single-spin flip dynamics in the Ising Model,"We study transition matrices for projected dynamics in the
+energy-magnetization space, magnetization space and energy space. Several
+single spin flip dynamics are considered such as the Glauber and Metropolis
+canonical ensemble dynamics and the Metropolis dynamics for three
+multicanonical ensembles: the flat energy-magnetization histogram, the flat
+energy histogram and the flat magnetization histogram. From the numerical
+diagonalization of the matrices for the projected dynamics we obtain the
+sub-dominant eigenvalue and the largest relaxation times for systems of varying
+size. Although, the projected dynamics is an approximation to the full state
+space dynamics comparison with some available results, obtained by other
+authors, shows that projection in the magnetization space is a reasonably
+accurate method to study the scaling of relaxation times with system size. The
+transition matrices for arbitrary single-spin flip dynamics are obtained from a
+single Monte-Carlo estimate of the infinite temperature transition-matrix, for
+each system size, which makes the method an efficient tool to evaluate the
+relative performance of any arbitrary local spin-flip dynamics. We also present
+new results for appropriately defined average tunnelling times of magnetization
+and compute their finite-size scaling exponents that we compare with results of
+energy tunnelling exponents available for the flat energy histogram
+multicanonical ensemble.",0701408v1
+2005-12-08,Physics of Complex Magnetic Materials: Quasiparticle Many-Body Dynamics,"A brief survey of the author's works on the quantum theory of magnetism.
+Theoretical foundation and applications of the generalized spin-fermion (sp-d)
+exchange lattice model to various magnetic systems, e.g., rare-earth metals and
+compounds, and magnetic and diluted magnetic semiconductors are discussed
+briefly. The main emphasis is put on the dynamic behavior of two interacting
+subsystems, the localized spins and spin density of itinerant carriers. A
+nonperturbative many-body approach was used to describe the quasiparticle
+dynamics. The approach permits to investigate and clarify the role of various
+interactions and disorder effects in combined quantum models of magnetism in
+unified and coherent fashion.",0512183v1
+2010-04-14,Dynamics of strongly magnetized ejecta in Gamma Ray Bursts,"We consider dynamical scales in magnetized GRB outflows, using the solutions
+to the Riemann problem of expanding arbitrarily magnetized outflows (Lyutikov
+2010). For high ejecta magnetization, the behavior of the forward shock closely
+resembles the so-called thick shell regime of the hydrodynamical expansion. The
+exception is at small radii, where the motion of the forward shock is
+determined by the dynamics of subsonic relativistic outflows. The behaviors of
+the reverse shock is different in fluid and magnetized cases: in the latter
+case, even for medium magnetization, sigma ~ 1, the reverse shock forms at
+fairly large distances, and may never form in a wind-type external density
+profile.",1004.2429v1
+2018-12-17,Dynamically generated magnetic moment in the Wigner-function formalism,"We study how the mass and magnetic moment of the quarks are dynamically
+generated in nonequilibrium quark matter. We derive the equal-time transport
+and constraint equations for the quark Wigner function in a magnetized quark
+model and solve them in the semi-classical expansion. The quark mass and
+magnetic moment are self-consistently coupled to the Wigner function and
+controlled by the kinetic equations. While the quark mass is dynamically
+generated at the classical level, the quark magnetic moment is a pure quantum
+effect, induced by the quark spin interaction with the external magnetic field.",1812.06684v1
+2023-09-27,Regulating spin dynamics in magnetic nanomaterials,"Magnetic nanomaterials can be used in the construction of devices for
+information processing and memory storage. For this purpose, they have to enjoy
+two contradictory properties, from one side being able of keeping for long time
+magnetization frozen, hence information stored, and from the other side
+allowing for quick change of magnetization required for fast erasing of memory
+and rewriting new information. Methods of resolving this dilemma are suggested
+based on triggering resonance, dynamic resonance tuning, and on quadratic
+Zeeman effect. These methods make it possible to realize effective regulation
+of spin dynamics in such materials as magnetic nanomolecules and magnetic
+nanoclusters.",2309.15568v1
+2006-01-27,Current-controlled magnetization dynamics in the spin-flip transistor,"The current driven magnetization dynamics of a thin-film, three magnetic
+terminal device (spin-flip transistor) is investigated theoretically. We
+consider a magnetization configuration in which all magnetizations are in the
+device plane, with source-drain magnetizations chosen fixed and antiparallel,
+whereas the third contact magnetization is allowed to move in a weak anisotropy
+field that guarantees thermal stability of the equilibrium structure at room
+temperature. We analyze the magnetization dynamics of the free layer under a dc
+source-drain bias current within the macrospin model and magneto-electronic
+circuit theory. A new tunable two-state behavior of the magnetization is found
+and the advantages of this phenomenon and potential applications are discussed.",0601632v1
+2017-07-11,Magnetophononics: ultrafast spin control through the lattice,"Using a combination of first-principles and magnetization-dynamics
+calculations, we study the effect of the intense optical excitation of phonons
+on the magnetic behavior in insulating magnetic materials. Taking the
+prototypical magnetoelectric \CrO\ as our model system, we show that excitation
+of a polar mode at 17 THz causes a pronounced modification of the magnetic
+exchange interactions through a change in the average Cr-Cr distance. In
+particular, the quasi-static deformation induced by nonlinear phononic coupling
+yields a structure with a modified magnetic state, which persists for the
+duration of the phonon excitation. In addition, our time-dependent
+magnetization dynamics computations show that systematic modulation of the
+magnetic exchange interaction by the phonon excitation modifies the
+magnetization dynamics. This temporal modulation of the magnetic exchange
+interaction strengths using phonons provides a new route to creating
+non-equilibrium magnetic states and suggests new avenues for fast manipulation
+of spin arrangements and dynamics.",1707.03216v3
+2023-01-09,X-ray detected ferromagnetic resonance techniques for the study of magnetization dynamics,"Element-specific spectroscopies using synchrotron-radiation can provide
+unique insights into materials properties. The recently developed technique of
+X-ray detected ferromagnetic resonance (XFMR) allows studying the magnetization
+dynamics of magnetic spin structures. Magnetic sensitivity in XFMR is obtained
+from the X-ray magnetic circular dichroism (XMCD) effect, where the phase of
+the magnetization precession of each magnetic layer with respect to the
+exciting radio frequency is obtained using stroboscopic probing of the spin
+precession. Measurement of both amplitude and phase response in the magnetic
+layers as a function of bias field can give a clear signature of spin-transfer
+torque (STT) coupling between ferromagnetic layers due to spin pumping. Over
+the last few years, there have been new developments utilizing X-ray scattering
+techniques to reveal the precessional magnetization dynamics of ordered spin
+structures in the GHz frequency range. The techniques of diffraction and
+reflectometry ferromagnetic resonance (DFMR and RFMR) provide novel ways for
+the probing of the dynamics of chiral and multilayered magnetic materials,
+thereby opening up new pathways for the development of high-density and
+low-energy consumption data processing solutions.",2301.03256v1
+2003-07-10,Tunable Magnetic Relaxation In Magnetic Nanoparticles,"We investigate the magnetization dynamics of a conducting magnetic
+nanoparticle weakly coupled to source and drain electrodes, under the
+assumption that all relaxation comes from exchange of electrons with the
+electrodes. The magnetization dynamics is characterized by a relaxation time
+$t_1$, which strongly depends on temperature, bias voltage, and gate voltage.
+While a direct measure of a nanoparticle magnetization might be difficult, we
+find that $t_1$ can be determined through a time resolved transport
+measurement. For a suitable choice of gate voltage and bias voltage, the
+magnetization performs a bias-driven Brownian motion regardless of the presence
+of anisotropy.",0307256v1
+2005-03-31,Boundary conditions for magnetization in magnetic nano-elements,"We show that the dynamic magnetization at the edges of a thin magnetic
+element with finite lateral size can be described by new effective boundary
+conditions that take into account inhomogeneous demagnetizing fields near the
+element edges. These fields play a dominant role in the effective pinning of
+the dynamic magnetization at the boundaries of mesoscopic and nano-sized
+magnetic elements. The derived effective boundary conditions generalize
+well-known Rado-Weertman boundary conditions and are reduced to them in the
+limiting case of a very thin magnetic element.",0503745v1
+2006-01-17,Electric field control of magnetization dynamics in ZnMnSe/ZnBeSe diluted-magnetic-semiconductor heterostructures,"We show that the magnetization dynamics in diluted magnetic semiconductors
+can be controlled separately from the static magnetization by means of an
+electric field. The spin-lattice relaxation (SLR) time of magnetic Mn2+ ions
+was tuned by two orders of magnitude by a gate voltage applied to n-type
+modulation-doped (Zn,Mn)Se/(Zn,Be)Se quantum wells. The effect is based on
+providing an additional channel for SLR by a two-dimensional electron gas
+(2DEG). The static magnetization responsible for the giant Zeeman spin
+splitting of excitons was not influenced by the 2DEG density.",0601383v1
+2008-10-28,"Anomalous magnetization behavior in Ce(Fe,Si)2","We report the effect of Si doping on the magnetization behavior of CeFe2. It
+is found that Si stabilizes the dynamic antiferromagnetic state of CeFe2.
+Multi-step magnetization behavior, unusual relaxation effect, thermal and
+magnetic history dependence, which are signatures of martensitic scenario, are
+found to be present in this system. We also show that one can induce the
+magnetization steps with the help of appropriate measurement protocol. Detailed
+magnetization relaxation studies have been carried out to understand the
+dynamics of magnetic phase transition.",0810.5017v1
+2014-06-18,Spin-lattice coupling induced weak dynamical magnetism in EuTiO_3 at high temperatures,"EuTiO_3, which is a G-type antiferromagnet below T_N = 5.5 K, has some
+fascinating properties at high temperatures, suggesting that macroscopically
+hidden dynamically fluctuating weak magnetism exists at high temperatures. This
+conjecture is substantiated by magnetic field dependent magnetization
+measurements, which exhibit pronounced anomalies below 200 K becoming more
+distinctive with increasing magnetic field strength. Additional results from
+muon spin rotation (${\mu}$SR) experiments provide evidence for weak
+fluctuating bulk magnetism induced by spin-lattice coupling which is strongly
+supported in increasing magnetic field.",1406.4915v1
+2015-03-27,Spin superradiance by magnetic nanomolecules and nanoclusters,"Spin dynamics of assemblies of magnetic nanomolecules and nanoclusters can be
+made coherent by inserting the sample into a coil of a resonant electric
+circuit. Coherence is organized through the arising feedback magnetic field of
+the coil. The coupling of a magnetic sample with a resonant circuit induces
+fast spin relaxation and coherent spin radiation, that is, superradiance. We
+consider spin dynamics described by a realistic Hamiltonian, typical of
+magnetic nanomolecules and nanoclusters. The role of magnetic anisotropy is
+studied. A special attention is paid to geometric effects related to the mutual
+orientation of the magnetic sample and resonator coil.",1503.08036v1
+2020-02-17,Periodic Magnetic Geodesics on Heisenberg Manifolds,"We study the dynamics of magnetic flows on Heisenberg groups. Let $H$ denote
+the three-dimensional simply connected Heisenberg Lie group endowed with a
+left-invariant Riemannian metric and an exact, left-invariant magnetic field.
+Let $\Gamma$ be a lattice subgroup of $H,$ so that $\Gamma\backslash H$ is a
+closed nilmanifold. We first find an explicit description of magnetic geodesics
+on $H$, then determine all closed magnetic geodesics and their lengths for
+$\Gamma \backslash H$. We then consider two applications of these results: the
+density of periodic magnetic geodesics and marked magnetic length spectrum
+rigidity.",2002.06982v1
+2011-11-28,Dynamical friction in a gaseous medium with a large-scale magnetic field,"The dynamical friction force experienced by a massive gravitating body moving
+through a gaseous medium is modified by sufficiently strong large-scale
+magnetic fields. Using linear perturbation theory, we calculate the structure
+of the wake generated by, and the gravitational drag force on, a body traveling
+in a straight-line trajectory in a uniformly magnetized medium. The functional
+form of the drag force as a function of the Mach number (V_0/c_s, where V_0 is
+the velocity of the body and c_s the sound speed) depends on the strength of
+the magnetic field and on the angle between the velocity of the perturber and
+the direction of the magnetic field. In particular, the peak value of the drag
+force is not near Mach number 1 for a perturber moving in a sufficiently
+magnetized medium. As a rule of thumb, we may state that for supersonic motion,
+magnetic fields act to suppress dynamical friction; for subsonic motion,
+magnetic fields tend to enhance dynamical friction. For perturbers moving along
+the magnetic field lines, the drag force at some subsonic Mach numbers may be
+stronger than it is at supersonic velocities. We also mention the relevance of
+our findings to black hole coalescence in galactic nuclei.",1111.6632v1
+2016-01-21,Vortex Dynamics-Mediated Low-Field Magnetization Switching in an Exchange-Coupled System,"A magnetic vortex has attracted significant attention since it is a
+topologically stable magnetic structure in a soft magnetic nanodisk. Many
+studies have been devoted to understanding the nature of magnetic vortex in
+isolated systems. Here we show a new aspect of a magnetic vortex the dynamics
+of which strongly affects the magnetic structures of environment. We exploit a
+nanodot of an exchange-coupled bilayer with a soft magnetic Ni81Fe19
+(permalloy; Py) having a magnetic vortex and a perpendicularly magnetized
+L10-FePt exhibiting a large switching field (Hsw). The vortex dynamics with
+azimuthal spin waves makes the excess energy accumulate in the Py, which
+triggers the reversed-domain nucleation in the L10-FePt at a low magnetic
+field. Our results shed light on the non-local mechanism of a reversed-domain
+nucleation, and provide with a route for efficient Hsw reduction that is needed
+for ultralow-power spintronic devices.",1601.05521v1
+2018-01-17,Magnetic effect on dynamical tide in rapidly rotating astronomical objects,"By numerically solving the equations of rotating magnetohydrodynamics (MHD),
+the magnetic effect on dynamical tide is studied. It is found that magnetic
+field has a significant impact not only on the flow structure, i.e. the
+internal shear layers in rotating flow can be destroyed in the presence of a
+moderate or stronger magnetic field (in the sense that the Alfv\'en velocity is
+at least of the order of 0.1 of the surface rotational velocity), but also on
+the dispersion relation of waves excited by tidal force such that the range of
+tidal resonance is broadened by magnetic field. A major result is that the
+total tidal dissipation scales as square of the field strength, which can be
+used to estimate the strength of internal magnetic field in the astronomical
+object of a binary system. Moreover, with a moderate or stronger field the
+ratio of the magnetic dissipation to the viscous dissipation is almost
+inversely proportional to magnetic Prandtl number (i.e. the ratio of viscosity
+to magnetic diffusivity), and therefore in the astrophysical situation at small
+magnetic Prandtl number magnetic dissipation dominates over viscous dissipation
+with a moderate or stronger field.",1801.05552v2
+2018-04-27,Excitation and coherent control of magnetization dynamics in magnetic tunnel junctions using acoustic pulses,"We experimentally study magnetization dynamics in magnetic tunnel junctions
+driven by femtosecond-laser-induced surface acoustic waves. The acoustic pulses
+induce a magnetization precession in the free layer of the magnetic tunnel
+junction through magnetoelastic coupling. The frequency and amplitude of the
+precession shows a pronounced dependence on the applied magnetic field and the
+laser excitation position. Comparing the acoustic-wave-induced precession
+frequencies with precession induced by charge currents and with micromagnetic
+simulations we identify spatially non-uniform magnetization modes localized
+close the edge regions as being responsible for the optically induced
+magnetization dynamics. The experimental scheme even allows us to coherently
+control the magnetization precession using two acoustic pulses. This might
+prove important for future applications requiring ultrafast spin manipulation.
+Additionally, our results directly pinpoint the importance of acoustic pulses
+since they could be relevant when investigating optically-induced temperature
+effects in magnetic structures.",1804.10503v1
+2021-12-02,Hamilton-Jacobi Equations of Nonholonomic Magnetic Hamiltonian Systems,"In order to describe the impact of different geometric structures and
+constraints for the dynamics of a Hamiltonian system, in this paper, for a
+magnetic Hamiltonian system defined by a magnetic symplectic form, we first
+drive precisely the geometric constraint conditions of magnetic symplectic form
+for the magnetic Hamiltonian vector field.which are called the Type I and Type
+II of Hamilton-Jacobi equation. Secondly, for the magnetic Hamiltonian system
+with nonholonomic constraint, we first define a distributional magnetic
+Hamiltonian system, then derive its two types of Hamilton-Jacobi equation.
+Moreover, we generalize the above results to nonholonomic reducible magnetic
+Hamiltonian system with symmetry. We define a nonholonomic reduced
+distributional magnetic Hamiltonian system, and prove two types of
+Hamilton-Jacobi theorem. These research work reveal the deeply internal
+relationships of the magnetic symplectic structure, nonholonomic constraint,
+the distributional two-form, and the dynamical vector field of the nonholonomic
+magnetic Hamiltonian system.",2112.00961v2
+2014-07-04,Mixed spin (1/2-1) hexagonal Ising nanowire: some dynamic behaviors,"The dynamic behaviors of a mixed spin (1/2-1) hexagonal Ising nanowire (HIN)
+with core-shell structure in the presence of a time dependent magnetic field
+are investigated by using the effective-field theory with correlations based on
+the Glauber-type stochastic dynamics (DEFT). According to the values of
+interaction parameters, temperature dependence of the dynamic magnetizations,
+the hysteresis loop areas and the dynamic correlations are investigated to
+characterize the nature (first- or second-order) of the dynamic phase
+transitions (DPTs). Dynamic phase diagrams, including compensation points, are
+also obtained. Moreover, from the thermal variations of the dynamic total
+magnetization, the five compensation types can be found under certain
+conditions, namely the Q-, R-, S-, P-, and N-types.",1407.1092v1
+2021-09-24,Fluidic Endogenous Magnetism and Magnetic Monopole Clues from Liquid Metal Droplet Machine,"Magnetism and magnetic monopole are classical issues in basic physics.
+Conventional magnets are generally composed of rigid materials with shapes and
+structures unchangeable which may face challenges sometimes to answer the above
+questions. Here, from an alternative other than rigid magnet, we disclosed an
+unconventional way to generate endogenous magnetism and then construct magnetic
+monopole through tuning liquid metal machine. Through theoretical
+interpretation and conceptual experiments, we illustrated that when gallium
+base liquid metal in solution rotates under actuation of an external electric
+field, it forms an endogenous magnetic field inside which well explains the
+phenomenon that two such discrete metal droplets could easily fuse together,
+indicating their reciprocal attraction via N and S poles. Further, we conceived
+that the self-driving liquid metal motor was also an endogenous magnet owning
+the electromagnetic homology. When liquid metal in solution swallowed aluminum
+inside, it formed a spin motor and dynamically variable charge distribution
+which produced an endogenous magnetic field. This finding explains the
+phenomena that there often happened reflection collision and attraction fusion
+between running liquid metal motors which were just caused by the dynamic
+adjustment of their N and S polarities. Finally, we conceived that such
+endogenous magnet could lead to magnetic monopole and four technical routes
+were suggested as: 1. Matching the interior flow field of liquid metal
+machines; 2. Superposition between external electric effect and magnetic field;
+3. Composite construction between magnetic particles and liquid metal motor; 4.
+Chemical ways such as via galvanic cell reaction. Overall, the fluidic
+endogenous magnet and the promising magnetic monopole it enabled may lead to
+unconventional magnetoelectric devices and applications in the near future.",2111.02867v1
+2017-12-20,Optical Manipulation of Magnetic Vortex Visualized in situ by 4D Electron Microscopy,"Understanding the fundamental dynamics of topological vortex and antivortex
+naturally formed in micro/nanoscale ferromagnetic building blocks under
+external perturbations is crucial to magnetic vortex based information
+processing and spintronic devices. All previous studies have focused on
+magnetic vortex-core switching via external magnetic fields, spin-polarized
+currents, or spin waves, which have largely prohibited the investigation of
+novel spin configurations that could emerge from the ground states in
+ferromagnetic disks and their underlying dynamics. Here, we report in situ
+visualization of femtosecond laser quenching induced magnetic vortex change in
+various symmetric ferromagnetic Permalloy disks by Lorentz phase imaging using
+4D electron microscopy. Besides the switching of magnetic vortex chirality and
+polarity, we observed with distinct occurrence frequencies a plenitude of
+complex magnetic structures that have never been observed by magnetic field or
+current assisted switching. These complex magnetic structures consist of a
+number of newly created topological magnetic defects (vortex and antivortex)
+strictly conserving the topological winding number, demonstrating the direct
+impact of topological invariant on the magnetization dynamics in ferromagnetic
+disks. Their spin configurations show mirror or rotation symmetry due to the
+geometrical confinement of the disks. Combined micromagnetic simulations with
+the experimental observations reveal the underlying magnetization dynamics and
+formation mechanism of the optical quenching induced complex magnetic
+structures. Their distinct occurrence rates are pertinent to their
+formation-growth energetics and pinning effects at the disk edge. Based on
+these findings, we propose a paradigm of optical-quenching-assisted fast
+switching of vortex cores for the control of magnetic vortex based information
+recording and spintronic devices.",1712.07280v1
+2004-11-11,Dynamical Symmetry Breaking on a Cylinder in Magnetic Field,"We study dynamical symmetry breaking on a cylinder in external magnetic field
+parallel to the axis of cylinder when magnetic field affects the dynamics of
+fermions only through the Aharonov-Bohm phase. We find that unlike other
+previously studied cases magnetic field in our case counteracts the generation
+of dynamical fermion mass which decreases with magnetic field. There exists
+also a purely kinematical contribution to the fermion gap which grows linearly
+with magnetic field. Remarkably, we find that the total fermion gap, which
+includes both the dynamical and kinematical contributions, always increases
+with magnetic field irrespectively the values of coupling constant and the
+radius of cylinder. Thus, although the dynamical mass is suppressed, external
+magnetic field does enhance the total fermion gap in the spectrum.",0411157v2
+2020-01-22,Imaging three-dimensional nanoscale magnetization dynamics,"The ability to experimentally map the three-dimensional structure and
+dynamics in bulk and patterned three-dimensional ferromagnets is essential both
+for understanding fundamental micromagnetic processes, as well as for
+investigating technologically-relevant micromagnets whose functions are
+connected to the presence and dynamics of fundamental micromagnetic structures,
+such as domain walls and vortices. Here, we demonstrate time-resolved magnetic
+laminography, a technique which offers access to the temporal evolution of a
+complex three-dimensional magnetic structure with nanoscale resolution. We
+image the dynamics of the complex three-dimensional magnetization state in a
+two-phase bulk magnet with a lateral spatial resolution of 50 nm, mapping the
+transition between domain wall precession and the dynamics of a uniform
+magnetic domain that is attributed to variations in the magnetization state
+across the phase boundary. The capability to probe three-dimensional magnetic
+structures with temporal resolution paves the way for the experimental
+investigation of novel functionalities arising from dynamic phenomena in bulk
+and three-dimensional patterned nanomagnets.",2001.07940v1
+2003-04-04,Dynamic exchange coupling and Gilbert damping in magnetic multilayers,"We theoretically study dynamic properties of thin ferromagnetic films in
+contact with normal metals. Moving magnetizations cause a flow of spins into
+adjacent conductors, which relax by spin flip, scatter back into the
+ferromagnet, or are absorbed by another ferromagnet. Relaxation of spins
+outside the moving magnetization enhances the overall damping of the
+magnetization dynamics in accordance with the Gilbert phenomenology. Transfer
+of spins between different ferromagnets by these nonequilibrium spin currents
+leads to a long-ranged dynamic exchange interaction and novel collective
+excitation modes. Our predictions agree well with recent
+ferromagnetic-resonance experiments on ultrathin magnetic films.",0304116v1
+2007-09-27,Dynamical Electron Mass in a Strong Magnetic Field,"Motivated by recent interest in understanding properties of strongly
+magnetized matter, we study the dynamical electron mass generated through
+approximate chiral symmetry breaking in QED in a strong magnetic field. We
+reliably calculate the dynamical electron mass by numerically solving the
+nonperturbative Schwinger-Dyson equations in a consistent truncation within the
+lowest Landau level approximation. It is shown that the generation of dynamical
+electron mass in a strong magnetic field is significantly enhanced by the
+perturbative electron mass that explicitly breaks chiral symmetry in the
+absence of a magnetic field.",0709.4427v3
+2011-02-14,Application of Resonance Perturbation Theory to Dynamics of Magnetization in Spin Systems Interacting with Local and Collective Bosonic Reservoirs,"We apply our recently developed resonance perturbation theory to describe the
+dynamics of magnetization in paramagnetic spin systems interacting
+simultaneously with local and collective bosonic environments. We derive
+explicit expressions for the evolution of the reduced density matrix elements.
+This allows us to calculate explicitly the dynamics of the macroscopic
+magnetization, including characteristic relaxation and dephasing time-scales.
+We demonstrate that collective effects (i) do not influence the character of
+the relaxation processes but merely renormalize the relaxation times, and (ii)
+significantly modify the dephasing times, leading in some cases to a
+complicated (time inhomogeneous) dynamics of the transverse magnetization,
+governed by an effective time-dependent magnetic field.",1102.2847v1
+2012-03-24,Dynamics of a dielectric droplet suspended in a magnetic fluid in electric and magnetic fields,"The behavior of a microdrop of dielectric liquid suspended in a magnetic
+fluid and exposed to the action of electric and magnetic fields is studied
+experimentally. With increasing electric field, the deformation of droplets
+into oblate ellipsoid, toroid and curved toroid was observed. At the further
+increase in the electric field, the bursting of droplets was also revealed. The
+electrorotation of deformed droplets was observed and investigated. The
+influence of an additional magnetic field on the droplet dynamics was studied.
+The main features of the droplet dynamics were interpreted and theoretically
+examined.",1203.5434v1
+2015-09-09,Inertial terms to magnetization dynamics in ferromagnetic thin films,"Inertial magnetization dynamics have been predicted at ultrahigh speeds, or
+frequencies approaching the energy relaxation scale of electrons, in
+ferromagnetic metals. Here we identify inertial terms to magnetization dynamics
+in thin Ni$_{79}$Fe$_{21}$ and Co films near room temperature. Effective
+magnetic fields measured in high-frequency ferromagnetic resonance (115-345
+GHz) show an additional stiffening term which is quadratic in frequency and
+$\sim$ 80 mT at the high frequency limit of our experiment. Our results extend
+understanding of magnetization dynamics at sub-picosecond time scales.",1509.02836v1
+2018-10-04,Domain wall dynamics in easy-cone magnets,"We theoretically and numerically investigate magnetic domain wall dynamics in
+a nanowire of easy-cone magnet. The easy-cone domain wall exhibits several
+distinguishing dynamic features in comparison to the easy-axis domain wall. The
+features of easy-cone domain wall are related to the generation of additional
+chiral spin textures due to the domain wall precession, which is common for
+various driving sources such as magnetic fields and spin-transfer torques. The
+unique easy-cone domain wall dynamics could enrich magnetic domain wall study
+and find use in device applications based on easy-cone domain walls.",1810.02216v1
+2020-05-12,Analysis in k-space of Magnetization Dynamics Driven by Strong Terahertz Fields,"Demagnetization in a thin film due to a terahertz pulse of magnetic field is
+investigated. Linearized LLG equation in the Fourier space to describe the
+magnetization dynamics is derived, and spin waves time evolution is studied.
+Finally, the demagnetization due to spin waves dynamics and recent experimental
+observations on similar magnetic system are compared. As a result of it, the
+marginal role of spin waves dynamics in loss of magnetization is established.",2005.05742v1
+1999-09-27,Topological Constraints on the Relaxation of Complex Magnetic Fields,"Newly emerging magnetic flux can show a complicated linked or interwoven
+topology of the magnetic field. The complexity of this linkage or knottedness
+of magnetic flux is related to the free energy stored in the magnetic field.
+Magnetic reconnection provides a process to release this energy on the time
+scale of the dynamics. At the same time it approximately conserves the total
+magnetic helicity. Therefore the conservation of total magnetic helicity is a
+crucial constraint for the relaxation of complex magnetic fields. However, the
+total magnetic helicity is only the first, most elementary, quantity of an
+infinite series of topological invariants of the magnetic field. All these
+invariants are strictly conserved in ideal magnetohydrodynamics. As an example
+a preliminary set of these invariants is derived. The relevance of these higher
+order invariants for the final state of relaxation under magnetic reconnection
+and their implications for the release of magnetic energy are discussed.",9909443v1
+2014-08-05,Tunable asymmetric magnetoimpedance effect in ferromagnetic NiFe/Cu/Co films,"We investigate the magnetization dynamics through the magnetoimpedance effect
+in ferromagnetic NiFe/Cu/Co films. We observe that the magnetoimpedance
+response is dependent on the thickness of the non-magnetic Cu spacer material,
+a fact associated to the kind of the magnetic interaction between the
+ferromagnetic layers. Thus, we present an experimental study on asymmetric
+magnetoimpedance in ferromagnetic films with biphase magnetic behavior and
+explore the possibility of tuning the linear region of the magnetoimpedance
+curves around zero magnetic field by varying the thickness of the non-magnetic
+spacer material, and probe current frequency. We discuss the experimental
+magnetoimpedance results in terms of the different mechanisms governing the
+magnetization dynamics at distinct frequency ranges, quasi-static magnetic
+properties, thickness of the non-magnetic spacer material, and the kind of the
+magnetic interaction between the ferromagnetic layers. The results place
+ferromagnetic films with biphase magnetic behavior exhibiting asymmetric
+magnetoimpedance effect as a very attractive candidate for application as probe
+element in the development of auto-biased linear magnetic field sensors.",1408.0992v1
+2020-09-03,Coincidence inelastic neutron scattering for detection of two-spin magnetic correlations,"Inelastic neutron scattering (INS) is one powerful technique to study the
+low-energy single-spin dynamics of magnetic materials. A variety of quantum
+magnets show novel magnetic correlations such as quantum spin liquids. These
+novel magnetic correlations are beyond the direct detection of INS. In this
+paper we propose a coincidence technique, coincidence inelastic neutron
+scattering (cINS), which can detect the two-spin magnetic correlations of the
+magnetic materials. In cINS there are two neutron sources and two neutron
+detectors with an additional coincidence detector. Two neutrons from the two
+neutron sources are incident on the target magnetic material, and they are
+scattered by the electron spins of the magnetic material. The two scattered
+neutrons are detected by the two neutron detectors in coincidence with the
+coincidence probability described by a two-spin Bethe-Salpeter wave function.
+Since the two-spin Bethe-Salpeter wave function defines the momentum-resolved
+dynamical wave function with two spins excited, cINS can explicitly detect the
+two-spin magnetic correlations of the magnetic material. Thus, it can be
+introduced to study the various spin valence bond states of the quantum
+magnets.",2009.01680v2
+2021-06-28,Stability of a Magnetically Levitated Nanomagnet in Vacuum: Effects of Gas and Magnetization Damping,"In the absence of dissipation a non-rotating magnetic nanoparticle can be
+stably levitated in a static magnetic field as a consequence of the spin origin
+of its magnetization. Here we study the effects of dissipation on the stability
+of the system, considering the interaction with the background gas and the
+intrinsic Gilbert damping of magnetization dynamics. At large applied magnetic
+fields we identify magnetization switching induced by Gilbert damping as the
+key limiting factor for stable levitation. At low applied magnetic fields and
+for small particle dimensions magnetization switching is prevented due to the
+strong coupling of rotation and magnetization dynamics, and the stability is
+mainly limited by the gas-induced dissipation. In the latter case, high vacuum
+should be sufficient to extend stable levitation over experimentally relevant
+timescales. Our results demonstrate the possibility to experimentally observe
+the phenomenon of quantum spin stabilized magnetic levitation.",2106.14858v3
+2004-11-11,Magnetic Soret effect: Application of the ferrofluid dynamics theory,"The ferrofluid dynamics theory is applied to thermodiffusive problems in
+magnetic fluids in the presence of magnetic fields. The analytical form for the
+magnetic part of the chemical potential and the most general expression of the
+mass flux are given. By employing these results to experiments, global Soret
+coefficients in agreement with measurements are determined. Also an estimate
+for a hitherto unknown transport coefficient is made.",0411308v1
+2009-11-11,Wavelets spectra of magnetization dynamics in geometry driven magnetic thin layers,"Squared cobalt thin layers of different thickness and width were investigated
+by numerical simulations. Using zero-valued externally applied magnetic field
+(geometry driven regime) and different initial conditions the magnetization
+dynamics were examined. The wavelet-based spectral analysis was applied.
+Transient states of different types were identified.",0911.1994v1
+2014-05-26,Magneto-Optical Spectrum Analyzer,"We present a method for the investigation of gigahertz magnetization dynamics
+of single magnetic nano elements. By combining a frequency domain approach with
+a micro focus Kerr effect detection, a high sensitivity to magnetization
+dynamics with submicron spatial resolution is achieved. It allows spectra of
+single nanostructures to be recorded. Results on the uniform precession in soft
+magnetic platelets are presented.",1405.6551v1
+2016-03-30,Distributed chaos and solitons at the edges of magnetically confined plasmas,"It is shown, using results of measurements of ion saturation current in the
+plasma edges of different magnetic fusion confinement devices (tokamaks and
+stellarators), that the plasma dynamics in the edges is dominated by
+distributed chaos with spontaneously broken translational symmetry at low
+magnetic field, and with spontaneously broken reflexional symmetry (by helical
+solitons) at high magnetic field.",1603.09186v2
+2014-11-26,The dynamic magnetic behaviors of the Blume-Capel Ising bilayer system,"The dynamic magnetic behaviors of the spin-1 Blume-Capel Ising bilayer system
+(BCIS) are studied in an oscillating external magnetic field on a two-layer
+square lattice by utilizing the mean field theory based on Glauber-type
+stochastic dynamics (DMFT). The dynamic equations describing the
+time-dependencies of the average magnetizations are obtained with the Master
+equation. The dynamic phases in this system are found by solving these dynamic
+equations. The temperature dependence of the dynamic order parameters is
+examined to characterize the nature (continuous or discontinuous) of the phase
+transitions and to obtain the dynamic phase transition points (DPT). The
+dynamic phase diagrams are shown for ferromagnetic / ferromagnetic,
+antiferromagnetic / antiferromagnetic, antiferromagnetic / antiferromagnetic
+interactions in the plane of the reduced temperature versus magnetic field
+amplitude and they display dynamic tricritical and reentrant behavior as well
+as the dynamic triple point.",1411.7146v1
+2002-04-09,Local Circumstellar Magnetic Fields Around Evolved Stars,"I argue that the presence of magnetic fields around evolved stars, e.g.,
+asymptotic giant branch stars, and in PNe, does not necessarily imply that the
+magnetic field plays a global dynamical role in shaping the circumstellar
+envelope. Instead, I favor magnetic fields with small coherence lengths, which
+result from stellar magnetic spots or from jets blown by an accreting
+companion. Although the magnetic field does not play a global role in shaping
+the circumstellar envelope, it may enhance local motion (turbulent) via
+magnetic tension and reconnection. The locally strong magnetic tension may
+enforce coherence flow which may favor the masing process.",0204157v1
+2016-02-29,Gyrotropic skyrmion modes in ultrathin magnetic circular dots,"We calculate low-frequency gyrotropic spin excitation modes of the skyrmion
+ground state ultrathin cylindrical magnetic dots. The skyrmion is assumed to be
+stabilized at room temperature and zero external magnetic field due to an
+interplay of the isotropic and Dzyaloshinskii-Moriya exchange interactions,
+perpendicular magnetic anisotropy and magnetostatic interaction. We consider
+Bloch- and Neel-type magnetic skyrmions and assume that the dot magnetization
+does not depend on the thickness coordinate. The skyrmion gyrotropic
+frequencies are calculated in GHz range as a function of the skyrmion
+equilibrium radius, dot radius and the dot magnetic parameters. Recent
+experiments on magnetic skyrmion gyrotropic dynamics in nanodots are discussed.",1603.00072v1
+2016-07-19,MHD flow and heat transfer due to the axisymmetric stretching of a sheet with induced magnetic field,"The full MHD equations, governing the flow due to the axisymmetric stretching
+of a sheet in the presence of a transverse magnetic field, can be cast in a
+self similar form. This allows evaluation of the induced magnetic field and its
+effect on the flow and heat transfer. The problem involves three parameters-
+the magnetic Prandtl number, the magnetic interaction number, and the Prandtl
+number. Numerical solutions are obtained for the velocity field, the magnetic
+field, and the temperature, at different values of the magnetic Prandtl number
+and the magnetic interaction number. The contributions of the viscous
+dissipation, Joule heating, and streamwise diffusion to the heat flux toward
+the sheet are assessed.",1607.05722v1
+2017-02-27,Magnetization reversal by superconducting current in $\varphi_0$ Josephson junctions,"We study magnetization reversal in a $\varphi_0$ Josephson junction with
+direct coupling between magnetic moment and Josephson current. Our simulations
+of magnetic moment dynamics show that by applying an electric current pulse, we
+can realize the full magnetization reversal. We propose different protocols of
+full magnetization reversal based on the variation of the Josephson junction
+and pulse parameters, particularly, electric current pulse amplitude, damping
+of magnetization and spin-orbit interaction. We discuss experiments which can
+probe the magnetization reversal in $\varphi_0$-junctions.",1702.08394v4
+2022-04-11,Deformation of a magnetic liquid drop and unsteady flow inside and outside it in a non-stationary magnetic field,"Small steady-state deformational oscillations of a drop of a viscous magnetic
+liquid in a non-stationary uniform magnetic field are theoretically
+investigated for low Reynolds numbers. The drop is suspended in another viscous
+magnetic liquid immiscible with the former. The non-stationary magnetic field
+causes flow inside and outside the drop. The inertia is taken into account by
+regarding the flow as essentially unsteady. The variation of the magnetic field
+is so slow that the approximation of quasi-stationary magnetic field may be
+used.",2204.05387v2
+2019-11-21,Coupled spin-charge dynamics in magnetic van der Waals heterostructures,"We present a phenomenological theory for coupled spin-charge dynamics in
+magnetic van der Waals heterostructures. The system studied consists of a
+layered antiferromagnet inserted into a capacitive vdW heterostructure. It has
+been recently demonstrated that charge doping in such layered antiferromagnets
+can modulate the strength, and even the sign, of exchange coupling between the
+layer magnetizations. This provides a mechanism for electrically generating
+magnetization dynamics. The central result we predict here is that the
+magnetization dynamics reciprocally results in inducing charge dynamics. Such
+dynamics makes magnetic van der Waals heterostructures interesting candidates
+for spintronics applications. To this end, we also show that these systems can
+be used to convert sub-THz radiation induced magnetization dynamics into
+electrical signals.",1911.09688v2
+2021-04-14,Non-resonant circles for strong magnetic fields on surfaces,"We study non-resonant circles for strong magnetic fields on a closed,
+connected, oriented surface and show how these can be used to prove the
+existence of trapping regions and of periodic magnetic geodesics with
+prescribed low speed. As a corollary, there exist infinitely many periodic
+magnetic geodesics for every low speed in the following cases: i) the surface
+is not the two-sphere, ii) the magnetic field vanishes somewhere.",2104.06733v1
+2020-07-26,Effect of the anomalous magnetic moment of quarks on magnetized QCD matter and meson spectra,"We systematically investigate the effect of the anomalous magnetic
+moment(AMM) of quarks on the magnetized QCD matter, including the magnetic
+susceptibility, the inverse magnetic catalysis around the critical temperature
+and the neutral/charged pion and rho meson spectra under magnetic fields. The
+dynamical AMM of quarks, its coupling with magnetic field causes Zeeman
+splitting of the dispersion relation of quarks thus changes the magnetism
+properties and meson mass spectra under magnetic fields. It is found that
+including the AMM of quarks cannot fully understand lattice results of the
+magnetized matter: The AMM of quarks reduces the dynamical quark mass thus
+causes the inverse magnetic catalysis around $T_c$. The neutral pion mass is
+very sensitive to the AMM, it decreases with magnetic field quickly, and the
+charged pion mass shows a nonlinear behavior, i.e., firstly linearly increases
+with the magnetic field and then saturates at strong magnetic field. For rho
+meson, it is observed that AMM reduces the mass of neutral rho meson mass with
+different $s_z$, and reduces the mass of $s_z=+1,0$ component charged rho meson
+mass but enhances the $s_z=-1$ component charged rho meson mass. The magnetic
+susceptibility at low temperature can be either positive or negative with
+different AMM.",2007.13122v3
+2023-07-28,Reversible magnetic domain reorientation induced by magnetic field pulses with fixed direction,"Nanoscale magnetic domains with controllable configurations could be used for
+classical and quantum applications, where the switching of magnetization
+configurations is an essential operation for information processing. Here, we
+report that the magnetic domain reorientation in a notched ferromagnetic
+nanotrack can be realized and effectively controlled by applying uniform
+magnetic field pulses in a fixed in-plane direction perpendicular to the
+nanotrack. Our micromagnetic simulation results show that the configurations of
+magnetic domains in the notched nanotrack can be switched between a
+head-to-head state and a tail-to-tail state in a reversible manner driven by
+magnetic field pulses, while it is unnecessary to reverse the direction of the
+magnetic field. Such a unique magnetic domain reorientation dynamics is found
+to depend on magnetic parameters and nanotrack geometries. The reorientation
+dynamics of magnetic domains also depends on the strength and length of the
+applied magnetic field pulse. In addition, we point out that the notches at the
+center of the nanotrack play an important role for the stabilization of the
+head-to-head and tail-to-tail states during the magnetic domain reorientation.
+We also qualitatively explain the field-induced reorientation phenomenon with a
+simplified two-dimensional macrospin model. Our results may make it possible to
+build spintronic devices driven by a fixed magnetic field. Our findings may
+also motivate future studies to investigate the classical and quantum
+applications based on nanoscale magnetic domains.",2307.15263v1
+2006-06-02,Magnetically tuned spin dynamics resonance,"We present the experimental observation of a magnetically tuned resonance
+phenomenon resulting from spin mixing dynamics of ultracold atomic gases. In
+particular we study the magnetic field dependence of spin conversion in F=2
+87Rb spinor condensates in the crossover from interaction dominated to
+quadratic Zeeman dominated dynamics. We discuss the observed phenomenon in the
+framework of spin dynamics as well as matter wave four wave mixing. Furthermore
+we show that the validity range of the single mode approximation for spin
+dynamics is significantly extended in the regime of high magnetic field.",0606046v1
+2007-12-07,Short-time critical dynamics at perfect and non-perfect surface,"We report Monte Carlo simulations of critical dynamics far from equilibrium
+on a perfect and non-perfect surface in the 3d Ising model. For an ordered
+initial state, the dynamic relaxation of the surface magnetization, the line
+magnetization of the defect line, and the corresponding susceptibilities and
+appropriate cumulant is carefully examined at the ordinary, special and surface
+phase transitions. The universal dynamic scaling behavior including a dynamic
+crossover scaling form is identified. The exponent $\beta_1$ of the surface
+magnetization and $\beta_2$ of the line magnetization are extracted. The impact
+of the defect line on the surface universality classes is investigated.",0712.1087v1
+2021-04-24,Theory of magnetic inertial dynamics in two-sublattice ferromagnets,"The magnetic inertial dynamics have been investigated for one sublattice
+ferromagnets. Here, we develop the magnetization dynamics in two-sublattice
+ferromagnets including the intra- and inter-sublattice inertial dynamics.
+First, we derive the magnetic susceptibility of such a ferromagnet. Next, by
+finding the poles of the susceptibility, we calculate the precession and
+nutation resonance frequencies. Our results suggest that while the resonance
+frequencies show decreasing behavior with the increasing intra-sublattice
+relaxation time, the effect of inter-sublattice inertial dynamics is
+contrasting.",2104.11878v2
+2023-09-08,Emergence of Chaos in Magnetic-Field-Driven Skyrmions,"We explore magnetic-field-driven chaos in magnetic skyrmions. Oscillating
+magnetic fields induce nonlinear dynamics in skyrmions, arising from the
+coupling of the secondary gyrotropic mode with a non-uniform, breathing-like
+mode. Through micromagnetic simulations, we observe complex patterns of
+hypotrochoidal motion in the orbital trajectories of the skyrmions, which are
+interpreted using bifurcation diagrams and local Lyapunov exponents. Our
+findings demonstrate that different nonlinear behaviors of skyrmions emerge at
+distinct temporal stages, depending on the nonlinear dynamic parameters.
+Investigating the abundant dynamic patterns of skyrmions during the emergence
+of chaos not only enhances device reliability but also provides useful
+guidelines for establishing chaos computing based on skyrmion dynamics.",2309.04243v1
+2007-07-16,Magnetodipolar interlayer interaction effect on the magnetization dynamics of a trilayer square element with the Landau domain structure,"We present a detailed numerical simulation study of the effects caused by the
+magnetodipolar interaction between ferromagnetic (FM) layers of a trilayer
+magnetic nanoelement on its magnetization dynamics. As an example we use a
+Co/Cu/Ni80Fe20 element with a square lateral shape where the magnetization of
+FM layers forms a closed Landau-like domain pattern. First we show that when
+the thickness of the non-magnetic (NM) spacer is in the technology relevant
+region h ~ 10 nm, magnetodipolar interaction between 90o Neel domain walls in
+FM layers qualitatively changes the equilibrium magnetization state of these
+layers. In the main of the paper we compare the magnetization dynamics induced
+by a sub-nsec field pulse in a single-layer Ni80Fe20 (Py) element and in the
+Co/Cu/Py trilayer element. Here we show that (i) due to the spontaneous
+symmetry breaking of the Landau state in the FM/NM/FM trilayer its domains and
+domain walls oscillate with different frequencies and have different spatial
+oscillation patterns; (ii) magnetization oscillations of the trilayer domains
+are strongly suppressed due to different oscillation frequencies of domains in
+Co and Py; (iii) magnetization dynamics qualitatively depends on the relative
+rotation sense of magnetization states in Co and Py layers and on the
+magnetocrystalline anisotropy kind of Co crystallites. Finally we discuss the
+relation of our findings with experimental observations of magnetization
+dynamics in magnetic trilayers, performed using the element-specific
+time-resolved X-ray microscopy.",0707.2344v1
+2009-05-11,Dynamically Generated Anomalous Magnetic Moment in Massless QED,"In this paper we investigate the non-perturbative generation of an anomalous
+magnetic moment for massless fermions in the presence of an external magnetic
+field. In the context of massless QED in a magnetic field, we prove that the
+phenomenon of magnetic catalysis of chiral symmetry breaking, which has been
+associated in the literature with dynamical mass generation, is also
+responsible for the generation of a dynamical anomalous magnetic moment. As a
+consequence, the degenerate energy of electrons in Landau levels higher than
+zero exhibits Zeeman splitting. We explicitly report the splitting for the
+first Landau level and find the non-perturbative Lande $\textit{g}$-factor and
+Bohr magneton. We anticipate that a dynamically generated anomalous magnetic
+moment will be a universal feature of theories with magnetic catalysis. Our
+findings can be important for condensed planar systems as graphene, as well as
+for highly magnetized dense systems as those forming the core of compact stars.",0905.1733v2
+2015-07-24,Coherent zero-field magnetization resonance in a dipolar spin-1 Bose-Einstein condensate,"With current magnetic field shielding and high precision detection in dipolar
+spinor Bose-Einstein condensates, it is possible to experimentally detect the
+low or zero field nonsecular dipolar dynamics. Here we analytically investigate
+the zero-field nonsecular magnetic dipolar interaction effect, with an emphasis
+on magnetization dynamics in a spin-1 Bose-Einstein condensate under the single
+spatial mode approximation within the mean field theory. Due to the biaxial
+nature of the dipolar interaction, a novel resonance occurs in the condensate
+magnetization oscillation, contrast to the previous assumption of a conserved
+magnetization in strong magnetic fields. Furthermore, we propose a
+dynamical-decoupling detection method for such a resonance, which cancels the
+stray magnetic fields in experiments but restores the magnetization dynamics.
+Our results shed new lights on the dipolar systems and may find potential
+applications beyond cold atoms.",1507.06729v1
+2019-03-17,"Dynamical symmetry breaking, magnetization and induced charge in graphene: Interplay between magnetic and pseudomagnetic fields","In this paper, we investigate the two competing effects of strains and
+magnetic fields in single-layer graphene to explore its impact on various
+phenomena of quantum field theory, such as induced charge density, magnetic
+catalysis, symmetry breaking, dynamical mass generation and magnetization. We
+show that the interplay between strains and magnetic fields produces not only a
+breaking of chiral symmetry, as it happens in QED$_{2+1}$, but also parity and
+time-reversal symmetry breaking. The last two symmetry breakings are related to
+the dynamical generation of a Haldane mass term. We find that it is possible to
+modify the magnetization and the dynamical mass independently for each valley,
+by strain and varying the external magnetic field. Furthermore, we discover
+that the presence of a non-zero pseudomagnetic field, unlike the magnetic one,
+allows us to observe an induced ""vacuum"" charge and a parity anomaly in
+strained graphene. Finally, because the combined effect of real and
+pseudomagnetic fields produces an induced valley polarization, the results
+presented here may provide new tools to design valleytronic devices.",1903.07180v2
+2020-03-28,Spin transport and dynamic properties of two-dimensional spin-momentum locked states,"Materials with spin-momentum locked surface or interface states provide an
+interesting playground for studying physics and application of charge-spin
+current conversion. To characterize their non-equilibrium magnetic and
+transport properties in the presence of a time-dependent external magnetic
+field and a spin injection from a contact, we introduce three macroscopic
+variables: a vectorial helical magnetization, a scaler helical magnetization,
+and the conventional magnetization. We derive a set of closed dynamic equations
+for these variables by using the spinor Boltzmann approach with the collision
+terms consistent with the symmetry of spin-momentum locked states. By solving
+the dynamic equations, we predict several intriguing magnetic and transport
+phenomena which are experimentally accessible, including magnetic resonant
+response to an AC applied magnetic field, charge-spin conversion, and spin
+current induced by the dynamics of helical magnetization.",2003.12700v1
+2022-11-15,Nonlinear sub-switching regime of magnetization dynamics in photo-magnetic garnets,"We analyze, both experimentally and numerically, the nonlinear regime of the
+photo-induced coherent magnetization dynamics in cobalt-doped yttrium iron
+garnet films. Photo-magnetic excitation with femtosecond laser pulses reveals a
+strongly nonlinear response of the spin subsystem with a significant increase
+of the effective Gilbert damping. By varying both laser fluence and the
+external magnetic field, we show that this nonlinearity originates in the
+anharmonicity of the magnetic energy landscape. We numerically map the
+parameter workspace for the nonlinear photo-induced spin dynamics below the
+photo-magnetic switching threshold. Corroborated by numerical simulations of
+the Landau-Lifshitz-Gilbert equation, our results highlight the key role of the
+cubic symmetry of the magnetic subsystem in reaching the nonlinear spin
+precession regime. These findings expand the fundamental understanding of
+laser-induced nonlinear spin dynamics as well as facilitate the development of
+applied photo-magnetism.",2211.08048v2
+2002-06-16,Nonlinear Turbulent Magnetic Diffusion and Mean-Field Dynamo,"The nonlinear coefficients defining the mean electromotive force (i.e., the
+nonlinear turbulent magnetic diffusion, the nonlinear effective velocity, the
+nonlinear kappa-tensor, etc.) are calculated for an anisotropic turbulence. A
+particular case of an anisotropic background turbulence (i.e., the turbulence
+with zero mean magnetic field) with one preferential direction is considered.
+It is shown that the toroidal and poloidal magnetic fields have different
+nonlinear turbulent magnetic diffusion coefficients. It is demonstrated that
+even for a homogeneous turbulence there is a nonlinear effective velocity which
+exhibits diamagnetic or paramagnetic properties depending on anisotropy of
+turbulence and level of magnetic fluctuations in the background turbulence.
+Analysis shows that an anisotropy of turbulence strongly affects the nonlinear
+mean electromotive force. Two types of nonlinearities (algebraic and dynamic)
+are also discussed. The algebraic nonlinearity implies a nonlinear dependence
+of the mean electromotive force on the mean magnetic field. The dynamic
+nonlinearity is determined by a differential equation for the magnetic part of
+the alpha-effect. It is shown that for the alpha-Omega axisymmetric dynamo the
+algebraic nonlinearity alone cannot saturate the dynamo generated mean magnetic
+field while the combined effect of the algebraic and dynamic nonlinearities
+limits the mean magnetic field growth. Astrophysical applications of the
+obtained results are discussed.",0206261v1
+2020-01-13,Gate-tunable spin waves in antiferromagnetic atomic bilayers,"The emergence of two-dimensional (2D) layered magnetic materials has opened
+an exciting playground for both fundamental studies of magnetism in 2D and
+explorations of spinbased applications. Remarkable properties, including spin
+filtering in magnetic tunnel junctions and gate control of magnetic states,
+have recently been demonstrated in 2D magnetic materials. While these studies
+focus on the static properties, dynamic magnetic properties such as excitation
+and control of spin waves have remained elusive. Here we excite spin waves and
+probe their dynamics in antiferromagnetic CrI3 bilayers by employing an
+ultrafast optical pump/magneto-optical Kerr probe technique. We identify
+sub-terahertz magnetic resonances under an in-plane magnetic field, from which
+we determine the anisotropy and interlayer exchange fields and the spin damping
+rates. We further show tuning of antiferromagnetic resonances by tens of
+gigahertz through electrostatic gating. Our results shed light on magnetic
+excitations and spin dynamics in 2D magnetic materials, and demonstrate their
+unique potential for applications in ultrafast data storage and processing.",2001.04044v1
+2020-09-02,Magnetized Decaying Turbulence in the Weakly Compressible Taylor-Green Vortex,"Magnetohydrodynamic turbulence affects both terrestrial and astrophysical
+plasmas. The properties of magnetized turbulence must be better understood to
+more accurately characterize these systems. This work presents ideal MHD
+simulations of the compressible Taylor-Green vortex under a range of initial
+sub-sonic Mach numbers and magnetic field strengths. We find that regardless of
+the initial field strength, the magnetic energy becomes dominant over the
+kinetic energy on all scales after at most several dynamical times. The
+spectral indices of the kinetic and magnetic energy spectra become shallower
+than $k^{-5/3}$ over time and generally fluctuate. Using a shell-to-shell
+energy transfer analysis framework, we find that the magnetic fields facilitate
+a significant amount of the energy flux and that the kinetic energy cascade is
+suppressed. Moreover, we observe nonlocal energy transfer from the large scale
+kinetic energy to intermediate and small scale magnetic energy via magnetic
+tension. We conclude that even in intermittently or singularly driven weakly
+magnetized systems, the dynamical effects of magnetic fields cannot be
+neglected.",2009.01331v2
+1995-05-03,Magnetic Field Effect in a Two-dimensional Array of Short Josephson Junctions,"We study analytically the effect of a constant magnetic field on the dynamics
+of a two dimensional Josephson array. The magnetic field induces spatially
+dependent states and coupling between rows, even in the absence of an external
+load. Numerical simulations support these conclusions.",9504017v1
+2017-06-13,The Dynamics of Magnetic Vortices in Type II Superconductors with Pinning Sites Studied by the Time Dependent Ginzburg-Landau Model,"We investigate the dynamics of magnetic vortices in type II superconductors
+with normal state pinning sites using the Ginzburg-Landau equations. Simulation
+results demonstrate hopping of vortices between pinning sites, influenced by
+external magnetic fields and external currents. The system is highly nonlinear
+and the vortices show complex nonlinear dynamical behaviour.",1706.04002v1
+2018-12-18,Dynamical response of the Ising model to the amplitude modulated time dependent magnetic field,"The dynamical Ising model under the effect of the amplitude modulated time
+dependent periodic magnetic field has been solved by using EFT with Glauber
+type of stochastic process. Several cases with amplitude modulation have been
+investigated. It has been shown that, amplitude modulation could display
+dynamical phase transition on the magnetic system.",1812.07610v1
+2009-05-28,Hydrodynamic theory of coupled current and magnetization dynamics in spin-textured ferromagnets,"We develop the hydrodynamical theory of collinear spin currents coupled to
+magnetization dynamics in metallic ferromagnets. The collective spin density
+couples to the spin current through a U(1) Berry-phase gauge field determined
+by the local texture and dynamics of the magnetization. We determine
+phenomenologically the dissipative corrections to the equation of motion for
+the electronic current, which consist of a dissipative spin-motive force
+generated by magnetization dynamics and a magnetic texture-dependent
+resistivity tensor. The reciprocal dissipative, adiabatic spin torque on the
+magnetic texture follows from the Onsager principle. We investigate the effects
+of thermal fluctuations and find that electronic dynamics contribute to a
+nonlocal Gilbert damping tensor in the Landau-Lifshitz-Gilbert equation for the
+magnetization. Several simple examples, including magnetic vortices, helices,
+and spirals, are analyzed in detail to demonstrate general principles.",0905.4544v2
+2011-05-02,Magnetization Oscillation of a Spinor Condensate Induced by Magnetic Field Gradient,"We study the spin mixing dynamics of ultracold spin-1 atoms in a weak
+non-uniform magnetic field with field gradient $G$, which can flip the spin
+from +1 to -1 so that the magnetization $m=\rho_{+}-\rho_{-}$ is not any more a
+constant. The dynamics of $m_F=0$ Zeeman component $\rho_{0}$, as well as the
+system magnetization $m$, are illustrated for both ferromagnetic and polar
+interaction cases in the mean-field theory. We find that the dynamics of system
+magnetization can be tuned between the Josephson-like oscillation similar to
+the case of double well, and the interesting self-trapping regimes, i.e. the
+spin mixing dynamics sustains a spontaneous magnetization. Meanwhile the
+dynamics of $\rho_0$ may be sufficiently suppressed for initially imbalanced
+number distribution in the case of polar interaction. A ""beat-frequency""
+oscillation of the magnetization emerges in the case of balanced initial
+distribution for polar interaction, which vanishes for ferromagnetic
+interaction.",1105.0280v1
+2018-02-28,Roles of chiral renormalization on magnetization dynamics in chiral magnets,"In metallic ferromagnets, the interaction between local magnetic moments and
+conduction electrons renormalizes parameters of the Landau-Lifshitz-Gilbert
+equation such as the gyromagnetic ratio and the Gilbert damping, and makes them
+dependent on the magnetic configurations. Although the effects of the
+renormalization for nonchiral ferromagnets are usually minor and hardly
+detectable, we show that the renormalization does play a crucial role for
+chiral magnets. Here the renormalization is chiral and as such we predict
+experimentally identifiable effects on the phenomenology of magnetization
+dynamics. In particular, our theory for the self-consistent magnetization
+dynamics of chiral magnets allows for a concise interpretation of domain wall
+creep motion. We also argue that the conventional creep theory of the domain
+wall motion, which assumes Markovian dynamics, needs critical reexamination
+since the gyromagnetic ratio makes the motion non-Markovian. The non-Markovian
+nature of the domain wall dynamics is experimentally checkable by the chirality
+of the renormalization.",1803.00017v2
+2018-06-12,"Dynamical and current-induced Dzyaloshinskii-Moriya interaction: Role for damping, gyromagnetism, and current-induced torques in noncollinear magnets","Both applied electric currents and magnetization dynamics modify the
+Dzyaloshinskii-Moriya interaction (DMI), which we call current-induced DMI
+(CIDMI) and dynamical DMI (DDMI), respectively. We report a theory of CIDMI and
+DDMI. The inverse of CIDMI consists in charge pumping by a time-dependent
+gradient of magnetization $\partial^2 M(r,t)/\partial r\partial t$, while the
+inverse of DDMI describes the torque generated by $\partial^2 M(r,t)/\partial
+r\partial t$. In noncollinear magnets CIDMI and DDMI depend on the local
+magnetization direction. The resulting spatial gradients correspond to torques
+that need to be included into the theories of Gilbert damping, gyromagnetism,
+and current-induced torques (CITs) in order to satisfy the Onsager reciprocity
+relations. CIDMI is related to the modification of orbital magnetism induced by
+magnetization dynamics, which we call dynamical orbital magnetism (DOM), and
+spatial gradients of DOM contribute to charge pumping. We present applications
+of this formalism to the CITs and to the torque-torque correlation in textured
+Rashba ferromagnets.",1806.04782v3
+2020-11-10,Ultrafast high-harmonic nanoscopy of magnetization dynamics,"Light-induced magnetization changes, such as all-optical switching, skyrmion
+nucleation, and intersite spin transfer, unfold on temporal and spatial scales
+down to femtoseconds and nanometers, respectively. Pump-probe spectroscopy and
+diffraction studies indicate that spatio-temporal dynamics may drastically
+affect the non-equilibrium magnetic evolution. Yet, direct real-space magnetic
+imaging on the relevant timescale has remained challenging. Here, we
+demonstrate ultrafast high-harmonic nanoscopy employing circularly polarized
+high-harmonic radiation for real-space imaging of femtosecond magnetization
+dynamics. We observe the reversible and irreversible evolution of nanoscale
+spin textures following femtosecond laser excitation. Specifically, we map
+quenched magnetic domains and localized spin structures in Co/Pd multilayers
+with a sub-wavelength spatial resolution down to 16 nm, and strobosocopically
+trace the local magnetization dynamics with 40 fs temporal resolution. Our
+approach enables the highest spatio-temporal resolution of magneto-optical
+imaging to date. Facilitating ultrafast imaging with an extreme sensitivity to
+various microscopic degrees of freedom expressed in chiral and linear
+dichroism, we envisage a wide range of applications spanning magnetism, phase
+transitions, and carrier dynamics.",2011.05450v1
+2022-05-13,Precession dynamics of a small magnet with non-Markovian damping: Theoretical proposal for an experiment to determine the correlation time,"Recent advances in experimental techniques have made it possible to
+manipulate and measure the magnetization dynamics on the femtosecond time scale
+which is the same order as the correlation time of the bath degrees of freedom.
+In the equations of motion of magnetization, the correlation of the bath is
+represented by the non-Markovian damping. For development of the science and
+technologies based on the ultrafast magnetization dynamics it is important to
+understand how the magnetization dynamics depend on the correlation time. It is
+also important to determine the correlation time experimentally. Here we study
+the precession dynamics of a small magnet with the non-Markovian damping.
+Extending the theoretical analysis of Miyazaki and Seki [J. Chem. Phys. 108,
+7052 (1998)] we obtain analytical expressions of the precession angular
+velocity and the effective damping constant for any values of the correlation
+time under assumption of small Gilbert damping constant. We also propose a
+possible experiment for determination of the correlation time.",2205.06399v1
+2023-05-26,Magnetized dusty plasma: On issues of its complexity and magnetization of charged dust particles,"It is possible to excite various linear and non-linear low-frequency modes in
+dusty plasma which is an admixture of electrons, ions, gas atoms, and
+negatively charged solid particles. The experimental as well as theoretical
+study of these low-frequency dynamical modes in dusty plasma is very complex
+because of the involvement of dynamics of electrons, ions, and neutrals. If the
+external magnetic field is introduced to dusty plasma then the dynamics of it
+will be more complex. The complexity of magnetized dusty plasma where plasma
+species are magnetized is discussed by keeping the experimental observations in
+magnetized dusty plasma devices in mind. The requirement of theoretical
+modeling, as well as computation experiments in understanding the dynamics of
+dusty plasma in the presence of a strong magnetic field, is highlighted in the
+context of experimental findings. The major challenges to magnetizing charged
+massive particles in experiments and some expected solutions are discussed in
+this report.",2305.16898v1
+2006-09-15,Superconducting pipes and levitating magnets,"Motivated by a beautiful demonstration of the Faraday's and Lenz's law in
+which a small neodymium magnet falls slowly through a conducting
+non-ferromagnetic tube, we consider the dynamics of a magnet falling through a
+superconducting pipe. Unlike the case of normal conducting pipes, in which the
+magnet quickly reaches the terminal velocity, inside a superconducting tube the
+magnet falls freely. On the other hand, to enter the pipe the magnet must
+overcome a large electromagnetic energy barrier. For sufficiently strong
+magnets, the barrier is so large that the magnet will not be able to penetrate
+it and will be suspended over the front edge. We calculate the work that must
+done to force the magnet to enter a superconducting tube. The calculations show
+that superconducting pipes are very efficient at screening magnetic fields. For
+example, the magnetic field of a dipole at the center of a short pipe of radius
+$a$ and length $L \approx a$ decays, in the axial direction, with a
+characteristic length $\xi \approx 0.26 a$. The efficient screening of the
+magnetic field might be useful for shielding highly sensitive superconducting
+quantum interference devices, SQUIDs. Finally, the motion of the magnet through
+a superconducting pipe is compared and contrasted to the flow of ions through a
+trans-membrane channel.",0609141v1
+2008-05-26,Magnetic field induced incommensurate resonance in cuprate superconductors,"The influence of a uniform external magnetic field on the dynamical spin
+response of cuprate superconductors in the superconducting state is studied
+based on the kinetic energy driven superconducting mechanism. It is shown that
+the magnetic scattering around low and intermediate energies is dramatically
+changed with a modest external magnetic field. With increasing the external
+magnetic field, although the incommensurate magnetic scattering from both low
+and high energies is rather robust, the commensurate magnetic resonance
+scattering peak is broadened. The part of the spin excitation dispersion seems
+to be an hourglass-like dispersion, which breaks down at the heavily low energy
+regime. The theory also predicts that the commensurate resonance scattering at
+zero external magnetic field is induced into the incommensurate resonance
+scattering by applying an external magnetic field large enough.",0805.3922v2
+2012-06-29,Enhancement of critical current density in superconducting/magnetic multi-layers with slow magnetic relaxation dynamics and large magnetic susceptibility,"We propose to use superconductor-magnet multi-layer structure to achieve high
+critical current density by invoking polaronic mechanism of pinning. The
+magnetic layers should have large magnetic susceptibility to enhance the
+coupling between vortices and magnetization in magnetic layers. The relaxation
+of the magnetization should be slow. When the velocity of vortices is low, they
+are dressed by nonuniform magnetization and move as polarons. In this case, the
+viscosity of vortices proportional to the magnetic relaxation time is enhanced
+significantly. As velocity increases, the polarons dissociate and the viscosity
+drops to the usual Bardeen-Stephen one, resulting in a jump in the I-V curve.
+Experimentally the jump shows up as a depinning transition and the
+corresponding current at the jump is the depinning current. For Nb and proper
+magnet multi-layer structure, we estimate the critical current density $J_c\sim
+10^{9}\ \rm{A/m^2}$ at magnetic field $B\approx 1$ T.",1206.6929v2
+2018-09-13,On the role of magnetic fields in star formation,"Magnetic fields are observed in star forming regions. However simulations of
+the late stages of star formation that do not include magnetic fields provide a
+good fit to the properties of young stars including the initial mass function
+(IMF) and the multiplicity. We argue here that the simulations that do include
+magnetic fields are unable to capture the correct physics, in particular the
+high value of the magnetic Prandtl number, and the low value of the magnetic
+diffusivity. The artificially high (numerical and uncontrolled) magnetic
+diffusivity leads to a large magnetic flux pervading the star forming region.
+We argue further that in reality the dynamics of high magnetic Prandtl number
+turbulence may lead to local regions of magnetic energy dissipation through
+reconnection, meaning that the regions of molecular clouds which are forming
+stars might be essentially free of magnetic fields. Thus the simulations that
+ignore magnetic fields on the scales on which the properties of stellar masses,
+stellar multiplicities and planet-forming discs are determined, may be closer
+to reality than those which include magnetic fields, but can only do so in an
+unrealistic parameter regime.",1809.04921v1
+2015-12-30,Magnetization dynamics and spin pumping induced by standing elastic waves,"The magnetization dynamics induced by standing elastic waves excited in a
+thin ferromagnetic film is described with the aid of micromagnetic simulations
+taking into account the magnetoelastic coupling between spins and lattice
+strains. The simulations have been performed for the 2 nm thick Fe81Ga19 film
+dynamically strained by longitudinal and transverse standing waves with various
+frequencies, which span a wide range around the resonance frequency nu_res of
+coherent magnetization precession in unstrained Fe81Ga19 film. It is found that
+standing elastic waves give rise to complex local magnetization dynamics and
+spatially inhomogeneous dynamic magnetic patterns. The spatio-temporal
+distributions of the magnetization oscillations in standing elastic waves have
+the form of standing spin waves with the same wavelength. Remarkably, the
+amplitude of magnetization precession does not go to zero at the nodes of these
+spin waves, which cannot be precisely described by simple analytical formulae.
+In the steady-state regime, the magnetization oscillates with the frequency of
+elastic wave, except for the case of longitudinal waves with frequencies well
+below nu_res, where the magnetization precesses with a variable frequency
+strongly exceeding the wave frequency. The precession amplitude at the
+antinodes of standing spin waves strongly increases when the frequency of
+elastic wave becomes close to nu_res. The results obtained for the
+magnetization dynamics driven by elastic waves are used to calculate the spin
+current pumped from the dynamically strained ferromagnet into adjacent
+paramagnetic metal. Importantly, the transverse charge current created by the
+spin current via the inverse spin Hall effect is high enough to be measured
+experimentally.",1512.09051v1
+2016-05-18,Standing magnetic wave on Ising ferromagnet: Nonequilibrium phase transition,"The dynamical response of an Ising ferromagnet to a plane polarised standing
+magnetic field wave is modelled and studied here by Monte Carlo simulation in
+two dimensions. The amplitude of standing magnetic wave is modulated along the
+direction x. We have detected two main dynamical phases namely, pinned and
+oscillating spin clusters. Depending on the value of field amplitude the system
+is found to undergo a phase transition from oscillating spin cluster to pinned
+as the system is cooled down. The time averaged magnetisation over a full cycle
+of magnetic field oscillations is defined as the dynamic order parameter. The
+transition is detected by studying the temperature dependences of the variance
+of the dynamic order parameter, the derivative of the dynamic order parameter
+and the dynamic specific heat. The dependence of the transition temperature on
+the magnetic field amplitude and on the wavelength of the magnetic field wave
+is studied at a single frequency. A comprehensive phase boundary is drawn in
+the plane described by the temperature and field amplitude for two different
+wavelengths of the magnetic wave. The variation of instantaneous line
+magnetisation during a period of magnetic field oscillation for standing wave
+mode is compared to those for the propagating wave mode. Also the probability
+that a spin at any site, flips, is calculated. The above mentioned variations
+and the probability of spin flip clearly distinguish between the dynamical
+phases formed by propagating magnetic wave and by standing magnetic wave in an
+Ising ferromagnet.",1605.05643v2
+2022-02-15,The effect of inter-particle hydrodynamic and magnetic interactions in a magnetorheological fluid,"A magnetorheological fluid, which consists of magnetic particles suspended in
+a viscous fluid, flows freely with well-dispersed particles in a the absence of
+a magnetic field, but particle aggregation results in flow cessation when a
+field is applied. The mechanism of dynamical arrest is examined by analysing
+interactions between magnetic particles in a magnetic field subject to a shear
+flow. An isolated spherical magnetic particle undergoes a transition between a
+rotating state at low magnetic field and a static orientation at high magnetic
+field. The effect of interactions for spherical dipolar and polarisable
+particles with static orientation is examined for a dilute viscous suspension.
+There are magnetic interactions due to the magnetic field disturbance at one
+particle caused by the dipole moment of another, hydrodynamic interactions due
+to the antisymmetric force moment of a non-rotating particle in a shear flow,
+and a modification of the magnetic field due to the particle magnetic moment
+density. When there is a concentration variation, the torque balance condition
+results in a disturbance to the orientation of the particle magnetic moment.
+The net force and the drift velocity due to these disturbances is calculated,
+and the collective motion generated is equivalent to an anisotropic diffusion
+process. When the magnetic field is in the flow plane, the diffusion
+coefficients in the two directions perpendicular to the field direction are
+negative, implying that concentration fluctuations are unstable in these
+directions. This instability could initiate field-induced dynamical arrest in a
+magnetorheological fluid.",2202.07488v1
+2019-03-26,Dynamical evolution of magnetic fields in the intracluster medium,"We investigate the evolution of magnetic fields in galaxy clusters starting
+from constant primordial fields using highly resolved ($\approx \rm 4 ~kpc$)
+cosmological MHD simulations. The magnetic fields in our sample exhibit
+amplification via a small-scale dynamo and compression during structure
+formation. In particular, we study how the spectral properties of magnetic
+fields are affected by mergers, and we relate the measured magnetic energy
+spectra to the dynamical evolution of the intracluster medium. The magnetic
+energy grows by a factor of $\sim$ 40-50 in a time-span of $\sim 9$ Gyr and
+equipartition between kinetic and magnetic energy occurs on a range of scales
+($< 160 \rm ~kpc$ at all epochs) depending on the turbulence state of the
+system. We also find that, in general, the outer scale of the magnetic field
+and the MHD scale are not simply correlated in time. The effect of major
+mergers is to shift the peak magnetic spectra to it smaller scales, whereas the
+magnetic amplification only starts after $\lesssim$ 1 Gyr. In contrast,
+continuous minor mergers promote the steady growth of the magnetic field. We
+discuss the implications of these findings in the interpretation of future
+radio observations of galaxy clusters.",1903.11052v1
+2020-11-20,An Investigation of Commercial Iron Oxide Nanoparticles: Advanced Structural and Magnetic Properties Characterization,"Magnetic nanoparticles (MNPs) have been extensively used as tiny heating
+sources in magnetic hyperthermia therapy, contrast agents in magnetic resonance
+imaging (MRI), tracers in magnetic particle imaging (MPI), carriers for
+drug/gene delivery, etc. There have emerged many magnetic
+nanoparticle/microbeads suppliers since the last decade, such as Ocean
+NanoTech, Nanoprobes, US Research Nanomaterials, Miltenyi Biotec, micromod
+Partikeltechnologie GmbH, and nanoComposix, etc. In this paper, we report the
+physical and magnetic characterizations on iron oxide nanoparticle products
+from Ocean NanoTech. Standard characterization tools such as Vibrating-Sample
+Magnetometer (VSM), X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS),
+Transmission Electron Microscopy (TEM), and Zeta Potential Analyzer are used to
+provide magnetic nanoparticle customers and researchers with an overview of
+these iron oxide nanoparticle products. In addition, the dynamic magnetic
+responses of these iron oxide nanoparticles in aqueous solutions are
+investigated under low and high frequency alternating magnetic fields, giving a
+standardized operating procedure for characterizing the MNPs from Ocean
+NanoTech, thereby yielding the best of magnetic nanoparticles for different
+applications.",2011.10215v1
+2023-12-05,THz-Driven Coherent Magnetization Dynamics in a Labyrinth Domain State,"Terahertz (THz) light pulses can be used for an ultrafast coherent
+manipulation of the magnetization. Driving the magnetization at THz frequencies
+is currently the fastest way of writing magnetic information in ferromagnets.
+Using time-resolved resonant magnetic scattering, we gain new insights to the
+THz-driven coherent magnetization dynamics on nanometer length scales. We
+observe ultrafast demagnetization and coherent magnetization oscillations that
+are governed by a time-dependent damping. This damping is determined by the
+interplay of lattice heating and magnetic anisotropy reduction revealing an
+upper speed limit for THz-induced magnetization switching. We show that in the
+presence of nanometer-sized magnetic domains, the ultrafast magnetization
+oscillations are associated with a correlated beating of the domain walls. The
+overall domain structure thereby remains largely unaffected which highlights
+the applicability of THz-induced switching on the nanoscale.",2312.02654v1
+2023-12-18,Enhancing thermal stability of optimal magnetization reversal in nanoparticles,"Energy-efficient switching of nanoscale magnets requires the application of a
+time-varying magnetic field characterized by microwave frequency. At finite
+temperatures, even weak thermal fluctuations create perturbations in the
+magnetization that can accumulate in time, break the phase locking between the
+magnetization and the applied field, and eventually compromise magnetization
+switching. It is demonstrated here that the magnetization reversal is mostly
+disturbed by unstable perturbations arising in a certain domain of the
+configuration space of a nanomagnet. The instabilities can be suppressed and
+the probability of magnetization switching enhanced by applying an additional
+stimulus such as a weak longitudinal magnetic field that ensures bounded
+dynamics of the perturbations. Application of the stabilizing longitudinal
+field to a uniaxial nanomagnet makes it possible to reach a desired probability
+of magnetization switching even at elevated temperatures. The principle of
+suppressing instabilities provides a general approach to enhancing thermal
+stability of magnetization dynamics.",2312.11293v1
+1997-09-19,Zero-temperature dynamic transition in the random field Ising model: A Monte Carlo study,"The dynamics of a random (quenched) field Ising model (in two dimension) at
+zero temperature in the presence of an additional sinusoidally oscillating
+homogeneous (in space) magnetic field has been studied by Monte Carlo
+simulation using the Metropolis single spin flip dynamics. The instantaneous
+magnetisation is found to be periodic with the same periodicity of the
+oscillating magnetic field. For very low values of amplitude of oscillating
+field and the width of randomly quenched magnetic field, the magnetisation
+oscillates asymmetrically about a nonzero value and the oscillation becomes
+symmetric about a zero value for higher values of amplitude of oscillating
+field and the width of the quenched disorder. The time averaged magnetisation
+over a full cycle of the oscillating magnetic field defines the dynamic order
+parameter. This dynamic order parameter is nonzero for very low values of
+amplitude of oscillating magnetic field and the width of randomly quenched
+field. A phase boundary line is drawn in the plane formed by the amplitude of
+the oscillating magnetic field and the width of the randomly quenched magnetic
+field. A tricritical point has been located, on the phase boundary line, which
+separates the nature (discontinuous /continuous) of the dynamic transition.",9709217v1
+2009-12-18,Stochastic resonance of a nanomagnet excited by spin transfer torque,"Spin transfer torque from spin-polarized electrical current can excite
+large-amplitude magnetization dynamics in metallic ferromagnets of nanoscale
+dimensions. Since magnetic anisotropy energies of nanomagnets are comparable to
+the thermal energy scale, temperature can have a profound effect on the
+dynamics of a nanomagnet driven by spin transfer torque. Here we report the
+observation of unusual types of microwave-frequency nonlinear magnetization
+dynamics co-excited by alternating spin transfer torque and thermal
+fluctuations. In these dynamics, temperature amplifies the amplitude of
+GHz-range precession of magnetization and enables excitation of highly
+nonlinear dynamical states of magnetization by weak alternating spin transfer
+torque. We explain these thermally activated dynamics in terms of non-adiabatic
+stochastic resonance of magnetization driven by spin transfer torque. This type
+of magnetic stochastic resonance may find use in sensitive nanometer-scale
+microwave signal detectors.",0912.3842v1
+2016-05-02,Electrical Detection of Magnetization Dynamics via Spin Rectification Effects,"The purpose of this article is to review the current status of a frontier in
+dynamic spintronics and contemporary magnetism, in which much progress has been
+made in the past decade, based on the creation of a variety of micro- and
+nano-structured devices that enable electrical detection of magnetization
+dynamics. The primary focus is on the physics of spin rectification effects,
+which are well suited for studying magnetization dynamics and spin transport in
+a variety of magnetic materials and spintronic devices. Intended to be
+intelligible to a broad audience, the paper begins with a pedagogical
+introduction, comparing the methods of electrical detection of charge and spin
+dynamics in semiconductors and magnetic materials respectively. After that it
+provides a comprehensive account of the theoretical study of both the angular
+dependence and line shape of electrically detected ferromagnetic resonance
+(FMR), which is summarized in a handbook formate easy to be used for analyzing
+experimental data. We then review and examine the similarity and differences of
+various spin rectification effects found in ferromagnetic films, magnetic
+bilayers and magnetic tunnel junctions, including a discussion of how to
+properly distinguish spin rectification from the spin pumping/inverse spin Hall
+effect generated voltage. After this we review the broad applications of
+rectification effects for studying spin waves, nonlinear dynamics, domain wall
+dynamics, spin current, and microwave imaging. We also discuss spin
+rectification in ferromagnetic semiconductors. The paper concludes with both
+historical and future perspectives, by summarizing and comparing three
+generations of FMR spectroscopy which have been developed for studying
+magnetization dynamics.",1605.00710v2
+2005-09-11,Orbital magnetic dynamics in chiral p-wave superconductors,"We present a theory of orbital magnetic dynamics for a chiral p-wave
+superconductor with broken time-reversal symmetry. In contrast to the common
+Landau-Lifshitz theory for spin ferromagnets, the case of orbital magnetism
+cannot be described in terms of local magnetization density. Hence it is
+impossible to define unambiguously the spontaneous magnetic moment: the latter
+would depend on conditions of its experimental investigation.
+  As an example of this we consider orbital magnetization waves and the domain
+structure energy.",0509277v2
+2008-05-15,Dynamical Casimir effect for magnons in a spinor Bose-Einstein condensate,"Magnon excitation in a spinor Bose-Einstein condensate by a driven magnetic
+field is shown to have a close analogy with the dynamical Casimir effect. A
+time-dependent external magnetic field amplifies quantum fluctuations in the
+magnetic ground state of the condensate, leading to magnetization of the
+system. The magnetization occurs in a direction perpendicular to the magnetic
+field breaking the rotation symmetry. This phenomenon is numerically
+demonstrated and the excited quantum field is shown to be squeezed.",0805.2210v1
+2008-06-29,Dynamical Regimes Induced by Spin Transfer in Magnetic Nanopillars,"We demonstrate the predicted out-of-plane precession induced by spin transfer
+in magnetic nanostructures with in-plane magnetic field. We show that other
+magnetic excitations have a significant effect on the stability of the out-of
+plane precession, making it extremely sensitive to the orientation of the
+applied magnetic field. The data are supported with micromagnetic simulations.
+Our results elucidate the relation between the excitation spectrum and the
+specific dynamical behaviors of nanoscale magnets.",0806.4731v2
+2009-11-14,Symmetry-breaking magnetization dynamics of spinor dipolar Bose-Einstein condensates,"Symmetry-breaking magnetization dynamics of a spin-1 Bose-Einstein condensate
+(BEC) due to the dipole-dipole interaction are investigated using the
+mean-field and Bogoliubov theories. When a magnetic field is applied along the
+symmetry axis of a pancake-shaped BEC in the m = 0 hyperfine sublevel,
+transverse magnetization develops breaking the chiral or axial symmetry. A
+variety of magnetization patterns are formed depending on the strength of the
+applied magnetic field. The proposed phenomena can be observed in 87Rb and 23Na
+condensates.",0911.2741v1
+2011-08-01,A non isothermal phase-field model for the ferromagnetic transition,"We propose a model for non isothermal ferromagnetic phase transition based on
+a phase field approach, in which the phase parameter is related but not
+identified with the magnetization. The magnetization is split in a paramagnetic
+and in a ferromagnetic contribution, dependent on a scalar phase parameter and
+identically null above the Curie temperature. The dynamics of the magnetization
+below the Curie temperature is governed by the order parameter evolution
+equation and by a Landau-Lifshitz type equation for the magnetization vector.
+In the simple situation of a uniaxial magnet it is shown how the order
+parameter dynamics reproduces the hysteresis effect of the magnetization.",1108.0378v1
+2013-12-13,"Quantum states, symmetry and dynamics in degenerate spin s=1 magnets","The article deals with spin s=1 magnets. The symmetry conditions for normal
+and degenerate equilibrium states are defined and types of magnetic ordering
+found out. For each type of symmetry breaking the structure of source in the
+Gibbs statistical operator has been obtained and additional thermodynamic
+parameters introduced. The algebra of Poisson bracket for magnetic degrees of
+freedom has been established and nonlinear dynamic equations have been derived.
+Using the models of the exchange interaction, we have calculated the spectra of
+collective excitations for two degenerate states whose order parameters have
+digerent signature under the time reversal transformation.",1312.3799v2
+2015-08-15,On an integrable magnetic geodesic flow on the two-torus,"We completely integrate the magnetic geodesic flow on a flat two-torus with
+the magnetic field $F = \cos (x) dx \wedge dy$ and describe all contractible
+periodic magnetic geodesics. It is shown that there are no such geodesics for
+energy $E \geq 1/2$, for $E< 1/2$ simple periodic magnetic geodesics form two
+$S^1$-families for which the (fixed energy) action functional is positive and
+therefore there are no periodic magnetic geodesics for which the action
+functional is negative.",1508.03745v2
+2017-11-08,Charge pumping induced by magnetic texture dynamics in Weyl semimetals,"Spin-momentum locking in Weyl semimetals correlates the orbital motion of
+electrons with background magnetic textures. We show here that the dynamics of
+a magnetic texture in a magnetic Weyl semimetal induces a pumped electric
+current that is free from Joule heating. This pumped current can be regarded as
+a Hall current induced by axial electromagnetic fields equivalent to the
+magnetic texture. Taking a magnetic domain wall as a test case, we demonstrate
+that a moving domain wall generates a pumping current corresponding to the
+localized charge.",1711.03135v1
+2024-03-11,Magnetic vortex polarity reversal induced gyrotropic motion spectrum splitting in a ferromagnetic disk,"We investigate the gyrotropic motion of the magnetic vortex core in a chain
+of a few micron-sized Permalloy disks by electrical resistance measurement with
+amplitude-modulated magnetic field. We observe a distinctive splitting of the
+resistance peak due to the resonant vortex-core motion under heightened radio
+frequency (RF) magnetic field excitation. Our micromagnetic simulation
+identifies the splitting of the resonant peak as an outcome of vortex polarity
+reversal under substantial RF amplitudes. This study enhances our understanding
+of nonlinear magnetic vortex dynamics amidst large RF amplitudes and proposes a
+potential pathway for spintronic neural computing thanks to their unique and
+controllable magnetization dynamics.",2403.06491v1
+2003-08-15,Current-Driven Magnetization Dynamics in Magnetic Multilayers,"We develop a quantum analog of the classical spin-torque model for
+current-driven magnetic dynamics. The current-driven magnetic excitation at
+finite field becomes significantly incoherent. This excitation is described by
+an effective magnetic temperature rather than a coherent precession as in the
+spin-torque model. However, both the spin-torque and effective temperature
+approximations give qualitatively similar switching diagrams in the
+current-field coordinates, showing the need for detailed experiments to
+establish the proper physical model for current-driven dynamics.",0308320v2
+2004-03-03,Current-Induced Nanomagnet Dynamics for Magnetic Fields Perpendicular to the Sample Plane,"We present electrical measurements of high-frequency magnetic dynamics
+excited by spin-polarized currents in Co/Cu/Ni80Fe20 nanopillar devices, with a
+magnetic field applied perpendicular to the sample layers. As a function of
+current and magnetic field, the dynamical phase diagram contains several
+distinguishable precessional modes and also static magnetic states. Using
+detailed comparisons with numerical simulations, we provide rigorous tests of
+the theory of spin-transfer torques.",0403100v1
+2004-07-07,Roles of non-equilibrium conduction electrons on magnetization dynamics of ferromagnets,"The mutual dependence of spin-dependent conduction and magnetization dynamics
+of ferromagnets provides the key mechanisms in various spin-dependent
+phenomena. We compute the response of the conduction electron spins to a
+spatial and time varying magnetization ${\bf M} ({\bf r},t)$ within the
+time-dependent semiclassical transport theory. We show that the induced
+non-equilibrium conduction spin density in turn generates four spin torques
+acting on the magnetization--with each torque playing different roles in
+magnetization dynamics. By comparing with recent theoretical models, we find
+that one of these torques that has not been previously identified is crucial to
+consistently interpret experimental data on domain wall motion.",0407174v2
+2005-02-08,Microwave spectroscopy on magnetization reversal dynamics of nanomagnets with electronic detection,"We demonstrate a detection method for microwave spectroscopy on magnetization
+reversal dynamics of nanomagnets. Measurement of the nanomagnet anisotropic
+magnetoresistance was used for probing how magnetization reversal is resonantly
+enhanced by microwave magnetic fields. We used Co strips of 2 um x 130 nm x 40
+nm, and microwave fields were applied via an on-chip coplanar wave guide. The
+method was applied for demonstrating single domain-wall resonance, and studying
+the role of resonant domain-wall dynamics in magnetization reversal.",0502197v2
+2006-06-21,Current-excited magnetization dynamics in narrow ferromagnetic wires,"We investigate the current-excited magnetization dynamics in a narrow
+ferromagnetic Permalloy wire by means of Lorentz microscopy, together with the
+results of simultaneous transport measurements. A detailed structural evolution
+of the magnetization is presented as a function of the applied current density.
+Local structural deformation, bidirectional displacement, and magnetization
+reversal are found below the Curie temperature with increasing the current
+density. We discuss probable mechanisms of observed features of the
+current-excited magnetization dynamics.",0606547v1
+2008-06-21,Limiting Dynamics for Spherical Models of Spin Glasses with Magnetic Field,"We study the Langevin dynamics for the family of spherical spin glass models
+of statistical physics, in the presence of a magnetic field. We prove that in
+the limit of system size N approaching infinity, the empirical state
+correlation, the response function, the overlap and the magnetization for these
+N-dimensional coupled diffusions converge to the non-random unique strong
+solution of four explicit non-linear integro-differential equations, that
+generalize the system proposed by Cugliandolo and Kurchan in the presence of a
+magnetic field. We then analyze the system and provide a rigorous derivation of
+the FDT regime in a large area of the temperature-magnetization plane.",0806.3519v1
+2009-01-28,Ultrafast Magnetization Dynamics in Diluted Magnetic Semiconductors,"We present a dynamical model that successfully explains the observed time
+evolution of the magnetization in diluted magnetic semiconductor quantum wells
+after weak laser excitation. Based on the pseudo-fermion formalism and a second
+order many-particle expansion of the exact p-d exchange interaction, our
+approach goes beyond the usual mean-field approximation. It includes both the
+sub-picosecond demagnetization dynamics and the slower relaxation processes
+which restore the initial ferromagnetic order in a nanosecond time scale. In
+agreement with experimental results, our numerical simulations show that,
+depending on the value of the initial lattice temperature, a subsequent
+enhancement of the total magnetization may be observed within a time scale of
+few hundreds of picoseconds.",0901.4541v1
+2010-06-30,Supercurrent-Induced Magnetization Dynamics,"We investigate supercurrent-induced magnetization dynamics in a Josephson
+junction with two misaligned ferromagnetic layers, and demonstrate a variety of
+effects by solving numerically the Landau-Lifshitz-Gilbert equation. In
+particular, we demonstrate the possibility to obtain supercurrent-induced
+magnetization switching for an experimentally feasible set of parameters, and
+clarify the favorable condition for the realization of magnetization reversal.
+These results constitute a superconducting analogue to conventional
+current-induced magnetization dynamics and indicate how spin-triplet
+supercurrents may be utilized for practical purposes in spintronics.",1007.0004v1
+2012-10-15,Optimal Control of Stochastic Magnetization Dynamics by Spin Current,"Fluctuation-induced stochastic magnetization dynamics plays an important role
+in magnetic recording and writing. Here we propose that the magnetization
+dynamics can be optimally controlled by the spin current to minimize or
+maximize the Freidlin-Wentzell action functional of the system hence to
+increase or decrease the happening probability of the rare event. We apply this
+method to study thermal-driven magnetization switching problem and to
+demonstrate the advantage of the optimal control strategy.",1210.4036v1
+2014-03-26,Driving ferromagnets into a critical region of a magnetic phase diagram,"Exciting a ferromagnetic sample with an ultrashort laser pulse leads to a
+quenching of the magne- tization on a subpicosecond timescale. On the basis of
+the equilibration of intensive thermodynamic variables we establish a powerful
+model to describe the demagnetization dynamics. We demonstrate that the
+magnetization dynamics is mainly driven by the equilibration of chemical
+potentials. The minimum of magnetization is revealed as a transient electronic
+equilibrium state. Our method iden- tifies the slowing down of ultrafast
+magnetization dynamics by a critical region within a magnetic phase diagram.",1403.6885v2
+2015-06-18,Dynamical systems study in single-phase multiferroic materials,"Electric field induced magnetization switching in single-phase multiferroic
+materials is intriguing for both fundamental studies and potential
+technological applications. Here we develop a framework to study the switching
+dynamics of coupled polarization and magnetization in such multiferroic
+materials. With the coupling term between the polarization and magnetization as
+an invariant dictated by the Dzyaloshinsky-Moriya vector, the dynamical systems
+study reveals switching failures and oscillatory mode of magnetization if the
+polarization and magnetization relax slowly during switching.",1506.07864v1
+2018-05-10,Spatial dynamics analysis of polarized atom vapor,"We analyze the spatial dynamics of polarized atom vapor and present a
+mathematical method to eliminate the diffusion effect partially. It is found
+that the diffusion effect of polarized atoms can be regarded as a low pass
+filter in spatial frequency domain and fits well with a Butterworth filter. The
+fitted spatial filter can be used to restore the original magnetic image before
+being blurred by the diffusion, thus improving the magnetic spatial resolution.
+The results of spatial dynamics simulation and magnetic image restoration show
+the potential usage of this method in magnetic gradiometer and atomic magnetic
+microscopy.",1805.03823v1
+2019-11-19,On the Dynamics of Inverse Magnetic Billiards,"Consider a strictly convex set $\Omega$ in the plane, and a homogeneous,
+stationary magnetic field orthogonal to the plane whose strength is $B$ on the
+complement of $\Omega$ and $0$ inside $\Omega$. The trajectories of a charged
+particle in this setting are straight lines concatenated with circular arcs of
+Larmor radius $\mu$. We examine the dynamics of such a particle and call this
+inverse magnetic billiards. Comparisons are made to standard Birkhoff billiards
+and magnetic billiards, as some theorems regarding inverse magnetic billiards
+are consistent with each of these billiard variants while others are not.",1911.08144v1
+2020-03-10,Spin dynamics of a hydrogen atom in a periodic magnetic structure,"The spin dynamics of a hydrogen atom during the passage of a periodic
+magnetic structure is discussed. The occupation numbers of the components of
+the hyperfine structure are considered as a function of time. The
+characteristic low-frequency oscillations are visible, which have a direct
+analogue in the effect of nuclear magnetic resonance. An envelope forms of
+these oscillations are found using the Krylov-Bogolyubov-Mitropol'skii method.
+The dependence of spin dynamics on the parameters of the magnetic structure is
+investigated. It is shown that this dependence is very sensitive to the
+structure of the magnetic field.",2003.04653v1
+2021-01-15,Spin dynamics from a constrained magnetic Tight-Binding model,"A dynamics of the precession of coupled atomic moments in the tight-binding
+(TB) approximation is presented. By implementing an angular penalty functional
+in the energy that captures the magnetic effective fields self-consistently,
+the motion of the orientation of the local magnetic moments is observed faster
+than the variation of their magnitudes. This allows the computation of the
+effective atomic magnetic fields that are found consistent with the
+Heisenberg's exchange interaction, by comparison with classical atomistic spin
+dynamics on Fe, Co and Ni magnetic clusters.",2101.06121v2
+2023-08-11,Dynamical Majorana Ising spin response in a topological superconductor-magnet hybrid by microwave irradiation,"We study a dynamical spin response of surface Majorana modes in a topological
+superconductor-magnet hybrid under microwave irradiation. We find a method to
+toggle between dissipative and non-dissipative Majorana Ising spin dynamics by
+adjusting the external magnetic field angle and the microwave frequency. This
+reflects the topological nature of the Majorana modes, enhancing the Gilbert
+damping of the magnet, thereby, providing a detection method for the Majorana
+Ising spins. Our findings illuminate a magnetic probe for Majorana modes,
+paving the path to innovative spin devices.",2308.05955v2
+2014-01-08,Generating buoyant magnetic flux ropes in solar-like convective dynamos,"Our Sun exhibits strong convective dynamo action which results in magnetic
+flux bundles emerging through the stellar surface as magnetic spots.
+Global-scale dynamo action is believed to generate large-scale magnetic
+structures in the deep solar interior through the interplay of convection,
+rotation, and shear. Portions of these large-scale magnetic structures are then
+believed to rise through the convective layer, forming magnetic loops which
+then pierce the photosphere as sunspot pairs. Previous global simulations of 3D
+MHD convection in rotating spherical shells have demonstrated mechanisms
+whereby large-scale magnetic wreaths can be generated in the bulk of the
+convection zone. Our recent simulations have achieved sufficiently high levels
+of turbulence to permit portions of these wreaths to become magnetically
+buoyant and rise through the simulated convective layer through a combination
+of magnetic buoyancy and advection by convective giant cells. These buoyant
+magnetic loops are created in the bulk of the convective layer as strong
+Lorentz force feedback in the cores of the magnetic wreaths dampen small-scale
+convective motions, permitting the amplification of local magnetic energies to
+over 100 times the local kinetic energy. While the magnetic wreaths are largely
+generated the shearing of axisymmetric poloidal magnetic fields by axisymmetric
+rotational shear (the $\Omega$-effect), the loops are amplified to their peak
+field strengths before beginning to rise by non-axisymmetric processes. This
+further extends and enhances a new paradigm for the generation of emergent
+magnetic flux bundles, which we term turbulence-enabled magnetic buoyancy.",1401.1826v1
+2016-06-29,Dynamic Elastic Moduli in Magnetic Gels: Normal Modes and Linear Response,"In the perspective of developing smart hybrid materials with customized
+features, ferrogels and magnetorheological elastomers allow a synergy of
+elasticity and magnetism. The interplay between elastic and magnetic properties
+gives rise to a unique reversible control of the material behavior by applying
+an external magnetic field. Albeit few works have been performed on the
+time-dependent properties so far, understanding the dynamic behavior is the key
+to model many practical situations, e.g. applications as vibration absorbers.
+Here we present a way to calculate the frequency-dependent elastic moduli based
+on the decomposition of the linear response to an external stress in normal
+modes. We use a minimal three-dimensional dipole-spring model to theoretically
+describe the magnetic and elastic interactions on the mesoscopic level.
+Specifically, the magnetic particles carry permanent magnetic dipole moments
+and are spatially arranged in a prescribed way, before they are linked by
+elastic springs. An external magnetic field aligns the magnetic moments. On the
+one hand, we study regular lattice-like particle arrangements to compare with
+previous results in the literature. On the other hand, we calculate the dynamic
+elastic moduli for irregular, more realistic particle distributions. Our
+approach measures the tunability of the linear dynamic response as a function
+of the particle arrangement, the system orientation with respect to the
+external magnetic field, as well as the magnitude of the magnetic interaction
+between the particles. The strength of the present approach is that it
+explicitly connects the relaxational modes of the system with the rheological
+properties as well as with the internal rearrangement of the particles in the
+sample, providing new insight into the dynamics of these remarkable materials.",1606.09104v2
+2022-09-06,Temperature- and field angular-dependent helical spin period characterized by magnetic dynamics in a chiral helimagnet $MnNb_3S_6$,"The chiral magnets with topological spin textures provide a rare platform to
+explore topology and magnetism for potential application implementation. Here,
+we study the magnetic dynamics of several spin configurations on the monoaxial
+chiral magnetic crystal $MnNb_3S_6$ via broadband ferromagnetic resonance (FMR)
+technique at cryogenic temperature. In the high-field forced ferromagnetic
+state (FFM) regime, the obtained frequency f vs. resonance field Hres
+dispersion curve follows the well-known Kittel formula for a single FFM, while
+in the low-field chiral magnetic soliton lattice (CSL) regime, the dependence
+of Hres on magnetic field angle can be well-described by our modified Kittel
+formula including the mixture of a helical spin segment and the FFM phase.
+Furthermore, compared to the sophisticated Lorentz micrograph technique, the
+observed magnetic dynamics corresponding to different spin configurations allow
+us to obtain temperature- and field-dependent proportion of helical spin
+texture and helical spin period ratio L(H)/L(0) via our modified Kittel
+formula. Our results demonstrated that field- and temperature-dependent
+nontrivial magnetic structures and corresponding distinct spin dynamics in
+chiral magnets can be an alternative and efficient approach to uncovering and
+controlling nontrivial topological magnetic dynamics.",2209.02266v1
+2010-10-21,Nonequilibrium phase transition in the kinetic Ising model driven by propagating magnetic field wave,"The two dimensional ferromagnetic Ising model in the presence of a
+propagating magnetic field wave (with well defined frequency and wavelength) is
+studied by Mone Carlo simulation. This study differs from all of the earlier
+studies done so far, where the oscillating magnetic field was considered to be
+uniform in space. The time average magnetisation over a full cycle (the time
+period) of the propagating magnetic field acts as the dynamic order parameter.
+The dynamical phase transition is observed. The temperature variation of the
+dynamic order parameter, the mean square deviation of the dynamic order
+parameter, the dynamic specific heat and the derivative of the dynamic order
+parameter are studied. The mean square deviation of the dynamic order
+parameter, dynamic specific heat show sharp maxima near the transition point.
+The derivative of dynamic order parameter shows sharp minimum near the
+transition point. The transition temperature is found to depend also on the
+speed of propagation of the magnetic field wave.",1010.4366v4
+2007-01-29,Scaling laws of turbulent dynamos,"We consider magnetic fields generated by homogeneous isotropic and parity
+invariant turbulent flows. We show that simple scaling laws for dynamo
+threshold, magnetic energy and Ohmic dissipation can be obtained depending on
+the value of the magnetic Prandtl number.",0701319v1
+2010-09-09,Closed magnetic geodesics on closed hyperbolic Riemann surfaces,"We prove the existence of Alexandrov embedded closed magnetic geodesics on
+closed hyperbolic surfaces. Closed magnetic geodesics correspond to closed
+curves with prescribed geodesic curvature.",1009.1723v1
+2019-04-01,Mechanism of Electron Spin Relaxation in Spiral Magnetic Structures,"Spin dynamics in spiral magnetic structures has been investigated. It has
+been shown that the internal spatially dependent magnetic field in such
+structures produces a new mechanism of spin relaxation.",1904.00564v1
+2019-06-12,Dynamics of magnetic flux tubes in accretion discs of T Tauri stars,"Dynamics of slender magnetic flux tubes (MFT) in the accretion discs of T
+Tauri stars is investigated. We perform simulations taking into account
+buoyant, aerodynamic and turbulent drag forces, radiative heat exchange between
+MFT and ambient gas, magnetic field of the disc. The equations of MFT dynamics
+are solved using Runge-Kutta method of the fourth order. The simulations show
+that there are two regimes of MFT motion in absence of external magnetic field.
+In the region $r<0.2$ au, the MFT of radii $0.05 \leq a_0 \leq 0.16\,H$ ($H$ is
+the scale height of the disc) with initial plasma beta of 1 experience thermal
+oscillations above the disc. The oscillations decay over some time, and MFT
+continue upward motion afterwards. Thinner or thicker MFT do not oscillate. MFT
+velocity increases with initial radius and magnetic field strength. MFT rise
+periodically with velocities up to 5-15 km s$^{-1}$ and periods of $0.5-10$ yr
+determined by the toroidal magnetic field generation time. Approximately 20 %
+of disc mass and magnetic flux can escape to disc atmosphere via the magnetic
+buoyancy over characteristic time of disc evolution. MFT dispersal forms
+expanding magnetized corona of the disc. External magnetic field causes MFT
+oscillations near the disc surface. These magnetic oscillations have periods
+from several days to 1-3 months at $r < 0.6$ au. The magnetic oscillations
+decay over few periods. We simulate MFT dynamics in accretion discs in the
+Chameleon I cluster. The simulations demonstrate that MFT oscillations can
+produce observed IR-variability of T Tauri stars.",1906.05133v1
+2019-08-23,Massively parallel atomistic simulation of ultrafast thermal spin dynamics of a permalloy vortex,"Ultrafast magnetization dynamics probes the most fundamental properties of
+magnetic materials, exploring questions about the fundamental interactions
+responsible for magnetic phenomena. Thermal effects are known to be extremely
+important for laser-induced dynamics in metallic systems, but the dynamics of
+topological magnetic structures are little understood. Here we apply a
+massively parallel atomistic spin dynamics simulation to study the response of
+a permalloy vortex to a 50 fs laser pulse. We find that macroscopically the
+short timescale dynamics are indistinguishable from the bulk, but that strong
+edge spin waves lead to a complex time evolution of the magnetic structure and
+long-lived oscillations on the nanosecond timescale. In the near future such
+simulations will provide unprecedented insight into the dynamics of magnetic
+materials and devices beyond the approximations of continuum micromagnetics.",1908.08885v1
+2020-11-14,Generic Theory of the Dynamic Magnetic Response of Ferrofluids,"Ferrofluids belong to an important class of highly functional soft matter,
+benefiting from their magnetically controllable physical properties. Therefore,
+it is of central importance to quantitatively predict the dynamic magnetic
+response of ferrofluids. Traditional dynamic theories, however, are often
+restricted to the near-equilibrium regime and/or only apply to nearly ideal
+ferrofluids that are monodisperse, dilute enough, and weakly interacting. In
+this paper I develop a self-consistent and nonperturbative dynamical mean field
+theory for typical ferrofluids which are often polydisperse, concentrated, and
+strongly interacting, possibly driven far from equilibrium. I obtain a general
+nonperturbative expression for the dynamic magnetic susceptibility,
+quantitatively agreeing with the spectra obtained from Brownian Dynamics
+simulations on both mono- and bidisperse samples. Furthermore, I derive a
+generic magnetization relaxation equation (MRE) for both mono- and polydisperse
+ferrofluids by employing the projection operator technique in nonequlibrium
+statistical mechanics. This MRE is in simple closed form and independent of
+which model is employed to approximate the equilibrium magnetization curve.
+Existing models can be recovered as low-order approximations of my generic and
+nonperturbative MRE. My theory can play a key role in studying the dynamics of
+ferrofluids and other polar fluids. It may also have substantial and immediate
+consequences to various ferrofluid applications.",2011.07277v1
+2021-03-12,Dynamically induced magnetism in KTaO$_3$,"Dynamical multiferroicity features entangled dynamic orders: fluctuating
+electric dipoles induce magnetization. Hence, the material with paraelectric
+fluctuations can develop magnetic signatures if dynamically driven. We identify
+the paraelectric KTaO$_3$ (KTO) as a prime candidate for the observation of the
+dynamical multiferroicity. We show that when a KTO sample is exposed to a
+circularly polarized laser pulse, the dynamically induced ionic magnetic
+moments are of the order of 5\% of the nuclear magneton per unit cell. We
+determine the phonon spectrum using ab initio methods and identify T$_{1u}$ as
+relevant soft phonon modes that couple to the external field and induce
+magnetic polarization. We also predict a corresponding electron effect for the
+dynamically induced magnetic moment which is enhanced by several orders of
+magnitude due to the significant mass difference between electron and ionic
+nucleus.",2103.07244v1
+2009-09-28,Magnetic properties and spin dynamics in single molecule paramagnets Cu6Fe and Cu6Co,"The magnetic properties and the spin dynamics of two molecular magnets have
+been investigated by magnetization and d.c. susceptibility measurements,
+Electron Paramagnetic Resonance (EPR) and proton Nuclear Magnetic Resonance
+(NMR) over a wide range of temperature (1.6-300K) at applied magnetic fields,
+H=0.5 and 1.5 Tesla. The two molecular magnets consist of
+CuII(saldmen)(H2O)}6{FeIII(CN)6}](ClO4)38H2O in short Cu6Fe and the analog
+compound with cobalt, Cu6Co. It is found that in Cu6Fe whose magnetic core is
+constituted by six Cu2+ ions and one Fe3+ ion all with s=1/2, a weak
+ferromagnetic interaction between Cu2+ moments through the central Fe3+ ion
+with J = 0.14 K is present, while in Cu6Co the Co3+ ion is diamagnetic and the
+weak interaction is antiferromagnetic with J = -1.12 K. The NMR spectra show
+the presence of non equivalent groups of protons with a measurable contact
+hyperfine interaction consistent with a small admixture of s-wave function with
+the d-function of the magnetic ion. The NMR relaxation results are explained in
+terms of a single ion (Cu2+, Fe3+, Co3+) uncorrelated spin dynamics with an
+almost temperature independent correlation time due to the weak magnetic
+exchange interaction. We conclude that the two molecular magnets studied here
+behave as single molecule paramagnets with a very weak intramolecular
+interaction, almost of the order of the dipolar intermolecular interaction.
+Thus they represent a new class of molecular magnets which differ from the
+single molecule magnets investigated up to now, where the intramolecular
+interaction is much larger than the intermolecular one.",0909.5063v1
+2013-01-03,Coherent spin dynamics of nanomolecules and magnetic nanoclusters,"Spin dynamics of nanomolecules and nanoclusters are analyzed. The nanosizes
+of these objects make it possible to consider them as single-domain magnets
+with a large total spin, where the motion of the spins of all atoms, composing
+a nanocluster, occurs in a coherent way. Another meaning of coherence in spin
+dynamics is the coherent spin motion of several nanomolecules or nanoclusters.
+Different approaches for treating spin dynamics are compared and the main
+mechanisms influencing the spin motion are studied. Spin dynamics of separate
+magnetic nanomolecules and nanoclusters are investigated, as well as the spin
+dynamics of the ensembles of these nano-objects.",1301.0421v1
+2005-03-31,Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion,"In magnetic superconductors a moving vortex lattice is accompanied by an ac
+magnetic field which leads to the generation of spin waves. At resonance
+conditions the dynamics of vortices in magnetic superconductors changes
+drastically, resulting in strong peaks in the dc I-V characteristics at
+voltages at which the washboard frequency of vortex lattice matches the spin
+wave frequency $\omega_s({\bf g})$, where ${\bf g}$ are the reciprocal vortex
+lattice vectors. We show that if washboard frequency lies above the magnetic
+gap, peaks in the I-V characteristics in borocarbides and cuprate layered
+magnetic superconductors are strong enough to be observed over the background
+determined by the quasiparticles.",0504006v1
+2005-08-26,Kinetic arrest of the first order ferromagnetic to antiferromagnetic transition in Ce(Fe$_{0.96}$Ru$_{0.04}$)$_2$ : formation of a magnetic-glass,"We present results of dc magnetization and magnetic relaxation study showing
+the kinetic arrest of a first order ferromagnetic to antiferromagnetic
+transition in Ce(Fe$_{0.96}$Ru$_{0.04}$)$_2$. This leads to the formation of a
+non-ergodic glass-like magnetic state. The onset of the magnetic-glass
+transformation is tracked through the slowing down of the magnetization
+dynamics. This glassy state is formed with the assistance of an external
+magnetic field and this is distinctly different from the well known
+'spin-glass' state.",0508625v1
+1995-09-27,Does Magnetic Charge Imply a Massive Photon ?,"In Abelian theories of monopoles the magnetic charge is required to be
+enormous. Using the electric-magnetic duality of electromagnetism it is argued
+that the existence of such a large, non-perturbative magnetic coupling should
+lead to a phase transition where magnetic charge is permanently confined and
+the photon becomes massive. The apparent masslessness of the photon could then
+be used as an argument against the existence of such a large, non-perturbative
+magnetic charge. Finally it is shown that even in the presence of this
+dynamical mass generation the Cabbibo-Ferrari formulation of magnetic charge
+gives a consistent theory.",9509157v1
+2006-08-03,Magnetization of rotating ferrofluids: the effect of polydispersity,"The influence of polydispersity on the magnetization is analyzed in a
+nonequilibrium situation where a cylindrical ferrofluid column is enforced to
+rotate with constant frequency like a rigid body in a homogeneous magnetic
+field that is applied perpendicular to the cylinder axis. Then, the
+magnetization and the internal magnetic field are not longer parallel to each
+other and their directions differ from that of the applied magnetic field.
+Experimental results on the transverse magnetization component perpendicular to
+the applied field are compared and analyzed as functions of rotation frequency
+and field strength with different polydisperse Debye models that take into
+account the polydispersity in different ways and to a varying degree.",0608033v1
+2010-09-22,Direct Measurement of Effective Magnetic Diffusivity in Turbulent Flow of Liquid Sodium,"The first direct measurements of effective magnetic diffusivity in turbulent
+flow of electro-conductive fluids (the so-called beta-effect) under magnetic
+Reynolds number Rm >> 1 are reported. The measurements are performed in a
+nonstationary turbulent flow of liquid sodium, generated in a closed toroidal
+channel. The peak level of the Reynolds number reached Re \approx 3 10^6, which
+corresponds to the magnetic Reynolds number Rm \approx 30. The magnetic
+diffusivity of the liquid metal was determined by measuring the phase shift
+between the induced and the applied magnetic fields. The maximal deviation of
+magnetic diffusivity from its basic (laminar) value reaches about 50% .",1009.4333v1
+2015-04-05,Magnetic states in multiply-connected flat nano-elements,"Flat magnetic nano-elements are an essential component of current and future
+spintronic devices. By shaping an element it is possible to select and
+stabilize chosen metastable magnetic states, control its magnetization
+dynamics. Here, using a recent significant development in mathematics of
+conformal mapping, complex variable based approach to the description of
+magnetic states in planar nano-elements is extended to the case when elements
+are multiply-connected (that is, contain holes or magnetic anti-dots). We show
+that presence of holes implies a certain restriction on the set of magnetic
+states of nano-element.",1504.01162v1
+2018-03-19,Dynamics of a Magnetic Needle Magnetometer: Sensitivity to Landau-Lifshitz-Gilbert Damping,"An analysis of a single-domain magnetic needle in the presence of an external
+magnetic field ${\bf B}$ is carried out with the aim of achieving a high
+precision magnetometer. We determine the uncertainty $\Delta B$ of such a
+device due to Gilbert dissipation and the associated internal magnetic field
+fluctuations that gives rise to diffusion of the magnetic needle axis direction
+${\bf n}$ and the needle orbital angular momentum. The levitation of the
+magnetic needle in a magnetic trap and its stability are also analyzed.",1803.10064v2
+2020-12-23,Magnetic Moment Tensor Potentials for collinear spin-polarized materials reproduce different magnetic states of bcc Fe,"We present the magnetic Moment Tensor Potentials (mMTPs), a class of
+machine-learning interatomic potentials, accurately reproducing both
+vibrational and magnetic degrees of freedom as provided, e.g., from
+first-principles calculations. The accuracy is achieved by a two-step
+minimization scheme that coarse-grains the atomic and the spin space. The
+performance of the mMTPs is demonstrated for the prototype magnetic system bcc
+iron, with applications to phonon calculations for different magnetic states,
+and molecular dynamics simulations with fluctuating magnetic moments.",2012.12763v2
+2022-06-21,Magnetic Forces in Paramagnetic Fluids,"An overview of the effect of a magnetic field gradient on fluids with linear
+magnetic susceptibilities is given. It is shown that two commonly encountered
+expressions, the magnetic field gradient force and the concentration gradient
+force for paramagnetic species in solution are equivalent for incompressible
+fluids. The magnetic field gradient and concentration gradient forces are
+approximations of the Kelvin force and Korteweg-Helmholtz force densities,
+respectively. The criterion for the appearance of magnetically induced
+convection is derived. Experimental work in which magnetically induced
+convection plays a role is reviewed.",2206.10529v4
+2023-07-02,Unveiling Stable One-dimensional Magnetic Solitons in Magnetic Bilayers,"We propose a novel model which efficiently describes the magnetization
+dynamics in a magnetic bilayer system. By applying a particular gauge
+transformation to the Landau-Lifshitz-Gilbert (LLG) equation, we successfully
+convert the model into an exactly integrable framework. Thus the obtained
+analytical solutions allows us to predict a 1D magnetic soliton pair existed by
+tunning the thickness of the spacing layer between the two ferrimagnetic
+layers. The decoupling-unlocking-locking transition of soliton motion is
+determined at various interaction intensitiy. Our results have implications for
+the manipulation of magnetic solitons and the design of magnetic soliton-based
+logic devices.",2307.00471v1
+1997-12-11,Global three-dimensional simulations of magnetic field evolution in a galactic disk,"The evolution of three-dimensional, large-scale, magnetic fields, in a
+galactic disk is investigated numerically. The N-body simulations of galactic
+dynamics are incorporated into the kinematic calculations of induction
+equations to study the influence of non-axisymmetric gas flows on the galactic
+magnetic field. The time-dependent gas velocity fields are introduced as input
+parameters for the MHD-simulations. Our principal concern is to check how
+dynamical evolution of the galactic gas affects the global magnetic field
+structure and intensity. We have found that the magnetic field responds
+sensitively to changes in the gas velocity field, and even slight variations of
+the dynamical parameters, such as the gas mass/total mass ratio results in
+nonuniform intensity structures, i.e. magnetic arms. The magnetic lines of
+force are well aligned with spiral arms and bar due to compressional flows in
+these features. In the inter-arm regions the areas with magnetic vectors going
+opposite to the main magnetic spirals are present.",9712148v1
+1999-04-07,Magnetic field correlations in kinematic two-dimensional magnetohydrodynamic turbulence,"The scaling properties of the second order magnetic structure function
+D_2^{(B)}(r) and the corresponding magnetic correlation function C_2^{(B)}(r)
+are derived for two-dimensional magnetohydrodynamic turbulence in the kinematic
+regime where the ratio of kinetic energy to magnetic energy is much larger than
+one. In this regime the magnetic flux function $\psi$ can be treated as a
+passive scalar advected in a two-dimensional turbulent flow. Its structure
+function $D_2^{(\psi)}(r)$ and the one for the magnetic field D_2^{(B)}(r) are
+connected by an exact relation. We calculate D_2^{(\psi)}(r) and thus
+D_2^{(B)}(r) within geometric measure theory over a wide range of scales r and
+magnetic Prandtl numbers Pr_m. The magnetic field correlations follow a
+r^{-4/3} - scaling law and show an anticorrelation at the beginning of the
+Batchelor regime indicative of the formation of strongly filamented current
+sheets. Differences to the full dynamic regime, where the ratio of kinetic to
+magnetic energies is smaller than in the kinematic case, are discussed.",9904014v2
+1997-09-10,Dynamical symmetry breaking in the external gravitational and constant magnetic fields,"We investigate the effects of the external gravitational and constant
+magnetic fields to the dynamical symmetrybreaking. As simple models of the
+dynamical symmetry breaking we consider the Nambu-Jona-Lasinio (NJL) model and
+the supersymmetric Nambu-Jona-Lasinio (SUSY NJL) model non-minimally
+interacting with the external gravitational field and minimally interacting
+with constant magnetic field. The explicit expressions for the scalar and
+spinor Green functions are found up to the linear terms on the spacetime
+curvature and exactly for a constant magnetic field. We obtain the effective
+potential of the above models from the Green functions in the magnetic field in
+curved spacetime. Calculating the effective potential numerically with the
+varying curvature and/or magnetic fields we show the effects of the external
+gravitational and magnetic fields to the phase structure of the theories. In
+particular, increase of the curvature in the spontaneously broken chiral
+symmetry phase due to the fixed magnetic field makes this phase to be less
+broken. On the same time strong magnetic field quickly induces chiral symmetry
+breaking even at the presence of fixed gravitational field within nonbroken
+phase.",9709077v1
+2013-11-25,Magnetic catalysis in flavored ABJM,"We study the magnetic catalysis of chiral symmetry breaking in the ABJM
+Chern-Simons matter theory with unquenched flavors in the Veneziano limit. We
+consider a magnetized D6-brane probe in the background of a flavored black hole
+which includes the backreaction of massless smeared flavors in the ABJM
+geometry. We find a holographic realization for the running of the quark mass
+due to the dynamical flavors. We compute several thermodynamic quantities of
+the brane probe and analyze the effects of the dynamical quarks on the
+fundamental condensate and on the phase diagram of the model. The dynamical
+flavors have an interesting effect on the magnetic catalysis. At zero
+temperature and fixed magnetic field, the magnetic catalysis is suppressed for
+small bare quark masses whereas it is enhanced for large values of the mass.
+When the temperature is non-zero there is a critical magnetic field, above
+which the magnetic catalysis takes place. This critical magnetic field
+decreases with the number of flavors, which we interpret as an enhancement of
+the catalysis.",1311.6265v3
+2014-03-25,Simulations of magnetic nanoparticle Brownian motion,"Magnetic nanoparticles are useful in many medical applications because they
+interact with biology on a cellular level thus allowing microenvironmental
+investigation. An enhanced understanding of the dynamics of magnetic particles
+may lead to advances in imaging directly in magnetic particle imaging (MPI) or
+through enhanced MRI contrast and is essential for nanoparticle sensing as in
+magnetic spectroscopy of Brownian motion (MSB). Moreover, therapeutic
+techniques like hyperthermia require information about particle dynamics for
+effective, safe, and reliable use in the clinic. To that end, we have developed
+and validated a stochastic dynamical model of rotating Brownian nanoparticles
+from a Langevin equation approach. With no field, the relaxation time toward
+equilibrium matches Einstein's model of Brownian motion. In a static field, the
+equilibrium magnetization agrees with the Langevin function. For high frequency
+or low amplitude driving fields, behavior characteristic of the linearized
+Debye approximation is reproduced. In a higher field regime where magnetic
+saturation occurs, the magnetization and its harmonics compare well with the
+effective field model. On another level, the model has been benchmarked against
+experimental results, successfully demonstrating that harmonics of the
+magnetization carry enough information to infer environmental parameters like
+viscosity and temperature.",1403.6427v1
+2015-01-28,Superconductor Dynamics,"Superconductors used in magnet technology could carry extreme currents
+because of their ability to keep the magnetic flux motionless. The dynamics of
+the magnetic flux interaction with superconductors is controlled by this
+property. The cases of electrical transport in a round wire and the
+magnetization of wires of various shapes (circular, elliptical, plate) in an
+external magnetic field are analysed. Resistance to the magnetic field
+penetration means that the field produced by the superconducting magnet is no
+longer proportional to the supplied current. It also leads to a dissipation of
+electromagnetic energy. In conductors with unequal transverse dimensions, such
+as flat cables, the orientation with respect to the magnetic field plays an
+essential role. A reduction of magnetization currents can be achieved by
+splitting the core of a superconducting wire into fine filaments; however, new
+kinds of electrical currents that couple the filaments consequently appear.
+Basic formulas allowing qualitative analyses of various flux dynamic cases are
+presented.",1501.07159v1
+2015-05-26,Vacancy defects and monopole dynamics in oxygen-deficient pyrochlores,"The idea of magnetic monopoles in spin ice has enjoyed much success at
+intermediate temperatures, but at low temperatures a description in terms of
+monopole dynamics alone is insufficient. Recently, numerical simulations were
+used to argue that magnetic impurities account for this discrepancy by
+introducing a magnetic equivalent of residual resistance in the system. Here we
+propose that oxygen deficiency is the leading cause of magnetic impurities in
+as-grown samples, and we determine the defect structure and magnetism in
+Y2Ti2O(7-\delta) using diffuse neutron scattering and magnetization
+measurements. These defects are eliminated by oxygen annealing. The
+introduction of oxygen vacancies causes Ti4+ to transform to magnetic Ti3+ with
+quenched orbital magnetism, but the concentration is anomalously low. In the
+spin-ice material Dy2Ti2O7 we find that the same oxygen-vacancy defects
+suppress moments on neighbouring rare-earth sites, and that these magnetic
+distortions dramatically slow down the long-time monopole dynamics at
+sub-Kelvin temperatures.",1505.07035v1
+2018-04-16,Triple Exponential Relaxation Dynamics in a Metallacrown-Based {$Dy^{III}Cu^{II}_5$} 3d-4f Single-Molecule Magnet,"The interplay of strong single-ion anisotropy and magnetic interactions often
+give rise to novel magnetic behavior and can provide additional routes for
+controlling magnetization dynamics. However, novel effects arising from
+interactions between lanthanide and transition-metal ions are nowadays rarely
+observed. Herein, a {$Dy^{III}Cu^{II}_5$} 3d-4f single-molecule magnet (SMM) is
+constructed as a rigid and planar [15-MC-5] metallacrown (MC), where the
+$Dy^{III}$ ion is trapped in the central pseudo-$D_{5h}$ pocket. A strong axial
+crystal field (CF) imbues the $Dy^{III}$ ion with large Ising-type magnetic
+anisotropy, and we are able to observe and model the magnetic interactions
+between the $Cu^{II}-Cu^{II}$ and $Dy^{III}-Cu^{II}$ pairs. Butterfly-shaped
+magnetic hysteresis shows clear steps at $\pm$0.4 T, coincident with level
+crossings in our model exchange Hamiltonian between the {$Cu^{II}_5$} and
+$Dy^{III}$ spin systems. Most intriguingly, this air-stable SMM exhibits three
+distinct regimes in its magnetic relaxation dynamics, all clearly displaying an
+exponential dependence on temperature.",1804.05818v1
+2019-03-27,Real-space imaging and flux noise spectroscopy of magnetic dynamics in Ho$_2$Ti$_2$O$_7$,"Holmium titanate (Ho$_2$Ti$_2$O$_7$) is a rare earth pyrochlore and a
+canonical example of a classical spin ice material. Despite the success of
+magnetic monopole models, a full understanding of the energetics and relaxation
+rates in this material has remained elusive, while recent studies have shown
+that defects play a central role in the magnetic dynamics. We used a scanning
+superconducting quantum interference device (SQUID) microscope to study the
+spatial and temporal magnetic fluctuations in three regions with different
+defect densities from a Ho$_2$Ti$_2$O$_7$ single crystal as a function of
+temperature. We found that the magnetic flux noise power spectra are not
+determined by simple thermally-activated behavior and observed evidence of
+magnetic screening that is qualitatively consistent with Debye-like screening
+due to a dilute gas of low-mobility magnetic monopoles. This work establishes
+magnetic flux spectroscopy as a powerful tool for studying materials with
+complex magnetic dynamics, including frustrated correlated spin systems.",1903.11465v1
+2020-07-15,Magnetic Charge Propagation upon a 3D Artificial Spin-ice,"Magnetic charge propagation in bulk frustrated materials has yielded a
+paradigm-shift in science, allowing the symmetry between electricity and
+magnetism to be studied. Recent work is now suggesting magnetic charge dynamics
+upon the spin-ice surface may have important implications in determining the
+ordering and associated phase space. Here we detail a 3D artificial spin-ice, a
+3D nanostructured array of magnetic islands which captures the exact geometry
+of bulk systems, allowing field-driven dynamics of magnetic charge to be
+directly visualized upon the surface. Using magnetic microscopy, we observe
+vastly different magnetic charge dynamics along two principle directions. These
+striking differences are found to be due to the surface-termination and
+associated coordination which yields different energetics and interaction
+strengths for magnetic charges upon the surface.",2007.07618v2
+2021-09-28,Dynamical Switching of Magnetic Topology in Microwave-Driven Itinerant Magnet,"We theoretically demonstrate microwave-induced dynamical switching of
+magnetic topology in centrosymmetric itinerant magnets by taking the
+Kondo-lattice model on a triangular lattice, which is known to exhibit two
+types of skyrmion lattices with different magnetic topological charges of |Nsk|
+= 1 and 2. Our numerical simulations reveal that intense excitation of a
+resonance mode with circularly polarized microwave field can switch the
+magnetic topology, i.e., from the skyrmion lattice with |Nsk| = 1 to another
+skyrmion lattice with |Nsk| = 2 or to a nontopological magnetic order with
+|Nsk| = 0 depending on the microwave frequency. This magnetic-topology
+switching shows various distinct behaviors, that is, deterministic irreversible
+switching, probabilistic irreversible switching, and temporally random
+fluctuation depending on the microwave frequency and the strength of the
+external magnetic field, the variety of which is attributable to different
+energy landscapes in the dynamical regime. The obtained results are also
+discussed in the light of time-evolution equations based on an effective model
+derived using perturbation expansions.",2109.13511v1
+2022-06-24,All-optical non-linear chiral ultrafast magnetization dynamics driven by circularly polarized magnetic fields,"Ultrafast laser pulses provide unique tools to manipulate magnetization
+dynamics at femtosecond timescales, where the interaction of the electric field
+-- such as excitation of spin carriers to non-equilibrium states, generation of
+localized charge currents, demagnetization, or inverse Faraday effect --
+dominates over the magnetic field. Recent proposals using structured laser
+beams have enlightened the possibility to generate intense femtosecond magnetic
+fields, spatially isolated from the electric field. Here we demonstrate the
+relevance of this novel scenario to femtomagnetism, unveiling the purely
+precessional, non-linear, chiral response of the magnetization when subjected
+to circularly polarized magnetic fields. This fundamental result not only opens
+an avenue in the study of laser-induced ultrafast magnetization dynamics, but
+also sustains technological implications as a route to promote all-optical
+non-thermal magnetization switching both at shorter timescales -- towards the
+attosecond regime -- and at THz frequencies.",2206.12238v2
+1997-12-02,Rotational Dynamics of the Magnetic Particles in Ferrofluids,"A new theory for the dynamics of the magnetic particles and their magnetic
+moments in ferrofluids is developed. Based on a generalized Lagrangian
+formulation for the equations of motion of the colloidal particle, we introduce
+its interaction with the solvent fluid via dissipative and random noise
+torques, as well as the interactions between the particle and its magnetic
+moment, treated as an independent physical entity and characterized by three
+generalized coordinates, its two polar angles and its modulus. It has been
+recognized recently that inertial effects, as well as the particle's rotational
+Brownian motion, may play important roles on the dynamic susceptibility of a
+class of magnetic fluids. No satisfactory theory existed, up to now, that takes
+this effects into account. The theory presented here is a first-principles
+3-dimensional approach, in contrast to some phenomenological 2-dimensional
+approaches that can be found in the recent literature. It is appropriate for
+superparamagnetic, non-superparamagnetic and mixed magnetic fluids. As a simple
+application, the blocked limit (magnetic moment fixed in the particle) is
+treated numerically. The rotational trajectory of the particles in presence of
+a magnetic field, as well as the response functions and dynamic susceptibility
+matrices are explicitly calculated for some values of the parameters",9712025v1
+2007-10-12,Dynamics of Magnetized Spherical Accretion Flows,"Transonic accretion flow with self-consistent treatment of random magnetic
+field is presented.",0710.2543v1
+2009-07-17,Current-induced dynamics in non-collinear dual spin-valves,"Spin-transfer torque and current induced spin dynamics in spin-valve
+nanopillars with the free magnetic layer located between two magnetic films of
+fixed magnetic moments is considered theoretically. The spin-transfer torque in
+the limit of diffusive spin transport is calculated as a function of magnetic
+configuration. It is shown that non-collinear magnetic configuration of the
+outermost magnetic layers has a strong influence on the spin torque and spin
+dynamics of the central free layer. Employing macrospin simulations we make
+some predictions on the free layer spin dynamics in spin valves composed of
+various magnetic layers. We also present a formula for critical current in
+non-collinear magnetic configurations, which shows that the magnitude of
+critical current can be several times smaller than that in typical single spin
+valves.",0907.3094v2
+2012-09-06,Field-driven femtosecond magnetization dynamics induced by ultrastrong coupling to THz transients,"Controlling ultrafast magnetization dynamics by a femtosecond laser is
+attracting interest both in fundamental science and industry because of the
+potential to achieve magnetic domain switching at ever advanced speed. Here we
+report experiments illustrating the ultrastrong and fully coherent light-matter
+coupling of a high-field single-cycle THz transient to the magnetization vector
+in a ferromagnetic thin film. We could visualize magnetization dynamics which
+occur on a timescale of the THz laser cycle and two orders of magnitude faster
+than the natural precession response of electrons to an external magnetic
+field, given by the Larmor frequency. We show that for one particular
+scattering geometry the strong coherent optical coupling can be described
+within the framework of a renormalized Landau Lifshitz equation. In addition to
+fundamentally new insights to ultrafast magnetization dynamics the coherent
+interaction allows for retrieving the complex time-frequency magnetic
+properties and points out new opportunities in data storage technology towards
+significantly higher storage speed.",1209.1280v1
+2016-02-10,The inverse thermal spin-orbit torque and the relation of the Dzyaloshinskii-Moriya interaction to ground-state energy currents,"Using the Kubo linear-response formalism we derive expressions to calculate
+the heat current generated by magnetization dynamics in magnets with broken
+inversion symmetry and spin-orbit interaction (SOI). The effect of producing
+heat currents by magnetization dynamics constitutes the Onsager reciprocal of
+the thermal spin-orbit torque (TSOT), i.e., the generation of torques on the
+magnetization due to temperature gradients. We find that the energy current
+driven by magnetization dynamics contains a contribution from the
+Dzyaloshinskii-Moriya interaction (DMI), which needs to be subtracted from the
+Kubo linear response of the energy current in order to extract the heat
+current. We show that the expressions of the DMI coefficient can be derived
+elegantly from the DMI energy current. Guided by formal analogies between the
+Berry phase theory of DMI on the one hand and the modern theory of orbital
+magnetization on the other hand we are led to an interpretation of the latter
+in terms of energy currents as well. Based on \textit{ab-initio} calculations
+we investigate the heat current driven by magnetization dynamics in Mn/W(001)
+magnetic bilayers. We predict that fast domain walls drive strong ITSOT heat
+currents.",1602.03319v1
+2017-03-06,Ultra-low-energy Electric field-induced Magnetization Switching in Multiferroic Heterostructures,"Electric field-induced magnetization switching in multiferroics is intriguing
+for both fundamental studies and potential technological applications. Here, we
+review the recent developments on electric field-induced magnetization
+switching in multiferroic heterostructures. Particularly, we study the dynamics
+of magnetization switching between the two stable states in a shape-anisotropic
+single-domain nanomagnet using stochastic Landau-Lifshitz-Gilbert (LLG)
+equation in the presence of thermal fluctuations. For magnetostrictive
+nanomagnets in strain-coupled multiferroic composites, such study of
+magnetization dynamics, contrary to steady-state scenario, revealed intriguing
+new phenomena on binary switching mechanism. While the traditional method of
+binary switching requires to tilt the potential profile to the desired state of
+switching, we show that no such tilting is necessary to switch successfully
+since the magnetization's excursion out of magnet's plane can generate a
+built-in asymmetry during switching. We also study the switching dynamics in
+multiferroic heterostructures having magnetoelectric coupling at the interface
+and magnetic exchange coupling that can facilitate to maintain the direction of
+switching with the polarity of the applied electric field. We calculate the
+performance metrics like switching delay and energy dissipation during
+switching while simulating LLG dynamics. The performance metrics turn out to be
+very encouraging for potential technological applications.",1706.03039v1
+2017-12-01,Relativistic Dynamics of Point Magnetic Moment,"The covariant motion of a classical point particle with magnetic moment in
+the presence of (external) electromagnetic fields is revisited. We are
+interested in understanding Lorentz force extension involving point particle
+magnetic moment (Stern-Gerlach force) and how the spin precession dynamics is
+modified for consistency. We introduce spin as a classical particle property
+inherent to Poincare\'e symmetry of space-time. We propose a covariant
+formulation of the magnetic force based on a \lq magnetic\rq\ 4-potential and
+show how the point particle magnetic moment relates to the Amperian (current
+loop) and Gilbertian (magnetic monopole) description. We show that covariant
+spin precession lacks a unique form and discuss connection to $g-2$ anomaly. We
+consider variational action principle and find that a consistent extension of
+Lorentz force to include magnetic spin force is not straightforward. We look at
+non-covariant particle dynamics, and present a short introduction to dynamics
+of (neutral) particles hit by a laser pulse of arbitrary shape.",1712.01825v1
+2018-03-05,Generation and stability of dynamical skyrmions and droplet solitons,"A spin-polarized current in a nanocontact to a magnetic film can create
+collective magnetic oscillations by compensating the magnetic damping. In
+particular, in materials with uniaxial magnetic anisotropy, droplet solitons
+have been observed a self-localized excitation consisting of partially reversed
+magnetization that precesses coherently in the nanocontact region. It is also
+possible to generate topological droplet solitons, known as \emph{dynamical
+skyrmions}. Here we study the conditions that promote either droplet or
+dynamical skyrmion formation and describe their stability in magnetic films
+without Dzyaloshinskii-Moriya interactions. We show that Oersted fields from
+the applied current as well as the initial magnetization state can determine
+whether a droplet or dynamical skyrmion forms. Dynamical skyrmions are found to
+be more stable than droplets. We also discuss electrical characteristics that
+can be used distinguish these magnetic objects.",1803.01750v1
+2022-11-28,Superfluid-like spin transport in the dynamic states of easy-axis magnets,"The existing proposals for superfluid-like spin transport have been based on
+easy-plane magnets where the U(1) spin-rotational symmetry is spontaneously
+broken in equilibrium, and this has been limiting material choices for
+realizing superfluid-like spin transport to restricted class of magnets. In
+this work, we lift this limitation by showing that superfluid-like spin
+transport can also be realized based on easy-axis magnets, where the U(1)
+spin-rotational symmetry is intact in equilibrium but can be broken in
+non-equilibrium. Specifically, we find the condition to engender a
+non-equilibrium easy-cone state by applying a spin torque to easy-axis magnets,
+which dynamically induces the spontaneous breaking of the U(1) spin-rotational
+symmetry and thereby can support superfluid-like spin transport. By exploiting
+this dynamic easy-cone state, we show theoretically that superfluid-like spin
+transport can be achieved in easy-axis magnets under suitable conditions and
+confirmed the prediction by micromagnetic simulations. We envision that our
+work broadens material library for realizing superfluid-like spin transport,
+showing the potential utility of dynamic states of magnets as venue to look for
+spin-transport phenomena that do not occur in static magnetic backgrounds.",2211.15091v1
+2023-05-25,Crystallization dynamics of magnetic skyrmions in a frustrated itinerant magnet,"We investigate the phase ordering kinetics of skyrmion lattice (SkL) in a
+metallic magnet. The SkL can be viewed as a superposition of magnetic stripes
+whose periods are determined by the quasi-nesting wave vectors of the
+underlying Fermi surface. An effective magnetic Hamiltonian that describes the
+electron-mediated spin-spin interaction is obtained for a two-dimensional s-d
+model with the Rashba spin-orbit coupling. Large-scale Landau-Lifshitz-Gilbert
+dynamics simulations based on the effective spin Hamiltonian reveal a two-stage
+phase ordering of the SkL phase after a thermal quench. The initial fast
+crystallization of skyrmions is followed by a slow relaxation dominated by the
+annihilation dynamics of dislocations, which are topological defects of the
+constituent magnetic stripe orders. The late-stage phase ordering also exhibits
+a dynamical scaling symmetry. We further show that the annihilation of
+dislocations follows a power-law time dependence with a logarithmic correction
+that depends on magnetic fields. Implications of our results for SkL phases in
+magnetic materials are also discussed.",2305.16182v1
+2019-10-17,Magnetic textures and dynamics in magnetic Weyl semimetals,"Recent theoretical and experimental attemps have been successful in finding
+magnetic Weyl semimetal phases, which show both nodal-point structure in the
+electronic bands and magnetic orders. Beyond uniform ferromagnetic or
+antiferromagnetic orders, nonuniform magnetic textures, such as domain walls
+and skyrmions, may even more enrich the properties of the Weyl electrons in
+such materials. This article gives a topical review on interplay between Weyl
+electrons and magnetic textures in those magnetic Weyl semimetals. The basics
+of magnetic textures in non-topological magnetic metals are reviewed first, and
+then the effect of magnetic textures in Weyl semimetals is discussed, regarding
+the recent theoretical and experimental progress therein. The idea of the
+fictitious ""axial gauge fields"" is pointed out, which effectively describes the
+effect of magnetic textures on the Weyl electrons and can well account for the
+properties of the electrons localized around magnetic domain walls.",1910.07774v1
+2020-03-09,Magnetic Noise Enabled Biocompass,"The discovery of magnetic protein provides a new understanding of a
+biocompass at the molecular level. However, the mechanism by which magnetic
+protein enables a biocompass is still under debate, mainly because of the
+absence of permanent magnetism in the magnetic protein at room temperature.
+Here, based on a widely accepted radical pair model of a biocompass, we propose
+a microscopic mechanism that allows the biocompass to operate without a finite
+magnetization of the magnetic protein in a biological environment. With the
+structure of the magnetic protein, we show that the magnetic fluctuation,
+rather than the permanent magnetism, of the magnetic protein can enable
+geomagnetic field sensing. An analysis of the quantum dynamics of our
+microscopic model reveals the necessary conditions for optimal sensitivity. Our
+work clarifies the mechanism by which magnetic protein enables a biocompass.",2003.13816v2
+2020-04-25,Pulse-assisted magnetization switching in magnetic nanowires at picosecond and nanosecond timescales with low energy,"Detailed understanding of spin dynamics in magnetic nanomaterials is
+necessary for developing ultrafast, low-energy and high-density spintronic
+logic and memory. Here, we develop micromagnetic models and analytical
+solutions to elucidate the effect of increasing damping and uniaxial anisotropy
+on magnetic field pulse-assisted switching time, energy and field requirements
+of nanowires with perpendicular magnetic anisotropy and yttrium iron
+garnet-like spin transport properties. A nanowire is initially magnetized using
+an external magnetic field pulse (write) and self-relaxation. Next, magnetic
+moments exhibit deterministic switching upon receiving 2.5 ns-long external
+magnetic pulses in both vertical polarities. Favorable damping
+({\alpha}~0.1-0.5) and anisotropy energies (10^4-10^5 J m^-3) allow for as low
+as picosecond magnetization switching times. Magnetization reversal with fields
+below coercivity was observed using spin precession instabilities. A
+competition or a nanomagnetic trilemma arises among the switching rate, energy
+cost and external field required. Developing magnetic nanowires with optimized
+damping and effective anisotropy could reduce the switching energy barrier down
+to 3163kBT at room temperature. Thus, pulse-assisted picosecond and low energy
+switching in nanomagnets could enable ultrafast nanomagnetic logic and cellular
+automata.",2004.12243v1
+2023-11-10,Exchange stiffness proportional to power of magnetization in permalloy co-doped with Mo and Cu,"The exchange stiffness of magnetic materials is one of the essential
+parameters governing magnetic texture and its dynamics in magnetic devices. The
+effect of single-element doping on exchange stiffness has been investigated for
+several doping elements for permalloy (NiFe alloy), a soft magnetic material
+whose soft magnetic properties can be controlled by doping. However, the impact
+of more practical multi-element doping on the exchange stiffness of permalloy
+is unknown. This study investigates the typical magnetic properties, including
+exchange stiffness, of permalloy systematically co-doped with Mo and Cu using
+broadband ferromagnetic resonance spectroscopy. We find that the exchange
+stiffness, which decreases with increasing doping levels, is proportional to a
+power of magnetization, which also decreases with increasing doping levels. The
+magnetization, $M_{\rm s}$, dependence of the exchange stiffness constant, $A$,
+of all the investigated samples, irrespective of the doping levels of each
+element, lies on a single curve expressed as $A\propto M_{\rm s}^n$ with
+exponent $n$ close to 2. This empirical power-law relationship provides a
+guideline for predicting unknown exchange stiffness in non-magnetic
+element-doped permalloy systems.",2311.05852v2
+2011-03-23,Nonlinear Dynamics of Magnetic Islands Imbedded in Small-Scale Turbulence,"The nonlinear dynamics of magnetic tearing islands imbedded in a pressure
+gradient driven turbulence is investigated numerically in a reduced
+magnetohydrodynamic model. The study reveals regimes where the linear and
+nonlinear phases of the tearing instability are controlled by the properties of
+the pressure gradient. In these regimes, the interplay between the pressure and
+the magnetic flux determines the dynamics of the saturated state. A secondary
+instability can occur and strongly modify the magnetic island dynamics by
+triggering a poloidal rotation. It is shown that the complex nonlinear
+interaction between the islands and turbulence is nonlocal and involves small
+scales.",1103.4443v1
+2012-05-29,Magnetization dynamics at elevated temperatures,"By using the quantum kinetic approach with the instantaneous local
+equilibrium approximation, we propose an equation that is capable of addressing
+magnetization dynamics for a wide range of temperatures. The equation reduces
+to the Landau-Lifshitz equation at low temperatures and to the paramagnetic
+Bloch equation at high temperatures. Near the Curie temperature, the
+magnetization reversal and dynamics depend on both transverse and longitudinal
+relaxations. We further include the stochastic fields in the dynamic equation
+in order to take into account fluctuation at high temperatures. Our proposed
+equation may be broadly used for modeling laser pump-probe experiments and heat
+assisted magnetic recording.",1205.6506v1
+2013-09-14,Dynamics of the polarization of a pinned domain wall in a magnetic nanowire,"We consider the dynamics of polarization of a single domain wall in a
+magnetic nanowire, which is strongly pinned by impurities. In this case the
+equation of motion for the polarization parameter does not include any other
+dynamical variables and is nonlinear due to magnetic anisotropy. We calculated
+numerically the magnetization dynamics for different choices of parameters
+under short current pulses inducing polarization switching. Our results show
+that the switching is most effective for very rapid current pulses. Damping
+also enhances the switching probability.",1309.3687v1
+2014-08-27,On planar quantum dynamics of a magnetic dipole moment in the presence of electric and magnetic fields,"The planar quantum dynamics of a neutral particle with a magnetic dipole
+moment in the presence of electric and magnetic fields is considered. The
+criteria to establish the planar dynamics reveal that the resulting
+nonrelativistic Hamiltonian has a simplified expression without making
+approximations, and some terms have crucial importance for system dynamics.",1408.6578v2
+2019-07-29,Magnetization Dynamics in Holographic Ferromagnets: Landau-Lifshitz Equation from Yang-Mills Fields,"We introduce a new approach to understand magnetization dynamics in
+ferromagnets based on the holographic realization of ferromagnets. A
+Landau-Lifshitz equation describing the magnetization dynamics is derived from
+a Yang-Mills equation in the dual gravitational theory, and temperature
+dependences of the spin-wave stiffness and spin transfer torque appearing in
+the holographic Landau-Lifshitz equation are investigated by the holographic
+approach. The results are consistent with the known properties of magnetization
+dynamics in ferromagnets with conduction electrons.",1907.12306v1
+2020-06-25,Novel dynamic critical phenomena induced by superfluidity and the chiral magnetic effect in Quantum Chromodynamics,"In this thesis, we study the novel dynamic critical phenomena induced by
+superfluidity and the chiral magnetic effect in Quantum Chromodynamics (QCD),
+respectively. In particular, we find the new dynamic universality class of the
+high-density QCD critical point between the nuclear and quark superfluid phases
+beyond the conventional Hohnenberg and Halperin's classification. We also
+consider the second-order chiral phase transition under an external magnetic
+field and find that the inclusion of the chiral magnetic effect changes the
+dynamic universality class from the model E into model A within the
+conventional classification.",2006.14127v1
+2005-05-12,Dynamics of magnetization coupled to a thermal bath of elastic modes,"We study the dynamics of magnetization coupled to a thermal bath of elastic
+modes using a system plus reservoir approach with realistic magnetoelastic
+coupling. After integrating out the elastic modes we obtain a self-contained
+equation for the dynamics of the magnetization.
+  We find explicit expressions for the memory friction kernel and hence, {\em
+via} the Fluctuation-Dissipation
+  Theorem, for the spectral density of the magnetization thermal fluctuations.
+  For magnetic samples in which the single domain approximation is valid, we
+derive an equation for the dynamics of the uniform mode.
+  Finally we apply this equation to study the dynamics of the uniform
+magnetization mode in insulating ferromagnetic thin films.
+  As experimental consequences we find that the fluctuation correlation time is
+of the order of the ratio between the film thickness, $h$, and the speed of
+sound in the magnet and that the line-width of the ferromagnetic resonance peak
+should scale as $B_1^2h$ where $B_1$ is the magnetoelastic coupling constant.",0505331v3
+2009-03-22,Quantum Spinodal Phenomena,"We study the dynamical magnetization process in the ordered ground-state
+phase of the transverse Ising model under sweeps of magnetic field with
+constant velocities. In the case of very slow sweeps and for small systems
+studied previously (Phys. Rev. B 56, 11761 (1997)), non-adiabatic transitions
+at avoided level-crossing points give the dominant contribution to the shape of
+magnetization process. In contrast, in the ordered phase of this model and for
+fast sweeps, we find significant, size-independent jumps in the magnetization
+process. We study this phenomenon in analogy to the spinodal decomposition in
+classical ordered state and investigate its properties and its dependence on
+the system parameters. An attempt to understand the magnetization dynamics
+under field sweep in terms of the energy-level structure is made. We discuss a
+microscopic mechanism of magnetization dynamics from a viewpoint of local
+cluster flips and show that this provides a picture that explains the size
+independence. The magnetization dynamics in the fast-sweep regime is studied by
+perturbation theory and we introduce a perturbation scheme based on interacting
+Landau-Zener type processes to describe the local cluster flip dynamics.",0903.3739v1
+2011-09-07,A theoretical analysis of inertia-like switching in magnets: applications to a synthetic antiferromagnet,"The magnetization dynamics of a synthetic antiferromagnet subject to a short
+magnetic field pulse, has been studied by using a combination of
+first-principles and atomistic spin dynamics simulations. We observe switching
+phenomena on the time scale of tens of picoseconds, and inertia-like behavior
+in the magnetization dynamics. We explain the latter in terms of a dynamic
+redistribution of magnetic energy from the applied field pulse to other
+possible energy terms, such as the exchange interaction and the magnetic
+anisotropy, without invoking concepts such as inertia of an antiferromagnetic
+vector. We also demonstrate that such dynamics can also be observed in a
+ferromagnetic material where the incident field pulse pumps energy to the
+magnetic anisotropy.",1109.1414v1
+2018-06-04,Monte Carlo simulation of equilibrium and dynamic phase transition properties of an Ising bilayer,"Magnetic properties of an Ising bilayer system defined on a honeycomb lattice
+with non-magnetic interlayers which interact via an indirect exchange coupling
+have been investigated by Monte Carlo simulation technique. Equilibrium
+properties of the system exhibit ferrimagnetism with $P$-, $N$- and $Q$- type
+behaviors. Compensation phenomenon suddenly disappears with decreasing strength
+of indirect ferrimagnetic interlayer exchange coupling. Qualitative properties
+are in a good agreement with those obtained by effective field theory. In order
+to investigate the stochastic dynamics of kinetic Ising bilayer, we have
+introduced two different types of dynamic magnetic fields, namely a square
+wave, and a sinusoidally oscillating magnetic field form. For both field types,
+compensation point and critical temperature decrease with increasing amplitude
+and field period. Dynamic ferromagnetic region in the presence of square wave
+magnetic field is narrower than that obtained for sinusoidally oscillating
+magnetic field when the amplitude and the field period are the same for each
+type of dynamic magnetic fields.",1806.01002v2
+2021-06-24,Modeling Magnetic Particle Imaging for Dynamic Tracer Distributions,"Magnetic Particle Imaging (MPI) is a promising tracer-based, functional
+medical imaging technique which measures the non-linear magnetization response
+of magnetic nanoparticles to a dynamic magnetic field. For image
+reconstruction, system matrices from time-consuming calibration scans are used
+predominantly. Finding modeled forward operators for magnetic particle imaging,
+which are able to compete with measured matrices in practice, is an ongoing
+topic of research. The existing models for magnetic particle imaging are by
+design not suitable for arbitrary dynamic tracer concentrations. Neither
+modeled nor measured system matrices account for changes in the concentration
+during a single scanning cycle. In this paper we present a new MPI forward
+model for dynamic concentrations. A static model will be introduced briefly,
+followed by the changes due to the dynamic behavior of the tracer
+concentration. Furthermore, the relevance of this new extended model is
+examined by investigating the influence of the extension and example
+reconstructions with the new and the standard model.",2106.13102v2
+2022-11-14,Magnetization Dynamics in Synthetic Antiferromagnets with Perpendicular Magnetic Anisotropy,"Understanding the rich physics of magnetization dynamics in perpendicular
+synthetic antiferromagnets (p-SAFs) is crucial for developing next-generation
+spintronic devices. In this work, we systematically investigate the
+magnetization dynamics in p-SAFs combining time-resolved magneto-optical Kerr
+effect (TR-MOKE) measurements with theoretical modeling. These model analyses,
+based on a Landau-Lifshitz-Gilbert approach incorporating exchange coupling,
+provide details about the magnetization dynamic characteristics including the
+amplitudes, directions, and phases of the precession of p-SAFs under varying
+magnetic fields. These model-predicted characteristics are in excellent
+quantitative agreement with TR-MOKE measurements on an asymmetric p-SAF. We
+further reveal the damping mechanisms of two procession modes co-existing in
+the p-SAF and successfully identify individual contributions from different
+sources, including Gilbert damping of each ferromagnetic layer, spin pumping,
+and inhomogeneous broadening. Such a comprehensive understanding of
+magnetization dynamics in p-SAFs, obtained by integrating high-fidelity TR-MOKE
+measurements and theoretical modeling, can guide the design of p-SAF-based
+architectures for spintronic applications.",2211.07744v2
+2003-03-15,Dynamical magnetic relaxation: A nonlinear magnetically driven dynamo,"A non-linear, time-dependent, magnetically driven dynamo theory which shows
+how magnetically dominated configurations can relax to become helical on the
+largest scale available is presented. Coupled time-dependent differential
+equations for large scale magnetic helicity, small scale magnetic helicity,
+velocity, and the electromotive force are solved. The magnetic helicity on
+small scales relaxes to drive significant large scale helical field growth on
+dynamical (Alfv\'en crossing) time scales, independent of the magnitude of
+finite microphysical transport coefficients, after which the growing kinetic
+helicity slows the growth to a viscously limited pace. This magnetically driven
+dynamo complements the nonlinear kinetic helicity driven dynamo; for the
+latter, the growing magnetic helicity fluctuations suppress, rather than drive,
+large scale magnetic helicity growth. A unified set of equations accommodates
+both types of dynamos.",0303354v2
+2001-10-04,Dynamics of Magnetization Reversal in Models of Magnetic Nanoparticles and Ultrathin Films,"We discuss numerical and theoretical results for models of magnetization
+switching in nanoparticles and ultrathin films. The models and computational
+methods include kinetic Ising and classical Heisenberg models of highly
+anisotropic magnets which are simulated by dynamic Monte Carlo methods, and
+micromagnetics models of continuum-spin systems that are studied by
+finite-temperature Langevin simulations. The theoretical analysis builds on the
+fact that a magnetic particle or film that is magnetized in a direction
+antiparallel to the applied field is in a metastable state. Nucleation theory
+is therefore used to analyze magnetization reversal as the decay of this
+metastable phase to equilibrium. We present numerical results on magnetization
+reversal in models of nanoparticles and films, and on hysteresis in magnets
+driven by oscillating external fields.",0110103v1
+2008-10-01,Lattice disorder and Ferromagnetism in La0.67Ca0.33MnO3 nanoparticle,"We study the ferromagnetism of La0.67Ca0.33MnO3 in bulk polycrystalline,
+nanocrystalline and amorphous phase. The structural change from crystalline
+phase to amorphous phase exhibited a systematic decrease of TC(paramagnetic to
+ferromagnetic transition temperature) and spontaneous magnetization (MS). The
+experimental results suggested few more features, e.g., appearance of large
+magnetic irreversibility in the temperature dependence of magnetization, lack
+of magnetic saturation at high magnetic field, blocking of magnetization below
+TB, and enhancement of coercivity. In addition, the magnetic phase transition
+near to TC has changed from first order character in bulk sample to second
+order character in nanocrystalline and amorphous samples. We understand the
+observed magnetic features as the effects of decreasing particle size and
+increasing magnetic (spin- lattice) disorder. We noted that magnetic dynamics
+of amorphous samples is distinctly different from the nanocrystalline samples.
+The ferromagnetism of amorphous samples are comparable with the properties of
+reported amorphous ferromagnetic nanoparticles. We also demonstrate the effect
+of disorder shell in controlling the dynamics of ferromagnetic cores.",0810.0090v1
+2011-03-24,Spontaneous demagnetization of a dipolar spinor Bose gas at ultra-low magnetic field,"Quantum degenerate Bose gases with an internal degree of freedom, known as
+spinor condensates, are natural candidates to study the interplay between
+magnetism and superfluidity. In the spinor condensates made of alkali atoms
+studied so far, the spinor properties are set by contact interactions, while
+magnetization is dynamically frozen, due to small magnetic dipole-dipole
+interactions. Here, we study the spinor properties of S=3 $^{52}$Cr atoms, in
+which relatively strong dipole-dipole interactions allow changes in
+magnetization. We observe a phase transition between a ferromagnetic phase and
+an unpolarized phase when the magnetic field is quenched to an extremely low
+value, below which interactions overwhelm the linear Zeeman effect. The BEC
+magnetization changes due to magnetic dipole-dipole interactions that set the
+dynamics. Our work opens up the experimental study of quantum magnetism with
+free magnetization using ultra-cold atoms.",1103.4819v1
+2012-05-25,Dynamics of the Chiral Magnetic Effect in a weak magnetic field,"We investigate the real-time dynamics of the chiral magnetic effect in
+quantum electrodynamics (QED) and quantum chromodynamics (QCD). We consider a
+field configuration of parallel (chromo)electric and (chromo)magnetic fields
+with a weak perpendicular electromagnetic magnetic field. The chiral magnetic
+effect induces an electromagnetic current along this perpendicular magnetic
+field, which we will compute using linear response theory. We discuss specific
+results for a homogeneous sudden switch-on and a pulsed (chromo)electric field
+in a static and homogeneous (chromo)magnetic field. Our methodology can be
+easily extended to more general situations. The results are useful for
+investigating the chiral magnetic effect with heavy ion collisions and with
+lasers that create strong electromagnetic fields. As a side result we obtain
+the rate of chirality production for massive fermions in parallel electric and
+magnetic fields that are static and homogeneous.",1205.5679v1
+2013-06-05,Magnetic chains: From self-buckling to self-assembly,"Spherical neodymium-iron-boron magnets are perman-ent magnets that can be
+assembled into a variety of structures due to their high magnetic strength. A
+one-dimensional chain of these magnets responds to mechanical loadings in a
+manner reminiscent of an elastic rod. We investigate the macroscopic mechanical
+properties of assemblies of ferromagnetic spheres by considering chains, rings,
+and chiral cylinders of magnets. Based on energy estimates and simple
+experiments, we introduce an effective magnetic bending stiffness for a chain
+of magnets and show that, used in conjunction with classic results for elastic
+rods, it provides excellent estimates for the buckling and vibration dynamics
+of magnetic chains. We then use this estimate to understand the dynamic
+self-assembly of a cylinder from an initially straight chain of magnets.",1306.1014v2
+2015-02-23,Torsion induced effects in magnetic nanowires,"Magnetic helix wire is one of the most simple magnetic systems which manifest
+properties of both curvature and torsion. There exist two equilibrium states in
+the helix wire with easy-tangential anisotropy: a quasi-tangential
+magnetization distribution in case of relatively small curvatures and torsions,
+and an onion state in opposite case. In the last case the magnetization is
+close to tangential one, deviations are caused by the torsion and curvature.
+Possible equilibrium magnetization states in the helix magnet with different
+anisotropy directions are studied theoretically. The torsion also essentially
+influences the spin-wave dynamics, acting as an effective magnetic field.
+Originated from the curvature induced effective Dzyaloshinskii interaction,
+this magnetic field leads to the coupling between the helix chirality and the
+magnetochirality, it breaks mirror symmetry in spin-wave spectrum. All
+analytical predictions on magnetization statics an dynamics are well confirmed
+by the direct spin lattice simulations.",1502.06482v3
+2017-02-15,Triad interactions and the bidirectional turbulent cascade of magnetic helicity,"Using direct numerical simulations we demonstrate that magnetic helicity
+exhibits a bidirectional turbulent cascade at high but finite magnetic Reynolds
+numbers. Despite the injection of positive magnetic helicity in the flow, we
+observe that magnetic helicity of opposite signs is generated between large and
+small scales. We explain these observations by carrying out an analysis of the
+magnetohydrodynamic equations reduced to triad interactions using the Fourier
+helical decomposition. Within this framework, the direct cascade of positive
+magnetic helicity arises through triad interactions that are associated with
+small scale dynamo action, while the occurrence of negative magnetic helicity
+at large scales is explained through triad interactions that are related to
+stretch-twist-fold dynamics and small scale dynamo action, which compete with
+the inverse cascade of positive magnetic helicity. Our analytical and numerical
+results suggest that the direct cascade of magnetic helicity is a finite
+magnetic Reynolds number $Rm$ effect that will vanish in the limit $Rm \to
+\infty$.",1702.04787v2
+2017-04-12,Ultra-fast magnetization manipulation using single femtosecond light and hot-electrons pulse,"Current induced magnetization manipulation is a key issue for spintronic
+application. Therefore, deterministic switching of the magnetization at the
+picoseconds timescale with a single electronic pulse represents a major step
+towards the future developments of ultrafast spintronic. Here, we have studied
+the ultrafast magnetization dynamics in engineered Gdx[FeCo]1-x based structure
+to compare the effect of femtosecond laser and hot-electrons pulses. We
+demonstrate that a single femtosecond hot-electrons pulse allows a
+deterministic magnetization reversal in either Gd-rich and FeCo-rich alloys
+similarly to a femtosecond laser pulse. In addition, we show that the limiting
+factor of such manipulation for perpendicular magnetized films arises from the
+multi-domain formation due to dipolar interaction. By performing time resolved
+measurements under various field, we demonstrate that the same magnetization
+dynamics is observed for both light and hot-electrons excitation and that the
+full magnetization reversal take place within 5 ps. The energy efficiency of
+the ultra-fast current induced magnetization manipulation is optimized thanks
+to the ballistic transport of hot-electrons before reaching the GdFeCo magnetic
+layer.",1704.03749v1
+2019-10-02,Magnetic Scattering Chapter,"The present chapter reviews current neutron and x-ray scattering techniques
+employed to elucidate the magnetic structures and spin dynamics of magnetic
+materials. Both techniques provide measurements as a function of the energy and
+the momentum transferred from the spin system to the probe particles, in terms
+of five-dimensional data sets as a function of various thermodynamic fields at
+the control of the experimenter. These scattering techniques yield fundamental
+information about the equal-time correlations such the magnetic configuration
+and symmetry, as well as the dynamics that determine the exchange interactions
+for prototypical systems that behave as linear, planar, or three-dimensional
+systems. Historically, neutron scattering has been the magnetic scattering
+technique of choice for such investigations, but the extraordinary advances in
+resonant x-ray scattering techniques have enable new types of magnetic
+scattering measurements. The type of information obtained with the two
+techniques is largely complementary and depends on the interests of the
+investigators. We discuss these possibilities and provide numerous examples of
+the techniques applied to different classes of magnetic systems.",1910.01218v1
+2022-08-02,Emergence of low temperature glassy dynamics in Ru substituted non magnetic insulator CaHfO3,"Non magnetic insulators/semiconductors with induced magnetism introduced via
+transition metal substitution are one of the promising materials in the field
+of spintronic, magnetoelectronics and magneto optical devices. In this context,
+here, we focus on magnetism induced in a non magnetic insulator CaHfO3, by the
+substitution of 4d element Ru, at Hf site. Structural investigations indicate
+that substitution of Ru4+ (up to 50%) does not affect the original crystal
+structure of the parent compound. Magnetic studies divulge a crossover from a
+diamagnetic to paramagnetic state with 20% Ru substitution. Further replacement
+of Hf results in a glassy magnetic state in CaHf1-xRuxO3 (0.3 < x < 0.5). The
+nature of the low temperature glassiness (below 20 K) in these compositions is
+confirmed through Vogel Fulcher and Power law, along with, magnetic memory
+effect and relaxation dynamics. The observed glassiness is explained through
+the phenomenological hierarchical model. Our studies indicate that the presence
+of competing short range interactions among randomly arranged Ru cations in non
+magnetic insulator CaHfO3 are responsible for the observed low temperature
+magnetic state in this series with compositions > 0.25.",2208.01282v1
+2022-11-02,A study of global magnetic helicity in self-consistent spherical dynamos,"Magnetic helicity is a fundamental constraint in both ideal and resistive
+magnetohydrodynamics. Measurements of magnetic helicity density on the Sun and
+other stars are used to interpret the internal behaviour of the dynamo
+generating the global magnetic field. In this note, we study the behaviour of
+the global relative magnetic helicity in three self-consistent spherical dynamo
+solutions of increasing complexity. Magnetic helicity describes the global
+linkage of the poloidal and toroidal magnetic fields (weighted by magnetic
+flux), and our results indicate that there are preferred states of this
+linkage. This leads us to propose that global magnetic reversals are, perhaps,
+a means of preserving this linkage, since, when only one of the poloidal or
+toroidal fields reverses, the preferred state of linkage is lost. It is shown
+that magnetic helicity indicates the onset of reversals and that this signature
+may be observed at the outer surface.",2211.01356v1
+2020-05-19,Numerical Analysis of the Screening Current-Induced Magnetic Field in the HTS Insert Dipole Magnet Feather-M2.1-2,"Screening currents are field-induced dynamic phenomena which occur in
+superconducting materials, leading to persistent magnetization. Such currents
+are of importance in ReBCO tapes, where the large size of the superconducting
+filaments gives rise to strong magnetization phenomena. In consequence,
+superconducting accelerator magnets based on ReBCO tapes might experience a
+relevant degradation of the magnetic field quality in the magnet aperture,
+eventually leading to particle beam instabilities. Thus, persistent
+magnetization phenomena need to be accurately evaluated. In this paper, the 2D
+finite element model of the Feather-M2.1-2 magnet is presented. The model is
+used to analyze the influence of the screening current-induced magnetic field
+on the field quality in the magnet aperture. The model relies on a coupled
+field formulation for eddy current problems in time-domain. The formulation is
+introduced and verified against theoretical references. Then, the numerical
+model of the Feather-M2.1-2 magnet is detailed, highlighting the key
+assumptions and simplifications. The numerical results are discussed and
+validated with available magnetic measurements. A satisfactory agreement is
+found, showing the capability of the numerical tool in providing accurate
+analysis of the dynamic behavior of the Feather-M2.1-2 magnet.",2005.09467v2
+2014-07-08,Competing magnetic phases and field-induced dynamics in DyRuAsO,"Analysis of neutron diffraction, dc magnetization, ac magnetic
+susceptibility, heat capacity, and electrical resistivity for DyRuAsO in an
+applied magnetic field are presented at temperatures near and below those at
+which the structural distortion (T_S = 25 K) and subsequent magnetic ordering
+(T_N = 10.5 K) take place. Powder neutron diffraction is used to determine the
+antiferromagnetic order of Dy moments of magnitude 7.6(1) mu_B in the absence
+of a magnetic field, and demonstrate the reorientation of the moments into a
+ferromagnetic configuration upon application of a magnetic field. Dy magnetism
+is identified as the driving force for the structural distortion. The magnetic
+structure of analogous TbRuAsO is also reported. Competition between the two
+magnetically ordered states in DyRuAsO is found to produce unusual physical
+properties in applied magnetic fields at low temperature. An additional phase
+transition near T* = 3 K is observed in heat capacity and other properties in
+fields greater than about 3 T. Magnetic fields of this magnitude also induce
+spin-glass-like behavior including thermal and magnetic hysteresis, divergence
+of zero-field-cooled and field-cooled magnetization, frequency dependent
+anomalies in ac magnetic susceptibility, and slow relaxation of the
+magnetization. This is remarkable since DyRuAsO is a stoichiometric material
+with no disorder detected by neutron diffraction, and suggests analogies with
+spin-ice compounds and related materials with strong geometric frustration.",1407.2184v1
+2020-03-18,On the saturation mechanism of the fluctuation dynamo at ${\text{Pr}_\mathrm{M}} \ge 1$,"The presence of magnetic fields in many astrophysical objects is due to
+dynamo action, whereby a part of the kinetic energy is converted into magnetic
+energy. A turbulent dynamo that produces magnetic field structures on the same
+scale as the turbulent flow is known as the fluctuation dynamo. We use
+numerical simulations to explore the nonlinear, statistically steady state of
+the fluctuation dynamo in driven turbulence. We demonstrate that as the
+magnetic field growth saturates, its amplification and diffusion are both
+affected by the back-reaction of the Lorentz force upon the flow. The
+amplification of the magnetic field is reduced due to stronger alignment
+between the velocity field, magnetic field, and electric current density.
+Furthermore, we confirm that the amplification decreases due to a weaker
+stretching of the magnetic field lines. The enhancement in diffusion relative
+to the field line stretching is quantified by a decrease in the computed local
+value of the magnetic Reynolds number. Using the Minkowski functionals, we
+quantify the shape of the magnetic structures produced by the dynamo as
+magnetic filaments and ribbons in both kinematic and saturated dynamos and
+derive the scalings of the typical length, width, and thickness of the magnetic
+structures with the magnetic Reynolds number. We show that all three of these
+magnetic length scales increase as the dynamo saturates. The magnetic
+intermittency, strong in the kinematic dynamo (where the magnetic field
+strength grows exponentially) persists in the statistically steady state, but
+intense magnetic filaments and ribbons are more volume-filling.",2003.07997v1
+2002-08-20,Dynamics of QCD in a Strong Magnetic Field,"QCD in a strong magnetic field yields an example of a rich, sophisticated and
+controllable dynamics.",0208180v1
+2012-03-27,A Generic Property of Exact Magnetic Lagrangians,"We prove that for the set of Exact Magnetic Lagrangians the property ""There
+exist finitely many static classes for every cohomology class"" is generic. We
+also prove some dynamical consequences of this property.",1203.6095v1
+2017-02-21,Numerical simulations of magnetic billiards in a convex domain in $\mathbb{R}^2$,"We present numerical simulations of magnetic billiards inside a convex domain
+in the plane.",1702.06309v1
+2003-06-03,Local Relaxation and Collective Stochastic Dynamics,"Damping and thermal fluctuations have been introduced to collective normal
+modes of a magnetic system in recent modeling of dynamic thermal magnetization
+processes. The connection between this collective stochastic dynamics and
+physical local relaxation processes is investigated here. A system of two
+coupled magnetic grains embedded in two separate oscillating thermal baths is
+analyzed with no \QTR{it}{a priori} assumptions except that of a Markovian
+process. It is shown explicitly that by eliminating the oscillating thermal
+bath variables, collective stochastic dynamics occurs in the normal modes of
+the magnetic system. The grain interactions cause local relaxation to be felt
+by the collective system and the dynamic damping to reflect the system
+symmetry. This form of stochastic dynamics is in contrast to a common
+phenomenological approach where a thermal field is added independently to the
+dynamic equations of each discretized cell or interacting grain. The dependence
+of this collective stochastic dynamics on the coupling strength of the magnetic
+grains and the relative local damping is discussed.",0306047v1
+2016-11-09,Simultaneous imaging of strain waves and induced magnetization dynamics at the nanometer scale,"Changes in strain can be used to modify electronic and magnetic properties in
+crystal structures, to manipulate nanoparticles and cells, or to control
+chemical reactions. The magneto-elastic (ME) effect--the change of magnetic
+properties caused by the elastic deformation (strain) of a magnetic
+material--has been proposed as an alternative approach to magnetic fields for
+the low power control of magnetization states of nanoelements since it avoids
+charge currents, which entail ohmic losses. Multiferroic heterostructures
+\cite{Zheng2004} and nanocomposites have exploited this effect in search of
+electric control of magnetic states, mostly in the static regime. Quantitative
+studies combining strain and magnetization dynamics are needed for practical
+applications and so far, a high resolution technique for this has been lacking.
+Here, we have studied the effect of the dynamic strain accompanying a surface
+acoustic wave on magnetic nanostructures. We have simultaneously imaged the
+temporal evolution of both strain waves and magnetization dynamics of
+nanostructures at the picosecond timescale. The newly developed experimental
+technique, based on X-ray microscopy, is versatile and provides a pathway to
+the study of strain-induced effects at the nanoscale. Our results provide
+fundamental insight in the coupling between strain and magnetization in
+nanostructures at the picosecond timescale, having implications in the design
+of strain-controlled magnetostrictive nano-devices.",1611.02847v1
+2020-11-16,Magnetic Dynamic Polymers for Modular Assembling and Reconfigurable Morphing Architectures,"Shape morphing magnetic soft materials, composed of magnetic particles in a
+soft polymer matrix, can transform shapes reversibly, remotely, and rapidly,
+finding diverse applications in actuators, soft robotics, and biomedical
+devices. To achieve on-demand and sophisticated shape morphing, the
+manufacturing of structures with complex geometry and magnetization
+distribution is highly desired. Here, we report a magnetic dynamic polymer
+composite composed of hard-magnetic microparticles in a dynamic polymer network
+with thermal-responsive reversible linkages, which permit functionalities
+including targeted welding, magnetization reprogramming, and structural
+reconfiguration. These functions not only provide highly desirable structural
+and material programmability and reprogrammability but also enable the
+manufacturing of structures with complex geometry and magnetization
+distribution. The targeted welding is exploited for modular assembling of
+fundamental building modules with specific logics for complex actuation. The
+magnetization reprogramming enables altering the morphing mode of the
+manufactured structures. The shape reconfiguration under magnetic actuation is
+coupled with network plasticity to remotely transform two-dimensional
+tessellations into complex three-dimensional architectures, providing a new
+strategy of manufacturing functional soft architected materials such as
+three-dimensional kirigami. We anticipate that the reported magnetic dynamic
+polymer provides a new paradigm for the design and manufacturing of future
+multifunctional assemblies and reconfigurable morphing architectures and
+devices.",2011.07736v1
+2024-02-08,Balancing a 3D Inverted Pendulum using Remote Magnetic Manipulation,"Remote magnetic manipulation offers wireless control over magnetic objects,
+which has important medical applications, such as targeted drug delivery and
+minimally invasive surgeries. Magnetic manipulation systems are categorized
+into systems using permanent magnets and systems based on electromagnets.
+Electro-Magnetic Navigation Systems (eMNSs) are believed to have a superior
+actuation bandwidth, facilitating trajectory tracking and disturbance
+rejection. This greatly expands the range of potential medical applications and
+includes even dynamic environments as encountered in cardiovascular
+interventions. In order to highlight the dynamic capabilities of eMNSs, we
+successfully stabilize a (non-magnetic) inverted pendulum on the tip of a
+magnetically driven arm. Our method employs a model-based design approach,
+where we capture the dynamics that describe the interaction of the pendulum
+system and the magnetic field through Lagrangian mechanics. Using system
+identification we estimate the system parameters, the actuation bandwidth, and
+characterize the system's nonlinearity. We design a state-feedback controller
+to stabilize the inherently unstable dynamics, and compensate for errors
+arising from the calibration of the magnetic field and the angle measurement
+system. Additionally, we integrate an iterative learning control scheme that
+allows us to accurately track non-equilibrium trajectories while concurrently
+maintaining stability of the inverted pendulum. To our knowledge, this is the
+first effort to stabilize a 3D inverted pendulum through remote magnetic
+manipulation.",2402.06012v1
+2013-01-14,Polarised Electromagnetic wave propagation through the ferromagnet: Phase boundary of dynamic phase transition,"The dynamical responses of ferromagnet to the propagating electromagnetic
+field wave passing through it are modelled and studied here by Monte Carlo
+simulation in two dimensional Ising ferromagnet. Here, the electromagnetic wave
+is linearly polarised in such a way that the direction of magnetic field is
+parallel to that of the magnetic momemts (spins). The coherent propagating mode
+of spin-clusters is observed. The time average magnetisation over the full
+cycle (time) of the field defines the order parameter of the dynamic
+transition. Depending on the value of the temperature and the amplitude of the
+propagating magnetic field wave, a dynamical phase transition is observed. The
+dynamic transition was detected by studying the temperature dependences of the
+dynamic order parameter, the variance of the dynamic order parameter, the
+derivative of the dynamic order parameter and the dynamic specific heat. The
+phase boundaries of the dynamic transitions were drawn for two different values
+of the wave lengths of the propagating magnetic field wave. The phase boundary
+was observed to shrink (inward) for lower speed of propagation of the EM wave.
+The divergence of the releavant length scale was observed at the transition
+point.",1301.3071v2
+2013-08-19,Dynamical bar-mode instability in rotating and magnetized relativistic stars,"We present three-dimensional simulations of the dynamical bar-mode
+instability in magnetized and differentially rotating stars in full general
+relativity. Our focus is on the effects that magnetic fields have on the
+dynamics and the onset of the instability. In particular, we perform
+ideal-magnetohydrodynamics simulations of neutron stars that are known to be
+either stable or unstable against the purely hydrodynamical instability, but to
+which a poloidal magnetic field in the range of $10^{14}$--$10^{16}$ G is
+superimposed initially. As expected, the differential rotation is responsible
+for the shearing of the poloidal field and the consequent linear growth in time
+of the toroidal magnetic field. The latter rapidly exceeds in strength the
+original poloidal one, leading to a magnetic-field amplification in the the
+stars. Weak initial magnetic fields, i.e. $ \lesssim 10^{15}$ G, have
+negligible effects on the development of the dynamical bar-mode instability,
+simply braking the stellar configuration via magnetic-field shearing, and over
+a timescale for which we derived a simple algebraic expression. On the other
+hand, strong magnetic fields, i.e. $\gtrsim 10^{16}$ G, can suppress the
+instability completely, with the precise threshold being dependent also on the
+amount of rotation. As a result, it is unlikely that very highly magnetized
+neutron stars can be considered as sources of gravitational waves via the
+dynamical bar-mode instability.",1308.3989v1
+2023-04-19,Real-time observation of magnetization and magnon dynamics in a two-dimensional topological antiferromagnet MnBi2Te4,"Atomically thin van der Waals magnetic materials have not only provided a
+fertile playground to explore basic physics in the two-dimensional (2D) limit
+but also created vast opportunities for novel ultrafast functional devices.
+Here we systematically investigate ultrafast magnetization dynamics and spin
+wave dynamics in few-layer topological antiferromagnetic MnBi2Te4 crystals as a
+function of layer number, temperature, and magnetic field. We find
+laser-induced (de)magnetization processes can be used to accurately track the
+distinct magnetic states in different magnetic field regimes, including showing
+clear odd-even layer number effects. In addition, strongly field-dependent
+antiferromagnetic magnon modes with tens of gigahertz frequencies are optically
+generated and directly observed in the time domain. Remarkably, we find that
+magnetization and magnon dynamics can be observed in not only the time-resolved
+magneto-optical Kerr effect but also the time resolved reflectivity, indicating
+strong correlation between the magnetic state and electronic structure. These
+measurements present the first comprehensive overview of ultrafast spin
+dynamics in this novel 2D antiferromagnet, paving the way for potential
+applications in 2D antiferromagnetic spintronics and magnonics as well as
+further studies of ultrafast control of both magnetization and topological
+quantum states.",2304.09390v2
+2009-06-09,Unified nonequilibrium dynamical theory for exchange bias and training effects,"We investigate the exchange bias and training effects in the FM/AF
+heterostructures using a unified Monte Carlo dynamical approach. This real
+dynamical method has been proved reliable and effective in simulating dynamical
+magnetization of nanoscale magnetic systems. The magnetization of the
+uncompensated AF layer is still open after the first field cycling is finished.
+Our simulated results show obvious shift of hysteresis loops (exchange bias)
+and cycling dependence of exchange bias (training effect) when the temperature
+is below 45 K. The exchange bias fields decrease with decreasing the cooling
+rate or increasing the temperature and the number of the field cycling. With
+the simulations, we show the exchange bias can be manipulated by controlling
+the cooling rate, the distributive width of the anisotropy energy, or the
+magnetic coupling constants. Essentially, these two effects can be explained on
+the basis of the microscopical coexistence of both reversible and irreversible
+moment reversals of the AF domains. Our simulated results are useful to really
+understand the magnetization dynamics of such magnetic heterostructures. This
+unified nonequilibrium dynamical method should be applicable to other exchange
+bias systems.",0906.1753v1
+2017-10-26,Dynamical spin accumulation in large-spin magnetic molecules,"The frequency-dependent transport through a nano-device containing a
+large-spin magnetic molecule is studied theoretically in the Kondo regime.
+Specifically, the effect of magnetic anisotropy on dynamical spin accumulation
+is of primary interest. Such accumulation arises due to finite off-diagonal in
+spin components of the dynamical conductance. Here, employing the Kubo
+formalism and the numerical renormalization group (NRG) method, we demonstrate
+that the dynamical transport properties strongly depend on magnetic
+configuration of the device and intrinsic parameters of the molecule.
+Specifically, the effect of dynamical spin accumulation is found to be greatly
+affected by the type of magnetic anisotropy exhibited by the molecule, and it
+develops for frequencies corresponding to the Kondo temperature. For the
+parallel magnetic configuration of the device, the presence of dynamical spin
+accumulation is conditioned by the interplay of ferromagnetic-lead-induced
+exchange field and the Kondo correlations.",1710.09623v1
+2019-03-20,Nonlinear magnetization dynamics driven by strong terahertz fields,"We present a comprehensive experimental and numerical study of magnetization
+dynamics triggered in a thin metallic film by single-cycle terahertz pulses of
+$\sim20$ MV/m electric field amplitude and $\sim1$ ps duration. The
+experimental dynamics is probed using the femtosecond magneto-optical Kerr
+effect (MOKE), and it is reproduced numerically using macrospin simulations.
+The magnetization dynamics can be decomposed in three distinct processes: a
+coherent precession of the magnetization around the terahertz magnetic field,
+an ultrafast demagnetization that suddenly changes the anisotropy of the film,
+and a uniform precession around the equilibrium effective field that is relaxed
+on the nanosecond time scale, consistent with a Gilbert damping process.
+Macrospin simulations quantitatively reproduce the observed dynamics, and allow
+us to predict that novel nonlinear magnetization dynamics regimes can be
+attained with existing table-top terahertz sources.",1903.08395v2
+2023-03-29,General-relativistic simulations of the formation of a magnetized hybrid star,"Strongly magnetized neutron stars are popular candidates for producing
+detectable electromagnetic and gravitational-wave signals. A rapid density
+increase in a neutron star core could also trigger the phase transition from
+hadrons to deconfined quarks and form a hybrid star. This formation process
+could release a considerable amount of energy in the form of gravitational
+waves and neutrinos. Hence, the formation of a magnetized hybrid star is an
+interesting scenario for detecting all these signals. These detections may
+provide essential probes for the magnetic field and composition of such stars.
+Thus far, a dynamical study of the formation of a magnetized hybrid star has
+yet to be realized. Here, we investigate the formation dynamics and the
+properties of a magnetized hybrid star through dynamical simulations. We find
+that the maximum values of rest-mass density and magnetic field strength
+increase slightly and these two quantities are coupled in phase during the
+formation. We then demonstrate that all microscopic and macroscopic quantities
+of the resulting hybrid star vary dramatically when the maximum magnetic field
+strength goes beyond a threshold of $\sim 5 \times 10^{17}$ G but they are
+insensitive to the magnetic field below this threshold. Specifically, the
+magnetic deformation makes the rest-mass density drop significantly,
+suppressing the matter fraction in the mixed phase. Therefore, this work
+provides a solid support for the magnetic effects on a hybrid star, so it is
+possible to link observational signals from the star to its magnetic field
+configuration.",2303.16820v1
+2022-07-14,Attosecond magnetization dynamics in non-magnetic materials driven by intense femtosecond lasers,"Irradiating solids with ultrashort laser pulses is known to initiate
+femtosecond timescale magnetization dynamics. However, sub-femtosecond spin
+dynamics have not yet been observed or predicted. Here, we explore ultrafast
+light-driven spin dynamics in a highly non-resonant strong-field regime.
+Through state-of-the-art ab-initio calculations, we predict that a non-magnetic
+material can be transiently transformed into a magnetic one via dynamical
+extremely nonlinear spin-flipping processes, which occur on attosecond
+timescales and are mediated by a combination of multi-photon and spin-orbit
+interactions. These are non-perturbative non-resonant analogues to the inverse
+Faraday effect that build up from cycle-to-cycle as electrons gain angular
+momentum. Remarkably, we show that even for linearly polarized driving, where
+one does not intuitively expect any magnetic response, the magnetization
+transiently oscillates as the system interacts with light. This oscillating
+response is enabled by transverse anomalous light-driven currents in the solid,
+and typically occurs on timescales of ~500 attoseconds. We further demonstrate
+that the speed of magnetization can be controlled by tuning the laser
+wavelength and intensity. An experimental set-up capable of measuring these
+dynamics through pump-probe transient absorption spectroscopy is outlined and
+simulated. Our results pave the way for new regimes of ultrafast manipulation
+of magnetism.",2207.06711v1
+2002-04-08,Determining the Saddle Point in Micromagnetic Models of Magnetization Switching,"A numerical model of single-domain nanoscale iron magnets fabricated using
+scanning-microscope-assisted chemical vapor deposition is simulated using
+finite-temperature micromagnetics. A Projective-dynamics method is used to
+determine the magnetization at the saddle point as a function of temperature.
+This magnetization is found to decrease linearly as the temperature is raised.",0204180v1
+2004-01-08,On Effective Hamiltonians for Adiabatic Perturbations of Magnetic Schrodinger Operators,"We construct almost invariant subspaces and the corresponding effective
+Hamiltonian for magnetic Bloch bands. We also discuss the question of the
+dynamics related to the effective Hamiltonian. We assume that the magnetic and
+electric potentials are slowly varying perturbations of the potential of a
+constant magnetic field and a periodic lattice potential, respectively.",0401017v1
+2003-10-01,Compressible dynamics of magnetic field lines for incompressible MHD flows,"It is demonstrated that the deformation of magnetic field lines in
+incompressible magnetohydrodynamic flows results from a compressible mapping.
+Appearance of zeroes for the mapping Jacobian correspond to the breaking of
+magnetic field lines, associated with local blowup of the magnetic field. The
+possibility of such events is found to be unlikely in two dimensions but not in
+three dimensions.",0310006v1
+2009-04-21,Chaotic magnetic field reversals in turbulent dynamos,"We present direct numerical simulations of reversals of the magnetic field
+generated by swirling flows in a spherical domain. In agreement with a recent
+model, we observe that coupling dipolar and quadrupolar magnetic modes by an
+asymmetric forcing of the flow generates field reversals. In addition, we show
+that this mechanism strongly depends on the value of the magnetic Prandtl
+number.",0904.3343v1
+2011-11-22,On magnetic leaf-wise intersections,"In this article we introduce the notion of a magnetic leaf-wise intersection
+point which is a generalization of the leaf-wise intersection point with
+magnetic effects. We also prove the existence of magnetic leaf-wise
+intersection points under certain topological assumptions.",1111.5115v2
+2014-11-27,The critical relaxation of the model of iron-vanadium magnetic superlattice,"The critical relaxation of iron-vanadium magnetic superlattice in case of the
+equality between interlayer and intralayer exchange interactions is
+investigated. The dynamic and static critical exponents of the model are
+calculated. A value of the critical temperature is evaluated.",1411.7505v1
+2019-09-30,Integrable magnetic flows on the two-torus: Zoll examples and systolic inequalities,"In this paper we study some aspects of integrable magnetic systems on the
+two-torus. On the one hand, we construct the first non-trivial examples with
+the property that all magnetic geodesics with unit speed are closed. On the
+other hand, we show that those integrable magnetic systems admitting a global
+surface of section satisfy a sharp systolic inequality.",1909.13821v1
+2022-05-11,Homotopy transitions and 3D magnetic solitons,"This work provides a concept for three-dimensional magnetic solitons based on
+mapping the homotopy path between various two-dimensional solutions onto the
+third spatial axis. The representative examples of statically stable
+configurations of that type in the model of an isotropic chiral magnet are
+provided. Various static and dynamic properties of such three-dimensional
+magnetic solitons are discussed in detail.",2205.05379v1
+2022-07-25,Spin Coulomb drag by non-equilibrium magnetic textures,"Interaction between local magnetization and conduction electrons is
+responsible for a variety of phenomena in magnetic materials. We have shown
+that the spin-dependent motive force induced by magnetization dynamics in a
+conducting ferromagnet lead to the spin Coulomb drag effect. The spin Coulomb
+drag an intrinsic friction mechanism which operates whenever the average
+velocities of up-spin and down-spin electrons differ.",2207.11978v1
+1997-08-03,A Vorticity-Magnetic Field Dynamo Instability,"We generalize the mean field magnetic dynamo to include local evolution of
+the mean vorticity in addition to the mean magnetic field. The coupled
+equations exhibit a general mean field dynamo instability that enables the
+transfer of turbulent energy to the magnetic field and vorticity on larger
+scales. The growth of the vorticity and magnetic field both require helical
+turbulence which can be supplied by an underlying global rotation. The dynamo
+coefficients are derived including the backreaction from the mean magnetic
+field to lowest order. We find that a mean vorticity field can actually seed
+exponential growth of mean magnetic field from only a small scale seed magnetic
+field, without the need for a seed mean magnetic field. The equations decouple
+when the fluctuating velocity and magnetic field cross-correlations vanish,
+resulting in the separate mean field magnetic and mean field vorticity dynamo
+equations.",9708019v1
+2006-09-22,Buoyant magnetic flux ropes in a magnetized stellar envelope: Idealized numerical 2.5-D MHD simulations,"Context: The context of this paper is buoyant toroidal magnetic flux ropes,
+which is a part of flux tube dynamo theory and the framework of solar-like
+magnetic activity. Aims: The aim is to investigate how twisted magnetic flux
+ropes interact with a simple magnetized stellar model envelope--a magnetic
+""convection zone""--especially to examine how the twisted magnetic field
+component of a flux rope interacts with a poloidal magnetic field in the
+convection zone. Method: Both the flux ropes and the atmosphere are modelled as
+idealized 2.5-dimensional concepts using high resolution numerical
+magneto-hydrodynamic (MHD) simulations. Results: It is illustrated that twisted
+toroidal magnetic flux ropes can interact with a poloidal magnetic field in the
+atmosphere to cause a change in both the buoyant rise dynamics and the flux
+rope's geometrical shape. The details of these changes depend primarily on the
+polarity and strength of the atmospheric field relative to the field strength
+of the flux rope. It is suggested that the effects could be verified
+observationally.",0609630v1
+2002-11-21,Temperature-dependent magnetization in diluted magnetic semiconductors,"We calculate magnetization in magnetically doped semiconductors assuming a
+local exchange model of carrier-mediated ferromagnetic mechanism and using a
+number of complementary theoretical approaches. In general, we find that the
+results of our mean-field calculations, particularly the dynamical mean field
+theory results, give excellent qualitative agreement with the experimentally
+observed magnetization in systems with itinerant charge carriers, such as
+Ga_{1-x}Mn_xAs with 0.03 < x < 0.07, whereas our percolation-theory-based
+calculations agree well with the existing data in strongly insulating
+materials, such as Ge_{1-x}Mn_x. We comment on the issue of non-mean-field like
+magnetization curves and on the observed incomplete saturation magnetization
+values in diluted magnetic semiconductors from our theoretical perspective. In
+agreement with experimental observations, we find the carrier density to be the
+crucial parameter determining the magnetization behavior. Our calculated
+dependence of magnetization on external magnetic field is also in excellent
+agreement with the existing experimental data.",0211496v1
+2014-12-29,Magnetic balltracking: Tracking the photospheric magnetic flux,"Context: One aspect of understanding the dynamics of the quiet Sun is to
+quantify the evolution of the flux within small-scale magnetic features. These
+features are routinely observed in the quiet photosphere and were given various
+names, such as pores, knots, magnetic patches. Aims: This work presents a new
+algorithm for tracking the evolution of the broad variety of small-scale
+magnetic features in the photosphere, with a precision equal to the
+instrumental resolution. Methods: We have developed a new technique to track
+the evolution of the individual magnetic features from magnetograms, called
+""magnetic balltracking"". It quantifies the flux of the tracked features, and it
+can track the footpoints of magnetic field lines inferred from magnetic field
+extrapolation. The algorithm can detect and quantify flux emergence, as well as
+flux cancellation. Results: The capabilities of magnetic balltracking are
+demonstrated with the detection and the tracking of two cases of magnetic flux
+emergence that lead to the brightening of X-ray loops. The maximum emerged flux
+ranges from 10^{18} Mx to 10^{19} Mx (unsigned flux) when the X-ray loops are
+observed.",1412.8294v1
+2015-09-02,Dynamo model for the inverse transfer of magnetic energy in a nonhelical decaying magnetohydrodynamic turbulence,"The inverse cascade of magnetic energy occurs when helicity or rotational
+instability exists in the magnetohydrodynamic (MHD) system. This well known
+phenomenon has been considered as a basis for the large scale magnetic field in
+universe. However nonhelical magnetic energy in a decaying MHD system also
+migrates toward the large scale, which holds vital clues to the origin of large
+scale magnetic field in a quiescent astrophysical system. Zeldovich's rope
+dynamo model is considered as a basic and symbolistic model of magnetic field
+amplification. However, the rope model assuming specific external forces like
+buoyancy or Coriolis force is not appropriate for a decaying turbulent system
+without any external force. So we suggest a new dynamo model based on magnetic
+induction equation excluding a forcing source. This model shows the expansion
+and growth of magnetic field (flux) is basically the redistribution of energy
+in the system. The transfer of magnetic energy is in fact a successive
+induction of magnetic field resulted from the interaction between the fluid
+motion and seed magnetic field. We also discuss about an analytic theorem based
+on the scaling invariant MHD equation.",1509.00788v3
+2020-01-27,Non-exponential magnetic relaxation in magnetic nanoparticles for hyperthermia,"Magnetic nanoparticle based hyperthermia emerged as a potential tool for
+treating malignant tumours. The efficiency of the method relies on the
+knowledge of magnetic properties of the samples; in particular, knowledge of
+the frequency dependent complex magnetic susceptibility is vital to optimize
+the irradiation conditions and to provide feedback for material science
+developments. We study the frequency-dependent magnetic susceptibility of an
+aqueous ferrite suspension for the first time using non-resonant and resonant
+radiofrequency reflectometry. We identify the optimal measurement conditions
+using a standard solenoid coil, which is capable of providing the complex
+magnetic susceptibility up to 150 MHz. The result matches those obtained from a
+radiofrequency resonator for a few discrete frequencies. The agreement between
+the two different methods validates our approach. Surprisingly, the dynamic
+magnetic susceptibility cannot be explained by an exponential magnetic
+relaxation behavior even when we consider a particle size-dependent
+distribution of the relaxation parameter.",2001.09774v1
+2020-03-18,Thermally induced generation and annihilation of magnetic chiral skyrmion bubbles and achiral bubbles in Mn-Ni-Ga Magnets,"Magnetic chiral skyrmion bubbles and achiral bubbles are two independent
+magnetic domain structures, in which the former with equivalent winding number
+to skyrmions offers great promise as information carriers for further
+spintronic devices. Here, in this work, we experimentally investigate the
+generation and annihilation of magnetic chiral skyrmion bubbles and achiral
+bubbles in the Mn-Ni-Ga thin plate by using the Lorentz transmission electron
+microscopy (L-TEM). The two independent magnetic domain structures can be
+directly controlled after the field cooling manipulation by varying the titled
+angles of external magnetic fields. By imaging the magnetization reversal with
+increasing temperature, we found an extraordinary annihilation mode of magnetic
+chiral skyrmion bubbles and a non-linear frequency for the winding number
+reversal. Quantitative analysis of such dynamics was performed by using L-TEM
+to directly determine the barrier energy for the magnetization reversal of
+magnetic chiral skyrmion bubbles.",2003.08035v1
+2020-07-24,Can the dynamics of test particles around charged stringy black holes mimic the spin of Kerr black holes?,"We study the motion of electrically charged particles, magnetic monopoles,
+and magnetic dipoles around electrically and magnetically charged stringy black
+holes. From the analysis of the radius of the innermost stable circular orbit
+(ISCO) of electrically charged particles, we show that the electric charge $Q$
+of stringy black holes can mimic well the spin of Kerr black holes; the black
+hole magnetic charge $Q_m$ can mimic spins up to $a_* \simeq 0.85$ for magnetic
+dipoles; the magnetic charge parameter $g$ of a magnetic monopole can mimic
+spins up to $a_* \simeq 0.8$. This is due to the destructive character of the
+magnetic field and such a result excludes the existence of an appreciable black
+hole magnetic charge in astrophysical black holes from the observation of
+rapidly rotating objects with dimensionless spin up to $a_* \simeq 0.99$. We
+then consider the magnetar SGR (PSR) J1745-2900 as a magnetic dipole orbiting
+the supermassive black hole Sagittarius A* (Sgr A*). We show that Sgr A* may be
+interpreted as a stringy black hole with magnetic charge $Q_{\rm m}/M \leq
+0.4118$.",2007.12462v1
+2020-10-10,Dynamics of charged and magnetized particles around cylindrical black holes immersed in external magnetic field,"This paper investigates the motion and acceleration of a particle that is
+electrically and magnetically charged, which rotates around a cylindrical black
+hole in the presence of an external asymptotically uniform magnetic field
+parallel to the z axis. Basically, the work considers the circular orbits of
+particles rotating around the central object and studies the dependence of the
+most internal stable circular orbits (ISCO) on the so-called magnetic coupling
+parameters, which are responsible for the interaction between the external
+magnetic field and magnetized and charged particles. It is also shown that the
+ISCO radius decreases with increasing magnetized parameter. Therefore,
+collisions of magnetized particles around a cylindrical black hole immersed in
+an external magnetic field were also studied, and it was shown that the
+magnetic field can act as a particle accelerator around non-rotating
+cylindrical black holes.",2010.04969v1
+2021-07-02,Off-axis gyration induces large-area circular motion of anisotropic microparticles in a dynamic magnetic trap,"Magnetic tweezers are crucial for single-molecule and atomic
+characterization, and biomedical isolation of microparticle carriers. The
+trapping component of magnetic tweezing can be relying on a magnetic potential
+well that can confine the relevant species to a localized region. Here, we
+report that magnetic microparticles with tailored anisotropy can transition
+from localized off-axis gyration to large-area locomotion in a rotating
+magnetic trap. The microparticles, consisting of assemblies of magnetic cores,
+are observed to either rotate about its structural geometric center or gyrate
+about one of the magnetic cores, the switching of which can be modulated by the
+external field. Raising the magnetic field strength above a threshold, the
+particles can go beyond the traditional synchronous-rotation and
+asynchronous-oscillation modes, and into a scenario of large-area circular
+motion. This results in peculiar retrograde locomotion related to the
+magnetization maxima of the microparticle. Our finding suggests the important
+role of the microparticle's magnetic morphology in the controlled transport of
+microparticles and developing smart micro-actuators and micro-robot devices.",2107.00869v1
+2022-05-10,Non-hermitian off-diagonal magnetic response of Dirac fermions,"We perform a comparative study for the magnetization dynamics within linear
+response theory of one and two dimensional massive Dirac electrons, after
+switching on either a real (hermitian) or an imaginary (non-hermitian) magnetic
+field. While hermitian dc magnetic fields polarize the spins in the direction
+of the external magnetic field, non-hermitian magnetic fields induce only off
+diagonal response. An imaginary dc magnetic field perpendicular to the mass
+term induces finite magnetization in the third direction only according to the
+right hand rule. This can be understood by analyzing the non-hermitian equation
+of motion of the spin, which becomes analogous to a classical particle in
+crossed electric and magnetic fields. Therein, the spin expectation value, the
+mass term and imaginary magnetic field play the role of the classical momentum,
+magnetic and electric field, respectively. The latter two create a drift
+velocity perpendicular to them, which gives rise to the off-diagonal component
+of the dc spin susceptibility, similarly to how the Hall effect develops in the
+classical description.",2205.04795v2
+2021-03-19,Spin-Injection-Generated Shock Waves and Solitons in a Ferromagnetic Thin Film,"Unsteady nonlinear magnetization dynamics are studied in an easy-plane
+ferromagnetic channel subject to spin injection at one edge. The model
+Landau-Lifshitz equation is known to support steady-state solutions, termed
+dissipative exchange flows (DEFs) or spin superfluids. In this work, by means
+of numerical simulations and theoretical analysis, we provide a full
+description of the injection-induced, large-amplitude, nonlinear magnetization
+dynamics up to the steady state. The dynamics prior to reaching steady state
+are driven by spin injection, the perpendicular applied magnetic field, the
+exchange interaction, and local demagnetizing fields. We show that the dynamics
+take well-defined profiles in the form of rarefaction waves (RW), dispersive
+shock waves (DSW), and solitons. The combination of these building blocks
+depends on the interplay between the spin injection strength and the applied
+magnetic field. A solitonic feature at the injection boundary, signaling the
+onset of the magnetic ""supersonic"" condition at the injection edge, rapidly
+develops and persists in the steady-state configuration of a contact soliton
+DEF. We also demonstrate the existence of sustained soliton-train dynamics in
+long time that can only arise in a nonzero applied magnetic field scenario. The
+dynamical evolution of spin-injection-induced magnetization dynamics presented
+here may help guide observations in long-distance spin transport experiments.",2103.10616v1
+1996-07-16,Turbulent behaviour in magnetic hydrodynamics is not universal,"A short distance expansion method (SDE) that is well known in the quantum
+field theory for analysis of turbulent behaviour of stochastic magnetic
+hydrodynamics of incompressible conductive fluid is applied. As a result is
+shown that in an inertial range the turbulent spectra of magnetic hydrodynamics
+depend on a scale of arising of curls.",9607009v1
+1998-10-30,Large Coherent Structure Formation by Magnetic Stretching Term in Two-Dimensional MHD Turbulence,"Using EDQNM approximation, it is shown that the magnetic stretching term is
+responsible for turning the small-scale turbulent structures into the large
+coherent magnetic structures in the 2-D MHD turbulence.",9810036v1
+2006-03-05,"Magnetic Schroeodinger Operator: Geometry, Classical and Quantum Dynamics and Spectral Aymptotics","I study the Schroedinger operator with the strong magnetic field, considering
+links between geometry of magnetic field, classical and quantum dynamics
+associated with operator and spectral asymptotics.",0603120v3
+2007-06-12,Triplet Josephson effect with magnetic feedback,"We study AC Josephson effect in a superconductor-ferromagnet heterostructure
+with a variable magnetic configuration. The system supports triplet proximity
+correlations whose dynamics is coupled to the magnetic dynamics. This feedback
+dramatically modifies the behavior of the junction. The current-phase relation
+becomes double-periodic at both very low and high Josephson frequencies
+$\omega_J$. At intermediate frequencies, the periodicity in $\omega_J t$ may be
+lost.",0706.1746v2
+2008-06-23,A simple mechanism for the reversals of Earth's magnetic field,"We show that a model, recently used to describe all the dynamical regimes of
+the magnetic field generated by the dynamo effect in the VKS experiment [1],
+also provides a simple explanation of the reversals of Earth's magnetic field,
+despite strong differences between both systems.",0806.3756v3
+2009-04-22,Dynamic equations for three different qudits in a magnetic field,"A closed system of equations for the local Bloch vectors and spin correlation
+functions of three magnetic qudits, which are in an arbitrary, time-dependent,
+external magnetic field, is obtained using decomplexification of the
+Liouville-von Neumann equation. The algorithm of the derivation of the dynamic
+equations is presented. In the basis convenient for the important physical
+applications structure constants of algebra su(2S+1) are calculated.",0904.3533v1
+2020-05-06,Inverse-Magnetic Billiards on a Square,"We consider a polygon in a two-dimensional plane with a homogeneous constant
+magnetic field orthogonal to such plane, but inside the polygon, the magnetic
+field is zero. We study the dynamics of an electron with an initial velocity in
+this setting. Problems arise because we have a boundary with corners. In the
+square case, we generalize velocities with a rational slope and show numerical
+evidence of a chaotic-like behavior with other initial conditions.",2005.02713v1
+2020-10-31,Low-temperature asymptotics for the transverse dynamical structure factor for a magnetically polarized $XX$ chain at small and negative frequencies,"Using the truncated form factor expansion the low-temperature asymptotics for
+the transverse dynamical structure factor of the magnetically polarized $XX$
+chain is studied. Unlike the previous paper we do not use the representation of
+structure factor in terms of the corresponding magnetic susceptibility. This
+enables to obtain correct results at small and negative frequencies.",2011.00326v1
+2021-06-10,Linear Stability of Periodic Trajectories in Inverse Magnetic Billiards,"We study the stability of periodic trajectories of planar inverse magnetic
+billiards, a dynamical system whose trajectories are straight lines inside a
+connected planar domain $\Omega$ and circular arcs outside $\Omega$. Explicit
+examples are calculated in circles, ellipses, and the one parameter family of
+curves $x^{2k}+y^{2k}=1$. Comparisons are made to the linear stability of
+periodic billiard and magnetic billiard trajectories.",2106.05676v1
+2011-11-30,Relation of Astrophysical Turbulence and Magnetic Reconnection,"Astrophysical fluids are generically turbulent and this must be taken into
+account for most transport processes. We discuss how the preexisting turbulence
+modifies magnetic reconnection and how magnetic reconnection affects the MHD
+turbulent cascade. We show the intrinsic interdependence and interrelation of
+magnetic turbulence and magnetic reconnection, in particular, that strong
+magnetic turbulence in 3D requires reconnection and 3D magnetic turbulence
+entails fast reconnection. We follow the approach in Eyink, Lazarian & Vishniac
+2011 to show that the expressions of fast magnetic reconnection in Lazarian &
+Vishniac 1999 can be recovered if Richardson diffusion of turbulent flows is
+used instead of ordinary Ohmic diffusion. This does not revive, however, the
+concept of magnetic turbulent diffusion which assumes that magnetic fields can
+be mixed up in a passive way down to a very small dissipation scales. On the
+contrary, we are dealing the reconnection of dynamically important magnetic
+field bundles which strongly resist bending and have well defined mean
+direction weakly perturbed by turbulence. We argue that in the presence of
+turbulence the very concept of flux-freezing requires modification. The
+diffusion that arises from magnetic turbulence can be called reconnection
+diffusion as it based on reconnection of magnetic field lines. The reconnection
+diffusion has important implications for the continuous transport processes in
+magnetized plasmas and for star formation. In addition, fast magnetic
+reconnection in turbulent media induces the First order Fermi acceleration of
+energetic particles, can explain solar flares and gamma ray bursts. However,
+the most dramatic consequence of these developments is the fact that the
+standard flux freezing concept must be radically modified in the presence of
+turbulence.",1112.0022v1
+2012-10-13,Full-disk nonlinear force-free field extrapolation of SDO/HMI and SOLIS/VSM magnetograms,"Extrapolation codes in Cartesian geometry for modelling the magnetic field in
+the corona do not take the curvature of the Sun's surface into account and can
+only be applied to relatively small areas, e.g., a single active region. We
+compare the analysis of the photospheric magnetic field and subsequent
+force-free modeling based on full-disk vector maps from Helioseismic and
+Magnetic Imager (HMI) on board solar dynamics observatory (SDO) and Vector
+Spectromagnetograph (VSM) of the Synoptic Optical Long-term Investigations of
+the Sun (SOLIS). We use Helioseismic and Magnetic Imager and Vector
+Spectromagnetograph photospheric magnetic field measurements to model the
+force-free coronal field above multiple solar active regions, assuming magnetic
+forces to dominate. We solve the nonlinear force-free field equations by
+minimizing a functional in spherical coordinates over a full disk excluding the
+poles. After searching for the optimum modeling parameters for the particular
+data sets, we compare the resulting nonlinear force-free model fields. We
+compare quantities like the total magnetic energy content and free magnetic
+energy, the longitudinal distribution of the magnetic pressure and surface
+electric current density using our spherical geometry extrapolation code. The
+magnetic field lines obtained from nonlinear force-free extrapolation based on
+Helioseismic and Magnetic Imager and Vector Spectromagnetograph data have good
+agreement. However, the nonlinear force-free extrapolation based on
+Helioseismic and Magnetic Imager data have more contents of total magnetic
+energy, free magnetic energy, the longitudinal distribution of the magnetic
+pressure and surface electric current density compared to the one from Vector
+Spectromagnetograph data.",1210.3668v1
+2017-12-13,Studying the transfer of magnetic helicity in solar active regions with the connectivity-based helicity flux density method,"In the solar corona, magnetic helicity slowly and continuously accumulates in
+response to plasma flows tangential to the photosphere and magnetic flux
+emergence through it. Analyzing this transfer of magnetic helicity is key for
+identifying its role in the dynamics of active regions (ARs). The
+connectivity-based helicity flux density method was recently developed for
+studying the 2D and 3D transfer of magnetic helicity in ARs. The method takes
+into account the 3D nature of magnetic helicity by explicitly using knowledge
+of the magnetic field connectivity, which allows it to faithfully track the
+photospheric flux of magnetic helicity. Because the magnetic field is not
+measured in the solar corona, modeled 3D solutions obtained from force-free
+magnetic field extrapolations must be used to derive the magnetic connectivity.
+Different extrapolation methods can lead to markedly different 3D magnetic
+field connectivities, thus questioning the reliability of the
+connectivity-based approach in observational applications. We address these
+concerns by applying this method to the isolated and internally complex AR
+11158 with different magnetic field extrapolation models. We show that the
+connectivity-based calculations are robust to different extrapolation methods,
+in particular with regards to identifying regions of opposite magnetic helicity
+flux. We conclude that the connectivity-based approach can be reliably used in
+observational analyses and is a promising tool for studying the transfer of
+magnetic helicity in ARs and relate it to their flaring activity.",1712.04691v1
+2021-05-31,Theoretical development in the viscosity of ferrofluid,"The viscosity of ferrofluid has an important role in liquid sealing of the
+hard disk drives, biomedical applications as drug delivery, hyperthermia, and
+magnetic resonance imaging. In the absence of a magnetic field, the viscosity
+of ferrofluid depends on the volume concentration of magnetic nanoparticles
+including surfactant layers. However, under the influence of a stationary
+magnetic field, the viscosity of ferrofluid depends on the angle between the
+applied magnetic field and vorticity in the flow. If this angle is 90o, then
+there is a maximum increase in the viscosity. If the magnetic field and the
+vorticity in the flow are parallel to each other, then there is no change in
+the viscosity since the applied magnetic field does not change the speed of the
+rotation of magnetic nanoparticles in the fluid. The viscosity of ferrofluid in
+the presence of an alternating magnetic field demonstrates interesting
+behavior. When field frequency matches with the relaxation time, known as
+resonance condition, then there is no impact of an alternating magnetic field
+in the viscosity of ferrofluid. If the frequency of an alternating magnetic
+field is less than resonance frequency, then an alternating magnetic field
+increases the viscosity of ferrofluid. Using higher frequency than resonance
+condition reduces the viscosity of ferrofluid and researchers reported this
+incident as the negative viscosity effect. If the frequency of an alternating
+magnetic field tends to infinite, then ferrofluid ceases to feel a magnetic
+field. In this case, there is no impact of an alternating magnetic field on the
+viscosity of ferrofluid.",2105.14721v1
+2022-06-28,Turbulent magnetic helicity fluxes in solar convective zone,"Combined action of helical motions of plasma (the $\alpha$ effect) and
+non-uniform (differential) rotation is a key dynamo mechanism of solar and
+galactic large-scale magnetic fields. Dynamics of magnetic helicity of
+small-scale fields is a crucial mechanism in a nonlinear dynamo saturation
+where turbulent magnetic helicity fluxes allow to avoid catastrophic quenching
+of the $\alpha$ effect. The convective zone of the Sun and solar-like stars as
+well as galactic discs are the source for production of turbulent magnetic
+helicity fluxes. In the framework of the mean-field approach and the spectral
+$\tau$ approximation, we derive turbulent magnetic helicity fluxes using the
+Coulomb gauge in a density-stratified turbulence. The turbulent magnetic
+helicity fluxes include non-gradient and gradient contributions. The
+non-gradient magnetic helicity flux is proportional to a nonlinear effective
+velocity (which vanishes in the absence of the density stratification)
+multiplied by small-scale magnetic helicity, while the gradient contributions
+describe turbulent magnetic diffusion of the small-scale magnetic helicity. In
+addition, the turbulent magnetic helicity fluxes contain source terms
+proportional to the kinetic $\alpha$ effect or its gradients, and also
+contributions caused by the large-scale shear (solar differential rotation). We
+have demonstrated that the turbulent magnetic helicity fluxes due to the
+kinetic $\alpha$ effect and its radial derivative in combination with the
+nonlinear magnetic diffusion of the small-scale magnetic helicity are dominant
+in the solar convective zone.",2206.14152v2
+1998-05-25,Magnetic Catalysis of Dynamical Symmetry Breaking and Aharonov-Bohm Effect,"The phenomenon of the magnetic catalysis of dynamical symmetry breaking is
+based on the dimensional reduction $D\to D-2$ in the dynamics of fermion
+pairing in a magnetic field. We discuss similarities between this phenomenon
+and the Aharonov-Bohm effect. This leads to the interpretation of the dynamics
+of the (1+1)-dimensional Gross-Neveu model with a non-integer number of fermion
+colors as a quantum field theoretical analogue of the Aharonov-Bohm dynamics.",9805159v2
+2009-11-12,Groebli solution for three magnetic vortices,"The dynamics of N point vortices in a fluid is described by the
+Helmholtz-Kirchhoff (HK) equations which lead to a completely integrable
+Hamiltonian system for N=2 or 3 but chaotic dynamics for N>3. Here we consider
+a generalization of the HK equations to describe the dynamics of magnetic
+vortices within a collective-coordinate approximation. In particular, we
+analyze in detail the dynamics of a system of three magnetic vortices by a
+suitable generalization of the solution for three point vortices in an ordinary
+fluid obtained by Groebli more than a century ago. The significance of our
+results for the dynamics of ferromagnetic elements is briefly discussed.",0911.2377v1
+2014-07-11,"Dynamic phase transition properties for the mixed spin-(1/2, 1) Ising model in an oscillating magnetic field","We study the dynamic phase transition properties for the mixed spin-(1/2, 1)
+Ising model on a square lattice under a time-dependent magnetic field by means
+the effective-field theory (EFT) based on the Glauber dynamics. We present the
+dynamic phase diagrams in the reduced magnetic field amplitude and reduced
+temperature plane and find that the phase diagrams exhibit the dynamic
+tricitical behavior, the multicritical and zero-temperature critical points as
+well as reentrant behavior. We also investigate the influence of the frequency
+(w) and observe that for small values of w the mixed phase disappears, but high
+values it appears and the system displays reentrant behavior as well as
+critical end point.",1407.3188v1
+2019-07-03,Dynamic magnetic features of a mixed ferro-ferrimagnetic ternary alloy in the form of AB$_p$C$_{1-p}$,"Dynamic magnetic features of a mixed ferro-ferrimagnetic ternary alloy in the
+form of AB$_p$C$_{1-p}$, especially. The effect of Hamiltonian parameters on
+the dynamic magnetic features of the system are investigated. For this aim, an
+AB$_p$C$_{1-p}$ ternary alloy system was simulated within the mean-field
+approximation based on a Glauber type stochastic dynamic and for simplicity, A,
+B and C ions as SA = 1/2, SB = 1 and SC = 3/2, were chosen respectively. It was
+found that in our dynamic system the critical temperature was always dependent
+on the concentration ratio of the ternary alloy.",1907.01850v1
+2016-11-10,Magnetism and ultra-fast magnetization dynamics of Co and CoMn alloys at finite temperature,"Temperature-dependent magnetic experiments like pump-probe measurements
+generated by a pulsed laser have become a crucial technique for switching the
+magnetization in the picosecond time scale. Apart from having practical
+implications on the magnetic storage technology, the research field of
+ultrafast magnetization poses also fundamental physical questions. To correctly
+describe the time evolution of the atomic magnetic moments under the influence
+of a temperature-dependent laser pulse, it remains crucial to know if the
+magnetic material under investigation has magnetic excitation spectrum that is
+more or less dependent on the magnetic configuration, e.g. as reflected by the
+temperature dependence of the exchange interactions. In this article, we
+demonstrate from first-principles theory that the magnetic excitation spectra
+in Co with fcc, bcc and hcp structures are nearly identical in a wide range of
+non-collinear magnetic configurations. This is a curious result of a balance
+between the size of the magnetic moments and the strength of the Heisenberg
+exchange interactions, that in themselves vary with configuration, but put
+together in an effective spin Hamiltonian results in a configuration
+independent effective model. We have used such a Hamiltonian, together with
+ab-initio calculated damping parameters, to investigate the magnon dispersion
+relationship as well as the ultrafast magnetisation dynamics of Co and Co-rich
+CoMn alloys.",1611.03541v2
+2018-08-09,Effect of Magnetic Field Strength on Solar Differential Rotation and Meridional Circulation,"We studied the solar surface flows (differential rotation and meridional
+circulation) using a magnetic element feature tracking technique by which the
+surface velocity is obtained using magnetic field data. We used the
+line-of-sight magnetograms obtained by the Helioseismic and Magnetic Imager
+aboard the Solar Dynamics Observatory from 01 May 2010 to 16 August 2017
+(Carrington rotations 2096 to 2193) and tracked the magnetic element features
+every hour. Using our method, we estimated the differential rotation velocity
+profile. We found rotation velocities of $\sim$ 30 and -170 m s$^{-1}$ at
+latitudes of 0$^{\circ}$ and 60$^{\circ}$ in the Carrington rotation frame,
+respectively. Our results are consistent with previous results obtained by
+other methods, such as direct Doppler, time-distance helioseismology, or cross
+correlation analyses. We also estimated the meridional circulation velocity
+profile and found that it peaked at $\sim$12 m s$^{-1}$ at a latitude of
+45$^{\circ}$, which is also consistent with previous results. The dependence of
+the surface flow velocity on the magnetic field strength was also studied. In
+our analysis, the magnetic elements having stronger and weaker magnetic fields
+largely represent the characteristics of the active region remnants and solar
+magnetic networks, respectively. We found that magnetic elements having a
+strong (weak) magnetic field show faster (slower) rotation speed. On the other
+hand, magnetic elements having a strong (weak) magnetic field show slower
+(faster) meridional circulation velocity. These results might be related to the
+Sun's internal dynamics.",1808.03005v1
+2020-06-21,Rotational properties of annulus dusty plasma in a strong magnetic field,"The collective dynamics of annulus dusty plasma formed between a co-centric
+conducting (non-conducting) disk and ring configuration is studied in a
+strongly magnetized radio-frequency (rf) discharge. A superconducting
+electromagnet is used to introduce a homogeneous magnetic field to the dusty
+plasma medium. In absence of the magnetic field, dust grains exhibit thermal
+motion around their equilibrium position. The dust grains start to rotate in
+anticlockwise direction with increasing magnetic field (B $>$ 0.02 T), and the
+constant value of the angular frequency at various strengths of magnetic field
+confirms the rigid body rotation. The angular frequency of dust grains linearly
+increases up to a threshold magnetic field (B $>$ 0.6 T) and after that its
+value remains nearly constant in a certain range of magnetic field. Further
+increase in magnetic field (B $>$ 1 T) lowers the angular frequency. Low value
+of angular frequency is expected by reducing the width of annulus dusty plasma
+or the input rf power. The azimuthal ion drag force due to the magnetic field
+is assumed to be the energy source which drives the rotational motion. The
+resultant radial electric field in the presence of magnetic field determines
+the direction of rotation. The variation of floating (plasma) potential across
+the annular region at given magnetic field explains the rotational properties
+of the annulus dusty plasma in the presence of magnetic field.",2006.11710v1
+2020-09-28,Magnetic domains and domain wall pinning in two-dimensional ferromagnets revealed by nanoscale imaging,"Magnetic-domain structure and dynamics play an important role in
+understanding and controlling the magnetic properties of two-dimensional
+magnets, which are of interest to both fundamental studies and
+applications[1-5]. However, the probe methods based on the spin-dependent
+optical permeability[1,2,6] and electrical conductivity[7-10] can neither
+provide quantitative information of the magnetization nor achieve nanoscale
+spatial resolution. These capabilities are essential to image and understand
+the rich properties of magnetic domains. Here, we employ cryogenic scanning
+magnetometry using a single-electron spin of a nitrogen-vacancy center in a
+diamond probe to unambiguously prove the existence of magnetic domains and
+study their dynamics in atomically thin CrBr$_3$. The high spatial resolution
+of this technique enables imaging of magnetic domains and allows to resolve
+domain walls pinned by defects. By controlling the magnetic domain evolution as
+a function of magnetic field, we find that the pinning effect is a dominant
+coercivity mechanism with a saturation magnetization of about 26~$\mu_B$/nm$^2$
+for bilayer CrBr$_3$. The magnetic-domain structure and pinning-effect
+dominated domain reversal process are verified by micromagnetic simulation. Our
+work highlights scanning nitrogen-vacancy center magnetometry as a quantitative
+probe to explore two-dimensional magnetism at the nanoscale.",2009.13440v1
+2006-07-31,Dynamical and thermal effects in nanoparticle systems driven by a rotating magnetic field,"We study dynamical and thermal effects that are induced in nanoparticle
+systems by a rotating magnetic field. Using the deterministic Landau-Lifshitz
+equation and appropriate rotating coordinate systems, we derive the equations
+that characterize the steady-state precession of the nanoparticle magnetic
+moments and study a stability criterion for this type of motion. On this basis,
+we describe (i) the influence of the rotating field on the stability of the
+small-angle precession, (ii) the dynamical magnetization of nanoparticle
+systems, and (iii) the switching of the magnetic moments under the action of
+the rotating field. Using the backward Fokker-Planck equation, which
+corresponds to the stochastic Landau-Lifshitz equation, we develop a method for
+calculating the mean residence times that the driven magnetic moments dwell in
+the up and down states. Within this framework, the features of the induced
+magnetization and magnetic relaxation are elucidated.",0607820v1
+2007-04-25,Dynamical models and the phase ordering kinetics of the s=1 spinor condensate,"The $s=1$ spinor Bose condensate at zero temperature supports ferromagnetic
+and polar phases that combine magnetic and superfluid ordering. We investigate
+the formation of magnetic domains at finite temperature and magnetic field in
+two dimensions in an optical trap. We study the general ground state phase
+diagram of a spin-1 system and focus on a phase that has a magnetic Ising order
+parameter and numerically determine the nature of the finite temperature
+superfluid and magnetic phase transitions. We then study three different
+dynamical models: model A, which has no conserved quantities, model F, which
+has a conserved second sound mode and the Gross-Pitaevskii (GP) equation which
+has a conserved density and magnetization. We find the dynamic critical
+exponent to be the same for models A and F ($z=2$) but different for GP ($z
+\approx 3$). Externally imposed magnetization conservation in models A and F
+yields the value $z \approx 3$, which demonstrates that the only conserved
+density relevant to domain formation is the magnetization density.",0704.3440v2
+2009-07-29,Interactions between magnetohydrodynamic shear instabilities and convective flows in the solar interior,"Motivated by the interface model for the solar dynamo, this paper explores
+the complex magnetohydrodynamic interactions between convective flows and
+shear-driven instabilities. Initially, we consider the dynamics of a forced
+shear flow across a convectively-stable polytropic layer, in the presence of a
+vertical magnetic field. When the imposed magnetic field is weak, the dynamics
+are dominated by a shear flow (Kelvin-Helmholtz type) instability. For stronger
+fields, a magnetic buoyancy instability is preferred. If this stably stratified
+shear layer lies below a convectively unstable region, these two regions can
+interact. Once again, when the imposed field is very weak, the dynamical
+effects of the magnetic field are negligible and the interactions between the
+shear layer and the convective layer are relatively minor. However, if the
+magnetic field is strong enough to favour magnetic buoyancy instabilities in
+the shear layer, extended magnetic flux concentrations form and rise into the
+convective layer. These magnetic structures have a highly disruptive effect
+upon the convective motions in the upper layer.",0907.5068v1
+2011-03-23,Zero-temperature spin-glass freezing in self-organized arrays of Co nanoparticles,"We study, by means of magnetic susceptibility and magnetic aging experiments,
+the nature of the glassy magnetic dynamics in arrays of Co nanoparticles,
+self-organized in N layers from N=1 (two-dimensional limit) up to N=20
+(three-dimensional limit). We find no qualitative differences between the
+magnetic responses measured in these two limits, in spite of the fact that no
+spin-glass phase is expected above T=0 in two dimensions. More specifically,
+all the phenomena (critical slowing down, flattening of the field-cooled
+magnetization below the blocking temperature and the magnetic memory induced by
+aging) that are usually associated with this phase look qualitatively the same
+for two-dimensional and three-dimensional arrays. The activated scaling law
+that is typical of systems undergoing a phase transition at zero temperature
+accounts well for the critical slowing down of the dc and ac susceptibilities
+of all samples. Our data show also that dynamical magnetic correlations
+achieved by aging a nanoparticle array below its superparamagnetic blocking
+temperature extend mainly to nearest neighbors. Our experiments suggest that
+the glassy magnetic dynamics of these nanoparticle arrays is associated with a
+zero-temperature spin-glass transition.",1103.4492v1
+2011-04-08,Magnetization Dissipation in Ferromagnets from Scattering Theory,"The magnetization dynamics of ferromagnets are often formulated in terms of
+the Landau-Lifshitz-Gilbert (LLG) equation. The reactive part of this equation
+describes the response of the magnetization in terms of effective fields,
+whereas the dissipative part is parameterized by the Gilbert damping tensor. We
+formulate a scattering theory for the magnetization dynamics and map this
+description on the linearized LLG equation by attaching electric contacts to
+the ferromagnet. The reactive part can then be expressed in terms of the static
+scattering matrix. The dissipative contribution to the low-frequency
+magnetization dynamics can be described as an adiabatic energy pumping process
+to the electronic subsystem by the time-dependent magnetization. The Gilbert
+damping tensor depends on the time derivative of the scattering matrix as a
+function of the magnetization direction. By the fluctuation-dissipation
+theorem, the fluctuations of the effective fields can also be formulated in
+terms of the quasistatic scattering matrix. The theory is formulated for
+general magnetization textures and worked out for monodomain precessions and
+domain wall motions. We prove that the Gilbert damping from scattering theory
+is identical to the result obtained by the Kubo formalism.",1104.1625v1
+2011-10-21,Classical Orbital Magnetic Moment in a Dissipative Stochastic System,"We present an analytical treatment of the dissipative-stochastic dynamics of
+a charged classical particle confined bi-harmonically in a plane with a uniform
+static magnetic field directed perpendicular to the plane. The stochastic
+dynamics gives a steady state in the long-time limit. We have examined the
+orbital magnetic effect of introducing a parametrized deviation ($\eta$ -1)
+from the second fluctuation-dissipation (II-FD) relation that connects the
+driving noise and the frictional memory kernel in the standard Langevin
+dynamics. The main result obtained here is that the moving charged particle
+generates a finite orbital magnetic moment in the steady state, and that the
+moment shows a crossover from para-to dia-magnetic sign as the parameter $\eta$
+is varied. It is zero for $\eta = 1$ that makes the steady state correspond to
+equilibrium, as it should. The magnitude of the orbital magnetic moment turns
+out to be a non-monotonic function of the applied magnetic field, tending to
+zero in the limit of an infinitely large as well as an infinitesimally small
+magnetic field. These results are discussed in the context of the classic
+Bohr-van Leeuwen theorem on the absence of classical orbital diamagnetism.
+Possible realization is also briefly discussed.",1110.4749v2
+2011-12-08,Dynamics of artificial spin ice: continuous honeycomb network,"We model the dynamics of magnetization in an artificial analog of spin ice
+specializing to the case of a honeycomb network of connected magnetic
+nanowires. The inherently dissipative dynamics is mediated by the emission,
+propagation and absorption of domain walls in the links of the lattice. These
+domain walls carry two natural units of magnetic charge, whereas sites of the
+lattice contain a unit magnetic charge. Magnetostatic Coulomb forces between
+these charges play a major role in the physics of the system, as does quenched
+disorder caused by imperfections of the lattice. We identify and describe
+different regimes of magnetization reversal in an applied magnetic field
+determined by the orientation of the applied field with respect to the initial
+magnetization. One of the regimes is characterized by magnetic avalanches with
+a 1/n distribution of lengths.",1112.1857v3
+2017-03-16,Relaxation dynamics of modulated magnetic phases in skyrmion host GaV4S8: an ac magnetic susceptibility study,"We report on the slow magnetization dynamics observed upon the magnetic phase
+transitions of GaV4S8, a multiferroic compound featuring a long-ranged
+cycloidal magnetic order and a N\'eel-type skyrmion lattice in a relatively
+broad temperature range below its Curie temperature. The fundamental difference
+between GaV4S8 and the chiral helimagnets, wherein the skyrmion phase was first
+discovered, lies within the polar symmetry of GaV4S8, promoting a cycloidal
+instead of a helical magnetic order and rendering the magnetic phase diagram
+essentially different from that in the cubic helimagnets. Our ac magnetic
+susceptibility study reveals slow relaxation dynamics at the field-driven phase
+transitions between the cycloidal, skyrmion lattice and field-polarized states.
+At each phase boundary, the characteristic relaxation times were found to
+exhibit a strong temperature dependence, starting from the minute range at low
+temperatures, decreasing to the micro- to millisecond range at higher
+temperatures.",1703.10928v1
+2018-03-19,"Magnetic susceptibility, nanorheology, and magnetoviscosity of magnetic nanoparticles in viscoelastic environments","While magnetic nanoparticles suspended in Newtonian solvents (ferrofluids)
+have been intensively studied in recent years, the effects of viscoelasticity
+of the surrounding medium on the nanoparticle dynamics are much less
+understood. Here we investigate a mesoscopic model for the orientational
+dynamics of isolated magnetic nanoparticles subject to external fields, viscous
+and viscoelastic friction as well as the corresponding random torques. We solve
+the model analytically in the overdamped limit for weak viscoelasticity. By
+comparison to Brownian Dynamics simulations we establish the limits of validity
+of the analytical solution. We find that viscoelasticity does not only slow
+down the magnetization relaxation, shift the peak of the imaginary magnetic
+susceptibility $\chi''$ to lower frequencies and increase the magnetoviscosity,
+it also leads to non-exponential relaxation and a broadening of $\chi''$. The
+model we study also allows to test a recent proposal for using magnetic
+susceptibility measurements as a nanorheological tool using a variant of the
+Germant-DiMarzio-Bishop relation. We find for the present model and certain
+parameter ranges that the relation of the magnetic susceptibility to the shear
+modulus is satisfied to a good approximation.",1803.07188v1
+2018-04-11,Continuous Nucleation Dynamics of Magnetic Skyrmions in T-shaped Helimagnetic Nanojunction,"Magnetic skyrmions are topologically-protected spin textures existing in
+helimagentic materials, which can be utilized as information carriers for
+non-volatile memories and logic circuits in spintronics. Searching simple and
+controllable way to create isolated magnetic skyrmions is desirable for further
+technology developments and industrial designs. Based on micromagnetic
+simulations, we show that the temporal dissipative structure can be developed
+in the T-shaped helimagnetic nanojunction when it is driven to the
+far-from-equilibrium regime by a constant spin-polarized current. Then the
+magnetic skyrmions can be continuously nucleated during the periodic
+magnetization dynamics of the nanojunction. We have systematically investigated
+the effects of current density, Dzyaloshinskii-Moriya interaction, external
+magnetic field, and thermal fluctuation on the nucleation dynamics of the
+magnetic skyrmions. Our results here suggest a novel and promising mechanism to
+continuously create magnetic skyrmions for the development of skyrmion-based
+spintronics devices.",1804.04022v1
+2018-04-26,Orbital quantum magnetism in spin dynamics of strongly interacting magnetic lanthanide atoms,"Laser cooled lanthanide atoms are ideal candidates with which to study strong
+and unconventional quantum magnetism with exotic phases. Here, we use
+state-of-the-art closed-coupling simulations to model quantum magnetism for
+pairs of ultracold spin-6 erbium lanthanide atoms placed in a deep optical
+lattice. In contrast to the widely used single-channel Hubbard model
+description of atoms and molecules in an optical lattice, we focus on the
+single-site multi-channel spin evolution due to spin-dependent contact,
+anisotropic van der Waals, and dipolar forces. This has allowed us to identify
+the leading mechanism, orbital anisotropy, that governs molecular spin dynamics
+among erbium atoms. The large magnetic moment and combined orbital angular
+momentum of the 4f-shell electrons are responsible for these strong anisotropic
+interactions and unconventional quantum magnetism. Multi-channel simulations of
+magnetic Cr atoms under similar trapping conditions show that their
+spin-evolution is controlled by spin-dependent contact interactions that are
+distinct in nature from the orbital anisotropy in Er. The role of an external
+magnetic field and the aspect ratio of the lattice site on spin dynamics is
+also investigated.",1804.10102v1
+2018-06-06,Control of magnetization dynamics by spin Nernst torque,"Control of magnetization dynamics is one of the primary goals in spintronics.
+It has been demonstrated using spin Hall effect i.e charge current to spin
+current conversion in non-magnetic metal which has large spin-orbit coupling
+such as Pt, W etc. Recently different groups have shown generation of spin
+current in Pt, W while thermal gradient is created by virtue of spin Nernst
+effect. In this work we show the evidence of magnetization control by spin
+Nernst torque in Pt/Py bi-layer. We compared relative strength of spin Nernst
+Torque and spin Hall torque by measuring the systematic variation of magnetic
+linewidth on application of constant heat or charge current. Spin-torque
+ferromagnetic resonance (ST-FMR) technique is adopted to excite the magnet and
+to measure line-width precisely from the symmetric and anti-symmetric voltage
+component. Control of magnetization dynamics by spin Nernst torque will emerge
+as an alternative way to manipulate nano-magnets.",1806.01978v1
+2018-06-07,Terahertz Emission from Compensated Magnetic Heterostructures,"Terahertz emission spectroscopy (TES) has recently played an important role
+in unveiling the spin dynamics at a terahertz (THz) frequency range. So far,
+ferromagnetic (FM)/nonmagnetic (NM) heterostructures have been intensively
+studied as THz sources. Compensated magnets such as a ferrimagnet (FIM) and
+antiferromagnet (AFM) are other types of magnetic materials with interesting
+spin dynamics. In this work, we study TES from compensated magnetic
+heterostructures including CoGd FIM alloy or IrMn AFM layers. Systematic
+measurements on composition and temperature dependences of THz emission from
+CoGd/Pt bilayer structures are conducted. It is found that the emitted THz
+field is determined by the net spin polarization of the laser induced spin
+current rather than the net magnetization. The temperature robustness of the
+FIM based THz emitter is also demonstrated. On the other hand, an AFM plays a
+different role in THz emission. The IrMn/Pt bilayer shows negligible THz
+signals, whereas Co/IrMn induces sizable THz outputs, indicating that IrMn is
+not a good spin current generator, but a good detector. Our results not only
+suggest that a compensated magnet can be utilized for robust THz emission, but
+also provide a new approach to study the magnetization dynamics especially near
+the magnetization compensation point.",1806.02517v1
+2019-06-15,Bursty magnetic friction between polycrystalline thin films with domain walls,"Two magnets in relative motion interact through their dipolar fields, making
+individual magnetic moments dynamically adapt to the changes in the energy
+landscape and bringing about collective magnetization dynamics. Some of the
+energy of the system is irrevocably lost through various coupling mechanisms
+between the spin degrees of freedom and those of the underlying lattice,
+resulting in magnetic friction. In this work, we use micromagnetic simulations
+to study magnetic friction in a system of two thin ferromagnetic films
+containing quenched disorder mimicking a polycrystalline structure. We observe
+bursts of magnetic activity resulting from repeated domain wall pinning due to
+the disorder and subsequent depinning triggered by the dipolar interaction
+between the moving films. These domain wall jumps result in strong energy
+dissipation peaks. We study how the properties of the polycrystalline structure
+such as grain size and strength of the disorder, along with the driving
+velocity and the width of the films, affect the magnetization dynamics, average
+energy dissipation as well as the statistical properties of the energy
+dissipation bursts.",1906.06506v1
+2019-08-19,Steady states of non-axial dipolar rods driven by rotating fields,"We investigate a two-dimensional system of magnetic colloids with anisotropic
+geometry (rods) subjected to an oscillating external magnetic field. The
+structural and dynamical properties of the steady states are analyzed, by means
+of Langevin Dynamics simulations, as a function of the misalignment of the
+intrinsic magnetic dipole moment of the rods with respect to their axial
+direction, and also in terms of the strength and rotation frequency of an
+external magnetic field. The misalignment of the dipole relative to their axial
+direction is inspired by recent studies, and this is extremely relevant in the
+microscopic aggregation states of the system. The dynamical response of the
+magnetic rods to the external magnetic field is strongly affected by such a
+misalignment. Concerning the synchronization between the magnetic rods and the
+direction of the external magnetic field, we define three distinct regimes of
+synchronization. A set of steady states diagrams are presented, showing the
+magnitude and rotation frequency intervals in which the distinct self-organized
+structures are observed.",1908.06718v1
+2020-05-07,Ultrafast All Optical Magnetization Control for Broadband Terahertz Spin Wave Generation,"Terahertz spin waves could be generated on-demand via all-optical
+manipulation of magnetization by femtosecond laser pulse. Here, we present an
+energy balance model, which explains the energy transfer rates from laser pulse
+to electron bath coupled with phonon, spin, and magnetization of five different
+magnetic metallic thin films: Iron, Cobalt, Nickel, Gadolinium and Ni$_{2}$MnSn
+Heusler alloy. Two types of transient magnetization dynamics emerge in metallic
+magnetic thin films based on their Curie temperatures (T$_{C}$): type I (Fe,
+Co, and Ni with T$_{C}$ > room temperature, RT) and type II films (Gd and
+Ni$_{2}$MnSn with T$_{C}$ $\approx$ RT). We study the effect of laser fluence
+and pulse width for single Gaussian laser pulses and the effect of metal film
+thickness on magnetization dynamics. Spectral dynamics show that broadband spin
+waves up to 24 THz could be generated by all-optical manipulation of
+magnetization in these nanofilms.",2005.03493v1
+2020-05-14,Magnetic field dependent 't Hooft determinant extended Nambu--Jona-Lasinio Model,"We study the implications of recent lattice QCD results for the magnetic
+field dependence of the quarks dynamical masses on the 't Hooft determinant
+extended Nambu--Jona-Lasinio Model in the light and strange quark sectors
+(\emph{up}, \emph{down} and \emph{strange}). The parameter space is constrained
+at vanishing magnetic field, using the quarks dynamical masses and the meson
+spectra, whereas at non-vanishing magnetic field strength the dependence of the
+dynamical masses of two of the quark flavors is used to fit a magnetic field
+dependence on the model couplings, both the four-fermion Nambu--Jona-Lasinio
+interaction and the six-fermion 't Hooft flavor determinant. We found that this
+procedure reproduces the inverse magnetic catalysis, and the strength of the
+scalar coupling decreases with the magnetic field, while the strength of the
+six-fermion 't Hooft flavor determinant increases with the magnetic field.",2005.07049v2
+2021-07-06,Static and dynamic magnetic properties of K3CrO4,"We report on the magnetic properties of geometrically frustrated K3CrO4, in
+which Cr5+ cations are arranged on a distorted pyrochlore lattice. The crystal
+structure, static and dynamic magnetic properties of the compound are
+investigated in detail. A combination of DC and AC magnetic susceptibility
+measurements together with thermoremanent magnetization decay measurements
+reveal several magnetic transitions: the onset of glassy canted
+antiferromagnetic order occurs at 36 K, followed by the appearance of
+ferromagnetic/ferrimagnetic cluster glass behavior below the freezing
+temperature of 20 K. Further field-induced, temperature-dependent transitions
+are observed in the range 3-10 K. The frequency dependence of the freezing
+temperature for the cluster glass state is analyzed on the basis of dynamic
+scaling laws including the critical slowing down formula and the Vogel-Fulcher
+law.",2107.02878v1
+2022-01-12,The angular dependence of magnetization dynamics induced by a GHz range strain pulse,"The dynamics of magnetization is important in spintronics, where the coupling
+between phonon and magnon attracts much attention. In this work, we study the
+angular dependence of the coupling between longitudinal-wave phonon and magnon.
+We investigated the magnetization dynamics using the time-resolved
+magneto-optical Kerr effect, which allows measuring spin-wave resonances and
+the magnetic echo signal. The frequency, mode number, and amplitude of the
+spin-wave resonance change with the out-of-plane angle of the external magnetic
+field. The amplitude of the magnetic echo signal caused by the strain pulse
+also changes with the angle. We calculate these angular dependences based on
+the Landau-Lifshitz-Gilbert equation and find that the angles of the external
+field and magnetic moment are important factors for the phonon-magnon coupling
+when phonon propagates in the thickness direction under the out-of-plane
+magnetic field.",2201.04396v1
+2022-03-30,Atomistic modeling of spin and electron dynamics in two-dimensional magnets switched by two-dimensional topological insulators,"To design fast memory devices, we need material combinations which can
+facilitate fast read and write operation. We present a heterostructure
+comprising a two-dimensional (2D) magnet and a 2D topological insulator (TI) as
+a viable option for designing fast memory devices. We theoretically model
+spin-charge dynamics between the 2D magnets and 2D TIs. Using the adiabatic
+approximation, we combine the non-equilibrium Green's function method for
+spin-dependent electron transport, and time-quantified Monte-Carlo for
+simulating magnetization dynamics. We show that it is possible to switch the
+magnetic domain of a ferromagnet using spin-torque from spin-polarized edge
+states of 2D TI. We further show that the switching between TIs and 2D magnets
+is strongly dependent on the interface exchange ($J_{\mathrm{int}}$), and an
+optimal interface exchange depending on the exchange interaction within the
+magnet is required for efficient switching. Finally, we compare the
+experimentally grown Cr-compounds and show that Cr-compounds with higher
+anisotropy (such as $\rm CrI_3$) results in lower switching speed but more
+stable magnetic order.",2203.16008v1
+2022-10-13,Influence of Ferromagnetic Interlayer Exchange Coupling on Current-induced Magnetization Switching and Dzyaloshinskii-Moriya Interaction in Co/Pt/Co Multilayer System,"This paper investigates the relationship among interlayer exchange coupling
+(IEC), Dzyaloshinskii-Moriya interaction (DMI), and multilevel magnetization
+switching within a Co/Pt/Co heterostructure, where varying Pt thicknesses
+enable control over the coupling strength. Employing Brillouin Light Scattering
+to quantify the effective DMI, we explore its potential role in magnetization
+dynamics and multilevel magnetization switching. Experimental findings show
+four distinct resistance states under an external magnetic field and spin Hall
+effect related spin current. We explain this phenomenon based on the asymmetry
+between Pt/Co and Co/Pt interfaces and the interlayer coupling, which, in turn,
+influences DMI and subsequently impacts the magnetization dynamics. Numerical
+simulations, including macrospin, 1D domain wall, and simple spin wave models,
+further support the experimental observations of multilevel switching and help
+uncover the underlying mechanisms. Our proposed explanation, supported by
+magnetic domain observation using polar-magnetooptical Kerr microscopy, offers
+insights into both the spatial distribution of magnetization and its dynamics
+for different IECs, thereby shedding light on its interplay with DMI, which may
+lead to potential applications in storage devices.",2210.07357v2
+2023-02-27,Rotating hematite cube chains,"Recently a two-dimensional chiral fluid was experimentally demonstrated. It
+was obtained from cubic-shaped hematite colloidal particles placed in a
+rotating magnetic field. Here we look at building blocks of that fluid, by
+analyzing short hematite chain behavior in a rotating magnetic field. We find
+equilibrium structures of chains in static magnetic fields and observe chain
+dynamics in rotating magnetic fields. We find and experimentally verify that
+there are three planar motion regimes and one where the cube chain goes out of
+the plane of the rotating magnetic field. In this regime we observe interesting
+dynamics -- the chain rotates slower than the rotating magnetic field. In order
+to catch up with the magnetic field, it rolls on an edge and through rotation
+in the third dimension catches up with the magnetic field. The same dynamics is
+also observable for a single cube when gravitational effects are explicitly
+taken into account.",2302.13978v3
+2023-05-31,Magnetization dynamics in a three-dimensional interconnected nanowire array,"Three-dimensional magnetic nanostructures have recently emerged as artificial
+magnetic material types with unique properties bearing potential for
+applications, including magnonic devices. Interconnected magnetic nanowires are
+a sub-category within this class of materials that is attracting particular
+interest. We investigate the high-frequency magnetization dynamics in a cubic
+array of cylindrical magnetic nanowires through micromagnetic simulations based
+on a frequency-domain formulation of the linearized Landau-Lifshitz-Gilbert
+equation. The small-angle high-frequency magnetization dynamics excited by an
+external oscillatory field displays clear resonances at distinct frequencies.
+These resonances are identified as oscillations connected to specific geometric
+features and micromagnetic configurations. The geometry- and
+configuration-dependence of the nanowire array's absorption spectrum
+demonstrates the potential of such magnetic systems for tuneable and
+reprogrammable magnonic applications.",2306.00174v1
+2002-02-20,A Laboratory Plasma Experiment for Studying Magnetic Dynamics of Accretion Discs and Jets,"This work describes a laboratory plasma experiment and initial results which
+should give insight into the magnetic dynamics of accretion discs and jets. A
+high-speed multiple-frame CCD camera reveals images of the formation and
+helical instability of a collimated plasma, similar to MHD models of disc jets,
+and also plasma detachment associated with spheromak formation, which may have
+relevance to disc winds and flares. The plasmas are produced by a planar
+magnetized coaxial gun. The resulting magnetic topology is dependent on the
+details of magnetic helicity injection, namely the force-free state eigenvalue
+alpha_gun imposed by the coaxial gun.",0202380v1
+2004-12-15,Importance of magnetic helicity in dynamos,"Magnetic helicity is nearly conserved and its evolution equation provides a
+dynamical feedback on the alpha effect that is distinct from the conventional
+algebraic alpha quenching. The seriousness of this dynamical alpha quenching is
+particularly evident in the case of closed or periodic boxes. The explicit
+connection with catastrophic alpha quenching is reviewed and the alleviating
+effects of magnetic and current helicity fluxes are discussed.",0412366v1
+1997-07-08,Nonequilibrium Magnetization Dynamics of Nickel,"Ultrafast magnetization dynamics of nickel has been studied for different
+degrees of electronic excitation, using pump-probe second-harmonic generation
+with 150 fs/800 nm laser pulses of various fluences. Information about the
+electronic and magnetic response to laser irradiation is obtained from sums and
+differences of the SHG intensity for opposite magnetization directions. The
+classical M(T)-curve can be reproduced for delay times larger than the electron
+thermalization time of about 280 fs, even when electrons and lattice have not
+reached thermal equilibrium. Further we show that the transient magnetization
+reaches its minimum approx. 50 fs before electron thermalization is completed.",9707078v1
+1998-04-19,Switching dynamics between metastable ordered magnetic state and nonmagnetic ground state - A possible mechanism for photoinduced ferromagnetism -,"By studying the dynamics of the metastable magnetization of a statistical
+mechanical model we propose a switching mechanism of photoinduced
+magnetization. The equilibrium and nonequilibrium properties of the Blume-Capel
+(BC) model, which is a typical model exhibiting metastability, are studied by
+mean field theory and Monte Carlo simulation. We demonstrate reversible changes
+of magnetization in a sequence of changes of system parameters, which would
+model the reversible photoinduced magnetization. Implications of the calculated
+results are discussed in relation to the recent experimental results for
+prussian blue analogs.",9804203v3
+2000-11-13,Spin Excitations in Localized and Itinerant Magnets,"Collective excitations in magnetic materials can be investigated by means of
+inelastic neutron scattering. We show that this experimental method gives
+access to the complete spectrum of magnetic fluctuations through the energy-
+and momentum-dependence of the dynamical susceptibility. We focus on the
+dynamical properties of magnets with localized spin densities and of metals.
+  From such studies, microscopic parameters like exchange integrals, spin-wave
+stiffness and relaxation times can be determined. This is of great help to test
+current theories in magnetism.",0011220v1
+1996-11-25,Dynamical mass generation in 2+1-dimensional electrodynamics in an external magnetic field,"The influence of a magnetic field on the mass generation in 2+1 dimensional
+QED is considered.It is shown that the magnetic field is a catalyst of the
+generation of a fermion dynamical mass. The mass arises in the system with
+arbitrary number of fermions, not only with $N\leq 4$, as it is in the system
+without the magnetic field. The polarization tensor is calculated for a
+constant magnetic field.",9611412v1
+2006-04-11,Magnetic friction due to vortex fluctuation,"We use Monte Carlo and molecular dynamics simulation to study a magnetic
+tip-sample interaction. Our interest is to understand the mechanism of heat
+dissipation when the forces involved in the system are magnetic in essence. We
+consider a magnetic crystalline substrate composed of several layers
+interacting magnetically with a tip. The set is put thermally in equilibrium at
+temperature T by using a numerical Monte Carlo technique. By using that
+configuration we study its dynamical evolution by integrating numerically the
+equations of motion. Our results suggests that the heat dissipation in this
+system is closed related to the appearing of vortices in the sample.",0604092v1
+2007-01-11,A non local shell model of turbulent dynamo,"We derive a new shell model of magnetohydrodynamic (MHD) turbulence in which
+the energy transfers are not necessary local. Like the original MHD equations,
+the model conserves the total energy, magnetic helicity, cross-helicity and
+volume in phase space (Liouville's theorem) apart from the effects of external
+forcing, viscous dissipation and magnetic diffusion. In the absence of magnetic
+field the model exhibits a statistically stationary kinetic energy solution
+with a Kolmogorov spectrum. The dynamo action from a seed magnetic field by the
+turbulent flow and the non linear interactions are studied for a wide range of
+magnetic Prandtl numbers in both kinematic and dynamic cases. The non locality
+of the energy transfers are clearly identified.",0701141v1
+2010-01-26,Spin-wave instabilities in spin-transfer-driven magnetization dynamics,"We study the stability of magnetization precessions induced in spin-transfer
+devices by the injection of spin-polarized electric currents. Instability
+conditions are derived by introducing a generalized, far-from-equilibrium
+interpretation of spin-waves. It is shown that instabilities are generated by
+distinct groups of magnetostatically coupled spin-waves. Stability diagrams are
+constructed as a function of external magnetic field and injected
+spin-polarized current. These diagrams show that applying larger fields and
+currents has a stabilizing effect on magnetization precessions. Analytical
+results are compared with numerical simulations of spin-transfer-driven
+magnetization dynamics.",1001.4806v1
+2010-07-09,Polarization and magnetization dynamics of a field-driven multiferroic structure,"We consider a multiferroic chain with a linear magnetoelectric coupling
+induced by the electrostatic screening at the ferroelectric/ferromagnet
+interface. We study theoretically the dynamic ferroelectric and magnetic
+response to external magnetic and electric fields by utilizing an approach
+based on coupled Landau- Khalatnikov and finite-temperature
+Landau-Lifshitz-Gilbert equations. Additionally, we compare with Monte Carlo
+calculations. It is demonstrated that for material parameters corresponding to
+BaTiO3/Fe the polarization and the magnetization are controllable by external
+magnetic and electric fields respectively.",1007.1543v1
+2011-05-11,Dynamic fields in the partial magnetization plateau of Ca3Co2O6,"Fluctuation dynamics in magnetization plateaux are a relatively poorly
+explored area in frustrated magnetism. Here we use muon spin relaxation to
+determine the fluctuation timescale and associated field distribution width in
+the partial magnetization plateau of Ca3Co2O6. The muon spin relaxation rate
+has a simple and characteristic field dependence which we model and by fitting
+to the data at 15 K extract a fluctuation timescale tau = 880(30) ps and a
+field distribution width Delta = 40.6(3) mT. Comparison with previous results
+on Ca3Co2O6 suggests that this fluctuation timescale can be associated with
+short-range, slowly fluctuating magnetic order.",1105.2200v1
+2011-05-24,Low-dimensionality and predictability of solar wind and global magnetosphere during magnetic storms,"The storm index SYM-H, the solar wind velocity v, and interplanetary magnetic
+field Bz show no signatures of low-dimensional dynamics in quiet periods, but
+tests for determinism in the time series indicate that SYM-H exhibits a
+significant low-dimensional component during storm time, suggesting that
+self-organization takes place during magnetic storms. Even though our analysis
+yields no discernible change in determinism during magnetic storms for the
+solar wind parameters, there are significant enhancement of the predictability
+and exponents measuring persistence. Thus, magnetic storms are typically
+preceded by an increase in the persistence of the solar wind dynamics, and this
+increase is also present in the magnetospheric response to the solar wind.",1105.4763v1
+2011-06-13,Quantum Dynamics of a Nanomagnet driven by Spin-Polarized Current,"A quantum theory of magnetization dynamics of a nanomagnet as a sequence of
+scatterings of each electron spin with the macrospin state of the magnetization
+results in each encounter a probability distribution of the magnetization
+recoil state associated with each outgoing state of the electron. The quantum
+trajectory of the magnetization contains the average motion tending in the
+large spin limit to the semi-classical results of spin transfer torque and the
+fluctuations giving rise to a quantum magnetization noise and an additional
+noise traceable to the current noise.",1106.2359v1
+2013-11-07,Dynamics of two-dimensional complex plasmas in a magnetic field,"We consider a two-dimensional complex plasma layer containing charged dust
+particles in a perpendicular magnetic field. Computer simulations of both
+one-component and binary systems are used to explore the equilibrium particle
+dynamics in the fluid state. The mobility is found to scale with the inverse of
+the magnetic field strength (Bohm diffusion) for strong fields. For bidisperse
+mixtures, the magnetic field dependence of the long-time mobility depends on
+the particle species providing an external control of their mobility ratio. For
+large magnetic fields, even a two-dimensional model porous matrix can be
+realized composed by the almost immobilized high-charge particles which act as
+obstacles for the mobile low-charge particles.",1311.1668v1
+2015-04-23,Magnetization damping in noncollinear spin valves with antiferromagnetic interlayer couplings,"We study the magnetic damping in the simplest of synthetic antiferromagnets,
+i.e. antiferromagnetically exchange-coupled spin valves in which applied
+magnetic fields tune the magnetic configuration to become noncollinear. We
+formulate the dynamic exchange of spin currents in a noncollinear texture based
+on the spindiffusion theory with quantum mechanical boundary conditions at the
+ferrromagnet|normal-metal interfaces and derive the Landau-Lifshitz-Gilbert
+equations coupled by the static interlayer non-local and the dynamic exchange
+interactions. We predict non-collinearity-induced additional damping that can
+be sensitively modulated by an applied magnetic field. The theoretical results
+compare favorably with published experiments.",1504.06042v1
+2016-02-09,A problem of Ulam about magnetic fields generated by knotted wires,"In the context of magnetic fields generated by wires, we study the connection
+between the topology of the wire and the topology of the magnetic lines. We
+show that a generic knotted wire has a magnetic line of the same knot type, but
+that given any pair of knots there is a wire isotopic to the first knot having
+a magnetic line isotopic to the second. These questions can be traced back to
+Ulam in 1935.",1602.03142v1
+2016-04-21,Non-equilibrium magnetic fields in ab initio spin dynamics,"Starting from the continuity equation for the magnetization in time-dependent
+spin-density functional theory, we derive an expression for the effective
+time-dependent magnetic fields driving the out-of-equilibrium spin dynamics in
+magnetic systems. We evaluate these, so called, kinetic magnetic fields in the
+ultrafast demagnetization response to optical pulse excitations of
+ferromagnetic iron-based materials, namely Fe$_6$ cluster and bulk bcc Fe. We
+identify spatial ""hot spots"" where the demagnetization is particularly enhanced
+as a result of the increased kinetic torque.",1604.06262v2
+2016-09-27,Sustained Turbulence in Differentially Rotating Magnetized Fluids at Low Magnetic Prandtl Number,"We show for the first time that sustained turbulence is possible at low
+magnetic Prandtl number for Keplerian flows with no mean magnetic flux. Our
+results indicate that increasing the vertical domain size is equivalent to
+increasing the dynamical range between the energy injection scale and the
+dissipative scale. This has important implications for a large variety of
+differentially rotating systems with low magnetic Prandtl number such as
+protostellar disks and laboratory experiments.",1609.08543v1
+2018-04-15,Re-orientation of easy axis in $\varphi_0$ junction,"We study theoretically a dynamics of $\varphi_0$ junction with direct
+coupling between magnetic moment and Josephson current which shows features
+close to Kapitza pendulum. We have found that starting with oscillations along
+$z$-axis, the character of magnetization dynamics changes crucially and stable
+position of magnetic moment $\vec m$ is realized between $z-$ and $y$-axes
+depending on parameters of the system. Changes in critical current and
+spin-orbit interaction lead to the different stability regions for
+magnetization. An excellent agreement between analytical and numerical results
+is obtained for low values of the Josephson to magnetic energy ratio.",1804.05391v1
+2018-04-19,Damping of magnetization dynamics by phonon pumping,"We theoretically investigate pumping of phonons by the dynamics of a magnetic
+film into a non-magnetic contact. The enhanced damping due to the loss of
+energy and angular momentum shows interference patterns as a function of
+resonance frequency and magnetic film thickness that cannot be described by
+viscous (""Gilbert"") damping. The phonon pumping depends on magnetization
+direction as well as geometrical and material parameters and is observable,
+e.g., in thin films of yttrium iron garnet on a thick dielectric substrate.",1804.07080v2
+2018-07-13,On the classical dynamics of charged particle in special class of spatially non-uniform magnetic field,"Motion of a charged particle in uniform magnetic field has been studied in
+detail, classically as well as quantum mechanically. However, classical
+dynamics of a charged particle in non-uniform magnetic field is solvable only
+for some specific cases. We present in this paper, a general integral equation
+for some specific class of non-uniform magnetic field and its solutions for
+some of them. We also examine the supersymmetry of Hamiltonians in
+exponentially decaying magnetic field with radial dependence and conclude that
+this kind of non-uniformity breaks supersymmetry.",1807.05216v1
+2019-03-22,Learning magnetization dynamics,"Deep neural networks are used to model the magnetization dynamics in magnetic
+thin film elements. The magnetic states of a thin film element can be
+represented in a low dimensional space. With convolutional autoencoders a
+compression ratio of 1024:1 was achieved. Time integration can be performed in
+the latent space with a second network which was trained by solutions of the
+Landau-Lifshitz-Gilbert equation. Thus the magnetic response to an external
+field can be computed quickly.",1903.09499v1
+2019-05-10,Lagrangian formulation for emergent elastic waves in magnetic emergent crystals,"Magnetic emergent crystals are periodic alignment of ""particle-like"" spin
+textures that emerge in magnets. Instead of focusing on an individual spin or a
+macroscopic magnetization field, we analyze the dynamical behaviors of these
+novel states by taking a solid-state point of view. Based on variational
+principles, the basic equations for lattice dynamics of any emergent
+crystalline states appearing in magnetic materials is established. For small
+amplitude emergent elastic waves propagating in emergent crystals, the basic
+equations reduce to an eigenvalue problem, from which the dispersion relation
+and vibrational patterns for all emergent phonons are determined at the long
+wavelength limit.",1905.03991v1
+2019-12-22,Observation of magnetic solitons in two-component Bose-Einstein condensates,"We experimentally investigate the dynamics of spin solitary waves (magnetic
+solitons) in a harmonically trapped, binary superfluid mixture. We measure the
+in-situ density of each pseudospin component and their relative local phase via
+an interferometric technique we developed, and as such, fully characterise the
+magnetic solitons while they undergo oscillatory motion in the trap. Magnetic
+solitons exhibit non-dispersive, dissipationless long-time dynamics. By
+imprinting multiple magnetic solitons in our ultracold gas sample, we engineer
+binary collisions between solitons of either same or opposite magnetisation and
+map out their trajectories.",1912.10513v2
+2022-04-08,Particle dynamics in non-rotating Konoplya and Zhidenko black hole immersed in an external uniform magnetic field,"In this paper, we investigate the dynamics of particles in the background of
+non-rotating Konoplya and Zhidenko black hole that is immersed in an external
+uniform magnetic field. The work involves circular motion of electric and
+magnetic particles and particle acceleration. First the motion of electric
+charged particles is considered. The effective potential, energy and angular
+momentum expressions are obtained along with their graphs. The analysis of ISCO
+shows that radii of ISCO decrease with magnetic interaction parameter. Motion
+of magnetically charged particles has also been studied.",2204.04195v1
+2022-09-28,Unidirectional magnetic coupling,"We show that interlayer Dzyaloshinskii-Moriya interaction in combination with
+non-local Gilbert damping gives rise to unidirectional magnetic coupling. That
+is, the coupling between two magnetic layers -- say the left and right layer --
+is such that dynamics of the left layer leads to dynamics of the right layer,
+but not vice versa. We discuss the implications of this result for the magnetic
+susceptibility of a magnetic bilayer, electrically-actuated spin-current
+transmission, and unidirectional spin-wave packet generation and propagation.
+Our results may enable a route towards spin-current and spin-wave diodes and
+further pave the way to design spintronic devices via reservoir engineering.",2209.14179v1
+2007-02-14,Dynamic Phase Transition in the Kinetic Spin-3/2 Blume-Capel Model: Phase Diagrams in the Temperature and Crystal-Field Interaction Plane,"We analyze, within a mean-field approach, the stationary states of the
+kinetic spin-3/2 Blume-Capel model by the Glauber-type stochastic dynamics and
+subject to a time-dependent oscillating external magnetic field. The dynamic
+phase transition points are obtained by investigating the behavior of the
+dynamic magnetization as a function of temperature and as well as calculating
+the Liapunov exponent. Phase diagrams are constructed in the temperature and
+crystal-field interaction plane. We find five fundamental types of phase
+diagrams for the different values of the reduced magnetic field amplitude
+parameter (h) in which they present a disordered, two ordered phases and the
+coexistences phase regions. The phase diagrams also exhibit a dynamic double
+critical end point for 0<h<1.44, one dynamic tricritical point for 1.44<h<5.06
+and two dynamic tricritical points for h>5.06.",0702325v1
+2013-11-14,Nonequilibrium dynamics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic system with a time dependent oscillating magnetic field source,"Nonequilibrium phase transition properties of a mixed Ising ferrimagnetic
+model consisting of spin-1/2 and spin-3/2 on a square lattice under the
+existence of a time dependent oscillating magnetic field have been investigated
+by making use of Monte Carlo simulations with single-spin flip Metropolis
+algorithm. A complete picture of dynamic phase boundary and magnetization
+profiles have been illustrated and the conditions of a dynamic compensation
+behavior have been discussed in detail. According to our simulation results,
+the considered system does not point out a dynamic compensation behavior, when
+it only includes the nearest-neighbor interaction, single-ion anisotropy and an
+oscillating magnetic field source. As the next-nearest-neighbor interaction
+between the spins-1/2 takes into account and exceeds a characteristic value
+which sensitively depends upon values of single-ion anisotropy and only of
+amplitude of external magnetic field, a dynamic compensation behavior occurs in
+the system. Finally, it is reported that it has not been found any evidence of
+dynamically first-order phase transition between dynamically ordered and
+disordered phases, which conflicts with the recently published molecular field
+investigation, for a wide range of selected system parameters.",1311.3537v2
+2014-06-25,Cylindrical Ising Nanowire in an Oscillating Magnetic Field and Dynamic Compensation Temperature,"The magnetic properties of a nonequilibrium spin-1/2 cylindrical Ising
+nanowire system with core/shell in an oscillating magnetic field are studied by
+using a mean-field approach based on the Glauber-type stochastic dynamics
+(DMFT). We employ the Glaubertype stochastic dynamics to construct set of the
+coupled mean-field dynamic equations. First, we study the temperature
+dependence of the dynamic order parameters to characterize the nature of the
+phase transitions and to obtain the dynamic phase transition points. Then, we
+investigate the temperature dependence of the total magnetization to find the
+dynamic compensation points as well as to determine the type of behavior. The
+phase diagrams in which contain the paramagnetic, ferromagnetic,
+antiferromagnetic, nonmagnetic, surface fundamental phases and tree mixed
+phases as well as reentrant behavior are presented in the reduced magnetic
+field amplitude and reduced temperature plane. According to values of
+Hamiltonian parameters, the compensation temperatures, or the N-, Q-, P-, R-,
+S-type behaviors in the Neel classification nomenclature exist in the system.",1406.6552v1
+2018-03-03,"Dynamics in a one-dimensional ferrogel model: relaxation, pairing, shock-wave propagation","Ferrogels are smart soft materials, consisting of a polymeric network and
+embedded magnetic particles. Novel phenomena, such as the variation of the
+overall mechanical properties by external magnetic fields, emerge consequently.
+However, the dynamic behavior of ferrogels remains largely unveiled. In this
+paper, we consider a one-dimensional chain consisting of magnetic dipoles and
+elastic springs between them as a simple model for ferrogels. The model is
+evaluated by corresponding simulations. To probe the dynamics theoretically, we
+investigate a continuum limit of the energy governing the system and the
+corresponding equation of motion. We provide general classification scenarios
+for the dynamics, elucidating the touching/detachment dynamics of the magnetic
+particles along the chain. In particular, it is verified in certain cases that
+the long-time relaxation corresponds to solutions of shock-wave propagation,
+while formations of particle pairs underlie the initial stage of the dynamics.
+We expect that these results will provide insight into the understanding of the
+dynamics of more realistic models with randomness in parameters and
+time-dependent magnetic fields.",1803.01225v1
+2018-07-09,Hybrid-State Free Precession in Nuclear Magnetic Resonance,"The dynamics of large spin-1/2 ensembles in the presence of a varying
+magnetic field are commonly described by the Bloch equation. Most magnetic
+field variations result in unintuitive spin dynamics, which are sensitive to
+small deviations in the driving field. Although simplistic field variations can
+produce robust dynamics, the captured information content is impoverished.
+Here, we identify adiabaticity conditions that span a rich experiment design
+space with tractable dynamics. These adiabaticity conditions trap the spin
+dynamics in a one-dimensional subspace. Namely, the dynamics is captured by the
+absolute value of the magnetization, which is in a transient state, while its
+direction adiabatically follows the steady state. We define the hybrid state as
+the co-existence of these two states and identify the polar angle as the
+effective driving force of the spin dynamics. As an example, we optimize this
+drive for robust and efficient quantification of spin relaxation times and
+utilize it for magnetic resonance imaging of the human brain.",1807.03424v1
+2021-01-21,Effects of the dynamical magnetization state on spin transfer,"We utilize simulations of electron scattering by a chain of dynamical quantum
+spins, to analyze the interplay between the spin transfer effect and the
+magnetization dynamics. We show that the complex interactions between the
+spin-polarized electrons and the dynamical states of the local spins can be
+decomposed into separate processes involving electron reflection and
+transmission, as well as absorption and emission of magnons - the quanta of
+magnetization dynamics. Analysis shows that these processes are substantially
+constrained by the energy and momentum conversation laws, resulting in a
+significant dependence of spin transfer on the electron's energy and the
+dynamical state of the local spins. Our results suggest that exquisite control
+of spin transfer efficiency and of the resulting dynamical magnetization states
+may be achievable by tailoring the spectral characteristics of the conduction
+electrons and of the magnetic systems.",2101.08868v1
+2021-11-26,Three-dimensional Resonant Magnetization Dynamics Unraveled by Time-Resolved Soft X-ray Laminography,"The imaging of magneto-dynamical processes has been, so far, mostly a
+two-dimensional business, due to the constraints of the available experimental
+techniques. In this manuscript, building on the recent developments of soft
+X-ray magnetic laminography, we present an experimental setup where
+magneto-dynamical processes can be resolved in all three spatial dimensions and
+in time, with the possibility to freely tune the frequency of the dynamical
+process. We then employ this setup to investigate the three-dimensional
+dynamics of two resonant magneto-dynamical modes in a CoFeB microstructure
+occurring at different frequencies, namely the fundamental vortex gyration mode
+and a magnetic field-induced domain wall excitation mode. This new technique
+provides much needed capabilities for the experimental investigation of the
+magnetization dynamics of three-dimensional magnetic systems.",2111.13533v1
+2022-05-04,Exceptional points as signatures of dynamical magnetic phase transitions,"One of the most fascinating and puzzling aspects of non-Hermitian systems is
+their spectral degeneracies, i.e., exceptional points (EPs), at which both
+eigenvalues and eigenvectors coalesce to form a defective state space. While
+coupled magnetic systems are natural hosts of EPs, the relation between the
+linear and nonlinear spin dynamics in the proximity of EPs remains relatively
+unexplored. Here we theoretically investigate the spin dynamics of easy-plane
+magnetic bilayers in the proximity of exceptional points. We show that the
+interplay between the intrinsically dissipative spin dynamics and external
+drives can yield a rich dynamical phase diagram. In particular, we find that,
+in antiferromagnetically coupled bilayers, a periodic oscillating dynamical
+phase emerges in the region enclosed by EPs. Our results not only offer a
+pathway for probing magnetic EPs and engineering magnetic nano-oscillators with
+large-amplitude oscillations, but also uncover the relation between exceptional
+points and dynamical phase transitions in systems displaying non-linearities.",2205.02308v2
+2013-05-22,Self-consistent calculation of spin transport and magnetization dynamics,"A spin-polarized current transfers its spin-angular momentum to a local
+magnetization, exciting current-induced magnetization dynamics. So far, most
+studies in this field have focused on the direct effect of spin transport on
+magnetization dynamics, but ignored the feedback from the magnetization
+dynamics to the spin transport and back to the magnetization dynamics. Although
+the feedback is usually weak, there are situations when it can play an
+important role in the dynamics. In such situations, self-consistent
+calculations of the magnetization dynamics and the spin transport can
+accurately describe the feedback. This review describes in detail the feedback
+mechanisms, and presents recent progress in self-consistent calculations of the
+coupled dynamics. We pay special attention to three representative examples,
+where the feedback generates non-local effective interactions for the
+magnetization. Possibly the most dramatic feedback example is the dynamic
+instability in magnetic nanopillars with a single magnetic layer. This
+instability does not occur without non-local feedback. We demonstrate that full
+self-consistent calculations generate simulation results in much better
+agreement with experiments than previous calculations that addressed the
+feedback effect approximately. The next example is for more typical spin valve
+nanopillars. Although the effect of feedback is less dramatic because even
+without feedback the current can induce magnetization oscillation, the feedback
+can still have important consequences. For instance, we show that the feedback
+can reduce the linewidth of oscillations, in agreement with experimental
+observations. Finally, we consider nonadiabatic electron transport in narrow
+domain walls. The non-local feedback in these systems leads to a significant
+renormalization of the effective nonadiabatic spin transfer torque.",1305.5087v1
+2005-05-29,Dynamical Aspects of Photoinduced Magnetism and Spin-Crossover phenomena in Prussian Blue Analogs,"We present dynamical properties of spin crossover compounds with
+photomagnetization, proposing a new model in which the spin-crossover phenomena
+and magnetic ordering are incorporated in a unified way. By using this model,
+the novel characteristics observed in Prussian blue analogs are qualitatively
+well reproduced. We investigate the time evolution of the magnetization and
+high spin fraction taking into account multi-time scales in a master equation
+approach for the magnetic relaxation, the lattice (electronic) relaxation, and
+the photoexcitation process. In particular, processes with different
+temperature cycles starting from the photoinduced saturated magnetic state are
+studied including the effect of photoirradiation. In the temperature cycle in
+the low temperature region where the high spin state has a strong
+metastability, the magnetization almost exactly follows the quasi-static
+process. On the other hand, when the temperature is raised above the region,
+the dynamics of the spin state and the magnetization couple and exhibit various
+types of dynamical cooperative phenomena under time-dependent control of
+temperature and photoirradiation.",0505702v1
+2006-06-23,Dynamical spin chirality and spin anisotropy in gapped S=1/2 quantum systems,"We have studied the spin anisotropy in spin-singlet ground state compounds
+and the magnetic chirality, as measured by inelastic polarized neutron
+scattering techniques, in the chain-sublattice of Sr14Cu24O41. In-plane and out
+of plane magnetic fluctuations are measured to be anisotropic and further
+discussed in the light of the current hypothesis of spin-orbit coupling. We
+show that under appropriate conditions of magnetic field and neutron
+polarization, the \textit{trivial} magnetic chirality selects only one of the
+Zeeman splitted triplet states for scattering and erases the other one that
+posses opposite helicity. Our analysis pertains to previous studies on
+dynamical magnetic chirality and chiral critical exponents, where the ground
+state is chiral itself, the so-called \textit{non-trivial} dynamical magnetic
+chirality. As it turns out, both \textit{trivial} and \textit{non-trivial}
+dynamical magnetic chirality have identical selection rules for inelastic
+polarized neutron scattering experiments and it is not at all evident that they
+can be distinguished in a paramagnetic compound.",0606598v1
+2004-05-10,Convective plan-form two-scale dynamos in a plane layer,"We study generation of magnetic fields, involving large spatial scales, by
+convective plan-forms in a horizontal layer. Magnetic modes and their growth
+rates are expanded in power series in the scale ratio, and the magnetic eddy
+diffusivity (MED) tensor is derived for flows, symmetric about the vertical
+axis in a layer. For convective rolls magnetic eddy correction is demonstrated
+to be always positive. For rectangular cell patterns, the region in the
+parameter space of negative MED coincides with that of small-scale magnetic
+field generation. No instances of negative MED in hexagonal cells are found. A
+family of plan-forms with a smaller symmetry group than that of rectangular
+cell patterns has been found numerically, where MED is negative for molecular
+magnetic diffusivity over the threshold for the onset of small-scale magnetic
+field generation.",0405045v2
+2007-05-03,Planar spin-transfer device with a dynamic polarizer,"In planar nano-magnetic devices magnetization direction is kept close to a
+given plane by the large easy-plane magnetic anisotropy, for example by the
+shape anisotropy in a thin film. In this case magnetization shows effectively
+in-plane dynamics with only one angle required for its description. Moreover,
+the motion can become overdamped even for small values of Gilbert damping. We
+derive the equations of effective in-plane dynamics in the presence of
+spin-transfer torques. The simplifications achieved in the overdamped regime
+allow to study systems with several dynamic magnetic pieces (``free layers'').
+A transition from a spin-transfer device with a static polarizer to a device
+with two equivalent magnets is observed. When the size difference between the
+magnets is less than critical, the device does not exhibit switching, but goes
+directly into the ``windmill'' precession state.",0705.0406v1
+2015-05-28,Dynamics of an ensemble of clumps embedded in a magnetized ADAF,"We investigate effects of a global magnetic field on the dynamics of an
+ensemble of clumps within a magnetized advection-dominated accretion flow by
+neglecting interactions between the clumps and then solving the collisionless
+Boltzman equation. In the strong-coupling limit, in which the averaged radial
+and the rotational velocities of the clumps follow the ADAF dynamics, the
+averaged radial velocity square of the clumps is calculated analytically for
+different magnetic field configurations. The value of the averaged radial
+velocity square of the clumps increases with increasing the strength of the
+radial or vertical components of the magnetic field. But a purely toroidal
+magnetic field geometry leads to a reduction of the value of the averaged
+radial velocity square of the clumps at the inner parts with increasing the
+strength of this component. Moreover, dynamics of the clumps strongly depends
+on the amount of the advected energy so that the value of the averaged radial
+velocity square of the clumps increases in the presence of a global magnetic
+field as the flow becomes more advective.",1505.07566v1
+2016-05-17,Direct observation of dynamic modes excited in a magnetic insulator by pure spin current,"Excitation of magnetization dynamics by pure spin currents has been recently
+recognized as an enabling mechanism for spintronics and magnonics, which allows
+implementation of spin-torque devices based on low-damping insulating magnetic
+materials. Here we report the first spatially-resolved study of the dynamic
+modes excited by pure spin current in nanometer-thick microscopic insulating
+Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear
+self-broadening preventing the formation of the self-localized magnetic bullet,
+which plays a crucial role in the stabilization of the single-mode
+magnetization oscillations in all-metallic systems. This peculiarity associated
+with the efficient nonlinear mode coupling in low-damping materials can be
+among the main factors governing the interaction of pure spin currents with the
+dynamic magnetization in high-quality magnetic insulators.",1605.05211v1
+2016-11-18,Propagating spin-wave normal modes: A dynamic matrix approach using plane-wave demagnetizating tensors,"We present a finite-difference micromagnetic approach for determining the
+normal modes of spin-waves propagating in extended magnetic films and strips,
+which is based on the linearized Landau-Lifshitz equation and uses the dynamic
+matrix method. The model takes into account both short range exchange
+interactions and long range dipole-dipole interactions. The latter are
+accounted for through plane-wave dynamic demagnetization factors, which depend
+not only on the geometry and relative positions of the magnetic cells, as usual
+demagnetization factors do, but also on the wave vector of the propagating
+waves. Such a numerical model is most relevant when the spin-wave medium is
+spatially inhomogeneous perpendicular to the direction of propagation, either
+in its magnetic properties or in its equilibrium magnetic configuration. We
+illustrate this point by studying surface spin-waves in magnetic bilayer films
+and spin-waves channelized along magnetic domain walls in perpendicularly
+magnetized strips. In both cases, dynamic dipolar interactions produce
+non-reciprocity effects, where counter-propagative spin-waves have different
+frequencies.",1611.06153v1
+2019-04-25,Electrical response of S-F-TI-S junctions on magnetic texture dynamics,"We consider a hybrid structure consisting of superconducting or normal leads
+with a combined ferromagnet-3D topological insulator interlayer. We compare
+responses of a Josephson junction and a normal junction to magnetic texture
+dynamics. In both cases the electromotive force resulting from the
+magnetization dynamics generates a voltage between the junction leads. For an
+open circuit this voltage is the same for normal and superconducting leads and
+allows for electrical detection of magnetization dynamics and a structure of a
+given magnetic texture. However, under the applied current the electrical
+response of the Josephson junction is essentially different due to the strong
+dependence of the critical Josephson current on the magnetization direction and
+can be used for experimental probing of this dependence. We propose a setup,
+which is able to detect a defect motion and to provide detailed information
+about the structure of magnetic inhomogeneity. The discussed effect could be of
+interest for spintronics applications.",1904.11193v3
+2019-05-29,Extracting the Dynamic Magnetic Contrast in Time-Resolved X-ray Transmission Microscopy,"Using a time-resolved detection scheme in scanning transmission X-ray
+microscopy (STXM) we measured element resolved ferromagnetic resonance (FMR) at
+microwave frequencies up to 10\,GHz and a spatial resolution down to 20\,nm at
+two different synchrotrons. We present different methods to separate the
+contribution of the background from the dynamic magnetic contrast based on the
+X-ray magnetic circular dichroism (XMCD) effect. The relative phase between the
+GHz microwave excitation and the X-ray pulses generated by the synchrotron, as
+well as the opening angle of the precession at FMR can be quantified. A
+detailed analysis for homogeneous and inhomogeneous magnetic excitations
+demonstrates that the dynamic contrast indeed behaves as the usual XMCD effect.
+The dynamic magnetic contrast in time-resolved STXM has the potential be a
+powerful tool to study the linear and non-linear magnetic excitations in
+magnetic micro- and nano-structures with unique spatial-temporal resolution in
+combination with element selectivity.",1905.12497v2
+2023-06-23,Spintronic reservoir computing without driving current or magnetic field,"Recent studies have shown that nonlinear magnetization dynamics excited in
+nanostructured ferromagnets are applicable to brain-inspired computing such as
+physical reservoir computing. The previous works have utilized the
+magnetization dynamics driven by electric current and/or magnetic field. This
+work proposes a method to apply the magnetization dynamics driven by voltage
+control of magnetic anisotropy to physical reservoir computing, which will be
+preferable from the viewpoint of low-power consumption. The computational
+capabilities of benchmark tasks in single MTJ are evaluated by numerical
+simulation of the magnetization dynamics and found to be comparable to those of
+echo-state networks with more than 10 nodes.",2306.13270v1
+2000-10-07,Properties of Simulated Magnetized Galaxy Clusters,"We study the evolution of magnetized clusters in a cosmological environment
+using magneto-hydro dynamical simulations. Large scale flows and merging of
+subclumps generate shear flows leading to Kelvin-Helmholtz instabilities,
+which, in addition to the compression of the gas where the magnetic field is
+frozen in, further amplify the magnetic field during the evolution of the
+cluster. Therefore, well-motivated initial magnetic fields of
+$<B^2>^{1/2}=10^{-9} {\rm G}$ reach the observed $\sim\mu{\rm G}$ field
+strengths in the cluster cores at $z=0$. These magnetized clusters can be used
+to study the final magnetic field structure, the dynamical importance of
+magnetic fields for the interpretation of observed X-Ray properties, and help
+to constrain further processes in galaxy clusters like the population of
+relativistic particles giving rise to the observed radio halos or the behavior
+of magnetized cooling flows.",0010149v1
+2010-01-15,Control of the chirality and polarity of magnetic vortices in triangular nanodots,"Magnetic vortex dynamics in lithographically prepared nanodots is currently a
+subject of intensive research, particularly after recent demonstration that the
+vortex polarity can be controlled by in-plane magnetic field. This has
+stimulated the proposals of non-volatile vortex magnetic random access
+memories. In this work, we demonstrate that triangular nanodots offer a real
+alternative where vortex chirality, in addition to polarity, can be controlled.
+In the static regime, we show that vortex chirality can be tailored by applying
+in-plane magnetic field, which is experimentally imaged by means of
+Variable-Field Magnetic Force Microscopy. In addition, the polarity can be also
+controlled by applying a suitable out-of-plane magnetic field component. The
+experiment and simulations show that to control the vortex polarity, the
+out-of-plane field component, in this particular case, should be higher than
+the in-plane nucleation field. Micromagnetic simulations in the dynamical
+regime show that the magnetic vortex polarity can be changed with
+short-duration magnetic field pulses, while longer pulses change the vortex
+chirality.",1001.2682v1
+2014-05-09,Magnetization dynamics and damping due to electron-phonon scattering in a ferrimagnetic exchange model,"We present a microscopic calculation of magnetization damping for a magnetic
+""toy model."" The magnetic system consists of itinerant carriers coupled
+antiferromagnetically to a dispersionless band of localized spins, and the
+magnetization damping is due to coupling of the itinerant carriers to a phonon
+bath in the presence of spin-orbit coupling. Using a mean-field approximation
+for the kinetic exchange model and assuming the spin-orbit coupling to be of
+the Rashba form, we derive Boltzmann scattering integrals for the distributions
+and spin coherences in the case of an antiferromagnetic exchange splitting,
+including a careful analysis of the connection between lifetime broadening and
+the magnetic gap. For the Elliott-Yafet type itinerant spin dynamics we extract
+dephasing and magnetization times T_1 and T_2 from initial conditions
+corresponding to a tilt of the magnetization vector, and draw a comparison to
+phenomenological equations such as the Landau-Lifshitz or the Gilbert damping.
+We also analyze magnetization precession and damping for this system including
+an anisotropy field and find a carrier mediated dephasing of the localized spin
+via the mean-field coupling.",1405.2347v1
+2014-06-26,Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient,"Interaction between local magnetization and conduction electrons is
+responsible for a variety of phenomena in magnetic materials. It has been
+recently shown that spin current and associated electric voltage can be induced
+by magnetization that depends on both time and space. This effect, called
+spinmotive force, provides for a powerful tool for exploring the dynamics and
+the nature of magnetic textures, as well as a new source for electromotive
+force. Here we theoretically demonstrate the generation of electric voltages in
+magnetic bubble array systems subjected to a magnetic field gradient. It is
+shown by deriving expressions for the electric voltages that the present system
+offers a direct measure of phenomenological parameter that describes
+non-adiabaticity in the current induced magnetization dynamics. This spinmotive
+force opens a door for new types of spintronic devices that exploit the
+field-gradient.",1406.6964v2
+2014-11-10,Induced magnetic moment in the magnetic catalysis of chiral symmetry breaking,"The chiral symmetry breaking in a Nambu-Jona-Lasinio effective model of
+quarks in the presence of a magnetic field is investigated. We show that new
+interaction tensor channels open up via Fierz identities due to the explicit
+breaking of the rotational symmetry by the magnetic field. We demonstrate that
+the magnetic catalysis of chiral symmetry breaking leads to the generation of
+two independent condensates, the conventional chiral condensate and a spin-one
+condensate. While the chiral condensate generates, as usual, a dynamical
+fermion mass, the new condensate enters as a dynamical anomalous magnetic
+moment in the dispersion of the quasiparticles. Since the pair, formed by a
+quark and an antiquark with opposite spins, possesses a resultant magnetic
+moment, an external magnetic field can align it giving rise to a net magnetic
+moment for the ground state. The two condensates contribute to the effective
+mass of the LLL quasiparticles in such a way that the critical temperature for
+chiral symmetry restoration becomes enhanced.",1411.2493v1
+2016-04-03,Spin relaxation signature of colossal magnetic anisotropy in platinum atomic chains,"Recent experimental data demonstrate emerging magnetic order in platinum
+atomically thin nanowires. Furthermore, an unusual form of magnetic anisotropy
+-- colossal magnetic anisotropy (CMA) -- was earlier predicted to exist in
+atomically thin platinum nanowires. Using spin dynamics simulations based on
+first-principles calculations, we here explore the spin dynamics of atomically
+thin platinum wires to reveal the spin relaxation signature of colossal
+magnetic anisotropy, comparing it with other types of anisotropy such as
+uniaxial magnetic anisotropy (UMA). We find that the CMA alters the spin
+relaxation process distinctly and, most importantly, causes a large speed-up of
+the magnetic relaxation compared to uniaxial magnetic anisotropy. The magnetic
+behavior of the nanowire exhibiting CMA should be possible to identify
+experimentally at the nanosecond time scale for temperatures below 5 K. This
+time-scale is accessible in e.g., soft x-ray free electron laser experiments.",1604.00626v1
+2018-12-03,Engineering planar transverse domain walls in biaxial magnetic nanostrips by tailoring transverse magnetic fields with uniform orientation,"Designing and realizing various magnetization textures in magnetic
+nanostructures are essential for developing novel magnetic nanodevices in
+modern information industry. Among all these textures, planar transverse domain
+walls (pTDWs) are the simplest and the most basic, which make them popular in
+device physics. In this work, we report the engineering of pTDWs with arbitrary
+tilting attitude in biaxial magnetic nanostrips by transverse magnetic field
+profiles with uniform orientation but tunable strength distribution. Both
+statics and axial-field-driven dynamics of these pTDWs are analytically
+investigated. It turns out that for statics these pTDWs are robust again
+disturbances which are not too abrupt, while for dynamics it can be tailored to
+acquire higher velocity than Walker's ansatz predicts. These results should
+provide inspirations for designing magnetic nanodevices with novel
+one-dimensional magnetization textures, such as 360$^\circ$ walls, or even
+two-dimensional ones, for example vortices, skyrmions, etc.",1812.00581v1
+2019-07-23,Transverse magnetic field influence on wakefield in complex plasmas,"We present the results of an investigation of the wakefield around a
+stationary charged grain in an external magnetic field with non-zero transverse
+component with respect to the ion flow direction. The impact of the orientation
+of magnetic field on the wake behavior in streaming complex plasmas is
+assessed. In contrast to previously reported significant suppression of the
+wake oscillations due to longitudinal magnetic field applied along flow, in the
+presence of transverse to flow magnetic field the wakefield exhibits a long
+range recurrent oscillations. Extensive investigation for a wide range of
+parameters reveal that in the sonic and supersonic regimes the wake has strong
+dependence on the direction of the magnetic field and exhibits sensitivity to
+even a meager deviation of magnetic field from the longitudinal orientation.
+The tool obtained with the study of impact of transverse component of magnetic
+field on the wake around grain in streaming ions can be used to potentially
+maneuver the grain-grain interaction to achieve controlled grain dynamics.",1907.09833v2
+2021-03-24,Current-induced magnetization dynamics in single and double layer magnetic nanopillars grown by molecular beam epitaxy,"Molecular beam epitaxy is used to fabricate magnetic single and double layer
+junctions which are deposited in prefabricated nanostencil masks. For all Co |
+Cu | Co double layer junctions we observe a stable intermediate resistance
+state which can be reached by current starting from the parallel configuration
+of the respective ferromagnetic layers. The generation of spin waves is
+investigated at room temperature in the frequency domain by spectrum analysis,
+demonstrating both in-plane and out-of-plane precessions of the magnetization
+of the free magnetic layer. Current-induced magnetization dynamics in magnetic
+single layer junctions of Cu | Co | Cu has been investigated in magnetic fields
+which are applied perpendicular to the magnetic layer. We find a hysteretic
+switching in the current sweeps with resistance changes significantly larger
+than the anisotropic magnetoresistance effect.",2103.13099v1
+2021-06-10,Conserving Local Magnetic Helicity in Numerical Simulations,"Magnetic helicity is robustly conserved in systems with very large magnetic
+Reynolds numbers, including most systems of astrophysical interest, and unlike
+kinetic and magnetic energy is not dissipated at small scales. This plays a
+major role in suppressing the kinematic large-scale dynamo and may also be
+responsible for driving the large-scale dynamo through the magnetic helicity
+flux. Numerical simulations of astrophysical systems typically lack sufficient
+resolution to enforce global magnetic helicity over several dynamical times. In
+these simulations, magnetic helicity is lost either through numerical errors or
+through the action of an unrealistically large resistivity. Errors in the
+internal distribution of magnetic helicity are equally important and typically
+larger. Here we propose an algorithm for enforcing strict local conservation of
+magnetic helicity in the Coulomb gauge in numerical simulations so that their
+evolution more closely approximates that of real systems.",2106.06078v2
+2021-11-24,Thermal generation of droplet soliton in chiral magnet,"Controlled creation of localized magnetic textures beyond conventional
+$\pi$-skyrmions is an important problem in the field of magnetism. Here by
+means of spin dynamics simulations, Monte Carlo simulations and harmonic
+transition state theory we demonstrate that an elementary chiral magnetic
+soliton with zero topological charge -- the chiral droplet -- can be reliably
+created by thermal fluctuations in the presence of the tilted magnetic field.
+The proposed protocol relies on an unusual kinetics combining the effects of
+the entropic stabilization and low energy barrier for the nucleation of a
+topologically-trivial state. Following this protocol by varying temperature and
+the tilt of the external magnetic field one can selectively generate chiral
+droplets or $\pi$-skyrmions in a single system. The coexistence of two distinct
+magnetic solitons establishes a basis for a rich magnetization dynamics and
+opens up the possibility for the construction of more complex magnetic textures
+such as skyrmion bags and skyrmions with chiral kinks.",2111.12342v1
+2022-02-03,Magnetic domain wall dynamics under external electric field in bilayer CrI$_3$,"Motivated by manipulating the magnetic order of bilayer CrI$_3$, we carry out
+microscopic calculations to find the magnetic order and various magnetic
+domains of the system in the presence of an electric field. Making use of
+density functional simulations, a spin model Hamiltonian is introduced
+consisting of isotropic exchange couplings, Dzyaloshinskii-Moriya (DM)
+interaction, and on-site magnetic anisotropy. The spin dynamics of two
+well-known states of bilayer CrI$_3$, low temperature (LT) and high temperature
+(HT) phases, are obtained by solving the Landau-Lifshitz-Gilbert equation. We
+show that the magnetic texture is stacking-dependent in bilayer CrI$_3$ and
+stable magnetic domains can appear in the HT stack which are tunable by
+external electric and magnetic fields. Therefore, we suggest that the HT phase
+represents a promising candidate for data storage in the modern generation of
+spintronic devices working on magnetic domain engineering.",2202.01394v2
+2022-02-20,Magneto-optical Spectroscopy with RAMBO: A Table-Top 30 T Magnet,"Optically probing materials in high magnetic fields can provide enlightening
+insight into field-modified electronic states and phases, while optically
+driving materials in high magnetic fields can induce novel nonequilibrium
+many-body dynamics of spin and charge carriers. While there are high-field
+magnets compatible with standard optical spectroscopy methods, they are
+generally bulky and have limited optical access, which prohibit performing
+state-of-the-art ultrafast and/or nonlinear optical experiments. The Rice
+Advanced Magnet with Broadband Optics (RAMBO), a unique 30-T pulsed mini-coil
+magnet system with direct optical access, has enabled previously challenging
+experiments using femtosecond optical pulses, including time-domain terahertz
+spectroscopy, in cutting-edge materials placed in strong magnetic fields. Here,
+we review recent experimental advances made possible by the first-generation
+RAMBO setup. After summarizing technological aspects of combining optical
+spectroscopic techniques with the mini-coil magnet, we describe results of
+magneto-optical studies of a wide variety of materials, providing new insight
+into the states and dynamics of four types of quasiparticles in solids -
+excitons, plasmons, magnons, and phonons - in high magnetic fields.",2202.09732v1
+2022-10-09,Method of dynamic resonance tuning in spintronics of nanosystems,"A method is advanced allowing for fast regulation of magnetization direction
+in magnetic nanosystems. The examples of such systems are polarized
+nanostructures, magnetic nanomolecules, magnetic nanoclusters, magnetic
+graphene, dipolar and spinor trapped atoms, and quantum dots. The emphasis in
+the paper is on magnetic nanomolecules and nanoclusters. The method is based on
+two principal contrivances: First, the magnetic sample is placed inside a coil
+of a resonant electric circuit creating a feedback field, and second, there is
+an external magnetic field that can be varied so that to dynamically support
+the resonance between the Zeeman frequency of the sample and the natural
+frequency of the circuit during the motion of the sample magnetization. This
+method can find applications in the production of memory devices and other
+spintronic appliances.",2210.04262v1
+2022-11-15,Nonlinear chiral photocurrent in parity-violating magnetic Weyl semimetals,"The strong correlation between the non-trivial band topology and the magnetic
+texture makes magnetic Weyl semimetals excellent candidates for the
+manipulation and detection of magnetization dynamics. The parity violation
+together with the Pauli blocking cause only one Weyl node to contribute to the
+photocurrent response, which in turn affects the magnetic texture due to the
+spin transfer torque. Utilizing the Landau-Lifshitz-Gilbert equation and the
+spin-transfer torque in non-centrosymmetric Weyl magnets, we show that the
+chiral photocurrent rotates the magnetization from the easy c axis to the a or
+b axis, which leads to an exotic current next to the photocurrent response. The
+chiral photocurrent is calculated in the context of quantum kinetic theory and
+it has a strong resonance on the order of mA/W near the Weyl nodes, the
+magnitude of which is controlled by the momentum relaxation time. Remarkably,
+we study the influence of magnetic texture dynamics on the topological
+nonlinear photocurrent response, including shift and injection currents along
+with the new chiral photocurrent, and show that both the magnitude and the
+in-plane orientation of the chiral photocurrent are strongly correlated with
+the direction of the magnetic moments.",2211.08521v1
+2023-03-27,Magnetic manipulation of superparamagnetic colloids in droplet-based optical devices,"Magnetically assembled superparamagnetic colloids have been exploited as
+fluid mixers, swimmers and delivery systems in several microscale applications.
+The encapsulation of such colloids in droplets may open new opportunities to
+build magnetically controlled displays and optical components. Here, we study
+the assembly of superparamagnetic colloids inside droplets under rotating
+magnetic fields and exploit this phenomenon to create functional optical
+devices. Colloids are encapsulated in monodisperse droplets produced by
+microfluidics and magnetically assembled into dynamic two-dimensional clusters.
+Using an optical microscope equipped with a magnetic control setup, we
+investigate the effect of the magnetic field strength and rotational frequency
+on the size, stability and dynamics of 2D colloidal clusters inside droplets.
+Our results show that cluster size and stability depend on the magnetic forces
+acting on the structure under the externally imposed field. By rotating the
+cluster in specific orientations, we illustrate how magnetic fields can be used
+to control the effective refractive index and the transmission of light through
+the colloid-laden droplets, thus demonstrating the potential of the
+encapsulated colloids in optical applications.",2303.15336v1
+2009-03-13,Spin-torque driven magnetization dynamics in a nanocontact setup for low external fields: numerical simulation study,"We present numerical simulation studies of the steady-state magnetization
+dynamics driven by a spin-polarized current in a point contact geometry for the
+case of a relatively large contact diameter (D = 80 nm) and small external
+field (H = 30 Oe). We show, that under these conditions the magnetization
+dynamics is qualitatively different from the dynamics observed for small
+contacts in large external fields. In particular, the 'bullet' mode with a
+homogeneous mode core, which was the dominating localized mode for small
+contacts, is not found here. Instead, all localized oscillation modes observed
+in simulations correspond to different motion kinds of vortex-antivortex (V-AV)
+pairs. These kinds include rotational and translational motion of pairs with
+the V-AV distance d ~ D and creation/annihilation of much smaller (satellite)
+V-AV pairs. We also show that for the geometry studied here the Oersted field
+has a qualitative effect on the magnetization dynamics of a 'free' layer. This
+effect offers a possibility to control magnetization dynamics by a suitable
+electric contact setup, optimized to produce a desired Oersted field. Finally,
+we demonstrate that when the magnetization dynamics of the 'fixed' layer
+(induced only by the stray field interaction with the 'free' layer) is taken
+into account, the threshold current for the oscillation onset is drastically
+reduced and new types of localized modes appear. In conclusion, we show that
+our simulations reproduce semiquantitatively several important features of the
+magnetization dynamics in a point contact system for low external fields
+reported experimentally.",0903.2416v1
+2006-09-10,Nonlinear shear-current dynamo and magnetic helicity transport in sheared turbulence,"The nonlinear mean-field dynamo due to a shear-current effect in a nonhelical
+homogeneous turbulence with a mean velocity shear is discussed. The transport
+of magnetic helicity as a dynamical nonlinearity is taken into account. The
+shear-current effect is associated with the ${\bf W} {\bf \times} {\bf J}$ term
+in the mean electromotive force, where ${\bf W}$ is the mean vorticity due to
+the large-scale shear motions and ${\bf J}$ is the mean electric current. This
+effect causes the generation of large-scale magnetic field in a turbulence with
+large hydrodynamic and magnetic Reynolds numbers. The dynamo action due to the
+shear-current effect depends on the spatial scaling of the correlation time
+$\tau(k)$ of the background turbulence, where $k$ is the wave number. For
+Kolmogorov scaling, $\tau(k) \propto k^{-2/3}$, the dynamo instability occurs,
+while when $\tau(k) \propto k^{-2}$ (small hydrodynamic and magnetic Reynolds
+numbers) there is no the dynamo action in a sheared nonhelical turbulence. The
+magnetic helicity flux strongly affects the magnetic field dynamics in the
+nonlinear stage of the dynamo action. Numerical solutions of the nonlinear
+mean-field dynamo equations which take into account the shear-current effect,
+show that if the magnetic helicity flux is not small, the saturated level of
+the mean magnetic field is of the order of the equipartition field determined
+by the turbulent kinetic energy. Turbulence with a large-scale velocity shear
+is a universal feature in astrophysics, and the obtained results can be
+important for elucidation of origin of the large-scale magnetic fields in
+astrophysical sheared turbulence.",0609256v1
+2015-11-24,Dynamical magnetoelectric phenomena of multiferroic skyrmions,"Magnetic skyrmions, vortex-like swirling spin textures characterized by a
+quantized topological invariant, realized in chiral-lattice magnets are
+currently attracting intense research interest. In particular, their dynamics
+under external fields is an issue of vital importance both for fundamental
+science and for technical application. Whereas observations of magnetic
+skyrmions had been limited to metallic magnets so far, their realization was
+discovered also in a chiral-lattice insulating magnet Cu2OSeO3 in 2012.
+Skyrmions in the insulator turned out to exhibit multiferroic nature with
+spin-induced ferroelectricity. Strong magnetoelectric coupling between
+noncollinear skyrmion spins and electric polarizations mediated by relativistic
+spin-orbit interaction enables us to drive motion and oscillation of magnetic
+skyrmions by application of electric fields instead of injection of electric
+currents. Insulating materials also provide an environment suitable for
+detection of pure spin dynamics through spectroscopic measurements owing to
+absence of appreciable charge excitations. In this article, we review recent
+theoretical and experimental studies on multiferroic properties and dynamical
+magnetoelectric phenomena of magnetic skyrmions in insulators. We argue that
+multiferroic skyrmions show unique coupled oscillation modes of magnetizations
+and polarizations, so-called electromagnon excitations, which are both
+magnetically and electrically active, and interference between the electric and
+magnetic activation processes leads to peculiar magnetoelectric effects in a
+microwave frequency regime.",1511.07761v1
+2018-07-21,Uniform and Nonuniform Precession of a Nanoparticle with Finite Anisotropy in a Liquid: Opportunities and Limitations for Magnetic Fluid Hyperthermia,"We focus on an in-depth study of the forced dynamics of a ferromagnetic
+single-domain uniaxial nanoparticle placed in a viscous fluid and driven by an
+external rotating magnetic field. The process of conversion of magnetic and
+mechanical energies into heat is a physical basis for magnetic fluid
+hyperthermia that is very promising for cancer treatment. The dynamical
+approximation allows us to establish the limits of the heating rate and
+understand the logic of selection of the system parameters to optimize the
+therapy. Based on the developed analytical and numerical tools, we analyze from
+a single viewpoint the synchronous and asynchronous rotation of the
+nanoparticle or/and its magnetization in the following three cases. For the
+beginning, we actualize the features of the internal magnetic dynamics, when
+the nanoparticle body is supposed to be fixed. Then, we study the rotation of
+the whole nanoparticle, when its magnetization is supposed to be locked to the
+crystal lattice. And, finally, we realize the analysis of the coupled motion,
+when the internal magnetic dynamics is performed in the rotated nanoparticle
+body. In all these cases, we describe analytically the uniform mode, or
+synchronous rotation along with an external field, while the nonuniform mode,
+or asynchronous rotation, is investigated numerically.",1807.08120v1
+2019-05-08,Flare Energy Release at the Magnetic Field Polarity Inversion Line During M1.2 Solar Flare of 2015 March 15. II. Investigation of Photospheric Electric Current and Magnetic Field Variations Using HMI 135-second Vector Magnetograms,"This work is a continuation of Paper I [Sharykin et al., 2018] devoted to
+analysis of nonthermal electron dynamics and plasma heating in the confined
+M1.2 class solar flare SOL2015-03-15T22:43 revealing energy release in the
+highly sheared interacting magnetic loops in the low corona, above the polarity
+inversion line (PIL). The scope of the present work is to make the first
+extensive quantitative analysis of the photospheric magnetic field and
+photospheric vertical electric current (PVEC) dynamics in the confined flare
+region near the PIL using new vector magnetograms obtained with the
+Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory
+(SDO) with high temporal resolution of 135 s. Data analysis revealed sharp
+changes of the magnetic structure and PVEC associated with the flare onset near
+the PIL. It was found that the strongest plasma heating and electron
+acceleration were associated with the largest increase of the magnetic
+reconnection rate, total PVEC and effective PVEC density in the flare ribbons.
+Observations and non-linear force-free field (NLFFF) extrapolations showed that
+the magnetic field structure around the PIL is consistent with the
+tether-cutting magnetic reconnection (TCMR) geometry. We gave qualitative
+interpretation of the observed dynamics of the flare ribbons, magnetic field
+and PVEC, and electron acceleration, within the TCMR scenario.",1905.03352v2
+1999-06-17,Small-scale turbulent dynamo,"Kinematic dynamo theory is presented here for turbulent conductive fluids. We
+describe how inhomogeneous magnetic fluctuations are generated below the
+viscous scale of turbulence where the spatial smoothness of the velocity
+permits a systematic analysis of the Lagrangian path dynamics. We find
+analytically the moments and multi-point correlation functions of the magnetic
+field at small yet finite magnetic diffusivity. We show that the field is
+concentrated in long narrow strips and describe anomalous scalings and angular
+singularities of the multi-point correlation functions which are manifestations
+of field's intermittency. The growth rate of the magnetic field in a typical
+realization is found to be half the difference of two Lyapunov exponents of the
+same sign.",9906030v1
+2008-07-28,Static and dynamic properties of vortices in anisotropic magnetic disks,"We investigate the effect of the magnetic anisotropy ($K_z$) on the static
+and dynamic properties of magnetic vortices in small disks. Our micromagnetic
+calculations reveal that for a range of $K_z$ there is an enlargement of the
+vortex core. We analyze the influence of $K_z$ on the dynamics of the vortex
+core magnetization reversal under the excitation of a pulsed field. The
+presence of $K_z$, which leads to better resolved vortex structures, allows us
+to discuss in more details the role played by the in-plane and perpendicular
+components of the gyrotropic field during the vortex-antivortex nucleation and
+annihilation.",0807.4546v1
+2009-01-22,Monopole and Topological Electron Dynamics in Adiabatic Spintronic and Graphene Systems,"A unified theoretical treatment is presented to describe the physics of
+electron dynamics in semiconductor and graphene systems. Electron spin fast
+alignment with the Zeeman magnetic field (physical or effective) is treated as
+a form of adiabatic spin evolution which necessarily generates a monopole in
+magnetic space. One could transform this monopole into the physical and
+intuitive topological magnetic fields in the useful momentum (K) or real spaces
+(R). The physics of electron dynamics related to spin Hall, torque,
+oscillations and other technologically useful spinor effects can be inferred
+from the topological magnetic fields in spintronic, graphene and other SU(2)
+systems.",0901.3411v1
+2010-02-10,"Dynamics of Rotating, Magnetized Neutron Stars","Using a fully general relativistic implementation of ideal
+magnetohydrodynamics with no assumed symmetries in three spatial dimensions,
+the dynamics of magnetized, rigidly rotating neutron stars are studied.
+Beginning with fully consistent initial data constructed with Magstar, part of
+the Lorene project, we study the dynamics and stability of rotating, magnetized
+polytropic stars as models of neutron stars. Evolutions suggest that some of
+these rotating, magnetized stars may be minimally unstable occurring at the
+threshold of black hole formation.",1002.2217v1
+2010-10-22,Dipole-Quadrupole dynamics during magnetic field reversals,"The shape and the dynamics of reversals of the magnetic field in a turbulent
+dynamo experiment are investigated. We report the evolution of the dipolar and
+the quadrupolar parts of the magnetic field in the VKS experiment, and show
+that the experimental results are in good agreement with the predictions of a
+recent model of reversals: when the dipole reverses, part of the magnetic
+energy is transferred to the quadrupole, reversals begin with a slow decay of
+the dipole and are followed by a fast recovery, together with an overshoot of
+the dipole. Random reversals are observed at the borderline between stationary
+and oscillatory dynamos.",1010.4771v1
+2011-03-05,Dynamical TAP equations for non-equilibrium Ising spin glasses,"We derive and study dynamical TAP equations for Ising spin glasses obeying
+both synchronous and asynchronous dynamics using a generating functional
+approach. The system can have an asymmetric coupling matrix, and the external
+fields can be time-dependent. In the synchronously updated model, the TAP
+equations take the form of self consistent equations for magnetizations at time
+$t+1$, given the magnetizations at time $t$. In the asynchronously updated
+model, the TAP equations determine the time derivatives of the magnetizations
+at each time, again via self consistent equations, given the current values of
+the magnetizations. Numerical simulations suggest that the TAP equations become
+exact for large systems.",1103.1044v1
+2011-06-12,Qutrit: entanglement dynamics in the finite qutrit chain in the consistent magnetic field,"Based on the Liouville-von Neumann equation, we obtain closed system of
+equations for the description of a qutrit or coupled qutrits in arbitrary
+time-dependent external magnetic field. The dependence of the dynamics on the
+initial states and magnetic field modulation is studied analytically and
+numerically. We compare the relative entanglement measure's dynamics in the
+bi-qutrit system with permutation particle symmetry. We find the magnetic field
+modulation which retains the entanglement in the system of two coupled qutrits.
+Analytical formulas for entanglement measures in the chain from 2 to 6 qutrits
+are presented.",1106.2297v1
+2012-05-03,Dynamical Friction in a magnetized gas,"When a gravitating point mass moves subsonically through a magnetized and
+isothermal medium, the dynamical structure of the flow is studied far from the
+mass using a perturbation analysis. Analytical solutions for the first-order
+density and the velocity perturbations are presented. Validity of our solutions
+is restricted to the cases where the Alfven velocity in the ambient medium is
+less than the accretor's velocity. The density field is less dense because of
+the magnetic effects according to the solutions and the dynamical friction
+force becomes lower as the strength of the magnetic field increases.",1205.0795v1
+2013-02-01,Entanglement dynamics in finite qudit chain in consistent magnetic field,"Based on the Liouville-von Neumann equation, we obtain a closed system of
+equations for the description of a qutrit or coupled qutrits in an arbitrary,
+time-dependent, external magnetic field. The dependence of the dynamics on the
+initial states and the magnetic field modulation is studied analytically and
+numerically. We compare the relative entanglement measure's dynamics in
+bi-qudits with permutation particle symmetry. We find the magnetic field
+modulation which retains the entanglement in the system of two coupled qutrits.
+Analytical formulae for the entanglement measures in finite chains from 2 to 6
+qutrits or 3 quartits are presented.",1302.0105v1
+2013-03-06,A Quantum Approach of Meso-Magnet Dynamics with Spin Transfer Torque,"We present a theory of magnetization dynamics driven by spin-polarized
+current in terms of the quantum master equation. In the spin coherent state
+representation, the master equation becomes a Fokker-Planck equation, which
+naturally includes the spin transfer and quantum fluctuation. The current
+electron scattering state is correlated to the magnet quantum states, giving
+rise to quantum correction to the electron transport properties in the usual
+semiclassical theory. In the large spin limit, the magnetization dynamics is
+shown to obey the Hamilton-Jacobi equation or the Hamiltonian canonical
+equations.",1303.1250v2
+2013-09-18,Dynamical barrier for flux penetration in a superconducting film in the flux flow state,"The penetration of transverse magnetic flux into a thin superconducting
+square film in the flux flow state is considered by numerical simulation. Due
+to the film self-field, the governing equations are nonlinear, and in
+combination with the finite viscosity of the moving vortices, this sets up a
+dynamical barrier for flux penetration into the sample. The corresponding
+magnetization loop is hysteric, with the peak in magnetization shifted from the
+zero position. The magnetic field in increasing applied field is found to form
+a well-defined front of propagation. Numerical estimates shows that the
+dynamical barrier should be measurable on films with low volume pinning.",1309.4641v1
+2015-08-09,Laser-induced spatiotemporal dynamics of magnetic films,"We present a theory for the coherent magnetization dynamics induced by a
+focused ultrafast laser beam in magnetic films, taking into account nonthermal
+(inverse Faraday effect) and thermal (heating) actuation. The dynamic
+conversion between spin waves and phonons is induced by the magnetoelastic
+coupling that allows efficient propagation of angular momentum. The anisotropy
+of the magnetoelastic coupling renders characteristic angle dependences of the
+magnetization propa-gation that are strikingly different for thermal and
+nonthermal actuation.",1508.02094v2
+2018-06-14,Boundary effects on the magnetic Hamiltonian dynamics in two dimensions,"We study the Hamiltonian dynamics of a charged particle submitted to a pure
+magnetic field in a two-dimensional domain. We provide conditions on the
+magnetic field in a neighbourhood of the boundary to ensure the confinement of
+the particle. We also prove a formula for the scattering angle in the case of
+radial magnetic fields.",1806.05395v1
+2020-02-10,Collisionless particle dynamic in an axi-symmetric diamagnetic trap,"Particle dynamic in an axi-symmetric mirror machine with an extremely high
+plasma pressure equal to pressure of vacuum magnetic field (so-called regime of
+diamagnetic confinement) is investigated. Extrusion of magnetic field from
+central region due to plasma diamagnetism leads to non-conservation of the
+magnetic moment and can result in chaotic movement and fast losses of
+particles. The following mechanisms can provide particle confinement for
+unlimited time: absolute confinement of particles with high azimuthal velocity
+and conservation of adiabatic invariant for particle moving in smooth magnetic
+field. The criteria of particle confinement and estimations of lifetime of
+unconfined particles are obtained and verified in direct numerical simulation.
+Particle confinement time in the diamagnetic trap in regime of gas-dynamic
+outflow is discussed.",2002.03535v1
+2020-08-07,Anisotropic Ultrafast Spin Dynamics in Epitaxial Cobalt,"We investigate the ultrafast spin dynamics in an epitaxial hcp(1100) cobalt
+thin film. By performing pump-probe magneto-optical measurements with the
+magnetization along either the easy or hard magnetic axis, we determine the
+demagnetization and recovery times for the two axes. We observe a 35% slower
+dynamics along the easy magnetization axis, which we attribute to
+magneto-crystalline anisotropy of the electron-phonon coupling, supported by
+our ab initio calculations. This points towards an unambiguous and previously
+undisclosed role of anisotropic electron-lattice coupling in ultrafast
+magnetism.",2008.03119v1
+2021-11-16,Dynamic alignment and plasmoid formation in relativistic magnetohydrodynamic turbulence,"We present high resolution 2D and 3D simulations of magnetized decaying
+turbulence in relativistic resistive magneto-hydrodynamics. The simulations
+show dynamic formation of large scale intermittent long-lived current sheets
+being disrupted by the tearing instability into plasmoid chains. These current
+sheets are locations of enhanced magnetic field dissipation and heating of the
+plasma. We find magnetic energy spectra $\propto k^{-3/2}$, together with
+strongly pronounced dynamic alignment of Elsasser fields and of velocity and
+magnetic fields, for strong guide-field turbulence, whereas we retrieve spectra
+$\propto k^{-5/3}$ for the case of a weak guide-field.",2111.08188v1
+2021-11-12,Chaotic dynamics of a suspended string in a gravitational background with magnetic field,"We study the effects of a magnetic field on the chaotic dynamics of a string
+with endpoints on the boundary of an asymptotically AdS$_5$ space with black
+hole. We study Poincar\'e sections and compute the Lyapunov exponents for the
+string perturbed from the static configuration, for two different orientations,
+with position of the endpoints on the boundary orthogonal and parallel to the
+magnetic field. We find that the magnetic field stabilizes the string dynamics,
+with the largest Lyapunov exponent remaining below the
+Maldacena-Shenker-Stanford bound.",2111.09441v1
+2023-03-28,Role of intersublattice exchange interaction on ultrafast longitudinal and transverse magnetization dynamics in Permalloy,"We report about element specific measurements of ultrafast demagnetization
+and magnetization precession damping in Permalloy (Py) thin films.
+Magnetization dynamics induced by optical pump at $1.5$eV is probed
+simultaneously at the $M_{2,3}$ edges of Ni and Fe with High order Harmonics
+for moderate demagnetization rates (less than $50$%). The role of the
+intersublattice exchange interaction on both longitudinal and transverse
+dynamics is analyzed with a Landau Lifshitz Bloch description of
+ferromagnetically coupled Fe and Ni sublattices. It is shown that the
+intersublattice exchange interaction governs the dissipation during
+demagnetization as well as precession damping of the magnetization vector.",2303.15837v1
+2023-11-30,Excitation of the Gyrotropic Mode in a Magnetic Vortex by Time-Varying Strain,"We demonstrate excitation of the gyrotropic mode in a magnetostrictive vortex
+by time-varying strain. The vortex dynamics is driven by a time-varying voltage
+applied to the piezoelectric substrate and detected electrically by spin
+rectification at subthreshold values of rf current. When the frequency of the
+time-varying strain matches the gyrotropic frequency at given in-plane magnetic
+field, the strain-induced in-plane magnetic anisotropy leads to a resonant
+excitation of the gyration dynamics in a magnetic vortex. We show that
+nonlinear gyrotropic dynamics can be excited already for moderate amplitudes of
+the time-varying strain.",2311.18517v1
+1999-02-05,Nonlinear Dynamics of A Damped Magnetic Oscillator,"We consider a damped magnetic oscillator, consisting of a permanent magnet in
+a periodically oscillating magnetic field. A detailed investigation of the
+dynamics of this dissipative magnetic system is made by varying the field
+amplitude $A$. As $A$ is increased, the damped magnetic oscillator, albeit
+simple looking, exhibits rich dynamical behaviors such as symmetry-breaking
+pitchfork bifurcations, period-doubling transitions to chaos,
+symmetry-restoring attractor-merging crises, and saddle-node bifurcations
+giving rise to new periodic attractors. Besides these familiar behaviors, a
+cascade of ``resurrections'' (i.e., an infinite sequence of alternating
+restabilizations and destabilizations) of the stationary points also occurs. It
+is found that the stationary points restabilize (destabilize) through
+alternating subcritical (supercritical) period-doubling and pitchfork
+bifurcations. We also discuss the critical behaviors in the period-doubling
+cascades.",9902005v1
+2002-11-26,Magnetic Z(N) symmetry in 2+1 dimensions,"This review describes the role of magnetic symmetry in 2+1 dimensional gauge
+theories. In confining theories without matter fields in fundamental
+representation the magnetic symmetry is spontaneously broken. Under some mild
+assumptions, the low-energy dynamics is determined universally by this
+spontaneous breaking phenomenon. The degrees of freedom in the effective theory
+are magnetic vortices. Their role in confining dynamics is similar to that
+played by pions and sigma in the chiral symmetry breaking dynamics.
+  I give an explicit derivation of the effective theory in (2+1)-dimensional
+weakly coupled confining models and argue that it remains qualitatively the
+same in strongly coupled (2+1)-dimensional gluodynamics. Confinement in this
+effective theory is a very simple classical statement about the long range
+interaction between topological solitons, which follows (as a result of a
+simple direct classical calculation) from the structure of the effective
+Lagrangian. I show that if fundamentally charged dynamical fields are present
+the magnetic symmetry becomes local rather than global. The modifications to
+the effective low energy description in the case of heavy dynamical fundamental
+matter are discussed. This effective lagrangian naturally yields a bag like
+description of baryonic excitations. I also discuss the fate of the magnetic
+symmetry in gauge theories with the Chern-Simons term.",0211248v1
+2012-01-26,Dynamics of Magnetized Vortex Tubes in the Solar Chromosphere,"We use 3D radiative MHD simulations to investigate the formation and dynamics
+of small-scale (less than 0.5 Mm in diameter) vortex tubes spontaneously
+generated by turbulent convection in quiet-Sun regions with initially weak mean
+magnetic fields. The results show that the vortex tubes penetrate into the
+chromosphere and substantially affect the structure and dynamics of the solar
+atmosphere. The vortex tubes are mostly concentrated in intergranular lanes and
+are characterized by strong (near sonic) downflows and swirling motions that
+capture and twist magnetic field lines, forming magnetic flux tubes that expand
+with height and which attain magnetic field strengths ranging from 200 G in the
+chromosphere to more than 1 kG in the photosphere. We investigate in detail the
+physical properties of these vortex tubes, including thermodynamic properties,
+flow dynamics, and kinetic and current helicities, and conclude that magnetized
+vortex tubes provide an important path for energy and momentum transfer from
+the convection zone into the chromosphere.",1201.5442v1
+2017-09-27,Geometric Dynamics of Magnetization: Electronic Contribution,"To give a general description of the influences of electric fields or
+currents on magnetization dynamics, we developed a semiclassical theory for the
+magnetization implicitly coupled to electronic degrees of freedom. In the
+absence of electric fields the Bloch electron Hamiltonian changes the Berry
+curvature, the effective magnetic field, and the damping in the dynamical
+equation of the magnetization, which we classify into intrinsic and extrinsic
+effects. Static electric fields modify these as first-order perturbations,
+using which we were able to give a physically clear interpretation of the
+current-induced spin-orbit torques. We used a toy model mimicking a
+ferromagnet-topological-insulator interface to illustrate the various effects,
+and predicted an anisotropic gyromagnetic ratio and the dynamical stability for
+an in-plane magnetization. Our formalism can also be applied to the slow
+dynamics of other order parameters in crystalline solids.",1709.09513v3
+2018-08-27,Dynamics of the antiferromagnetic skyrmion induced by a magnetic anisotropy gradient,"The dynamics of antiferromagnets is a current hot topic in condensed matter
+physics and spintronics. However, the dynamics of insulating antiferromagnets
+cannot be excited by an electric current, which is a method usually used to
+manipulate ferromagnetic metals. Here, we propose to use the voltage-controlled
+magnetic anisotropy gradient as an excitation source to manipulate insulating
+antiferromagnetic textures. We analytically and numerically study the dynamics
+of an antiferromagnetic skyrmion driven by a magnetic anisotropy gradient. Our
+analytical calculations demonstrate that such a magnetic anisotropy gradient
+can effectively drive an antiferromagnetic skyrmion towards the area of lower
+magnetic anisotropy. The micromagnetic simulations are in good agreement with
+our analytical solution. Furthermore, the magnetic anisotropy gradient induced
+velocity of an antiferromagnetic skyrmion is compared with that of a
+ferromagnetic skyrmion. Our results are useful for the understanding of
+antiferromagnetic skyrmion dynamics and may open a new way for the design of
+antiferromagnetic spintronic devices.",1808.08664v2
+2019-10-03,Finite size effects on the ultrafast remagnetization dynamics of FePt,"We investigate the ultrafast magnetization dynamics of FePt in the L10 phase
+after an optical heating pulse, as used in heat assisted magnetic recording. We
+compare continuous and nanogranular thin films and emphasize the impact of the
+finite size on the remagnetization dynamics. The remagnetization speeds up
+significantly with increasing external magnetic field only for the continuous
+film, where domain wall motion governs the dynamics. The ultrafast
+remagnetization dynamics in the continuous film are only dominated by heat
+transport in the regime of high magnetic fields, whereas the timescale required
+for cooling is prevalent in the granular film for all magnetic field strengths.
+These findings highlight the necessary conditions for studying the intrinsic
+heat transport properties in magnetic materials.",1910.01413v1
+2023-04-28,Competing signatures of intersite and interlayer spin transfer in the ultrafast magnetization dynamics,"Optically driven intersite and interlayer spin transfer are individually
+known as the fastest processes for manipulating the spin order of magnetic
+materials on the sub 100 fs time scale. However, their competing influence on
+the ultrafast magnetization dynamics remains unexplored. In our work, we show
+that optically induced intersite spin transfer (also known as OISTR) dominates
+the ultrafast magnetization dynamics of ferromagnetic alloys such as Permalloy
+(Ni80Fe20) only in the absence of interlayer spin transfer into a substrate.
+Once interlayer spin transfer is possible, the influence of OISTR is
+significantly reduced and interlayer spin transfer dominates the ultrafast
+magnetization dynamics. This provides a new approach to control the
+magnetization dynamics of alloys on extremely short time scales by fine-tuning
+the interlayer spin transfer.",2304.14957v1
+2023-05-24,Time-reversal Invariance Violation and Quantum Chaos Induced by Magnetization in Ferrite-Loaded Resonators,"We investigate the fluctuation properties in the eigenfrequency spectra of
+flat cylindrical microwave cavities that are homogeneously filled with
+magnetized ferrite. These studies are motivated by experiments in which only
+small pieces of ferrite were embedded in the cavity and magnetized with an
+external static magnetic field to induce partial time-reversal (T ) invariance
+violation. We use two different shapes of the cavity, one exhibiting an
+integrable wave dynamics, the other one a chaotic one. We demonstrate that in
+the frequency region where only transverse-magnetic modes exist, the
+magnetization of the ferrites has no effect on the wave dynamics and does not
+induce T -invariance violation whereas it is fully violated above the cutoff
+frequency of the first transverse-electric mode. Above all, independently of
+the shape of the resonator, it induces a chaotic wave dynamics in that
+frequency range in the sense that for both resonator geometries the spectral
+properties coincide with those of quantum systems with a chaotic classical
+dynamics and same invariance properties under application of the generalized T
+operator associated with the resonator geometry.",2305.14753v1
+2013-12-30,Dynamic behaviors of the hexagonal Ising nanowire,"By utilizing the effective-field theory based on the Glauber-type stochastic
+dynamics, the dynamic behaviors of the hexagonal Ising nanowire (HIN) system in
+the presence of a time dependent magnetic field are obtained. The time
+variations of average order parameters and the thermal behavior of the dynamic
+order parameters are studied to analyze the nature of transitions and to obtain
+the dynamic phase transition points. The dynamic phase diagrams are introduced
+in the plane of the reduced temperature versus magnetic field amplitude. The
+dynamic phase diagrams exhibit coexistence phase region, several ordered phases
+and critical point as well as a reentrant behavior.",1312.7786v1
+2023-04-28,Persistent dynamic magnetic state in artificial honeycomb spin ice,"Topological magnetic charges, arising due to the non-vanishing magnetic flux
+on spin ice vertices, serve as the origin of magnetic monopoles that traverse
+the underlying lattice effortlessly. Unlike spin ice materials of atomic
+origin, the dynamic state in artificial honeycomb spin ice is conventionally
+described in terms of finite size domain wall kinetics that require magnetic
+field or current application. Contrary to this common understanding, here we
+show that thermally tunable artificial permalloy honeycomb lattice manifests a
+perpetual dynamic state due to self-propelled magnetic charge defect relaxation
+in the absence of any external tuning agent. Quantitative investigation of
+magnetic charge defect dynamics using neutron spin echo spectroscopy reveals
+sub-ns relaxation times that are comparable to monopole's relaxation in bulk
+spin ices. Most importantly, the kinetic process remains unabated at low
+temperature where thermal fluctuation is negligible. This suggests that dynamic
+phenomena in honeycomb spin ice are mediated by quasi-particle type entities,
+also confirmed by quantum Monte-Carlo simulations that replicate the kinetic
+behavior. Our research unveils a new `macroscopic' magnetic particle that
+shares many known traits of quantum particles, namely magnetic monopole and
+magnon.",2305.00093v1
+2023-07-12,Quasi-static magnetization dynamics in a compensated ferrimagnetic half-metal -- Mn$_2$Ru$_x$Ga,"Exploring anisotropy and diverse magnetization dynamics in specimens with
+vanishing magnetic moments presents a significant challenge using traditional
+magnetometry, as the low resolution of existing techniques hinders the ability
+to obtain accurate results. In this study, we delve deeper into the examination
+of magnetic anisotropy and quasi-static magnetization dynamics in \mrg\,(MRG)
+thin films, as an example of a compensated ferrimagnetic half-metal, by
+employing anomalous Hall effect measurements within a tetragonal crystal
+lattice system. Our research proposes an innovative approach to accurately
+determine the complete set of anisotropy constants of these MRG thin films. To
+achieve this, we perform anomalous Hall voltage curve fitting, using torque
+models under the macrospin approximation, which allow us to obtain out-of-plane
+anisotropy constants $K_1=4.0\times10^4$ J m$^{-3}$ ($K_1/M=0.655$\,T) and
+$K_2=2.54\times10^4$ J m$^{-3}$ ($K_2/M=0.416$\,T), along with a weaker
+in-plane anisotropy constant $K_3=3.48\times10^3$ J m$^{-3}$
+($K_3/M=0.057$\,T). By additionally employing first-order reversal curves
+(FORC) and classical Preisach hysteresis (hysterons) models, we are able to
+validate the efficacy of the macrospin model in capturing the magnetic behavior
+of MRG thin films. Furthermore, our investigation substantiates that the
+complex quasi-static magnetization dynamics of MRG thin films can be
+effectively modelled using a combination of hysteronic and torque models. This
+approach facilitates the exploration of both linear and non-linear quasi-static
+magnetization dynamics, in the presence of external magnetic field and/or
+current-induced effective fields, generated by the spin-orbit torque and spin
+transfer torque mechanisms.",2307.06403v1
+2000-12-20,Numerical Analysis of Magnetic Field Amplification by Turbulence,"We apply a Fourier spectral numerical method to 3D incompressible MHD
+turbulence with a magnetic Prandtl number $Pr \geq 1$. We examine the processes
+by which an initially weak, large-scale seed magnetic field and an initially
+weak, small-scale, impulse-like seed magnetic field are amplified. We find that
+in both cases the magnetic energy spectrum grows at all scales. The growth
+rates at different amplification stages are analyzed. For a large-scale seed
+magnetic field, the magnetic energy density grows as $\sim t^2$ for the first
+few turbulence eddy turnover times, followed by a dynamic growth stage, where
+nonlinear interactions between different scales of the turbulence contribute to
+an exponential growth rate that is largely determined by the turbulence eddy
+turnover time. For a seed magnetic field that is initially set up at a small
+scale in the turbulence, during the kinematic development stage, the growth
+rate of magnetic energy is $\propto 1/\tau_{max}$, where $\tau_{max}$ is the
+eddy turnover time of the smallest eddies of the turbulence. The kinematic
+growth stage is followed by a dynamic growth stage, where nonlinearity plays
+important role. During such dynamic growth stage, the growth rate of total
+magnetic energy is determined by both the magnetic energy amplification within
+the turbulence inertial range and that within the turbulence dissipation range.",0012447v2
+2015-02-23,Table-top Measurement of Local Magnetization Dynamics Using Picosecond Thermal Gradients: Toward Nanoscale Magnetic Imaging,"Recent advances in nanoscale magnetism have demonstrated the potential for
+spin-based technology including magnetic random access memory, nanoscale
+microwave sources, and ultra-low power signal transfer. Future engineering
+advances and new scientific discoveries will be enabled by research tools
+capable of examining local magnetization dynamics at length and time scales
+fundamental to spatiotemporal variations in magnetic systems - typically 10 -
+200 nm and 5 - 50 ps. A key problem is that current table-top magnetic
+microscopy cannot access both of these scales simultaneously. In this letter,
+we introduce a spatiotemporal magnetic microscopy that uses
+magneto-thermoelectric interactions to measure local magnetization via the
+time-resolved anomalous Nernst effect (TRANE). By generating a short-lived,
+local thermal gradient, the magnetic moment is transduced into an electrical
+signal. Experimentally, we show that TRANE microscopy has time resolution below
+30 ps and spatial resolution limited by the thermal excitation area.
+Furthermore, we present numerical simulations to show that the thermal spot
+size sets the limits of the spatial resolution, even at 50 nm. The thermal
+effects used for TRANE microscopy have no fundamental limit on their spatial
+resolution, therefore a future TRANE microscope employing a scanning plasmon
+antenna could enable measurements of nanoscale magnetic dynamics.",1502.06505v1
+2019-02-04,Magnetic eddy viscosity of mean shear flows in two-dimensional magnetohydrodynamics,"Magnetic induction in magnetohydrodynamic fluids at magnetic Reynolds number
+(Rm) less than~1 has long been known to cause magnetic drag. Here, we show that
+when $\mathrm{Rm} \gg 1$ and the fluid is in a hydrodynamic-dominated regime in
+which the magnetic energy is much smaller than the kinetic energy, induction
+due to a mean shear flow leads to a magnetic eddy viscosity. The magnetic
+viscosity is derived from simple physical arguments, where a coherent response
+due to shear flow builds up in the magnetic field until decorrelated by
+turbulent motion. The dynamic viscosity coefficient is approximately
+$(B_p^2/2\mu_0) \tau_{\rm corr}$, the poloidal magnetic energy density
+multiplied by the correlation time. We confirm the magnetic eddy viscosity
+through numerical simulations of two-dimensional incompressible
+magnetohydrodynamics. We also consider the three-dimensional case, and in
+cylindrical or spherical geometry, theoretical considerations similarly point
+to a nonzero viscosity whenever there is differential rotation. Hence, these
+results serve as a dynamical generalization of Ferraro's law of isorotation.
+The magnetic eddy viscosity leads to transport of angular momentum and may be
+of importance to zonal flows in astrophysical domains such as the interior of
+some gas giants.",1902.01105v3
+2019-03-02,Microwave excitations and hysteretic magnetization dynamics of stripe domain films,"FeNi films with the stripe domain (SD) pattern are prepared by
+electrodeposition and sputtering methods. The magnetic domain, static magnetic
+parameters, and quality factor, as well as dynamic properties of the two films,
+are respectively performed. The results show the magnetizations of the film
+were dependent on the direction of SD, and the rotation of the SD is lagging
+behind the magnetization reversal. The microwave properties of the SD emerge
+dynamic hysteresis before the saturation magnetic field. These microwave
+properties are selectively excited with acoustic mode, optical mode, and
+spin-wave mode. The frequency and intensity of different resonance modes of
+stripe domain are determined by the local magnetization. The magnetization
+variations and the rotation of SD of different modes are further illuminated by
+the micromagnetic simulation. The magnetic anisotropy and the resonance
+intensity of permeability of different modes were finally described by the
+modified resonance equations.",1903.00656v2
+2023-10-25,Post-dynamical inspiral phase of common envelope evolution. The role of magnetic fields,"During common envelope evolution, an initially weak magnetic field may
+undergo amplification by interacting with spiral density waves and turbulence
+generated in the stellar envelope by the inspiralling companion. Using 3D
+magnetohydrodynamical simulations on adaptively refined spherical grids with
+excised central regions, we studied the amplification of magnetic fields and
+their effect on the envelope structure, dynamics, and the orbital evolution of
+the binary during the post-dynamical inspiral phase. About $95\%$ of magnetic
+energy amplification arises from magnetic field stretching, folding, and
+winding due to differential rotation and turbulence while compression against
+magnetic pressure accounts for the remaining $\sim 5\%$. Magnetic energy
+production peaks at a scale of $3a_\text{b}$, where $a_\text{b}$ is the
+semimajor axis of the central binary's orbit. Because the magnetic energy
+production declines at large radial scales, the conditions are not favorable
+for the formation of magnetically collimated bipolar jet-like outflows unless
+they are generated on small scales near the individual cores, which we did not
+resolve. Magnetic fields have a negligible impact on binary orbit evolution,
+mean kinetic energy, and the disk-like morphology of angular momentum
+transport, but turbulent Maxwell stress can dominate Reynolds stress when
+accretion onto the central binary is allowed, leading to an $\alpha$-disk
+parameter of $\simeq 0.034$. Finally, we discovered accretion streams arising
+from the stabilizing effect of the magnetic tension from the toroidal field
+about the orbital plane, which prevents overdensities from being destroyed by
+turbulence and enables them to accumulate mass and eventually migrate toward
+the binary.",2310.16880v2
+2024-01-24,Magnetism and spin dynamics of an S=3/2 frustrated trillium lattice antiferromagnet K2CrTi(PO4)3,"Competing magnetic interactions, frustration driven quantum fluctuations, and
+spin correlations offer an ideal route for the experimental realization of
+emergent quantum phenomena and exotic quasi particle excitations in 3D
+frustrated magnets. In this context, trillium lattice, wherein magnetic ions
+decorate a three-dimensional chiral network of corner-shared equilateral
+triangular motifs, provides a viable ground. Herein, we present the crystal
+structure, magnetic susceptibility, specific heat, electron spin-resonance,
+muSR results on the polycrystalline samples of K2CrTi(PO4)3 wherein the Cr3+
+ions form a perfect trillium lattice without any detectable anti-site disorder.
+The Curie-Weiss fit of the magnetic susceptibility data above 100 K yields a
+Curie-Weiss temperature of -23 K, which indicates the presence of dominant
+antiferromagnetic interactions between Cr3+ (S=3/2) moments. The specific heat
+measurements reveal the occurrence of two consecutive phase transitions, at
+temperatures TL = 4.3 K and TH = 8 K, corresponding to two different magnetic
+phases and it unveils the existence of short-range spin correlations above the
+ordering temperature TH. The power-law behavior of ESR linewidth suggests the
+persistence of short-range spin correlations over a relatively wide critical
+region in agreement with the specific heat results. The muSR resultsprovide
+concrete evidence of two different phases corresponding to two transitions,
+coupled with thecritical slowing down of spin fluctuations above TL and
+persistent spin dynamics below TL, consistent with the thermodynamic results.
+Moreover, the muSR results reveal the coexistence of static and dynamic local
+magnetic fields below TL, signifying the presence of complex magnetic phases
+owing to the entwining of spin correlations and competing magnetic interactions
+in this three-dimensional frustrated magnet.",2401.13445v1
+2002-05-16,Helicity Balance and Steady-State Strength of the Dynamo Generated Galactic Magnetic Field,"We demonstrate that the inclusion of the helicity flux in the magnetic
+helicity balance in the nonlinear stage of galactic dynamo action results in a
+radical change in the magnetic field dynamics. The equilibrium value of the
+large-scale magnetic field is then approximately the equipartition level. This
+is in contrast to the situation without the flux of helicity, when the magnetic
+helicity is conserved locally, which leads to substantially subequipartition
+values for the equilibrium large-scale magnetic field.",0205266v1
+2003-02-20,Turbulent magnetic Prandtl number and magnetic diffusivity quenching from simulations,"Forced turbulence simulations are used to determine the turbulent kinematic
+viscosity, nu_t, from the decay rate of a large scale velocity field. Likewise,
+the turbulent magnetic diffusivity, eta_t, is determined from the decay of a
+large scale magnetic field. In the kinematic regime, when the field is weak,
+the turbulent magnetic Prandtl number, nu_t/eta_t, is about unity. When the
+field is nonhelical, eta_t is quenched when magnetic and kinetic energies
+become comparable. For helical fields the quenching is stronger and can be
+described by a dynamical quenching formula.",0302425v2
+2003-10-28,On magnetic field generation in Kolmogorov turbulence,"We analyze the initial, kinematic stage of magnetic field evolution in an
+isotropic and homogeneous turbulent conducting fluid with a rough velocity
+field, v(l) ~ l^alpha, alpha<1. We propose that in the limit of small magnetic
+Prandtl number, i.e. when ohmic resistivity is much larger than viscosity, the
+smaller the roughness exponent, alpha, the larger the magnetic Reynolds number
+that is needed to excite magnetic fluctuations. This implies that numerical or
+experimental investigations of magnetohydrodynamic turbulence with small
+Prandtl numbers need to achieve extremely high resolution in order to describe
+magnetic phenomena adequately.",0310780v2
+2005-04-27,Magnetic-field generation in helical turbulence,"We investigate analytically the amplification of a weak magnetic field in a
+homogeneous and isotropic turbulent flow lacking reflectional symmetry (helical
+turbulence). We propose that the spectral distributions of magnetic energy and
+magnetic helicity can be found as eigenmodes of a self-adjoint,
+Schr\""odinger-type system of evolution equations. We argue that large-scale and
+small-scale magnetic fluctuations cannot be effectively separated, and that the
+conventional alpha-model is, in general, not an adequate description of the
+large-scale dynamo mechanism. As a consequence, the correct numerical modeling
+of such processes should resolve magnetic fluctuations down to the very small,
+resistive scales.",0504588v2
+2004-01-28,Microscopic mechanisms of magnetization reversal,"Two principal scenarios of magnetization reversal are considered. In the
+first scenario all spins perform coherent motion and an excess of magnetic
+energy directly goes to a nonmagnetic thermal bath. A general dynamic equation
+is derived which includes a tensor damping term similar to the
+Bloch-Bloembergen form but the magnetization magnitude remains constant for any
+deviation from equilibrium. In the second reversal scenario, the absolute value
+of the averaged sample magnetization is decreased by a rapid excitation of
+nonlinear spin-wave resonances by uniform magnetization precession. We have
+developed an analytic k-space micromagnetic approach that describes this entire
+reversal process in an ultra-thin soft ferromagnetic film for up to 90^{o}
+deviation from equilibrium. Conditions for the occurrence of the two scenarios
+are discussed.",0401590v1
+2005-10-05,Magnetization dynamics using ultrashort magnetic field pulses,"Very short and well shaped magnetic field pulses can be generated using
+ultra-relativistic electron bunches at Stanford Linear Accelerator. These
+fields of several Tesla with duration of several picoseconds are used to study
+the response of magnetic materials to a very short excitation. Precession of a
+magnetic moment by 90 degrees in a field of 1 Tesla takes about 10 picoseconds,
+so we explore the range of fast switching of the magnetization by precession.",0510121v2
+2004-07-22,Anomalous magnetic moment in parity-conserving QED3,"In this article we derive the anomalous magnetic moment of fermions in
+(2+1)-dimensional parity-conserving QED3, in the presence of an externally
+applied constant magnetic field. We use a spectral representation of the photon
+propagator to avoid infrared divergences. We also discuss the scaling with the
+magnetic field intensity in the case of strong external fields, where there is
+dynamical mass generation for fermions induced by the magnetic field itself
+(magnetic catalysis). The results of this paper may be of relevance to the
+physics of high-temperature superconductors.",0407265v1
+2006-09-19,Magnetic Induced Axion Mass,"We study the effect of a uniform magnetic field on the dynamics of axions. In
+particular, we show that the Peccei-Quinn symmetry is explicitly broken by the
+presence of an external magnetic field. This breaking is induced by the
+non-conservation of the magnetic helicity and generates an electromagnetic
+contribution to the axion mass. We compute the magnetic axion mass in one loop
+approximation, with no restriction on the intensity of the magnetic field, and
+including thermal effects.",0609199v1
+2006-04-08,On the photon anomalous magnetic moment,"It is shown that due to radiative corrections a photon having a non vanishing
+component of its momentum perpendicular to it, bears a non-zero magnetic
+moment. All modes of propagation of the polarization operator in one loop
+approximation are discussed and in this field regime the dispersion equation
+and the corresponding magnetic moment are derived. Near the first thresholds of
+cyclotron resonance the photon magnetic moment has a peak larger than the
+electron anomalous magnetic moment. Related to this magnetic moment, the
+arising of some sort of photon ""dynamical mass"" and a gyromagnetic ratio are
+discussed. These latter results might be interesting in an astrophysical
+context.",0604059v1
+2003-02-24,"Remarks on magnetic flows and magnetic billiards, Finsler metrics and a magnetic analog of Hilbert's fourth problem","We interpret magnetic billiards as Finsler ones and describe an analog of the
+string construction for magnetic billiards. Finsler billiards for which the law
+""angle of incidence equals angle of reflection"" are described. We characterize
+the Finsler metrics in the plane whose geodesics are circles of a fixed radius.
+This is a magnetic analog of Hilbert's fourth problem asking to describe the
+Finsler metrics whose geodesics are straight lines.",0302288v1
+2006-11-26,Optical Magnetometry,"Some of the most sensitive methods of measuring magnetic fields utilize
+interactions of resonant light with atomic vapor. Recent developments in this
+vibrant field are improving magnetometers in many traditional areas such as
+measurement of geomagnetic anomalies and magnetic fields in space, and are
+opening the door to new ones, including, dynamical measurements of bio-magnetic
+fields, detection of nuclear magnetic resonance (NMR), magnetic-resonance
+imaging (MRI), inertial-rotation sensing, magnetic microscopy with cold atoms,
+and tests of fundamental symmetries of Nature.",0611246v1
+2007-05-12,"Comment on six papers published by M.A. El-Hakiem and his co-workers in International Communications in Heat and Mass Transfer, Journal of Magnetism and Magnetic Materials and Heat and Mass Transfer","Comment on six papers published by M.A. El-Hakiem and his co-workers in
+International Communications in Heat and Mass Transfer, Journal of Magnetism
+and Magnetic Materials and Heat and Mass Transfer",0705.1803v1
+2008-01-02,On scaling laws in turbulent magnetohydrodynamic Rayleigh-Benard convection,"We invoke the concepts of magnetic boundary layer and magnetic Rayleigh
+number and use the magnetic energy dissipation rates in the bulk and the
+boundary layers to derive some scaling laws expressing how Nusselt number
+depends on magnetic Rayleigh number, Prandtl number and magnetic Prandtl number
+for the simple case of turbulent magnetohydrodynamic Rayleigh-Benard convection
+in the presence of uniform vertical magnetic field.",0801.0347v2
+2008-01-23,Magnetic properties of the extended periodic Anderson model,"We study magnetic properties of the extended periodic Anderson model, which
+includes electron correlations within and between itinerant and localized
+bands. By combining dynamical mean-field theory with the numerical
+renormalization group we calculate the sublattice magnetization and the
+staggered susceptibility to determine the phase diagram in the particle-hole
+symmetric case. We find that two kinds of magnetically ordered states compete
+with the Kondo insulating state at zero temperature, which induces
+non-monotonic behavior in the temperature-dependent magnetization. It is
+furthermore clarified that a novel magnetic metallic state is stabilized at
+half filling by the competition between Hund's coupling and the hybridization.",0801.3668v1
+2008-11-06,Magnetic exchange interaction between rare-earth and Mn ions in multiferroic hexagonal manganites,"We report a study of magnetic dynamics in multiferroic hexagonal manganite
+HoMnO3 by far-infrared spectroscopy. Low-temperature magnetic excitation
+spectrum of HoMnO3 consists of magnetic-dipole transitions of Ho ions within
+the crystal-field split J=8 manifold and of the triangular antiferromagnetic
+resonance of Mn ions. We determine the effective spin Hamiltonian for the Ho
+ion ground state. The magnetic-field splitting of the Mn antiferromagnetic
+resonance allows us to measure the magnetic exchange coupling between the
+rare-earth and Mn ions.",0811.0999v1
+2009-06-30,Determination of a flow generating a neutral magnetic mode,"The problem of reconstruction of a flow of conducting incompressible fluid
+generating a given magnetic mode is considered. We use the magnetic induction
+equation to derive ordinary differential equations along the magnetic field
+lines, which give an opportunity to determine the generating flow, if
+additional data is provided on a two-dimensional manifold transversal to
+magnetic field lines, and show that an arbitrary solenoidal vector field can
+not be a neutral magnetic mode sustained by any flow of conducting fluid.",0906.5431v1
+2009-07-25,Magnetic Nanoparticle Assemblies,"This chapter provides an introduction to the fundamental physical ideas and
+models relevant to the phenomenon of magnetic hysteresis in nanoparticle
+assemblies. The concepts of single-domain particles and superparamagnetism are
+discussed. The mechanisms of magnetization by coherent rotation and the role of
+temperature in the gradual decay of magnetization are analyzed in the framework
+of simple analytical models. Modern numerical techniques (Monte Carlo
+simulations, Magnetization Dynamics) used to study dense nanoparticle
+assemblies are presented. An overview of the most common experimental
+techniques used to measure the magnetic hysteresis effect in nanoparticle
+assemblies are presented and the underlying principles are exposed.",0907.4417v2
+2009-09-08,"Memory, Aging and Spin Glass Nature: A Study of NiO Nanoparticles","We report studies on magnetization dynamics in NiO nanoparticles of average
+size 5 nm. Temperature and time dependence of dc magnetization, wait time
+dependence of magnetic relaxation (aging) and memory phenomena in the dc
+magnetization are studied with various temperature and field protocols. We
+observe that the system shows memory and aging in field cooled and zero field
+cooled magnetization measurements. These experiments show that the magnetic
+behavior of NiO nanoparticles is similar to spin glasses. We argue that the
+spin glass behavior originates from the freezing of spins at the surface of the
+individual particles.",0909.1391v2
+2010-01-11,Nonlocal effects on magnetism in the diluted magnetic semiconductor Ga_{1-x}Mn_{x}As,"The magnetic properties of the diluted magnetic semiconductor
+Ga_{1-x}Mn_{x}As are studied within the dynamical cluster approximation. We use
+the k-dot-p Hamiltonian to describe the electronic structure of GaAs with
+spin-orbit coupling and strain effects. We show that nonlocal effects are
+essential for explaining the experimentally observed transition temperature and
+saturation magnetization. We also demonstrate that the cluster anisotropy is
+very strong and induces rotational frustration and a cube-edge direction
+magnetic anisotropy at low temperature. With this, we explain the
+temperature-driven spin reorientation in this system.",1001.1716v1
+2010-02-17,Isothermal remanent magnetization and the spin dimensionality of spin glasses,"The isothermal remanent magnetization is used to investigate dynamical
+magnetic properties of spatially three dimensional spin glasses with different
+spin dimensionality (Ising, XY, Heisenberg). The isothermal remanent
+magnetization is recorded vs. temperature after intermittent application of a
+weak magnetic field at a constant temperature $T_h$. We observe that in the
+case of the Heisenberg spin glasses, the equilibrated spin structure and the
+direction of the excess moment are recovered at $T_h$. The isothermal remanent
+magnetization thus reflects the directional character of the
+Dzyaloshinsky-Moriya interaction present in Heisenberg systems.",1002.3209v1
+2011-05-22,Generalization of radiative jet energy loss to non-zero magnetic mass,"Reliable predictions for jet quenching in ultra-relativistic heavy ion
+collisions require accurate computation of radiative energy loss. With this
+goal, an energy loss formalism in a realistic finite size dynamical QCD medium
+was recently developed. While this formalism assumes zero magnetic mass - in
+accordance with the one-loop perturbative calculations - different
+non-perturbative approaches report a non-zero magnetic mass at RHIC and LHC. We
+here generalize the energy loss to consistently include a possibility for
+existence of non-zero magnetic screening. We also present how the inclusion of
+finite magnetic mass changes the energy loss results. Our analysis indicates a
+fundamental constraint on magnetic to electric mass ratio.",1105.4359v1
+2011-11-02,Dynamics of the magnetic flux penetration into type II superconductors,"The magnetic flux penetration into the half-space superconductor sample is
+studied in the flux flow regime in parallel geometry assuming that an external
+magnetic field increasing with time in accordance with the power law. Assuming
+that the flux flow resistivity as a power-law function of the magnetic field
+induction we found an exact analytical solution for the nonlinear local
+magnetic flux diffusion equation. The obtained solution describes space-time
+distribution of the magnetic induction in the sample.",1111.0397v2
+2012-02-18,Measuring spectrum of spin wave using vortex dynamics,"We propose to measure the spectrum of magnetic excitation in magnetic
+materials using motion of vortex lattice driven by both ac and dc current in
+superconductors. When the motion of vortex lattice is resonant with oscillation
+of magnetic moments, the voltage decreases at a given current. From transport
+measurement, one can obtain frequency of the magnetic excitation with the wave
+number determined by vortex lattice constant. By changing the lattice constant
+through applied magnetic fields, one can obtains the spectrum of the magnetic
+excitation up to a wave vector of order $10\rm{\ nm^{-1}}$.",1202.4048v1
+2012-02-27,Fast magnetization reversal of nanoclusters in resonator,"An effective method for ultrafast magnetization reversal of nanoclusters is
+suggested. The method is based on coupling a nanocluster to a resonant electric
+circuit. This coupling causes the appearance of a magnetic feedback field
+acting on the cluster, which drastically shortens the magnetization reversal
+time. The influence of the resonator properties, nanocluster parameters, and
+external fields on the magnetization dynamics and reversal time is analyzed.
+The magnetization reversal time can be made many orders shorter than the
+natural relaxation time. The reversal is studied for both the cases of a single
+nanocluster as well as for the system of many nanoclusters interacting through
+dipole forces.",1202.5873v1
+2012-10-15,Dynamic Control of Magnetically Trapped Indirect Excitons by Using External Magnetic Bias,"We demonstrate an on demand spatial control of excitonic magnetic lattices
+for the potential applications of excitonic-based quantum optical devices. A
+two dimensional magnetic lattice of indirect excitons can form a transition to
+one dimensional lattice configuration under the influence of external magnetic
+bias fields. The transition is identified by measuring the spatial distribution
+of two dimensional photoluminance for several values of the external magnetic
+bias fields. The number of the trapped excitons is found to increase between
+sites along a perpendicular direction exhibiting two to one dimensional lattice
+transition. This work may apply for various controllable quantum simulations,
+such as superfluid-Mott-insulators, in quantum optical devices.",1210.3933v1
+2013-07-05,Magnetic properties of the nucleon in a uniform background field,"We present results for the magnetic moment and magnetic polarisability of the
+neutron and the magnetic moment of the proton. These results are calculated
+using the uniform background field method on 32^3 x 64 dynamical QCD lattices
+provided by the PACS-CS collaboration as part of the ILDG. We use a uniform
+background magnetic field quantised by the periodic spatial volume. We
+investigate ways to improve the effective energy plots used to calculate
+magnetic polarisabilities, including the use of correlation matrix techniques
+with various source smearings.",1307.1509v1
+2013-07-15,Quantum interference oscillations of the superparamagnetic blocking in an Fe8 molecular nanomagnet,"We show that the dynamic magnetic susceptibility and the superparamagnetic
+blocking temperature of an Fe8 single molecule magnet oscillate as a function
+of the magnetic field Hx applied along its hard magnetic axis. These
+oscillations are associated with quantum interferences, tuned by Hx, between
+different spin tunneling paths linking two excited magnetic states. The
+oscillation period is determined by the quantum mixing between the ground S=10
+and excited multiplets. These experiments enable us to quantify such mixing. We
+find that the weight of excited multiplets in the magnetic ground state of Fe8
+amounts to approximately 11.6%.",1307.3829v1
+2014-01-18,Acceleration of magnetic dipoles by the sequence of current turns,"Acceleration of magnetic dipoles is carried out by the running gradient of
+the magnetic field formed while sequent switching on the current turns.
+Magnetic dipoles, with a diameter of sixty millimeters and full length one
+meter, are pre-accelerated by using the gas-dynamic method to speed one
+kilometer per second, corresponding to the injection rate into the main
+accelerator. To prevent the turning of the dipoles by one hundred eighty
+degrees in the field of the accelerating pulse and focus them, the magnetic
+dipoles are accelerated inside the titanium tube. The magnetic dipoles have
+mass two kilograms and acquire the finite speed five kilometers per second on
+the acceleration length three hundreds meters.",1401.4518v1
+2014-06-23,Magnetic energy dissipation and mean magnetic field generation in planar convection driven dynamos,"A numerical study of dynamos in rotating convecting plane layers is presented
+which focuses on magnetic energies and dissipation rates, and the generation of
+mean fields (where the mean is taken over horizontal planes). The scaling of
+the magnetic energy with the flux Rayleigh number is different from the scaling
+proposed in spherical shells, whereas the same dependence of the magnetic
+dissipation length on the magnetic Reynolds number is found for the two
+geometries. Dynamos both with and without mean field exist in rapidly rotating
+convecting plane layers.",1406.5939v1
+2015-08-12,Simultaneous electronic and the magnetic excitation of a ferromagnet by intense THz pulses,"The speed of magnetization reversal is a key feature in magnetic data
+storage. Magnetic fields from intense THz pulses have been recently shown to
+induce small magnetization dynamics in Cobalt thin film on the sub-picosecond
+time scale. Here, we show that at higher field intensities, the THz electric
+field starts playing a role, strongly changing the dielectric properties of the
+cobalt thin film. Both the electronic and magnetic responses are found to occur
+simultaneously, with the electric field response persistent on a time scale
+orders of magnitude longer than the THz stimulus",1508.02921v1
+2016-04-29,Ferroelectrics Manipulate Magnetic Bloch Skyrmions in a Composite Bilayer,"Theoretical investigation demonstrates that the composite bilayer (i.e.,
+chiral-magnetic/ferroelectric bilayer) offers the possibility of
+electric-induced magnetic Skyrmions [Phys. Rev. B \textbf{94}, 014311 (2016)].
+In this Article, we propose a micromagnetic model to physically manipulate
+magnetic Bloch Skyrmions propagating in a chiral-magnetic thin film with a
+polarized ferroelectric essential to drive the system through the converse
+magnetoelectric effect. Effects caused by different velocities of the
+propagation, sizes of the thin film, and strength of the magnetoelectric
+couplings strongly impact on quality and quantity of the magnetic Skyrmions.",1604.08780v2
+2016-12-21,Critical current density of a spin-torque oscillator with an in-plane magnetized free layer and an out-of-plane magnetized polarizer,"Spin-torque induced magnetization dynamics in a spin-torque oscillator with
+an in-plane (IP) magnetized free layer and an out-of-plane (OP) magnetized
+polarizer under IP shape-anisotropy field ($H_{\rm k}$) and applied IP magnetic
+field ($H_{\rm a}$) was theoretically studied based on the macrospin model. The
+rigorous analytical expression of the critical current density ($J_{\rm c1}$)
+for the OP precession was obtained. The obtained expression successfully
+reproduces the experimentally obtained $H_{\rm a}$-dependence of $J_{\rm c1}$
+reported in [D. Houssameddine $et$ $al$., Nat. Mater. 6, 447 (2007)].",1612.06951v1
+2017-06-11,The contribution of kinetic helicity to turbulent magnetic diffusivity,"Using numerical simulations of forced turbulence, it is shown that for
+magnetic Reynolds numbers larger than unity, i.e., beyond the regime of
+quasilinear theory, the turbulent magnetic diffusivity attains an additional
+negative contribution that is quadratic in the kinetic helicity. In particular,
+for large magnetic Reynolds numbers, the turbulent magnetic diffusivity without
+helicity is about twice the value with helicity. Such a contribution was not
+previously anticipated, but, as we discuss, it turns out to be important when
+accurate estimates of the turbulent magnetic diffusivity are needed.",1706.03421v2
+2018-01-24,Voltage-induced precessional switching at zero-bias magnetic field in a conically magnetized free layer,"Voltage-induced magnetization dynamics in a conically magnetized free layer
+with an elliptic cylinder shape is theoretically studied on the basis of the
+macrospin model. It is found that an application of voltage pulse can induce
+the precessional switching of magnetization even at zero-bias magnetic field,
+which is of substantial importance for device applications such as
+voltage-controlled nonvolatile memory. Analytical expressions of the conditions
+for precessional switching are derived.",1801.07842v1
+2017-10-11,"Diamagnetism of 2D-Fermions in the Strong Nonhomogeneous Static Magnetic Field $( {\bf B} =B( 0, 0, 1/cosh^{2}( \frac{x-x_{0} }{ δ})))$ : gas magnetization, ... and gas compressibility","We study diamagnetism of a gas of fermions moving in a nonhomogeneous
+magnetic field $( {\bf B} =B( 0, 0, 1/cosh^{2}( \frac{x-x_{0} }{ \delta })))$
+The gas magnetization, the static magnetic susceptibility, the chemical
+potential and the gas compressibility are discussed and compared with the
+uniform field case. General need to study dynamics of electrons in different
+types of magnetic fields follows from a large number of experimental situations
+in which its understanding enables physicists to obtain new information.",1802.01460v1
+2019-01-22,Ultrashort magnetic impulses driven by coherent control with vector beams,"We introduce a new technique for the generation of magnetic impulses. This
+technique is based on coherent control of electrical currents using cylindrical
+laser beams with azimuthal polarization. When used to ionize a medium, in this
+case atomic hydrogen is considered, an azimuthal current impulse is driven. The
+spatial distribution of this current bears close resemblance to that of a
+solenoid, and produces a magnetic field impulse. The excitation and relaxation
+dynamics of this current temporally confine the resulting magnetic field to a
+Tesla-scale, terahertz bandwidth impulse. Importantly, the magnetic fields are
+spatially isolated from electric fields. This all-optical approach will enable
+ultrafast time-domain spectroscopy of magnetic phenomena.",1901.07444v1
+2019-04-29,Spontaneous Transport Barriers Quench Turbulent Resistivity in 2D MHD,"This Letter identifies the physical mechanism for the quench of turbulent
+resistivity in 2D MHD. Without an imposed, ordered magnetic field, a
+multi-scale, blob-and-barrier structure of magnetic potential forms
+spontaneously. Magnetic energy is concentrated in thin, linear barriers,
+located at the interstices between blobs. The barriers quench the transport and
+kinematic decay of magnetic energy. The local transport bifurcation underlying
+barrier formation is linked to the inverse cascade of $\langle A^2\rangle$ and
+negative resistivity, which induce local bistability. For small scale forcing,
+spontaneous layering of the magnetic potential occurs, with barriers located at
+the interstices between layers. This structure is effectively a magnetic
+staircase.",1904.12892v1
+2019-10-08,On the rigidity of Zoll magnetic systems on surfaces,"In this paper we study rigidity aspects of Zoll magnetic systems on closed
+surfaces. We characterize magnetic systems on surfaces of positive genus given
+by constant curvature metrics and constant magnetic functions as the only
+magnetic systems such that the associated Hamiltonian flow is Zoll, i.e. every
+orbit is closed, on every energy level. We also prove the persistence of
+possibly degenerate closed geodesics under magnetic perturbations in different
+instances.",1910.03285v1
+2021-01-26,Independent Control and Path Planning of Microswimmers with a Uniform Magnetic Field,"Artificial bacteria flagella (ABFs) are magnetic helical micro-swimmers that
+can be remotely controlled via a uniform, rotating magnetic field. Previous
+studies have used the heterogeneous response of microswimmers to external
+magnetic fields for achieving independent control. Here we introduce analytical
+and reinforcement learning control strategies for path planning to a target by
+multiple swimmers using a uniform magnetic field. The comparison of the two
+algorithms shows the superiority of reinforcement learning in achieving minimal
+travel time to a target. The results demonstrate, for the first time, the
+effective independent navigation of realistic micro-swimmers with a uniform
+magnetic field in a viscous flow field.",2101.10628v2
+2024-02-29,Quantum droplets with magnetic vortices in spinor dipolar Bose-Einstein condensates,"Motivated by the recent experimental realization of a Bose-Einstein
+condensate (BEC) of europium atoms, we investigate the self-bound droplet state
+of a europium BEC with spin degrees of freedom. Under a sufficiently weak
+magnetic field, the droplet has a torus shape with circulating spin vectors,
+which is referred to as a magnetic vortex. The ground state transforms from the
+torus to cigar shape through bistability with an increase in the magnetic
+field. Dynamical change of the magnetic field causes the torus to rotate due to
+the Einstein-de Haas effect. The magnetic vortices form a supersolid in a
+confined system.",2402.18885v1
+2009-09-07,On the dynamic efficiency of internal shocks in magnetized relativistic outflows,"We study the dynamic efficiency of conversion of kinetic-to-thermal/magnetic
+energy of internal shocks in relativistic magnetized outflows. We model
+internal shocks as being caused by collisions of shells of plasma with the same
+energy flux and a non-zero relative velocity. The contact surface, where the
+interaction between the shells takes place, can break up either into two
+oppositely moving shocks (in the frame where the contact surface is at rest),
+or into a reverse shock and a forward rarefaction. We find that for moderately
+magnetized shocks (magnetization $\sigma\simeq 0.1$), the dynamic efficiency in
+a single two-shell interaction can be as large as 40%. Thus, the dynamic
+efficiency of moderately magnetized shocks is larger than in the corresponding
+unmagnetized two-shell interaction. If the slower shell propagates with a
+sufficiently large velocity, the efficiency is only weakly dependent on its
+Lorentz factor. Consequently, the dynamic efficiency of shell interactions in
+the magnetized flow of blazars and gamma-ray bursts is effectively the same.
+These results are quantitatively rather independent on the equation of state of
+the plasma. The radiative efficiency of the process is expected to be a
+fraction $f_r<1$ of the estimated dynamic one, the exact value of $f_r$
+depending on the particularities of the emission processes which radiate away
+the thermal or magnetic energy of the shocked states.",0909.1328v1
+2015-05-17,"Equilibria, Dynamics and Current Sheets Formation in Magnetically Confined Coronae","The dynamics of magnetic fields in closed regions of solar and stellar
+coronae are investigated with a reduced magnetohydrodynamic (MHD) model in the
+framework of Parker scenario for coronal heating. A novel analysis of reduced
+MHD equilibria shows that their magnetic fields have an asymmetric structure in
+the axial direction with variation length-scale $z_\ell \sim \ell B_0/b$, where
+$B_0$ is the intensity of the strong axial guide field, $b$ that of the
+orthogonal magnetic field component, and $\ell$ the scale of $\mathbf{b}$.
+Equilibria are then quasi-invariant along the axial direction for variation
+scales larger than approximatively the loop length $z_\ell \gtrsim L_z$, and
+increasingly more asymmetric for smaller variation scales $z_\ell \lesssim
+L_z$. The $critical$ $length$ $z_\ell \sim L_z$ corresponds to the magnetic
+field intensity threshold $b \sim \ell B_0/L_z$. Magnetic fields stressed by
+photospheric motions cannot develop strong axial asymmetries. Therefore fields
+with intensities below such threshold evolve quasi-statically, readjusting to a
+nearby equilibrium, without developing nonlinear dynamics nor dissipating
+energy. But stronger fields cannot access their corresponding asymmetric
+equilibria, hence they are out-of-equilibrium and develop nonlinear dynamics.
+The subsequent formation of current sheets and energy dissipation is
+$necessary$ for the magnetic field to relax to equilibrium, since dynamically
+accessible equilibria have variation scales larger than the loop length $z_\ell
+\gtrsim L_z$, with intensities smaller than the threshold $b \lesssim \ell
+B_0/L_z$. The dynamical implications for magnetic fields of interest to solar
+and stellar coronae are investigated numerically and the impact on coronal
+physics discussed.",1505.04370v2
+2019-01-28,Study of Dynamo Action in Three Dimensional Magnetohydrodynamic Plasma with Arnold-Beltrami-Childress Flow,"For a three dimensional magnetohydrodynamic (MHD) plasma the dynamo action
+with ABC flow as initial condition has been studied. The study delineates
+crucial parameter that gives a transition from coherent nonlinear oscillation
+to dynamo. Further, for both kinematic and dynamic models at magnetic Prandtl
+number equal to unity the dynamo action is studied for driven ABC flows. The
+magnetic resistivity has been chosen at a value where the fast dynamo occurs
+and the growth rate shows no further variation with the change of magnetic
+Reynold's number. The exponent of growth of magnetic energy increases,
+indicating a faster dynamo, if a higher wave number is excited compared to the
+one with a lower wave number. The result has been found to hold good for both
+kinematic and externally forced dynamic dynamos where the backreaction of
+magnetic field on the velocity field is no more negligible. In case of an
+externally forced dynamic dynamo, the super Alfvenic flows have been found to
+excite strong dynamos giving rise to the growth of magnetic energy of seven
+orders of magnitude. The back-reaction of magnetic field on the velocity field
+through Lorentz force term has been found to affect the dynamics of the
+velocity field and in turn the dynamics of magnetic field, leading to a
+saturation, when the dynamo action is very prominent.",1901.09610v1
+2020-11-27,Vector Hamiltonian Formalism for Nonlinear Magnetization Dynamics,"Vector Hamiltonian formalism (VHF) for the description of a weakly nonlinear
+magnetization dynamics has been developed. Transformation from the traditional
+Landau-Lifshitz equation, describing dynamics of a magnetization vector
+$\vec{m}(\vec{r}, t)$ on a sphere, to a vector Hamiltonian equation, describing
+dynamics of a \emph{spin excitation vector} $\vec{s}(\vec{r}, t)$ on a plane,
+is done using the azimuthal Lambert transformation that preserves both the
+phase-space area and vector structure of dynamical equations, and guarantees
+that the plane containing vector $\vec{s}(\vec{r}, t)$ is at each value of the
+coordinate $\vec{r}$ perpendicular to the a stationary vector
+$\vec{m}_0(\vec{r})$ describing the magnetization ground state of the system.
+By expanding vector $\vec{s}(\vec{r}, t)$ in a complete set of linear magnetic
+vector eigemodes $\vec{s}_\nu(\vec{r})$ of the studied system, and using a
+weakly nonlinear approximation $|\vec{s}(\vec{r}, t)| \ll 1$, it is possible to
+express the Hamiltonian function of the system in the form of integrals over
+the vector eigenmode profiles $\vec{s}_\nu(\vec{r})$, and calculate all the
+coefficients of this Hamiltonian. The developed approach allows one to describe
+weakly nonlinear dynamics in micro- and nano-scale magnetic systems with
+complicated geometries and spatially non-uniform ground states by numerically
+calculating linear spectrum and eigenmode profiles, and semi-analytically
+evaluating amplitudes of multi-mode nonlinear interactions. Examples of
+applications of the developed formalism to the magnetic systems having
+spatially nonuniform ground state of magnetization are presented.",2011.13562v1
+2022-11-10,Electron dynamics in planar radio frequency magnetron plasmas: III. Comparison of experimental investigations of power absorption dynamics to simulation results,"In magnetized capacitively coupled radio-frequency discharges operated at low
+pressure the influence of the magnetic flux density on discharge properties has
+been studied recently both by experimental investigations and in simulations.
+It was found that the Magnetic Asymmetry Effect allows for a control of the DC
+self-bias and the ion energy distribution by tuning the magnetic field
+strength. In this study, we focus on experimental investigations of the
+electron power absorption dynamics in the presence of a magnetron-like magnetic
+field configuration in a low pressure capacitive RF discharge operated in
+argon. Phase Resolved Optical Emission Spectroscopy measurements provide
+insights into the electron dynamics on a nanosecond-timescale. The magnetic
+flux density and the neutral gas pressure are found to strongly alter these
+dynamics. For specific conditions energetic electrons are efficiently trapped
+by the magnetic field in a region close to the powered electrode, serving as
+the target surface. Depending on the magnetic field strength an electric field
+reversal is observed that leads to a further acceleration of electrons during
+the sheath collapse. These findings are supported by 2-dimensional Particle in
+Cell simulations that yield deeper insights into the discharge dynamics.",2211.05479v1
+2023-10-13,Midpoint geometric integrators for inertial magnetization dynamics,"We consider the numerical solution of the inertial version of
+Landau-Lifshitz-Gilbert equation (iLLG), which describes high-frequency
+nutation on top of magnetization precession due to angular momentum relaxation.
+The iLLG equation defines a higher-order nonlinear dynamical system with very
+different nature compared to the classical LLG equation, requiring twice as
+many degrees of freedom for space-time discretization. It exhibits essential
+conservation properties, namely magnetization amplitude preservation,
+magnetization projection conservation, and a balance equation for generalized
+free energy, leading to a Lyapunov structure (i.e. the free energy is a
+decreasing function of time) when the external magnetic field is constant in
+time. We propose two second-order numerical schemes for integrating the iLLG
+dynamics over time, both based on implicit midpoint rule. The first scheme
+unconditionally preserves all the conservation properties, making it the
+preferred choice for simulating inertial magnetization dynamics. However, it
+implies doubling the number of unknowns, necessitating significant changes in
+numerical micromagnetic codes and increasing computational costs especially for
+spatially inhomogeneous dynamics simulations. To address this issue, we present
+a second time-stepping method that retains the same computational cost as the
+implicit midpoint rule for classical LLG dynamics while unconditionally
+preserving magnetization amplitude and projection. Special quasi-Newton
+techniques are developed for solving the nonlinear system of equations required
+at each time step due to the implicit nature of both time-steppings. The
+numerical schemes are validated on analytical solution for macrospin terahertz
+frequency response and the effectiveness of the second scheme is demonstrated
+with full micromagnetic simulation of inertial spin waves propagation in a
+magnetic thin-film.",2310.09043v1
+2017-06-19,Origin and Structures of Solar Eruptions II: Magnetic Modeling (Invited Review),"The topology and dynamics of the three-dimensional magnetic field in the
+solar atmosphere govern various solar eruptive phenomena and activities, such
+as flares, coronal mass ejections, and filaments/prominences. We have to
+observe and model the vector magnetic field to understand the structures and
+physical mechanisms of these solar activities. Vector magnetic fields on the
+photosphere are routinely observed via the polarized light, and inferred with
+the inversion of Stokes profiles. To analyze these vector magnetic fields, we
+need first to remove the 180$^\circ$ ambiguity of the transverse components and
+correct the projection effect. Then, the vector magnetic field can be served as
+the boundary conditions for a force-free field modeling after a proper
+preprocessing. The photospheric velocity field can also be derived from a time
+sequence of vector magnetic fields. Three-dimensional magnetic field could be
+derived and studied with theoretical force-free field models, numerical
+nonlinear force-free field models, magnetohydrostatic models, and
+magnetohydrodynamic models. Magnetic energy can be computed with
+three-dimensional magnetic field models or a time series of vector magnetic
+field. The magnetic topology is analyzed by pinpointing the positions of
+magnetic null points, bald patches, and quasi-separatrix layers. As a well
+conserved physical quantity, magnetic helicity can be computed with various
+methods, such as the finite volume method, discrete flux tube method, and
+helicity flux integration method. This quantity serves as a promising parameter
+characterizing the activity level of solar active regions.",1706.05769v1
+2019-11-14,Suspensions of magnetic nanogels at zero field: equilibrium structural properties,"Magnetic nanogels represent a cutting edge of magnetic soft matter research
+due to their numerous potential applications. Here, using Langevin dynamics
+simulations, we analyse the influence of magnetic nanogel concentration and
+embedded magnetic particle interactions on the self-assembly of magnetic
+nanogels at zero field. For this, we calculated radial distribution functions
+and structure factors for nanogels and magnetic particles within them. We found
+that, in comparison to suspensions of free magnetic nanoparticles, where the
+self-assembly is already observed if the interparticle interaction strength
+exceeds the thermal fluctuations by approximately a factor of three,
+self-assembly of magnetic nanogels only takes place by increasing such ratio
+above six. This magnetic nanogel self-assembly is realised by means of
+favourable close contacts between magnetic nanoparticles from different
+nanogels. It turns out that for high values of interparticle interactions,
+corresponding to the formation of internal rings in isolated nanogels, in their
+suspensions larger magnetic particle clusters with lower elastic penalty can be
+formed by involving different nanogels. Finally, we show that when the
+self-assembly of these nanogels takes place, it has a drastic effect on the
+structural properties even if the volume fraction of magnetic nanoparticles is
+low.",1911.06031v1
+2020-07-14,"Inverse energy transfer in decaying, three dimensional, nonhelical magnetic turbulence due to magnetic reconnection","It has been recently shown numerically that there exists an inverse transfer
+of magnetic energy in decaying, nonhelical, magnetically dominated,
+magnetohydrodynamic turbulence in 3-dimensions (3D). We suggest that magnetic
+reconnection is the underlying physical mechanism responsible for this inverse
+transfer. In the two-dimensional (2D) case, the inverse transfer is easily
+inferred to be due to smaller magnetic islands merging to form larger ones via
+reconnection. We find that the scaling behaviour is similar between the 2D and
+the 3D cases, i.e., the magnetic energy evolves as $t^{-1}$, and the magnetic
+power spectrum follows a slope of $k^{-2}$. We show that on normalizing time by
+the magnetic reconnection timescale, the evolution curves of the magnetic field
+in systems with different Lundquist numbers collapse onto one another.
+Furthermore, transfer function plots show signatures of magnetic reconnection
+driving the inverse transfer. We also discuss the conserved quantities in the
+system and show that the behaviour of these quantities is similar between the
+2D and 3D simulations, thus making the case that the dynamics in 3D could be
+approximately explained by what we understand in 2D. Lastly, we also conduct
+simulations where the magnetic field is subdominant to the flow. Here, too, we
+find an inverse transfer of magnetic energy in 3D. In these simulations, the
+magnetic energy evolves as $ t^{-1.4}$ and, interestingly, a dynamo effect is
+observed.",2007.07325v1
+2023-11-16,Meridional Circulations of the Solar Magnetic Fields of Different Strength,"The meridional circulation of the solar magnetic fields in Solar Cycles 21-24
+was considered. Data from both ground-based and space observatories were used.
+Three types of time-latitude distributions of photospheric magnetic fields and
+their meridional circulations were identified depending on the magnetic field
+intensity. (i) low-strength magnetic fields. They were distributed evenly
+across latitude and weakly depended on the magnetic fields of active regions
+and their cycle variation; (ii) medium-strength magnetic fields. For these
+fields a wave-like, pole-to-pole, antiphase meridional circulation with a
+period of approximately 22 years was revealed. The velocities of meridional
+flows were slower at the minima of solar activity, when they were at high
+latitudes in the opposite hemispheres, and maximal at the solar maxima, when
+the positive- and negative-polarity waves crossed the equator. The meridional
+circulation of these fields reflects the solar global magnetic field dynamics
+and determines the solar polar field reversal; (iii) high-strength (active
+region) magnetic fields. They were distributed symmetrically in the Northern
+and Southern hemispheres. Magnetic fields of both leading and following sunspot
+polarity migrated from high to low latitudes. The meridional-flow velocities of
+high-strength magnetic fields were higher at the rising and maxima phases than
+at the minima. Some of the high-latitude active region magnetic fields were
+captured by the second type meridional circulation flows and transported along
+with them to the appropriate pole. But the magnetic fields of active regions
+are not the main ones in the solar polar field reversal. The results indicate
+that high-strength magnetic fields were not the main source of weak ones.",2311.09900v1
+1997-03-12,Scaling picture of magnetism formation in the anomalous f-systems: interplay of the Kondo effect and spin dynamics,"Formation of magnetically ordered state in the Kondo lattices is treated
+within the degenerate $s-f$ exchange and Coqblin-Schrieffer models. The Kondo
+renormalizations of the effective coupling parameter, magnetic moment and spin
+excitation frequencies are calculated within perturbation theory. The results
+of one-loop scaling consideration of the magnetic state in Kondo lattices are
+analyzed. The dependence of the critical values of the bare model parameters on
+the type of the magnetic phase and space dimensionality is investigated.
+Renormalization of the effective Kondo temperature by the interatomic exchange
+interactions is calculated. An important role of the character of spin dynamics
+(existence of well-defined magnon excitations, presence of magnetic anisotropy
+etc.) is demonstrated. The regime of strongly suppressed magnetic moments,
+which corresponds to magnetic heavy-fermion system, may occur in a rather
+narrow parameter region only. At the same time, in the magnetically ordered
+phases the renormalized Kondo temperature depends weakly on the bare coupling
+parameter in some interval. The critical behavior, corresponding to the
+magnetic transition with changing the bare $s-f$ coupling parameter, is
+investigated. In the vicinity of the strong coupling regime, the spectrum of
+the Bose excitations becomes softened. Thus on the borderline of magnetic
+instability the Fermi-liquid picture is violated in some temerature interval
+due to scattering of electrons by these bosons. This may explain the fact that
+a non-Fermi-liquid behavior often takes place in the heavy-fermion systems near
+the onset of magnetic ordering.",9703125v1
+2008-07-10,Magnetic field distribution in the quiet Sun: a simplified model approach,"We simulate the dynamics and the evolution of quiet Sun magnetic elements to
+produce a probability density function of the field strengths associated with
+such elements. The dynamics of the magnetic field are simulated through a
+numerical model in which magnetic elements are passively driven by an advection
+field presenting spatio-temporal correlations which mimicks the granulation and
+the mesogranulation scales observed on the solar surface. The field strength
+can increase due to an amplification process which takes place where the
+magnetic elements converge. Starting from a delta-like probability density
+function centered on B=30 G, we obtain magnetic field strengths up to 2 kG (in
+absolute value). To derive the statistical properties of the magnetic elements
+several simulation runs are performed. The model is able to produce kG magnetic
+fields in a time interval of the order of the granulation time scale. The mean
+unsigned flux density and the mean magnetic energy density of the synthetic
+quiet Sun reach respectively 100 G and 350 G in the stationary regime. The
+derived probability density function of the magnetic field strength decreases
+rapidly from B=30 G to B=100 G and presents a secondary maximum for B=2 kG.
+  From this result it follows that magnetic fields >700 G dominate the unsigned
+flux density and magnetic energy density although the probability density
+function of the field strength presents a maximum for B=30 G.",0807.1625v2
+2016-09-08,Influence of non-magnetic impurity scattering on the spin dynamics in diluted magnetic semiconductors,"The doping of semiconductors with magnetic impurities gives rise not only to
+a spin-spin interaction between quasi-free carriers and magnetic impurities,
+but also to a local spin-independent disorder potential for the carriers. Based
+on a quantum kinetic theory for the carrier and impurity density matrices as
+well as the magnetic and non-magnetic carrier-impurity correlations, the
+influence of the non-magnetic scattering potential on the spin dynamics in DMS
+after optical excitation with circularly polarized light is investigated using
+the example of Mn-doped CdTe. It is shown that non-Markovian effects, which are
+predicted in calculations where only the magnetic carrier-impurity interaction
+is accounted for, can be strongly suppressed in the presence of non-magnetic
+impurity scattering. This effect can be traced back to a significant
+redistribution of carriers in $\mathbf{k}$-space which is enabled by the
+build-up of large carrier-impurity correlation energies. A comparison with the
+Markov limit of the quantum kinetic theory shows that, in the presence of an
+external magnetic field parallel to the initial carrier polarization, the
+asymptotic value of the spin polarization at long times is significantly
+different in the quantum kinetic and the Markovian calculations. This effect
+can also be attributed to the formation of strong correlations which
+invalidates the semiclassical Markovian picture and it is stronger when the
+non-magnetic carrier-impurity interaction is accounted for. In an external
+magnetic field perpendicular to the initial carrier spin, the correlations are
+also responsible for a renormalization of the carrier spin precession
+frequency.",1609.02582v1
+2018-06-13,Observational Evidence of Magnetic Reconnection Associated with Magnetic Flux Cancellation,"Using high spatial and temporal data from the \emph{Solar Dynamics
+Observatory} (\emph{SDO}) and the \emph{Interface Region Imaging Spectrograph}
+(\emph{IRIS}), several observational signatures of magnetic reconnection in the
+course of magnetic flux cancellation are presented, including two loop-loop
+interaction processes, multiple plasma blob ejections, and a sheet-like
+structure that appeared above the flux cancellation sites with a Y-shaped and
+an inverted Y-shaped ends. The \emph{IRIS} 1400 \AA\ observations show that the
+plasma blobs were ejected from the tip of the Y-shaped ends of the sheet-like
+structure. Obvious photospheric magnetic flux cancellation occurred after the
+first loop-loop interaction and continued until the end of the observation.
+Complemented by the nonlinear force-free field extrapolation, we found that two
+sets of magnetic field lines, which reveal an X-shaped configuration, align
+well with the interacted coronal loops. Moreover, a magnetic null point is
+found to be situated at about $0.9$ Mm height right above the flux cancellation
+sites and located between the two sets of magnetic field lines. These results
+suggest that the flux cancellation might be a result of submergence of magnetic
+field lines following magnetic reconnection that occurs in the lower atmosphere
+of the Sun, and the ejected plasma blobs should be plasmoids created in the
+sheet-like structure due to the tearing-mode instability. This observation
+reveals detailed magnetic field structure and dynamic process above the flux
+cancellation sites and will help us to understand magnetic reconnection in the
+lower atmosphere of the Sun.",1806.04857v1
+2019-12-05,Steering magnonic dynamics and permeability at exceptional points in a parity-time symmetric waveguide,"Tuning the low-energy magnetic dynamics is a key element in designing novel
+magnetic metamaterials, spintronic devices and magnonic logic circuits. This
+study uncovers a new, highly effective way of controlling the magnetic
+permeability via shaping the magnonic properties in coupled magnetic waveguides
+separated by current carrying spacer with strong spin-orbit coupling. The
+spin-orbit torques exerted on the waveguides leads to an externally tunable
+enhancement of magnetic damping in one waveguide and a decreased damping in the
+other, constituting so a magnetic parity-time (PT) symmetric system with
+emergent magnetic properties at the verge of the exceptional point where
+magnetic gains/losses are balanced. In addition to controlling the magnetic
+permeability, phenomena inherent to PT-symmetric systems are identified,
+including the control on magnon power oscillations, nonreciprocal magnon
+propagation, magnon trapping and enhancement as well as the increased
+sensitivity to magnetic perturbation and abrupt spin reversal. These
+predictions are demonstrated analytically and confirmed by full numerical
+simulations under experimentally feasible conditions. The position of the
+exceptional points and the strength of the spontaneous PT symmetry breaking can
+be tuned by external electric and/or magnetic fields. The roles of the
+intrinsic magnetic damping, and the possibility of an electric control via
+Dzyaloshinskii-Moriya interaction are exposed and utilized for mode dispersion
+shaping and magnon amplification and trapping. The results point to a new route
+to designing optomagnonic waveguides, traps, sensors, and circuits.",1912.02500v1
+2020-07-29,Impact of magnetic dopants on magnetic and topological phases in magnetic topological insulators,"A topological insulator doped with random magnetic impurities is studied. The
+system is modelled by the Kane-Mele model with a random spin exchange between
+conduction electrons and magnetic dopants. The dynamical mean field theory for
+disordered systems is used to investigate the electron dynamics. The magnetic
+long-range order and the topological invariant are calculated within the mean
+field theory. They reveal a rich phase diagram, where different magnetic
+long-range orders such as antiferromagnetic or ferromagnetic one can exist in
+the metallic or insulating phases, depending on electron and magnetic impurity
+fillings. It is found that insulator only occurs at electron half filling,
+quarter filling and when electron filling is equal to magnetic impurity
+filling. However, non-trivial topology is observed only in half-filling
+antiferromagnetic insulator and quarter-filling ferromagnetic insulator. At
+electron half filling, the spin Hall conductance is quantized and it is robust
+against magnetic doping, while at electron quarter filling, magnetic dopants
+drive the ferromagnetic topological insulator to ferromagnetic metal. The
+quantum anomalous Hall effect is observed only at electron quarter filling and
+dense magnetic doping.",2007.14687v1
+2023-06-12,Modeling Magnetically Channeled Winds in 3D: I. Isothermal Simulations of a Magnetic O Supergiant,"In this paper we present the first set of 3D magnetohydrodynamic (MHD)
+simulations performed with the riemann geomesh code. We study the dynamics of
+the magnetically channeled winds of magnetic massive stars in full three
+dimensions using a code that is uniquely suited to spherical problems.
+Specifically, we perform isothermal simulations of a smooth wind on a rotating
+star with a tilted, initially dipolar field. We compare the mass-loss, angular
+momentum loss, and magnetospheric dynamics of a template star (with the
+properties that are reminiscent of the O4 supergiant {\zeta} Pup) over a range
+of rotation rates, magnetic field strengths, and magnetic tilt angles. The
+simulations are run up to a quasi-steady state and the results are observed to
+be consistent with the existing literature, showing the episodic centrifugal
+breakout events of the mass outflow, confined by the magnetic field loops that
+form the closed magnetosphere of the star. The catalogued results provide
+perspective on how angular-momentum loss varies for different configurations of
+rotation rate, magnetic field strength, and large magnetic tilt angles. In
+agreement with previous 2D MHD studies, we find that high magnetic confinement
+reduces the overall mass-loss rate, and higher rotation increases the mass-loss
+rate. This and future studies will be used to estimate the angular-momentum
+evolution, spin-down time, and mass-loss evolution of magnetic massive stars as
+a function of magnetic field strength, rotation rate, and dipole tilt.",2306.06835v1
+2022-09-21,Dynamics of photo-induced ferromagnetism in oxides with orbital degeneracy,"By using intense coherent electromagnetic radiation, it may be possible to
+manipulate the properties of quantum materials very quickly, or even induce new
+and potentially useful phases that are absent in equilibrium. For instance,
+ultrafast control of magnetic dynamics is crucial for a number of proposed
+spintronic devices and can also shed light on the possible dynamics of
+correlated phases out of equilibrium. Inspired by recent experiments on
+spin-orbital ferromagnet YTiO$_3$ we consider the nonequilibrium dynamics of
+Heisenberg ferromagnetic insulator with low-lying orbital excitations. We model
+the dynamics of the magnon excitations in this system following an optical
+pulse which resonantly excites infrared-active phonon modes. As the phonons
+ring down they can dynamically couple the orbitals with the low-lying magnons,
+leading to a dramatically modified effective bath for the magnons. We show this
+transient coupling can lead to a dynamical acceleration of the magnetization
+dynamics, which is otherwise bottlenecked by small anisotropy. Exploring the
+parameter space more we find that the magnon dynamics can also even completely
+reverse, leading to a negative relaxation rate when the pump is blue-detuned
+with respect to the orbital bath resonance. We therefore show that by using
+specially targeted optical pulses, one can exert a much greater degree of
+control over the magnetization dynamics, allowing one to optically steer
+magnetic order in this system. We conclude by discussing interesting parallels
+between the magnetization dynamics we find here and recent experiments on
+photo-induced superconductivity, where it is similarly observed that depending
+on the initial pump frequency, an apparent metastable superconducting phase
+emerges.",2209.10567v1
+2002-05-16,Anomalous Scalings and Dynamics of Magnetic Helicity,"It is demonstrated that the two-point correlation function of the magnetic
+helicity in the case of zero mean magnetic field has anomalous scalings for
+both, compressible and incompressible turbulent helical fluid flow. The
+magnetic helicity in the limit of very high electrical conductivity is
+conserved. This implies that the two-point correlation function of the
+conserved property does not necessarily have normal scaling. The reason for the
+anomalous scalings of the magnetic helicity correlation function is that the
+magnetic field in the equation for the two-point correlation function of the
+magnetic helicity plays a role of a pumping with anomalous scalings. It is
+shown also that when magnetic fluctuations with zero mean magnetic field are
+generated the magnetic helicity is very small even if the hydrodynamic helicity
+is large. Astrophysical applications of the obtained results are discussed.",0205270v1
+2000-06-01,"Magnetization plateaus of the Shastry-Sutherland model for SrCu_2(BO_3)_2: SDW, supersolid and bound states","We study the Heisenberg antiferromagnet on the Shastry-Sutherland lattice
+under magnetic fields, to clarify the magnetic properties of SrCu_2(BO_3)_2.
+Treating magnetic excitations promoted by the field as Bose particles and using
+strong coupling expansion, we derive an effective Hamiltonian for the effective
+magnetic particles. Anisotropic repulsive interactions between effective
+particles induce `insulating' states with a stripe SDW structure at
+magnetization m/m_{sat}=1/3 and a checkerboard structure at 1/2, and thereby
+form magnetization plateaus. Supersolid phases appear around insulating SDW
+phases by changing the magnetic field. Nature of these supersolid phases is
+discussed in detail. We also demonstrate how the geometry of the
+Shastry-Sutherland lattice affects dynamical properties of magnetic excitations
+significantly and makes a novel type of quintuplet (S=2) boundstates condense
+for very small magnetization.",0006020v2
+2007-02-01,Negative magnetic susceptibility and nonequivalent ensembles for the mean-field $φ^4$ spin model,"We calculate the thermodynamic entropy of the mean-field $\phi^4$ spin model
+in the microcanonical ensemble as a function of the energy and magnetization of
+the model. The entropy and its derivative are obtained from the theory of large
+deviations, as well as from Rugh's microcanonical formalism, which is
+implemented by computing averages of suitable observables in microcanonical
+molecular dynamics simulations. Our main finding is that the entropy is a
+concave function of the energy for all values of the magnetization, but is
+nonconcave as a function of the magnetization for some values of the energy.
+This last property implies that the magnetic susceptibility of the model can be
+negative when calculated microcanonically for fixed values of the energy and
+magnetization. This provides a magnetization analog of negative heat
+capacities, which are well-known to be associated in general with the
+nonequivalence of the microcanonical and canonical ensembles. Here, the two
+ensembles that are nonequivalent are the microcanonical ensemble in which the
+energy and magnetization are held fixed and the canonical ensemble in which the
+energy and magnetization are fixed only on average by fixing the temperature
+and magnetic field.",0702004v1
+2007-02-13,Inverse cascades and alpha-effect at low magnetic Prandtl number,"Dynamo action in a fully helical Beltrami (ABC) flow is studied using both
+direct numerical simulations and subgrid modeling. Sufficient scale separation
+is given in order to allow for large-scale magnetic energy build-up. Growth of
+magnetic energy obtains down to a magnetic Prandtl number PM=RM/RV close to
+0.005, where RV and RM are the kinetic and magnetic Reynolds numbers. The
+critical magnetic Reynolds number for dynamo action RMc seems to saturate at
+values close to 20. Detailed studies of the dependence of the amplitude of the
+saturated magnetic energy with PM are presented. In order to decrease PM,
+numerical experiments are conducted with either RV or RM kept constant. In the
+former case, the ratio of magnetic to kinetic energy saturates to a value
+slightly below unity as PM decreases. Examination of energy spectra and
+structures in real space both reveal that quenching of the velocity by the
+large-scale magnetic field takes place, with an inverse cascade of magnetic
+helicity and a force-free field at large scale in the saturated regime.",0702109v1
+2008-11-12,Magnetic Response of NiFe2O4 nanoparticles in polymer matrix,"We report the magnetic properties of magnetic nano-composite, consisting of
+different quantity of NiFe2O4 nanoparticles in polymer matrix. The
+nanoparticles exhibited a typical magnetization blocking, which is sensitive on
+the variation of magnetic field, mode of zero field cooled/field cooled
+experiments and particle quantity in the matrix. The samples with lower
+particle quantity showed an upturn of magnetization down to 5 K, whereas the
+blocking of magnetization dominates at lower temperatures as the particle
+quantity increases in the polymer. We examine such magnetic behaviour in terms
+of the competitive magnetic ordering between core and surface spins of
+nanoparticles, taking into account the effect of inter-particle (dipole-dipole)
+interactions on nanoparticle magnetic dynamics.",0811.1838v1
+2013-01-24,Optimal conditions for magnetization reversal of nanocluster assemblies with random properties,"Magnetization dynamics in the system of magnetic nanoclusters with randomly
+distributed properties are studied by means of computer simulations. The main
+attention is paid to the possibility of coherent magnetization reversal from a
+strongly nonequilibrium state with a mean cluster magnetization directed
+opposite to an external magnetic field. Magnetic nanoclusters are known to be
+characterized by large magnetic anisotropy and strong dipole interactions. It
+is also impossible to produce a number of nanoclusters with identical
+properties. As a result, any realistic system of nanoclusters is composed of
+the clusters with randomly varying anisotropies, effective spins, and dipole
+interactions. Despite this randomness, it is possible to find conditions when
+the cluster spins move coherently and display fast magnetization reversal due
+to the feedback action of resonator. By analyzing the influence of different
+cluster parameters, we find their optimal values providing fast magnetization
+reversal.",1301.5789v1
+2013-08-10,Measurements of Coronal and Chromospheric Magnetic Fields using Polarization Observations by the Nobeyama Radioheliograph,"Coronal and chromospheric magnetic fields are derived from polarization and
+spectral observations of the thermal free-free emission using the Nobeyama
+Radioheliograph (NoRH). In magnetized plasma, the ordinary and extraordinary
+modes of free-free emission have different optical depths. This creates a
+circularly polarized component in an atmosphere with a temperature gradient. We
+observed an active region on April 13, 2012 to derive its coronal and
+chromospheric magnetic fields. The observed degree of circular polarization was
+between 0.5 % and 1.7 %. The radio circular polarization images were compared
+with ultraviolet images observed by the Atmospheric Imaging Assembly and the
+photospheric magnetic field observed by the Helioseismic and Magnetic Imager,
+both on board the Solar Dynamic Observatory. At the edge of the active region,
+the radio circular polarization was emitted mainly from coronal loops, and the
+coronal magnetic field was derived to be about 70 G. At the center of the
+active region, the chromospheric and coronal components cannot be separated.
+The derived magnetic field is about 20 % to 50 % of the corresponding
+photospheric magnetic field, which is an emission-measure-weighted average of
+the coronal and chromospheric magnetic fields.",1308.2283v1
+2015-02-27,Magnetic catalysis and inverse magnetic catalysis in QCD,"We investigate the effects of strong magnetic fields on the QCD phase
+structure at vanishing density by solving the gluon and quark gap equations,
+and by studying the dynamics of the quark scattering with the four-fermi
+coupling. The chiral crossover temperature as well as the chiral condensate are
+computed. For asymptotically large magnetic fields we find magnetic catalysis,
+while we find inverse magnetic catalysis for intermediate magnetic fields.
+Moreover, for large magnetic fields the chiral phase transition for massless
+quarks turns into a crossover. The underlying mechanisms are then investigated
+analytically within a few simplifications of the full numerical analysis. We
+find that a combination of gluon screening effects and the weakening of the
+strong coupling is responsible for the phenomenon of inverse catalysis. In
+turn, the magnetic catalysis at large magnetic field is already indicated by
+simple arguments based on dimensionality.",1502.08011v2
+2015-08-06,Near-Sun Speed of CMEs and the Magnetic Non-potentiality of their Source Active Regions,"We show that the speed of the fastest coronal mass ejections (CMEs) that an
+active region (AR) can produce can be predicted from a vector magnetogram of
+the AR. This is shown by logarithmic plots of CME speed (from the SOHO LASCO
+CME catalog) versus each of ten AR-integrated magnetic parameters (AR magnetic
+flux, three different AR magnetic-twist parameters, and six AR
+free-magnetic-energy proxies) measured from the vertical and horizontal field
+components of vector magnetograms (from the {\it Solar Dynamics Observatory's
+Helioseismic and Magnetic Imager}) of the source ARs of 189 CMEs. These plots
+show: (1) the speed of the fastest CMEs that an AR can produce increases with
+each of these whole-AR magnetic parameters, and (2) that one of the AR
+magnetic-twist parameters and the corresponding free-magnetic-energy proxy each
+determine the CME-speed upper-limit line somewhat better than any of the other
+eight whole-AR magnetic parameters.",1508.01532v1
+2016-10-30,Cosmic ray acceleration via magnetic reconnection of magnetic islands/flux-ropes,"The dynamic processes of magnetic reconnection and turbulence cause magnetic
+islands/flux-ropes generation. The in-situ observations suggest that the
+coalescence or/and contraction of magnetic islands are responsible to the
+charged particle acceleration (keV to MeV energy range). Numerical simulations
+also support this acceleration mechanism. However, the most fundamental
+question raise here is, does this mechanism contribute to the cosmic rays
+acceleration? To answer this, we report, in-situ evidence of flux-ropes
+formation, their magnetic re-connection and its manifestation as cosmic ray
+(GeV charged particle) acceleration in interplanetary counterpart of coronal
+mass ejection(ICME). Further, we propose that cosmic ray (high and/or
+ultra-high energy) acceleration by Fermi mechanism is valid not only through
+stochastic reflections of particles from the shock boundaries but also through
+the boundaries of contracting magnetic islands or/and their merging via
+magnetic re-connection. This has significant implications on cosmic ray origin
+and their acceleration process.",1610.09628v2
+2017-06-16,Observation of Various and Spontaneous Magnetic Skyrmionic Bubbles at Room-Temperature in a Frustrated Kagome Magnet with Uniaxial Magnetic Anisotropy,"Various and spontaneous magnetic skyrmionic bubbles are experimentally
+observed for the first time, at room temperature in a frustrated kagome magnet
+Fe3Sn2 with unixial magnetic anisotropy. The magnetization dynamics were
+investigated using in-situ Lorentz transmission electron microscopy, revealing
+that the transformation between different magnetic bubbles and domains are via
+the motion of Bloch lines driven by applied external magnetic field. The
+results demonstrate that Fe3Sn2 facilitates a unique magnetic control of
+topological spin textures at room temperature, making it a promising candidate
+for further skyrmion-based spintronic devices.",1706.05177v1
+2019-08-18,Magnetic stochasticity and diffusion,"We develop a quantitative relationship between magnetic diffusion and the
+level of randomness, or stochasticity, of the diffusing magnetic field in a
+magnetized medium. A general mathematical formulation of magnetic stochasticity
+in turbulence has been developed in previous work in terms of the ${\cal
+L}_p$-norm $S_p(t)={1\over 2}|| 1-\hat{\bf B}_l.\hat{\bf B}_L||_p$, $p$th order
+magnetic stochasticity of the stochastic field ${\bf B}({\bf x}, t)$, based on
+the coarse-grained fields, ${\bf B}_l$ and ${\bf B}_L$, at different scales,
+$l\neq L$. For laminar flows, stochasticity level becomes the level of field
+self-entanglement or spatial complexity. In this paper, we establish a
+connection between magnetic stochasticity $S_p(t)$ and magnetic diffusion in
+magnetohydrodynamic (MHD) turbulence and use a homogeneous, incompressible MHD
+simulation to test this prediction. Our results agree with the well-known fact
+that magnetic diffusion in turbulent media follows the super-linear Richardson
+dispersion scheme. This is intimately related to stochastic magnetic
+reconnection in which super-linear Richardson diffusion broadens the matter
+outflow width and accelerates the reconnection process.",1908.06474v2
+2019-09-10,Are gravitating magnetic monopoles stable?,"The gravitating Julia-Zee dyon is a particle-like solution with both electric
+and magnetic charge. It is found in the Einstein-Yang-Mills-Higgs system of
+SU(2) with a scalar field in the adjoint representation coupled to gravity.
+Within the magnetic ansatz this system is reduced from describing dyons to
+describing the gravitating 't Hooft-Polyakov magnetic monopole. The stability
+of the well-known static gravitating magnetic monopole solutions with respect
+to perturbations within the magnetic ansatz--so-called magnetic
+perturbations--is well studied, but their stability with respect to
+perturbations outside the magnetic ansatz--so-called sphaleronic
+perturbations--is not. I undertake a purely numerical study by adding
+sphaleronic perturbations to gravitating magnetic monopole solutions and then
+dynamically evolving the system. For large perturbations I find that the system
+heads toward a dyon configuration, as expected. For sufficiently small
+perturbations, however, the system oscillates about the magnetic ansatz in a
+manner consistent with oscillations about a stable equilibrium.",1909.04205v1
+2021-04-01,The Magnetic Field Across the Molecular Warped Disk of Centaurus A,"Magnetic fields are amplified as a consequence of galaxy formation and
+turbulence-driven dynamos. Galaxy mergers can potentially amplify the magnetic
+fields from their progenitors, making the magnetic fields dynamically
+important. However, the effect of mergers on magnetic fields is still poorly
+understood. We use thermal polarized emission observations to trace the
+magnetic fields in the molecular disk of the nearest radio active galaxy,
+Centaurus A, which is thought to be the remnant of a merger. Here, we detect
+that the magnetic field orientations in the plane of the sky are tightly
+following the $\sim3.0$ kpc-scale molecular warped disk. Our simple regular
+large-scale axisymmetric spiral magnetic field model can explain, to some
+extent, the averaged magnetic field orientations across the disk projected on
+the sky. Our observations also suggest the presence of small-scale turbulent
+fields, whose relative strength increases with velocity dispersion and column
+density. These results have strong implications for understanding the
+generation and role of magnetic fields in the formation of galaxies across
+cosmic time.",2104.00688v1
+2021-07-27,Updated Magnetized Transport Coefficients: Impact on Laser-Plasmas with Self-Generated or Applied Magnetic Fields,"Errors in the Epperlein & Haines [PoF (1986)] transport coefficients were
+recently found at low electron magnetizations, with new magnetic transport
+coefficients proposed simultaneously by two teams [Sadler, Walsh & Li, PRL
+(2021) and Davies, Wen, Ji & Held, PoP (2021)]; these two separate sets of
+updated coefficients are shown in this paper to be in agreement. The importance
+of these new coefficients in laser-plasmas with either self-generated or
+applied magnetic fields is demonstrated. When an external magnetic field is
+applied, the cross-gradient-Nernst term twists the field structure; this
+twisting is reduced by the new coefficients in the low magnetization regime.
+For plasmas where only self-generated magnetic fields are present, the new
+coefficients are found to result in the magnetic field moving with the
+Righi-Leduc heat-flow, enhancing the impact of MHD. Simulations of Biermann
+Battery magnetic fields around ICF hot-spot perturbations are presented, with
+cross-gradient-Nernst transport increasing spike penetration.",2107.12988v1
+2021-10-21,Magnetic hysteresis of individual Janus particles with hemispherical exchange-biased caps,"We use sensitive dynamic cantilever magnetometry to measure the magnetic
+hysteresis of individual magnetic Janus particles. These particles consist of
+hemispherical caps of magnetic material deposited on micrometer-scale silica
+spheres. The measurements, combined with corresponding micromagnetic
+simulations, reveal the magnetic configurations present in these individual
+curved magnets. In remanence, ferromagnetic Janus particles are found to host a
+global vortex state with vanishing magnetic moment. In contrast, a remanent
+onion state with significant moment is recovered by imposing an exchange bias
+to the system via an additional antiferromagnetic layer in the cap. A robust
+remanent magnetic moment is crucial for most applications of magnetic Janus
+particles, in which an external magnetic field actuates their motion.",2110.11158v1
+2022-02-11,Mutual conversion between a magnetic Neel hopfion and a Neel toron,"Three-dimensional (3D) magnetic textures attract great attention from
+researchers due to their fascinating structures and dynamic behaviors. Magnetic
+hopfion is a prominent example of 3D magnetic textures. Here, we numerically
+study the mutual conversion between a Neel-type hopfion and a Neel-type toron
+under an external magnetic field. We also investigate the excitation modes of
+hopfions and torons in a film with strong perpendicular magnetic anisotropy. It
+is found that the Neel-type hopfion could be a stable state in the absence of
+the external magnetic field, and its diameter varies with the out-of-plane
+magnetic field. The Neel-type hopfion may transform to a Neel-type toron at an
+out-of-plane magnetic field of about 20 mT, where the cross section structure
+is a Neel-type skyrmion. The hopfion and toron show different excitation modes
+in the presence of an in-plane microwave magnetic field. Our results provide a
+method to realize the conversion between a Neel-type hopfion and a Neel-type
+toron, which also gives a way to distinguish Bloch-type and Neel-type hopfions.",2202.05622v1
+2022-03-04,Second-order magnetic responses in quantum magnets: Magnetization under ac magnetic fields,"We investigate second-order magnetic responses of quantum magnets against ac
+magnetic fields. We focus on the case where the $z$ component of the spin is
+conserved in the unperturbed Hamiltonian and the driving field is applied in
+the $xy$ plane. We find that linearly polarized driving fields induce a
+second-harmonic response, while circularly polarized fields generate only a
+zero-frequency response, leading to a magnetization with a direction determined
+by the helicity. Employing an unbiased numerical method, we demonstrate the
+nonlinear magnetic effect driven by the circularly polarized field in the XXZ
+model and show that the magnitude of the magnetization can be predicted by the
+dynamical spin structure factor in the linear response regime.",2203.02145v2
+2022-06-17,Theory of ultrafast magnetization of non-magnetic semiconductors with localized conduction bands,"The magnetization of a non-magnetic semiconductor by femtosecond light pulses
+is crucial to achieve an all-optical control of the spin dynamics in materials
+and to develop faster memory devices. However, the conditions for its detection
+are largely unknown. In this work we identify the criteria for the observation
+of ultrafast magnetization and critically discuss the difficulties hindering
+its experimental detection. We show that ultrafast magnetization of a non
+magnetic semiconductor can be observed in compounds with very localized
+conduction band states and more delocalized valence bands, such as in the case
+of a p-d charge transfer gap. By using constrained and time dependent density
+functional theory simulations, we demonstrate that a transient ferrimagnetic
+state can be induced in diamagnetic semiconductor V2O5 via ultrafast pulses at
+realistic fluences. The ferrimagnetic state has opposite magnetic moments on
+vanadium (conduction) and oxygen (valence) states. Our methodology outruns the
+case of V2O5 as it identifies the key requirements for a computational
+screening of ultrafast magnetism in non-magnetic semiconductors.",2206.08624v1
+2022-09-23,Magnetic interactions in orbital dynamics,"The magnetic field of a host star can impact the orbit of a stellar partner,
+planet, or asteroid if the orbiting body is itself magnetic or electrically
+conducting. Here, we focus on the instantaneous magnetic forces on an orbiting
+body in the limit where the dipole approximation describes its magnetic
+properties as well as those of its stellar host. A permanent magnet in orbit
+about a star will be inexorably drawn toward the stellar host if the magnetic
+force is comparable to gravity due to the steep radial dependence of the
+dipole-dipole interaction. While magnetic fields in observed systems are much
+too weak to drive a merger event, we confirm that they may be high enough in
+some close compact binaries to cause measurable orbital precession. When the
+orbiting body is a conductor, the stellar field induces a time-varying magnetic
+dipole moment that leads to the possibility of eccentricity pumping and
+resonance trapping. The challenge is that the orbiter must be close to the
+stellar host, so that magnetic interactions must compete with tidal forces and
+the effects of intense stellar radiation.",2209.11574v1
+2023-05-17,Material Parameters for Faster Ballistic Switching of an In-plane Magnetized Nanomagnet,"High-speed magnetization switching of a nanomagnet is necessary for faster
+information processing. The ballistic switching by a pulsed magnetic filed is a
+promising candidate for the high-speed switching. It is known that the
+switching speed of the ballistic switching can be increased by increasing the
+magnitude of the pulsed magnetic field. However it is difficult to generate a
+strong and short magnetic field pulse in a small device. Here we explore
+another direction to achieve the high-speed ballistic switching by designing
+material parameters such as anisotropy constant, saturation magnetization, and
+the Gilbert damping constant. We perform the macrospin simulations for the
+ballistic switching of in-plane magnetized nano magnets with varying material
+parameters. The results are analyzed based on the switching dynamics on the
+energy density contour. We show that the pulse width required for the ballistic
+switching can be reduced by increasing the magnetic anisotropy constant or by
+decreasing the saturation magnetization. We also show that there exists an
+optimal value of the Gilbert damping constant that minimizes the pulse width
+required for the ballistic switching.",2305.10111v1
+2023-08-24,Coercivity Mechanisms of Single-Molecule Magnets,"Magnetic hysteresis has become a crucial aspect for characterizing
+single-molecule magnets, but the comprehension of the coercivity mechanism is
+still a challenge. By using analytical derivation and quantum dynamical
+simulations, we reveal fundamental rules that govern magnetic relaxation of
+single molecule magnets under the influence of external magnetic fields, which
+in turn dictates the hysteresis behavior. Specifically, we find that energy
+level crossing induced by magnetic fields can drastically increase the
+relaxation rate and set a coercivity limit. The activation of
+optical-phonon-mediated quantum tunneling accelerates the relaxation and
+largely determines the coercivity. Intra-molecular exchange interaction in
+multi-ion compounds may enhance the coercivity by suppressing key relaxation
+processes. Unpaired bonding electrons in mixed-valence complexes bear a
+pre-spin-flip process, which may facilitate magnetization reversal. Underlying
+these properties are magnetic relaxation processes modulated by the interplay
+of magnetic fields, phonon spectrum and spin state configuration, which also
+proposes a fresh perspective for the nearly centurial coercive paradox.",2308.12616v2
+2024-01-03,Local distortion driven magnetic phase switching in pyrochlore $Yb_2(Ti_{1-x}Sn_x)_2O_7$,"While it is commonly accepted that the disorder induced by magnetic ion
+doping in quantum magnets usually generates a rugged free-energy landscape
+resulting in slow or glassy spin dynamics, the disorder/distortion effects
+associated with non-magnetic ion sites doping are still illusive. Here, using
+AC susceptibility measurements, we show that the mixture of Sn/Ti on the
+non-magnetic ion sites of pyrochlore $Yb_2(Ti_{1-x}Sn_x)_2O_7$ induces an
+antiferromagnetic ground state despite both parent compounds, $Yb_2Ti_2O_7$,
+and $Yb_2Sn_2O_7$, order ferromagnetically. Local structure studies through
+neutron total scattering reveals the local distortion in the non-magnetic ion
+sites and its strong correlation with the magnetic phase switching. Our study,
+for the first time, demonstrates the local distortion as induced by the
+non-magnetic ion site mixture could be a new path to achieve magnetic phase
+switching, which has been traditionally obtained by external stimuli such as
+temperature, magnetic field, pressure, strain, light, etc.",2401.01807v1
+2017-06-13,Dynamic phase transition features of the cylindrical nanowire driven by a propagating magnetic field,"Magnetic response of the spin-$1/2$ cylindrical nanowire to the propagating
+magnetic field wave has been investigated by means of Monte Carlo simulation
+method based on Metropolis algorithm. The obtained microscopic spin
+configurations suggest that the studied system exhibits two types of dynamical
+phases depending on the considered values of system parameters: Coherent
+propagation of spin bands and spin-frozen or pinned phases, as in the case of
+the conventional bulk systems under the influence of a propagating magnetic
+field. By benefiting from the temperature dependencies of variances of dynamic
+order parameter, internal energy and the derivative of dynamic order parameter
+of the system, dynamic phase diagrams are also obtained in related planes for
+varying values of the wavelength of the propagating magnetic field. Our
+simulation results demonstrate that as the strength of the field amplitude is
+increased, the phase transition points tend to shift to the relatively lower
+temperature regions. Moreover, it has been observed that dynamic phase boundary
+line shrinks inward when the value of wavelength of the external field
+decreases.",1706.04089v1
+2019-12-13,Magnetism in Massive Stars,"Massive stars are the drivers of star formation and galactic dynamics due to
+their relatively short lives and explosive demises, thus impacting all of
+astrophysics. Since they are so impactful on their environments, through their
+winds on the main sequence and their ultimate supernovae, it is crucial to
+understand how they evolve. Recent photometric observations with space-based
+platforms such as CoRoT, K2, and now TESS have permitted access to their
+interior dynamics through asteroseismology, while ground-based
+spectropolarimetric measurements such as those of ESPaDOnS have given us a
+glimpse at their surface magnetic fields. The dynamics of massive stars involve
+a vast range of scales. Extant methods can either capture the long-term
+structural evolution or the short-term dynamics such as convection, magnetic
+dynamos, and waves due to computational costs. Thus, many mysteries remain
+regarding the impact of such dynamics on stellar evolution, but they can have
+strong implications both for how they evolve and what they leave behind when
+they die. Some of these dynamics including rotation, tides, and magnetic fields
+have been addressed in recent work, which is reviewed in this paper.",1912.06422v1
+2020-01-02,Three-dimensional dynamics of magnetic hopfion driven by spin transfer torque,"Magnetic hopfion is three-dimensional (3D) topological soliton with novel
+spin structure that would enable exotic dynamics. Here we study the current
+driven 3D dynamics of a magnetic hopfion with unit Hopf index in a frustrated
+magnet. Attributed to spin Berry phase and symmetry of the hopfion, the phase
+space entangles multiple collective coordinates, thus the hopfion exhibits rich
+dynamics including longitudinal motion along the current direction, transverse
+motion perpendicular to the current direction, rotational motion and dilation.
+Furthermore, the characteristics of hopfion dynamics is determined by the ratio
+between the non-adiabatic spin transfer torque parameter and the damping
+parameter. Such peculiar 3D dynamics of magnetic hopfion could shed light on
+understanding the universal physics of hopfions in different systems and boost
+the prosperous development of 3D spintronics.",2001.00417v1
+2013-09-18,Tunable non-equilibrium dynamics: field quenches in spin ice,"We present non-equilibrium physics in spin ice as a novel setting which
+combines kinematic constraints, emergent topological defects, and magnetic long
+range Coulomb interactions. In spin ice, magnetic frustration leads to highly
+degenerate yet locally constrained ground states. Together, they form a highly
+unusual magnetic state -- a ""Coulomb phase"" -- whose excitations are pointlike
+defects -- magnetic monopoles -- in the absence of which effectively no
+dynamics is possible. Hence, when they are sparse at low temperature, dynamics
+becomes very sluggish. When quenching the system from a monopole-rich to a
+monopole-poor state, a wealth of dynamical phenomena occur the exposition of
+which is the subject of this article. Most notably, we find reaction diffusion
+behaviour, slow dynamics due to kinematic constraints, as well as a regime
+corresponding to the deposition of interacting dimers on a honeycomb lattice.
+We also identify new potential avenues for detecting the magnetic monopoles in
+a regime of slow-moving monopoles. The interest in this model system is further
+enhanced by its large degree of tunability, and the ease of probing it in
+experiment: with varying magnetic fields at different temperatures, geometric
+properties -- including even the effective dimensionality of the system -- can
+be varied. By monitoring magnetisation, spin correlations or zero-field Nuclear
+Magnetic Resonance, the dynamical properties of the system can be extracted in
+considerable detail. This establishes spin ice as a laboratory of choice for
+the study of tunable, slow dynamics.",1309.4676v2
+1996-07-02,Generalized Dynamic Scaling for Critical Relaxations,"The dynamic relaxation process for the two dimensional Potts model at
+criticality starting from an initial state with very high temperature and
+arbitrary magnetization is investigated with Monte Carlo methods. The results
+show that there exists universal scaling behaviour even in the short-time
+regime of the dynamic evolution. In order to describe the dependence of the
+scaling behaviour on the initial magnetization, a critical characteristic
+function is introduced.",9607013v1
+1996-08-29,Magnetic Field Symmetry of Dynamic Capacitances,"While the static capacitance matrix is always symmetric and thus an even
+function of the magnetic field, the dynamic capacitance matrix of
+multi-terminal samples obeys in general only the weaker Onsager-Casimir
+symmetry relations. Our results are in accordance with recent experimental
+observations of asymmetric dynamic capacitances in quantized Hall systems. We
+predict quantization of the four-terminal resistances of an insulating Hall
+sample.",9608154v1
+1997-03-14,Geometric magnetism in classical transport theory,"The effective dynamics of a slow classical system coupled to a fast chaotic
+environment is described by means of a Master equation. We show how this
+approach permits a very simple derivation of geometric magnetism.",9703154v2
+1996-07-05,Dynamical Magnetic Susceptibility for the $t$-$J$ Model,"We present results for the {\em dynamical}\/ magnetic susceptibility of the
+$t$-$J$ model, calculated with the dynamical mean field theory. For $J=0$ we
+find enhanced ferromagnetic correlations but an otherwise relatively
+$\vec{q}$-independent dynamical magnetic susceptibility. For $J>0$ the explicit
+antiferromagnetic exchange leads to a dynamic spin structure factor with the
+expected peak at the antiferromagnetic Bragg point.",9607034v1
+1997-11-05,Dynamics of topological magnetic solitons,"A direct link between the topological complexity of magnetic media and their
+dynamics is established through the construction of unambiguous conservation
+laws for the linear and angular momenta as moments of a topological vorticity.
+As a consequence, the dynamics of topological magnetic solitons is shown to
+exhibit the characteristic features of the Hall effect of electrodynamics or
+the Magnus effect of fluid dynamics. The main points of this program are
+reviewed here for both ferromagnets and antiferromagnets, while a
+straightforward extension to the study of superfluids is also discussed
+briefly.",9711035v1
+2010-09-09,Hydrodynamic equation of a spinor dipolar Bose-Einstein condensate,"We introduce equations of motion for spin dynamics in a ferromagnetic
+Bose-Einstein condensate with magnetic dipole-dipole interaction, written using
+a vector expressing the superfluid velocity and a complex scalar describing the
+magnetization. This simple hydrodynamical description extracts the dynamics of
+spin wave and affords a straightforward approach by which to investigate the
+spin dynamics of the condensate. To demonstrate the advantages of the
+description, we illustrate dynamical instability and magnetic fluctuation
+preference, which are expressed in analytical forms.",1009.1671v3
+2011-04-03,Dynamical magnetoelectric effects in multiferroic oxides,"Multiferroics with coexistent ferroelectric and magnetic orders can provide
+an interesting laboratory to test unprecedented magnetoelectric responses and
+their possible applications. One such example is the dynamical and/or resonant
+coupling between magnetic and electric dipoles in a solid. As the examples of
+such dynamical magnetoelectric effects, (1) the multiferroic domain wall
+dynamics and (2) the electric-dipole active magnetic responses are discussed
+with the overview of recent experimental observations.",1104.0357v1
+2012-10-27,Nonequilibrium quench dynamics in quantum quasicrystals,"We study the nonequilibrium dynamics of a quasiperiodic quantum Ising chain
+after a sudden change in the strength of the transverse field at zero
+temperature. In particular we consider the dynamics of the entanglement entropy
+and the relaxation of the magnetization. The entanglement entropy increases
+with time as a power-law, and the magnetization is found to exhibit
+stretched-exponential relaxation. These behaviors are explained in terms of
+anomalously diffusing quasiparticles, which are studied in a wave packet
+approach. The nonequilibrium magnetization is shown to have a dynamical phase
+transition.",1210.7328v2
+2013-05-25,Thermally-Assisted Spin-Transfer Torque Dynamics in Energy Space,"We consider the general Landau-Lifshitz-Gilbert theory underlying the
+magnetization dynamics of a macrospin magnet subject to spin-torque effects and
+thermal fluctuations. Thermally activated dynamical properties are analyzed by
+averaging the full magnetization equations over constant- energy orbits. After
+averaging, all the relevant dynamical scenarios are a function of the ratio
+between hard and easy axis anisotropies. We derive analytically the range of
+currents for which limit cycles exist and discuss the regimes in which the
+constant energy orbit averaging technique is applicable.",1305.5945v2
+2022-10-03,Probing domain wall dynamics in magnetic Weyl semimetals via the non-linear anomalous Hall effect,"The magnetic textures of Weyl semimetals are embedded into their topological
+structure and interact dynamically with it. Here, we examine electric
+field-induced structural phase transitions in domain walls mediated by the spin
+transfer torque, and their footprint in charge transport. Remarkably, domain
+wall dynamics lead to a transient, local, non-linear anomalous Hall effect and
+non-linear anomalous drift current, which serve as direct probes of the
+magnetization dynamics and of the domain wall location. We discuss experimental
+observation in state-of-the-art samples.",2210.01150v1
+2023-02-10,Feedback Assisted Spin Dynamics in an Inhomogeneous Bias Magnetic Field,"We study dynamics of spins in the presence of a feedback magnetic field. The
+inhomogeneity of the bias magnetic field results in that of the Larmor
+frequencies of the spins. We find that the system exhibits rich nonlinear
+dynamics: beyond limit cycles which have been the focus of previous studies,
+quasi-periodic orbits and chaos emerge in a wide parameter space. The stable
+regions of each phases are determined analytically or numerically. We establish
+the relation between the synchronization frequency of limit cycles and the
+field inhomogeneity. Our results have important implications to precision
+measurement.",2302.05264v1
+2001-11-21,Dynamics of Relativistic Magnetized Blast Waves,"The dynamics of a relativistic blast wave propagating through magnetized
+medium is considered taking into account possible inhomogeneities of density
+and magnetic field and additional energy supply. Under the simplifying
+assumption of a spherically symmetric explosion in a medium with toroidal
+magnetic field self-similar solutions for the internal dynamics of the flow are
+derived. In the weakly magnetized case, when the bulk of the flow may be
+described by the unmagnetized solutions, there is a strongly magnetized sheath
+near the contact discontinuity (when it exists). Self-similar solutions inside
+the sheath are investigated. In the opposite limit of strongly magnetized
+upstream plasma new analytical self-similar solutions are found. Possible
+application to the physics of Gamma-Ray Bursts is discussed.",0111402v1
+2006-01-18,Magnetic domain structure and dynamics in interacting ferromagnetic stacks with perpendicular anisotropy,"The time and field dependence of the magnetic domain structure at
+magnetization reversal were investigated by Kerr microscopy in interacting
+ferromagnetic Co/Pt multilayers with perpendicular anisotropy. Large local
+inhomogeneous magnetostatic fields favor mirroring domain structures and domain
+decoration by rings of opposite magnetization. The long range nature of these
+magnetostatic interactions gives rise to ultra-slow dynamics even in zero
+applied field, i.e. it affects the long time domain stability. Due to this
+additionnal interaction field, the magnetization reversal under short magnetic
+field pulses differs markedly from the well-known slow dynamic behavior.
+Namely, in high field, the magnetization of the coupled harder layer has been
+observed to reverse more rapidly by domain wall motion than the softer layer
+alone.",0601401v1
+2007-01-15,Magnetization dynamics in the single-molecule magnet Fe8 under pulsed microwave irradiation,"We present measurements on the single molecule magnet Fe8 in the presence of
+pulsed microwave radiation at 118 GHz. The spin dynamics is studied via time
+resolved magnetization experiments using a Hall probe magnetometer. We
+investigate the relaxation behavior of magnetization after the microwave pulse.
+The analysis of the experimental data is performed in terms of different
+contributions to the magnetization after-pulse relaxation. We find that the
+phonon bottleneck with a characteristic relaxation time of 10 to 100 ms
+strongly affects the magnetization dynamics. In addition, the spatial effect of
+spin diffusion is evidenced by using samples of different sizes and different
+ways of the sample's irradiation with microwaves.",0701324v1
+2008-01-30,Femtosecond Control of the Magnetization in Ferromagnetic Semiconductors,"We develop a theory of collective spin dynamics triggered by ultrafast
+optical excitation of ferromagnetic semiconductors. Using the density matrix
+equations of motion in the mean field approximation and including magnetic
+anisotropy and hole spin dephasing effects, we predict the development of a
+light--induced magnetization tilt during ultra--short time intervals comparable
+to the pulse duration. This femtosecond dynamics in the coherent temporal
+regime is governed by the interband nonlinear optical polarizations and is
+followed by a second temporal regime governed by the magnetic anisotropy of the
+Fermi sea. We interpret our numerical results by deriving a
+Landau--Gilbert--like equation for the collective spin, which demonstrates an
+ultrafast correction to the magnetic anisotropy effective field due to second
+order coherent nonlinear optical processes. Using the Lindblad semigroup
+method, we also derive a contribution to the interband polarization dephasing
+determined by the Mn spin and the hole spin dephasing. Our predicted
+magnetization tilt and subsequent nonlinear dynamics due to the magnetic
+anisotropy can be controlled by varying the optical pulse intensity, duration,
+and helicity and can be observed with pump--probe magneto--optical
+spectroscopy.",0801.4641v1
+2008-12-07,Improved time-resolved magneto-optical Kerr effect technique and dynamic magnetization reversal mechanism of perpendicularly magnetized $L1_{\mathrm{0}}$ FePt films,"The dynamic coercivity cannot be measured rigorously by the conventional
+time-resolved magneto-optical Kerr effect technique because the irreversible
+deviation of the transient magnetization is accumulated. In order to remove the
+accumulation effect, the alternating magnetic field is employed and
+synchronized with the femtosecond laser pulse. Since the sample is reset before
+each single laser pulse, the accumulation effect of the irreversible deviation
+of the transient magnetization is removed. For perpendicularly magnetized
+$L1_{\mathrm{0}}$ FePt films, the dynamic magnetization reversal process is
+accomplished by the nucleation of reversed domains and the pinned domain wall
+motion.",0812.1360v2
+2009-11-03,Dynamical Bar-Mode Instability in Differentially Rotating Magnetized Neutron Stars,"This paper presents a numerical study over a wide parameter space of the
+likelihood of the dynamical bar-mode instability in differentially rotating
+magnetized neutron stars. The innovative aspect of this study is the
+incorporation of magnetic fields in such a context, which have thus far been
+neglected in the purely hydrodynamical simulations available in the literature.
+The investigation uses the Cosmos++ code which allows us to perform three
+dimensional simulations on a cylindrical grid at high resolution. A sample of
+Newtonian magneto-hydrodynamical simulations starting from a set of models
+previously analyzed by other authors without magnetic fields has been
+performed, providing estimates of the effects of magnetic fields on the
+dynamical bar-mode deformation of rotating neutron stars. Overall, our results
+suggest that the effect of magnetic fields are not likely to be very
+significant in realistic configurations. Only in the most extreme cases are the
+magnetic fields able to suppress growth of the bar mode.",0911.0670v2
+2012-10-22,Accelerating the switching of logical units by anisotropy driven magnetization dynamics,"In this work the magnetization dynamics of clusters supported on non-magnetic
+substrates is shown to exhibit an unprecedented complex response when subjected
+to external magnetic fields. The field-driven magnetization reversal of small
+Co clusters deposited on a Cu(111) surface has been studied by means of
+first-principles calculations and atomistic spin dynamics simulations. For
+applied fields ranging from 1 Tesla to 10 Tesla, we observe a coherent
+magnetization reversal with switching times in the range of several tenths of
+picoseconds to several nanoseconds, depending on the field strength. We find a
+non-monotonous dependence of the switching times with respect to the strength
+of the applied field, which we prove to have its origin in the complex magnetic
+anisotropy landscape of these low dimensional systems. This effect is shown to
+be stable for temperatures around 10 K, and is possible to realize over a range
+of exchange interactions and anisotropy landscapes. Possible experimental
+routes to achieve this unique switching behaviour are discussed.",1210.5836v1
+2013-01-28,Theoretical study of spin-torque oscillator coupled with a nano-magnet by dipole-dipole interaction,"The dynamics of a spin-torque-oscillator (STO) coupled with a nano-magnet
+through dipole-dipole interaction was studied numerically by using the
+macrospin model for the application of the STO as a read head sensor of hard
+disk drives. We found that the current, which is required to induce the
+oscillation of the free-layer (FL) of the STO, depends strongly on the distance
+between the FL and the nano-magnet as well as on the relative orientation of
+the magnetizations between them. To determine the dynamics of the STO it is
+indispensable to consider the dynamics of the dipole-coupled nano-magnet. We
+showed that we could detect the orientation of the magnetization of a
+nano-magnet, or a recording-bit, by the modulation of the oscillation frequency
+of the STO.",1301.6458v1
+2013-04-09,Exchange randomness and spin dynamics in the frustrated magnetic Keplerate {W72V30},"The magnetic properties and spin dynamics of the spin frustrated
+polyoxometalate {W72V30}, where 30 V^{4+} ions (s = 1/2) occupy the sites of an
+icosidodecahedron, have been investigated by low temperature magnetization,
+magnetic susceptibility, proton and vanadium nuclear magnetic resonance, and
+theoretical studies. The field-dependent magnetization at 0.5 K increases
+monotonically up to 50 T without any sign of staircase behavior. This
+low-temperature behavior cannot be explained by a Heisenberg model based on a
+single value of the nearest-neighbor exchange coupling. We analyze this
+behavior upon assuming a rather broad distribution of nearest-neighbor exchange
+interactions. Slow spin dynamics of {W72V30} at low temperatures is observed
+from the magnetic field and temperature dependence of nuclear spin-lattice
+relaxation rate 1/T_1 measurements.",1304.2603v1
+2013-05-30,Guided self-assembly of magnetic beads for biomedical applications,"Micromagnetic beads are widely used in biomedical applications for cell
+separation, drug delivery, and hypothermia cancer treatment. Here we propose to
+use self-organized magnetic bead structures which accumulate on fixed magnetic
+seeding points to isolate circulating tumor cells. The analysis of circulating
+tumor cells is an emerging tool for cancer biology research and clinical cancer
+management including the detection, diagnosis and monitoring of cancer.
+Microfluidic chips for isolating circulating tumor cells use either affinity,
+size or density capturing methods. We combine multiphysics simulation
+techniques to understand the microscopic behavior of magnetic beads interacting
+with Nickel accumulation points used in lab-on-chip technologies. Our proposed
+chip technology offers the possibility to combine affinity and size capturing
+with special antibody-coated bead arrangements using a magnetic gradient field
+created by Neodymium Iron Boron permanent magnets. The multiscale simulation
+environment combines magnetic field computation, fluid dynamics and discrete
+particle dynamics.",1305.7072v1
+2014-04-04,Evolution of magnetic dynamics in an artificially frustrated Fe nanoparticle system,"Frustrated lattices1-3, characterized by minor breakdown in local order in an
+otherwise periodic lattice, lead to simultaneous possibilities of several
+ground states which can trigger unique physical properties, in condensed matter
+systems. In magnetic materials with atomic spins, frustration takes another
+shape with added possibilities to construct various topological arrangements of
+spins, whereby magnetic order is disturbed2,4. We have achieved a new approach
+to introduce positional atomic disorder inside a Fe nanoparticle lattice,
+forming domains without boundaries to study magnetic dynamics of the
+constituent spins. This magnetism overrides the exchange bias derived magnetic
+enhancement, appears only at temperatures around 200 K and is characterized by
+a dynamic polarity, p = +/-1 (positive or negative) with a precise frequency.
+The material otherwise behaves like a superparamagnet with characteristic
+magnetization behaviour at room temperature and 2 K.",1404.1163v1
+2014-12-18,Effective Equations for the Precession Dynamics of Electron Spins and Electron-Impurity Correlations in Diluted Magnetic Semiconductors,"Starting from a quantum kinetic theory for the spin dynamics in diluted
+magnetic semiconductors, we derive simplified equations that effectively
+describe the spin transfer between carriers and magnetic impurities for an
+arbitrary initial impurity magnetization. Taking the Markov limit of these
+effective equations, we obtain good quantitative agreement with the full
+quantum kinetic theory for the spin dynamics in bulk systems at high magnetic
+doping. In contrast, the standard rate description where the carrier-dopant
+interaction is treated according to Fermi's golden rule, which involves the
+assumption of a short memory as well as a perturbative argument, has been shown
+previously to fail if the impurity magnetization is non-zero. The Markov limit
+of the effective equations is derived, assuming only a short memory, while
+higher order terms are still accounted for. These higher order terms represent
+the precession of the carrier-dopant correlations in the effective magnetic
+field due to the impurity spins. Numerical calculations show that the Markov
+limit of our effective equations reproduces the results of the full quantum
+kinetic theory very well. Furthermore, this limit allows for analytical
+solutions and for a physically transparent interpretation.",1412.5898v1
+2015-06-16,Visualization of superparamagnetic dynamics in magnetic topological insulators,"Quantized Hall conductance is a generic feature of two dimensional electronic
+systems with broken time reversal symmetry. In the quantum anomalous Hall state
+recently discovered in magnetic topological insulators, time reversal symmetry
+is believed to be broken by long-range ferromagnetic order, with quantized
+resistance observed even at zero external magnetic field. Here, we use scanning
+nanoSQUID magnetic imaging to provide a direct visualization of the dynamics of
+the quantum phase transition between the two anomalous Hall plateaus in a
+Cr-doped (Bi,Sb)$_2$Te$_3$ thin film. Contrary to naive expectations based upon
+macroscopic magnetometry, our measurements reveal a superparamagnetic state
+formed by weakly interacting magnetic domains with a characteristic size of few
+tens of nanometers. The magnetic phase transition occurs through random
+reversals of these local moments, which drive the electronic Hall plateau
+transition. Surprisingly, we find that the electronic system can in turn drive
+the dynamics of the magnetic system, revealing a subtle interplay between the
+two coupled quantum phase transitions.",1506.05114v1
+2017-06-19,Magnetic Excitations and Continuum of a Field-Induced Quantum Spin Liquid in $α$-RuCl$_3$,"We report on terahertz spectroscopy of quantum spin dynamics in
+$\alpha$-RuCl$_3$, a system proximate to the Kitaev honeycomb model, as a
+function of temperature and magnetic field. An extended magnetic continuum
+develops below the structural phase transition at $T_{s2}=62$K. With the onset
+of a long-range magnetic order at $T_N=6.5$K, spectral weight is transferred to
+a well-defined magnetic excitation at $\hbar \omega_1 = 2.48$meV, which is
+accompanied by a higher-energy band at $\hbar \omega_2 = 6.48$meV. Both
+excitations soften in magnetic field, signaling a quantum phase transition at
+$B_c=7$T where we find a broad continuum dominating the dynamical response.
+Above $B_c$, the long-range order is suppressed, and on top of the continuum,
+various emergent magnetic excitations evolve. These excitations follow clear
+selection rules and exhibit distinct field dependencies, characterizing the
+dynamical properties of the field-induced quantum spin liquid.",1706.06157v1
+2018-06-05,Electromagnetic effects induced by time-dependent axion field,"We studied the dynamics of the so-called $\theta$-term, which exists in
+topological materials and is related to a hypothetical field predicted by
+Peccei-Quinn in particle physics, in a magnetic superlattice constructed using
+a topological insulator and two ferromagnetic insulators, where the
+ferromagnetic insulators had perpendicular magnetic anisotropies and different
+magnetic coercive fields. We examined a way to drive the dynamics of the
+$\theta$-term in the magnetic superlattice through changing the inversion
+symmetry (from an anti-parallel to a parallel magnetic configuration) using an
+external magnetic field. As a result, we found that unconventional
+electromagnetic fields, which are magnetic field-induced charge currents and
+vice versa, are generated by the nonzero dynamics of the $\theta$-term.",1806.01548v1
+2018-07-30,Dynamics of topological defects in a two-dimensional magnetic domain stripe pattern,"Two dimensional magnetic films with perpendicular magnetization spontaneously
+form magnetic domain patterns that evolve or undergo symmetry transformations
+as a function of temperature. When the system is driven from equilibrium by a
+rapid change in temperature, topological pattern defects are the elementary
+pattern excitations that affect this evolution. An elastic continuum model is
+adapted to describe how a metastable population of topological defects alters
+the domain density and the magnetic susceptibility of the ""stripe"" magnetic
+domain pattern. Temporal changes in the susceptibility are interpreted using a
+dynamical equation describing the defect population. Recent experiments provide
+a quantitative verification of the model, and illustrate the use of the
+magnetic susceptibility to follow the population dynamics of topological
+defects in this system, and its potential role in investigating a pattern
+melting phase transition.",1807.11424v1
+2019-03-30,Dynamical sign reversal of magnetic correlations in dissipative Hubbard models,"In quantum magnetism, the virtual exchange of particles mediates an
+interaction between spins. Here, we show that an inelastic Hubbard interaction
+fundamentally alters the magnetism of the Hubbard model due to dissipation in
+spin-exchange processes, leading to sign reversal of magnetic correlations in
+dissipative quantum dynamics. This mechanism is applicable to both fermionic
+and bosonic Mott insulators, and can naturally be realized with ultracold atoms
+undergoing two-body inelastic collisions. The dynamical reversal of magnetic
+correlations can be detected by using a double-well optical lattice or
+quantum-gas microscopy, the latter of which facilitates the detection of the
+magnetic correlations in one-dimensional systems because of spin-charge
+separation. Our results open a new avenue toward controlling quantum magnetism
+by dissipation.",1904.00154v3
+2019-05-14,Rayleigh-Benard convection in a nonuniformly rotating electrically conductive medium in an external spiral magnetic field,"The research is devoted to the stability of convective flow in a nonuniformly
+rotating layer of an electrically conducting fluid in a spiral magnetic field.
+The stationary and oscillatory modes of magnetic convection are considered
+depending on the profile of the angular rotation velocity (Rossby number
+$\textrm{Ro}$) and on the profile of the external azimuthal magnetic field
+(magnetic Rossby number $\textrm{Rb}$). The nonlinear dynamic system of Lorentz
+type equations is obtained by using the Galerkin method. Numerical analysis of
+these equations has shown the presence of chaotic behavior of convective flows.
+The criteria of the occurrence of chaotic movements are found. It depends on
+the parameters of convection: dimensionless numbers of Rayleigh $\textrm{Ra}$,
+Chandrasekhar $\textrm{Q}$, Taylor $\textrm{Ta}$, and external azimuthal
+magnetic field with the Rossby magnetic number $\textrm{Rb}=-1$ for Rayleigh
+$(\textrm{Ro}=-1)$ and Kepler $(\textrm{Ro}=-3/4)$ profiles of the angular
+rotation velocity of the medium.",1905.05472v1
+2020-03-11,"Degenerate states, emergent dynamics and fluid mixing by magnetic rotors","We investigate the collective motion of magnetic rotors suspended in a
+viscous fluid under an uniform rotating magnetic field. The rotors are
+positioned on a square lattice, and low Reynolds hydrodynamics is assumed. For
+a $3 \times 3$ array of magnets, we observe three characteristic dynamical
+patterns as the external field strength is varied: a synchronized pattern, an
+oscillating pattern, and a chessboard pattern. The relative stability of these
+depends on the competition between the energy due to the external magnetic
+field and the energy of the magnetic dipole-dipole interactions among the
+rotors. We argue that the chessboard pattern can be understood as an
+alternation in the stability of two degenerate states, characterized by striped
+and spin-ice configurations, as the applied magnetic field rotates. For larger
+arrays, we observe propagation of slip waves that are similar to metachronal
+waves. The rotor arrays have potential as microfluidic devices that can mix
+fluids and create vortices of different sizes.",2003.05082v1
+2020-04-28,The photometric and polarimetric variability of magnetic O-type stars,"Massive star winds are important contributors to the energy, momentum and
+chemical enrichment of the interstellar medium. Strong, organized and
+predominantly dipolar magnetic fields have been firmly detected in a small
+subset of massive O-type stars. Magnetic massive stars are known to exhibit
+phase-locked variability of numerous observable quantities that is hypothesized
+to arise due to the presence of an obliquely rotating magnetosphere formed via
+the magnetic confinement of their strong outflowing winds. Analyzing the
+observed modulations of magnetic O-type stars is thus a key step towards the
+better understanding of the physical processes that occur within their
+magnetospheres. The dynamical processes that lead to the formation of a
+magnetosphere are formally solved utilizing complex MHD simulations. Recently,
+an Analytic Dynamical Magnetosphere (ADM) model has been developed that can
+quickly be employed to compute the time-averaged density, temperature and
+velocity gradients within a dynamical magnetosphere. Here, we exploit the ADM
+model to compute photometric and polarimetric observables of magnetic Of?p
+stars, to test geometric models inferred from magnetometry. We showcase
+important results on the prototypical Of?p-type star HD 191612, that lead to a
+better characterization of massive star wind and magnetic properties.",2004.13594v1
+2020-08-18,Dark soliton-like magnetic domain walls in a two-dimensional ferromagnetic superfluid,"We report a stable magnetic domain wall in a uniform ferromagnetic spin-1
+condensate, characterized by the magnetization having a dark soliton profile
+with nonvanishing superfluid density. We find exact stationary solutions for a
+particular ratio of interaction parameters with and without magnetic fields,
+and develop an accurate analytic solution applicable to the whole ferromagnetic
+phase. In the absence of magnetic fields, this domain wall relates various
+distinct solitary excitations in binary condensates through $\textrm{SO}(3)$
+spin rotations, which otherwise are unconnected. Remarkably, studying the
+dynamics of a quasi-two-dimensional (quasi-2D) system we show that standing
+wave excitations of the domain wall oscillate without decay, being stable
+against the snake instability. The domain wall is dynamically unstable to modes
+that cause the magnetization to grow perpendicularly while leaving the domain
+wall unchanged. Real time dynamics in the presence of white noise reveals that
+this ""spin twist"" instability does not destroy the topological structure of the
+magnetic domain wall.",2008.08175v2
+2020-10-29,Collective spin dynamics under dissipative spin Hall torque,"Current-induced spin torques in layered magnetic heterostructures have many
+commonalities across broad classes of magnetic materials. These include not
+only collinear ferromagnets, ferrimagnets, and antiferromagnets, but also more
+complex noncollinear spin systems. We develop a general Lagrangian-Rayleigh
+approach for studying the role of dissipative torques, which can pump energy
+into long-wavelength magnetic dynamics, causing dynamic instabilities. While
+the Rayleigh structure of such torques is similar for different magnetic
+materials, their consequences depend sensitively on the nature of the order
+and, in particular, on whether there is a net magnetic moment. The latter
+endows the system with a unipolar switching capability, while magnetically
+compensated materials tend to evolve towards limit cycles, at large torques,
+with chirality dependent on the torque sign. Apart from the ferromagnetic and
+antiferromagnetic cases, we discuss ferrimagnets, which display an intricate
+competition between switching and limit cycles. As a simple case for
+compensated noncollinear order, we consider isotropic spin glasses, as well as
+a scenario of their coexistence with a collinear magnetic order.",2010.15994v1
+2021-01-15,The dynamics of local magnetic moments induced by itinerant Weyl electrons,"We derive the effective interactions between local magnetic moments which are
+mediated by Weyl electrons in magnetic topological semimetals. The resulting
+spin dynamics is governed by the induced Heisenberg, Kitaev and
+Dzyaloshinskii-Moriya (DM) interactions with extended range and oscillatory
+dependence on the distance between the spins. These interactions are realized
+in multiple competing channels shaped by the multitude of Weyl nodes in the
+electron spectrum. Microscopic spins need to be spatially modulated with a
+channel-dependent wavevector in order to take advantage of the interactions.
+The DM vector is parallel to the displacement between the two interacting
+spins, and requires the presence of Weyl electron Fermi surfaces. We also
+derive the Weyl-induced chiral three-spin interaction in the presence of an
+external magnetic field. This interaction has an extended range as well, and
+acts upon the spatially modulated spins in various channels. Its tendency is to
+produce a skyrmion lattice or a chiral spin liquid which exhibits topological
+Hall effect. Ultimately, the theory developed here addresses magnetic dynamics
+in relativistic metals even when chiral magnetism is microscopically precluded.
+We discuss insights into the ordered state of the magnetic Weyl semimetal
+NdAlSi.",2101.06274v1
+2021-02-05,Time-resolved imaging of Œrsted field induced magnetization dynamics in cylindrical magnetic nanowires,"Recent studies in three dimensional spintronics propose that the \OE rsted
+field plays a significant role in cylindrical nanowires. However, there is no
+direct report of its impact on magnetic textures. Here, we use time-resolved
+scanning transmission X-ray microscopy to image the dynamic response of
+magnetization in cylindrical Co$_{30}$Ni$_{70}$ nanowires subjected to
+nanosecond \OE rsted field pulses. We observe the tilting of longitudinally
+magnetized domains towards the azimuthal \OE rsted field direction and create a
+robust model to reproduce the differential magnetic contrasts and extract the
+angle of tilt. Further, we report the compression and expansion, or breathing,
+of a Bloch-point domain wall that occurs when weak pulses with opposite sign
+are applied. We expect that this work lays the foundation for and provides an
+incentive to further studying complex and fascinating magnetization dynamics in
+nanowires, especially the predicted ultra-fast domain wall motion and
+associated spin wave emissions.",2102.03067v3
+2021-10-12,Magnetization dynamics in the density matrix formalism,"Magnetization dynamics described by the Landau-Lifshitz-Gilbert-Slonczewski
+(LLGS) equation can be formulated to have the form of the well-known
+two-level-system (TLS) equations. Recently, we showed that a DC spin-transfer
+torque (STT) term in the LLGS equation can be mapped to a modulation of the
+carrier relaxation rates in the analogous TLS equations. Here, we extend the
+analogy to the TLS dynamics by including the AC magnetic field, AC
+demagnetization field, and AC STT excitation that we show constitute the
+interaction term in the analogous TLS picture. Interestingly, we find that the
+carrier injection rate in the TLS equations that is responsible for transitions
+between the excited and ground states of the system naturally translates to an
+intense short magnetic pulse that reverses the magnetization state.
+Furthermore, we also show that the two helicities of circularly polarized
+magnetic pulses correspond to the two carrier injection rates in the analogous
+TLS picture. In the context of the highly debated all-optical helicity
+dependent switching experiment, it offers a new explanation of the
+magnetization reversal from first principles.",2110.06138v3
+2022-05-10,A Machine-Learned Spin-Lattice Potential for Dynamic Simulations of Defective Magnetic Iron,"A machine-learned spin-lattice interatomic potential (MSLP) for magnetic iron
+is developed and applied to mesoscopic scale defects. It is achieved by
+augmenting a spin-lattice Hamiltonian with a neural network term trained to
+descriptors representing a mix of local atomic configuration and magnetic
+environments. It reproduces the cohesive energy of BCC and FCC phases with
+various magnetic states. It predicts the formation energy and complex magnetic
+structure of point defects in quantitative agreement with density functional
+theory (DFT) including the reversal and quenching of magnetic moments near the
+core of defects. The Curie temperature is calculated through spin-lattice
+dynamics showing good computational stability at high temperature. The
+potential is applied to study magnetic fluctuations near sizable dislocation
+loops. The MSLP transcends current treatments using DFT and molecular dynamics,
+and surpasses other spin-lattice potentials that only treat near-perfect
+crystal cases.",2205.04732v1
+2022-08-07,Transition state theory characterizes thin film macrospin dynamics driven by an oscillatory magnetic field: Inertial effects,"Understanding the magnetization switching process in ferromagnetic thin films
+is essential for many technological applications. We investigate the effects of
+periodic driving via magnetic fields on a macrospin system under explicit
+consideration of inertial dynamics. This is usually achieved by extending the
+Landau-Lifshitz-Gilbert equation with a term including the second time
+derivative of the magnetization. The dynamics of the magnetization switching
+can then be characterized by its switching rate. We apply methods from
+transition state theory for driven systems to resolve the rate of magnetization
+switching in this general case. In doing so, we find that magnetization
+exhibits resonance-like behavior under certain driving conditions, and it can
+be affected strongly by the system's relaxation rate.",2208.03613v1
+2022-12-16,Dynamical magnetic fields in heavy-ion collisions,"The magnetic fields in heavy-ion collisions are important ingredients for
+many interesting phenomena, such as the Chiral Magnetic Effect, Chiral Magnetic
+Wave, the directed flow $v_1$ of $D^0$ mesons and the splitting of the spin
+polarization of the $\Lambda$/$\bar{\Lambda}$. Quantitative studies of these
+phenomena however suffer from limited understanding on the dynamical evolution
+of these fields in the medium created by the collisions, which remains a
+critical and challenging problem. The initial magnetic fields from the
+colliding nuclei decay very fast in the vacuum but their lifetime could be
+extended through medium response due to electrically conducting quarks and
+antiquarks. Here we perform a detailed analysis of such medium effect on the
+dynamical magnetic fields by numerically solving the Maxwell's equations
+concurrently with the expanding medium described by viscous hydrodynamics,
+under the assumption of negligible back reaction of the fields on the fluid
+evolution. Our results suggest a considerable enhancement of late time magnetic
+fields, the magnitude of which depends sensitively on the fireball expansion as
+well as the medium electric conductivity both before and during hydrodynamic
+stage.",2212.08579v2
+2023-09-22,Laser-induced real-space topology control of spin wave resonances,"Femtosecond laser excitation of materials that exhibit magnetic spin textures
+promises advanced magnetic control via the generation of ultrafast and
+non-equilibrium spin dynamics. We explore such possibilities in ferrimagnetic
+[Fe(0.35 nm)/Gd(0.40 nm)]$_{160}$ multilayers, which host a rich diversity of
+magnetic textures from stripe domains at low magnetic fields, a dense
+bubble/skyrmion lattice at intermediate fields, and a single domain state for
+high magnetic fields. Using femtosecond magneto-optics, we observe distinct
+coherent spin wave dynamics in response to a weak laser excitation allowing us
+to unambiguously identify the different magnetic spin textures. Moreover,
+employing strong laser excitation we show that we achieve versatile control of
+the coherent spin dynamics via non-equilibrium and ultrafast transformation of
+magnetic spin textures by both creating and annihilating bubbles/skyrmions. We
+corroborate our findings by micromagnetic simulations and by Lorentz
+transmission electron microscopy before and after laser exposure.",2309.12956v1
+2023-11-07,"Magnetism in AV3Sb5 (A = Cs, Rb, K): Complex Landscape of the Dynamical Magnetic Textures","We have investigated the dynamical magnetic properties of the V-based kagome
+stibnite compounds by combining the ab-initio calculated magnetic parameters of
+a spin Hamiltonian like inter-site exchange parameters, magnetocrystalline
+anisotropy and site projected magnetic moments, with full-fledged simulations
+of atomistic spin-dynamics. Our calculations reveal that in addition to a
+ferromagnetic order along the [001] direction, the system hosts a complex
+landscape of magnetic configurations comprised of commensurate and
+incommensurate spin-spirals along the [010] direction. The presence of such
+chiral magnetic textures may be the key to solve the mystery about the origin
+of the experimentally observed inherent breaking of the C6 rotational symmetry-
+and the time-reversal symmetry.",2311.04099v1
+2023-12-17,Magnetic Fluctuations in Niobium Pentoxide,"Using a spin-polarized muon beam we were able to capture magnetic dynamics in
+an amorphous niobium pentoxide thin film. Muons are used to probe internal
+magnetic fields produced by defects. Magnetic fluctuations could be described
+by the dynamical Kubo-Toyabe model considering a time-dependent local magnetic
+field. We state that observed fluctuations result from the correlated motion of
+electron spins. We expect that oxygen vacancies play a significant role in
+these films and lead to a complex magnetic field distribution which is
+non-stationary. The characteristic average rate of magnetic field change is on
+the order of 100~MHz. The observed dynamics may provide insight into potential
+noise sources in Nb-based superconducting devices, while also highlighting the
+limitations imposed by amorphous oxides.",2312.10697v1
+2024-01-01,Calculation of Gilbert damping and magnetic moment of inertia using torque-torque correlation model within ab initio Wannier framework,"Magnetization dynamics in magnetic materials are well described by the
+modified semiclassical Landau-Lifshitz-Gilbert (LLG) equation, which includes
+the magnetic damping $\alpha$ and the magnetic moment of inertia $\mathrm{I}$
+tensors as key parameters. Both parameters are material-specific and physically
+represent the time scales of damping of precession and nutation in
+magnetization dynamics. $\alpha$ and $\mathrm{I}$ can be calculated quantum
+mechanically within the framework of the torque-torque correlation model. The
+quantities required for the calculation are torque matrix elements, the real
+and imaginary parts of the Green's function and its derivatives. Here, we
+calculate these parameters for the elemental magnets such as Fe, Co and Ni in
+an ab initio framework using density functional theory and Wannier functions.
+We also propose a method to calculate the torque matrix elements within the
+Wannier framework. We demonstrate the effectiveness of the method by comparing
+it with the experiments and the previous ab initio and empirical studies and
+show its potential to improve our understanding of spin dynamics and to
+facilitate the design of spintronic devices.",2401.00714v1
+2011-11-21,Multiscale dynamics of solar magnetic structures,"Multiscale topological complexity of solar magnetic field is among the
+primary factors controlling energy release in the corona, including associated
+processes in the photospheric and chromospheric boundaries. We present a new
+approach for analyzing multiscale behavior of the photospheric magnetic flux
+underlying this dynamics as depicted by a sequence of high-resolution solar
+magnetograms. The approach involves two basic processing steps: (1)
+identification of timing and location of magnetic flux origin and demise events
+(as defined by DeForest et al., 2007) by tracking spatiotemporal evolution of
+unipolar and bipolar photospheric regions, and (2) analysis of collective
+behavior of the detected magnetic events using a generalized version of
+Grassberger - Procaccia correlation integral algorithm. The scale-free nature
+of the developed algorithms makes it possible to characterize the dynamics of
+the photospheric network across a wide range of distances and relaxation times.
+Three types of photospheric conditions are considered to test the method: a
+quiet photosphere, a solar active region (NOAA 10365) in a quiescent
+non-flaring state, and the same active region during a period of M-class
+flares. The results obtained show (1) the presence of a topologically complex
+asymmetrically fragmented magnetic network in the quiet photosphere driven by
+meso- and supergranulation, (2) the formation of non-potential magnetic
+structures with complex polarity separation lines inside the active region, and
+(3) statistical signatures of canceling bipolar magnetic structures coinciding
+with flaring activity in the active region. Each of these effects can represent
+an unstable magnetic configuration acting as an energy source for coronal
+dissipation and heating.",1111.5053v2
+2015-02-12,A Multiscale Dynamo Model Driven by Quasi-geostrophic Convection,"A convection-driven multiscale dynamo model is developed in the limit of low
+Rossby number for the plane layer geometry in which the gravity and rotation
+vectors are aligned. The small-scale fluctuating dynamics are described by a
+magnetically-modified quasi-geostrophic equation set, and the large-scale mean
+dynamics are governed by a diagnostic thermal wind balance. The model utilizes
+three timescales that respectively characterize the convective timescale, the
+large-scale magnetic evolution timescale, and the large-scale thermal evolution
+timescale. Distinct equations are derived for the cases of order one and low
+magnetic Prandtl number. It is shown that the low magnetic Prandtl number model
+is characterized by a magnetic to kinetic energy ratio that is asymptotically
+large, with ohmic dissipation dominating viscous dissipation on the
+large-scales. For the order one magnetic Prandtl number model the magnetic and
+kinetic energies are equipartitioned and both ohmic and viscous dissipation are
+weak on the large-scales; large-scale ohmic dissipation occurs in thin magnetic
+boundary layers adjacent to the solid boundaries. For both magnetic Prandtl
+number cases the Elsasser number is small since the Lorentz force does not
+enter the leading order force balance. The new models can be considered fully
+nonlinear, generalized versions of the dynamo model originally developed by
+Childress and Soward [Phys. Rev. Lett., \textbf{29}, p.837, 1972]. These models
+may be useful for understanding the dynamics of convection-driven dynamos in
+regimes that are only just becoming accessible to direct numerical simulations.",1502.03856v2
+2016-04-01,On the relationship between G-band bright point dynamics and their magnetic field strengths,"G-band bright points (GBPs) are regarded as good manifestations of magnetic
+flux concentrations. We aim to investigate the relationship between the dynamic
+properties of GBPs and their longitudinal magnetic field strengths. High
+spatial and temporal resolution observations were recorded simultaneously with
+G-band filtergrams and Narrow-band Filter Imager (NFI) Stokes I and V images
+with Hinode /Solar Optical Telescope. The GBPs are identified and tracked in
+the G-band images automatically, and the corresponding longitudinal magnetic
+field strength of each GBP is extracted from the calibrated NFI magnetograms by
+a point-to-point method. After categorizing the GBPs into five groups by their
+longitudinal magnetic field strengths, we analyze the dynamics of GBPs of each
+group. The results suggest that with increasing longitudinal magnetic field
+strengths of GBPs correspond to a decrease in their horizontal velocities and
+motion ranges as well as by showing more complicated motion paths. This
+suggests that magnetic elements showing weaker magnetic field strengths prefer
+to move faster and farther along straighter paths, while stronger ones move
+more slowly in more erratic paths within a smaller region. The dynamic
+behaviors of GBPs with different longitudinal magnetic field strengths can be
+explained by that the stronger flux concentrations withstand the convective
+flows much better than weaker ones.",1604.00152v1
+2019-02-05,The Dynamics of Magnetism in Fe-Cr Alloys with Cr Clustering,"The dynamics of magnetic moments in iron-chromium alloys with different
+levels of Cr clustering show unusual features resulting from the fact that even
+in a perfect body-centred cubic structure, magnetic moments experience
+geometric magnetic frustration resembling that of a spin glass. Due to the long
+range exchange coupling and configuration randomness, magnetic moments of Cr
+solutes remain non-collinear at all temperatures. To characterise magnetic
+properties of Fe-Cr alloys, we explore the temperature dependence of
+magnetisation, susceptibility, Curie temperature and spin-spin correlations
+with spatial resolution. The static and dynamic magnetic properties are
+correlated with the microstructure of Fe-Cr, where magnetisation and
+susceptibility are determined by the size of Cr precipitates at nominal Cr
+concentrations. The Curie temperature is always maximised when the solute
+concentration of Cr in the $\alpha$ phase is close to 5 to 6 at.\%, and the
+susceptibility of Fe atoms is always enhanced at the boundary between a
+precipitate and solid solution. Interaction between Cr and Fe stimulates
+magnetic disorder, lowering the effective Curie temperature. Dynamic simulation
+of evolution of magnetic correlations shows that the spin-spin relaxation time
+in Fe-Cr alloys is in the 20 to 40 ps range.",1902.01645v1
+2020-05-25,Dynamics of ferromagnetic bimerons driven by spin currents and magnetic fields,"Magnetic bimeron composed of two merons is a topological counterpart of
+magnetic skyrmion in in-plane magnets, which can be used as the nonvolatile
+information carrier in spintronic devices. Here we analytically and numerically
+study the dynamics of ferromagnetic bimerons driven by spin currents and
+magnetic fields. Numerical simulations demonstrate that two bimerons with
+opposite signs of topological numbers can be created simultaneously in a
+ferromagnetic thin film via current-induced spin torques. The current-induced
+spin torques can also drive the bimeron and its speed is analytically derived,
+which agrees with the numerical results. Since the bimerons with opposite
+topological numbers can coexist and have opposite drift directions, two-lane
+racetracks can be built in order to accurately encode the data bits. In
+addition, the dynamics of bimerons induced by magnetic field gradients and
+alternating magnetic fields are investigated. It is found that the bimeron
+driven by alternating magnetic fields can propagate along a certain direction.
+Moreover, combining a suitable magnetic field gradient, the
+Magnus-force-induced transverse motion can be completely suppressed, which
+implies that there is no skyrmion Hall effect. Our results are useful for
+understanding of the bimeron dynamics and may provide guidelines for building
+future bimeron-based spintronic devices.",2005.11924v2
+2022-05-18,Influence of Magnetic Fields on the Gas Rotation in the Galaxy $NGC\;6946$,"Magnetic fields can play an important role in the energy balance and
+formation of gas structures in galaxies. However, their dynamical effect on the
+rotation curve of galaxies is immensely unexplored. We investigate the
+dynamical effect of the known magnetic arms of $NGC\;6946$ on its circular gas
+rotation traced in HI, considering two dark matter mass density models, ISO,
+and the universal NFW profile. We used a three-dimensional model for the
+magnetic field structure to fit the modeled rotation curve to the observed data
+via an $\chi$-squared minimization method. The shape of the HI gas rotation
+curve is reproduced better including the effect of the magnetic field,
+especially in the outer part, where the dynamical effect of the magnetic field
+could become important. The typical amplitude of the regular magnetic field
+contribution in the rotation curve is about $ 6 - 14 \; km s^{-1}$ in the outer
+gaseous disk of the galaxy $NGC\;6946$. The contribution ratio of the regular
+magnetic field to the observed circular velocity and to dark matter increases
+with the galactocentric radius. Its ratio to the observed rotational velocity
+is about five percent and to dark matter is about 10 percent in the outer
+regions of the galaxy $NGC\;6946$. Therefore, the large-scale magnetic fields
+cannot be completely ignored in the large-scale dynamics of spiral galaxies,
+especially in the outer parts of galaxies.",2205.09069v2
+2023-10-23,Nonlinear Optical Effects Due to Magnetization Dynamics In a Ferromagnet,"We theoretically consider magnetization dynamics in a ferromagnetic slab
+induced by the magnetic field of a strong femtosecond laser pulse. The
+longitudinal geometry, in which the initial magnetization lies in both the
+plane of incidence and the sample plane, is studied. The magnetization
+oscillations at the optical wave frequency are calculated with the use of the
+Kapitza pendulum approach taking into account that the optical frequency is
+much greater than the magnetization oscillation eigenfrequency. We study the
+reflection of the electromagnetic wave from a ferromagnet %with such a dynamics
+and show that this laser-induced low-frequency magnetization dynamics leads to
+the appearance of the second-order nonlinearity in the Maxwell's equations,
+which in turn gives rise to both the second harmonic generation (SHG) and
+rectification effect. Although the amplitude of the magnetization oscillations
+is small, the considered effect may be responsible for the SHG with the
+efficiency comparable to that of nonmagnetic SHG from metal surfaces. Our
+estimations show that the suggested mechanism may explain the recent
+experiments on magnetization induced modulation of the SHG intensity in a
+``forbidden'' $P_{in}P_{out}$ combination of incident and reflected waves in
+cobalt/heavy metal systems, where it can be even more pronounced due to the
+spin current flow through the ferromagnet/ heavy metal interface.",2310.14967v1
+2002-12-19,Evolution of Magnetic Fields around a Kerr Black Hole,"The evolution of magnetic fields frozen to a perfectly conducting plasma
+fluid around a Kerr black hole is investigated. We focus on the plunging region
+between the black hole horizon and the marginally stable circular orbit in the
+equatorial plane. Adopting the kinematic approximation where the dynamical
+effects of magnetic fields are ignored, we exactly solve Maxwell's equations
+with the assumptions that the geodesic motion of the fluid is stationary and
+axisymmetric, the magnetic field has only radial and azimuthal components and
+depends only on time and radial coordinates. We show that the stationary state
+of the magnetic field in the plunging region is uniquely determined by the
+boundary conditions at the marginally stable circular orbit. If the magnetic
+field at the marginally stable circular orbit is in a stationary state, the
+magnetic field in the plunging region will quickly settle into a stationary
+state if it is not so initially, in a time determined by the dynamical time
+scale. The radial component of the magnetic field at the marginally stable
+circular orbit is more important than the toroidal component in determining the
+structure and evolution of the magnetic field in the plunging region. Even if
+at the marginally stable circular orbit the toroidal component is zero, in the
+plunging region a toroidal component is quickly generated from the radial
+component by the shear motion of the fluid. Finally, we show that the dynamical
+effects of magnetic fields are unimportant in the plunging region if they are
+negligible on the marginally stable circular orbit. This supports the
+``no-torque inner boundary condition'' of thin disks, contrary to the claim in
+the recent literature.",0212456v1
+2011-02-28,First Flare-related Rapid Change of Photospheric Magnetic Field Observed by Solar Dynamics Observatory,"Photospheric magnetic field not only plays important roles in building up
+free energy and triggering solar eruptions, but also has been observed to
+change rapidly and permanently responding to the coronal magnetic field
+restructuring due to coronal transients. The Helioseismic and Magnetic Imager
+instrument (HMI) on board the newly launched Solar Dynamics Observatory (SDO)
+produces seeing-free full-disk vector magnetograms at consistently high
+resolution and high cadence, which finally makes possible an unambiguous and
+comprehensive study of this important back-reaction process. In this study, we
+present a near disk-center, GOES-class X2.2 flare occurred at NOAA AR 11158 on
+2011 February 15 using the magnetic field measurements made by HMI. We obtained
+the first solid evidence of an enhancement in the transverse magnetic field at
+the flaring magnetic polarity inversion line (PIL) by a magnitude of 70%. This
+rapid and irreversible field evolution is unequivocally associated with the
+flare occurrence, with the enhancement area located in between the two
+chromospheric flare ribbons. Similar findings have been made for another two
+major flare events observed by SDO. These results strongly corroborate our
+previous suggestion that the photospheric magnetic field near the PIL must
+become more horizontal after eruptions.
+  In-depth studies will follow to further link the photospheric magnetic field
+changes with the dynamics of coronal mass ejections, when full Stokes inversion
+is carried out to generate accurate magnetic field vectors.",1103.0027v1
+2012-02-24,Dynamical Magnetic and Nuclear Polarization in Complex Spin Systems: Semi-magnetic II-VI Quantum Dots,"Dynamical magnetic and nuclear polarization in complex spin systems is
+discussed on the example of transfer of spin from exciton to the central spin
+of magnetic impurity in a quantum dot in the presence of a finite number of
+nuclear spins. The exciton is described in terms of the electron and heavy hole
+spins interacting via exchange interaction with magnetic impurity, via
+hypeprfine interaction with a finite number of nuclear spins and via dipole
+interaction with photons. The time-evolution of the exciton, magnetic impurity
+and nuclear spins is calculated exactly between quantum jumps corresponding to
+exciton radiative recombination. The collapse of the wavefunction and the
+refilling of the quantum dot with new spin polarized exciton is shown to lead
+to build up of magnetization of the magnetic impurity as well as nuclear spin
+polarization. The competition between electron spin transfer to magnetic
+impurity and to nuclear spins simultaneous with the creation of dark excitons
+is elucidated. The technique presented here opens up the possibility of
+studying optically induced Dynamical Magnetic and Nuclear Polarization in
+Complex Spin Systems.",1202.5352v3
+2012-07-20,Magnetic Catalysis: A Review,"We give an overview of the magnetic catalysis phenomenon. In the framework of
+quantum field theory, magnetic catalysis is broadly defined as an enhancement
+of dynamical symmetry breaking by an external magnetic field. We start from a
+brief discussion of spontaneous symmetry breaking and the role of a magnetic
+field in its a dynamics. This is followed by a detailed presentation of the
+essential features of the phenomenon. In particular, we emphasize that the
+dimensional reduction plays a profound role in the pairing dynamics in a
+magnetic field. Using the general nature of underlying physics and its
+robustness with respect to interaction types and model content, we argue that
+magnetic catalysis is a universal and model-independent phenomenon. In support
+of this claim, we show how magnetic catalysis is realized in various models
+with short-range and long-range interactions. We argue that the general nature
+of the phenomenon implies a wide range of potential applications: from certain
+types of solid state systems to models in cosmology, particle and nuclear
+physics. We finish the review with general remarks about magnetic catalysis and
+an outlook for future research.",1207.5081v2
+2017-12-20,Second-harmonic magnetic response characterizing magnetite-based colloid,"Nonlinear second-harmonic magnetic response (M2) was used to characterize an
+aqueous colloidal solution of dextran-coated magnetite (Fe3O4) nanoparticles.
+Data analysis with the formalism based on Gilbert-Landau-Lifshitz equation for
+stochastic dynamics of superparamagnetic (SP) particles ensured extensive
+quantifying of the system via a set of magnetic and magnetodynamic parameters,
+such as the mean magnetic moment, the damping constant, the longitudinal
+relaxation time, the magnetic anisotropy field and energy, and others. Combined
+with transmission electron microscopy and dynamic light scattering, M2
+technique allowed obtaining additional parameters, viz., the dextran-coating
+thickness and the interparticle magnetic dipolar energy. Aggregated colloidal
+nanoparticles were shown to be magnetically correlated inside the aggregate due
+to magnetic dipole-dipole (d-d) coupling within the correlation radius ~50 nm.
+With the d-d coupling account, the volume distribution of the aggregates
+recovered from M2 measurements is well consistent with electron microscopy
+results. From electron magnetic resonance, abrupt change of SP dynamics with
+increasing external magnetic field was observed and explained. The presented
+study exemplifies a novel M2-based procedure of comprehensive quantitative
+characterization applicable for a wide variety of SP systems.",1712.07534v1
+2019-10-15,Irregularly Shaped γ'-Fe4N Nanoparticles for Hyperthermia Treatment and T2 Contrast-Enhanced Magnetic Resonance Imaging with Minimum Dose,"Magnetic nanoparticles (MNPs) have been extensively used in drug/gene
+delivery, hyperthermia therapy, magnetic particle imaging (MPI), magnetic
+resonance imaging (MRI), magnetic bioassays, etc. With proper surface chemical
+modifications, physicochemically stable and non-toxic MNPs are emerging
+contrast agents and tracers for in vivo MRI and MPI applications. Herein, we
+report the high magnetic moment, irregularly shaped {\gamma}'-Fe4N
+nanoparticles for enhanced hyperthermia therapy and T2 contrast agent for MRI
+application. The static and dynamic magnetic properties of {\gamma}'-Fe4N
+nanoparticles are characterized by vibrating sample magnetometer (VSM) and
+magnetic particle spectroscopy (MPS) systems, respectively. Compared to the
+{\gamma}-Fe2O3 nanoparticles, {\gamma}'-Fe4N show at least 3 times higher
+saturation magnetization (in emu/g), which, as a result, gives rise to the
+stronger dynamic magnetic responses as proved in the MPS measurement results.
+In addition, {\gamma}'-Fe4N nanoparticles are functionalized with oleic acid
+layer by a wet mechanical milling process, the morphologies of as-milled
+nanoparticles are characterized by transmission electron microscopy (TEM),
+dynamic light scattering (DLS) and nanoparticle tracking analyzer (NTA). We
+report that with proper surface chemical modification and tuning on
+morphologies, {\gamma}'-Fe4N nanoparticles could be used as tiny heating
+sources for hyperthermia and contrast agents for MRI applications with minimum
+dose.",1910.06842v1
+2021-11-26,Numerical Analysis of the Nanoparticle Dynamics in a Viscous Liquid: Deterministic Approach,"We study the deterministic dynamics of single-domain ferromagnetic
+nanoparticles in a viscous liquid induced by the joint action of the gradient
+and uniform magnetic fields. It is assumed that the gradient field depends on
+time harmonically and the uniform field has two components, perpendicular and
+parallel to the gradient one. We also assume that the anisotropy magnetic field
+is so strong that the nanoparticle magnetization lies along the anisotropy
+axis, i.e., the magnetization vector is ""frozen"" into the particle body. With
+these assumptions and neglecting inertial effects we derive the torque and
+force balance equations that describe the rotational and translational motions
+of particles. We reduce these equations to a set of two coupled equations for
+the magnetization angle and particle coordinate, solve them numerically in a
+wide range of the system parameters and analyze the role of the parallel
+component of the uniform magnetic field. It is shown, in particular, that
+nanoparticles perform only periodic rotational and translational motions if the
+perpendicular component of the uniform magnetic field is absent. In contrast,
+the nanoparticle dynamics in the presence of this component becomes
+non-periodic, resulting in the drift motion (directed transport) of
+nanoparticles. By analyzing the short and long-time dependencies of the
+magnetization angle and particle coordinate we show that the increase in the
+parallel component of the uniform magnetic field decreases both the particle
+displacement for a fixed time and its average drift velocity on each period of
+the gradient magnetic field.",2111.13534v2
+2022-04-25,Reduced effective magnetization and damping by slowly-relaxing impurities in strained $γ$-$\mathrm{Fe_2O_3}$ thin films,"We study the static and dynamic magnetic properties of epitaxially strained
+$\gamma$-$\mathrm{Fe_2O_3}$ (maghemite) thin films grown via pulsed-laser
+deposition on MgO substrates by SQUID magnetometry and cryogenic broadband
+ferromagnetic resonance experiments. SQUID magnetometry measurements reveal
+hysteretic magnetization curves for magnetic fields applied both in- and out of
+the sample plane. From the magnetization dynamics of our thin films, we find a
+small negative effective magnetization in agreement with a strain induced
+perpendicular magnetic anisotropy. Moreover, we observe a non-linear evolution
+of the ferromagnetic resonance-linewidth as function of the microwave frequency
+and explain this finding with a model based on slowly relaxing impurities, the
+so-called slow relaxor model. By investigating the magnetization dynamics in
+our maghemite thin films as a function of frequency and temperature, we can
+isolate the temperature dependent contribution of the slowly relaxing
+impurities to the resonance linewidth and, in particular, observe a sign change
+in the effective magnetization. This finding provides evidence for a transition
+of the magnetic anisotropy from a perpendicular easy axis to an easy in-plane
+anisotropy for reduced temperatures.",2204.11498v1
+2020-07-14,Magnetic field transport in compact binaries,"Dwarf novae (DNe) and low mass X-ray binaries (LMXBs) show eruptions that are
+thought to be due to a thermal-viscous instability in their accretion disk.
+These eruptions provide constraints on angular momentum transport mechanisms.
+We explore the idea that angular momentum transport could be controlled by the
+dynamical evolution of the large scale magnetic field. We study the impact of
+different prescriptions for the magnetic field evolution on the dynamics of the
+disk. This is a first step in confronting the theory of magnetic field
+transport with observations. We develop a version of the disk instability model
+that evolves the density, the temperature and the large scale vertical magnetic
+flux together. We take into account the accretion driven by turbulence or by a
+magnetized outflow. To evolve the magnetic flux, we use a toy model with
+physically motivated prescriptions depending mainly on the local magnetization.
+We find that allowing magnetic flux to be advected inwards provides the best
+agreement with DNe lightcurves. This leads to a hybrid configuration with an
+inner magnetized disk, driven by angular momentum losses to an MHD outflow,
+sharply transiting to an outer weakly-magnetized turbulent disk, where the
+eruptions are triggered. The dynamical impact is equivalent to truncating a
+viscous disk so that it does not extend down to the compact object, with the
+truncation radius dependent on the magnetic flux and evolving as
+$\dot{M}^{-2/3}$. Models of DNe and LMXBs lightcurves typically require the
+outer, viscous disk to be truncated in order to match observations. There is no
+generic explanation for this truncation. We propose that it is a natural
+outcome of the presence of large-scale magnetic fields in both DNe and LMXBs,
+the magnetic flux accumulating towards the center to produce a magnetized disk
+with a fast accretion timescale.",2007.07277v1
+2006-03-14,Spin dynamics and magnetic order in magnetically frustrated Tb2Sn2O7,"We report a study of the geometrically frustrated magnetic material Tb2Sn2O7
+by the positive muon spin relaxation technique. No signature of a static
+magnetically ordered state is detected while neutron magnetic reflections are
+observed in agreement with a published report. This is explained by the
+dynamical nature of the ground state of Tb2Sn2O7: the Tb3+ magnetic moment
+characteristic fluctuation time is ~ 10^{-10} s. The strong effect of the
+magnetic field on the muon spin-lattice relaxation rate at low fields indicates
+a large field-induced increase of the magnetic density of states of the
+collective excitations at low energy.",0603379v1
+2006-12-15,Domain Nucleation and Annihilation in Uniformly Magnetized State under Current Pulses in Narrow Ferromagnetic Wires,"We investigate the current-driven magnetization dynamics in narrow Permalloy
+wires by means of Lorentz microscopy and electron holography. Current pulses
+are found to transform the magnetic structure in the uniformly magnetized state
+below the Curie temperature. A variety of magnetic states including reversed
+magnetic domains are randomly obtained in low probability. The dynamics of
+vortices found in most of observed magnetic states seems to play a key role in
+triggering the magnetization reversal.",0612383v2
+2001-05-02,The Ising Model on a Dynamically Triangulated Disk with a Boundary Magnetic Field,"We use Monte Carlo simulations to study a dynamically triangulated disk with
+Ising spins on the vertices and a boundary magnetic field. For the case of zero
+magnetic field we show that the model possesses three phases. For one of these
+the boundary length grows linearly with disk area, while the other two phases
+are characterized by a boundary whose size is on the order of the cut-off. A
+line of continuous magnetic transitions separates the two small boundary
+phases. We determine the critical exponents of the continuous magnetic phase
+transition and relate them to predictions from continuum 2-d quantum gravity.
+This line of continuous transitions appears to terminate on a line of
+discontinuous phase transitions dividing the small boundary phases from the
+large boundary phase. We examine the scaling of bulk magnetization and boundary
+magnetization as a function of boundary magnetic field in the vicinity of this
+tricritical point.",0105002v1
+2008-08-15,Alignment Dynamics of Single-Walled Carbon Nanotubes in Pulsed Ultrahigh Magnetic Fields,"We have measured the dynamic alignment properties of single-walled carbon
+nanotube (SWNT) suspensions in pulsed high magnetic fields through linear
+dichroism spectroscopy. Millisecond-duration pulsed high magnetic fields up to
+56 T as well as microsecond-duration pulsed ultrahigh magnetic fields up to 166
+T were used. Due to their anisotropic magnetic properties, SWNTs align in an
+applied magnetic field, and because of their anisotropic optical properties,
+aligned SWNTs show linear dichroism. The characteristics of their overall
+alignment depend on several factors, including the viscosity and temperature of
+the suspending solvent, the degree of anisotropy of nanotube magnetic
+susceptibilities, the nanotube length distribution, the degree of nanotube
+bundling, and the strength and duration of the applied magnetic field. In order
+to explain our data, we have developed a theoretical model based on the
+Smoluchowski equation for rigid rods that accurately reproduces the salient
+features of the experimental data.",0808.2205v1
+2008-11-13,Selection rules for Single-Chain-Magnet behavior in non-collinear Ising systems,"The magnetic behavior of molecular Single-Chain Magnets is investigated in
+the framework of a one-dimensional Ising model with single spin-flip Glauber
+dynamics. Opportune modifications to the original theory are required in order
+to account for reciprocal non-collinearity of local anisotropy axes and the
+crystallographic (laboratory) frame. The extension of Glauber's theory to the
+case of a collinear Ising ferrimagnetic chain is also discussed. Within this
+formalism, both the dynamics of magnetization reversal in zero field and the
+response of the system to a weak magnetic field, oscillating in time, are
+studied. Depending on the geometry, selection rules are found for the
+occurrence of slow relaxation of the magnetization at low temperatures, as well
+as for resonant behavior of the a.c. susceptibility as a function of
+temperature at low frequencies. The present theory applies successfully to some
+real systems, namely Mn-, Dy-, and Co-based molecular magnetic chains, showing
+that Single-Chain-Magnet behavior is not only a feature of collinear ferro- and
+ferrimagnetic, but also of canted antiferromagnetic chains.",0811.2118v1
+2008-12-29,Temperature dependent dynamic and static magnetic response in magnetic tunnel junctions with Permalloy layers,"Ferromagnetic resonance and static magnetic properties of CoFe/Al2O3/CoFe/Py
+and CoFe/Al2O3/CoFeB/Py magnetic tunnel junctions and of 25nm thick
+single-layer Permalloy(Py) films have been studied as a function of temperature
+down to 2K. The temperature dependence of the ferromagnetic resonance excited
+in the Py layers in magnetic tunnel junctions shows knee-like enhancement of
+the resonance frequency accompanied by an anomaly in the magnetization near
+60K. We attribute the anomalous static and dynamic magnetic response at low
+temperatures to interface stress induced magnetic reorientation transition at
+the Py interface which could be influenced by dipolar soft-hard layer coupling
+through the Al2O3 barrier.",0812.4953v1
+2009-03-19,Magnetic Anisotropy and Magnetization Dynamics of Individual Atoms and Clusters of Fe and Co on Pt(111),"The recently discovered giant magnetic anisotropy of single magnetic Co atoms
+raises the hope of magnetic storage in small clusters. We present a joint
+experimental and theoretical study of the magnetic anisotropy and the spin
+dynamics of Fe and Co atoms, dimers, and trimers on Pt(111). Giant anisotropies
+of individual atoms and clusters as well as lifetimes of the excited states
+were determined with inelastic scanning tunneling spectroscopy. The short
+lifetimes due to hybridization-induced electron-electron scattering oppose the
+magnetic stability provided by the magnetic anisotropies.",0903.3337v1
+2010-05-21,Magnetization jumps and relaxation effect in doped CeFe2,"For the first time, we find that the dynamic antiferromagnetic phase present
+in CeFe2 gets stabilized with Ga and Si substitutions. We find that phenomena
+such as strain-induced first order jumps in the magnetization curves, asymmetry
+between the M-H curves during the increasing and decreasing field cycles, the
+envelope curve being inside the virgin curve, occur in these compounds.
+Temperature and time dependences of magnetization show that the compounds
+possess glassy behavior at low temperatures. Multi-step magnetization behavior,
+unusual relaxation effect, thermal and magnetic history dependence, which are
+signatures of the martensitic scenario due to the strong magneto-structural
+coupling, are found to be present in this system. We also show that one can
+induce the magnetization steps with the help of appropriate measurement
+protocol. Detailed magnetization relaxation studies have been carried out to
+understand the dynamics of magnetic phase transition.",1005.3931v1
+2010-10-13,Paramagnetic Leidenfrost Drops,"We present a fluid dynamics video showing the behavior of drops of liquid
+oxygen, at room temperature. Due to their low boiling point, these drops
+levitate on a cushion of their own vapour. This property gives them a high
+mobility, as known more generally in such Leidenfrost situations. But liquid
+oxygen is also paramagnetic, and thus likely to be manipulated using a magnet.
+It is first shown that the shape of the drop can be modified by changing the
+drop/magnet distance; approaching the magnet acts as reinforcing gravity, so
+that the drops get flattened by this action. The transformation is of course
+reversible: as the magnet is withdrawn, the liquid recovers its quasi-spherical
+shape. Magnets can also be used to trap the oxygen drops. As they pass above a
+magnet, they slow down significantly, a consequence of their deformation:
+despite a very low friction, the vibrations induced by the drop deformations
+represent an important source of dissipation: below a well-defined velocity,
+drops can even be stopped in the magnetic trap. Quicker ones can be decelerated
+and then captured by series of magnets. Oberving the same events from the top
+reveals the complex shapes adopted by the liquid as it crosses the traps.",1010.2611v1
+2011-10-05,Self-organizing magnetic beads for biomedical applications,"In the field of biomedicine magnetic beads are used for drug delivery and to
+treat hyperthermia. Here we propose to use self-organized bead structures to
+isolate circulating tumor cells using lab-on-chip technologies. Typically blood
+flows past microposts functionalized with antibodies for circulating tumor
+cells. Creating these microposts with interacting magnetic beads makes it
+possible to tune the geometry in size, position and shape. We developed a
+simulation tool that combines micromagnetics and discrete particle dynamics, in
+order to design micropost arrays made of interacting beads. The simulation
+takes into account the viscous drag of the blood flow, magnetostatic
+interactions between the magnetic beads and gradient forces from external
+aligned magnets. We developed a particle-particle particle-mesh method for
+effective computation of the magnetic force and torque acting on the particles.",1110.0983v1
+2012-01-18,Dynamics of Current Induced Magnetic Superstructures in Exchange-Spring Devices,"Thermoelectric manipulation of the magnetization of a magnetic layered stack
+in which a low-Curie temperature magnet is sandwiched between two strong
+magnets (exchange spring device) is considered. Controllable Joule heating
+produced by a current flowing in the plane of the magnetic stack (CIP
+configuration) induces a spatial magnetic and thermal structure along the
+current flow --- a magneto-thermal-electric domain (soliton). We show that such
+a structure can experience oscillatory in time dynamics if the magnetic stack
+is incorporated into an electric circuit in series with an inductor. The
+excitation of these magneto-thermionic oscillations follow the scenario either
+of ""soft"" of ""hard"" instability: in the latter case oscillations arise if the
+initial perturbation is large enough. The frequency of the temporal
+oscillations is of the order of $10^5 \div 10^7 s^{-1}$ for current densities
+$j\sim 10^6 \div 10^7 A/cm^3$.",1201.3854v1
+2012-08-30,Heavy and Light Monopoles in Magnetic Reversion in Artificial Spin Ice,"This work makes a theoretical study of the dynamics of emergent elemental
+excitations in artificial spin ice systems with hexagonal geometry during the
+magnetic reversion of the system. The magnetic and physical parameters of the
+nanoislands that form the array are considered as variables in the study. The
+parameters considered are: the energy barrier for the inversion of each
+nanoisland, the magnetic moment of the nanomagnets and the possible disorder in
+the sample. Our results show that the reversion dynamic presents two distinct
+mechanisms of magnetic reversion, with different elemental excitations for each
+mechanism. The first mechanism presents a reversion with the appearance of
+magnetic monopoles that do not move in the samples (heavy monopoles) and the
+absence of Dirac chains. In the other mechanism elemental magnetic excitations
+(light monopoles) appear that move great distances in the sample, giving rise
+to extensive Dirac chains during the magnetic reversion.",1208.6284v1
+2012-11-06,"Spin dynamics of hard-soft magnetic multi-layer systems: Effect of Exchange, Dipolar and Dzyaloshinski-Moriya interactions","We investigate the effect of coupling (intensity and nature), applied field,
+and anisotropy on the spin dynamics of a multi-layer system composed of a hard
+magnetic slab coupled to a soft magnetic slab through a nonmagnetic spacer. The
+soft slab is modeled as a stack of several atomic layers while the hard layer,
+of a different material, is either considered as a pinned macroscopic magnetic
+moment or as an atomic multi-layer system. We compute the magnetization profile
+and hysteresis loop of the multi-layer system by solving the Landau-Lifshitz
+equations for the net magnetic moment of each (atomic) layer. We study the
+competition between the intra-layer anisotropy and exchange interaction,
+applied magnetic field, and the inter-slab exchange, dipolar or
+Dzyaloshinski-Moriya interaction. Comparing the effects on the magnetization
+profile of the three couplings shows that despite the strong effect of the
+exchange coupling, the dipolar and Dzyaloshinski-Moriya interactions induce a
+slight (but non negligible) deviation in either the polar or azimuthal
+direction thus providing more degrees of freedom for adjusting the spin
+configuration in the multi-layer system.",1211.1217v1
+2013-07-29,Energy transfers and magnetic energy growth in small-scale dynamo,"In this letter we investigate the dynamics of magnetic energy growth in
+small-scale dynamo by studying energy transfers, mainly energy fluxes and
+shell-to-shell energy transfers. We perform dynamo simulations for magnetic
+Prandtl number $\mathrm{Pm}=20$ on $1024^3$ grid using pseudospectral method.
+We demonstrate that the magnetic energy growth is caused by nonlocal energy
+transfers from the large-scale or forcing-scale velocity field to small-scale
+magnetic field. The peak of these energy transfers move towards lower
+wavenumbers as dynamo evolves, which is the reason why the integral scale of
+the magnetic field increases with time. The energy transfers $U2U$ (velocity to
+velocity) and $B2B$ (magnetic to magnetic) are forward and local.",1307.7465v3
+2013-08-28,The chiral magnetic nanomotors,"Propulsion of the chiral magnetic nanomotors powered by a rotating magnetic
+field is in the focus of the modern biomedical applications. This technology
+relies on strong interaction of dynamic and magnetic degrees of freedom of the
+system. Here we study in detail various experimentally observed regimes of the
+helical nanomotor orientation and propulsion depending on the actuation
+frequency, and establish the relation of these two properties with remanent
+magnetization and geometry of the helical nanomotors. The theoretical
+predictions for the transition between the regimes and nanomotor orientation
+and propulsion speed are in excellent agreement with available experimental
+data. The proposed theory offers a few simple guidelines towards the optimal
+design of the magnetic nanomotors. In particular, efficient nanomotors should
+be fabricated of hard magnetics, e.g., cobalt, magnetized transversally and
+have the geometry of a normal helix with a helical angle of 35-45 degrees.",1308.6115v1
+2014-12-23,Current-induced spin torque resonance of a magnetic insulator,"Pure spin currents transport angular momentum without an associated charge
+flow. This unique property makes them attractive for spintronics applications,
+such as torque induced magnetization control in nanodevices that can be used
+for sensing, data storage, interconnects and logics. Up to now, however, most
+spin transfer torque studies focused on metallic ferromagnets, while magnetic
+insulators were largely ignored, in spite of superior magnetic quality factors.
+Here, we report the observation of spin torque-induced magnetization dynamics
+in a magnetic insulator. Our experiments show that in ultrathin magnetic
+insulators the spin torque induced magnetization dynamics can be substantially
+larger than those generated by the Oersted field. This opens new perspectives
+for the efficient integration of ferro-, ferri-, and antiferromagnetic
+insulators into electronic devices.",1412.7460v1
+2016-02-24,Synchrotron Magnetic Fields from Rayleigh-Taylor Instability in Supernovae,"Synchrotron emission from a supernova necessitates a magnetic field, but it
+is unknown how strong the relevant magnetic fields are, and what mechanism
+generates them. In this study, we perform high-resolution numerical gas
+dynamics calculations to determine the growth of turbulence due to
+Rayleigh-Taylor instability, and the resulting kinetic energy in turbulent
+fluctuations, to infer the strength of magnetic fields amplified by this
+turbulence. We find that Rayleigh-Taylor instability can produce turbulent
+fluctuations strong enough to amplify magnetic fields to a few percent of
+equipartition with the thermal energy. This turbulence stays concentrated near
+the reverse shock, but averaging this magnetic energy throughout the shocked
+region (weighting by emissivity) sets the magnetic fields at a minimum of 0.3
+percent of equipartition. This suggests a minimum effective magnetic field
+strength ($\epsilon_B > 0.003$) which should be present in all interacting
+supernovae.",1602.07692v1
+2016-02-25,Dependence of stellar magnetic activity cycles on rotational period in nonlinear solar-type dynamo,"We study turbulent generation of large-scale magnetic fields using nonlinear
+dynamo models for solar-type stars in the range of rotational periods from 14
+to 30 days. Our models take into account non-linear effects of dynamical
+quenching of magnetic helicity, and escape of magnetic field from the dynamo
+region due to magnetic buoyancy. The results show that the observed correlation
+between the period of rotation and the duration of activity cycles can be
+explained in the framework of a distributed dynamo model with a dynamical
+magnetic feedback acting on the turbulent generation either from magnetic
+buoyancy or magnetic helicity. We discuss implications of our findings for the
+understanding of dynamo processes operating in solar-like stars.",1602.07815v1
+2016-04-12,Voltage-driven magnetization switching and spin pumping in Weyl semimetals,"We demonstrate electrical magnetization switching and spin pumping in
+magnetically doped Weyl semimetals. The Weyl semimetal is a new class of
+topological semimetals, known to have nontrivial coupling between the charge
+and the magnetization due to the chiral anomaly. By solving the
+Landau-Lifshitz-Gilbert equation for a multilayer structure of a Weyl
+semimetal, an insulator and a metal whilst taking the charge-magnetization
+coupling into account, magnetization dynamics is analyzed. It is shown that the
+magnetization dynamics can be driven by the electric voltage. Consequently,
+switching of the magnetization with a pulsed electric voltage can be achieved,
+as well as precession motion with an applied oscillating electric voltage. The
+effect requires only a short voltage pulse and may therefore be more
+energetically efficient for us in spintronics devices compared to conventional
+spin transfer torque switching.",1604.03326v1
+2016-08-02,Effect of temperature and magnetic field on two-flavor superconducting quark matter,"We investigate the effect of turning on temperature for the charge neutral
+phase of two-flavor color superconducting (2SC) dense quark matter in presence
+of constant external magnetic field. Within the Nambu-Jona-Lasinio model, by
+tuning the diquark coupling strength, we study the interdependent evolution of
+the quark Bardeen-Cooper-Schrieffer gap and dynamical mass as functions of
+temperature and magnetic field. We find that magnetic field $B \gtrsim 0.02$
+GeV$^2$ ($10^{18}$ G) leads to anomalous temperature behavior of the gap in the
+gapless 2SC phase (moderately strong coupling), reminiscent of previous results
+in the literature found in the limit of weak coupling without magnetic field.
+The 2SC gap in the strong coupling regime is abruptly quenched at ultrahigh
+magnetic field due to the mismatched Fermi surfaces of up and down quarks
+imposed by charge neutrality and oscillation of the gap due to Landau level
+quantization. The dynamical quark mass also displays strong oscillation and
+magnetic catalysis at high magnetic field, although the latter effect is
+tempered by nonzero temperature. We discuss the implications for newly born
+compact stars with superconducting quark cores.",1608.00882v2
+2016-10-21,Spin-torque switching in large size nano-magnet with perpendicular magnetic fields,"DC current induced magnetization reversal and magnetization oscillation was
+observed in 500 nm large size Co90Fe10/Cu/Ni80Fe20 pillars. A perpendicular
+external field enhanced the coercive field separation between the reference
+layer (Co90Fe10) and free layer (Ni80Fe20) in the pseudo spin valve, allowing a
+large window of external magnetic field for exploring the free-layer reversal.
+The magnetization precession was manifested in terms of the multiple peaks on
+the differential resistance curves. Depending on the bias current and applied
+field, the regions of magnetic switching and magnetization precession on a
+dynamical stability diagram has been discussed in details. Micromagnetic
+simulations are shown to be in good agreement with experimental results and
+provide insight for synchronization of inhomogenieties in large sized device.
+The ability to manipulate spin-dynamics on large size devices could prove
+useful for increasing the output power of the spin-transfer nano-oscillators
+(STNOs).",1610.06959v1
+2016-12-20,Nanosecond magnetization dynamics during spin Hall switching of in-plane magnetic tunnel junctions,"We present a study of the magnetic dynamics associated with nanosecond scale
+magnetic switching driven by the spin Hall effect in 3-terminal nanoscale
+magnetic tunnel junctions (3T-MTJs) with in-plane magnetization. Utilizing fast
+pulse measurements in a variety of material stacks and detailed micromagnetic
+simulations, we demonstrate that this unexpectedly fast and reliable magnetic
+reversal is facilitated by the self-generated Oersted field, and the
+short-pulse energy efficiency can be substantially enhanced by micromagnetic
+curvature in the magnetic free layer. The sign of the Oersted field is
+essential for this enhancement --- in simulations in which we artificially
+impose a field-like torque with a sign opposite to the effect of the Oersted
+field, the result is a much slower and stochastic switching process that is
+reminiscent of the so-called incubation delay in conventional 2-terminal
+spin-torque-switched MTJs.",1612.06463v3
+2017-01-07,Dynamics of exciton magnetic polarons in CdMnSe/CdMgSe quantum wells: the effect of self-localization,"We study the exciton magnetic polaron (EMP) formation in (Cd,Mn)Se/(Cd,Mg)Se
+diluted-magnetic-semiconductor quantum wells using time-resolved
+photoluminescence (PL). The magnetic field and temperature dependencies of this
+dynamics allow us to separate the non-magnetic and magnetic contributions to
+the exciton localization. We deduce the EMP energy of 14 meV, which is in
+agreement with time-integrated measurements based on selective excitation and
+the magnetic field dependence of the PL circular polarization degree. The
+polaron formation time of 500 ps is significantly longer than the corresponding
+values reported earlier. We propose that this behavior is related to strong
+self-localization of the EMP, accompanied with a squeezing of the heavy-hole
+envelope wavefunction. This conclusion is also supported by the decrease of the
+exciton lifetime from 600 ps to 200 - 400 ps with increasing magnetic field and
+temperature.",1701.01824v1
+2017-07-24,Magnetic order and spin dynamics in the helical magnetic system Fe$_3$PO$_4$O$_3$,"The 3$d$-electronic spin dynamics and the magnetic order in Fe$_3$PO$_4$O$_3$
+were investigated by muon spin rotation and relaxation ($\mu$SR) and $^{57}$Fe
+M\""ossbauer spectroscopy. Zero-field (ZF)-$\mu$SR and $^{57}$Fe M\""ossbauer
+studies confirm static long range magnetic ordering below $T_{\mathrm{N}}$
+$\approx$ 164\,K. Both transverse-field (TF) and ZF-$\mu$SR results evidence
+100\% magnetic volume fraction in the ordered state. The ZF-$\mu$SR time
+spectra can be best described by a Bessel function, which is consistent with
+the helical magnetic structure proposed by neutron scattering experiments. The
+M\""ossbauer spectra are described in detail by considering the specific angular
+distribution of the local hyperfine field $B_{\mathrm{hyp}}$ with respect to
+the local electric field gradient. The $\mu$SR spin-lattice relaxation rate
+exhibits two peaks: One at the magnetic ordering temperature related to
+critical magnetic fluctuations and another peak at 35\,K signaling the presence
+of a secondary low energy scale in Fe$_3$PO$_4$O$_3$.",1707.07433v1
+2018-02-19,Static properties and current-induced dynamics of pinned $90$ degree magnetic domain walls under applied fields: an analytic approach,"Magnetic domain walls are pinned strongly by abrupt changes in magnetic
+anisotropy. When driven into oscillation by a spin-polarized current, locally
+pinned domain walls can be exploited as tunable sources of short-wavelength
+spin waves. Here, we develop an analytical framework and discrete Heisenberg
+model to describe the static and dynamic properties of pinned domain walls with
+a head-to-tail magnetic structure. We focus on magnetic domain walls that are
+pinned by 90$^\circ$ rotations of uniaxial magnetic anisotropy. Our model
+captures the domain wall response to a spin-transfer torque that is exerted by
+an electric current. Model predictions of the domain wall resonance frequency
+and its evolution with magnetic anisotropy strength and external magnetic field
+are compared to micromagnetic simulations.",1802.06741v3
+2019-02-20,Interplay of magnetization dynamics with microwave waveguide at cryogenic temperatures,"In this work, magnetization dynamics is studied at low temperatures in a
+hybrid system that consists of thin epitaxial magnetic film coupled with
+superconducting planar microwave waveguide. The resonance spectrum was observed
+in a wide magnetic field range, including low fields below the saturation
+magnetization and both polarities. Analysis of the spectrum via a developed
+fitting routine allowed to derive all magnetic parameters of the film at
+cryogenic temperatures, to detect waveguide-induced uniaxial magnetic
+anisotropies of the first and the second order, and to uncover a minor
+misalignment of magnetic field. A substantial influence of the superconducting
+critical state on resonance spectrum is observed and discussed.",1902.07566v2
+2020-02-14,Wide-field dynamic magnetic microscopy using double-double quantum driving of a diamond defect ensemble,"Wide-field magnetometry can be realized by imaging the optically-detected
+magnetic resonance of diamond nitrogen vacancy (NV) center ensembles. However,
+NV ensemble inhomogeneities significantly limit the magnetic-field sensitivity
+of these measurements. We demonstrate a double-double quantum (DDQ) driving
+technique to facilitate wide-field magnetic imaging of dynamic magnetic fields
+at a micron scale. DDQ imaging employs four-tone radio frequency pulses to
+suppress inhomogeneity-induced variations of the NV resonant response. As a
+proof-of-principle, we use the DDQ technique to image the dc magnetic field
+produced by individual magnetic-nanoparticles tethered by single DNA molecules
+to a diamond sensor surface. This demonstrates the efficacy of the diamond NV
+ensemble system in high-frame-rate magnetic microscopy, as well as
+single-molecule biophysics applications.",2002.06237v3
+2020-06-18,Large Surface Magnetization in Noncentrosymmetric Antiferromagnets,"Thin-film antiferromagnets (AFs) with Rashba spin-orbit coupling are
+theoretically investigated. We demonstrate that the relativistic
+Dzyaloshinskii-Moriya interaction (DMI) produces a large surface magnetization
+and a boundary-driven twist state in the antiferromagnetic N\' eel vector. We
+predict a magnetization on the order of $2.3\cdot 10^4$~A/m, which is
+comparable to the magnetization of ferromagnetic semiconductors. Importantly,
+the magnetization is characterized by ultra-fast terahertz dynamics and
+provides new approaches for efficiently probing and controlling the spin
+dynamics of AFs as well as detecting the antiferromagnetic DMI. Notably, the
+magnetization does not lead to any stray magnetic fields except at corners
+where weak magnetic monopole fields appear.",2006.10435v2
+2020-09-09,Micromagnetic instabilities in spin-transfer switching of perpendicular magnetic tunnel junctions,"Micromagnetic instabilities and non-uniform magnetization states play a
+significant role in spin transfer induced switching of nanometer scale magnetic
+elements. Here we model domain wall mediated switching dynamics in
+perpendicularly magnetized magnetic tunnel junction nanopillars. We show that
+domain wall surface tension always leads to magnetization oscillations and
+instabilities associated with the disk shape of the junction. A collective
+coordinate model is developed that captures aspects of these instabilities and
+illustrates their physical origin. Model results are compared to those of
+micromagnetic simulations. The switching dynamics is found to be very sensitive
+to the domain wall position and phase, which characterizes the angle of the
+magnetization in the disk plane. This sensitivity is reduced in the presence of
+spin torques and the spin current needed to displace a domain wall can be far
+less than the threshold current for switching from a uniformly magnetized
+state. A prediction of this model is conductance oscillations of increasing
+frequency during the switching process.",2009.04376v1
+2021-07-26,Sub-second Temporal Magnetic Field Microscopy Using Quantum Defects in Diamond,"Wide field-of-view magnetic field microscopy has been realised by probing
+shifts in optically detected magnetic resonance (ODMR) spectrum of Nitrogen
+Vacancy (NV) defect centers in diamond. However, these widefield diamond NV
+magnetometers require few to several minutes of acquisition to get a single
+magnetic field image, rendering the technique temporally static in it's current
+form. This limitation prevents application of diamond NV magnetometers to novel
+imaging of dynamically varying microscale magnetic field processes. Here, we
+show that the magnetic field imaging frame rate can be significantly enhanced
+by performing lock-in detection of NV photo-luminescence (PL), simultaneously
+over multiple pixels of a lock-in camera. A detailed protocol for
+synchronization of frequency modulated PL of NV centers with fast camera frame
+demodulation, at few kilohertz frequencies, has been experimentally
+demonstrated. This experimental technique allows magnetic field imaging of
+sub-second varying microscale currents in planar microcoils with imaging frame
+rates in the range of 50 to 200 frames per second (fps). Our work demonstrates
+that widefield per-pixel lock-in detection of frequency modulated NV ODMR
+enables dynamic magnetic field microscopy.",2107.12232v2
+2023-09-06,Magnetic curvature and existence of closed magnetic geodesics on low energy levels,"To a Riemannian manifold ${(M, g)}$ endowed with a magnetic form ${\sigma}$
+and its Lorentz operator ${\Omega}$ we associate an operator ${M^{\Omega}}$,
+called the magnetic curvature operator. Such an operator encloses the classical
+Riemannian curvature of the metric ${g}$ together with terms of perturbation
+due to the magnetic interaction of ${\sigma}$. From ${M^{\Omega}}$ we derive
+the magnetic sectional curvature ${\mathrm{Sec}^{\Omega}}$ and the magnetic
+Ricci curvature ${\mathrm{Ric}^{\Omega}}$. On closed manifolds, with a
+Bonnet-Myers argument, we show that if ${\mathrm{Ric}^{\Omega}}$ is positive on
+an energy level below the critical value then, on that energy level, the
+magnetic dynamics carries a contractible periodic orbit. In particular, when
+${\sigma}$ is nowhere vanishing, this implies the existence of contractible
+periodic orbits on every energy level close to zero. Finally, on closed
+oriented even dimensional manifolds, we discuss about the topological
+restrictions which appear when one requires ${\mathrm{Sec}^{\Omega}}$ to be
+positive.",2309.03159v1
+2024-02-06,Field-dependent magnetic relaxation times of magnetic nanoparticle systems: analytic approximations supported by numerical simulations,"Many estimates for the magnetic relaxation time of magnetic nanoparticle
+systems neglect the effect of the applied field strength. This is despite many
+applications of magnetic nanoparticles involving relaxation dynamics under the
+influence of applied fields. Here, an analytic approximation for the
+field-dependent Brownian relaxation time of single-domain, spherical magnetic
+nanoparticles in an external applied field is developed mathematically. This
+expression is validated by comparison with existing empirically-derived
+expressions and by comparison to particle-level simulations that allow particle
+rotations. Our approximation works particularly well for larger particles. We
+then use the developed expression to analytically calculate the total magnetic
+relaxation time when both Brownian and N\'eel relaxation mechanisms are at
+play. Again, we show that the results match those found using particle-level
+simulations, this time with both particle rotations and internal magnetization
+dynamics allowed. However, for some particle parameters and for large field
+strengths, our simulations reveal that the Brownian and N\'eel relaxation
+mechanisms are decoupled and it is not appropriate to combine these to
+calculate a total relaxation time.",2402.04427v1
+2003-11-22,Influence of a Uniform Current on Collective Magnetization Dynamics in a Ferromagnetic Metal,"We discuss the influence of a uniform current, $\vec{j} $, on the
+magnetization dynamics of a ferromagnetic metal. We find that the magnon energy
+$\epsilon(\vec{q})$ has a current-induced contribution proportional to
+$\vec{q}\cdot \vec{\cal J}$, where $\vec{\cal J}$ is the spin-current, and
+predict that collective dynamics will be more strongly damped at finite ${\vec
+j}$. We obtain similar results for models with and without local moment
+participation in the magnetic order. For transition metal ferromagnets, we
+estimate that the uniform magnetic state will be destabilized for $j \gtrsim
+10^{9} {\rm A} {\rm cm}^{-2}$. We discuss the relationship of this effect to
+the spin-torque effects that alter magnetization dynamics in inhomogeneous
+magnetic systems.",0311522v1
+2006-01-10,Engineering of spin-lattice relaxation dynamics by digital growth of diluted magnetic semiconductor CdMnTe,"The technological concept of ""digital alloying"" offered by molecular-beam
+epitaxy is demonstrated to be a very effective tool for tailoring static and
+dynamic magnetic properties of diluted magnetic semiconductors. Compared to
+common ""disordered alloys"" with the same Mn concentration, the spin-lattice
+relaxation dynamics of magnetic Mn ions has been accelerated by an order of
+magnitude in (Cd,Mn)Te digital alloys, without any noticeable change in the
+giant Zeeman spin splitting of excitonic states, i.e. without effect on the
+static magnetization. The strong sensitivity of the magnetization dynamics to
+clustering of the Mn ions opens a new degree of freedom for spin engineering.",0601194v1
+2007-12-04,Microwave excitations associated with a wavy angular dependence of the spin transfer torque : model and experiments,"The spin transfer torque (STT) can lead to steady precession of magnetization
+without any external applied field in magnetic spin valve where the magnetic
+layer have very different spin diffusion length. This effect is associated with
+an unusual angular dependence of the STT, called ""wavy"" (WAD-STT), predicted in
+the frame of diffusive models of spin transfer. In this article, we present a
+complete experimental characterization of the magnetization dynamics in the
+presence of a WAD-STT. The results are compared to the prediction of the
+magnetization dynamics obtained by single domain magnetic simulations
+(macrospin approximation). The macrospin simulations well reproduced the main
+static and dynamical experimental features (phase diagram, R(I) curves,
+dependence of frequency with current and field) and suggest that the dynamical
+excitations observed experimentally are associated with a large angle
+out-of-plane precession mode. The present work validates the diffusive models
+of the spin transfer and underlines the role of the spin accumulation and the
+spin relaxation effects on the STT.",0712.0548v1
+2008-07-29,Spin-Torque-Induced Rotational Dynamics of a Magnetic Vortex Dipole,"We study, both experimentally and by numerical modeling, the magnetic
+dynamics that can be excited in a magnetic thin-film nanopillar device using
+the spin torque from a spatially localized current injected via a
+10s-of-nm-diameter aperture. The current-driven magnetic dynamics can produce
+large amplitude microwave emission at zero magnetic field, with a frequency
+well below that of the uniform ferromagnetic resonance mode. Micromagnetic
+simulations indicate that the physical origin of this efficient microwave
+nano-oscillator is the nucleation and subsequent steady-state rotational
+dynamics of a magnetic vortex dipole driven by the localized spin torque. These
+results show this novel implementation of a spintronic nano-oscillator is a
+promising candidate for microwave technology applications.",0807.4660v2
+2008-10-14,Theoretical study of the magnetization dynamics of non-dilute ferrofluids,"The paper is devoted to the theoretical investigation of the magnetodipolar
+interparticle interaction effect on remagnetization dynamics in moderately
+concentrated ferrofluids. We consider a homogeneous (without particle
+aggregates) ferrofluid consisting of identical spherical particles and employ a
+rigid dipole model, where magnetic moment of a particle is fixed with respect
+to the particle itself. In particular, for the magnetization relaxation after
+the external field is instantly switched off, we show that the magnetodipolar
+interaction leads to the increase of the initial magnetization relaxation time.
+For the complex ac-susceptibility we find that the this interaction leads to an
+overall increase of the imaginary susceptibility part and shifts the peak on
+its frequency dependence towards lower frequencies. Comparing results obtained
+with our analytical approach (second order virial expansion) to numerical
+simulation data (Langevin dynamics method), we demonstrate that the employed
+virial expansion approximation gives a good qualitative description of the
+ferrofluid magnetization dynamics and provides a satisfactory quantitative
+agreement with numerical simulations for the dc magnetization relaxation - up
+to the particle volume fraction c ~ 10% and for the ac-susceptibility - up to c
+~ 5 %.",0810.2421v1
+2009-04-18,Brownian Dynamics of charged particles in a constant magnetic field,"Numerical algorithms are proposed for simulating the Brownian dynamics of
+charged particles in an external magnetic field, taking into account the
+Brownian motion of charged particles, damping effect and the effect of magnetic
+field self-consistently. Performance of these algorithms is tested in terms of
+their accuracy and long-time stability by using a three-dimensional Brownian
+oscillator model with constant magnetic field. Step-by-step recipes for
+implementing these algorithms are given in detail. It is expected that these
+algorithms can be directly used to study particle dynamics in various dispersed
+systems in the presence of a magnetic field, including polymer solutions,
+colloidal suspensions and, particularly complex (dusty) plasmas. The proposed
+algorithms can also be used as thermostat in the usual molecular dynamics
+simulation in the presence of magnetic field.",0904.2849v1
+2010-05-26,Spin diffusion in the Mn2+ ion system of II-VI diluted magnetic semiconductor heterostructures,"The magnetization dynamics in diluted magnetic semiconductor heterostructures
+based on (Zn,Mn)Se and (Cd,Mn)Te has been studied experimentally by optical
+methods and simulated numerically. In the samples with nonhomogeneous magnetic
+ion distribution this dynamics is contributed by spin-lattice relaxation and
+spin diffusion in the Mn spin system. The spin diffusion coefficient of
+7x10^(-8) cm^2/s has been evaluated for Zn(0.99)Mn(0.01)Se from comparison of
+experimental and numerical results. Calculations of the giant Zeeman splitting
+of the exciton states and the magnetization dynamics in the ordered alloys and
+parabolic quantum wells fabricated by the digital growth technique show perfect
+agreement with the experimental data. In both structure types the spin
+diffusion has an essential contribution to the magnetization dynamics.",1005.4862v1
+2012-03-29,Influence of a uniform magnetic field on dynamical chiral symmetry breaking in QED$_3$,"We study dynamical chiral symmetry breaking (DCSB) in an effective QED$_{3}$
+theory of d-wave high temperature cuprate superconductors under a uniform
+magnetic field. At zero temperature, the external magnetic field induces a
+mixed state by generating vortices in the condensate of charged holons. The
+growing magnetic field suppresses the superfluid density and thus reduces the
+gauge field mass which is opened via the Anderson-Higgs mechanism. By
+numerically solving the Dyson-Schwinger gap equation, we show that the massless
+fermions acquires a dynamical gap through DCSB mechanism when the magnetic
+field strength $H$ is above a critical value $H_{c}$ and the fermion flavors
+$N$ is below a critical value $N_{c}$. Further, it is found that both $N_{c}$
+and the dynamical fermion gap increase as the magnetic field $H$ grows. It is
+expected that our result can be tested in phenomena in high temperature cuprate
+superconductors.",1203.6423v1
+2013-04-22,Vortex dynamics and second magnetization peak in PrFeAsO$_{0.60}$F$_{0.12}$ superconductor,"We have studied the vortex dynamics in the PrFeAsO$_{0.60}$F$_{0.12}$
+superconducting sample by dc magnetization and dynamic magnetization-relaxation
+rate $(Q)$ measurements. The field dependence of the superconducting
+irreversible magnetization $M_s$ reveals a second magnetization peak or
+fishtail effect. The large value of $Q$ is an indication of moderate vortex
+motion and relatively weak pinning energy. Data analysis based on the
+generalized inversion scheme suggests that the vortex dynamics can be described
+by the collective pinning model. The temperature dependence of the critical
+current is consistent with the pinning due to the spatial variation in the mean
+free path near a lattice defect ($\delta l$ pinning). The temperature and field
+dependence of $Q$ indicates a crossover from elastic to plastic vortex creep
+with increasing temperature and magnetic field. Finally, we have constructed
+the vortex phase diagram based on the present data.",1304.5978v1
+2014-01-07,$α-γ$ transition in cerium: magnetic form factor and dynamic magnetic susceptibility in dynamical mean-field theory,"The nature of the elemental cerium phases, undergoing an isostructural volume
+collapse transition, cannot be understood using conventional solid state
+concepts. Using the combination of density functional theory and dynamical
+mean-field theory, we study the magnetic properties of both the $\alpha$ and
+the $\gamma$ phases. We compute the magnetic form factor, and show that it is
+very close to free ion behavior in both the local moment $\gamma$ phase as well
+as the more itinerant $\alpha$ phase, in agreement with neutron scattering
+experiments. In sharp contrast, the dynamic local magnetic susceptibility of
+the two phases is strikingly different. In the $\gamma$ phase, the sharp low
+energy peak due to local moment formation and consequently low Kondo
+temperature dominates the spectra. In the $\alpha$ phase two broad peaks can be
+identified, the first is due to Kondo screening, and the second is due to
+Hund's coupling. This shows that hybridization plays a central role in the
+$\alpha-\gamma$ transition in cerium, and that from the point of view of
+magnetic properties, the $4f$ electrons are strongly correlated in both phases.",1401.1245v1
+2014-02-26,Improved Domain Wall Dynamics and Magnonic Torques using Topological Insulators,"We investigate the magnetization dynamics that arise when a thin-film
+ferromagnet is deposited on a topological insulator (TI), focusing in
+particular on domain-wall motion via current and the possibility of a spin-wave
+torque acting on the magnetization. We show analytically that the coupling
+between the magnetic domain wall and the TI removes the degeneracy of the wall
+profile with respect to its chirality and topological charge. Moreover, we find
+that the threshold for Walker breakdown of domain wall motion is substantially
+increased and determined by the interaction with the TI, allowing for higher
+attainable wall velocities than in the conventional case where the hard axis
+anisotropy determines the Walker threshold. Finally, we show that the allowed
+modes of spin-wave excitations and the ensuing magnetization dynamics in the
+presence of a TI coupling enable a magnonic torque acting even on homogeneous
+magnetization textures. Our results indicate that the TI-ferromagnet
+interaction has a similar effect on the magnetization dynamics as an intrinsic
+Dzyaloshinskii-Moriya interaction in ferromagnets.",1402.6701v2
+2014-06-26,Tunable dynamic response of magnetic gels: impact of structural properties and magnetic fields,"Ferrogels and magnetic elastomers feature mechanical properties that can be
+reversibly tuned from outside through magnetic fields. Here we concentrate on
+the question how their dynamic response can be adjusted. The influence of three
+factors on the dynamic behavior is demonstrated using appropriate minimal
+models: first, the orientational memory imprinted into one class of the
+materials during their synthesis; second, the structural arrangement of the
+magnetic particles in the materials; and third, the strength of an external
+magnetic field. To illustrate the latter point, structural data are extracted
+from a real experimental sample and analyzed. Understanding how internal
+structural properties and external influences impact the dominant dynamical
+properties helps to design materials that optimize the requested behavior.",1406.6979v2
+2015-10-07,Spin dynamics in paramagnetic diluted magnetic semiconductors,"Microscopic properties of low-energy spin dynamics in diluted magnetic
+semiconductor are addressed in a framework of the Kondo lattice model including
+random distribution of magnetic dopants. Based on the fluctuation-dissipation
+theorem, we derive an explicit dependence of the spin diffusion coefficient on
+the single-particle Green function which is directly evaluated by dynamical
+mean-field theory. In the paramagnetic state, the magnetic scattering has been
+manifested to suppress spin diffusion. In agreement with other ferromagnet
+systems, we also point out that the spin diffusion in diluted magnetic
+semiconductors at small carrier concentration displays a monotonic $1/T$-like
+temperature dependence. By investigating the spin diffusion coefficient on a
+wide range of the model parameters, the obtained results have provided a
+significant scenario to understand the spin dynamics in the paramagnetic
+diluted magnetic semiconductors.",1510.01807v1
+2016-12-13,Dynamics in quantum Ising chain driven by inhomogeneous transverse magnetization,"We study the dynamics caused by transport of transverse magnetization in one
+dimensional transverse Ising chain at zero temperature. We observe that a class
+of initial states having product structure in fermionic momentum-space and
+satisfying certain criteria, produce spatial variation in transverse
+magnetization. Starting from such a state, we obtain the transverse
+magnetization analytically and then observe its dynamics in presence of a
+homogeneous constant field $\Gamma$. In contradiction with general expectation,
+whatever be the strength of the field, the magnetization of the system does not
+become homogeneous even after infinite time. At each site, the dynamics is
+associated with oscillations having two different timescales. The envelope of
+the larger timescale oscillation decays algebraically with an exponent which is
+invariant for all such special initial states. The frequency of this
+oscillation varies differently with external field in ordered and disordered
+phases. The local magnetization after infinite time also characterizes the
+quantum phase transition.",1612.04066v2
+2017-06-21,Uniform magnetization dynamics of a submicron ferromagnetic coin driven by the spin-orbit coupled spin torque,"A simple model of magnetization dynamics in a ferromagnet/doped semiconductor
+hybrid structure with Rashba spin-orbit interaction (SOI) driven by an applied
+pulse of the electric field is proposed. The electric current excited by the
+applied field is spin-polarized due to the SOI and therefore it induces the
+magnetization rotation in the ferromagnetic layer via s-d exchange coupling.
+Magnetization dynamics dependence on the electric pulse shape and magnitude is
+analyzed for realistic values of parameters. We show that it is similar to the
+dynamics of a damped nonlinear oscillator with the time-dependent frequency
+proportional to the square root of the applied electric field. The
+magnetization switching properties of an elliptic magnetic element are examined
+as a function of the applied field magnitude and direction.",1706.06909v1
+2017-09-29,Non-local Gilbert damping tensor within the torque-torque correlation model,"An essential property of magnetic devices is the relaxation rate in magnetic
+switching which depends strongly on the damping in the magnetisation dynamics.
+It was recently measured that damping depends on the magnetic texture and,
+consequently, is a non-local quantity. The damping enters the
+Landau-Lifshitz-Gilbert equation as the phenomenological Gilbert damping
+parameter $\alpha$, that does not, in a straight forward formulation, account
+for non-locality. Efforts were spent recently to obtain Gilbert damping from
+first principles for magnons of wave vector $\mathbf{q}$. However, to the best
+of our knowledge, there is no report about real space non-local Gilbert damping
+$\alpha_{ij}$. Here, a torque-torque correlation model based on a tight binding
+approach is applied to the bulk elemental itinerant magnets and it predicts
+significant off-site Gilbert damping contributions, that could be also
+negative. Supported by atomistic magnetisation dynamics simulations we reveal
+the importance of the non-local Gilbert damping in atomistic magnetisation
+dynamics. This study gives a deeper understanding of the dynamics of the
+magnetic moments and dissipation processes in real magnetic materials. Ways of
+manipulating non-local damping are explored, either by temperature, material's
+doping or strain.",1709.10365v1
+2017-10-09,Nanoscale mapping of ultrafast magnetization dynamics with femtosecond Lorentz microscopy,"Novel time-resolved imaging techniques for the investigation of ultrafast
+nanoscale magnetization dynamics are indispensable for further developments in
+light-controlled magnetism. Here, we introduce femtosecond Lorentz microscopy,
+achieving a spatial resolution below 100 nm and a temporal resolution of 700
+fs, which gives access to the transiently excited state of the spin system on
+femtosecond timescales and its subsequent relaxation dynamics. We demonstrate
+the capabilities of this technique by spatio-temporally mapping the
+light-induced demagnetization of a single magnetic vortex structure and
+quantitatively extracting the evolution of the magnetization field after
+optical excitation. Tunable electron imaging conditions allow for an
+optimization of spatial resolution or field sensitivity, enabling future
+investigations of ultrafast internal dynamics of magnetic topological defects
+on 10-nanometer length scales.",1710.03307v1
+2018-08-19,Fast spin dynamics in hexagonal arrays of Fe atoms on metallic surface,"Understanding the nature of magnetic interactions in ultra-small magnetic
+ensembles and their intrinsic properties is vital to uncover the dynamics
+therein. In this study we reveal the spin dynamics of hexagonally arranged Fe
+atoms on metallic surface that are triggered by magnetic pulse. The switching
+process among various spin configurations and their relative magnetic order is
+tuned by the amplitude and duration of the magnetic pulse. Even more we observe
+a parity effect in the switching time as the size of the cluster varies in
+which even number of Fe atoms shows faster dynamics. The changes in the
+multistable magnetic states and switching times are explained by using the
+relaxation of the exchange and anisotropy energies in time.",1808.06165v1
+2019-11-05,Numerical methods for antiferromagnetics,"Compared with ferromagnetic counterparts, antiferromagnetic materials are
+considered as the future of spintronic applications since these materials are
+robust against the magnetic perturbation, produce no stray field, and display
+ultrafast dynamics. There are (at least) two sets of magnetic moments in
+antiferromagnets (with magnetization of the same magnitude but antiparallel
+directions) and ferrimagnets (with magnetization of the different magnitude).
+The coupled dynamics for the bipartite collinear antiferromagnets is modeled by
+a coupled system of Landau-Lifshitz-Gilbert equations with an additional term
+originated from the antiferromagnetic exchange, which leads to femtosecond
+magnetization dynamics. In this paper, we develop three Gauss-Seidel projection
+methods for micromagnetics simulation in antiferromagnets and ferrimagnets.
+They are first-order accurate in time and second-order in space, and only solve
+linear systems of equations with constant coefficients at each step.
+Femtosecond dynamics, N\'{e}el wall structure, and phase transition in presence
+of an external magnetic field for antiferromagnets are provided with the
+femtosecond stepsize.",1911.01717v1
+2020-10-13,A simulation framework for particle magnetization dynamics of large ensembles of single domain particles: Numerical treatment of Brown/Néel dynamics and parameter identification problems in magnetic particle imaging,"Magnetic nanoparticles and their magnetization dynamics play an important
+role in many applications. We focus on magnetization dynamics in large
+ensembles of single domain nanoparticles being characterized by either Brownian
+or N\'{e}el rotation mechanisms. Simulations of the respective behavior are
+obtained by solving advection-diffusion equations on the sphere, for which a
+unified computational framework is developed and investigated. This builds the
+basis for solving two parameter identification problems, which are formulated
+in the context of the chosen application, magnetic particle imaging. The
+functionality of the computational framework is illustrated by numerical
+results in the parameter identification problems either compared quantitatively
+or qualitatively to measured data.",2010.07772v1
+2021-07-15,Wide-field magneto-optical microscope to access quantitative magnetization dynamics with femtosecond temporal and sub-micrometer spatial resolution,"We introduce a wide-field magneto-optical microscope to probe magnetization
+dynamics with femtosecond temporal and sub-micrometer spatial resolution. We
+carefully calibrate the non-linear dependency between the magnetization of the
+sample and the detected light intensity by determining the absolute values of
+the magneto-optical polarization rotation. With that, an analytical transfer
+function is defined to directly map the recorded intensity to the corresponding
+magnetization, which results in significantly reduced acquisition times and
+relaxed computational requirements. The performance of the instrument is
+characterized by probing the magnetic all-optical switching dynamics of GdFe in
+a pump-probe experiment. The high spatial resolution of the microscope allows
+for accurately subdividing the laser-excited area into different
+fluence-regions in order to capture the strongly non-linear magnetization
+dynamics as a function of the optical pump intensity in a single measurement.",2107.07375v2
+2021-08-13,Optical signatures of the coupled spin-mechanics of a levitated magnetic microparticle,"We propose a platform that combines the fields of cavity optomagnonics and
+levitated optomechanics in order to control and probe the coupled
+spin-mechanics of magnetic dielectric particles. We theoretically study the
+dynamics of a levitated Faraday-active dielectric microsphere serving as an
+optomagnonic cavity, placed in an external magnetic field and driven by an
+external laser. We find that the optically driven magnetization dynamics
+induces angular oscillations of the particle with low associated damping.
+Further, we show that the magnetization and angular motion dynamics can be
+probed via the power spectrum of the outgoing light. Namely, the characteristic
+frequencies attributed to the angular oscillations and the spin dynamics are
+imprinted in the light spectrum by two main resonance peaks. Additionally, we
+demonstrate that a ferromagnetic resonance setup with an oscillatory
+perpendicular magnetic field can enhance the resonance peak corresponding to
+the spin oscillations and induce fast rotations of the particle around its
+anisotropy axis.",2108.06214v1
+2021-11-29,Element selective ultrafast magnetization dynamics of hybrid Stoner-Heisenberg magnets,"Stoner and Heisenberg excitations in magnetic materials are inherently
+different. The former involves an effective reduction of the exchange
+splitting, whereas the latter comprises excitation of spin-waves. In this work,
+we test the impact of these two excitations in the hybrid Stoner-Heisenberg
+system FePd. We present a microscopic picture of ultrafast demagnetization
+dynamics in this alloy, which represents both components of strong local
+exchange splitting in Fe, and induced polarization in Pd. We identify
+spin-orbit coupling and optical inter-site spin transfer as the two dominant
+factors for demagnetization at ultrashort timescales. By tuning the external
+laser pulse, the extrinsic inter-site spin transfer can be manipulated for site
+selective demagnetization on femtosecond time scales providing the fastest way
+for optical and selective control of the magnetization dynamics in alloys.
+Remarkably, the drastic difference in origin of the magnetic moment of the Fe
+and Pd species is not deciding the initial magnetization dynamics in this
+alloy.",2111.14607v1
+2024-01-19,Analysis of the nonlinear dynamics of a single pendulum driven by a magnetic field using the magnetic charges interaction model and the experimentally fitted interaction model,"In this work, we analyzed theoretically and experimentally the nonlinear
+dynamics of a magnetic pendulum driven by a coil-magnet interaction. The force
+between the magnetic elements and the resulting torque on the pendulum are
+derived using both the magnetic charges interaction model and the
+experimentally fitted interaction model. This enables the comparison between
+the two models. The current in the coil is taken first as a sinusoidal current
+and then as a square current. The comparison of the structure of each
+interaction model is conducted and it appears that they give qualitatively
+similar characteristics. The harmonic balance method is used to approximate the
+frequency responses of the pendulum leading to both symmetric and asymmetric or
+one-side (intrawell) oscillations. The two-parameters bifurcation diagrams are
+plotted showing the different dynamical behaviors considering the current
+amplitude and frequency as the control parameters. Good agreements are found
+between our theoretical results and experimental ones.",2401.10957v1
+2024-02-16,Magneto-Permeability Effect in Ferrofluid Flow through Porous Media studied via Multiparticle Collision Dynamics,"As more and more promising applications of magnetic nanoparticles in
+complicated environments are explored, their flow properties in porous media
+are of increasing interest. We here propose a hybrid approach based on the
+Multiparticle Collision Dynamics Method extended to porous media via friction
+forces and coupled with Brownian Dynamics simulations of the rotational motion
+of magnetic nanoparticles' magnetic moment. We simulate flow in planar channels
+homogeneously filled with a porous medium and verify our implementation by
+reproducing the analytical velocity profile of the Darcy-Brinkman model in the
+non-magnetic case. In the presence of an externally applied magnetic field, the
+non-equilibrium magnetization and friction forces lead to field-dependent
+velocity profiles that result in effective, field-dependent permeabilities. We
+provide a theoretical expression for this magneto-permeability effect in
+analogy with the magneto-viscous effect. Finally, we study the flow through
+planar channels, where only the walls are covered with a porous medium. We find
+a smooth crossover from the Poiseuille profile in the center of the channel to
+the Brinkman-Darcy flow in the porous layers. We propose a simple estimate of
+the thickness of the porous layer based on the flow rate and maximum flow
+velocity.",2402.10799v1
+2015-01-29,Dynamical evolution of the chiral magnetic effect: Applications to the quark-gluon plasma,"We study the dynamical evolution of the so-called chiral magnetic effect in
+an electromagnetic conductor. To this end, we consider the coupled set of
+corresponding Maxwell and chiral anomaly equations, and we prove that these can
+be derived from chiral kinetic theory. After integrating the chiral anomaly
+equation over space in a closed volume, it leads to a quantum conservation law
+of the total helicity of the system. A change in the magnetic helicity density
+comes together with a modification of the chiral fermion density. We study in
+Fourier space the coupled set of anomalous equations and we obtain the
+dynamical evolution of the magnetic fields, magnetic helicity density, and
+chiral fermion imbalance. Depending on the initial conditions we observe how
+the helicity might be transferred from the fermions to the magnetic fields, or
+vice versa, and find that the rate of this transfer also depends on the scale
+of wavelengths of the gauge fields in consideration. We then focus our
+attention on the quark-gluon plasma phase, and analyze the dynamical evolution
+of the chiral magnetic effect in a very simple toy model. We conclude that an
+existing chiral fermion imbalance in peripheral heavy ion collisions would
+affect the magnetic field dynamics, and consequently, the charge dependent
+correlations measured in these experiments.",1501.07608v2
+2023-11-03,Simulating Heavy-Hex Transverse Field Ising Model Magnetization Dynamics Using Programmable Quantum Annealers,"Recently, a Hamiltonian dynamics simulation was performed on a kicked
+ferromagnetic 2D transverse field Ising model with a connectivity graph native
+to the 127 qubit heavy-hex IBM Quantum architecture using ZNE quantum error
+mitigation. We demonstrate that one of the observables in this Trotterized
+Hamiltonian dynamics simulation, namely magnetization, can be efficiently
+simulated on current superconducting qubit-based programmable quantum annealing
+computers. We show this using two distinct methods: reverse quantum annealing
+and h-gain state encoding. This simulation is possible because the 127 qubit
+heavy-hex connectivity graph can be natively embedded onto the D-Wave Pegasus
+quantum annealer hardware graph and because there exists a direct equivalence
+between the energy scales of the two types of quantum computers. We derive
+equivalent anneal pauses in order to simulate the Trotterized quantum circuit
+dynamics for varying Rx rotations $\theta_h \in (0, \frac{\pi}{2}]$, using
+quantum annealing processors. Multiple disjoint instances of the Ising model of
+interest can be embedded onto the D-Wave Pegasus hardware graph, allowing for
+parallel quantum annealing. We report equivalent magnetization dynamics using
+quantum annealing for time steps of 20, 50 up to 10,000, which we find are
+consistent with exact classical 27 qubit heavy-hex Trotterized circuit
+magnetization dynamics, and we observe reasonable, albeit noisy, agreement with
+the existing simulations for single site magnetization at 20 Trotter steps. The
+quantum annealers are able to simulate equivalent magnetization dynamics for
+thousands of time steps, significantly out of the computational reach of the
+digital quantum computers on which the original Hamiltonian dynamics
+simulations were performed.",2311.01657v1
+2011-10-01,Spin-orbital phase synchronization in the magnetic field-driven electron dynamics in a double quantum dot,"We study the dynamics of an electron confined in a one-dimensional double
+quantum dot in the presence of driving external magnetic fields. The orbital
+motion of the electron is coupled to the spin dynamics by spin orbit
+interaction of the Dresselhaus type. We derive an effective time-dependent
+Hamiltonian model for the orbital motion of the electron and obtain a
+synchronization condition between the orbital and the spin dynamics. From this
+model we deduce an analytical expression for the Arnold tongue and propose an
+experimental scheme for realizing the synchronization of the orbital and spin
+dynamics.",1110.0114v1
+2009-02-01,Neutron Studies of the Iron-based Family of High TC Magnetic Superconductors,"We review neutron scattering investigations of the crystal structures,
+magnetic structures, and spin dynamics of the iron-based RFe(As,P)O (R=La, Ce,
+Pr, Nd), (Ba,Sr,Ca)Fe2As2, and Fe1+x(Te-Se) systems. On cooling from room
+temperature all the undoped materials exhibit universal behavior, where a
+tetragonal-to-orthorhombic/monoclinic structural transition occurs, below which
+the systems become antiferromagnets. For the first two classes of materials the
+magnetic structure within the a-b plane consists of chains of parallel Fe spins
+that are coupled antiferromagnetically in the orthogonal direction, with an
+ordered moment typically less than one Bohr magneton. Hence these are itinerant
+electron magnets, with a spin structure that is consistent with Fermi-surface
+nesting and a very energetic spin wave bandwidth ~0.2 eV. With doping, the
+structural and magnetic transitions are suppressed in favor of
+superconductivity. Magnetic correlations are observed in the superconducting
+regime, with a magnetic resonance that follows the superconducting order
+parameter just like the cuprates. The rare-earth moments order
+antiferromagnetically at low T like conventional magnetic-superconductors.
+Pressure in CaFe2As2 transforms the system from a magnetically ordered
+orthorhombic material to a collapsed non-magnetic tetragonal system. Tetragonal
+Fe1+xTe transforms to a low T monoclinic structure at small x that changes to
+orthorhombic at larger x, which is accompanied by a crossover from commensurate
+to incommensurate magnetic order. Se doping suppresses the magnetic order.",0902.0091v2
+2012-09-25,Magnetic Energy and Helicity Budgets in the Active-Region Solar Corona. II. Nonlinear Force-Free Approximation,"Expanding on an earlier work that relied on linear force-free magnetic
+fields, we self-consistently derive the instantaneous free magnetic energy and
+relative magnetic helicity budgets of an unknown three-dimensional nonlinear
+force-free magnetic structure extending above a single, known lower-boundary
+magnetic field vector. The proposed method does not rely on the detailed
+knowledge of the three-dimensional field configuration but is general enough to
+employ only a magnetic connectivity matrix on the lower boundary. The
+calculation yields a minimum free magnetic energy and a relative magnetic
+helicity consistent with this free magnetic energy. The method is directly
+applicable to photospheric or chromospheric vector magnetograms of solar active
+regions. Upon validation, it basically reproduces magnetic energies and
+helicities obtained by well-known, but computationally more intensive and
+non-unique, methods relying on the extrapolated three-dimensional magnetic
+field vector. We apply the method to three active regions, calculating the
+photospheric connectivity matrices by means of simulated annealing, rather than
+a model-dependent nonlinear force-free extrapolation. For two of these regions
+we correct for the inherent linear force-free overestimation in free energy and
+relative helicity that is larger for larger, more eruptive, active regions. In
+the third studied region, our calculation can lead to a physical interpretation
+of observed eruptive manifestations. We conclude that the proposed method,
+including the proposed inference of the magnetic connectivity matrix, is
+practical enough to contribute to a physical interpretation of the dynamical
+evolution of solar active regions.",1209.5606v1
+2014-07-23,Magnetic Reconnection in Astrophysical Environments,"Magnetic reconnection is a process that changes magnetic field topology in
+highly conducting fluids. Traditionally, magnetic reconnection was associated
+mostly with solar flares. In reality, the process must be ubiquitous as
+astrophysical fluids are magnetized and motions of fluid elements necessarily
+entail crossing of magnetic frozen in field lines and magnetic reconnection. We
+consider magnetic reconnection in realistic 3D geometry in the presence of
+turbulence. This turbulence in most astrophysical settings is of pre-existing
+nature, but it also can be induced by magnetic reconnection itself. In this
+situation turbulent magnetic field wandering opens up reconnection outflow
+regions, making reconnection fast. We discuss Lazarian \& Vishniac (1999) model
+of turbulent reconnection, its numerical and observational testings, as well as
+its connection to the modern understanding of the Lagrangian properties of
+turbulent fluids. We show that the predicted dependences of the reconnection
+rates on the level of MHD turbulence make the generally accepted Goldreich \&
+Sridhar (1995) model of turbulence self-consistent. Similarly, we argue that
+the well-known Alfv\'en theorem on flux freezing is not valid for the turbulent
+fluids and therefore magnetic fields diffuse within turbulent volumes.
+  This is an element of magnetic field dynamics that was not accounted by
+earlier theories. For instance, the theory of star formation that was
+developing assuming that it is only the drift of neutrals that can violate the
+otherwise perfect flux freezing, is affected and we discuss the consequences of
+the turbulent diffusion of magnetic fields mediated by reconnection.",1407.6356v1
+2014-11-24,Manipulating Femtosecond Spin--Orbit Torques with Laser Pulse Sequences to Control Magnetic Memory States and Ringing,"Femtosecond (fs) coherent control of collective order parameters is important
+for non--equilibrium phase dynamics in correlated materials. Here we propose a
+possible scheme for fs control of a ferromagnetic order parameter based on
+non--adiabatic optical manipulation of electron--hole ($e$--$h$)
+photoexcitations between spin--orbit--coupled bands that are exchange--split by
+magnetic interaction with local spins. We photoexcite fs carrier spin--pulses
+with controllable direction and time profile without using
+circularly--polarized light, via time--reversal symmetry--breaking by
+non--perturbative interplay between spin--orbit and magnetic exchange coupling
+of coherent photocarriers. We manipulate photoexcited {\em fs spin--orbit
+torques} to control complex switching pathways of the magnetization between
+multiple magnetic memory states. We calculate the photoinduced fs magnetic
+anisotropy in the time domain by using density matrix equations of motion
+rather than the quasi--equilibrium free energy. By comparing to pump--probe
+experiments, we identify a ""sudden"" magnetization canting induced by laser
+excitation, which displays magnetic hysteresis absent in static
+magneto--optical measurements and agrees with switchings measured by Hall
+magnetoresistivity. The fs magnetization canting switches direction with
+magnetic state and laser frequency, which distinguishes it from nonlinear
+optical and demagnetization longitudinal effects. By shaping two--color
+laser--pulse sequences analogous to multi--dimensional Nuclear Magnetic
+Resonance (NMR) spectroscopy, we show that sequences of clockwise or
+counter--clockwise fs spin--orbit torques can enhance or suppress magnetic
+ringing and switching rotation at any desired time. We propose protocols that
+can provide controlled access to four magnetic states via consequative 90$^{o}$
+switchings.",1411.6662v1
+2014-12-01,Quantifying magnetic anisotropy dispersion: Theoretical and experimental study of the magnetic properties of anisotropic FeCuNbSiB ferromagnetic films,"The Stoner-Wohlfarth model is a traditional and efficient tool to calculate
+magnetization curves and it can provides further insights on the fundamental
+physics associated to the magnetic properties and magnetization dynamics. Here,
+we perform a theoretical and experimental investigation of the quasi-static
+magnetic properties of anisotropic systems. We consider a theoretical approach
+which corresponds to a modified version of the Stoner-Wohlfarth model to
+describe anisotropic systems and a distribution function to express the
+magnetic anistropy dispersion. We propose a procedure to calculate the magnetic
+properties for the anisotropic case of the SW model from experimental results
+of the quadrature of magnetization curves, thus quantifying the magnetic
+anisotropy dispersion. To test the robustness of the approach, we apply the
+theoretical model to describe the quasi-static magnetic properties of amorphous
+FeCuNbSiB ferromagnetic films. We perform calculations and directly compare
+theoretical results with longitudinal and transverse magnetization curves
+measured for the films. Thus, our results provide experimental evidence to
+confirm the validity of the theoretical approach to describe the magnetic
+properties of anisotropic amorphous ferromagnetic films, revealed by the
+excellent agreement between numerical calculation and experimental results.",1412.0563v1
+2017-09-28,Angular Momentum Transport in Thin Magnetically Arrested Disks,"In accretion disks with large-scale ordered magnetic fields, the
+magnetorotational instability (MRI) is marginally suppressed, so other
+processes may drive angular momentum transport leading to accretion. Accretion
+could then be driven by large-scale magnetic fields via magnetic braking, but
+large-scale magnetic flux can build-up onto the black hole and within the disk
+leading to a magnetically-arrested disk (MAD). Such a MAD state is unstable to
+the magnetic Rayleigh-Taylor (RT) instability, which itself leads to vigorous
+turbulence and the emergence of low-density highly-magnetized bubbles. This
+instability was studied in a thin (ratio of half-height H to radius R, $H/R
+\approx 0.1$) MAD simulation, where it has a more dramatic effect on the
+dynamics of the disk than for thicker disks. We find that the low-density
+bubbles created by the magnetic RT instability decrease the stress (leading to
+angular momentum transport) in the disk rather than increasing magnetic
+torques. Indeed, we find that the dominant component of the stress is due to
+turbulent magnetic fields, despite the suppression of the axisymmetric MRI and
+the dominant presence of large-scale magnetic fields. This suggests that the
+magnetic RT instability plays a significant role in driving angular momentum
+transport in MADs.",1709.10113v2
+2018-03-26,Nonkinematic solar dynamo models with double-cell meridional circulation,"Employing the standard solar interior model as input we construct a
+dynamically-consistent nonlinear dynamo model that takes into account the
+detailed description of the \Lambda- effect, turbulent pumping, magnetic
+helicity balance, and magnetic feedback on the differential rotation and
+meridional circulation. The background mean-field hydrodynamic model of the
+solar convection zone accounts the solar-like angular velocity profile and the
+double-cell meridional circulation. We investigate an impact of the nonlinear
+magnetic field generation effects on the long-term variability and properties
+of the magnetic cycle. The nonlinear dynamo solutions are studied in the wide
+interval of the \alpha effect parameter from a slightly subcritical to
+supercritical values. It is found that the magnetic cycle period decreases with
+the increasing cycle's magnitude. The periodic long-term variations of the
+magnetic cycle are excited in case of the overcritical \alpha effect. These
+variations result from the hemispheric magnetic helicity exchange. It depends
+on the magnetic diffusivity parameter and the magnetic helicity production
+rate. The large-scale magnetic activity modifies the distribution of the
+differential rotation and meridional circulation inside convection zone. It is
+found that the magnetic feedback on the global flow affects the properties of
+the long-term magnetic cycles. We confront our findings with solar and stellar
+magnetic activity observations.",1803.09459v2
+2021-04-05,Efficient determination of the true magnetic structure in a high-throughput ab initio screening: the MDMC method,"Finding the true magnetic structure at given external conditions is crucial
+for describing magnetic materials and predicting their properties. This is
+especially important for high-throughput screening of potentially good magnets
+that without adequate description of the magnetic structure may result in an
+enormous waste of computational resources. I introduce a method, which
+accurately and efficiently treats magnetic ordering in the course of standard
+first-principles calculations. The method is suitable for all temperatures and
+is based on Monte Carlo (MC) technique. At high temperatures MC is coupled to
+ab initio molecular dynamics, therefore treating atomic vibrations and magnetic
+ordering simultaneously. The method takes care of the convergence to the true
+ground-state magnetic structure at 0 K, coupling between spins and atomic
+vibrations at high temperatures, and spin-spin interactions in non-Heisenberg
+systems, i.e. it naturally goes beyond the usual pair-like effective exchange
+interactions at all temperatures. I show that the method nicely reproduces the
+magnetic structures at low and high temperatures even on relatively small
+supercells and provides a ground for truly ab initio calculations of magnetic
+systems in high-throughput studies. In its general formulation the MDMC method
+deals with non-collinear magnetism, but its collinear version may be more
+suitable for fast high-throughput calculations. The examples of the application
+of the MDMC method addressed in this paper are $\alpha$-Mn; body-centered cubic
+Fe, which is ferromagnetic at low and paramagnetic at high temperatures; and
+MnB$_2$W$_2$, a new magnetic compound with non-trivial magnetism.",2104.02106v1
+2021-12-11,Macroscopic Magnetic Monopoles in a 3D-Printed Mechano-Magnet,"The notion of magnetic monopoles has puzzled physicists since the
+introduction of Maxwell's Equations and famously Dirac had hypothesized them in
+the context of quantum mechanics. While they have proved experimentally elusive
+as elementary particles, the concept has come to describe excitations or
+topological defects in various material systems, from liquid crystals, to Hall
+systems, skyrmion lattices, and Bose-Einstein condensate. Perhaps the most
+versatile manifestation of magnetic monopoles as quasiparticles in matter has
+been in so-called spin ice materials. There, they represent violations of the
+ice rule, carry a magnetic charge, and can move freely unbound. Spin ice
+emergent magnetic monopoles appear at the atomic scale in rare earth
+pyrochlores or at the nano-scale in artificial spin ices systems. Here we
+demonstrate for the first time that the notion of magnetic monopoles can be
+transported at the macroscopic scale. We have built a mechano-magnet realized
+via 3D-printing, that consists of mechanical rotors on which macroscopic
+magnets can pivot. By controlling the relative height of the rotors we can
+achieve different regimes for magnetic monopoles, including the free monopole
+state. We then explore their driven dynamics under field. In the future,
+integration of our proof of principle in an elastic matrix can lead to novel
+macroscopic mechano-magnetic materials, to explore unusual piezomagnetism and
+magnetostriction, with applications to actuators and soft-robotics.",2112.06058v2
+2022-09-03,Core orientations and magnetic fields in isolated molecular clouds,"Molecular clouds are sites of star formation. Magnetic fields are believed to
+play an important role in their dynamics and shaping morphology. We aim to
+study any possible correlation that might exist between the magnetic fields
+orientation inside the clouds and the magnetic fields at envelope scales and
+their connection with respect to the observed morphology of the selected
+clouds. We examine the magnetic field orientation towards the clouds L1512,
+L1523, L1333, L1521E, L1544, L1517, L1780, and L183 using optical and
+\textit{Planck} polarization observations. We also found the correlation
+between the ambient magnetic field and core orientations derived using
+\textit{Astrodendrogram} on the \textit{Herschel} 250 $\mu$m data. We find that
+the magnetic fields derived from optical and \textit{Planck} agree with each
+other. The derived magnetic fields are aligned along the observed emission of
+each cloud as seen in \textit{Herschel} 250 $\mu$m data. We also find that the
+relative orientation between the cores and the magnetic fields is random. This
+lack of correlation may arise due to the fact that the core orientation could
+also be influenced by the different magnetization within individual clouds at
+higher densities or the feedback effects which may vary from cloud to cloud.
+The estimated magnetic field strength and the mass-to-flux ratio suggest that
+all the clouds are in a magnetically critical state except L1333, L1521E, and
+L183 where the cloud envelope could be strongly supported by the magnetic field
+lines.",2209.01509v1
+2022-11-01,Effects of strong fringing magnetic fields on turbulent thermal convection,"We study the influence of fringing magnetic fields on turbulent thermal
+convection in a horizontally extended rectangular domain. The magnetic field is
+created in the gap between two semi-infinite planar magnetic poles, with the
+convection layer located near the edge of the gap. We employ direct numerical
+simulations in this setup for fixed Rayleigh and small Prandtl numbers, but
+vary the fringe-width by controlling the gap between the magnetic poles and the
+convection cell. The magnetic field generated by the magnets is strong enough
+to cease the flow in high magnetic flux region of the convection cell. We
+observe that as the local vertical magnetic field strength increases, the large
+scale structures become thinner and align themselves perpendicular to the
+longitudinal sidewalls. We determine the local Nusselt and Reynolds numbers as
+functions of the local Hartmann number (based on the vertical component of the
+magnetic field) and estimate the global heat and momentum transport. We show
+that the global heat transport decreases with increasing fringe-width for
+strong magnetic fields but increases with increasing fringe-width for weak
+magnetic fields. In the regions of large vertical magnetic fields, the
+convective motion becomes confined to the vicinity of the sidewalls. The
+amplitudes of these wall modes show a non-monotonic dependence on the
+fringe-width.",2211.00559v3
+2023-04-22,A Multi-frequency Magnetic Particle Spectroscopy System for the Characterization of Magnetic Nanoparticles,"Magnetic particle spectroscopy (MPS) is one of the most versatile methods to
+characterize the magnetic properties of magnetic nanoparticles (MNPs). The
+excitation magnetic field is one of the most crucial factors that affects the
+MPS signal of the MNPs. In this study, a multi-frequency MPS system is
+developed to investigate the MPS signal of MNPs in different ac magnetic
+fields. The MPS system consists of a multi-channel excitation module for the
+generation of different-frequency ac magnetic fields and a detection module for
+the measurement of the magnetic response of the MNPs. The MPS system allows to
+generate ac magnetic fields with a frequency up to 32.6 kHz and amplitude up to
+25 mT. The MPS signals of the MNPs in different ac magnetic fields are measured
+to systematically evaluate the performance of the multi-frequency MPS system,
+including the MNP spectra and its dynamic magnetization curve. In addition, the
+signal-to-noise ratio (SNR) of the MPS system is quantitively assessed with
+measured MPS signals of a given MNP sample and DI water. Furthermore, a series
+of MNP samples with different iron concentrations are prepared and measured to
+evaluate the limit-of-detection (LOD) in terms of iron concentration. The
+influence of the excitation magnetic field, including frequency and amplitude,
+is discussed based on the SNRs of the measured harmonics. Experimental results
+show that the LOD is 2.3 ng in terms of iron.",2304.11290v1
+2023-07-12,Magnetohydrodynamics simulation of magnetic flux rope formation in a quadrupolar magnetic field configuration,"Magnetic flux ropes (MFRs) play an important role in high-energetic events
+like solar flares and coronal mass ejections in the solar atmosphere.
+Importantly, solar observations suggest an association of some flaring events
+with quadrupolar magnetic configurations. However, the formation and subsequent
+evolution of MFRs in such magnetic configurations still need to be fully
+understood. In this paper, we present idealized magnetohydrodynamics (MHD)
+simulations of MFR formation in a quadrupolar magnetic configuration. A
+suitable initial magnetic field having a quadrupolar configuration is
+constructed by modifying a three-dimensional (3D) linear force-free magnetic
+field. The initial magnetic field contains neutral lines, which consist of
+X-type null points. The simulated dynamics initially demonstrate the oppositely
+directed magnetic field lines located across the polarity inversion lines
+(PILs) moving towards each other, resulting in magnetic reconnections. Due to
+these reconnections, four highly twisted MFRs form over the PILs. With time,
+the foot points of the MFRs move towards the X-type neutral lines and
+reconnect, generating complex magnetic structures around the neutral lines,
+thus making the MFR topology more complex in the quadrupolar configuration than
+those formed in bipolar loop systems. Further evolution reveals the non-uniform
+rise of the MFRs. Importantly, the simulations indicate that the pre-existing
+X-type null points in magnetic configurations can be crucial to the evolution
+of the MFRs and may lead to the observed brightenings during the onset of some
+flaring events in the quadrupolar configurations.",2307.06025v1
+2023-11-30,Properties of Mars' Dayside Low-Altitude Induced Magnetic Field and Comparisons with Venus,"Our research objective is to characterize Mars' low-altitude (250 km) induced
+magnetic fields using data from NASA's MAVEN (Mars Atmosphere and Volatile
+EvolutioN) Mission. We aim to assess how the induced magnetic fields behave
+under different solar zenith angles and solar wind conditions, and
+additionally, understand how planet-specific properties (such as Mars crustal
+magnetism) alter the formation and structure of the magnetic fields. We then
+use data from the Pioneer Venus Orbiter to compare induced magnetic fields at
+Venus with those at Mars. At Venus, the vertical structure of the magnetic
+field tends to exist in one of two states (magnetized or unmagnetized) but we
+find the induced fields at Mars are more complicated, and we are unable to use
+this simple classification scheme. We also find the low-altitude induced field
+strength in the ionospheres of both Venus and Mars vary with as cosine of the
+angle between solar wind velocity and the magnetic pileup boundary. The
+low-altitude field strength at Venus tends to be higher than Mars. However,
+Venus field strengths are lower than theoretical predictions assuming pressure
+balance and negligible thermal pressure. For Mars, low-altitude field strengths
+are higher than expected given these assumptions. Induced field strengths
+exhibit a trend with solar wind dynamic pressure that is consistent with
+pressure balance expectations at both planets, however there is significant
+uncertainty in the Venus fit due to lack of upstream solar wind data. Our
+results highlight major differences between the induced magnetic fields at
+Venus and Mars, suggesting planet-specific properties such as size and the
+presence of crustal magnetism affect the induced ionospheric magnetic fields at
+non magnetized planets.",2311.18217v1
+1999-01-05,On the Exchange of Kinetic and Magnetic Energy Between Clouds and the Interstellar Medium,"We investigate, through 2D MHD numerical simulations, the interaction of a
+uniform magnetic field oblique to a moving interstellar cloud. In particular we
+explore the transformation of cloud kinetic energy into magnetic energy as a
+result of field line stretching. Some previous simulations have emphasized the
+possible dynamical importance of a ``magnetic shield'' formed around clouds
+when the magnetic field is perpendicular to the cloud motion (Jones et al.
+1996, Miniati et al. 1998). It was not clear, however, how dependent those
+findings were to the assumed field configuration and cloud properties. To
+expand our understanding of this effect, we examine several new cases by varing
+the magnetic field orientation angle with respect to the cloud motion (\theta),
+the cloud-background density contrast, and the cloud Mach number.
+  We show that in 2D and with \theta large enough, the magnetic field tension
+can become dominant in the dynamics of the motion of high density contrast, low
+Mach number clouds. In such cases a significant fraction of cloud kinetic
+energy can be transformed into magnetic energy with the magnetic pressure at
+the cloud nose exceeding the ram pressure of the impinging flow. We derive a
+characteristic timescale for this process of energy ``conversion''. We find
+also that unless the cloud motion is highly aligned to the magnetic field,
+reconnection through tearing mode instabilities in the cloud wake limit the
+formation of a strong flux rope feature following the cloud. Finally we attempt
+to interpret some observational properties of the magnetic field in view of our
+results.",9901048v1
+2005-05-05,Current-driven magnetic rearrangements in spin-polarized point contacts,"A new method for investigating the dynamics of atomic magnetic moments in
+current-carrying magnetic point contacts under bias is presented. This combines
+the non-equilibrium Green's function (NEGF) method for evaluating the current
+and the charge density with a description of the dynamics of the magnetization
+in terms of quasistatic thermally-activated transitions between stationary
+configurations. This method is then implemented in a tight-binding (TB) model
+with parameters chosen to simulate the main features of the electronic
+structures of magnetic transition metals. We investigate the domain wall (DW)
+migration in magnetic monoatomic chains sandwiched between magnetic leads, and
+for realistic parameters find that collinear arrangement of the magnetic
+moments of the chain is always favorable. Several stationary magnetic
+configurations are identified, corresponding to a different number of Bloch
+walls in the chain and to a different current. The relative stability of these
+configurations depends on the geometrical details of the junction and on the
+bias, however we predict transitions between different configurations with
+activation barriers of the order of a few tens of meV. Since different magnetic
+configurations are associated to different resistances, this suggests an
+intrinsic random telegraph noise at microwave frequencies in the I-V
+characteristics of magnetic atomic point contacts at room temperature. Finally,
+we investigate whether or not current induced torques are conservative.",0505134v1
+2006-07-20,Dipolar interaction effects in the magnetic and magnetotransport properties of ordered nanoparticle arrays,"Assemblies of magnetic nanoparticles exhibit interesting physical properties
+arising from the competition of intraparticle dynamics and interparticle
+interactions. In ordered arrays of magnetic nanoparticles magnetostatic
+interparticle interactions introduce collective dynamics acting competitively
+to random anisotropy. Basic understanding, characterization and control of
+dipolar interaction effects in arrays of magnetic nanoparticles is an issue of
+central importance. To this end, numerical simulation techniques offer an
+indispensable tool. We report on Monte Carlo studies of the magnetic hysteresis
+and spin-dependent transport in thin films formed by ordered arrays of magnetic
+nanoparticles. Emphasis is given to the modifications of the single-particle
+behavior due to interparticle dipolar interactions as these arise in quantities
+of experimental interest, such as, the magnetization, the susceptibility and
+the magnetoresistance. We investigate the role of the structural parameters of
+an array (interparticle separation, number of stacked monolayers) and the role
+of the internal structure of the nanoparticles (single phase, core-shell).
+Dipolar interactions are responsible for anisotropic magnetic behavior between
+the in-plane and out-of-plane directions of the sample, which is reflected on
+the investigated magnetic properties (magnetization, transverse susceptibility
+and magnetoresistance) and the parameters of the array (remanent magnetization,
+coercive field, and blocking temperature). Our numerical results are compared
+to existing measurements on self-assembled arrays of Fe-based and Co
+nanoparticles is made.",0607520v3
+2008-12-31,Photospheric and Subphotospheric Dynamics of Emerging Magnetic Flux,"Magnetic fields emerging from the Sun's interior carry information about
+physical processes of magnetic field generation and transport in the convection
+zone. Soon after appearance on the solar surface the magnetic flux gets
+concentrated in sunspot regions and causes numerous active phenomena on the
+Sun. This paper discusses some properties of the emerging magnetic flux
+observed on the solar surface and in the interior. A statistical analysis of
+variations of the tilt angle of bipolar magnetic regions during the emergence
+shows that the systematic tilt with respect to the equator (the Joy's law) is
+most likely established below the surface. However, no evidence of the
+dependence of the tilt angle on the amount of emerging magnetic flux, predicted
+by the rising magnetic flux rope theories, is found. Analysis of surface plasma
+flows in a large emerging active region reveals strong localized upflows and
+downflows at the initial phase of emergence but finds no evidence for
+large-scale flows indicating future appearance a large-scale magnetic
+structure. Local helioseismology provides important tools for mapping
+perturbations of the wave speed and mass flows below the surface. Initial
+results from SOHO/MDI and GONG reveal strong diverging flows during the flux
+emergence, and also localized converging flows around stable sunspots. The wave
+speed images obtained during the process of formation of a large active region,
+NOAA 10488, indicate that the magnetic flux gets concentrated in strong field
+structures just below the surface. Further studies of magnetic flux emergence
+require systematic helioseismic observations from the ground and space, and
+realistic MHD simulations of the subsurface dynamics.",0901.0035v1
+2012-11-13,Magnetic Wreaths and Cycles in Convective Dynamos,"Solar-type stars exhibit a rich variety of magnetic activity. Seeking to
+explore the convective origins of this activity, we have carried out a series
+of global 3D magnetohydrodynamic (MHD) simulations with the anelastic spherical
+harmonic (ASH) code. Here we report on the dynamo mechanisms achieved as the
+effects of artificial diffusion are systematically decreased. The simulations
+are carried out at a nominal rotation rate of three times the solar value
+(3$\Omega_\odot$), but similar dynamics may also apply to the Sun. Our previous
+simulations demonstrated that convective dynamos can build persistent toroidal
+flux structures (magnetic wreaths) in the midst of a turbulent convection zone
+and that high rotation rates promote the cyclic reversal of these wreaths. Here
+we demonstrate that magnetic cycles can also be achieved by reducing the
+diffusion, thus increasing the Reynolds and magnetic Reynolds numbers. In these
+more turbulent models, diffusive processes no longer play a significant role in
+the key dynamical balances that establish and maintain the differential
+rotation and magnetic wreaths. Magnetic reversals are attributed to an
+imbalance in the poloidal magnetic induction by convective motions that is
+stabilized at higher diffusion levels. Additionally, the enhanced levels of
+turbulence lead to greater intermittency in the toroidal magnetic wreaths,
+promoting the generation of buoyant magnetic loops that rise from the deep
+interior to the upper regions of our simulated domain. The implications of such
+turbulence-induced magnetic buoyancy for solar and stellar flux emergence are
+also discussed.",1211.3129v1
+2013-04-12,Comparison of force-free coronal magnetic field modeling using vector fields from Hinode and Solar Dynamics Observatory,"Photospheric magnetic vector maps from two different instruments are used to
+model the nonlinear force-free coronal magnetic field above an active region.
+We use vector maps inferred from polarization measurements of the Solar
+Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) and the Solar
+Optical Telescope Spectropolarimeter (SP) aboard Hinode. Besides basing our
+model calculations on HMI data, we use both, SP data of original resolution and
+scaled down to the resolution of HMI. This allows us to compare the model
+results based on data from different instruments and to investigate how a
+binning of high-resolution data effects the model outcome. The resulting 3D
+magnetic fields are compared in terms of magnetic energy content and magnetic
+topology. We find stronger magnetic fields in the SP data, translating into a
+higher total magnetic energy of the SP models. The net Lorentz forces of the
+HMI and SP lower boundaries verify their force-free compatibility. We find
+substantial differences in the absolute estimates of the magnetic field energy
+but similar relative estimates, e.g., the fraction of excess energy and of the
+flux shared by distinct areas. The location and extension of neighboring
+connectivity domains differs and the SP model fields tend to be higher and more
+vertical. Hence, conclusions about the magnetic connectivity based on
+force-free field models are to be drawn with caution. We find that the
+deviations of the model solution when based on the lower-resolution SP data are
+small compared to the differences of the solutions based on data from different
+instruments.",1304.3619v1
+2014-03-15,Global evolution of the magnetic field in a thin disc and its consequences for protoplanetary systems,"The strength and structure of the large-scale magnetic field in
+protoplanetary discs are still unknown, although they could have important
+consequences for the dynamics and evolution of the disc. Using a mean-field
+approach in which we model the effects of turbulence through enhanced diffusion
+coefficients, we study the time-evolution of the large-scale poloidal magnetic
+field in a global model of a thin accretion disc, with particular attention to
+protoplanetary discs. With the transport coefficients usually assumed, the
+magnetic field strength does not significantly increase radially inwards,
+leading to a relatively weak magnetic field in the inner part of the disc. We
+show that with more realistic transport coefficients that take into account the
+vertical structure of the disc and the back-reaction of the magnetic field on
+the flow as obtained by Guilet & Ogilvie (2012), the magnetic field can
+significantly increase radially inwards. The magnetic-field profile adjusts to
+reach an equilibrium value of the plasma $\beta$ parameter (the ratio of
+midplane thermal pressure to magnetic pressure) in the inner part of the disc.
+This value of $\beta$ depends strongly on the aspect ratio of the disc and on
+the turbulent magnetic Prandtl number, and lies in the range $10^4-10^7$ for
+protoplanetary discs. Such a magnetic field is expected to affect significantly
+the dynamics of protoplanetary discs by increasing the strength of MHD
+turbulence and launching an outflow. We discuss the implications of our results
+for the evolution of protoplanetary discs and for the formation of powerful
+jets as observed in T-Tauri star systems.",1403.3732v1
+2017-10-03,"Long-range dynamical magnetic order and spin tunneling in the cooperative paramagnetic states of the pyrochlore analogous spinel antiferromagnets CdYb2X4 (X = S, Se)","Magnetic systems with spins sitting on a lattice of corner sharing regular
+tetrahedra have been particularly prolific for the discovery of new magnetic
+states for the last two decades. The pyrochlore compounds have offered the
+playground for these studies, while little attention has been comparatively
+devoted to other compounds where the rare earth R occupies the same
+sub-lattice, e.g. the spinel chalcogenides CdR2X4 (X = S, Se). Here we report
+measurements performed on powder samples of this series with R = Yb using
+specific heat, magnetic susceptibility, neutron diffraction and
+muon-spin-relaxation measurements. The two compounds are found to be
+magnetically similar. They long-range order into structures described by the
+\Gamma_5 irreducible representation. The magnitude of the magnetic moment at
+low temperature is 0.77 (1) and 0.62 (1) mu_B for X = S and Se, respectively.
+Persistent spin dynamics is present in the ordered states. The spontaneous
+field at the muon site is anomalously small, suggesting magnetic moment
+fragmentation. A double spin-flip tunneling relaxation mechanism is suggested
+in the cooperative paramagnetic state up to 10 K. The magnetic space groups
+into which magnetic moments of systems of corner-sharing regular tetrahedra
+order are provided for a number of insulating compounds characterized by null
+propagation wavevectors.",1710.01062v1
+2018-04-09,Three Dimensional Aggregation of Magnetic Particles,"Magnetic drug delivery is a promising therapeutic because of magnetic fields'
+ability to permeate unperturbed in human tissue. One of the long-standing
+challenges in magnetic drug delivery is the inability to generate 3D
+aggregation non-invasively within the interior of the body. Earnshaw's theorem,
+which proves the impossibility of creating an energetic minimum in a curl-free
+and divergence-free field such as a magnetic field. However, one of the
+assumptions of Earnshaw's theorem is a static field. Here we show that it is
+possible to utilize a dynamically changing field and a dissipative force such
+as the drag, which is generally present, to create a stable aggregation point
+for magnetic particles. We also introduce a theoretical framework for designing
+the suitable magnetic fields for controlling a given magnetic particle in a
+particular fluid. This framework enables accurate determination of the
+necessary parameters for aggregation across a wide variety of magnetic
+particles and across multiple biologically-relevant fluids. By coating magnetic
+particles with desired therapeutic agents or attaching them to cells, a new
+class of treatment methodologies can be created in therapies such as targeted
+drug delivery and cell-based therapies. By dynamically changing the aggregation
+point, agents can also be guided along a particular path in the body. This
+technique of using dissipative forces to create a stable 3D aggregation point
+for particles could possibly be extended to a broad range of applications such
+as microscopic and macroscopic manipulation, robotics, guided self-assembly,
+magnetic plasma confinement, tissue engineering, and ion traps for quantum
+computers.",1804.02778v1
+2019-09-30,"High-harmonic generation by electric polarization, spin current, and magnetization","High-harmonic generation (HHG), a typical nonlinear optical effect, has been
+actively studied in electron systems such as semiconductors and
+superconductors. As a natural extension, we theoretically study HHG from
+electric polarization, spin current and magnetization in magnetic insulators
+under terahertz (THz) or gigahertz (GHz) electromagnetic waves. We use simple
+one-dimensional spin chain models with or without multiferroic coupling between
+spins and the electric polarization, and study the dynamics of the spin chain
+coupled to an external ac electric or magnetic field. We map spin chains to
+two-band fermions and invoke an analogy of semiconductors and superconductors.
+With a quantum master equation and Lindblad approximation, we compute the time
+evolution of the electric polarization, spin current, and magnetization,
+showing that they exhibit clear harmonic peaks. We also show that the
+even-order HHG by magnetization dynamics can be controlled by static magnetic
+fields in a wide class of magnetic insulators. We propose experimental setups
+to observe these HHG, and estimate the required strength of the ac electric
+field $E_0$ for detection as $E_0\sim100$kV/cm--1MV/cm, which corresponds to
+the magnetic field $B_0\sim0.1$T--1T. The estimated strength would be relevant
+also for experimental realizations of other theoretically-proposed nonlinear
+optical effects in magnetic insulators such as Floquet engineering of magnets.",1910.00146v3
+2020-02-20,Stoner-Wohlfarth switching of the condensate magnetization in a dipolar spinor gas and the metrology of excitation damping,"We consider quasi-one-dimensional dipolar spinor Bose-Einstein condensates in
+the homogeneous-local-spin-orientation approximation, that is with
+unidirectional local magnetization. By analytically calculating the exact
+effective dipole-dipole interaction, we derive a Landau-Lifshitz-Gilbert
+equation for the dissipative condensate magnetization dynamics, and show how it
+leads to the Stoner-Wohlfarth model of a uni-axial ferro-magnetic particle,
+where the latter model determines the stable magnetization patterns and
+hysteresis curves for switching between them. For an external magnetic field
+pointing along the axial, long direction, we analytically solve the
+Landau-Lifshitz-Gilbert equation. The solution explicitly demonstrates that the
+magnetic dipole-dipole interaction {\it accelerates} the dissipative dynamics
+of the magnetic moment distribution and the associated dephasing of the
+magnetic moment direction. Under suitable conditions, dephasing of the
+magnetization direction due to dipole-dipole interactions occurs within time
+scales up to two orders of magnitude smaller than the lifetime of currently
+experimentally realized dipolar spinor condensates, e.g., produced with the
+large magnetic-dipole-moment atoms ${}^{166} \textrm{Er}$. This enables
+experimental access to the dissipation parameter $\Gamma$ in the
+Gross-Pitaevski\v\i~mean-field equation, for a system currently lacking a
+complete quantum kinetic treatment of dissipative processes and, in particular,
+an experimental check of the commonly used assumption that $\Gamma$ is a single
+scalar independent of spin indices.",2002.08723v2
+2020-11-09,Quantum-torque-induced breaking of magnetic interfaces in ultracold gases,"A rich variety of physical effects in spin dynamics arises at the interface
+between different magnetic materials. Engineered systems with interlaced
+magnetic structures have been used to implement spin transistors, memories and
+other spintronic devices. However, experiments in solid state systems can be
+difficult to interpret because of disorder and losses. Here, we realize
+analogues of magnetic junctions using a coherently-coupled mixture of ultracold
+bosonic gases. The spatial inhomogeneity of the atomic gas makes the system
+change its behavior from regions with oscillating magnetization -- resembling a
+magnetic material in the presence of an external transverse field -- to regions
+with a defined magnetization, as in magnetic materials with a ferromagnetic
+anisotropy stronger than external fields. Starting from a far-from-equilibrium
+fully polarized state, magnetic interfaces rapidly form. At the interfaces, we
+observe the formation of short-wavelength magnetic waves. They are generated by
+a quantum torque contribution to the spin current and produce strong spatial
+anticorrelations in the magnetization. Our results establish ultracold gases as
+a platform for the study of far-from-equilibrium spin dynamics in regimes that
+are not easily accessible in solid-state systems.",2011.04271v2
+2021-09-26,Disorder-Induced Complex Magnetization Dynamics in Planar Ensembles of Nanoparticles,"The magnetic relaxation characteristics are investigated in the
+two-dimensional ($l^{}_x\times l^{}_y$) assembly of nanoparticles as a function
+of out-of-plane positional disorder strength $\Delta(\%)$ using numerical
+simulations. Such defects are redundantly observed in experimentally fabricated
+nanostructures, resulting in unusual magnetization dynamics. The magnetization
+decays exponentially for small and negligible dipolar interaction strength
+$h^{}_d\leq0.2$. In such a case, the magnetization relaxation does not depend
+on $\Delta$ and aspect ratio $A^{}_r=l^{}_y/l^{}_x$, as expected. In
+square-like MNPs ensembles and perfectly ordered system ($\Delta(\%)=0$), the
+magnetization relaxes rapidly with an increase in $h^{}_d$. Consequently, the
+effective N\'eel relaxation time $\tau^{}_N$ decreases with $h^{}_d$. The
+dipolar interaction of sufficient strength promotes antiferromagnetic coupling
+in such a system, resulting in rapid magnetization decay. Remarkably, the
+out-of-plane disorder instigates the magnetic moment to interact
+ferromagnetically in the presence of large $h^{}_d$, even in the square-like
+assembly of MNPs. As a result, magnetization relaxation slows down, resulting
+in a monotonous increase of $\tau^{}_N$ with an increase in $\Delta$ and
+$h^{}_d$ in such cases. Notably, there is a prolonged magnetization decay in
+the highly anisotropic system with large $h^{}_d$. The dipolar interaction
+induces ferromagnetic coupling along the long axis of the system in such cases.
+Therefore, the magnetization ceases to relax as a function of time for large
+$h^{}_d$, irrespective of disorder strength $\Delta(\%)$. The present work
+could provide a concrete theoretical basis to explain the unexpected relaxation
+behaviour observed in experiments. These results are also beneficial in digital
+data storage and spintronics based applications where such nanostructures are
+extensively used.",2109.12596v1
+2021-10-11,Simulations of the line-driven instability in magnetic hot star winds,"Line-driven winds of hot, luminous stars are intrinsically unstable due to
+the line-deshadowing instability (LDI). In non-magnetic hot stars, the LDI
+leads to the formation of an inhomogeneous wind consisting of small-scale,
+spatially separated clumps that can have great effects on observational
+diagnostics. However, for magnetic hot stars the LDI generated structures, wind
+dynamics, and effects on observational diagnostics have not been directly
+investigated so far. We investigated the non-linear development of LDI
+generated structures and dynamics in a magnetic line-driven wind of a typical
+O-supergiant. We employed two-dimensional axisymmetric magnetohydrodynamic
+(MHD) simulations of the LDI using the Smooth Source Function approximation for
+evaluating the assumed one-dimensional line force. To facilitate the
+interpretation of these magnetic models, they were compared with a
+corresponding non-magnetic LDI simulation as well as a magnetic simulation
+neglecting the LDI. A central result obtained is that the wind morphology and
+wind clumping properties change strongly with increasing wind-magnetic
+confinement. Most notably, in magnetically confined flows, the LDI leads to
+large-scale, shellular sheets ('pancakes') that are quite distinct from the
+spatially separate, small-scale clumps in non-magnetic line-driven winds. We
+discuss the impact of these findings for observational diagnostic studies and
+stellar evolution models of magnetic hot stars.",2110.05302v1
+2023-07-12,Magnetic Fields in Multiphase Turbulence: Impacts on Dynamics and Structure,"Both multiphase gas and magnetic fields are ubiquitous in astrophysics.
+However, the influence of magnetic fields on mixing of the different phases is
+still largely unexplored. In this study, we use both turbulent radiative mixing
+layer (TRML) and turbulent box simulations to examine the effects of magnetic
+fields on cold gas growth rates, survival, and the morphology of the multiphase
+gas. Our findings indicate that, in general, magnetic fields suppress mixing in
+TRMLs while turbulent box simulations show comparatively marginal differences
+in growth rates and survival of the cold gas. We reconcile these two seemingly
+contrasting results by demonstrating that similar turbulent properties result
+in comparable mixing -- regardless of the presence or absence of magnetic
+fields. We, furthermore, find the cold gas clump size distribution to be
+independent of the magnetic fields but the clumps are more filamentary in the
+MHD case. Synthetic MgII absorption lines support this picture being marginally
+different with and without magnetic fields; both cases aligning well with
+observations. We also examine the magnetic field strength and structure in
+turbulent boxes. We generally observe a higher mean magnetic field in the cold
+gas phase due to flux freezing and reveal fractal-like magnetic field lines in
+a turbulent environment.",2307.06411v1
+2023-08-10,Spinning magnetized particles orbiting magnetized Schwarzschild black holes,"A way to test electromagnetic field and spacetime properties around black
+holes is by considering the dynamics of test particles. In fact, in real
+astrophysical scenarios, it is hard to determine spacetime geometry which is
+dominating due to degeneracy gravitational effects in parameters of gravity
+theories. In this work, we study for the first time the dynamics of spinning
+particles that have magnetic dipole moments around Schwarzschild black holes
+immersed in an external asymptotically uniform magnetic field using the
+Mathisson-Papapetrou-Dixon (MPD) equation. There are two combined interactions:
+gravitational interaction between the spin of the particle and
+(electro)magnetic interaction between the external magnetic field and the
+magnetic dipole moment of the particle to be taken into account. First, we
+derive the effective potential of the test spinning magnetized particles in
+motion around the black hole. We also study the combined effects of spin and
+magnetic interactions on innermost stable circular orbits (ISCOs), the energy,
+and angular momentum of the particles at ISCO together with superluminal
+bounds. We investigated the collision of the particles and evaluated the
+center-of-mass energy in the collisions. Finally, we consider various cases in
+which neutron stars and rotating stellar mass black holes can be treated as
+spinning magnetized particles, evaluating the effects of the spin and magnetic
+moment of objects around supermassive and intermediate-mass black holes.",2308.05392v1
+2011-07-01,Slow magnetic dynamics and hysteresis loops of a bulk ferromagnet,"Magnetic dynamics of a bulk ferromagnet, a new single crystalline compound
+Co7(TeO3)4Br6, was studied by ac susceptibility and the related techniques.
+Very large Arrhenius activation energy of 17.2 meV (201 K) and long attempt
+time (2x10^(-4)s) span the full spectrum of magnetic dynamics inside a
+convenient frequency window, offering a rare opportunity for general studies of
+magnetic dynamics. Within the experimental window the ac susceptibility data
+build almost ideally semicircular Cole-Cole plots. Comprehensive study of
+experimental dynamic hysteresis loops of the compound is presented and
+interpreted within a simple thermal-activation-assisted spin lattice relaxation
+model for spin reversal. Quantitative agreement between the experimental
+results and the model's prediction for dynamic coercive field is achieved by
+assuming the central physical quantity, the Debye relaxation rate, to depend on
+frequency, as well as on the applied field strength and sample temperature.
+Cross-over between minor- to major hysteresis loops is carefully analyzed.
+Low-frequency limitations of the model, relying on domain wall pinning effects,
+are experimentally detected and appropriately discussed.",1107.0255v2
+2013-06-04,Dynamic susceptibility and dynamic correlations in spin ice,"Here we calculate the dynamic susceptibility and dynamic correlation function
+in spin ice using the model of emergent magnetic monopoles. Calculations are
+based on a method originally suggested for the description of dynamic processes
+in water ice (non-equilibrium thermodynamics approach). We show that for zero
+temperature the dynamic correlation function reproduces the transverse dipole
+correlations (static correlation function) characteristic of spin ice in its
+ground state. At non-zero temperatures the dynamic correlation function
+includes an additional longitudinal component which decreases as the
+temperature decreases. Both terms (transverse and longitudinal) exhibit
+identical Debye-like dependences on frequency but with different relaxation
+times: the magnetic Coulomb interaction of monopoles reduces the longitudinal
+relaxation time with respect to the transverse one. We calculate the dielectric
+function for the magnetic monopole gas and discuss how the non-equilibrium
+thermodynamics approach exposes corrections to the Debye-Huckel theory of
+magnetic monopoles and the concept of ""entropic charge"".",1306.0653v1
+2023-10-20,Heat equation from a deterministic dynamics,"We derive the heat equation for the thermal energy under diffusive space-time
+scaling for a purely deterministic microscopic dynamics satisfying Newton
+equations perturbed by an external chaotic force acting like a magnetic field.",2310.13338v2
+2022-01-11,Coronal magnetic field evolution over the cycle 24,"The photospheric magnetic field vector is continuously derived from
+measurements, while reconstruction of the three-dimensional (3D) coronal
+magnetic field requires modelling with photospheric measurements as a boundary
+condition. For decades the cycle variation of the magnetic field in the
+photosphere has been investigated. To present, there is no study to show the
+evolution of the coronal magnetic flux in the corona, nor the evolution of
+solar cycle magnetic free energy. The paper aims to analyze the temporal
+variation of the magnetic field and free magnetic energy in the solar corona
+for the solar cycle 24 and how the magnetic field behaves in the two
+hemispheres. We investigate if we can obtain better estimates of the magnetic
+field at Earth using the nonlinear force-free field (NLFFF) extrapolation
+method. To model the magnetic field over cycle 24 we apply the NLFFF
+optimization method to the synoptic vector magnetic maps derived from the
+observations of Heliospheric and Magnetic Imager (HMI) onboard Solar Dynamic
+Observatory (SDO). We found that during the solar cycle 24, the maximum of the
+Sun's dynamics is different from the sunspot number (SSN) maximum peak. The
+major contribution to the total unsigned flux is provided by the flux coming
+from the magnetic field structures other than sunspots (MSOS) within latitudes
+between -30 and +30 degrees. The magnetic flux variation during the solar cycle
+24 shows a different evolution in the corona than in the photosphere. We found
+a correlation value of 0.8 between the derived magnetic energy from our model
+and the flare energy index derived from observations. On average, cycle 24 had
+a higher number of sunspots in the northern hemisphere (NH) but stronger flux
+in the southern hemisphere (SH) which could more effectively reach the higher
+layers of the atmosphere. The coupling between the hemispheres increases with
+height.",2201.03853v1
+2022-07-04,Three-dimensional decaying magnetic field belonging to Beltrami flow,"This study analysed a three-dimensional Taylor decaying vortex under an
+applied magnetic field as a benchmark test problem to verify the calculation
+method of an electromagnetic fluid flow and investigated the validity of the
+decaying magnetic field model. First, we observed the flow structure of a
+three-dimensional Taylor decaying vortex without an applied magnetic field. We
+investigated the changes in the error between the calculation result and the
+exact solution when the number of grid points and the Reynolds number varied
+and showed the effectiveness of the benchmark test. Next, we analysed a
+three-dimensional Taylor decaying vortex under an applied magnetic field and
+clarified the characteristics of the decaying magnetic field. When a magnetic
+field is applied, low magnetic pressure regions are connected in a mesh
+pattern, and the magnetic pressure distribution with a distorted cubic
+structure occurs to surround a high magnetic pressure region. In a stagnation
+region, the magnetic energy becomes low, and the magnetic flux line is similar
+to the streamline of the velocity field. High current densities occur in a grid
+pattern, and the magnetic flux lines swirl around the high current density
+region. The magnetic pressure and magnetic energy are high in the high current
+density region. When the Reynolds number and the magnetic Reynolds number vary,
+the decay trends of various energies agree well with the exact solution. The
+transition to turbulent flow occurs at a high Reynolds number, and the kinetic
+and total energies decrease rapidly. After the dissipation rate of kinetic
+energy becomes maximum, the vortex structure decays, and the flow field
+approaches a stationary state without magnetic fields. The three-dimensional
+Taylor decaying magnetic field belonging to the Beltrami flow is a valuable
+model for verifying the calculation method of electromagnetic fluid flows.",2207.01154v3
+1995-09-22,Critical Dynamics of Magnets,"We review our current understanding of the critical dynamics of magnets above
+and below the transition temperature with focus on the effects due to the
+dipole--dipole interaction present in all real magnets. Significant progress in
+our understanding of real ferromagnets in the vicinity of the critical point
+has been made in the last decade through improved experimental techniques and
+theoretical advances in taking into account realistic spin-spin interactions.
+We start our review with a discussion of the theoretical results for the
+critical dynamics based on recent renormalization group, mode coupling and spin
+wave theories. A detailed comparison is made of the theory with experimental
+results obtained by different measuring techniques, such as neutron scattering,
+hyperfine interaction, muon--spin--resonance, electron--spin--resonance, and
+magnetic relaxation, in various materials. Furthermore we discuss the effects
+of dipolar interaction on the critical dynamics of three--dimensional isotropic
+antiferromagnets and uniaxial ferromagnets. Special attention is also paid to a
+discussion of the consequences of dipolar anisotropies on the existence of
+magnetic order and the spin--wave spectrum in two--dimensional ferromagnets and
+antiferromagnets. We close our review with a formulation of critical dynamics
+in terms of nonlinear Langevin equations.",9509141v1
+2004-08-04,Conservation laws for the voter model in complex networks,"We consider the voter model dynamics in random networks with an arbitrary
+distribution of the degree of the nodes. We find that for the usual node-update
+dynamics the average magnetization is not conserved, while an average
+magnetization weighted by the degree of the node is conserved. However, for a
+link-update dynamics the average magnetization is still conserved. For the
+particular case of a Barabasi-Albert scale-free network the voter model
+dynamics leads to a partially ordered metastable state with a finite size
+survival time. This characteristic time scales linearly with system size only
+when the updating rule respects the conservation law of the average
+magnetization. This scaling identifies a universal or generic property of the
+voter model dynamics associated with the conservation law of the magnetization.",0408101v1
+2010-01-14,Interaction quench dynamics in the Kondo model in presence of a local magnetic field,"In this work we investigate the quench dynamics in the Kondo model on the
+Toulouse line in presence of a local magnetic field. It is shown that this
+setup can be realized by either applying the local magnetic field directly or
+by preparing the system in a macroscopically spin-polarized initial state. In
+the latter case, the magnetic field results from a subtlety in applying the
+bosonization technique where terms that are usually referred to as finite-size
+corrections become important in the present non-equilibrium setting. The
+transient dynamics is studied by analyzing exact analytical results for the
+local spin dynamics. The time scale for the relaxation of the local dynamical
+quantities turns out to be exclusively determined by the Kondo scale. In the
+transient regime, one observes damped oscillations in the local correlation
+functions with a frequency set by the magnetic field.",1001.2418v2
+2011-12-09,Influence of crystal anisotropy on the critical state stability and flux jumps dynamics in a single crystal of La(1.85)Sr(0.15)CuO(4),"We studied the critical state stability in a large cubic sample of a single
+crystalline La(1.85)Sr(0.15)CuO(4) for different sample orientations with
+respect to the external magnetic field as well as the dynamics of the flux
+jumps. It is shown that thermomagnetic avalanches develop in dynamic conditions
+characterized by significantly lower magnetic diffusivity than the thermal one.
+In this case, critical state stability depends strongly on cooling conditions.
+We compared predictions of the isothermal model and of the model for the weakly
+cooled sample with experimental results. In both models, the field of the first
+flux jump decreases with an increase of sweep rate of the external magnetic
+field. We also investigated the influence of external magnetic field on the
+dynamics of the following stages of the thermomagnetic avalanche. It is shown
+that the dynamics of the flux jumps is correlated with the magnetic diffusivity
+proportional to the flux flow resistivity.",1112.2111v1
+2013-12-27,Spin Transfer Torque and Electric Current in Helical Edge States in Quantum Spin Hall Devices,"We study the dynamics of a quantum spin Hall edge coupled to a magnet with
+its own dynamics. Using spin transfer torque principles, we analyze the
+interplay between spin currents in the edge state and dynamics of the axis of
+the magnet, and draw parallels with circuit analogies. As a highlighting
+feature, we show that while coupling to a magnet typically renders the edge
+state insulating by opening a gap, in the presence of a small potential bias,
+spin-transfer torque can restore perfect conductance by transferring angular
+momentum to the magnet. In the presence of interactions within the edge state,
+we employ a Luttinger liquid treatment to show that the edge, when subject to a
+small voltage bias, tends to form a unique dynamic rotating spin wave state
+that naturally couples into the dynamics of the magnet. We briefly discuss
+realistic physical parameters and constraints for observing this interplay
+between quantum spin Hall and spin-transfer torque physics.",1312.7303v1
+2014-04-12,Dynamical magnetic skyrmions,"Spin transfer torque (STT) affords magnetic nanodevices the potential to act
+as memory, computing, and microwave elements operating at ultra-low currents
+and at a low energy cost. Spin transfer torque is not only effective in
+manipulating well-known magnetic structures, such as domain walls and vortices,
+but can also nucleate previously unattainable nano-magnetic objects, such as
+magnetic droplets and skyrmions. While the droplet and the skyrmion are both
+solitons, the former is inherently dynamic and non-topological, whereas the
+latter is static but topologically protected. Here we show that it is possible
+to combine these properties into a novel topologically protected dynamical
+skyrmion, which adds additional degrees of freedom, and functionality, to both
+droplet and skyrmion based applications. Unlike static skyrmions, the dynamical
+skyrmion can be nucleated and sustained without Dzyaloshinskii-Moriya
+interaction (DMI) or dipole-dipole interaction (DDI), and is a generic soliton
+solution independent of STT and damping once nucleated. In the presence of
+large DMI, the dynamical skyrmion experiences strong breathing with particular
+promise for skyrmion-based memory and microwave applications.",1404.3281v2
+2014-11-27,Short-Time Dynamics of Fe2/V13 Magnetic Superlattice Models,"Critical relaxation from a low-temperature fully ordered state of Fe2/V13
+iron-vanadium magnetic superlattice models has been studied using the method of
+short-time dynamics. Systems with three variants of the ratio R of inter- to
+intralayer exchange coupling have been considered. Particles with N = 262144
+spins have been simulated with periodic boundary conditions. Calculations have
+been performed using the standard Metropolis algorithm of the Monte Carlo
+method. The static critical exponents of magnetization and correlation radius,
+as well as the dynamic critical exponent, have been calculated for three R
+values. It is established that a small decrease in the exchange ratio (from R =
+1.0 to 0.8) does not significantly influence the character of the short-time
+dynamics in the models studied. A further significant decrease in this ratio
+(to R = 0.01), for which a transition from three-dimensional to
+quasi-twodimensional magnetism is possible, leads to significant changes in the
+dynamic behavior of iron-vanadium magnetic superlattice models.",1411.7546v1
+2014-12-11,Deviation From the Landau-Lifshitz-Gilbert equation in the Inertial regime of the Magnetization,"We investigate in details the inertial dynamics of a uniform magnetization in
+the ferromagnetic resonance (FMR) context. Analytical predictions and numerical
+simulations of the complete equations within the Inertial
+Landau-Lifshitz-Gilbert (ILLG) model are presented. In addition to the usual
+precession resonance, the inertial model gives a second resonance peak
+associated to the nutation dynamics provided that the damping is not too large.
+The analytical resolution of the equations of motion yields both the precession
+and nutation angular frequencies. They are function of the inertial dynamics
+characteristic time $\tau$, the dimensionless damping $\alpha$ and the static
+magnetic field $H$. A scaling function with respect to $\alpha\tau\gamma H$ is
+found for the nutation angular frequency, also valid for the precession angular
+frequency when $\alpha\tau\gamma H\gg 1$. Beyond the direct measurement of the
+nutation resonance peak, we show that the inertial dynamics of the
+magnetization has measurable effects on both the width and the angular
+frequency of the precession resonance peak when varying the applied static
+field. These predictions could be used to experimentally identify the inertial
+dynamics of the magnetization proposed in the ILLG model.",1412.3783v1
+2015-03-23,Local dynamics of topological magnetic defects in the itinerant helimagnet FeGe,"Chiral magnetic interactions induce complex spin textures including helical
+and conical spin waves, as well as particle-like objects such as magnetic
+skyrmions and merons. These spin textures are the basis for innovative device
+paradigms and give rise to exotic topological phenomena, thus being of interest
+for both applied and fundamental sciences. Present key questions address the
+dynamics of the spin system and emergent topological defects. Here we analyze
+the micromagnetic dynamics in the helimagnetic phase of FeGe. By combining
+magnetic force microscopy, single-spin magnetometry, and
+Landau-Lifschitz-Gilbert simulations we show that the nanoscale dynamics are
+governed by the depinning and subsequent motion of magnetic edge dislocations.
+The motion of these topologically stable objects triggers perturbations that
+can propagate over mesoscopic length scales. The observation of stochastic
+instabilities in the micromagnetic structure provides new insight to the
+spatio-temporal dynamics of itinerant helimagnets and topological defects, and
+discloses novel challenges regarding their technological usage.",1503.06622v2
+2016-05-04,On the magnetism and dynamics of prominence legs hosting tornadoes,"Solar tornadoes are dark vertical filamentary structures observed in the
+extreme ultraviolet associated with prominence legs and filament barbs. Their
+true nature and relationship to prominences requires understanding their
+magnetic structure and dynamic properties. Recently, a controversy has arisen:
+is the magnetic field organized forming vertical, helical structures or is it
+dominantly horizontal? And concerning their dynamics, are tornadoes really
+rotating or is it just a visual illusion? Here, we analyze four consecutive
+spectropolarimetric scans of a prominence hosting tornadoes on its legs which
+help us shed some light on their magnetic and dynamical properties. We show
+that the magnetic field is very smooth in all the prominence, probably an
+intrinsic property of the coronal field. The prominence legs have vertical
+helical fields that show slow temporal variation probably related to the motion
+of the fibrils. Concerning the dynamics, we argue that 1) if rotation exists,
+it is intermittent, lasting no more than one hour, and 2) the observed velocity
+pattern is also consistent with an oscillatory velocity pattern (waves).",1605.01183v1
+2016-06-22,Thermally induced magnetic relaxation in square artificial spin ice,"The properties of natural and artificial assemblies of interacting elements,
+ranging from Quarks to Galaxies, are at the heart of Physics. The collective
+response and dynamics of such assemblies are dictated by the intrinsic
+dynamical properties of the building blocks, the nature of their interactions
+and topological constraints. Here we report on the relaxation dynamics of the
+magnetization of artificial assemblies of mesoscopic spins. In our model
+nano-magnetic system - square artificial spin ice - we are able to control the
+geometrical arrangement and interaction strength between the magnetically
+interacting building blocks by means of nano-lithography. Using time resolved
+magnetometry we show that the relaxation process can be described using the
+Kohlrausch law and that the extracted temperature dependent relaxation times of
+the assemblies follow the Vogel-Fulcher law. The results provide insight into
+the relaxation dynamics of mesoscopic nano-magnetic model systems, with
+adjustable energy and time scales, and demonstrates that these can serve as an
+ideal playground for the studies of collective dynamics and relaxations.",1606.06899v1
+2016-07-10,Magnetic Hamiltonian Monte Carlo,"Hamiltonian Monte Carlo (HMC) exploits Hamiltonian dynamics to construct
+efficient proposals for Markov chain Monte Carlo (MCMC). In this paper, we
+present a generalization of HMC which exploits \textit{non-canonical}
+Hamiltonian dynamics. We refer to this algorithm as magnetic HMC, since in 3
+dimensions a subset of the dynamics map onto the mechanics of a charged
+particle coupled to a magnetic field. We establish a theoretical basis for the
+use of non-canonical Hamiltonian dynamics in MCMC, and construct a symplectic,
+leapfrog-like integrator allowing for the implementation of magnetic HMC.
+Finally, we exhibit several examples where these non-canonical dynamics can
+lead to improved mixing of magnetic HMC relative to ordinary HMC.",1607.02738v2
+2017-06-23,Dynamic Simulation of Structural Phase Transitions in Magnetic Iron,"The occurrence of bcc-fcc ($\alpha$-$\gamma$) and fcc-bcc ($\gamma$-$\delta$)
+phase transitions in magnetic iron stems from the interplay between magnetic
+excitations and lattice vibrations. However, this fact has never been proven by
+a direct dynamic simulation, treating non-collinear magnetic fluctuations and
+dynamics of atoms, and their coupling at a finite temperature. Starting from a
+large set of data generated by ab initio simulations, we derive non-collinear
+magnetic many-body potentials for bcc and fcc iron describing fluctuations in
+the vicinity of near perfect lattice positions. We then use spin-lattice
+dynamics simulations to evaluate the difference between free energies of bcc
+and fcc phases, assessing their relative stability within a unified dynamic
+picture. We find two intersections between the bcc and fcc free energy curves,
+which correspond to $\alpha$-$\gamma$ bcc-fcc and $\gamma$-$\delta$ fcc-bcc
+phase transitions. The maximum fcc-bcc free energy difference over the
+temperature interval between the two phase transition points is 2 meV, in
+agreement with other experimental and theoretical estimates.",1706.07635v1
+2018-03-20,Does the chiral magnetic effect change the dynamic universality class in QCD?,"In QCD matter under an external magnetic field, the chiral magnetic effect
+(CME) leads to the collective gapless mode called the chiral magnetic wave
+(CMW). Since dynamic universality class generally depends on low-energy gapless
+modes, it is nontrivial whether the CME and the resulting CMW change that of
+the second-order chiral phase transition in QCD. To address this question, we
+study the critical dynamics near the chiral phase transition in massless
+two-flavor QCD under an external magnetic field. By performing the dynamic
+renormalization-group analysis within the epsilon expansion, we find that the
+presence of the CME changes the dynamic universality class to that of model A.
+We also show that the transport coefficient of the CME is not renormalized by
+the critical fluctuations of the order parameter.",1803.07267v2
+2018-10-10,Magnetization Dynamics,"Magnetism primarily describes the physics and materials science of systems
+presenting a magnetization -- a macroscopic order parameter characterizing
+electron angular momentum. The order parameter is associated with the
+electronic exchange interactions, which is fundamentally quantum mechanical.
+Its dynamic behavior bridges the macroscopic and the microscopic worlds. On
+macroscopic length and time-scales, it interacts with electromagnetic fields
+dictated by the Maxwells equations. On a microscopic scale, it involves the
+quantum-mechanical electronic states both in spin-space and momentum space,
+thus giving rise to a wide range of behavior that extend down to femtoseconds.
+Thanks to the development of modern metrology, there have been many new and
+noteworthy observations of magnetism-related phenomena across the entire range
+-- from spin-torque induced antidamping dynamics, to ultrafast laser induced
+femtosecond electron dynamics that involve spin current and angular momentum
+conservation. In this review we introduce some observations on magnetodynamics,
+and the scientific subjects these new results give rise to.",1810.04591v1
+2018-12-20,Tunable Angle Dependent Magnetization Dynamics in Ni80Fe20 Nano-cross Structures of Varying Size,"We demonstrate a large angular dependence of magnetization dynamics in
+Ni80Fe20 nano-cross arrays of varying sizes. By subtle variation of the
+azimuthal angle of an in-plane bias magnetic field, the spin configuration and
+the ensuing spin-wave dynamics, including mode softening, mode splitting, mode
+crossover and mode merging, can be drastically varied to the extent that a
+frequency minimum corresponding to mode softening converts to a mode crossover,
+various mode splitting and mode crossover disappear and additional mode
+splitting appears. Numerically simulated spin-wave spectra and phase profiles
+revealed the nature of various spin-wave modes and the origin of above
+variation of the dynamics with bias-field angle. All of these above
+observations are further modified with the variation of dimensions of the
+nano-cross. The numerically calculated magnetostatic field distributions
+further supports the variation of dynamics with bias-field angle. These results
+open a new avenue for engineering the nano-cross based magnetic devices such as
+magnetic storage, spin-wave logic and on-chip data communication devices.",1812.08393v1
+2021-07-23,Anomalous magnetic noise in imperfect flat bands in the topological magnet Dy2Ti2O7,"The spin ice compound Dy_2Ti_2O_7 stands out as the first topological magnet
+in three dimensions, with its tell-tale emergent fractionalized magnetic
+monopole excitations. Its real-time dynamical properties have been an enigma
+from the very beginning. Using ultrasensitive, non-invasive SQUID measurements,
+we show that Dy_2Ti_2O_7 exhibits a highly anomalous noise spectrum, in three
+qualitatively different regimes: equilibrium spin ice, a `frozen' regime
+extending to ultra-low temperatures, as well as a high-temperature `anomalous'
+paramagnet. We show that in the simplest model of spin ice, the dynamics is not
+anomalous, and we present several distinct mechanisms which give rise to a
+coloured noise spectrum. In addition, we identify the structure of the
+single-ion dynamics as a crucial ingredient for any modelling. Thus, the
+dynamics of spin ice Dy_2Ti_2O_7 reflects the interplay of local dynamics with
+emergent topological degrees of freedom and a frustration-generated imperfectly
+flat energy landscape, and as such should be relevant for a broad class of
+magnetic materials.",2107.11379v1
+2021-07-24,Electron-Phonon Scattering governs both Ultrafast and Precessional Magnetization Dynamics in Co-Fe Alloys,"Recent investigations have advanced the understanding of how
+structure-property relationships in ferromagnetic metal alloys affect the
+magnetization dynamics on nanosecond time-scales. A similar understanding for
+magnetization dynamics on femto- to pico-second time-scales does not yet exist.
+To address this, we perform time-resolved magneto optic Kerr effect (TRMOKE)
+measurements of magnetization dynamics in Co-Fe alloys on femto- to nano-second
+regimes. We show that Co-Fe compositions that exhibit low Gilbert damping
+parameters also feature prolonged ultrafast demagnetization upon
+photoexcitation. We analyze our experimental TR-MOKE data with the
+three-temperature-model (3TM) and the Landau-Lifshitz-Gilbert equation. These
+analyses reveal a strong compositional dependence of the dynamics across all
+time-scales on the strength of electron-phonon interactions. Our findings are
+beneficial to the spintronics and magnonics community, and will aid in the
+quest for energy-efficient magnetic storage applications.",2107.11699v1
+2023-11-28,Machine learning force-field models for metallic spin glass,"Metallic spin glass systems, such as dilute magnetic alloys, are
+characterized by randomly distributed local moments coupled to each other
+through a long-range electron-mediated effective interaction. We present a
+scalable machine learning (ML) framework for dynamical simulations of metallic
+spin glasses. A Behler-Parrinello type neural-network model, based on the
+principle of locality, is developed to accurately and efficiently predict
+electron-induced local magnetic fields that drive the spin dynamics. A crucial
+component of the ML model is a proper symmetry-invariant representation of
+local magnetic environment which is direct input to the neural net. We develop
+such a magnetic descriptor by incorporating the spin degrees of freedom into
+the atom-centered symmetry function methods which are widely used in ML
+force-field models for quantum molecular dynamics. We apply our approach to
+study the relaxation dynamics of an amorphous generalization of the s-d model.
+Our work highlights the promising potential of ML models for large-scale
+dynamical modeling of itinerant magnets with quenched disorder.",2311.16964v1
+2016-06-01,Large Deviations of the Finite-Time Magnetization of the Curie-Weiss Random Field Ising Model,"We study the large deviations of the magnetization at some finite time in the
+Curie-Weiss Random Field Ising Model with parallel updating. While relaxation
+dynamics in an infinite time horizon gives rise to unique dynamical
+trajectories (specified by initial conditions and governed by first-order
+dynamics of the form $m_{t+1}=f(m_t)$), we observe that the introduction of a
+finite time horizon and the specification of terminal conditions can generate a
+host of metastable solutions obeying \textit{second-order} dynamics. We show
+that these solutions are governed by a Newtonian-like dynamics in discrete time
+which permits solutions in terms of both the first order relaxation (""forward"")
+dynamics and the backward dynamics $m_{t+1} = f^{-1}(m_t)$. Our approach allows
+us to classify trajectories for a given final magnetization as stable or
+metastable according to the value of the rate function associated with them. We
+find that in analogy to the Freidlin-Wentzell description of the stochastic
+dynamics of escape from metastable states, the dominant trajectories may switch
+between the two types (forward and backward) of first-order dynamics.",1606.00316v1
+2004-07-28,Gamma-ray burst internal shocks with magnetization,"(Please note that the abstract has been significantly shorted) We investigate
+Gamma-ray Burst (GRB) internal shocks with moderate magnetization, with the
+magnetization parameter $\sigma$ ranging from 0.001 to 10. Possible magnetic
+dissipation in the stripped magnetized shells is also taken into account
+through introducing a parameter $k$ ($0<k\leq 1$), which is the ratio of the
+electric field strength of the downstream and the upstream. By solving the
+general MHD jump conditions, we show that the dynamic evolution of the shock
+with magnetic dissipation is different from the familiar one obtained in the
+ideal MHD limit. In view of the possible high degree of linear polarization of
+GRB 021206 and the identification of a possible highly magnetized flow in GRB
+990123 and GRB 021211, we suggest that a mildly magnetized internal shock model
+($0.01<\sigma<1$) with moderate magnetic dissipation is a good candidate to
+explain the GRB prompt emission data.",0407581v2
+2005-12-14,Turbulent Origin of the Galactic-Center Magnetic Field: Nonthermal Radio Filaments,"A great deal of study has been carried out over the last twenty years on the
+origin of the magnetic activity in the Galactic center. One of the most popular
+hypotheses assumes milli-Gauss magnetic field with poloidal geometry, pervading
+the inner few hundred parsecs of the Galactic-center region. However, there is
+a growing observational evidence for the large-scale distribution of a much
+weaker field of B \lesssim 10 micro G in this region. Here, we propose that the
+Galactic-center magnetic field originates from turbulent activity that is known
+to be extreme in the central hundred parsecs. In this picture the spatial
+distribution of the magnetic field energy is highly intermittent, and the
+regions of strong field have filamentary structures. We propose that the
+observed nonthermal radio filaments appear in (or, possibly, may be identified
+with) such strongly magnetized regions. At the same time, the large-scale
+diffuse magnetic field is weak. Both results of our model can explain the
+magnetic field measurements of the the Galactic-center region. In addition, we
+discuss the role of ionized outflow from stellar clusters in producing the long
+magnetized filaments perpendicular to the Galactic plane.",0512373v1
+2001-05-31,Dynamic Oscillations of Magnetization in High Spin Magnetic Clusters,"We have studied the time evolution of magnetization of a high spin magnetic
+cluster in the ground state, in the presence of a sinusoidal axial magnetic
+field and a static transverse field by explicitly solving time dependent
+schr\""odinger equation. We observe oscillations of magnetization in the plateau
+region which has all the characteristics reminiscent of the oscillation of
+probability of occupation of a state in a two level lattice in the presence of
+an oscillating electric field. The high spin of the ground state leads to a
+large but finite two-level pseudo-lattice. The oscillations in magnetization
+occur at amplitude of magnetic fields achievable in a laboratory and they also
+persist for a wide range of spin-dipolar interactions.
+  Thus, our study provides a magnetic analog of the optical two-level lattice.",0105616v1
+2004-09-20,Switching of magnetization by non-linear resonance studied in single nanoparticles,"Magnetization reversal in magnetic particles is one of the fundamental issues
+in magnetic data storage. Technological improvements require the understanding
+of dynamical magnetization reversal processes at nanosecond time scales. New
+strategies are needed to overcome current limitations. For example, the problem
+of thermal stability of the magnetization state (superparamagnetic limit) can
+be pushed down to smaller particle sizes by increasing the magnetic anisotropy.
+High fields are then needed to reverse the magnetization that are difficult to
+achieve in current devices. Here we propose a new method to overcome this
+limitation. A constant applied field, well below the switching field, combined
+with a radio-frequency (RF) field pulse can reverse the magnetization of a
+nanoparticle. The efficiency of this method is demonstrated on a 20 nm cobalt
+particle by using the micro-SQUID technique. Other applications of this method
+might be nucleation or depinning of domain walls.",0409502v1
+2005-05-06,Relaxation of thermo-remanent magnetization in Fe-Cr GMR multilayers,"The time decay of the thermo-remanent magnetization (TRM) in Fe-Cr giant
+magnetoresistive (GMR) multilayers has been investigated. The magnetization in
+these multilayers relaxes as a function of time after being cooled in a small
+magnetic field of 100 Oe to a low temperature and then the magnetic field is
+switched off. Low-field ($<$ 500 Oe) magnetization studies of these samples
+have shown hysteresis. This spin-glass-like behavior may originate from
+structural imperfections at the interfaces and in the bulk. We find that the
+magnetization relaxation is logarithmic. Here the magnetic viscosity is found
+to increase first with increasing temperature, then it reaches a maximum around
+T$_g$, and then it decreases with increasing temperature. This behavior is
+different from that of conventional spin glasses where the logarithmic creep
+rate is observed to increase with temperature. Power law also gives good fits
+and it is better than the logarithmic fit at higher temperatures. The dynamical
+effects of these multilayers are related to the relaxation of thermally blocked
+superparamagnetic grains and magnetic domains in the film layers.",0505145v1
+2007-11-13,Dynamics of charged dust particles in protoplanetary discs,"We study the effect of an imposed magnetic field on the motion of charged
+dust particles in magnetically active regions of a protoplanetary disc.
+Assuming a power law structure for the vertical and the toroidal components of
+the magnetic field for the regions beyond magnetically dead region of the disc,
+the radial and the vertical velocities of the charged particles, in the
+asymptotic case of small particles, are calculated analytically. While grains
+with radii smaller than a critical radius significantly are affected by the
+magnetic force, motion of the particles with larger radii is independent of the
+magnetic field. The critical radius depends on the magnetic geometry and the
+charge of the grains. Assuming that a grain particle has one elementary charge
+and the physical properties of the disc correspond to a minimum-mass solar
+nebula, we show that only micron-sized grains are affected by the magnetic
+force. Also, charge polarity determines direction of the radial velocity. For
+such small particles, both the radial and the vertical velocities increase due
+to the magnetic force.",0711.2090v2
+2007-12-15,Magnetized Ekman Layer and Stewartson Layer in a Magnetized Taylor-Couette Flow,"In this paper we present axisymmetric nonlinear simulations of magnetized
+Ekman and Stewartson layers in a magnetized Taylor-Couette flow with a
+centrifugally stable angular-momemtum profile and with a magnetic Reynolds
+number below the threshold of magnetorotational instability. The magnetic field
+is found to inhibit the Ekman suction. The width of the Ekman layer is reduced
+with increased magnetic field normal to the end plate. A uniformly-rotating
+region forms near the outer cylinder. A strong magnetic field leads to a steady
+Stewartson layer emanating from the junction between differentially rotating
+rings at the endcaps. The Stewartson layer becomes thinner with larger Reynolds
+number and penetrates deeper into the bulk flow with stronger magnetic field
+and larger Reynolds number. However, at Reynolds number larger than a critical
+value $\sim 600$, axisymmetric, and perhaps also nonaxisymmetric, instabilities
+occur and result in a less prominent Stewartson layer that extends less far
+from the boundary.",0712.2543v2
+2008-06-18,Selective Heating Mechanism of Magnetic Metal Oxides by Alternating Magnetic Field in Microwave Sintering Process,"The mechanism of rapid and selective heating of magnetic metal oxides under
+the magnetic field of microwaves which continues beyond the Curie temperature $
+T_{c} $ is identified by using the Heisenberg model. Monte Carlo calculations
+based on the energy principle show that such heating is caused by non-resonant
+response of electron spins in the unfilled 3d shell to the wave magnetic field.
+Small spin reorientation thus generated leads to a large internal energy change
+through the exchange interactions between spins, which becomes maximal around $
+T_{c} $ for magnetite $ {\rm Fe}_{3}{\rm O}_{4} $. The dissipative spin
+dynamics simulation yields the imaginary part of the magnetic susceptibility,
+which becomes largest around $ T_{c} $ and for the microwave frequency around 2
+GHz. Hematite $ {\rm Fe}_{2}{\rm O}_{3} $ with weak spontaneous magnetization
+responds much less to microwaves as observed in experiments. The heating of
+titanium oxide by microwave magnetic field only when oxygen defects are present
+is also explained by our theory in terms of the absence of spontaneous
+magnetization.",0806.3055v3
+2008-11-29,Magnetic fingerprints of solar and stellar oscillations,"Waves connect all the layers of the Sun, from its interior to the upper
+atmosphere. It is becoming clear now the important role of magnetic field on
+the wave propagation. Magnetic field modifies propagation speed of waves, thus
+affecting the conclusions of helioseismological studies. It can change the
+direction of the wave propagation, help channeling them straight up to the
+corona, extending the dynamic and magnetic couplings between all the layers.
+Modern instruments provide measurements of complex patterns of oscillations in
+solar active regions and of tiny effects such as temporal oscillations of the
+magnetic field. The physics of oscillations in a variety of magnetic structures
+of the Sun is similar to that of pulsations of stars that posses strong
+magnetic fields, such as roAp stars. All these arguments point toward a need of
+systematic self-consistent modeling of waves in magnetic structures that is
+able to take into account the complexity of the magnetic field configurations.
+In this paper, we describe simulations of this kind, summarize our recent
+findings and bring together results from the theory and observations.",0812.0042v1
+2010-10-29,Nonlinear dynamos at infinite magnetic Prandtl number,"The dynamo instability is investigated in the limit of infinite magnetic
+Prandtl number. In this limit the fluid is assumed to be very viscous so that
+the inertial terms can be neglected and the flow is slaved to the forcing. The
+forcing consist of an external forcing function that drives the dynamo flow and
+the resulting Lorentz force caused by the back reaction of the magnetic field.
+The flows under investigation are the Archontis flow, and the ABC flow forced
+at two different scales. The investigation covers roughly three orders of
+magnitude of the magnetic Reynolds number above onset. All flows show a weak
+increase of the averaged magnetic energy as the magnetic Reynolds number is
+increased. Most of the magnetic energy is concentrated in flat elongated
+structures that produce a Lorentz force with small solenoidal projection so
+that the resulting magnetic field configuration was almost force-free. Although
+the examined system has zero kinetic Reynolds number at sufficiently large
+magnetic Reynolds number the structures are unstable to small scale
+fluctuations that result in a chaotic temporal behavior.",1010.6276v1
+2011-05-31,Magnetic field dependence of the quantum tunneling of normal-superconductor interfaces in a type-I Pb superconductor,"We report experimental evidence of the effect of an applied magnetic field on
+the non-thermal magnetic relaxation in a disk-shaped type-I lead
+superconductor. The time evolution of the irreversible magnetization proves to
+be logarithmic for a wide range of temperatures and magnetic field values along
+the descending branch of the hysteresis cycle. When the intensity of the
+magnetic field increases, the crossover temperature separating the thermal and
+non-thermal regimes of magnetic relaxation is found to decrease, whereas the
+rate at which such relaxation occurs is observed to increase. These results are
+discussed in the framework of a recent model for quantum tunneling of
+normal-superconductor interfaces through the distribution of pinning energy
+barriers generated by structural defects in the sample, considering that the
+strength of the barriers decreases with the magnetic field. A phase diagram
+describing the dynamics of interfaces during flux expulsion in the intermediate
+state as a function of temperature and magnetic field is constructed.",1105.6222v1
+2012-06-22,The MiMeS Survey of Magnetism in Massive Stars,"The Magnetism in Massive Stars (MiMeS) survey represents a high precision
+systematic search for magnetic fields in hot, massive OB stars. To date, MiMeS
+Large Programs (ESPaDOnS@CFHT, Narval@TBL, HARPSpol@ESO3.6) and associated PI
+programs (FORS@VLT) have yielded nearly 1200 circular spectropolarimetric
+observations of over 350 OB stars. Within this sample, 20 stars are detected as
+magnetic. Follow-up observations of new detections reveals (i) a large
+diversity of magnetic properties, (ii) evidence for magnetic wind confinement
+in optical spectra of all magnetic O stars, (iii) the presence of strong,
+organized magnetic fields in all known Galactic Of?p stars, and (iv) a complete
+absence of magnetic fields in classical Be stars.",1206.5163v2
+2012-08-26,Thermal Stability of the Magnetization in Perpendicularly Magnetized Thin Film Nanomagnets,"Understanding the stability of thin film nanomagnets with perpendicular
+magnetic anisotropy (PMA) against thermally induced magnetization reversal is
+important when designing perpendicularly magnetized patterned media and
+magnetic random access memories. The leading-order dependence of magnetization
+reversal rates are governed by the energy barrier the system needs to surmount
+in order for reversal to proceed. In this paper we study the reversal dynamics
+of these systems and compute the relevant barriers using the string method of
+E, Vanden-Eijnden, and Ren. We find the reversal to be often spatially
+incoherent; that is, rather than the magnetization flipping as a rigid unit,
+reversal proceeds instead through a soliton-like domain wall sweeping through
+the system. We show that for square nanomagnetic elements the energy barrier
+increases with element size up to a critical length scale, beyond which the
+energy barrier is constant. For circular elements the energy barrier continues
+to increase indefinitely, albeit more slowly beyond a critical size. In both
+cases the energy barriers are smaller than those expected for coherent
+magnetization reversal.",1208.5233v1
+2013-07-12,MHD Shock-Clump Evolution with Self-Contained Magnetic Fields,"We study the interaction of strong shock waves with magnetized clumps.
+Previous numerical work focused on the simplified scenario in which shocked
+clumps are immersed in a globally uniform magnetic field that extends through
+both the clump and the ambient medium. Here we consider the complementary
+circumstance in which the field is completely self-contained within the clumps.
+This could arise naturally during clump formation via dynamical or thermal
+instabilities for example as magnetic field pinches off from the ambient
+medium. Using our AMR MHD code AstroBEAR, we carry out a series of simulations
+with magnetized clumps that have different self-contained magnetic field
+configurations. We find that the clump and magnetic evolution are sensitive to
+the fraction of magnetic field aligned with versus perpendicular to the shock
+normal. The relative strength of magnetic pressure and tension in the different
+field configurations allows us to analytically understand the different cases
+of post-shock evolution. We also show how turbulence and the mixing it implies
+depends of the initial field configuration and suggest ways in which observed
+shock-clump morphology may be used as a proxy for identifying internal field
+topologies a posteriori.",1307.3316v1
+2013-09-27,Constrained non-collinear magnetism in disordered Fe and Fe-Cr alloys,"The development of quantitative models for radiation damage effects in iron,
+iron alloys and steels, particularly for the high temperature properties of the
+alloys, requires understanding of magnetic interactions, which control the
+phase stability of ferritic-martensitic, ferritic, and austenitic steels. In
+this work, disordered magnetic configurations of pure iron and Fe-Cr alloys are
+investigated using Density Functional Theory (DFT) formalism, in the form of
+constrained non-collinear magnetic calculations, with the objective of creating
+a database of atomic magnetic moments and forces acting between the atoms. From
+a given disordered atomic configuration of either pure Fe or Fe-Cr alloy, a
+penalty contribution to the usual spin-polarized DFT total energy has been
+calculated by constraining the magnitude and direction of magnetic moments. An
+extensive database of non-collinear magnetic moment and force components for
+various atomic configurations has been generated and used for interpolating the
+spatially-dependent magnetic interaction parameters, for applications in
+large-scale spin-lattice dynamics and magnetic Monte-Carlo simulations.",1309.7183v1
+2013-10-22,The Effect of Toroidal Magnetic Field on Thickness of a Viscose-Resistive Hot Accreting Flow,"By taking into account the effect of toroidal magnetic field and its
+correspond heating, we determine the thickness of advection-dominated accretion
+flows. We consider an axisymetric, rotating, steady viscous-resistive,
+magnetized accretion flow under an advection dominated stage. The dominant
+mechanism of energy dissipation is assumed to be turbulence viscosity and
+magnetic diffusivity. We adopt a self-similar assumption in the radial
+direction to obtain the dynamical quantities, that is, radial, azimuthal, sound
+and Alfv\' en velocities. Our results show the vertical component of magnetic
+force acts in the opposite direction of gravity and compresses the disc, thus
+compared with the non-magnetic case, in general the disc half-thikness,
+$\Delta\theta$, significantly is reduced. On the other hand, two parameters,
+appearing due to action of magnetic field and reaction of the flow, affect the
+disc thickness. The first one, $\beta_0$, showing the magnetic field strength
+at the equatorial plane, decreases $\Delta\theta$. The other one, $\eta_0$ is
+the magnetic resistivity parameter and when it increases, $\Delta\theta$
+increases, too.",1310.6317v1
+2014-04-29,The AC multi-harmonic magnetic susceptibility measurement setup at the LNF-INFN,"The AC magnetic susceptibility is a fundamental method in materials science,
+which allows to probe the dynamic magnetic response of magnetic materials and
+superconductors. The LAMPS laboratory at the Laboratori Nazionali di Frascati
+of the INFN hosts an AC multi-harmonic magnetometer that allows performing
+experiments with an AC magnetic field ranging from 0.1 to 20 Gauss and in the
+frequency range from 17 to 2070 Hz. A DC magnetic field from 0 to 8 T produced
+by a superconducting magnet can be applied, while data may be collected in the
+temperature range 4.2-300 K using a liquid He cryostat under different
+temperature cycles setups. The first seven AC magnetic multi-harmonic
+susceptibility components can be measured with a magnetic sensitivity of 1x10-6
+emu and a temperature precision of 0.01 K. Here we will describe in detail
+about schematic of the magnetometer, special attention will be dedicated to the
+instruments control, data acquisition framework and the user-friendly
+LabVIEW-based software platform.",1404.7389v1
+2014-10-15,The Magnetic Field in the Solar Atmosphere,"This publication provides an overview of magnetic fields in the solar
+atmosphere with the focus lying on the corona. The solar magnetic field couples
+the solar interior with the visible surface of the Sun and with its atmosphere.
+It is also responsible for all solar activity in its numerous manifestations.
+Thus, dynamic phenomena such as coronal mass ejections and flares are
+magnetically driven. In addition, the field also plays a crucial role in
+heating the solar chromosphere and corona as well as in accelerating the solar
+wind. Our main emphasis is the magnetic field in the upper solar atmosphere so
+that photospheric and chromospheric magnetic structures are mainly discussed
+where relevant for higher solar layers. Also, the discussion of the solar
+atmosphere and activity is limited to those topics of direct relevance to the
+magnetic field. After giving a brief overview about the solar magnetic field in
+general and its global structure, we discuss in more detail the magnetic field
+in active regions, the quiet Sun and coronal holes.",1410.4214v1
+2014-12-30,Structure and Evolution of Magnetic Fields Associated with Solar Eruptions (Invited Review),"This paper reviews the studies of solar photospheric magnetic field evolution
+in active regions and its relationship to solar flares. It is divided into two
+topics, the magnetic structure and evolution leading to solar eruptions and the
+rapid changes of photospheric magnetic field associated with eruptions. For the
+first topic, we describe the magnetic complexity, new flux emergence, flux
+cancellation, shear motions, sunspot rotation, and magnetic helicity injection,
+which may all contribute to the storage and buildup of energy and triggering of
+solar eruptions. For the second topic, we concentrate on the observations of
+rapid and irreversible changes of photospheric magnetic field associated with
+flares, and the implication on the restructuring of three-dimensional magnetic
+field. In particular, we emphasize the recent advances in observations of
+photospheric magnetic field, as state-of-the-art observing facilities (such as
+Hinode and Solar Dynamic Observatory) become available. The linkage between
+observations and theories and future prospectives in this research area are
+also discussed.",1412.8676v1
+2015-01-05,Interfacial deformation and jetting of a magnetic fluid,"An attractive technique for forming and collecting aggregates of magnetic
+material at a liquid--air interface by an applied magnetic field gradient was
+recently addressed theoretically and experimentally [Soft Matter, (9) 2013,
+8600-8608]: when the magnetic field is weak, the deflection of the liquid--air
+interface has a steady shape, while for sufficiently strong fields, the
+interface destabilizes and forms a jet that extracts magnetic material.
+Motivated by this work, we develop a numerical model for the closely related
+problem of solving two-phase Navier--Stokes equations coupled with the static
+Maxwell equations. We computationally model the forces generated by a magnetic
+field gradient produced by a permanent magnet and so determine the interfacial
+deflection of a magnetic fluid (a pure ferrofluid system) and the transition
+into a jet. We analyze the shape of the liquid--air interface during the
+deformation stage and the critical magnet distance for which the static
+interface transitions into a jet. We draw conclusions on the ability of our
+numerical model to predict the large interfacial deformation and the consequent
+jetting, free of any fitting parameter.",1501.01000v1
+2015-04-16,Magnetized plasminos in cold and hot QED plasmas,"The complete quasi-particle spectrum of a magnetized electromagnetic plasma
+is systematically explored at zero and nonzero temperatures. To this purpose,
+the general structure of the one-loop corrected propagator of magnetized
+fermions is determined, and the dispersion relations arising from the pole of
+this propagator are numerically solved. It turns out that in the lowest Landau
+level, where only one spin direction is allowed, the spectrum consists of one
+positively (negatively) charged fermionic mode with positive (negative) spin.
+In contrast, in higher Landau levels, as an indirect consequence of the double
+spin degeneracy of fermions, the spectrum consists of two massless collective
+modes with left- and right-chiralities. The mechanism through which these new
+collective excitations are created in a uniform magnetic field is similar to
+the production mechanism of dynamical holes (plasminos) at finite temperature
+and zero magnetic fields. Whereas cold magnetized plasminos appear for moderate
+magnetic fields and for all positive momenta of propagating fermions, hot
+magnetized plasminos appear only in the limit of weak magnetic fields and soft
+momenta.",1504.04268v2
+2015-07-08,Enhancement of artificial magnetism via resonant bianisotropy,"All-dielectric ""magnetic light"" nanophotonics based on high refractive index
+nanoparticles allows controlling magnetic component of light at nanoscale
+without having high dissipative losses. The artificial magnetic optical
+response of such nanoparticles originates from circular displacement currents
+excited inside those structures and strongly depends on geometry and dispersion
+of optical materials. Here a new approach for increasing magnetic response via
+resonant bianisotropy effect is proposed and analyzed. The key mechanism of
+enhancement is based on electric-magnetic interaction between two electrically
+and magnetically resonant nanoparticles of all-dielectric dimer nanoantenna. It
+was shown that proper geometrical arrangement of the dimer in respect to the
+incident illumination direction allows flexible control over all vectorial
+components of magnetic polarizability, tailoring the later in the dynamical
+range of 100 % and enhancement up to 36 % relative to performances of
+standalone spherical particles. The proposed approach provides pathways for
+designs of all-dielectric metamaterials and metasurfaces with strong magnetic
+response.",1507.02098v1
+2015-09-18,Simulation of Stacks of High Temperature Superconducting Coated Conductors Magnetized by Pulsed Field Magnetization Using Controlled Magnetic Density Distribution Coils,"High temperature superconducting (HTS) stacks of coated conductors (CCs) can
+work as strong trapped field magnets (TFMs) and show potential in electrical
+applications. Pulsed field magnetization (PFM) is a practical method to
+magnetize such TFMs, but due to heat generation during the dynamic process, it
+cannot achieve a trapped field as high as field cooling can. In this work, we
+construct a 2D electromagnetic-thermal coupled model to simulate stacks of HTS
+CCs with realistic laminated structures magnetized by PFM. The model considers
+temperature and anisotropic magnetic field dependent Jc of HTS and other
+temperature dependent thermal and electrical material properties. Based on the
+model, a configuration of controlled magnetic density distribution coils is
+suggested to improve the trapped field compared to that obtained by ordinary
+solenoids.",1509.05541v1
+2015-10-01,Dynamos at extreme magnetic Prandtl numbers: Insights from shell models,"We present an MHD shell model suitable for computation of various energy
+fluxes of magnetohydrodynamic turbulence for very small and very large magnetic
+Prandtl numbers $\mathrm{Pm}$; such computations are inaccessible to direct
+numerical simulations. For small $\mathrm{Pm}$, we observe that both kinetic
+and magnetic energy spectra scale as $k^{-5/3}$ in the inertial range, but the
+dissipative magnetic energy scales as $k^{-11/3}\exp(-k/k_\eta)$. Here, the
+kinetic energy at large length scale feeds the large-scale magnetic field that
+cascades to small-scale magnetic field, which gets dissipated by Joule heating.
+The large-$\mathrm{Pm}$ dynamo has a similar behaviour except that the
+dissipative kinetic energy scales as $k^{-13/3}$. For this case, the
+large-scale velocity field transfers energy to the large-scale magnetic field,
+which gets transferred to small-scale velocity and magnetic fields; the energy
+of the small-scale magnetic field also gets transferred to the small-scale
+velocity field, and the energy thus accumulated is dissipated by the viscous
+force.",1510.00122v2
+2015-11-11,Electric-field Controlled Magnetization Switching in Co/Pt thin-Film Ferromagnets,"A study of dynamic and reversible voltage controlled magnetization switching
+in ferromagnetic Co/Pt thin film with perpendicular magnetic anisotropy at room
+temperature is presented. The change in the magnetic properties of the system
+is observed in a relatively thick film of 15 nm. A surface charge is induced by
+the formation of electrochemical double layer between the metallic thin film
+and non-aqueous lithium LiClO4 electrolyte to manipulate the magnetism. The
+change in the magnetic properties occurred by the application of an external
+electric field. As the negative voltage was increased, the coercivity and the
+switching magnetic field decreased thus activating magnetization switching. The
+results are envisaged to lead to faster and ultra-low power magnetization
+switching as compared to spin-transfer torque (STT) switching in spintronic
+devices.",1511.03717v1
+2016-07-07,Understanding the focusing of charged particle for 2D sheet beam in a cusped magnetic field,"The requirement of axial magnetic field for focusing and transportation of
+sheet beam using cusped magnets is less as compared to solenoid magnetic fields
+which is uniform. There is often some confusion about how a cusped magnetic
+field focuses high current density sheet beam because it is generally
+understood that non-uniform magnetic field cannot guide the particle beam along
+its axis of propagation .In this paper, we perform simple analysis of the
+dynamics of sheet beam in a cusped magnetic field with single electron model
+and emphasize an intuitive understanding of interesting features (as beam
+geometry, positioning of permanent magnets, particle radius,particle
+velocity,radius of curvature of particle inside cusped magnetic field)",1607.02492v1
+2016-08-11,Chiral magnetic excitations in FeGe films,"Although chiral magnetic materials have emerged as a potential ingredient in
+future spintronic memory devices, there are few comprehensive studies of
+magnetic properties in scalably-grown thin films. We present growth, systematic
+physical and magnetic characterization, and microwave absorption spectroscopy
+of B20 FeGe thin films. We also perform micromagnetic simulations and
+analytical theory to understand the dynamical magnetic behavior of this
+material. We find magnetic resonance features in both the helical and
+field-polarized magnetic states that are well explained by micromagnetic
+simulations and analytical calculations. In particular, we show the resonant
+enhancement of spin waves along the FeGe film thickness that has a wave vector
+matching the helical vector. Using our analytic model, we also describe the
+resonance frequency of a helical magnetic state, which depends solely on its
+untwisting field. Our results pave the way for understanding and manipulating
+high frequency spin waves in thin-film chiral-magnet FeGe near room
+temperature.",1608.03582v1
+2016-11-11,Intra-layer doping effects on the high-energy magnetic correlations in NaFeAs,"We have used Resonant Inelastic X-ray Scattering (RIXS) and dynamical
+susceptibility calculations to study the magnetic excitations in
+NaFe$_{1-x}$Co$_x$As (x = 0, 0.03, and 0.08). Despite a relatively low ordered
+magnetic moment, collective magnetic modes are observed in parent compounds (x
+= 0) and persist in optimally (x = 0.03) and overdoped (x = 0.08) samples.
+Their magnetic bandwidths are unaffected by doping within the range
+investigated. High energy magnetic excitations in iron pnictides are robust
+against doping, and present irrespectively of the ordered magnetic moment.
+Nevertheless, Co doping slightly reduces the overall magnetic spectral weight,
+differently from previous studies on hole-doped BaFe$_{2}$As$_{2}$, where it
+was observed constant. Finally, we demonstrate that the doping evolution of
+magnetic modes is different for the dopants being inside or outside the Fe-As
+layer.",1611.03621v1
+2017-03-10,Magnetic micro-droplet in rotating field: numerical simulation and comparison with experiment,"Magnetic droplets obtained by induced phase separation in a magnetic colloid
+show a large variety of shapes when exposed to an external field. However, the
+description of shapes is often limited. Here we formulate an algorithm based on
+three dimensional boundary-integral equations for strongly magnetic droplets in
+a high-frequency rotating magnetic field, allowing us to find their figures of
+equilibrium in three dimensions. The algorithm is justified by a series of
+comparisons with known analytical results. We compare the calculated
+equilibrium shapes with experimental observations and find a good agreement.
+The main features of these observations are the oblate-prolate transition, the
+flattening of prolate shapes with the increase of magnetic field strength and
+the formation of star-fish like equilibrium shapes. We show both numerically
+and in experiments that the magnetic droplet behaviour may be described with a
+tri-axial ellipsoid approximation. Directions for further research are
+mentioned, including the dipolar interaction contribution to the surface
+tension of the magnetic droplets, account for the large viscosity contrast
+between the magnetic droplet and the surrounding fluid.",1703.03654v1
+2017-12-18,Complex magnetic behaviour and evidence of superspin glass state in a binary intermetallic compound Er5Pd2,"A binary intermetallic compound Er5Pd2 has been investigated using dc and ac
+magnetic susceptibilities, magnetic memory effect, isothermal magnetization,
+non-linear dc susceptibility, heat capacity and magnetocaloric effect studies.
+Interestingly, even though the compound does not show geometrical frustration
+it undergoes glassy magnetic phase transition below 17.2 K. Investigation of dc
+magnetisation and heat capacity data divulged absence of long-ranged magnetic
+ordering. Through magnetic memory effect, time dependent magnetization and ac
+susceptibility studies it was revealed that the compound undergoes glass-like
+freezing below 17.2 K. Analysis of frequency dependence of this transition
+temperature through scaling and Arrhenius law; along with Mydosh parameter
+indicate, that the dynamics in Er5Pd2 is due to the presence of strongly
+interacting superspins rather than individual spins. This phase transition was
+further investigated by non-linear dc susceptibility and was characterized by
+static critical exponents {\gamma} and {\delta}. Our results indicate that this
+compound show signature of superspin glass at low temperature. Additionally,
+both conventional and inverse magnetocaloric effect was observed with large
+value of magnetic entropy change and relative cooling power. Our results
+suggest that Er5Pd2 can be classified as a superspin glass system with large
+magnetocaloric effect.",1712.06388v1
+2018-08-14,Interplay of uniform U(1) quantum spin liquid and magnetic phases in rare earth pyrochlore magnets : a fermionic parton approach,"We study the uniform time reversal invariant $U(1)$ quantum spin liquid (QSL)
+with low energy fermionic quasi-particles for rare earth pyrochlore magnets and
+explore its magnetic instability employing an augmented fermionic parton mean
+field theory approach. Self consistent calculations stabilise an uniform $U(1)$
+QSL with both gapped and gapless parton excitations as well as fractionalised
+magnetically ordered phases in an experimentally relevant part of the phase
+diagram near the classical phase boundaries of the magnetically ordered phases.
+The gapped QSL has a band-structure with a non-zero $Z_2$ topological
+invariant. The fractionalised magnetic ordered phases bears signature of both
+QSL through fermionic excitations as well as magnetic order. Thus this provides
+a possible way to understand the unconventional diffuse neutron scattering in
+rare-earth pyrochlores such as Yb$_2$Ti$_2$O$_7$, Er$_2$Sn$_2$O$_7$ and
+Er$_2$Pt$_2$O$_7$ at low/zero external magnetic fields. We calculate the
+dynamic spin structure factor to understand the nature of the diffuse
+two-particle continuum.",1808.04861v1
+2019-03-14,Unidirectional propulsion of planar magnetic nanomachines,"Steering of magnetic nano-/microhelices by a rotating magnetic field is
+considered as a promising technique for controlled navigation of tiny objects
+through viscous fluidic environments. It has been recently demonstrated that
+simple geometrically achiral planar structures can also be steered efficiently.
+Such planar propellers are interesting for practical reasons, as they can be
+mass-fabricated using standard micro/nanolithography techniques. While planar
+magnetic structures are prone to in-plane magnetization, under the effect of an
+in-plane rotating magnetic field, they exhibit, at most, propulsion due to
+spontaneous symmetry breaking, i.e., they can propel either parallel or
+anti-parallel to the rotation axis of the field depending on their initial
+orientation. Here we demonstrate that actuation by a conically rotating
+magnetic field (i.e., superposition of in-plane rotating field and constant
+field orthogonal to it) can yield efficient unidirectional propulsion of planar
+and magnetized in-plane structures. In particular, we found that a highly
+symmetrical V-shape magnetized along its symmetry axis which exhibits no net
+propulsion in in-plane rotating field, exhibits unidirectional in-sync
+propulsion with a constant (frequency-independent) velocity when actuated by
+the conically rotating field.",1903.06298v2
+2019-05-10,Periodicity of magnetization reversals in $\varphi_0$ Josephson junction,"The magnetization reversal in ${\varphi_0}$-Josephson junction with direct
+coupling between magnetic moment and Josephson current has been studied. By
+adding pulse signal, the dynamics of magnetic moment components have been
+simulated and the full magnetization reversal at different parameters of the
+junction has been demonstrated. We obtain a detailed pictures representing the
+intervals of the damping parameter $\alpha$, Josephson to magnetic energy
+relation $G$ and spin-orbit coupling parameter $r$ with full magnetization
+reversal. A periodicity in the appearance of magnetization reversal intervals
+with increase in Josephson to magnetic energy relation is found. The obtained
+results might be used in different fields of superconducting spintronics.",1905.03895v1
+2019-08-07,Deformation of flexible ferromagnetic filaments under a rotating magnetic field,"Research on magnetic particles dispersed in a fluid medium, actuated by a
+rotating magnetic field, is becoming increasingly active for both lab-on-chip
+and bio-sensing applications. In this study, we experimentally investigate the
+behaviour of ferromagnetic filaments in a rotating field. Filaments are
+synthesized by linking micron-sized ferromagnetic particles with DNA strands.
+The experiments were conducted under different magnetic field strengths,
+frequencies and filament sizes, and deformation of the filaments was registered
+via microscope and camera. The results obtained showed that the body
+deformation is larger for longer filaments and higher frequencies and lower for
+larger magnetic field. The angle between the filament tangent at the centre and
+the magnetic field direction increases linearly with frequency at low-frequency
+regime. A further increase in the frequency will result in filament movement
+out of plane when the angle approaches 90 degrees. The experimental results
+were used to estimate magnetic moment and the bending elasticity of the
+filament.",1908.02604v2
+2019-08-14,"Rivalry of diffusion, external field and gravity in micro-convection of magnetic colloids","Magnetic fields and magnetic materials have promising microfluidic
+applications. For example, magnetic micro-convection can enhance mixing
+considerably. However, previous studies have not explained increased effective
+diffusion during this phenomenon. Here we show that enhanced interface smearing
+comes from a gravity induced convective motion within a thin microfluidic
+channel, caused by a small density difference between miscible magnetic and
+non-magnetic fluids. This motion resembles diffusive behavior and can be
+described with an effective diffusion coefficient. We explain this with a
+theoretical model, based on a dimensionless gravitational Rayleigh number, and
+verify it by numerical simulations and experiments with different cell
+thicknesses. Results indicate the applicability and limitations for
+microfluidic applications of other colloidal systems. Residual magnetic
+micro-convection follows earlier predictions.",1908.05011v2
+2019-10-25,The influence of crosslinkers and magnetic particle distribution along the filament backbone on the magnetic properties of supracolloidal linear polymer-like chains,"Diverse polymer crosslinking techniques allow the synthesis of linear
+polymer-like structures whose monomers are colloidal particles. In the case
+where all or part of these colloidal particles are magnetic, one can control
+the behaviour of these supracolloidal polymers, known as magnetic filaments
+(MFs), by applied magnetic fields. However, the response of MFs strongly
+depends on the crosslinking procedure. In the present study, we employ Langevin
+dynamics simulations to investigate the influence of the type of crosslinking
+and the distribution of magnetic particles within MFs on their response to an
+external magnetic field. We found that if the rotation of the dipole moment of
+particles is not coupled to the backbone of the filament, the impact of the
+magnetic content is strongly decreased.",1910.11607v1
+2019-11-10,Dipolar-drift and collective instabilities of skyrmions in crossed nonuniform electric and magnetic fields in a chiral magnetic insulator,"Skyrmions dynamics in the approximation of point-particle skyrmions is
+considered in the multiferroic insulators, where the spiral magnetic structure
+is accompanied by finite electric dipole moment. The skyrmion motion is studied
+in the gradients of perpendicular magnetic and electric fields. The nonuniform
+magnetic field with a fixed gradient magnitude leads to the spiral motion,
+where skyrmion circulates in the plane perpendicular to the direction of
+magnetic field. The frequency of circulation is fixed by the derivative of the
+external magnetic field and the magnitude of the dipole moment. Application of
+additional electric field which perpendicular to the magnetic field, but their
+gradients have same direction leads to the drift motion of skyrmions resulting
+in the magneto-dipolar Hall effect. Hydrodynamics of the gas of interacting
+skyrmions in crossed nonuniform electric and magnetic fields shows the new type
+of hydrodynamical instability caused by the drift motion. Three regimes of
+instability are described.",1911.03986v1
+2020-01-04,Magnetic billiards: Non-integrability for strong magnetic field; Gutkin type examples,"We consider magnetic billiards under a strong constant magnetic field. The
+purpose of this paper is two-folded. We examine the question of existence of
+polynomial integral of billiard magnetic flow. We succeed to reduce this
+question to algebraic geometry test on existence of polynomial integral, which
+shows polynomial non-integrability for all but finitely many values of the
+magnitude. In the second part of the paper we construct examples of magnetic
+billiards which have the so called $\delta$-Gutkin property, meaning that any
+Larmor circle entering the domain with angle $\delta$ exits the domain with the
+same angle $\delta$. For ordinary Birkhoff billiard in the plane such examples
+were introduced by E. Gutkin and are very explicit. Our construction of Gutkin
+magnetic billiards relies on beautiful examples by F.Wegner of the so called
+Zindler curves, which are related to the problem of floating bodies in
+equilibrium, which goes back to S.Ulam. We prove that Gutkin magnetic billiard
+can be obtained as a parallel curve to a Wegner curve. Wegner curves can be
+written by elliptic functions in polar coordinates so the construction of
+magnetic Gutkin billiard is rather explicit but much more complicated.",2001.02119v1
+2020-02-04,Magnetically controlled vector based on E coli Nissle 1917,"In this paper, it is first discovered that EcN has natural magnetically
+controlled properties, that is, E coli Nissle 1917 cells move in a gradient
+magnetic field of permanent magnets without artificial magnetic labeling. It is
+also shown in the paper that the cultivation of EcN in a medium enriched with
+iron chelates and under the influence of an external magnetic field increases
+several times the magnetophoretic mobility of E coli Nissle 1917 cells compared
+to cultivation under standard conditions. Thus, the speed of movement of E coli
+Nissle 1917 cells in a gradient magnetic field of laboratory magnets is
+achieved of the order of several mm/s. It has also been shown for the first
+time that the cultivation of E coli Nissle 1917 biomass is accelerated by
+cultivation in an external magnetic field, while the change in the
+concentration of iron chelates in the medium has no effect on the cultivation
+dynamics of the E coli Nissle 1917 culture.",2002.01958v1
+2020-03-26,Spin textures in chiral magnetic monolayers with suppressed nearest-neighbor exchange,"High tunability of two dimensional magnetic materials (by strain, gating,
+heterostructuring or otherwise) provides unique conditions for studying
+versatile magnetic properties and controlling emergent magnetic phases.
+Expanding the scope of achievable magnetic phenomena in such materials is
+important for both fundamental and technological advances. Here we perform
+atomistic spin-dynamics simulations to explore the (chiral) magnetic phases of
+atomic monolayers in the limit of suppressed first-neighbors exchange
+interaction. We report the rich phase diagram of exotic magnetic
+configurations, obtained for both square and honeycomb lattice symmetries,
+comprising coexistence of ferromagnetic and antiferromagnetic spin-cycloids, as
+well as multiple types of magnetic skyrmions. We perform a minimum-energy path
+analysis for the skyrmion collapse to evaluate the stability of such
+topological objects, and reveal that magnetic monolayers could be good
+candidates to host the antiferromagnetic skyrmions that are experimentally
+evasive to date.",2003.11933v1
+2020-04-21,Magnetized particle motion around 4-D Einstein-Gauss-Bonnet Black Hole,"In this paper, we have investigated the dynamics of magnetized particles
+around 4-D Einstein-Gauss-Bonnet black hole immersed in an external
+asymptotically uniform magnetic field. We have shown that the magnetic
+interaction parameter responsible for circular orbits decreases for negative
+values of the Gauss-Bonnet parameter $\alpha$ and the range where magnetized
+particle's stable circular orbits are allowed increases for the positive values
+of the parameter $\alpha$. The study of the collisions of magnetized, charged
+and neutral particles has shown that the center-of-mass energy of the particles
+increases in the presence of positive Gauss-Bonnet parameter. Finally, we show
+how the magnetic interaction and Gauss-Bonnet parameter may mimic the effect of
+rotation of the Kerr black hole giving the same ISCO radius for magnetized
+particles. Detailed analysis of the ISCO show that spin of Kerr black hole can
+not be mimicked by the effects of magnetic interaction and the Gauss-Bonnet
+parameters when $\alpha<-4.37$ and the spin parameter $a > 0.237$.",2004.10031v1
+2020-04-28,A new 3D model for magnetic particle imaging using realistic magnetic field topologies for algebraic reconstruction,"We derive a new 3D model for magnetic particle imaging (MPI) that is able to
+incorporate realistic magnetic fields in the reconstruction process. In real
+MPI scanners, the generated magnetic fields have distortions that lead to
+deformed magnetic low-field volumes (LFV) with the shapes of ellipsoids or
+bananas instead of ideal field-free points (FFP) or lines (FFL), respectively.
+Most of the common model-based reconstruction schemes in MPI use however the
+idealized assumption of an ideal FFP or FFL topology and, thus, generate
+artifacts in the reconstruction. Our model-based approach is able to deal with
+these distortions and can generally be applied to dynamic magnetic fields that
+are approximately parallel to their velocity field. We show how this new 3D
+model can be discretized and inverted algebraically in order to recover the
+magnetic particle concentration. To model and describe the magnetic fields, we
+use decompositions of the fields in spherical harmonics. We complement the
+description of the new model with several simulations and experiments.",2004.13357v1
+2020-09-07,Time-Domain Terahertz Spectroscopy in High Magnetic Fields,"There are a variety of elementary and collective terahertz-frequency
+excitations in condensed matter whose magnetic field dependence contains
+significant insight into the states and dynamics of the electrons involved.
+Often, determining the frequency, temperature, and magnetic field dependence of
+the optical conductivity tensor, especially in high magnetic fields, can
+clarify the microscopic physics behind complex many-body behaviors of solids.
+While there are advanced terahertz spectroscopy techniques as well as high
+magnetic field generation techniques available, combination of the two has only
+been realized relatively recently. Here, we review the current state of
+terahertz time-domain spectroscopy experiments in high magnetic fields. We
+start with an overview of time-domain terahertz detection schemes with a
+special focus on how they have been incorporated into optically accessible
+high-field magnets. Advantages and disadvantages of different types of magnets
+in performing terahertz time-domain spectroscopy experiments are also
+discussed. Finally, we highlight some of the new fascinating physical phenomena
+that have been revealed by terahertz time-domain spectroscopy in high magnetic
+fields.",2009.03359v2
+2020-10-12,Peculiarities of magnetic ordering in the S = 5/2 two-dimensional square-lattice antimonate NaMnSbO4,"An orthorhombic compound, NaMnSbO4, represents a square net of magnetic Mn2+
+ions residing in vertex-shared oxygen octahedra. Its static and dynamic
+magnetic properties were studied using magnetic susceptibility, specific heat,
+magnetization, electron spin resonance (ESR), nuclear magnetic resonance (NMR)
+and density functional calculations. Thermodynamic data indicate an
+establishment of the long-range magnetic order with TN about 44 K, which is
+preceded by a short-range one at about 55 K. In addition, a non-trivial
+wasp-waisted hysteresis loop of the magnetization was observed, indicating that
+the ground state is most probably canted antiferromagnetic. Temperature
+dependence of the magnetic susceptibility is described reasonably well in the
+framework of 2D square lattice model with the main exchange parameter J = -5.3
+K, which is in good agreement with density functional analysis, NMR and ESR
+data.",2010.05653v1
+2020-10-14,Spin torque gate magnetic field sensor,"Spin-orbit torque provides an efficient pathway to manipulate the magnetic
+state and magnetization dynamics of magnetic materials, which is crucial for
+energy-efficient operation of a variety of spintronic devices such as magnetic
+memory, logic, oscillator, and neuromorphic computing. Here, we describe and
+experimentally demonstrate a strategy for the realization of a spin torque gate
+magnetic field sensor with extremely simple structure by exploiting the
+longitudinal field dependence of the spin torque driven magnetization
+switching. Unlike most magnetoresistance sensors which require a delicate
+magnetic bias to achieve a linear response to the external field, the spin
+torque gate sensor can achieve the same without any magnetic bias, which
+greatly simplifies the sensor structure. Furthermore, by driving the sensor
+using an ac current, the dc offset is automatically suppressed, which
+eliminates the need for a bridge or compensation circuit. We verify the concept
+using the newly developed WTe2/Ti/CoFeB trilayer and demonstrate that the
+sensor can work linearly in the range of 3-10 Oe with negligible dc offset.",2010.07158v1
+2021-01-29,Data-driven MHD simulation of successive solar plasma eruptions,"Solar flares and plasma eruptions are sudden releases of magnetic energy
+stored in the plasma atmosphere. To understand the physical mechanisms
+governing their occurrences, three-dimensional magnetic fields from the
+photosphere up to the corona must be studied. The solar photospheric magnetic
+fields are observable, whereas the coronal magnetic fields cannot be measured.
+One method for inferring coronal magnetic fields is performing data-driven
+simulations, which involves time-series observational data of the photospheric
+magnetic fields with the bottom boundary of magnetohydrodynamic simulations. We
+developed a data-driven method in which temporal evolutions of the
+observational vector magnetic field can be reproduced at the bottom boundary in
+the simulation by introducing an inverted velocity field. This velocity field
+is obtained by inversely solving the induction equation and applying an
+appropriate gauge transformation. Using this method, we performed a data-driven
+simulation of successive small eruptions observed by the Solar Dynamics
+Observatory and the Solar Magnetic Activity Telescope in November 2017. The
+simulation well reproduced the converging motion between opposite-polarity
+magnetic patches, demonstrating successive formation and eruptions of helical
+flux ropes.",2101.12395v1
+2021-02-04,Nanoscale magnetization and current imaging using scanning-probe magneto-thermal microscopy,"Magnetic microscopy that combines nanoscale spatial resolution with
+picosecond scale temporal resolution uniquely enables direct observation of the
+spatiotemporal magnetic phenomena that are relevant to future high-speed,
+high-density magnetic storage and logic technologies. Magnetic microscopes that
+combine these metrics has been limited to facility-level instruments. To
+address this gap in lab-accessible spatiotemporal imaging, we develop a
+time-resolved near-field magnetic microscope based on magneto-thermal
+interactions. We demonstrate both magnetization and current density imaging
+modalities, each with spatial resolution that far surpasses the optical
+diffraction limit. In addition, we study the near-field and time-resolved
+characteristics of our signal and find that our instrument possesses a spatial
+resolution on the scale of 100 nm and a temporal resolution below 100 ps. Our
+results demonstrate an accessible and comparatively low-cost approach to
+nanoscale spatiotemporal magnetic microscopy in a table-top form to aid the
+science and technology of dynamic magnetic devices with complex spin textures.",2102.02792v1
+2021-02-23,Magnetic charge's relaxation propelled electricity in two-dimensional magnetic honeycomb lattice,"Emerging new concepts, such as magnetic charge dynamics in two-dimensional
+magnetic material, can provide novel mechanism for spin based electrical
+transport at macroscopic length. In artificial spin ice of single domain
+elements, magnetic charge's relaxation can create an efficient electrical
+pathway for conduction by generating fluctuations in local magnetic field that
+couple with conduction electrons spins. In a first demonstration, we show that
+the electrical conductivity is propelled by more than an order of magnitude at
+room temperature due to magnetic charge defects sub-picosecond relaxation in
+artificial magnetic honeycomb lattice. The direct evidence to the proposed
+electrical conduction mechanism in two-dimensional frustrated magnet points to
+the untapped potential for spintronic applications in this system.",2102.11949v1
+2022-01-27,Spin motive force by the momentum-space Berry phase in magnetic Weyl semimetals,"We show that the magnetic precession of ferromagnetic moments in a
+noncentrosymmetric magnetic Weyl semimetal induces an electric current through
+a mechanism analogous to the adiabatic charge pumping. The current is a
+consequence of a Berry phase in the momentum space resulting from the circular
+motion of Weyl nodes induced by the precession. This mechanism resembles the
+Faraday effect, namely, induced magnetic field by circular electric current.
+The circular motion of Weyl nodes induces magnetic charge current in the
+momentum space, which results in a Berry phase that describes the adiabatic
+pump. Experimentally, this phenomenon is similar to spin motive force, which is
+an electric current induced by magnetic precision in the presence of the
+spatial gradient of magnetization. However, unlike the conventional spin motive
+force, this current occurs without a magnetization gradient. The result
+demonstrates a nontrivial interplay between the topological electronic state
+and magnetic dynamics.",2201.11568v2
+2024-02-16,Nonlinear optics driven magnetism reorientation in semiconductors,"Based on nonlinear optics, we develop a band theory to elucidate how light
+could manipulate magnetization, which is rooted by the quantum geometric
+structure and topological nature of electronic wavefunctions. Their existence
+are determined by the light polarization and specific material symmetry, based
+on the magnetic group theory. In general, both circularly and linearly
+polarized light could exert an effective magnetic field and torque effect, to
+reorient the magnetization. They are contributed by spin and orbital angular
+momenta simultaneously. Aided by group theory and first-principles
+calculations, we illustrate this theory using a showcase example of monolayer
+NiCl2, showing that light irradiation effectively generates an out-of-plane
+effective magnetic torque, which lifts its in-plane easy magnetization.
+According to magnetic dynamic simulations, the in-plane magnetization could be
+switched to the out-of-plane direction in a few nanoseconds under a modest
+light intensity, demonstrating its ultrafast nature desirable for quantum
+manipulation.",2402.10518v1
+2012-02-07,Nonequilibrium critical dynamics with domain wall and surface,"With Monte Carlo simulations, we investigate the relaxation dynamics with a
+domain wall for magnetic systems at the critical temperature. The dynamic
+scaling behavior is carefully analyzed, and a dynamic roughening process is
+observed. For comparison, similar analysis is applied to the relaxation
+dynamics with a free or disordered surface.",1202.1338v1
+1998-03-15,Mean magnetic field renormalization and Kolmogorov's energy spectrum in MHD turbulence,"In this paper we construct a self-consistent renormalization group procedure
+for MHD turbulence in which small wavenumber modes are averaged out, and
+effective mean magnetic field at large wavenumbers is obtained. In this scheme
+the mean magnetic field scales as $k^{-1/3}$, while the energy spectrum scales
+as $k^{-5/3}$ similar to that in fluid turbulence. We also deduce from the
+formalism that the magnitude of cascade rate decreases as the strength of the
+mean magnetic field is increased.",9803021v1
+1999-12-13,The boundary integral method for magnetic billiards,"We introduce a boundary integral method for two-dimensional quantum billiards
+subjected to a constant magnetic field. It allows to calculate spectra and wave
+functions, in particular at strong fields and semiclassical values of the
+magnetic length. The method is presented for interior and exterior problems
+with general boundary conditions. We explain why the magnetic analogues of the
+field-free single and double layer equations exhibit an infinity of spurious
+solutions and how these can be eliminated at the expense of dealing with
+(hyper-)singular operators. The high efficiency of the method is demonstrated
+by numerical calculations in the extreme semiclassical regime.",9912022v1
+1997-05-22,Generalized Dynamic Scaling for Critical Magnetic Systems,"The short-time behaviour of the critical dynamics for magnetic systems is
+investigated with Monte Carlo methods. Without losing the generality, we
+consider the relaxation process for the two dimensional Ising and Potts model
+starting from an initial state with very high temperature and arbitrary
+magnetization. We confirm the generalized scaling form and observe that the
+critical characteristic functions of the initial magnetization for the Ising
+and the Potts model are quite different.",9705233v1
+1998-11-11,Dynamical Mean Field Theory of the Antiferromagnetic Metal to Antiferromagnetic Insulator Transition,"We study the antiferromagnetic metal to antiferromagnetic insulator using
+dynamical mean field theory and exact diagonalization methods. We find two
+qualitatively different behaviors depending on the degree of magnetic
+correlations. For strong correlations combined with magnetic frustration, the
+transition can be described in terms of a renormalized slater theory, with a
+continuous gap closure driven by the magnetism but strongly renormalized by
+correlations. For weak magnetic correlations, the transition is weakly first
+order.",9811144v2
+1999-03-11,Localization by interference: Square billiard with a magnetic flux,"Eigenstates and energy levels of a square quantum billiard in a magnetic
+field, or with an Aharonov-Bohm flux line, are found in quasiclassical
+approximation, that is, for high enough energy. Explicit formulas for the
+energy levels and wavefunctions are found. There are localized states, never
+before noticed in this well studied problem, whose localization is due to phase
+interference, even though there is no or negligible classical effect of the
+magnetic field. These and related states account almost entirely for the
+magnetic response in certain temperature ranges, and thus have a bearing on the
+experiments of Levy et al.",9903193v1
+1999-09-17,"Commensurate dynamic magnetic correlations in La2(Cu,Li)O4","When sufficient numbers of holes are introduced into the two-dimensional CuO2
+square lattice, dynamic magnetic correlations become incommensurate with
+underlying lattice in all previously investigated La_{2-x}A_xCu_{1-z}B_zO_{4+y}
+(A=Sr or Nd, B=Zn) including high T_C superconductors and insulators, and in
+bilayered superconducting YBa_2Cu_3O_{6.6} and Bi_2Sr_2CaCu_2O_8. Magnetic
+correlations also become incommensurate in structurally related La_2NiO_4 when
+doped with Sr or O. We report an exception to this so-far well established
+experimental ""rule"" in La_2Cu_{1-z}Li_{z}O_4 in which magnetic correlations
+remain commensurate.",9909256v2
+2000-01-13,Quantum Dynamics in Nanoscale Magnets in Dissipative Environments,"In discrete energy structure of nanoscale magnets, nonadiabatic transitions
+at avoided level crossings lead to fundamental processes of dynamics of
+magnetizations. The thermal environment causes dissipative effects on these
+processes. In this paper we review the features of the nonadiabatic transition
+and the influence of the thermal environment. In particular we discuss the
+temperature independent stepwise structure of magnetization at very low
+temperatures (deceptive nonadiabatic transition), the alternate enhancement of
+relaxation in the sequence of resonant tunneling points (parity effects), and
+processes caused by combinations of nonadiabatic transitions and disturbance
+due to external noises.",0001179v1
+2001-06-22,Transition temperature of ferromagnetic semiconductors: a dynamical mean field study,"We formulate a theory of doped magnetic semiconductors such as
+Ga$_{1-x}$Mn$_x$As which have attracted recent attention for their possible use
+in spintronic applications. We solve the theory in the dynamical mean field
+approximation to find the magnetic transition temperature $T_c$ as a function
+of magnetic coupling strength $J$ and carrier density $n$. We find that $T_c$
+is determined by a subtle interplay between carrier density and magnetic
+coupling.",0106455v1
+2002-12-05,Dynamic stiffness of spin valves,"The dynamics of the magnetic order parameters of
+ferromagnet/normal-metal/ferromagnet spin valves and isolated ferromagnets may
+be very different. We investigate the role of the nonequilibrium spin-current
+exchange between the ferromagnets in the magnetization precession and
+switching. We find a (low-temperature) critical current bias for a coherent
+current-induced magnetization excitation in spin valves, which unifies and
+generalizes previous ideas of Slonczewski and Berger. In the absence of an
+applied bias, the effect of the spin transfer can be expressed as
+magnetic--configuration-dependent Gilbert damping.",0212130v2
+2003-03-18,Dynamics of magnetic moments of a nanoscopic array,"Dynamics of nanoscopic arrays of monodomain magnetic elements is simulated by
+means of the Pardavi-Horvath algorithm. Experimental hysteresis loop is
+reproduced for the arrays of Ni, with the period 100 nm and the mean coercive
+field 710 Oe.We investigate the box-counting fractal dimension of a cluster of
+elements with given orientation of magnetic moments. No fractal behavior is
+found. Also, the damage spreading technique is applied to check the
+criticality. We find that the consequences of a local flip of one magnetic
+element remainlimited to a finite area. We conclude that the system does not
+show a critical behavior.",0303330v2
+2003-06-06,Projective Dynamics Analysis of Magnetization Reversal,"The computational Projective Dynamics method is used to analyze simulations
+of magnetization reversal in nanoscale magnetic pillars. It is shown that this
+method can be used to determine the magnetizations corresponding to the
+metastable minimum and saddle point in the free energy, and the free-energy
+barrier associated with those points. For the nanopillars studied here, entropy
+is found to provide a significant contribution to the free-energy barrier which
+determines the reversal time scale.",0306168v1
+2003-07-18,Dynamics of a nanoparticle as a one-spin system and beyond,"We review some recent results beyond the now established theory of
+magnetization switching of a nanoparticle within the single-spin approximation.
+The first extension is that of the Stoner-Wohlfarth model for magnetization
+static switching under applied magnetic field including the effect of
+temperature at long-time scales. The second concerns a generalization of the
+N\'eel-Brown model for thermoactivated dynamic magnetization switching to
+include the effect of exchange interaction in the framework of Langer's theory
+in the intermediate-to-high damping limit. We finally argue why the single-spin
+approximation is not appropriate for very small nanoparticles.",0307457v1
+2004-10-20,Static properties and spin dynamics of the ferromagnetic spin-1 Bose gas in magnetic field,"Properties of spin-1 Bose gases with ferromagnetic interaction in the
+presence of a nonzero magnetic field are studied. The equation of state and
+thermodynamic quantities are worked out with the help of a mean-field
+approximation. The phase diagram besides Bose-Einstein condensation contains a
+first order transition where two values of the magnetization coexist. The
+dynamics is investigated with the help of the Random Phase Approximation. The
+soft mode corresponding to the critical point of the magnetic phase transition
+is found to behave like in conventional theory.",0410501v1
+2005-03-02,Entropic sampling dynamics of the globally-coupled kinetic Ising model,"The entropic sampling dynamics based on the reversible information transfer
+to and from the environment is applied to the globally coupled Ising model in
+the presence of an oscillating magnetic field. When the driving frequency is
+low enough, coherence between the magnetization and the external magnetic field
+is observed; such behavior tends to weaken with the system size. The time-scale
+matching between the intrinsic time scale, defined in the absence of the
+external magnetic field, and the extrinsic time scale, given by the inverse of
+the driving frequency, is used to explain the observed coherence behavior.",0503047v1
+2005-07-29,Magnetic flux dynamics in critical state of one-dimensional discrete superconductor,"We give a theoretical description of avalanche-like dynamics of magnetic flux
+in the critical state of ""hard"" type-II superconductors using a model of a
+one-dimensional multijunction SQUID that well reproduces the main magnetic
+properties of these objects. We show that the system under consideration
+demonstrates the self-organized criticality. The avalanches of vortices
+manifest themselves as jumps of the total magnetic flux in the sample. The
+sizes of these jumps have a power-law distribution. Our results are in
+qualitative agreement with experiments.",0507703v1
+2005-08-07,Ultrafast light-induced magnetization dynamics in ferromagnetic semiconductors,"We develop a theory of the magnetization dynamics triggered by ultrafast
+optical excitation of ferromagnetic semiconductors. We describe the effects of
+the strong carrier spin relaxation on the nonlinear optical response by using
+the Lindblad semigroup method. We demonstrate magnetization control during
+femtosecond timescales via the interplay between circularly polarized optical
+excitation, hole-spin damping, polarization dephasing, and the Mn-hole spin
+interactions. Our results show a light-induced magnetization precession and
+relaxation for the duration of the optical pulse.",0508178v1
+2005-11-07,Current-induced switching in single ferromagnetic layer nanopillar junctions,"Current induced magnetization dynamics in asymmetric Cu/Co/Cu single magnetic
+layer nanopillars has been studied experimentally at room temperature and in
+low magnetic fields applied perpendicular to the thin film plane. In sub-100 nm
+junctions produced using a nanostencil process a bistable state with two
+distinct resistance values is observed. Current sweeps at fixed applied fields
+reveal hysteretic and abrupt transitions between these two resistance states.
+The current induced resistance change is 0.5%, a factor of 5 greater than the
+anisotropic magnetoresistance (AMR) effect. We present an experimentally
+obtained low field phase diagram of current induced magnetization dynamics in
+single ferromagnetic layer pillar junctions.",0511144v1
+2000-03-13,Hyperbolic Magnetic Billiards on Surfaces of Constant Curvature,"We consider classical billiards on surfaces of constant curvature, where the
+charged billiard ball is exposed to a homogeneous, stationary magnetic field
+perpendicular to the surface.
+  We establish sufficient conditions for hyperbolicity of the billiard
+dynamics, and give lower estimation for the Lyapunov exponent. This extends our
+recent results for non-magnetic billiards on surfaces of constant curvature.
+Using these conditions, we construct large classes of magnetic billiard tables
+with positive Lyapunov exponents on the plane, on the sphere and on the
+hyperbolic plane.",0003033v1
+2004-11-24,Stochastic Dynamics of Magnetosomes in Cytoskeleton,"Rotations of microscopic magnetic particles, magnetosomes, embedded into the
+cytoskeleton and subjected to the influence of an ac magnetic field and thermal
+noise are considered. Magnetosome dynamics is shown to comply with the
+conditions of the stochastic resonance under not-too-tight constraints on the
+character of the particle's fastening. The excursion of regular rotations
+attains the value of order of radian that facilitates explaining the biological
+effects of low-frequency weak magnetic fields and geomagnetic fluctuations.
+Such 1-rad rotations are effectively controlled by slow magnetic field
+variations of the order of 200 nT.",0411225v1
+2004-12-03,Numerical solutions of the three-dimensional magnetohydrodynamic alpha-model,"We present direct numerical simulations and alpha-model simulations of four
+familiar three-dimensional magnetohydrodynamic (MHD) turbulence effects:
+selective decay, dynamic alignment, inverse cascade of magnetic helicity, and
+the helical dynamo effect. The MHD alpha-model is shown to capture the
+long-wavelength spectra in all these problems, allowing for a significant
+reduction of computer time and memory at the same kinetic and magnetic Reynolds
+numbers. In the helical dynamo, not only does the alpha-model correctly
+reproduce the growth rate of magnetic energy during the kinematic regime, but
+it also captures the nonlinear saturation level and the late generation of a
+large scale magnetic field by the helical turbulence.",0412025v1
+2007-05-14,The dynamical response to the node defect in thermally activated remagnetization of magnetic dot array,"The influence of nonmagnetic central node defect on dynamical properties of
+regular square-shaped 5 x 5 segment of magnetic dot array under the thermal
+activation is investigated via computer simulations. Using stochastic
+Landau-Lifshitz-Gilbert equation we simulate hysteresis and relaxation
+processes. The remarkable quantitative and qualitative differences between
+magnetic dot arrays with nonmagnetic central node defect and magnetic dot
+arrays without defects have been found.",0705.1889v1
+2008-01-11,Thermal Dynamics in Symmetric Magnetic Nanopillars Driven by Spin Transfer,"We study the effects of spin transfer on thermally activated dynamics of
+magnetic nanopillars with identical thicknesses of the magnetic layers. The
+symmetric nanopillars exhibit anomalous dependencies of switching statistics on
+magnetic field and current. We interpret our data in terms of simultaneous
+current-induced excitation of both layers. We also find evidence for coupling
+between the fluctuations of the layers due to the spin transfer.",0801.1807v1
+2008-08-26,Dynamical pinning of domain wall in magnetic nanowire induced by Walker breakdown,"Transmission probability of a domain wall through a magnetic nanowire is
+investigated as a function of the external magnetic field. Very intriguing
+phenomenon is found that the transmission probability shows a significant drop
+after exceeding the threshold driving field, which contradicts our intuition
+that a domain wall is more mobile in the higher magnetic field. The
+micromagnetics simulation reveals that the domain wall motion in the wire with
+finite roughness causes the dynamical pinning due to the Walker breakdown,
+which semi-quantitatively explains our experimental results.",0808.3446v1
+2008-09-03,Detection of coherent magnons via ultrafast pump-probe reflectance spectroscopy in multiferroic Ba0.6Sr1.4Zn2Fe12O22,"We report the detection of a magnetic resonance mode in multiferroic
+Ba0.6Sr1.4Zn2Fe12O22 using time domain pump-probe reflectance spectroscopy.
+Magnetic sublattice precession is coherently excited via picosecond thermal
+modification of the exchange energy. Importantly, this precession is recorded
+as a change in reflectance caused by the dynamic magnetoelectric effect. Thus,
+transient reflectance provides a sensitive probe of magnetization dynamics in
+materials with strong magnetoelectric coupling, such as multiferroics,
+revealing new possibilities for application in spintronics and ultrafast
+manipulation of magnetic moments.",0809.0672v1
+2009-01-23,Non-equilibrium reversible dynamics of work production in four-spin system in a magnetic field,"A closed system of the equations for the local Bloch vectors and spin
+correlation functions is obtained by decomplexification of the Liouville-von
+Neumann equation for 4 magnetic particles with the exchange interaction that
+takes place in an arbitrary time-dependent external magnetic field. The
+analytical and numerical analysis of the quantum thermodynamic variables is
+carried out depending on separable mixed initial state and the magnetic field
+modulation. Under unitary evolution, non-equilibrium reversible dynamics of
+power production in the finite environment is investigated.",0901.3637v3
+2009-02-03,Dependence of critical current of spin transfer torque-driven magnetization dynamics on free layer thickness,"The dependence of the critical current of spin transfer torque-driven
+magnetization dynamics on the free-layer thickness was studied by taking into
+account both the finite penetration depth of the transverse spin current and
+spin pumping. We showed that the critical current remains finite in the
+zero-thickness limit of the free layer for both parallel and anti-parallel
+alignments. We also showed that the remaining value of the critical current of
+parallel to anti-parallel switching is larger than that of anti-parallel to
+parallel switching.",0902.0420v1
+2009-08-02,Nonlinear response of a thin metamaterial film containing Josephson junctions,"An interaction of electromagnetic field with metamaterial thin film
+containing split-ring resonators with Josephson junctions is considered. It is
+shown that dynamical self-inductance in a split rings results in reduction of
+magnetic flux through a ring and this reduction is proportional to a time
+derivative of split ring magnetization. Evolution of thin film magnetization
+taking into account dynamical self-inductance is studied. New mechanism for
+excitation of waves in one dimensional array of split-ring resonators with
+Josephson junctions is proposed. Nonlinear magnetic susceptibility of such thin
+films is obtained in the weak amplitude approximation.",0908.0103v1
+2009-12-15,Trapped low magnetic field dynamics in YBCO single crystals,"Trapped low magnetic flux dynamics including local ones are investigated in
+YBCO single crystals in the strong thermal fluctuations domain near the
+superconducting phase transition temperatures. The essential difference from
+quasi-logarithmic isothermal relaxation of a magnetization behavior (observed
+earlier in high magnetic fields) was established. Within the framework of
+classic model of a thermal activated vortices creep the estimation of an
+effective pinning potential was made at these temperatures.",0912.2835v1
+2010-01-15,Periodic magnetic geodesics on almost every energy level via variational methods,"For strong exact magnetic fields the action functional (i.e., the length plus
+the linear magnetic term) is not bounded from below on the space of closed
+contractible curves and the lower estimates for critical levels are derived by
+using the principle of throwing out cycles. It is proved that for almost every
+energy level the principle of throwing out cycles gives periodic magnetic
+geodesics on the critical levels defined by the ""thrown out"" cycles.",1001.2677v1
+2010-11-03,Convection and dynamo action in B stars,"Main-sequence massive stars possess convective cores that likely harbor
+strong dynamo action. To assess the role of core convection in building
+magnetic fields within these stars, we employ the 3-D anelastic spherical
+harmonic (ASH) code to model turbulent dynamics within a 10 solar mass
+main-sequence (MS) B-type star rotating at 4 times the solar rate. We find that
+strong (900 kG) magnetic fields arise within the turbulence of the core and
+penetrate into the stably stratified radiative zone. These fields exhibit
+complex, time-dependent behavior including reversals in magnetic polarity and
+shifts between which hemisphere dominates the total magnetic energy.",1011.1016v1
+2011-03-30,Wave turbulence on the surface of a ferrofluid in a horizontal magnetic field,"We report observations of wave turbulence on the surface of a ferrofluid
+submitted to a magnetic field parallel to the fluid surface. The magnetic wave
+turbulence shows several differences compared to the normal field case reported
+recently. The inertial zone of the magnetic wave turbulence regime is notably
+found to be strongly increased with respect to the normal field case, and to be
+well described by our theoretical predictions. The dispersion relation of
+linear waves is also measured and differs from the normal field case due to the
+absence of the Rosensweig instability.",1103.5847v1
+2011-06-16,Thermomagnonic spin transfer and Peltier effects in insulating magnets,"We study the coupled magnon energy transport and collective magnetization
+dynamics in ferromagnets with magnetic textures. By constructing a
+phenomenological theory based on irreversible thermodynamics, we describe
+motion of domain walls by thermal gradients and generation of heat flows by
+magnetization dynamics. From microscopic description based on magnon kinetics,
+we estimate the transport coefficients and analyze the feasibility of
+energy-related applications in insulating ferromagnets, such as yttrium iron
+garnet and europium oxide.",1106.3135v2
+2011-07-18,Molecular-spin dynamics study of electromagnons in multiferroic RMn$_2$O$_5$,"We investigate the electromagnon in magnetoferroelectrics RMn$_2$O$_5$ using
+combined molecular-spin dynamics simulations. We identify the origin of the
+electromagnon modes observed in the optical spectra and reproduce the most
+salient features of the electromagnon in these compounds. We find that the
+electromagnon frequencies are very sensitive to the magnetic wave vector along
+the $a$ direction. We further investigate the electromagnon in magnetic field.
+Although the modes frequencies change significant under magnetic field, the
+static dielectric constant electromagnon does not change much in the magnetic
+field.",1107.3349v1
+2011-12-06,Instability in magnetic materials with dynamical axion field,"It has been pointed out that the axion electrodynamics exhibits instability
+in the presence of a background electric field. We show that the instability
+leads to a complete screening of an applied electric field above a certain
+critical value and the excess energy is converted into a magnetic field. We
+clarify the physical origin of the screening effect and discuss its possible
+experimental realization in magnetic materials where magnetic fluctuations play
+the role of the dynamical axion field.",1112.1414v2
+2012-01-11,Frequency domain studies of current-induced magnetization dynamics in single magnetic-layer nanopillars,"Spin transfer torque-induced high-frequency dynamics of single thin
+cobalt-layer nanopillars of circular and elliptical shape have been observed
+directly. Two types of precessional modes can be identified as a function of
+magnetic field perpendicular to the layer plane, excited for negative current
+polarity only. They are assigned to vortex-core and transverse spin-wave
+excitations, which corroborate recent model predictions. The observed narrow
+linewidth of 4 MHz at room temperature indicates the high coherence of the
+magnetic excitations.",1201.2268v1
+2012-03-19,Dynamics of Vortex Nucleation in Nanomagnets with Broken Symmetry,"We investigate fundamental processes that govern dynamics of vortex
+nucleation in sub-100 nm mesoscopic magnets. We focus on a structure with
+broken symmetry - Pacman-like nanomagnet shape - in which we study
+micromagnetic behavior both by means of a simple model and numerically. We show
+that it is possible to establish desired vortex chirality and polarity by
+applying only quasi-static in-plane magnetic field along specific directions.
+We identify the modes of vortex nucleation that are very robust against
+external magnetic field noise. These vortex nucleation modes are common among
+wide range of sub-100 nm magnets with broken rotational symmetry.",1203.4191v1
+2012-04-23,Dynamics of a suspended nanowire driven by an ac Josephson current in an inhomogeneous magnetic field,"We consider a voltage-biased nanoelectromechanical Josephson junction, where
+a suspended nanowire forms a superconducting weak-link, in an inhomogeneous
+magnetic field. We show that a nonlinear coupling between the Josephson current
+and the magnetic field generates a Laplace force that induces a whirling motion
+of the nanowire. By performing an analytical and a numerical analysis, we
+demonstrate that at resonance, the amplitude-phase dynamics of the whirling
+movement present different regimes depending on the degree of inhomogeneity of
+the magnetic field: time independent, periodic and chaotic. Transitions between
+these regimes are also discussed.",1204.5020v1
+2012-08-15,Inertia and chiral edge modes of a skyrmion magnetic bubble,"The dynamics of a vortex in a thin-film ferromagnet resembles the motion of a
+charged massless particle in a uniform magnetic field. Similar dynamics is
+expected for other magnetic textures with a nonzero skyrmion number. However,
+recent numerical simulations revealed that skyrmion magnetic bubbles show
+significant deviations from this model. We show that a skyrmion bubble
+possesses inertia and derive its mass from the standard theory of a thin-film
+ferromagnet. Besides center-of-mass motion, other low energy modes are waves on
+the edge of the bubble traveling with different speeds in opposite directions.",1208.3123v2
+2013-09-04,Dynamical Process of Liner Implosion in the Electromagnetic Flux Compression for Ultra-high Magnetic Fields,"The spatial distribution of magnetic fields that are generated by the
+electromagnetic flux compression technique is investigated, with emphasis on
+the dynamical processes of an imploding liner. By comparing with the results of
+computer simulations, we found that the non-uniform implosion of a liner is
+important in order to explain the magnetic field's distribution during the
+liner's implosion. In addition, our results suggest that the initial inwards
+compressing spool-like motion of the liner subsequently turns out to be
+outwards stretching barrel-like motion along the magnetic field axis.",1309.1038v1
+2014-05-28,Breathing modes of confined skyrmions in ultrathin magnetic dots,"The dynamics of individual magnetic skyrmions confined in ultrathin film dots
+is studied theoretically. The systems considered are transition metal
+ferromagnets possessing perpendicular magnetic anisotropy and particular
+attention is given to the dynamic response of the skyrmions to perpendicular
+driving fields. By using micromagnetics simulations, it is shown that breathing
+modes can hybridize with geometrically-quantized spin wave eigenmodes of the
+circular dots considered, leading to distinct features in the power spectrum
+that differ to the behavior expected for uniformly magnetized systems. The
+field dependence of the breathing modes offers a direct means of detecting and
+characterizing such skyrmion states in experiment.",1405.7414v1
+2014-09-26,Magnetic field reversals and long-time memory in conducting flows,"Employing a simple ideal magnetohydrodynamic model in spherical geometry,we
+show that the presence of either rotation or finite magnetic helicity is
+sufficient to induce dynamical reversals of the magnetic dipole moment. The
+statistical character of the model is similar to that of terrestrial magnetic
+field reversals, with the similarity being stronger when rotation is
+present.The connection between long time correlations, $1/f$ noise, and
+statistics of reversals is supported, consistent with earlier suggestions.",1409.7568v1
+2015-05-10,Approaches for modeling magnetic nanoparticle dynamics,"Magnetic nanoparticles are useful biological probes as well as therapeutic
+agents. There have been several approaches used to model nanoparticle
+magnetization dynamics for both Brownian as well as N\'eel rotation. The
+magnetizations are often of interest and can be compared with experimental
+results. Here we summarize these approaches including the Stoner-Wohlfarth
+approach, and stochastic approaches including thermal fluctuations.
+Non-equilibrium related temperature effects can be described by a distribution
+function approach (Fokker-Planck equation) or a stochastic differential
+equation (Langevin equation). Approximate models in several regimes can be
+derived from these general approaches to simplify implementation.",1505.02450v1
+2015-08-19,Dynamical quenching of tunneling in molecular magnets,"It is shown that a single molecular magnet placed in a rapidly oscillating
+magnetic field displays the phenomenon of quenching of tunneling processes. The
+results open a way to manipulate the quantum states of molecular magnets by
+means of radiation in the terahertz range. Our analysis separates the time
+evolution into slow and fast components thereby obtaining an effective theory
+for the slow dynamics. This effective theory presents quenching of the tunnel
+effect. In particular, stands out its difference with the so-called coherent
+destruction of tunneling. We support our prediction with numerical evidence
+based on an exact solution of the Schr\""odinger's equation.",1508.04499v1
+2015-08-24,Spin Dynamics Simulation of the Magneto-Electric Effect in a Composite Multiferroic Chain,"A composite multiferroic chain with an interfacial linear magneto-electric
+coupling is used to study the magnetic and electric responses to an external
+magnetic or electric field. The simulation uses continuous spin dynamics
+through the Landau-Lifshitz-Gilbert equations of the magnetic spin and the
+electric pseudo-spin. The results demonstrate an accurate description of the
+distribution of the magnetisation and polarisation are induced by applied
+electric and magnetic field, respectively.",1508.05693v1
+2015-10-14,Stable determination of coefficients in the dynamical Schrödinger equation in a magnetic field,"In this paper we consider the inverse problem of determining on a compact
+Riemannian manifold the electric potential or the magnetic field in a
+Schr\""odinger equation with Dirichlet data from measured Neumann boundary
+observations. This information is enclosed in the dynamical
+Dirichlet-to-Neumann map associated to the magnetic Schr\""odinger equation. We
+prove that the knowledge of the Dirichlet-to-Neumann map for the Schr\""odinger
+equation uniquely determines the magnetic field and the electric potential and
+we establish H\""older-type stability.",1510.04247v1
+2015-11-14,Incoherent magnetization dynamics in strain mediated switching of magnetostrictive nanomagnets,"Micromagnetic studies of the magnetization change in magnetostrictive
+nanomagnets subjected to stress are performed for nanomagnets of different
+sizes. The interplay between demagnetization, exchange and stress anisotropy
+energies is used to explain the rich physics of size-dependent magnetization
+dynamics induced by modulating stress anisotropy in planar nanomagnets. These
+studies have important implications for strain mediated ultralow energy
+magnetization change in nanomagnets and its application in energy-efficient
+nanomagnetic computing systems.",1511.04617v1
+2015-12-14,Gauge and emergent electromagnetic fields for moving magnetic topological solitons,"We apply the general conception of non-Abelian gauge fields for description
+of magnetic soliton excitations. We show that the component of the gauge field
+along the soliton local magnetization (Abelian part of the gauge potential)
+determines dynamics of spin fluctuations over the soliton background in a
+ferromagnet. Assumption that the gauge field is a pure gauge allows calculating
+the gauge field components and finding simple expressions for the emergent
+electromagnet fields related to the soliton motion. The gauge field results in
+soliton-magnon interaction leading to renormalization of the soliton and magnon
+dynamics. The presented approach allows reaching more deep understanding of a
+relationship of the field theory and condensed matter magnetism.",1512.04396v1
+2016-02-12,Velocity Autocorrelation Function of Magnetized Two-Dimensional One-Component Plasma,"The velocity autocorrelation function (VAF) for a two-dimensional
+one-component plasma (OCP) is investigated by employing molecular dynamics
+techniques. The VAF exhibits well defined oscillations whose frequency is
+independent of the dimensionless coupling parameter Gamma. However, the
+presence of a uniform perpendicular external magnetic field increases the
+height of the first peak. Molecular dynamics computer simulation results are
+presented for a two-dimensional OCP in a perpendicular magnetic field as a
+function of the Plasma parameter. Our simulation results clearly indicate that
+at high temperature, the magnetic field affects the VAF in a substantial way.",1602.04176v1
+2016-11-02,Heavy-Quark Diffusion Dynamics in Quark-Gluon Plasma under Strong Magnetic Fields,"We discuss heavy-quark dynamics in the quark-gluon plasma under a strong
+magnetic field induced by colliding nuclei. By the use of the diagrammatic
+resummation techniques for Hard Thermal Loop and the external magnetic field,
+we show analytic results of heavy-quark diffusion coefficient and drag force
+which become anisotropic due to the preferred spatial orientation in the
+magnetic field. We argue that the anisotropic diffusion coefficient gives rise
+to an enhancement/suppression of the heavy-quark elliptic flow depending on the
+transverse momentum.",1611.00500v1
+2016-11-16,Dynamic chiral magnetic effect and Faraday rotation in macroscopically disordered helical metals,"We develop an effective medium theory for electromagnetic wave propagation
+through gapless non-uniform systems with dynamic chiral magnetic effect. The
+theory allows to calculate macroscopic-disorder-induced corrections to the
+values of optical, as well as chiral magnetic conductivities. In particular, we
+show that spatial fluctuations of optical conductivity induce corrections to
+the effective value of the chiral magnetic conductivity. Experimentally, these
+corrections can be observed as sharp features in the Faraday rotation angle
+near frequencies that correspond to the bulk plasmon resonances of a material.
+Such features are not expected to be present in single crystal samples.",1611.05491v1
+2017-10-23,Clustering of Magnetic Swimmers in a Poiseuille Flow,"We investigate the collective behavior of magnetic swimmers, which are
+suspended in a Poiseuille flow and placed under an external magnetic field,
+using analytical techniques and Brownian dynamics simulations. We find that the
+interplay between intrinsic activity, external alignment, and magnetic
+dipole-dipole interactions leads to longitudinal structure formation. Our work
+sheds light on a recent experimental observation of a clustering instability in
+this system.",1710.08339v2
+2018-07-27,Thick Permalloy films for the imaging of spin texture dynamics in perpendicularly magnetized systems,"We demonstrated that thick Permalloy films exhibiting a weak growth-induced
+perpendicular magnetic anisotropy can be employed as an ideal test system for
+the investigation of gyration dynamics in topologically trivial and non-trivial
+magnetic states ranging from an isolated magnetic skyrmion to more complex
+n$\pi$ spin configurations.",1807.10654v1
+2019-12-12,"Cluster glass behavior of frustrated birnessites AxMnO2*yH2O (A = Na, K)","We report on the synthesis and magnetic properties of frustrated
+Na0.22MnO2*0.39H2O and K0.6MnO2*0.48H2O with the birnessite structure. The
+structure, static and dynamic magnetic properties of the compounds are
+investigated in detail. A combination of DC and AC magnetic susceptibility
+measurements and magnetization decay measurements reveal cluster glass behavior
+below the freezing temperature of 4 K for Na-birnessite and 6 K for
+K-birnessite. The frequency dependence of the freezing temperature is analyzed
+on the basis of dynamic scaling laws including the critical slowing down
+formula and the Vogel-Fulcher law, which further confirm cluster glass
+formation in both compounds.",1912.05997v1
+2020-03-05,Unidirectional Pumping of Phonons by Magnetization Dynamics,"We propose a method to control surface phonon transport by weak magnetic
+fields based on the pumping of surface acoustic waves (SAWs) by
+magnetostriction. We predict that the magnetization dynamics of a nanowire on
+top of a dielectric films injects SAWs with opposite angular momenta into
+opposite directions. Two parallel nanowires form a phononic cavity that at
+magnetic resonances pump a unidirectional SAW current into half of the
+substrate.",2003.02519v2
+2020-07-23,No feedback is possible in small-scale turbulent magnetic field,"Evolution of stochastically homogeneous magnetic field advected by
+incompressible turbulent flow with large magnetic Prandtl numbers is considered
+at the scales less than Kolmogorov viscous scale. It is shown that, despite
+unlimited growth of the magnetic field, its feedback on the fluid's dynamics
+remains negligibly small.",2007.11940v1
+2020-12-15,Dynamically stabilized spin superfluidity in frustrated magnets,"We study the onset of spin superfluidity, namely coherent spin transport
+mediated by a topological spin texture, in frustrated exchange-dominated
+magnetic systems, engendered by an external magnetic field. We show that for
+typical device geometries used in nonlocal magnetotransport experiments, the
+magnetic field stabilizes a spin superflow against fluctuations, up to a
+critical current. For a given current, the critical field depends on the
+precessional frequency of the texture, which can be separately controlled. We
+contrast such dynamic stabilization of a spin superfluid to the conventional
+approaches based on topological stabilization.",2012.08340v1
+2021-01-30,Nearly ideal memristive functionality based on viscous magnetization dynamics,"We experimentally demonstrate a proof-of-principle implementation of an
+almost ideal memristor - a two-terminal circuit element whose resistance is
+approximately proportional to the integral of the input signal over time. The
+demonstrated device is based on a thin-film ferromagnet/antiferromagnet
+bilayer, where magnetic frustration results in viscous magnetization dynamics
+enabling memristive functionality, while the external magnetic field plays the
+role of the driving input. The demonstrated memristor concept is amenable to
+downscaling and can be adapted for electronic driving, making it attractive for
+applications in neuromorphic circuits.",2102.00123v1
+2022-02-12,Trace formula for the magnetic Laplacian on a compact hyperbolic surface,"We compute the trace formula for the magnetic Laplacian on a compact
+hyperbolic surface of constant curvature with constant magnetic field for
+energies above the Mane critical level of the corresponding magnetic geodesic
+flow. We discuss the asymptotic behavior of the coefficients of the trace
+formula when the energy approaches the Mane critical level.",2202.06055v3
+2022-10-20,Numerical study of the Transverse Diffusion coefficient for a one component model of plasma,"In this paper we discuss the results of some Molecular Dynamics simulations
+of a magnetized One Component Plasma, targeted to estimate the diffusion
+coefficient $D_{\perp}$ in the plane orthogonal to the magnetic field lines. We
+find that there exists a threshold with respect to the magnetic field strength
+$|\vec B|$: for weak magnetic field the diffusion coefficients scales as
+$1/|\vec B|^2$, while a slower decay appears at high field strength. The
+relation of this transition with the different mixing properties of the
+microscopic dynamics is investigated by looking at the behavior of the velocity
+auto correlation.",2210.11125v1
+2023-04-17,Skyrmion dynamics in moiré magnets,"We consider a twisted magnetic bilayer subject to the perpendicular electric
+field. The interplay of induced Dzyaloshinskii - Moriya interaction and
+spatially varying moir\'e exchange potential results in complex non-collinear
+magnetic phases in these structures. We numerically demonstrate the coexistence
+of intralayer skyrmions and bound interlayer skyrmion pairs and show that they
+are characterized by distinct dynamics under the action of external in-plane
+electric field. Specifically we demonstrate the railing behaviour of skyrmions
+along the domain walls which could find applications in spintronic devices
+based on van der Waals magnets.",2304.08306v2
+2023-07-07,Time-dependent parameter identification in a Fokker-Planck equation based magnetization model of large ensembles of nanoparticles,"In this article, we consider a model motivated by large ensembles of
+nanoparticles' magnetization dynamics using the Fokker-Planck equation and
+analyze the underlying parabolic PDE being defined on a smooth, compact
+manifold without boundary with respect to time-dependent parameter
+identification using regularization schemes. In the context of magnetic
+particle imaging, possible fields of application can be found including
+calibration procedures improved by time-dependent particle parameters and
+dynamic tracking of nanoparticle orientation. This results in reconstructing
+different parameters of interest, such as the applied magnetic field and the
+particles' easy axis. These problems are in particular addressed in the
+accompanied numerical study.",2307.03560v1
+2023-08-28,Laser-enhanced magnetism in SmFeO$_3$,"To coherently enhance inherent weak magnetic interactions in rare-earth
+orthoferrite SmFeO$_3$ as a functional material for spintronic applications, we
+simulate the dissipative spin dynamics that are linearly and quadratically
+coupled to laser-driven infrared-active phonons. When linear coupling
+dominates, we discover a magnetophononic dynamical first-order phase transition
+in the nonequilibrium steady state which can inhibit strong enhancement of
+magnetic interactions. By contrast, when quadratic spin-phonon coupling
+dominates, no phase transition exists at experimentally relevant parameters. By
+utilizing a chirp protocol, the phase transition can be engineered, enabling
+stronger magnetic interactions. We also discuss the route for experimental
+observation of our results.",2308.14939v2
+2023-12-01,Magnetic-field-induced critical dynamics in magnetoelectric TbPO$_4$,"We report on the magnetoelectric dynamics in the linear magnetoelectric
+antiferromagnet TbPO$_4$ studied by broadband dielectric spectroscopy. For the
+phase transition into the magnetoelectric antiferromagnetic phase at $T_{N}
+\approx 2.3$ K, a finite magnetic field $H$ induces critical behavior in the
+quasi-static permittivity $\varepsilon'$. Plotting the corresponding anomaly as
+function of $T/T_N(H)$, we observe the scaling behavior $\Delta \varepsilon'
+\propto H^2$, a clear fingerprint of linear magnetoelectric antiferromagnets.
+Above the phase transition, we find a critical slowing down of the ferroic
+fluctuations in finite magnetic field. This behaviour can be understood via a
+magnetic-field-induced relaxational response that resembles the soft-mode
+behaviour in canonical ferroelectrics and multiferroics.",2312.00726v1
+2023-12-22,Magnetic droplet solitons,"Magnetic droplets are nanoscale, non-topological, dynamical solitons that can
+be nucleated in different spintronic devices, such as spin torque
+nano-oscillators (STNOs) and spin Hall nano-oscillators (SHNOs). This chapter
+first briefly discusses the theory of spin current driven dissipative magnetic
+droplets in ferromagnetic thin films with uniaxial anisotropy. We then
+thoroughly review the research literature on magnetic droplets and their
+salient features, as measured using electrical, microwave, and synchrotron
+techniques, and as envisaged by micromagnetic simulations. We also touch upon a
+closely related soliton, the dynamical skyrmion. Finally, we present an outlook
+of new routes in droplet science.",2312.14621v1
+2024-02-05,Modelling nanomagnet vertex dynamics through Coulomb charges,"We investigate the magnetization dynamics in nanomagnet vertices often found
+in artificial spin ices. Our analysis involves creating a simplified model that
+depicts edge magnetization using magnetic charges. We utilize the model to
+explore the energy landscape, its associated curvatures, and the fundamental
+modes. Our study uncovers specific magnonic regimes and transitions between
+magnetization states, marked by zero-modes, which can be understood within the
+framework of Landau theory. To verify our model, we compare it with
+micromagnetic simulations, demonstrating a noteworthy agreement.",2402.03036v1
+2020-08-13,Magnetization Dynamics of Nanoscale Magnetic Materials: A Perspective,"Nanomagnets form the building blocks for a gamut of miniaturized
+energy-efficient devices including data storage, memory, wave-based computing,
+sensors and biomedical devices. They also offer a span of exotic phenomena and
+stern challenges. The progress in the magnetization dynamics of single
+nanomagnets and one- and two-dimensional arrays of nanostructures in the form
+of dots, antidots, nanoparticles, binary and bicomponent structures and
+patterned multilayers have been presented. Progress in unconventional and new
+structures like artificial spin ice and three-dimensional nanomagnets and spin
+textures like domain walls, vortex and skyrmions have been presented.
+Furthermore, a huge variety of new topics in the magnetization dynamics of
+magnetic nanostructures are rapidly emerging. An overview of the steadily
+evolving topics like spatio-temporal imaging of fast dynamics of
+nanostructures, dynamics of spin textures, artificial spin ice have been
+discussed. In addition, dynamics of contemporary and newly transpired magnetic
+architectures such as nanomagnet arrays with complex basis and symmetry,
+magnonic quasicrystals, fractals, defect structures, novel three-dimensional
+structures have been introduced. Effects of various spin-orbit coupling and
+ensuing spin textures as well as quantum hybrid systems comprising of
+magnon-photon, magnon-phonon and magnon-magnon coupling, antiferromagnetic
+nanostructures are rapidly growing and are expected to dominate this research
+field in the coming years. Finally, associated topics like nutation dynamics
+and nanomagnet antenna are briefly discussed. Despite showing a great progress,
+only a small fraction of nanomagnetism and its ancillary topics have been
+explored so far and huge efforts are envisaged in this evergrowing research
+area in the generations to come.",2008.05819v1
+1999-07-12,Differential rotation and magnetic fields in stellar interiors,"The processes contributing to the evolution of an initially weak magnetic
+field in a differentially rotating star are reviewed. These include rotational
+smoothing (akin to convective expulsion) and a list of about 5 instabilities,
+among them magnetorotational instability, byoyancy instability, and pinch-type
+instabilities. The important effects of thermal and magnetic diffusion on these
+instabilities are analyzed in some detail. The first instability to set in is a
+pinch-type instability. It becomes important in modifying the field
+configuration before magnetic buoyancy-driven instabilities set in. The
+evolution of an initially strong field remains a more open question, including
+the old problem whether dynamically stable magnetic equilibria exist in stars.",9907138v1
+2001-01-17,The temperature-mass relation in magnetized galaxy clusters,"We use cosmological, magneto-hydrodynamic simulations of galaxy clusters to
+quantify the dynamical importance of magnetic fields in these clusters. The
+set-up of initial magnetic field strengths at high redshifts is chosen such
+that observed Faraday-rotation measurements in low-redshift clusters are well
+reproduced in the simulations. We compute the radial profiles of the
+intracluster gas temperature and of the thermal and magnetic pressure in a set
+of clusters simulated in the framework of an Einstein-de Sitter and a
+low-density, spatially-flat CDM cosmological model. We find that, for a
+realistic range of initial magnetic field strengths, the temperature of the
+intracluster gas changes by less than $\approx5%$.",0101302v1
+2006-11-17,Magnetic field vector retrieval with the Helioseismic and Magnetic Imager,"We investigate the accuracy to which we can retrieve the solar photospheric
+magnetic field vector using the Helioseismic and Magnetic Imager (HMI) that
+will fly onboard of the Solar Dynamics Observatory (SDO) by inverting simulated
+HMI profiles. The simulated profiles realistically take into account the
+effects of the photon noise, limited spectral resolution, instrumental
+polarization modulation, solar p modes and temporal averaging. The accuracy of
+the determination of the magnetic field vector is studied considering the
+different operational modes of the instrument.",0611565v1
+1995-11-02,"Berry phase, hyperorbits, and the Hofstadter spectrum: semiclassical dynamics in magnetic Bloch bands","We have derived a new set of semiclassical equations for electrons in
+magnetic Bloch bands. The velocity and energy of magnetic Bloch electrons are
+found to be modified by the Berry phase and magnetization. This semiclassical
+approach is used to study general electron transport in a DC or AC electric
+field. We also find a close connection between the cyclotron orbits in magnetic
+Bloch bands and the energy subbands in the Hofstadter spectrum. Based on this
+formalism, the pattern of band splitting, the distribution of Hall conduct-
+ivities, and the positions of energy subbands in the Hofstadter spectrum can be
+understood in a simple and unified picture.",9511014v1
+1997-08-06,Macroscopic Quantum Coherence in Molecular Magnets,"We study macroscopic quantum coherence in antiferromagnetic molecular magnets
+in the presence of magnetic fields. Such fields generate artificial tunnel
+barriers with externally tunable strength. We give detailed semi-classical
+predictions for the tunnel splitting in various regimes for low and high
+magnetic fields. We show that the tunneling dynamics of the Neel vector can be
+directly measured via the static magnetization and the specific heat. We also
+report on a new quantum phase arising from fluctuations. The analytic results
+are complemented by numerical simulations.",9708042v1
+1998-01-13,Skyrmion in a real magnetic film,"Skyrmions are the magnetic defects in an ultrathin magnetic film, similar to
+the bubble domains in the thicker films. Even weak uniaxial anisotropy
+determines its radius unambiguously. We consider the dynamics of the skyrmion
+decay. We show that the discreteness of the lattice in an isotropic 2D magnet
+leads to a slow rotation of the local magnetization in the skyrmion and,
+provided a small dissipation, to decay of the skyrmion. The radius of such a
+skyrmion as a function of time is calculated. We prove that uniaxial anisotropy
+stabilizes the skyrmion and study the relaxation process.",9801114v1
+1998-06-05,Magnetic Particles,"We present an overview of the subject of Magnetic Particles, starting at a
+level suitable for advanced high-school students and ending at a level suitable
+for current practitioners in the field. The sub-topics covered include: Types
+of Magnetic Materials, Relationships Between the Vector Fields, Magnetic
+Energies, Dynamics of Magnetic Particles, and Magnetocaloric Effects.",9806082v1
+1999-11-08,Feedback Effect on Landau-Zener-Stueckelberg Transitions in Magnetic Systems,"We examine the effect of the dynamics of the internal magnetic field on the
+staircase magnetization curves observed in large-spin molecular magnets. We
+show that the size of the magnetization steps depends sensitively on the
+intermolecular interactions, even if these are very small compared to the
+intra-molecular couplings.",9911106v2
+2000-04-19,Statistical coarse-graining as an approach to multiscale problems in magnetism,"Multiscale phenomena which include several processes occuring simultaneously
+at different length scales and exchanging energy with each other, are
+widespread in magnetism. These phenomena often govern the magnetization
+reversal dynamics, and their correct modeling is important. In the present
+paper, we propose an approach to multiscale modeling of magnets, applying the
+ideas of coarse graining. We have analyzed the choice of the weighting function
+used in coarse graining, and propose an optimal form for this function. Simple
+tests provide evidence that this approach may be useful for modeling of
+realistic magnetic systems.",0004338v1
+2001-01-29,Magnetic Properties for the One-Dimensional Multicomponent Spin-Gap System,"Magnetic properties for the one-dimensional multicomponent quantum spin
+system with the excitation gap are studied based on the integrable spin model
+introduced by Bariev {\it et al}. By exactly computing the magnetization, we
+show how the characteristic structure with plateaus and cusps appears in the
+magnetization process. To study low-energy dynamics of the system, we apply the
+finite-size scaling analysis to the excitation spectrum, and thereby evaluate
+the power-law exponent as well as the enhancement factor for the
+low-temperature NMR relaxation rate $1/T_1$. We discuss the critical properties
+of $1/T_1$ around plateaus and cusps in the magnetization curve.",0101423v1
+2002-09-04,Correlation Effects on Magnetic Anisotropy in Fe and Ni,"We calculate magnetic anisotropy energy of Fe and Ni by taking into account
+the effects of strong electronic correlations, spin-orbit coupling, and
+non-collinearity of intra-atomic magnetization. The LDA+U method is used and
+its equivalence to dynamical mean-field theory in the static limit is derived.
+The effects of strong correlations are studied along several paths in $(U,J)$
+parameter space. Both experimental magnitude of MAE and direction of
+magnetization are predicted correctly near $U=1.9 eV$, $J=1.2 eV$ for Ni and
+$U=1.2 eV$, $J=0.8 eV$ for Fe. The modified one-electron spectra by strong
+correlations are emphasized in conjunction with magnetic anisotropy.",0209073v1
+2002-11-05,Magnetic fluctuations and resonant peak in cuprates: a microscopic theory,"The theory for the dynamical spin susceptibility within the t-J model is
+developed, as relevant for the resonant magnetic peak and normal-state magnetic
+response in superconducting (SC) cuprates. The analysis is based on the
+equations of motion for spins and the memory-function presentation of magnetic
+response where the main damping of the low-energy spin collective mode comes
+from the decay into fermionic degrees of freedom. It is shown that the damping
+function at low doping is closely related to the c-axis optical conductivity.
+The analysis reproduces doping-dependent features of the resonant magnetic
+scattering.",0211090v1
+2002-11-25,Electrical Manipulation of Nanomagnets,"We demonstrate a possibility to manipulate the magnetic coupling between two
+nanomagnets with a help of ac electric field. In the scheme suggested the
+magnetic coupling in question is mediated by a magnetic particle contacting
+with both of the nanomagnets through the tunnel barriers. The electric field
+providing a successive suppression of the barriers leads to pumping of
+magnetization through the mediating particle. Time dependent dynamics of the
+particle magnetization allows to to switch between ferro- and antiferromagnetic
+couplings.",0211563v1
+2003-05-21,From Bubble to Skyrmion: Dynamic Transformation Mediated by a Strong Magnetic Tip,"Skyrmions in thin metallic ferromagnetic films are stable due to competition
+between the RKKY interaction and uniaxial magnetic anisotropy. We mimic the
+RKKY interaction by the next-nearest-neighbors ferromagnetic and
+antiferromagnetic exchange interactions. We demonstrate analytically and
+numerically dissipative transformation of a bubble created by a strong
+cylindrical magnetic tip into a stable Skyrmion.",0305487v1
+2003-11-28,Rectangular quantum dots in high magnetic fields,"We use density-functional methods to study the effects of an external
+magnetic field on two-dimensional quantum dots with a rectangular hard-wall
+confining potential. The increasing magnetic field leads to spin polarization
+and formation of a highly inhomogeneous maximum-density droplet at the
+predicted magnetic field strength. At higher fields, we find an oscillating
+behavior in the electron density and in the magnetization of the dot. We
+identify a rich variety of phenomena behind the periodicity and analyze the
+complicated many-electron dynamics, which is shown to be highly dependent on
+the shape of the quantum dot.",0311639v1
+2004-03-29,The origin of the glassy magnetic dynamics of the phase segregated state in perovskites,"In this paper we address many of the fundamental open questions regarding the
+glassy behavior of the magnetic/electronic phase segregated state in rare earth
+perovskites. In particular, magnetic relaxation experiments support that the
+collective effects (memory, ageing, etc.) are due to interparticle
+interactions, rather than the double-exchange vs. superexchange competition. A
+careful study of the non-linear susceptibility in the critical region is
+performed, and the critical exponents contrasted with those of conventional
+spin-glasses and concentrated quenched ferrofluids. The phase segregated state
+constitutes a sort of self-generated assembly of magnetic particles in which
+magnetic interaction introduces collectivity among the clusters.",0403686v1
+2004-05-13,Precessional dynamics of elemental moments in a ferromagnetic alloy,"We demonstrate an element-specific measurement of magnetization precession in
+a metallic ferromagnetic alloy, separating Ni and Fe moment motion in Ni81Fe19.
+Pump-probe X-ray magnetic circular dichroism (XMCD), synchronized with short
+magnetic field pulses, is used to measure free magnetization oscillations up to
+2.6 GHz with elemental specificity and a rotational resolution of < 2 deg.
+Magnetic moments residing on Ni sites and Fe sites in a Ni81Fe19(50nm) thin
+film are found to precess together at all frequencies, coupled in phase within
+instrumental resolution of 90 ps.",0405295v1
+2004-08-10,Dynamics of liquid crystalline domains in magnetic field,"We study microscopic single domains nucleating and growing within the
+coexistence region of the Isotropic (I) and Nematic (N) phases in magnetic
+field. By rapidly switching on the magnetic field the time needed to align the
+nuclei of sufficiently large size is measured, and is found to decrease with
+the square of the magnetic field. When the field is removed the disordering
+time is observed to last on a longer time scale. The growth rate of the nematic
+domains at constant temperature within the coexistence region is found to
+increase when a magnetic field is applied.",0408208v2
+2005-05-30,Dynamical Symmetry Breaking in Quasistatic Magnetic Oscillations,"Recent microwave experiments demonstrate the anapole-moment and
+magnetoelectric properties in quasi-2D ferrite particles with
+magnetic-dipolar-wave oscillating spectra. The theory developed in this paper
+shows that there are the macroscopically quantum topological effects. Quantum
+coherence for macroscopic systems refers to circumstances when large numbers of
+particles can collectively cooperate in a single quantum state. These effects
+are rarely observed through macroscopic measurements because statistical
+averaging over many states usually masks all evidence of quantum discreteness.
+Magnetic-dipolar oscillating modes in normally magnetized ferrite disks
+demonstrate properties of a Hamiltonian system. The purpose of this paper is to
+show that because of the adiabatic motion process for such a Hamiltonian system
+one has macroscopic quantum effects of symmetry breaking, magnetic currents,
+and eigen electric moments.",0505717v1
+2006-05-15,Sculpting microscopic magnetic flux landscapes in a BSCCO2212 vortex lens,"We demonstrate experimentally that the micromagnetic profile of the
+out-of-plane component of magnetic induction, B_z, in the crossing lattices
+regime of layered superconductors can be manipulated by varying the in-plane
+magnetic field, H_{||}. Moving Josephson vortices drag/push pancake vortex
+stacks, and the magnetic profile, B_z(x), can be controllably sculpted across
+the entire single crystal sample. Depending on the H-history and temperature we
+can increase or decrease the flux density at the center and near the edges of
+the crystal by as much as 40%, realising both 'convex' and 'concave' magnetic
+flux lenses. Our experimental results are well described by molecular dynamics
+simulations.",0605375v1
+2006-09-01,Calculations of Magnetic Exchange Interactions in Mott--Hubbard Systems,"An efficient method to compute magnetic exchange interactions in systems with
+strong correlations is introduced. It is based on a magnetic force theorem
+which evaluates linear response due to rotations of magnetic moments and uses a
+novel spectral density functional framework combining our exact diagonalization
+based dynamical mean field and local density functional theories. Applications
+to spin waves and magnetic transition temperatures of 3d metal mono--oxides as
+well as high--T_{c} superconductors are in good agreement with experiment.",0609006v1
+2006-11-02,Spin-phonon coupling in ZnCr2Se4,"Spin-phonon coupling and magnetodielectric effects of ZnCr2Se4 were
+investigated by means of infrared (IR) spectroscopy as a function of
+temperature and magnetic field. ZnCr2Se4 is dominated by ferromagnetic exchange
+but undergoes antiferromagnetic order at T = 21 K. In the magnetically ordered
+phase the low-frequency IR active phonon splits, indicating strong dynamic
+anisotropy via magnetic exchange interactions. Antiferromagnetic order and
+concomitantly the phonon splitting is wiped out by external magnetic fields.
+Hence, ZnCr2Se4 is a prominent example of a spin-driven Jahn-Teller effect
+which can be fully suppressed in external magnetic fields.",0611041v1
+1992-12-03,Magnetic Fields and Passive Scalars in Polyakov's Conformal Turbulence,"Polyakov has suggested that two dimensional turbulence might be described by
+a minimal model of conformal field theory. However, there are many minimal
+models satisfying the same physical inputs as Polyakov's solution (p,q)=(2,21).
+Dynamical magnetic fields and passive scalars pose different physical
+requirements. For large magnetic Reynolds number other minimal models arise.
+The simplest one, (p,q)=(2,13) makes reasonable predictions that may be tested
+in the astrophysical context. In particular, the equipartition theorem between
+magnetic and kinetic energies does not hold: the magnetic one dominates at
+larger distances.",9212021v1
+2004-11-04,Structure formation in electromagnetically driven granular media,"We report structure formation in submonolayers of magnetic microparticles
+subjected to periodic electrostatic and magnetic excitations. Depending on the
+excitation parameters, we observe the formation of a rich variety of
+structures: clusters, rings, chains, and networks. The growth dynamics and
+shapes of the structures are strongly dependent on the amplitude and frequency
+of the external magnetic field. We find that for pure ac magnetic driving at
+low densities of particles, the low-frequency magnetic excitation favors
+clusters while high frequency excitation favors chains and net-like structures.
+An abrupt phase transition from chains to a network phase was observed for a
+high density of particles.",0411013v1
+2000-10-19,Magnetic Field Saturation in the Riga Dynamo Experiment,"After the dynamo experiment in November 1999 had shown magnetic field
+self-excitation in a spiraling liquid metal flow, in a second series of
+experiments emphasis was placed on the magnetic field saturation regime as the
+next principal step in the dynamo process. The dependence of the strength of
+the magnetic field on the rotation rate is studied. Various features of the
+saturated magnetic field are outlined and possible saturation mechanisms are
+discussed.",0010047v1
+2007-07-09,Magnetic strings in Lattice QCD as Nonabelian Vortices,"Lattice studies indicate existence of magnetic strings in QCD vacuum. We
+argue that recently found nonabelian strings with rich worldsheet dynamics
+provide a proper pattern for the strings observed on the lattice. In
+particular, within this pattern we explain the localization of the
+monopole-antimonopole pairs on the magnetic string worldsheet and the negative
+contribution of the magnetic strings into the vacuum energy and gluon
+condensate. We suggest the D2 brane realization of the magnetic string which
+explains the temperature dependence of its tension.",0707.1284v1
+2007-09-12,Two Ferromagnetic Phases in Spin-Fermion Systems,"We consider spin-fermion systems which get their magnetic properties from a
+system of localized magnetic moments being coupled to conducting electrons. The
+dynamical degrees of freedom are spin-$s$ operators of localized spins and
+spin-1/2 fermi operators of itinerant electrons. We develop modified spin-wave
+theory and obtain that system has two ferromagnetic phases. At the
+characteristic temperature T* the magnetization of itinerant electrons becomes
+zero, and high temperature ferromagnetic phase (T*<T<T_C) is a phase where only
+localized electrons give contribution to the magnetization of the system. An
+anomalous increasing of magnetization below T* is obtained in a good agrement
+with experimental measurements of the ferromagnetic phase of UGe2.",0709.1759v2
+2008-06-24,Reduction of velocity fluctuations in a turbulent flow of gallium by an external magnetic field,"The magnetic field of planets or stars is generated by the motion of a
+conducting fluid through a dynamo instability. The saturation of the magnetic
+field occurs through the reaction of the Lorentz force on the flow. In relation
+to this phenomenon, we study the effect of a magnetic field on a turbulent flow
+of liquid Gallium. The measurement of electric potential differences provides a
+signal related to the local velocity fluctuations. We observe a reduction of
+velocity fluctuations at all frequencies in the spectrum when the magnetic
+field is increased.",0806.3872v1
+2008-09-03,Magnetic dynamo action in astrophysical turbulence,"We investigate the structure of magnetic field amplified by turbulent
+velocity fluctuations, in the framework of the kinematic Kazantsev-Kraichnan
+model. We consider Kolmogorov distribution of velocity fluctuations, and assume
+that both Reynolds number and magnetic Reynolds number are very large. We
+present the full numerical solution of the model for the spectra and the growth
+rates of magnetic fluctuations. We consider astrophysically relevant limits of
+large and small magnetic Prandtl numbers, and address both helical and
+nonhelical cases.",0809.0720v2
+2008-11-13,Optical spin orientation of a single manganese atom in a quantum dot,"A hight degree of spin polarization is achieved for a Mn atom localized in a
+semiconductor quantum dot using quasi-resonant optical excitation at zero
+magnetic field. Optically created spin polarized carriers generate an energy
+splitting of the Mn spin and enable magnetic moment orientation controlled by
+the photon helicity and energy. The dynamics and the magnetic field dependence
+of the optical pumping mechanism shows that the spin lifetime of an isolated Mn
+atom at zero magnetic field is controlled by a magnetic anisotropy induced by
+the built-in strain in the quantum dots.",0811.2165v1
+2008-12-02,Local control of ultrafast dynamics in magnetic nanoparticles,"Using the local control theory we derive analytical expressions for magnetic
+field pulses that steer the magnetization of a monodomain magnetic nanoparticle
+to a predefined state. Finite-temperature full numerical simulations confirm
+the analytical results and show that a magnetization switching or freezing is
+achievable within few precessional periods and that the scheme is exploitable
+for fast thermal switching.",0812.0584v1
+2009-03-12,Self-organized patterns of macroscopic quantum tunneling in molecular magnets,"We study low temperature resonant spin tunneling in molecular magnets induced
+by a field sweep with account of dipole-dipole interactions. Numerical
+simulations uncovered formation of self-organized patterns of the magnetization
+and of the ensuing dipolar field that provide resonant condition inside a
+finite volume of the crystal. This effect is robust with respect to disorder
+and should be relevant to the dynamics of the magnetization steps observed in
+molecular magnets.",0903.2247v1
+2009-06-13,Single-shot time-domain studies of spin-torque-driven switching in magnetic tunnel junctions,"We report single-shot measurements of resistance versus time for thermally
+assisted spin-torque-driven switching in magnetic tunnel junctions. We achieve
+sufficient sensitivity to resolve the resistance signals leading up to
+switching, including the variations between individual switching events.
+Analyses of pre-switching thermal fluctuations allow detailed measurements of
+coherence times and variations in magnetization precession amplitude. We find
+that with a small in-plane hard-axis magnetic field the magnetization dynamics
+are more spatially coherent than for the case of zero field.",0906.2476v1
+2009-10-10,Light-induced valley currents and magnetization in graphene rings,"We study the non-equilibrium dynamics in a mesoscopic graphene ring excited
+by picoseconds shaped electromagnetic pulses. We predict an ultrafast buildup
+of charge polarization, currents and orbital magnetization. Applying the light
+pulses identified here, non-equilibrium valley currents are generated in a
+graphene ring threaded by a stationary magnetic flux. We predict a finite
+graphene ring magnetization even for a vanishing charge current; the
+magnetization emerges due to the light-induced difference of the valley
+populations.",0910.1950v1
+2010-02-12,Real-time dynamics of the Chiral Magnetic Effect,"In quantum chromodynamics, a gauge field configuration with nonzero
+topological charge generates a difference between the number of left- and
+right-handed quarks. When a (electromagnetic) magnetic field is added to this
+configuration, an electromagnetic current is induced along the magnetic field;
+this is called the chiral magnetic effect. We compute this current in the
+presence of a color flux tube possessing topological charge, with a magnetic
+field applied perpendicular to it. We argue that this situation is realized at
+the early stage of relativistic heavy-ion collisions.",1002.2495v1
+2010-08-06,Ferromagnetic phases in spin-Fermion systems,"Spin-Fermion systems which obtain their magnetic properties from a system of
+localized magnetic moments being coupled to conducting electrons are
+considered. The dynamical degrees of freedom are spin-$s$ operators of
+localized spins and spin-1/2 Fermi operators of itinerant electrons.
+Renormalized spin-wave theory, which accounts for the magnon-magnon
+interaction, and its extension are developed to describe the two ferrimagnetic
+phases in the system: low temperature phase $0<T<T^{*}$, where all electrons
+contribute the ordered ferromagnetic moment, and high temperature phase
+$T^{*}<T<T_C$, where only localized spins form magnetic moment. The
+magnetization as a function of temperature is calculated. The theoretical
+predictions are utilize to interpret the experimentally measured
+magnetization-temperature curves of $UGe_2$..",1008.1148v1
+2010-09-04,Magnetization Reversal by Electric-Field Decoupling of Magnetic and Ferroelectric Domains Walls in Multiferroic-Based Heterostructures,"We demonstrate that the magnetization of a ferromagnet in contact with an
+antiferromagnetic multiferroic (LuMnO3) can be speedily reversed by electric
+field pulsing, and the sign of the magnetic exchange bias can switch and
+recover isothermally. As LuMnO3 is not ferroelastic, our data conclusively show
+that this switching is not mediated by strain effects but is a unique
+electric-field driven decoupling of the ferroelectric and ferromagnetic domains
+walls. Their distinct dynamics are essential for the observed magnetic
+switching.",1009.0820v1
+2011-05-05,Strains and pseudo-magnetic fields in circular graphene rings,"We demonstrate that circular graphene ring under a shear stress displays
+strong pseudo-magnetic fields. We calculate the pseudo-magnetic field both from
+continuum elasticity theory as well as molecular dynamics simulations. Stable
+wrinkles are induced by shear deformations and lead to enhancement of the
+pseudo-magnetic field. The strong pseudo-magnetic field found here can be
+observed by imaging graphene flake at the atomic level e.g. through scanning
+tunneling microscope.",1105.1026v2
+2011-06-17,Current effect on magnetization oscillations in a ferromagnet - antiferromagnet junction,"Spin-polarized current effect is studied on the static and dynamic
+magnetization of the antiferromagnet in a ferromagnet - antiferromagnet
+junction. The macrospin approximation is generalized to antiferromagnets.
+Canted antiferromagnetic configuration and resulting magnetic moment are
+induced by an external magnetic field. The resonance frequency and damping are
+calculated, as well as the threshold current density corresponding to
+instability appearance. A possibility is shown of generating low-damping
+magnetization oscillations in terahertz range. The fluctuation effect is
+discussed on the canted antiferromagnetic configuration.",1106.3519v1
+2011-11-15,Magnetization dynamics induced by in-plane currents in ultrathin magnetic nanostructures,"Ultrathin magnetic systems have properties qualitatively different from their
+thicker counterparts, implying that different physics governs their properties.
+We demonstrate that various such properties can be explained naturally by the
+Rashba spin-orbit coupling in ultrathin magnetic systems. This work will be
+valuable for the development of next generation spintronic devices based on
+ultrathin magnetic systems.",1111.3422v2
+2012-02-06,Possibility of superradiance by magnetic nanoclusters,"The possibility of realizing spin superradiance by an assembly of magnetic
+nanoclusters is analyzed. The known obstacles for realizing such a coherent
+radiation by magnetic nanoclusters are their large magnetic anisotropy, strong
+dephasing dipole interactions, and an essential nonuniformity of their sizes.
+In order to give a persuasive conclusion, a microscopic theory is developed,
+providing an accurate description of nanocluster spin dynamics. It is shown
+that, despite the obstacles, it is feasible to organize such a setup that
+magnetic nanoclusters would produce strong superradiant emission.",1202.1115v1
+2012-05-24,High Performance Calculation of Magnetic Properties and Simulation of Nonequilibrium Phenomena in nanofilms,"Images of surface topography of ultrathin magnetic films have been used for
+Monte Carlo simulations in the framework of the ferromagnetic Ising model to
+study the hysteresis and thermal properties of nanomaterials. For high
+performance calculations was used super-scalable parallel algorithm for the
+finding of the equilibrium configuration. The changing of a distribution of
+spins on the surface during the reversal of the magnetization and the dynamics
+of nanodomain structure of thin magnetic films under the influence of changing
+external magnetic field was investigated.",1205.5588v1
+2012-10-27,Magnet traveling through a conducting pipe: a variation on the analytical approach,"We present an analytical study of magnetic damping. In particular, we
+investigate the dynamics of a cylindrical neodymium magnet as it moves through
+a conducting tube. Owing to the very high degree of uniformity of the
+magnetization for neodymium magnets, we are able to provide completely
+analytical results for the EMF generated in the pipe, and the consequent
+retarding force. Our analytical expressions are shown to have excellent
+agreement with experimental observations.",1210.7796v1
+2012-11-02,Magnetic power inverter: AC voltage generation from DC magnetic fields,"We propose a method that allows power conversion from DC magnetic fields to
+AC electric voltages using domain wall (DW) motion in ferromagnetic nanowires.
+The device concept relies on spinmotive force, voltage generation due to
+magnetization dynamics. Sinusoidal modulation of the nanowire width introduces
+a periodic potential for a DW the gradient of which exerts variable pressure on
+the traveling DW. This results in time variation of the DW precession frequency
+and the associated voltage. Using a one-dimensional model we show that the
+frequency and amplitude of the AC outputs can be tuned by the DC magnetic
+fields and wire-design.",1211.0372v1
+2013-01-09,Onset of a Propagating Self-Sustained Spin Reversal Front in a Magnetic System,"The energy released in a magnetic material by reversing spins as they relax
+toward equilibrium can lead to a dynamical instability that ignites
+self-sustained rapid relaxation along a deflagration front that propagates at a
+constant subsonic speed. Using a trigger heat pulse and transverse and
+longitudinal magnetic fields, we investigate and control the crossover between
+thermally driven magnetic relaxation and magnetic deflagration in single
+crystals of Mn$_{12}$-acetate.",1301.1900v2
+2013-03-12,In-Plane Magnetic Field Tolerance of a Dispersive Aluminum Nanobridge SQUID Magnetometer,"We characterize the flux sensitivity of a dispersive 3D aluminum nanobridge
+SQUID magnetometer as a function of applied in-plane magnetic field. In zero
+field, we observe an effective flux noise of 17 n$\Phi_0$/Hz$^{1/2}$ with 25
+MHz of bandwidth. Flux noise increased by less than a factor of three with
+parallel magnetic fields up to 61 mT. Operation in higher fields may be
+possible by decreasing the dimensions of the shunt capacitor in the
+magnetometer circuit. These devices are thus well suited for observing
+high-speed dynamics in nanoscale magnets, even in the presence of moderate bias
+magnetic fields.",1303.2737v1
+2013-03-19,Magnetoelectric Resonances and Predicted Microwave Diode Effect of Skyrmion Crystal in Multiferroic Chiral-Lattice Magnet,"We theoretically discover that unique eigenmodes of skyrmion crystal (SkX)
+are not only magnetically active to ac magnetic field (H^w) but also
+electrically active to ac electric field (E^w) in a multiferroic chiral-lattice
+magnet Cu2OSeO3, which amplifies the dynamical magnetoelectric coupling between
+E^w and the spin texture. The resulting intense interference between their
+electric and magnetic activation processes can lead to unprecedentedly large
+diode effect on the microwave, i.e., its absorption by SkX changes up to ~20%
+when the incident direction is reversed. Our results demonstrate that the
+skyrmion can be a promising building block for microwave devices.",1303.4491v1
+2013-05-21,Switching of a single ferromagnetic layer driven by spin Hall effect,"The magnetization switching of a thin ferromagnetic layer placed on top of a
+heavy metal (such as Pt, Ta or W) driven by an in-plane current has been
+observed in recent experiments. The magnetization dynamics of these processes
+is studied in a full micromagnetic framework which takes into account the
+transfer-torque from spin Hall effect due to the spin-orbit coupling.
+Simulations indicate that the reversal occurs via nucleation of complex
+magnetization patterns. In particular, magnetic bubbles appear during the
+reversal of the magnetization in the perpendicular configuration while for the
+in-plane configuration, nucleation of vortexes are observed.",1305.4806v1
+2013-10-24,High-Speed DC Magnetricity in Spinor Polariton Condensates,"We investigate the spin dynamics of half-solitons in polariton Bose-Einstein
+condensates. Half-solitons, which behave as magnetic monopoles, can be
+accelerated in the presence of the effective magnetic field of the microcavity.
+We study the generation of DC magnetic currents in a gas of half-solitons. At
+low densities, the current is suppressed due to the dipolar oscillations. At
+moderate densities, a magnetic current is recovered as a consequence of the
+collisions between the carriers. We show a deviation from Ohm's law due to the
+competition between magnetic dipoles and monopoles.",1310.6588v1
+2013-10-28,Probing the structure of local magnetic field of solar features with helioseismology,"Motivated by the problem of local solar subsurface magnetic structure, we
+have used numerical simulation to investigate the propagation of waves through
+monolithic magnetic flux tubes of different size. A cluster model can be a good
+approximation to simulate sunspots as well as solar plage regions which are
+composed of an ensemble of compactly packed thin flux tubes. Simulations of
+this type is a powerful tool to probe the structure and the dynamic of various
+solar features which are related directly to solar magnetic field activity.",1310.7398v1
+2014-03-25,Magnetic nanoparticle sensing: decoupling the magnetization from the excitation field,"Remote sensing of magnetic nanoparticles has exciting applications for
+magnetic nanoparticle hyperthermia and molecular detection. We introduce,
+simulate, and experimentally demonstrate an innovation---a sensing coil that is
+geometrically decoupled from the excitation field---for magnetic nanoparticle
+spectroscopy that increases the flexibility and capabilities of remote
+detection. The decoupling enhances the sensitivity absolutely; to small amounts
+of nanoparticles, and relatively; to small changes in the nanoparticle
+dynamics. We adapt a previous spectroscopic method that measures the relaxation
+time of nanoparticles and demonstrate a new measurement of nanoparticle
+temperature that could potentially be used concurrently during hyperthermia.",1403.6432v1
+2014-06-16,Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles,"The applications of exchange coupled bi-magnetic hard/soft and soft/hard
+ferromagnetic core/shell nanoparticles are reviewed. After a brief description
+of the main synthesis approaches and the core/shell structural-morphological
+characterization, the basic static and dynamic magnetic properties are
+presented. Five different types of perspective applications, based on diverse
+patents and research articles, are described: permanent magnets, recording
+media, microwave absorption, biomedical applications and other applications.
+Both the advantages of the core/shell morphology and some of the remaining
+challenges are discussed.",1406.3966v2
+2014-06-24,Atomistic calculation of the thickness and temperature dependence of exchange coupling through a dilute magnetic oxide,"The exchange coupling of two magnetic layers via a diffuse oxide interlayer
+is studied with an atomistic spin model. We investigate the effect of magnetic
+concentration and oxide layer thickness on the effective exchange coupling
+strength and find an exponential dependence of the coupling strength on the
+oxide thickness without the need for magnetic pinholes. Furthermore we show
+that exchange coupling has a strong temperature dependence which is significant
+for the reversal dynamics during heat assisted magnetic recording.",1406.6214v1
+2015-05-01,Ising incommensurate spin resonance of CeCoIn$_{5}$: a dynamical precursor of the Q-phase,"It is shown by detailed inelastic neutron scattering experiments that the
+gapped collective magnetic excitation of the unconventional superconductor
+CeCoIn$_{5}$, the spin resonance mode, is incommensurate and that the
+corresponding fluctuations are of Ising nature. The incommensurate peak
+position of these fluctuations corresponds to the propagation vector of the
+adjacent field induced static magnetic ordered phase, the so-called Q-phase.
+Furthermore, the direction of the magnetic moment fluctuations is also the
+direction of the ordered magnetic moments of the Q-phase. Hence the resonance
+mode and the Q-phase share the same symmetry and this strongly supports a
+scenario where the static order is realized by a condensation of the magnetic
+excitation.",1505.00206v1
+2015-12-08,Topological Entropy of Left-Invariant Magnetic Flows on 2-Step Nilmanifolds,"We consider magnetic flows on 2-step nilmanifolds $M = \Gamma \backslash G$,
+where the Riemannian metric $g$ and the magnetic field $\sigma$ are
+left-invariant. Our first result is that when $\sigma$ represents a rational
+cohomology class and its restriction to $\mathfrak{g} = T_eG$ vanishes on the
+derived algebra, then the associated magnetic flow has zero topological
+entropy. In particular, this is the case when $\sigma$ represents a rational
+cohomology class and is exact. Our second result is the construction of a
+magnetic field on a 2-step nilmanifold that has positive topological entropy
+for arbitrarily high energy levels.",1512.02612v1
+2016-01-04,Generation of coherent radiation by magnetization reversal in graphene,"Local magnetic moments can be created in graphene by incorporating different
+defects. The possibility of regulating dynamics of magnetization in graphene,
+by employing the Purcell effect, is analyzed. The role of the system parameters
+in magnetization reversal is studied. The characteristics of such a reversal
+can be varied in a wide range, which can be used for various applications in
+spintronics. It is shown that fast magnetization reversal generates coherent
+radiation.",1601.00464v1
+2016-02-22,Spintronics with magnetic nanomolecules and graphene flakes,"We show how the magnetization of nano-objects can be efficiently regulated.
+Several types of nanosystems are considered: magnetics nanomolecules, magnetic
+nanoclusters, polarized nanomolecules, and magnetic graphene. These
+nano-objects and the structures composed of them enjoy many common properties,
+with the main difference being in the type of particle interactions. The
+possibility of governing spin dynamics is important for spintronics.",1602.06834v1
+2016-03-12,Covariant Magnetic Connection Hypersurfaces,"In the single fluid, nonrelativistic, ideal-Magnetohydrodynamic (MHD) plasma
+description magnetic field lines play a fundamental role by defining
+dynamically preserved ""magnetic connections"" between plasma elements. Here we
+show how the concept of magnetic connection needs to be generalized in the case
+of a relativistic MHD description where we require covariance under arbitrary
+Lorentz transformations. This is performed by defining 2-D {\it magnetic
+connection hypersurfaces} in the 4-D Minkowski space. This generalization
+accounts for the loss of simultaneity between spatially separated events in
+different frames and is expected to provide a powerful insight into the 4-D
+geometry of electromagnetic fields when ${\bf E} \cdot {\bf B} = 0$.",1603.03909v1
+2016-07-12,Tailoring the topological details of the magnetic skyrmion by the spin configuration at the edges,"The magnetic skyrmion structure can be formed in the chiral magnets (CMs)
+with strong Dzyaloshinskii-Moriya interactions. In this work, we propose a way
+of artificially tailoring the topological details of the skyrmion such as its
+radial and whirling symmetric patterns by external magnetic fields besieging
+the CM slab. As long as the boundary magnetic fields are strong enough to fix
+the boundary ferromagnetism, the attained skyrmion profile is stable over time.
+The dynamics of spins is considered by numerically solving the non-equilibrium
+Landau-Lifshitz-Gilbert equation.",1607.03268v2
+2016-08-02,Topologically protected colloidal transport above a square magnetic lattice,"We theoretically study the motion of magnetic colloidal particles above a
+magnetic pattern and compare the predictions with Brownian dynamics
+simulations. The pattern consists of alternating square domains of positive and
+negative magnetization. The colloidal motion is driven by periodic modulation
+loops of an external magnetic field. There exist loops that induce
+topologically protected colloidal transport between two different unit cells of
+the pattern. The transport is very robust against internal and external
+perturbations. Theory and simulations are in perfect agreement.",1608.00808v2
+2017-01-01,Non-Abelian bootstrap of primordial magnetism,"We point out that a primordial magnetic field can be generated in the
+electroweak phase transition by a non-Abelian bootstrap, where the field is
+generated by currents of W's, which in turn are extracted from the vacuum by
+the magnetic field. This magnetic field is produced as a vortex condensate at
+the electroweak phase transition. It becomes stringy as a consequence of the
+dynamical evolution due to magnetohydrodynamics.",1701.00245v3
+2017-03-06,Controlling topological superconductivity by magnetization dynamics,"We study theoretically a chain of precessing classical magnetic impurities in
+an $s$-wave superconductor. Utilizing a rotating wave description, we derive an
+effective Hamiltonian that describes the emergent Shiba band. We find that this
+Hamiltonian shows non-trivial topological properties, and we obtain the
+corresponding topological phase diagrams both numerically and analytically. We
+show that changing the precession frequency offers a control over topological
+phase transitions and the emergence of Majorana bound states. We propose
+driving the magnetic impurities or magnetic texture into precession by means of
+spin-transfer torque in a spin-Hall setup, and manipulate it using spin
+superfluidity in the case of planar magnetic order.",1703.01870v1
+2017-08-21,Amplification of large-scale magnetic field in nonhelical magnetohydrodynamics,"It is typically assumed that the kinetic and magnetic helicities play a
+crucial role in the growth of large-scale dynamo. In this paper we demonstrate
+that helicity is not essential for the amplification of large-scale magnetic
+field. For this purpose, we perform nonhelical magnetohydrodynamic (MHD)
+simulation, and show that the large-scale magnetic field can grow in nonhelical
+MHD when random external forcing is employed at scale $1/10$ the box size. The
+energy fluxes and shell-to-shell transfer rates computed using the numerical
+data show that the large-scale magnetic energy grows due to the energy
+transfers from the velocity field at the forcing scales.",1708.06120v1
+2017-11-14,Spin-Noise and Damping in Individual Metallic Ferromagnetic Nanoparticles,"We introduce a highly sensitive and relatively simple technique to observe
+magnetization motion in single Ni nanoparticles, based on charge sensing by
+electron tunneling at millikelvin temperature. Sequential electron tunneling
+via the nanoparticle drives nonequilibrium magnetization dynamics, which
+induces an effective charge noise that we measure in real time. In the free
+spin diffusion regime, where the electrons and magnetization are in detailed
+balance, we observe that magnetic damping time exhibits a peak with the
+magnetic field, with a record long damping time of $\simeq 10$~ms.",1711.05142v1
+2017-11-15,Reduction of electron heating by magnetizing ultracold neutral plasma,"Electron heating in an ultracold neutral plasma is modeled using classical
+molecular dynamics simulations in the presence of an externally applied
+magnetic field. A sufficiently strong magnetic field is found to reduce
+disorder induced heating and three body recombination heating of electrons by
+constraining electron motion, and therefore heating, to the single dimension
+aligned with the magnetic field. A strong and long-lasting temperature
+anisotropy develops, and the overall kinetic electron temperature is
+effectively reduced by a factor of three. These results suggest that
+experiments may increase the effective electron coupling strength using an
+applied magnetic field.",1711.05617v1
+2017-12-30,Chiral symmetry breaking in a semi-localized magnetic field,"In this work, I'm going to explore the pattern of chiral symmetry breaking
+and restoration in a solvable magnetic distribution within Nambu--Jona-Lasinio
+model. The special semi-localized static magnetic field can roughly simulate
+the realistic situation in peripheral heavy ion collisions, thus the study is
+important for the dynamical evolution of quark matter. I find that the magnetic
+field dependent contribution from discrete spectra usually dominates over that
+from continuum ones and chiral symmetry breaking is locally catalyzed by both
+the magnitude and scale of the magnetic field.",1801.00134v1
+2020-04-27,Nonreciprocal directional dichroism induced by a temperature gradient as a probe for mobile spin dynamics in quantum magnets,"Novel states of matter in quantum magnets like quantum spin liquids attract
+considerable interest recently. Despite the existence of a plenty of candidate
+materials, there is no confirmed quantum spin liquid, largely due to the lack
+of proper experimental probes. For instance, spectrosocopy experiments like
+neutron scattering receive contributions from disorder-induced local modes,
+while thermal transport experiments receive contributions from phonons. Here we
+propose a thermo-optic experiment which directly probes the mobile magnetic
+excitations in spatial-inversion symmetric and/or time-reversal symmetric Mott
+insulators: the temperature-gradient-induced nonreciprocal directional
+dichroism (TNDD) spectroscopy. Unlike traditional probes, TNDD directly detects
+mobile magnetic excitations and decouples from phonons and local magnetic
+modes.",2004.13047v1
+2020-09-03,Measurements of sub-nT dynamic magnetic field shielding with soft iron and mu-metal for use in linear colliders,"There is an increasing need to shield beams and accelerator elements from
+stray magnetic fields. The application of magnetic shielding in linear
+colliders is discussed. The shielding performance of soft iron and mu-metal is
+measured for magnetic fields of varying amplitude and frequency. Special
+attention is given to characterise the shielding performance for very
+small-amplitude magnetic fields.",2009.01519v2
+2020-09-29,Stationary solution for quasi-homogeneous small-scale magnetic field advected by non-Gaussian turbulent flow,"We consider fluctuations of magnetic field excited by external force and
+advected by isotropic turbulent flow. It appears that non-Gaussian velocity
+gradient statistics and finite region of pumping force provide the existence of
+stationary solution. The mean-square magnetic field is calculated for arbitrary
+velocity gradient statistics. An estimate for possible feedback of magnetic
+field on velocity shows that, for wide range of parameters, stationarity
+without feedback would take place even in the case of intensive pumping of
+magnetic field.",2009.13746v1
+2021-03-26,Linear damping and depletion in flowing plasma with strong sheared magnetic fields,"In this paper, we study the long-time behavior of the solution for the
+linearized ideal MHD around sheared velocity and magnetic field under Stern
+stability condition. We prove that the velocity and magnetic field will
+converge to sheared velocity and magnetic field as time approaches infinity.
+Moreover a new depletion phenomenon is proved: the horizontal velocity and
+magnetic field at the critical points will decay to 0 as time approaches
+infinity.",2103.14614v1
+2023-10-02,Magnetization of Antiferromagnetic Cactus Graph Model with Exact Dimer Ground State,"We introduce and explore the magnetization behavior in a quantum spin system
+on a cactus graph, deemed the Cactus Graph Model (CGM), featuring an exact
+dimer singlet ground state. We analyze the singlet-triplet gap, interactions
+among excited triplets, and correlated hopping under an external magnetic field
+using a strong coupling expansion. Employing an effective hard-core boson
+representation, we unveil density wave magnetization plateaus and supersolid
+phases, revealing the intricate interplay between interactions and hopping
+dynamics. Furthermore, we conjecture that correlated hopping gives rise to
+multi-triplet bound states, and potentially engendering to the stabilization of
+additional low-lying magnetization plateaus.",2310.01570v1
+2023-10-30,Motions of a homopolar motor inside a conducting tube,"We analyze the physics of a type of homopolar motor comprising an AA battery
+with two cylindrical neodymium magnets on each end that roll inside a metal
+cylindrical tube. The motion of the motor results from the interaction between
+the magnetic field of the magnets and the magnetic field created by the current
+inside the magnets. We develop a model to describe the dynamics of the system,
+including the calculation of the terminal velocity of the motor due to eddy
+currents.",2310.19249v1
+2023-11-01,Topological transport of vorticity on curved magnetic membranes,"In this work, we study the transport of vorticity on curved dynamical
+two-dimensional magnetic membranes. We find that topological transport can be
+controlled by geometrically reducing symmetries, which enables processes that
+are not present in flat magnetic systems. To this end, we construct a vorticity
+3-current which obeys a continuity equation. This continuity equation is immune
+to local fluctuations of the magnetic texture as well as spatiotemporal
+fluctuations of the membrane. We show how electric current can manipulate
+vortex transport in geometrically nontrivial magnetic systems. As an
+illustrative example, we propose a minimal setup that realizes an
+experimentally feasible energy storage device.",2311.00323v1
+2023-12-08,Decay and Fission of Magnetic Quivers,"In exploring supersymmetric theories with 8 supercharges, the Higgs branches
+present an intriguing window into strong coupling dynamics. Magnetic quivers
+serve as crucial tools for understanding these branches. Here, we introduce the
+decay and fission algorithm for unitary magnetic quivers. It efficiently
+derives complete phase diagrams (Hasse diagrams) through convex linear algebra.
+It allows magnetic quivers to undergo decay or fission, reflecting Higgs branch
+RG-flows in the theory. Importantly, the algorithm generates magnetic quivers
+for the RG fixed points and simplifies the understanding of transverse slice
+geometry with no need for a list of minimal transitions. In contrast, the
+algorithm hints to the existence of a new minimal transition, whose geometry
+and physics needs to be explored.",2312.05304v1
+2023-12-24,A Novel Field-Free SOT Magnetic Tunnel Junction With Local VCMA-Induced Switching,"By integrating the local voltage-controlled magnetic anisotropy (VCMA)
+effect, Dzyaloshinskii-Moriya interaction (DMI) effect, and spin-orbit torque
+(SOT) effect, we propose a novel device structure for field-free magnetic
+tunnel junction (MTJ). Micromagnetic simulation shows that the device utilizes
+the chiral symmetry breaking caused by the DMI effect to induce a non-collinear
+spin texture under the influence of SOT current. This, combined with the
+perpendicular magnetic anisotropy (PMA) gradient generated by the local VCMA
+effect, enables deterministic switching of the MTJ state without an external
+field. The impact of variations in DMI strength and PMA gradient on the
+magnetization dynamics is analyzed.",2312.15481v1
+2002-01-02,A Coupled Dynamical and Chemical Model of Starless Cores of Magnetized Molecular Clouds: I. Formulation and Initial Results,"We develop a detailed chemical model for the starless cores of strongly
+magnetized molecular clouds, with the ambipolar diffusion-driven dynamic
+evolution of the clouds coupled to the chemistry through ion abundances. We
+concentrate on two representative model clouds in this initial study, one with
+magnetic fields and the other without. The model predictions on the peak values
+and spatial distributions of the column densities of CO, CCS, N$_2$H$^+$ and
+HCO$^+$ are compared with those observationally inferred for the well-studied
+starless core L1544, which is thought to be on the verge of star formation. We
+find that the magnetic model, in which the cloud is magnetically supported for
+several million years before collapsing dynamically, provides a reasonable
+overall fit to the available data on L1544; the fit is significantly worse for
+the non-magnetic model, in which the cloud collapses promptly. The observed
+large peak column density for N$_2$H$^+$ and clear central depression for CCS
+favor the magnetically-retarded collapse over the free-fall collapse. A
+relatively high abundance of CCS is found in the magnetic model, resulting most
+likely from an interplay of depletion and late-time hydrocarbon chemistry
+enhanced by CO depletion. These initial results lend some support to the
+standard picture of dense core formation in strongly magnetized clouds through
+ambipolar diffusion. They are at variance with those of Aikawa et al. (2001)
+who considered a set of models somewhat different from ours and preferred one
+in which the cloud collapses more or less freely for L1544.",0201019v1
+2011-07-22,Interaction of Josephson and magnetic oscillations in Josephson tunnel junctions with a ferromagnetic layer,"We study the dynamics of Josephson junctions with a thin ferromagnetic layer
+F [superconductor-ferromagnet-insulator-ferromagnet-superconductor (SFIFS)
+junctions]. In such junctions, the phase difference $\phi$ of the
+superconductors and magnetization $M$ in the F layer are two dynamic parameters
+coupled to each other. We derive equations describing the dynamics of these two
+parameters and formulate the conditions of validity. The coupled Josephson
+plasma waves and oscillations of the magnetization $M$ affect the form of the
+current-voltage ($I$-$V$) characteristics in the presence of a weak magnetic
+field (Fiske steps). We calculate the modified Fiske steps and show that the
+magnetic degree of freedom not only changes the form of the Fiske steps but
+also the overall view of the $I$-$V$ curve (new peaks related to the magnetic
+resonance appear). The $I$-$V$ characteristics are shown for different lengths
+of the junction including those which correspond to the current experimental
+situation. We also calculate the power $P$ absorbed in the system if a
+microwave radiation with an ac in-plane magnetic field is applied (magnetic
+resonance). The derived formula for the power $P$ essentially differs from the
+one which describes the power absorption in an isolated ferromagnetic film. In
+particular, this formula describes the peaks related to the excitation of
+standing plasma waves as well as the peak associated with the magnetic
+resonance.",1107.4493v2
+2015-03-02,Spin-glass-like freezing of inner and outer surface layers in hollow γFe$_2$O$_3$ nanoparticles,"Disorder among surface spins largely dominates the magnetic response of
+ultrafine magnetic particle systems. In this work, we examine time-dependent
+magnetization in high-quality, monodisperse hollow maghemite nanoparticles with
+a 14.8 $\pm$ 0.5 nm outer diameter and enhanced surface-to-volume ratio. The
+nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging
+and memory protocols and ac magnetic susceptibility. The dynamics of the system
+slows near 50 K, and becomes frozen on experimental time scales below 20 K.
+Remanence curves indicate the development of magnetic irreversibility
+concurrent with the freezing of the spin dynamics. A strong exchange-bias
+effect and its training behavior point to highly frustrated surface spins that
+rearrange much more slowly than interior spins with bulk coordination. Monte
+Carlo simulations of a hollow particle reproducing the experimental morphology
+corroborated strongly disordered surface layers with complex energy landscapes
+that underlie both glass-like dynamics and magnetic irreversibility. Calculated
+hysteresis loops reveal that magnetic behavior is not identical at the inner
+and outer surfaces, with spins at the outer surface layer of the 15 nm hollow
+particles exhibiting a higher degree of frustration. Our study sheds light on
+the origin of spin-glass-like phenomena and the role of surface spins in
+magnetic hollow nanostructures.",1503.00602v2
+2018-09-24,Quantum spin-transfer torque induced nonclassical magnetization dynamics and electron-magnetization entanglement,"The standard spin-transfer torque (STT)---where spin-polarized current drives
+dynamics of magnetization viewed as a classical vector---requires
+noncollinearity between electron spins carried by the current and magnetization
+of a ferromagnetic layer. However, recent experiments [A. Zholud et al., Phys.
+Rev. Lett. 119, 257201 (2017)] observing magnetization dynamics in spin valves
+at cryogenic temperatures, even when electron spin is collinear to
+magnetization, point at overlooked quantum effects in STT which can lead to
+highly nonclassical magnetization states. Using fully quantum many-body
+treatment, where an electron injected as spin-polarized wave packet interacts
+with local spins comprising the anisotropic quantum Heisenberg ferromagnetic
+chain, we define quantum STT as any time evolution of local spins due to
+initial many-body state not being an eigenstate of electron+local-spins system.
+For time evolution caused by injected spin-down electron scattering off local
+up-spins, entanglement between electron subsystem and local spins subsystem
+takes place leading to decoherence and, therefore, shrinking of the total
+magnetization but without rotation from its initial orientation which explains
+the experiments. Furthermore, the same processes---entanglement and thereby
+induced decoherence---are present also in standard noncollinear geometry,
+together with the usual magnetization rotation. This is because STT in quantum
+many-body picture is caused only by electron spin-down factor state, and the
+only difference between collinear and noncollinear geometries is in relative
+size of the contribution of initial many-body state containing such factor
+state to superpositions of separable many-body quantum states generated during
+time evolution.",1809.09090v1
+2019-11-28,Manipulating Spin Chirality of Magnetic Skyrmion Bubbles by In-Plane Re-versed Magnetic Fields in (Mn$_{1-x}$Ni$_x$)$_{65}$Ga$_{35}$ ($x = 0.45$) magnet,"Understanding the dynamics of the magnetic skyrmion, a particle-like
+topologically stable spin texture, and its response dynamics to external fields
+are indis-pensable for the applications in spintronic devices. In this letter,
+the Lorentz transmis-sion electron microscopy (LTEM) was used to investigate
+the spin chirality of the mag-netic skyrmion bubbles (SKBs) in the
+centrosymmetric magnet MnNiGa at room tem-perature. The reversal of SKBs
+excited by the in-plane magnetic field has been revealed. Moreover, the
+collective behavior of interacting spin chirality can be manipulated by
+reversing the directions of the magnetic fields on a wedge-shaped thin plate.
+The dy-namic behavior of the bubbles at different position of the thin plate
+has been explored with the micromagnetic simulation, indicating a non-uniform
+and nontrivial dynamic magnetization on the surfaces and center of the thin
+plate during the spin chirality re-versal. The results suggest that the
+controllable symmetry breaking of the SKBs arising from thickness variation
+provides an ability to manipulate the collective behavior of the spin chirality
+with small external fields, leading to a promising application in nonvola-tile
+spintronic devices for magnetic skyrmions.",1911.12497v1
+2019-12-20,Picosecond spin-orbit torque switching of ferrimagnets,"Spintronics provides an efficient platform for realizing non-volatile memory
+and logic devices. In these systems, data is stored in the magnetization of
+magnetic materials, and magnetization is switched in the writing process. In
+conventional spintronic devices, ferromagnetic materials are used which have a
+magnetization dynamics timescale of around the nanoseconds, setting a limit for
+the switching speed. Increasing the magnetization switching speed has been one
+of the challenges in spintronic research. In this work we take advantage of the
+ultrafast magnetization dynamics in ferrimagnetic materials instead of
+ferromagnets, and we use femtosecond laser pulses and a photoconductive Auston
+switch to create picosecond current pulses for switching the ferrimagnet. By
+anomalous Hall and magneto-optic Kerr (MOKE) measurement, we demonstrate the
+robust picosecond SOT driven magnetization switching of ferrimagnetic GdFeCo.
+The time-resolved MOKE shows more than 50 GHz magnetic resonance frequency of
+GdFeCo, indicating faster than 20 ps spin dynamics and tens of picosecond SOT
+switching speed. Our work provides a promising route to realize picosecond
+operation speed for non-volatile magnetic memory and logic applications.",1912.10129v1
+2020-01-21,Multi-scale dynamics of magnetic flux tubes and inverse magnetic energy transfer,"We report on an analytical and numerical study of the dynamics of a
+three-dimensional array of identical magnetic flux tubes in the
+reduced-magnetohydrodynamic description of the plasma. We propose that the
+long-time evolution of this system is dictated by flux-tube mergers and that
+such mergers are dynamically constrained by the conservation of the pertinent
+(ideal) invariants, {\it viz.} the magnetic potential and axial fluxes of each
+tube. We also propose that in the direction perpendicular to the merging plane,
+flux tubes evolve in critically-balanced fashion. These notions allow us to
+construct an analytical model for how quantities such as the magnetic energy
+and the energy-containing scale evolve as functions of time. Of particular
+importance is the conclusion that, like its two-dimensional counterpart, this
+system exhibits an inverse transfer of magnetic energy that terminates only at
+the system scale. We perform direct numerical simulations that confirm these
+predictions and reveal other interesting aspects of the evolution of the
+system. We find, for example, that the early time evolution is characterized by
+a sharp decay of the initial magnetic energy, which we attribute to the
+ubiquitous formation of current sheets. We also show that a quantitatively
+similar inverse transfer of magnetic energy is observed when the initial
+condition is a random, small-scale magnetic seed field.",2001.07291v2
+2023-01-17,Three Dimensional Odd Viscosity in Ferrofluids with Vorticity-Magnetization Coupling,"Ferrofluids are a synthetic magnetic colloid consisting of magnetized
+nanoparticles surrounded by a repulsive surfactant layer. When subjected to an
+external magnetic field the ferrofluid acquires a macroscopic magnetization
+density which leads to magnetic behavior that is intricately coupled to the
+ambient fluid dynamics. Ferrofluids share several features with the chiral
+active fluids composed of unidirectionally spinning hematite cubes, which have
+been shown to possess a 2D non-dissipative odd viscosity term (Nature Physics,
+15, 1188-1194(2019)). In standard ferrofluid dynamics, 3D versions of parity
+breaking terms are not commonly observed, partly because of the small size of
+the magnetic particles. In this work, we investigate if there are unique
+mechanisms in ferrofluids that can lead to a 3D odd viscosity term. Our results
+show that coupling the fluid vorticity ($\vec{\omega}$) to the magnetization
+($\vec{M}$) with a term proportional to $\vec{\omega}\cdot\vec{M}$ leads to
+parity breaking terms in ferrofluid hydrodynamics, and results in a three
+dimensional odd viscosity term when the magnetization is relaxed to the
+direction of a uniform and static applied field. Hele-Shaw cells are commonly
+used devices to investigate ferrofluids and we demonstrate that this coupling
+reproduces the parity odd generalization of Darcy's Law discussed in a recent
+work (Phys. Rev. Fluids 7, 114201 (2022)). A potential experimental setup is
+discussed which may reveal the presence of this coupling in a ferrofluid
+confined to a Hele-Shaw cell.",2301.07096v1
+2023-06-02,Phase separation of a magnetic fluid: Asymptotic states and non-equilibrium kinetics,"We study self-assembly in a colloidal suspension of magnetic particles by
+performing comprehensive molecular dynamics simulations of the Stockmayer (SM)
+model which comprises spherical particles decorated by a magnetic moment. The
+SM potential incorporates dipole-dipole interactions along with the usual
+Lennard-Jones interaction and exhibits a gas-liquid phase coexistence observed
+experimentally in magnetic fluids. When this system is quenched from the
+high-temperature homogeneous phase to the coexistence region, the
+non-equilibrium evolution to the condensed phase proceeds with the development
+of spatial as well as magnetic order. We observe density-dependent coarsening
+mechanisms - a diffusive growth law $\ell(t)\sim t^{1/3}$ in the nucleation
+regime, and hydrodynamics-driven inertial growth law $\ell(t)\sim t^{2/3}$ in
+the spinodal regimes. [$\ell(t)$ is the average size of the condensate at time
+$t$ after the quench.] While the spatial growth is governed by the expected
+conserved order parameter dynamics, the growth of magnetic order in the
+spinodal regime exhibits unexpected non-conserved dynamics. The asymptotic
+morphologies have density-dependent shapes which typically include the
+isotropic sphere and spherical bubble morphologies in the nucleation region,
+and the anisotropic cylinder, planar slab, cylindrical bubble morphologies in
+the spinodal region. The structures are robust and nonvolatile and exhibit
+characteristic magnetic properties. For example, the oppositely magnetized
+hemispheres in the spherical morphology impart the characteristics of a {\it
+Janus particle} to it. The observed structures have versatile applications in
+catalysis, drug delivery systems, memory devices, and magnetic photonic
+crystals, to name a few.",2306.01430v2
+2023-07-16,Magnetic Field-Based Reward Shaping for Goal-Conditioned Reinforcement Learning,"Goal-conditioned reinforcement learning (RL) is an interesting extension of
+the traditional RL framework, where the dynamic environment and reward sparsity
+can cause conventional learning algorithms to fail. Reward shaping is a
+practical approach to improving sample efficiency by embedding human domain
+knowledge into the learning process. Existing reward shaping methods for
+goal-conditioned RL are typically built on distance metrics with a linear and
+isotropic distribution, which may fail to provide sufficient information about
+the ever-changing environment with high complexity. This paper proposes a novel
+magnetic field-based reward shaping (MFRS) method for goal-conditioned RL tasks
+with dynamic target and obstacles. Inspired by the physical properties of
+magnets, we consider the target and obstacles as permanent magnets and
+establish the reward function according to the intensity values of the magnetic
+field generated by these magnets. The nonlinear and anisotropic distribution of
+the magnetic field intensity can provide more accessible and conducive
+information about the optimization landscape, thus introducing a more
+sophisticated magnetic reward compared to the distance-based setting. Further,
+we transform our magnetic reward to the form of potential-based reward shaping
+by learning a secondary potential function concurrently to ensure the optimal
+policy invariance of our method. Experiments results in both simulated and
+real-world robotic manipulation tasks demonstrate that MFRS outperforms
+relevant existing methods and effectively improves the sample efficiency of RL
+algorithms in goal-conditioned tasks with various dynamics of the target and
+obstacles.",2307.08033v1
+2023-09-12,Quantum Diamond Microscope for Dynamic Imaging of Magnetic Fields,"Wide-field imaging of magnetic signals using ensembles of nitrogen-vacancy
+(NV) centers in diamond has garnered increasing interest due to its combination
+of micron-scale resolution, millimeter-scale field of view, and compatibility
+with diverse samples from across the physical and life sciences. Recently,
+wide-field NV magnetic imaging based on the Ramsey protocol has achieved
+uniform and enhanced sensitivity compared to conventional measurements. Here,
+we integrate the Ramsey-based protocol with spin-bath driving to extend the NV
+spin dephasing time and improve magnetic sensitivity. We also employ a
+high-speed camera to enable dynamic wide-field magnetic imaging. We benchmark
+the utility of this quantum diamond microscope (QDM) by imaging magnetic fields
+produced from a fabricated wire phantom. Over a $270\times270
+\hspace{0.08333em} \mu\mathrm{m}$$^2$ field of view, a median per-pixel
+magnetic sensitivity of
+$4.1(1)\hspace{0.08333em}\mathrm{nT}$$/\sqrt{\mathrm{Hz}}$ is realized with a
+spatial resolution
+$\lesssim\hspace{0.08333em}10\hspace{0.08333em}\mu\mathrm{m}$ and
+sub-millisecond temporal resolution. Importantly, the spatial magnetic noise
+floor can be reduced to the picotesla scale by time-averaging and signal
+modulation, which enables imaging of a magnetic-field pattern with a
+peak-to-peak amplitude difference of about $300\hspace{0.08333em}\mathrm{pT}$.
+Finally, we discuss potential new applications of this dynamic QDM in studying
+biomineralization and electrically-active cells.",2309.06587v1
+2023-11-07,Chaotic transport in symplectic maps: Applications in plasma,"Chaotic transport is related to the complex dynamical evolution of chaotic
+trajectories in Hamiltonian systems, which models various physical processes.
+In magnetically confined plasma, it is possible to qualitatively describe the
+configuration of the magnetic field via the phase space of suitable symplectic
+maps. These phase spaces are of mixed type, where chaos coexists with regular
+motion, and the complete understanding of the chaotic transport is a challenge
+that, when overcomed, may provide further knowledge into the behaviour of
+confined fusion plasma. In this research, we focus our investigation on
+properties of chaotic transport in mixed phase spaces of two symplectic maps
+that model the magnetic field lines of tokamaks under distinct configurations.
+The single-null divertor map, or Boozer map, models the field lines of tokamaks
+with poloidal divertors. The ergodic magnetic limiter map, or Ullmann map,
+models the magnetic configuration of tokamaks assembled with ergodic magnetic
+limiters. We propose two numerical methods developed to study and illustrate
+the differences between the transient behaviour of open field lines in both
+models while considering induced magnetic configurations that either enhance or
+restrain the escaping field lines. The first analysis shows that the spatial
+organisation of invariant manifolds creates fitting transport channels for the
+open field lines, influencing the average dynamical evolution in the selected
+magnetic configurations. The second identifies trajectories that widely differs
+from the average chaotic behaviour, specifically detecting the stickiness
+phenomenon, which can be related to additional confinement regions in the
+nearest surroundings of magnetic islands in the plasma edge. These analyses
+may, ultimately, assist in selecting optimal experimental parameters to achieve
+specific goals in tokamak discharges.",2311.04028v1
+2004-09-22,On the Rotational Dynamics of Magnetically Threaded Disks around Neutron Stars,"We investigate the rotational dynamics of disk accretion around a strongly
+magnetized neutron star with an aligned dipole field. The magnetospheric field
+is assumed to thread the disk plasma both inside and outside the corotation
+radius. As a result of disk-star interaction, the magnetic torque on the disk
+affects the structure of accretion flow to yield the observed spin-up or
+spin-down rates for a source of given fastness, magnetic field strength, and
+mass accretion rate. Within the model we obtain a prescription for the
+dynamical viscosity of such magnetically modified solutions for a Keplerian
+disk. We then use this prescription to find a model solution for the rotation
+rate profile throughout the entire disk including the non-Keplerian inner disk.
+We find that the non-Keplerian angular velocity transition region is not
+necessarily narrow for a source of given spin state. The boundary layer
+approximation, as in the standard magnetically threaded disk model, holds only
+in the case of dynamical viscosity decreasing all the way to the innermost edge
+of the disk. These results are applied to several observed disk-fed X-ray
+pulsars that have exhibited quasi-periodic oscillations (QPOs). The QPO
+frequencies provide a constraint on the fastness parameter and enable one to
+determine uniquely the width of the angular velocity transition zone for each
+source within model assumptions. We discuss the implications of these results
+on the value of the critical fastness parameter for a magnetized star in spin
+equilibrium. Applications of our model are also made with relevant parameters
+from recent numerical simulations of quasi-stationary disk-magnetized star
+interactions.",0409545v1
+2005-04-12,Complex Topology of the Magnetic Field in Strong Flares,"We report the ""5+1"" dynamical classification of the most frequently observed
+topologies of the magnetic field in sunspot groups associated with powerful
+flares.",0504259v1
+2007-02-19,Dynamics of magnetized relativistic tori oscillating around black holes,"We present a numerical study of the dynamics of magnetized, relativistic,
+non-self-gravitating, axisymmetric tori orbiting in the background spacetimes
+of Schwarzschild and Kerr black holes. The initial models have a constant
+specific angular momentum and are built with a non-zero toroidal magnetic field
+component, for which equilibrium configurations have recently been obtained. In
+this work we extend our previous investigations which dealt with purely
+hydrodynamical thick discs, and study the dynamics of magnetized tori subject
+to perturbations which, for the values of the magnetic field strength
+considered here, trigger quasi-periodic oscillations lasting for tens of
+orbital periods. Overall, we have found that the dynamics of the magnetized
+tori analyzed is very similar to that found in the corresponding unmagnetized
+models. The spectral distribution of the eigenfrequencies of oscillation shows
+the presence of a fundamental p mode and of a series of overtones in a harmonic
+ratio 2:3:.... These simulations, therefore, extend the validity of the model
+of Rezzolla et al.(2003a) for explaining the high-frequency QPOs observed in
+the spectra of LMXBs containing a black-hole candidate also to the case of
+magnetized discs with purely toroidal magnetic field distribution. If
+sufficiently compact and massive, these oscillations can also lead to the
+emission of intense gravitational radiation which is potentially detectable for
+sources within the Galaxy.",0702485v1
+2007-02-26,Electrical switching of vortex core in a magnetic disk,"A magnetic vortex is a curling magnetic structure realized in a ferromagnetic
+disk, which is a promising candidate of a memory cell for future nonvolatile
+data storage devices. Thus, understanding of the stability and dynamical
+behaviour of the magnetic vortex is a major requirement for developing magnetic
+data storage technology. Since the experimental proof of the existence of a
+nanometre-scale core with out-of-plane magnetisation in the magnetic vortex,
+the dynamics of a vortex has been investigated intensively. However, the way to
+electrically control the core magnetisation, which is a key for constructing a
+vortex core memory, has been lacking. Here, we demonstrate the electrical
+switching of the core magnetisation by utilizing the current-driven resonant
+dynamics of the vortex; the core switching is triggered by a strong dynamic
+field which is produced locally by a rotational core motion at a high speed of
+several hundred m/s. Efficient switching of the vortex core without magnetic
+field application is achieved thanks to resonance. This opens up the
+potentiality of a simple magnetic disk as a building block for spintronic
+devices like a memory cell where the bit data is stored as the direction of the
+nanometre-scale core magnetisation.",0702589v1
+2010-09-30,The dynamics of magnetization in phase separated manganite around half doping: a case study for Pr$_{0.5}$Sr$_{0.5}$Mn$_{0.925}$Ga$_{0.075}$O$_{3}$,"We investigate the dynamics of magnetization in the phase separated (PS)
+state after introducing the quenched disorder at the Mn-site of a manganite
+around half doping. The compound,
+Pr$_{0.5}$Sr$_{0.5}$Mn$_{0.925}$Ga$_{0.075}$O$_{3}$, exhibits PS with the
+coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) clusters where
+the size of the FM clusters is substantially reduced due to the disorder
+introduced by nonmagnetic Ga substitution. At low temperature, the system
+develops a new magnetic anomaly, which is marked by a peak in the zero field
+cooled magnetization. Detailed study of linear as well as nonlinear ac
+susceptibilities coupled with dc magnetization indicates that this peak arises
+due to the thermal blocking of nanometer size FM clusters demonstrating
+superparamagnetic behavior. The system, however, exhibits slow magnetic
+relaxation, aging effect, memory effect in both field cooled and zero field
+cooled magnetization below the blocking temperature. These imply the presence
+of collective behavior induced by the interaction between the clusters.
+Moreover, the magnetic relaxation measured with positive and negative
+temperature excursions exhibits asymmetric response suggesting that the
+dynamics in this phase separated system is accounted by the hierarchical model
+rather than the droplet model which are commonly used to describe the similar
+collective dynamics in glassy system.",1009.6156v1
+2016-01-05,Generic properties of magnetic flows,"We obtain Kupka-Smale theorem and Franks lemma for magnetic flows on
+manifolds with any dimension. This improves Miranda result on surfaces. However
+our methods relies on geometric control theory, like in Rifford and Ruggiero
+articles.",1601.00935v1
+2016-06-16,Calculating rotating hydrodynamic and magneto-hydrodynamic waves to understand magnetic effects on dynamical tides,"For understanding magnetic effects on dynamical tides, we study the rotating
+magneto-hydrodynamic (MHD) flow driven by harmonic forcing. The linear
+responses are analytically derived in a periodic box under the local WKB
+approximation. Both the kinetic and Ohmic dissipations at the resonant
+frequencies are calculated and the various parameters are investigated.
+Although magnetic pressure may be negligible compared to thermal pressure,
+magnetic field can be important for the first-order perturbation, e.g.
+dynamical tides. It is found that magnetic field splits the resonant frequency,
+namely the rotating hydrodynamic flow has only one resonant frequency but the
+rotating MHD flow has two, one positive and the other negative. In the weak
+field regime the dissipations are asymmetric around the two resonant
+frequencies and this asymmetry is more striking with a weaker magnetic field.
+It is also found that both the kinetic and Ohmic dissipations at the resonant
+frequencies are inversely proportional to the Ekman number and the square of
+wavenumber. The dissipation at the resonant frequency on small scales is almost
+equal to the dissipation at the non-resonant frequencies, namely the resonance
+takes its effect on the dissipation at intermediate length scales. Moreover,
+the waves with phase propagation perpendicular to magnetic field are much more
+damped. It is also interesting to find that the frequency-averaged dissipation
+is constant. This result suggests that in compact objects magnetic effects on
+tidal dissipation should be considered.",1606.06232v1
+2017-05-18,"Comment on ""On the nature of magnetic stripes in cuprate superconductors,"" by H. Jacobsen et al., arXiv:1704.08528v2","Dynamics reduces the orthorhombicity of magnetic stripes in La_2CuO_4+y. The
+measured stripe incommensuration can be used to determine the oxygen content of
+the sample.",1705.06986v1
+2017-12-14,Real Time Visualization of Dynamic Magnetic Fields with a Nanomagnetic FerroLens,"Due to advancements in nanomagnetism and latest nanomagnetic materials and
+devices, a new potential field has been opened up for research and applications
+which was not possible before. We herein propose a new research field and
+application for nanomagnetism for the visualization of dynamic magnetic fields
+in real-time. In short, Nano Magnetic Vision. A new methodology, technique and
+apparatus were invented and prototyped in order to demonstrate and test this
+new application. As an application example the visualization of the dynamic
+magnetic field on a transmitting antenna was chosen. Never seen before
+high-resolution, photos and real-time color video revealing the actual dynamic
+magnetic field inside a transmitting radio antenna rod has been captured for
+the first time. The antenna rod is fed with six hundred volts, orthogonal
+pulses. This unipolar signal is in the very low frequency (i.e. VLF) range. The
+signal combined with an extremely short electrical length of the rod, ensures
+the generation of a relatively strong fluctuating magnetic field, analogue to
+the signal transmitted, along and inside the antenna. This field is induced
+into a ferrolens and becomes visible in real-time within the normal human eyes
+frequency spectrum. The name we have given to the new observation apparatus is,
+SPIONs Superparamagnetic Ferrolens Microscope (SSFM), a powerful passive
+scientific observation tool with many other potential applications in the near
+future.",1712.05436v1
+2018-07-11,Transport phenomena with chiral fermions in strong magnetic fields,"I discuss the electrical conductivity, bulk viscosity, and heavy-quark
+diffusion coefficient in strong magnetic fields putting emphasis on
+consequences of the chirality conservation on the perturbative relaxation
+dynamics.",1807.04150v1
+2023-08-21,Magnetic fields in solar plage regions: insights from high-sensitivity spectropolarimetry,"Plage regions are patches of concentrated magnetic field in the Sun's
+atmosphere where hot coronal loops are rooted. While previous studies have shed
+light on the properties of plage magnetic fields in the photosphere, there are
+still challenges in measuring the overlying chromospheric magnetic fields,
+which are crucial to understanding the overall heating and dynamics. Here, we
+utilize high-sensitivity, spectropolarimetric data obtained by the four-meter
+Daniel K. Inouye Solar Telescope (DKIST) to investigate the dynamic environment
+and magnetic field stratification of an extended, decaying plage region. The
+data show strong circular polarization signals in both plage cores and
+surrounding fibrils. Notably, weak linear polarization signals clearly
+differentiate between plage patches and the fibril canopy, where they are
+relatively stronger. Inversions of the Ca II 8542 $\mathring{A}$ spectra show
+an imprint of the fibrils in the chromospheric magnetic field, with typical
+field strength values ranging from $\sim$ 200-300 G in fibrils. We confirm the
+weak correlation between field strength and cooling rates in the lower
+chromosphere. Additionally, we observe supersonic downflows and strong velocity
+gradients in the plage periphery, indicating dynamical processes occurring in
+the chromosphere. These findings contribute to our understanding of the
+magnetic field and dynamics within plages, emphasizing the need for further
+research to explore the expansion of magnetic fields with height and the
+three-dimensional distribution of heating rates in the lower chromosphere.",2308.10983v1
+2008-04-08,Convective intensification of magnetic fields in the quiet Sun,"Kilogauss-strength magnetic fields are often observed in intergranular lanes
+at the photosphere in the quiet Sun. Such fields are stronger than the
+equipartition field $B_e$, corresponding to a magnetic energy density that
+matches the kinetic energy density of photospheric convection, and comparable
+with the field $B_p$ that exerts a magnetic pressure equal to the ambient gas
+pressure. We present an idealised numerical model of three-dimensional
+compressible magnetoconvection at the photosphere, for a range of values of the
+magnetic Reynolds number. In the absence of a magnetic field, the convection is
+highly supercritical and is characterised by a pattern of vigorous,
+time-dependent, ``granular'' motions. When a weak magnetic field is imposed
+upon the convection, magnetic flux is swept into the convective downflows where
+it forms localised concentrations. Unless this process is significantly
+inhibited by magnetic diffusion, the resulting fields are often much greater
+than $B_e$, and the high magnetic pressure in these flux elements leads to
+their being partially evacuated. Some of these flux elements contain
+ultra-intense magnetic fields that are significantly greater than $B_p$. Such
+fields are contained by a combination of the thermal pressure of the gas and
+the dynamic pressure of the convective motion, and they are constantly
+evolving. These ultra-intense fields develop owing to nonlinear interactions
+between magnetic fields and convection; they cannot be explained in terms of
+``convective collapse'' within a thin flux tube that remains in overall
+pressure equilibrium with its surroundings.",0804.1238v1
+2008-04-29,Anisotropic magnetization and sign change of dynamic susceptibility in Na0.85CoO2 single crystal,"The DC and AC magnetic susceptibilities of Na0.85CoO2 single crystals were
+measured for the different crystal orientations of H//(ab)- and H//(c)-axis.
+The DC-magnetic susceptibility for H//(c)-direction exhibited the
+antiferromagnetic transition at TN= 22 K. The thermal hysteresis between the
+zero-field-cooled (ZFC) and the field-cooled (FC) magnetization below TN and
+the large frustration parameter indicated the spin frustration along the
+(c)-axis. For an applied magnetic field in H//(ab)-plane, the DC magnetic
+susceptibility exhibited the logarithmic divergent behavior at low temperatures
+(T < 6.8 K). This could be understood by the impurity spin effect, dressed by
+the spin fluctuation. From the AC magnetic susceptibility measurements, the
+real part of the AC-susceptibility for H//(ab) exhibited the spin glass-like
+behavior at low temperatures (T < 4 K). Remarkably, for an applied AC magnetic
+field with H//(c)-axis, the sign of the AC magnetic susceptibility changed from
+a positive to a negative value with increasing AC magnetic field frequency (f >
+3 kHz) at low temperatures (T > 7 K). We interpret the sign change of AC
+magnetic susceptibility along the (c)-axis in terms of the sudden sign reversal
+of the phase difference from in-phase to out-of-phase response with an applied
+AC magnetic field in the AC-susceptibility phase space.",0804.4532v1
+2011-05-28,Magnetic Flux Expulsion in Star Formation,"Stars form in dense cores of magnetized molecular clouds. If the magnetic
+flux threading the cores is dragged into the stars, the stellar field would be
+orders of magnitude stronger than observed. This well-known ""magnetic flux
+problem"" demands that most of the core magnetic flux be decoupled from the
+matter that enters the star. We carry out the first exploration of what happens
+to the decoupled magnetic flux in 3D, using an MHD version of the ENZO adaptive
+mesh refinement code. The field-matter decoupling is achieved through a sink
+particle treatment, which is needed to follow the protostellar accretion phase
+of star formation. We find that the accumulation of the decoupled flux near the
+accreting protostar leads to a magnetic pressure buildup. The high pressure is
+released anisotropically, along the path of least resistance. It drives a
+low-density expanding region in which the decoupled magnetic flux is expelled.
+This decoupling-enabled magnetic structure has never been seen before in 3D MHD
+simulations of star formation. It generates a strong asymmetry in the
+protostellar accretion flow, potentially giving a kick to the star. In the
+presence of an initial core rotation, the structure presents an obstacle to the
+formation of a rotationally supported disk, in addition to magnetic braking, by
+acting as a rigid magnetic wall that prevents the rotating gas from completing
+a full orbit around the central object. We conclude that the decoupled magnetic
+flux from the stellar matter can strongly affect the protostellar collapse
+dynamics.",1105.5739v1
+2012-01-04,Radiatively Efficient Magnetized Bondi Accretion,"We have carried out a numerical study of the effect of large scale magnetic
+fields on the rate of accretion from a uniform, isothermal gas onto a
+resistive, stationary point mass. Only mass, not magnetic flux, accretes onto
+the point mass. The simulations for this study avoid complications arising from
+boundary conditions by keeping the boundaries far from the accreting object.
+Our simulations leverage adaptive refinement methodology to attain high spatial
+fidelity close to the accreting object. Our results are particularly relevant
+to the problem of star formation from a magnetized molecular cloud in which
+thermal energy is radiated away on time scales much shorter than the dynamical
+time scale. Contrary to the adiabatic case, our simulations show convergence
+toward a finite accretion rate in the limit in which the radius of the
+accreting object vanishes, regardless of magnetic field strength. For very weak
+magnetic fields, the accretion rate first approaches the Bondi value and then
+drops by a factor ~ 2 as magnetic flux builds up near the point mass. For
+strong magnetic fields, the steady-state accretion rate is reduced by a factor
+~ 0.2 \beta^{1/2} compared to the Bondi value, where \beta is the ratio of the
+gas pressure to the magnetic pressure. We give a simple expression for the
+accretion rate as a function of the magnetic field strength. Approximate
+analytic results are given in the Appendixes for both time-dependent accretion
+in the limit of weak magnetic fields and steady-state accretion for the case of
+strong magnetic fields.",1201.0816v1
+2012-06-06,Magnetic-field-dependent photodynamics of single NV defects in diamond: Application to qualitative all-optical magnetic imaging,"Magnetometry and magnetic imaging with nitrogen-vacancy (NV) defects in
+diamond rely on the optical detection of electron spin resonance (ESR).
+However, this technique is inherently limited to magnetic fields that are weak
+enough to avoid electron spin mixing. Here we focus on the high off-axis
+magnetic field regime for which spin mixing alters the NV defect spin dynamics.
+We first study in a quantitative manner the dependence of the NV defect optical
+properties on the magnetic field vector B. Magnetic-field-dependent
+time-resolved photoluminescence (PL) measurements are compared to a seven-level
+model of the NV defect that accounts for field-induced spin mixing. The model
+reproduces the decreases in (i) ESR contrast, (ii) PL intensity and (iii)
+excited level lifetime with an increasing off-axis magnetic field. We next
+demonstrate that those effects can be used to perform all-optical magnetic
+imaging in the high off-axis magnetic field regime. Using a scanning NV defect
+microscope, we map the stray field of a magnetic hard disk through both PL and
+fluorescence lifetime imaging. This all-optical method for high magnetic field
+imaging at the nanoscale might be of interest in the field of nanomagnetism,
+where samples producing fields in excess of several tens of milliteslas are
+typical.",1206.1201v2
+2012-08-23,Solar Force-free Magnetic Fields,"The structure and dynamics of the solar corona is dominated by the magnetic
+field. In most areas in the corona magnetic forces are so dominant that all
+non-magnetic forces like plasma pressure gradient and gravity can be neglected
+in the lowest order. This model assumption is called the force-free field
+assumption, as the Lorentz force vanishes. This can be obtained by either
+vanishing electric currents (leading to potential fields) or the currents are
+co-aligned with the magnetic field lines. First we discuss a mathematically
+simpler approach that the magnetic field and currents are proportional with one
+global constant, the so-called linear force-free field approximation. In the
+generic case, however, the relation between magnetic fields and electric
+currents is nonlinear and analytic solutions have been only found for special
+cases, like 1D or 2D configurations. For constructing realistic nonlinear
+force-free coronal magnetic field models in 3D, sophisticated numerical
+computations are required and boundary conditions must be obtained from
+measurements of the magnetic field vector in the solar photosphere. This
+approach is currently of large interests, as accurate measurements of the
+photospheric field become available from ground-based (for example SOLIS) and
+space-born (for example Hinode and SDO) instruments. If we can obtain accurate
+force-free coronal magnetic field models we can calculate the free magnetic
+energy in the corona, a quantity which is important for the prediction of
+flares and coronal mass ejections. Knowledge of the 3D structure of magnetic
+field lines also help us to interpret other coronal observations, e.g.,
+EUV-images of the radiating coronal plasma.",1208.4693v1
+2012-11-29,Effects of Resistivity on Magnetized Core-Collapse Supernovae,"We studied roles of a turbulent resistivity in the core-collapse of a
+strongly magnetized massive star, carrying out 2D-resistive-MHD simulations.
+The three cases with different initial strengths of magnetic field and rotation
+are investigated; 1. strongly magnetized rotating core; 2.moderately magnetized
+rotating core; 3. very strongly magnetized non-rotating core. In each case,
+both an ideal-MHD model and resistive-MHD models are computed. As a result of
+computations, each model shows a matter eruption helped by a magnetic
+acceleration (and also by a centrifugal acceleration in the rotating cases). We
+found that a resistivity attenuates the explosion in case~1 and 2, while it
+enhances the explosion in case~3. We also found that in the rotating cases,
+main mechanisms for the amplification of a magnetic field in the post-bounce
+phase are an outward advection of magnetic field and a winding of poloidal
+magnetic field-lines by differential rotation, which are somewhat dampened down
+with the presence of a resistivity. Although the magnetorotational instability
+seems to occur in the rotating models, it will play only a minor role in a
+magnetic field amplification. Another impact of resistivity is that on the
+aspect ratio. In the rotating cases, a large aspect ratio of the ejected
+matters, $> 2.5$, attained in a ideal-MHD model is reduced to some extent in a
+resistive model. These results indicate that a resistivity possibly plays an
+important role in the dynamics of strongly magnetized supernovae.",1211.6817v2
+2013-07-18,Steady state rheological behaviour of multi-component magnetic suspensions,"In this paper we study the rheological behaviour (in the absence of magnetic
+field and upon its application) of multi-component magnetic suspensions that
+consist of a mixture of magnetic (iron) and non-magnetic (PMMA) particles
+dispersed in a liquid carrier. These suspensions exhibit considerably higher
+viscosity and yield stress in the absence of magnetic field than
+single-component suspensions of the same solid fraction, as a consequence of
+the adsorption of the iron particles on the PMMA ones. The adsorbed layer of
+iron particles on the PMMA ones is observed through optical microscopy of
+dilute samples and confirmed by attenuated total reflectance. Microscopic
+observations also show that the resulting non-magnetic-core-magnetic-shell
+composites move upon magnetic field application and aggregate into particle
+structures aligned with the applied field. These structures, which consist of
+both types of particles, give rise to high values of the static and dynamic
+yield stresses upon field application. Actually, both quantities are much
+higher than those of a suspension with the same volume fraction of magnetic
+particles, and increase when the amount of non-magnetic ones increases. These
+trends are adequately predicted by a theoretical model that considers that the
+main contribution to the yield stress is the change of the suspension magnetic
+permeability when particle chains are deformed by the shear.",1307.4975v1
+2015-09-09,The magnetic field of zeta Orionis A,"Zeta Ori A is a hot star claimed to host a weak magnetic field, but no clear
+magnetic detection was obtained so far. In addition, it was recently shown to
+be a binary system composed of a O9.5I supergiant and a B1IV star. We aim at
+verifying the presence of a magnetic field in zeta Ori A, identifying to which
+of the two binary components it belongs (or whether both stars are magnetic),
+and characterizing the field.Very high signal-to-noise spectropolarimetric data
+were obtained with Narval at the Bernard Lyot Telescope (TBL) in France.
+Archival HEROS, FEROS and UVES spectroscopic data were also used. The data were
+first disentangled to separate the two components. We then analyzed them with
+the Least-Squares Deconvolution (LSD) technique to extract the magnetic
+information. We confirm that zeta Ori A is magnetic. We find that the
+supergiant component zeta Ori Aa is the magnetic component: Zeeman signatures
+are observed and rotational modulation of the longitudinal magnetic field is
+clearly detected with a period of 6.829 d. This is the only magnetic O
+supergiant known as of today. With an oblique dipole field model of the Stokes
+V profiles, we show that the polar field strength is ~ 140 G. Because the
+magnetic field is weak and the stellar wind is strong, zeta Ori Aa does not
+host a centrifugally supported magnetosphere. It may host a dynamical
+magnetosphere. Its companion zeta Ori Ab does not show any magnetic signature,
+with an upper limit on the undetected field of $\sim$ 300 G.",1509.02773v1
+2015-12-30,Bose-Einstein Condensation of Bound Pairs of Relativistic Fermions in a Magnetic Field,"The Bose-Einstein condensation of bound pairs made of equally and oppositely
+charged fermions in a magnetic field is investigated using a relativistic
+model. The Gaussian fluctuations have been taken into account in order to study
+the spectrum of bound pairs in the strong coupling region. We found, in weak
+coupling reagion, the condensation temperature increases with an increasing
+magnetic field displaying the magnetic catalysis effect. In strong coupling
+region, the inverse magnetic catalysis appears when the magnetic field is low
+and is replaced by the usual magnetic catalysis effect when magnetic field is
+sufficiently high, in contrast to the nonrelativistic case where the inverse
+magnetic catalysis prevails in strong coupling region regardless of the
+strength of the magnetic field. The resulting response to the magnetic field is
+the consequence of the competition between the dimensional reduction by Landau
+orbitals in pairing dynamics and the anisotropy of the kinetic spectrum of the
+bound pairs. We thus conclude that dimensional reduction dominates in weak
+domain and strong coupling one except the small magnetic field region, where
+the enhanced fluctuations dominates.",1512.08894v2
+2016-11-29,Calculation of Evaluation Variables for High Gradient Magnetic Separation with an Idealized Capture Model,"This paper regards feed mine as a mixture of intergrowths and pure
+non-magnetic mineral particles, presents a method to calculate the evaluation
+variables such as grade and recovery in high gradient magnetic separation
+(HGMS). A idealized capture model is constructed in which the interaction
+between particles is not taken into account and only for the initial
+aggregation condition that the separator has the highest capture efficiency. In
+the model we adopt the functions that use nominal particle radius and magnetic
+mineral content as independent variables to describe volume fraction
+distribution and capture efficiency of intergrowths respectively. Through
+adding multi-wire magnetic fields and setting periodic boundary conditions in
+flow field analysis, we modify the computational domain of the single-wire
+capture theory to a element domain that periodically appears in the multi-wire
+matrix. By means of finite element software, particle trajectories, flow field
+and magnetic field are clearly exhibited, and then capture efficiency function
+is obtained by interpolation method. The calculated evaluation variables
+theoretically represent the best performance of magnetic separator for a given
+feed. They can assist mineral engineers to evaluate or compare the effects of
+different magnetic separation systems in advance. We use removal of iron
+impurity from kaolin as an example to illustrate the presented calculation
+method. The results quantitatively compare the evaluation variables of the
+separation at different magnetic fields and show that the advantage of higher
+magnetic field in separation efficiency decreases with the increase of
+saturation magnetization of magnetic mineral.",1611.09481v1
+2017-07-03,Distortion of Magnetic Fields in a Starless Core: Near-Infrared Polarimetry of FeSt 1-457,"Magnetic fields are believed to play an important role in controlling the
+stability and contraction of dense condensations of gas and dust leading to the
+formation of stars and planetary systems. In the present study, the magnetic
+field of FeSt 1-457, a cold starless molecular cloud core, was mapped on the
+basis of the polarized near-infrared light from 185 background stars after
+being dichroically absorbed by dust aligned with the magnetic field in the
+core. A distinct ""hourglass-shaped"" magnetic field was identified in the region
+of the core, which was interpreted as the first evidence of a magnetic field
+structure distorted by mass condensation in a starless core. The steep
+curvature of the magnetic field lines obtained in the present study indicates
+that the distortion was mainly created during the formation phase of the dense
+core. The derived mass-to-magnetic flux ratio indicates that the core is in a
+magnetically supercritical state. However, the stability of the core can be
+considered to be in a nearly critical state if the additional contributions
+from the thermal and turbulent support are included. Further diffusion of the
+magnetic field and/or turbulent dissipation would cause the onset of dynamical
+collapse of the core. The geometrical relationship between the direction of the
+magnetic field lines and the elongation of the core was found to be in good
+agreement with the theoretical predictions for the formation of Sun-like stars
+under the influence of a magnetic field.",1707.00720v1
+2017-09-15,Fragmentation of Filamentary Cloud Permeated by Perpendicular Magnetic Field,"We examine the linear stability of an isothermal filamentary cloud permeated
+by a perpendicular magnetic field. Our model cloud is assumed to be supported
+by gas pressure against the self-gravity in the unperturbed state. For
+simplicity, the density distribution is assumed to be symmetric around the
+axis. Also for simplicity, the initial magnetic field is assumed to be uniform
+and turbulence is not taken into account. The perturbation equation is
+formulated to be an eigenvalue problem. The growth rate is obtained as a
+function of the wavenumber for fragmentation along the axis and the magnetic
+field strength. The growth rate depends critically on the outer boundary. If
+the displacement vanishes in the region very far from the cloud axis (fixed
+boundary), cloud fragmentation is suppressed by a moderate magnetic field,
+which means the plasma beta is below 1.67 on the cloud axis. If the
+displacement is constant along the magnetic field in the region very far from
+the cloud, the cloud is unstable even when the magnetic field is infinitely
+strong. The cloud is deformed by circulation in the plane perpendicular to the
+magnetic field. The unstable mode is not likely to induce dynamical collapse,
+since it is excited even when the whole cloud is magnetically subcritical. For
+both the boundary conditions the magnetic field increases the wavelength of the
+most unstable mode. We find that the magnetic force suppresses compression
+perpendicular to the magnetic field especially in the region of low density.",1709.05149v1
+2017-11-25,Magnetism and the Invisible Man: The mysteries of coronal cavities,"Magnetism defines the complex and dynamic solar corona. Twists and tangles in
+coronal magnetic fields build up energy and ultimately erupt, hurling plasma
+into interplanetary space. These coronal mass ejections (CMEs) are transient
+riders on the ever-outflowing solar wind, which itself possesses a
+three-dimensional morphology shaped by the global coronal magnetic field.
+Coronal magnetism is thus at the heart of any understanding of the origins of
+space weather at the Earth. However, we have historically been limited by the
+difficulty of directly measuring the magnetic fields of the corona, and have
+turned to observations of coronal plasma to trace out magnetic structure. This
+approach is complicated by the fact that plasma temperatures and densities vary
+among coronal magnetic structures, so that looking at any one wavelength of
+light only shows part of the picture. In fact, in some regimes it is the lack
+of plasma that is a significant indicator of the magnetic field. Such a case is
+the coronal cavity: a dark, elliptical region in which strong and twisted
+magnetism dwells. I will elucidate these enigmatic features by presenting
+observations of coronal cavities in multiple wavelengths and from a variety of
+observing vantages, including unprecedented coronal magnetic field measurements
+now being obtained by the Coronal Multichannel Polarimeter (CoMP). These
+observations demonstrate the presence of twisted magnetic fields within
+cavities, and also provide clues to how and why cavities ultimately erupt as
+CMEs.",1711.09254v1
+2017-12-01,Kinetic simulation of magnetic field generation and collisionless shock formation in expanding laboratory plasmas,"Recent laboratory experiments with laser-produced plasmas have observed and
+studied a number of fundamental physical processes relevant to magnetized
+astrophysical plasmas, including magnetic reconnection, collisionless shocks,
+and magnetic field generation by Weibel instability, opening up new
+experimental platforms for laboratory astrophysics. We develop a fully kinetic
+simulation model for first-principles simulation of these systems including the
+dynamics of magnetic fields---magnetic field generation by the Biermann battery
+effect or Weibel instability; advection by the ion flow, Hall effect, and
+Nernst effect; and destruction of the field by dissipative mechanisms. Key
+dimensionless parameters describing the system are derived for scaling between
+kinetic simulation, recent experiments, and astrophysical plasmas. First,
+simulations are presented which model Biermann battery magnetic field
+generation in plasmas expanding from a thin target. Ablation of two neighboring
+plumes leads to the formation of a current sheet as the opposing
+Biermann-generated fields collide, modeling recent laser-driven magnetic
+reconnection experiments. Second, we simulate recent experiments on
+collisionless magnetized shock generation, by expanding a piston plasma into a
+pre-magnetized ambient plasma. For parameters considered, the Biermann effect
+generates additional magnetic fields in the curved shock front and thereby
+increases shock particle reflection. Both cases show the importance of kinetic
+processes in the interaction of plasmas with magnetic fields, and open
+opportunities to benchmark these important processes through comparison of
+theory and experiments.",1712.00152v1
+2017-12-13,Magnetically gated accretion in an accreting 'non-magnetic' white dwarf,"White dwarfs are often found in binary systems with orbital periods ranging
+from tens of minutes to hours in which they can accrete gas from their
+companion stars. In about 15% of these binaries, the magnetic field of the
+white dwarf is strong enough ($\geq 10^6$ Gauss) to channel the accreted matter
+along field lines onto the magnetic poles. The remaining systems are referred
+to as ""non-magnetic"", since to date there has been no evidence that they have a
+dynamically significant magnetic field. Here we report an analysis of archival
+optical observations of the ""non-magnetic"" accreting white dwarf in the binary
+system MV Lyrae (hereafter MV Lyr), whose lightcurve displayed quasi-periodic
+bursts of $\approx 30$ minutes duration every $\approx 2$ hours. The
+observations indicate the presence of an unstable magnetically-regulated
+accretion mode, revealing the existence of magnetically gated accretion, where
+disk material builds up around the magnetospheric boundary (at the co-rotation
+radius) and then accretes onto the white dwarf, producing bursts powered by the
+release of gravitational potential energy. We infer a surface magnetic field
+strength for the white dwarf in MV Lyr between $2 \times 10^4 \leq B \leq 10^5$
+Gauss, too low to be detectable by other current methods. Our discovery
+provides a new way of studying the strength and evolution of magnetic fields in
+accreting white dwarfs and extends the connections between accretion onto white
+dwarfs, young stellar objects and neutron stars, for which similar magnetically
+gated accretion cysles have been identified.",1712.04949v1
+2018-07-11,Parametric study and optimization trends for the Von-Kármán-Sodium dynamo experiment,"We present magneto-hydrodynamic simulations of liquid sodium flow with the
+PLUTO compressible MHD code. We investigate the influence of the remnant
+magnetic field orientation and intensity, impinging velocity field due to Ekman
+pumping as well as the impeller dimensions on the magnetic field collimation by
+helical flows in between the impeller blades. For a simplified cartesian
+geometry we model the flow dynamics of a multi-blades impeller inspired by the
+Von-Karman-Sodium (VKS) experiment. The study shows that a remnant magnetic
+field oriented in the toroidal direction is the less efficient configuration to
+collimate the magnetic field, although if the radial or vertical components are
+not negligible the collimation is significantly improved. If the intensity of
+the remnant magnetic field increases the system magnetic energy is larger but
+the magnetic field collimation efficiency is the same, so the gain of magnetic
+energy is smaller as the remnant magnetic field intensity increases. The
+magnetic field collimation is modified if the impinging velocity field changes:
+the collimation is weaker if the impinging velocity increases from Gamma=0.8 to
+0.9, slightly larger if the impinging velocity decreases from Gamma=0.8 to 0.7.
+The analysis of the impeller dimensions points out that the most efficient
+configuration to collimate the magnetic field requires a ratio between impeller
+blade height and base longitude between 0.375 - 0.5. The largest enhancement of
+the hypothetical alpha^2 dynamo loop, compared to the hypothetical Omega-alpha
+dynamo loop, is observed for the model that mimics TM 73 impeller configuration
+rotating in the unscooping direction with a remnant magnetic field of 10^-3 T
+orientated in the radial or vertical direction. The optimization trends
+obtained in the parametric analysis are also confirmed in simulations with
+higher resolution and turbulence degree.",1807.03956v1
+2019-08-27,Magnetized 1.5-dimensional advective accretion flows around black holes,"We address the role of large scale magnetic stress in the angular momentum
+transport, as well as the formation of different kinds of magnetic barrier in
+geometrically thick, optically thin, vertically averaged 1.5-dimensional
+advective accretion flows around black holes. The externally generated magnetic
+fields are captured by the accretion process from the environment, say,
+companion stars or interstellar medium. This field becomes dynamically dominant
+near the event horizon of a black hole due to continuous advection of the
+magnetic flux. In such magnetically dominated accretion flows, the accreting
+matter either decelerates or faces magnetic barrier in vicinity of the black
+hole depending on the magnetic field geometry. We find that the accumulated
+strong poloidal fields along with certain toroidal field geometry help in the
+formation of magnetic barrier which may knock the matter to infinity. When
+matter is trying to go back to infinity after getting knocked out by the
+barrier, in some cases it is prevented being escaped due to cumulative action
+of strong magnetic tension and gravity, and hence another magnetic barrier. We
+suggest, this kind of flow may be responsible for the formation of episodic
+jets in which magnetic field can lock the matter in between these two barriers.
+We also find that for the toroidally dominated disc, the accreting matter
+rotates very fast and decelerates towards the central black hole.",1908.10043v1
+2020-03-10,Potential Vorticity Mixing in a Tangled Magnetic Field,"A theory of potential vorticity (PV) mixing in a disordered (tangled)
+magnetic field is presented. The analysis is in the context of $\beta$-plane
+MHD, with a special focus on the physics of momentum transport in the stably
+stratified, quasi-2D solar tachocline. A physical picture of mean PV evolution
+by vorticity advection and tilting of magnetic fields is proposed. In the case
+of weak-field perturbations, quasi-linear theory predicts that the Reynolds and
+magnetic stresses balance as turbulence Alfv\'enizes for a larger mean magnetic
+field. Jet formation is explored quantitatively in the mean field-resistivity
+parameter space. However, since even a modest mean magnetic field leads to
+large magnetic perturbations for large magnetic Reynolds number, the physically
+relevant case is that of a strong but disordered field. We show that numerical
+calculations indicate that the Reynolds stress is modified well before
+Alfv\'enization -- i.e. before fluid and magnetic energies balance. To
+understand these trends, a double-average model of PV mixing in a stochastic
+magnetic field is developed. Calculations indicate that mean-square fields
+strongly modify Reynolds stress phase coherence and also induce a magnetic drag
+on zonal flows. The physics of transport reduction by tangled fields is
+elucidated and linked to the related quench of turbulent resistivity. We
+propose a physical picture of the system as a resisto-elastic medium threaded
+by a tangled magnetic network. Applications of the theory to momentum transport
+in the tachocline and other systems are discussed in detail.",2003.04944v1
+2020-04-12,Signatures of Untwisting Magnetic Field in a Small Emerging Bipole in the Solar Photosphere,"We perform a study of fluid motions and its temporal evolution in and around
+a small bipolar emerging flux region using observations made by the
+Helioseismic and Magnetic Imager (HMI) on-board the Solar Dynamics Observatory
+(SDO). We employ local correlation tracking of the Doppler observations to
+follow horizontal fluid motions and line-of-sight magnetograms to follow the
+flux emergence. Changes in vertical vorticity and horizontal divergence are
+used to derive signatures of evolving twists in the magnetic field. Our
+analysis reveals that the two polarities of the magnetic flux swirl in opposite
+directions in early stages of flux emergence indicating an unwinding of the
+pre-emergence twists in the magnetic field. We further find that during the
+emergence, there is an increase in swirly motions in the neighbouring
+non-magnetic regions. We estimate the magnetic and kinetic energies and find
+that magnetic energy is about a factor of ten larger than the kinetic energy.
+During the evolution, when the magnetic energy decreases, an increase in the
+kinetic energy is observed indicating transfer of energy from the unwinding of
+magnetic flux tube to the surrounding fluid motions. Our results thus
+demonstrate the presence of pre-emergence twists in emerging magnetic field
+that is important in the context of the hemispheric helicity rule warranting a
+detailed statistical study in this context. Further, our observations point to
+a possible widespread generation of torsional waves in emerging flux regions
+due to the untwisting magnetic field with implications for upward energy
+transport to the corona.",2004.05615v1
+2020-06-23,Hall cascade with fractional magnetic helicity in neutron star crusts,"The ohmic decay of magnetic fields in the crusts of neutron stars is
+generally believed to be governed by Hall drift which leads to what is known as
+a Hall cascade. Here we show that helical and fractionally helical magnetic
+fields undergo strong inverse cascading like in magnetohydrodynamics (MHD), but
+the magnetic energy decays more slowly with time $t$: $\propto t^{-2/5}$
+instead of $\propto t^{-2/3}$ in MHD. Even for a nonhelical magnetic field
+there is a certain degree of inverse cascading for sufficiently strong magnetic
+fields. The inertial range scaling with wavenumber $k$ is compatible with
+earlier findings for the forced Hall cascade, i.e., proportional to $k^{-7/3}$,
+but in the decaying cases, the subinertial range spectrum steepens to a novel
+$k^5$ slope instead of the $k^4$ slope in MHD. The energy of the large-scale
+magnetic field can increase quadratically in time through inverse cascading.
+For helical fields, the energy dissipation is found to be inversely
+proportional to the large-scale magnetic field and proportional to the fifth
+power of the root-mean square (rms) magnetic field. For neutron star conditions
+with an rms magnetic field of a few times $10^{14}\,$G, the large-scale
+magnetic field might only be $10^{11}\,$G, while still producing magnetic
+dissipation of $10^{33}\,$erg$\,$s$^{-1}$ for thousands of years, which could
+manifest itself through X-ray emission. Finally, it is shown that the
+conclusions from local unstratified models agree rather well with those from
+stratified models with boundaries.",2006.12984v4
+2021-03-02,"On the alignment of haloes, filaments and magnetic fields in the simulated cosmic web","The continuous flow of gas and dark matter across scales in the cosmic web
+can generate correlated dynamical properties of haloes and filaments (and the
+magnetic fields they contain). With this work, we study the halo spin
+properties and orientation with respect to filaments, and the morphology of the
+magnetic field around these objects, for haloes with masses in the range
+1e8-1e14 Msun and filaments up to 8 Mpc long. Furthermore, we study how these
+properties vary in presence, or lack thereof, of different (astro)physical
+processes and with different magnetic initial conditions. We perform
+cosmological magnetohydrodynamical simulations with the Eulerian code Enzo and
+we develop a simple and robust algorithm to study the filamentary connectivity
+of haloes in three dimensions. We investigate the morphological and magnetic
+properties and focus on the alignment of the magnetic field along filaments:
+our analysis suggests that the degree of this alignment is partially dependent
+on the physical processes involved, as well as on magnetic initial conditions.
+We discuss the contribution of this effect on a potential attempt to detect the
+magnetic field surrounding these objects: we find that it introduces a bias in
+the estimation of the magnetic field from Faraday rotation measure techniques.
+Specifically, given the strong tendency we find for extragalactic magnetic
+fields to align with the filaments axis, the value of the magnetic field can be
+underestimated by a factor 3, because this effect contributes to making the
+line-of-sight magnetic field (for filaments in the plane of the sky) much
+smaller than the total one.",2103.01943v1
+2021-03-05,Relationship between magnetic field properties and statistical flow using numerical simulation and magnetic feature tracking on solar photosphere,"We perform radiative magnetohydrodynamic calculations for the solar quiet
+region to investigate the dependence of statistical flow on magnetic properties
+and the three-dimensional (3D) structure of magnetic patches in the presence of
+large-scale flow that mimics differential rotation. It has been confirmed that
+strong magnetic field patches move faster in the longitudinal direction at the
+solar surface. Consequently, strong magnetic patches penetrate deeper into the
+solar interior. The motion of the deep-rooted magnetic patches is influenced by
+the faster differential rotation in the deeper layer. In this study, we perform
+realistic radiative magnetohydrodynamic calculations using R2D2 code to
+validate that stronger patches have deeper roots. We also add large-scale flow
+to mimic the differential rotation. The magnetic patches are automatically
+detected and tracked, and we evaluate the depth of 30,000 magnetic patches. The
+velocities of 2.9 million magnetic patches are then measured at the
+photosphere. We obtain the dependence of these values on the magnetic
+properties, such as field strength and flux. Our results confirm that strong
+magnetic patches tend to show deeper roots and faster movement, and we compare
+our results with observations using the point spread function of instruments at
+the Hinode and Solar Dynamics Observatory (SDO). Our result is quantitatively
+consistent with previous observational results of the SDO.",2103.03789v1
+2021-11-14,Spontaneous Formation of Outflows Powered by Rotating Magnetized Accretion Flows in a Galactic Center,"We investigate how magnetically driven outflows are powered by a rotating,
+weakly magnetized accretion flow onto a supermassive black hole using
+axisymmetric magnetohydrodynamic simulations. Our proposed model focuses on the
+accretion dynamics on an intermediate scale between the Schwarzschild radius
+and the galactic scale, which is $\sim$1-100 pc. We demonstrate that a rotating
+disk formed on a parsec-scale acquires poloidal magnetic fields via accretion
+and this produces an asymmetric bipolar outflow at some point. The formation of
+the outflow was found to follow the growth of strongly magnetized regions
+around disk surfaces (magnetic bubbles). The bipolar outflow grew continuously
+inside the expanding bubbles. We theoretically derived the growth condition of
+magnetic bubbles for our model that corresponds to a necessary condition for
+outflow growth. We found that the north-south asymmetric structure of the
+bipolar outflow originates from the complex motions excited by accreting flows
+around the outer edge of the disk. The bipolar outflow comprises multiple
+mini-outflows and downflows (failed outflows). The mini-outflows emanate from
+the magnetic concentrations (magnetic patches). The magnetic patches exhibit
+inward drifting motions, thereby making the outflows unsteady. We demonstrate
+that the inward drift can be modeled using a simple magnetic patch model that
+considers magnetic angular momentum extraction. This study could be helpful for
+understanding how asymmetric and non-steady outflows with complex substructures
+are produced around supermassive black holes without the help of strong
+radiation from accretion disks or entrainment by radio jets such as molecular
+outflows in radio-quiet active galactic nuclei, NGC 1377.",2111.07373v1
+2022-03-28,Nonlinear geometrically exact dynamics of fluid-conveying cantilevered hard magnetic soft pipe with uniform and nonuniform magnetizations,"It is generally acknowledged that a hanging cantilevered pipe conveying fluid
+becomes unstable by flutter-type instability at a critical flow velocity;
+moreover, the pipe undergoes periodic self-excited oscillations in the
+post-flutter region. Additionally, the critical flow velocity increases when
+the magnetized pipe is exposed to an actuating parallel magnetic field. The
+question arises as to whether the actuating magnetic field leads to lessening
+the oscillation amplitude of the system in the post-flutter region. To answer
+the question, the nonlinear responses of a fluid-conveying cantilevered hard
+magnetic soft pipe with uniform and nonuniform magnetizations under an
+actuating parallel magnetic field are examined. In the case of the nonuniform
+magnetization, the mass density and elastic modulus of the pipe in addition to
+its residual magnetic flux density vary along its length. The mathematical
+formulation is constructed via a nonlinear geometrically exact model and is
+solved by employing the Galerkin technique in conjunction with the Runge-Kutta
+finite difference scheme. The numerical results are then analyzed to reveal the
+role of magnetization in the magneto-hydro-elastic responses of the system in
+the absence and presence of magnetic field.",2203.14618v2
+2022-09-30,Tunable Magnets: modeling and validation for dynamic and precision applications,"Actuator self-heating limits the achievable force and can cause unwanted
+structural deformations. This is especially apparent in quasi-static actuation
+systems that require the actuator to maintain a stable position over an
+extended period. As a solution, we use the concept of a Tunable Magnet. Tunable
+magnets rely on in-situ magnetization state tuning of AlNico to create an
+infinitely adjustable magnetic flux. They consist of an AlNiCo low coercivity
+permanent magnet together with a magnetizing coil. After tuning, the AlNiCo
+retains its magnetic field without further energy input, which eliminates the
+static heat dissipation. To enable implementation in actuation systems, the
+AlNiCo needs to be robustly tunable in the presence of a varying system
+air-gap. We achieve this by implementing a magnetization state tuning method,
+based on a magnetic circuit model of the actuator, measured AlNiCo BH data and
+air-gap flux feedback control. The proposed tuning method consists of 2 main
+steps. The prediction step, during which the required magnet operating point is
+determined, and the demagnetization step, where a feedback controller drives a
+demagnetization current to approach this operating point. With this method
+implemented for an AlNiCo 5 tunable magnet in a reluctance actuator
+configuration, we achieve tuning with a maximum error of 15.86 ""mT"" and a
+minimum precision of 0.67 ""mT"" over an air-gap range of 200 ""{\mu}m"". With this
+tuning accuracy, actuator heating during static periods is almost eliminated.
+Only a small bias current is needed to compensate for the tuning error.",2210.00142v1
+2023-05-04,Magnetic properties of Nd6Fe13Cu single crystals,"The understanding of coercivity mechanism in high performance Nd-Fe-B
+permanent magnets relies on the analysis of the magnetic properties of all
+phases present in the magnets. By adding Cu in such compounds, a new Nd6Fe13Cu
+grain boundary phase is formed, however, the magnetic properties of this phase
+and its role in the magnetic decoupling of the matrix Nd2Fe14B grains are still
+insufficiently studied. In this work, we have grown Nd6Fe13Cu single crystals
+by the reactive flux method and studied their magnetic properties in detail. It
+is observed that below the N\'eel temperature (TN = 410 K), the Nd6Fe13Cu is
+antiferromagnetic in zero magnetic field; whereas when a magnetic field is
+applied along the a-axis, a spin-flop transition occurs at approx. 6 T,
+indicating a strong competition between antiferromagnetic and ferromagnetic
+interactions in two Nd layers below and above the Cu layers. Our atomistic spin
+dynamics simulation confirms that an increase in temperature and/or magnetic
+field can significantly change the antiferromagnetic coupling between the two
+Nd layers below and above the Cu layers, which, in turn, is the reason for the
+observed spin-flop transition. These results suggest that the role of
+antiferromagnetic Nd6Fe13Cu grain boundary phase in the coercivity enhancement
+of Nd-Fe-B-Cu magnets is more complex than previously thought, mainly due to
+the competition between its antiferro- and ferro-magnetic exchange
+interactions.",2305.02889v1
+2023-08-03,Unconventional Metallic Magnetism: Non-analyticity and Sign-changing Behavior of Orbital Magnetization in ABC Trilayer Graphene,"We study an unique form of metallic ferromagnetism in which orbital moments
+surpasses the role of spin moments in shaping the overall magnetization. This
+system emerges naturally upon doping a topologically non-trivial Chern band in
+the recently identified quarter metal phase of rhombohedral trilayer graphene.
+Our comprehensive scan of the density-interlayer potential parameter space
+reveals an unexpected landscape of orbital magnetization marked by two sign
+changes and a line of singularities. The sign change originates from an intense
+Berry curvature concentrated close to the band-edge, and the singularity arises
+from a topological Lifshitz transition that transform a simply connected Fermi
+sea into an annular Fermi sea. Importantly, these variations occur while the
+groundstate order-parameter (i.e. valley and spin polarization) remains
+unchanged. This unconventional relationship between the order parameter and
+magnetization markedly contrasts traditional spin ferromagnets, where spin
+magnetization is simply proportional to the groundstate spin polarization via
+the gyromagnetic ratio. We compute energy and magnetization curves as functions
+of collective valley rotation to shed light on magnetization dynamics and to
+expand the Stoner-Wohlfarth magnetization reversal model. We provide
+predictions on the magnetic coercive field that can be readily tested in
+experiments. Our results challenge established perceptions of magnetism,
+emphasising the important role of orbital moments in two-dimensional materials
+such as graphene and transition metal dichalcogenides, and in turn, expand our
+understanding and potential manipulation of magnetic behaviors in these
+systems.",2308.01996v2
+2023-12-11,Advancing solar magnetic field extrapolations through multi-height magnetic field measurements,"Non-linear force-free extrapolations are a common approach to estimate the 3D
+topology of coronal magnetic fields based on photospheric vector magnetograms.
+The force-free assumption is a valid approximation at coronal heights, but for
+the dense plasma conditions in the lower atmosphere, this assumption is not
+satisfied. In this study, we utilize multi-height magnetic field measurements
+in combination with physics-informed neural networks to advance solar magnetic
+field extrapolations. We include a flexible height-mapping, which allows us to
+account for the different formation heights of the observed magnetic field
+measurements. The comparison to analytical and simulated magnetic fields
+demonstrates that including chromospheric magnetic field measurements leads to
+a significant improvement of our magnetic field extrapolations. We also apply
+our method to chromospheric line-of-sight magnetograms, from the Vector
+Spectromagnetograph (VSM) on the Synoptic Optical Long-term Investigations of
+the Sun (SOLIS) observatory, in combination with photospheric vector
+magnetograms, from the Helioseismic Magnetic Imager (HMI) onboard the Solar
+Dynamic Observatory (SDO). The comparison to observations in extreme
+ultraviolet wavelengths shows that the additional chromospheric information
+leads to a better agreement with the observed coronal structures. In addition,
+our method intrinsically provides an estimate of the corrugation of the
+observed magnetograms. With this new approach, we make efficient use of
+multi-height magnetic field measurements and advance the realism of coronal
+magnetic field simulations.",2312.06823v1
+2017-07-10,One-loop QCD thermodynamics in a strong homogeneous and static magnetic field,"We have studied how the equation of state of thermal QCD with two light
+flavours is modified in strong magnetic field by calculating the thermodynamic
+observables of hot QCD matter up to one-loop, where the magnetic field affects
+mainly the quark contribution and the gluonic part is largely unaffected except
+for the softening of the screening mass due to the strong magnetic field. To
+begin with the effect of magnetic field on the thermodynamics, we have first
+calculated the pressure of a thermal QCD medium in strong magnetic field limit
+(SML), where the pressure at fixed temperature increases with the magnetic
+field faster than the increase with the temperature at constant magnetic field.
+This can be envisaged from the dominant scale of thermal medium in SML, which
+is the magnetic field, like the temperature in thermal medium in absence of
+strong magnetic field. Thus although the presence of strong magnetic field
+makes the pressure of hot QCD medium harder but the increase of pressure with
+respect to the temperature becomes less steeper. Corroborated to the above
+observations, the entropy density is found to decrease with the temperature in
+the ambience of strong magnetic field which resonates with the fact that the
+strong magnetic field restricts the dynamics of quarks in two dimensions, hence
+the phase space gets squeezed resulting the reduction of number of microstates.
+Moreover the energy density is seen to decrease and the speed of sound of
+thermal QCD medium is increased in the presence of strong magnetic field. These
+crucial findings in strong magnetic field could have phenomenological
+implications in heavy ion collisions because the expansion dynamics of the
+medium produced in noncentral ultrarelativistic heavy ion collisions is
+effectively controlled by both the energy density and the speed of sound.",1707.02890v1
+2007-10-31,Spin-Torque Driven Magnetization Dynamics: Micromagnetic Modelling,"In this paper we present an overview of recent progress made in the
+understanding of the spin-torque induced magnetization dynamics in nanodevices
+using mesoscopic micromagnetic simulations. We first specify how a spin-torque
+term may be added to the usual Landau-Lifshitz-Gilbert equation of
+magnetization motion and detail its physical meaning. After a brief description
+of spin-torque driven dynamics in the macrospin approximation, we discuss the
+validity of this approximation for various experimentally relevant geometries.
+Next, we perform a detailed comparison between accurate experimental data
+obtained from nanopillar devices and corresponding numerical modelling. We show
+that, on the one hand, many qualitatively important features of the observed
+magnetization dynamics (e.g., non-linear frequency shift and frequency jumps
+with increasing current) can be satisfactory explained by sophisticated
+micromagnetic models, but on the other hand, understanding of these experiments
+is still far from being complete. We proceed with the numerical analysis of
+point-contact experiments, where an even more complicated magnetization
+dynamics is observed. Simulations reveal that such a rich behaviour is due to
+the formation of several strongly non-linear oscillation modes. In the last
+part of the paper we emphasize the importance of sample characterization and
+conclude with some important remarks concerning the relation between
+micromagnetic modelling and real experiments.",0710.5924v1
+2011-05-16,Finite-size effects on the dynamic susceptibility of CoPhOMe single-chain molecular magnets in presence of a static magnetic field,"The static and dynamic properties of the single-chain molecular magnet
+[Co(hfac)$_2$NITPhOMe] are investigated in the framework of the Ising model
+with Glauber dynamics, in order to take into account both the effect of an
+applied magnetic field and a finite size of the chains. For static fields of
+moderate intensity and short chain lengths, the approximation of a
+mono-exponential decay of the magnetization fluctuations is found to be valid
+at low temperatures; for strong fields and long chains, a multi-exponential
+decay should rather be assumed. The effect of an oscillating magnetic field,
+with intensity much smaller than that of the static one, is included in the
+theory in order to obtain the dynamic susceptibility $\chi(\omega)$. We find
+that, for an open chain with $N$ spins, $\chi(\omega)$ can be written as a
+weighted sum of $N$ frequency contributions, with a sum rule relating the
+frequency weights to the static susceptibility of the chain. Very good
+agreement is found between the theoretical dynamic susceptibility and the ac
+susceptibility measured in moderate static fields ($H_{\rm dc}\le 2$ kOe),
+where the approximation of a single dominating frequency turns out to be valid.
+For static fields in this range, new data for the relaxation time, $\tau$
+versus $H_{\rm dc}$, of the magnetization of CoPhOMe at low temperature are
+also well reproduced by theory, provided that finite-size effects are included.",1105.3009v1
+2015-07-30,Asymmetric driven dynamics of Dzyaloshinskii domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy,"The dynamics of domain walls in ultrathin ferromagnetic strips with
+perpendicular magnetic anisotropy is studied from both numerical and analytical
+micromagnetics. The influence of the interfacial Dzyaloshinskii-Moriya
+interaction associated to a bi-layer strip arrangement has been considered,
+giving rise to the formation of Dzyaloshinskii domain walls. Such walls possess
+under equilibrium conditions an inner magnetization structure defined by a
+certain orientation angle that make them to be considered as intermediate
+configurations between Bloch and N\'eel walls. Two different dynamics are
+considered, a field-driven and a current-driven dynamics, in particular, the
+one promoted by the spin torque due to the Spin-Hall effect. Results show an
+inherent asymmetry associated with the rotation of the domain wall
+magnetization orientation before reaching the stationary regime, characterized
+by a constant terminal speed. For a certain initial DW magnetization
+orientation at rest, the rotation determines whether the reorientation of the
+DW magnetization prior to reach stationary motion is smooth or abrupt. This
+asymmetry affects the DW motion that can even reverse for a short period of
+time. Additionally, it is found that the terminal speed in the case of the
+current-driven dynamics may depend on either the initial DW magnetization
+orientation at rest or the sign of the longitudinally injected current.",1507.08406v2
+2016-11-20,The effect of dynamical compressive and shear strain on magnetic anisotropy in low symmetry ferromagnetic film,"Dynamical strain generated upon excitation of a metallic film by a
+femtosecond laser pulse may become a versatile tool enabling control of
+magnetic state of thin films and nanostructures via inverse magnetostriction on
+a picosecond time scale. Here we explore two alternative approaches to
+manipulate magnetocrystalline anisotropy and excite magnetization precession in
+a low-symmetry film of a magnetic metallic alloy galfenol (Fe,Ga) either by
+injecting picosecond strain pulse into it from a substrate or by generating
+dynamical strain of complex temporal profile in the film directly. In the
+former case we realize ultrafast excitation of magnetization dynamics solely by
+strain pulses. In the latter case optically-generated strain emerged abruptly
+in the film modifies its magnetocrystalline anisotropy, competing with
+heat-induced change of anisotropy parameters. We demonstrate that the
+optically-generated strain remains efficient for launching magnetization
+precession, when the heat-induced changes of anisotropy parameters do not
+trigger the precession anymore. We emphasize that in both approaches the
+ultrafast change of magnetic anisotropy mediating the precession excitation
+relies on mixed, compressive and shear, character of the dynamical strain,
+which emerges due to low-symmetry of the metallic film under study.",1611.06599v3
+2018-03-03,Evidence for a dynamical ground state in a frustrated pyrohafnate Tb2Hf2O7,"We report the physical properties of Tb2Hf2O7 based on ac magnetic
+susceptibility \chi_ac(T), dc magnetic susceptibility \chi(T), isothermal
+magnetization M(H), and heat capacity C_p(T) measurements combined with muon
+spin relaxation (\muSR) and neutron powder diffraction measurements. No
+evidence for long-range magnetic order is found down to 0.1 K. However,
+\chi_ac(T) data present a frequency-dependent broad peak (near 0.9 K at 16 Hz)
+indicating slow spin dynamics. The slow spin dynamics is further evidenced from
+the \muSR data (characterized by a stretched exponential behavior) which show
+persistent spin fluctuations down to 0.3 K. The neutron powder diffraction data
+collected at 0.1 K show a broad peak of magnetic origin (diffuse scattering)
+but no magnetic Bragg peaks. The analysis of the diffuse scattering data
+reveals a dominant antiferromagnetic interaction in agreement with the negative
+Weiss temperature. The absence of long-range magnetic order and the presence of
+slow spin dynamics and persistent spin fluctuations together reflect a
+dynamical ground state in Tb2Hf2O7.",1803.01193v1
+2019-07-03,Dynamic magnetostriction for antiferromagnets,"In this paper we study the switching properties of the dynamics of magnetic
+moments, that interact with an elastic medium. To do so we construct a
+Hamiltonian framework, that can take into account the dynamics in phase space
+of the variables that describe the magnetic moments in a consistent way. It is
+convenient to describe the magnetic moments as bilinears of anticommuting
+variables that are their own conjugates. However, we show how it is possible to
+avoid having to deal directly with the anticommuting variables themselves, only
+using them to deduce non-trivial constraints on the magnetoelastic couplings.
+We construct the appropriate Poisson bracket and a geometric integration
+scheme, that is symplectic in the extended phase space and that allows us to
+study the switching properties of the magnetization, that are relevant for
+applications, for the case of a toy model for antiferromagnetic NiO, under
+external stresses. In the absence of magnetoelastic coupling, we recover the
+results reported in the literature and in our previous studies. In the presence
+of the magnetoelastic coupling, the characteristic oscillations of the
+mechanical system have repercussions on the N\'eel order parameter dynamics.
+This is particularly striking for the spin accumulation which is more than
+doubled by the coupling to the strain ; here as well, the mechanical
+oscillations are reflected on the magnetic dynamics. As a consequence of such a
+stress induced strain, the switching time of the magnetization is slightly
+faster and the amplitude of the magnetization enhanced.",1907.01857v2
+2021-07-13,Dynamical and static spin structure factors of Heisenberg antiferromagnet on honeycomb lattice in the presence of Dzyaloshinskii-Moriya interaction,"We have theoretically studied the spin structure factors of Heisenberg model
+on honeycomb lattice in the presence of longitudinal magnetic field, i.e.
+magnetic field perpendicular to the honeycomb plane, and Dzyaloshinskii-Moriya
+interaction. The possible effects of next nearest neighbor exchange constant
+are investigated in terms of anisotropy in the Heisenberg interactions. This
+spatial anisotropy is due to the difference between nearest neighbor exchange
+coupling constant and next nearest neighbor exchange coupling constant. The
+original spin model hamiltonian is mapped to a bosonic model via a hard core
+bosonic transformation where an infinite hard core repulsion is imposed to
+constrain one boson occupation per site. Using Green's function approach, the
+energy spectrum of quasiparticle excitation has been obtained. The spectrum of
+the bosonic gas has been implemented in order to obtain two particle propagator
+which corresponds to spin structure factor of original Heisenberg chain model
+Hamiltonian. The results show the position of peak in the dynamical transverse
+spin structure factor at fixed value for Dzyaloshinskii Moriya interaction
+moves to higher frequency with magnetic field. Also the intensity of dynamical
+transverse spin structure factor is not affected by magnetic field. However the
+Dzyaloshinskii Moriya interaction strength causes to decrease the intensity of
+dynamical transverse spin structure factor. The increase of magnetic field does
+not varied the frequency position of peaks in dynamical longitudinal spin
+susceptibility however the intensity reduces with magnetic field. Our results
+show static transverse structure factor is found to be monotonically decreasing
+with magnetic field and temperature for different vlaues of next nearest
+neighbor coupling exchange constant.",2107.05862v1
+2021-10-27,Hamilton-Jacobi Equations of Controlled Magnetic Hamiltonian System with Nonholonomic Constraint,"In order to describe the impact of different geometric structures and
+constraints for the dynamics of a regular controlled Hamiltonian system, in
+this paper, we first define a kind of controlled magnetic Hamiltonian (CMH)
+system, and give a good expression of the dynamical vector field of the CMH
+system, such that we can describe the magnetic vanishing condition and the
+CMH-equivalence, and derive precisely the geometric constraint conditions of
+the magnetic symplectic form for the dynamical vector field of the CMH system,
+which are called the Type I and Type II of Hamilton-Jacobi equation. Secondly,
+we prove that the CMH-equivalence for the CMH systems leaves the solutions of
+corresponding to Hamilton-Jacobi equations invariant, if the associated
+magnetic Hamiltonian systems are equivalent. Thirdly, we consider the CMH
+system with nonholonomic constraint, and derive a distributional CMH system,
+which is determined by a non-degenerate distributional two-form induced from
+the magnetic symplectic form. Then we drive precisely two types of
+Hamilton-Jacobi equation for the distributional CMH system. Moreover, we
+generalize the above results for the nonholonomic reducible CMH system with
+symmetry, and prove two types of Hamilton-Jacobi theorems for the nonholonomic
+reduced distributional CMH system. These research works reveal the deeply
+internal relationships of the magnetic symplectic forms, the nonholonomic
+constraints, the dynamical vector fields and controls of the CMH systems.",2110.14175v2
+2022-05-20,A feasibility analysis towards the simulation of hysteresis with spin-lattice dynamics,"We use spin-lattice dynamics simulations to study the possibility of modeling
+the magnetic hysteresis behavior of a ferromagnetic material. The temporal
+evolution of the magnetic and mechanical degrees of freedom is obtained through
+a set of two coupled Langevin equations. Hysteresis loops are calculated for
+different angles between the external field and the magnetocrystalline
+anisotropy axes. The influence of several relevant parameters is studied,
+including the field frequency, magnetic damping, magnetic anisotropy (magnitude
+and type), magnetic exchange, and system size. The role played by a moving
+lattice is also discussed. For a perfect bulk ferromagnetic system we find
+that, at low temperatures, the exchange and lattice dynamics barely affect the
+loops, while the field frequency and magnetic damping have a large effect on
+it. The influence of the anisotropy magnitude and symmetry are found to follow
+the expected behavior. We show that a careful choice of simulation parameters
+allows for an excellent agreement between the spin-lattice dynamics
+measurements and the paradigmatic Stoner-Wohlfarth model. Furthermore, we
+extend this analysis to intermediate and high temperatures for the perfect bulk
+system and for spherical nanoparticles, with and without defects, reaching
+values close to the Curie temperature. In this temperature range, we find that
+lattice dynamics has a greater role on the magnetic behavior, especially in the
+evolution of the defective samples. The present study opens the possibility for
+more accurate inclusion of lattice defects and thermal effects in hysteresis
+simulations",2205.10418v3
+2000-07-13,Dynamical Structure Factors of the S=1/2 Bond-Alternating Spin Chain with a Next-Nearest-Neighbor Interaction in Magnetic Fields,"The dynamical structure factor of the S=1/2 bond-alternating spin chain with
+a next-nearest-neighbor interaction in magnetic field is investigated using the
+continued fraction method based on the Lanczos algorithm. When the plateau
+exists on the magnetization curve, the longitudinal dynamical structure factor
+shows a large intensity with a periodic dispersion relation, while the
+transverse one shows a large intensity with an almost dispersionless mode. The
+periodicity and the amplitude of the dispersion relation in the longitudinal
+dynamical structure factor are sensitive to the coupling constants. The
+dynamical structure factor of the S=1/2 two-leg ladder in magnetic field is
+also calculated in the strong interchain-coupling regime.
+  The dynamical structure factor shows gapless or gapful behavior depending on
+the wave vector along the rung.",0007219v1
+2003-10-13,Multiple dynamic transitions in anisotropic Heisenberg ferromagnet driven by polarised magnetic field,"Uniaxially (Z-axis) anisotropic Heisenberg ferromagnet, in presence of time
+dependent (but uniform over space) magnetic field, is studied by Monte Carlo
+simulation. The time dependent magnetic field was taken as elliptically
+polarised where the resultant field vector rotates in X-Z plane. The system is
+cooled (in presence of the elliptically polarised magnetic field) from high
+temperature. As the temperature decreases, it was found that in the low
+anisotropy limit the system undergoes three successive dynamical phase
+transitions. These three dynamic transitions were confirmed by studying the
+temperature variation of dynamic 'specific heat'. The temperature variation of
+dynamic 'specific heat' shows three peaks indicating three dynamic transition
+points.",0310288v2
+2010-04-23,Fast-forward of quantum adiabatic dynamics in electro-magnetic field,"We show a method to accelerate quantum adiabatic dynamics of wavefunctions
+under electro-magnetic field by developing the previous theory (Masuda &
+Nakamura 2008 and 2010). Firstly we investigate the orbital dynamics of a
+charged particle. We derive the driving field which accelerates quantum
+adiabatic dynamics in order to obtain the final adiabatic states except for the
+spatially uniform phase such as the adiabatic phase in any desired short time.
+Fast-forward of adiabatic squeezing and transport in the electro-magnetic field
+is exhibited. Secondly we investigate spin dynamics under the magnetic field,
+showing the fast-forward of adiabatic spin inversion and of adiabatic dynamics
+in Landau-Zener model. The connection of the present framework with
+Kato-Berry's transitionless quantum driving is elucidated in Appendix.",1004.4108v1
+2011-12-12,Theory of laser-induced demagnetization at high temperatures,"Laser-induced demagnetization is theoretically studied by explicitly taking
+into account interactions among electrons, spins and lattice. Assuming that the
+demagnetization processes take place during the thermalization of the
+sub-systems, the temperature dynamics is given by the energy transfer between
+the thermalized interacting baths. These energy transfers are accounted for
+explicitly through electron-magnons and electron-phonons interaction, which
+govern the demagnetization time scale. By properly treating the spin system in
+a self-consistent random phase approximation, we derive magnetization dynamic
+equations for a broad range of temperature. The dependence of demagnetization
+on the temperature and pumping laser intensity is calculated in detail. In
+particular, we show several salient features for understanding magnetization
+dynamics near the Curie temperature. While the critical slowdown in dynamics
+occurs, we find that an external magnetic field can restore the fast dynamics.
+We discuss the implication of the fast dynamics in the application of heat
+assisted magnetic recording.",1112.2428v1
+2014-11-27,The critical dynamics of the models of iron-vanadium magnetic superlattice,"We report the results of a numerical investigation of static and dynamic
+critical behavior of the anisotropic easy-plane Heisenberg model which is used
+as a model for iron-vanadium magnetic superlattices. Models of iron-vanadium
+magnetic superlattice investigated with different values of intralayer and
+interlayer exchange interactions ratio. Numerical experiment technique, based
+on the dynamic finite-size scaling theory. Basic features of the time evolution
+of dynamic parameters for the researched systems are studied. The effect of
+interlayer exchange interaction value on a character of the critical dynamics
+is determined. It is confirmed the possibility of application of the
+Hamiltonian with strong easy-plane anisotropy for investigation both static and
+dynamic critical behavior of complex planar magnetic models.",1411.7509v1
+2018-10-17,Unified theory of magnetization dynamics with relativistic and nonrelativistic spin torques,"Spin torques play a crucial role in operative properties of modern spintronic
+devices. To study current-driven magnetization dynamics, spin-torque terms
+providing the action of spin-polarized currents have previously often been
+added in a phenomenological way to the Landau-Lifshitz-Gilbert equation
+describing the local spin dynamics, yet without derivation from fundamental
+principles. Here, starting from the Dirac-Kohn-Sham theory and incorporating
+nonlocal spin transport we rigorously derive the various spin-torque terms that
+appear in current-driven magnetization dynamics. In particular we obtain an
+extended magnetization dynamics equation that precisely contains the
+nonrelativistic adiabatic and relativistic nonadiabatic spin-transfer torques
+(STTs) of the Berger and Zhang-Li forms as well as relativistic spin-orbit
+torques (SOTs). We derive in addition a previously unnoticed relativistic
+spin-torque term and moreover show that the various obtained spin-torque terms
+do not appear in the same mathematical form in both the Landau-Lifshitz and
+Landau-Lifshitz-Gilbert equations of spin dynamics.",1810.07438v1
+2020-01-24,MagNet: Discovering Multi-agent Interaction Dynamics using Neural Network,"We present the MagNet, a neural network-based multi-agent interaction model
+to discover the governing dynamics and predict evolution of a complex
+multi-agent system from observations. We formulate a multi-agent system as a
+coupled non-linear network with a generic ordinary differential equation (ODE)
+based state evolution, and develop a neural network-based realization of its
+time-discretized model. MagNet is trained to discover the core dynamics of a
+multi-agent system from observations, and tuned on-line to learn agent-specific
+parameters of the dynamics to ensure accurate prediction even when physical or
+relational attributes of agents, or number of agents change. We evaluate MagNet
+on a point-mass system in two-dimensional space, Kuramoto phase synchronization
+dynamics and predator-swarm interaction dynamics demonstrating orders of
+magnitude improvement in prediction accuracy over traditional deep learning
+models.",2001.09001v2
+2021-02-24,udkm1Dsim -- A Python toolbox for simulating 1D ultrafast dynamics in condensed matter,"The udkm1Dsim toolbox is a collection of Python classes and routines to
+simulate the thermal, structural, and magnetic dynamics after laser excitation
+as well as the according X-ray scattering response in one-dimensional sample
+structures. The toolbox provides the capabilities to define arbitrary layered
+structures on the atomic level including a rich database of element-specific
+physical properties. The excitation of dynamics is represented by an
+$N$-temperature-model which is commonly applied in ultrafast physics.
+Structural dynamics due to thermal stresses are calculated by a linear-chain
+model of masses and springs. The implementation of specific magnetic dynamics
+can be easily accomplished by the user employing a generalized magnetization
+interface class. The resulting X-ray diffraction response is computed by
+kinematical or dynamical X-ray theory which can also include
+polarization-dependent magnetic scattering. The udkm1Dsim toolbox is highly
+modular and allows for injecting user-defined inputs at any step within the
+simulation procedure.",2102.12144v2
+2024-03-19,Unraveling the dynamics of magnetization in topological insulator-ferromagnet heterostructures via spin-orbit torque,"Spin-orbit coupling stands as a pivotal determinant in the realm of condensed
+matter physics. In recent, its profound influence on spin dynamics opens up a
+captivating arena with promising applications. Notably, the topological
+insulator-ferromagnet heterostructure has been recognized for inducing spin
+dynamics through applied current, driven by spin-orbit torque. Building upon
+recent observations revealing spin flip signals within this heterostructure,
+our study elucidates the conditions governing spin flips by studying the
+magnetization dynamics. We establish that the interplay between spin-anisotropy
+and spin-orbit torque plays a crucial role in shaping the physics of
+magnetization dynamics within the heterostructure. Furthermore, we categorize
+various modes of magnetization dynamics, constructing a comprehensive phase
+diagram across distinct energy scales, damping constants, and applied
+frequencies. This research not only offers insights into controlling spin
+direction but also charts a new pathway to the practical application of
+spin-orbit coupled systems.",2403.12701v1
+2014-08-22,Collective modes and Kosterlitz-Thouless transition in a magnetic field in the planar Nambu--Jona-Lasino model,"It is known that a constant magnetic field is a strong catalyst of dynamical
+chiral symmetry breaking in 2+1 dimensions, leading to generating dynamical
+fermion mass even at weakest attraction. In this work we investigate the
+collective modes associated with the dynamical chiral symmetry breaking in a
+constant magnetic field in the (2+1)-dimensional Nambu--Jona-Lasinio model with
+continuous U(1) chiral symmetry. We introduce a self-consistent scheme to
+evaluate the propagators of the collective modes at the leading order in 1/N.
+The contributions from the vacuum and from the magnetic field are separated
+such that we can employ the well-established regularization scheme for the case
+of vanishing magnetic field. The same scheme can be applied to the study of the
+next-to-leading order correction in 1/N. We show that the sigma mode is always
+a lightly bound state with its mass being twice the dynamical fermion mass for
+arbitrary strength of the magnetic field. Since the dynamics of the collective
+modes is always 2+1 dimensional, the finite temperature transition should be of
+the Kosterlitz-Thouless (KT) type. We determine the KT transition temperature
+$T_{\rm KT}$ as well as the mass melting temperature $T^*$ as a function of the
+magnetic field. It is found that the pseudogap domain $T_{\rm KT}<T<T^*$ is
+enlarged with increasing strength of the magnetic field. The influence of a
+chiral imbalance or axial chemical potential $\mu_5$ is also studied. We find
+that even a constant axial chemical potential $\mu_5$ can lead to inverse
+magnetic catalysis of the KT transition temperature in 2+1 dimensions. The
+inverse magnetic catalysis behavior is actually the de Haas--van Alphen
+oscillation induced by the interplay between the magnetic field and the Fermi
+surface.",1408.5364v2
+2002-09-06,The Transition State in Magnetization Reversal,"We consider a magnet with uniaxial anisotropy in an external magnetic field
+along the anisotropy direction, but with a field magnitude smaller than the
+coercive field. There are three representative magnetization configurations
+corresponding to three extrema of the free energy. The equilibrium and
+metastable configurations, which are magnetized approximately parallel and
+antiparallel to the applied field, respectively, both correspond to local
+free-energy minima. The third extremum configuration is the saddle point
+separating these minima. It is also called the transition state for
+magnetization reversal. The free-energy difference between the metastable and
+transition-state configurations determines the thermal stability of the magnet.
+However, it is difficult to determine the location of the transition state in
+both experiments and numerical simulations. Here it is shown that the
+computational Projective Dynamics method, applied to the time dependence of the
+total magnetization, can be used to determine the transition state. From
+large-scale micromagnetic simulations of a simple model of magnetic nanowires
+with no crystalline anisotropy, the magnetization associated with the
+transition state is found to be linearly dependent on temperature, and the
+free-energy barrier is found to be dominated by the entropic contribution at
+reasonable temperatures and external fields. The effect of including
+crystalline anisotropy is also discussed. Finally, the influence of the spin
+precession on the transition state is determined by comparison of the
+micromagnetic simulations to kinetic Monte Carlo simulations of precession-free
+(overdamped) dynamics.",0209166v1
+2007-10-21,New mechanism of generation of large-scale magnetic field in a sheared turbulent plasma,"A review of recent studies on a new mechanism of generation of large-scale
+magnetic field in a sheared turbulent plasma is presented. This mechanism is
+associated with the shear-current effect which is related to the W x J-term in
+the mean electromotive force. This effect causes the generation of the
+large-scale magnetic field even in a nonrotating and nonhelical homogeneous
+sheared turbulent convection whereby the alpha effect vanishes. It is found
+that turbulent convection promotes the shear-current dynamo instability, i.e.,
+the heat flux causes positive contribution to the shear-current effect.
+However, there is no dynamo action due to the shear-current effect for small
+hydrodynamic and magnetic Reynolds numbers even in a turbulent convection, if
+the spatial scaling for the turbulent correlation time is k^{-2}, where k is
+the small-scale wave number. We discuss here also the nonlinear mean-field
+dynamo due to the shear-current effect and take into account the transport of
+magnetic helicity as a dynamical nonlinearity. The magnetic helicity flux
+strongly affects the magnetic field dynamics in the nonlinear stage of the
+dynamo action. When the magnetic helicity flux is not small, the saturated
+level of the mean magnetic field is of the order of the equipartition field
+determined by the turbulent kinetic energy. The obtained results are important
+for elucidation of origin of the large-scale magnetic fields in astrophysical
+and cosmic sheared turbulent plasma.",0710.3934v1
+2009-09-28,Magnetic order and dynamics of the charge-ordered antiferromagnet La1.5Sr0.5CoO4,"We describe neutron scattering experiments performed to investigate the
+magnetic order and dynamics of half-doped La1.5Sr0.5CoO4. This layered
+perovskite exhibits a near-ideal checkerboard pattern of Co2+/Co3+ charge order
+at temperatures below ~ 800 K. Magnetic correlations are observed at
+temperatures below ~ 60 K but static magnetic order only becomes established at
+31 K, a temperature at which a kink is observed in the susceptibility. On
+warming above 31 K we observed a change in the magnetic correlations which we
+attribute either to a spin canting or to a change in the proportion of
+inequivalent magnetic domains. The magnetic excitation spectrum is dominated by
+an intense band extending above a gap of approximately 3 meV up to a maximum
+energy of 16 meV. A weaker band exists in the energy range 20-30 meV. We show
+that the excitation spectrum is in excellent quantitative agreement with the
+predictions of a spin-wave theory generalized to include the full magnetic
+degrees of freedom of high-spin Co2+ ions in an axially distorted crystal
+field, coupled by Heisenberg exchange interactions. The magnetic order is found
+to be stabilized by dominant antiferromagnetic Co2+ -- Co2+ interactions acting
+in a straight line through Co3+. No evidence is found for magnetic scattering
+from the Co3+ ions, supporting the view that Co3+ is in the S = 0 state in this
+material.",0909.4964v1
+2010-04-30,Dynamical Monte Carlo investigation of spin reversals and nonequilibrium magnetization of single-molecule magnets,"In this paper, we combine thermal effects with Landau-Zener (LZ) quantum
+tunneling effects in a dynamical Monte Carlo (DMC) framework to produce
+satisfactory magnetization curves of single-molecule magnet (SMM) systems. We
+use the giant spin approximation for SMM spins and consider regular lattices of
+SMMs with magnetic dipolar interactions (MDI). We calculate spin reversal
+probabilities from thermal-activated barrier hurdling, direct LZ tunneling, and
+thermal-assisted LZ tunnelings in the presence of sweeping magnetic fields. We
+do systematical DMC simulations for Mn$_{12}$ systems with various temperatures
+and sweeping rates. Our simulations produce clear step structures in
+low-temperature magnetization curves, and our results show that the thermally
+activated barrier hurdling becomes dominating at high temperature near 3K and
+the thermal-assisted tunnelings play important roles at intermediate
+temperature. These are consistent with corresponding experimental results on
+good Mn$_{12}$ samples (with less disorders) in the presence of little
+misalignments between the easy axis and applied magnetic fields, and therefore
+our magnetization curves are satisfactory. Furthermore, our DMC results show
+that the MDI, with the thermal effects, have important effects on the LZ
+tunneling processes, but both the MDI and the LZ tunneling give place to the
+thermal-activated barrier hurdling effect in determining the magnetization
+curves when the temperature is near 3K. This DMC approach can be applicable to
+other SMM systems, and could be used to study other properties of SMM systems.",1004.5461v2
+2010-05-28,Magnetic helicity fluxes in interface and flux transport dynamos,"Dynamos in the Sun and other bodies tend to produce magnetic fields that
+possess magnetic helicity of opposite sign at large and small scales,
+respectively. The build-up of magnetic helicity at small scales provides an
+important saturation mechanism. In order to understand the nature of the solar
+dynamo we need to understand the details of the saturation mechanism in
+spherical geometry. In particular, we want to understand the effects of
+magnetic helicity fluxes from turbulence and meridional circulation. We
+consider a model with just radial shear confined to a thin layer (tachocline)
+at the bottom of the convection zone. The kinetic alpha owing to helical
+turbulence is assumed to be localized in a region above the convection zone.
+The dynamical quenching formalism is used to describe the build-up of mean
+magnetic helicity in the model, which results in a magnetic alpha effect that
+feeds back on the kinetic alpha effect. In some cases we compare with results
+obtained using a simple algebraic alpha quenching formula. In agreement with
+earlier findings, the magnetic alpha effect in the dynamical alpha quenching
+formalism has the opposite sign compared with the kinetic alpha effect and
+leads to a catastrophic decrease of the saturation field strength with
+increasing magnetic Reynolds numbers. However, at high latitudes this quenching
+effect can lead to secondary dynamo waves that propagate poleward due to the
+opposite sign of alpha. Magnetic helicity fluxes both from turbulent mixing and
+from meridional circulation alleviate catastrophic quenching.",1005.5335v1
+2016-05-11,"Optical orientation of hole magnetic polarons in (Cd,Mn)Te/(Cd,Mn,Mg)Te quantum wells","The optically induced spin polarization in (Cd,Mn)Te/(Cd,Mn,Mg)Te
+diluted-magnetic-semiconductor quantum wells is investigated by means of
+picosecond pump-probe Kerr rotation. At 1.8 K temperature, additionally to the
+oscillatory signals from photoexcited electrons and Manganese spins precessing
+about an external magnetic field, a surprisingly long-lived (up to 60 ns)
+nonoscillating spin polarization is detected. This polarization is related to
+optical orientation of equilibrium magnetic polarons involving resident holes.
+The suggested mechanism for the optical orientation of the equilibrium magnetic
+polarons indicates that the detected polaron dynamics originates from unexcited
+magnetic polarons. The polaron spin dynamics is controlled by the anisotropic
+spin structure of the heavy-hole resulting in a freezing of the polaron
+magnetic moment in one of the two stable states oriented along the structure
+growth axis. Spin relaxation between these states is prohibited by a potential
+barrier, which depends on temperature and magnetic field. The magnetic polaron
+relaxation is accelerated with increasing temperature and in magnetic field.",1605.03362v1
+2017-03-09,Influence of a large-scale field on energy dissipation in magnetohydrodynamic turbulence,"In magnetohydrodynamic (MHD) turbulence, the large-scale magnetic field sets
+a preferred local direction for the small-scale dynamics, altering the
+statistics of turbulence from the isotropic case. This happens even in the
+absence of a total magnetic flux, since MHD turbulence forms randomly oriented
+large-scale domains of strong magnetic field. It is therefore customary to
+study small-scale magnetic plasma turbulence by assuming a strong background
+magnetic field relative to the turbulent fluctuations. This is done, for
+example, in reduced models of plasmas, such as reduced MHD, reduced-dimension
+kinetic models, gyrokinetics, etc., which make theoretical calculations easier
+and numerical computations cheaper. Recently, however, it has become clear that
+the turbulent energy dissipation is concentrated in the regions of strong
+magnetic field variations. A significant fraction of the energy dissipation may
+be localized in very small volumes corresponding to the boundaries between
+strongly magnetized domains. In these regions the reduced models are not
+applicable. This has important implications for studies of particle heating and
+acceleration in magnetic plasma turbulence. The goal of this work is to
+systematically investigate the relationship between local magnetic field
+variations and magnetic energy dissipation, and to understand its implications
+for modeling energy dissipation in realistic turbulent plasmas.",1703.03433v1
+2017-05-31,Lattice and spin dynamics in a low-symmetry antiferromagnet NiWO$_4$,"Lattice and magnetic dynamics of NiWO$_4$ single crystals were studied with
+the use of polarized Raman spectroscopy in a wide temperature range of 10-300 K
+including the antiferromagnetic ordering temperature $T_N$=62 K. Static
+magnetic measurements were used for characterizing the single crystals. All
+Raman-active phonons predicted by the group theory were observed and
+characterized. Magnetic symmetry analysis was used to determine possible
+magnetic space groups for NiWO$_4$ which can be also applied to any other
+isostructural crystal with the same magnetic propagation vector k=(1/2,0,0).
+Though the magnetic structure of NiWO$_4$ is relatively simple, a rich set of
+narrow and broad magnetic excitations with different polarization properties
+and temperature behavior in the very broad frequency range of 10-200 cm$^{-1}$
+was observed, with some modes surviving at temperatures much higher than $T_N$
+up to 220 K. Part of the magnetic excitations was identified as acoustic and
+optical spin-wave branches which allow us to construct exchange structure and
+estimate exchange and anisotropy constants with the use of linear spin-wave
+theory. Since the magnetic structure can be described as exchange-coupled AFM
+chains of $S=1$ ions, previously unobserved magnetic excitation at 24 cm$^{-1}$
+is tentatively assigned to a Haldane gap mode.",1705.11137v1
+2018-05-24,Magnetic suppression of zonal flows on a beta plane,"Zonal flows in rotating systems have been previously shown to be suppressed
+by the imposition of a background magnetic field aligned with the direction of
+rotation. Understanding the physics behind the suppression may be important in
+systems found in astrophysical fluid dynamics, such as stellar interiors.
+However, the mechanism of suppression has not yet been explained. In the
+idealized setting of a magnetized beta plane, we provide a theoretical
+explanation that shows how magnetic fluctuations directly counteract the growth
+of weak zonal flows. Two distinct calculations yield consistent conclusions.
+The first, which is simpler and more physically transparent, extends the
+Kelvin-Orr shearing wave to include magnetic fields and shows that weak,
+long-wavelength shear flow organizes magnetic fluctuations to absorb energy
+from the mean flow. The second calculation, based on the quasilinear,
+statistical CE2 framework, is valid for arbitrary wavelength zonal flow and
+predicts a self-consistent growth rate of the zonal flow. We find that a
+background magnetic field suppresses zonal flow if the bare Alfven frequency is
+comparable to or larger than the bare Rossby frequency. However, suppression
+can occur for even smaller magnetic fields if the resistivity is sufficiently
+small enough to allow sizable magnetic fluctuations. Our calculations reproduce
+the $\eta/B_0^2 = \text{const.}$ scaling that describes the boundary of
+zonation, as found in previous work, and we explicitly link this scaling to the
+amplitude of magnetic fluctuations.",1805.09847v2
+2019-01-05,Investigating the Effect of Magnetic Dipole-Dipole Interaction on Magnetic Particle Spectroscopy (MPS): Implications for Magnetic Nanoparticle-based Bioassays and Magnetic Particle Imaging (MPI),"Superparamagnetic iron oxide nanoparticles (SPIONs), with comparable size to
+biomolecules (such as proteins, nucleic acids, etc.) and unique magnetic
+properties, good biocompatibility, low toxicity, potent catalytic behavior, are
+promising candidates for many biomedical applications. There is one property
+present in most SPION systems, yet it has not been fully exploited, which is
+the dipole-dipole interaction (also called dipolar interaction) between the
+SPIONs. It is known that the magnetic dynamics of an ensemble of SPIONs are
+substantially influenced by the dipolar interactions. However, the exact way it
+affects the performance of magnetic particle-based bioassays and magnetic
+particle imaging (MPI) is still an open question. The purpose of this paper is
+to give a partial answer to this question. This is accomplished by numerical
+simulations on the dipolar interactions between two nearby SPIONs and
+experimental measurements on an ensemble of SPIONs using our lab-based magnetic
+particle spectroscopy (MPS) system. Our results show that even moderate changes
+in the SPION concentration may have substantial effects on the magnetic
+dynamics of the SPION system and the harmonic signal magnitudes can be
+increased or decreased by 60%, depending on the values of MPS system
+parameters.",1901.01355v1
+2020-11-12,Dynamics of test particles around a Bardeen black hole surrounded by perfect fluid dark matter,"We study the dynamics of (i) neutral test particles, (ii) magnetically
+charged test particles, and (iii) test magnetic dipole around a regular Bardeen
+black hole surrounded by perfect fluid dark matter (PFDM). It has been shown
+how the magnetic charge of the black hole and the parameter of the surrounding
+PFDM can influence the innermost stable circular orbit (ISCO) radius of a test
+particle. We have found that the ISCO radius is strongly affected as a
+consequence of the combined effect of the magnetic charge parameter and the
+perfect fluid dark matter. The black hole magnetic charge parameter $g$ and the
+combined effect of perfect fluid dark matter can mimic the black hole rotation
+parameter up to $a/M\approx 0.9$. It has been observed that the ISCO for
+magnetic dipole disappears at the values exceeding the calculated upper value
+for the magnetic interaction parameter $\beta$. The upper limit decreases with
+the increase of both the dark matter and magnetic charge parameters. Finally,
+as an astrophysical application, we have analyzed degeneracy effects of spin of
+Kerr black holes and magnetic charge of regular Bardeen black holes for the
+different values of the dark matter parameter providing exactly the same value
+for ISCO radius of a magnetic dipole with the same value of the parameter
+$\beta=10.2$ of the magnetar called PSR J1745-2900 orbiting around supermassive
+black hole Sagittarius A*.",2011.06148v1
+2021-03-08,Optical Magnetic Multipolar Resonances in Large Dynamic Metamolecules,"Dynamic metamolecules (DMMs) are composed of a dielectric core made of
+hydrogel surrounded by randomly-packed plasmonic beads that can display
+magnetic resonances when excited by light at optical frequencies. Their optical
+properties can be controlled by controlling their core diameter through
+temperature variations. We have recently shown that DMMs display strong optical
+magnetism, including magnetic dipole and magnetic quadrupole resonances,
+offering significant potential for novel applications. Here, we use a T-matrix
+approach to characterize the magnetic multipole resonance modes of model
+metamolecules and explore their presence in experimental data. We show that
+high-order multipole resonances become prominent as the bead size and the
+overall structure sizes are increased, and when the the inter-bead gap is
+decreased. In this limit, mode mixing among high-order magnetic multipole modes
+also become significant, particularly in the directional scattering spectra. We
+discuss trends in magnetic scattering observed in both experiments and
+simulations, and provide suggestions for experimental design and verification
+of high-order optical magnetic resonances in the forward or backward scattering
+spectra. In addition, angular scattering of higher-order magnetic modes can
+display Fano-like interference patterns that should be experimentally
+detectable.",2103.04495v2
+2021-03-20,Dynamics of charged particles and magnetic dipoles around magnetized quasi-Schwarzschild black holes,"In the present paper, we have investigated the motion of charged particles
+together with magnetic dipoles to determine how well the spacetime deviation
+parameter $\epsilon$ and external uniform magnetic field can mimic the spin of
+a rotating Kerr black hole. Investigation of charged particle motion has shown
+that the deviation parameter $\epsilon$ in the absence of external magnetic
+fields can mimic the rotation parameter of Kerr spacetime up to $a/M
+\approx0.5$. The combination of external magnetic field and deviation parameter
+can do even a better job mimicking the rotation parameter up to
+$a/M\simeq0.93$, which corresponds to the rapidly rotating case. Study of the
+dynamics of magnetic dipoles around quasi-Schwarzschild black holes in the
+external magnetic field has shown that there are degeneracy values of ISCO
+radius of test particles at $\epsilon_{cr}>\epsilon\geq 0.35$ which may lead to
+two different values of the innermost stable circular orbit (ISCO) radius. When
+the deviation parameter is in the range of $\epsilon \in (-1,\ 1)$, it can
+mimic the spin of a rotating Kerr black hole in the range $a/M \in (0.0537, \
+0.3952)$ for magnetic dipoles with values of magnetic coupling parameter $\beta
+\in [-0.25,\ 0.25]$ in corotating orbits.",2103.11090v1
+2021-07-26,Pseudo-magnetic field-induced ultra-slow carrier dynamics in periodically strained graphene,"The creation of pseudo-magnetic fields in strained graphene has emerged as a
+promising route to allow observing intriguing physical phenomena that would be
+unattainable with laboratory superconducting magnets. Scanning tunneling
+spectroscopy experiments have successfully measured the pseudo-Landau levels
+and proved the existence of pseudo-magnetic fields in various strained graphene
+systems. These giant pseudo-magnetic fields observed in highly deformed
+graphene can substantially alter the optical properties of graphene beyond a
+level that can be feasible with an external magnetic field, but the
+experimental signatures of the influence of such pseudo-magnetic fields have
+yet to be unveiled. Here, using time-resolved infrared pump-probe spectroscopy,
+we provide unambiguous evidence for ultra-slow carrier dynamics enabled by
+pseudo-magnetic fields in periodically strained graphene. Strong
+pseudo-magnetic fields of ~100 T created by non-uniform strain in graphene
+nanopillars are found to significantly decelerate the relaxation processes of
+hot carriers by more than an order of magnitude. Our finding presents
+unforeseen opportunities for harnessing the new physics of graphene enabled by
+pseudo-magnetic fields for optoelectronics and condensed matter physics.",2107.11973v1
+2021-07-27,Dynamo instabilities in plasmas with inhomogeneous chiral chemical potential,"We study the dynamics of magnetic fields in chiral magnetohydrodynamics,
+which takes into account the effects of an additional electric current related
+to the chiral magnetic effect in high energy plasmas. We perform direct
+numerical simulations, considering weak seed magnetic fields and
+inhomogeneities of the chiral chemical potential mu_5 with a zero mean. We
+demonstrate that a small-scale chiral dynamo can occur in such plasmas if
+fluctuations of mu_5 are correlated on length scales that are much larger than
+the scale on which the dynamo growth rate reaches its maximum. Magnetic
+fluctuations grow by many orders of magnitude due to the small-scale chiral
+dynamo instability. Once the nonlinear backreaction of the generated magnetic
+field on fluctuations of mu_5 sets in, the ratio of these scales decreases and
+the dynamo saturates. When magnetic fluctuations grow sufficiently to drive
+turbulence via the Lorentz force before reaching maximum field strength, an
+additional mean-field dynamo phase is identified. The mean magnetic field grows
+on a scale that is larger than the integral scale of turbulence after the
+amplification of the fluctuating component saturates. The growth rate of the
+mean magnetic field is caused by a magnetic alpha effect that is proportional
+to the current helicity. With the onset of turbulence, the power spectrum of
+mu_5 develops a universal k^(-1) scaling independently of its initial shape,
+while the magnetic energy spectrum approaches a k^(-3) scaling.",2107.13028v3
+2022-03-04,Reservoir Computing with Spin Waves in Skyrmion Crystal,"Magnetic skyrmions are nanometric spin textures characterized by a quantized
+topological invariant in magnets and often emerge in a crystallized form called
+skyrmion crystal in an external magnetic field. We propose that magnets hosting
+a skyrmion crystal possess high potential for application to reservoir
+computing, which is one of the most successful information processing
+techniques inspired by functions of human brains. Our skyrmion-based reservoir
+exploits precession dynamics of magnetizations, i.e., spin waves, propagating
+in the skyrmion crystal. Because of complex interferences and slow relaxations
+of the spin-wave dynamics, the skyrmion spin-wave reservoir attains several
+important characteristics required for reservoir computing, e.g., the
+generalization ability, the nonlinearity, and the short-term memory. We
+investigate these properties by imposing three standard tasks to test the
+performances of reservoir, i.e., the duration-estimation task, the short-term
+memory task, and the parity-check task. Through these investigations, we
+demonstrate that magnetic skyrmion crystals are promising materials for
+spintronics reservoir devices. Because magnetic skyrmions emerge spontaneously
+in magnets via self-organization process under application of a static magnetic
+field, the proposed skyrmion reservoir requires neither advanced
+nanofabrication nor complicated manufacturing for production in contrast to
+other previously proposed magnetic reservoirs constructed with fabricated
+spintronics devices. Our proposal is expected to realize a breakthrough in the
+research of spintronics reservoirs of high performance.",2203.02160v1
+2022-03-15,Some Aspects of Rotation and Magnetic Field Morphology in the Infrared Dark Cloud G34.43+00.24,"The infrared dark clouds (IRDCs) are molecular clouds with relatively greater
+values in their magnetic field strengths. For example, the IRDC G34.43+00.24
+(G34) has magnetic field strength of the order of a few hundred micro-Gauss. In
+this study, we investigate if the dynamic motions of charged particles in an
+IRDC such as G34 can produce this magnetic field strength inside it. The
+observations show that the line-of-sight velocity of G34 has global gradient.
+We assume that the measured global velocity gradient can correspond to the
+cloud rotation. We attribute a large-scale current density to this rotating
+cloud by considering a constant value for the incompleteness of charge
+neutrality and the velocity differences between the positive and negative
+particles with very low ionization fractions. We use the numerical package
+FISHPACK to obtain the magnetic field strength and its morphology on the
+plane-of-sky within G34. The results show that the magnetic field strengths are
+of the order of several hundred micro-Gauss, and its morphology in the
+plane-of-sky is somewhat consistent with the observational results. We also
+obtain the relationship between magnetic field strength and density in G34. The
+results show that with increasing density, the magnetic field strength
+increases approximately as a power-law function. The amount of power is
+approximately equal to 0.45, which is suitable for molecular clouds with strong
+magnetic fields. Therefore, we can conclude that the dynamical motion of IRDCs,
+and especially their rotations, can amplify the magnetic field strengths within
+them.",2203.07689v1
+2022-04-12,Magnetization statics and dynamics in (Ir/Co/Pt)$_6$ multilayers with Dzyaloshinskii-Moriya interaction,"Magnetic multilayers of (Ir/Co/Pt)$_6$ with interfacial Dzyaloshinskii-Moriya
+interaction (IDMI) were deposited by magnetron sputtering with Co thickness
+$d=1.8$ nm. Exploiting magneto-optical Kerr effect in longitudinal mode
+microscopy, magnetic force microscopy, and vibrating sample magnetometry, the
+magnetic field-driven evolution of domain structures and magnetization
+hysteresis loops have been studied. The existence of weak stripe domains
+structure was deduced -- tens micrometers size domains with in-plane ""core""
+magnetization modulated by hundred of nanometers domains with out-of-plane
+magnetization. Micromagnetic simulations interpreted such magnetization
+distribution. Quantitative evaluation of IDMI was carried out using Brillouin
+light scattering (BLS) spectroscopy as the difference between Stokes and
+anti-Stokes peak frequencies $\Delta f$. Due to the additive nature of IDMI,
+the asymmetric combination of Ir and Pt covers led to large values of effective
+IDMI energy density $D_\mathrm{eff}$. It was found that Stokes and anti-Stokes
+frequencies as well as $\Delta f$, measured as a function of in-plane applied
+magnetic field, show hysteresis. These results are explained under the
+consideration of the influence of IDMI on the dynamics of the in-plane
+magnetized ""core"" with weak stripe domains.",2204.05956v1
+2022-12-25,Theory of superdiffusive spin transport in noncollinear magnetic multilayers,"Ultrafast demagnetization induced by femtosecond laser pulses in thin
+metallic layers is caused by the outflow of spin-polarized hot electron
+currents describable by the superdiffusive transport model. These
+laser-generated spin currents can cross the interface into another magnetic
+layer and give rise to magnetization dynamics in magnetic spin valves with
+noncollinear magnetizations. To describe ultrafast transport and spin dynamics
+in such nanostructures we develop here the superdiffusive theory for general
+noncollinear magnetic multilayers. Specifically, we introduce an Al/Ni/Ru/Fe/Ru
+multilayer system with noncollinear Ni and Fe magnetic moments and analyze how
+the ultrafast demagnetization and spin-transfer torque depend on the
+noncollinearity. We employ ab initio calculations to compute the spin- and
+energy-dependent transmissions of hot electrons at the interfaces of the
+multilayer. Taking into account multiple electron scattering at interfaces and
+spin mixing in the spacer layer we find that the laser-induced demagnetization
+of the Ni layer and magnetization change of the Fe layer strongly depend on the
+angle between their magnetizations. Similarly, the spin-transfer torques on the
+Ni and Fe layers and the total spin momentum absorbed in the Ni and Fe layer
+are found to vary markedly with the amount of noncollinearity.
+  These results suggest that changing the amount of noncollinearity in magnetic
+multilayers one can efficiently control the hot electron spin transport, which
+may open a way toward achieving fast, laser-driven spintronic devices.",2212.12961v1
+2001-02-16,Finite-temperature magnetism of transition metals: an LDA+DMFT approach,"We present an ab initio quantum theory of the finite temperature magnetism of
+iron and nickel. A recently developed technique which combines dynamical
+mean-field theory with realistic electronic structure methods, successfully
+describes the many-body features of the one electron spectra and the observed
+magnetic moments below and above the Curie temperature.",0102297v1
+2001-10-30,Nonlinear Hall effect in an AC electric field and related phenomena,"It has been shown that in metals and semiconductors the joint action of
+permanent magnetic and AC electric fields leads to arising of DC surface
+electric current. This is due to essentially non-linear dynamics of electronic
+gas in surface layer.The surface current is linear with respect to external
+magnetic field and depends quadratically on an amplitude of AC electric
+field.The conditions for spontaneous generation of magnetic field have been
+found.",0110616v1
+2002-10-31,Superradiant Operation of Spin Masers,"The theory of spin superradiance, developed earlier for nuclear magnets, is
+generalized to a wider class of spin systems, such as granular magnets and
+molecular magnets. The latter may possess strong single-site magnetocrystalline
+anisotropy, whose role in nonlinear spin dynamics is analysed. Transient as
+well as pulsing superradiant regimes are described. These coherent regimes may
+be employed in the operation of spin masers.",0210698v1
+2003-03-02,Long Range Dynamics Related to Magnetic Impurity in the 2D Heisenberg Antiferromagnet,"We consider a magnetic impurity in the two-dimensional Heisenberg
+antifferomagnet with long range antiferromagnetic order. At low temperature the
+impurity magnetic susceptibility has a Curie term ($\propto 1/T$) and a
+logarithmic correction ($\propto \ln(T)$). We calculate the correction and
+derive related Ward identity for the impurity-spin-wave vertex.",0303016v1
+2003-12-10,Spin Gain Transistor in Ferromagnetic Semiconductors: the Semiconductor Bloch Equations Approach,"Scheme and principle of operation of a spin gain transistor are proposed: a
+large unmagnetized current creates density sufficient for the ferromagnetic
+transition; a small magnetized current initiates spontaneous magnetization;
+large magnetized current is extracted. Therefore spin gain of more than 1000 is
+predicted. Collective dynamics of spins under Coulomb exchange interaction is
+described via Semiconductor Bloch Equations.",0312243v1
+2003-12-22,Spin dynamics of the ferromagnetic superconductor UGe$_{2}$,"Inelastic neutron scattering was used to study the low energy magnetic
+excitations of the ferromagnetic superconductor UGe$_{2}$. The ferromagnetic
+fluctuations are of Ising nature with a non-conserved magnetization and have an
+intermediate behavior between localized and itinerant magnetism.",0312584v1
+2007-03-24,Critical exponents of small one-dimensional ising magnetic,"Within the framework of a generalized Ising model, a one-dimensional magnetic
+of a finite length with free ends is considered. The correlation length
+exponent, dynamic critical exponent z of the magnet is calculated taking into
+account the next nearest neighbor interactions and the external field.",0703639v1
+2006-02-07,Magnetic Geodesic Flows on Coadjoint Orbits,"We describe a class of completely integrable $G$-invariant magnetic geodesic
+flows on (co)adjoint orbits of a compact connected Lie group $G$ with magnetic
+field given by the Kirillov-Konstant 2-form.",0602016v2
+2006-03-10,Dynamo in Helical MHD Turbulence: Quantum Field Theory Approach,"A quantum field model of helical MHD stochastically forced by gaussian
+hydrodynamic, magnetic and mixed noices is investigated. These helical noises
+lead to an exponential increase of magnetic fluctuations in the large scale
+range. Instabilities, which are produced in this process, are eliminated by
+spontaneous symmetry breaking mechanism accompanied by creation of the
+homogeneous stationary magnetic field.",0603020v1
+2002-08-08,Bayesian analysis of magnetic island dynamics,"We examine a first order differential equation with respect to time coming up
+in the description of magnetic islands in magnetically confined plasmas. The
+free parameters of this equation are obtained by employing Bayesian probability
+theory. Additionally a typical Bayesian change point is solved in the process
+of obtaining the data.",0208036v1
+2002-09-12,Dipolar relaxation of cold sodium atoms in a magnetic field,"A quantum mechanical close coupling theory of spin relaxation in the
+stretched hyperfine level of sodium is presented. We calculate the dipolar
+relaxation rate of magnetically trapped cold sodium atoms in the magnetic
+field. The influence of shape resonances and the anisotropy of the dipolar
+interaction on the collision dynamics are explored. We examine the sensitivity
+of the calculated cross sections on the choice of asymptotic atomic state
+basis.",0209052v2
+2007-04-23,Fluctuation theorems and orbital magnetism in nonequilibrium state,"We study Langevin dynamics of a driven charged particle in the presence as
+well as in the absence of magnetic field. We discuss the validity of various
+work fluctuation theorems using different model potentials and external drives.
+We also show that one can generate an orbital magnetic moment in a
+nonequilibrium state which is absent in equilibrium.",0704.2992v1
+2007-05-04,Numerical study of liquid metal flow in a rectangular duct under the influence of a heterogenous magnetic field,"The paper presents 3D numerical results for the laminar liquid metal flow in
+a rectangular duct compared with experimental results. It is shown that the
+magnetic interaction parameter $N$ is the main parameter governing the flow
+provided turbulent pulsations are locally suppressed by magnetic field.",0705.0633v1
+2007-05-15,Controlled vortex core switching in a magnetic nanodisk by a rotating field,"The switching process of the vortex core in a Permalloy nanodisk affected by
+a rotating magnetic field is studied theoretically. A detailed description of
+magnetization dynamics is obtained by micromagnetic simulations.",0705.2046v2
+2008-02-08,The algorithm for simulating of phase transition in Ising magnetic,"Simple algorithm of dynamics of Ising magnetic is described. The algorithm
+can be implemented on conventional digital computer and can be used for
+construction of specialized processor for simulation of ferromagnetic systems.
+The algorithm gives a simple way to calculate 1D correlation functions for 1D
+Ising magnetic.",0802.1133v2
+2008-07-03,Supersymmetry of the magnetic vortex,"The N=2 supersymmetry of the Pauli Hamiltonian in any static magnetic field
+in the plane combines, for the magnetic vortex, with Jackiw's bosonic
+$o(2)\times o(2,1)$ symmetry, into an $o(2)\times osp(1/2)$ dynamical
+supersymmetry.",0807.0569v1
+2008-08-25,Magnetization of a half-quantum vortex in a spinor Bose-Einstein condensate,"Magnetization dynamics of a half-quantum vortex in a spin-1 Bose-Einstein
+condensate with a ferromagnetic interaction are investigated by mean-field and
+Bogoliubov analyses. The transverse magnetization is shown to break the
+axisymmetry and form threefold domains. This phenomenon originates from the
+topological structure of the half-quantum vortex and spin conservation.",0808.3315v1
+2008-10-21,"Coherent manipulation of magnetization precession in ferromagnetic semiconductor (Ga,Mn)As with successive optical pumping","We report dynamic control of magnetization precession by light alone. A
+ferromagnetic (Ga,Mn)As epilayer was used for experiments. Amplitude of
+precession was modulated to a large extent by tuning the time interval between
+two successive optical pump pulses which induced torques on magnetization
+through a non-thermal process. Nonlinear effect in precession motion was also
+discussed.",0810.3728v1
+2009-04-14,Poisson-Vlasov in a strong magnetic field: A stochastic solution approach,"Stochastic solutions are obtained for the Maxwell-Vlasov equation in the
+approximation where magnetic field fluctuations are neglected and the
+electrostatic potential is used to compute the electric field. This is a
+reasonable approximation for plasmas in a strong external magnetic field. Both
+Fourier and configuration space solutions are constructed.",0904.2214v2
+2012-05-09,Asymmetric chiral alignment in magnetized plasma turbulence,"Multi species turbulence in inhomogeneous magnetised plasmas is found to
+exhibit symmetry breaking in the dynamical alignment of a third species with
+the fluctuating electron density and vorticity with respect to the magnetic
+field direction and the species' relative background gradients. The possibility
+of truly chiral aggregation of charged molecules in magnetized space plasma
+turbulence is discussed.",1205.1891v3
+2012-11-16,Measurement of a time-periodic magnetic field by rotating coil,"A novel technique of the measurement data processing is developed which
+allows to apply the rotating coil method for measurement of a dynamic magnetic
+field, periodic in time. The developed technique allows to obtain
+time-dependent multipoles in a single measurement which takes place during one
+power cycle of the magnet or the coil rotation period, whichever is longer.",1211.3974v1
+2016-07-04,Analogue Magnetism: An Ansatz,"We present an ansatz for the relationship between magnetic flux density and
+fluid vorticity evolution equations. We also suggest that the magnetic flux
+density evolution equations be compared to the evolution equation for an
+effective vorticity ($\omega_{eff}$), which bears a power law relation to the
+ordinary vorticity.",1607.00980v2
+2016-12-03,Euler potentials and Magnetic fields,"It is known that the cross product of gradients of two scalars, the Euler
+potentials (EP), may represent magnetic fields lines. We examine the utility of
+such potential in the broader magneto-genesis and dynamo theories, and find
+that a reinterpretation of the potentials offer a new understanding of the role
+EP may play in the evolution of magnetic fields.",1612.00956v2
+2018-05-25,Carleman estimate for the Schrödinger equation and application to magnetic inverse problems,"We prove that the stationary magnetic potential vector and the electrostatic
+potential entering the dynamic magnetic Schr\""odinger equation can be Lipschitz
+stably retrieved through finitely many local boundary measurements of the
+solution. The proof is by means of a specific global Carleman estimate for the
+Schr\""odinger equation, established in the first part of the paper.",1805.10076v1
+2018-07-05,Mechanisms for magnetic Field generation in precessing cubes,"It is shown that flows in precessing cubes develop at certain parameters
+large axisymmetric components in the velocity field which are large enough to
+either generate magnetic fields by themselves, or to contribute to the dynamo
+effect if inertial modes are already excited and acting as a dynamo. This
+effect disappears at small Ekman numbers. The critical magnetic Reynolds number
+also increases at low Ekman numbers because of turbulence and small scale
+structures.",1807.02047v1
+2023-01-24,Spin Dynamics in van der Waals Magnetic Systems,"The discovery of atomic monolayer magnetic materials has stimulated intense
+research activities in the two-dimensional (2D) van der Waals (vdW) materials
+community. The field is growing rapidly and there has been a large class of 2D
+vdW magnetic compounds with unique properties, which provides an ideal platform
+to study magnetism in the atomically thin limit. In parallel, based on
+tunneling magnetoresistance and magneto-optical effect in 2D vdW magnets and
+their heterostructures, emerging concepts of spintronic and optoelectronic
+applications such as spin tunnel field-effect transistors and spin-filtering
+devices are explored. While the magnetic ground state has been extensively
+investigated, reliable characterization and control of spin dynamics play a
+crucial role in designing ultrafast spintronic devices. Ferromagnetic resonance
+(FMR) allows direct measurements of magnetic excitations, which provides
+insight into the key parameters of magnetic properties such as exchange
+interaction, magnetic anisotropy, gyromagnetic ratio, spin-orbit coupling,
+damping rate, and domain structure. In this review article, we present an
+overview of the essential progress in probing spin dynamics of 2D vdW magnets
+using FMR techniques. Given the dynamic nature of this field, we focus mainly
+on broadband FMR, optical FMR, and spin-torque FMR, and their applications in
+studying prototypical 2D vdW magnets. We conclude with the recent advances in
+laboratory- and synchrotron-based FMR techniques and their opportunities to
+broaden the horizon of research pathways into atomically thin magnets.",2301.09822v2
+2006-02-07,Do magnetic fields contribute to the dynamical stability of the secondaries of CVs against mass transfer?,"We show the presence of CVs with orbital periods in the range 3.5-7 h and
+mass ratios q=M2/M1 above the critical values for dynamically stable mass
+transfer. We explore whether the magnetic fields produced in the secondaries
+alter the theoretical mass ratio limits allowing dynamical stability. Since
+magnetic fields change the specific heats and the polytropic exponent gamma of
+the gas in the convective envelope, the mass-radius adiabatic exponent xi_ad
+also changes. We find that turbulent magnetic fields can produce 10% less
+restrictive critical q-profiles while large-scale toroidal and poloidal fields
+have smaller effects. Thus, magnetic fields alone do not account for the
+stability of all the anomalous CVs. However, we found that the small variations
+of xi_ad induced by solar-type magnetic cycles explain the amplitudes of the
+cyclic accretion luminosity variations shown by several CVs.",0602157v3
+1998-12-01,Simulation of Magnetization Switching in Biaxial Single-Domain Ferromagnetic Particles,"The magnetization switching dynamics of biaxial single-domain homogeneous
+ferromagnetic particles, in which the two easy axes are perpendicular to each
+other, is simulated using a 4-state clock model. A zero-field mapping of the
+statics between the symmetric 4-state clock model and two decoupled Ising
+models is extended to non-zero field statics and to the dynamics. This
+significantly simplifies the analysis of the simulation results. We measure the
+magnetization switching time of the model and analyze the results using droplet
+theory. The switching dynamics in the asymmetric model is more complicated. If
+the easy axis is perpendicular to the stable magnetization direction, the
+system can switch its magnetization via two different channels, one very fast
+and the other very slow. A maximum value for the switching field as a function
+of system size is obtained. The asymmetry affects the switching fields
+differently, depending on whether the switching involves one single droplet or
+many droplets of spins in the stable magnetization configuration. The angular
+dependence of the switching field in symmetric and asymmetric models is also
+studied.",9812010v1
+2001-07-02,Thermodynamics and Spin Tunneling Dynamics in Ferric Wheels with Excess Spin,"We study theoretically the thermodynamic properties and spin dynamics of a
+class of magnetic rings closely related to ferric wheels, antiferromagnetic
+ring systems, in which one of the Fe (III) ions has been replaced by a dopant
+ion to create an excess spin. Using a coherent-state spin path integral
+formalism, we derive an effective action for the system in the presence of a
+magnetic field. We calculate the functional dependence of the magnetization and
+tunnel splitting on the magnetic field and show that the parameters of the spin
+Hamiltonian can be inferred from the magnetization curve. We study the spin
+dynamics in these systems and show that quantum tunneling of the Neel vector
+also results in tunneling of the total magnetization. Hence, the spin
+correlation function shows a signature of Neel vector tunneling, and electron
+spin resonance (ESR) techniques or AC susceptibility measurements can be used
+to measure both the tunneling and the decoherence rate. We compare our results
+with exact diagonalization studies on small ring systems. Our results can be
+easily generalized to a wide class of nanomagnets, such as ferritin.",0107025v1
+2001-10-09,"Ruthenocuprates RuSr2(Eu,Ce)2Cu2O10: Intrinsic magnetic multilayers","We report ac susceptibility data on RuSr_2(Eu,Ce)_2Cu_2O_(10-y) (Ru-1222, Ce
+content x=0.5 and 1.0), RuSr_2GdCu_2O_8 (Ru-1212) and SrRuO_3. Both Ru-1222
+(x=0.5, 1.0) sample types exhibit unexpected magnetic dynamics in low magnetic
+fields: logarithmic time relaxation, switching behavior, and `inverted'
+hysteresis loops. Neither Ru-1212 nor SrRuO_3 exhibit such magnetic dynamics.
+The results are interpreted as evidence of the complex magnetic order in
+Ru-1222. We propose a specific multilayer model to explain the data, and note
+that superconductivity in the ruthenocuprate is compatible with both the
+presence and absence of the magnetic dynamics.",0110181v1
+2003-12-18,Current induced magnetization dynamics in current perpendicular to the plane spin valves,"We observe magnetization dynamics induced by spin momentum transfer in the
+noise spectra of current perpendicular to the plane giant magnetoresistance
+spin valves. The dynamics are observable only for those combinations of current
+direction and magnetic configuration in which spin transfer acts to reorient
+the free layer magnetization away from the direction set by the net magnetic
+field. Detailed measurements as a function of magnetic configuration reveal an
+evolution of the noise spectra, going from a spectrum with a well-defined noise
+peak when the free layer is roughly collinear with the pinned layer to a
+spectrum dominated by 1/f noise when the free layer is in an orthogonal
+configuration. Finally, the amplitude of the corresponding resistance noise
+increases rapidly with increasing current until it saturates at a value that is
+a substantial fraction of the magnetoresistance between parallel and
+antiparallel states.",0312504v2
+2004-08-18,Spin-Fermion Model of Magnetism: Quasi-particle Many-Body Dynamics,"Theoretical foundations and applications of the generalized spin-fermion
+(sp-d) exchange lattice model to various magnetic systems, e.g. rare-earth
+metals and compounds and magnetic semiconductors are discussed. The
+capabilities of the model to describe spin quasi-particle spectra are
+investigated. The main emphasis is made on the dynamical behavior of two
+interacting subsystems, the localized spins and spin density of itinerant
+carriers. A nonperturbative many-body approach, the Irreducible Green Functions
+(IGF) method, is used to describe the quasi-particle dynamics.
+  Scattering states are investigated and three branches of magnetic excitations
+are calculated in the regime characteristic of a magnetic semiconductor. For a
+simplified version of the model (Kondo lattice model) we study the spectra of
+quasi-particle excitations with special attention given to diluted magnetic
+semiconductors in simple approximation, to demonstrate the possibilities of the
+IGF approach. For this, to include the effects of disorder, a modified mean
+fields are determined self-consistently. The approach permits to investigate
+and clarify the role of various interactions and disorder effects in unified
+and coherent fashion.",0408406v1
+2006-11-01,Self-assembly and dynamics of magnetic holes,"Nonmagnetic particles in magnetized ferrofluids have been denoted magnetic
+holes and are in many ways ideal model systems to test various forms of
+particle self assembly and dynamics. Some case studies to be reviewed here
+include:
+  Chaining of magnetic holes
+  Braid theory and Zipf relation used in dynamics of magnetic microparticles
+  Interactions of magnetic holes in ferrofluid layers
+  The objectives of these works have been to find simple characterizations of
+complex behavior of particles with dipolar interactions.",0611008v1
+2007-02-01,High-energy magnetic excitations from dynamic stripes in LBCO (x=1/8),"We use inelastic neutron scattering to study the temperature dependence of
+magnetic excitations (for energies up to 100 meV) in the cuprate
+La$_{1.875}$Ba$_{0.125}$CuO$_4$. This compound exhibits stripe order below a
+temperature of ~50 K; previous measurements have shown that the magnetic
+excitations of the stripe-ordered phase have an hour-glass-like dispersion,
+with a saddle point at ~50 meV. Here we compare measurements in the disordered
+phase taken at 65 and 300 K. At energies on the scale of $k_{\rm B}T$, there is
+substantial momentum-broadening of the signal, and the low-energy
+incommensurate features can no longer be resolved at 300 K. In contrast, there
+is remarkably little change in the scattered signal for energies greater than
+$k_{\rm B}T$. In fact, the momentum-integrated dynamic susceptibility is almost
+constant with temperature. We suggest that the continuity of higher-energy
+magnetic excitations is strong evidence for dynamic stripes in the
+high-temperature, disordered phase. We reconsider the nature of the magnetic
+dispersion, and we discuss the correspondences between the thermal evolution of
+magnetic stripe correlations with other electronic properties of the cuprates.",0702027v1
+2007-08-10,Dynamic Origin of Vortex Core Switching in Soft Magnetic Nanodots,"The magnetic vortex with the in-plane curling magnetization and the
+out-of-plane magnetization at the core is a unique ground state in nanoscale
+magnetic elements. This kind of magnetic vortex can be used as a memory unit
+for information storage, through its downward or upward core-orientation and,
+thus, controllable core switching deserves some special attention. Our
+analytical and micromagnetic calculations reveal that the origin of the vortex
+core reversal is a gyrotropic field. This field is induced by vortex dynamic
+motion and is proportional to the velocity of the moving vortex. Our
+calculations elucidate the physical origin of the vortex core dynamic reversal
+and offer a key to effective manipulation of the vortex-core orientation.",0708.1359v1
+2007-10-26,Electron Transport Driven by Nonequilibrium Magnetic Textures,"Spin-polarized electron transport driven by inhomogeneous magnetic dynamics
+is discussed in the limit of a large exchange coupling. Electron spins rigidly
+following the time-dependent magnetic profile experience spin-dependent
+fictitious electric and magnetic fields. We show that the electric field
+acquires important corrections due to spin dephasing, when one relaxes the
+spin-projection approximation. Furthermore, spin-flip scattering between the
+spin bands needs to be taken into account in order to calculate voltages and
+spin accumulations induced by the magnetic dynamics. A phenomenological
+approach based on the Onsager reciprocity principle is developed, which allows
+us to capture the effect of spin dephasing and make a connection to the well
+studied problem of current-driven magnetic dynamics. A number of results that
+recently appeared in the literature are related and generalized.",0710.5193v2
+2008-05-21,Non-equilibrium thermodynamic study of magnetization dynamics in the presence of spin-transfer torque,"The dynamics of magnetization in the presence of spin-transfer torque was
+studied. We derived the equation for the motion of magnetization in the
+presence of a spin current by using the local equilibrium assumption in
+non-equilibrium thermodynamics. We show that, in the resultant equation, the
+ratio of the Gilbert damping constant, $\alpha$, and the coefficient, $\beta$,
+of the current-induced torque, called non-adiabatic torque, depends on the
+relaxation time of the fluctuating field $\tau_{c}$. The equality
+$\alpha=\beta$ holds when $\tau_c$ is very short compared to the time scale of
+magnetization dynamics. We apply our theory to current-induced magnetization
+reversal in magnetic multilayers and show that the switching time is a
+decreasing function of $\tau_{c}$.",0805.3306v1
+2008-08-19,Magnetization and spin dynamics of a Cr-based magnetic cluster: Cr$_{7}$Ni,"We study the magnetization and the spin dynamics of the Cr$_7$Ni ring-shaped
+magnetic cluster. Measurements of the magnetization at high pulsed fields and
+low temperature are compared to calculations and show that the spin Hamiltonian
+approach provides a good description of Cr$_7$Ni magnetic molecule. In
+addition, the phonon-induced relaxation dynamics of molecular observables has
+been investigated. By assuming the spin-phonon coupling to take place through
+the modulation of the local crystal fields, it is possible to evaluate the
+decay of fluctuations of two generic molecular observables. The nuclear
+spin-lattice relaxation rate $1/T_1$ directly probes such fluctuations, and
+allows to determine the magnetoelastic coupling strength.",0808.2621v1
+2010-02-05,Direct observation of Oersted-field-induced magnetization dynamics in magnetic nanostripes,"We have used time-resolved x-ray photoemission electron microscopy to
+investigate the magnetization dynamics induced by nanosecond current pulses in
+NiFe/Cu/Co nanostripes. A large tilt of the NiFe magnetization in the direction
+transverse to the stripe is observed during the pulses. We show that this
+effect cannot be quantitatively understood from the amplitude of the Oersted
+field and the shape anisotropy. High frequency oscillations observed at the
+onset of the pulses are attributed to precessional motion of the NiFe
+magnetization about the effective field. We discuss the possible origins of the
+large magnetization tilt and the potential implications of the static and
+dynamic effects of the Oersted field on current-induced domain wall motion in
+such stripes.",1002.1302v3
+2011-11-22,Magnetic Dynamics and Spin Freezing in the Ferromagnetic Phase of Ba-Doped Perovskite Cobaltites,"The magnetic properties of polycrystaline La0.5Ba0.5CoO2.5+d (d = 0.44 and
+0.485) where investigated using muon spin relaxation and bulk magnetization
+experiments. Below a Curie temperature of T_C = 160 K and 180 K, respectively,
+a magnetic phase with a macroscopic ferromagnetic moment forms. muSR proves
+that the full volume inhomogeneously orders at T_C but that there is
+microscopically a phase separation into phase volumes possessing a fully static
+and a slow magnetic dynamic behavior. A peak in the dynamic relaxation rate 35
+K respectively 55 K below the Curie temperature indicates the freezing of spin
+components. The spin fluctuations are thermally activated with a typical
+Jahn-Teller like phonon energy of E_a = 340 K. Together with co-operative
+Jahn-Teller distortions appearing below the spin freezing temperature, this
+points to a strong magneto elastic coupling as the cause for the magnetic
+fluctuations and the spin freezing.",1111.5232v1
+2011-12-01,Relativistic magnetohydrodynamics in one dimension,"We derive a number of solution for one-dimensional dynamics of relativistic
+magnetized plasma that can be used as benchmark estimates in relativistic
+hydrodynamic and magnetohydrodynamic numerical codes.
+  First, we analyze the properties of simple waves of fast modes propagating
+orthogonally to the magnetic field in relativistically hot plasma. The magnetic
+and kinetic pressures obey different equations of state, so that the system
+behaves as a mixture of gases with different polytropic indices. We find the
+self-similar solutions for the expansion of hot strongly magnetized plasma into
+vacuum.
+  Second, we derive linear hodograph and Darboux equations for the relativistic
+Khalatnikov potential, which describe arbitrary one-dimensional isentropic
+relativistic motion of cold magnetized plasma and find their general and
+particular solutions. The obtained hodograph and Darboux equations are very
+powerful: system of highly non-linear, relativistic, time dependent equations
+describing arbitrary (not necessarily self-similar) dynamics of highly
+magnetized plasma reduces to a single linear differential equation.",1112.0249v1
+2012-01-31,Nonreciprocal Directional Dichroism and Toroidalmagnons in Helical Magnets,"We investigate a dynamical magnetoelectric effect due to a magnetic resonance
+in helical spin structures through the coupling between magnetization and
+electric polarization via a spin current mechanism. We show that the magnon has
+both the dynamical magnetic moment $\Delta M^\omega$ and the electric moment
+$\Delta P^\omega$ ($\perp \Delta M^\omega$), i.e., a dynamical toroidal moment,
+under external magnetic fields, and thus it is named the {\em toroidalmagnon}.
+The toroidalmagnon exists in most conical spin structures owing to the
+generality of the spin current mechanism. In the absorption of electromagnetic
+waves, the toroidalmagnon excitation process generally induces a nonreciprocal
+directional dichroism as a consequence of an interference of the magnetic and
+electric responses.",1201.6458v1
+2012-03-19,Bistability between equatorial and axial dipoles during magnetic field reversals,"Numerical simulations of the geodynamo in presence of an heterogeneous
+heating are presented. We study the dynamics and the structure of the magnetic
+field when the equatorial symmetry of the flow is broken. If the symmetry
+breaking is sufficiently strong, the m = 0 axial dipolar field is replaced by
+an hemispherical magnetic field, dominated by an oscillating m = 1 magnetic
+field. Moreover, for moderate symmetry breaking, a bistability between the
+axial and the equatorial dipole is observed. In this bistable regime, the axial
+magnetic field exhibits chaotic switches of its polarity, involving the
+equatorial dipole during the transition period. This new scenario for magnetic
+field reversals is discussed within the framework of the Earth's dynamo.",1203.4144v1
+2012-05-31,Time-Resolved Magnetic Relaxation of a Nanomagnet on Subnanosecond Time Scales,"We present a two-current-pulse temporal correlation experiment to study the
+intrinsic subnanosecond nonequilibrium magnetic dynamics of a nanomagnet during
+and following a pulse excitation. This method is applied to a model
+spin-transfer system, a spin valve nanopillar with perpendicular magnetic
+anisotropy. Two-pulses separated by a short delay (< 500 ps) are shown to lead
+to the same switching probability as a single pulse with a duration that
+depends on the delay. This demonstrates a remarkable symmetry between magnetic
+excitation and relaxation and provides a direct measurement of the magnetic
+relaxation time. The results are consistent with a simple finite temperature
+Fokker-Planck macrospin model of the dynamics, suggesting more coherent
+magnetization dynamics in this short time nonequilibrium limit than near
+equilibrium.",1205.7034v1
+2013-03-28,Spin Torque on Magnetic Textures Coupled to the Surface of a Three-Dimensional Topological Insulator,"We investigate theoretically the spin torque and magnetization dynamic in a
+thin ferromagnetic (FM) layer with spatially varying magnetization. The FM
+layer is deposited on the surface of a topological insulator (TI). In the limit
+of the adiabatic relaxation of electron spin along the magnetization, the
+interaction between the exchange interaction and the Rashba-like surface
+texture of a TI yields a topological gauge field. Under the gauge field and an
+applied current, spin torque is induced according to the direction of the
+current. We derived the corresponding effective anisotropy field and hence the
+modified Landau-Lifshitz-Gilbert equation, which describes the spin torque and
+the magnetization dynamic. In addition, we study the effective field for
+exemplary magnetic textures, such as domain wall, skyrmion, and vortex
+configurations. The estimated strength of the effective field is comparable to
+the switching fields of typical FM materials, and hence can significantly
+influence the dynamics of the FM layer.",1303.7031v1
+2013-10-24,Towards wafer scale inductive determination of magnetostatic and dynamic parameters of magnetic thin films and multilayers,"We investigate an inductive probe head suitable for non-invasive
+characterization of the magnetostatic and dynamic parameters of magnetic thin
+films and multilayers on the wafer scale. The probe is based on a planar
+waveguide with rearward high frequency connectors that can be brought in close
+contact to the wafer surface. Inductive characterization of the magnetic
+material is carried out by vector network analyzer ferromagnetic resonance.
+Analysis of the field dispersion of the resonance allows the determination of
+key material parameters such as the saturation magnetization MS or the
+effective damping parameter Meff. Three waveguide designs are tested. The
+broadband frequency response is characterized and the suitability for inductive
+determination of MS and Meff is compared. Integration of such probes in a wafer
+prober could in the future allow wafer scale in-line testing of magnetostatic
+and dynamic key material parameters of magnetic thin films and multilayers.",1310.6578v1
+2013-12-20,SU(2s+1) symmetry and nonlinear dynamic equations of spin s magnets,"The article is devoted to the description of dynamics of magnets with
+arbitrary spin on the basis of the Hamiltonian formalism. The relationship
+between the magnetic ordering and Poisson bracket subalgebras of the magnetic
+degrees of freedom for spin s=1/2; 1; 3/2 has been established. We have been
+obtained non-linear dynamic equations without damping for normal and degenerate
+non-equilibrium states of high-spin magnets with the properties of the SO(3),
+SU(4), SU(2)$\times$SU(2), SU(3), SO(4), SO(5) symmetry of exchange
+interaction. The connection between models of the magnetic exchange energy and
+the Casimir invariants has been discussed.",1312.5828v2
+2013-12-22,Dynamical Skyrmion State in a Spin Current Nano-Oscillator with Perpendicular Magnetic Anisotropy,"We study the spectral characteristics of spin current nano-oscillators based
+on the Pt/[Co/Ni] magnetic multilayer with perpendicular magnetic anisotropy.
+By varying the applied magnetic field and current, both localized and
+propagating spin wave modes of the oscillation are achieved. At small fields,
+we observe an abrupt onset of the modulation sidebands. We use micromagnetic
+simulations to identify this state as a dynamical magnetic skyrmion stabilized
+in the active device region by spin current injection, whose current-induced
+dynamics is accompanied by the gyrotropic motion of the core due to the skew
+deflection. Our results demonstrate a practical route for controllable skyrmion
+manipulation by spin current in magnetic thin films.",1312.6343v2
+2014-01-21,Dynamics of clumps embedded in a hot accretion flow with toroidal magnetic field,"Dynamics of clumps within a magnetized advection dominated accretion flow is
+investigated by solving the collisionless Boltzmann equation and considering
+the drag force due to the relative velocity between the clumps and the gas.
+Toroidal component of the magnetic field is assumed to be dominant. Dynamical
+properties of the hot gaseous component such as the radial and the rotational
+velocities are affected by the magnetic effects, and so, drag force varies
+depending on the strength of magnetic field and the velocity dispersion of the
+clumps is then modified significantly. We show that when magnetic pressure is
+less than the gas pressure, the root of the averaged radial velocity square of
+the clumps decreases at the inner parts of the hot flow and increases slightly
+at its outer edge.",1401.5190v1
+2014-05-09,Current-induced magnetization dynamics in two magnetic insulators separated by a normal metal,"We study the dynamics of spin valves consisting of two layers of magnetic
+insulators separated by a normal metal in the macrospin model. A current
+through the spacer generates a spin Hall current that can actuate the
+magnetization via the spin-transfer torque. We derive expressions for the
+effective Gilbert damping and the critical currents for the onset of
+magnetization dynamics including the effects of spin pumping that can be tested
+by ferromagnetic resonance experiments. The current generates an amplitude
+asymmetry between the in-phase and out-of-phase modes. We briefly discuss
+superlattices of metals and magnetic insulators.",1405.2267v1
+2014-06-18,Quantum magnetism with ultracold molecules,"This article gives an introduction to the realization of effective quantum
+magnetism with ultracold molecules in an optical lattice, reviews experimental
+and theoretical progress, and highlights future opportunities opened up by
+ongoing experiments. Ultracold molecules offer capabilities that are otherwise
+difficult or impossible to achieve in other effective spin systems, such as
+long-ranged spin-spin interactions with controllable degrees of spatial and
+spin anisotropy and favorable energy scales. Realizing quantum magnetism with
+ultracold molecules provides access to rich many-body behaviors, including many
+exotic phases of matter and interesting excitations and dynamics.
+Far-from-equilibrium dynamics plays a key role in our exposition, just as it
+did in recent ultracold molecule experiments realizing effective quantum
+magnetism. In particular, we show that dynamical probes allow the observation
+of correlated many-body spin physics, even in polar molecule gases that are not
+quantum degenerate. After describing how quantum magnetism arises in ultracold
+molecules and discussing recent observations of quantum magnetism with polar
+molecules, we survey prospects for the future, ranging from immediate goals to
+long-term visions.",1406.4758v1
+2014-07-28,Eddy current effects in the magnetization dynamics of ferromagnetic metal nanoparticles,"We develop an analytical model for describing the magnetization dynamics in
+ferromagnetic metal nanoparticles, which is based on the coupled system of the
+Landau-Lifshitz-Gilbert (LLG) and Maxwell equations. By solving Maxwell's
+equations in the quasi-static approximation and finding the magnetic field of
+eddy currents, we derive the closed LLG equation for the magnetization that
+fully accounts for the effects of conductivity. We analyze the difference
+between the LLG equations in metallic and dielectric nanoparticles and show
+that these effects can strongly influence the magnetization dynamics. As an
+example illustrating the importance of eddy currents, the phenomenon of
+precessional switching of magnetization is considered.",1407.7466v1
+2014-12-08,Magnetization Dynamics driven by Non-equilibrium Spin-Orbit Coupled Electron Gas,"The dynamics of magnetization coupled to an electron gas via s-d exchange
+interaction is investigated by using density matrix technique. Our theory shows
+that non-equilibrium spin accumulation induces a spin torque and the electron
+bath leads to a damping of the magnetization. For the two-dimensional
+magnetization thin film coupled to the electron gas with Rashba spin-orbit
+coupling, the result for the spin-orbit torques is consistent with the previous
+semi-classical theory. Our theory predicts a damping of the magnetization,
+which is absent in the semi-classical theory. The magnitude of the damping due
+to the electron bath is comparable to the intrinsic Gilbert damping and may be
+important in describing the magnetization dynamics of the system.",1412.2479v1
+2016-04-02,Exploring the Origin and Dynamics of Solar Magnetic Fields,"The Sun is a magnetically active star and is the source of the solar wind,
+electromagnetic radiation and energetic particles which affect the heliosphere
+and the Earths atmosphere. The magnetic field of the Sun is responsible for
+most of the dynamic activity of the Sun. This thesis research seeks to
+understand solar magnetic field generation and the role that magnetic fields
+play in the dynamics of the solar atmosphere. Specifically, this thesis focuses
+on two themes: in the first part, we study the origin and behaviour of solar
+magnetic fields using magnetohydrodynamic dynamo theory and modelling, and in
+the second part, utilizing observations and data analysis we study two major
+problems in solar physics, namely, the coronal heating problem and initiation
+mechanisms of solar flares.",1604.00563v1
+2016-05-26,Handling magnetic anisotropy and dynamic magnetic response of ferromagnetic multilayers in flexible substrates,"We investigate the dynamic magnetic response of ferromagnetic flexible
+NiFe/Ta and FeCuNbSiB/Ta multilayers under external stress. We explore the
+possibility of handling magnetic anisotropy and dynamic magnetic response of
+flexible magnetostrictive nanostructures. We quantify the sensitivity of the
+multilayers under external stress by calculating the ratio $|\Delta
+\textrm{MI}|/|\Delta \bar{\sigma}|$ and show that considerable values can be
+reached by tuning the magnetic field, frequency, magnetostriction constant, and
+external stress. The results reveal possibilities of application of flexible
+magnetostrictive multilayers under external stress and place them as very
+attractive candidates as element sensor for the development of sensitive smart
+touch sensors.",1605.08193v2
+2016-05-27,Edge states and skyrmion dynamics in nanostripes of frustrated magnets,"Magnetic skyrmions are particle-like topological excitations recently
+discovered in chiral magnets. Their small size, topological protection and the
+ease with which they can be manipulated by electric currents generated much
+interest in using skyrmions for information storage and processing. Recently,
+it was suggested that skyrmions with additional degrees of freedom can exist in
+magnetically frustrated materials. Here, we show that dynamics of skyrmions and
+antiskyrmions in nanostripes of frustrated magnets is strongly affected by
+complex spin states formed at the stripe edges. These states create multiple
+edge channels which guide the skyrmion motion. Non-trivial topology of edge
+states gives rise to complex current-induced dynamics, such as emission of
+skyrmion-antiskyrmion pairs. The edge state topology can be controlled with an
+electric current through the exchange of skyrmions and antiskyrmions between
+the edges of a magnetic nanostructure. These results can lead to conceptually
+new electronic devices.",1605.08645v1
+2016-06-06,Tracking local magnetic dynamics via high-energy charge excitations in a relativistic Mott insulator,"We use time- and energy-resolved optical spectroscopy to investigate the
+coupling of electron-hole excitations to the magnetic environment in the
+relativistic Mott insulator Na$_2$IrO$_3$. We show that, on the picosecond
+timescale, the photoinjected electron-hole pairs delocalize on the hexagons of
+the Ir lattice via the formation of quasi-molecular orbital (QMO) excitations
+and the exchange of energy with the short-range-ordered zig-zag magnetic
+background. The possibility of mapping the magnetic dynamics, which is
+characterized by typical frequencies in the THz range, onto high-energy (1-2
+eV) charge excitations provides a new platform to investigate, and possibly
+control, the dynamics of magnetic interactions in correlated materials with
+strong spin-orbit coupling, even in the presence of complex magnetic phases.",1606.01667v2
+2016-08-12,Ultrafast inhomogeneous magnetization dynamics analyzed by interface-sensitive nonlinear magneto-optics,"We analyze laser-induced ultrafast, spatially inhomogeneous magnetization
+dynamics of epitaxial Co/Cu(001) films in a 0.4-10 nm thickness range with
+time-resolved magnetization-induced second harmonic generation, which probes
+femtosecond spin dynamics at the vacuum/Co and Co/Cu interfaces. The
+interference of these two contributions makes the overall signal particularly
+sensitive to differences in the transient magnetization redistribution between
+the two interfaces, i.e. ultrafast magnetization profiles in the ferromagnetic
+film. We find in films of up to 3 nm thickness a stronger demagnetization at
+the surface, because the film thickness is smaller than the effective mean free
+path of the spin current mediating the demagnetization, i.e. the difference
+between the mean free paths of the majority and minority carriers. For film
+thicknesses larger than 3 nm, the magnetization profile reverses, since
+majority spins can escape into the conducting substrate only from the
+interface-near region.",1608.03842v1
+2017-08-02,Strongly exchange-coupled and surface-state-modulated magnetization dynamics in Bi2Se3/YIG heterostructures,"We report strong interfacial exchange coupling in Bi2Se3/yttrium iron garnet
+(YIG) bilayers manifested as large in-plane interfacial magnetic anisotropy
+(IMA) and enhancement of damping probed by ferromagnetic resonance (FMR). The
+IMA and spin mixing conductance reached a maximum when Bi2Se3 was around 6
+quintuple-layer (QL) thick. The unconventional Bi2Se3 thickness dependence of
+the IMA and spin mixing conductance are correlated with the evolution of
+surface band structure of Bi2Se3, indicating that topological surface states
+play an important role in the magnetization dynamics of YIG.
+Temperature-dependent FMR of Bi2Se3/YIG revealed signatures of magnetic
+proximity effect of $T_c$ as high as 180 K, and an effective field parallel to
+the YIG magnetization direction at low temperature. Our study sheds light on
+the effects of topological insulators on magnetization dynamics, essential for
+development of TI-based spintronic devices.",1708.00593v1
+2018-07-05,Domain wall dynamics for an in-plane magnetized thin film with large perpendicular hard axis anisotropy including Dzyaloshinskii-Moriya interaction,"We consider a thin ferromagnetic layer to which an external field or a
+current are applied along an in plane easy axis. The perpendicular hard axis
+anisotropy constant is large so that the out of plane magnetization component
+is smaller than the in plane components. A perturbation approach is used to
+obtain the profile and velocity of the moving domain wall. The dynamics of the
+in plane components of the magnetization is governed by a reaction diffusion
+equation which determines the speed of the profile. We find a simple analytic
+expression for the out of plane magnetization showing a symmetric distortion
+due to the motion in addition to the asymmetric component due to the
+Dzyaloshinskii--Moriya interaction. The results obtained complement previous
+studies in which either the Dzyalozhinskii vector or the out of plane hard axis
+anisotropy were assumed small. In the regime studied the Walker breakdown is
+not observed but the reaction diffusion dynamics predicts a slowing down of the
+domain wall for sufficiently large magnetic field. The transition point depends
+on the applied field, saturation magnetization and easy axis anisotropy.",1807.02032v1
+2019-07-04,Resonant Acoustic Wave Assisted Spin-Transfer-Torque Switching of Nanomagnets,"We report the possibility of achieving an order of magnitude reduction in the
+energy dissipation needed to write bits in perpendicular magnetic tunnel
+junctions (p-MTJs) by simulating the magnetization dynamics under a combination
+of resonant surface acoustic waves (r-SAW) and spin-transfer-torque (STT). The
+magnetization dynamics were simulated using the Landau-Lifshitz-Gilbert
+equation under macrospin assumption with the inclusion of thermal noise. The
+resonant magnetization dynamics in the magnetostrictive nanomagnet build over
+few 10s of cycles of SAW application that drives the magnetization to precess
+in a cone with a deflection of ~45 degrees from the perpendicular direction.
+This reduces the STT current density required to switch the magnetization
+direction without increasing the STT application time or degrading the
+switching probability in the presence of room temperature thermal noise. This
+could lead to a pathway to achieve energy efficient switching of spin transfer
+torque random access memory (STTRAM) whose lateral dimensions can be scaled
+aggressively despite using materials with low magnetostriction by employing
+resonant excitation.",1907.02255v1
+2020-01-28,Magnetic oscillation modes in square lattice artificial spin ice,"Small amplitude dipolar oscillations are considered in artificial spin ice on
+a square lattice in two dimensions. The net magnetic moment of each elongated
+magnetic island in the spin ice is assumed to have Heisenberg-like dynamics.
+Each island's magnetic moment is assumed to be influenced by shape anisotropies
+and by the dipolar interactions with its nearest neighbors. The magnetic
+dynamics is linearized around one of the ground states, leading to an $8\times
+8$ matrix to be diagonalized for the magnetic spin wave modes. Analytic
+solutions are found and classified as antisymmetric and symmetric with regard
+to their in-plane dynamic fluctuations. Although only the leading dipolar
+interactions are included, modes similar to these may be observable
+experimentally.",2001.10409v1
+2020-07-23,Nonreciprocal surface magnetoelastic dynamics,"Motivated by recent experiments, we investigate the nonreciprocal
+magnetoelastic interaction between the surface acoustic phonons of dielectric
+non-magnetic substrates and magnons of proximity nanomagnets. The magnetization
+dynamics exerts rotating forces at the edges of the nanomagnet that causes the
+nonreciprocal interaction with surface phonons due to its rotation-momentum
+locking. This coupling induces the nonreciprocity of the surface phonon
+transmission and a nearly complete phonon diode effect by several (tens of)
+magnetic nanowires of high (ordinary) magnetic quality. Phase-sensitive
+microwave transmission is also nonreciprocal that can pick up clear signals of
+the coherent phonons excited by magnetization dynamics. Nonreciprocal pumping
+of phonons by precessing magnetization is predicted using Landauer-B\""uttiker
+formalism.",2007.12240v3
+2020-10-21,A Frustrated Bimeronium: Static Structure and Dynamics,"We show a topological spin texture called ""bimeronium"" in magnets with
+in-plane magnetization. It is a topological counterpart of skyrmionium in
+perpendicularly magnetized magnets and can be seen as a combination of two
+bimerons with opposite topological charges. We report the static structure and
+spin-orbit-torque-induced dynamics of an isolated bimeronium in a magnetic
+monolayer with frustrated exchange interactions. We study the anisotropy and
+magnetic field dependences of a static bimeronium. We also explore the
+bimeronium dynamics driven by the damping-like spin-orbit torque. We find that
+the bimeronium shows steady rotation when the spin polarization direction is
+parallel to the easy axis. Moreover, we demonstrate the annihilation of the
+bimeronium when the spin polarization direction is perpendicular to the easy
+axis. Our results are useful for understanding fundamental properties of
+bimeronium structures and may offer an approach to build bimeronium-based
+spintronic devices.",2010.10822v2
+2020-11-13,Magnetic dynamics with Weyl fermions,"Transport of charge and valley degrees of freedom coupled to order-parameter
+dynamics in magnetic Weyl semimetals is studied in the framework of
+nonequilibrium thermodynamics. In addition to the established valley-related
+transport anomalies that are rooted in band-structure topology, we construct
+dissipative couplings between the three dynamic constituents of the system
+driven out of equilibrium by electromagnetic perturbations. We show how the
+valley degree of freedom mediates an effective coupling between the charge and
+magnetic sectors of the system, through a combination of the chiral anomaly, on
+the electric side, and the Onsager-paired valley torque and pumping, on the
+magnetic side. This work compliments previous studies of magnetic Weyl
+semimetals by a more systematic analysis of collective dissipation. We discuss
+several concrete examples of the valley-mediated current-driven magnetic
+instabilities and charge pumping, and extend the theory to the
+antiferromagnetic case.",2011.07141v1
+2021-01-12,"Shielding of external magnetic field by dynamic nuclear polarization in (In,Ga)As quantum dots","The dynamics of the coupled electron-nuclear spin system is studied in an
+ensemble of singly-charged (In,Ga)As/GaAs quantum dots (QDs) using periodic
+optical excitation at 1 GHz repetition rate. In combination with the
+electron-nuclei interaction, the highly repetitive excitation allows us to lock
+the electron spins into magnetic resonance in a transverse external magnetic
+field. Sweeping the field to higher values, the locking leads to an effective
+""diamagnetic"" response of significant strength due to dynamic nuclear
+polarization, which shields the QD electrons at least partly from the external
+field and can even keep the internal magnetic field constant up to 1.3 T field
+variation. We model the effect through a magnetic field-dependent polarization
+rate of the nuclei, from which we suggest a strategy for adjusting the nuclear
+polarization through the detuning between optical excitation and electronic
+transition, in addition to tuning the magnetic field.",2101.04469v2
+2021-01-26,Tuning the dynamics of magnetic droplet solitons using dipolar interactions,"Magnetic droplets are dissipative magnetodynamical solitons that can form
+under current driven nanocontacts in magnetic layers with large perpendicular
+magnetic anisotropy. Here, we extend the original droplet theory by studying
+the impact of the dipolar interactions on the dynamics of droplet solitons. By
+varying the thickness of the free layer of a spin torque nano-oscillator, we
+systematically tune the internal field of the free layer to investigate the
+dynamics of droplet solitons. Our numerical results show that increasing the
+free layer thickness increases the droplet threshold current, decreases the
+droplet frequency and diameter, enlarges the current hysteresis and also
+modifies the structure of the droplet. The Oersted field of the current breaks
+the phase coherency and deteriorates the stability of the droplet in free
+layers with larger thicknesses. Moreover, our findings show a simple relation
+to determine the impact of the free layer thickness on the droplet nucleation
+boundaries. Our study presents the missing brick on the physics behind magnetic
+droplet solitons, and further illustrates that magnetic droplets in thinner
+layers possess more promising characteristics for spintronic applications and
+enable devices with higher speed of operation.",2101.10716v1
+2021-04-12,Strongly anisotropic spin dynamics in magnetic topological insulators,"The recent discovery of magnetic topological insulators has opened new
+avenues to explore exotic states of matter that can emerge from the interplay
+between topological electronic states and magnetic degrees of freedom, be it
+ordered or strongly fluctuating. Motivated by the effects that the dynamics of
+the magnetic moments can have on the topological surface states, we investigate
+the magnetic fluctuations across the
+(MnBi$_{\text{2}}$Te$_{\text{4}}$)(Bi$_{\text{2}}$Te$_{\text{3}}$)$_{\text{n}}$
+family. Our paramagnetic electron spin resonance experiments reveal contrasting
+Mn spin dynamics in different compounds, which manifests in a strongly
+anisotropic Mn spin relaxation in MnBi$_{\text{2}}$Te$_{\text{4}}$ while being
+almost isotropic in MnBi$_{\text{4}}$Te$_{\text{7}}$. Our density-functional
+calculations explain these striking observations in terms of the sensitivity of
+the local electronic structure to the Mn spin-orientation, and indicate that
+the anisotropy of the magnetic fluctuations can be controlled by the carrier
+density, which may directly affect the electronic topological surface states.",2104.05659v1
+2021-06-21,Spin structure factors of doped monolayer Germanene in the presence of spin-orbit coupling,"In this paper, we present a Kane-Mele model in the presence of magnetic field
+and next nearest neighbors hopping amplitudes for investigations of the spin
+susceptibilities of Germanene layer. Green's function approach has been
+implemented to find the behavior of dynamical spin susceptibilities of
+Germanene layer within linear response theoryand in the presence of magnetic
+field and spin-orbit coupling at finite temperature. Our results show the
+magnetic excitation mode for both longitudinal and transverse components of
+spin tends to higher frequencies with spin-orbit coupling strength. Moreover
+the frequency positions of sharp peaks in longitudinal dynamical spin
+susceptibility are not affected by variation of magnetic field while the peaks
+in transverse dynamical susceptibility moves to lower frequencies with magnetic
+field. The effects of electron doping on frequency behaviors of spin
+susceptibilities have been addressed in details. Finally the temperature
+dependence of static spin structure factors due to the effects of spin-orbit
+coupling, magnetic field and chemical potential has been studied.",2106.11377v1
+2021-09-27,Absence of Normal Fluctuations in an Integrable Magnet,"We investigate dynamical fluctuations of transferred magnetization in the
+one-dimensional lattice Landau--Lifshitz magnet with uniaxial anisotropy,
+representing an emblematic model of interacting spins. We demonstrate that the
+structure of fluctuations in thermal equilibrium depends radically on the
+characteristic dynamical scale. In the ballistic regime, typical fluctuations
+are found to follow a normal distribution and scaled cumulants are finite. In
+stark contrast, on the diffusive and superdiffusive timescales, relevant
+respectively for the easy-axis and isotropic magnet at vanishing total
+magnetization, typical fluctuations are no longer Gaussian and, remarkably,
+scaled cumulants are divergent. The observed anomalous features disappear upon
+breaking integrability, suggesting that the absence of normal fluctuations is
+intimately tied to the presence of soliton modes. In a nonequilibrium setting
+of the isotropic magnet with weakly polarized step-profile initial state we
+find a slow drift of dynamical exponent from the superdiffusive towards the
+diffusive value.",2109.13088v3
+2021-12-22,Dynamic structure factor of the magnetized one-component plasma: crossover from weak to strong coupling,"Plasmas in strong magnetic fields have been mainly studied in two distinct
+limiting cases--that of weak and strong nonideality with very different
+physical properties. While the former is well described by the familiar theory
+of Braginskii, the latter regime is closer to the behavior of a Coulomb liquid.
+Here we study in detail the transition between both regimes. We focus on the
+evolution of the dynamic structure factor of the magnetized one-component
+plasma from weak to strong coupling, which is studied with first-principle
+molecular dynamics simulations. The simulations show the vanishing of Bernstein
+modes and the emergence of higher harmonics of the upper hybrid mode across the
+magnetic field, a redistribution of spectral power between the two main
+collective modes under oblique angles, and a suppression of plasmon damping
+along the magnetic field. Comparison with results from various models,
+including the random phase approximation, a Mermin-type dielectric function,
+and the Quasi-Localized Charge Approximation show that none of the theories is
+capable of reproducing the crossover that occurs when the coupling parameter is
+on the order of unity. The findings are relevant to the scattering spectra,
+stopping power, and transport coefficients of correlated magnetized plasmas.",2112.11981v1
+2022-08-19,Phononic-crystal cavity magnomechanics,"Establishing a way to control magnetic dynamics and elementary excitations
+(magnons) is crucial to fundamental physics and the search for novel phenomena
+and functions in magnetic solid-state systems. Electromagnetic waves have been
+developed as means of driving and sensing in magnonic and spintronics devices
+used in magnetic spectroscopy, non-volatile memory, and information processors.
+However, their millimeter-scale wavelengths and undesired cross-talk have
+limited operation efficiency and made individual control of densely integrated
+magnetic systems difficult. Here, we utilize acoustic waves (phonons) to
+control magnetic dynamics in a miniaturized phononic crystal micro-cavity and
+waveguide architecture. We demonstrate acoustic pumping of localized
+ferromagnetic magnons, where their back-action allows dynamic and
+mode-dependent modulation of phononic cavity resonances. The phononic crystal
+platform enables spatial driving, control and read-out of tiny magnetic states
+and provides a means of tuning acoustic vibrations with magnons. This
+alternative technology enhances the usefulness of magnons and phonons for
+advanced sensing, communications and computation architectures that perform
+transduction, processing, and storage of classical and quantum information.",2208.09105v1
+2022-09-06,Current-driven magnetization dynamics and their correlation with magnetization configurations in perpendicularly magnetized tunnel junctions,"We study spin-transfer-torque driven magnetization dynamics of a
+perpendicular magnetic tunnel junction (MTJ) nanopillar. Based on the
+combination of spin-torque ferromagnetic resonance and microwave spectroscopy
+techniques, we demonstrate that the free layer (FL) and the weak pinned
+reference layer (RL) exhibit distinct dynamic behaviors with opposite frequency
+vs. field dispersion relations. The FL can support a single coherent spin-wave
+(SW) mode for both parallel and antiparallel configurations, while the RL
+exhibits spin-wave excitation only for the antiparallel state. These two SW
+modes corresponding to the FL and RL coexist at an antiparallel state and
+exhibit a crossover phenomenon of oscillation frequency with increasing the
+external magnetic field, which could be helpful in the mutual synchronization
+of auto-oscillations for SW-based neuromorphic computing.",2209.02271v1
+2022-12-07,Emergent Magneto-multipoles and Nonlinear Responses of a Magnetic Hopfion,"The three-dimensional emergent magnetic field $\textbf{B}^e$ of a magnetic
+hopfion gives rise to emergent magneto-multipoles in a similar manner to the
+multipoles of classical electromagnetic field. Here, we show that the nonlinear
+responses of a hopfion are characterized by its emergent magnetic toroidal
+moment ${T}^e_z = \frac{1}{2}\int (\textbf{r}\times \textbf{B}^e)_z dV$ and
+emergent magnetic octupole component ${\it \Gamma}^e =\int [(x^2+y^2)B^e_z - xz
+B^e_x - y z B^e_y] dV$. The hopfion exhibits nonreciprocal dynamics (nonlinear
+hopfion Hall effect) under an ac driving current applied along (perpendicular
+to) the direction of ${T}^e_z$. The sign of nonreciprocity and nonlinear Hall
+angle is determined by the polarity and chirality of hopfion. The nonlinear
+electrical transport induced by a magnetic hopfion is also discussed. This work
+reveals the vital roles of emergent magneto-multipoles in nonlinear hopfion
+dynamics and could stimulate further investigations on the dynamical responses
+of topological spin textures induced by emergent electromagnetic multipoles.",2212.03500v1
+2023-01-04,Dynamics of Argon Gas Bubbles Rising in Liquid Steel in the Presence of Transverse Magnetic Field,"Bubbly flows are present in various industrial processes including
+metallurgical processes in which gas bubbles are injected at the bottom of bulk
+liquid metal to stir the liquid metal and homogenize the metal. Understanding
+the motion of such bubbles is essential, as it has been shown that bubble
+flotation can remove inclusions. In this work, we have numerically studied
+three-dimensional dynamics of a pair of inline Argon bubbles rising in molten
+steel under the influence of a transverse magnetic field. We have explored the
+effects of two transverse magnetic field strengths (Bx = 0 and 0.2 T). The
+bubbles' motion and transient rise velocities are compared under different
+magnetic fields. The shape deformations and path of the bubbles are discussed.
+The flow structures behind the bubbles are analyzed. We found that structures
+are more organized and elongated under a magnetic field, whereas it is complex
+and intertwined when the magnetic field is not included. We have used a
+geometry construction-based volume of fluid (VOF) method to track interface,
+maintain mass balance and estimate the interface curvature. Additionally, we
+have incorporated a Sharp Surface Force Method (SSF) for surface tension
+forces. The algorithm is able to minimize the spurious velocities.",2301.01797v1
+2023-01-09,Dynamic structure factor and excitation spectrum of the one-component plasma: the case of weak to moderate magnetization,"Magnetized plasmas are well known to exhibit a rich spectrum of collective
+modes. Here, we focus on the density modes in dense or cold plasmas, where
+strong coupling effects alter the mode spectrum known from traditional weakly
+coupled plasmas. In particular, we study the dynamic structure factor (DSF) of
+the magnetized one-component plasma with molecular dynamics simulations.
+Extending our previous results [H.~K\""ahlert and M.~Bonitz, Phys. Rev. Research
+\textbf{2022}, 4, 013197], it is shown that Bernstein modes can be observed in
+the weakly magnetized regime, where they are found below the upper hybrid
+frequency, provided the coupling strength is sufficiently low. We investigate
+the DSF for a variety of different wave numbers and plasma parameters and show
+that even small magnetization can give rise to a strong zero-frequency mode
+perpendicular to the magnetic field and change the dispersion as well as the
+damping of the upper hybrid mode.",2301.03425v1
+2023-02-10,Photocarrier Transport of Ferroelectric Photovoltaic Thin Films Detected by the Magnetic Dynamics of Adjacent Ferromagnetic Layers,"We have observed photocarrier transport behaviors in
+BiFeO$_3$/La$_{1-x}$Sr$_x$MnO$_3$~(BFO/LSMO) heterostructures by using
+time-resolved synchrotron x-ray magnetic circular dichroism in reflectivity.
+The magnetization of LSMO layers was used as a probe of photo-induced carrier
+dynamics in the photovoltaic BFO layers. During the photo-induced
+demagnetization process, the decay time of LSMO~($x$=0.2) magnetization
+strongly depends on the ferroelectric polarization direction of the BFO layer.
+The variation of decay time should be attributed to the different sign of
+accumulated photocarriers at the BFO/LSMO interface induced by the photovoltaic
+effect of the BFO layer. The photocarriers can reach the BFO/LSMO interface and
+influence the magnetization distribution in the LSMO layers within the
+timescale of $\sim$100~ps. Our results provide a novel strategy to investigate
+carrier dynamics and mechanisms of optical control of magnetization in thin
+film heterostructures.",2302.05000v1
+2023-03-28,Analysis of ultrafast magnetization switching dynamics in exchange-coupled ferromagnet-ferrimagnet heterostructures,"Magnetization switching in ferromagnets has so far been limited to the
+current-induced spin-orbit-torque effects. Recent observation of
+helicity-independent all-optical magnetization switching in exchange-coupled
+ferromagnet ferrimagnet heterostructures expanded the range and applicability
+of such ultrafast heat-driven magnetization switching. Here we report the
+element-resolved switching dynamics of such an exchange-coupled system, using a
+modified microscopic three-temperature model. We have studied the effect of i)
+the Curie temperature of the ferromagnet, ii) ferrimagnet composition, iii) the
+long-range RKKY exchange-coupling strength, and iv) the absorbed optical energy
+on the element-specific time-resolved magnetization dynamics. The phase-space
+of magnetization illustrates how the RKKY coupling strength and the absorbed
+optical energy influence the switching time. Our analysis demonstrates that the
+threshold switching energy depends on the composition of the ferrimagnet and
+the switching time depends on the Curie temperature of the ferromagnet as well
+as RKKY coupling strength. This simulation anticipates new insights into
+developing faster and more energy-efficient spintronics devices.",2303.16294v1
+2023-08-28,Real-time dynamics of axial charge and chiral magnetic current in a non-Abelian expanding plasma,"Understanding axial charge dynamics driven by changes in Chern-Simons number
+densities is a key aspect in understanding the chiral magnetic effect (CME) in
+heavy-ion collisions. Most phenomenological simulations assume that a large
+amount of axial charge is produced in the initial stages and that axial charge
+is conserved throughout the simulation. Within an (expanding) homogeneous
+holographic plasma, we investigate the real-time axial charge relaxation
+dynamics and their impact on the chiral magnetic current. Moreover, we discuss
+the real-time interplay of the non-Abelian and the Abelian chiral anomaly in
+the presence of a strong magnetic field. In the expanding plasma, the
+Chern-Simons diffusion rate and thus the axial charge relaxation rate are time
+dependent due to the decaying magnetic field. We quantify the changes in the
+late time falloffs and establish a horizon formula for the chiral magnetic
+current.",2308.14829v2
+2023-10-12,Dynamics of particles with electric charge and magnetic dipole moment near Schwarzschild-MOG black hole,"Investigations of electromagnetic interactions between test-charged and
+magnetized particles are important in the dynamics of the particles in strong
+gravitational fields around black holes. Here, we study the dynamics of a
+particle having an electric charge and a magnetic dipole moment in the
+spacetime of a Schwarzschild black hole in modified gravity (MOG), called
+Schwarzschild-MOG black hole. First, we provide a solution of Maxwell equations
+for the angular component of electromagnetic four potentials in the
+Schwarzschild-MOG spacetime. Then, we derive equations of motion and effective
+potential for circular motion of such particles using a hybrid form of the
+Hamilton-Jacobi equation which includes both interactions of electric charge
+and magnetic dipole moment with the external magnetic field assumed as
+asymptotically uniform, and interaction between the particles and the MOG
+field. Also, we investigate the effects of the three types of interactions on
+the radius of innermost stable circular orbits (ISCOs) and the energy \&
+angular momentum of the particles at their corresponding ISCOs. Finally, we
+provide detailed analyses of the effects of the three interactions mentioned
+above on the center of mass energy in the collisions between neutral,
+electrically charged, and magnetized particles.",2310.08046v1
+2024-01-26,Efficient Control of Magnetization Dynamics Via W/CuO$_\text{x}$ Interface,"Magnetization dynamics, which determine the speed of magnetization switching
+and spin information propagation, play a central role in modern spintronics.
+Gaining its control will satisfy the different needs of various spintronic
+devices. In this work, we demonstrate that the surface oxidized Cu
+(CuO$_\text{x}$) can be employed for the tunability of magnetization dynamics
+of ferromagnet (FM)/heavy metal (HM) bilayer system. The capping CuO$_\text{x}$
+layer in CoFeB/W/CuO$_\text{x}$ trilayer reduces the magnetic damping value in
+comparison with the CoFeB/W bilayer. The magnetic damping even becomes lower
+than that of the CoFeB/CuO$_\text{x}$ by ~ 16% inferring the stabilization of
+anti-damping phenomena. Further, the reduction in damping is accompanied by a
+very small reduction in the spin pumping-induced output DC voltage in the
+CoFeB/W/CuO$_\text{x}$ trilayer. The simultaneous observation of anti-damping
+and spin-to-charge conversion can be attributed to the orbital Rashba effect
+observed at the HM/CuO$_\text{x}$ interface. Our experimental findings
+illustrate that the cost-effective CuO$_\text{x}$ can be employed as an
+integral part of modern spintronics devices owing to its rich underneath
+spin-orbital physics.",2401.14708v1
+2000-12-10,Helicity in Hydro and MHD Reconnection,"Helicity, a measure of the linkage of flux lines, has subtle and largely
+unknown effects upon dynamics. Both magnetic and hydrodynamic helicity are
+conserved for ideal systems and could suppress nonlinear dynamics. What
+actually happens is not clear because in a fully three-dimensional system there
+are additional channels whereby intense, small-scale dynamics can occur. This
+contribution shows one magnetic and one hydrodynamic case where for each the
+presence of helicity does not suppress small-scale intense dynamics of the type
+that might lead to reconnection.",0012210v1
+1999-03-03,Dynamics of Ordering of Isotropic Magnets,"We study the dynamics of ordering of the nonconserved and conserved
+Heisenberg magnet. The dynamics consists of two parts - an irreversible
+dissipation into a heat bath and a reversible precession induced by a torque
+due to the local molecular field. For quenches both to T=0 and T=T_c, we show
+that the torque is irrelevant when the dynamics is nonconserved but relevant
+when the dynamics is conserved and is governed by a new nontrivial fixed point.",9903052v1
+2015-04-18,Dynamic phase transitions in a ferromagnetic thin film system: A Monte Carlo simulation study,"Dynamic phase transition properties of ferromagnetic thin film system under
+the influence both bias and time dependent magnetic fields have been elucidated
+by means of kinetic Monte Carlo simulation with local spin update Metropolis
+algorithm. The obtained results after a detailed analysis suggest that bias
+field is the conjugate field to dynamic order parameter, and it also appears to
+define a phase line between two antiparallel dynamic ordered states depending
+on the considered system parameters. Moreover, the data presented in this study
+well qualitatively reproduce the recently published experimental findings where
+time dependent magnetic behavior of a uniaxial cobalt films is studied in the
+neighborhood of dynamic phase transition point.",1504.04749v1
+2018-02-08,Anomalous phonon lifetime shortening in paramagnetic CrN caused by magneto-lattice coupling: A combined spin and ab initio molecular dynamics study,"We study the mutual coupling of spin fluctuations and lattice vibrations in
+paramagnetic CrN by combining atomistic spin dynamics and ab initio molecular
+dynamics. The two degrees of freedom are dynamically coupled leading to
+non-adiabatic effects. Those effects suppress the phonon life times at low
+temperature compared to an adiabatic approach. The here identified dynamic
+coupling provides an explanation for the experimentally observed unexpected
+temperature dependence of the thermal conductivity of magnetic semiconductors
+above the magnetic ordering temperature.",1802.02934v1
+2020-06-04,Analytical model of the inertial dynamics of a magnetic vortex,"We present an analytical model to account for the inertial dynamics of a
+magnetic vortex. The model is based on a deformation of the core profile based
+on the D\""oring kinetic field, whereby the deformation amplitudes are promoted
+to dynamical variables in a collective-coordinate approach that provides a
+natural extension to the Thiele model. This extended model accurately describes
+complex transients due to inertial effects and the variation of the effective
+mass with velocity. The model also provides a quantitative description of the
+inertial dynamics leading up to vortex core reversal, which is analogous to the
+Walker transition in domain wall dynamics.",2006.02866v1
+2001-06-18,Turbulent Dynamo in Asymptotic Giant Branch Stars,"Using recent results on the operation of turbulent dynamos, we show that a
+turbulent dynamo can amplify a large scale magnetic field in the envelopes of
+asymptotic giant branch (AGB) stars. We propose that a slow rotation of the AGB
+envelope can fix the symmetry axis, leading to the formation of an axisymmetric
+magnetic field structure. Unlike solar-type alpha-omega dynamos, the rotation
+has only a small role in amplifying the toroidal component of the magnetic
+field. The large-scale magnetic field is strong enough for the formation of
+magnetic cool spots on the AGB stellar surface. The spots can regulate dust
+formation, hence mass loss rate, leading to axisymmetric mass loss and the
+formation of elliptical planetary nebulae (PNe). Despite its role in forming
+cool spots, the large scale magnetic field is too weak to play a dynamic role
+and directly influence the wind from the AGB star. We find other problems in
+models where the magnetic field plays a dynamic role in shaping the AGB winds,
+and argue that they cannot explain the formation of nonspherical PNe.",0106301v1
+2002-01-30,Magnetic Aggregation I: Aggregation Dynamics and Numerical Modelling,"Focussing on preplanetary grains growth, we discuss the properties of dust
+aggregation driven by magnetic dipole forces. While there is no direct evidence
+for the existence of magnetic grains present in the solar nebula, there are
+reasons to assume they may have been present. We derive analytical expressions
+for the cross-section of two interacting dipoles. The effective cross section
+depends upon the strength of the magnetic dipoles and the initial velocities.
+For typical conditions the magnetic cross section is between 2 and 3 orders of
+magnitude larger than the geometric cross section. We study the growth dynamics
+of magnetic grains and find that the mass of the aggregates should increase
+with time like t^3.2 whereas Brownian motion growth behaves like t^2. A
+numerical tool is introduced which can be used to model dust aggregation in
+great detail, including the treatment of contact forces, aggregate
+restructuring processes and long-range forces. This tool is used to simulate
+collisions between magnetic grains or clusters and to validate the analytical
+cross-sections. The numerically derived cross section is in excellent agreement
+with the analytical expression. The numerical tool is also used to demonstrate
+that structural changes in the aggregates during collisions can be significant.",0201500v1
+2002-09-15,The Mean Electromotive Force for MHD Turbulence: the Case of a Weak Mean Magnetic Field and Slow Rotation,"The mean electromotive force in the framework of mean--field
+magnetohydrodynamics is found with a particular attention to the effect of a
+mean rotation of the fluid on the mean electromotive force. Anisotropy of the
+turbulence due to gradients of its intensity or its helicity are admitted. The
+mean magnetic field is considered to be weak enough to exclude quenching
+effects. Magnetic fluctuations with a zero mean magnetic field are taken into
+account. The Omega x J -effect works in the same way with velocity fluctuations
+and magnetic fluctuations. A contribution to the electromotive force connected
+with the symmetric parts of the gradient tensor of the mean magnetic field was
+found in the case of rotation, resulting from velocity or magnetic
+fluctuations. The implications of the results for the mean electromotive force
+for mean--field dynamo models are discussed with special emphasis to dynamos
+working without alpha-effect.",0209287v1
+2006-02-06,Magnetic field vector retrieval with HMI,"The Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics
+Observatory (SDO), will begin data acquisition in 2008. It will provide the
+first full disk, high temporal cadence observations of the full Stokes vector
+with a 0.5 arc sec pixel size. This will allow for a continuous monitoring of
+the Solar magnetic field vector. HMI data will advance our understanding of the
+small and large-scale magnetic field evolution, its relation to the solar and
+global dynamic processes, coronal field extrapolations, flux emergence,
+magnetic helicity and the nature of the polar magnetic fields. We summarize
+HMI's expected operation modes, focusing on the polarization cross-talk induced
+by the solar oscillations and how this affects the magnetic field vector
+determinations.",0602130v1
+2004-03-10,Role of Correlation and Exchange for Quasi-particle Spectra of Magnetic and Diluted Magnetic Semiconductors,"Theoretical foundation and application of the generalized spin-fermion (sp-d)
+exchange lattice model to magnetic and diluted magnetic semiconductors are
+discussed. The capabilities of the model to describe spin quasi-particle
+spectra are investigated. The main emphasis is made on the dynamic behavior of
+two interacting subsystems, the localized spins and spin density of itinerant
+carriers. A nonperturbative many-body approach, the Irreducible Green Functions
+(IGF) method, is used to describe the quasi-particle dynamics. Scattering
+states are investigated and three branches of magnetic excitations are
+calculated in the regime, characteristic of a magnetic semiconductor. For a
+simplified version of the model (Kondo lattice model) we study the spectra of
+quasi-particle excitations with special attention given to diluted magnetic
+semiconductors. For this, to include the effects of disorder, modified mean
+fields are determined self-consistently. The role of the Coulomb correlation
+and exchange is clarified by comparing of both the cases.",0403266v1
+2004-08-18,Theory of Magnetic Polaron,"The concept of magnetic polaron is analysed and developed to elucidate the
+nature of itinerant charge carrier states in magnetic semiconductors and
+similar complex magnetic materials. By contrasting the scattering and bound
+states of carriers within the $s-d$ exchange model, the nature of bound states
+at finite temperatures is clarified. The free magnetic polaron at certain
+conditions is realized as a bound state of the carrier (electron or hole) with
+the spin wave. Quite generally, a self-consistent theory of a magnetic polaron
+is formulated within a nonperturbative many-body approach, the Irreducible
+Green Functions (IGF) method which is used to describe the quasiparticle
+many-body dynamics at finite temperatures. Within the above many-body approach
+we elaborate a self-consistent picture of dynamic behavior of two interacting
+subsystems, the localized spins and the itinerant charge carriers. In
+particular, we show that the relevant generalized mean fields emerges naturally
+within our formalism. At the same time, the correct separation of elastic
+scattering corrections permits one to consider the damping effects (inelastic
+scattering corrections) in the unified and coherent fashion. The damping of
+magnetic polaron state, which is quite different from the damping of the
+scattering states, finds a natural interpretation within the present
+self-consistent scheme.",0408404v2
+2007-07-03,Strings and D-branes in a supersymmetric magnetic flux background,"We investigate how the presence of RR magnetic $F_{p+2}$ fluxes affects the
+energy of classical Dp branes, for specific string theory supersymmetric
+backgrounds which are solutions to the leading order in $\alpha'$ including
+back-reaction effects. The Dp brane dynamics is found to be similar to the well
+known dynamics of particles and strings moving in magnetic fields. We find a
+class of BPS solutions which generalize the BPS fundamental strings or BPS
+branes with momentum and winding to the case of non-zero magnetic fields.
+Remarkably, the interaction with the magnetic fields does not spoil the
+supersymmetry of the solution, which turns out to be invariant under four
+supersymmetry transformations. We find that magnetic fields can significantly
+reduce the energy of some BPS strings and Dp branes, in particular, some
+macroscopic Dp branes become light for sufficiently large magnetic fields.",0707.0455v2
+2008-02-12,Temperature dependent magnetization dynamics of magnetic nanoparticles,"Recent experimental and theoretical studies show that the switching behavior
+of magnetic nanoparticles can be well controlled by external time-dependent
+magnetic fields. In this work, we inspect theoretically the influence of the
+temperature and the magnetic anisotropy on the spin-dynamics and the switching
+properties of single domain magnetic nanoparticles (Stoner-particles). Our
+theoretical tools are the Landau-Lifshitz-Gilbert equation extended as to deal
+with finite temperatures within a Langevine framework. Physical quantities of
+interest are the minimum field amplitudes required for switching and the
+corresponding reversal times of the nanoparticle's magnetic moment. In
+particular, we contrast the cases of static and time-dependent external fields
+and analyze the influence of damping for a uniaxial and a cubic anisotropy.",0802.1740v1
+2008-04-29,Magnetic fields in star formation: from galaxies to stars,"Magnetic fields are important at every scale in the star formation process:
+from the dynamics of the ISM in galaxies, to the collapse of turbulent
+molecular clouds to form stars and in the fragmentation of individual star
+forming cores. The recent development of a robust algorithm for MHD in the
+Smoothed Particle Hydrodynamics method has enabled us to perform simulations of
+star formation including magnetic fields at each of these scales. This paper
+focusses on three questions in particular: What is the effect of magnetic
+fields on fragmentation in star forming cores? How do magnetic fields affect
+the collapse of turbulent molecular clouds to form stars? and: What effect do
+magnetic fields have on the dynamics of the interstellar medium?",0804.4647v1
+2008-06-28,Theory of spin magnetohydrodynamics,"We develop a phenomenological hydrodynamic theory of coherent magnetic
+precession coupled to electric currents. Exchange interaction between electron
+spin and collective magnetic texture produces two reciprocal effects:
+spin-transfer torque on the magnetic order parameter and the Berry-phase gauge
+field experienced by the itinerant electrons. The dissipative processes are
+governed by three coefficients: the ohmic resistance, Gilbert damping of the
+magnetization, and the ""beta coefficient"" describing viscous coupling between
+magnetic dynamics and electric current, which stems from spin mistracking of
+the magnetic order. We develop general magnetohydrodynamic equations and
+discuss the net dissipation produced by the coupled dynamics. The latter in
+particular allows us to determine a lower bound on the magnetic-texture
+resistivity.",0806.4656v2
+2008-10-08,Self-Similar Solution of Hot Accretion Flows with Ordered Magnetic Field and Outflow,"Observations and numerical magnetohydrodynamic (MHD) simulations indicate the
+existence of outflows and ordered large-scale magnetic fields in the inner
+region of hot accretion flows. In this paper we present the self-similar
+solutions for advection-dominated accretion flows (ADAFs) with outflows and
+ordered magnetic fields. Stimulated by numerical simulations, we assume that
+the magnetic field has a strong toroidal component and a vertical component in
+addition to a stochastic component. We obtain the self-similar solutions to the
+equations describing the magnetized ADAFs, taking into account the dynamical
+effects of the outflow. We compare the results with the canonical ADAFs and
+find that the dynamical properties of ADAFs such as radial velocity, angular
+velocity and temperature can be significantly changed in the presence of
+ordered magnetic fields and outflows. The stronger the magnetic field is, the
+lower the temperature of the accretion flow will be, and the faster the flow
+rotates. The relevance to observations is briefly discussed.",0810.1341v1
+2009-06-04,Thermoelectric spin transfer in textured magnets,"We study charge and energy transport in a quasi-1D magnetic wire in the
+presence of magnetic textures. The energy flows can be expressed in a fashion
+similar to charge currents, leading to new energy-current induced spin torques.
+In analogy to charge currents, we can identify two reciprocal effects:
+spin-transfer torque on the magnetic order parameter induced by energy current
+and the Berry-phase gauge field induced energy flow. In addition, we
+phenomenologically introduce new $\beta-$like viscous coupling between magnetic
+dynamics and energy current into the LLG equation, which originates from spin
+mistracking of the magnetic order. We conclude that the new viscous term should
+be important for the thermally induced domain wall motion. We study the
+interplay between charge and energy currents and find that many of the effects
+of texture motion on the charge currents can be replicated with respect to
+energy currents. For example, the moving texture can lead to energy flows which
+is an analogue of the electromotive force in case of charge currents. We
+suggest a realization of cooling effect by magnetic texture dynamics.",0906.1002v2
+2009-07-03,Compaction dynamics of a magnetized powder,"We have investigated experimentally the influence of a magnetic interaction
+between the grains on the compaction dynamics of a granular pile submitted to a
+series of taps. The granular material used to perform this study is a mixture
+of metallic and glass grains. The packing is immersed in an homogeneous
+external magnetic field. The magnetic field induces an interaction between the
+metallic grains that constitutes the tunable cohesion. The compaction
+characteristic time and the asymptotic packing fraction have been measured as a
+function of the Bond number which is the ratio between the cohesive magnetic
+force and the grain weight. These measurements have been performed for
+different fractions of metallic beads in the pile. When the pile is only made
+of metallic grains, the characteristic compaction time increases as the square
+root of the Bond number. While the asymptotic packing fraction decreases as the
+inverse of the Bond number. For mixtures, when the fraction of magnetized
+grains in the pile is increased, the characteristic time increases while the
+asymptotic packing fraction decreases. A simple mesoscopic model based on the
+formation of granular chains along the magnetic field direction is proposed to
+explain the observed macroscopic properties of the packings.",0907.0646v1
+2009-07-28,Global galactic dynamo driven by cosmic-rays and exploding magnetized stars,"We report first results of first global galactic-scale CR-MHD simulations of
+cosmic-ray-driven dynamo. We investigate the dynamics of magnetized
+interstellar medium (ISM), which is dynamically coupled with the cosmic-ray
+(CR) gas. We assume that exploding stars deposit small-scale, randomly
+oriented, dipolar magnetic fields into the differentially rotating ISM,
+together with a portion of cosmic rays, accelerated in supernova shocks. We
+conduct numerical simulations with the aid of a new parallel MHD code PIERNIK.
+We find that the initial magnetization of galactic disks by exploding
+magnetized stars forms a favourable conditions for the cosmic-ray-driven
+dynamo. We demonstrate that dipolar magnetic fields supplied on small
+SN-remnant scales, can be amplified exponentially, by the CR-driven dynamo, to
+the present equipartition values, and transformed simultaneously to large
+galactic-scales. The resulting magnetic field structure in an evolved galaxy
+appears spiral in the face-on view and reveals the so called X-shaped structure
+in the edge-on view.",0907.4891v2
+2009-10-08,Morphology and Dynamics of the Low Solar Chromosphere,"The Interferometric Bidimensional Spectrometer (IBIS) installed at the Dunn
+Solar Telescope of the NSO/SP is used to investigate the morphology and
+dynamics of the lower chromosphere and the virtually non-magnetic fluctosphere
+below. The study addresses in particular the structure of magnetic elements
+that extend into these layers. We choose different quiet Sun regions in and
+outside coronal holes. In inter-network regions with no significant magnetic
+flux contributions above the detection limit of IBIS, we find intensity
+structures with the characteristics of a shock wave pattern. The magnetic flux
+elements in the network are long lived and seem to resemble the spatially
+extended counterparts to the underlying photospheric magnetic elements. We
+suggest a modification to common methods to derive the line-of-sight magnetic
+field strength and explain some of the difficulties in deriving the magnetic
+field vector from observations of the fluctosphere.",0910.1381v1
+2009-12-17,Morphology and dynamics of photospheric and chromospheric magnetic fields,"We use joint observations obtained with the Hinode space observatory and the
+Interferometric Bidimensional Spectrometer (IBIS) installed at the DST of the
+NSO/SP to investigate the morphology and dynamics of (a) non-magnetic and (b)
+magnetic regions in the fluctosphere. In inter-network regions with no
+significant magnetic flux contributions above the detection limit of IBIS, we
+find intensity structures with similar characteristics as those seen in
+numerical simulations by Wedemeyer-B\""ohm (2008). The magnetic flux elements in
+the network are stable and seem to resemble the spatially extended counterparts
+to the underlying photospheric magnetic elements. We will explain some of the
+difficulties in deriving the magnetic field vector from observations of the
+fluctosphere.",0912.3285v1
+2010-03-30,Dynamics of braided coronal loops II: Cascade to multiple small-scale reconnection events,"Aims: Our aim is to investigate the resistive relaxation of a magnetic loop
+that contains braided magnetic flux but no net current or helicity. The loop is
+subject to line-tied boundary conditions. We investigate the dynamical
+processes that occur during this relaxation, in particular the magnetic
+reconnection that occurs, and discuss the nature of the final equilibrium.
+Methods: The three-dimensional evolution of a braided magnetic field is
+followed in a series of resistive MHD simulations. Results: It is found that,
+following an instability within the loop, a myriad of thin current layers
+forms, via a cascade-like process. This cascade becomes more developed and
+continues for a longer period of time for higher magnetic Reynolds number.
+During the cascade, magnetic flux is reconnected multiple times, with the level
+of this `multiple reconnection' positively correlated with the magnetic
+Reynolds number. Eventually the system evolves into a state with no more
+small-scale current layers. This final state is found to approximate a
+non-linear force-free field consisting of two flux tubes of oppositely-signed
+twist embedded in a uniform background field.",1003.5784v2
+2010-04-13,Incommensurate magnetic order and dynamics induced by spinless impurities in YBa$_2$Cu$_3$O$_{6.6}$,"We report an inelastic-neutron-scattering and muon-spin-relaxation study of
+the effect of 2% spinless (Zn) impurities on the magnetic order and dynamics of
+YBa$_2$Cu$_3$O$_{6.6}$, an underdoped high-temperature superconductor that
+exhibits a prominent spin-pseudogap in its normal state. Zn substitution
+induces static magnetic order at low temperatures and triggers a large-scale
+spectral-weight redistribution from the magnetic resonant mode at 38 meV into
+uniaxial, incommensurate spin excitations with energies well below the
+spin-pseudogap. These observations indicate a competition between
+incommensurate magnetic order and superconductivity close to a quantum critical
+point. Comparison to prior data on La$_{2-x}$Sr$_x$CuO$_{4}$ suggests that this
+behavior is universal for the layered copper oxides and analogous to
+impurity-induced magnetic order in one-dimensional quantum magnets.",1004.2139v1
+2010-10-22,Thermally activated magnetization reversal in monoatomic magnetic chains on surfaces studied by classical atomistic spin-dynamics simulations,"We analyze the spontaneous magnetization reversal of supported monoatomic
+chains of finite length due to thermal fluctuations via atomistic spin-dynamics
+simulations. Our approach is based on the integration of the Landau-Lifshitz
+equation of motion of a classical spin Hamiltonian at the presence of
+stochastic forces. The associated magnetization lifetime is found to obey an
+Arrhenius law with an activation barrier equal to the domain wall energy in the
+chain. For chains longer than one domain-wall width, the reversal is initiated
+by nucleation of a reversed magnetization domain primarily at the chain edge
+followed by a subsequent propagation of the domain wall to the other edge in a
+random-walk fashion. This results in a linear dependence of the lifetime on the
+chain length, if the magnetization correlation length is not exceeded. We
+studied chains of uniaxial and tri-axial anisotropy and found that a tri-axial
+anisotropy leads to a reduction of the magnetization lifetime due to a higher
+reversal attempt rate, even though the activation barrier is not changed.",1010.4730v2
+2010-11-04,Probing the magnetic ground state of the molecular Dysprosium triangle,"We present zero field muon spin lattice relaxation measurements of a
+Dysprosium triangle molecular magnet. The local magnetic fields sensed by the
+implanted muons indicate the coexistence of static and dynamic internal
+magnetic fields below $T^* ~35$ K. Bulk magnetization and heat capacity
+measurements show no indication of magnetic ordering below this temperature. We
+attribute the static fields to the slow relaxation of the magnetization in the
+ground state of Dy3. The fluctuation time of the dynamic part of the field is
+estimated to be ~0.55 $\mu$s at low temperatures",1011.1164v1
+2011-07-27,The effects of plasma beta and anisotropy instabilities on the dynamics of reconnecting magnetic fields in the heliosheath,"The plasma {\beta} (the ratio of the plasma pressure to the magnetic
+pressure) of a system can have a large effect on its dynamics as high {\beta}
+enhances the effects of pressure anisotropies. We investigate the effects of
+{\beta} in a system of stacked current sheets that break up into magnetic
+islands due to magnetic reconnection. We find significant differences between
+{\beta} < 1 and {\beta} > 1. At low {\beta} growing magnetic islands are
+modestly elongated and become round as contraction releases magnetic stress and
+reduces magnetic energy. At high {\beta} the increase of the parallel pressure
+in contracting islands causes saturation of modestly elongated islands as
+island cores approach the marginal firehose condition. Only highly elongated
+islands reach finite size. The kinking associated with the Weibel and firehose
+instabilities prevents full contraction of these islands, leading to a final
+state of highly elongated islands in which further reconnection is suppressed.
+The results are directly relevant to reconnection in the sectored region of the
+heliosheath and possibly to saturation mechanisms of the magnetorotational
+instability in accretion flows.",1107.5558v2
+2011-11-14,Efficiency of internal shocks in magnetized relativistic jets,"We study the dynamic and radiative efficiency of conversion of
+kinetic-to-thermal/magnetic energy by internal shocks in relativistic
+magnetized outflows. A parameter study of a large number of collisions of
+cylindrical shells is performed. We explore how, while keeping the total flow
+luminosity constant, the variable fluid magnetization influences the efficiency
+and find that the interaction of shells in a mildly magnetized jet yields
+higher dynamic, but lower radiative efficiency than in a non-magnetized flow. A
+multi-wavelength radiative signature of different shell magnetization is
+computed assuming that relativistic particles are accelerated at internal
+shocks.",1111.3170v2
+2011-12-11,Spin-polarized current effect on antiferromagnet magnetization in a ferromagnet - antiferromagnet nanojunction: Theory and simulation,"Spin-polarized current effect is studied on the static and dynamic
+magnetization of the antiferromagnet in a ferromagnet - antiferromagnet
+nanojunction. The macrospin approximation is generalized to antiferromagnets.
+Canted antiferromagnetic configuration and resulting magnetic moment are
+induced by an external magnetic field. The resonance frequency and damping are
+calculated, as well as the threshold current density corresponding to
+instability appearance. A possibility is shown of generating low-damping
+magnetization oscillations in terahertz range. The fluctuation effect is
+discussed on the canted antiferromagnetic configuration. Numerical simulation
+is carried out of the magnetization dynamics of the antiferromagnetic layer in
+the nanojunction with spin-polarized current. Outside the instability range,
+the simulation results coincide completely with analytical calculations using
+linear approximation. In the instability range, undamped oscillations occur of
+the longitudinal and transverse magnetization components.",1112.2362v1
+2012-02-23,Radiation effects in a muon collider ring and dipole magnet protection,"The requirements and operating conditions for a Muon Collider Storage Ring
+(MCSR) pose significant challenges to superconducting magnets. The dipole
+magnets should provide a high magnetic field to reduce the ring circumference
+and thus maximize the number of muon collisions during their lifetime. One
+third of the beam energy is continuously deposited along the lattice by the
+decay electrons at the rate of 0.5 kW/m for a 1.5-TeV c.o.m. and a luminosity
+of 1034 cm-2s-1. Unlike dipoles in proton machines, the MCSR dipoles should
+allow this dynamic heat load to escape the magnet helium volume in the
+horizontal plane, predominantly towards the ring center. This paper presents
+the analysis and comparison of radiation effects in MCSR based on two dipole
+magnets designs. Tungsten masks in the interconnect regions are used in both
+cases to mitigate the unprecedented dynamic heat deposition and radiation in
+the magnet coils.",1202.5333v1
+2012-03-14,Turbulent Magnetic Field Amplification from Spiral SASI Modes: Implications for Core-Collapse Supernovae and Proto-Neutron Star Magnetization,"We extend our investigation of magnetic field evolution in three-dimensional
+flows driven by the stationary accretion shock instability (SASI) with a suite
+of higher-resolution idealized models of the post-bounce core-collapse
+supernova environment. Our magnetohydrodynamic simulations vary in initial
+magnetic field strength, rotation rate, and grid resolution. Vigorous
+SASI-driven turbulence inside the shock amplifies magnetic fields
+exponentially; but while the amplified fields reduce the kinetic energy of
+small-scale flows, they do not seem to affect the global shock dynamics. The
+growth rate and final magnitude of the magnetic energy are very sensitive to
+grid resolution, and both are underestimated by the simulations. Nevertheless
+our simulations suggest that neutron star magnetic fields exceeding $10^{14}$ G
+can result from dynamics driven by the SASI, \emph{even for non-rotating
+progenitors}.",1203.3108v1
+2012-09-19,From Weakly to Strongly Magnetized Isotropic MHD Turbulence,"High Reynolds number isotropic magneto-hydro-dynamic turbulence in the
+presence of large scale magnetic fields is investigated as a function of the
+magnetic field strength. For a variety of flow configurations the energy
+dissipation rate \epsilon, follows the Kolmogorov scaling \epsilon ~ U^3/L even
+when the large scale magnetic field energy is twenty times larger than the
+kinetic. Further increase of the magnetic energy showed a transition to the
+\epsilon ~ U^2 B / L scaling implying that magnetic shear becomes more
+efficient at this point at cascading the energy than the velocity fluctuations.
+Strongly helical configurations form helicity condensates that deviate from
+these scalings. Weak turbulence scaling was absent from the investigation.
+Finally, the magnetic energy spectra showed support for the Kolmogorov spectrum
+k^{-5/3} while kinetic energy spectra are closer to the Iroshnikov-Kraichnan
+spectrum k^{-3/2}.",1209.4225v1
+2013-06-27,Current Sheets Formation in Tangled Coronal Magnetic Fields,"We investigate the dynamical evolution of magnetic fields in closed regions
+of solar and stellar coronae. To understand under which conditions current
+sheets form, we examine dissipative and ideal reduced magnetohydrodynamic
+models in cartesian geometry, where two magnetic field components are present:
+the strong guide field $B_0$, extended along the axial direction, and the
+dynamical orthogonal field $\mathbf{b}$. Magnetic field lines thread the system
+along the axial direction, that spans the length $L$, and are line-tied at the
+top and bottom plates. The magnetic field $b$ initially has only large scales,
+with its gradient (current) length-scale of order $\ell_b$. We identify the
+magnetic intensity threshold $b/B_0 \sim \ell_b/L$. For values of $b$ below
+this threshold, field-line tension inhibits the formation of current sheets,
+while above the threshold they form quickly on fast ideal timescales. In the
+ideal case, above the magnetic threshold, we show that current sheets thickness
+decreases in time until it becomes smaller than the grid resolution, with the
+analyticity strip width $\delta$ decreasing at least exponentially, after which
+the simulations become under-resolved.",1306.6634v1
+2013-08-08,Domain wall tilting in the presence of the Dzyaloshinskii-Moriya interaction in out-of-plane magnetized magnetic nanotracks,"We show that the Dzyaloshinskii-Moriya interaction (DMI) can lead to a
+tilting of the domain wall (DW) surface in perpendicularly magnetized magnetic
+nanotracks when DW dynamics is driven by an easy axis magnetic field or a spin
+polarized current. The DW tilting affects the DW dynamics for large DMI and the
+tilting relaxation time can be very large as it scales with the square of the
+track width. The results are well explained by an analytical model based on a
+Lagrangian approach where the DMI and the DW tilting are included. We propose a
+simple way to estimate the DMI in a magnetic multilayers by measuring the
+dependence of the DW tilt angle on a transverse static magnetic field. Our
+results shed light on the current induced DW tilting observed recently in Co/Ni
+multilayers with inversion asymmetry, and further support the presence of DMI
+in these systems.",1308.1824v1
+2013-10-18,Ultrafast thermally induced magnetic switching in synthetic ferrimagnets,"Synthetic ferrimagnets are composite magnetic structures formed from two or
+more anti- ferromagnetically coupled magnetic sublattices with different
+magnetic moments. Here we report on atomistic spin simulations of the
+laser-induced magnetization dynamics on such synthetic ferrimag- nets, and
+demonstrate that the application of ultrashort laser pulses leads to
+sub-picoscond magnetization dynamics and all-optical switching in a similar
+manner as in ferrimagnetic alloys. Moreover, we present the essential material
+properties for successful laser-induced switching, demonstrating the
+feasibility of using a synthetic ferrimagnet as a high density magnetic storage
+element without the need of a write field.",1310.5170v2
+2014-03-24,Magnetic structure and dynamics of a strongly one-dimensional cobalt$^{II}$ metal-organic framework,"We investigate the magnetism of the
+Co$^{II}_4$(OH)$_2$(C$_1$$_0$H$_1$$_6$O$_4$)$_3$ metal-organic framework which
+displays complex inorganic chains separated from each other by distances of 1
+to 2 nm, and which orders at ~5.4 K. The zero-field magnetic structure is
+determined using neutron powder diffraction: it is mainly antiferromagnetic but
+posseses a ferromagnetic component along the $\textbf{c}$-axis. This magnetic
+structure persists in presence of a magnetic field. Ac susceptibility
+measurements confirm the existence of a single thermally activated regime over
+7 decades in frequency ($E/k_B\approx64 K$) whereas time-dependent relaxation
+of the magnetization after saturation in an external field leads to a two times
+smaller energy barrier. These experiments probe the slow dynamics of domain
+walls within the chains: we propose that the ac measurements are sensitive to
+the motion of existing domain walls within the chains, while the magnetization
+measurements are governed by the creation of domain walls.",1403.5931v1
+2014-12-28,Tunable Transient Decay Times in Nonlinear Systems: Application to Magnetic Precession,"The dynamical motion of the magnetization plays a key role in the properties
+of magnetic materials. If the magnetization is initially away from the
+equilibrium direction in a magnetic nanoparticle, it will precess at a natural
+frequency and, with some damping present, will decay to the equilibrium
+position in a short lifetime. Here we investigate a simple but important
+situation where a magnetic nanoparticle is driven non-resonantly by an
+oscillating magnetic field, not at the natural frequency. We find a surprising
+result that the lifetime of the transient motion is strongly tunable, by
+factors of over 10,000, by varying the amplitude of the driving field.",1412.8224v3
+2015-09-17,Antiferromagnetic spintronics,"Antiferromagnetic materials are magnetic inside, however, the direction of
+their ordered microscopic moments alternates between individual atomic sites.
+The resulting zero net magnetic moment makes magnetism in antiferromagnets
+invisible on the outside. It also implies that if information was stored in
+antiferromagnetic moments it would be insensitive to disturbing external
+magnetic fields, and the antiferromagnetic element would not affect
+magnetically its neighbors no matter how densely the elements were arranged in
+a device. The intrinsic high frequencies of antiferromagnetic dynamics
+represent another property that makes antiferromagnets distinct from
+ferromagnets. The outstanding question is how to efficiently manipulate and
+detect the magnetic state of an antiferromagnet. In this article we give an
+overview of recent works addressing this question. We also review studies
+looking at merits of antiferromagnetic spintronics from a more general
+perspective of spin-ransport, magnetization dynamics, and materials research,
+and give a brief outlook of future research and applications of
+antiferromagnetic spintronics.",1509.05296v1
+2015-11-02,A practical approach to extract symplectic transfer maps numerically for arbitrary magnetic elements,"We introduce a practical approach to extract the symplectic transfer maps for
+arbitrary magnetic beam-line elements. Beam motion in particle accelerators
+depends on linear and nonlinear magnetic fields of the beam-line elements.
+These elements are usually modeled as magnetic multipoles with constant field
+strengths in the longitudinal direction (i.e., hard-edge model) in accelerator
+design and modeling codes. For magnets with complicated structures such as
+insertion devices or fields with significant longitudinal variation effects,
+the simplified models may not be sufficient to char- acterize beam dynamics
+behaviors accurately. A numerical approach has been developed to extract
+symplectic transfer maps from particle trajectory tracking simulation that uses
+magnetic field data provided by three-dimensional magnetic field modeling codes
+or experimental measurements. The extracted transfer maps can be used in linear
+optics design and nonlinear dynamics optimization to achieve more realistic
+results.",1511.00710v1
+2015-12-01,Epitaxial patterning of nanometer-thick Y3Fe5O12 films with low magnetic damping,"Magnetic insulators such as yttrium iron garnet, Y3Fe5O12, with extremely low
+magnetic damping have opened the door for low power spin-orbitronics due to
+their low energy dissipation and efficient spin current generation and
+transmission. We demonstrate reliable and efficient epitaxial growth and
+nanopatterning of Y3Fe5O12 thin-film based nanostructures on insulating
+Gd3Ga5O12 substrates. In particular, our fabrication process is compatible with
+conventional sputtering and liftoff, and does not require aggressive ion
+milling which may be detrimental to the oxide thin films. Structural and
+magnetic properties indicate good qualities, in particular low magnetic damping
+of both films and patterned structures. The dynamic magnetic properties of the
+nanostructures are systematically investigated as a function of the lateral
+dimension. By comparing to ferromagnetic nanowire structures, a distinct edge
+mode in addition to the main mode is identified by both experiments and
+simulations, which also exhbits cross-over with the main mode upon varying the
+width of the wires. The non-linear evolution of dynamic modes over
+nanostructural dimensions highlights the important role of size confinement to
+their material properties in magnetic devices where Y3Fe5O12 nanostructures
+serve as the key functional component.",1512.00286v1
+2016-04-29,Current induced magnetization dynamics and magnetization switching in superconducting ferromagnetic hybrid (F$|$S$|$F) structures,"We investigate the current induced magnetization dynamics and magnetization
+switching in an unconventional p-wave superconductor sandwiched between two
+misaligned ferromagnetic layers by numerically solving Landau-Lifshitz-Gilbert
+equation modified with current induced Slonczewski's spin torque term. A
+modified form of Ginzburg-Landau free energy functional has been used for this
+purpose. We demonstrated the possibility of current induced magnetization
+switching in the spin-triplet ferromagnetic superconducting hybrid structures
+with strong easy axis anisotropy and the condition for magnetization reversal.
+The switching time for such arrangement is calculated and is found to be highly
+dependent on the magnetic configuration along with the biasing current. This
+study would be useful in designing practical superconducting-spintronic
+devices.",1604.08704v3
+2017-02-12,Electric-field-driven domain wall dynamics in perpendicularly magnetized multilayers,"We report on reversible electric-field-driven magnetic domain wall motion in
+a Cu/Ni multilayer on a ferroelectric BaTiO$_3$ substrate. In our
+heterostructure, strain-coupling to ferroelastic domains with in-plane and
+perpendicular polarization in the BaTiO$_3$ substrate causes the formation of
+domains with perpendicular and in-plane magnetic anisotropy, respectively, in
+the Cu/Ni multilayer. Walls that separate magnetic domains are elastically
+pinned onto ferroelectric domain walls. Using magneto-optical Kerr effect
+microscopy, we demonstrate that out-of-plane electric field pulses across the
+BaTiO$_3$ substrate move the magnetic and ferroelectric domain walls in unison.
+Our experiments indicate an exponential increase of domain wall velocity with
+electric field strength and opposite domain wall motion for positive and
+negative field pulses. Magnetic fields do not affect the velocity of magnetic
+domain walls, but independently tailor their internal spin structure, causing a
+change in domain wall dynamics at high velocities.",1702.03553v1
+2017-05-02,Self-similar structure of ultra-relativistic magnetized termination shocks and the role of reconnection in long-lasting GRB ouflows,"We consider the double-shock structure of ultra-relativistic flows produced
+by the interaction of magnetized wind with magnetized external medium. The
+contact discontinuity (CD) is a special point in the flow - density, kinetic
+pressure and magnetic field experience a jump or are non-analytic on the CD. To
+connect dynamically the outside region (the forward shock flow) with the inside
+region (the reverse shock flow) requires resolving flow singularities at the
+contact discontinuity. On the CD the pressure is communicated exclusively by
+the magnetic field on both sides - the CD becomes an Alfven tangential
+discontinuity. Thus, the dynamic amplification of the magnetic field leads to a
+formation of a narrow magnetosheath. We discussed a possibility that particles
+emitting early $X$-ray afterglows, as well as Fermi GeV photons, are
+accelerated via magnetic reconnection processes in the post-reverse shock
+region, and in the magnetosheath in particular.",1705.01014v1
+2017-06-10,Mapping the magnonic landscape in patterned magnetic structures,"We report the development of a hybrid numerical / analytical model capable of
+mapping the spatially-varying distributions of the local ferromagnetic
+resonance (FMR) frequency and dynamic magnetic susceptibility in a wide class
+of patterned and compositionally modulated magnetic structures. Starting from
+the numerically simulated static micromagnetic state, the magnetization is
+deliberately deflected orthogonally to its equilibrium orientation, and the
+magnetic fields generated in response to this deflection are evaluated using
+micromagnetic software. This allows us to calculate the elements of the
+effective demagnetizing tensor, which are then used within a linear analytical
+formalism to map the local FMR frequency and dynamic magnetic susceptibility.
+To illustrate the typical results that one can obtain using this model, we
+analyze three micromagnetic systems boasting non-uniformity in either one or
+two dimensions, and successfully explain the spin-wave emission observed in
+each case, demonstrating the ubiquitous nature of the Schl\""omann excitation
+mechanism underpinning the observations. Finally, the developed model of local
+FMR frequency could be used to explain how spin waves could be confined and
+steered using magnetic non-uniformities of various origins, rendering it a
+powerful tool for the mapping of the graded magnonic index in magnonics.",1706.03212v1
+2017-06-27,How to form a millisecond magnetar? Magnetic field amplification in protoneutron stars,"Extremely strong magnetic fields of the order of $10^{15}\,{\rm G}$ are
+required to explain the properties of magnetars, the most magnetic neutron
+stars. Such a strong magnetic field is expected to play an important role for
+the dynamics of core-collapse supernovae, and in the presence of rapid rotation
+may power superluminous supernovae and hypernovae associated to long gamma-ray
+bursts. The origin of these strong magnetic fields remains, however, obscure
+and most likely requires an amplification over many orders of magnitude in the
+protoneutron star. One of the most promising agents is the magnetorotational
+instability (MRI), which can in principle amplify exponentially fast a weak
+initial magnetic field to a dynamically relevant strength. We describe our
+current understanding of the MRI in protoneutron stars and show recent results
+on its dependence on physical conditions specific to protoneutron stars such as
+neutrino radiation, strong buoyancy effects and large magnetic Prandtl number.",1706.08733v1
+2017-10-03,Orbital Effect of the Magnetic Field in Dynamical Mean-Field Theory,"The availability of large magnetic fields at international facilities and of
+simulated magnetic fields that can reach the flux-quantum-per-unit-area level
+in cold atoms, calls for systematic studies of orbital effects of the magnetic
+field on the self-energy of interacting systems. Here we demonstrate
+theoretically that orbital effects of magnetic fields can be treated within
+single-site dynamical mean-field theory with a translationally invariant
+quantum impurity problem. As an example, we study the one-band Hubbard model on
+the square lattice using iterated perturbation theory as an impurity solver. We
+recover the expected quantum oscillations in the scattering rate and we show
+that the magnetic fields allow the interaction-induced effective mass to be
+measured through the single-particle density of states accessible in tunneling
+experiments. The orbital effect of magnetic fields on scattering becomes
+particularly important in the Hofstadter butterfly regime.",1710.01396v1
+2018-02-12,Dynamics and morphology of chiral magnetic bubbles in perpendicularly magnetized ultra-thin films,"We study bubble domain wall dynamics using micromagnetic simulations in
+perpendicularly magnetized ultra-thin films with disorder and
+Dzyaloshinskii-Moriya interaction. Disorder is incorporated into the material
+as grains with randomly distributed sizes and varying exchange constant at the
+edges. As expected, magnetic bubbles expand asymmetrically along the axis of
+the in-plane field under the simultaneous application of out-of-plane and
+in-plane fields. Remarkably, the shape of the bubble has a ripple-like part
+which causes a kink-like (steep decrease) feature in the velocity versus
+in-plane field curve. We show that these ripples originate due to the
+nucleation and interaction of vertical Bloch lines. Furthermore, we show that
+the Dzyaloshinskii-Moriya interaction field is not constant but rather depends
+on the in-plane field. We also extend the collective coordinate model for
+domain wall motion to a magnetic bubble and compare it with the results of
+micromagnetic simulations.",1802.04215v1
+2018-07-16,Magnetic freezing transition in a CoO/Permalloy bilayer revealed by transverse ac susceptibility,"We utilize variable-temperature, variable-frequency magneto-optical
+transverse magnetic susceptibility technique to study the static and dynamical
+magnetic properties of a thin-film CoO/Permalloy bilayer. Our measurements
+demonstrate that in the studied system, the directional asymmetry of the
+hysteresis loop is associated mainly with the difference in the reversal
+mechanisms between the two reversed states of magnetization stabilized by the
+exchange-induced uniaxial anisotropy. The latter is found to be much larger
+than the exchange-induced unidirectional anisotropy of the ferromagnet. We also
+observe an abrupt variation of the frequency-dependent imaginary part of ac
+susceptibility near the exchange bias blocking temperature, consistent with the
+magnetic freezing transition inferred from the previous time-domain studies of
+magnetic aging in similar systems. The developed measurement approach enables
+precise characterization of the dynamical and static characteristics of
+thin-film magnetic heterostructures that can find applications in
+reconfigurable magnonic and neuromorphic circuits.",1807.05990v2
+2018-11-02,Large-scale Model of the Axisymmetric Dynamo with Feedback Effects,"A dynamo model is presented, based on a previously introduced kinematic
+model, in which the reaction of the magnetic field on the mass flow through the
+Lorentz force is included. Given the base mass flow corresponding to the case
+with no magnetic field, and assuming that the modification of this flow due to
+the Lorentz force can be treated as a perturbation, a complete model of the
+large-scale magnetic field dynamics can be obtained. The input needed consists
+in the large-scale meridional and zonal flows, the small-scale magnetic
+diffusivity, and a constant parameter entering the expression of the
+$\alpha$-effect. When applied to a solar-like star, the model shows a realistic
+dynamics of the magnetic field, including cycle duration, consistent field
+amplitudes with the correct parity, progression of the zonal magnetic field
+towards the equator, and motion toward the poles of the radial field at high
+latitudes. Also, the radial and zonal components show a correct phase relation,
+and, at the surface level, the magnetic helicity is predominantly negative in
+the northern hemisphere and positive in the southern hemisphere.",1811.00933v1
+2019-03-26,Nuclear spin assisted quantum tunnelling of magnetic monopoles in spin ice,"Extensive work on single molecule magnets has identified a fundamental mode
+of relaxation arising from the nuclear-spin assisted quantum tunnelling of
+nearly independent and quasi-classical magnetic dipoles. Here we show that
+nuclear-spin assisted quantum tunnelling can also control the dynamics of
+purely emergent excitations: magnetic monopoles in spin ice. Our low
+temperature experiments were conducted on canonical spin ice materials with a
+broad range of nuclear spin values. By measuring the magnetic relaxation, or
+monopole current, we demonstrate strong evidence that dynamical coupling with
+the hyperfine fields bring the electronic spins associated with magnetic
+monopoles to resonance, allowing the monopoles to hop and transport magnetic
+charge. Our result shows how the coupling of electronic spins with nuclear
+spins may be used to control the monopole current. It broadens the relevance of
+the assisted quantum tunnelling mechanism from single molecular spins to
+emergent excitations in a strongly correlated system.",1903.11122v1
+2019-09-04,Two-axis cavity optomechanical torque characterization of magnetic microstructures,"Significant new functionality is reported for torsion mechanical tools aimed
+at full magnetic characterizations of both spin statics and dynamics in micro-
+and nanostructures. Specifically, two orthogonal torque directions are
+monitored and the results co-analyzed to separate magnetic moment and magnetic
+susceptibility contributions to torque, as is desired for characterization of
+anisotropic three-dimensional structures. The approach is demonstrated through
+application to shape and microstructural disorder-induced magnetic anisotropies
+in lithographically patterned permalloy, and will have utility for the
+determination of important magnetic thin-film and multilayer properties
+including interface anisotropy and exchange bias. The results reflect
+remarkable sensitivity of the out-of-plane magnetic torque to the nature of
+small edge domains perpendicular to the applied field direction, and also
+contain tantalizing indications of direct coupling to spin dynamics at the
+frequency of the mechanics.",1909.01949v1
+2020-04-28,"Current-Induced Dynamics of Chiral Magnetic Structures: Creation, Motion, and Applications","Magnetic textures can be manipulated by electric currents via the mechanisms
+of spin-transfer and spin-orbit-torques. We review how these torques can be
+exploited to create chiral magnetic textures in magnets with broken inversion
+symmetries, including domain walls and skyrmions. These chiral textures can
+also be moved by (electric) currents and obey very rich dynamics. For example,
+magnetic domain walls feature the famous Walker breakdown, and magnetic whirls
+are subject to the skyrmion Hall effect, which is rooted in their real-space
+topology. These properties led to a variety of potential novel applications
+which we briefly overview.",2004.13535v2
+2020-05-06,Distinct Ultrafast Electronic and Magnetic Response in M-edge Magnetic Circular Dichroism,"Experimental investigations of ultrafast magnetization dynamics increasingly
+employ resonant magnetic spectroscopy in the ultraviolet spectral range.
+Besides allowing to disentangle the element-specific transient response of
+functional magnetic systems, these techniques also promise to access attosecond
+to few-femtosecond dynamics of spin excitations. Here, we report on a
+systematic study of transient magnetic circular dichroism (MCD) on the
+transition metals Fe, Co and Ni as well as on a FeNi and GdFe alloy and reveal
+a delayed onset between the electronic and magnetic response. Supported by
+\textit{ab-initio} calculations, we attribute our observation to a transient
+energy shift of the absorption and MCD spectra at the corresponding elemental
+resonances due to non-equilibrium changes of electron occupations.",2005.02872v1
+2020-08-19,Field-Induced Magnetic Monopole Plasma in Artificial Spin Ice,"Artificial spin ices (ASIs) are interacting arrays of
+lithographically-defined nanomagnets in which novel frustrated magnetic phases
+can be intentionally designed. A key emergent description of fundamental
+excitations in ASIs is that of magnetic monopoles -- mobile quasiparticles that
+carry an effective magnetic charge. Here we demonstrate that the archetypal
+square ASI lattice can host, in specific regions of its magnetic phase diagram,
+high-density plasma-like regimes of mobile magnetic monopoles. By passively
+""listening"" to spontaneous monopole noise in thermal equilibrium, we reveal
+their intrinsic dynamics and show that monopole kinetics are minimally
+correlated (that is, most diffusive) in the plasma phase. These results open
+the door to on-demand monopole regimes having field-tunable densities and
+dynamic properties, thereby providing a new paradigm for probing the physics of
+effective magnetic charges in synthetic matter.",2008.08635v1
+2020-09-17,Peculiar magnetic dynamics across the in-field transition in Ca3Co2O6,"The discovery of multiple coexisting magnetic phases in a
+crystallographically homogeneous compound Ca$_3$Co$_2$O$_6$ has stimulated an
+ongoing research activity. In recent years the main focus has been on the zero
+field state properties, where exceedingly long time scales have been
+established. In this study we report a detailed investigation of static and
+dynamic properties of Ca$_3$Co$_2$O$_6$ across the magnetic field induced
+transition around 3.5 T. This region has so far been practically neglected
+while we argue that in some aspects it represents a simpler version of the
+transition across the $B = 0$ state. Investigating the frequency dependence of
+the ac susceptibility we reveal that on the high field side ($B > 3.5$ T) the
+response corresponds to a relatively narrow distribution of magnetic clusters.
+The distribution appears very weakly dependent on magnetic field, with an
+associated energy barrier of around 200 K. Below 3.5 T a second contribution
+arises, with much smaller characteristic frequencies and a strong temperature
+and magnetic field dependence. We discuss these findings in the context of
+intra-chain and inter-chain clustering of magnetic moments.",2009.08201v1
+2020-12-06,Properties and dynamics of meron topological spin textures in the two-dimensional magnet CrCl3,"Merons are nontrivial topological spin textures highly relevant for many
+phenomena in solid state physics. Despite their importance, direct observation
+of such vortex quasiparticles is scarce and has been limited to a few complex
+materials. Here we show the emergence of merons and antimerons in recently
+discovered two-dimensional (2D) CrCl3 at zero magnetic field. We show their
+entire evolution from pair creation, their diffusion over metastable domain
+walls, and collision leading to large magnetic monodomains. Both quasiparticles
+are stabilized spontaneously during cooling at regions where in-plane magnetic
+frustration takes place. Their dynamics is determined by the interplay between
+the strong in-plane dipolar interactions and the weak out-of-plane magnetic
+anisotropy stabilising a vortex core within a radius of 8-10 nm. Our results
+push the boundary to what is currently known about non-trivial spin structures
+in 2D magnets and open exciting opportunities to control magnetic domains via
+topological quasiparticles.",2012.03296v2
+2021-07-21,Radical pairs can explain magnetic field and lithium effects on the circadian clock,"Drosophila's circadian clock can be perturbed by magnetic fields, as well as
+by lithium administration. Cryptochromes are critical for the circadian clock.
+Further, the radical pairs in cryptochrome also can explain magnetoreception in
+animals. Based on a simple radical pair mechanism model of the animal magnetic
+compass, we show that both magnetic fields and lithium can influence the spin
+dynamics of the naturally occurring radical pairs and hence modulate the
+circadian clock's rhythms. Using a simple chemical oscillator model for the
+circadian clock, we show that the spin dynamics influence a rate in the
+chemical oscillator model, which translates into a change in the circadian
+period. Our model can reproduce the results of two independent experiments,
+magnetic fields and lithium effects on the circadian clock. Our model predicts
+that stronger magnetic fields would shorten the clock's period. We also predict
+that lithium influences the clock in an isotope-dependent manner. Furthermore,
+our model also predicts that magnetic fields and hyperfine interactions
+modulate oxidative stress. The findings of this work suggest that quantum
+nature and entanglement of radical pairs might play roles in the brain, as
+another piece of evidence in addition to recent results on xenon anesthesia and
+lithium effects on hyperactivity.",2107.10677v1
+2021-09-23,Drift of suspended single-domain nanoparticles in a harmonically oscillating gradient magnetic field,"We study the nonlinear dynamics of single-domain ferromagnetic nanoparticles
+in a viscous liquid induced by a harmonically oscillating gradient magnetic
+field in the absence and presence of a static uniform magnetic field. Under
+some physically reasonable assumptions, we derive a coupled set of stiff
+ordinary differential equations for the magnetization angle and particle
+coordinate describing the rotational and translational motions of
+nanoparticles. Analytical solutions of these equations are determined for
+nanoparticles near and far from the coordinate origin, and their correctness is
+confirmed numerically. We show that if a uniform magnetic field is absent, the
+magnetization angle and particle coordinate of each nanoparticle are periodic
+functions of time. In contrast, the presence of a uniform magnetic field makes
+these functions aperiodic. In this case, we perform a detailed analysis of the
+nanoparticle dynamics and predict the appearance of the drift motion (directed
+transport) of nanoparticles. We calculate both analytically and numerically the
+drift velocity, study its dependence on time and model parameters, analyze the
+physical origin of the drift phenomenon and discuss its potential biomedical
+applications.",2109.11253v1
+2021-11-09,Instability and Turbulent Relaxation in a Stochastic Magnetic Field,"An analysis of instability dynamics in a stochastic magnetic field is
+presented for the tractable case of the resistive interchange. Externally
+prescribed static magnetic perturbations convert the eigenmode problem to a
+stochastic differential equation, which is solved by the method of averaging.
+The dynamics are rendered multi-scale, due to the size disparity between the
+test mode and magnetic perturbations. Maintaining quasi-neutrality at all
+orders requires that small-scale convective cell turbulence be driven by
+disparate scale interaction. The cells in turn produce turbulent mixing of
+vorticity and pressure, which is calculated by fluctuation-dissipation type
+analyses, and are relevant to pump-out phenomena. The development of
+correlation between the ambient magnetic perturbations and the cells is
+demonstrated, showing that turbulence will `lock on' to ambient stochasticity.
+Magnetic perturbations are shown to produce a magnetic braking effect on
+vorticity generation at large scale. Detailed testable predictions are
+presented. The relations of these findings to the results of available
+simulations and recent experiments are discussed.",2111.05396v1
+2022-02-03,Entropic force and real-time dynamics of holographic quarkonium in a magnetic field,"We continue the study of a recently constructed holographic QCD model
+supplemented with magnetic field. We consider the holographic dual of a quark,
+anti-quark pair and investigate its entropy beyond the deconfinement phase
+transition in terms of interquark distance, temperature and magnetic field. We
+obtain a clear magnetic field dependence in the strongly decreasing entropy
+near deconfinement and in the entropy variation for growing interquark
+separation. We uncover various supporting evidences for inverse magnetic
+catalysis. The emergent entropic force is found to become stronger with
+magnetic field, promoting the quarkonium dissociation. We also probe the
+dynamical dissociation of the quarkonium state, finding a faster dissociation
+with magnetic field. At least the static predictions should become amenable to
+a qualitative comparison with future lattice data.",2202.01486v2
+2022-05-02,Relativistic magnetic explosions,"Many explosive astrophysical events, like magnetars' bursts and flares, are
+magnetically driven. We consider dynamics of such magnetic explosions -
+relativistic expansion of highly magnetized and highly magnetically
+over-pressurized clouds. The corresponding dynamics is qualitatively different
+from fluid explosions due to the topological constraint of the conservation of
+the magnetic flux. Using analytical, relativistic MHD as well as force-free
+calculations, we find that the creation of a relativistically expanding,
+causally disconnected flow obeys a threshold condition: it requires
+sufficiently high initial over-pressure and sufficiently quick decrease of the
+pressure in the external medium (the pre-explosion wind). In the subcritical
+case the magnetic cloud just ""puffs-up"" and quietly expands with the pre-flare
+wind. We also find a compact analytical solution to the Prendergast's problem -
+expansion of force-free plasma into vacuum.",2205.00695v1
+2022-06-21,Magnetism in doped infinite-layer NdNiO2 studied by combined density functional theory and dynamical mean-field theory,"The recent observation of superconductivity in infinite-layer nickelates has
+brought intense debate on the established knowledge of unconventional
+superconductivity based on the cuprates. Despite many similarities, the
+nickelates differ from the cuprates in many characteristics, the most notable
+one among which is the magnetism. Instead of a canonical antiferromagnetic Mott
+insulator as the undoped cuprates, from which the superconductivity is
+generally believed to arise upon doping, the undoped nickelates show no sign of
+magnetic ordering in experiments. Through a combined density functional theory,
+dynamical mean-field theory, and model study, we show that although the
+increased energy splitting between O-$p$ orbital and Cu/Ni-$d$ orbital
+($\Delta_{dp}$) results in larger magnetic moment in nickelates, it also leads
+to stronger antiferromagnetism/ferromagnetism competition, and weaker magnetic
+exchange coupling. Meanwhile, the self-doping effect caused by Nd-$d$ orbital
+screens the magnetic moment of Ni. The Janus-faced effect of $\Delta_{dp}$ and
+self-doping effect together give a systematic understanding of magnetic
+behavior in nickelates and explain recent experimental observations.",2206.10094v2
+2023-01-04,Magnetization dynamics with time-dependent spin-density functional theory: significance of exchange-correlation torques,"In spin-density-functional theory (SDFT) for noncollinear magnetic materials,
+the Kohn-Sham system features exchange-correlation (xc) scalar potentials and
+magnetic fields. The significance of the xc magnetic fields is not very well
+explored; in particular, they can give rise to local torques on the
+magnetization, which are absent in standard local and semilocal approximations.
+Exact benchmark solutions for a five-site extended Hubbard lattice at half
+filling and in the presence of spin-orbit coupling are compared with SDFT
+results obtained using orbital-dependent exchange-only approximations. The
+magnetization dynamics following short-pulse excitations is found to be
+reasonably well described in the exchange-only approximation for weak to
+moderate interactions. For stronger interactions and near transitions between
+magnetically ordered and frustrated phases, exchange and correlation torques
+tend to compensate each other and must both be accounted for.",2301.01509v1
+2023-04-12,Micromagnetics simulations and phase transitions of ferromagnetics with Dzyaloshinskii-Moriya interaction,"Magnetic skyrmions widely exist in a diverse range of magnetic systems,
+including chiral magnets with a non-centrosymmetric structure characterized by
+Dzyaloshinkii-Moriya interaction~(DMI). In this study, we propose a generalized
+semi-implicit backward differentiation formula projection method, enabling the
+simulations of the Landau-Lifshitz~(LL) equation in chiral magnets in a typical
+time step-size of $1$ ps, markedly exceeding the limit subjected by existing
+numerical methods of typically $0.1$ ps. Using micromagnetics simulations, we
+show that the LL equation with DMI reveals an intriguing dynamic instability in
+magnetization configurations as the damping varies. Both the isolated
+skyrmionium and skyrmionium clusters can be consequently produced using a
+simple initialization strategy and a specific damping parameter. Assisted by
+the string method, the transition path between skyrmion and skyrmionium, along
+with the escape of a skyrmion from the skyrmion clusters, are then thoroughly
+examined. The numerical methods developed in this work not only provide a
+reliable paradigm to investigate the skyrmion-based textures and their
+transition paths, but also facilitate the understandings for magnetization
+dynamics in complex magnetic systems.",2304.05789v1
+2023-05-25,Energetic perspective on emergent inductance exhibited by magnetic textures in the pinned regime,"Spatially varying magnetic textures can exhibit electric-current-induced
+dynamics as a result of the spin-transfer torque effect. When such a magnetic
+system is electrically driven, an electric field is generated, which is called
+the emergent electric field. In particular, when magnetic-texture dynamics are
+induced under the application of an AC electric current, the emergent electric
+field also appears in an AC manner, notably, with an out-of-phase time profile,
+thus exhibiting inductor behaviour, often called an emergent inductor. Here we
+show that the emergent inductance exhibited by magnetic textures in the pinned
+regime can be explained in terms of the current-induced energy stored in the
+magnetic system. We numerically find that the inductance values defined from
+the emergent electric field and the current-induced magnetization-distortion
+energy, respectively, are in quantitative agreement in the so-called adiabatic
+limit. Our findings indicate that emergent inductors retain the basic concept
+of conventional inductors; that is, the energy is stored under the application
+of electric current.",2305.16123v2
+2023-06-06,Large effective magnetic fields from chiral phonons in rare-earth halides,"Time-reversal symmetry (TRS) is pivotal for materials optical, magnetic,
+topological, and transport properties. Chiral phonons, characterized by atoms
+rotating unidirectionally around their equilibrium positions, generate dynamic
+lattice structures that break TRS. Here we report that coherent chiral phonons,
+driven by circularly polarized terahertz light pulses, can polarize the
+paramagnetic spins in CeF3 like a quasi-static magnetic field on the order of 1
+Tesla. Through time-resolved Faraday rotation and Kerr ellipticity, we found
+the transient magnetization is only excited by pulses resonant with phonons,
+proportional to the angular momentum of the phonons, and growing with magnetic
+susceptibility at cryogenic temperatures, as expected from the spin-phonon
+coupling model. The time-dependent effective magnetic field quantitatively
+agrees with that calculated from phonon dynamics. Our results may open a new
+route to directly investigate mode-specific spin-phonon interaction in
+ultrafast magnetism, energy-efficient spintronics, and non-equilibrium phases
+of matter with broken TRS.",2306.03852v1
+2023-06-12,Correlation of density fluctuation in a magnetized QCD matter near the critical end point,"The dynamical correlation of density fluctuation in quark gluon plasma with a
+critical end point has been investigated within the scope of the
+M\""uller-Israel-Stewart theory in the presence of static ultra-high external
+magnetic field. The dynamic structure factor of the density fluctuation
+exhibits three Lorentzian peaks in absence of external magnetic field- a
+central Rayleigh peak and two Brillouin peaks situated symmetrically on the
+opposite sides of the Rayleigh peak. The spectral structure displays five peaks
+in presence of the magnetic field due to the coupling of the magnetic field
+with the hydrodynamic fields in second-order hydrodynamics. The emergence of
+the extra peaks is due to the asymmetry in the pressure gradient caused by the
+external magnetic field in the system. Interestingly, it is observed that near
+the critical end point, all the Brillouin peaks disappear irrespective of the
+presence or absence of the external magnetic field.",2306.06905v2
+2023-09-06,In-plane dominant anisotropy stochastic magnetic tunnel junction for probabilistic computing: A Fokker-Planck study,"Recently there is considerable interest to realize efficient and low-cost
+true random number generators (RNGs) for practical applications. One important
+way is through the use of bistable magnetic tunnel junctions (MTJs). Here we
+study the magnetization dynamics of an MTJ, with a focus to realize efficient
+random bit generation under the assumption that the orientation dependence of
+the energy of the nanomagnet is described by two perpendicular in-plane
+anisotropies. We find that a high rate of random bit generation is achievable
+away from the pure easy-axis situation by tuning a single parameter $H_z$ so
+that it is either (a) toward a barrierless-like single easy plane situation
+when $H_z$ reduces to zero, or (b) toward a stronger easy plane situation when
+$H_z$ becomes increasingly negative where transitions between low energy states
+are confined in the stronger easy plane that contains the saddle points. We
+find that the MTJs maintain their fast magnetization dynamical characteristics
+even in the presence of a magnetic field. Our findings provide a valuable guide
+to achieving efficient generation of probabilistic bits for applications in
+probabilistic computing.",2309.03056v1
+2023-10-10,Dynamic Terahertz Beamforming Based on Magnetically Switchable Hyperbolic Materials,"In this work, we introduce a concept to enable dynamic beamforming of
+terahertz (THz) wavefronts using applied magnetic fields (B). The proposed
+system exploits the magnetically switchable hyperbolic dispersion of the InSb
+semiconductor. This phenomenology, combined with diffractive surfaces and
+magnetic tilting of scattered fields, allows the design of a metasurface that
+works with either circularly or linearly polarized wavefronts. In particular,
+we demonstrate numerically that the transmitted beam tilting can be manipulated
+with the direction and magnitude of B. Numerical results, obtained through the
+finite element method (FEM), are qualitatively supported by semi-analytical
+results from the generalized dipole theory. Motivated by potential applications
+in future Tera-WiFi active links, a proof of concept is conducted for the
+working frequency f = 300 GHz. The results indicate that the transmitted field
+can be actively tuned to point in five different directions with beamforming of
+45{\deg}, depending on the magnitude and direction of B. In addition to
+magnetic beamforming, we also demonstrate that our proposal exhibits magnetic
+circular dichroism (MCD), which can also find applications in magnetically
+tunable THz isolators for one-way transmission/reflection.",2310.06529v1
+2006-06-26,Dynamical PN Evolution with Magnetic Fields,"Hydrodynamical simulations played an important role in understanding the
+dynamics and shaping of planetary nebulae in the past century. However,
+hydrodynamical simulations were just a first order approach. The new millennium
+arrived with the generalized understanding that the effects of magnetic fields
+were necessary to study the dynamics of planetary nebulae. Thus, B-fields
+introduced a whole new number of physical possibilities for the modeling. In
+this paper, we review observational works done in the last 5 years and several
+works on magnetohydrodynamics about proto-planetary nebulae, since all the
+effort has been focused on that stage, and discuss different scenarios for the
+origin of magnetized winds, and the relation binary-bipolararity.",0606632v1
+1998-10-21,Large scale instabilities in two-dimensional magnetohydrodynamics,"The stability of a sheared magnetic field is analyzed in two-dimensional
+magnetohydrodynamics with resistive and viscous dissipation. Using a
+multiple-scale analysis, it is shown that at large enough Reynolds numbers the
+basic state describing a motionless fluid and a layered magnetic field, becomes
+unstable with respect to large scale perturbations. The exact expressions for
+eddy-viscosity and eddy-resistivity are derived in the nearby of the critical
+point where the instability sets in. In this marginally unstable case the
+nonlinear phase of perturbation growth obeys to a Cahn-Hilliard-like dynamics
+characterized by coalescence of magnetic islands leading to a final new
+equilibrium state. High resolution numerical simulations confirm quantitatively
+the predictions of multiscale analysis.",9810026v1
+1996-01-11,Universality and Scaling in Short-time Critical Dynamics,"Numerically we simulate the short-time behaviour of the critical dynamics for
+the two dimensional Ising model and Potts model with an initial state of very
+high temperature and small magnetization. Critical initial increase of the
+magnetization is observed. The new dynamic critical exponent $\theta$ as well
+as the exponents $z$ and $2\beta/\nu$ are determined from the power law
+behaviour of the magnetization, auto-correlation and the second moment.
+Furthermore the calculation has been carried out with both Heat-bath and
+Metropolis algorithms. All the results are consistent and therefore
+universality and scaling are confirmed.",9601037v1
+2001-05-29,Dynamics of a tunneling magnetic impurity: Kondo effect induced incoherence,"We study how the formation of the Kondo compensation cloud influences the
+dynamical properties of a magnetic impurity that tunnels between two positions
+in a metal. The Kondo effect dynamically generates a strong tunneling
+impurity-conduction electron coupling, changes the temperature dependence of
+the tunneling rate, and may ultimately result in the destruction of the
+coherent motion of the particle at zero temperature. We find an interesting
+two-channel Kondo fixed point as well for a vanishing overlap between the
+electronic states that screen the magnetic impurity. We propose a number of
+systems where the predicted features could be observed.",0105548v1
+2002-12-10,Nonlinear Dynamics of a Bose-Einstein Condensate in a Magnetic Waveguide,"We have studied the internal and external dynamics of a Bose-Einstein
+condensate in an anharmonic magnetic waveguide. An oscillating condensate
+experiences a strong coupling between the center of mass motion and the
+internal collective modes. Due to the anharmonicity of the magnetic potential,
+not only the center of mass motion shows harmonic frequency generation, but
+also the internal dynamics exhibit nonlinear frequency mixing. We describe the
+data with a theoretical model to high accuracy. For strong excitations we test
+the experimental data for indications of a chaotic behavior.",0212220v2
+2003-12-10,Dynamic scaling of fronts in the quantum XX chain,"The dynamics of the transverse magnetization in the zero-temperature XX chain
+is studied with emphasis on fronts emerging from steplike initial magnetization
+profiles. The fronts move with fixed velocity and display a staircase like
+internal structure whose dynamic scaling is explored both analytically and
+numerically. The front region is found to spread with time sub-diffusively with
+the height and the width of the staircase steps scaling as t^(-1/3) and t^1/3,
+respectively. The areas under the steps are independent of time, thus the
+magnetization relaxes in quantized ""steps"" of spin-flips.",0312250v1
+2005-05-09,Dynamical properties of S=1 bond-alternating Heisenberg chains in transverse magnetic fields,"We calculate dynamical structure factors of the S=1 bond-alternating
+Heisenberg chain with a single-ion anisotropy in transverse magnetic fields,
+using a continued fraction method based on the Lanczos algorithm. In the
+Haldane-gap phase and the dimer phase, dynamical structure factors show
+characteristic field dependence. Possible interpretations are discussed. The
+numerical results are in qualitative agreement with recent results for
+inelastic neutron-scattering experiments on the S=1 bond-alternating
+Heisenberg-chain compound $\rm{Ni(C_{9}D_{24}N_{4})(NO_{2})ClO_{4}}$ and the
+S=1 Haldane-gap compound $\rm{Ni(C_{5}D_{14}N_{2})_{2}N_{3}(PF_{6})}$ in
+transverse magnetic fields.",0505196v1
+2006-08-10,Spin Dynamics of a Magnetic Antivortex,"We report on a study of the dynamics of a magnetic antivortex in a submicron,
+asteroid shaped, permalloy ferromagnet using micromagnetic simulations. As with
+vortex states in disk and square geometries, a gyrotropic mode was found in
+which a shifted antivortex core orbits about the center of the asteroid. Pulsed
+magnetic fields were used to generate azimuthal or radial spin wave modes,
+depending on the field orientation. The degeneracy of low frequency azimuthal
+mode frequencies is lifted by gyrotropic motion of the antivortex core, and
+restored by inserting a hole in the center of the particle to suppress this
+motion. We briefly compare the dynamics of the vortex state of the asteroid to
+the antivortex. The size dependence of the antivortex modes is reported.",0608245v1
+1994-12-08,Dimensional Reduction and Dynamical Chiral Symmetry Breaking by a Magnetic Field in $3+1$ Dimensions,"It is shown that in $3+1$ dimensions, a constant magnetic field is a catalyst
+of dynamical chiral symmetry breaking, leading to generating a fermion mass
+even at the weakest attractive interaction between fermions. The essence of
+this effect is the dimensional reduction $D \rightarrow D-2$ ($3+1 \rightarrow
+1+1$) in the dynamics of fermion pairing in a magnetic field. The effect is
+illustrated in the Nambu-Jona-Lasinio model. Possible applications of this
+effect are briefly discussed.",9412257v1
+1995-11-30,Catalysis of Dynamical Symmetry Breaking by a Magnetic Field,"A constant magnetic field in 3+1 and 2+1 dimensions is a strong catalyst of
+dynamical chiral symmetry breaking, leading to the generation of a fermion mass
+even at the weakest attractive interaction between fermions. The essence of
+this effect is the dimensional reduction $D/rightarrow D-2$ in the dynamics of
+fermion pairing in a magnetic field. The effect is illustrated in the
+Nambu-Jona-Lasinio model and QED. Possible applications of this effect and its
+extension to inhomogeneous field configurations are discussed.",9511224v1
+2003-03-31,Charged Grains In Saturn's F-Ring: Interaction With Saturn's Magnetic Field,"Saturn's dynamic F-Ring still presents a challenge for understanding and
+explaining the kinematic processes that lead to the changing structure visible
+in our observations of this ring. This study examines the effect of Saturn's
+magnetic field on the dynamics of micron-sized grains that may become
+electrically charged due to interaction with plasma in Saturn's rigidly
+corotating magnetosphere. The numerical model calculates the dynamics of
+charged dust grains and includes forces due to Saturn's gravitational field,
+the plasma polarization electric field, a third order harmonic expansion of
+Saturn's magnetic field, and the F Ring's Shepherding moons, Prometheus and
+Pandora.",0303123v1
+1995-05-05,Topics in nonhamiltonian (magnetic-type) interaction of classical hamiltonian dynamical systems. I,"A convenient algebraic structure to describe some forms of dynamics of two
+hamiltonian systems with nonpotential (magnetic--type) interaction is
+considered. An algebraic mechanism of generation of such dynamics is explored
+on simple ""toy"" examples and models. Nonpotential chains and their continuum
+limits are also considered. Examples of hybrid couplings with both potential
+and nonpotential (magnetic--type) interactions are discussed.",9505001v2
+2007-06-27,Molecular dynamics simulations of the dipolar-induced formation of magnetic nanochains and nanorings,"Iron, cobalt and nickel nanoparticles, grown in the gas phase, are known to
+arrange in chains and bracelet-like rings due to the long-range dipolar
+interaction between the ferromagnetic (or super-paramagnetic) particles. We
+investigate the dynamics and thermodynamics of such magnetic dipolar
+nanoparticles for low densities using molecular dynamics simulations and
+analyze the influence of temperature and external magnetic fields on two- and
+three-dimensional systems. The obtained phase diagrams can be understood by
+using simple energetic arguments.",0706.3920v1
+2008-02-12,Dynamical Coupling Between Ferromagnets Due to Spin Transfer Torque,"We use a combination of analytic calculations and numerical simulations to
+demonstrate that electrical current flowing through a magnetic bilayer induces
+dynamical coupling between the layers. The coupling originates from the
+dependence of the spin transfer torque exerted on the layers on the relative
+orientations of their magnetic moments. We demonstrate that such coupling
+modifies the behaviors of both layers, significantly affecting the the
+stability of the current-induced dynamical regimes and the efficiency of
+current-induced magnetic reversal.",0802.1560v1
+2008-03-14,Does there arise a significant enhancement of the dynamical quark mass in external magnetic field?,"Recently, it was found in QED that the generation of a dynamical electron
+mass in a strong magnetic field is significantly enhanced by the perturbative
+electron mass. In the present paper, the related question of a possible
+enhancement of the dynamical quark mass in an external magnetic field and with
+a bare mass term is investigated in the Nambu--Jona-Lasinio model.",0803.2191v2
+2008-10-05,Current-Induced Dynamics in Almost Symmetric Magnetic Nanopillars,"Magnetic nanodevices usually include a free layer whose configuration can be
+changed by spin-polarized current via the spin transfer effect, and a fixed
+reference layer. Here, we demonstrate that the roles of the free and the
+reference layers interchange over a small range of their relative thicknesses.
+Precession of both layers can be induced by spin transfer in symmetric devices,
+but the dynamics of one of the layers is rapidly suppressed in asymmetric
+devices. We interpret our results in terms of the dynamical coupling between
+magnetic layers due to spin transfer.",0810.0863v1
+2009-07-08,Magnetic hysteresis in a molecular Ising ferrimagnet: Glauber dynamics approach,"Motivated by recent experimental results reporting giant coercive fields in
+Co(II)-based molecular magnets we present a theory of hysteresis phenomena
+based on the Glauber stochastic dynamics. Unusual form of hysteresis loops is
+similar to those of found in Co-based quasi-one-dimensional ferrimagnet CoPhOMe
+at low temperatures. Temperature dependence of the coercive field has a
+characteristic form with an inflection that may serve as an indicator of the
+Glauber dynamics in real compounds. A relevance of the model for other Co-based
+molecular magnets is discussed.",0907.1348v1
+2009-10-23,Hamiltonian reduction for the magnetic dynamics in antiferromagnetic crystals,"The nonlinear spin dynamics in antiferromagnetic crystals is studied for the
+magnetic structures similar to that of hematite. For the case when only two
+magnetization vectors are non-zero and the Hamiltonian has an axial symmetry, a
+reduction to a Hamiltonian system with one degree of freedom is performed,
+based on the corresponding conservation law. The analysis of the phase
+portraits of this system provides tractable analytical and geometric
+descriptions of the regimes of nonlinear spin dynamics in the crystal.",0910.4527v3
+2009-12-09,Microscopic Theory of Current-Spin Interaction in Ferromagnets,"Interplay between magnetization dynamics and electric current in a conducting
+ferromagnet is theoretically studied based on a microscopic model calculation.
+First, the effects of the current on magnetization dynamics (spin torques) are
+studied with special attention to the ""dissipative"" torques arising from
+spin-relaxation processes of conduction electrons. Next, an analysis is given
+of the ""spin motive force"", namely, a spin-dependent 'voltage' generation due
+to magnetization dynamics, which is the reaction to spin torques. Finally, an
+attempt is presented of a unified description of these effects.",0912.1676v1
+2010-01-12,Dynamics of random dipoles : chaos {\it vs} ferromagnetism,"The microcanonical dynamics of an ensemble of random magnetic dipoles in a
+needle has been investigated. Analyzing magnetic reversal times, a transition
+between a chaotic paramagnetic phase and an integrable ferromagnetic phase has
+been numerically found. In particular, a simple criterium for transition has
+been formulated. Close to the transition point the statistics of average
+magnetic reversal times and fluctuations have been studied and critical
+exponents numerically given.",1001.1849v2
+2010-07-02,Stochastic heating of a molecular nanomagnet,"We study the excitation dynamics of a single molecular nanomagnet by static
+and pulsed magnetic fields. Based on a stability analysis of the classical
+magnetization dynamics we identify analytically the fields parameters for which
+the energy is stochastically pumped into the system in which case the
+magnetization undergoes diffusively and irreversibly a large angle deflection.
+An approximate analytical expression for the diffusion constant in terms of the
+fields parameters is given and assessed by full numerical calculations.",1007.0360v1
+2011-07-01,Current induced magnetization reversal on the surface of a topological insulator,"We study dynamics of the magnetization coupled to the surface Dirac fermions
+of a three di- mensional topological insulator. By solving the
+Landau-Lifshitz-Gilbert equation in the presence of charge current, we find
+current induced magnetization dynamics and discuss the possibility of mag-
+netization reversal. The torque from the current injection depends on the
+transmission probability through the ferromagnet and shows nontrivial
+dependence on the exchange coupling. The mag- netization dynamics is a direct
+manifestation of the inverse spin-galvanic effect and hence another ferromagnet
+is unnecessary to induce spin transfer torque in contrast to the conventional
+setup.",1107.0116v1
+2011-09-30,Topological charge pumping effect by the magnetization dynamics on the Surface of Three-Dimensional Topological Insulators,"We discuss a current dynamics on the surface of a 3-dimensional topological
+insulator induced by magnetization precession of a ferromagnet attached. It is
+found that the magnetization dynamics generates a direct charge current when
+the precession axis is within the surface plane. This rectification effect is
+due to a quantum anomaly and is topologically protected. The robustness of the
+rectification effect against first-varying exchange field and impurities is
+confirmed by explicit calculation.",1109.6816v2
+2011-11-16,Magnetic Sensitivity and Entanglement Dynamics of the Chemical Compass,"We present the quantum limits to the magnetic sensitivity of a new kind of
+magnetometer based on biochemical reactions. Radical-ion-pair reactions, the
+biochemical system underlying the chemical compass, are shown to offer a new
+and unique physical realization of a magnetic field sensor competitive to
+modern atomic or condensed matter magnetometers. We elaborate on the quantum
+coherence and entanglement dynamics of this sensor, showing that they provide
+the physical basis for testing our understanding of the fundamental quantum
+dynamics of radical-ion-pair reactions.",1111.3974v2
+2012-03-29,Soliton Magnetization Dynamics in Spin-Orbit Coupled Bose-Einstein Condensates,"Ring-trapped Bose-Einstein condensates subject to spin-orbit coupling support
+localized dark soliton excitations that show periodic density dynamics in real
+space. In addition to the density feature, solitons also carry a localized
+pseudo-spin magnetization that exhibits a rich and tunable dynamics. Analytic
+results for Rashba-type spin-orbit coupling and spin-invariant interactions
+predict a conserved magnitude and precessional motion for the soliton
+magnetization that allows for the simulation of spin-related geometric phases
+recently seen in electronic transport measurements.",1203.6684v1
+2012-06-11,Scaling in Dynamic Susceptibility of Herbertsmithite and Heavy-Fermion Metals,"We present a theory of the dynamic magnetic susceptibility of quantum spin
+liquid. The obtained results are in good agreement with experimental facts
+collected on herbertsmithite ZnCu3(OH)6Cl2 and on heavy-fermion metals, and
+allow us to predict a new scaling in magnetic fields in the dynamic
+susceptibility. Under the application of strong magnetic fields quantum spin
+liquid becomes completely polarized. We show that this polarization can be
+viewed as a manifestation of gapped excitations when investigating the
+spin-lattice relaxation rate.",1206.2324v2
+2012-12-03,Numerically Exact Long Time Magnetization Dynamics at the Nonequilibrium Kondo Crossover of the Anderson Impurity Model,"We investigate the dynamical and steady-state spin response of the
+nonequilibrium Anderson model to magnetic fields, bias voltage, and temperature
+using a numerically exact method combining a bold-line quantum Monte Carlo
+technique with the memory function formalism. We obtain converged results in a
+range of previously inaccessible regimes, in particular the crossover to the
+Kondo domain. We provide detailed predictions for novel nonequilibrium
+phenomena, including non-monotonic temperature dependence of observables at
+high bias voltage and oscillatory quench dynamics at high magnetic fields.",1212.0546v1
+2012-12-10,Mechanism of Fast Axially--Symmetric Reversal of Magnetic Vortex Core,"The magnetic vortex core in a nanodot can be switched by an alternating
+transversal magnetic field. We propose a simple collective coordinate model
+which describes comprehensive vortex core dynamics, including resonant
+behavior, weakly nonlinear regimes, and reversal dynamics. A chaotic dynamics
+of the vortex polarity is predicted. All analytical results were confirmed by
+micromagnetic simulations.",1212.2183v1
+2013-06-05,Inertial longitudinal magnetization reversal for non-Heisenberg ferromagnets,"We analyze theoretically the novel pathway of ultrafast spin dynamics for
+ferromagnets with high enough single-ion anisotropy (non-Heisenberg
+ferromagnets). This longitudinal spin dynamics includes the coupled
+oscillations of the modulus of the magnetization together with the quadrupolar
+spin variables, which are expressed through quantum expectation values of
+operators bilinear on the spin components. Even for a simple single-element
+ferromagnet, such a dynamics can lead to an inertial magnetization reversal
+under the action of an ultrashort laser pulse.",1306.1108v2
+2013-09-10,Spin rectification induced by dynamical Hanle effect,"Dynamic response of spin accumulation to a time-dependent magnetic field has
+been investigated in a ferromagnetic/nonmagnetic bilayer under ferromagnetic
+resonance. In this system, magnetization precession driven by a microwave
+generates direct-current (dc) and alternate-current (ac) spin accumulation in
+the nonmagnetic layer by the spin pumping. The ac spin accumulation is coupled
+with the microwave magnetic field through a dynamical Hanle spin precession,
+giving rise to rectified spin accumulation comparable with the dc spin
+accumulation directly generated by the spin pumping.",1309.2365v1
+2013-12-19,Cyclotron dynamics of interacting bosons in artificial magnetic fields,"We study theoretically quantum dynamics of interacting bosons in artificial
+magnetic fields as engineered in recent ultracold atomic experiments, where
+quantum cyclotron orbital motion has been observed. With exact numerical
+simulations and perturbative analyses, we find that interactions induce damping
+in the cyclotron motion. The damping time is found to be dependent on
+interaction and tunneling strengths monotonically, while its dependence on
+magnetic flux is non-monotonic. Sufficiently strong interactions would render
+bosons dynamically localized inhibiting the cyclotron motion. The damping
+predicted by us can be construed as an interaction-induced quantum decoherence
+of the cyclotron motion.",1312.5747v2
+2018-07-17,Stability of paramagnetic spheroid in precessing field,"Stability analysis of paramagnetic prolate and oblate spheroidal particle in
+precessing magnetic field is studied. Bifurcation diagram is calculated
+analytically in dependence of magnetic field frequency and precession angle.
+The direction of particle in synchronous regime is calculated. Rotational
+dynamics and mean rotational frequency in asynchronous regime is found.
+Obtained theoretical model gives possibility to calculate analytically dynamics
+of the particle in limiting case (when motion is periodic). Theoretically
+obtained models were compared with experimental results of rod like particle
+dynamics in precessing magnetic field. Experimental results are in good
+agreement with proposed theory.",1807.06379v1
+2018-08-01,Long range dynamical coupling between magnetic adatoms mediated by a 2D topological insulator,"We study the spin excitation spectra and the dynamical exchange coupling
+between iron adatoms on a Bi bilayer nanoribbon. We show that the topological
+character of the edge states is preserved in the presence of the magnetic
+adatoms. Nevertheless, they couple significantly to the edge spin currents, as
+witnessed by the large and long-ranged dynamical coupling we obtain in our
+calcula- tions. The large effective magnetocrystalline anisotropy of the
+magnetic adatoms combined with the transport properties of the topologically
+protected edge states make this system a strong candidate for implementation of
+spintronics devices and quantum information and/or computation protocols.",1808.00347v1
+2018-12-28,Exponential energy-preserving methods for charged-particle dynamics in a strong and constant magnetic field,"In this paper, exponential energy-preserving methods are formulated and
+analysed for solving charged-particle dynamics in a strong and constant
+magnetic field. The resulting method can exactly preserve the energy of the
+dynamics. Moreover, it is shown that the magnetic moment of the considered
+system is nearly conserved over a long time along this exponential
+energy-preserving method, which is proved by using modulated Fourier
+expansions. Other properties of the method including symmetry and convergence
+are also studied. An illustrated numerical experiment is carried out to
+demonstrate the long-time behaviour of the method.",1812.11038v1
+2018-12-31,Quench dynamics and defects formation in the Ising chain in a transverse magnetic field,"We study analytically and numerically quench dynamics and defects formation
+in the quantum Ising model in the presence of a time-dependent transverse
+magnetic field. We generalize the Landau-Ziner formula to the case of
+non-adiabatic evolution of the quantum system. For a quasi-static magnetic
+field, with a slow dependence on time, our outcomes are similar to the results
+predicted by the Landau-Zener formula. However, a quench dynamics under a
+shock-wave load is more complicated. The final state of the system depends on
+the amplitude and pulse velocity, resulting in the mixture of ground and
+excited states and significant density of defects.",1812.11887v1
+2020-04-04,Energy and momentum conservation in spin transfer,"We utilize simulations of spin-polarized electron scattering by a chain of
+localized quantum spins to show that energy and linear momentum conservation
+laws impose strong constraints on the properties of magnetic excitations
+induced by spin transfer. In turn, electron's orbital and spin dynamics depends
+on the dynamical characteristics of the local spins. Our results suggest the
+possibility to achieve precise control of spin transfer-driven magnetization
+dynamics by tailoring the spectral characteristics of the magnetic systems and
+the driving electrons.",2004.01957v1
+2020-06-14,Ideal memristor based on viscous magnetization dynamics driven by spin torque,"We show that ideal memristors - devices whose resistance is proportional to
+the charge that flows through them - can be realized using spin torque-driven
+viscous magnetization dynamics. The latter can be accomplished in the spin
+liquid state of thin-film heterostructures with frustrated exchange, where
+memristive response is tunable by proximity to the glass transition, while
+current-induced Joule heating facilitates nonvolatile operation and
+second-order memristive functionality beneficial for neuromorphic applications.
+Ideal memristive behaviors can be achieved in other systems characterized by
+viscous dynamics of physical, electronic, or magnetic degrees of freedom.",2006.07996v1
+2020-09-01,The relativistic dynamics of oppositely charged two fermions interacting with external uniform magnetic field,"We investigated the relativistic dynamics of oppositely charged two fermions
+interacting with an external uniform magnetic field. We chose the interaction
+of each fermion with the external magnetic field in the symmetric gauge, and
+obtained a precise solution of the corresponding fully-covariant two-body Dirac
+equation that derived from Quantum Electrodynamics via Action principle. The
+dynamic symmetry of the system we deal with allowed us to determine the
+relativistic Landau levels of such a spinless composite system, without using
+any group theoretical method. As a result, we determined the eigenfunctions and
+eigenvalues of the corresponding two-body Dirac Hamiltonian",2009.06380v2
+2003-04-06,Large N dynamics in QED in a magnetic field,"The expression for the dynamical mass of fermions in QED in a magnetic field
+is obtained for a large number of the fermion flavor N in the framework of 1/N
+expansion. The existence of a threshold value N_{thr}, dividing the theories
+with essentially different dynamics, is established. For the number of flavors
+N << N_{thr}, the dynamical mass is very sensitive to the value of the coupling
+constant \alpha_b, related to the magnetic scale \mu = |eB|. For N of order
+N_{thr} or larger, a dynamics similar to that in the Nambu-Jona-Lasinio model
+with cutoff of order |eB| and the dimensional coupling constant G \sim
+1/(N|eB|) takes place. In this case, the value of the dynamical mass is
+essentially \alpha_b independent (the dynamics with an infrared stable fixed
+point). The value of N_{thr} separates a weak coupling dynamics (with
+\tilde{\alpha}_b \equiv N\alpha_b << 1) from a strong coupling one (with
+\tilde{\alpha}_b \gtrsim 1) and is of order 1/\alpha_b.",0304059v1
+2019-05-11,Guiding center dynamics as motion on a formal slow manifold in loop space,"Since the late 1950's, the dynamics of a charged particle's ``guiding center""
+in a strong, inhomogeneous magnetic field have been understood in terms of
+near-identity coordinate transformations. The basic idea has been to
+approximately transform away the coupling between the fast gyration around
+magnetic fields lines and the remaining slow dynamics. This basic understanding
+now serves as a foundation for describing the kinetic theory of strongly
+magnetized plasmas. I present a new way to understand guiding center dynamics
+that does not involve complicated coordinate transformations. Starting from a
+dynamical systems formulation of the motion of parameterized loops in a charged
+particle's phase space, I identify a formal slow manifold in loop space.
+Dynamics on this formal slow manifold are equivalent to guiding center dynamics
+to all orders in perturbation theory. After demonstrating that loop space
+dynamics comprises an infinite-dimensional noncanonical Hamiltonian system, I
+recover the well-known Hamiltonian formulation of guiding center motion by
+restricting the (pre-) symplectic structure on loop space to the
+finite-dimensional guiding center formal slow manifold.",1905.04410v2
+2020-06-25,Temperature-Dependent Anisotropic Magnetoresistance and Spin-Torque-Driven Vortex Dynamics in a Single Microdisk,"Spin-orbit-torque-driven dynamics have recently gained interest in the field
+of magnetism due to the reduced requirement of current densities and an
+increase in efficiency, as well as the ease of implementation of different
+devices and materials. From a practical point of view, the low-frequency
+dynamics below 1 GHz is particularly interesting since dynamics associated with
+magnetic domains lie in this frequency range. While spin-torque excitation of
+high-frequency modes has been extensively studied, the intermediate
+low-frequency dynamics have received less attention, although spin torques
+could potentially be used for both manipulation of the spin texture, as well as
+the excitation of dynamics. In this work, we demonstrate that it is possible to
+drive magnetic vortex dynamics in a single microdisk by spin-Hall torque at
+varying temperatures, and relate the results to transport properties. We find
+that the gyrotropic mode of the core couples to the low-frequency microwave
+signal and produces a measurable voltage. The dynamic measurements are in
+agreement with magnetic transport measurements and are supported by
+micromagnetic simulations. Our results open the door for integrating magnetic
+vortex devices in spintronic applications.",2006.14454v1
+2010-03-13,The nonisothermal stage of magnetic star formation. II. Results,"In a previous paper we formulated the problem of the formation and evolution
+of fragments (or cores) in magnetically-supported, self-gravitating molecular
+clouds in axisymmetric geometry, accounting for the effects of ambipolar
+diffusion and Ohmic dissipation, grain chemistry and dynamics, and radiative
+transfer. Here we present results of star formation simulations that accurately
+track the evolution of a protostellar fragment over eleven orders of magnitude
+in density (from 300 cm^-3 to \approx 10^14 cm^-3), i.e., from the early
+ambipolar-diffusion--initiated fragmentation phase, through the magnetically
+supercritical, dynamical-contraction phase and the subsequent magnetic
+decoupling stage, to the formation of a protostellar core in near hydrostatic
+equilibrium. As found by Fiedler & Mouschovias (1993), gravitationally-driven
+ambipolar diffusion leads to the formation and subsequent dynamic contraction
+of a magnetically supercritical core. Moreover, we find that ambipolar
+diffusion, not Ohmic dissipation, is responsible for decoupling all the species
+except the electrons from the magnetic field, by a density \approx 3 x 10^12
+cm^-3. Magnetic decoupling precedes the formation of a central stellar object
+and ultimately gives rise to a concentration of magnetic flux (a `magnetic
+wall') outside the hydrostatic core --- as also found by Tassis & Mouschovias
+(2005a,b) through a different approach. At approximately the same density at
+which Ohmic dissipation becomes more important than ambipolar diffusion
+(\gtrsim 7 x 10^12 cm^-3), the grains carry most of the electric charge as well
+as the electric current. The prestellar core remains disclike down to radii ~
+10 AU, inside which thermal pressure becomes important. The magnetic flux
+problem of star formation is resolved for at least strongly magnetic newborn
+stars by this stage of the evolution, i.e., by a central density \approx 10^14
+cm^-3. The hydrostatic core has radius \approx 2 AU, density \approx 10^14
+cm^-3, temperature \approx 300 K, magnetic field strength \approx 0.2 G,
+magnetic flux \approx 5 x 10^18 Wb, luminosity ~ 10^-3 L_\odot, and mass ~
+10^-2 M_\odot.",1003.2722v1
+2011-07-13,Evolution and Distribution of Magnetic Fields from AGNs in Galaxy Clusters II. The Effects of Cluster Size and Dynamical State,"Theory and simulations suggest that magnetic fields from radio jets and lobes
+powered by their central super massive black holes can be an important source
+of magnetic fields in the galaxy clusters. This is paper II in a series of
+studies where we present self-consistent high-resolution adaptive mesh
+refinement cosmological magnetohydrodynamic (MHD) simulations that
+simultaneously follow the formation of a galaxy cluster and evolution of
+magnetic fields ejected by an active galactic nucleus (AGN). We studied 12
+different galaxy clusters with virial masses ranging from 1 $\times$ 10$^{14}$
+to 2 $\times$ 10$^{15}$ M$_{\odot}$. In this work we examine the effects of the
+mass and merger history on the final magnetic properties. We find that the
+evolution of magnetic fields is qualitatively similar to those of previous
+studies. In most clusters, the injected magnetic fields can be transported
+throughout the cluster and be further amplified by the intra-cluster medium
+(ICM) turbulence during the cluster formation process with hierarchical
+mergers, while the amplification history and the magnetic field distribution
+depend on the cluster formation and magnetism history. This can be very
+different for different clusters. The total magnetic energies in these clusters
+are between 4 $\times$ 10$^{57}$ and $10^{61}$ erg, which is mainly decided by
+the cluster mass, scaling approximately with the square of the total mass.
+Dynamically older relaxed clusters usually have more magnetic fields in their
+ICM. The dynamically very young clusters may be magnetized weakly since there
+is not enough time for magnetic fields to be amplified.",1107.2599v2
+2020-11-11,Destruction of long-range magnetic order in an external magnetic field and the associated spin dynamics in Cu2GaBO5 and Cu2AlBO5 ludwigites,"The quantum spin systems Cu$_2$M'BO$_5$ (M' = Al, Ga) with the ludwigite
+crystal structure consist of a structurally ordered Cu$^{2+}$ sublattice in the
+form of three-leg ladders, interpenetrated by a structurally disordered
+sublattice with a statistically random site occupation by magnetic Cu$^{2+}$
+and nonmagnetic Ga$^{3+}$ or Al$^{3+}$ ions. A microscopic analysis based on
+density-functional-theory calculations for Cu$_2$GaBO$_5$ reveals a frustrated
+quasi-two-dimensional spin model featuring five inequivalent antiferromagnetic
+exchanges. A broad low-temperature $^{11}$B nuclear magnetic resonance points
+to a considerable spin disorder in the system. In zero magnetic field,
+antiferromagnetic order sets in below $T_\text{N}$ $\approx$ 4.1 K and ~2.4 K
+for the Ga and Al compounds, respectively. From neutron diffraction, we find
+that the magnetic propagation vector in Cu$_2$GaBO$_5$ is commensurate and lies
+on the Brillouin-zone boundary in the (H0L) plane, $\mathbf{q}_\text{m}$ =
+(0.45 0 -0.7), corresponding to a complex noncollinear long-range ordered
+structure with a large magnetic unit cell. Muon spin relaxation is monotonic,
+consisting of a fast static component typical for complex noncollinear spin
+systems and a slow dynamic component originating from the relaxation on
+low-energy spin fluctuations. Gapless spin dynamics in the form of a diffuse
+quasielastic peak is also evidenced by inelastic neutron scattering. Most
+remarkably, application of a magnetic field above 1 T destroys the static
+long-range order, which is manifested in the gradual broadening of the magnetic
+Bragg peaks. We argue that such a crossover from a magnetically long-range
+ordered state to a spin-glass regime may result from orphan spins on the
+structurally disordered magnetic sublattice, which are polarized in magnetic
+field and thus act as a tuning knob for field-controlled magnetic disorder.",2011.05819v1
+1999-01-28,Doped bilayer antiferromagnets: Hole dynamics on both sides of a magnetic ordering transition,"The two-layer square lattice quantum antiferromagnet with spins 1/2 shows a
+magnetic order-disorder transition at a critical ratio of the interplane to
+intraplane couplings. We investigate the dynamics of a single hole in a bilayer
+antiferromagnet described by a t-J Hamiltonian. To model the spin background we
+propose a ground-state wave function for the undoped system which covers both
+magnetic phases and includes transverse as well as longitudinal spin
+fluctuations. The photoemission spectrum is calculated using the spin-polaron
+picture for the whole range of the ratio of the magnetic couplings. This allows
+for the study of the hole dynamics of both sides of the magnetic order-disorder
+transition. For small interplane coupling we find a quasiparticle with
+properties known from the single-layer antiferromagnet, e.g., the dispersion
+minimum is at (pi/2,pi/2). For large interplane coupling the hole dispersion is
+similar to that of a free fermion (with reduced bandwidth). The cross-over
+between these two scenarios occurs inside the antiferromagnetic phase which
+indicates that the hole dynamics is governed by the local environment of the
+hole.",9901326v2
+2004-01-28,Muon-spin-relaxation and magnetic-susceptibility studies of effects of the magnetic impurity Ni on the Cu-spin dynamics and superconductivity in La_2-x_Sr_x_Cu_1-y_Ni_y_O_4_ with x = 0.13,"Effects of the magnetic impurity Ni on the Cu-spin dynamics and
+superconductivity have been studied in La_2-x_Sr_x_Cu_1-y_Ni_y_O_4_ with x =
+0.13 changing y finely up to 0.10. Compared with the case of the nonmagnetic
+impurity Zn, it has been found from the muon-spin-relaxation measurements that
+a large amount of Ni is required to stabilize a magnetic order of Cu spins.
+However, the evolution toward the stabilization of the magnetic order with
+increasing impurity concentration is qualitatively similar to each other. The
+area of the non-superconducting and slowly fluctuating or static region of Cu
+spins around Ni has been found to be smaller than that around Zn, suggesting
+that the pinning of rather long-ranged dynamical spin correlation such as the
+so-called dynamical stripe by Ni is weaker than that by Zn. This may be the
+reason why Zn destroys the superconductivity in the hole-doped high-T_c_
+cuprates more markedly than Ni.",0401566v2
+2006-01-28,Electric readout of magnetization dynamics in a ferromagnet-semiconductor system,"We apply an analysis of time-dependent spin-polarized current in a
+semiconductor channel at room temperature to establish how the magnetization
+configuration and dynamics of three ferromagnetic terminals, two of them biased
+and third connected to a capacitor, affect the currents and voltages. In a
+steady state, the voltage on the capacitor is related to spin accumulation in
+the channel. When the magnetization of one of the terminals is rotated, a
+transient current is triggered. This effect can be used for electrical
+detection of magnetization reversal dynamics of an electrode or for dynamical
+readout of the alignment of two magnetic contacts.",0601642v2
+2006-09-18,General Form of Magnetization Damping: Magnetization dynamics of a spin system evolving nonadiabatically and out of equilibrium,"Using an effective Hamiltonian including the Zeeman and internal
+interactions, we describe the quantum theory of magnetization dynamics when the
+spin system evolves non-adiabatically and out of equilibrium. The
+Lewis-Riesenfeld dynamical invariant method is employed along with the
+Liouville-von Neumann equation for the density matrix. We derive a dynamical
+equation for magnetization defined with respect to the density operator with a
+general form of magnetization damping that involves the non-equilibrium
+contribution in addition to the Landau-Lifshitz-Gilbert equation. Two special
+cases of the radiation-spin interaction and the spin-spin exchange interaction
+are considered. For the radiation-spin interaction, the damping term is shown
+to be of the Gilbert type, while in the spin-spin exchange interaction case the
+results depend on a coupled chain of correlation functions.",0609431v2
+2006-02-22,Dynamical mass generation in strongly coupled Quantum Electrodynamics with weak magnetic fields,"We study the dynamical generation of masses for fundamental fermions in
+quenched quantum electrodynamics in the presence of weak magnetic fields using
+Schwinger-Dyson equations. Contrary to the case where the magnetic field is
+strong, in the weak field limit the coupling should exceed certain critical
+value in order for the generation of masses to take place, just as in the case
+where no magnetic field is present. The weak field limit is defined as eB <<
+m(0)^2, where m(0) is the value of the dynamically generated mass in the
+absence of the field. We carry out a numerical analysis to study the magnetic
+field dependence of the mass function above critical coupling and show that in
+this regime the dynamically generated mass and the chiral condensate for the
+lowest Landau level increase proportionally to (eB)^2.",0602209v2
+2002-07-28,Generation of multiscale magnetic field by parity-invariant time-periodic flows,"We study generation of magnetic fields involving large spatial scales by
+time- and space-periodic small-scale parity-invariant flows. The anisotropic
+magnetic eddy diffusivity tensor is calculated by the standard procedure
+involving expansion of magnetic modes and their growth rates in power series in
+the scale ratio. Our simulations, conducted for flows with random harmonic
+composition and exponentially decaying energy spectra, demonstrate that
+enlargement of the spatial scale of magnetic field is beneficial for generation
+by time-periodic flows. However, they turn out, in general, to be less
+efficient dynamos, than steady flows.",0207112v3
+2009-12-22,Billiards in magnetic fields: A molecular dynamics approach,"We present a computational scheme based on classical molecular dynamics to
+study chaotic billiards in static external magnetic fields. The method allows
+to treat arbitrary geometries and several interacting particles. We test the
+scheme for rectangular single-particle billiards in magnetic fields and find a
+sequence of regularity islands at integer aspect ratios. In the case of two
+Coulomb-interacting particles the dynamics is dominated by chaotic behavior.
+However, signatures of quasiperiodicity can be identified at weak interactions,
+as well as regular trajectories at strong magnetic fields. Our scheme provides
+a promising tool to monitor the classical limit of many-electron semiconductor
+nanostructures and transport systems up to high magnetic fields.",0912.4336v1
+2010-01-06,Critical properties of Sudden Quench Dynamics in the anisotropic XY Model,"We study the zero temperature quantum dynamical critical behavior of the
+anisotropic XY chain under a sudden quench in a transverse field. We
+demonstrate theoretically that both quench magnetic susceptibility and
+two-particle quench correlation can be used to describe the dynamical quantum
+phase transition (QPT) properties. Either the quench magnetic susceptibility or
+the derivative of correlation functions as a function of initial magnetic field
+$a$ exhibits a divergence at the critical points when final magnetic field $b$
+is fixed. A special case that final magnetic field $b$ is just at the critical
+point is discussed separately. Some of the critical exponents of the dynamical
+QPT are obtained and the long-range correlation of the quench system is
+analyzed. We also compare our result with that of the static QPT.",1001.0909v3
+2011-11-21,Electron-phonon scattering dynamics in ferromagnets on ultrafast timescales: Influence of the phonon temperature,"The magnetization response of bulk ferromagnets after excitation by an
+ultrashort optical pulse is calculated using a dynamical model of the
+Elliott-Yafet type that includes the effects of the spin-orbit interaction in
+the ab-initio ferromagnetic band structure, the electron-phonon interaction at
+the level of Boltzmann scattering integrals, and dynamical changes in the
+temperature of the phonon bath. Using realistic parameters for the ultrashort
+optical pulse, the computed maximum magnetization quenching achievable with
+electron-phonon scattering in a fixed band structure is much smaller than the
+quenching observed in experiments. Heating of the phonon bath is found to not
+appreciably change the magnetization dynamics on ultrashort timescales.",1111.4783v1
+2011-12-26,Thin-Film Magnetization Dynamics on the Surface of a Topological Insulator,"We theoretically study the magnetization dynamics of a thin ferromagnetic
+film exchange-coupled with a surface of a strong three-dimensional topological
+insulator. We focus on the role of electronic zero modes imprinted by domain
+walls (DW's) or other topological textures in the magnetic film.
+Thermodynamically reciprocal hydrodynamic equations of motion are derived for
+the DW responding to electronic spin torques, on the one hand, and fictitious
+electromotive forces in the electronic chiral mode fomented by the DW, on the
+other. An experimental realization illustrating this physics is proposed based
+on a ferromagnetic strip, which cuts the topological insulator surface into two
+gapless regions. In the presence of a ferromagnetic DW, a chiral mode
+transverse to the magnetic strip acts as a dissipative interconnect, which is
+itself a dynamic object that controls (and, inversely, responds to) the
+magnetization dynamics.",1112.5884v2
+2012-10-08,Many-body dynamics of p-wave Feshbach molecule production: a mean-field approach,"We study the mean-field dynamics of p-wave Feshbach molecule production in an
+ultra cold gas of Fermi atoms in the same internal state. We derive a separable
+potential to describe the low-energy scattering properties of such atoms, and
+use this potential to solve the mean-field dynamics during a magnetic field
+sweep. Initially, on the negative scattering length side of a Feshbach
+resonance the gas is described by the BCS theory. We adapt the method by
+Szyma\'{n}ska et al. [Phys. Rev. Lett. 94, 170402 (2005)] to p-wave interacting
+Fermi gases and model the conversion dynamics of the gas into a Bose-Einstein
+condensate of molecules on the other side of the resonance under the influence
+of a linearly varying magnetic field. We have analyzed the dependence of the
+molecule production efficiency on the density of the gas, temperature, initial
+value of the magnetic field, and magnetic field ramp speed. Our results show
+that in this approximation molecule production by a linear magnetic field sweep
+is highly dependent on the initial state.",1210.2317v2
+2012-12-12,Magnetic moment type of lifting from particle dynamics to Vlasov-Maxwell dynamics,"Techniques for coordinate changes that depend on both dependent and
+independent variables are developed and applied to the Maxwell-Vlasov
+Hamiltonian theory. Particle coordinate changes with a new velocity variable
+dependent on the magnetic field, with spatial coordinates unchanged, are lifted
+to transform the noncanonical Poisson bracket and, thus, the field Hamiltonian
+structure of the Vlasov-Maxwell equation. Several examples are given including
+magnetic coordinates, where the velocity is decomposed into components parallel
+and perpendicular to the local magnetic field, and the case of spherical
+velocity coordinates. An example of the lifting procedure is performed to
+obtain a simplified version of gyrokinetics, where the magnetic moment is used
+as a coordinate and the dynamics is reduced by elimination of the electric
+field energy in the Hamiltonian.",1212.3007v1
+2013-05-29,Hydrodynamic theory of coupled current and magnetization dynamics in spin-textured antiferromagnets,"Antiferromagnets with vanishingly small (or zero) magnetization are
+interesting candidates for spintronics applications. In the present paper we
+propose two models for description of the current-induced phenomena in
+antiferromagnetic textures. We show that the magnetization that originates from
+rotation or oscillations of antiferromagnetic vector can, via $sd$-exchange
+coupling, polarize the current and give rise to adiabatic and nonadiabatic spin
+torques. Due to the Lorentz-type dynamics of antiferromagnetic moments (unlike
+the Galilenian-like dynamics in ferromagnets), the adiabatic spin torque
+affects the characteristic lengthscale of the moving texture. Nonadiabatic spin
+torque contributes to the energy pumping and can induce the stable motion of
+antiferromagnetic texture, but, in contrast to ferromagnets, has pure dynamic
+origin. We also consider the current-induced phenomena in artificial
+antiferromagnets where the current maps the staggered magnetization of the
+structure. In this case the effect of nonadiabatic spin torque is similar to
+that in ferromagnetic constituents of the structure. In particular, the current
+can remove degeneracy of the translational antiferromagnetic domains
+indistinguishable in the external magnetic field and thus can set into motion
+the 180$^\circ$ domain wall.",1305.6734v2
+2013-07-17,Role of helicities for the dynamics of turbulent magnetic fields,"Investigations of the inverse cascade of magnetic helicity are conducted with
+pseudospectral, three-dimensional direct numerical simulations of forced and
+decaying incompressible magnetohydrodynamic turbulence. The high-resolution
+simulations which allow for the necessary scale-separation show that the
+observed self-similar scaling behavior of magnetic helicity and related
+quantities can only be understood by taking the full nonlinear interplay of
+velocity and magnetic fluctuations into account. With the help of the
+eddy-damped quasi-normal Markovian approximation a probably universal relation
+between kinetic and magnetic helicities is derived that closely resembles the
+extended definition of the prominent dynamo pseudoscalar $\alpha$. This
+unexpected similarity suggests an additional nonlinear quenching mechanism of
+the current-helicity contribution to $\alpha$.",1307.4603v2
+2013-09-01,Quasistationarity in a long-range interacting model of particles moving on a sphere,"We consider a long-range interacting system of $N$ particles moving on a
+spherical surface under an attractive Heisenberg-like interaction of infinite
+range, and evolving under deterministic Hamilton dynamics. The system may also
+be viewed as one of globally coupled Heisenberg spins. In equilibrium, the
+system has a continuous phase transition from a low-energy magnetized phase, in
+which the particles are clustered on the spherical surface, to a high-energy
+homogeneous phase. The dynamical behavior of the model is studied analytically
+by analyzing the Vlasov equation for the evolution of the single-particle
+distribution, and numerically by direct simulations. The model is found to
+exhibit long lived non-magnetized quasistationary states (QSSs) which in the
+thermodynamic limit are dynamically stable within an energy range where the
+equilibrium state is magnetized. For finite $N$, these states relax to
+equilibrium over a time that increases algebraically with $N$. In the
+dynamically unstable regime, non-magnetized states relax fast to equilibrium
+over a time that scales as $\log N$. These features are retained in presence of
+a global anisotropy in the magnetization.",1309.0194v2
+2013-11-28,Conservative effects in spin-transfer-driven magnetization dynamics,"It is shown that under appropriate conditions spin-transfer-driven
+magnetization dynamics in a single-domain nanomagnet is conservative in nature
+and admits a specific integral of motion, which is reduced to the usual
+magnetic energy when the spin current goes to zero. The existence of this
+conservation law is connected to the symmetry properties of the dynamics under
+simultaneous inversion of magnetisation and time. When one applies an external
+magnetic field parallel to the spin polarization, the dynamics is transformed
+from conservative into dissipative. More precisely, it is demonstrated that
+there exists a state function such that the field induces a monotone relaxation
+of this function toward its minima or maxima, depending on the field
+orientation. These results hold in the absence of intrinsic damping effects.
+When intrinsic damping is included in the description, a competition arises
+between field-induced and damping-induced relaxations, which leads to the
+appearance of limit cycles, that is, of magnetization self-oscillations.",1311.7344v1
+2014-05-25,Spin Hall phenomenology of magnetic dynamics,"We study the role of spin-orbit interactions in the coupled magnetoelectric
+dynamics of a ferromagnetic film coated with an electrical conductor. While the
+main thrust of this work is phenomenological, several popular simple models are
+considered microscopically in some detail, including Rashba and Dirac
+two-dimensional electron gases coupled to a magnetic insulator, as well as a
+diffusive spin Hall system. We focus on the long-wavelength magnetic dynamics
+that experiences current-induced torques and produces fictitious electromotive
+forces. Our phenomenology provides a suitable framework for analyzing
+experiments on current-induced magnetic dynamics and reciprocal charge pumping,
+including the effects of magnetoresistance and Gilbert-damping anisotropies,
+without a need to resort to any microscopic considerations or modeling.
+Finally, some remarks are made regarding the interplay of spin-orbit
+interactions and magnetic textures.",1405.6354v2
+2015-01-06,Berry-phase effects and electronic dynamics in noncollinear antiferromagnetic texture,"Antiferromagnets (AFMs), in contrast to ferromagnets, show a nontrivial
+magnetic structure with zero net magnetization. However, they share a number of
+spintronic effects with ferromagnets, including spin-pumping and spin transfer
+torques. Both phenomena stem from the coupled dynamics of free carriers and
+localized magnetic moments. In the present paper I study the adiabatic dynamics
+of a spin-polarized electrons in a metallic AFM exhibiting a noncollinear
+120$^\circ$ magnetic structure. I show that the slowly varying AFM spin texture
+produces a non-Abelian gauge potential related to the time/space gradients of
+the N\'{e}el vectors. Corresponding emergent electric and magnetic fields
+induce rotation of spin and influence the orbital dynamics of free electrons. I
+discuss both the possibility of a topological spin Hall effect in the vicinity
+of topological AFM solitons with nonzero curvature and rotation of the electron
+spin traveling through the AFM domain wall.",1501.01189v2
+2015-03-11,Dynamical influence of vortex-antivortex pairs in magnetic vortex oscillators,"We study the magnetization dynamics in a nanocontact magnetic vortex
+oscillators as function of temperature. Low temperature experiments reveal that
+the dynamics at low and high currents differ qualitatively. At low currents, we
+excite a temperature independent standard oscillation mode, consisting in the
+gyrotropic motion of a free layer vortex about the nanocontact. Above a
+critical current, a sudden jump of the frequency is observed, concomitant with
+a substantial increase of the frequency versus current slope factor. Using
+micromagnetic simulation and analytical modeling, we associate this new regime
+to the creation of a vortex-antivortex pair in the pinned layer of the spin
+valve. The vortex-antivortex distance depends on the Oersted field which favors
+a separation, and on the exchange bias field, which favors pair merging. The
+pair in the pinned layer provides an additional spin torque altering the
+dynamics of the free layer vortex, which can be quantitatively accounted for by
+an analytical model.",1503.03365v2
+2015-04-11,Magnetic response of a disordered binary ferromagnetic alloy to an oscillating magnetic field,"By means of Monte Carlo simulation with local spin update Metropolis
+algorithm, we have elucidated non-equilibrium phase transition properties and
+stationary-state treatment of a disordered binary ferromagnetic alloy of the
+type $A_{p}B_{1-p}$ on a square lattice. After a detailed analysis, we have
+found that the system shows many interesting and unusual thermal and magnetic
+behaviors, for instance, the locations of dynamic phase transition points
+change significantly depending upon amplitude and period of the external
+magnetic field as well as upon the active concentration of $A-$ type
+components. Much effort has also been dedicated to clarify the hysteresis
+tools, such as coercivity, dynamic loop area as well as dynamic correlations
+between time dependent magnetizations and external time dependent applied field
+as a functions of period and amplitude of field as well as active concentration
+of of $A-$ type components, and outstanding physical findings have been
+reported in order to better understand the dynamic process underlying present
+system.",1504.02874v1
+2015-05-09,Simulation of flux expulsion and associated dynamics in a two-dimensional magnetohydrodynamic channel flow,"We consider a plane channel flow of an electrically conducting fluid which is
+driven by a mean pressure gradient in the presence of an applied magnetic field
+that is streamwise periodic with zero mean. Magnetic flux expulsion and the
+associated bifurcation in such a configuration is explored using direct
+numerical simulations (DNS). The structure of the flow and magnetic fields in
+the Hartmann regime (where the dominant balance is through Lorentz forces) and
+the Poiseuille regime (where viscous effects play a significant role) are
+studied and detailed comparisons to the existing one-dimensional model of
+Kamkar and Moffatt (J. Fluid. Mech., Vol.90, pp 107-122, 1982) are drawn to
+evaluate the validity of the model. Comparisons show good agreement of the
+model with DNS in the Hartmann regime, but significant diferences arising in
+the Poiseuille regime when non-linear effects become important. The effects of
+various parameters like the magnetic Reynolds number, imposed field wavenumber
+etc. on the bifurcation of the flow are studied. Magnetic field line
+reconnections occuring during the dynamic runaway reveal a specific two-step
+pattern that leads to the gradual expulsion of flux in the core region.",1505.02313v1
+2016-03-25,The influence of the structural transition on magnetic fluctuations in NaFeAs,"NaFeAs belongs to a class of Fe-based superconductors which parent compounds
+show separated structural and magnetic transitions. Effects of the structural
+transition on spin dynamics therefore can be investigated separately from the
+magnetic transition. A plateau in dynamic spin response is observed in a
+critical region around the structural transition temperature T_S. It is
+interpreted as due to the stiffening of spin fluctuations along the in-plane
+magnetic hard axis due to the dxz and dyz orbital ordering. The appearance of
+anisotropic spin dynamics in the critical region above the T_S at T* offers a
+dynamic magnetic scattering mechanism for anisotropic electronic properties in
+the commonly referred ""nematic phase"".",1603.07873v2
+2016-08-24,Dynamics of small trapped one-dimensional Fermi gas under oscillating magnetic fields,"Deterministic preparation of an ultracold harmonically trapped
+one-dimensional Fermi gas consisting of a few fermions has been realized by the
+Heidelberg group. Using Floquet formalism, we study the time dynamics of two-
+and three-fermion systems in a harmonic trap under an oscillating magnetic
+field. The oscillating magnetic field produces a time-dependent interaction
+strength through a Feshbach resonance. We explore the dependence of these
+dynamics on the frequency of the oscillating magnetic field for
+non-interacting, weakly interacting, and strongly interacting systems. We
+identify the regimes where the system can be described by an effective
+two-state model and an effective three-state model. We find an unbounded
+coupling to all excited states at the infinitely strong interaction limit and
+several simple relations that characterize the dynamics. Based on our findings,
+we propose a technique for driving transition from the ground state to the
+excited states using an oscillating magnetic field.",1608.06966v2
+2017-04-15,Cross effect of magnetic field and charge current on antiferromagnetic dynamics,"We theoretically examine a cross effect of magnetic field and charge current
+on antiferromagnetic domain wall dynamics. Since antiferromagnetic materials
+are largely insensitive to external magnetic fields in general, charge current
+has been shown recently as an alternative and efficient way to manipulate
+antiferromagnets. We find a new role of the magnetic field in the
+antiferromagnetic dynamics that appears when it is combined with charge
+current, demonstrating a domain wall motion in the presence of both field and
+current. We show that a spatially-varying magnetic field can shift the
+current-driven domain-wall velocity, depending on the domain-wall structure and
+the direction of the field-gradient. Our result suggests a novel concept of
+field-control of current-driven antiferromagnetic dynamics.",1704.04602v1
+2017-05-09,Topological spin dynamics in cubic FeGe near room temperature,"Understanding spin-wave dynamics in chiral magnets is a key step for the
+development of high-speed, spin-wave based spintronic devices that take
+advantage of chiral and topological spin textures for their operation. Here we
+present an experimental and theoretical study of spin-wave dynamics in a cubic
+B20 FeGe single crystal. Using the combination of waveguide microwave
+absorption spectroscopy (MAS), micromagnetic simulations, and analytical
+theory, we identify the resonance dynamics in all magnetic phases (field
+polarized, conical, helical, and skyrmion phases). Because the resonance
+frequencies of specific chiral spin textures are unique, quantitative agreement
+between our theoretical predictions and experimental findings for all resonance
+frequencies and spin wave modes enables us to unambiguously identify chiral
+magnetic phases and to demonstrate that MAS is a powerful tool to efficiently
+extract a magnetic phase diagram. These results provide a new tool to
+accelerate the integration of chiral magnetic materials into spintronic
+devices.",1705.03397v1
+2018-01-26,Dynamics of magnetic skyrmion clusters driven by spin-polarized current with a spatially varied polarization,"Magnetic skyrmions are promising candidates for future information
+technology. Here, we present a micromagnetic study of isolated skyrmions and
+skyrmion clusters in ferromagnetic nanodisks driven by the spin-polarized
+current with spatially varied polarization. The current-driven skyrmion
+clusters can be either dynamic steady or static, depending on the spatially
+varied polarization profile. For the dynamic steady state, the skyrmion cluster
+moves in a circle in the nanodisk, while for the static state, the skyrmion
+cluster is static. The frequency of the circular motion of skyrmion is also
+studied. Furthermore, the dependence of the skyrmion cluster dynamics on the
+magnetic anisotropy and Dzyaloshinskii-Moriya interaction is investigated. Our
+results may provide a pathway to realize magnetic skyrmion cluster based
+devices.",1801.08699v3
+2018-04-04,Velocity enhancement by synchronization of magnetic domain walls,"Magnetic domain walls are objects whose dynamics is inseparably connected to
+their structure. In this work we investigate magnetic bilayers, which are
+engineered such that a coupled pair of domain walls, one in each layer, is
+stabilized by a cooperation of Dzyaloshinskii-Moriya interaction and
+flux-closing mechanism. The dipolar field mediating the interaction between the
+two domain walls, links not only their position but also their structure. We
+show that this link has a direct impact on their magnetic field induced
+dynamics. We demonstrate that in such a system the coupling leads to an
+increased domain wall velocity with respect to single domain walls. Since the
+domain wall dynamics is observed in a precessional regime, the dynamics
+involves the synchronization between the two walls, to preserve the flux
+closure during motion. Properties of these coupled oscillating walls can be
+tuned by an additional in-plane magnetic field enabling a rich variety of
+states, from perfect synchronization to complete detuning.",1804.01385v1
+2018-04-23,Probing condensed matter physics with magnetometry based on nitrogen-vacancy centres in diamond,"The magnetic fields generated by spins and currents provide a unique window
+into the physics of correlated-electron materials and devices. Proposed only a
+decade ago, magnetometry based on the electron spin of nitrogen-vacancy (NV)
+defects in diamond is emerging as a platform that is excellently suited for
+probing condensed matter systems: it can be operated from cryogenic
+temperatures to above room temperature, has a dynamic range spanning from DC to
+GHz, and allows sensor-sample distances as small as a few nanometres. As such,
+NV magnetometry provides access to static and dynamic magnetic and electronic
+phenomena with nanoscale spatial resolution. Pioneering work focused on
+proof-of-principle demonstrations of its nanoscale imaging resolution and
+magnetic field sensitivity. Now, experiments are starting to probe the
+correlated-electron physics of magnets and superconductors and to explore the
+current distributions in low-dimensional materials. In this Review, we discuss
+the application of NV magnetometry to the exploration of condensed matter
+physics, focusing on its use to study static and dynamic magnetic textures, and
+static and dynamic current distributions.",1804.08742v1
+2018-12-17,Phonon-induced quantum ratchet in the exciton spin dynamics in diluted magnetic semiconductors in a magnetic field,"Magnetically doped semiconductors are well known for their giant Zeeman
+splittings which can reach several meV even in relatively small external
+magnetic fields. After preparing a nonequilibrium exciton distribution via
+optical excitation, the spin dynamics in diluted magnetic semiconductor quantum
+wells is typically governed by spin-flip scattering processes due to the
+exciton-impurity exchange interaction. Our theoretical calculations show that
+the giant Zeeman splitting in these materials in combination with the influence
+of longitudinal acoustic phonons lead to a quantum ratchet-type dynamics,
+resulting in an almost complete reversal of the carrier spin polarization at
+very low temperatures. Furthermore, we find that the predictions of a much
+simpler rate-equation approach qualitatively agree with a more advanced and
+numerically demanding quantum kinetic description of the spin dynamics for a
+wide range of temperatures, although quantitative difference are noticeable.",1812.06734v2
+2019-10-11,Hannay Angles in Magnetic Dynamics,"We consider, within the framework developed by Hannay for classical
+integrable systems [Journal of Physics A: Mathematical and General {\bf 18},
+221 (1985)], the geometric phases that occur in semi-classical magnetic
+dynamics. Such geometric phases are generically referred to as Hannay angles,
+and, in the context of magnetic dynamics, may arise as a result of both
+adiabatically-varying ellipticity and axis of magnetization precession. We
+elucidate both effects and their interplay for single-domain magnetic dynamics
+within a simple model with time-dependent anisotropies and external field.
+Subsequently, we consider spin waves and rederive, from our classical approach,
+some known results on what is commonly referred to as the magnon Berry phase.
+As an aside, these results are used to give an interpretation for geometric
+phases that occur in superfluids. Finally, we develop a Green's function
+formalism for elliptical magnons. Within this formalism, we consider magnon
+transport in a mesoscopic ring and show how it is influenced by interference
+effects that are tuned by the Hannay angle that results from a varying
+ellipticity. Our results may inform the field of magnonics that seeks to
+utilize spin waves in applications.",1910.05099v2
+2020-06-23,Magnetization dynamics in synthetic antiferromagnets: Role of dynamical energy and mutual spin pumping,"We investigate magnetization dynamics in asymmetric interlayer exchange
+coupled Py/Ru/Py trilayers using both vector network analyzer-based and
+electrically detected ferromagnetic resonance techniques. Two different
+ferromagnetic resonance modes, in-phase and out-of-phase, are observed across
+all three regimes of the static magnetization configurations, through
+antiparallel alignment at low fields, the spin-flop transition at intermediate
+fields, and parallel alignment at high fields. The nonmonotonic behavior of the
+modes as a function of the external field is explained in detail by analyzing
+the interlayer exchange and Zeeman energies and is found to be solely governed
+by the interplay of their dynamical components. In addition, the linewidths of
+both modes were determined across the three regimes and the different behaviors
+of the linewidths versus external magnetic field are attributed to mutual spin
+pumping induced in the samples. Interestingly, the difference between the
+linewidths of the out-of-phase and in-phase modes decreases at the spin-flop
+transition and is reversed between the antiparallel and parallel aligned
+magnetization states.",2006.13031v1
+2020-12-24,Dynamical correlation enhanced orbital magnetization in VI$_{3}$,"The effect of electronic correlations on the orbital magnetization in real
+materials has not been explored beyond a static mean-field level. Based on the
+dynamical mean-field theory, the effect of electronic correlations on the
+orbital magnetization in layered ferromagnet VI$_3$ has been studied. A
+comparison drawn with the results obtained from density functional theory
+calculations robustly establishes the crucial role of dynamical correlations in
+this case. In contrast to the density functional theory that leads to
+negligible orbital magnetization in VI$_3$, in dynamical mean-field approach
+the orbital magnetization is greatly enhanced. Further analysis show that this
+enhancement is mainly due to the enhanced local circulations of electrons,
+which can be attributed to a better description of the localization behavior of
+correlated electrons in VI$_3$. The conclusion drawn in our study could be
+applicable to a wide range of layered materials in this class.",2012.13151v1
+2021-07-21,Dynamics of two ferromagnetic insulators coupled by superconducting spin current,"A conventional superconductor sandwiched between two ferromagnets can
+maintain coherent equilibrium spin current. This spin supercurrent results from
+the rotation of odd-frequency spin correlations induced in the superconductor
+by the magnetic proximity effect. In the absence of intrinsic magnetization,
+the superconductor cannot maintain multiple rotations of the triplet component
+but instead provides a Josephson type weak link for the spin supercurrent. We
+determine the analogue of the current-phase relation in various circumstances
+and show how it can be accessed in experiments on dynamic magnetization. In
+particular, concentrating on the magnetic hysteresis and the ferromagnetic
+resonance response, we show how the spin supercurrent affects the
+nonequilibrium dynamics of magnetization which depends on a competition between
+spin supercurrent mediated static exchange contribution and a dynamic spin
+pumping contribution. Depending on the outcome of this competition, a mode
+crossing in the system can either be an avoided crossing or mode locking.",2107.09959v2
+2021-10-07,Ultrafast element- and depth-resolved magnetization dynamics probed by transverse magneto-optical Kerr effect spectroscopy in the soft x-ray range,"We report on time- and angle-resolved transverse magneto-optical Kerr effect
+spectroscopy in the soft x-ray range that, by analysis via
+polarization-dependent magnetic scattering simulations, allows us to determine
+the spatio-temporal and element-specific evolution of femtosecond laser-induced
+spin dynamics in nanostructured magnetic materials. In a ferrimagnetic GdFe
+thin film system, we correlate a reshaping spectrum of the magneto-optical Kerr
+signal to depth-dependent magnetization dynamics and disentangle contributions
+due to non-equilibrium electron transport and nanoscale heat diffusion on their
+intrinsic time scales. Our work provides a quantitative insight into
+light-driven spin dynamics occurring at buried interfaces of complex magnetic
+heterostructures, which can be tailored and functionalized for future
+opto-spintronic devices.",2110.03599v2
+2022-03-15,Standing spin wave excitation in Bi:YIG films via temperature induced anisotropy changes and magnetoacoustic coupling,"Based on micromagnetic simulations and experimental observations of the
+magnetization and lattice dynamics following the direct optical excitation of
+the magnetic insulator Bi:YIG or indirect excitation via an optically opaque
+Pt/Cu double layer, we disentangle the dynamical effects of magnetic anisotropy
+and magnetoelastic coupling. The strain and temperature of the lattice are
+quantified via modeling ultrafast x-ray diffraction data. Measurements of the
+time-resolved magneto-optical Kerr effect agree well with the magnetization
+dynamics simulated according to the excitation via two mechanisms: The
+magneto-acoustic coupling to the experimentally verified strain dynamics and
+the ultrafast temperature-induced transient change in the magnetic anisotropy.
+The numerical modeling proves that for direct excitation both mechanisms drive
+the fundamental mode with opposite phase. The relative ratio of standing
+spin-wave amplitudes of higher order modes indicates that both mechanisms are
+substantially active.",2203.07851v1
+2022-03-17,A 3D BEM algorithm for simulations of magnetic fluid droplet dynamics,"This paper outlines a numerical algorithm that could be used for simulating
+full 3D dynamics of magnetic fluid droplet shapes in external magnetic fields,
+by solving boundary integral equations. The algorithm works with arbitrary
+droplet and carrier fluid viscosity ratios. It is validated with known
+theoretical relationships. Thus it may be used to evaluate various
+approximations often used in description of ellipsoidal droplets by comparing
+droplet dynamics calculated from them to the results obtained numerically from
+first principles here. The algorithm may be used for investigations of droplet
+configurations in arbitrary magnetic fields, as well as for indirectly
+calculating its physical properties and predicting the magnetic field
+thresholds above which droplet shape can develop instabilities in the form of
+various spikes.",2203.09499v1
+2022-03-26,Nonequilibrium dynamics in a spin valve with noncollinear magnetization,"We utilize a hybrid quantum-classical equation of motion approach to
+investigate the spin dynamics and spin-transfer torque in a spin valve under
+bias voltage. We show that the interplay between localized classical magnetic
+moments and conduction electrons induces a complex effective exchange coupling
+between the magnetic layers. This leads to a declination of magnetizations from
+layers anisotropy axes even in equilibrium. Introducing a finite bias voltage
+triggers spin currents and related spin-transfer torques which further tilt the
+magnetizations and govern the relaxation processes of the spin dynamics.
+Analyzing different scenarios of the applied bias voltage, we show that
+symmetric and asymmetric voltage drops can lead to relaxation times of the spin
+dynamics that differ by several orders of magnitude at comparable charge
+currents. In both cases we observe resonant features, where the relaxation is
+boosted whenever the chemical potential of the leads matches the maxima in the
+density of the states of the spin-valve electrons.",2203.14068v2
+2023-01-04,Role of ionic surfactant in magnetic dynamics of self-assembled dispersions of nanoplatelets,"In complex colloidal systems, interparticle interactions strongly affect the
+dynamics of the constituting particles. A study of the dynamical response also
+provides invaluable information on the character of those interactions. Here we
+demonstrate how tuning the electrostatic interactions by an ionic surfactant in
+dispersions of magnetic nanoplatelets leads to developing new dynamic modes in
+magnetic response spectra. The collective modes can be induced or suppressed by
+either varying the concentration ratio of the magnetic nanoplatelets (MP) to
+the surfactant or increasing the MP concentration reflecting the nanoscale
+characteristics of this fluid magnet.",2301.01652v1
+2023-07-11,Quantum dynamic response-based NV-diamond magnetometry: Robustness to decoherence and applications in motion detection of magnetic nanoparticles,"We propose a novel quantum sensing protocol that leverages the dynamical
+response of physical observables to quenches in quantum systems. Specifically,
+we use the nitrogen-vacancy (NV) color center in diamond to realize both scalar
+and vector magnetometry via quantum response. Furthermore, we suggest a method
+for detecting the motion of magnetic nanoparticles, which is challenging with
+conventional interference-based sensors. To achieve this, we derive the closed
+exact form of the Berry curvature corresponding to NV centers and design
+quenching protocols to extract the Berry curvature via dynamical response. By
+constructing and solving non-linear equations, the magnetic field and
+instantaneous motion velocity of the magnetic nanoparticle can be deduced. We
+investigate the feasibility of our sensing scheme in the presence of
+decoherence and show through numerical simulations that it is robust to
+decoherence. Intriguingly, we have observed that a vanishing nuclear spin
+polarization in diamond actually benefits our dynamic sensing scheme, which
+stands in contrast to conventional Ramsey-based schemes. In comparison to
+Ramsey-based sensing schemes, our proposed scheme can sense an arbitrary
+time-dependent magnetic field, as long as its time dependence is nearly
+adiabatic.",2307.05255v1
+2023-09-26,Orbital Pumping by Magnetization Dynamics in Ferromagnets,"We show that dynamics of the magnetization in ferromagnets can pump the
+orbital angular momentum, which we denote by orbital pumping. This is the
+reciprocal phenomenon to the orbital torque that induces magnetization dynamics
+by the orbital angular momentum in non-equilibrium. The orbital pumping is
+analogous to the spin pumping established in spintronics but requires the
+spin-orbit coupling for the orbital angular momentum to interact with the
+magnetization. We develop a formalism that describes the generation of the
+orbital angular momentum by magnetization dynamics within the adiabatic
+perturbation theory. Based on this, we perform first-principles calculation of
+the orbital pumping in prototypical $3d$ ferromagnets, Fe, Co, and Ni. The
+results show that the ratio between the orbital pumping and the spin pumping
+ranges from 5 to 15 percents, being smallest in Fe and largest in Ni. This
+implies that ferromagnetic Ni is a good candidate for measuring the orbital
+pumping. Implications of our results on experiments are also discussed.",2309.14817v2
+2023-10-13,Unified framework of the microscopic Landau-Lifshitz-Gilbert equation and its application to Skyrmion dynamics,"The Landau-Lifshitz-Gilbert (LLG) equation is widely used to describe
+magnetization dynamics. We develop a unified framework of the microscopic LLG
+equation based on the nonequilibrium Green's function formalism. We present a
+unified treatment for expressing the microscopic LLG equation in several
+limiting cases, including the adiabatic, inertial, and nonadiabatic limits with
+respect to the precession frequency for a magnetization with fixed magnitude,
+as well as the spatial adiabatic limit for the magnetization with slow
+variation in both its magnitude and direction. The coefficients of those terms
+in the microscopic LLG equation are explicitly expressed in terms of
+nonequilibrium Green's functions. As a concrete example, this microscopic
+theory is applied to simulate the dynamics of a magnetic Skyrmion driven by
+quantum parametric pumping. Our work provides a practical formalism of the
+microscopic LLG equation for exploring magnetization dynamics.",2310.08807v1
+2023-12-14,Passive dynamical decoupling of trapped ion qubits and qudits,"We propose a method to dynamically decouple every magnetically sensitive
+hyperfine sublevel of a trapped ion from magnetic field noise, simultaneously,
+using integrated circuits to adiabatically rotate its local quantization field.
+These integrated circuits allow passive adjustment of the effective
+polarization of any external (control or noise) field. By rotating the ion's
+quantization direction relative to this field's polarization, we can perform
+`passive' dynamical decoupling (PDD), inverting the linear Zeeman sensitivity
+of every hyperfine sublevel. This dynamically decouples the entire ion, rather
+than just a qubit subspace. Fundamentally, PDD drives the transition
+$m_{F}\rightarrow -m_{F}$ for every magnetic quantum number $m_{F}$ in the
+system--with only one operation--indicating it applies to qudits with constant
+overhead in the dimensionality of the qudit. We show how to perform pulsed and
+continuous PDD, weighing each technique's insensitivity to external magnetic
+fields versus their sensitivity to diabaticity and control errors. Finally, we
+show that we can tune the sinusoidal oscillation of the quantization axis to a
+motional mode of the crystal in order to perform a laser-free two qubit gate
+that is insensitive to magnetic field noise.",2312.09399v1
+2017-05-25,Spin-orbit torque-driven skyrmion dynamics revealed by time-resolved X-ray microscopy,"Magnetic skyrmions are topologically-protected spin textures with attractive
+properties suitable for high-density and low-power spintronic device
+applications. Much effort has been dedicated to understanding the dynamical
+behaviours of the magnetic skyrmions. However, experimental observation of the
+ultrafast dynamics of this chiral magnetic texture in real space, which is the
+hallmark of its quasiparticle nature, has so far remained elusive. Here, we
+report nanosecond-dynamics of a 100 nm-size magnetic skyrmion during a current
+pulse application, using a time-resolved pump-probe soft X-ray imaging
+technique. We demonstrate that distinct dynamic excitation states of magnetic
+skyrmions, triggered by current-induced spin-orbit torques, can be reliably
+tuned by changing the magnitude of spin-orbit torques. Our findings show that
+the dynamics of magnetic skyrmions can be controlled by the spin-orbit torque
+on the nanosecond time scale, which points to exciting opportunities for
+ultrafast and novel skyrmionic applications in the future.",1705.09019v1
+2019-06-28,Dynamics of groups of magnetically driven artificial microswimmers,"Magnetically driven artificial microswimmers have the potential to
+revolutionize many biomedical technologies, such as minimally-invasive
+microsurgery, micro-particle manipulation, and localized drug delivery.
+However, many of these applications will require the controlled dynamics of
+teams of these micro-robots with minimal feedback. In this work, we study the
+motion and fluid dynamics produced by groups of artificial microswimmers driven
+by a torque induced through a uniform, rotating magnetic field. Through
+Stokesian dynamics simulations, we show that the swimmer motion produces a
+rotational velocity field in the plane orthogonal to the direction of the
+magnetic field's rotation, which causes two interacting swimmers to move in
+circular trajectories in this plane around a common center. The resulting over
+all motion is on a helical trajectory for the swimmers. We compare the highly
+rotational velocity field of the fluid to the velocity field generated by a
+rotlet, the point-torque singularity of Stokes flows, showing that this is a
+reasonable approximation on the time average. Finally, we study the motion of
+larger groups of swimmers and show that these groups tend to move coherently,
+especially when swimmer magnetizations are uniform. This coherence is achieved
+because the group center remains almost constant in the plane orthogonal to the
+net motion of the swimmers. The results in the paper will prove useful for
+controlling the ensemble dynamics of small collections of magnetic swimmers.",1906.12049v2
+2022-07-02,Robust magnetic order upon ultrafast excitation of an antiferromagnet,"The ultrafast manipulation of magnetic order due to optical excitation is
+governed by the intricate flow of energy and momentum between the electron,
+lattice and spin subsystems. While various models are commonly employed to
+describe these dynamics, a prominent example being the microscopic three
+temperature model (M3TM), systematic, quantitative comparisons to both the
+dynamics of energy flow and magnetic order are scarce. Here, we apply a M3TM to
+the ultrafast magnetic order dynamics of the layered antiferromagnet
+GdRh$_2$Si$_2$. The femtosecond dynamics of electronic temperature, surface
+ferromagnetic order, and bulk antiferromagnetic order were explored at various
+pump fluences employing time- and angle-resolved photoemission spectroscopy and
+time-resolved resonant magnetic soft x-ray diffraction, respectively. After
+optical excitation, both the surface ferromagnetic order and the bulk
+antiferromagnetic order dynamics exhibit two-step demagnetization behaviors
+with two similar timescales (<1 ps, ~10 ps), indicating a strong exchange
+coupling between localized 4f and itinerant conduction electrons. Despite a
+good qualitative agreement, the M3TM predicts larger demagnetization than our
+experimental observation, which can be phenomenologically described by a
+transient, fluence-dependent increased N\'eel temperature. Our results indicate
+that effects beyond a mean-field description have to be considered for a
+quantitative description of ultrafast magnetic order dynamics.",2207.00789v1
+2024-03-29,Theory of the inverse Faraday effect in dissipative Rashba electron systems: Floquet engineering perspective,"We theoretically study the inverse Faraday effect (IFE), i.e., photo-induced
+magnetization, in two-dimensional Rashba spin-orbit coupled electron systems
+irradiated by a circularly polarized light. Quantum master (GKSL) equation
+enables us to accurately compute the laser driven dynamics, taking inevitable
+dissipation effects into account. To find the universal features of
+laser-driven magnetization and its dynamics, we investigate (i) the
+nonequilibrium steady state (NESS) driven by a continuous wave (CW) and (ii)
+ultrafast spin dynamics driven by short laser pulses. In the NESS (i), the
+laser-induced magnetization and its dependence of several parameters (laser
+frequency, laser field strength, temperature, dissipation strength, etc.) are
+shown to be in good agreement with the predictions from Floquet theory for
+dissipative systems in the high-frequency regime. In the case (ii), we focus on
+ferromagnetic metal states by introducing an effective magnetic field to the
+Rashba model as the mean field of electron-electron interaction. We find that a
+precession of the magnetic moment occurs due to the pulse-driven instantaneous
+magnetic field and the initial phase of the precession is controlled by
+changing the sign of light polarization. This is well consistent with the spin
+dynamics observed in experiments of laser-pulse-driven IFE. We discuss how the
+pulse-driven dynamics are captured by the Floquet theory. Our results provides
+a microscopic method to compute ultrafast dynamics in many electron systems
+irradiated by intense light.",2403.20110v1
+2023-07-16,Emergent electric field from magnetic resonances in a one-dimensional chiral magnet,"The emergent electric field (EEF) is a fictitious electric field acting on
+conduction electrons through the Berry phase mechanism. The EEF is generated by
+the dynamics of noncollinear spin configurations and becomes nonzero even in
+one dimension. Although the EEF has been studied for several one-dimensional
+chiral magnets, most of the theoretical studies were limited with respect to
+the strength and direction of the magnetic fields. Furthermore, the effect of
+edges of the system has not been clarified, whereas it can be crucial in nano-
+and micro-scale samples. Here, we perform a theoretical study on the
+momentum-frequency profile of the EEF in a one-dimensional chiral magnet while
+changing the strength and direction of the magnetic field for both bulk and
+finite-size chains with edges. As the bulk contributions, we find that the EEF
+is resonantly enhanced at the magnetic resonance frequencies; interestingly,
+the higher resonance modes are more clearly visible in the EEF response than in
+the magnetic one. Furthermore, we show that the EEF is amplified along with the
+solitonic feature of the spin texture introduced by the static magnetic field
+perpendicular to the chiral axis. We also show that the static magnetic field
+parallel to the chiral axis drives the EEF in the field direction, in addition
+to much slower drift motion in the opposite direction associated with the
+Archimedean screw dynamics, suggesting a DC electric current generation. As the
+edge contributions, we find additional resonance modes localized at the edges
+of the system that are also more clearly visible in the EEF response than the
+magnetic one. Our results reveal that the emergent electric phenomena in
+one-dimensional chiral magnets can be tuned by the magnetic field and the
+sample size, and provide not only a good probe of the magnetic resonances but
+also a platform for the applications to electronic devices.",2307.08017v1
+2022-02-09,Magnetic helicity and energy of emerging solar active regions and their erruptivity,"Aims. We investigate the role of the accumulation of both magnetic helicity
+and magnetic energy in the generation of coronal mass ejections (CMEs) from
+emerging solar active regions (ARs). Methods. Using vector magnetic field data
+obtained by the Helioseismic and Magnetic Imager on board the Solar Dynamics
+Observatory, we calculate the magnetic helicity and magnetic energy injection
+rates as well as the resulting accumulated budgets in 52 emerging ARs from the
+start time of magnetic flux emergence until they reach heliographic longitude
+of 45$^{\circ}$ West (W45). Results. Seven of the ARs produced CMEs while 45
+did not. In a statistical sense, the eruptive ARs accumulate larger budgets of
+both magnetic helicity and energy than the noneruptive ones over intervals that
+start from flux emergence start time and end (i) at the end of flux emergence
+phase, and (ii) when the AR produces its first CME or crosses W45, whichever
+happens first. We found magnetic helicity and energy thresholds of $9 \times
+10^{41}$ Mx$^2$ and $2 \times 10^{32}$ erg, respectively, which, if crossed,
+ARs are likely to erupt. The segregation, in terms of accumulated magnetic
+helicity and energy budgets, of the eruptive ARs from the noneruptive ones is
+violated in one case when an AR erupts early in its emergence phase and in six
+cases with noneruptive ARs exhibiting large magnetic helicity and energy
+budgets. Decay index calculations may indicate that these ARs did not erupt
+because the overlying magnetic field provided stronger or more extended
+confinement than in eruptive ARs. Conclusions. Our results indicate that
+emerging ARs tend to produce CMEs when they accumulate significant budgets of
+both magnetic helicity and energy. Any study of their eruptive potential should
+place magnetic helicity on equal footing with magnetic energy.",2202.04353v2
+2022-04-22,Nuclear spin self compensation system for moving MEG sensing with optical pumped atomic spin co-magnetometer,"Recording the moving MEGs of a person in which a person's head could move
+freely as we record the brain's magnetic field is a hot topic in recent years.
+Traditionally, atomic magnetometers are utilized for moving MEGs recording and
+a large compensation coil system is utilized for background magnetic field
+compensation. Here we described a new potential candidate: an optically pumped
+atomic co-magnetometer(OPACM) for moving MEGs recording. In the OPACM,
+hyper-polarized nuclear spins could produce a magnetic field which will shield
+the background fluctuation low frequency magnetic field noise while the the
+fast changing MEGs signal could be recorded. The nuclear spins look like an
+automatic magnetic field shields and dynamically compensate the fluctuated
+background magnetic field noise. In this article, the magnetic field
+compensation is studied theoretically and we find that the compensation is
+closely related to several parameters such as the electron spin magnetic field,
+the nuclear spin magnetic field and the holding magnetic field. Based on the
+model, the magnetic field compensation could be optimized. We also
+experimentally studied the magnetic field compensation and the responses of the
+OPACM to different frequencies of magnetic field are measured. We show that the
+OPACM owns a clear suppression of low frequency magnetic field under 1Hz and
+response to magnetic field's frequencies around the band of the MEGs. Magnetic
+field sensitivity of $3fT/Hz^{1/2}$ has been achieved. Finally, we do a
+simulation for the OPACM as it is utilized for moving MEGs recording. For
+comparison, the traditional compensation system for moving MEGs recording is
+based on a coil which is around 2m in dimension while our compensation system
+is only 2mm in dimension. Moreover, our compensation system could work in situ
+and will not affect each other.",2204.10481v1
+1993-08-13,Escape of trapped electrons from a helium surface: a dynamical theory,"We present a dynamical theory which incorporates the electron-electron
+correlations and the effects of external magnetic fields for an electron
+escaping from a helium surface. Analytical expressions for the escape rate can
+be obtained in various limits. In particular, the tunneling rate with a
+parallel magnetic field is presented explicitly.",9308020v1
+2003-09-26,Vortex dynamics in dilute two dimensional Josephson junction arrays,"We have investigated the dynamics of vortices in a dilute two dimensional
+Josephson junction array where a fraction of the superconducting islands is
+missing. We have used the multiple trapping model to calculate the mobility of
+vortices and the frequency dependence of the resistance and inductance of the
+array.",0309620v1
+2005-05-26,Jordan-Wigner Approach to Dynamic Correlations in 2D Spin-1/2 Models,"We discuss the dynamic properties of the square-lattice spin-1/2 XY model
+obtained using the two-dimensional Jordan-Wigner fermionization approach. We
+argue the relevancy of the fermionic picture for interpreting the neutron
+scattering measurements in the two-dimensional frustrated quantum magnet
+Cs_2CuCl_4.",0505641v1
+2002-06-27,"Comment on ``Electron Mass Operator in a Strong Magnetic Field and Dynamical Chiral Symmetry Breaking""","This is a comment on the paper ``Electron Mass Operator in a Strong Magnetic
+Field and Dynamical Chiral Symmetry Breaking"" by A. V. Kuznetsov and N. V.
+Mikheev [Phys. Rev. Lett. 89 (2002) 011601]. We show that the main conclusions
+of the paper are incorrect.",0206289v1
+2007-05-28,The Dynamical Mechanism of the Aharonov-Bohm Effect,"In this paper, it is emphasized that the dynamical cause for the A-B effect
+is the superimposed energy between the magnetic field produced by the moving
+charges and that in the solenoid, instead of the existence of the vector
+potential. If such a superposition between the magnetic fields can be
+eliminated, the A-B effect should not be observed any more. To verify this
+viewpoint, a new experimental method using a SQUID is suggested in this paper.",0705.4011v1
+2008-06-24,Magnetic Susceptibility of Quark Matter,"Magnetic properties of quark matter is discussed by evaluating the spin
+susceptibility within Fermi-liquid theory. We take into account the dynamical
+and static screening effects. At finite temperature, an anomalous T^2 ln T term
+for susceptibity is shown as a non-Fermi-liquid effect due to the dynamical
+screening of transverse gluons.",0806.3882v1
+2008-11-02,Static and Dynamic irreversible magnetic properties of high temperature superconductors,"This thesis describes experimental and theoretical study of static and
+dynamic aspects of the irreversible magnetic behavior of high-Tc
+superconductors. Experimentally, conventional magnetometry and novel Hall-probe
+array techniques are employed. Using both techniques extends significantly the
+experimental possibilities and yields a wealth of new experimental results.",0811.0177v1
+2010-09-16,Momentum conservation in dissipationless reduced-fluid dynamics,"The momentum conservation law for general dissipationless reduced-fluid
+(e.g., gyrofluid) models is derived by Noether method from a variational
+principle. The reduced-fluid momentum density and the reduced-fluid canonical
+momentum-stress tensor both exhibit polarization and magnetization effects as
+well as an internal torque associated with dynamical reduction. As an
+application, we derive an explicit gyrofluid toroidal angular-momentum
+conservation law for axisymmetric toroidal magnetized plasmas.",1009.3218v1
+2012-08-27,Positive topological entropy for multi-bump magnetic fields,"We study the dynamics of a charged particle in a planar magnetic field which
+consists of $n\geq 2$ disjoint localized peaks. We show that, under mild
+geometric conditions, this system is semi-conjugated to the full shift on $n$
+symbols and, hence, carries positive topological entropy.",1208.5437v1
+2014-02-14,Extremely high-resolution measurements of microwave magnetisation dynamics in magnetic thin films and nanostructures,"In this work we discuss the use of interferometric measurement technique to
+study microwave magnetization dynamics on ferromagnetic nanostructures. We
+demonstrate that in this way one can resolve features which are impossible to
+resolve with broadband ferromagnetic resonance and traveling spin wave
+spectroscopy otherwise.",1402.3459v1
+2015-04-16,Dynamical localization of Dirac particles in electromagnetic fields with dominating magnetic potentials,"We consider two-dimensional massless Dirac operators in a radially symmetric
+electromagnetic field. In this case the fields may be described by
+one-dimensional electric and magnetic potentials $V$ and $A$. We show dynamical
+localization in the regime when $\displaystyle\lim_{r\to\infty}|V|/|A |<1$,
+where dense point spectrum occurs.",1504.04077v1
+2016-09-22,Manipulation of magnetic Skyrmions with a Scanning Tunneling Microscope,"The dynamics of a single magnetic Skyrmion in an atomic spin system under the
+influence of Scanning Tunneling Microscope is investigated by computer
+simulations solving the Landau-Lifshitz-Gilbert equation. Two possible
+scenarios are described: manipulation with aid of a spin-polarized tunneling
+current and by an electric field created by the scanning tunneling microscope.
+The dynamics during the creation and annihilation process is studied and the
+possibility to move single Skyrmions is showed.",1609.06797v1
+2017-08-22,Dynamics of X-state in anisotropic Heisenberg spin with magnetic field,"We study the dynamics of X-state for anisotropic Heisenberg spin system using
+quantum fidelity. It is shown that while Bell diagonal state, a special class
+of X-state, is stationary, there exists a set of two parametric states which
+are stationary in presence of external uniform magnetic field.",1708.06632v1
+2019-04-22,About stability of plasma in a magnetic field,"The dynamics of the oscillator system is investigated. The conditions under
+which this dynamics becomes unstable are determined. In particular, it is shown
+that plasma in constant magnetic field becomes unstable if its density exceeds
+a certain critical value. The role of chaotic regimes on confinement of
+particles (oscillators) in confining potentials is studied.",1904.09950v1
+2002-02-19,Mass loading of pulsar winds,"The dynamics of relativistic magnetized mass loaded outflows carrying
+toroidal magnetic field is analyzed in the context of Pulsar Wind Nebulae
+(PWNs). Mass loading is very efficient in slowing down super-relativistic
+magnetized flows and weakening of relativistic shocks. We suggest that
+weakening of relativistic reverse shocks by mass loading in PWNs is responsible
+for the low radiative efficiencies of the majority of the PWNs. Mass loading
+may also result in a shock transition near the fast magnetosonic point; this is
+unlikely to happen in majority of PWNs. The evolution of magnetized mass loaded
+flows beyond the reverse shock is complicated: after initial deceleration to
+the minimal velocity required to transport the magnetic flux, the mass loaded
+flows have to {\it accelerate}. In order to be able to expand to infinity,
+magnetized flows should either become time dependent or destroy the toroidal
+magnetic flux by developing internal instabilities. Destruction of the magnetic
+flux initiated by mass loading may allow for the flow to slow down to
+sub-relativistic velocities and resolve the $\sigma$ paradox of the pulsar wind
+nebula.",0202344v1
+2005-01-28,Why Magnetic Fields Cannot be the Main Agent Shaping Planetary Nebulae,"An increasing amount of literature reports the detection of magnetic fields
+in asymptotic giant branch (AGB) stars and in central stars of planetary
+nebulae (PNs). These detections lead to claims that the magnetic fields are the
+main agent shaping the PNs. In this paper, I examine the energy and angular
+momentum carried by magnetic fields expelled from AGB stars, as well as other
+physical phenomena that accompany the presence of large scale fields, such as
+those claimed in the literature. I show that a single star cannot supply the
+energy and angular momentum if the magnetic fields have the large coherent
+structure required to shape the circumstellar wind. Therefore, the structure of
+non-spherical planetary nebulae cannot be attributed to dynamically important
+large scale magnetic fields. I conclude that the observed magnetic fields
+around evolved stars can be understood by locally enhanced magnetic loops which
+can have a secondary role in the shaping of the PN. The primary role, I argue,
+rests with the presence of a companion.",0501647v2
+1999-04-22,Deceptive Apparent Nonadiabatic Magnetization Process,"We discuss the effect of the thermal environment on the low-temperature
+response of the magnetization of uniaxial magnets to a time-dependent applied
+magnetic field. At sufficiently low temperatures the staircase magnetization
+curves observed in molecular magnets such as Mn_{12} and Fe_8 display little
+temperature dependence. However the changes of the magnetization at each step
+do not seem to be directly related to the probability for a quantum mechanical
+nonadiabatic transition. In order to explain this deceptive apparent
+nonadiabatic behavior, we study the quantum dynamics of the system in a thermal
+environment and propose a relation between the observed magnetization steps and
+the quantum mechanical transition probability due to the nonadiabatic
+transition.",9904323v4
+2003-03-15,Carrier States and Ferromagnetism in Diluted Magnetic Semiconductors,"Applying the dynamical coherent potential approximation to a simple model, we
+have systematically studied the carrier states in $A_{1-x}$Mn$_xB$-type diluted
+magnetic semiconductors (DMS's). The model calculation was performed for three
+typical cases of DMS's: The cases with strong and moderate exchange
+interactions in the absence of nonmagnetic potentials, and the case with strong
+attractive nonmagnetic potentials in addition to moderate exchange interaction.
+When the exchange interaction is sufficiently strong, magnetic impurity bands
+split from the host band. Carriers in the magnetic impurity band mainly stay at
+magnetic sites, and coupling between the carrier spin and the localized spin is
+very strong. The hopping of the carriers among the magnetic sites causes
+ferromagnetism through a {\it double-exchange (DE)-like} mechanism. We have
+investigated the condition for the DE-like mechanism to operate in DMS's. The
+result reveals that the nonmagnetic attractive potential at the magnetic site
+assists the formation of the magnetic impurity band and makes the DE-like
+mechanism operative by substantially enhancing the effect of the exchange
+interaction. Using conventional parameters we have studied the carrier states
+in Ga$_{1-x}$Mn$_x$As. The result shows that the ferromagnetism is caused
+through the DE-like mechanism by the carriers in the bandtail originating from
+the impurity states.",0303285v1
+2005-06-06,Thin superconductors and SQUIDs in perpendicular magnetic field,"It is shown how the static and dynamic electromagnetic properties can be
+calculated for thin flat superconducting films of any shape and size, also
+multiply connected as used for SQUIDs, and for any value of the effective
+magnetic London penetration depth Lambda. As examples, the distributions of
+sheet current and magnetic field are obtained for rectangular and circular
+films without and with slits and holes, in response to an applied perpendicular
+magnetic field and to magnetic vortices moving in the film. The self energy and
+interaction of vortices with each other and with an applied magnetic field
+and/or transport current are given. Due to the long ranging magnetic stray
+field, these energies depend on the size and shape of the film and on the
+vortex position even in large films, in contrast to the situation in large bulk
+superconductors. The focussing of magnetic flux into the central hole of square
+films without and with a radial slit is compared.",0506144v1
+2006-10-06,Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/Al$\_2$O$\_3$/Co magnetic tunnel junctions,"We have studied the magnetization reversal dynamics of FeNi/Al$\_2$O$\_3$/Co
+magnetic tunnel junctions deposited on step-bunched Si substrates using
+magneto-optical Kerr effect and time-resolved x-ray photoelectron emission
+microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM).
+Different reversal mechanisms have been found depending on the substrate miscut
+angle. Larger terraces (smaller miscut angles) lead to a higher nucleation
+density and stronger domain wall pinning. The width of domain walls with
+respect to the size of the terraces seems to play an important role in the
+reversal. We used the element selectivity of XMCD-PEEM to reveal the strong
+influence of the stray field of domain walls in the hard magnetic layer on the
+magnetic switching of the soft magnetic layer.",0610174v1
+2001-01-09,Hysteresis in layered spring magnets,"This article addresses a problem of micromagnetics: the reversal of magnetic
+moments in layered spring magnets. A one-dimensional model is used of a film
+consisting of several atomic layers of a soft material on top of several atomic
+layers of a hard material. Each atomic layer is taken to be uniformly
+magnetized, and spatial inhomogeneities within an atomic layer are neglected.
+The state of such a system is described by a chain of magnetic spin vectors.
+Each spin vector behaves like a spinning top driven locally by the effective
+magnetic field and subject to damping (Landau-Lifshitz-Gilbert equation). A
+numerical integration scheme for the LLG equation is presented that is
+unconditionally stable and preserves the magnitude of the magnetization vector
+at all times. The results of numerical investigations for a bilayer in a
+rotating in-plane magnetic field show hysteresis with a basic period of $2\pi$
+at moderate fields and hysteresis with a basic period of $\pi$ at strong
+fields.",0101077v1
+2006-06-29,Positive Topological Entropy for Magnetic Flows on Surfaces,"We study the topological entropy of the magnetic flow on a closed riemannian
+surface. We prove that if the magnetic flow has a non-hyperbolic closed orbit
+in some energy set T^cM= E^{-1}(c), then there exists an exact $
+C^\infty$-perturbation of the 2-form $ \Omega $ such that the new magnetic flow
+has positive topological entropy in T^cM. We also prove that if the magnetic
+flow has an infinite number of closed orbits in T^cM, then there exists an
+exact C^1-perturbation of $ \Omega $ with positive topological entropy in T^cM.
+The proof of the last result is based on an analog of Franks' lemma for
+magnetic flows on surfaces, that is proven in this work, and Ma\~n\'e's
+techniques on dominated splitting. As a consequence of those results, an exact
+magnetic flow on S^2 in high energy levels admits a C^1-perturbation with
+positive topological entropy. In the appendices we show that an exact magnetic
+flow on the torus in high energy levels admits a $ C^\infty $-perturbation with
+positive topological entropy.",0606740v3
+2007-09-12,Numerical Simulations of Equatorially-Asymmetric Magnetized Supernovae: Formation of Magnetars and Their Kicks,"A series of numerical simulations on magnetorotational core-collapse
+supernovae are carried out. Dipole-like configurations which are offset
+northward are assumed for the initially strong magnetic fields together with
+rapid differential rotations. Aims of our study are to investigate effects of
+the offset magnetic field on magnetar kicks and on supernova dynamics. Note
+that we study a regime where the proto-neutron star formed after collapse has a
+large magnetic field strength approaching that of a ``magnetar'', a highly
+magnetized slowly rotating neutron star. As a result, equatorially-asymmetric
+explosions occur with a formation of the bipolar jets. Resultant magnetar's
+kick velocities are $\sim 300-1000$ km s$^{-1}$. We find that the acceleration
+is mainly due to the magnetic pressure while the somewhat weaker magnetic
+tension works toward the opposite direction, which is due to stronger magnetic
+field in the northern hemisphere. Noted that observations of magnetar's proper
+motions are very scarce, our results supply a prediction for future
+observations. Namely, magnetars possibly have large kick velocities, several
+hundred km s$^{-1}$, as ordinary neutron stars do, and in an extreme case they
+could have those up to 1000 km s$^{-1}$.",0709.1795v1
+2008-09-22,Elementary transitions and magnetic correlations in two-dimensional disordered nanoparticle ensembles,"The magnetic relaxation processes in disordered two-dimensional ensembles of
+dipole-coupled magnetic nanoparticles are theoretically investigated by
+performing numerical simulations. The energy landscape of the system is
+explored by determining saddle points, adjacent local minima, energy barriers,
+and the associated minimum energy paths (MEPs) as functions of the structural
+disorder and particle density. The changes in the magnetic order of the
+nanostructure along the MEPs connecting adjacent minima are analyzed from a
+local perspective. In particular, we determine the extension of the correlated
+region where the directions of the particle magnetic moments vary
+significantly. It is shown that with increasing degree of disorder the magnetic
+correlation range decreases, i.e., the elementary relaxation processes become
+more localized. The distribution of the energy barriers, and their relation to
+the changes in the magnetic configurations are quantified. Finally, some
+implications for the long-time magnetic relaxation dynamics of nanostructures
+are discussed.",0809.3640v1
+2009-03-19,Turbulent transport and dynamo in sheared MHD turbulence with a non-uniform magnetic field,"We investigate three-dimensional magnetohydrodynamics turbulence in the
+presence of both a large-scale velocity and non-uniform magnetic field. By
+assuming a turbulence driven by an external forcing with both helical and
+non-helical spectra, we investigate the combined effect of these two shears on
+turbulence intensity and turbulent transport represented by turbulent
+diffusivities (turbulent viscosity, $\alpha$ and $\beta$ effect) in analogy
+with Reynolds. We show that turbulence viscosity and diffusivity are quenched
+for strong flow shear and magnetic field in the limits of weak and strong
+magnetic field, respectively. For a weak flow shear, we further show that the
+magnetic shear increases the turbulence intensity while decreasing the
+turbulent transport. In the presence of a strong flow shear, the effect of the
+magnetic shear is found to oppose the effect of flow shear (which reduces
+turbulence due to shear stabilization) by enhancing turbulence and transport,
+thereby weakening the strong quenching by flow shear stabilization. In the case
+of a strong magnetic field (compared to flow shear), magnetic shear increases
+turbulence intensity and quenches turbulent transport.",0903.3352v2
+2009-05-03,Small-scale magnetic helicity losses from a mean-field dynamo,"Using mean-field models with a dynamical quenching formalism we show that in
+finite domains magnetic helicity fluxes associated with small-scale magnetic
+fields are able to alleviate catastrophic quenching. We consider fluxes that
+result either from advection by a mean flow, the turbulent mixing down the
+gradient of mean small-scale magnetic helicity concentration, or the explicit
+removal which may be associated with the effects of coronal mass ejections in
+the Sun. In the absence of shear, all the small-scale magnetic helicity fluxes
+are found to be equally strong both for large-scale and small-scale fields. In
+the presence of shear there is also an additional magnetic helicity flux
+associated with the mean field, but this flux does not alleviate catastrophic
+quenching. Outside the dynamo-active region there are neither sources nor sinks
+of magnetic helicity, so in a steady state this flux must be constant. It is
+shown that unphysical behavior emerges if the small-scale magnetic helicity
+flux is forced to vanish within the computational domain.",0905.0242v1
+2010-07-02,Bohr quantum theory of the magnetic monopoles and classical electron electromagnetic mass problem,"In the first part of this work we apply Bohr (old or naive quantum atomic)
+theory for analysis of the remarkable electro-dynamical problem of magnetic
+monopoles. We reproduce formally exactly some basic elements of the Dirac
+magnetic monopoles theory, especially Dirac electric/magnetic charge
+quantization condition. It follows after application of Bohr theory at the
+system, simply called magnetic monopole ""atom"", consisting of the practically
+standing, massive magnetic monopole as the ""nucleus"" and electron rotating
+stable around magnetic monopole under magnetic and electrostatic interactions.
+Also, in the second part of this work we suggest a simple solution of the
+classical electron electromagnetic mass problem.",1007.0340v9
+2011-02-01,One-dimentional magnonic crystal as a medium with magnetically tunable disorder on a periodical lattice,"We show that periodic magnetic nanostructures (magnonic crystals) represent
+an ideal system for studying excitations on disordered periodical lattices
+because of the possibility of controlled variation of the degree of disorder by
+varying the applied magnetic field. Ferromagnetic resonance (FMR) data
+collected inside minor hysteresis loops for a periodic array of Permalloy
+nanowires of alternating width and magnetic force microscopy images of the
+array taken after running each of these loops were used to establish convincing
+evidence that there is a strong correlation between the type of FMR response
+and the degree of disorder of the magnetic ground state. We found two types of
+dynamic responses: anti-ferromagnetic (AFM) and ferromagnetic (FM), which
+represent collective spin wave modes or collective magnonic states. Depending
+on the history of sample magnetization either AFM or FM state is either the
+fundamental FMR mode or represents a state of a magnetic defect on the
+artificial crystal. A fundamental state can be transformed into a defect one
+and vice versa by controlled magnetization of the sample.",1102.0069v1
+2011-10-04,Negative magnetization of Li2Ni2Mo3O12 having a spin system composed of distorted honeycomb lattices and linear chains,"We study themagnetism of a spin-1 substance Li2Ni2Mo3O12. The spin system
+consists of distorted honeycomb lattices and linear chains of Ni2+ spins. Li+
+ions enter about 25% and 50% of the honeycomb and chain Ni sites, respectively,
+creating disorder in both spin subsystems. A magnetic phase transition occurs
+at Tc = 8.0 K in the zero magnetic field. In low magnetic fields, the
+magnetization increases rapidly below Tc, decreases below 7 K, and finally
+becomes negative at low temperatures. We determine the magnetic structure using
+neutron powder diffraction results. The honeycomb lattices and linear chains
+show antiferromagnetic and ferromagnetic long-range order, respectively. We
+investigate static and dynamic magnetic properties using the local probe
+technique of muon spin relaxation. We discuss the origin of the negative
+magnetization.",1110.0587v1
+2011-10-27,Magnetically Controlling the Explosion of Dirac Fermions during the Oxidation of Graphene,"The different physical properties of multilayered graphene or graphite
+relative to single layer graphene result from the Dirac spins symmetry in
+graphene and the Pauli spin symmetry in graphite. The Dirac symmetry in
+multilayers of graphene (graphite) is hindered by interlayer interactions.
+Different magnetizations, electronics and chemistry of graphite and graphene
+follow from absence of interlayer interactions in graphene. The distinct
+kinetics and dynamics of graphite and graphene by oxidation by the Hummer's
+method in weak external magnetic field are observed in this work. Graphite
+manifest enhanced non-explosive oxidation of Pauli spins in weak magnetic field
+with background paramagnetic oxygen slowing the magnetic acceleration. Graphene
+and graphite oxide manifest explosive oxidation and magnetically decelerated
+explosive oxidation of Dirac spins in weak magnetic field for temperatures
+below 20 oCelsius. The explosive oxidation of graphene and its deceleration in
+weak external magnetic field are interpreted resulting from the giant
+nonlocality and spin Hall Effect in the chemically reacting graphene. This is
+the first identification, analysis and interpretation of the chemistry of the
+Dirac spins and the magnetochemistry of relativistic electrons.",1110.6060v1
+2012-01-05,Direct measurement of the three dimensional magnetization vector trajectory in GaMnAs by a magneto-optical pump-and-probe method,"We report on a quantitative experimental determination of the
+three-dimensional magnetization vector trajectory in GaMnAs by means of the
+static and time-resolved pump-and-probe magneto-optical measurements. The
+experiments are performed in a normal incidence geometry and the time evolution
+of the magnetization vector is obtained without any numerical modeling of
+magnetization dynamics. Our experimental method utilizes different polarization
+dependences of the polar Kerr effect and magnetic linear dichroism to
+disentangle the pump-induced out-of-plane and in-plane motions of
+magnetization, respectively. We demonstrate that the method is sensitive enough
+to allow for the determination of small angle excitations of the magnetization
+in GaMnAs. The method is readily applicable to other magnetic materials with
+sufficiently strong circular and linear magneto-optical effects.",1201.1213v1
+2012-02-01,Magnet designs for muon collider ring and interactions regions,"Conceptual designs of superconducting magnets for the storage ring of a Muon
+Collider with a 1.5 TeV c.o.m. energy and an average luminosity of 10 34
+cm-2s-1 are presented. All magnets are based on Nb3Sn superconductor and
+designed to provide an adequate operating field/field gradient in the aperture
+with the critical current margin required for reliable magnet operation in the
+machine. Magnet cross-sections were optimized to achieve the accelerator field
+quality in the magnet aperture occupied with beams. The magnets and
+corresponding protective measures are designed to handle about 0.5 kW/m of
+dynamic heat load from the muon beam decays. Magnet parameters are reported and
+compared with the requirements.",1202.0270v1
+2012-03-26,Local electric current correlation function in an exponentially decaying magnetic field,"The effect of an exponentially decaying magnetic field on the dynamics of
+Dirac fermions in 3+1 dimensions is explored. The spatially decaying magnetic
+field is assumed to be aligned in the third direction, and is defined by
+{\mathbf{B}}(x)=B(x){\mathbf{e}}_{z}, with B(x)=B_{0}e^{-\xi\ x/\ell_{B}}.
+Here, \xi\ is a dimensionless damping factor and \ell_{B}=(eB_{0})^{-1/2} is
+the magnetic length. As it turns out, the energy spectrum of fermions in this
+inhomogeneous magnetic field can be analytically determined using the Ritus
+method. Assuming the magnetic field to be strong, the chiral condensate and the
+\textit{local} electric current correlation function are computed in the lowest
+Landau level (LLL) approximation and the results are compared with those
+arising from a strong homogeneous magnetic field. Although the constant
+magnetic field B_{0} can be reproduced by taking the limit of \xi-> 0 and/or
+x-> 0 from B(x), these limits turn out to be singular once the quantum
+corrections are taken into account.",1203.5634v2
+2012-09-26,Fermi Surface Reconstruction by Dynamic Magnetic Fluctuations and Spin-Charge Separation Near an O(3) Quantum Critical Point,"Stimulated by the small/large Fermi surface controversy in the cuprates we
+consider a small number of holes injected into the bilayer antiferromagnet. The
+system has an O(3) quantum critical point (QCP) separating the magnetically
+ordered and the magnetically disordered phases. We demonstrate that nearly
+critical quantum magnetic fluctuations can change the Fermi surface topology
+and also lead to spin charge separation (SCS) in two dimensions. We demonstrate
+that in the physically interesting regime there is a magnetically driven
+Lifshitz point (LP) inside the magnetically disordered phase. At the LP the
+topology of the hole Fermi surface is changed. The position of the LP, while
+being close to the position of the QCP is generally different. Dependent on the
+additional hole hopping integrals $t^{\prime}$ and $t^{\prime\prime}$, the LP
+can be located either in the magnetically ordered phase and/or in the
+magnetically disordered phase. We also demonstrate that in this regime the hole
+spin and charge necessarily separate when approaching the QCP. The considered
+model sheds light on generic problems concerning the physics of the cuprates.",1209.6051v1
+2012-10-06,Magnetic induction maps in a magnetized spherical Couette flow experiment,"The DTS experiment is a spherical Couette flow experiment with an imposed
+dipolar magnetic field. Liquid sodium is used as a working fluid. In a series
+of measurement campaigns, we have obtained data on the mean axisymmetric
+velocity, the mean induced magnetic field and electric potentials. All these
+quantities are coupled through the induction equation. In particular, a strong
+omega-eff ect is produced by di fferential rotation within the fluid shell,
+inducing a significant azimuthal magnetic field. Taking advantage of the simple
+spherical geometry of the experiment, I expand the azimuthal and meridional
+fields into Legendre polynomials and derive the expressions that relate all
+measurements to the radial functions of the velocity field for each harmonic
+degree. For small magnetic Reynolds numbers Rm the relations are linear, and
+the azimuthal and meridional equations decouple. Selecting a set of
+measurements for a given rotation frequency of the inner sphere (Rm = 9.4), I
+invert simultaneously the velocity and the magnetic data and thus reconstruct
+both the azimuthal and the meridional fields within the fluid shell. The
+results demonstrate the good internal consistency of the measurements, and
+indicate that turbulent non-axisymmetric fluctuations do not contribute
+significantly to the axisymmetric magnetic induction.",1210.1990v2
+2012-10-12,Reversal of magnetization of a single-domain magnetic particle by the ac field of time-dependent frequency,"We report numerical and analytical studies of the reversal of the magnetic
+moment of a single-domain magnetic particle by a circularly polarized ac field
+of time-dependent frequency. For the time-linear frequency sweep, the phase
+diagrams are computed that illustrate the dependence of the reversal on the
+frequency sweep rate v, the amplitude of the ac field h, the magnetic
+anisotropy field d, and the damping parameter alpha. It is shown that the most
+efficient magnetization reversal requires a non-linear time dependence of the
+frequency, omega(t), for which an exact analytical formula is derived with
+account of damping. The necessary condition of the reversal is h > alpha d.
+Implementation of a small-scale magnetization reversal is proposed in which a
+nanomagnet is electromagnetically coupled to two weak superconducting links
+controlled by the voltage. Dynamics of such a system is analyzed with account
+of the back effect of the magnet on the superconducting links.",1210.3530v1
+2012-12-06,A Superparamagnetic State Induced by a Spin Reorientation Transition in Ultrathin Magnetic Films,"We investigate a spin reorientation transition (SRT) in ultrathin magnetic
+films by Monte-Carlo simulations. We assume that the lateral size of the film
+is relatively small and it has a single-domain structure. To gain insights into
+the SRT, we measure a free-energy as a function of perpendicular and in-plane
+magnetizations. As a result, we find that the system is in a superparamagnetic
+state at the SRT temperature. The disappearance of magnetization around the SRT
+temperature, which is observed in experiments, emerges due to dynamical
+fluctuations in magnetization which are inherent in the superparamagnetic
+state. This observation is in contrast to that in large ultrathin magnetic
+films that the disappearance of magnetization is caused by a static magnetic
+structure with many complex domains.",1212.1228v2
+2013-04-10,"Reconnection Diffusion, Star Formation and Numerical Simulations","We consider fast magnetic reconnection that takes place within turbulent
+magnetic flux and show that the process results in diffusion of magnetic fields
+and matter, which we term reconnection diffusion. The process of reconnection
+diffusion is based on the model of 3D reconnection of weakly turbulent magnetic
+fields and is applicable to both fully ionized and partially ionized gas. The
+rate of reconnection diffusion does not depend on the level of ionization and
+therefore the usually employed ambipolar diffusion idea gets irrelevant for
+magnetic field transport in turbulent fluids. We claim that the reconnection
+diffusion process is a manifestation of the violation of flux conservation in
+highly conducting turbulent fluids. We discuss the consequences of reconnection
+diffusion for star formation and stress. We show that reconnection diffusion on
+large scales is independent of small scale magnetic field dynamics of magnetic
+fields. We conclude that numerical simulations correctly represents the
+diffusion of actual astrophysical magnetic fields in flows with substantially
+larger Lundquist numbers if these simulated regions regions are turbulent.",1304.3133v1
+2013-04-14,Influence of initial conditions on the large-scale dynamo growth rate,"To investigate the effect of energy and helicity on the growth of magnetic
+field, helical kinetic forcing was applied to the magnetohydrodynamic(MHD)
+system that had a specific distribution of energy and helicity as initial
+conditions. Simulation results show the saturation of a system is not
+influenced by the initial conditions, but the growth rate of large scale
+magnetic field is proportionally dependent on the initial large scale magnetic
+energy and helicity. It is already known that the helical component of small
+scale magnetic field(i.e., current helicity $<{\bf j}\cdot {\bf b}>$) quenches
+the growth of large scale magnetic field. However, $<{\bf j}\cdot {\bf b}>$ can
+also boost the growth of large scale magnetic field by changing its sign and
+magnitude. In addition, simulation shows the nonhelical magnetic field can
+suppress the velocity field through Lorentz force. Comparison of the profiles
+of evolving magnetic and kinetic energy indicates that kinetic energy migrates
+backward when the external energy flows into the three dimensional MHD system,
+which means the velocity field may play a preceding role in the very early MHD
+dynamo stage.",1304.3870v3
+2013-05-06,Inverse magnetic catalysis induced by sphalerons,"The recently discovered inverse magnetic catalysis around the critical
+temperature indicates that some important information is missing in our current
+understanding of conventional chiral dynamics of QCD, which is enhanced by the
+magnetic field. In this work, we provide a mechanism to explain that the
+inverse magnetic catalysis around the critical temperature is induced by
+sphalerons. At high temperatures, sphaleron transitions between distinct
+classical vacua cause an asymmetry between the number of right- and left-handed
+quarks due to the axial anomaly of QCD. In the presence of a strong magnetic
+field, the chiral imbalance is enhanced and destroys the right- and left-handed
+pairings, which naturally induces a decreasing critical temperature of the
+chiral phase transition for increasing magnetic field. The inverse magnetic
+catalysis at finite baryon density, and the critical end point in the presence
+of a strong magnetic field is also explored in this work.",1305.1100v1
+2013-07-29,Electrocapillary instability of magnetic fluid peak,"The paper presents an experimental study of the capillary electrostatic
+instability occurring under effect of a constant electric field on a magnetic
+fluid individual peak. The peaks under study occur at disintegration of a
+magnetic fluid layer applied on a flat electrode surface under effect of a
+perpendicular magnetic field. The electrocapillary instability shows itself as
+an emission of charged drops jets from the peak point in direction of the
+opposing electrode. The charged drops emission repeats periodically and results
+in the peak shape pulsations. It is shown that a magnetic field affects the
+electrocapillary instability occurrence regularities and can stimulate its
+development. The critical electric and magnetic field strengths at which the
+instability occurs have been measured; their dependence on the peak size is
+shown. The hysteresis in the system has been studied; it consists in that the
+charged drops emission stops at a lesser electric (or magnetic) field strength
+than that of the initial occurrence. The peak pulsations frequency depending on
+the magnetic and electric field strengths and on the peak size has been
+measured.",1307.7734v1
+2013-12-05,Transient jet formation and state transitions from large-scale magnetic reconnection in black hole accretion discs,"Magnetically arrested accretion discs (MADs), where the magnetic pressure in
+the inner disc is dynamically important, provide an alternative mechanism for
+regulating accretion to what is commonly assumed in black hole systems. We show
+that a global magnetic field inversion in the MAD state can destroy the jet,
+significantly increase the accretion rate, and move the effective inner disc
+edge in to the marginally stable orbit. Reconnection of the MAD field in the
+inner radii launches a new type of transient outflow containing hot plasma
+generated by magnetic dissipation. This transient outflow can be as powerful as
+the steady magnetically-dominated Blandford-Znajek jet in the MAD state. The
+field inversion qualitatively describes many of the observational features
+associated with the high luminosity hard to soft state transition in black hole
+X-ray binaries: the jet line, the transient ballistic jet, and the drop in rms
+variability. These results demonstrate that the magnetic field configuration
+can influence the accretion state directly, and hence the magnetic field
+structure is an important second parameter in explaining observations of
+accreting black holes across the mass and luminosity scales.",1312.1691v1
+2014-01-05,Generation of Magnetic Field on the Accretion Disk around a Proto-First-Star,"The generation process of magnetic field around a proto-first-star is
+studied. Utilizing the recent numerical result of proto-first-star formation
+based upon the radiation hydrodynamics simulations, we assess the magnetic
+field strength generated by the radiative force and the Biermann battery
+effect. We find that magnetic field of \sim 10^{-9} G is generated on the
+surface of the accretion disk around the proto-first-star. The field strength
+on the accretion disk is smaller by two orders of magnitude than the critical
+value, above which the gravitational fragmentation of the disk is suppressed.
+Thus, the generated seed magnetic field hardly affect the dynamics of on-site
+first star formation directly, unless efficient amplification process is taken
+into consideration. We also find that the generated magnetic field is
+continuously blown out from the disk on the outflows to the poles, that are
+driven by the thermal pressure of photoheated gas. The strength of the diffused
+magnetic field in low density regions is \sim 10^{-14}-10^{-13}G at n_H=10^3
+cm^{-3} which could play important roles on the next generation star formation,
+as well as the seeds of magnetic field exist in present-day universe.",1401.0905v1
+2014-02-04,Laser-induced magnetization curve,"We propose an all optical ultrafast method to highly magnetize general
+quantum magnets using a circularly polarized terahertz laser. The key idea is
+to utilize a circularly polarized laser and its chirping. Through this method,
+one can obtain magnetization curves of a broad class of quantum magnets as a
+function of time even without any static magnetic field. We numerically
+demonstrate the laser-induced magnetization process in realistic quantum spin
+models and find a condition for the realization. The onset of magnetization can
+be described by a many-body version of Landau-Zener mechanism. In a particular
+model, we show that a plateau state with topological properties can be realized
+dynamically.",1402.0881v2
+2014-04-14,Orbital magnetization of correlated electrons with arbitrary band topology,"Spin-orbit coupling introduces chirality into electronic structure. This can
+have profound effects on the magnetization induced by orbital motion of
+electrons. Here we derive a formula for the orbital magnetization of
+interacting electrons in terms of the full Green's function and vertex
+functions. The formula is applied within dynamical mean-field theory to the
+Kane-Mele-Hubbard model that allows both topological and trivial insulating
+phases. We study the insulating and metallic phases in the presence of an
+exchange magnetic field. In the presence of interactions, the orbital
+magnetization of the quantum spin Hall insulating phase with inversion symmetry
+is renormalized by the bulk quasi-particle weight. The orbital magnetization
+vanishes for the in-plane antiferromagnetic phase with trivial topology. In the
+metallic phase, the enhanced effective spin-orbit coupling due to the
+interaction sometimes leads to an enhancement of the orbital magnetization.
+However, at low doping, magnetization is suppressed at large interaction
+strengths.",1404.3673v3
+2014-04-28,Magnetic Prandtl number dependence of kinetic to magnetic dissipation ratio,"Using direct numerical simulations of three-dimensional hydromagnetic
+turbulence, either with helical or non-helical forcing, we show that the ratio
+of kinetic-to-magnetic energy dissipation always increases with the magnetic
+Prandtl number, i.e., the ratio of kinematic viscosity to magnetic diffusivity.
+This dependence can always be approximated by a power law, but the exponent is
+not the same in all cases. For non-helical turbulence, the exponent is around
+1/3, while for helical turbulence it is between 0.6 and 2/3. In the
+statistically steady state, the rate of the energy conversion from kinetic into
+magnetic by the dynamo must be equal to the Joule dissipation rate. We
+emphasize that for both small-scale and large-scale dynamos, the efficiency of
+energy conversion depends sensitively on the magnetic Prandtl number, and thus
+on the microphysical dissipation process. To understand this behavior, we also
+study shell models of turbulence and one-dimensional passive and active scalar
+models. We conclude that the magnetic Prandtl number dependence is
+qualitatively best reproduced in the one-dimensional model as a result of
+dissipation via localized Alfven kinks.",1404.6964v2
+2014-04-29,Nanowire Spin Torque Oscillator Driven by Spin Orbit Torques,"Spin torque from spin current applied to a nanoscale region of a ferromagnet
+can act as negative magnetic damping and thereby excite self-oscillations of
+its magnetization. In contrast, spin torque uniformly applied to the
+magnetization of an extended ferromagnetic film does not generate
+self-oscillatory magnetic dynamics but leads to reduction of the saturation
+magnetization. Here we report studies of the effect of spin torque on a system
+of intermediate dimensionality - a ferromagnetic nanowire. We observe coherent
+self-oscillations of magnetization in a ferromagnetic nanowire serving as the
+active region of a spin torque oscillator driven by spin orbit torques. Our
+work demonstrates that magnetization self-oscillations can be excited in a
+one-dimensional magnetic system and that dimensions of the active region of
+spin torque oscillators can be extended beyond the nanometer length scale.",1404.7262v2
+2014-06-08,Perpendicular magnetic anisotropy and magnetization process in CoFeB/Pd multilayer films,"Perpendicular magnetic anisotropy (PMA) and dynamic magnetization reversal
+process in [CoFeB $t$ nm/Pd 1.0 nm]$_n$ ($t$ = 0.4, 0.6, 0.8, 1.0, and 1.2 nm;
+$n$ = 2 - 20) multilayer films have been studied by means of magnetic
+hysteresis and Kerr effect measurements. Strong and controllable PMA with an
+effective uniaxial anisotropy up to 7.7$\times$ 10$^6$ J.m$^{-3}$ and a
+saturation magnetization as low as 200 emu/cc are achieved. Surface/interfacial
+anisotropy of CoFeB/Pd interfaces, the main contribution to the PMA, is
+separated from the effective uniaxial anisotropy of the films, and appears to
+increase with the number of the CoFeB/Pd bilayers. Observation of the magnetic
+domains during a magnetization reversal process using polar magneto-optical
+Kerr microscopy shows the detailed behavior of nucleation and displacement of
+the domain walls.",1406.2028v1
+2014-06-27,On the plasma flow inside magnetic tornadoes on the Sun,"High-resolution observations with the Swedish 1-m Solar Telescope (SST) and
+the Solar Dynamics Observatory (SDO) reveal rotating magnetic field structures
+that extend from the solar surface into the chromosphere and the corona. These
+so-called magnetic tornadoes are primarily detected as rings or spirals of
+rotating plasma in the Ca II 854.2 nm line core (also known as chromospheric
+swirls). Detailed numerical simulations show that the observed chromospheric
+plasma motion is caused by the rotation of magnetic field structures, which
+again are driven by photospheric vortex flows at their footpoints. Under the
+right conditions, two vortex flow systems are stacked on top of each other. We
+refer to the lower vortex, which extends from the low photosphere into the
+convection zone, as intergranular vortex flow (IVF). Once a magnetic field
+structure is co-located with an IVF, the rotation is mediated into the upper
+atmospheric layers and an atmospheric vortex flow (AVF, or magnetic tornado) is
+generated. In contrast to the recent work by Shelyag et al., we demonstrate
+that particle trajectories in a simulated magnetic tornado indeed follow
+spirals and argue that the properties of the trajectories decisively depend on
+the location in the atmosphere and the strength of the magnetic field.",1406.7270v1
+2014-09-05,Effect of Size of the Computational Domain on Spherical Nonlinear Force-Free Modeling of Coronal Magnetic Field Using SDO/HMI Data,"The solar coronal magnetic field produces solar activity, including extremely
+energetic solar flares and coronal mass ejections (CMEs). Knowledge of the
+structure and evolution of the magnetic field of the solar corona is important
+for investigating and understanding the origins of space weather. Although the
+coronal field remains difficult to measure directly, there is considerable
+interest in accurate modeling of magnetic fields in and around sunspot regions
+on the Sun using photospheric vector magnetograms as boundary data. In this
+work, we investigate effects of the size of the domain chosen for coronal
+magnetic field modeling on resulting model solution. We apply spherical
+Optimization procedure to vector magnetogram data of Helioseismic and Magnetic
+Imager (HMI) onboard Solar Dynamics Observatory (SDO) with four Active Region
+observed on 09 March 2012 at 20:55UT. The results imply that quantities like
+magnetic flux density, electric current density and free magnetic energy
+density of ARs of interest are significantly different from the corresponding
+quantities obtained in the same region within the wider field of view. The
+difference is even more pronounced in the regions where there are connections
+to outside the domain.",1409.1775v1
+2014-09-15,Nonlinear magneto-optical response to light carrying orbital angular momentum,"We predict a non-thermal magneto-optical effect for magnetic insulators
+subject to intense light carrying orbital angular momentum (OAM). Using a
+classical approach to second harmonic generation in non-linear media with
+specific symmetry properties we predict a significant nonlinear contribution to
+the local magnetic field triggered by light with OAM. The resulting magnetic
+field originates from the displacement of electrons driven by the electrical
+field (with amplitude $E_0$) of the spatially inhomogeneous optical pulse,
+modeled here as a Laguerre-Gaussian beam carrying OAM. In particular, the
+symmetry properties of the irradiated magnet allow for magnetic field responses
+which are second-order ($\sim E_0^2$) and fourth-order ($\sim E_0^4$) in
+electric-field strength and have opposite signs. For sufficiently high laser
+intensities, terms $\sim E_0^4$ dominate and generate magnetic field strengths
+which can be as large as several Tesla. Moreover, changing the OAM of the laser
+beam is shown to determine the direction of the total light-induced magnetic
+field, which is further utilized to study theoretically the non-thermal
+magnetization dynamics.",1409.4385v1
+2014-10-08,Flat-band ferromagnetism in the multilayer Lieb optical lattice,"We theoretically study magnetic properties of two-component cold fermions in
+half-filled multilayer Lieb optical lattices, i.e., two, three, and several
+layers, using the dynamical mean-field theory. We clarify that the magnetic
+properties of this system become quite different depending on whether the
+number of layers is odd or even. In odd-number-th layers in an odd-number-layer
+system, finite magnetization emerges even with an infinitesimal interaction.
+This is a striking feature of the flatband ferromagnetic state in multilayer
+systems as a consequence of the Lieb theorem. In contrast, in even-number
+layers, magnetization develops from zero on a finite interaction. These
+different magnetic behaviours are triggered by the flat bands in the local
+density of states and become identical in the limit of the infinite-layer
+(i.e., three-dimensional) system. We also address how interlayer hopping
+affects the magnetization process. Further, we point out that layer
+magnetization, which is a population imbalance between up and down atoms on a
+layer, can be employed to detect the emergence of the flat-band ferromagnetic
+state without addressing sublattice magnetization.",1410.2166v1
+2015-07-12,"Non-equilibrium behavior of the magnetization in the helimagnetic phases of the rare earth alloys R_{1-x}Y_{x} (R = Gd, Tb, Dy)","We have performed DC and AC magnetization measurements for the rare-earth
+magnetic alloy systems Gd_{0.62}Y_{0.38}, Tb_{0.86}Y_{0.14}, and
+Dy_{0.97}Y_{0.03}. These materials commonly exhibit a proper helical magnetic
+structure, and ferromagnetic structure at lower temperatures.In all of these
+materials, a difference between zero-field-cooled (ZFC) magnetization and
+field-cooled (FC) magnetization and a hysteresis loop in the M-H curve have
+been observed in the helimagnetic phases. The non-equilibrium behavior is
+possibly caused by a common nature, e. g., chiral domain structures. In
+addition to the above behavior, strong non-linearity of the magnetization and
+slow spin dynamics have been observed around the N'eel temperature only in
+Gd$_{0.62}$Y$_{0.38}$. The spin-glass like behavior observed in
+Gd_{0.62}Y_{0.38} could be related to a novel glassy state such as a
+helical-glass state.",1507.03202v3
+2015-08-17,Increased magnetic damping of a single domain wall and adjacent magnetic domains detected by spin torque diode in a nanostripe,"We use spin-torque resonance to probe simultaneously and separately the
+dynamics of a magnetic domain wall and of magnetic domains in a nanostripe
+magnetic tunnel junction. Thanks to the large associated resistance variations
+we are able to analyze quantitatively the resonant properties of these single
+nanoscale magnetic objects. In particular, we find that the magnetic damping of
+both domains and domain walls is doubled compared to the damping value of their
+host magnetic layer. We estimate the contributions to damping arising from
+dipolar couplings between the different layers in the junction and from the
+intralayer spin pumping effect. We find that they cannot explain the large
+damping enhancement that we observe. We conclude that the measured increased
+damping is intrinsic to large amplitudes excitations of spatially localized
+modes or solitons such as vibrating or propagating domain walls",1508.04043v1
+2015-09-25,Self-similar inverse cascade of magnetic helicity driven by the chiral anomaly,"For systems with charged chiral fermions, the imbalance of chirality in the
+presence of magnetic field generates an electric current - this is the Chiral
+Magnetic Effect (CME). We study the dynamical real-time evolution of
+electromagnetic fields coupled by the anomaly to the chiral charge density and
+the CME current by solving the Maxwell-Chern-Simons equations. We find that the
+CME induces the inverse cascade of magnetic helicity towards the large
+distances, and that at late times this cascade becomes self-similar, with
+universal exponents. We also find that in terms of gauge field topology the
+inverse cascade represents the transition from linked electric and magnetic
+fields (Hopfions) to the knotted configuration of magnetic field
+(Chandrasekhar-Kendall states). The magnetic reconnections are accompanied by
+the pulses of the CME current directed along the magnetic field lines. We
+devise an experimental signature of these phenomena in heavy ion collisions,
+and speculate about implications for condensed matter systems.",1509.07790v2
+2016-01-29,Switching of chiral magnetic skyrmions by picosecond magnetic field pulses via transient topological states,"Magnetic chiral skyrmions are vortex like spin structures that appear as
+stable or meta-stable states in magnetic materials due to the interplay between
+the symmetric and antisymmetric exchange interactions, applied magnetic field
+and/or uniaxial anisotropy. Their small size and internal stability make them
+prospective objects for data storage but for this, the controlled switching
+between skyrmion states of opposite polarity and topological charge is
+essential. Here we present a study of magnetic skyrmion switching by an applied
+magnetic field pulse based on a discrete model of classical spins and atomistic
+spin dynamics. We found a finite range of coupling parameters corresponding to
+the coexistence of two degenerate isolated skyrmions characterized by mutually
+inverted spin structures with opposite polarity and topological charge. We
+demonstrate how for a wide range of material parameters a short inclined
+magnetic field pulse can initiate the reliable switching between these states
+at GHz rates. Detailed analysis of the switching mechanism revealed the complex
+path of the system accompanied with the excitation of a chiral-achiral meron
+pair and the formation of an achiral skyrmion.",1601.08212v1
+2016-02-12,Magnetized quark matter with a magnetic-field dependent coupling,"It was recently derived that the QCD running coupling is a function of the
+magnetic field strength under the strong magnetic field approximation. Inspired
+by this progress and based on the self-consistent solutions of gap equations,
+the properties of two-flavor and three-flavor quark matter are studied in the
+framework of the Nambu-Jona-Lasinio model with a magnetic-field dependent
+running coupling. We find that the dynamical quark masses as functions of the
+magnetic field strength are not monotonous in the fully chirally broken phase.
+Furthermore, the stability of magnetized quark matter with the running coupling
+is enhanced by lowering the free energy per baryon, which is expected to be
+more stable than that of the conventional constant coupling case. It is
+concluded that the magnetized strange quark matter described by running
+coupling can be absolutely stable.",1602.03939v2
+2016-03-03,Cloaking the magnons,"We propose two approaches to cloak the spin waves (magnons) by investigating
+magnetization dynamics. One approach is based on a spatially inhomogeneous
+anisotropic magnetic moment tensor. The other mechanism is using a spatially
+inhomogeneous anisotropic gyromagnetic factor tensor and an inhomogeneous
+external magnetic field. For both approaches, the damping tensor is also
+inhomogeneous and anisotropic. The magnetic characteristic functions of the
+magnetic materials have been theoretically derived for both mechanisms. A
+non-magnetic core, which prevents magnons from entering and consequently
+distorts the spin wave propagation, can be cloaked by a structured magnetic
+shell to redirect the spin wave around the core using the above design
+mechanisms. We discuss the feasibility of the proposed mechanisms in an
+ensemble of quantum dot molecules and magnetic semiconductors. The proposed
+approaches shed light on transformation magnonics, and can be utilized for
+future spin-wave lenses, concentrators, low back-scattering waveguides, and
+ultimately quantum computing.",1603.01000v1
+2016-05-11,Algebraic non-integrability of magnetic billiards,"We consider billiard ball motion in a convex domain of the Euclidean plane
+bounded by a piece-wise smooth curve influenced by the constant magnetic field.
+We show that if there exists a polynomial in velocities integral of the
+magnetic billiard flow then every smooth piece $\gamma$ of the boundary must be
+algebraic and either is a circle or satisfies very strong restrictions. In
+particular in the case of ellipse it follows that magnetic billiard is
+algebraically not integrable for all magnitudes of the magnetic field. We
+conjecture that circle is the only integrable magnetic billiard not only in the
+algebraic sense, but for a broader meaning of integrability. We also introduce
+the model of Outer magnetic billiards. As an application of our method we prove
+analogous results on algebraically integrable Outer magnetic billiards.",1605.03372v1
+2016-05-31,The diamagnetic phase transition in Magnetars,"Neutron stars are ideal astrophysical laboratories for testing theories of
+the de Haas-van Alphen (dHvA) effect and diamagnetic phase transition which is
+associated with magnetic domain formation. The ""magnetic interaction"" between
+delocalized magnetic moments of electrons (the Shoenberg effect), can result in
+an effect of the diamagnetic phase transition into domains of alternating
+magnetization (Condon's domains). Associated with the domain formation are
+prominent magnetic field oscillation and anisotropic magnetic stress which may
+be large enough to fracture the crust of magnetar with a super-strong field.
+Even if the fracture is impossible as in ""low-field"" magnetar, the depinning
+phase transition of domain wall motion driven by low field rate (mainly due to
+the Hall effect) in the randomly perturbed crust can result in a
+catastrophically variation of magnetic field. This intermittent motion, similar
+to the avalanche process, makes the Hall effect be dissipative. These
+qualitative consequences about magnetized electron gas are consistent with
+observations of magnetar emission, and especially the threshold critical
+dynamics of driven domain wall can partially overcome the difficulties of
+""low-field"" magnetar bursts and the heating mechanism of transient, or
+""outbursting"" magnetar.",1605.09467v1
+2016-06-22,Induced magnetization and power loss for a periodically driven system of ferromagnetic nanoparticles with randomly oriented easy axes,"We study the effect of an elliptically polarized magnetic field on a system
+of non-interacting, single-domain ferromagnetic nanoparticles characterized by
+a uniform distribution of easy axis directions. Our main goal is to determine
+the average magnetization of this system and the power loss in it. In order to
+calculate these quantities analytically, we develop a general perturbation
+theory for the Landau-Lifshitz-Gilbert (LLG) equation and find its steady-state
+solution for small magnetic field amplitudes. On this basis, we derive the
+second-order expressions for the average magnetization and power loss,
+investigate their dependence on the magnetic field frequency, and analyze the
+role of subharmonic resonances resulting from the nonlinear nature of the LLG
+equation. For arbitrary amplitudes, the frequency dependence of these
+quantities is obtained from the numerical solution of this equation. The impact
+of transitions between different regimes of regular and chaotic dynamics of
+magnetization, which can be induced in nanoparticles by changing the magnetic
+field frequency, is examined in detail.",1606.07131v1
+2016-07-05,Magnetic moment of inertia within the breathing model,"An essential property of magnetic devices is the relaxation rate in magnetic
+switching which strongly depends on the energy dissipation and magnetic inertia
+of the magnetization dynamics. Both parameters are commonly taken as a
+phenomenological entities. However very recently, a large effort has been
+dedicated to obtain Gilbert damping from first principles. In contrast, there
+is no ab initio study that so far has reproduced measured data of magnetic
+inertia in magnetic materials. In this letter, we present and elaborate on a
+theoretical model for calculating the magnetic moment of inertia based on the
+torque-torque correlation model. Particularly, the method has been applied to
+bulk bcc Fe, fcc Co and fcc Ni in the framework of the tight-binding
+approximation and the numerical values are comparable with recent experimental
+measurements. The theoretical results elucidate the physical origin of the
+moment of inertia based on the electronic structure. Even though the moment of
+inertia and damping are produced by the spin-orbit coupling, our analysis shows
+that they are caused by undergo different electronic structure mechanisms.",1607.01307v1
+2016-09-28,Effective magnetic correlations in hole-doped graphene nanoflakes,"The magnetic properties of zig-zag graphene nanoflakes (ZGNF) are
+investigated within the framework of the dynamical mean-field theory. At
+half-filling and for realistic values of the local interaction, the ZGNF is in
+a fully compensated antiferromagnetic (AF) state, which is found to be robust
+against temperature fluctuations. Introducing charge carriers in the AF
+background drives the ZGNF metallic and stabilizes a magnetic state with a net
+uncompensated moment at low temperature. The change in magnetism is ascribed to
+the delocalization of the doped holes in the proximity of the edges, which
+mediate ferromagnetic correlations between the localized magnetic moments.
+Depending on the hole concentration, the magnetic transition may display a
+pronounced hysteresis over a wide range of temperature, indicating the
+coexistence of magnetic states with different symmetry. This suggests the
+possibility of achieving the electrostatic control of the magnetic state of
+ZGNFs to realize a switchable spintronic device.",1609.08812v1
+2016-10-28,Spin-Orbit Torque Efficiency in Compensated Ferrimagnetic Cobalt-Terbium Alloys,"Despite the potential advantages of information storage in
+antiferromagnetically coupled materials, it remains unclear whether one can
+control the magnetic moment orientation efficiently because of the cancelled
+magnetic moment. Here, we report spin-orbit torque induced magnetization
+switching of ferrimagnetic Co1-xTbx films with perpendicular magnetic
+anisotropy. Current induced switching is demonstrated in all of the studied
+film compositions, including those near the magnetization compensation point.
+The spin-orbit torque induced effective field is further quantified in the
+domain wall motion regime. A divergent behavior that scales with the inverse of
+magnetic moment is confirmed close to the compensation point, which is
+consistent with angular momentum conservation. Moreover, we also quantify the
+Dzyaloshinskii-Moriya interaction energy in the Ta/Co1-xTbx system and we find
+that the energy density increases as a function of the Tb concentration. The
+demonstrated spin-orbit torque switching, in combination with the fast magnetic
+dynamics and minimal net magnetization of ferrimagnetic alloys, promises
+spintronic devices that are faster and with higher density than traditional
+ferromagnetic systems.",1610.09200v1
+2016-11-21,Spectropolarimetric evidence for a siphon flow along an emerging magnetic flux tube,"We study the dynamics and topology of an emerging magnetic flux concentration
+using high spatial resolution spectropolarimetric data acquired with the
+Imaging Magnetograph eXperiment on board the Sunrise balloon-borne solar
+observatory. We obtain the full vector magnetic field and the line-of-sight
+(LOS) velocity through inversions of the Fe I line at 525.02 nm with the SPINOR
+code. The derived vector magnetic field is used to trace magnetic field lines.
+Two magnetic flux concentrations with different polarity and LOS velocities are
+found to be connected by a group of arch-shaped magnetic field lines. The
+positive polarity footpoint is weaker (1100 G) and displays an upflow, while
+the negative polarity footpoint is stronger (2200 G) and shows a downflow. This
+configuration is naturally interpreted as a siphon flow along an arched
+magnetic flux tube.",1611.06732v1
+2016-11-23,Dynamics of magnetic nano-flake vortices in Newtonian fluids,"We study the rotational motion of nano-flake ferromagnetic discs suspended in
+a Newtonian fluid, as a potential material owing the vortex-like magnetic
+configuration. Using analytical expressions for hydrodynamic, magnetic and
+Brownian torques, the stochastic angular momentum equation is determined in the
+dilute limit conditions under applied magnetic field. Results are compared
+against experimental ones and excellent agreement is observed. We also estimate
+the uncertainty in the orientation of the discs due to the Brownian torque when
+an external magnetic field aligns them. Interestingly, this uncertainty is
+roughly proportional to the ratio of thermal energy of fluid to the magnetic
+energy stored in the discs. Our approach can be implemented in many practical
+applications including biotechnology and multi-functional fluidics.",1611.07680v1
+2016-12-07,Effects of a small magnetic field on homoclinic bifurcations in a low-Prandtl-number fluid,"Effects of a uniform magnetic field on homoclinic bifurcations in
+Rayleigh-B\'{e}nard convection in a fluid of Prandtl number $Pr = 0.01$ are
+investigated using direct numerical simulations (DNS). A uniform magnetic field
+is applied either in the vertical or in the horizontal direction. For a weak
+vertical magnetic field, the possibilities of both forward and backward
+homoclinic bifurcations are observed leading to a spontaneous merging of two
+limit cycles into one as well as a spontaneous breaking of a limit cycle into
+two for lower values of the Chandrasekhar's number ($Q\leq 5$). A slightly
+stronger magnetic field makes the convective flow time independent giving the
+possibility of stationary patterns at the secondary instability. For horizontal
+magnetic field, the $x\leftrightharpoons y$ symmetry is destroyed and neither a
+homoclinic gluing nor a homoclinic breaking is observed. Two low-dimensional
+models are also constructed: one for a weak vertical magnetic field and another
+for a weak horizontal magnetic field. The models qualitatively capture the
+features observed in DNS and help understanding the unfolding of bifurcations
+close to the onset of magnetoconvection.",1612.02137v1
+2017-03-08,"Interplay of Dirac electrons and magnetism in AMnBi2 (A=Ca, Sr)","Dirac materials exhibit intriguing low-energy carrier dynamics that offer a
+fertile ground for novel physics discovery. Of particular interest is the
+interplay of Dirac carriers with other quantum phenomena, such as magnetism.
+Here we report on a two-magnon Raman scattering study of AMnBi2 (A=Ca, Sr), a
+prototypical magnetic Dirac system comprising alternating Dirac-carrier and
+magnetic layers. We present the first accurate determination of the exchange
+energies in these compounds and, by comparison to the reference compound
+BaMn2Bi2, we show that the Dirac-carrier layers in AMnBi2 significantly enhance
+the exchange coupling between the magnetic layers, which in turn drives a
+charge-gap opening along the Dirac locus. Our findings break new grounds in
+unveiling the fundamental physics of magnetic Dirac materials, which offer a
+novel platform for probing a distinct type of spin-Fermion interaction. The
+outstanding properties of these materials allow a delicate manipulation of the
+interaction between the Dirac carriers and magnetic moments, thus holding great
+promise for applications in magnetic Dirac devices.",1703.02712v1
+2017-09-12,Effect of magnetic field on the phase transition in a dusty plasma,"The formation of self-consistent crystalline structure is a well-known
+phenomenon in complex plasmas. In most experiments the pressure and rf power
+are the main controlling parameters in determining the phase of the system. We
+have studied the effect of externally applied magnetic field on the
+configuration of plasma crystals, suspended in the sheath of a radio-frequency
+discharge using the Magnetized Dusty Plasma Experiment (MDPX) device.
+Experiments are performed at a fixed pressure and rf power where a crystalline
+structure is formed within a confining ring. The magnetic field is then
+increased from 0 to 1.28 T. We report on the breakdown of the crystalline
+structure with increasing magnetic field. The magnetic field affects the
+dynamics of the plasma particles and first leads to a rotation of the crystal.
+At higher magnetic field, there is a radial variation (shear) in the angular
+velocity of the moving particles which we believe leads to the melting of the
+crystal. This melting is confirmed by evaluating the variation of the pair
+correlation function as a function of magnetic field.",1709.03744v1
+2017-10-03,Synchronous magnetic control of water droplets in bulk ferrofluid,"We present a microfluidic platform for two-dimensional manipulation of water
+droplets immersed in bulk oil-based ferrofluid. Although non-magnetic, the
+droplets are exclusively controlled by magnetic fields, without any
+pressure-driven flow. The diphasic fluid layer is trapped in a submillimeter
+Hele-Shaw chamber that includes permalloy tracks on its substrate. An in-plane
+rotating magnetic field magnetizes the permalloy tracks, thus producing local
+magnetic gradients, while an orthogonal magnetic field magnetizes the bulk
+ferrofluid. To minimize the magnetostatic energy of the system, droplets are
+attracted towards the locations of the tracks where ferrofluid is repelled.
+Using this technique, we demonstrate synchronous generation and propagation of
+water droplets, analyze PIV data of the bulk ferrofluid flow and study the
+kinematics of propagation. In addition, we show controlled break-up of droplets
+and droplet-to-droplet interactions. Finally, we discuss future applications
+owing to the potential biocompatibility of the droplets.",1710.00961v2
+2018-02-13,"From mean-field localized magnetism to itinerant spin fluctuations in the ""Non-metallic metal"" - FeCrAs","FeCrAs displays an unusual electrical response that is neither metallic in
+character nor divergent at low temperatures, as expected for an insulating
+response, and therefore it has been termed a ""nonmetal-metal"". We carried out
+neutron scattering experiments on powder and single crystal samples to study
+the magnetic dynamics and critical fluctuations in FeCrAs. Magnetic neutron
+diffraction measurements find Cr3+ magnetic order setting in at 115 K with the
+mean-field critical exponent. Neutron spectroscopy, however, observes gapless
+stiff magnetic fluctuations emanating from magnetic positions with propagation
+wave vector q_0=(1/3,1/3), which persists up to at least 80 meV. The magnetism
+in FeCrAs therefore displays a response which resembles that of itinerant
+magnets at high energy transfers, such as chromium alloys. We suggest that the
+presence of stiff high-energy spin fluctuations is the origin of the unusual
+temperature dependence of the resistivity.",1802.05271v2
+2018-06-20,Magnetic field dependence of antiferromagnetic resonance in NiO,"We report on measurements of magnetic field and temperature dependence of
+antiferromagnetic resonances in the prototypical antiferromagnet NiO. The
+frequencies of the magnetic resonances in the vicinity of 1 THz have been
+determined in the time-domain via time-resolved Faraday measurements after
+selective excitation by narrow-band superradiant terahertz (THz) pulses at
+temperatures down to 3K and in magnetic fields up to 10 T. The measurements
+reveal two antiferromagnetic resonance modes, which can be distinguished by
+their characteristic magnetic field dependencies. The nature of the two modes
+is discussed by comparison to an eight-sublattice antiferromagnetic model,
+which includes superexchange between the next-nearest-neighbor Ni spins,
+magnetic dipolar interactions, cubic magneto-crystalline anisotropy, and Zeeman
+interaction with the external magnetic field. Our study indicates that a
+two-sublattice model is insufficient for the description of spin dynamics in
+NiO, while the magnetic-dipolar interactions and magneto-crystalline anisotropy
+play important roles.",1806.07968v1
+2018-07-10,The dual nature of magnetism in a uranium heavy fermion system,"The duality between localized and itinerant nature of magnetism in
+$5\textit{f}$ electron systems has been a longstanding puzzle. Here, we report
+inelastic neutron scattering measurements, which reveal both local and
+itinerant aspects of magnetism in a single crystalline system of
+UPt$_{2}$Si$_{2}$. In the antiferromagnetic state, we observe broad continuum
+of diffuse magnetic scattering with a resonance-like gap of $\approx$ 7 meV,
+and surprising absence of coherent spin-waves, suggestive of itinerant
+magnetism. While the gap closes above the Neel temperature, strong dynamic spin
+correlations persist to high temperature. Nevertheless, the size and
+temperature dependence of the total magnetic spectral weight can be well
+described by local moment with $J=4$. Furthermore, polarized neutron
+measurements reveal that the magnetic fluctuations are mostly transverse, with
+little or none of the longitudinal component expected for itinerant moments.
+These results suggest that a dual description of local and itinerant magnetism
+is required to understand UPt$_{2}$Si$_{2}$, and by extension, other 5$f$
+systems in general.",1807.03686v1
+2019-01-17,"Influences of interfacial oxidization on surface magnetic energy, magnetic damping and spin-orbit-torques in Pt / ferromagnet / capping structures","We investigate the effect of capping layer (CAP) on the interfacial magnetic
+anisotropy energy density (K_S), magnetic damping ({\alpha}), and spin-orbit
+torques (SOTs) in heavy-metal (Pt) / ferromagnet (Co or Py) / CAP (MgO/Ta,
+HfOx, or TaN). At room temperature (RT) the CAP materials influence the
+effective magnitude of K_S, which is associated with a formation of interfacial
+magnetic oxides. The dynamical dissipation parameters of Co are considerably
+influenced by the CAP (especially MgO) while those of Py are not. This is
+possibly due to an extra magnetic damping via spin-pumping process across the
+Co/CoO interface and incoherent magnon generation (spin fluctuation) in the
+interfacial CoO. It is also observed that both anti-damping and field-like SOT
+efficiencies vary marginally with the CAP in the thickness ranges we examined.
+Our results reveal the crucial role of interfacial oxides on the perpendicular
+magnetic anisotropy, magnetic damping, and SOTs.",1901.05777v1
+2019-02-06,Measuring magnetic fields with magnetic field insensitive transitions,"Magnetometry is an important tool prevalent in many applications such as
+fundamental research, material characterization and biological imaging. Atomic
+magnetometry conventionally makes use of two quantum states, the energy
+difference of which depends linearly on the magnetic field due to the Zeeman
+effect. The magnetic field is evaluated from repeated measurements of the
+accumulated dynamic phase between the two Zeeman states in a superposition.
+Here we propose a magnetometry method that employs a superposition of clock
+states with energies that do not depend, to first-order, on the magnetic field
+magnitude. Our method makes use of the geometrical dependence of the
+clock-states wavefunctions on the magnetic field orientation. We propose
+detailed schemes for measuring both static and time-varying magnetic fields,
+and analyze the sensitivity of these methods. We show that, similarly to
+Zeeman-based methods, the smallest measurable signal scales inversely with the
+system coherence-time, which for clock transitions is typically significantly
+longer than for magnetically sensitive transitions. Finally, we experimentally
+demonstrate our method on an ensemble of optically trapped 87Rb atoms.",1902.02370v1
+2019-02-24,Evidence of a cluster spin-glass state in the B-site disordered perovskite SrTi0.5Mn0.5O3,"SrTi0.5Mn0.5O3 (STMO) is a chemically disordered perovskite having random
+distribution of Ti and Mn over 1b site. Striking discrepancies about the
+structural and magnetic properties of STMO demands detailed analysis which is
+addressed. To explore the magnetic ground state of STMO, static and dynamic
+magnetic properties were studied over a broad temperature range (2-300 K). The
+dc, ac magnetization show a cusp like peak at Tf ~ 14 K, which exhibits field
+and frequency dependence. The thermoremanent magnetization is characterized by
+using stretched exponential function and characteristic time suggests the
+existence of spin clusters. Also the other features observed in magnetic memory
+effect, muon spin resonance/rotation and neutron powder diffraction confirm the
+existence of cluster spin glass state in STMO, rather than the long range
+ordered ground state. Intriguingly, the observed spin relaxation can be
+attributed to the dilute magnetism due to non-magnetic doping at Mn-site and
+competing antiferromagnetic and ferromagnetic interactions resulting from the
+site disorder.",1902.08961v1
+2019-02-27,Emergence of Flat-Band Magnetism and Half-Metallicity in Twisted Bilayer Graphene,"Evidence of flat-band magnetism and half-metallicity in compressed twisted
+bilayer graphene is provided with first-principles calculations. We show that
+dynamic band-structure engineering in twisted bilayer graphene is possible by
+controlling the chemical composition with extrinsic doping, the interlayer
+coupling strength with pressure, and the magnetic ordering with external
+electric field. By varying the rotational order and reducing the interlayer
+separation an unbalanced distribution of charge density resulting in the
+spontaneous apparition of localized magnetic moments without disrupting the
+structural integrity of the bilayer. Weak exchange correlation between magnetic
+moments is estimated in large unit cells. External electric field switches the
+local magnetic ordering from ferromagnetic to anti-ferromagnetic.
+Substitutional doping shifts the chemical potential of one spin distribution
+and leads to half-metallicity. Flakes of compressed twisted bilayer graphene
+exhibit spontaneous magnetization, demonstrating that correlation between
+magnetic moments is not a necessary condition for their formation.",1902.10287v2
+2019-10-22,Controlled nonlinear magnetic damping in spin-Hall nano-devices,"Large-amplitude magnetization dynamics is substantially more complex compared
+to the low-amplitude linear regime, due to the inevitable emergence of
+nonlinearities. One of the fundamental nonlinear phenomena is the nonlinear
+damping enhancement, which imposes strict limitations on the operation and
+efficiency of magnetic nanodevices. In particular, nonlinear damping prevents
+excitation of coherent magnetization auto-oscillations driven by the injection
+of spin current into spatially extended magnetic regions. Here, we propose and
+experimentally demonstrate that nonlinear damping can be controlled by the
+ellipticity of magnetization precession. By balancing different contributions
+to anisotropy, we minimize the ellipticity and achieve coherent magnetization
+oscillations driven by spatially extended spin current injection into a
+microscopic magnetic disk. Our results provide a novel route for the
+implementation of efficient active spintronic and magnonic devices driven by
+spin current.",1910.09801v1
+2019-10-22,Magnetic properties of clusters of supracolloidal magnetic polymers with central attraction,"Supracolloidal magnetic polymers (SMPs) are structures made by crosslinking
+magnetic particles. In this work, using Langevin dynamics simulations, we study
+the zero-field magnetic properties of clusters formed in suspensions of SMPs
+with different topologies -- chains, rings, X and Y -- that interact via
+Stockmayer potential. We find that the presence of central attraction,
+resulting in the formation of large compact clusters, leads to a dramatic
+decrease of the suspension initial susceptibility, independently from SMP
+topology. However, the largest decrease corresponds to chain-like SMPs with
+strongly interacting particles. This is due to the higher rotational degrees of
+freedom of SMPs with such topology, which allows the particles to reorganise
+themselves inside the clusters in such a way that their magnetic moments form
+energetically advantageous vortex structures with negligible net magnetic
+moments.",1910.10040v1
+2019-11-04,Negative Magnetic Diffusivity beta replacing alpha effect in Helical Dynamo,"The alpha effect is known to be an indispensable energy source of the
+poloidal magnetic field in the sun or planet. However, the alpha effect is
+quenched as the magnetic field grows due to the conservation of magnetic
+helicity. With these conventional understanding, what indeed generates and
+sustains the observed poloidal magnetic field remains a mystery. To solve this
+contradiction between theory and real nature, we derived a semi-analytic
+representation of alpha and beta using large scale magnetic helicity and
+energy. Applying the simulation data to alpha and beta, we found that the
+negative beta effect is a promising substitution of the quenched alpha effect.
+However, since the negative beta effect contradicts the conventional dynamo
+theory, we derived the new beta expression referring to the field structure
+model. This analytic result with the field relation between velocity U and
+magnetic field B shows that the beta effect in the helical system is not a
+fixed one. Rather, it plays a variable and dynamic role in dynamo depending on
+the interaction between the poloidal velocity field and relative strength of
+the large scale magnetic field.",1911.01039v1
+2019-11-08,GMC Collisions as Triggers of Star Formation. VII. The Effect of Magnetic Field Strength on Star Formation,"We investigate the formation of stars within giant molecular clouds (GMCs)
+evolving in environments of different global magnetic field strength and
+large-scale dynamics. Building upon a series of magnetohydrodynamic (MHD)
+simulations of non-colliding and colliding GMCs, we employ density- and
+magnetically-regulated star formation sub-grid models in clouds which range
+from moderately magnetically supercritical to near critical. We examine gas and
+star cluster morphologies, magnetic field strengths and relative orientations,
+pre-stellar core densities, temperatures, mass-to-flux ratios and velocities,
+star formation rates and efficiencies over time, spatial clustering of stars,
+and kinematics of the stars and natal gas. The large scale magnetic criticality
+of the region greatly affects the overall gas evolution and star formation
+properties. GMC collisions enhance star formation rates and efficiencies in
+magnetically supercritical conditions, but may actually inhibit them in the
+magnetically critical case. This may have implications for star formation in
+different Galactic environments such as the Galactic Center and the main
+Galactic disk.",1911.03141v2
+2020-05-09,Bulk and surface topological indices for a skyrmion string,"The magnetic skyrmion is a topological magnetic vortex, and its topological
+nature is characterized by an index called skyrmion number which is a mapping
+of the magnetic moments defined on a two-dimensional space to a unit sphere. In
+three-dimensions, a skyrmion, i.e., a vortex penetrating though the magnet
+naturally forms a string, which terminates at the surfaces of the magnet or in
+the bulk. For such a string, the topological indices, which control its
+topological stability are less trivial. Here, we show theoretically, in terms
+of numerical simulation for the current-driven motion of a skyrmion string in a
+film sample with the step edges on the surface, that the topological indices
+relevant to the stability are the followings; (i) skyrmion number along the
+developed surface, and (ii) the monopole charge in the bulk defined as the
+integral over the surface enclosing a singular magnetic configuration. As long
+as the magnetic configuration is slowly varying, the former is conserved while
+its changes is associated with nonzero monopole charge. The skyrmion number and
+the monoplole charge offer a coherent understanding of the stability of the
+topological magnetic texture and the nontrivial dynamics of skyrmion strings.",2005.04516v1
+2020-05-13,Magneto-optics of excitons interacting with magnetic ions in CdSe/CdMnS colloidal nanoplatelets,"Excitons in diluted magnetic semiconductors represent excellent probes for
+studying the magnetic properties of these materials. Various magneto-optical
+effects, which depend sensitively on the exchange interaction of the excitons
+with the localized spins of the magnetic ions can be used for probing. Here, we
+study core/shell CdSe/(Cd,Mn)S colloidal nanoplatelets hosting diluted magnetic
+semiconductor layers. The inclusion of the magnetic Mn$^{2+}$ ions is evidenced
+by three magneto-optical techniques using high magnetic fields up to 15 T:
+polarized photoluminescence, optically detected magnetic resonance, and
+spin-flip Raman scattering. In particular, information on the Mn$^{2+}$
+concentration in the CdS shell layers can be obtained from the spin-lattice
+relaxation dynamics of the Mn$^{2+}$ spin system.",2005.06548v1
+2020-05-27,Effects of the Zhang-Li Torque on Spin Torque nano Oscillators,"Spin-torque nano-oscillators (STNO) are microwave auto-oscillators based on
+magnetic resonances having a nonlinear response with the oscillating amplitude,
+which provides them with a large frequency tunability including the possibility
+of mutual synchronization. The magnetization dynamics in STNO are induced by
+spin transfer torque (STT) from spin currents and can be detected by changes in
+electrical resistance due to giant magnetoresistance or tunneling
+magnetoresistance. The STT effect is usually treated as a damping-like term
+that reduces magnetic dissipation and promotes excitation of magnetic modes.
+However, an additional term, known as Zhang-Li term has an effect on
+magnetization gradients such as domain walls, and could have an effect on
+localized magnetic modes in STNO. Here we study the effect of Zhang-Li torques
+in magnetic excitations produced in STNO with a nanocontact geometry. Using
+micromagnetic simulations we find that Zhang-Li torque modify threshold
+currents of magnetic modes and their effective sizes. Additionally we show that
+effects can be controlled by changing the ratio between nanocontact size and
+layer thickness.",2005.13364v1
+2020-06-15,Magnetic Droplet Solitons,"Magnetic droplet solitons are dynamical magnetic textures that form due to an
+attractive interaction between spin waves in thin films with perpendicular
+magnetic anisotropy. Spin currents and the spin torques associated with these
+currents enable their formation as they provide a means to excite
+non-equilibrium spin wave populations and compensate their decay. Recent years
+have seen rapid advances in experiments that realize and study magnetic
+droplets. Important advances include the first direct x-ray images of droplets,
+determination of their threshold and sustaining currents, measurement of their
+generation and annihilation time and evidence for drift instabilities, which
+can limit their lifetime in spin-transfer nanocontacts. This article reviews
+these studies and contrasts these solitons to other types of spin-current
+excitations such as spin-wave bullets, and static magnetic textures, including
+magnetic vortices and skyrmions. Magnetic droplet solitons can also serve as
+current controlled microwave frequency oscillators with potential applications
+in neuromorphic chips as nonlinear oscillators with memory.",2006.08808v2
+2020-07-16,Viscosity of the magnetized strongly coupled one-component plasma,"The viscosity tensor of the magnetized one-component plasma, consisting of
+five independent shear viscosity coefficients, a bulk viscosity coefficient,
+and a cross coefficient, is computed using equilibrium molecular dynamics
+simulations and the Green-Kubo relations. A broad range of Coulomb coupling and
+magnetization strength conditions are studied. Magnetization is found to
+strongly influence the shear viscosity coefficients when the gyrofrequency
+exceeds the Coulomb collision frequency. Three regimes are identified as the
+Coulomb coupling strength and magnetization strength are varied. The Green-Kubo
+relations are used to separate kinetic and potential energy contributions to
+each viscosity coefficient, showing how each contribution depends upon the
+magnetization strength. The shear viscosity coefficient associated with the
+component of the stress tensor parallel to the magnetic field, and the two
+coefficients associated with the component perpendicular to the magnetic field,
+are all found to merge to a common value at strong Coulomb coupling.",2007.08417v1
+2020-09-04,Strong enhancement of magnetic order from bulk to stretched monolayer FeSe as Hund's metals,"Despite of the importance of magnetism in possible relation to other key
+properties in iron-based superconductors, its understanding is still far from
+complete especially for FeSe systems. On one hand, the origin of the absence of
+magnetic orders in bulk FeSe is yet to be clarified. On the other hand, it is
+still not clear how close monolayer FeSe on SrTiO$_3$, with the highest
+transition temperature among iron-based superconductors, is to a magnetic
+instability. Here we investigate magnetic properties of bulk and monolayer FeSe
+using dynamical mean-field theory combined with density-functional theory. We
+find that suppressed magnetic order in bulk FeSe is associated with the
+reduction of inter-orbital charge fluctuations, an effect of Hund's coupling,
+enhanced by a larger crystal field splitting. Meanwhile, spatial isolation of
+Fe atoms in expanded monolayer FeSe leads into a strong magnetic order, which
+is completely destroyed by a small electron doping. Our work provides a
+comprehensive understanding of the magnetic order in iron-based superconductors
+and other general multi-orbital correlated systems as Hund's metals.",2009.02024v1
+2020-09-14,Nonlinear high-frequency magnetic response of magnetoferritin metacrystals governed by spin thermodynamics,"A theory is developed of the time-dependent magnetization of the metacrystal
+composed of magnetoferritin macromolecules. Such superstructures, comprising up
+to several millions of superparamagnetic nanoparticles encapsulated in protein
+shells, can be created artificially using biochemical assembling technologies.
+They have been also shown to occur naturally in sensitive cells of the inner
+ear of birds, which suggests their possible involvement in the detection of the
+geomagnetic field for orientation and navigation of migratory animals. The
+dynamics of the magnetic system of the magnetoferritin metacrystal, comprising
+a very large number of magnetic moments coupled by long-range dipole forces, is
+exceedingly complex. In order to find the response of the metacrystal to
+high-frequency magnetic fields, we used a thermodynamic approach borrowed from
+the theory of nuclear spin systems of solids. The resulted theory yields the
+time-dependent superspin temperature and magnetization induced by oscillating
+magnetic fields of arbitrary strength. The predicted dependence of the
+high-frequency response on the static magnetic field can be used for
+experimental detection and characterization of magnetoferritin metacrystals in
+biological tissues.",2009.06235v1
+2020-11-20,A phenomenological theory of the optical magnetization reversal,"All-optical switching of the magnetization in magnetic nanostructures by
+femtosecond circularly polarized laser pulses has been demonstrated in several
+systems. We present a Landau-Lifshitz-Lambda (LLL) model which describes the
+magnetization dynamics using three density states: two ferromagnetic grounds
+states and an excited optical state. One of the ferromagnetic ground states is
+optically excited by circularly polarized light to a spin reversed state, which
+is then ""Coulomb collapsed"" to the magnetization reversed ground state. The
+time evolution of the optically excited states is described by a Lindblad
+master equation, in which the optical excitation is introduced via the
+Hamiltonian. Dissipation terms are introduced via Lindblad operators. The LLL
+model combines the precessional motion of the magnetization described by the
+Landau-Lifshitz theory, with the response of the three level Lambda system. The
+optical excitation lasts for the duration of the laser pulse and the system
+relaxes at a fast rate due to the electron-electron interaction. We study the
+solution of the eigenvalues problem of the optical equation of motion for the
+magnetization and identify a coherent and incoherent regimes and derive an LLL
+model that can be integrated with existing micromagnetic codes to describe
+optical excitation of magnetic materials.",2011.10247v1
+2021-06-02,Topological Magnons: A Review,"At sufficiently low temperatures magnetic materials often enter a correlated
+phase hosting collective, coherent magnetic excitations such as magnons or
+triplons. Drawing on the enormous progress on topological materials of the last
+few years, recent research has led to new insights into the geometry and
+topology of these magnetic excitations. Berry phases associated to magnetic
+dynamics can lead to observable consequences in heat and spin transport while
+analogues of topological insulators and semimetals can arise within magnon band
+structures from natural magnetic couplings. Magnetic excitations offer a
+platform to explore the interplay of magnetic symmetries and topology, to drive
+topological transitions using magnetic fields. examine the effects of
+interactions on topological bands and to generate topologically protected spin
+currents at interfaces. In this review, we survey progress on all these topics,
+highlighting aspects of topological matter that are unique to magnon systems
+and the avenues yet to be fully investigated.",2106.01430v1
+2021-09-06,Magnetic loading of magnetars' flares,"Magnetars, the likely sources of Fast Radio Bursts (FRBs), produce both
+steady highly relativistic magnetized winds, and occasional ejection events. We
+demonstrate that the requirement of conservation of the magnetic flux dominates
+the overall dynamics of magnetic explosions. This is missed in conventional
+hydrodynamic models of the ejections as expanding shell with parametrically
+added magnetic field, as well as one-dimensional models of magnetic
+disturbances. Most of the initial free energy of an explosion is actually spent
+on stretching its own internal magnetic field, while doing minimal $pdV$ work
+against the surrounding. Magnetic explosions from magnetars come into force
+balance with the pre-flares wind close to the light cylinder. They are then
+advected quietly with the wind, or propagate as electromagnetic disturbances.
+No powerful shock waves are generated in the wind.",2109.02524v1
+2021-10-22,Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^{4}$ magnet,"The competition between spin-orbit coupling $\lambda$ and electron-electron
+interaction $U$ leads to a plethora of novel states of matter, extensively
+studied in the context of $t_{2g}^4$ and $t_{2g}^5$ materials, such as
+ruthenates and iridates. Excitonic magnets -- the antiferromagnetic state of
+bounded electron-hole pairs -- is a prominent example of phenomena driven by
+those competing energy scales. Interestingly, recent theoretical studies
+predicted that excitonic magnets can be found in the ground-state of
+spin-orbit-coupled $t_{2g}^4$ Hubbard models. Here, we present a detailed
+computational study of the magnetic excitations in that excitonic magnet,
+employing one-dimensional chains (via density matrix renormalization group) and
+small two-dimensional clusters (via Lanczos). Specifically, first we show that
+the low-energy spectrum is dominated by a dispersive (acoustic) magnonic mode,
+with extra features arising from the $\lambda=0$ state in the phase diagram.
+Second, and more importantly, we found a novel magnetic excitation forming a
+high-energy optical mode with the highest intensity at wavevector $q\to 0$. In
+the excitonic condensation regime at large $U$, we also have found a novel
+high-energy $\pi$-mode composed solely of orbital excitations. These unique
+fingerprints of the $t_{2g}^4$ excitonic magnet are important in the analysis
+of neutron and RIXS experiments.",2110.11828v1
+2021-10-31,Thermally induced all-optical ferromagnetic resonance in thin YIG films,"All-optical ferromagnetic resonance (AO-FMR) is a powerful tool for local
+detection of micromagnetic parameters, such as magnetic anisotropy, Gilbert
+damping or spin stiffness. In this work we demonstrate that the AO-FMR method
+can be used in thin films of Yttrium Iron Garnet (YIG) if a metallic capping
+layer (Au, Pt) is deposited on top of the film. Magnetization precession is
+triggered by heating of the metallic layer with femtosecond laser pulses. The
+heating modifies the magneto-crystalline anisotropy of the YIG film and shifts
+the quasi-equilibrium orientation of magnetization, which results in
+precessional magnetization dynamics. The laser-induced magnetization precession
+corresponds to a uniform (Kittel) magnon mode, with the precession frequency
+determined by the magnetic anisotropy of the material as well as the external
+magnetic field, and the damping time set by a Gilbert damping parameter. The
+AO-FMR method thus enables measuring local magnetic properties, with spatial
+resolution given only by the laser spot size.",2111.00586v1
+2021-11-04,Mechanism of magnetic diode in artificial honeycomb lattice,"Spin diode is important prerequisite to practical manifestation of spin
+electronics. Yet, a functioning magnetic diode at room temperature is still
+illusive. Here, we reveal diode-type phenomena due to magnetic charge mediated
+conduction in artificial honeycomb geometry, made of concave shape single
+domain permalloy element. We find that honeycomb lattice defies symmetry by
+populating vertices with low and high multiplicity magnetic charges, causing
+asymmetric magnetization, in applied current of opposite polarity. High
+multiplicity units create highly resistive network, thereby inhibiting magnetic
+charge dynamics propelled electrical conduction. However, practical realization
+of this effect requires modest demagnetization factor in constituting element.
+Concave structure fulfills the condition. Subsequently, magnetic diode behavior
+emerges across broad thermal range of $T$ = 40K - 300K. The finding is a
+departure from the prevailing notion of spin-charge interaction as the sole
+guiding principle behind spintronics. Consequently, a new vista, mediated by
+magnetic charge interaction, is envisaged for spintronic research",2111.02929v3
+2021-12-02,Observing Magnetic Monopoles in Spin Ice using Electron Holography,"While there is compelling evidence for the existence of magnetic monopoles in
+spin ice, the direct observation of a point-like source of magnetic field in
+these systems remains an open challenge. One promising approach is electron
+holography, which combines atomic-scale resolution with extreme sensitivity to
+magnetic vector potentials, through the Aharonov-Bohm effect. Here we explore
+what holography can teach us about magnetic monopoles in spin ice, through
+experiments on artificial spin ice, and numerical simulations of pyrochlore
+spin ice. In the case of artificial spin ice, we show that holograms can be
+used to measure local magnetic charge. For pyrochlore spin ice, we demonstrate
+that holographic experiments are capable of resolving both magnetic monopoles
+and their dynamics, including the emergence of electric fields associated with
+fluctuations of closed loops of spins. These results establish that the
+observation of both magnetic monopoles and emergent electric fields in
+pyrochlore spin ice is a realistic possibility in an electron microscope with
+sufficiently--high phase resolution.",2112.01362v2
+2022-04-29,Saturation of turbulent helical dynamos,"The presence of large scale magnetic fields in nature is often attributed to
+the inverse cascade of magnetic helicity driven by turbulent helical dynamos.
+In this work we show that in turbulent helical dynamos, the inverse flux of
+magnetic helicity towards the large scales $\Pi_{\mathcal{H}}$ is bounded by
+$|\Pi_{\mathcal{H}}|\le c \epsilon k_\eta^{-1}$, where $\epsilon$ is the energy
+injection rate, $k_\eta$ is the Kolmogorov magnetic dissipation wavenumber and
+$c$ an order one constant. Assuming the classical isotropic turbulence scaling,
+the inverse flux of magnetic helicity $\Pi_{\mathcal{H}}$ decreases at least as
+a $-3/4$ power-law with the magnetic Reynolds number $Rm$ : $|\Pi_{\mathcal{H}}
+| \le c \epsilon \ell_f Rm^{-3/4}\max[Pm,1]^{1/4}$, where $Pm$ the magnetic
+Prandtl number and $\ell_f$ the forcing lengthscale. We demonstrate this
+scaling with $Rm$ using direct numerical simulations of turbulent dynamos
+forced at intermediate scales. The results further indicate that nonlinear
+saturation is achieved by a balance between the inverse cascade and dissipation
+at domain size scales $L$ for which the saturation value of the magnetic energy
+is bounded by ${\mathcal{E}}_\text{m}\leq c L (\epsilon \ell_f)^{2/3}
+Rm^{1/4}\max[1,Pm]^{1/4}$. Numerical simulations also demonstrate this bound.",2204.14091v2
+2022-09-07,Intrinsic chiral field as vector potential of the magnetic current in the zig-zag lattice of magnetic dipoles,"Chiral magnetic insulators manifest novel phases of matter where the sense of
+rotation of the magnetization is associated with exotic transport phenomena.
+Effective control of such phases and their dynamical evolution points to the
+search and study of chiral fields like the Dzyaloshinskii-Moriya interaction.
+Here we combine experiments, numerics, and theory to study a zig-zag dipolar
+lattice as a model of an interface between magnetic in-plane layers with
+perpendicular magnetization. The zig-zag lattice comprises two parallel
+sublattices of dipoles with perpendicular easy plane of rotation. The dipolar
+energy of the system is exactly separable into a sum of symmetric and
+antisymmetric long-range exchange interactions between dipoles, where the
+antisymmetric coupling generates a nonlocal Dzyaloshinskii-Moriya field which
+stabilizes winding textures with the form of chiral solitons. The
+Dzyaloshinskii-Moriya interaction acts as a vector potential or gauge field of
+the magnetic current and gives rise to emergent magnetic and electric fields
+that allow the manifestation of the magnetoelectric effect in the system.",2209.03052v2
+2022-11-07,Determining Perpendicular Magnetic Anisotropy in Fe/MgO/Fe Magnetic Tunnel Junction: A DFT-Based Spin-Orbit Torque Method,"In our JunPy package, we have combined the first-principles calculated
+self-consistent Hamiltonian with divide-and-conquer technique to successfully
+determine the magnetic anisotropy (MA) in an Fe/MgO/Fe magnetic tunnel junction
+(MTJ). We propose a comprehensive analytical derivation to clarify the crucial
+roles of spin-orbit coupling that mediates the exchange and spin-orbit
+components of spin torque, and the kinetic and spin-orbit components of spin
+current accumulation. The angular dependence of cumulative spin-orbit torque
+(SOT) indicates a uniaxial MA corresponding to the out-of-plane rotations of
+magnetic moments of the free Fe layers. Different from the conventional MA
+energy calculation and the phenomenological theory for a whole MTJ, our results
+provide insight into the orbital-resolved SOT for atomistic spin dynamics
+simulation in emergency complex magnetic heterojunctions.",2211.03603v3
+2023-05-19,Hall effect on the magnetic reconnections during the evolution of a three-dimensional magnetic flux rope,"We present a novel Hall magnetohydrodynamics (HMHD) numerical simulation of a
+three-dimensional (3D) magnetic flux rope (MFR) -- generated by magnetic
+reconnections from an initial 3D bipolar sheared field. Magnetic reconnections
+during the HMHD evolution are compared with the MHD. In both simulations, the
+MFRs generate as a consequence of the magnetic reconnection at null points
+which has not been realized in contemporary simulations. Interestingly, the
+evolution is faster and more intricate in the HMHD simulation. Repetitive
+development of the twisted magnetic field lines (MFL) in the vicinity of 3D
+nulls (reconnection site) is unique to the HMHD evolution of the MFR. The
+dynamical evolution of magnetic field lines around the reconnection site being
+affected by the Hall forcing, correspondingly affects the large-scale
+structures.",2305.11660v1
+2023-07-02,Magnetic braking during direct collapse black hole formation,"Magnetic fields are expected to be efficiently amplified during the formation
+of the first massive black holes via the small-scale dynamo and in the presence
+of strong accretion shocks occurring during gravitational collapse. Here, we
+analyze high-resolution cosmological magneto-hydrodynamical simulations of
+gravitational collapse in atomic cooling halos, exploring the dynamical role of
+magnetic fields, particularly concerning the effect of magnetic braking and
+angular momentum transport. We find that after the initial amplification,
+magnetic fields contribute to the transport of angular momentum and reduce it
+compared to pure hydrodynamical simulations. However, the magnetic and Reynolds
+torques do not fully compensate for the inward advection of angular momentum,
+which still accumulates over timescales of $\sim1$~Myr. A Jeans analysis
+further shows that magnetic pressure strongly contributes to suppressing
+fragmentation on scales of $0.1-10$~pc. Overall, the presence of magnetic
+fields thus aids in the transport of angular momentum and favors the formation
+of massive objects.",2307.02256v1
+2023-07-28,Complex Network View of the Sun's Magnetic Patches: I. Identification,"Solar and stellar magnetic patches (i.e., magnetic fluxes that reach the
+surface from the interior) are believed to be the primary sources of a star's
+atmospheric conditions. Hence, detecting and identifying these features (also
+known as magnetic elements) are among the essential topics in the community.
+Here, we apply the complex network approach to recognize the solar magnetic
+patches. For this purpose, we use the line-of-sight magnetograms provided by
+the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory. We
+construct the magnetic network following a specific visibility graph condition
+between pairs of pixels with opposite polarities and search for possible links
+between these regions. The complex network approach also provides the ability
+to rank the patches based on their connectivity (i.e., degree of nodes) and
+importance (i.e., PageRank). The use of the developed algorithm in the
+identification of magnetic patches is examined by tracking the features in
+consecutive frames, as well as making a comparison with the other approaches to
+identification. We find that this method could conveniently identify features
+regardless of their sizes. For small-scale (one or two pixels) features, we
+estimate the average of 8% false-positive and 1% false-negative errors.",2307.15523v1
+2023-08-29,Layer-dependent magnetism and spin fluctuations in atomically thin van der Waals magnet CrPS4,"van der Waals (vdW) magnets, an emerging family of two-dimensional (2D)
+materials, have received tremendous attention due to their rich fundamental
+physics and significant potential for cutting-edge technological applications.
+In contrast to the conventional bulk counterparts, vdW magnets exhibit
+significant tunability of local material properties, such as stacking
+engineered interlayer coupling and layer-number dependent magnetic and
+electronic interactions, which promise to deliver previously unavailable merits
+to develop multifunctional microelectronic devices. As a further ingredient of
+this emerging topic, here we report nanoscale quantum sensing and imaging of
+atomically thin vdW magnet chromium thiophosphate CrPS4, revealing its
+characteristic layer-dependent 2D static magnetism and dynamic spin
+fluctuations. We also show a large tunneling magnetoresistance in CrPS4-based
+spin filter vdW heterostructures. The excellent material stability, robust
+strategy against environmental degradation, in combination with tailored
+magnetic properties highlight the potential of CrPS4 in developing
+state-of-the-art 2D spintronic devices for next-generation information
+technologies.",2308.15396v1
+2023-09-01,Wall-attached convection under strong inclined magnetic fields,"We employ a linear stability analysis and direct numerical simulations to
+study the characteristics of wall-modes in thermal convection in a rectangular
+box under strong and inclined magnetic fields. The walls of the convection cell
+are electrically insulated. The stability analysis assumes periodicity in the
+spanwise direction perpendicular to the plane of the homogeneous magnetic
+field. Our study shows that for a fixed vertical magnetic field, the imposition
+of horizontal magnetic fields results in an increase of the critical Rayleigh
+number along with a decrease in the wavelength of the wall modes. The wall
+modes become tilted along the direction of the resulting magnetic fields and
+therefore extend further into the bulk as the horizontal magnetic field is
+increased. Once the modes localized on the opposite walls interact, the
+critical Rayleigh number decreases again and eventually drops below the value
+for onset with a purely vertical field. We find that for sufficiently strong
+horizontal magnetic fields, the steady wall modes occupy the entire bulk and
+therefore convection is no longer restricted to the sidewalls. The above
+results are confirmed by direct numerical simulations of the nonlinear
+evolution of magnetoconvection.",2309.00745v1
+2023-09-23,Magnetic Reconnection and Associated Particle Acceleration in High-energy Astrophysics,"Magnetic reconnection occurs ubiquitously in the universe and is often
+invoked to explain fast energy release and particle acceleration in high-energy
+astrophysics. The study of relativistic magnetic reconnection in the
+magnetically dominated regime has surged over the past two decades, revealing
+the physics of fast magnetic reconnection and nonthermal particle acceleration.
+Here we review these recent progresses, including the magnetohydrodynamic and
+collisionless reconnection dynamics as well as particle energization. The
+insights in astrophysical reconnection strongly connect to the development of
+magnetic reconnection in other areas, and further communication is greatly
+desired. We also provide a summary and discussion of key physics processes and
+frontier problems, toward a better understanding to the roles of magnetic
+reconnection in high-energy astrophysics.",2309.13382v1
+1999-04-09,"Magnetically Driven Warping, Precession and Resonances in Accretion Disks","The inner region of the accretion disk onto a rotating magnetized central
+star (neutron star, white dwarf or T Tauri star) is subjected to magnetic
+torques which induce warping and precession of the disk. The origin of these
+torques lies in the interaction between the (induced) surface current on the
+disk and the horizontal magnetic field (parallel to the disk) produced by the
+inclined magnetic dipole. Under quite general conditions, there exists a
+magnetic warping instability in which the magnetic torque drives the disk plane
+away from the equatorial plane of the star toward a state where the disk normal
+vector is perpendicular to the spin axis. Viscous stress tends to suppress the
+warping instability at large radii, but the magnetic torque always dominates as
+the disk approaches the magnetosphere boundary. The magnetic torque also drives
+the tilted inner disk into retrograde precession around the stellar spin axis.
+Moreover, resonant magnetic forcing on the disk can occur which may affect the
+dynamics of the disk. The magnetically driven warping instability and
+precession may be related to a number observational puzzles, including: (1)
+Spin evolution (torque reversal) of accreting X-ray pulsars; (2) Quasi-periodic
+oscillations in low-mass X-ray binaries; (3) Super-orbital periods in X-ray
+binaries; (4) Photometric period variations of T Tauri stars.",9904110v3
+1999-12-07,The Formation and Structure of a Strongly Magnetized Corona above Weakly Magnetized Accretion Disks,"We use three-dimensional magnetohydrodynamical (MHD) simulations to study the
+formation of a corona above an initially weakly magnetized, isothermal
+accretion disk. We also describe a modification to time-explicit numerical
+algorithms for MHD which enables us to evolve highly stratified disks for many
+orbital times. We find that MHD turbulence driven by the magnetorotational
+instability (MRI) produces strong amplification of weak fields within two scale
+heights of the disk midplane in a few orbital times. About 25 % of the magnetic
+energy generated by the MRI within two scale heights escapes due to buoyancy,
+producing a strongly magnetized corona above the disk. Most of the buoyantly
+rising magnetic energy is dissipated between 3 and 5 scale heights, suggesting
+the corona will also be hot. The average vertical disk structure consists of a
+weakly magnetized turbulent core below a strongly magnetized corona which is
+stable to the MRI. The largescale field structure in both the disk and corona
+is toroidal. The functional form of the stress is flat within two scale
+heights, but proportional to the density above two scale heights.
+  For initially weak uniform vertical fields, we find the exponential growth of
+magnetic field via axisymmetric vertical modes of the MRI produces strongly
+buoyant sheets of magnetic energy which break the disk apart into horizontal
+channels. These channels rise several scale heights vertically before the onset
+of the Parker instability distorts the sheets and allows matter to flow back
+towards the midplane and reform a disk. We suggest this evolution may be
+relevant to the dynamical processes which disrupt the inner regions of a disk
+when it interacts with a strongly magnetized central object.",9912135v1
+2005-11-25,Magnetar giant flares and afterglows as relativistic magnetized explosions,"(Abridged) We propose that giant flares on Soft Gamma-Ray Repeaters produce
+relativistic, strongly magnetized, weakly baryon loaded magnetic clouds,
+somewhat analogous to solar coronal mass ejection (CME) events. Flares are
+driven by unwinding of internal non-potential magnetic fields which leads to
+slow build-up of magnetic energy outside of the neutron star. For large
+magnetospheric currents, corresponding to a large twist of external magnetic
+field, magnetosphere becomes dynamically unstable on \Alfven crossing times
+scale of inner magnetosphere, $t_A \sim R_{NS}/c \sim 30 \mu$sec. Released
+magnetic energy results in formation of a strongly magnetized, pair-loaded,
+quasi-spherically expanding flux rope, topologically connected by magnetic
+field to the neutron star during the prompt flare emission. Magnetic stresses
+of the tied flux rope lead to late collimation of the expansion, on time scales
+longer than giant flare duration. Relativistic bulk motion of the expanding
+magnetic cloud, directed at an angle $\theta \sim 135^\circ$ to the line of
+sight (away from the observer), results in a strongly non-spherical forward
+shock with observed non-relativistic apparent expansion and bulk motion
+velocities $\beta_{app} \sim \cot \theta/2 \sim 0.4 $ at times of first radio
+observations approximately one week after the burst. Interaction with a shell
+of wind-shocked ISM and then with the unshocked ISM leads to deceleration to
+non-relativistic velocities approximately one month after the flare.",0511711v1
+2006-08-31,Stability Properties of Magnetic Tower Jets,"Stability properties of ``magnetic tower'' jets propagating in the
+gravitationally stratified background have been examined by performing
+three-dimensional magnetohydrodynamic simulations. The current-carrying,
+Poynting flux-dominated magnetic tower jet, which possesses a highly wound
+helical magnetic field, is subject to the current-driven instability (CDI). We
+find that, under general physical conditions including small perturbations in
+the initial background profiles, the propagating magnetic tower jets develop
+the non-axisymmetric, $m=1$ kink mode of the CDI. The kink mode grows on the
+local Alfv\'en crossing time scale. In addition, two types of kink modes appear
+in the system. At the central region where external thermal pressure
+confinement is strong, only the internal kink mode is excited and will grow. A
+large distance away from the central region where the external thermal pressure
+becomes low, the external kink mode is observed. As a result, the exterior of
+magnetic tower jets will be deformed into a large-scale wiggled structure. We
+also discuss extensively the different physical processes that contribute to
+the overall stability properties of the magnetic tower jets. Specifically, when
+the jet propagates in an initially unperturbed background, we find that they
+can survive the kink mode beyond the point predicted by the well-known
+Kruskal-Shafranov (K-S) criterion. The stabilization in this case comes mainly
+from the dynamical relaxation of magnetic twists during the propagation of
+magnetic towers; the magnetic pitch is reduced and the corresponding K-S
+critical wavelength becomes longer as the tower jet proceeds. Furthermore, we
+show that the pressure-driven and Kelvin-Helmholtz instabilities do not occur
+in the magnetic tower jets.",0609007v1
+2007-05-26,Catastrophic eruption of magnetic flux rope in the corona and solar wind with and without magnetic reconnection,"It is generally believed that the magnetic free energy accumulated in the
+corona serves as a main energy source for solar explosions such as coronal mass
+ejections (CMEs). In the framework of the flux rope catastrophe model for CMEs,
+the energy may be abruptly released either by an ideal magnetohydrodynamic
+(MHD) catastrophe, which belongs to a global magnetic topological instability
+of the system, or by a fast magnetic reconnection across preexisting or
+rapidly-developing electric current sheets. Both ways of magnetic energy
+release are thought to be important to CME dynamics. To disentangle their
+contributions, we construct a flux rope catastrophe model in the corona and
+solar wind and compare different cases in which we either prohibit or allow
+magnetic reconnection to take place across rapidly-growing current sheets
+during the eruption. It is demonstrated that CMEs, even fast ones, can be
+produced taking the ideal MHD catastrophe as the only process of magnetic
+energy release. Nevertheless, the eruptive speed can be significantly enhanced
+after magnetic reconnection sets in. In addition, a smooth transition from slow
+to fast eruptions is observed when increasing the strength of the background
+magnetic field, simply because in a stronger field there is more free magnetic
+energy at the catastrophic point available to be released during an eruption.
+This suggests that fast and slow CMEs may have an identical driving mechanism.",0705.3885v1
+2008-04-07,A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers,"Context: The role of magnetic fields during high-mass star formation is a
+matter of fierce debate, yet only a few direct probes of magnetic field
+strengths are available.
+  Aims: The magnetic field is detected in a number of massive star-forming
+regions through polarization observations of 6.7 GHz methanol masers. Although
+these masers are the most abundant of the maser species occurring during
+high-mass star formation, most magnetic field measurements in the high-density
+gas currently come from OH and H2 O maser observations.
+  Methods: The 100-m Effelsberg telescope was used to measure the Zeeman
+splitting of 6.7 GHz methanol masers for the first time. The observations were
+performed on a sample of 24 bright northern maser sources.
+  Results: Significant Zeeman splitting is detected in 17 of the sources with
+an average magnitude of 0.56 m/s . Using the current best estimate of the 6.7
+GHz methanol maser Zeeman splitting coefficient and a geometrical correction,
+this corresponds to an absolute magnetic field strength of 23 mG in the
+methanol maser region.
+  Conclusions: The magnetic field is dynamically important in the dense maser
+regions. No clear relation is found with the available OH maser magnetic field
+measurements. The general sense of direction of the magnetic field is
+consistent with other Galactic magnetic field measurements, although a few of
+the masers display a change of direction between different maser features. Due
+to the abundance of methanol masers, measuring their Zeeman splitting provides
+the opportunity to construct a comprehensive sample of magnetic fields in
+high-mass star-forming regions.",0804.1141v1
+2009-04-13,Magnetic Coupling in the Quiet Solar Atmosphere,"Three kinds of magnetic couplings in the quiet solar atmosphere are
+highlighted and discussed, all fundamentally connected to the Lorentz force.
+First the coupling of the convecting and overshooting fluid in the surface
+layers of the Sun with the magnetic field. Here, the plasma motion provides the
+dominant force, which shapes the magnetic field and drives the surface dynamo.
+Progress in the understanding of the horizontal magnetic field is summarized
+and discussed. Second, the coupling between acoustic waves and the magnetic
+field, in particular the phenomenon of wave conversion and wave refraction. It
+is described how measurements of wave travel times in the atmosphere can
+provide information about the topography of the wave conversion zone, i.e., the
+surface of equal Alfv\'en and sound speed. In quiet regions, this surface
+separates a highly dynamic magnetic field with fast moving magnetosonic waves
+and shocks around and above it from the more slowly evolving field of high-beta
+plasma below it. Third, the magnetic field also couples to the radiation field,
+which leads to radiative flux channeling and increased anisotropy in the
+radiation field. It is shown how faculae can be understood in terms of this
+effect. The article starts with an introduction to the magnetic field of the
+quiet Sun in the light of new results from the Hinode space observatory and
+with a brief survey of measurements of the turbulent magnetic field with the
+help of the Hanle effect.",0904.2026v1
+2009-07-16,Particle size effect on magnetic properties of interacting La0.67Sr0.33MnO3 nanoparticles,"Magnetic nanoparticles of La0.67Sr0.33MnO3 (LSMO) manganite with mean
+particle sizes of 13, 16, 18 and 21 nm were prepared by the sol-gel method. The
+crystal structure and mean particle size of the synthesized powders were
+estimated by X-ray diffraction (XRD) analysis using rietveld refinement and
+transmission electron microscopy (TEM). Fourier transform infrared (FTIR)
+transmission spectroscopy revealed that stretching and bending modes are
+influenced by calcinations temperature. Dc magnetization versus magnetic field
+of the samples was carried out at room temperature. Magnetic dynamics of the
+samples was studied by the measurement of ac magnetic susceptibility versus
+temperature at different frequencies and ac magnetic fields. A
+frequency-dependent peak was observed in ac magnetic susceptibility versus
+temperature which is well described by Vogel-Fulcher and critical slowing down
+laws, and empirical and parameters. By fitting the experimental data with
+Vogel-Fulcher and critical slowing down laws, the relaxation time,
+characteristic temperature, magnetic anisotropy energy, effective magnetic
+anisotropy constant and critical exponent zv have been estimated. The obtained
+values of c1, c2, T0 and t0 from the Vogel-Fulcher law support of the presence
+of strong interaction between magnetic nanoparticles. The values of zv and t0
+obtained from critical slowing down fit suggest the presence of superspin glass
+behavior in LSMO nanoparticles of different sizes.",0907.2815v1
+2011-03-10,Special Relativistic Magnetohydrodynamic Simulation of Two-Component Outflow Powered by Magnetic Explosion on Compact Stars,"The nonlinear dynamics of outflows driven by magnetic explosion on the
+surface of a compact star is investigated through special relativistic
+magnetohydrodynamic simulations. We adopt, as the initial equilibrium state, a
+spherical stellar object embedded in hydrostatic plasma which has a density
+$\rho(r) \propto r^{- \alpha}$ and is threaded by a dipole magnetic field. The
+injection of magnetic energy at the surface of compact star breaks the
+equilibrium and triggers a two-component outflow. At the early evolutionary
+stage, the magnetic pressure increases rapidly around the stellar surface,
+initiating a magnetically driven outflow. A strong forward shock driven outflow
+is then excited. The expansion velocity of the magnetically driven outflow is
+characterized by the Alfv\'en velocity on the stellar surface, and follows a
+simple scaling relation $v_{\rm mag} \propto {v_{\rm A}}^{1/2}$. When the
+initial density profile declines steeply with radius, the strong shock is
+accelerated self-similarly to relativistic velocity ahead of the magnetically
+driven component. We find that it evolves according to a self-similar relation
+$\Gamma_{\rm sh} \propto r_{\rm sh}$, where $\Gamma_{\rm sh}$ is the Lorentz
+factor of the plasma measured at the shock surface $r_{\rm sh}$. Purely
+hydrodynamic process would be responsible for the acceleration mechanism of the
+shock driven outflow. Our two-component outflow model, which is the natural
+outcome of the magnetic explosion, can provide a better understanding of the
+magnetic active phenomena on various magnetized compact stars.",1103.1939v1
+2013-07-19,Quantitative magnetic imaging at the nanometer scale by ballistic electron magnetic microscopy,"We demonstrate quantitative ballistic electron magnetic microscopy (BEMM)
+imaging of simple model Fe(001) nanostructures. We use in situ nanostencil
+shadow mask resistless patterning combined with molecular beam epitaxy
+deposition to prepare under ultra-high vacuum conditions nanostructured
+epitaxial Fe/Au/Fe/GaAs(001) spin-valves. In this epitaxial system, the
+magnetization of the bottom Fe/GaAs(001) electrode is parallel to the [110]
+direction, defining accurately the analysis direction for the BEMM experiments.
+The large hot-electron magnetoresistance of the Fe/Au/Fe/GaAs(001) epitaxial
+spin-valve allows us to image various stable magnetic configurations on the
+as-grown Fe(001) microstructures with a high sensitivity, even for small
+misalignments of both magnetic electrodes. The angular dependence of the
+hot-electron magnetocurrent is used to convert magnetization maps calculated by
+micromagnetic simulations into simulated BEMM images. The calculated BEMM
+images and magnetization rotation profiles show quantitative agreement with
+experiments and allow us to investigate the magnetic phase diagram of these
+model Fe(001) microstructures. Finally, magnetic domain reversals are observed
+under high current density pulses. This opens the way for further BEMM
+investigations of current-induced magnetization dynamics.",1307.5150v1
+2013-12-17,Measurement of the magnetic interaction between two electrons,"Electrons have an intrinsic, indivisible, magnetic dipole aligned with their
+internal angular momentum (spin). The magnetic interaction between two
+electrons can therefore impose a change in their spin orientation. This
+process, however, was never observed in experiment. The challenge is two-fold.
+At the atomic scale, where the coupling is relatively large, the magnetic
+interaction is often overshadowed by the much larger coulomb exchange
+counterpart. In typical situations where exchange is negligible, magnetic
+interactions are also very weak and well below ambient magnetic noise. Here we
+report on the first measurement of the magnetic interaction between two
+electronic spins. To this end, we used the ground state valence electrons of
+two $^{88}$Sr$^+$ ions, co-trapped in an electric Paul trap and separated by
+more than two micrometers. We measured the weak, millihertz scale
+(alternatively $10^{-18}$ eV or $10^{-14}$ K), magnetic interaction between
+their electronic spins. This, in the presence of magnetic noise that was six
+orders of magnitude larger than the respective magnetic fields the electrons
+apply on each other. Cooperative spin dynamics was kept coherent for 15 s
+during which spin-entanglement was generated. The sensitivity necessary for
+this measurement was provided by restricting the spin evolution to a
+Decoherence-Free Subspace (DFS) which is immune to collective magnetic field
+noise. Finally, by varying the separation between the two ions, we were able to
+recover the inverse cubic distance dependence of the interaction. The reported
+method suggests an alternative route to the search of long-range anomalous
+spin-spin forces and can be generalized to include Quantum Error Correction
+codes for other cases of extremely weak signal detection.",1312.4881v1
+2014-05-19,Approaching the Ground State of Frustrated A-site Spinels: A Combined Magnetization and Polarized Neutron Scattering Study,"We re-investigate the magnetically frustrated, {\it
+diamond-lattice-antiferromagnet} spinels FeAl$_2$O$_4$ and MnAl$_2$O$_4$ using
+magnetization measurements and diffuse scattering of polarized neutrons. In
+FeAl$_2$O$_4$, macroscopic measurements evidence a ""cusp"" in zero field-cooled
+susceptibility around 13~K. Dynamic magnetic susceptibility and {\it memory
+effect} experiments provide results that do not conform with a canonical
+spin-glass scenario in this material. Through polarized neutron scattering
+studies, absence of long-range magnetic order down to 4~K is confirmed in
+FeAl$_2$O$_4$. By modeling the powder averaged differential magnetic neutron
+scattering cross-section, we estimate that the spin-spin correlations in this
+compound extend up to the third nearest-neighbour shell. The estimated value of
+the Land\'{e} $g$ factor points towards orbital contributions from Fe$^{2+}$.
+This is also supported by a Curie-Weiss analysis of the magnetic
+susceptibility. MnAl$_2$O$_4$, on the contrary, undergoes a magnetic phase
+transition into a long-range ordered state below $\approx$ 40~K, which is
+confirmed by macroscopic measurements and polarized neutron diffraction.
+However, the polarized neutron studies reveal the existence of prominent
+spin-fluctuations co-existing with long-range antiferromagnetic order. The
+magnetic diffuse intensity suggests a similar short range order as in
+FeAl$_2$O$_4$. Results of the present work supports the importance of spin-spin
+correlations in understanding magnetic response of frustrated magnets like
+$A$-site spinels which have predominant short-range spin correlations
+reminiscent of the ""spin liquid"" state.",1405.4694v1
+2014-08-08,Stable Magnetic Droplet Solitons in Spin Transfer Nanocontacts,"Magnetic thin films with perpendicular magnetic anisotropy (PMA) have
+localized excitations that correspond to reversed dynamically precessing
+magnetic moments, known as magnetic droplet solitons. Fundamentally, these
+excitations are associated with an attractive interaction between elementary
+spin-excitations (i.e., magnons) and were predicted to occur in PMA materials
+in the absence of damping [1,2]. While damping, present in all magnetic
+materials, suppresses these excitations, it is now possible to compensate
+damping by spin transfer torques through electrical current flow in nanometer
+scale contacts to ferromagnetic thin films [3,4]. A theory predicts the
+appearance of magnetic droplet solitons at a threshold current in nanocontacts
+[5] and, recently, experimental signatures of droplet nucleation have been
+reported [6]. However, thus far, they have been observed to be nearly
+reversible excitations, with only partially reversed magnetization and to be
+subject to instabilities that cause them to drift away from the nanocontacts
+(i.e., drift instabilities) [6]. Here we show that magnetic droplet solitons
+can be stabilized in a spin transfer nanocontact. Further, they exhibit a
+strong hysteretic response to fields and currents and a nearly fully reversed
+magnetization in the contact. These observations, in addition to their
+fundamental interest, open up new applications for magnetic droplet solitons as
+multi-state high frequency current and field tunable oscillators.",1408.1902v1
+2015-08-10,Magneto-optical imaging of thin magnetic films using spins in diamond,"Imaging the fields of magnetic materials provides crucial insight into the
+physical and chemical processes surrounding magnetism, and has been a key
+ingredient in the spectacular development of magnetic data storage. Existing
+approaches using the magneto-optic Kerr effect (MOKE), x-ray and electron
+microscopy have limitations that constrain further development, and there is
+increasing demand for imaging and characterisation of magnetic phenomena in
+real time with high spatial resolution. In this work, we show how the
+magneto-optical response of an array of negatively-charged nitrogen-vacancy
+spins in diamond can be used to image and map the sub-micron stray magnetic
+field patterns from thin ferromagnetic films. Using optically detected magnetic
+resonance, we demonstrate wide-field magnetic imaging over 100x100 {\mu}m^2
+with a diffraction-limited spatial resolution of 440 nm at video frame rates,
+under ambient conditions. We demonstrate a novel all-optical spin relaxation
+contrast imaging approach which can image magnetic structures in the absence of
+an applied microwave field. Straightforward extensions promise imaging with
+sub-{\mu}T sensitivity and sub-optical spatial and millisecond temporal
+resolution. This work establishes practical diamond-based wide-field microscopy
+for rapid high-sensitivity characterisation and imaging of magnetic samples,
+with the capability for investigating magnetic phenomena such as domain wall
+and skyrmion dynamics and the spin Hall effect in metals.",1508.02135v1
+2015-10-05,A hybrid finite-difference/boundary element procedure for the simulation of turbulent MHD duct flow at finite magnetic Reynolds numbers,"A conservative coupled finite difference-boundary element computational
+procedure for the simulation of turbulent magnetohydrodynamic flow in a
+straight rectangular duct at finite magnetic Reynolds number is presented. The
+flow is assumed to be periodic in the streamwise direction and is driven by a
+mean pressure gradient. The duct walls are considered to be electrically
+insulating. The co-evolution of the velocity and magnetic fields as described
+respectively by the Navier-Stokes and the magnetic induction equations,
+together with the coupling of the magnetic field between the conducting domain
+and the non-conducting exterior is solved using the magnetic field formulation.
+The aim is to simulate localized magnetic fields interacting with turbulent
+duct flow. Detailed verification of the implementation of the numerical scheme
+is conducted in the limiting case of low magnetic Reynolds number by comparing
+with the results obtained using a quasistatic approach that has no coupling
+with the exterior. The rigorous procedure with non-local magnetic boundary
+conditions is compared versus simplified pseudo-vacuum boundary conditions and
+the differences are quantified. Our first direct numerical simulations of
+turbulent Hartmann duct flow at moderate magnetic Reynolds numbers and a low
+flow Reynolds number show significant differences in the duct flow turbulence,
+even at low interaction level between the flow and magnetic field",1510.01205v1
+2015-10-15,Time-resolved magnetophotoluminescence studies of magnetic polaron dynamics in type-II quantum dots,"We used continuous wave photoluminescence (cw-PL) and time resolved
+photoluminescence (TR-PL) spectroscopy to compare the properties of magnetic
+polarons (MP) in two related spatially indirect II-VI epitaxially grown quantum
+dot systems. In the ZnTe/(Zn,Mn)Se system the holes are confined in the
+non-magnetic ZnTe quantum dots (QDs), and the electrons reside in the magnetic
+(Zn,Mn)Se matrix. On the other hand, in the (Zn,Mn)Te/ZnSe system, the holes
+are confined in the magnetic (Zn,Mn)Te QDs, while the electrons remain in the
+surrounding non-magnetic ZnSe matrix. The magnetic polaron formation energies
+in both systems were measured from the temporal red-shift of the band-edge
+emission. The magnetic polaron exhibits distinct characteristics depending on
+the location of the Mn ions. In the ZnTe/(Zn,Mn)Se system the magnetic polaron
+shows conventional behavior with decreasing with increasing temperature T and
+increasing magnetic field B. In contrast, in the (Zn,Mn)Te/ZnSe system has
+unconventional dependence on temperature T and magnetic field B; is weakly
+dependent on T as well as on B. We discuss a possible origin for such a
+striking difference in the MP properties in two closely related QD systems.",1510.04376v1
+2016-09-15,Bright hot impacts by erupted fragments falling back on the Sun: magnetic channelling,"Dense plasma fragments were observed to fall back on the solar surface by the
+Solar Dynamics Observatory after an eruption on 7 June 2011, producing strong
+EUV brightenings. Previous studies investigated impacts in regions of weak
+magnetic field. Here we model the $\sim~300$ km/s impact of fragments
+channelled by the magnetic field close to active regions. In the observations,
+the magnetic channel brightens before the fragment impact. We use a 3D-MHD
+model of spherical blobs downfalling in a magnetized atmosphere. The blob
+parameters are constrained from the observation. We run numerical simulations
+with different ambient density and magnetic field intensity. We compare the
+model emission in the 171\AA~ channel of the Atmospheric Imaging Assembly with
+the observed one. We find that a model of downfall channelled in a $\sim~1$MK
+coronal loop confined by a magnetic field of $\sim~10-20$G, best explains
+qualitatively and quantitatively the observed evolution. The blobs are highly
+deformed, further fragmented, when the ram pressure becomes comparable to the
+local magnetic pressure and they are deviated to be channelled by the field,
+because of the differential stress applied by the perturbed magnetic field.
+Ahead of them, in the relatively dense coronal medium, shock fronts propagate,
+heat and brighten the channel between the cold falling plasma and the solar
+surface. This study shows a new mechanism which brightens downflows channelled
+by the magnetic field, such as in accreting young stars, and also works as a
+probe of the ambient atmosphere, providing information about the local plasma
+density and magnetic field.",1609.04634v1
+2016-10-26,Conversion of Internal Gravity Waves into Magnetic Waves,"Asteroseismology probes the interiors of stars by studying oscillation modes
+at a star's surface. Although pulsation spectra are well understood for
+solar-like oscillators, a substantial fraction of red giant stars observed by
+Kepler exhibit abnormally low-amplitude dipole oscillation modes. Fuller et al.
+(2015) suggests this effect is produced by strong core magnetic fields that
+scatter dipole internal gravity waves (IGWs) into higher multipole IGWs or
+magnetic waves. In this paper, we study the interaction of IGWs with a magnetic
+field to test this mechanism. We consider two background stellar structures:
+one with a uniform magnetic field, and another with a magnetic field that
+varies both horizontally and vertically. We derive analytic solutions to the
+wave propagation problem and validate them with numerical simulations. In both
+cases, we find perfect conversion from IGWs into magnetic waves when the IGWs
+propagate into a region exceeding a critical magnetic field strength. Downward
+propagating IGWs cannot reflect into upward propagating IGWs because their
+vertical wavenumber never approaches zero. Instead, they are converted into
+upward propagating slow (Alfvenic) waves, and we show they will likely
+dissipate as they propagate back into weakly magnetized regions. Therefore,
+strong internal magnetic fields can produce dipole mode suppression in red
+giants, and gravity modes will likely be totally absent from the pulsation
+spectra of sufficiently magnetized stars.",1610.08506v2
+2019-02-09,Full particle-in-cell simulation of the interaction between two plasmas for laboratory experiments on the generation of magnetized collisionless shocks with high-power lasers,"A preliminary numerical experiment is conducted for laboratory experiments on
+the generation of magnetized collisionless shocks with high-power lasers by
+using one-dimensional particle-in-cell simulation. The present study deals with
+the interaction between a moving Aluminum plasma and a Nitrogen plasma at rest.
+In the numerical experiment, the Nitrogen plasma is unmagnetized or magnetized
+by a weak external magnetic field. Since the previous study suggested the
+generation of spontaneous magnetic field in the piston (Aluminum) plasma due to
+the Biermann battery, the effect of the magnetic field is of interest. Sharp
+jumps of electron density and magnetic field are observed around the interface
+between the two plasmas as long as one of the two plasmas is magnetized, which
+indicates the formation of tangential electron-magneto-hydro-dynamic
+discontinuity. When the Aluminum plasma is magnetized, strong compression of
+both density and magnetic field takes place in the pure Aluminum plasma during
+the gyration of Nitrogen ions in the Aluminum plasma region. The formation of a
+shock downstream is indicated from the shock jump condition. The result
+suggests that the spontaneous magnetic field in the piston (Aluminum) plasma
+plays an essential role in the formation of a perpendicular collisionless
+shock.",1902.03345v1
+2019-02-21,Interpreting magnetic helicity flux in solar flux emergence,"Magnetic helicity flux gives information about the topology of a magnetic
+field passing through a boundary. In solar physics applications, this boundary
+is the photosphere and magnetic helicity flux has become an important quantity
+in analysing magnetic fields emerging into the solar atmosphere. In this work
+we investigate the evolution of magnetic helicity flux in magnetohydrodynamic
+(MHD) simulations of solar flux emergence. We consider emerging magnetic fields
+with different topologies and investigate how the magnetic helicity flux
+patterns corresponds to the dynamics of emergence. To investigate how the
+helicity input is connected to the emergence process, we consider two forms of
+the helicity flux. The first is the standard form giving topological
+information weighted by magnetic flux. The second form represents the net
+winding and can be interpreted as the standard helicity flux less the magnetic
+flux. Both quantities provide important and distinct information about the
+structure of the emerging field and these quantities differ significantly for
+mixed sign helicity fields. A novel aspect of this study is that we account for
+the varying morphology of the photosphere due to the motion of the dense plasma
+lifted into the chromosphere. Our results will prove useful for the
+interpretation of magnetic helicity flux maps in solar observations.",1902.07997v1
+2019-04-15,Improvements of the Longitudinal Magnetic Field Measurement from the Solar Magnetic Field Telescope at Huairou Solar Observing Station,"The weak-field approximation implying linear relationship between Stokes
+$V/I$ and longitudinal magnetic field, $B_{\Vert}$, often suffers from
+saturation observed in strong magnetic field regions such as sunspot umbra. In
+this work, we intend to improve the magnetic field observations carried out by
+the \textit{Solar Magnetic Field Telescope} (SMFT) at Huairou Solar Observing
+Station, China. We propose using non-linear relationship between Stokes $V/I$
+and $B_{\Vert}$ to derive the magnetic field. To determine the form of the
+relationship, we perform a cross-calibration of the observed SMFT data and
+magnetograms provided by the \textit{Helioseismic and Magnetic Imager} on board
+the \textit{Solar Dynamics Observatory}. The algorithm of the magnetic field
+derivation is described in details. We show that using non-linear relationship
+between Stokes $V/I$ and $B_{\Vert}$ allows us to eliminate magnetic field
+saturation inside sunspot umbra. The proposed technique enables one to enhance
+the reliability of the SMFT magnetic field data obtained even long before the
+space-based instrumentation era, since 1987.",1904.07081v7
+2019-05-02,Evolution of Magnetic Helicity in Solar Cycle 24,"We propose a novel approach to reconstruct the surface magnetic helicity
+density on the Sun or sun-like stars. The magnetic vector potential is
+determined via decomposition of vector magnetic field measurements into
+toroidal and poloidal components. The method is verified using data from a
+non-axisymmetric dynamo model. We apply the method to vector field synoptic
+maps from Helioseismic and Magnetic Imager (HMI) onboard of Solar Dynamics
+Observatory (SDO) to study evolution of the magnetic helicity density during
+solar cycle 24. It is found that the mean helicity density of the
+non-axisymmetric magnetic field of the Sun evolves in a way which is similar to
+that reported for the current helicity density of the solar active regions. It
+has predominantly the negative sign in the northern hemisphere, and it is
+positive in the southern hemisphere. Also, the hemispheric helicity rule for
+the non-axisymmetric magnetic field showed the sign inversion at the end of
+cycle 24. Evolution of magnetic helicity density of large-scale axisymmetric
+magnetic field is different from that expected in dynamo theory. On one hand,
+the mean large- and small-scale components of magnetic helicity density display
+the hemispheric helicity rule of opposite sign at the beginning of cycle 24.
+However, later in the cycle, the two helicities exhibit the same sign in
+contrast with the theoretical expectations.",1905.00772v1
+2019-08-28,Non-monotonic response of a sheared magnetic liquid crystal to an external field,"Utilizing molecular dynamics simulations, we report a non-monotonic
+dependence of the shear stress on the strength of an external magnetic field
+($H$) in a liquid-crystalline mixture of magnetic and non-magnetic anisotropic
+particles. This non-monotonic behavior is in sharp contrast with the
+well-studied monotonic $H$-dependency of the shear stress in conventional
+ferrofluids, where the shear stress increases with $H$ until it reaches a
+saturation value. We relate the origin of this non-monotonicity to the
+competing effects of particle alignment along the shear-induced direction, on
+the one hand, and the magnetic field direction, on the other hand. To isolate
+the role of these competing effects, we consider a two-component mixture
+composed of particles with effectively identical steric interactions, where the
+orientations of a small fraction, i.e.\ the magnetic ones, are coupled to the
+external magnetic field. By increasing $H$ from zero, the orientations of the
+magnetic particles show a Fr\'{e}ederickz-like transition and eventually start
+deviating from the shear-induced orientation, leading to an increase in shear
+stress. Upon further increase of $H$, a demixing of the magnetic particles from
+the non-magnetic ones occurs which leads to a drop in shear stress, hence
+creating a non-monotonic response to $H$. Unlike the equilibrium demixing
+phenomena reported in previous studies, the demixing observed here is neither
+due to size-polydispersity nor due to a wall-induced nematic transition. Based
+on a simplified Onsager analysis, we rather argue that it occurs solely due to
+packing entropy of particles with different shear- or magnetic-field-induced
+orientations.",1908.10815v1
+2019-11-11,Gate Tunable Magnetism and Giant Magnetoresistance in ABC-stacked Few-Layer Graphene,"Magnetism is a prototypical phenomenon of quantum collective state, and has
+found ubiquitous applications in semiconductor technologies such as dynamic
+random access memory (DRAM). In conventional materials, it typically arises
+from the strong exchange interaction among the magnetic moments of d- or
+f-shell electrons. Magnetism, however, can also emerge in perfect lattices from
+non-magnetic elements. For instance, flat band systems with high density of
+states (DOS) may develop spontaneous magnetic ordering, as exemplified by the
+Stoner criterion. Here we report tunable magnetism in rhombohedral-stacked
+few-layer graphene (r-FLG). At small but finite doping (n~10^11 cm-2), we
+observe prominent conductance hysteresis and giant magnetoconductance that
+exceeds 1000% as a function of magnetic fields. Both phenomena are tunable by
+density and temperature, and disappears for n>10^12 cm-2 or T>5K. These results
+are confirmed by first principles calculations, which indicate the formation of
+a half-metallic state in doped r-FLG, in which the magnetization is tunable by
+electric field. Our combined experimental and theoretical work demonstrate that
+magnetism and spin polarization, arising from the strong electronic
+interactions in flat bands, emerge in a system composed entirely of carbon
+atoms. The electric field tunability of magnetism provides promise for
+spintronics and low energy device engineering.",1911.04450v1
+2020-05-28,Unconventional critical behaviors at the magnetic phase transition of Co3Sn2S2 kagome ferromagnet,"Co3Sn2S2 has generated a growing interest as a rare example of the highly
+uniaxial anisotropic kagome ferromagnet showing a combination of
+frustrated-lattice magnetism and topology. Recently, via precise measurements
+of the magnetization and AC susceptibility we have found a low-field anomalous
+magnetic phase (A-phase) with very slow spin dynamics that appears just below
+the Curie temperature (T_C). The A-phase hosts high-density domain bubbles
+after cooling through T_C as revealed in a previous in-situ Lorentz-TEM study.
+Here, we present further signatures of the anomalous magnetic transition (MT)
+at T_C revealed by a study of the critical behaviors of the magnetization and
+magnetocaloric effect using a high-quality single crystal. Analyses of numerous
+magnetization isotherms around T_C (177 K) using different approaches (the
+modified Arrot plot, Kouvel-Fisher method and magnetocaloric effect) result in
+consistent critical exponents that do not satisfy the theoretical predictions
+of standard second-order-MT models. Scaling analyses for the magnetization,
+magnetic entropy change and field-exponent of the magnetic entropy change, all
+consistently show low-field deviations below TC from the universal curves. Our
+results reveal that the MT of Co3Sn2S2 can not be explained as a conventional
+second-order type and suggest an anomalous magnetic state below T_C.",2005.13920v2
+2020-08-10,Investigation of temperature dependence of magnetic properties of Cr$_2$O$_3$ thin film structure using a magnetic field imaging technique based on Nitrogen-Vacancy centres in diamond crystal,"This work presents a magnetic field imaging method based on color centres in
+diamond crystal applied to thin film structure. To demonstrate the capacity of
+our device we have used it for characterization of magnetic properties in
+microscopic scale of Cr$_2$O$_3$ thin film structure above and below N\'eel
+temperature. The obtained measurement results clearly identify the detection of
+the magnetic phase transition of Cr$_2$O$_3$ thin film with an unexpected
+diamagnetic like behaviour at 19$^{\circ}$C (below the N\'eel temperature of
+Cr$_2$O$_3$). To have better insights in the magnetic fields created by the
+thin films we present simulations of the magnetic fields near the thin film
+surface. We also analysed the optically detected magnetic resonance (ODMR)
+profiles to be sure that the measured property is related only to the shift of
+the optically detected magnetic resonance. We demonstrate how Nitrogen-Vacancy
+centre based magnetometry can deliver a convenient platform for research of
+phase transition dynamics and spatial magnetic field distributions of thin
+films, that can rival other widely used measurement techniques.",2008.04371v2
+2022-02-19,Formation and Immediate Deformation of a Small Filament Through Intermittent Magnetic Interactions,"It is generally believed that filament formation involves a process of the
+accumulation of magnetic energy. However, in this paper we discuss the idea
+that filaments will not erupt and will only deform when the stored magnetic
+energy is released gradually. Combining high-quality observations from Solar
+Dynamics Observatory and other instruments, we present the formation and
+immediate deformation of a small filament (F1) in the active region (AR) 12760
+on 28-30 April 2020. Before the filament formation, three successive dipoles
+quickly emerged with separation motions in the center of AR 12760. Due to the
+magnetic interaction between magnetic dipoles and pre-existing positive
+polarities, coronal brightenings consequently appeared in the overlying
+atmosphere. Subsequently, because of the continuous cancellation of magnetic
+flux that happened around the adjacent ends of F1 and another nearby filament
+(F2), the magnetic reconections occurred intermittently occurred between F1 and
+F2. Finally, F1 lessened in the shear, and F2 became shorter. All the results
+show that the formation of F1 was closely associated with intermittent
+interactions between the sequence of emerging dipoles and pre-existing magnetic
+polarities, and the immediate deformation of F1 was intimately related to
+intermittent interactions between F1 and F2. We also suggest that the
+intermittent magnetic interactions driven by the continuous magnetic activities
+(magnetic-flux emergence, cancellation, and convergence) play an important role
+in the formation and deformation of filaments.",2202.09633v2
+2022-05-16,Pseudostreamer influence on flux rope evolution,"A critical aspect of solar activity is the coupling between eruptions and the
+surrounding coronal magnetic field, which determines the trajectory and
+morphology of the eruptive event. Pseudostreamers (PSs) are coronal magnetic
+structures formed by arcs of twin loops capped by magnetic field lines from
+coronal holes of the same polarity that meet at a central spine. They contain a
+single magnetic null point in the spine, potentially influencing the evolution
+of nearby flux ropes (FRs). To understand the net effect of the PS on FR
+eruptions is first necessary to study diverse and isolated FR-PS scenarios,
+which are not influenced by other magnetic structures. We performed numerical
+simulations in which a FR structure is in the vicinity of a PS magnetic
+configuration. The combined magnetic field of the PS and the FR results in the
+formation of two magnetic null points. We evolve this scenario by numerically
+solving the magnetohydrodynamic equations in 2.5D. The simulations consider a
+fully ionised compressible ideal plasma in the presence of a gravitational
+field and a stratified atmosphere. We find that the dynamic behaviour of the FR
+can be categorised into three different classes based on the FR trajectories
+and whether it is eruptive or confined. Our analysis indicates that the
+magnetic null points are decisive in the direction and intensity of the FR
+deflection and their hierarchy depends on the topological arrangement of the
+scenario. Moreover, the PS lobe acts as a magnetic cage enclosing the FR. We
+report that the total unsigned magnetic flux of the cage is a key parameter
+defining whether the FR is ejected or not.",2205.07936v1
+2023-12-19,Data-driven simulations of magnetic field evolution in Active Region 11429: Magneto-friction method using PENCIL code,"Coronal magnetic fields evolve quasi statically over long time scales and
+dynamically over short time scales. As of now there exists no regular
+measurements of coronal magnetic fields, and therefore generating the coronal
+magnetic field evolution using the observations of the magnetic field at the
+photosphere is of fundamental requirement to understand the origin of the
+transient phenomena from the solar active regions. Using the magnetofriction
+(MF) approach, we aim to simulate the coronal field evolution in the solar
+active region 11429. The MF method is implemented in open source \PC along with
+a driver module to drive the initial field with different boundary conditions
+prescribed from observed vector magnetic fields at the photosphere. In order to
+work with vector potential and the observations, we prescribe three types of
+bottom boundary drivers with varying free-magnetic energy. The MF simulation
+reproduces the magnetic structure, which better matches to the sigmoidal
+morphology exhibited by AIA images at the pre-eruptive time. We found that the
+already sheared field further driven by the sheared magnetic field, will
+maintain and further build the highly sheared coronal magnetic configuration,
+as seen in AR 11429. Data-driven MF simulation is a viable tool to generate the
+coronal magnetic field evolution, capturing the formation of the twisted flux
+rope and its eruption.",2312.12124v1
+2024-01-10,Quantum magnetism in the frustrated square lattice oxyhalides YbBi2IO4 and YbBi2ClO4,"Square-lattice systems offer a direct route for realizing 2D quantum
+magnetism with frustration induced by competing interactions. In this work, the
+square-lattice materials YbBi2IO4 and YbBi2ClO4 were investigated using a
+combination of magnetization and specific heat measurements on polycrystalline
+samples. Specific heat measurements provide evidence for long-range magnetic
+order below TN = 0.21 K (0.25 K) for YbBi2IO4 (YbBi2ClO4). On the other hand, a
+rather broad maximum is found in the temperature-dependent magnetic
+susceptibility, located at Tmax = 0.33 K (0.38 K) in YbBi2IO4 (YbBi2ClO4),
+consistent with the quasi-2D magnetism expected for the large separation
+between the magnetic layers. Estimation of the magnetic entropy supports the
+expected Kramers' doublet ground state for Yb3+ and the observed paramagnetic
+behavior is consistent with a well-isolated doublet. Roughly two-thirds of the
+entropy is consumed above TN, due to a combination of the quasi-2D behavior and
+magnetic frustration. The impact of frustration is examined from the viewpoint
+of a simplified J1-J2 square lattice model, which is frustrated for
+antiferromagnetic interactions. Specifically, a high-temperature series
+expansion analysis of the temperature-dependent specific heat and magnetization
+data yields J2/J1 = 0.30 (0.23) for YbBi2IO4 (YbBi2ClO4). This simplified
+analysis suggests strong frustration that should promote significant quantum
+fluctuations in these compounds, and thus motivates future work on the static
+and dynamic magnetic properties of these materials.",2401.05283v1
+2024-02-03,Role of time-varying magnetic field on QGP equation of state,"The phase diagram of quantum chromodynamics (QCD) and its associated
+thermodynamic properties of quark gluon plasma (QGP) are studied in the
+presence of time dependent magnetic field. The study plays a pivotal role in
+the field of cosmology, astrophysics, and heavy ion collisions. In order to
+explore the structure of quark gluon plasma to deal with the dynamics of quarks
+and gluons, we investigate the equation of state (EoS) not only in the
+environment of static magnetic field but also in the presence of time-varying
+magnetic fields. So, for determining the equation of state of QGP at non zero
+magnetic fields, we revisited our earlier model where the effect of time
+varying magnetic field was not taken into consideration. Using the
+phenomenological model, some appealing features are noticed depending upon the
+three different scales; effective mass of quark, temperature, and time
+independent as well as time-dependent magnetic field. Earlier the effective
+mass of quark was incorporated in our calculations and in the current work, it
+is modified for static and time-varying magnetic fields. Thermodynamic
+observables including pressure, energy density, entropy, etc. are calculated
+for a wide range of temperature and time-dependent as well as time-independent
+magnetic fields. Finally, we claim that the EoS are highly affected in the
+presence of a magnetic field. Our results are notable compared to other
+approaches and found to be advantageous for the measurement of QGP equation of
+state. These crucial findings with and without time-varying magnetic field
+could have phenomenological implications in various sectors of high energy
+physics.",2402.02176v1
+2022-11-15,Picosecond Spin-Orbit Torque Induced Coherent Magnetization Switching in a Ferromagnet,"Electrically controllable non-volatile magnetic memories show great potential
+for the replacement of semiconductor-based technologies. Recently there has
+been strong interest in spin-orbit torque (SOT) induced magnetization reversal
+due to the device's increased lifetime and speed of operation. However, recent
+SOT switching studies reveal an incubation delay in the ~ns range due to
+stochasticity in the nucleation of a magnetic domain during reversal. Here, we
+experimentally demonstrate ultrafast SOT-induced magnetization switching
+dynamics of a ferromagnet with no incubation delay by avoiding the nucleation
+process and driving the magnetization coherently. We employ an ultrafast
+photo-conducting switch and a co-planar strip line to generate and guide ~ps
+current pulses into the heavy metal/ferromagnet layer stack and induce
+ultrafast SOT. We use magneto-optical probing to investigate the magnetization
+switching dynamics with sub-picosecond time resolution. Depending on the
+relative current pulse and in-plane magnetic field polarities, we observe
+either an ultrafast demagnetization and subsequent recovery along with a
+SOT-induced precessional oscillation, or ultrafast SOT switching. The
+magnetization zero-crossing occurs in ~70 ps, which is approximately an order
+of magnitude faster than previous studies. Complete switching needs ~250 ps and
+is limited by the heat diffusion to the substrate. We use a macro-magnetic
+simulation coupled with an ultrafast heating model to analyze the effect of
+ultrafast thermal anisotropy torque and current-induced torque in the observed
+dynamics. Good agreement between our experimental results and the macro-spin
+model shows that the switching dynamics are coherent and present no noticeable
+incubation delay. Our work suggests a potential pathway toward dramatically
+increasing the writing speed of SOT magnetic random-access memory devices.",2211.08266v1
+2009-01-23,Magnetically-actuated artificial cilia for microfluidic propulsion,"Natural cilia are hair-like microtubule-based structures that are able to
+move fluid at low Reynolds number through asymmetric motion. In this paper we
+follow a biomimetic approach to design artificial cilia lining the inner
+surface of microfluidic channels with the goal to propel fluid. The artificial
+cilia consist of polymer films filled with magnetic nanoparticles. The
+asymmetric, non-reciprocating motion is generated by tuning an external
+magnetic field. To obtain the magnetic field and associated magnetization local
+to the cilia we solve the Maxwell equations, from which the magnetic torques
+can be deduced. To obtain the ciliary motion we solve the dynamic equations of
+motion which are then fully coupled to the fluid dynamic equations that
+describe fluid flow around the cilia. By doing so we show that by properly
+tuning the applied magnetic field, asymmetric ciliary motion can be generated
+that is able to propel fluid in a microchannel. The results are presented in
+terms of three dimensionless parameters that fully delineate the asymmetry and
+cycle time as a function of the relative contribution of elastic, inertial,
+magnetic and viscous fluid forces.",0901.3687v1
+2010-07-10,Magnetic Lattice Dynamics of the Oxygen-Free FeAs Pnictides: How Sensitive are Phonons to Magnetic Ordering?,"To shed light on the role of magnetism on the superconducting mechanism of
+the oxygen-free FeAs pnictides, we investigate the effect of magnetic ordering
+on phonon dynamics in the low-temperature orthorhombic parent compounds, which
+present a spin-density wave. The study covers both the 122 (AFe2As2; A=Ca, Sr,
+Ba) and 1111 (AFeAsF; A=Ca, Sr) phases. We extend our recent work on the Ca
+(122 and 1111) and Ba (122) cases by treating computationally and
+experimentally the 122 and 1111 Sr compounds. The effect of magnetic ordering
+is investigated through detailed non-magnetic and magnetic lattice dynamical
+calculations. The comparison of the experimental and calculated phonon spectra
+shows that the magnetic interactions/ordering have to be included in order to
+reproduce well the measured density of states. This highlights a
+spin-correlated phonon behavior which is more pronounced than the apparently
+weak electron-phonon coupling estimated in these materials. Furthermore, there
+is no noticeable difference between phonon spectra of the 122 Ba and Sr,
+whereas there are substantial differences when comparing these to CaFe2As2
+originating from different aspects of structure and bonding.",1007.1711v1
+2010-10-18,Investigation of Dynamics of Self-Similarly Evolving Magnetic Clouds,"Magnetic clouds (MCs) are ""magnetized plasma clouds"" moving in the solar
+wind. MCs transport magnetic flux and helicity away from the Sun. These
+structures are not stationary but feature temporal evolution. Commonly,
+simplified MC models are considered. The goal of the present study is to
+investigate the dynamics of more general, radially expanding MCs. They are
+considered as cylindrically symmetric magnetic structures with low plasma
+{\beta}. In order to study MC`evolution the self-similar approach method and a
+numerical approach are used. It is shown that the forces are balanced in the
+considered self-similarly evolving, cylindrically symmetric magnetic
+structures. Explicit analytical expressions for magnetic field, plasma
+velocity, density and pressure within MCs are derived. These solutions are
+characterized by conserved values of magnetic flux and helicity. We also
+investigate the dynamics of self-similarly evolving MCs by means of the
+numerical code ""Graale"". In addition, their expansion in a medium with higher
+density and higher plasma {\beta} is studied. It is shown that the physical
+parameters of the MCs maintain their self-similar character throughout their
+evolution. Conclusions. A comparison of the different self-similar and
+numerical solutions allows us to conclude that the evolving MCs are quite
+adequately described by our self-similar solutions - they retain their
+self-similar, coherent nature for quite a long time and over large distances
+from the Sun.",1010.3573v1
+2011-02-28,High Reynolds number magnetohydrodynamic turbulence using a Lagrangian model,"With the help of a model of magnetohydrodynamic (MHD) turbulence tested
+previously, we explore high Reynolds number regimes up to equivalent
+resolutions of 6000^3 grid points in the absence of forcing and with no imposed
+uniform magnetic field. For the given initial condition chosen here, with equal
+kinetic and magnetic energy, the flow ends up being dominated by the magnetic
+field, and the dynamics leads to an isotropic Iroshnikov-Kraichnan energy
+spectrum. However, the locally anisotropic magnetic field fluctuations
+perpendicular to the local mean field follow a Kolmogorov law. We find that the
+ratio of the eddy turnover time to the Alfven time increases with wavenumber,
+contrary to the so-called critical balance hypothesis. Residual energy and
+helicity spectra are also considered; the role played by the conservation of
+magnetic helicity is studied, and scaling laws are found for the magnetic
+helicity and residual helicity spectra. We put these results in the context of
+the dynamics of a globally isotropic MHD flow which is locally anisotropic
+because of the influence of the strong large-scale magnetic field, leading to a
+partial equilibration between kinetic and magnetic modes for the energy and the
+helicity.",1102.5581v2
+2015-07-11,"Realization of the thermal equilibrium in inhomogeneous magnetic systems by the Landau-Lifshitz-Gilbert equation with stochastic noise, and its dynamical aspects","It is crucially important to investigate effects of temperature on magnetic
+properties such as critical phenomena, nucleation, pinning, domain wall motion,
+coercivity, etc. The Landau-Lifshitz-Gilbert (LLG) equation has been applied
+extensively to study dynamics of magnetic properties. Approaches of Langevin
+noises have been developed to introduce the temperature effect into the LLG
+equation. To have the thermal equilibrium state (canonical distribution) as the
+steady state, the system parameters must satisfy some condition known as the
+fluctuation-dissipation relation. In inhomogeneous magnetic systems in which
+spin magnitudes are different at sites, the condition requires that the ratio
+between the amplitude of the random noise and the damping parameter depends on
+the magnitude of the magnetic moment at each site. Focused on inhomogeneous
+magnetic systems, we systematically showed agreement between the stationary
+state of the stochastic LLG equation and the corresponding equilibrium state
+obtained by Monte Carlo simulations in various magnetic systems including
+dipole-dipole interactions. We demonstrated how violations of the condition
+result in deviations from the true equilibrium state. We also studied the
+characteristic features of the dynamics depending on the choice of the
+parameter set. All the parameter sets satisfying the condition realize the same
+stationary state (equilibrium state). In contrast, different choices of
+parameter set cause seriously different relaxation processes. We show two
+relaxation types, i.e., magnetization reversals with uniform rotation and with
+nucleation.",1507.03075v1
+2016-12-22,Imaging Magnetization Structure and Dynamics in Ultrathin YIG/Pt Bilayers with High Sensitivity Using the Time-Resolved Longitudinal Spin Seebeck Effect,"We demonstrate an instrument for time-resolved magnetic imaging that is
+highly sensitive to the in-plane magnetization state and dynamics of thin-film
+bilayers of yttrium iron garnet (Y3Fe5O12,YIG)/Pt: the time-resolved
+longitudinal spin Seebeck (TRLSSE) effect microscope. We detect the local,
+in-plane magnetic orientation within the YIG by focusing a picosecond laser to
+generate thermally-driven spin current from the YIG into the Pt by the spin
+Seebeck effect, and then use the inverse spin Hall effect in the Pt to
+transduce this spin current to an output voltage. To establish the time
+resolution of TRLSSE, we show that pulsed optical heating of patterned YIG (20
+nm)/Pt(6 nm)/Ru (2 nm) wires generates a magnetization-dependent voltage pulse
+of less than 100 ps. We demonstrate TRLSSE microscopy to image both static
+magnetic structure and gigahertz-frequency magnetic resonance dynamics with
+sub-micron spatial resolution and a sensitivity to magnetic orientation below
+0.3$^{\circ}/\sqrt{\text{Hz}}$ in ultrathin YIG.",1612.07610v2
+2018-09-19,Magnetic non-contact friction from domain wall dynamics actuated by oscillatory mechanical motion,"Magnetic friction is a form of non-contact friction arising from the
+dissipation of energy in a magnet due to spin reorientation in a magnetic
+field. In this paper we study magnetic friction in the context of
+micromagnetics, using our recent implementation of smooth spring-driven motion
+[Phys. Rev. E. 97, 053301 (2018)] to simulate ring-down measurements in two
+setups where domain wall dynamics is induced by mechanical motion. These
+include a single thin film with a domain wall in an external field and a setup
+mimicking a magnetic cantilever tip and substrate, in which the two magnets
+interact through dipolar interactions. We investigate how various micromagnetic
+parameters influence the domain wall dynamics actuated by the oscillatory
+spring-driven mechanical motion and the resulting damping coefficient. Our
+simulations show that the magnitude of magnetic friction can be comparable to
+other forms of non-contact friction. For oscillation frequencies lower than
+those inducing excitations of the internal structure of the domain walls, the
+damping coefficient is found to be independent of frequency. Hence, our results
+obtained in the frequency range from 8 to 112 MHz are expected to be relevant
+also for typical experimental setups operating in the 100 kHz range.",1809.07130v2
+2019-01-05,Tunable Magnetic Skyrmions in Ultrathin Magnetic Nanostructures for Cellular-Level Neurostimulation,"In 2016, the Global Burden of Disease reported that neurological disorders
+were the principal cause of disability-adjusted life years (DALYs) and the
+second leading cause of deaths. Research in the last decade has pushed
+neuroscience to design and implement low-cost, efficient, implantable, flexible
+electrodes/probes and 3D arrays for neuron stimulation and sensing. Electrical
+arrays used in current CMOS-based technologies can be affected by the migration
+of cells (such as astrocytes) that attempt to seal off the electronic devices,
+causing increased impedance and alternations in the electric field. In this
+regard, magnetic nanodevices can be better candidates. A wide assortment of
+magnetic skyrmion-based device ideas and models have as of late been proposed
+featuring their potential applications. In this paper we propose a highly
+tunable skyrmion-based spintronic nanodevice for neuron stimulation. The
+effects of tunable material and magnetic properties specifically
+Dzyaloshinskii-Moriya interaction (DMI), perpendicular magnetic anisotropy
+(PMA) constant, number of skyrmions and device dimensions on stable skyrmion
+nucleation and smooth skyrmion dynamics in a magnetic ultra-thin film have been
+extensively studied. The aim of this study was to meet the standard therapeutic
+specifications of neuron stimulation, which is an electric field of about 10
+mV/mm for a duration of 50 {\mu}s. From Faraday's Laws of Induction, skyrmion
+dynamics that generates an alternating magnetic flux density induces an
+electric field for a certain time duration in the ultra-thin film. The results
+of this work show that on tuning the skyrmion dynamics, the induced electric
+field can reach the standard value required for neurostimulation, thereby
+providing a strong futuristic possibility to exploit skyrmion-based spintronic
+nanodevices for neuron stimulation.",1901.01349v1
+2020-10-24,Dynamics of test particles around regular black holes in modified gravity,"In the work, we have presented detailed analyses of the event horizon and
+curvature properties of spacetime around a regular black hole in modified
+gravity so-called regular MOG black hole. The motion of neutral, electrically
+charged and magnetized particles with magnetic dipole moment, in the close
+environment of the regular MOG black hole immersed in an external
+asymptotically uniform magnetic field has been also explored. Through the study
+on the motion of the neutral test particle, we have obtained that the positive
+(negative) values of the MOG parameter mimic the spin of a rotating Kerr black
+hole giving the same values for innermost stable pro-grade (retrograde) orbits
+of the particles in the range of the spin parameter $a/M \in(-0.4125, \
+0.6946)$. The efficiency of energy release from the accretion disk by the
+Novikov-Thorne model has been calculated and shown that the efficiency is
+linearly proportional to the increase of the MOG parameter $\alpha$, and
+exceeds up to 15 \% at the critical limiting value of the MOG parameter
+$\alpha_{\rm cr}$. The study of the charged particles dynamics has shown that
+innermost stable circular orbits (ISCOs) of the particle increases with the
+increase of the MOG parameter, while the increase of cyclotron frequency being
+responsible to the magnetic interaction causes the decrease of the latter.
+Moreover, the dynamics of magnetic dipoles has shown that the increase of the
+MOG and the magnetic coupling parameters lead to an increase of the inner
+radius and the width of the accretion disk consisting of magnetized particles.
+Finally, we have focused on showing the range of values of the magnetic
+coupling parameter causing the orbits to be stable.",2010.12863v1
+2021-06-23,Spin dynamics of itinerant electrons: local magnetic moment formation and Berry phase,"The state-of-the-art theoretical description of magnetic materials relies on
+solving effective Heisenberg spin problems or their generalizations to
+relativistic or multi-spin-interaction cases that explicitly assume the
+presence of local magnetic moments in the system. We start with a general
+interacting fermionic model that is often obtained in ab initio electronic
+structure calculations and show that the corresponding spin problem can be
+introduced even in the paramagnetic regime, which is characterized by a zero
+average value of the magnetization. Further, we derive a physical criterion for
+the formation of the local magnetic moment and confirm that the latter exists
+already at high temperatures well above the transition to the ordered magnetic
+state. The use of path-integral techniques allows us to disentangle spin and
+electronic degrees of freedom and to carefully separate rotational dynamics of
+the local magnetic moment from Higgs fluctuations of its absolute value. It
+also allows us to accurately derive the topological Berry phase and relate it
+to a physical bosonic variable that describes dynamics of the spin degrees of
+freedom. As the result, we demonstrate that the equation of motion in the case
+of a large magnetic moment takes a conventional Landau-Lifshitz form that
+explicitly accounts for the Gilbert damping due to itinerant nature of the
+original electronic model.",2106.12462v3
+2021-12-16,Plastic vortex creep and dimensional crossovers in the highly anisotropic superconductor HgBa$_2$CuO$_{4+x}$,"In type-II superconductors exposed to magnetic fields between upper and lower
+critical values, $H_{c1}$ and $H_{c2}$, penetrating magnetic flux forms a
+lattice of vortices whose motion can induce dissipation. Consequently, the
+magnetization $M$ of superconductors is typically progressively weakened with
+increasing magnetic field $B \propto n_v$ (for vortex density $n_v$). However,
+some materials exhibit a non-monotonic $M(B)$, presenting a maximum in $M$ at
+what is known as the second magnetization peak. This phenomenon appears in most
+classes of superconductors, including low $T_c$ materials, iron-based, and
+cuprates, complicating pinpointing its origin and garnering intense interest.
+Here, we report on vortex dynamics in optimally doped and overdoped
+HgBa$_2$CuO$_{4+x}$ crystals, with a focus on a regime in which plastic
+deformations of the vortex lattice govern magnetic properties. Specifically, we
+find that both crystals exhibit conspicuous second magnetization peaks and,
+from measurements of the field- and temperature- dependent vortex creep rates,
+identify and characterize phase boundaries between elastic and plastic vortex
+dynamics, as well as multiple previously unreported transitions within the
+plastic flow regime. We find that the second magnetization peak coincides with
+the elastic-to-plastic crossover for a very small range of high fields, and a
+sharp crossover within the plastic flow regime for a wider range of lower
+fields. We find evidence that this transition in the plastic flow regime is due
+to a dimensional crossover, specifically a transition from 3D to 2D plastic
+dynamics.",2112.08667v1
+2022-04-05,Reverse shock forming condition for magnetized relativistic outflows: reconciling theories and simulations,"Reverse shock (RS) emission can be used to probe the properties of the
+relativistic ejecta, especially the degree of magnetization $\sigma$, in
+gamma-ray burst (GRB) afterglows. However, there has been confusion in the
+literature regarding the physical condition for the RS formation, and the role
+of magnetic fields in the RS dynamics in the Poynting-flux-dominated regime is
+not fully understood. Exploiting the shock jump conditions, we characterize the
+properties of a magnetized RS. We compare the RS dynamics and forming
+conditions from different theories and numerical simulations, and reconcile the
+discrepancies among them. The strict RS forming condition is found to be
+$\sigma < \sigma_\mathrm{cr}=(8/3)\gamma_4^2(n_1/n_4)$, where $n_4$ and $n_1$
+are the rest-frame number densities of the ejecta and the ambient medium,
+respectively, $\gamma_4$ is the bulk Lorentz factor, and $\sigma_\mathrm{cr}$
+is the critical magnetization. Contrary to previous claims, we prove that this
+condition agrees with other theoretical and simulated results, which can be
+further applied to the setup and consistency check of future numerical
+simulations. Using this condition, we propose a characteristic radius for RS
+formation, and categorize the magnetized shell into three regimes: 'thick
+shell' (relativistic RS), 'thin shell' (trans-relativistic RS), and 'no RS'
+regimes. The critical magnetization $\sigma_\mathrm{cr}$ is generally below
+unity for thin shells, but can potentially reaches $\sim 100-1000$ in the
+'thick shell' regime. Our results could be applied to the dynamical evolution
+of Poynting-flux-dominated ejecta, with potential applications to
+self-consistent lightcurve modelling of magnetized relativistic outflows.",2204.02315v2
+2022-06-03,Anisotropic Laser-Pulse-Induced Magnetization Dynamics in van der Waals Magnet Fe$_3$GeTe$_2$,"Femtosecond laser-pulse excitation provides an energy efficient and fast way
+to control magnetization at the nanoscale, providing great potential for
+ultrafast next-generation data manipulation and nonvolatile storage devices.
+Ferromagnetic van der Waals materials have garnered much attention over the
+past few years due to their low dimensionality, excellent magnetic properties,
+and large response to external stimuli. Nonetheless, their behaviour upon fs
+laser-pulse excitation remains largely unexplored. Here, we investigate the
+ultrafast magnetization dynamics of a thin flake of Fe$_3$GeTe$_2$ (FGT) and
+extract its intrinsic magnetic properties using a microscopic framework. We
+find that our data is well described by our modelling, with FGT undergoing a
+slow two-step demagnetization, and we experimentally extract the
+spin-relaxation timescale as a function of temperature, magnetic field and
+excitation fluence. Our observations indicate a large spin-flip probability in
+agreement with a theoretically expected large spin-orbit coupling, as well as a
+weak interlayer exchange coupling. The spin-flip probability is found to
+increase when the magnetization is pulled away from its quantization axis,
+opening doors to an external control over the spins in this material. Our
+results provide a deeper understanding of the dynamics van der Waals materials
+upon fs laser-pulse excitation, paving the way towards two-dimensional
+materials-based ultrafast spintronics.",2206.01452v1
+2022-09-29,Spin Dynamics in Patterned Magnetic Multilayers with Perpendicular Magnetic Anisotropy,"The magnetization dynamics in nanostructures has been extensively studied in
+the last decades, and nanomagnetism has evolved significantly over that time,
+discovering new effects, developing numerous applications, and identifying
+promising new directions. This includes magnonics, an emerging research field
+oriented on the study of spin-wave dynamics and their applications. In this
+context, thin ferromagnetic films with perpendicular magnetic anisotropy (PMA)
+offer interesting opportunities to study spin waves, in particular, due to
+out-of-plane magnetization in remanence or at relatively weak external magnetic
+fields. This is the only magnetization configuration offering isotropic
+in-plane spin-wave propagation within the sample plane, the forward volume
+magnetostatic spin-wave geometry. The isotropic dispersion relation is highly
+important in designing signal-processing devices, offering superior prospects
+for direct replicating various concepts from photonics into magnonics.
+Analogous to photonic or phononic crystals, which are the building blocks of
+optoelectronics and phononics, magnonic crystals are considered as key
+components in magnonics applications. Arrays of nanodots and structured
+ferromagnetic thin films with a periodic array of holes, popularly known as
+antidot lattices based on PMA multilayers have been recently studied. Novel
+magnonic properties related to propagating spin-wave modes, exploitation of the
+band gaps, and confined modes, were demonstrated. Also, the existence of
+nontrivial magnonic band topologies has been shown. Moreover, the combination
+of PMA and Dzyaloshinskii-Moriya interaction leads to the formation of chiral
+magnetization states, including N\'eel domain walls, skyrmions, and skyrmionium
+states.",2209.14824v2
+2023-03-08,Improving Néel domain walls dynamics and skyrmion stability using He ion irradiation,"Magnetization reversal and domain wall dynamics in Pt/Co/AlOx trilayers have
+been tuned by He+ ion irradiation. Fluences up to 1.5x10$^{15}$ ions/cm$^2$
+strongly decrease the perpendicular magnetic anisotropy (PMA), without
+affecting neither the spontaneous magnetization nor the strength of the
+Dzyaloshinskii-Moriya interaction (DMI). This confirms the robustness of the
+DMI interaction against interfacial chemical intermixing, already predicted by
+theory. In parallel with the decrease of the PMA in the irradiated samples, a
+strong decrease of the depinning field is observed. This allows the domain
+walls to reach large maximum velocities with lower magnetic fields with respect
+to those needed for the pristine films. Decoupling PMA from DMI can therefore
+be beneficial for the design of low energy devices based on domain wall
+dynamics. When the samples are irradiated with larger He+ fluences, the
+magnetization gets close to the out-of-plane/in-plane reorientation transition
+where 100nm size magnetic skyrmions are stabilized. We observe that as the He+
+fluence increases, the skyrmion size decreases while these magnetic textures
+become more stable against the application of an external magnetic field.",2303.04543v1
+2024-01-21,Study of Reconnection Dynamics and Plasma Relaxation in MHD simulation of a Solar Flare,"Self-organization in continuous systems is associated with dissipative
+processes. In particular, for magnetized plasmas, it is known as magnetic
+relaxation, where the magnetic energy is converted into heat and kinetic energy
+of flow through the process of magnetic reconnection. An example of such a
+system is the solar corona, where reconnection manifests as solar transients
+like flares and jets. Consequently, toward investigation of plasma relaxation
+in solar transients, we utilize a novel approach of data-constrained MHD
+simulation for an observed solar flare. The selected active region NOAA 12253
+hosts a GOES M1.3 class flare. The investigation of extrapolated coronal
+magnetic field in conjunction with the spatiotemporal evolution of the flare
+reveals a hyperbolic flux tube (HFT), overlying the observed brightenings. MHD
+simulation is carried out with the EULAG-MHD numerical model to explore the
+corresponding reconnection dynamics. The overall simulation shows signatures of
+relaxation. For a detailed analysis, we consider three distinct sub-volumes. We
+analyze the magnetic field line dynamics along with time evolution of
+physically relevant quantities like magnetic energy, current density, twist,
+and gradients in magnetic field. In the terminal state, none of the sub-volumes
+are seen to reach a force-free state, thus remaining in non-equilibrium,
+suggesting the possibility of further relaxation. We conclude that the extent
+of relaxation depends on the efficacy and duration of reconnection, and hence,
+on the energetics and time span of the flare.",2401.11417v1
+2014-06-26,"Spin Supercurrent, Magnetization Dynamics, and Phi-State in Spin-Textured Josephson Junctions","The prospect of combining the dissipationless nature of superconducting
+currents with the spin-polarization of magnetic materials is interesting with
+respect to exploring superconducting analogues of topics in spintronics. In
+order to accomplish this aim, it is pivotal to understand how
+spin-supercurrents interact dynamically with magnetization textures. We
+investigate the appearance of a spin-supercurrent and the resulting
+magnetization dynamics in a textured magnetic Josephson current by using three
+experimentally relevant models: i) a S/F/S junction with spin-active
+interfaces, ii) a S/F1/F2/F3/S Josephson junction with a ferromagnetic
+trilayer, and iii) a Josephson junction containing a domain wall. In all of
+these cases, the supercurrent is spin-polarized and exerts a spin-transfer
+torque on the ferromagnetic interlayers which causes magnetization dynamics.
+Using a scattering matrix formalism in the clean limit, we compute the
+Andreev-bound states and free energy of the system which is used to solve the
+Landau-Lifshiftz-Gilbert equation. We compute both how the inhomogeneous
+magnetism influences the phase-dependence of the charge supercurrent as well as
+the magnetization dynamics caused by the spin-supercurrent. Using a realistic
+experimental parameter set, we find that the supercurrent can induce
+magnetization switching that is controlled by the superconducting phase
+difference. Moreover, we demonstrate that the combined effect of chiral spin
+symmetry breaking and interface scattering causes the system to act as a phase
+battery that may supply any superconducting phase difference phi in the ground
+state. Such a phi junction is accompanied by an anomalous supercurrent
+appearing even at zero phase difference, and we demonstrate that the flow
+direction of this current is controlled by the chirality of the magnetization
+configuration.",1406.7016v1
+2014-10-26,Ising Metamagnet Driven by Propagating Magnetic Field Wave: Nonequilibrium Phases and Transitions,"The nonequilibrium responses of Ising metamagnet (layered antiferromagnet) to
+the propagating magnetic wave are studied by Monte Carlo simulation. Here, the
+spatio-temporal variations of magnetic field keeps the system away from
+equilibrium. The sublattice magnetisations show dynamical symmetry breaking in
+the low temperature ordered phase. The nonequilibrium phase transitions are
+studied from the temperature dependences of dynamic staggered order parameter,
+its derivative and the dynamic specific heat. The transitions are marked by the
+peak position of dynamic specific heat and the position of dip of the
+derivative of dynamic staggered order parameter. It is observed that, for lower
+values of the amplitudes of the propagating magnetic field, if the system is
+cooled from a high temperature, it undergoes a phase transition showing sharp
+peak of dynamic specific heat and sharp dip of the derivative of the dynamic
+staggered order parameter. However, for higher values of the amplitude of the
+propagating magnetic field, system exhibits multiple phase transitions. A
+comprehensive phase diagram is also plotted. The transition, for vanishingly
+small value of the amplitude of the propagating wave, is very close to that for
+equilibrium ferro-para phase transition of cubic Ising ferromagnet.",1410.6983v2
+2007-03-21,Modeling the (upper) solar atmosphere including the magnetic field,"The atmosphere of the Sun is highly structured and dynamic in nature. From
+the photosphere and chromosphere into the transition region and the corona
+plasma-$\beta$ changes from above to below one, i.e. while in the lower
+atmosphere the energy density of the plasma dominates, in the upper atmosphere
+the magnetic field plays the governing role -- one might speak of a ``magnetic
+transition''. Therefore the dynamics of the overshooting convection in the
+photosphere, the granulation, is shuffling the magnetic field around in the
+photosphere. This leads not only to a (re-)structuring of the magnetic field in
+the upper atmosphere, but induces also the dynamic reaction of the coronal
+plasma e.g. due to reconnection events. Therefore the (complex) structure and
+the interaction of various magnetic patches is crucial to understand the
+structure, dynamics and heating of coronal plasma as well as its acceleration
+into the solar wind.
+  The present article will emphasize the need for three-dimensional modeling
+accounting for the complexity of the solar atmosphere to understand these
+processes. Some advances on 3D modeling of the upper solar atmosphere in
+magnetically closed as well as open regions will be presented together with
+diagnostic tools to compare these models to observations. This highlights the
+recent success of these models which in many respects closely match the
+observations.",0703575v1
+2008-06-13,Coherent control of nanomagnet dynamics via ultrafast spin torque pulses,"The magnetization orientation of a nanoscale ferromagnet can be manipulated
+using an electric current via the spin transfer effect. Time domain
+measurements of nanopillar devices at low temperatures have directly shown that
+magnetization dynamics and reversal occur coherently over a timescale of
+nanoseconds. By adjusting the shape of a spin torque waveform over a timescale
+comparable to the free precession period (100-400 ps), control of the
+magnetization dynamics in nanopillar devices should be possible. Here we report
+coherent control of the free layer magnetization in nanopillar devices using a
+pair of current pulses as narrow as 30 ps with adjustable amplitudes and delay.
+We show that the switching probability can be tuned over a broad range by
+timing the current pulses with the underlying free-precession orbits, and that
+the magnetization evolution remains coherent for more than 1 ns even at room
+temperature. Furthermore, we can selectively induce transitions along
+free-precession orbits and thereby manipulate the free magnetic moment motion.
+We expect this technique will be adopted for further elucidating the dynamics
+and dissipation processes in nanomagnets, and will provide an alternative for
+spin torque driven spintronic devices, such as resonantly pumping microwave
+oscillators, and ultimately, for efficient reversal of memory bits in magnetic
+random access memory (MRAM).",0806.2297v1
+2010-12-11,Dynamical efficiency of collisionless magnetized shocks in relativistic jets,"The so-called internal shock model aims to explain the light-curves and
+spectra produced by non-thermal processes originated in the flow of blazars and
+gamma-ray bursts. A long standing question is whether the tenuous collisionless
+shocks, driven inside a relativistic flow, are efficient enough to explain the
+amount of energy observed as compared with the expected kinetic power of the
+outflow. In this work we study the dynamic efficiency of conversion of
+kinetic-to- thermal/magnetic energy of internal shocks in relativistic
+magnetized outflows. We find that the collision between shells with a non-zero
+relative velocity can yield either two oppositely moving shocks (in the frame
+where the contact surface is at rest), or a reverse shock and a forward
+rarefaction. For moderately magnetized shocks (magnetization {\sigma} ~ 0.1),
+the dynamic efficiency in a single two-shell interaction can be as large as
+40%. Hence, the dynamic efficiency of moderately magnetized shocks is larger
+than in the corresponding unmagnetized two-shell interaction. We find that the
+efficiency is only weakly dependent on the Lorentz factor of the shells and,
+thus internal shocks in the magnetized flow of blazars and gamma-ray bursts are
+approximately equally efficient.",1012.2474v1
+2012-09-13,Random field Ising model swept by propagating magnetic field wave: Athermal nonequilibrium phase diagram,"The dynamical steady state behaviour of the random field
+  Ising ferromagnet swept by a propagating magnetic field wave is studied at
+zero temperature by Monte Carlo simulation in two dimensions. The distribution
+of the random field is bimodal type. For a fixed set of values of the frequency
+and wavelength of propagating magnetic field wave and the strength of the
+random field, four distinct dynamical steady states or nonequilibrium phases
+were identified. These four nonequilibrium phases are characterised by
+different values of structure factors. State of first kind, where all spins are
+parallel (up). The second one is, the propagating type, where the sharp strips
+formed by parallel spins are found to move coherently. The third one is also
+propagating type, where the boundary of the strips of spins is not very sharp.
+The fourth kind, shows no propagation of stripes of magnetic spins, forming a
+homogeneous distribution of up and down spins. This is disordered phase The
+appearance of these four dynamical phases or modes depends on the value of the
+amplitude of propagating magnetic field wave and the strength of random
+(static) field. A phase diagram has also been drawn, in the plane formed by the
+amplitude of propagating field and the strength of random field. It is checked
+that, the existence of these dynamical phases is neither a finite size effect
+nor a transient phenomenon.",1209.2841v2
+2012-09-27,"Magnetic order, magnetic correlations and spin dynamics in the pyrochlore antiferromagnet Er2Ti2O7","Er2Ti2O7 is believed to be a realization of an XY antiferromagnet on a
+frustrated lattice of corner-sharing regular tetrahedra. It is presented as an
+example of the order-by-disorder mechanism in which fluctuations lift the
+degeneracy of the ground state, leading to an ordered state. Here we report
+detailed measurements of the low temperature magnetic properties of Er2Ti2O7,
+which displays a second-order phase transition at T_N \simeq 1.2 K with
+coexisting short- and long-range orders. Magnetic-susceptibility studies show
+that there is no spin-glass-like irreversible effect. Heat-capacity
+measurements reveal that the paramagnetic critical exponent is typical of a
+3-dimensional XY magnet while the low-temperature specific heat sets an upper
+limit on the possible spin-gap value and provides an estimate for the spin-wave
+velocity. Muon spin relaxation measurements show the presence of spin dynamics
+in the nanosecond time scale down to 21 mK. This time range is intermediate
+between the shorter time characterizing the spin dynamics in Tb2Sn2O7, which
+also displays long- and short-range magnetic order, and the time scale typical
+of conventional magnets. Hence the ground state is characterized by exotic spin
+dynamics. We determine the parameters of a symmetry-dictated Hamiltonian
+restricted to the spins in a tetrahedron, by fitting the paramagnetic diffuse
+neutron scattering intensity for two reciprocal lattice planes. These data are
+recorded in a temperature region where the assumption that the correlations are
+limited to nearest neighbors is fair.",1209.6153v1
+2013-01-02,The Equations of Magnetoquasigeostrophy,"The dynamics contained in magnetized layers of exoplanet atmospheres are
+important to understand in order to characterize what observational signatures
+they may provide for future observations. It is important to develop a
+framework to begin studying and learning the physical processes possible under
+those conditions and what, if any, features contained in them may be observed
+in future observation missions. The aims of this study is to formally derive,
+from scaling arguments, a manageable reduced set of equations for analysis,
+i.e. a magnetic formulation of the equations of quasigeostrophy appropriate for
+a multi-layer atmosphere. The main goal is to provide a simpler theoretical
+platform to explore the dynamics possible within confined magnetized layers of
+exoplanet atmospheres. We primarily use scaling arguments to derive the reduced
+equations of ""magnetoquasigeostrophy"" which assumes dynamics to take place in
+an atmospheric layer which is vertically thin compared to its horizontal
+scales. The derived equation set retains features existing in standard
+shallow-water magnetohydrodynamic equations but are absent in more classical
+derivations of the quasi-geostrophic limit, namely, the non-divergence of the
+in-plane components of the magnetic field. We liken this non-divergence of the
+in-plane magnetic fields as indicative of a quantity whose behaviour mimics a
+two-dimensional ""pseudo""-magnetic monopole source. We also find, using the same
+scaling argument procedures, appropriate limits of the fundamental parameters
+of the system which yield reduced equations describing the flow dynamics
+primarily characterized by magnetostrophic balance. The standard scaling
+arguments employed here show how traditional magnetized quasigeostrophic
+equations connect to their magnetized shallow water forms. The equations
+derived are amenable to analysis using well-known techniques.",1301.0285v1
+2015-09-09,Emergence of non-twisted magnetic fields in the Sun: Jets and atmospheric response,"Aims. We study the emergence of a non-twisted flux tube from the solar
+interior into the solar atmosphere. We investigate whether the length of the
+buoyant part of the flux tube (i.e. {\lambda}) affects the emergence of the
+field and the dynamics of the evolving magnetic flux system. Methods. We
+perform three-dimensional (3D), time-dependent, resistive, compressible MHD
+simulations using the Lare3D code. Results. We find that there are considerable
+differences in the dynamics of the emergence of a magnetic flux tube when
+{\lambda} is varied. In the solar interior, for larger values of {\lambda}, the
+rising magnetic field emerges faster and expands more due to its lower magnetic
+tension. As a result, its field strength decreases and its emergence above the
+photosphere occurs later than in the smaller {\lambda} case. However, in both
+cases, the emerging field at the photosphere becomes unstable in two places,
+forming two magnetic bipoles that interact dynamically during the evolution of
+the system. Most of the dynamic phenomena occur at the current layer, which is
+formed at the interface between the interacting bipoles. We find the formation
+and ejection of plasmoids, the onset of successive jets from the interface, and
+the impulsive heating of the plasma in the solar atmosphere. We discuss the
+triggering mechanism of the jets and the atmospheric response to the emergence
+of magnetic flux in the two cases.",1509.02850v1
+2016-11-10,Spin-charge coupled dynamics driven by a time-dependent magnetization,"The spin-charge coupled dynamics in a thin, magnetized metallic system are
+investigated. The effective driving force acting on the charge carriers is
+generated by a dynamical magnetic texture, which can be induced, e.g., by a
+magnetic material in contact with a normal-metal system. We consider a general
+inversion-asymmetric substrate/normal-metal/magnet structure, which, by
+specifying the precise nature of each layer, can mimick various experimentally
+employed setups. Inversion symmetry breaking gives rise to an effective Rashba
+spin-orbit interaction. We derive general spin-charge kinetic equations which
+show that such spin-orbit interaction, together with anisotropic Elliott-Yafet
+spin relaxation, yields significant corrections to the magnetization-induced
+dynamics. In particular, we present a consistent treatment of the spin density
+and spin current contributions to the equations of motion, inter alia
+identifying a novel term in the effective force which appears due to a spin
+current polarized parallel to the magnetization. This ""inverse spin filter""
+contribution depends markedly on the parameter which describes the anisotropy
+in spin relaxation. To further highlight the physical meaning of the different
+contributions, the spin pumping configuration of typical experimental setups is
+analyzed in detail. In the two-dimensional limit the build-up of a DC voltage
+is dominated by the spin galvanic (inverse Edelstein) effect. A measuring
+scheme that could isolate this contribution is discussed.",1611.03378v3
+2019-05-20,Injection locking at fractional frequencies of magnetic tunnel junction (MTJ)-based read sensors' ferromagnetic resonance modes,"Being nonlinear dynamic systems, magnetic read sensors should respond to an
+excitation signal of a frequency considerably different from their natural
+ferromagnetic resonance (FMR) frequencies. Because of the magnetization
+dynamics' inherent nonlinear nature, the sensors' response should be measured
+at the DC, excitation frequency, and its multiples (harmonics). In this paper,
+we present results of such measurements, accomplished using a one-port
+nonlinear vector network analyzer (NVNA), which show distinct resonances at
+fractional frequencies of the free layer (FL) FMR mode. Identification of these
+resonances, resulting from the nonlinear nature of the spin-torque (ST)-induced
+magnetization dynamics, was performed using micromagnetic modeling. In
+particular, we show that the measured DC response at the above-mentioned
+fractional frequencies can be explained by a low-order nonlinearity and strong
+magnetodipolar feedback between magnetic layers adjacent to an MgO barrier.
+Additionally, we determined that the simulated harmonic response is strongly
+enhanced by the mutual ST effect between these layers. Finally, we demonstrate
+that the read sensors' nonlinear magnetization dynamics and, by extension,
+their harmonic response are highly sensitive to various magnetic and ST
+parameters. Thus, this study shows that using NVNA measurements in conjunction
+with micromagnetic modeling can clarify the uncertainty in the definition of
+these parameters.",1905.08183v2
+2019-09-12,The Hofstadter Butterfly in a Dynamic Cavity-Induced Synthetic Magnetic Field,"Energy bands of electrons in a square lattice potential threaded by a uniform
+magnetic field exhibit a fractal structure known as the Hofstadter butterfly.
+Here we study a Fermi gas in a 2D optical lattice within a linear cavity with a
+tilt along the cavity axis. The hopping along the cavity axis is only induced
+by resonant Raman scattering of transverse pump light into a standing wave
+cavity mode. Choosing a suitable pump geometry allows to realize the
+Hofstadter-Harper model with a cavity-induced dynamical synthetic magnetic
+field, which appears at the onset of the superradiant phase transition. The
+dynamical nature of this cavity-induced synthetic magnetic field arises from
+the delicate interplay between collective superradiant scattering and the
+underlying fractal band structure. Using a sixth-order expansion of the free
+energy as function of the order parameter and by numerical simulations we show
+that at low magnetic fluxes the superradiant ordering phase transition is first
+order, while it becomes second order for higher flux. The dynamic nature of the
+magnetic field induces a non-trivial deformation of the Hofstadter butterfly in
+the superradiant phase. At strong pump far above the self-ordering threshold we
+recover the Hofstadter butterfly one would obtain in a static magnetic field.",1909.05975v2
+2020-03-01,Topological transitions in superconductor nanomembranes in a magnetic field with submicron inhomogeneity under a strong transport current,"Under a strong transport current, the induced voltage in superconductor
+nanomembranes in a magnetic field with submicron inhomogeneity shows a pulse on
+a certain interval of the magnetic field. It is a manifestation of a wide
+phase-slip domain. The topological transition accompanying the phase-slip
+effect consists in the occurrence of two new loops of weak superconducting
+currents connecting two regions of superconducting screening currents, which
+are disconnected in case of vortex-chain dynamics. In the middle of the
+phase-slip domain, rapid dynamics of the superconducting order parameter
+consists in decoupling of a spontaneously nucleated vortex-antivortex pair,
+subsequent motion of a vortex and an antivortex in the opposite directions
+followed by their annihilation with an antivortex and a vortex from the
+adjacent pairs. The submicron-scale inhomogeneity of the magnetic field can be
+achieved through a direct patterning of the magnetic field applied to a planar
+membrane or using advanced nanostructuring, such as roll-up technology, focused
+ion-beam deposition or coating carbon nanotubes by superconducting materials.
+If the applied magnetic field is orthogonal to the axis of a microtube, which
+carries transport current in the azimuthal direction, the phase-slip regime is
+characterized by the vortex-antivortex lifetime of 10E-15 s versus 10E-12 s for
+disconnected vortex dynamics in the half-tubes. The phase-slip dynamics
+determines the voltage-magnetic field and voltage-current characteristics in
+nanoarchitectures with multiple disconnected loops of superconducting screening
+currents.",2003.00508v1
+2021-11-17,Probing the magnetic polaron state in the ferromagnetic semiconductor HgCr$_2$Se$_4$ with resistance fluctuation and muon-spin spectroscopy measurements,"Combined resistance noise and muon-spin relaxation ($\mu$SR) measurements of
+the ferromagnetic semiconductor HgCr$_2$Se$_4$ suggest a degree of
+magnetoelectric coupling and provide evidence for the existence of isolated
+magnetic polarons. These form at elevated temperatures and undergo a
+percolation transition with a drastic enhancement of the low-frequency
+1/$f$-type charge fluctuations at the insulator-to-metal transition at $\sim 95
+- 98$ K in the vicinity of the magnetic ordering temperature $T_C \sim 105 -
+107$ K. Upon approaching the percolation threshold from above, the strikingly
+unusual dynamics of a distinct two-level fluctuator superimposed on the $1/f$
+noise can be described by a slowing down of the dynamics of a nanoscale
+magnetic cluster, a magnetic polaron, when taking into account an effective
+radius of the polaron depending on the spin correlation length. Coinciding
+temperature scales found in $\mu$SR and noise measurements suggest changes in
+the magnetic dynamics over a wide range of frequencies and are consistent with
+the existence of large polarized and domain-wall-like regions at low
+temperatures, that result from the freezing of spin dynamics at the magnetic
+polaron percolation transition.",2111.08990v1
+2022-06-06,Probing spin dynamics of ultra-thin van der Waals magnets via photon-magnon coupling,"Layered van der Waals (vdW) magnets can maintain a magnetic order even down
+to the single-layer regime and hold promise for integrated spintronic devices.
+While the magnetic ground state of vdW magnets was extensively studied, key
+parameters of spin dynamics, like the Gilbert damping, crucial for designing
+ultra-fast spintronic devices, remains largely unexplored. Despite recent
+studies by optical excitation and detection, achieving spin wave control with
+microwaves is highly desirable, as modern integrated information technologies
+predominantly are operated with these. The intrinsically small numbers of
+spins, however, poses a major challenge to this.
+  Here, we present a hybrid approach to detect spin dynamics mediated by
+photon-magnon coupling between high-Q superconducting resonators and ultra-thin
+flakes of Cr$_2$Ge$_2$Te$_6$ (CGT) as thin as 11\,nm. We test and benchmark our
+technique with 23 individual CGT flakes and extract an upper limit for the
+Gilbert damping parameter. These results are crucial in designing on-chip
+integrated circuits using vdW magnets and offer prospects for probing spin
+dynamics of monolayer vdW magnets.",2206.02460v2
+2022-12-30,Commensurate and incommensurate magnetic order in the doped two-dimensional Hubbard model: dynamical mean-field theory analysis,"We develop a dynamical mean-field theory approach for the spiral magnetic
+order, changing to a local coordinate frame with preferable spin alignment
+along the $z$-axis, which can be considered with the impurity solvers treating
+the spin diagonal local Green's function. We furthermore solve the
+Bethe-Salpeter equations for nonuniform dynamic magnetic susceptibilities in
+the local coordinate frame. We apply this approach to describe the evolution of
+magnetic order with doping in the $t-t'$ Hubbard model with $t'=0.15$, which is
+appropriate for the description of the doped La$_2$CuO$_4$ high-temperature
+superconductor. We find that with doping the antiferromagnetic order changes to
+the $(Q,\pi)$ incommensurate one, and then to the paramagnetic phase. The
+spectral weight at the Fermi level is suppressed near half filling and
+continuously increases with doping. The dispersion of holes in the
+antiferromagnetic phase shows qualitative agreement with the results of the
+$t$-$J$ model consideration. In the incommensurate phase we find two branches
+of hole dispersions, one of which crosses the Fermi level. The resulting Fermi
+surface forms hole pockets. We also consider the dispersion of the magnetic
+excitations, obtained from the non-local dynamic magnetic susceptibilities. The
+transverse spin excitations are gapless, fulfilling the Goldstone theorem; in
+contrast to the mean-field approach the obtained magnetic state is found to be
+stable. The longitudinal excitations are characterized by a small gap, showing
+the rigidity of the spin excitations. For realistic hopping and interaction
+parameters we reproduce the experimentally measured spin-wave dispersion of
+La$_2$CuO$_4$.",2212.14656v2
+2023-06-20,High frequency oscillations in spin-torque nano oscillator due to bilinear coupling,"Exchange coupling in an interfacial context is crucial for spin-torque nano
+oscillator (STNO) that consists of a non-magnetic spacer which is alloyed with
+a ferromagnetic material. Currently, investigations on the dynamics of the free
+layer magnetization and frequency enhancement in the STNO with bilinear
+coupling are still being actively pursued. In the present work, we investigate
+the dynamics of the STNO in the presence of bilinear coupling but in the
+absence of an external magnetic field by analyzing the associated
+Landau-Lifshitz-Gilbert-Sloncewski(LLGS) equation, and consequently the impact
+of the bilinear coupling on the dynamics of the magnetization of the free layer
+is studied. It is observed that the frequency of the oscillations in the
+magnetization component along the direction of the pinned layer polarization
+can be enhanced above 300 GHz by positive bilinear coupling and up to around 30
+GHz by negative bilinear coupling. We further reveal a transition from in-plane
+to out-of-plane precession both for positive and negative bi-linear couplings.
+We also analyze the switching of the magnetization for different values of
+current and bilinear coupling. Our detailed investigations of STNO with
+bilinear coupling aim at the possibilities of high-frequency devices by
+considering the applied current and bilinear coupling in the absence of a
+magnetic field.",2306.11415v1
+2011-10-21,Thermodynamics of trajectories of the one-dimensional Ising model,"We present a numerical study of the dynamics of the one-dimensional Ising
+model by applying the large-deviation method to describe ensembles of dynamical
+trajectories. In this approach trajectories are classified according to a
+dynamical order parameter and the structure of ensembles of trajectories can be
+understood from the properties of large-deviation functions, which play the
+role of dynamical free-energies. We consider both Glauber and Kawasaki
+dynamics, and also the presence of a magnetic field. For Glauber dynamics in
+the absence of a field we confirm the analytic predictions of Jack and Sollich
+about the existence of critical dynamical, or space-time, phase transitions at
+critical values of the ""counting"" field $s$. In the presence of a magnetic
+field the dynamical phase diagram also displays first order transition
+surfaces. We discuss how these non-equilibrium transitions in the 1$d$ Ising
+model relate to the equilibrium ones of the 2$d$ Ising model. For Kawasaki
+dynamics we find a much simple dynamical phase structure, with transitions
+reminiscent of those seen in kinetically constrained models.",1110.4857v1
+2015-12-26,An Empirical Relation Between The Large-Scale Magnetic Field And The Dynamical Mass In Galaxies,"The origin and evolution of cosmic magnetic fields as well as the influence
+of the magnetic fields on the evolution of galaxies are unknown. Though not
+without challenges, the dynamo theory can explain the large-scale coherent
+magnetic fields which govern galaxies, but observational evidence for the
+theory is so far very scarce. Putting together the available data of
+non-interacting, non-cluster galaxies with known large-scale magnetic fields,
+we find a tight correlation between the integrated polarized flux density,
+S(PI), and the rotation speed, v(rot), of galaxies. This leads to an almost
+linear correlation between the large-scale magnetic field B and v(rot),
+assuming that the number of cosmic ray electrons is proportional to the star
+formation rate, and a super-linear correlation assuming equipartition between
+magnetic fields and cosmic rays. This correlation cannot be attributed to an
+active linear alpha-Omega dynamo, as no correlation holds with global shear or
+angular speed. It indicates instead a coupling between the large-scale magnetic
+field and the dynamical mass of the galaxies, B ~ M^(0.25-0.4). Hence, faster
+rotating and/or more massive galaxies have stronger large-scale magnetic
+fields. The observed B-v(rot) correlation shows that the anisotropic turbulent
+magnetic field dominates B in fast rotating galaxies as the turbulent magnetic
+field, coupled with gas, is enhanced and ordered due to the strong gas
+compression and/or local shear in these systems. This study supports an
+stationary condition for the large-scale magnetic field as long as the
+dynamical mass of galaxies is constant.",1512.08145v2
+2018-02-27,Dynamic magnetism in the disordered hexagonal double perovskite BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$,"Magnetic frustration and disorder are key ingredients to prevent the onset of
+magnetic order. In the disordered hexagonal double perovskite
+BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$, Mn$^{4+}$ cations, with $S=3/2$ spins, can
+either form highly correlated states of magnetic trimers or dimers or remain as
+weakly interacting orphan spins. At low temperature ($T$), the dimer response
+is negligible, and magnetism is dominated by the trimers and orphans. To
+explore the role of magnetic frustration, disorder and possibly of quantum
+fluctuations, the low-$T$ magnetic properties of the remaining magnetic degrees
+of freedom of BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$ are investigated. Heat-capacity
+data and magnetic susceptibility display no evidence for a phase transition to
+a magnetically ordered phase but indicate the formation of a correlated spin
+state. The low-temperature spin dynamics of this state is then explored by
+$\mu$SR experiments. The zero field $\mu^{+}$ relaxation rate data show no
+static magnetism down to $T=19$ mK and longitudinal field experiments support
+as well that dynamic magnetism persists at low $T$. Our results are interpreted
+in terms of a spin glass state which stems from a disordered lattice of orphans
+spins and trimers. A spin liquid state in BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$,
+however, is not excluded and is also discussed.",1802.09950v2
+2022-05-06,Tuning the dynamics of chiral domain walls of ferrimagnetic films with the magneto-ionic effect,"The manipulation of magnetism with a gate voltage is expected to lead the way
+towards the realization of energy-efficient spintronics devices and
+high-performance magnetic memories. Exploiting magneto-ionic effects under
+micro-patterned electrodes in solid-state devices adds the possibility to
+modify magnetic properties locally, in a non-volatile and reversible way.
+Tuning magnetic anisotropy, magnetization and Dzyaloshinskii-Moriya interaction
+allows modifying at will the dynamics of non trivial magnetic textures such as
+skyrmions and chiral domain walls in magnetic race tracks. In this work, we
+illustrate efficient magneto-ionic effects in a ferrimagnetic Pt/Co/Tb stack
+using a ZrO2 thin layer as a solid state ionic conductor. When a thin layer of
+terbium is deposited on top of cobalt, it acquires a magnetic moment that
+aligns antiparallel to that of cobalt, reducing the effective magnetization.
+Below the micro-patterned electrodes, the voltage-driven migration of oxygen
+ions in a ZrO2 towards the ferrimagnetic stack partially oxidizes the Tb layer,
+leading to the local variation not only of the spontaneous magnetization, but
+also of the effective magnetic anisotropy and of the Dzyaloshinskii-Moriya
+interaction. This leads to a huge increase of the domain wall velocity, which
+varies from 10 m/s in the pristine state to 250 m/s after gating. This
+non-volatile and reversible tuning of the domain wall dynamics may lead to
+applications to reprogrammable magnetic memories or other spintronic devices.",2205.03158v1
+2023-10-11,Modern topics in relativistic spin dynamics and magnetism,"Magnetism is a rich subject touching all aspects of physics. My goal with
+this dissertation is to explore spin and magnetic moments in
+\emph{relativistic} mechanics from both a quantum and classical perspective. We
+emphasize the special case of gyromagnetic ratio $g\!=\!2$ and its relationship
+to the algebraic spin structure of wave equations. In relativistic quantum
+mechanics, we investigate generalizations of the Dirac equation for arbitrary
+magnetic moments for fermions. We analyze the homogeneous magnetic field case
+and the Coulomb problem for hydrogen-like atoms with emphasis on the role of
+the anomalous magnetic moment (AMM). We explore alternative approaches which
+combine mass and the magnetic moment. Classically, we propose a relativistic
+covariant model of the Stern-Gerlach force via the introduction of a magnetic
+four-potential. This model modifies the covariant torque equations and unites
+the Amp\`erian and Gilbertian models for magnetic moments.
+  We further study (transition) magnetic dipoles in Majorana neutrinos
+specifically analyzing the relationship between flavor mixing and
+electromagnetic (EM) fields. We demonstrate EM flavor mixing explicitly in the
+2-flavor model and develop a dynamical mass basis with an EM rotation matrix.
+EM induced neutrino mass splitting is compared to neutrino mass hierarchy.
+  An interesting application of these theoretical developments is to study
+primordial magnetization in the early universe during the hot dense
+electron-positron plasma epoch. We propose a model of magnetic thermal
+matter-antimatter plasmas. We analyze the paramagnetic characteristics of
+electron-positron plasma when exposed to an external primordial field.
+  Future research outlooks include: Second order equations for anomalous
+quantum chromodynamic (QCD) moments, neutrino CP violation in strong EM fields,
+and fifth-dimension spin dynamics in Kaluza-Klein theory.",2310.07193v1
+1995-09-18,Dimensional Reduction and Catalysis of Dynamical Symmetry Breaking by a Magnetic Field,"It is shown that a constant magnetic field in 3+1 and 2+1 dimensions is a
+strong catalyst of dynamical chiral symmetry breaking, leading to the
+generation of a fermion dynamical mass even at the weakest attractive
+interaction between fermions. The essence of this effect is the dimensional
+reduction $D\to D-2$ in the dynamics of fermion pairing in a magnetic field.
+The effect is illustrated in the Nambu--Jona--Lasinio (NJL) model and QED. In
+the NJL model in a magnetic field, the low--energy effective action and the
+spectrum of long wavelength collective excitations are derived. In QED (in
+ladder and improved ladder approximations) the dynamical mass of fermions
+(energy gap in the fermion spectrum) is determined. Possible applications of
+this effect and its extension to inhomogeneous field configurations are
+discussed.",9509320v2
+2000-09-11,Influence of guiding magnetic field on emission of stimulated photons in generators utilizing periodic slow-wave structures,"Effect of guiding magnetic field on evolution of stimulated emission is
+considered. It is shown that the transverse dynamics of electrons contributes
+to generation process and that contribution decreases with the magnetic field
+grows. The equation of generation for stimulated radiation of electron beam
+passing over periodic medium in magnetic field of arbitrary value is derived.
+The critical value of guiding field for which the transverse dynamics of
+electron don't contribute to emission is determined. It is shown, that
+transverse dynamics of electron modifies the boundary conditions. It follows
+from the derived generation equation that transverse dynamics yields to ~25%
+increase of the increment magnitude in high gain regime. In the limit of small
+signal the generation gain twice increases when transverse dynamics evolves.
+Obtained results are valid for every FEL system, which use the mechanism of
+waves slowing in the slow-wave structures for generation.",0009037v1
+2009-10-20,Bifurcation and chaos in spin-valve pillars in a periodic applied magnetic field,"We study the bifurcation and chaos scenario of the macro-magnetization vector
+in a homogeneous nanoscale-ferromagnetic thin film of the type used in
+spin-valve pillars. The underlying dynamics is described by a generalized
+Landau-Lifshitz-Gilbert (LLG) equation. The LLG equation has an especially
+appealing form under a complex stereographic projection, wherein the
+qualitative equivalence of an applied field and a spin-current induced torque
+is transparent. Recently chaotic behavior of such a spin vector has been
+identified by Zhang and Li using a spin polarized current passing through the
+pillar of constant polarization direction and periodically varying magnitude,
+owing to the spin-transfer torque effect. In this paper we show that the same
+dynamical behavior can be achieved using a periodically varying applied
+magnetic field, in the presence of a constant DC magnetic field and constant
+spin current, which is technically much more feasible, and demonstrate
+numerically the chaotic dynamics in the system for an infinitely thin film.
+Further, it is noted that in the presence of a nonzero crystal anisotropy field
+chaotic dynamics occurs at much lower magnitudes of the spin-current and DC
+applied field.",0910.3776v1
+2011-03-11,Dynamical constraints from field line topology in magnetic flux tubes,"A topological constraint on the dynamics of a magnetic field in a flux tube
+arises from the fixed point indices of its field line mapping. This can explain
+unexpected behaviour in recent resistive-magnetohydrodynamic simulations of
+magnetic relaxation. Here we present the theory for a general periodic flux
+tube, representing, for example, a toroidal confinement device or a solar
+coronal loop. We show how an ideal dynamics on the side boundary of the tube
+implies that the sum of indices over all interior fixed points is invariant.
+This constraint applies to any continuous evolution inside the tube, which may
+be turbulent and/or dissipative. We also consider the analogous invariants
+obtained from periodic points (fixed points of the iterated mapping). Although
+there is a countably infinite family of invariants, we show that they lead to
+at most two independent dynamical constraints. The second constraint applies
+only in certain magnetic configurations. Several examples illustrate the
+theory.",1103.2284v2
+2011-04-21,Quantitative Aspects of the Dynamical CPA in Harmonic Approximation,"Magnetic and electronic properties of the Hubbard model on the Bethe and fcc
+lattices in infinite dimensions have been investigated numerically on the basis
+of the dynamical coherent potential approximation (CPA) theory combined with
+the harmonic approximation (HA) in order to clarify the quantitative aspects of
+the theory. It is shown that the dynamical CPA+HA reproduces well the
+sublattice magnetization, the magnetizations, susceptibilities, and the N\'eel
+temperatures ($T_{\rm N}$) as well as the Curie temperatures calculated by the
+Quantum Monte-Carlo (QMC) method. The critical Coulomb interactions ($U_{\rm
+c}$) for the metal-insulator (MI) transition are also shown to agree with the
+QMC results above $T_{\rm N}$. Below $T_{\rm N}$, $U_{\rm c}$ deviate from the
+QMC values by about 30% at low temperature regime. These results indicate that
+the dynamical CPA+HA is applicable to the quantitative description of the
+magnetic properties in high dimensional systems, but one needs to take into
+account higher-order dynamical corrections in order to describe the MI
+transition quantitatively at low temperatures.",1104.4250v1
+2013-10-16,Dynamics of skyrmions in chiral magnets: dynamic phase transitions and equation of motion,"We study the dynamics of skyrmions in a metallic chiral magnet. First we show
+that skyrmions can be created dynamically by destabilizing the ferromagnetic
+background state through a spin polarized current. We then treat skyrmions as
+rigid particles and derive the corresponding equation of motion. The dynamics
+of skyrmions is dominated by the Magnus force, which accounts for the weak
+pinning of skyrmions observed in experiments. Finally we discuss the quantum
+motion of skyrmions.",1310.4255v2
+2013-10-28,Interaction-Tuned Dynamical Transitions in a Rashba Spin-Orbit Coupled Fermi Gas,"We consider the time evolution of the magnetization in a Rashba
+spin-orbit-coupled Fermi gas, starting from a fully-polarized initial state. We
+model the dynamics using a Boltzmann equation, which we solve in the
+Hartree-Fock approximation. The resulting non-linear system of equations gives
+rise to three distinct dynamical regimes with qualitatively different
+asymptotic behaviors of the magnetization at long times. The distinct regimes
+and the transitions between them are controlled by the interaction strength:
+for weakly interacting fermions, the magnetization decays to zero. For
+intermediate interactions, it displays undamped oscillations about zero and for
+strong interactions, a partially magnetized state is dynamically stabilized.
+The dynamics we find is a spin analog of interaction induced self-trapping in
+double-well Bose Einstein condensates. The predicted phenomena can be realized
+in trapped Fermi gases with synthetic spin-orbit interactions.",1310.7639v1
+2014-09-10,Flow dynamics and magnetic induction in the von-Karman plasma experiment,"The von-Karman plasma experiment is a novel versatile experimental device
+designed to explore the dynamics of basic magnetic induction processes and the
+dynamics of flows driven in weakly magnetized plasmas. A high-density plasma
+column (10^16 - 10^19 particles.m^-3) is created by two radio-frequency plasma
+sources located at each end of a 1 m long linear device. Flows are driven
+through JxB azimuthal torques created from independently controlled emissive
+cathodes. The device has been designed such that magnetic induction processes
+and turbulent plasma dynamics can be studied from a variety of time-averaged
+axisymmetric flows in a cylinder. MHD simulations implementing
+volume-penalization support the experimental development to design the most
+efficient flow-driving schemes and understand the flow dynamics. Preliminary
+experimental results show that a rotating motion of up to nearly 1 km/s is
+controlled by the JxB azimuthal torque.",1409.3139v1
+2014-11-25,2D Superexchange mediated magnetization dynamics in an optical lattice,"The competition of magnetic exchange interactions and tunneling underlies
+many complex quantum phenomena observed in real materials. We study
+non-equilibrium magnetization dynamics in an extended 2D system by loading
+effective spin-1/2 bosons into a spin-dependent optical lattice, and we use the
+lattice to separately control the resonance conditions for tunneling and
+superexchange. After preparing a non-equilibrium anti-ferromagnetically ordered
+state, we observe relaxation dynamics governed by two well-separated rates,
+which scale with the underlying Hamiltonian parameters associated with
+superexchange and tunneling. Remarkably, with tunneling off-resonantly
+suppressed, we are able to observe superexchange dominated dynamics over two
+orders of magnitude in magnetic coupling strength, despite the presence of
+vacancies. In this regime, the measured timescales are in agreement with simple
+theoretical estimates, but the detailed dynamics of this 2D, strongly
+correlated, and far-from-equilibrium quantum system remain out of reach of
+current computational techniques.",1411.7036v1
+2015-08-04,Evolution and Dynamics of a Solar Active Prominence,"The life of a solar active prominence, one of the most remarkable objects on
+the Sun, is full of dynamics; after first appearing on the Sun the prominence
+continuously evolves with various internal motions and eventually produces a
+global eruption toward the interplane- tary space. Here we report that the
+whole life of an active prominence is successfully re- produced by performing
+as long-term a magnetohydrodynamic simulation of a magnetized prominence plasma
+as was ever done. The simulation reveals underlying dynamic processes that give
+rise to observed properties of an active prominence: invisible subsurface flows
+self- consistently produce the cancellation of magnetic flux observed at the
+photosphere, while observed and somewhat counterintuitive strong upflows are
+driven against gravity by en- hanced gas pressure gradient force along a
+magnetic field line locally standing vertical. The most highlighted dynamic
+event, transition into an eruptive phase, occurs as a natural con- sequence of
+the self-consistent evolution of a prominence plasma interacting with a
+magnetic field, which is obtained by seamlessly reproducing dynamic processes
+involved in the forma- tion and eruption of an active prominence.",1508.00672v1
+2015-12-02,Dynamical Axion Field in a Magnetic Topological Insulator Superlattice,"We propose that the dynamical axion field can be realized in a magnetic
+topological insulator superlattice or a topological paramagnetic insulator. The
+magnetic fluctuations of these systems produce a pseudoscalar field which has
+an axionic coupling to the electromagnetic field, and thus it gives a
+condensed-matter realization of the axion electrodynamics. Compared to the
+previously proposed dynamical axion materials where a long range
+antiferromagnetic order is required, the systems proposed here have the
+advantage that only a uniform magnetization or a paramagnetic state is needed
+for the dynamic axion. We further propose several experiments to detect such a
+dynamical axion field.",1512.00534v1
+2016-03-27,"A Model of Charge Transfer Excitons: Diffusion, Spin Dynamics, and Magnetic Field Effects","In this letter we explore how the microscopic dynamics of charge transfer
+(CT) excitons are influenced by the presence of an external magnetic field in
+disordered molecular semiconductors. This influence is driven by the dynamic
+interplay between the spin and spatial degrees of freedom of the electron-hole
+pair. To account for this interplay we have developed a numerical framework
+that combines a traditional model of quantum spin dynamics with a
+coarse-grained model of stochastic charge transport. This combination provides
+a general and efficient methodology for simulating the effects of magnetic
+field on CT state dynamics, therefore providing a basis for revealing the
+microscopic origin of experimentally observed magnetic field effects. We
+demonstrate that simulations carried out on our model are capable of
+reproducing experimental results as well as generating theoretical predictions
+related to the efficiency of organic electronic materials.",1603.08160v2
+2016-04-15,Direct observation of magnetization dynamics generated by nano-contact spin-torque vortex oscillators,"Time-resolved scanning Kerr microscopy has been used to directly image the
+magnetization dynamics of nano-contact (NC) spin-torque vortex oscillators
+(STVOs) when phase-locked to an injected microwave (RF) current. The Kerr
+images reveal free layer magnetization dynamics that extend outside the NC
+footprint, where they cannot be detected electrically, but which are crucial to
+phase-lock STVOs that share common magnetic layers. For a single NC, dynamics
+were observed not only when the STVO frequency was fully locked to that of the
+RF current, but also for a partially locked state characterized by periodic
+changes in the core trajectory at the RF frequency. For a pair of NCs, images
+reveal the spatial character of dynamics that electrical measurements show to
+have enhanced amplitude and reduced linewidth. Insight gained from these images
+may improve understanding of the conditions required for mutual phase-locking
+of multiple STVOs, and hence enhanced microwave power emission.",1604.04455v1
+2016-06-07,A functional calculus for the magnetization dynamics,"A functional calculus approach is applied to the derivation of evolution
+equations for the moments of the magnetization dynamics of systems subject to
+stochastic fields. It allows us to derive a general framework for obtaining the
+master equation for the stochastic magnetization dynamics, that is applied to
+both, Markovian and non-Markovian dynamics. The formalism is applied for
+studying different kinds of interactions, that are of practical relevance and
+hierarchies of evolution equations for the moments of the distribution of the
+magnetization are obtained. In each case, assumptions are spelled out, in order
+to close the hierarchies. These closure assumptions are tested by extensive
+numerical studies, that probe the validity of Gaussian or non--Gaussian closure
+Ans\""atze.",1606.02137v1
+2017-03-28,Coarsening dynamics of an isotropic ferromagnetic superfluid,"In zero magnetic field the ground state manifold of a ferromagnetic spin-1
+condensate is SO(3) and exhibits $\mathbb{Z}_2$ vortices as topological
+defects. We investigate the phase ordering dynamics of this system after being
+quenched into this ferromagnetic phase from a zero temperature unmagnetized
+phase. Following the quench, we observe the ordering of both magnetic and gauge
+domains. We find that these domains grow diffusively, i.e. with domain size
+$L(t)\sim t^{1/2}$, and exhibit dynamic scale invariance. The coarsening
+dynamics progresses as $\mathbb{Z}_2$ vortices annihilate, however we find that
+at finite energy a number of these vortices persist in small clumps without
+influencing magnetic or gauge order. We consider the influence of a small
+non-zero magnetic field, which reduces the ground state symmetry, and show that
+this sets a critical length scale such that when the domains reach this size
+the system dynamically transitions in order parameter and scaling behaviour
+from an isotropic to an anisotropic ferromagnetic superfluid.",1703.09360v2
+2018-01-29,Recurrence based quantification of dynamical complexity in the Earth's magnetosphere at geospace storm timescales,"Magnetic storms are the most prominent global manifestations of
+out-of-equilibrium magnetospheric dynamics. Investigating the dynamical
+complexity exhibited by geomagnetic observables can provide valuable insights
+into relevant physical processes as well as temporal scales associated with
+this phenomenon. In this work, we utilize several innovative data analysis
+techniques enabling a quantitative nonlinear analysis of the nonstationary
+behavior of the disturbance storm time (Dst) index together with some of the
+main drivers of its temporal variability, the $VB_{South}$ electric field
+component, the vertical component of the interplanetary magnetic field, $B_z$,
+and the dynamic pressure of the solar wind, $P_{dyn}$. Using recurrence
+quantification analysis (RQA) and recurrence network analysis (RNA), we obtain
+several complementary complexity measures that serve as markers of different
+physical processes underlying quiet and storm time magnetospheric dynamics.
+Specifically, our approach discriminates the magnetospheric activity in
+response to external (solar wind) forcing from primarily internal variability
+and provides a physically meaningful classification of magnetic storm periods
+based on observations made at the Earth's surface. In this regard, the proposed
+methodology could provide a relevant step towards future improved space weather
+and magnetic storm forecasts.",1801.09412v1
+2018-07-09,Dynamic phase transition properties of kinetic Ising model in the presence of additive white noise,"Using Monte Carlo simulations based on the Metropolis algorithm, we
+investigate the dynamic phase transition properties of kinetic Ising model
+driven by a sinusoidally oscillating magnetic field in the presence of additive
+white noise. We calculate equilibrium and dynamic properties such as the
+temperature dependence of average magnetization and magnetic specific heat, as
+well as the period dependence of dynamic order parameter and scaled variance.
+After determining the critical period at which order-disorder transition takes
+place, we perform finite size scaling analysis to extract the exponent ratios,
+and discuss the variation of these properties in the presence of noisy magnetic
+field. As a general result, we show that for a noisy system, DPT does not fall
+into a universality class of the conventional dynamic (and also equilibrium)
+universality class of the Ising model.",1807.03077v1
+2021-07-17,Magnetization switching in the inertial regime,"We have numerically solved the Landau-Lifshitz-Gilbert (LLG) equation in its
+standard and inertial forms to study the magnetization switching dynamics in a
+$3d$ thin film ferromagnet. The dynamics is triggered by ultrashort magnetic
+field pulses of varying width and amplitude in the picosecond and Tesla range.
+We have compared the solutions of the two equations in terms of switching
+characteristic, speed and energy analysis. Both equations return qualitatively
+similar switching dynamics, characterized by regions of slower precessional
+behavior and faster ballistic motion. In case of inertial dynamics, ballistic
+switching is found in a 25 % wider region in the parameter space given by the
+magnetic field amplitude and width. The energy analysis of the dynamics is
+qualitatively different for the standard and inertial LLG equations. In the
+latter case, an extra energy channel, interpreted as the kinetic energy of the
+system, is available. Such extra channel is responsible for a resonant energy
+absorption at THz frequencies, consistent with the occurence of spin nutation.",2107.08234v1
+2022-04-06,Multiparticle Collision Dynamics for Ferrofluids,"Detailed studies of the intriguing field-dependent dynamics and transport
+properties of confined flowing ferrofluids require efficient mesoscopic
+simulation methods that account for fluctuating ferrohydrodynamics. Here, we
+propose such a new mesoscopic model for the dynamics and flow of ferrofluids,
+where we couple the multi-particle collision dynamics method as a solver for
+the fluctuating hydrodynamics equations to the stochastic magnetization
+dynamics of suspended magnetic nanoparticles. This hybrid model is validated by
+reproducing the magnetoviscous effect in Poiseuille flow, obtaining the
+rotational viscosity in quantitative agreement with theoretical predictions. We
+also illustrate the new method for the benchmark problem of flow around a
+square cylinder. Interestingly, we observe that the length of the recirculation
+region is increased whereas the drag coefficient is decreased in ferrofluids
+when an external magnetic field is applied, compared with the field-free case
+at the same effective Reynolds number. The presence of thermal fluctuations and
+the flexibility of this particle-based mesoscopic method provides a promising
+tool to investigate a broad range of flow phenomena of magnetic fluids and
+could also serve as an efficient way to simulate solvent effects when colloidal
+particles are immersed in ferrofluids.",2204.03060v1
+2022-06-29,Strongly enhanced dynamics of a charged Rouse dimer by an external magnetic field,"While the dynamics of dimers and polymer chains in a viscous solvent is well
+understood within the celebrated Rouse model, the effect of an external
+magnetic field on the dynamics of a charged chain is much less understood. Here
+we generalize the Rouse model for a charged dimer to include the effect of an
+external magnetic field. Our analytically solvable model allows a fundamental
+insight into the magneto-generated dynamics of the dimer in the overdamped
+limit as induced by the Lorentz-force. Surprisingly, for a dimer of oppositely
+charged particles, we find an enormous enhancement of the dynamics of the dimer
+center which exhibits even a transient superballistic behavior. This is highly
+unusual in an overdamped system for there is neither inertia nor any internal
+or external driving. We attribute this to a significant translation and
+rotation coupling due to the Lorentz force. We also find that magnetic field
+reduces the mobility of a dimer along its orientation and its effective
+rotational diffusion coefficient. In principle, our predictions can be tested
+by experiments with colloidal particles and complex plasmas.",2206.14883v1
+2022-09-30,Nonlinear dynamics and bifurcations of a planar undulating magnetic microswimmer,"Swimming micro-organisms such as flagellated bacteria and sperm cells have
+fascinating locomotion capabilities. Inspired by their natural motion, there is
+an ongoing effort to develop artificial robotic nano-swimmers for potential
+in-body biomedical applications. A leading method for actuation of
+nano-swimmers is by applying a time-varying external magnetic field. Such
+systems have rich and nonlinear dynamics that calls for simple fundamental
+models. A previous work studied forward motion of a simple two-link model with
+passive elastic joint, assuming small-amplitude planar oscillations of the
+magnetic field about a constant direction. In this work, we found that there
+exists a faster, backward motion of the swimmer with very rich dynamics. By
+relaxing the small-amplitude assumption, we analyze the multiplicity of
+periodic solutions, as well as their bifurcations, symmetry breaking, and
+stability transitions. We have also found that the net displacement and/or mean
+swimming speed are maximized for optimal choices of various parameters.
+Asymptotic calculations are performed for the bifurcation condition and the
+swimmer's mean speed. The results may enable significantly improving the design
+aspects of magnetically-actuated robotic microswimmer.",2209.15299v3
+2022-10-27,Electron-phonon mediated spin-flip as driving mechanism for ultrafast magnetization dynamics in 3$d$ ferromagnets,"Despite intense experimental effort, theoretical proposals and modeling
+approaches, a lack of consensus exists about the intrinsic mechanisms driving
+ultrafast magnetization dynamics in 3$d$ ferromagnets. In this work, we find
+evidence of electron-phonon mediated spin-flip as the driving mechanism for the
+ultrafast magnetization dynamics in all three 3$d$ ferromagnets; nickel, iron
+and cobalt. We use a microscopic three temperature model with parameters
+calculated from first-principles, which has been validated by direct comparison
+to the electron and lattice dynamics extracted from previous experiments. By
+direct comparison to the experimentally measured magnetization dynamics for
+different laser fluence, we determine the spin-flip probability of each
+material. In contrast to previous findings but in agreement to ab-initio
+predictions, we find that relatively small values of the spin-flip probability
+enable ultrafast demagnetization in all three 3$d$ ferromagnets.",2210.15269v1
+2024-03-05,Canonical Hamiltonian Guiding Center Dynamics and Its Intrinsic Magnetic Moment,"The concept of guiding center is potent in astrophysics, space plasmas,
+fusion researches, and arc plasmas to solve the multi-scale dynamics of
+magnetized plasmas. In this letter, we rigorously prove that the guiding center
+dynamics can generally be described as a constrained canonical Hamiltonian
+system with two constraints in six dimensional phase space, and that the
+solution flow of the guiding center lies on a canonical symplectic
+sub-manifold. The guiding center can thus be modeled as a pseudo-particle with
+an intrinsic magnetic moment, which properly replaces the charged particle
+dynamics on time scales larger than the gyro-period. The complete dynamical
+behaviors, such as the velocity and force, of the guiding center
+pseudo-particle can be clearly deduced from the model. Furthermore, a series of
+related theories, such as symplectic numerical methods, the canonical
+gyro-kinetic theory, and canonical particle-in-cell algorithms can be
+systematically developed based on the canonical guiding center system. The
+canonical guiding center theory also provides an enlightenment for the origin
+of the intrinsic magnetic moment.",2403.02883v1
+2017-07-14,Nonequilibrium phase transition in spin-S Ising ferromagnet driven by Propagating and Standing magnetic field wave,"The dynamical response of spin-S (S=1, 3/2, 2, 3) Ising ferromagnet to the
+plane propagating wave , standing magnetic field wave and uniformly oscillating
+field with constant frequency are studied separately in two dimensions by
+extensive Monte Carlo simulation. Depending upon the strength of the magnetic
+field and the value of the spin state of the Ising spin lattice two different
+dynamical phases are observed. For a fixed value of S and the amplitude of the
+propagating magnetic field wave the system undergoes a dynamical phase
+transition from propagating phase to pinned phase as the temperature of the
+system is cooled down. Similarly in case with standing magnetic wave the system
+undergoes dynamical phase transition from high temperature phase where spins
+oscillates coherently in alternate bands of half wavelength of the standing
+magnetic wave to the low temperature pinned or spin frozen phase. For a fixed
+value of the amplitude of magnetic field oscillation the transition temperature
+is observed to decrease to a limiting value as the value of spin S is
+increased. The time averaged magnetisation over a full cycle of the magnetic
+field oscillation plays the role of the dynamic order parameter. A
+comprehensive phase boundary is drawn in the plane of magnetic field amplitude
+and dynamic transition temperature. It is found that the phase boundary shrinks
+inwards for high value of spin state S. Also in the low temperature (and high
+field) region the phase boundaries are closely spaced.",1707.04404v4
+2007-05-03,"On the Dynamical Ferromagnetic, Quantum Hall, and Relativistic Effects on the Carbon Nanotubes Nucleation and Growth Mechanism","The mechanism of carbon nanotube (CNT) nucleation and growth has been a
+mystery for over 15 years. Prior models have attempted the extension of older
+classical transport mechanisms. In July 2000, a more detailed and accurate
+nonclassical, relativistic mechanism was formulated considering the detailed
+dynamics of the electronics of spin and orbital rehybridization between the
+carbon and catalyst via novel mesoscopic phenomena and quantum dynamics.
+Ferromagnetic carbon was demonstrated. Here, quantum (Hall) effects and
+relativistic effects of intense many body spin-orbital interactions for novel
+orbital rehybridization dynamics (Little Effect) are proposed in this new
+dynamical magnetic mechanism. This dynamic ferromagnetic mechanism is proven by
+imposing dynamic and static magnetic fields during CNT syntheses and observing
+the different influence of these external magnetic environments on the
+catalyzing spin currents and spin waves and the resulting CNT formation.",0705.0407v1
+2008-12-03,Field theory of bicritical and tetracritical points. III. Relaxational dynamics including conservation of magnetization (Model C),"We calculate the relaxational dynamical critical behavior of systems of
+$O(n_\|)\oplus O(n_\perp)$ symmetry including conservation of magnetization by
+renormalization group (RG) theory within the minimal subtraction scheme in two
+loop order. Within the stability region of the Heisenberg fixed point and the
+biconical fixed point strong dynamical scaling holds with the asymptotic
+dynamical critical exponent $z=2\phi/\nu-1$ where $\phi$ is the crossover
+exponent and $\nu$ the exponent of the correlation length. The critical
+dynamics at $n_\|=1$ and $n_\perp=2$ is governed by a small dynamical transient
+exponent leading to nonuniversal nonasymptotic dynamical behavior. This may be
+seen e.g. in the temperature dependence of the magnetic transport coefficients.",0812.0675v1
+2011-05-21,Magnetic and electric contributions to the energy loss in a dynamical QCD medium,"The computation of radiative energy loss in a finite size QCD medium with
+dynamical constituents is a key ingredient for obtaining reliable predictions
+for jet quenching in ultra-relativistic heavy ion collisions. It was previously
+shown that energy loss in dynamical QCD medium is significantly higher compared
+to static QCD medium. To understand this difference, we here analyze magnetic
+and electric contributions to energy loss in dynamical QCD medium. We find that
+the significantly higher energy loss in the dynamical case is entirely due to
+appearance of magnetic contribution in the dynamical medium. While for
+asymptotically high energies, the energy loss in static and dynamical medium
+approach the same value, we find that the physical origin of the energy loss in
+these two cases is different.",1105.4288v1
+2022-01-22,Dynamics of a Charged Thomas Oscillator in an External Magnetic Field,"In this letter, we provide a detailed numerical examination of the dynamics
+of a charged Thomas oscillator in an external magnetic field. We do so by
+adopting and then modifying the cyclically symmetric Thomas oscillator to study
+the dynamics of a charged particle in an external magnetic field. These
+dynamical behaviours for weak and strong field strength parameters fall under
+two categories; conservative and dissipative. The system shows a complex
+quasi-periodic attractor whose topology depends on initial conditions for high
+field strengths in the conservative regime. There is a transition from
+adiabatic motion to chaos on decreasing the field strength parameter. In the
+dissipative regime, the system is chaotic for weak field strength and weak
+damping but shows a limit cycle for high field strengths. Such behaviour is due
+to an additional negative feedback loop that comes into action at high field
+strengths and forces the system dynamics to be stable in periodic oscillations.
+For weak damping and weak field strength, the system dynamics mimic Brownian
+motion via chaotic walks.",2202.02383v2
+2022-07-21,Probing dynamics of a two-dimensional dipolar spin ensemble using single qubit sensor,"Understanding the thermalization dynamics of quantum many-body systems at the
+microscopic level is among the central challenges of modern statistical
+physics. Here we experimentally investigate individual spin dynamics in a
+two-dimensional ensemble of electron spins on the surface of a diamond crystal.
+We use a near-surface NV center as a nanoscale magnetic sensor to probe
+correlation dynamics of individual spins in a dipolar interacting surface spin
+ensemble. We observe that the relaxation rate for each spin is significantly
+slower than the naive expectation based on independently estimated dipolar
+interaction strengths with nearest neighbors and is strongly correlated with
+the timescale of the local magnetic field fluctuation. We show that this
+anomalously slow relaxation rate is due to the presence of strong dynamical
+disorder and present a quantitative explanation based on dynamic resonance
+counting. Finally, we use resonant spin-lock driving to control the effective
+strength of the local magnetic fields and reveal the role of the dynamical
+disorder in different regimes. Our work paves the way towards microscopic study
+and control of quantum thermalization in strongly interacting disordered spin
+ensembles.",2207.10688v2
+2023-06-23,Input-driven chaotic dynamics in vortex spin-torque oscillator,"A new research topic in spintronics relating to the operation principles of
+brain-inspired computing is input-driven magnetization dynamics in nanomagnet.
+In this paper, the magnetization dynamics in a vortex spin-torque oscillator
+(STO) driven by a series of random magnetic field are studied through a
+numerical simulation of the Thiele equation. It is found that input-driven
+synchronization occurs in the weak perturbation limit, as found recently. As
+well, chaotic behavior is newly found to occur in the vortex core dynamics for
+a wide range of parameters, where synchronized behavior is disrupted by an
+intermittency. Ordered and chaotic dynamical phases are examined by evaluating
+the Lyapunov exponent. The relation between the dynamical phase and the
+computational capability of physical reservoir computing is also studied.",2306.13278v1
+1999-09-09,Micromagnetic simulations of thermally activated magnetization reversal of nanoscale magnets,"Numerical integration of a stochastic Landau-Lifshitz-Gilbert equation is
+used to study dynamic processes in single-domain nanoscale magnets at nonzero
+temperatures. Special attention is given to including thermal fluctuations as a
+Langevin term, and the Fast Multipole Method is used to calculate dipole-dipole
+interactions. It is feasible to simulate these dynamics on the nanosecond time
+scale for spatial discretizations that involve on the order of 10000 nodes
+using a desktop workstation. The nanoscale magnets considered here are single
+pillars with large aspect ratio. Hysteresis-loop simulations are employed to
+study the stable and metastable configurations of the magnetization. Each
+pillar has magnetic end caps. In a time-dependent field the magnetization of
+the pillars is observed to reverse via nucleation, propagation, and coalescence
+of the end caps. In particular, the end caps propagate into the magnet and meet
+near the middle. A relatively long-lived defect is formed when end caps with
+opposite vorticity meet. Fluctuations are more important in the reversal of the
+magnetization for fields weaker than the zero-temperature coercive field, where
+the reversal is thermally activated. In this case, the process must be
+described by its statistical properties, such as the distribution of switching
+times, averaged over a large number of independent thermal histories.",9909136v2
+2005-09-10,Magnetic dipolar ordering and relaxation in the high-spin molecular cluster compound Mn6,"Few examples of magnetic systems displaying a transition to pure dipolar
+magnetic order are known to date, and single-molecule magnets can provide an
+interesting example. The molecular cluster spins and thus their dipolar
+interaction energy can be quite high, leading to reasonably accessible ordering
+temperatures, provided the crystal field anisotropy is sufficiently small. This
+condition can be met for molecular clusters of sufficiently high symmetry, as
+for the Mn6 compound studied here. Magnetic specific heat and susceptibility
+experiments show a transition to ferromagnetic dipolar order at T_{c} = 0.16 K.
+Classical Monte-Carlo calculations indeed predict ferromagnetic ordering and
+account for the correct value of T_{c}. In high magnetic fields we detected the
+contribution of the ^{55}Mn nuclei to the specific heat, and the characteristic
+timescale of nuclear relaxation. This was compared with results obtained
+directly from pulse-NMR experiments. The data are in good mutual agreement and
+can be well described by the theory for magnetic relaxation in highly polarized
+paramagnetic crystals and for dynamic nuclear polarization, which we
+extensively review. The experiments provide an interesting comparison with the
+recently investigated nuclear spin dynamics in the anisotropic single molecule
+magnet Mn12-ac.",0509261v2
+2012-04-23,Dynamical mean-field theory of indirect magnetic exchange,"To analyze the physical properties arising from indirect magnetic exchange
+between several magnetic adatoms and between complex magnetic nanostructures on
+metallic surfaces, the real-space extension of dynamical mean-field theory
+(R-DMFT) appears attractive as it can be applied to systems of almost arbitrary
+geometry and complexity. While R-DMFT describes the Kondo effect of a single
+adatom exactly, indirect magnetic (RKKY) exchange is taken into account on an
+approximate level only. Here, we consider a simplified model system consisting
+of two magnetic Hubbard sites (""adatoms"") hybridizing with a non-interacting
+tight-binding chain (""substrate surface""). This two-impurity Anderson model
+incorporates the competition between the Kondo effect and indirect exchange but
+is amenable to an exact numerical solution via the density-matrix
+renormalization group (DMRG). The particle-hole symmetric model at half-filling
+and zero temperature is used to benchmark R-DMFT results for the magnetic
+coupling between the two adatoms and for the magnetic properties induced in the
+substrate. In particular, the dependence of the local adatom and the nonlocal
+adatom-adatom static susceptibilities as well as the magnetic response of the
+substrate on the distance between the adatoms and on the strength of their
+coupling with the substrate is studied. We find both, excellent agreement with
+the DMRG data even on subtle details of the competition between RKKY exchange
+and the Kondo effect but also complete failure of the R-DMFT, depending on the
+parameter regime considered. R-DMFT calculations are performed using the
+Lanczos method as impurity solver. With the real-space extension of the
+two-site DMFT, we also benchmark a simplified R-DMFT variant.",1204.5111v2
+2012-12-06,Simulations of magnetic fields in isolated disk galaxies,"Magnetic fields are known to be dynamically important in the interstellar
+medium of our own Galaxy, and they are ubiquitously observed in diffuse gas in
+the halos of galaxies and galaxy clusters. Yet, magnetic fields have typically
+been neglected in studies of the formation of galaxies, leaving their global
+influence on galaxy formation largely unclear. We extend our MHD implementation
+in the moving-mesh code Arepo to cosmological problems which include radiative
+cooling and the formation of stars. In particular, we replace our previously
+employed divergence cleaning approach with a Powell 8-wave scheme, which turns
+out to be significantly more stable, even in very dynamic environments. We
+verify the improved accuracy through simulations of the MRI in accretion disks,
+that reproduce its correct linear growth rate. Using this new MHD code, we
+simulate the formation of isolated disk galaxies similar to the Milky Way using
+idealized initial conditions with and without magnetic fields. We find that the
+magnetic field is quickly amplified in the initial starburst and the
+differential rotation of the forming disk until it eventually saturates when it
+becomes comparable to the thermal pressure. The additional pressure component
+leads to a lower star formation rate at late times compared to simulations
+without magnetic fields, and induces changes in the spiral arm structures of
+the gas disk. In addition, we observe highly magnetized fountain-like outflows
+from the disk. These results are robust with numerical resolution and are
+largely independent of the initial magnetic seed field assumed in the initial
+conditions, as the amplification process is rapid and self-regulated. Our
+findings suggest an important influence of magnetic fields on galaxy formation
+and evolution, cautioning against their neglect in theoretical models of
+structure formation.",1212.1452v1
+2013-01-04,Dynamics of the Transition corona,"Magnetic reconnection between open and closed magnetic field in the corona is
+believed to play a crucial role in the corona/heliosphere coupling. At large
+scale, the exchange of open/closed connectivity is expected to occur in
+pseudo-streamer structures. However, there is neither clear observational
+evidence of how such coupling occurs in pseudo-streamers, nor evidence for how
+the magnetic reconnection evolves. Using a newly-developed technique, we
+enhance the off-limb magnetic fine structures observed with AIA and identify a
+pseudo-streamer-like feature located close to the northern coronal hole. After
+extrapolating the magnetic field with the PFSS model, we obtain a
+pseudo-streamer magnetic topology, null-point related topology bounded by open
+field. We compare the magnetic configuration with the UV observations and
+identify the magnetic structures expected to be involved in the event. Using an
+3D MHD simulation of interchange reconnection, we showed that the evolution of
+the UV structures follows the magnetic field dynamics and the UV emitting
+structures have a pattern very similar to the plasma emission derived from the
+simulation. Our results highlight that the exchange between open and closed in
+the pseudo-streamer topology related to an observed event occurs at least
+partially at the null-point, similarly to the interchange reconnection in a
+single null-point topology. However, our results also indicate that the
+interchange reconnection in pseudo-streamers is a gradual physical process
+which opposes to the impulsive reconnection of the solar-jet model.",1301.0740v2
+2013-01-28,Magnetization dynamics in Co2$MnGe/Al2$O3$/Co tunnel junctions grown on different substrates,"We study static and dynamic magnetic properties of Co2MnGe (13 nm)/Al2O3 (3
+nm)/Co (13 nm) tunnel magnetic junctions (TMJ), deposited on various single
+crystalline substrates (a-plane sapphire, MgO(100), Si(111)). The results are
+compared to the magnetic properties of Co and of Co$_{2}$MnGe single films
+lying on sapphire substrates. X-rays diffraction always shows a (110)
+orientation of the Co$_{2}$MnGe films. Structural observations obtained by high
+resolution transmission electron microscopy confirmed the high quality of the
+TMJ grown on sapphire. Our vibrating sample magnetometry measurements reveal
+in-plane anisotropy only in samples grown on a sapphire substrate. Depending on
+the substrate, the ferromagnetic resonance spectra of the TMJs, studied by the
+microstrip technique, show one or two pseudo-uniform modes. In the case of MgO
+and of Si substrates only one mode is observed: it is described by magnetic
+parameters (g-factor, effective magnetization, in-plane magnetic anisotropy)
+derived in the frame of a simple expression of the magnetic energy density;
+these parameters are practically identical to those obtained for the Co single
+film. With a sapphire substrate two modes are present: one of them does not
+appreciably differ from the observed mode in the Co single film while the other
+one is similar to the mode appearing in the Co$_{2}$MnGe single film: their
+magnetic parameters can thus be determined independently, using a classical
+model for the energy density in the absence of interlayer exchange coupling.",1301.6563v1
+2013-11-14,New look at the QCD ground state in a magnetic field,"We explore chiral symmetry breaking in a magnetic field within a
+Nambu-Jona-Lasinio model of interacting massless quarks including tensor
+channels. We show that the new interaction channels open up via Fierz
+identities due to the explicit breaking of the rotational symmetry by the
+magnetic field. We demonstrate that the magnetic catalysis of chiral symmetry
+breaking leads to the generation of two independent condensates, the
+conventional chiral condensate and a spin-one condensate. While the chiral
+condensate generates a dynamical fermion mass, the new condensate gives rise to
+a dynamical anomalous magnetic moment for the fermions. As a consequence, the
+spectrum of the excitations in all Landau levels, except the lowest one,
+exhibits Zeeman splitting. Since the pair, formed by a quark and an antiquark
+with opposite spins, possesses a resultant magnetic moment, an external
+magnetic field can align it giving rise to a net magnetic moment for the ground
+state. This is the physical interpretation of the spin-one condensate. Our
+results show that the magnetically catalyzed ground state in QCD is actually
+richer than previously thought. The two condensates contribute to the effective
+mass of the LLL quasiparticles in such a way that the critical temperature for
+chiral symmetry restoration becomes enhanced.",1311.3400v3
+2015-06-22,The Intrinsic Magnetization of Antiferromagnetic Textures,"Antiferromagnets (AFMs) exhibit intrinsic magnetization when the order
+parameter spatially varies. This intrinsic spin is present even at equilibrium
+and can be interpreted as a twisting of the homogeneous AFM into a state with a
+finite spin. Because magnetic moments couple directly to external magnetic
+fields, the intrinsic magnetization can alter the dynamics of antiferromagnetic
+textures under such influence. Starting from the discrete Heisenberg model, we
+derive the continuum limit of the free energy of AFMs in the exchange
+approximation and explicitly rederive that the spatial variation of the
+antiferromagnetic order parameter is associated with an intrinsic magnetization
+density. We calculate the magnetization profile of a domain wall and discuss
+how the intrinsic magnetization reacts to external forces. We show
+conclusively, both analytically and numerically, that a spatially inhomogeneous
+magnetic field can move and control the position of domain walls in AFMs. By
+comparing our model to a commonly used alternative parametrization procedure
+for the continuum fields, we show that the physical interpretations of these
+fields depend critically on the choice of parametrization procedure for the
+discrete-to-continuous transition. This can explain why a significant amount of
+recent studies of the dynamics of AFMs, including effective models that
+describe the motion of antiferromagnetic domain walls, have neglected the
+intrinsic spin of the textured order parameter.",1506.06561v2
+2015-10-15,Rashba Torque Driven Domain Wall Motion in Magnetic Helices,"Manipulation of the domain wall propagation in magnetic wires is a key
+practical task for a number of devices including racetrack memory and magnetic
+logic. Recently, curvilinear effects emerged as an efficient mean to impact
+substantially the statics and dynamics of magnetic textures. Here, we
+demonstrate that the curvilinear form of the exchange interaction of a magnetic
+helix results in an effective anisotropy term and Dzyaloshinskii--Moriya
+interaction with a complete set of Lifshitz invariants for a one-dimensional
+system. In contrast to their planar counterparts, the geometrically induced
+modifications of the static magnetic texture of the domain walls in magnetic
+helices offer unconventional means to control the wall dynamics relying on
+spin-orbit Rashba torque. The chiral symmetry breaking due to the
+Dzyaloshinskii-Moriya interaction leads to the opposite directions of the
+domain wall motion in left- or right-handed helices. Furthermore, for the
+magnetic helices, the emergent effective anisotropy term and
+Dzyaloshinskii-Moriya interaction can be attributed to the clear geometrical
+parameters like curvature and torsion offering intuitive understanding of the
+complex curvilinear effects in magnetism.",1510.04725v2
+2016-04-15,"Relationships between fluid vorticity, kinetic helicity and magnetic field at the small-scale (quiet-network) on the Sun","We derive horizontal fluid motions on the solar surface over large areas
+covering the quiet-Sun magnetic network from local correlation tracking of
+convective granules imaged in continuum intensity and Doppler velocity by the
+Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory
+(SDO). From these we calculate horizontal divergence, vertical component of
+vorticity, and kinetic helicity of fluid motions. We study the correlations
+between fluid divergence and vorticity, and that between vorticity (kinetic
+helicity) and magnetic field. We find that the vorticity (kinetic helicity)
+around small-scale fields exhibits a hemispherical pattern (in sign) similar to
+that followed by the magnetic helicity of large-scale active regions
+(containing sunspots). We identify this pattern to be a result of the Coriolis
+force acting on supergranular-scale flows (both the outflows and inflows), and
+is consistent with earlier studies using local helioseismology. Further, we
+show that the magnetic fields cause transfer of vorticity from supergranular
+inflow regions to outflow regions, and that they tend to suppress the vortical
+motions around them when magnetic flux densities exceed about 300 G (HMI). We
+also show that such action of magnetic fields leads to marked changes in the
+correlations between fluid divergence and vorticity. These results are
+speculated to be of importance to local dynamo action if present, and to the
+dynamical evolution of magnetic helicity at the small-scale.",1604.04439v1
+2016-09-11,Strongly coupled non-Abelian plasmas in a magnetic field,"In this dissertation we use the gauge/gravity duality approach to study the
+dynamics of strongly coupled non-Abelian plasmas. Ultimately, we want to
+understand the properties of the quark-gluon plasma (QGP), whose scientifc
+interest by the scientific community escalated exponentially after its
+discovery in the 2000's through the collision of ultrarelativistic heavy ions.
+  One can enrich the dynamics of the QGP by adding an external field, such as
+the baryon chemical potential (needed to study the QCD phase diagram), or a
+magnetic field. In this dissertation, we choose to investigate the magnetic
+effects. Indeed, there are compelling evidences that strong magnetic fields of
+the order $eB\sim 10 m_\pi^2$ are created in the early stages of
+ultrarelativistic heavy ion collisions.
+  The chosen observable to scan possible effects of the magnetic field on the
+QGP was the viscosity, due to the famous result $\eta/s=1/4\pi$ obtained via
+holography. In a first approach we use a caricature of the QGP, the
+$\mathcal{N}=4$ super Yang-Mills plasma to calculate the deviations of the
+viscosity as we add a magnetic field. We must emphasize, though, that a
+magnetized plasma has a priori seven viscosity coefficients (five shears and
+two bulks). In addition, we also study in this same model the anisotropic heavy
+quark-antiquark potential in the presence of a magnetic field.
+  In the end, we propose a phenomenological holographic QCD-like model, which
+is built upon the lattice QCD data, to study the thermodynamics and the
+viscosity of the QGP with an external strong magnetic field.",1609.03104v1
+2016-09-21,"Magnetic Susceptibility of Dirac Fermions, Bi-Sb Alloys, Interacting Bloch Fermions, Dilute Nonmagnetic Alloys, and Kondo Alloys","Wide ranging interest in Dirac Hamiltomian is due to the emergence of novel
+materials, namely, graphene, topological insulators and superconductors, the
+newly-discovered Weyl semimetals, and still actively-sought after Majorana
+fermions in real materials. We give a brief review of the relativistic Dirac
+quantum mechanics and its impact in the developments of modern physics. The
+quantum band dynamics of Dirac Hamiltonian is crucial in resolving the giant
+diamagnetism of bismuth and Bi-Sb alloys. Quantitative agreement of the theory
+with the experiments on Bi-Sb alloys has been achieved, and physically
+meaningful contributions to the diamagnetism has been identified. We also treat
+relativistic Dirac fermion as an interband dynamics in uniform magnetic fields.
+For the interacting Bloch electrons, the role of translation symmetry for
+calculating the magnetic susceptibility avoids any approximation to second
+order in the field. The magnetic susceptibility of Hubbard model and those of
+Fermi liquids are readily obtained as limiting cases. The expressions for
+magnetic susceptibility of dilute nonmagnetic alloys give a firm theoretical
+foundation of the empirical formulas used in fitting experimental results. For
+completeness, the magnetic susceptibility of dilute magnetic or Kondo alloys is
+also given for high and low temperature regimes.",1609.06419v1
+2016-10-26,On the nature of the magnetic Rayleigh-Taylor instability in Astrophysical Plasma: The case of uniform magnetic field strength,"The magnetic Rayleigh-Taylor instability has been shown to play a key role in
+many astrophysical systems. The equation for the growth rate of this
+instability in the incompressible limit, and the most-unstable mode that can be
+derived from it, are often used to estimate the strength of the magnetic field
+that is associated with the observed dynamics. However, there are some issues
+with the interpretations given. Here we show that the class of most unstable
+modes $k_u$ for a given $\theta$, the class of modes often used to estimate the
+strength of the magnetic field from observations, for the system leads to the
+instability growing as $\sigma^2=1/2 A g k_u$, a growth rate which is
+independent of the strength of the magnetic field and which highlights that
+small scales are preferred by the system, but not does not give the fastest
+growing mode for that given $k$. We also highlight that outside of the
+interchange ($\mathbf{k}\cdot\mathbf{B}=0$) and undular ($\mathbf{k}$ parallel
+to $\mathbf{B}$) modes, all the other modes have a perturbation pair of the
+same wavenumber and growth rate that when excited in the linear regime can
+result in an interference pattern that gives field aligned filamentary
+structure often seen in 3D simulations. The analysis was extended to a sheared
+magnetic field, where it was found that it was possible to extend the results
+for a non-sheared field to this case. We suggest that without magnetic shear it
+is too simplistic to be used to infer magnetic field strengths in astrophysical
+systems.",1610.08317v1
+2017-03-22,Magnetic field effects on dynamics of the ethylammonium nitrate ionic liquid confined between polar glass plates,"Self-diffusion and NMR relaxation of ethylammonium (EA) cations were studied
+in the protic ionic liquid ethylammonium nitrate (EAN) confined between
+parallel polar glass plates separated by a few um as a function of time after
+placement in a magnetic field of 9.40 T. Immediately after sample placement,
+the diffusion coefficient of EA (D) increased by a factor of 2, while the
+transverse NMR relaxation of NH3 protons decreased by factors of up to 22 in
+comparison with bulk EAN, according to previously published data. Further
+exposure to the magnetic field leads to gradual changes of D, T1 and T2 with a
+time constant of 70 min and a total equilibration time of longer than 4 hours.
+This process does not depend on the orientation of the glass plates relative to
+the magnetic field. Removing the sample from the magnetic field and repeating
+the experiment demonstrated that complete recovery of the sample to the
+accelerated D and shortened T2 occurs in approximately 24 hours. Thus, EA
+cation dynamics is accelerated relative to bulk when the cation is confined
+between polar glass plates and stored in the absence of a strong magnetic
+field, but demonstrate a trend to change to bulk values of D and T2 after
+exposure to a magnetic field. Because the observed characteristic times of the
+change far exceed molecular process times in EAN, we relate this phenomenon to
+reversible phase transformations occurring with EAN between polar plates
+outside the strong magnetic field, and reverse change of the phases after
+placing the sample in the magnetic field. This conclusion was confirmed by data
+of Raman spectroscopy.",1703.07648v1
+2017-03-30,A novel energy-based phase field model for ferrodroplet deformation and breakup in a uniform magnetic field,"In this paper, we propose a novel, thermodynamically consistent phase field
+model to simulate the deformation and breakup of a ferrodroplet that is
+immersed in a viscous medium and subject to an applied uniform magnetic field.
+Instead of using the magnetic body force in the traditional Rosensweig model,
+the key idea of this model is to propose a new magnetic energy that enables
+direct effects of the magnetic field on the interface evolution. The model can
+thereby be derived from the variational principle via minimizing the free
+energy of the total system. This energy based modeling idea can be easily
+extended to include more external fields in a convenient and consistent way for
+more complicated applications involving multiple external fields. We validate
+the model by performing a series of numerical simulations, including the
+comparison with analytic solutions, the investigation of the effect of
+different types of magnetic fields, the dynamical behaviors of the ferrodroplet
+breakup under the strong magnetic field, magnetic/velocity/pressure field
+distributions, the magnetic energy density, and the inertial phenomenon, etc.",1704.00645v2
+2017-07-27,Common Glass-Forming Spin-Liquid State in the Pyrochlore Magnets Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$,"Despite a well-ordered pyrochlore crystal structure and strong magnetic
+interactions between the Dy$^{3+}$ or Ho$^{3+}$ ions, no long range magnetic
+order has been detected in the pyrochlore titanates Ho$_2$Ti$_2$O$_7$ and
+Dy$_2$Ti$_2$O$_7$. To explore the actual magnetic phase formed by cooling these
+materials, we measure their magnetization dynamics using toroidal,
+boundary-free magnetization transport techniques. We find that the dynamical
+magnetic susceptibility of both compounds has the same distinctive
+phenomenology, that is indistinguishable in form from that of the dielectric
+permittivity of dipolar glass-forming liquids. Moreover, Ho$_2$Ti$_2$O$_7$ and
+Dy$_2$Ti$_2$O$_7$ both exhibit microscopic magnetic relaxation times that
+increase along the super-Arrhenius trajectories analogous to those observed in
+glass-forming dipolar liquids. Thus, upon cooling below about 2K,
+Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$ both appear to enter the same magnetic
+state exhibiting the characteristics of a glass-forming spin-liquid.",1707.09014v3
+2018-07-01,Dynamic modeling of levitation of a superconducting bulk by coupled $H$-magnetic field and Arbitrary Lagrangian-Eulerian formulations,"Intrinsically stable magnetic levitation between superconductors and
+permanent magnets can be exploited in a variety of applications of great
+technical interest in the field of transportation (rail transportation), energy
+(flywheels) and industry. In this contribution, we present a new model for the
+calculation of levitation forces between superconducting bulks and permanent
+magnet, based on the $H$-formulation of Maxwell's equations coupled with an
+Arbitrary Lagrangian-Eulerian formulation. The model uses a moving mesh that
+adapts at each time step based on the time-change of the distance between a
+superconductor bulk and a permanent magnet. The model is validated against a
+fixed mesh model (recently in turn validated against experiments) that uses an
+analytical approach for calculating the magnetic field generated by the moving
+permanent magnet. Then, it is used to analyze the magnetic field dynamics both
+in field-cooled and zero-field-cooled conditions and successively used to test
+different configurations of permanent magnets and to compare them in terms of
+levitation forces. The easiness of implementation of this model and its
+flexibility in handling different geometries, material properties, and
+application scenarios make the model an attractive tool for the analysis and
+optimization of magnetic levitation-based applications.",1807.00329v2
+2019-05-31,Heat transfer and flow regimes in quasi-static magnetoconvection with a vertical magnetic field,"Numerical simulations of quasi-static magnetoconvection with a vertical
+magnetic field are carried out up to a Chandrasekhar number of $Q=10^8$ over a
+broad range of Rayleigh numbers $Ra$. Three magnetoconvection regimes are
+identified: two of the regimes are magnetically-constrained in the sense that a
+leading-order balance exists between the Lorentz and buoyancy forces, whereas
+the third regime is characterized by unbalanced dynamics that is similar to
+non-magnetic convection. Each regime is distinguished by flow morphology,
+momentum and heat equation balances, and heat transport behavior. One of the
+magnetically-constrained regimes appears to represent an `ultimate'
+magnetoconvection regime in the dual limit of asymptotically-large buoyancy
+forcing and magnetic field strength; this regime is characterized by an
+interconnected network of anisotropic, spatially-localized fluid columns
+aligned with the direction of the imposed magnetic field that remain
+quasi-laminar despite having large flow speeds. As for non-magnetic convection,
+heat transport is controlled primarily by the thermal boundary layer.
+Empirically, the scaling of the heat transport and flow speeds with $Ra$ appear
+to be independent of the thermal Prandtl number within the
+magnetically-constrained, high-$Q$ regimes.",1905.13688v2
+2020-03-18,A local view of the laser induced magnetic domain dynamics in CoPd stripe domains at the picosecond time scale,"The dynamic of the magnetic structure in a well ordered ferromagnetic CoPd
+stripe domain pattern has been investigated upon excitation by femtosecond
+infrared laser pulses. Time-resolved X-ray magnetic circular dichroism in
+photoemission electron microscopy (TR-XMCD-PEEM) is used to perform real space
+magnetic imaging with 100 ps time resolution in order to show local
+transformations of the domains structures. Using the time resolution of the
+synchrotron radiation facility of the Helmholtz-Zentrum Berlin, we are able to
+image the transient magnetic domains in a repetitive pump and probe experiment.
+In this work, we study the reversible and irreversible transformations of the
+excited magnetic stripe domains as function of the laser fluence. Our results
+can be explained by thermal contributions, reducing the XMCD amplitude in each
+stripe domain below a threshold fluence of 12 mJ/cm2. Above this threshold
+fluence, irreversible transformations of the magnetic domains are observed.
+Static XMCD-PEEM images reveal the new partially ordered stripe domain
+structures characterized by a new local magnetic domain distribution showing an
+organized pattern at the micrometer scale. This new arrangement is attributed
+to the recovery of the magnetic anisotropy during heat dissipation under an
+Oersted field.",2003.08121v4
+2020-04-23,Momentum broadening of heavy quark in a magnetized thermal QCD medium,"Anisotropic momentum diffusion coefficients of heavy quarks have been
+computed in a strongly magnetized quark-gluon plasma beyond the static limit
+within the framework of Langevin dynamics. Depending on the orientation of the
+motion of the heavy quark with respect to the direction of the magnetic field,
+five momentum diffusion coefficients of heavy quark have been estimated in the
+magnetized thermal medium. Specifically, we have focussed our attention to
+temperature range and strength of magnetic field satisfying the condition,
+$\it{i.e.}$ $M\gg\sqrt{eB}\gg T$, $M$ being the mass of heavy quark. The light
+quarks/antiquarks follow $1+1-$dimensional lowest Landau level (LLL)
+kinematics, and heavy quark dynamics are not directly affected by the magnetic
+field in the medium. The thermal gluon contribution to the diffusion
+coefficient is proportions to $T^3$, whereas, the contribution of light quarks
+in the lowest Landau state to the same is seen to be proportional to $T|eB|$.
+Furthermore, it is observed that for the case of heavy quark motion parallel to
+the magnetic field, the component of diffusion coefficient transverse both to
+the field and the heavy quark velocity $(\kappa^{\parallel}_{TT})$ turns out to
+be dominant as compared to the component longitudinal to both the field and
+motion $(\kappa^{\parallel}_{LL})$, $i.e.$, $\kappa^{\parallel}_{TT}\gg
+\kappa^{\parallel}_{LL}$. Further, for the case of heavy quark moving
+perpendicular to the magnetic field, it is seen that the diffusion coefficients
+transverse to the magnetic field are dominant, i.e., $\kappa^{\perp}_{LT},
+\kappa^{\perp}_{TT}\gg \kappa^{\perp}_{TL}$.",2004.11092v2
+2020-07-24,Analysis of solar wind energy and the Akasofu parameter for energy dynamics assessment during Supersubstorm,"Solar activities have significant impact on the member of the solar systems
+including earth. As earth is a planet with its own magnetic field, solar
+emissions with magnetic fields do interact with the earth's own magnetic field
+to create geo-magnetic disturbances. Substorms are geo-magnetic disturbances of
+shorter duration (few hours or less) which are mainly concentrated in the
+auroral region and originates due to the ionospheric current injection at high
+latitudes. Supersubstorm are intense substorms as identified by peak activities
+in geo-magnetic indices. In this thesis, we have investigated the energy
+dynamics during the supersubstorm and analyzed the relation of the energy
+components with different geo-magnetic indices and interplanetary magnetic
+field (IMF) components. In particular, the solar wind energy levels and the
+energy coupled into the magnetosphere as captured by the Akasofu parameter are
+studied. A qualitative analysis of the computed energy and its relationship
+with different geo-magnetic indices is presented. Correlation and
+cross-correlation analysis have been used to get insights into the nature of
+the relationship between the energy components and indices. This for example
+uncovered the negative relationship between the solar wind energy and the
+Akasofu parameter. A summary analysis of the supersubstorm event in comparison
+with the quiet phases are made. This has led to insights for example showing
+the higher energy levels during supersubstorm and different energy ratios
+(Akasofu parameter divided by the solar wind energy) existing for different
+supersubstorm.",2007.12352v2
+2020-07-30,MHD accretion-ejection: jets launched by a non-isotropic accretion disk dynamo. I. Validation and application of selected dynamo tensorial components,"Astrophysical jets are launched from strongly magnetized systems that host an
+accretion disk surrounding a central object. The origin of the jet launching
+magnetic field is one of the open questions for modeling the accretion-ejection
+process. Here we address the question how to generate the accretion disk
+magnetization and field structure required for jet launching. Applying the
+PLUTO code, we present the first resistive MHD simulations of jet launching
+including a non-scalar accretion disk mean-field $\alpha^2\Omega$-dynamo in the
+context of large scale disk-jet simulations. Essentially, we find the
+$\alpha_\phi$-dynamo component determining the amplification of the poloidal
+magnetic field, which is strictly related to the disk magnetization (and, as a
+consequence, to the jet speed, mass and collimation), while the $\alpha_R$ and
+$\alpha_\theta$-dynamo components trigger the formation of multiple,
+anti-aligned magnetic loops in the disk, with strong consequences on the
+stability and dynamics of the disk-jet system. In particular, such loops
+trigger the formation of dynamo inefficient zones, which are characterized by a
+weak magnetic field, and therefore a lower value of the magnetic diffusivity.
+The jet mass, speed and collimation are strongly affected by the formation of
+the dynamo inefficient zones. Moreover, the $\theta$-component of the
+$\alpha$-dynamo plays a key role when interacting with a non-radial component
+of the seed magnetic field. We also present correlations between the strength
+of the disk toy dynamo coefficients and the dynamical parameters of the jet
+that is launched.",2007.15701v1
+2021-05-01,Charged particle motion around a magnetized Reissner-Nordström black hole,"We investigate the dynamics of neutral and charged test particles around
+axially symmetric magnetized black hole spacetime. We consider its
+electromagnetic field in the black hole vicinity and study its impact on the
+dynamics of test particles. We determine the radius of the innermost stable
+circular orbit (ISCO) for neutral and charged test particles and show that the
+combined effect of black hole electric charge and magnetic field strongly
+affects the ISCO radius, thus shrinking its values. We also show that the ISCO
+radius of positively (negatively) charged particle initially gets increased
+(decreased) and then gets radically altered with an increase in the value of
+both black hole electric charge and test particle charge. It turns out that the
+repulsive (attractive) Coulomb force dominates over the Lorentz force arising
+from the black hole magnetic field. Typically, black hole rotation causes
+axially symmetric spacetime case. Similarly, it turns out that a magnetized
+black hole solution also causes axially symmetric spacetime as a consequence of
+the presence of magnetic field. We study a degeneracy for the value of the ISCO
+between the Kerr and the magnetized Reissner-Nordstr\""{o}m black hole
+geometries and show that the combined effects of black hole charge and magnetic
+field can be mimicked by Kerr spacetime with the spin parameter up to
+$a/M\approx 0.8$. Finally, we consider the center of mass energy of colliding
+particles and show that an increase in the values of black hole magnetic field
+and electric charge leads to high center of mass energy extracted by collision
+of two particles.",2105.00342v2
+2021-12-27,"Design, Dynamics, and Dissipation of a Torsional-Magnetic Spring Mechanism","We present an analytical and experimental study of torsional magnetic
+mechanism where the restoring torque is due to magnetic field interactions
+between rotating and fixed permanent magnets. The oscillator consists of a ball
+bearing-supported permanent magnet, called the rotor, placed between two fixed
+permanent magnets called the stators. Perturbing the rotor from its equilibrium
+angle induces a restoring magnetic torque whose effect is modeled as a
+torsional spring. This restoring effect is accompanied by dissipation
+mechanisms arising from structural viscoelasticity, air and electromagnetic
+damping, as well as friction in the ball bearings. To investigate the system
+dynamics, we constructed an experimental setup capable of mechanical,
+electrical and magnetic measurements. For various rotor-stator gaps in this
+setup, we validated an analytical model that assumes viscous and dry (Coulomb)
+damping during the rotor free response. Moreover, we forced the rotor by a
+neighboring electromagnetic coil into high amplitude oscillations. We observed
+unusual resonator nonlinearity: at large rotor-stator gaps, the oscillations
+are softening; at reduced gaps, the oscillations stiffen-then-soften. The
+developed reduced-order models capture the nonlinear effects of the
+rotor-to-stator and the rotor-to-coil distances. These magnetic oscillators are
+promising in low-frequency electromagnetic signal transmission and in designing
+magneto-elastic metamaterials with tailorable nonlinearity.",2112.13806v1
+2022-01-16,Perspective: magnetic nanoparticles in theranostic applications,"Nanomedicine research started exploring the combination of therapy and
+diagnostics, so-called theranostics, to offer a more flexible care with
+improved outcome. As magnetic nanoparticles show great potential in many
+diagnostic and therapeutic applications, they are prime candidates to be used
+in a theranostic setting. This perspective gives an overview of
+state-of-the-art magnetic nanoparticle-based imaging techniques and theranostic
+applications and discusses their opportunities and challenges. To address these
+challenges and exploit these opportunities to the fullest, we provide three
+promising research directions. The first considers novel magnetic field
+sequences, utilizing the rich magnetic dynamics of the particles, which boost
+the capabilities of many nanoparticle-based applications. Secondly ,we
+introduce the concept of smart theranostics based on feedback mechanisms
+between the particle applications and their supporting imaging procedure to
+enhance the performance of both and allow real-time monitoring of treatment
+efficiency. Finally, we show how data-driven models could enhance therapy and
+diagnostics, and handle the platform's large amount of data and decision
+support algorithms. The latter research track also includes hybrid models in
+which physics-based and data-driven models are combined to overcome challenges
+of applications with limited data, as well as to uncover unknown nanoparticle
+dynamics. Contrasting other literature, which mainly focuses on developing
+magnetic nanoparticles with the right characteristics, we put forward advances
+in magnetic nanoparticle imaging techniques and applications to enable the use
+of a broader range of magnetic nanoparticles in theranostics. We encourage
+researchers to also investigate these aspects to advance theranostic
+applications of magnetic nanoparticles to clinical environments.",2201.06058v1
+2022-11-22,Bifurcation analysis of a two-dimensional magnetic Rayleigh-Bénard problem,"We perform bifurcation analysis of a two-dimensional magnetic
+Rayleigh-B\'enard problem using a numerical technique called deflated
+continuation. Our aim is to study the influence of the magnetic field on the
+bifurcation diagram as the Chandrasekhar number $Q$ increases, and compare it
+to the standard (non-magnetic) Rayleigh-B\'enard problem. We compute steady
+states at a high Chandrasekhar number of $Q=10^3$ over a range of the Rayleigh
+number $0\leq \text{Ra}\leq 10^5$. These solutions are obtained by combining
+deflation with a continuation of steady states at low Chandrasekhar number,
+which allows us to explore the influence of the strength of the magnetic field
+as $Q$ increases from low coupling, where the magnetic effect is almost
+negligible, to strong coupling at $Q=10^3$. We discover a large profusion of
+states with rich dynamics and observe a complex bifurcation structure with
+several pitchfork, Hopf and saddle-node bifurcations. Our numerical simulations
+show that the onset of bifurcations in the problem is delayed when $Q$
+increases, while solutions with fluid velocity patterns aligning with the
+background vertical magnetic field are privileged. Additionally, we report a
+branch of states that stabilizes at high magnetic coupling, suggesting that one
+may take advantage of the magnetic field to discriminate solutions.",2211.12163v1
+2023-01-13,Vibronic effects on the quantum tunnelling of magnetisation in Kramers single-molecule magnets,"Single-molecule magnets are among the most promising platforms for achieving
+molecular-scale data storage and processing. Their magnetisation dynamics are
+determined by the interplay between electronic and vibrational degrees of
+freedom, which can couple coherently, leading to complex vibronic dynamics.
+Building on an ab initio description of the electronic and vibrational
+Hamiltonians, we formulate a non-perturbative vibronic model of the low-energy
+magnetic degrees of freedom in monometallic single-molecule magnets. Describing
+their low-temperature magnetism in terms of magnetic polarons, we are able to
+quantify the vibronic contribution to the quantum tunnelling of the
+magnetisation, a process that is commonly assumed to be independent of
+spin-phonon coupling. We find that the formation of magnetic polarons lowers
+the tunnelling probability in both amorphous and crystalline systems by
+stabilising the low-lying spin states. This work, thus, shows that spin-phonon
+coupling subtly influences magnetic relaxation in single-molecule magnets even
+at extremely low temperatures where no vibrational excitations are present.",2301.05557v2
+2024-01-19,Exploration of magnon-magnon coupling in an antidot lattice: The role of non-uniform magnetization texture,"We numerically study the spin wave dynamics in an antidot lattice based on a
+Co/Pd multilayer structure with reduced perpendicular magnetic anisotropy at
+the edges of the antidots. This structure forms a magnonic crystal with a
+periodic antidot pattern and a periodic magnetization configuration consisting
+of out-of-plane magnetized bulk and in-plane magnetized rims. Our results show
+the different behavior of spin waves in the bulk and in the rims under varying
+out-of-plane external magnetic field strength, revealing complex spin-wave
+spectra and hybridizations between the modes of these two subsystems. A
+particularly strong magnon-magnon coupling, due to exchange interactions, is
+found between the fundamental bulk spin-wave mode and the second-order radial
+rim modes. However, the dynamical coupling between the spin-wave modes at low
+frequencies, involving the first-order radial rim modes, is masked by the
+changes in the static magnetization at the bulk-rim interface with magnetic
+field changes. The study expands the horizons of magnonic-crystal research by
+combining periodic structural patterning and non-collinear magnetization
+texture to achieve strong magnon-magnon coupling, highlighting the significant
+role of exchange interactions in the coupling.",2401.10540v2
+2012-02-07,Relaxation-to-creep transition of domain-wall motion in two- dimensional random-field Ising model with ac driving field,"With Monte Carlo simulations, we investigate the relaxation dynamics with a
+domain wall for magnetic systems at the critical temperature. The dynamic
+scaling behavior is carefully analyzed, and a dynamic roughening process is
+observed. For comparison, similar analysis is applied to the relaxation
+dynamics with a free or disordered surface",1202.1343v1
+2001-09-11,Dynamic Transitions in Pure Ising Magnets under Pulsed and Oscillating Fields,"Response of pure Ising systems to time-dependent external magnetic fields,
+like pulsed and oscillating fields, are discussed and compared here. Because of
+the two time scales involved, namely the thermodynamic relaxation time of the
+system and the pulse width or the time period of the external field,
+dynamically broken symmetric phases appear spontaneously when both become
+comparable. A particularly simple case is that of an Ising ferromagnet below
+its static critical temperature, when it is perturbed for a short duration by a
+pulsed magnetic field competing with the existing order in the system. If the
+field strength and duration is more than the threshold (dependent on the
+temperature), the system, and consequently the magnetization, switches from one
+minimum to the other of the static free energy. This magnetization reversal
+transition here shows intriguing dynamic transition behaviour, similar to those
+for oscillating fields. Monte Carlo studies for such dynamic transitions are
+discussed and compared with the mean field results for the same and the Monte
+Carlo results for the oscillating field case. In particular, we discuss about
+the Monte Carlo results for the fluctuations and their growth behaviour near
+this magnetization reversal (dynamic) transition point.",0109188v1
+2013-07-02,Local and Nonlocal Advected Invariants and Helicities in Magnetohydrodynamics and Gas Dynamics I: Lie Dragging Approach,"In this paper we discuss conservation laws in ideal magnetohydrodynamics
+(MHD) and gas dynamics associated with advected invariants. The invariants in
+some cases, can be related to fluid relabelling symmetries associated with the
+Lagrangian map. There are different classes of invariants that are advected or
+Lie dragged with the flow. Simple examples are the advection of the entropy S
+(a 0-form), and the conservation of magnetic flux (an invariant 2-form advected
+with the flow). The magnetic flux conservation law is equivalent to Faraday's
+equation. We discuss the gauge condition required for the magnetic helicity to
+be advected with the flow. The conditions for the cross helicity to be an
+invariant are discussed. We discuss the different variants of helicity in fluid
+dynamics and in MHD, including: fluid helicity, cross helicity and magnetic
+helicity. The fluid helicity conservation law and the cross helcity
+conservation law in MHD are derived for the case of a barotropic gas. If the
+magnetic field lies in the constant entropy surface, then the gas pressure can
+depend on both the entropy and the density. In these cases the conservation
+laws are local conservation laws. We obtain nonlocal conservation laws for
+fluid helicity and cross helicity for non-barotropic fluids using the Clebsch
+variable formulation of gas dynamics and MHD. Ertel's theorem and potential
+vorticity, the Hollman invariant, and the Godbillon Vey invariant for special
+flows for which the magnetic helicity is zero are also discussed.",1307.1105v2
+2017-01-05,Structural dynamics during laser induced ultrafast demagnetization,"The mechanism underlying femtosecond laser pulse induced ultrafast
+magnetization dynamics remains elusive despite two decades of intense research
+on this phenomenon. Most experiments focused so far on characterizing
+magnetization and charge carrier dynamics, while first direct measurements of
+structural dynamics during ultrafast demagnetization were reported only very
+recently. We here present our investigation of the infrared laser pulse induced
+ultrafast demagnetization process in a thin Ni film, which characterizes
+simultaneously magnetization and structural dynamics. This is achieved by
+employing femtosecond time resolved X-ray resonant magnetic reflectivity
+(tr-XRMR) as probe technique. The experimental results reveal unambiguously
+that the sub-picosecond magnetization quenching is accompanied by strong
+changes in non-magnetic X-ray reflectivity. These changes vary with reflection
+angle and changes up to 30$\%$ have been observed. Modeling the X-ray
+reflectivity of the investigated thin film, we can reproduce these changes by a
+variation of the apparent Ni layer thickness of up to 1$\%$. Extending these
+simulations to larger incidence angles we show that tr-XRMR can be employed to
+discriminate experimentally between currently discussed models describing the
+ultrafast demagnetization phenomenon.",1701.01375v3
+2017-05-07,Magnetohydrodynamic modeling of solar coronal dynamics with an initial non-force-free magnetic field,"The magnetic fields in the solar corona are generally neither force-free nor
+axisymmetric and have complex dynamics that are difficult to characterize. Here
+we simulate the topological evolution of solar coronal magnetic field lines
+(MFLs) using a magnetohydrodynamic model. The simulation is initialized with a
+non-axisymmetric non-force-free magnetic field that best correlates with the
+observed vector magnetograms of solar active regions (ARs). To focus on these
+ideas, simulations are performed for the flaring AR 11283 noted for its
+complexity and well-documented dynamics. The simulated dynamics develops as the
+initial Lorentz force pushes the plasma and facilitates successive magnetic
+reconnections at the two X-type null lines present in the initial field.
+Importantly, the simulation allows for the spontaneous development of mass
+flow, unique among contemporary works, that preferentially reconnects field
+lines at one of the X-type null lines. Consequently, a flux rope consisting of
+low-lying twisted MFLs, which approximately traces the major polarity inversion
+line, undergoes an asymmetric monotonic rise. The rise is attributed to a
+reduction in the magnetic tension force at the region overlying the rope,
+resulting from the reconnection. A monotonic rise of the rope is in conformity
+with the standard scenario of flares. Importantly, the simulated dynamics leads
+to bifurcations of the flux rope, which, being akin to the observed filament
+bifurcation in AR 11283, establishes the appropriateness of the initial field
+in describing ARs.",1705.02568v1
+2018-03-13,Magneto-optic dynamics in a ferromagnetic nematic liquid crystal,"We investigate dynamic magneto-optic effects in a ferromagnetic nematic
+liquid crystal experimentally and theoretically. Experimentally we measure the
+magnetization and the phase difference of the transmitted light when an
+external magnetic field is applied. As a model we study the coupled dynamics of
+the magnetization, M, and the director field, n, associated with the liquid
+crystalline orientational order. We demonstrate that the experimentally studied
+macroscopic dynamic behavior reveals the importance of a dynamic cross-coupling
+between M and n. The experimental data are used to extract the value of the
+dissipative cross-coupling coefficient. We also make concrete predictions about
+how reversible cross-coupling terms between the magnetization and the director
+could be detected experimentally by measurements of the transmitted light
+intensity as well as by analyzing the azimuthal angle of the magnetization and
+the director out of the plane spanned by the anchoring axis and the external
+magnetic field. We derive the eigenmodes of the coupled system and study their
+relaxation rates. We show that in the usual experimental set-up used for
+measuring the relaxation rates of the splay-bend or twist-bend eigenmodes of a
+nematic liquid crystal one expects for a ferromagnetic nematic liquid crystal a
+mixture of at least two eigenmodes.",1803.04898v1
+2019-04-12,The emergence of magnetic flux and its role on the onset of solar dynamic events,"A plethora of solar dynamic events, such as the formation of active regions,
+the emission of jets and the occurrence of eruptions is often associated to the
+emergence of magnetic flux from the interior of the Sun to the surface and
+above. Here, we present a short review on the onset, driving and/or triggering
+of such events by magnetic flux emergence. We briefly describe some key
+observational examples, theoretical aspects and numerical simulations, towards
+revealing the mechanisms that govern solar dynamics and activity related to
+flux emergence. We show that the combination of important physical processes
+like shearing and reconnection of magnetic fieldlines in emerging flux regions
+or at their vicinity, can power some of the most dynamic phenomena in the Sun
+on various temporal and spatial scales. Based on previous and recent
+observational and numerical studies, we highlight that, in most cases, none of
+these processes alone can drive and also trigger explosive phenomena releasing
+considerable amount of energy towards the outer solar atmosphere and space,
+such as flares, jets and large-scale eruptions (e.g. CMEs). In addition, one
+has to take into account the physical properties of the emerging field (e.g.
+strength, amount of flux, relative orientation to neighbouring and pre-existing
+magnetic fields, etc.) in order to better understand the exact role of magnetic
+flux emergence on the onset of solar dynamic events.",1904.06274v1
+2022-11-01,Deformation and necking of liquid droplets in a magnetic field,"Pendant droplets of water and paramagnetic solutions are studied in the
+presence of uniform and nonuniform magnetic fields produced by small permanent
+magnet arrays, both in static conditions and during dynamic pinch-off. Static
+measurements of the droplet shape are analysed in terms of an apparent surface
+tension {\gamma}app or an effective density \r{ho}eff. The change of surface
+tension of deionized water in a uniform field of 450 mT is insignificant, 0.19
+- 0.21 mNm-1. Measurements on droplets of compensated zero-susceptibility
+solutions of Cu2+, Mn2+ and Dy3+ where the shape is unaffected by any magnetic
+body force show changes of surface tension of about -1% in 500 mT. Magnetic
+field gradients of up to 100 T2m-1 deform the droplets and lead to changes of
+\r{ho}eff that are negative for diamagnetic solutions (buoyancy effect) and
+positive for paramagnetic solutions. The droplet profile of
+strongly-paramagnetic 0.1 Dy M DyCl3 solution is analysed, treating the
+nonuniform vertical field gradient as a spatial variation of gravity. The
+influence of Maxwell stress on droplet shape is discussed. In dynamic
+measurements, the droplet shape at pinch-off is recorded by high-speed
+photography and analysed in terms of a relative change of dynamic surface
+tension in the presence of a magnetic field. The surface-tension-dependent
+pre-factor of the scaling law that governs the pinch-off dynamics shows no
+difference for pure water or 0.11 M DyCl3 solutions in the field. The
+nonuniform field has no influence in the pinch-off region because the filament
+diameter is much less than the capillary length.",2211.00431v1
+2005-03-30,Master Equations for pulsed magnetic fields: Application to magnetic molecules,"We extend spin-lattice relaxation theory to incorporate the use of pulsed
+magnetic fields for probing the hysteresis effects and magnetization steps and
+plateaus exhibited, at low temperatures, by the dynamical magnetization of
+magnetic molecules. The main assumption made is that the lattice degrees of
+freedom equilibrate in times much shorter than both the experimental time scale
+(determined by the sweep rate) and the typical spin-lattice relaxation time. We
+first consider the isotropic case (a magnetic molecule with a ground state of
+spin $S$ well separated from the excited levels and also the general isotropic
+Heisenberg Hamiltonian where all energy levels are relevant) and then we
+include small off-diagonal terms in the spin Hamiltonian to take into account
+the Landau-Zener-St\""{u}ckelberg (LZS) effect. In the first case, and for an
+$S=1/2$ magnetic molecule we arrive at the generalized Bloch equation recently
+used for the magnetic molecule \{V$_6$\} in Phys. Rev. Lett. 94, 147204 (2005).
+An analogous equation is derived for the magnetization, at low temperatures, of
+antiferromagnetic ring systems. The LZS effect is discussed for magnetic
+molecules with a low spin ground state, for which we arrive at a very
+convenient set of equations that take into account the combined effects of LZS
+and thermal transitions. In particular, these equations explain the deviation
+from exact magnetization reversal at $B\approx 0$ observed in \{V$_6$\}. They
+also account for the small magnetization plateaus (``magnetic Foehn effect''),
+following the LZS steps, that have been observed in several magnetic molecules.
+Finally, we discuss the role of the Phonon Bottleneck effect at low
+temperatures and specifically we indicate how this can give rise to a
+pronounced Foehn effect.",0503695v2
+2012-04-24,Magnetic buoyancy instabilities in the presence of magnetic flux pumping at the base of the solar convection zone,"We perform idealised numerical simulations of magnetic buoyancy instabilities
+in a model of the solar tachocline. We introduce a simplified model of magnetic
+flux pumping in an upper layer (the convection zone), and study the effects of
+its inclusion on the evolution of buoyancy instabilities in a lower layer (the
+radiative interior). We study its effects on the instability of both a
+preconceived magnetic slab and of a shear-generated magnetic layer. In the
+former, we find that in the regime in which the downward pumping velocity is
+comparable with the Alfven speed of the magnetic layer, flux pumping is able to
+hold back the bulk of the magnetic field, with only small pockets of strong
+field able to rise into the upper layer. In simulations in which the magnetic
+layer is generated by shear, we find that the shear velocity is not necessarily
+required to exceed that of the pumping (therefore the kinetic energy of the
+shear is not required to exceed that of the overlying convection), for strong
+localised pockets of magnetic field to be produced which can rise into the
+upper layer. This is because magnetic flux pumping acts to store the field
+below the interface, allowing it to be amplified both by the shear, and by
+vortical fluid motions, until pockets of field can achieve sufficient strength
+to rise into the upper layer. In addition, we find that the interface between
+the two layers is a natural location for the production of strong vertical
+gradients in the magnetic field. If these gradients are sufficiently strong to
+allow the development of magnetic buoyancy instabilities, strong shear is not
+necessarily required to drive them (c.f. previous work by Vasil & Brummell). We
+find that the addition of magnetic flux pumping appears to be able to assist
+shear-driven magnetic buoyancy in producing strong flux concentrations that can
+rise into the convection zone from the radiative interior.",1204.5432v1
+2012-12-25,The Small-Scale Dynamo at Low Magnetic Prandtl Numbers,"The present-day Universe is highly magnetized, even though the first magnetic
+seed fields were most probably extremely weak. To explain the growth of the
+magnetic field strength over many orders of magnitude fast amplification
+processes need to operate. The most efficient mechanism known today is the
+small-scale dynamo, which converts turbulent kinetic energy into magnetic
+energy leading to an exponential growth of the magnetic field. The efficiency
+of the dynamo depends on the type of turbulence indicated by the slope of the
+turbulence spectrum v(l) \propto l^{theta}, where v(l) is the eddy velocity at
+a scale l. We explore turbulent spectra ranging from incompressible Kolmogorov
+turbulence with theta = 1/3 to highly compressible Burgers turbulence with
+theta = 1/2. In this work we analyze the properties of the small-scale dynamo
+for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic
+Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev
+equation, which describes the evolution of the small-scale magnetic field,
+using the WKB approximation. In the limit of low magnetic Prandtl numbers the
+growth rate is proportional to Rm^{(1-theta)/(1+theta)}. We furthermore discuss
+the critical magnetic Reynolds number Rm_crit, which is required for
+small-scale dynamo action. The value of Rm_crit is roughly 100 for Kolmogorov
+turbulence and 2700 for Burgers. Furthermore, we discuss that Rm_crit provides
+a stronger constraint in the limit of low Pm than it does for large Pm. We
+conclude that the small-scale dynamo can operate in the regime of low magnetic
+Prandtl numbers, if the magnetic Reynolds number is large enough. Thus, the
+magnetic field amplification on small scales can take place in a broad range of
+physical environments and amplify week magnetic seed fields on short
+timescales.",1212.5979v1
+2018-07-23,The Quantum Field Of A Magnet Shown By A Nanomagnetic Ferrolens,"It has been more than two hundred years since the first iron filings
+experiment, showing us the 2D macroscopic magnetic imprint of the field of a
+permanent magnet. However, latest developments in modern nanomagnetic passive
+direct observation devices reveal in real-time and color a more intriguing 3D
+dynamic and detailed image of the field of a magnet, with surprising new
+findings, that can change our perspective for dipole magnetism forever and lead
+to new research. This research is a continuation of our previous work (DOI:
+10.1016/j.jmmm.2017.12.023). The magnetostatic fields were under our scope and
+examined with the aid of the ferrolens. We are presenting experimental and
+photographical evidence, demonstrating the true complex 3D Euclidian geometry
+of the quantum field of permanent magnets that have never been seen before and
+the classic iron filings experiment, apart of its 2D limitations, fails to
+depict. An analysis of why and what these iron filings inherent limitations
+are, giving us an incomplete and also in some degree misguiding image of the
+magnetic field of a magnet is carried out, whereas, as we prove the ferrolens
+is free of these limitations and its far more advanced visualization
+capabilities is allowing it to show the quantum image with depth of field
+information, of the dipole field of a permanent magnet. For the first time the
+domain wall (i.e. Bloch or Neel wall) region of the field of a magnet is
+clearly made visible by the ferrolens along with what phenomenon is actually
+taking place there, leading to the inescapable conclusion, novel observation
+and experimental evidence that the field of any dipole magnet actually consists
+of two distinct and separate toroidal shaped 3D magnetic bubbles, each located
+at either side of the dipole around the exact spatial regions where the two
+poles of the magnet reside.",1807.08751v1
+2016-01-27,Dynamic nuclear polarization in a magnetic resonance force microscope experiment,"We report achieving enhanced nuclear magnetization in a magnetic resonance
+force microscope experiment at 0.6 tesla and 4.2 kelvin using the dynamic
+nuclear polarization (DNP) effect. In our experiments a microwire coplanar
+waveguide delivered radiowaves to excite nuclear spins and microwaves to excite
+electron spins in a 250 nm thick nitroxide-doped polystyrene sample. Both
+electron and proton spin resonance were observed as a change in the mechanical
+resonance frequency of a nearby cantilever having a micron-scale nickel tip.
+NMR signal, not observable from Curie-law magnetization at 0.6 tesla, became
+observable when microwave irradiation was applied to saturate the electron
+spins. The resulting NMR signal's size, buildup time, dependence on microwave
+power, and dependence on irradiation frequency was consistent with a transfer
+of magnetization from electron spins to nuclear spins. Due to the presence of
+an inhomogenous magnetic field introduced by the cantilever's magnetic tip, the
+electron spins in the sample were saturated in a microwave-resonant slice 10's
+of nm thick. The spatial distribution of the nuclear polarization enhancement
+factor $\epsilon$ was mapped by varying the frequency of the applied
+radiowaves. The observed enhancement factor was zero for spins in the center of
+the resonant slice, was $\epsilon = +10$ to $+20$ for spins proximal to the
+magnet, and was $\epsilon = -10$ to $-20$ for spins distal to the magnet. We
+show that this bipolar nuclear magnetization profile is consistent with
+cross-effect DNP in a $\sim \! 10^{5} \: \mathrm{T} \: \mathrm{m}^{-1}$
+magnetic field gradient. Potential challenges associated with generating and
+using DNP-enhanced nuclear magnetization in a nanometer-resolution magnetic
+resonance imaging experiment are elucidated and discussed.",1601.07253v2
+2018-10-19,Magnetogenesis at Cosmic Dawn: Tracing the Origins of Cosmic Magnetic Fields,"Despite their ubiquity, the origin of cosmic magnetic fields remains unknown.
+Various mechanisms have been proposed for their existence including primordial
+fields generated by inflation, or amplification and injection by compact
+astrophysical objects. Separating the potential impact of each magnetogenesis
+scenario on the magnitude and orientation of the magnetic field and their
+impact on gas dynamics may give insight into the physics that magnetised our
+Universe. In this work, we demonstrate that because the induction equation and
+solenoidal constraint are linear with $B$, the contribution from different
+sources of magnetic field can be separated in cosmological magnetohydrodynamics
+simulations and their evolution and influence on the gas dynamics can be
+tracked. Exploiting this property, we develop a magnetic field tracer algorithm
+for cosmological simulations that can track the origin and evolution of
+different components of the magnetic field. We present a suite of cosmological
+magnetohydrodynamical RAMSES simulations that employ this algorithm where the
+primordial field strength is varied to determine the contributions of the
+primordial and supernovae-injected magnetic fields to the total magnetic energy
+as a function of time and spatial location. We find that, for our specific
+model, the supernova-injected fields rarely penetrate far from haloes, despite
+often dominating the total magnetic energy in the simulations. The magnetic
+energy density from the supernova-injected field scales with density with a
+power-law slope steeper than 4/3 and often dominates the total magnetic energy
+inside of haloes. However, the star formation rates in our simulations are not
+affected by the presence of magnetic fields, for the ranges of primordial field
+strengths examined. These simulations represent a first demonstration of the
+magnetic field tracer algorithm (abridged).",1810.08619v2
+2022-03-22,Dynamic Magnetic Crossover at the Origin of the Hidden-Order in van der Waals Antiferromagnet CrSBr,"The van der Waals material CrSBr stands out as a promising two-dimensional
+magnet. Especially, its high magnetic ordering temperature and versatile
+magneto-transport properties make CrSBr an important candidate for new devices
+in the emergent field of two-dimensional magnetic materials. To date, the
+magnetic and structural properties of CrSBr have not been fully elucidated.
+Here, we report on the detailed temperature-dependent magnetic and structural
+properties of this material, by comprehensively combining neutron scattering,
+muon spin relaxation spectroscopy, synchrotron X-ray diffraction, and
+magnetization measurements. We evidence that this material undergoes a
+transition to an A-type antiferromagnetic state below $T_{\rm N} \approx$ 140
+K, with a pronounced two-dimensional character as deduced from the determined
+critical exponent of $\beta \approx $ 0.18. In our analysis of the
+field-induced metamagnetic transition, we find that the ferromagnetic
+correlations within the monolayers persist clearly above the N\'eel temperature
+in this material. Furthermore, we unravel the low-temperature (i.e. $T < T_{\rm
+N}$) magnetic hidden order within the long-range magnetically ordered state. We
+find that it is associated to a slowing down of the magnetic fluctuations,
+accompanied by a continuous reorientation of the internal magnetic field. These
+take place upon cooling below $T_s$ $\approx$ 100 K, until a spin freezing
+process occurs at $T$* $\approx$ 40 K. We argue this complex dynamic behavior
+to reflect a magnetic crossover driven by the in-plane uniaxial anisotropy,
+which is ultimately caused by the mixed-anion character of the material. Our
+findings indicate that the magnetic and structural properties of CrSBr widen
+its potential application as a component for spin-based electronic devices.",2203.11785v1
+2000-01-20,Short-time dynamics and magnetic critical behavior of two-dimensional random-bond Potts model,"The critical behavior in the short-time dynamics for the random-bond Potts
+ferromagnet in two-dimensions is investigated by short-time dynamic Monte Carlo
+simulations. The numerical calculations show that this dynamic approach can be
+applied efficiently to study the scaling characteristic, which is used to
+estimate the critical exponents theta, beta/nu and z for the quenched disorered
+systems from the power-law behavior of the kth moments of magnetizations.",0001284v2
+2000-09-26,Dynamical process for switching dynamics between metastable ordered magnetic state and nonmagnetic ground state in photoinduced phase transition,"We propose a dynamical mechanism of the two-way switching between the
+metastable state and the stable state, which has been found in experiments of
+photoinduced reversible magnetization and photoinduced structural phase
+transition. We find that the two-way switching with a non-symmetry breaking
+perturbation such as illumination is possible only in systems with appropriate
+parameters. We make it clear that the existence of two time scales in the
+dynamical process is important for the two-way switching.",0009392v2
+2001-03-06,Short-time dynamics of random-bond Potts ferromagnet with continuous self-dual quenched disorders,"We present Monte Carlo simulation results of random-bond Potts ferromagnet
+with the Olson-Young self-dual distribution of quenched disorders in
+two-dimensions. By exploring the short-time scaling dynamics, we find universal
+power-law critical behavior of the magnetization and Binder cumulant at the
+critical point, and thus obtain estimates of the dynamic exponent $z$ and
+magnetic exponent $\eta$, as well as the exponent $\theta$. Our special
+attention is paid to the dynamic process for the $q$=8 Potts model.",0103130v1
+2003-06-04,Nuclear Spin Dynamics in Parabolic Quantum Wells,"We present a detailed analytical and numerical analysis of the nuclear spin
+dynamics in parabolic quantum wells. The shallow potential of parabolic quantum
+wells permits substantial modification of the electronic wave function in small
+electric fields. The nuclear spin relaxation via the hyperfine interaction
+depends on the electronic local density of states, therefore the local nuclear
+relaxation time depends sensitively on the electric field. For an inhomogeneous
+nuclear magnetization, such as generated by dynamic nuclear polarization, the
+total nuclear magnetization dynamics can similarly be altered. We examine this
+effect quantitatively and the effect of temperature, field, well thickness, and
+nuclear spin diffusion.",0306098v2
+2004-06-21,Dynamics and thermodynamics in spinor quantum gases,"We discuss magnetism in spinor quantum gases theoretically and experimentally
+with emphasis on temporal dynamics of the spinor order parameter in the
+presence of an external magnetic field. In a simple coupled Gross-Pitaevskii
+picture we observe a dramatic suppression of spin dynamics due to quadratic
+Zeeman ''dephasing''. In view of an inhomogeneous density profile of the
+trapped condensate we present evidence of spatial variations of spin dynamics.
+In addition we study spinor quantum gases as a model system for thermodynamics
+of Bose-Einstein condensation. As a particular example we present measurements
+on condensate magnetisation due to the interaction with a thermal bath.",0406485v1
+2001-07-26,Dynamics with unitary phase operator:implications for Wigner's problem,"We show that for general deformations of SU(2) algebra, the dynamics in terms
+of ladder operators is preserved. This is done for a system of precessing
+magnetic dipole in magnetic field, using the unitary phase operator which
+arises in the polar decomposition of SU(2) operators. It is pointed out that
+there is a single phase operator dynamics underlying the dynamics of usual and
+deformed ladder operators.",0107133v2
+2010-10-06,Theory of Local Dynamical Magnetic Susceptibilities from the Korringa-Kohn-Rostoker Green Function Method,"Within the framework of time-dependent density functional theory combined
+with the Korringa-Kohn-Rostoker Green function formalism, we present a real
+space methodology to investigate dynamical magnetic excitations from
+first-principles. We set forth a scheme which enables one to deduce the correct
+effective Coulomb potential needed to preserve the spin-invariance signature in
+the dynamical susceptibilities, i.e. the Goldstone mode. We use our approach to
+explore the spin dynamics of 3d adatoms and different dimers deposited on a
+Cu(001) with emphasis on their decay to particle-hole pairs.",1010.1293v1
+2014-08-14,PT-symmetry in macroscopic magnetic structures,"We introduce the notion of PT-symmetry in magnetic nanostructures and show
+that they can support a new type of non-Hermitian dynamics. Using the simplest
+possible set-up consisting of two coupled ferromagnetic films, one with loss
+and another one with a balanced amount of gain, we demonstrate the existence of
+a spontaneous PT-symmetry breaking point where both the eigenfrequencies and
+eigenvectors are degenerate. Below this point the frequency spectrum is real
+indicating stable dynamics while above this point it is complex signaling
+unstable dynamics.",1408.3285v1
+2015-11-10,Static and dynamic properties of vortex pairs in asymmetric nanomagnets,"Stacked spin-vortex pairs in magnetic multilayered nanopillars, with vertical
+separation between the vortices small compared to the vortex core size, exhibit
+spin dynamics absent in individual vortices. This dynamics is nonlinear and is
+due to the strong direct core-core coupling in the system, dominating
+energetically for small- signal excitation. We observe and explain the
+appearance of spin resonance modes, forbidden within linear dynamics, and
+discuss how they depend on the magnetic and morphological asymmetries in the
+samples.",1511.03092v1
+2011-09-15,Dynamic mean-field and cavity methods for diluted Ising systems,"We compare dynamic mean-field and dynamic cavity as methods to describe the
+stationary states of dilute kinetic Ising models. We compute dynamic mean-field
+theory by expanding in interaction strength to third order, and compare to the
+exact dynamic mean-field theory for fully asymmetric networks. We show that in
+diluted networks the dynamic cavity method generally predicts magnetizations of
+individual spins better than both first order (""naive"") and second order
+(""TAP"") dynamic mean field theory.",1109.3399v3
+2016-02-02,Dynamics of spinor Bose-Einstein condensate subject to dissipation,"We investigate the internal dynamics of the spinor Bose-Einstein Condensates
+subject to dissipation by solving the Lindblad master equation. It is shown
+that for the condensates without dissipation its dynamics always evolve along
+specific orbital in the phase space of ($n_0$, $\theta$) and display three
+kinds of dynamical properties including Josephson-like oscillation,
+self-trapping-like oscillation and 'running phase'. In contrast, the
+condensates subject to dissipation will not evolve along the specific dynamical
+orbital. If component-1 and component-(-1) dissipate in different rates, the
+magnetization $m$ will not conserve and the system transits between different
+dynamical regions. The dynamical properties can be exhibited in the phase space
+of ($n_0$, $\theta$, $m$).",1602.00807v1
+1999-12-20,Jet Acceleration by Tangled Magnetic Fields,"We explore the possibility that extragalactic radio jets might be accelerated
+by highly disorganized magnetic fields that are strong enough to dominate the
+dynamics until the terminal Lorentz factor is reached. Following the
+twin-exhaust model by Blandford & Rees (1974), the collimation under this
+scenario is provided by the stratified thermal pressure from an external
+medium. The acceleration efficiency then depends on the pressure gradient of
+that medium. In order for this mechanism to work there must be continuous
+tangling of the magnetic field, changing the magnetic equation of state away
+from pure flux freezing (otherwise conversion of Poynting flux to kinetic
+energy flux is suppressed). This is a complementary approach to models in which
+the plasma is accelerated by large scale ordered fields. We include a simple
+prescription for magnetic dissipation, which leads to tradeoffs among
+conversion of magnetic energy into bulk kinetic energy, random particle energy,
+and radiation. We present analytic dynamical solutions of such jets, assess the
+effects of radiation drag, and comment on observational issues, such as the
+predicted polarization and synchrotron brightness. Finally, we try to make the
+connection to observed radio galaxies and gamma-ray bursts.",9912429v1
+2001-08-15,Qualitative Properties of Magnetic Fields in Scalar Field Cosmology,"We study the qualitative properties of the class of spatially homogeneous
+Bianchi VI_o cosmological models containing a perfect fluid with a linear
+equation of state, a scalar field with an exponential potential and a uniform
+cosmic magnetic field, using dynamical systems techniques. We find that all
+models evolve away from an expanding massless scalar field model in which the
+matter and the magnetic field are negligible dynamically. We also find that for
+a particular range of parameter values the models evolve towards the usual
+power-law inflationary model (with no magnetic field) and, furthermore, we
+conclude that inflation is not fundamentally affected by the presence of a
+uniform primordial magnetic field. We investigate the physical properties of
+the Bianchi I magnetic field models in some detail.",0108268v1
+2001-10-30,Cluster Magnetic Fields,"Magnetic fields in galaxy clusters have been measured using a variety of
+techniques, including: studies of synchrotron relic and halo radio sources
+within clusters, studies of inverse Compton X-ray emission from clusters,
+surveys of Faraday rotation measures of polarized radio sources both within and
+behind clusters, and studies of Cluster Cold Fronts in X-ray images. These
+measurements imply that most cluster atmospheres are substantially magnetized,
+with typical field strengths of order 1 microGauss with high areal filling
+factors out to Mpc radii. There is likely, however, to be considerable
+variation in field strengths and topologies both within and between clusters,
+especially when comparing dynamically relaxed clusters to those that have
+recently undergone a merger. In some locations, such as the cores of cooling
+flow clusters, the magnetic fields reach levels of 10 - 40 microGauss, and may
+be dynamically important. In all clusters the magnetic fields have a
+significant effect on energy transport in the intracluster medium. We also
+review current theories on the origin of cluster magnetic fields.",0110655v1
+2002-10-18,Nonlinear Magnetic Diffusion and Magnetic Helicity Transport in Galactic Dynamos,"We have extended our previous mean-field galactic dynamo model which included
+algebraic and dynamic alpha nonlinearities (Kleeorin et al., A&A, v. 387, 453,
+2002), to include also a quenching of turbulent diffusivity. We readily obtain
+equilibrium states for the large-scale magnetic field in the local disc dynamo
+model, and these fields have strengths that are comparable to the equipartition
+field strength. We find that the algebraic nonlinearity alone (i.e. quenching
+of both the alpha effect and turbulent magnetic diffusion) cannot saturate the
+growth of the mean magnetic field; only the combined effect of algebraic and
+dynamic nonlinearities can limit the growth of the mean magnetic field.
+However, in contrast to our earlier work without quenching of the turbulent
+diffusivity, we cannot now find satisfactory solutions in the no-z
+approximation to the axisymmetric galactic dynamo problem.",0210430v1
+2005-08-24,Effects of Magnetic Fields on Proto-Neutron Star Winds,"We discuss effects of magnetic fields on proto-neutron star winds by
+performing numerical simulation. We assume that the atmosphere of proto-neutron
+star has a homogenous magnetic field (ranging from ~10^{12} G to ~10^{15} G)
+perpendicular to the radial direction and examine the dependence of the three
+key quantities (dynamical time scale, electron fraction, and entropy per
+baryon) for the successful r-process on the magnetic field strength. Our
+results show that even with a magneter-class field strength, ~10^{15} G, the
+feature of the wind dynamics varies only little from that of non-magnetic
+winds, and that the condition for successful r-process is not realized.",0508512v2
+2006-11-16,Cosmology with inhomogeneous magnetic fields,"We review spacetime dynamics in the presence of large-scale electromagnetic
+fields and then consider the effects of the magnetic component on perturbations
+to a spatially homogeneous and isotropic universe. Using covariant techniques,
+we refine and extend earlier work and provide the magnetohydrodynamic equations
+that describe inhomogeneous magnetic cosmologies in full general relativity.
+Specialising this system to perturbed Friedmann-Robertson-Walker models, we
+examine the effects of the field on the expansion dynamics and on the growth of
+density inhomogeneities, including non-adiabatic modes. We look at scalar
+perturbations and obtain analytic solutions for their linear evolution in the
+radiation, dust and inflationary eras. In the dust case we also calculate the
+magnetic analogue of the Jeans length. We then consider the evolution of vector
+perturbations and find that the magnetic presence generally reduces the decay
+rate of these distortions. Finally, we examine the implications of magnetic
+fields for the evolution of cosmological gravitational waves.",0611537v4
+1996-09-02,Tunneling with the Lorentz Force and the Friction,"We present a semiclassical study of a transport process, the tunneling, in
+the presence of a magnetic field and a dissipative environment. We have found
+that the problem can be mapped onto an effective one-dimensional one, and the
+tunneling rate is strongly affected by the magnetic field, such as a complete
+suppression by a large parallel magnetic field, an example of the dynamical
+localization. In such case a small perpendicular component of the field, or the
+dissipation, can enhance the tunneling rate. In the small parallel field and
+finite temperatures the tunneling rate is finite. Explicit expressions will be
+presented in those cases. If viewing the tunneling in the presence of a
+magnetic field as a dissipative tunneling process, by varying the magnetic
+field and the potential one can obtain the dissipative spectral function
+between the subohmic $s =0$ and the superohmic $s = \infty$. In combination
+with a real dissipative spectral function, the effect of the magnetic field can
+map the spectral function from $s $ to $2-s$, with $s>2$ mapping to $ s = 0$,
+revealing a dual symmetry between the friction and the Lorentz force. Two cases
+relevant to experiments, the edge state tunneling in a Hall bar and the
+tunneling near the dynamical localization will be discussed in detail.",9609021v1
+2002-06-21,Heisenberg Dimer Single Molecule Magnets in a Strong Magnetic Field,"We calculate the static and dynamic properties of single crystal, single
+molecule magnets consisting of equal spin $S=1/2$ or 5/2 dimers. The spins in
+each dimer interact with each other via the Heisenberg exchange interaction and
+with the magnetic induction ${\bf B}$ via the Zeeman interaction, and
+interdimer interactions are negligible. For antiferromagnetic couplings, the
+static magnetization and specific heat exhibit interesting low temperature $T$
+and strong ${\bf B}$ quantum effects. We calculate the frequency spectrum of
+the Fourier transform of the real part of the time autocorrelation function
+${\cal C}_{11}(t)$ for arbitrary $T, {\bf B}$, and compare our results with
+those obtained for classical spins. We also calculate the inelastic neutron
+magnetic dynamical structure factor $S({\bf q},\omega)$ at arbitrary $T, {\bf
+B}$.",0206406v2
+2003-02-17,Magnetization dynamics with a spin-transfer torque,"The magnetization reversal and dynamics of a spin valve pillar, whose lateral
+size is 64$\times$64 nm$^2$, are studied by using micromagnetic simulation in
+the presence of spin transfer torque. Spin torques display both characteristics
+of magnetic damping (or anti-damping) and of an effective magnetic field. For a
+steady-state current, both M-I and M-H hysteresis loops show unique features,
+including multiple jumps, unusual plateaus and precessional states. These
+states originate from the competition between the energy dissipation due to
+Gilbert damping and the energy accumulation due to the spin torque supplied by
+the spin current. The magnetic energy oscillates as a function of time even for
+a steady-state current. For a pulsed current, the minimum width and amplitude
+of the spin torque for achieving current-driven magnetization reversal are
+quantitatively determined. The spin torque also shows very interesting thermal
+activation that is fundamentally different from an ordinary damping effect.",0302337v1
+2003-07-25,Dynamics of a magnetic moment induced by a spin-polarized current,"Effects of an incoming spin-polarized current on a magnetic moment are
+explored. We found that the spin torque occurs only when the incoming spin
+changes as a function of time inside of the magnetic film. This implies that
+some modifications are necessary in a phenomenological model where the
+coefficient of the spin torque term is a constant, and the coefficient is
+determined by dynamics instead of geometrical details. The precession of the
+magnetization reversal depends on the incoming energy of electrons in the
+spin-polarized current. If the incoming energy is smaller than the interaction
+energy, the magnetization does not precess while reversing its direction. We
+also found that the relaxation time associated with the reversal depends on the
+incoming energy. The coupling between an incoming spin and a magnetic moment
+can be estimated by measuring the relaxation time.",0307633v1
+2003-09-12,Anisotropy of exchange stiffness and its effect on the properties of magnets,"Using the spin-spiral formulation of the tight-binding linear muffin-tin
+orbital method, the principal components of the exchange stiffness tensor are
+calculated for typical hard magnets including tetragonal CoPt-type and
+hexagonal YCo5 alloys. The exchange stiffness is strongly anisotropic in all
+studied alloys. This anisotropy makes the domain wall surface tension
+anisotropic. Competition between this anisotropic surface tension and
+magnetostatic energy controls the formation and dynamics of nanoscale domain
+structures in hard magnets. Anisotropic domain wall bending is described in
+detail from the general point of view and with application to cellular Sm-Co
+magnets. It is shown that the repulsive cell-boundary pinning mechanism in
+these magnets is feasible only due to the anisotropic exchange stiffness if
+suitably oriented initial pinning centers are available. In polytwinned
+CoPt-type magnets the exchange stiffness anisotropy controls the orientation of
+macrodomain wall segments. These segments may reorient both statically during
+microstructural coarsening and dynamically during the macrodomain wall
+splitting in external field. Reorientation of segments may facilitate their
+pinning at antiphase boundaries.",0309321v1
+2003-10-18,Dynamics of the superconducting condensate in the presence of a magnetic field. Channelling of vortices in superconducting strips at high currents,"On the basis of the time-dependent Ginzburg-Landau equation we studied the
+dynamics of the superconducting condensate in a wide two-dimensional sample in
+the presence of a perpendicular magnetic field and applied current. We could
+identify two critical currents: the current at which the pure superconducting
+state becomes unstable ($J_{c2}$ \cite{self1}) and the current at which the
+system transits from the resistive state to the superconducting state
+($J_{c1}<J_{c2}$). The current $J_{c2}$ decreases monotonically with external
+magnetic field, while $J_{c1}$ exhibits a maximum at $H^*$. For sufficient
+large magnetic fields the hysteresis disappears and $J_{c1}=J_{c2}=J_c$. In
+this high magnetic field region and for currents close to $J_c$ the voltage
+appears as a result of the motion of separate vortices. With increasing current
+the moving vortices form 'channels' with suppressed order parameter along which
+the vortices can move very fast. This leads to a sharp increase of the voltage.
+These 'channels' resemble in some respect the phase slip lines which occur at
+zero magnetic field.",0310438v1
+2004-01-16,Observation of a Transient Magnetization Plateau in a Quantum Antiferromagnet on the Kagome Lattice,"The magnetization process of an S=1/2 antiferromagnet on the kagome lattice,
+[Cu_3(titmb)_2(OCOCH_3)_6]H_2O {titmb= 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6
+trimethylbenzene} has been measured at very low temperatures in both pulsed and
+steady fields. We have found a new dynamical behavior in the magnetization
+process: a plateau at one third of the saturation magnetization appears in the
+pulsed field experiments for intermediate sweep rates of the magnetic field and
+disappears in the steady field experiments. A theoretical analysis using exact
+diagonalization yields J_1=-19K and J_2=6K, for the nearest neighbor and second
+nearest neighbor interactions, respectively. This set of exchange parameters
+explains the very low saturation field and the absence of the plateau in the
+thermodynamic equilibrium as well as the two-peak feature in the magnetic heat
+capacity. Supported by numerical results we argue that a dynamical order by
+disorder phenomenon could explain the transient appearance of the 1/3 plateau
+in pulsed field experiments.",0401288v2
+2004-04-26,Glauber dynamics in a single-chain magnet: From theory to real systems,"The Glauber dynamics is studied in a single-chain magnet. As predicted, a
+single relaxation mode of the magnetization is found. Above 2.7 K, the
+thermally activated relaxation time is mainly governed by the effect of
+magnetic correlations and the energy barrier experienced by each magnetic unit.
+This result is in perfect agreement with independent thermodynamical
+measurements. Below 2.7 K, a crossover towards a relaxation regime is observed
+that is interpreted as the manifestation of finite-size effects. The
+temperature dependences of the relaxation time and of the magnetic
+susceptibility reveal the importance of the boundary conditions.",0404620v1
+2005-08-11,Magnetization self-organization in a single-domain ferromagnet subject to a spin current,"The Landau-Lifshitz equation for the magnetization dynamics of a
+single-domain magnetic system is solved using the methods of self-organization.
+The description takes into account the torque due to spin transfer. The
+potential energy of the system includes the uniaxial and easy-plane
+anisotropies, and the Zeeman energy due to an external magnetic field. The
+equilibrium and stationary states are investigated as a function of the spin
+current and external magnetic field. The presented bifurcation diagram allows
+to determine the margins of a neutral stability mode of the equilibrium and
+stationary states for different values of the easy-plane anisotropy constant.
+Using the power spectral density method, the trajectory tracing, Hausdorff
+dimension, and maximum Lyapunov exponent, the dynamics of the phase states in
+an external magnetic field is demonstrated. The analytical transcendent
+equations for switching between different equilibrium states are also obtained,
+proving the importance of phase averaging.",0508280v1
+2005-10-29,First-principles approach to Non-Collinear Magnetism: towards Spin-dynamics,"A description of non-collinear magnetism in the framework of spin-density
+functional theory is presented for the exact exchange energy functional which
+depends explicitly on two-component spinor orbitals. The equations for the
+effective Kohn-Sham scalar potential and magnetic field are derived within the
+optimized effective potential (OEP) framework. With the example of a
+magnetically frustrated Cr monolayer it is shown that the resulting
+magnetization density exhibits much more non-collinear structure than standard
+calculations. Furthermore, a time-dependent generalization of the non-collinear
+OEP method is well suited for an ab-initio description of spin dynamics. We
+also show that the magnetic moments of solids Fe, Co and Ni are well
+reproduced.",0510800v3
+2005-11-04,Synchronized Magnetization Oscillations in F/N/F Nanopillars,"Current-induced magnetization dynamics in a trilayer structure composed of
+two ferromagnetic free layers and a nonmagnetic spacer is examined. Both free
+layers are treated as a monodomain magnetic body with an uniform agnetization.
+The dynamics of the two magnetizations is modeled by modified
+Landau-Lifshitz-Gilbert equations with spin-transfer torque terms. By solving
+the equations simultaneously, we discuss their various solutions in detail. We
+show that there exists the synchronous motion of two magnetizations among the
+various solutions; the magnetizations are resonantly coupled via spin-transfer
+torques and perform precessional motions with the same period. The condition to
+excite the synchronous motion depends on the difference between the intrinsic
+frequencies of the two ferromagnetic free layers as well as the magnitude of
+current.",0511095v1
+2006-04-28,Magnetic neutron scattering in hole doped cuprate superconductors,"A review is presented of the static and dynamic magnetic properties of
+hole-doped cuprate superconductors measured with neutron scattering. A wide
+variety of experiments are described with emphasis on the monolayer
+La_{2-x}(Sr,Ba)_{x}CuO_{4} and bilayer YBa_{2}Cu_{3}O_{6+x} cuprates. At zero
+hole doping, both classes of materials are antiferromagnetic insulators with
+large superexchange constants of J > 100 meV. For increasing hole doping, the
+cuprates become superconducting at a critical hole concentration of
+x_{c}=0.055. The development of new instrumentation at neutron beam sources
+coupled with the improvement in materials has lead to a better understanding of
+these materials and the underlying spin dynamics over a broad range of hole
+dopings. We will describe how the spin dispersion changes across the insulating
+to superconducting boundary as well as the static magnetic properties which are
+directly coupled with the superconductivity. Experiments directly probing the
+competing magnetic and superconducting order parameters involving magnetic
+fields, impurity doping, and structural order will be examined. Correlations
+between superconductivity and magnetism will also be discussed.",0604667v1
+2004-06-26,Two-fluid magnetic island dynamics in slab geometry: II - Islands interacting with resistive walls or static external resonant magnetic perturbations,"The dynamics of a propagating magnetic island interacting with a resistive
+wall or a static external magnetic perturbation is investigated using
+two-fluid, drift-MHD theory in slab geometry. In both cases, the island
+equation of motion is found to take exactly the same form as that predicted by
+single-fluid MHD theory. Three separate ion polarization terms are found in the
+Rutherford island width evolution equation. The first is the drift-MHD
+polarization term for an isolated island, and is completely unaffected by
+interaction with a wall or magnetic perturbation. Next, there is the
+polarization term due to interaction with a wall or magnetic perturbation which
+is predicted by single-fluid MHD theory. Finally, there is a hybrid of the
+other two polarization terms. The sign of this term depends on many factors.
+However, under normal conditions, it is stabilizing if the unperturbed island
+propagates in the ion diamagnetic direction (in the lab. frame), and
+destabilizing if it propagates in the electron diamagnetic direction.",0406133v1
+2007-10-29,Buoyancy Instabilities in Weakly Magnetized Low Collisionality Plasmas,"I calculate the linear stability of a stratified low collisionality plasma in
+the presence of a weak magnetic field. Heat is assumed to flow only along
+magnetic field lines. In the absence of a heat flux in the background plasma,
+Balbus (2000) demonstrated that plasmas in which the temperature increases in
+the direction of gravity are buoyantly unstable to convective-like motions (the
+``magnetothermal instability''). I show that in the presence of a background
+heat flux, an analogous instability is present when the temperature decreases
+in the direction of gravity. The instability is driven by the background heat
+flux and the fastest growing mode has a growth time of order the local
+dynamical time. Thus, independent of the sign of the temperature gradient,
+weakly magnetized low collisionality plasmas are unstable on a dynamical time
+to magnetically-mediated buoyancy instabilities. The instability described in
+this paper is predicted to be present in clusters of galaxies at radii from ~
+0.1-100 kpc, where the observed temperature increases outwards. Possible
+consequences for the origin of cluster magnetic fields, ``cooling flows,'' and
+the thermodynamics of the intercluster medium are briefly discussed.",0710.5521v1
+2007-11-13,On the existence of a reverse shock in magnetized GRB ejecta,"The role of magnetic fields in gamma-ray burst (GRB) flows remains
+controversial. The study of the early afterglow phases and, in particular, of
+the reverse shock dynamics and associated emission offers a promising probe of
+the magnetization of the ejecta. In this paper, we derive the conditions for
+the existence of a reverse shock in arbitrarily magnetized ejecta that
+decelerate and interact with the circumburst medium. Both constant and
+wind-like density profiles are considered. We show, in contrast to previous
+estimates, that ejecta with magnetization larger than unity are not crossed by
+a reverse shock for a large fraction of the parameter space relevant to GRB
+flows. Allowing for shell spreading, there is always a relativistic or mildly
+relativistic reverse shock forming in sigma_o < 0.3 ejecta. From this, we
+conclude that the paucity of optical flashes, believed to be a distinctive
+signature of a reverse shock, may be explained by the existence of dynamically
+important magnetic fields in the ejecta.",0711.1980v2
+2007-11-23,Dynamics of magnetic topological solitons in soft magnetic nanostripes,"The motions of domain walls driven by magnetic field in soft magnetic
+nanostripes were calculated. The domain walls reveal steady motions in the low
+fields and oscillations of their internal structure above a critical field. A
+developed soliton model of the walls explains its dynamics by the motions of a
+limited number of magnetic topological solitons such as vortex and antivortex.
+We predict the reduced wall velocity and critical field in the low-field
+regime, and increased wall-oscillation frequency in nanostripes, compared to 1D
+Walker solution for bulk magnets. The critical field and velocity are
+determined by the nanostripe sizes, whereas the oscillation frequency depends
+only on the field strength.",0711.3680v1
+2008-08-18,The dynamics of internal working surfaces in MHD jets,"The dynamical effects of magnetic fields in models of radiative, Herbig-Haro
+(HH) jets have been studied in a number of papers. For example, magnetized,
+radiative jets from variable sources have been studied with axisymmetric and 3D
+numerical simulations. In this paper, we present an analytic model describing
+the effect of a toroidal magnetic field on the internal working surfaces that
+result from a variability in the ejection velocity. We find that for parameters
+appropriate for HH jets the forces associated with the magnetic field dominate
+over the gas pressure force within the working surfaces. Depending on the ram
+pressure radial cross section of the jet, the magnetic field can produce a
+strong axial pinch, or, alternatively, a broadening of the internal working
+surfaces. We check the validity of the analytic model with axisymmetric
+numerical simulations of variable, magnetized jets.",0808.2346v1
+2009-01-06,Analytic models of heterogenous magnetic fields for liquid metal flow simulations,"A physically consistent approach is considered for defining an external
+magnetic field as needed in computational fluid dynamics problems involving
+magnetohydrodynamics (MHD). The approach results in simple analytical formulae
+that can be used in numerical studies where an inhomogeneous magnetic field
+influences a liquid metal flow. The resulting magnetic field is divergence and
+curl-free, and contains two components and parameters to vary. As an
+illustration, the following examples are considered: peakwise, stepwise,
+shelfwise inhomogeneous magnetic fields, and the field induced by a solenoid.
+Finally, the impact of the streamwise magnetic field component is shown
+qualitatively to be significant for rapidly changing fields.",0901.0624v2
+2009-03-05,Signature of magnetic monopole and Dirac string dynamics in spin ice,"Magnetic monopoles have eluded experimental detection since their prediction
+nearly a century ago by Dirac. Recently it has been shown that classical
+analogues of these enigmatic particles occur as excitations out of the
+topological ground state of a model magnetic system, dipolar spin ice. These
+quasi-particle excitations do not require a modification of Maxwell's
+equations, but they do interact via Coulombs law and are of magnetic origin. In
+this paper we present an experimentally measurable signature of monopole
+dynamics and show that magnetic relaxation measurements in the spin ice
+material $Dy_{2}Ti_{2}O_{7}$ can be interpreted entirely in terms of the
+diffusive motion of monopoles in the grand canonical ensemble, constrained by a
+network of ""Dirac strings"" filling the quasi-particle vacuum. In a magnetic
+field the topology of the network prevents charge flow in the steady state, but
+there is a monopole density gradient near the surface of an open system.",0903.1074v3
+2009-07-13,A topological gauge field in nanomagnets: spin wave excitations over a slowly moving magnetization background,"We introduce a topological gauge vector potential which influences spin wave
+excitations over arbitrary non-uniform, slowly moving magnetization
+distribution. The time-component of the gauge potential plays a principal role
+in magnetization dynamics, whereas its spatial components can be often
+neglected for typical magnetic nanostructures. As an example, we consider spin
+modes excited in the vortex state magnetic dots. It is shown that the vortex/
+spin wave interaction can be described as a consequence of the gauge field
+arising due to non uniform moving vortex magnetization distribution. The
+coupled equations of motion of the vortex and spin waves are solved within
+small excitation amplitude approximation. The model yields a giant frequency
+splitting of the spin wave modes having non-zero overlapping with the vortex
+mode as well as a finite vortex mass of dynamical origin.",0907.2226v1
+2009-08-26,Influence of an external magnetic field on forced turbulence in a swirling flow of liquid metal,"We report an experimental investigation on the influence of an external
+magnetic field on forced 3D turbulence of liquid gallium in a closed vessel. We
+observe an exponential damping of the turbulent velocity fluctuations as a
+function of the interaction parameter N (ratio of Lorentz force over inertial
+terms of the Navier-Stokes equation). The flow structures develop some
+anisotropy but do not become bidimensional. From a dynamical viewpoint, the
+damping first occurs homogeneously over the whole spectrum of frequencies. For
+larger values of N, a very strong additional damping occurs at the highest
+frequencies. However, the injected mechanical power remains independent of the
+applied magnetic field. The simultaneous measurement of induced magnetic field
+and electrical potential differences shows a very weak correlation between
+magnetic field and velocity fluctuations. The observed reduction of the
+fluctuations is in agreement with a previously proposed mechanism for the
+saturation of turbulent dynamos and with the order of magnitude of the Von
+Karman Sodium dynamo magnetic field.",0908.3821v1
+2009-12-18,Dynamic correlated Cu(2) magnetic moments in superconducting YBa_2(Cu_0.96Co_0.04)_3O_y (y ~ 7),"We have examined the magnetic properties of superconducting
+YBa_2(Cu_0.96Co_0.04)_3O_y (y ~ 7, T_sc = 65 K) using elastic neutron
+scattering and muon spin relaxation (muSR) on single crystal samples. The
+elastic neutron scattering measurements evidence magnetic reflections which
+correspond to a commensurate antiferromagnetic Cu(2) magnetic structure with an
+associated Neel temperature T_N ~ 400 K. This magnetically correlated state is
+not evidenced by the muSR measurements. We suggest this apparent anomaly arises
+because the magnetically correlated state is dynamic in nature. It fluctuates
+with rates that are low enough for it to appear static on the time scale of the
+elastic neutron scattering measurements, whereas on the time scale of the muSR
+measurements, at least down to ~ 50 K, it fluctuates too fast to be detected.
+The different results confirm the conclusions reached from work on equivalent
+polycrystalline compounds: the evidenced fluctuating, correlated Cu(2) moments
+coexist at an atomic level with superconductivity.",0912.3637v1
+2010-01-19,Dynamical behaviour of the `beads' along the magnetic field lines near a rotating black hole,"The elements of the cold magnetic driven flows behave like beads on the
+magnetic field line. The inclination of the field lines at the surface of the
+disc plays a crucial role on the nature of the magnetically driven outflow. For
+the non-relativistic case, a centrifugally driven outflow of matter from the
+disc is possible, if the poloidal component of the magnetic field makes an
+angle of less than a critical 60 degrees with the disc surface. The collimated
+flows ejected from active galactic nuclei may probably start from the region
+near the black hole. We investigate the dynamical behavior of the 'beads' on
+the magnetic field line start from the disc near a black hole. It is found that
+the critical angle becomes larger than 60 degrees for the rotating black hole
+case (close to 90 degrees for a=1), which may imply that the flows are easy
+accelerated in the inner edge of the disk surrounding a rotating black hole.",1001.3201v1
+2010-03-09,Effect of induced shape anisotropy on magnetic properties of ferromagnetic cobalt nanocubes,"We report on the synthesis of ferromagnetic cobalt nanocubes of various sizes
+using thermal pyrolysis method and the effect of shape anisotropy on the static
+and dynamic magnetic properties were studied. Shape anisotropy of approximately
+10 % was introduced in nanocubes by making nanodiscs using a linear chain amine
+surfactant during synthesis process. It has been observed that, ferromagnetism
+persisted above room temperature and a sharp drop in magnetic moment at low
+temperatures in zero-field cooled magnetization may be associated with the spin
+disorder due to the effective anisotropy present in the system. Dynamic
+magnetic properties were studied using RF transverse susceptibility
+measurements at different temperatures and the singularities due to anisotropy
+fields were probed at low temperatures. Symmetrically located broad peaks are
+observed in the frozen state at the effective anisotropy fields and the peak
+structure is strongly affected by shape anisotropy and temperature.
+Irrespective of size the shape anisotropy gave rise to higher coercive fields
+and larger transverse susceptibility ratio at all temperatures. The role of
+shape anisotropy and the size of the particles on the observed magnetic
+behaviour were discussed.",1003.1855v1
+2010-04-01,Strong coupling to magnetic fluctuations in the charge dynamics of Fe-based superconductors,"We present a comprehensive comparison of the infrared charge response of two
+systems, characteristic of classes of the 122 pnictide (SrFe2As2) and 11
+chalcogenide (Fe_1.087Te) Fe compounds with magnetically-ordered ground states.
+In the 122 system, the magnetic phase shows a decreased plasma frequency and
+scattering, and associated appearance of strong mid-infrared features. The 11
+system, with a different magnetic ordering pattern, also shows decreased
+scattering, but an increase in the plasma frequency, while no clear
+mid-infrared features appear below the ordering temperature. We suggest how
+this marked contrast can be understood in terms of the diverse magnetic
+ordering patterns of the ground state, and conclude that while the high
+temperature phases of these systems are similar, the magnetic ordering strongly
+affects the charge dynamical response. In addition, we propose an optical
+absorption mechanism which appears to be consistent with information gained
+from several different experiments.",1004.0111v1
+2010-06-04,Magnetization dynamics of a CrO$_2$ grain studied by micro-Hall magnetometry,"Micro-Hall magnetometry is employed to study the magnetization dynamics of a
+single, micron-size CrO$_2$ grain. With this technique we track the motion of a
+single domain wall, which allows us to probe the distribution of imperfections
+throughout the material. An external magnetic field along the grain's easy
+magnetization direction induces magnetization reversal, giving rise to a series
+of sharp jumps in magnetization. Supported by micromagnetic simulations, we
+identify the transition to a state with a single cross-tie domain wall, where
+pinning/depinning of the wall results in stochastic Barkhausen jumps.",1006.0889v1
+2010-06-29,Spin dynamics of current driven single magnetic adatoms and molecules,"A scanning tunneling microscope can probe the inelastic spin excitations of a
+single magnetic atom in a surface via spin-flip assisted tunneling in which
+transport electrons exchange spin and energy with the atomic spin. If the
+inelastic transport time, defined as the average time elapsed between two
+inelastic spin flip events, is shorter than the atom spin relaxation time, the
+STM current can drive the spin out of equilibrium. Here we model this process
+using rate equations and a model Hamiltonian that describes successfully spin
+flip assisted tunneling experiments, including a single Mn atom, a Mn dimer and
+Fe Phthalocyanine molecules. When the STM current is not spin polarized, the
+non-equilibrium spin dynamics of the magnetic atom results in non-monotonic
+$dI/dV$ curves. In the case of spin polarized STM current, the spin orientation
+of the magnetic atom can be controlled parallel or anti-parallel to the
+magnetic moment of the tip. Thus, spin polarized STM tips can be used both to
+probe and to control the magnetic moment of a single atom.",1006.5608v1
+2010-08-31,Influence of Magnetic Helicity in MHD,"Observations have shown that the Sun's magnetic field has helical structures.
+The helicity content in magnetic field configurations is a crucial constraint
+on the dynamical evolution of the system. Since helicity is connected with the
+number of links we investigate configurations with interlocked magnetic flux
+rings and one with unlinked rings. It turns out that it is not the linking of
+the tubes which affects the magnetic field decay, but the content of magnetic
+helicity.",1008.5235v2
+2010-09-17,Time resolved X-ray Resonant Magnetic Scattering in reflection geometry,"We present a new setup to measure element-selective magnetization dynamics
+using the ALICE chamber (RSI \textbf{74}, 4048 (2003)) at the BESSY II
+synchrotron at the Helmholtz-Zentrum Berlin. A magnetic field pulse serves as
+excitation, and the magnetization precession is probed by element selective
+X-ray Resonant Magnetic Scattering (XRMS). With the use of single bunch
+generated x-rays a temporal resolution well below 100 ps is reached. The setup
+is realized in reflection geometry and enables investigations of thin films
+described here, multilayers, and laterally structured samples. The combination
+of the time resolved setup with a cryostat in the ALICE chamber will allow to
+conduct temperature-dependent studies of precessional magnetization dynamics
+and of damping constants over a large temperature range and for a large variety
+of systems in reflection geometry.",1009.3389v1
+2010-11-21,Optical detection of spin transport in non-magnetic metals,"We determine the dynamic magnetization induced in non-magnetic metal wedges
+composed of silver, copper and platinum by means of Brillouin light scattering
+(BLS) microscopy. The magnetization is transferred from a ferromagnetic
+Ni80Fe20 layer to the metal wedge via the spin pumping effect. The spin pumping
+efficiency can be controlled by adding an insulating but transparent interlayer
+between the magnetic and non-magnetic layer. By comparing the experimental
+results to a dynamical macroscopic spin-transport model we determine the
+transverse relaxation time of the pumped spin current which is much smaller
+than the longitudinal relaxation time.",1011.4656v2
+2010-12-14,The Magnetic Field of the Milky Way Galaxy,"Cosmic magnetic fields are an integral component of the interstellar medium
+(ISM), having influence on scales ranging from star formation to galactic
+dynamics. While observations of external galaxies offer a `birds-eye-view' of
+magnetic fields within galaxies, it is equally important to explore the
+magnetic field of our own Milky Way Galaxy, which offers a more detailed,
+albeit more complicated view. Over the past decade there has been a significant
+increase in interest in the Galactic magnetic field, fueled largely by
+innovations developed through the Canadian Galactic Plane Survey. In this
+paper, I review the current state of understanding of the Galactic magnetic
+field, and discuss briefly new and future observations that will provide
+exciting new insights about the field.",1012.2932v1
+2011-01-26,Domain wall dynamics in a single CrO$_2$ grain,"Recently we have reported on the magnetization dynamics of a single CrO$_2$
+grain studied by micro Hall magnetometry (P. Das \textit{et al.}, Appl. Phys.
+Lett. \textbf{97} 042507, 2010). For the external magnetic field applied along
+the grain's easy magnetization direction, the magnetization reversal takes
+place through a series of Barkhausen jumps. Supported by micromagnetic
+simulations, the ground state of the grain was found to correspond to a flux
+closure configuration with a single cross-tie domain wall. Here, we report an
+analysis of the Barkhausen jumps, which were observed in the hysteresis loops
+for the external field applied along both the easy and hard magnetization
+directions. We find that the magnetization reversal takes place through only a
+few configuration paths in the free-energy landscape, pointing to a high purity
+of the sample. The distinctly different statistics of the Barkhausen jumps for
+the two field directions is discussed.",1101.5101v1
+2011-03-31,On the effect of rotation on magnetohydrodynamic turbulence at high magnetic Reynolds number,"This article is focused on the dynamics of a rotating electrically conducting
+fluid in a turbulent state. As inside the Earth's core or in various industrial
+processes, a flow is altered by the presence of both background rotation and a
+large scale magnetic field. In this context, we present a set of 3D direct
+numerical simulations of incompressible decaying turbulence. We focus on
+parameters similar to the ones encountered in geophysical and astrophysical
+flows, so that the Rossby number is small, the interaction parameter is large,
+but the Elsasser number, defining the ratio between Coriolis and Lorentz
+forces, is about unity. These simulations allow to quantify the effect of
+rotation and thus inertial waves on the growth of magnetic fluctuations due to
+Alfv\'en waves. Rotation prevents the occurrence of equipartition between
+kinetic and magnetic energies, with a reduction of magnetic energy at
+decreasing Elsasser number {\Lambda}. It also causes a decrease of energy
+transfer mediated by cubic correlations. In terms of flow structure, a decrease
+of {\Lambda} corresponds to an increase in the misalignment of velocity and
+magnetic field.",1103.6236v1
+2011-06-12,Critical Behavior of AC Antiferromagnetic and Ferromagnetic Susceptibilities of a Spin-1/2 Metamagnetic Ising System,"In this study, the temperature variations of the equilibrium and the
+non-equilibrium antiferromagnetic and ferromagnetic susceptibilities of a
+metamagnetic system are examined near the critical point. The kinetic equations
+describing the time dependencies of the total and staggered magnetizations are
+derived by utilizing linear response theory. In order to obtain dynamic
+magnetic relaxation behavior of the system, the stationary solutions of the
+kinetic equations in existence of sinusoidal staggered and physical external
+magnetic fields are performed. In addition, the static and dynamical mean field
+critical exponents are calculated in order to formulate the critical behavior
+of antiferromagnetic and ferromagnetic magnetic response of a metamagnetic
+system. Finally, a comparison of the findings of this study with previous
+theoretical and experimental studies is represented and it is shown that a good
+agreement is found with our results.",1106.2306v1
+2011-06-23,"Dynamics of a magnetic dimer with exchange, dipolar and Dzyalozhinski-Moriya interaction","We investigate the dynamics of a magnetic system consisting of two magnetic
+moments coupled by either exchange, dipole-dipole, or Dzyalozhinski-Moriya
+interaction. We compare the switching mechanisms and switching rates as induced
+by the three couplings. For each coupling and each configuration of the two
+anisotropy axes, we describe the switching modes and, using the kinetic theory
+of Langer, we provide (semi-)analytical expressions for the switching rate. We
+then compare the three interactions with regard to their efficiency in the
+reversal of the net magnetic moment of the dimer. We also investigate how the
+energy barriers vary with the coupling. For the dipole-dipole interaction we
+find that the energy barrier may either increase or decrease with the coupling
+depending on whether the latter is weak or strong. Finally, upon comparing the
+various switching rates, we find that the dipole-dipole coupling leads to the
+slowest magnetic dimer, as far as the switching of its net magnetic moment is
+concerned.",1106.4713v2
+2011-09-15,Waves of magnetic moment and generation of waves by neutron beam in quantum magnetized plasma,"This paper is devoted to studying of dispersion of waves in the magnetized
+plasma with the spin and exploring of new methods of the generation wave in the
+plasma. We consider the dispersion of waves, existed in the plasma in
+consequence of dynamic of the magnetic moments. It is shown there are nine new
+waves in the magnetized plasma because of the magnetic moments dynamic. We show
+there are instabilities at propagation of the neutron beam through the plasma.
+Increments of instabilities caused by neutron beam are calculated. For studying
+of this effects we generalize and use the method of the many-particle quantum
+hydrodynamics. Described processes can play important role at calculation of
+the stability and the safeness of the nuclear reactors and the studying of the
+processes in the atmosphere of the neutron stars.",1109.3335v2
+2011-10-07,Nonlinear Dynamics in a Magnetic Josephson Junction,"We theoretically consider a Josephson junction formed by a ferromagnetic
+spacer with a strong spin-orbit interaction or a magnetic spin valve, i.e., a
+bilayer with one static and one free layer. Electron spin transport facilitates
+a nonlinear dynamical coupling between the magnetic moment and charge current,
+which consists of normal and superfluid components. By phenomenologically
+adding reactive and dissipative interactions (guided by structural and Onsager
+symmetries), we construct magnetic torques and charge pumping, whose
+microscopic origins are also discussed. A stability analysis of our coupled
+nonlinear systems generates a rich phase diagram with fixed points, limit
+cycles, and quasiperiodic states. Our findings reduce to the known phase
+diagrams for current-biased nonmagnetic Josephson junctions, on the one hand,
+and spin-torque driven magnetic films, on the other, in the absence of coupling
+between the magnetic and superconducting order parameters.",1110.1680v1
+2011-10-26,Instability of the origami of a ferrofluid drop in a magnetic field,"Capillary origami is the wrapping of an usual fluid drop by a planar elastic
+membrane due to the interplay between capillary and elastic forces. Here, we
+use a drop of magnetic fluid whose shape is known to strongly depend on an
+applied magnetic field. We study the quasi-static and dynamical behaviors of
+such a magnetic capillary origami. We report the observation of an overturning
+instability that the origami undergoes at a critical magnetic field. This
+instability is triggered by an interplay between magnetic and gravitational
+energies in agreement with the theory presented here. Additional effects of
+elasticity and capillarity on this instability are also discussed.",1110.5768v1
+2012-03-05,A dynamical magnetosphere model for periodic Halpha emission from the slowly rotating magnetic O star HD191612,"The magnetic O-star HD191612 exhibits strongly variable, cyclic Balmer line
+emission on a 538-day period. We show here that its variable Halpha emission
+can be well reproduced by the rotational phase variation of synthetic spectra
+computed directly from full radiation magneto-hydrodynamical simulations of a
+magnetically confined wind. In slow rotators such as HD191612, wind material on
+closed magnetic field loops falls back to the star, but the transient
+suspension of material within the loops leads to a statistically overdense, low
+velocity region around the magnetic equator, causing the spectral variations.
+We contrast such ""dynamical magnetospheres"" (DMs) with the more steady-state
+""centrifugal magnetospheres"" of stars with rapid rotation, and discuss the
+prospects of using this DM paradigm to explain periodic line emission from also
+other non-rapidly rotating magnetic massive stars.",1203.1050v1
+2012-06-22,Ultrasonic triggering of giant magnetocaloric effect in MnAs thin films,"Mechanical control of magnetic properties in magnetostrictive thin films
+offers the unexplored opportunity to employ surface wave acoustics in such a
+way that acoustic triggers dynamic magnetic effects. The strain-induced
+modulation of the magnetic anisotropy can play the role of a high frequency
+varying effective magnetic field leading to ultrasonic tuning of electronic and
+magnetic properties of nanostructured materials, eventually integrated in
+semiconductor technology. Here, we report about the opportunity to employ
+surface acoustic waves to trigger magnetocaloric effect in
+MnAs(100nm)/GaAs(001) thin films. During the MnAs magnetostructural phase
+transition, in an interval range around room temperature (0{\deg}C -
+60{\deg}C), ultrasonic waves (170 MHz) are strongly attenuated by the phase
+coexistence (up to 150 dB/cm). We show that the giant magnetocaloric effect of
+MnAs is responsible of the observed phenomenon. By a simple anelastic model we
+describe the temperature and the external magnetic field dependence of such a
+huge ultrasound attenuation. Strain-manipulation of the magnetocaloric effect
+could be a further interesting route for dynamic and static caloritronics and
+spintronics applications in semiconductor technology.",1206.5217v1
+2013-10-11,Self-assembling paramagnetic colloids in oscillating magnetic fields,"Many fascinating phenomena such as large-scale collective flows, enhanced
+fluid mixing and pattern formation have been observed in so-called active
+fluids, which are composed of particles that can absorb energy and dissipate it
+into the fluid medium. In order to investigate the role of hydrodynamic
+interactions in the collective behavior of an active fluid, we choose a model
+system: paramagnetic particles submerged in water and activated by an
+oscillating magnetic field. The magnetic field induces magnetic attractions
+among the paramagnetic particles, activating the particles, and injecting
+energy into the fluid. Over many cycles, the particles aggregate together and
+form clusters. In order to form clusters, however, the particles must overcome
+viscous drag. We investigate the relative roles of viscosity and magnetism.
+When the role of viscosity is important, the particles cannot form large
+clusters. But when the role of magnetism is important, the particles rapidly
+form organized, large clusters. Our results shown in this fluid dynamics video
+suggest that viscous stresses slow the clustering rate and decrease the size of
+clusters in a self-assembling colloidal system.",1310.3212v2
+2014-09-25,Tuning the Band Structures of a 1D Width-Modulated Magnonic Crystal by a Transverse Magnetic Field,"Theoretical studies, based on three independent techniques, of the band
+structure of a one-dimensional width-modulated magnonic crystal under a
+transverse magnetic field are reported. The band diagram is found to display
+distinct behaviors when the transverse field is either larger or smaller than a
+critical value. The widths and center positions of bandgaps exhibit unusual
+non-monotonic and large field-tunability through tilting the direction of
+magnetization. Some bandgaps can be dynamically switched on and off by simply
+tuning the strength of such a static field. Finally, the impact of the lowered
+symmetry of the magnetic ground state on the spin-wave excitation efficiency of
+an oscillating magnetic field is discussed. Our finding reveals that the
+magnetization direction plays an important role in tailoring magnonic band
+structures and hence in the design of dynamic spin-wave switches.",1409.7183v1
+2014-12-01,All-optical magnetization switching in ferrimagnetic alloys: deterministic vs thermally activated dynamics,"Using photo-emission electron microscopy with X-ray magnetic circular
+dichroism as a contrast mechanism, new insights into the all-optical
+magnetization switching (AOS) phenomenon in GdFe based rare-earth transition
+metal ferrimagnetic alloys are provided. From a sequence of static images taken
+after single linearly polarized laser pulse excitation, the repeatability of
+AOS can be measured with a correlation coefficient. It is found that low
+coercivity enables thermally activated domain wall motion, limiting in turn the
+repeatability of the switching. Time-resolved measurement of the magnetization
+dynamics reveal that while AOS occurs below and above the magnetization
+compensation temperature $T_\text{M}$, it is not observed in GdFe samples where
+$T_\text{M}$ is absent. Finally, AOS is experimentally demonstrated against an
+applied magnetic field of up to 180 mT.",1412.0396v1
+2015-02-23,The nature of Itinerant Ferromagnetism of SrRuO3 : A DFT+DMFT Study,"We have investigated the temperature (T)-dependent evolution of electronic
+structures and magnetic properties of an itinerant ferromagnet SrRuO3,
+employing the combined scheme of the density functional theory and the
+dynamical mean-field theory (DFT+DMFT). The inclusion of finite dynamical
+correlation effects beyond the DFT well describes not only the incoherent hump
+structure observed in the photoemission experiment but also the T-dependent
+magnetic properties in accordance with experiments. We have shown that the
+magnetization of SrRuO3 evolves with the Stoner behavior below the Curie
+temperature (Tc), reflecting the weak itinerant ferromagnetic behavior, but the
+local residual magnetic moment persists even above Tc, indicating the local
+magnetic moment behavior. We suggest that the ferromagnetism of SrRuO3 has dual
+nature of both weak and local moment limits, even though the magnetism of
+SrRuO3 is more itinerant than that of Fe.",1502.06322v1
+2015-03-04,"Electromagnetic Torques, Precession and Evolution of Magnetic Inclination of Pulsars","We present analytic calculations of the electromagnetic torques acting on a
+magnetic neutron star rotating in vacuum, including near-zone torques
+associated with the inertia of dipole and quadrupole magnetic fields. We
+incorporate these torques into the rotational dynamics of a rigid-body neutron
+star, and show that the effects of the inertial torque can be understood as a
+modification of the moment of inertia tensor of the star. We apply our
+rotational dynamics equation to the Crab pulsar, including intrinsic
+distortions of the star and various electromagnetic torques, to investigate the
+possibility that the counter-alignment of the magnetic inclination angle, as
+suggested by recent observations, could be explained by pulsar precession. We
+find that if the effective principal axis of the pulsar is nearly aligned with
+either the magnetic dipole axis or the rotation axis, then precession may
+account for the observed counter-alignment over decade timescales. Over the
+spindown timescale of the pulsar, the magnetic inclination angle always
+decreases.",1503.01486v2
+2015-05-29,Time-resolved imaging of pulse-induced magnetization reversal with a microwave assist field,"The reversal of the magnetization under the influence of a field pulse has
+been previously predicted to be an incoherent process with several competing
+phenomena such as domain wall relaxation, spin wave-mediated instability
+regions, and vortex-core mediated reversal dynamics. However, there has been no
+study on the direct observation of the switching process with the aid of a
+microwave signal input. We report a time-resolved imaging study of
+magnetization reversal in patterned magnetic structures under the influence of
+a field pulse with microwave assistance. The microwave frequency is varied to
+demonstrate the effect of resonant microwave-assisted switching. We observe
+that the switching process is dominated by spin wave dynamics generated as a
+result of magnetic instabilities in the structures, and identify the
+frequencies that are most dominant in magnetization reversal.",1505.07936v1
+2015-08-10,Timelike geodesics of a modified gravity black hole immersed in an axially symmetric magnetic field,"We investigate the dynamics of a neutral and a charged particle around a
+black hole in modified gravity immersed in magnetic field. Our focus is on the
+scalar-tensor-vector theory as modified gravity. We are interested to explore
+the conditions on the energy of the particle under which it can escape to
+infinity after collision with another neutral particle in the vicinity of the
+black hole. We calculate escape velocity of particle orbiting in the innermost
+stable circular orbit (ISCO) after the collision. We study the effects of
+modified gravity on the dynamics of particles. Further we discuss how the
+presence of magnetic field in the vicinity of black hole, effects the motion of
+the orbiting particle. We show that the stability of ISCO increases due to
+presence of magnetic field. It is observed that a particle can go arbitrary
+close to the black hole due to presence of magnetic field. Furthermore ISCO for
+black hole is more stable as compared with Schwarzschild black hole. We also
+discuss the Lyapunov exponent and the effective force acting on the particle in
+the presence of magnetic field.",1508.02123v1
+2015-08-26,Non-circular skyrmion and its anisotropic response in thin films of chiral magnets under tilted magnetic field,"We study the equilibrium and dynamical properties of skyrmions in thin films
+of chiral magnets with oblique magnetic field. The shape of an individual
+skyrmion is non-circular and the skyrmion density decreases with the tilt angle
+from the normal of films. As a result, the interaction between two skyrmions
+depends on the relative angle between them in addition to their separation. The
+triangular lattice of skyrmions under a perpendicular magnetic field is
+distorted into a centered rectangular lattice for a tilted magnetic field. For
+a low skyrmion density, skyrmions form a chain like structure. The dynamical
+response of the non-circular skyrmions depends on the direction of external
+currents.",1508.06361v1
+2015-11-03,Nd2Sn2O7: an all-in-all-out pyrochlore magnet with no divergence-free field and anomalously slow paramagnetic spin dynamics,"We report measurements performed on a polycrystalline sample of the
+pyrochlore compound Nd2Sn2O7. It undergoes a second order magnetic phase
+transition at Tc ~ 0.91 K to a noncoplanar all-in-all-out magnetic structure of
+the Nd3+ magnetic moments. The thermal behavior of the low temperature specific
+heat fingerprints excitations with linear dispersion in a three-dimensional
+lattice. The temperature independent spin-lattice relaxation rate measured
+below Tc and the anomalously slow paramagnetic spin dynamics detected up to ~
+30 Tc are suggested to be due to magnetic short-range correlations in
+unidimensional spin clusters, i.e., spin loops. The observation of a
+spontaneous field in muon spin relaxation measurements is associated with the
+absence of a divergence-free field for the ground state of an all-in-all-out
+pyrochlore magnet as predicted recently.",1511.00987v1
+2015-12-17,A self-consistent spin-diffusion model for micromagnetics,"We propose a three-dimensional micromagnetic model that dynamically solves
+the Landau-Lifshitz-Gilbert equation coupled to the full spin-diffusion
+equation. In contrast to previous methods, we solve for the magnetization
+dynamics and the electric potential in a self-consistent fashion. This
+treatment allows for an accurate description of magnetization dependent
+resistance changes. Moreover, the presented algorithm describes both spin
+accumulation due to smooth magnetization transitions and due to material
+interfaces as in multilayer structures. The model and its finite-element
+implementation are validated by current driven motion of a magnetic vortex
+structure. In a second experiment, the resistivity of a magnetic multilayer
+structure in dependence of the tilting angle of the magnetization in the
+different layers is investigated. Both examples show good agreement with
+reference simulations and experiments respectively.",1512.05519v4
+2016-01-06,Dynamic response of an artificial square spin ice,"Magnetization dynamics in an artificial square spin-ice lattice made of
+Ni80Fe20 with magnetic field applied in the lattice plane is investigated by
+broadband ferromagnetic resonance spectroscopy. The experimentally observed
+dispersion shows a rich spectrum of modes corresponding to different
+magnetization states. These magnetization states are determined by exchange and
+dipolar interaction between individual islands, as is confirmed by a
+semianalytical model. In the low field regime below 400 Oe a hysteretic
+behavior in the mode spectrum is found. Micromagnetic simulations reveal that
+the origin of the observed spectra is due to the initialization of different
+magnetization states of individual nanomagnets. Our results indicate that it
+might be possible to determine the spin-ice state by resonance experiments and
+are a first step towards the understanding of artificial geometrically
+frustrated magnetic systems in the high-frequency regime.",1601.01219v1
+2016-03-30,Exchange symmetry and low-frequency asymptotics of Green's functions in spin s=1 magnets,"The paper contains the description of the dynamics of non-equilibrium
+processes of spin $s=1$ magnets in an external variable field. We have obtained
+nonlinear dynamic equations with sources and calculated low-frequency
+asymptotics of two-time Green's functions for ferro- and quadrupole magnetic
+states with $SO(3)$ and $SU(3)$ exchange symmetry of the Hamiltonian. It has
+been shown that for ferro- and quadrupole magnetic states singularities of
+Green's functions in wave vectors $1/k$, $1/k^2$ and frequencies $1/\omega,
+1/\omega^2$ have well-known character. We set the exact form of the magnetic
+anisotropy of these Green's functions. For states with $SO(3)$ symmetry of the
+exchange Hamiltonian, we have found Green's functions with quadrupole degrees
+of freedom and compared them with Green's functions of magnets having exchange
+$SU(3)$ symmetry.",1603.09204v2
+2016-06-15,Driving Skyrmions in a Composite Bilayer,"Magnetic Skyrmions and multiferroics are the most interesting objects in
+nanostructure science that have great potential in future spin-electronic
+technology. The study of multiferroic Skyrmions has attracted much interest in
+recent years. This article reports magnetic Bloch Skyrmions induced by an
+electric driving field in a composite bilayer (chiral-magnetic/ferroelectric
+bilayer) lattice. By using the spin dynamics method, we use a classical
+magnetic spin model and an electric pseudospin model, which are coupled by a
+strong magnetoelectric coupling in the dynamical simulations. Interestingly, we
+observe some skyrmion-like objects in the electric component either during the
+switching process or by applying a magnetic field, which is due to the
+connection between the electric and the magnetic structures.",1606.04595v3
+2016-06-23,Spin-Hall nano-oscillator with oblique magnetization and Dzyaloshinskii-Moriya interaction as generator of skyrmions and nonreciprocal spin-waves,"Spin-Hall oscillators are promising sources of spin-wave signals for
+magnonics applications, and can serve as building blocks for magnonic logic in
+ultralow power computation devices. Here, we analytically and micromagnetically
+study magnetization dynamics excited in a Spin-Hall oscillator with oblique
+magnetization when the spin-Hall effect and interfacial Dzyaloshinskii-Moriya
+interaction act simultaneously. Our key results are (i) excitation of
+nonreciprocal spin-waves propagating perpendicularly to the in-plane projection
+of the static magnetization, (ii) skyrmions generation by pure spin-current,
+(iii) excitation of a new spin-wave mode with a spiral spatial profile
+originating from a gyrotropic rotation of a dynamical skyrmion. These results
+demonstrate that Spin-Hall oscillators can be used as generators of magnetic
+skyrmions and different types of propagating spin-waves for magnetic data
+storage and signal processing applications.",1606.07280v1
+2016-08-11,Parametric study of the solar wind interaction with the Hermean magnetosphere for a weak interplanetary magnetic field,"The aim of this study is to simulate the interaction of the solar wind with
+the Hermean magnetosphere when the interplanetary magnetic field is weak,
+performing a parametric study for all the range of hydrodynamic values of the
+solar wind predicted on Mercury for the ENLIL + GONG WSA + Cone SWRC model:
+density from $12$ to $180$ cm$^{-3}$, velocity from $200$ to $500$ km/s and
+temperatures from $2 \cdot 10^4$ to $18 \cdot 10^4$ K, and compare the results
+with a real MESSENGER orbit as reference case. We use the code PLUTO in
+spherical coordinates and an asymmetric multipolar expansion for the Hermean
+magnetic field. The study shows for all simulations a stand off distance larger
+than the Mercury radius and the presence of close magnetic field lines on the
+day side of the planet, so the dynamic pressure of the solar wind is not high
+enough to push the magnetopause on the planet surface if the interplanetary
+magnetic field is weak. The simulations with large dynamic pressure lead to a
+large compression of the Hermean magnetic field modifying its topology in the
+inner magnetosphere as well as the plasma flows from the magnetosheath towards
+the planet surface.",1608.03606v1
+2016-10-14,Nambu mechanics for stochastic magnetization dynamics,"The Landau-Lifshitz-Gilbert (LLG) equation describes the dynamics of a damped
+magnetization vector that can be understood as a generalization of Larmor spin
+precession. The LLG equation cannot be deduced from the Hamiltonian framework,
+by introducing a coupling to a usual bath, but requires the introduction of
+additional constraints. It is shown that these constraints can be formulated
+elegantly and consistently in the framework of dissipative Nambu mechanics.
+This has many consequences for both the variational principle and for
+topological aspects of hidden symmetries that control conserved quantities. We
+particularly study how the damping terms of dissipative Nambu mechanics affect
+the consistent interaction of magnetic systems with stochastic reservoirs and
+derive a master equation for the magnetization. The proposals are supported by
+numerical studies using symplectic integrators that preserve the topological
+structure of Nambu equations. These results are compared to computations
+performed by direct sampling of the stochastic equations and by using closure
+assumptions for the moment equations, deduced from the master equation.",1610.04598v2
+2017-02-13,Voltage-driven charge-mediated fast 180 degree magnetization switching in nanoheterostructure at room temperature,"Voltage-driven 180$^\circ$ magnetization switching without electric current
+provides the possibility for revolutionizing the spintronics. We demonstrated
+the voltage-driven charge-mediated 180$^\circ$ magnetization switching at room
+temperature by combining first-principles calculations and
+temperature-dependent magnetization dynamics simulation. The electric field
+($E$) induced interface charge is found to allow a giant modulation of the
+magnetic anisotropy ($K$) of the nanomagnet. Particularly $K$ is revealed to
+vary linearly with respect to $E$ and the epitaxial strain. Magnetization
+dynamics simulations using the so-obtained $K$ show that both in-plane and
+perpendicular 180$^\circ$ switching can be achieved by $E$ pulses. The
+temperature effect renders the 180$^\circ$ switching as probability events.
+Statistical analysis indicates a fast (around 4 ns) and low-error-probability
+180$^\circ$ switching achievable at room temperature by controlling the
+magnitude of $E$ and the pulse width. The study inspires the rational design of
+miniaturized nanoscale spintronic devices where thermal fluctuation has a great
+impact.",1702.03670v2
+2017-04-07,Effect of picosecond magnetic pulse on dynamics of electron's subbands in semiconductor bilayer nanowire,"We report on possibility of charge current generation in nanowire made of two
+tunnel coupled one-dimensional electron waveguides by means of single magnetic
+pulse lasting up to 20 ps. Existence of interlayer tunnel coupling plays a
+crucial role in the effect described here as it allows for hybridization of the
+wave functions localized in different layers which can be dynamically modified
+by applying a time changeable in-plane magnetic field. Results of
+time-dependent DFT calculations performed for a bilayer nanowire confining many
+electrons show that the effect of such magnetic hybridization relies on tilting
+of electrons' energy subbands, to the left or to the right, depending on a sign
+of time derivative of oscillating magnetic field due to the Faraday law.
+Consequently, the tilted subbands become a source of charge flow along the
+wire. Strength of such magneto-induced current oscillations may achieve even
+$0.6\mu\textrm{A}$ but it depends on duration of magnetic pulse as well as on
+charge density confined in nanowire which has to be unequally distributed
+between both transport layers to observe this effect.",1704.02150v1
+2017-06-02,Power Loss for a Periodically Driven Ferromagnetic Nanoparticle in a Viscous Fluid: the Finite Anisotropy Aspects,"The joint magnetic and mechanical motion of a ferromagnetic nanoparticle in a
+viscous fluid is considered within the dynamical approach. The equation based
+on the total momentum conservation law is used for the description of the
+mechanical rotation, while the modified Landau-Lifshitz-Gilbert equation is
+utilized for the description of the internal magnetic dynamics. The exact
+expressions for the particles trajectories and the power loss are obtained in
+the linear approximation. The comparison with the results of other widespread
+approaches, such as the model of fixed particle and the model of frozen
+magnetic moment, is performed. It is established that in the small oscillations
+mode the damping precession of the nanopartile magnetic moment is the main
+channel of energy dissipation, but the motion of the nanoparticle easy axis can
+significantly influence the value of the resulting power loss.",1706.00777v2
+2017-06-14,Broadband conversion of microwaves into propagating spin waves in patterned magnetic structures,"We have used time-resolved scanning Kerr microscopy (TRSKM) and micromagnetic
+simulations to demonstrate that, when driven by spatially uniform microwave
+field, the edges of patterned magnetic samples represent both efficient and
+highly tunable sources of propagating spin waves. The excitation is due to the
+local enhancement of the resonance frequency induced by the non-uniform dynamic
+demagnetizing field generated by precessing magnetization aligned with the
+edges. Our findings represent a crucial step forward in the design of nanoscale
+spin-wave sources for magnonic architectures, and are also highly relevant to
+the understanding and interpretation of magnetization dynamics driven by
+spatially-uniform magnetic fields in patterned magnetic samples.",1706.04409v2
+2017-10-30,Dissipated power within a turbulent flow forced homogeneously by magnetic particles,"We report measurements of global dissipated power within a turbulent flow
+homogeneously forced at small scale by a new forcing technique. The forcing is
+random in both time and space within the fluid by using magnetic particles in
+an alternating magnetic field. By measuring the growth rate of the fluid
+temperature, we show how the dissipated power is governed by the external
+control parameters (magnetic field, and number N of particles). We
+experimentally found that the mean dissipated power scales linearly with these
+parameters, as expected from the magnetic injected power scalings. These
+experimental results are well described by simple scaling arguments showing
+that the main origins of the energy dissipation are due to viscous turbulent
+friction of particles within the fluid and to the inelasticity of collisions.
+Finally, by measuring the particle collision statistics, we also show that the
+particle velocity is independent of N, and is only fixed by the magnetic
+""thermostat"".",1710.10935v1
+2017-12-06,Dynamic quantum kagome ice,"The search for two dimensional quantum spin liquids, exotic magnetic states
+with an entangled ground state remaining disordered down to zero temperature,
+has been a great challenge in frustrated magnetism during the last decades.
+Recently, fractionalized excitations, called spinons, emerging from these
+states, have been evidenced in kagome and triangular antiferromagnets. In
+contrast, quantum ferromagnetic spin liquids in two dimensions, namely quantum
+kagome ices, have been less investigated, yet their classical counterparts
+exhibit amazing properties, magnetic monopole crystals as well as magnetic
+fragmentation. Here we show that, by applying a magnetic field on the
+pyrochlore oxide Nd$_2$Zr$_2$O$_7$, which has been shown to develop three
+dimensional quantum magnetic fragmentation in zero field, we are able to reduce
+the dimension of the system and to create a dynamic kagome ice state. Our
+results open the way to the observation of the quantum kagome ice state which
+was recently investigated theoretically.",1712.02418v2
+2017-12-10,Magnetic field gradient driven dynamics of isolated skyrmions and antiskyrmions in frustrated magnets,"The study of skyrmion/antiskyrmion motion in magnetic materials is very
+important in particular for the spintronics applications. In this work, we
+study the dynamics of isolated skyrmions and antiskyrmions in frustrated
+magnets driven by magnetic field gradient, using the Landau-Lifshitz-Gilbert
+simulations on the frustrated classical Heisenberg model on the triangular
+lattice. A Hall-like motion induced by the gradient is revealed in bulk system,
+similar to that in the well-studied chiral magnets. More interestingly, our
+work suggests that the lateral confinement in nano-stripes of the frustrated
+system can completely suppress the Hall motion and significantly speed up the
+motion along the gradient direction. The simulated results are well explained
+by the Thiele theory. It is demonstrated that the acceleration of the motion is
+mainly determined by the Gilbert damping constant, which provides useful
+information for finding potential materials for skyrmion-based spintronics.",1712.03550v1
+2018-02-12,Easy-Plane Magnetic Strip as a Long Josephson Junction,"Spin-torque-biased magnetic dynamics in an easy-plane ferromagnet (EPF) is
+theoretically studied in the presence of a weak in-plane anisotropy. While this
+anisotropy spoils U(1) symmetry thereby quenching the conventional spin
+superfluidity, we show that the system instead realizes a close analog of a
+long Josephson junction (LJJ) model. The traditional magnetic-field and
+electric-current controls of the latter map respectively onto the symmetric and
+antisymmetric combinations of the out-of-plane spin torques applied at the ends
+of the magnetic strip. This suggests an alternative route towards realizations
+of superfluid-like transport phenomena in insulating magnetic systems. We study
+spin-torque-biased phase diagram, providing an analytical solution for static
+multidomain phases in the EPF. We adapt an existing self-consistency method for
+the LJJ to develop an approximate solution for the EPF dynamics. The LJJ-EPF
+mapping allows us to envision superconducting circuit functionality at elevated
+temperatures. The results apply equally to antiferromagnets with suitable
+effective free energy in terms of the N\'{e}el order instead of magnetization.",1802.04229v1
+2018-05-13,Steady and dynamic magnetic phase transitions in interacting quantum dots arrays coupled with leads,"We apply the Hubbard model, non-equilibrium Green's function (NEGF) theory,
+exact diagonalization (ED) and the hierarchical equations of motion (HEOM)
+method to investigate abundant magnetic phase transitions in the 1D interacting
+quantum dots arrays (QDA) sandwiched by non-interaction leads. The spin
+polarization phase transitions are firstly studied with a mean-field
+approximation. The many-body calculation of the ED method is then used to
+verify such transitions. We find with the weak device-leading couplings, the
+anti-ferromagnetic (AF) state only exists in the uniform odd-numbered QDA or
+the staggered-hopping QDA systems. With increasing the coupling strength or the
+bias potentials, there exists the magnetism-to non-magnetism phase transition.
+With the spin-resolved HEOM method we also investigate the detailed dynamic
+phase transition process of these lead-QDA-lead systems.",1805.04939v1
+2018-05-27,Integer quantum Hall conductivity and longitudinal conductivity in silicene under the electric field and magnetic field,"We investigate the integer Hall conductivity and longitudinal conductivity of
+silicene under the magnetic field, electric field, and exchange field in this
+letter. We focus not only on the low-temperature and $\delta$-function
+impurities (i.e., independent of the scattering momentum) case, which only
+exist the intra-Landau level transition, but also on the case of inter-Landau
+level transition which also with the non-elastic scattering. The resulting
+longitudinal conductivity is very different with the intra-Landau level one at
+low-temperature. The exprssions of the Hall conductivity, longitudinal
+conductivity, valley contributed Hall conductivity, and the spin or valley Hall
+conductivity, are deduced in this letter. We also compute the dynamical
+polarization under the magnetic field which is a important quantity and has
+many exciting and novel properties, and with the screened scattering due to the
+charged impurities. The polarization function here is also related to the
+Landau level index under the magnetic field, and shows step-like feature rather
+than the logarithmically divergenas which appears for the zero-magnetic field
+case, and it's also naturally related to the conductivity in silicene. The
+generalized Laguerre polynomial is used in both the longitudinal conductivity
+and dynamical polarization function under magnetic field.",1805.10656v1
+2019-04-05,Common universal behaviors of magnetic domain walls driven by spin-polarized electrical current and magnetic field,"We explore universal behaviors of magnetic domain wall driven by the
+spin-transfer of an electrical current, in a ferromagnetic (Ga,Mn)(As,P) thin
+film with perpendicular magnetic anisotropy. For a current direction transverse
+to domain wall, the dynamics of the thermally activated creep regime and the
+depinning transition are found to be compatible with a self-consistent
+universal description of magnetic field induced domain wall dynamics. This
+common universal behavior, characteristic of the so-called quenched
+Edwards-Wilkinson universality class, is confirmed by a complementary and
+independent analysis of domain wall roughness. However, the tilting of domain
+walls and the formation of facets is produced by the directionality of
+interaction with the current, which acts as a magnetic field only in the
+direction transverse to domain wall.",1904.03047v2
+2019-06-07,Dynamics of position-phase probability density in magnetic resonance,"We consider the behaviour of precessional angle (phase) carried by molecules
+of a diffusing specimen under magnetic fields typical of magnetic resonance
+experiments. An evolution equation for the ensemble of particles is
+constructed, which treats the phase as well as the position of the molecules as
+random variables. This ""position-phase (probability) density"" (PPD) is shown to
+encode solutions to a family of Bloch-Torrey equations (BTE) for transverse
+magnetization density, which is because the PPD is a more fundamental quantity
+than magnetization density; the latter emerges from the former upon averaging.
+The present paradigm represents a conceptual advantage, since the PPD is a true
+probability density subject to Markovian dynamics, rather than an aggregate
+magnetization density whose evolution is less intuitive. We also work out the
+analytical solution for suitable special cases.",1906.04046v1
+2019-10-13,Modelling the photometric variability of magnetic massive stars with the Analytical Dynamical Magnetosphere model,"In this paper, we investigate the photometric variability of magnetic O-type
+stars. Such stars possess oblique, predominantly dipolar magnetic fields that
+confine their winds roughly axisymmetrically about the magnetic equator, thus
+forming a magnetosphere. We interpret their photometric variability as
+phase-dependent magnetospheric occultations. For massive star winds dominated
+by electron scattering opacity in the optical and NIR, we can compute synthetic
+light curves from simply knowing the magnetosphere's mass density distribution.
+We exploit the newly-developed Analytical Dynamical Magnetosphere model (ADM)
+in order to obtain the predicted circumstellar density structures of magnetic
+O-type stars. The simplicity in our light curve synthesis model allows us to
+readily conduct a parameter space study. For validation purposes, we first
+apply our algorithm to HD 191612, the prototypical Of?p star. Next, we attempt
+to model the photometric variability of the Of?p-type stars identified in the
+Magellanic Clouds using OGLE photometry. We evaluate the compatibility of the
+ADM predictions with the observed photometric variations, and discuss the
+magnetic field properties that are implied by our modelling.",1910.05792v1
+2019-10-24,Magnetic Field Effect in the Fine-Structure Constant and Electron Dynamical Mass,"We investigate the effect of an applied constant and uniform magnetic field
+in the fine-structure constant of massive and massless QED. In massive QED, it
+is shown that a strong magnetic field removes the so called Landau pole and
+that the fine-structure constant becomes anisotropic having different values
+along and transverse to the field direction. Contrary to other results in the
+literature, we find that the anisotropic fine-structure constant always
+decreases with the field. We also study the effect of the running of the
+coupling constant with the magnetic field on the electron mass. We find that in
+both cases of massive and massless QED, the electron dynamical mass always
+decreases with the magnetic field, what can be interpreted as an inverse
+magnetic catalysis effect.",1910.11245v1
+2020-01-23,Charged particle dynamics near an X-point of a non-symmetric magnetic field with closed field lines,"Understanding particle drifts in a non-symmetric magnetic field is of primary
+interest in designing optimized stellarators to minimize the neoclassical
+radial loss of particles. Quasisymmetry and omnigeneity, two distinct
+properties proposed to ensure radial localization of collisionless trapped
+particles in stellarators, have been explored almost exclusively for magnetic
+fields that generate nested flux surfaces. In this work, we extend these
+concepts to the case where all the field lines are closed. We then study
+charged particle dynamics in the exact non-symmetric vacuum magnetic field with
+closed field lines, obtained recently by Weitzner and Sengupta
+(arXiv:1909.01890), which possesses X-points. The magnetic field can be used to
+construct magnetohydrodynamic equilibrium in the limit of vanishing plasma
+pressure. Expanding in the amplitude of the non-symmetric fields, we explicitly
+evaluate the omnigeneity and quasisymmetry constraints. We show that the
+magnetic field is omnigeneous in the sense that the drift surfaces coincide
+with the pressure surfaces. However, it is not quasisymmetric according to the
+standard definitions.",2001.08470v1
+2020-02-06,Domain structure dynamics in the ferromagnetic Kagome-lattice Weyl semimetal Co$_3$Sn$_2$S$_2$,"Co$_3$Sn$_2$S$_2$, a Weyl semimetal that consists of layers of Kagome
+lattices, transitions from a high-temperature paramagnetic phase to a
+low-temperature ferromagnetic phase below 177 K. The phase transition occurs
+through an intermediate non-trivial magnetic phase, the so-called ""A""-phase
+just below the Curie temperature. The ""A""-phase was earlier linked with a
+competing anti-ferromagnetic phase, a spin-glass phase and certain indirect
+measurements indicated the possibility of magnetic Skyrmions in this phase. We
+have imaged the magnetic domain structure in a single crystal of
+Co$_3$Sn$_2$S$_2$ at different temperatures, magnetic fields and field-angles
+by magnetic force microscopy. At low temperatures, we observed stripe domains
+indicating presence of uniaxial anisotropy. Above 130 K, the domain walls
+become mobile and they tend to align relatively easily when the magnetic field
+is increased along the $c$-axis than in the $a-b$ plane. Our detailed study of
+field-dependent domain dynamics reveal that the anomalous nature of the phase
+transition just below $T_c$ is dominantly governed by domain wall motion.",2002.02494v1
+2020-02-07,Spin-dependent transport through a Weyl semimetal surface,"We experimentally compare two types of interface structures with magnetic and
+non-magnetic Weyl semimetals. They are the junctions between a gold normal
+layer and magnetic Weyl semimetal Ti$_2$MnAl, and a ferromagnetic nickel layer
+and non-magnetic Weyl semimetal WTe$_2$, respectively. Due to the ferromagnetic
+side of the junction, we investigate spin-polarized transport through the Weyl
+semimetal surface. For both structures, we demonstrate similar current-voltage
+characteristics, with hysteresis at low currents and sharp peaks in
+differential resistance at high ones. Despite this behavior resembles the known
+current-induced magnetization dynamics in ferromagnetic structures, evolution
+of the resistance peaks with magnetic field is unusual. We connect the observed
+effects with current-induced spin dynamics in Weyl topological surface states.",2002.02673v2
+2020-05-22,Error estimates of some splitting schemes for charged-particle dynamics under strong magnetic field,"In this work, we consider the error estimates of some splitting schemes for
+the charged-particle dynamics under a strong magnetic field. We first propose a
+novel energy-preserving splitting scheme with computational cost per step
+independent from the strength of the magnetic field. Then under the maximal
+ordering scaling case, we establish for the scheme and in fact for a class of
+Lie-Trotter type splitting schemes, a uniform (in the strength of the magnetic
+field) and optimal error bound in the position and in the velocity parallel to
+the magnetic field. For the general strong magnetic field case, the modulated
+Fourier expansions of the exact and the numerical solutions are constructed to
+obtain a convergence result. Numerical experiments are presented to illustrate
+the error and energy behaviour of the splitting schemes.",2005.11192v1
+2020-05-28,Nonequilibrium quasistationary spin disordered state in the Kitaev-Heisenberg magnet $α$-RuCl$_3$,"Excitation by light pulses enables the manipulation of phases of quantum
+condensed matter. Here, we photoexcite high-energy holon-doublon pairs as a way
+to alter the magnetic free energy landscape of the Kitaev-Heisenberg magnet
+$\alpha$-RuCl$_3$, with the aim to dynamically stabilize a proximate spin
+liquid phase. The holon-doublon pair recombination through multimagnon emission
+is tracked through the time-evolution of the magnetic linear dichroism
+originating from the competing zigzag spin ordered ground state. A small
+holon-doublon density suffices to reach a spin disordered state. The phase
+transition is described within a dynamic Ginzburg-Landau framework,
+corroborating the quasistationary nature of the transient spin disordered
+phase. Our work provides insight into the coupling between the electronic and
+magnetic degrees of freedom in $\alpha$-RuCl$_3$ and suggests a new route to
+reach a proximate spin liquid phase in Kitaev-Heisenberg magnets.",2005.14189v1
+2020-06-05,Emergent pattern formation of active magnetic suspensions in an external field,"We study collective self-organization of weakly magnetic active suspensions
+in a uniform external field by analyzing a mesoscopic continuum model that we
+have recently developed. Our model is based on a Smoluchowski equation for a
+particle probability density function in an alignment field coupled to a
+mean-field description of the flow arising from the activity and the alignment
+torque. Performing linear stability analysis of the Smoluchowski equation and
+the resulting orientational moment equations combined with non-linear 3D
+simulations, we provide a comprehensive picture of instability patterns as a
+function of strengths of activity and magnetic field. For sufficiently high
+activity and moderate magnetic field strengths, the competition between the
+activity-induced flow and external magnetic torque renders a homogeneous polar
+steady state unstable. As a result, four distinct dynamical patterns of
+collective motion emerge. The instability patterns for pushers include
+traveling bands governed by bend-twist instabilities and dynamical aggregates.
+For pullers, finite-sized and system spanning pillar-like concentrated regions
+predominated by splay deformations emerge which migrate in the field direction.
+Notably, at very strong magnetic fields, we observe a reentrant hydrodynamic
+stability of the polar steady state.",2006.03352v1
+2020-06-19,Topological transport of deconfined hedgehogs in magnets,"We theoretically investigate the dynamics of magnetic hedgehogs, which are
+three-dimensional topological spin textures that exist in common magnets,
+focusing on their transport properties and connections to spintronics. We show
+that fictitious magnetic monopoles carried by hedgehog textures obey a
+topological conservation law, based on which a hydrodynamic theory is
+developed. We propose a nonlocal transport measurement in the disordered phase,
+where the conservation of the hedgehog flow results in a nonlocal signal
+decaying inversely proportional to the distance. The bulk-edge correspondence
+between hedgehog number and skyrmion number, the fictitious electric charges
+arising from magnetic dynamics, and the analogy between bound states of
+hedgehogs in ordered phase and the quark confinement in quantum chromodynamics
+are also discussed. Our study points to a practical potential in utilizing
+hedgehog flows for long-range neutral signal propagation or manipulation of
+skyrmion textures in three-dimensional magnetic materials.",2006.10910v3
+2020-09-13,The links between magnetic fields and filamentary clouds III: field regulated mass cumulative functions,"During the past decade the dynamical importance of magnetic fields in
+molecular clouds has been increasingly recognized, as observational evidence
+has accumulated. However, how a magnetic field affect star formation is still
+unclear. Typical star formation models still treat a magnetic fields as an
+isotropic pressure, ignoring the fundamental property of dynamically important
+magnetic fields: their direction. This study builds on our previous work which
+demonstrated how the mean magnetic field orientation relative to the global
+cloud elongation can affect cloud fragmentation. After the linear mass
+distribution reported earlier, we show here that the mass cumulative function
+(MCF) of a cloud is also regulated by the field orientation. A cloud elongated
+closer to the field direction tends to have a shallower MCF, in other words, a
+higher portion of the gas in high density. The evidence is consistent with our
+understanding of bimodal star formation efficiency discovered earlier, which is
+also correlated with the field orientations.",2009.05915v1
+2020-09-28,Thermal Magnetic Fluctuations of a Ferroelectric Quantum Critical Point,"Entanglement of two different quantum orders is of an interest of the modern
+condensed matter physics. One of the examples is the dynamical multiferroicity,
+where fluctuations of electric dipoles lead to magnetization. We investigate
+this effect at finite temperature and demonstrate an elevated magnetic response
+of a ferroelectric near the ferroelectric quantum critical point (FE QCP). We
+calculate the magnetic susceptibility of a bulk sample on the paraelectric side
+of the FE QCP at finite temperature and find enhanced magnetic susceptibility
+near the FE QCP. We propose quantum paraelectric strontium titanate (STO) as a
+candidate material to search for dynamic multiferroicity. We estimate the
+magnitude of the magnetic susceptibility for this material and find that it is
+detectable experimentally.",2009.12995v1
+2020-10-02,The relative orientation between the magnetic field and gas density structures in non-gravitating turbulent media,"Magnetic fields are a dynamically important agent for regulating structure
+formation in the interstellar medium. The study of the relative orientation
+between the local magnetic field and gas (column-) density gradient has become
+a powerful tool to analyse the magnetic field's impact on the dense gas
+formation in the Galaxy. In this study, we perform numerical simulations of a
+non-gravitating, isothermal gas, where the turbulence is driven either
+solenoidally or compressively. We find that only simulations with an initially
+strong magnetic field (plasma-$\beta<1$) show a change in the preferential
+orientation between the magnetic field and isodensity contours, from mostly
+parallel at low densities to mostly perpendicular at higher densities. Hence,
+compressive turbulence alone is not capable of inducing the transition observed
+towards nearby molecular clouds. At the same high initial magnetisation, we
+find that solenoidal modes produce a sharper transition in the relative
+orientation with increasing density than compressive modes. We further study
+the time evolution of the relative orientation and find that it remains
+unchanged by the turbulent forcing after one dynamical timescale.",2010.01178v1
+2020-10-21,Ambipolar diffusion velocity and magnetic field evolution in magnetar core: Generalised theoretical approach,"The magnetic field associated with neutron stars is generally believed to be
+threaded inside the star. In the presence of a magnetic field, the plasma
+present in the interior of the star goes through several processes that lead to
+magnetic field evolution. It is thought that magnetar activities are mainly due
+to field decay. The most important process of field decay inside the core of
+the star is the ambipolar diffusion of the charged particles present in the
+interior plasma. The decay rate due to ambipolar diffusion is directly
+connected to the ambipolar velocity of the charged particles under the
+influence of the present magnetic field. The ambipolar velocity of the charged
+particles depends on the internal dynamics of the particles. We outline a
+general method to solve the particle dynamics in the presence of a magnetic
+field using a magnetohydrodynamic equation for ambipolar velocity. The equation
+is general and applies to all possible surrounding conditions \eg temperature,
+and matter states like normal or superfluid.",2010.10776v4
+2020-11-17,Single-shot dynamics of spin-orbit torque and spin transfer torque switching in three-terminal magnetic tunnel junctions,"Current-induced spin-transfer torques (STT) and spin-orbit torques (SOT)
+enable the electrical switching of magnetic tunnel junctions (MTJs) in
+nonvolatile magnetic random access memories. In order to develop faster memory
+devices, an improvement of the timescales underlying the current driven
+magnetization dynamics is required. Here we report all-electrical time-resolved
+measurements of magnetization reversal driven by SOT in a three-terminal MTJ
+device. Single-shot measurements of the MTJ resistance during current injection
+reveal that SOT switching involves a stochastic two-step process consisting of
+a domain nucleation time and propagation time, which have different genesis,
+timescales, and statistical distributions compared to STT switching. We further
+show that the combination of SOT, STT, and voltage control of magnetic
+anisotropy (VCMA) leads to reproducible sub-ns switching with a spread of the
+cumulative switching time smaller than 0.2 ns. Our measurements unravel the
+combined impact of SOT, STT, and VCMA in determining the switching speed and
+efficiency of MTJ devices.",2011.08709v1
+2021-01-18,Topological electric driving of magnetization dynamics in insulators,"Established forms of electromagnetic coupling are usually conservative (in
+insulators) or dissipative (in metals and semiconductors). Here we point out
+the possibility of nondissipative electric driving of magnetization dynamics,
+if the valence electronic states have nontrivial topology in the combined space
+of crystal momentum and magnetization configuration. We provide a hybrid
+insulator system to demonstrate that the topology-based nonconservative
+electrical generalized force is capable of supporting sustained magnetization
+motion in the presence of Gilbert damping, with quantized and steady energy
+pumping into magnetization motion from the electric field. We also generalize
+our results to magnetic textures, and discuss electric field induced
+Dzyaloshinskii-Moriya interaction which can be nonconservative.",2101.07164v3
+2021-02-05,Symmetry-Driven Spin-Wave Gap Modulation in Nanolayered SrRuO3/SrTiO3 Heterostructures: Implications for Spintronic Applications,"A strong correlation between magnetic interaction and topological symmetries
+leads to unconventional magneto-transport behavior. Weyl fermions induce
+topologically protected spin-momentum locking, which is closely related to
+spin-wave gap formation in magnetic crystals. Ferromagnetic SrRuO3, regarded as
+a strong candidate for Weyl semimetal, inherently possesses a nonzero spin-wave
+gap owing to its strong magnetic anisotropy. In this paper, we propose a method
+to control the spin-wave dynamics by nanolayer designing of the SrRuO3/SrTiO3
+superlattices. In particular, the six-unit-cell-thick SrRuO3 layers within the
+superlattices undergo a phase transition in crystalline symmetry from
+orthorhombic to tetragonal, as the thickness of the SrTiO3 layers is modulated
+with atomic-scale precision. Consequently, the magnetic anisotropy, anomalous
+Hall conductivity, and spin-wave gap could be systematically manipulated. Such
+customization of magnetic anisotropy via nanoscale heterostructuring offers a
+novel control knob to tailor the magnon excitation energy for future spintronic
+applications, including magnon waveguides and filters. Our nanolayer approach
+unveils the important correlation between the tunable lattice degrees of
+freedom and spin dynamics in topologically non-trivial magnetic materials.",2102.03008v1
+2021-02-22,Robust formation of nanoscale magnetic skyrmions in easy-plane thin film multilayers with low damping,"We experimentally demonstrate the formation of room-temperature skyrmions
+with radii of about 25\,nm in easy-plane anisotropy multilayers with
+interfacial Dzyaloshinskii-Moriya interaction (DMI). We detect the formation of
+individual magnetic skyrmions by magnetic force microscopy and find that the
+skyrmions are stable in out-of-plane fields up to about 200 mT. We determine
+the interlayer exchange coupling as well as the strength of the interfacial
+DMI. Additionally, we investigate the dynamic microwave spin excitations by
+broadband magnetic resonance spectroscopy. From the uniform Kittel mode we
+determine the magnetic anisotropy and low damping $\alpha_{\mathrm{G}} < 0.04$.
+We also find clear magnetic resonance signatures in the non-uniform (skyrmion)
+state. Our findings demonstrate that skyrmions in easy-plane multilayers are
+promising for spin-dynamical applications.",2102.11117v1
+2021-03-24,Large Magnetic Moment in Flexoelectronic Silicon at Room Temperature,"Time-dependent rotational electric polarizations have been proposed to
+generate temporally varying magnetic moments, for example, through a
+combination of ferroelectric polarization and optical phonons. This phenomenon
+has been called dynamical multiferroicity, but explicit experimental
+demonstrations have been elusive to date. Here, we report the detection of a
+temporal magnetic moment as high as 1.2 mu_B/atom in charge-doped thin film of
+silicon under flexural strain. We demonstrate that the magnetic moment is
+generated by a combination of electric polarization arising from a
+flexoelectronic charge separation along the strain gradient and the deformation
+potential of phonons. The effect can be controlled by adjusting the external
+strain gradient, doping concentration and dopant, and can be regarded as a
+dynamical multiferroic effect involving flexoelectronics polarization instead
+of ferroelectricity. The discovery of a large magnetic moment in silicon may
+enable the use of non-magnetic and non-ferroelectric semiconductors in various
+multiferroic and spintronic applications.",2103.12907v1
+2021-04-02,Dynamical evolution of magnetic field in the pre-equilibrium quark-gluon plasma,"High-energy heavy-ion collisions generate extremely strong magnetic field
+which plays a key role in a number of novel quantum phenomena in quark-gluon
+plasma (QGP), such as the chiral magnetic effect (CME). However, due to the
+complexity in theoretical modellings of the coupled electromagnetic fields and
+the QGP system, especially in the pre-equilibrium stages, the lifetime of the
+magnetic field in the QGP medium remains undetermined. We establish, for the
+first time, a kinetic framework to study the dynamical decay of the magnetic
+field in the early stages of a weakly coupled QGP by solving the coupled
+Boltzmann and Maxwell equations. We find that at late times a
+magnetohydrodynamical description of the coupled system emerges. With respect
+to realistic collisions at RHIC and the LHC, we estimate the residual strength
+of the magnetic field in the QGP when the system start to evolve
+hydrodynamically.",2104.00831v1
+2021-05-03,Dislocation-driven relaxation processes at the conical to helical phase transition in FeGe,"The formation of topological spin textures at the nanoscale has a significant
+impact on the long-range order and dynamical response of magnetic materials. We
+study the relaxation mechanisms at the conical-to-helical phase transition in
+the chiral magnet FeGe. By combining ac susceptibility, magnetic force
+microscopy measurements and micromagnetic simulations, we demonstrate how the
+motion of magnetic topological defects, here edge dislocations, impacts the
+local formation of a stable helimagnetic spin structure. Although the
+simulations show that the edge dislocations move with a velocity of about 100
+m/s through the helimagnetic background, their dynamics are observed to disturb
+the magnetic order on the timescale of minutes due to pinning by randomly
+distributed structural defects. The results corroborate the substantial impact
+of dislocation motions on the nanoscale spin structure in chiral magnets,
+revealing previously hidden effects on the formation of helimagnetic domains
+and domain walls.",2105.00658v1
+2021-06-26,Orbital Magnetism of Active Viscoelastic Suspension,"We consider a dilute suspension of active (self-propelling) particles in a
+visco-elastic fluid. Particles are charged and constrained to move in a two
+dimensional harmonic trap. Their dynamics is coupled to a constant magnetic
+field applied perpendicular to their motion via Lorentz force. Due to the
+finite activity, the generalised fluctuation-dissipation relation (GFDR) breaks
+down, driving the system away from equilibrium. While breaking GFDR, we have
+shown that the system can have finite classical orbital magnetism only when the
+dynamics of the system contains finite inertia. The orbital magnetic moment has
+been calculated exactly. Remarkably, we find that when the elastic dissipation
+time scale of the medium is larger (smaller) than the persistence time scale of
+the self-propelling particles, the system is diamagnetic (paramagnetic).
+Therefore, for a given strength of the magnetic field, the system undergoes a
+novel transition from diamagnetic to paramagnetic state (and vice-versa) simply
+by tuning the time scales of underlying physical processes, such as, active
+fluctuations and visco-elastic dissipation. Interestingly, we also find that
+the magnetic moment, which vanishes at equilibrium, behaves non-monotonically
+with respect to increasing persistence of self-propulsion, that drives the
+system out of equilibrium",2106.13918v1
+2021-06-29,Magnetic Bloch-point hopping in multilayer skyrmions and associated emergent electromagnetic signatures,"Magnetic multilayers are promising tuneable systems for hosting magnetic
+skyrmions at/above room temperature. Revealing their intriguing switching
+mechanisms and associated inherent electrical responses are prerequisites for
+developing skyrmionic devices. In this work, we theoretically demonstrate the
+annihilation of single skyrmions occurring through a multilayer structure,
+which is mediated by hopping dynamics of topological hedgehog singularities
+known as Bloch points. The emerging intralayer dynamics of Bloch points are
+dominated by the Dzyaloshinskii-Moriya interaction, and their propagation can
+give rise to solenoidal emergent electric fields in the vicinity. Moreover, as
+the topology of spin textures can dominate their emergent magnetic properties,
+we show that the Bloch-point hopping through the multilayer will modulate the
+associated topological Hall response, with the magnitude proportional to the
+effective topological charge. We also investigate the thermodynamic stability
+of these states regarding the layer-dependent magnetic properties. This study
+casts light on the emergent electromagnetic signatures of skyrmion-based
+spintronics, rooted in magnetic-multilayer systems.",2106.15463v1
+2021-07-08,Chiral domain wall dynamics in magnetic heterostructures with bulk Dzyaloshinskii-Moriya interactions,"In this work, dynamics of chiral domain walls in long and narrow magnetic
+heterostructures based on non-centrosymmetric chiral magnets with bulk
+Dzyaloshinskii-Moriya interactions (DMI) and perpendicular magnetic anisotropy
+is systematically investigated. The driving forces can be out-of-plane magnetic
+fields and in-plane currents, correspondingly both steady and precessional
+flows are considered. Their dividing points (the Walker critical field and
+current density) are obtained as functions of bulk DMI strength
+($D_{\mathrm{b}}$) and the ratio ($\kappa$) of total (crystalline plus shape)
+anisotropy in the hard axis over that in the easy one. When far beyond Walker
+breakdown, the dependence curve of wall velocity on external in-plane bias
+field takes parabolic shape around the compensation point where the total
+in-plane field disappears. The center shift is determined by $D_{\mathrm{b}}$,
+$\kappa$, and the wall's topological charge, thus can be used to measure the
+bulk DMI strength in chiral magnets.",2107.03586v1
+2021-07-27,Evidence of symmetry lowering in antiferromagnetic metal TmB12 with dynamic charge stripes,"Precise angle-resolved magnetoresistance and magnetization measurements have
+revealed (i) strong charge transport and magnetic anisotropy and (ii) emergence
+of a huge number of magnetic phases in the ground state of TmB12
+antiferromagnetic metal with fcc crystal structure and dynamic charge stripes.
+By analyzing the angular H-fi magnetic phase diagrams reconstructed from
+experimental angle-resolved magnetoresistance and magnetization data we argue
+that the symmetry lowering is a consequence of suppression of the indirect
+Ruderman- Kittel-Kasuya-Yosida (RKKY) exchange along 110 directions between
+nearest neighboring magnetic moments of Tm3+ ions and subsequent redistribution
+of conduction electrons to quantum fluctuations of the electron density
+(stripes). Magnetoresistance components are discussed in terms of charge
+scattering on the spin density wave, itinerant ferromagnetic nano-domains and
+on-site Tm3+ spin fluctuations.",2107.12896v1
+2021-10-26,"Structure and magnetic studies of geometrically frustrated disordered pyrochlores A$_{2}$Zr$_{2}$O$_{7}$: (A = Eu, Gd, Er)","The spin ice system Dy$_{2}$Ti$_{2}$O$_{7}$ exhibits strong
+frequency-dependent spin-freezing at $\sim$ 16 K temperature. Although it has
+been a matter of discussion for years, the origin of this unusual spin freezing
+is still unknown. The replacement of Ti with isovalent Zr leads to the dynamic
+magnetic ground state at low temperatures in Dy$_{2}$Zr$_{2}$O$_{7}$ and
+prevents the formation of high-temperature spin freezing. Interestingly the
+high-temperature spin freezing re-emerges in the presence of the magnetic
+field. In this direction, we have studied a series of disordered pyrochlore
+oxides A$_{2}$Zr$_{2}$O$_{7}$ (A = Eu, Gd, Er) and compared their crystal
+structure, magnetic, and heat capacity behavior with that of
+Dy$_{2}$Zr$_{2}$O$_{7}$ and Ho$_{2}$Zr$_{2}$O$_{7}$ systems. Our study shows
+that depending on the disordered parameter, the spin-freezing behavior can be
+retained by slowing down the spin dynamic with a suitable choice of the
+magnetic field. We observe that unlike titanates, modification at the rare
+earth site does not make considerable change in the magnetic ground state of
+these zirconates compounds.",2110.13573v1
+2022-01-07,On the role of magnetic fields into the dynamics and gravitational wave emission of binary neutron stars,"Modelling as a dipole the magnetic interaction of a binary system of neutron
+stars, we are able to include the magnetic effects in the Newtonian and in the
+inspiral dynamics of the system using an equivalent one-body description.
+Furthermore, in the inspiral stage we determine the role of the magnetic
+interaction in the waveforms generated by the system and obtain explicit
+formulas for the decrease in the separation of the stars, the time to reach a
+minimal radius, the gravitational luminosity and the change of gravitational
+wave frequency, all this within the quadrupole approximation. For the magnitude
+of the magnetic field that is consider to exist in these binaries $\sim 10^{16}
+{\rm G}$ we are able to show that its effect on the observable quantities is of
+the order of the 2PN correction, already close to the detection range of the
+gravitational waves observatories. %} We also discuss cases in which the
+magnetic field could have a more significant influence.",2201.02287v1
+2022-03-19,Spin wave excitation and directional propagation in presence of magnetic charges in square artificial spin ice,"Artificial spin ice is a special class of engineered lattice of highly shape
+anisotropic single domain magnetic nanostructures which is used as one of the
+model systems to study the spin ice behavior observed in pyrochlore oxides. The
+nanomagnets interact via dipolar interaction which results in correlated
+magnetization dynamics exhibiting macroscopic spin configuration states. Here,
+we exploit the interplay of underlying magnetic state and external bias field
+orientation to study controlled spin wave propagation in square Artificial Spin
+Ice (sASI) by performing detailed micromagnetic simulations. We report that
+careful selection of vertices with local magnetic charges can effectively
+direct the anisotropic spin wave in presence of an external field. Further, we
+explore the influence of local charges due to the excited state in
+even-coordinated vertices as well as uncompensated charges due to
+odd-coordinated vertices on spin wave behavior. Our studies suggest that there
+is no perceptible difference on spin wave dynamical behavior due to the origin
+of local magnetic charge in sASI. Our results of controlled and directional
+spin wave propagation in sASI system may be useful for low-power consumption
+based all magnonic on-chip devices.",2203.10345v1
+2022-04-14,Effect of Magnetism on Lattice Vibrations: Mössbauer Spectroscopic Evidence,"Based on the available literature reviewed are results pertinent to the
+effect of magnetism on lattice dynamics obtained by M\""ossbauer spectroscopy at
+57Fe and 119Sn probe atoms. Presented and discussed are sigma-phase Fe-Cr,
+Fe-V, Fe-Cr-Ni and lambda-phase (C14 Laves) NbFe2 compounds that belong to the
+Frank-Kasper family of phases, metallic chromium and iron mono-arsenide, FeAs.
+The common feature of all these metallic systems is itinerant character of
+their magnetism. Two spectral parameters relevant to the lattice dynamics viz.
+the center shift, CS, and/or the recoil-free fraction, f, are considered as
+figures of merit. Their temperature dependences show anomalies at magnetic
+ordering temperatures giving evidence that that vibrations in the magnetic
+phase are different than those in the paramagnetic phase. The lower the
+magnetic ordering temperature, the stronger the difference.",2204.06881v1
+2022-05-03,Mechanism for Sequestering Magnetic Energy at Large Scales in Shear-Flow Turbulence,"Straining of magnetic fields by large-scale shear flow, generally assumed to
+lead to intensification and generation of small scales, is re-examined in light
+of the persistent observation of large-scale magnetic fields in astrophysics.
+It is shown that, in magnetohydrodynamic turbulence, unstable shear flows have
+the unexpected effect of sequestering magnetic energy at large scales, due to
+counteracting straining motion of nonlinearly excited large-scale stable
+eigenmodes. This effect is quantified via dissipation rates, energy transfer
+rates, and visualizations of magnetic field evolution by artificially removing
+the stable modes. These analyses show that predictions based upon physics of
+the linear instability alone miss substantial dynamics, including those of
+magnetic fluctuations.",2205.01298v2
+2022-06-12,Thermally Activated Transitions Between Micromagnetic States,"We review work by the authors on thermal activation in nanoscopic magnetic
+systems. These systems present unique difficulties in analyzing noise-induced
+escape over a barrier, including the presence of nonlocal interactions,
+nongradient terms in the energy functional, and dynamical textures as initial
+or saddle states. We begin with a discussion of magnetic reversal between
+single-domain configurations of the magnetization. Here the transition (saddle)
+state can be either a single-domain or a spatially varying (instanton-like)
+configuration, and depending on the system parameters can exhibit either
+Arrhenius or non-Arrhenius reversal rates. We then turn to a discussion of
+transitions between magnetic textures, which can be either static and
+topologically protected or dynamic and not topologically protected. An example
+of the latter case is the droplet soliton, a rotating
+nontopologically-protected configuration, which we find can occur either as a
+metastable or transition state in a nanoscopic magnetic system. After
+discussing various issues in calculating transition rates, we present results
+for the activation barriers for creation and annihilation of these magnetic
+textures. We conclude with a discussion of activated transitions between
+topologically protected skyrmion textures and other configurations, on which
+work is ongoing.",2206.05826v1
+2022-06-14,Broadband microwave detection using electron spins in a hybrid diamond-magnet sensor chip,"Quantum sensing has developed into a main branch of quantum science and
+technology. It aims at measuring physical quantities with high resolution,
+sensitivity, and dynamic range. Electron spins in diamond are powerful magnetic
+field sensors, but their sensitivity in the microwave regime is limited to a
+narrow band around their resonance frequency. Here, we realize broadband
+microwave detection using spins in diamond interfaced with a thin-film magnet.
+A pump field locally converts target microwave signals to the sensor-spin
+frequency via the non-linear spin-wave dynamics of the magnet. Two
+complementary conversion protocols enable sensing and high-fidelity spin
+control over a gigahertz bandwidth, allowing characterization of the spin-wave
+band at multiple gigahertz above the sensor-spin frequency. The pump-tunable,
+hybrid diamond-magnet sensor chip opens the way for spin-based sensing in the
+100-gigahertz regime at small magnetic bias fields.",2206.07013v1
+2022-08-03,Magnetic field driven dynamics in twisted bilayer artificial spin ice at superlattice angles,"Geometrical designs of interacting nanomagnets have been studied extensively
+in the form of two dimensional arrays called artificial spin ice. These systems
+are usually designed to create geometrical frustration and are of interest for
+the unusual and often surprising phenomena that can emerge. Advanced
+lithographic and element growth techniques have enabled the realization of
+complex designs that can involve elements arranged in three dimensions. Using
+numerical simulations employing the dumbbell approximation, we examine possible
+magnetic behaviours for bilayer artificial spin ice (BASI) in which the
+individual layers are rotated with respect to one another. The goal is to
+understand how magnetization dynamics are affected by long-range dipolar
+coupling that can be modified by varying the layer separation and layer
+alignment through rotation. We consider bilayers where the layers are both
+either square or pinwheel arrangements of islands. Magnetic reversal processes
+are studied and discussed in terms of domain and domain wall configurations of
+the magnetic islands. Unusual magnetic ordering is predicted for special angles
+which define lateral spin superlattices for the bilayer systems.",2208.02243v1
+2022-08-22,Ultrafast Spin Dynamics and Photoinduced Insulator-to-Metal Transition in $α$-$RuCl_3$,"Laser-induced ultrafast demagnetization is a phenomenon of utmost interest
+and attracts significant attention because it enables potential applications in
+ultrafast optoelectronics and spintronics. As a spin-orbit coupling assisted
+magnetic insulator, $\alpha$-$RuCl_3$ provides an attractive platform to
+explore the physics of electronic correlations and related unconventional
+magnetism. Using time-dependent density functional theory, we explore the
+ultrafast laser-induced dynamics of the electronic and magnetic structures in
+$\alpha$-$RuCl_3$. Our study unveils that laser pulses can introduce ultrafast
+demagnetizations in $\alpha$-$RuCl_3$, accompanied by an out-of-equilibrium
+insulator-to-metal transition in a few tens of femtoseconds. The spin response
+significantly depends on the laser wavelength and polarization on account of
+the electron correlations, band renormalizations and charge redistributions.
+These findings provide physical insights into the coupling between the
+electronic and magnetic degrees of freedom in $\alpha$-$RuCl_3$ and shed light
+on suppressing the long-range magnetic orders and reaching a proximate spin
+liquid phase for two-dimensional magnets on an ultrafast timescale.",2208.10222v1
+2022-09-18,Magnetically confined wind shock,"Many stars across all classes possess strong enough magnetic fields to
+influence dynamical flow of material off the stellar surface. For the case of
+massive stars (O and B types), about 10\% of them harbour strong, globally
+ordered (mostly dipolar) magnetic fields. The trapping and channeling of their
+stellar winds in closed magnetic loops leads to {\it magnetically confined wind
+shocks} (MCWS), with pre-shock flow speeds that are some fraction of the wind
+terminal speed that can be a few thousand km s$^{-1}$. These shocks generate
+hot plasma, a source of X-rays. In the last decade, several developments took
+place, notably the determination of the hot plasma properties for a large
+sample of objects using \xmm\ and \ch, as well as fully self-consistent MHD
+modelling and the identification of shock retreat effects in weak winds. In
+addition, these objects are often sources of H$\alpha$ emission which is
+controlled by either sufficiently high mass loss rate or centrifugal breakout.
+Here we review the theoretical aspects of such magnetic massive star wind
+dynamics.",2209.08540v1
+2022-11-16,Spin structure and dynamics of the topological semimetal Co$_{3}$Sn$_{2-x}$In$_{x}$S$_{2}$,"The anomalous Hall effect (AHE), typically observed in ferromagnetic (FM)
+metals with broken time-reversal symmetry, depends on electronic and magnetic
+properties. In Co$_{3}$Sn$_{2-x}$In$_{x}$S$_{2}$, a giant AHE has been
+attributed to Berry curvature associated with the FM Weyl semimetal phase, yet
+recent studies report complicated magnetism. We use neutron scattering to
+determine the spin dynamics and structures as a function of $x$ and provide a
+microscopic understanding of the AHE and magnetism interplay. Spin gap and
+stiffness indicate a contribution from Weyl fermions consistent with the AHE.
+The magnetic structure evolves from $c$-axis ferromagnetism at $x$ = 0 to a
+canted antiferromagnetic (AFM) structure with reduced $c$-axis moment and
+in-plane AFM order at $x$ = 0.12 and further reduced $c$-axis FM moment at $x$
+= 0.3. Since noncollinear spins can induce non-zero Berry curvature in real
+space acting as a fictitious magnetic field, our results revealed another AHE
+contribution, establishing the impact of magnetism on transport.",2211.08660v1
+2022-11-23,Anatomy of spin wave driven magnetic texture motion via magnonic torques,"The interplay between spin wave and magnetic texture represents the
+information exchange between the fast and slow dynamical parts of magnetic
+systems. Here we formulate a set of magnonic torques acting on background
+magnetic texture, by extracting time-invariant information from the fast
+precessing spin waves. Under the frame of magnonic torques, we use theoretical
+formulations and micromagnetic simulations to investigate the spin wave driven
+domain wall motion in two typical symmetry-breaking situations: the rotational
+symmetry broken by the Dzyaloshinkii-Moriya interaction, and the translational
+symmetry broken by magnetic damping. The torque-based microscopic analyses
+provide compact yet quantitative tools to reinterpret the magnetic texture
+dynamics induced by spin wave, beyond the conventional framework of global
+momentum conservation.",2211.12958v1
+2022-12-16,"Unraveling effects of electron correlation in two-dimensional Fe$_{n}$GeTe$_{2}$ (n=3, 4, 5) by dynamical mean field theory","The Fe$_{n}$GeTe$_{2}$ systems are newly discovered two-dimensional
+van-der-Waals materials, exhibiting magnetism at room temperature. The
+sub-systems belonging to Fe$_{n}$GeTe$_{2}$ class are special because they show
+site-dependent magnetic behavior. We focus on the critical evaluation of
+magnetic properties and electron correlation effects in Fe$_{n}$GeTe$_{2}$
+($n$= 3, 4, 5) (FGT) systems performing first-principles calculations. Three
+different ab-initio approaches have been used, viz., i) standard density
+functional theory (DFT), ii) incorporating static electron correlation (DFT+U)
+and iii) inclusion of dynamic electron correlation effect (DFT+DMFT). Our
+results show that DFT+DMFT is the most accurate technique to correctly
+reproduce the magnetic interactions and experimentally observed transition
+temperatures. The inaccurate values of structural parameters, magnetic moments
+and exchange interactions obtained from DFT+U make this method inapplicable for
+the FGT family. Correct determination of magnetic properties for this class of
+materials is important since they are promising candidates for spin transport
+and spintronic applications at room temperature.",2212.08552v1
+2022-12-22,Laser Cooling of Trapped Ions in Strongly Inhomogeneous Magnetic Fields,"Hybrid traps for the simultaneous confinement of neutrals and ions have
+recently emerged as versatile tools for studying interactions between these
+species at very low temperatures. Such traps rely on the combination of
+different types of external fields for the confinement of either species
+raising the question of interactions between the individual traps. Here, the
+influence of a strongly inhomogeneous magnetic field used for trapping neutrals
+on the trapping and laser cooling of a single Ca$^+$ ion in a radiofrequency
+ion trap is studied theoretically using molecular-dynamics simulations based on
+multilevel rate equations. The inhomogeneous magnetic field couples the
+different components of the ion motion and introduces position-dependent Zeeman
+splittings. Nonetheless, laser cooling is still found to work efficiently as
+the ion samples different magnetic field strengths and directions along its
+trajectory. Offsetting the centres of the two traps generates a linear
+magnetic-field gradient so that multiple lasers are required to address the
+resulting range of Zeeman splittings in order to ensure efficient cooling. The
+present study yields detailed insights into the ion cooling dynamics in
+combined magnetic and radiofrequency electric fields relevant for the
+characterisation and optimisation of hybrid trapping experiments.",2212.11863v1
+2023-03-13,Intrinsic spin-orbit torque mechanism for deterministic all-electric switching of noncollinear antiferromagnets,"Using a pure electric current to control kagome noncollinear antiferromagnets
+is promising in information storage and processing, but a full description is
+still lacking, in particular, on intrinsic (i.e., no external magnetic fields
+or external spin currents) spin-orbit torques. In this work, we
+self-consistently describe the relations among the electronic structure,
+magnetic structure, spin accumulations, and intrinsic spin-orbit torques, in
+the magnetic dynamics of a noncollinear antiferromagnet driven by a pure
+electric current. Our calculation can yield a critical current density
+comparable with those in the experiments, when considering the boost from the
+out-of-plane magnetic dynamics induced by the current-driven spin accumulation
+on individual magnetic moments. We stress the parity symmetry breaking in
+deterministic switching among magnetic structures. This work will be helpful
+for future applications of noncollinear antiferromagnets.",2303.06929v2
+2023-03-28,Anisotropic and frame dependent chaos of suspended strings from a dynamical holographic QCD model with magnetic field,"We investigate both from a qualitative as well as quantitative perspective
+the emergence of chaos in the QCD confining string in a magnetic field from a
+holographic viewpoint. We use an earlier developed bottom-up solution of the
+Einstein-Maxwell-Dilaton action that mimics QCD and its thermodynamics quite
+well. Surprisingly, our predictions depend on the used frame: the magnetic
+field tends to suppress the chaos in both perpendicular and parallel directions
+relative to the magnetic field in the string frame whilst in the Einstein
+frame, the chaos suppression only happens in the perpendicular direction, with
+an enhanced chaos along the magnetic field. The amount of
+suppression/enhancement in both frames does depend on the relative orientation
+of the string and magnetic field.",2303.15716v2
+2023-06-17,Coherent two-dimensional THz magnetic resonance spectroscopies for molecular magnets: Analysis of Dzyaloshinskii-Moriya interaction,"To investigate the novel quantum dynamic behaviors of magnetic materials that
+arise from complex spin-spin interactions, it is necessary to probe the
+magnetic response at a speed greater than the spin-relaxation and dephasing
+processes. Recently developed two-dimensional (2D) terahertz magnetic resonance
+(THz-MR) spectroscopy techniques use the magnetic components of laser pulses,
+and this allows investigation of the details of the ultrafast dynamics of spin
+systems. For such investigations, quantum treatment -- not only of the spin
+system itself but also of the environment surrounding the spin system -- is
+important. In our method, based on the theory of multidimensional optical
+spectroscopy, we formulate nonlinear THz-MR spectra using an approach based on
+the numerically rigorous hierarchical equations of motion. We conduct numerical
+calculations of both linear (1D) and 2D THz-MR spectra for a linear chiral spin
+chain. The pitch and direction of chirality (clockwise or anticlockwise) are
+determined by the strength and sign of the Dzyaloshinskii-Moriya interaction
+(DMI). We show that not only the strength but also the sign of the DMI can be
+evaluated through the use of 2D THz-MR spectroscopic measurements, while 1D
+measurements allow us to determine only the strength.",2306.10222v1
+2023-06-27,Statistics of a 2D immersed granular gas magnetically forced in volume,"We present an experimental study of the dynamics of a set of magnets within a
+fluid in which a remote torque applied by a vertical oscillating magnetic field
+transfers angular momentum to individual magnets. This system differs from
+previous experimental studies of granular gas where the energy is injected by
+vibrating the boundaries. Here, we do not observe any cluster formation,
+orientational correlation and equipartition of the energy. The magnets' linear
+velocity distributions are stretched exponentials, similar to 3D
+boundary-forced dry granular gas systems, but the exponent does not depend on
+the number of magnets. The value of the exponent of the stretched exponential
+distributions is close to the value of 3/2 previously derived theoretically.
+Our results also show that the conversion rate of angular momentum into linear
+momentum during the collisions controls the dynamics of this
+homogenously-forced granular gas. We report the differences between this
+homogeneously-forced granular gas, ideal gas, and nonequilibrium
+boundary-forced dissipative granular gas.",2306.15456v1
+2023-09-18,Tunable Tesla-scale magnetic attosecond pulses through ring-current gating,"Coherent control over electron dynamics in atoms and molecules using
+high-intensity circularly-polarized laser pulses gives rise to current loops,
+resulting in the emission of magnetic fields. We propose and demonstrate with
+ab-initio calculations ``current-gating"" schemes to generate direct or
+alternating-current magnetic pulses in the infrared spectral region, with
+highly tunable waveform and frequency, and showing femtosecond-to-attosecond
+pulse duration. In optimal conditions, the magnetic pulse can be highly
+isolated from the driving laser and exhibits a high flux density ($\sim1$ Tesla
+at few hundred nanometers from the source, with a pulse duration of 787
+attoseconds) for application in forefront experiments of ultrafast
+spectroscopy. Our work paves the way toward the generation of attosecond
+magnetic fields to probe ultrafast magnetization, chiral responses, and spin
+dynamics.",2309.09654v1
+2023-10-27,Polarization vs. magnetic field: competing eigenbases in laser-driven atoms,"We present experimental results and a theoretical model that illustrate how
+competing eigenbases can determine the dynamics of a fluorescing atom. In the
+absence of a magnetic field, the atom can get trapped in a dark state, which
+inhibits fluorescence. In general, this will happen when the magnetic
+degeneracy of the ground state is greater than the one of the excited state. A
+canonical way to avoid optical pumping to dark states is to apply a magnetic
+field at an angle with respect to the polarization of the exciting light. This
+generates a competition of eigenbases which manifests as a crossover between
+two regimes dominated either by the laser or the magnetic field. We illustrate
+this crossover with fluorescence measurements on a single laser-cooled calcium
+ion in a Paul trap and find that it occurs at a critical laser intensity that
+is proportional to the external magnetic field. We contrast our results with
+numerical simulations of the atomic levels involved and also present a simple
+theoretical model that provides excellent agreement with experimental results
+and facilitates the understanding of the dynamics.",2310.18525v1
+2023-12-05,Can we distinguish black holes with electric and magnetic charges from quasinormal modes?,"We compute the quasinormal modes of static and spherically symmetric black
+holes (BHs) with electric and magnetic charges. For the electrically charged
+case, the dynamics of perturbations separates into the odd- and even-parity
+sectors with two coupled differential equations in each sector. In the presence
+of both electric and magnetic charges, the differential equations of four
+dynamical degrees of freedom are coupled with each other between odd- and
+even-parity perturbations. Despite this notable modification, we show that, for
+a given total charge and mass, a BH with mixed electric and magnetic charges
+gives rise to the same quasinormal frequencies for fundamental modes. This
+includes the case in which two BHs have equal electric and magnetic charges for
+each of them. Thus, the gravitational-wave observations of quasinormal modes
+during the ringdown phase alone do not distinguish between electrically and
+magnetically charged BHs.",2312.03191v1
+2023-12-18,Comparative simulations of Kelvin-Helmholtz induced magnetic reconnection at the Earth's magnetospheric flanks,"This study presents 3D resistive Hall-magnetohydrodynamic numerical
+simulations focusing on the Kelvin-Helmholtz instability (KHI) dynamics at
+Earth's magnetospheric flanks during northward interplanetary magnetic field
+(IMF) periods. Through a comparative analysis of two simulations, we explore
+the impact of distinct magnetic field orientations on plasma dynamics and
+magnetic reconnection events. In one configuration, a uniform magnetic field
+results in (double) Mid-Latitude Reconnection (MLR), while in the second
+configuration, a magnetic shear induces both Type I Vortex Induced Reconnection
+and MLR. Key findings include the symmetries and asymmetries in the latitudinal
+distribution of KHI vortices and current sheets and a quantitative comparison
+of reconnection events. Particularly noteworthy is the quantification of newly
+closed field lines that experienced double reconnection, ultimately becoming
+embedded in solar wind plasma at low latitudes while remaining connected to
+magnetospheric plasma at high latitudes. The varying abundance of such lines in
+the two simulations holds implications for plasma transport at the
+magnetopause. This work significantly advances our understanding of
+magnetospheric processes, emphasizing the essential role of a three-dimensional
+perspective in accurately simulating magnetospheric plasma phenomena.",2312.11161v1
+2024-03-12,Plasmon-driven creation of magnetic topological structures,"In the present research, we demonstrate the usage of plasmonic effects in
+thin film structures to control magnetic topological textures, specifically
+skyrmions and skyrmioniums. We investigate numerically the generation and
+alteration of these topological structures caused by hemisphere gold
+nanoparticle placed over a magnetic layer coated with a dielectric material.
+The electromagnetic and photothermal models are used to clarify the processes
+of producing heat and absorption, and the results were implemented in
+micromagnetic formalism to reveal the dynamics of magnetization under various
+conditions. Our findings demonstrate the significance of the laser pulse
+duration and the contact area between nanoparticles and the underlying magnetic
+layer in forming topological textures. In particular, we show how to generate a
+single skyrmion, multiple skyrmions, and skyrmioniums, and how to dynamically
+transition between these states. These results highlight the possibility of
+manipulating magnetic textures by using plasmonic effects, which presents
+significant opportunities for spintronics and non-conventional computer
+applications.",2403.07382v1
+2024-03-15,"Structure, control, and dynamics of altermagnetic textures","We present a phenomenological theory of altermagnets, that captures their
+unique magnetization dynamics and allows modelling magnetic textures in this
+new magnetic phase. Focusing on the prototypical d-wave altermagnets, e.g.
+RuO$_2$, we can explain intuitively the characteristic lifted degeneracy of
+their magnon spectra, by the emergence of an effective sublattice-dependent
+anisotropic spin stiffness arising naturally from the phenomenological theory.
+We show that as a consequence the altermagnetic domain walls, in contrast to
+antiferromagnets, have a finite gradient of the magnetization, with its
+strength and gradient direction connected to the altermagnetic anisotropy, even
+for 180$^\circ$ domain walls. This gradient generates a ponderomotive force in
+the domain wall in the presence of a strongly inhomogeneous external magnetic
+field, which may be achieved through magnetic force microscopy techniques. The
+motion of these altermagentic domain walls is also characterized by an
+anisotropic Walker breakdown, with much higher speed limits of propagation than
+ferromagnets but lower than antiferromagnets.",2403.10218v2
+1997-08-23,Dynamics of fluctuating magnetic fields in turbulent dynamos incorporating ambipolar drifts,"Turbulence with a large magnetic Reyonolds number, generically leads to
+rapidly growing magnetic noise over and above any mean field. We revisit the
+dynamics of this fluctuating field, in homogeneous, isotropic, helical
+turbulence. Assuming the turbulence to be Markovian, we first rederive, in a
+fairly transparent manner, the equation for the mean field, and corrected
+Fokker-Plank type equations for the magnetic correlations. In these equations,
+we also incorporate the effects of ambipolar drift which would obtain if the
+turbulent medium has a significant neutral component. We apply these equations
+to discuss a number of astrophysically interesting problems: (a) the small
+scale dynamo in galactic turbulence with a model Kolmogorov spectrum,
+incorporating the effect of ambipolar drift; (b) current helicity dynamics and
+the quasilinear corrections to the alpha effect; (c) growth of the current
+helicity and large-scale magnetic fields due to nonlinear effects.",9708216v1
+2005-03-02,On the Spectrum of Magnetohydrodynamic Turbulence,"We propose a phenomenological model for incompressible magnetohydrodynamic
+turbulence. We argue that nonlinear-wave interaction weakens as the energy
+cascade proceeds to small scales, however, the anisotropy of fluctuations along
+the large-scale magnetic field increases, which makes turbulence strong at all
+scales. To explain the weakening of the interaction, we propose that
+small-scale fluctuations of the velocity and magnetic fields become
+increasingly dynamically aligned as their scale decreases, so that turbulent
+eddies become locally anisotropic in the plane perpendicular to the large-scale
+magnetic field. In the limit of weak anisotropy, that is, weak large-scale
+magnetic field, our model reproduces the Goldreich-Sridhar spectrum, while the
+limit of strong anisotropy, that is, strong large-scale magnetic field,
+corresponds to the Iroshnikov-Kraichnan scaling of the spectrum. This is in
+good agreement with recent numerical results.",0503053v2
+1997-09-16,Stability of Relativistic Matter With Magnetic Fields,"Stability of matter with Coulomb forces has been proved for non-relativistic
+dynamics, including arbitrarily large magnetic fields, and for relativistic
+dynamics without magnetic fields. In both cases stability requires that the
+fine structure constant alpha be not too large. It was unclear what would
+happen for both relativistic dynamics and magnetic fields, or even how to
+formulate the problem clearly. We show that the use of the Dirac operator
+allows both effects, provided the filled negative energy `sea' is defined
+properly. The use of the free Dirac operator to define the negative levels
+leads to catastrophe for any alpha, but the use of the Dirac operator with
+magnetic field leads to stability.",9709171v1
+1998-11-05,Zero Temperature Phase Transition in Spin-ladders: Phase Diagram and Dynamical studies of Cu(Hp)Cl,"In a magnetic field, spin-ladders undergo two zero-temperature phase
+transitions at the critical fields Hc1 and Hc2. An experimental review of
+static and dynamical properties of spin-ladders close to these critical points
+is presented. The scaling functions, universal to all quantum critical points
+in one-dimension, are extracted from (a) the thermodynamic quantities
+(magnetization) and (b) the dynamical functions (NMR relaxation). A simple
+mapping of strongly coupled spin ladders in a magnetic field on the exactly
+solvable XXZ model enables to make detailed fits and gives an overall
+understanding of a broad class of quantum magnets in their gapless phase
+(between Hc1 and Hc2). In this phase, the low temperature divergence of the NMR
+relaxation demonstrates its Luttinger liquid nature as well as the novel
+quantum critical regime at higher temperature. The general behaviour close
+these quantum critical points can be tied to known models of quantum magnetism.",9811068v2
+1999-03-10,Classical and Quantum Dynamics in a Random Magnetic Field,"Using the supersymmetry approach, we study spectral statistical properties of
+a two-dimensional quantum particle subject to a non-uniform magnetic field. We
+focus mainly on the problem of regularisation of the field theory. Our analysis
+begins with an investigation of the spectral properties of the purely classical
+evolution operator. We show that, although the kinetic equation is formally
+time-reversible, density relaxation is controlled by {\em irreversible}
+classical dynamics. In the case of a weak magnetic field, the effective kinetic
+operator corresponds to diffusion in the angle space, the diffusion constant
+being determined by the spectral resolution of the inhomogeneous magnetic
+field. Applying these results to the quantum problem, we demonstrate that the
+low-lying modes of the field theory are related to the eigenmodes of the
+irreversible classical dynamics, and the higher modes are separated from the
+zero mode by a gap associated with the lowest density relaxation rate. As a
+consequence, we find that the long-time properties of the system are
+characterised by universal Wigner-Dyson statistics. For a weak magnetic field,
+we obtain a description in terms of the quasi one-dimensional non-linear
+$\sigma$-model.",9903169v1
+2000-05-08,Spin dynamics of Mn12-acetate in the thermally-activated tunneling regime: ac-susceptibility and magnetization relaxation,"In this work, we study the spin dynamics of Mn12-acetate molecules in the
+regime of thermally assisted tunneling. In particular, we describe the system
+in the presence of a strong transverse magnetic field. Similar to recent
+experiments, the relaxation time/rate is found to display a series of
+resonances; their Lorentzian shape is found to stem from the tunneling. The
+dynamic susceptibility $\chi(w)$ is calculated starting from the microscopic
+Hamiltonian and the resonant structure manifests itself also in $\chi(w)$.
+Similar to recent results reported on another molecular magnet, Fe8, we find
+oscillations of the relaxation rate as a function of the transverse magnetic
+field when the field is directed along a hard axis of the molecules. This
+phenomenon is attributed to the interference of the geometrical or Berry phase.
+We propose susceptibility experiments to be carried out for strong transverse
+magnetic fields to study of these oscillations and for a better resolution of
+the sharp satellite peaks in the relaxation rates.",0005135v3
+2000-12-08,Interaction potential between dynamic dipoles: polarized excitons in strong magnetic fields,"The interaction potential of a two-dimensional system of excitons with
+spatially separated electron-hole layers is considered in the strong magnetic
+field limit. The excitons are assumed to have free dynamics in the $x$-$y$
+plane, while being constrained or `polarized' in the $z$ direction. The model
+simulates semiconductor double layer systems under strong magnetic field normal
+to the layers. The {\em residual} interaction between excitons exhibits
+interesting features, arising from the coupling of the center-of-mass and
+internal degrees of freedom of the exciton in the magnetic field. This coupling
+induces a dynamical dipole moment proportional to the center-of-mass magnetic
+moment of the exciton. We show the explicit dependence of the inter-exciton
+potential matrix elements, and discuss the underlying physics. The unusual
+features of the interaction potential would be reflected in the collective
+response and non-equilibrium properties of such system.",0012131v1
+2001-04-28,Origin of enhanced dynamic nuclear polarization and all-optical nuclear magnetic resonance in GaAs quantum wells,"Time-resolved optical measurements of electron-spin dynamics in a (110) GaAs
+quantum well are used to study the consequences of a strongly anisotropic
+electron g-tensor, and the origin of previously discovered all-optical nuclear
+magnetic resonance. All components of the g-tensor are measured, and a strong
+anisotropy even along the in-plane directions is found. The amplitudes of the
+spin signal allow the study of the spatial directions of the injected spin and
+its precession axis. Surprisingly efficient dynamic nuclear polarization in a
+geometry where the electron spins are injected almost transverse to the applied
+magnetic field is attributed to an enhanced non-precessing electron spin
+component. The small absolute value of the electron g-factor combined with
+efficient nuclear spin polarization leads to large nuclear fields that dominate
+electron spin precession at low temperatures. These effects allow for sensitive
+detection of all-optical nuclear magnetic resonance induced by periodically
+excited quantum-well electrons. The mechanism of previously observed Delta m =
+2 transitions is investigated and found to be attributable to electric
+quadrupole coupling, whereas Delta m = 1 transitions show signatures of both
+quadrupole and electron-spin induced magnetic dipole coupling.",0104564v1
+2001-07-03,Polarizable particles aggregation under rotating magnetic fields using scattering dichroism,"We used scattering dichroism to study the combined effects of viscous and
+magnetic forces on the dynamics of dipolar chains induced in magnetorheological
+suspensions under rotating magnetic fields. We found that the chains adjust
+their size to rotate synchronously with the field but with a constant phase
+lag. Two different behaviors for the dichroism (proportional to the total
+number of aggregated particles) and the phase lag are found below or above a
+critical frequency. We obtained a linear dependence of the critical frequency
+with the square of the magnetization and with the inverse of the viscosity. The
+Mason number (ratio of viscous to magnetic forces) governs the dynamics.
+Therefore there is a critical Mason number below which, the dichroism remains
+almost constant and above which, the rotation of the field prevents the
+particle aggregation process from taken place being this the mechanism
+responsible for the decrease of dichroism. Our experimental results have been
+corroborated with particle dynamics simulations showing good agreement.",0107070v1
+2003-05-22,Detection of the Vortex Dynamic Regimes in MgB2 by Third Harmonic AC Susceptibility Measurements,"In a type-II superconductor the generation of higher harmonics in the
+magnetic response to an alternating magnetic field is a consequence of the
+non-linearity in the I-V relationship. The shape of the current-voltage (I-V)
+curve is determined by the current dependence of the thermal activation energy
+U(J) and is thus related to the dynamical regimes governing the vortex motion.
+In order to investigate the vortex dynamics in MgB2 bulk superconductors we
+have studied the fundamental (chi1) and third (chi3) harmonics of the ac
+magnetic susceptibility. Measurements have been performed as a function of the
+temperature and the dc magnetic field, up to 9 T, for various frequencies and
+amplitudes of the ac field. We show that the analysis of the behaviour in
+frequency of chi3(T) and chi3(B) curves can provide clear information about the
+non-linearity in different regions of the I-V characteristic. By comparing the
+experimental curves with numerical simulations of the non-linear diffusion
+equation for the magnetic field we are able to resolve the crossover between a
+dissipative regime governed by flux creep and one dominated by flux flow
+phenomena.",0305523v1
+2004-03-18,Nonadiabatic effects in the dynamics of atoms confined in a cylindric time-orbiting-potential magnetic trap,"In a time-orbiting-potential magnetic trap the neutral atoms are confined by
+means of an inhomogeneous magnetic field superimposed to an uniform rotating
+one. We perform an analytic study of the atomic motion by taking into account
+the nonadiabatic effects arising from the spin dynamics about the local
+magnetic field. Geometric-like magnetic-fields determined by the Berry's phase
+appear within the quantum description. The application of a variational
+procedure on the original quantum equation leads to a set of dynamical
+evolution equations for the quantum average value of the position operator and
+of the spin variables. Within this approximation we derive the
+quantum-mechanical ground state configuration matching the classical adiabatic
+solution and perform some numerical simulations.",0403466v1
+2005-03-16,Dynamic phase separation in La(5/8-y)Pr(y)Ca(3/8)MnO(3),"Detailed magnetization measurements in La_{5/8-y}Pr_{y}Ca_{3/8} MnO_{3},
+including magnetic relaxation properties, demonstrate the dynamic nature of the
+phase separated state in manganites. The difference between the
+field-cooled-cooling and zero-field-cooled magnetization curves signals the
+existence in the latter of blocked metastable states separated by high energy
+barriers. Results of the magnetic viscosity show that the system becomes
+unblocked in a certain temperature window, where large relaxation rates are
+observed. We propose a simple phenomenological model in which the system
+evolves through a hierarchy of energy barriers, which separates the coexisting
+phases. The calculated magnetization curves using this model reproduce all the
+qualitative features of the experimental data. The overall results allowed us
+to construct an H-T phase diagram, where frozen and dynamical phase separation
+regions are clearly distinguished.",0503406v2
+2005-12-14,Measurement of Magnetization Dynamics in Single-Molecule Magnets Induced by Pulsed Millimeter-Wave Radiation,"We describe an experiment aimed at measuring the spin dynamics of the Fe8
+single-molecule magnet in the presence of pulsed microwave radiation. In
+earlier work, heating was observed after a 0.2-ms pulse of intense radiation,
+indicating that the spin system and the lattice were out of thermal equilibrium
+at millisecond time scale [Bal et al., Europhys. Lett. 71, 110 (2005)]. In the
+current work, an inductive pick-up loop is used to probe the photon-induced
+magnetization dynamics between only two levels of the spin system at much
+shorter time scales (from ns to us). The relaxation time for the magnetization,
+induced by a pulse of radiation, is found to be on the order of 10 us.",0512289v1
+2006-05-10,Spin-flip processes and ultrafast magnetization dynamics in Co - unifying the microscopic and macroscopic view of femtosecond magnetism,"The femtosecond magnetization dynamics of a thin cobalt film excited with
+ultrashort laser pulses has been studied using two complementary pump-probe
+techniques, namely spin-, energy- and time-resolved photoemission and
+time-resolved magneto-optical Kerr effect. Combining the two methods it is
+possible to identify the microscopic electron spin-flip mechanisms responsible
+for the ultrafast macroscopic magnetization dynamics of the cobalt film. In
+particular, we show that electron-magnon excitation does not affect the overall
+magnetization even though it is an efficient spin-flip channel on the sub-200
+fs timescale. Instead we find experimental evidence for the relevance of
+Elliott-Yafet type spin-flip processes for the ultrafast demagnetization taking
+place on a time scale of 300 fs.",0605272v2
+2006-09-18,Critical spin liquid at 1/3 magnetization in a spin-1/2 triangular antiferromagnet,"Although magnetically ordered at low temperatures, the spin-1/2 triangular
+antiferromagnet Cs_2CuCl_4 exhibits remarkable spin dynamics that strongly
+suggest proximity to a spin liquid phase. Here we address the question of
+whether a proximate spin liquid may also occur in an applied magnetic field,
+leaving a similar imprint on the dynamical spin correlations of this material.
+Specifically, we explore a spatially anisotropic Heisenberg spin-1/2 triangular
+antiferromagnet at 1/3 magnetization from a dual vortex perspective, and indeed
+find a new ``critical'' spin liquid phase described by QED3 with an emergent
+SU(6) symmetry. A number of nontrivial predictions are given for the dynamical
+spin structure factor in this ``algebraic vortex liquid'' phase, which can be
+tested experimentally via inelastic neutron scattering. We also discuss how the
+well-studied ``up-up-down'' magnetization plateaus can be captured within our
+approach, and further predict the existence of a stable gapless solid phase in
+a weakly ordered up-up-down state. Finally, we predict several anomalous
+``roton'' minima in the excitation spectrum in the regime of lattice anisotropy
+where the canted Neel state appears.",0609439v2
+1992-09-17,Differential cross-sections and escape plots for low energy $SU(2)$ BPS magnetic monopole dynamics,"We compute the low-energy classical differential scattering cross-section for
+BPS $SU(2)$ magnetic monopoles using the geodesic approximation to the actual
+dynamics and 16K parallel processors on a CM2. Numerical experiments suggest
+that the quantum BPS magnetic monopole differential cross-section is
+well-approximated by the classical BPS magnetic monopole differential
+cross-section. In particular, the expected quantum interference effects for
+bosons at scattering angle $\theta=\pi/2$ (CoM frame) are contradicted
+numerically. We argue that this is due to the topology of the classical
+configuration space for these solitons. We also study the scattering and
+bounded classical motions of BPS dyons and their global structure in phase
+space by constructing `escape plots'. The escape plots contain a surprising
+amount of structure, and suggest that the classical dynamics of two BPS $SU(2)$
+magnetic monopoles is chaotic and that there are closed and bounded two dyon
+motions with isolated energies.",9209063v1
+2008-03-29,Tunnel-barrier-enhanced dc voltage signals induced by magnetization dynamics in magnetic tunnel junctions,"We theoretically study the recently observed tunnel-barrier-enhanced dc
+voltage signals generated by magnetization precession in magnetic tunnel
+junctions. While the spin pumping is suppressed by the high tunneling
+impedance, two complimentary processes are predicted to result in a sizable
+voltage generation in ferromagnet (F)|insulator (I)|normal-metal (N) and F|I|F
+junctions, with one ferromagnet being resonantly excited. Magnetic dynamics in
+F|I|F systems induces a robust charge pumping, translating into voltage in open
+circuits. In addition, dynamics in a single ferromagnetic layer develops
+longitudinal spin accumulation inside the ferromagnet. A tunnel barrier then
+acts as a nonintrusive probe that converts the spin accumulation into a
+measurable voltage. Neither of the proposed mechanisms suffers from spin
+relaxation, which is typically fast on the scale of the exponentially slow
+tunneling rates. The longitudinal spin-accumulation buildup, however, is very
+sensitive to the phenomenological ingredients of the spin-relaxation picture.",0803.4228v2
+2008-06-18,Hybrid Planar FEM in Magnetoresonance Regime: Control of Dynamical Chaos,"We establish the influence of nonlinear electron dynamics in the
+magnetostatic field of a hybrid planar free-electron maser on its gain and
+interaction efficiency. Even for the `ideal' undulator magnetic field the
+presence of uniform longitudinal (guide) magnetic field potentially leads to
+the existence of chaotic zone around certain (magnetoresonant) value of the
+guide magnetic field. The width of the chaotic zone is given by the Chirikov
+resonance-overlap criterion applied to the normal undulator and cyclotron
+frequencies with respect to the coupling induced by the undulator magnetic
+field. Using analytical asymptotically exact solutions for trajectories of
+individual test electrons, we show that the magnetoresonant multiplier in
+electron trajectories is also present in the expression for the gain. The same
+Chirikov resonance-overlap criterion allows us to estimate analytically the
+maximal magnetoresonant gain of a hybrid planar free-electron maser showing
+that, in spite of the well-known drop in the gain for the exact
+magnetoresonance, the operation regime in the zone of regular dynamics slightly
+above the magnetoresonant value of the guide magnetic field is the preferable
+one.",0806.2997v1
+2008-08-06,Granularity and vortex dynamics in LaO_0.92F_0.08FeAs as probed by harmonics of the AC magnetic susceptibility,"Fundamental and higher harmonics of the AC magnetic susceptibility have been
+measured on a LaO_0.92F_0.08FeAs sample as a function of the temperature, at
+various amplitudes and frequencies of the AC magnetic field, with a small
+superimposed DC field parallel to the AC field. The granularity of the sample
+has been investigated and the inter-grain and intra-grain contributions have
+been clearly individuated looking at both the first and third harmonics. The
+vortex dynamics has been also analyzed, and a comparison with the magnetic
+behavior of both the MgB_2 and the cuprate superconductors has been performed.
+Some vortex dissipative phenomena, i.e. the thermally activated flux flow and
+the flux creep, have been detected in the presented measurements, similar to
+what obtained on YBCO. Nevertheless, although the general behavior is similar,
+several differences have been also evidenced between these different classes of
+superconductors, mainly in the third harmonics. We infer that different vortex
+dynamics have to be included into the analysis of the magnetic response in this
+iron-based new material.",0808.0804v1
+2009-04-23,Kolmogorov-Sinai entropy in field line diffusion by anisotropic magnetic turbulence,"The Kolmogorov-Sinai (KS) entropy in turbulent diffusion of magnetic field
+lines is analyzed on the basis of a numerical simulation model and theoretical
+investigations. In the parameter range of strongly anisotropic magnetic
+turbulence the KS entropy is shown to deviate considerably from the earlier
+predicted scaling relations [Rev. Mod. Phys. {\bf 64}, 961 (1992)]. In
+particular, a slowing down logarithmic behavior versus the so-called Kubo
+number $R\gg 1$ ($R = (\delta B / B_0) (\xi_\| / \xi_\bot)$, where $\delta B /
+B_0$ is the ratio of the rms magnetic fluctuation field to the magnetic field
+strength, and $\xi_\bot$ and $\xi_\|$ are the correlation lengths in respective
+dimensions) is found instead of a power-law dependence. These discrepancies are
+explained from general principles of Hamiltonian dynamics. We discuss the
+implication of Hamiltonian properties in governing the paradigmatic
+""percolation"" transport, characterized by $R\to\infty$, associating it with the
+concept of pseudochaos (random non-chaotic dynamics with zero Lyapunov
+exponents). Applications of this study pertain to both fusion and astrophysical
+plasma and by mathematical analogy to problems outside the plasma physics.
+  This research article is dedicated to the memory of Professor George M.
+Zaslavsky",0904.3610v1
+2010-11-25,Edge-Soliton-Mediated Vortex-Core Reversal Dynamics,"We report a new reversal mechanism of magnetic vortex cores in nanodot
+elements driven by out-of-plane currents, occurring through two coupled
+edge-solitons via dynamic transformations between magnetic solitons of
+different topological charges. This mechanism differs completely from the well
+known switching process mediated by the creation and annihilation of
+vortex-antivortex pairs in terms of the associated topological solitons,
+energies, and spin-wave emissions. Strongly localized out-of-plane gyrotropic
+fields induced by the fast motion of the two coupled edge-solitons enable a
+magnetization dip that plays a crucial role in the formation of the reversed
+core magnetization. This work provides a new physical insight into the dynamic
+transformations of magnetic solitons in nanoelements.",1011.5625v1
+2010-12-25,External Fields and the Dynamics of Fundamental Flavours in Holographic Duals of Large N Gauge Theories,"Using the gauge-gravity duality we study strongly coupled dynamics of
+fundamental flavours in large N_c gauge theories in a constant external field.
+We primarily focus on the effects of an external magnetic field. We use two
+holographic models realized in the Type IIB and Type IIA supergravity and
+present a comparative case study. In both these models, by studying the
+dynamics of probe branes, we explicitly demonstrate and discuss the
+magnetically induced chiral symmetry breaking effect (""magnetic catalysis"") in
+the flavour sector. We also study the associated thermodynamics and the meson
+spectrum and realize e.g. Zeeman splitting, stability enhancement of the mesons
+in the presence of an external magnetic field etc. By studying the quasinormal
+modes of the probe brane fluctuation in the hydrodynamic limit we also obtain
+an analytic dispersion relation in the presence of a magnetic field in the Type
+IIA model. This dispersion relation consists of a propagating sound mode in the
+otherwise diffusive channel and is sourced by the quantum anomaly of the global
+U(1) current. We briefly discuss the effects of an external electric field and
+observe that the flavour bound states dissociate for sufficiently high electric
+fields and an electric current is induced.",1012.5450v1
+2011-03-22,Magnetic Interactions in Ball-Milled Spinel Ferrites,"Spinel Fe3O4 nanoparticles have been produced through ball milling in
+methyl-alcohol (CH3OH), aiming to obtain samples with similar average particle
+sizes <d> and different interparticle interactions. Three samples having
+Fe3O4/CH3(OH) mass ratios R of 3 %, 10 % and 50 % wt. were milled for several
+hours until particle size reached a steady value (<d> ~ 7-10 nm). A detailed
+study of static and dynamic magnetic properties has been undertaken by
+measuring magnetization, ac susceptibility and M\""ossbauer data. As expected
+for small particles, the Verwey transition was not observed, but instead
+superparamagnetic (SPM) behavior was found with transition to a blocked state
+at TB ~ 10-20 K. Spin disorder of the resulting particles, independent of its
+concentration, was inferred from the decrease of saturation magnetization MS at
+low temperatures. For samples having 3% wt. of magnetic particles, dynamic ac
+susceptibility measurements show a thermally activated Arrhenius dependence of
+the blocking temperature with applied frequency. This behaviour is found to
+change as interparticle interactions begin to rule the dynamics of the system,
+yielding a spin-glass-like state at low temperatures for R = 50 wt.% sample.",1103.4390v1
+2011-08-15,Effects of Magnetic Turbulence on the Dynamics of Pickup Ions in the Ionosheath of Mars,"We study some of the effects that magnetic turbulent fluctuations have on the
+dynamics of pickup O+ ions in the magnetic polar regions of the Mars
+ionosheath. In particular we study their effect on the bulk velocity profiles
+of ions as a function of altitude over the magnetic poles, in order to compare
+them with recent Mars Express data; that indicate that their average velocity
+is very low and essentially in the anti-sunward direction. We find that, while
+magnetic field fluctuations do give rise to deviations from simple ExB-drift
+gyromotion, even fluctuation amplitudes much greater than those of in situ
+measurements are {\it not} able to reproduce the vertical velocity profile of
+O+ ions. We conclude that other physical mechanisms, different from a pure
+charged particle dynamics, are acting on pickup ions at the Martian terminator.
+A possibility being a viscous-like interaction between the Solar Wind and the
+Martian ionosphere at low altitudes.",1108.2935v1
+2011-09-30,"Magnetization Dynamics, Gyromagnetic Relation, and Inertial Effects","The gyromagnetic relation - i.e. the proportionality between the angular
+momentum $\vec L$ (defined by an inertial tensor) and the magnetization $\vec
+M$ - is evidence of the intimate connections between the magnetic properties
+and the inertial properties of ferromagnetic bodies. However, inertia is absent
+from the dynamics of a magnetic dipole (the Landau-Lifshitz equation, the
+Gilbert equation and the Bloch equation contain only the first derivative of
+the magnetization with respect to time). In order to investigate this
+paradoxical situation, the lagrangian approach (proposed originally by T. H.
+Gilbert) is revisited keeping an arbitrary nonzero inertial tensor. A dynamic
+equation generalized to the inertial regime is obtained. It is shown how both
+the usual gyromagnetic relation and the well-known Landau-Lifshitz-Gilbert
+equation are recovered at the kinetic limit, i.e. for time scales above the
+relaxation time $\tau$ of the angular momentum.",1109.6782v1
+2012-01-03,The inverse cascade of magnetic helicity in magnetohydrodynamic turbulence,"The nonlinear dynamics of magnetic helicity, $H^M$, which is responsible for
+large-scale magnetic structure formation in electrically conducting turbulent
+media is investigated in forced and decaying three-dimensional
+magnetohydrodynamic turbulence. This is done with the help of high resolution
+direct numerical simulations and statistical closure theory. The numerically
+observed spectral scaling of $H^M$ is at variance with earlier work using a
+statistical closure model [Pouquet et al., J. Fluid Mech. \textbf{77} 321
+(1976)]. By revisiting this theory a universal dynamical balance relation is
+found that includes effects of kinetic helicity, as well as kinetic and
+magnetic energy on the inverse cascade of $H^M$ and explains the
+above-mentioned discrepancy. Considering the result in the context of
+mean-field dynamo theory suggests a nonlinear modification of the
+$\alpha$-dynamo effect important in the context of magnetic field excitation in
+turbulent plasmas.",1201.0717v3
+2013-01-22,Stripe disorder and dynamics in the hole-doped antiferromagnetic insulator La5/3Sr1/3CoO4,"We report on an investigation into the dynamics of the stripe phase of
+La5/3Sr1/3CoO4, a material recently shown to have an hour-glass magnetic
+excitation spectrum. A combination of magnetic susceptibility, muon-spin
+relaxation and nuclear magnetic resonance measurements strongly suggest that
+the physics is determined by a disordered configuration of charge and spin
+stripes whose frustrated magnetic degrees of freedom are strongly dynamic at
+high temperature and which freeze out in a glassy manner as the temperature is
+lowered. Our results broadly confirm a recent theoretical prediction, but show
+that the charge quenching remains incomplete well below the charge ordering
+temperature and reveal, in detail, the manner in which the magnetic degrees of
+freedom are frozen.",1301.5124v2
+2014-04-10,Optical gyrotropy as a test for dynamic chiral magnetic effect of Weyl semimetals,"Recent angle resolved photoemission spectroscopy measurements have identified
+an inversion symmetry breaking Weyl semimetal phase in TaAs and NbAs. In an
+inversion symmetry breaking Weyl semimetal the left and the right handed Weyl
+points can occur at different energies and the energy mismatch between the Weyl
+points of opposite chirality is known as the chiral chemical potential. In the
+presence of the chiral chemical potential, the nontrivial Berry curvature of
+the Weyl fermions gives rise to the \emph{dynamic} chiral magnetic effect. This
+describes how a time dependent magnetic field leads to an electrical current
+along the applied field direction, which is also proportional to the field
+strength. We derive a general formula for the dynamic chiral magnetic
+conductivity of the inversion symmetry breaking Weyl semimetal. We show that
+the measurement of the natural optical activity or rotary power provides a
+direct confirmation of the existence of the dynamic chiral magnetic effect in
+inversion symmetry breaking Weyl semimetals.",1404.2927v2
+2015-01-01,Dynamic rotor mode in antiferromagnetic nanoparticles,"We present experimental, numerical, and theoretical evidence for a new mode
+of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering
+experiments on 8 nm particles of hematite display a loss of diffraction
+intensity with temperature, the intensity vanishing around 150 K. However, the
+signal from inelastic neutron scattering remains above that temperature,
+indicating a magnetic system in constant motion. In addition, the precession
+frequency of the inelastic magnetic signal shows an increase above 100 K.
+Numerical Langevin simulations of spin dynamics reproduce all measured neutron
+data and reveal that thermally activated spin canting gives rise to a new type
+of coherent magnetic precession mode. This ""rotor"" mode can be seen as a
+high-temperature version of superparamagnetism and is driven by exchange
+interactions between the two magnetic sublattices. The frequency of the rotor
+mode behaves in fair agreement with a simple analytical model, based on a high
+temperature approximation of the generally accepted Hamiltonian of the system.
+The extracted model parameters, as the magnetic interaction and the axial
+anisotropy, are in excellent agreement with results from Mossbauer
+spectroscopy.",1501.00313v1
+2015-01-09,"Collective magnetization dynamics in ferromagnetic (Ga,Mn)As mediated by photo-excited carriers","We present a study of photo-excited magnetization dynamics in ferromagnetic
+(Ga,Mn)As films observed by time-resolved magneto-optical measurements. The
+magnetization precession triggered by linearly polarized optical pulses in the
+absence of an external field shows a strong dependence on photon frequency when
+the photo-excitation energy approaches the band-edge of (Ga,Mn)As. This can be
+understood in terms of magnetic anisotropy modulation by both laser heating of
+the sample and by hole-induced non-thermal paths. Our findings provide a means
+for identifying the transition of laser-triggered magnetization dynamics from
+thermal to non-thermal mechanisms, a result that is of importance for ultrafast
+optical spin manipulation in ferromagnetic materials via non-thermal paths.",1501.02083v1
+2015-03-15,Time-Dependent Meson Melting in External Magnetic Field,"The dynamics of a probe D7-brane in an asymptotically AdS-Vaidya background
+has been investigated in the presence of an external magnetic field.
+Holographically, this is dual to the dynamical meson melting in the N = 2 super
+Yang-Milles theory. If the final temperature of the system is large enough, the
+probe D7-brane will dynamically cross the horizon (black hole embedding). By
+turning on the external magnetic field and raising it sufficiently, the final
+embedding of the corresponding D7-brane changes to Minkowski embedding. In the
+field theory side, this means that the mesons which melt due to the raise in
+the temperature, will form bound states again by applying an external magnetic
+field. We will also show that the evolution of the system to its final
+equilibrium state is postponed due to the presence of the magnetic field.",1503.04439v2
+2015-03-31,Nonstandard electron dynamics in topological insulators subjected to magnetic field: the Berry phase effects,"The quasiclassical dynamics is studied for charge carriers moving on the
+surface of 3D topological insulator of Bi2Te3 type and subjected to static
+magnetic field. The effects connected to the symmetry changes of electron
+isoenergetic surfaces (contours) and to the nonzero Berry curvature are taken
+into account. It is shown that in contrast to the standard dynamics of the
+electrons moving in constant and uniform magnetic field along the trajectories
+defined by the equations E(k)=const and pz=const, here some new effects are
+arising, being related to both the appearance of the anomalous velocity term
+proportional to the Berry curvature, and to the trajectory bending related to
+the additional term for the energy proportional to the orbital momentum of the
+wavepacket. This should lead to the changes in cyclotron resonance conditions
+of the surface electrons. Although the time reversal invariance and the
+topological order are broken in the magnetic field, the investigation of
+cyclotron resonance allows determining whether this insulator was trivial or
+nontrivial at zero magnetic field.",1503.08959v1
+2015-04-06,Dynamics of molecular superrotors in external magnetic field,"We excite diatomic oxygen and nitrogen to high rotational states with an
+optical centrifuge and study their dynamics in external magnetic field. Ion
+imaging is employed to directly visualize, and follow in time, the rotation
+plane of molecular superrotors. The two different mechanisms of interaction
+between the magnetic field and the molecular angular momentum in paramagnetic
+oxygen and non-magnetic nitrogen lead to the qualitatively different behaviour.
+In nitrogen, we observe the precession of the molecular angular momentum around
+the field vector. In oxygen, strong spin-rotation coupling results in faster
+and richer dynamics, encompassing the splitting of the rotation plane in three
+separate components. As the centrifuged molecules evolve with no significant
+dispersion of the molecular wave function, the observed magnetic interaction
+presents an efficient mechanism for controlling the plane of molecular
+rotation.",1504.01432v1
+2015-04-09,Spin-transfer torque effects in the dynamic forced response of the magnetization of nanoscale ferromagnets in superimposed ac and dc bias fields in the presence of thermal agitation,"Spin-transfer torque (STT) effects on the stationary forced response of
+nanoscale ferromagnets subject to thermal fluctuations and driven by an ac
+magnetic field of arbitrary strength and direction are investigated via a
+generic nanopillar model of a spin-torque device comprising two ferromagnetic
+strata representing the free and fixed layers and a nonmagnetic conducting
+spacer all sandwiched between two ohmic contacts. The STT effects are treated
+via the Brown magnetic Langevin equation generalized to include the Slonczewski
+STT term thereby extending the statistical moment method [Y. P. Kalmykov et
+al., Phys. Rev. B 88, 144406 (2013)] to the forced response of the most general
+version of the nanopillar model. The dynamic susceptibility, nonlinear
+frequency-dependent dc magnetization, dynamic magnetic hysteresis loops, etc.
+are then evaluated highlighting STT effects on both the low-frequency thermal
+relaxation processes and the high-frequency ferromagnetic resonance, etc.,
+demonstrating a pronounced dependence of these on the spin polarization current
+and facilitating interpretation of STT experiments.",1504.02319v2
+2015-06-02,Detection of spin torque magnetization dynamics through low frequency noise,"We present a comparative study of high frequency dynamics and low frequency
+noise in elliptical magnetic tunnel junctions with lateral dimensions under 100
+nm presenting current-switching phenomena. The analysis of the high frequency
+oscillation modes with respect to the current reveals the onset of a
+steady-state precession regime for negative bias currents above $J=10^7
+A/cm^2$, when the magnetic field is applied along the easy axis of
+magnetization. By the study of low frequency noise for the same samples, we
+demonstrate the direct link between changes in the oscillation modes with the
+applied current and the normalised low frequency (1/f) noise as a function of
+the bias current. These findings prove that low frequency noise studies could
+be a simple and powerful technique to investigate spin-torque based
+magnetization dynamics.",1506.00901v1
+2015-09-18,Nonlinear ac stationary response and dynamic magnetic hysteresis of quantum uniaxial superparamagnets,"The nonlinear ac stationary response of uniaxial paramagnets and
+superparamagnets - nanoscale solids or clasters with spin number S ~ 10^0 -
+10^4 - in superimposed uniform ac and dc bias magnetic fields of arbitrary
+strength, each applied along the easy axis of magnetization, is determined by
+solving the evolution equation for the reduced density matrix represented as a
+finite set of three-term differential-recurrence relations for its diagonal
+matrix elements. The various harmonic components of the magnetization, dynamic
+magnetic hysteresis loops, etc. are then evaluated via matrix continued
+fractions indicating a pronounced dependence of the nonlinear response on S
+arising from the quantum spin dynamics. In the linear response approximation,
+the results concur with existing solutions.",1509.05616v2
+2015-11-17,Itinerant and localized magnetization dynamics in antiferromagnetic Ho,"Using femtosecond time-resolved resonant magnetic x-ray diffraction at the Ho
+L3 absorption edge, we investigate the demagnetization dynamics in
+antiferromagnetically ordered metallic Ho after femtosecond optical excitation.
+Tuning the x-ray energy to the electric dipole (E1, 2p -> 5d) or quadrupole
+(E2, 2p -> 4f) transition allows us to selectively and independently study the
+spin dynamics of the itinerant 5d and localized 4f electronic subsystems via
+the suppression of the magnetic (2 1 3-tau ) satellite peak. We find
+demagnetization timescales very similar to ferromagnetic 4f systems, suggesting
+that the loss of magnetic order occurs via a similar spin-flip process in both
+cases. The simultaneous demagnetization of both subsystems demonstrates strong
+intra-atomic 4f-5d exchange coupling. In addition, an ultrafast lattice
+contraction due to the release of magnetostriction leads to a transient shift
+of the magnetic satellite peak.",1511.05315v1
+2016-03-02,Electric-Field-Induced Spin Resonance in Antiferromagnetic Insulators: Inverse Process of the Dynamical Chiral Magnetic Effect,"We propose a realization of the electric-field-induced antiferromagnetic
+resonance. We consider three-dimensional antiferromagnetic insulators with
+spin-orbit coupling characterized by the existence of a topological term called
+the $\theta$ term. By solving the Landau-Lifshitz-Gilbert equation in the
+presence of the $\theta$ term, we show that, in contrast to conventional
+methods using ac magnetic fields, the antiferromagnetic resonance state is
+realized by ac electric fields along with static magnetic fields. This
+mechanism can be understood as the inverse process of the dynamical chiral
+magnetic effect, an alternating current generation by magnetic fields. In other
+words, we propose a way to electrically induce the dynamical axion field in
+condensed matter. We discuss a possible experiment to observe our proposal,
+which utilizes the spin pumping from the antiferromagnetic insulator into a
+heavy metal contact.",1603.00614v3
+2016-05-05,Large-scale dynamics of magnetic helicity,"In this paper we investigate the dynamics of magnetic helicity in
+magnetohydrodynamic (MHD) turbulent flows focusing at scales larger than the
+forcing scale. Our results show a nonlocal inverse cascade of magnetic
+helicity, which occurs directly from the forcing scale into the largest scales
+of the magnetic field. We also observe that no magnetic helicity and no energy
+is transferred to an intermediate range of scales sufficiently smaller than the
+container size and larger than the forcing scale. Thus, the statistical
+properties of this range of scales, which increases with scale separation, is
+shown to be described to a large extent by the zero flux solutions of the
+absolute statistical equilibrium theory exhibited by the truncated ideal MHD
+equations.",1605.01697v3
+2017-03-20,Relativistic theory of magnetic inertia in ultrafast spin dynamics,"The influence of possible magnetic inertia effects has recently drawn
+attention in ultrafast magnetization dynamics and switching. Here we derive
+rigorously a description of inertia in the Landau-Lifshitz-Gilbert equation on
+the basis of the Dirac-Kohn-Sham framework. Using the Foldy-Wouthuysen
+transformation up to the order of $1/c^4$ gives the intrinsic inertia of a pure
+system through the 2$^{\rm nd}$ order time-derivative of magnetization in the
+dynamical equation of motion. Thus, the inertial damping $\mathcal{I}$ is a
+higher order spin-orbit coupling effect, $\sim 1/c^4$, as compared to the
+Gilbert damping $\Gamma$ that is of order $1/c^2$. Inertia is therefore
+expected to play a role only on ultrashort timescales (sub-picoseconds). We
+also show that the Gilbert damping and inertial damping are related to one
+another through the imaginary and real parts of the magnetic susceptibility
+tensor respectively.",1704.01559v1
+2017-12-25,Dynamics of magnetic flux tubes and IR-variability of Young Stellar Objects,"We simulate the dynamics of slender magnetic flux tubes (MFTs) in the
+accretion disks of T Tauri stars. The dynamical equations of our model take
+into account the aerodynamic and turbulent drag forces, and the radiative heat
+exchange between the MFT and ambient gas. The structure of the disk is
+calculated with the help of our MHD model of the accretion disks. We consider
+the MFTs formed at the distances $0.027-0.8$ au from the star with various
+initial radii and plasma betas $\beta_0$. The simulations show that the MFT
+with weak magnetic field ($\beta_0=10$) rise slowly with speeds less than the
+sound speed. The MFTs with $\beta_0=1$ form outflowing magnetized corona of the
+disk. Strongly magnetized MFTs ($\beta_0=0.1$) can cause the outflows with
+velocities $20-50$ km s$^{-1}$. The tubes rise periodically over times from
+several days to several months according to our simulations. We propose that
+periodically rising MFTs can absorb stellar radiation and contribute to the
+IR-variability of Young Stellar Objects.",1712.09094v1
+2018-06-29,Optical probing of Rayleigh wave driven magneto-acoustic resonance,"The resonant interaction of electrically excited travelling surface acoustic
+waves and magnetization has been hitherto probed through the acoustic
+component. In this work it is investigated using time-resolved magneto-optical
+detection of magnetization dynamics. To that end, we develop an experimental
+scheme where laser pulses are used both to generate the acoustic wave frequency
+and to probe magnetization dynamics thus ensuring perfect phase locking. The
+light polarization dependence of the signal enables to disentangle elasto-optic
+and magneto-optic contributions and to obtain the in-plane and out-of-plane
+dynamic magnetization components. Magnetization precession is proved to be
+driven solely by the acoustic wave. Its amplitude is shown to resonate at the
+same field at which we detect piezo-electrically the resonant attenuation of
+the acoustic wave, clearly evidencing the magneto-acoustic resonance with high
+sensitivity.",1806.11410v1
+2018-07-12,Capture and chaotic scattering of a charged particle by magnetic monopole under uniform electric field,"Motivated by the realization of magnetic monopole of Berry curvature by the
+energy crossing point, we theoretically study the effect of magnetic monopole
+under a uniform electric field in the semiclassical dynamics, which is relevant
+to many physical situations such as relaxation through the diabolic point. We
+found that the competition between the backward scattering by the monopole
+magnetic field and the acceleration by the electric field leads to the bound
+state, i.e., capture of a particle near the monopole. Furthermore, the
+nonlinearity induced by the magnetic monopole leads to the chaotic behavior in
+the transient dynamics, i.e., the transient chaos. We computed characteristic
+quantities of the strange saddle which gives rise to the transient chaos, and
+verified that the abrupt bifurcation occurs as we tune the system parameter
+toward the parameter region in which the system is solvable.",1807.04451v1
+2018-12-20,Laser Controlled Spin Dynamics of Ferromagnetic Thin Film from Femtosecond to Nanosecond Timescale,"Laser induced modulation of the magnetization dynamics occurring over various
+time-scales have been unified here for a Ni80Fe20 thin film excited by
+amplified femtosecond laser pulses. The weak correlation between
+demagnetization time and pump fluence with substantial enhancement in
+remagnetization time is demonstrated using three-temperature model considering
+the temperatures of electron, spin and lattice. The picosecond magnetization
+dynamics is modeled using the Landau-Lifshitz-Gilbert equation. With increasing
+pump fluence the Gilbert damping parameter shows significant enhancement from
+its intrinsic value due to increment in the ratio of electronic temperature to
+Curie temperature within very short time scale. The precessional frequency
+experiences noticeable red shift with increasing pump fluence. The changes in
+the local magnetic properties due to accumulation and dissipation of thermal
+energy within the probed volume are described by the evolution of temporal
+chirp parameter in a comprehensive manner. A unification of ultrafast magnetic
+processes and its control over broad timescale would enable the integration of
+various magnetic processes in a single device and use one effect to control
+another.",1812.08404v1
+2019-04-12,A dynamical magnetic field accompanying the motion of ferroelectric domain walls,"The recently proposed dynamical multiferroic effect describes the generation
+of magnetization from temporally varying electric polarization. Here, we show
+that the effect can lead to a magnetic field at moving ferroelectric domain
+walls, where the rearrangement of ions corresponds to a rotation of
+ferroelectric polarization in time. We develop an expression for the dynamical
+magnetic field, and calculate the relevant parameters for the example of
+90$^\circ$ and 180$^\circ$ domain walls in BaTiO$_3$ using a combination of
+density functional theory and phenomenological modeling. We find that the
+magnetic field reaches the order of several $\mu$T at the center of the wall,
+and we propose two experiments to measure the effect with nitrogen-vacancy
+center magnetometry.",1904.06335v1
+2019-05-11,Magnetic field line twisting by photospheric vortices: energy storage and release,"We investigate the dynamics of a closed corona cartesian reduced
+magnetohydrodynamic (MHD) model where photospheric vortices twist the coronal
+magnetic field lines. We consider two corotating or counter-rotating vortices
+localized at the center of the photospheric plate, and additionally more
+corotating vortices that fill the plate entirely. Our investigation is
+specifically devoted to study the fully nonlinear stage, after the linear stage
+during which the vortices create laminar and smoothly twisting flux tubes. Our
+main goal is to understand the dynamics of photospheric vortices twisting the
+field lines of a coronal magnetic field permeated by finite amplitude broadband
+fluctuations. We find that depending on the arrangement and handedness of the
+photospheric vortices an inverse cascade storing a significant amount of
+magnetic energy may occur or not. In the first case a reservoir of magnetic
+energy available to large events such as destabilization of a pre-CME
+configuration develops, while in the second case the outcome is a turbulent
+heated corona. Although our geometry is simplified our simulations are shown to
+have relevant implications for coronal dynamics and CME initiation.",1905.04420v1
+2019-05-30,Interface moment dynamics and its contribution to spin-transfer torque switching process in magnetic tunnel junctions,"A practical problem for memory applications involving perpendicularly
+magnetized magnetic tunnel junctions is the reliability of switching
+characteristics at high-bias voltage. Often it has been observed that at
+high-bias, additional error processes are present that cause a decrease in
+switching probability upon further increase of bias voltage. We identify the
+main cause of such error-rise process through examination of switching
+statistics as a function of bias voltage and applied field, and the junction
+switching dynamics in real time. These experiments show a coincidental onset of
+error-rise and the presence of a new low-frequency microwave emission well
+below that dictated by the anisotropy field. We show that in a few-macrospin
+coupled numerical model, this is consistent with an interface region with
+concentrated perpendicular anisotropy, and where the magnetic moment has
+limited exchange coupling to the rest of the layers. These results point to the
+important role high-frequency interface magnetic moment dynamics play in
+determining the switching characteristics of these tunnel junction devices.",1905.13253v1
+2019-06-30,"Non-linear spin torque, pumping and cooling in superconductor/ferromagnet systems","We study the effects of the coupling between magnetization dynamics and the
+electronic degrees of freedom in a heterostructure of a metallic nanomagnet
+with dynamic magnetization coupled with a superconductor containing a steady
+spin-splitting field. We predict how this system exhibits a non-linear spin
+torque, which can be driven either with a temperature difference or a voltage
+across the interface. We generalize this notion to arbitrary magnetization
+precession by deriving a Keldysh action for the interface, describing the
+coupled charge, heat and spin transport in the presence of a precessing
+magnetization. We characterize the effect of superconductivity on the
+precession damping and the anti-damping torques. We also predict the full
+non-linear characteristic of the Onsager counterparts of the torque, showing up
+via pumped charge and heat currents. For the latter, we predict a spin-pumping
+cooling effect, where the magnetization dynamics can cool either the nanomagnet
+or the superconductor.",1907.00424v2
+2019-07-22,Heavy quark dynamics in a hot magnetized QCD medium,"The heavy quark drag and momentum diffusion have been investigated in a hot
+magnetized quark-gluon plasma, along the directions parallel and perpendicular
+to the magnetic field. The analysis is done within the framework of
+Fokker-Planck dynamics by considering the heavy quark scattering with thermal
+quarks and gluons at the leading order in the coupling constant. An extended
+quasiparticle model is adopted to encode the thermal QCD medium interactions in
+the presence of a magnetic field. Further, the higher Landau level effects on
+the temperature behaviour of the parallel and perpendicular components of the
+drag force and diffusion coefficients have studied. It has been observed that
+both the equation of state and the magnetic field play key roles in the
+temperature dependence of the heavy quark dynamics.",1907.09556v1
+2019-10-11,Analytical and Numerical Methods and Test Calculations of One-Dimensional Force--Free Magnetodynamics on Arbitrary Magnetic Surfaces across Horizons of Spinning Black Holes,"Numerical simulations of the force-free magnetodynamics (FFMD) of the
+electromagnetic field around a spinning black hole are useful to investigate
+the dynamic electromagnetic processes around a spinning black hole, such as the
+emergence of the Blandford--Znajek mechanism. To reveal the basic physics of
+magnetic fields around a black hole through the dynamic process, we use
+one-dimensional (1D) FFMD along the axisymmetric magnetic surface, which
+provides a relatively simple, sufficiently precise, and powerful tool to
+analyze the dynamic process around a spinning black hole. We review the
+analytic and numerical aspects of 1D FFMD for an arbitrary magnetic surface
+around a black hole. In addition, we also show some numerical simulation test
+results for three types of magnetic surfaces at the equatorial plane of the
+black hole.",1910.04929v1
+2020-04-03,Spin-Phonon Coupling and Thermodynamic Behaviour in YCrO3 and LaCrO3: Inelastic Neutron Scattering and Lattice Dynamics,"We report detailed temperature-dependent inelastic neutron scattering and
+ab-initio lattice dynamics investigation of magnetic perovskites YCrO3 and
+LaCrO3. The magnetic neutron scattering from the Cr ions exhibits significant
+changes with temperature and dominates at low momentum transfer regime.
+Ab-inito calculations performed including magnetic interactions show that the
+effect of magnetic interaction is very signicant on the low- as well as
+high-energy phonon modes. We have also shown that the inelastic neutron
+spectrum of YCrO3 mimics the magnon spectrum from a G-type antiferromagnetic
+system, which is consistent with previously reported magnetic structure in the
+compound. The ab-initio lattice dynamics calculations in both the compounds
+exhibit anisotropic thermal expansion behaviour in the orthorhombic structure
+and predict negative thermal expansion along the crystallographic a-axis at low
+temperatures. We identify the anharmonic phonon modes responsible for this
+anamolous behaviour in LaCrO3 involving low-energy La vibrations and
+distortions of the CrO6 octahedra.",2004.01731v1
+2020-08-13,Dynamics of a magnetic gear with two cogging-free operation modes,"The coupling of two rotating spherical magnets is investigated
+experimentally. For two specific angles between the input and output rotation
+axes, a cogging-free coupling is observed, where the driven magnet is
+phase-locked to the driving one. The striking difference between these two
+modes of operation is the reversed sense of rotation of the driven magnet. For
+other angles the experiments reveal a more complex dynamical behavior, which is
+divided in three different classes. This is done by analysing the deviation
+from a periodic motion of the driven magnet, and by measuring the total
+harmonic distortion of this rotation. The experimental results can be
+understood by a mathematical model based on pure dipole-dipole interaction,
+with the addition of adequate friction terms.",2008.05922v1
+2020-09-07,Breaking of Coulomb blockade by macrospin-assisted tunneling,"A magnet with precessing magnetization pumps a spin current into adjacent
+leads. As a special case of this spin pumping, a precessing macrospin
+(magnetization) can assist electrons in tunneling. In small systems, however,
+the Coulomb blockade effect can block the transport of electrons. Here, we
+investigate the competition between macrospin-assisted tunneling and Coulomb
+blockade for the simplest system where both effects meet; namely, for a single
+tunnel junction between a normal metal and a metallic ferromagnet with
+precessing magnetization. By combining Fermi's golden rule with magnetization
+dynamics and charging effects, we show that the macrospin-assisted tunneling
+can soften or even break the Coulomb blockade. The details of these effects --
+softening and breaking of Coulomb blockade -- depend on the macrospin dynamics.
+This allows, for example, to measure the macrospin dynamics via a system's
+current-voltage characteristics. It also allows to control a spin current
+electrically. From a general perspective, our results provide a platform for
+the interplay between spintronics and electronics on the mesoscopic scale. We
+expect our work to provide a basis for the study of Coulomb blockade in more
+complicated spintronic systems.",2009.03373v3
+2020-10-17,Fluctuation relations for dissipative systems in constant external magnetic field: theory and molecular dynamics simulations,"It has recently been pointed out that Hamiltonian particle systems in
+constant magnetic fields satisfy generalized time-reversal symmetries that
+enable to prove useful statistical relationships based on equilibrium
+phase-space probability distributions without the need to invert, as commonly
+considered necessary, the magnetic field. Among these relations, that hold
+without need of Casimir modifications, one finds the standard linear response
+Green-Kubo relations, and consequently the Onsager reciprocal relations. Going
+beyond linear response is also possible, for instance in terms of transient and
+steady state Fluctuation Relations (FRs). Here we highlight how the generalized
+time-reversal symmetries ensure that the (transient) FRs theory directly
+applies also for systems in external magnetic fields. Furthermore we show that
+transient FR can indeed be verified in nonequilibrium molecular dynamics
+simulations, for systems subjected to magnetic and electric fields, which are
+thermostatted \`a la Nos\'e-Hoover. The result is nontrivial because, since it
+is not immediate within which sizes and time scales the effects can actually be
+observable, it is not obvious what one may obtain by real molecular dynamics
+simulations.",2010.08831v1
+2020-11-02,How correlations change the magnetic structure factor of the kagome Hubbard model,"The kagome Hubbard model (KHM) is a paradigmatic example of a frustrated
+two-dimensional model. While its strongly correlated regime, described by a
+Heisenberg model, is of topical interest due to its enigmatic prospective
+spin-liquid ground state, the weakly and moderately correlated regimes remain
+largely unexplored. Motivated by the rapidly growing number of metallic kagome
+materials (e.g., Mn$_3$Sn, Fe$_3$Sn$_2$, FeSn, Co$_3$Sn$_2$S$_2$,
+Gd$_3$Ru$_4$Al$_{12}$), we study the respective regimes of the KHM by means of
+three complementary numerical methods: the dynamical mean-field theory (DMFT),
+the dynamical vertex approximation (D$\Gamma$A), and determinant quantum Monte
+Carlo (DQMC). In contrast to the archetypal square-lattice, we find no
+tendencies towards magnetic ordering, as magnetic correlations remain
+short-range. Nevertheless, the magnetic correlations undergo a remarkable
+crossover as the system approaches the metal-to-insulator transition. The Mott
+transition itself does however not affect the magnetic correlations. Our
+equal-time and dynamical structure factors can be used as a reference for
+inelastic neutron scattering experiments on the growing family of metallic
+kagome materials.",2011.01085v1
+2020-11-09,Regimes of motion of magnetocapillary swimmers,"The dynamics of a triangular magnetocapillary swimmer is studied using the
+lattice Boltzmann method. Performing extensive numerical simulations taking
+into account the coupled dynamics of the fluid-fluid interface and of magnetic
+particles floating on it and driven by external magnetic fields we identify
+several regimes of the swimmer motion. In the regime of high frequencies the
+swimmer's maximum velocity is centered around the particle's inverse coasting
+time. Modifying the ratio of surface tension and magnetic forces allows to
+study the swimmer propagation in the regime of significantly lower frequencies
+mainly defined by the strength of the magnetocapillary potential. Finally,
+introducing a constant magnetic contribution in each of the particles in
+addition to their magnetic moment induced by external fields leads to another
+regime characterised by strong in-plane swimmer reorientations that resemble
+experimental observations.",2011.07144v1
+2021-01-04,Mechanism of barrier crossing dynamics in the presence of both time dependent and independent magnetic fields,"In this paper we have presented the mechanism of the barrier crossing
+dynamics of a Brownian particle which is coupled to a thermal bath in the
+presence of both time independent and fluctuating magnetic fields. Here the
+following three aspects are important in addition to the role of the thermal
+bath on the barrier crossing dynamics. Magnetic field induced coupling may
+introduce a resonance like effect. Another role of the field is that
+enhancement of its strength reduces the frequency factor of the barrier
+crossing rate constant. Finally, the fluctuating magnetic field introduces an
+induced electric field which activates the Brownian particle to cross the
+energy barrier. As a result of interplay among these aspects versatile
+non-monotonic behavior may appear in the variation of the rate constant as a
+function of the strength of the time independent magnetic field.",2101.00861v1
+2021-02-12,Manipulation of magnetic domain wall by ferroelectric switching: Dynamic magnetoelectricity at the nanoscale,"Controlling magnetism using voltage is highly desired for applications, but
+remains challenging due to fundamental contradiction between polarity and
+magnetism. Here we propose a mechanism to manipulate magnetic domain walls in
+ferrimagnetic or ferromagnetic multiferroics using electric field. Different
+from those studies based on static domain-level couplings, here the
+magnetoelectric coupling relies on the collaborative spin dynamics around
+domain walls. Accompanying the reversal of spin chirality driven by
+polarization switching, a ""rolling-downhill""-like motion of domain wall is
+achieved at the nanoscale, which tunes the magnetization locally. Our mechanism
+opens an alternative route to pursuit practical and fast converse
+magnetoelectric functions via spin dynamics.",2102.06471v2
+2021-04-06,All-Optical Control of Magnetization in Quantum-Confined Ultrathin Magnetic Metals,"All-optical control dynamics of magnetization in sub-10 nm metallic thin
+films are investigated, as these films with quantum confinement undergo unique
+interactions with femtosecond laser pulses. Our theoretical derivations based
+on the free electron model show that the density of states at Fermi level
+(DOS_F) and electron-phonon coupling coefficients (G_ep) in ultrathin metals
+have very high sensitivity to film thickness within a few Angstroms. As DOS_F
+and G_ep depend on thickness, we show that completely different magnetization
+dynamics characteristics emerge compared with bulk metals. Our model suggests
+highly-efficient energy transfer from fs laser photons to spin waves due to
+minimal energy absorption by phonon. This sensitivity to thickness and
+efficient energy transfer offers an opportunity to obtain ultrafast on-chip
+magnetization dynamics.",2104.02608v1
+2021-07-29,Magnon band structure of skyrmion crystals and stereographic projection approach,"Using semiclassical method combined with stereographic projection approach,
+we investigate the magnetic dynamics of the skyrmion crystal (SkX), formed in
+planar ferromagnet with both Dzyaloshinskii-Moriya interaction and uniform
+magnetic field. The topologically non-trivial ground state of SkX is described
+in stereographic projection by the complex valued function with simple poles at
+skyrmions' positions. We use the earlier proposed ansatz for this ground state
+function in the form of the sum of individual skyrmions. The dynamics follows
+from the second variation of the classical action. Numerical analysis yields
+the magnon band structure of tight-binding form in accordance with previously
+known results. There are two sets of bands, one set with a flat dispersion,
+topologically trivial and rapidly evolving with magnetic field. Another set is
+robust to magnetic field, characterized by pronounced dispersion and with the
+Berry curvature which may be sign-reversal in the Brillouin zone. The developed
+theory can be straightforwardly generalized for the analysis of magnetic
+dynamics in topological spin structures of other types.",2107.14335v1
+2021-09-30,Observation of the orbital Hall effect in a light metal Ti,"The orbital angular momentum is a core ingredient of orbital magnetism, spin
+Hall effect, giant Rashba spin splitting, orbital Edelstein effect, and
+spin-orbit torque. However, its experimental detection is tricky. In
+particular, direct detection of the orbital Hall effect remains elusive despite
+its importance for electrical control of magnetic nanodevices. Here we report
+the direct observation of the orbital Hall effect in a light metal Ti. The Kerr
+rotation by the accumulated orbital magnetic moment is measured at Ti surfaces,
+whose result agrees with theoretical calculations semiquantitatively and is
+supported by the orbital torque measurement in Ti-based magnetic
+heterostructures. The results confirm the electron orbital angular momentum as
+an essential dynamic degree of freedom, which may provide a novel mechanism for
+the electric control of magnetism. The results may also deepen the
+understanding of spin, valley, phonon, and magnon dynamics coupled with orbital
+dynamics.",2109.14847v1
+2022-03-12,The mass-lumped midpoint scheme for computational micromagnetics: Newton linearization and application to magnetic skyrmion dynamics,"We discuss a mass-lumped midpoint scheme for the numerical approximation of
+the Landau-Lifshitz-Gilbert equation, which models the dynamics of the
+magnetization in ferromagnetic materials. In addition to the classical
+micromagnetic field contributions, our setting covers the non-standard
+Dzyaloshinskii-Moriya interaction, which is the essential ingredient for the
+enucleation and stabilization of magnetic skyrmions. Our analysis also includes
+the inexact solution of the arising nonlinear systems, for which we discuss
+both a constraint preserving fixed-point solver from the literature and a novel
+approach based on the Newton method. We numerically compare the two
+linearization techniques and show that the Newton solver leads to a
+considerably lower number of nonlinear iterations. Moreover, in a numerical
+study on magnetic skyrmions, we demonstrate that, for magnetization dynamics
+that are very sensitive to energy perturbations, the midpoint scheme, due to
+its conservation properties, is superior to the dissipative tangent plane
+schemes from the literature.",2203.06445v1
+2022-02-23,"Biot-Savart type magnetic field quantization via prime number theory, applications to symbolic dynamics","In the present work we propose an algorithm based on the theory of prime
+numbers for the estimation of the magnetic field in a device of current
+carrying circular rings. Using the proposed algorithm, the magnetic field can
+be determined in a very good agreement with that resulting from an algorithm
+based on the Biot-Savart law. In addition, the prime-numbers-based algorithm
+gives quantized values of the magnetic field and reveals previously unknown
+behaviors such as special properties of the distribution of the waiting times
+at the quantized magnetic field values. Applications of the proposed
+prime-numbers-based algorithm to systems exhibiting symbolic dynamics is
+presented, proving its ability to provide a measure of the existence or not of
+dynamics in the system.",2204.00420v1
+2022-06-02,Anisotropic Gigahertz Antiferromagnetic Resonances of the Easy-Axis van der Waals Antiferromagnet CrSBr,"We report measurements of antiferromagnetic resonances in the van der Waals
+easy-axis antiferromagnet CrSBr. The interlayer exchange field and
+magnetocrystalline anisotropy fields are comparable to laboratory magnetic
+fields, allowing a rich variety of gigahertz-frequency dynamical modes to be
+accessed. By mapping the resonance frequencies as a function of the magnitude
+and angle of applied magnetic field we identify the different regimes of
+antiferromagnetic dynamics. The spectra show good agreement with a
+Landau-Lifshitz model for two antiferromagnetically-coupled sublattices,
+accounting for inter-layer exchange and triaxial magnetic anisotropy. Fits
+allow us to quantify the parameters governing the magnetic dynamics: at 5 K,
+the interlayer exchange field is $\mu_0 H_E =$ 0.395(2) T, and the hard and
+intermediate-axis anisotropy parameters are $\mu_0 H_c =$ 1.30(2) T and $\mu_0
+H_a =$ 0.383(7) T. The existence of within-plane anisotropy makes it possible
+to control the degree of hybridization between the antiferromagnetic resonances
+using an in-plane magnetic field.",2206.01286v2
+2022-11-07,Dynamic self-organisation and pattern formation by magnon-polarons,"Nonlinear dynamics can give rise, via the processes of self-organisation and
+pattern formation, to the spontaneous manifestation of order in open and
+complex systems far from equilibrium. Self-organising systems, transforming the
+inflow of energy into information, are ubiquitously found in current topical
+areas of science ranging from brainwave entrainment and neuromorphic computing
+to energy-efficient data storage technologies. In the latter, magnetic
+materials play a pivotal role combining very fast switching with permanent
+retention of information. However, it has been shown that, at very short time
+scales, magnetisation dynamics become chaotic due to internal instabilities,
+resulting in incoherent spin-wave excitations that ultimately destroy magnetic
+ordering. Here, contrary to all expectations, we show that such chaos gives
+rise to a periodic pattern of reversed magnetic domains, with a feature size
+far smaller than the spatial extent of the excitation. We explain this pattern
+as a result of phase-synchronisation of magnon-polaron waves, driven by strong
+coupling of magnetic and elastic modes. Our results reveal not only the
+peculiar formation and evolution of magnon-polarons at short time-scales, but
+also present a novel mechanism of magnetization reversal driven by coherent
+packets of short-wavelength quasiparticles.",2211.03723v1
+2022-11-21,Inertial dynamics and equilibrium correlation functions of magnetization at short times,"The method of moments is developed and employed to analyze the equilibrium
+correlation functions of the magnetization of ferromagnetic nanoparticles in
+the case of inertial magnetization dynamics. The method is based on the Taylor
+series expansion of the correlation functions and the estimation of the
+expansion coefficients. This method significantly reduces the complexity of
+analysis of equilibrium correlation functions. Analytical expressions are
+derived for the first three coefficients for the longitudinal and transverse
+correlation functions for the uniaxial magnetocrystalline anisotropy of
+ferromagnetic nanoparticles with a longitudinal magnetic field. The limiting
+cases of very strong and negligibly weak external longitudinal fields are
+considered. The Gordon sum rule for inertial magnetization dynamics is
+discussed. In addition, we show that finite analytic series can be used as a
+simple and satisfactory approximation for the numerical calculation of
+correlation functions at short times.",2211.11515v2
+2022-12-19,A systematic formulation of chiral anomalous magnetohydrodynamics,"We present a new way of deriving effective theories of dynamical
+electromagnetic fields in general media. It can be used to give a systematic
+formulation of magnetohydrodynamics (MHD) with strong magnetic fields,
+including systems with chiral matter and Adler-Bell-Jackiw (ABJ) anomaly. We
+work in the regime in which velocity and temperature fluctuations can be
+neglected. The resulting chiral anomalous MHD incorporates and generalizes the
+chiral magnetic effect, the chiral separation effect, the chiral electric
+separation effect, as well as recently derived strong-field MHD, all in a
+single coherent framework. At linearized level, the theory predicts that the
+chiral magnetic wave does not survive dynamical electromagnetic fields. A
+different chiral wave, to which we refer as the chiral magnetic electric
+separation wave, emerges as a result of dynamical versions of the chiral
+electric separation effect and the chiral magnetic effect. We predict its wave
+velocity. We also introduce a simple, but solvable nonlinear model to explore
+the fate of the chiral instability.",2212.09757v2
+2023-02-06,Observation of Coherently Coupled Cation Spin Dynamics in an Insulating Ferrimagnetic Oxide,"Many technologically useful magnetic oxides are ferrimagnetic insulators,
+which consist of chemically distinct cations. Here, we examine the spin
+dynamics of different magnetic cations in ferrimagnetic NiZnAl-ferrite
+(Ni$_{0.65}$Zn$_{0.35}$Al$_{0.8}$Fe$_{1.2}$O$_4$) under continuous microwave
+excitation. Specifically, we employ time-resolved x-ray ferromagnetic resonance
+to separately probe Fe$^{2+/3+}$ and Ni$^{2+}$ cations on different sublattice
+sites. Our results show that the precessing cation moments retain a rigid,
+collinear configuration to within $\approx$2$^\circ$. Moreover, the effective
+spin relaxation is identical to within $<$10% for all magnetic cations in the
+ferrite. We thus validate the oft-assumed ``ferromagnetic-like'' dynamics in
+resonantly driven ferrimagnetic oxides, where the magnetic moments from
+different cations precess as a coherent, collective magnetization.",2302.03100v1
+2023-07-28,Reciprocal Reservoir Induced Non-Hermitian Skin Effect,"The non-Hermitian skin effect (NHSE), which describes the localization of
+macroscopic fraction of eigenstates at a specific boundary, is inherently tied
+to nonreciprocity. Here, we show that the NHSE can be engineered in an open
+magnetic system interacting with a reciprocal reservoir, through the interplay
+between the reservoir-induced coherent and dissipative couplings. Based on a
+Lindbladian time evolution, we investigate the transient nonreciprocal dynamics
+along a spin chain and its unidirectional limit, which allow us to reveal both
+consistency with and limitation of the non-Hermitian Hamiltonian approach. We
+comment on the connection to the semiclassical dissipative magnetization
+dynamics, and identify the key ingredients underlying the NHSE in magnetic
+systems as Dzyaloshinskii-Moriya interaction (DMI) and dissipative coupling,
+analogous to those in multi-layered magnet-metal heterostructures. Our work
+suggests the generality of nonreciprocal dynamics in magnetic systems and may
+inspire new schemes for engineering nonreciprocity in other quantum platforms.",2307.15792v1
+2023-12-13,Emergent Fermion Dynamical Symmetry for Monolayer Graphene in a Strong Magnetic Field,"We review the physics of monolayer graphene in a strong magnetic field, with
+emphasis on highly collective states that emerge from the weakly interacting
+system because of correlations (emergent states). After reviewing the general
+properties of graphene and of electrons in a magnetic field, we give a brief
+introduction to the integer quantum Hall effect (IQHE) and the fractional
+quantum Hall effect (FQHE) in a 2D electron gas as foundation to show that
+monolayer graphene in a magnetic field exhibits both effects, but with
+properties modified by the influence of the graphene crystal. After giving an
+introduction to standard methods of dealing with emergent states for this
+system, we show that an SO(8) fermion dynamical symmetry governs the emergent
+degrees of freedom and that the algebraic and group properties of the dynamical
+symmetry provide a new view of strongly correlated states observed in monolayer
+graphene subject to a strong magnetic field.",2312.08475v1
+2024-02-14,Davydov's soliton in an external alternating magnetic field,"The influence of an external oscillating in time magnetic field on the
+dynamics of the Davydov's soliton is investigated. It is shown that it
+essentially depends not only on the amplitude and frequency of the magnetic
+field, but also on the field orientation with respect to the molecular chain
+axis. The soliton velocity and phase are calculated. They are oscillating in
+time functions with the frequency of the main harmonic, given by the external
+field frequency, and higher multiple harmonics. It is concluded that such
+complex effects of external time-depending magnetic fields on the dynamics of
+solitons modify the charge transport in low-dimensional molecular systems,
+which can affect functioning of the devices based on such systems. These
+results suggest also the physical mechanism of therapeutic effects of
+oscillating magnetic fields, based on the field influence on the dynamics of
+solitons which provide charge transport through biological macro-molecules in
+the redox processes.",2402.09172v1
+2024-03-11,Effect of Ir growth pressure on the domain wall dynamics in Ta/Pt/Co/Ir/Ta stacks,"The dynamical response of magnetic domain walls to external magnetic fields
+in ultra-thin multilayer magnetic films is determined not only by the
+composition and thickness of the layers but also by the growth conditions.
+Growth conditions can induce significant structural changes inside the layers
+and at the interfaces between them, affecting in particular the dynamics of
+domain walls, their mobility, elastic tension, and the pinning forces acting on
+them. In this work, we focus specifically on the effect of Ir layer growth
+pressure in Ta/Pt/Co/Ir/Ta ultra-thin multilayers films. Measurements of the DC
+magnetic properties, domain wall velocity and domain morphology in the creep
+regime for both constant and alternating field pulses, were performed for a
+batch of samples where the Ir layer was grown at different pressures. We find
+that the saturation magnetization, the effective anisotropy constant and the
+domain wall surface tension grow with increasing pressure and saturate at a
+threshold pressure, while the Dzyaloshinskii-Moriya field and the strength of
+the disorder remain practically unaltered over the range of pressures
+considered.",2403.07141v1
+2024-03-16,Machine Learning Exchange Fields for Ab-initio Spin Dynamics,"We add the magnetic degrees of freedom to the widely used Gaussian
+Approximation Potential of machine learning (ML) and present a model that
+describes the potential energy surface of a crystal based on the atomic
+coordinates as well as their noncollinear magnetic moments. Assuming an
+adiabatic approximation for the spin directions and magnitudes, the ML model
+depends solely on spin coordinates and orientation, resulting in computational
+efffciency and enabling ab initio spin dynamics. Leveraging rotational
+symmetries of magnetic interactions, the ML model can incorporate various
+magnetic interactions, expanding into two-body, three-body terms, etc.,
+following the spirit of cluster expansion. For simplicity, we implement the ML
+model with a two-body form for the exchange interaction. Comparing total
+energies and local fields predicted by the model for noncollinear spin
+arrangements with explicit results of constrained noncollinear density
+functional calculations for bcc Fe yields excellent results, within 1 meV/spin
+for the total energy. Further optimization, including three-body and other
+terms, is expected to encompass diverse magnetic interactions and enhance the
+model's accuracy. This will extend the model's applicability to a wide range of
+materials and facilitate the machine learning ab initio spin dynamics.",2403.10769v1
+2015-11-09,Acceleration of charged particles due to chaotic scattering in the combined black hole gravitational field and asymptotically uniform magnetic field,"To test the role of large-scale magnetic fields in accretion processes, we
+study dynamics of charged test particles in vicinity of a black hole immersed
+into an asymptotically uniform magnetic field. Using the Hamiltonian formalism
+of charged particle dynamics, we examine chaotic scattering in the effective
+potential related to the black hole gravitational field combined with the
+uniform magnetic field. Energy interchange between the translational and
+oscillatory modes od the charged particle dynamics provides mechanism for
+charged particle acceleration along the magnetic field lines. This energy
+transmutation is an attribute of the chaotic charged particle dynamics in the
+combined gravitational and magnetic fields only, the black hole rotation is not
+necessary for such charged particle acceleration. The chaotic scatter can cause
+transition to the motion along the magnetic field lines with small radius of
+the Larmor motion or vanishing Larmor radius, when the speed of the particle
+translational motion is largest and can be ultra-relativistic. We discuss
+consequences of the model of ionization of test particles forming a neutral
+accretion disc, or heavy ions following off-equatorial circular orbits, and we
+explore the fate of heavy charged test particles after ionization where no kick
+of heavy ions is assumed and only switch-on effect of the magnetic field is
+relevant. We demonstrate that acceleration and escape of the ionized particles
+can be efficient along the Kerr black hole symmetry axis parallel to the
+magnetic field lines. We show that strong acceleration of ionized particles to
+ultra-relativistic velocities is preferred in the direction close to the
+magnetic field lines. Therefore, the process of ionization of Keplerian discs
+around Kerr black holes can serve as a model of relativistic jets.",1511.02936v1
+2005-11-03,High-Field Low-Frequency Spin Dynamics,"The theory of exchange symmetry of spin ordered states is extended to the
+case of high magnetic field. Low frequency spin dynamics equation for
+quasi-goldstone mode is derived for two cases of collinear and noncollinear
+antiferromagnets.",0511090v1
+2006-10-12,The Curie-Weiss model with dynamical external field,"We study a Curie-Weiss model with a random external field generated by a
+dynamical system. Probabilistic limit theorems (weak law of large numbers,
+central limit theorems) are proven for the corresponding magnetization.",0610394v1
+2000-04-10,Classical and quantum dynamics of a spin-1/2,"We reply to a comment on `Semiclassical dynamics of a spin-1/2 in an
+arbitrary magnetic field'.",0004046v1
+2012-02-20,Variational description of Gibbs-non-Gibbs dynamical transitions for the Curie-Weiss model,"We perform a detailed study of Gibbs-non-Gibbs transitions for the
+Curie-Weiss model subject to independent spin-flip dynamics
+(""infinite-temperature"" dynamics). We show that, in this setup, the program
+outlined in van Enter, Fern\'andez, den Hollander and Redig can be fully
+completed, namely that Gibbs-non-Gibbs transitions are equivalent to
+bifurcations in the set of global minima of the large-deviation rate function
+for the trajectories of the magnetization conditioned on their endpoint. As a
+consequence, we show that the time-evolved model is non-Gibbs if and only if
+this set is not a singleton for some value of the final magnetization. A
+detailed description of the possible scenarios of bifurcation is given, leading
+to a full characterization of passages from Gibbs to non-Gibbs -and vice versa-
+with sharp transition times (under the dynamics Gibbsianness can be lost and
+can be recovered).
+  Our analysis expands the work of Ermolaev and Kulske who considered zero
+magnetic field and finite-temperature spin-flip dynamics. We consider both zero
+and non-zero magnetic field but restricted to infinite-temperature spin-flip
+dynamics. Our results reveal an interesting dependence on the interaction
+parameters, including the presence of forbidden regions for the optimal
+trajectories and the possible occurrence of overshoots and undershoots in the
+optimal trajectories. The numerical plots provided are obtained with the help
+of MATHEMATICA.",1202.4205v2
+2017-06-13,Dynamical storage of quantum states,"We consider a dynamical method of storage of quantum states based on the
+spin-1/2 systems with the dipole-dipole interactions in a strong external
+magnetic field { supplemented with the special time-reversion procedure}. The
+stored information can be extracted at certain time instants.",1706.03945v1
+2020-11-14,"Dynamical Effective Field Model for Interacting Ferrofluids: I. Derivations for homogeneous, inhomogeneous, and polydisperse cases","Quite recently I have proposed a nonperturbative dynamical effective field
+model (DEFM) to quantitatively describe the dynamics of interacting
+ferrofluids. Its predictions compare very well with the results from
+simulations. In this paper I put the DEFM on firm theoretical ground by
+deriving it within the framework of dynamical density functional theory (DDFT),
+in which the relevant part of correlation-induced free energy is approximated
+by a function of the instantaneous magnetization. The DEFM is generalized to
+inhomogeneous finite-size samples for which the macroscopic and mesoscopic
+scale separation is nontrivial due to the presence of long-range dipole-dipole
+interactions. The demagnetizing field naturally emerges from microscopic
+considerations and is consistently accounted for. The resulting particle
+dynamics on the mesoscopic scale only involves macroscopically local quantities
+such as local magnetization and Maxwell field. Nevertheless, the local
+demagnetizing field essentially couples to magnetization at distant macroscopic
+locations. Thus, a two-scale parallel algorithm, involving information transfer
+between different macroscopic locations, can be applied to fully resolve
+particle rotational dynamics in an inhomogeneous sample. I also derive the DEFM
+for polydisperse ferrofluids, in which the dynamics of particles belonging to
+different species can be strongly coupled to each other. I discuss the
+underlying assumptions in obtaining a thermodynamically consistent polydisperse
+magnetization relaxation equation, which is of the same generic form as that
+for monodisperse ferrofluids. The theoretical advances presented in this paper
+are important for both qualitative understanding and quantitative modeling of
+ferrofluid dynamics.",2011.07287v2
+2006-10-06,Axisymmetric oscillations of magnetic neutron stars,"We calculate axisymmetric oscillations of rotating neutron stars composed of
+the surface fluid ocean, solid crust, and fluid core, taking account of a
+dipole magnetic field as strong as $B_S\sim 10^{15}$G at the surface. The
+adiabatic oscillation equations for the solid crust threaded by a dipole
+magnetic field are derived in Newtonian dynamics, on the assumption that the
+axis of rotation is aligned with the magnetic axis so that perturbations on the
+equilibrium can be represented by series expansions in terms of spherical
+harmonic functions $Y_l^m(\theta,\phi)$ with different degrees $l$ for a given
+azimuthal wave number $m$ around the the magnetic axis. Although the three
+component models can support a rich variety of oscillation modes, axisymmetric
+($m=0$) toroidal $_{l}t_n$ and spheroidal $_ls_n$ shear waves propagating in
+the solid crust are our main concerns, where $l$ and $n$ denote the harmonic
+degree and the radial order of the modes, respectively. In the absence of
+rotation, axisymmetric spheroidal and toroidal modes are completely decoupled,
+and we consider the effects of rotation on the oscillation modes only in the
+limit of slow rotation. We find that the oscillation frequencies of the
+fundamental toroidal torsional modes $_{l}t_n$ in the crust are hardly affected
+by the magnetic field as strong as $B_S\sim 10^{15}$G at the surface. As the
+radial order $n$ of the shear modes in the crust becomes higher, however, both
+spheroidal and toroidal modes become susceptible to the magnetic field and
+their frequencies in general get higher with increasing $B_S$. We also find
+that the surface $g$ modes and the crust/ocean interfacial modes are suppressed
+by a strong magnetic field, and that there appear magnetic modes in the
+presence of a strong magnetic field.",0610182v1
+2006-10-18,Magnetic Properties and Metastable States in Spin-Crossover Transition of Co-Fe Prussian Blue Analogues,"The combination of spin transitions and magnetic ordering provides an
+interesting structure of phase transitions in Prussian blue analogues (PBAs).
+To understand the structure of stable and metastable states of Co-Fe PBA, it is
+necessary to clarify free energy as a function of magnetization and the
+fraction of the high-temperature component. Including the magnetic interaction
+between high-temperature states, we study the magnetic phase transition of
+Co-Fe PBA in addition to spin transitions. Here, we take into account the
+degeneracy changes due to charge transfer between Co and Fe atoms accompanying
+the spin transition. In this study, the charge transfer between Co and Fe atoms
+is explicitly taken into account and also the ferrimagnetic structure of Co-Fe
+PBAs is expressed in the proper way. First, we found systematic changes in the
+structures of stable and metastable states as functions of system parameters
+using mean field theory. In particular, the existence of a metastable
+magnetic-ordered high-temperature state is confirmed at temperatures lower than
+that of the hysteresis region of spin transitions. Second, we found that the
+magnetic interaction causes complex ordering processes of a spin transition and
+a magnetic phase transition. The effect of a magnetic field on the phase
+structure is also investigated and we found metamagnetic magnetization
+processes. Finally, the dynamical properties of this metastable state are
+studied by Monte Carlo method.",0610500v2
+2005-05-26,"Shell to shell energy transfer in MHD, Part II: Kinematic dynamo","We study the transfer of energy between different scales for forced
+three-dimensional MHD turbulent flows in the kinematic dynamo regime. Two
+different forces are examined: a non-helical Taylor Green flow with magnetic
+Prandtl number P_M=0.4, and a helical ABC flow with P_M=1. This analysis allows
+us to examine which scales of the velocity flow are responsible for dynamo
+action, and identify which scales of the magnetic field receive energy directly
+from the velocity field and which scales receive magnetic energy through the
+cascade of the magnetic field from large to small scales. Our results show that
+the turbulent velocity fluctuations are responsible for the magnetic field
+amplification in the small scales (small scale dynamo) while the large scale
+field is amplified mostly due to the large scale flow. A direct cascade of the
+magnetic field energy from large to small scales is also present and is a
+complementary mechanism for the increase of the magnetic field in the small
+scales. Input of energy from the velocity field in the small magnetic scales
+dominates over the energy that is cascaded down from the large scales until the
+large-scale peak of the magnetic energy spectrum is reached. At even smaller
+scales, most of the magnetic energy input is from the cascading process.",0505189v1
+2005-10-30,Measurements of the magnetic field induced by a turbulent flow of liquid metal,"Initial results from the Madison Dynamo Experiment provide details of the
+inductive response of a turbulent flow of liquid sodium to an applied magnetic
+field. The magnetic field structure is reconstructed from both internal and
+external measurements. A mean toroidal magnetic field is induced by the flow
+when an axial field is applied, thereby demonstrating the omega effect.
+Poloidal magnetic flux is expelled from the fluid by the poloidal flow.
+Small-scale magnetic field structures are generated by turbulence in the flow.
+The resulting magnetic power spectrum exhibits a power-law scaling consistent
+with the equipartition of the magnetic field with a turbulent velocity field.
+The magnetic power spectrum has an apparent knee at the resistive dissipation
+scale. Large-scale eddies in the flow cause significant changes to the
+instantaneous flow profile resulting in intermittent bursts of non-axisymmetric
+magnetic fields, demonstrating that the transition to a dynamo is not smooth
+for a turbulent flow.",0510265v3
+2006-02-17,"Numerical simulations of current generation and dynamo excitation in a mechanically-forced, turbulent flow","The role of turbulence in current generation and self-excitation of magnetic
+fields has been studied in the geometry of a mechanically driven, spherical
+dynamo experiment, using a three dimensional numerical computation. A simple
+impeller model drives a flow which can generate a growing magnetic field,
+depending upon the magnetic Reynolds number, Rm, and the fluid Reynolds number.
+When the flow is laminar, the dynamo transition is governed by a simple
+threshold in Rm, above which a growing magnetic eigenmode is observed. The
+eigenmode is primarily a dipole field tranverse to axis of symmetry of the
+flow. In saturation the Lorentz force slows the flow such that the magnetic
+eigenmode becomes marginally stable. For turbulent flow, the dynamo eigenmode
+is suppressed. The mechanism of suppression is due to a combination of a time
+varying large-scale field and the presence of fluctuation driven currents which
+effectively enhance the magnetic diffusivity. For higher Rm a dynamo reappears,
+however the structure of the magnetic field is often different from the laminar
+dynamo; it is dominated by a dipolar magnetic field which is aligned with the
+axis of symmetry of the mean-flow, apparently generated by fluctuation-driven
+currents. The fluctuation-driven currents have been studied by applying a weak
+magnetic field to laminar and turbulent flows. The magnetic fields generated by
+the fluctuations are significant: a dipole moment aligned with the symmetry
+axis of the mean-flow is generated similar to those observed in the experiment,
+and both toroidal and poloidal flux expulsion are observed.",0602126v2
+2007-08-07,Spin Pumping of Current in Non-Uniform Conducting Magnets,"Using irreversible thermodynamics we show that current-induced spin transfer
+torque within a magnetic domain implies spin pumping of current within that
+domain. This has experimental implications for samples both with conducting
+leads and that are electrically isolated. These results are obtained by
+deriving the dynamical equations for two models of non-uniform conducting
+magnets: (1) a generic conducting magnet, with net conduction electron density
+n and net magnetization $\vec{M}$; and (2) a two-band magnet, with up and down
+spins each providing conduction and magnetism. For both models, in regions
+where the equilibrium magnetization is non-uniform, voltage gradients can drive
+adiabatic and non-adiabatic bulk spin torques. Onsager relations then ensure
+that magnetic torques likewise drive adiabatic and non-adiabatic currents --
+what we call bulk spin pumping. For a given amount of adiabatic and
+non-adiabatic spin torque, the two models yield similar but distinct results
+for the bulk spin pumping, thus distinguishing the two models. As in the recent
+spin-Berry phase study by Barnes and Maekawa, we find that within a domain wall
+the ratio of the effective emf to the magnetic field is approximately given by
+$P(2\mu_{B}/e)$, where P is the spin polarization. The adiabatic spin torque
+and spin pumping terms are shown to be dissipative in nature.",0708.0997v1
+2007-09-04,Magnetic Braking and Protostellar Disk Formation: The Ideal MHD Limit,"Magnetic fields are usually considered dynamically important in star
+formation when the dimensionless mass-to-flux ratio is close to, or less than,
+unity (lambda<~1). We show that, in disk formation, the requirement is far less
+stringent. This conclusion is drawn from a set of 2D (axisymmetric) simulations
+of the collapse of rotating, magnetized, singular isothermal cores. We find
+that a weak field corresponding to 1ambda~100 can begin to disrupt the
+rotationally supported disk through magnetic braking, by creating regions of
+rapid, supersonic collapse in the disk. These regions are separated by one or
+more centrifugal barriers, where the rapid infall is temporarily halted. The
+number of centrifugal barriers increases with lambda. When lambda>~100, they
+merge together to form a more or less contiguous, rotationally supported disk.
+Even though the magnetic field in such a case is extremely weak on the scale of
+dense cores, it is amplified by collapse and differential rotation, to the
+extent that its pressure dominates the thermal pressure in both the disk and
+its surrounding region. For relatively strongly magnetized cores with
+lambda<~10, the disk formation is suppressed completely, as found previously. A
+new feature is that the mass accretion is highly episodic, due to reconnection
+of the accumulated magnetic field lines. For rotationally supported disks to
+appear during the protostellar mass accretion phase of star formation in dense
+cores with realistic field strengths, the powerful magnetic brake must be
+weakened, perhaps through nonideal MHD effects and/or protostellar winds. We
+discuss the possibility of observing a generic product of the magnetic braking,
+an extended circumstellar region that is supported by a combination of toroidal
+magnetic field and rotation - a ""magnetogyrosphere"".",0709.0445v1
+2009-02-18,Magnetized massive stars as magnetar progenitors,"The origin of ultra-intense magnetic fields on magnetars is a mystery in
+modern astrophysics. We model the core collapse dynamics of massive progenitor
+stars with high surface magnetic fields in the theoretical framework of a
+self-similar general polytropic magnetofluid under the self-gravity with a
+quasi-spherical symmetry. With the specification of physical parameters such as
+mass density, temperature, magnetic field and wind mass loss rate on the
+progenitor stellar surface and the consideration of a rebound shock breaking
+through the stellar interior and envelope, we find a remnant compact object
+(i.e. neutron star) left behind at the centre with a radius of $\sim 10^6$ cm
+and a mass range of $\sim 1-3$ solar masses. Moreover, we find that surface
+magnetic fields of such kind of compact objects can be $\sim 10^{14}-10^{15}$
+G, consistent with those inferred for magnetars which include soft gamma-ray
+repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The magnetic field
+enhancement factor critically depends on the self-similar scaling index $n$,
+which also determines the initial density distribution of the massive
+progenitor. We propose that magnetized massive stars as magnetar progenitors
+based on the magnetohydrodynamic evolution of the gravitational core collapse
+and rebound shock. Our physical mechanism, which does not necessarily require
+ad hoc dynamo amplification within a fast spinning neutron star, favours the
+`fossil field' scenario of forming magnetars from the strongly magnetized core
+collapse inside massive progenitor stars. With a range of surface magnetic
+field strengths over massive progenitor stars, our scenario allows a continuum
+of magnetic field strengths from pulsars to magnetars.",0902.3111v1
+2009-11-24,Magnetic Rossby waves in the solar tachocline and Rieger-type periodicities,"Apart from the 11-year solar cycle, another periodicity around 155-160 days
+was discovered during solar cycle 21 in high energy solar flares, and its
+presence in sunspot areas and strong magnetic flux has been also reported. This
+periodicity has an elusive and enigmatic character, since it usually appears
+only near the maxima of solar cycles, and seems to be related with a periodic
+emergence of strong magnetic flux at the solar surface. Therefore, it is
+probably connected with the tachocline, a thin layer located near the base of
+the solar convection zone, where strong dynamo magnetic field is stored. We
+study the dynamics of Rossby waves in the tachocline in the presence of a
+toroidal magnetic field and latitudinal differential rotation. Our analysis
+shows that the magnetic Rossby waves are generally unstable and that the growth
+rates are sensitive to the magnetic field strength and to the latitudinal
+differential rotation parameters. Variation of the differential rotation and
+the magnetic field strength throughout the solar cycle enhance the growth rate
+of a particular harmonic in the upper part of the tachocline around the maximum
+of the solar cycle. This harmonic is symmetric with respect to the equator and
+has a period of 155-160 days. A rapid increase of the wave amplitude could give
+place to a magnetic flux emergence leading to observed periodicities in solar
+activity indicators related with magnetic flux.",0911.4591v1
+2010-07-02,Core of the Magnetic Obstacle,"Rich recirculation patterns have been recently discovered in the electrically
+conducting flow subject to a local external magnetic termed ""the magnetic
+obstacle"" [Phys. Rev. Lett. 98 (2007), 144504]. This paper continues the study
+of magnetic obstacles and sheds new light on the core of the magnetic obstacle
+that develops between magnetic poles when the intensity of the external field
+is very large. A series of both 3D and 2D numerical simulations have been
+carried out, through which it is shown that the core of the magnetic obstacle
+is streamlined both by the upstream flow and by the induced cross stream
+electric currents, like a foreign insulated insertion placed inside the
+ordinary hydrodynamic flow. The closed streamlines of the mass flow resemble
+contour lines of electric potential, while closed streamlines of the electric
+current resemble contour lines of pressure. New recirculation patterns not
+reported before are found in the series of 2D simulations. These are composed
+of many (even number) vortices aligned along the spanwise line crossing the
+magnetic gap. The intensities of these vortices are shown to vanish toward to
+the center of the magnetic gap, confirming the general conclusion of 3D
+simulations that the core of the magnetic obstacle is frozen. The implications
+of these findings for the case of turbulent flow are discussed briefly.",1007.0336v1
+2010-10-28,Global magnetic cycles in rapidly rotating younger suns,"Observations of sun-like stars rotating faster than our current sun tend to
+exhibit increased magnetic activity as well as magnetic cycles spanning
+multiple years. Using global simulations in spherical shells to study the
+coupling of large-scale convection, rotation, and magnetism in a younger sun,
+we have probed effects of rotation on stellar dynamos and the nature of
+magnetic cycles. Major 3-D MHD simulations carried out at three times the
+current solar rotation rate reveal hydromagnetic dynamo action that yields
+wreaths of strong toroidal magnetic field at low latitudes, often with opposite
+polarity in the two hemispheres. Our recent simulations have explored behavior
+in systems with considerably lower diffusivities, achieved with sub-grid scale
+models including a dynamic Smagorinsky treatment of unresolved turbulence. The
+lower diffusion promotes the generation of magnetic wreaths that undergo
+prominent temporal variations in field strength, exhibiting global magnetic
+cycles that involve polarity reversals. In our least diffusive simulation, we
+find that magnetic buoyancy coupled with advection by convective giant cells
+can lead to the rise of coherent loops of magnetic field toward the top of the
+simulated domain.",1010.6073v1
+2011-07-18,Rossby waves and polar spots in rapidly rotating stars: Implications for stellar wind evolution,"Rapidly rotating stars show short-period oscillations in magnetic activity
+and polar appearance of starspots. The aim of this paper is to study
+large-scale shallow water waves in the tachoclines of rapidly rotating stars
+and their connection to the periodicity and the formation of starspots at high
+latitudes. Shallow-water magnetohydrodynamic equations were used to study the
+dynamics of large-scale waves at the rapidly rotating stellar tachoclines in
+the presence of toroidal magnetic field. Dispersion relations and latitudinal
+distribution of wave modes were derived. We found that low-frequency magnetic
+Rossby waves tend to be located at poles, but high-frequency magnetic Poincare
+waves are concentrated near the equator in rapidly rotating stars. These
+results have important implications for the evolution of the stellar wind in
+young Sun-like stars. Unstable magnetic Rossby waves may lead to the local
+enhancement of magnetic flux at high latitudes of tachoclines in rapidly
+rotating stars. The enhanced magnetic flux may rise upwards owing to the
+magnetic buoyancy in the form of tubes and appear as starspots at polar
+regions. Magnetic Rossby waves may also cause observed short-term periodicity
+in the stellar magnetic activity.",1107.3395v1
+2011-09-21,Magnetic Field Amplification by Small-Scale Dynamo Action: Dependence on Turbulence Models and Reynolds and Prandtl Numbers,"The small-scale dynamo is a process by which turbulent kinetic energy is
+converted into magnetic energy, and thus is expected to depend crucially on the
+nature of turbulence. In this work, we present a model for the small-scale
+dynamo that takes into account the slope of the turbulent velocity spectrum
+v(l) ~ l^theta, where l and v(l) are the size of a turbulent fluctuation and
+the typical velocity on that scale. The time evolution of the fluctuation
+component of the magnetic field, i.e., the small-scale field, is described by
+the Kazantsev equation. We solve this linear differential equation for its
+eigenvalues with the quantum-mechanical WKB-approximation. The validity of this
+method is estimated as a function of the magnetic Prandtl number Pm. We
+calculate the minimal magnetic Reynolds number for dynamo action, Rm_crit,
+using our model of the turbulent velocity correlation function. For Kolmogorov
+turbulence (theta=1/3), we find that the critical magnetic Reynolds number is
+approximately 110 and for Burgers turbulence (theta=1/2) approximately 2700.
+Furthermore, we derive that the growth rate of the small-scale magnetic field
+for a general type of turbulence is Gamma ~ Re^((1-theta)/(1+theta)) in the
+limit of infinite magnetic Prandtl numbers. For decreasing magnetic Prandtl
+number (down to Pm approximately larger than 10), the growth rate of the
+small-scale dynamo decreases. The details of this drop depend on the
+WKB-approximation, which becomes invalid for a magnetic Prandtl number of about
+unity.",1109.4571v2
+2012-04-03,Magnetic moment non-conservation in magnetohydrodynamic turbulence models,"The fundamental assumptions of the adiabatic theory do not apply in presence
+of sharp field gradients as well as in presence of well developed
+magnetohydrodynamic turbulence. For this reason in such conditions the magnetic
+moment $\mu$ is no longer expected to be constant. This can influence particle
+acceleration and have considerable implications in many astrophysical problems.
+  Starting with the resonant interaction between ions and a single parallel
+propagating electromagnetic wave, we derive expressions for the magnetic moment
+trapping width $\Delta \mu$ (defined as the half peak-to-peak difference in the
+particle magnetic moment) and the bounce frequency $\omega_b$. We perform
+test-particle simulations to investigate magnetic moment behavior when
+resonances overlapping occurs and during the interaction of a ring-beam
+particle distribution with a broad-band slab spectrum.
+  We find that magnetic moment dynamics is strictly related to pitch angle
+$\alpha$ for a low level of magnetic fluctuation, $\delta B/B_0 = (10^{-3}, \,
+10^{-2})$, where $B_0$ is the constant and uniform background magnetic field.
+Stochasticity arises for intermediate fluctuation values and its effect on
+pitch angle is the isotropization of the distribution function $f(\alpha)$.
+This is a transient regime during which magnetic moment distribution $f(\mu)$
+exhibits a characteristic one-sided long tail and starts to be influenced by
+the onset of spatial parallel diffusion, i.e., the variance $<(\Delta z)^2 >$
+grows linearly in time as in normal diffusion. With strong fluctuations
+$f(\alpha)$ isotropizes completely, spatial diffusion sets in and $f(\mu)$
+behavior is closely related to the sampling of the varying magnetic field
+associated with that spatial diffusion.",1204.0748v1
+2013-09-27,Phonons correlation with magnetic excitations in weak ferromagnet YCrO3,"We report on the temperature dependent Raman spectroscopic studies of
+orthorombic distorted perovskite YCrO3 in the temperature range of 20-300K.
+Temperature dependence of DC-magnetization measurement under field cooled and
+zero field cooled modes confirmed the transition temperature (TN ~142K) and
+anomalous characteristic temperature (T* ~60K), above which magnetization tends
+to saturate. Magnetization isotherm recorded below TN at 125K shows clear loop
+opening without magnetization saturation up to 20kOe, indicating the
+coexistence of antiferromagnetic (AFM) interaction with weak ferromagnetic
+(WFM) phase. Mean field calculation for exchange constants further confirms the
+complex magnetic phase below TN. Temperature evolution of lineshape parameters
+of selected modes (associated with the octahedral rotation and A-shift in the
+unit cell) revealed anomalous phonon shift near Cr3+ magnetic ordering
+temperature (TN ~142K). Additional phonon anomaly was identified at T* ~60K in
+agreement with the magnetization results and reflects the change in spin
+dynamics, plausibly due to the change in Cr-spin configuration. Moreover, the
+positive and negative shift in Raman frequency below TN revel the existence of
+competing WFM and AFM exchanges. The phonon shift of B3g (3)-octahedral
+rotation mode fairly scaled with the square of sublattice magnetization from TN
+to T*, below which it start to depart from theconventional behaviour and need
+further attention. This correlation between magnetic and Raman data elucidate
+the spin-phonon coupling owing to the multiferroic phenomenon in YCrO3.",1309.7254v1
+2013-11-05,Cluster glass magnetism in the phase-separated Nd2/3Ca1/3MnO3 perovskite,"A detailed study of the low-temperature magnetic state and the relaxation in
+the phase-separated colossal magnetoresistance Nd2/3Ca1/3MnO3 perovskite has
+been carried out. Clear experimental evidence of the cluster-glass magnetic
+behavior of this compound has been revealed. Well defined maxima in the
+in-phase linear ac susceptibility $\chi ^{/}(T)$ were observed, indicative of
+the magnetic glass transition at $T_{g}$ = 60 K. Strongly divergent
+zero-field-cooled and field-cooled static magnetizations and frequency
+dependent ac susceptibility are evident of the glassy-like magnetic state of
+the compound at low temperatures. The frequency dependence of the cusp
+temperature Tmax of the $\chi ^{/}(T)$ susceptibility was found to follow the
+critical slowing down mechanism. The Cole-Cole analysis of the dynamic
+susceptibility at low temperature has shown extremely broad distribution of
+relaxation times, indicating that spins are frozen at ""macroscopic"" time scale.
+Slow relaxation in the zero-field-cooled magnetization has been experimentally
+revealed. The obtained results do not agree with a canonical spin-glass state
+and indicate a cluster glass magnetic state of the compound below $T_{g}$,
+associated with its antiferromagnetic-ferromagnetic nano-phase segregated
+state. It was found that the relaxation mechanisms below the cluster glass
+freezing temperature $T_{g}$ and above it are strongly different. Magnetic
+field up to about $\mu_{0}$H = 0.4 T suppresses the glassy magnetic state of
+the compound.",1311.1123v2
+2013-11-18,Kelvin-Helmholtz instability of twisted magnetic flux tubes in the solar wind,"Solar wind plasma is supposed to be structured in magnetic flux tubes carried
+from the solar surface. Tangential velocity discontinuity near the boundaries
+of individual tubes may result in Kelvin-Helmholtz instability, which may
+contribute into the solar wind turbulence. While the axial magnetic field may
+stabilize the instability, a small twist in the magnetic field may allow to
+sub-Alfvenic motions to be unstable. We aim to study the Kelvin-Helmholtz
+instability of twisted magnetic flux tube in the solar wind with different
+configurations of external magnetic field. We use magnetohydrodynamic equations
+in the cylindrical geometry and derive the dispersion equations governing the
+dynamics of twisted magnetic flux tube moving along its axis in the cases of
+untwisted and twisted external fields. Then we solve the dispersion equations
+analytically and numerically and found thresholds for Kelvin-Helmholtz
+instability in both cases of external field. Both analytical and numerical
+solutions show that the Kelvin-Helmholtz instability is suppressed in the
+twisted tube by external axial magnetic field for sub-Alfvenic motions.
+However, even small twist in the external magnetic field allows the
+Kelvin-Helmholtz instability to be developed for any sub-Alfvenic motions. The
+unstable harmonics correspond to vortices with high azimuthal mode numbers,
+which are carried by the flow. Twisted magnetic flux tubes can be unstable to
+Kelvin-Helmholtz instability when they move with small speed relative to main
+solar wind stream, then the Kelvin-Helmholtz vortices may significantly
+contribute into the solar wind turbulence.",1311.4383v1
+2014-07-10,Magnetic induction and diffusion mechanisms in a liquid sodium spherical Couette experiment,"We present a reconstruction of the mean axisymmetric azimuthal and meridional
+flows in the DTS liquid sodium experiment. The experimental device sets a
+spherical Couette flow enclosed between two concentric spherical shells where
+the inner sphere holds a strong dipolar magnet, which acts as a magnetic
+propeller when rotated. Measurements of the mean velocity, mean induced
+magnetic field and mean electric potentials have been acquired inside and
+outside the fluid for an inner sphere rotation rate of 9 Hz (Rm 28). Using the
+induction equation to relate all measured quantities to the mean flow, we
+develop a nonlinear least square inversion procedure to reconstruct a fully
+coherent solution of the mean velocity field. We also include in our inversion
+the response of the fluid layer to the non-axisymmetric time-dependent magnetic
+field that results from deviations of the imposed magnetic field from an axial
+dipole. The mean azimuthal velocity field we obtain shows super-rotation in an
+inner region close to the inner sphere where the Lorentz force dominates, which
+contrasts with an outer geostrophic region governed by the Coriolis force, but
+where the magnetic torque remains the driver. The meridional circulation is
+strongly hindered by the presence of both the Lorentz and the Coriolis forces.
+Nevertheless, it contributes to a significant part of the induced magnetic
+energy. Our approach sets the scene for evaluating the contribution of velocity
+and magnetic fluctuations to the mean magnetic field, a key question for dynamo
+mechanisms.",1407.2703v2
+2015-06-06,Saturation of the Turbulent Dynamo,"The origin of strong magnetic fields in the Universe can be explained by
+amplifying weak seed fields via turbulent motions on small spatial scales and
+subsequently transporting the magnetic energy to larger scales. This process is
+known as the turbulent dynamo and depends on the properties of turbulence, i.e.
+on the hydrodynamical Reynolds number and the compressibility of the gas, and
+on the magnetic diffusivity. While we know the growth rate the magnetic energy
+in the linear regime, the saturation level, i.e. the ratio of magnetic energy
+to turbulent kinetic energy that can be reached, is not known from analytical
+calculations. In this paper we present the first scale-dependent saturation
+model based on an effective turbulent resistivity which is determined by the
+turnover timescale of turbulent eddies and the magnetic energy density. The
+magnetic resistivity increases compared to the Spitzer value and the effective
+scale on which the magnetic energy spectrum is at its maximum moves to larger
+spatial scales. This process ends when the peak reaches a characteristic
+wavenumber k* which is determined by the critical magnetic Reynolds number. The
+saturation level of the dynamo also depends on the type of turbulence and
+differs for the limits of large and small magnetic Prandtl numbers Pm. With our
+model we find saturation levels between 43.8% and 1.3% for Pm>>1 and between
+2.43% and 0.135% for Pm<<1, where the higher values refer to incompressible
+turbulence and the lower ones to highly compressible turbulence.",1506.02182v2
+2016-03-08,Magnetic fields in early protostellar disk formation,"We consider formation of accretion disks from a realistically turbulent
+molecular gas using 3D MHD simulations. In particular, we analyze the effect of
+the fast turbulent reconnection described by the Lazarian & Vishniac (1999)
+model for the removal of magnetic flux from a disk. With our numerical
+simulations we demonstrate how the fast reconnection enables protostellar disk
+formation resolving the so-called ""magnetic braking catastrophe"". In
+particular, we provide a detailed study of the dynamics of a 0.5 M$_\odot$
+protostar and the formation of its disk for up to several thousands years. We
+measure the evolution of the mass, angular momentum, magnetic field, and
+turbulence around the star. We consider effects of two processes that strongly
+affect the magnetic transfer of angular momentum, both of which are based on
+turbulent reconnection: the first, ""reconnection diffusion"", removes the
+magnetic flux from the disk, the other involves the change of the magnetic
+field's topology, but does not change the absolute value of the magnetic flux
+through the disk. We demonstrate that for the first mechanism, turbulence
+causes a magnetic flux transport outward from the inner disk to the ambient
+medium, thus decreasing the coupling of the disk to the ambient material. A
+similar effect is achieved through the change of the magnetic field's topology
+from a split monopole configuration to a dipole configuration. We explore how
+both mechanisms prevent the catastrophic loss of disk angular momentum and
+compare both above turbulent reconnection mechanisms with alternative
+mechanisms from the literature.",1603.02691v1
+2016-05-16,"Accretion, Outflows, and Winds of Magnetized Stars","Many types of stars have strong magnetic fields that can dynamically
+influence the flow of circumstellar matter. In stars with accretion disks, the
+stellar magnetic field can truncate the inner disk and determine the paths that
+matter can take to flow onto the star. These paths are different in stars with
+different magnetospheres and periods of rotation. External field lines of the
+magnetosphere may inflate and produce favorable conditions for outflows from
+the disk-magnetosphere boundary. Outflows can be particularly strong in the
+propeller regime, wherein a star rotates more rapidly than the inner disk.
+Outflows may also form at the disk-magnetosphere boundary of slowly rotating
+stars, if the magnetosphere is compressed by the accreting matter. In isolated,
+strongly magnetized stars, the magnetic field can influence formation and/or
+propagation of stellar wind outflows. Winds from low-mass, solar-type stars may
+be either thermally or magnetically driven, while winds from massive, luminous
+O and B type stars are radiatively driven. In all of these cases, the magnetic
+field influences matter flow from the stars and determines many observational
+properties. In this chapter we review recent studies of accretion, outflows,
+and winds of magnetized stars with a focus on three main topics: (1) accretion
+onto magnetized stars; (2) outflows from the disk-magnetosphere boundary; and
+(3) winds from isolated massive magnetized stars. We show results obtained from
+global magnetohydrodynamic simulations and, in a number of cases compare global
+simulations with observations.",1605.04979v1
+2016-05-19,"Magnetic field in atypical prominence structures: Bubble, tornado and eruption","Spectropolarimetric observations of prominences have been obtained with the
+THEMIS telescope during four years of coordinated campaigns. Our aim is now to
+understand the conditions of the cool plasma and magnetism in `atypical'
+prominences, namely when the measured inclination of the magnetic field
+departs, to some extent, from the predominantly horizontal field found in
+`typical' prominences. What is the role of the magnetic field in these
+prominence types? Are plasma dynamics more important in these cases than the
+magnetic support? We focus our study on three types of `atypical' prominences
+(tornadoes, bubbles and jet-like prominence eruptions) that have all been
+observed by THEMIS in the He I D_3 line, from which the Stokes parameters can
+be derived. The magnetic field strength, inclination and azimuth in each pixel
+are obtained by using the Principal Component Analysis inversion method on a
+model of single scattering in the presence of the Hanle effect. The magnetic
+field in tornadoes is found to be more or less horizontal, whereas for the
+eruptive prominence it is mostly vertical. We estimate a tendency towards
+higher values of magnetic field strength inside the bubbles than outside in the
+surrounding prominence. In all of the models in our database, only one magnetic
+field orientation is considered for each pixel. While sufficient for most of
+the main prominence body, this assumption appears to be oversimplified in
+atypical prominence structures. We should consider these observations as the
+result of superposition of multiple magnetic fields, possibly even with a
+turbulent field component.",1605.05964v1
+2016-06-22,The global distribution of magnetic helicity in the solar corona,"By defining an appropriate field line helicity, we apply the powerful concept
+of magnetic helicity to the problem of global magnetic field evolution in the
+Sun's corona. As an ideal-magnetohydrodynamic invariant, the field line
+helicity is a meaningful measure of how magnetic helicity is distributed within
+the coronal volume. It may be interpreted, for each magnetic field line, as a
+magnetic flux linking with that field line. Using magneto-frictional
+simulations, we investigate how field line helicity evolves in the
+non-potential corona as a result of shearing by large-scale motions on the
+solar surface. On open magnetic field lines, the helicity injected by the Sun
+is largely output to the solar wind, provided that the coronal relaxation is
+sufficiently fast. But on closed magnetic field lines, helicity is able to
+build up. We find that the field line helicity is non-uniformly distributed,
+and is highly concentrated in twisted magnetic flux ropes. Eruption of these
+flux ropes is shown to lead to sudden bursts of helicity output, in contrast to
+the steady flux along the open magnetic field lines.",1606.06863v3
+2016-12-31,Experimental demonstration of complete 180 degree reversal of magnetization in isolated Co-nanomagnets on a PMN-PT substrate with voltage generated strain,"Rotating the magnetization of a shape anisotropic magnetostrictive nanomagnet
+with voltage-generated stress/strain dissipates much less energy than most
+other magnetization rotation schemes, but its application to writing bits in
+non-volatile magnetic memory has been hindered by the fundamental inability of
+stress/strain to rotate magnetization by full 180 degrees. Normally,
+stress/strain can rotate the magnetization of a shape anisotropic elliptical
+nanomagnet by only up to 90 degrees, resulting in incomplete magnetization
+reversal. Recently, we predicted that applying uniaxial stress sequentially
+along two different axes that are not collinear with the major or minor axis of
+the elliptical nanomagnet will rotate the magnetization by full 180 degrees.
+Here, we demonstrate this complete 180 degree rotation in elliptical
+Co-nanomagnets (fabricated on a piezoelectric substrate) at room temperature.
+The two stresses are generated by sequentially applying voltages to two pairs
+of shorted electrodes placed on the substrate such that the line joining the
+centers of the electrodes in one pair intersects the major axis of a nanomagnet
+at ~+30 degrees and the line joining the centers of the electrodes in the other
+pair intersects at ~ -30 degrees. A finite element analysis has been performed
+to determine the stress distribution underneath the nanomagnets when one or
+both pairs of electrodes are activated, and this has been approximately
+incorporated into a micromagnetic simulation of magnetization dynamics to
+confirm that the generated stress can produce the observed magnetization
+rotations. This result portends an extremely energy-efficient non-volatile
+""straintronic"" memory technology predicated on writing bits in nanomagnets with
+electrically generated stress.",1701.00042v1
+2017-02-28,"Photon-Axion Conversion, Magnetic Field Configuration, and Polarization of Photons","We study the evolution of photon polarization during the photon-axion
+conversion process with focusing on the magnetic field configuration
+dependence. Most previous studies have been carried out in a conventional model
+where a network of magnetic domains is considered and each domain has a
+constant magnetic field. We investigate a more general model where a network of
+domains is still assumed, but each domain has a helical magnetic field. We find
+that the asymptotic behavior does not depend on the configuration of magnetic
+fields. Remarkably, we analytically obtain the asymptotic values of the
+variance of polarization in the conventional model. When the helicity is small,
+we show that there appears the damped oscillating behavior in the early stage
+of evolution. Moreover, we see that the constraints on the axion coupling and
+the cosmological magnetic fields using polarization observations are affected
+by the magnetic field configuration. This is because the different transient
+behavior of polarization dynamics is caused by the different magnetic field
+configuration. Recently, [C. Wang and D. Lai, J. Cosmol. Astropart. Phys. 06
+(2016) 006.] claimed that the photon-axion conversion in helical model behaves
+peculiarly. However, our helical model gives much closer predictions to the
+conventional discontinuous magnetic field configuration model.",1702.08843v2
+2017-05-26,Compression of turbulent magnetized gas in Giant Molecular Clouds,"Interstellar gas clouds are often both highly magnetized and supersonically
+turbulent, with velocity dispersions set by a competition between driving and
+dissipation. This balance has been studied extensively in the context of gases
+with constant mean density. However, many astrophysical systems are contracting
+under the influence of external pressure or gravity, and the balance between
+driving and dissipation in a contracting, magnetized medium has yet to be
+studied. In this paper we present three-dimensional (3D) magnetohydrodynamic
+(MHD) simulations of compression in a turbulent, magnetized medium that
+resembles the physical conditions inside molecular clouds. We find that in some
+circumstances the combination of compression and magnetic fields leads to a
+rate of turbulent dissipation far less than that observed in non-magnetized
+gas, or in non-compressing magnetized gas. As a result, a compressing,
+magnetized gas reaches an equilibrium velocity dispersion much greater than
+would be expected for either the hydrodynamic or the non-compressing case. We
+use the simulation results to construct an analytic model that gives an
+effective equation of state for a coarse-grained parcel of the gas, in the form
+of an ideal equation of state with a polytropic index that depends on the
+dissipation and energy transfer rates between the magnetic and turbulent
+components. We argue that the reduced dissipation rate and larger equilibrium
+velocity dispersion produced by compressing, magnetized turbulence has
+important implications for the driving and maintenance of turbulence in
+molecular clouds, and for the rates of chemical and radiative processes that
+are sensitive to shocks and dissipation.",1705.09657v2
+2017-08-14,Solar Multiple Eruptions From a Confined Magnetic Structure,"How eruption can recur from a confined magnetic structure is discussed based
+on the {\it Solar Dynamics Observatory} (SDO) observations of the NOAA active
+region 11444, which produced three eruptions within 1.5 hours on March 27,
+2012. The active region had the positive polarity magnetic fields in the center
+surrounded by the negative polarity fields around. Since such a distribution of
+magnetic polarity tends to form a dome-like magnetic fan structure confined
+over the active region, the multiple eruptions was puzzling. Our investigation
+reveals that this event exhibits several properties distinct from other
+eruptions associated with magnetic fan structures: (i) a long filament
+encircling the active region was present before the eruptions; (ii) expansion
+of the open-closed boundary of the field lines after each eruption suggestive
+of the growing fan-dome structure, and (iii) the ribbons inside the closed
+magnetic polarity inversion line evolving in response to the expanding
+open-closed boundary. It thus appears that in spite of multiple eruptions the
+fan-dome structure remained undamaged, and the closing back field lines after
+each eruption rather reinforced the fan-dome structure. We argue that the
+multiple eruptions could occur in this active region in spite of its confined
+magnetic structure because the filament encircling the active region was
+adequate for slipping through the magnetic separatrix to minimize the damage to
+its overlying fan-dome structure. The result of this study provides a new
+insight into the productivity of eruptions from a confined magnetic structure.",1708.04056v1
+2017-10-05,Transport theory for femtosecond laser-induced spin-transfer torques,"Ultrafast demagnetization of magnetic layers pumped by a femtosecond laser
+pulse is accompanied by a nonthermal spin-polarized current of hot electrons.
+These spin currents are studied here theoretically in a spin valve with
+noncollinear magnetizations. To this end, we introduce an extended model of
+superdiffusive spin transport that enables to treat noncollinear magnetic
+configurations, and apply it to the perpendicular spin valve geometry. We show
+how spin-transfer torques arise due to this mechanism and calculate their
+action on the magnetization present, as well as how the latter depends on the
+thicknesses of the layers and other transport parameters. We demonstrate that
+there exists a certain optimum thickness of the out-of-plane magnetized
+spin-current polarizer such that the torque acting on the second magnetic layer
+is maximal. Moreover, we study the magnetization dynamics excited by the
+superdiffusive spin-transfer torque due to the flow of hot electrons employing
+the Landau-Lifshitz-Gilbert equation. Thereby we show that a femtosecond laser
+pulse applied to one magnetic layer can excite small-angle precessions of the
+magnetization in the second magnetic layer. We compare our calculations with
+recent experimental results.",1710.02083v2
+2017-10-13,The first in-situ observation of torsional Alfven waves during the interaction of large-scale magnetic clouds,"The large-scale magnetic cloud such as coronal mass ejections (CMEs) is the
+fundamental driver of the space weather. The interaction of the multiple CMEs
+in interplanetary space affects their dynamic evolution and geo-effectiveness.
+The complex and merged multiple magnetic clouds appear as the in-situ signature
+of the interacting CMEs. The Alfven waves are speculated to be one of the major
+possible energy exchange/dissipation mechanism during the interaction. However,
+no such observational evidence has been found in the literature. The case
+studies of CME-CME collision events suggest that the magnetic and thermal
+energy of the CME is converted into the kinetic energy. Moreover, the magnetic
+reconnection process is justified to be responsible for the merging of multiple
+magnetic clouds. Here, we present unambiguous evidence of sunward torsional
+Alfven waves in the interacting region after the super-elastic collision of
+multiple CMEs. The Walen relation is used to confirm the presence of Alfven
+waves in the interacting region of multiple CMEs/magnetic clouds. We conclude
+that Alfven waves and magnetic reconnection are the possible energy
+exchange/dissipation mechanisms during large-scale magnetic clouds collisions.
+The present study has significant implications not only in CME-magnetosphere
+interactions but also in the interstellar medium where interactions of
+large-scale magnetic clouds are possible.",1710.05755v2
+2018-01-13,"Probing Twisted Magnetic Field Using Microwave Observations in an M Class Solar Flare on 11 February, 2014","This work demonstrates the possibility of magnetic field topology
+investigations using microwave polarimetric observations. We study a solar
+flare of GOES M1.7 class that occurred on 11 February, 2014. This flare
+revealed a clear signature of spatial inversion of the radio emission
+polarization sign. We show that the observed polarization pattern can be
+explained by nonthermal gyrosynchrotron emission from the twisted magnetic
+structure. Using observations of the Reuven Ramaty High Energy Solar
+Spectroscopic Imager, Nobeyama Radio Observatory, Radio Solar Telescope
+Network, and Solar Dynamics Observatory, we have determined the parameters of
+nonthermal electrons and thermal plasma and identified the magnetic structure
+where the flare energy release occurred. To reconstruct the coronal magnetic
+field, we use nonlinear force-free field (NLFFF) and potential magnetic field
+approaches. Radio emission of nonthermal electrons is simulated by the GX
+Simulator code using the extrapolated magnetic field and the parameters of
+nonthermal electrons and thermal plasma inferred from the observations; the
+model radio maps and spectra are compared with observations. We have found that
+the potential magnetic field approach fails to explain the observed circular
+polarization pattern; on the other hand, the Stokes $V$ map is successfully
+explained by assuming nonthermal electrons to be distributed along the twisted
+magnetic structure determined by the NLFFF extrapolation approach. Thus, we
+show that the radio polarization maps can be used for diagnosing the topology
+of the flare magnetic structures where nonthermal electrons are injected.",1801.04400v1
+2018-03-23,Observation of hedgehog skyrmions in sub-100 nm soft magnetic nanodots,"Magnetic skyrmions are nanometric spin textures of outstanding potential for
+spintronic applications due to unique features governed by their non-trivial
+topology. It is well known that skyrmions of definite chirality are stabilized
+by the Dzyaloshinskii-Moriya exchange interaction (DMI) in bulk
+non-centrosimmetric materials or ultrathin films with strong spin-orbit
+coupling in the interface. In this work, we report on the detection of magnetic
+hedgehog-skyrmions at room temperature in confined systems with neither DMI nor
+perpendicular magnetic anisotropy. We show that soft magnetic (permalloy)
+nanodots are able to host non- chiral hedgehog skyrmions that can be further
+stabilized by the magnetic field arising from the Magnetic Force Microscopy
+probe. Analytical calculations and micromagnetic simulations confirmed the
+existence of metastable N\'eel skyrmions in permalloy nanodots even without
+external stimuli in a certain size range. Our work implies the existence of a
+new degree of freedom to create and manipulate skyrmions in soft nanodots. The
+stabilization of skyrmions in soft magnetic materials opens a possibility to
+study the skymion magnetization dynamics otherwise limited due to the large
+damping constant coming from the high spin-orbit coupling in materials with
+high magnetic anisotropy.",1803.08768v1
+2018-05-15,"Flare Energy Release in the Magnetic Field Polarity Inversion Line During M1.2 Solar Flare of March 15, 2015. Paper I. Onset of Plasma Heating and Electrons Acceleration","We present the study of SOL2015-03-15 M1.2 flare, revealing acceleration of
+electrons and plasma heating in the sheared twisted magnetic structure in the
+polarity inversion line (PIL). The scope is to make the analysis of nonthermal
+electrons dynamics and plasma heating in the highly stressed magnetic loops
+interacting in the PIL by using X-ray, microwave, ultraviolet, and optical
+observations. It is found that the most probable scenario for the energy
+release in the PIL is the tether-cutting magnetic reconnection between the
+low-lying (3 Mm above the photosphere) magnetic loops within a twisted magnetic
+flux rope. Energetic electrons with the hardest spectrum were appeared at the
+onset of plasma heating up to the super-hot temperature of 40 MK. These
+electrons are localized in a thin magnetic channel with width of around 0.5 Mm
+with high average magnetic field of about 1200 G. The plasma beta in the
+super-hot region is less than 0.01. The estimated density of accelerated
+electrons is about 10^9 cm^-3 that is much less than the super-hot plasma
+density. The energy density flux of non-thermal electrons is estimated up to
+3x10^12 ergs cm^-2s^-1 that is much higher than in the currently available
+radiative hydrodynamic models. These results revealed that one need to develop
+new self-consisting flare models reproducing 3D magnetic reconnection in the
+PIL with strong magnetic field, spatial filamentation of energy release,
+formation of high energy density populations of nonthermal electrons and
+appearance of the super-hot plasma.",1805.05792v1
+2018-05-24,Coronal Hole and Solar Global Magnetic Field Evolution in 1976-2012,"Coronal hole spatial-temporal evolution is studied and comparison made with
+that of the solar global magnetic field in cycles 21-23 (1976-2012). The
+latitude-longitude distribution dynamics of coronal holes and the regularities
+in the global magnetic field associated with the solar polar field reversal are
+analyzed. Polar and non-polar coronal hole populations are considered. The
+investigation reveals some temporal and spatial regularities in coronal hole
+distributions that match well the global magnetic-field cycle evolution. The
+results show that the non-polar coronal hole longitudinal distribution follows
+all configuration changes in the global magnetic-field structure.
+Reorganizations of the global magnetic-field and coronal hole distributions
+occur simultaneously during a time interval of a few solar rotations. The cycle
+evolution of the non-polar coronal holes reflects the transition of the solar
+global magnetic field from the zonal structure to sectorial andvice versa. Two
+different type waves of non-polar coronal holes are revealed from their
+latitudinal distribution. The first one is short poleward waves. They trace the
+poleward motion of the unipolar photospheric magnetic fields from approximately
+35 deg to the associated pole in each hemisphere and the redevelopment of a
+new-polarity polar CH. Although they start the poleward movement before the
+change of the polar magnetic field in the associated hemisphere, they reach the
+pole after the polar reversal. The other type of non-polar CH wave forms two
+sinusoidal branches associated with the positive- and negative-polarity
+magnetic fields. The complete period of the wave was equal to approximately 268
+CRs (22 years). These wave CHs arrive at high latitudes during declining phases
+when the new polarity polar CHs are already completely formed.",1805.09543v1
+2018-05-26,Distinct spin-lattice and spin-phonon interactions in monolayer magnetic CrI$_3$,"We apply the density-functional theory to study various phases (including
+non-magnetic (NM), anti-ferromagnetic (AFM), and ferromagnetic (FM)) in
+monolayer magnetic chromium triiodide (CrI$_3$), a recently fabricated 2D
+magnetic material. It is found that: (1) the introduction of magnetism in
+monolayer CrI$_3$ gives rise to metal-to-semiconductor transition; (2) the
+electronic band topologies as well as the nature of direct and indirect band
+gaps in either AFM or FM phases exhibit delicate dependence on the magnetic
+ordering and spin-orbit coupling; and (3)the phonon modes involving Cr atoms
+are particularly sensitive to the magnetic ordering, highlighting distinct
+spin-lattice and spin-phonon coupling in this magnet. First-principles
+simulations of the Raman spectra demonstrate that both frequencies and
+intensities of the Raman peaks strongly depend on the magnetic ordering. The
+polarization dependent $A_{1g}$ modes at 77 cm$^{-1}$ and 130 cm$^{-1}$ along
+with the $E_g$ mode at about 50 cm$^{-1}$ in the FM phase may offer a useful
+fingerprint to characterize this material. Our results not only provide a
+detailed guiding map for experimental characterization of CrI$_3$, but also
+reveal how the evolution of magnetism can be tracked by its lattice dynamics
+and Raman response.",1805.10479v2
+2018-08-14,Magnetic Nanoparticle Based Molecular Communication in Microfluidic Environments,"The possibility to guide and control magnetic nanoparticles in a non-invasive
+manner has spawned various applications in biotechnology such as targeted drug
+delivery and sensing of biological substances. These applications are
+facilitated by the engineering of the size, selective chemical reactivity, and
+general chemical composition of the employed particles. Motivated by their
+widespread use and favorable properties, in this paper, we provide a
+theoretical study of the potential benefits of magnetic nanoparticles for the
+design of molecular communication systems. In particular, we consider magnetic
+nanoparticle based communication in a microfluidic channel where an external
+magnetic field is employed to attract the information-carrying particles to the
+receiver. We show that the particle transport affected by Brownian motion,
+fluid flow, and an external magnetic field can be mathematically modeled as
+diffusion with drift. Thereby, we reveal that the key parameters determining
+the magnetic force are the particle size and the magnetic field gradient.
+Moreover, we derive an analytical expression for the channel impulse response,
+which is used to evaluate the potential gain in the expected number of observed
+nanoparticles due to the magnetic field. Furthermore, adopting the symbol error
+rate as performance metric, we show that using magnetic nanoparticles can
+enable reliable communication in the presence of disruptive fluid flow.
+Numerical results obtained by particle-based simulation validate the accuracy
+of the derived analytical expressions.",1808.05147v2
+2018-08-30,Growth Pattern of Magnetic Field Treated Bacteria,"A study of the induced effect of different types of weak magnetic field
+exposure on bacterial growth is performed, comparing the relative changes after
+removal from the magnetic fields. This investigation is relevant to understand
+the effect of magnetic field exposure on human beings due to electronic
+devices. For this purpose, we use four species of common bacteria in reference
+to human health and safety including Escherichia coli, Staphylococcus aureus,
+Staphylococcus epidermidis, and Pseudomonas aeruginosa. The choice of these
+four bacteria also allows us to check for effects which rely upon the
+Gram-staining properties or shapes of bacterial species. These species were
+initially exposed to static, non-homogeneous and alternating weak magnetic
+fields, and then they were grown in incubators in the same environment at 37
+{\deg}C simultaneously. Comparative measurements of optical density are then
+used to track the sustained impact on bacterial growth in the experimental
+samples. Bacteria was first grown in different weak magnetic fields on a plain
+glass surface both in liquid and solid media. Magnetic field treated bacteria
+were then transferred into similar test tubes to grow in an incubator
+concurrently. Bacterial cultures in liquid nutrient broth on plain glass
+proliferated faster in most species. Different magnetic fields affect the
+growth pattern of bacteria differently, depending on the bacterial strain. The
+weak magnetic field seems to decelerate the growth rate, even after the
+magnetic field is removed. With application of this study, we can potentially
+investigate the effect of weak field exposures on Eukaryotic cells and gene
+dynamics.",1808.10333v2
+2018-11-02,Spinning superconductors and ferromagnets,"When a magnetic field is applied to a ferromagnetic body it starts to spin
+(Einstein-de Haas effect). This demonstrates the intimate connection between
+the electron's magnetic moment $\mu_B=e\hbar/2m_ec$, associated with its spin
+angular momentum $S=\hbar/2$, and ferromagnetism. When a magnetic field is
+applied to a superconducting body it also starts to spin (gyromagnetic effect),
+and when a normal metal in a magnetic field becomes superconducting and expels
+the magnetic field (Meissner effect) the body also starts to spin. Yet
+according to the conventional theory of superconductivity the electron's spin
+only role is to label states, and the electron's magnetic moment plays no role
+in superconductivity. Instead, within the unconventional theory of hole
+superconductivity, the electron's spin and associated magnetic moment play a
+fundamental role in superconductivity. Just like in ferromagnets the
+magnetization of superconductors is predicted to result from an aggregation of
+magnetic moments with angular momenta $\hbar/2$. This gives rise to a ""Spin
+Meissner effect"", the existence of a spin current in the ground state of
+superconductors. The theory explains how a superconducting body starts spinning
+when it expels magnetic fields, it provides a dynamical explanation for the
+Meissner effect, and it explains how supercurrents stop without dissipation,
+all of which we argue the conventional theory fails to explain. Essential
+elements of the theory of hole superconductivity are that superconductivity is
+driven by lowering of kinetic energy, which we have also proposed is true for
+ferromagnets], that the normal state charge carriers in superconducting
+materials are holes, and that the spin-orbit interaction plays a key role in
+superconductivity. The theory is proposed to apply to all superconductors.",1811.03938v1
+2019-04-30,Tunable ferromagnetic resonance in coupled trilayers with crossed in-plane and perpendicular magnetic anisotropies,"A novel approach to tune the ferromagnetic resonance frequency of a soft
+magnetic Ni$_{80}$Fe$_{20}$ (Permalloy = Py) film with in-plane magnetic
+anisotropy (IMA) based on the controlled coupling to a hard magnetic
+NdCo$_\text{x}$ film with perpendicular magnetic anisotropy (PMA) through a
+non-magnetic Al spacer is studied. Using transverse magneto-optical Kerr effect
+(TMOKE), alternating gradient magnetometry (AGM) as well as vector network
+analyzer ferromagnetic resonance (VNA-FMR) spectroscopy, the influence of both
+Co concentration and Al spacer thickness on the static and dynamic magnetic
+properties of the coupled IMA/PMA system is investigated. Compared to a single
+Py film, two striking effects of the coupling between IMA and PMA layers can be
+observed in their FMR spectra. First, there is a significant increase in the
+zero-field resonance frequency from 1.3 GHz up to 6.6 GHz, and second, an
+additional frequency hysteresis occurs at low magnetic fields applied along the
+hard axis. The maximum frequency difference between the frequency branches for
+increasing and decreasing magnetic field is as high as 1 GHz, corresponding to
+a tunability of about 20% at external fields of typically less than $\pm$70 mT.
+The origin of the observed features in the FMR spectra is discussed by means of
+magnetization reversal curves.",1904.13275v1
+2019-05-14,Versatile Hall magnetometer with variable sensitivity assembly for characterization of the magnetic properties of nanoparticles,"A Hall magnetometer with variable sensitivity is constructed to measure the
+magnetic properties of magnetic nanoparticles manufactured by different
+methods. This novel magnetometer can also be used to measure bulk materials and
+samples in liquids. The magnetometer is constructed with two commercial
+Hall-effect sensors in an acrylic structure, which serves as the support for a
+micrometer and the circuit board with the sensors. For operation, the
+magnetometer it acquires a complete magnetization curve in a few minutes. If
+has a magnetic moment sensitivity of 1.3*10-9 Am2 to sensitivity of 493 mV/mT,
+the sensitivity can be adjustable in the range of 10 to 493 mV/mT. Its
+performance is tested with magnetic nanoparticles. As an application example,
+we estimate the mean diameter of the nanoparticles using the magnetic curves.
+The results are compared with those obtained by other techniques, such as
+transmission electron microscopy (TEM), X-ray diffraction (XRD) and dynamic
+light scattering (DLS). The magnetization results are also compared with those
+obtained by independent commercial magnetometers, which reveals errors of
+approximately 0.31 Am2/kg (i.e., 0.6%) in the saturation region.",1905.05741v2
+2020-02-26,The Trigger Mechanism of Recurrent Solar Active Region Jets Revealed by the Magnetic Properties of a Coronal Geyser Site,"Solar active region jets are small-scale collimated plasma eruptions that are
+triggered from magnetic sites embedded in sunspot penumbral regions. Multiple
+trigger mechanisms for recurrent jets are under debate. Vector magnetic field
+data from SDO-HMI observations are used to analyze a prolific photospheric
+configuration, identified in extreme ultraviolet observations as a `Coronal
+Geyser', that triggered a set of at least 10 recurrent solar active region
+jets. We focus on interpreting the magnetic fields of small-scale flaring sites
+aiming to understand the processes that govern recurrent jet eruptions. We
+perform a custom reprocessing of the SDO-HMI products, including disambiguation
+and uncertainty estimation. We scrutinized the configuration and dynamics of
+the photospheric magnetic structures. The magnetic configuration is described
+via the analysis of the photospheric magnetic vertical fields, to identify the
+process is responsible for driving the jet eruptions. We report that the two
+widely debated magnetic trigger processes, namely magnetic flux cancellation
+and magnetic flux emergence, appear to be responsible on a case by case basis
+for generating each eruption in our set. We find that 4 of 10 jets were due to
+flux cancellation while the rest were clearly not, and were more likely due to
+flux emergence.",2002.11819v1
+2020-05-20,How primordial magnetic fields shrink galaxies,"As one of the prime contributors to the interstellar medium energy budget,
+magnetic fields naturally play a part in shaping the evolution of galaxies.
+Galactic magnetic fields can originate from strong primordial magnetic fields
+provided these latter remain below current observational upper limits. To
+understand how such magnetic fields would affect the global morphological and
+dynamical properties of galaxies, we use a suite of high-resolution constrained
+transport magneto-hydrodynamic cosmological zoom simulations where we vary the
+initial magnetic field strength and configuration along with the prescription
+for stellar feedback. We find that strong primordial magnetic fields delay the
+onset of star formation and drain the rotational support of the galaxy,
+diminishing the radial size of the galactic disk and driving a higher amount of
+gas towards the centre. This is also reflected in mock UVJ observations by an
+increase in the light profile concentration of the galaxy. We explore the
+possible mechanisms behind such a reduction in angular momentum, focusing on
+magnetic braking. Finally, noticing that the effects of primordial magnetic
+fields are amplified in the presence of stellar feedback, we briefly discuss
+whether the changes we measure would also be expected for galactic magnetic
+fields of non-primordial origin.",2005.10269v1
+2020-08-06,Paramagnetic spin Hall magnetoresistance,"Spin Hall magnetoresistance (SMR) refers to a resistance change in a metallic
+film reflecting the magnetization direction of a magnet attached to the film.
+The mechanism of this phenomenon is spin exchange between conduction-electron
+spins and magnetization at the interface. SMR has been used to read out
+information written in a small magnet and to detect magnetization dynamics, but
+it has been limited to magnets; magnetic ordered phases or instability of
+magnetic phase transition has been believed to be indispensable. Here, we
+report the observation of SMR in a paramagnetic insulator
+Gd$_{3}$Ga$_{5}$O$_{12}$ (GGG) without spontaneous magnetization combined with
+a Pt film. The paramagnetic SMR can be attributed to spin-transfer torque
+acting on localized spins in GGG. We determine the efficiencies of spin torque
+and spin-flip scattering at the Pt/GGG interface, and demonstrate these
+quantities can be tuned with external magnetic fields. The results clarify the
+mechanism of spin-transport at a metal/paramagnetic insulator interface, which
+gives new insight into the spintronic manipulation of spin states in
+paramagnetic systems.",2008.02446v2
+2020-10-07,Magnetostriction in elastomers with mixtures of magnetically hard and soft microparticles: effects of non-linear magnetization and matrix rigidity,"In this contribution a magnetoactive elastomer (MAE) of mixed content, i.e.,
+a polymer matrix filled with a mixture of magnetically soft and magnetically
+hard spherical particles, is considered. The object we focus at is an
+elementary unit of this composite, for which we take a set consisting of a
+permanent spherical micromagnet surrounded by an elastomer layer filled with
+magnetically soft microparticles. We present a comparative treatment of this
+unit from two essentially different viewpoints. The first one is a
+coarse-grained molecular dynamics simulation model, which presents the
+composite as a bead-spring assembly and is able to deliver information of all
+the microstructural changes of the assembly. The second approach is entirely
+based on the continuum magnetomechanical description of the system, whose
+direct yield is the macroscopic field-induced response of the MAE to external
+field, as this model ignores all the microstructural details of the
+magnetization process. We find that, differing in certain details, both
+frameworks are coherent in predicting that a unit comprising magnetically soft
+and hard particles may display a non-trivial re-entrant
+(prolate/oblate/prolate) axial deformation under variation of the applied field
+strength.
+  The flexibility of the proposed combination of the two complementary
+frameworks enables us to look deeper into the manifestation of the magnetic
+response: with respect to the magnetically soft particles, we compare the
+linear regime of magnetization to that with saturation, which we describe by
+the Fr\""{o}hlich-Kennelly approximation; with respect to the polymer matrix, we
+analyze the dependence of the re-rentrant deformation on its rigidity.",2010.03684v1
+2020-11-09,Evolution of three-dimensional coherent structures in Hall magnetohydrodynamics,"The work extends the computational model EULAG-MHD to include Hall
+magnetohydrodynamics (HMHD)---important to explore physical systems undergoing
+fast magnetic reconnection at the order of the ion inertial length scale.
+Examples include solar transients along with reconnections in magnetosphere,
+magnetotail and
+  laboratory plasmas. The paper documents the results of two distinct sets of
+implicit large-eddy simulations in the presence and absence of the Hall forcing
+term, initiated with an unidirectional sinusoidal magnetic field. The HMHD
+simulation while benchmarking the code also emphasizes the complexity of three
+dimensional (3D) evolution over its two dimensional (2D) counterpart. The
+magnetic reconnections onset significantly earlier in HMHD. Importantly, the
+magnetic field generated by the Hall term breaks any inherent symmetry,
+ultimately making the evolution 3D. The resulting 3D reconnections develop
+magnetic flux ropes and magnetic flux tubes. Projected on the reconnection
+plane, the ropes and tubes appear as magnetic islands, which later break into
+secondary islands, and finally coalesce to generate an X-type neutral point.
+These findings are in agreement with the theory and contemporary simulations of
+HMHD, and thus verify our extension of the EULAG-MHD model. The second set
+explores the influence of the Hall forcing on generation and ascend of a
+magnetic flux rope from sheared magnetic arcades---a novel scenario instructive
+in understanding the coronal transients. The rope evolves through intermediate
+complex structures, ultimately breaking locally because of reconnections.
+Interestingly, the breakage occurs earlier in the presence of the Hall term,
+signifying faster dynamics leading to magnetic topology favorable for
+reconnections.",2011.04223v1
+2021-01-28,Universal field dependence of magnetic resonance near zero frequency,"Magnetic resonance is a widely-established phenomenon that probes magnetic
+properties such as magnetic damping and anisotropy. Even though the typical
+resonance frequency of a magnet ranges from gigahertz to terahertz, experiments
+also report the resonance near zero frequency in a large class of magnets. Here
+we revisit this phenomenon by analyzing the symmetry of the system and find
+that the resonance frequency ($\omega$) follows a universal power law $\omega
+\varpropto |H-H_c|^p$, where $H_c$ is the critical field at which the resonance
+frequency is zero. When the magnet preserves the rotational symmetry around the
+external field ($H$), $p = 1$. Otherwise, $p=1/2$. The magnon excitations are
+gapped above $H_c$, gapless at $H_c$ and gapped again below $H_c$. The zero
+frequency is often accompanied by a reorientation transition in the
+magnetization. For the case that $p=1/2$, this transition is described by a
+Landau theory for second-order phase transitions. We further show that the spin
+current driven by thermal gradient and spin-orbit effects can be significantly
+enhanced when the resonance frequency is close to zero, which can be measured
+electrically by converting the spin current into electric signals. This may
+provide an experimentally accessible way to characterize the critical field.
+Our findings provide a unified understanding of the magnetization dynamics near
+the critical field, and may, furthermore, inspire the study of magnon transport
+near magnetic transitions.",2101.12292v1
+2021-07-27,Exploring extreme magnetization phenomena in directly-driven imploding cylindrical targets,"This paper uses extended-magnetohydrodynamics (MHD) simulations to explore an
+extreme magnetized plasma regime realisable by cylindrical implosions on the
+OMEGA laser facility. This regime is characterized by highly compressed
+magnetic fields (greater than 10~kT across the fuel), which contain a
+significant proportion of the implosion energy and induce large electrical
+currents in the plasma. Parameters governing the different magnetization
+processes such as Ohmic dissipation and suppression of instabilities by
+magnetic tension are presented, allowing for optimization of experiments to
+study specific phenomena. For instance, a dopant added to the target gas-fill
+can enhance magnetic flux compression while enabling spectroscopic diagnosis of
+the imploding core. In particular, the use of Ar K-shell spectroscopy is
+investigated by performing detailed non-LTE atomic kinetics and radiative
+transfer calculations on the MHD data. Direct measurement of the core electron
+density and temperature would be possible, allowing for both the impact of
+magnetization on the final temperature and thermal pressure to be obtained. By
+assuming the magnetic field is frozen into the plasma motion, which is shown to
+be a good approximation for highly magnetized implosions, spectroscopic
+diagnosis could be used to estimate which magnetization processes are ruling
+the implosion dynamics; for example, a relation is given for inferring whether
+thermally-driven or current-driven transport is dominating.",2107.13032v1
+2021-10-01,Numerical Simulation of Superparamagnetic Nanoparticle Motion in Blood Vessels for Magnetic Drug Delivery,"A numerical model is developed for the motion of superparamagnetic
+nanoparticles in a non-Newtonian blood flow under the influence of a magnetic
+field. The rheological properties of blood are modeled by the Carreau flow and
+viscosity, and the stochastic effects of Brownian motion and red blood cell
+collisions are considered. The model is validated with existing data and good
+agreement with experimental results is shown. The effectiveness of magnetic
+drug delivery in various blood vessels is assessed and found to be most
+successful in arterioles and capillaries. A range of magnetic field strengths
+are modeled using equations for both a bar magnet and a point dipole: it is
+shown that the bar magnet is effective at capturing nanoparticles in limited
+cases while the point dipole is highly effective across a range of conditions.
+A parameter study is conducted to show the effects of changing the dipole
+moment, the distance from the magnet to the blood vessel, and the initial
+release point of the nanoparticles. The distance from the magnet to the blood
+vessel is shown to play a significant role in determining nanoparticle capture
+rate. The optimal initial release position is found to be located within the
+tumor radius in capillaries and arterioles to prevent rapid diffusion to the
+edges of the blood vessel prior to arriving at the tumor, and near the edge of
+the magnet when a bar magnet is used.",2110.01988v2
+2021-11-05,Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet,"The microscopic origins of emergent behaviours in condensed matter systems
+are encoded in their excitations. In ordinary magnetic materials, single
+spin-flips give rise to collective dipolar magnetic excitations called magnons.
+Likewise, multiple spin-flips can give rise to multipolar magnetic excitations
+in magnetic materials with spin $\mathbf{S} \boldsymbol{\ge} \mathbf{1}$.
+Unfortunately, since most experimental probes are governed by dipolar selection
+rules, collective multipolar excitations have generally remained elusive. For
+instance, only dipolar magnetic excitations have been observed in isotropic
+$\mathbf{S}\boldsymbol{=}\mathbf{1}$ Haldane spin systems. Here, we unveil a
+hidden quadrupolar constituent of the spin dynamics in antiferromagnetic
+$\mathbf{S}\boldsymbol{=}\mathbf{1}$ Haldane chain material
+Y$_\mathbf{2}$BaNiO$_\mathbf{5}$ using Ni $\mathbf{L_3}$-edge resonant
+inelastic x-ray scattering. Our results demonstrate that pure quadrupolar
+magnetic excitations can be probed without direct interactions with dipolar
+excitations or anisotropic perturbations. Originating from on-site double
+spin-flip processes, the quadrupolar magnetic excitations in
+Y$_\mathbf{2}$BaNiO$_\mathbf{5}$ show a remarkable dual nature of collective
+dispersion. While one component propagates as non-interacting entities, the
+other behaves as a bound quadrupolar magnetic wave. This result highlights the
+rich and largely unexplored physics of higher-order magnetic excitations.",2111.03625v1
+2022-02-16,Another type of anomalous velocity caused by the singularity of the magnetic Bloch function in the magnetic Brillouin zone,"The quantum Hall effect is known to be caused by the anomalous velocity that
+is expressed as the Berry curvature of the magnetic Bloch band. It is also
+known that the Hall conductivity is expressed by the Chern number that is given
+as an integral of the Berry curvature and has a nonzero value because of the
+singularity of the magnetic Bloch function in the magnetic Brillouin zone. We
+have investigated the dynamics of a wave packet composed of magnetic Bloch
+functions. It is shown that another type of the anomalous velocity appears in
+addition to the group velocity and the anomalous velocity of the magnetic Bloch
+state. This another type of the anomalous velocity is caused by the singularity
+of the magnetic Bloch function in the magnetic first Brillouin zone (MBZ) and
+is perpendicular to the electric field. Furthermore, we present the
+acceleration theorem that describes the motion of the wave packet in the MBZ.
+It is found that the expression for the acceleration theorem includes novel
+terms that come from the singularity of the magnetic Bloch function in the MBZ.",2202.07810v3
+2022-04-28,The Role of Magnetic Fields in Triggered Star Formation of RCW 120,"We report on the near-infrared polarimetric observations of RCW 120 with the
+1.4 m IRSF telescope. The starlight polarization of the background stars
+reveals for the first time the magnetic field of RCW 120. The global magnetic
+field of RCW 120 is along the direction of $20^\circ$, parallel to the Galactic
+plane. The field strength on the plane of the sky is $100\pm26\,\mu$G. The
+magnetic field around the eastern shell shows evidence of compression by the
+HII region. The external pressure (turbulent pressure + magnetic pressure) and
+the gas density of the ambient cloud are minimum along the direction where RCW
+120 breaks out, which explains the observed elongation of RCW 120. The
+dynamical age of RCW 120, depending on the magnetic field strength, is
+$\sim\,1.6\,\mathrm{Myr}$ for field strength of $100\,\mu$G, older than the
+hydrodynamic estimates. In direction perpendicular to the magnetic field, the
+density contrast of the western shell is greatly reduced by the strong magnetic
+field. The strong magnetic field in general reduces the efficiency of triggered
+star formation, in comparison with the hydrodynamic estimates. Triggered star
+formation via the ""collect and collapse"" mechanism could occur in the direction
+along the magnetic field. Core formation efficiency (CFE) is found to be higher
+in the southern and eastern shells of RCW 120 than in the infrared dark cloud
+receiving little influence from the HII region, suggesting increase in the CFE
+related to triggering from ionization feedback.",2204.13296v2
+2022-07-28,Evolution of short-range magnetic correlations in ferromagnetic Ni-V alloys,"We experimentally study how the magnetic correlations develop in a binary
+alloy close to the ferromagnetic quantum critical point with small-angle
+neutron scattering (SANS). Upon alloying the itinerant ferromagnet nickel with
+vanadium, the ferromagnetic order is continuously suppressed. The critical
+temperature Tc vanishes when vanadium concentrations reach the critical value
+of xc=0.116 indicating a quantum critical point separating the ferromagnetic
+and paramagnetic phases. Earlier magnetization and $\mu$SR data have indicated
+the presence of magnetic inhomogeneities in Ni(1-x)V(x) and, in particular,
+recognize the magnetic clusters close to xc, on the paramagnetic and on the
+ferromagnetic sides with nontrivial dynamical properties [R. Wang et al., Phys.
+Rev. Lett. 118, 267202 (2017)]. We present the results of SANS study with full
+polarization analysis of polycrystalline Ni(1-x)V(x) samples with x=0.10 and
+x=0.11 with low critical temperatures Tc below 50 K. For both Ni-V samples
+close to xc we find isotropic magnetic short-range correlations in the
+nanometer-scale persisting at low temperatures. They are suppressed gradually
+in higher magnetic fields. In addition, signatures of long-range ordered
+magnetic domains are present below Tc. The fraction of these magnetic clusters
+embedded in the ferromagnetic ordered phase grows towards xc and agrees well
+with the cluster fraction estimate from the magnetization and $\mu$SR data. Our
+SANS studies provide new insights into the nature of the inhomogeneities in a
+ferromagnetic alloy close to a quantum critical point.",2207.14196v2
+2023-01-17,Magnetic frustration driven by conduction carrier blocking in Nd$_2$Co$_{0.85}$Si$_{2.88}$,"The intermetallic compound Nd$_2$Co$_{0.85}$Si$_{2.88}$ having a triangular
+lattice could be synthesized in single-phase only with defect crystal
+structure. Investigation through different experimental techniques indicate the
+presence of two magnetic transitions in the system. As verified experimentally
+and theoretically, the high-temperature transition T$_H$ ~ 140 K is associated
+with the development of ferromagnetic interaction between itinerant Co moments,
+whereas the low-temperature transition at T$_L$ ~ 6.5 K is due to the coupling
+among Nd-4f and Co-3d moments, which is antiferromagnetic in nature. Detailed
+studies of temperature-dependent dc magnetic susceptibility, field dependence
+of isothermal magnetization, non-equilibrium dynamical behavior, viz. magnetic
+relaxation, aging effect, magnetic-memory effect, and temperature dependence of
+heat capacity, along with density functional theory (DFT) calculations, suggest
+that the ground state is magnetically frustrated spin-glass in nature, having
+competing magnetic interactions of equivalent energies. DFT results further
+reveal that the 3d/5d-conduction carriers are blocked in the system and act as
+a barrier for the 4f-4f RKKY interactions, resulting in spin-frustration.
+Presence of vacancy defects in the crystal are also conducive to the
+spin-frustration. This is an unique mechanism of magnetic frustration, not
+emphasized so far in any of the ternary R$_2$TX$_3$ (R=rare-earth, T=transition
+elements and X=Si, Ge, In) type compounds. Due to the competing character of
+the itinerant 3d and localized 4f moments, the compound exhibits anomalous
+field dependence of magnetic coercivity.",2301.07140v1
+2023-04-19,Thickness-dependent magnetic properties in Pt[CoNi]n multilayers with perpendicular magnetic anisotropy,"We systematically investigated the Ni and Co thickness-dependent
+perpendicular magnetic anisotropy (PMA) coefficient, magnetic domain
+structures, and magnetization dynamics of Pt(5 nm)/[Co(t_Co nm)/Ni(t_Ni
+nm)]5/Pt(1 nm) multilayers by combining the four standard magnetic
+characterization techniques. The magnetic-related hysteresis loops obtained
+from the field-dependent magnetization M and anomalous Hall resistivity (AHR)
+\r{ho}_xy found that the two serial multilayers with t_Co = 0.2 and 0.3 nm have
+the optimum PMA coefficient K_U well as the highest coercivity H_C at the Ni
+thickness t_Ni = 0.6 nm. Additionally, the magnetic domain structures obtained
+by Magneto-optic Kerr effect (MOKE) microscopy also significantly depend on the
+thickness and K_U of the films. Furthermore, the thickness-dependent linewidth
+of ferromagnetic resonance is inversely proportional to K_U and H_C, indicating
+that inhomogeneous magnetic properties dominate the linewidth. However, the
+intrinsic Gilbert damping constant determined by a linear fitting of
+frequency-dependent linewidth does not depend on Ni thickness and K_U. Our
+results could help promote the PMA [Co/Ni] multilayer applications in various
+spintronic and spin-orbitronic devices.",2304.09366v1
+2023-05-05,Complete replacement of magnetic flux in a flux rope during a coronal mass ejection,"Solar coronal mass ejections are the most energetic events in the Solar
+System. In their standard formation model, a magnetic flux rope builds up into
+a coronal mass ejection through magnetic reconnection that continually converts
+overlying, untwisted magnetic flux into twisted flux enveloping the
+pre-existing rope. However, only a minority of coronal mass ejections carry a
+coherent magnetic flux rope as their core structure, which casts doubt on the
+universality of this orderly wrapping process. Here we provide observational
+evidence of a different formation and eruption mechanism of a magnetic flux
+rope from an S-shaped thread, where its magnetic flux is fully replaced via
+flare reconnections. One of the footpoints of the sigmoidal feature slipped and
+expanded during the formation, and then moved to a completely new place,
+associated with the highly dynamical evolution of flare ribbons and a twofold
+increase in magnetic flux through the footpoint, during the eruption. Such a
+configuration is not predicted by standard formation models or numerical
+simulations and highlights the three-dimensional nature of magnetic
+reconnections between the flux rope and the surrounding magnetic field.",2305.03217v1
+2023-07-04,Reconciling the magnetic field in central disc galaxies with the dynamical mass using the cosmological simulations,"The Universe is pervaded by magnetic fields in different scales, although for
+simplicity, they are ignored in most cosmological simulations. In this paper,
+we use the TNG50, which is a large cosmological galaxy formation simulation
+that incorporates magnetic fields with an unprecedented resolution. We study
+the correlation of the magnetic field with various galaxy properties such as
+the total, stellar and gaseous mass, circular velocity, size and star formation
+rate. We find a linear correlation between the average magnetic field pervading
+the disc of galaxies in relative isolation and their circular velocities. In
+addition we observed that in this sample the average magnetic field in the disc
+is correlated with the total mass as $\overline{B}\sim
+M_{\mathrm{tot,\,R_{\star}}}^{0.2}$. We also find that the massive galaxies
+with active wind-driven black hole feedback, do not follow this trend, as their
+magnetic field is substantially affected by this feedback mode in the TNG50
+simulation. We show that the correlation of the magnetic field with the star
+formation rate is a little weaker than the circular velocity. Moreover, we
+compare the magnetic field components of the above sample with a compiled
+observational sample of non-cluster non-interacting nearby galaxies. Similar to
+the observation, we find a coupling between the ordered magnetic field and the
+circular velocity of the flat part of the rotation curve in the simulation,
+although contrary to the observation, the ordered component is dominant in the
+simulation.",2307.01431v2
+2023-07-11,Simulation of magnetohydrodynamic flows of liquid metals with heat transfer or magnetic stirring,"We discuss the effects of nonhomogeneous magnetic fields in liquid metal
+flows in two different configurations. In the first configuration, we briefly
+report the impact of fringing magnetic fields in a turbulent
+Rayleigh-B{\'e}nard convection setup, where it was shown that the global heat
+transport decreases with an increase of fringe-width. The convective motion in
+regions of strong magnetic fields is confined near the sidewalls. In the second
+configuration, we numerically study the effects of an oscillating magnetic
+obstacle with different frequencies of oscillation on liquid metal flow in a
+duct. The Reynolds number is low such that the wake of the stationary magnetic
+obstacle is steady. The transverse oscillation of the magnet creates a
+sinusoidal time-dependent wake reminiscent of the vortex shedding behind solid
+obstacles. We examine the behavior of the streamwise and spanwise components of
+the Lorentz forces as well as the work done by the magnets on the fluid. The
+frequency of the oscillation of the streamwise component of Lorentz force is
+twice that of the spanwise component as in the case of lift and drag on solid
+cylindrical obstacles. The total drag force and the energy transferred from the
+magnets to the fluid show a non-monotonic dependence on the frequency of
+oscillation of the magnetic obstacle indicative of a resonant excitation of the
+sinusoidal vortex shedding.",2307.05465v1
+2023-10-24,Evolution of MHD Torus and Mass Outflow Around Spinning AGN,"We perform axisymmetric, two-dimensional magnetohydrodynamic (MHD)
+simulations to investigate accretion flows around spinning AGN. To mimic the
+space-time geometry of spinning black holes, we consider effective Kerr
+potential, and the mass of the black holes is $10^8 M_{\odot}$. We initialize
+the accretion disc with a magnetized torus by adopting the toroidal component
+of the magnetic vector potential. The initial magnetic field strength is set by
+using the plasma beta parameter ($\beta_0$). We observe self-consistent
+turbulence generated by magneto rotational instability (MRI) in the disc. The
+MRI turbulence transports angular momentum in the disc, resulting in an angular
+momentum distribution that approaches a Keplerian distribution. We investigate
+the effect of the magnetic field on the dynamics of the torus and associated
+mass outflow from the disc around a maximally spinning black hole $(a_k =
+0.99)$. For the purpose of our analysis, we investigate the magnetic state of
+our simulation model. The model $\beta_0 = 10$ indicates the behaviour similar
+to the ""magnetically arrested disk (MAD)'' state, and all the other low
+magnetic model remains in the SANE state. We observe that mass outflow rates
+are significantly enhanced with the increased magnetic field in the disc. We
+find a positive correlation between the magnetic field and mass outflow rates.
+We also investigate the effect of black hole spin on the magnetized torus
+evolution. However, we have not found any significant effect of black hole spin
+on mass outflows in our model. Finally, we discuss the possible astrophysical
+applications of our simulation results.",2310.15501v1
+2023-10-25,Controllable magnetic states in chains of coupled phi-0 Josephson junctions with ferromagnetic weak links,"A superconductor/ferromagnet/superconductor Josephson junction with anomalous
+phase shift (phi_0-S/F/S JJ) is a system, where the anomalous ground state
+shift phi_0 provides a direct magnetoelectric coupling between a magnetic
+moment and a phase of the superconducting condensate. If a chain of such
+phi_0-S/F/S JJs are coupled via superconducting leads, the condensate phase,
+being a macroscopic quantity, mediates a long-range interaction between the
+magnetic moments of the weak links. We study static and dynamic magnetic
+properties of such a system. It is shown that it manifests properties of
+n-level system, where the energies of the levels are only determined by
+projections of the total magnetic moment onto the easy magnetic axis. It is
+similar to a magnetic atom in a Zeeman field, but the role of the field is
+played by the magnetoelectric coupling. However, unlike an atom in a magnetic
+field, the relative order of energies of different states is controlled by
+electrical means. It is also demonstrated that the total magnetic moment can be
+fully controlled by a supercurrent and the response of the magnetic system to
+local external perturbations is highly nonlocal.",2310.16543v2
+2023-10-31,Magnetorotational dynamo can generate large-scale vertical magnetic fields in 3D GRMHD simulations of accreting black holes,"Jetted astrophysical phenomena with black hole (BH) engines, including binary
+mergers, jetted tidal disruption events, and X-ray binaries, require a
+large-scale vertical magnetic field for efficient jet formation. However, a
+dynamo mechanism that could generate these crucial large-scale magnetic fields
+has not been identified and characterized. We have employed 3D global general
+relativistic magnetohydrodynamical (MHD) simulations of accretion disks to
+quantify, for the first time, a dynamo mechanism that generates large-scale
+magnetic fields. This dynamo mechanism primarily arises from the nonlinear
+evolution of the magnetorotational instability (MRI). In this mechanism, large
+non-axisymmetric MRI-amplified shearing wave modes, mediated by the
+axisymmetric azimuthal magnetic field, generate and sustain the large-scale
+vertical magnetic field through their nonlinear interactions. We identify the
+advection of magnetic loops as a crucial feature, transporting the large-scale
+vertical magnetic field from the outer regions to the inner regions of the
+accretion disk. This leads to a larger characteristic size of the, now
+advected, magnetic field when compared to the local disk height. We
+characterize the complete dynamo mechanism with two timescales: one for the
+local magnetic field generation, $t_{\rm g}$, and one for the large-scale scale
+advection, $t_{\rm adv}$. Whereas the dynamo we describe is nonlinear, we
+explore the potential of linear mean field models to replicate its core
+features. Our findings indicate that traditional $\alpha$-dynamo models, often
+computed in stratified shearing box simulations, are inadequate and that the
+effective large-scale dynamics is better described by the shear current effects
+or stochastic $\alpha$-dynamos.",2311.00034v1
+2023-11-22,Twisted Magnetic Knots and Links,"For magnetic knots and links in plasmas we introduce an internal twist and
+study their dynamical behavior in numerical simulations. We use a set of
+helical and non-helical configurations and add an internal twist that cancels
+the helicity of the helical configurations or makes a non-helical system
+helical. These fields are then left to relax in a magnetohydrodynamic
+environment. In line with previous works we confirm the importance of magnetic
+helicity in field relaxation. However, an internal twist, as could be observed
+in coronal magnetic loops, does not just add or subtract helicity, but also
+introduces an alignment of the magnetic field with the electric current, which
+is the source term for helicity. This source term is strong enough to lead to a
+significant change of magnetic helicity, which for some cases leads to a loss
+of the stabilizing properties expressed in the realizability condition. Even a
+relatively weak internal twist in these magnetic fields leads to a strong
+enough source term for magnetic helicity that for various cases even in a low
+diffusion environment we observe an inversion in sign of magnetic helicity
+within time scales much shorter than the diffusion time. We conclude that in
+solar and stellar fields an internal twist does not automatically result in a
+structurally stable configuration and that the alignment of the magnetic field
+with the electric current must be taken into account.",2311.13660v1
+2023-12-01,The Magnetic Field Calibration of the Full-Disk Magnetograph onboard the Advanced Space based Solar Observatory (ASO-S/FMG),"The Full-disk magnetograph is a main scientific payload onboard the Advanced
+Space based Solar Observatory (ASO-S/FMG) that through Stokes parameter
+observation to measures the vector magnetic field. The accuracy of
+magnetic-field values is an important aspect of checking the quality of the FMG
+magnetic-field measurement. According to the design of the FMG, the linear
+calibration method under the weak-field approximation is the preferred scheme
+for magnetic-field calibration. However, the spacecraft orbital velocity can
+affect the position of observed spectral lines, then result in a change of the
+polarization-signal strength. Thus, the magnetic field is modulated by the
+orbit velocity of the spacecraft. In this article, through cross calibration
+between FMG and HMI (Helioseismic and Magnetic Imager onboard the Solar Dynamic
+Observatory), the effects of spacecraft orbital velocity on the coefficient of
+magnetic-field calibration are investigated. By comparing the magnetic field of
+FMG and HMI with spacecraft orbital velocity as an auxiliary reference, the
+revised linear-calibration coefficients that depend on spacecraft orbital
+velocity are obtained. Magnetic field of FMG corrected by the revised
+calibration coefficients removing the effect of spacecraft orbital velocity
+will be more accurate and suitable for scientific research.",2312.00319v1
+2024-01-05,Machine learning inspired models for Hall effects in non-collinear magnets,"The anomalous Hall effect has been front and center in solid state research
+and material science for over a century now, and the complex transport
+phenomena in nontrivial magnetic textures have gained an increasing amount of
+attention, both in theoretical and experimental studies. However, a clear path
+forward to capturing the influence of magnetization dynamics on anomalous Hall
+effect even in smallest frustrated magnets or spatially extended magnetic
+textures is still intensively sought after. In this work, we present an
+expansion of the anomalous Hall tensor into symmetrically invariant objects,
+encoding the magnetic configuration up to arbitrary power of spin. We show that
+these symmetric invariants can be utilized in conjunction with advanced
+regularization techniques in order to build models for the electric transport
+in magnetic textures which are, on one hand, complete with respect to the point
+group symmetry of the underlying lattice, and on the other hand, depend on a
+minimal number of order parameters only. Here, using a four-band tight-binding
+model on a honeycomb lattice, we demonstrate that the developed method can be
+used to address the importance and properties of higher-order contributions to
+transverse transport. The efficiency and breadth enabled by this method
+provides an ideal systematic approach to tackle the inherent complexity of
+response properties of noncollinear magnets, paving the way to the exploration
+of electric transport in intrinsically frustrated magnets as well as
+large-scale magnetic textures.",2401.03044v1
+2024-01-21,Nonlinear Model Predictive Detumbling of Small Satellites with a Single-axis Magnetorquer,"Various actuators are used in spacecraft to achieve attitude stabilization,
+including thrusters, momentum wheels, and control moment gyros. Small
+satellites, however, have stringent size, weight, and cost constraints, which
+makes many actuator choices prohibitive. Consequently, magnetic torquers have
+commonly been applied to spacecraft to attenuate angular rates. Approaches for
+dealing with under-actuation due to magnetic control torque's dependency on the
+magnetic field and required high magnetic flux densities have been previously
+considered. Generally speaking, control of a satellite that becomes
+under-actuated as a result of on-board failures has been a recurrent theme in
+the literature. Methods for controlling spacecraft with fewer actuators than
+degrees of freedom are increasingly in demand due to the increased number of
+small satellite launches. Magnetic torquers have been extensively investigated
+for momentum management of spacecraft with momentum wheels and for nutation
+damping of spin satellites, momentum-biased, and dual-spin satellites.
+Nonetheless, severely under-actuated small spacecraft that carry only a
+single-axis magnetic torquer have not been previously treated. This note
+considers the detumbling of a small spacecraft using only a single-axis
+magnetic torquer. Even with a three-axis magnetic torquer, the spacecraft is
+under-actuated, while, in the case of only a single axis magnetic torquer, the
+problem is considerably more demanding. Our note examines the feasibility of
+spacecraft attitude control with a single-axis magnetic torquer and possible
+control methods that can be used.",2401.11536v1
+2024-02-02,Emerging topological states in EuMn$_2$Bi$_2$: A first principles prediction,"New materials with magnetic order driven topological phases are hugely sought
+after for their immense application potential. In this work, we propose a new
+compound EuMn$_2$Bi$_2$ from our first principles density functional theory
+calculations to host novel topological phases such as Dirac/Weyl semimetal and
+topological insulator in its different magnetic states which are energetically
+close to one another. We started with an isostructural compound EuMn$_2$As$_2$
+where the magnetic structure has been studied experimentally. From our
+calculations we could explain the nature of two magnetic transitions observed
+experimentally in this system and could also establish the correct magnetic
+ground state. Our electronic structure calculations reveal the insulating
+nature of the ground state consistent with the experiments. By replacing all As
+by Bi in EuMn$_2$As$_2$ and by optimizing the new structure, we obtained the
+new compound EuMn$_2$Bi$_2$. We observe this compound to be dynamically stable
+from our phonon calculations supporting its experimental preparation in future.
+By comparing the total energies of various possible magnetic structures we
+identified the ground state. Though the magnetic ground state is found to be
+insulating in nature with tiny band gap which is an order of magnitude less
+than the same in EuMn$_2$As$_2$, there were other magnetic states energetically
+very close to the ground state which display remarkable non-trivial band
+topology such as Dirac/Weyl points close to the Fermi level and topological
+insulator state. The energetic proximity of these magnetic order driven
+topological phases makes them tunable via external handle which indicates that
+the proposed new material EuMn$_2$Bi$_2$ would be a very versatile magnetic
+topological material.",2402.01328v1
+2024-03-25,Self-similar solutions in cylindrical magneto-hydrodynamic blast waves with energy injection at the centre,"The evolution of shocks induced by massive stars does not depend only on the
+ambient magnetic field strength, but also on its orientation. In the present
+work, the dynamics of a magnetized blast wave is investigated under the
+influence of both azimuthal and axial ambient magnetic fields. The blast wave
+is driven by a central source and forms a shell that results from the
+accumulation of interstellar matter behind the shock front. A similarity form
+of the ambient magnetic field and a cylindrical geometry of the blast wave are
+assumed to obtain self-similar solutions. The model is studied separately for
+both azimuthal and axial magnetic field and applied to stellar wind bubbles and
+supernova remnants respectively, using 1D numerical simulations. We found that
+the magnetized blast wave differs from the self-similar case without an ambient
+magnetic field. The forward shock front goes slower in the azimuthal case and
+faster in the axial one. For both tangential orientations, the thickness of the
+shell increases with the magnetic strength. In the azimuthal case, the thermal
+energy can be converted to magnetic energy near the inner boundary of the
+shell. Thus, the temperature drops and the magnetic field increases at the
+tangential discontinuity of the stellar wind bubble. In the axial case of a
+supernova remnant, the numerical solution al w ays follows a special curve in
+the parameter space given by the self-similar model.",2403.16675v1
+2013-02-27,Dynamic phase diagrams of the Blume-Capel model in an oscillating field by the path probability method,"We calculate the dynamic phase transition (DPT) temperatures and present the
+dynamic phase diagrams in the Blume-Capel model under the presence of a
+time-dependent oscillating external magnetic field by using the path
+probability method. We study the time variation of the average order parameters
+to obtain the phases in the system and the paramagnetic (P), ferromagnetic (F)
+and the F + P mixed phases are found. We also investigate the thermal behavior
+of the dynamic order parameters to analyze the nature (continuous and
+discontinuous) of transitions and to obtain the DPT points. We present the
+dynamic phase diagrams in three planes, namely (T, h), (d, T) and (k2/k1, T),
+where T is the reduced temperature, h the reduced magnetic field amplitude, d
+the reduced crystal-field interaction and the k2, k1 rate constants. The phase
+diagrams exhibit dynamic tricritical and reentrant behaviors as well as a
+double critical end point and triple point, strongly depending on the values of
+the interaction parameters and the rate constants. We compare and discuss the
+dynamic phase diagrams with dynamic phase diagrams that are obtained within the
+Glauber-type stochastic dynamics based on the mean-field theory and the
+effective field theory.",1302.6769v1
+2022-08-04,Dynamics of magnetized accretion disks of young stars,"We investigate the dynamics of the accretion disks of young stars with fossil
+large-scale magnetic field. The author's magnetohydrodynamic (MHD) model of the
+accretion disks is generalized to consider the dynamical influence of the
+magnetic field on gas rotation speed and vertical structure of the disks. With
+the help of the developed MHD model, the structure of an accretion disk of a
+solar mass T Tauri star is simulated for different accretion rates $\dot{M}$
+and dust grain sizes $a_d$. The simulations of the radial structure of the disk
+show that the magnetic field in the disk is kinematic, and the electromagnetic
+force does not affect the rotation speed of the gas for typical values
+$\dot{M}=10^{-8}\,M_\odot\,\mbox{yr}^{-1}$ and $a_d=0.1 \mu$m. In the case of
+large dust grains, $a_d\geq 1$ mm, the magnetic field is frozen into the gas
+and a dynamically strong magnetic field is generated at radial distances from
+the star $r\gtrsim 30$ au, the tensions of which slow down the rotation speed
+by $\lesssim 1.5$ % of the Keplerian velocity. This effect is comparable to the
+contribution of the radial gradient of gas pressure and can lead to the
+increase in the radial drift velocity of dust grains in the accretion disks. In
+the case of high accretion rate, $\dot{M}\geq
+10^{-7}\,M_\odot\,\mbox{yr}^{-1}$, the magnetic field is also dynamically
+strong in the inner region of the disk, $r<0.2$ au. The simulations of the
+vertical structure of the disk show that, depending on the conditions on the
+surface of the disk, the vertical gradient of magnetic pressure can lead to
+both decrease and increase in the characteristic thickness of the disk as
+compared to the hydrostatic one by 5-20 %. The change in the thickness of the
+disk occurs outside the region of low ionization fraction and effective
+magnetic diffusion (`dead' zone), which extends from $r=0.3$ to $20$ au at
+typical parameters.",2208.02871v1
+2007-11-01,Draping of Cluster Magnetic Fields over Bullets and Bubbles -- Morphology and Dynamic Effects,"High-resolution X-ray observations have revealed cavities and `cold fronts'
+with sharp edges in temperature, density, and metallicity within galaxy
+clusters. Their presence poses a puzzle since these features are not expected
+to be hydrodynamically stable, or to remain sharp in the presence of diffusion.
+However, a moving core or bubble in even a very weakly magnetized plasma
+necessarily sweeps up enough magnetic field to build up a dynamically important
+sheath around the object; the layer's strength is set by a competition between
+`plowing up' of field and field lines slipping around the core. We show that a
+two-dimensional approach to the problem is quite generally not possible. In
+three dimensions, we show with analytic arguments and in numerical experiments,
+that this magnetic layer modifies the dynamics of a plunging core, greatly
+modifies the effects of hydrodynamic instabilities on the core, modifies the
+geometry of stripped material, and even slows the fall of the core through
+magnetic tension. We derive an expression for the maximum magnetic field
+strength, the thickness of the layer, and the opening angle of the magnetic
+wake. The morphology of the magnetic draping layer implies the suppression of
+thermal conduction across the layer, thus conserving strong temperature
+gradients over the contact surface. The intermittent amplification of the
+magnetic field as well as the injection of MHD turbulence in the wake of the
+core is identified to be due to vorticity generation within the magnetic
+draping layer. These results have important consequences for understanding the
+physical properties and the complex gasdynamical processes of the intra-cluster
+medium, and apply quite generally to motions through other magnetized
+environments, e.g., the ISM.",0711.0213v2
+2016-04-08,Ultrafast energy and momentum resolved dynamics of magnetic correlations in photo-doped Mott insulator Sr$_2$IrO$_4$,"Measuring how the magnetic correlations throughout the Brillouin zone evolve
+in a Mott insulator as charges are introduced dramatically improved our
+understanding of the pseudogap, non-Fermi liquids and high $T_C$
+superconductivity. Recently, photoexcitation has been used to induce similarly
+exotic states transiently. However, understanding how these states emerge has
+been limited because of a lack of available probes of magnetic correlations in
+the time domain, which hinders further investigation of how light can be used
+to control the properties of solids. Here we implement magnetic resonant
+inelastic X-ray scattering at a free electron laser, and directly determine the
+magnetization dynamics after photo-doping the Mott insulator Sr$_2$IrO$_4$. We
+find that the non-equilibrium state 2~ps after the excitation has strongly
+suppressed long-range magnetic order, but hosts photo-carriers that induce
+strong, non-thermal magnetic correlations. The magnetism recovers its
+two-dimensional (2D) in-plane N\'eel correlations on a timescale of a few ps,
+while the three-dimensional (3D) long-range magnetic order restores over a far
+longer, fluence-dependent timescale of a few hundred ps. The dramatic
+difference in these two timescales, implies that characterizing the
+dimensionality of magnetic correlations will be vital in our efforts to
+understand ultrafast magnetic dynamics.",1604.02439v2
+2016-09-06,Effects of magnetic and kinetic helicities on the growth of magnetic fields in laminar and turbulent flows by helical-Fourier decomposition,"We present a numerical and analytical study of incompressible homogeneous
+conducting fluids using a helical Fourier representation. We analytically study
+both small- and large-scale dynamo properties, as well as the inverse cascade
+of magnetic helicity, in the most general minimal subset of interacting
+velocity and magnetic fields on a closed Fourier triad. We mainly focus on the
+dependency of magnetic field growth as a function of the distribution of
+kinetic and magnetic helicities among the three interacting wavenumbers. By
+combining direct numerical simulations of the full magnetohydrodynamics
+equations with the helical Fourier decomposition we numerically confirm that in
+the kinematic dynamo regime the system develops a large-scale magnetic helicity
+with opposite sign compared to the small-scale kinetic helicity, a sort of
+triad-by-triad $\alpha$-effect in Fourier space. Concerning the small-scale
+perturbations, we predict theoretically and confirm numerically that the
+largest instability is achieved for the magnetic component with the same
+helicity of the flow, in agreement with the Stretch-Twist-Fold mechanism. Vice
+versa, in presence of a Lorentz feedback on the velocity, we find that the
+inverse cascade of magnetic helicity is mostly local if magnetic and kinetic
+helicities have opposite sign, while it is more nonlocal and more intense if
+they have the same sign, as predicted by the analytical approach. Our
+analytical and numerical results further demonstrate the potential of the
+helical Fourier decomposition to elucidate the entangled dynamics of magnetic
+and kinetic helicities both in fully developed turbulence and in laminar flows.",1609.01781v2
+1994-11-10,Angular Momemtum and Large-Scale Magnetic Field in Textures Seeded Models,"We start by pedagigically reviewing the problem of large scale magnetic
+fields. We explain the acquisition of angular momentum in the general context
+of Dark Matter models and we use this result to derive a dynamical mechanism
+for magnetic field generation. This mechanism does not produce any magnetic
+field for standard CDM, but it does for a large class of other models. We apply
+this mechanism in the context of the texture scenario of large-scale structure
+formation. Resulting constraints on the texture scenario and other models are
+discussed.",9411039v1
+1998-12-29,Genesis of Flux Ropes Observed by Pioneer-Venus Orbiter in the Photoequilibrium Region At Venus,"Genesis of flux ropes observed by Pioneer-Venus Orbiter in the
+photoequilibrium region at Venus is analysed. Stability analysis of the
+large-scale magnetic field pushed deep inside during period of high dynamic
+pressure of solar wind had shown that the top-side boundary of the magnetic
+belt located within the region of photoequilibrium is unstable. The finite
+conductivity of plasma tends to stabilise the instability so that the
+bottom-side part of the magnetic belt is regular. Non-numerous flux ropes which
+were observed above the predicted instability region are likely moving upward
+because of the magnetic buoyancy.",9812461v1
+1999-02-18,Magnetized Accretion Inside the Marginally Stable Orbit around a Black Hole,"Qualitative arguments are presented to demonstrate that the energy density of
+magnetic fields in matter accreting onto a black hole inside the marginally
+stable orbit is automatically comparable to the rest-mass energy density of the
+accretion flow. Several consequences follow: magnetic effects must be
+dynamically significant, but cannot be so strong as to dominate; outward energy
+transport in Alfven waves may alter the effective efficiency of energy
+liberation; and vertical magnetic stresses in this region may contribute to
+""coronal"" activity.",9902267v1
+2000-09-25,Magnetic Fields are not ignorable in the dynamics of disks,"Magnetic fields are considered to be dominant when
+$\epsilon_{B}\geq\epsilon_{K}$, being $\epsilon_{B}=B^{2}/8\pi$ the magnetic
+energy density and $\epsilon_{K}=1/2 \rho\theta^{2}$ the rotation energy
+density, for a conventional moderate B= 1 $\mu$G. They are considered to be
+negligible when $\epsilon_{B}<\epsilon_{K}$ for $B\sim 10 \mu$G. With no
+assumption and no theoretical calculation, we show that magnetic fields cannot
+be ignored in the outer parts of a galaxy like the Milky Way and in the whole
+disk of a dwarf galaxy.",0009391v1
+2005-07-17,Non-leptonic Weak Interaction in Magnetized Quark matter,"We investigated the non-leptonic weak interaction in magnetic field.
+  We discussed an improvement of previous method to analytical work out the
+rate for weak field case.Our result easily goes over to field-free limit.Then
+we calculated the reaction rate in strong magnetic field where the charged
+particles are confined to the lowest Landau level. A strong magnetic field
+strongly suppressed the rate,which will be foreseen to affect viscous dynamics
+in SQM .We also derived a few approximation formulae under given conditions
+that can be conveniently applied.",0507390v1
+2005-12-23,Galactic dynamo and helicity losses through fountain flow,"Nonlinear behaviour of galactic dynamos is studied, allowing for magnetic
+helicity removal by the galactic fountain flow. A suitable advection speed is
+estimated, and a one-dimensional mean-field dynamo model with dynamic
+alpha-effect is explored. It is shown that the galactic fountain flow is
+efficient in removing magnetic helicity from galactic discs. This alleviates
+the constraint on the galactic mean-field dynamo resulting from magnetic
+helicity conservation and thereby allows the mean magnetic field to saturate at
+a strength comparable to equipartition with the turbulent kinetic energy.",0512592v2
+2006-01-30,Magnetized Tori around Kerr Black Holes: Analytic Solutions with a Toroidal Magnetic Field,"The dynamics of accretion discs around galactic and extragalactic black holes
+may be influenced by their magnetic field. In this paper we generalise the
+fully relativistic theory of stationary axisymmetric tori in Kerr metric of
+Abramowicz et al.(1978) by including strong toroidal magnetic field and
+construct analytic solutions for barotropic tori with constant angular
+momentum. This development is particularly important for the general
+relativistic computational magnetohydrodynamics that suffers from the lack of
+exact analytic solutions that are needed to test computer codes.",0601678v3
+2007-03-20,Traveling waves in magnetized Taylor-Couette flow,"We investigate numerically a traveling wave pattern observed in experimental
+magnetized Taylor-Couette flow at low magnetic Reynolds number. By accurately
+modeling viscous and magnetic boundaries in all directions, we reproduce the
+experimentally measured wave patterns and their amplitudes. Contrary to
+previous claims, the waves are shown to be transiently amplified disturbances
+launched by viscous boundary layers rather than globally unstable
+magnetorotational modes.",0703525v2
+1994-08-31,Magnetic von-Neumann lattice for two-dimensional electrons in the magnetic field,"One-particle eigenstates and eigenvalues of two-dimensional electrons in the
+strong magnetic field with short range impurity and impurities, cosine
+potential, boundary potential, and periodic array of short range potentials are
+obtained by magnetic von-Neumann lattice in which Landau level wave functions
+have minimum spatial extensions. We find that there is a dual correspondence
+between cosine potential and lattice kinetic term and that the representation
+based on the von-Neumann lattice is quite useful for solving the system's
+dynamics.",9408098v1
+1997-02-10,Non magnetic molecular Jahn-Teller Mott insulators,"Narrow-band conductors may turn insulating and magnetic as a consequence of
+strong electron-electron correlation. In molecular conductors, the concomitance
+of a strong Jahn-Teller coupling may give rise to the alternative possibility
+of a non-magnetic insulator, with or without a static cooperative Jahn-Teller
+distortion. In the latter case the insulator has Mott-like properties, with an
+interesting interplay between electron-electron repulsion and the Jahn-Teller
+effect, which is dynamical. We study this kind of non-magnetic insulator in a
+very simple $E\otimes e$ Jahn-Teller model and we discuss its general
+properties in a more general context, also in connection with the insulating
+state of K_{4}C_{60} and Rb_{4}C_{60}.",9702079v1
+1997-03-02,On the Self-Consistent Spin-Wave Theory of Two-Dimensional Magnets With Impurities,"The self-consistent spin-wave theory is applied to investigate the
+magnetization distribution around the impurity in isotropic and easy-axis
+two-dimensional ferro- and antiferromagents. The temperature dependences of
+host magnetization disturbance and impurity magnetization are calculated. The
+short-range order in the isotropic case is investigated. Importance of dynamic
+and kinematic interactions of spin waves is demonstrated.",9703010v1
+1997-10-22,Muon spin rotation and relaxation in magnetic materials,"A review of the muon spin rotation and relaxation ($\mu$SR) studies on
+magnetic materials published from July 1993 is presented. It covers the
+investigation of magnetic phase diagrams, of spin dynamics and the analysis of
+the magnetic properties of superconductors. We have chosen to focus on selected
+experimental works in these different topics. In addition, a list of published
+works is provided.",9710235v1
+1998-12-15,Magnetic and Charge Correlations of the 2-dimensional $t-t'-U$ Hubbard model,"Using a spin-rotation invariant six-slave boson representation, we study the
+square lattice Hubbard model with nearest-neighbor hopping $t$ and next-nearest
+neighbor hopping $t'$. We discuss the influence of $t'$ on the charge and
+magnetic properties. In the hole-doped domain, we find that a negative $t'$
+strongly favors itinerant ferromagnetism over any incommensurate phase,
+especially in the strong coupling regime. For positive $t'$ magnetic
+fluctuations are suppressed. A tight connection between frustrated charge
+dynamics and large magnetic fluctuations is pointed out. A clear tendency
+towards striped charge ordering is found in the regime of large positive $t'$.",9812242v1
+1999-05-24,Proton NMR for Measuring Quantum-Level Crossing in the Magnetic Molecular Ring Fe10,"The proton nuclear spin-lattice relaxation rate 1/T1 has been measured as a
+function of temperature and magnetic field (up to 15 T) in the molecular
+magnetic ring Fe10. Striking enhancement of 1/T1 is observed around magnetic
+field values corresponding to a crossing between the ground state and the
+excited states of the molecule. We propose that this is due to a
+cross-relaxation effect between the nuclear Zeeman reservoir and the reservoir
+of the Zeeman levels of the molecule. This effect provides a powerful tool to
+investigate quantum dynamical phenomena at level crossing.",9905346v1
+1999-12-01,Impurity relaxation mechanism for dynamic magnetization reversal in a single domain grain,"The interaction of coherent magnetization rotation with a system of two-level
+impurities is studied. Two different, but not contradictory mechanisms, the
+`slow-relaxing ion' and the `fast-relaxing ion' are utilized to derive a system
+of integro-differential equations for the magnetization. In the case that the
+impurity relaxation rate is much greater than the magnetization precession
+frequency, these equations can be written in the form of the Landau-Lifshitz
+equation with damping. Thus the damping parameter can be directly calculated
+from these microscopic impurity relaxation processes.",9912014v1
+2000-01-21,Theory of Diluted Magnetic Semiconductor Ferromagnetism,"We present a theory of carrier-induced ferromagnetism in diluted magnetic
+semiconductors (III_{1-x} Mn_x V) which allows for arbitrary itinerant-carrier
+spin polarization and dynamic correlations. Both ingredients are essential in
+identifying the system's elementary excitations and describing their
+properties. We find a branch of collective modes, in addition to the spin waves
+and Stoner continuum which occur in metallic ferromagnets, and predict that the
+low-temperature spin stiffness is independent of the strength of the exchange
+coupling between magnetic ions and itinerant carriers. We discuss the
+temperature dependence of the magnetization and the heat capacity.",0001320v2
+2000-06-23,Importance of Correlation Effects on Magnetic Anisotropy in Fe and Ni,"We calculate magnetic anisotropy energy of Fe and Ni by taking into account
+the effects of strong electronic correlations, spin-orbit coupling, and
+non-collinearity of intra-atomic magnetization. The LDA+U method is used and
+its equivalence to dynamical mean-field theory in the static limit is
+emphasized. Both experimental magnitude of MAE and direction of magnetization
+are predicted correctly near U=4 eV for Ni and U=3.5 eV for Fe. Correlations
+modify one-electron spectra which are now in better agreement with experiments.",0006385v1
+2001-07-03,Importance of Correlation Effects on Magnetic Anisotropy in Fe and Ni,"We calculate magnetic anisotropy energy of Fe and Ni by taking into account
+the effects of strong electronic correlations, spin-orbit coupling, and
+non-collinearity of intra--atomic magnetization. The LDA+U method is used and
+its equivalence to dynamical mean--field theory in the static limit is
+emphasized. Both experimental magnitude of MAE and direction of magnetization
+are predicted correctly near U=1.9 eV, J=1.2 eV for Ni and U=1.2 eV, J=0.8 eV
+for Fe. Correlations modify the one--electron spectra which are now in better
+agreement with experiments.",0107063v1
+2001-09-27,Electric field induced by magnetic flux motion in superconductor containing fractal clusters of a normal phase,"The influence of the fractal clusters of a normal phase, which act as pinning
+centers, on the dynamics of magnetic flux in percolative type-II superconductor
+is considered. The voltage-current characteristics of such a superconductor are
+obtained taking into account the effect of fractal properties of cluster
+boundaries on the magnetic flux trapping. It is revealed that the fractality
+reduces the electric field arising from magnetic flux motion and thereby raises
+the critical current of a superconductor.",0109523v1
+2002-03-05,Scaling behaviour of the relaxation in quantum chains,"We consider the nonequilibrium time evolution of the transverse magnetization
+in the critical Ising and $XX$ quantum chains. For some inhomogeneously
+magnetized initial states we derive analytically the transverse magnetization
+profiles and show that they evolve into scaling forms in the long-time limit.
+In particular it is seen that the Ising chain exhibits some similarities with
+the conserved dynamics $XX$ chain. That is, after a transient regime, the total
+residual magnetization in the transverse direction is also conserved in the
+Ising case. A class of general initial states is also considered.",0203078v1
+2002-09-02,Quasiperiodic tilings under magnetic field,"We study the electronic properties of a two-dimensional quasiperiodic tiling,
+the isometric generalized Rauzy tiling, embedded in a magnetic field. Its
+energy spectrum is computed in a tight-binding approach by means of the
+recursion method. Then, we study the quantum dynamics of wave packets and
+discuss the influence of the magnetic field on the diffusion and spectral
+exponents. Finally, we consider a quasiperiodic superconducting wire network
+with the same geometry and we determine the critical temperature as a function
+of the magnetic field.",0209037v1
+2002-09-03,Evidence for weak itinerant long-range magnetic correlations in UGe2,"Positive muon spin relaxation measurements performed on the ferromagnet UGe2
+reveal, in addition to the well known localized 5f-electron density responsible
+for the bulk magnetic properties, the existence of itinerant quasi-static
+magnetic correlations. Their critical dynamics is well described by the
+conventional dipolar Heisenberg model. These correlations involve small
+magnetic moments.",0209054v1
+2002-11-22,Nonlinear microscopic relaxation of uniform magnetization precession,"Dynamic relaxation for nonlinear magnetization excitation is analyzed. For
+direct processes, such as magnon-electron scattering and two-magnon scattering,
+the relaxation rate is determined from the linear case simply by utilizing the
+magnetization oscillation frequency for nonlinear excitation. For an indirect
+process, such as slow-relaxing impurities, the analysis gives an additional
+relaxation term proportional to the excitation level. In all cases the
+effective magnetization damping is increased compared to
+Landau-Lifshitz-Gilbert damping.",0211499v1
+2002-12-16,Characterization of the Energy Structure and Adiabatic Magnetization Process of V15,"The energy structure of the V$_{15}$ is studied using exact diagonalization
+methods, and the adiabatic changes of the magnetization in the system with the
+sweeping field are investigated. We confirm that the Dzyaloshinskii-Moriya
+interaction leads to an energy gap which allows the adiabatic change of the
+magnetization which has been found experimentally by Chiorescu et al., and also
+predict novel dynamics of the magnetization due to this energy level structure.",0212354v1
+2003-05-22,Coherent Spin Oscillations in a Disordered Magnet,"Most materials freeze when cooled to sufficiently low temperature. We find
+that magnetic dipoles randomly distributed in a solid matrix condense into a
+spin liquid with spectral properties on cooling that are the diametric opposite
+of those for conventional glasses. Measurements of the non-linear magnetic
+dynamics in the low temperature liquid reveal the presence of coherent spin
+oscillations composed of hundreds of spins with lifetimes up to ten seconds.
+These excitations can be labeled by frequency, manipulated by the magnetic
+fields from a loop of wire, and permit the encoding of information at multiple
+frequencies simultaneously.",0305541v1
+2003-06-11,Magnetic energy-level diagrams of high-spin (Mn$_{12}$-acetate) and low-spin (V$_{15}$) molecules,"The magnetic energy-level diagrams for models of the Mn12 and V15 molecule
+are calculated using the Lanczos method with full orthogonalization and a
+Chebyshev-polynomial-based projector method. The effect of the
+Dzyaloshinskii-Moriya interaction on the appearance of energy-level repulsions
+and its relevance to the observation of steps in the time-dependent
+magnetization data is studied. We assess the usefulness of simplified models
+for the description of the zero-temperature magnetization dynamics.",0306275v1
+2004-02-10,Effect of uniaxial and biaxial crystal-field potential on magnetic properties of a mixed spin-1/2 and spin-1 Ising model on honeycomb lattice,"Magnetic properties of a mixed spin-1/2 and spin-1 Ising model on honeycomb
+lattice are exactly investigated within the framework of generalized
+star-triangle mapping transformation. The particular attention is focused on
+the effect of uniaxial and biaxial crystal-field anisotropies that basically
+influence the magnetic behaviour of the spin-1 atoms. Our results for the basic
+thermodynamic quantities, as well as the dynamical time-dependent
+autocorrelation function indicate the spin tunneling between the $| +1>$ and $|
+- 1>$ states in the magnetically ordered phase.",0402280v2
+2004-07-20,Field-induced phase transition in the periodic Anderson model,"We investigate the effect of magnetic fields on a Kondo insulator by using
+the periodic Anderson model. The analysis by dynamical mean field theory
+combined with quantum Monte Carlo simulations reveals that the magnetic field
+drives the Kondo insulator to a transverse antiferromagnetic insulator at low
+temperatures. We calculate the staggered spin susceptibility and find its
+divergence signaling the antiferromagnetic instability. Further investigation
+of the spin correlation functions and the magnetization process clarifies how
+the magnetic field suppresses the Kondo singlet formation and induces the
+transverse antiferromagnetic ordering.",0407518v1
+2004-07-28,Magnetic properties of a mixed spin-1/2 and spin-3/2 Ising model with an uniaxial and biaxial crystal-field potential,"Magnetic properties of a mixed spin-1/2 and spin-3/2 Ising model on honeycomb
+lattice are investigated within the framework of an exact star-triangle mapping
+transformation. The particular attention is focused on the effect of uniaxial
+and biaxial crystal-field potentials that basically influence the magnetic
+behaviour of the spin-3/2 atoms. Our results for the basic thermodynamic
+quantities, as well as the dynamical time-dependent autocorrelation function
+indicate the spin tunneling between the $| \pm \frac32>$ and $| \mp \frac12>$
+states in two different magnetically ordered phases OP$_1$ and OP$_2$,
+respectively.",0407726v2
+2004-11-09,Magnetization reversal in spin patterns with complex geometry,"We study field-driven dynamics of spins with antiferromagnetic interaction
+along the links of a complex substrate geometry, which is modeled by graphs of
+a controlled connectivity distribution. The magnetization reversal occurs in
+avalanches of spin flips, which are pinned by the topological constraints of
+the underlying graph. The hysteresis loop and avalanche sizes are analyzed and
+classified in terms of graph's connectivity and clustering. The results are
+relevant for magnets with a hierarchical spatial inhomogeneity and for design
+of nanoscale magnetic devices.",0411223v1
+2005-04-13,Current-induced suppression of superconductivity in tantalum thin films at zero magnetic field,"We report our findings on the mechanism of current-induced suppression of
+superconductivity in amorphous tantalum films as thin as 5nm under zero applied
+magnetic field. Our results indicate that the applied current generates
+magnetic vortices threading the films, and the dynamics of these vortices leads
+to the suppression of the superconductivity. Our findings also imply that the
+motion of current-generated magnetic vortices gives rise to nonlinear transport
+of which characteristics closely resemble those expected in Kosterlitz-Thouless
+theories with strong finite size effects.",0504340v1
+2005-08-30,Effects of spin current on ferromagnets,"When a spin-polarized current flows through a ferromagnet, the local
+magnetization receives a spin torque. Two consequences of this spin torque are
+studied. First, the uniformly magnetized ferromagnet becomes unstable if a
+sufficiently large current is applied. The characteristics of the instability
+include spin wave generation and magnetization chaos. Second, the spin torque
+has profound effects on the structure and dynamics of the magnetic domain wall.
+A detail analysis on the domain wall mass, kinetic energy and wall depinning
+threshold is given.",0508735v1
+2005-08-31,Quantum Spin Effect and Short-Range Order above the Curie Temperature,"Using quantum Heisenberg model calculations with Green's function technique
+generalized for arbitrary spins, we found that for a system of small spins the
+quantum spin effects significantly contribute to the magnetic short-range order
+and strongly affect physical properties of magnets. The spin dynamics
+investigation confirms that these quantum spin effects favor the persistence of
+propagating spin-wave excitations above the Curie temperature. Our
+investigation suggests a reconsideration of prevailing point of view on finite
+temperature magnetism to include quantum effects and the magnetic short-range
+order.",0508781v1
+2005-11-09,Magnetic properties of artificially prepared ordered two-dimensional shunted and unshunted Nb-AlO_x-Nb Josephson Junction Arrays,"In this Chapter, we present our latest experimental results (along with their
+theoretical interpretation) related to some unusual magnetic properties of
+artificially prepared ordered two-dimensional Josephson junction arrays (of
+both shunted and unshunted Nb-AlO_x-Nb tunnel junctions). Namely, we address
+the following topics: (i) influence of non-uniform critical current density
+profile on magnetic field behavior of AC susceptibility, (ii) origin of the
+so-called dynamic reentrance phenomenon, and (iii) manifestation of novel
+geometric quantization effects in temperature behavior of AC magnetic response.",0511218v1
+2006-01-11,Relaxing-Precessional Magnetization Switching,"A new way of magnetization switching employing both the spin-transfer torque
+and the torque by a magnetic field is proposed. The solution of the
+Landau-Lifshitz-Gilbert equation shows that the dynamics of the magnetization
+in the initial stage of the switching is similar to that in the precessional
+switching, while that in the final stage is rather similar to the relaxing
+switching. We call the present method the relaxing-precessional switching. It
+offers a faster and lower-power-consuming way of switching than the relaxing
+switching and a more controllable way than the precessional switching.",0601227v1
+2006-03-10,Stray-field-induced modification of coherent spin dynamics,"Electron spins in an InGaAs semiconductor quantum well are used as a
+magnetometer of magnetic stray-fields from patterned Fe stripes. Using
+time-resolved Faraday rotation, the coherent precession of quantum-well spins
+in the inhomogeneous field below the Fe stripes is measured for varying
+magnetic fields. Comparing with reference stripes made of Au, we find an
+enhancement of the spin precession frequency proportional to the Fe
+magnetization, in line with a decrease of the spin decay time, which is
+attributed to the inhomogeneous magnetic stray-field in the quantum well layer.",0603296v1
+2006-07-03,On-chip detection of ferromagnetic resonance of a single submicron permalloy strip,"We measured ferromagnetic resonance of a single submicron ferromagnetic
+strip, embedded in an on-chip microwave transmission line device. The method
+used is based on detection of the oscillating magnetic flux due to the
+magnetization dynamics, with an inductive pick-up loop. The dependence of the
+resonance frequency on applied static magnetic field agrees very well with the
+Kittel formula, demonstrating that the uniform magnetization precession mode is
+being driven.",0607036v1
+2006-09-05,Out-of-plane spin polarization from in-plane electric and magnetic fields,"We show that the joint effect of spin-orbit and magnetic fields leads to a
+spin polarization perpendicular to the plane of a two-dimensional electron
+system with Rashba spin-orbit coupling and in-plane parallel dc magnetic and
+electric fields, for angle-dependent impurity scattering or nonparabolic energy
+spectrum, while only in-plane polarization persists for simplified models. We
+derive Bloch equations, describing the main features of recent experiments,
+including the magnetic field dependence of static and dynamic responses.",0609078v1
+2006-11-09,Chiral scattering in complex magnets,"General properties of the chiral scattering of polarized neutrons are
+considered for two possible axial vector interactions: Zeeman energy and
+non-alternating Dzyaloshinskii-Moriya interaction. Behavior in magnetic field
+of helical magnetic structures is discussed for $Mn Si$ and magneto-electric
+materials. The dynamical chiral fluctuations in magnetic field are considered
+briefly. The chiral fluctuations in materials with the Dzyaloshinskii-Moriya
+interaction are discussed and an assumption is made that above the transition
+temperature they have to be incommensurate.",0611244v1
+2006-11-27,Microscopic Calculation of Spin Torques and Forces,"Spin torques, that is, effects of conduction electrons on magnetization
+dynamics, are calculated microscopically in the first order in spatial gradient
+and time derivative of magnetization. Special attention is paid to the
+so-called \beta-term and the Gilbert damping, \alpha, in the presence of
+electrons' spin-relaxation processes, which are modeled by quenched magnetic
+impurities. Two types of forces that the electric/spin current exerts on
+magnetization are identified based on a general formula relating the force to
+the torque.",0611669v1
+2006-12-05,Dynamics of Spontaneous Magnetization Reversal in Exchange Biased Heterostructures,"The dependence of thermally induced spontaneous magnetization reversal on
+time-dependent cooling protocols was studied. Slower cooling and longer waiting
+close to the N\`{e}el temperature of the antiferromagnet ($T_N$) enhances the
+magnetization reversal. Cycling the temperature around $T_N$ leads to a thermal
+training effect under which the reversal magnitude increases with each cycle.
+These results suggest that spontaneous magnetization reversal is energetically
+favored, contrary to our present understanding of positive exchange bias.",0612113v1
+1996-08-23,The effect of Silk damping on primordial magnetic fields,"We study the effects of plasma viscosity on the dynamics of primordial
+magnetic fields by simulating magnetohydrodynamics in the early universe by
+appropriate non-linear cascade models. We find numerically that even in the
+presence of large kinetic viscosity, magnetic energy is transferred to large
+length scales. There are indications, however, that the inverse cascade stops
+at a given time which depends on the magnitude of viscosity. For realistic
+viscosities we do not find equipartition between magnetic and kinetic energies.",9608422v1
+2002-03-02,Spin waves in the magnetized plasma of a supernova and its excitation by neutrino fluxes,"The spin effects on electromagnetic waves in a strongly magnetized plasma
+with rare collisions is considered with the help of relativistic kinetic
+equations, which takes into account the electron spin dynamics in the
+selfconsistent electric and magnetic fields. It is shown that for
+electromagnetic waves propagating almost perpendicular to ambient magnetic
+field the spin effects become essential in the vicinity of electron
+gyrofrequency and the corresponding wave dispersion and growth rate of the
+electromagnetic spin waves in the presence of intense quasi monoenergetic
+fluxes of neutrino is determined.",0203020v1
+2005-06-22,Primordial magnetic seed fields from extra dimensions,"Dynamical extra dimensions break the conformal invariance of Maxwell's
+equations in four dimensions. A higher dimensional background with $n$
+contracting extra dimensions and four expanding dimensions is matched to an
+effectively four dimensional standard radiation dominated universe. The
+resulting spectrum for the magnetic field is calculated taking into account
+also the momenta along the extra dimensions. Imposing constraints from
+observations an upper limit on the strength of magnetic seed fields is found.
+Depending on the number of extra dimensions, cosmologically interesting
+magnetic fields can be created.",0506212v1
+2004-10-04,"Magnetic condensation, Abelian dominance, and instability of Savvidy vacuum in Yang-Mills theory","We propose a novel type of color magnetic condensation originating from
+magnetic monopoles so that it provides the mass of off-diagonal gluons in the
+Yang-Mills theory.
+  This dynamical mass generation enables us to explain the infrared Abelian
+dominance and monopole dominance by way of a non-Abelian Stokes theorem, which
+supports the dual superconductivity picture of quark confinement. Moreover, we
+show that the instability of Savvidy vacuum disappears by sufficiently large
+color magnetic condensation.",0410024v1
+2005-10-24,A Stable Magnetic Background in SU(2) QCD,"Motivated by the instability of the Savvidy-Nielsen-Olesen (SNO) vacuum we
+make a systematic search for a stable magnetic background in pure SU(2) QCD. It
+is shown that Wu-Yang monopole-antimonopole pair is unstable under vacuum
+fluctuations. However, it is shown that a pair of axially symmetric
+monopole-antimonopole string configuration is stable, provided the distance
+between the two strings is small enough (less than a critical value). The
+existence of a stable monopole-antimonopole string background strongly supports
+that a magnetic condensation of monopole-antimonopole pairs can indeed generate
+a dynamical symmetry breaking, and thus a desired magnetic confinement of
+color, in QCD.",0510201v1
+2006-03-04,Sharp Spectral Asymptotics for two-dimensional Schrödinger operator with a strong degenerating magnetic field,"I consider two-dimensional Schr\""odinger operator with degenerating magnetic
+field and in the generic situation I derive spectral asymptotics as $h\to +0$
+and $\mu\to +\infty$ where $h$ and $\mu$ are Planck and coupling parameters
+respectively. The remainder estimate is $O(\mu^{-{\frac 1 2}}h^{-1})$ which is
+between $O(\mu^{-1}h^{-1})$ valid as magnetic field non-degenerates and
+$O(h^{-1})$ valid as magnetic field is identically 0. As $\mu$ is close to its
+maximal reasonable value $O(h^{-2})$ the principal part contains correction
+terms associated with short periodic trajectories of the corresponding
+classical dynamics.",0603114v1
+2001-05-01,Rectangular microwave resonators with magnetic anisotropy. Mapping onto pseudo integrable rhombus,"The rectangular microwave resonator filed by a ferrite with uniaxial magnetic
+anisotropy is considered. It is shown that this task can be reduced to an empty
+rhombus resonator with vertex angle defined by external magnetic field provided
+the magnetic anisotropy of the ferrite is strong. Therefore statistics of eigen
+frequencies for TM modes is described by the Brody or semi-Poisson distribution
+with some exceptional cases.",0105001v1
+2001-11-23,Shape transformations in rotating ferrofluid drops,"Floating drops of magnetic fluid can be brought into rotation by applying a
+rotating magnetic field. We report theoretical and experimental results on the
+transition from a spheroid equilibrium shape to non-axissymmetrical three-axes
+ellipsoids at certain values of the external field strength. The transitions
+are continuous for small values of the magnetic susceptibility and show
+hysteresis for larger ones. In the non-axissymmetric shape the rotational
+motion of the drop consists of a vortical flow inside the drop combined with a
+slow rotation of the shape. Nonlinear magnetization laws are crucial to obtain
+quantitative agreement between theory and experiment.",0111054v1
+2001-12-09,On Generation of magnetic field in astrophysical bodies,"In this letter we compute energy transfer rates from velocity field to
+magnetic field in MHD turbulence using field-theoretic method. The striking
+result of our field theoretic calculation is that there is a large energy
+transfer rate from the large-scale velocity field to the large-scale magnetic
+field. We claim that the growth of large-scale magnetic energy is primarily due
+to this transfer. We reached the above conclusion without any linear
+approximation like that in $\alpha$-dynamo.",0112013v1
+2002-12-03,Exact solutions for magnetic annihilation in curvilinear geometry,"New exact solutions of the steady and incompressible 2D MHD equations in
+polar coordinates are presented. The solutions describe the process of
+reconnective magnetic annihilation in a curved current layer. They are
+particularly interesting for modeling magnetic reconnection in solar flares
+caused by the interaction of three photospheric magnetic sources.",0212017v1
+2004-03-22,Relativistic Quasilinear Diffusion in Axisymmetric Magnetic Geometry for Arbitrary-Frequency Electromagnetic Fluctuations,"A relativistic bounce-averaged quasilinear diffusion equation is derived to
+describe stochastic particle transport associated with arbitrary-frequency
+electromagnetic fluctuations in a nonuniform magnetized plasma. Expressions for
+the elements of a relativistic quasilinear diffusion tensor are calculated
+explicitly for magnetically-trapped particle distributions in axisymmetric
+magnetic geometry in terms of gyro-drift-bounce wave-particle resonances. The
+resonances can destroy any one of the three invariants of the unperturbed
+guiding-center Hamiltonian dynamics.",0403105v2
+2004-11-17,From normal state to magnetic storms in terms of fractal dynamics,"We show that distinctive alterations in scaling parameters of Dst index time
+series occur as a strong magnetic storm approaches. These alterations reveal a
+gradual reduction of complexity as the catastrophic event approaches. The
+increase of the susceptibility coupled with the transition from anti-persistent
+to persistent behavior may indicate that the onset of a severe magnetic storm
+is imminent. The preparation of a major magnetic storm could be studied in
+terms of ""Intermittent Criticality"". The analysis also suggests that the
+continuous scale invariance is partially broken into a discrete scale
+invariance symmetry.",0411157v1
+2005-05-26,Low magnetic Prandtl number dynamos with helical forcing,"We present direct numerical simulations of dynamo action in a forced Roberts
+flow. The behavior of the dynamo is followed as the mechanical Reynolds number
+is increased, starting from the laminar case until a turbulent regime is
+reached. The critical magnetic Reynolds for dynamo action is found, and in the
+turbulent flow it is observed to be nearly independent on the magnetic Prandtl
+number in the range from 0.3 to 0.1. Also the dependence of this threshold with
+the amount of mechanical helicity in the flow is studied. For the different
+regimes found, the configuration of the magnetic and velocity fields in the
+saturated steady state are discussed.",0505192v1
+2005-06-29,Dynamic and Stagnating Plasma Flow Leading to Magnetic Flux Tube Collimation,"Highly collimated, plasma-filled magnetic flux tubes are frequently observed
+on galactic, stellar and laboratory scales. We propose that a single, universal
+magnetohydrodynamic pumping process explains why such collimated, plasma-filled
+magnetic flux tubes are ubiquitous. Experimental evidence from carefully
+diagnosed laboratory simulations of astrophysical jets confirms this assertion
+and is reported here. The magnetohydrodynamic process pumps plasma into a
+magnetic flux tube and the stagnation of the resulting flow causes this flux
+tube to become collimated.",0506221v1
+2006-07-28,Suppressing the Rayleigh-Taylor instability with a rotating magnetic field,"The Rayleigh-Taylor instability of a magnetic fluid superimposed on a
+non-magnetic liquid of lower density may be suppressed with the help of a
+spatially homogeneous magnetic field rotating in the plane of the undisturbed
+interface. Starting from the complete set of Navier-Stokes equations for both
+liquids a Floquet analysis is performed which consistently takes into account
+the viscosities of the fluids. Using experimentally relevant values of the
+parameters we suggest to use this stabilization mechanism to provide controlled
+initial conditions for an experimental investigation of the Rayleigh-Taylor
+instability.",0607263v1
+2006-10-19,Dynamic detection of a single bacterium: nonlinear rotation rate shifts of driven magnetic microsphere stages,"We report on a new technique which was used to detect single Escherichia coli
+that is based on the changes in the nonlinear rotation of a magnetic
+microsphere driven by an external magnetic field. The presence of one
+Escherichia Coli bacterium on the surface of a 2.0 micron magnetic microsphere
+caused an easily measurable change in the drag of the system and, therefore, in
+the nonlinear rotation rate. The straight-forward measurement uses standard
+microscopy techniques and the observed average shift in the nonlinear rotation
+rate changed by a factor of ~3.8.",0610144v1
+2004-04-20,Wave function collapses in a single spin magnetic resonance force microscopy,"We study the effects of wave function collapses in the oscillating cantilever
+driven adiabatic reversals (OSCAR) magnetic resonance force microscopy (MRFM)
+technique. The quantum dynamics of the cantilever tip (CT) and the spin is
+analyzed and simulated taking into account the magnetic noise on the spin. The
+deviation of the spin from the direction of the effective magnetic field causes
+a measurable shift of the frequency of the CT oscillations. We show that the
+experimental study of this shift can reveal the information about the average
+time interval between the consecutive collapses of the wave function",0404105v1
+2006-10-20,Three-qubit dynamics of entanglement in magnetic field,"A closed system of the equations for the local Bloch vectors and spin
+correlation functions is obtained by decomplexification of the Liouville-von
+Neumann equation for three magnetic qubits with the exchange interaction, that
+takes place in an arbitrary time-dependent external magnetic field. The
+numerical comparative analysis of entanglement is carried out depending on
+initial conditions and the magnetic field modulation. The present study may be
+useful for analysis of interference experiments and in the field of quantum
+computing.",0610176v1
+2007-07-11,Experimental application of sum rules for electron energy loss magnetic chiral dichroism,"We present a derivation of the orbital and spin sum rules for magnetic
+circular dichroic spectra measured by electron energy loss spectroscopy in a
+transmission electron microscope. These sum rules are obtained from the
+differential cross section calculated for symmetric positions in the
+diffraction pattern. Orbital and spin magnetic moments are expressed explicitly
+in terms of experimental spectra and dynamical diffraction coefficients. We
+estimate the ratio of spin to orbital magnetic moments and discuss first
+experimental results for the Fe L_{2,3} edge.",0707.1585v1
+2007-11-15,Potential for measurement of the tensor magnetic polarizability of the deuteron in storage ring experiments,"General formulas describing deuteron spin dynamics in storage rings with
+allowance for the tensor electric and magnetic polarizabilities are derived. It
+is found that an initially tensor-polarized deuteron beam can acquire a final
+horizontal vector polarization of the order of 1%. This effect allows one to
+measure the tensor magnetic polarizability of the deuteron in storage ring
+experiments. We also confirm an existence of the effect found by Baryshevsky
+and Gurinovich, hep-ph/0506135 and Baryshevsky, hep-ph/0510158; hep-ph/0603191
+that the tensor magnetic polarizability of the deuteron causes the spin
+rotation with two frequencies and experiences beating for polarized deuteron
+beams in storage rings.",0711.2390v2
+2008-05-15,Dynamical Theory of Artificial Optical Magnetism Produced by Rings of Plasmonic Nanoparticles,"We present a detailed analytical theory for the plasmonic nanoring
+configuration first proposed in [A. Alu, A. Salandrino, N. Engheta, Opt. Expr.
+14, 1557 (2006)], which is shown to provide negative magnetic permeability and
+negative index of refraction at infrared and optical frequencies. We show
+analytically how the nanoring configuration may provide superior performance
+when compared to some other solutions for optical negative index materials,
+offering a more 'pure' magnetic response at these high frequencies, which is
+necessary for lowering the effects of radiation losses and absorption.
+Sensitivity to losses and the bandwidth of operation of this magnetic inclusion
+are also investigated in details and compared with other available setups.",0805.2329v1
+2008-08-27,"Coherent control of magnetization precession in ferromagnetic semiconductor (Ga,Mn)As","We report single-color, time resolved magneto-optical measurements in
+ferromagnetic semiconductor (Ga,Mn)As. We demonstrate coherent optical control
+of the magnetization precession by applying two successive ultrashort laser
+pulses. The magnetic field and temperature dependent experiments reveal the
+collective Mn-moment nature of the oscillatory part of the time-dependent Kerr
+rotation, as well as contributions to the magneto-optical signal that are not
+connected with the magnetization dynamics.",0808.3738v2
+2008-09-16,Stochastic dynamics of magnetization in a ferromagnetic nanoparticle out of equilibrium,"We consider a small metallic particle (quantum dot) where ferromagnetism
+arises as a consequence of Stoner instability. When the particle is connected
+to electrodes, exchange of electrons between the particle and the electrodes
+leads to a temperature- and bias-driven Brownian motion of the direction of the
+particle magnetization. Under certain conditions this Brownian motion is
+described by the stochastic Landau-Lifshitz-Gilbert equation. As an example of
+its application, we calculate the frequency-dependent magnetic susceptibility
+of the particle in a constant external magnetic field, which is relevant for
+ferromagnetic resonance measurements.",0809.2611v1
+2008-10-23,Magnetic moment manipulation by a Josephson current,"We consider a Josephson junction where the weak-link is formed by a
+non-centrosymmetric ferromagnet. In such a junction, the superconducting
+current acts as a direct driving force on the magnetic moment. We show that the
+a.c. Josephson effect generates a magnetic precession providing then a feedback
+to the current. Magnetic dynamics result in several anomalies of current-phase
+relations (second harmonic, dissipative current) which are strongly enhanced
+near the ferromagnetic resonance frequency.",0810.4286v3
+2008-12-10,Magnetic Bianchi I Universe in Loop Quantum Cosmology,"We examine the dynamical consequences of homogeneous cosmological magnetic
+fields in the framework of loop quantum cosmology. We show that a big-bounce
+occurs in a collapsing magnetized Bianchi I universe, thus extending the known
+cases of singularity-avoidance. Previous work has shown that perfect fluid
+Bianchi I universes in loop quantum cosmology avoid the singularity via a
+bounce. The fluid has zero anisotropic stress, and the shear anisotropy in this
+case is conserved through the bounce. By contrast, the magnetic field has
+nonzero anisotropic stress, and shear anisotropy is not conserved through the
+bounce. After the bounce, the universe enters a classical phase. The addition
+of a dust fluid does not change these results qualitatively.",0812.1889v1
+2009-02-16,Control of Transport-barrier relaxations by Resonant Magnetic Perturbations,"Transport-barrier relaxation oscillations in the presence of resonant
+magnetic perturbations are investigated using three-dimensional global fluid
+turbulence simulations from first principles at the edge of a tokamak. It is
+shown that resonant magnetic perturbations have a stabilizing effect on these
+relaxation oscillations and that this effect is due mainly to a modification of
+the pressure profile linked to the presence of both residual residual magnetic
+island chains and a stochastic layer.",0902.2710v1
+2009-04-11,Planetary dynamos,"The theory of planetary dynamos and its applications to observed phenomena of
+planetary magnetism are outlined. It is generally accepted that convection
+flows driven by thermal or compositional buoyancy are the most likely source
+for the sustenance of global planetary magnetic fields. While the existence of
+dynamos in electrically conducting fluid planetary cores provides constraints
+on properties of the latter, the lack of knowledge about time dependences of
+the magnetic fields and about their toroidal components together with the
+restricted parameter regions accessible to theory have prevented so far a full
+understanding of the phenomena of planetary magnetism.",0904.1795v1
+2009-06-02,Magnetic reversals in a simple model of MHD,"We study a simple magnetohydrodynamical approach in which hydrodynamics and
+MHD turbulence are coupled in a shell model, with given dynamo constrains in
+the large scales. We consider the case of a low Prandtl number fluid for which
+the inertial range of the velocity field is much wider than that of the
+magnetic field. Random reversals of the magnetic field are observed and it
+shown that the magnetic field has a non trivial evolution linked to the nature
+of the hydrodynamics turbulence.",0906.0427v1
+2009-07-08,Estimate of the magnetic field strength in heavy-ion collisions,"Magnetic fields created in the noncentral heavy-ion collision are studied
+within a microscopic transport model, namely the Ultrarelativistic Quantum
+Molecular Dynamics model (UrQMD). Simulations were carried out for different
+impact parameters within the SPS energy range ($E_{lab} = 10 - 158 A$ GeV) and
+for highest energies accessible for RHIC. We show that the magnetic field
+emerging in heavy-ion collisions has the magnitude of the order of $eB_y \sim
+10^{-1} m_\pi^2$ for the SPS energy range and $eB_y \sim m_\pi^2$ for the RHIC
+energies. The estimated value of the magnetic field strength for the LHC energy
+amounts to $eB_y \sim 15 m_\pi^2$.",0907.1396v1
+2009-07-15,Quantum Melting of Spin Ice: Emergent Cooperative Quadrupole and Chirality,"A quantum melting of the spin ice is proposed for pyrochlore-lattice magnets
+Pr$_2TM_2$O$_7$ ($TM=$Ir, Zr, and Sn). The quantum superexchange Hamiltonian
+having a nontrivial magnetic anisotropy is derived in the basis of atomic
+non-Kramers magnetic doublets. The ground states exhibit a cooperative
+ferroquadrupole and pseudospin chirality, forming a magnetic analog of smectic
+liquid crystals. Our theory accounts for dynamic spin-ice behaviors
+experimentally observed in Pr$_2TM_2$O$_7$.",0907.2536v3
+2009-12-27,Electron structure of the Falicov-Kimball model with a magnetic field,"The two-dimensional Falicov-Kimball model in the presence of a perpendicular
+magnetic field is investigated by the dynamical mean-field theory. Within the
+model the interplay between electron correlations and the fine electron
+structure due to the magnetic field is essentially emerged. Without electron
+correlations the magnetic field induces the electron structure to the so-called
+Hofstadter butterfly. It is found that when electron correlations drives the
+metal-insulator transition, they simultaneously smear out the fine structure of
+the Hofstadter butterfly. In a long-range ordered phase, the electron
+correlation induced gap preserves the fine structure, but it separates the
+Hofstadter butterfly into two wings.",0912.5082v1
+2010-01-04,Evolutions of Magnetized and Rotating Neutron Stars,"We study the evolution of magnetized and rigidly rotating neutron stars
+within a fully general relativistic implementation of ideal
+magnetohydrodynamics with no assumed symmetries in three spatial dimensions.
+The stars are modeled as rotating, magnetized polytropic stars and we examine
+diverse scenarios to study their dynamics and stability properties. In
+particular we concentrate on the stability of the stars and possible critical
+behavior. In addition to their intrinsic physical significance, we use these
+evolutions as further tests of our implementation which incorporates new
+developments to handle magnetized systems.",1001.0575v2
+2010-01-15,On the Sensitivity of the H$α$ Scattering Polarization to Chromospheric Magnetism,"A particularly interesting line for exploring the physical conditions of the
+quiet solar chromosphere is H$\alpha$, but its intensity profile is
+magnetically insensitive and the small circular polarization signatures
+produced by the longitudinal Zeeman effect come mainly from the underlying
+photosphere. Here we show that the Hanle effect in H$\alpha$ provides
+quantitative information on the magnetism of the quiet chromosphere. To this
+end, we calculate the response function of the emergent scattering polarization
+to perturbations in the magnetic field.",1001.2720v1
+2010-02-12,Spectropolarimetric investigations of the magnetization of the quiet Sun chromosphere,"This paper reviews some recent advances in the development and application of
+polarized radiation diagnostics to infer the mean magnetization of the quiet
+solar atmosphere, from the near equilibrium photosphere to the highly
+non-equilibrium upper chromosphere. In particular, I show that interpretations
+of the scattering polarization observed in some spectral lines suggest that
+while the magnetization of the photosphere and upper chromosphere is very
+significant, the lower chromosphere seems to be weakly magnetized.",1002.2615v1
+2010-05-14,Local helioseismology and the active Sun,"The goal of local helioseismology is to elicit three-dimensional information
+about the sub-surface (or far-side) structure and dynamics of the Sun from
+observations of the helioseismic wave field at the surface. The physical
+quantities of interest include flows, sound-speed deviations and magnetic
+fields. However, strong surface magnetic fields induce large perturbations to
+the waves making inversions difficult to interpret. The purpose of this paper
+is to outline the methods of analysis used in local helioseismology, review
+discoveries associated with the magnetic Sun made using local helioseismology
+from the past three years, and highlight the efforts towards imaging the
+interior in the presence of strong magnetic fields.",1005.2526v1
+2010-05-17,Splitting of the Landau levels by magnetic perturbations and Anderson transition in 2D-random magnetic media,"In this note we consider a Landau Hamiltonian perturbed by a random magnetic
+potential of Anderson type. For a given number of bands, we prove the existence
+of both strongly localized states at the edges of the spectrum and dynamical
+delocalization near the center of the bands in the sense that wave packets
+travel at least at a given minimum speed. We provide explicit examples of
+magnetic perturbations that split the Landau levels into full intervals of
+spectrum.",1005.2789v2
+2010-05-25,Dynamics of Bianchi I Universe with Magnetized Anisotropic Dark Energy,"We study Bianchi type $I$ cosmological model in the presence of magnetized
+anisotropic dark energy. The energy-momentum tensor consists of anisotropic
+fluid with anisotropic EoS $p=\omega{\rho}$ and a uniform magnetic field of
+energy density $\rho_B$. We obtain exact solutions to the field equations using
+the condition that expansion is proportional to the shear scalar. The physical
+behavior of the model is discussed with and without magnetic field. We conclude
+that universe model as well as anisotropic fluid do not approach isotropy
+through the evolution of the universe.",1005.4480v1
+2010-08-06,Spin Resonance and dc Current Generation in a Quantum Wire,"We show that in a quantum wire the spin-orbit interaction leads to a narrow
+spin resonance at low temperatures, even in the absence of an external magnetic
+field. A relatively weak dc magnetic field of a definite direction strongly
+increases the resonance absorption. Linearly polarized resonance radiation
+produces dynamic magnetization as well as electric and spin currents. The
+effect strongly depends on the external magnetic field.",1008.1225v1
+2010-09-24,Relaxation properties in classical diamagnetism,"In the present paper the problem of the relaxation of magnetization to
+equilibrium (i.e., with no magnetization) is investigated numerically for a
+variant of the well-known model introduced by Bohr to study the diamagnetism of
+electrons in metals. Such a model is mathematically equivalent to a billiard
+with obstacles in a magnetic field. We show that it is not guaranteed that
+equilibrium is attained within the typical time scales of microscopic dynamics.
+Indeed, considering an out of equilibrium state produced by an adiabatic
+switching on of a magnetic field, we show that, depending on the values of the
+parameters, one has a relaxation either to equilibrium or to a diamagnetic
+(presumably metastable) state. The analogy with the relaxation properties in
+the FPU problem is also pointed out.",1009.4861v1
+2010-10-28,Magnetic field correlations in a random flow with strong steady shear,"We analyze magnetic kinematic dynamo in a conducting fluid where the
+stationary shear flow is accompanied by relatively weak random velocity
+fluctuations. The diffusionless and diffusion regimes are described. The growth
+rates of the magnetic field moments are related to the statistical
+characteristics of the flow describing divergence of the Lagrangian
+trajectories. The magnetic field correlation functions are examined, we
+establish their growth rates and scaling behavior. General assertions are
+illustrated by explicit solution of the model where the velocity field is
+short-correlated in time.",1010.5904v1
+2010-11-17,Magnetotransport and spin dynamics in an electron gas formed at oxide interfaces,"We investigate the spin-dependent transport properties of a two-dimensional
+electron gas formed at oxides' interface in the presence of a magnetic field.
+We consider several scenarios for the oxides' properties, including oxides with
+co-linear or spiral magnetic and ferroelectric order. For spiral multiferroic
+oxides, the magnetoelectric coupling and the topology of the localized magnetic
+moments introduce additional, electric field controlled spin-orbit coupling
+that affects the magneto-oscillation of the current. An interplay of this
+spin-orbit coupling, the exchange field, and of the applied magnetic field
+results in a quantum, gate-controlled spin and charge Hall conductance.",1011.3924v1
+2010-12-25,Dark Soliton Interaction of Spinor Bose-Einstein Condensates in an Optical Lattice,"We study the magnetic soliton dynamics of spinor Bose-Einstein condensates in
+an optical lattice which results in an effective Hamiltonian of anisotropic
+pseudospin chain. An equation of nonlinear Schr\""odinger type is derived and
+exact magnetic soliton solutions are obtained analytically by means of Hirota
+method. Our results show that the critical external field is needed for
+creating the magnetic soliton in spinor Bose-Einstein condensates. The soliton
+size, velocity and shape frequency can be controlled in practical experiment by
+adjusting the magnetic field. Moreover, the elastic collision of two solitons
+is investigated in detail.",1012.5469v1
+2011-02-01,Fast vacuum decay into particle pairs in strong electric and magnetic fields,"We discuss fermion pair productions in strong electric and magnetic fields.
+We point out that, in the case of massless fermions, the vacuum persistency
+probability per unit time and volume is zero in the strong electric and
+magnetic fields, while it is finite when the magnetic field is absent. The
+contribution from the lowest Landau level (LLL) dominates this phenomenon. We
+also discuss dynamics of the vacuum decay, using an effective theory of the LLL
+projection, taking into account the back reaction.",1102.0050v1
+2011-05-24,Tunable anisotropic magnetism in trapped two-component Bose gases,"We theoretically address magnetic ordering at zero and finite temperature in
+both homogeneous and trapped Bose-Bose mixtures in optical lattices. By using
+Bosonic Dynamical Mean-Field Theory, we obtain the phase diagram of the
+homogeneous two-component Bose-Hubbard model in a three-dimensional (3D) cubic
+lattice, which features competing magnetic order of XY-ferromagnetic and
+anti-ferromagnetic type in addition to the Mott and superfluid states. We show
+that these magnetic phases persist also in the presence of a harmonic trap.",1105.4886v1
+2011-07-25,Magnetic control of particle-injection in plasma based accelerators,"The use of an external transverse magnetic field to trigger and to control
+electron self-injection in laser- and particle-beam driven wakefield
+accelerators is examined analytically and through full-scale particle-in-cell
+simulations. A magnetic field can relax the injection threshold and can be used
+to control main output beam features such as charge, energy, and transverse
+dynamics in the ion channel associated with the plasma blowout. It is shown
+that this mechanism could be studied using state-of-the-art magnetic fields in
+next generation plasma accelerator experiments.",1107.4912v1
+2011-11-14,Subdiffusive transport in intergranular lanes on the Sun. The Leighton model revisited,"In this paper we consider a random motion of magnetic bright points (MBP)
+associated with magnetic fields at the solar photosphere. The MBP transport in
+the short time range [0-20 minutes] has a subdiffusive character as the
+magnetic flux tends to accumulate at sinks of the flow field. Such a behavior
+can be rigorously described in the framework of a continuous time random walk
+leading to the fractional Fokker-Planck dynamics. This formalism, applied for
+the analysis of the solar subdiffusion of magnetic fields, generalizes the
+Leighton's model.",1111.3234v1
+2012-02-16,Stability of nonstationary states of spin-2 Bose-Einstein condensates,"The dynamical stability of nonstationary states of homogeneous spin-2
+rubidium Bose-Einstein condensates is studied. The states considered are such
+that the spin vector remains parallel to the magnetic field throughout the time
+evolution, making it possible to study the stability analytically. These states
+are shown to be stable in the absence of an external magnetic field, but they
+become unstable when a finite magnetic field is introduced. It is found that
+the growth rate and wavelength of the instabilities can be controlled by tuning
+the strength of the magnetic field and the size of the condensate.",1202.3658v2
+2012-03-03,Motion of a deformable drop of magnetic fluid on a solid surface in a rotating magnetic field,"The behavior of a magnetic fluid drop lying on a solid horizontal surface and
+surrounded by a nonmagnetic liquid under the action of a uniform magnetic field
+which is rotating in a vertical plane with low frequency (of the order of 1 Hz)
+has been investigated experimentally. Shape deformation and translatory motion
+of the drop were observed and studied. The drop translation velocity for
+different field amplitudes and field frequencies has been measured.",1203.0680v1
+2012-03-05,Thermo-mechanical sensitivity calibration of nanotorsional magnetometers,"We report on the fabrication of sensitive nanotorsional resonators, which can
+be utilized as magnetometers for investigating the magnetization dynamics in
+small magnetic elements. The thermo-mechanical noise is calibrated with the
+resonator displacement in order to determine the ultimate mechanical torque
+sensitivity of the magnetometer.",1203.0998v1
+2012-05-02,Piezoelectric control of the magnetic anisotropy via interface strain coupling in a composite multiferroic structure,"We investigate theoretically the magnetic dynamics in a
+ferroelectric/ferromagnetic heterostructure coupled via strain-mediated
+magnetoelectric interaction. We predict an electric field-induced magnetic
+switching in the plane perpendicular to the magneto-crystalline easy axis, and
+trace this effect back to the piezoelectric control of the magnetoelastic
+coupling. We also investigate the magnetic remanence and the electric
+coercivity.",1205.0391v1
+2012-11-27,Solar magneto-convection,"An overview is given about recent developments and results of comprehensive
+simulations of magneto-convective processes in the near-surface layers and
+photosphere of the Sun. Simulations now cover a wide range of phenomena, from
+whole active regions, over individual sunspots and pores, magnetic flux
+concentrations and vortices in intergranular lanes, down to the intricate
+mixed-polarity structure of the magnetic field generated by small-scale dynamo
+action. The simulations in concert with high-resolution observations have
+provided breakthroughs in our understanding of the structure and dynamics of
+the magnetic fields in the solar photosphere.",1211.6253v1
+2012-12-03,Magnetic resonance spectroscopy and characterization of magnetic phases for spinor Bose-Einstein condensates,"The response of spinor Bose-Einstein condensates to dynamical modulation of
+magnetic fields is discussed with linear response theory. As an experimentally
+measurable quantity, the energy absorption rate (EAR) is considered, and the
+response function is found to access quadratic spin correlations which come
+from the perturbation of the quadratic Zeeman term. By applying our formalism
+to spin-1 condensates, we demonstrate that the EAR spectrum as a function of
+the modulation frequency is able to characterize the different magnetically
+ordered phases.",1212.0482v2
+2012-12-10,Magnetic properties of the neutron in a uniform background field,"We present calculations of the magnetic moment and magnetic polarisability of
+the neutron from the background field method. The calculations are performed on
+$32^3\times64$ dynamical lattices generated by the PACS-CS collaboration and
+made available via the ILDG. We consider uniform fields quantised by the
+periodic spatial volume. We explore different approaches for improving the
+quality of the fits used in the results. Also included are initial results for
+the magnetic moment of the lowest lying negative parity nucleon states.",1212.1963v1
+2012-12-20,Low-Temperature Magnetization Dynamics of Magnetic Molecular Solids in a Swept Field,"The swept-field experiments on magnetic molecular solids such as \Fe8 are
+studied using Monte Carlo simulations. A kinetic equation is developed to
+understand the phenomenon. It is found that the simulations provide a
+quantitatively accurate account of the experiments. The kinetic equation
+provides a similarly accurate account except at very low sweep velocities,
+where it fails modestly. This failure is due to the neglect of short-range
+correlations between the dipolar magnetic fields seen by the molecular spins.
+Both the simulations and the kinetic equation provide a good understanding of
+the distribution of these dipolar fields.",1212.5292v2
+2013-02-04,Beam dynamics performances and applications of a low-energy electron-beam magnetic bunch compressor,"Many front-end applications of electron linear accelerators rely on the
+production of temporally-compressed bunches. The shortening of electron bunches
+is often realized with magnetic bunch compressors located in high-energy
+sections of accelerators. Magnetic compression is subject to collective effects
+including space charge and self interaction via coherent synchrotron radiation.
+In this paper we explore the application of magnetic compression to low-energy
+($\sim 40$ MeV), high-charge (nC) electron bunches with low normalized
+transverse emittances ($< 5$ $\mu$m).",1302.0726v1
+2013-02-06,Quantum dynamics of vortices in mesoscopic magnetic disks,"Model of quantum depinning of magnetic vortex cores from line defects in a
+disk geometry and under the application of an in-plane magnetic field has been
+developed within the framework of the Caldeira-Leggett theory. The
+corresponding instanton solutions are computed for several values of the
+magnetic field. Expressions for the crossover temperature Tc and for the
+depinning rate \Gamma(T) are obtained. Fitting of the theory parameters to
+experimental data is also presented.",1302.1406v1
+2013-05-08,On the existence of three closed magnetic geodesics for subcritical energies,"We consider exact magnetic flows on closed orientable surfaces. We show that
+for almost every energy $\kappa$ below Ma\~n\'e's critical value of the
+universal covering there are always at least three distinct closed magnetic
+geodesics with energy $\kappa$. If in addition the energy level is assumed to
+be non-degenerate we prove existence of infinitely many closed magnetic
+geodesics.",1305.1871v1
+2013-07-29,Theoretical Study of Spin-Torque Oscillator with Perpendicularly Magnetized Free Layer,"The magnetization dynamics of spin torque oscillator (STO) consisting of a
+perpendicularly magnetized free layer and an in-plane magnetized pinned layer
+was studied by solving the Landau-Lifshitz-Gilbert equation. We derived the
+analytical formula of the relation between the current and the oscillation
+frequency of the STO by analyzing the energy balance between the work done by
+the spin torque and the energy dissipation due to the damping. We also found
+that the field-like torque breaks the energy balance, and change the
+oscillation frequency.",1307.7427v1
+2013-08-06,Broadband ferromagnetic resonance characterization of GaMnAs thin films,"The precessional magnetization dynamics of GaMnAs thin films are
+characterized by broadband network analyzer ferromagnetic resonance (FMR) in a
+coplanar geometry at cryogenic temperatures. The FMR frequencies are
+characterized as function of in-plane field angle and field amplitude. Using an
+extended Kittel model of the FMR dispersion the magnetic film parameters such
+as saturation magnetization and anisotropies are derived. The modification of
+the FMR behavior and of the magnetic parameters of the thin film upon annealing
+is analyzed.",1308.1232v1
+2013-08-09,A Scaling Theory for ac Magnetic Response in Kagome Ice,"A theory for frequency-dependent magnetic susceptibility \chi(\omega) is
+developed for thermally activated magnetic monopoles in kagome ice. By mapping
+this system to a two-dimensional (2D) Coulomb gas and then to a sine-Gordon
+model, we have shown that the susceptibility has a scaling form
+\chi(\omega)/\chi(0)={\cal F}(\omega/\omega_1), where the characteristic
+\omega_1 is related to a charge correlation length between diffusively moving
+monopoles, and to the sine-Gordon principal breather. The dynamical scaling is
+universal among superfluid and superconducting films, and 2D XY magnets above
+Kosterlitz-Thouless transitions.",1308.2049v1
+2013-11-11,Visualization of Rabi oscillations in a magnetic resonance,"A visualization scheme for dynamics of a qudit polarization vector in a
+time-dependent magnetic field is presented by solving equations for a density
+matrix in Hermitian basis. This is realized by means of mapping solution for
+the polarization vector on the three-dimensional spherical curve (vector
+hodograph).
+  The obtained results obviously display the interference of precessional and
+nutational effects on the polarization vector in a magnetic resonance. The
+study can find the practical applications in a magnetic resonance and 3D
+visualization of computational data.",1311.2537v2
+2013-11-12,Electron and Ion Heating during Magnetic Reconnection in Weakly Collisional Plasmas,"Gyrokinetic simulations of magnetic reconnection are presented to investigate
+plasma heating for strongly magnetized, weakly collisional plasmas. For a low
+plasma beta case, parallel and perpendicular phase mixing strongly enhance
+energy dissipation yielding electron heating. Heating occurs for a long time
+period after a dynamical process of magnetic reconnection ended. For a higher
+beta case, the ratio of ion to electron dissipation rate increases, suggesting
+that ion heating (via phase-mixing) may become an important dissipation channel
+in high beta plasmas.",1311.2728v2
+2013-12-05,The Study on the Effects of Chromaticity and Magnetic Field Tracking Errors at CSNS/RCS,"The Rapid Cycling Synchrotron (RCS) is a key component of the China
+Spallation Neutron Source (CSNS). For this type of high intensity proton
+synchrotron, the chromaticity, space charge effects and magnetic field tracking
+errors between the quadrupoles and the dipoles can induce beta function
+distortion and tune shift, and induce resonances. In this paper the combined
+effects of chromaticity, magnetic field tracking errors and space charge on
+beam dynamics at CSNS/RCS are studied systemically. 3-D simulations with
+different magnetic field tracking errors are performed by using the code ORBIT,
+and the simulation results are compared with the case without tracking errors.",1312.1475v1
+2013-12-09,Magnetic Fields in Stars: Origin and Impact,"Various types of magnetic fields occur in stars: small scale fields, large
+scale fields, and internal toroidal fields. While the latter may be ubiquitous
+in stars due to differential rotation, small scale fields (spots) may be
+associated with envelop convection in all low and high mass stars. The stable
+large scale fields found in only about 10 per cent of intermediate mass and
+massive stars may be understood as a consequence of dynamical binary
+interaction, e.g., the merging of two stars in a binary. We relate these ideas
+to magnetic fields in white dwarfs and neutron stars, and to their role in
+core-collapse and thermonuclear supernova explosions.",1312.2373v1
+2013-12-16,SQUID Metamaterials: Tuneability and Multistability,"An overview of several dynamic properties of SQUID metamaterials is given in
+the presence of both constant and alternating magnetic field. The total current
+as a function of the driving frequency exhibits hysteretic effects which are
+favored by low levels of disorder. Multistability in the current states leads
+to multiple magnetic responses with different value of magnetic permeability.
+SQUID metamaterials exhibit wide-band tuneability which is periodic with the
+applied constant magnetic field; the numerical calculations reproduce fairly
+well recent experimental results. Current work also reveals the possibility for
+wave transmission through nonlinear bands, which is briefly discussed.",1312.4320v1
+2013-12-18,Electromagnetic way of accelerating the magnetic dipoles,"The article considers an opportunity of electrodynamics accelerating the
+magnetic dipoles at initial velocity six hundred meters per second, which is
+the magnetic dipole gain after pre-gas-dynamic acceleration to finite velocity
+eight and half kilometers per second. The acceleration length is more than two
+kilometers. When selecting the drag coefficient and the lift coefficient equal
+to one hundredth, the dipoles rise to height ten kilometers during a period of
+time fourteen seconds, thus reaching the vertical velocity one kilometer per
+second and reducing the forward velocity till seven and a half kilometer per
+second. The magnetic dipoles reach flight range twelve thousand three hundred
+kilometers.",1312.5046v1
+2014-04-09,Current-induced spin torque resonance of magnetic insulators,"We formulate a theory of the AC spin Hall magnetoresistance (SMR) in a
+bilayer system consisting of a magnetic insulator such as yttrium iron garnet
+(YIG) and a heavy metal such as platinum (Pt). We derive expressions for the DC
+voltage generation based on the drift-diffusion spin model and quantum
+mechanical boundary condition at the interface that reveal a spin torque
+ferromagnetic resonance (ST-FMR). We predict that ST-FMR experiments will
+reveal valuable information on the current-induced magnetization dynamics of
+magnetic insulators and AC spin Hall effect.",1404.2360v2
+2014-04-17,Self Diffusion of Yukawa system in presence of external magnetic field,"Diffusion of dust particles is one of the most significant transport
+processes of strongly coupled dusty plasma that reflect the nature of inter
+particle interaction and characterize thermodynamics of the system. In this
+paper the effect of magnetic field on diffusion of dust particles in strongly
+coupled dusty plasma is investigated by using molecular dynamics simulations.
+Self- diffusion coefficients of Yukawa systems are obtained for a wide range of
+plasma parameters and magnetic field strength using Green- Kubo expression
+which is based on integrated velocity autocorrelation function (VACF). It is
+assumed that dust particles interact with each other by modified Yukawa (i.e.
+screened Coulomb) potential. The study gives interesting results of dust
+particle diffusion in magnetized plasma.",1404.4462v1
+2014-10-13,Vortex gyration mediated by spin waves driven by an out-of-plane oscillating magnetic field,"In this letter we address the vortex core dynamics involved in gyration
+excitation and damping change by out-of-plane oscillating magnetic fields. When
+the vortex core is at rest under the effect of in-plane bias magnetic fields,
+the spin waves excited by the perpendicular magnetic field can induce obvious
+vortex gyration. When simultaneously excite spin waves and vortex gyrotropic
+motion, the gyration damping changes. Analysis of the system energy allows us
+to explain the origin of the spin-wave-mediated vortex gyration.",1410.3230v1
+2014-11-03,Optimum reduction of the dynamo threshold by a ferromagnetic layer located in the flow,"We consider a fluid dynamo model generated by the flow on both sides of a
+moving layer. The magnetic permeability of the layer is larger than that of the
+flow. We show that there exists an optimum value of magnetic permeability for
+which the critical magnetic Reynolds number for dynamo onset is smaller than
+for a nonmagnetic material and also smaller than for a layer of infinite
+magnetic permeability. We present a mechanism that provides an explanation for
+recent experimental results. A similar effect occurs when the electrical
+conductivity of the layer is large.",1411.0449v1
+2015-01-13,Spin crossover in ferropericlase from first-principles molecular dynamics,"Ferropericlase, (Mg,Fe)O, is the second-most abundant mineral of the Earth's
+lower mantle. With increasing pressure, the Fe ions in the material begin to
+collapse from a magnetic to non-magnetic spin state. We present a
+finite-temperature first-principles phase diagram of this spin crossover,
+finding a broad pressure range with coexisting magnetic and non-magnetic ions
+due to favorable enthalpy of mixing of the two. Furthermore, we find the
+electrical conductivity of the mineral to reach semi-metallic values inside the
+Earth.",1501.02902v1
+2015-03-30,Generation of magnetic fields by large-scale vortices in rotating convection,"We propose a new self-consistent dynamo mechanism for the generation of
+large-scale magnetic fields in natural objects. Recent computational studies
+have described the formation of large-scale vortices (LSVs) in rotating
+turbulent convection. Here we demonstrate that for magnetic Reynolds numbers
+below the threshold for small-scale dynamo action, such turbulent flows can
+sustain large-scale magnetic fields --- i.e. fields with a significant
+component on the scale of the system.",1503.08599v1
+2015-10-18,Two-Fluid Theory for Spin Superfluidity in Magnetic Insulators,"We investigate coupled spin and heat transport in easy-plane magnetic
+insulators. These materials display a continuous phase transition between
+normal and condensate states that is controlled by an external magnetic field.
+Using hydrodynamic equations supplemented by Gross-Pitaevski phenomenology and
+magnetoelectric circuit theory, we derive a two-fluid model to describe the
+dynamics of thermal and condensed magnons, and the appropriate boundary
+conditions in a hybrid normal-metal|magnetic-insulator|normal-metal
+heterostructure. We discuss how the emergent spin superfluidity can be
+experimentally probed via a spin Seebeck effect measurement.",1510.05316v2
+2016-01-06,Wave-induced motion of magnetic spheres,"We report an experimental study of the motion of magnetized beads driven by a
+travelling wave magnetic field. For sufficiently large wave speed, we report
+the existence of a backward motion, in which the sphere can move in the
+direction opposite to the driving wave. We show that the transition to this new
+state is strongly subcritical and can lead to chaotic motion of the bead. For
+some parameters, this counter-propagation of the sphere can be one order of
+magnitude faster than the driving wave speed. These results are understood in
+the framework of a model based on the interplay among solid friction, air
+resistance and magnetic torque.",1601.01111v1
+2016-03-28,Three axis vector atomic magnetometer utilizing polarimetric technique,"The three axis magnetic field measurement based on the interaction of a
+single elliptically polarized light beam with an atomic system is described.
+The magnetic field direction dependent atomic responses are extracted by the
+polarimetric detection in combination with laser frequency modulation and
+magnetic field modulation techniques. The magnetometer offers additional
+critical requirements like compact size and large dynamic range for space
+application. Further, the three axis magnetic field is measured using only
+reflected signal from the polarimeter, thus can be easily expanded to make
+spatial array of detectors or / and high sensitivity field gradient measurement
+as required for biomedical application.",1603.08303v1
+2016-04-12,Magnetization distribution and domain wall dynamics in nanotube with surface anisotropy,"The period of magnetization oscillations that occur near the surface of a
+nanotube or nanowire under the influence of surface magnetic anisotropy is
+determined by means of numerical simulation as a function of nanowire geometry
+and material parameters. The hopping mode is observed for stationary movement
+of a head-to-head domain wall along nanowire axis in applied magnetic field.
+The average speed of the domain wall in the hopping mode is found to be several
+times less than the stationary velocity of the wall in the absence of surface
+anisotropy.",1604.03523v1
+2016-04-15,Electron magnetic resonance in magnetic nanoparticles: dependence on the particle size and applicability of the modified giant spin model,"Superparamagnetic nanoparticles containing hundreds and thousands of coupled
+electron spins are on the boundary between classical and quantum behavior, and
+demonstrate features which are typical for paramagnetic spins and absent in
+macroscopic ferromagnetic systems. In order to better understand the evolution
+of magnetization dynamics from quantum to classical behavior with the increase
+in the system size, we study the electron magnetic resonance signal in
+suspensions of iron oxide nanoparticles as the function of the particle size.
+The experimental data are compared with numerical simulations based on the
+giant spin approach.",1604.04594v2
+2016-05-10,Fermion self-energy in magnetized chirally asymmetric QED matter,"The fermion self-energy is calculated for a cold QED plasma with chiral
+chemical potential in a magnetic field. It is found that a momentum shift
+parameter dynamically generated in such a plasma leads to a modification of the
+chiral magnetic effect current. It is argued that the momentum shift parameter
+can be relevant for the evolution of magnetic field in the chirally asymmetric
+primordial plasma in the early Universe.",1605.03225v1
+2016-06-21,Technical Considerations in Magnetic Analogue Models,"The analogy between vorticity and magnetic fields has been a subject of
+interest to researchers for a considerable period of time, mainly because of
+the structural similarities between the systems of equations that govern the
+evolution of the two fields. We recently presented the analysis of magnetic
+fields and hydrodynamics vorticity fields and argued for a formal theory of
+analogue magnetism. This article provides in depth technical details of the
+relevant considerations for the simulation procedures and extends the analyses
+to a range of fluids.",1606.06725v1
+2016-07-04,Transversal-rotational and zero group velocity modes in tunable magneto-granular phononic crystals,"We report on the design and operation of a 1D magneto-granular phononic
+crystal composed of a chain of steel spherical beads on top of permanent
+magnets. The magnetic field of the permanent magnets induces forces in the
+granular structure. By changing its strength, we can tune the dynamic response
+of the granular structure. We present experimental results with evidence of
+coupled transversal-rotational modes, and zero group velocities modes. These
+observations are well supported by a proposed model taking into account the
+mechanical coupling between the beads and the magnets by linear stiffnesses and
+including all degrees of freedom in translations and rotations.",1607.00831v2
+2016-07-25,MHD stagnation point flow toward a linearly-stretching thermally-insulated sheet with induced magnetic field,"The equations governing the magnetohydrodynamic stagnation point flow toward
+a non-conducting, thermally insulated, nonporous, linearly stretching sheet are
+cast in a self similar form. Consistent boundary conditions on the velocity,
+magnetic field and temperature are invoked. The flow problem involves three
+parameters- the magnetic Prandtl number, the magnetic interaction number, and
+the ratio of the stretching rate to the strength of the stagnation point flow.
+The energy equation includes viscous dissipation and Joule heating, and
+introduces the Prandtl number as a fourth parameter. Numerical solutions are
+obtained and sample results are presented.",1607.07374v1
+2016-08-06,Combined effect of horizontal magnetic field and vorticity on Rayleigh Taylor instability,"In this research, the height, curvature and velocity of the bubble tip in
+Rayleigh-Taylor instability at arbitrary Atwood number with horizontal magnetic
+field are investigated. To support the earlier simulation and experimental
+results, the vorticity generation inside the bubble is introduced. It is found
+that, in early nonlinear stage, the temporal evolution of the bubble tip
+parameters depend essentially on the strength and initial perturbation of the
+magnetic field, although the asymptotic nature coincides with the non magnetic
+case. The model proposed here agrees with the previous linear, nonlinear and
+simulation observations.",1608.02072v1
+2016-09-18,Detecting Chiral Magnetic Effect by Lattice Dynamics,"In the present paper, we propose that the chiral magnetic effect, the direct
+consequence of the presence of Weyl points in the band structure, can be
+detected by its coupling to certain phonon modes, which behave like pseudo
+scalars under point group transformations. Such coupling can generate resonance
+between intrinsic plasmon oscillation and the corresponding phonon modes,
+leading to dramatic modification of the optical response by the external
+magnetic field, which provides a new way to study chiral magnetic effect by
+optical measurements.",1609.05442v1
+2016-10-07,Magnonic black holes,"We show that the interaction between spin-polarized current and magnetization
+dynamics can be used to implement black-hole and white-hole horizons for
+magnons - the quanta of oscillations in the magnetization direction in magnets.
+We consider three different systems: easy-plane ferromagnetic metals, isotropic
+antiferromagnetic metals, and easy-plane magnetic insulators. Based on
+available experimental data, we estimate that the Hawking temperature can be as
+large as 1 K. We comment on the implications of magnonic horizons for spin-wave
+scattering and transport experiments, and for magnon entanglement.",1610.02313v1
+2016-12-13,Magnetic Bloch Skyrmion Transport by Electric Fields in a Composite Bilayer,"We investigate a mechanical method to manipulate magnetic Bloch Skyrmions by
+applying an electric field in a composite chiral-magnetic (CM)/ferroelectric
+(FE) bilayer. The magnetoelectric coupling at the interface allows the electric
+field to stimulate magnetic ordering. Therefore it offers the possibility to
+generate Skyrmions [Phys. Rev. B 94, 014311 (2016)]. Here, we design a movable
+and localized electric field source to drive skyrmion transport along the
+bilayer. A traveling velocity of the electric field source must be carefully
+chosen to show the stability and effciency of this process. The effects of high
+speed operation will be discussed.",1612.03995v1
+2017-01-10,The giant effect of magnetic ordering on a sound velocity in a sigma-Fe55Cr45 alloy,"We studied atomic dynamics of sigma-Fe(100-x)Cr(x) (x=45 and 49.5) alloys
+using nuclear inelastic scattering of synchrotron radiation. For the
+sigma-Fe55Cr45 alloy, the derived reduced iron-partial density of phonon states
+reveal a huge difference in the low-energy region between magnetic and
+paramagnetic states. The latter implies a ca.36% increase of the sound velocity
+in the magnetic phase, which testifies to a magnetically-induced hardening of
+the lattice.",1701.02467v1
+2017-04-27,Nucleon Magnetic Properties from Lattice QCD with the Background Field Method,"The magnetic moment and magnetic polarisability of the neutron and proton are
+investigated using the uniform background-field method and lattice QCD. The
+results are calculated using 32^3 x 64 dynamical QCD lattices provided by the
+PACS-CS collaboration through the ILDG. Methods of isolating the energy of the
+hadrons accounting for Landau level energies are explored. Effective energy
+shifts are formed from combinations of correlation functions and their
+efficiency in isolating the magnetic moment and polarisability terms is
+determined.",1704.08435v1
+2017-09-05,Gate-controlled magnonic-assisted switching of magnetization in ferroelectric/ferromagnetic junctions,"Interfacing a ferromagnet with a polarized ferroelectric gate generates a
+non-uniform, interfacial spin density coupled to the ferroelectric polarization
+allowing so for an electric field control of effective transversal field to
+magnetization. Here we study the dynamic magnetization switching behavior of
+such a multilayer system based on the Landau-Lifshitz-Baryakhtar equation,
+demonstrating that interfacial magnetoelectric coupling is utilizable as a
+highly localized and efficient tool for manipulating magnetism.",1709.01286v1
+2017-09-14,Remarks on the derivation of Gross-Pitaevskii equation with magnetic Laplacian,"The effective dynamics for a Bose-Einstein condensate in the regime of high
+dilution and subject to an external magnetic field is governed by a magnetic
+Gross-Pitaevskii equation. We elucidate the steps needed to adapt to the
+magnetic case the proof of the derivation of the Gross-Pitaevskii equation
+within the ""projection counting"" scheme.",1709.04841v1
+2017-11-27,Shape and fission instabilities of ferrofluids in non-uniform magnetic fields,"We study static distributions of ferrofluid submitted to non-uniform magnetic
+fields. We show how the normal-field instability is modified in the presence of
+a weak magnetic field gradient. Then we consider a ferrofluid droplet and show
+how the gradient affects its shape. A rich phase transitions phenomenology is
+found. We also investigate the creation of droplets by successive splits when a
+magnet is vertically approached from below and derive theoretical expressions
+which are solved numerically to obtain the number of droplets and their aspect
+ratio as function of the field configuration. A quantitative comparison is
+performed with previous experimental results, as well as with our own
+experiments, and yields good agreement with the theoretical modeling.",1711.09942v1
+2017-12-31,Magnetic Field Inspired Contact Angle Hysteresis Drives Floating Polyolefin Rafts,"Displacement of floating polymer (polyolefin) rafts by steady magnetic field
+is reported. The effect is due to the interplay of gravity deforming the
+water/vapor interface, contact angle hysteresis and diamagnetic properties of
+the liquid support. Magnetic field (ca. 0.06 T) deformed the water/vapor
+interface and impacted the interfacial apparent contact angle. This deformation
+gave rise to the propulsion force, displacing the polymer raft. The velocity of
+displacement of the center of mass of rafts was registered. The effect is
+related to the contact angle hysteresis affected by the magnetic field,
+enabling the change in the apparent interfacial contact angle. The
+semi-quantitative model of the process is suggested",1801.00294v1
+2018-01-11,Fullerene Faraday Cage Keeps Magnetic Properties of Inner Cluster Pristine,"Any single molecular magnets (SMM) perspective for application is as good as
+its magnetization stability in ambient conditions. Endohedral metallofullerenes
+(EMFs) provide a solid basis for promising SMMs. In this study, we investigated
+the behavior of functionalized EMFs on a gold surface (EMF-L-Au). Having
+followed the systems molecular dynamics paths, we observed that the chemically
+locked inner cluster inside fullerene cage will remain locked even at room
+temperature due to the ligand-effect. We have located multiple possible minima
+with different charge arrangements between EMF-L-Au fragments. Remarkably, the
+charge state of the EMF inner cluster remained virtually constant and so
+magnetic properties are expected to be untouched.",1801.03808v2
+2018-04-11,Magnetic gravity compensation,"Magnetic gravity compensation in fluids is increasingly popular as a means to
+achieve low-gravity forphysical and life sciences studies. We explain the
+basics of the magnetic gravity compensation and analyzeits advantages and
+drawbacks. The main drawback is the spatial heterogeneity of the residual
+gravity field.We discuss its causes. Some new results concerning the
+heterogeneity estimation and measurement arepresented. A review of the existing
+experimental installations and works involving the magnetic gravitycompensation
+is given for both physical and life sciences.",1804.03838v1
+2018-06-10,Quantum Collapse of a Magnetic Skyrmion,"Quantum collapse of a small skyrmion in a thin magnetic film with
+Dzyalishinskii-Moriya (DMI) interaction has been studied. The energy of the
+skyrmion and the stability threshold determined by the DMI, the external
+magnetic field, and the underlying atomic lattice are investigated analytically
+and numerically. The Lagrangian describing the coupled dynamics of the skyrmion
+size and the chirality angle is derived. Equations of motion possess an
+instanton solution that corresponds to the skyrmion underbarrier contraction
+via quantum tunneling with subsequent collapse and decay of the topological
+charge. The tunneling rate is computed and the conditions needed to observe
+quantum collapse of a skyrmion in a magnetic film are discussed.",1806.03675v1
+2018-09-21,Influence of the particle shape on the equilibrium morphologies of supracolloidal magnetic filaments,"We investigate the equilibrium morphologies of linear and ring-shaped
+magnetic filaments made from crosslinked ferromagnetic spherical or ellipsoidal
+colloidal particles. Using Langevin dynamics simulations, we calculate the
+radius of gyration and total magnetic moment of a single filament at zero field
+and different temperatures, analyzing the influence of the particles shape, the
+strength of their magnetic moment and the filament length. Our results show
+that, among such parameters, the shape of the particles has the strongest
+qualitative impact on the equilibrium behavior of the filaments.",1809.08094v1
+2018-10-17,Out-of-plane auto-oscillation in spin Hall oscillator with additional polarizer,"The theoretical investigation on magnetization dynamics excited by the spin
+Hall effect in metallic multilayers having two ferromagnets is discussed. The
+relaxation of the transverse spin in one ferromagnet enables us to manipulate
+the direction of the spin-transfer torque excited in another ferromagnet,
+although the spin-polarization originally generated by the spin Hall effect is
+geometrically fixed. Solving the Landau-Lifshitz-Gilbert-Slonczewski equation,
+the possibility to excite an out-of-plane auto-oscillation of an in-plane
+magnetized ferromagnet is presented. An application to magnetic recording using
+microwave-assisted magnetization reversal is also discussed.",1810.07831v1
+2019-02-13,"An extension of the fewest switches surface hopping algorithm to complex Hamiltonians and photophysics in magnetic fields: Berry's phase and ""magnetic"" forces","We present a preliminary extension of the fewest switches surface hopping
+(FSSH) algorithm to the case of complex Hamiltonians as appropriate for
+modeling the dynamics of photoexcited molecules in magnetic fields. We make
+ansatze for the direction of momentum rescaling and we account for Berry's
+phase effects through ""magnetic"" forces as applicable in the adiabatic limit.
+Because Berry's phase is a nonlocal, topological characteristic of a set of
+entangled potential energy surfaces, we find that Tully's local FSSH algorithm
+can only partially capture the correct physics.",1902.05115v1
+2019-07-04,Helical distributed chaos in magnetic field of solar wind,"Helical distributed chaos in magnetic field has been studied using results of
+direct numerical simulations (dominated by magnetic helicity), of a laboratory
+experiment with plasma wind tunnel and of solar wind measurements (dominated by
+combined magnetic and cross helicity effects). The solar wind measurements,
+used for the spectral computations, were produced by Helios-1 and Ulysses
+missions for low and high heliolatitudes respectively and for high solar wind
+speed at $0.4 < R <4.5$ AU (where $R$ is distance from the Sun).",1907.02425v1
+2019-07-06,Angle-resolved broadband ferromagnetic resonance apparatus enabled through a spring-loaded sample mounting manipulator,"Broadband ferromagnetic resonance is a useful technique to determine the
+magnetic anisotropy and study the magnetization dynamics of magnetic thin
+films. We report a spring-loaded sample loading manipulator for reliable sample
+mounting and rotation. The manipulator enables maximum signal, enhances system
+stability and is particularly useful for fully automated in-plane-field
+angle-resolved measurements. This angle-resolved broadband ferromagnetic
+resonance apparatus provides a viable method to study anisotropic damping and
+weak magnetic anisotropies, both vital for fundamental research and
+applications.",1907.03097v1
+2019-08-19,Amorphous Ferrimagnets: an Ideal Host for Ultra-Small Skyrmions at Room Temperature,"Recently, magnetic skyrmion has emerged as an active topic of fundamental
+study and applications in magnetic materials research. Magnetic skyrmions are
+vortex-like spin excitations with topological protection and therefore are more
+robust to pinning compared with magnetic domain walls. We employ atomistic
+simulations to create room-temperature ultra-small Neel skyrmions in amorphous
+ferrimagnet. The fast propagation and low-dissipation dynamics of ultra-small
+ferrimagnetic skyrmions make them attractive for utilization as an alternative
+to domain walls in spin-based memory and logic devices.",1908.07003v2
+2020-05-25,Multiple Spin-Phonon Relaxation Pathways in a Kramer Single-Ion Magnet,"We present a first-principles investigation of spin-phonon relaxation in a
+molecular crystal of Co(II) single-ion magnets. Our study combines electronic
+structure calculations with machine-learning force fields and unravels the
+nature of both the Orbach and the Raman relaxation channels in terms of
+atomistic processes. We find that although both mechanisms are mediated by the
+excited spin states, the low temperature spin dynamics is dominated by phonons
+in the THz energy range, which partially suppress the benefit of having a large
+magnetic anisotropy. This study also determines the importance of
+intra-molecular motions for both the relaxation mechanisms and paves the way to
+the rational design of a new generation of single-ion magnets with tailored
+spin-phonon coupling.",2005.12429v1
+2020-07-01,Quantum droplet states of a binary magnetic gas,"Quantum droplets can emerge in bosonic binary magnetic gases (BMGs) from the
+interplay of short- and long-ranged interactions, and quantum fluctuations. We
+develop an extended meanfield theory for this system and use it to predict
+equilibrium and dynamical properties of BMG droplets. We present a phase
+diagram and characterize miscible and immiscible droplet states. We also show
+that a single component self-bound droplet can be used to bind another magnetic
+component which is not in the droplet regime. Our results should be realizable
+in experiments with mixtures of highly-magnetic lanthanide atoms.",2007.00366v1
+2020-08-01,Magnetic ratchet effect in phosphorene,"The magnetic ratchet effect has been studied in phosphorene by the use of the
+Boltzmann kinetic equation that is a semi-classical approach. The Hamiltonian
+of phosphorene in a steady parallel magnetic field is derived using the
+tight-binding model. We consider the effect of the magnetic field on
+non--linear dynamics in the presence of an ac laser field and spatial inversion
+asymmetry. We have shown that for anisotropic 2D materials and phosphorene, the
+ratchet current has the response to three different light polarizations:
+linearly polarized light, circularly polarized light, and unpolarized light.",2008.01561v3
+2020-11-12,Magnetically powered metachronal waves induce locomotion in self-assemblies,"When tiny soft ferromagnetic particles are placed along a liquid interface
+and exposed to a vertical magnetic field, the balance between capillary
+attraction and magnetic repulsion leads to self-organization into well-defined
+patterns. Here, we demonstrate experimentally that precessing magnetic fields
+induce metachronal waves on the periphery of these assemblies, similar to the
+ones observed in ciliates and some arthropods. The outermost layer of particles
+behaves like an array of cilia or legs whose sequential movement causes a net
+and controllable locomotion. This bioinspired many-particle swimming strategy
+is effective even at low Reynolds number, using only spatially uniform fields
+to generate the waves.",2011.06442v1
+2021-04-13,Dynamic Magnetoelastic Boundary Conditions and the Pumping of Phonons,"We derive boundary conditions at the interfaces of magnetoelastic
+heterostructures under ferromagnetic resonance for arbitrary magnetization
+directions and interface shapes. We apply our formalism to
+magnet$\vert$nonmagnet bilayers and magnetic grains embedded in a nonmagnetic
+thin film, revealing a nontrivial magnetization angle dependence of acoustic
+phonon pumping.",2104.05992v2
+2021-04-27,Field-driven dynamics of magnetic Hopfions,"We present micromagnetic simulations on resonant spin wave modes of magnetic
+Hopfions up to 15 GHz driven by external magnetic fields. A sharp transition is
+found around 32 mT coinciding with a transition from Hopfions to magnetic
+torons. The modes exhibit characteristic amplitudes in frequency space
+accompanied by unique localization patterns in real space, and are found to be
+robust to damping around topological features, particularly vortex lines in
+Hopfions and Bloch points in torons. The marked differences in spin wave
+spectra between Hopfions, torons and target skyrmions can serve as fingerprints
+in future experimental validation studies of these novel 3d topological spin
+textures.",2104.13349v1
+2021-08-21,Bursty magnetic reconnection at the Earth's magnetopause triggered by high-speed jets,"The impact of high-speed jets -- dynamic pressure enhancements in the
+magnetosheath -- on the Earth's magnetopause has been observed to trigger local
+magnetic reconnection. We perform a three-dimensional hybrid simulation to
+study the magnetosheath and magnetopause under turbulent conditions using a
+quasi-radial southward interplanetary magnetic field (IMF). In contrast to
+quasi-steady reconnection with a strong southward IMF, we show that after the
+impact of a jet on the magnetopause, the magnetopause moves inwards, the
+current sheet is compressed and intensified and signatures of local magnetic
+reconnection are observed, showing similarities to spacecraft measurements",2108.09419v1
+2021-11-22,Single-layer Skyrmions in a van der Waals Antiferromagnet,"Transition metal halides are quasi-two-dimensional van der Waals magnets that
+can potentially host antiferromagnetic (AFM) skyrmions induced by competing
+exchange interactions. We study theoretically magnetic states of Fe-doped
+NiBr$_2$ using spin interactions obtained by fitting experimental data. We find
+that AFM interlayer interactions suppress skyrmion lattices but allow for
+skyrmions with topological charges $1,2$ and $3$ confined to a single magnetic
+layer. These single-layer skyrmions exist in three different magnetic phases
+and their dynamics changes drastically at the transition from a uniform to a
+non-collinear modulated state.",2111.11420v2
+2021-12-08,Electric dipole in a magnetic field: some aspects of the problem,"In the paper some regimes of motion of an electric dipole placed in a uniform
+magnetic field are considered. The motion of both three-dimensional and
+two-dimensional dipole in the plane perpendicular to the magnetic field is
+studied. In the case of a two-dimensional dipole is discussed, in particular,
+the regime of chaotic dipole motion, which arises when, along with the magnetic
+field, there is an electric field rotating in the plane of motion. The motion
+of a three-dimensional dipole is discussed in cases that allow for analytical
+consideration. Finally, the same examples are used to discuss the
+quantum-mechanical approach to the problem.",2112.04349v1
+2021-12-09,Detection of weak magnetic fields using nitrogen-vacancy centers with maximum confidence,"The problem of detection of magnetic fields using NV centers, that is, to
+check whether a weak magnetic field is present or not, can be tackled using
+quantum state discrimination theory. In this regard, we find the POVMs that
+maximize the confidence of any given measurement, taking the interaction time
+as well as decoherence into account. We apply our formalism over a wide range
+of scenarios encompassing constant and oscillating magnetic fields, while also
+using techniques such as dynamical decoupling to improve the confidence and
+extending our treatment to ensembles of NV centers.",2112.04856v1
+2022-02-22,Skyrmions in magnetic materials,"Skyrmions are vortex-like textures of magnetic moments found in some
+magnetically ordered materials. Here we describe the origin of the skyrmion and
+discuss the experimental realization of skyrmions in magnetic materials, the
+dynamic properties of the skyrmion and the potentially useful interaction of
+skyrmions with electrons. Our discussion is based on the physics of fields and
+allows us to touch on notions from field theory and topology that illustrate
+how skyrmions can be understood as part of a family of defects in an ordered
+field, and hint at other topological objects that await our discovery.",2202.11019v1
+2022-07-08,Fast and Furious dynamo action in the anisotropic dynamo,"In the limit of large magnetic Reynolds numbers, it is shown that a smooth
+differential rotation can lead to fast dynamo action, provided that the
+electrical conductivity or magnetic permeability is anisotropic. If the shear
+is infinite, for example between two rotating solid bodies, the anisotropic
+dynamo becomes furious, meaning that the magnetic growth rate increases toward
+infinity with an increasing magnetic Reynolds number.",2207.03950v1
+2023-04-01,All-optical magnetization control in CrI$_3$ monolayers: a microscopic theory,"Bright excitons in ferromagnetic monolayers CrI$_3$ efficiently interact with
+lattice magnetization, which makes possible all-optical resonant magnetization
+control in this material. Using the combination of ab-initio simulations within
+Bethe-Salpeter approach, semiconductor Bloch equations and Landau-Lifshitz
+equations, we construct a microscopic theory of this effect. Solving
+numerically the resulting system of the coupled equations describing the
+dynamics of atomic spins and spins of the excitons, we demonstrate the
+possibility of a tunable control of macroscopic magnetization of a sample.",2304.00331v2
+2023-08-08,Dispersive decay estimates for the magnetic Schrödinger equations,"In this paper, we present a proof of dispersive decay for both linear and
+nonlinear magnetic Schr\""odinger equations. To achieve this, we introduce the
+fractional distorted Fourier transforms with magnetic potentials and define the
+fractional differential operator $\arrowvert J_{A}(t)\arrowvert^{s}$. By
+leveraging the properties of the distorted Fourier transforms and the
+Strichartz estimates of $\arrowvert J_{A}\arrowvert^{s}u$, we establish the
+dispersive bounds with the decay rate $t^{-\frac{n}{2}}$. This decay rate
+provides valuable insights into the spreading properties and long-term dynamics
+of the solutions to the magnetic Schr\""odinger equations.",2308.04121v1
+2023-09-21,Chaotic studies in Magnetic Dipoles,"The present work investigates the effect of an external rotating magnetic
+field on a magnetic needle, and aims to study chaotic behaviour. The equation
+of motion is modified to include damping and gravity. The bifurcation behaviour
+of such evolving systems is also studied. Furthermore, the coupling in pairs of
+magnetic needles is also analyzed. In addition, a 2-dimensional array of
+coupled needles is set up, and the synchronization properties of the population
+is studied. The study is completed by carrying out an investigation of the
+effects of noise on the synchronization of such a system.",2309.12180v1
+2023-10-10,Video recognition by physical reservoir computing in magnetic materials,"Nonlinear spin dynamics in magnetic materials offers a promising avenue for
+implementing physical reservoir computing, one of the most accomplished
+brain-inspired frameworks for information processing. In this study, we
+investigate the practical utility of magnetic physical reservoirs by assessing
+their performance in a video recognition task. Leveraging a recently developed
+spatiotemporal parallelization scheme, our reservoir achieves accurate
+classifications of previously provided images. Our findings pave the way for
+the development of visual sensors based on the magnetic physical reservoir
+computing.",2310.06497v1
+2023-10-16,Dynamical magneto-rotational instability,"Magneto-rotational instability (MRI) is an important instability mechanism
+for rotating flows with magnetic fields. In particular, when the strength of
+the magnetic field tends to zero, the stability criterion for rotating flows is
+generally different from the classical Rayleigh criterion for rotating flows
+without a magnetic field. MRI has wide applications in astrophysics,
+particularly to the turbulence and enhanced angular momentum transport in
+accretion disks. For the case of vertical magnetic fields, we give rigorous
+proof of linear MRI and a complete description of the spectra and semigroup
+growth of the linearized operator. Moreover, we prove nonlinear stability and
+instability from the sharp linear stability/instability criteria.",2310.10075v3
+2023-12-08,Phase Shift in AC Magnetocaloric Effect Measurements as an Indicator of the Order of Magnetic Phase Transitions,"It is shown that the phase shift between an applied weak alternating magnetic
+field and the magnetocaloric response signal of the magnetic material is
+drastically sensitive to the order of phase transition. Namely, at the
+second-order phase transition, the phase shift does not depend on the magnetic
+field magnitude, while in the first-order phase transition this one depends
+significantly on the field strength. We have shown that this effect follows
+from the general critical dynamics theory.",2312.04979v1
+2008-09-26,Ultra-fast spin dynamics: the effect of colored noise,"Recent experimental results have pushed the limits of magnetization dynamics
+to pico- and femtosecond timescales. This ultra-fast spin dynamics occurs in
+extreme conditions of strong and rapidly varying fields and high temperatures.
+This situation requires new description of magnetization dynamics, even on a
+phenomenological level of the atomistic Landau-Lifshitz-Gilbert equation,
+taking into account that the correlation time for electron system could be of
+the order of the inverse characteristic spin frequency. For this case we
+introduce the thermodynamically correct phenomenological approach for spin
+dynamics based on the Landau-Lifshitz-Miyasaki-Seki equation. The influence of
+the noise correlation time on longitudinal and transverse magnetization
+relaxation is investigated. We also demonstrate the effect of the noise
+correlation time on demagnetisation rate of different materials during
+laser-induced dynamics.",0809.4595v1
+2010-03-09,Magnetic Field Control of the Quantum Chaotic Dynamics of Hydrogen Analogues in an Anisotropic Crystal Field,"We report magnetic field control of the quantum chaotic dynamics of hydrogen
+analogues in an anisotropic solid state environment. The chaoticity of the
+system dynamics was quantified by means of energy level statistics. We analyzed
+the magnetic field dependence of the statistical distribution of the impurity
+energy levels and found a smooth transition between the Poisson limit and the
+Wigner limit, i.e. transition between regular Poisson and fully chaotic Wigner
+dynamics. Effect of the crystal field anisotropy on the quantum chaotic
+dynamics, which manifests itself in characteristic transitions between
+regularity and chaos for different field orientations, was demonstrated.",1003.1778v1
+2011-12-19,Dynamical phases and intermittency of the dissipative quantum Ising model,"We employ the concept of a dynamical, activity order parameter to study the
+Ising model in a transverse magnetic field coupled to a Markovian bath. For a
+certain range of values of the spin-spin coupling, magnetic field and
+dissipation rate, we identify a first order dynamical phase transition between
+active and inactive {\em dynamical phases}. We demonstrate that dynamical
+phase-coexistence becomes manifest in an intermittent behavior of the bath
+quanta emission. Moreover, we establish the connection between the dynamical
+order parameter that quantifies the activity, and the longitudinal
+magnetization that serves as static order parameter. The system we consider can
+be implemented in current experiments with Rydberg atoms and trapped ions.",1112.4273v2
+2014-01-13,Pseudo Slice Energy Spread in Dynamics of Electron Beams Moving through Magnetic Bends,"In the previous canonical formulation of beam dynamics for an electron bunch
+moving ultrarelativistically through magnetic bending systems, we have shown
+that the transverse dynamics equation for a particle in the bunch has a driving
+term which behaves as the centrifugal force caused by the particle's initial
+potential energy due to collective particle interactions within the bunch. As a
+result, the initial potential energy at the entrance of a bending system, which
+we call pseudo (kinetic) energy, is indistinguishable from the usual kinetic
+energy offset from the design energy in its perturbation to particle optics
+through dispersion and momentum compaction. In this paper, in identifying this
+centrifugal force on particles as the remnant of the CSR cancellation effect in
+transverse particle dynamics, we show how the dynamics equation in terms of the
+canonical momentum for beam motion on a curved orbit is related to the
+Panofsky-Wenzel theorem for wakefields for beam motion on a straight path. It
+is shown that the effect of pseudo energy spread can be measurable only for a
+high-peak-current bunch when the pseudo slice energy spread is appreciable
+compared to the slice kinetic energy spread. The implication of the pseudo
+slice energy spread for bunch dynamics in magnetic bends is discussed.",1401.2868v1
+2014-02-25,Leapfrogging vortex rings in the Landau-Lifshitz equation,"Vortex rings are ubiquitous in fluids, with smoke rings being a familiar
+example. The interaction of multiple vortex rings produces complex dynamical
+behaviour, such as the leapfrogging motion first analysed by Helmholtz more
+than a century and a half ago. Here we report on numerical investigations of
+vortex ring dynamics in a different setting from fluids, namely, as solutions
+of the Landau-Lifshitz equation that models the evolution of the local
+magnetization in a ferromagnetic medium. We present the results of the first
+study on the dynamics of interacting magnetic vortex rings and provide a novel
+link between fluids and magnetism, by showing that a range of phenomena
+familiar in fluids are reproduced in ferromagnets. This includes the
+leapfrogging motion of a pair of vortex rings and evidence for the chaotic
+dynamics of a trio of rings.",1402.6165v1
+2015-02-17,Orientational hysteresis in swarms of active particles in external field,"Structure and ordering in swarms of active particles have much in common with
+condensed matter systems like magnets or liquid crystals. A number of important
+characteristics of such materials can be obtained via dynamic tests such as
+hysteresis. In this work, we show that dynamic hysteresis can be observed also
+in swarms of active particles and possesses similar properties to the
+counterparts in magnetic materials. To study the swarm dynamics, we use
+computer simulations of the active Brownian particle model with dissipative
+interactions. The swarm is confined to a narrow linear channel and the
+one-dimensional polar order parameter is measured. In an oscillating external
+field, the order parameter demonstrates dynamic hysteresis with the shape of
+the loop and its area varying with the amplitude and frequency of the applied
+field, swarm density and the noise intensity. We measure the scaling exponents
+for the hysteresis loop area, which can be associated with the controllability
+of the swarm. Although the exponents are non-universal and depend on the
+system's parameters, their limiting values can be predicted using a generic
+model of dynamic hysteresis. We also discuss similarities and differences
+between the swarm ordering dynamics and two-dimensional magnets.",1502.05071v2
+2017-06-11,Dynamically order-disorder transition in triangular lattice driven by a time dependent magnetic field,"We have elucidated the dynamic phase transition features and finite-size
+scaling analysis of the triangular lattice system under the presence of a
+square-wave magnetic field. It has been found that as the value of half-period
+of the external field reaches its critical value, whose location is estimated
+by means of Binder cumulant, the system presents a dynamic phase transition
+between dynamically ordered and disordered phases. Moreover, at the dynamic
+phase transition point, finite-size scaling of the Monte Carlo results for the
+dynamic order parameter and susceptibility give the critical exponents
+$\beta/\nu=0.143\pm0.004$ and $\gamma/\nu=1.766\pm0.036$, respectively. The
+obtained critical exponents show that present magnetic system belongs to same
+universality class with the two-dimensional equilibrium Ising model.",1706.03351v1
+2017-11-30,Dynamic MRI Reconstruction from Undersampled Data with an Anatomical Prescan,"The goal of dynamic magnetic resonance imaging (dynamic MRI) is to visualize
+tissue properties and their local changes over time that are traceable in the
+MR signal. We propose a new variational approach for the reconstruction of
+subsampled dynamic MR data, which combines smooth, temporal regularization with
+spatial total variation regularization. In particular, it furthermore uses the
+infimal convolution of two total variation Bregman distances to incorporate
+structural a-priori information from an anatomical MRI prescan into the
+reconstruction of the dynamic image sequence. The method promotes the
+reconstructed image sequence to have a high structural similarity to the
+anatomical prior, while still allowing for local intensity changes which are
+smooth in time. The approach is evaluated using artificial data simulating
+functional magnetic resonance imaging (fMRI), and experimental dynamic
+contrast-enhanced magnetic resonance data from small animal imaging using
+radial golden angle sampling of the k-space.",1712.00099v1
+2019-07-24,Approximate dynamical eigenmodes of the Ising model with local spin-exchange moves,"We establish that the Fourier modes of the magnetization serve as the
+dynamical eigenmodes for the two-dimensional Ising model at the critical
+temperature with local spin-exchange moves, i.e., Kawasaki dynamics. We obtain
+the dynamical scaling properties for these modes, and use them to calculate the
+time evolution of two dynamical quantities for the system, namely the
+autocorrelation function and the mean-square deviation of the line
+magnetizations. At intermediate times $1 \lesssim t \lesssim L^{z_c}$, where
+$z_c=4-\eta=15/4$ is the dynamical critical exponent of the model, we find that
+the line magnetization undergoes anomalous diffusion. Following our recent work
+on anomalous diffusion in spin models, we demonstrate that the Generalized
+Langevin Equation (GLE) with a memory kernel consistently describes the
+anomalous diffusion, verifying the corresponding fluctuation-dissipation
+theorem with the calculation of the force autocorrelation function.",1907.10296v1
+2020-01-08,Observation of Dynamical Quantum Phase Transition with Correspondence in Excited State Phase Diagram,"Dynamical quantum phase transitions are closely related to equilibrium
+quantum phase transitions for ground states. Here, we report an experimental
+observation of a dynamical quantum phase transition in a spinor condensate with
+correspondence in an excited state phase diagram, instead of the ground state
+one. We observe that the quench dynamics exhibits a non-analytical change with
+respect to a parameter in the final Hamiltonian in the absence of a
+corresponding phase transition for the ground state there. We make a connection
+between this singular point and a phase transition point for the highest energy
+level in a subspace with zero spin magnetization of a Hamiltonian. We further
+show the existence of dynamical phase transitions for finite magnetization
+corresponding to the phase transition of the highest energy level in the
+subspace with the same magnetization. Our results open a door for using
+dynamical phase transitions as a tool to probe physics at higher energy
+eigenlevels of many-body Hamiltonians.",2001.02686v2
+2020-08-26,Critical Dynamics of Anisotropic Antiferromagnets in an External Field,"We numerically investigate the non-equilibrium critical dynamics in
+three-dimensional anisotropic antiferromagnets in the presence of an external
+magnetic field. The phase diagram of this system exhibits two critical lines
+that meet at a bicritical point. The non-conserved components of the staggered
+magnetization order parameter couple dynamically to the conserved component of
+the magnetization density along the direction of the external field. Employing
+a hybrid computational algorithm that combines reversible spin precession with
+relaxational Monte Carlo updates, we study the aging scaling dynamics for the
+model C critical line, identifying the critical initial slip, autocorrelation,
+and aging exponents for both the order parameter and conserved field, thus also
+verifying the dynamic critical exponent. We further probe the model F critical
+line by investigating the system size dependence of the characteristic spin
+wave frequencies near criticality, and measure the dynamic critical exponents
+for the order parameter including its aging scaling at the bicritical point.",2008.11541v2
+2021-04-22,Dynamical Backaction Magnomechanics,"Dynamical backaction resulting from radiation pressure forces in
+optomechanical systems has proven to be a versatile tool for manipulating
+mechanical vibrations. Notably, dynamical backaction has resulted in the
+cooling of a mechanical resonator to its ground-state, driving phonon lasing,
+the generation of entangled states, and observation of the optical-spring
+effect. In certain magnetic materials, mechanical vibrations can interact with
+magnetic excitations (magnons) via the magnetostrictive interaction, resulting
+in an analogous magnon-induced dynamical backaction. In this article, we
+directly observe the impact of magnon-induced dynamical backaction on a
+spherical magnetic sample's mechanical vibrations. Moreover, dynamical
+backaction effects play a crucial role in many recent theoretical proposals;
+thus, our work provides the foundation for future experimental work pursuing
+many of these theoretical proposals.",2104.11218v2
+2021-10-13,Eigenvalue-based micromagnetic analysis of switching in spin-torque-driven structures,"We present an eigenvalue-based approach for studying the magnetization
+dynamics in magnetic nanostructures driven by spintronic excitations, such as
+spin transfer torque and spin orbit torque. The approach represents the system
+dynamics in terms of normal oscillation modes (eigenstates) with corresponding
+complex eigenfrequencies. The dynamics is driven by a small number of active
+eigenstates and often considering just a single eigenstate is sufficient. We
+develop a perturbation theory that provides semi-analytical dynamic solutions
+by using eigenstates for the case in the absence of damping and spintronic
+excitations as a basis. The approach provides important insights into dynamics
+in such systems and allows solving several difficulties in their modeling, such
+as extracting the switching current in magnetic random access memories (MRAM)
+and understanding switching mechanisms. We show that the presented approach
+directly predicts the critical switching current, i.e., switching current for
+an infinite time. The approach also provides solutions for the switching
+dynamics allowing obtaining the switching current for a finite switching time,
+provided that the system symmetry is broken, e.g., by tilting the polarizer, so
+that switching by a finite pulse is possible.",2110.07085v2
+1999-12-14,Influence of direct URCA processes in a strong magnetic field on dynamics of collapsing star envelope,"Direct URCA processes in a collapsing star envelope with a strong magnetic
+field are investigated. It is shown that in the toroidal magnetic field these
+processes can develope a torque which quickly unwinds an envelope. A general
+expression for a force density along the field direction is obtained. An
+influence of the neutrino unwinding effect on a dynamics of the collapsar
+envelope is discussed and numerically estimated.",9912288v1
+2003-12-03,Stationary perturbation configurations in a composite system of stellar and coplanarly magnetized gaseous singular isothermal discs,"We construct aligned and unaligned stationary perturbation configurations in
+a composite system of stellar and coplanarly magnetized gaseous singular
+isothermal discs (SIDs) coupled by gravity. In comparison with SID problems
+studied earlier, there exist three possible classes of stationary solutions
+allowed by more dynamic freedoms. Our exact global perturbation solutions and
+critical points are valuable for testing numerical magnetohydrodynamic codes.
+For galactic applications, our model analysis contains more realistic elements
+and offer useful insights for structures and dynamics of disc galaxies
+consisting of stars and magnetized gas.",0312082v1
+1997-10-14,Orbit stability in billiards in magnetic field,"We study the stability properties of orbits in dispersing billiards in a
+homogeneous magnetic field by using a modified formalism based on the
+Bunimovich-Sinai curvature (horocycle method). We identify simple periodic
+orbits that can be stabilized by the magnetic field in the four-disk model and
+the square-lattice Lorentz gas. The stable orbits can play a key role in
+determining the transport properties of these models.",9710009v1
+1993-04-02,Dynamical Correlation Theory for an Escape Process,"A dynamical theory which incorporates the electron-electron correlations and
+the effects of external magnetic fields for an electron escaping from a helium
+surface is presented. The degrees of freedom in the calculation of the escape
+rate is reduced from $3N$ to 3 as compared with other approach. Explicit
+expressions for the escape rate in various situations are obtained. In
+particular, in the weak parallel magnetic field limit the tunneling rate has an
+exponential dependence quadratic with magnetic field strength and an unusual
+exponential increase linear with temperature.",9304003v1
+1996-08-06,Dynamics of the Two-Site Hubbard Model,"The dynamical evolution of a two-site Hubbard model is derived in the
+presence of an uniform external magnetic field for a general initial state. The
+time evolution of the half-filled (two-particle) case has a complex behaviour.
+Under certain initial conditions, the average number of fermions in
+one-particle state, in the half-filled case, is not necessarily periodic, even
+though the magnetization remains periodic. The results obtained may be applied
+to study the magnetization and the transition dipole moment of the organic
+charge-transfer salts in the in-phase mode.",9608025v1
+1996-12-17,Dynamical Localization: Hydrogen Atoms in Magnetic and Microwave fields,"We show that dynamical localization for excited hydrogen atoms in magnetic
+and microwave fields takes place at quite low microwave frequency much lower
+than the Kepler frequency. The estimates of localization length are given for
+different parameter regimes, showing that the quantum delocalization border
+drops significantly as compared to the case of zero magnetic field. This opens
+up broad possibilities for laboratory investigations.",9612155v1
+1997-05-19,Nucleation Theory of Magnetization Switching in Nanoscale Ferromagnets,"A nucleation picture of magnetization switching in single-domain
+ferromagnetic nanoparticles with high local anisotropy is discussed. Relevant
+aspects of nucleation theory are presented, stressing the effects of the
+particle size on the switching dynamics. The theory is illustrated by Monte
+Carlo simulations and compared with experiments on single particles.",9705189v1
+1997-08-27,Dynamical Magnetic Susceptibilities in Cu Benzoate,"Recent experiments on the quasi 1-D antiferromagnet Cu Benzoate revealed a
+magentic field induced gap coexisting with (ferro)magnetic order. A theory
+explaining these findings has been proposed by Oshikawa and Affleck. In the
+present work we discuss consequences of this theory for inelastic neutron
+scattering experiments by calculating the dynamical magnetic susceptibilities
+close to the antiferromagnetic wave vector by the formfactor method.",9708208v3
+1999-03-18,Coherent dynamics of localized spins coupled with a two-dimensional hole gas in diluted-magnetic quantum wells,"Spin dynamics in a quantum well made of diluted-magnetic semiconductor is
+studied theoretically. The exchange interaction of the ensemble of localized
+spins with two-dimensional heavy-hole gas is shown to affect time evolution of
+the spin system in an in-plane magnetic field. The Larmor frequency of
+localized spins is reduced under influence of an oscillating effective field of
+holes.",9903280v1
+1999-10-20,Magnetic-field dependence of dynamical vortex response in two-dimensional Josephson junction arrays and superconducting films,"The dynamical vortex response of a two-dimensional array of the resistively
+shunted Josephson junctions in a perpendicular magnetic field is inferred from
+simulations. It is found that, as the magnetic field is increased at a fixed
+temperature, the response crosses over from normal to anomalous, and that this
+crossover can be characterized by a single dimensionless parameter. It is
+described how this crossover should be reflected in measurements of the complex
+impedance for Josephson junction arrays and superconducting films.",9910300v2
+2001-02-12,Nonlinear Dynamics of Quasiclassical Spin Moment in a Swept Field,"Quantum dynamics of anisotropic spin system with large spin moment in a swept
+magnetic field is theoretically investigated. Magnetic field of this type
+induces vortex static electrical field, that breaks down the axial symmetry and
+induces new coherent quantum phenomena: the occurrence of band energy spectrum
+with continuous spin states, Bloch-type oscillations and interband Zener
+tunnelling effect. These quantum phenomena display themselves, in particular,
+in magnetization jumps and susceptibility peaks in the investigated spin
+system.",0102198v2
+2001-04-09,Spin transport in inhomogeneous magnetic fields: a proposal for Stern-Gerlach-like experiments with conduction electrons,"Spin dynamics in spatially inhomogeneous magnetic fields is studied within
+the framework of Boltzmann theory. Stern-Gerlach-like separation of spin up and
+spin down electrons occurs in ballistic and diffusive regimes, before spin
+relaxation sets in. Transient dynamics and spectral response to time-dependent
+inhomogeneous magnetic fields are investigated, and possible experimental
+observations of our findings are discussed.",0104146v2
+2001-05-14,Thermal and Dynamic Effects in Langevin Simulation of Hysteresis in Nanoscale Pillars,"Dynamic quantities related to hysteresis have been measured in micromagnetic
+simulations of single-domain nanoscale magnets at nonzero temperature. The
+hysteresis-loop area and magnetization-field correlation display the
+characteristics of resonance, and the resonance frequency is found to be
+temperature dependent. The period-averaged magnetization displays symmetry
+breaking at high frequencies.",0105279v1
+2001-06-18,Vortex avalanches and magnetic flux fragmentation in superconductors,"We report results of numerical simulations of non isothermal dendritic flux
+penetration in type-II superconductors. We propose a generic mechanism of
+dynamic branching of a propagating hotspot of a flux flow/normal state
+triggered by a local heat pulse. The branching occurs when the flux hotspot
+reflects from inhomogeneities or the boundary on which magnetization currents
+either vanish, or change direction. Then the hotspot undergoes a cascade of
+successive splittings, giving rise to a dissipative dendritic-type flux
+structure. This dynamic state eventually cools down, turning into a frozen
+multi-filamentary pattern of magnetization currents.",0106353v1
+2001-08-03,Frequency dependence of the intergranular magnetic flux penetration in ceramic $YBa_2Cu_3O_x$ uperconductor,"By means of small magnetic field ac susceptibility measurement at 10 kHz we
+found that the real and imaginary parts of ceramic $YBa_2Cu_3O_ x$
+susceptibility in presence of the external low frequency field close to 0.1 Hz
+exhibit frequency dependence. The wide maximum of hysteresis losses and
+{\color{black} the exponential dependence} of the {\color{black} effectiveness
+of flux penetration} with increasing of external field frequency were obtained.
+We observed a nonlinear dynamic magnetic response in presence dc field and we
+suggest that this behavior is due to the dynamic and static Josephson
+vortex-vortex interaction.",0108060v1
+2001-08-04,Magnetic Field Pinning of a Dynamic Electron-Spin-Resonance Line in a GaAs/AlGaAs Heterostructure,"Electrically detected electron spin resonance (ESR) is used to study the
+hyperfine interaction of the two-dimensional electrons and the nuclei of the
+host lattice in a GaAs/AlGaAs heterostructure. Under the microwave and radio-
+frequency double excitations, we have observed that the ESR line can be pinned
+in a very narrow range of magnetic field - in the vicinity of the nuclear
+magnetic resonance (NMR) of the nuclei of the GaAs crystal. Our observations
+suggest that this pinning effect is the result of a competition process between
+the ESR induced dynamic nuclear polarization and the NMR induced
+depolarization.",0108080v1
+2002-11-01,Exploring dynamical magnetism with time-dependent density-functional theory: from spin fluctuations to Gilbert damping,"We use time-dependent spin-density-functional theory to study dynamical
+magnetic phenomena. First, we recall that the local-spin-density approximation
+(LSDA) fails to account correctly for magnetic fluctuations in the paramagnetic
+state of iron and other itinerant ferromagnets. Next, we construct a
+gradient-dependent density functional that does not suffer from this problem of
+the LSDA. This functional is then used to derive, for the first time, the
+phenomenological Gilbert equation of micromagnetics directly from
+time-dependent density-functional theory. Limitations and extensions of Gilbert
+damping are discussed on this basis, and some comparisons with phenomenological
+theories and experiments are made.",0211021v1
+2002-11-27,Hidden symmetries of two-electron quantum dots in a magnetic field,"Using a classical and quantum mechanical analysis, we show that the magnetic
+field gives rise to dynamical symmetries of a three-dimensional axially
+symmetric two-electron quantum dot with a parabolic confinement. These
+symmetries manifest themselves as near-degeneracies in the quantum spectrum at
+specific values of the magnetic field and are robust at any strength of the
+electron-electron interaction.",0211631v1
+2003-03-26,Extended Dynamical Mean Field Theory Study of the Periodic Anderson Model,"We investigate the competition of the Kondo and the RKKY interactions in
+heavy fermion systems. We solve a periodic Anderson model using Extended
+Dynamical Mean Field Theory (EDMFT) with QMC. We monitor simultaneously the
+evolution of the electronic and magnetic properties. As the RKKY coupling
+increases the heavy fermion quasiparticle unbinds and a local moment forms. At
+a critical RKKY coupling there is an onset of magnetic order. Within EDMFT the
+two transitions occur at different points and the disapparence of the magnetism
+is not described by a local quantum critical point.",0303539v2
+2003-04-22,Optical spin transfer in ferromagnetic semiconductors,"Circularly polarized laser pulses that excite electron-hole pairs across the
+band gap of (III,Mn)V ferromagnetic semiconductors can be used to manipulate
+and to study collective magnetization dynamics. The initial spin orientation of
+a photocarrier in a (III,V) semiconductors is determined by the polarization
+state of the laser. We show that the photocarrier spin can be irreversibly
+transferred to the collective magnetization, whose dynamics can consequently be
+flexibly controlled by suitably chosen laser pulses. As illustrations we
+demonstrate the feasibility of all optical ferromagnetic resonance and optical
+magnetization reorientation.",0304492v2
+2003-08-29,Magnetic Order and Dynamics in Stripe-Ordered La2-xSrxNiO4,"We have studied magnetic correlations in several compositions of
+stripe-ordered La2-xSrxNiO4. In this paper we show how polarized-neutron
+scattering has helped uncover important features of the magnetic ordering and
+spin dynamics. In particular, polarization analysis has enabled us (1) to
+characterize a spin reorientation transition, (2) to identify anisotropy gaps
+in the spin excitation spectrum, and (3) to investigate an anomalous dip in the
+spin-wave intensity suggestive of coupling between collective spin and charge
+excitations.",0308631v1
+2004-06-22,Josephson vortex dynamic in superconducting $YBa_2Cu_3O_x$ ceramics,"The Josephson vortices dynamic in superconducting $YBa_2Cu_3O_x$ ceramics was
+studied in frequency range 0.01-0.5 Hz by ac susceptibility measurements in non
+complete magnetic flux penetration regime. We have found that with the increase
+of magnetic field frequency starting from 0.01 Hz the ac magnetic response
+shows complex frequency dependence: in one half period of a sinusoidal field
+appear two asymmetrical peaks of real $\Delta\chi\prime$ and imaginary
+$\chi\prime\prime$ parts of the ac susceptibility. The analysis of experimental
+results has led to an idea that probably the volume (diameter) of Josephson
+vortices increases during its movement. The experimental results are discussed
+in terms of Josephson vortex - vortex interactions.",0406523v1
+2004-07-27,Dynamical Mean Field Theory of Temperature and Field Dependent Band Shifts in Magnetically Coupled Semimetals: Applocation to EuB6,"A model for semimetals such as $EuB_6$, in which band overlaps are controlled
+by magnetic order, is presented and is solved in the dynamical mean field
+approximation. First order phase boundaries are computed by evaluating free
+energies of different states. The phase diagram is determined. A specific and
+physically reasonable choice of parameters is found to approximately reproduce
+the available data on $EuB_6$. For this material, predictions are made for the
+location of a metamagnetic transition and its associated endpoint, and a change
+in the order of the magnetic transition.",0407706v1
+2004-07-28,Large quantum nonlinear dynamic susceptibility of single-molecule magnets,"The nonlinear dynamical response of Mn$_{12}$ single-molecule magnets is
+experimentally found to be very large, quite insensitive to the spin-lattice
+coupling constant, and displaying peaks reversed with respect to classical
+superparamagnets. It is shown that these features are caused by the strong
+field dependence of the relaxation rate due to the detuning of energy levels
+between which tunneling takes place. The nonlinear susceptibility technique,
+previously overlooked, is thus proposed as a privileged probe to ascertain the
+occurrence of quantum effects in mesoscopic magnetic systems.",0407738v1
+2004-10-20,Spin-Transfer Torque and Electron-Magnon Scattering,"According to the spin-torque model, current-driven magnetic dynamics in
+ferromagnetic multilayers is determined by the transfer of electron spin
+perpendicular to the layers' magnetizations. By separating the largest
+contributions to the magnetic dynamics, we demonstrate that the dominant effect
+of spin-torque is rather due to the electron spin parallel to the field. We
+show that this effect can be equivalently described as stimulated
+current-driven excitation of spin-waves, and discuss four specifically
+quantum-mechanical aspects of spin-transfer, not described by the spin-torque.",0410520v1
+2005-07-26,Butterfly hysteresis curve is a signature of adiabatic Landau-Zener transition,"We stress that the so-called butterfly hysteresis curves observed in
+dynamical magnetization measurements on systems of low-spin magnetic molecules
+such as V-15 and V-6 are a signature of adiabatic Landau-Zener transitions
+rather than that of a phonon bottleneck. We investigate the magnetization
+dynamics analytically with the help of a simple relaxation theory in the basis
+of the adabatic energy levels of the spin 1/2, to a qualitative accordance with
+experimental observations. In particular, reversible behavior is found near
+zero field, the corresponding susceptibility being bounded by the equilibrium
+and adiabatic susceptibilities from below and above, respectively.",0507618v1
+2005-10-21,Magnetic Vortex Core Dynamics in a Ferromagnetic Dot,"We report direct imaging by means of x-ray photoemission electron microscopy
+of the dynamics of magnetic vortices confined in micron-size circular Permalloy
+dots that are 30 nm thick. The vortex core positions oscillate on a 10-ns
+timescale in a self-induced magnetostatic potential well after the in-plane
+magnetic field is turned off. The measured oscillation frequencies as a
+function of the aspect ratio (thickness/radius) of the dots are in agreement
+with theoretical calculations presented for the same geometry.",0510595v1
+2006-07-04,Dynamics of Pinned Magnetic Vortices,"We observe the dynamics of a single magnetic vortex in the presence of a
+random array of pinning sites. At low excitation amplitudes, the vortex core
+gyrates about its equilibrium position with a frequency that is characteristic
+of a single pinning site. At high amplitudes, the frequency of gyration is
+determined by the magnetostatic energy of the entire vortex, which is confined
+in a micron-scale disk. We observe a sharp transition between these two
+amplitude regimes that is due to depinning of the vortex core from a local
+defect. The distribution of pinning sites is determined by mapping fluctuations
+in the frequency as the vortex core is displaced by a static in-plane magnetic
+field.",0607095v1
+2006-08-25,"Revivals, collapses and magnetic-pulse generation in quantum rings","Using a microscopic theory based on the density matrix formalism we
+investigate quantum revivals and collapses of the charge polarization and
+charge current dynamics in mesoscopic rings driven by short asymmetric
+electromagnetic pulses. The collapsed state is utilized for sub-picosecond
+switching of the current and associated magnetization, enabling thus the
+generation of pulsed magnetic fields with a tunable time structure and shape
+asymmetry which provides a new tool to study ultrafast spin-dynamics and
+ratchet-based effects.",0608559v1
+2006-10-11,Magnetic Field Dependence of Dephasing Rate due to Diluted Kondo Impurities,"We investigate the dephasing rate, 1/tau_phi, of weakly disordered electrons
+due to scattering from diluted dynamical impurities. Our previous result for
+the weak-localization dephasing rate is generalized from diluted Kondo
+impurities to arbitrary dynamical defects with typical energy transfer larger
+than 1/tau_phi. For magnetic impurities, we study the influence of magnetic
+fields on the dephasing of Aharonov-Bohm oscillations and universal conductance
+fluctuations both analytically and using the numerical renormalization group.
+These results are compared to recent experiments.",0610304v3
+2006-11-07,Enhanced pinning and proliferation of matching effects in a superconducting film with a Penrose array of magnetic dots,"The vortex dynamics in superconducting films deposited on top of a five-fold
+Penrose array of magnetic dots is studied by means of transport measurements.
+We show that in the low pinning regime (demagnetized dots) a few periodic and
+aperiodic matching features coexist. In the strong pinning regime (magnetized
+dots) a richer structure of unforeseen periodic and aperiodic vortex patterns
+appear giving rise to a clear enhancement of the critical current in a broader
+field range. Possible stable vortex configurations are determined by molecular
+dynamics simulations.",0611173v1
+2007-03-19,Nonequilibrium charge dynamics of light-driven rings threaded by a magnetic flux,"We study theoretically the charge polarization and the charge current
+dynamics of a mesoscopic ring driven by short asymmetric electromagnetic pulses
+and threaded by an external static magnetic flux. It is shown that the
+pulse-induced charge polarization and the associated light-emission is
+controllable by tuning the external magnetic flux. Applying two mutually
+perpendicular pulses triggers a charge current in the ring. The interplay
+between this nonequilibrium and the persistent currents is investigated and the
+conditions under which the pulses stop the persistent current are identified.",0703502v1
+1998-09-09,SU(2) vacuum dynamics in applied external magnetic field,"The vacuum dynamics of SU(2) lattice gauge theory is studied by means of a
+gauge-invariant effective action, both at zero and finite temperature. Working
+with lattices up to 32^4 we check the scaling of the energy density with the
+magnetic length. We find that the screening at zero temperature of the applied
+external magnetic field weakens by increasing the temperature.",9809042v1
+1995-01-16,Dynamical Chiral Symmetry Breaking by a Magnetic Field in QED,"It is shown that the chiral symmetry is spontaneously broken by a constant
+magnetic field in QED. The dynamical mass of fermions (energy gap in the
+fermion spectrum) is $m_{dyn}\simeq
+C\sqrt{eB}\exp\left[-\left(\pi/\alpha\right) ^{1/2}\right]$, where $B$ is the
+magnetic field, the constant $C$ is of order one and $\alpha=e^2/4\pi$ is the
+renormalized coupling constant. Possible applications of this effect are
+discussed.",9501304v3
+1997-09-14,Magnetic Catalysis of Chiral Symmetry Breaking in QED at Finite Temperature,"The catalysis of chiral symmetry breaking by a magnetic field in the massless
+weak-coupling phase of QED is studied. The dynamical mass of a fermion (energy
+gap in the fermion spectrum) is shown to depend essentially nonanalytically on
+the renormalized coupling constant $\alpha$ in a strong magnetic field. The
+temperature of the symmetry restoration is calculated analytically as
+$T_c\approx m_{dyn}$, where $m_{dyn}$ is the dynamical mass of a fermion at
+zero temperature.",9709339v1
+1998-10-25,Yukawa Coupling Contribution to Magnetic Field Induced Dynamical Mass,"By solving the gap equation in the quenched, ladder approximation for an
+Abelian gauge model with Yukawa interaction in the presence of a constant
+magnetic field, we show that the Yukawa interactions enhance the dynamical
+generation of fermion mass. The theory is then studied at finite temperature,
+where we prove that the critical magnetic field, required for the mass
+generation to be important at temperatures comparable to the electroweak
+critical temperature, can be substantially decreased due to the Yukawa
+coupling.",9810473v1
+2000-01-11,Magnetic Catalysis of Chiral Symmetry Breaking in Gauge Theories,"Non-perturbative effect of the formation of a chiral symmetry breaking
+condensate <\bar\psi\psi> and of a dynamically generated fermion mass in QED in
+the presence of an external magnetic field is considered. The dynamical mass of
+a fermion (energy gap in the fermion spectrum) is shown to depend essentially
+nonanalytically on the renormalized coupling constant \alpha in a strong
+magnetic field. Possible applications of this effect are discussed.",0001070v1
+2003-07-22,A realistic example of chaotic tunneling: The hydrogen atom in parallel static electric and magnetic fields,"Statistics of tunneling rates in the presence of chaotic classical dynamics
+is discussed on a realistic example: a hydrogen atom placed in parallel uniform
+static electric and magnetic fields, where tunneling is followed by ionization
+along the fields direction. Depending on the magnetic quantum number, one may
+observe either a standard Porter-Thomas distribution of tunneling rates or, for
+strong scarring by a periodic orbit parallel to the external fields, strong
+deviations from it. For the latter case, a simple model based on random matrix
+theory gives the correct distribution.",0307038v1
+2001-01-30,Intermittency and turbulence in a magnetically confined fusion plasma,"We investigate the intermittency of magnetic turbulence as measured in
+Reversed Field Pinch plasmas. We show that the Probability Distribution
+Functions of magnetic field differences are not scale invariant, that is the
+wings of these functions are more important at the smallest scales, a classical
+signature of intermittency. We show that scaling laws appear also in a region
+very close to the external wall of the confinement device, and we present
+evidences that the observed intermittency increases moving towards the wall.",0101106v1
+2001-07-11,On the Dynamical Invariants and the Geometric Phases for a General Spin System in a Changing Magnetic Field,"We consider a class of general spin Hamiltonians of the form
+$H_s(t)=H_0(t)+H'(t)$ where $H_0(t)$ and $H'(t)$ describe the dipole
+interaction of the spins with an arbitrary time-dependent magnetic field and
+the internal interaction of the spins, respectively. We show that if $H'(t)$ is
+rotationally invariant, then $H_s(t)$ admits the same dynamical invariant as
+$H_0(t)$. A direct application of this observation is a straightforward
+rederivation of the results of Yan et al [Phys. Lett. A, Vol: 251 (1999) 289
+and Vol: 259 (1999) 207] on the Heisenberg spin system in a changing magnetic
+field.",0107063v1
+2007-07-13,Multiphoton antiresonance in large-spin systems,"We study nonlinear response of a spin $S>1/2$ with easy-axis anisotropy. The
+response displays sharp dips or peaks when the modulation frequency is
+adiabatically swept through multiphoton resonance. The effect is a consequence
+of a special symmetry of the spin dynamics in a magnetic field for the
+anisotropy energy $\propto S_z^2$. The occurrence of the dips or peaks is
+determined by the spin state. Their shape strongly depends on the modulation
+amplitude. Higher-order anisotropy breaks the symmetry, leading to sharp steps
+in the response as function of frequency. The results bear on the dynamics of
+molecular magnets in a static magnetic field.",0707.2107v1
+2008-05-09,"Spin dynamics in (III,Mn)V ferromagnetic semiconductors: the role of correlations","We address the role of correlations between spin and charge degrees of
+freedom on the dynamical properties of ferromagnetic systems governed by the
+magnetic exchange interaction between itinerant and localized spins. For this
+we introduce a general theory that treats quantum fluctuations beyond the
+Random Phase Approximation based on a correlation expansion of the Green's
+function equations of motion. We calculate the spin susceptibility, spin--wave
+excitation spectrum, and magnetization precession damping. We find that
+correlations strongly affect the magnitude and carrier concentration dependence
+of the spin stiffness and magnetization Gilbert damping.",0805.1320v2
+2008-06-04,Magnetization dynamics in optically excited nanostructured nickel films,"In this work, Laser-induced magnetization dynamics of nanostructured nickel
+films is investigated. The influence of the nanosize is discussed considering
+the time-scale of hundreds of femtoseconds as well as the GHz regime. While no
+nanosize effect is observed on the short time-scale, the excited magnetic mode
+in the GHz regime can be identified by comparison with micromagnetic
+simulations. The thickness dependence reveals insight on the dipole interaction
+between single nickel structures. Also, transient reflectivity changes are
+discussed.",0806.0711v1
+2008-06-05,Magnetization Relaxation and Collective Vortex Pinning in the Fe-Based Superconductor SmFeAsO_0.9F_0.1,"By measuring the dynamic and traditional magnetization relaxations we
+investigate the vortex dynamics of the newly discovered superconductor
+SmFeAsO_0.9F_0.1 with Tc = 55K. It is found that the relaxation rate is rather
+large reflecting a small characteristic pinning energy. Moreover it shows a
+weak temperature dependence in wide temperature region, which resembles the
+behavior of the cuprate superconductors. Combining with the resistive data
+under different magnetic fields, a vortex phase diagram is obtained. Our
+results strongly suggest that the model of collective vortex pinning applies to
+this new superconductor very well.",0806.0980v2
+2008-06-11,Critical current of spin transfer torque-driven magnetization dynamics in magnetic multilayers,"The critical current of the spin transfer torque-driven magnetization
+dynamics was studied by taking into account both spin pumping and the finite
+penetration depth of the transverse spin current. We successfully reproduced
+the recent experimental results obtained by Chen et al. [Phys. Rev. B {\bf 74},
+144408 (2006)] and found that the critical current remains finite even in the
+zero-thickness limit of the free layer. We showed that the remaining value of
+the critical current is determined mainly by spin pumping.",0806.1822v2
+2008-07-18,Current-induced dynamics of spiral magnet,"We study the dynamics of the spiral magnet under the charge current by
+solving the Landau-Lifshitz-Gilbert equation numerically. In the steady state,
+the current ${\vec j}$ induces (i) the parallel shift of the spiral pattern
+with velocity $v=(\beta/\alpha)j$ ($\alpha$, $\beta$: the Gilbert damping
+coefficients), (ii) the uniform magnetization $M$ parallel or anti-parallel to
+the current depending on the chirality of the spiral and the ratio $\beta /
+\alpha $, and (iii) the change in the wavenumber $k$ of the spiral. These are
+analyzed by the continuum effective theory using the scaling argument, and the
+various nonequilibrium phenomena such as the chaotic behavior and
+current-induced annealing are also discussed.",0807.2901v1
+2008-07-29,Dynamically Induced Zeeman Effect in Massless QED,"It is shown that in non-perturbative massless QED an anomalous magnetic
+moment is dynamically induced by an applied magnetic field. The induced
+magnetic moment produces a Zeeman splitting for electrons in Landau levels
+higher than $l=0$. The expressions for the non-perturbative Lande g-factor and
+Bohr magneton are obtained. Possible applications of this effect are outlined.",0807.4744v2
+2008-11-28,Effect of Nonlocal Spin-Transfer Torque on Current-Induced Magnetization Dynamics,"Using the self-consistent model, we present nonlocal spin-transfer effects
+caused by the feedback between inhomogeneous magnetization and spin-transfer
+torque on the current-induced magnetization dynamics in nanomagnets. The
+nonlocal effects can substantially improve the coherence time of precession in
+nanomagnets and thus reduce the linewidth of power spectrum. This narrow
+linewidth results from the nonlinear damping of spin-waves due to the nonlocal
+spin torque which is inherent and thus should be considered in future
+experiments.",0811.4649v1
+2009-01-23,Magnetic pseudodifferential operators with coefficients in C*-algebras,"In previous articles, a magnetic pseudodifferential calculus and a family of
+C*-algebras associated with twisted dynamical systems were introduced and the
+connections between them have been established. We extend this formalism to
+symbol classes of H\""ormander type with an x-behavior modelized by an abelian
+C*-algebra. Some of these classes generate C*-algebras associated with the
+twisted dynamical system. We show the relevance of these classes to the
+spectral analysis of pseudodifferential operators with anisotropic symbols and
+magnetic fields.",0901.3704v1
+2009-07-03,Dynamical electron transport through a nanoelectromechanical wire in a magnetic field,"We investigate dynamical transport properties of interacting electrons moving
+in a vibrating nanoelectromechanical wire in a magnetic field. We have built an
+exactly solvable model in which electric current and mechanical oscillation are
+treated fully quantum mechanically on an equal footing. Quantum mechanically
+fluctuating Aharonov-Bohm phases obtained by the electrons cause nontrivial
+contribution to mechanical vibration and electrical conduction of the wire. We
+demonstrate our theory by calculating the admittance of the wire which are
+influenced by the multiple interplay between the mechanical and the electrical
+energy scales, magnetic field strength, and the electron-electron interaction.",0907.0546v1
+2009-11-08,Nonequilibrium dynamical ferromagnetism of interacting Single-Molecule Magnets,"We propose a nonequilibrium Monte Carlo (MC) approach to explore
+nonequilibrium dynamical ferromagnetism of interacting single molecule magnets
+(SMMs). Both quantum spin tunneling and thermally activated spin reversal are
+successfully implemented in the same MC simulation framework. Applied to a
+typical example, this simulation method satisfactorily reproduces experimental
+magnetization curves with experimental parameters. Our results show that both
+quantum and classical effects are essential to determine the hysteresis
+behaviors. This method is effective and reliable to gain deep insights into
+SMMs.",0911.1539v1
+2010-03-01,Vortex dynamics in superconducting channels with periodic constrictions,"Vortices confined to superconducting easy flow channels with periodic
+constrictions exhibit reversible oscillations in the critical current at which
+vortices begin moving as the external magnetic field is varied. This
+commensurability scales with the channel shape and arrangement, although
+screening effects play an important role. For large magnetic fields, some of
+the vortices become pinned outside of the channels, leading to magnetic
+hysteresis in the critical current. Some channel configurations also exhibit a
+dynamical hysteresis in the flux-flow regime near the matching fields.",1003.0387v2
+2010-05-10,Nonlinearity in a dynamo,"Using a rotating flat layer heated from below as an example, we consider
+effects which lead to stabilizing an exponentially growing magnetic field in
+magnetostrophic convection in transition from the kinematic dynamo to the full
+non-linear dynamo. We present estimates of the energy redistribution over the
+spectrum and helicity quenching by the magnetic field. We also study the
+alignment of the velocity and magnetic fields. These regimes are similar to
+those in planetary dynamo simulations.",1005.1557v1
+2010-06-21,Quantum Fluctuations and Dynamic Clustering of Fluctuating Cooper Pairs,"We derive exact expressions for the fluctuation conductivity in two
+dimensional superconductors as a function of temperature and magnetic field in
+the whole fluctuation region above the upper critical field H_{c2}(T). Focusing
+on the vicinity of the quantum phase transition near zero temperature, we
+propose that as the magnetic field approaches the line near H_{c2}(0) from
+above, a peculiar dynamic state consisting of clusters of coherently rotating
+fluctuation Cooper-pairs forms and estimate the characteristic size and
+lifetime of such clusters. We find the zero temperature magnetic field
+dependence of the the transverse magnetoconductivity above H_{c2}(0) in layered
+superconductors.",1006.4124v1
+2010-10-12,Coherent spin-current oscillations in transverse magnetic fields,"We address the coherence of the dynamics of spin-currents with components
+transverse to an external magnetic field for the spin-1/2 Heisenberg chain. We
+study current autocorrelations at finite temperatures and the real-time
+dynamics of currents at zero temperature. Besides a coherent Larmor
+oscillation, we find an additional collective oscillation at higher
+frequencies, emerging as a coherent many-magnon effect at low temperatures.
+Using numerical and analytical methods, we analyze the oscillation frequency
+and decay time of this coherent current-mode versus temperature and magnetic
+field.",1010.2351v2
+2010-12-16,Magnetic dynamics driven by the spin-current generated via spin-Seebeck effect,"We consider the spin-current driven dynamics of a magnetic nanostructure in a
+conductive magnetic wire under a heat gradient in an open circuit, spin Seebeck
+effect geometry. It is shown that the spin-current scattering results in a
+spin-current torque acting on the nanostructure and leading to precession and
+displacement. The scattering leads also to a redistribution of the spin
+electrochemical potential along the wire resulting in a break of the
+polarity-reversal symmetry of the inverse spin Hall effect voltage with respect
+to the heat gradient inversion.",1012.3552v2
+2011-02-11,Dynamics of nonlinear ion-waves in Fermi-Dirac electron-positron-ion magnetoplasmas,"Oblique propagation and head-on collisions of solitary structures is studied
+in a dense magnetized plasma comprised of relativistic ultra-cold electrons and
+positrons and positive dynamic ions using conventional extended multi-scales
+technique, in the ground of quantum hydrodynamics model. The variations of
+head-on collision phase-shift as well as the characteristic soliton amplitude
+and width is evaluated numerically in terms of other plasma parameters such as
+mass-density, normalized magnetic field strength, its angle with respect to the
+soliton propagation and the relative positron number-density. The relevance of
+current investigations, with appropriate plasma parameters for the
+astrophysical dense magnetized objects such as white-dwarfs, is addressed.",1102.2365v1
+2011-04-21,Spin Damping Monopole,"We present theoretical evidence that a magnetic monopole emerges in dynamic
+magnetic systems in the presence of the spin-orbit interaction. The monopole
+field is expressed in terms of spin damping associated with magnetization
+dynamics. We demonstrate that the observation of this spin damping monopole is
+accomplished electrically using Ampere's law for monopole current. Our
+discovery suggests the integration of monopoles into electronics, namely,
+monopolotronics.",1104.4215v2
+2011-05-30,Nonlogarithmic magnetization relaxation in HTSC,"An experimental study of low density captured magnetic flux dynamics in YBCO
+single crystal samples near the superconducting phase transition point has been
+performed. Vortex dynamics similar to thermally assisted flux flow regime
+(TAFF) has been observed for the first time in such weak fields. It will be
+shown that Zeldov's thermoactivated creep model successfully describes the
+behavior of the magnetization in the YBCO single crystals in our experiments.
+Within the framework of this model the estimation of normalized relaxation rate
+was made.",1105.5896v1
+2011-11-23,Rashba spin torque in an ultrathin ferromagnetic metal layer,"In a two-dimensional ferromagnetic metal layer lacking inversion symmetry,
+the itinerant electrons mediate the interaction between the Rashba spin-orbit
+interaction and the ferromagnetic order parameter, leading to a Rashba spin
+torque exerted on the magnetization. Using Keldysh technique, in the presence
+of both magnetism and a spin-orbit coupling, we derive a spin diffusion
+equation that provides a coherent description to the diffusive spin dynamics.
+The characteristics of the spin torque and its implication on magnetization
+dynamics are discussed in the limits of large and weak spin-orbit coupling.",1111.5466v1
+2012-01-27,Dynamics of Successive Minor Hysteresis Loops,"Cumulative growth of successive minor hysteresis loops in Co/Pd multilayers
+with perpendicular anisotropy was studied in the context of time dependent
+magnetization reversal dynamics. We show that in disordered ferromagnets, where
+magnetization reversal involves nucleation, domains' expansion and
+annihilation, differences between the time dependencies of these processes are
+responsible for accumulation of nuclei for rapid domain expansion, for the
+asymmetry of forward and backward magnetization reversals and for the
+respective cumulative growth of hysteresis loops. Loops stop changing and
+become macroscopically reproducible when populations of upward and downward
+nucleation domains balance each other and the respective upward and downward
+reversal times stabilize.",1201.5791v1
+2012-05-12,Ultrafast Time-Resolved Faraday Rotation in EuO Thin Films,"We have investigated the ultrafast spin dynamics in EuO thin films by
+time-resolved Faraday rotation spectroscopy. The photoinduced magnetization is
+found to be increased in a transient manner, accompanied with subsequent
+demagnetization. The dynamical magnetization enhancement showed a maximum
+slightly below the Curie temperature with prolonged tails toward both lower and
+higher temperatures and dominates the demagnetization counterpart at 55 K. The
+magnetization enhancement component decays in ~1 ns. The realization of the
+transient collective ordering is attributable to the enhancement of the f-d
+exchange interaction.",1205.2818v2
+2012-07-17,Ultrafast dynamical path for the switching of a ferrimagnet after femtosecond heating,"Ultrafast laser-induced magnetic switching in rare earth, transition metal
+ferrimagnetic alloys has recently been reported to occur by ultrafast heating
+alone. Using atomistic simulations and a ferrimagnetic Landau-Lifshitz-Bloch
+formalism, we demonstrate that for switching to occur it is necessary that
+angular momentum is transferred from the longitudinal to transverse
+magnetization components. This dynamical path leads to magnetization switching
+and subsequent ultrafast precession caused by the inter-sublattice exchange
+field on the nanoscale.",1207.4092v2
+2013-01-11,Exact Relation with Two-point Correlation Functions and Phenomenological Approach for Compressible Magnetohydrodynamic Turbulence,"Compressible isothermal magnetohydrodynamic turbulence is analyzed under the
+assumption of statistical homogeneity and in the asymptotic limit of large
+kinetic and magnetic Reynolds numbers. Following Kolmogorov we derive an exact
+relation for some two-point correlation functions which generalizes the
+expression recently found for hydrodynamics. We show that the magnetic field
+brings new source and flux terms into the dynamics which may act on the
+inertial range similarly as a source or a sink for the mean energy transfer
+rate. The introduction of a uniform magnetic field simplifies significantly the
+exact relation for which a simple phenomenology may be given. A prediction for
+axisymmetric energy spectra is eventually proposed.",1301.2470v1
+2013-01-16,Kinematic and dynamic vortices in a thin film driven by an applied current and magnetic field,"Using a Ginzburg-Landau model, we study the vortex behavior of a rectangular
+thin film superconductor subjected to an applied current fed into a portion of
+the sides and an applied magnetic field directed orthogonal to the film.
+  Through a center manifold reduction we develop a rigorous bifurcation theory
+for the appearance of periodic solutions in certain parameter regimes near the
+normal state. The leading order dynamics yield in particular a motion law for
+kinematic vortices moving up and down the center line of the sample. We also
+present computations that reveal the co-existence and periodic evolution of
+kinematic and magnetic vortices.",1301.3801v1
+2013-05-23,Absolute cross-section normalization of magnetic neutron scattering data,"We discuss various methods to obtain the resolution volume for neutron
+scattering experiments, in order to perform absolute normalization on inelastic
+magnetic neutron scattering data. Examples from previous experiments are given.
+We also try to provide clear definitions of a number of physical quantities
+which are commonly used to describe neutron magnetic scattering results,
+including the dynamic spin correlation function and the imaginary part of the
+dynamic susceptibility. Formulas that can be used for general purposes are
+provided and the advantages of the different normalization processes are
+discussed.",1305.5521v1
+2013-07-18,Spin correlated dielectric memory and rejuvenation in relaxor ferroelectric CuCrS2,"CuCrS2, a Heisenberg antiferromagnet with layered edge sharing triangular
+lattice, exhibits a spiral magnetic order. Dielectric (E) and polarization
+studies show magnetoelectric (ME) coupling at Neel temperature (T_N=38 K) where
+simultaneous dielectric and magnetic long range order occur. The compound shows
+a diffused ferroelectric (FE) transition and slow relaxation dynamics above
+T_N, indicative of relaxor FE behavior. Interestingly, memory effect and
+magnetic field induced rejuvenation are also observed in E, establishing
+cooperative glassy dynamics and ME coupling even above T_N. We discuss the role
+of geometrical frustration and metal ligand hybridization for these unusual
+properties.",1307.4859v1
+2013-11-06,Competing interaction in magnets: the root of ordered disorder or only frustration?,"What does the equilibrium atomic, molecular or spin configuration of a glass
+phase look like? Is there only one unique equilibrium configuration or are
+there infinitely many configurations of equal energy? The processes and
+mechanisms governing the path towards equilibrium, i.e. the dynamics of glassy
+systems, provide insights to these questions. Here we discuss the intrinsic
+dynamics of different glassy magnets: of spin-glasses, frustrated ferromagnets,
+superspin-glasses and other nanostructured systems with competing ferro- and
+antiferromagnetic interactions and randomness in their spatial distribution.
+This paper is intended as a brief update on some unsolved problems and the
+current empirical status in the field of disordered and frustrated magnetism.",1311.1350v1
+2013-12-03,Dynamical properties of three terminal magnetic tunnel junctions: spintronics meets spin-orbitronics,"This letter introduces a micromagnetic model able to characterize the
+magnetization dynamics in three terminal magnetic tunnel junctions, where the
+effects of spin-transfer torque and spin-orbit torque are taken into account.
+Our results predict that the possibility to separate electrically those two
+torque sources is very promising from a technological point of view for both
+next generation of nanoscale spintronic oscillators and microwave detectors. A
+scalable synchronization scheme based on the parallel connection of those three
+terminal devices is also proposed.",1312.0806v1
+2014-05-15,Larmor precession of the octet baryons in view of the general QCD parametrization,"We apply general QCD parametrization to describe an octet baryon at rest in a
+static and uniform magnetic field, in order to demonstrate a dynamical
+implementation of the hadron model. The derived evolution has the asymptote of
+Larmor precession, governed by an effective magnetic dipole moment coupling.
+The parameters appear in the effective magnetic dipole moment has been studied
+in the original works in kinematic settings. Here we show that the parameters
+have actual dynamical meaning, and are indeed measured by the process.",1405.3779v1
+2014-06-18,Axial Current driven by Magnetization Dynamics in Weyl Semimetals,"We theoretically study the axial current $\bm{j}_5$ (defined as the
+difference between the charge current with opposite chirality) in doped Weyl
+semimetal using a Green's function technique. We show that the axial current is
+controlled by the magnetization dynamics in a magnetic insulator attached to a
+Weyl semimetal. We find that the induced axial current can be detected by using
+ferromagnetic resonance or the inverse spin Hall effect and can be converted
+into charge current with no accompanying energy loss. These properties make
+Weyl semimetal advantageous for application to low-consumption electronics with
+new functionality.",1406.4636v1
+2014-07-21,Josephson junction with a magnetic vortex,"We have studied Josephson tunneling through a circularly polarized micron or
+submicron-size disk of a soft ferromagnetic material. Such a disk contains a
+vortex that exhibits rich classical dynamics and has recently been proposed as
+a tool to study quantum dynamics of the nanoscale vortex core. The change in
+the Josephson current that is related to a tiny displacement of the vortex core
+has been computed analytically and plotted numerically for permalloy disks used
+in experiments. It is shown that a Josephson junction with a magnetic disk in
+the vortex state can be an interesting physical system that may be used to
+measure the nanoscale motion of the magnetic vortex.",1407.5419v1
+2014-08-22,The mean-field dynamo model,"The 2D Parker's mean-field dynamo equations with a various distributions of
+the $\alpha$- and $\omega$-effects are considered. We show that smooth profiles
+of $\alpha$ and $\omega$ can produce dipole configuration of the magnetic field
+with the realistic magnetic energy spectrum. We emphasize that fluctuating
+$\alpha$-effect leads to increase of the magnetic energy at the small scales,
+breaking the dipole configuration of the field. The considered geostrophic
+profiles of $\alpha$ and $\omega$ correspond to the small-scale
+polarwards/equatorwards travelling waves with the small dipole field
+contribution. The same result is observed for the dynamic form of the
+$\alpha$-quenching, where two branches of the weak and strong solution coexist.",1408.5202v1
+2014-09-29,On heteroclinic separators of magnetic fields in electrically conducting fluids,"In this paper we partly solve the problem of existence of separators of a
+magnetic field in plasma. We single out in plasma a 3-body with a boundary in
+which the movement of plasma is of special kind which we call an (a-d)-motion.
+We prove that if the body is the 3-annulus or the ""fat"" orientable surface with
+two holes the magnetic field necessarily have a heteroclinic separator. The
+statement of the problem and the suggested method for its solution lead to some
+theoretical problems from Dynamical Systems Theory which are of interest of
+their own.",1409.8189v2
+2014-10-14,Dynamics and thermodynamics of a pair of interacting magnetic dipoles,"We consider the dynamics and thermodynamics of a pair of magnetic dipoles
+interacting via their magnetic fields. We consider only the ""spin"" degrees of
+freedom; the dipoles are fixed in space. With this restriction it is possible
+to provide the general solution of the equations of motion in analytical form.
+Thermodynamic quantities, such as the specific heat and the zero field
+susceptibility are calculated by combining low temperature asymptotic series
+and a complete high temperature expansion. The thermal expectation value of the
+autocorrelation function is determined for the low temperature regime including
+terms linear in $T$. Furthermore, we compare our analytical results with
+numerical calculations based on Monte Carlo simulations.",1410.3700v1
+2014-10-21,Magnetic switching dynamics in a ferrimagnetic two sub-lattice model including ultrafast exchange scattering,"We study the heat-induced magnetization dynamics in a toy model of a
+ferrimagnetic alloy, which includes localized spins antiferromagnetically
+coupled to an itinerant carrier system with a Stoner gap. We determine the
+one-particle spin-density matrix including exchange scattering between
+localized and itinerant bands as well as scattering with phonons. While a
+transient ferromagnetic-like state can always be achieved by a sufficiently
+strong excitation, this transient ferromagnetic-like state only leads to
+magnetization switching for model parameters that also yield a compensation
+point in the equilibrium M(T) curve.",1410.5745v2
+2015-01-28,Field induced anisotropic cooperativity in a magnetic colloidal glass,"The translational dynamics in a repulsive colloidal glass-former is probed by
+time-resolved X-ray Photon Correlation Spectroscopy. In this dense dispersion
+of charge-stabilized and magnetic nanoparticles, the interaction potential can
+be tuned, from quasi-isotropic to anisotropic by applying an external magnetic
+field. Structural and dynamical anisotropies are reported on interparticle
+lengthscales associated with highly anisotropic cooperativity, almost two
+orders of magnitude larger in the field direction than in the perpendicular
+direction and in zero field.",1501.07208v2
+2015-03-07,Collisionless spin dynamics in a magnetic field gradient,"We study the collisionless spin dynamics of a harmonically trapped Fermi gas
+in a magnetic field gradient. In the absence of interactions, the system
+evolution is periodic: the magnetization develops twists, which evolve into a
+longitudinal polarization. Recurrences follow. For weak interaction, the
+exchange interactions lead to beats in these oscillations. We present an array
+of analytic and numerical techniques for studying this physics.",1503.02131v2
+2015-04-02,Magnetic Phenomena in Holographic Superconductivity with Lifshitz Scaling,"We investigate the effects of Lifshitz dynamical critical exponent z on a
+family of minimal D=4+1 holographic superconducting models, with a particular
+focus on magnetic phenomena. We see that it is possible to have a consistent
+Ginzburg-Landau approach to holographic superconductivity in a Lifshitz
+background. By following this phenomenological approach we are able to compute
+a wide array of physical quantities. We also calculate the Ginzburg-Landau
+parameter for different condensates, and conclude that in systems with higher
+dynamical critical exponent, vortex formation is more strongly unfavored
+energetically and exhibit a stronger Type I behavior. Finally, following the
+perturbative approach proposed by Maeda, Natsuume and Okamura, we calculate the
+critical magnetic field of our models for different values of z.",1504.00444v1
+2015-04-09,Quantum dynamics of a spin-1/2 charged particle in the presence of magnetic field with scalar and vector couplings,"The quantum dynamics of a spin-1/2 charged particle in the presence of
+magnetic field is analyzed for the general case where scalar and vector
+couplings are considered. The energy spectra are explicitly computed for
+different physical situations, as well as their dependencies on the magnetic
+field strength, spin projection parameter and vector and scalar coupling
+constants.",1504.02316v1
+2015-05-08,Thermal vector potential theory of magnon-driven magnetization dynamics,"Thermal vector potential formulation is applied to study thermal dynamics of
+magnetic structures in insulating ferromagnets. By separating variables of the
+magnetic structure and magnons, the equation of motion for the structure
+including spin-transfer effect due to thermal magnons is derived in the case of
+a domain wall and a vortex. The magnon current is evaluated based on a linear
+response theory with respect to the thermal vector potential representing the
+temperature gradient. It is shown that the velocity of a domain wall when
+driven by thermal magnon has a strong temperature dependence unlike the case of
+an electrically-driven domain wall in metals.",1505.01908v1
+2015-08-23,Rotational properties of ferromagnetic nanoparticles driven by a precessing magnetic field in a viscous fluid,"We study the deterministic and stochastic rotational dynamics of
+ferromagnetic nanoparticles in a precessing magnetic field. Our approach is
+based on the system of effective Langevin equations and on the corresponding
+Fokker-Planck equation. Two key characteristics of the rotational dynamics, the
+average angular frequency of precession of nanoparticles and their average
+magnetization, are of our interest. Using the Langevin and Fokker-Planck
+equations, we calculate both analytically and numerically these characteristics
+in the deterministic and stochastic cases, determine their dependence on the
+model parameters, and analyze in detail the role of thermal fluctuations.",1508.05651v1
+2016-03-29,Kinematic dynamo in two-dimensional chaotic flow: the initial and final stages,"The small-scale kinematic dynamo in a two-dimensional chaotic flow is
+studied. The analytic approach is developed in framework of the
+Kraichnan-Kazantsev model. It is shown that the growth of magnetic field
+$\bm{B}$ fluctuations stops at large times in accordance with so-called
+anti-dynamo theorems. The value of $\bm{B}^2$ increased therewith in square of
+the magnetic Prandtl number times. The spatial structure of the correlation
+tensor of the magnetic field is found.",1603.08771v1
+2016-08-22,Four dimensional quantum oscillator and magnetic-monopole with U(1) dynamical group,"By using of an appropriate transformation, it was shown that the quantum
+system of 4 dimensional simple harmonic oscillator can describe the motion of a
+charged particle in the presence of a magnetic monopole field. It was shown
+that the Dirac magnetic monopole has the hidden algebra of U(1) symmetry and by
+reducing of the dimensions of space, the U(1)*U(1) dynamical group for 4D
+harmonic oscillator quantum system was obtained. Using the group representation
+and based on explicit solution of the obtained differential equation, the
+spectrum of system was calculated.",1608.06085v1
+2017-06-06,Search for torsional oscillations in isolated sunspots,"In this work we seek evidence for global torsional oscillations in alpha
+sunspots. We have used long time series of continuum intensity and magnetic
+field vector maps from the Helioseismic and Magnetic Imager (HMI) instrument on
+board the Solar Dynamics Observatory (SDO) spacecraft. The time series analysed
+here span the total disk passage of 25 isolated sunspots. We found no evidence
+of global long-term periodic oscillations in the azimuthal angle of the sunspot
+magnetic field within $\sim$ 1 degree. This study could help us to understand
+the sunspot dynamics and its internal structure.",1706.01952v1
+2017-10-11,Oscillatory behavior of the domain wall dynamics in a curved cylindrical magnetic nanowire,"Understanding the domain wall dynamics is an important issue in modern
+magnetism. Here we present results of domain wall displacement in curved
+cylindrical nanowires at a constant magnetic field. We show that the average
+velocity of a transverse domain wall increases with curvature. Contrary to what
+it is observed in stripes, in a curved wire the transverse domain wall
+oscillates along and rotates around the nanowire with the same frequency. These
+results open the possibility of new oscillation-based applications.",1710.04316v1
+2017-12-11,Testing the Dynamic Time Warping algorithm in the Seafloor Spreading Rate Problem,"We offer to apply the powerful Dynamic Time Warping (DTW) algorithm to find
+the spreading rate variation by comparing profiles of marine magnetic anomalies
+with the synthetic field constructed by the magnetic polarity reference scale.
+For the fixed spreading rate and the given interval of the polarity scale we
+generate the synthetic magnetic fields which we compare with the field obtained
+for temporal variations of seafloor spreading rate.",1712.03920v1
+2018-03-08,Relativistic quantum dynamics of twisted electron beams in arbitrary electric and magnetic fields,"General relativistic quantum dynamics of twisted (vortex) Dirac particles is
+constructed. The Hamiltonian and equations of motion in the Foldy-Wouthuysen
+representation are derived for a twisted relativistic electron in arbitrary
+electric and magnetic fields. A critical experiment for a verification of the
+results is proposed. The new important effect of a radiative orbital
+polarization of a twisted electron beam in a magnetic field resulting in a
+nonzero average projection of the intrinsic orbital angular momentum on the
+field direction is predicted.",1803.07410v2
+2018-05-13,The contact property for magnetic flows on surfaces,"This is the author's PhD Thesis (University of Cambridge, 2014) in its
+original form. In the first part, using an invariance result, we compute the
+symplectic homology of contact-type energy levels for magnetic systems on
+surfaces, provided the energy is very large or very small. In the second part,
+which is partially contained in the later paper (Benedetti, Ergod. Theory
+Dynam. Syst., 2016), we discuss some rotationally symmetric examples and
+establish dynamical convexity for symplectic magnetic flows on low energy
+levels.",1805.04916v1
+2018-10-18,Spectral analysis of magnetic fields in simulated galaxy clusters,"We introduce a new sample of galaxy clusters obtained from a cosmological
+simulation covering an unprecedented dynamical range. All the clusters in our
+sample show a clear signature of small-scale dynamo amplification. We show that
+it is possible to use dynamo theory for studying the magnetic spectrum in the
+intracluster medium. We study if the intrinsic variations on the spectra depend
+on the dynamical history of each cluster or on some host cluster properties.",1810.08009v1
+2018-10-26,Pointwise vanishing velocity helicity of a flow does not preclude magnetic field generation,"Pointwise zero velocity helicity density is shown not to prevent steady flows
+from acting as kinematic dynamos. We present numerical evidences that such
+flows can generate both small-scale magnetic fields as well as, by the magnetic
+$\alpha$-effect or negative eddy diffusivity mechanisms, large-scale ones. The
+flows are constructed as curls of analytically defined space-periodic steady
+solenoidal flows, whose vorticity helicity (i.e., kinetic helicity) density is
+everywhere zero.",1811.00859v3
+2019-06-14,Rotational tuning of the dipole-dipole interaction in a Bose gas of magnetic atoms,"We investigate the dynamics of a Bose-Einstein condensate of magnetic atoms
+in which the dipoles are rotated by an external magnetic field. The
+time-averaged dipole-dipole interaction between the atoms is effectively tuned
+by this rotation, however recent experimental and theoretical developments show
+that dynamic instabilities emerge that may cause heating. We present
+simulations of a realistic tuning sequence in this system, and characterize the
+system behavior and the emergence of instabilities. Our results indicate that
+the instabilities develop more slowly as the rotation frequency increases, and
+indicate that experiments with tuned dipole-dipole interactions should be
+feasible.",1906.06115v2
+2019-06-27,Density functional perturbation theory for lattice dynamics with fully relativistic ultrasoft pseudopotentials: the magnetic case,"We extend density functional perturbation theory for lattice dynamics with
+fully relativistic ultrasoft pseudopotentials to magnetic materials. Our
+approach is based on the application of the time-reversal operator to the
+Sternheimer linear system and to its self-consistent solutions. Moreover, we
+discuss how to include in the formalism the symmetry operations of the magnetic
+point group which require the time-reversal operator. We validate our
+implementation by comparison with the frozen phonon method in fcc Ni and in a
+monatomic ferromagnetic Pt wire.",1906.11673v1
+2019-09-19,Magnetization dynamics of the compensated ferrimagnet $Mn_{2}Ru_{x}Ga$,"Here we study both static and time-resolved dynamic magnetic properties of
+the compensated ferrimagnet from room temperature down to 10K, thus crossing
+the magnetic compensation temperature $T_{M}$. The behaviour is analysed with a
+model of a simple collinear ferrimagnet with uniaxial anisotropy and
+site-specific gyromagnetic ratios. We find a maximum zero-applied-field
+resonance frequency of $\sim$160GHz and a low intrinsic Gilbert damping
+$\alpha$$\sim$0.02, making it a very attractive candidate for various
+spintronic applications.",1909.09085v1
+2019-11-04,Sum rules in zone axis STEM-orbital angular momentum resolved electron magnetic chiral dichroism,"In this work we derive sum rules for orbital angular momentum(OAM) resolved
+electron magnetic chiral dichroism (EMCD) which enable the evaluation of the
+strength of spin and orbital components of the atomic magnetic moments in a
+crystalline sample. We also demonstrate through numerical simulations that
+these rules appear to be only slightly dependent from the dynamical diffraction
+of the electron beam in the sample, making possible their application without
+the need of additional dynamical diffraction calculations.",1911.02006v1
+2019-11-11,The Rayleigh Bubble in Quark Matter under a Strong Magnetic Field,"The transition of QGP from fluid-dynamical regime to freeze-out is
+accompanied by the onset of instabilities. In the present paper we investigate
+the impact of the magnetic field on the Rayleigh instability. We show that
+extremely strong field generated in peripheral heavy ion collisions has an
+insignificant influence on the Rayleigh bubble dynamics. Magnetic ""friction""
+turns out to be much weaker than the viscous one.",1911.04148v2
+2020-01-29,Relative Equilibria of Magnetic Micro-Swimmers,"We revisit the dynamics of a permanent-magnetic rigid body submitted to a
+spatially-uniform steadily-rotating magnetic field in Stokes flow. We propose
+an analytical parameterisation of the full set of equilibria depending on two
+key experimental parameters, and show how it brings further understanding that
+helps to optimise magnetisation and operating parameters. The system is often
+bistable when it reaches its optimal swimming velocity. A handling strategy is
+proposed that guarantees that the correct equilibrium is reached.",2002.00740v1
+2020-08-05,Time scales in the thermal dynamics of magnetic dipolar clusters,"The collective behavior of thermally active structures offers clues on the
+emergent degrees of freedom and the physical mechanisms that determine the low
+energy state of a variety of systems. Here, the thermally active dynamics of
+magnetic dipoles at square plaquettes is modeled in terms of Brownian
+oscillators in contact with a heat bath. Solution of the Langevin equation for
+a set of interacting x-y dipoles allows the identification of the time scales
+and correlation length that reveal how interactions, temperature, damping and
+inertia may determine the frequency modes of edge and bulk magnetic mesospins
+in artificial dipolar systems.",2008.01891v2
+2020-08-27,Nutation Resonance in Ferromagnets,"The inertial dynamics of magnetization in a ferromagnet is investigated
+theoretically. The analytically derived dynamic response upon microwave
+excitation shows two peaks: ferromagnetic and nutation resonances. The exact
+analytical expressions of frequency and linewidth of the magnetic nutation
+resonance are deduced from the frequency dependent susceptibility determined by
+the inertial Landau-Lifshitz-Gilbert equation. The study shows that the
+dependence of nutation linewidth on the Gilbert precession damping has a
+minimum, which becomes more expressive with increase of the applied magnetic
+field.",2008.12221v3
+2021-01-19,Dynamics of quantum discord of two coupled spin-1/2 subjected to time-dependent magnetic fields,"We describe the dynamics of quantum discord of two interacting spin-1/2
+subjected to controllable time-dependent magnetic fields. The exact time
+evolution of discord is given for various input mixed states consisting of
+classical mixtures of two Bell states. The quantum discord manifests a complex
+oscillatory behaviour in time and is compared with that of quantum
+entanglement, measured by concurrence. The interplay of the action of the
+time-dependent magnetic fields and the spin-coupling mechanism in the
+occurrence and evolution of quantum correlations is examined in detail.",2101.07697v1
+2021-06-03,Ultrafast Electron Dynamics in Magnetic Thin Films,"In past decades, ultrafast spin dynamics in magnetic systems have been
+associated with heat deposition from high energy laser pulses, limiting the
+selective access to spin order. Here we use a long wavelength terahertz pump
+optical probe setup to measure structural features in the ultrafast time scale.
+We find that complete demagnetisation is possible with <6 THz pulses. This
+occurs concurrently with longitudinal acoustic phonons and an electronic
+response, followed by the magnetic response. The required fluence for full
+demagnetisation is low, ruling out the necessity of a high power light source.",2106.01828v1
+2022-06-01,Dynamic Fingerprints of Synthetic Antiferromagnet Nanostructures with Interfacial Dzyaloshinskii-Moriya Interaction,"Synthetic antiferromagnet (SAF) nanostructures with interfacial
+Dzyaloshinskii-Moriya interaction can host topologically distinct spin textures
+such as skyrmions and thus are regarded as promising candidates for both
+spintronics and magnonics applications. Here, we present comprehensive
+micromagnetic simulations of such material systems and discuss the rich phase
+diagrams that contain various types of magnetic configurations. Aside from the
+static properties, we further discuss the resonant excitations of the
+calculated magnetic states which include individual skyrmions and skyrmioniums.
+Finally, the internal modes of SAF skyrmion clusters are studied and discussed
+in the context of magnetic sensing applications based on the dynamic
+fingerprint in broadband ferromagnetic resonance measurements.",2206.00554v2
+2023-06-13,Angle dependence of $^{15}$N nuclear spin dynamics in diamond NV centers,"We report on the dynamics of the Rabi oscillation and the Larmor precession
+of $^{15}$N nuclear spin using nonselective short microwave pulses for
+initialization of $^{15}$N nuclear spins. We observe the Larmor precession of
+$^{15}$N nuclear spin depending on the angle between the applied magnetic field
+and the axis of the nitrogen vacancy center. We propose to utilize the change
+of the Larmor frequency of the nuclear spins to detect static magnetic fields
+at high sensitivity. Our results may contribute to enhancing the sensitivity of
+dc magnetic fields and devising novel protocols using $^{15}$N nuclear spin in
+nitrogen vacancy centers in diamonds.",2306.07556v1
+2023-06-14,A magnetic falling-sphere viscometer,"We present a falling-sphere viscometer with a magnetized sphere and fluxgate
+magnetometers continuously measuring the magnetic field produced at the sensor
+positions by the falling sphere. With a fluid volume of 15 ml and within a few
+seconds, we directly measure dynamical viscosities in a range between 200 cP
+and 3000 cP with a precision of 3\%.",2306.08725v2
+2023-09-06,Optimal Control of the 2D Landau-Lifshitz-Gilbert Equation with Control Energy in Effective Magnetic Field,"The optimal control of magnetization dynamics in a ferromagnetic sample at a
+microscopic scale is studied. The dynamics of this model is governed by the
+Landau-Lifshitz-Gilbert equation on a two-dimensional bounded domain with the
+external magnetic field (the control) applied through the effective field. We
+prove the global existence and uniqueness of a regular solution in $\mathbb
+S^2$ under a smallness condition on control and initial data. We establish the
+existence of optimal control and derive a first-order necessary optimality
+condition using the Fr\'echet derivative of the control-to-state operator and
+adjoint problem approach.",2309.02786v1
+2023-10-19,Crossover from string to cluster dynamics following a field quench in spin ice,"We investigate quench dynamics of spin ice after removal of a strong magnetic
+field along the [100] crystal direction, using Monte Carlo simulations and
+theoretical arguments. We show how the early-time relaxation of the
+magnetization can be understood in terms of nucleation and growth of strings of
+flipped spins, in agreement with an effective stochastic model that we
+introduce and solve analytically. We demonstrate a crossover at longer times to
+a regime dominated by approximately isotropic clusters, which we characterize
+in terms of their morphology, and present evidence for a percolation transition
+as a function of magnetization.",2310.12410v2
+2024-01-17,Dynamic behavior of the antiferromagnetically coupled bilayer Ising model,"Using the path probability and lowest approximation of cluster variation
+method, we study the dynamic and equilibrium properties of a bilayer magnetic
+system, consisting of two ferromagnetic monolayers antiferromagnetically
+coupled for different spins $(\sigma=1/2$ and $S=1)$. Firstly, numerical
+results of the monolayer and total magnetizations are presented under the
+effect of the diverse physical parameters, and the phase diagrams of bilayer
+system are discussed. Then, since it is well established that the path
+probability method is an effective method for the existence of metastable
+states, the time evolution of monolayer- and total magnetizations is
+investigated.",2401.09360v1
+2009-10-06,Diffusion of magnetic field and removal of magnetic flux from clouds via turbulent reconnection,"The diffusion of astrophysical magnetic fields in conducting fluids in the
+presence of turbulence depends on whether magnetic fields can change their
+topology via reconnection in highly conducting media. Recent progress in
+understanding fast magnetic reconnection in the presence of turbulence is
+reassuring that the magnetic field behavior in computer simulations and
+turbulent astrophysical environments is similar, as far as magnetic
+reconnection is concerned. Our studies of magnetic field diffusion in turbulent
+medium reveal interesting new phenomena. In the presence of gravity and
+turbulence, our 3D simulations show the decrease of the magnetic flux-to-mass
+ratio as the gaseous density at the center of the gravitational potential
+increases. We observe this effect both in the situations when we start with
+equilibrium distributions of gas and magnetic field and when we follow the
+evolution of collapsing dynamically unstable configurations. Thus the process
+of turbulent magnetic field removal should be applicable both to quasi-static
+subcritical molecular clouds and cores and violently collapsing supercritical
+entities. The increase of the gravitational potential as well as the
+magnetization of the gas increases the segregation of the mass and magnetic
+flux in the saturated final state of the simulations, supporting the notion
+that the reconnection-enabled diffusivity relaxes the magnetic field + gas
+system in the gravitational field to its minimal energy state. This effect is
+expected to play an important role in star formation, from its initial stages
+of concentrating interstellar gas to the final stages of the accretion to the
+forming protostar.",0910.1117v3
+2016-11-29,Magnetic field evolution in tidal disruption events,"When a star gets tidally disrupted by a supermassive black hole, its magnetic
+field is expected to pervade its debris. In this paper, we study this process
+via smoothed particle magnetohydrodynamical simulations of the disruption and
+early debris evolution including the stellar magnetic field. As the gas
+stretches into a stream, we show that the magnetic field evolution is strongly
+dependent on its orientation with respect to the stretching direction. In
+particular, an alignment of the field lines with the direction of stretching
+induces an increase of the magnetic energy. For disruptions happening well
+within the tidal radius, the star compression causes the magnetic field
+strength to sharply increase by an order of magnitude at the time of pericentre
+passage. If the disruption is partial, we find evidence for a dynamo process
+occurring inside the surviving core due to the formation of vortices. This
+causes an amplification of the magnetic field strength by a factor of $\sim
+10$. However, this value represents a lower limit since it increases with
+numerical resolution. For an initial field strength of 1 G, the magnetic field
+never becomes dynamically important. Instead, the disruption of a star with a
+strong 1 MG magnetic field produces a debris stream within which magnetic
+pressure becomes similar to gas pressure a few tens of hours after disruption.
+If the remnant of one or multiple partial disruptions is eventually fully
+disrupted, its magnetic field could be large enough to magnetically power the
+relativistic jet detected from Swift J1644+57. Magnetized streams could also be
+significantly thickened by magnetic pressure when it overcomes the confining
+effect of self-gravity.",1611.09853v2
+2020-01-19,Disentangling magnetic and grain contrast in polycrystalline FeGe thin films using four-dimensional Lorentz scanning transmission electron microscopy,"The study of nanoscale chiral magnetic order in polycrystalline materials
+with a strong Dzyaloshinkii-Moriya interaction (DMI) is interesting for the
+observation of magnetic phenomena at grain boundaries and interfaces. One such
+material is sputter-deposited B20 FeGe on Si, which has been actively
+investigated as the basis for low-power, high-density magnetic memory
+technology in a scalable material platform. Although conventional Lorentz
+electron microscopy provides the requisite spatial resolution to probe chiral
+magnetic textures in single-crystal FeGe, probing the magnetism of sputtered
+B20 FeGe is more challenging because the sub-micron crystal grains add
+confounding contrast. We address the challenge of disentangling magnetic and
+grain contrast by applying 4-dimensional Lorentz scanning transmission electron
+microscopy using an electron microscope pixel array detector. Supported by
+analytical and numerical models, we find that the most important parameter for
+imaging magnetic materials with polycrystalline grains is the ability for the
+detector to sustain large electron doses, where having a high-dynamic range
+detector becomes extremely important. Despite the small grain size in sputtered
+B20 FeGe on Si, using this approach we are still able to observe helicity
+switching of skyrmions and magnetic helices across two adjacent grains as they
+thread through neighboring grains. We reproduce this effect using micromagnetic
+simulations by assuming that the grains have distinct orientation and magnetic
+chirality and find that magnetic helicity couples to crystal chirality. Our
+methodology for imaging magnetic textures is applicable to other thin-film
+magnets used for spintronics and memory applications, where an understanding of
+how magnetic order is accommodated in polycrystalline materials is important.",2001.06900v3
+2020-05-07,A global model of the magnetorotational instability in protoneutron stars,"Magnetars are highly magnetized neutron stars whose magnetic dipole ranges
+from $10^{14}$ to $10^{15}$ G. The MRI is considered to be a promising
+mechanism to amplify the magnetic field in fast-rotating protoneutron stars and
+form magnetars. This scenario is supported by many local studies showing that
+magnetic fields could be amplified by the MRI on small scales. However, the
+efficiency of the MRI at generating a dipole field is still unknown. To answer
+this question, we study the MRI dynamo in an idealized global model of a fast
+rotating protoneutron star with differential rotation. We perform 3D
+incompressible MHD simulations in spherical geometry with explicit
+diffusivities where the differential rotation is forced at the outer boundary.
+We vary the initial magnetic field and investigated different magnetic boundary
+conditions. These simulations were compared to local shearing box simulations.
+We obtain a self-sustained turbulent MRI-driven dynamo, whose saturated state
+is independent of the initial magnetic field. The MRI generates a strong
+turbulent magnetic field of $B \geq 2\times 10^{15}$ G and a non-dominant
+magnetic dipole, which represents systematically about $5\%$ of the averaged
+magnetic field strength. Interestingly, this dipole is tilted towards the
+equatorial plane. We find that local shearing box models can reproduce fairly
+well several characteristics of global MRI turbulence such as the kinetic and
+magnetic spectra. The turbulence is nonetheless more vigorous in the local
+models than in the global ones. Overall, our results support the ability of the
+MRI to form magnetar-like large-scale magnetic fields. They furthermore predict
+the presence of a stronger small-scale magnetic field. The resulting magnetic
+field could be important to power outstanding stellar explosions, such as
+superluminous supernovae and GRBs.",2005.03567v2
+2020-06-08,Field-induced oscillation of magnetization blocking in holmium metallacrown magnet,"Single-molecule magnets (SMMs) are promising elements for quantum
+informatics. In the presence of strong magnetic anisotropy, they exhibit
+magnetization blocking - a magnetic memory effect at the level of a single
+molecule. Recent studies have shown that the SMM performance scales with the
+height of magnetization blocking barrier. By employing molecular engineering
+this can be significantly modified, remaining independent from other external
+factors such as magnetic field. Taking advantage of hyperfine coupling of
+electronic and nuclear spins further enhances their functionality, however, a
+poor understanding of relaxation mechanisms in such SMMs limits the
+exploitation of nuclear-spin molecular qubits. Here we report the opening
+discovery of field-dependent oscillation of the magnetization blocking barrier
+in a new holmium metallacrown magnet driven by the switch of relaxation
+mechanisms involving hyperfine interaction. Single-crystal magnetic hysteresis
+measurements combined with first-principles calculations reveal an activated
+temperature dependence of magnetic relaxation dominated either by incoherent
+quantum tunneling of magnetization at anti-crossing points of
+exchange-hyperfine states or by Orbach-like processes at crossing points. We
+demonstrate that these relaxation mechanisms can be consecutively switched on
+and off by increasing the external field, which paves a way for manipulating
+the magnetization dynamics of SMMs using hyperfine interaction.",2006.04401v1
+2021-09-19,Improvement of the Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Inversion Code,"A spectral line inversion code, Very Fast Inversion of the Stokes Vector
+(VFISV), has been used since May 2010 to infer the solar atmospheric parameters
+from the spectropolarimetric observations taken by the Helioseismic and
+Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO). The magnetic
+filling factor, the fraction of the surface with a resolution element occupied
+by magnetic field, is set to have a constant value of one in the current
+version of VFISV. This report describes an improved inversion strategy for the
+spectropolarimetric data observed with HMI for magnetic field strengths of
+intermediate values in areas spatially not fully resolved. The VFISV inversion
+code has been modified to enable inversion of the Stokes profiles with two
+different components: one magnetic and one non-magnetic. In this scheme, both
+components share the atmospheric components except for the magnetic field
+strength, inclination, and azimuth. In order to determine whether the new
+strategy is useful, we evaluate the inferred parameters inverted with one
+magnetic component (the original version of the HMI inversion) and with two
+components (the improved version) using a Bayesian analysis. In pixels with
+intermediate magnetic field strengths (e.g. plages), the new version provides
+statistically significant values of filling fraction and magnetic field vector.
+Not only does the fitting of the Stokes profile improve, but the inference of
+the magnetic parameters and line-of-sight velocity are obtained uniquely. The
+new strategy is also proven to be effective for mitigating the anomalous
+hemispheric bias in the east-west magnetic field component in moderate field
+regions.",2109.09131v2
+2023-09-23,Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of 6H-perovskite Ba3HoRu2O9,"The compound Ba3HoRu2O9 magnetically orders at 50 K (TN1) followed by another
+complex magnetic ordering at 10 K (TN2). The 2nd magnetic phase transition was
+characterized by the co-existence of two competing magnetic ground states
+associated with two different magnetic wave vectors (K1=1/2 0 0 and K2=1/4 1/4
+0). We have investigated the compound through time-of-flight neutron
+diffraction, ac susceptibility, complex dielectric spectroscopy, and
+magnetization under external pressure. We demonstrate that the non-colinear
+structure involving two different magnetic ions, Ru(4d) and Ho(4f), breaks the
+spatial inversion symmetry via inverse Dzyaloshinskii-Moriya (D-M) interaction
+through strong4d-4f magnetic correlation, which shifts the oxygen atoms and
+results in non-zero polarization. Such an observation of inverse D-M
+interaction from two different magnetic spins ions which caused
+ferroelectricity is rarely observed. The stronger spin-orbit coupling of
+4d-orbital might play a major role in creating D-M interaction of non-collinear
+spins. We have systematically studied the spin and dipolar dynamics, which
+exhibit intriguing behavior with shorter coherence lengths of 2nd magnetic
+phase associated with the K2-wave vector. The results manifest the development
+of magnetoelectric domains instead of true long-range ordering which justifies
+the experimentally obtained low value of ferroelectric polarization. Further,
+we have investigated the effect of external pressure on this complex magnetism.
+The result reveals an enhancement of ordering temperature by the application of
+external pressure (1.6K/GPa). The external pressure might favor stabilizing the
+ground state associated with 2nd magnetic phase. Our study shows an
+unconventional mechanism of spin-driven ferroelectricity involving inverse D-M
+interaction between Ru(4d) and Ho(4f) magnetic ions due to strong 4d-4f
+cross-coupling.",2309.13465v3
+1998-06-05,Collapse-Driven Outflow in Star-Forming Molecular Cores,"Dynamical collapses of magnetized molecular cloud cores are studied with
+magnetohydrodynamical simulations from the run-away collapse phase to the
+accretion phase. In the run-away collapse phase, a disk threaded by magnetic
+field lines is contracting due to its self-gravity and its evolution is well
+expressed by a self-similar solution. The central density increases greatly in
+a finite time scale and reaches a density at which an opaque core is formed at
+the center. After that, matter accretes to the newly formed core (accretion
+phase). In this stage, a rotationally supported disk is formed in a cloud core
+without magnetic fields. In contrast, the disk continues to contract in the
+magnetized cloud core, since the magnetic fields transfer angular momentum from
+the disk. Its rotation motion winds up the threading magnetic field lines.
+Eventually, strong toroidal magnetic fields are formed and begin to drive the
+outflow, even if there is no toroidal field component initially. Bipolar
+molecular outflows observed in protostar candidates are naturally explained by
+this model.",9806085v1
+1998-09-16,A magnetic model for acoustic modes in roAp stars,"The mechanism for excitation of p-modes in rapidly oscillating, peculiar A
+(roAp, or cool chemically peculiar, CP) stars is unknown. Observations strongly
+suggest that acoustic modes in roAp stars are causally linked to the stars'
+magnetic field. We propose that small fluctuations in the shape of the mean
+magnetic field drive magnetosonic waves, which are observed as p-modes in these
+stars.
+  The dynamic edge region of roAp stars is a force-free spherical shell. When
+strongly coupled to the magnetic field, a force-free plasma can oscillate about
+a minimum in its mean magnetic energy. We describe the stable eigenmodes for
+this energy minimum in a spherical shell with an open boundary. The
+wavenumbers, frequencies, and energies of resulting oscillations are consistent
+with observations of p-modes in roAp stars. Our magnetic model for p-mode
+oscillations in stars does not invoke convection or opacity mechanisms. We also
+suggest the possibility of a nonlinear dynamo for such magnetic stars, which
+lack the convection needed for the usual (-( dynamo.",9809215v1
+2000-01-16,Solar-Like Cycle in Asymptotic Giant Branch Stars,"I propose that the mechanism behind the formation of concentric semi-periodic
+shells found in several planetary nebulae (PNs) and proto-PNs, and around one
+asymptotic giant branch (AGB) star, is a solar-like magnetic activity cycle in
+the progenitor AGB stars. The time intervals between consecutive ejection
+events is about 200-1,000 years, which is assumed to be the cycle period (the
+full magnetic cycle can be twice as long, as is the 22-year period in the sun).
+The magnetic field has no dynamical effects; it regulates the mass loss rate by
+the formation of magnetic cool spots. The enhanced magnetic activity at the
+cycle maximum results in more magnetic cool spots, which facilitate the
+formation of dust, hence increasing the mass loss rate. The strong magnetic
+activity implies that the AGB star is spun up by a companion, via a tidal or
+common envelope interaction. The strong interaction with a stellar companion
+explains the observations that the concentric semi-periodic shells are found
+mainly in bipolar PNs.",0001281v1
+2002-06-22,Stability and heating of magnetically driven jets from Keplerian accretion discs,"We have performed 3-D numerical magnetohydrodynamic (MHD) jet experiments to
+study the instabilities associated with strongly toroidal magnetic fields and
+determine if such magnetic configurations in jets are as unstable as similar
+situations are found to be in the laboratory and in analytical estimates. A
+perfectly conducting Keplerian disc with fixed density, rotational velocity and
+pressure is used as a lower boundary for the jet. The energy equation is
+solved, with the inclusion of self-consistently computed heating by viscous and
+magnetic dissipation. The resulting jets evolve into time-dependent,
+non-axisymmetric configurations, but we find only minor disruption of the jets
+by for example the kink instability. We find that magnetic dissipation may have
+profound effects on the jet flow as: 1) it turns on in highly wound up magnetic
+field regions and helps to prevent critical kink situations; 2) it influences
+jet dynamics by re-organizing the magnetic field structure and increasing
+thermal pressure in the jet; and 3) it influences mass loading by increasing
+temperature and pressure at the base of the jet.",0206394v1
+2002-07-10,Magnetic dissipation: Spatial and temporal structure,"A magnetically dominated plasma driven by motions on boundaries at which
+magnetic field lines are anchored is forced to dissipate the work being done
+upon it, no matter how small the electrical resistivity. Numerical experiments
+have clarified that dissipation is achieved through the formation of a
+hierarchy of electrical current sheets. The probability distribution function
+of the local winding of magnetic field lines is nearly Gaussian, with a width
+of the order unity. The dissipation is highly irregular in space and time, but
+the average level of dissipation is well described by a scaling law that is
+independent of the electrical resistivity. If the boundary driving is suspended
+for a period of time the magnetic dissipation rapidly drops to insignificant
+levels, leaving the magnetic field in a nearly force-free state. Renewed
+boundary driving leads to a quick return to dissipation levels compatible with
+the rate of boundary work, with dissipation starting much more rapidly than
+when starting from idealized initial conditions with a uniform magnetic field.
+Application of these concepts to the solar corona lends credibility to
+realistic, three-dimensional numerical models that predict emission measures,
+coronal structures, and heating rates compatible with observations.",0207205v1
+2002-09-06,Scaling laws in decaying helical hydromagnetic turbulence,"We study the evolution of growth and decay laws for the magnetic field
+coherence length xi, energy E_M and magnetic helicity H in freely decaying 3D
+MHD turbulence. We show that with certain assumptions, self-similarity of the
+magnetic power spectrum alone implies that xi~t^{1/2}. This in turn implies
+that magnetic helicity decays as H~t^{-2s}, where s=(xi_{diff}/xi_H)^2, in
+terms of xi_{diff}, the diffusion length scale, and xi_H, a length scale
+defined from the helicity power spectrum. The relative magnetic helicity
+remains constant, implying that the magnetic energy decays as E_M~t^{-1/2-2s}.
+The parameter s is inversely proportional to the magnetic Reynolds number Re_M,
+which is constant in the self-similar regime.",0209119v2
+2004-07-04,Bihelical Magnetic Relaxation and Large Scale Magnetic Field Growth,"A unified, three-scale system of equations accommodating nonlinear velocity
+driven helical dynamos, as well as time-dependent relaxation of magnetically
+dominated unihelical or bihelical systems is derived and solved herein. When
+opposite magnetic helicities of equal magnitude are injected on the
+intermediate and small scales, the large scale magnetic helicity grows
+kinematically (independent of the magnetic Reynolds number) to equal that on
+the intermediate scale. For both free and driven relaxation large scale fields
+are rapidly produced. Subsequently, a dissipation-limited dynamo, driven by
+growth of small scale kinetic helicity, further amplifies the large scale
+field. The results are important for astrophysical coronae fed with bihelical
+structures by dynamos in their host rotators. The large scale for the rotator
+corresponds to the intermediate scale for the corona. That bihelical magnetic
+relaxation can produce global scale fields may help to explain the formation of
+astrophysical coronal holes and magnetohydrodynamic outflows.",0407073v2
+2006-04-27,Gravitational collapse of magnetized clouds. I. Ideal MHD accretion flow,"We study the self-similar collapse of an isothermal magnetized rotating cloud
+in the ideal magnetohydrodynamic (MHD) regime. In the limit of small distance
+from the accreting protostar we find an analytic solution that corresponds to
+free-fall onto a central mass point. The density distribution is not
+spherically symmetric but depends on the mass loading of magnetic field lines,
+which can be obtained by matching our inner solution to an outer collapse
+solution previously computed by Allen, Shu & Li. The concentration of magnetic
+field trapped by the central mass point under field-freezing, independent on
+the details of the starting state, creates a split monopole configuration where
+the magnetic field strength increases as the inverse square of the distance
+from the center. Under such conditions, the inflow eventually becomes
+subalfvenic and the outward transfer of angular momentum by magnetic braking
+very efficient, thus preventing the formation of a centrifugally supported
+disk. Instead, the azimuthal velocity of the infalling gas decreases to zero at
+the center, and the gas spirals into the star. Therefore, the dissipation of
+dynamically important levels of magnetic field is a fundamental requisite for
+the formation of protoplanetary disks around young stars.",0604573v1
+2006-12-29,The Role of Ambipolar Diffusion in the Formation Process of Moderately Magnetized Diffuse Clouds,"We investigate the dynamical condensation process in a magnetized thermally
+bistable medium. We perform one-dimensional two fluid numerical simulations
+that describe the neutral and ionized components in the interstellar medium
+with purely transverse magnetic fields. We find that the clouds that are formed
+as a consequence of the thermal instability always have a magnetic field
+strength on the order of a few microgauss irrespective of the initial strength.
+This shows good agreement with the measurements of the magnetic field strength
+in diffuse clouds. We show analytically that the final magnetic field strength
+in the clouds is determined by the balance between ambipolar diffusion and the
+accumulation of the magnetic field due to condensation.",0612770v2
+2007-03-06,"Rossby waves in ""shallow water"" magnetohydrodynamics","The influence of a toroidal magnetic field on the dynamics of Rossby waves in
+a thin layer of ideal conductive fluid on a rotating sphere is studied in the
+""shallow water"" magnetohydrodynamic approximation for the first time.
+Dispersion relations for magnetic Rossby waves are derived analytically in
+Cartesian and spherical coordinates. It is shown that the magnetic field causes
+the splitting of low order (long wavelength) Rossby waves into two different
+modes, here denoted fast and slow {\em magnetic Rossby waves}. The high
+frequency mode (the fast magnetic Rossby mode) corresponds to an ordinary
+hydrodynamic Rossby wave slightly modified by the magnetic field, while the low
+frequency mode (the slow magnetic Rossby mode) has new and interesting
+properties since its frequency is significantly smaller than that of the same
+harmonics of pure Rossby and Alfv{\'e}n waves.",0703105v2
+2000-03-21,Ground-State Magnetization in Disordered Systems : Exchange vs. Off-Diagonal Interaction Fluctuations,"In a Hartree-Fock picture, itinerant ferromagnetism results from a
+competition between kinetic and exchange energy, with the magnetized state
+being favored at large interaction strength. In a recent paper \cite{spings} we
+showed that in contrast to this average effect, fluctuations of off-diagonal
+interaction matrix elements systematically reduce the ground-state
+magnetization. When the interaction dominates, the occurence of a non-zero
+ground-state magnetization depends on the ratio $\lambda$ between average
+exchange energy and the fluctuation amplitude of the off-diagonal matrix
+elements, and a nonzero critical value $\lambda_c$ is necessary to magnetize
+the ground-state. We extend these results by numerical studies of $\lambda$ for
+standard tight-binding models which indicate a regime of intermediate disorder
+where off-diagonal fluctuations should play an important role for ground-state
+magnetization. We also emphasize the presence of strong correlations between
+minimal eigenvalues of different magnetization blocks which further reduce the
+probability of a nonzero ground-state spin.",0003352v1
+2000-11-03,Spin-Glass State in $\rm CuGa_2O_4$,"Magnetic susceptibility, magnetization, specific heat and positive muon spin
+relaxation (\musr) measurements have been used to characterize the magnetic
+ground-state of the spinel compound $\rm CuGa_2O_4$. We observe a spin-glass
+transition of the S=1/2 $\rm Cu^{2+}$ spins below $\rm T_f=2.5K$ characterized
+by a cusp in the susceptibility curve which suppressed when a magnetic field is
+applied. We show that the magnetization of $\rm CuGa_2O_4$ depends on the
+magnetic histo Well below $\rm T_f$, the muon signal resembles the dynamical
+Kubo-Toyabe expression reflecting that the spin freezing process in $\rm
+CuGa_2O_4$ results Gaussian distribution of the magnetic moments. By means of
+Monte-Carlo simulati we obtain the relevant exchange integrals between the $\rm
+Cu^{2+}$ spins in this compound.",0011055v1
+2001-01-09,Classical and quantum magnetization reversal studied in nanometer-sized particles and clusters,"Nanometer-sized magnetic particles have generated continuous interest as the
+study of their properties has proved to be scientifically and technologically
+very challenging. In this article we reviewed the most important theories and
+experimental results concerning the magnetization reversal of single-domain
+particles,clusters and molecular clusters. Sect.1 reviews briefly the commonly
+used measuring techniques. Among them, electrical transport measurements, Hall
+probes and micro-SQUID techniques seem to be the most convenient techniques for
+low temperature measurements. Sect.2 discusses the mechanisms of magnetization
+reversal in single domain particles at zero Kelvin. The influence of
+temperature on the magnetization reversal is reported in Sect.3. Finally,
+Sect.4 shows that for very small systems or very low temperature, magnetization
+can reverse via quantum tunneling. The boundary between classical and quantum
+physics has become a very attractive field of research. This section discusses
+detailed measurements which demonstrated that molecular magnets offer an unique
+opportunity to explore the quantum dynamics of a large but finite spin. We then
+discussed tunneling in nanoparticles and showed how one might give a definite
+proof of their quantum character at low temperature.",0101104v1
+2001-07-12,Neutron scattering study of dipolar spin ice Ho_2Sn_2O_7: Frustrated pyrochlore magnet,"By means of neutron scattering techniques we have investigated the frustrated
+pyrochlore magnet Ho_2Sn_2O_7, which was found to show a ferromagnetic spin-ice
+behavior below T \simeq 1.4 K by susceptibility measurements. High-resolution
+powder-neutron-diffraction shows no detectable disorder of the lattice, which
+implies appearance of a random magnetic state solely by frustrated geometry,
+i.e., the corner sharing tetrahedra. Magnetic inelastic-scattering spectra show
+that Ho magnetic moments behave as an Ising spin system at low temperatures,
+and that the spin fluctuation has static character. The system remains in a
+short-range ordered state down to T = 0.4 K. By analyzing the wave-number
+dependence of the magnetic scattering using a mean field theory, it is
+clarified that the Ising spins interact via the dipolar interaction. Therefore
+we conclude that Ho_2Sn_2O_7 belongs to the dipolar-spin-ice family. Slow spin
+dynamics is exhibited as thermal hysteresis and time dependence of the magnetic
+scattering.",0107278v2
+2004-03-15,Superparamagnetic relaxation in Cu_{x}Fe_{3-x}O_{4} (x=0.5 and x=1) nanoparticles,"The scope of this article is to report very detailed results of the
+measurements of magnetic relaxation phenomena in the new
+Cu$_{0.5}$Fe$_{2.5}$O$_{4}$ nanoparticles and known CuFe$_{2}$O$_{4}$
+nanoparticles. The size of synthesized particles is (6.5$\pm $1.5)nm. Both
+samples show the superparamagnetic behaviour, with the well-defined phenomena
+of blocking of magnetic moment. This includes the splitting of
+zero-field-cooled and field-cooled magnetic moment curves, dynamical
+hysteresis, slow quasi-logarithmic relaxation of magnetic moment below blocking
+temperature. The scaling of the magnetic moment relaxation data at different
+temperatures confirms the applicability of the simple thermal relaxation model.
+The two copper-ferrites with similar structures show significantly different
+magnetic anisotropy density and other magnetic properties. Investigated systems
+exhibit the consistency of all obtained results.",0403358v1
+2004-04-16,Symmetry of Magnetic Quantum Tunneling in the Single-Molecule Magnet Mn12-Acetate,"The symmetry of magnetic quantum tunneling (MQT) in the single molecule
+magnet Mn12-acetate has been determined by sensitive low-temperature magnetic
+measurements in the pure quantum tunneling regime and high frequency EPR
+spectroscopy in the presence of large transverse magnetic fields. The combined
+data set definitely establishes the transverse anisotropy terms responsible for
+the low temperature quantum dynamics. MQT is due to a disorder induced locally
+varying quadratic transverse anisotropy associated with rhombic distortions in
+the molecular environment (2nd order in the spin-operators). This is
+superimposed on a 4th order transverse magnetic anisotropy consistent with the
+global (average) S4 molecule site symmetry. The hard axes associated with these
+forms of the transverse anisotropy are not collinear, leading to a complex
+interplay between local and global symmetries, the consequences of which are
+analyzed in detail.",0404390v2
+2006-11-23,Quantum dissipation theory of slow magnetic relaxation mediated by domain-wall motion in one-dimensional chain compound [Mn(hfac)_{2}BNO_{H}}],"Based on a quantum dissipation theory of open systems, we present a
+theoretical study of slow dynamics of magnetization for the ordered state of
+the new molecule-based magnetic complex [Mn(hfac)_{2}BNO_{H}] composed from
+antiferromagnetically coupled ferrimagnetic (5/2,1) spin chains. Experimental
+investigations of the magnetization process in pulsed fields have shown that
+this compound exhibits a metamagnetic AF-FI transition at a critical field in
+the order of the interchain coupling. A strong frequency dependence for the
+ac-susceptibility has been revealed in the vicinity of the AF-FI transition and
+was associated with an AF-FI interface kink motion. We model these processes by
+a field-driven domain-wall motion along the field-unfavorable chains correlated
+with a dissipation effect due to a magnetic system-bath coupling. The
+calculated longitudinal magnetization has a two-step relaxation after the field
+is switched off and are found in good agreement with the experiment. The
+relaxation time determined from the imaginary part of the model
+ac-susceptibility agrees qualitatively with that found from the remanent
+magnetization data.",0611610v1
+2006-12-12,Magnetic and Resonance Properties of the Compound (NH3)2(CH2)3CoCl4 - an Antiferromagnet with the Dzyaloshinskii Interaction,"The static magnetic and dynamic properties of the compound (NH3)2(CH2)3CoCl4
+are investigated in the temperature interval 0.5-50 K. It is shown that at TN
+=2.05 K this compound undergoes a transition to a magnetically ordered
+antiferromagnet state. A distinctive feature of this compound is the presence
+of temperature hysteresis at the transition to the ordered state (corresponding
+to a first order magnetic phase transition) and of a spontaneous magnetic
+moment along the x axis. The paramagnetic Curie temperatures are determined.
+The frequency-field curves of the AFMR spectrum in the xy plane are
+investigated at a temperature below TN. The main magnetic parameters of the
+biaxial AFM - the value of the low-frequency gap and the effective magnetic
+anisotropy field - are determined.",0612285v1
+2007-01-31,Rapidly driven nanoparticles: Mean first-passage times and relaxation of the magnetic moment,"We present an analytical method of calculating the mean first-passage times
+(MFPTs) for the magnetic moment of a uniaxial nanoparticle which is driven by a
+rapidly rotating, circularly polarized magnetic field and interacts with a heat
+bath. The method is based on the solution of the equation for the MFPT derived
+from the two-dimensional backward Fokker-Planck equation in the rotating frame.
+We solve these equations in the high-frequency limit and perform precise,
+numerical simulations which verify the analytical findings. The results are
+used for the description of the rates of escape from the metastable domains
+which in turn determine the magnetic relaxation dynamics. A main finding is
+that the presence of a rotating field can cause a drastic decrease of the
+relaxation time and a strong magnetization of the nanoparticle system. The
+resulting stationary magnetization along the direction of the easy axis is
+compared with the mean magnetization following from the stationary solution of
+the Fokker-Planck equation.",0702001v2
+1997-07-30,Electroweak Origin of Cosmological Magnetic Fields,"Magnetic fields may have been generated in the electroweak phase transition
+through spontaneous symmetry breaking or through the subsequent dynamical
+evolution of semiclassical field configurations. Here I demonstrate explicitly
+how magnetic fields emerge spontaneously in the phase transition also when no
+gradients of the Higgs field are present. Using a simple model, I show that no
+magnetic fields are generated, at least initially, from classical two-bubble
+collisions in a first-order phase transition. An improved gauge-invariant
+definition of the electromagnetic field is advocated which is more appropriate
+in the sense that it never allows electrically neutral fields to serve as
+sources for the electromagnetic field. In particular, semiclassical
+configurations of the Z field alone do not generate magnetic fields. The
+possible generation of magnetic fields in the decay of unstable Z-strings is
+discussed.",9707513v2
+1998-08-12,Anomalous Global Strings and Primordial Magnetic Fields,"We propose a new mechanism for the generation of primordial magnetic fields,
+making use of the magnetic fields which are induced by anomalous global strings
+which couple to electromagnetism via Wess-Zumino type interactions. This
+mechanism can be realized in QCD by utilizing pion strings, global vortices
+which appear in the linear sigma model which describes physics below the QCD
+confinement scale. During the chiral symmetry breaking phase transition, pion
+strings can be produced, thus leading to primordial magnetic fields. We
+calculate the magnitude and coherence length of these fields. They are seen to
+depend on the string dynamics. With optimistic assumptions, both the magnitude
+and coherence scale of the induced magnetic fields can be large enough to
+explain the seed magnetic fields of greater than $10^{-23}$ Gauss necessary to
+produce the observed galactic magnetic fields via the galactic dynamo
+mechanism.",9808306v2
+2006-04-15,Magnetic Fields Boosted by Gluon Vortices in Color Superconductivity,"We investigate the effects of an external magnetic field in the gluon
+dynamics of a color superconductor with three massless quark flavors. In the
+framework of gluon mean-field theory at asymptotic densities, we show that the
+long-range component $\widetilde{H}$ of the external magnetic field that
+penetrates the CFL phase produces an instability when its strength becomes
+larger than the Meissner mass of the charged gluons. As a consequence, the
+magnetic field causes the formation of a vortex state characterized by the
+condensation of charged gluons and the creation of magnetic flux tubes. Inside
+the flux tubes the magnetic field is stronger than the applied one. This
+antiscreening effect is connected to the anomalous magnetic moment of the gluon
+field. We suggest how this same mechanism could serve to remove the
+chromomagnetic instabilities existing in gapless color superconductivity.",0604136v2
+2007-01-24,Evolution of Mixed Dirac Particles Interacting with an External Magnetic Field,"We study in the framework of relativistic quantum mechanics the evolution of
+a system of two Dirac neutrinos that mix with each other and have non-vanishing
+magnetic moments. The dynamics of this system in an external magnetic field is
+determined by solving the Pauli-Dirac equation with a given initial condition.
+We consider first neutrino spin-flavor oscillations in a constant magnetic
+field and derive an analytical expression for the transition probability of
+spin-flavor conversion in the limit of small magnetic interactions. We then
+investigate ultrarelativistic neutrinos in an transversal magnetic field and
+derive their wave functions and transition probabilities with no limitation for
+the size of transition magnetic moments. Although we consider neutrinos, our
+formalism is straightforwardly applicable to any spin-1/2 particles.",0701209v4
+2004-09-27,Magnetic Rigidity of Horocycle flows,"Let $M$ be a closed oriented surface endowed with a Riemannian metric $g$ and
+let $\Omega$ be a 2-form. We show that the magnetic flow of the pair
+$(g,\Omega)$ has zero asymptotic Maslov index and zero Liouville action if and
+only $g$ has constant Gaussian curvature, $\Omega$ is a constant multiple of
+the area form of $g$ and the magnetic flow is a horocycle flow.
+  This characterization of horocycle flows implies that if the magnetic flow of
+a pair $(g,\Omega)$ is $C^1$-conjugate to the horocycle flow of a hyperbolic
+metric $\bar{g}$ then there exists a constant $a>0$, such that $ag$ and
+$\bar{g}$ are isometric and $a^{-1}\Omega$ is, up to a sign, the area form of
+$g$. The characterization also implies that if a magnetic flow is Ma\~n\'e
+critical and uniquely ergodic it must be the horocycle flow.
+  As a by-product we also obtain results on existence of closed magnetic
+geodesics for almost all energy levels in the case weakly exact magnetic fields
+on arbitrary manifolds.",0409528v1
+2003-08-03,Energy transfer and locality in magnetohydrodynamic turbulence,"The shell-to-shell energy transfer rates for magnetohydrodynamic (MHD)
+turbulence are computed analytically, which shows local energy transfer rates
+from velocity to velocity, velocity to magnetic, magnetic to velocity, and
+magnetic to magnetic fields for nonhelical MHD in the inertial range. It is
+also found that for kinetic-energy dominated MHD fluid, there is a preferential
+shell-to-shell energy transfer from kinetic to magnetic energy; the transfer is
+reversed for magnetic-energy dominated MHD fluid. This property is the reason
+for the asymptotic value of Alfven ratio to be close to 0.5. The analytical
+results are in close agreement with recent numerical results. When magnetic and
+kinetic helicities are turned on, the helical contributions are opposite to the
+corresponding nonhelical contributions. The helical energy transfers have
+significant nonlocal components.",0308005v3
+1999-11-23,Magnetic Oscillations in the Nambu - Jona-Lasinio model,"The phase structure of a simple Nambu-Jona-Lasinio model has been
+investigated at non-zero values of $\mu$ and H, where H is an external magnetic
+field and $\mu$ is the chemical potential. On this basis magnetic oscillations
+effects were considered. It was shown that there are standard (periodic) van
+Alphen-de Haas magnetic oscillations of some thermodynamical quantities,
+including magnetization, pressure and particle density in the NJL system.
+Besides, we have found non-standard, i.e. non-periodic, magnetic oscillations,
+since the frequency of oscillations is a H-dependent quantity. Finally, there
+arises an oscillating behaviour not only for thermodynamical quantities, but
+also for a dynamical quantity like the quark mass. The possibility for magnetic
+oscillations of some physical quantities inside neutron stars is discussed.",9911073v1
+2001-07-14,A route to magnetic field reversals: an example of an ABC-forced non-linear dynamo,"We are investigating numerically the non-linear behavior of a space-periodic
+MHD system with ABC forcing. Most computations are performed for magnetic
+Reynolds numbers increasing from 0 to 60 and a fixed kinematic Reynolds number,
+small enough for the trivial solution with a zero magnetic field to be stable
+to velocity perturbations. At the critical magnetic Reynolds number for the
+onset of instability of the trivial solution the dominant eigenvalue of the
+kinematic dynamo problem is real. In agreement with the bifurcation theory new
+steady states with non-vanishing magnetic field appear in this bifurcation.
+Subsequent bifurcations are investigated. A regime is detected, where chaotic
+variations of the magnetic field orientation (analogous to magnetic field
+reversals) are observed in the temporal evolution of the system.",0107029v3
+2006-07-12,The Stoner-Wohlfarth model of Ferromagnetism: Dynamic and Statistical properties,"The physics of magnetic state change or reversal in single domain magnetic
+grains (called Stoner particles) is interesting from the fundamental as well as
+the applied points of view. A change in magnetization can be finely tuned with
+a specific time variation o f an externally applied magnetic field. It may also
+occur naturally (without application of a field) at very low tempe rature with
+quantum tunneling and at higher temperature with thermal excitation. The
+optimal (usually shortest) time altering the magn etisation along with the
+smallest applied magnetic field are sought in technological applications s uch
+as high-density reading or writing of information, spintronics, quantum inform
+ation and quantum communication systems. This work reviews the magnetization
+change with a time dependent field and tem perature and discusses the time it
+takes to alter the magnetization as a function of the control parameter chosen,
+temperature and material parameters.",0607118v4
+2007-07-09,Self-Similar Solutions of Viscous-Resistive ADAFs With Poloidal Magnetic Fields,"We carry out the self-similar solutions of viscous-resistive accretion flows
+around a magnetized compact object. We consider an axisymmetric, rotating,
+isotheral steady accretion flow which contains a poloidal magnetic field of the
+central star. The dominant mechanism of energy dissipation is assumed to be the
+turbulence viscosity and magnetic diffusivity due to magnetic field of the
+central star. We explore the effect of viscosity on a rotating disk in the
+presence of constant magnetic diffusivity. We show that the dynamical
+quantities of ADAFs are sensitive to the advection and viscosity parameters.
+Increase of the $\alpha$ coefficient in the $\alpha$-prescription model
+decreases the radial velocity and increases the density of the flow. It also
+affects the poloidal magnetic field considerably.",0707.1253v1
+2007-07-19,Map of metastable states for thin circular magnetic nano-cylinders,"Nano-magnetic systems of artificially shaped ferromagnetic islands, recently
+became a popular subject due to their current and potential applications in
+spintronics, magneto-photonics and superconductivity. When the island size is
+close to the exchange length of magnetic material (around 15 nm), its magnetic
+structure becomes markedly different. It determines both static and dynamic
+magnetic properties of elements, but strongly depends on their shape and size.
+Here we map this dependence for circular cylindrical islands of a few exchange
+lengths in size. We outline the region of metastability of ""C""-type magnetic
+states, proving that they are indeed genuine and not a result of pinning on
+particle imperfections. A way to create the smallest particles with guaranteed
+magnetic vortex state at zero field becomes evident. It is expected that the
+map will help focus the efforts in planning of experiments and devices.",0707.2938v2
+2007-11-13,Evidence for weak magnetic fields in early-type emission stars,"We report the results of our study of magnetic fields in a sample of 15 Be
+stars using spectropolarimetric data obtained at the European Southern
+Observatory with the multi-mode instrument FORS1 installed at the 8m Kueyen
+telescope. We detect weak photospheric magnetic fields in four stars, HD56014,
+HD148184, HD155806, and HD181615. We note that for HD181615 the evolutionary
+status is not obvious due to the fact that it is a binary system currently
+observed in the initial rapid phase of mass exchange between the two
+components. Further, we notify the possible presence of distinct circular
+polarisation features in the circumstellar components of Ca II H&K in three
+stars, HD58011, HD117357, and HD181615, hinting at a probable presence of
+magnetic fields in the circumstellar mass loss disks of these stars. We
+emphasize the need for future spectropolarimetric observations of Be stars with
+detected magnetic fields to study the temporal evolution of their magnetic
+fields and the correlation of magnetic field properties with dynamical
+phenomena taking place in the gaseous circumstellar disks of these stars.",0711.2085v1
+2007-11-30,"Magnetic fields, spots and weather in chemically peculiar stars","New observational techniques and sophisticated modelling methods has led to
+dramatic breakthroughs in our understanding of the interplay between the
+surface magnetism, atomic diffusion and atmospheric dynamics in chemically
+peculiar stars. Magnetic Doppler images, constructed using spectropolarimetric
+observations of Ap stars in all four Stokes parameters, reveal the presence of
+small-scale field topologies. Abundance Doppler mapping has been perfected to
+the level where distributions of many different chemical elements can be
+deduced self-consistently for one star. The inferred chemical spot structures
+are diverse and do not always trace underlying magnetic field geometry.
+Moreover, horizontal chemical inhomogeneities are discovered in non-magnetic CP
+stars and evolving chemical spots are observed for the first time in the bright
+mercury-manganese star alpha And. These results show that in addition to
+magnetic fields, another important non-magnetic structure formation mechanism
+acts in CP stars.",0711.4905v1
+2007-12-12,Reentrant spin glass transition in LuFe2O4,"We have carried out a comprehensive investigation of magnetic properties of
+LuFe$_2$O$_4$, using AC susceptibility, DC magnetization and specific heat. A
+magnetic phase transition around $\sim$236 K was observed with DC magnetization
+and specific heat measurements, which is identified as a paramagnetic to
+ferrimagnetic transition based on the nonlinear susceptibility data. Upon
+further cooling below this temperature, we also observed highly relaxational
+magnetic behavior: the DC magnetization exhibits history and time dependence,
+and the real and imaginary part of the AC susceptibility shows large frequency
+dependence. Dynamic scaling of the AC susceptibility data suggests that this
+low temperature phase can be described as a reentrant spin glass phase. We also
+discuss magnetic field dependence of the spin glass transition and aging,
+memory and rejuvenation effect below the glass transition temperature around
+228 K.",0712.1975v1
+2008-01-03,Two-Fluid MHD Simulations of Converging HI Flows in the Interstellar Medium. I: Methodology and Basic Results,"We develop an unconditionally stable numerical method for solving the
+coupling between two fluids (frictional forces/heatings, ionization, and
+recombination), and investigate the dynamical condensation process of thermally
+unstable gas that is provided by the shock waves in a weakly ionized and
+magnetized interstellar medium by using two-dimensional two-fluid
+magnetohydrodynamical simulations. If we neglect the effect of magnetic field,
+it is known that condensation driven by thermal instability can generate high
+density clouds whose physical condition corresponds to molecular clouds
+(precursor of molecular clouds). In this paper, we study the effect of magnetic
+field on the evolution of supersonic converging HI flows and focus on the case
+in which the orientation of magnetic field to converging flows is orthogonal.
+We show that the magnetic pressure gradient parallel to the flows prevents the
+formation of high density and high column density clouds, but instead generates
+fragmented, filamentary HI clouds. With this restricted geometry, magnetic
+field drastically diminishes the opportunity of fast molecular cloud formation
+directly from the warm neutral medium, in contrast to the case without magnetic
+field.",0801.0486v2
+2008-01-28,Magnetized Neutron Star Mergers and Gravitational Wave Signals,"We investigate the influence of magnetic fields upon the dynamics of and
+resulting gravitational waves from a binary neutron star merger in full general
+relativity coupled to ideal magnetohydrodynamics (MHD). We consider two merger
+scenarios, one where the stars begin with initially aligned poloidal magnetic
+fields and one with no magnetic field. Both mergers result in a strongly
+differentially rotating object. In comparison to the non-magnetized scenario,
+the aligned magnetic fields delay the final merger of the two stars. During and
+after merger we observe phenomena driven by the magnetic field, including
+Kelvin-Helmholtz instabilities in shear layers, winding of the field lines, and
+transition from poloidal to toroidal fields. These effects not only produce
+electromagnetic radiation, but also can have a strong influence on the
+gravitational waves. Thus, there are promising prospects for studying such
+systems with both types of waves.",0801.4387v2
+2008-03-14,Magnetoresistance and spin-transfer torque in magnetic tunnel junctions,"We comment on both recent progress and lingering puzzles related to research
+on magnetic tunnel junctions (MTJs). MTJs are already being used in
+applications such as magnetic-field sensors in the read heads of disk drives,
+and they may also be the first device geometry in which spin-torque effects are
+applied to manipulate magnetic dynamics, in order to make nonvolatile magnetic
+random access memory. However, there remain many unanswered questions about
+such basic properties as the magnetoresistance of MTJs, how their properties
+change as a function of tunnel-barrier thickness and applied bias, and what are
+the magnitude and direction of the spin-transfer-torque vector induced by a
+tunnel current.",0803.2254v1
+2008-04-24,Oersted fields and current density profiles in spin-torque driven magnetization dynamics -- Finite element modelling of realistic geometries,"The classical impact of electrical currents on magnetic nanostructures is
+analyzed with numerical calculations of current-density distributions and
+Oersted fields in typical contact geometries. For the Oersted field
+calculation, a hybrid finite element / boundary element method (FEM/BEM)
+technique is presented which can be applied to samples of arbitrary shape.
+Based on the FEM/BEM analysis, it is argued that reliable micromagnetic
+simulations on spin-tranfer-torque driven magnetization processes should
+include precise calculations of the Oersted field, particularly in the case of
+pillar contact geometries. Similarly, finite-element simulations demonstrate
+that numerical calculations of current-density distributions are required,
+e.g., in the case of magnetic strips with an indentation. Such strips are
+frequently used for the design of devices based on current-driven domain-wall
+motion. A dramatic increase of the current density is found at the apex of the
+notch, which is expected to strongly affect the magnetization processes in such
+strips.",0804.4010v1
+2008-05-18,Evolution of neutron stars with toroidal magnetic fields: Axisymmetric simulation in full general relativity,"We study the stability of neutron stars with toroidal magnetic fields by
+magnetohydrodynamic simulation in full general relativity under assumption of
+axial symmetry. Nonrotating and rigidly rotating neutron stars are prepared for
+a variety of magnetic field configuration. For modeling the neutron stars, the
+polytropic equation of state with the adiabatic index $\Gamma=2$ is used for
+simplicity. It is found that nonrotating neutron stars are dynamically unstable
+for the case that toroidal magnetic field strength varies $\propto
+\varpi^{2k-1}$ with $k\geq 2$ (here $\varpi$ is the cylindrical radius),
+whereas for $k=1$ the neutron stars are stable. After the onset of the
+instability, unstable modes grow approximately in the Alfv\'en time scale and,
+as a result, a convective motion is excited to change the magnetic field
+profile until a new state, which is stable against axisymmetric perturbation,
+is reached. We also find that rotation plays a role in stabilization, although
+the instability still sets in in the Alfv\'en time scale when the ratio of
+magnetic energy to rotational kinetic energy is larger than a critical value
+$\sim 0.2$. Implication for the evolution of magnetized protoneutron stars is
+discussed.",0805.2712v1
+2008-07-23,N-body + Magnetohydrodynamical Simulations of Merging Clusters of Galaxies: Characteristic Magnetic Field Structures Generated by Bulk Flow Motion,"We present results from N-body + magnetohydrodynamical simulations of merging
+clusters of galaxies. We find that cluster mergers cause various characteristic
+magnetic field structures because of the strong bulk flows in the intracluster
+medium. The moving substructures result in cool regions surrounded by the
+magnetic field. These will be recognized as magnetized cold fronts in the
+observational point of view. A relatively ordered magnetic field structure is
+generated just behind the moving substructure. Eddy-like field configurations
+are also formed by Kelvin-Helmholtz instabilities. These features are similarly
+seen even in off-center mergers though the detailed structures change slightly.
+The above-mentioned characteristic magnetic field structures are partly
+recognized in Faraday rotation measure maps. The higher absolute values of the
+rotation measure are expected when observed along the collision axis, because
+of the elongated density distribution and relatively ordered field structure
+along the axis. The rotation measure maps on the cosmic microwave background
+radiation, which covers clusters entirely, could be useful probes of not only
+the magnetic field structures but also the internal dynamics of the
+intracluster medium.",0807.3765v1
+2008-08-08,Magnetic Fields In Astrophysical Objects,"Magnetic fields are known to reside in many astrophysical objects and are now
+believed to be crucially important for the creation of phenomena on a wide
+variety of scales. However, the role of the magnetic field in the bodies that
+we observe has not always been clear. In certain situations, the importance of
+a magnetic field has been over looked on the grounds that the large-scale
+magnetic field was believed to be too weak to play and important role in the
+dynamics.
+  In this article I discuss some of the recent developments concerning magnetic
+fields in stars, planets and accretion discs. I choose to emphasise some of the
+situations where it has been suggested that weak magnetic fields may play a
+more significant role than previously thought. At the end of the article I list
+some of the questions to be answered in the future.",0808.1118v2
+2008-12-01,Two dimensional frustrated magnetic state in superconducting RuSr2Eu1.5Ce0.5Cu2O10 (Ru-1222),"In this paper we investigate the magnetic state and the role of the
+crystalline structure in RuSr2Eu1.5Ce0.5Cu2O10 (Ru-1222). Measurements were
+made in the isomorphic series (Nb1-xRux)Sr2Eu1.5Ce0.5Cu2O10 [(Nb,Ru)-1222],
+with x between 0 and 1. 3D XY fluctuations above the magnetic transition were
+not observed in Ru-1222, suggesting a weak inter-plane coupling between the
+RuO2 layers. The compositional dependence of the magnetic susceptibility shows
+a rapid broadening with increasing Nb content, explained in terms of a
+cluster-glass state. The variation of several superconducting parameters as a
+function of Ru content is linear in the whole concentration range, with no
+jumps at the critical concentration for which percolation of long range order
+is expected. 3D Arrhenius and Vogel-Fulcher-type dependencies fail to describe
+the dynamic properties. Fitting of a generalized Vogel-Fulcher-type dependence,
+with ln(tau/tau0) = A(T-T0)^-B, yield B = 2.0, in excellent agreement with
+Monte Carlo simulations for 2D systems. The value deduced for T0 agrees well
+with the re-opening of hysteresis in the M(H) curves. The observed
+superconducting and magnetic features are explained in terms of a scenario of
+2D magnetic islands at the RuO2 layers, with no long range magnetic order.",0812.0137v1
+2009-01-16,Double-diffusive instabilities of a shear-generated magnetic layer,"Previous theoretical work has speculated about the existence of
+double-diffusive magnetic buoyancy instabilities of a dynamically evolving
+horizontal magnetic layer generated by the interaction of forced vertically
+sheared velocity and a background vertical magnetic field. Here we confirm
+numerically that if the ratio of the magnetic to thermal diffusivities is
+sufficiently low then such instabilities can indeed exist, even for high
+Richardson number shear flows. Magnetic buoyancy may therefore occur via this
+mechanism for parameters that are likely to be relevant to the solar
+tachocline, where regular magnetic buoyancy instabilities are unlikely.",0901.2388v2
+2009-03-24,Theoretical Models of Sunspot Structure and Dynamics,"Recent progress in theoretical modeling of a sunspot is reviewed. The
+observed properties of umbral dots are well reproduced by realistic simulations
+of magnetoconvection in a vertical, monolithic magnetic field. To understand
+the penumbra, it is useful to distinguish between the inner penumbra, dominated
+by bright filaments containing slender dark cores, and the outer penumbra, made
+up of dark and bright filaments of comparable width with corresponding magnetic
+fields differing in inclination by some 30 degrees and strong Evershed flows in
+the dark filaments along nearly horizontal or downward-plunging magnetic
+fields. The role of magnetic flux pumping in submerging magnetic flux in the
+outer penumbra is examined through numerical experiments, and different
+geometric models of the penumbral magnetic field are discussed in the light of
+high-resolution observations. Recent, realistic numerical MHD simulations of an
+entire sunspot have succeeded in reproducing the salient features of the
+convective pattern in the umbra and the inner penumbra. The siphon-flow
+mechanism still provides the best explanation of the Evershed flow,
+particularly in the outer penumbra where it often consists of cool, supersonic
+downflows.",0903.4106v1
+2009-06-26,"Magnetic anomalies in nanocrystalline Ca3CoRhO6, a geometrically frustrated spin-chain compound,","We have investigated the magnetic behavior of the nano crystals, synthesized
+by high-energy ball-milling, for a well-known geometrically frustrated
+spin-chain system, Ca3CoRhO6, and compared its magnetic characteristics with
+those of the bulk form by measuring ac and dc magnetization. The features
+attributable to the onset of 'partially disordered antiferromagnetism'
+(characterizing the bulk form) are not seen in the magnetization data of the
+nano particles; the magnetic moment at high fields in the very low temperature
+range in the magnetically ordered state gets relatively enhanced in the nano
+particles. It appears that the ferromagnetic intrachain interaction, judged by
+the sign of the paramagnetic Curie temperature, is preserved in the nano
+particles. These trends are opposite to those seen in Ca3Co2O6. However, the
+complex spin-dynamics as evidenced by large frequency dependence of ac
+susceptibility is retained in the nano particles as well. Thus, there are some
+similarities and dissimilarities between the properties of the nano particles
+and those of the bulk. We believe that these findings would be useful to
+understand correlation lengths deciding various properties of geometrical
+frustration and/or spin-chain phenomena.",0906.4886v1
+2010-02-14,Turbulent small-scale dynamo action in solar surface simulations,"We demonstrate that a magneto-convection simulation incorporating essential
+physical processes governing solar surface convection exhibits turbulent
+small-scale dynamo action. By presenting a derivation of the energy balance
+equation and transfer functions for compressible magnetohydrodynamics (MHD), we
+quantify the source of magnetic energy on a scale-by-scale basis. We rule out
+the two alternative mechanisms for the generation of small-scale magnetic field
+in the simulations: the tangling of magnetic field lines associated with the
+turbulent cascade and Alfvenization of small-scale velocity fluctuations
+(""turbulent induction""). Instead, we find the dominant source of small-scale
+magnetic energy is stretching by inertial-range fluid motions of small-scale
+magnetic field lines against the magnetic tension force to produce (against
+Ohmic dissipation) more small-scale magnetic field. The scales involved become
+smaller with increasing Reynolds number, which identifies the dynamo as a
+small-scale turbulent dynamo.",1002.2750v3
+2010-05-03,Dynamics of a stored Zeeman coherence grating in an external magnetic field,"We investigate the evolution of a Zeeman coherence grating induced in a cold
+atomic cesium sample in the presence of an external magnetic field. The
+gratings are created in a three-beam light storage configuration using two
+quasi-collinear writing laser pulses and reading with a counterpropagating
+pulse after a variable time delay. The phase conjugated pulse arising from the
+atomic sample is monitored. Collapses and revivals of the retrieved pulse are
+observed for different polarizations of the laser beams and for different
+directions of the applied magnetic field. While magnetic field inhomogeneities
+are responsible for the decay of the coherent atomic response, a five-fold
+increase in the coherence decay time, with respect to no applied magnetic
+field, is obtained for an appropriate choice of the direction of the applied
+magnetic field. A simplified theoretical model illustrates the role of the
+magnetic field mean and its inhomogeneity on the collective atomic response.",1005.0282v1
+2010-06-30,Micromagnetic analysis of magnetic noise in ferromagnetic nanowires,"We investigate the magnetic thermal noise in magnetic nanowires with and
+without a domain wall by employing micromagnetic simulations. The magnetic
+thermal noise due to random thermal fluctuation fields gives important physical
+quantities related with the magnetic susceptibility. We find that the resonance
+frequency of a domain wall is distinguishable from one of a magnetic domain
+itself. For the single domain without a domain wall, the resonance frequency is
+well described by the Kittel's formula considering a ferromagnetic specimen as
+a simple ellipsoid with demagnetizing factors for various wire widths and
+thicknesses. However, additional resonance frequencies from the magnetic domain
+wall show the different dependences of the wire width and thickness. It implies
+that the spins inside the domain wall have different effective fields and the
+spin dynamics.",1006.5763v1
+2010-07-02,External field control of collective spin excitations in an optical lattice of $^2Σ$ molecules,"We show that an ensemble of $^2\Sigma$ molecules in the rotationally ground
+state trapped on an optical lattice exhibits collective spin excitations that
+can be controlled by applying superimposed electric and magnetic fields. In
+particular, we show that the lowest energy excitation of the molecular ensemble
+at certain combinations of electric and magnetic fields leads to the formation
+of a magnetic Frenkel exciton. The exciton bandwidth can be tuned by varying
+the electric or magnetic fields. We show that the exciton states can be
+localized by creating vacancies in the optical lattice. The localization
+patterns of the magnetic exciton states are sensitive to the number and
+distribution of vacancies, which can be exploited for engineering many-body
+entangled spin states. We consider the dynamics of magnetic exciton wavepackets
+and show that the spin excitation transfer between molecules in an optical
+lattice can be accelerated or slowed down by tuning an external magnetic or
+electric field.",1007.0458v1
+2011-02-07,Cosmic-ray driven dynamo in galaxies,"We present recent developments of global galactic-scale numerical models of
+the Cosmic Ray (CR) driven dynamo, which was originally proposed by Parker
+(1992). We conduct a series of direct CR+MHD numerical simulations of the
+dynamics of the interstellar medium (ISM), composed of gas, magnetic fields and
+CR components. We take into account CRs accelerated in randomly distributed
+supernova (SN) remnants, and assume that SNe deposit small-scale, randomly
+oriented, dipolar magnetic fields into the ISM. The amplification timescale of
+the large-scale magnetic field resulting from the CR-driven dynamo is
+comparable to the galactic rotation period. The process efficiently converts
+small-scale magnetic fields of SN-remnants into galactic-scale magnetic fields.
+The resulting magnetic field structure resembles the X-shaped magnetic fields
+observed in edge-on galaxies.",1102.1300v1
+2011-02-25,Excitation of Slow-Modes in Network Magnetic Elements Through Magnetic Pumping,"From radiation magnetohydrodynamic simulations of the solar atmosphere we
+find a new mechanism for the excitation of longitudinal slow modes within
+magnetic flux concentrations. We find that the convective downdrafts in the
+immediate surroundings of magnetic elements are responsible for the excitation
+of slow modes. The coupling between the external downdraft and the plasma
+motion internal to the flux concentration is mediated by the inertial forces of
+the downdraft that act on the magnetic flux concentration. These forces, in
+conjunction with the downward movement, pump the internal atmosphere in the
+downward direction, which entails a fast downdraft in the photospheric and
+chromospheric layers of the magnetic element. Subsequent to the transient
+pumping phase, the atmosphere rebounds, causing a slow mode traveling along the
+magnetic flux concentration in the upward direction. It develops into a shock
+wave in chromospheric heights, possibly capable of producing some kind of
+dynamic fibril. We propose an observational detection of this process.",1102.5164v1
+2011-03-08,Injection and extraction magnets: kicker magnets,"Each stage of an accelerator system has a limited dynamic range and therefore
+a chain of stages is required to reach high energy. A combination of septa and
+kicker magnets is frequently used to inject and extract beam from each stage.
+The kicker magnets typically produce rectangular field pulses with fast rise-
+and/or fall-times, however, the field strength is relatively low. To compensate
+for their relatively low field strength, the kicker magnets are generally
+combined with electromagnetic septa. The septa provide relatively strong field
+strength but are either DC or slow pulsed. This paper discusses injection and
+extraction systems with particular emphasis on the hardware required for the
+kicker magnet.",1103.1583v1
+2011-04-13,Magnetic fields in nearby galaxies,"Observations of synchrotron radiation and the Faraday rotation of its
+polarized component allow us to investigate the magnetic properties of the
+diffuse interstellar medium in nearby galaxies, on scales down to roughly one
+hundred parsecs. All disc galaxies seem to have a mean, or regular, magnetic
+field component that is ordered on length scales comparable to the size of the
+galaxy as well as a random magnetic field of comparable or greater strength. I
+present an overview of what is currently known observationally about galactic
+magnetic fields, focusing on the common features among galaxies that have been
+studied rather than the distinctive or unusual properties of individual
+galaxies. Of particular interest are the azimuthal patterns formed by regular
+magnetic fields and their pitch angles as these quantities can be directly
+related to the predictions of the mean field dynamo theory, the most promising
+theoretical explanation for the apparent ubiquitous presence of regular
+magnetic fields in disc galaxies.",1104.2427v1
+2011-07-31,Avoiding power broadening in optically detected magnetic resonance of single NV defects for enhanced DC-magnetic field sensitivity,"We report a systematic study of the magnetic field sensitivity of a magnetic
+sensor based on a single Nitrogen-Vacancy (NV) defect in diamond, by using
+continuous optically detected electron spin resonance (ESR) spectroscopy. We
+first investigate the behavior of the ESR contrast and linewidth as a function
+of the microwave and optical pumping power. The experimental results are in
+good agreement with a simplified model of the NV defect spin dynamics, yielding
+to an optimized sensitivity around 2 \mu T/\sqrt{\rm Hz}. We then demonstrate
+an enhancement of the magnetic sensitivity by one order of magnitude by using a
+simple pulsed-ESR scheme. This technique is based on repetitive excitation of
+the NV defect with a resonant microwave \pi-pulse followed by an optimized
+read-out laser pulse, allowing to fully eliminate power broadening of the ESR
+linewidth. The achieved sensitivity is similar to the one obtained by using
+Ramsey-type sequences, which is the optimal magnetic field sensitivity for the
+detection of DC magnetic fields.",1108.0178v2
+2012-05-31,Magnetic excitations in underdoped Ba(Fe1-xCox)2As2 with x=0.047,"The magnetic excitations in the paramagnetic-tetragonal phase of underdoped
+Ba(Fe0.953Co0.047)2As2, as measured by inelastic neutron scattering, can be
+well described by a phenomenological model with purely diffusive spin dynamics.
+At low energies, the spectrum around the magnetic ordering vector Q_AFM
+consists of a single peak with elliptical shape in momentum space. At high
+energies, this inelastic peak is split into two peaks across the direction
+perpendicular to Q_AFM. We use our fittings to argue that such a splitting is
+not due to incommensurability or propagating spin-wave excitations, but is
+rather a consequence of the anisotropies in the Landau damping and in the
+magnetic correlation length, both of which are allowed by the tetragonal
+symmetry of the system. We also measure the magnetic spectrum deep inside the
+magnetically-ordered phase, and find that it is remarkably similar to the
+spectrum of the paramagnetic phase, revealing the strongly overdamped character
+of the magnetic excitations.",1206.0040v1
+2012-06-22,How is the magnetic reconnection derived from magnetohydrodynamics equations?,"We clarify how magnetic reconnection can be derived from magnetohydrodynamics
+(MHD) equations in a way that is easily understandable to university students.
+The essential mechanism governing the time evolution of the magnetic field is
+diffusion dynamics. The magnetic field is represented by two components. It is
+clarified that the diffusion of a component causes a generation of another
+component that is initially zero and, accordingly, that the magnetic force
+lines are reconnected. For this reconnection to occur correctly, the initial
+magnetic field must be directed oppositely in the two regions, e.g., $y>0$ and
+$y<0$; must be concave (convex) for $y>0$ ($y<0$); and must be saturated for
+$y$ far from the x axis, which would indicate the existence of the current
+sheet. It will be clear that our comprehension based on diffusion runs parallel
+to the common qualitative explanation about the magnetic reconnection.",1206.5161v1
+2012-08-10,Unique Topological Characterization of Braided Magnetic Fields,"We introduce a topological flux function to quantify the topology of magnetic
+braids: non-zero, line-tied magnetic fields whose field lines all connect
+between two boundaries. This scalar function is an ideal invariant defined on a
+cross-section of the magnetic field, and measures the average poloidal magnetic
+flux around any given field line, or the average pairwise crossing number
+between a given field line and all others. Moreover, its integral over the
+cross-section yields the relative magnetic helicity. Using the fact that the
+flux function is also an action in the Hamiltonian formulation of the field
+line equations, we prove that it uniquely characterizes the field line mapping
+and hence the magnetic topology.",1208.2286v2
+2012-09-07,Optimization of the magnetic dynamo,"In stars and planets, magnetic fields are believed to originate from the
+motion of electrically conducting fluids in their interior, through a process
+known as the dynamo mechanism. In this Letter, an optimization procedure is
+used to simultaneously address two fundamental questions of dynamo theory:
+""Which velocity field leads to the most magnetic energy growth?"" and ""How large
+does the velocity need to be relative to magnetic diffusion?"" In general, this
+requires optimization over the full space of continuous solenoidal velocity
+fields possible within the geometry. Here the case of a periodic box is
+considered. Measuring the strength of the flow with the root-mean-square
+amplitude, an optimal velocity field is shown to exist, but without limitation
+on the strain rate, optimization is prone to divergence. Measuring the flow in
+terms of its associated dissipation leads to the identification of a single
+optimal at the critical magnetic Reynolds number necessary for a dynamo. This
+magnetic Reynolds number is found to be only 15% higher than that necessary for
+transient growth of the magnetic field.",1209.1559v2
+2012-11-27,Boundary and finite-size effects in the competition between indirect magnetic exchange and Kondo screening,"A system of conduction electrons can mediate an indirect magnetic exchange
+between magnetic impurites. The nonlocal exchange typically competes with the
+local Kondo screening of the impurity magnetic moments. In case of magnetic
+adatoms on non-magnetic surfaces this competition is expected to be affected by
+different confinement effects. Here we study this situation in the regime of
+intermediate hybridization strengths by means of real-space dynamical
+mean-field theory for a one-dimensional two-impurity Anderson model. Depending
+on the presence of a boundary and depending on the system size, a crossover
+between nonlocal and local singlet formation is observed in corresponding
+magnetic susceptibilities. The crossover is driven by the strong sensitivity of
+the Kondo temperature on the local density of states.",1211.6307v2
+2013-03-22,Electro/Magnetically Induced Controllable Rotation In Small-scale Liquid Flow,"We study all the possibilities of producing rotating flow in an
+incompressible fluid by electric and magnetic fields. We start with a general
+theoretical basis and look for different configurations and set-ups which
+electric/magnetic field and an electric current affect the vorticity of fluid
+resulting in rotation on liquid flow. We assume steady-state conditions and
+time-independent electric and magnetic fields as the external body torque.
+Regarding the theoretical basis, we propose three experimental set-ups in which
+by applying fields on a fluid, rotational vortices are produced: (a) a uniform
+electric field and a uniform electric current, (b) a uniform electric current
+and a non-uniform magnetic field, and (c) a non-uniform electric current and a
+uniform magnetic field. The first case has been reported in detail named
+""Liquid Film Motor"". The two other cases are experimentally investigated here
+for a cubic an cylindrical cells. The rotational velocity patterns are obtained
+by PIV technique, and the results are discussed and justified by a preliminary
+estimation based on the torque exerted by magnetic fields on electric currents.
+From the log-log plot of angular velocity versus current, the non-linearity
+factors of the rotational flow for cylindrical and rectangular geometries are
+obtained.",1303.5657v1
+2013-05-09,Low-temperature muon spin rotation studies of the monopole charges and currents in Y doped Ho2Ti2O7,"In the ground state of Ho2Ti2O7 spin ice, the disorder of the magnetic
+moments follows the same rules as the proton disorder in water ice. Excitations
+take the form of magnetic monopoles that interact via a magnetic Coulomb
+interaction. Muon spin rotation has been used to probe the low-temperature
+magnetic behaviour in single crystal Ho2-xYxTi2O7 (x=0, 0.1, 1, 1.6 and 2). At
+very low temperatures, a linear field dependence for the relaxation rate of the
+muon precession lambda(B), that in some previous experiments on Dy2Ti2O7 spin
+ice has been associated with monopole currents, is observed in samples with
+x=0, and 0.1. A signal from the magnetic fields penetrating into the silver
+sample plate due to the magnetization of the crystals is observed for all the
+samples containing Ho allowing us to study the unusual magnetic dynamics of Y
+doped spin ice.",1305.2048v1
+2013-05-13,Backhopping effect in magnetic tunnel junctions: comparison between theory and experiment,"We report on the magnetic switching and backhopping effects due to
+spin-transfer-torque in magnetic tunnel junctions. Experimental data on the
+current-induced switching in junctions with MgO tunnel barrier reveal a random
+back-and-forth switching between the magnetization states, which appears when
+the current direction favors the parallel magnetic configuration. The effect
+depends on the barrier thickness $t_b$, and is not observed in tunnel junctions
+with very thin MgO tunnel barriers, $t_b$ $<$ 0.95 nm. Switching dependence on
+the bias voltage and barrier thickness is explained in terms of the macrospin
+model, with the magnetization dynamics described by the modified
+Landau-Lifshitz-Gilbert equation. Numerical simulations indicate that the
+competition between in-plane and out-of-plane torque components can result at
+high bias voltages in a non-deterministic switching behavior, in agreement with
+experimental observations. When the barrier thickness is reduced, the overall
+coupling between the magnetic layers across the barrier becomes ferromagnetic,
+which suppresses the backhopping effect.",1305.2711v1
+2013-09-17,Dependence of solar plasma flows on magnetic field obliquity,"Interactions between flows and magnetic fields in the Sun's plasma can change
+surface waves and flows near active regions, are evident in cyclic changes of
+large-scale phenomena such as the meridional circulation, and contribute to
+dynamics in the long-term solar magnetic cycle, e.g. during the recent
+prolonged solar minimum. We investigate possible relationships between these
+phenomena.
+  We have observed changes in solar surface flow patterns in active regions,
+dependent on magnetic field strength and orientation, consistent with the
+theoretically predicted Proctor Effect. Other researchers have observed
+relationships between changes in solar magnetic fields and meridional
+circulation flows. We explore similarities between the Proctor Effect and the
+observed interdependence of larger-scale magnetic fields and flows. This may
+contribute to understanding of fundamental solar convection and dynamo
+processes, e.g. the prolonged magnetic minimum of the most recent cycle.",1309.4468v2
+2013-12-11,Chiral dynamics in a magnetic field from the functional renormalization group,"We investigate the quark-meson model in a magnetic field using the exact
+functional renormalization group equation beyond the local-potential
+approximation. Our truncation of the effective action involves anisotropic wave
+function renormalization for mesons, which allows us to investigate how the
+magnetic field distorts the propagation of neutral mesons. Solving the flow
+equation numerically, we find that the transverse velocity of mesons decreases
+with the magnetic field at all temperatures, which is most prominent at zero
+temperature. The meson screening masses and the pion decay constants are also
+computed. The constituent quark mass is found to increase with magnetic field
+at all temperatures, resulting in the crossover temperature that increases
+monotonically with the magnetic field. This tendency is consistent with most
+model calculations but not with the lattice simulation performed at the
+physical point. Our work suggests that the strong anisotropy of meson
+propagation may not be the fundamental origin of the inverse magnetic
+catalysis.",1312.3124v2
+2014-02-27,Sensitive Magnetic Force Detection with a Carbon Nanotube Resonator,"We propose a technique for sensitive magnetic point force detection using a
+suspended carbon nanotube (CNT) mechanical resonator combined with a magnetic
+field gradient generated by a ferromagnetic gate electrode. Numerical
+calculations of the mechanical resonance frequency show that single Bohr
+magneton changes in the magnetic state of an individual magnetic molecule
+grafted to the CNT can translate to detectable frequency shifts, on the order
+of a few kHz. The dependences of the resonator response to device parameters
+such as length, tension, CNT diameter, and gate voltage are explored and
+optimal operating conditions are identified. A signal-to-noise analysis shows
+that in principle, magnetic switching at the level of a single Bohr magneton
+can be read out in a single shot on timescales as short as 10 microseconds.
+This force sensor should enable new studies of spin dynamics in isolated single
+molecule magnets, free from the crystalline or ensemble settings typically
+studied.",1402.6780v1
+2014-03-06,Influence of small scale magnetic energy and helicity on the growth of large scale magnetic field,"The influence of initially given small scale magnetic energy($E_M(0)$) and
+helicity($H_M(0)$) on the magnetohydrodynamics(MHD) dynamo was investigated.
+Equations for $E_M$(t), $H_M$(t), and electromotive force($\langle {\bf
+v}\times {\bf b}\rangle$, $EMF$) were derived and solved. The solutions
+indicate small scale magnetic field(${\bf b}_i$) caused by $E_M$(0) modifies
+$EMF$ and generates additional terms of which effect depends on magnetic
+diffusivity $\eta$, position of initial conditions($IC$s) $k_f$, and time
+($\sim e^{-\eta k_f^2 t}$). ${\bf b}_i$ increases the inverse cascade of energy
+resulting in the enhanced growth of large scale magnetic field($\overline{{\bf
+B}}$). Simulation data show that $E_M$(0) in small scale boosts the growth
+rate, which also proportionally depends on $H_M(0)$. If $E_M$(0) is the same,
+positive $H_M(0)$ is more effective for MHD dynamo than negative $H_M(0)$ is.
+It was discussed why large scale magnetic helicity should have the opposite
+sign of the injected kinetic helicity.",1403.1328v3
+2014-03-17,A reentrant phenomenon in magnetic and dielectric properties of Dy2BaNiO5 and an intriguing influence of external magnetic field,"We report that the spin-chain compound Dy2BaNiO5 recently proven to exhibit
+magnetoelectric coupling below its Neel temperature (T_N) of 58 K, exhibits
+strong frequency-dependent behavior in ac magnetic susceptibility and complex
+dielectric properties at low temperatures (<10K), mimicking 'reentrant'
+multiglass phenomenon. Such a behavior is not known among undoped compounds. A
+new finding in the field of multiferroics is that the characteristic magnetic
+feature at such low temperatures moves towards higher temperatures in the
+presence of a magnetic-field (H), whereas the corresponding dielectric feature
+shifts towards lower temperatures with H, unlike the situation near T_N. This
+observation indicates that the alignment of spins by external magnetic fields
+tends to inhibit glassy-like slow electric-dipole dynamics, at least in this
+system, possibly arising from peculiarities in the magnetic structure.",1403.4166v1
+2014-03-27,Shock Corrugation by Rayleigh-Taylor Instability in GRB Afterglow Jets,"Afterglow jets are Rayleigh-Taylor unstable and therefore turbulent during
+the early part of their deceleration. There are also several processes which
+actively cool the jet. In this letter, we demonstrate that if cooling
+significantly increases the compressibility of the flow, the turbulence
+collides with the forward shock, destabilizing and corrugating it. In this
+case, the forward shock is turbulent enough to produce the magnetic fields
+responsible for synchrotron emission via small scale turbulent dynamo. We
+calculate light curves assuming the magnetic field is in energy equipartition
+with the turbulent kinetic energy and discover that dynamic magnetic fields are
+well-approximated by a constant magnetic-to- thermal energy ratio of 1%, though
+there is a sizeable delay in the time of peak flux as the magnetic field turns
+on only after the turbulence has activated. The reverse shock is found to be
+significantly more magnetized than the forward shock, with a
+magnetic-to-thermal energy ratio of order 10%. This work motivates future
+Rayleigh-Taylor calculations using more physical cooling models.",1403.6895v2
+2014-05-09,Statistical study of free magnetic energy and flare productivity of solar active regions,"Photospheric vector magnetograms from Helioseismic and Magnetic Imager on
+board the Solar Dynamic Observatory are utilized as the boundary conditions to
+extrapolate both non-linear force-free and potential magnetic fields in solar
+corona. Based on the extrapolations, we are able to determine the free magnetic
+energy (FME) stored in active regions (ARs). Over 3000 vector magnetograms in
+61 ARs were analyzed. We compare FME with ARs' flare index (FI) and find that
+there is a weak correlation ($<60\%$) between FME and FI. FME shows slightly
+improved flare predictability relative to total unsigned magnetic flux of ARs
+in the following two aspects: (1) the flare productivity predicted by FME is
+higher than that predicted by magnetic flux and (2) the correlation between FI
+and FME is higher than that between FI and magnetic flux. However, this
+improvement is not significant enough to make a substantial difference in
+time-accumulated FI, rather than individual flare, predictions.",1405.2131v1
+2014-07-12,Generalized dyons and magnetic dipoles: the issue of angular momentum,"It is known that a non-Abelian magnetic monopole cannot rotate globally
+(although it may possess a nonzero angular momentum density). At the same time,
+the total angular momentum of a magnetic dipole equals the electric charge. In
+this work we question the generality of these results by considering a number
+of generalizations of the Georgi-Glashow model. We study two different types of
+finite energy, regular configurations: solutions with net magnetic charge and
+monopole-antimonopole pairs with zero net magnetic charge. These configurations
+are endowed with an electric charge and carry also a nonvanishing angular
+momentum density. However, we argue that the qualitative results found in the
+Georgi-Glashow model are generic and thus a magnetic monopole cannot spin as
+long as the matter fields feature the usual ""monopole"" asymptotic behaviour
+independently of the dynamics of the model. A study of the properties of the
+dyons and magnetic dipoles in some generalizations of the Georgi-Glashow model
+supplemented with higher order Skyrme-like terms in the gauge curvature and
+Higgs fields is given quantitatively.",1407.3378v1
+2014-07-25,Energy transfers in dynamos with small magnetic Prandtl numbers,"We perform numerical simulation of dynamo with magnetic Prandtl number
+$\mathrm{Pm} =0.2$ on $1024^3$ grid, and compute the energy fluxes and the
+shell-to-shell energy transfers. These computations indicate that the magnetic
+energy growth takes place mainly due to the energy transfers from large-scale
+velocity field to large-scale magnetic field and that the magnetic energy flux
+is forward. The steady-state magnetic energy is much smaller than the kinetic
+energy, rather than equipartition; this is because the magnetic Reynolds number
+is near the dynamo transition regime. We also contrast our results with those
+for dynamo with $\mathrm{Pm} =20$ and decaying dynamo.",1407.6855v2
+2014-08-12,"Mechano-sysntesis and structural, magnetic and thermal characterization of $α$-Fe nanoparticles embedded in a Wüstite matrix","Magnetic materials for specific applications require an accurate control and
+complete comprehension of their magnetic properties. In particular,
+nanoparticles embedded in a polycrystalline matrix emerge as good candidates
+for applications due to the possibility of tuning the magnetic properties
+through interface interaction effects. Here, iron/w\""ustite composite is
+prepared using high energy mechanical milling from iron powder and water. The
+sample is analyzed by X-ray diffraction, dynamic laser light scattering,
+M\""ossbauer spectroscopy, field cooling and zero field cooling curves,
+magnetization curves, and magnetic hyperthermia. Based on the results, we
+identify that the produced sample is like Fe nanoparticles embedded in a
+w\""ustite matrix, with high stability in time, and shows noticeable features
+such as exchange bias effect at low temperatures and promising temperatures
+reached in a short time interval when considered magnetic hyperthermia, $\sim
+46\,^\circ$C, becoming an interesting candidate for biological applications,
+such as the one employed for cancer therapy.",1408.2703v1
+2014-08-14,Particle Capture Efficiency in a Multi-Wire Model for High Gradient Magnetic Separation,"High gradient magnetic separation (HGMS) is an efficient way to remove
+magnetic and paramagnetic particles, such as heavy metals, from waste water. As
+the suspension flows through a magnetized filter mesh, high magnetic gradients
+around the wires attract and capture the particles, removing them from the
+fluid. We model such a system by considering the motion of a paramagnetic
+tracer particle through a periodic array of magnetized cylinders. We show that
+there is a critical Mason number (ratio of viscous to magnetic forces) below
+which the particle is captured irrespective of its initial position in the
+array. Above this threshold, particle capture is only partially successful and
+depends on the particle's entry position. We determine the relationship between
+the critical Mason number and the system geometry using numerical and
+asymptotic calculations. If a capture efficiency below 100% is sufficient, our
+results demonstrate how operating the HGMS system above the critical Mason
+number but with multiple separation cycles may increase efficiency.",1408.3313v1
+2014-09-16,"Magnetic field configurations of a magnetar throughout its interior and exterior -- core, crust and magnetosphere","We obtained the magnetic field configurations, including both poloidal and
+toroidal components, throughout the interior and exterior of magnetars using a
+realistic equation of state. We divided the magnetized star into the
+hydromagnetic equilibrium core, Hall equilibrium crust and twisted force-free
+magnetosphere. We systematically and simultaneously calculated these regions
+under various boundary conditions using the Green function relaxation method,
+and noted the following interesting characteristics of these numerical results.
+First, the strength and structure of core magnetic fields affect the crustal
+magnetic fields. Second, the current sheet on the core-crust interface affects
+both internal and external magnetic field configurations. Third, the twisted
+magnetosphere makes a cross-point of magnetic field lines, such as X-point
+geometry, in the magnetosphere. The X-point geometry appears and disappears
+according to the strength of the twisted field in the magnetosphere or the
+core-crust boundary conditions. Our results mean that both Hall
+magnetohydrodynamics secular evolution and magnetospheric dynamical evolution
+are deeply affected by conditions of another region and the core-crust stress
+of magnetars.",1409.4547v2
+2014-09-25,Quantitative simulation of temperature dependent magnetization dynamics and equilibrium properties of elemental ferromagnets,"Atomistic spin model simulations are immensely useful in determining
+temperature dependent magnetic prop- erties, but are known to give the
+incorrect dependence of the magnetization on temperature compared to exper-
+iment owing to their classical origin. We find a single parameter rescaling of
+thermal fluctuations which gives quantitative agreement of the temperature
+dependent magnetization between atomistic simulations and experi- ment for the
+elemental ferromagnets Ni, Fe, Co and Gd. Simulating the sub-picosecond
+magnetization dynam- ics of Ni under the action of a laser pulse we also find
+quantitative agreement with experiment in the ultrafast regime. This enables
+the quantitative determination of temperature dependent magnetic properties
+allowing for accurate simulations of magnetic materials at all temperatures.",1409.7397v2
+2014-11-12,Block magnetic excitations in the orbitally selective Mott insulator BaFe2Se3,"Iron pnictides and selenides display a variety of unusual magnetic phases
+originating from the interplay between electronic, orbital, and lattice degrees
+of freedom. Using powder inelastic neutron scattering on the two-leg ladder
+BaFe2Se3, we fully characterize the static and dynamic spin correlations
+associated with the Fe4 block state, an exotic magnetic ground state observed
+in this low-dimensional magnet and in Rb0.89Fe1.58Se2. All the magnetic
+excitations of the Fe4 block state predicted by an effective Heisenberg model
+with localized spins are observed below 300 meV and quantitatively reproduced.
+However, the data only account for 16 mub^2 per Fe2+, approximatively 2/3 of
+the total spectral weight expected for localized S=2 moments. Our results
+highlight how orbital degrees of freedom in iron-based magnets can conspire to
+stabilize an exotic magnetic state.",1411.3337v2
+2014-11-13,Review: Magnetic fields of O stars,"Since 2002, strong, organized magnetic fields have been firmly detected at
+the surfaces of about 10 Galactic O-type stars. In this paper I will review the
+characteristics of the inferred fields of individual stars, as well as the
+overall population. I will discuss the extension of the 'magnetic desert',
+first inferred among the A-type stars, to O stars up to 60 solar masses. I will
+discuss the interaction of the winds of the magnetic stars with the fields
+above their surfaces, generating complex 'dynamical magnetosphere' structures
+detected in optical and UV lines, and in X-ray lines and continuum. Finally, I
+will discuss the detection of a small number of variable O stars in the LMC and
+SMC that exhibit spectral characteristics analogous to the known Galactic
+magnetic stars, and that almost certainly represent the first known examples of
+extra-Galactic magnetic stars.",1411.3604v1
+2014-11-14,Photo-induced magnetization enhancement in two-dimensional weakly anisotropic Heisenberg magnets,"By comparing the photo-induced magnetization dynamics in simple layered
+systems we show how light-induced modifications of the magnetic anisotropy
+directly enhance the magnetization. It is observed that the spin precession in
+(CH3NH3)2CuCl4, initiated by a light pulse, increases in amplitude at the
+critical temperature TC. The phenomenon is related to the dependence of the
+critical temperature on the axial magnetic anisotropy. The present results
+underline the possibility and the importance of the optical modifications of
+the anisotropy, opening new paths toward the control of the magnetization state
+for ultrafast memories.",1411.3918v1
+2015-02-21,Geometrically induced magnetic catalysis and critical dimensions,"We discuss the combined effect of magnetic fields and geometry in interacting
+fermionic systems. At leading order in the heat-kernel expansion, the infrared
+singularity (that in flat space leads to the magnetic catalysis) is regulated
+by the chiral gap effect, and the catalysis is deactivated by the effect of the
+scalar curvature. We discover that an infrared singularity is found in
+higher-order terms that mix the magnetic field with curvature, and these lead
+to a novel form of geometrically induced magnetic catalysis. The dynamical mass
+squared is then modified not only due to the chiral gap effect by an amount
+proportional to the curvature, but also by a magnetic shift $\propto (4-D)eB$,
+where $D$ represents the number of space-time dimensions. We argue that $D=4$
+is a critical dimension across which the behavior of the magnetic shift changes
+qualitatively.",1502.06090v2
+2015-04-16,Ferrogels cross-linked by magnetic particles: Field-driven deformation and elasticity studied using computer simulations,"Ferrogels, i.e. swollen polymer networks into which magnetic particles are
+immersed, can be considered as ""smart materials"" since their shape and
+elasticity can be controlled by an external magnetic field. Using molecular
+dynamics simulations on the coarse-grained level we study a ferrogel in which
+the magnetic particles act as the cross-linkers of the polymer network. In a
+homogeneous external magnetic field the direct coupling between the orientation
+of the magnetic moments and the polymers by means of covalent bonds gives rise
+to a deformation of the gel, independent of the interparticle dipole-dipole
+interaction. In this paper we report quantitative measurements of this
+deformation, the gel's elastic moduli and its magnetic response. Our results
+demonstrate that these properties depend significantly on the topology of the
+polymer network.",1504.04280v2
+2015-05-04,High-topological-number magnetic skyrmions and topologically protected dissipative structure,"The magnetic skyrmion with the topological number of unity ($Q=1$) is a
+well-known nanometric swirling spin structure in the nonlinear $\sigma$ model
+with the Dzyaloshinskii-Moriya interaction. Here, we show that magnetic
+skyrmion with the topological number of two ($Q=2$) can be created and
+stabilized by applying vertical spin-polarized current though it cannot exist
+as a static stable excitation. Magnetic skyrmion with $Q=2$ is a nonequilibrium
+dynamic object, subsisting on a balance between the energy injection from the
+current and the energy dissipation by the Gilbert damping. Once it is created,
+it becomes a topologically protected object against fluctuations of various
+variables including the injected current itself. Hence, we may call it a
+topologically protected dissipative structure. We also elucidate the nucleation
+and destruction mechanisms of the magnetic skyrmion with $Q=2$ by studying the
+evolutions of the magnetization distribution, the topological charge density as
+well as the energy density. Our results will be useful for the study of the
+nontrivial topology of magnetic skyrmions with higher topological numbers.",1505.00522v2
+2015-06-12,Generation of large-scale magnetic fields by small-scale dynamo in shear flows,"We propose a new mechanism for turbulent mean-field dynamo in which the
+magnetic fluctuations resulting from a small-scale dynamo drive the generation
+of large-scale magnetic fields. This is in stark contrast to the common idea
+that small-scale magnetic fields should be harmful to large-scale dynamo
+action. These dynamos occur in the presence of large-scale velocity shear and
+do not require net helicity, resulting from off-diagonal components of the
+turbulent resistivity tensor as the magnetic analogue of the ""shear-current""
+effect. Given the inevitable existence of non-helical small-scale magnetic
+fields in turbulent plasmas, as well as the generic nature of velocity shear,
+the suggested mechanism may help to explain generation of large-scale magnetic
+fields across a wide range of astrophysical objects.",1506.04109v2
+2015-06-17,Continuous wave approach for simulating Ferromagnetic Resonance in nanosized elements,"We present a numerical approach to simulate the Ferromagnetic Resonance (FMR)
+of micron and nanosized magnetic elements by a micromagnetic finite difference
+method. In addition to a static magnetic field a linearly polarized oscillating
+magnetic field is utilized to excite and analyze the spin wave excitations
+observed by Ferromagnetic Resonance in the space- and time-domain. Our
+continuous wave approach (CW) provides an alternative to the common simulation
+method, which uses a pulsed excitation of the magnetic system. It directly
+models conventional FMR-experiments and permits the determination of the real
+and imaginary part of the complex dynamic susceptibility without the need of
+post-processing. Furthermore not only the resonance fields, but also
+linewidths, ellipticity, phase relations and relative intensities of the
+excited spin wave modes in a spectrum can be determined and compared to
+experimental data. The magnetic responses can be plotted as a function of
+spatial dimensions yielding a detailed visualization of the spin wave modes and
+their localization as a function of external magnetic field and frequency. This
+is illustrated for the case of a magnetic micron sized stripe.",1506.05292v1
+2015-06-17,The terahertz frontier for ultrafast coherent magnetic switching: Terahertz-induced demagnetization in ferromagnets,"The transition frequency between nonthermal coherent magnetic precessions and
+ultrafast demagnetization is arguably the most sought after answer in magnetism
+science and technology nowadays. So far, it is believed to be in the terahertz
+(THz) range. Here, using an ultra-intense low frequency THz bullet, and thin
+magnetic layers, we report on experimental evidences that fully coherent
+nonthermal THz magnetic switching may never be reachable in conventional
+ferromagnetic thin films. At high excitation intensities, while the spins still
+coherently precess with the THz magnetic field, the deposited THz energy
+initiates ultrafast demagnetization and ultimately material damage. These
+series of phenomena are found to take place simultaneously. The reported
+experiments set fundamental limits and raise questions on the coupling between
+electronic and magnetic systems and the associated structural dynamics on the
+ultrafast time scale.",1506.05397v1
+2015-09-17,Dynamics of magnetic single domain particles embedded in a viscous liquid,"Kinetic equations for magnetic nano particles dispersed in a viscous liquid
+are developed and analyzed numerically. Depending on the amplitude of an
+applied oscillatory magnetic field the particles orient their time averaged
+anisotropy axis perpendicular to the applied field for low magnetic field
+amplitudes and nearly parallel to the direction of the field for high
+amplitudes. The transition between these regions takes place in a narrow field
+interval. In the low field region the magnetic moment is locked to some crystal
+axis and the energy absorption in an oscillatory driving field is dominated by
+viscous losses associated with particle rotation in the liquid. In the opposite
+limit the magnetic moment rotates within the particle while its easy axis being
+nearly parallel to the external field direction oscillates. The kinetic
+equations are generalized to include thermal fluctuations. This leads to a
+significant increase of the power absorption in the low and intermediate field
+region with a pronounced absorption peak as function of particle size. In the
+high field region, on the other hand, the inclusion of thermal fluctuations
+reduces the power absorption. The illustrative numerical calculations presented
+are performed for magnetic parameters typical for iron oxide.",1509.05233v1
+2015-10-19,Effect of magnetism on lattice dynamics in SrFe$_2$As$_2$ as seen via high resolution inelastic x-ray scattering,"Phonon spectra of detwinned {SrFe$_2$As$_2$} crystals, as measured by
+inelastic x-ray scattering, show clear anisotropy accompanying the
+magneto-structural transition at 200 K. We model the mode splitting using
+magnetic DFT calculations, including a phenomenological reduction in
+force-constant anisotropy that can be attributed to magnetic fluctuations. This
+serves as a starting point for a general model of phonons in this material
+applicable to both magnetic and non-magnetic phase. Using this model, the
+measured splitting in the magnetic phase below $\it T_{N}$, and the measured
+phonon linewidth, we set a lower bound on the mean magnetic fluctuation
+frequency above $\it T_{N}$ at 210 K.",1510.05487v2
+2016-02-26,The magnetic monopole and the separation between fast and slow magnetic degrees of freedom,"The Landau-Lifshitz-Gilbert (LLG) equation that describes the dynamics of a
+macroscopic magnetic moment finds its limit of validity at very short times.
+The reason for this limit is well understood in terms of separation of the
+characteristic time scales between slow degrees of freedom (the magnetization)
+and fast degrees of freedom. The fast degrees of freedom are introduced as the
+variation of the angular momentum responsible for the inertia. In order to
+study the effect of the fast degrees of freedom on the precession, we calculate
+the geometric phase of the magnetization (i.e. the Hannay angle) and the
+corresponding magnetic monopole. In the case of the pure precession (the slow
+manifold), a simple expression of the magnetic monopole is given as a function
+of the slowness parameter, i.e. as a function of the ratio of the slow over the
+fast characteristic times.",1602.08470v1
+2016-07-26,Two-phase flow of ferrofluids,"Ferrofluids currently are the only type of magnetic liquid materials with
+wide practical use. The theory on ferrofluids is an example of success to apply
+statistics to science. Ferrofluids are two-phase liquids consisting of
+dispersed nanoscale ferromagnetic particles suspended in a carrier fluid. Due
+to their tiny size, individual ferromagnetic particles clearly exhibit Brownian
+motions. Only when a large number of randomly-moving particles are subject to
+an external magnetic field, can they collectively exhibit magnetization at a
+macroscale. Using statistical theory, the magnetization of a ferrofluid can be
+characterized by the celebrated Langevin equation. The monograph combines
+statistical theory and the method of Dirac function to establish equations for
+ferrofluids under several conditions, including magnetization relaxation,
+magnetization equilibrium, and magnetization freezing. It thus provides a quite
+complete account of the theory of ferrofluid dynamics.",1607.07838v1
+2016-09-10,Vortex disruption by magnetohydrodynamic feedback,"In an electrically conducting fluid, vortices stretch out a weak, large-scale
+magnetic field to form strong current sheets on their edges. Associated with
+these current sheets are magnetic stresses, which are subsequently released
+through reconnection, leading to vortex disruption, and possibly even
+destruction. This disruption phenomenon is investigated here in the context of
+two-dimensional, homogeneous, incompressible magnetohydrodynamics. We derive a
+simple order of magnitude estimate for the magnetic stresses --- and thus the
+degree of disruption --- that depends on the strength of the background
+magnetic field (measured by the parameter $M$, a ratio between the Alfv\'en
+speed and a typical flow speed) and on the magnetic diffusivity (measured by
+the magnetic Reynolds number $\mbox{Rm}$). The resulting estimate suggests that
+significant disruption occurs when $M^{2}\mbox{Rm} = O(1)$. To test our
+prediction, we analyse direct numerical simulations of vortices generated by
+the breakup of unstable shear flows with an initially weak background magnetic
+field. Using the Okubo--Weiss vortex coherence criterion, we introduce a vortex
+disruption measure, and show that it is consistent with our predicted scaling,
+for vortices generated by instabilities of both a shear layer and a jet.",1609.03069v1
+2016-09-29,Jet formation in solar atmosphere due to magnetic reconnection,"Using numerical simulations, we show that jets with features of type II
+spicules and cold coronal jets corresponding to temperatures $10^{4}$ K can be
+formed due to magnetic reconnection in a scenario in presence of magnetic
+resistivity. For this we model the low chromosphere-corona region using the C7
+equilibrium solar atmosphere model and assuming Resistive MHD rules the
+dynamics of the plasma. The magnetic filed configurations we analyze correspond
+to two neighboring loops with opposite polarity. The separation of the loops'
+feet determines the thickness of a current sheet that triggers a magnetic
+reconnection process, and the further formation of a high speed and sharp
+structure. We analyze the cases where the magnetic filed strength of the two
+loops is equal and different. In the first case, with a symmetric configuration
+the spicules raise vertically whereas in an asymmetric configuration the
+structure shows an inclination. With a number of simulations carried out under
+a 2.5D approach, we explore various properties of excited jets, namely, the
+morphology, inclination and velocity. The parameter space involves magnetic
+field strength between 20 and 40 G, and the resistivity is assumed to be
+uniform with a constant value of the order $10^{-2}\Omega\cdot m$",1609.09422v1
+2016-10-05,"Orbital frustration in the S = 1/2 kagome magnet vesignieite, BaCu3V2O8(OD)2","Here we report crystallographic and magnetic studies on high quality samples
+of the magnetically frustrated S = 1/2 kagome antiferromagnet vesignieite,
+BaCu3V2O8(OD)2. Powder neutron diffraction data collected from samples obtained
+by a new hydrothermal synthetic route reveal a previously unobserved trigonal
+P3121 structure, similar to the isoelectronic mineral SrCu3V2O8(OH)2. The
+refined structure is consistent with orbital frustration of the eg d-orbitals
+in a sublattice of the Cu2+ kagome network due to a dynamic Jahn-Teller effect,
+which persists below the magnetic transition at TN = 9K and makes the material
+an interesting candidate for exploring concomitant spin and orbital
+frustration. A combination of crystallographic strain analysis and
+magnetisation measurements indicate strong magnetostructural coupling which may
+explain the varied magnetic behaviour between samples of vesignieite in the
+literature. The revised orbital structure is similar to that found in
+volborthite, rather than the quantum spin liquid herbertsmithite, and provides
+a convincing argument for the differing magnetic properties found in these
+frustrated magnets.",1610.01436v1
+2016-12-22,Tunable Finite-Sized Chains to Control Magnetic Relaxation,"The magnetic dynamics of low-dimensional iron ion chains have been studied
+with regards to the tunable finite-sized chain length using iron phthalocyanine
+thin films. The deposition temperature varies the diffusion length during thin
+film growth by limiting the average crystal size in the range from 40 to 110
+nm. Using a method common for single chain magnets, the magnetic relaxation
+time for each chain length is determined from temporal remanence data and fit
+to a stretched exponential form in the temperature range below 5 K, the onset
+for magnetic hysteresis. A temperature-independent master curve is generated by
+scaling the remanence by its relaxation time to fit the energy barrier for spin
+reversal, and the single spin relaxation time. The energy barrier of 95 K is
+found to be independent of the chain length. In contrast, the single spin
+relaxation time increases with longer chains from under 1 ps to 800 ps. We show
+that thin films provide the nano-architecture to control magnetic relaxation
+and a testbed to study finite-size effects in low-dimensional magnetic systems.",1612.07397v1
+2017-02-17,Magnetic anisotropy in Permalloy: hidden quantum mechanical features,"By means of relativistic, first principles calculations, we investigate the
+microscopic origin of the vanishingly low magnetic anisotropy of Permalloy,
+here proposed to be intrinsically related to the local symmetries of the alloy.
+It is shown that the local magnetic anisotropy of individual atoms in Permalloy
+can be several orders of magnitude larger than that of the bulk sample, and
+5-10 times larger than that of elemental Fe or Ni. We, furthermore, show that
+locally there are several easy axis directions that are favored, depending on
+local composition. The results are discussed in the context of perturbation
+theory, applying the relation between magnetic anisotropy and orbital moment.
+Permalloy keeps its strong ferromagnetic nature due to the exchange energy to
+be larger than the magnetocrystalline anisotropy. Our results shine light on
+the magnetic anisotropy of permalloy and of magnetic materials in general, and
+in addition enhance the understanding of pump-probe measurements and ultrafast
+magnetization dynamics.",1702.05414v1
+2017-02-21,Topological staggered field-electric effect with bipartite magnets,"We study the interface physics of bipartite magnetic materials deposited on a
+topological insulator. This comprises antiferromagnets as well as ferrimagnets
+and ferromagnets with multiple magnetic moments per unit cell. If an energy gap
+is induced in the Dirac states on the topological surface, a topological
+magnetoelectric effect has been predicted. Here, we show that this effect can
+act in opposite directions on the two components of the magnet in certain
+parameter regions. Consequently, an electric field will mainly generate a
+staggered field rather than a net magnetization in the plane. This is relevant
+for the current attempts to detect the magnetoelectric effect experimentally,
+as well as for possible applications. We take a field-theoretic approach that
+includes the quantum fluctuations of both the Dirac fermions on the topological
+surface as well as the fermions in the surface layer of the magnet in an
+analytically solvable model. The effective Lagrangian and the Landau-Lifshitz
+equation describing the interfacial magnetization dynamics are derived.",1702.06483v2
+2017-05-25,Fourier optical processing enables new capabilities in diamond magnetic imaging,"Diamond-based magnetic field sensors have attracted great interest in recent
+years. In particular, wide-field magnetic imaging using nitrogen-vacancy (NV)
+centers in diamond has been previously demonstrated in condensed matter,
+biological, and paleomagnetic applications. Vector magnetic imaging with NV
+ensembles typically requires an applied field (>10 G) to separate the
+contributions from four crystallographic orientations, hindering studies of
+magnetic samples that require measurement in low or independently specified
+bias fields. Here we decompose the NV ensemble magnetic resonance spectrum
+without such a bias field by modulating the collected light at the microscope's
+Fourier plane. In addition to enabling vector magnetic imaging at arbitrarily
+low fields, our method can be used to extend the dynamic range at a given bias
+field. As demonstrated here, optically-detected diamond magnetometry stands to
+benefit from Fourier optical approaches, which have already found widespread
+utility in other branches of photonics.",1705.09241v1
+2017-07-25,Skyrmion mediated voltage controlled switching of ferromagnets for reliable and energy efficient 2-terminal memory,"We propose a two terminal nanomagnetic memory element based on magnetization
+reversal of a perpendicularly magnetized nanomagnet employing a unipolar
+voltage pulse that modifies the perpendicular anisotropy of the system. Our
+work demonstrates that the presence of Dzyaloshinskii-Moriya Interaction (DMI)
+can create alternative route for magnetization reversal that obviates the need
+for utilizing precessional magnetization dynamics as well as a bias magnetic
+field that are employed in traditional voltage control of magnetic anisotropy
+(VCMA) based switching of perpendicular magnetization. We show with extensive
+micromagnetic simulation, in the presence of thermal noise, that the proposed
+skyrmion mediated VCMA switching mechanism is robust at room temperature
+leading to extremely low error switching while also being potentially 1-2
+orders of magnitude more energy efficient than state of the art spin transfer
+torque (STT) based switching.",1707.07777v1
+2017-10-05,Magnetic Skyrmionic Polarons,"We study a two-dimensional electron gas exchanged-coupled to a system of
+classical magnetic ions. For large Rashba spin-orbit coupling a single electron
+can become self-trapped in a skyrmion spin texture self-induced in the magnetic
+ions system. This new quasiparticle carries electrical and topological charge
+as well as a large spin, and we named it as magnetic skyrmionic polaron. We
+study the range of parameters; temperature, exchange coupling, Rashba coupling
+and magnetic field, for which the magnetic skyrmionic polaron is the
+fundamental state in the system. The dynamics of this quasiparticle is studied
+using the collective coordinate approximation, and we obtain that in presence
+of an electric field the new quasiparticle shows, because the chirality of the
+skyrmion, a Hall effect. Finally we argue that the magnetic skyrmionic polarons
+can be found in large Rashba spin-orbit coupling semiconductors as GeMnTe.",1710.02182v1
+2017-10-18,Magnetization plateau as a result of the uniform and gradual electron doping in a coupled spin-electron double-tetrahedral chain,"The double-tetrahedral chain in a longitudinal magnetic field, whose nodal
+lattice sites occupied by the localized Ising spins regularly alternate with
+triangular plaquettes with the dynamics described by the Hubbard model, is
+rigorously investigated. It is demonstrated that the uniform change of electron
+concentration controlled by the chemical potential in a combination with the
+competition between model parameters and the external magnetic field leads to
+the formation of one chiral and seven non-chiral phases at the absolute zero
+temperature. Rational plateaux at one-third and one-half of the saturation
+magnetization can also be identified in the low-temperature magnetization
+curves. On the other hand, the gradual electron doping results in eleven
+different ground-state regions which distinguish from each other by the
+evolution of the electron distribution during this process. Several
+doping-dependent magnetization plateaux are observed in the magnetization
+process as a result of the continuous change of electron content in the model.",1710.06822v1
+2017-11-03,THz-driven demagnetization with Perpendicular Magnetic Anisotropy: Towards ultrafast ballistic switching,"We study THz-driven spin dynamics in thin CoPt films with perpendicular
+magnetic anisotropy. Femtosecond magneto-optical Kerr effect measurements show
+that demagnetization amplitude of about $1\%$ can be achieved with a peak THz
+electric field of $300$~kV/cm, and a corresponding peak magnetic field of
+$0.1$~T. The effect is more than an order of magnitude larger than observed in
+samples with easy-plane anisotropy irradiated with the same field strength. We
+also utilize finite-element simulations to design a meta-material structure
+that can enhance the THz magnetic field by more than an order of magnitude,
+over an area of several tens of square micrometers. Magnetic fields exceeding
+$1$~Tesla, generated in such meta-materials with the available laser-based THz
+sources, are expected to produce full magnetization reversal via ultrafast
+ballistic precession driven by the THz radiation. Our results demonstrate the
+possibility of table-top ultrafast magnetization reversal induced by THz
+radiation.",1711.01234v2
+2017-11-13,Guided flows in coronal magnetic flux tubes,"There is evidence for coronal plasma flows to break down into fragments and
+to be laminar. We investigate this effect by modeling flows confined along
+magnetic channels. We consider a full MHD model of a solar atmosphere box with
+a dipole magnetic field. We compare the propagation of a cylindrical flow
+perfectly aligned to the field to that of another one with a slight
+misalignment. We assume a flow speed of 200 km/s, and an ambient magnetic field
+of 30 G. We find that while the aligned flow maintains its cylindrical symmetry
+while it travels along the magnetic tube, the misaligned one is rapidly
+squashed on one side, becoming laminar and eventually fragmented because of the
+interaction and backreaction of the magnetic field. This model could explain an
+observation of erupted fragments that fall back as thin and elongated strands
+and end up onto the solar surface in a hedge-like configuration, made by the
+Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The
+initial alignment of plasma flow plays an important role in determining the
+possible laminar structure and fragmentation of flows while they travel along
+magnetic channels.",1711.04641v1
+2017-11-15,Competition of striped magnetic order and partial Kondo screened state in the Kondo lattice model,"We analyze the magnetically ordered phases in the Kondo lattice model on a
+square lattice around quarter filling using the dynamical mean field theory. We
+find that close to quarter filling besides the paramagnetic phase, at least
+three magnetic phases compete. These phases are a ferromagnetic state, a
+partial Kondo screened state, which is a combination of charge order and
+magnetic order, and a striped magnetic phase, which is ferromagnetically
+ordered in one direction and antiferromagnetically in the other direction. We
+analyze the spectral properties of these states and show that the PKS state is
+insulating with a flat band above the Fermi energy, while the other states are
+metallic. Furthermore, we demonstrate that the energy gain by the Kondo effect
+is larger in the PKS state, while the striped magnetic state can gain more
+energy from the RKKY interaction. Thus, while the striped magnetic state is
+stable at weak coupling, the PKS state becomes stable at intermediate coupling.",1711.05402v1
+2018-01-12,Moving magnets in a micromagnetic finite difference framework,"We present a method and an implementation for smooth linear motion in a
+finite difference-based micromagnetic simulation code, to be used in simulating
+magnetic friction and other phenomena involving moving microscale magnets. Our
+aim is to accurately simulate the magnetization dynamics and relative motion of
+magnets while retaining high computational speed. To this end, we combine
+techniques for fast scalar potential calculation and cubic b-spline
+interpolation, parallelizing them on a Graphics Processing Unit (GPU). The
+implementation also includes the possibility of explicitly simulating eddy
+currents in the case of conducting magnets. We test our implementation by
+providing numerical examples of stick-slip motion of thin films pulled by a
+spring and the effect of eddy currents on the switching time of magnetic
+nanocubes.",1801.04181v2
+2018-01-31,How to manipulate magnetic states of antiferromagnets,"Antiferromagnetic materials, which have drawn considerable attention
+recently, have fascinating features: they are robust against perturbation,
+produce no stray fields, and exhibit ultrafast dynamics. Discerning how to
+efficiently manipulate the magnetic state of an antiferromagnet is key to the
+development of antiferromagnetic spintronics. In this review, we introduce four
+main methods (magnetic, strain, electrical, and optical) to mediate the
+magnetic states and elaborate on intrinsic origins of different
+antiferromagnetic materials. Magnetic control includes a strong magnetic field,
+exchange bias, and field cooling, which are traditional and basic. Strain
+control involves the magnetic anisotropy effect or metamagnetic transition.
+Electrical control can be divided into two parts, electric field and electric
+current, both of which are convenient for practical applications. Optical
+control includes thermal and electronic excitation, an inertia-driven
+mechanism, and terahertz laser control, with the potential for ultrafast
+antiferromagnetic manipulation. This review sheds light on effective usage of
+antiferromagnets and provides a new perspective on antiferromagnetic
+spintronics.",1801.10332v1
+2018-02-07,"Rotation of the photospheric magnetic field through solar cycles 21, 22, 23","Rotation of the large scale solar magnetic field has a great importance for
+the understanding of solar dynamic, for the search of longitidinal structure
+and for the study of solar-terrestrial relations. 30-year long observations
+taken at the Wilcox Solar Observatory (USA) in 21-23 cycles have been analysed
+carefully to deduce magnetic field rotation rate at different latitudes in both
+hemispheres and its variability in time. The WSO data appear to indicate that
+additionally to the differential rotation along the latitudes there are running
+waves of fast rotation of the magnetic field. These torsional waves are running
+from the poles to the equator with a period of 11 years. The rotation of the
+magnetic field (RMF) is almost rigid at latitudes above 55 degrees in both
+hemispheres. The rotation rate in the sub-polar regions is slower when the
+magnetic field is strong there (during minima of solar activity), and faster
+when the magnetic field changes polarity (during maxima of solar activity).",1802.02461v1
+2018-04-04,Anomalous nonlinearity of the magnonic edge mode,"Nonlinearity of magneto-dynamics is typically described by a single constant,
+$\mathcal{N}$, with positive and negative values indicating repulsion and
+attraction of magnons, respectively. In thin magnetic films with easy-plane
+magnetic anisotropy, magnon attraction is typically achieved for an in-plane
+magnetization. At sufficient stimulus, e.g. via application of spin transfer
+torque, the attraction can give rise to self-localized magnetic solitons, such
+as spin wave bullets, which shrink as their amplitude increases. In contrast,
+for an oblique magnetization above a certain critical angle, the repulsion of
+magnons only allows for propagating modes, which expand when pumped more
+strongly. Here we demonstrate, both analytically and using micromagnetic
+simulations, that such a dichotomic description is inadequate for magnonic edge
+modes, which naturally appear in confined magnetic systems. In particular, we
+demonstrate that the confinement potential of such modes is nonlinear in nature
+and its contribution makes $\mathcal{N}$ non-monotonically dependent on their
+amplitude. As a prominent example, edge modes show compression and expansion
+for negative and positive $\mathcal{N}$, yet remain localized. In striking
+contrast to the extended geometries, edge magnons might also repeal even for an
+in-plane magnetization.",1804.01585v1
+2018-04-13,Magnetic states in a three-dimensional topological Kondo insulator,"We theoretically study the magnetic phase diagram of a three-dimensional
+topological Kondo insulator by means of real-space dynamical mean field theory.
+We find that ferromagnetically ordered states become stable upon hole doping.
+Besides a wide ferromagnetic phase, we observe surface magnetism close to
+half-filling, which corresponds to an A-type antiferromagnetic state. We
+further study the impact of the magnetism on the symmetry protected surface
+states and find that depending on the surface and the magnetization direction,
+surface states are still protected by reflection symmetry present in our model.
+The symmetry protected surface states are shifted away by the magnetization
+from their original high symmetry momenta in the Brillouin zone. Remarkably,
+due to the magnetization, the surface states are deformed, resulting in the
+appearance of arcs in the momentum resolved spectrum.",1804.04802v1
+2018-06-20,Magnetic Imaging and Microscopy,"The magnetic domain configuration of a system reveals a wealth of information
+about the fundamental magnetic properties of that system and can be a critical
+factor in the operation of magnetic devices. Not only are the details of the
+domain structure strongly governed by materials parameters, but in thin-films
+and mesoscopic elements the geometry has an often pivotal effect, providing a
+convenient handle to tailor desired domain states. Furthermore a full
+understanding of a system requires, in addition, investigation of the dynamic
+evolution of the spin-state, which is of particular importance for applications
+relying on e.g. the switching of magnetic elements. Here we review some of the
+main modern techniques for magnetic imaging, highlighting their respective
+advantages and limitations. The methods for imaging domain configurations and
+spin structures cover various spatial and temporal resolution scales and
+encompass those based on electron and x-ray microscopy as well as scanning
+probe techniques. Furthermore, away from the discipline of condensed-matter
+physics, magnetic effects are instrumental in a number of techniques for
+medical imaging, some key examples of which we also present.",1806.07767v2
+2018-07-11,Dynamical coupling of dilute magnetic impurities with quantum spin liquid state in the S = 3/2 dimer compound Ba3ZnRu2O9,"We have investigated the dilute magnetic impurity effect on the magnetic
+properties of a quantum spin liquid candidate Ba3ZnRu2O9 and a spin gapped
+compound Ba3CaRu2O9. The magnetic ground state of each compound stands against
+2% substitution of magnetic impurities for Zn or Ca. We have found that the
+magnetic response of these impurities, which behave as paramagnetic spins,
+depends on the host materials and the difference of the two manifests itself in
+the Weiss temperature, which can hardly be explained by the dilute magnetic
+impurities alone in the case of Ba3ZnRu2O9. We consider a contribution from the
+Ru5+ ions which would appear only in the substituted Ba3ZnRu2O9 and discuss a
+possible physical meaning of the observed Weiss temperature.",1807.04076v1
+2018-12-25,Quiet Region Jet by Eruption of Minifilament and Associated Change in Magnetic Flux,"We observe a coronal jet around 22:08 UT on 23 rd March of 2017, in a quiet
+region towards the north-east of the solar disk. A minifilament eruption leads
+to this jet. We analyze dynamics of the minifilament from its formation until
+its eruption. We observe that the minifilament starts forming around 15:50 UT.
+Then at a later time, it disappears but again appears and finally erupts as a
+blowout jet around 22:08 UT. We study the evolution of photospheric magnetic
+field beneath the minifilament. Initially, we observe subsequent increase and
+decrease of positive magnetic flux. Prior to the initiation of the eruption,
+positive magnetic flux shows a continuous decrease until the minifilament
+disappears. The positive magnetic flux increases and decreases due to new
+positive flux emergence and cancellation of positive magnetic flux with
+negative magnetic flux respectively.",1812.10090v1
+2019-02-28,The growth of chiral magnetic instability in a large-scale magnetic field,"The chiral magnetic effect emerges from a miroscopic level, and its
+interesting consequences have been discussed in the dynamics of the early
+universe, neutron stars and quark-gluon plasma. An instability is caused by
+anomalous electric current along magnetic field. We investigate effects of
+plasma motion on the instability in terms of linearized perturbation theory. A
+magnetic field can inhibit magnetohydrodynamic waves to a remarkable degree and
+thereby affects the instability mode. We also found that the unstable mode is
+consisted of coupling between Alfven and one of magneto-acoustic waves.
+Therefore, the propagation of a mixed Alfven wave driven by magnetic tension is
+very important. The direction of unperturbed magnetic field favors the wave
+propagation of the instability mode, when Alfven speed exceeds sound speed.",1902.10888v1
+2019-03-11,High Field Anomalies of Equilibrium and Ultrafast Magnetism in Rare-Earth-Transition Metal Ferrimagnets,"Magneto-optical spectroscopy in fields up to 30 Tesla reveals anomalies in
+the equilibrium and ultrafast magnetic properties of the ferrimagnetic
+rare-earth-transition metal alloy TbFeCo. In particular, in the vicinity of the
+magnetization compensation temperature, each of the magnetizations of the
+antiferromagnetically coupled Tb and FeCo sublattices show triple hysteresis
+loops. Contrary to state-of-the-art theory, which explains such loops by sample
+inhomogeneities, here we show that they are an intrinsic property of the
+rare-earth ferrimagnets. Assuming that the rare-earth ions are paramagnetic and
+have a non-zero orbital momentum in the ground state and, therefore, a large
+magnetic anisotropy, we are able to reproduce the experimentally observed
+behavior in equilibrium. The same theory is also able to describe the
+experimentally observed critical slowdown of the spin dynamics in the vicinity
+of the magnetization compensation temperature, emphasizing the role played by
+the orbital momentum in static and ultrafast magnetism of ferrimagnets.",1903.04293v1
+2019-04-02,Controlled self-aggregation of polymer-based nanoparticles employing shear flow and magnetic fields,"Star polymers with magnetically functionalized end groups are presented as a
+novel polymeric system whose morphology, self-aggregation, and orientation can
+easily be tuned by exposing these macromolecules simultaneously to an external
+magnetic field and to shear forces. Our investigations are based on a
+specialized simulation technique which faithfully takes into account the
+hydrodynamic interactions of the surrounding, Newtonian solvent. We find that
+the combination of magnetic field (including both strength and direction) and
+shear rate controls the mean number of magnetic clusters, which in turn is
+largely responsible for the static and dynamic behavior. While some properties
+are similar to comparable non-magnetic star polymers, others exhibit novel
+phenomena; examples of the latter include the breakup and reorganization of the
+clusters beyond a critical shear rate, and a strong dependence of the
+efficiency with which shear rate is translated into whole-body rotations on the
+direction of the magnetic field.",1904.01535v1
+2019-05-02,Direct Evidence of Torque-mediated Optical Magnetism,"We report experimental evidence of a mechanism that supports and intensifies
+induced magnetization at optical frequencies without the intervention of
+spin-orbit or spin-spin interactions. Energy-resolved spectra of scattered
+light, recorded at moderate intensities (108 W/cm2) and short timescales (<150
+fs) in a series of non-magnetic molecular liquids, reveal the signature of
+torque dynamics driven jointly by the electric and magnetic field components of
+light at the molecular level. While past experiments have recorded radiant
+magnetization from magneto-electric interactions of this type, no evidence has
+been provided to date of the inelastic librational features expected in
+cross-polarized light scattering spectra due to the Lorentz force acting in
+combination with optical magnetic torque. Here, torque is shown to account for
+inelastic components in the magnetic scattering spectrum under conditions that
+produce no such features in electric dipole scattering, in excellent agreement
+with quantum theoretical predictions",1905.00552v1
+2019-05-10,Sedimentation of a suspension of paramagnetic particles in an external magnetic field,"We investigate the sedimentation of initially packed paramagnetic particles
+in presence of a homogeneous external magnetic field, in a Hele-Shaw cell
+filled with water. Although the magnetic susceptibility of the particles is
+small and the particle-particle induced magnetic interactions are significantly
+smaller compared to the gravitational acceleration, we do observe a measurable
+reduction of the decompaction rate as the amplitude of the applied magnetic
+field is increased. While induced magnetic dipole-dipole interactions between
+particles can be either attracting or repulsive depending on the particles
+relative alignment, our observations reveal an effective overall enhancement of
+the cohesion of the initial pack of particles due to the induced interactions,
+very likely promoting internal chain forces in the initial pack of particles.
+The influence of the magnetic field on the particles once they disperse after
+being decompacted is on the other hand found to remain marginal.",1905.04036v1
+2019-06-23,Probing magnetism via spin dynamics in graphene/2D-ferromagnet heterostructures,"The recent discovery of two-dimensional magnetic insulators has generated a
+great deal of excitement over their potential for nanoscale manipulation of
+spin or magnetism. One intriguing use for these materials is to put them in
+contact with graphene, with the goal of making graphene magnetic while
+maintaining its unique electronic properties. Such a system could prove useful
+in applications such as magnetic memories, or could serve as a host for exotic
+states of matter. Proximity to a magnetic insulator will alter the spin
+transport properties of graphene, and the strength of this interaction can be
+probed with Hanle spin precession experiments. To aid in the analysis of such
+experiments, in this work we derive an explicit expression for Hanle spin
+precession in graphene interfaced with a ferromagnetic insulator whose
+magnetization points perpendicular to the graphene plane. We find that this
+interface results in a shifted and asymmetric Hanle response, and we discuss
+how this behavior can be used to interpret measurements of spin transport in
+these systems.",1906.09568v2
+2019-07-12,Extending generalized Debye analysis to long timescale magnetic relaxation,"As the ability to generate magnetic anisotropy in molecular materials
+continues to hit new milestones, concerted effort has shifted towards
+understanding, and potentially controlling, the mechanisms of magnetic
+relaxation across a large time and temperature space. Slow magnetic relaxation
+in molecules is highly temperature-, field-, and environment-dependent with the
+relevant timescale easily traversing ten orders of magnitude for current
+single-molecule magnets (SMM). The prospect of synthetic control over the
+nature of (and transition probabilities between) magnetic states make
+unraveling the underlying mechanisms an important yet daunting challenge.
+Currently, instrumental considerations dictate that the characteristic
+relaxation time, $\tau$, is determined by separate methods depending on the
+timescale of interest. Static and dynamic probe fields are used for long and
+short timescales, respectively. Each method captures a distinct,
+non-overlapping time range, and experimental differences lead to the
+possibility of fundamentally different meanings for $\tau$ being plotted and
+fitted globally as a function of temperature. Herein, we present a method to
+generate long-timescale waveforms with standard vibrating sample magnetometry
+(VSM) instrumentation, allowing extension of alternating current (AC) magnetic
+impedance measurements to SMMs and other superparamagnets with arbitrarily long
+relaxation time.",1907.05962v1
+2019-07-25,Non-destructive Ultrafast Steering of Magnetic Vortex by Terahertz Pulses,"Electric control of magnetic vortex dynamics in a reproducible way and on an
+ultrafast time scale is key element in the quest for efficient spintronic
+devices with low-energy consumption. To be useful the control scheme should
+ideally be swift, scalable, non-invasive, and resulting in reliable magnetic
+switching. Such requirements and in particular the reproducibility of altering
+the vortex chirality and/or polarity are not yet met by magnetic vortex
+switching via external magnetic fields, spin-polarized currents, spin waves, or
+laser pulses. Here we demonstrate a novel packaged-skyrmion mediated vortex
+switching process driven by a simple sequence of picosecond electrical field
+pulses via magneto-electric interactions. Both the vortex chirality and
+polarity show a well-defined reversal behaviour. The unambiguously repeated
+switching between four different magnetic vortex states provides an
+energy-efficient, highly localized and coherent control method for non-volatile
+magnetic vortex-based information storage and handling.",1907.11275v1
+2019-08-09,Modeling Spin Dynamics in the Singlet Ground State Garnet Ho3Ga5O12,"Materials containing non-Kramers magnetic ions can show unusual quantum
+excitations because of the exact mapping of the two-singlet crystal-field
+ground state to a quantum model of Ising spins in a transverse magnetic field.
+Here, we model the magnetic excitation spectrum of garnet-structured Ho3Ga5O12,
+which has a two-singlet crystal-field ground state. We use a reaction-field
+approximation to explain published inelastic neutron-scattering data [Zhou et
+al., Phys. Rev. B 78, 140406(R) (2008)] using a three-parameter model
+containing the magnetic dipolar interaction, the two-singlet crystal-field
+splitting, and the nuclear hyperfine coupling. Our study clarifies the magnetic
+Hamiltonian of Ho3Ga5O12, reveals that the nuclear hyperfine interaction drives
+magnetic ordering in this system, and provides a framework for quantitative
+analysis of magnetic excitation spectra of materials with singlet crystal-field
+ground states.",1908.03530v1
+2019-08-28,Raman scattering study of lattice and magnetic excitations in CrAs,"We report on the lattice and spin dynamics in the monopnictide CrAs using
+polarized Raman scattering. This system exhibits a first-order
+magneto-structural phase transition at T_N~ 265 K, below which the magnetic
+moments of Cr form an incommensurate double helical magnetic structure while
+the unit cell volume abruptly expands. Across the transition, the frequencies
+of the fully symmetric Ag phonons strongly renormalize, which along with the
+results of first-principle calculations suggest the presence of a sizeable
+coupling of the phonons to the magnetic degrees of freedom in this compound. In
+addition, we observe two broad modes around 350 and 1700 cm-1 in the magnetic
+phase, which we associate with two-magnon Raman scattering. This work provides
+one of the few examples of magnetic Raman scattering from a non-collinear
+magnet.",1908.10908v2
+2019-09-06,Time-dependent Ginzburg-Landau treatment of RF Magnetic Vortices in Superconductors: Vortex-Semiloops in a Spatially Nonuniform Magnetic Field,"We apply time-dependent Ginzburg Landau (TDGL) numerical simulations to study
+the finite frequency electrodynamics of superconductors subjected to intense rf
+magnetic field. Much recent TDGL work has focused on spatially uniform external
+magnetic field and largely ignores the Meissner state screening response of the
+superconductor. In this work, we solve the TGDL equations for a spatially
+non-uniform magnetic field created by a point magnetic dipole in the vicinity
+of a semi-infinite superconductor. A novel two-domain simulation is performed
+to accurately capture the effect of the inhomogeneous applied fields and the
+resulting screening currents. The creation and dynamics of vortex semiloops
+penetrating deep into the superconductor domain is observed and studied, and
+the resulting third-harmonic nonlinear response of the sample is calculated.
+The effect of point-like defects on vortex semi-loop behaviour is also studied.
+This simulation method will assist our understanding of the limits of
+superconducting response to intense rf magnetic fields.",1909.02714v2
+2019-09-16,Dissipation-induced rotation of suspended ferromagnetic nanoparticles,"We report the precessional rotation of magnetically isotropic ferromagnetic
+nanoparticles in a viscous liquid that are subjected to a rotating magnetic
+field. In contrast to magnetically anisotropic nanoparticles, the rotation of
+which occurs due to coupling between the magnetic and lattice subsystems
+through magnetocrystalline anisotropy, the rotation of isotropic nanoparticles
+is induced only by magnetic dissipation processes. We propose a theory of this
+phenomenon based on a set of equations describing the deterministic magnetic
+and rotational dynamics of such particles. Neglecting inertial effects, we
+solve these equations analytically, find the magnetization and particle
+precessions in the steady state, determine the components of the particle
+angular velocity and analyze their dependence on the model parameters. The
+possibility of experimental observation of this phenomenon is also discussed.",1909.07450v2
+2019-11-26,Magnetic domain wall motion in SrRuO$_3$ thin films,"Influence of substrate miscut on magnetization dynamics in SrRuO$_3$ (SRO)
+thin films was studied. Two films were grown on SrTiO$_3$ substrates with high
+($\sim1^{\circ}$) and low ($\sim0.1^{\circ}$) miscut angles, respectively. As
+expected, high miscut angle leads to suppression of multi-variant growth. By
+means of SQUID magnetometry, comparable relaxation effects were observed in
+both the multi-variant and the nearly single-variant sample. Differences in the
+magnetization reversal process were revealed by magnetic force microscopy. It
+showed that the multi-variant growth leads to higher density of defects acting
+as pinning or nucleation sites for magnetic domains, which consequently results
+in deterioration of magnetic properties. It was demonstrated that the use of
+high miscut substrate is important for fabrication of high quality SRO thin
+films with low density of crystallographic defects and excellent magnetic
+properties.",1911.11655v1
+2019-12-08,Magnetic excitations in magnetization plateaux of a frustrated spin ladder,"Magnetization plateaux emerging in quantum spin systems due to spontaneously
+breaking of translational symmetry have been reported both theoretically and
+experimentally. The broken symmetry can induce reconstruction of elementary
+excitations such as Goldstone and Higgs modes, whereas its microscopic
+mechanism and reconstructed quasi-particle in magnetization-plateau phases have
+remained unclear so far. Here we theoretically study magnetic excitations in
+the magnetization-plateau phases of a frustrated spin ladder by using dynamical
+density-matrix renormalization-group method. Additionally, analytical
+approaches with perturbation theory are performed to obtain intuitive view of
+magnetic excitations. Comparison between numerical and analytical results
+indicates the presence of a reconstructed quasi-particle originating from
+spontaneously broken translational symmetry, which is realized as a collective
+mode of spin trimer called trimeron.",1912.03693v2
+2020-01-08,Thermal Fluctuations In The Landau-Lifshitz-Bloch Model,"A formulation for thermal noise in the stochastic form of the Landau Lifshitz
+Bloch equation used for modeling the magnetization dynamics at elevated
+temperatures is presented. The diffusion coefficients for thermal fluctuations
+are obtained via the Fokker-Plank equation using the mean field approximation
+of the field in defining the free energy. The presented model leads to a mean
+magnetization consistent with the equilibrium magnetization for small and large
+particles. The distribution of the magnetization magnitude is of a Poisson-like
+type rather than the classical Boltzmann distribution. The presented model was
+tested by studying the equilibrium magnetization in macrospin particles at high
+temperatures. The model is appealing for multi-scale modeling, such as modeling
+heat assisted magnetic recording systems and all-optical magnetization reversal",2001.02403v2
+2020-01-27,Acoustic ferromagnetic resonance and spin pumping induced by surface acoustic waves,"Voltage induced magnetization dynamics of magnetic thin films is a valuable
+tool to study anisotropic fields, exchange couplings, magnetization damping and
+spin pumping mechanism. A particularly well established technique is the
+ferromagnetic resonance (FMR) generated by the coupling of microwave photons
+and magnetization eigenmodes in the GHz range. Here we review the basic
+concepts of the so-called acoustic ferromagnetic resonance technique (a-FMR)
+induced by the coupling of surface acoustic waves (SAW) and magnetization of
+thin films. Interestingly, additional to the benefits of the microwave excited
+FMR technique, the coupling between SAW and magnetization also offers fertile
+ground to study magnon-phonon and spin rotation couplings. We describe the
+in-plane magnetic field angle dependence of the a-FMR by measuring the
+absorption / transmission of SAW and the attenuation of SAW in the presence of
+rotational motion of the lattice, and show the consequent generation of spin
+current by acoustic spin pumping.",2001.09581v1
+2020-03-06,Spin-accumulation induced magnetic texture in a metal-insulator bilayer,"We consider the influence of a spin accumulation in a normal metal on the
+magnetic statics and dynamics in an adjacent magnetic insulator. In particular,
+we focus on arbitary angles between the spin accumulation and the easy-axis of
+the magnetic insulator. Based on Landau-Lifshitz-Gilbert phenomenology
+supplemented with magnetoelectronic circuit theory, we find that the magnetic
+texture twists into a stable configuration that turns out to be described by a
+virtual, or image, domain wall configuration, i.e., a domain wall outside the
+ferromagnet. We show that even when the spin accumulation is perpendicular to
+the anisotropy axis, the magnetic texture develops a component parallel to the
+spin accumulation for sufficiently large spin bias. The emergence of this
+parallel component gives rise to threshold behavior in the spin Hall
+magnetoresistance and nonlocal magnon transport. This threshold can be used to
+design novel spintronic and magnonic devices that can be operated without
+external magnetic fields.",2003.03226v1
+2020-03-09,The impact of magnetic field on the conformations of supracolloidal polymer-like structures with super-paramagnetic monomers,"We investigate the properties of magnetic supracolliodal polymers -- magnetic
+filaments (MFs) -- with super-paramagnetic monomers, with and without Van der
+Waals (VdW) attraction between them. We employ molecular dynamics (MD)
+simulations to elucidate the impact of crosslinking mechanism on the structural
+and magnetic response of MFs to an applied external homogeneous magnetic field.
+We consider two models: plain crosslinking, which results in a flexible
+backbone; and constrained crosslinking, which provides significant stiffens
+against bending. We find that for plain crosslinking, even a slight increase of
+the central attraction leads to collapsed MF conformations. Structures that
+initially exhibit spherical symmetry evolve into cylindrically symmetric ones,
+with growing magnetic field strength. Plain crosslinking also allows for
+conformational bistability. MFs with constrained crosslinking tend to, instead,
+unravel in field. In both crosslinking scenarios, central attraction is able to
+hinder low-field magnetic response of MFs, albeit the bistability of plainly
+crosslinked MFs manifests itself also in the high-field region.",2003.04200v1
+2020-03-25,Two-photon driven magnon-pair resonance as a signature of spin-nematic order,"We theoretically study the nonlinear magnetic resonance driven by intense
+laser or electromagnetic wave in a fully polarized frustrated magnet near a
+less-visible spin-nematic ordered phase. In general, both magnons and magnon
+pairs (two-magnon bound state) appear as the low-energy excitation in the
+saturated state of spin-nematic magnets. Their excitation energies are usually
+in terahertz (THz) or gigahertz range. Magnon pairs with angular momentum
+2$\hbar$ can be excited by the simultaneous absorption of two photons, and such
+multi-photon processes occur if the applied THz laser is strong enough. We
+compute laser-driven magnetic dynamics of a frustrated four-spin system with
+both magnon ($\hbar$) and magnon-pair (2$\hbar$) like excitations which is
+analogous to a macroscopic frustrated magnet with a spin nematic phase. We
+estimate the required strength of magnetic field of laser for the realization
+of two photon absorption, taking into account dissipation effects with the
+Lindblad equation. We show that intense THz laser with ac magnetic field of
+0.1-1.0 Tesla is enough to observe magnon-pair resonance.",2003.11240v2
+2020-03-26,Energy storage in magnetic textures driven by vorticity flow,"An experimentally feasible energy-storage concept is formulated based on
+vorticity (hydro)dynamics within an easy-plane insulating magnet. The free
+energy, associated with the magnetic winding texture, is built up in a circular
+easy-plane magnetic structure by injecting a vorticity flow in the radial
+direction. The latter is accomplished by electrically induced spin-transfer
+torque, which pumps energy into the magnetic system in proportion to the vortex
+flux. The resultant magnetic metastable state with a finite winding number can
+be maintained for a long time because the process of its relaxation via phase
+slips is exponentially suppressed when the temperature is well below the Curie
+temperature. We propose to characterize the vorticity-current interaction
+underlying the energy-loading mechanism through its contribution to the
+effective electric inductance in the rf response. Our proposal may open an
+avenue for naturally powering spintronic circuits and nontraditional
+magnet-based neuromorphic networks.",2003.12121v1
+2020-03-30,Electronic correlation effects and local magnetic moments in L1$_0$ phase of FeNi,"We study the electronic and magnetic properties of L1$_0$ phase of FeNi, a
+perspective rare-earth-free permanent magnet, by using a combination of density
+functional and dynamical mean-field theory. Although L1$_0$ FeNi has a slightly
+tetragonally distorted fcc lattice, we find that magnetic properties of its
+constituent Fe atoms resemble those in pure bcc Fe. In particular, our results
+indicate the presence of well-localized magnetic moments on Fe sites, which are
+formed due to Hund's exchange. At the same time, magnetism of Ni sites is much
+more itinerant. Similarly to pure bcc Fe, the self-energy of Fe $3d$ states is
+found to show the non-Fermi-liquid behavior. This can be explained by
+peculiarities of density of Fe $3d$ states, which has pronounced peaks near the
+Fermi level. Our study of local spin correlation function and momentum
+dependence of particle-hole bubble suggests that the magnetic exchange in this
+substance is expected to be of RKKY-type, with iron states providing
+local-moment contribution, and the states corresponding to nickel sites
+(including virtual hopping to iron sites) providing itinerant contribution.",2003.13347v2
+2020-07-20,Stacking Domain Wall Magnons in Twisted van der Waals Magnets,"Using bilayer CrI$_3$ as an example, we demonstrate that stacking domain
+walls in van der Waals magnets can host one dimensional (1D) magnon channels,
+which have lower energies than bulk magnons. Interestingly, some magnon
+channels are hidden in magnetically homogeneous background and can only be
+inferred with the knowledge of stacking domain walls. Compared to 1D magnons
+confined in magnetic domain walls, 1D magnons in stacking domain walls are more
+stable against external perturbations. We show that the relaxed moir\'e
+superlattices of small-angle twisted bilayer CrI$_3$ is a natural realization
+of stacking domain walls and host interconnected moir\'e magnon network. Our
+work reveals the importance of stacking domain walls in understanding magnetic
+properties of van der Waals magnets, and extends the scope of stacking
+engineering to magnetic dynamics.",2007.10398v2
+2020-08-05,Magnetism of Nd$_2$O$_3$ single crystals near the Néel temperature,"Single crystals of Nd$_2$O$_3$ were grown and characterized using neutron
+scattering and thermodynamic measurements. Nd$_2$O$_3$ has long-range
+antiferromagnetic order below $T_{\rm N}$ = 0.55 K and specific heat
+measurements have demonstrated that a significant amount of the magnetic
+entropy is released above $T_{\rm N}$. Inelastic neutron scattering experiments
+reveal a magnetic mode(s) with little dispersion peaked at $\approx$ 0.37 meV
+that is of greatest intensity below $T_{\rm N}$ but persists above 2$T_{\rm
+N}$. This persistence of dynamic correlations is likely related to frustrated
+interactions associated with the nearly-ideal stacked triangular lattice
+geometry of $J_{\textrm{eff}}$ = 1/2 spins on Nd$^{3+}$ ions. The magnetization
+is observed to be strongly anisotropic at all temperatures due to crystal field
+effects, with easy-plane anisotropy observed. A non-compensated magnetic
+structure is inferred from the temperature-dependence of the magnetization when
+a magnetic field of sufficient strength is applied within the basal plane near
+$T_{\rm N}$, and the evolution of the long-range order is summarized in a
+temperature-field phase diagram.",2008.02298v1
+2020-08-14,Inefficient magnetic-field amplification in supersonic laser-plasma turbulence,"We report a laser-plasma experiment that was carried out at the LMJ-PETAL
+facility and realized the first magnetized, turbulent, supersonic plasma with a
+large magnetic Reynolds number ($\mathrm{Rm} \approx 45$) in the laboratory.
+Initial seed magnetic fields were amplified, but only moderately so, and did
+not become dynamically significant. A notable absence of magnetic energy at
+scales smaller than the outer scale of the turbulent cascade was also observed.
+Our results support the notion that moderately supersonic,
+low-magnetic-Prandtl-number plasma turbulence is inefficient at amplifying
+magnetic fields.",2008.06594v1
+2020-09-07,Magnetic vortex liquid and anomalous thermal Hall conductivity in frustrated magnets with bond-dependent interactions,"Recently, the observation of large thermal Hall conductivities in correlated
+insulators with no apparent broken symmetry have generated immense interest and
+debates on the underlying ground states. Here, considering frustrated magnets
+with bond-dependent interactions, which are realized in the so-called Kitaev
+materials, we theoretically demonstrate that a large thermal Hall conductivity
+can originate from a classical ground state without any magnetic order. We
+discover a novel liquid state of magnetic vortices, which are inhomogeneous
+spin textures embedded in the background of polarized spins, under out-of-plane
+magnetic fields. In the classical regime, different configurations of vortices
+form a degenerate manifold. We study the static and dynamical properties of the
+magnetic vortex liquid state at zero and finite temperatures. In particular, we
+show that the spin excitation spectrum resembles a continuum of nearly flat
+Chern bands, which ultimately leads to a large thermal Hall conductivity.
+Possible connections to experiments are discussed.",2009.03332v1
+2020-09-24,Magnetic anisotropy and exchange paths for octa- and tetrahedrally coordinated Mn$^{2+}$ ions in the honeycomb multiferroic Mn$_2$Mo$_3$O$_8$,"We investigated the static and dynamic magnetic properties of the polar
+ferrimagnet Mn$_2$Mo$_3$O$_8$ in three magnetically ordered phases via
+magnetization, magnetic torque, and THz absorption spectroscopy measurements.
+The observed magnetic field dependence of the spin-wave resonances, including
+Brillouin zone-center and zone-boundary excitations, magnetization, and torque,
+are well described by an extended two-sublattice antiferromagnetic classical
+mean-field model. In this orbitally quenched system, the competing weak
+easy-plane and easy-axis single-ion anisotropies of the two crystallographic
+sites are determined from the model and assigned to the tetra- and octahedral
+sites, respectively, by ab initio calculations.",2009.11683v1
+2020-10-15,Magnetic Manifold Hamiltonian Monte Carlo,"Markov chain Monte Carlo (MCMC) algorithms offer various strategies for
+sampling; the Hamiltonian Monte Carlo (HMC) family of samplers are MCMC
+algorithms which often exhibit improved mixing properties. The recently
+introduced magnetic HMC, a generalization of HMC motivated by the physics of
+particles influenced by magnetic field forces, has been demonstrated to improve
+the performance of HMC. In many applications, one wishes to sample from a
+distribution restricted to a constrained set, often manifested as an embedded
+manifold (for example, the surface of a sphere). We introduce magnetic manifold
+HMC, an HMC algorithm on embedded manifolds motivated by the physics of
+particles constrained to a manifold and moving under magnetic field forces. We
+discuss the theoretical properties of magnetic Hamiltonian dynamics on
+manifolds, and introduce a reversible and symplectic integrator for the HMC
+updates. We demonstrate that magnetic manifold HMC produces favorable sampling
+behaviors relative to the canonical variant of manifold-constrained HMC.",2010.07753v1
+2020-11-13,Magnetic anisotropy of individual maghemite mesocrystals,"Interest in creating magnetic metamaterials has led to methods for growing
+superstructures of magnetic nanoparticles. Mesoscopic crystals of maghemite
+($\gamma\text{-Fe}_2\text{O}_3$) nanoparticles can be arranged into highly
+ordered body-centered tetragonal lattices of up to a few micrometers. Although
+measurements on disordered ensembles have been carried out, determining the
+magnetic properties of individual mesoscopic crystals is challenging due to
+their small total magnetic moment. Here, we overcome these challenges by
+utilizing sensitive dynamic cantilever magnetometry to study individual
+micrometer-sized $\gamma\text{-Fe}_2\text{O}_3$ mesocrystals. These
+measurements reveal an unambiguous cubic anisotropy, resulting from the
+crystalline anisotropy of the constituent maghemite nanoparticles and their
+alignment within the mesoscopic lattice. The signatures of anisotropy and its
+orgins come to light because we combine the self-assembly of highly ordered
+mesocrystals with the ability to resolve their individual magnetism. This
+combination is promising for future studies of the magnetic anisotropy of other
+nanoparticles, which are too small to investigate individually.",2011.06885v1
+2020-11-17,Improving magnetic nanothermometry accuracy through mixing-frequency excitation,"In this study, we proposed a temperature model of magnetic nanoparticle
+relaxation and a phase measurement method under a mixing-frequency excitation
+field, which can improve the temperature accuracy of magnetic nanothermometry.
+According to the Debye-based magnetization model for magnetic nanoparticles,
+the phases at the mixing frequencies are used to solve the relaxation phase
+delay to the magnetic field with the higher frequency. The method could improve
+the signal-to-noise ratio of the magnetic response signal, and also weaken the
+phase shift of the detection coils caused by temperature changes. Experimental
+results show that the method can achieve static temperature measurement error
+less than 0.1K and dynamic temperature measurement error less than 0.2K.",2011.08532v1
+2020-12-23,Electric manipulation of domain walls in magnetic Weyl semimetals via the axial anomaly,"We show how the axial (chiral) anomaly induces a spin torque on the
+magnetization in magnetic Weyl semimetals. The anomaly produces an imbalance in
+left- and right-handed chirality carriers when non-orthogonal electric and
+magnetic fields are applied. Such imbalance generates a spin density which
+exerts a torque on the magnetization, the strength of which can be controlled
+by the intensity of the applied electric field. We show how this results in an
+electric control of the chirality of domain walls, as well as in an improvement
+of the domain wall dynamics, by delaying the onset of the Walker breakdown. The
+measurement of the electric field mediated changes in the domain wall chirality
+would constitute a direct proof of the axial anomaly. Additionally, we show how
+quantum fluctuations of electronic Fermi arc states bound to the domain wall
+naturally induce an effective magnetic anisotropy, allowing for high domain
+wall velocities even if the intrinsic anisotropy of the magnetic Weyl semimetal
+is small.",2012.12785v2
+2021-02-19,Collective modes of polarizable holographic media in magnetic fields,"We consider a neutral holographic plasma with dynamical electromagnetic
+interactions in a finite external magnetic field. The Coulomb interactions are
+introduced via mixed boundary conditions for the Maxwell gauge field. The
+collective modes at finite wave-vector are analyzed in detail and compared to
+the magneto-hydrodynamics results valid only at small magnetic fields.
+Surprisingly, at large magnetic field, we observe the appearance of two
+plasmon-like modes whose corresponding effective plasma frequency grows with
+the magnetic field and is not supported by any background charge density.
+Finally, we identify a mode collision which allows us to study the radius of
+convergence of the linearized hydrodynamics expansion as a function of the
+external magnetic field. We find that the radius of convergence in momentum
+space, related to the diffusive transverse electromagnetic mode, increases
+quadratically with the strength of the magnetic field.",2102.09969v2
+2021-05-25,Dynamics of particles with cubic magnetic anisotropy in a viscous liquid,"The specific absorption rate (SAR) of a dilute assembly of spherical iron
+nanoparticles with cubic anisotropy distributed in a viscous liquid is
+calculated using the solution of stochastic Landau - Lifshitz equation for unit
+magnetization vector and stochastic equations for multiple particle directors
+that specify the spatial orientation of the nanoparticle in a liquid. The
+viscous and magnetic magnetization reversal modes of particles are revealed at
+low and sufficiently high amplitudes of alternating magnetic field,
+respectively. The SAR of iron nanoparticle assembly is shown to exceed
+significantly that of iron oxide nanoparticles with uniaxial anisotropy at the
+same amplitudes and frequencies of applied magnetic field. The linear response
+theory is shown to be valid only at small magnetic field amplitudes, H0 < 50 -
+70 Oe.",2105.11916v1
+2021-06-17,Quantum error as an emergent magnetic field,"We investigate the effect of quantum errors on a monitored Brownian
+Sachdev-Ye-Kitaev (SYK) model featuring a measurement-induced phase transition
+that can be understood as a symmetry-breaking transition of an effective $Z_4$
+magnet in the replica space. The errors describe the loss of information about
+the measurement outcomes and are applied during the non-unitary evolution or at
+the end of the evolution. In the former case, we find that this error can be
+mapped to an emergent magnetic field in the $Z_4$ magnet, and as a consequence,
+the symmetry is explicitly broken independent of the measurement rate. R\'enyi
+entropies computed by twisting boundary conditions now generate domain walls
+even in the would-be symmetric phase at a high measurement rate. The entropy is
+therefore volume-law irrespective of the measurement rate. In the latter case,
+the error-induced magnetic field only exists near the boundary of the magnet.
+Varying the magnetic field leads to a pinning transition of domain walls,
+corresponding to error threshold of the quantum code prepared by the
+non-unitary SYK dynamics.",2106.09635v1
+2021-07-14,Magnetic correlations in triangular antiferromagnet FeGa$_2$S$_4$,"The crystal structure and magnetic correlations in triangular antiferromagnet
+FeGa$_2$S$_4$ are studied by x-ray diffraction, magnetic susceptibility,
+neutron diffraction and neutron inelastic scattering. We report significant
+mixing at the cation sites and disentangle magnetic properties dominated by
+major and minor magnetic sites. The magnetic short-range correlations at 0.77
+\AA$^{-1}$ correspond to the major sites and being static at base temperature
+they evolve into dynamic correlations around 30 - 50 K. The minor sites
+contribute to the magnetic peak at 0.6 \AA$^{-1}$, which vanishes at 5.5 K. Our
+analytical studies of triangular lattice models with bilinear and biquadratic
+terms provide the ratios between exchanges for the proposed ordering vectors.
+The modelling of the inelastic neutron spectrum within linear spin wave theory
+results in the set of exchange couplings $J_1=1.7$\,meV, $J_2=0.9$\,meV,
+$J_3=0.8$\,meV for the bilinear Heisenberg Hamiltonian. However, not all
+features of the excitation spectrum are explained with this model.",2107.06904v1
+2021-07-27,Production of a chiral magnetic anomaly with emerging turbulence and mean-field dynamo action,"In relativistic magnetized plasmas, asymmetry in the number densities of
+left- and right-handed fermions, i.e., a non-zero chiral chemical potential
+mu_5, leads to an electric current along the magnetic field. This causes a
+chiral dynamo instability for a uniform mu_5, but our simulations reveal a
+dynamo even for fluctuating mu_5 with zero mean. It produces
+magnetically-dominated turbulence and generates mean magnetic fields via the
+magnetic alpha effect. Eventually, a universal scale-invariant k^(-1) spectrum
+of mu_5 and a k^(-3) magnetic spectrum are formed independently of the initial
+condition.",2107.12945v3
+2021-09-22,Spin precession of binary neutron stars with magnetic dipole moments,"Spin precession equations including the spin-orbit (SO), spin-spin (SS),
+quadrupole-monopole (QM) and magnetic dipole-magnetic dipole (DD) leading-order
+interactions are derived for compact binary systems in order to investigate the
+DD contribution in the orbit-averaged spin precession equations for binary
+neutron star systems neglecting the gravitational radiation-reaction effect. It
+is known that the magnitudes of spins are not conserved quantities due to the
+DD interaction. We give a simple analytical description for the pure DD
+interaction making the magnitudes of spins almost constant by neglecting the
+SO, SS and QM contributions. We also demonstrate the evolutions of the relative
+angles of spins and magnetic dipoles with the help of numeric simulations
+including all contributions (SO, SS, QM and DD) and introduce a dimensionless
+magnetic dipole parameter to characterize the strength of magnetic fields for
+some realistic neutron star binaries. We find that for realistic configurations
+the strong magnetic fields of neutron stars can modify the spin dynamics over
+long periods of time.",2109.10722v1
+2021-11-29,What Seismic Minimum Reveals About Solar Magnetism Below the Surface?,"The Sun's magnetic field varies in multiple time scales. Observations show
+that the minimum between cycles 24 and 25 was the second consecutive minimum
+which was deeper and wider than several earlier minima. Since the active
+regions observed at the Sun's surface are manifestations of the magnetic field
+generated in the interior, it is crucial to investigate/understand the dynamics
+below the surface. In this context, we report, by probing the solar interior
+with helioseismic techniques applied to long-term oscillations data from the
+Global Oscillation Network Group (GONG), that the seismic minima in deeper
+layers have been occurring about a year earlier than that at the surface for
+the last two consecutive solar cycles. Our findings also demonstrate a decrease
+in strong magnetic fields at the base of the convection zone, the primary
+driver of the surface magnetic activity. We conclude that the magnetic fields
+located in the core and near-surface shear layers, in addition to the
+tachocline fields, play an important role in modifying the oscillation
+frequencies. This provides evidence that further strengthens the existence of a
+relic magnetic field in the Sun's core since its formation.",2111.14323v1
+2021-12-02,Stability of plasmas through magnetic helicity,"Magnetic helicity, and more broadly magnetic field line topology, imposes
+constraints on the plasma dynamics. Helically interlocked magnetic rings are
+harder to bring into a topologically non-trivial state than two rings that are
+not linked. This particular restriction has the consequence that helical
+plasmas exhibit increased stability in laboratory devices, in the Sun and in
+the intergalactic medium. Here we discuss how a magnetic field is stabilizing
+the plasma and preventing it from disruption by the presence of magnetic
+helicity. We present observational results, numerical experiments and
+analytical results that illustrate how helical magnetic fields strongly
+contribute to the long-term stability of some plasmas. We discuss several
+cases, such as that of solar corona, tokamaks, the galactic and extragalactic
+medium, with a special emphasis on extragalactic bubbles.",2112.01193v1
+2021-12-07,Gradual charge order melting in Bi0.5Ca0.5MnO3 induced by ultrahigh magnetic field,"We have investigated the magnetic properties of Bi0.5Ca0.5MnO3 under
+ultrahigh magnetic fields by magnetization measurements. This compound shows
+the metamagnetic transition which indicates the magnetic field induced charge
+order melting at the room temperature T = 293 K. We reveled that the
+temperature dependence of the critical field, where the highest critical field
+is higher than 100 T. At low temperatures, it has been found that the
+metamagnetic transitions become broad and vanish in the field ascending process
+below 70 K. On the other hand, in the field descending process, a clear
+metamagnetic transition is observed even below 70 K. This unusual behavior can
+be understood as the gradual charge order melting by magnetic field, and its
+simultaneous reformation. A coexistence of multiple order parameters can
+account for the observed characteristic dynamics of the first order phase
+transition. Finally, we constructed the B-T phase diagram with the unusual
+critical feature at ultrahigh magnetic fields.",2112.03507v1
+2022-01-31,Anisotropic magnetized neutron star,"As we know, the effect of strong magnetic field causes the anisotropy for the
+magnetized compact objects. Therefore, in this paper, we have studied the
+structure properties of anisotropic case of magnetized neutron star. We have
+derived the equation of state (EoS) of neutron star matter for two forms of
+magnetic fields, one uniform and one density dependent. We have solved the
+generalized Tolman Oppenheimer Volkoff equations to examine the maximum mass
+and corresponding radius, Schwarzschild radius, graviitational redshift,
+Kretschmann scalar, and Buchdahl theorem for this system. It was shown that the
+maximum mass and radius of neutron star are increasing functions of the
+magnetic field. Also redshift, strength of gravity, and Kretschmann scalar
+increase as the magnetic field increases. In addition, the dynamical stability
+of anisotrop neutron star has been investigated, and finally a comparison with
+the empirical results has been made.",2202.01207v1
+2022-02-08,"Electronic, Magnetic and Vibrational Properties of Single Layer Aluminum Oxide","The structural, magnetic, vibrational and electronic properties of single
+layer aluminum oxide (AlO2) are investigated by performing state-of-the-art
+first-principles calculations. Total energy optimization and phonon
+calculations reveal that aluminum oxide forms a distorted octahedral structure
+(1T'-AlO2) in its single layer limit. It is also shown that surfaces of
+1T'-AlO2 display magnetic behavior originating from the O atoms. While the
+ferromagnetic (FM) state is the most favorable magnetic order for 1T'-AlO2,
+transformation to a dynamically stable antiferromagnetic (AFM) state upon a
+slight distortion in the crystal structure is also possible. It is also shown
+that Raman activities (350-400 cm^-1) obtained from the vibrational spectrum
+can be utilized to distinguish the possible magnetic phases of the crystal
+structure. Electronically, both FM and the AFM phases are semiconductors with
+an indirect band gap and they can form a type-III vdW heterojunction with
+graphene-like ultra-thin materials. Moreover, it is predicted that presence of
+oxygen defects that inevitably occur during synthesis and production do not
+alter the magnetic state, even at high vacancy density. Apparently, ultra-thin
+1T'-AlO2 with its stable crystal structure, semiconducting nature and robust
+magnetic state is a quite promising material for nanoscale device applications.",2202.04144v1
+2022-02-10,Field-driven skyrmion motion through velocity equipartition between skyrmions and a domain wall,"Magnetic skyrmions, as a whirling spin texture with axisymmetry, cannot be
+propelled by a uniform magnetic field. Therefore, reported skyrmion motions
+have been induced using other sorts of stimuli; typically, electric currents in
+magnetic metals as well as spin waves, thermal gradient, and field gradient
+have manifested their ability to drive skyrmion motion. Here, we demonstrate,
+through micromagnetic simulations and analytically, that magnetic skyrmions can
+be displaced by a uniform perpendicular magnetic field via a domain-wall (DW)
+mediator. For a fixed field strength, the velocity of a skyrmion train evolves
+in terms of 1 / (1 + Ns) with Ns denoting the number of skyrmions. Based on
+Thiele's model, we reproduce the velocity-Ns relation first identified from
+numerical results and reveal that the skyrmion-DW and inter-skyrmion repulsions
+offer the direct driving force for skyrmion motion. This study underlines the
+role of spin textures' interaction in skyrmion dynamics, and opens an
+alternative route for skyrmion manipulation especially relevant to insulating
+magnets. Given the correspondence between magnetism and electricity, we
+anticipate that the scheme should also work for polar skyrmions in
+ferroelectrics.",2202.05149v1
+2022-02-15,Notes about collapse in magnetohydrodynamics,"We discuss a problem about magnetic collapse as a possible process for
+singularity formation of the magnetic field in a finite time within ideal
+magneto-hydrodynamics for incompressible fluids. This process is very important
+from the point of view of various astrophysical applications, in particular, as
+a mechanism of magnetic filaments formation in the convective zone of the Sun.
+The collapse possibility is connected with compressibility of continuously
+distributed magnetic field lines. A well-known example of the formation of
+magnetic filaments in the kinematic dynamo approximation with a given velocity
+field, first considered by Parker in 1963, rather indicates that the increase
+in the magnetic field is exponential in time. In the case of the kinematic
+approximation for the induction equation, the magnetic filaments formation is
+shown to occur in areas with a hyperbolic velocity profile.",2202.08121v1
+2022-04-09,Spectra of magnetic turbulence in a relativistic plasma,"We present a phenomenological and numerical study of strong Alfv\'enic
+turbulence in a magnetically dominated collisionless relativistic plasma with a
+strong background magnetic field. In contrast with the non-relativistic case,
+the energy in such turbulence is contained in magnetic and electric
+fluctuations. We argue that such turbulence is analogous to turbulence in a
+strongly magnetized non-relativistic plasma in the regime of broken
+quasi-neutrality. Our 2D particle-in-cell numerical simulations of turbulence
+in a relativistic pair plasma find that the spectrum of the total energy has
+the scaling $k^{-3/2}$, while the difference between the magnetic and electric
+energies, the so-called residual energy, has the scaling $k^{-2.4}$. The
+electric and magnetic fluctuations at scale $\ell$ exhibit dynamic alignment
+with the alignment-angle scaling close to $\cos\phi_\ell\propto \ell^{1/4}$. At
+scales smaller than the (relativistic) plasma inertial scale, the energy
+spectrum of relativistic inertial Alfv\'en turbulence steepens to $k^{-3.5}$.",2204.04530v3
+2022-04-29,Magnetic domains in 2D moiré lattices with square and hexagonal symmetry,"We report the persistence of magnetic domains lying in moir\'e patterns with
+square and hexagonal symmetries. Our investigation is based on the dynamical
+description of two magnetic domains represented by a two species bosonic
+mixture of $^{87}$Rb ultracold atoms, being each specie initially localized in
+the left and right halves of a moir\'e lattice defined by a specific angle
+$\theta$. To demonstrate the persistence of such initial domains, we follow the
+time evolution of the superfluid spin texture, and in particular, the
+magnetization on each halve. The two-component superfluid, confined in the
+moir\'e pattern plus a harmonic trap, was described through the time dependent
+Gross-Pitaevskii coupled equations for moir\'e lattices having $90 \times 90$
+sites. Results showed the existence of rotation-angle-dependent structures for
+which the initial magnetic domain is preserved for both, square and hexagonal
+moir\'e patterns; above $\theta >10^\circ$ the initial magnetic domain is never
+destroyed. Stationary magnetic states for a single component Bose condensate
+allowed us to identify the lattice parameter associated with moir\'e crystals
+that emerge for twisting angles belonging to the intervals $\theta \in
+\left(0^\circ ,30^\circ \right)$ and $\theta \in \left(0^\circ ,45^\circ
+\right)$ for hexagonal and square geometries respectively.",2204.14200v1
+2022-05-17,Restriction on the form of quark anomalous magnetic moment from lattice QCD results,"The quark anomalous magnetic moment (AMM) is dynamically generated through
+the spontaneous chiral symmetry breaking. It has been revealed that even though
+its exact form is still unknown, the quark AMM is essential to explore quark
+matter properties and QCD phase structure under external magnetic fields. In
+this study, we take three different forms of the quark AMM and investigate its
+influence on the chiral phase transition under magnetic field. In general, a
+negative quark AMM plays the role as magnetic catalyzer and a positive quark
+AMM plays the role of magnetic inhibition. It is found that a constant quark
+AMM drives an unexpected 1st order chiral phase transition; a quark AMM
+proportional to the chiral condensate gives a flip of the sign on the chiral
+condensate; and a quark AMM proportional to the square of chiral condensate can
+produce results of chiral condensate as functions of the temperature and the
+magnetic field in good agreement with the lattice result.",2205.08169v1
+2022-07-01,Whistler Waves As a Signature of Converging Magnetic Holes in Space Plasmas,"Magnetic holes are plasma structures that trap a large number of particles in
+a magnetic field that is weaker than the field in its surroundings. The
+unprecedented high time-resolution observations by NASA's Magnetospheric
+Multi-Scale (MMS) mission enable us to study the particle dynamics in magnetic
+holes in the Earth's magnetosheath in great detail. We reveal the local
+generation mechanism of whistler waves by a combination of Landau-resonant and
+cyclotron-resonant wave-particle interactions of electrons in response to the
+large-scale evolution of a magnetic hole. As the magnetic hole converges, a
+pair of counter-streaming electron beams form near the hole's center as a
+consequence of the combined action of betatron and Fermi effects. The beams
+trigger the generation of slightly-oblique whistler waves. Our conceptual
+prediction is supported by a remarkable agreement between our observations and
+numerical predictions from the Arbitrary Linear Plasma Solver (ALPS). Our study
+shows that wave-particle interactions are fundamental to the evolution of
+magnetic holes in space and astrophysical plasmas.",2207.00273v1
+2022-09-05,Generation and routing of nanoscale droplet solitons without compensation of magnetic damping,"Magnetic droplet soliton is a localized dynamic spin state which can serve as
+a nanoscale information carrier and nonlinear oscillator. The present opinion
+is that the formation of droplet solitons requires the compensation of magnetic
+damping by a torque created by a spin-polarized electric current or pure spin
+current. Here we demonstrate theoretically that nanoscale droplet solitons can
+be generated and routed in ferromagnetic nanostructures with voltage-controlled
+magnetic anisotropy in the presence of uncompensated magnetic damping.
+Performing micromagnetic simulations for the MgO/Fe/MgO trilayer with almost
+perpendicular-to-plane magnetization, we reveal the formation of the droplet
+soliton under a nanoscale gate electrode subjected to a sub-nanosecond voltage
+pulse. The soliton lives up to 50 ns at room temperature and can propagate over
+micrometer distances in a ferromagnetic waveguide due to nonzero gradient of
+the demagnetizing field. Furthermore, we show that an electrical routing of the
+soliton to different outputs of a spintronic device can be realized with the
+aid of an additional semiconducting nanostripe electrode creating controllable
+gradient of the perpendicular magnetic anisotropy.",2209.01893v1
+2022-09-19,Dissipative magnetic structures and scales in small-scale dynamos,"Small-scale dynamos play important roles in modern astrophysics, especially
+on Galactic and extragalactic scales. Owing to dynamo action, purely
+hydrodynamic Kolmogorov turbulence hardly exists and is often replaced by
+hydromagnetic turbulence. Understanding the size of dissipative magnetic
+structures is important in estimating the time scale of Galactic scintillation
+and other observational and theoretical aspects of interstellar and
+intergalactic small-scale dynamos. Here we show that, during the kinematic
+phase of the small-scale dynamo, the cutoff wavenumber of the magnetic energy
+spectra scales as expected for large magnetic Prandtl numbers, but continues in
+the same way also for moderately small values - contrary to what is expected.
+For a critical magnetic Prandtl number of about 0.3, the dissipative and
+resistive cutoffs are found to occur at the same wavenumber. In the nonlinearly
+saturated regime, the critical magnetic Prandtl number becomes unity. The
+cutoff scale now has a shallower scaling with magnetic Prandtl number below a
+value of about three, and a steeper one otherwise compared to the kinematic
+regime.",2209.08717v2
+2023-01-01,Magnetized Thick Disks around Boson Stars,"The effects of magnetic fields on accretion disks around compact objects are
+of high importance in the study of their general properties and dynamics. Here
+we analyze the influence of magnetic fields on thick accretion disks around
+rotating boson stars. We assume a uniform constant specific angular momentum
+distribution and a polytropic equation of state. The purely hydrodynamical
+thick disk solutions are extended to magnetized solutions by adding a toroidal
+magnetic field and then analyzed in terms of a magnetization parameter. We
+consider one-centered solutions as well as two-centered solutions and focus on
+retrograde tori, since they are more distinctive due to their unique
+properties. Our computed solutions indicate that strong magnetic fields
+influence the characteristics of thick disks around rotating boson stars and
+possibly affect their unique features.",2301.00449v2
+2023-02-15,Unique Compact Representation of Magnetic Fields using Truncated Solid Harmonic Expansions,"Precise knowledge of magnetic fields is crucial in many medical imaging
+applications like magnetic resonance imaging or magnetic particle imaging (MPI)
+as they are the foundation of these imaging systems. For the investigation of
+the influence of field imperfections on imaging, a compact and unique
+representation of the magnetic fields using real solid spherical harmonics,
+which can be obtained by measuring a few points of the magnetic field only, is
+of great assistance. In this manuscript, we review real solid harmonic
+expansions as a general solution of Laplace's equation including an efficient
+calculation of their coefficients using spherical t-designs. We also provide a
+method to shift the reference point of an expansion by calculating the
+coefficients of the shifted expansion from the initial ones. These methods are
+used to obtain the magnetic fields of an MPI system. Here, the field-free-point
+of the spatial encoding field serves as unique expansion point. Lastly, we
+quantify the severity of the distortions of the static and dynamic fields in
+MPI by analyzing the expansion coefficients.",2302.07591v1
+2023-03-21,Revealing Emergent Magnetic Charge in an Antiferromagnet with Diamond Quantum Magnetometry,"Whirling topological textures play a key role in exotic phases of magnetic
+materials and offer promise for logic and memory applications. In
+antiferromagnets, these textures exhibit enhanced stability and faster dynamics
+with respect to ferromagnetic counterparts, but they are also difficult to
+study due to their vanishing net magnetic moment. One technique that meets the
+demand of highly sensitive vectorial magnetic field sensing with negligible
+backaction is diamond quantum magnetometry. Here, we show that the archetypal
+antiferromagnet, hematite, hosts a rich tapestry of monopolar, dipolar and
+quadrupolar emergent magnetic charge distributions. The direct readout of the
+previously inaccessible vorticity of an antiferromagnetic spin texture provides
+the crucial connection to its magnetic charge through a duality relation. Our
+work defines a novel paradigmatic class of magnetic systems to explore
+two-dimensional monopolar physics, and highlights the transformative role that
+diamond quantum magnetometry could play in exploring emergent phenomena in
+quantum materials.",2303.12125v1
+2023-03-27,Switching the Magnetization in Quantum Antiferromagnets,"The orientation of the order parameter of quantum magnets can be used to
+store information in a dense and efficient way. Switching this order parameter
+corresponds to writing data. To understand how this can be done, we study a
+precessional reorientation of the sublattice magnetization in an (an)isotropic
+quantum antiferromagnet induced by an applied magnetic field. We use a
+description including the leading quantum and thermal fluctuations, namely
+Schwinger boson mean-field theory, because this theory allows us to describe
+both ordered phases and the phases in between them, as is crucial for
+switching. An activation energy has to be overcome requiring a minimum applied
+field $h_\text{t}$ which is given essentially by the spin gap. It can be
+reduced significantly for temperatures approaching the N\'eel temperature
+facilitating switching. The time required for switching diverges when the field
+approaches $h_\text{t}$ which is the signature of an inertia in the
+magnetization dynamics. The temporal evolution of the magnetization and of the
+energy reveals signs of dephasing. The switched state has lost a part of its
+coherence because the magnetic modes do not evolve in phase.",2303.15398v1
+2023-04-27,Magnetic Field Line Separation by Random Ballistic Decorrelation in Transverse Magnetic Turbulence,"The statistics of the magnetic field line separation provide insight into how
+a bundle of field lines spreads out and the dispersion of non-thermal particles
+in a turbulent environment, which underlies various astrophysical phenomena.
+Its diffusive character depends on the distance along the field line, the
+initial separation, and the characteristics of the magnetic turbulence. This
+work considers the separation of two magnetic field lines in general transverse
+turbulence in terms of the magnetic power spectrum in three-dimensional
+wavenumber space. We apply non-perturbative methods using Corrsin's hypothesis
+and assume random ballistic decorrelation to calculate the ensemble average
+field line separation for general transverse magnetic turbulence. For 2D+slab
+power spectra, our analytic formulae and computer simulations give similar
+results, especially at low slab fraction. Our analytical expression also
+demonstrates several features of field line separation that are verified by
+computer simulations.",2304.14067v1
+2023-05-13,Dual Nature of Magnetism Driven by Momentum Dependent f-d Kondo Hybridization,"Intricate nature of magnetism in uranium-based Kondo lattices is a
+consequence of correlations between U-5$f$ and conduction electrons. Using
+linearized quasiparticle self-consistent GW plus dynamical mean-field theory,
+we demonstrate a crossover from incoherent to coherent $f$-$d$ Kondo cloud in
+the paramagnetic phase of UTe$_2$ with reduced volumes, USbTe and USbSe. As the
+transition occurs, we observe an augmented $f$-$d$ coherence and Pauli-like
+magnetic susceptibility, with a substantial frozen magnetic moment of U-5$f$
+persisting. We show that momentum dependent $f$-$d$ hybridization is
+responsible for the magnetic moments arising from the renormalized $f$
+electrons' van Hove singularity. Our findings provide a unique perspective to
+explain the dual nature of magnetism and the long-range magnetic ordering
+induced by pressure in UTe$_2$.",2305.08003v1
+2023-06-14,An N-loop potential energy model for levitated mm-scale magnets in cm-scale superconducting coaxial microwave resonators,"The levitation of a macroscopic object within a superconducting resonator
+provides a unique and novel platform to study optomechanics, quantum
+information, and gravitational wave detection. Existing mirror-method and
+single-loop models for calculating magnet levitation are insufficient for
+predicting the position and motion of the levitated magnet. If the
+cavity-magnet interaction is modeled using a large number of smaller surface
+current loops, one can quantitatively model the dynamics of the levitation of
+the magnet within the cavity. The magnet's most-likely position and orientation
+can be predicted for non-trivial cavity geometries and cavity orientations.
+Knowing the potential energy landscape within the cavity configuration also
+provides a means to estimate the resonant mechanical frequencies at which the
+levitated magnet vibrates, and enables tailoring the cavity design for specific
+outcomes.",2306.08662v1
+2023-10-19,Micromagnetic Simulation of Three-dimensional Nanoarchitectures,"The thesis discusses micromagnetic simulation studies on high-frequency
+magnetic dynamics in three-dimensional ferromagnetic nanoarchitectures made of
+interconnected magnetic nanowire networks. Such artificial magnetic materials
+with nanoscale features have recently emerged as a vivid topic of research, as
+their geometry has a decisive impact on their magnetic properties. By studying
+their static magnetization structure, we find that these systems display a
+behavior analogous to that of 3D artificial spin ice lattices, with frustrated
+interactions and the emergence of monopole-like defect structures at the wires'
+intersection points. Our simulations reveal a high activity of these defect
+sites in the magnonic high-frequency spectrum. We study various 3D
+nanoarchitectures and show that their geometry and magnetization state results
+in characteristic high-frequency signatures. Controlling these features could
+open new pathways for magnonics research and reprogrammable magnetic
+metamaterials.",2310.12839v1
+2023-11-10,Magnetic Field Strength Effects on Nucleosynthesis from Neutron Star Merger Outflows,"Magnetohydrodynamic turbulence drives the central engine of post-merger
+remnants, potentially powering both a nucleosynthetically active disk wind and
+the relativistic jet behind a short gamma ray burst. We explore the impact of
+the magnetic field on this engine by simulating three post-merger black hole
+accretion disks using general relativistic magnetohydrodynamics with Monte
+Carlo neutrino transport, in each case varying the initial magnetic field
+strength. We find increasing ejecta masses associated with increasing magnetic
+field strength. We find that a fairly robust main r -process pattern is
+produced in all three cases, scaled by the ejected mass. Changing the initial
+magnetic field strength has a considerable effect on the geometry of the
+outflow and hints at complex central engine dynamics influencing lanthanide
+outflows. We find that actinide production is especially sensitive to magnetic
+field strength, with overall actinide mass fraction calculated at 1 Gyr
+post-merger increasing by more than a factor of six with a tenfold increase in
+magnetic field strength. This hints at a possible connection to the variability
+in actinide enhancements exhibited by metal poor, r -process-enhanced stars.",2311.05796v1
+2023-12-20,Spin wave confinement in hybrid superconductor-ferrimagnet nanostructure,"Eddy currents in a superconductor shield the magnetic field in its interior
+and are responsible for the formation of a magnetic stray field outside of the
+superconducting structure. The stray field can be controlled by the external
+magnetic field and affect the magnetization dynamics in the magnetic system
+placed in its range. In the case of a hybrid system consisting of a
+superconducting strip placed over a magnetic layer, we predict theoretically
+the confinement of spin waves in the well of the static stray field. The number
+of bound states and their frequencies can be controlled by an external magnetic
+field. We have presented the results of semi-analytical calculations
+complemented by numerical modeling.",2312.13029v1
+2024-02-02,THz spin-wave excitations in the transverse conical phase of BiFeO$_3$,"Although BiFeO$_3$ is one of the most studied multiferroic materials, recent
+magnetization and neutron scattering studies have revealed a new magnetic phase
+in this compound - the transverse conical phase. To study the collective spin
+excitations of this phase, we performed THz spectroscopy in magnetic fields up
+to 17 T at and above room temperature. We observed five spin-wave branches in
+the magnetic phase with long wavelength conical modulation. Using a numerical
+spin dynamics model we found two kinds of excitations with magnetic moments
+oscillating either along or perpendicular to the static fields. Remarkably, we
+detected strong directional dichroism, an optical manifestation of the
+magnetoelectric effect, for two spin-wave modes of the conical phase. According
+to our experiments, the stability of the conical state is sensitive to the
+magnetic field history and it can become (meta)stable at or close to zero
+magnetic field, which may allow exploiting its magnetoelectric properties at
+room temperature.",2402.01417v1
+2024-02-09,Capturing the slow relaxation time of superparamagnetic colloids in time-varying fields,"Superparamagnetic colloids present interesting assembly dynamics and
+propulsion in time-varying magnetic fields due to their magnetic relaxation.
+However, little is known about the mechanisms governing this magnetic
+relaxation, which is commonly attributed to the interactions and polydispersity
+of the ferromagnetic nanoparticles distributed within the colloid. We measure
+this relaxation from the effective potential between colloids subjected to
+rotating magnetic fields. Remarkably, our results indicate the presence of
+magnetic relaxation times much longer than what has been reported, which
+furthers our understanding of the magnetization of colloids in complex magnetic
+fields.",2402.06802v1
+2024-02-27,Origin of magnetic switching cascades in tetrahedral CoFe nanostructures,"We present a comprehensive study of small-scale three-dimensional (3D)
+tetrahedral CoFe nanostructure arrays prepared by focused electron beam-induced
+deposition (FEBID) and placed in two distinct orientations with respect to the
+direction of an external magnetic field. Using ultra-sensitive micro-Hall
+magnetometry we obtain angular-dependent magnetic stray field hysteresis loops
+that show characteristic cascading magnetic switching close to zero magnetic
+field. By employing micromagnetic simulations we could reproduce the hysteresis
+loops and identify characteristic field dependent magnetic configurations
+including a vortex-type groundstate. From this we derive a coarse-graining
+macrospin model and show that the complex switching behavior can be explained
+by the reorientation dynamics of non-interacting uniaxial anisotropic magnetic
+grains modeled as a superposition of Stoner-Wohlfarth particles.",2402.17594v1
+2024-03-11,$^{27}$Al NMR study of the magnetic Weyl semimetal CeAlGe,"Motivated by the recent observations of electronic correlation effect [M.
+Corasaniti \textit{et al}., Phys. Rev. B \textbf{104}, L121112 (2021)] and
+topology-stabilized magnetic fluctuations [N. Drucker \textit{et al}., Nat.
+Commun. \textbf{14}, 5182 (2023)] in the noncentrosymmetric magnetic Weyl
+semimetal candidate CeAlGe, we performed systematic studies on the local static
+and dynamic spin susceptibilities by $^{27}$Al nuclear magnetic resonance. Due
+to the large spin susceptibility from Ce-$4f$ electrons, the theoretically
+predicted responses from Weyl fermions are overwhelmed. A Knight-shift anomaly
+is observed below $T^*\sim50$ K, a signature of the onset of coherent Kondo
+coupling. In addition, an anomalous peak is found in $1/T_1T$ near 15 K, well
+above the magnetic ordering temperature $T_N \approx 5$ K, which probably is a
+consequence of topology-stabilized magnetic fluctuations. These results
+highlight the interplay among electronic correlation, magnetism and band
+topology in this family of Kondo Weyl semimetals.",2403.06476v1
+2024-03-29,Local magnetic moment formation and Kondo screening in the presence of Hund exchange: the two-band Hubbard model analysis,"We study formation and screening of local magnetic moments in the two-band
+Hubbard model in the presence of Hund exchange interaction using dynamic mean
+field theory approach. The characteristic temperatures of the formation,
+beginning and full screening of local magnetic moments are obtained from the
+analysis of temperature dependencies of the orbital, charge, and spin
+susceptibilities, as well as the respective instantaneous correlation
+functions. At half filling we find the phase diagram, which is similar to the
+single-orbital case with wide region of formation of local magnetic moments
+below the orbital Kondo temperature. Similarly to the single-orbital case, with
+decreasing temperature the screening of local magnetic moments is preceded by
+appearance of fermionic quasiparticles. In the two-band case the quasiparticles
+are however present also in some temperature region above the Mott insulating
+phase. At finite doping we find broad regime of presence of local magnetic
+moments, which coexist with incoherently or coherently moving holes. We also
+find, similarly to the half filled case, finite temperature interval in the
+doped regime, when the fermionic quasiparticles are formed, but do not yet
+screen local magnetic moments.",2403.20036v1
+2024-04-04,Direct visualization of local magnetic domain dynamics in a 2D Van der Walls material/ferromagnet interface,"Exploring new strategies for controlling the magnetic domain propagation is
+the key to realize ultrafast, high-density domain wall-based memory and logic
+devices for next generation computing. These strategies include strain
+modulation in multiferroic devices, geometric confinement and area-selective
+pinning of domain wall. 2D Van der Waals materials introduce localized
+modifications to the interfacial magnetic order, enabling control over the
+propagation of magnetic domains. Here, using Lorentz-Transmission Electron
+Microscopy (L-TEM) along with the Modified Transport of Intensity equations
+(MTIE), we demonstrate controlled domain expansion with in-situ magnetic field
+in a ferromagnet (Permalloy, NiFe) interfacing with a 2D Van der Waals material
+Graphene (Gr). The Gr/NiFe interface exhibits distinctive domain expansion rate
+with magnetic field selectively near the interface which is further analyzed
+using micromagnetic simulations. Our findings are crucial for comprehending
+direct visualization of interface controlled magnetic domain expansion,
+offering insights for developing future domain wall-based technology.",2404.03177v1
+2002-06-27,"A turn-over scenario for rotating magnetic white dwarfs: models with several values of mass, angular momentum, and magnetic field","We study a white dwarf with differential rotation and magnetic field, for
+which the symmetry axis of the toroidal field, the magnetic axis of the
+poloidal field, and the principal axis I_3 coincide permanently. This common
+axis, so-called ""magnetic symmetry axis"", inclines at a small angle relative to
+the spin axis of the model, the so-called ""turn-over angle"". Such an almost
+axisymmetric model undergoes an early evolutionary phase of secular timescale,
+with moment of inertia along the spin axis, I_{zz}=I_{33}, greater than the
+moments of inertia along the equatorial axes, I_{11}=I_{22}, since rotation and
+poloidal field (both deriving oblate configurations) dominate over the toroidal
+field (deriving prolate configurations). During this phase, the model suffers
+from secular angular momentum loss due to weak magnetic dipole radiation
+activated by the poloidal field, leading gradually to ""dynamical asymmetry""
+with I_{11}>I_{33}. However, a dynamically asymmetric configuration tends to
+turn over spontaneously, i.e., to rotate about axis with moment of inertia
+greater than I_{33}, with angular momentum remaining invariant. So, the fate of
+a dynamically asymmetric configuration is to become an oblique rotator and,
+eventually, a perpendicular rotator. During the so-called ""turn-over phase"",
+the turn-over angle increases spontaneously up to 90 degrees on a ""turn-over
+timescale"" t_{TOV}. In the present paper, we study numerically the turn-over
+phase for models of several masses, angular momenta, and magnetic fields.",0206476v1
+2000-07-27,Short range ferromagnetism and spin glass state in $\mathrm{Y_{0.7}Ca_{0.3}MnO_{3}}$,"Dynamic magnetic properties of $\mathrm{Y_{0.7}Ca_{0.3}MnO_{3}}$ are
+reported. The system appears to attain local ferromagnetic order at
+$T_{\mathrm{SRF}} \approx 70$ K. Below this temperature the low field
+magnetization becomes history dependent, i.e. the zero field cooled (ZFC) and
+field cooled (FC) magnetization deviate from each other and closely logarithmic
+relaxation appears at our experimental time scales (0.3-$10^{4}$ sec). The zero
+field cooled magnetization has a maximum at $T_{\mathrm{f}}\approx 30$ K,
+whereas the field cooled magnetization continues to increase, although less
+sharply, also below this temperature. Surprisingly, the dynamics of the system
+shows non-equilibrium spin glass (SG) features not only below the maximum in
+the ZFC magnetization, but also in the temperature region between this maximum
+and $T_{\mathrm{SRF}}$. The aging and temperature cycling experiments show only
+quantitative differences in the dynamic behavior above and below the maximum in
+the ZFC-magnetization; similarly, memory effects are observed in both
+temperature regions. We attribute the high temperature behavior to the
+existence of clusters of short range ferromagnetic order below
+$T_{\mathrm{SRF}}$; the configuration evolves into a conventional spin glass
+state at temperatures below $T_{\mathrm{f}}$.",0007439v2
+2004-09-09,Nonlocal magnetization dynamics in ferromagnetic heterostructures,"Two complementary effects modify the GHz magnetization dynamics of nanoscale
+heterostructures of ferromagnetic and normal materials relative to those of the
+isolated magnetic constituents: On the one hand, a time-dependent ferromagnetic
+magnetization pumps a spin angular-momentum flow into adjacent materials and,
+on the other hand, spin angular momentum is transferred between ferromagnets by
+an applied bias, causing mutual torques on the magnetizations. These phenomena
+are manifestly nonlocal: they are governed by the entire spin-coherent region
+that is limited in size by spin-flip relaxation processes. We review recent
+progress in understanding the magnetization dynamics in ferromagnetic
+heterostructures from first principles, focusing on the role of spin pumping in
+layered structures. The main body of the theory is semiclassical and based on a
+mean-field Stoner or spin-density--functional picture, but quantum-size effects
+and the role of electron-electron correlations are also discussed. A growing
+number of experiments support the theoretical predictions. The formalism should
+be useful to understand the physics and to engineer the characteristics of
+small devices such as magnetic random-access memory elements.",0409242v3
+2006-02-24,Magnetization dynamics in dysprosium orthoferrites via inverse Faraday effect,"The ultrafast non-thermal control of magnetization has recently become
+feasible in canted antiferromagnets through photomagnetic instantaneous pulses
+[A.V. Kimel {\it et al.}, Nature {\bf 435}, 655 (2005)]. In this experiment
+circularly polarized femtosecond laser pulses set up a strong magnetic field
+along the wave vector of the radiation through the inverse Faraday effect,
+thereby exciting non-thermally the spin dynamics of dysprosium orthoferrites. A
+theoretical study is performed by using a model for orthoferrites based on a
+general form of free energy whose parameters are extracted from experimental
+measurements. The magnetization dynamics is described by solving coupled
+sublattice Landau-Lifshitz-Gilbert equations whose damping term is associated
+with the scattering rate due to magnon-magnon interaction. Due to the inverse
+Faraday effect and the non-thermal excitation, the effect of the laser is
+simulated by magnetic field Gaussian pulses with temporal width of the order of
+hundred femtoseconds. When the field is along the z-axis, a single resonance
+mode of the magnetization is excited. The amplitude of the magnetization and
+out-of-phase behavior of the oscillations for fields in z and -z directions are
+in good agreement with the cited experiment. The analysis of the effect of the
+temperature shows that magnon-magnon scattering mechanism affects the decay of
+the oscillations on the picosecond scale. Finally, when the field pulse is
+along the x-axis, another mode is excited, as observed in experiments. In this
+case the comparison between theoretical and experimental results shows some
+discrepancies whose origin is related to the role played by anisotropies in
+orthoferrites.",0602593v1
+2009-01-13,Dynamic percolation of electric conductivity and a trend towards fractal skeletal structuring in a random ensemble of magnetized nanodust,"Numerical modeling of electrodynamic aggregation is carried out for a random
+ensemble of magnetized nanodust taken as a many body system of strongly
+magnetized thin rods (i.e., one-dimensional static magnetic dipoles), which
+possess electric conductivity and static electric charge, screened with its own
+static plasma sheath. The self-assembling of quasi-linear filaments from an
+ensemble of randomly situated basic blocks and the electric short-circuiting
+between biased electrodes are shown to be supported by the alignment of blocks
+in an external magnetic field. Statistical analysis of short-circuiting time
+allows tracing the dynamic percolation of electric conductivity and shows a
+decrease of percolation threshold for volume fraction, as compared with the
+observed percolation of carbon nanotubes in liquids and polymer composites.
+Modeling of short-circuiting stage of evolution is continued with tracing the
+dynamics of pinching of electric current filaments to show the interplay of all
+the magnetic and electric mechanisms of filaments networking. A trend towards a
+fractal skeletal structuring (namely, repeat of original basic block at a
+larger length scale) is illustrated with the evidence for generation of a
+bigger magnetic dipole.",0901.1835v1
+2010-07-30,Tests of Dynamical Flux Emergence as a Mechanism for CME Initiation,"Current coronal mass ejection (CME) models set their lower boundary to be in
+the lower corona. They do not calculate accurately the transfer of free
+magnetic energy from the convection zone to the magnetically dominated corona
+because they model the effects of flux emergence using kinematic boundary
+conditions or simply assume the appearance of flux at these heights. We test
+the importance of including dynamical flux emergence in CME modeling by
+simulating, in 2.5D, the emergence of sub-surface flux tubes into different
+coronal magnetic field configurations. We investigate how much free magnetic
+energy, in the form of shear magnetic field, is transported from the convection
+zone to the corona, and whether dynamical flux emergence can drive CMEs. We
+find that multiple coronal flux ropes can be formed during flux emergence, and
+although they carry some shear field into the corona, the majority of shear
+field is confined to the lower atmosphere. Less than 10% of the magnetic energy
+in the corona is in the shear field, and this, combined with the fact that the
+coronal flux ropes bring up significant dense material, means that they do not
+erupt. Our results have significant implications for all CME models which rely
+on the transfer of free magnetic energy from the lower atmosphere into the
+corona but which do not explicitly model this transfer. Such studies of flux
+emergence and CMEs are timely, as we have new capabilities to observe this with
+Hinode and SDO, and therefore to test the models against observations.",1007.5484v2
+2010-12-17,Influence of vortices and phase fluctuations on thermoelectric transport properties of superconductors in a magnetic field,"We study heat transport and thermoelectric effects in two-dimensional
+superconductors in a magnetic field. These are modeled as granular
+Josephson-junction arrays, forming either regular or random lattices. We employ
+two different models for the dynamics, relaxational model-A dynamics or
+resistively and capacitively shunted Josephson junction (RCSJ) dynamics. We
+derive expressions for the heat current in these models, which are then used in
+numerical simulations to calculate the heat conductivity and the Nernst
+coefficient for different temperatures and magnetic fields. At low temperatures
+and zero magnetic field the heat conductivity in the RCSJ model is calculated
+analytically from a spin wave approximation, and is seen to have an anomalous
+logarithmic dependence on the system size, and also to diverge in the
+completely overdamped limit C -> 0. From our simulations we find at low
+magnetic fields that the Nernst signal displays a characteristic ""tilted hill""
+profile similar to experiments and a non-monotonic temperature dependence of
+the heat conductivity. We also investigate the effects of granularity and
+randomness, which become important for higher magnetic fields. In this regime
+geometric frustration strongly influences the results in both regular and
+random systems and leads to highly non-trivial magnetic field dependencies of
+the studied transport coefficients.",1012.3876v2
+2012-06-01,"Dynamics of Coronal Bright Points as seen by Sun Watcher using Active Pixel System detector and Image Processing (SWAP), Atmospheric Imaging Assembly AIA), and Helioseismic and Magnetic Imager (HMI)","The \textit{Sun Watcher using Active Pixel system detector and Image
+Processing}(SWAP) on board the \textit{PRoject for OnBoard Autonomy\todash 2}
+(PROBA\todash 2) spacecraft provides images of the solar corona in EUV channel
+centered at 174 \AA. These data, together with \textit{Atmospheric Imaging
+Assembly} (AIA) and the \textit{Helioseismic and Magnetic Imager} (HMI) on
+board \textit{Solar Dynamics Observatory} (SDO), are used to study the dynamics
+of coronal bright points. The evolution of the magnetic polarities and
+associated changes in morphology are studied using magnetograms and
+multi-wavelength imaging. The morphology of the bright points seen in
+low-resolution SWAP images and high-resolution AIA images show different
+structures, whereas the intensity variations with time show similar trends in
+both SWAP 174 and AIA 171 channels. We observe that bright points are seen in
+EUV channels corresponding to a magnetic-flux of the order of $10^{18}$ Mx. We
+find that there exists a good correlation between total emission from the
+bright point in several UV\todash EUV channels and total unsigned photospheric
+magnetic flux above certain thresholds. The bright points also show periodic
+brightenings and we have attempted to find the oscillation periods in bright
+points and their connection to magnetic flux changes. The observed periods are
+generally long (10\todash 25 minutes) and there is an indication that the
+intensity oscillations may be generated by repeated magnetic reconnection.",1206.0095v1
+2013-12-20,Exciton spin dynamics of colloidal CdTe nanocrystals in magnetic field,"The recombination and spin dynamics of excitons in colloidal CdTe
+nanocrystals (NCs) are studied by time-resolved photoluminescence in high
+magnetic fields up to 15 T and at cryogenic temperatures. The recombination
+decay shows a nonexponential temporal behavior, with the longest component
+corresponding to the dark excitons having 260 ns decay time at zero magnetic
+field and 4.2 K temperature. This long component shortens to 150 ns at 15 T due
+to the magnetic-field-induced mixing of the bright and dark exciton states. The
+spin dynamics, assessed through the evolution of the magnetic-field-induced
+circular polarization degree of the photoluminescence, has a fast component
+shorter than 1 ns related to the bright excitons and a slow component of 5-10
+ns associated with the dark excitons. The latter shortens with increasing
+magnetic field, which is characteristic for a phonon-assisted spin relaxation
+mechanism. The relatively low saturation level of the associated
+magnetic-field-induced circular polarization degree of -30 % is explained by a
+model that suggests the CdTe NCs to constitute an ensemble of prolate and
+oblate NCs, both having a structural quantization axis. The exciton g-factor of
+2.4-2.9 evaluated from fitting the experimental data in the frame of the
+suggested approach is in good agreement with the expected value for the dark
+excitons in CdTe NCs.",1312.5929v1
+2016-09-17,Quantum dynamics of a macroscopic magnet operating as environment of a mechanical oscillator,"We study the dynamics of a bipartite quantum system in a way such that its
+formal description keeps holding even if one of its parts becomes macroscopic:
+the problem is related with the analysis of the quantum-to-classical crossover,
+but our approach implies that the whole system stays genuinely quantum. Aim of
+the work is to understand 1) if, 2) to what extent, and possibly 3) how, the
+evolution of a macroscopic environment testifies to the coupling with its
+microscopic quantum companion. To this purpose we consider a magnetic
+environment made of a large number of spin-1/2 particles, coupled with a
+quantum mechanical oscillator, possibly in the presence of an external magnetic
+field. We take the value of the total environmental-spin S constant and large,
+which allows us to consider the environment as one single macroscopic system,
+and further deal with the hurdles of the spin-algebra via approximations that
+are valid in the large-S limit. We find an insightful expression for the
+propagator of the whole system, where we identify an effective ""back-action""
+term, i.e. an operator acting on the magnetic environment only, and yet missing
+in the absence of the quantum principal system. This operator emerges as a
+time-dependent magnetic anisotropy whose character, whether uniaxial or planar,
+also depends on the detuning between the level-splitting in the spectrum of the
+free magnetic system, induced by the possible presence of the external field,
+and the frequency of the oscillator. The time-dependence of the anisotropy is
+analysed, and its effects on the dynamics of the magnet, as well as its
+relation with the entangling evolution of the overall system, are discussed.",1609.05389v1
+2017-06-05,How important is non-ideal physics in simulations of sub-Eddington accretion onto spinning black holes?,"Black holes with accretion rates well below the Eddington rate are expected
+to be surrounded by low-density, hot, geometrically thick accretion disks. This
+includes the two black holes being imaged at sub-horizon resolution by the
+Event Horizon Telescope. In these disks, the mean free path for Coulomb
+interactions between charged particles is large, and the accreting matter is a
+nearly collisionless plasma. Despite this, numerical simulations have so far
+modeled these accretion flows using ideal magnetohydrodynamics. Here, we
+present the first global, general relativistic, 3D simulations of accretion
+flows onto a Kerr black hole including the non-ideal effects most likely to
+affect the dynamics of the disk: the anisotropy between the pressure parallel
+and perpendicular to the magnetic field, and the heat flux along magnetic field
+lines. We show that for both standard and magnetically arrested disks, the
+pressure anisotropy is comparable to the magnetic pressure, while the heat flux
+remains dynamically unimportant. Despite this large pressure anisotropy,
+however, the time-averaged structure of the accretion flow is strikingly
+similar to that found in simulations treating the plasma as an ideal fluid. We
+argue that these similarities are largely due to the interchangeability of the
+viscous and magnetic shear stresses as long as the magnetic pressure is small
+compared to the gas pressure, and to the sub-dominant role of pressure/viscous
+effects in magnetically arrested disks. We conclude by highlighting outstanding
+questions in modeling the dynamics of low collisionality accretion flows.",1706.01533v1
+2017-08-08,Spin-orbit-torque driven magnetoimpedance in Pt-layer/magnetic-ribbon heterostructures,"When a flow of electron passes through a paramagnetic layer with strong
+spin-orbit-coupling such as platinum (Pt), a net spin current is produced via
+spin Hall effect (SHE). This spin current can exert a torque on the
+magnetization of an adjacent ferromagnetic layer which can be probed via
+magnetization dynamic response, e.g. spin-torque ferromagnetic resonance
+(ST-FMR). Nevertheless, that effect in lower frequency magnetization dynamic
+regime (MHz) where skin effect occurs in high permeability ferromagnetic
+conductors namely the magneto-impedance (MI) effect can be fundamentally
+important which has not been studied so far. Here, by utilizing the MI effect
+in magnetic-ribbon/Pt heterostructure with high magnetic permeability that
+allows the ac current effectively confined at the skin depth of ~100 nm
+thickness, the effect of spin-orbit-torque (SOT) induced by the SHE probed via
+MI measurement is investigated. We observed a systematic MI frequency shift
+that increases by increasing the applied current amplitude and thickness of the
+Pt layer (varying from 0 nm to 20 nm). In addition, the role of Pt layer in
+ribbon/Pt heterostructure is evaluated with ferromagnetic resonance (FMR)
+effect representing standard Gilbert damping increase as the result of presence
+of the SHE. Our results unveil the role of SOT in dynamic control of the
+transverse magnetic permeability probed with impedance spectroscopy as useful
+and valuable technique for detection of future SHE devices.",1708.02402v2
+2017-09-10,Dynamical Anisotropic Response of Black Phosphorus under Magnetic Field,"Black phosphorus (BP) has emerged as a promising material candidate for next
+generation electronic and optoelectronic devices due to its high mobility,
+tunable band gap and highly anisotropic properties. In this work, polarization
+resolved ultrafast mid-infrared transient reflection spectroscopy measurements
+are performed to study the dynamical anisotropic optical properties of BP under
+magnetic fields up to 9 T. The relaxation dynamics of photoexcited carrier is
+found to be insensitive to the applied magnetic field due to the broadening of
+the Landau levels and large effective mass of carriers. While the anisotropic
+optical response of BP decreases with increasing magnetic field, its
+enhancement due to the excitation of hot carriers is similar to that without
+magnetic field. These experimental results can be well interpreted by the
+magneto-optical conductivity of the Landau levels of BP thin film, based on an
+effective k*p Hamiltonian and linear response theory. These findings suggest
+attractive possibilities of multi-dimensional controls of anisotropic response
+(AR) of BP with light, electric and magnetic field, which further introduces BP
+to the fantastic magnetic field sensitive applications.",1709.03079v1
+2017-12-04,Trend reversal in the magnetic-field dependence of exciton spin-transfer rates in diluted magnetic semiconductors due to non-Markovian dynamics,"We investigate theoretically the influence of an external magnetic field on
+the spin dynamics of excitons in diluted magnetic semiconductor quantum wells.
+To this end, we apply a quantum kinetic theory beyond the Markov approximation
+which reveals that non-Markovian effects can significantly influence the
+exciton spin dynamics. If the magnetic field is oriented parallel to the growth
+direction of the well, the Markovian spin-transfer rate decreases monotonically
+with increasing field as predicted by Fermi's golden rule. The quantum kinetic
+theory follows this result qualitatively but predicts pronounced quantitative
+differences in the spin-transfer rate as well as in the long-time spin
+polarization. However, for an in-plane magnetic field, where the Markovian
+spin-transfer rate first drops and then increases again, quantum kinetic
+effects become so pronounced that the Markovian trend is completely reversed.
+This is made evident by a distinct maximum of the rate followed by a monotonic
+decrease. The deviations can be traced back to a redistribution of carriers in
+energy space caused by correlations between excitons and magnetic dopants. The
+same effect leads to a finite electron-spin polarization at long times in
+longitudinal as well as transverse fields which is much larger than the
+corresponding Markovian prediction.",1712.00978v2
+2018-07-19,Magnetization nutation induced by surface effects in nanomagnets,"We investigate the magnetization dynamics of ferromagnetic nanoparticles in
+the atomistic approach taking account of surface anisotropy and the spin
+misalignment it causes. We demonstrate that such inhomogeneous spin
+configurations induce nutation in the dynamics of the particle's magnetization.
+More precisely, in addition to the ordinary precessional motion with frequency
+$f_{p}\sim10\,{\rm GHz}$, we find that the dynamics of the net magnetic moment
+exhibits two more resonance peaks with frequencies $f_{c}$ and $f_{n}$ which
+are higher than the frequency $f_{p} : f_{c}=4\times f_{p}\sim40\,{\rm GHz}$ is
+related with the oscillations of the particle's magnetic moment between the
+minima of the effective potential induced by weak surface anisotropy. On the
+other hand, the much higher frequency $f_{n}\sim1\,{\rm THz}$ is attributed to
+the magnetization fluctuations at the atomic level driven by exchange
+interaction. We have compared our results on nutation induced by surface
+effects with those rendered by the macroscopic approach based on the
+Landau-Lifshitz-Gilbert equation augmented by an inertial term (proportional to
+the second-order time derivative of the macroscopic moment) with a
+phenomenological coefficient. The good agreement between the two models have
+allowed us to estimate the latter coefficient in terms of the atomistic
+parameters such as the surface anisotropy constant. We have thus proposed a new
+origin for the magnetization nutations as being induced by surface effects and
+have interpreted the corresponding resonance peaks and their frequencies.",1807.07392v1
+2018-11-05,Evidence of long-range ferromagnetic order and spin frustration effects in the double perovskite $La_2CoMnO_6$,"We present a comprehensive study on the magnetic structure, dynamics, and
+phase evolution in the single-phase double perovskite $La_2CoMnO_6$. The mixed
+valence state due to oxygen deficiency is verified by X-ray photoelectron
+spectroscopy, and confirms a double ferromagnetic transition observed in DC
+magnetization. Neutron diffraction reveals that the magnetic structure is
+dominated by long-range ferromagnetic ordering, which is further corroborated
+by a critical exponents analysis of the paramagnetic to ferromagnetic phase
+transition. An analysis of the magnetization dynamics by means of linear and
+nonlinear ac magnetic susceptibilities marks the presence of two distinct
+cluster glass-like states that emerge at low temperatures. The isothermal
+entropy change as a function of temperature and magnetic field (H) is exploited
+to investigate the mechanism of stabilization of the magnetic phases across the
+H-T phase diagram. In the regime of the phase diagram where thermal energy is
+sufficiently low, regions of competing interactions due to local disorder
+become stabilized and display glass-like dynamics. The freezing mechanism of
+clusters is illustrated using a unique probe of transverse susceptibility that
+isolates the effects of the local anisotropy of the spin clusters. The results
+are summarized in a new H-T phase diagram of $La_2CoMnO_6$ revealed for the
+first time from these data.",1811.01835v1
+2019-03-13,Nutation spectroscopy of a nanomagnet driven into deeply nonlinear ferromagnetic resonance,"Strongly out-of-equilibrium regimes in magnetic nanostructures exhibit novel
+properties, linked to the nonlinear nature of magnetization dynamics, which are
+of great fundamental and practical interest. Here, we demonstrate that
+field-driven ferromagnetic resonance can occur with substantial spatial
+coherency at unprecedented large angle of magnetization precessions, which is
+normally prevented by the onset of spin-wave instabilities and magnetization
+turbulent dynamics. Our results show that this limitation can be overcome in
+nanomagnets, where the geometric confinement drastically reduces the density of
+spin-wave modes. The obtained deeply nonlinear ferromagnetic resonance regime
+is probed by a new spectroscopic technique based on the application of a second
+excitation field. This enables to resonantly drive slow coherent magnetization
+nutations around the large angle periodic trajectory. Our experimental findings
+are well accounted for by an analytical model derived for systems with uniaxial
+symmetry. They also provide new means for controlling highly nonlinear
+magnetization dynamics in nanostructures, which open interesting applicative
+opportunities in the context of magnetic nanotechnologies.",1903.05411v1
+2020-10-22,Magnetic properties and quench dynamics of two interacting ultracold molecules in a trap,"We theoretically investigate the magnetic properties and nonequilibrium
+dynamics of two interacting ultracold polar and paramagnetic molecules in a
+one-dimensional harmonic trap in external electric and magnetic fields. The
+molecules interact via a multichannel two-body contact potential, incorporating
+the short-range anisotropy of intermolecular interactions. We show that various
+magnetization states arise from the interplay of the molecular interactions,
+electronic spins, dipole moments, rotational structures, external fields, and
+spin-rotation coupling. The rich magnetization diagrams depend primarily on the
+anisotropy of the intermolecular interaction and the spin-rotation coupling.
+These specific molecular properties are challenging to calculate or measure.
+Therefore, we propose the quench dynamics experiments for extracting them from
+observing the time evolution of the analyzed system. Our results indicate the
+possibility of controlling the molecular few-body magnetization with the
+external electric field and pave the way towards studying the magnetization of
+ultracold molecules trapped in optical tweezers or optical lattices and their
+application in quantum simulation of molecular multichannel many-body
+Hamiltonians and quantum information storing.",2010.11899v3
+2021-07-13,Investigation of spin-phonon coupling and local magnetic properties in magnetoelectric Fe2TeO6,"Spin-phonon coupling originated from spin-lattice correlation depends upon
+different exchange interactions in transition metal oxides containing 3d
+magnetic ions. Spin-lattice coupling can influence the coupling mechanism in
+magnetoelectric material. To understand the spin-lattice correlation in inverse
+trirutile Fe2TeO6 (FTO), magnetic properties and phonon spectra are studied.
+Signature of short-range magnetic correlation induced by 5/2-5/2 dimeric
+interaction and magnetic anomaly at 150 K is perceived apart from the familiar
+sharp transition (TN~210K) corresponding to long-range order by magnetization
+and heat capacity measurement. The magnetic transitions and the spin dynamics
+are further locally probed by muon spin resonance ({\mu}SR) measurement in both
+zero fields (ZF) and longitudinal field (LF) mode. Three dynamically distinct
+temperature regimes; (i) T >TN, (ii) TN>T>150 K, and (iii) T<150 K, are
+observed. A swift change in spin dynamics is realized at 150K by {\mu}SR,
+though previous studies suggest long-range antiferromagnetic order. The
+observation of renormalization of different Raman modes below 210K suggests the
+existence of spin-phonon coupling in the material. The coupling strength is
+quantified as in the range 0.1-1.2 cm-1 following the two-spin cluster
+approximation. We propose that the spin-phonon coupling is mediated by the
+Fe-O2-Fe interbilayer exchange play a significant role in ME coupling observed
+in the material.",2107.06269v2
+2022-12-20,"A Global Simulation of the Dynamo, Zonal Jets, and Vortices on Saturn","The fluid dynamics in planet Saturn gives rise to alternating east-west jet
+streams, large cyclonic and anticyclonic vortices, and a dipole-dominant
+magnetic field which is highly axisymmetric about the planetary rotation axis.
+Modelling these features in a self-consistent manner is crucial for
+understanding the dynamics of Saturn's interior and atmosphere. Here we report
+a turbulent high-resolution dynamo simulation in a spherical shell which
+produces these features simultaneously for the first time. A crucial model
+ingredient is a long-hypothesised stably stratified layer (SSL), sandwiched
+between a deep metallic hydrogen layer and an outer low-conductivity molecular
+layer, born out of limited solubility of Helium inside metallic Hydrogen at
+certain depths. The model spontaneously produces polar cyclones and significant
+low and mid latitude jet stream activities in the molecular layer. The
+off-equatorial low-latitude jet streams partially penetrate into the SSL and
+interact with the magnetic field. This helps to axisymmetrize the magnetic
+field about the rotation axis and convert some of the poloidal magnetic field
+to toroidal field, which appears as two global magnetic energy rings
+surrounding the deeper dynamo region. The simulation also mimics a distinctive
+dip in the fifth spherical harmonic in Saturn's magnetic energy spectrum as
+inferred from the Cassini Grand Finale measurements. Our model highlights the
+role of an SSL in shaping the fluid dynamical and magnetic features of giant
+planets, as exemplified at Saturn.",2212.10617v1
+2023-11-06,A Reduced Ideal MHD System for Nonlinear Magnetic Field Turbulence in Plasmas with Approximate Flux Surfaces,"This paper studies the nonlinear evolution of magnetic field turbulence in
+proximity of steady ideal MHD configurations characterized by a small electric
+current, a small plasma flow, and approximate flux surfaces, a physical setting
+that is relevant for plasma confinement in stellarators. The aim is to gather
+insight on magnetic field dynamics, to elucidate accessibility and stability of
+three-dimensional MHD equilibria, as well as to formulate practical methods to
+compute them. Starting from the ideal MHD equations, a reduced dynamical system
+of two coupled nonlinear PDEs for the flux function and the angle variable
+associated with the Clebsch representation of the magnetic field is obtained.
+It is shown that under suitable boundary and gauge conditions such reduced
+system preserves magnetic energy, magnetic helicity, and total magnetic flux.
+The noncanonical Hamiltonian structure of the reduced system is identified, and
+used to show the nonlinear stability of steady solutions against perturbations
+involving only one Clebsch potential. The Hamiltonian structure is also applied
+to construct a dissipative dynamical system through the method of double
+brackets. This dissipative system enables the computation of MHD equilibria by
+minimizing energy until a critical point of the Hamiltonian is reached.
+Finally, an iterative scheme based on the alternate solution of the two steady
+equations in the reduced system is proposed as a further method to compute MHD
+equilibria. A theorem is proven which states that the iterative scheme
+converges to a nontrivial MHD equilbrium as long as solutions exist at each
+step of the iteration.",2311.03095v1
+2012-09-11,Study of the 3D Coronal Magnetic Field of Active Region 11117 Around the Time of a Confined Flare Using a Data-Driven CESE--MHD Model,"We apply a data-driven MHD model to investigate the three-dimensional (3D)
+magnetic field of NOAA active region (AR) 11117 around the time of a C-class
+confined flare occurred on 2010 October 25. The MHD model, based on the
+spacetime conservation-element and solution-element (CESE) scheme, is designed
+to focus on the magnetic-field evolution and to consider a simplified solar
+atomsphere with finite plasma $\beta$. Magnetic vector-field data derived from
+the observations at the photoshpere is inputted directly to constrain the
+model. Assuming that the dynamic evolution of the coronal magnetic field can be
+approximated by successive equilibria, we solve a time sequence of MHD
+equilibria basing on a set of vector magnetograms for AR 11117 taken by the
+Helioseismic and Magnetic Imager (HMI) on board the {\it Solar Dynamic
+Observatory (SDO)} around the time of flare. The model qualitatively reproduces
+the basic structures of the 3D magnetic field, as supported by the visual
+similarity between the field lines and the coronal loops observed by the
+Atmospheric Imaging Assembly (AIA), which shows that the coronal field can
+indeed be well characterized by the MHD equilibrium in most time. The magnetic
+configuration changes very limited during the studied time interval of two
+hours. A topological analysis reveals that the small flare is correlated with a
+bald patch (BP, where the magnetic field is tangent to the photoshpere),
+suggesting that the energy release of the flare can be understood by magnetic
+reconnection associated with the BP separatrices. The total magnetic flux and
+energy keep increasing slightly in spite of the flare, while the computed
+magnetic free energy drops during the flare with an amount of $\sim 10^{30}$
+erg, which seems to be adequate to provide the energy budget of the minor
+C-class confined flare.",1209.2207v1
+2014-02-05,Magnetic Helicity and Large Scale Magnetic Fields: A Primer,"Magnetic fields of laboratory, planetary, stellar, and galactic plasmas
+commonly exhibit significant order on large temporal or spatial scales compared
+to the otherwise random motions within the hosting system. Such ordered fields
+can be measured in the case of planets, stars, and galaxies, or inferred
+indirectly by the action of their dynamical influence, such as jets. Whether
+large scale fields are amplified in situ or a remnant from previous stages of
+an object's history is often debated for objects without a definitive magnetic
+activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic
+field lines, is a unifying tool for understanding large scale field evolution
+for both mechanisms of origin. Its importance stems from its two basic
+properties: (1) magnetic helicity is typically better conserved than magnetic
+energy; and (2) the magnetic energy associated with a fixed amount of magnetic
+helicity is minimized when the system relaxes this helical structure to the
+largest scale available. Here I discuss how magnetic helicity has come to help
+us understand the saturation of and sustenance of large scale dynamos, the need
+for either local or global helicity fluxes to avoid dynamo quenching, and the
+associated observational consequences. I also discuss how magnetic helicity
+acts as a hindrance to turbulent diffusion of large scale fields, and thus a
+helper for fossil remnant large scale field origin models in some contexts. I
+briefly discuss the connection between large scale fields and accretion disk
+theory as well. The goal here is to provide a conceptual primer to help the
+reader efficiently penetrate the literature.",1402.0933v2
+2014-02-20,Diagnosis of Magnetic and Electric Fields of Chromospheric Jets through Spectropolarimetric Observations of HI Paschen Lines,"Magnetic fields govern the plasma dynamics in the outer layers of the solar
+atmosphere, and electric fields acting on neutral atoms that move across the
+magnetic field enable us to study the dynamical coupling between neutrals and
+ions in the plasma. In order to measure the magnetic and electric fields of
+chromospheric jets, the full Stokes spectra of the Paschen series of neutral
+hydrogen in a surge and in some active region jets that took place at the solar
+limb were observed on May 5, 2012, using the spectropolarimeter of the Domeless
+Solar Telescope at Hida observatory, Japan. First, we inverted the Stokes
+spectra taking into account only the effect of magnetic fields on the energy
+structure and polarization of the hydrogen levels. Having found no definitive
+evidence of the effects of electric fields in the observed Stokes profiles, we
+then estimated an upper bound for these fields by calculating the polarization
+degree under the magnetic field configuration derived in the first step, with
+the additional presence of a perpendicular (Lorentz type) electric field of
+varying strength. The inferred direction of the magnetic field on the plane of
+the sky (POS) approximately aligns to the active region jets and the surge,
+with magnetic field strengths in the range 10 G < B < 640 G for the surge.
+Using magnetic field strengths of 70, 200, and 600 G, we obtained upper limits
+for possible electric fields of 0.04, 0.3, and 0.8 V/cm, respectively. Because
+the velocity of neutral atoms of hydrogen moving across the magnetic field
+derived from these upper limits of the Lorentz electric field is far below the
+bulk velocity of the plasma perpendicular to the magnetic field as measured by
+the Doppler shift, we conclude that the neutral atoms must be highly frozen to
+the magnetic field in the surge.",1402.4903v1
+2018-10-23,"B-site spin-state and anti-site disorder driven multiple-magnetic phases: Griffiths phase, re-entrant cluster glass and exchange bias in double perovskite Pr$_2$CoFeO$_6$","We report the comprehensive experimental results identifying the magnetic
+spin ordering and the magnetization dynamics of a double perovskite Pr2CoFeO6
+by employing the (dc and ac) magnetization, powder neutron diffraction (NPD)
+and X-ray magnetic circular dichroism (XMCD) techniques. X-ray diffraction and
+neutron diffraction studies revealed that Pr2CoFeO6 adopts a B-site disordered
+orthorhombic structure with space group Pnma. Additionally, ab initio band
+structure calculations performed on this system suggested an insulating
+anti-ferromagnetic (Fe-Fe) ground state. Magnetometry study showed the system
+to possess a spectrum of interesting magnetic phases including long range
+antiferromagnetic (canted) spin ordering (TN ~269 K), Griffiths phase,
+re-entrant cluster glass (RCG) (TG~ 34 K) and exchange bias. However, the NPD
+study divulged the exhibition of a long range G-type (below TN ~269 K) of spin
+ordering by Fe spins. Spin dynamics study by ac susceptibility technique
+confirmed the system possessing long range ordering at higher
+temperatureundergoes a RCG transition at ~34 K. Existence of Griffiths phase
+was confirmed by non-analytic field variation of magnetization and Heisenberg
+type temporal spin relaxation above long range ordering temperature TN ~269 K.
+The anti-site disorder related to the B-sites (Co/Fe) is found to be the main
+driving force forthe observed multiple magnetic phases. Furthermore, the
+electronic structure probed by the X-ray absorption spectroscopy (XAS) study
+suggested a nominal valance state of +3 for both of the B-site ions (Co/Fe)
+which in turn triggered the anti-site disorder in the system. Magnetic, XRD,
+NPD and XAS analysis yielded a low spin state (LS) for the Co3+ ions. The
+random non-magnetic dilution of magnetic Fe3+ (HS) ions by Co3+ (LS) ions
+essentially played a crucial role in manifesting the magnetic properties of the
+system.",1810.09788v1
+2021-01-05,Magnetic Imaging of the Outer Solar Atmosphere (MImOSA): Unlocking the driver of the dynamics in the upper solar atmosphere,"The magnetic activity of the Sun directly impacts the Earth and human life.
+Likewise, other stars will have an impact on the habitability of planets
+orbiting these host stars. The lack of information on the magnetic field in the
+higher atmospheric layers hampers our progress in understanding solar magnetic
+activity. Overcoming this limitation would allow us to address four paramount
+long-standing questions: (1) How does the magnetic field couple the different
+layers of the atmosphere, and how does it transport energy? (2) How does the
+magnetic field structure, drive and interact with the plasma in the
+chromosphere and upper atmosphere? (3) How does the magnetic field destabilise
+the outer solar atmosphere and thus affect the interplanetary environment? (4)
+How do magnetic processes accelerate particles to high energies? New
+ground-breaking observations are needed to address these science questions. We
+suggest a suite of three instruments that far exceed current capabilities in
+terms of spatial resolution, light-gathering power, and polarimetric
+performance: (a) A large-aperture UV-to-IR telescope of the 1-3 m class aimed
+mainly to measure the magnetic field in the chromosphere by combining high
+spatial resolution and high sensitivity. (b) An extreme-UV-to-IR coronagraph
+that is designed to measure the large-scale magnetic field in the corona with
+an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30
+cm telescope that combines high throughput in the extreme UV with polarimetry
+to connect the magnetic measurements of the other two instruments. This mission
+to measure the magnetic field will unlock the driver of the dynamics in the
+outer solar atmosphere and thereby greatly advance our understanding of the Sun
+and the heliosphere.",2101.01566v1
+2004-11-17,Pulsar dynamics: magnetic dipole model revisited,Manuscript withdrawn by the authors.,0411507v2
+1999-06-14,Universal property of single topological singularity dynamics,"Using the random matrix theory we demonstrate explicitly the insensitivity of
+the transverse force on a moving vortex to non-intrinsic and non-magnetic
+impurities in a superconductor.",9906189v1
+2005-02-18,Dynamics of coupled vortices in layered magnetic nanodots,"The spin dynamics are calculated for a model system consisting of
+magnetically soft, layered nanomagnets, in which two ferromagnetic (F)
+cylindrical dots, each with a magnetic vortex ground state, are separated by a
+non-magnetic spacer (N). This permits a study of the effects of interlayer
+magnetostatic interactions on the vortex dynamics. The system was explored by
+applying the equations of motion for the vortex core positions. The restoring
+force was calculated taking into account the magnetostatic interactions
+assuming a realistic surface charge free spin distribution. For tri-layer F/N/F
+dots with opposite chiralities and the same core polarizations (lowest energy
+state), two eigenmodes are predicted analytically and confirmed via
+micromagnetic simulations. One mode is in the sub-GHz range for submicron dot
+diameters and corresponds to quasi-circular rotation of the cores about the dot
+center. A second mode is in the MHz range corresponding to a small amplitude
+rotation of the mean core position. The eigenfrequencies depend strongly on the
+geometrical parameters of the system, suggesting that magnetostatic effects
+play a dominant role in determining the vortex dynamics.",0502469v1
+1994-07-26,Dynamical Flavor Symmetry Breaking by a Magnetic Field in $2+1$ Dimensions,"It is shown that in $2+1$ dimensions, a constant magnetic field is a strong
+catalyst of dynamical flavor symmetry breaking, leading to generating a fermion
+dynamical mass even at the weakest attractive interaction between fermions. The
+essence of this effect is that in a magnetic field, in $2+1$ dimensions, the
+dynamics of fermion pairing is essentially one-dimensional. The effect is
+illustrated in the Nambu-Jona-Lasinio model in a magnetic field. The low-energy
+effective action in this model is derived and the thermodynamic properties of
+the model are considered. The relevance of this effect for planar condensed
+matter systems and for $3+1$ dimensional theories at high temperature is
+pointed out.",9407168v2
+2005-11-23,Fluctuation of magnetic induction in von Kármán swirling flows,"Studies of magnetic induction in von K\'arm\'an swirling flows have so far
+linked the time-averaged induced magnetic field to the structure of the mean
+flow. They have evidenced the Omega and Parker mechanism generated respectively
+by the flow differential rotation and helicity, which underly the Duddley and
+James \cite{DuddleyJames} dynamos. Using an array of Hall probes we study here
+the dynamical regime. In the experimental flow, turbulence is fully developed
+and large fluctuations are observed in the magnetic induction processes. We
+find that the large scale turbulent fluctuations have different characteristics
+when induction results from the differential rotation or from the dynamics of
+the stagnation point in the mid plane of the von K\'arm\'an flow. Symmetry
+considerations indicate that the dynamical flow spends half of its time away
+from the time-averaged structure. The consequences of these observations for
+dynamo experiments are discussed.",0511204v1
+2006-06-27,Investigation of the Chaotic Dynamics of an Electron Beam with a Virtual Cathode in an External Magnetic Field,"The effect of the strength of the focusing magnetic field on chaotic dynamic
+processes occurring inan electron beam with a virtual cathode, as well as on
+the processes whereby the structures form in the beamand interact with each
+other, is studied by means of two-dimensional numerical simulations based on
+solving a self-consistent set of Vlasov-Maxwell equations. It is shown that, as
+the focusing magnetic field is decreased,the dynamics of an electron beam with
+a virtual cathode becomes more complicated due to the formation andinteraction
+of spatio-temporal longitudinal and transverse structures in the interaction
+region of a vircator. The optimum efficiency of the interaction of an electron
+beam with the electromagnetic field of the vircator isachieved at a
+comparatively weak external magnetic field and is determined by the
+fundamentally two-dimensional nature of the motion of the beam electrons near
+the virtual cathode.",0606235v1
+2008-11-09,X-ray imaging of the dynamic magnetic vortex core deformation,"Magnetic platelets with a vortex configuration are attracting considerable
+attention. The discovery that excitation with small in-plane magnetic fields or
+spin polarised currents can switch the polarisation of the vortex core did not
+only open the possibility of using such systems in magnetic memories, but also
+initiated the fundamental investigation of the core switching mechanism itself.
+Micromagnetic models predict that the switching is mediated by a
+vortex-antivortex pair, nucleated in a dynamically induced vortex core
+deformation. In the same theoretical framework, a critical core velocity is
+predicted, above which switching occurs. Although these models are extensively
+studied and generally accepted, experimental support has been lacking until
+now. In this work, we have used high-resolution time-resolved X-ray microscopy
+to study the detailed dynamics in vortex structures. We could reveal the
+dynamic vortex core deformation preceding the core switching. Also, the
+threshold velocity could be measured, giving quantitative comparison with
+micromagnetic models.",0811.1348v2
+2009-03-16,Non-stationary magnetization dynamics driven by spin transfer torque,"This paper shows that the presence of two dynamical regimes, characterized by
+different precessional-axis, is the origin of the non-monotonic behavior of the
+output integrated power for large-amplitude magnetization precession driven by
+spin-polarized current in nanoscale exchange biased spin-valves. In particular,
+at the transition current between those two regimes exists an abruptly loss in
+the integrated output power. After the introduction of a time-frequency
+analysis of magnetization dynamics based on the wavelet transform, we performed
+a numerical experiment by means of micromagnetic simulations. Our results
+predicted that, together with a modulation of the frequency of the main excited
+mode of the magnetization precession, at high non-linear dynamical regime the
+instantaneous output power of the spin-torque oscillator can disappear and then
+reappear at nanosecond scale.",0903.2751v1
+2009-03-27,Dynamical magnetoelectric effects induced by the Dzyaloshinskii-Moriya interaction in multiferroics,"We study the dynamical interplay between ferroelectricity and magnetism in a
+multiferroic with a helical magnetic order. We show that the dynamical
+exchange-striction induces a biquadratic interaction between the spins and
+transverse phonons resulting in quantum fluctuations of the spontaneous
+ferroelectric polarization $\mathbf{P}$ in the ferroelectric phase. The
+hybridization between the spin wave and the fluctuation of the electric
+polarization leads to low-lying transverse phonon modes. Those are
+perpendicular to $\mathbf{P}$ and to the helical spins at small wave vector but
+then turn parallel to $\mathbf{P}$ at a wave vector close to the magnetic
+modulation vector. For helical magnetic structure, the spin chirality which
+determines the direction of $\mathbf{P}$, also possesses a long-range order.
+Due to the dynamical Dzyaloshiskii-Moriya interaction, the spin-chirality is
+strongly coupled to the spin fluctuation which implies an on-site inversion of
+the spin-chirality in the ordered spin-1/2 system and results in a finite
+scattering intensity of polarized neutrons from a cycloidal helimagnet.",0903.4751v1
+2010-06-25,Spin and charge dynamics in [TbPc$_2$]$^0$ and [DyPc$_2$]$^0$ single molecule magnets,"Magnetization, AC susceptibility and $\mu$SR measurements have been performed
+in neutral phthalocyaninato lanthanide ([LnPc$_2]^0$) single molecule magnets
+in order to determine the low-energy levels structure and to compare the
+low-frequency spin excitations probed by means of macroscopic techniques, such
+as AC susceptibility, with the ones explored by means of techniques of
+microscopic character, such as $\mu$SR. Both techniques show a high temperature
+thermally activated regime for the spin dynamics and a low temperature
+tunneling one. While in the activated regime the correlation times for the spin
+fluctuations estimated by AC susceptibility and $\mu$SR basically agree, clear
+discrepancies are found in the tunneling regime. In particular, $\mu$SR probes
+a faster dynamics with respect to AC susceptibility. It is argued that the
+tunneling dynamics probed by $\mu$SR involves fluctuations which do not yield a
+net change in the macroscopic magnetization probed by AC susceptibiliy. Finally
+resistivity measurements in [TbPc$_2]^0$ crystals show a high temperature
+nearly metallic behaviour and a low temperature activated behaviour.",1006.4919v1
+2010-10-05,Magnetic Monopole Dynamics in Spin Ice,"One of the most remarkable examples of emergent quasi-particles, is that of
+the ""fractionalization"" of magnetic dipoles in the low energy configurations of
+materials known as ""spin ice"", into free and unconfined magnetic monopoles
+interacting via Coulomb's 1/r law [Castelnovo et. al., Nature, 451, 42-45
+(2008)]. Recent experiments have shown that a Coulomb gas of magnetic charges
+really does exist at low temperature in these materials and this discovery
+provides a new perspective on otherwise largely inaccessible phenomenology. In
+this paper, after a review of the different spin ice models, we present
+detailed results describing the diffusive dynamics of monopole particles
+starting both from the dipolar spin ice model and directly from a Coulomb gas
+within the grand canonical ensemble. The diffusive quasi-particle dynamics of
+real spin ice materials within ""quantum tunneling"" regime is modeled with
+Metropolis dynamics, with the particles constrained to move along an underlying
+network of oriented paths, which are classical analogues of the Dirac strings
+connecting pairs of Dirac monopoles.",1010.0970v1
+2010-10-15,"Length matters, periodically (the movie)","We perform Rayleigh-Taylor Instability experiments, using magnetic levitation
+to force a controlled initial perturbation.",1010.3157v1
+2011-06-15,Dissipative hydrodynamic equation of a ferromagnetic Bose-Einstein condensate: Analogy to magnetization dynamics in conducting ferromagnets,"The hydrodynamic equation of a spinor Bose-Einstein condensate (BEC) gives a
+simple description of spin dynamics in the condensate. We introduce the
+hydrodynamic equation of a ferromagnetic BEC with dissipation originating from
+the energy dissipation of the condensate. The dissipative hydrodynamic equation
+has the same form as an extended Landau-Lifshitz-Gilbert (LLG) equation, which
+describes the magnetization dynamics of ferromagnets interacting with
+spin-polarized currents. Employing the dissipative hydrodynamic equation, we
+demonstrate the magnetic domain pattern dynamics of a ferromagnetic BEC in the
+presence and absence of a current of particles, and discuss the effects of the
+current on domain pattern formation. We also discuss the characteristic lengths
+of domain patterns that have domain walls with and without finite
+magnetization.",1106.2876v4
+2012-03-05,Coherent multi-flavour spin dynamics in a fermionic quantum gas,"Microscopic spin interaction processes are fundamental for global static and
+dynamical magnetic properties of many-body systems. Quantum gases as pure and
+well isolated systems offer intriguing possibilities to study basic magnetic
+processes including non-equilibrium dynamics. Here, we report on the
+realization of a well-controlled fermionic spinor gas in an optical lattice
+with tunable effective spin ranging from 1/2 to 9/2. We observe long-lived
+intrinsic spin oscillations and investigate the transition from two-body to
+many-body dynamics. The latter results in a spin-interaction driven melting of
+a band insulator. Via an external magnetic field we control the system's
+dimensionality and tune the spin oscillations in and out of resonance. Our
+results open new routes to study quantum magnetism of fermionic particles
+beyond conventional spin 1/2 systems.",1203.0948v1
+2013-01-25,Driven skyrmions and dynamical transitions in chiral magnets,"We study the dynamics of skyrmions in chiral magnets in the presence of a
+spin polarized current. The motion of skyrmions in the ferromagnetic background
+excites spin waves and contributes to additional damping. At a large current,
+the spin wave spectrum becomes gapless and skyrmions are created dynamically
+from the ferromagnetic state. At an even higher current, these skyrmions are
+strongly deformed due to the damping and become unstable at a threshold
+current, leading to a chiral liquid. We show how skyrmions can be created by
+increasing the current in the magnetic spiral state. We then construct a
+dynamic phase diagram for a chiral magnet with a current. The instability
+transitions between different states can be observed as experimentally clear
+signatures in the transport measurements, such as jumps and hysteresis.",1301.5963v2
+2013-03-26,A unified model for the dynamics of driven ribbon with strain and magnetic order parameters,"We develop a unified model to explain the dynamics of driven one dimensional
+ribbon for materials with strain and magnetic order parameters. We show that
+the model equations in their most general form explain several results on
+driven magnetostrictive metallic glass ribbons such as the period doubling
+route to chaos as a function of a dc magnetic field in the presence of a
+sinusoidal field, the quasiperiodic route to chaos as a function of the
+sinusoidal field for a fixed dc field, and induced and suppressed chaos in the
+presence of an additional low amplitude near resonant sinusoidal field. We also
+investigate the influence of a low amplitude near resonant field on the period
+doubling route. The model equations also exhibit symmetry restoring crisis with
+an exponent close to unity. The model can be adopted to explain certain results
+on magnetoelastic beam and martensitic ribbon under sinusoidal driving
+conditions. In the latter case, we find interesting dynamics of a periodic one
+orbit switching between two equivalent wells as a function of an ac magnetic
+field that eventually makes a direct transition to chaos under resonant driving
+condition. The model is also applicable to magnetomartensites and materials
+with two order parameters.",1303.6621v1
+2013-09-10,Vortices and Impurities,"We describe the BPS dynamics of vortices in the presence of impurities. We
+argue that a moduli space of solitons survives the addition of both electric
+and magnetic impurities. However, dynamics on the moduli space is altered. In
+the case of electric impurities, the metric remains unchanged but the dynamics
+is accompanied by a connection term, acting as an effective magnetic field over
+the moduli space. We give an expression for this connection and compute the
+vortex-impurity bound states in simple cases. In contrast, magnetic impurities
+distort the metric on the moduli space. We show that magnetic impurities can be
+viewed as vortices associated to a second, frozen, gauge group. We provide a
+D-brane description of the dynamics of vortices in product gauge groups and
+show how one can take the limit such that a subset of the vortices freeze.",1309.2644v2
+2014-08-26,Chimeras in SQUID Metamaterials,"Regular lattices comprising superconducting quantum interference devices
+(SQUIDs) form magnetic metamaterials exhibiting extraordinary properties,
+including tunability, dynamic multistability, and negative magnetic
+permeability. The SQUIDs in a metamaterial interact through nonlocal, magnetic
+dipole-dipole forces that makes it possible for counter-intuitive dynamic
+states referred to as chimera states to appear; the latter feature clusters of
+SQUIDs with synchronous dynamics which coexist with clusters exhibiting
+asynchronous behavior. The spontaneous appearance of chimera states is
+demonstrated numerically for one-dimensional SQUID metamaterials driven by an
+alternating magnetic field in which the fluxes threading the SQUID rings are
+randomly initialized; then, chimera states appear generically for sufficiently
+strong initial excitations, which exhibit relatively long lifetimes. The
+synchronization and metastability levels of the chimera states are discussed in
+terms of appropriate measures. Given that both one- and two-dimensional SQUID
+metamaterials have been already fabricated and investigated in the laboratory,
+the presence of a chimera state could in principle be detected with presently
+available experimental setups.",1408.6072v3
+2015-05-22,Relaxation dynamics of vortex lines in disordered type-II superconductors following magnetic field and temperature quenches,"We study the effects of rapid temperature and magnetic field changes on the
+non-equilibrium relaxation dynamics of magnetic vortex lines in disordered
+type-II superconductors by employing an elastic line model and performing
+Langevin molecular dynamics simulations. In a previously equilibrated system,
+either the temperature is suddenly changed, or the magnetic field is
+instantaneously altered which is reflected in adding or removing flux lines to
+or from the system. The subsequent aging properties are investigated in samples
+with either randomly distributed point-like or extended columnar defects, which
+allows to distinguish the complex relaxation features that result from either
+type of pinning centers. One-time observables such as the radius of gyration
+and the fraction of pinned line elements are employed to characterize
+steady-state properties, and two-time correlation functions such as the vortex
+line height autocorrelations and their mean-square displacement are analyzed to
+study the non-linear stochastic relaxation dynamics in the aging regime.",1505.06240v2
+2015-08-19,Chiral Magnetic Effect and Anomalous Hall Effect in Antiferromagnetic Insulators with Spin-Orbit Coupling,"We search for dynamical magnetoelectric phenomena in three-dimensional
+correlated systems with spin-orbit coupling. We focus on the antiferromagnetic
+insulator phases where the dynamical axion field is realized by the fluctuation
+of the antiferromagnetic order parameter. It is shown that the dynamical chiral
+magnetic effect, an alternating current generation by magnetic fields, emerges
+due to the time dependences of the order parameter such as antiferromagnetic
+resonance. It is also shown that the anomalous Hall effect arises due to the
+spatial variations of the order parameter such as antiferromagnetic domain
+walls. Our study indicates that spin excitations in antiferromagnetic
+insulators with spin-orbit coupling can result in nontrivial charge responses.
+Moreover, observing the chiral magnetic effect and anomalous Hall effect in our
+system is equivalent to detecting the dynamical axion field in condensed
+matter.",1508.04590v2
+2016-06-18,Enhanced diffusion and anomalous transport of magnetic colloids driven above a two-state flashing potential,"We combine experiment and theory to investigate the diffusive and
+subdiffusive dynamics of paramagnetic colloids driven above a two-state
+flashing potential. The magnetic potential was realized by periodically
+modulating the stray field of a magnetic bubble lattice in a uniaxial ferrite
+garnet film. At large amplitudes of the driving field, the dynamics of
+particles resembles an ordinary random walk with a frequency-dependent
+diffusion coefficient. However, subdiffusive and oscillatory dynamics at short
+time scales is observed when decreasing the amplitude. We present a persistent
+random walk model to elucidate the underlying mechanism of motion, and perform
+numerical simulations to demonstrate that the anomalous motion originates from
+the dynamic disorder in the structure of the magnetic lattice, induced by
+slightly irregular shape of bubbles.",1606.05783v1
+2016-07-01,Orientational dynamics of colloidal ribbons self-assembled from microscopic magnetic ellipsoids,"We combine experiments and theory to investigate the orientational dynamics
+of dipolar ellipsoids, which self-assemble into elongated ribbon-like
+structures due to the presence in each particle of a permanent magnetic moment
+perpendicular to the long axis. Monodisperse hematite ellipsoids are
+synthesized via sol-gel technique, and arrange into ribbons in presence of
+static or time-dependent magnetic fields. We find that under an oscillating
+field, the ribbons reorient perpendicular to the field direction, in contrast
+with the behaviour observed under a static field. This observation is explained
+theoretically by treating a chain of interacting ellipsoids as a single
+particle with an orientational and demagnetizing field energy. The model allows
+describing the orientational behaviour of the chain and captures well its
+dynamics at different strengths of the actuating field. The understanding of
+the complex dynamics and assembly of anisotropic magnetic colloids is a
+necessary step towards controlling the structure formation which has direct
+applications in different fluid-based microscale technologies.",1607.00256v1
+2016-10-17,Anisotropic Boltzmann-Gibbs dynamics of strongly magnetized Vlasov-Fokker-Planck equations,"We consider various sets of Vlasov-Fokker-Planck equations modeling the
+dynamics of charged particles in a plasma under the effect of a strong magnetic
+field. For each of them in a regime where the strength of the magnetic field is
+effectively stronger than that of collisions we first formally derive
+asymptotically reduced models. In this regime, strong anisotropic phenomena
+occur; while equilibrium along magnetic field lines is asymptotically reached
+our asymptotic models capture a non trivial dynamics in the perpendicular
+directions. We do check that in any case the obtained asymptotic model defines
+a well-posed dynamical system and when self consistent electric fields are
+neglected we provide a rigorous mathematical justification of the formally
+derived systems. In this last step we provide a complete control on solutions
+by developing anisotropic hypocoercive estimates.",1610.05138v2
+2016-12-07,Non-equilibrium study of the Chiral Magnetic Effect from real-time simulations with dynamical fermions,"We present a real-time lattice approach to study the non-equilibrium dynamics
+of vector and axial charges in $SU(N) \times U(1)$ gauge theories. Based on a
+classical description of the non-Abelian and Abelian gauge fields, we include
+dynamical fermions and develop operator definitions for (improved) Wilson and
+overlap fermions that allow us to study real-time manifestations of the axial
+anomaly from first principles. We present a first application of this approach
+to anomalous transport phenomena such as the Chiral Magnetic Effect (CME) and
+Chiral Separation Effect (CSE) by studying the dynamics of fermions during and
+after a $SU(N)$ sphaleron transition in the presence of a $U(1)$ magnetic
+field. We investigate the fermion mass and magnetic field dependence of the
+suggested signatures of the CME and CSE and point out some important aspects
+which need to be accounted for in the macroscopic description of anomalous
+transport phenomena.",1612.02477v2
+2017-02-15,Current Induced Dynamics of Multiple Skyrmions with Domain Wall Pair and Skyrmion-based Majority Gate Design,"As an intriguing ultra-small particle-like magnetic texture, skyrmion has
+attracted lots of research interests in next-generation ultra-dense and low
+power magnetic memory/logic designs. Previous studies have demonstrated a
+single skyrmion-domain wall pair collision in a specially designed magnetic
+racetrack junction. In this work, we investigate the dynamics of multiple
+skyrmions with domain wall pair in a magnetic racetrack. The numerical
+micromagnetic simulation results indicate that the domain wall pair could be
+pinned or depinned by the rectangular notch pinning site depending on both the
+number of skyrmions in the racetrack and the magnitude of driving current
+density. Such emergent dynamical property could be used to implement a
+threshold-tunable step function, in which the inputs are skyrmions and
+threshold could be tuned by the driving current density. The threshold-tunable
+step function is widely used in logic and neural network applications. We also
+present a three-input skyrmion-based majority logic gate design to demonstrate
+the potential application of such dynamic interaction of multiple skyrmions and
+domain wall pair.",1702.04814v2
+2017-02-21,Spin texture motion in antiferromagnetic and ferromagnetic nanowires,"We propose a Hamiltonian dynamics formalism for the current and magnetic
+field driven dynamics of ferromagnetic and antiferromagnetic domain walls in
+one dimensional systems. To demonstrate the power of this formalism, we derive
+Hamilton equations of motion via Poisson brackets based on the
+Landau-Lifshitz-Gilbert phenomenology, and add dissipative dynamics via the
+evolution of the energy. We use this approach to study current induced domain
+wall motion and compute the drift velocity. For the antiferromagnetic case, we
+show that a nonzero magnetic moment is induced in the domain wall, which
+indicates that an additional application of a magnetic field would influence
+the antiferromagnetic domain-wall dynamics. We consider both cases of the
+magnetic field being parallel and transverse to the N{\'e}el field. Based on
+this formalism, we predict an orientation switch mechanism for
+antiferromagnetic domain walls which can be tested with the recently discovered
+N{\'e}el spin orbit torques.",1702.06274v1
+2018-03-14,Dynamics of distorted skyrmions in strained chiral magnets,"In this work, we study the microscopic dynamics of distorted skyrmions in
+strained chiral magnets [K. Shibata et al., Nat. Nanotech. 10, 589 (2015)]
+under gradient magnetic field or electric current by Landau-Lifshitz-Gilbert
+simulations of the anisotropic spin model. It is observed that the dynamical
+responses are also anisotropic, and the velocities of the distorted skyrmions
+are periodically dependent on the directions of the external stimuli.
+Furthermore, in addition to the uniform motion, our work also demonstrates
+anti-phase harmonic vibrations of the two skyrmions in nanostripes, and the
+frequencies are mainly determined by the exchange anisotropy. The simulated
+results are well explained by Thiele theory, which may provide useful
+information in understanding the dynamics of the distorted skyrmions in
+strained chiral magnets.",1803.05298v1
+2018-10-26,Phonon impact on the dynamics of resonantly excited and hot excitons in diluted magnetic semiconductors,"Phonons are well known to be the main mechanism for the coupling between
+bright and dark excitons in nonmagnetic semiconductors. Here, we investigate
+diluted magnetic semiconductors where this process is in direct competition
+with the scattering at localized magnetic impurities. To this end, a recently
+developed quantum kinetic description of the exciton spin dynamics in diluted
+magnetic semiconductor quantum wells is extended by the scattering with
+longitudinal acoustic phonons. A strong phonon impact is found in the
+redistribution of exciton momenta on the exciton parabola that becomes
+especially prominent for high temperatures and exciton distributions further
+away from the exciton resonance which are optically dark. Despite their impact
+on the energetic redistribution, acoustic phonons virtually do not affected the
+exciton spin dynamics as the exciton-impurity interaction always dominates.
+Furthermore, it turns out that the exciton spin lifetime increases by roughly
+one order of magnitude for nonequilibrium hot exciton distributions and, in
+addition, pronounced quantum kinetic signatures in the exciton spin dynamics
+appearing after resonant optical excitation are drastically reduced.",1810.11241v2
+2018-10-05,Zero-field dynamics stabilized by in-plane shape anisotropy in MgO-based spin-torque oscillators,"Here we demonstrate numerically that shape anisotropy in MgO-based
+spin-torque nano-oscillators consisting of an out-of-plane magnetized free
+layer and an in-plane polarizer is necessary to stabilize out-of-plane
+magnetization precession without the need of external magnetic fields. As the
+in-plane anisotropy is increased, a gradual tilting of the magnetization
+towards the in-plane easy direction is introduced, favouring zero-field
+dynamics over static in-plane states. Above a critical value, zero-field
+dynamics are no longer observed. The optimum ratio of in-plane shape to
+out-of-plane uniaxial anisotropy, for which large angle out-of-plane zero-field
+dynamics occur within the widest current range, is reported.",1811.00106v1
+2019-10-17,A multi-scale approach for magnetisation dynamics: Unraveling exotic magnetic states of matter,"Crystallographic lattice defects strongly influence dynamical properties of
+magnetic materials at both microscopic and macroscopic length scales. A
+multi-scale approach to magnetisation dynamics, which is presented in this
+paper, accurately captures such effects. The method is illustrated using
+examples of systems with localized, non-trivial topological properties, e.g. in
+the form of skyrmions and chiral domain walls that interact with lattice
+dislocations. Technical aspects of the methodology involve multi-scale
+magnetisation dynamics that connects atomistic and continuum descriptions. The
+technique is capable of solving the Landau-Lifshitz-Gilbert equations
+efficiently in two regions of a magnetic material --- the mesoscopic and the
+atomistic regions, which are coupled in a seamless way. It is demonstrated that
+this methodology allows simulating realistically-sized magnetic skyrmions
+interacting with material defects and novel physical effects, uncovered using
+this theoretical methodology, are described.",1910.07807v1
+2020-02-03,Dynamical phase transitions for the activity biased Ising model in a magnetic field,"We consider large deviations of the dynamical activity -- defined as the
+total number of configuration changes within a time interval -- for mean-field
+and one-dimensional Ising models, in the presence of a magnetic field. We
+identify several dynamical phase transitions that appear as singularities in
+the scaled cumulant generating function of the activity. In particular, we find
+low-activity ferromagnetic states and a novel high-activity phase, with
+associated first- and second-order phase transitions. The high-activity phase
+has a negative susceptibility to the magnetic field. In the mean-field case, we
+analyse the dynamical phase coexistence that occurs on first-order transition
+lines, including the optimal-control forces that reproduce the relevant large
+deviations. In the one-dimensional model, we use exact diagonalisation and
+cloning methods to perform finite-size scaling of the first-order phase
+transition at non-zero magnetic field.",2002.00905v2
+2020-10-06,Emergent spin dynamics enabled by lattice interactions in a bicomponent artificial spin ice,"Artificial spin ice (ASI) are arrays on nanoscaled magnets that can serve
+both as models for frustration in atomic spin ice as well as for exploring new
+spin-wave-based strategies to transmit, process, and store information. Here,
+we exploit the intricate interplay of the magnetization dynamics of two
+dissimilar ferromagnetic metals arranged on complimentary lattice sites in a
+square ASI to effectively modulate the spin-wave properties. We show that the
+interaction between the two sublattices results in unique spectra attributed to
+each sublattice and we observe inter- and intra-lattice dynamics facilitated by
+the distinct magnetization properties of the two materials. The dynamic
+properties are systematically studied by angular-dependent broadband
+ferromagnetic resonance and confirmed by micromagnetic simulations. We show
+that the combination of materials with dissimilar magnetic properties enables
+the realization of a wide range of two-dimensional structures potentially
+opening the door to new concepts in nanomagnonics.",2010.03008v1
+2021-03-22,Universal dynamics of magnetic monopoles in two-dimensional kagomé ice,"A magnetic monopole in spin ice is a novel quasiparticle excitation in
+condensed matter physics, and we found that the ac frequency dependent magnetic
+susceptibility $\chi(\omega)$ in the two-dimensional (2D) spin ice (so-called
+kagom\'{e} ice) of Dy$_2$Ti$_2$O$_7$ shows a single scaling form. This behavior
+can be understood in terms of the dynamical scaling law for 2D Coulomb gas (CG)
+systems [Phys. Rev. B 90, 144428 (2014)], characterized by the charge
+correlation length $\xi (\propto1/\sqrt{\omega_1})$, where $\omega_{1}$ is a
+characteristic frequency proportional to the peak position of the imaginary
+part of $\chi(\omega)$. It is a generic behavior among a wide variety of models
+such as the vortex dynamics of 2D superconductors, 2D superfluids, classical XY
+magnets, and dynamics of melting of Wigner crystals.",2103.12101v1
+2021-08-28,Intrinsic Spike Timing Dependent Plasticity in Stochastic Magnetic Tunnel Junctions Mediated by Heat Dynamics,"The quest for highly efficient cognitive computing has led to extensive
+research interest for the field of neuromorphic computing. Neuromorphic
+computing aims to mimic the behavior of biological neurons and synapses using
+solid-state devices and circuits. Among various approaches, emerging
+non-volatile memory technologies are of special interest for mimicking
+neuro-synaptic behavior. These devices allow the mapping of the rich dynamics
+of biological neurons and synapses onto their intrinsic device physics. In this
+letter, we focus on Spike Timing Dependent Plasticity (STDP) behavior of
+biological synapses and propose a method to implement the STDP behavior in
+Magnetic Tunnel Junction (MTJ) devices. Specifically, we exploit the
+time-dependent heat dynamics and the response of an MTJ to the instantaneous
+temperature to imitate the STDP behavior. Our simulations, based on a
+macro-spin model for magnetization dynamics, show that, STDP can be imitated in
+stochastic magnetic tunnel junctions by applying simple voltage waveforms as
+the spiking response of pre- and post-neurons across an MTJ device.",2108.12684v1
+2022-10-31,Dynamical fractal and anomalous noise in a clean magnetic crystal,"Fractals -- objects with non-integer dimensions -- occur in manifold settings
+and length scales in nature, ranging from snowflakes and lightning strikes to
+natural coastlines. Much effort has been expended to generate fractals for use
+in many-body physics. Here, we identify an emergent dynamical fractal in a
+disorder-free, stoichiometric three-dimensional magnetic crystal in
+thermodynamic equilibrium. The phenomenon is born from constraints on the
+dynamics of the magnetic monopole excitations in spin ice, which restrict them
+to move on the fractal. This observation explains the anomalous exponent found
+in magnetic noise experiments in the spin ice compound Dy$_2$Ti$_2$O$_7$, and
+it resolves a long standing puzzle about its rapidly diverging relaxation time.
+The capacity of spin ice to exhibit such striking phenomena holds promise of
+further surprising discoveries in the cooperative dynamics of even simple
+topological many-body systems.",2211.00051v2
+2022-11-10,Transition to chaos and modal structure of magnetized Taylor-Couette flow,"Taylor-Couette flow is often used as a simplified model for complex rotating
+flows in the interior of stars and accretion disks. The flow dynamics in these
+objects is influenced by magnetic fields. For example, quasi-Keplerian flows in
+Taylor-Couette geometry become unstable to a travelling or standing wave in an
+external magnetic field if the fluid is conducting; there is an instability
+even when the flow is hydrodynamically stable. This magnetorotational
+instability leads to the development of chaotic states and, eventually,
+turbulence, when the cylinder rotation is sufficiently fast. The transition to
+turbulence in this flow can be complex, with the coexistence of parameter
+regions with spatio-temporal chaos and regions with quasi-periodic behaviour,
+involving one or two additional modulating frequencies. Although the unstable
+modes of a periodic flow can be identified with Floquet analysis, here we adopt
+a more flexible equation-free data-driven approach. We analyse the data from
+the transition to chaos in the magnetized Taylor-Couette flow and identify the
+flow structures related to the modulating frequencies with Dynamic Mode
+Decomposition; this method is based on approximating nonlinear dynamics with a
+linear infinite-dimensional Koopman operator. With the use of these structures,
+one can construct a nonlinear reduced model for the transition.",2211.05545v1
+2023-03-27,Inertial effects in ultrafast spin dynamics,"The dynamics of magnetic moments consist of a precession around the magnetic
+field direction and a relaxation towards the field to minimize the energy.
+While the magnetic moment and the angular momentum are conventionally assumed
+to be parallel to each other, at ultrafast time scales their directions become
+separated due to inertial effects. The inertial dynamics give rise to
+additional high-frequency modes in the excitation spectrum of magnetic
+materials. Here, we review the recent theoretical and experimental advances in
+this emerging topic and discuss the open challenges and opportunities in the
+detection and the potential applications of inertial spin dynamics.",2303.15251v2
+2023-05-31,Novel slow dynamics of phase transition in the partially ordered frustrated magnet DyRu2Si2,"DyRu2Si2 is a frustrated magnet to exhibit multiple magnetic phase transition
+in zero and finite magnetic fields. We investigated and characterized the phase
+transition between the partially-ordered antiferromagnetic phases at zero field
+by ac susceptibility measurements. Detailed ac susceptibility measurements
+reveal the novel critical dynamics of the phase transition; extremely slow
+dynamics with the relaxation time in the order of 10-100 msec, speed-up of the
+dynamics on cooling indicating its non-thermally activated origin and growing
+of the ferromagnetic correlations towards the phase transition temperature. On
+the basis of these findings, we propose the novel phase transition process,
+namely, the spontaneous striped-arrangement of the precedently emergent
+""belt-like"" ferromagnetic spin texture.",2305.19656v2
+2023-11-15,Single- and two-particle observables in the Emery model: a dynamical mean-field perspective,"We compare the dynamical mean-field descriptions of the single-band Hubbard
+model and the three-band Emery model at the one- and two-particle level for
+parameters relevant to high-Tc superconductors. We show that even within
+dynamical mean-field theory, accounting solely for temporal fluctuations, the
+intrinsic multi-orbital nature of the Emery model introduces effective
+non-local correlations. These lead to a non-Curie-like temperature-dependence
+of the magnetic susceptibility, also seen in nuclear magnetic resonance
+experiments in the pseudogap regime by M. Avramovska, et al. [Journal of
+Superconductivity and Novel Magnetism 33, 2621 (2020)]. We demonstrate the
+agreement of our results with these experiments for a large range of dopings
+and trace back the effective non-local correlations to an emerging
+oxygen-copper singlet by analyzing a minimal finite-size cluster model. Despite
+this correct description of the hallmark of the pseudogap at the two-particle
+level, i.e., the drop in the Knight shift of nuclear magnetic resonance,
+dynamical mean-field theory fails to properly describe the spectral properties
+of the pseudogap.",2311.09023v1
+2024-02-27,Semiclassical approach to spin dynamics of a ferromagnetic S=1 chain,"Motivated by recent experimental progress in the quasi-one-dimensional
+quantum magnet NiNb$_2$O$_6$, we study the spin dynamics of an S=1
+ferromagnetic Heisenberg chain with single-ion anisotropy by using a
+semiclassical molecular dynamics approach. This system undergoes a quantum
+phase transition from a ferromagnetic to a paramagnetic state under a
+transverse magnetic field, and the magnetic responses reflecting this
+transition is well described by our semiclassical method. We show that at
+low-temperature the transverse component of the dynamical structure factor
+depicts clearly the magnon dispersion, and the longitudinal component exhibits
+two continua associated with single- and two-magnon excitations, respectively.
+These spin excitation spectra show interesting temperature dependence as
+effects of magnon interactions.Our findings shed light on experimental
+detection of spin excitations in a large class of quasi-one-dimensional
+magnets.",2402.17416v1
+1998-01-30,Global three-dimensional simulations of magnetic field evolution in a galactic disk. II. Gas rich galaxies,"A fully three-dimensional computation of induction processes in a disk is
+performed to investigate the evolution of a large-scale magnetic field in
+gas-rich barred and spiral galaxies in the presence of field diffusion. As
+input parameters we use time dependent velocity fields obtained from
+self-consistent 3D N-body calculations of galactic dynamics. Our present work
+primarily analyzes the influence of the gas flows in non-axisymmetric
+gravitational disturbances (like spiral arms and bars) on the behavior of the
+magnetic field. The magnetic field is found to evolve towards structures
+resembling dynamical spiral arms and bars, however its distribution is often
+much more complicated than the velocity field itself. We show that a random
+configuration of seed magnetic fields quickly dissipates, and is therefore
+unable to explain the magnetic field strength observed in nearby galaxies. The
+detailed comparison between the simulated velocity and magnetic fields allows
+us to establish that the reversals of magnetic vectors appear in the vicinity
+of the corotation radius of non-axisymmetric disk structures, where the
+velocity field shows rather abrupt changes. We argue that this explains the
+observed field reversals in our Galaxy.",9801311v1
+1998-08-13,Constraints on the Formation and Evolution of Circumstellar Disks in Rotating Magnetized Cloud Cores,"We use magnetic collapse models to place some constraints on the formation
+and angular momentum evolution of circumstellar disks which are embedded in
+magnetized cloud cores. Previous models have shown that the early evolution of
+a magnetized cloud core is governed by ambipolar diffusion and magnetic
+braking, and that the core takes the form of a nonequilibrium flattened
+envelope which ultimately collapses dynamically to form a protostar. In this
+paper, we focus on the inner centrifugally-supported disk, which is formed only
+after a central protostar exists, and grows by dynamical accretion from the
+flattened envelope. We estimate a centrifugal radius for the collapse of mass
+shells within a rotating, magnetized cloud core. The centrifugal radius of the
+inner disk is related to its mass through the two important parameters
+characterizing the background medium: the background rotation rate $\Omb$ and
+the background magnetic field strength $\Bref$. We also revisit the issue of
+how rapidly mass is deposited onto the disk (the mass accretion rate) and use
+several recent models to comment upon the likely outcome in magnetized cores.
+Our model predicts that a significant centrifugal disk (much larger than a
+stellar radius) will be present in the very early (Class 0) stage of
+protostellar evolution. Additionally, we derive an upper limit for the disk
+radius as it evolves due to internal torques, under the assumption that the
+star-disk system conserves its mass and angular momentum even while most of the
+mass is transferred to a central star.",9808140v1
+2002-01-14,"Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow","We present numerical magnetohydrodynamic (MHD) simulations of the effect of
+stellar dipole magnetic fields on line-driven wind outflows from hot, luminous
+stars. Unlike previous fixed-field analyses, the simulations here take full
+account of the dynamical competition between field and flow, and thus apply to
+a full range of magnetic field strength, and within both closed and open
+magnetic topologies. A key result is that the overall degree to which the wind
+is influenced by the field depends largely on a single, dimensionless, `wind
+magnetic confinement parameter', $\eta_{\ast}$ ($ = B_{eq}^2 R_\ast^2/{\dot M}
+v_\infty$), which characterizes the ratio between magnetic field energy density
+and kinetic energy density of the wind. For weak confinement $\eta_{\ast} \le
+1$, the field is fully opened by the wind outflow, but nonetheless for
+confinements as small as $\eta_{\ast}=1/10$ can have a significant
+back-influence in enhancing the density and reducing the flow speed near the
+magnetic equator. For stronger confinement $\eta_{\ast} > 1$, the magnetic
+field remains closed over a limited range of latitude and height about the
+equatorial surface, but eventually is opened into a nearly radial configuration
+at large radii.",0201195v1
+2009-05-06,Formation of gaseous arms in barred galaxies with dynamically important magnetic field : 3D MHD simulations,"We present results of three-dimensional nonlinear MHD simulations of a
+large-scale magnetic field and its evolution inside a barred galaxy with the
+back reaction of the magnetic field on the gas. The model does not consider the
+dynamo process. To compare our modeling results with observations, we construct
+maps of the high-frequency (Faraday-rotation-free) polarized radio emission on
+the basis of simulated magnetic fields. The model accounts for the effects of
+projection and the limited resolution of real observations. We performed 3D MHD
+numerical simulations of barred galaxies and polarization maps. The main result
+is that the modeled magnetic field configurations resemble maps of the
+polarized intensity observed in barred galaxies. They exhibit polarization
+vectors along the bar and arms forming coherent structures similar to the
+observed ones. In the paper, we also explain the previously unsolved issue of
+discrepancy between the velocity and magnetic field configurations in this type
+of galaxies. The dynamical influence of the bar causes gas to form spiral waves
+that travel outwards. Each gaseous spiral arm is accompanied by a magnetic
+counterpart, which separates and survives in the inter-arm region. Because of a
+strong compression, shear of non-axisymmetric bar flows and differential
+rotation, the total energy of modeled magnetic field grows constantly, while
+the azimuthal flux grows slightly until $0.05\Gyr$ and then saturates.",0905.0845v1
+2010-10-19,Numerical Simulations of Dynamos Generated in Spherical Couette Flows,"We numerically investigate the efficiency of a spherical Couette flow at
+generating a self-sustained magnetic field. No dynamo action occurs for
+axisymmetric flow while we always found a dynamo when non-axisymmetric
+hydrodynamical instabilities are excited. Without rotation of the outer sphere,
+typical critical magnetic Reynolds numbers $Rm_c$ are of the order of a few
+thousands. They increase as the mechanical forcing imposed by the inner core on
+the flow increases (Reynolds number $Re$). Namely, no dynamo is found if the
+magnetic Prandtl number $Pm=Rm/Re$ is less than a critical value $Pm_c\sim 1$.
+Oscillating quadrupolar dynamos are present in the vicinity of the dynamo
+onset. Saturated magnetic fields obtained in supercritical regimes (either
+$Re>2 Re_c$ or $Pm>2Pm_c$) correspond to the equipartition between magnetic and
+kinetic energies. A global rotation of the system (Ekman numbers $E=10^{-3},
+10^{-4}$) yields to a slight decrease (factor 2) of the critical magnetic
+Prandtl number, but we find a peculiar regime where dynamo action may be
+obtained for relatively low magnetic Reynolds numbers ($Rm_c\sim 300$). In this
+dynamical regime (Rossby number $Ro\sim -1$, spheres in opposite direction) at
+a moderate Ekman number ($E=10^{-3}$), a enhanced shear layer around the inner
+core might explain the decrease of the dynamo threshold. For lower $E$
+($E=10^{-4}$) this internal shear layer becomes unstable, leading to small
+scales fluctuations, and the favorable dynamo regime is lost. We also model the
+effect of ferromagnetic boundary conditions. Their presence have only a small
+impact on the dynamo onset but clearly enhance the saturated magnetic field in
+the ferromagnetic parts. Implications for experimental studies are discussed.",1010.3859v2
+2011-04-20,Stokes Diagnostics of Magneto-Acoustic Wave Propagation in the Magnetic Network on the Sun,"The solar atmosphere is magnetically structured and highly dynamic. Owing to
+the dynamic nature of the regions in which the magnetic structures exist, waves
+can be excited in them. Numerical investigations of wave propagation in
+small-scale magnetic flux concentrations in the magnetic network on the Sun
+have shown that the nature of the excited modes depends on the value of plasma
+beta (the ratio of gas to magnetic pressure) where the driving motion occurs.
+Considering that these waves should give rise to observable characteristic
+signatures, we have attempted a study of synthesized emergent spectra from
+numerical simulations of magneto-acoustic wave propagation. We find that the
+signatures of wave propagation in a magnetic element can be detected when the
+spatial resolution is sufficiently high to clearly resolve it, enabling
+observations in different regions within the flux concentration. The
+possibility to probe various lines of sight around the flux concentration bears
+the potential to reveal different modes of the magnetohydrodynamic waves and
+mode conversion. We highlight the feasibility of using the Stokes-V asymmetries
+as a diagnostic tool to study the wave propagation within magnetic flux
+concentrations. These quantities can possibly be compared with existing and new
+observations in order to place constraints on different wave excitation
+mechanisms.",1104.4069v2
+2012-01-06,Experimental observation of the optical spin transfer torque,"The spin transfer torque is a phenomenon in which angular momentum of a spin
+polarized electrical current entering a ferromagnet is transferred to the
+magnetization. The effect has opened a new research field of electrically
+driven magnetization dynamics in magnetic nanostructures and plays an important
+role in the development of a new generation of memory devices and tunable
+oscillators. Optical excitations of magnetic systems by laser pulses have been
+a separate research field whose aim is to explore magnetization dynamics at
+short time scales and enable ultrafast spintronic devices. We report the
+experimental observation of the optical spin transfer torque, predicted
+theoretically several years ago building the bridge between these two fields of
+spintronics research. In a pump-and-probe optical experiment we measure
+coherent spin precession in a (Ga,Mn)As ferromagnetic semiconductor excited by
+circularly polarized laser pulses. During the pump pulse, the spin angular
+momentum of photo-carriers generated by the absorbed light is transferred to
+the collective magnetization of the ferromagnet. We interpret the observed
+optical spin transfer torque and the magnetization precession it triggers on a
+quantitative microscopic level. Bringing the spin transfer physics into optics
+introduces a fundamentally distinct mechanism from the previously reported
+thermal and non-thermal laser excitations of magnets. Bringing optics into the
+field of spin transfer torques decreases by several orders of magnitude the
+timescales at which these phenomena are explored and utilized.",1201.1436v1
+2012-05-20,Externally-driven transformations of vortex textures in flat submicrometer magnets,"Two effects of oscillatory transformations of vortex textures in flat
+nanomagnets due to the application of an external field or a spin-polarized
+electric current are analytically described with relevance to soft-magnetic
+structures of submicrometer sizes (whose thickness is significantly bigger than
+the magnetostatic exchange length). These are changes of a domain wall (DW)
+structure in a long magnetic stripe (oscillations between a transverse DW, a
+vortex DW, and an antivortex DW) and periodic vortex-core reversals in a
+circular magnetic dot which are accompanied by oscillatory displacements of the
+vortex from the dot center. In nanostructures of smaller thicknesses
+(comparable to the exchange length), where nonlocal magnetostatic effects are
+very strong because of fast spatial variation of the magnetization, similar
+phenomena have been widely studied previously. Here, the dynamics is
+investigated within a local approach including magnetostatic field via boundary
+conditions on solutions to the Landau-Lifshitz-Gilbert equation only. Both the
+DWs in stripes and vortex states of the dot are treated as fragments of a
+cross-tie DW. Despite similarity of the cyclic transformations of the ordering
+to the dynamics of more strongly confined nanomagnets, details of motion
+(trajectories) of the vortices and antivortices (Bloch lines) of the textures
+under study are different, which is related to prohibition of rapid jumps of
+the polarization of Bloch lines. In addition to the magnetization rotation
+about the direction of magnetic field or current polarization, the evolution of
+textures is shown to relate to oscillatory changes of the direction of a
+cross-tie DW with respect to any arbitrary axis in the magnet plane accompanied
+by oscillations of the DW width.",1205.5008v1
+2012-06-24,Dynamical Relaxation of Coronal Magnetic Fields. III. 3D Spiral Nulls,"Context: The majority of studies on stressed 3D magnetic null points consider
+magnetic reconnection driven by an external perturbation, but the formation of
+a genuine current sheet equilibrium remains poorly understood. This problem has
+been considered more extensively in two-dimensions, but lacks a generalization
+into 3D fields.
+  Aims: 3D magnetic nulls are more complex than 2D nulls and the field can take
+a greater range of magnetic geometries local to the null. Here, we focus on one
+type and consider the dynamical non-resistive relaxation of 3D spiral nulls
+with initial spine-aligned current. We aim to provide a valid
+magnetohydrostatic equilibrium, and describe the electric current accumulations
+in various cases, involving a finite plasma pressure.
+  Methods: A full MHD code is used, with the resistivity set to zero so that
+reconnection is not allowed, to run a series of experiments in which a
+perturbed spiral 3D null point is allowed to relax towards an equilibrium, via
+real, viscous damping forces. Changes to the initial plasma pressure and other
+magnetic parameters are investigated systematically.
+  Results: For the axi-symmetric case, the evolution of the field and the
+plasma is such that it concentrates the current density in two cone-shaped
+regions along the spine, thus concentrating the twist of the magnetic field
+around the spine, leaving a radial configuration in the fan plane. The plasma
+pressure redistributes in order to maintain the current density accumulations.
+However, it is found that changes in the initial plasma pressure do not modify
+the final state significantly. In the cases where the initial magnetic field is
+not axi-symmetric, a infinite-time singularity of current perpendicular to the
+fan is found at the location of the null.",1206.5527v1
+2013-10-21,The influence of the magnetic field on the spectral properties of blazars,"We explore the signature imprinted by dynamically relevant magnetic fields on
+the spectral energy distribution (SED) of blazars. It is assumed that the
+emission from these sources originates from the collision of cold plasma
+shells, whose magnetohydrodynamic evolution we compute by numerically solving
+Riemann problems. We compute the SEDs including the most relevant radiative
+processes and scan a broad parameter space that encompasses a significant
+fraction of the commonly accepted values of not directly measurable physical
+properties. We reproduce the standard double hump SED found in blazar
+observations for unmagnetized shells, but show that the prototype double hump
+structure of blazars can also be reproduced if the dynamical source of the
+radiation field is very ultrarelativistic both, in a kinematically sense
+(namely, if it has Lorentz factors \gtrsim 50) and regarding its magnetization
+(e.g., with flow magnetizations \sigma \simeq 0.1). A fair fraction of the {\em
+blazar sequence} could be explained as a consequence of shell magnetization:
+negligible magnetization in FSRQs, and moderate or large (and uniform)
+magnetization in BL Lacs. The predicted photon spectral indices (\gph) in the
+\gamma-ray band are above the observed values (\Gamma_{\rm ph, obs} \lesssim
+2.6 for sources with redshifts 0.4\le z \le 0.6) if the magnetization of the
+sources is moderate (\sigma \simeq 10^{-2}).",1310.5441v2
+2014-10-23,First detection of surface magnetic fields in Post-AGB stars : the cases of U Monocerotis and R Scuti,"While several observational investigations have revealed the presence of
+magnetic fields in the circumstellar envelopes, jets and outflows of
+post-Asymptotic Giant Branch stars (PAGBs) and planetary nebulae (PNe), none
+has clearly demonstrated their presence at the stellar surface. The lack of
+information on the strength of the surface magnetic fields prevents us from
+performing any thorough assessment of their dynamic capability (i.e. material
+mixing, envelope shaping, etc). We present new high resolution
+spectropolarimetric (Stokes V ) observations of a sample of PAGB stars,
+realised with the instruments ESPaDOnS and Narval, where we searched for the
+presence of photospheric magnetic fields. Out of the seven targets investigated
+the RV Tauri stars U Mon and R Sct display a clear Zeeman signature and return
+a definite detection after performing a least squares deconvolution (LSD)
+analysis. The remaining five PAGBs show no significant detection. We derived
+longitudinal magnetic fields of 10.2 +/- 1.7 G for U Mon and 0.6 +/- 0.6 G for
+R Sct. In both cases the Stokes profiles point towards an interaction of the
+magnetic field with the atmosphere dynamics. This first discovery of weak
+magnetic fields (i.e. ~10 gauss level) at the stellar surface of PAGB stars
+opens the door to a better understanding of magnetism in evolved stars.",1410.6224v1
+2015-03-16,Dynamics of Current and Field Driven Domain Wall Motion under the Influence of Transverse Magnetic Field,"The dynamics of transverse Neel domain wall in a ferromagnetic nanostrip in
+the presence of driving field, current and transverse magnetic field is
+investigated by the Landau-Lifshitz-Gilbert(LLG) equation with the adiabatic
+and non-adiabatic spin-transfer torques both analytically and numerically. The
+analytical expressions for the velocity, width, excitation angle and
+displacement for the domain wall are obtained by using small angle
+approximation along with Walkers trial function. The results show that the
+initial velocity of the domain wall can be controlled by the adiabatic
+spin-transfer torque and the saturated velocity can be controlled by the
+non-adiabatic spin-transfer torque and driving field. The large increase in the
+saturated velocity of the domain wall driven by current and field due to the
+transverse magnetic field is identified through the presence of driving field.
+There is no impact in the saturated velocity of the domain wall driven by
+current from the transverse magnetic field. For the domain wall driven by the
+current in the presence of the transverse magnetic field, the saturated
+velocity remains constant. The transverse magnetic field along with current and
+driving field is more advantageous that the transverse magnetic field along
+with current for increasing the saturated velocity of the domain wall. The
+numerical results showed that the saturated velocity is increased by the
+transverse magnetic field with the irrespective of the directions of the
+driving field and current further it is higher and lower when the directions of
+driving field and current are antiparallel and parallel respectively. The
+obtained analytical solutions are closely coincided with the computed numerical
+results.",1503.04560v2
+2015-05-06,Anisotropy of the solar network magnetic field around the average supergranule,"Supergranules in the quiet Sun are outlined by a web-like structure of
+enhanced magnetic field strength, the so-called magnetic network. We aim to map
+the magnetic network field around the average supergranule near disk center. We
+use observations of the line-of-sight component of the magnetic field from the
+Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory
+(SDO). The average supergranule is constructed by coaligning and averaging over
+3000 individual supergranules. We determine the positions of the supergranules
+with an image segmentation algorithm that we apply on maps of the horizontal
+flow divergence measured using time-distance helioseismology. In the center of
+the average supergranule the magnetic (intranetwork) field is weaker by about
+2.2 Gauss than the background value (3.5 Gauss), whereas it is enhanced in the
+surrounding ring of horizontal inflows (by about 0.6 Gauss on average). We find
+that this network field is significantly stronger west (prograde) of the
+average supergranule than in the east (by about 0.3 Gauss). With time-distance
+helioseismology, we find a similar anisotropy. The observed anisotropy of the
+magnetic field adds to the mysterious dynamical properties of solar
+supergranulation.",1505.01427v2
+2015-10-05,Chiral magnetic effect and natural optical activity in (Weyl) metals,"We consider the phenomenon of natural optical activity, and related chiral
+magnetic effect in metals with low carrier concentration. To reveal the
+correspondence between the two phenomena, we compute the optical conductivity
+of a noncentrosymmetric metal to linear order in the wave vector of the light
+wave, specializing to the low-frequency regime. We show that it is the orbital
+magnetic moment of quasiparticles that is responsible for the natural optical
+activity, and thus the chiral magnetic effect. While for purely static magnetic
+fields the chiral magnetic effect is known to have a topological origin and to
+be related to the presence of Berry curvature monopoles (Weyl points) in the
+band structure, we show that the existence of Berry monopoles is not required
+for the dynamic chiral magnetic effect to appear; the latter is thus not unique
+to Weyl metals. The magnitude of the dynamic chiral magnetic effect in a
+material is related to the trace of its gyrotropic tensor. We discuss the
+conditions under which this trace is non-zero; in noncentrosymmetric Weyl
+metals it is found to be proportional to the energy-space dipole moment of
+Berry curvature monopoles. The calculations are done within both the
+semiclassical kinetic equation, and Kubo linear response formalisms, with
+coincident results.",1510.01304v1
+2016-12-19,The Effects of Magnetic Fields on the Dynamics of Radiation Pressure Dominated Massive Star Envelopes,"We use three dimensional radiation magneto-hydrodynamic simulations to study
+the effects of magnetic fields on the energy transport and structure of
+radiation pressure dominated main sequence massive star envelopes at the region
+of the iron opacity peak. We focus on the regime where the local thermal
+timescale is shorter than the dynamical timescale, corresponding to inefficient
+convective energy transport. We begin with initially weak magnetic fields
+relative to the thermal pressure, from 100-1000G in differing geometries. The
+unstable density inversion amplifies the magnetic field, increasing the
+magnetic energy density to values close to equipartition with the turbulent
+kinetic energy density. By providing pressure support, the magnetic field's
+presence significantly increases the density fluctuations in the turbulent
+envelope, thereby enhancing the radiative energy transport by allowing photons
+to diffuse out through low density regions. Magnetic buoyancy brings small
+scale magnetic fields to the photosphere and increases the vertical energy
+transport with the energy advection velocity proportional to the Alfv\'en
+velocity, although in all cases we study photon diffusion still dominates the
+energy transport. The increased radiative and advective energy transport causes
+the stellar envelope to shrink by several scale heights. We also find larger
+turbulent velocity fluctuations compared to the purely hydrodynamic case,
+reaching $\approx$ 100 km/s at the stellar photosphere. The photosphere also
+shows vertical oscillations with similar averaged velocities and periods of a
+few hours. The increased turbulent velocity and oscillations will have strong
+impacts on the line broadening and periodic signals in massive stars.",1612.06434v1
+2017-06-20,Energy transfer in compressible magnetohydrodynamic turbulence,"Magnetic fields, compressibility and turbulence are important factors in many
+terrestrial and astrophysical processes. While energy dynamics, i.e. how energy
+is transferred within and between kinetic and magnetic reservoirs, has been
+previously studied in the context of incompressible magnetohydrodynamic (MHD)
+turbulence, we extend shell-to-shell energy transfer analysis to the
+compressible regime. We derive four new transfer functions specifically
+capturing compressibility effects in the kinetic and magnetic cascade, and
+capturing energy exchange via magnetic pressure. To illustrate their viability,
+we perform and analyze four simulations of driven isothermal MHD turbulence in
+the sub- and supersonic regime with two different codes. On the one hand, our
+analysis reveals robust characteristics across regime and numerical method. For
+example, energy transfer between individual scales is local and forward for
+both cascades with the magnetic cascade being stronger than the kinetic one.
+Magnetic tension and magnetic pressure related transfers are less local and
+weaker than the cascades. We find no evidence for significant nonlocal
+transfer. On the other hand, we show that certain functions, e.g., the
+compressive component of the magnetic energy cascade, exhibit a more complex
+behavior that varies both with regime and numerical method. Having established
+a basis for the analysis in the compressible regime, the method can now be
+applied to study a broader parameter space.",1706.06339v2
+2018-02-27,Magnetic field dependence of the nonlinear magnetic response and tricritical point in the monoaxial chiral helimagnet Cr$_{1/3}$NbS$_{2}$,"We present a comprehensive study of the magnetization dynamics and phase
+evolution in Cr$_{1/3}$NbS$_{2}$, which realizes a chiral soliton lattice
+(CSL). The magnetic field dependence of the ac magnetic response is analyzed
+for five harmonic components, $M_{n\omega}(H)$ $(n =1-5)$, using a phase
+sensitive measurement over a frequency range, $f = 11 - 10,000$ Hz. At a
+critical field, the modulated CSL continuously evolves from a helicity-rich to
+a ferromagnetic domain-rich structure, where the crossover is revealed by the
+onset of an anomalous nonlinear magnetic response that coincides with extremely
+slow dynamics. The behavior is indicative of the formation of a spatially
+coherent array of large ferromagnetic domains which relax on macroscopic
+time-scales. The frequency dependence of the ac magnetic loss displays an
+asymmetric distribution of relaxation times across the highly nonlinear CSL
+regime, which shift to shorter time-scales with increasing temperature. We
+experimentally resolve the tricritical point at $T_{TCP}$ in a temperature
+regime above the ferromagnetic Curie temperature which separates the linear and
+nonlinear regimes of the CSL at the phase transition. A comprehensive phase
+diagram is constructed which summarized the features of the field and
+temperature dependence of the magnetic crossovers and phase transitions in
+Cr$_{1/3}$NbS$_{2}$.",1802.09742v2
+2018-03-02,Response and phase transition of a Kitaev spin liquid in a local magnetic field,"We study the response of the Kitaev spin liquid (KSL) to a local magnetic
+field perpendicular to the Kitaev honeycomb lattice. The local magnetic field
+induces a dynamical excitation of a flux pair in the spin liquid and the system
+can be described by a generally particle-hole asymmetric interacting resonant
+level model. The dynamical excitation of the flux pair closes the flux gap in
+the spectrum of the spin correlation function locally for the gapless KSL even
+from the perturbative response to a weak magnetic field. Beyond the
+perturbative regime, the p-h asymmetry competes with the magnetic field and
+results in a rich phase diagram. Moreover, the magnetic field breaks the gauge
+equivalence of the ferromagnetic and anti-ferromagnetic Kitaev couplings of the
+ground state and leads to very different behaviors for the two cases. The
+anti-ferromagnetic case experiences a first order phase transition to the
+polarized state during magnetization whereas the ferromagnetic case does not.
+This study can be generalized to the Kitaev model in a uniform magnetic field
+and may help understand issues in recent experiments on KSL candidates.",1803.01011v4
+2018-05-15,Non-linear Galactic Dynamos and the Magnetic Rädler Effect,"We show that the magnetic analogue of the R\""{a}dler effect of mean-field
+dynamo theory leads to a non-linear backreaction that quenches a large-scale
+galactic dynamo, and can result in saturation of the large-scale magnetic field
+at near-equipartition with turbulent kinetic energy density. In a rotating
+fluid containing small-scale magnetic fluctuations, anisotropic terms in the
+mean electromotive force are induced via the Coriolis effect and these terms
+lead to a reduction of the growth rate in a predominantly $\alpha\Omega$-type
+galactic dynamo (Chamandy & Singh 2017). By including the generation of
+small-scale magnetic fluctuations by turbulent tangling of the large-scale
+magnetic field, one obtains a negative feedback effect that quenches the dynamo
+and leads to the saturation of the large-scale field. This saturation mechanism
+is found to be competitive with the dynamical $\alpha$-quenching mechanism for
+realistic galactic parameter values. Furthermore, in the context of the
+dynamical $\alpha$-quenching model, a separate non-linear term is obtained
+which has the same form as the helicity flux term of Vishniac & Cho (2001), but
+which depends on the strength of small-scale magnetic fluctuations. We briefly
+discuss the observational implications of the magnetic R\""{a}dler effect for
+galaxies.",1805.05548v2
+2018-05-21,Confinement of the Crab Nebula with tangled magnetic field by its supernova remnant,"A pulsar wind is a relativistic outflow dominated by Poynting energy at its
+base. Based on the standard ideal magnetohydrodynamic (MHD) model of pulsar
+wind nebulae (PWNe) with the ordered magnetic field, the observed slow
+expansion $v_{\rm PWN} \ll c$ requires the wind to be dominated by kinetic
+energy at the upstream of its termination shock, which conflicts with the
+pulsar wind theory ($\sigma$-problem). In this paper, we extend the standard
+model of PWNe by phenomenologically taking into account conversion of the
+ordered to turbulent magnetic field and dissipation of the turbulent magnetic
+field. Disordering of the magnetic structure is inferred from the recent
+three-dimensional relativistic ideal MHD simulations, while magnetic
+dissipation is a non-ideal MHD effect requiring a finite resistivity. We apply
+this model to the Crab Nebula and find that the conversion effect is important
+for the flow deceleration, while the dissipation effect is not. Even for
+Poynting-dominated pulsar wind, we obtain the Crab Nebula's $v_{\rm PWN}$ by
+adopting a finite conversion time-scale of $\sim 0.3$ yr. Magnetic dissipation
+primarily affects the synchrotron radiation properties. Any values of the
+pulsar wind magnetization $\sigma_{\rm w}$ are allowed within the present model
+of the PWN dynamics alone, and even a small termination shock radius of $\ll
+0.1$ pc reproduces the observed dynamical features of the Crab Nebula. In order
+to establish a high-$\sigma_{\rm w}$ model of PWNe, it is important to extend
+the present model by taking into account the broadband spectrum and its spacial
+profiles.",1805.08325v1
+2018-06-22,"Magnetic clustering, half-moons, and shadow pinch points as signals of a proximate Coulomb phase in frustrated Heisenberg magnets","We study the formation of magnetic clusters in frustrated magnets in their
+cooperative paramagnetic regime. For this purpose, we consider the
+$J_1$-$J_2$-$J_3$ classical Heisenberg model on kagome and pyrochlore lattices
+with $J_2 = J_3=J$. In the absence of farther-neighbor couplings, $J=0$, the
+system is in the Coulomb phase with magnetic correlations well characterized by
+pinch-point singularities. Farther-neighbor couplings lead to the formation of
+magnetic clusters, which can be interpreted as a counterpart of
+topological-charge clusters in Ising frustrated magnets [T. Mizoguchi, L. D. C.
+Jaubert and M. Udagawa, Phys. Rev. Lett. {\bf 119}, 077207 (2017)]. The
+concomitant static and dynamical magnetic structure factors, respectively
+$\mathcal{S}({\bm{q}})$ and $\mathcal{S}({\bm{q}},\omega)$, develop half-moon
+patterns. As $J$ increases, the continuous nature of the Heisenberg spins
+enables the half-moons to coalesce into connected `star' structures spreading
+across multiple Brillouin zones. These characteristic patterns are a dispersive
+complement of the pinch point singularities, and signal the proximity to a
+Coulomb phase. Shadows of the pinch points remain visible at finite energy,
+$\omega$. This opens the way to observe these clusters through (in)elastic
+neutron scattering experiments. The origin of these features are clarified by
+complementary methods: large-$N$ calculations, semi-classical dynamics of the
+Landau-Lifshitz equation, and Monte Carlo simulations. As promising candidates
+to observe the clustering states, we revisit the origin of ""spin molecules""
+observed in a family of spinel oxides $AB_2$O$_4$ ($A=$ Zn, Hg, Mg, $B=$ Cr,
+Fe).",1806.08534v2
+2018-12-13,Dispersion of small magnetic elements inside active regions on the Sun,"A process of diffusion of small-scale magnetic elements inside four active
+regions (ARs) was analyzed. Line-of-sight magnetograms acquired by the
+Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory
+(SDO) during a two-day time interval around the AR culmination time were
+utilized. Small magnetic elements of size of 3-100 squared HMI pixels with the
+field strength above the detection threshold of 30 Mx cm$^{-2}$ were detected
+and tracked. The turbulent diffusion coefficient was retrieved using the
+pair-separation technique. Comparison with the previously reported quiet-sun
+(QS) diffusivity was performed. It was found that: i) dispersion of small-scale
+magnetic elements inside the AR area occurs in the regime close to normal
+diffusion, whereas well-pronounced super-diffusion is observed in QS; ii) the
+diffusivity regime operating in an AR (the magnitude of the spectral index and
+the range of the diffusion coefficient) does not seem to depend on the
+individual properties of an AR, such as total unsigned magnetic flux, state of
+evolution, and flaring activity. We conclude that small-scale magnetic elements
+inside an AR do not represent an undisturbed photosphere, but they rather are
+intrinsic part of the whole coherent magnetic structure forming an active
+region. Moreover, turbulence of small-scale elements in an AR is not closely
+related to processes above the photosphere, but it rather carries the footprint
+of the sub-photospheric dynamics.",1812.05469v1
+2019-02-05,Unconventional magnetism in the 4d$^{4}$ based ($S=1$) honeycomb system Ag$_{3}$LiRu$_{2}$O$_{6}$,"We have investigated the thermodynamic and local magnetic properties of the
+Mott insulating system Ag$_{3}$LiRu$_{2}$O$_{6}$ containing Ru$^{4+}$
+(4$d$$^{4}$) for novel magnetism. The material crystallizes in a monoclinic
+$C2/m$ structure with RuO$_{6}$ octahedra forming an edge-shared
+two-dimensional honeycomb lattice with limited stacking order along the
+$c$-direction. The large negative Curie-Weiss temperature ($\theta_{CW}$ = -57
+K) suggests antiferromagnetic interactions among Ru$^{4+}$ ions though magnetic
+susceptibility and heat capacity show no indication of magnetic long-range
+order down to 1.8 K and 0.4 K, respectively. $^{7}$Li nuclear magnetic
+resonance (NMR) shift follows the bulk susceptibility between 120-300 K and
+levels off below 120 K. Together with a power-law behavior in the temperature
+dependent spin-lattice relaxation rate between 0.2 and 2 K, it suggest dynamic
+spin correlations with gapless excitations. Electronic structure calculations
+suggest an $S = 1$ description of the Ru-moments and the possible importance of
+further neighbour interactions as also bi-quadratic and ring-exchange terms in
+determining the magnetic properties. Analysis of our $\mu$SR data indicates
+spin freezing below 5 K but the spins remain on the borderline between static
+and dynamic magnetism even at 20 mK.",1902.01653v1
+2019-03-07,Spin-orbit Torque and Spin Hall Effect-based Cellular Level Therapeutic Neuromodulators: Modulating Neuron Activities through Spintronic Nanodevices,"Artificial modulation of a neuronal subset through ion channels activation
+can initiate firing patterns of an entire neural circuit in vivo. As nanovalves
+in the cell membrane, voltage-gated ion channels can be artificially controlled
+by the electric field gradient that caused by externally applied time varying
+magnetic fields. Herein, we theoretically investigate the feasibility of
+modulating neural activities by using magnetic spintronic nanostructures. An
+antiferromagnet/ferromagnet (AFM/FM) structure is explored as neuromodulator.
+For FM layer with perpendicular magnetization, stable bidirectional
+magnetization switching can be achieved by applying in-plane currents through
+AFM layer to induce the spin-orbit torque (SOT) due to the spin Hall effect
+(SHE). This Spin-orbit Torque Neurostimulator (SOTNS) utilizes in-plane charge
+current pulses to switch the magnetization in FM layer. The time changing
+magnetic stray field induces electric field that modulates the surrounding
+neurons. The Object Oriented Micromagnetic Framework (OOMMF) is used to
+calculate space and time dependent magnetic dynamics of SOTNS structure. The
+current driven magnetization dynamics in SOTNS has no mechanically moving
+parts. Furthermore, the size of SOTNS can be down to tens of nanometers, thus,
+arrays of SOTNSs could be fabricated, integrated together and patterned on a
+flexible substrate, which gives us much more flexible control of the
+neuromodulation with cellular resolution.",1903.02726v1
+2019-04-05,Coexistence of magnetic order and persistent spin dynamics in a quantum kagome antiferromagnet with no intersite mixing,"One of the key questions concerning frustrated lattices that has lately
+emerged is the role of disorder in inducing spin-liquid-like properties. In
+this context, the quantum kagome antiferromagnets YCu$_3$(OH)$_6$Cl$_3$, which
+has been recently reported as the first geometrically perfect realization of
+the kagome lattice with negligible magnetic/non-magnetic intersite mixing and a
+possible quantum-spin-liquid ground state, is of particular interest. However,
+contrary to previous conjectures, here we show clear evidence of bulk magnetic
+ordering in this compound below $T_N=15$\,K by combining bulk magnetization and
+heat capacity measurements, and local-probe muon spin relaxation measurements.
+The magnetic ordering in this material is rather unconventional in several
+respects. Firstly, a crossover regime where the ordered state coexists with the
+paramagnetic state extends down to $T_N/3$ and, secondly, the fluctuation
+crossover is shifted far below $T_N$. Moreover, a reduced magnetic-entropy
+release at $T_N$ and persistent spin dynamics that is observed at temperatures
+as low as $T/T_N=1/300$ could be a sign of emergent excitations of correlated
+spin-loops or, alternatively, a sign of fragmentation of each magnetic moment
+into an ordered and a fluctuating part.",1904.02878v2
+2019-05-28,Magnetic Inhibition of Centrifugal Instability in Astrophysical Jets,"Recently it was shown that the centrifugal instability may be important in
+the dynamics of astrophysical jets undergoing reconfinement by external
+pressure. However, these studies were limited to the case of unmagnetised
+flows. Here we explore the role of the magnetic field within both the Newtonian
+and relativistic frameworks. Since the jet problem is rather complicated, we
+focus instead on the simpler problem of cylindrical rotation and axial magnetic
+field, which shares significant similarity with the jet problem, and consider
+only axisymmetric perturbations. The studied equilibrium configurations involve
+a cylindrical interface and they are stable to non-magnetic centrifugal and
+magneto-rotational instabilities everywhere except this interface. We use a
+heuristic approach to derive the local stability criterion for the interface in
+the magnetic case and numerical simulations to verify the role of the magnetic
+field. The theory and simulations agree quite well for Newtonian models but
+indicate a potential discrepancy for the relativistic models in the limit of
+high Lorentz factor of the rotational motion at the interface. In general, the
+magnetic field sets a critical wavelength below which the centrifugal modes are
+stabilised. We discuss the implication of our findings for the astrophysical
+jets, which suggest that the centrifugal instability develops only in jets with
+relatively low magnetisation. Namely, the magnetic pressure has to be below the
+thermal one and for the relativistic case the jets have to be kinetic-energy
+dominated.",1905.11650v2
+2020-02-19,Softening of breathing elastic mode and trigonal elastic mode in disordered pyrochlore magnet NaCaCo$_2$F$_7$,"Cobalt pyrochlore fluoride NaCaCo$_2$F$_7$ is a disordered frustrated magnet
+composed of Co$^{2+}$ ions with an effective spin-$\frac{1}{2}$ magnetic moment
+and exhibits spin freezing below $T_f \sim$2.4 K. We perform ultrasound
+velocity measurements on a single crystal of the cubic NaCaCo$_2$F$_7$. The
+temperature dependence of the bulk modulus (the breathing elastic mode)
+exhibits Curie-type softening upon cooling below $\sim$20 K down to $T_f$,
+which is suppressed by the magnetic field. This Curie-type softening should be
+a precursor to the enhancement of the strength of exchange disorder via the
+spin-lattice coupling, which causes the spin freezing. In contrast to the
+magnetic-field-suppressed Curie-type softening in the bulk modulus, the
+trigonal shear modulus exhibits softening with a characteristic minimum upon
+cooling, which is enhanced by the magnetic field at temperatures below $\sim$20
+K. This magnetic-field-enhanced elastic anomaly in the trigonal shear modulus
+suggests a coupling of the lattice to the dynamical spin-cluster state. For
+NaCaCo$_2$F$_7$, the observed elastic anomalies reveal an occurrence of
+magnetic-field-induced crossover from an isostructural lattice instability
+toward the spin freezing to a trigonal lattice instability arising from the
+emergent dynamical spin-cluster state.",2002.07980v2
+2020-04-07,Magnetic Order Driven Ultrafast Phase Transition in NdNiO$_3$,"Ultrashort x-ray pulses can be used to disentangle magnetic and structural
+dynamics and are accordingly utilized here to study the photoexcitation of
+NdNiO$_3$ (NNO), a model nickelate exhibiting structural and magnetic dynamics
+that conspire to induce an IMT. During the course of the photoinduced insulator
+to metal transition (IMT) with above gap excitation, we observe an ultrafast
+($<$ 180 fs) quenching of magnetic order followed by a time delayed collapse of
+the insulating phase probed by X-ray absorption and THz transmission (~ 450 fs)
+that correlates with the slowest optical phonon mode involved in the structural
+transition. A simultaneous order-disorder response at the Ni site and
+displacive response at the Nd site coexist in the ultrafast magnetic response.
+Crucially, we observe the optical phonon through its coherent coupling with Nd
+magnetic order, demonstrating that the magnetic and structural degrees of
+freedom both contribute in driving the IMT. Density functional theory (DFT)
+calculations reveal a consistent scenario where optically driven inter-site
+charge transfer (ICT) drives a collapse of antiferromagnetic order that in turn
+destabilizes the charge-ordered phase resulting in an IMT. These experiments
+provide new modalities for control of electronic phase transitions in quantum
+materials based on ultrafast interplay between structural and magnetic orders
+created by femtosecond photoexcitation.",2004.03694v2
+2020-08-20,Two-dimensional numerical study for magnetic field dependence of neutrino-driven core-collapse supernova models,"We study the effects of the magnetic field on the dynamics of non-rotating
+stellar cores by performing two-dimensional (2D), magnetohydrodynamics (MHD)
+simulations. To this end, we have updated our neutrino-radiation-hydrodynamics
+supernova code to include MHD employing a divergence cleaning method with both
+careful treatments of finite volume and area reconstructions. By changing the
+initial strength of the magnetic field, the evolution of $15.0$, $18.4$ and
+$27.0$ $M_\odot$ presupernova progenitors is investigated. An intriguing
+finding in our study is that the neutrino-driven explosion occurs regardless of
+the strength of the initial magnetic field. For the 2D models presented in this
+work, the neutrino heating is the main driver for the explosion, whereas the
+magnetic field secondary contributes to the pre-explosion dynamics. Our results
+show that the strong magnetic field weakens the growth of the neutrino-driven
+turbulence in the small scale compared to the weak magnetic field. This results
+in the slower increase of the turbulent kinetic energy in the postshock region,
+leading to the slightly delayed onset of the shock revival for models with the
+stronger initial magnetic field.",2008.08984v2
+2020-10-10,Coherent Helicity-Dependent Spin-Phonon Oscillations in the Ferromagnetic van der Waals Crystal CrI3,"The discovery of two-dimensional (2D) systems hosting intrinsic long-range
+magnetic order represents a seminal addition to the rich physical landscape of
+van der Waals (vdW) materials. CrI3 has emerged as perhaps the most salient
+example, as the interdependence of crystalline structure and magnetic order,
+along with strong light-matter interactions provides a promising platform to
+explore the optical control of magnetic, vibrational, and charge degrees of
+freedom at the 2D limit. However, the fundamental question of how this
+relationship between structure and magnetism manifests on their intrinsic
+timescales has rarely been explored. Here, we use ultrafast optical
+spectroscopy to probe magnetic and vibrational dynamics in CrI3, revealing
+demagnetization dynamics governed by spin-flip scattering and remarkably, a
+strong transient exchange-mediated interaction between lattice vibrations and
+spin oscillations. The latter yields a coherent spin-coupled phonon mode that
+is highly sensitive to the helicity of the driving pulse in the magnetically
+ordered phase. Our results shed light on the nature of spin-lattice coupling in
+vdW magnets on ultrafast timescales and highlight their potential for
+applications requiring non-thermal, high-speed control of magnetism at the
+nanoscale.",2010.04915v1
+2020-11-18,Magnetoelastic effect in impact dynamics of nonNewtonian ferrofluid droplets,"In this article, we propose, with the aid of detailed experiments and scaling
+analysis, the existence of magneto-elastic effects in the impact hydrodynamics
+of non-Newtonian ferrofluid droplets on superhydrophobic (SH) surfaces in
+presence of a magnetic field. The effects of magnetic Bond number (Bom), Weber
+number (We), polymer concentration and magnetic nanoparticle (Fe3O4)
+concentration in the ferrofluids were investigated. In comparison to Newtonian
+ferrofluid droplets, addition of polymers caused rebound suppression of the
+droplets relatively at lower Bom for a fixed magnetic nanoparticle
+concentration and We. We further observed that for a fixed polymer
+concentration and We, increasing magnetic nanoparticle concentration also
+triggers earlier rebound suppression with increasing Bom. In the absence of the
+magnetic nanoparticles, the non-Newtonian droplets do not show rebound
+suppression for the range of Bom investigated. Likewise, the Newtonian
+ferrofluids show rebound suppression at large Bom. This intriguing interplay of
+elastic effects of polymer chains and the magnetic nanoparticles, dubbed as the
+magneto-elastic effect is noted to lead to the rebound suppression. We
+establish a scaling relationship to show that the rebound suppression is
+observed as manifestation of onset of magneto-elastic instability only when the
+proposed magnetic Weissenberg number (Wim) exceeds unity. We also put forward a
+phase map to identify the various regimes of impact ferrohydrodynamics of such
+droplets, and the occurrence of the magneto-elastic effect.",2011.09258v1
+2021-06-18,Global Three-Dimensional Simulations of Outer Protoplanetary Disks with Ambipolar Diffusion,"The structure and evolution of protoplanetary disks (PPDs) are largely
+governed by disk angular momentum transport, mediated by magnetic fields. In
+the most observable outer disk, PPD gas dynamics is primarily controlled by
+ambipolar diffusion as the dominant non-ideal magnetohydrodynamic (MHD) effect.
+In this work, we study the gas dynamics in outer PPDs by conducting a set of
+global 3D non-ideal MHD simulations with ambipolar diffusion and net poloidal
+magnetic flux, using the Athena++ MHD code, with resolution comparable to local
+simulations. Our simulations demonstrate the co-existence of magnetized disk
+wind and turbulence driven by the magneto-rotational instability (MRI). While
+MHD wind dominates disk angular momentum transport, the MRI turbulence also
+contributes significantly. We observe that magnetic flux spontaneously
+concentrate into axisymmetric flux sheets, leading to radial variations in
+turbulence levels, stresses, and accretion rates. Annular substructures arise
+as a natural consequence of magnetic flux concentration. The flux concentration
+phenomena show diverse properties with different levels of disk magnetization
+and ambipolar diffusion. The disk generally loses magnetic flux over time,
+though flux sheets could prevent the leak of magnetic flux in some cases. Our
+results demonstrate the ubiquity of disk annular substructures in weakly MRI
+turbulent outer PPDs, and imply a stochastic nature of disk evolution.",2106.10167v2
+2021-09-23,Translatory and rotatory motion of Exchange-Bias capped Janus particles controlled by dynamic magnetic field landscapes,"Magnetic Janus particles (MJPs), fabricated by covering a non-magnetic
+spherical particle with a hemispherical magnetic in-plane exchange-bias layer
+system cap, display an onion magnetization state for comparably large diameters
+of a few microns. In this work, the motion characteristics of these MJPs will
+be investigated when they are steered by a magnetic field landscape over
+prototypical parallel-stripe domains, dynamically varied by superposed external
+magnetic field pulse sequences, in an aqueous medium. We demonstrate, that due
+to the engineered magnetization state in the hemispherical cap, a comparably
+fast, directed particle transport and particle rotation can be induced.
+Additionally, by modifying the frequency of the applied pulse sequence and the
+strengths of the individual field components, we observe a possible separation
+between a combined or an individual occurrence of these two types of motion.
+Our findings bear importance for lab-on-a-chip systems, where particle
+immobilization on a surface via analyte bridges shall be used for low
+concentration analyte detection and a particle rotation over a defined position
+of a substrate may dramatically increase the immobilization (and therefore
+analyte detection) probability.",2109.11533v1
+2021-12-12,Effects of forcing mechanisms on the multiscale properties of magnetohydrodynamics,"We performed numerical simulations to study the response of
+magnetohydrodynamics (MHD) to large-scale stochastic forcing mechanisms
+parametrized by one parameter, $0 \le a \le1$, going from direct injection on
+the velocity field ($a = 1$) to stirring acts on the magnetic field only ($a =
+0$). We study the multi-scale properties of the energy transfer, by splitting
+the total flux in channels mediated by (i) the kinetic non-linear advection,
+(ii) the Lorentz force, (iii) the magnetic advection and (iv) magnetic
+stretching term. We further decompose the fluxes in two sub-channels given by
+heterochiral and homochiral components in order to distinguish forward, inverse
+and flux-loop cascades. We show that there exists a quasi-singular role of the
+magnetic forcing mechanism for $a \sim 1$: a small injection on the magnetic
+field $a < 1$ can strongly deplete the mean flux of kinetic energy transfer
+throughout the kinetic non-linear advection channel. We also show that this
+negligible mean flux is the result of a flux-loop balance between heterochiral
+(direct) and homochiral (inverse) transfers. Conversely, both homochiral and
+heterochiral channels transfer energy forward for the other three channels.
+Cross exchange between velocity and the magnetic field is reversed around $a =
+0.4$ and except when $a \sim 1$ we always observe that heterochiral mixed
+velocity-magnetic energy triads tend to move energy from magnetic to velocity
+fields. Our study is an attempt to further characterize the multi-scale nature
+of MHD dynamics, by disentangling different properties of the total energy
+transfer mechanisms, which can be useful for improving sub-grid-modelling.",2112.06286v1
+2021-12-24,Magnetic field amplification and structure formation by the Rayleigh-Taylor instability,"We report on results of high resolution two fluid non-linear simulations of
+the Rayleigh Taylor Instability (RTI) at the interface between a solar
+prominence and the corona. These follow results reported earlier by Popescu
+Braileanu et al. (2021a,b) on linear and early non-linear RTI dynamics in this
+environment. The simulations use a two fluid model that includes collisions
+between neutrals and charges, including ionization/recombination, energy and
+momentum transfer, and frictional heating. High resolution 2.5D magnetized RTI
+simulations with the magnetic field dominantly normal to and slightly sheared
+with respect to the prominence plane demonstrate that in a fully developed
+state of RTI a large fraction of the gravitational energy of a prominence
+thread can be converted into quasi-turbulent energy of the magnetic field. RTI
+magnetic energy generation is further accompanied by magnetic and plasma
+density structure formation, including dynamic formation, break-up, and merging
+of current sheets and plasmoid sub-structures. The simulations show the role of
+flow decoupling and ionization/recombination reactions between the neutrals and
+charges on the structure formation in magnetized RTI. We provide a careful
+examination of sources and form of numerical dissipation of the evolving
+magnetic field structures.",2112.13043v3
+2022-01-05,Controllable nonreciprocal optical response and handedness-switching in magnetized spin orbit coupled graphene,"Starting from a low-energy effective Hamiltonian model, we theoretically
+calculate the dynamical optical conductivity and permittivity tensor of a
+magnetized graphene layer with Rashba spin orbit coupling (SOC). Our results
+reveal a transverse Hall conductivity correlated with the usual nonreciprocal
+longitudinal conductivity. Further analysis illustrates that for intermediate
+magnetization strengths, the relative magnitudes of the magnetization and SOC
+can be identified experimentally by two well-separated peaks in the dynamical
+optical response (both the longitudinal and transverse components) as a
+function of photon frequency. Moreover, the frequency dependent permittivity
+tensor is obtained for a wide range of chemical potentials and magnetization
+strengths. Employing experimentally realistic parameter values, we calculate
+the circular dichroism of a representative device consisting of magnetized spin
+orbit coupled graphene and a dielectric insulator layer, backed by a metallic
+plate. The results reveal that this device has different relative
+absorptivities for right-handed and left-handed circularly polarized
+electromagnetic waves. It is found that the magnetized spin orbit coupled
+graphene supports strong handedness-switchings, effectively controlled by
+varying the chemical potential and magnetization strength with respect to the
+SOC strength.",2201.01779v2
+2022-04-30,Constraints on the magnetized Ernst black hole spacetime through quasiperiodic oscillations,"We study the dynamics of test particles around a magnetized Ernst black hole
+considering its magnetic field in the environment surrounding the black hole.
+We show how its magnetic field can influence the dynamics of particles and
+epicyclic motion around the black hole. Based on the analysis, we find that the
+radius of the innermost stable circular orbit (ISCO) for both neutral and
+charged test particles and epicyclic frequencies are strongly affected by the
+influence of the magnetic field. We also show that the ISCO radius of charged
+particles decreases rapidly. It turns out that the gravitational and Lorentz
+forces of the magnetic field are combined, thus strongly shrinking the values
+of the ISCO of charged test particles. Finally, we obtain the generic form for
+the epicyclic frequencies and select three microquasars with known
+astrophysical quasiperiodic oscillation (QPO) data to constrain the magnetic
+field.We show that the magnetic field is of the order of magnitude $B\sim
+10^{-7}$ Gauss, taking into account the motion of neutral particles in circular
+orbit about the black hole.",2205.00270v3
+2022-05-24,Competing magnetic phases in the frustrated spin-1/2 chain compound $β$-TeVO$_4$ probed by NMR,"In frustrated spin-1/2 chains the competition between the nearest- and
+next-nearest-neighbor exchange interactions leads to a rich phase diagram that
+becomes even richer in the presence of perturbations in their material
+realizations. These effects are still largely unexplored, so that new insight
+into static and dynamic magnetism, in particular by sensitive local probes, is
+highly desired. Here we present a comprehensive $^{17}$O nuclear magnetic
+resonance study of $\beta$-TeVO$_4$, where the anisotropy of the main exchange
+interactions and additional weak interchain exchange interactions complement
+the theoretical phase diagram. Our results confirm the dynamical nature of the
+intriguing spin-stripe phase that has been reported in previous studies. In
+addition, we find that the magnetic order in the high-field phase, which
+develops just below the magnetization saturation, is consistent with an unusual
+type of spin-density-wave (SDW) order with different alignments of the magnetic
+moments on the neighboring chains. This is reminiscent of the ordering in the
+SDW phase, realized in the absence of the magnetic field, and is thus most
+likely stabilized by magnetic anisotropy.",2205.11875v1
+2023-01-30,Viscoelastic response of an active particle under the action of magnetic field,"We consider the dynamics of a charged inertial active Ornstein-Uhlenbeck
+particle in a viscoelastic suspension under the action of an uniform magnetic
+field. With the help of both numerical simulation and analytical framework, we
+exactly investigate the viscoelastic response of the particle to the magnetic
+field by means of particle trajectories, mean displacement, and mean square
+displacement (MSD) calculations. The simulated particle trajectories and MSD
+calculations reveal that the steady state response of a confined harmonic
+particle to the magnetic field show interesting features due to the complex
+interplay of underlying physical processes such as elastic dissipation and
+active fluctuations in the medium. When the activity time scale of the dynamics
+is larger than the elastic dissipation timescale (or vice-versa), the steady
+state MSD shows an enhancement (or suppression) with increase in the field
+strength. In both the cases, for very strong magnetic field the MSD
+interestingly approaches the value at the equilibrium limit where the
+generalized fluctuation dissipation relation is satisfied and the particle
+behaves like an inertial passive Brownian particle. Thus, for a finite magnetic
+field, the system exhibits a re-entrant type transition from active to passive
+and then to active behaviour with persistence of elastic dissipation in the
+medium. However, for a free particle, the overall displacement covered always
+gets suppressed with increase in the strength of the magnetic field and finally
+approaches zero for a very strong magnetic field.",2301.13179v1
+2023-02-20,"Magnetic support, wind-driven accretion, coronal heating, and fast outflows in a thin magnetically arrested disc","Accretion discs properties should deviate from standard theory when magnetic
+pressure exceeds the thermal pressure. To quantify these deviations, we present
+a systematic study of the dynamical properties of magnetically arrested discs
+(MADs), the most magnetized type of accretion disc. Using an artificial cooling
+function to regulate the gas temperature, we study MADs of three different
+thermal thicknesses, $h_\mathrm{th}/r=0.3, 0.1$ and $0.03$. We find that the
+radial structure of the disc is never mostly supported by the magnetic field.
+In fact, thin MADs are very near Keplerian. However, as discs gets colder, they
+become more magnetized and the largest deviations from standard theory appear
+in our thinnest disc with $h_\mathrm{th}/r=0.03$. In this case, the disc is
+much more extended vertically and much less dense than in standard theory
+because of vertical support from the turbulent magnetic pressure and
+wind-driven angular momentum transport that enhances the inflow speed. The thin
+disc also dissipates a lot of thermal energy outside of $z/r = \pm 0.03$ and a
+significant fraction of this dissipation happens in mildly relativistic winds.
+The enhanced dissipation in low-density regions could possibly feed coronae in
+X-ray binaries (XRBs) and active galactic nuclei (AGN). Wind-driven accretion
+will also impact the dynamical evolution of accretion discs and could provide a
+mechanism to explain the rapid evolution of changing-look AGN and the secular
+evolution of XRBs. Finally, our MAD winds have terminal velocities and mass
+loss rates in good agreement with the properties of ultra-fast outflows
+observed in AGN.",2302.10226v2
+2023-05-25,Observation of c-axis Magnetization at Low Temperatures in Weak Ferromagnet FeBO$_3$ Reveals a Spin-Reorientation Transition,"The weak ferromagnet FeBO$_3$ is well known for being a unique system for
+modelling and testing magnetic dynamics primarily due to relatively simple and
+localized magnetic structure and its interesting spin wave dynamics. At room
+temperature, it has slightly canted iron moments lying in the a-b plane that
+result in a strong antiferromagnetic moment and a weak ferromagnetic moment,
+which results in pronounced ferromagnetic and antiferromagnetic spin modes.
+However, some previous studies have shown unusual low-temperature behavior that
+suggests a phase transition. By performing low-temperature magnetization
+measurements, both in bulk and on the mesoscale, we have observed a low
+temperature magnetic texture in this material in which a large c-axis
+magnetization occurs. Magnetic fields along the c-axis as high as 1300 Oe were
+observed close to the sample surface. This presents evidence for the onset of a
+Morin transition or another type of spin-reorientation phase transition wherein
+the Fe3+ moments would acquire a c-axis component to their canting below a
+critical temperature. The observation of this c-axis magnetization suggests
+that there is a different ground state in this material than has been
+previously expected and could be due to as yet unexplored intricacies of the
+Dzyaloshinskii-Moriya interaction.",2305.16082v1
+2023-06-26,Deciphering competing interactions of Kitaev-Heisenberg-$Γ$ system in clusters,"We study Kitaev-Heisenberg-$\Gamma$ Hamiltonian on finite size clusters and
+investigate various zero and finite temperature properties in detail and
+explore the key differences due to relative sign and magnitude of Kitaev($K$),
+Heisenberg $(J)$) and $\Gamma$ interaction in the presence of magnetic field.
+Nearest-neighbor spin-spin correlation function shows step like character when
+$J$ is positive only irrespective of sign of $K$. Similarly the low energy
+spectrum under magnetic field depends on the sign of $K$. Dynamics of Majorana
+fermions depend greatly on external magnetic field which can even stabilize the
+gauge fields to Kitaev limit in the presence of $J$. Majorana dynamics also
+shows that $K-J-\Gamma$ model to be a testbed to manipulate quantum speed
+limit. For small magnetic field, magnetization shows a dome like structure for
+an intermediate temperature range for positive $K$. However a positive $J$ can
+cause this for negative $K$ also. The zero temperature magnetisation and
+susceptibility shows large dependence on external magnetic field and relative
+sign and magnitude of $K$ and $J$. Either a negative $K$ or $J$ is shown to
+give qualitatively similar susceptibility for different magnetic field only.
+For the specific heat a negative $K$ or $J$ favors mostly single peak structure
+while a two peak structure is favored for positive $K$ or $J$, though the
+magnitude of magnetic field can causes re-entrant behavior also. We briefly
+discuss effect of $\Gamma$ and compare with recent experiments.",2306.14839v1
+2023-07-13,Manifestation of chiral magnetic current in Floquet-Weyl semimetals,"Materials that can host macroscopic persistent current are important because
+they are useful for energy storage. However, there are very few examples of
+such materials in nature. Superconductors are known as an example in which flow
+of supercurrent can persist up to 100,000 years. The chiral magnetic current is
+possibly the second example predicted by the chiral magnetic effect. It was
+proposed to be realized in recently discovered Weyl semimetals. However, a
+no-go theorem negates the chiral magnetic effect and shows that the chiral
+magnetic current is generally absent in any equilibrium condensed-matter
+system. Here we show how to break the no-go theorem by resorting to dynamical
+transitions in time-frequency space. By driving an insulator using a
+time-periodic potential and coupling it to a phonon heat bath that provides
+suitable dissipation, we show that a Floquet-Weyl semi-metallic phase with
+Fermi-Dirac-like distribution emerges. Furthermore, we show that even in the
+presence of a static magnetic field, the resulting steady Floquet-Weyl
+semimetal supports non-vanishing chiral magnetic current. Our dynamical model
+provides a systematic way to fully realize the chiral magnetic effect in
+condensed matter systems.",2307.06735v1
+2023-09-25,Tunable topological magnetism in superlattices of nonmagnetic B20 systems,"We predict topological magnetic properties of B20 systems, that are organized
+in atomically thin multilayers. In particular we focus on FeSi/CoSi and
+FeSi/FeGe superlattices with different number of layers and interface
+structure. We demonstrate that absence of long range magnetic order, previously
+observed in bulk FeSi and CoSi, is broken near the FeSi/CoSi interface, where a
+magnetic state with non-trivial topology appears. Using electronic structure
+calculations in combination with the magnetic force theorem, we calculate the
+Heisenberg and Dzyaloshinskii-Moriya (DM) interactions in these systems. With
+this information, we perform atomistic spin dynamics simulations at finite
+temperature and applied magnetic field for large supercells with up to
+$2\cdot10^6$ spins to capture the complexity of non-collinear textures induced
+by the DM interaction. The spin dynamics simulations predict the formation of
+antiskyrmions in a [001]-oriented FeSi/CoSi multilayer, intermediate skyrmions
+in a [111]-oriented FeSi/CoSi system and Bloch skyrmions in the FeSi/FeGe (001)
+system. The size of different types of skyrmions is found to vary between 7 nm
+and 37 nm. The varying topological magnetic texture in these systems can be
+attributed to the complex asymmetric structure of the DM micromagnetic matrix,
+which is different from previously known topological magnets. Furthermore,
+through structural engineering, we demonstrate that both FM and AFM skyrmions
+can be stabilized, where the latter are especially appealing for applications
+due to the zero skyrmion Hall effect. The proposed B20 multilayers show
+potential for further exploration and call for experimental confirmation.",2309.14421v1
+2023-11-06,A new quantum hydrodynamic description of ferroelectricity in spiral magnets,"The strong coupling between magnetism and ferroelectricity was found in rare
+earth manganites, where the electric polarization could be induced by special
+magnetic ordering. There is no theoretical model that would allow us to study
+the static and dynamic properties of electric polarization in strongly
+correlated magnetic dielectrics. In the presented research, we have taken the
+main step towards the construction of such a fundamental model, and made a
+direct connection between the microscopic Katsura-Nagaosa-Balatsky theory and
+Mostovoy's phenomenological model for magnetically induced polarization. A
+novel description of the ferroelectricity of spin origin is proposed within the
+framework of the many-particle quantum hydrodynamics method. It is applied to
+the study of cells of magnetic ions, where the electric dipole moment is
+proportional to the vector product of spins. Our approach is based on the
+many-particle Pauli equation, where the influence of an external magnetic field
+is considered. We define the electric dipole moment operator of the ion cell
+and introduce the macroscopic polarization as the quantum mechanical average of
+that operator. We formulate a model for the description of nonequilibrium
+polarization and derive a new polarization evolution equation. The polarization
+switching in ferroelectric magnets with the spiral spin-density-wave state is
+considered, and we demonstrate that the proposed model yields known results and
+can predict novel effects. The dynamic magnetoelectric effect can be
+investigated by employing this novel equation to study the evolution of
+polarization.",2311.03610v4
+2023-11-10,Kinetic versus Magnetic Chaos in Toroidal Plasmas: A systematic quantitative comparison,"Magnetic field line chaos occurs under the presence of non-axisymmetric
+perturbations of an axisymmetric equilibrium and is manifested by the
+destruction of smooth flux surfaces formed by the field lines. These
+perturbations also render the particle motion, as described by the guiding
+center dynamics, non-integrable and, therefore, chaotic. However, the
+chaoticities of the magnetic field lines and the particle orbits significantly
+differ both in strength and radial location in a toroidal configuration, except
+for the case of very low-energy particles whose orbits closely follow the
+magnetic field lines. The chaoticity of more energetic particles, undergoing
+large drifts with respect to the magnetic field lines, crucially determines the
+confinement properties of a toroidal device but cannot be inferred from that of
+the underlying magnetic field. In this work, we implement the Smaller ALignment
+Index (SALI) method for detecting and quantifying chaos, allowing for a
+systematic comparison between magnetic and kinetic chaos. The efficient
+quantification of chaos enables the assignment of a value characterizing the
+chaoticity of each orbit in the space of the three constants of the motion,
+namely energy, magnetic moment and toroidal momentum. The respective diagrams
+provide a unique overview of the different effects of a specific set of
+perturbations on the entire range of trapped and passing particles, as well as
+the radial location of the chaotic regions, offering a valuable tool for the
+study of particle energy and momentum transport and confinement properties of a
+toroidal fusion device.",2311.06213v2
+2023-12-29,Spin-glass states generated in van der Waals magnet Cr$_2$Ge$_2$Te$_6$ by alkali-ion intercalation,"Tuning magnetic properties in layered van der Waals (vdW) materials has
+captured a significant attention due to the efficient control of ground-states
+by heterostructuring and external stimuli. Electron doping by electrostatic
+gating, interfacial charge transfer and intercalation is particularly effective
+in manipulating the exchange and spin-orbit properties, resulting in a control
+of Curie temperature ($T_{\text{C}}$) and magnetic anisotropy. Here, we
+discover an uncharted role of intercalation to generate magnetic frustration.
+As a model study, we intercalate Na atoms into the vdW gaps of pristine
+Cr$_2$Ge$_2$Te$_6$ (CGT) where generated magnetic frustration leads to emerging
+spin-glass states coexisting with a ferromagnetic order. A series of dynamic
+magnetic susceptibility measurements/analysis confirms the formation of
+magnetic clusters representing slow dynamics with a distribution of relaxation
+times. The intercalation also modifies other macroscopic physical parameters
+including the significant enhancement of $T_{\text{C}}$ from 66K\, to 240\,K
+and the switching of magnetic easy-hard axis direction. Our study identifies
+intercalation as a unique route to generate emerging frustrated spin states in
+simple vdW crystals.",2312.17554v2
+2005-03-18,Relativistic Magnetohydrodynamics In Dynamical Spacetimes: Numerical Methods And Tests,"Many problems at the forefront of theoretical astrophysics require the
+treatment of magnetized fluids in dynamical, strongly curved spacetimes. Such
+problems include the origin of gamma-ray bursts, magnetic braking of
+differential rotation in nascent neutron stars arising from stellar core
+collapse or binary neutron star merger, the formation of jets and magnetized
+disks around newborn black holes, etc. To model these phenomena, all of which
+involve both general relativity (GR) and magnetohydrodynamics (MHD), we have
+developed a GRMHD code capable of evolving MHD fluids in dynamical spacetimes.
+Our code solves the Einstein-Maxwell-MHD system of coupled equations in
+axisymmetry and in full 3+1 dimensions. We evolve the metric by integrating the
+BSSN equations, and use a conservative, shock-capturing scheme to evolve the
+MHD equations. Our code gives accurate results in standard MHD code-test
+problems, including magnetized shocks and magnetized Bondi flow. To test our
+code's ability to evolve the MHD equations in a dynamical spacetime, we study
+the perturbations of a homogeneous, magnetized fluid excited by a gravitational
+plane wave, and we find good agreement between the analytic and numerical
+solutions.",0503420v2
+2003-06-10,Muon-spin-relaxation and magnetic-susceptibility studies of the effects of nonmagnetic impurities on the Cu-spin dynamics and superconductivity in La_2-x_Sr_x_Cu_1-y_Zn_y_O_4_ around x = 0.115,"Zero-field muon-spin-relaxation (muSR) and magnetic-susceptibility
+measurements have been carried out in La_2-x_Sr_x_Cu_1-y_Zn_y_O_4_ with x =
+0.10, 0.115 and 0.13 changing the Zn-concentration y finely up to 0.10, with
+the aim to clarify effects of the nonmagnetic impurity Zn on the Cu-spin
+dynamics and superconductivity. The muSR measurements have revealed that, in
+each x, a magnetic order of Cu spins is observed at y ~ 0.0075, while it
+disappears and Cu spins turn into a fast fluctuating state for y > 0.03. From
+the magnetic-susceptibility measurements, on the other hand, it has been found
+that the volume fraction of the superconducting state rapidly decreases through
+the slight doping of Zn and that its y dependence corresponds to the y
+dependence of the volume fraction of the fast fluctuating region of Cu spins
+estimated from the muSR results. Both the rapid decrease of the volume fraction
+of the superconducting state and the formation of the magnetic order through
+the slight doping of Zn can be interpreted in terms of the development of the
+so-called ""Swiss cheese"" model. That is, it is concluded that Cu spins in a
+non-superconducting region around Zn exhibit slowing-down of the fluctuations
+or form an incoherent or coherent static magnetic order. Moreover, the
+formation of a non-superconducting region around Zn is considered to be due to
+the pinning of the dynamical spin correlation or dynamical stripe correlations.",0306233v2
+2008-07-26,Dynamical Feedback of Self-generated Magnetic Fields in Cosmic Ray Modified Shocks,"We present a semi-analytical kinetic calculation of the process of non-linear
+diffusive shock acceleration (NLDSA) which includes the magnetic field
+amplification due to cosmic ray induced streaming instability, the dynamical
+reaction of the amplified magnetic field and the possible effects of turbulent
+heating. The approach is specialized to parallel shock waves and the parameters
+we chose are the ones appropriate to forward shocks in Supernova Remnants. Our
+calculation allows us to show that the net effect of the amplified magnetic
+field is to enhance the maximum momentum of accelerated particles while
+reducing the concavity of the spectra, with respect to the standard predictions
+of NLDSA. This is mainly due to the dynamical reaction of the amplified field
+on the shock, which noticeably reduces the modification of the shock precursor.
+The total compression factors which are obtained for parameters typical of
+supernova remnants are $R_{tot}\sim 7-10$, in good agreement with the values
+inferred from observations. The strength of the magnetic field produced through
+excitation of streaming instability is found in good agreement with the values
+inferred for several remnants if the thickness of the X-ray rims are
+interpreted as due to severe synchrotron losses of high energy electrons. We
+also discuss the relative role of turbulent heating and magnetic dynamical
+reaction in driving the reduction of the precursor modification.",0807.4261v2
+2012-07-09,Dynamic phase transition properties and hysteretic behavior of a ferrimagnetic core-shell nanoparticle in the presence of a time dependent magnetic field,"We have presented dynamic phase transition features and stationary-state
+behavior of a ferrimagnetic small nanoparticle system with a core-shell
+structure. By means of detailed Monte Carlo simulations, a complete picture of
+the phase diagrams and magnetization profiles have been presented and the
+conditions for the occurrence of a compensation point $T_{comp}$ in the system
+have been investigated. According to N\'{e}el nomenclature, the magnetization
+curves of the particle have been found to obey P-type, N-type and Q-type
+classification schemes under certain conditions. Much effort has been devoted
+to investigation of hysteretic response of the particle and we observed the
+existence of triple hysteresis loop behavior which originates from the
+existence of a weak ferromagnetic core coupling $J_{c}/J_{sh}$, as well as a
+strong antiferromagnetic interface exchange interaction $J_{int}/J_{sh}$. Most
+of the calculations have been performed for a particle in the presence of
+oscillating fields of very high frequencies and high amplitudes in comparison
+with exchange interactions which resembles a magnetic system under the
+influence of ultrafast switching fields. Particular attention has also been
+paid on the influence of the particle size on the thermal and magnetic
+properties, as well as magnetic features such as coercivity, remanence and
+compensation temperature of the particle. We have found that in the presence of
+ultrafast switching fields, the particle may exhibit a dynamic phase transition
+from paramagnetic to a dynamically ordered phase with increasing ferromagnetic
+shell thickness.",1207.2023v2
+2017-05-03,Linearly polarized GHz magnetization dynamics of spin helix modes in the ferrimagnetic insulator Cu$_{2}$OSeO$_{3}$,"Linear dichroism -- the polarization dependent absorption of electromagnetic
+waves -- is routinely exploited in applications as diverse as structure
+determination of DNA or polarization filters in optical technologies. Here
+filamentary absorbers with a large length-to-width ratio are a prerequisite.
+For magnetization dynamics in the few GHz frequency regime strictly linear
+dichroism was not observed for more than eight decades. Here, we show that the
+bulk chiral magnet Cu$_{2}$OSeO$_{3}$ exhibits linearly polarized magnetization
+dynamics at an unexpectedly small frequency of about 2 GHz. Unlike optical
+filters that are assembled from filamentary absorbers, the magnet provides
+linear polarization as a bulk material for an extremely wide range of
+length-to-width ratios. In addition, the polarization plane of a given mode can
+be switched by 90$^\circ$ via a tiny variation in width. Our findings shed a
+new light on magnetization dynamics in that ferrimagnetic ordering combined
+with anisotropic exchange interaction offers strictly linear polarization and
+cross-polarized modes for a broad spectrum of sample shapes. The discovery
+allows for novel design rules and optimization of microwave-to-magnon
+transduction in emerging microwave technologies.",1705.01582v1
+2018-07-03,Observations of solar chromospheric heating at sub-arcsec spatial resolution,"A wide variety of phenomena such as gentle but persistent brightening,
+dynamic slender features (~100 km), and compact (~1'') ultraviolet (UV) bursts
+are associated with the heating of the solar chromosphere. High spatio-temporal
+resolution is required to capture the finer details of the likely magnetic
+reconnection-driven, rapidly evolving bursts. Such observations are also needed
+to reveal their similarities to large-scale flares, which are also thought to
+be reconnection driven, and more generally their role in chromospheric heating.
+Here we report observations of chromospheric heating in the form of a UV burst
+obtained with the balloon-borne observatory, SUNRISE. The observed burst
+displayed a spatial morphology similar to that of a large-scale solar flare
+with circular ribbon. While the co-temporal UV observations at 1.5'' spatial
+resolution and 24s cadence from the Solar Dynamics Observatory showed a compact
+brightening, the SUNRISE observations at diffraction-limited spatial resolution
+of 0.1'' at 7s cadence revealed a dynamic sub-structure of the burst that it is
+composed of extended ribbon-like features and a rapidly evolving arcade of thin
+(~0.1'' wide) magnetic loop-like features, similar to post-flare loops. Such a
+dynamic sub-structure reveals the small-scale nature of chromospheric heating
+in these bursts. Furthermore, based on magnetic field extrapolations, this
+heating event is associated with a complex fan-spine magnetic topology. Our
+observations strongly hint at a unified picture of magnetic heating in the
+solar atmosphere from some large-scale flares to small-scale bursts, all being
+associated with such a magnetic topology.",1807.01078v1
+2018-07-30,Comparison of dynamical and equilibrium surface spin-reorientations: Inferences on the nature of the phase transitions in the presence of dipole interactions,"The influence of long-range dipole interactions on two dimensional magnetism
+has been studied extensively in the spin-reorientation transition of
+ferromagnetic ultrathin films. Although there is a great deal of experimental
+information on the perpendicular domain phase that is stabilized by dipole
+interactions, the transitions to or from the domain phase are subtle and
+difficult to characterize experimentally. Magnetic susceptibility measurements
+show no divergence in the vicinity of the spin-reorientation transition as a
+function of thickness -- a null result that is difficult to interpret with
+confidence. This article reports separate dynamical and equilibrium versions of
+the reorientation transition in Fe/2ML Ni/W(110) films, using measurements of
+the magnetic susceptibility as the films are grown. The dynamical version
+occurs when increasing the film thickness causes the domain walls to depin, and
+the system moves from a configuration that minimizes local energetics to one
+that minimizes global energetics. The dynamical transition \textit{is} marked
+by a divergent magnetic susceptibility measured with a field applied along the
+in-plane W[001] direction. A comparative study of the two versions of the same
+spin-reorientation transition aids in the experimental characterization of the
+effects of dipole interactions on the phase transitions. This comparison
+confirms the original null result found in magnetic susceptibility measurements
+of the equilibrium transition; despite its name, the spin-reorientation
+transition in ferromagnetic ultrathin films has no critical phase transition in
+either the magnetization or its orientation.",1807.11434v2
+2019-02-27,Deterministic field-free skyrmion nucleation at a nano-engineered injector device,"Magnetic skyrmions are topological solitons that exhibit an increased
+stability against annihilation, and can be displaced with low current
+densities, making them a promising candidate as an information carrier. In
+order to demonstrate a viable skyrmion-based memory device, it is necessary to
+reliably and reproducibly nucleate, displace, detect, and delete the magnetic
+skyrmions. While the skyrmion displacement and detection have both been
+investigated in detail, much less attention has been dedicated to the study of
+the sub-ns dynamics of the skyrmion nucleation process. Only limited studies on
+the statics and above-ns dynamics have been performed, leaving still many open
+questions on the dynamics of the nucleation process. Furthermore, the vast
+majority of the presently existing studies focus on the nucleation from random
+natural pinning sites, or from patterned constrictions in the magnetic material
+itself, which limit the functionality of the skyrmion-based device. Those
+limitations can be overcome by the fabrication of a dedicated injector device
+on top of the magnetic material. In this study, we investigate the nucleation
+of magnetic skyrmions from a dedicated nano-engineered injector, demonstrating
+the reliable magnetic skyrmion nucleation at the remnant state. The sub-ns
+dynamics of the skyrmion nucleation process were also investigated, allowing us
+to shine light on the physical processes driving the nucleation.",1902.10435v1
+2019-11-16,Characterizing Magnetized Plasmas with Dynamic Mode Decomposition,"Accurate and efficient plasma models are essential to understand and control
+experimental devices. Existing magnetohydrodynamic or kinetic models are
+nonlinear, computationally intensive, and can be difficult to interpret, while
+often only approximating the true dynamics. In this work, data-driven
+techniques recently developed in the field of fluid dynamics are leveraged to
+develop interpretable reduced-order models of plasmas that strike a balance
+between accuracy and efficiency. In particular, dynamic mode decomposition
+(DMD) is used to extract spatio-temporal magnetic coherent structures from the
+experimental and simulation datasets of the HIT-SI experiment.
+Three-dimensional magnetic surface probes from the HIT-SI experiment are
+analyzed, along with companion simulations with synthetic internal magnetic
+probes. A number of leading variants of the DMD algorithm are compared,
+including the sparsity-promoting and optimized DMD. Optimized DMD results in
+the highest overall prediction accuracy, while sparsity-promoting DMD yields
+physically interpretable models that avoid overfitting. These DMD algorithms
+uncover several coherent magnetic modes that provide new physical insights into
+the inner plasma structure. These modes were subsequently used to discover a
+previously unobserved three-dimensional structure in the simulation, rotating
+at the second injector harmonic. Finally, using data from probes at
+experimentally accessible locations, DMD identifies a resistive kink mode, a
+ubiquitous instability seen in magnetized plasmas.",1911.06938v1
+2021-08-20,NMR measurements in dynamically controlled field pulse,"We present the architecture of the versatile NMR spectrometer with
+software-defined radio (SDR) technology and its application to the dynamically
+controlled pulsed magnetic fields. The pulse-field technology is the only
+solution to access magnetic fields greater than 50 T, but the NMR experiment in
+the pulsed magnetic field was difficult because of the continuously changing
+field strength. The dynamically controlled field pulse allows us to perform NMR
+experiment in a quasi-steady field condition by creating a constant magnetic
+field for a short time around the peak of the field pulse. We confirmed the
+reproducibility of the field pulses using the NMR spectroscopy as a high
+precision magnetometer. With the highly reproducible field strength we
+succeeded in measuring the nuclear spin-lattice relaxation rate $1/T_1$, which
+had never been measured by the pulse-field NMR experiment without dynamic field
+control. We also implement the NMR spectrum measurement with both the
+frequency-sweep and field-sweep modes and discuss the appropriate choice of
+these modes depending on the magnetic properties of sample to be measured. This
+development, with further improvement at a long-duration field pulse, will
+innovate the microscopic measurement in extremely high magnetic fields.",2108.09163v1
+2021-12-11,Optical excitation of electromagnons in hexaferrite,"Understanding ultrafast magnetization dynamics on the microscopic level is of
+strong current interest due to the potential for applications in information
+storage. In recent years, the spin-lattice coupling has been recognized to be
+essential for ultrafast magnetization dynamics. Magnetoelectric multiferroics
+of type II possess intrinsic correlations among magnetic sublattices and
+electric polarization (P) through spin-lattice coupling, enabling fundamentally
+coupled dynamics between spins and lattice. Here we report on ultrafast
+magnetization dynamics in a room-temperature multiferroic hexaferrite
+possessing ferrimagnetic and antiferromagnetic sublattices, revealed by
+time-resolved resonant x-ray diffraction. A femtosecond above-bandgap
+excitation triggers a coherent magnon in which the two magnetic sublattices
+entangle and give rise to a transient modulation of P. A novel microscopic
+mechanism for triggering the coherent magnon in this ferrimagnetic insulator
+based on the spin-lattice coupling is proposed. Our finding opens up a novel
+but general pathway for ultrafast control of magnetism.",2112.05961v1
+2023-07-27,The dynamical magnetic-induced quark spin polarization at the early stage in heavy-ion collisions,"There has been significant interest in recent years in studying the spin
+polarization of hyperons in heavy-ion collisions. However, describing the
+dynamic spin polarization of quarks in quark-gluon plasma fireballs in detail
+presents a significant challenge. In this study, we conducted a
+phenomenological investigation of the dynamical spin polarization of quarks
+induced by the magnetic field at the pre-thermal stage in heavy-ion collisions
+using the recently developed theoretical tool of chiral kinetic theory. This
+study presents a comprehensive analysis of the dynamic process of quark spin
+polarization induced by magnetic fields. Our findings demonstrate that the spin
+polarization of quarks is highly sensitive to the interactions between quarks.
+These interactions can delay the decay of the early spin polarization vector
+while accelerating the decay of the later spin polarization vector.
+Specifically, our simulations model the detailed process of how magnetic fields
+polarize quarks within the fireball by the average spin vector and reveal that
+quark interactions lead to an acceleration effect on the average spin, causing
+it to rapidly increase from zero before being rapidly destroyed. Notably, the
+induced magnetic field in the fireball has an incomplete electromagnetic
+response effect, and its increase in the opposite direction of the external
+magnetic field decaying has a delay effect.",2308.00075v1
+2024-03-05,Dynamics of magnetic self-propelled particles in a harmonic trap,"Artificial active particles, exemplified by Hexbugs (HB), serve as valuable
+tools for investigating the intricate dynamics of active matter systems.
+Leveraging their stochastic motion, Hexbugs provides an excellent experimental
+model. In this study, we utilize Hexbugs equipped with disk-like armor and
+embedded magnetic dipoles, transforming them into Magnetic Self-Propelled
+Particles (MSPP). We explore the emergence of collective and stationary states
+numerically and experimentally by confining these MSPPs within a parabolic
+domain acting as a harmonic potential. Our findings unveil a diverse range of
+metastable configurations intricately linked to the complex dynamics inherent
+in the system. We discern that particle number, activity, and the balance
+between magnetic and harmonic potential strengths predominantly influence the
+metastability of these structures. By employing these parameters as control
+factors, we compare and contrast the behavior of MSPPs with disk-like magnetic
+Active Brownian Particles (ABPs) in the overdamped limit of vanishing inertia.
+Our numerical predictions reproduce most of the experimental observations,
+highlighting the crucial role of magnetic dipole interactions in developing
+novel configurations for active particles within parabolic domains. These
+configurations include chains, clusters, and vortex formations characterized by
+a specific pattern in the particle spatial distribution. Notably, we observe
+that the influence of inertia is not fundamental in generating metastable
+configurations in these confined systems. Instead, the particle's shape,
+activity, and orientation are dominant factors. This comparative analysis
+provides insights into the distinctive features and dynamics of MSPP within
+confined environments, shedding light on the role of short-range polar
+interactions.",2403.02569v1
+2008-09-30,Dynamics of diluted magnetic semiconductors from atomistic spin dynamics simulations: Mn doped GaAs as a case study,"The dynamical behavior of the magnetism of diluted magnetic semiconductors
+(DMS) has been investigated by means of atomistic spin dynamics simulations.
+The conclusions drawn from the study are argued to be general for DMS systems
+in the low concentration limit, although all simulations are done for 5%
+Mn-doped GaAs with various concentrations of As antisite defects. The
+magnetization curve, $M(T)$, and the Curie temperature $T_C$ have been
+calculated, and are found to be in good correspondence to results from Monte
+Carlo simulations and experiments. Furthermore, equilibrium and non-equilibrium
+behavior of the magnetic pair correlation function have been extracted. The
+dynamics of DMS systems reveals a substantial short ranged magnetic order even
+at temperatures at or above the ordering temperature, with a non-vanishing pair
+correlation function extending up to several atomic shells. For the high As
+antisite concentrations the simulations show a short ranged anti-ferromagnetic
+coupling, and a weakened long ranged ferromagnetic coupling. For sufficiently
+large concentrations we do not observe any long ranged ferromagnetic
+correlation. A typical dynamical response shows that starting from a random
+orientation of moments, the spin-correlation develops very fast ($\sim$ 1ps)
+extending up to 15 atomic shells. Above $\sim$ 10 ps in the simulations, the
+pair correlation is observed to extend over some 40 atomic shells. The
+autocorrelation function has been calculated and compared with ferromagnets
+like bcc Fe and spin-glass materials. We find no evidence in our simulations
+for a spin-glass behaviour, for any concentration of As antisites. Instead the
+magnetic response is better described as slow dynamics, at least when compared
+to that of a regular ferromagnet like bcc Fe.",0809.5187v1
+2004-09-30,A Study of Dynamic Finite Size Scaling Behavior of the Scaling Functions-Calculation of Dynamic Critical Index of Wolff Algorithm,"In this work we have studied the dynamic scaling behavior of two scaling
+functions and we have shown that scaling functions obey the dynamic finite size
+scaling rules. Dynamic finite size scaling of scaling functions opens
+possibilities for a wide range of applications. As an application we have
+calculated the dynamic critical exponent ($z$) of Wolff's cluster algorithm for
+2-, 3- and 4-dimensional Ising models. Configurations with vanishing initial
+magnetization are chosen in order to avoid complications due to initial
+magnetization. The observed dynamic finite size scaling behavior during early
+stages of the Monte Carlo simulation yields $z$ for Wolff's cluster algorithm
+for 2-, 3- and 4-dimensional Ising models with vanishing values which are
+consistent with the values obtained from the autocorrelations. Especially, the
+vanishing dynamic critical exponent we obtained for $d=3$ implies that the
+Wolff algorithm is more efficient in eliminating critical slowing down in Monte
+Carlo simulations than previously reported.",0409762v1
+2018-03-16,Energetics of turbulence generated by chiral MHD dynamos,"An asymmetry in the number density of left- and right-handed fermions is
+known to give rise to a new term in the induction equation that can result in a
+dynamo instability. At high temperatures, when a chiral asymmetry can survive
+for long enough, this chiral dynamo instability can amplify magnetic fields
+efficiently, which in turn drive turbulence via the Lorentz force. While it has
+been demonstrated in numerical simulations that this chiral magnetically driven
+turbulence exists and strongly affects the dynamics of the magnetic field, the
+details of this process remain unclear. The goal of this paper is to analyse
+the energetics of chiral magnetically driven turbulence and its effect on the
+generation and dynamics of the magnetic field using direct numerical
+simulations. We study these effects for different initial conditions, including
+a variation of the initial chiral chemical potential and the magnetic Prandtl
+number, Pm. In particular, we determine the ratio of kinetic to magnetic
+energy, Upsilon, in chiral magnetically driven turbulence. Within the parameter
+space explored in this study, Upsilon reaches a value of approximately
+0.064-0.074 -independently of the initial chiral asymmetry and for Pm=1. Our
+simulations suggest, that Upsilon decreases as a power law when increasing Pm
+by decreasing the viscosity. While the exact scaling depends on the details of
+the fitting criteria and the Reynolds number regime, an approximate result of
+Upsilon(Pm)=0.1 Pm^{-0.4} is reported. Using the findings from our numerical
+simulations, we analyse the energetics of chiral magnetically driven turbulence
+in the early Universe.",1803.06350v2
+2011-11-16,Non-Equilibrium Chemistry of Dynamically Evolving Prestellar Cores: I. Basic Magnetic and Non-Magnetic Models and Parameter Studies,"We combine dynamical and non-equilibrium chemical modeling of evolving
+prestellar molecular cloud cores, and explore the evolution of molecular
+abundances in the contracting core. We model both magnetic cores, with varying
+degrees of initial magnetic support, and non-magnetic cores, with varying
+collapse delay times. We explore, through a parameter study, the competing
+effects of various model parameters in the evolving molecular abundances,
+including the elemental C/O ratio, the temperature, and the cosmic-ray
+ionization rate. We find that different models show their largest quantitative
+differences at the center of the core, whereas the outer layers, which evolve
+slower, have abundances which are severely degenerate among different dynamical
+models. There is a large range of possible abundance values for different
+models at a fixed evolutionary stage (central density), which demonstrates the
+large potential of chemical differentiation in prestellar cores. However,
+degeneracies among different models, compounded with uncertainties induced by
+other model parameters, make it difficult to discriminate among dynamical
+models. To address these difficulties, we identify abundance ratios between
+particular molecules, the measurement of which would have maximal potential for
+discrimination among the different models examined here. In particular, we find
+that the ratios between NH3 and CO; NH2 and CO; NH3 and HCO+ are sensitive to
+the evolutionary timescale, and that the ratio between HCN and OH is sensitive
+to the C/O ratio. Finally, we demonstrate that measurements of the central
+deviation (central depletion or enhancement) of abundances of certain molecules
+are good indicators of the dynamics of the core.",1111.3948v2
+2016-06-27,Blume-Capel ferromagnet driven by propagating and standing magnetic field wave: Dynamical modes and nonequilibrium phase transition,"The dynamical responses of Blume-Capel (S=1) ferromagnet to the plane
+propagating (with fixed frequency and wavelength) and standing magnetic field
+waves are studied sepa- rately in two dimensions by extensive Monte Carlo
+simulation. Depending on the values of temperature, amplitude of the
+propagating magnetic field and the strength of anisotropy, two different
+dynamical phases are observed. For a fixed value of anisotropy and the
+amplitude of the propagating magnetic field, the system undergoes a dynamical
+phase transition from a driven spin wave propagating phase to a pinned or spin
+frozen state as the system is cooled down. The time averaged magnetisation over
+a full cycle of the propagating magnetic field plays the role of the dynamic
+order parameter. A comprehensive phase diagram is plotted in the plane formed
+by the amplitude of the propagating wave and the temperature of the system. It
+is found that the phase boundary shrinks inward as the anisotropy increases.
+The phase boundary, in the plane described by the strength of the anisotropy
+and temperature, is also drawn. This phase boundary was observed to shrink
+inward as the field amplitude increases.",1606.08155v3
+2018-06-14,Magnetohydrodynamics and magneto-solutal transport mediated evaporation dynamics in paramagnetic pendent droplets under field stimulus,"Evaporation kinetics of pendant droplets is an area of immense importance in
+several applications in addition to possessing rich fluid and thermal transport
+physics. The present article experimentally and analytically sheds insight into
+the augmented evaporation dynamics of paramagnetic pendent droplets in the
+presence of a magnetic field stimulus. Literature provides information that
+solutal advection and solutal Marangoni effect lead to enhancement of
+evaporation in droplets with ionic inclusions. The major crux of the present
+article remains to modulate the thermosolutal advection with the aid of
+magnetic field and comprehend the dynamics of the evaporation process under
+such complex multiphysics interactions. Experimental observations reveal that
+the evaporation rate enhances as a direct function of the magnetic moment of
+the solvated magnetic element ions, thereby pinpointing at the magnetophoretic
+and magneto-solutal advection. Additionally, flow visualization by PIV
+illustrates that the internal advection currents within the droplet are
+strengthened in magnitude as well as distorted in orientation by the magnetic
+field. A mathematical formalism based on magnetothermal and magnetosolutal
+advection effects has been proposed via scaling analysis of the species and
+energy conservation equations. The formalism takes into account all major
+governing factors such as the magnetothermal and magnetosolutal Marangoni
+numbers, magneto Prandtl and magneto Schmidt numbers and the Hartmann number.
+The modeling establishes the magnetosolutal advection component to be the
+domineering factor in augmented evaporation dynamics. Accurate validation of
+the experimental internal circulation velocity is obtained from the proposed
+model. The present study reveals rich insight on the magneto thermosolutal
+hydrodynamics aspects in paramagnetic droplets.",1806.05627v1
+2018-11-27,Hybrid magneto-dynamical modes in a single magnetostrictive nanomagnet on a piezoelectric substrate arising from magneto-elastic modulation of precessional dynamics,"Magneto-elastic (or ""straintronic"") switching has emerged as an extremely
+energy-efficient mechanism for switching the magnetization of magnetostrictive
+nanomagnets in magnetic memory, logic and non-Boolean circuits. Here, we
+investigate the ultrafast magneto-dynamics associated with straintronic
+switching in a single quasi-elliptical magnetostrictive Co nanomagnet deposited
+on a piezoelectric PMN-PT substrate using time-resolved magneto-optical Kerr
+effect (TR-MOKE) measurements. The pulsed laser pump beam in the TR-MOKE plays
+a dual role: it causes precession of the nanomagnet's magnetization about an
+applied bias magnetic field and it also generates surface acoustic waves (SAWs)
+in the piezoelectric substrate that produce periodic strains in the
+magnetostrictive nanomagnet and modulate the precessional dynamics. This
+modulation gives rise to intriguing hybrid magneto-dynamical modes in the
+nanomagnet, with rich spin wave texture. The characteristic frequencies of
+these modes are 5-15 GHz, indicating that strain can affect magnetization in a
+magnetostrictive nanomagnet in time scales much smaller than 1 ns (~100 ps).
+This can enable ~10 GHz-range magneto-elastic nano-oscillators that are
+actuated by strain instead of a spin-polarized current, as well as ultrafast
+magneto-electric generation of spin waves for magnonic logic circuits,
+holograms, etc.",1811.11297v1
+2019-08-29,High-temperature spin dynamics in the Heisenberg chain: Magnon propagation and emerging KPZ-scaling in the zero-magnetization limit,"The large-scale dynamics of quantum integrable systems is often dominated by
+ballistic modes due to the existence of stable quasi-particles. We here
+consider as an archetypical example for such a system the spin-$\frac{1}{2}$
+XXX Heisenberg chain that features magnons and their bound states. An
+interesting question, which we here investigate numerically, arises with
+respect to the fate of ballistic modes at finite temperatures in the limit of
+zero magnetization $m{=}0$. At a finite magnetization density $m$, the spin
+autocorrelation function $\Pi(x,t)$ (at high temperatures) typically exhibits a
+trimodal behavior with left- and right-moving quasi-particle modes and a broad
+center peak with slower dynamics. The broadening of the fastest propagating
+modes exhibits a sub-diffusive $t^{1/3}$ scaling at large magnetization
+densities, $m {\rightarrow} \frac{1}{2}$, familiar from non-interacting models;
+it crosses over into a diffusive scaling $t^{1/2}$ upon decreasing the
+magnetization to smaller values. The behavior of the center peak appears to
+exhibit a crossover from transient super-diffusion to ballistic relaxation at
+long times. In the limit $m{\to}0$, the weight carried by the propagating peaks
+tends to zero; the residual dynamics is carried only by the central peak; it is
+sub-ballistic and characterized by a dynamical exponent $z$ close to the value
+$\frac{3}{2}$ familiar from Kardar-Parisi-Zhang (KPZ) scaling. We confirm,
+employing elaborate finite-time extrapolations, that the spatial scaling of the
+correlator $\Pi$ is in excellent agreement with KPZ-type behavior and analyze
+the corresponding corrections.",1908.11432v2
+2019-09-24,Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer,"Here, we present an analytical and numerical model describing the
+magnetization dynamics in MgO-based spin-torque nano-oscillators with an
+in-plane magnetized polarizer and an out-of-plane free layer. We introduce the
+spin-transfer torque asymmetry by considering the cosine angular dependence of
+the resistance between the two magnetic layers in the stack. For the analytical
+solution, dynamics are determined by assuming a circular precession trajectory
+around the direction perpendicular to the plane, as set by the effective field,
+and calculating the energy integral over a single precession period. In a more
+realistic approach, we include the bias dependence of the tunnel
+magnetoresistance, which is assumed empirically to be a piecewise linear
+function of the applied voltage. The dynamical states are found by solving the
+stability condition for the Jacobian matrix for out-of-plane static states. We
+find that the bias dependence of the tunnel magnetoresistance, which is an
+inseparable effect in every tunnel junction, exhibits drastic impact on the
+spin-torque nano-oscillator phase diagram, mainly by increasing the critical
+current for dynamics and quenching the oscillations at high currents. The
+results are in good agreement with our experimental data published elsewhere.",1909.10983v1
+2019-12-16,Spin-current manipulation of photoinduced magnetization dynamics in heavy metal / ferromagnet double layer based nanostructures,"Spin currents offer a way to control static and dynamic magnetic properties,
+and therefore they are crucial for next-generation MRAM devices or spin-torque
+oscillators. Manipulating the dynamics is especially interesting within the
+context of photo-magnonics. In typical $3d$ transition metal ferromagnets like
+CoFeB, the lifetime of light-induced magnetization dynamics is restricted to
+about 1 ns, which e.g. strongly limits the opportunities to exploit the wave
+nature in a magnonic crystal filtering device. Here, we investigate the
+potential of spin-currents to increase the spin wave lifetime in a functional
+bilayer system, consisting of a heavy metal (8 nm of $\beta$-Tantalum
+(Platinum)) and 5 nm CoFeB. Due to the spin Hall effect, the heavy metal layer
+generates a transverse spin current when a lateral charge current passes
+through the strip. Using time-resolved all-optical pump-probe spectroscopy, we
+investigate how this spin current affects the magnetization dynamics in the
+adjacent CoFeB layer. We observed a linear spin current manipulation of the
+effective Gilbert damping parameter for the Kittel mode from which we were able
+to determine the system's spin Hall angles. Furthermore, we measured a strong
+influence of the spin current on a high-frequency mode. We interpret this mode
+an an exchange dominated higher order spin-wave resonance. Thus we infer a
+strong dependence of the exchange constant on the spin current.",1912.07728v1
+2020-02-10,Faster chiral versus collinear magnetic order recovery after optical excitation revealed by femtosecond XUV scattering,"While chiral spin structures stabilized by Dzyaloshinskii-Moriya interaction
+(DMI) are candidates as novel information carriers, their dynamics on the fs-ps
+timescale is little known. Since with the bulk Heisenberg exchange and the
+interfacial DMI two distinct exchange mechanisms are at play, the ultra-fast
+dynamics of the chiral order needs to be ascertained and compared to the
+dynamics of the conventional collinear order. Using an XUV free-electron laser
+we determine the fs-ps temporal evolution of the chiral order in domain walls
+in a magnetic thin film sample by an IR pump - X-ray magnetic scattering probe
+experiment. Upon demagnetisation we observe that the dichroic (CL-CR) signal
+connected with the chiral order correlator $m_z m_x$ in the domain walls
+recovers significantly faster than the (CL+CR) sum signal representing the
+average collinear domain magnetisation $m_z^2 + m_x^2$. We explore possible
+explanations based on spin structure dynamics and reduced transversal
+magnetisation fluctuations inside the domain walls and find that the latter can
+explain the experimental data leading to different dynamics for collinear
+magnetic order and chiral magnetic order.",2002.03971v2
+2020-05-28,Spintronics meets nonadiabatic molecular dynamics: Geometric spin torque and damping on noncollinear classical magnetism due to electronic open quantum system,"We analyze a quantum-classical hybrid system of steadily precessing slow
+classical localized magnetic moments, forming a head-to-head domain wall,
+embedded into an open quantum system of fast nonequilibrium electrons. The
+electrons reside within a metallic wire connected to macroscopic reservoirs.
+The model captures the essence of dynamical noncollinear and noncoplanar
+magnetic textures in spintronics, while making it possible to obtain the exact
+time-dependent nonequilibrium density matrix of electronic system and split it
+into four contributions. The Fermi surface contribution generates dissipative
+(or damping-like in spintronics terminology) spin torque on the moments, and
+one of the two Fermi sea contributions generates geometric torque dominating in
+the adiabatic regime. When the coupling to the reservoirs is reduced, the
+geometric torque is the only nonzero contribution. Locally it has both
+nondissipative (or field-like in spintronics terminology) and damping-like
+components, but with the sum of latter being zero, which act as the
+counterparts of geometric magnetism force and electronic friction in
+nonadiabatic molecular dynamics. Such current-independent geometric torque is
+absent from widely used micromagnetics or atomistic spin dynamics modeling of
+magnetization dynamics based on the Landau-Lifshitz-Gilbert equation, where
+previous analysis of Fermi surface-type torque has severely underestimated its
+magnitude.",2005.14153v2
+2022-02-03,Nonequilibrium dynamics of $α$-RuCl$_{3}$ -- a time-resolved magneto-optical spectroscopy study,"We present time-resolved magneto-optical spectroscopy on the magnetic
+Mott-Hubbard-insulating Kitaev spin liquid candidate $\alpha$-RuCl$_3$ to
+investigate the nonequilibrium dynamics of its antiferromagnetically ordered
+zigzag groundstate after photoexcitation. A systematic study of the transient
+magnetic linear dichroism under different experimental conditions (temperature,
+external magnetic field, photoexcitation density) gives direct access to the
+dynamical interplay of charge excitations with the zigzag ordered state on
+ultrashort time scales. We observe a rather slow initial demagnetization (few
+to 10s of ps) followed by a long-lived non-thermal antiferromagnetic
+spin-disordered state (100$-$1000s of ps), which can be understood in terms of
+holons and doublons disordering the antiferromagnetic background after
+photoexcitation. Varying temperature and fluence in the presence of an external
+magnetic field reveals two distinct photoinduced dynamics associated with the
+zigzag and quantum paramagnetic disordered phases. The photo-induced
+non-thermal spin-disordered state shows universal compressed-exponential
+recovery dynamics related to the growth and propagation of zigzag domains on
+nanosecond time scales, which is interpreted within the framework of the
+Fatuzzo-Labrune model for magnetization reversal. The study of nonequilibrium
+states in strongly correlated materials is a relatively unexplored topic, but
+our results are expected to be extendable to a large class of Mott-Hubbard
+insulator materials with strong spin-orbit coupling.",2202.01648v1
+2023-02-28,Magnetic field control of light-induced spin accumulation in monolayer MoSe$_2$,"Semiconductor transition metal dichalcogenides (TMDs) have equivalent
+dynamics for their two spin/valley species. This arises from their
+energy-degenerated spin states, connected via time-reversal symmetry. When an
+out-of-plane magnetic field is applied, time-reversal symmetry is broken and
+the energies of the spin-polarized bands shift, resulting in different bandgaps
+and dynamics in the K$_+$ and K$_-$ valleys. Here, we use time-resolved Kerr
+rotation to study the magnetic field dependence of the spin dynamics in
+monolayer MoSe$_2$. We show that the magnetic field can control the
+light-induced spin accumulation of the two valley states, with a small effect
+on the recombination lifetimes. We unveil that the magnetic field-dependent
+spin accumulation is in agreement with hole spin dynamics at the longer
+timescales, indicating that the electron spins have faster relaxation rates. We
+propose a rate equation model that suggests that lifting the energy-degeneracy
+of the valleys induces an ultrafast spin-flip toward the stabilization of the
+valley with the higher valence band energy. Our results provide an experimental
+insight into the ultrafast charge and spin dynamics in TMDs and a way to
+control it, which will be useful for the development of new spintronic and
+valleytronic applications.",2302.14206v1
+2023-06-20,Convolutional neural networks for large-scale dynamical modeling of itinerant magnets,"Complex spin textures in itinerant electron magnets hold promises for
+next-generation memory and information technology. The long-ranged and often
+frustrated electron-mediated spin interactions in these materials give rise to
+intriguing localized spin structures such as skyrmions. Yet, simulations of
+magnetization dynamics for such itinerant magnets are computationally difficult
+due to the need for repeated solutions to the electronic structure problems. We
+present a convolutional neural network (CNN) model to accurately and
+efficiently predict the electron-induced magnetic torques acting on local
+spins. Importantly, as the convolutional operations with a fixed kernel
+(receptive field) size naturally take advantage of the locality principle for
+many-electron systems, CNN offers a scalable machine learning approach to spin
+dynamics. We apply our approach to enable large-scale dynamical simulations of
+skyrmion phases in itinerant spin systems. By incorporating the CNN model into
+Landau-Lifshitz-Gilbert dynamics, our simulations successfully reproduce the
+relaxation process of the skyrmion phase and stabilize a skyrmion lattice in
+larger systems. The CNN model also allows us to compute the effective receptive
+fields, thus providing a systematic and unbiased method for determining the
+locality of the original electron models.",2306.11833v1
+2023-07-10,Kibble-Zurek Mechanism for Nonequilibrium Generation of Magnetic Monopoles in Spin Ices,"The proliferation of topological defects is a common out-of-equilibrium
+phenomenon when a system is driven into a phase of broken symmetry. The
+Kibble-Zurek mechanism (KZM) provides a theoretical framework for the critical
+dynamics and generation of topological defects in such scenarios. One of the
+early applications of KZM is the estimation of heavy magnetic monopoles left
+behind by the cosmological phase transitions in the early universe. The
+scarcity of such relic monopoles, which contradicts the prediction of KZM, is
+one of the main motivations for cosmological inflationary theories. On the
+other hand, magnetic monopoles as emergent quasi-particles have been observed
+in spin ices, a peculiar class of frustrated magnets that remain disordered at
+temperatures well below the energy scale of exchange interaction. Here we study
+the annihilation dynamics of magnetic monopoles when spin ice is cooled to zero
+temperature in a finite time. Through extensive Glauber dynamics simulations,
+we find that the density of residual monopole follows a power law dependence on
+the annealing rate. A kinetic reaction theory that precisely captures the
+annihilation process from Monte Carlo simulations is developed. We further show
+that the KZM can be generalized to describe the critical dynamics of spin ice,
+where the exponent of the power-law behavior is determined by the dynamic
+critical exponent $z$ and the cooling protocol.",2307.05267v1
+1999-09-22,Deterministic Equations of Motion and Dynamic Critical Phenomena,"Taking the two-dimensional $\phi^4$ theory as an example, we numerically
+solve the deterministic equations of motion with random initial states.
+Short-time behavior of the solutions is systematically investigated. Assuming
+that the solutions generate a microcanonical ensemble of the system, we
+demonstrate that the second order phase transition point can be determined
+already from the short-time dynamic behavior. Initial increase of the
+magnetization and critical slowing down are observed. The dynamic critical
+exponent z, the new exponent $\theta$ and the static exponents $\beta$ and
+$\nu$ are estimated. Interestingly, the deterministic dynamics with random
+initial states is in a same dynamic universality class of Monte Carlo dynamics.",9909322v1
+2002-06-29,Solvable Kinetic Gaussian Model in External Field,"In this paper, the single-spin transition dynamics is used to investigate the
+kinetic Gaussian model in a periodic external field. We first derive the
+fundamental dynamic equations, and then treat an isotropic d-dimensional
+hypercubic lattice Gaussian spin system with Fourier's transformation method.
+We obtain exactly the local magnetization and the equal-time pair correlation
+function. The critical characteristics of the dynamical, the complex
+susceptibility, and the dynamical response are discussed. The results show that
+the time evolution of the dynamical quantities and the dynamical responses of
+the system strongly depend on the frequency and the wave vector of the external
+field.",0207007v1
+2007-10-29,Dynamic Phase Transitions in Superconductivity,"In this Letter, the dynamic phase transitions of the time-dependent
+Ginzburg-Landau equations are analyzed using a newly developed dynamic
+transition theory and a new classification scheme of dynamics phase
+transitions. First, we demonstrate that there are two type of dynamic
+transitions, jump and continuous, dictated by the sign of a nondimensional
+parameter R. This parameter is computable, and depends on the material
+property, the applied field, and the geometry of domain that the sample
+occupies. Second, using the parameter R, precise analytical formulas for
+critical domain size, and for critical magnetic fields are derived.",0710.5436v1
+2008-10-09,Dynamics of strongly correlated ions in a partially ionized quantum plasma,"A scheme which allows to compute the dynamics of strongly correlated
+classical ions embedded into a partiallzy ionized quantum plasma by first
+principles molecular dynamics is presented. The dynamically screened dust
+approach of Joyce and Lampe [Phys. Rev. Lett. {\bf 88}, 095006 (2002] ist
+generalized to quantum systems. The electrons are treated fully
+quantum-mechanically taking into account their dynamical screening of the
+ion-ion interaction in linear response on the basis of an extended Mermin
+formula. The scheme allows to include the effect of the electron dynamics,
+electron streaming, wake effects and electron magnetization.",0810.1659v1
+2016-06-15,Quantum dynamics of trapped ions in a dynamic field gradient using dressed states,"Novel ion traps that provide either a static or a dynamic magnetic gradient
+field allow for the use of radio frequency (rf) radiation for coupling internal
+and motional states of ions, which is essential for conditional quantum logic.
+We show that the coupling mechanism in the presence of a dynamic gradient is
+the same, in a dressed state basis, as in the case of a static gradient. Then,
+it is shown how demanding experimental requirements arising when using a
+dynamic gradient could be overcome. Thus, using dressed states in a dynamic
+gradient field could decisively reduce experimental complexity on the route
+towards a scalable device for quantum information science based on rf-driven
+trapped ions.",1606.04821v1
+2007-10-18,Magnetic fields and the dynamics of spiral galaxies,"We investigate the dynamics of magnetic fields in spiral galaxies by
+performing 3D MHD simulations of galactic discs subject to a spiral potential.
+Recent hydrodynamic simulations have demonstrated the formation of inter-arm
+spurs as well as spiral arm molecular clouds provided the ISM model includes a
+cold HI phase. We find that the main effect of adding a magnetic field to these
+calculations is to inhibit the formation of structure in the disc. However,
+provided a cold phase is included, spurs and spiral arm clumps are still
+present if $\beta \gtrsim 0.1$ in the cold gas. A caveat to two phase
+calculations though is that by assuming a uniform initial distribution, $\beta
+\gtrsim 10$ in the warm gas, emphasizing that models with more consistent
+initial conditions and thermodynamics are required. Our simulations with only
+warm gas do not show such structure, irrespective of the magnetic field
+strength. Furthermore, we find that the introduction of a cold HI phase
+naturally produces the observed degree of disorder in the magnetic field, which
+is again absent from simulations using only warm gas. Whilst the global
+magnetic field follows the large scale gas flow, the magnetic field also
+contains a substantial random component that is produced by the velocity
+dispersion induced in the cold gas during the passage through a spiral shock.
+Without any cold gas, the magnetic field in the warm phase remains relatively
+well ordered apart from becoming compressed in the spiral shocks. Our results
+provide a natural explanation for the observed high proportions of disordered
+magnetic field in spiral galaxies and we thus predict that the relative
+strengths of the random and ordered components of the magnetic field observed
+in spiral galaxies will depend on the dynamics of spiral shocks.",0710.3558v1
+2021-09-18,"Time-dependent, long-term hydrodynamic simulations of the inner protoplanetary disk I: The importance of stellar magnetic torques","We conduct simulations of the inner regions of protoplanetary disks (PPDs) to
+investigate the effects of protostellar magnetic fields on their long-term
+evolution. We use an inner boundary model that incorporates the influence of a
+stellar magnetic field. The position of the inner disk is dependent on the mass
+accretion rate as well as the magnetic field strength. We use this model to
+study the response of a magnetically truncated inner disk to an episodic
+accretion event. Additionally, we vary the protostellar magnetic field strength
+and investigate the consequences of the magnetic field on the long-term
+behavior of PPDs. We use the fully implicit 1+1D TAPIR code which solves the
+axisymmetric hydrodynamic equations self-consistently. Our model allows us to
+investigate disk dynamics close to the star and to conduct long-term evolution
+simulations simultaneously and includes the radial radiation transport in the
+stationary diffusion limit. We include stellar magnetic torques, the influence
+of a pressure gradient, and a variable inner disk radius in the TAPIR code to
+describe the innermost disk region in a more self-consistent manner and can
+show that this approach alters the disk dynamics considerably compared to a
+simplified diffusive evolution equation, especially during outbursts. The
+influences of a prescribed stellar magnetic field, local pressure gradients,
+and a variable inner disk radius result in a more consistent description of the
+gas dynamics in the innermost regions of PPDs. Combining magnetic torques
+acting on the innermost disk regions with the long-term evolution of PPDs
+yields previously unseen results, whereby the whole disk structure is affected
+over its entire lifetime. Additionally, we want to emphasize that a combination
+of our 1+1D model with more sophisticated multi-dimensional codes could improve
+the understanding of PPDs even further.",2109.08919v1
+2022-01-05,Insensitivity of a turbulent laser-plasma dynamo to initial conditions,"It has recently been demonstrated experimentally that a turbulent plasma
+created by the collision of two inhomogeneous, asymmetric, weakly magnetised
+laser-produced plasma jets can generate strong stochastic magnetic fields via
+the small-scale turbulent dynamo mechanism, provided the magnetic Reynolds
+number of the plasma is sufficiently large. In this paper, we compare such a
+plasma with one arising from two pre-magnetised plasma jets whose creation is
+identical save for the addition of a strong external magnetic field imposed by
+a pulsed magnetic field generator (`MIFEDS'). We investigate the differences
+between the two turbulent systems using a Thomson-scattering diagnostic, X-ray
+self-emission imaging and proton radiography. The Thomson-scattering spectra
+and X-ray images suggest that the presence of the external magnetic field has a
+limited effect on the plasma dynamics in the experiment. While the presence of
+the external magnetic field induces collimation of the flows in the colliding
+plasma jets and the initial strengths of the magnetic fields arising from the
+interaction between the colliding jets are significantly larger as a result of
+the external field, the energy and morphology of the stochastic magnetic fields
+post-amplification are indistinguishable. We conclude that, for turbulent
+laser-plasmas with super-critical magnetic Reynolds numbers, the
+dynamo-amplified magnetic fields are determined by the turbulent dynamics
+rather than the seed fields and modest changes in the initial flow dynamics of
+the plasma, a finding consistent with theoretical expectations and simulations
+of turbulent dynamos.",2201.01705v1
+2017-06-06,Driven spin wave modes in XY ferromagnet: Nonequilibrium phase transition,"The dynamical responses of XY ferromagnet driven by linearly polarised
+propagating and standing magnetic field wave have been studied by Monte Carlo
+simulation in three dimensions. In the case of propagating magnetic field wave
+(with specified amplitude, frequency and the wavelength), the low temperature
+dynamical mode is a propagating spin wave and the system becomes structureless
+(or random) in the high temperature. A dynamical symmetry breaking phase
+transition is observed at a finite (nonzero) temperature. This symmetry
+breaking is confirmed by studying the statistical distribution of the angle of
+the spin vector. The dynamic nonequilibrium transition temperature was found to
+decrease as the amplitude of the propagating magnetic field wave increased. A
+comprehensive phase boundary is drawn in the plane formed by temperature and
+amplitude of propagating field wave. The phase boundary was observed to shrink
+(in the low temperature side) for longer wavelength of the propagating magnetic
+wave. In the case of standing magnetic field wave, the low temperature
+excitation is a standing spin wave which becomes structureless (or random) in
+the high temperature. Here also, like the case of propagating magnetic wave, a
+dynamical symmetry breaking nonequilibrium phase transition was observed. A
+comprehensive phase boundary is drawn. Unlike the case of propagating magnetic
+wave, the phase boundary does not show any systematic variation with the
+wavelength of the standing magnetic field wave. In the limit of vanishingly
+small amplitude of the field, the phase boundaries approach the recent Monte
+Carlo estimate of equilibrium transition temperature.",1706.01619v6
+2022-06-17,Quantum Dynamics of Magnetic Skyrmions: Consistent Path Integral Formulation,"We present a path integral formalism for the intrinsic quantum dynamics of
+magnetic skyrmions coupled to a thermal background of magnetic fluctuations.
+Upon promoting the skyrmion's collective coordinate $\boldsymbol{R}$ to a
+dynamic variable and integrating out the magnonic heat bath, we derive the
+generalized equation of motion for $\boldsymbol{R}$ with a non-local damping
+term that describes a steady-state skyrmion dynamics at finite temperatures.
+Being essentially temperature dependent, the intrinsic damping is shown to
+originate from the coupling of thermally activated magnon modes to the
+adiabatic potential driven by a rigid skyrmion motion, which can be regarded as
+another manifestation of emergent electrodynamics inherent to topological
+magnetic textures. We further argue that the diagonal components of the damping
+term act as the source of dissipation and inertia, while its off-diagonal
+components modify the gyrotropic motion of a magnetic skyrmion. By means of
+numerical calculations for the lattice spin model of chiral ferromagnets, we
+study the temperature behavior of the intrinsic damping as a function of
+magnetic field in periodic and confined geometries. The intrinsic damping is
+demonstrated to be highly non-local, revealing its quantum-mechanical nature,
+that becomes more pronounced with increasing temperature. At high temperatures
+when the magnon occupation factors are large, the intrinsic damping is shown to
+yield a modified Thiele's equation with the additional non-local dissipative
+and mass terms that exhibit an almost linear temperature behavior. Our results
+provide a microscopic background for semiclassical magnetization dynamics and
+establish a framework for understanding spin caloritronics effects in
+topological magnetic textures.",2206.08532v2
+2022-02-28,"Density Functional description of spin, lattice, and spin-lattice dynamics in antiferromagnetic and paramagnetic phases at finite temperatures","Describing the (a) electronic and magnetic properties (EMP) of
+antiferromagnetic or paramagnetic phases of compounds generally requires the
+knowledge of (b) the spin configurations and lattice structure (SCLS) of such
+phases at a given temperature. Indeed, studying the coupling between (a) and
+(b) has been an outstanding challenge in the theory of magnetism. The
+traditional approach to electronic phases of matter has generally focused on
+solving the problem of EMP regarding the SCLS as a spectator degree of freedom
+(DOF). Yet, it has been recognized that EMP of a compound generally respond
+self-consistently to changes in SCLS and vice versa. We construct here a
+practical, density functional theory (DFT)-based approach that provides the
+SCLS as a function of temperature, involving the description of spin, lattice,
+and spin-lattice dynamics of different magnetic phases. We distinguish three
+Levels of dynamics: (I) dynamics of the spin DOF treated via noncollinear
+Heisenberg Monte-Carlo with exchange energies from DFT, (II) dynamics of the
+lattice DOF treated by ab initio molecular dynamics (AIMD) employing a fixed
+spin configuration from Level I at the simulated temperature, and (III)
+coupling of spin and lattice dynamics via Landau-Lifshitz-Gilbert spin dynamics
+combined with AIMD. Such SCLS at each of the three levels are used as inputs to
+DFT supercell calculations, providing the EMP at each temperature. The results
+of this sequence include electronic band structures, band gaps, density of
+states, as well as the statistical distribution of local moments and the
+short-range order parameters, each as a function of temperature. Using NiO as a
+test case, we address the separability of the DOF in magnetic insulators for a
+minimal description of electronic and magnetic properties, demonstrating that
+inclusion of spin dynamics and, to some level, lattice dynamics is enough to
+explain the EMP.",2202.13723v2
+2018-03-01,Classical and quantum spin dynamics of the honeycomb $Γ$ model,"Quantum to classical crossover is a fundamental question in dynamics of
+quantum many-body systems. In frustrated magnets, for example, it is highly
+non-trivial to describe the crossover from the classical spin liquid with a
+macroscopically-degenerate ground-state manifold, to the quantum spin liquid
+phase with fractionalized excitations. This is an important issue as we often
+encounter the demand for a sharp distinction between the classical and quantum
+spin liquid behaviors in real materials. Here we take the example of the
+classical spin liquid in a frustrated magnet with novel bond-dependent
+interactions to investigate the classical dynamics, and critically compare it
+with quantum dynamics in the same system. In particular, we focus on signatures
+in the dynamical spin structure factor. Combining Landau-Lifshitz dynamics
+simulations and the analytical Martin-Siggia-Rose (MSR) approach, we show that
+the low energy spectra are described by relaxational dynamics and highly
+constrained by the zero mode structure of the underlying degenerate classical
+manifold. Further, the higher energy spectra can be explained by precessional
+dynamics. Surprisingly, many of these features can also be seen in the
+dynamical structure factor in the quantum model studied by finite-temperature
+exact diagonalization. We discuss the implications of these results, and their
+connection to recent experiments on frustrated magnets with strong spin-orbit
+coupling.",1803.00601v2
+2021-10-01,Intrinsic energy flow in laser-excited 3$d$ ferromagnets,"Ultrafast magnetization dynamics are governed by energy flow between
+electronic, magnetic, and lattice degrees of freedom. A quantitative
+understanding of these dynamics must be based on a model that agrees with
+experimental results for all three subsystems. However, ultrafast dynamics of
+the lattice remain largely unexplored experimentally. Here, we combine
+femtosecond electron diffraction experiments of the lattice dynamics with
+energy-conserving atomistic spin dynamics (ASD) simulations and ab-initio
+calculations to study the intrinsic energy flow in the 3d ferromagnets cobalt
+(Co) and iron (Fe). The simulations yield a good description of experimental
+data, in particular an excellent description of our experimental results for
+the lattice dynamics. We find that the lattice dynamics are influenced
+significantly by the magnetization dynamics due to the energy cost of
+demagnetization. Our results highlight the role of the spin system as the
+dominant heat sink in the first hundreds of femtoseconds. Together with
+previous findings for nickel [Zahn et al., Phys. Rev. Research 3, 023032
+(2021)], our work demonstrates that energy-conserving ASD simulations provide a
+general and consistent description of the laser-induced dynamics in all three
+elemental 3d ferromagnets.",2110.00525v2
+2003-10-07,Magnetic Spin-Up of Line-Driven Winds,"We summarize recent 2D MHD simulations of line-driven stellar winds from
+rotating hot-stars with a dipole magnetic field aligned to the star's rotation
+axis. For moderate to strong fields, much wind outflow is initially along
+closed magnetic loops that nearly corotate as a solid body with the underlying
+star, thus providing a torque that results in an effective angular momentum
+spin-up of the outflowing material. But instead of forming the ``magnetically
+torqued disk'' (MTD) postulated in previous phenemenological analyses, the
+dynamical simulations here show that material trapped near the tops of such
+closed loops tends either to fall back or break out, depending on whether it is
+below or above the Keplerian corotation radius. Overall the results raise
+serious questions about whether magnetic torquing of a wind outflow could
+naturally result in a Keplerian circumstellar disk. However, for very strong
+fields, it does still seem possible to form a %``magnetically confined,
+centrifugally supported, rigid-body disk'', centrifugally supported,
+``magnetically rigid disk'' (MRD), in which the field not only forces material
+to maintain a rigid-body rotation, but for some extended period also holds it
+down against the outward centrifugal force at the loop tops. We argue that such
+rigid-body disks seem ill-suited to explain the disk emission from Be stars,
+but could provide a quite attractive paradigm for circumstellar emission from
+the magnetically strong Bp and Ap stars.",0310179v1
+2004-01-30,Neutrino Processes in Strong Magnetic Fields and Implications for Supernova Dynamics,"The processes of neutrino (antineutrino) absorption and electron (positron)
+capture on nucleons provide the dominant mechanisms for heating and cooling the
+material between the protoneutron star and the stalled shock in a core-collapse
+supernova. Observations suggest that some neutron stars are born with magnetic
+fields of at least 10^15 G while theoretical considerations give an upper limit
+of 10^18 G for the protoneutron star magnetic fields. We calculate the rates
+for the above neutrino processes in strong magnetic fields of 10^16 G. We find
+that the main effect of such magnetic fields is to change the equations of
+state through the phase space of electron and positron, which differs from the
+classical case due to quantization of the motion of electron and positron
+perpendicular to the magnetic field. As a result, the cooling rate can be
+greatly reduced by magnetic fields of 10^16 G for typical conditions below the
+stalled shock and a nonuniform protoneutron star magnetic field (e.g., a dipole
+field) can introduce a large angular dependence of the cooling rate. In
+addition, strong magnetic fields always lead to an angle-dependent heating rate
+by polarizing the spin of nucleons. The implications of our results for the
+neutrino-driven supernova mechanism are discussed.",0401634v2
+2004-10-20,A Genetic Algorithm-Based Exploration of Three Filament Models: A Case for the Magnetic Support of the G11.11-0.12 Infrared-Dark Cloud,"The G11.11-0.12 infrared-dark cloud has a filamentary appearance, both in
+extinction against the diffuse infrared emission of the Galactic plane and in
+emission at 850 microns. We use a novel computational technique based on an
+advanced genetic algorithm to explore thoroughly 3 different models of
+self-gravitating, pressure truncated filaments and to constrain their
+parameters. Specifically, the models tested are the non-magnetic Ostriker
+(1964) model, a generalized version of the magnetic Stodolkiewicz (1963) model,
+and the magnetic Fiege & Pudritz (2000) model. Previous results showed that
+G11.11-0.12 has a much steeper r^{-4} radial density profile than other
+filaments, where the density varies approximately as r^{-2}, and that this
+steep density profile is consistent with the Ostriker (1964) model. We present
+a more complete analysis that shows that the radial structure of G11.11-0.12 is
+consistent with regimes of each of these models. All of the magnetic models
+that agree with the data are threaded by a dominant poloidal magnetic field,
+and most have dynamically significant fields. Thus, G11.11-0.12 is an excellent
+candidate for radial support by a magnetic field that is predominantly
+poloidal. We predict the polarization patterns expected for both magnetic
+models and show that the two magnetic models produce different polarization
+patterns that should be distingished by observations.",0410474v1
+2006-08-31,The Cosmic Battery Revisited,"We reinvestigate the generation and accumulation of magnetic flux in
+optically thin accretion flows around active gravitating objects. The source of
+the magnetic field is the azimuthal electric current associated with the
+Poynting-Robertson drag on the electrons of the accreting plasma. This current
+generates magnetic field loops which open up because of the differential
+rotation of the flow. We show through simple numerical simulations that what
+regulates the generation and accumulation of magnetic flux near the center is
+the value of the plasma conductivity. Although the conductivity is usually
+considered to be effectively infinite for the fully ionized plasmas expected
+near the inner edge of accretion disks, the turbulence of those plasmas may
+actually render them much less conducting due to the presence of anomalous
+resistivity. We have discovered that if the resistivity is sufficiently high
+throughout the turbulent disk while it is suppressed interior to its inner
+edge, an interesting steady-state process is established: accretion carries and
+accumulates magnetic flux of one polarity inside the inner edge of the disk,
+whereas magnetic diffusion releases magnetic flux of the opposite polarity to
+large distances. In this scenario, magnetic flux of one polarity grows and
+accumulates at a steady rate in the region inside the inner edge and up to the
+point of equipartition when it becomes dynamically important. We argue that
+this inward growth and outward expulsion of oppositely-directed magnetic fields
+that we propose may account for the ~30 min cyclic variability observed in the
+galactic microquasar GRS1915+105.",0608701v1
+2003-01-16,Magnetic Relaxation in the Peak Effect Region of CeRu$_2$,"The different pinning strengths of the flux line lattice in the peak effect
+(PE) region of a polycrystalline sample of CeRu$_2$ with a superconducting
+transition temperature {$T_c = 6.1$ K} have been probed by means of
+magnetization measurements with a SQUID magnetometer as the temperature $T$ and
+the magnetic field $H$ are varied. Magnetic relaxation measurements were used
+to monitor the flux line dynamics in the PE region. For {$T < 4.5$ K} and $H <
+H_P$, where $H_P$ is the field where the magnetization reaches a maximum in the
+PE region, the relaxation rate was found to be significantly larger in the
+descending-field branch of the PE than it is in other sections of the PE
+region. For {$T \geq 4.5$ K}, the relaxation rate in the entire PE region is so
+large that the magnetization reached a stable (equilibrium) value within
+{$10^4$ s}. This experimentally determined stable state appears as an increase
+of the magnetization in the PE region and has a dome shape superimposed on a
+linear interpolation through the PE region. It was also found that the PE in
+CeRu$_2$ can be suppressed by rapid thermal cycling of the sample between {10
+K} and {300 K} four times. The reversible magnetization after the PE has been
+suppressed coincides with the linear interpolation through the PE region, in
+contrast to the behavior of the equilibrium magnetization when the PE is
+present.
+  PACS number: 74.25.Qt, 74.70.Ad",0301281v1
+2004-07-28,Ab initio study of canted magnetism of finite atomic chains at surfaces,"By using ab initio methods on different levels we study the magnetic ground
+state of (finite) atomic wires deposited on metallic surfaces. A
+phenomenological model based on symmetry arguments suggests that the
+magnetization of a ferromagnetic wire is aligned either normal to the wire and,
+generally, tilted with respect to the surface normal or parallel to the wire.
+  From a first principles point of view, this simple model can be best related
+to the so--called magnetic force theorem calculations being often used to
+explore magnetic anisotropy energies of bulk and surface systems. The second
+theoretical approach we use to search for the canted magnetic ground state is
+first principles adiabatic spin dynamics extended to the case of fully
+relativistic electron scattering. First, for the case of two adjacent Fe atoms
+an a Cu(111) surface we demonstrate that the reduction of the surface symmetry
+can indeed lead to canted magnetism. The anisotropy constants and consequently
+the ground state magnetization direction are very sensitive to the position of
+the dimer with respect to the surface. We also performed calculations for a
+seven--atom Co chain placed along a step edge of a Pt(111) surface. As far as
+the ground state spin orientation is concerned we obtain excellent agreement
+with experiment. Moreover, the magnetic ground state turns out to be slightly
+noncollinear.",0407732v1
+2008-02-04,Cosmological MHD simulation of a cooling flow cluster,"Various observations of magnetic fields in the Intra-Cluster Medium (ICM),
+most of the time restricted to cluster cores, point towards field strength of
+the order of a few microG (synchrotron radiation from radio relics and radio
+halos, inverse Compton radiation in X-rays and Faraday rotation measure of
+polarised background sources). Both the origin and the spatial structure of
+galaxy clusters magnetic fields are still under debate. In particular, the
+radial profile of the magnetic field, from the core of clusters to their
+outskirts, is of great importance for cosmic rays propagation within the Cosmic
+Web. In this letter, we highlight the importance of cooling processes in
+amplifying the magnetic field in the core of galaxy clusters up to one order of
+magnitude above the typical amplification obtained for a pure adiabatic
+evolution. We have performed a ""zoom'' cosmological simulation of a 3 keV
+cluster, including dark matter and gas dynamics, atomic cooling, UV heating and
+star formation using the newly developed MHD solver in the AMR code RAMSES.
+Magnetic field amplification proceeds mainly through gravitational contraction.
+Shearing motions due to turbulence provide additional amplification in the
+outskirts of the cluster, while magnetic reconnection during mergers causes
+magnetic field dissipation in the core. Cooling processes have a strong impact
+on the magnetic field structure in the cluster. First, due to the sharp rise of
+the gas density in the centre, gravitational amplification is significantly
+amplified, when compared to the non--radiative run. Second, due to cooling
+processes, shearing motions are much stronger in the core than in the adiabatic
+case, leading to additional field amplification and no significant magnetic
+reconnection.",0802.0490v3
+2008-12-30,Covalent bonding and magnetism in cuprates,"The importance of covalent bonding for the magnetism of 3d metal complexes
+was first noted by Pauling in 1931. His point became moot, however, with the
+success of the ionic picture of Van Vleck, where ligands influence magnetic
+electrons of 3d ions mainly through electrostatic fields. Anderson's theory of
+spin superexchange later established that covalency is at the heart of
+cooperative magnetism in insulators, but its energy scale was believed to be
+small compared to other inter-ionic interactions and therefore it was
+considered a small perturbation of the ionic picture. This assertion fails
+dramatically in copper oxides, which came to prominence following the discovery
+of high critical temperature superconductors (HTSC). Magnetic interactions in
+cuprates are remarkably strong and are often considered the origin of the
+unusually high superconducting transition temperature, Tc. Here we report a
+detailed survey of magnetic excitations in the one-dimensional cuprate Sr2CuO3
+using inelastic neutron scattering (INS). We show that although the
+experimental dynamical spin structure factor is well described by the model
+S=1/2 nearest-neighbour Heisenberg Hamiltonian typically used for cuprates, the
+magnetic intensity is modified dramatically by strong hybridization of Cu 3d
+states with O p states, showing that the ionic picture of localized 3d
+Heisenberg spin magnetism is grossly inadequate. Our findings provide a natural
+explanation for the puzzle of the missing INS magnetic intensity in cuprates
+and have profound implications for understanding current and future
+experimental data on these materials.",0812.5007v1
+2009-01-20,A Model of Magnetically Induced Disc-Corona for Black Hole Binaries,"We propose a model of magnetic connection (MC) of a black hole with its
+surrounding accretion disc based on large-scale magnetic field. The MC gives
+rise to transport of energy and angular momentum between the black hole and the
+disc, and the closed field lines pipe the hot matter evaporated from the disc,
+and shape it in the corona above the disc to form a magnetically induced
+disc-corona system, in which the corona has the same configuration as the
+large-scale magnetic field. We numerically solve the dynamic equations in the
+context of the Kerr metric, in which the large-scale magnetic field is
+determined by dynamo process and equipartition between magnetic pressure and
+gas pressure. Thus we can obtain a global solution rather than assuming the
+distribution of large-scale magnetic field beforehand. The main MC effects lie
+in three aspects. (1) The rotational energy of a fast-spinning black hole can
+be extracted, enhancing the dissipation in the accretion disc, (2) the closed
+field lines provide a natural channel for corona matter escaping from disc and
+finally falling into black hole, and (3) the scope of the corona can be bounded
+by the conservation of magnetic flux. We simulate the high-energy spectra of
+this system by using Monte-Carlo method, and find that the relative hardness of
+the spectra decreases as accretion rate or black hole spin $a_*$ increases. We
+fit the typical X-ray spectra of three black-hole binaries (GRO J1655-40, XTE
+1118+480 and GX 339-4) in the low/hard or very high state.",0901.3002v1
+2009-02-02,Stray-fields based features observed for low and high magnetic fields in Ni$_{80}$Fe$_{20}$-Nb-Ni$_{80}$Fe$_{20}$ trilayers,"We report on the influence of stray fields for both low and high magnetic
+fields applied parallel to trilayers consisting of a low-T Nb interlayer and
+two outer Ni Fe layers having in-plane anisotropy. At low magnetic fields these
+trilayers exhibit a pronounced magnetoresistance effect. Its dynamic transport
+behavior is presented through detailed I-V characteristics. More importantly,
+the detailed evolution of the longitudinal and transverse magnetic components
+of the trilayers is presented from close to well below T . These data clearly
+show that below T and for low magnetic fields the transport properties of the
+Nb interlayer are influenced by transverse stray-fields that motivate
+subsequent transverse magnetic coupling of the outer Ni Fe layers. By
+generalizing this experimental finding we propose that the generic prerequisite
+for the occurrence of intense magnetoresistance effects in relative trilayers
+is that the coercive fields of the outer ferromagnetic layers should almost
+coincide since the simultaneous occurrence of magnetic domains all over their
+surface will promote a transverse magnetic coupling mediated by the
+accompanying transverse stray fields. Finally, the trilayer's upper-critical
+field exhibits a pronounced suppression for low magnetic fields indicative of a
+behavior, while for high values the conventional behavior is recovered. A
+similar process is observed in both Nb-Ni Fe bilayers and Nb single layers.
+However, significant qualitative and quantitative differences exist between
+these samples. Based on a mechanism that is motivated by longitudinal
+stray-fields existing exclusively in the high-field regime we propose a
+possible interpretation for this experimental finding.",0902.0314v1
+2009-12-16,Protostellar collapse: radiative and magnetic feedbacks on small scale fragmentation,"It is established that both radiative transfer and magnetic field have a
+strong impact on the collapse and the fragmentation of prestellar dense cores,
+but no consistent calculation exists yet at such scales. We present original
+AMR calculations including magnetic field (in the ideal MHD limit) and
+radiative transfer, within the Flux Limited Diffusion approximation, of the
+collapse of a 1 solar mass dense core. We compare the results with calculations
+performed with a barotropic EOS. We show that radiative transfer has an
+important impact on the collapse and the fragmentation, through the cooling or
+heating of the gas, and is complementary of the magnetic field. A larger field
+yields a stronger magnetic braking, increasing the accretion rate and thus the
+effect of the radiative feedback. Even for a strongly magnetized core, where
+the dynamics of the collapse is dominated by the magnetic field, radiative
+transfer is crucial to determine the temperature and optical depth
+distributions, two potentially accessible observational diagnostics. A
+barotropic EOS cannot account for realistic fragmentation. The diffusivity of
+the numerical scheme, however, is found to strongly affect the output of the
+collapse, leading eventually to spurious fragmentation. Both radiative transfer
+and magnetic field must be included in numerical calculations of star formation
+to obtain realistic collapse configurations and observable signatures.
+Nevertheless, the numerical resolution and the robustness of the solver are of
+prime importance to obtain reliable results. When using an accurate solver, the
+fragmentation is found to always remain inhibited by the magnetic field, at
+least in the ideal MHD limit, even when radiative transfer is included.",0912.3138v2
+2010-04-09,Oscillations of weakly viscous conducting liquid drops in a strong magnetic field,"We analyse small-amplitude oscillations of a weakly viscous electrically
+conducting liquid drop in a strong uniform DC magnetic field. An asymptotic
+solution is obtained showing that the magnetic field does not affect the shape
+eigenmodes, which remain the spherical harmonics as in the non-magnetic case.
+Strong magnetic field, however, constrains the liquid flow associated with the
+oscillations and, thus, reduces the oscillation frequencies by increasing
+effective inertia of the liquid. In such a field, liquid oscillates in a
+two-dimensional (2D) way as solid columns aligned with the field. Two types of
+oscillations are possible: longitudinal and transversal to the field. Such
+oscillations are weakly damped by a strong magnetic field - the stronger the
+field, the weaker the damping, except for the axisymmetric transversal and
+inherently 2D modes. The former are overdamped because of being incompatible
+with the incompressibility constraint, whereas the latter are not affected at
+all because of being naturally invariant along the field. Since the magnetic
+damping for all other modes decreases inversely with the square of the field
+strength, viscous damping may become important in a sufficiently strong
+magnetic field. The viscous damping is found analytically by a simple energy
+dissipation approach which is shown for the longitudinal modes to be equivalent
+to a much more complicated eigenvalue perturbation technique. This study
+provides a theoretical basis for the development of new measurement methods of
+surface tension, viscosity and the electrical conductivity of liquid metals
+using the oscillating drop technique in a strong superimposed DC magnetic
+field.",1004.1548v2
+2010-04-26,Magnetic helicity fluxes in an alpha-squared dynamo embedded in a halo,"We present the results of simulations of forced turbulence in a slab where
+the mean kinetic helicity has a maximum near the mid-plane, generating
+gradients of magnetic helicity of both large and small-scale fields. We also
+study systems that have poorly conducting buffer zones away from the midplane
+in order to assess the effects of boundaries. The dynamical alpha quenching
+phenomenology requires that the magnetic helicity in the small-scale fields
+approaches a nearly static, gauge independent state. To stress-test this steady
+state condition we choose a system with a uniform sign of kinetic helicity, so
+that the total magnetic helicity can reach a steady state value only through
+fluxes through the boundary, which are themselves suppressed by the velocity
+boundary conditions. Even with such a set up, the small-scale magnetic helicity
+is found to reach a steady state. In agreement with earlier work, the magnetic
+helicity fluxes of small-scale fields are found to be turbulently diffusive. By
+comparing results with and without halos, we show that artificial constraints
+on magnetic helicity at the boundary do not have a significant impact on the
+evolution of the magnetic helicity, except that ""softer"" (halo) boundary
+conditions give a lower energy of the saturated mean magnetic field.",1004.4591v1
+2010-06-21,Simulation of the Formation of a Solar Active Region,"We present a radiative magnetohydrodynamics simulation of the formation of an
+Active Region on the solar surface. The simulation models the rise of a buoyant
+magnetic flux bundle from a depth of 7.5 Mm in the convection zone up into the
+solar photosphere. The rise of the magnetic plasma in the convection zone is
+accompanied by predominantly horizontal expansion. Such an expansion leads to a
+scaling relation between the plasma density and the magnetic field strength
+such that $B\propto\varrho^{1/2}$. The emergence of magnetic flux into the
+photosphere appears as a complex magnetic pattern, which results from the
+interaction of the rising magnetic field with the turbulent convective flows.
+Small-scale magnetic elements at the surface first appear, followed by their
+gradual coalescence into larger magnetic concentrations, which eventually
+results in the formation of a pair of opposite polarity spots. Although the
+mean flow pattern in the vicinity of the developing spots is directed radially
+outward, correlations between the magnetic field and velocity field
+fluctuations allow the spots to accumulate flux. Such correlations result from
+the Lorentz-force driven, counter-streaming motion of opposite-polarity
+fragments. The formation of the simulated Active Region is accompanied by
+transient light bridges between umbrae and umbral dots. Together with recent
+sunspot modeling, this work highlights the common magnetoconvective origin of
+umbral dots, light bridges and penumbral filaments.",1006.4117v2
+2011-01-15,Disk Formation in Magnetized Clouds Enabled by the Hall Effect,"Stars form in dense cores of molecular clouds that are observed to be
+significantly magnetized. A dynamically important magnetic field presents a
+significant obstacle to the formation of protostellar disks. Recent studies
+have shown that magnetic braking is strong enough to suppress the formation of
+rotationally supported disks in the ideal MHD limit. Whether non-ideal MHD
+effects can enable disk formation remains unsettled. We carry out a first study
+on how disk formation in magnetic clouds is modified by the Hall effect, the
+least explored of the three non-ideal MHD effects in star formation (the other
+two being ambipolar diffusion and Ohmic dissipation). For illustrative
+purposes, we consider a simplified problem of a non-self-gravitating,
+magnetized envelope collapsing onto a central protostar of fixed mass. We find
+that the Hall effect can spin up the inner part of the collapsing flow to
+Keplerian speed, producing a rotationally supported disk. The disk is generated
+through a Hall-induced magnetic torque. Disk formation occurs even when the
+envelope is initially non-rotating, provided that the Hall coefficient is large
+enough. When the magnetic field orientation is flipped, the direction of disk
+rotation is reversed as well. The implication is that the Hall effect can in
+principle produce both regularly rotating and counter-rotating disks around
+protostars. We conclude that the Hall effect is an important factor to consider
+in studying the angular momentum evolution of magnetized star formation in
+general and disk formation in particular.",1101.3018v1
+2011-03-09,Fast Magnetic Reconnection and Spontaneous Stochasticity,"Magnetic field-lines in astrophysical plasmas are expected to be frozen-in at
+scales larger than the ion gyroradius. The rapid reconnection of magnetic flux
+structures with dimensions vastly larger than the gyroradius requires a
+breakdown in the standard Alfv\'en flux-freezing law. We attribute this
+breakdown to ubiquitous MHD plasma turbulence with power-law scaling ranges of
+velocity and magnetic energy spectra. Lagrangian particle trajectories in such
+environments become ""spontaneously stochastic"", so that infinitely-many
+magnetic field-lines are advected to each point and must be averaged to obtain
+the resultant magnetic field. The relative distance between initial magnetic
+field lines which arrive to the same final point depends upon the properties of
+two-particle turbulent dispersion. We develop predictions based on the
+phenomenological Goldreich & Sridhar theory of strong MHD turbulence and on
+weak MHD turbulence theory. We recover the predictions of the Lazarian &
+Vishniac theory for the reconnection rate of large-scale magnetic structures.
+Lazarian & Vishniac also invoked ""spontaneous stochasticity"", but of the
+field-lines rather than of the Lagrangian trajectories. More recent theories of
+fast magnetic reconnection appeal to microscopic plasma processes that lead to
+additional terms in the generalized Ohm's law, such as the collisionless Hall
+term. We estimate quantitatively the effect of such processes on the
+inertial-range turbulence dynamics and find them to be negligible in most
+astrophysical environments. For example, the predictions of the
+Lazarian-Vishniac theory are unchanged in Hall MHD turbulence with an extended
+inertial range, whenever the ion skin depth $\delta_i$ is much smaller than the
+turbulent integral length or injection-scale $L_i.$",1103.1882v2
+2011-09-15,Suppression of the large-scale Lorentz force by turbulence,"The components of the total stress tensor (Reynolds stress plus Maxwell
+stress) are computed within the quasilinear approximation for a driven
+turbulence influenced by a large-scale magnetic background field. The
+conducting fluid has an arbitrary magnetic Prandtl number and the turbulence
+without the background field is assumed as homogeneous and isotropic with a
+free Strouhal number St. The total large-scale magnetic tension is always
+reduced by the turbulence with the possibility of a `catastrophic quenching'
+for large magnetic Reynolds number Rm so that even its sign is reversed. The
+total magnetic pressure is enhanced by turbulence with short correlation time
+(`white noise') but it is reduced by turbulence with long correlation time.
+Also in this case the sign of the total pressure may reverse but only for
+special turbulences with sufficiently large St> 1.
+  The turbulence-induced terms of the stress tensor are suppressed by strong
+magnetic fields. For the tension term this quenching grows with the square of
+the Hartmann number of the magnetic field. For microscopic (i.e. small)
+diffusivity values the magnetic tension term becomes thus highly quenched even
+for field amplitudes much smaller than their equipartition value. In the
+opposite case of large-eddy simulations the magnetic quenching is only mild but
+then also the turbulence-induced Maxwell tensor components for weak fields
+remain rather small.",1109.3345v2
+2011-12-02,General relativistic simulations of black hole-neutron star mergers: Effects of magnetic fields,"As a neutron star (NS) is tidally disrupted by a black hole (BH) companion at
+the end of a BH-NS binary inspiral, its magnetic fields will be stretched and
+amplified. If sufficiently strong, these magnetic fields may impact the
+gravitational waveforms, merger evolution and mass of the remnant disk.
+Formation of highly-collimated magnetic field lines in the disk+spinning BH
+remnant may launch relativistic jets, providing the engine for a short-hard
+GRB. We analyze this scenario through fully general relativistic,
+magnetohydrodynamic (GRMHD) BHNS simulations from inspiral through merger and
+disk formation. Different initial magnetic field configurations and strengths
+are chosen for the NS interior for both nonspinning and moderately spinning
+(a/M=0.75) BHs aligned with the orbital angular momentum. Only strong interior
+(Bmax~10^17 G) initial magnetic fields in the NS significantly influence merger
+dynamics, enhancing the remnant disk mass by 100% and 40% in the nonspinning
+and spinning BH cases, respectively. However, detecting the imprint of even a
+strong magnetic field may be challenging for Advanced LIGO. Though there is no
+evidence of mass outflows or magnetic field collimation during the preliminary
+simulations we have performed, higher resolution, coupled with longer disk
+evolutions and different initial magnetic field configurations, may be required
+to definitively assess the possibility of BHNS binaries as short-hard GRB
+progenitors.",1112.0568v4
+2011-12-16,Response of the Photospheric Magnetic Field to the X2.2 Flare on 2011 February 15,"It is well known that the long-term evolution of the photospheric magnetic
+field plays an important role in building up free energy to power solar
+eruptions. Observations, despite being controversial, have also revealed a
+rapid and permanent variation of the photospheric magnetic field in response to
+the coronal magnetic field restructuring during the eruption. The Helioseismic
+and Magnetic Imager instrument (HMI) on board the newly launched Solar Dynamics
+Observatory (SDO) produces seeing-free full-disk vector magnetograms at
+consistently high resolution and high cadence, which finally makes possible an
+unambiguous and comprehensive study of this important back-reaction process. In
+this study, we present a near disk-center, GOES -class X2.2 flare, which
+occurred in NOAA AR 11158 on 2011 February 15. Using the magnetic field
+measurements made by HMI, we obtained the first solid evidence of a rapid (in
+about 30 minutes) and irreversible enhancement in the horizontal magnetic field
+at the flaring magnetic polarity inversion line (PIL) by a magnitude of ~30%.
+It is also shown that the photospheric field becomes more sheared and more
+inclined. This field evolution is unequivocally associated with the flare
+occurrence in this sigmoidal active region, with the enhancement area located
+in between the two chromospheric flare ribbons and the initial conjugate hard
+X-ray footpoints. These results strongly corroborate our previous conjecture
+that the photospheric magnetic field near the PIL must become more horizontal
+after eruptions, which could be related to the newly formed low-lying fields
+resulted from the tether-cutting reconnection.",1112.3948v1
+2012-03-09,Requirements for the Analysis of Quiet Sun Internetwork Magnetic Elements with EST and ATST,"The quiet Sun internetwork is permeated by weak and highly inclined magnetic
+fields whose physical properties, dynamics, and magnetic interactions are not
+fully understood. High spatial resolution magnetograms show them as discrete
+magnetic elements that appear/emerge and disappear/cancel continuously over the
+quiet Sun surface. The 4-m European Solar Telescope (EST) and the Advanced
+Technology Solar Telescope (ATST) will obtain two-dimensional, high cadence,
+high precision polarimetric measurements at the diffraction limit (30 km).
+Here, we compile the basic requirements for the observation of internetwork
+fields with EST and ATST (field of view, cadence, instrument configuration,
+etc). More specifically, we concentrate on the field-of-view requirements. To
+set them we analyze the proper motion of internetwork magnetic elements across
+the solar surface. We use 13 hours of magnetograms taken with the Hinode
+satellite to identify and track thousands of internetwork magnetic element in
+an isolated supergranular cell. We calculate the velocity components of each
+element and the mean distance they travel. The results show that, on average,
+magnetic elements in the interior of supergranular cells move toward the
+network. The radial velocity is observed to depend on the distance to the
+center of the supergranule. Internetwork magnetic elements travel 400 on
+average. These results suggest that ATST and EST should cover, at least, one
+supergranular cell to obtain a complete picture of the quiet Sun internetwork.",1203.2185v1
+2012-03-20,Linear stability analysis of the Hall magnetorotational instability in a spherical domain,"We investigate the stability of the Hall-MHD system and determine its
+importance for neutron stars at their birth, when they still consist of
+differentially rotating plasma permeated by extremely strong magnetic fields.
+We solve the linearised Hall-MHD equations in a spherical shell threaded by a
+homogeneous magnetic field. With the fluid/flow coupling and the Hall effect
+included, the magnetorotational instability and the Hall effect are both acting
+together. Results differ for magnetic fields aligned with the rotation axis and
+anti-parallel magnetic fields. For a positive alignment of the magnetic field
+the instability grows on a rotational time-scale for any sufficiently large
+magnetic Reynolds number. Even the magnetic fields which are stable against the
+MRI due to the magnetic diffusion are now susceptible to the shear-Hall
+instability. In contrast, the negative alignment places strong restrictions on
+the growth and the magnitude of the fields, hindering the effectiveness of the
+Hall-MRI. While non-axisymmetric modes of the MRI can be suppressed by strong
+enough rotation, there is no such restriction when the Hall effect is present.
+The implications for the magnitude and the topology of the magnetic field of a
+young neutron star may be significant.",1203.4348v2
+2012-09-27,Flares and Magnetic Non-potentiality of NOAA AR 11158,"The magnetic non-potentiality is important for understanding flares and other
+solar activities in active regions (ARs). Five non-potential parameters, i.e.,
+electric current, current helicity, source field, photospheric free energy, and
+angular shear, are calculated in this work to quantify the non-potentiality of
+NOAA AR 11158. Benefited from high spatial resolution, high cadence, and
+continuously temporal coverage of vector magnetograms from the Helioseismic and
+Magnetic Imager on board the Solar Dynamics Observatory, both the long-term
+evolution of the AR and the rapid change during flares have been studied. We
+confirmed that, comparing with the magnetic flux, the magnetic non-potentiality
+has a closer connection with the flare, and the emerging flux regions are
+important for the magnetic non-potentiality and flares. The main results of
+this work are as follows. (1) The vortex in the source field directly displays
+the deflection of horizontal magnetic field. The deflection is corresponding to
+the fast rotated sunspot with a time delay, which suggests that the sunspot
+rotation leads to an increase of the non-potentiality. (2) Two areas that have
+evident changes of the azimuth of the vector magnetic field are found near the
+magnetic polarity inversion line. The change rates of the azimuth are about 1.3
+deg/h and 3.6 deg/h, respectively. (3) Rapid and prominent increases are found
+in the variation of helicity during four flares in their initial brightening
+regions. The recovery of the increases takes 3-4 h for the two biggest flares
+(X2.2 and M6.6), while only takes about 2 h for the other two smaller flares
+(M2.2 and M1.6).",1209.6192v1
+2012-10-14,Self-induced pinning of vortices in the presence of ac driving force in magnetic superconductors,"We derive the response of the magnetic superconductors in the vortex state to
+the ac Lorentz force, $F_L(t)=F_{{\rm ac}}\sin(\omega t)$, taking into account
+the interaction of vortices with the magnetic moments described by the
+relaxation dynamics (polaronic effect). At low amplitudes of the driving force
+$F_{{\rm ac}}$ the dissipation in the system is suppressed due to the
+enhancement of the effective viscosity at low frequencies and due to formation
+of the magnetic pinning at high frequencies $\omega$. In the adiabatic limit
+with low frequencies $\omega$ and high amplitude of the driving force $F_{ac}$,
+the vortex and magnetic polarization form a vortex polaron when $F_L(t)$ is
+small. When $F_L$ increases, the vortex polaron accelerates and at a threshold
+driving force, the vortex polaron dissociates and the motion of vortex and the
+relaxation of magnetization are decoupled. When $F_L$ decreases, the vortex is
+retrapped by the background of remnant magnetization and they again form vortex
+polaron. This process repeats when $F_L(t)$ increases in the opposite
+direction. Remarkably, after dissociation, decoupled vortices move in the
+periodic potential induced by magnetization which remains for some periods of
+time due to retardation after the decoupling. At this stage vortices oscillate
+with high frequencies determined by the Lorentz force at the moment of
+dissociation. We derive also the creep rate of vortices and show that magnetic
+moments suppress creep rate.",1210.3820v2
+2012-12-05,"High Precision Magnetic Linear Dichroism Measurements in (Ga,Mn)As","Investigation of magnetic materials using the first-order magneto-optical
+Kerr effects (MOKE) is well established and is frequently used in the
+literature. On the other hand, the utilization of the second-order (or
+quadratic) magneto-optical (MO) effects for the material research is rather
+rare. This is due to the small magnitude of quadratic MO signals and the fact
+that the signals are even in magnetization (i.e., they do not change a sign
+when the magnetization orientation is flipped), which makes it difficult to
+separate second-order MO signals from various experimental artifacts. In 2005 a
+giant quadratic MO effect - magnetic linear dichroism (MLD) - was observed in
+the ferromagnetic semiconductor (Ga,Mn)As. This discovery not only provided a
+new experimental tool for the investigation of in-plane magnetization dynamics
+in (Ga,Mn)As using light at normal incidence, but it also motivated the
+development of experimental techniques for the measurement of second-order MO
+effects in general. In this paper we compare four different experimental
+techniques that can be used to measure MLD and to separate it from experimental
+artifacts. We show that the most reliable results are obtained when the
+harmonic dependence of MLD on a mutual orientation of magnetization and light
+polarization plane is used together with the in-situ rotation of the sample
+followed by the magnetic field-induced rotation of magnetization. Using this
+technique we measure the MLD spectra of (Ga,Mn)As in a broad spectral range
+from 0.1 eV to 2.7 eV and we observe that MLD has a comparable magnitude as
+polar MOKE signals in this material.",1212.0956v1
+2012-12-21,Magnetic fields in our Milky Way Galaxy and nearby galaxies,"Magnetic fields in our Galaxy and nearby galaxies have been revealed by
+starlight polarization, polarized emission from dust grains and clouds at
+millimeter and submillimeter wavelength, the Zeeman effect of spectral lines or
+maser lines from clouds or clumps, diffuse radio synchrotron emission from
+relativistic electrons in interstellar magnetic fields, and the Faraday
+rotation of background radio sources as well as pulsars for our Milky Way. It
+is easy to get a global structure for magnetic fields in nearby galaxies, while
+we have observed many details of magnetic fields in our Milky Way, especially
+by using pulsar rotation measure data. In general, magnetic fields in spiral
+galaxies probably have a large-scale structure. The fields follow the spiral
+arms with or without the field direction reversals. In the halo of spiral
+galaxies magnetic fields exist and probably also have a large-scale structure
+as toroidal and poloidal fields, but seem to be slightly weaker than those in
+the disk. In the central region of some galaxies, poloidal fields have been
+detected as vertical components. Magnetic field directions in galaxies seem to
+have been preserved during cloud formation and star formation, from large-scale
+diffuse interstellar medium to molecular clouds and then to the cloud cores in
+star formation regions or clumps for the maser spots. Magnetic fields in
+galaxies are passive to dynamics.",1212.5464v2
+2013-01-08,Magnetic energy cascade in spherical geometry: I. The stellar convective dynamo case,"We present a method to characterize the spectral transfers of magnetic energy
+between scales in simulations of stellar convective dynamos. The full triadic
+transfer functions are computed thanks to analytical coupling relations of
+spherical harmonics based on the Clebsch-Gordan coefficients. The method is
+applied to mean field $\alpha\Omega$ dynamo models as benchmark tests. From the
+physical standpoint, the decomposition of the dynamo field into primary and
+secondary dynamo families proves very instructive in the $\alpha\Omega$ case.
+The same method is then applied to a fully turbulent dynamo in a solar
+convection zone, modeled with the 3D MHD ASH code. The initial growth of the
+magnetic energy spectrum is shown to be non-local. It mainly reproduces the
+kinetic energy spectrum of convection at intermediate scales. During the
+saturation phase, two kinds of direct magnetic energy cascades are observed in
+regions encompassing the smallest scales involved in the simulation. The first
+cascade is obtained through the shearing of magnetic field by the large scale
+differential rotation that effectively cascades magnetic energy. The second is
+a generalized cascade that involves a range of local magnetic and velocity
+scales. Non-local transfers appear to be significant, such that the net
+transfers cannot be reduced to the dynamics of a small set of modes. The
+saturation of the large scale axisymmetric dipole and quadrupole are detailed.
+In particular, the dipole is saturated by a non-local interaction involving the
+most energetic scale of the magnetic energy spectrum, which points out the
+importance of the magnetic Prandtl number for large-scale dynamos.",1301.1606v1
+2014-03-21,Imaging superconducting vortex core and lattice with the scanning tunneling microscope,"The observation of vortices in superconductors was a major breakthrough in
+developing the conceptual background for superconducting applications. Each
+vortex carries a flux quantum, and the magnetic field radially decreases from
+the center. Techniques used to make magnetic field maps, such as magnetic
+decoration, give vortex lattice images in a variety of systems. However, strong
+type II superconductors allow penetration of the magnetic field over large
+distances, of order of the magnetic penetration depth \lambda.
+Superconductivity survives up to magnetic fields where, for imaging purposes,
+there is nearly no magnetic contrast. Static and dynamic properties of vortices
+are largely unknown at such high magnetic fields. Reciprocal space studies
+using neutron scattering give insight into the collective behavior. But the
+microscopic details of vortex arrangements and their motion remain difficult to
+obtain. Direct real space visualization can be made using scanning tunneling
+microscopy and spectroscopy (STM/S). Instead of using magnetic contrast, the
+electronic density of states describes spatial variations of the quasiparticle
+and pair wavefunction properties. These are of order of the superconducting
+coherence length \xi, which is much smaller than \lambda. In principle,
+individual vortices can be imaged using STM up to the upper critical field
+where vortex cores, of size \xi, overlap. In this review, we describe recent
+advances in vortex imaging made with scanning tunneling microscopy and
+spectroscopy. We introduce the technique and discuss vortex images which reveal
+the influence of the Fermi surface distribution of the superconducting gap on
+the internal structure of vortices, the collective behavior of the lattice in
+different materials and conditions, and the observation of vortex lattice
+melting.",1403.5514v1
+2014-06-02,Low-metallicity star formation: Relative impact of metals and magnetic fields,"Low-metallicity star formation poses a central problem of cosmology, as it
+determines the characteristic mass scale and distribution for the first and
+second generations of stars forming in our Universe. Here, we present a
+comprehensive investigation assessing the relative impact of metals and
+magnetic fields, which may both be present during low-metallicity star
+formation. We show that the presence of magnetic fields generated via the
+small-scale dynamo stabilises the protostellar disc and provides some degree of
+support against fragmentation. In the absence of magnetic fields, the
+fragmentation timescale in our model decreases by a factor of ~10 at the
+transition from Z=0 to Z>0, with subsequently only a weak dependence on
+metallicity. Similarly, the accretion timescale of the cluster is set by the
+large-scale dynamics rather than the local thermodynamics. In the presence of
+magnetic fields, the primordial disc can become completely stable, therefore
+forming only one central fragment. At Z>0, the number of fragments is somewhat
+reduced in the presence of magnetic fields, though the shape of the mass
+spectrum is not strongly affected in the limits of the statistical
+uncertainties. The fragmentation timescale, however, increases by roughly a
+factor of 3 in the presence of magnetic fields. Indeed, our results indicate
+comparable fragmentation timescales in primordial runs without magnetic fields
+and Z>0 runs with magnetic fields.",1406.0346v1
+2014-07-11,Modelling MHD accretion-ejection - from the launching area to propagation scales,"We present results of axisymmetric magnetohydrodynamic (MHD) simulations
+investigating the launching of jets and outflows from a magnetically diffusive
+accretion disk. The time evolution of the disk structure is self-consistently
+taken into account. In contrast to previous works we have applied {\em
+spherical} coordinates for the numerical grid, implying substantial benefits
+concerning the numerical resolution and the stability of the simulation. Thanks
+to the new setup we were able to run simulations for more than 150,000
+dynamical times on a domain extending 1500 inner disk radii with a resolution
+of up to 24 cells per disk height in the inner disk. Depending on the disk
+magnetization, jet launching occurs in two different but complementary regimes
+- jets driven predominantly by centrifugal or magnetic forces. These regimes
+differ in the ejection efficiency concerning mass, energy and angular momentum.
+We show that it is the {\em actual} disk magnetization and not so much the
+initial magnetization which describes the disk-jet evolution best. Considering
+the actual disk magnetization we also find that simulations starting with
+different initial magnetization evolve in a similar - typical - way as due to
+advection and diffusion the magnetic flux in the disk evolves in time.
+Exploring a new, modified diffusivity model we confirm the self-similar
+structure of the global jet-launching disk, obtaining power laws for the radial
+profiles of the disk physical variables such as density, magnetic field
+strength, or accretion velocity.",1407.3136v1
+2015-02-06,The magnetic structure of surges in small-scale emerging flux regions,"Aims: To investigate the relationship between surges and magnetic
+reconnection during the emergence of small-scale active regions. In particular,
+to examine how the large-scale geometry of the magnetic field, shaped by
+different phases of reconnection, guides the flowing of surges. Methods: We
+present three flux emergence models. The first model, and the simplest,
+consists of a region emerging into a horizontal ambient field that is initially
+parallel to the top of the emerging region. The second model is the same as the
+first but with an extra smaller emerging region which perturbs the main region.
+This is added to create a more complex magnetic topology and to test how this
+complicates the development of surges compared to the first model. The last
+model has a non-uniform ambient magnetic field to model the effects of
+emergence near a sunspot field and impose asymmetry on the system through the
+ambient magnetic field. At each stage, we trace the magnetic topology to
+identify the locations of reconnection. This allows for field lines to be
+plotted from different topological regions, highlighting how their geometry
+affects the development of surges. Results: In the first model, we identify
+distinct phases of reconnection. Each phase is associated with a particular
+geometry for the magnetic field and this determines the paths of the surges.
+The second model follows a similar pattern to the first but with a more complex
+magnetic topology and extra eruptions. The third model highlights how an
+asymmetric ambient field can result in preferred locations for reconnection,
+subsequently guiding the direction of surges.",1502.01842v1
+2015-03-25,Rigorous numerical study of strong microwave photon-magnon coupling in all-dielectric magnetic multilayers,"We demonstrate theoretically a strong local enhancement of the intensity of
+the in-plane microwave magnetic field in multilayered structures made from a
+magneto-insulating yttrium iron garnet (YIG) layer sandwiched between two
+non-magnetic layers with a high dielectric constant matching that of YIG. The
+enhancement is predicted for the excitation regime when the microwave magnetic
+field is induced inside the multilayer by the transducer of a stripline
+Broadband Ferromagnetic Resonance (BFMR) setup. By means of a rigorous
+numerical solution of the Landau-Lifshitz-Gilbert equation consistently with
+the Maxwell's equations, we investigate the magnetisation dynamics in the
+multilayer. We reveal a strong photon-magnon coupling, which manifests itself
+as anti-crossing of the ferromagnetic resonance (FMR) magnon mode supported by
+the YIG layer and the electromagnetic resonance mode supported by the whole
+multilayered structure. The frequency of the magnon mode depends on the
+external static magnetic field, which in our case is applied tangentially to
+the multilayer in the direction perpendicular to the microwave magnetic field
+induced by the stripline of the BFMR setup. The frequency of the
+electromagnetic mode is independent of the static magnetic field. Consequently,
+the predicted photon-magnon coupling is sensitive to the applied magnetic field
+and thus can be used in magnetically tuneable metamaterials based on
+simultaneously negative permittivity and permeability achievable thanks to the
+YIG layer. We also suggest that the predicted photon-magnon coupling may find
+applications in microwave quantum information systems.",1503.07282v1
+2015-08-22,3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere,"The outer solar atmosphere, i.e., the corona and the chromosphere, is replete
+with small energy-release events, which are accompanied by transient
+brightening and jet-like ejections. These events are considered to be magnetic
+reconnection events in the solar plasma, and their dynamics have been studied
+using recent advanced observations from the Hinode spacecraft and other
+observatories in space and on the ground. These events occur at different
+locations in the solar atmosphere, and vary in their morphology and amount of
+the released energy. The magnetic field configurations of these reconnection
+events are inferred based on observations of magnetic fields at the
+photospheric level. Observations suggest that these magnetic configurations can
+be classified into two groups. In the first group, two anti-parallel magnetic
+fields reconnect to each other, yielding a 2D emerging flux configuration. In
+the second group, helical or twisted magnetic flux tubes are parallel or at a
+relative angle to each other. Reconnection can occur only between anti-parallel
+components of the magnetic flux tubes and may be referred to as component
+reconnection. The latter configuration type may be more important for the
+larger class of small-scale reconnection events. The two types of magnetic
+configurations can be compared to counter-helicity and co-helicity
+configurations, respectively, in laboratory plasma collision experiments.",1508.05481v1
+2015-12-14,The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo,"A novel large-scale dynamo mechanism, the magnetic shear-current effect, is
+discussed and explored. The effect relies on the interaction of magnetic
+fluctuations with a mean shear flow, meaning the saturated state of the
+small-scale dynamo can drive a large-scale dynamo -- in some sense the inverse
+of dynamo quenching. The dynamo is nonhelical, with the mean-field $\alpha$
+coefficient zero, and is caused by the interaction between an off-diagonal
+component of the turbulent resistivity and the stretching of the large-scale
+field by shear flow. Following up on previous numerical and analytic work, this
+paper presents further details of the numerical evidence for the effect, as
+well as an heuristic description of how magnetic fluctuations can interact with
+shear flow to produce the required electromotive force. The pressure response
+of the fluid is fundamental to this mechanism, which helps explain why the
+magnetic effect is stronger than its kinematic cousin, and the basic idea is
+related to the well-known lack of turbulent resistivity quenching by magnetic
+fluctuations. As well as being interesting for its applications to general high
+Reynolds number astrophysical turbulence, where strong small-scale magnetic
+fluctuations are expected to be prevalent, the magnetic shear-current effect is
+a likely candidate for large-scale dynamo in the unstratified regions of
+ionized accretion disks. Evidence for this is discussed, as well as future
+research directions and the challenges involved with understanding details of
+the effect in astrophysically relevant regimes.",1512.04511v2
+2016-03-14,Lifshitz scaling effects on holographic paramagnetism/ferromagneism phase transition,"In the probe limit, we investigate holographic paramagnetism-ferromagnetism
+phase transition in the four-dimensional (4D) and five-dimensional(5D) Lifshitz
+black holes by means of numerical and semi-analytical methods, which is
+realized by introducing a massive 2-form field coupled to the Maxwell field. We
+find that the Lifshitz dynamical exponent $z$ contributes evidently to magnetic
+moment and hysteresis loop of single magnetic domain quantitatively not
+qualitatively. Concretely, in the case without external magnetic field, the
+spontaneous magnetization and ferromagnetic phase transition happen when the
+temperature gets low enough, and the critical exponent for the magnetic moment
+is always $1/2$, which is in agreement with the result from mean field theory.
+And the increasing $z$ enhances the phase transition and increases the DC
+resistivity which behaves as the colossal magnetic resistance effect in some
+materials. Furthermore, in the presence of the external magnetic field, the
+magnetic susceptibility satisfies the Cure-Weiss law with a general $z$. But
+the increase of $z$ will result in shortening the period of the external
+magnetic field.",1603.04149v1
+2016-04-25,Dynamically flavored description of holographic QCD in the presence of a magnetic field,"We construct the gravitational solution of the Witten-Sakai-Sugimoto model by
+introducing a magnetic field on the flavor brane. With taking into account
+their backreaction, we re-solve the type IIA supergravity in the presence of
+the magnetic field. Our calculation shows the gravitational solutions are
+magnetic-dependent and analytic both in the bubble (confined) and black brane
+(deconfined) case. We study the dual field theory at the leading order in the
+ratio of the number of flavors and colors, also in the Veneziano limit. Some
+physical properties related to the hadronic physics in an external magnetic
+field are discussed by using our confined backreaction solution
+holographically. We also investigate the thermodynamics and holographic
+renormalization of this model in both phases by our solution. Since the
+backreaction of the magnetic field is considered in our gravitational solution,
+it allows us to study the Hawking-Page transition with flavors and colors of
+this model in the presence of the magnetic field. Finally we therefore obtain
+the holographic phase diagram with the contributions from the flavors and the
+magnetic field. Our holographic phase diagram is in agreement with lattice QCD
+result qualitatively, which thus can be interpreted as the inhibition of
+confinement or chirally broken symmetry by the magnetic field.",1604.07197v6
+2016-05-12,Temporal and spatial relationship of flare signatures and the force-free coronal magnetic field,"We investigate the plasma and magnetic environment of active region NOAA
+11261 on 2 August 2011 around a GOES M1.4 flare/CME (SOL2011-08-02T06:19). We
+compare coronal emission at (extreme) ultraviolet and X-ray wavelengths, using
+SDO AIA and RHESSI images, in order to identify the relative timing and
+locations of reconnection-related sources. We trace flare ribbon signatures at
+ultraviolet wavelengths, in order to pin down the intersection of previously
+reconnected flaring loops at the lower solar atmosphere. These locations are
+used to calculate field lines from 3D nonlinear force-free magnetic field
+models, established on the basis of SDO HMI photospheric vector magnetic field
+maps. With this procedure, we analyze the quasi-static time evolution of the
+coronal model magnetic field previously involved in magnetic reconnection. This
+allows us, for the first time, to estimate the elevation speed of the current
+sheet's lower tip during an on-disk observed flare, as a few kilometers per
+second. Comparison to post-flare loops observed later above the limb in STEREO
+EUVI images supports this velocity estimate. Furthermore, we provide evidence
+for an implosion of parts of the flaring coronal model magnetic field, and
+identify the corresponding coronal sub-volumes associated to the loss of
+magnetic energy. Finally, we spatially relate the build up of magnetic energy
+in the 3D models to highly sheared fields, established due to dynamic relative
+motions of polarity patches within the active region.",1605.03703v1
+2016-07-22,Magnetic diffuse scattering in artificial kagome spin ice,"The study of magnetic correlations in dipolar-coupled nanomagnet systems with
+synchrotron x-ray scattering provides a means to uncover emergent phenomena and
+exotic phases, in particular in systems with thermally active magnetic moments.
+From the diffuse signal of soft x-ray resonant magnetic scattering, we have
+measured magnetic correlations in a highly dynamic artificial kagome spin ice
+with sub-70-nm Permalloy nanomagnets. On comparing experimental scattering
+patterns with Monte Carlo simulations based on a needle-dipole model, we
+conclude that kagome ice I phase correlations exist in our experimental system
+even in the presence of moment fluctuations, which is analogous to bulk spin
+ice and spin liquid behavior. In addition, we describe the emergence of
+quasi-pinch-points in the magnetic diffuse scattering in the kagome ice I
+phase. These quasi-pinch-points bear similarities to the fully developed pinch
+points with singularities of a magnetic Coulomb phase, and continually evolve
+into the latter on lowering the temperature. The possibility to measure
+magnetic diffuse scattering with soft x rays opens the way to study magnetic
+correlations in a variety of nanomagnetic systems.",1607.06673v1
+2016-07-28,Convection-driven kinematic dynamos at low Rossby and magnetic Prandtl numbers,"Most large-scale planetary magnetic fields are thought to be driven by low
+Rossby number convection of a low magnetic Prandtl number fluid. Here kinematic
+dynamo action is investigated with an asymptotic, rapidly rotating dynamo model
+for the plane layer geometry that is intrinsically low magnetic Prandtl number.
+The thermal Prandtl number and Rayleigh number are varied to illustrate
+fundamental changes in flow regime, ranging from laminar cellular convection to
+geostrophic turbulence in which an inverse energy cascade is present. A
+decrease in the efficiency of the convection to generate a dynamo, as
+determined by an increase in the critical magnetic Reynolds number, is observed
+as the buoyancy forcing is increased. This decreased efficiency may result from
+both the loss of correlations associated with the increasingly disordered
+states of flow that are generated, and boundary layer behavior that enhances
+magnetic diffusion locally. We find that the spatial characteristics of
+$\alpha$, and thus the large-scale magnetic field, is dependent only weakly on
+changes in flow behavior. However, our results are limited to the linear,
+kinematic dynamo regime, and future simulations including the Lorentz force are
+therefore necessary to assess the robustness of this result. In contrast to the
+large-scale magnetic field, the behavior of the small-scale magnetic field is
+directly dependent on, and therefore shows significant variations with, the
+small-scale convective flow field.",1607.08346v1
+2017-01-16,Noncollinear magnetic ordering in the Shastry-Sutherland Kondo lattice model: Insulating regime and the role of Dzyaloshinskii-Moriya interaction,"We investigate the necessary conditions for the emergence of complex,
+noncoplanar magnetic configurations in a Kondo lattice model with classical
+local moments on the geometrically frustrated Shastry-Sutherland lattice and
+their evolution in an external magnetic field. We demonstrate that
+topologically nontrivial spin textures, including a new canted flux state, with
+nonzero scalar chirality arise dynamically from realistic short-range
+interactions. Our results establish that a finite Dzyaloshinskii-Moriya (DM)
+interaction is necessary for the emergence of these novel magnetic states when
+the system is at half filling, for which the ground state is insulating. We
+identify the minimal set of DM vectors that are necessary for the stabilization
+of chiral magnetic phases. The noncoplanarity of such structures can be tuned
+continually by applying an external magnetic field. This is the first part in a
+series of two papers; in the following paper the effects of frustration,
+thermal fluctuations, and magnetic field on the emergence of novel noncollinear
+states at metallic filling of itinerant electrons are discussed. Our results
+are crucial in understanding the magnetic and electronic properties of the
+rare-earth tetraboride family of frustrated magnets with separate spin and
+charge degrees of freedom.",1701.04297v2
+2017-09-13,Distortion of Magnetic Fields in a Starless Core II: 3D Magnetic Field Structure of FeSt 1-457,"Three dimensional (3D) magnetic field information on molecular clouds and
+cores is important for revealing their kinematical stability (magnetic support)
+against gravity which is fundamental for studying the initial conditions of
+star formation. In the present study, the 3D magnetic field structure of the
+dense starless core FeSt 1-457 is determined based on the near-infrared
+polarimetric observations of the dichroic polarization of background stars and
+simple 3D modeling. With an obtained angle of line-of-sight magnetic
+inclination axis $\theta_{\rm inc}$ of $45^{\circ}\pm10^{\circ}$ and previously
+determined plane-of-sky magnetic field strength $B_{\rm pol}$ of $23.8\pm12.1$
+$\mu{\rm G}$, the total magnetic field strength for FeSt 1-457 is derived to be
+$33.7\pm18.0$ $\mu{\rm G}$. The critical mass of FeSt 1-457, evaluated using
+both magnetic and thermal/turbulent support is ${M}_{\rm cr} = 3.70\pm0.92$
+${\rm M}_{\odot}$, which is identical to the observed core mass, $M_{\rm
+core}=3.55\pm0.75$ ${\rm M}_{\odot}$. We thus conclude that the stability of
+FeSt 1-457 is in a condition close to the critical state. Without infalling gas
+motion and no associated young stars, the core is regarded to be in the
+earliest stage of star formation, i.e., the stage just before the onset of
+dynamical collapse following the attainment of a supercritical condition. These
+properties would make FeSt 1-457 one of the best starless cores for future
+studies of the initial conditions of star formation.",1709.04544v2
+2017-10-04,The dynamo effect in decaying helical turbulence,"We show that in decaying hydromagnetic turbulence with initial kinetic
+helicity, a weak magnetic field eventually becomes fully helical. The sign of
+magnetic helicity is opposite to that of the kinetic helicity - regardless of
+whether or not the initial magnetic field was helical. The magnetic field
+undergoes inverse cascading with the magnetic energy decaying approximately
+like t^{-1/2}. This is even slower than in the fully helical case, where it
+decays like t^{-2/3}. In this parameter range, the product of magnetic energy
+and correlation length raised to a certain power slightly larger than unity, is
+approximately constant. This scaling of magnetic energy persists over long time
+scales. At very late times and for domain sizes large enough to accommodate the
+growing spatial scales, we expect a cross-over to the t^{-2/3} decay law that
+is commonly observed for fully helical magnetic fields. Regardless of the
+presence or absence of initial kinetic helicity, the magnetic field experiences
+exponential growth during the first few turnover times, which is suggestive of
+small-scale dynamo action. Our results have applications to a wide range of
+experimental dynamos and astrophysical time-dependent plasmas, including
+primordial turbulence in the early universe.",1710.01628v4
+2017-10-20,Tidal dissipation in rotating fluid bodies: the presence of a magnetic field,"We investigate effects of the presence of a magnetic field on tidal
+dissipation in rotating fluid bodies. We consider a simplified model consisting
+of a rigid core and a fluid envelope, permeated by a background magnetic field
+(either a dipolar field or a uniform axial field). The wavelike tidal responses
+in the fluid layer are in the form of magnetic-Coriolis waves, which are
+restored by both the Coriolis force and the Lorentz force. Energy dissipation
+occurs through viscous damping and Ohmic damping of these waves. Our numerical
+results show that the tidal dissipation can be dominated by Ohmic damping even
+with a weak magnetic field. The presence of a magnetic field smooths out the
+complicated frequency-dependence of the dissipation rate, and broadens the
+frequency spectrum of the dissipation rate, depending on the strength of the
+background magnetic field. However, the frequency-averaged dissipation is
+independent of the strength and structure of the magnetic field, and of the
+dissipative parameters, in the approximation that the wave-like response is
+driven only by the Coriolis force acting on the non-wavelike tidal flow.
+Indeed, the frequency-averaged dissipation quantity is in good agreement with
+previous analytical results in the absence of magnetic fields. Our results
+suggest that the frequency-averaged tidal dissipation of the wavelike
+perturbations is insensitive to detailed damping mechanisms and dissipative
+properties.",1710.07690v2
+2017-11-17,"Frustrated magnetism in tetragonal CoSe, analogue to superconducting FeSe","Recently synthesized metastable tetragonal CoSe, isostructural to the FeSe
+superconductor, offers a new avenue for investigating systems in close
+proximity to the iron-based superconductors. We present magnetic and transport
+property measurements on powders and single crystals of CoSe. High field
+magnetic susceptibility measurements indicate a suppression of the previously
+reported 10 K ferromagnetic transition with the magnetic susceptibility
+exhibiting time-dependence below the proposed transition. Dynamic scaling
+analysis of the time-dependence yields a critical relaxation time of $\tau^{*}
+= 0.064 \pm 0.008 $ s which in turn yields an activation energy of $E_{a}^{*}$
+= 14.84 $\pm$ 0.59 K and an ideal glass temperature $T_{0}^{*}$ = 8.91 $\pm$
+0.09 K from Vogel-Fulcher analysis. No transition is observed in resistivity
+and specific heat measurements, but both measurements indicate that CoSe is
+metallic. These results are interpreted on the basis of CoSe exhibiting
+frustrated magnetic ordering arising from competing magnetic interactions.
+Arrott analysis of single crystal magnetic susceptibility has indicated that
+the magnetic moments lie in the $ab$-plane so frustration may arise from
+intralayer magnetic fluctuations as well as interlayer coupling. The results
+have implications for understanding the superconductivity in the iron
+chalcogenide systems as well as utilizing CoSe as a host for chemical and
+physical manipulation to tune and explore emergent phenomena within an
+expanding new class of transition metal chalcogenides.",1711.06725v2
+2017-12-02,Magnetic reconnection in strongly magnetized regions of the low solar chromosphere,"Magnetic reconnection in strongly magnetized regions around the temperature
+minimum region of the low solar atmosphere is studied by employing MHD-based
+simulations of a partially ionized plasma within a reactive 2.5D multi-fluid
+model. It is shown that in the absence of magnetic nulls in a low $\beta$
+plasma the ionized and neutral fluid flows are well-coupled throughout the
+reconnection region. However, non-equilibrium ionization-recombination dynamics
+play a critical role in determining the structure of the reconnection region,
+lead to much lower temperature increases and a faster magnetic reconnection
+rate as compared to simulations that assume plasma to be in
+ionization-recombination equilibrium. The rate of ionization of the neutral
+component of the plasma is always faster than recombination within the current
+sheet region even when the initial plasma $\beta$ is as high as $\beta_0=1.46$.
+When the reconnecting magnetic field is in excess of a kilogauss and the plasma
+$\beta$ is lower than 0.0145, the initially weakly ionized plasmas can become
+fully ionized within the reconnection region and the current sheet can be
+strongly heated to above $2.5\times10^4$~K, even as most of the collisionally
+dissipated magnetic energy is radiated away. The Hall effect increases the
+reconnection rate slightly, but in the absence of magnetic nulls it does not
+result in significant asymmetries or change the characteristics of the
+reconnection current sheet down to meter scales.",1712.00582v2
+2017-12-12,Magnetic Activity in the Galactic Centre Region -- Fast Downflows along Rising Magnetic Loops,"We studied roles of the magnetic field on the gas dynamics in the Galactic
+bulge by a three-dimensional global magnetohydrodynamical simulation data,
+particularly focusing on vertical flows that are ubiquitously excited by
+magnetic activity. In local regions where the magnetic filed is stronger, it is
+frequently seen that fast down-flows slide along inclined magnetic field lines
+that are associated with buoyantly rising magnetic loops. The vertical velocity
+of these down-flows reaches ~ 100 km s$^{-1}$ near the foot-point of the loops
+by the gravitational acceleration toward the Galactic plane. The two footpoints
+of rising magnetic loops are generally located at different radial locations
+and the field lines are deformed by the differential rotation. The angular
+momentum is transported along the field lines, and the radial force balance
+breaks down. As a result, a fast downflow is often observed only at the one
+footpoint located at the inner radial position. The fast downflow compresses
+the gas to form a dense region near the footpoint, which will be important in
+star formation afterward. Furthermore, the horizontal components of the
+velocity are also fast near the foot-point because the down-flow is accelerated
+along the magnetic sliding slope. As a result, the high-velocity flow creates
+various characteristic features in a simulated position-velocity diagram,
+depending on the viewing angle.",1712.04209v2
+2018-04-16,Magnetic reconnection in the low solar chromosphere with a more realistic radiative cooling model,"Magnetic reconnection is the most likely mechanism responsible for the high
+temperature events that are observed in strongly magnetized locations around
+the temperature minimum in the low solar chromosphere. This work improves upon
+our previous work [""Magnetic Reconnection in Strongly Magnetized Regions of the
+Low Solar Chromosphere"", The Astrophysical Journal 852, 95 (2018) ] by using a
+more realistic radiative cooling model computed from the OPACITY project and
+the CHIANTI database. We find that the rate of ionization of the neutral
+component of the plasma is still faster than recombination within the current
+sheet region. For low $\beta$ plasmas, the ionized and neutral fluid flows are
+well-coupled throughout the reconnection region resembling the single-fluid
+Sweet-Parker model dynamics. Decoupling of the ion and neutral inflows appears
+in the higher $\beta$ case with $\beta_0=1.46$, which leads to a reconnection
+rate about three times faster than the rate predicted by the Sweet-Parker
+model. In all cases, the plasma temperature increases with time inside the
+current sheet, and the maximum value is above $2\times10^4$~K when the
+reconnection magnetic field strength is greater than $500$~G. While the more
+realistic radiative cooling model does not result in qualitative changes of the
+characteristics of magnetic reconnection, it is necessary for studying the
+variations of the plasma temperature and ionization fraction inside current
+sheets in strongly magnetized regions of the low solar atmosphere. It is also
+important for studying energy conversion during the magnetic reconnection
+process when the hydrogen-dominated plasma approaches full ionization.",1804.05631v2
+2018-06-23,The Higgs Factory Muon Collider Superconducting Magnets and Their Protection Against Beam Decay Radiation,"Low-energy medium-luminosity Muon Collider (MC) is being studied as a
+possible Higgs Factory (HF). Electrons from muon decays will deposit more than
+300 kW in superconducting magnets of the HF collider ring. This imposes
+significant challenges to superconducting (SC) magnets used in the MC storage
+ring (SR) and interaction regions (IR). The magnet designs are proposed which
+provide high operating gradient and magnetic field in a large aperture to
+accommodate the large size of muon beams due to low \b{eta}* as well as the
+cooling system to intercept the large heat deposition from the showers induced
+by decay electrons. Specific distribution of heat deposition in the lattice
+elements MC SR requires large aperture magnets to accommodate thick high-Z
+absorbers to protect the SC coils. Based on the developed MARS15 model and
+intense simulations, a sophisticated radiation protection system was designed
+for the collider SR and IR to bring the peak power density in the
+superconducting coils below the quench limit and reduce the dynamic heat
+deposition in the cold mass by a factor of 100. The system consists of tight
+tungsten masks in the magnet interconnect regions and elliptical tungsten
+liners in magnet aperture optimized for each magnet. It also reduces the
+background particle fluxes in the collider detector.",1806.08883v2
+2018-07-04,An orbitally derived single-atom magnetic memory,"A single magnetic atom on a surface epitomizes the scaling limit for magnetic
+information storage. Indeed, recent work has shown that individual atomic spins
+can exhibit magnetic remanence and be read out with spin-based methods,
+demonstrating the fundamental requirements for magnetic memory. However, atomic
+spin memory has been only realized on thin insulating surfaces to date,
+removing potential tunability via electronic gating or distance-dependent
+exchange-driven magnetic coupling. Here, we show a novel mechanism for
+single-atom magnetic information storage based on bistability in the orbital
+population, or so-called valency, of an individual Co atom on semiconducting
+black phosphorus (BP). Distance-dependent screening from the BP surface
+stabilizes the two distinct valencies and enables us to electronically
+manipulate the relative orbital population, total magnetic moment and spatial
+charge density of an individual magnetic atom without a spin-dependent readout
+mechanism. Furthermore, we show that the strongly anisotropic wavefunction can
+be used to locally tailor the switching dynamics between the two valencies.
+This orbital memory derives stability from the energetic barrier to atomic
+relaxation and demonstrates the potential for high-temperature single-atom
+information storage.",1807.01668v1
+2018-10-07,Spin dynamics and field-induced magnetic phase transition in the honeycomb Kitaev magnet $α$-Li$_2$IrO$_3$,"The layered honeycomb iridate $\alpha$-Li$_2$IrO$_3$ displays an
+incommensurate magnetic structure with counterrotating moments on
+nearest-neighbor sites, proposed to be stabilized by strongly-frustrated
+anisotropic Kitaev interactions between spin-orbit entangled Ir$^{4+}$ magnetic
+moments. Here we report powder inelastic neutron scattering measurements that
+observe sharply dispersive low-energy magnetic excitations centered at the
+magnetic ordering wavevector, attributed to Goldstone excitations of the
+incommensurate order, as well as an additional intense mode above a gap
+$\Delta\simeq2.3$ meV. Zero-field muon-spin relaxation measurements show clear
+oscillations in the muon polarization below the N\'{e}el temperature $T_{\rm
+N}\simeq15$ K with a time-dependent profile consistent with bulk incommensurate
+long-range magnetism. Pulsed field magnetization measurements observe that only
+about half the saturation magnetization value is reached at the maximum field
+of 64 T. A clear anomaly near 25 T indicates a transition to a phase with
+reduced susceptibility. The transition field has a Zeeman energy comparable to
+the zero-field gapped mode, suggesting gap suppression as a possible mechanism
+for the field-induced transition.",1810.03212v1
+2019-01-06,"Quasi-2D magnetism and origin of the Dirac semimetallic behavior in nonstoichiometric Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$ (y, z~$<$0.1)","Nonstoichiometric Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$ (y, z~$<$0.1) is known to
+exhibit a coexistence of magnetic order and the nontrivial semimetallic
+behavior related to Dirac or Weyl fermions. Here, we report inelastic neutron
+scattering analyses of the spin dynamics and density functional theory studies
+on the electronic properties of Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$. We observe a
+relatively large spin excitation gap $\approx$ 8.5 meV at 5 K, and the
+interlayer magnetic exchange constant only 2.8 \% of the dominant intralayer
+magnetic interaction, providing evidence that Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$
+exhibits a quasi-2D magnetism. Using density functional theory, we find a
+strong influence of magnetic orders on the electronic band structure and the
+Dirac dispersions near the Fermi level along the Y-S direction in the presence
+of a ferromagnetic ordering. Our study unveils novel interplay between the
+magnetic order, magnetic transition, and electronic property in
+Sr$_{1-y}$Mn$_{1-z}$Sb$_{2}$, and opens new pathways to control the
+relativistic band structure through magnetism in ternary compounds.",1901.01565v1
+2019-03-11,Novel dynamics and critical currents in fast superconducting vortices at high pulsed magnetic fields,"Non-linear electrical transport studies at high-pulsed magnetic fields, above
+the range accessible by DC magnets, are of direct fundamental relevance to the
+physics of superconductors, domain-wall, charge-density waves, and topological
+semi-metal. All-superconducting very-high field magnets also make it
+technologically relevant to study vortex matter in this regime. However, pulsed
+magnetic fields reaching 100 T in milliseconds impose technical and fundamental
+challenges that have prevented the realization of these studies. Here, we
+present a technique for sub-microsecond, smart, current-voltage measurements,
+which enables determining the superconducting critical current in pulsed
+magnetic fields, beyond the reach of any DC magnet. We demonstrate the
+excellent agreement of this technique with low DC field measurements on
+Y$_{0.77}$Gd$_{0.23}$Ba$_2$Cu$_3$O$_7$ coated conductors with and without
+BaHfO$_3$ nanoparticles. Exploring the uncharted high magnetic field region, we
+discover a characteristic influence of the magnetic field rate of change
+($dH/dt$) on the current-voltage curves in a superconductor. We fully capture
+this unexplored vortex physics through a theoretical model based on the
+asymmetry of the vortex velocity profile produced by the applied current.",1903.04658v2
+2019-03-26,"Precision measurement of magnetic field from near to far, from fine to large scales in ISM","Magnetic fields have important or dominant effects in many areas of
+astrophysics, but have been very difficult to quantify. Spectropolarimetry from
+Ground State Alignment (GSA) has been suggested as a direct tracer of magnetic
+field in interstellar diffuse medium. Owing to the long life of the atoms on
+ground states the Larmor precession in an external magnetic field imprints the
+direction of the field onto the polarization of absorbing species. This
+provides a unique tool for studies of sub-gauss magnetic fields using
+polarimetry of UV, optical and radio lines. Many spectral lines with strong
+signals from GSA are in the UV band. By discerning magnetic fields in gas with
+different dynamical properties, high spectral resolution measurement of
+spectral polarization will allow the study of 3D magnetic field distribution
+and interstellar turbulence. GSA provides also a unique chance to map 3D
+direction of magnetic field on small scales, e.g., disks, where grain alignment
+is unreliable. The range of objects suitable for studies is extremely wide and
+includes magnetic fields in the interplanetary medium, in the interstellar
+medium, and in circumstellar regions as well as diffuse media in extragalactic
+objects.",1903.11065v1
+2019-05-20,Micromagnetic Modelling of the Heat Assisted Switching Process in high Anisotropy FePt Granular Thin Films,"The dynamic process of assisted magnetic switchins has been simulated to
+investigate the associated physics. The model uses a Voronoi construction to
+determine the physical structure of the nano granular thin film recording
+media; and the Landau-Lifshitz-Bloch (LLB) equation is solved to evolve the
+magnetic system in time. The reduction of the magnetization is determined over
+a range of peak system temperatures and for a number of anisotropy values. The
+results show that the HAMR process is not simply magnetization reversal over a
+thermally reduced energy barrier. To achieve full magnetization reversal (for
+all anisotropies investigated) an applied field strength of at least 6kOe is
+required and the peak system temperature must reach at least the Curie point
+(Tc). When heated to Tc the magnetization associated with each grain is
+destroyed, which invokes the non-precessional linear reversal mode. Reversing
+the magnetization through this linear reversal mode is favourable, as the
+reversal time is two orders of magnitude smaller than that associated with
+precession. Under these conditions, as the temperature decreases to ambient,
+the magnetization recovers in the direction of the applied field, completing
+the reversal process. Also the model produces results which are consistent with
+the concept of thermal writability; when heating the media to Tc, the smaller
+grains require a larger field strength to reverse the magnetization.",1905.08134v1
+2019-07-15,Nature of the magnetic moment of cobalt in ordered FeCo alloy,"The magnets are typically classified into Stoner and Heisenberg type,
+depending on the itinerant or localized nature of the constituent magnetic
+moments. In this work, we investigate theoretically the behaviour of the
+magnetic moments of iron and cobalt in their B2-ordered alloy. The results
+based on local spin density approximation (LSDA) for the density functional
+theory (DFT) suggest that the Co magnetic moment strongly depends on the
+directions of the surrounding magnetic moments, which usually indicates the
+Stoner-type mechanism of magnetism. This is consistent with the disordered
+local moment (DLM) picture of the paramagnetic state, where the magnetic moment
+of cobalt gets substantially suppressed. We argue that this is due to the lack
+of strong on-site electron correlations, which we take into account by
+employing a combination of DFT and dynamical mean-field theory (DMFT). Within
+LDA+DMFT, we find a substantial quasiparticle mass renormalization and a non
+Fermi-liquid behaviour of Fe-$3d$ orbitals. The resulting spectral functions
+are in very good agreement with measured spin-resolved photoemission spectra.
+Our results suggest that local correlations play an essential role in
+stabilizing a robust local moment on Co in the absence of magnetic order at
+high temperatures.",1907.06613v5
+2019-07-18,Magnetic Power Spectra of Emerging Active Regions,"Magnetic field data provided by the Helioseismic and Magnetic Imager on board
+the Solar Dynamics Observatory were utilized to explore the changes in the
+magnetic energy of four active regions (ARs) during their emergence. We found
+that at the very early stage of the magnetic flux emergence, an abrupt
+steepening of the magnetic power spectrum takes place leading to rapid increase
+of the absolute value of the negative spectra power index $\alpha$ in $E(k)$
+$\sim$ $k^{\alpha}$. As the emergence proceeds, the energy increases at all
+scales simultaneously implying that elements of all sizes do appear in the
+photosphere. Meanwhile, the energy gain at scales larger than $\approx$10 Mm
+prevails as compared to that at smaller scales. Both direct (i.e.,
+fragmentation of large structures into smaller ones) and inverse (i.e., merging
+of small magnetic features into larger elements) cascades are readily observed
+during the emergence. However, in the case of inverse cascade, the total energy
+gained at large scales exceeds the energy loss at smaller scales assuming
+simultaneous appearance of large-scale magnetic entities from beneath the
+photosphere. We conclude that most of the time the energy may grow at all
+scales. We also cannot support the point of view regarding the dominant role of
+the inverse cascade in the formation of an AR. Although the coalescence of
+small magnetic elements into larger pores and sunspots is observed, our
+analysis shows that the prevailed energy contribution to an AR comes from
+emergence of large-scale structures.",1907.07952v1
+2019-07-26,Forecast of Daily Major Flare Probability Using Relationships between Vector Magnetic Properties and Flaring Rates,"We develop forecast models of daily probability of major flares (M- and
+X-class) based on empirical relationships between photospheric magnetic
+parameters and daily flaring rates from May 2010 to April 2018. In this study,
+we consider ten magnetic parameters characterizing size, distribution, and
+non-potentiality of vector magnetic fields from Solar Dynamics Observatory
+(SDO)/Helioseismic and Magnetic Imager (HMI) and Geostationary Operational
+Environmental Satellites (GOES) X-ray flare data. The magnetic parameters are
+classified into three types: the total unsigned parameters, the total signed
+parameters, and the mean parameters. We divide the data into two sets
+chronologically: 70% for training and 30% for testing. The empirical
+relationships between the parameters and flaring rates are used to predict
+flare occurrence probabilities for a given magnetic parameter value. Major
+results of this study are as follows. First, major flare occurrence rates are
+well correlated with ten parameters having correlation coefficients above 0.85.
+Second, logarithmic values of flaring rates are well approximated by linear
+equations. Third, the total unsigned and signed parameters achieved better
+performance for predicting flares than the mean parameters in terms of
+verification measures of probabilistic and converted binary forecasts. We
+conclude that the total quantity of non-potentiality of magnetic fields is
+crucial for flare forecasting among the magnetic parameters considered in this
+study. When this model is applied for operational use, this model can be used
+using the data of 21:00 TAI with a slight underestimation of 2 - 6.3%.",1907.11373v1
+2019-10-25,Nature of hyperfine interactions in TbPc$_2$ single-molecule magnets: Multireference ab-initio study,"Lanthanide-based single-ion magnetic molecules can have large magnetic
+hyperfine interactions as well as large magnetic anisotropy. Recent
+experimental studies reported tunability of these properties by changes of
+chemical environments or by application of external stimuli for device
+applications. In order to provide insight onto the origin and mechanism of such
+tunability, here we investigate the magnetic hyperfine and nuclear quadrupole
+interactions for $^{159}$Tb nucleus in TbPc$_2$ (Pc=phthalocyanine)
+single-molecule magnets using multireference ab-initio methods including
+spin-orbit interaction. Since the electronic ground and first-excited
+(quasi)doublets are well separated in energy, the microscopic Hamiltonian can
+be mapped onto an effective Hamiltonian with an electronic pseudo-spin $S=1/2$.
+From the ab-initio-calculated parameters, we find that the magnetic hyperfine
+coupling is dominated by the interaction of the Tb nuclear spin with electronic
+orbital angular momentum. The asymmetric $4f$-like electronic charge
+distribution leads to a strong nuclear quadrupole interaction with significant
+non-axial terms for the molecule with low symmetry. The ab-initio calculated
+electronic-nuclear spectrum including the magnetic hyperfine and quadrupole
+interactions is in excellent agreement with experiment. We further find that
+the non-axial quadrupole interactions significantly influence the avoided level
+crossings in magnetization dynamics and that the molecular distortions affect
+mostly the Fermi contact terms as well as the non-axial quadrupole
+interactions.",1910.11952v1
+2020-04-01,Selectively Controlled Magnetic Microrobots with Opposing Helices,"Magnetic microrobots that swim through liquid media are of interest for
+minimally invasive medical procedures, bioengineering, and manufacturing. Many
+of the envisaged applications, such as micromanipulation and targeted cargo
+delivery, necessitate the use and adequate control of multiple microrobots,
+which will increase the velocity, robustness, and efficacy of a procedure.
+While various methods involving heterogeneous geometries, magnetic properties,
+and surface chemistries have been proposed to enhance independent control, the
+main challenge has been that the motion between all microwsimmers remains
+coupled through the global control signal of the magnetic field. Katsamba and
+Lauga proposed transchiral microrobots, a theoretical design with magnetized
+spirals of opposite handedness. The competition between the spirals can be
+tuned to give an intrinsic nonlinearity that each device can function only
+within a given band of frequencies. This allows individual microrobots to be
+selectively controlled by varying the frequency of the rotating magnetic field.
+Here we present the experimental realization and characterization of
+transchiral micromotors composed of independently driven magnetic helices. We
+show a swimming micromotor that yields negligible net motion until a critical
+frequency is reached and a micromotor that changes its translation direction as
+a function of the frequency of the rotating magnetic field. This work
+demonstrates a crucial step towards completely decoupled and addressable
+swimming magnetic microrobots.",2004.00687v1
+2020-05-08,Sublattice magnetizations of ultrathin ferrimagnetic lamellar nanostructures between cobalt leads,"In this work we model the salient magnetic properties of the alloy lamellar
+ferrimagnetic nanostructures
+$[Co_{1-c}Gd_c]_{\ell^{\prime}}[Co]_\ell[Co_{1-c}Gd_c]_{\ell^{\prime}}$ between
+$Co$ semi-infinite leads. We have employed the Ising spin effective field
+theory (EFT) to compute the reliable magnetic exchange constants for the pure
+cobalt $J_{Co-Co}$ and gadolinium $J_{Gd-Gd}$ materials, in complete agreement
+with their experimental data. The sublattice magnetizations of the $Co$ and
+$Gd$ sites on the individual hcp atomic (0001) planes of the $Co-Gd$ layered
+nanostructures are computed for each plane and corresponding sites, by using
+the combined EFT and mean field theory (MFT) spin methods. The sublattice
+magnetizations, effective site magnetic moments, and ferrimagnetic compensation
+characteristics for the individual hcp atomic planes of the embedded
+nanostructures, are computed as a function of temperature, and for various
+stable eutectic concentrations in the range $c\leq$ 0.5. The theoretical
+results for the sublattice magnetizations and the local magnetic variables of
+these ultrathin ferrimagnetic lamellar nanostructured systems, between cobalt
+leads, are necessary for the study of their magnonic transport properties, and
+eventually their spintronic dynamic computations. The method developed in this
+work is general and can be applied to comparable magnetic systems
+nanostructured with other materials.",2005.03965v3
+2020-05-11,Constraining the primordial magnetic field with dwarf galaxy simulations,"Using a set of cosmological hydro-dynamical simulations, we constrained the
+properties of primordial magnetic fields by studying their impact on the
+formation and evolution of dwarf galaxies. We performed a large set of
+simulations (8 dark matter only and 72 chemo-hydrodynamical) including
+primordial magnetic fields through the extra density fluctuations they induce
+at small length scales ($k \geq 10\,h\,\rm{Mpc^{-1}}$) in the matter power
+spectrum. We explored a large variety of primordial magnetic fields with
+strength $B_\lambda$ ranging from $0.05$ to $0.50\,\textrm{nG}$ and magnetic
+energy spectrum slopes $n_B$ from $-2.9$ to $-2.1$. Strong magnetic fields
+characterized by a high amplitude ($B_\lambda=0.50,\,0.20\,\textrm{nG}$ with
+$n_B=-2.9$) or by a steep initial power spectrum slope ($n_B=-2.1,-2.4$, with
+$B_\lambda=0.05\,\textrm{nG}$) induce perturbations in the mass scales from
+$10^7$ to $10^9\,\rm{M}_{\odot}$. In this context emerging galaxies see their
+star formation rate strongly boosted. They become more luminous and metal rich
+than their counterparts without primordial magnetic fields. Such strong fields
+are ruled out by their inability to reproduce the observed scaling relations of
+dwarf galaxies. They predict dwarf galaxies to be at the origin of an
+unrealistically early reionization of the Universe and also overproduce
+luminous satellites in the Local Group. Weaker magnetic fields impacting the
+primordial density field at corresponding masses $\lesssim
+10^6\,\rm{M}_{\odot}$, produce a large number of mini dark halos orbiting the
+dwarfs, however out of reach for current lensing observations. This study
+allows for the first time to constrain the properties of primordial magnetic
+fields based on realistic cosmological simulations of dwarf galaxies.",2005.05401v1
+2020-09-03,Polarity Free Magnetic Repulsion and Magnetic Bound State,"This is a report on a dynamic autonomous magnetic interaction which does not
+depend on polarities resulting in short ranged repulsion involving one or more
+inertial bodies and a new class of bound state based on this interaction. Both
+effects are new to the literature, found so far. Experimental results are
+generalized and reported qualitatively. Working principles of these effects are
+provided within classical mechanics and found consistent with observations and
+simulations. The effects are based on the interaction of a rigid and finite
+inertial body (an object having mass and moment of inertia) endowed with a
+magnetic moment with a cyclic inhomogeneous magnetic field which does not
+require to have a local minimum. Such a body having some degrees of freedom
+involved in driven harmonic motion by this interaction can experience a net
+force in the direction of the weak field regardless of its position and
+orientation or can find stable equilibrium with the field itself autonomously.
+The former is called polarity free magnetic repulsion and the latter magnetic
+bound state. Experiments show that a bound state can be obtained between two
+free bodies having magnetic dipole moment. Various schemes of trapping bodies
+having magnetic moments by rotating fields are realized as well as rotating
+bodies trapped by a static dipole field in presence of gravity. Also, a special
+case of bound state called bipolar bound state between free dipole bodies is
+investigated.",2009.07082v1
+2020-10-12,Gravity and rotation drag the magnetic field in high-mass star formation,"The formation of hot stars out of the cold interstellar medium lies at the
+heart of astrophysical research. Understanding the importance of magnetic
+fields during star formation remains a major challenge. With the advent of the
+Atacama Large Millimeter Array, the potential to study magnetic fields by
+polarization observations has tremendously progressed. However, the major
+question remains how much magnetic fields shape the star formation process or
+whether gravity is largely dominating. Here, we show that for the high-mass
+star-forming region G327.3 the magnetic field morphology appears to be
+dominantly shaped by the gravitational contraction of the central massive gas
+core where the star formation proceeds. We find that in the outer parts of the
+region, the magnetic field is directed toward the gravitational center of the
+region. Filamentary structures feeding the central core exhibit U-shaped
+magnetic field morphologies directed toward the gravitational center as well,
+again showing the gravitational drag toward the center. The inner part then
+shows rotational signatures, potentially associated with an embedded disk, and
+there the magnetic field morphology appears to be rotationally dominated.
+Hence, our results demonstrate that for this region gravity and rotation are
+dominating the dynamics and shaping the magnetic field morphology.",2010.05825v1
+2020-12-03,"Polar magneto-optical Kerr effect in antiferromagnetic M$_2$As (M=Cr, Mn, Fe) under an external magnetic field","Antiferromagnetic metals attract tremendous interest for memory applications
+due to their expected fast response dynamics in the terahertz frequency regime.
+Reading from and writing information into these materials is not easily
+achievable using magnetic fields, due to weak high-order magneto-optical
+signals and robustness of the magnetic structure against external magnetic
+fields. Polarized electromagnetic radiation is a promising alternative for
+probing their response, however, when ideal antiferromagnetic symmetry is
+present, this response vanishes. Hence, in this work we combine
+first-principles simulations with measurements of the polar magneto-optical
+Kerr effect under external magnetic fields, to study magneto-optical response
+of antiferromagnetic M$_2$As (M=Cr, Mn, and Fe). We devise a computational
+scheme to compute the magnetic susceptibility from total-energy changes using
+constraints on magnetic-moment tilting. Our predictions of the spectral
+dependence of polar magneto-optical Kerr rotation and ellipticity allow us to
+attribute these effects to breaking of the magnetic symmetry. We show that
+tilting affects the exchange interaction, while the spin-orbit interaction
+remains unaffected as the tilting angle changes. Our work provides
+understanding of the polar magneto-optical Kerr effect on a band structure
+level and underscores the importance of the magnetic susceptibility when
+searching for materials with large magneto-optical response.",2012.02090v1
+2020-12-18,Untangling the global coronal magnetic field with multiwavelength observations,"Magnetism defines the complex and dynamic solar corona. Coronal mass
+ejections (CMEs) are thought to be caused by stresses, twists, and tangles in
+coronal magnetic fields that build up energy and ultimately erupt, hurling
+plasma into interplanetary space. Even the ever-present solar wind possesses a
+three-dimensional morphology shaped by the global coronal magnetic field,
+forming geoeffective corotating interaction regions. CME evolution and the
+structure of the solar wind depend intimately on the coronal magnetic field, so
+comprehensive observations of the global magnetothermal atmosphere are crucial
+both for scientific progress and space weather predictions. Although some
+advances have been made in measuring coronal magnetic fields locally, synoptic
+measurements of the global coronal magnetic field are not yet available.
+  We conclude that a key goal for 2050 should be comprehensive, ongoing 3D
+synoptic maps of the global coronal magnetic field. This will require the
+construction of new telescopes, ground and space-based, to obtain
+complementary, multiwavelength observations sensitive to the coronal magnetic
+field. It will also require development of inversion frameworks capable of
+incorporating multi-wavelength data, and forward analysis tools and simulation
+testbeds to prioritize and establish observational requirements on the proposed
+telescopes.",2012.09992v1
+2021-01-21,Spin liquid behavior of a three-dimensional magnetic system Ba$_3$NiIr$_2$O$_9$ with $S$ = 1,"The quantum spin liquid (QSL) is an exotic phase of magnetic materials where
+the spins continue to fluctuate without any symmetry breaking down to zero
+temperature. Among the handful reports of QSL with spin $S\ge$1, examples with
+magnetic ions on a three-dimensional magnetic lattice are extremely rare since
+both larger spin and higher dimension tend to suppress quantum fluctuations. In
+this work, we offer a new strategy to achieve 3-D QSL with high spin by
+utilizing two types of transition metal ions, both are magnetically active but
+located at crystallographically inequivalent positions. We design a 3-D
+magnetic system Ba$_3$NiIr$_2$O$_9$ consisting of interconnected corner shared
+NiO$_6$ octahedra and face shared Ir$_2$O$_9$ dimer, both having triangular
+arrangements in \textit{a-b} plane. X-ray absorption spectroscopy measurements
+confirm the presence of Ni$^{2+}$ ($S$=1). Our detailed thermodynamic and
+magnetic measurements reveal that this compound is a realization of gapless QSL
+state down to at least 100 mK. Ab-initio calculations find a strong magnetic
+exchange between Ir and Ni sublattices and in-plane antiferromagnetic coupling
+between the dimers, resulting in dynamically fluctuating magnetic moments on
+both the Ir and Ni sublattice.",2101.08445v1
+2021-02-02,Magnetically Modified Spherical Accretion in GRMHD: Reconnection-Driven Convection and Jet Propagation,"We present 3D general relativistic magnetohydrodynamic(GRMHD) simulations of
+zero angular momentum accretion around a rapidly rotating black hole, modified
+by the presence of initially uniform magnetic fields. We consider serveral
+angles between the magnetic field direction and the black hole spin. In the
+resulting flows, the midplane dynamics are governed by magnetic
+reconnection-driven turbulence in a magnetically arrested (or a nearly
+arrested) state. Electromagnetic jets with outflow efficiencies ~10-200% occupy
+the polar regions, reaching several hundred gravitational radii before they
+dissipate due to the kink instability. The jet directions fluctuate in time and
+can be tilted by as much as ~30 degrees with respect to black hole spin, but
+this tilt does not depend strongly on the tilt of the initial magnetic field. A
+jet forms even when there is no initial net vertical magnetic flux since
+turbulent, horizon-scale fluctuations can generate a net vertical field
+locally. Peak jet power is obtained for an initial magnetic field tilted by
+40-80 degrees with respect to the black hole spin because this maximizes the
+amount of magnetic flux that can reach the black hole. These simulations may be
+a reasonable model for low luminosity black hole accretion flows such as Sgr A*
+or M87.",2102.01694v1
+2021-05-13,In Search of Subsurface Oceans within the Uranian Moons,"The Galileo mission to Jupiter discovered magnetic signatures associated with
+hidden sub-surface oceans at the moons Europa and Callisto using the phenomenon
+of magnetic induction. These induced magnetic fields originate from
+electrically conductive layers within the moons and are driven by Jupiter's
+strong time-varying magnetic field. The ice giants and their moons are also
+ideal laboratories for magnetic induction studies. Both Uranus and Neptune have
+a strongly tilted magnetic axis with respect to their spin axis, creating a
+dynamic and strongly variable magnetic field environment at the orbits of their
+major moons. Although Voyager 2 visited the ice giants in the 1980s, it did not
+pass close enough to any of the moons to detect magnetic induction signatures.
+However, Voyager 2 revealed that some of these moons exhibit surface features
+that hint at recent geologically activity, possibly associated with sub-surface
+oceans. Future missions to the ice giants may therefore be capable of
+discovering sub-surface oceans, thereby adding to the family of known ocean
+worlds in our solar system. Here, we assess magnetic induction as a technique
+for investigating sub-surface oceans within the major moons of Uranus.
+Furthermore, we establish the ability to distinguish induction responses
+created by different interior characteristics that tie into the induction
+response: ocean thickness, conductivity, and depth, and ionospheric
+conductance. The results reported here demonstrate the possibility of
+single-pass ocean detection and constrained characterization within the moons
+of Miranda, Ariel, and Umbriel, and provide guidance for magnetometer selection
+and trajectory design for future missions to Uranus.",2105.06087v1
+2021-05-29,Magnetic Field and Frequency Dependent AC Susceptibility of High-Tc YBCO Single Crystal,"The temperature dependence of AC susceptibility (ACS) has been measured for a
+very high-quality plate-like slightly overdoped YBCO single crystal for
+different frequencies and AC magnetic field amplitudes. Frequency dependence of
+the ACS is weak irrespective of the magnetic field orientation but significant
+effects of field orientation with respect to the CuO2 planes and field
+magnitude on real and imaginary components of fundamental ACS were observed.
+The height of the loss peak saturates as full penetration of magnetic field is
+achieved. The peak temperature, Tp, in \c{hi}"" shifts to lower temperatures
+with increasing magnetic field amplitude for both HIIc and HIIab. The value of
+Tp depends on the orientation of the magnetic field with respect to the
+crystallographic axes, illustrating the anisotropy in the magnetic flux
+dynamics. The superconducting transition width increases weakly with increasing
+magnetic field. The Cole-Cole plot [\c{hi}""(\c{hi}')] shows qualitatively and
+quantitatively identical features for HIIc and HIIab, independent of the
+orientation of the magnetic field with respect to the sample geometry and
+shielding current paths. The general features of \c{hi}""(\c{hi}') implies that,
+there is no flux creep for the range of frequencies and AC fields employed in
+this investigation. The maximum value of the loss peak and its position with
+respect to \c{hi}' in the Cole-Cole plot are largely consistent with the Bean
+critical state model. Slightly increased peak value in comparison to the
+predicted peak value within the Bean critical state model is probably due to a
+weak field dependence of Jc. The results obtained here are compared with
+various theoretical models and experimental findings. Prominent differences are
+noted and discussed in details in this study.",2105.14321v1
+2022-03-17,"Solving Critical Problems of the Muon Collider Higgs Factory: Optics, Magnets and their Protection, Detector Backgrounds","A low-energy medium-luminosity Muon Collider (MC) is being studied as a
+possible Higgs Factory (HF). Electrons from muon decays will deposit more than
+300 kW in superconducting magnets of the HF collider ring. This imposes
+significant challenges to superconducting (SC) magnets used in the MC storage
+ring (SR) and interaction regions (IR). Magnet designs are proposed which
+provide high operating gradient and magnetic field in a large aperture to
+accommodate the large size of muon beams (due to low beta*), as well as a
+cooling system to intercept the large heat deposition from the showers induced
+by decay electrons. The distribution of heat deposition in the MC SR lattice
+elements requires large-aperture magnets in order to accommodate thick high-Z
+absorbers to protect the SC coils. Based on the developed MARS15 model and
+intensive simulations, a sophisticated radiation protection system was designed
+for the collider SR and IR to bring the peak power density in the
+superconducting coils below the quench limit and reduce the dynamic heat
+deposition in the cold mass by a factor of 100. The system consists of tight
+tungsten masks in the magnet interconnect regions and elliptical tungsten
+liners in the magnet aperture optimized individually for each magnet. These
+also reduce the background particle fluxes in the collider detector.",2203.09010v1
+2022-03-24,"Bipolar Ephemeral Active Regions, Magnetic Flux Cancellation, and Solar Magnetic Explosions","We examine the cradle-to-grave magnetic evolution of 10 bipolar ephemeral
+active regions (BEARs) in solar coronal holes, especially aspects of the
+magnetic evolution leading to each of 43 obvious microflare events. The data
+are from Solar Dynamics Observatory: 211 A coronal EUV images and line-of-sight
+photospheric magnetograms. We find evidence that (1) each microflare event is a
+magnetic explosion that results in a miniature flare arcade astride the
+polarity inversion line (PIL) of the explosive lobe of the BEARs anemone
+magnetic field; (2) relative to the BEAR's emerged flux-rope omega loop, the
+anemone's explosive lobe can be an inside lobe, an outside lobe, or an inside &
+outside lobe; (3) 5 events are confined explosions, 20 events are
+mostly-confined explosions, and 18 events are blowout explosions, which are
+miniatures of the magnetic explosions that make coronal mass ejections (CMEs);
+(4) contrary to the expectation of Moore et al (2010), none of the 18 blowout
+events explode from inside the BEARs omega loop during the omega loops
+emergence; (5) before and during each of the 43 microflare events there is
+magnetic flux cancellation at the PIL of the anemone's explosive lobe. From
+finding evident flux cancellation at the underlying PIL before and during all
+43 microflare events - together with BEARs evidently being miniatures of all
+larger solar bipolar active regions - we expect that in essentially the same
+way, flux cancellation in sunspot active regions prepares and triggers the
+magnetic explosions for many major flares and CMEs.",2203.13287v1
+2022-04-11,Magnetic order and spin liquid behavior in [Mo3+]^{11+} triangular magnets,"Molecular magnets based on [Mo$_3$]$^{11+}$ units with one unpaired electron
+per trimer have attracted recent interest due to the identification of quantum
+spin liquid candidacy in some family members. Here, we present comprehensive
+measurements on polycrystalline samples of ZnScMo$_3$O$_8$, MgScMo$_3$O$_8$,
+and Na$_3$Sc$_2$Mo$_5$O$_{16}$ with the same Mo$_3$O$_{13}$ magnetic building
+blocks. The crystal structures are characterized with x-ray or neutron powder
+diffraction and the magnetic ground states are determined by performing ac and
+dc susceptibility, specific heat, neutron powder diffraction, and $\mu$SR
+measurements. Our work indicates that ZnScMo$_3$O$_8$ and MgScMo$_3$O$_8$ have
+ferromagnetic Curie-Weiss temperatures of 18.5 K and 11.9 K, ordered ground
+states with net moments (low-moment ferromagnetism or canted
+antiferromagnetism), and zero field ordering temperatures of $T_c =$ 6 K and
+$<$ 2 K respectively. On the other hand, Na$_3$Sc$_2$Mo$_5$O$_{16}$ hosts a
+dynamical magnetic ground state with no evidence for magnetic ordering or spin
+freezing down to 20 mK despite an antiferromagnetic Curie-Weiss temperature of
+-36.2 K, and therefore is a candidate for quantum spin liquid behavior. By
+comparing the present results to past work on the same family of materials, we
+construct a phase diagram which illustrates that the magnetic ground states of
+these Mo-based molecular magnets are very sensitive to small changes in the
+nearest neighbor Mo-Mo distance.",2204.05377v1
+2022-04-19,Magnetic field effects in biology from the perspective of the radical pair mechanism,"A large and growing body of research shows that weak magnetic fields can
+significantly influence various biological systems, including plants, animals,
+and humans. However, the underlying mechanisms behind these phenomena remain
+elusive. It is remarkable that the magnetic energies implicated in these
+effects are much smaller than thermal energies. Here we review these
+observations, of which there are now hundreds, and we suggest that a viable
+explanation is provided by the radical pair mechanism, which involves the
+quantum dynamics of the electron and nuclear spins of naturally occurring
+transient radical molecules. While the radical pair mechanism has been studied
+in detail in the context of avian magnetoreception, the studies reviewed here
+show that magnetosensitivity is widespread throughout biology. We review
+magnetic field effects on various physiological functions, organizing them
+based on the type of the applied magnetic fields, namely static, hypomagnetic,
+and oscillating magnetic fields, as well as isotope effects. We then review the
+radical pair mechanism as a potential unifying model for the described magnetic
+field effects, and we discuss plausible candidate molecules that might
+constitute the radical pairs. We review recent studies proposing that the
+quantum nature of the radical pairs provides promising explanations for xenon
+anesthesia, lithium effects on hyperactivity, magnetic field and lithium
+effects on the circadian clock, and hypomagnetic field effects on neurogenesis
+and microtubule assembly. We conclude by discussing future lines of
+investigation in this exciting new area of quantum biology related to weak
+magnetic field effects.",2204.09147v1
+2022-09-29,Nonlinearity and Parametric Amplification of Superconducting Nanowire Resonators in Magnetic Field,"Nonlinear superconducting devices, typically based on Josephson Junction (JJ)
+nonlinearities, are the basis for superconducting quantum electronics,
+enabling, e.g., the formation of isolated two-level superconducting qubits and
+amplifiers. While emerging spin, hybrid spin/superconducting (including
+Majorana), and nano-magneto-optical quantum systems could benefit tremendously
+from superconducting nonlinearities, the presence of strong magnetic fields in
+these systems are incompatible with conventional JJ devices, which are highly
+sensitive to applied magnetic fields. One potential solution is the use of
+kinetic inductance (KI) nonlinearity. To date, only linear kinetic inductance
+(KI) devices have been shown to operate in high magnetic fields, while
+nonlinear KI device operation in high magnetic fields has received virtually no
+attention. Here, we study the nonlinearity of superconducting nanowire (NW) KI
+resonators and their performance as parametric amplifiers for in-plane magnetic
+fields. We study the Kerr coefficients of NW KI resonators made from 10 nm-thin
+NbTiN films with characteristic impedance up to 3 k$\Omega$, and demonstrate
+both nondegenerate and degenerate parametric amplification, at magnetic fields
+up to 2 T, for the first time. We find that narrow KI resonators of width 0.1
+$\mu$m are robust, in terms of gain, dynamic range and noise, to magnetic
+fields up to $\sim$2 T, while wider KI resonators of width 1 $\mu$m suffer
+significant suppression in the gain around at fields well below 2 T. Around 8
+dB deamplification is observed for coherent states for a 0.1 $\mu$m KI
+resonator, implying the capability of noise squeezing. These results open a new
+pathway to developing nonlinear quantum devices that operate in or generate
+high magnetic fields such as spin, hybrid spin/superconducting, and
+magneto-opto-mechanical devices.",2209.14523v1
+2022-10-19,Three-dimensional numerical simulations of ambipolar diffusion in NS cores in the one-fluid approximation: instability of poloidal magnetic field,"We numerically model evolution of magnetic fields inside a neutron star under
+the influence of ambipolar diffusion in the weak-coupling mode in the one-fluid
+MHD approximation. Our simulations are three-dimensional and performed in
+spherical coordinates. Our model covers the neutron star core and includes
+crust where the magnetic field decay is due to Ohmic decay. We discover an
+instability of poloidal magnetic field under the influence of ambipolar
+diffusion. This instability develops in the neutron star core and grows on a
+timescale of 0.2 dimensionless times, reaching saturation by 2 dimensionless
+times. The instability leads to formation of azimuthal magnetic field with
+azimuthal wavenumber $m=14$ (at the moment of saturation) which keeps merging
+and reaches $m=4$ by 16 dimensionless times. Over the course of our simulations
+(16 dimensionless times) the surface dipolar magnetic field decays, reaching 20
+percent of its original value and keeps decaying. The decay timescale for the
+total magnetic energy is six dimensionless times. The ambipolar diffusion
+induces electric currents in the crust where these currents dissipate
+efficiently. Strong electric currents in the crust lead to heating, which could
+correspond to luminosities of $\approx 10^{29}$ erg s$^{-1}$ during hundreds of
+Myrs for an initial magnetic field of $10^{14}$ G. Ambipolar diffusion leads to
+formation of small-scale magnetic fields at the neutron star surface.",2210.10869v1
+2022-11-04,Small-scale dynamo in cool main sequence stars. II. The effect of metallicity,"All cool main sequence stars including our Sun are thought to have magnetic
+fields. Observations of the Sun revealed that even in quiet regions small-scale
+turbulent magnetic fields are present. Simulations further showed that such
+magnetic fields affect the subsurface and photospheric structure, and thus the
+radiative transfer and emergent flux. Since small-scale turbulent magnetic
+fields on other stars cannot be directly observed, it is imperative to study
+their effects on the near surface layers numerically. Until recently
+comprehensive three-dimensional simulations capturing the effect of small-scale
+turbulent magnetic fields only exists for the solar case. A series of
+investigations extending SSD simulations for other stars has been started. Here
+we aim to examine small-scale turbulent magnetic fields in stars of solar
+effective temperature but different metallicity. We investigate the properties
+of three-dimensional simulations of the magneto-convection in boxes covering
+the upper convection zone and photosphere carried out with the MURaM code for
+metallicity values of $ \rm M/H = \{-1.0, 0.0, 0.5\}$ with and without a
+small-scale-dynamo. We find that small-scale turbulent magnetic fields enhanced
+by a small-scale turbulent dynamo noticeably affect the subsurface dynamics and
+significantly change the flow velocities in the photosphere. Moreover,
+significantly stronger magnetic field strengths are present in the convection
+zone for low metallicity. Whereas, at the optical surface the averaged vertical
+magnetic field ranges from 64G for M/H = 0.5 to 85G for M/H = -1.0.",2211.02722v1
+2022-11-15,Dynamical criticality of spin-shear coupling in van der Waals antiferromagnets,"The interplay between a multitude of electronic, spin, and lattice degrees of
+freedom underlies the complex phase diagrams of quantum materials. Layer
+stacking in van der Waals (vdW) heterostructures is responsible for exotic
+electronic and magnetic properties, which inspires stacking control of
+two-dimensional magnetism. Beyond the interplay between stacking order and
+interlayer magnetism, we discover a spin-shear coupling mechanism in which a
+subtle shear of the atomic layers can have a profound effect on the intralayer
+magnetic order in a family of vdW antiferromagnets. Using time-resolved x-ray
+diffraction and optical linear dichroism measurements, interlayer shear is
+identified as the primary structural degree of freedom that couples with
+magnetic order. The recovery times of both shear and magnetic order upon
+optical excitation diverge at the magnetic ordering temperature with the same
+critical exponent. The time-dependent Ginzburg-Landau theory shows that this
+concurrent critical slowing down arises from a linear coupling of the
+interlayer shear to the magnetic order, which is dictated by the broken mirror
+symmetry intrinsic to the monoclinic stacking. Our results highlight the
+importance of interlayer shear in ultrafast control of magnetic order via
+spin-mechanical coupling.",2211.08189v1
+2022-11-17,Shear viscosity coefficient of magnetized QCD medium near chiral phase transition,"We study the properties of the shear viscosity coefficient of quark matter at
+finite temperature and chemical potential near chiral phase transition in a
+strong background magnetic field. A strong magnetic field induces anisotropic
+features, phase-space Landau-level quantization, and if the magnetic field is
+sufficiently strong, interferes with prominent QCD phenomena such as dynamical
+quark mass generation, likely affecting the quark matter transport
+characteristics. The modified Nambu-Jona-Lasinio (NJL) model with inverse
+magnetic catalysis effect by fitting the Lattice QCD (LQCD) results is used to
+calculate the changes of quasiparticle related thermodynamic quantities, and
+the shear viscosity of the system medium, which is analyzed under the
+relaxation time approximation. We quantify the influence of the order of chiral
+phase transition and the critical endpoint on dissipative phenomena in such a
+magnetized medium. When the magnetic field exists, the shear viscosity
+coefficient of the dissipative fluid system can be decomposed into five
+different components. In strong field limit, we make a detailed study of the
+dependencies of $\eta_{2}$ and $\eta_{4}$ on temperature and magnetic field for
+the first order phase transition and critical endpoint transition.
+respectively. It is found that $\eta_{2}$ and $\eta_{4}$ both decrease with
+magnetic field and increase with temperature, and the discontinuities of
+$\eta_{2}$ and $\eta_{4}$ occur at the first order phase transition point.",2211.09281v2
+2022-12-23,Deformation transients of confined droplets within interacting electric and magnetic field environment,"A theoretical exploration and an analytical model for the
+electro-magneto-hydrodynamics (EMHD) of leaky dielectric liquid droplets,
+suspended in an immiscible confined fluid domain has been presented. The
+analytical solution for the system, under small deformation approximation, in
+creeping flow regime, has been put forward. Study of the droplet deformation
+suggests that its temporal evolution is exponential, and dependents on the
+electric and magnetic field interaction. Further, the direction of the applied
+magnetic field with respect to the electric field decides whether the
+contribution of magnetic forces opposes or aids the interfacial net electrical
+force due to the electric field. Validation of the proposed model at the
+asymptotic limits of vanishing magnetic field show that the model accurately
+reduces to the case of transient electrohydrodynamic model. We also propose a
+magnetic discriminating function to quantify the steady-state droplet
+deformation in the presence of interacting electric and magnetic fields. The
+change of droplets from spherical shape to prolate, and oblate spheroids,
+correspond to magnetic discriminating function >0 and <0 regimes, respectively.
+It is shown that with the aid of low magnitude magnetic field, a substantial
+augmentation in the deformation parameter, and the associated EMHD circulation
+within and around the droplet is achieved. The analysis also reveals the
+deformation lag and specific critical parameters that aid or suppressed this
+lag behaviour; discussed in terms of relevant non-dimensional parameters.",2212.12135v2
+2023-01-13,Exploring magnetic loops and serpentine fields in the quiet Sun with the GRIS-IFU,"Synthetic observations produced from radiative magnetohydronamic simulations
+have predicted that higher polarization fractions in the quiet solar
+photosphere would be revealed by increasing the total integration time of
+observations at GREGOR resolutions. We present recently acquired disk centre
+observations of the Fe I $15648.5$ $\mathrm{\AA}$ line obtained with the GREGOR
+telescope equipped with the GRIS-IFU during excellent seeing conditions,
+showing exceptionally high polarization fractions. Our observation reveal an
+internetwork region with a majority ($>60\%$) of magnetised pixels displaying a
+clear transverse component of the magnetic field. This result is in stark
+contrast to previous disk-centre GRIS-IFU observations in this spectral line,
+which had predominantly vertical magnetic fields in the deep photosphere. At
+the same time, the median magnetic field strength is weaker than previous
+GRIS-IFU observations, indicating that the larger fraction of polarization
+signals cannot be explained by a more active target. We use the Stokes
+Inversion based on Response functions (SIR) code to analyse the data,
+performing over $45$ million inversions, and interrogate the impact of two
+conflicting approaches to the treatment of noise on the retrieval of the
+magnetic inclination and azimuth. We present several case studies of the zoo of
+magnetic features present in these data, including small-scale magnetic loops
+that seem to be embedded in a sea of magnetism, and serpentine fields, focusing
+on regions where full-vector spectropolarimetry has been achieved. We also
+present a new open-source Python 3 analysis tool, SIR Explorer (SIRE), that we
+use to examine the dynamics of these small-scale magnetic features.",2301.05591v1
+2023-02-01,Temperature-independent ferromagnetic resonance shift in Bi-doped YIG garnets through magnetic anisotropy tuning,"Thin garnet films are becoming central for magnon-spintronics and
+spin-orbitronics devices as they show versatile magnetic properties together
+with low magnetic losses. These fields would benefit from materials in which
+heat does not affect the magnetization dynamics, an effect known as the
+non-linear thermal frequency shift. In this study, low damping Bi substituted
+Iron garnet (Bi:YIG) ultra-thin films have been grown using Pulsed Laser
+Deposition. Through a fine tuning of the growth parameters, the precise control
+of the perpendicular magnetic anisotropy allows to achieve a full compensation
+of the dipolar magnetic anisotropy. Strikingly, once the growth conditions are
+optimized, varying the growth temperature from 405 {\deg}C to 475 {\deg}C as
+the only tuning parameter induces the easy-axis to go from out-of-plane to
+in-plane. For films that are close to the dipolar compensation, Ferromagnetic
+Resonance measurements yield an effective magnetization $\mu _{0}M_{eff} (T)$
+that has almost no temperature dependence over a large temperature range (260 K
+to 400 K) resulting in an anisotropy temperature exponent of 2. These findings
+put Bi:YIG system among the very few materials in which the temperature
+dependence of the magnetic anisotropy varies at the same rate than the
+saturation magnetization. This interesting behavior is ascribed
+phenomenologically to the sizable orbital moment of $Bi^{3+}$.",2302.00585v1
+2023-02-23,Revealing magnetic field structure at the surfaces of protoplanetary disks via near-infrared circular polarization,"Context. Magnetic fields play a fundamental role in the dynamical evolution
+of protoplanetary disks, in particular via magnetically induced disk winds. The
+magnetic field structure at the disk surface is crucial for driving the disk
+winds; however, it is still poorly understood observationally. Aims. We explore
+a new method to probe the magnetic field structure at the disk surface using
+near-infrared (NIR) circular polarization. Near-infrared circular polarization
+arises when unpolarized stellar light is scattered by magnetically aligned
+grains at the disk surface. In this study, we aim to clarify to what extent the
+observed circular polarization pattern can be used to diagnose the magnetic
+field structure. Methods. We first calculated light scattering properties of
+aligned spheroids, and the results were then used to create expected
+observational images of the degree of circular polarization at a NIR
+wavelength. Results. Magnetically aligned grains can produce circular
+polarization, particularly when the field configuration deviates from a purely
+toroidal field. We find that disk azimuthal dependence of the degree of
+circular polarization tends to exhibit a double peaked profile when the field
+structure is favorable for driving disk winds by centrifugal force. We also
+find that even if the disk is spatially unresolved, a net circular polarization
+can possibly be nonzero. We also show that the amplitude of circular
+polarization is strongly dependent on grain composition and axis ratio.
+Conclusions. Our results suggest that circular polarization observations would
+be useful to study the magnetic field structure and dust properties at the disk
+surface.",2302.12340v1
+2023-07-17,"Unravelling the structure of magnetised molecular clouds with SILCC-Zoom: sheets, filaments and fragmentation","To what extent magnetic fields affect how molecular clouds (MCs) fragment and
+create dense structures is an open question. We present a numerical study of
+cloud fragmentation using the SILCC-Zoom simulations. These simulations follow
+the self-consistent formation of MCs in a few hundred parsec sized region of a
+stratified galactic disc; and include magnetic fields, self-gravity,
+supernova-driven turbulence, as well as a non-equilibrium chemical network. To
+discern the role of magnetic fields in the evolution of MCs, we study seven
+simulated clouds, five with magnetic fields, and two without, with a maximum
+resolution of 0.1 parsec. Using a dendrogram we identify hierarchical
+structures which form within the clouds. Overall, the magnetised clouds have
+more mass in a diffuse envelope with a number density between 1-100 cm$^{-3}$.
+We find that six out of seven clouds are sheet-like on the largest scales, as
+also found in recent observations, and with filamentary structures embedded
+within, consistent with the bubble-driven MC formation mechanism. Hydrodynamic
+simulations tend to produce more sheet-like structures also on smaller scales,
+while the presence of magnetic fields promotes filament formation. Analysing
+cloud energetics, we find that magnetic fields are dynamically important for
+less dense, mostly but not exclusively atomic structures (typically up to $\sim
+100 - 1000$~cm$^{-3}$), while the denser, potentially star-forming structures
+are energetically dominated by self-gravity and turbulence. In addition, we
+compute the magnetic surface term and demonstrate that it is generally
+confining, and some atomic structures are even magnetically held together. In
+general, magnetic fields delay the cloud evolution and fragmentation by $\sim$
+1 Myr.",2307.08746v1
+2023-07-23,How Magnetic Erosion Affects the Drag-Based Kinematics of Fast Coronal Mass Ejections,"In order to advance our understanding of the dynamic interactions between
+coronal mass ejections (CMEs) and the magnetized solar wind, we investigate the
+impact of magnetic erosion on the well-known aerodynamic drag force acting on
+CMEs traveling faster than the ambient solar wind. In particular, we start by
+generating empirical relationships for the basic physical parameters of CMEs
+that conserve their mass and magnetic flux. Furthermore, we examine the impact
+of the virtual mass on the equation of motion by studying a variable-mass
+system. We next implement magnetic reconnection into CME propagation, which
+erodes part of the CME magnetic flux and outer-shell mass, on the drag acting
+on CMEs, and we determine its impact on their time and speed of arrival at 1
+AU. Depending on the strength of the magnetic erosion, the leading edge of the
+magnetic structure can reach near-Earth space up to $\approx$ three hours
+later, compared to the non-eroded case. Therefore, magnetic erosion may have a
+significant impact on the propagation of fast CMEs and on predictions of their
+arrivals at 1 AU. Finally, the modeling indicates that eroded CMEs may
+experience a significant mass decrease. Since such a decrease is not observed
+in the corona, the initiation distance of erosion may lie beyond the
+field-of-view of coronagraphs (i.e. 30 $\mathrm{R_{\odot}}$).",2307.12370v1
+2023-07-25,Shear viscosity coefficient of magnetized QCD medium with anomalous magnetic moments near chiral phase transition,"We study the properties of the shear viscosity coefficient of quark matter
+near the chiral phase transition at finite temperature and chemical potential,
+and the kinds of high temperature, high density and strong magnetic field
+background. The strong magnetic field induces anisotropy, that is, the
+quantization of Landau energy levels in phase space. If the magnetic field is
+strong enough, it will interfere with significant QCD phenomena, such as the
+generation of dynamic quark mass, which may affect the transport properties of
+quark matter. The inclusion of the anomalous magnetic moments of the quarks at
+finite density into the Nambu-Jona-Lasinio model gives rise to additional spin
+polarization magnetic effects. It is found that both the ratio $\eta/s$ of
+shear viscosity coefficient to entropy and the collision relaxation time $\tau$
+show similar trend with temperature, both of which reach minima around the
+critical temperature. The shear viscosity coefficient of the dissipative fluid
+system can be decomposed into five different components as the strong magnetic
+field exists. The influences of the order of chiral phase transition and the
+critical end point on dissipative phenomena in such a magnetized medium are
+quantitatively investigated. It is found that ${\eta}_{1}$, ${\eta}_{2}$,
+${\eta}_{3}$, and ${\eta}_{4}$ all increase with temperature. For first-order
+phase transitions, ${\eta}_{1}$, ${\eta}_{2}$, ${\eta}_{3}$, and ${\eta}_{4}$
+exhibit discontinuous characteristics.",2307.13193v2
+2023-11-21,Magnetic helicity in rotating neutron stars,"We study the magnetic helicity evolution in neutron stars (NSs). First, we
+analyze how the surface terms affect the conservation law for the sum of the
+chiral imbalance of the charged particle densities and the density of the
+magnetic helicity. Our results are applied to a system with a finite volume,
+which can be a magnetized NS. We show that the contribution of these surface
+terms can potentially lead to the reconnection of magnetic field lines followed
+by X-ray or gamma bursts observed in magnetars. Comparing the new quantum
+surface term with the classical contribution known in the standard magnetic
+hydrodynamics, we obtain that its contribution dominates over the classical
+term only for NS with a rigid rotation. Second, we study the dynamics of chiral
+electrons which interact electroweakly with a background fermions having the
+velocity, arbitrarily depending on spatial coordinates, and the nonuniform
+density. We derive the the kinetic equations and the effective action for right
+and left particles. The correction to the Adler anomaly and to the anomalous
+electric current are obtained in the case of a rotating matter. Then, the
+obtained results are applied for the study of the magnetic helicity flow inside
+a magnetized rotating NS. We compute the characteristic time of the helicity
+change and demonstrate that it coincides with the the magnetic cycle period of
+certain pulsars.",2311.12557v1
+2024-02-02,Controllable frequency tunability and parabolic-like threshold current behavior in spin Hall nano-oscillators,"We investigate the individual impacts of critical magnetodynamical
+parameters-effective magnetization and magnetic damping-on the auto-oscillation
+characteristics of nano-constriction-based Spin Hall Nano-Oscillators (SHNOs).
+Our micromagnetic simulations unveil a distinctive non-monotonic relationship
+between current and auto-oscillation frequency in out-of-plane magnetic fields.
+The influence of effective magnetization on frequency tunability varies with
+out-of-plane field strengths. At large out-of-plane fields, the frequency
+tunability is predominantly governed by effective magnetization, achieving a
+current tunability of 1 GHz/mA-four times larger than that observed at the
+lowest effective magnetization. Conversely, at low out-of-plane fields,
+although a remarkably high-frequency tunability of 4 GHz/mA is observed, the
+effective magnetization alters the onset of the transition from a linear-like
+mode to a spin-wave bullet mode. Magnetic damping primarily affects the
+threshold current with negligible impact on auto-oscillation frequency
+tunability. The threshold current scales linearly with increased magnetic
+damping at a constant out-of-plane field but exhibits a parabolic behavior with
+variations in out-of-plane fields. This behavior is attributed to the
+qualitatively distinct evolution of the auto-oscillation mode across different
+out-of-plane field values. Our study not only extends the versatility of SHNOs
+for oscillator-based neuromorphic computing with controllable frequency
+tunability but also unveils the intricate auto-oscillation dynamics in
+out-of-plane fields.",2402.01570v1
+2024-02-17,Characterizing the dynamical magnetosphere of the extremely slowly rotating magnetic O9.7 V star HD 54879 using rotational modulation of the H $α$ profile,"The magnetic field in the O9.7 V star HD54879 has been monitored for almost a
+decade. Spectropolarimetric observations reveal a rather strong mean
+longitudinal magnetic field that varies with a period of about 7.41 yr.
+Observations in the H$\alpha$ line show a variation with the same period, while
+the H$\beta$ line shows only little variation. Assuming the periodic variation
+to be caused by a slow rotation and a dipolar magnetic field, we find a
+magnetic field strength of $\ge$2 kG at the magnetic poles. With the relatively
+low mass loss rate of $10^{-9} M_\odot$ yr$^{-1}$, this star is a case of
+extremely strong magnetic confinement. Both theoretical arguments and numerical
+simulations indicate the presence of an extended disk of increased gas density
+in the equatorial plane of the magnetic field, where gas from the line-driven
+stellar wind is trapped. This disk is likely to be the origin of the observed
+H$\alpha$ emission, which peaks together with the strongest line-of-sight
+magnetic field. The profile of the H$\alpha$ line is resolved in several
+components and shows a remarkable variability with the rotation period.",2402.11244v2
+2024-02-22,Unexpected versatile electrical transport behaviors of ferromagnetic nickel films,"Perpendicular magnetic anisotropy (PMA) of magnets is paramount for
+electrically controlled spintronics due to their intrinsic potentials for
+higher memory density, scalability, thermal stability and endurance, surpassing
+an in-plane magnetic anisotropy (IMA). Nickel film is a long-lived fundamental
+element ferromagnet, yet its electrical transport behavior associated with
+magnetism has not been comprehensively studied, hindering corresponding
+spintronic applications exploiting nickel-based compounds. Here, we
+systematically investigate the highly versatile magnetism and corresponding
+transport behavior of nickel films. As the thickness reduces within the general
+thickness regime of a magnet layer for a memory device, the hardness of nickel
+films' ferromagnetic loop of anomalous Hall effect increases and then
+decreases, reflecting the magnetic transitions from IMA to PMA and back to IMA.
+Additionally, the square ferromagnetic loop changes from a hard to a soft one
+at rising temperatures, indicating a shift from PMA to IMA. Furthermore, we
+observe a butterfly magnetoresistance resulting from the anisotropic
+magnetoresistance effect, which evolves in conjunction with the thickness and
+temperature-dependent magnetic transformations as a complementary support. Our
+findings unveil the rich magnetic dynamics and most importantly settle down the
+most useful guiding information for current-driven spintronic applications
+based on nickel film: The hysteresis loop is squarest for the ~8 nm-thick
+nickel film, of highest hardness with Rxyr/Rxys~1 and minimum Hs-Hc, up to 125
+K; otherwise, extra care should be taken for a different thickness or at a
+higher temperature.",2402.14275v1
+2024-03-24,Unveiling the underlying structure of axial-vector bottom-charm tetraquarks in the light of their magnetic moments,"The magnetic moment yields an excellent framework to explore the inner
+structure of particles determined by the quark-gluon dynamics of QCD, as it is
+the leading-order response of a bound system to a weak external magnetic field.
+Motivated by this, in this study, the magnetic moments of possible axial-vector
+$T_{bc\bar u \bar u}$, $T_{bc\bar d \bar d}$, and $T_{bc\bar u \bar d}$
+tetraquarks are obtained with the help of light-cone QCD sum rules. For this
+purpose, we assume that these states are represented as a diquark-antidiquark
+picture with different structures and interpolating currents. The magnetic
+moment results derived using different diquark-antidiquark configurations
+differ substantially from each other. This can be translated into more than one
+tetraquark state with the same quantum number and quark content yet possessing
+different magnetic moments. From the numerical results obtained, we have
+concluded that the magnetic moments of the $T_{bc}$ states can project their
+inner structure, which can be used for their quantum numbers and quark-gluon
+organization. The contribution of individual quarks to the magnetic moments is
+also analyzed for completeness. We hope that our predictions of the magnetic
+moments of the $T_{bc}$ tetraquarks, together with the results of other
+theoretical investigations of the spectroscopic parameters and decay widths of
+these interesting tetraquarks, may be valuable in the search for these states
+in future experiments and in unraveling the internal structure of these
+tetraquarks.",2403.16191v1
+2024-03-27,Complexity of emerging magnetic flux during lifetime of solar ephemeral regions,"As a relatively active region, ephemeral region (ER) exhibits highly complex
+pattern of magnetic flux emergence. We aim to study detailed secondary flux
+emergences (SFEs) which we define as bipoles that they appear close to ERs and
+finally coalesce with ERs after a period. We study the SFEs during the whole
+process from emergence to decay of 5 ERs observed by the Helioseismic and
+Magnetic Imager (HMI) aboard Solar Dynamics Observatory (SDO) . The maximum
+unsigned magnetic flux for each ER is around $10^{20}$ Mx. Each ER has tens of
+SFEs with an average emerging magnetic flux of approximately 5$\times10^{18}$
+Mx. The frequency of normalized magnetic flux for all the SFEs follows a power
+law distribution with an index of -2.08 . The majority of SFEs occur between
+the positive and negative polarities of ER , and their growth time is
+concentrated within one hour. The magnetic axis of SFE is found to exhibit a
+random distribution in the 5 ERs. We suggest that the relationship between SFEs
+and ERs can be understood by regarding the photospheric magnetic field
+observations as cross-sections of an emerging magnetic structure. Tracking the
+ERs' evolution, we propose that these SFEs in ERs may be sequent emergences
+from the bundle of flux tube of ERs, and that SFEs are partially emerged
+$\Omega$-loops.",2403.18979v1
+2013-03-25,"Polaron-like vortices, dissociation transition and self induced pinning in magnetic superconductors","In magnetic superconductors vortices polarize spins nonuniformly and
+repolarize them when moving. At a low spin relaxation rate and at low bias
+currents vortices carrying magnetic polarization clouds become polaron-like and
+their velocities are determined by the effective drag coefficient which is
+significantly bigger than the Bardeen-Stephen (BS) one. As current increases,
+vortices release polarization clouds and the velocity as well as the voltage in
+the I-V characteristics jump to values corresponding to the BS drag coefficient
+at a critical current $J_c$. The nonuniform components of the magnetic field
+and magnetization drop as velocity increases resulting in weaker polarization
+and {\it discontinuous} dynamic dissociation depinning transition.
+Experimentally the jump shows up as a depinning transition and the
+corresponding current at the jump is the depinning current. As current
+decreases, on the way back, vortices are retrapped by polarization clouds at
+the current $J_r<J_c$. As a result, polaronic effect suppresses dissipation and
+enhances critical current. Borocarbides (RE)Ni$_2$B$_2$C with a short
+penetration length and highly polarizable rare earth spins seem to be optimal
+systems for a detailed study of vortex polaron formation by measuring I-V
+characteristics. We propose also to use superconductor-magnet multilayer
+structure to study polaronic mechanism of pinning with the goal to achieve high
+critical currents. The magnetic layers should have large magnetic
+susceptibility to enhance the coupling between vortices and magnetization in
+magnetic layers while the relaxation of the magnetization should be slow. For
+Nb and proper magnet multilayer structure, we estimate the critical current
+density $J_c\sim 10^{9}\ \rm{A/m^2}$ at magnetic field $B\approx 1$ T.",1303.6184v1
+2013-04-19,Magnetic field strength distribution of magnetic bright points inferred from filtergrams and spectro-polarimetric data,"Small scale magnetic fields can be observed on the Sun in G-band filtergrams
+as MBPs (magnetic bright points) or identified in spectro-polarimetric
+measurements due to enhanced signals of Stokes profiles. These magnetic fields
+and their dynamics play a crucial role in understanding the coronal heating
+problem and also in surface dynamo models. MBPs can theoretically be described
+to evolve out of a patch of a solar photospheric magnetic field with values
+below the equipartition field strength by the so-called convective collapse
+model. After the collapse, the magnetic field of MBPs reaches a higher stable
+magnetic field level. The magnetic field strength distribution of small scale
+magnetic fields as seen by MBPs is inferred. Furthermore, we want to test the
+model of convective collapse and the theoretically predicted stable value of
+about 1300 G. We used four different data sets of high-resolution Hinode/SOT
+observations that were recorded simultaneously with the broadband filter device
+(G-band, Ca II-H) and the spectro-polarimeter. To derive the magnetic field
+strength distribution of these small scale features, the spectropolarimeter
+(SP) data sets were treated by the Merlin inversion code. The four data sets
+comprise different solar surface types: active regions (a sunspot group and a
+region with pores), as well as quiet Sun. In all four cases the obtained
+magnetic field strength distribution of MBPs is similar and shows peaks around
+1300 G. This agrees well with the theoretical prediction of the convective
+collapse model. The resulting magnetic field strength distribution can be
+fitted in each case by a model consisting of log-normal components. The
+important parameters, such as geometrical mean value and multiplicative
+standard deviation, are similar in all data sets, only the relative weighting
+of the components is different.",1304.5508v1
+2015-01-02,Measuring magnetism in the Milky Way with the Square Kilometre Array,"Magnetic fields in the Milky Way are present on a wide variety of sizes and
+strengths, influencing many processes in the Galactic ecosystem such as star
+formation, gas dynamics, jets, and evolution of supernova remnants or pulsar
+wind nebulae. Observation methods are complex and indirect; the most used of
+these are a grid of rotation measures of unresolved polarized extragalactic
+sources, and broadband polarimetry of diffuse emission. Current studies of
+magnetic fields in the Milky Way reveal a global spiral magnetic field with a
+significant turbulent component; the limited sample of magnetic field
+measurements in discrete objects such as supernova remnants and HII regions
+shows a wide variety in field configurations; a few detections of magnetic
+fields in Young Stellar Object jets have been published; and the magnetic field
+structure in the Galactic Center is still under debate.
+  The SKA will unravel the 3D structure and configurations of magnetic fields
+in the Milky Way on sub-parsec to galaxy scales, including field structure in
+the Galactic Center. The global configuration of the Milky Way disk magnetic
+field, probed through pulsar RMs, will resolve controversy about reversals in
+the Galactic plane. Characteristics of interstellar turbulence can be
+determined from the grid of background RMs. We expect to learn to understand
+magnetic field structures in protostellar jets, supernova remnants, and other
+discrete sources, due to the vast increase in sample sizes possible with the
+SKA. This knowledge of magnetic fields in the Milky Way will not only be
+crucial in understanding of the evolution and interaction of Galactic
+structures, but will also help to define and remove Galactic foregrounds for a
+multitude of extragalactic and cosmological studies.",1501.00416v1
+2015-03-02,Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals,"A range of quantum field theoretical phenomena driven by external magnetic
+fields and their applications in relativistic systems and quasirelativistic
+condensed matter ones, such as graphene and Dirac/Weyl semimetals, are
+reviewed. We start by introducing the underlying physics of the magnetic
+catalysis. The dimensional reduction of the low-energy dynamics of relativistic
+fermions in an external magnetic field is explained and its role in catalyzing
+spontaneous symmetry breaking is emphasized. The general theoretical
+consideration is supplemented by the analysis of the magnetic catalysis in
+quantum electrodynamics, chromodynamics and quasirelativistic models relevant
+for condensed matter physics. By generalizing the ideas of the magnetic
+catalysis to the case of nonzero density and temperature, we argue that other
+interesting phenomena take place. The chiral magnetic and chiral separation
+effects are perhaps the most interesting among them. In addition to the general
+discussion of the physics underlying chiral magnetic and separation effects, we
+also review their possible phenomenological implications in heavy-ion
+collisions and compact stars. We also discuss the application of the magnetic
+catalysis ideas for the description of the quantum Hall effect in monolayer and
+bilayer graphene, and conclude that the generalized magnetic catalysis,
+including both the magnetic catalysis condensates and the quantum Hall
+ferromagnetic ones, lies at the basis of this phenomenon. We also consider how
+an external magnetic field affects the underlying physics in a class of
+three-dimensional quasirelativistic condensed matter systems, Dirac semimetals.
+While at sufficiently low temperatures and zero density of charge carriers,
+such semimetals are expected to reveal the regime of the magnetic catalysis,
+the regime of Weyl semimetals with chiral asymmetry is realized at nonzero
+density...",1503.00732v2
+2018-06-28,Nature of the energy source powering solar coronal loops driven by nanoflares,"Magnetic energy is required to heat the corona, the outer atmosphere of the
+Sun, to millions of degrees. We study the nature of the magnetic energy source
+that is probably responsible for the brightening of coronal loops driven by
+nanoflares in the cores of solar active regions. We consider observations of
+two active regions (ARs), 11890 and 12234, in which nanoflares have been
+detected. To this end, we use ultraviolet (UV) and extreme ultraviolet (EUV)
+images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
+Observatory (SDO) for coronal loop diagnostics. These images are combined with
+the co-temporal line-of-sight magnetic field maps from the Helioseismic and
+Magnetic Imager (HMI) onboard SDO to investigate the connection between coronal
+loops and their magnetic roots in the photosphere. The core of these ARs
+exhibit loop brightening in multiple EUV channels of AIA, particularly in its
+9.4 nm filter. The HMI magnetic field maps reveal the presence of a complex
+mixed polarity magnetic field distribution at the base of these loops. We
+detect the cancellation of photospheric magnetic flux at these locations at a
+rate of about $10^{15}$ Mx s$^{-1}$. The associated compact coronal
+brightenings directly above the cancelling magnetic features are indicative of
+plasma heating due to chromospheric magnetic reconnection. We suggest that the
+complex magnetic topology and the evolution of magnetic field, such as flux
+cancellation in the photosphere and the resulting chromospheric reconnection,
+can play an important role in energizing active region coronal loops driven by
+nanoflares. Our estimate of magnetic energy release during flux cancellation in
+the quiet Sun suggests that chromospheric reconnection can also power the quiet
+corona.",1806.11045v2
+2020-03-19,Realizing an Isotropically Coercive Magnetic Layer for Memristive Applications by Analogy to Dry Friction,"We investigate the possibility of realizing a spintronic memristive device
+based on the dependence of the tunnel conductance on the relative angle between
+the magnetization of the two magnetic electrodes in in-plane magnetized tunnel
+junctions. For this, it is necessary to design a free layer whose magnetization
+can be stabilized along several or even any in-plane direction between the
+parallel and the antiparallel magnetic configurations. We experimentally show
+that this can be achieved by exploiting antiferromagnet-ferromagnet exchange
+interactions in a regime where the antiferromagnet is thin enough to induce
+enhanced coercivity and no exchange bias. The frustration of exchange
+interactions at the interfaces due to competing ferro- and antiferromagnetic
+interactions is at the origin of an isotropic dissipation mechanism yielding
+isotropic coercivity. From a modeling point of view, it is shown that this
+isotropic dissipation can be described by a dry friction term in the
+Landau-Lifshitz-Gilbert equation. The influence of this dry friction term on
+the magnetization dynamics of an in-plane magnetized layer submitted to a
+rotating in-plane field is investigated both analytically and numerically. The
+possibility to control the free layer magnetization orientation in an in-plane
+magnetized magnetic tunnel junction by using the spin transfer torque from an
+additional perpendicular polarizer is also investigated through macrospin
+simulation. It is shown that the memristor function can be achieved by the
+injection of current pulses through the stack in the presence of an in-plane
+static field transverse to the reference layer magnetization, the aim of which
+is to limit the magnetization rotation between 0{\deg} and 180{\deg}.",2003.08850v1
+2021-06-15,Modeling the Magnetization Dynamics for Large Ensembles of Immobilized Magnetic Nanoparticles in Multi-dimensional Magnetic Particle Imaging,"Magnetic nanoparticles (MNPs) play an important role in biomedical
+applications including imaging modalities such as MRI and magnetic particle
+imaging (MPI). The latter one exploits the non-linear magnetization response of
+a large ensemble of magnetic nanoparticles to magnetic fields which allows
+determining the spatial distribution of the MNP concentration from measured
+voltage signals. Currently, modeling the voltage signals of large ensembles of
+MNPs in an MPI environment is not yet accurately possible, especially for
+liquid tracers in multi-dimensional magnetic excitation fields. Thus, the
+voltage-to-image mapping is still obtained in a time consuming calibration
+procedure. While the ferrofluidic case can be seen as the typical setting, more
+recently immobilized and potentially oriented MNPs have received considerable
+attention. By aligning the particles during immobilization, one can encode the
+angle of the easy axis into the magnetization response providing a
+sophisticated benchmark system for model-based approaches. In this work, we
+address the modeling problem for immobilized, oriented MNPs in the context of
+MPI. We investigate a model-based approach where the magnetization response is
+simulated by a N\'eel rotation model for the particle's magnetic moments and
+the ensemble magnetization is obtained by solving a Fokker-Planck equation
+approach. Since the parameters of the model are a-priori unknown, we
+investigate different methods for performing a parameter identification and
+discuss two models: One where a single function vector is used from the space
+spanned by the model parameters and another where a superposition of function
+vectors is considered. We show that our model can much more accurately
+reproduce the orientation dependent signal response when compared to the
+equilibrium model, which marks the current state-of-the-art for model-based
+system matrix simulations in MPI.",2106.08040v1
+2014-07-19,Signatures of spin-glass behavior in the induced magnetic moment system PrRuSi3,"We have investigated the magnetic and transport properties of a ternary
+intermetallic compound PrRuSi3 using dc magnetization, ac susceptibility,
+specific heat, electrical resistivity, neutron diffraction, inelastic neutron
+scattering and muSR measurements. The magnetic susceptibility and specific heat
+data reveal the signatures of spin-glass behavior in PrRuSi3 with a freezing
+temperature of 9.8 K. At low magnetic fields, we observe two sharp anomalies
+(at 4.9 and 8.6 K) in magnetic susceptibility data. In contrast, the specific
+heat data show only a broad Schottky-type anomaly centered around 10 K.
+However, muSR reveals very low frequency coherent oscillations at 1.8 K with an
+onset of fast relaxation below 12 K indicating a long range magnetically
+ordered ground state with very small moment. On the other hand, no magnetic
+Bragg peaks are observed in low temperature neutron diffraction data at 1.8 K.
+These two contradictory ground states, spin-glass versus magnetic order, can be
+explained if the spin-glass behavior in PrRuSi3 is considered due to the
+dynamic fluctuations of the crystal field levels as has been proposed for
+spin-glass behavior in PrAu2Si2. Two sharp inelastic excitations near 2.4 meV
+and 14.7 meV are observed in the inelastic neutron scattering (INS) spectra
+between 4 K and 50 K. Further, exchange coupling J_ex obtained from the
+analysis of INS data with CEF model provides evidence for the spontaneously
+induced magnetic order with a CEF-split singlet (Gamma_t4) ground state.
+However, the exchange coupling seems to be close to the critical value for the
+induced moment magnetism, therefore we tend to believe that the dynamic
+fluctuations between the ground state singlet and excited doublet CEF levels is
+responsible for spin-glass behavior in PrRuSi3.",1407.5209v1
+2016-04-25,An extensive numerical survey of the correlation between outflow dynamics and accretion disk magnetization,"We investigate the accretion-ejection process of jets from magnetized
+accretion disks. We apply a novel approach to the jet-launching problem in
+order to obtain correlations between the physical properties of the jet and the
+underlying disk. We extend and confirm the previous works of
+\citet{2009MNRAS.400..820T} and \citet{2010A&A...512A..82M} by scanning a large
+parameter range for the disk magnetization, $\mu_{\rm D} = 10^{-3.5} ...
+10^{-0.7}$. We disentangle the disk magnetization at the foot point of the
+outflow as the main parameter that governs the properties of the outflow. We
+show how the four jet integrals known from steady-state MHD are correlated to
+the disk magnetization at the jet foot point. This agrees with the usual
+findings of the steady-state theory, however, here we obtain these correlations
+from time-dependent simulations that include the dynamical evolution of the
+disk in the treatment. In particular, we obtain robust correlations between the
+local disk magnetization and (i)the outflow velocity, (ii) the jet mass
+loading, (iii) jet angular momentum, and (iv) the local mass accretion rate.
+Essentially we find that strongly magnetized disks launch more energetic and
+faster jets, and, due to a larger Alfv\'en lever arm, these jets extract more
+angular momentum from the underlying disk. These kind of disk-jet systems have,
+however, a smaller mass loading parameter and a lower mass
+ejection-to-accretion ratio. The jets are launched at the disk surface where
+the magnetization is $\mu(r,z) \simeq 0.1$. The magnetization rapidly increases
+vertically providing the energy reservoir for subsequent jet acceleration. We
+find indication for a critical disk magnetization $\mu_{\rm D} \simeq 0.01$
+that separates the regimes of magnetocentrifugally-driven and magnetic
+pressure-driven jets.",1604.07313v1
+2019-02-21,EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions IV. Magnetic field strength limits and structure for 7 additional sources,"MHD simulations show that the magnetic field can drive molecular outflows
+during the formation of massive protostars. The best probe to observationally
+measure both the morphology and the strength of this magnetic field at scales
+of 10-100 au is maser polarization. We measure the direction of magnetic fields
+at mas resolution around a sample of massive star-forming regions to determine
+whether there is a relation between the orientation of the magnetic field and
+of the outflows. In addition, by estimating the magnetic field strength via the
+Zeeman splitting measurements, the role of magnetic field in the dynamics of
+the massive star-forming region is investigated. We selected a flux-limited
+sample of 31 massive star-forming regions to perform a statistical analysis of
+the magnetic field properties with respect to the molecular outflows
+characteristics. We report the linearly and circularly polarized emission of
+6.7 GHz CH3OH masers towards seven massive star-forming regions of the total
+sample with the EVN. The sources are: G23.44-0.18, G25.83-0.18, G25.71-0.04,
+G28.31-0.39, G28.83-0.25, G29.96-0.02, and G43.80-0.13. We identified a total
+of 219 CH3OH maser features, 47 and 2 of which showed linearly and circularly
+polarized emission, respectively. We measured well-ordered linear polarization
+vectors around all the massive YSOs and Zeeman splitting towards G25.71-0.04
+and G28.83-0.25. Thanks to recent theoretical results, we were able to provide
+lower limits to the magnetic field strength from our Zeeman splitting
+measurements. We further confirm (based on ~80% of the total flux-limited
+sample) that the magnetic field on scales of 10-100 au is preferentially
+oriented along the outflow axes. The estimated magnetic field strength of
+|B_{||}|>61 mG and >21 mG towards G25.71-0.04 and G28.83-0.2, respectively,
+indicates that it dominates the dynamics of the gas in both regions.",1902.08210v1
+2020-12-02,Reconnection-controlled decay of magnetohydrodynamic turbulence and the role of invariants,"We present a new theoretical picture of magnetically dominated, decaying
+turbulence in the absence of a mean magnetic field. We demonstrate that such
+turbulence is governed by the reconnection of magnetic structures, and not by
+ideal dynamics, as has previously been assumed. We obtain predictions for the
+magnetic-energy decay laws by proposing that turbulence decays on reconnection
+timescales, while respecting the conservation of certain integral invariants
+representing topological constraints satisfied by the reconnecting magnetic
+field. As is well known, the magnetic helicity is such an invariant for
+initially helical field configurations, but does not constrain non-helical
+decay, where the volume-averaged magnetic-helicity density vanishes. For such a
+decay, we propose a new integral invariant, analogous to the Loitsyansky and
+Saffman invariants of hydrodynamic turbulence, that expresses the conservation
+of the random (scaling as $\mathrm{volume}^{1/2}$) magnetic helicity contained
+in any sufficiently large volume. Our treatment leads to novel predictions for
+the magnetic-energy decay laws: in particular, while we expect the canonical
+$t^{-2/3}$ power law for helical turbulence when reconnection is fast (i.e.,
+plasmoid-dominated or stochastic), we find a shallower $t^{-4/7}$ decay in the
+slow `Sweet-Parker' reconnection regime, in better agreement with existing
+numerical simulations. For non-helical fields, for which there currently exists
+no definitive theory, we predict power laws of $t^{-10/9}$ and $t^{-20/17}$ in
+the fast- and slow-reconnection regimes, respectively. We formulate a general
+principle of decay of turbulent systems subject to conservation of Saffman-like
+invariants, and propose how it may be applied to MHD turbulence with a strong
+mean magnetic field and to isotropic MHD turbulence with initial equipartition
+between the magnetic and kinetic energies.",2012.01393v3
+2024-02-15,Time evolution of the galactic $B- ρ$ relation: the impact of the magnetic field morphology,"One of the most frequently used indicators to characterize the magnetic
+field's influence on star formation is the relation between magnetic field
+strength and gas density ($B-\rho$ relation), usually expressed as $B \propto
+\rho^{\kappa}$. The value of $\kappa$ is an indication of the dynamical
+importance of the magnetic field during gas compression. Investigating the
+global magnetic field's impact on this relation and its evolution, we conduct
+MHD simulations of Milky-Way-like galaxies including gravity, star formation,
+and supernova feedback along with non-equilibrium chemistry up to $H_2$
+formation fueling star formation. Two initial magnetic field morphologies are
+studied: one completely ordered (toroidal) and the other completely random. In
+these models, we study the dynamical importance of the magnetic field through
+the plasma $\beta$ and the $B-\rho$ relation. For both magnetic morphologies,
+low-density regions are thermally supported, while high-density regions are
+magnetically dominated. Equipartition is reached earlier and at lower densities
+in the toroidal model. However, the $B-\rho$ relation is not unique even within
+the same galaxy, as it consistently includes two different branches for a given
+density, with $\kappa$ ranging from about 0.2 to 0.8. The mean value of
+$\kappa$ for each model also displays significant variations over time, which
+supersede the differences between the two models. While our findings suggest
+that the magnetic field morphology does influence the galactic $B-\rho$
+relation, its impact is transient, since time-averaged differences between the
+models fall within the large temporal scatter. The context and time-dependent
+nature of the $B-\rho$ relation underscore the need for comprehensive research
+and observations to understand the intricate role of magnetic fields in star
+formation processes across diverse galactic environments.",2402.10268v2
+2002-10-11,Dynamics of spin-2 Bose condensate driven by external magnetic fields,"Dynamic response of the F=2 spinor Bose-Einstein condensate (BEC) under the
+influence of external magnetic fields is studied. A general formula is given
+for the oscillation period to describe population transfer from the initial
+polar state to other spin states. We show that when the frequency and the
+reduced amplitude of the longitudinal magnetic field are related in a specific
+manner, the population of the initial spin-0 state will be dynamically
+localized during time evolution. The effects of external noise and nonlinear
+spin exchange interaction on the dynamics of the spinor BEC are studied. We
+show that while the external noise may eventually destroy the Rabi oscillations
+and dynamic spin localization, these coherent phenomena are robust against the
+nonlinear atomic interaction.",0210252v1
+2003-02-27,A new approach to dynamic finite-size scaling,"In this work we have considered the Taylor series expansion of the dynamic
+scaling relation of the magnetization with respect to small initial
+magnetization values in order to study the dynamic scaling behaviour of 2- and
+3-dimensional Ising models. We have used the literature values of the critical
+exponents and of the new dynamic exponent $x_0$ to observe the dynamic
+finite-size scaling behaviour of the time evolution of the magnetization during
+early stages of the Monte Carlo simulation. For 3-dimensional Ising Model we
+have also presented that this method opens the possibility of calculating $z$
+and $x_0$ separately. Our results show good agreement with the literature
+values. Measurements done on lattices with different sizes seem to give very
+good scaling.",0302571v1
+2007-10-09,NMR Time Reversal as a Probe of Incipient Turbulent Spin Dynamics,"We demonstrate time reversal of nuclear spin dynamics in highly magnetized
+dilute liquid 3He-4He mixtures through effective inversion of long-range
+dipolar interactions. These experiments, which involve using magic sandwich NMR
+pulse sequences to generate spin echoes, probe the spatiotemporal development
+of turbulent spin dynamics and promise to serve as a versatile tool for the
+study and control of dynamic magnetization instabilities. We also show that a
+repeated magic sandwich pulse sequence can be used to dynamically stabilize
+modes of nuclear precession that are otherwise intrinsically unstable. To date,
+we have extended the effective precession lifetimes of our magnetized samples
+by more than three orders of magnitude.",0710.1765v1
+2008-08-06,Quantum response to time-dependent external fields,"Recently, explicit real time dynamics has been studied in various systems.
+These quantum mechanical dynamics could provide new recipes in information
+processing. We study quantum dynamics under time dependent external fields, and
+explore how to control the quantum state, and also how to bring the state into
+a target state. Here, we investigate a pure quantum mechanical dynamics,
+dynamics in quantum Monte Carlo simulation and also in quantum master equation.
+For the control magnetic states, operators which do not commute with
+magnetization are important. We study case of the transverse Ising model, in
+which we compare natures of thermal and quantum fluctuations. We also study the
+cases of the Dzyaloshinsky-Moriya interaction, where we find a peculiar energy
+level structure. Moreover we study the case of itinerant magnetic state, where
+we study the change from the Mott insulator to the Nagaoka ferromagnetic state.
+Effects of dissipation are also discussed.",0808.0815v4
+2008-10-01,Fractal geometry of Ising magnetic patterns: signatures of criticality and diffusive dynamics,"We investigate the geometric properties displayed by the magnetic patterns
+developing on a two-dimensional Ising system, when a diffusive thermal dynamics
+is adopted. Such a dynamics is generated by a random walker which diffuses
+throughout the sites of the lattice, updating the relevant spins. Since the
+walker is biased towards borders between clusters, the border-sites are more
+likely to be updated with respect to a non-diffusive dynamics and therefore, we
+expect the spin configurations to be affected. In particular, by means of the
+box-counting technique, we measure the fractal dimension of magnetic patterns
+emerging on the lattice, as the temperature is varied. Interestingly, our
+results provide a geometric signature of the phase transition and they also
+highlight some non-trivial, quantitative differences between the behaviors
+pertaining to the diffusive and non-diffusive dynamics.",0810.0216v1
+2009-01-19,Barriers for the reduction of transport due to the EXB drift in magnetized plasmas,"We consider a 1 1/2degrees of freedom Hamiltonian dynamical system, which
+models the chaotic dynamics of charged test-particles in a turbulent electric
+field, across the confining magnetic field in controlled thermonuclear fusion
+devices. The external electric field E = \nabla\bigvee is modeled by a
+phenomenological potential V and the magnetic field B is considered uniform. It
+is shown that, by introducing a small additive control term to the external
+electric field, it is possible to create a transport barrier for this dynamical
+system. The robustness of this control method is also investigated. This
+theoretical study indicates that alternative transport barriers can be
+triggered without requiring a control action on the device scale as in present
+Internal Transport Barriers (ITB).",0901.2848v1
+2009-08-21,Large-scale horizontal flows in the solar photosphere V: Possible evidence for the disconnection of bi-polar sunspot groups from their magnetic roots,"In a recent paper (Svanda et al., 2008, A&A 477, 285) we pointed out that,
+based on the tracking of Doppler features in the full-disc MDI Dopplergrams,
+the active regions display two dynamically different regimes. We speculated
+that this could be a manifestation of the sudden change in the active regions
+dynamics, caused by the dynamic disconnection of sunspots from their magnetic
+roots as proposed by Schuessler & Rempel (2005, A&A 441, 337). Here we
+investigate the dynamic behaviour of the active regions recorded in the
+high-cadence MDI data over the last solar cycle in order to confirm the
+predictions in the Schuessler's & Rempel's paper. We find that, after drastic
+reduction of the sample, which is done to avoid disturbing effects, a large
+fraction of active regions displays a sudden decrease in the rotation speed,
+which is compatible with the mechanism of the dynamic disconnection of sunspots
+from their parental magnetic structures.",0908.3183v1
+2011-10-05,A tunable cancer cell filter using magnetic beads: cellular and fluid dynamic simulations,"In the field of biomedicine magnetic beads are used for drug delivery and to
+treat hyperthermia. Here we propose to use self-organized bead structures to
+isolate circulating tumor cells using lab-on-chip technologies. Typically blood
+flows past microposts functionalized with antibodies for circulating tumor
+cells. Creating these microposts with interacting magnetic beads makes it
+possible to tune the geometry in size, position and shape. We develop a
+simulation tool that combines micromagnetics, discrete particle dynamics and
+fluid dynamics, in order to design micropost arrays made of interacting beads.
+For the simulation of blood flow we use the Lattice-Boltzmann method with
+immersed elastic blood cell models. Parallelization distributes large fluid and
+particle dynamic simulations over available resources to reduce overall
+calculation time.",1110.0995v1
+2014-03-21,Interface boundary conditions for dynamic magnetization and spin wave dynamics in a ferromagnetic layer with the interface Dzyaloshinskii-Moriya interaction,"In this work we derive the interface exchange boundary conditions for the
+classical linear dynamics of magnetization in ferromagnetic layers with the
+interface Dzyaloshinskii-Moriya interaction (IDMI). We show that IDMI leads to
+pinning of dynamic magnetization at the interface. An unusual peculiarity of
+the IDMI-based pinning is that its scales as the spin-wave wave number. We
+incorporate these boundary conditions into an existing numerical model for the
+dynamics of the Damon-Eshbach spin wave in ferromagnetic films. IDMI affects
+the dispersion and the frequency non-reciprocity of the traveling Damon-Eshbach
+spin wave. For a broad range of film thicknesses L and wave numbers the results
+of the numerical simulations of the spin wave dispersion are in a good
+agreement with a simple analytical expression which shows that the contribution
+of IDMI to the dispersion scales as 1/L, similarly to the effect of other types
+of interfacial anisotropy. Suggestions to experimentalists how to detect the
+presence of IDMI in a spin wave experiment are given.",1403.5385v4
+2014-10-07,Spin dynamics of a confined electron interacting with magnetic or nuclear spins: A semiclassical approach,"A physically transparent and mathematically simple semiclassical model is
+employed to examine dynamics in the central-spin problem. The results reproduce
+a number of previous findings obtained by various quantum approaches and, at
+the same time, provide information on the electron spin dynamics and Berry's
+phase effects over a wider range of experimentally relevant parameters than
+available previously. This development is relevant to dynamics of bound
+magnetic polarons and spin dephasing of an electron trapped by an impurity or a
+quantum dot, and coupled by a contact interaction to neighboring localized
+magnetic impurities or nuclear spins. Furthermore, it substantiates the
+applicability of semiclassical models to simulate dynamic properties of
+spintronic nanostructures with a mesoscopic number of spins.",1410.1717v1
+2015-11-14,Controlling skyrmion helicity via engineered Dzyaloshinskii-Moriya interactions,"Single magnetic skyrmion dynamics in chiral magnets with a spatially
+inhomogeneous Dzyaloshinskii-Moriya interaction (DMI) is considered. Based on
+the relation between DMI coupling and skyrmion helicity, it is argued that the
+latter must be included as an extra degree of freedom in the dynamics of
+skyrmions. An effective description of the skyrmion dynamics for an arbitrary
+inhomogeneous DMI coupling is obtained through the collective coordinates
+method. The resulting generalized Thiele's equation is a dynamical system for
+the center of mass position and helicity of the skyrmion. It is found that the
+dissipative tensor and hence the Hall angle become helicity dependent. The
+skyrmion position and helicity dynamics are fully characterized by our model in
+two particular examples of engineered DMI coupling: half-planes with
+opposite-sign DMI and linearly varying DMI. In light of the experiment of
+Shibata {\it et al}. [Nature Nanotech. {\bf 8}, 723 (2013)] on the magnitude
+and sign of the DMI, our results constitute the first step toward a more
+complete understanding of the skyrmion helicity as a new degree of freedom that
+could be harnessed in future high-density magnetic storage and logic devices.",1511.04584v1
+2016-05-10,Magnetic field induced dynamical instabilities in an anti-ferromagnetic spin-1 Bose-Einstein condensate,"We theoretically investigate four types of dynamical instability, in
+particular the periodic and oscillatory type $I_O$, in an anti-ferromagnetic
+spin-1 Bose-Einstein condensate in a nonzero magnetic field, by employing the
+coupled-mode theory and numerical method. This is in sharp contrast to the
+dynamical stability of the same system in zero field. Remarkably, a pattern
+transition from a periodic dynamical instability $I_O$ to a uniform one $III_O$
+occurs at a critical magnetic field. All the four types of dynamical
+instability and the pattern transition are ready to be detected in $^{23}$Na
+condensates within the availability of the current experimental techniques.",1605.02864v1
+2017-10-26,Spin dynamics in MgO based magnetic tunnel junctions with dynamical exchange coupling,"We study the spin dynamics in Fe|MgO|Fe tunnel junction with the dynamical
+exchange coupling by coupled Landau-Lifshitz-Gilbert equations. The effects of
+spin pumping on the spin dynamics are investigated in detail. It is observed
+that the spin pumping can stabilize a quasi-antiparallel state rather than a
+quasi-parallel one. More interestingly, our work suggests that the spin pumping
+torque can efficiently modulate the magnetization, similar to the
+thermal-bias-driven and electricbias-driven spin torques.",1710.09666v2
+2018-03-20,Dynamic magneto-optic coupling in a ferromagnetic nematic liquid crystal,"Hydrodynamics of complex fuids with multiple order parameters is governed by
+a set of dynamic equations with many material constants, of which only some are
+easily measurable. We present a unique example of a dynamic magneto-optic
+coupling in a ferromagnetic nematic liquid, in which long-range orientational
+order of liquid crystalline molecules is accompanied by long-range magnetic
+order of magnetic nanoplatelets. We investigate the dynamics of the
+magneto-optic response experimentally and theoretically and find out that it is
+significantly affected by the dissipative dynamic cross-coupling between the
+nematic and magnetic order parameters. The cross-coupling coefficient
+determined by fitting the experimental results with a macroscopic theory is of
+the same order of magnitude as the dissipative coefficient (rotational
+viscosity) that governs the reorientation of pure liquid crystals.",1803.07075v1
+2018-11-13,Phase locking of a pair of nano ferromagnetic oscillators on a topological insulator,"We investigate the magnetization dynamics of a pair of ferromagnetic
+insulators (FMIs) deposited on the surface of a topological insulator (TI). Due
+to the nonlinear nature of the underlying physics and intrinsic dynamics, the
+FMIs can exhibit oscillatory behaviors even under a constant applied voltage.
+The motion of the surface electrons of the TI, which obeys relativistic quantum
+mechanics, provides a mechanism of direct coupling between the FMIs. In
+particular, the spin polarized current of the TI surface electrons can affect
+the magnetization of the two FMIs, which in turn modulates the electron
+transport, giving rise to a hybrid relativistic quantum/classical nonlinear
+dynamical system. We find robust phase and anti-phase locking between the
+magnetization dynamics. As driving the surface electrons of a TI only requires
+extremely low power, our finding suggests that nano FMIs coupled by a spin
+polarized current on the surface of TI have the potential to serve as the
+fundamental building blocks of unconventional, low-power computing paradigms.",1811.05551v1
+2019-04-08,Learning time-stepping by nonlinear dimensionality reduction to predict magnetization dynamics,"We establish a time-stepping learning algorithm and apply it to predict the
+solution of the partial differential equation of motion in micromagnetism as a
+dynamical system depending on the external field as parameter. The data-driven
+approach is based on nonlinear model order reduction by use of kernel methods
+for unsupervised learning, yielding a predictor for the magnetization dynamics
+without any need for field evaluations after a data generation and training
+phase as precomputation. Magnetization states from simulated micromagnetic
+dynamics associated with different external fields are used as training data to
+learn a low-dimensional representation in so-called feature space and a map
+that predicts the time-evolution in reduced space. Remarkably, only two degrees
+of freedom in feature space were enough to describe the nonlinear dynamics of a
+thin-film element. The approach has no restrictions on the spatial
+discretization and might be useful for fast determination of the response to an
+external field.",1904.04215v3
+2019-05-28,The Effects of Solar Wind Dynamic Pressure on the Structure of the Topside Ionosphere of Mars,"We use Mars Atmosphere and Volatile EvolutioN observations of the upstream
+solar wind, and Mars Express observations of ionospheric electron densities and
+magnetic fields, to study how the topside ionosphere ($>$ 320 km) of Mars is
+affected by variations in solar wind dynamic pressure. We find that high solar
+wind dynamic pressures result in the topside ionosphere being depleted of
+plasma at all solar zenith angles, coincident with increased induced magnetic
+field strengths. The depletion of topside plasma in response to high solar wind
+dynamic pressures is observed in both weak and strong crustal magnetic field
+regions. Taken together, our results suggest that high solar wind dynamic
+pressures lead to ionospheric compression, increased ion escape, and reduced
+day-to-night plasma transport in the high-altitude nightside ionosphere.",1905.12011v2
+2019-08-25,Spin-reorientation critical dynamics in the two-dimensional XY model with a domain wall,"In recent years, static and dynamic properties of non-$180^\circ$ domain
+walls in magnetic materials have attracted a great deal of interest. In this
+paper, spin-reorientation critical dynamics in the two-dimensional XY model is
+investigated with Monte Carlo simulations and theoretical analyses based on the
+Langevin equation. At the Kosterlitz-Thouless phase transition, dynamic scaling
+behaviors of the magnetization and the two-time correlation function are
+carefully analyzed, and critical exponents are accurately determined. When the
+initial value of the angle between adjacent domains is slightly lower than
+$\pi$, a critical exponent is introduced to characterize the abnormal power-law
+increase of the magnetization in the horizontal direction inside the domain
+interface, which is measured to be $\psi=0.0568(8)$. Besides, the relation
+$\psi=\eta/2z$ is analytically deduced from the Langevin dynamics in the
+long-wavelength approximation, well consistent with numerical results.",1908.09247v1
+2020-06-08,Time-dependent spintronic anisotropy in magnetic molecules,"We theoretically study the quench dynamics of induced anisotropy of a
+large-spin magnetic molecule coupled to spin-polarized ferromagnetic leads. The
+real-time evolution is calculated by means of the time-dependent density-matrix
+numerical renormalization group method implemented within the matrix product
+states framework, which takes into account all correlations in very accurate
+manner. We determine the system's response to a quench in the spin-dependent
+coupling to ferromagnetic leads. In particular, we focus on the transient
+dynamics associated with crossing from the weak to the strong coupling regime,
+where the Kondo correlations become important. The dynamics is examined by
+calculating the time-dependent expectation values of the spin-quadrupole moment
+and the associated spin operators. We identify the relevant time scales
+describing the quench dynamics and determine the influence of the molecule's
+effective exchange coupling and leads spin-polarization on the dynamical
+behavior of the system. Furthermore, the generalization of our predictions for
+large values of molecule's spin is considered. Finally, we analyze the effect
+of finite temperature and show that it gives rise to a reduction of magnetic
+anisotropy by strong suppression of the time-dependent spin-quadrupole moment
+due to thermal fluctuations.",2006.04431v1
+2021-11-16,The effect of shaping on turbulent dynamics in RFP simulations,"We study the influence of the shape of the plasma container on the dynamics
+of the Reversed Field Pinch (RFP). The geometries we consider are periodic
+cylinders with elliptical and circular-shaped cross-sections. Numerical
+simulations of fully nonlinear visco-resistive magnetohydrodynamics are carried
+out to illustrate how the plasma dynamics are affected by shaping. It is shown
+that independent of the plasma shape, the quantity $\beta$, comparing the
+hydrodynamic pressure to the magnetic pressure, decreases for increasing values
+of the Lundquist number, but the pressure gradient fluctuations remain roughly
+constant, when compared to the Lorentz force. Different elliptical shapes of
+the cross-section of the domain lead to the excitation of different toroidal
+(or axial) magnetic and dynamic modes. Furthermore, it is found that in a
+geometry with circular cross-section a significant local poloidal angular
+momentum is observed, absent in the geometries with elliptical cross-section.
+Since the confinement is dominantly determined by plasma movement, and the
+dynamics of the velocity and magnetic field are modified by the modification of
+the geometry, shaping can thus affect the performance of RFP-devices.",2111.08790v1
+2022-03-02,A.C. susceptibility as a probe of low-frequency magnetic dynamics,"The experimental technique of a.c. susceptibility can be used as a probe of
+magnetic dynamics in a wide variety of systems. Its use is restricted to the
+low-frequency regime and thus is sensitive to relatively slow processes. Rather
+than measuring the dynamics of single spins, a.c. susceptibility can be used to
+probe the dynamics of collective objects, such as domain walls in ferromagnets
+or vortex matter in superconductors. In some frustrated systems, such as spin
+glasses, the complex interactions lead to substantial spectral weight of
+fluctuations in the low-frequency regime, and thus a.c. susceptibility can play
+a unique role. We review the theory underlying the technique and magnetic
+dynamics more generally and give applications of a.c. susceptibility to a wide
+variety of experimental situations.",2203.00989v1
+2023-05-26,Accounting for Quantum Effects in Atomistic Spin Dynamics,"Atomistic spin dynamics (ASD) is a standard tool to model the magnetization
+dynamics of a variety of materials. The fundamental dynamical model underlying
+ASD is entirely classical. In this letter, we present two approaches to
+effectively incorporate quantum effects into ASD simulations, thus enhancing
+their low temperature predictions. The first allows to simulate the magnetic
+behavior of a quantum spin system by solving the equations of motions of a
+classical spin system at an effective temperature. This effective temperature
+is determined a priori from the microscopic properties of the system. The
+second approach is based on a semi-classical model where classical spins
+interact with an environment with a quantum-like power spectrum. The parameters
+that characterize this model can be calculated ab initio or extracted from
+experiments. This semi-classical model quantitatively reproduces the
+low-temperature behavior of a magnetic system, thus accounting for the quantum
+mechanical aspects of its dynamics. The methods presented here can be readily
+implemented in current ASD simulations with no additional complexity cost.",2305.17082v1
+2024-02-27,Expansion dynamics of Bose-Einstein condensates in a synthetic magnetic field,"We investigate the expansion dynamics of spin-orbit-coupled Bose-Einstein
+condensates subjected to a synthetic magnetic field, after their release from
+an external harmonic trap. Our findings reveal that the condensate experiences
+a spin-dependent rotation and separation due to the rigid-like rotational
+velocity field, which leads to a spin density deflection. The deflection angle
+reaches a peak at a time that is inversely related to the frequency of the
+harmonic trap. When the detuning gradient is below a critical value for vortex
+nucleation, our analytical results derived from a spinor hydrodynamic theory
+align closely with numerical results using the coupled Gross-Pitaevskii
+equations. Beyond this critical value, we also numerically simulated the
+expansion dynamics of the condensates containing vortices with negative
+circulation. Our findings highlight the pivotal role of the rigid-like
+rotational velocity field on the dynamics of the condensate and may stimulate
+further experimental investigations into the rich superfluid dynamics induced
+by synthetic magnetic fields.",2402.17691v1
+2024-03-22,Coherent Phonon Control of Ultrafast Magnetization Dynamics in Fe$_\text{3}$GeTe$_\text{2}$ from Time-Dependent Ab Initio Theory,"Exploring ultrafast magnetization control in two-dimensional (2D) magnets
+through optically driven coherent phonons has been well-established. Yet, the
+microscopic interplay between spin dynamics and lattice degrees of freedom
+remains less explored. Employing real-time time-dependent density functional
+theory (rt-TDDFT) coupled with Ehrenfest dynamics, we systematically
+investigate laser-induced spin-nuclei dynamics with coherent phonon excitation
+in the 2D ferromagnet Fe3GeTe2. We found that selectively pre-exciting three
+typical coherent phonon modes results in up to a 53% additional spin moment
+loss in an out-of-plane A2 1g mode within ~50 fs. Coherent phonon control of
+spin dynamics is closely linked to laser pulse parameters. The underlying
+microscopic mechanism of this phenomenon is primarily governed by coherent
+phonon-induced asymmetric spin-resolved charge transfer following the
+disappearance of the laser pulse, thereby enabling effective control of the
+spin moment loss. Our findings offer a novel insight into the coupling of
+coherent phonons with spin systems in 2D limits on femtosecond timescales.",2403.15204v1
+1993-10-18,General Relativistic Dynamics of Irrotational Dust: Cosmological Implications,"The non--linear dynamics of cosmological perturbations of an irrotational
+collisionless fluid is analyzed within General Relativity. Relativistic and
+Newtonian solutions are compared, stressing the different role of boundary
+conditions in the two theories. Cosmological implications of relativistic
+effects, already present at second order in perturbation theory, are studied
+and the dynamical role of the magnetic part of the Weyl tensor is elucidated.",9310036v1
+1993-03-23,Kramers map approach for stabilization of hydrogen atom in a magnetic field,"The phenomenon of stabilization of highly excited states of hydrogen atom in
+a strong monochromatic field is discussed. Approximate description of dynamics
+by the introduced Kramers map allows to understand the main properties of this
+phenomenon on the basis of analogy with the Kepler map. Analogy between the
+stabilization and the channeling of particles in a crystal is also discussed.",9303014v1
+1994-02-17,Localization and dynamic persistent currents in long cylinders,"A dynamic response to a magnetic field in a long disordered cylinder is
+considered. We show that, although at high frequencies conduction is classical
+in all directions, the low frequency behavior corresponds to localization in
+the longitudinal direction and to a diamagnetic dynamic persistent current in
+the transversal one. The current density does not vanish even in the limit of
+the infinitely long cylinder.",9402071v1
+1997-03-04,Dissipative Dynamics of Solitons in Planar Ferromagnets,"Dynamics of magnetic bubbles in planar ferromagnets described by the
+Landau-Lifshitz equation with dissipation is analyzed. The pure O(3) sigma
+model has static multisoliton solutions, characterized by a number of
+parameters. The parameters describe a finite dimensional manifold. A small
+perturbation of energy functional with respect to the sigma model forces
+solitons to move. Multisoliton dynamics is effectively reduced to a flow in the
+parameter space.",9703045v1
+1993-03-23,Relativistic Dynamics of Spin in Strong External Fields,"The dynamics of relativistic spinning particles in strong external
+electromagnetic or gravitational fields is discussed. Spin-orbit coupling is
+shown to affect such relativistic phenomena as time-dilation and perihelion
+shift. Possible applications include muon decay in a magnetic field and the
+dynamics of neutron stars in binary systems.",9303124v1
+1994-12-29,Dynamical Supersymmetry of a Vortex System with $1/r^{2}$ Potential,"The Pauli Hamiltonian for a spin $\frac{1}{2}$ charged particle interacting
+with a point magnetic vortex and $1/r^{2}$ potential exhibits a dynamical
+supersymmetry $Osp(1,1)$ on the plane except at the origin. Using this
+symmetry, the spectrum and the wave functions have been obtained. And, the
+dynamical supersymmetry could be imported to the case when an external harmonic
+potential is added.",9412225v1
+2003-05-09,Applications of Hofer's geometry to Hamiltonian dynamics,"We prove the following three results in Hamiltonian dynamics.
+  1. The Weinstein conjecture holds true for every displaceable hypersurface of
+contact type. 2. Every magnetic flow on a closed Riemannian manifold has
+contractible closed orbits for a dense set of small energies. 3. Every closed
+Lagrangian submanifold of an arbitrary symplectic manifold whose fundamental
+group injects and which admits a Riemannian metric without closed geodesics has
+the intersection property.",0305146v1
+2003-12-24,Effective Dynamics of Magnetic Vortices,"We study solutions of Ginzburg-Landau-type evolution equations (both
+dissipative and Hamiltonian) with initial data representing collections of
+widely-spaced vortices. We show that for long times, the solutions continue to
+describe collections of vortices, and we identify (to leading order in the
+vortex separation) the dynamical system describing the motion of the vortex
+centres (effective dynamics).",0312438v1
+1996-10-31,Relativistic Dynamics and the Deuteron Axial Current,"The deuteron axial current is sensitive both to the form of the
+implementation of relativistic dynamics as well as to the details of the
+deuteron D state at moderate momentum transfer, making it a natural partner to
+the magnetic form factor for exploring details of nucleon-nucleon dynamics and
+associated electroweak properties.",9610050v1
+2000-08-13,Nonlinear Beam Dynamics and Effects of Wigglers,"We present the applications of variational--wavelet approach for the
+analytical/numerical treatment of the effects of insertion devices on beam
+dynamics. We investigate the dynamical models which have polynomial
+nonlinearities and variable coefficients. We construct the corresponding
+wavelet representation for wigglers and undulator magnets.",0008046v1
+2007-12-19,Dynamic Phase Transitions for Ferromagnetic Systems,"This article presents a phenomenological dynamic phase transition theory for
+ferromagnetism, leading to a precise description of the dynamic transitions,
+and to a physical predication on the spontaneous magnetization. The analysis
+also suggests asymmetry of fluctuations in both the ferromagnetism and the PVT
+systems.",0712.3082v1
+2009-09-30,Low energy dynamics of spinor condensates,"We present a derivation of the low energy Lagrangian governing the dynamics
+of the spin degrees of freedom in a spinor Bose condensate, for any phase in
+which the average magnetization vanishes. This includes all phases found within
+mean-field treatments except for the ferromagnet, for which the low energy
+dynamics has been discussed previously. The Lagrangian takes the form of a
+sigma model for the rotation matrix describing the local orientation of the
+spin state of the gas.",0909.5620v1
+1996-12-09,Classical Billiards in a Magnetic Field and a Potential,"We study billiards in plane domains, with a perpendicular magnetic field and
+a potential. We give some results on periodic orbits, KAM tori and adiabatic
+invariants. We also prove the existence of bound states in a related scattering
+problem.",9612016v1
+1992-04-10,Universal quantum critical dynamics of two-dimensional antiferromagnets,"The universal dynamic and static properties of two dimensional
+antiferromagnets in the vicinity of a zero-temperature phase transition from
+long-range magnetic order to a quantum disordered phase are studied. Random
+antiferromagnets with both N\'{e}el and spin-glass long-range magnetic order
+are considered. Explicit quantum-critical dynamic scaling functions are
+computed in a 1/N expansion to two-loops for certain non-random, frustrated
+square lattice antiferromagnets. Implications for neutron scattering
+experiments on the doped cuprates are noted.",9204001v2
+1997-03-12,Projected dynamics for metastable decay in Ising models,"The magnetization switching dynamics in the kinetic Ising model is projected
+onto a one-dimensional absorbing Markov chain. The resulting projected dynamics
+reproduces the direct simulation results with great accuracy. A scheme is
+proposed to utilize simulation data for small systems to obtain the metastable
+lifetime for large systems and/or for very weak magnetic fields, for which
+direct simulation is not feasible.",9703115v1
+1997-11-19,Nonequlibrium phase transition in the kinetic Ising model: Dynamical symmetry breaking by randomly varying magnetic field,"The nonequilibrium dynamic phase transition, in the two dimensional kinetic
+Ising model in presence of a randomly varying (in time but uniform in space)
+magnetic field, has been studied both by Monte Carlo simulation and by solving
+the mean field dynamic equation of motion for the average magnetisation. In
+both the cases, the time averaged magnetisation vanishes from a nonzero value
+depending upon the values of the width of randomly varying field and the
+temperature. The phase boundary lines are drawn in the plane formed by the
+width of the random field and the temperature.",9711191v2
+1997-12-10,Pseudo-gap behavior in dynamical properties of high-Tc cuprates,"Dynamical properties of 2D antiferromagnets with hole doping are investigated
+to see the effects of short range local magnetic order on the temperature
+dependence of the dynamical magnetic susceptibility. We show the pseudo-gap
+like behavior of the temperature dependence of the NMR relaxation rate. We also
+discuss implications of the results in relations to the observed spin gap like
+behavior of low-doped copper oxide high-$T_c$ superconductors.",9712104v2
+1999-11-08,Stability and dynamics of free magnetic polarons,"The stability and dynamics of a free magnetic polaron are studied by Monte
+Carlo simulation of a classical two-dimensional Heisenberg model coupled to a
+single electron. We compare our results to the earlier mean-field analysis of
+the stability of the polaron, finding qualitative similarity but quantitative
+differences. The dynamical simulations give estimates of the temperature
+dependence of the polaron diffusion, as well as a crossover to a tunnelling
+regime.",9911109v1
+2000-04-26,Generalized Numerical Renormalization Group for Dynamical Quantities,"In this paper we introduce a new approach for calculating dynamical
+properties within the numerical renormalization group. It is demonstrated that
+the method previously used fails for the Anderson impurity in a magnetic field
+due to the absence of energy scale separation. The problem is solved by
+evaluating the Green function with respect to the reduced density matrix of the
+full system, leading to accurate spectra in agreement with the static
+magnetization. The new procedure (denoted as DM-NRG) provides a unifying
+framework for calculating dynamics at any temperature and represents the
+correct extension of Wilson's original thermodynamic calculation.",0004458v1
+2000-12-05,Algorithm for molecular dynamics simulations of spin liquids,"A new symplectic time-reversible algorithm for numerical integration of the
+equations of motion in magnetic liquids is proposed. It is tested and applied
+to molecular dynamics simulations of a Heisenberg spin fluid. We show that the
+algorithm exactly conserves spin lengths and can be used with much larger time
+steps than those inherent in standard predictor-corrector schemes. The results
+obtained for time correlation functions demonstrate the evident dynamic
+interplay between the liquid and magnetic subsystems.",0012059v1
+2001-03-06,Monte Carlo Simulations of Short-time Critical Dynamics with a Conserved Quantity,"With Monte Carlo simulations, we investigate short-time critical dynamics of
+the three-dimensional anti-ferromagnetic Ising model with a globally conserved
+magnetization $m_s$ (not the order parameter). From the power law behavior of
+the staggered magnetization (the order parameter), its second moment and the
+auto-correlation, we determine all static and dynamic critical exponents as
+well as the critical temperature. The universality class of $m_s=0$ is the same
+as that without a conserved quantity, but the universality class of non-zero
+$m_s$ is different.",0103136v1
+2001-11-18,Length scales coupling for nonlinear dynamical problems in magnetism,"The dynamics of real magnets is often governed by several interacting
+processes taking place simultaneously at different length scales. For dynamical
+simulations the relevant length scales should be coupled, and the energy
+transfer accurately described. We show that in this case the micromagnetic
+theory is not always reliable. We present a coarse-graining approach applicable
+to nonlinear problems, which provides a unified description of all relevant
+length scales, allowing a smooth, seamless coupling. The simulations performed
+on model systems show that the coarse-graining approach achieves nearly the
+precision of all-atom simulations.",0111324v1
+2003-03-03,Dimensional Crossover of Vortex Dynamics Induced by Gd Substitution on Bi2212 Single Crystals,"The vortex dynamics of Bi$_2$Sr$_2$Ca$_{1-x}$Gd$_x$Cu$_2$O$_{8+\delta}$
+single crystals is investigated by magnetic relaxation and hysteresis
+measurements. By substituting $Ca$ with $Gd$, it is found that the interlayer
+Josephson coupling is weakened and the anisotropy is increased, which leads to
+the change of vortex dynamics from 3D elastic to 2D plastic vortex creep.
+Moreover, the second magnetization peak, which can be observed in samples near
+the optimal doping, is absent in the strongly underdoped (with 2D vortex)
+region.",0303020v1
+2004-11-04,Record dynamics and the observed temperature plateau in the magnetic creep rate of type II superconductors,"We use Monte Carlo simulations of a coarse grained three dimensional model to
+demonstrate that the experimentally observed approximate temperature
+independence of the magnetic creep rate for a broad range of temperatures may
+be explained in terms of record dynamics, {\it viz.} the dynamical properties
+of the times at which a stochastic fluctuating signal establishes records.",0411104v2
+2005-03-16,Artificial scaling laws of the dynamical magnetic susceptibility in heavy-fermion systems,"We report here how artificial, thus erroneous, scaling laws of the dynamical
+magnetic susceptibility can be obtained when data are not treated carefully. We
+consider the example of the heavy-fermion system
+Ce$_{0.925}$La$_{0.075}$Ru$_{2}$Si$_{2}$ and we explain how different kinds of
+artificial scaling laws in $E/T^\beta$ can be plotted in a low temperature
+regime where the dynamical susceptibility is nearly temperature independent.",0503410v1
+2005-05-25,Relaxation dynamics and colossal magnetocapacitive effect in CdCr2S4,"A thorough investigation of the relaxational dynamics in the recently
+discovered multiferroic CdCr2S4 showing a colossal magnetocapacitive effect has
+been performed. Broadband dielectric measurements without and with external
+magnetic fields up to 10 T provide clear evidence that the observed
+magnetocapacitive effect stems from enormous changes of the relaxation dynamics
+induced by the development of magnetic order.",0505629v1
+2006-03-15,Dynamic hysteresis from zigzag domain walls,"We investigate dynamic hysteresis in ferromagnetic thin films with zigzag
+domain walls. We introduce a discrete model describing the motion of a wall in
+a disordered ferromagnet with in-plane magnetization, driven by an external
+magnetic field, considering the effects of dipolar interactions and anisotropy.
+We analyze the effects of external field frequency and temperature on the
+coercive field by Monte Carlo simulations, and find a good agreement with the
+experimental data reported in literature for Fe/GaAs films. This implies that
+dynamic hysteresis in this case can be explained by a single propagating domain
+wall model without invoking domain nucleation.",0603406v2
+2006-05-25,Time Quantified Monte Carlo Algorithm for Interacting Spin Array Micromagnetic Dynamics,"In this paper, we reexamine the validity of using time quantified Monte Carlo
+(TQMC) method [Phys. Rev. Lett. 84, 163 (2000); Phys. Rev. Lett. 96, 067208
+(2006)] in simulating the stochastic dynamics of interacting magnetic
+nanoparticles. The Fokker-Planck coefficients corresponding to both TQMC and
+Langevin dynamical equation (Landau-Lifshitz-Gilbert, LLG) are derived and
+compared in the presence of interparticle interactions. The time quantification
+factor is obtained and justified. Numerical verification is shown by using TQMC
+and Langevin methods in analyzing spin-wave dispersion in a linear array of
+magnetic nanoparticles.",0605621v1
+2001-01-17,QED$_3$ with Dynamical Fermions in an External Magnetic Field,"In this paper, we present results of numerical lattice simulations of
+two-flavor QED in three space-time dimensions. First, we provide evidence that
+chiral symmetry is spontaneously broken in the chiral and continuum limit. Next
+we discuss the role of an external magnetic field $B$ on the dynamically
+generated fermion mass. We investigate the $B$-dependence of the condensate
+through calculations with dynamical fermions using the non-compact formulation
+of the gauge field, and compare the results with those of a comparable study
+using the quenched approximation.",0101011v1
+2000-07-15,Magnetogenesis and the dynamics of internal dimensions,"The dynamical evolution of internal space-like dimensions breaks the
+invariance of the Maxwell's equations under Weyl rescaling of the (conformally
+flat) four-dimensional metric. Depending upon the number and upon the dynamics
+of internal dimensions large scale magnetic fields can be created. The
+requirements coming from magnetogenesis together with the other cosmological
+constraints are examined under the assumption that the internal dimensions
+either grow or shrink (in conformal time) prior to a radiation dominated epoch.
+If the internal dimensions are growing the magnitude of the generated magnetic
+fields can seed the galactic dynamo mechanism.",0007163v1
+1997-01-17,"Magnetic Monopoles, Gauge Invariant Dynamical Variables and Georgi Glashow Model","We investigate Georgi-Glashow model in terms of a set of explicitly SO(3)
+gauge invariant dynamical variables. In the new description a novel compact
+abelian gauge invariance emerges naturally. As a consequence magnetic monopoles
+occur as point like ""defects"" in space time. Their non-perturbative
+contribution to the partition function is explicitly included. This procedure
+corresponds to dynamical ""abelian projection"" without gauge fixing. In the
+Higgs phase the above abelian invariance is to be identified with
+electromagnetism. We also study the effect of $\theta$ term in the above
+abelian theory.",9701083v1
+2000-07-13,The averaged dynamics of the hydrogen atom in crossed electric and magnetic fields as a perturbed Kepler problem,"We treat the classical dynamics of the hydrogen atom in perpendicular
+electric and magnetic fields as a celestial mechanics problem. By expressing
+the Hamiltonian in appropriate action-angle variables, we separate the
+different time scales of the motion. The method of averaging then allows us to
+reduce the system to two degrees of freedom, and to classify the most important
+periodic orbits.",0007018v1
+2005-12-05,Dynamically controlled toroidal and ring-shaped magnetic traps,"We present traps with toroidal $(T^{2})$ and ring-shaped topologies, based on
+adiabatic potentials for radio-frequency dressed Zeeman states in a ring-shaped
+magnetic quadrupole field. Simple adjustment of the radio-frequency fields
+provides versatile possibilities for dynamical parameter tuning, topology
+change, and controlled potential perturbation. We show how to induce toroidal
+and poloidal rotations, and demonstrate the feasibility of preparing degenerate
+quantum gases with reduced dimensionality and periodic boundary conditions. The
+great level of dynamical and even state dependent control is useful for atom
+interferometry.",0512017v2
+2007-02-27,Reduction and approximation in gyrokinetics,"The gyrokinetics formulation of plasmas in strong magnetic fields aims at the
+elimination of the angle associated with the Larmor rotation of charged
+particles around the magnetic field lines. In a perturbative treatment or as a
+time-averaging procedure, gyrokinetics is in general an approximation to the
+true dynamics. Here we discuss the conditions under which gyrokinetics is
+either an approximation or an exact operation in the framework of reduction of
+dynamical systems with symmetry",0702234v2
+1998-10-22,"Non-Abelian Geometric Phase, Floquet Theory, and Periodic Dynamical Invariants","For a periodic Hamiltonian, periodic dynamical invariants may be used to
+obtain non-degenerate cyclic states. This observation is generalized to the
+degenerate cyclic states, and the relation between the periodic dynamical
+invariants and the Floquet decompositions of the time-evolution operator is
+elucidated. In particular, a necessary condition for the occurrence of cyclic
+non-adiabatic non-Abelian geometrical phase is derived. Degenerate cyclic
+states are obtained for a magnetic dipole interacting with a precessing
+magnetic field.",9810064v1
+1999-04-29,Semiclassical dynamics of a spin-1/2 in an arbitrary magnetic field,"The spin coherent state path integral describing the dynamics of a
+spin-1/2-system in a magnetic field of arbitrary time-dependence is considered.
+Defining the path integral as the limit of a Wiener regularized expression, the
+semiclassical approximation leads to a continuous minimal action path with
+jumps at the endpoints. The resulting semiclassical propagator is shown to
+coincide with the exact quantum mechanical propagator. A non-linear
+transformation of the angle variables allows for a determination of the
+semiclassical path and the jumps without solving a boundary-value problem. The
+semiclassical spin dynamics is thus readily amenable to numerical methods.",9904102v1
+2003-06-13,Quantum Dynamics of Magnetic and Electric Dipoles and Berry's Phase,"We study the quantum dynamics of neutral particle that posseses a permanent
+magnetic and electric dipole moments in the presence of an electromagnetic
+field. The analysis of this dynamics demonstrates the appearance of a quantum
+phase that combines the Aharonov-Casher effect and the He-Mckellar-Wilkens
+effect. We demonstrate that this phase is a special case of the Berry's quantum
+phase. A series of field configurations where this phase would be found are
+presented. A generalized Casella-type effect is found in one these
+configurations. A physical scenario for the quantum phase in an interferometric
+experiment is proposed.",0306090v1
+2007-04-23,Dynamical stability for finite quantum spin chains against a time-periodic inhomogeneous perturbation,"We investigate dynamical stability of the ground state against a
+time-periodic and spatially-inhomogeneous magnetic field for finite quantum XXZ
+spin chains. We use the survival probability as a measure of stability and
+demonstrate that it decays as $P(t) \propto t^{-1/2}$ under a certain
+condition. The dynamical properties should also be related to the level
+statistics of the XXZ spin chains with a constant spatially-inhomogeneous
+magnetic field. The level statistics depends on the anisotropy parameter and
+the field strength. We show how the survival probability depends on the
+anisotropy parameter, the strength and frequency of the field.",0704.2922v1
+2007-08-15,Three-dimensional MHD simulation of expanding magnetic flux ropes,"Three-dimensional, time-dependent numerical simulations of the dynamics of
+magnetic flux ropes are presented. The simulations are targeted towards an
+experiment previously conducted at CalTech (Bellan, P. M. and J. F. Hansen,
+Phys. Plasmas, 5, 1991 (1998)) which aimed at simulating Solar prominence
+eruptions in the laboratory. The plasma dynamics is described by ideal MHD
+using different models for the evolution of the mass density. Key features of
+the reported experimental observations like pinching of the current loop, its
+expansion and distortion into helical shape are reproduced in the numerical
+simulations. Details of the final structure depend on the choice of a specific
+model for the mass density.",0708.2049v1
+2008-02-21,Effects of Quark Interactions on Dynamical Chiral Symmetry Breaking by a Magnetic Field,"It is shown how the strong interaction dynamics of a multi-quark Lagrangian
+affects the catalysis of dynamical symmetry breaking by a constant magnetic
+field in (3+1) dimensions. Attention is drawn to the local minima structure of
+the theory.",0802.3193v2
+2008-03-24,Geometric Phase for Neutral Particle in the Presence of a Topological Defect,"In this paper we study the quantum dynamics of a neutral particle in the
+presence of a topological defect. We investigate the appearance of a geometric
+phase in the relativistic quantum dynamics of neutral particle which possesses
+permanent magnetic and electric dipole moments in the presence of an
+electromagnetic fields in this curved background. The nonrelativistic quantum
+dynamics are investigated using the Foldy-Wouthuysen expansion. The
+gravitational Aharonov-Casher and He-Mckellar-Wilkens effects are investigated
+for a series of electric and magnetic fields configurations.",0803.3428v1
+2008-05-05,The Dynamics of Chern-Simons Vortices,"We study vortex dynamics in three-dimensional theories with Chern-Simons
+interactions. The dynamics is governed by motion on the moduli space M in the
+presence of a magnetic field. For Abelian vortices, the magnetic field is shown
+to be the Ricci form over M; for non-Abelian vortices, it is the first Chern
+character of a suitable index bundle. We derive these results by integrating
+out massive fermions and following the fate of their zero modes.",0805.0602v2
+2008-05-06,Short-time dynamics in the 1D long-range Potts model,"We present numerical investigations of the short-time dynamics at criticality
+in the 1D Potts model with power-law decaying interactions of the form
+1/r^{1+sigma}. The scaling properties of the magnetization, autocorrelation
+function and time correlations of the magnetization are studied. The dynamical
+critical exponents theta' and z are derived in the cases q=2 and q=3 for
+several values of the parameter $\sigma$ belonging to the nontrivial critical
+regime.",0805.0719v2
+2009-10-23,First-principles dynamical CPA to finite-temperature magnetism of transition metals,"We present here the first-principles dynamical CPA (coherent potential
+approximation) combined with the tight-binding LMTO LDA+U method towards
+quantitative calculations of the electronic structure and magnetism at finite
+temperatures in transition metals and compounds. The theory takes into account
+the single-site dynamical charge and spin fluctuations using the functional
+integral technique as well as an effective medium. Numerical results for Fe,
+Co, and Ni show that the theory explains quantitatively the high-temperature
+properties such as the effective Bohr magneton numbers and the excitation
+spectra in the paramagnetic state, and describes the Curie temperatures
+semiquantitatively.",0910.4486v1
+2010-07-08,Dynamical mobility edge for various random Landau Hamiltonians,"We review recent results obtained within the framework of the integer quantum
+Hall effect in the spirit of the work of Germinet, Klein, Schenker in
+\cite{GKS}. Landau Hamiltonians perturbed by random electric or magnetic
+perturbations are shown to exhibit a dynamical mobility edge, that is a
+transition between a regime of dynamical localization and a regime of non
+trivial transport at a minimal rate. The focus is put on three situations of
+interest: 1) unbounded ergodic electric potentials, for which Landau gaps are
+filled; 2) non ergodic electric potentials; 3) random magnetic potentials.",1007.1329v1
+2010-10-15,Dynamics of Ferrofluidic Drops Impacting Superhydrophobic Surfaces,"This is a fluid dynamics video illustrating the impact of ferrofluidic
+droplets on surfaces of variable wettability. Surfaces studied include mica,
+teflon, and superhydrophobic. A magnet is placed beneath each surface, which
+modifies the behavior of the ferrofluid by applying additional downward force
+apart from gravity resulting in reduced droplet size and increased droplet
+velocity. For the superhydrophobic droplet a jetting phenomena is shown which
+only occurs in a limited range of impact speeds, higher than observed before,
+followed by amplified oscillation due to magnetic field as the drop stabilizes
+on the surface.",1010.3297v1
+2011-01-29,The Quantum Hall Effect in Graphene,"We investigate the quantum Hall effect in graphene. We argue that in graphene
+in presence of an external magnetic field there is dynamical generation of mass
+by a rearrangement of the Dirac sea. We show that the mechanism breaks the
+lattice valley degeneracy only for the $n=0$ Landau levels and leads to the new
+observed $\nu = \pm 1$ quantum Hall plateaus. We suggest that our result can be
+tested by means of numerical simulations of planar Quantum Electro Dynamics
+with dynamical fermions in an external magnetic fields on the lattice.",1101.5703v2
+2011-06-14,Anisotropic Inverse Cascade toward Zonal Flow in Magnetically Confined Plasmas,"We propose a new mechanism for the generation of zonal flows in magnetically
+confined plasmas, complementing previous theories based on a modulational
+instability. We derive a new conservation law that operates in the regime of
+weakly nonlinear dynamics, and show that it serves to focus the inverse cascade
+of turbulent drift wave energy into zonal flows. This mechanism continues to
+operate in the absence of the separation of dynamical scales typically assumed
+in instability calculations.",1106.2746v1
+2012-07-13,Magnetic relaxation in bilayers of yttrium iron garnet/platinum due to the dynamic coupling at the interface,"We show that in ferromagnetic (FM)/normal metal (NM) bilayers the dynamic
+coupling at the interface transfers an additional magnetic relaxation from the
+heavily damped motion of the conduction electron spins in the NM layer to the
+FM spins. While the FM relaxation rates due to two-magnon scattering and spin
+pumping decrease rapidly with increasing FM film thickness, the damping due to
+the dynamic coupling does not depend on the FM film thickness. The proposed
+mechanism explains the very large broadening of ferromagnetic resonance lines
+in thick films of yttrium iron garnet after deposition of a Pt layer.",1207.3330v1
+2012-09-03,Critical domain-wall dynamics of model B,"With Monte Carlo methods, we simulate the critical domain-wall dynamics of
+model B, taking the two-dimensional Ising model as an example. In the
+macroscopic short-time regime, a dynamic scaling form is revealed. Due to the
+existence of the quasi-random walkers, the magnetization shows intrinsic
+dependence on the lattice size $L$. A new exponent which governs the
+$L$-dependence of the magnetization is measured to be $\sigma=0.243(8)$.",1209.0360v1
+2012-11-15,On a regularization of the magnetic gas dynamics system of equations,"A brief derivation of a specific regularization for the magnetic gas dynamic
+system of equations is given in the case of general equations of gas state (in
+presence of a body force and a heat source). The entropy balance equation in
+two forms is also derived for the system. For a constant regularization
+parameter and under a standard condition on the heat source, we show that the
+entropy production rate is nonnegative.",1211.3539v1
+2013-01-21,Dynamics of the One-Dimensional Ising Model without Detailed Balance Condition,"We study an irreversible Markov chain Monte Carlo method based on a skew
+detailed balance condition for an one-dimensional Ising model. Dynamical
+behavior of the magnetization density is analyzed in order to understand the
+properties of this method. As a result, it is found theoretically that the
+relaxation time of the magnetization density is reduced by using some
+transition probabilities satisfying the skew detailed balance condition, in
+comparison to that with the corresponding transition probability with the
+detailed balance condition, and that one of the transition probabilities
+changes the dynamical critical exponent even with a local spin update.",1301.4801v1
+2013-04-21,Dynamic Magnetoelectric Effect in Ferromagnet-Superconductor Tunnel Junctions,"We study the magnetization dynamics in a ferromagnet-insulator-superconductor
+tunnel junction and the associated buildup of the electrical polarization. We
+show that for an open circuit, the induced voltage varies strongly and
+nonmonotonically with the precessional frequency, and can be enhanced
+significantly by the superconducting correlations. For frequencies much smaller
+or much larger than the superconducting gap, the voltage drops to zero, while
+when these two energy scales are comparable, the voltage is peaked at a value
+determined by the driving frequency. We comment on the potential utilization of
+the effect for the low-temperature spatially-resolved spectroscopy of magnetic
+dynamics.",1304.5750v2
+2013-09-13,Domain dynamics in nonequilibrium random-field Ising models,"We employ Monte Carlo simulations in order to study dynamics of the
+magnetization and domain growth processes in the random-field Ising models with
+uniform and Gaussian random field distributions of varying strengths. Domain
+sizes are determined directly using the Hoshen-Kopelman algorithm. For either
+case, both the magnetization and the largest domain growth dynamics are found
+to follow the power law with generally different exponents, which exponentially
+decay with the random field strength. Moreover, for relatively small random
+fields the relaxation is confirmed to comply with different regimes at early
+and later times. No significant differences were found between the results for
+the uniform and Gaussian distributions, in accordance with the universality
+assumption.",1309.3589v2
+2014-05-02,Dynamic nuclear polarization from current-induced electron spin polarization,"Current-induced electron spin polarization is shown to produce nuclear
+hyperpolarization through dynamic nuclear polarization. Saturated fields of
+several millitesla are generated upon the application of electric field over a
+timescale of a hundred seconds in InGaAs epilayers and measured using optical
+Larmor magnetometry. The dependence on temperature, external magnetic field,
+and applied voltage is investigated. We find an asymmetry in which the
+saturation nuclear field depends on the relative alignment of the electrically
+generated spin polarization and the external magnetic field, which we attribute
+to an interplay between various electron spin dynamical processes.",1405.0342v1
+2015-04-22,Dynamical supersymmetry on the XXX spin chain,"We show the XXX model has the N = 2 dynamical supersymmetry. Using the
+supercharges defined by the Jordan-Wigner fermions, it was found that the
+anti-commutation relation of the supercharges gives the Hamiltonian of the XXX
+model with magnetic field. In order to compare the length-change supercharges
+with the conventional ones, we interpreted their actions in the spinon basis.
+In the last part of this paper, we propose the application of the dynamical
+supersymmetry to the models with magnetic impurities through the Bethe-ansatz
+analysis.",1504.05676v2
+2015-08-23,Event-chain algorithm for the Heisenberg model: Evidence for $z \simeq 1$ dynamic scaling,"We apply the event-chain Monte Carlo algorithm to the three-dimensional
+ferromagnetic Heisenberg model. The algorithm is rejection-free and also
+realizes an irreversible Markov chain that satisfies global balance. The
+autocorrelation functions of the magnetic susceptibility and the energy
+indicate a dynamical critical exponent $z \approx 1$ at the critical
+temperature, while that of the magnetization does not measure the performance
+of the algorithm. This seems to be the first report that the event-chain Monte
+Carlo algorithm substantially reduces the dynamical critical exponent from the
+conventional value of $z\simeq 2$.",1508.05661v2
+2016-02-29,Analogue Magnetism Revisited,"In this article we revisit the significance of the often debated structural
+similarity between the equations of electromagnetism and fluid dynamics.
+Although the matching of the two sets of equations has successfully been done
+for non-dissipative forms of the equations, little has been done for cases
+where the dissipative terms are non-negligible. We consider the consequence of
+non-negligible viscosity and diffusivity, and how the fine-tuning of these
+parameters could allow fluid dynamics to be used to indirectly study certain
+properties of magnetic fields.",1602.09105v1
+2016-04-15,Exactly solvable time-dependent models of two interacting two-level systems,"Two coupled two-level systems placed under external time-dependent magnetic
+fields are modeled by a general Hamiltonian endowed with a symmetry that
+enables us to reduce the total dynamics into two independent two-dimensional
+sub-dynamics. Each of the sub-dynamics is shown to be brought into an exactly
+solvable form by appropriately engineering the magnetic fields and thus we
+obtain an exact time evolution of the compound system. Several physically
+relevant and interesting quantities are evaluated exactly to disclose
+intriguing phenomena in such a system.",1604.04519v1
+2016-12-05,Dynamical realization of magnetic states in a strongly interacting Bose mixture,"We describe the dynamical preparation of magnetic states in a strongly
+interacting two-component Bose gas in a harmonic trap. By mapping this system
+to an effective spin chain model, we obtain the dynamical spin densities and
+the fidelities for a few-body system. We show that the spatial profiles transit
+between ferromagnetic and antiferromagnetic states as the intraspecies
+interaction parameter is slowly increased.",1612.01570v4
+2017-02-09,Transient spin dynamics in a single-molecule magnet,"We explore the limitations and validity of semi-classically formulated spin
+equations of motion. Using a single-molecule magnet as a test model, we employ
+three qualitatively different approximation schemes. From a microscopic model,
+we derive a generalized spin equation of motion in which the parameters have a
+non-local time-dependence. This dynamical equation is simplified to the
+Landau-Lifshitz-Gilbert equation with i) time-dependent, and ii)
+time-independent parameters. We show that transient dynamics is essentially
+non-existing in the latter approximation, while the former breaks down in the
+regime of strong coupling between the spin and the itinerant electrons.",1702.02820v2
+2017-05-11,Tunable spin dynamics in chiral soliton lattice,"We study dynamics of a chiral soliton lattice (CSL) in a classical
+one-dimensional spin chain coupled to the conduction electrons under an
+electric field. The CSL has attracted much interest because its period can be
+easily controlled by an external magnetic field. We clarify the dependence of
+the CSL dynamics on its period. A collective coordinate and an SU(2) gauge
+method are used for the analysis. It turns out that the velocity of the CSL
+becomes slower as the period becomes longer. We also mention a relation between
+the velocity and the magnetic resistance.",1705.04086v2
+2017-05-15,Spin and tunneling dynamics in an asymmetrical double quantum dot with spin - orbit coupling,"In this article we study the spin and tunneling dynamics as a function of
+magnetic field in a one-dimensional GaAs double quantum dot with both the
+Dresselhaus and Rashba spin-orbit coupling. In particular we consider different
+spatial widths for the spin-up and spin-down electronic states. We find that
+the spin dynamics is a superposition of slow as well as fast Rabi oscillations.
+It is found that the Rashba interaction strength as well as the external
+magnetic field strongly modifies the slow Rabi oscillations which is
+particularly useful for single qubit manipulation for possible quantum computer
+applications.",1705.05395v1
+2017-05-29,"Part of a collection of reviews on antiferromagnetic spintronics. Antiferromagnetic dynamics, spin-texures, and nanostructures","Antiferromagnets as active elements of spintronics can be faster than their
+ferromagnetic counterparts and more robust to magnetic noise. Owing to the
+strongly exchange-coupled magnetic sublattice structure, antiferromagnetic
+order parameter dynamics are qualitatively different and thus capable of
+engendering novel device functionalities. In this review, we discuss
+antiferromagnetic textures -- nanoparticles, domain walls, and skyrmions, --
+under the action of different spin torques. We contrast the antiferromagnetic
+and ferromagnetic dynamics, with a focus on the features that can be relevant
+for applications.",1705.10377v1
+2019-01-03,Observing zero-field spin dynamics with spin noise in a pi-pulse modulated field,"Spin noise spectroscopic study of spin dynamics in a zero magnetic field is
+commonly frustrated by the dominating 1/f noise. We show that in a pi-pulse
+modulated magnetic field, spin noise spectrum centered one-half of the field
+modulation frequency reveals spin dynamics in zero-fields, free of any
+low-frequency noises.",1901.00714v3
+2019-02-26,Dynamic spin-charge coupling: spin Hall magnetoresistance in non-magnetic conductors,"The dynamic coupling between spin and charge currents in non-magnetic
+conductors is considered. As a consequence of this coupling, the spin dynamics
+is directly reflected in the electrical impedance of the sample, with a
+relevant frequency scale defined by spin relaxation and spin diffusion. This
+allows the observation of the electron spin resonance by purely electrical
+measurements.",1902.09784v1
+2020-08-24,Reconstructions of the electron dynamics in magnetic field and the geometry of complex Fermi surfaces,"The paper considers the semiclassical dynamics of electrons on complex Fermi
+surfaces in the presence of strong magnetic fields. The reconstructions of the
+general topological structure of such dynamics are accompanied by the
+appearance of closed extremal trajectories of a special form, closely related
+to geometry and topology of the Fermi surface. The study of oscillation
+phenomena on such trajectories allows, in particular, to propose a relatively
+simple method for refining the parameters of the dispersion relation in metals
+with complex Fermi surfaces.",2008.10226v2
+2020-09-22,From Chaotic Spin Dynamics to Non-collinear Spin Textures in YIG Nano-films by Spin Current Injection,"In this article I report about a numerical investigation of nonlinear spin
+dynamics in a magnetic thin-film, made of Yttrium-Iron-Garnet (YIG). This film
+is exposed to a small in-plane oriented magnetic field, and strong spin
+currents. The rich variety of findings encompass dynamic regimes hosting
+localized, non-propagating solitons, a turbulent chaotic regime, which
+condenses into a quasi-static phase featuring a non-collinear spin texture.
+Eventually, at largest spin current, a homogeneously switched state is
+established.",2009.10628v1
+2020-10-02,Dynamic Phase Diagram of an Orthogonal Spin Torque device: Topological Category,"The magnetization evolution of the free layer in an orthogonal spin-torque
+device is studied based on a macrospin model. The trajectory of magnetization
+vector under various conditions has shown rich nonlinear properties. The phase
+diagram is obtained in the parameter spaces of current density and the
+polarization distribution (the ratio of in-plane and out-of-plane polarizers).
+These dynamic phases can be classified according to their nonlinear behaviors
+which are topologically different, namely limit point and/or limit cycle. The
+topological classification is meaningful to design the ultra-fast spin-torque
+devices under different dynamic conditions towards various applications such as
+memory and oscillators.",2010.00749v1
+2021-02-22,A review of modelling in ferrimagnetic spintronics,"In this review we introduce computer modelling and simulation techniques
+which are used for ferrimagnetic materials. We focus on models where thermal
+effects are accounted for, atomistic spin dynamics and finite temperature
+macrospin approaches. We survey the literature of two of the most commonly
+modelled ferrimagnets in the field of spintronics--the amorphous alloy GdFeCo
+and the magnetic insulator yttrium iron garnet. We look at how generic models
+and material specific models have been applied to predict and understand
+spintronic experiments, focusing on the fields of ultrafast magnetisation
+dynamics, spincaloritronics and magnetic textures dynamics and give an outlook
+for modelling in ferrimagnetic spintronics.",2102.11004v1
+2022-03-31,Long-time dynamical behavior for a piezoelectric system with magnetic effect and nonlinear dampings,"This paper is concerned with the long-time dynamical behavior of a
+piezoelectric system with magnetic effect, which has nonlinear damping terms
+and external forces with a parameter. At first, we use the nonlinear semigroup
+theory to prove the well-posedness of solutions. Then, we investigate the
+properties of global attractors and the existence of exponential attractors.
+Finally, the upper semicontinuity of global attractors has been investigated.",2203.16736v1
+2022-07-31,Dynamics of a particle in the generalised Ellis-Bronnikov wormhole on the rotating Archimede's spiral,"A particle moving on curved magnetic field lines in the wormhole metrics is
+considered. The dynamics of a single particle is studied on a co-rotating
+parameterized magnetic field line. Being interested in the force-free dynamics
+we choose the rotating Archimedes' spiral embedded in the generalized
+Ellis-Bronnikov metrics. By analysing the phase space, we explore how the
+physical parameters affect the motion of the particle and it is shown that the
+particles may reach the force free regime, eventually escaping the wormhole.",2208.00521v1
+1995-08-17,Reproducible noise in a macroscopic system: magnetic avalanches in Perminvar,"A study of magnetic avalanches in Perminvar, an Fe-Ni-Co alloy, shows that
+some avalanches are almost exactly reproducible from one magnetic field cycle
+to the next, while others show significant variability. Averaging over many
+cycles produces a fingerprint reflecting the reproducibility of the noise. The
+fingerprint is not strongly temperature or driving-rate dependent, indicating
+that the variability is a consequence of dynamical effects. We also find that
+the slope of the cycle-averaged magnetization, d<M>/dH, is correlated with the
+cycle-to-cycle variations in magnetization, suggesting an analogy with the
+fluctuation-dissipation relationship from equilibrium thermodynamics.",9508005v1
+1998-11-17,Magnetic Fields on the Dynamics of the ICM,"Could the discrepancies found in the determination of mass in clusters of
+galaxies, from gravitational lensing data and from X-rays observations, be
+consequence of the standard description of the ICM, in which it is assumed
+hydrostatic equilibrium maintained by thermal pressure? In analogy to the
+interstellar medium of the Galaxy, it is expected a non-thermal term of
+pressure, which contains contributions of magnetic fields. We follow the
+evolution of the ICM, considering a term of magnetic pressure, aiming at
+answering the question whether or not these discrepancies can be explained via
+non-thermal terms of pressure. Our results suggest that the magnetic pressure
+could only affect the dynamics of the ICM on scales as small as $\la 1 {\rm
+kpc}$. These results are compared to the observations of large and small scale
+magnetic fields and we are successful at reproducing the available data.",9811264v1
+1999-07-26,"A Spherical Model for ""Starless"" Cores of Magnetic Molecular Clouds and Dynamical Effects of Dust Grains","In the standard picture of isolated star formation, dense ``starless'' cores
+are formed out of magnetic molecular clouds due to ambipolar diffusion. Under
+the simplest spherical geometry, I demonstrate that ``starless'' cores formed
+this way naturally exhibit a large scale inward motion, whose size and speed
+are comparable to those detected recently by Taffala et al. and Williams et al.
+in ``starless'' core L1544. My model clouds have a relatively low mass (of
+order 10 $M_\odot$) and low field strength (of order 10 $\mu$G) to begin with.
+They evolve into a density profile with a central plateau surrounded by a
+power-law envelope, as found previously. The density in the envelope decreases
+with radius more steeply than those found by Mouschovias and collaborators for
+the more strongly magnetized, disk-like clouds.
+  At high enough densities, dust grains become dynamically important by greatly
+enhancing the coupling between magnetic field and the neutral cloud matter. The
+trapping of magnetic flux associated with the enhanced coupling leads, in the
+spherical geometry, to a rapid assemblage of mass by the central protostar,
+which exacerbates the so-called ``luminosity problem'' in star formation.",9907358v1
+2002-04-29,Dynamic nonlinearity in large scale dynamos with shear,"We supplement the mean field dynamo growth equation with the total magnetic
+helicity evolution equation. This provides an explicitly time dependent model
+for alpha quenching in dynamo theory. For dynamos without shear, this approach
+accounts for the observed large scale field growth and saturation in numerical
+simulations. After a significant kinematic phase, the dynamo is resistively
+quenched, i.e. the saturation time depends on the microscopic resistivity. This
+is independent of whether or not the turbulent diffusivity is resistively
+quenched. We find that the approach is also successful for dynamos that include
+shear and exhibit migratory waves (cycles). In this case however, whether or
+not the cycle period remains of the order of the dynamical time scale at large
+magnetic Reynolds numbers does depend how on how the turbulent magnetic
+diffusivity quenches. Since this is unconstrained by magnetic helicity
+conservation, the diffusivity is presently an input parameter. Comparison to
+current numerical experiments suggests a turbulent diffusivity that depends
+only weakly on the magnetic Reynolds number, but higher resolution simulations
+are needed.",0204497v2
+2006-06-02,Dynamics of the fast solar tachocline: II. Migrating field,"We present detailed numerical calculations of the fast solar tachocline based
+on the assumption that the dynamo field dominates over the dynamics of the
+tachocline. In the present paper of the series, we focus on three shortfalls of
+the earlier models. First, instead of the simple oscillating dipole poloidal
+field we study the more general magnetic field structures reminiscent of the
+butterfly diagram. The migrating field is prescribed as the observed
+axisymmetric radial magnetic field Stenflo (1988, 1994). Our results are in
+good agreement with our analitical estimate and our previous works in
+Forgacs-Dajka & Petrovay (2001,2002), but the polar ""dip"" in isorotational
+surfaces is strongly reduced in this case. On the other hand, a more realistic
+model should have a magnetic diffusivity decreasing significantly inside the
+radiative interior, so we also explore the effect of diffusivity and magnetic
+Prandtl number varying with depth. We found that the downwards decreasing
+magnetic diffusivity and Prandtl number have no significant effect on the
+solution, although the temporal variation of the tachocline thickness has
+decreased.",0606055v1
+1995-05-19,MAGNETISATION REVERSAL AND DOMAIN STRUCTURE IN THIN MAGNETIC FILMS: THEORY AND COMPUTER SIMULATION,"A model is introduced for the theoretical description of nanoscale magnetic
+films with high perpendicular anisotropy. In the model the magnetic film is
+described in terms of single domain magnetic grains, interacting via exchange
+as well as via dipolar forces. Additionally, the model contains anisotropy
+energy and a coupling to an external magnetic field. Disorder is taken into
+account in order to describe realistic domain and domain wall structures.
+Within this framework the dependence of the energy on the film thickness can be
+discussed. The influence of a finite temperature as well as the dynamics can be
+modeled by a Monte Carlo simulation. The results on the hysteresis loops, the
+domain configurations, and the dynamics during the reversal process are in good
+agreement with experimental findings.",9505084v1
+1996-11-30,Slow antiferromagnetic dynamics in the low temperature tetragonal phase of La_{2-x}Sr_xCuO_4 as revealed by ESR of Gd spin probes,"Measuring the ESR of Gd spin probes we have studied the magnetic properties
+of the copper oxide planes in the low temperature tetragonal (LTT) phase of Eu
+doped La_{2-x}Sr_xCuO_4. The data give evidence that at particular levels of Sr
+and Eu doping the frequency of the antiferromagnetic fluctuations in the LTT
+phase dramatically decreases at low temperatures by almost three orders of
+magnitude. However, no static magnetic order has been found for T>8K in
+contrast to the observation by neutron scattering of stripe ordering of spins
+below 50K in a Nd doped La_{2-x}Sr_xCuO_4 single crystal. To our opinion static
+order in the Nd doped compound is induced due to the interaction between the Cu
+spins with the rare earth magnetic moments. Therefore, a really characteristic
+property of the magnetism in the LTT structural phase may be not static
+magnetic order at elevated temperatures but rather extremely slow
+antiferromagnetic dynamics.",9612011v1
+1999-05-05,Vortex dynamics in bulk HTS with levitation techniques,"We have developed a set of experimental techniques with levitation to
+investigate the macroscopic magnetic properties of bulk HTS: (i) resonance
+oscillation technique; (ii) high speed magnetic rotor technique; (iii) the
+method of viscous motion of a permanent magnet through a HTS aperture under a
+steady force. Early, we used these techniques to investigate the magnetic flux
+dynamics in granular HTS. Now, we have extended and modified these techniques
+to study the large grain melt-textured HTS. With resonance oscillations
+technique we obtain the energy losses vs ac magnetic field amplitude at HTS
+surface and can derive the values of critical current density with high
+accuracy. We extract information about distribution of critical current in a
+thin undersurface layer and, in this way, check the HTS degradation processes.
+The treatment of the HTS surface that has influence on the surface pinning was
+investigated with this technique.",9905051v1
+2002-03-21,A molecular dynamics study on the equilibrium magnetization properties and structure of ferrofluids,"We investigate in detail the initial susceptibility, magnetization curves,
+and microstructure of ferrofluids in various concentration and particle dipole
+moment ranges by means of molecular dynamics simulations. We use the Ewald
+summation for the long-range dipolar interactions, take explicitly into account
+the translational and rotational degrees of freedom, coupled to a Langevin
+thermostat. When the dipolar interaction energy is comparable with the thermal
+energy, the simulation results on the magnetization properties agree with the
+theoretical predictions very well. For stronger dipolar couplings, however, we
+find systematic deviations from the theoretical curves. We analyze in detail
+the observed microstructure of the fluids under different conditions. The
+formation of clusters is found to enhance the magnetization at weak fields and
+thus leads to a larger initial susceptibility. The influence of the particle
+aggregation is isolated by studying ferro-solids, which consist of magnetic
+dipoles frozen in at random locations but which are free to rotate. Due to the
+artificial suppression of clusters in ferro-solids the observed susceptibility
+is considerably lowered when compared to ferrofluids.",0203445v1
+2004-03-08,Mean-field magnetization relaxation in conducting ferromagnets,"Collective ferromagnetic motion in a conducting medium is damped by the
+transfer of the magnetic moment and energy to the itinerant carriers. We
+present a calculation of the corresponding magnetization relaxation as a
+linear-response problem for the carrier dynamics in the effective exchange
+field of the ferromagnet. In electron systems with little intrinsic spin-orbit
+interaction, a uniform magnetization motion can be formally eliminated by going
+into the rotating frame of reference for the spin dynamics. The ferromagnetic
+damping in this case grows linearly with the spin-flip rate when the latter is
+smaller than the exchange field and is inversely proportional to the spin-flip
+rate in the opposite limit. These two regimes are analogous to the
+""spin-pumping"" and the ""breathing Fermi-surface"" damping mechanisms,
+respectively. In diluted ferromagnetic semiconductors, the hole-mediated
+magnetization can be efficiently relaxed to the itinerant-carrier degrees of
+freedom due to the strong spin-orbit interaction in the valence bands.",0403224v2
+2004-06-24,Models for the magnetic ac susceptibility of granular superferromagnetic CoFe/Al$_2$O$_3$,"The magnetization and magnetic ac susceptibility, $\chi = \chi' - i \chi''$,
+of superferromagnetic systems are studied by numerical simulations. The
+Cole-Cole plot, $\chi''$ vs. $\chi'$, is used as a tool for classifying
+magnetic systems by their dynamical behavior. The simulations of the
+magnetization hysteresis and the ac susceptibility are performed with two
+approaches for a driven domain wall in random media. The studies are motivated
+by recent experimental results on the interacting nanoparticle system
+Co$_{80}$Fe$_{20}$/Al$_{2}$O$_{3}$ showing superferromagnetic behavior. Its
+Cole-Cole plot indicates domain wall motion dynamics similarly to a disordered
+ferromagnet, including pinning and sliding motion. With our models we can
+successfully reproduce the features found in the experimental Cole-Cole plots.",0406590v2
+2004-12-07,Solving the Master Equation for Extremely Long Time Scale Calculations,"The dynamics of magnetic reversal process plays an important role in the
+design of the magnetic recording devices in the long time scale limit. In
+addition to long time scale, microscopic effects such as the entropic effect
+become important in magnetic nano-scale systems. Many advanced simulation
+methods have been developed, but few have the ability to simulate the long time
+scale limit and to accurately model the microscopic effects of nano-scale
+systems at the same time. We develop a new Monte Carlo method for calculating
+the dynamics of magnetic reversal at arbitrary long time. For example, actual
+calculations were performed up to 1e50 Monte Carlo steps. This method is based
+on microscopic interactions of many constituents and the master equation for
+magnetic probability distribution function is solved symbolically.",0412151v1
+2005-03-30,Dynamics of Magnetic Defects in Heavy Fermion LiV2O4 from Stretched Exponential 7Li NMR Relaxation,"7Li NMR measurements on LiV2O4 from 0.5 to 4.2 K are reported. A small
+concentration of magnetic defects within the structure drastically changes the
+7Li nuclear magnetization relaxation versus time from a pure exponential as in
+pure LiV2O4 to a stretched exponential, indicating glassy behavior of the
+magnetic defects. The stretched exponential function is described as arising
+from a distribution of 7Li nuclear spin-lattice relaxation rates and we present
+a model for the distribution in terms of the dynamics of the magnetic defects.
+Our results explain the origin of recent puzzling 7Li NMR literature data on
+LiV2O4 and our model is likely applicable to other glassy systems.",0503723v1
+2005-07-22,Dynamical Response of Fermi Condensate to Varying Magnetic Fields,"We investigate the dynamical response of strongly interacting ultra-cold
+fermionic atoms near Feshbach resonance to varying magnetic fields. Following
+the experimental practices, we calculate the response of the atoms to
+oscillating and to linearly ramped magnetic fields respectively. For
+oscillating magnetic fields, depending on the frequencies and the amplitudes of
+the oscillations, the response of the pair excitation gap shows either linear
+or rich non-linear behaviour. In addition, both the spectral studies through
+the linear response theory and the time-domain simulations suggest the
+existence of a resonant frequency corresponding to the pair dissociation
+threshold. For linearly ramped magnetic fields, the response of the excitation
+gap shows damped oscillations. The final value of the excitation gap depends on
+the rate of the field sweep.",0507540v1
+2005-08-30,Large angle magnetization dynamics measured by time-resolved ferromagnetic resonance,"A time-resolved ferromagnetic resonance technique was used to investigate the
+magnetization dynamics of a 10 nm thin Permalloy film. The experiment consisted
+of a sequence of magnetic field pulses at a repetition rate equal to the
+magnetic systems resonance frequency. We compared data obtained by this
+technique with conventional pulsed inductive microwave magnetometry. The
+results for damping and frequency response obtained by these two different
+methods coincide in the limit of a small angle excitation. However, when
+applying large amplitude field pulses, the magnetization had a non-linear
+response. We speculate that one possible cause of the nonlinearity is related
+to self-amplification of incoherence, known as the Suhl instabilities.",0508708v1
+2005-11-09,Current driven magnetization dynamics in helical spin density waves,"A mechanism is proposed for manipulating the magnetic state of a helical spin
+density wave using a current. In this paper, we show that a current through a
+bulk system with a helical spin density wave induces a spin transfer torque,
+giving rise to a rotation of the order parameter.The use of spin transfer
+torque to manipulate the magnetization in bulk systems does not suffer from the
+obstacles seen for magnetization reversal using interface spin transfer torque
+in multilayered systems. We demonstrate the effect by a quantitative
+calculation of the current induced magnetization dynamics of Erbium. Finally we
+propose a setup for experimental verification.",0511224v2
+2006-06-29,Dynamics of molecular nanomagnets in time-dependent external magnetic fields: Beyond the Landau-Zener-Stückelberg model,"The time evolution of the magnetization of a magnetic molecular crystal is
+obtained in an external time-dependent magnetic field, with sweep rates in the
+kT/s range. We present the 'exact numerical' solution of the time dependent
+Schr\""{o}dinger equation, and show that the steps in the hysteresis curve can
+be described as a sequence of two-level transitions between adiabatic states.
+The multilevel nature of the problem causes the transition probabilities to
+deviate significantly from the predictions of the Landau-Zener-St\""{u}ckelberg
+model. These calculations allow the introduction of an efficient approximation
+method that accurately reproduces the exact results. When including phase
+relaxation by means of an appropriate master equation, we observe an interplay
+between coherent dynamics and decoherence. This decreases the size of the
+magnetization steps at the transitions, but does not modify qualitatively the
+physical picture obtained without relaxation.",0606763v1
+2006-11-30,Edge singularities in high-energy spectra of gapped one-dimensional magnets in strong magnetic fields,"We use the dynamical density matrix renormalization group technique to show
+that the high-energy part of the spectrum of a S=1 Haldane chain, placed in a
+strong external magnetic field $H$ exceeding the Haldane gap $\Delta$, contains
+edge singularities, similar to those known to exist in the low-energy spectral
+response. It is demonstrated that in the frequency range $\omega\gtrsim \Delta$
+the longitudinal (with respect to the applied field) dynamical structure factor
+is dominated by the power-law singularity
+$S^{\parallel}(q=\pi,\omega)\propto(\omega-\omega_{0})^{-\alpha'}$. We study
+the behavior of the high-energy edge exponent $\alpha'$ and the edge
+$\omega_{0}$ as functions of the magnetic field. The existence of edge
+singularities at high energies is directly related to the Tomonaga-Luttinger
+liquid character of the ground state at $H>\Delta$ and is expected to be a
+general feature of one-dimensional gapped spin systems in high magnetic fields.",0611772v2
+2007-02-09,Magnetic vortex oscillator driven by dc spin-polarized current,"Transfer of angular momentum from a spin-polarized current to a ferromagnet
+provides an efficient means to control the dynamics of nanomagnets. A peculiar
+consequence of this spin-torque, the ability to induce persistent oscillations
+of a nanomagnet by applying a dc current, has previously been reported only for
+spatially uniform nanomagnets. Here we demonstrate that a quintessentially
+nonuniform magnetic structure, a magnetic vortex, isolated within a nanoscale
+spin valve structure, can be excited into persistent microwave-frequency
+oscillations by a spin-polarized dc current. Comparison to micromagnetic
+simulations leads to identification of the oscillations with a precession of
+the vortex core. The oscillations, which can be obtained in essentially zero
+magnetic field, exhibit linewidths that can be narrower than 300 kHz, making
+these highly compact spin-torque vortex oscillator devices potential candidates
+for microwave signal-processing applications, and a powerful new tool for
+fundamental studies of vortex dynamics in magnetic nanostructures.",0702253v1
+1998-02-17,Induced Magnetic moments in three-dimensional gauge theories with external magnetic fields,"We study the appearance of induced parity-violating magnetic moment, in the
+presence of external magnetic fields, for even-number of fermion species
+coupled to dynamical fields in three dimensions. Specifically, we use a
+SU(2)xU(1) gauge model for dynamical gauge symmetry breaking, which is also
+proposed recently as a field theoretical model for high-temperature
+superconductors. By decomposing the fermionic degrees of freedom in terms of
+Landau levels, we show that, in the effective theory with the lowest Landau
+levels, a parity-violating magnetic moment interaction is induced by the higher
+Landau levels when the fermions are massive. The possible relevance of this
+result for a recently observed phenomenon in high-temperature superconductors
+is also discussed.",9802119v2
+2004-03-11,Twisted Crossed Products and Magnetic Pseudodifferential Operators,"There is a connection between the Weyl pseudodifferential calculus and
+crossed product C*-algebras associated with certain dynamical systems. And in
+fact both topics are involved in the quantization of a non-relativistic
+particle moving in R^n. Our paper studies the situation in which a variable
+magnetic field is also present. The Weyl calculus has to be modified, giving a
+functional calculus for a family of operators (positions and magnetic momenta)
+with highly non-trivial commutation relations. On the algebraic side, the
+dynamical system is twisted by a cocyle defined by the flux of the magnetic
+field, leading thus to twisted crossed products. We outline the interplay
+between the modified pseudodifferential setting and the C*-algebraic formalism
+at an abstract level as well as in connection with magnetic field.",0403016v1
+1999-01-26,"Transverse wavevector dependent and frequency dependent dielectric function, magnetic permittivity and generalized conductivity of interaction site fluids. MD calculations for the TIP4P water","It is shown that the dielectric properties of interaction site models of
+polar fluids can be investigated in computer experiment using not only the
+charge fluctuations but also correlations corresponding to a current of moving
+charges. This current can be associated with a generalized dynamical
+polarization or separated into electric and magnetic components. The first
+approach deals with the dielectric permittivity related to a generalized
+conductivity, whereas the second one leads to the functions describing
+polarization and magnetization fluctuations separately. The last way is only
+the source to calculate the magnetic susceptibility for a system of interaction
+sites. The transverse wavevector- and frequency-dependent dielectric functions
+and magnetic susceptibility are evaluated for the TIP4P water model in a very
+wide scale of wavelengths and frequencies using molecular dynamics simulations.
+We demonstrate that the transverse part of the dielectric functions may differ
+drastically from their longitudinal component. A relationship between the two
+approaches is discussed and the limiting transition to the static dielectric
+constant in the infinite-wavelength regime is analyzed. The propagation of
+transverse electromagnetic waves in the TIP4P water is also considered.",9901048v1
+2004-11-08,"On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun","Measurements of the various plasma configurations produced by a planar
+magnetized coaxial gun provide insight into the magnetic topology evolution
+resulting from magnetic helicity injection. Important features of the
+experiments are a very simple coaxial gun design so that all observed
+geometrical complexity is due to the intrinsic physical dynamics rather than
+the source shape and use of a fast multiple-frame digital camera which provides
+direct imaging of topologically complex shapes and dynamics. Three key
+experimental findings were obtained: (1) formation of an axial collimated jet
+[Hsu and Bellan, Mon. Not. R. Astron. Soc. 334, 257 (2002)] that is consistent
+with a magnetohydrodynamic description of astrophysical jets, (2)
+identification of the kink instability when this jet satisfies the
+Kruskal-Shafranov limit, and (3) the nonlinear properties of the kink
+instability providing a conversion of toroidal to poloidal flux as required for
+spheromak formation by a coaxial magnetized source [Hsu and Bellan, Phys. Rev.
+Lett. 90, 215002 (2003)]. A new interpretation is proposed for how the n=1
+central column instability provides flux amplification during spheromak
+formation and sustainment, and it is shown that jet collimation can occur
+within one rotation of the background poloidal field.",0411089v1
+2005-05-13,Dynamics of Entanglement for One-Dimensional Spin Systems in an External Time-Dependent Magnetic Field,"We study the dynamics of entanglement for the XY-model, one-dimensional spin
+systems coupled through nearest neighbor exchange interaction and subject to an
+external time-dependent magnetic field. Using the two-site density matrix, we
+calculate the time-dependent entanglement of formation between nearest neighbor
+qubits. We investigate the effect of varying the temperature, the anisotropy
+parameter and the external time-dependent magnetic field on the entanglement.
+We have found that the entanglement can be localized between nearest neighbor
+qubits for certain values of the external time-dependent magnetic field.
+Moreover, as known for the magnetization of this model, the entanglement shows
+nonergodic behavior, it does not approach its equilibrium value at the infinite
+time limit.",0505101v1
+2007-09-05,Time-Domain Studies of Very-Large-Angle Magnetization Dynamics Excited by Spin Transfer Torques,"We describe time-domain measurements which provide new information about the
+large-angle nonlinear dynamics of nanomagnets excited by spin-transfer torque
+from a spin-polarized current. Sampling-oscilloscope measurements, which
+average over thousands of experimental time traces, show that the mean reversal
+time for spin-transfer-driven magnetic switching has a step-like dependence on
+magnetic field, because an integer number of precession cycles is required for
+reversal. Storage-oscilloscope measurements of individual experimental traces
+reveal non-periodic large-amplitude resistance variations at values of magnetic
+field and current in a crossover region between the regimes of
+spin-transfer-driven switching and steady-state precession. We also observe
+directly the existence of time-dependent switching, on the nanosecond scale,
+between different precessional modes and between a precessional mode and a
+static state, at particular values of magnetic field and current bias.",0709.0560v1
+2007-09-08,Transition rates for a S \ge 1 model coupled to a phonon bath,"We investigate transition rates between different spin configurations for $S
+\ge 1$ spins weakly coupled to a $d$-dimensional phonon bath. This study is
+motivated by understanding observed magnetization relaxation as a function of
+temperature in diverse magnetic systems such as arrays of magnetic
+nanoparticles and magnetic molecules. We assume that the magnetization of the
+spin system relaxes through consecutive emission or absorption of a single
+phonon. From a weak, linear spin-phonon coupling Hamiltonian, we derive
+transition rates that would be used to examine dynamic properties of the system
+in kinetic Monte Carlo simulations. Although the derived phonon-assisted
+transition rates satisfy detailed balance, in the case of two and three
+dimensional phonon baths, transitions between degenerate states are not
+allowed. Thus, if there are no alternative paths along which the spin system
+can relax, the relaxation time diverges. Otherwise, the system finds other
+paths, which leads to an increase in the relaxation time and energy barrier.
+However, when higher-order phonon processes are included in the transition
+rates, it is found that the system can reach the states which were inaccessible
+due to the forbidden transitions. As a result, the system recovers some of the
+dynamic properties obtained using the Glauber transition rate.",0709.1237v1
+2007-10-22,Dynamo quenching due to shear flow,"We provide a theory of dynamo ($\alpha$ effect) and momentum transport in
+three-dimensional magnetohydrodynamics. For the first time, we show that the
+$\alpha$ effect is severely reduced by the shear even in the absence of
+magnetic field. The $\alpha$ effect is further suppressed by magnetic fields
+well below equipartition (with the large-scale flow) with different scalings
+depending on the relative strength of shear and magnetic field. The turbulent
+viscosity is also found to be significantly reduced by shear and magnetic
+fields, with positive value. These results suggest a crucial effect of shear
+and magnetic field on dynamo quenching and momentum transport reduction, with
+important implications for laboratory and astrophysical plasmas, in particular
+for the dynamics of the Sun.",0710.4005v2
+2008-02-26,The Influence of Helical Magnetic Fields in the Dynamics and Emission of Relativistic Jets,"We present numerical relativistic magnetohydrodynamic and emission
+simulations aimed to study the role played by the magnetic field in the
+dynamics and emission of relativistic jets in Active Galactic Nuclei. We focus
+our analysis on the study of the emission from recollimation shocks since they
+may provide an interpretation for the stationary components seen at
+parsec-scales in multiple sources. We show that the relative brightness of the
+knots associated with the recollimation shocks decreases with increasing jet
+magnetization, suggesting that jets presenting stationary components may have a
+relatively weak magnetization, with magnetic fields of the order of
+equipartition or below.",0802.3826v1
+2008-03-01,External Fields and Chiral Symmetry Breaking in the Sakai-Sugimoto Model,"Using the Sakai-Sugimoto model we study the effect of an external magnetic
+field on the dynamics of fundamental flavours in both the confined and
+deconfined phases of a large N_c gauge theory. We find that an external
+magnetic field promotes chiral symmetry breaking, consistent with the ""magnetic
+catalysis"" observed in the field theory literature, and seen in other studies
+using holographic duals. The external field increases the separation between
+the deconfinement temperature and the chiral symmetry restoring temperature. In
+the deconfined phase we investigate the temperature-magnetic field phase
+diagram and observe, for example, there exists a maximum critical temperature
+(at which symmetry is restored) for very large magnetic field. We find that
+this and certain other phenomena persist for the Sakai-Sugimoto type models
+with probe branes of diverse dimensions. We comment briefly on the dynamics in
+the presence of an external electric field.",0803.0038v3
+2008-04-18,Polarisation selective magnetic vortex dynamics and core reversal in rotating magnetic fields,"A magnetic vortex occurs as an equilibrium configuration in thin
+ferromagnetic platelets of micron and sub-micron size and is characterised by
+an in-plane curling magnetisation. At the centre, a magnetic singularity is
+avoided by an out-of-plane magnetisation core. This core has a gyrotropic
+excitation mode, which corresponds to a circular motion of the vortex around
+its equilibrium position, where the rotation sense is determined by the
+direction of the vortex core magnetisation, its polarisation. Unlike linear
+fields or spin polarised currents, which excite both polarisation states, an
+in-plane rotating field can selectively excite one of the polarisation states.
+Here we report the observation of vortex dynamics in response to rotating
+magnetic fields, imaged with time-resolved scanning X-ray microscopy. We
+demonstrate that the rotating field only excites the gyrotropic mode if the
+rotation sense of the field coincides with the vortex gyration sense and that
+such a field can selectively reverse the vortex polarisation.",0804.2944v2
+2008-06-17,Dynamics of magnetization in frustrated spin-chain systems: Ca$_3$Co$_2$O$_6$,"The magnetization dynamics of the triangular lattice of Ising spin chains is
+investigated in the framework of a two-dimensional model. The rigid chains are
+assumed to interact with the nearest neighboring chains, an external magnetic
+field, and a heat reservoir that causes the chains to change their states
+randomly with time. A probability of a single spin-flip process is assumed in a
+Glauber-like form. This technique allows describing properly the steps in the
+magnetization curves observed in Ca$_3$Co$_2$O$_6$ and their dependence on a
+magnetic field sweep rate and temperature. A transition from a low-temperature
+to high-temperature phase is also observed.",0806.2692v1
+2008-10-08,Anti-vortex dynamics in magnetic nanostripes,"In a thin magnetic nanostripe, an anti-vortex nucleates inside a moving
+domain wall when driven by an in-plane magnetic field greater than the
+so-called Walker field. The nucleated anti-vortex must cross the width of the
+nanostripe before the domain wall can propagate again, leading to low average
+domain wall speeds. A large out-of-plane magnetic field, applied
+perpendicularly to the plane of the nanostripe, inhibits the nucleation of the
+anti-vortex leading to fast domain wall speeds for all in-plane driving fields.
+We present micromagnetic simulation results relating the anti-vortex dynamics
+to the strength of the out-of-plane field. An asymmetry in the motion is
+observed which depends on the alignment of the anti-vortex core magnetic
+moments to the direction of the out-of-plane field. The size of the core is
+directly related to its crossing speed, both depending on the strength of the
+perpendicular field and the alignment of the core moments and direction of the
+out-of-plane field.",0810.1538v1
+2008-10-17,"Magnetization dynamics down to zero field in dilute (Cd,Mn)Te quantum wells","The evolution of the magnetization in (Cd,Mn)Te quantum wells after a short
+pulse of magnetic field was determined from the giant Zeeman shift of
+spectroscopic lines. The dynamics in absence of magnetic field was found to be
+up to three orders of magnitude faster than that at 1 T. Hyperfine interaction
+and strain are mainly responsible for the fast decay. The influence of a hole
+gas is clearly visible: at zero field anisotropic holes stabilize the system of
+Mn ions, while in a magnetic field of 1 T they are known to speed up the decay
+by opening an additional relaxation channel.",0810.3100v1
+2008-11-12,Wave turbulence on the surface of a ferrofluid submitted to a magnetic field,"We report the observation of wave turbulence on the surface of a ferrofluid
+mechanically forced and submitted to a static normal magnetic field. We show
+that magnetic surface waves arise only above a critical field. The power
+spectrum of their amplitudes displays a frequency-power law leading to the
+observation of a magnetic wave turbulence regime which is experimentally shown
+to involve a 4-wave interaction process. The existence of the regimes of
+gravity, magnetic and capillary wave turbulence is reported in the phase space
+parameters as well as a triple point of coexistence of these three regimes.
+Most of these features are understood using dimensional analysis or the
+dispersion relation of the ferrohydrodynamics surface waves.",0811.1943v1
+2009-03-30,Universal Holographic Chiral Dynamics in an External Magnetic Field,"In this work we further extend the investigation of holographic gauge
+theories in external magnetic fields, continuing earlier work. We study the
+phenomenon of magnetic catalysis of mass generation in 1+3 and 1+2 dimensions,
+using D3/D7- and D3/D5-brane systems, respectively. We obtain the low energy
+effective actions of the corresponding pseudo Goldstone bosons and study their
+dispersion relations. The D3/D7 system exhibits the usual
+Gell-Mann--Oakes--Renner (GMOR) relation and a relativistic dispersion
+relation, while the D3/D5 system exhibits a quadratic non-relativistic
+dispersion relation and a modified linear GMOR relation. The low energy
+effective action of the D3/D5 system is related to that describing magnon
+excitations in a ferromagnet. We also study properties of general Dp/Dq systems
+in an external magnetic field and verify the universality of the magnetic
+catalysis of dynamical symmetry breaking.",0903.5345v2
+2009-06-29,Three-dimensional evolution of magnetic and velocity shear driven instabilities in a compressible magnetized jet,"The problem of three-dimensional combined magnetic and velocity shear driven
+instabilities of a compressible magnetized jet modeled with a plane
+neutral/current double vortex sheet in the framework of the resistive
+magnetohydrodynamics is addressed. The resulting dynamics given by the
+stream+current sheet interaction is analyzed and the effects of a variable
+geometry of the basic fields are considered. Depending on the basic asymptotic
+magnetic field configuration, a selection rule of the linear instability modes
+can be obtained. Hence, the system follows a two-stage path developing either
+through a fully three-dimensional dynamics with a rapid evolution of kink modes
+leading to a final turbulent state, or rather through a driving two-dimensional
+instability pattern that develops on parallel planes on which a
+reconnection+coalescence process takes place.",0906.5383v1
+2009-09-25,Modeling domain wall dynamics in thin magnetic strips with disorder,"We present a line-based model of transverse domain walls in thin magnetic
+strips, to study the effect of bulk disorder on the domain wall dynamics within
+the thermally activated creep regime. The creep velocity is found to exhibit a
+non-linear dependence on both applied magnetic fields and electric currents,
+characterized by similar creep exponents for both forms of the external drive.
+We discuss briefly the significance of the inherently stochastic thermally
+activated domain wall motion from the point of view of spintronics
+applications, where it generally is essential to be able to control the domain
+wall displacement in a deterministic manner.",0909.4659v1
+2009-10-06,Dynamics of reflection of ultracold atoms from a periodic 1D magnetic lattice potential,"We report on an experimental study of the dynamics of the reflection of
+ultracold atoms from a periodic one-dimensional magnetic lattice potential. The
+magnetic lattice potential of period 10 \textmu m is generated by applying a
+uniform bias magnetic field to a microfabricated periodic structure on a
+silicon wafer coated with a multilayered TbGdFeCo/Cr magneto-optical film. The
+effective thickness of the magnetic film is about 960 nm. A detailed study of
+the profile of the reflected atoms as a function of externally induced periodic
+corrugation in the potential is described. The effect of angle of incidence is
+investigated in detail. The experimental observations are supported by
+numerical simulations.",0910.0953v1
+2010-04-21,Effects of Spin Fluctuations and Anomalous Thermal Expansion of delta-Plutonium,"We suggest a model for the magnetic dynamics of - plutonium and its alloys in
+order to show that the dynamical fluctuations of the magnetization density, or
+spin fluctuations, may be responsible for the anomalies of their observed
+thermal expansion. We show that due to strong magneto-elastic coupling, spin
+fluctuations may essentially contribute to the volume strain by giving a
+negative magneto-volume contribution that is proportional to the squared local
+magnetic moment and the magnetic Gruneisen constant which is negative in -
+plutonium. In the presented model, the local magnetic moment increases as the
+temperature rises, resulting in the interplay between the positive
+contributions to the volume strain from the lattice and the negative
+contribution from spin fluctuations, and finally leads to the Invar anomaly or
+to the negative coefficient of thermal expansion. Our results agree closely
+with the measured thermal expansion data for Pu-Ga alloys.",1004.3658v1
+2010-07-06,The dynamics of magnetic vortex states in a single permalloy nanoparticle,"We demonstrate a novel method allowing the study of the magnetic state
+dynamics of a single nanoparticle by means of electron transport measurements.
+Elliptical 550 nm x 240 nm permalloy nanoparticles are wired with non-magnetic
+leads for magnetotransport measurements in the presence of a radio-frequency
+(RF) field. Their resistance exhibits sharp jumps due to the anisotropic
+magnetoresistance even at room temperature. An RF field induces DC voltage
+across the nanoparticle which can be partially depleted at a certain RF
+frequency when a magnetic vortex core resonance is present. An application of
+an additional DC magnetic field eliminates the vortex and reinstates the
+unperturbed DC voltage level. The vortex core resonance frequencies are found
+and the smallest resonance widths are estimated to be less than 6 MHz.",1007.0958v1
+2010-07-29,Effect of a high-frequency magnetic field on the resonant behavior displayed by a spin-$1/2$ particle under the influence of a rotating magnetic field,"In this paper, we investigate the role of a high-frequency magnetic field in
+the resonant behavior displayed by a spin-$1/2$ particle under the influence of
+a rotating magnetic field. We propose two alternative methods for analyzing the
+system dynamics, namely, the averaging method and the multiple scale method.
+The analytical results achieved by applying these two methods are compared with
+those obtained from the numerical solution of the Schr\""odinger equation. This
+comparison leads to the conclusion that the multiple scale method provides a
+better understanding of the system dynamics than the averaging method. In
+particular, the averaging method predicts the complete destruction of the
+resonant behavior by an appropriate choice of the parameter values of the
+high-frequency magnetic field. This conclusion is disproved both by the
+numerical results, and also by the results obtained from the multiple scale
+method.",1007.5194v1
+2010-08-12,Magnetization dynamics in the inertial regime: nutation predicted at short time scales,"The dynamical equation of the magnetization has been reconsidered with
+enlarging the phase space of the ferromagnetic degrees of freedom to the
+angular momentum. The generalized Landau-Lifshitz-Gilbert equation that
+includes inertial terms, and the corresponding Fokker-Planck equation, are then
+derived in the framework of mesoscopic non-equilibrium thermodynamics theory. A
+typical relaxation time $\tau$ is introduced describing the relaxation of the
+magnetization acceleration from the inertial regime towards the precession
+regime defined by a constant Larmor frequency. For time scales larger than
+$\tau$, the usual Gilbert equation is recovered. For time scales below $\tau$,
+nutation and related inertial effects are predicted. The inertial regime offers
+new opportunities for the implementation of ultrafast magnetization switching
+in magnetic devices.",1008.2177v1
+2010-10-20,Electron spin decoherence in diluted magnetic quantum wells,"We study electron spin dynamics in diluted magnetic quantum wells. The
+electrons are coupled by exchange interaction with randomly distributed
+magnetic ions polarized by magnetic field. This coupling leads to both spin
+relaxation and spin decoherence. We demonstrate that even very small spatial
+fluctuations of quantum well width dramatically increase rate of decoherence.
+Depending on the strength of exchange interaction and the amplitude of the
+fluctuations the decoherence can be homogeneous or inhomogeneous. In the
+homogeneous regime, the transverse (with respect to magnetic field) component
+of the electron spin decays on the short time scale exponentialy, while the
+long-time spin dynamics is non-exponential demonstrating long-lived power law
+tail. In the inhomogeneous case, the transverse spin component decays
+exponentially with the exponent quadratic in time.",1010.4284v1
+2010-12-27,Phenomenology of Current-Induced Dynamics in Antiferromagnets,"We derive a phenomenological theory of current-induced staggered
+magnetization dynamics in antiferromagnets. The theory captures the reactive
+and dissipative current-induced torques and the conventional effects of
+magnetic fields and damping. A Walker ansatz describes the dc current-induced
+domain-wall motion when there is no dissipation. If magnetic damping and
+dissipative torques are included, the Walker ansatz remains robust when the
+domain-wall moves slowly. As in ferromagnets, the domain-wall velocity is
+proportional to the ratio between the dissipative-torque and the magnetization
+damping. In addition, a current-driven antiferromagnetic domain-wall acquires a
+net magnetic moment.",1012.5655v2
+2011-01-18,Statistical Mechanics and the Physics of the Many-Particle Model Systems,"The development of methods of quantum statistical mechanics is considered in
+light of their applications to quantum solid-state theory. We discuss
+fundamental problems of the physics of magnetic materials and the methods of
+the quantum theory of magnetism, including the method of two-time temperature
+Green's functions, which is widely used in various physical problems of
+many-particle systems with interaction. Quantum cooperative effects and
+quasiparticle dynamics in the basic microscopic models of quantum theory of
+magnetism: the Heisenberg model, the Hubbard model, the Anderson Model, and the
+spin-fermion model are considered in the framework of novel
+self-consistent-field approximation. We present a comparative analysis of these
+models; in particular, we compare their applicability for description of
+complex magnetic materials. The concepts of broken symmetry, quantum
+protectorate, and quasiaverages are analyzed in the context of quantum theory
+of magnetism and theory of superconductivity. The notion of broken symmetry is
+presented within the nonequilibrium statistical operator approach developed by
+D.N. Zubarev. In the framework of the latter approach we discuss the derivation
+of kinetic equations for a system in a thermal bath. Finally, the results of
+investigation of the dynamic behavior of a particle in an environment, taking
+into account dissipative effects, are presented.",1101.3423v1
+2011-01-26,Magnetic dynamo action in random flows with zero and finite correlation times,"Hydromagnetic dynamo theory provides the prevailing theoretical description
+for the origin of magnetic fields in the universe. Here we consider the problem
+of kinematic, small-scale dynamo action driven by a random, incompressible,
+non-helical, homogeneous and isotropic flow. In the Kazantsev dynamo model the
+statistics of the driving flow are assumed to be instantaneously correlated in
+time. Here we compare the results of the model with the dynamo properties of a
+simulated flow that has equivalent spatial characteristics as the Kazantsev
+flow but different temporal statistics. In particular, the simulated flow is a
+solution of the forced Navier-Stokes equations and hence has a finite
+correlation time. We find that the Kazantsev model typically predicts a larger
+magnetic growth rate and a magnetic spectrum that peaks at smaller scales.
+However, we show that by filtering the diffusivity spectrum at small scales it
+is possible to bring the growth rates into agreement and simultaneously align
+the magnetic spectra.",1101.5181v2
+2011-06-17,Current-induced synchronized magnetization reversal of two-body Stoner particles with dipolar interaction,"We investigate magnetization reversal of two-body uniaxial Stoner particles,
+by injecting spin-polarized current through a spin-valve structure. The
+two-body Stoner particles perform synchronized dynamics and can act as an
+information bit in computer technology. In the presence of magnetic
+dipole-dipole interaction (DDI) between the two particles, the critical
+switching current $I_c$ for reversing the two dipoles is analytically obtained
+and numerically verified in two typical geometric configurations. $I_c$
+bifurcates at a critical DDI strength, where $I_c$ can be decreased to about
+70% of the usual value without DDI. Moreover, we also numerically investigate
+the magnetic hysteresis loop, magnetization self-precession, reversal time and
+the synchronization stability phase diagram for the two-body system in the
+synchronized dynamics regime.",1106.3454v1
+2011-07-01,Catastrophic quenching in alpha-Omega dynamos revisited,"At large magnetic Reynolds numbers, magnetic helicity evolution plays an
+important role in astrophysical large-scale dynamos. The recognition of this
+fact led to the development of the dynamical alpha quenching formalism, which
+predicts catastrophically low mean fields in open systems. Here we show that in
+oscillatory alpha-Omega dynamos this formalism predicts an unphysical magnetic
+helicity transfer between scales. An alternative technique is proposed where
+this artifact is removed by using the evolution equation for the magnetic
+helicity of the total field in the shearing--advective gauge. In the
+traditional dynamical alpha quenching formalism, this can be described as an
+additional magnetic helicity flux of small-scale fields that does not appear in
+homogeneous alpha-squared dynamos. In alpha-Omega dynamos, the alternative
+formalism is shown to lead to larger saturation fields than previously obtained
+with the traditional formalism.",1107.0238v2
+2011-07-28,Optimal control of vortex core polarity by resonant microwave pulses,"In a vortex-state magnetic nano-disk, the static magnetization is curling in
+the plane, except in the core region where it is pointing out-of-plane, either
+up or down leading to two possible stable states of opposite core polarity p.
+Dynamical reversal of p by large amplitude motion of the vortex core has
+recently been demonstrated experimentally,raising fundamental interest for
+potential application in magnetic storage devices. Here we demonstrate coherent
+control of p by single and double microwave pulse sequences, taking advantage
+of the resonant vortex dynamics in a perpendicular bias magnetic field.
+Optimization of the microwave pulse duration required to switch p allows to
+experimentally infer the characteristic decay time of the vortex core in the
+large oscillation regime. It is found to be more than twice shorter than in the
+small oscillation regime, raising the fundamental question of the non-linear
+behaviour of magnetic dissipation.",1107.5700v1
+2011-08-01,Spin Pumping and Spin Transfer,"Spin pumping is the emission of a spin current by a magnetization dynamics
+while spin transfer stands for the excitation of magnetization by spin
+currents. Using Onsager's reciprocity relations we prove that spin pumping and
+spin-transfer torques are two fundamentally equivalent dynamic processes in
+magnetic structures with itinerant electrons. We review the theory of the
+coupled motion of the magnetization order parameter and electron for textured
+bulk ferromagnets (e.g. containing domain walls) and heterostructures (such as
+spin valves). We present first-principles calculations for the
+material-dependent damping parameters of magnetic alloys. Theoretical and
+experimental results agree in general well.",1108.0385v3
+2011-09-04,Numerical simulations of relativistic magnetic reconnection with Galerkin methods,"We present the results of two-dimensional magnetohydrodynamical numerical
+simulations of relativistic magnetic reconnection, with particular emphasis on
+the dynamics of Petschek-type configurations with high Lundquist numbers, S ~
+10^5-10^8. The numerical scheme adopted, allowing for unprecedented accuracy
+for this type of calculations, is based on high order finite volume and
+discontinuous Galerkin methods as recently proposed by Dumbser & Zanotti
+(2009). The possibility of producing high Lorentz factors is discussed, by
+studying the effects produced on the dynamics by different magnetization and
+resistivity regimes. We show that Lorentz factors close to ~4 can be produced
+for a plasma magnetization parameter sigma=20. Moreover, we find that the
+Sweet-Parker layers are unstable, generating secondary magnetic islands, but
+only for S>S_c~10^8, much larger than what is reported in the Newtonian regime.",1109.0746v1
+2011-09-30,Phase separation dynamics in a two-dimensional magnetic mixture,"Based on classical density functional theory (DFT), we investigate the
+demixing phase transition of a two-dimensional, binary Heisenberg fluid
+mixture. The particles in the mixture are modeled as Gaussian soft spheres,
+where one component is characterized by an additional classical spin-spin
+interaction of Heisenberg type. Within the DFT we treat the particle
+interactions using a mean-field approximation. For certain magnetic coupling
+strengths we calculate phase diagrams in the density-concentration plane. For
+sufficiently large coupling strengths and densities, we find a demixing phase
+transition driven by the ferromagnetic interactions of the magnetic species. We
+also provide a microscopic description (i.e., density profiles) of the
+resulting non-magnetic/magnetic fluid-fluid interface. Finally, we investigate
+the phase separation using dynamical density functional theory (DDFT),
+considering both nucleation processes and spinodal demixing.",1109.6756v1
+2011-10-10,Star Formation and the Hall Effect,"Magnetic fields play an important role in star formation by regulating the
+removal of angular momentum from collapsing molecular cloud cores. Hall
+diffusion is known to be important to the magnetic field behaviour at many of
+the intermediate densities and field strengths encountered during the
+gravitational collapse of molecular cloud cores into protostars, and yet its
+role in the star formation process is not well-studied. This thesis describes a
+semianalytic self-similar model of the collapse of rotating isothermal
+molecular cloud cores with both Hall and ambipolar diffusion, presenting
+similarity solutions that demonstrate that the Hall effect has a profound
+influence on the dynamics of collapse.
+  ...
+  Hall diffusion also determines the strength of the magnetic diffusion and
+centrifugal shocks that bound the pseudo and rotationally-supported discs, and
+can introduce subshocks that further slow accretion onto the protostar. In
+cores that are not initially rotating Hall diffusion can even induce rotation,
+which could give rise to disc formation and resolve the magnetic braking
+catastrophe. The Hall effect clearly influences the dynamics of gravitational
+collapse and its role in controlling the magnetic braking and radial diffusion
+of the field would be worth exploring in future numerical simulations of star
+formation.",1110.2168v1
+2011-11-26,Quantum depinning of the magnetic vortex core in micron-size permalloy disks,"The vortex state, characterized by an in-plane closed flux domain structure
+and an out-of-plane magnetization at its centre (the vortex core), is one of
+the magnetic equilibria of thin soft ferromagnetic micron-size dots. In the
+last two decades many groups have been working on the dynamics of the magnetic
+moment in nanomagnetic materials at low temperatures, it giving rise to the
+observation of quantum relaxations and quantum hysteresis cycles. For the first
+time, we report experimental evidence of quantum dynamics of the vortex core of
+micron-size permalloy (Fe$_{19}$Ni$_{81}$) disks induced by the application of
+an in-plane magnetic field. It is attributed to the quantum tunneling of the
+vortex core through pinning barriers, which are associated to structural
+defects in the dots, towards its equilibrium position.",1111.6171v1
+2012-04-12,On the dynamics of mechanical failures in magnetized neutron-star crusts,"We consider the dynamics of a mechanical failure induced by a shear stress in
+a strongly magnetized neutron-star crust. We show that even if the elastic
+properties of the crust allow the creation of a shear crack, the strongly
+sheared magnetic field around the crack leads to a back-reaction from the
+Lorentz force which does not allow large relative displacement of the crack
+surfaces. Instead, the global evolution of the crack proceeds on a slow
+resistive time scale, and is unable to release any substantial mechanical
+energy. Our calculations demostrate that for {\it some} magnetic-field
+configurations, the magnetic forces cause, effectively, a plastic deformation
+of the crust when the resulting elastic shear stress exceeds the critical value
+for mechanical failure.",1204.2605v1
+2012-06-07,Magnetic particle hyperthermia: Power losses under circularly polarized field in anisotropic nanoparticles,"The deterministic Landau-Lifshitz-Gilbert equation has been used to
+investigate the nonlinear dynamics of magnetization and the specific loss power
+in magnetic nanoparticles with uniaxial anisotropy driven by a rotating
+magnetic field, generalizing the results obtained for the isotropic case found
+in [P. F. de Chatel, I. Nandori, J. Hakl, S. Meszaros and K. Vad, J. Phys.:
+Condens. Matter 21, 124202 (2009)]. As opposed to many applications of
+magnetization reversal in single-domain ferromagnetic particles where losses
+must be minimized, in this paper, we study the mechanisms of dissipation used
+in cancer therapy by hyperthermia which requires the enhancement of energy
+losses. We show that for circularly polarized field, the loss energy per cycle
+is decreased by the anisotropy compared to the isotropic case when only
+dynamical effects are taken into account. Thus, in this case, in the low
+frequency limit, a better heating efficiency can be achieved for isotropic
+nanoparticles. The possible role of thermal fluctuations is also discussed.
+Results obtained are compared to experimental data.",1206.1544v2
+2012-07-20,Current induced domain wall dynamics in the presence of a transverse magnetic field in out-of-plane magnetized materials,"An analytical model was developped to describe the current induced DW
+dynamics of a Bloch DW in the presence of an external transverse magnetic
+field. The model takes into account the DW deformation and the magnetization
+tilting in the domain. The model is compared to the results of micromagnetic
+simulation and an excellent agreement is obtained. In the steady state regime,
+the model shows that the domain tilting does not change the DW mobility. An
+external or current induced transverse magnetic field such as the Oersted or
+Rashba field can prevent the Walker breakdown leading to a higher domain wall
+velocity.",1207.4970v1
+2012-09-02,Heavy flavor suppression in a dynamical QCD medium with finite magnetic mass,"Reliable predictions for jet quenching in ultra-relativistic heavy ion
+collisions require accurate computation of radiative energy loss. While all
+available energy loss calculations assume zero magnetic mass, in accordance
+with the one-loop perturbative calculations, different non-perturbative
+approaches report a non-zero magnetic mass at RHIC and LHC. We generalized the
+dynamical energy loss formalism, to consistently include a possibility for
+existence of non-zero magnetic screening. We show that this generalization
+indicates a fundamental constraint on electric to magnetic mass ratio, which
+appears to be supported by lattice QCD simulations. Jet suppression patterns,
+obtained from this newly developed generalization, show reasonable agreement
+with the available RHIC and LHC measurements.",1209.0198v1
+2012-09-26,Nonequilibrium dynamics of a spin-3/2 Blume Capel model with quenched random crystal field,"The relaxation and complex magnetic susceptibility treatments of a spin-3/2
+Blume-Capel model with quenched random crystal field on a two dimensional
+square lattice are investigated by a method combining the statistical
+equilibrium theory and the thermodynamics of linear irreversible processes.
+Generalized force and flux are defined in irreversible thermodynamics limit.
+The kinetic equation for the magnetization is obtained by using linear response
+theory. Temperature and also crystal field dependencies of the relaxation time
+are obtained in the vicinity of phase transition points. We found that the
+relaxation time exhibits divergent treatment near the order-disorder phase
+transition point as well as near the isolated critical point whereas it
+displays cusp behavior near the first order phase transition point. In
+addition, much effort has been devoted to investigation of complex magnetic
+susceptibility response of the system to changing applied field frequencies and
+it is observed that the considered disordered magnetic system exhibits unusual
+and interesting behaviors. Furthermore, dynamical mean field critical exponents
+for the relaxation time and complex magnetic susceptibility are calculated in
+order to formulate the critical behavior of the system. Finally, a comparison
+of our observations with those of recently published studies is represented and
+it is shown that there exists a qualitatively good agreement.",1209.5880v1
+2012-09-28,Tunable diffusion of magnetic particles in a quasi-one-dimensional channel,"The diffusion of a system of ferromagnetic dipoles confined in a
+quasi-one-dimensional parabolic trap is studied using Brownian dynamics
+simulations. We show that the dynamics of the system is tunable by an in-plane
+external homogeneous magnetic field. For a strong applied magnetic field, we
+find that the mobility of the system, the exponent of diffusion and the
+crossover time among different diffusion regimes can be tuned by the
+orientation of the magnetic field. For weak magnetic fields, the exponent of
+diffusion in the subdiffusive regime is independent of the orientation of the
+external field.",1209.6472v2
+2013-03-19,Dynamics of Chromospheric Upflows and Underlying Magnetic Fields,"We used \ha-0.1 nm and magnetic field (at 1.56$\mu$) data obtained with the
+New Solar Telescope to study the origin of the disk counterparts to type II
+spicules, so-called rapid blueshifted excursions (RBEs). The high time cadence
+of our chromospheric (10 s) and magnetic field (45 s) data allowed us to
+generate x-t plots using slits parallel to the spines of the RBEs. These plots,
+along with potential field extrapolation, led us to suggest that the occurrence
+of RBEs is generally correlated with the appearance of new, mixed or unipolar
+fields in close proximity to network fields. RBEs show a tendency to occur at
+the interface between large-scale fields and small-scale dynamic magnetic loops
+and thus are likely to be associated with existence of a magnetic canopy.
+Detection of kinked and/or inverse ""Y"" shaped RBEs further confirm this
+conclusion.",1303.4766v1
+2013-05-01,Gravitational collapse of a magnetized fermion gas with finite temperature,"We examine the dynamics of a self--gravitating magnetized electron gas at
+finite temperature near the collapsing singularity of a Bianchi-I spacetime.
+Considering a general and appropriate and physically motivated initial
+conditions, we transform Einstein--Maxwell field equations into a complete and
+self--consistent dynamical system amenable for numerical work. The resulting
+numerical solutions reveal the gas collapsing into both, isotropic
+(""point-like"") and anisotropic (""cigar-like"") singularities, depending on the
+initial intensity of the magnetic field. We provide a thorough study of the
+near collapse behavior and interplay of all relevant state and kinematic
+variables: temperature, expansion scalar, shear scalar, magnetic field,
+magnetization and energy density. A significant qualitative difference in the
+behavior of the gas emerges in the temperature range $\hbox{T}
+sim10^{4}\hbox{K}$ and $\hbox{T}\sim 10^{7}\hbox{K}$.",1305.0308v1
+2013-05-30,Simulation of magnetic active polymers for versatile microfluidic devices,"We propose to use a compound of magnetic nanoparticles (20-100 nm) embedded
+in a flexible polymer (Polydimethylsiloxane PDMS) to filter circulating tumor
+cells (CTCs). The analysis of CTCs is an emerging tool for cancer biology
+research and clinical cancer management including the detection, diagnosis and
+monitoring of cancer. The combination of experiments and simulations lead to a
+versatile microfluidic lab-on-chip device. Simulations are essential to
+understand the influence of the embedded nanoparticles in the elastic PDMS when
+applying a magnetic gradient field. It combines finite element calculations of
+the polymer, magnetic simulations of the embedded nanoparticles and the fluid
+dynamic calculations of blood plasma and blood cells. With the use of magnetic
+active polymers a wide range of tunable microfluidic structures can be created.
+The method can help to increase the yield of needed isolated CTCs.",1305.7071v1
+2013-07-02,Field-induced magnetic structures in Tb2Ti2O7 spin liquid under field H || [111],"We have studied the field-induced magnetic structures of Tb2Ti2O7 pyrochlore
+by single-crystal neutron diffraction under a field applied along the [111]
+local anisotropy axis, up to H=12T and down to T=40mK. We collected a hundred
+magnetic Bragg peaks for each field and temperature value and refined the
+magnetic structures with k=0 propagation vector by performing a symmetry
+analysis in the space group R-3m, reducing the number of free parameters to
+three only. We observe a gradual reorientation of the Tb magnetic moments
+towards the field direction, close to a ""3-in, 1-out / 1-in, 3-out"" spin
+structure in the whole field range 0.05-12T. We perform a quantitative
+comparison with mean-field calculations and we propose the presence of a
+low-temperature dynamic symmetry breaking of the local trigonal symmetry, akin
+to a dynamic Jahn-Teller effect, i.e. preserving the overall cubic symmetry. We
+discuss the possible origin of this off-diagonal mixing term in the crystal
+field hamiltonian in terms of quadrupole-quadrupole interaction or
+magneto-elastic effects.",1307.0806v1
+2013-10-05,Estimation of Plasma Properties and Magnetic Field in a Prominence-like Structure as Observed by SDO/AIA,"We analyze a prominence-like cool plasma structure as observed by Atmospheric
+Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We perform
+the Differential Emission Measure (DEM) analysis using various filters of AIA,
+and also deduce the temperature and density structure in and around the
+observed flux-tube. In addition to deducing plasma parameters, we also find an
+evidence of multiple harmonics of fast magnetoacoustic kink waves in the
+observed prominence-like magnetic structure. Making use of estimated plasma
+parameters and observed wave parameters, under the baseline of MHD seismology,
+we deduce magnetic field in the flux-tube. The wave period ratio P1/P2 = 2.18
+is also observed in the flux-tube, which carries the signature of magnetic
+field divergence where we estimate the tube expansion factor as 1.27. We
+discuss constraints in the estimation of plasma and magnetic field properties
+in such a structure in the current observational perspective, which may shed
+new light on the localized plasma dynamics and heating scenario in the solar
+atmosphere.",1310.2135v1
+2013-11-02,Resonantly exited precession motion of three-dimensional vortex core in magnetic nanospheres,"We found resonantly excited precession motions of a three-dimensional vortex
+core in soft magnetic nanospheres and controllable precession frequency with
+the sphere diameter 2R, as studied by micromagnetic numerical and analytical
+calculations. The precession angular frequency for an applied static field
+$H_{DC}$ is given as $\omega_{MV}= \gamma_{eff} H_{DC}$, where $\gamma_{eff} =
+\gamma <m_{\Gamma}>$ is the effective gyromagnetic ratio in collective vortex
+dynamics, with the gyromagnetic ratio $\gamma$ and the average magnetization
+component $<m_{\Gamma}>$ of the ground-state vortex in the core direction.
+Fitting to the micromagnetic simulation data for $<m_{\Gamma}>$ yields a simple
+explicit form of $<m_{\Gamma}> = (73.6 \pm 3.4)(l_{ex}/2R)^{2.20 \pm 0.14}$,
+where $l_{ex}$ is the exchange length of a given material. This dynamic
+behavior might serve as a foundation for potential bio-applications of
+size-specific resonant excitation of magnetic vortex-state nanoparticles, for
+example, magnetic particle resonance imaging.",1311.0346v3
+2013-11-13,Thermally activated in-plane magnetization rotation induced by spin torque,"We study the role of thermal fluctuations on the spin dynamics of a thin
+permalloy film with a focus on the behavior of spin torque and find that the
+thermally assisted spin torque results in new aspects of the magnetization
+dynamics. In particular, we uncover the formation of a finite, spin
+torque-induced, in-plane magnetization component. The orientation of the
+in-plane magnetization vector depends on the temperature and the spin-torque
+coupling. We investigate and illustrate that the variation of the temperature
+leads to a thermally-induced rotation of the in-plane magnetization.",1311.3120v1
+2014-02-03,Influence of Magnetorotational Instability on Neutrino Heating: A New Mechanism for Weakly Magnetized Core-Collapse Supernovae,"We investigated the impacts of magnetorotational instability (MRI) on the
+dynamics of weakly magnetized, rapidly rotating core-collapse by conducting
+high resolution MHD simulations in axisymmetry with simplified neutrino
+transfer. We found that an initially sub-magnetar class magnetic field is
+drastically amplified by MRI and substantially affects the dynamics thereafter.
+Although the magnetic pressure is not strong enough to eject matter, the
+amplified magnetic field efficiently transfers angular momentum from higher to
+lower latitudes, which causes the expansion of the heating region at low
+latitudes due to the extra centrifugal force. This then enhance the efficiency
+of neutrino heating and eventually leads to neutrino-driven explosion. This is
+a new scenario of core-collapse supernovae that has never been demonstrated by
+numerical simulations so far.",1402.0513v2
+2014-02-05,Re-entrant superspin glass phase in La$_{0.82}$Ca$_{0.18}$MnO$_3$ ferromagnetic insulator,"We report results of magnetization and ac susceptibility measurements down to
+very low fields on a single crystal of the perovskite manganite,
+La$_{0.82}$Ca$_{0.18}$MnO$_3$. This composition falls in the intriguing
+ferromagnetic insulator region of the manganite phase diagram. In contrast to
+earlier beliefs, our investigations reveal that the system is magnetically (and
+in every other sense) single-phase with a ferromagnetic ordering temperature of
+$\sim$ 170 K. However, this ferromagnetic state is magnetically frustrated, and
+the system exhibits pronounced glassy dynamics below 90 K. Based on measured
+dynamical properties, we propose that this quasi-long-ranged ferromagnetic
+phase, and associated superspin glass behavior, is the true magnetic state of
+the system, rather than being a macroscopic mixture of ferromagnetic and
+antiferromagnetic phases as often suggested. Our results provide an
+understanding of the quantum phase transition from an antiferromagnetic
+insulator to a ferromagnetic metal via this ferromagnetic insulating state as a
+function of $x$ in La$_{1-x}$Ca$_x$MnO$_3$, in terms of the possible formation
+of magnetic polarons.",1402.1148v1
+2014-02-07,Dynamics and energetics of emergent magnetic monopoles in chiral magnets,"The formation and destruction of topologically quantized magnetic whirls,
+so-called skyrmions, in chiral magnets is driven by the creation and motion of
+singular hedgehog defects. These can be identified with emergent magnetic
+monopoles and antimonopoles. We investigate how the energetics of and forces
+between monopoles and antimonopoles influence their creation rate and dynamics.
+We study a single skyrmion line defect in the helical phase using both
+micromagnetic simulations and a Ginzburg-Landau analysis. Monopole-antimonople
+pairs are created in a thermally activated process, largely controlled by the
+(core) energy of the monopole. The force between monopoles and antimonopoles is
+linear in distance and described by a string tension. The sign and size of the
+string tension determines the stability of the phases and the velocity of the
+monopoles.",1402.1721v1
+2014-03-20,Spin Dynamics Simulation of the magnetization reversal process in FM/AFM bilayer structures by Anisotropic Heisenberg Model,"We have studied the magnetization reversal process in FM/AFM bilayer
+structures through of spin dynamics simulation. It has been observed that the
+magnetization behavior is different at each branch of the hysteresis loop as
+well as the exchange-bias behavior. On the descending branch a sudden change of
+the magnetization is observed while on the ascending branch is observed a bland
+change of the magnetization. The occurrence of the asymmetry in the hysteresis
+loop and the variation in the exchange-bias is due to anisotropy which is
+introduced only in the coupling between ferromagnetic (FM) and
+antiferromagnetic (AFM) layers.",1403.5279v1
+2014-03-24,Modeling an elastic beam with piezoelectric patches by including magnetic effects,"Models for piezoelectric beams using Euler-Bernoulli small displacement
+theory predict the dynamics of slender beams at the low frequency accurately
+but are insufficient for beams vibrating at high frequencies or beams with low
+length-to-width aspect ratios. A more thorough model that includes the effects
+of rotational inertia and shear strain, Mindlin-Timoshenko small displacement
+theory, is needed to predict the dynamics more accurately for these cases.
+Moreover, existing models ignore the magnetic effects since the magnetic
+effects are relatively small. However, it was shown recently \cite{O-M1} that
+these effects can substantially change the controllability and stabilizability
+properties of even a single piezoelectric beam. In this paper, we use a
+variational approach to derive models that include magnetic effects for an
+elastic beam with two piezoelectric patches actuated by different voltage
+sources. Both Euler-Bernoulli and Mindlin-Timoshenko small displacement
+theories are considered. Due to the magnetic effects, the equations are quite
+different from the standard equations.",1403.6144v1
+2014-04-28,Dynamics of Particles Around a Schwarzschild-like Black Hole in the Presence of Quintessence and Magnetic Field,"We investigate the dynamics of a neutral and a charged particle around a
+static and spherically symmetric black hole in the presence of quintessence
+matter and external magnetic field. We explore the conditions under which the
+particle moving around the black hole could escape to infinity after colliding
+with another particle. The innermost stable circular orbit (ISCO) for the
+particles are studied in detail. Mainly the dependence of ISCO on dark energy
+and on the presence of external magnetic field in the vicinity of black hole is
+discussed. By using the Lyapunov exponent, we compare the stabilities of the
+orbits of the particles in the presence and absence of dark energy and magnetic
+field. The expressions for the center of mass energies of the colliding
+particles near the horizon of the black hole are derived. The effective force
+on the particles due to dark energy and magnetic field in the vicinity of black
+hole is also discussed.",1404.7123v3
+2014-07-22,Explaining Jupiter's magnetic field and equatorial jet dynamics,"Spacecraft data reveal a very Earth-like Jovian magnetic field. This is
+surprising since numerical simulations have shown that the vastly different
+interiors of terrestrial and gas planets can strongly affect the internal
+dynamo process. Here we present the first numerical dynamo that manages to
+match the structure and strength of the observed magnetic field by embracing
+the newest models for Jupiter's interior. Simulated dynamo action primarily
+occurs in the deep high electrical conductivity region while zonal flows are
+dynamically constrained to a strong equatorial jet in the outer envelope of low
+conductivity. Our model reproduces the structure and strength of the observed
+global magnetic field and predicts that secondary dynamo action associated to
+the equatorial jet produces banded magnetic features likely observable by the
+Juno mission. Secular variation in our model scales to about 2000 nT per year
+and should also be observable during the one year nominal mission duration.",1407.5940v2
+2014-09-09,Magnetization pumping and dynamics in a Dzyaloshinskii-Moriya magnet,"We formulate a phenomenological description of thin ferromagnetic layers with
+inversion asymmetry where the single-domain magnetic dynamics experiences
+magnon current-induced torques and leads to magnon-motive forces. We first
+construct a phenomenological theory based on irreversible thermodynamics,
+taking into account the symmetries of the system. Furthermore, we confirm that
+these effects originate from Dzyaloshinskii-Moriya interactions from the
+analysis based on the stochastic Landau-Lifshitz-Gilbert equation. Our
+phenomenological results generalize to a general form of Dzyaloshinskii-Moriya
+interactions and to other systems, such as pyrochlore crystals and chiral
+magnets. Possible applications include spin current generation, magnetization
+reversal and magnonic cooling.",1409.2846v3
+2014-11-18,Particle Dynamics Around Weakly Magnetized Reissner-Nordström Black Hole,"Considering the geometry of Reissner-Nordstr\""{o}m (RN) black hole immersed
+in magnetic field we have studied the dynamics of neutral and charged
+particles. A collision of particles in the inner stable circular orbit is
+considered and the conditions for the escape of colliding particles from the
+vicinity of black hole are given. The trajectories of the escaping particle are
+discussed. Also the velocity required for this escape is calculated. It is
+observed that there are more than one stable regions if magnetic field is
+present in the accretion disk of black hole so the stability of ISCO increases
+in the presence of magnetic field. Effect of magnetic field on the angular
+motion of neutral and charged particles is observed graphically.",1411.4811v2
+2014-12-23,Morphology and dynamics of solar prominences from 3D MHD simulations,"In this paper we present a numerical study of the time evolution of solar
+prominences embedded in sheared magnetic arcades. The prominence is represented
+by a density enhancement in a background stratified atmosphere and is connected
+to the photosphere through the magnetic field. By solving the ideal
+magnetohydrodynamic (MHD) equations in three dimensions we study the dynamics
+for a range of parameters representative of real prominences. Depending on the
+parameters considered, we find prominences that are suspended above the
+photosphere, i.e., detached prominences, but also configurations resembling
+curtain or hedgerow prominences whose material continuously connects to the
+photosphere. The plasma$-\beta$ is an important parameter that determines the
+shape of the structure. In many cases magnetic Rayleigh-Taylor (MRT)
+instabilities and oscillatory phenomena develop. Fingers and plumes are
+generated, affecting the whole prominence body and producing vertical
+structures in an essentially horizontal magnetic field. However, magnetic shear
+is able to reduce or even to suppress this instability.",1412.7438v1
+2015-01-21,Perturbation Theory for Propagating Magnetic Droplet Solitons,"Droplet solitons are a strongly nonlinear, inherently dynamic structure in
+the magnetization of ferromagnets, balancing dispersion (exchange energy) with
+focusing nonlinearity (strong perpendicular anisotropy). Large droplet solitons
+have the approximate form of a circular domain wall sustained by precession
+and, in contrast to single magnetic vortices, are predicted to propagate in an
+extended, homogeneous magnetic medium. In this work, multiscale perturbation
+theory is utilized to develop an analytical framework for investigating the
+impact of additional physical effects on the behavior of a propagating droplet.
+After first developing soliton perturbation theory in the general context of
+Hamiltonian systems, a number of physical phenomena of current interest are
+investigated. These include droplet-droplet and droplet-boundary interactions,
+spatial magnetic field inhomogeneities, spin transfer torque induced forcing in
+a nanocontact device, and damping. Their combined effects demonstrate the
+fundamental mechanisms for a previously observed droplet drift instability and
+under what conditions a slowly propagating droplet can be supported by the
+nanocontact, important considerations for applications. This framework
+emphasizes the particle-like dynamics of the droplet, providing analytically
+tractable and practical predictions for modern experimental configurations.",1501.05276v1
+2015-02-05,Improved efficiency of heat generation in nonlinear dynamics of magnetic nanoparticles,"The deterministic Landau-Lifshitz-Gilbert equation has been used to
+investigate the nonlinear dynamics of magnetization and the specific loss power
+in magnetic nanoparticles with uniaxial anisotropy driven by a rotating
+magnetic field. We propose a new type of applied field, which is
+""simultaneously rotating and alternating"", i.e. the direction of the rotating
+external field changes periodically. We show that a more efficient heat
+generation by magnetic nanoparticles is possible with this new type of applied
+field and we suggest its possible experimental realization in cancer therapy
+which requires the enhancement of loss energies.",1502.01619v2
+2015-03-09,Magnetization reversal in exchange-spring bilayer system under circularly polarized microwave field,"Microwave assisted magnetization reversal are studied in the bulk bilayer
+exchange coupled system. We investigate the nonlinear magnetization reversal
+dynamics in a perpendicular exchange spring media using Landau-Lifshitz
+equation. In the limit of the infinite thickness of the system, the propagation
+field leads the reversal of the system. The reduction of the switching field
+and the magnetization profile in the extended system are studied numerically.
+The possibility to study the dynamics analytically is discussed and an
+approximation where two P-modes are coupled by an interaction field is
+presented. The ansatz used for the interaction field is validated by comparison
+with the numerical results. This approach is shown to be equivalent to two
+exchange coupled macrospins.",1503.02572v1
+2015-04-13,A theoretical study of the dynamics of paramagnetic superrotors in external magnetic fields,"We present a detailed theoretical study of oxygen molecules in high
+rotational states (molecular superrotors) interacting with an external magnetic
+field. The system shows rich dynamics, ranging from a spin-selective splitting
+of the angular distribution over molecular alignment to an inversion of the
+rotational direction. We find that the observed magneto-rotational effects are
+due to a spin-mediated precession of the orbital angular momentum around the
+magnetic field. Analytical expressions for the precession frequency in the
+limits of weak and strong magnetic fields are derived and used to support the
+proposed mechanism. In addition, we provide the procedure for a numerical
+treatment of oxygen superrotors in an external magnetic field.",1504.03278v2
+2015-06-08,Dynamical Generation of Topological Magnetic Lattices for Ultracold Atoms,"We propose a scheme to dynamically synthesize a space-periodic effective
+magnetic field for neutral atoms by time-periodic magnetic field pulses. When
+atomic spin adiabatically follows the direction of the effective magnetic
+field, an adiabatic scalar potential together with a geometric vector potential
+emerges for the atomic center-of-mass motion, due to the Berry phase effect.
+While atoms hop between honeycomb lattice sites formed by the minima of the
+adiabatic potential, complex Peierls phase factors in the hopping coefficients
+are induced by the vector potential, which facilitate a topological Chern
+insulator. With further tuning of external parameters, both a topological phase
+transition and topological flat bands can be achieved, highlighting realistic
+prospects for studying strongly correlated phenomena in this system. Our Letter
+presents an alternative pathway towards creating and manipulating topological
+states of ultracold atoms by magnetic fields.",1506.02418v2
+2015-10-14,Non-local topological magnetoelectric effect by Coulomb interaction at a topological insulator-ferromagnet interface,"The interface between a topological insulator and a ferromagnetic insulator
+exhibits an interesting interplay of topological Dirac electrons and magnetism.
+As has been shown recently, the breaking of time-reversal invariance by
+magnetic order generates a Chern-Simons term in the action, that in turn leads
+to a Berry phase and a magnetoelectric effect of topological origin. Here, we
+consider the system in the presence of long-range Coulomb interaction between
+the Dirac electrons, and find that the magnetoelectric effect of the
+fluctuating electric field becomes non-local. We derive a Landau-Lifshitz
+equation for the fluctuation-induced magnetization dynamics and the
+Euler-Lagrange equation of the Coulomb field by explicit one-loop calculations.
+Via the Coulomb interaction, divergences in the in-plane magnetization affect
+the magnetization dynamics over large distances in a topologically protected
+way.",1510.04285v2
+2015-11-11,Photoinduced demagnetization and insulator-to-metal transition in ferromagnetic insulating BaFeO$_3$ thin films,"We studied the electronic and magnetic dynamics of ferromagnetic insulating
+BaFeO3 thin films by using pump-probe time-resolved resonant x-ray reflectivity
+at the Fe 2p edge. By changing the excitation density, we found two distinctly
+different types of demagnetization with a clear threshold behavior. We assigned
+the demagnetization change from slow (~ 150 ps) to fast (< 70 ps) to a
+transition into a metallic state induced by laser excitation. These results
+provide a novel approach for locally tuning magnetic dynamics. In analogy to
+heat assisted magnetic recording, metallization can locally tune the
+susceptibility for magnetic manipulation, allowing to spatially encode magnetic
+information.",1511.03365v1
+2015-11-24,Electronic and Magnetic Properties of single Fe atoms on a CuN Surface; Effects of Electron Correlations,"The electronic structure and magnetic properties of a single Fe adatom on a
+CuN surface have been studied using density functional theory in the local spin
+density approximation (LSDA), the LSDA+U approach and the local density
+approximation plus dynamical mean-field theory (LDA+DMFT). The impurity problem
+in LDA+DMFT is solved through exact diagonalization and in the Hubbard-I
+approximation. The comparison of the one-particle spectral functions obtained
+from LSDA, LSDA+U and LDA+DMFT show the importance of dynamical correlations
+for the electronic structure of this system. Most importantly, we focused on
+the magnetic anisotropy and found that neither LSDA, nor LSDA+U can explain the
+measured, high values of the axial and transverse anisotropy parameters.
+Instead, the spin excitation energies obtained from our LDA+DMFT approach with
+exact diagonalization agree significantly better with experimental data. This
+affirms the importance of treating fluctuating magnetic moments through a
+realistic many-body treatment when describing this class of nano-magnetic
+systems. Moreover, it facilitates insight to the role of the hybridization with
+surrounding orbitals.",1511.07909v1
+2015-12-14,Formation of a Topological Monopole Lattice and its Dynamics in Three-dimensional Chiral Magnets,"Topologically protected swirl of the magnetic texture known as the Skyrmion
+has become ubiqui- tous in both metallic and insulating chiral magnets.
+Meanwhile the existence of its three-dimensional analogue, known as the
+magnetic monopole, has been suggested by various indirect experimental sig-
+natures in MnGe compound. Theoretically, Ginzburg-Landau arguments in favor of
+the formation of a three-dimensional crystal of monopoles and anti-monopoles
+have been put forward, however no microscopic model Hamiltonian was shown to
+support such a phase. Here we present strong numerical evidence from Monte
+Carlo simulations for the formation of a rock-salt crystal structure of
+monopoles and anti-monopoles in short-period chiral magnets. Real-time
+simulation of the spin dynamics suggests there is only one collective mode in
+the monopole crystal state in the frequency range of several GHz for the
+material parameters of MnGe.",1512.04153v1
+2016-01-19,Chimera states and synchronization in magnetically driven SQUID metamaterials,"Superconducting QUantum Interference Device (SQUID) metamaterials are
+superconducting artificial media whose function relies both on their geometry
+and the extraordinary properties of superconductivity and the Josephson effect.
+Recent experiments on one- and two-dimensional radio-frequency (rf) SQUID
+metamaterials have revealed their wide-band tuneability, significantly reduced
+losses, dynamic multistability, and tunable broadband transparency. The
+simplest version of an rf SQUID involves a superconducting ring interrupted by
+a Josephson junction; this device is a highly nonlinear resonator with a strong
+response to applied magnetic fields. SQUID metamaterials exhibit peculiar
+magnetic properties such as negative diamagnetic permeability, predicted both
+for the quantum and the classical regime. The applied alternating fields induce
+(super)currents in the SQUID rings, which are therefore coupled through
+dipole-dipole magnetic forces. This interaction is weak due to its magnetic
+nature. However, it couples the SQUIDs non-locally since it falls-off as the
+inverse cube of their center-to-center distance.",1601.04843v1
+2016-03-15,Temporal upscaling in micro magnetism via heterogeneous multiscale methods,"We consider a multiscale strategy addressing the disparate scales in the
+Landau-Lifschitz equations in micro-magnetism. At the microscopic scale, the
+dynamics of magnetic moments are driven by a high frequency field. On the
+macroscopic scale we are interested in simulating the dynamics of the
+magnetisation without fully resolving the microscopic scales.
+  The method follows the framework of heterogeneous multiscale methods and it
+has two main ingredients: a micro- and a macroscale model. The microscopic
+model is assumed to be known exactly whereas the macro model is incomplete as
+it lacks effective quantities. The two models use different temporal and
+spatial scales and effective parameter values for the macro model are computed
+on the fly, allowing for improved efficiency over traditional one-scale
+schemes.
+  For the analysis, we consider a single spin under a high frequency field and
+show that effective quantities can be obtained accurately with step-sizes much
+larger than the size of the microscopic scales required to resolve the
+microscopic features. Numerical results both for a single magnetic particle as
+well as a chain of interacting magnetic particles are given to validate the
+theory.",1603.04920v2
+2016-07-11,A Method for stability analysis of magnetic bearings : Basic stability criteria,"In this work I outline a general procedure for dynamic modeling and stability
+analysis of a magnetic bearing, which is a rotating shaft confined inside a
+chamber through electromagnetic forces alone. I consider the simplest type of
+self-propelled bearing, namely a permanent magnet synchronous motor and an
+induction motor rotor freely suspended inside the corresponding stator, and
+having no eccentricity-fedback control algorithm. Writing Euler's equations for
+the rotor mechanics and Maxwell's equations for the electromagnetic field leads
+to a systematic technique for analysing the dynamics of the complete system.
+Physical arguments indicate that that two essential components for rotor
+confinement are a spatial gradient in the stator magnetic field and a torque
+angle lying in the second quadrant. These predictions are confirmed through the
+linear stability analysis. The direct practical utility of the results is
+mitigated by the presence of a repeated eigenvalue in the linearized equations.
+Despite this limitation, the analysis presented can act as a good starting
+point for more accurate treatments of other magnetic bearing configurations.",1607.07889v1
+2016-09-29,Proposal for a Leaky-Integrate-Fire Spiking Neuron based on Magneto-Electric Switching of Ferro-magnets,"The efficiency of the human brain in performing classification tasks has
+attracted considerable research interest in brain-inspired neuromorphic
+computing. Hardware implementations of a neuromorphic system aims to mimic the
+computations in the brain through interconnection of neurons and synaptic
+weights. A leaky-integrate-fire (LIF) spiking model is widely used to emulate
+the dynamics of neuronal action potentials. In this work, we propose a spin
+based LIF spiking neuron using the magneto-electric (ME) switching of
+ferro-magnets. The voltage across the ME oxide exhibits a typical
+leaky-integrate behavior, which in turn switches an underlying ferro-magnet.
+Due to the effect of thermal noise, the ferro-magnet exhibits probabilistic
+switching dynamics, which is reminiscent of the stochasticity exhibited by
+biological neurons. The energy-efficiency of the ME switching mechanism coupled
+with the intrinsic non-volatility of ferro-magnets result in lower energy
+consumption, when compared to a CMOS LIF neuron. A device to system-level
+simulation framework has been developed to investigate the feasibility of the
+proposed LIF neuron for a hand-written digit recognition problem",1609.09158v1
+2016-11-07,Dynamics of the photosphere along the solar cycle from SDO/HMI,"As the global magnetic field of the Sun has an activity cycle, one expects to
+observe some variation of the dynamical properties of the flows visible in the
+photosphere. We investigate the flow field during the solar cycle by analysing
+SDO/HMI observations of continuum intensity, Doppler velocity and longitudinal
+magnetic field. We first picked data at disk center during 6 years along the
+solar cycle with a 48-hour time step in order to study the overall evolution of
+the continuum intensity and magnetic field. Then we focused on thirty 6-hour
+sequences of quiet regions without any remnant of magnetic activity separated
+by 6 months, in summer and winter, when disk center latitude B0 is close to
+zero. The horizontal velocity was derived from the local correlation tracking
+technique over a field of view of 216.4Mm x 216.4Mm located at disk center. Our
+measurements at disk center show the stability of the flow properties between
+meso- and supergranular scales along the solar cycle. The network magnetic
+field, produced locally at disk center independently from large scale dynamo,
+together with continuum contrast, vertical and horizontal flows, seem to remain
+constant during the solar cycle.",1611.02152v1
+2016-12-22,C-field smoothing by trajectory dynamically tracing compensation in rubidium fountain clock,"We present a trajectory dynamically tracing compensation method to smooth the
+spatial fluctuation of the static magnetic field (C-field) that provides a
+quantization axis in the fountain clock. The C-field coil current is
+point-to-point adjusted in accordance to the atoms experienced magnetic field
+along the flight trajectory. A homogeneous field with a 0.2 nT uncertainty is
+realized compared to 5 nT under the static magnetic field with constant current
+during the Ramsey interrogation. The corresponding uncertainty associated with
+the second-order Zeeman shift that we calculate is improved by one order of
+magnitude. The technique provides an alternative method to improve the magnetic
+field uniformity particularly for large-scale equipment that is difficult to
+machine with magnetic shielding. Our method is simple, robust, and essentially
+important in frequency evaluations concerning the dominant uncertainty
+contribution due to the quadratic Zeeman shift.",1612.07469v2
+2016-12-29,Theory of electron transport and magnetization dynamics in metallic ferromagnets,"Magnetic electric effects in ferromagnetic metals are discussed from the
+viewpoint of effective spin electromagnetic field that couples to conduction
+electron spin. The effective field in the adiabatic limit is the spin Berry's
+phase in space and time, and it leads to spin motive force (voltage generated
+by magnetization dynamics) and topological Hall effect due to spin chirality.
+Its gauge coupling to spin current describes the spin transfer effect, where
+magnetization structure is driven by an applied spin current. The idea of
+effective gauge field can be extended to include spin relaxation and Rashba
+spin-orbit interaction. Voltage generation by the inverse Edelstein effect in
+junctions is interpreted as due to the electric component of Rashba-induced
+spin gauge field. The spin gauge field arising from the Rashba interaction
+turns out to coincides with troidal moment, and causes asymmetric light
+propagation (directional dichroism) as a result of the Doppler shift. Rashba
+conductor without magnetization is shown to be natural metamaterial exhibiting
+negative refraction.",1612.09019v1
+2017-01-09,"Boundary-driven Lindblad dynamics of random quantum spin chains : strong disorder approach for the relaxation, the steady state and the current","The Lindblad dynamics of the XX quantum chain with large random fields $h_j$
+(the couplings $J_j$ can be either uniform or random) is considered for
+boundary-magnetization-drivings acting on the two end-spins. Since each
+boundary-reservoir tends to impose its own magnetization, we first study the
+relaxation spectrum in the presence of a single reservoir as a function of the
+system size via some boundary-strong-disorder renormalization approach. The
+non-equilibrium-steady-state in the presence of two reservoirs can be then
+analyzed from the effective renormalized Linbladians associated to the two
+reservoirs. The magnetization is found to follow a step profile, as found
+previously in other localized chains. The strong disorder approach allows to
+compute explicitly the location of the step of the magnetization profile and
+the corresponding magnetization-current for each disordered sample in terms of
+the random fields and couplings.",1701.02102v2
+2017-02-16,"Magnetization dynamics in magnonic structures with different geometries: interfaces, notches and waveguides","The discovery of the ultrafast magnetization dynamics twenty years ago has
+led to a broad variety of experimental techniques to explore phenomena in
+magnetic materials with high temporal resolution. In the present article we
+present a study dealing with broadband excitation of spin-wave packets at
+different magnonic crystal continuous magnetic film interfaces. Similar to
+protected conducting states on the surfaces of topological band insulators,
+these interfaces exhibit surface spin-wave modes that propagate out of the
+crystal into the continuous film. The propagation distance depends on the
+direction of the applied magnetic field as well as the surface geometry of the
+crystal.",1702.05041v1
+2017-04-01,Thermally nucleated magnetic reversal in CoFeB/MgO nanodots,"Power consumption is the main limitation in the development of new high
+performance random access memory for portable electronic devices. Magnetic RAM
+(MRAM) with CoFeB/MgO based magnetic tunnel junctions (MTJs) is a promising
+candidate for reducing the power consumption given its non-volatile nature
+while achieveing high performance. The dynamic properties and switching
+mechanisms of MTJs are critical to understanding device operation and to enable
+scaling of devices below 30 nm in diameter. Here we show that the magnetic
+reversal mechanism is incoherent and that the switching is thermally nucleated
+at device operating temperatures. Moreover, we find an intrinsic thermal
+switching field distribution arising on the sub-nanosecond timescale even in
+the absence of size and anisotropy distributions or material defects. These
+features represent the characteristic signature of the dynamic properties in
+MTJs and give an intrinsic limit to reversal reliability in small magnetic
+nanodevices.",1704.00106v1
+2017-04-26,Ferrofluid Capillary Rise in Porous Medium under the Action of Non-Uniform Magnetic Field,"The capillary flow of a ferrofluid in a single cylindrical capillary tube and
+through a sandy porous medium under the action of a non-uniform magnetic field
+is studied experimentally. The dynamics of the capillary rise and the static
+case have been considered. It has been shown that the non-uniform magnetic
+field with upward directed gradient accelerates the capillary rise; contrary,
+the non-uniform magnetic field with downward directed gradient decelerates the
+capillary rise. Time dependences of the ferrofluid height and maximum reachable
+height of ferrofluid have been analyzed. The method of the study of ferrofluid
+capillary rise based on the use of magnetic measurements has been proposed. It
+has been demonstrated that porous material parameters can be extracted from the
+results of measurements of the inductances of the solenoid with porous medium
+inside and the small sensing coil within a single experiment.",1704.08310v1
+2017-05-10,Focusing and sorting of ellipsoidal magnetic particles in microchannels,"We present a simple method to control the position of ellipsoidal magnetic
+particles in microchannel Poiseuille flow using a static uniform magnetic
+field. The magnetic field is utilized to pin the particle orientation, and the
+hydrodynamic interactions between ellipsoids and channel walls allow control of
+the transverse position of the particles. We employ a far-field hydrodynamic
+theory and simulations using the boundary element method and Brownian dynamics
+to show how magnetic particles can be focussed and segregated by size and
+shape. This is of importance for particle manipulation in lab-on-a-chip
+devices.",1705.03665v2
+2017-05-26,Static and Dynamic Magnetic Properties of FeMn/Pt Multilayers,"Recently we have demonstrated the presence of spin-orbit toque in FeMn/Pt
+multilayers which, in combination with the anisotropy field, is able to rotate
+its magnetization consecutively from 0o to 360o without any external field.
+Here, we report on an investigation of static and dynamic magnetic properties
+of FeMn/Pt multilayers using combined techniques of magnetometry, ferromagnetic
+resonance, inverse spin Hall effect and spin Hall magnetoresistance
+measurements. The FeMn/Pt multilayer was found to exhibit ferromagnetic
+properties, and its temperature dependence of saturation magnetization can be
+fitted well using a phenomenological model by including a finite distribution
+in Curie temperature due to subtle thickness variations across the multilayer
+samples. The non-uniformity in static magnetic properties is also manifested in
+the ferromagnetic resonance spectra, which typically exhibit a broad resonance
+peak. A damping parameter of around 0.106 is derived from the frequency
+dependence of ferromagnetic resonance linewidth, which is comparable to the
+reported values for other types of Pt-based multilayers. Clear inverse spin
+Hall signals and spin Hall magnetoresistance have been observed in all samples
+below the Curie temperature, which corroborate the strong spin-orbit torque
+effect observed previously.",1705.09423v1
+2017-07-18,Magnetocapillary self-assemblies: locomotion and micromanipulation along a liquid interface,"This paper presents an overview and discussion of magnetocapillary
+self-assemblies. New results are presented, in particular concerning the
+possible development of future applications. These self-organizing structures
+possess the notable ability to move along an interface when powered by an
+oscillatory, uniform magnetic field. The system is constructed as follows. Soft
+magnetic particles are placed on a liquid interface, and submitted to a
+magnetic induction field. An attractive force due to the curvature of the
+interface around the particles competes with an interaction between magnetic
+dipoles. Ordered structures can spontaneously emerge from these conditions.
+Furthermore, time-dependent magnetic fields can produce a wide range of dynamic
+behaviours, including non-time-reversible deformation sequences that produce
+translational motion at low Reynolds number. In other words, due to a
+spontaneous breaking of time-reversal symmetry, the assembly can turn into a
+surface microswimmer. Trajectories have been shown to be precisely
+controllable. As a consequence, this system offers a way to produce microrobots
+able to perform different tasks. This is illustrated in this paper by the
+capture, transport and release of a floating cargo, and the controlled mixing
+of fluids at low Reynolds number.",1707.05515v1
+2017-07-25,Probing $α$-RuCl$_3$ Beyond Magnetic Order: Effects of Temperature and Magnetic Field,"Recent studies have brought $\alpha$-RuCl$_3$ to the forefront of
+experimental searches for materials realizing Kitaev spin-liquid physics. This
+material exhibits strongly anisotropic exchange interactions afforded by the
+spin-orbit coupling of the 4d Ru centers. We investigate the dynamical response
+at finite temperature and magnetic field for a realistic model of the magnetic
+interactions in $\alpha$-RuCl$_3$. These regimes are thought to host
+unconventional paramagnetic states that emerge from the suppression of magnetic
+order. Using exact diagonalization calculations of the quantum model
+complemented by semi-classical analysis, we find a very rich evolution of the
+spin dynamics as the applied field suppresses the zigzag order and stabilizes a
+quantum paramagnetic state that is adiabatically connected to the fully
+polarized state at high fields. At finite temperature, we observe large
+redistributions of spectral weight that can be attributed to the anisotropic
+frustration of the model. These results are compared to recent experiments, and
+provide a roadmap for further studies of these regimes.",1707.08144v2
+2017-09-22,Effects of the temperature and magnetic-field dependent coupling on the properties of QCD matter,"To reflect the asymptotic freedom in the thermal direction, a
+temperature-dependent coupling was proposed in the literature. We investigate
+its effect on QCD matter with and without strong magnetic fields. Compared with
+the fixed coupling constant, the running coupling leads to a drastic change in
+the dynamical quark mass, entropy density, sound velocity, and specific heat.
+The crossover transition of QCD matter at finite temperature is characterized
+by the pseudocritical temperature $T_\mathrm{pc}$, which is generally
+determined by the peak of the derivative of the quark condensate with respect
+to the temperature $d\phi/dT$, or equivalently, by the derivative of the quark
+dynamical mass $d M/dT$. In a strong magnetic field, the temperature- and
+magnetic-field-dependent coupling $G(eB,T)$ was recently introduced to account
+for inverse magnetic catalysis. We propose an analytical relation between the
+two criteria $d\phi/dT$ and $dM/dT$ and show a discrepancy between them in
+finding the pseudocritical temperature. The magnitude of the discrepancy
+depends on the behavior of $dG/dT$.",1709.07773v1
+2017-10-24,Magnetic field in expanding quark-gluon plasma,"Intense electromagnetic fields are created in the quark-gluon plasma by the
+external ultra-relativistic valence charges. The time-evolution and the
+strength of this field are strongly affected by the electrical conductivity of
+the plasma. Yet, it has recently been observed that the effect of the magnetic
+field on the plasma flow is small. We compute the effect of plasma flow on
+magnetic field and demonstrate that it is less than 10\%. These observations
+indicate that the plasma hydrodynamics and the dynamics of electromagnetic
+field decouple. Thus, it is a very good approximation, on the one hand, to
+study QGP in the background electromagnetic field generated by external sources
+and, on the other hand, to investigate the dynamics of magnetic field in the
+background plasma. We also argue that the wake induced by the magnetic field in
+plasma is negligible.",1710.08793v1
+2017-11-15,Oscillatory spin-orbit torque switching induced by field-like torques,"Deterministic magnetization switching using spin-orbit torque (SOT) has
+recently emerged as an efficient means to electrically control the magnetic
+state of ultrathin magnets. The SOT switching still lacks in oscillatory
+switching characteristics over time, therefore, it is limited to bipolar
+operation where a change in polarity of the applied current or field is
+required for bistable switching. The coherent rotation based oscillatory
+switching schemes cannot be applied to SOT because the SOT switching occurs
+through expansion of magnetic domains. Here, we experimentally achieve
+oscillatory switching in incoherent SOT process by controlling domain wall
+dynamics. We find that a large field-like component can dynamically influence
+the domain wall chirality which determines the direction of SOT switching.
+Consequently, under nanosecond current pulses, the magnetization switches
+alternatively between the two stable states. By utilizing this oscillatory
+switching behavior we demonstrate a unipolar deterministic SOT switching scheme
+by controlling the current pulse duration.",1711.05369v1
+2017-11-21,Coupling magneto-elastic Lagrangians to spin transfer torque sources,"The consequences of coupling magnetic and elastic degrees of freedom, where
+spins and deformations are carried by point-like objects subject to local
+interactions, are studied, theoretically and by detailed numerical simulations.
+From the constrained Lagrangians we derive consistent equations of motion for
+the coupled dynamical variables. In order to probe the dynamics of such a
+system, we consider external perturbations, such as spin transfer torques for
+the magnetic part, and homogeneous stresses for the elastic part, associated to
+their corresponding damping. This approach is applied to the study of ultrafast
+switching processes in anti-ferromagnetic systems, which have recently
+attracted attention as candidates for anti-ferromagnetic spintronic devices.
+Our strategy is then checked in simple, but instructive, situations. We carried
+out numerical experiments to study, in particular, how the magnetostrictive
+coupling and external stresses affect the nature of the switching processes in
+a prototype anti-ferromagnetic material.",1711.08062v2
+2017-12-20,Strong fields and neutral particle magnetic moment dynamics,"Interaction of magnetic moment of point particles with external
+electromagnetic fields experiences unresolved theoretical and experimental
+discrepancies. In this work we point out several issues within the relativistic
+quantum mechanics and the QED and we describe effects related to a new
+covariant classical model of magnetic moment dynamics. Using this framework we
+explore the invariant acceleration experienced by neutral particles coupled to
+an external plane wave field through the magnetic moment: we study the case of
+ultra relativistic Dirac neutrinos with magnetic moment in the range of
+$10^{-11}$ to $10^{-20}$ $\mu_\mathrm{B}$; and we address the case of slowly
+moving neutrons. We explore how critical accelerations for neutrinos can be
+experimentally achieved in laser-pulse interactions. The radiation of
+accelerated neutrinos can serve as an important test distinguishing between
+Majorana and Dirac nature of neutrinos.",1712.07698v2
+2018-01-22,Magnetic domain wall creep and depinning: a scalar field model approach,"Magnetic domain wall motion is at the heart of new magneto-electronic
+technologies and hence the need for a deeper understanding of domain wall
+dynamics in magnetic systems. In this context, numerical simulations using
+simple models can capture the main ingredients responsible for the complex
+observed domain wall behavior. We present a scalar-field model for the
+magnetization dynamics of quasi-two-dimensional systems with a perpendicular
+easy axis of magnetization which allows a direct comparison with typical
+experimental protocols, used in polar magneto-optical Kerr effect microscopy
+experiments. We show that the thermally activated creep and depinning regimes
+of domain wall motion can be reached, and the effect of different quenched
+disorder implementations can be assessed with the model. In particular, we show
+that the depinning field increases with the mean grain size of a Voronoi
+tessellation model for the disorder.",1801.07324v1
+2018-03-20,All-optical nonequilibrium pathway to stabilizing magnetic Weyl semimetals in pyrochlore iridates,"Nonequilibrium many-body dynamics is becoming one of the central topics of
+modern condensed matter physics. Floquet topological states were suggested to
+emerge in photodressed band structures in the presence of periodic laser
+driving. Here we propose a viable nonequilibrium route without requiring
+coherent Floquet states to reach the elusive magnetic Weyl semimetallic phase
+in pyrochlore iridates by ultrafast modification of the effective
+electron-electron interaction with short laser pulses. Combining \textit{ab
+initio} calculations for a time-dependent self-consistent reduced Hubbard $U$
+controlled by laser intensity and nonequilibrium magnetism simulations for
+quantum quenches, we find dynamically modified magnetic order giving rise to
+transiently emerging Weyl cones that are probed by time- and angle-resolved
+photoemission spectroscopy. Our work offers a unique and realistic pathway for
+nonequilibrium materials engineering beyond Floquet physics to create and
+sustain Weyl semimetals. This may lead to ultrafast, tens-of-femtoseconds
+switching protocols for light-engineered Berry curvature in combination with
+ultrafast magnetism.",1803.07447v2
+2018-04-06,Quantum-impurity relaxometry of magnetization dynamics,"Prototypes of quantum impurities (QI), such as NV and SiV centers in diamond,
+have been recently growing in popularity due to their minimally invasive and
+high-resolution magnetic field sensing. Here, we focus on quantum-impurity
+relaxometry as a method to probe collective excitations in magnetic insulators.
+We develop a general framework that relates the experimentally-measurable
+quantum-impurity relaxation rates to the properties of a magnetic system via
+the noise emitted by the latter. We suggest that, when the quantum-impurity
+frequency lies within the spin-wave gap, quantum-impurity relaxometry can be
+effectively deployed to detect signatures of the coherent spin dynamics, such
+as magnon condensation, both in ferromagnetic and antiferromagnetic systems, as
+well as open prospects to nonintrusively probe spin-wave transport regimes in
+magnetic insulators.",1804.02417v1
+2018-04-30,Modular Compact Modeling of Magnetic Tunnel Junction Devices,"This paper describes a robust, modular, and physics- based circuit framework
+to model conventional and emerging Magnetic Tunnel Junction (MTJ) devices.
+Magnetization dynamics are described by the stochastic Landau-Lifshitz-Gilbert
+(sLLG) equation whose results are rigorously benchmarked with a Fokker-Planck
+Equation (FPE) description of magnet dynamics. We then show how sLLG is coupled
+to transport equations of MTJ-based devices in a unified circuit platform. Step
+by step, we illustrate how the physics-based MTJ model can be extended to
+include different spintronics phenomena, including spin-transfer-torque (STT),
+voltage-control of magnetic anisotropy (VCMA) and spin-orbit torque (SOT)
+phenomena by experimentally benchmarked examples. To demonstrate how our
+approach can be used in the exploration of novel MTJ-based devices, we also
+present a recently proposed MEMS resonator- driven spin-torque nano oscillator
+(STNO) that can reduce the phase noise of STNOs. We briefly elaborate on the
+use of our framework beyond conventional devices.",1805.00066v2
+2018-06-11,Spin dynamics of coupled spin ladders near quantum criticality in Ba2CuTeO6,"We report inelastic neutron scattering measurements of the magnetic
+excitations in Ba2CuTeO6, proposed by ab initio calculations to magnetically
+realize weakly coupled antiferromagnetic two-leg spin-1/2 ladders. Isolated
+ladders are expected to have a singlet ground state protected by a spin gap.
+Ba2CuTeO6 orders magnetically, but with a small Neel temperature relative to
+the exchange strength, suggesting that the interladder couplings are relatively
+small and only just able to stabilize magnetic order, placing Ba2CuTeO6 close
+in parameter space to the critical point separating the gapped phase and Neel
+order. Through comparison of the observed spin dynamics with linear spin wave
+theory and quantum Monte Carlo calculations, we propose values for all relevant
+intra- and interladder exchange parameters, which place the system on the
+ordered side of the phase diagram in proximity to the critical point. We also
+compare high field magnetization data with quantum Monte Carlo predictions for
+the proposed model of coupled ladders.",1806.04052v2
+2018-06-27,Dynamic interface formation in magnetic thin film heterostructures,"Magnetic thin film heterostructures have been widely studied for fundamental
+interests in the emergence of novel phenomena accompanied by the
+heterointerface formation as well as their promising practical potential.
+Combining x-ray magnetic circular dichroism with scanning tunneling microscopy,
+we show for Mn/Fe thin film heterostructures that the interfacial factors
+dominating electronic and magnetic properties of the entire system dynamically
+change with the amount of the Mn overlayer. Element specific magnetization
+curves of the Fe layer exhibit a two-step spin reorientation transition from
+out-of-plane to in-plane direction with increasing the Mn coverage.
+Atomic-scale characterizations of structural and electronic properties in
+combination with the first-principles calculations successfully unravel the
+roles of the entangled interfacial factors, and clarify the driving forces of
+the transition. The first step of the transition at a low Mn coverage is
+dominantly induced by the formation of FeMn disordered alloy at the
+heterointerface, and the electronic hybridization with interfacial FeMn ordered
+alloy is dominant as the origin of the second step of the transition at a high
+Mn coverage.",1806.10543v1
+2018-07-02,Picosecond acoustic excitation driven ultrafast magnetization dynamics in dielectric Bi-substituted yttrium iron garnet,"Using femtosecond optical pulses, we have investigated the ultrafast
+magnetization dynamics induced in a dielectric film of bismuth-substituted
+yttrium iron garnet (Bi-YIG) buried below a thick Cu/Pt metallic bilayer. We
+show that exciting the sample from Pt surface launches an acoustic strain pulse
+propagating into the garnet film. We discovered that this strain pulse induces
+a coherent magnetization precession in the Bi-YIG at the frequency of the
+ferromagnetic resonance. The observed phenomena can be explain by
+strain-induced changes of magnetocristalline anisotropy via the inverse
+magnetostriction effect. These findings open new perspectives toward the
+control of the magnetization in magnetic garnets embedded in complex
+heterostructure devices.",1807.00610v1
+2018-08-16,Dynamic multiferroicity of a ferroelectric quantum critical point,"Quantum matter hosts a large variety of phases, some coexisting, some
+competing; when two or more orders occur together, they are often entangled and
+cannot be separated. Dynamical multiferroicity, where fluctuations of electric
+dipoles lead to magnetisation, is an example where the two orders are
+impossible to disentangle. Here we demonstrate elevated magnetic response of a
+ferroelectric near the ferroelectric quantum critical point (FE QCP) since
+magnetic fluctuations are entangled with ferroelectric fluctuations. We thus
+suggest that any ferroelectric quantum critical point is an \textit{inherent}
+multiferroic quantum critical point. We calculate the magnetic susceptibility
+near the FE QCP and find a region with enhanced magnetic signatures that
+appears near the FE QCP, and controlled by the tuning parameter of the
+ferroelectric phase. The effect is small but observable - we propose quantum
+paraelectric strontium titanate as a candidate material where the magnitude of
+the induced magnetic moments can be $\sim 5 \times 10^{-7} \mu_{B}$ per unit
+cell near the FE QCP.",1808.05509v2
+2018-08-25,Optically driven collective spin excitations and magnetization dynamics in the Néel-type skyrmion host GaV$_4$S$_8$,"GaV$_4$S$_8$ is a multiferroic semiconductor hosting magnetic cycloid (Cyc)
+and N\'eel-type skyrmion lattice (SkL) phases with a broad region of thermal
+and magnetic stability. Here, we use time-resolved magneto-optical Kerr
+spectroscopy and micro-magnetic simulations to demonstrate the coherent
+generation of collective spin excitations in the Cyc and SkL phases driven by
+an optically-induced modulation of uniaxial anisotropy. Our results shed light
+on spin-dynamics in anisotropic materials hosting skyrmions and pave a new
+pathway for the optical control of their magnetic order.",1808.08476v1
+2018-10-12,High resolution dynamic imaging of the delay- and tilt-free motion of Néel domain walls in perpendicularly magnetized superlattices,"We report on the time-resolved investigation of current- and field-induced
+domain wall motion in perpendicularly magnetized microwires exhibiting
+asymmetric exchange interaction by means of scanning transmission x-ray
+microscopy using a time step of 200 ps. Dynamical domain wall velocities on the
+order of 50-100 m s$^{-1}$ were observed. The improvement in the temporal
+resolution allowed us to observe the absence of incubation times for the motion
+of the domain wall, together with indications for a negligible inertia.
+Furthermore, we observed that, for short current and magnetic field pulses, the
+magnetic domain walls do not exhibit a tilting during its motion, providing a
+mechanism for the fast, tilt-free, motion of magnetic domain walls.",1810.05384v1
+2018-10-26,Dynamics of a high-density plasma in a magnetic field,"The paper considers the dynamics of the plasma generated by the
+explosive-emission cells of the cathode spot of a vacuum arc in a magnetic
+field. It is shown that the expansion of the (high-density) plasma in a
+transverse magnetic field may cause asymmetry in the plasma density
+distribution at the cathode spot boundary. The asymmetry, in turn, increases
+the probability of the ignition of new explosive-emission cells in the region
+of a stronger magnetic field in the 'anti-amperian' direction of BxI. The
+disturbed plasma density distribution estimated in the MHD approximation is
+presented. In addition, the velocity of the 'retrograde' spot motion (ignition
+of new explosive-emission cells) in the stronger field region is estimated as a
+function of the external magnetic field strength. The velocity estimates (a few
+to tens of m/(s T)) are shown to agree with experimental data",1810.11384v2
+2018-12-04,Effect of (Cu/Fe)O5 bipyramid size and separation on magnetic and dielectric properties of rare earth layered perovskite LaBaCuFeO5 and LuBaCuFeO5,"We report structural, magnetic and dielectric properties of layered
+perovskite materials LnBaCuFeO5 (Ln = La and Lu). LaBaCuFeO5 shows magnetic
+cluster glass behavior below 60 K owing to the competing ferromagnetic and
+antiferromagnetic exchange interactions. Glassy dynamics of electric dipoles
+has also been observed in the vicinity of the magnetic glass transition
+temperature. The presence of significant coupling between spin and polar
+degrees of freedom results in the multiglass feature in LaBaCuFeO5. The
+LuBaCuFeO5 compound undergoes YBaCuFeO5 like commensurate to incommensurate
+antiferromagnetic transition at 175 K. Large magnetic irreversibility below 17
+K in this compound suggests the presence of strong spin anisotropy. In
+addition, in this compound the interaction between the dipoles is not strong
+enough, which results in the absence of glassy dynamics of electric dipoles.
+The contrasting behavior of two compounds is possibly due to variation in the
+ferromagnetic and antiferromagnetic interactions along c-axis, which is the
+manifestation of structural modification arising out of the difference in the
+ionic radii of La and Lu.",1812.01239v2
+2018-12-13,Current-induced nucleation and dynamics of skyrmions in a Co-based Heusler alloy,"We demonstrate room-temperature stabilization of dipolar magnetic skyrmions
+with diameters in the range of $100$ nm in a single ultrathin layer of the
+Heusler alloy Co$_2$FeAl (CFA) under moderate magnetic fields. Current-induced
+skyrmion dynamics in microwires is studied with a scanning Nitrogen-Vacancy
+magnetometer operating in the photoluminescence quenching mode. We first
+demonstrate skyrmion nucleation by spin-orbit torque and show that its
+efficiency can be significantly improved using tilted magnetic fields, an
+effect which is not specific to Heusler alloys and could be advantageous for
+future skyrmion-based devices. We then show that current-induced skyrmion
+motion remains limited by strong pinning effects, even though CFA is a magnetic
+material with a low magnetic damping parameter.",1812.05345v1
+2019-01-17,Trace formula for the magnetic Laplacian,"The Guillemin-Uribe trace formula is a semiclassical version of the Selberg
+trace formula and more general Duistermaat-Guillemin formula for elliptic
+operators on compact manifolds, which reflects the dynamics of magnetic
+geodesic flows in terms of eigenvalues of a natural differential operator (the
+magnetic Laplacian) associated with the magnetic field. In this paper, we give
+a survey of basic notions and results related with the Guillemin-Uribe trace
+formula and provide concrete examples of its computation for two-dimensional
+constant curvature surfaces with constant magnetic fields and for the Katok
+example.",1901.05699v2
+2019-02-24,Magnetic Nanoparticle Relaxation Dynamics-based Magnetic Particle Spectroscopy (MPS) for Rapid and Wash-free Molecular Sensing,"Magnetic nanoparticles (MNPs) have been extensively used as contrasts and
+tracers for bioimaging, heating sources for tumor therapy, carriers for
+controlled drug delivery, and labels for magnetic immunoassays. Here, we
+describe a MNP relaxation dynamics-based magnetic particle spectroscopy (MPS)
+method for the quantitative detection of molecular biomarkers. In MPS
+measurements, the harmonics of oscillating MNPs are recorded and used as a
+metric for the freedom of rotational motion, which indicates the bound states
+of the MNPs. These harmonics can be collected from microgram quantities of iron
+oxide nanoparticles within 10 seconds. Using a streptavidin-biotin binding
+system, we demonstrate the feasibility of using MPS to sense these molecular
+interactions, showing this method is able to achieve rapid, wash-free
+bioassays, and is suitable for future point-of-care (POC), sensitive, and
+versatile diagnosis.",1902.08867v2
+2019-07-03,Anisotropic string tensions and inversely magnetic catalyzed deconfinement from a dynamical AdS/QCD model,"We extend previous work on dynamical AdS/QCD models by introducing an extra
+ingredient under the form of a background magnetic field, this to gain insight
+into the influence such field can have on crucial QCD observables. Therefore,
+we construct a closed form analytic solution to an Einstein-Maxwell-dilaton
+system with a magnetic field. We specifically focus on the deconfinement
+transition, reporting inverse magnetic catalysis, and on the string tension,
+reporting a weaker/stronger confinement along/perpendicular to the magnetic
+field. The latter, being of importance to potential modelling of heavy
+quarkonia, is in qualitative agreement with lattice findings.",1907.01852v2
+2019-09-02,Spontaneous order in ensembles of rotating magnetic droplets,"Ensembles of elongated magnetic droplets in a rotating field are studied
+experimentally. In a given range of field strength and frequency the droplets
+form rotating structures with a triangular order - rotating crystals. A model
+is developed to describe ensembles of several droplets, taking into account the
+hydrodynamic interactions between the rotating droplets in the presence of a
+solid wall below the rotating ensemble. A good agreement with the
+experimentally observed periodic dynamics for an ensemble of four droplets is
+obtained. During the rotation, the tips of the elongated magnetic droplets
+approach close to one another. An expression is derived that gives the magnetic
+interaction between such droplets by taking into account the coulombian forces
+between magnetic charges on the droplet tips.",1909.00661v1
+2019-10-09,Multi-accretion events from corotating and counterrotating SMBHs tori,"Ringed accretion disks (RADs) are aggregates of corotating and
+counterrotating toroidal accretion disks orbiting a central Kerr super-massive
+Black Hole (SMBH) in AGNs. The dimensionless spin of the central BH and the
+fluids relative rotation are proved to strongly affect the RAD dynamics. There
+is evidence of a strict correlation between SMBH spin, fluid rotation and
+magnetic fields in RADs formation and evolution. Recently, the model was
+extended to consider RADs constituted by several magnetized accretion tori and
+the effects of a toroidal magnetic field in RAD dynamics have been
+investigated. The analysis poses constraints on tori formation and emergence of
+RADs instabilities in the phases of accretion onto the central attractor and
+tori collision emergence. Magnetic fields and fluids rotation are proved to be
+strongly constrained and influence tori formation and evolution in RADs, in
+dependence on the toroidal magnetic fields parameters. Eventually, the RAD
+frame investigation constraints specific classes of tori that could be observed
+around some specific SMBHs identified by their dimensionless spin",1910.03925v1
+2019-12-15,A semi-analytical approach to calculating the dynamic modes of magnetic vortices with Dzyaloshinskii-Moriya interactions,"Here we introduce a Landau-Lifshitz based diagonalization (LLD) method, and
+use this approach to calculate the effects of the interfacial Dzyaloshinskii
+Moriya interactions (DMI) on the radial-type spin wave modes of magnetic
+vortices in circular disks. The LLD method is a semi-analytical approach that
+involves the diagonalization of the magnetostatic kernel, exchange, and DMI
+contributions to extract the system eigenfrequencies and eigenmodes. The
+magnetic vortex state provides a convenient model system in which to
+investigate the effects of the DMI on the dynamics of a magnetic structures
+with confined geometries. Our calculations show that the DMI leads to shifts of
+the mode frequencies that are similar in magnitude to what is observed for spin
+waves of a comparable wavelength in extended films. However, unlike what is
+found in thin films, only the down-shifted modes are observed in the disks, and
+these corresponds to modes that propagate either radially outward or inward,
+depending on the vortex circulation. The semi-analytical calculations agree
+well with full micromagnetic simulations. This technique also applies to other
+systems with cylindrical symmetry, for example, magnetic skyrmions.",1912.06963v1
+2020-03-03,Optical and magnetic excitations in the underscreened quasi-quartet Kondo lattice,"The underscreened Kondo lattice consisting of a single twofold degenerate
+conduction band and a CEF split 4f-electron quasi-quartet has non-conventional
+quasiparticle dispersions obtained from the constrained mean-field theory. An
+additional genuinely heavy band is found in the main hybridization band gap of
+the upper and lower hybridzed bands whose heavy effective mass is controlled by
+the CEF splitting. Its presence should profoundly influence the dynamical
+optical and magnetic response functions. In the former, the onset of the
+optical conductivity is not the main hybridisation energy but the much lower
+Kondo energy scale which appears in the direct transitions to the additional
+heavy band. The dynamical magnetic response is also strongly modified by the
+in-gap heavy band which can lead to unconventional resonant excitations that
+may be interpreted as coherent CEF-Kondo lattice magnetic exciton bands. Their
+instability at low temperature signifies the onset of induced excitonic
+magnetism in the underscreened Kondo lattice.",2003.01535v2
+2020-03-10,Wide-bandwidth atomic magnetometry via instantaneous-phase retrieval,"We develop and demonstrate a new protocol that allows sensing of magnetic
+fields in an extra-ordinary regime for atomic magnetometry. Until now, the
+demonstrated bandwidth for atomic magnetometry has been constrained to be
+slower than the natural precession of atomic spins in a magnetic field---the
+Larmor frequency. We demonstrate a new approach that tracks the instantaneous
+phase of atomic spins to measure arbitrarily modulated magnetic fields with
+frequencies up to fifty times higher than the Larmor frequency. By accessing
+this regime, we demonstrate magnetic-field measurements across four decades in
+frequency up to 400 kHz, over three orders of magnitude wider than conventional
+atomic magnetometers. Furthermore, we demonstrate that our protocol can
+linearly detect transient fields 100--fold higher in amplitude than
+conventional methods. We highlight the bandwidth and dynamic range of the
+technique by measuring a magnetic field with a broad and dynamical spectrum.",2003.04526v1
+2020-03-20,Normal forms for strong magnetic systems on surfaces: Trapping regions and rigidity of Zoll systems,"We prove a normal form for strong magnetic fields on a closed, oriented
+surface and use it to derive two dynamical results for the associated flow.
+First, we show the existence of KAM tori and trapping regions provided a
+natural non-resonance condition holds. Second, we prove that the flow cannot be
+Zoll unless (i) the Riemannian metric has constant curvature and the magnetic
+function is constant, or (ii) the magnetic function vanishes and the metric is
+Zoll. We complement the second result by exhibiting an exotic magnetic field on
+a flat two-torus yielding a Zoll flow for arbitrarily small rescalings.",2003.09141v4
+2020-03-25,Magnon Trap by Chiral Spin Pumping,"Chiral spin pumping is the generation of a unidirectional spin current in
+half of ferromagnetic films or conductors by dynamic dipolar stray fields from
+close-by nanomagnets. We formulate a general theory of long-range chiral
+interactions between magnets mediated by unidirectional traveling waves, e.g.,
+spin waves in a magnetic film or microwaves in a waveguide. The traveling waves
+emitted by an excited magnet can be perfectly trapped by a second, initially
+passive, magnet by a dynamical interference effect. When both magnets are
+excited by a uniform microwave, the chiral interaction between them creates a
+large imbalance in their magnon numbers.",2003.11581v2
+2020-05-10,Charged particle motion around non-singular black holes in conformal gravity in the presence of external magnetic field,"We consider electromagnetic fields and charged particle dynamics around
+non-singular black holes in conformal gravity immersed in an external,
+asymptotically uniform magnetic field. First, we obtain analytic solutions of
+the electromagnetic field equation around rotating non-singular black holes in
+conformal gravity. We show that the radial components of the electric and
+magnetic fields increase with the increase of the parameters $L$ and $N$ of the
+black hole solution. Second, we study the dynamics of charged particles. We
+show that the increase of the values of the parameters $L$ and $N$ and of
+magnetic field causes a decrease in the radius of the innermost stable circular
+orbits (ISCO) and the magnetic coupling parameter can mimic the effect of
+conformal gravity giving the same ISCO radius up to $\omega_{\rm B}\leq 0.07$
+when $N=3$.",2005.04752v2
+2020-05-25,Complex magnetic ordering and associated topological Hall effect in a two-dimensional metallic chiral magnet,"Motivated by recent experiments on the observation of room temperature
+skyrmions in a layered heterostructure and subsequent demonstration of
+topological Hall effect in the same system, we have studied a minimal model of
+itinerant electrons coupled to local moments with competing interactions in an
+external magnetic field. Working in the limit of strong magneto-electric
+coupling where the fast dynamics of the electrons can be decoupled from the
+slow dynamics of the local moments (treated as classical spins), we analyze the
+multiple field induced magnetic phases and the associated electronic transport
+properties in these regimes. Our results help understand the microscopic origin
+of the observed phenomena and further provide crucial insight into
+unconventional magneto-transport in metallic chiral magnets.",2005.12307v1
+2020-06-03,Generation of Solar Spicules and Subsequent Atmospheric Heating,"Spicules are rapidly evolving fine-scale jets of magnetized plasma in the
+solar chromosphere. It remains unclear how these prevalent jets originate from
+the solar surface and what role they play in heating the solar atmosphere.
+Using the Goode Solar Telescope at the Big Bear Solar Observatory, we observed
+spicules emerging within minutes of the appearance of opposite-polarity
+magnetic flux around dominant-polarity magnetic field concentrations. Data from
+the Solar Dynamics Observatory showed subsequent heating of the adjacent
+corona. The dynamic interaction of magnetic fields (likely due to magnetic
+reconnection) in the partially ionized lower solar atmosphere appears to
+generate these spicules and heat the upper solar atmosphere.",2006.02571v1
+2020-09-03,Measurements and modelling of stray magnetic fields and the simulation of their impact on the Compact Linear Collider at 380 GeV,"The Compact Linear Collider (CLIC) targets a nanometre beam size at the
+collision point. Realising this beam size requires the generation and transport
+of ultra-low emittance beams. Dynamic imperfections can deflect the colliding
+beams, leading to a collision with a relative offset. They can also degrade the
+emittance of each beam. Both of these effects can significantly impact the
+luminosity of CLIC. In this paper, we examine a newly considered dynamic
+imperfection: stray magnetic fields. Measurements of stray magnetic fields in
+the Large Hadron Collider tunnel are presented and used to develop a
+statistical model that can be used to realistically generate stray magnetic
+fields in simulations. The model is used in integrated simulations of CLIC at
+380GeV including mitigation systems for stray magnetic fields to evaluate their
+impact on luminosity.",2009.01524v2
+2020-09-27,Local negative magnetic permeability and possibility of observation of breather excitations in magnetic metamaterials,"It is shown that the long-wave dynamics and magnetic properties of
+one-dimensional systems constructed of the inductively and capacitively coupled
+split-ring resonators are described by the regularized nonlinear dispersive
+Klein-Gordon equations. It is found that in such systems a highfrequency
+magnetic field excites dynamic solitons on a \glqq pedestal\grqq-stable
+breathers, oscillating in anti-phase with respect to the background of uniform
+oscillations, which means the existence of regions with a negative magnetic
+permeability in the system. If supplemented by a medium with negative
+permittivity, such a system forms a \glqq left-handed\grqq metamaterial in
+which the regions with the breather excitations are transparent to
+electromagnetic radiation. This makes it possible to observe them
+experimentally.",2009.12792v1
+2020-12-21,Nonlinear dynamics of topological ferromagnetic textures for frequency multiplication,"We propose that the non-linear radio-frequency dynamics and nanoscale size of
+topological magnetic structures associated to their well-defined internal modes
+advocate for their use as in-materio scalable frequency multipliers for
+spintronic systems. Frequency multipliers allow for frequency conversion
+between input and output frequencies, and thereby significantly increase the
+range of controllably accessible frequencies. In particular, we explore the
+excitation of eigenmodes of topological magnetic textures by fractions of the
+corresponding eigenfrequencies. We show via micromagnetic simulations that
+low-frequency perturbations to the system can efficiently excite bounded modes
+with a higher amplitude. For example, we excited the eigenmodes of isolated
+ferromagnetic skyrmions by applying half, a third and a quarter of the
+corresponding eigenfrequency. We predict that the frequency multiplication via
+magnetic structures is a general phenomenon which is independent of the
+particular properties of the magnetic texture, and works also for magnetic
+vortices, droplets and other topological textures.",2012.11481v2
+2021-02-17,Temperature induced collapse of spin dimensionality in magnetic metamaterials,"Spin and spatial dimensionalities are universal concepts, essential for
+describing both phase transitions and dynamics in magnetic materials. Lately,
+these ideas have been adopted to describe magnetic properties of metamaterials,
+as well as to replicate and explore ensembles of mesospins belonging to
+different universality classes. Here, we take the next step by investigating
+magnetic metamaterials not conforming to the conventional framework of
+continuous phase transitions. Instead of a continuous decrease in the moment
+with temperature, discrete steps are possible, resulting in a binary transition
+in the interactions of the elements. The transition is enabled by nucleation
+and annihilation of vortex cores, shifting topological charges between the
+interior and the edges of the elements. Consequently, the mesospins can be
+viewed as shifting their spin dimensionality, from 2 (XY-like) to 0, (vortices)
+at the transition. The results provide insight into how dynamics at different
+length-scales couple, which can lead to thermally driven topological
+transitions in magnetic metamaterials.",2102.08731v2
+2021-02-11,Magnonics in collinear magnetic insulating systems,"In the last decades, collinear magnetic insulating systems have emerged as
+promising energy-saving information carriers. Their elementary collective spin
+excitations, i.e., magnons, can propagate for long distances bypassing the
+Joule heating effects that arise from electron scattering in metal-based
+devices. This tutorial article provides an introduction to theoretical and
+experimental advances in the study of magnonics in collinear magnetic
+insulating systems. We start by outlining the quantum theory of spin waves in
+ferromagnetic and antiferromagnetic systems and we discuss their quantum
+statistics. We review the phenomenology of spin and heat transport of the
+coupled coherent and incoherent spin dynamics and the interplay between
+magnetic excitations and lattice degrees of freedom. Finally, we introduce the
+reader to the key ingredients of two experimental probes of magnetization
+dynamics, spin transport and NV-center relaxometry setups, and discuss
+experimental findings relevant to the outlined theory.",2102.08829v1
+2021-04-08,Probing the interplay between lattice dynamics and short-range magnetic correlations in CuGeO3 with femtosecond RIXS,"Investigations of magnetically ordered phases on the femtosecond timescale
+have provided significant insights into the influence of charge and lattice
+degrees of freedom on the magnetic sub-system. However, short-range magnetic
+correlations occurring in the absence of long-range order, for example in
+spin-frustrated systems, are inaccessible to many ultrafast techniques. Here,
+we show how time-resolved resonant inelastic X-ray scattering (trRIXS) is
+capable of probing such short-ranged magnetic dynamics in a charge-transfer
+insulator through the detection of a Zhang-Rice singlet exciton. Utilizing
+trRIXS measurements at the O K-edge, and in combination with model
+calculations, we probe the short-range spin-correlations in the frustrated spin
+chain material CuGeO3 following photo-excitation, revealing a strong coupling
+between the local lattice and spin sub-systems.",2104.03557v1
+2021-04-14,Persisting correlation between electrical transport and magnetic dynamics in M-type hexaferrites,"In this work we present frequency-dependent magnetic susceptibility and dc
+electric transport properties of three different compositions of hexaferrite
+Ba$_{1-x}$Pb$_{x}$Fe$_{12-y}$Al$_{y}$O$_{19}$. We find a correlation between
+activation energies of dc electric transport and ac magnetic susceptibility
+which persists in the whole researched range of aluminium substitution $x=0$ to
+$3.3$. This result is discussed in the context of charged magnetic domain
+walls, the pinning of which is determined by charge carriers activated over the
+transport gap. Our work points toward a general relaxational mechanism in
+ferrimagnetic semiconductors which directly affects dynamic magnetic properties
+via electric transport.",2104.06964v2
+2021-04-15,Magnetic connections across the chromosphere-corona transition region,"The plasma contributing to emission from the Sun between the cool
+chromosphere ($\le 10^4$K) and hot corona ($\ge 10^6$K) has been subjected to
+many different interpretations. Here we look at the magnetic structure of this
+transition region (TR) plasma, based upon the implications of CLASP2 data of an
+active region recently published by Ishikawa et al., and earlier IRIS and SDO
+data of quiet regions. Ishikawa et al. found that large areas of sunspot plages
+are magnetically unipolar as measured in the cores of \ion{Mg}{2} resonance
+lines, formed in the lower transition region under low plasma-$\beta$
+conditions. Here we show that IRIS images in the line cores have fibrils which
+well aligned with the overlying coronal loop segments seen in the 171 \AA{}
+channel of SDO. When the TR emission in active regions arise from plasma
+magnetically and thermally connected to the corona, then the line cores can
+provide the first credible magnetic boundary conditions for force-free
+calculations extended to the corona. We also re-examine IRIS images of dynamic
+TR cool loops previously reported as a major contributor to transition region
+emission from the quiet Sun. Dynamic cool loops contribute only a small
+fraction of the total TR emission from the quiet Sun.",2104.07753v1
+2021-05-28,Characterization of the stability and dynamics of a laser-produced plasma expanding across strong magnetic field,"Magnetized laser-produced plasmas are central to many new studies in
+laboratory astrophysics, inertial confinement fusion, and industrial
+applications. Here we present the results of large-scale, three-dimensional
+magneto-hydrodynamic simulations of the dynamics of a laser-produced plasma
+expanding into a transverse magnetic field with a strength of tens of Tesla.
+The simulations show the plasma is confined by the strong magnetic field into a
+slender slab structured by the magnetized Rayleigh-Taylor instability that
+develops at the plasma-vacuum interface. We find that by perturbing the initial
+velocity of the plume the slab can develop kink-like motion which disrupts its
+propagation.",2105.13800v1
+2021-07-21,Pinning and gyration dynamics of magnetic vortices revealed by correlative Lorentz and bright-field imaging,"Topological magnetic textures are of great interest in various scientific and
+technological fields. To allow for precise control of nanoscale magnetism, it
+is of great importance to understand the role of intrinsic defects in the host
+material. Here, we use conventional and time-resolved Lorentz microscopy to
+study the effect of grain size in polycrystalline permalloy films on the
+pinning and gyration orbits of vortex cores inside magnetic nanoislands. To
+assess static pinning, we use in-plane magnetic fields to shift the core across
+the island while recording its position. This enables us to produce highly
+accurate two-dimensional maps of pinning sites. Based on this technique, we can
+generate a quantitative map of the pinning potential for the core, which we
+identify as being governed by grain boundaries. Furthermore, we investigate the
+effects of pinning on the dynamic behavior of the vortex core using
+stroboscopic Lorentz microscopy, harnessing a new photoemission source that
+accelerates image acquisition by about two orders of magnitude. We find
+characteristic changes to the vortex gyration in the form of increased
+dissipation and enhanced bistability in samples with larger grains.",2107.10208v1
+2021-08-19,Saturation of large-scale dynamo in anisotropically forced turbulence,"Turbulent dynamo theories have faced difficulties in obtaining evolution of
+large-scale magnetic fields on short dynamical time-scales due to the
+constraint imposed by magnetic helicity balance. This has critical implications
+for understanding the large-scale magnetic field evolution in astrophysical
+systems like the Sun, stars and galaxies. Direct numerical simulations (DNS) in
+the past with isotropically forced helical turbulence have shown that
+large-scale dynamo saturation time-scales are dependent on the magnetic
+Reynolds number (Rm). In this work, we have carried out periodic box DNS of
+helically forced turbulence leading to a large-scale dynamo with two kinds of
+forcing function, an isotropic one based on that used in PENCIL-CODE and an
+anisotropic one based on Galloway-Proctor flows. We show that when the
+turbulence is forced anisotropically, the nonlinear (saturation) behaviour of
+the large-scale dynamo is only weakly dependent on Rm. In fact the magnetic
+helicity evolution on small and large scales in the anisotropic case is
+distinctly different from that in the isotropic case. This result possibly
+holds promise for the alleviation of important issues like catastrophic
+quenching.",2108.08740v2
+2021-09-07,Inertial spin dynamics in epitaxial cobalt films,"We investigate the spin dynamics driven by terahertz magnetic fields in
+epitaxial thin films of cobalt in its three crystalline phases. The terahertz
+magnetic field generates a torque on the magnetization which causes it to
+precess for about 1 ps, with a sub-picosecond temporal lag from the driving
+force. Then, the magnetization undergoes natural damped THz oscillations at a
+frequency characteristic of the crystalline phase. We describe the experimental
+observations solving the inertial Landau-Lifshitz-Gilbert equation. Using the
+results from the relativistic theory of magnetic inertia, we find that the
+angular momentum relaxation time $\eta$ is the only material parameter needed
+to describe all the experimental evidence. Our experiments suggest a
+proportionality between $\eta$ and the strength of the magneto-crystalline
+anisotropy.",2109.03076v2
+2021-09-26,Transition state dynamics of a driven magnetic free layer,"Magnetization switching in ferromagnetic structures is an important process
+for technical applications such as data storage in spintronics, and therefore
+the determination of the corresponding switching rates becomes essential. We
+investigate a free-layer system in an oscillating external magnetic field
+resulting in an additional torque on the spin. The magnetization dynamics
+including inertial damping can be described by the phenomenological Gilbert
+equation. The magnetization switching between the two stable orientations on
+the sphere then requires the crossing of a potential region characterized by a
+moving rank-1 saddle. We adopt and apply recent extensions of transition state
+theory for driven systems to compute both the time-dependent and average
+switching rates of the activated spin system in the saddle region.",2109.12605v1
+2021-10-09,Single-shot imaging of ultrafast all-optical magnetization dynamics with a spatio-temporal resolution,"We present a laboratory system for single-shot magneto-optical (MO) imaging
+of ultrafast magnetization dynamics with high-sensitivity of MO rotation. We
+create a stack of MO images repeatedly employing a single pair of a pump and
+defocused probe pulses to induce and visualize MO changes in the sample. Both
+laser beams are independently wavelength-tunable allowing for a flexible,
+resonant adjustable two-color pump and probe scheme. To increase the MO
+contrast the probe beam is spatially filtered. We performed the all-optical
+switching experiment in Co-doped yttrium iron garnet films (YIG:Co) to
+demonstrate the capability of the presented method. We determine the
+spatial-temporal distribution of the effective field of photo-induced
+anisotropy driving the all-optical switching of the magnetization in YIG:Co
+film without an external magnetic field. Moreover, using this imaging method,
+we tracked the process of the laser-induced magnetization precession.",2110.04506v1
+2021-10-21,Dynamics of the multiferroic LiCuVO4 influenced by electric field,"We present the electron spin resonance study of the influence of an electric
+field on the low-field multiferroic magnetic state in LiCuVO4. The shift of the
+magnetic resonance spectra in the electric field has been observed
+experimentally. Symmetry analysis has been conducted in order to describe the
+static properties of the magnetic system. The low-frequency dynamics of LiCuVO4
+in magnetic and electric fields was considered in the framework of hydrodynamic
+approach. It was shown that the application of the external electric field
+leads to the change of the configuration of the magnetic system before and
+after spin-flop reorientation. Satisfactory agreement was obtained between the
+results of experimental studies and theoretical consideration.",2110.11095v1
+2021-10-25,Topological defects in superconducting open nanotubes under gradual and abrupt switch-on of the transport current and magnetic field,"We analyze the dynamics of the order parameter in superconducting open
+nanotubes under a strong transport current in an external homogeneous magnetic
+field using the time-dependent Ginzburg-Landau equation. Near the critical
+transport current, the dissipation processes are driven by vortex and phase
+slip dynamics. The transition between the vortex and phase-slip regimes is
+found to depend on the external magnetic field only weakly if the magnetic
+field and/or the transport current are switched on gradually. In the case of an
+abrupt switch-on of the magnetic field or transport current, the system can be
+triggered to the stable phase-slip regime, within a certain window of
+parameters. Finally, a hysteresis effect in the current-voltage characteristics
+is predicted in superconducting open nanotubes.",2110.12745v2
+2021-12-23,Electric-field-induced parametric excitation of exchange magnons in a CoFeB/MgO junction,"Electric-field controlled magnetization dynamics is an important integrant in
+low power spintronic devices. In this letter, we demonstrate electric-field
+induced parametric excitation for CoFeB/MgO junctions by using interfacial
+in-plane magnetic anisotropy. When the in-plane magnetic anisotropy and the
+external magnetic field are parallel to each other, magnons are efficiently
+excited by using electric-field induced parametric excitation. Its wavelength
+and wavenumber are tuned by changing input power and frequency of the applied
+voltage. A generalized phenomenological model is developed to explain the
+underlying role of the electric-field torque. Electrical excitation with no
+Joule heating offers a good opportunity for developing magnonic devices and
+exploring various nonlinear dynamics in magnetic systems.",2112.12308v2
+2021-12-23,Nutation spin waves in ferromagnets,"Magnetization dynamics and spin waves in ferromagnets are investigated using
+the inertial Landau-Lifshitz-Gilbert equation. Taking inertial magnetization
+dynamics into account, dispersion relations describing the propagation of
+nutation spin waves in an arbitrary direction relative to the applied magnetic
+field are derived via Maxwell's equations. It is found that the inertia of
+magnetization causes the hybridization of electromagnetic waves and nutation
+spin waves in ferromagnets, hybrid nutation spin waves emerge, and the redshift
+of frequencies of precession spin waves is initiated, which transforms to
+precession-nutation spin waves. These effects depend sharply on the direction
+of wave propagation relative to the applied magnetic field. Moreover, the waves
+propagating parallel to the applied field are circularly polarized, while the
+waves propagating perpendicular to that field are elliptically polarized. The
+characteristics of these spin nutation waves are also analyzed.",2112.12503v3
+2022-01-25,Complex vortex-antivortex dynamics in the magnetic superconductor EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$,"We report on the investigation of the magnetic superconductor
+EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$ based on muon-spin spectroscopy and ac
+magnetic susceptibility ($\chi$) measurements. The dependence of the internal
+field at the muon site on temperature is indicative of a ferromagnetic ordering
+of Eu$^{2+}$ magnetic moments and only the conventional magnon scattering
+governs the longitudinal relaxation rate at low temperatures. At the same time,
+we observe a rich phenomenology for the imaginary component of the
+susceptibility $\chi^{\prime\prime}$ by means of both standard ac
+susceptibility and a novel technique based on a microwave coplanar waveguide
+resonator. In particular, we detect activated trends for several features in
+$\chi^{\prime\prime}$ over frequencies spanning ten orders of magnitude. We
+interpret our results in terms of the complex dynamics of vortices and
+antivortices influenced by the underlying structure of magnetic domains.",2201.10216v1
+2022-02-04,Vector vorticity of skyrmionic texture: an internal degree of freedom tunable by magnetic field,"Different from the skyrmion driven by the Dzyaloshinskii-Moriya interaction
+in non-centrosymmetric materials, the skyrmionic texture in centrosymmetric
+magnet may possess the extra internal degrees of freedom, which greatly enrich
+its morphologies, imply the continuous deformation allowed by topological
+protection, and enable flexible tunability and potential functionality. To
+describe the internal degree of freedom to full extent, the conventional
+integer-valued scalar vorticity is extended into a vector vorticity with
+continuous rotation allowed. The further simplified vorticity angle, together
+with helicity angle, represents the whole rotation freedom of spin space. The
+centrosymmetric magnet with frustration provides a perfect platform for
+realizing a controllable manipulation on these internal degrees of freedom,
+where the magnetic field can be applied to tune vorticity continuously in both
+crystal and isolated forms of skyrmionic texture, and the helicity can be
+further controlled by electric field. Moreover, the simulation reveals the
+distinctive dynamic effects related to the vorticity modulation, namely, a
+straight motion can be generated by rotating magnetic field to tune vorticity,
+and the vorticity can also be controlled to modulate the dynamics induced by
+the spin polarized current.",2202.02091v1
+2022-03-10,Ultrafast optically induced magnetic state transition in 2D antiferromagnets,"Manipulating spin in antiferromagnetic (AFM) materials has great potential in
+AFM opto-spintronics. Laser pulses can induce a transient ferromagnetic (FM)
+state in AFM metallic systems, but have never been proven in two-dimensional
+(2D) AFM semiconductors and related van der Waals (vdW) heterostructures. Here,
+using 2D vdW heterostructures of FM MnS2 and AFM MXenes as prototypes, we
+investigated optically induced interlayer spin transfer dynamics based on the
+real-time time-dependent density functional theory (rt-TDDFT). We observed that
+laser pulses induce significant spin injection and the interfacial
+atom-mediated spin transfer from MnS2 to Cr2CCl2. In particular, we first
+demonstrated the transient FM state in semiconducting AFM/FM heterostructures
+during photoexcited processes. Because the proximity magnetism breaks the
+magnetic symmetry of Cr2CCl2 in heterostructures. Our results provide the
+microscopic understanding for optically controlled interlayer spin dynamics in
+2D magnetic heterostructures and open a new way to manipulate magnetic orders
+in ultrafast opto-spintronics.",2203.05124v1
+2022-04-21,Temperature-dependent magnetism in Fe foams via spin-lattice dynamics,"Spin-lattice dynamics is used to study the magnetic properties of Fe foams.
+The temperature dependence of the magnetization in foams is determined as a
+function of the fraction of surface atoms in foams, nsurf. The Curie
+temperature of foams decreases approximately linearly with nsurf, while the
+critical exponent of the magnetization increases considerably more strongly. If
+the data are plotted as a function of the fraction of surface atoms, reasonable
+agreement with recent data on vacancy-filled Fe crystals and novel data on
+void-filled crystals is observed for the critical . Critical temperature and
+critical exponent also depend on the coordination of surface atoms. Although
+the decrease we find is relatively small, it hints to the possibility of
+improved usage of topology to taylor magnetic properties.",2204.10123v1
+2022-07-03,Continuous-stage symplectic adapted exponential methods for charged-particle dynamics with arbitrary electromagnetic fields,"This paper is devoted to the numerical symplectic approximation of the
+charged-particle dynamics (CPD) with arbitrary electromagnetic fields. By
+utilizing continuous-stage methods and exponential integrators, a general class
+of symplectic methods is formulated for CPD under a homogeneous magnetic field.
+Based on the derived symplectic conditions, two practical symplectic methods up
+to order four are constructed where the error estimates show that the proposed
+second order scheme has a uniform accuracy in the position w.r.t. the strength
+of the magnetic field. Moreover, the symplectic methods are extended to CPD
+under non-homogeneous magnetic fields and three algorithms are formulated.
+Rigorous error estimates are investigated for the proposed methods and one
+method is proved to have a uniform accuracy in the position w.r.t. the strength
+of the magnetic field. Numerical experiments are provided for CPD under
+homogeneous and non-homogeneous magnetic fields, and the numerical results
+support the theoretical analysis and demonstrate the remarkable numerical
+behavior of our methods.",2207.00970v1
+2022-07-18,Magnetoelectric effects in Josephson junctions,"The review is devoted to the fundamental aspects and characteristic features
+of the magnetoelectric effects, reported in the literature on Josephson
+junctions (JJs). The main focus of the review is on the manifestations of the
+direct and inverse magnetoelectric effects in various types of Josephson
+systems. They provide a coupling of the magnetization in
+superconductor/ferromagnet/superconductor JJs to the Josephson current. The
+direct magnetoelectric effect is a driving force of spin torques acting on the
+ferromagnet inside the JJ. Therefore it is of key importance for the electrical
+control of the magnetization. The inverse magnetoelectric effect accounts for
+the back action of the magnetization dynamics on the Josephson subsystem, in
+particular, making the JJ to be in the resistive state in the presence of the
+magnetization dynamics of any origin. The perspectives of the coupling of the
+magnetization in JJs with ferromagnetic interlayers to the Josephson current
+via the magnetoelectric effects are discussed.",2207.08876v1
+2022-07-21,Modeling the Photometric Variability of Alpha$^2$ CVn with a Dynamical Magnetosphere,"Alpha$^2$ Canum Venaticorum (AM CVn) is a strongly magnetic star with
+peculiar chemical signatures and periodic variability that have been long
+attributed to the diffusion of magnetic elements through the photosphere,
+leading to chemical spots across the stellar surface. However, recent studies
+of other magnetic hot stars are consistent with magnetospheric clouds above the
+surface. Here we take a renewed approach to modeling AM CVn with a simplified
+dynamical magnetosphere (DM) and a tilted, offset magnetic dipole to reproduce
+its Transiting Exoplanet Survey Satellite (TESS) variability. Our dipole model
+also reproduces well the magnetic surface map of AM CVn from Silvester,
+Kochukhov, & Wade (2014). Its ultraviolet variability, from IUE archival
+spectra, is also consistent with traditional reddening models. We further
+discuss the implications of a magnetosphere on other observable quantities from
+the system to conclude that it is unlikely to be present in AM CVn.",2207.11151v1
+2022-08-20,Unravelling the contributions to spin-lattice relaxation in Kramers single-molecule magnets,"The study of how spin interacts with lattice vibrations and relaxes to
+equilibrium provides unique insights on its chemical environment and the
+relation between electronic structure and molecular composition. Despite its
+importance for several disciplines, ranging from magnetic resonance to quantum
+technologies, a convincing interpretation of spin dynamics in crystals of
+magnetic molecules is still lacking due to the challenging experimental
+determination of the correct spin relaxation mechanism. We apply ab initio spin
+dynamics to a series of twelve coordination complexes of Co(II) and Dy(III)
+ions selected among $\sim$240 compounds that largely cover the literature on
+single-molecule magnets and well represent different regimes of spin
+relaxation. Simulations reveal that the Orbach spin relaxation rate of known
+compounds mostly depends on the ions' zero-field splitting and little on the
+details of molecular vibrations. Raman relaxation is instead found to be also
+significantly affected by the features of low-energy phonons. These results
+provide a complete understanding of the factors limiting spin lifetime in
+single-molecule magnets and revisit years of experimental investigations by
+making it possible to transparently distinguish Orbach and Raman relaxation
+mechanisms.",2208.09674v1
+2022-09-07,Convergence analysis of an implicit finite difference method for the inertial Landau-Lifshitz-Gilbert equation,"The Landau-Lifshitz-Gilbert (LLG) equation is a widely used model for fast
+magnetization dynamics in ferromagnetic materials. Recently, the inertial LLG
+equation, which contains an inertial term, has been proposed to capture the
+ultra-fast magnetization dynamics at the sub-picosecond timescale.
+Mathematically, this generalized model contains the first temporal derivative
+and a newly introduced second temporal derivative of magnetization.
+Consequently, it produces extra difficulties in numerical analysis due to the
+mixed hyperbolic-parabolic type of this equation with degeneracy. In this work,
+we propose an implicit finite difference scheme based on the central difference
+in both time and space. A fixed point iteration method is applied to solve the
+implicit nonlinear system. With the help of a second order accurate constructed
+solution, we provide a convergence analysis in $H^1$ for this numerical scheme,
+in the $\ell^\infty (0, T; H_h^1)$ norm. It is shown that the proposed method
+is second order accurate in both time and space, with unconditional stability
+and a natural preservation of the magnetization length. In the hyperbolic
+regime, significant damping wave behaviors of magnetization at a shorter
+timescale are observed through numerical simulations.",2209.02914v2
+2022-09-13,Inter-Correlation Between Sunspot Oscillations and Their Internal Structures,"Three- and five-minute oscillations are commonly found in any sunspot. As
+they are modulated by the internal thermal and magnetic structures of a
+sunspot, therehence, they could be used as an effective tool for sunspot
+seismology. In this paper, we investigate the properties of oscillations in
+sunspot groups with varying size and magnetic field, and aim to establish the
+relationships between sunspot oscillations and its internal structure
+comparatively. We selected three groups of unipolar sunspot with approximately
+axial-symmetric magnetic field and calculated their Fourier spectra based on
+the Ultraviolet(UV)/Extreme ultraviolet(EUV) emission intensity variations
+recorded by the Solar Dynamics Observatory/Atmospheric Imaging Assembly
+(SDO/AIA). We found that the distribution of three minute oscillation is
+defined by the joint effect of diverging magnetic field and the stratification
+of sunspot atmosphere. Its distribution could be modified by any invading
+magnetic structures in the umbra. Whereas the five minute oscillations are more
+prominent in small spots, it implies that five minute oscillation is very
+closely connected with umbral dynamics.",2209.05982v1
+2022-09-28,Analytic characterization of sub-Alfvénic turbulence energetics,"Magnetohydrodynamic (MHD) turbulence is a cross-field process relevant to
+many systems. A prerequisite for understanding these systems is to constrain
+the role of MHD turbulence, and in particular the energy exchange between
+kinetic and magnetic forms. The energetics of strongly magnetized and
+compressible turbulence has so far resisted attempts to understand them.
+Numerical simulations reveal that kinetic energy can be orders of magnitude
+larger than fluctuating magnetic energy. We solve this lack-of-balance puzzle
+by calculating the energetics of compressible and sub-Alfv\'enic turbulence
+based on the dynamics of coherent cylindrical fluid parcels. Using the MHD
+Lagrangian, we prove analytically that the bulk of the magnetic energy
+transferred to kinetic is the energy stored in the coupling between the ordered
+and fluctuating magnetic field. The analytical relations are in striking
+agreement with numerical data, up to second order terms.",2209.14143v5
+2023-02-22,Reversal of coupled vortices in advanced spintronics: A mechanistic study,"This study conducts a comprehensive investigation into the reversal mechanism
+of magnetic vortex cores in a nanopillar system composed of two coupled
+ferromagnetic dots under zero magnetic field conditions. The research employs a
+combination of experimental and simulation methods to gain a deeper
+understanding of the dynamics of magnetic vortex cores. The findings reveal
+that by applying a constant direct current, the orientation of the vortex cores
+can be manipulated, resulting in a switch in one of the dots at a specific
+current value. The micromagnetic simulations provide evidence that this switch
+is a consequence of a deformation in the vortex profile caused by the
+increasing velocity of the vortex cores resulting from the constant amplitude
+of the trajectory as frequency increases. These findings offer valuable new
+insights into the coupled dynamics of magnetic vortex cores and demonstrate the
+feasibility of manipulating their orientation using direct currents under zero
+magnetic field conditions. The results of this study have potential
+implications for the development of vortex-based non-volatile memory
+technologies. \end{abstract}",2302.11616v1
+2023-04-18,Guidance of the resonance energy flow in the mechanism of coupled magnetic pendulums,"This paper presents a methodology of controlling the resonance energy
+exchange in mechanical system consisting of two weakly coupled magnetic
+pendulums interacting with the magnetic field generated by coils placed
+underneath. It is shown that properly guided magnetic fields can effectively
+change mechanical potentials in a way that the energy flow between the
+oscillators takes the desired direction. Studies were considered by using a
+specific set of descriptive functions characterizing the total excitation
+level, its distribution between the pendulums, and the phase shift. The
+developed control strategies are based on the observation that, in the case of
+antiphase oscillation, the energy is moving from the pendulum subjected to the
+repelling magnetic field, to the oscillator under the attracting field. In
+contrast, during the inphase oscillations, the energy flow is reversed.
+Therefore, closed-loop controller requires only the information about phase
+shift, which is easily estimated from dynamic state signals through the
+coherency index. Advantage of suggested control strategy is that the temporal
+rate of inputs is dictated by the speed of beating, which is relatively slow
+compared to the carrying oscillations.",2304.09755v1
+2023-05-23,Non-equilibrium dynamics of dipole-charged fields in the Proca theory,"We discuss the dynamics of field configurations encoded in the certain class
+of electric (magnetic) dipole-charged states in the Proca theory of the real
+massive vector field. We construct such states so as to ensure that the long
+distance structure of the mean electromagnetic field in them is initially set
+by the formula describing the electromagnetic field of the electric (magnetic)
+dipole. We analyze then how such a mean electromagnetic field evolves in time.
+We find that far away from the center of the initial field configuration, the
+long range component of the mean electromagnetic field harmonically oscillates,
+which leads to the phenomenon of the periodic oscillations of the electric
+(magnetic) dipole moment. We also find that near the center of the initial
+field configuration, the mean electromagnetic field escapes from its initial
+arrangement and a spherical shock wave propagating with the speed of light
+appears in the studied system. A curious configuration of the axisymmetric mean
+electric field is found to accompany the mean magnetic field in magnetic
+dipole-charged states.",2305.13908v1
+2023-06-14,Propagators for molecular dynamics in a magnetic field,"Ab initio molecular dynamics in a magnetic field requires solving equations
+of motion with velocity-dependent forces -- namely, the Lorentz force arising
+from the nuclear charges moving in a magnetic field and the Berry force arising
+from the shielding of these charges from the magnetic field by the surrounding
+electrons. In this work, we revisit two existing propagators for these
+equations of motion, the auxiliary-coordinates-and-momenta (ACM) propagator and
+the Tajima propagator (TAJ), and compare them with a new exponential (EXP)
+propagator based on the Magnus expansion. Additionally, we explore limits (for
+example, the zero-shielding limit), the implementation of higher-order
+integration schemes, and series truncation to reduce computational cost by
+carrying out simulations of a HeH$^+$ model system for a wide range of field
+strengths. While being as efficient as the TAJ propagator, the EXP propagator
+is the only propagator that converges to both the schemes of Spreiter and
+Walter (derived for systems without shielding of the Lorentz force) and to the
+exact cyclotronic motion of a charged particle. Since it also performs best in
+our model simulations, we conclude that the EXP propagator is the recommended
+propagator for molecules in magnetic fields.",2306.08332v1
+2023-06-26,Repulsively bound magnon excitations of a spin-1/2 XXZ chain in a staggered transverse field,"We study the excitation spectrum of the one-dimensional spin-1/2 XXZ chain
+with antiferromagnetic Ising anisotropy across a magnetic quantum phase
+transition induced by the application of a site-dependent transverse magnetic
+field. Motivated by the chain antiferromagnet BaCo$_2$V$_2$O$_8$, we consider a
+situation where the transverse magnetic field has a strong uniform component
+and a weaker staggered part. To determine the nature of the excitations giving
+rise to the spin dynamical structure factor, we use a combination of analytical
+approaches and the numerically exact time-dependent matrix product state
+method. We identify below the quantum phase transition high-energy many-body
+two-magnon and three-magnon repulsively bound states which are clearly visible
+due to the staggered component of the magnetic field. At high magnetic fields
+and low temperature, single magnons dominate the dynamics. Our theory results
+are in very good agreement with terahertz spectroscopy experimental results
+presented in [Wang et al., in preparation].",2306.14742v2
+2023-07-10,Angular dependence of spin-orbit torque in monolayer $Fe_3GeTe_2$,"In ferromagnetic systems lacking inversion symmetry, an applied electric
+field can control the ferromagnetic order parameters through the spin-orbit
+torque. The prototypical example is a bilayer heterostructure composed of a
+ferromagnet and a heavy metal that acts as a spin current source. In addition
+to such bilayers, spin-orbit coupling can mediate spin-orbit torques in
+ferromagnets that lack bulk inversion symmetry. A recently discovered example
+is the two-dimensional monolayer ferromagnet $Fe_3GeTe_2$. In this work, we use
+first-principles calculations to study the spin-orbit torque and ensuing
+magnetic dynamics in this material. By expanding the torque versus
+magnetization direction as a series of vector spherical harmonics, we find that
+higher order terms (up to $\ell=4$) are significant and play important roles in
+the magnetic dynamics. They give rise to deterministic, magnetic field-free
+electrical switching of perpendicular magnetization.",2307.04900v2
+2023-08-28,Spin-wave spectral analysis in crescent-shaped ferromagnetic nanorods,"The research on the properties of spin waves (SWs) in three-dimensional
+nanosystems is an innovative idea in the field of magnonics. Mastering and
+understanding the nature of magnetization dynamics and binding of SWs at
+surfaces, edges, and in-volume parts of three-dimensional magnetic systems
+enables the discovery of new phenomena and suggests new possibilities for their
+use in magnonic and spintronic devices. In this work, we use numerical methods
+to study the effect of geometry and external magnetic field manipulations on
+the localization and dynamics of SWs in crescent-shaped (CS) waveguides. It is
+shown that changing the magnetic field direction in these waveguides breaks the
+symmetry and affects the localization of eigenmodes with respect to the static
+demagnetizing field. This in turn has a direct effect on their frequency.
+Furthermore, CS structures were found to be characterized by significant
+saturation at certain field orientations, resulting in a cylindrical
+magnetization distribution. Thus, we present chirality-based nonreciprocal
+dispersion relations for high-frequency SWs, which can be controlled by the
+field direction (shape symmetry) and its amplitude (saturation).",2308.14678v1
+2023-09-06,Creation and dynamics of spin fluctuations in a noisy magnetic field,"We theoretically and numerically investigate the spin fluctuations induced in
+a thermal atomic ensemble by an external fluctuating uniaxial magnetic field,
+in the context of a standard spin noise spectroscopy (SNS) experiment. We show
+that additional spin noise is excited, which dramatically depends on the
+magnetic noise variance and bandwidth, as well as on the power of the probe
+light and its polarization direction. We develop an analytical perturbative
+model proving that this spin noise first emerges from the residual optical
+pumping in the medium, which is then converted into spin fluctuations by the
+magnetic noise and eventually detected using SNS. The system studied is a
+spin-1 system, which thus shows both Faraday rotation and ellipticity noises
+induced by the random magnetic fluctuations. The analytical model gives results
+in perfect agreement with the numerical simulations, with potential
+applications in future experimental characterization of stray field properties
+and their influence on spin dynamics.",2309.02916v1
+2023-09-14,Spiking Dynamics in Dual Free Layer Perpendicular Magnetic Tunnel Junctions,"Spintronic devices have recently attracted a lot of attention in the field of
+unconventional computing due to their non-volatility for short and long term
+memory, non-linear fast response and relatively small footprint. Here we report
+how voltage driven magnetization dynamics of dual free layer perpendicular
+magnetic tunnel junctions enable to emulate spiking neurons in hardware. The
+output spiking rate was controlled by varying the dc bias voltage across the
+device. The field-free operation of this two terminal device and its robustness
+against an externally applied magnetic field make it a suitable candidate to
+mimic neuron response in a dense Neural Network (NN). The small energy
+consumption of the device (4-16 pJ/spike) and its scalability are important
+benefits for embedded applications. This compact perpendicular magnetic tunnel
+junction structure could finally bring spiking neural networks (SNN) to
+sub-100nm size elements.",2309.07535v1
+2023-10-23,How gravity stabilises instability: the case of magnetic micro-convection,"Finding solutions for better mixing in microfluidics remains an important
+challenge, including understanding fundamental aspects of these processes. Here
+we investigate the magnetic micro-convection on water and miscible magnetic
+fluid interface in a vertical microfluidic chip to understand what is the role
+of gravity, as fluids have different densities. Our model is reduced to two
+dimensionless quantities - magnetic and gravitational Rayleigh numbers.
+Numerical simulation results show that static magnetic field generate rich
+dynamics. This is confirmed quantitatively with careful experiments in
+initially stagnant fluids. We also show that the length of resulting mixing is
+limited by gravity. For this we construct a master curve, exploiting the
+measurements of critical field. A three-fluid layer model and linear stability
+analysis on its interfaces allows us to explain the limitation mechanism. Our
+results can help in the development of instability based micromixers.",2310.15323v1
+2024-01-11,Room-temperature Magnetic Thermal Switching by Suppressing Phonon-Magnon Scattering,"Thermal switching materials, whose thermal conductivity can be controlled
+externally, show great potential in contemporary thermal management.
+Manipulating thermal transport properties through magnetic fields has been
+accomplished in materials that exhibit a high magnetoresistance. However, it is
+generally understood that the lattice thermal conductivity attributed to
+phonons is not significantly impacted by the magnetic fields. In this study, we
+experimentally demonstrate the significant impact of phonon-magnon scattering
+on the thermal conductivity of the rare-earth metal gadolinium near room
+temperature, which can be controlled by a magnetic field to realize thermal
+switching. Using first-principles lattice dynamics and spin-lattice dynamics
+simulations, we attribute the observed change in phononic thermal conductivity
+to field-suppressed phonon-magnon scattering. This research suggests that
+phonon-magnon scattering in ferromagnetic materials is crucial for determining
+their thermal conductivity, opening the door to innovative
+magnetic-field-controlled thermal switching materials.",2401.05607v1
+2004-07-27,Relativistic field theories in a magnetic background as noncommutative field theories,"We study the connection of the dynamics in relativistic field theories in a
+strong magnetic field with the dynamics of noncommutative field theories
+(NCFT). As an example, the Nambu-Jona-Lasinio models in spatial dimensions $d
+\geq 2$ are considered. We show that this connection is rather sophisticated.
+In fact, the corresponding NCFT are different from the conventional ones
+considered in the literature. In particular, the UV/IR mixing is absent in
+these theories. The reason of that is an inner structure (i.e., dynamical
+form-factors) of neutral composites which plays an important role in providing
+consistency of the NCFT. An especially interesting case is that for a magnetic
+field configuration with the maximal number of independent nonzero tensor
+components. In that case, we show that the NCFT are finite for even $d$ and
+their dynamics is quasi-(1+1)-dimensional for odd $d$. For even $d$, the NCFT
+describe a confinement dynamics of charged particles. The difference between
+the dynamics in strong magnetic backgrounds in field theories and that in
+string theories is briefly discussed.",0407219v3
+2019-11-07,Charged dust close to outer mean-motion resonances in the heliosphere,"We investigate the dynamics of charged dust close to outer mean-motion
+resonances with planet Jupiter. The importance of the interplanetary magnetic
+field on the orbital evolution of dust is clearly demonstrated. New dynamical
+phenomena are found that do not exist in the classical problem of uncharged
+dust. We find changes in the orientation of the orbital planes of dust
+particles, an increased amount of chaotic orbital motions, sudden 'jumps' in
+the resonant argument, and a decrease in time of temporary capture due to the
+Lorentz force. Variations in the orbital planes of dust grain orbits are found
+to be related to the angle between the orbital angular momentum and magnetic
+axes of the heliospheric field and the rotation rate of the Sun. These
+variations are bound using a simplified model derived from the full dynamical
+problem using first order averaging theory. It is found that the interplanetary
+magnetic field does not affect the capture process, that is still dominated by
+the other non-gravitational forces. Our study is based on a dynamical model in
+the framework of the inclined circular restricted three-body problem.
+Additional forces include solar radiation pressure, solar wind drag, the
+Poynting-Robertson effect, and the influence of a Parker spiral type
+interplanetary magnetic field model. The analytical estimates are derived on
+the basis of Gauss' form of planetary equations of motion. Numerical results
+are obtained by simulations of dust grain orbits together with the system of
+variational equations. Chaotic regions in phase space are revealed by means of
+Fast Lyapunov Chaos Indicators.",1911.02778v1
+2020-08-11,"Lattice dynamics and ultrafast energy flow between electrons, spins, and phonons in a 3d ferromagnet","The ultrafast dynamics of magnetic order in a ferromagnet are governed by the
+interplay between electronic, magnetic and lattice degrees of freedom. In order
+to obtain a microscopic understanding of ultrafast demagnetization, information
+on the response of all three subsystems is required. A consistent description
+of demagnetization and microscopic energy flow, however, is still missing.
+Here, we combine a femtosecond electron diffraction study of the ultrafast
+lattice response of nickel to laser excitation with ab initio calculations of
+the electron-phonon interaction and energy-conserving atomistic spin dynamics
+simulations. Our model is in agreement with the observed lattice dynamics and
+previously reported electron and magnetization dynamics. Our approach reveals
+that the spin system is the dominating heat sink in the initial few hundreds of
+femtoseconds and implies a transient non-thermal state of the spins. Our
+results provide a clear picture of the microscopic energy flow between
+electronic, magnetic and lattice degrees of freedom on ultrafast timescales and
+constitute a foundation for theoretical descriptions of demagnetization that
+are consistent with the dynamics of all three subsystems.",2008.04611v2
+2021-03-06,Exceptional spectrum and dynamic magnetization,"A macroscopic effect can be induced by a local non-Hermitian term in a
+many-body system, when it manifests simultaneously level coalescence of a full
+real degeneracy spectrum, leading to exceptional spectrum. In this paper, we
+propose a family of systems that support such an intriguing property. It is
+generally consisted of two arbitrary identical Hermitian sub-lattices in
+association with unidirectional couplings between them. We show exactly that
+all single-particle eigenstates coalesce in pairs even only single
+unidirectional coupling appears. It means that all possible initial states obey
+the exceptional dynamics, resulting in some macroscopic phenomena, which never
+appears in a Hermitian system. As an application, we study the dynamic
+magnetization induced by complex fields in an itinerant electron system. It
+shows that an initial saturated ferromagnetic state at half-filling can be
+driven into its opposite state according to the dynamics of high-order
+exceptional point. Any Hermitian quench term cannot realize a steady opposite
+saturated ferromagnetic state. Numerical simulations for the dynamical
+processes of magnetization are performed for several representative situations,
+including lattice dimensions, global random and local impurity distributions.
+It shows that the dynamic magnetization processes exhibit universal behavior.",2103.04109v2
+2021-11-25,The role of q-spin singlet pairs of physical spins in the dynamical properties of the spin-1/2 Heisenberg-Ising XXZ chain,"Dynamical correlation functions contain important physical information on
+correlated spin models. Here a dynamical theory suitable suitable to the
+isotropic spin-1/2 Heisenberg chain in a longitudinal magnetic field is
+extended to anisotropy larger than one . The aim of this paper is the study of
+the line shape of the spin dynamical structure factor components +-, -+ and zz
+of the spin-1/2 Heisenberg-Ising chain in a longitudinal magnetic field near
+their sharp peaks. To reach that goal, the nature of the specific type of
+elementary magnetic configurations both unbound and associated with real
+Bethe-ansatz rapidities and bound and described by complex Bethe strings is
+clarified: They are singlet q-spin pairs of physical spins 1/2. We derive
+analytical expressions for the line shapes of dynamical structure factor
+components +-, -+ and zz valid in the vicinity of lines of sharp peaks. Those
+are mostly located at and just above lower thresholds of continua associated
+with both real-rapidity states with only unbound q-spin singlet pairs and
+states with real and complex rapidities populated by such unbound pairs and a
+single 2-string or a single 3-string. The latter contain 2 and 3 bound q-spin
+singlet pairs, respectively. Our results provide physically interesting and
+important information on the microscopic processes that determine the dynamical
+properties of the non-perturbative spin-1/2 Heisenberg-Ising chain in a
+longitudinal magnetic field.",2111.13118v1
+2022-03-22,Adiabatic spin dynamics and effective exchange interactions from constrained tight-binding electronic structure theory: Beyond the Heisenberg regime,"We consider an implementation of the adiabatic spin dynamics approach in a
+tight-binding description of the electronic structure. The adiabatic
+approximation for spin-degrees of freedom assumes that the faster electronic
+degrees of freedom are always in a quasi-equilibrium state, which significantly
+reduces the numerical complexity in comparison to the full electron dynamics.
+Non-collinear magnetic configurations are stabilized by a constraining field,
+which allows to directly obtain the effective magnetic field from the negative
+of the constraining field. While the dynamics are shown to conserve energy, we
+demonstrate that adiabatic spin dynamics does not conserve the total spin
+angular momentum when the lengths of the magnetic moments are allowed to
+change, which is confirmed by numerical simulations. Furthermore, we develop a
+method to extract an effective two-spin exchange interaction from the energy
+curvature tensor of non-collinear states, which we calculate at each time step
+of the numerical simulations. We demonstrate the effect of non-collinearity on
+this effective exchange and limitations due to multi-spin interactions in
+strongly non-collinear configurations beyond the regime where the Heisenberg
+model is valid. The relevance of the results are discussed with respect to
+experimental pump-probe experiments that follow the ultra-fast dynamics of
+magnetism.",2203.11759v3
+2022-09-20,Terahertz spin dynamics in rare-earth orthoferrites,"Recent interest in developing fast spintronic devices and laser-controllable
+magnetic solids has sparked tremendous experimental and theoretical efforts to
+understand and manipulate ultrafast dynamics in materials. Studies of spin
+dynamics in the terahertz (THz) frequency range are particularly important for
+elucidating microscopic pathways toward novel device functionalities. Here, we
+review THz phenomena related to spin dynamics in rare-earth orthoferrites, a
+class of materials promising for antiferromagnetic spintronics. We expand this
+topic into a description of four key elements. (1) We start by describing THz
+spectroscopy of spin excitations for probing magnetic phase transitions in
+thermal equilibrium. While acoustic magnons are useful indicators of spin
+reorientation transitions, electromagnons that arise from dynamic
+magnetoelectric couplings serve as a signature of inversion-symmetry-breaking
+phases at low temperatures. (2) We then review the strong laser driving
+scenario, where the system is excited far from equilibrium and thereby subject
+to modifications to the free energy landscape. Microscopic pathways for
+ultrafast laser manipulation of magnetic order are discussed. (3) Furthermore,
+we review a variety of protocols to manipulate coherent THz magnons in time and
+space, which are useful capabilities for antiferromagnetic spintronic
+applications. (4) Finally, new insights on the connection between dynamic
+magnetic coupling in condensed matter and the Dicke superradiant phase
+transition in quantum optics are provided. By presenting a review on an array
+of THz spin phenomena occurring in a single class of materials, we hope to
+trigger interdisciplinary efforts that actively seek connections between
+subfields of spintronics, which will facilitate the invention of new protocols
+of active spin control and quantum phase engineering.",2209.09468v1
+2022-12-30,Selection rules for ultrafast laser excitation and detection of spin correlations dynamics in a cubic antiferromagnet,"Exchange interactions determine the correlations between microscopic spins in
+magnetic materials. Probing the dynamics of these spin correlations on
+ultrashort length and time scales is, however rather challenging, since it
+requires simultaneously high spatial and high temporal resolution. Recent
+experimental demonstrations of laser-driven two-magnon modes - zone-edge
+excitations in antiferromagnets governed by exchange coupling - posed questions
+about the microscopic nature of the observed spin dynamics, the mechanism
+underlying its excitation, and their macroscopic manifestation enabling
+detection. Here, on the basis of a simple microscopic model, we derive the
+selection rules for cubic systems that describe the polarization of pump and
+probe pulses required to excite and detect dynamics of nearest-neighbor spin
+correlations, and can be employed to isolate such dynamics from other magnetic
+excitations and magneto-optical effects. We show that laser-driven spin
+correlations contribute to optical anisotropy of the antiferromagnet even in
+the absence of spin-orbit coupling. In addition, we highlight the role of
+subleading anisotropy in the spin system and demonstrate that the dynamics of
+the antiferromagnetic order parameter occurs only in next-to-leading order,
+determined by the smallness of the magnetic anisotropy as compared to the
+isotropic exchange interactions in the system. We expect that our results will
+stimulate and support further studies of magnetic correlations on the shortest
+length and time scale.",2212.14698v2
+2023-05-23,Laminar and transiently disordered dynamics of a magnetic skyrmion pipe flow,"The world is full of fluids that flow. The fluid nature of flowing skyrmionic
+quasiparticles is of fundamental physical interest and plays an essential role
+in the transport of many skyrmions. Here, we report the laminar and transiently
+disordered dynamic behaviors of many magnetic skyrmions flowing in a pipe
+channel. The skyrmion flow driven by a uniform current may show a lattice
+structural transition. The skyrmion flow driven by a non-uniform current shows
+a dynamically varying lattice structure. A large uniform current could result
+in the compression of skyrmions toward the channel edge, leading to the
+transition of the skyrmion pipe flow into an open-channel flow with a free
+surface. Namely, the width of the skyrmion flow could be adjusted by the
+driving current. Skyrmions on the free surface may form a single shear layer
+adjacent to the main skyrmion flow. In addition, although we focus on the
+skyrmion flow dynamics in a clean pipe channel without any pinning or defect
+effect, we also show that a variation of magnetic anisotropy in the pipe
+channel could lead to more complicated skyrmion flow dynamics and pathlines.
+Our results reveal the fluid nature of skyrmionic quasiparticles that may
+motivate future research on the complex flow physics of magnetic textures.",2305.13590v2
+2002-11-14,The magnetic state of Yb in Kondo-lattice YbNi2B2C,"We report neutron scattering experiments performed to investigate the dynamic
+magnetic properties of the Kondo-lattice compound YbNi2B2C. The spectrum of
+magnetic excitations is found to be broad, extending up to at least 150 meV,
+and contains inelastic peaks centred near 18 meV and 43 meV. At low energies we
+observe quasielastic scattering with a width Gamma = 2.1 meV. The results
+suggest a Yb3+ ground state with predominantly localized 4f electrons subject
+to (i) a crystalline electric field (CEF) potential, and (ii) a Kondo
+interaction, which at low temperatures is about an order of magnitude smaller
+than the CEF interaction. From an analysis of the dynamic magnetic response we
+conclude that the crystalline electric field acting on the Yb ions has a
+similar anisotropy to that in other RNi2B2C compounds, but is uniformly
+enhanced by almost a factor of 2. The static and dynamic magnetic properties of
+YbNi2B2C are found to be reconciled quite well by means of an approximation
+scheme to the Anderson impurity model, and this procedure also indicates that
+the effective Kondo interaction varies with temperature due to the crystal
+field splitting. We discuss the nature of the correlated-electron ground state
+of YbNi2B2C based on these and other experimental results, and suggest that
+this compound might be close to a quantum critical point on the non-magnetic
+side.",0211277v3
+2003-03-11,Magnetic artificial atoms based on thin-film ferrite disk particles,"Semiconductor quantum wells can be considered as an example of artificial
+atoms. Following the ideas used in the effective-mass theory, one can describe
+electron states in the quantum-well structure based on the Schrodinger-like
+equation for the envelope function. In recent years, there has been a renewed
+interest in high frequency dynamic properties of finite size magnetic
+structures. In a series of new publications, confinement phenomena of
+high-frequency magnetization dynamics in magnetic particles have been the
+subject of much experimental and theoretical attention. Till now, however,
+there are no phenomenological models of a ferrite particle with high-frequency
+magnetization dynamics that use the effective-mass approximation and the
+Schrodinger-like equation to analyze energy eigenstates of a whole
+ferrite-particle system, similarly to semiconductor quantum wells.
+Magnetostatic (MS) oscillations in ferrite samples have the wavelength much
+smaller than the electromagnetic wavelength at the same frequency and, at the
+same time, much larger than the exchange-interaction spin wavelength. This
+intermediate position between the pure electromagnetic and spin-wave
+(exchange-interaction) processes reveals very special behaviors of the
+geometrical effects. The confined effects for MS oscillations in normally
+magnetized thin-film ferrite disks demonstrate very unique properties of
+artificial atomic structures.",0303196v1
+2007-11-21,How to fix a broken symmetry: Quantum dynamics of symmetry restoration in a ferromagnetic Bose-Einstein condensate,"We discuss the dynamics of a quantum phase transition in a spin-1
+  Bose-Einstein condensate when it is driven from the magnetized
+broken-symmetry phase to the unmagnetized ``symmetric'' polar phase. We
+determine where the condensate goes out of equilibrium as it approaches the
+critical point, and compute the condensate magnetization at the critical point.
+This is done within a quantum Kibble-Zurek scheme traditionally employed in the
+context of symmetry-breaking quantum phase transitions. Then we study the
+influence of the nonequilibrium dynamics near a critical point on the
+condensate magnetization. In particular, when the quench stops at the critical
+point, nonlinear oscillations of magnetization occur. They are characterized by
+a period and an amplitude that are inversely proportional. If we keep driving
+the condensate far away from the critical point through the unmagnetized
+``symmetric'' polar phase, the amplitude of magnetization oscillations slowly
+decreases reaching a non-zero asymptotic value. That process is described by
+the equation that can be mapped onto the classical mechanical problem of a
+particle moving under the influence of harmonic and ``anti-friction'' forces
+whose interplay leads to surprisingly simple fixed-amplitude oscillations. We
+obtain several scaling results relating the condensate magnetization to the
+quench rate, and verify numerically all analytical predictions.",0711.3431v3
+2010-10-22,Spin-Transfer Torque Induced Vortex Dynamics in Fe/Ag/Fe Nanopillars,"We report experimental and analytical work on spin-transfer torque induced
+vortex dynamics in metallic nanopillars with in-plane magnetized layers. We
+study nanopillars with a diameter of 150 nm, containing two Fe layers with a
+thickness of 15 nm and 30 nm respectively, separated by a 6 nm Ag spacer. The
+sample geometry is such that it allows for the formation of magnetic vortices
+in the Fe disks. As confirmed by micromagnetic simulations, we are able to
+prepare states where one magnetic layer is homogeneously magnetized while the
+other contains a vortex. We experimentally show that in this configuration
+spin-transfer torque can excite vortex dynamics and analyze their dependence on
+a magnetic field applied in the sample plane. The center of gyration is
+continuously dislocated from the disk center, and the potential changes its
+shape with field strength. The latter is reflected in the field dependence of
+the excitation frequency. In the second part we propose a novel mechanism for
+the excitation of the gyrotropic mode in nanopillars with a perfectly
+homogeneously magnetized in-plane polarizing layer. We analytically show that
+in this configuration the vortex can absorb energy from the spin-polarized
+electric current if the angular spin-transfer efficiency function is
+asymmetric. This effect is supported by micromagnetic simulations.",1010.4791v2
+2010-12-07,Effects of Magnetic Fields on Photoionised Pillars and Globules,"The effects of initially uniform magnetic fields on the formation and
+evolution of dense pillars and cometary globules at the boundaries of H II
+regions are investigated using 3D radiation-magnetohydrodynamics simulations.
+It is shown, in agreement with previous work, that a strong initial magnetic
+field is required to significantly alter the non-magnetised dynamics because
+the energy input from photoionisation is so large that it remains the dominant
+driver of the dynamics in most situations. Additionally it is found that for
+weak and medium field strengths an initially perpendicular field is swept into
+alignment with the pillar during its dynamical evolution, matching magnetic
+field observations of the `Pillars of Creation' in M16 and also some cometary
+globules. A strong perpendicular magnetic field remains in its initial
+configuration and also confines the photoevaporation flow into a bar-shaped
+dense ionised ribbon which partially shields the ionisation front and would be
+readily observable in recombination lines. A simple analytic model is presented
+to explain the properties of this bright linear structure. These results show
+that magnetic field strengths in star-forming regions can in principle be
+significantly constrained by the morphology of structures which form at the
+borders of H II regions.",1012.1500v2
+2011-03-22,Dipolar Interactions between Iron-Oxide Nanoparticles in Frozen Ferrofluids and Ferronematics,"We present a detailed study of the magnetic behavior of iron-oxide
+(gamma-Fe2O3 and Fe3O4) nanoparticles constituents of ferrofluids (FF's) with
+average particle sizes <d> = 2.5 and 10 nm. The particles were dispersed in the
+frozen liquid carrier (pure FF) and in a frozen lyotropic liquid crystalline
+matrix in the nematic phase or ferronematic (FN) (ferrolyomesophase). Both FF
+and FN phases displayed superparamagnetic (SPM) behaviour at room temperature,
+with blocking temperatures T_B ~ 10 and 100 K for <d> = 2.5 and 10 nm,
+respectively. Dynamic ac susceptibility measurements showed a thermally
+activated N\'eel-Brown dependence of the blocking temperature with applied
+frequency. Our results show that dipolar interactions are small, but
+non-negligible, as compared to the single-particle energy barriers from
+magnetic anisotropy. From the fit of ac susceptibility we calculated the
+effective magnetic anisotropy constant K_{eff} for 2.5 nm maghemite particles.
+Although interparticle interactions present in highly diluted samples do not
+appreciably modify the dynamic magnetic behavior of isolated particles, the
+calculated magnetic anisotropy were abut one order of magnitude larger that the
+bulk materials, suggesting the existence of large surface anisotropy. Using the
+thermally activated model to fit the dynamic data yielded effective energy
+barriers Ea = 3.5x10^{-21} J. From these data, we obtained K_{eff} = 422 kJ/m^3
+for the single-particle effective magnetic anisotropy.",1103.4403v1
+2011-03-30,Quantum simulation of frustrated magnetism in triangular optical lattices,"Magnetism plays a key role in modern technology as essential building block
+of many devices used in daily life. Rich future prospects connected to
+spintronics, next generation storage devices or superconductivity make it a
+highly dynamical field of research. Despite those ongoing efforts, the
+many-body dynamics of complex magnetism is far from being well understood on a
+fundamental level. Especially the study of geometrically frustrated
+configurations is challenging both theoretically and experimentally. Here we
+present the first realization of a large scale quantum simulator for magnetism
+including frustration. We use the motional degrees of freedom of atoms to
+comprehensively simulate a magnetic system in a triangular lattice. Via a
+specific modulation of the optical lattice, we can tune the couplings in
+different directions independently, even from ferromagnetic to
+antiferromagnetic. A major advantage of our approach is that standard
+Bose-Einstein-condensate temperatures are sufficient to observe magnetic
+phenomena like N\'eel order and spin frustration. We are able to study a very
+rich phase diagram and even to observe spontaneous symmetry breaking caused by
+frustration. In addition, the quantum states realized in our spin simulator are
+yet unobserved superfluid phases with non-trivial long-range order and
+staggered circulating plaquette currents, which break time reversal symmetry.
+These findings open the route towards highly debated phases like spin-liquids
+and the study of the dynamics of quantum phase transitions.",1103.5944v1
+2012-04-16,Non-perturbative Euler-Heisenberg Lagrangian and Paraelectricity in Magnetized Massless QED,"In this paper we calculate the non-perturbative Euler-Heisenberg Lagrangian
+for massless QED in a strong magnetic field $H$, where the breaking of the
+chiral symmetry is dynamically catalyzed by the external magnetic field via the
+formation of an electro-positron condensate. This chiral condensate leads to
+the generation of dynamical parameters that have to be found as solutions of
+non-perturbative Schwinger-Dyson equations. Since the electron-positron pairing
+mechanism leading to the breaking of the chiral symmetry is mainly dominated by
+the contributions from the infrared region of momenta much smaller than
+$\sqrt{eH}$, the magnetic field introduces a dynamical ultraviolet cutoff in
+the theory that also enters in the non-perturbative Euler-Heisenberg action.
+Using this action, we show that the system exhibits a significant
+paraelectricity in the direction parallel to the magnetic field. The
+nonperturbative nature of this effect is reflected in the non-analytic
+dependence of the obtained electric susceptibility on the fine-structure
+constant. The strong paraelectricity in the field direction is linked to the
+orientation of the electric dipole moments of the pairs that form the chiral
+condensate. The large electric susceptibility can be used to detect the
+realization of the magnetic catalysis of chiral symmetry breaking in physical
+systems.",1204.3660v2
+2012-09-29,Emergence and Frustration of Magnetic Order with Variable-Range Interactions in a Trapped Ion Quantum Simulator,"Frustration, or the competition between interacting components of a network,
+is often responsible for the complexity of many body systems, from social and
+neural networks to protein folding and magnetism. In quantum magnetic systems,
+frustration arises naturally from competing spin-spin interactions given by the
+geometry of the spin lattice or by the presence of long-range antiferromagnetic
+couplings. Frustrated magnetism is a hallmark of poorly understood systems such
+as quantum spin liquids, spin glasses and spin ices, whose ground states are
+massively degenerate and can carry high degrees of quantum entanglement. The
+controlled study of frustrated magnetism in materials is hampered by short
+dynamical time scales and the presence of impurities, while numerical modeling
+is generally intractable when dealing with dynamics beyond N~30 particles.
+Alternatively, a quantum simulator can be exploited to directly engineer
+prescribed frustrated interactions between controlled quantum systems, and
+several small-scale experiments have moved in this direction. In this article,
+we perform a quantum simulation of a long-range antiferromagnetic quantum Ising
+model with a transverse field, on a crystal of up to N = 16 trapped Yb+ atoms.
+We directly control the amount of frustration by continuously tuning the range
+of interaction and directly measure spin correlation functions and their
+dynamics through spatially-resolved spin detection. We find a pronounced
+dependence of the magnetic order on the amount of frustration, and extract
+signatures of quantum coherence in the resulting phases.",1210.0142v1
+2016-02-29,Universal Dynamic Magnetism in Yb-Pyrochlores with Disparate Ground States,"The ytterbium pyrochlore magnets, Yb2B2O7 (B = Sn, Ti, Ge) are well described
+by S_eff = 1/2 quantum spins decorating a network of corner-sharing tetrahedra
+and interacting via anisotropic exchange. Structurally, only the non-magnetic
+B-site cation, and hence, primarily the lattice parameter, is changing across
+the series. Nonetheless, a range of magnetic behaviors are observed: the low
+temperature magnetism in Yb2Ti2O7 and Yb2Sn2O7 has ferromagnetic character,
+while Yb2Ge2O7 displays an antiferromagnetically ordered Neel state at low
+temperatures. While the static properties of the ytterbium pyrochlores are
+distinct, inelastic neutron scattering measurements reveal a common character
+to their exotic spin dynamics. All three ytterbium pyrochlores show a gapless
+continuum of spin excitations, resembling over-damped ferromagnetic spin waves
+at low Q. Furthermore, the specific heat of the series also follows a common
+form, with a broad, high-temperature anomaly followed by a sharp
+low-temperature anomaly at T_C or T_N. The novel spin dynamics we report
+correlate strongly with the broad specific heat anomaly only, remaining
+unchanged across the sharp anomaly. This result suggests that the primary order
+parameter in the ytterbium pyrochlores associated with the sharp anomaly is
+""hidden"" and not simple magnetic dipole order.",1602.09011v1
+2016-07-29,"A rock-salt type Li-based oxide, Li3Ni2RuO6, exhibiting a chaotic ferrimagnetism with cluster spin-glass dynamics and thermally frozen charge carriers","The area of research to discover new Li containing materials and to
+understand their physical properties has been of constant interest due to
+applications potential for rechargeable batteries. Here, we present the results
+of magnetic investigations on a Li compound, Li3Ni2RuO6, which was believed to
+be a ferrimagnet below 80K. While our neutron diffraction (ND) and isothermal
+magnetization (M) data support ferrimagnetism, more detailed magnetic studies
+establish that this ferrimagnetic phase exhibits some features similar to
+spin-glasses. In addition, we find another broad magnetic anomaly around 40-55
+K in magnetic susceptibility, attributable to cluster spin-glass phenomenon.
+Gradual dominance of cluster spin-glass dynamics with a decrease of temperature
+(T) and the apparent spread in freezing temperature suggest that the
+ferrimagnetism of this compound is a chaotic one. The absence of a unique
+freezing temperature for a crystalline material is interesting. In addition,
+pyroelectric current data reveals a feature in the range 40-50 K, attributable
+to thermally stimulated depolarization current. We hope this finding motivates
+future work to explore whether there is any intriguing correlation of such a
+feature with spin-glass dynamics. We attribute these magnetic and electric
+dipole anomalies to the crystallographic disorder intrinsic to this compound.",1607.08689v1
+2016-08-16,Incommensurate spiral magnetic order on anisotropic triangular lattice: Dynamical mean field study in a spin-rotating frame,"We study the ground-state magnetism of the half-filled Hubbard model on the
+anisotropic triangular lattice, where two out of three bonds have hopping $t$
+and the third one has $t^\prime$ in a unit triangle. Working in a spin-rotating
+frame and using the density matrix renormalization group method as an impurity
+solver, we provide a proper description of incommensurate magnetizations at
+zero temperature in the framework of the dynamical mean-field theory (DMFT). It
+is shown that the incommensurate spiral magnetic order for $t^\prime/t\gtrsim
+0.7$ survives the dynamical fluctuations of itinerant electrons in the Hubbard
+interaction range from the strong-coupling (localized-spin) limit down to the
+insulator-to-metal transition. We also find that the magnetic moment reduction
+from the localized-spin limit is pronounced in the vicinity of the transition
+between the commensurate N\'eel and incommensurate spiral phases at
+$t^\prime/t\sim 0.7$. When the anisotropy parameter $t^\prime/t$ increases from
+the N\'eel-to-spiral transition, the magnitude of the magnetic moment
+immediately reaches a maximum and then rapidly decreases in the range of larger
+$t^\prime/t$ including the isotropic triangular lattice point $t^\prime/t=1$.
+This work gives a solid foundation for further extension of the study including
+nonlocal correlation effects neglected at the standard DMFT level.",1608.04490v1
+2018-08-10,Interactions between Gas Dynamics and Magnetic Fields in the Massive Dense Cores of the DR21 Filament,"We report Submillimeter Array molecular line observations in the 345 GHz band
+of five massive dense cores, Cyg-N38, Cyg-N43, Cyg-N48, Cyg-N51, and Cyg-N53 in
+the DR21 filament. The molecular line data reveal several dynamical features of
+the cores: (1) prominent outflows in all cores seen in the CO and SiO lines,
+(2) significant velocity gradients in Cyg-N43 and Cyg-N48 seen in the H13CN and
+H13CO+ lines suggesting 0.1-pc-scale rotational motions, and (3) possible
+infalls in Cyg-N48 found in the SiO and SO lines. Comparing the molecular line
+data and our dust polarization data in Ching et al. (2017), we find that the
+gradients of line-of-sight velocities appear to be randomly oriented relative
+to the plane-of-sky magnetic fields. Our simulations suggest that this random
+alignment implies parallel or random alignment between the velocity gradients
+and magnetic fields in the three dimensional space. The linewidths of H13CN
+emission are consistently wider than those of H13CO+ emission in the 3''-10''
+detectable scales, which can be explained by the existence of ambipolar
+diffusion with maximum plane-of-the-sky magnetic field strengths of 1.9 mG and
+5.1 mG in Cyg-N38 and Cyg-N48, respectively. Our results suggest that the gas
+dynamics may distort the magnetic fields of the cores of into complex
+structures and ambipolar diffusion could be important in dissipating the
+magnetic energies of the cores.",1808.03459v1
+2019-03-07,Maltese Cross anisotropy in Ho0.8Lu0.2B12 antiferromagnetic metal with dynamic charge stripes,"The model strongly correlated electron system Ho0.8Lu0.2B12 which
+demonstrates a cooperative Jahn-Teller instability of the boron sub-lattice in
+combination with rattling modes of Ho(Lu) ions, dynamic charge stripes and
+unusual antiferromagnetic (AF) ground state has been studied in detail at low
+temperatures by magnetoresistance, magnetization and heat capacity
+measurements. Based on received results it turns out that the angular H-fi-T
+magnetic phase diagrams of this non-equilibrium AF metal can be reconstructed
+in the form of a Maltese cross. The dramatic AF ground state symmetry lowering
+of this dodecaboride with fcc crystal structure can be attributed to the
+redistribution of conduction electrons which leave the RKKY oscillations of the
+electron spin density to participate in the dynamic charge stripes providing
+with extraordinary changes in the indirect exchange interaction between
+magnetic moments of Ho3+ ions and resulting in the emergence of a number of
+various magnetic phases. It is also shown that the two main contributions to
+magnetoresistance in the complex AF phase, the (i) positive linear on magnetic
+field and the (ii) negative quadratic component can be separated and analyzed
+quantitatively, correspondingly, in terms of charge carrier scattering on spin
+density wave (5d) component of the magnetic structure and on local 4f-5d spin
+fluctuations of holmium sites.",1903.03000v1
+2020-04-06,Effect of Nd and Rh substitution on the spin dynamics of Kondo insulator CeFe2Al10,"The dynamic magnetic properties of the Kondo-insulator state in CeFe2Al10
+(spin gap, resonance mode) have been investigated using polarized neutrons on a
+single crystal of pure CeFe2Al10. The results indicate that the magnetic
+excitations are polarized mainly along the orthorhombic a axis and their
+dispersion along the orthorhombic c direction could be determined.
+Polycrystalline samples of Nd- and Rh-doped CeFe2Al0 were also studied by the
+time-of-flight technique, with the aim of finding out how the low-energy
+magnetic excitation spectra change upon isoelectronic substitution of the
+rare-earth (Nd) on the magnetic Ce site or electron doping (Rh) on the
+transition-element Fe sublattice. The introduction of magnetic Nd impurities
+strongly modifies the spin gap in the Ce dynamic magnetic response and causes
+the appearance of a quasielastic signal. The crystal-field excitations of Nd,
+studied in both LaFe2Al10 and CeFe2Al10, also reveal a significant influence of
+f-electron hybridization (largest in the case of Ce) on the crystal-field
+potential. As a function of the Rh concentration, a gradual change is observed
+from a Kondo-insulator to a metallic Kondo-lattice response, likely reflecting
+the decrease in the hybridization energy.",2004.02572v2
+2020-05-08,$s$-$d$ model for local and nonlocal spin dynamics in laser-excited magnetic heterostructures,"We discuss a joint microscopic theory for the laser-induced magnetization
+dynamics and spin transport in magnetic heterostructures based on the $s$-$d$
+interaction. Angular momentum transfer is mediated by scattering of itinerant
+$s$ electrons with the localized ($d$ electron) spins. We use the corresponding
+rate equations and focus on a spin one-half $d$ electron system, leading to a
+simplified analytical expression for the dynamics of the local magnetization
+that is coupled to an equation for the non-equilibrium spin accumulation of the
+$s$ electrons. We show that this description converges to the microscopic
+three-temperature model in the limit of a strong $s$-$d$ coupling. The equation
+for the spin accumulation is used to introduce diffusive spin transport. The
+presented numerical solutions show that during the laser-induced
+demagnetization in a ferromagnetic metal a short-lived spin accumulation is
+created that counteracts the demagnetization process. Moreover, the spin
+accumulation leads to the generation of a spin current at the interface of a
+ferromagnetic and non-magnetic metal. Depending on the specific magnetic
+system, both local spin dissipation and interfacial spin transport are able to
+enhance the demagnetization rate by providing relaxation channels for the spin
+accumulation that is build up during demagnetization in the ferromagnetic
+material.",2005.03905v2
+2020-05-26,"From magnetic order to quantum disorder: a $μ$SR study of the Zn-barlowite series of $S={\frac{1}{2}}$ kagomé antiferromagnets, Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$FBr","We report a comprehensive muon spectroscopy study of the Zn-barlowite series
+of $S={\frac{1}{2}}$ kagom\'e antiferromagnets, Zn$_x$Cu$_{4-x}$(OH)$_{6}$FBr,
+for $x=0.00$ to $0.99(1)$. By combining muon spin relaxation and rotation
+measurements with state-of-the-art density-functional theory muon-site
+calculations, we observe the formation of both $\mu$--F and $\mu$--OH complexes
+in Zn-barlowite. From these stopping sites, implanted muon spins reveal the
+suppression of long-range magnetic order into a possible quantum spin liquid
+state upon increasing concentration of Zn-substitution. In the parent compound
+($x=0$), static long-range magnetic order below $T_{\mathsf{N}}=15$ K manifests
+itself in the form of spontaneous oscillations in the time-dependent muon
+asymmetry signal consistent with the dipolar fields expected from the
+calculated muon stopping sites and the previously determined magnetic structure
+of barlowite. Meanwhile, in the $x=1.0$ end-member of the series---in which
+antiferromagnetic kagom\'e layers of Cu$^{2+}$ $S={\frac{1}{2}}$ moments are
+decoupled by diamagnetic Zn$^{2+}$ ions---we observe that dynamic magnetic
+moment fluctuations persist down to at least 50 mK, indicative of a quantum
+disordered ground state. We demonstrate that this crossover from a static to
+dynamic magnetic ground state occurs for compositions of Zn-barlowite with
+$x>0.5$, which bears resemblance to dynamical behaviour of the widely studied
+Zn-paratacamite series that contains the quantum spin liquid candidate
+herbertsmithite.",2005.12615v1
+2020-07-08,Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere,"In this work, a state-of-the-art vortex detection method, Instantaneous
+Vorticity Deviation, is applied to locate three-dimensional vortex tube
+boundaries in numerical simulations of solar photospheric magnetoconvection
+performed by the MURaM code. We detected three-dimensional vortices distributed
+along intergranular regions and displaying coned shapes that extend from the
+photosphere to the low chromosphere. Based on a well-defined vortex center and
+boundary, we were able to determine averaged radial profiles and thereby
+investigate the dynamics across the vortical flows at different height levels.
+The solar vortex tubes present nonuniform angular rotational velocity, and, at
+all height levels, there are eddy viscosity effects within the vortices, which
+slow down the plasma as it moves toward the center. The vortices impact the
+magnetic field as they help to intensify the magnetic field at the sinking
+points, and in turn, the magnetic field ends up playing an essential role in
+the vortex dynamics. The magnetic field was found to be especially important to
+the vorticity evolution. On the other hand, it is shown that, in general,
+kinematic vortices do not give rise to magnetic vortices unless their
+tangential velocities at different height levels are high enough to overcome
+the magnetic tension.",2007.04371v1
+2020-08-28,Equation of motion and the constraining field in ab initio spin dynamics,"It is generally accepted that the effective magnetic field acting on a
+magnetic moment is given by the gradient of the energy with respect to the
+magnetization. However, in ab initio spin dynamics within the adiabatic
+approximation, the effective field is also known to be exactly the negative of
+the constraining field, which acts as a Lagrange multiplier to stabilize an
+out-of-equilibrium, non-collinear magnetic configuration. We show that for
+Hamiltonians without mean-field parameters both of these fields are exactly
+equivalent, while there can be a finite difference for mean-field Hamiltonians.
+For density-functional theory (DFT) calculations the constraining field
+obtained from the auxiliary Kohn-Sham Hamiltonian is not exactly equivalent to
+the DFT energy gradient. This inequality is highly relevant for both ab initio
+spin dynamics and the ab initio calculation of exchange constants and effective
+magnetic Hamiltonians. We argue that the effective magnetic field and exchange
+constants have the highest accuracy in DFT when calculated from the energy
+gradient and not from the constraining field.",2008.12547v2
+2020-11-13,Cell dynamics simulations of coupled charge and magnetic phase transformation in correlated oxides,"We present a comprehensive numerical study on the kinetics of phase
+transition that is characterized by two non-conserved scalar order parameters
+coupled by a special linear-quadratic interaction. This particular
+Ginzburg-Landau theory has been proposed to describe the coupled charge- and
+magnetic transition in nickelates and the collinear stripe phase in cuprates.
+The inhomogeneous state of such systems at low temperatures consists of
+magnetic domains separated by quasi-metallic domain-walls where the
+charge-order is reduced. By performing large-scale cell dynamics simulations,
+we find a two-stage phase-ordering process in which a short period of
+independent evolution of the two order parameters is followed by a correlated
+coarsening process. The long-time growth and coarsening of magnetic domains is
+shown to follow the Allen-Cahn power law. We further show that the
+nucleation-and-growth dynamics during phase transformation to the ordered
+states is well described by the Kolmogorov-Johnson-Mehl-Avrami theory in two
+dimensions. On the other hand, the presence of quasi-metallic magnetic domain
+walls in the ordered states gives rise to a very different kinetics for phase
+transition to the high temperature paramagnetic phase. In this new scenario,
+the phase transformation is initiated by the decay of magnetic domain walls
+into two insulator-metal boundaries, which subsequently move away from each
+other. Implications of our findings to recent nano-imaging experiments on
+nickelates are also discussed.",2011.07045v2
+2021-03-07,Exploring self-consistency of the equations of axion electrodynamics in Weyl semimetals,"Recent works have provided evidence that an axial anomaly can arise in Weyl
+semimetals. If this is the case, then the electromagnetic response of Weyl
+semimetals should be governed by the equations of axion electrodynamics. These
+equations capture both the chiral magnetic and anomalous Hall effects in the
+limit of linear response, while at higher orders their solutions can provide
+detectable electromagnetic signatures of the anomaly. In this work, we consider
+three versions of axion electrodynamics that have been proposed in the Weyl
+semimetal literature. These versions differ in the form of the chiral magnetic
+term and in whether or not the axion is treated as a dynamical field. In each
+case, we look for solutions to these equations for simple sample geometries
+subject to applied external fields. We find that in the case of a linear chiral
+magnetic term generated by a non-dynamical axion, self-consistent solutions can
+generally be obtained. In this case, the magnetic field inside of the Weyl
+semimetal can be magnified significantly, providing a testable signature for
+experiments. Self-consistent solutions can also be obtained for dynamical
+axions, but only in cases where the chiral magnetic term vanishes identically.
+Finally, for a nonlinear form of the chiral magnetic term frequently considered
+in the literature, we find that there are no self-consistent solutions aside
+from a few special cases.",2103.04232v2
+2021-05-08,Comparative study of electric currents and energetic particle fluxes in a solar flare and Earth magnetospheric substorm,"Magnetic field-line reconnection is a universal plasma process responsible
+for the conversion of magnetic field energy to the plasma heating and charged
+particle acceleration. Solar flares and Earth's magnetospheric substorms are
+two most investigated dynamical systems where magnetic reconnection is believed
+to be responsible for global magnetic field reconfiguration and energization of
+plasma populations. Such a reconfiguration includes formation of a long-living
+current systems connecting the primary energy release region and cold dense
+conductive plasma of photosphere/ionosphere. In both flares and substorms the
+evolution of this current system correlates with formation and dynamics of
+energetic particle fluxes. Our study is focused on this similarity between
+flares and substorms. Using a wide range of datasets available for flare and
+substorm investigations, we compare qualitatively dynamics of currents and
+energetic particle fluxes for one flare and one substorm. We showed that there
+is a clear correlation between energetic particle bursts (associated with
+energy release due to magnetic reconnection) and magnetic field
+reconfiguration/formation of current system. We then discuss how datasets of
+in-situ measurements in the magnetospheric substorm can help in interpretation
+of datasets gathered for the solar flare.",2105.03772v1
+2021-10-27,Quasi-static magnetoconvection with a tilted magnetic field,"A numerical study of convection with stress-free boundary conditions in the
+presence of an imposed magnetic field that is tilted with respect to the
+direction of gravity is carried out in the limit of small magnetic Reynolds
+number. The dynamics are investigated over a range of Rayleigh number $Ra$ and
+Chandrasekhar numbers up to $Q = 2\times10^6$, with the tilt angle between the
+gravity vector and imposed magnetic field vector fixed at $45^{\circ}$. For a
+fixed value of $Q$ and increasing $Ra$, the convection dynamics can be broadly
+characterized by three primary flow regimes: (1) quasi-two-dimensional
+convection rolls near the onset of convection; (2) isolated convection columns
+aligned with the imposed magnetic field; and (3) unconstrained convection
+reminiscent of non-magnetic convection. The influence of varying $Q$ and $Ra$
+on the various fields is analyzed. Heat and momentum transport, as
+characterized by the Nusselt and Reynolds numbers, are quantified and compared
+with the vertical field case. Ohmic dissipation dominates over viscous
+dissipation in all cases investigated. Various mean fields are investigated and
+their scaling behavior is analyzed. Provided $Ra$ is sufficiently large, all
+investigated values of $Q$ exhibit an inverse kinetic energy cascade that
+yields strong `zonal' flows. Relaxation oscillations, as characterized by a
+quasi-periodic shift in the predominance of either the zonal or non-zonal
+component of the mean flow, appear for sufficiently large $Ra$ and $Q$.",2110.14721v2
+2022-02-07,Effects of kinematic and magnetic boundary conditions on the dynamics of convection-driven plane layer dynamos,"Rapidly rotating convection-driven dynamos are investigated under different
+kinematic and magnetic boundary conditions using DNS. At a fixed rotation rate,
+represented by the Ekman number $E=5\times10^{-7}$, the thermal forcing is
+varied from 2 to 20 times its value at the onset of convection
+($\mathcal{R}=Ra/Ra_c=2-20$), keeping the fluid properties constant
+($Pr=Pr_m=1$). The statistical behavior, force balance and heat transport
+characteristics of the dynamos depend on boundary conditions that dictate both
+boundary layer and the interior dynamics. At a fixed thermal forcing
+($\mathcal{R}=3$), the Ekman plumes in the presence of viscous boundary layers
+lead to energetic vortices that result in higher enstrophy and kinetic helicity
+with no-slip boundaries compared to free-slip boundaries. The structure and
+strength of the magnetic field are also dictated by the boundary conditions.
+Though the leading order force balance remains geostrophic, Lorentz force
+dominates inside the thermal boundary layer with no-slip, electrically
+conducting walls. Here, the Lorentz work term in the turbulent kinetic energy
+budget is found to have components that exchange energy from the velocity field
+to the magnetic field, and vice-versa. However, with no-slip, insulated walls,
+all Lorentz work components perform unidirectional energy transfer to produce
+magnetic energy from the kinetic energy of the fluid. The heat transfer
+enhancement in dynamos, compared to non-magnetic rotating convection, exhibits
+a peak in the range $\mathcal{R}=3-5$. For free-slip conditions, dynamo action
+may alter the heat transport by suppressing the formation of large-scale
+vortices. However, the highest heat transfer enhancement occurs when the
+boundaries are no-slip, electrically conducting walls.",2202.03235v1
+2022-04-22,Controlling magnetism with light in a zero orbital angular momentum antiferromagnet,"Antiferromagnetic materials feature intrinsic ultrafast spin dynamics, making
+them ideal candidates for future magnonic devices operating at THz frequencies.
+A major focus of current research is the investigation of optical methods for
+the efficient generation of coherent magnons in antiferromagnetic insulators.
+In magnetic lattices endowed with orbital angular momentum, spin-orbit coupling
+enables spin dynamics through the resonant excitation of low-energy electric
+dipoles such as phonons and orbital resonances which interact with spins.
+However, in magnetic systems with zero orbital angular momentum, microscopic
+pathways for the resonant and low-energy optical excitation of coherent spin
+dynamics are lacking. Here, we consider experimentally the relative merits of
+electronic and vibrational excitations for the optical control of zero orbital
+angular momentum magnets, focusing on a limit case: the antiferromagnet
+manganese thiophoshate (MnPS3), constituted by orbital singlet Mn2+ ions. We
+study the correlation of spins with two types of excitations within its band
+gap: a bound electron orbital excitation from the singlet orbital ground state
+of Mn2+ into an orbital triplet state, which causes coherent spin precession,
+and a vibrational excitation of the crystal field that causes thermal spin
+disorder. Our findings cast orbital transitions as key targets for magnetic
+control in insulators constituted by magnetic centers of zero orbital angular
+momentum.",2204.10574v1
+2022-06-17,Multiscale Modelling of the Antiferromagnet Mn2Au: From ab-initio to Micromagnetics,"Antiferromagnets (AFMs) are strong candidates for the future spintronic and
+memory applications largely because of their inherently fast dynamics and lack
+of stray fields, with Mn2Au being one of the most promising. For the numerical
+modelling of magnetic material properties, it is common to use ab-initio
+methods, atomistic models and micromagnetics. However, each method alone
+describes the physics within certain limits. Multiscale methods bridging the
+gap between these three approaches have been already proposed for ferromagnetic
+materials. Here, we present a complete multiscale model of the AFM Mn2Au as an
+exemplar material, starting with results from ab-initio methods going via
+atomistic spin dynamics (ASD) to an AFM Landau-Lifshitz-Bloch (AFM-LLB) model.
+Firstly, bulk is modelled using a classical spin Hamiltonian constructed based
+on earlier first-principles calculations. Secondly, this spin model is used in
+the stochastic Landau-Lifshitz-Gilbert (LLG) to calculate temperature-dependent
+equilibrium properties, such as magnetization and magnetic susceptibilities.
+Thirdly, the temperature dependent micromagnetic parameters are used in the
+AFM-LLB. We validate our approach by comparing the ASD and AFM-LLB models for
+three paradigmatic cases; (i) Damped magnetic oscillations, (ii) magnetization
+dynamics following a heat pulse resembling pump-probe experiments, (iii)
+magnetic domain wall motion under thermal gradients.",2206.08625v1
+2022-10-28,Field-free-switching state diagram of perpendicular magnetization subjected to conventional and unconventional spin-orbit torques,"The lack of certain crystalline symmetries in strong spin-orbit-coupled
+non-magnetic materials allows for the existence of uncoventional spin Hall
+responses, with electrically generated transverse spin currents possessing
+collinear flow and spin directions. The injection of such spin currents into an
+adjacent ferromagnetic layer can excite magnetization dynamics via
+unconventional spin-orbit torques, leading to deterministic switching in
+ferromagnets with perpendicular magnetic anisotropy. We study the interplay
+between conventional and unconventional spin-orbit torques on the magnetization
+dynamics of a perpendicular ferromagnet in the small intrinsic damping limit,
+and identify a rich set of dynamical regimes that includes deterministic and
+probabilistic switching, precessional and pinning states. Contrary to common
+belief, we found that there exists a critical conventional spin Hall angle,
+beyond which deterministic magnetization switching transitions to a
+precessional or pinned state. Conversely, we showed that larger unconventional
+spin Hall angle is generally beneficial for deterministic switching. We derive
+an approximate expression that qualitatively describes the state diagram
+boundary between the full deterministic switching and precessional states and
+discuss a criterion for searching symmetry-broken spin Hall materials in order
+to maximize switching efficiency. Our work offers a roadmap towards energy
+efficient spintronic devices, which might opens doors for applications in
+advanced in-memory computing technologies.",2210.16344v1
+2022-11-22,Spatially Nonuniform Oscillations in Ferrimagnets Based on an Atomistic Model,"The ferrimagnets, such as GdxFeCo(1-x), can produce ultrafast magnetic
+switching and oscillation due to the strong exchange field. The two-sublattices
+macrospin model has been widely used to explain the experimental results.
+However, it fails in describing the spatial nonuniform magnetic dynamics which
+gives rises to many important phenomenons such as the domain walls and
+skyrmions. Here we develop the two-dimensional atomistic model and provide a
+torque analysis method to study the ferrimagnetic oscillation. Under the
+spin-transfer torque, the magnetization oscillates in the exchange mode or the
+flipped exchange mode. When the Gd composition is increased, the exchange mode
+firstly disappears, and then appears again as the magnetization compensation
+point is reached. We show that these results can only be explained by analyzing
+the spatial distribution of magnetization and effective fields. In particular,
+when the sample is small, a spatial nonuniform oscillation is also observed in
+the square film. Our work reveals the importance of spatial magnetic
+distributions in understanding the ferrimagnetic dynamics. The method developed
+in this paper provides an important tool to gain a deeper understanding of
+ferrimagnets and antiferromagnets. The observed ultrafast dynamics can also
+stimulate the development of THz oscillators.",2211.12247v1
+2022-11-30,Unconventional spin dynamics in the non-collinear phase of a ferrimagnet,"Ferrimagnets containing several partially compensated magnetic sublattices
+are considered the most promising materials for all-optical data storage and
+for ultrafast communications based on spin waves. There are two magnetic phases
+of the ferrimagnets: collinear and non-collinear ones. Up to now spin dynamics
+in ferrimagnets has been studied mostly in the collinear state without paying
+much attention to the kind of the magnetic phase. Here we investigate laser
+induced ultrafast spin dynamics in a rare-earth iron garnet film in the
+noncollinear phase as well. We identify a crucial influence of the magnetic
+phase on the excited spin modes which allowed us to discover several prominent
+effects previously overlooked. In particular, the non-collinearity makes the
+quasi-antiferromagnetic mode sensitive to the external magnetic field and
+brings its frequency close to the frequency of the quasiferromagnetic mode. The
+latter maximizes near the magnetization compensation point and vanishes towards
+the collinear phase. Spectacularly, at the phase transition the
+quasiferromagnetic mode becomes soft and its amplitude significantly increases
+reaching 7{\deg}. This opens new opportunities for the ultrafast control of
+spins in ferrimagnets for nonthermal data storage and data processing.",2212.00085v2
+2023-01-22,Easy-plane spin Hall oscillator,"Spin Hall oscillators (SHOs) based on bilayers of a ferromagnet (FM) and a
+non-magnetic heavy metal (HM) are electrically tunable nanoscale microwave
+signal generators. Achieving high output power in SHOs requires driving
+large-amplitude magnetization dynamics by a direct spin Hall current. The
+maximum possible amplitude of such oscillations with the precession cone angle
+nearing $90^\circ$ is predicted for FM layers with easy-plane magnetic
+anisotropy and spin Hall current polarization perpendicular to the easy plane.
+While many FMs exhibit natural easy-plane anisotropy in the FM film plane, the
+spin Hall current in a HM|FM bilayer is polarized in this plane and thus cannot
+drive large-amplitude magneto-dynamics. Here we present a new type of SHO
+engineered to have the easy-plane anisotropy oriented normal to the film plane,
+enabling large-amplitude easy-plane dynamics driven by spin Hall current. Our
+experiments and micromagnetic simulations demonstrate that the desired
+easy-plane anisotropy can be achieved by tuning the magnetic shape anisotropy
+and perpendicular magnetic anisotropy in a nanowire SHO, leading to a
+significant enhancement of the generated microwave power. The easy-plane SHO
+experimentally demonstrated here is an ideal candidate for realization of a
+spintronic spiking neuron. Our results provide a new approach to design of
+high-power SHOs for wireless communications, neuromorphic computing, and
+microwave assisted magnetic recording.",2301.09228v1
+2023-02-08,Phase transitions and spin dynamics of the quasi-one dimensional Ising-like antiferromagnet BaCo$_{2}$V$_{2}$O$_{8}$ in a longitudinal magnetic field,"By combining inelastic neutron scattering and numerical simulations, we study
+the quasi-one dimensional Ising-like quantum antiferromagnet
+BaCo$_{2}$V$_{2}$O$_{8}$ in a longitudinal magnetic field applied along the
+magnetic anisotropy axis, which is also the chain direction. The external field
+closes the excitation gap due to the magnetic anisotropy, inducing a transition
+from the N\'eel ordered state to an incommensurate longitudinal spin density
+wave phase. If the field is increased further, another transition into a
+transverse antiferromagnetic phase takes place at 9 T due to the competition
+between longitudinal and transverse correlations. We numerically and
+experimentally show that the model of XXZ chains connected by a weak interchain
+interaction well reproduces this transition. We also calculate the dynamical
+susceptibility and demonstrate that it agrees quantitatively with inelastic
+neutron scattering measurements. In contrast to the abrupt change of magnetic
+ordering, the spectra do not change much at the transition at 9 T, and the spin
+dynamics can be described as a Tomonaga-Luttinger liquid. We also refine the
+modeling of BaCo$_{2}$V$_{2}$O$_{8}$ by including a four-site periodic term
+arising from the crystal structure which enables to account for an anomaly of
+the magnetic susceptibility appearing at 19 T as well as for the anticrossing
+observed in the inelastic neutron scattering spectra.",2302.03833v1
+2023-02-09,Latitudinal Dynamics and Sectoral Structure of the Solar Magnetic Field,"The study of the global structure of the large-scale magnetic field of the
+Sun is extremely important for creating a theoretical model of the dynamics of
+the Sun and predictions of the real situation in the helio- and
+geomagnetosphere. The purpose of the present study was to calculate the
+differential rotation period of a large-scale photospheric magnetic field, to
+study its behavior over time and to find out whether there is a sectoral
+structure of this field along the longitude. However, the choice of the
+coordinate system in which to search for it is far from unambiguous. This is
+closely related to the fact that the rotation of the Sun is differential in
+latitude and varies with depth and over time. Based on the observational data
+of the J. Wilcox Solar Observatory for three complete cycles of solar activity
+21, 22 and 23, the period of rotation of the magnetic field at various
+latitudes and its change in time were calculated. A uniquely stable over 30
+years longitude structure was found. It was determined that its speed of
+rotation coincides with the one with which the base of the convective shell
+rotates, that is, the structuring of the magnetic field of the Sun occurs in
+tachocline. This result clearly demonstrates the close connection of solar
+activity processes with the topology of magnetic fields, with their dynamics
+and depth stratification.",2302.04943v1
+2023-02-20,(Nonequilibrium) dynamics of diffusion processes with non-conservative drifts,"The nonequilibrium Fokker-Planck dynamics with a non-conservative drift
+field, in dimension $N\geq 2$, can be related with the non-Hermitian quantum
+mechanics in a real scalar potential $V$ and in a purely imaginary vector
+potential -$iA$ of real amplitude $A$. Since Fokker-Planck probability density
+functions may be obtained by means of Feynman's path integrals, the previous
+observation points towards a general issue of ""magnetically affine""
+propagators, possibly of quantum origin, in real and Euclidean time. In below
+we shall follow the $N=3$ ""magnetic thread"", within which one may keep under a
+computational control formally and conceptually different implementations of
+magnetism (or surrogate magnetism) in the dynamics of diffusion processes. We
+shall focus on interrelations (with due precaution to varied, not evidently
+compatible, notational conventions) of: (i) the pertinent non-conservatively
+drifted diffusions, (ii) the classic Brownian motion of charged particles in
+the (electro)magnetic field, (iii) diffusion processes arising within so-called
+Euclidean quantum mechanics (which from the outset employs non-Hermitian
+""magnetic"" Hamiltonians), (iv) limitations of the usefulness of the Euclidean
+map $\exp(-itH_{quant}) \rightarrow \exp(-tH_{Eucl})$, regarding the
+probabilistic significance of inferred (path) integral kernels in the
+description of diffusion processes.",2302.10154v5
+2023-04-29,Dynamics and reversible control of the vortex Bloch-point vortex domain wall in short cylindrical magnetic nanowires,"Fast and efficient switching of nanomagnets is one of the main challenges in
+the development of future magnetic memories. We numerically investigate the
+evolution of the static and dynamic spin wave (SW) magnetization in short
+(50-400 nm length and 120 nm diameter) cylindrical ferromagnetic nanowires,
+where competing single vortex (SV) and vortex domain wall with a Bloch point
+(BP-DW) magnetization configurations could be formed. For a limited nanowire
+length range (between 150 and 300 nm) we demonstrate a reversible microwave
+field induced (forward) and opposite spin currents (backwards) transitions
+between the topologically different SV and BP-DW states. By tuning the nanowire
+length, excitation frequency, the microwave pulse duration and the spin current
+values we show that the optimum (low power) manipulation of the BP-DW could be
+reached by a microwave excitation tuned to the main SW mode and for nanowire
+lengths around 230-250 nm, where single vortex domain wall magnetization
+reversal via nucleation and propagation of SV-DW takes place. An analytical
+model for dynamics of the Bloch point provides an estimation of the gyrotropic
+mode frequency close the one obtained via micromagnetic simulations. A
+practical implementation of the method on a device has been proposed involving
+microwave excitation and the generation of the opposite spin currents via spin
+orbit torque. Our findings open a new pathway for the creation of unforeseen
+topological magnetic memories.",2305.00346v1
+2023-08-03,A general flux-Based Circuit Theory for Superconducting Josephson Junction Circuits,"Superconducting quantum interference devices (SQUIDs), single flux-quantum
+(SFQ) logic circuits, and quantum Josephson junction circuits have been
+developed into a family of superconductor integrated circuit, and are widely
+applied for subtle magnetic-field measurements, energy-efficient computing, and
+quantum computing, respectively. They are Josephson junction networks composed
+of Josephson junctions and normal resistor-inductor-capacitor (RLC) components,
+working with the fluxoid-quantization principle and Josephson effects to
+achieve unique flux-modulated dynamics and characteristics; they react to the
+vector potential of magnetic fields rather than the electric potential.
+However, the conventional circuit diagrams and nodal analysis methods focus on
+the electric charges flowing though branches and nodes, ignoring dynamics of
+the magnetic fluxes flowing from loop to loop. This article introduces a
+general flux-based circuit theory to unify the analyses of Josephson junction
+circuits and normal RLC circuits. This theory presents a
+magnetic-flux-generator (MFG) concept to unify Josephson junctions and normal
+circuit elements, and abstract both Josephson junction circuits and normal RLC
+circuits as MFG network; it derives a general network equation to describe
+dynamics of Josephson junction circuits, and invents a kind of magnetic-flux
+flow (MFF) diagram to depict the working principles of magnetic-flux flows
+inside Josephson junction circuits. The flux-based theory is complementary to
+the conventional circuit theories in the design and analysis of superconductor
+integrated circuits.",2308.01693v1
+2023-10-14,"Chiral magnetism, lattice dynamics, and anomalous Hall conductivity in the novel V$_3$AuN antiferromagnetic antiperovskite","Antiferromagnetic antiperovskites, where magnetically active 3$d$ metal
+cations are placed in the octahedral corners of a perovskite structure, are in
+the spotlight due to their intertwined magnetic structure and topological
+properties. Especially their anomalous Hall conductivity, which can be
+controlled by applied strain and/or electric field, makes them highly
+attractive in different electronic applications. Here, we present the study and
+theoretical understanding of a new antiperovskite compound that can offer
+enormous opportunities in a broad set of applications. Using first-principles
+calculations, we investigated the structure, lattice dynamics, noncollinear
+magnetic ordering, and electronic behavior in the Vanadium-based antiperovskite
+V$_3$AuN. We found an antiperovskite structure centered on N similar to the
+Mn$_3A$N family as the structural ground state. In such a phase, a
+\emph{Pm$\bar{3}$m} ground state was found in contrast to the \emph{Cmcm}
+post-antiperovskite layered structure, as in the V$_3A$N, $A$ = Ga, Ge, As, and
+P. We studied the lattice dynamics and electronic properties, demonstrating its
+vibrational stability in the cubic structure and a chiral antiferromagnetic
+noncollinear ordering as a magnetic ground state. Finally, we found that the
+anomalous Hall conductivity, associated with the topological features induced
+by the magnetic symmetry, is $\sigma_{xy}$ = $-$291 S$\cdot$cm$^{-1}$
+($\sigma_{111}$ = $-$504 S$\cdot$cm$^{-1}$). The latter is the largest reported
+in the antiferromagnetic antiperovskite family of compounds.",2310.09616v1
+2024-02-01,Quantum phase transitions and composite excitations of antiferromagnetic quantum spin trimer chains in a magnetic field,"Motivated by recent advancements in theoretical and experimental studies on
+the high-energy excitations, we theoretically explore the quantum phase
+transitions and composite excitations of the antiferromagnetic trimer chains in
+a magnetic field using the exact diagonalization, density matrix
+renormalization group, time-dependent variational principle and cluster
+perturbation theory. We utilize the entanglement entropy to uncover the phase
+diagram, encompassing the XY-I, $1/3$ magnetization plateau, XY-II and
+ferromagnetic phases. The critical XY-I and XY-II phases are both described by
+the conformal field theory with the central charge $c \simeq 1$. We reveal the
+diverse features of spin dynamics in various phases by using the dynamical
+structure factor. In the weak intertrimer interaction regime, we identify the
+intermediate-energy and high-energy modes in the XY-I and $1/3$ magnetization
+plateau phases as the internal trimer excitations, corresponding to the
+propagation of doublon and quarton, respectively. Notably, the magnetic field
+splits the high-energy spectra into two branches labeled as the upper quarton
+and lower quarton. Furthermore, we also explore the spin dynamics of a
+trimerized model closely related to the quantum magnet \ce{Na_2Cu_3Ge_4O_12},
+and discuss the possibility of the quarton Bose-Einstein condensation. Our
+results can be verified in the inelastic neutron scattering experiments and
+provide deep insights for exploring the high-energy exotic excitations.",2402.00272v1
+2002-05-01,Recent Developments in Magnetic Dynamo Theory,"Some recent results and open issues in magnetic dynamo theory are addressed.
+The distinction between small-scale and mean-field dynamo (MFD) action in
+forced turbulent flows is emphasized. Though useful, the MFD has been
+controversial. This is partly due to concerns about its need for helically
+forced turbulence, but mainly because simple ""textbook"" treatments are
+kinematic and linear. The non-linear backreaction of the growing magnetic field
+has been suspected to prematurely quench MFD action. To resolve the
+controversy, we must first understand those non-linear MFDs which can be
+numerically simulated. Recently, there has been progress on this front. For
+simple MFDs in closed systems, dynamical quenching models that incorporate a
+transfer of magnetic helicity between small and large scales agree reasonably
+well with fully 3-D numerical periodic box simulations. Unresolved issues such
+as the quenching of turbulent diffusion and the additional physics needed to
+apply these results to real systems are also discussed herein. The following
+summarizes conceptual progress in describing mean-field magnetic energy growth
+in the simplest MFDs:
+  For a closed turbulent flow, the non-linear mean-field dynamo, is first fast
+and kinematic, then slow and dynamic, and magnetic helicity transfer makes it
+so.",0205002v2
+2002-07-22,A Cosmic Battery Reconsidered,"We revisit the problem of magnetic field generation in accretion flows onto
+black holes owing to the excess radiation force on electrons. This excess force
+may arise from the Poynting-Robertson effect.
+  Instead of a recent claim of the generation of dynamically important magnetic
+fields, we establish the validity of earlier results from 1977 which show only
+small magnetic fields are generated.
+  The radiative force causes the magnetic field to initially grow linearly with
+time. However, this linear growth holds for only a {\it restricted} time
+interval which is of the order of the accretion time of the matter.
+  The large magnetic fields recently found result from the fact that the linear
+growth is unrestricted.
+  A model of the Poynting-Robertson magnetic field generation close to the
+horizon of a Schwarzschild black hole is solved exactly using General
+Relativity, and the field is also found to be dynamically insignificant.
+  These weak magnetic fields may however be important as seed fields for
+dynamos.",0207476v1
+2002-07-23,A model of nonlinear evolution and saturation of the turbulent MHD dynamo,"The growth and saturation of magnetic field in conducting turbulent media
+with large magnetic Prandtl numbers are investigated. This regime is very
+common in low-density hot astrophysical plasmas. During the early (kinematic)
+stage, weak magnetic fluctuations grow exponentially and concentrate at the
+resistive scale, which lies far below the hydrodynamic viscous scale. The
+evolution becomes nonlinear when the magnetic energy is comparable to the
+kinetic energy of the viscous-scale eddies. A physical picture of the ensuing
+nonlinear evolution of the MHD dynamo is proposed. Phenomenological
+considerations are supplemented with a simple Fokker--Planck model of the
+nonlinear evolution of the magnetic-energy spectrum. It is found that, while
+the shift of the bulk of the magnetic energy from the subviscous scales to the
+velocity scales may be possible, it occurs very slowly -- at the resistive,
+rather than dynamical, time scale (for galaxies, this means that generation of
+large-scale magnetic fields cannot be explained by this mechanism). The role of
+Alfvenic motions and the implications for the fully developed isotropic MHD
+turbulence are discussed.",0207503v2
+2005-01-18,Plasma instabilities and magnetic-field growth in clusters of galaxies,"We show that under very general conditions, cluster plasmas threaded by weak
+magnetic fields are subject to very fast growing plasma instabilities driven by
+the anisotropy of the plasma pressure (viscous stress) with respect to the
+local direction of the magnetic field. Such an anisotropy will naturally arise
+in any weakly magnetized plasma that has low collisionality and is subject to
+stirring. The magnetic field must be sufficiently weak for the instabilities to
+occur, viz., beta>Re^{1/2}. The instabilities are captured by the extended MHD
+model with Braginskii viscosity. However, their growth rates are proportional
+to the wavenumber down to the ion gyroscale, so MHD equations with Braginskii
+viscosity are not well posed and a fully kinetic treatment is necessary. The
+instabilities can lead to magnetic fields in clusters being amplified from seed
+strength of ~10^{-18} G to dynamically important strengths of ~10 microG on
+cosmologically trivial time scales (~10^8 yr). The fields produced during the
+amplification stage are at scales much smaller than observed. Predicting the
+saturated field scale and structure will require a kinetic theory of magnetized
+cluster turbulence.",0501362v3
+2005-10-14,The Magnetic Field in the Star-forming Region Cepheus A from Water Maser Polarization Observations,"We present linear and circular polarization observations of the water masers
+in 4 distinct regions spread over 1x2 arcseconds around the HW2 high-mass young
+stellar object in the Cepheus A star-forming region. We find magnetic fields
+between 100-500 mG in the central maser region, which has been argued to trace
+a circumstellar disk. The masers further from HW2 have field strengths between
+30-100 mG. In all cases the magnetic field pressure is found to be similar to
+the dynamic pressure, indicating that the magnetic field is capable of
+controlling the outflow dynamics around HW2. In addition to several water maser
+complexes observed before, we also detect a new maser filament, ~1 arcsec (~690
+AU) East of HW2, which we interpret as a shocked region between the HW2 outflow
+and the surrounding medium. We detect a linear polarization gradient along the
+filament as well as a reversal of the magnetic field direction. This is thought
+to mark the transition between the magnetic field associated with the outflow
+and that found in the surrounding molecular cloud. In addition to the magnetic
+field we determine several other physical properties of the maser region,
+including density and temperatures as well as the maser beaming angles.",0510452v1
+2007-02-06,Magnetic Fields in Stellar Jets,"Although several lines of evidence suggest that jets from young stars are
+driven magnetically from accretion disks, existing observations of field
+strengths in the bow shocks of these flows imply that magnetic fields play only
+a minor role in the dynamics at these locations. To investigate this apparent
+discrepancy we performed numerical simulations of expanding magnetized jets
+with stochastically variable input velocities with the AstroBEAR MHD code.
+Because the magnetic field B is proportional to the density n within
+compression and rarefaction regions, the magnetic signal speed drops in
+rarefactions and increases in the compressed areas of velocity-variable flows.
+In contrast, B ~ n^0.5 for a steady-state conical flow with a toroidal field,
+so the Alfven speed in that case is constant along the entire jet. The
+simulations show that the combined effects of shocks, rarefactions, and
+divergent flow cause magnetic fields to scale with density as an intermediate
+power 1 > p > 0.5. Because p > 0.5, the Alfven speed in rarefactions decreases
+on average as the jet propagates away from the star. This behavior is extremely
+important to the flow dynamics because it means that a typical Alfven velocity
+in the jet close to the star is significantly larger than it is in the
+rarefactions ahead of bow shocks at larger distances, the one place where the
+field is a measurable quantity. We find that the observed values of weak fields
+at large distances are consistent with strong fields required to drive the
+observed mass loss close to the star. For a typical stellar jet the crossover
+point inside which velocity perturbations of 30 - 40 km/s no longer produce
+shocks is ~ 300 AU from the source.",0702174v1
+1995-12-14,Analytical and computational study of magnetization switching in kinetic Ising systems with demagnetizing fields,"An important aspect of real ferromagnetic particles is the demagnetizing
+field resulting from magnetostatic dipole-dipole interaction, which causes
+large particles to break up into domains. Sufficiently small particles,
+however, remain single-domain in equilibrium. This makes such small particles
+of particular interest as materials for high-density magnetic recording media.
+In this paper we use analytic arguments and Monte Carlo simulations to study
+the effect of the demagnetizing field on the dynamics of magnetization
+switching in two-dimensional, single-domain, kinetic Ising systems. For systems
+in the ``Stochastic Region,'' where magnetization switching is on average
+effected by the nucleation and growth of fewer than two well-defined critical
+droplets, the simulation results can be explained by the dynamics of a simple
+model in which the free energy is a function only of magnetization. In the
+``Multi-Droplet Region,'' a generalization of Avrami's Law involving a
+magnetization-dependent effective magnetic field gives good agreement with our
+simulations.",9512110v1
+2005-03-24,Fast magnetization switching of Stoner particles: A nonlinear dynamics picture,"The magnetization reversal of Stoner particles is investigated from the point
+of view of nonlinear dynamics within the Landau-Lifshitz-Gilbert formulation.
+The following results are obtained. 1) We clarify that the so-called
+Stoner-Wohlfarth (SW) limit becomes exact when damping constant is infinitely
+large. Under the limit, the magnetization moves along the steepest energy
+descent path. The minimal switching field is the one at which there is only one
+stable fixed point in the system. 2) For a given magnetic anisotropy, there is
+a critical value for the damping constant, above which the minimal switching
+field is the same as that of the SW-limit. 3) We illustrate how fixed points
+and their basins change under a field along different directions. This change
+explains well why a non-parallel field gives a smaller minimal switching field
+and a short switching time. 4) The field of a ballistic magnetization reversal
+should be along certain direction window in the presence of energy dissipation.
+The width of the window depends on both of the damping constant and the
+magnetic anisotropy. The upper and lower bounds of the direction window
+increase with the damping constant. The window width oscillates with the
+damping constant for a given magnetic anisotropy. It is zero for both zero and
+infinite damping. Thus, the perpendicular field configuration widely employed
+in the current experiments is not the best one since the damping constant in a
+real system is far from zero.",0503594v1
+2005-06-09,Magnetic Quantum Phase Transitions in Kondo Lattices,"The identification of magnetic quantum critical points in heavy fermion
+metals has provided an ideal setting for experimentally studying quantum
+criticality. Motivated by these experiments, considerable theoretical efforts
+have recently been devoted to reexamine the interplay between Kondo screening
+and magnetic interactions in Kondo lattice systems. A local quantum critical
+picture has emerged, in which magnetic interactions suppress Kondo screening
+precisely at the magnetic quantum critical point (QCP). The Fermi surface
+undergoes a large reconstruction across the QCP and the coherence scale of the
+Kondo lattice vanishes at the QCP. The dynamical spin susceptibility exhibits
+$\omega/T$ scaling and non-trivial exponents describe the temperature and
+frequency dependence of various physical quantities. These properties are to be
+contrasted with the conventional spin-density-wave (SDW) picture, in which the
+Kondo screening is not suppressed at the QCP and the Fermi surface evolves
+smoothly across the phase transition. In this article we discuss recent
+microscopic studies of Kondo lattices within an extended dynamical mean field
+theory (EDMFT). We summarize the earlier work based on an analytical
+$\epsilon$-expansion renormalization group method, and expand on the more
+recent numerical results. We also discuss the issues that have been raised
+concerning the magnetic phase diagram. We show that the zero-temperature
+magnetic transition is second order when double counting of the RKKY
+interactions is avoided in EDMFT.",0506207v2
+2008-02-29,Indirect exchange coupling between localized magnetic moments in carbon nanotubes: a dynamic approach,"Magnetic moments dilutely dispersed in a metallic host tend to be coupled
+through the conduction electrons of the metal. This indirect exchange coupling,
+known to occur for a variety of magnetic materials embedded in several
+different metallic structures, is of rather long range, especially for
+low-dimensional structures like carbon nanotubes. Motivated by recent claims
+that the indirect coupling between magnetic moments in precessional motion has
+a much longer range than its static counterpart, here we consider how magnetic
+atoms adsorbed to the walls of a metallic nanotube respond to a time-dependent
+perturbation that induces their magnetic moments to precess. By calculating the
+frequency-dependent spin susceptibility we are able to identify resonant peaks
+whose respective widths provide information about the dynamic aspect of the
+indirect exchange coupling. We show that by departing from a purely static
+representation to another in which the moments are allowed to precess, we
+change from what is already considered a long range interaction to another
+whose range is far superior. In other words, localized magnetic moments
+embedded in a metallic structure can feel each other's presence more easily
+when they are set in precessional motion. We argue that such an effect can have
+useful applications leading to large-scale spintronics devices.",0803.0028v1
+2008-03-24,Effect of static and dynamic disorder on electronic transport of $RCo_2$ compounds: a study of $Ho(Al_xCo_{1-x})_2$ alloys,"We present experimental results on thermoelectric power ({\em S}) and
+electrical resistivity ($\rho $) of pseudobinary alloys
+Ho(Al$_x$Co$_{1-x}$)$_2$ ($0 \leq x \leq 0.1 $), in the temperature range 4.2 K
+to 300 K. The work focuses on the effects of static (induced by alloying) and
+dynamic (induced by temperature) disorder on the magnetic state and electronic
+transport in a metallic system with itinerant metamagnetic instability. Spatial
+fluctuations of the local magnetic susceptibility in the alloys lead to a
+development of a partially ordered magnetic ground state of the itinerant 3d
+electron system. This results in a strong increase of the residual resistivity
+and a suppression of the temperature-dependent resistivity. Thermopower
+exhibits a complex temperature variation in both the magnetically ordered and
+in the paramagnetic state. This complex temperature variation is referred to
+the electronic density of states features in vicinity of Fermi energy and to
+the interplay of magnetic and impurity scattering. Our results indicate that
+the magnetic enhancement of the Co 3d-band in RCo$_{\rm 2}$--based alloys upon
+a substitution of Co by non-magnetic elements is mainly related to a
+progressive localization of the Co -- 3d electrons caused by disorder. We show
+that the magnitude of the resistivity jump at the Curie temperature for
+RCo$_{\rm 2}$ compounds exhibiting a first order phase transition is a
+non-monotonic function of the Curie temperature due to a saturation of the
+3d--band spin fluctuation magnitude at high temperatures.",0803.3380v3
+2008-04-29,A new general relativistic magnetohydrodynamics code for dynamical spacetimes,"We present a new numerical code which solves the general relativistic
+magneto-hydrodynamics (GRMHD) equations coupled to the Einstein equations for
+the evolution of a dynamical spacetime within the conformally-flat
+approximation. This code has been developed with the main objective of studying
+astrophysical scenarios in which both, high magnetic fields and strong
+gravitational fields appear, such as the magneto-rotational collapse of stellar
+cores, the collapsar model of GRBs, and the evolution of neutron stars. The
+code is based on an existing and thoroughly tested purely hydrodynamics code
+and on its extension to accommodate weakly magnetized fluids (passive magnetic
+field approximation). The numerical code we present here is based on
+high-resolution shock-capturing schemes to solve the GRMHD equations together
+with the flux constraint transport method to ensure the solenoidal condition of
+the magnetic field. Since the astrophysical applications envisaged do not
+deviate much from spherical symmetry, the conformal flatness condition
+approximation is used for the formulation of the Einstein equations. In
+addition, the code can handle several equations of state, from simple
+analytical expressions to microphysical tabulated ones. In this paper we
+present stringent tests of our new GRMHD numerical code, which show its ability
+to handle all aspects appearing in the astrophysical scenarios for which the
+code is intended, namely relativistic shocks, highly magnetized fluids, and
+equilibrium configurations of magnetized neutron stars. As an application,
+magneto-rotational core collapse simulations of a realistic progenitor are
+presented, comparing the results with our previous finding in the passive
+magnetic field approximation.",0804.4572v2
+2008-07-23,A key role for unusual spin dynamics in ferropnictides,"The 2008 discovery of superconducting ferropnictides with Tc~26K-56K
+introduced a new family of materials into the category of high Tc
+superconductors. The ongoing project of understanding the superconducting
+mechanism and pairing symmetry has already revealed a complicated and often
+contradictory underlying picture of the structural and magnetic properties.
+There is an almost unprecedented sensitivity of the calculated magnetism and
+Fermi surface to structural details that prohibits correspondence with
+experiment. Furthermore, experimental probes of the order parameter symmetry
+are in surprisingly strong disagreement, even considering the relative
+immaturity of the field. Here we outline all of the various and seemingly
+contradictory evidences, both theoretical and experimental, and show that they
+can be rectified if the system is assumed to be highly magnetic with a spin
+density wave that is well-defined but with magnetic twin and anti-phase
+boundaries that are dynamic on the time-scale of experiments. Under this
+assumption, we find that our calculations can accurately reproduce even very
+fine details of the structure, and a natural explanation for the temperature
+separation of structural and magnetic transitions is provided. Thus, our theory
+restores agreement between experiment and theory in crucial areas, making
+further cooperative progress possible on both fronts. We believe that
+fluctuating magnetic domains will be an essential component of unravelling the
+interplay between magnetic interactions and superconductivity in these newest
+high Tc superconductors.",0807.3737v1
+2008-11-07,Electrically driven magnetization of diluted magnetic semiconductors actuated by Overhauser effect,"It is well-known that the Curie temperature, and hence the magnetization, in
+diluted magnetic semiconductor (DMS) like Ga$_{1-x}$Mn$_x$As can be controlled
+by changing the equilibrium density of holes in the material. Here, we propose
+that even with a constant hole density, large changes in the magnetization can
+be obtained with a relatively small imbalance in the quasi-Fermi levels for
+up-spin and down-spin electrons. We show, by coupling mean field theory of
+diluted magnetic semiconductor ferromagnetism with master equations governing
+the Mn spin-dynamics, that a mere splitting of the up-spin and down-spin
+quasi-Fermi levels by 0.1 meV will produce the effect of an external magnetic
+field as large as 1 T as long as the alternative relaxation paths for Mn spins
+(i.e. spin-lattice relaxation) can be neglected. The physics is similar to the
+classic Overhauser effect, also called the dynamic nuclear polarization, with
+the Mn impurities playing the role of the nucleus. We propose that a lateral
+spin-valve structure in anti-parallel configuration with a DMS as the channel
+can be used to demonstrate this effect as quasi-Fermi level splitting of such
+magnitude, inside the channel of similar systems, have already been
+experimentally demonstrated to produce polarization of paramagnetic impurity
+spins.",0811.1225v2
+2010-06-15,Applications of Magnetic PsiDO Techniques to Space-adiabatic Perturbation Theory,"In this review, we show how advances in the theory of magnetic
+pseudodifferential operators (magnetic $\Psi$DO) can be put to good use in
+space-adiabatic perturbation theory (SAPT). As a particular example, we extend
+results of [PST03] to a more general class of magnetic fields: we consider a
+single particle moving in a periodic potential which is subjectd to a weak and
+slowly-varying electromagnetic field. In addition to the semiclassical
+parameter $\eps \ll 1$ which quantifies the separation of spatial scales, we
+explore the influence of additional parameters that allow us to selectively
+switch off the magnetic field.
+  We find that even in the case of magnetic fields with components in
+$C_b^{\infty}(\R^d)$, e. g. for constant magnetic fields, the results of
+Panati, Spohn and Teufel hold, i.e. to each isolated family of Bloch bands,
+there exists an associated almost invariant subspace of $L^2(\R^d)$ and an
+effective hamiltonian which generates the dynamics within this almost invariant
+subspace. In case of an isolated non-degenerate Bloch band, the full quantum
+dynamics can be approximated by the hamiltonian flow associated to the
+semiclassical equations of motion found in [PST03].",1006.3103v4
+2010-10-25,Study on the large scale dynamo transition,"Using the magnetohydrodynamic (MHD) description, we develop a nonlinear
+dynamo model that couples the evolution of the large scale magnetic field with
+turbulent dynamics of the plasma at small scale by electromotive force (e.m.f.)
+in the induction equation at large scale. The nonlinear behavior of the plasma
+at small scale is described by using a MHD shell model for velocity field and
+magnetic field fluctuations.The shell model allow to study this problem in a
+large parameter regime which characterizes the dynamo phenomenon in many
+natural systems and which is beyond the power of supercomputers at today. Under
+specific conditions of the plasma turbulent state, the field fluctuations at
+small scales are able to trigger the dynamo instability. We study this
+transition considering the stability curve which shows a strong decrease in the
+critical magnetic Reynolds number for increasing inverse magnetic Prandlt
+number $\textrm{Pm}^{-1}$ in the range $[10^{-6},1]$ and slows an increase in
+the range $[1,10^{8}]$. We also obtain hysteretic behavior across the dynamo
+boundary reveling the subcritical nature of this transition. The system,
+undergoing this transition, can reach different dynamo regimes, depending on
+Reynolds numbers of the plasma flow. This shows the critical role that the
+turbulence plays in the dynamo phenomenon. In particular the model is able to
+reproduce the dynamical situation in which the large-scale magnetic field jumps
+between two states which represent the opposite polarities of the magnetic
+field, reproducing the magnetic reversals as observed in geomagnetic dynamo and
+in the VKS experiments.",1010.5213v1
+2011-02-25,Dynamo in the Intra-Cluster Medium: Simulation of CGL-MHD Turbulent Dynamo,"The standard magnetohydrodynamic (MHD) description of the plasma in the hot,
+magnetized gas of the intra-cluster (ICM) medium is not adequate because it is
+weakly collisional. In such collisionless magnetized gas, the microscopic
+velocity distribution of the particles is not isotropic, giving rise to kinetic
+effects on the dynamical scales. These kinetic effects could be important in
+understanding the turbulence, as so as the amplification and maintenance of the
+magnetic fields in the ICM. It is possible to formulate fluid models for
+collisonless or weakly collisional gas by introducing modifications in the MHD
+equations. These models are often referred as kinetic MHD (KMHD). Using a KMHD
+model based on the CGL-closure, which allows the adiabatic evolution of the two
+components of the pressure tensor (the parallel and perpendicular components
+with respect to the local magnetic field), we performed 3D numerical
+simulations of forced turbulence in order to study the amplification of an
+initially weak seed magnetic field. We found that the growth rate of the
+magnetic energy is comparable to that of the ordinary MHD turbulent dynamo, but
+the magnetic energy saturates in a level smaller than of the MHD case. We also
+found that a necessary condition for the dynamo works is to impose limits to
+the anisotropy of the pressure.",1102.5139v1
+2012-08-07,Magnetar Giant Flares --- Flux Rope Eruptions in Multipolar Magnetospheric Magnetic Fields,"We address a primary question regarding the physical mechanism that triggers
+the energy release and initiates the onset of eruptions in the magnetar
+magnetosphere. A self-consistent stationary, axisymmetric model of the magnetar
+magnetosphere is constructed based on a force-free magnetic field configuration
+which contains a helically twisted force-free flux rope. Given the complex
+multipolar magnetic fields at the magnetar surface, we also develop a
+convenient numerical scheme to solve the GS equation. Depending on the surface
+magnetic field polarity, there exist two kinds of magnetic field
+configurations, inverse and normal. For these two kinds of configurations,
+variations of the flux rope equilibrium height in response to gradual surface
+physical processes, such as flux injections and crust motions, are carefully
+examined. We find that equilibrium curves contain two branches, one represents
+a stable equilibrium branch, the other an unstable equilibrium branch. As a
+result, the evolution of the system shows a catastrophic behavior: when the
+magnetar surface magnetic field evolves slowly, the height of flux rope would
+gradually reach a critical value beyond which stable equilibriums can no longer
+be maintained. Subsequently the flux rope would lose equilibrium and the
+gradual quasi-static evolution of the magnetar magnetosphere will be replaced
+by a fast dynamical evolution. In addition to flux injections, the relative
+motion of active regions would give rise to the catastrophic behavior and lead
+to magnetic eruptions as well. We propose that a gradual process could lead to
+a sudden release of magnetosphere energy on a very short dynamical timescale,
+without being initiated by a sudden fracture in the crust of the magnetar. Some
+implications of our model are also discussed.",1208.1459v1
+2012-10-19,Effects of Strong Magnetic Fields on Photoionised Clouds,"Simulations are presented of the photoionisation of three dense gas clouds
+threaded by magnetic fields, showing the dynamical effects of different initial
+magnetic field orientations and strengths. For moderate magnetic field
+strengths the initial radiation-driven implosion phase is not strongly affected
+by the field geometry, and the photoevaporation flows are also similar. Over
+longer timescales, the simulation with an initial field parallel to the
+radiation propagation direction (parallel field) remains basically
+axisymmetric, whereas in the simulation with a perpendicular initial field the
+pillar of neutral gas fragments in a direction aligned with the magnetic field.
+For stronger initial magnetic fields, the dynamics in all gas phases are
+affected at all evolutionary times. In a simulation with a strong initially
+perpendicular field, photoevaporated gas forms filaments of dense ionised gas
+as it flows away from the ionisation front along field lines. These filaments
+are potentially a useful diagnostic of magnetic field strengths in H II regions
+because they are very bright in recombination line emission. In the strong
+parallel field simulation the ionised gas is constrained to flow back towards
+the radiation source, shielding the dense clouds and weakening the ionisation
+front, eventually transforming it to a recombination front.",1210.5385v1
+2013-11-07,Spin-Orbit Torques and Anisotropic Magnetization Damping in Skyrmion Crystals,"The length scale of the magnetization gradients in chiral magnets is
+determined by the relativistic Dzyaloshinskii-Moriya interaction. Thus, even
+conventional spin-transfer torques are controlled by the relativistic
+spin-orbit coupling in these systems, and additional relativistic corrections
+to the current-induced torques and magnetization damping become important for a
+complete understanding of the current-driven magnetization dynamics. We
+theoretically study the effects of reactive and dissipative homogeneous
+spin-orbit torques and anisotropic damping on the current-driven skyrmion
+dynamics in cubic chiral magnets. Our results demonstrate that spin-orbit
+torques play a significant role in the current-induced skyrmion velocity. The
+dissipative spin-orbit torque generates a relativistic Magnus force on the
+skyrmions, whereas the reactive spin-orbit torque yields a correction to both
+the drift velocity along the current direction and the transverse velocity
+associated with the Magnus force. The spin-orbit torque corrections to the
+velocity scale linearly with the skyrmion size, which is inversely proportional
+to the spin-orbit coupling. Consequently, the reactive spin-orbit torque
+correction can be the same order of magnitude as the non-relativistic
+contribution. More importantly, the dissipative spin-orbit torque can be the
+dominant force that causes a deflected motion of the skyrmions if the torque
+exhibits a linear or quadratic relationship with the spin-orbit coupling. In
+addition, we demonstrate that the skyrmion velocity is determined by
+anisotropic magnetization damping parameters governed by the skyrmion size.",1311.1778v1
+2014-03-11,Non-linear galactic dynamos: A toolbox,"We compare various models and approximations for non-linear mean-field
+dynamos in disc galaxies to assess their applicability and accuracy, and thus
+to suggest a set of simple solutions suitable to model the large-scale galactic
+magnetic fields in various contexts. The dynamo saturation mechanisms
+considered are the magnetic helicity balance involving helicity fluxes (the
+dynamical $\alpha$-quenching) and an algebraic $\alpha$-quenching. The
+non-linear solutions are then compared with the marginal kinematic and
+asymptotic solutions. We also discuss the accuracy of the no-$z$ approximation.
+Although these tools are very different in the degree of approximation and
+hence complexity, they all lead to remarkably similar solutions for the mean
+magnetic field. In particular, we show that the algebraic $\alpha$-quenching
+non-linearity can be obtained from a more physical dynamical $\alpha$-quenching
+model in the limit of nearly azimuthal magnetic field. This suggests, for
+instance, that earlier results on galactic disc dynamos based on the simple
+algebraic non-linearity are likely to be reliable, and that estimates based on
+simple, even linear models are often a good starting point. We suggest improved
+no-$z$ and algebraic $\alpha$-quenching models, and also incorporate galactic
+outflows into a simple analytical dynamo model to show that the outflow can
+produce leading magnetic spirals near the disc surface. The simple dynamo
+models developed are applied to estimate the magnetic pitch angle and the
+arm-interarm contrast in the saturated magnetic field strength for realistic
+parameter values.",1403.2562v2
+2014-08-03,Nonlinear Force-Free Field Modeling of the Solar Magnetic Carpet and Comparison with SDO/HMI and Sunrise/IMaX Observations,"In the quiet solar photosphere, the mixed polarity fields form a magnetic
+carpet, which continuously evolves due to dynamical interaction between the
+convective motions and magnetic field. This interplay is a viable source to
+heat the solar atmosphere. In this work, we used the line-of-sight (LOS)
+magnetograms obtained from the Helioseismic and Magnetic Imager (HMI) on the
+\textit{Solar Dynamics Observatory} (\textit{SDO}), and the Imaging
+Magnetograph eXperiment (IMaX) instrument on the \textit{Sunrise} balloon-borne
+observatory, as time dependent lower boundary conditions, to study the
+evolution of the coronal magnetic field. We use a magneto-frictional relaxation
+method, including hyperdiffusion, to produce time series of three-dimensional
+(3D) nonlinear force-free fields from a sequence of photospheric LOS
+magnetograms. Vertical flows are added up to a height of 0.7 Mm in the modeling
+to simulate the non-force-freeness at the photosphere-chromosphere layers.
+Among the derived quantities, we study the spatial and temporal variations of
+the energy dissipation rate, and energy flux. Our results show that the energy
+deposited in the solar atmosphere is concentrated within 2 Mm of the
+photosphere and there is not sufficient energy flux at the base of the corona
+to cover radiative and conductive losses. Possible reasons and implications are
+discussed. Better observational constraints of the magnetic field in the
+chromosphere are crucial to understand the role of the magnetic carpet in
+coronal heating.",1408.0497v1
+2014-12-01,Experimental and Numerical Understanding of Localized Spin Wave Mode Behavior in Broadly Tunable Spatially Complex Magnetic Configurations,"Spin wave modes confined in a ferromagnetic film by the spatially
+inhomogeneous magnetic field generated by a scanned micromagnetic tip of a
+ferromagnetic resonance force microscope (FMRFM) enable microscopic imaging of
+the internal fields and spin dynamics in nanoscale magnetic devices. Here we
+report a detailed study of spin wave modes in a thin ferromagnetic film
+localized by magnetic field configurations frequently encountered in FMRFM
+experiments, including geometries in which the probe magnetic moment is both
+parallel and antiparallel to the applied uniform magnetic field. We demonstrate
+that characteristics of the localized modes, such as resonance field and
+confinement radius, can be broadly tuned by controlling the orientation of the
+applied field relative to the film plane. Micromagnetic simulations accurately
+reproduce our FMRFM spectra allowing quantitative understanding of the
+localized modes. Our results reveal a general method of generating tightly
+confined spin wave modes in various geometries with excellent spatial
+resolution that significantly facilitates the broad application of FMRFM. This
+paves the way to imaging of magnetic properties and spin wave dynamics in a
+variety of contexts for uncovering new physics of nanoscale spin excitations.",1412.0726v1
+2015-03-24,Spin dynamics and frequency dependence of magnetic damping study in soft ferromagnetic FeTaC film with a stripe domain structure,"Perpendicular magnetic anisotropy (PMA) and low magnetic damping are the key
+factors for the free layer magnetization switching by spin transfer torque
+technique in magnetic tunnel junction devices. The magnetization precessional
+dynamics in soft ferromagnetic FeTaC thin film with a stripe domain structure
+was explored in broad band frequency range by employing micro-strip
+ferromagnetic resonance technique. The polar angular variation of resonance
+field and linewidth at different frequencies have been analyzed numerically
+using Landau-Lifshitz-Gilbert equation by taking into account the total free
+energy density of the film. The numerically estimated parameters Land\'{e}
+$g$-factor, PMA constant, and effective magnetization are found to be 2.1,
+2$\times10^{5}$ erg/cm$^{3}$ and 7145 Oe, respectively. The frequency
+dependence of Gilbert damping parameter ($\alpha$) is evaluated by considering
+both intrinsic and extrinsic effects into the total linewidth analysis. The
+value of $\alpha$ is found to be 0.006 at 10 GHz and it increases with
+decreasing precessional frequency.",1503.07043v5
+2015-05-07,"Magnetization relaxation, critical current density and vortex dynamics in a Ba$_{0.66}$K$_{0.32}$BiO$_{3+δ}$ single crystal","We have conducted extensive investigations on the magnetization and its
+dynamical relaxation on a Ba$_{0.66}$K$_{0.32}$BiO$_{3+\delta}$ single crystal.
+It is found that the magnetization relaxation rate is rather weak compared with
+that in the cuprate superconductors, indicating a higher collective vortex
+pinning potential (or activation energy), although the intrinsic pinning
+potential $U_\mathrm{c}$ is weaker. Detailed analysis leads to the following
+discoveries: (1) A second-peak effect on the magnetization-hysteresis-loop was
+observed in a very wide temperature region, ranging from 2K to 24K. Its general
+behavior looks like that in YBa$_2$Cu$_3$O$_7$; (2) Associated with the second
+peak effect, the magnetization relaxation rate is inversely related to the
+transient superconducting current density $J_\mathrm{s}$ revealing a quite
+general and similar mechanism for the second peak effect in many high
+temperature superconductors; (3) A detailed analysis based on the collective
+creep model reveals a large glassy exponent $\mu$ and a small intrinsic pinning
+potential $U_\mathrm{c}$; (4) Investigation on the volume pinning force density
+shows that the data can be scaled to the formula $F_{p}\propto b^p(1-b)^q$ with
+$p=2.79$ and $q=3.14$, here $b$ is the reduced magnetic field to the
+irreversible magnetic field. The maximum normalized pinning force density
+appears near $b\approx0.47$. Finally, a vortex phase diagram is drawn for
+showing the phase transitions or crossovers between different vortex phases.",1505.01717v1
+2015-11-23,Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser,"X-ray magnetic circular dichroism spectroscopy using an X-ray free electron
+laser is demonstrated with spectra over the Fe L$_{3,2}$-edges. This new
+ultrafast time-resolved capability is then applied to a fluence-dependent study
+of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in
+a GdFeCo thin film above its magnetization compensation temperature. At the
+magnetic switching fuence, we corroborate the existence of a transient
+ferromagnetic-like state. The timescales of the dynamics, however, are longer
+than previously observed below the magnetization compensation temperature.
+Above and below the switching fluence range, we observe secondary
+demagnetization with about 5 ps timescales. This indicates that the spin
+thermalization takes longer than 5 ps.",1511.07372v1
+2016-07-14,Spin dynamics of diamond nitrogen-vacancy centres at the ground state level anti-crossing and all-optical low frequency magnetic field sensing,"We investigate the photo-induced spin dynamics of single nitrogen-vacancy
+(NV) centres in diamond near the electronic ground state level anti-crossing
+(GSLAC), which occurs at an axial magnetic field around 1024 G. Using optically
+detected magnetic resonance spectroscopy, we first find that the electron spin
+transition frequency can be tuned down to 100 kHz for the \NV{14} centre, while
+for the \NV{15} centre the transition strength vanishes for frequencies below
+about 2 MHz owing to the GSLAC level structure. Using optical pulses to prepare
+and readout the spin state, we observe coherent spin oscillations at 1024 G for
+the \NV{14}, which originate from spin mixing induced by residual transverse
+magnetic fields. This effect is responsible for limiting the smallest
+observable transition frequency, which can span two orders of magnitude from
+100 kHz to tens of MHz depending on the local magnetic noise. A similar feature
+is observed for the \NV{15} centre at 1024 G. As an application of these
+findings, we demonstrate all-optical detection and spectroscopy of
+externally-generated fluctuating magnetic fields at frequencies from 8 MHz down
+to 500 kHz, using a \NV{14} centre. Since the Larmor frequency of most nuclear
+spin species lies within this frequency range near the GSLAC, these results
+pave the way towards all-optical, nanoscale nuclear magnetic resonance
+spectroscopy, using longitudinal spin cross-relaxation.",1607.04006v1
+2016-07-20,Magnetic Field Amplification During the Common Envelope Phase,"During the common envelope (CE) phase, a giant star in a binary system
+overflows its Roche lobe and unstable mass transfer leads to a spiral-in of the
+companion, resulting in a close binary system or in a merger of the stellar
+cores. Dynamo processes during the CE phase have been proposed as a mechanism
+to generate magnetic fields that are important for forming magnetic white
+dwarfs (MWDs) and for shaping planetary nebulae. Here, we present the first
+magnetohydrodynamics simulations of the dynamical spiral-in during a CE phase.
+We find that magnetic fields are strongly amplified in the accretion stream
+around the $1M_\odot$ companion as it spirals into the envelope of a $2M_\odot$
+RG. This leads to field strengths of 10 to 100 kG throughout the envelope after
+120 d. The magnetic field amplification is consistent with being driven by the
+magnetorotational instability. The field strengths reached in our simulation
+make the magnetic field interesting for diagnostic purposes, but they are
+dynamically irrelevant. They are also too small to explain the formation of the
+highest fields found in MWDs, but may be relevant for luminous red novae, and
+detecting magnetic fields in these events would support the scenario as
+proposed here.",1607.05996v1
+2016-08-05,Optical determination of the Neel vector in a CuMnAs thin-film antiferromagnet,"Recent breakthroughs in electrical detection and manipulation of
+antiferromagnets have opened a new avenue in the research of non-volatile
+spintronic devices. Antiparallel spin sublattices in antiferromagnets,
+producing zero dipolar fields, lead to the insensitivity to magnetic field
+perturbations, multi-level stability, ultra-fast spin dynamics and other
+favorable characteristics which may find utility in fields ranging from
+magnetic memories to optical signal processing. However, the absence of a net
+magnetic moment and the ultra-short magnetization dynamics timescales make
+antiferromagnets notoriously difficult to study by common magnetometers or
+magnetic resonance techniques. In this paper we demonstrate the experimental
+determination of the Neel vector in a thin film of antiferromagnetic CuMnAs
+which is the prominent material used in the first realization of
+antiferromagnetic memory chips. We employ a femtosecond pump-probe
+magneto-optical experiment based on magnetic linear dichroism. This table-top
+optical method is considerably more accessible than the traditionally employed
+large scale facility techniques like neutron diffraction and X-ray magnetic
+dichroism measurements. This optical technique allows an unambiguous direct
+determination of the Neel vector orientation in thin antiferromagnetic films
+utilized in devices directly from measured data without fitting to a
+theoretical model.",1608.01941v1
+2016-08-25,"Charged dust grain dynamics subject to solar wind, Poynting-Robertson drag, and the interplanetary magnetic field","We investigate the combined effect of solar wind, Poynting-Robertson drag,
+and the frozen-in interplanetary magnetic field on the motion of charged dust
+grains in our solar system. For this reason we derive a secular theory of
+motion by the means of averaging method and validate it with numerical
+simulations of the un-averaged equations of motions. The theory predicts that
+the secular motion of charged particles is mainly affected by the z-component
+of the solar magnetic axis, or the normal component of the interplanetary
+magnetic field. The normal component of the interplanetary magnetic field leads
+to an increase or decrease of semi-major axis depending on its functional form
+and sign of charge of the dust grain. It is generally accepted that the
+combined effects of solar wind and photon absorption and re-emmision
+(Poynting-Robertson drag) lead to a decrease in semi-major axis on secular time
+scales. On the contrary, we demonstrate that the interplanetary magnetic field
+may counteract these drag forces under certain circumstances. We derive a
+simple relation between the parameters of the magnetic field, the physical
+properties of the dust grain as well as the shape and orientation of the
+orbital ellipse of the particle, which is a necessary conditions for the
+stabilization in semi-major axis.",1608.07040v1
+2017-01-27,The nature of spin excitations in the one-third magnetization plateau phase of Ba$_3$CoSb$_2$O$_9$,"Magnetization plateaus in quantum magnets---where bosonic quasiparticles
+crystallize into emergent spin superlattices---are spectacular yet simple
+examples of collective quantum phenomena escaping classical description. While
+magnetization plateaus have been observed in a number of spin-1/2
+antiferromagnets, the description of their magnetic excitations remains an open
+theoretical and experimental challenge. Here, we investigate the dynamical
+properties of the triangular-lattice spin-1/2 antiferromagnet
+Ba$_3$CoSb$_2$O$_9$ in its one-third magnetization plateau phase using a
+combination of nonlinear spin-wave theory and neutron scattering measurements.
+The agreement between our theoretical treatment and the experimental data
+demonstrates that magnons behave semiclassically in the plateau in spite of the
+purely quantum origin of the underlying magnetic structure. This allows for a
+quantitative determination of Ba$_3$CoSb$_2$O$_9$ exchange parameters. We
+discuss the implication of our results to the deviations from semiclassical
+behavior observed in zero-field spin dynamics of the same material and conclude
+they must have an intrinsic origin.",1701.07971v4
+2017-02-13,Strain-mediated magnetoelectric effect for the electric-field control of magnetic states in nanomagnets,"Electric-field control of magnetism without electric currents potentially
+revolutionizes spintronics towards ultralow power. Here by using mechanically
+coupled phase field simulations, we computationally demonstrate the application
+of the strain-mediated magnetoelectric effect for the electric-field control of
+magnetic states in heterostructure. In the model heterostructure constituted of
+the soft nanomagnet Co and the piezoelectric substrate PMN-PT, both the
+volatility of magnetic states and the magnetization switching dynamics excited
+by the electric field are explored. It is found that an electric field can
+drive the single-domain nanomagnet into an equilibrium vortex state. The
+nanomagnet remains in the vortex state even after removing the electric field
+or applying a reverse electric field, i.e. the vortex state is extremely stable
+and nonvolatile. Only by utilizing the precessional magnetization dynamics, the
+180$^\circ$ magnetization switching is possible in small-sized nanomagnets
+which are free of the stable vortex state. Electric-field pulses can realize
+the deterministic 180$^\circ$ switching if the electric-field magnitude, pulse
+width, and ramp time are carefully designed. The minimum switching time is
+found to be less than 10 ns. These results provide useful information for the
+design of low-power, reliable, and fast electric-field-controlled spintronics.",1702.03672v2
+2017-04-02,Effect of strong magnetic fields on the crust-core transition and inner crust of neutron stars,"The Vlasov equation is used to determine the dispersion relation for the
+eigenmodes of magnetized nuclear and neutral stellar matter, taking into
+account the anomalous magnetic moment of nucleons. The formalism is applied to
+the determination of the dynamical spinodal section, a quantity that gives a
+good estimation of the crust-core transition in neutron stars. We study the
+effect of strong magnetic fields, of the order of $10^{15}-10^{17}$ G, on the
+extension of the crust of magnetized neutron stars. The dynamical instability
+region of neutron-proton-electron ($npe$) matter at subsaturation densities is
+determined within a relativistic mean field model. It is shown that a strong
+magnetic field has a large effect on the instability region, defining the
+crust-core transition as a succession of stable and unstable regions due to the
+opening of new Landau levels. The effect of the anomalous magnetic moment is
+non-negligible for fields larger than 10$^{15}$ G. The complexity of the crust
+at the transition to the core and the increase of the crust thickness may have
+direct impact on the properties of neutrons stars related with the crust.",1704.00375v1
+2017-04-21,Time- and spatially-resolved magnetization dynamics driven by spin-orbit torques,"Current-induced spin-orbit torques (SOTs) represent one of the most effective
+ways to manipulate the magnetization in spintronic devices. The orthogonal
+torque-magnetization geometry, the strong damping, and the large domain wall
+velocities inherent to materials with strong spin-orbit coupling make SOTs
+especially appealing for fast switching applications in nonvolatile memory and
+logic units. So far, however, the timescale and evolution of the magnetization
+during the switching process have remained undetected. Here, we report the
+direct observation of SOT-driven magnetization dynamics in Pt/Co/AlO$_x$ dots
+during current pulse injection. Time-resolved x-ray images with 25 nm spatial
+and 100 ps temporal resolution reveal that switching is achieved within the
+duration of a sub-ns current pulse by the fast nucleation of an inverted domain
+at the edge of the dot and propagation of a tilted domain wall across the dot.
+The nucleation point is deterministic and alternates between the four dot
+quadrants depending on the sign of the magnetization, current, and external
+field. Our measurements reveal how the magnetic symmetry is broken by the
+concerted action of both damping-like and field-like SOT and show that
+reproducible switching events can be obtained for over $10^{12}$ reversal
+cycles.",1704.06402v1
+2017-05-04,EUV and Magnetic Activities Associated with Type-I Solar Radio Bursts,"Type-I bursts (i.e. noise storms) are the earliest-known type of solar radio
+emission at the metre wavelength. They are believed to be excited by
+non-thermal energetic electrons accelerated in the corona. The underlying
+dynamic process and exact emission mechanism still remain unresolved. Here,
+with a combined analysis of extreme ultraviolet (EUV), radio and photospheric
+magnetic field data of unprecedented quality recorded during a type-I storm on
+30 July 2011, we identify a good correlation between the radio bursts and the
+co-spatial EUV and magnetic activities. The EUV activities manifest themselves
+as three major brightening stripes above a region adjacent to a compact
+sunspot, while the magnetic field there presents multiple moving magnetic
+features (MMFs) with persistent coalescence or cancelation and a
+morphologically similar three-part distribution. We find that the type-I
+intensities are correlated with those of the EUV emissions at various
+wavelengths with a correlation coefficient of 0.7-0.8. In addition, in the
+region between the brightening EUV stripes and the radio sources there appear
+consistent dynamic motions with a series of bi-directional flows, suggesting
+ongoing small-scale reconnection there. Mainly based on the induced connection
+between the magnetic motion at the photosphere and the EUV and radio activities
+in the corona, we suggest that the observed type-I noise storms and the EUV
+brightening activities are the consequence of small-scale magnetic reconnection
+driven by MMFs. This is in support of the original proposal made by Bentely et
+al. (Solar Phys. 193, 227, 2000).",1705.01666v1
+2017-05-12,Switching dynamics of the spin density wave in superconducting CeCoIn5,"The ordering wave vector $\mathbf{Q}$ of a spin density wave (SDW),
+stabilized within the superconducting state of $\mathrm{CeCoIn_5}$ in a high
+magnetic field, has been shown to be hypersensitive to the direction of the
+field. $\mathbf{Q}$ can be switched from a nodal direction of the $d$-wave
+superconducting order parameter to a perpendicular node by rotating the
+in-plane magnetic field through the antinodal direction within a fraction of a
+degree. Here, we address the dynamics of the switching of $\mathbf{Q}$. We use
+a free energy functional based on the magnetization density, which describes
+the condensation of magnetic fluctuations of nodal quasiparticles, and show
+that the switching process includes closing of the SDW gap at one $\mathbf{Q}$
+and then reopening the SDW gap at another $\mathbf{Q}$ perpendicular to the
+first one. The magnetic field couples to $\mathbf{Q}$ through the spin-orbit
+interaction. Our calculations show that the width of the hysteretic region of
+switching depends linearly on the deviation of magnetic field from the critical
+field associated with the SDW transition, consistent with our thermal
+conductivity measurements. The agreement between theory and experiment supports
+our scenario of the hypersensitivity of the $Q$ phase on the direction of
+magnetic field, as well as the magnon condensation as the origin of the SDW
+phase in $\mathrm{CeCoIn_5}$.",1705.04655v1
+2017-08-04,Magnetic field-dependent dynamics and field-driven metal-to-insulator transition of the half-filled Hubbard model: A DMFT+DMRG study,"We study the magnetic field driven metal-to-insulator transition in
+half-filled Hubbard model on the Bethe lattice, using the dynamical mean-field
+theory by solving the quantum impurity problem with density-matrix
+renormalization group algorithm. The method enables us to obtain a
+high-resolution spectral densities in the presence of a magnetic field. It is
+found that the Kondo resonance at the Fermi level splits at relatively high
+magnetic field: the spin-up and spin-down components move away from the Fermi
+level and finally form a spin polarized band insulator. By calculating the
+magnetization and spin susceptibility, we clarify that an applied magnetic
+field drives a transition from a paramagnetic metallic phase to a band
+insulting phase. In the weak interaction regime, the nature of the transition
+is continuous and captured by the Stoner's description, while in the strong
+interaction regime the transition is very likely to be metamagnetic, evidenced
+by the hysteresis curve. Furthermore, we determine the phase boundary by
+tracking the kink in the magnetic susceptibility, and the step-like change of
+the entanglement entropy and the entanglement gap closing. Interestingly, the
+phase boundary determined from these two different ways are largely consistent
+with each other.",1708.01687v1
+2017-09-29,Half-metallicity and magnetism in the Co$_2$MnAl/CoMnVAl heterostructure,"We present a study of the electronic structure and magnetism of Co$_2$MnAl,
+CoMnVAl and their heterostructure. We employ a combination of
+density-functional theory and dynamical mean-field theory (DFT+DMFT). We find
+that Co$_2$MnAl is a half-metallic ferromagnet, whose electronic and magnetic
+properties are not drastically changed by strong electronic correlations,
+static or dynamic. Non-quasiparticle states are shown to appear in the minority
+spin gap without affecting the spin-polarization at the Fermi level predicted
+by standard DFT. We find that CoMnVAl is a semiconductor or a semi-metal,
+depending on the employed computational approach. We then focus on the
+electronic and magnetic properties of the Co$_2$MnAl/CoMnVAl heterostructure,
+predicted by previous first principle calculations as a possible candidate for
+spin-injecting devices. We find that two interfaces, Co-Co/V-Al and
+Co-Mn/Mn-Al, preserve the half-metallic character, with and without including
+electronic correlations. We also analyse the magnetic exchange interactions in
+the bulk and at the interfaces. At the Co-Mn/Mn-Al interface, competing
+magnetic interactions are likely to favor the formation of a non-collinear
+magnetic order, which is detrimental for the spin-polarization.",1709.10464v2
+2018-05-31,Resonate and Fire Neuron with Fixed Magnetic Skyrmions,"In the brain, the membrane potential of many neurons oscillates in a
+subthreshold damped fashion and fire when excited by an input frequency that
+nearly equals their eigen frequency. In this work, we investigate theoretically
+the artificial implementation of such ""resonate-and-fire"" neurons by utilizing
+the magnetization dynamics of a fixed magnetic skyrmion in the free layer of a
+magnetic tunnel junction (MTJ). To realize firing of this nanomagnetic
+implementation of an artificial neuron, we propose to employ voltage control of
+magnetic anisotropy or voltage generated strain as an input (spike or
+sinusoidal) signal, which modulates the perpendicular magnetic anisotropy
+(PMA). This results in continual expansion and shrinking (i.e. breathing) of a
+skyrmion core that mimics the subthreshold oscillation. Any subsequent input
+pulse having an interval close to the breathing period or a sinusoidal input
+close to the eigen frequency drives the magnetization dynamics of the fixed
+skyrmion in a resonant manner. The time varying electrical resistance of the
+MTJ layer due to this resonant oscillation of the skyrmion core is used to
+drive a Complementary Metal Oxide Semiconductor (CMOS) buffer circuit, which
+produces spike outputs. By rigorous micromagnetic simulation, we investigate
+the interspike timing dependence and response to different excitatory and
+inhibitory incoming input pulses. Finally, we show that such resonate and fire
+neurons have potential application in coupled nanomagnetic oscillator based
+associative memory arrays.",1806.00076v1
+2018-06-29,Post-adiabatic supernova remnants in an interstellar magnetic field: oblique shocks and non-uniform environment,"We present very-high-resolution 1D MHD simulations of the late-stage
+supernova remnants (SNR). In the post-adiabatic stage the magnetic field has an
+important and significant dynamical effect on the shock dynamics, the flow
+structure, and hence the acceleration and emission of cosmic rays. We find that
+the tangential component of the magnetic field provides pressure support that
+to a fair degree prevents the collapse of the radiative shell and thus limits
+the total compression ratio of the partially or fully radiative forward shock.
+A consequence is that the spectra of cosmic rays would not be as hard as in
+hydrodynamic simulations. We also investigated the effect on the flow profiles
+of the magnetic-field inclination and a large-scale gradient in the gas density
+and/or the magnetic field. A positive density gradient shortens the
+evolutionary stages whereas a shock obliquity lowers the shock compression. The
+compression of the tangential component of the magnetic field leads to its
+dominance in the downstream region of post-adiabatic shocks for a wide range of
+orientation of the upstream field, which may explain why one preferentially
+observes tangential radio polarization in old SNRs. As most cosmic rays are
+produced at late stages of SNR evolution, the post-adiabatic phase and the
+influence of the magnetic field during it are most important for modeling the
+cosmic-ray acceleration at old SNRs and the gamma-ray emission from late-stage
+SNRs interacting with clouds.",1806.11396v1
+2018-07-09,Spiral-arm instability - II: magnetic destabilisation,"Fragmentation of spiral arms can drive the formation of giant clumps and
+induce intense star formation in disc galaxies. Based on the spiral-arm
+instability analysis of our Paper I, we present linear perturbation theory of
+dynamical instability of self-gravitating spiral arms of magnetised gas,
+focusing on the effect of toroidal magnetic fields. Spiral arms can be
+destabilised by the toroidal fields which cancel Coriolis force, i.e.
+magneto-Jeans instability. Our analysis can be applied to multi-component
+systems that consist of gas and stars. To test our analysis, we perform ideal
+magneto-hydrodynamics simulations of isolated disc galaxies and examine the
+simulation results. We find that our analysis can characterise dynamical
+instability leading arms to fragment and form clumps if magnetic fields are
+nearly toroidal. We propose that dimensionless growth rate of the most unstable
+perturbation, which is computed from our analysis, can be used to predict
+fragmentation of spiral arms within an orbital time-scale. Our analysis is
+applicable as long as magnetic fields are nearly toroidal. Using our analytic
+model, we estimate a typical mass of clumps forming from spiral-arm
+fragmentation to be consistent with observed giant clumps $\sim10^{7-8}~{\rm
+M_\odot}$. Furthermore, we find that, although the magnetic destabilisation can
+cause low-density spiral arms to fragment, the estimated mass of resultant
+clumps is almost independent from strength of magnetic fields since marginal
+instability occurs at long wavelengths which compensate the low densities of
+magnetically destabilised arms.",1807.02988v2
+2018-09-11,Time variations of the non-potential and volume-threading magnetic helicities,"Relative magnetic helicity is a gauge invariant quantity suitable for the
+study of the magnetic helicity content of heliospheric plasmas. Relative
+magnetic helicity can be decomposed uniquely into two gauge invariant
+quantities, the magnetic helicity of the non-potential component of the field,
+and a complementary volume-threading helicity. Recent analysis of numerical
+experiments simulating the generation of solar eruptions have shown that the
+ratio of the non-potential helicity to the total relative helicity is a clear
+marker of the eruptivity of the magnetic system, and that the high value of
+that quantity could be a sufficient condition for the onset of the instability
+generating the eruptions. The present study introduces the first analytical
+examination of the time variations of these non-potential and volume-threading
+helicities. The validity of the analytical formulas derived are confirmed with
+analysis of three-dimensional (3D) magnetohydrodynamics (MHD) simulations of
+solar coronal dynamics. Both the analytical investigation, and the numerical
+application show that, unlike magnetic helicity, the non-potential and the
+volume-threading helicities are not conserved quantities, even in the ideal MHD
+regime. A term corresponding to the transformation between the non-potential
+and volume-threading helicities frequently dominates their dynamics. This
+finding has an important consequence for their estimation in the solar corona:
+unlike with relative helicity, their volume coronal evolution cannot be
+ascertained by the flux of these quantities through the volume's boundaries.
+Only techniques extrapolating the 3D coronal field will enable both the proper
+study of the non-potential and volume-threading helicities, and the
+observational analysis of helicity-based solar-eruptivity proxies.",1809.03765v1
+2018-12-25,Solar Magnetic Flux Rope Eruption Simulated by a Data-Driven Magnetohydrodynamic Model,"The combination of magnetohydrodynamic (MHD) simulation and multi-wavelength
+observations is an effective way to study mechanisms of magnetic flux rope
+eruption. We develop a data-driven MHD model using the zero-$\beta$
+approximation. The initial condition is provided by nonlinear force-free field
+derived by the magneto-frictional method based on vector magnetic field
+observed by the Helioseismic and Magnetic Imager (HMI) aboard the Solar
+Dynamics Observatory (SDO). The bottom boundary uses observed time series of
+the vector magnetic field and the vector velocity derived by the Differential
+Affine Velocity Estimator for Vector Magnetograms (DAVE4VM). We apply the
+data-driven model to active region 11123 observed from 06:00 UT on 2011
+November 11 to about 2 hours later. The evolution of the magnetic field
+topology coincides with the flare ribbons observed in the 304 and 1600 \AA $ $
+wavebands by the Atmospheric Imaging Assembly. The morphology, propagation
+path, and propagation range of the flux rope are comparable with the
+observations in 304 \AA . We also find that a data-constrained boundary
+condition, where the bottom boundary is fixed to the initial values, reproduces
+a similar simulation result. This model can reproduce the evolution of a
+magnetic flux rope in its dynamic eruptive phase.",1812.10030v1
+2019-05-31,Fingerprints of Kitaev physics in the magnetic excitations of honeycomb iridates,"In the quest for realizations of quantum spin liquids, the exploration of
+Kitaev materials - spin-orbit entangled Mott insulators with strong
+bond-directional exchanges - has taken center stage. However, in these
+materials the local spin-orbital j=1/2 moments typically show long-range
+magnetic order at low temperature, thus defying the formation of a spin-liquid
+ground state. Using resonant inelastic x-ray scattering (RIXS), we here report
+on a proximate spin liquid regime with clear fingerprints of Kitaev physics in
+the magnetic excitations of the honeycomb iridates alpha-Li2IrO3 and Na2IrO3.
+We observe a broad continuum of magnetic excitations that persists up to at
+least 300K, more than an order of magnitude larger than the magnetic ordering
+temperatures. We prove the magnetic character of this continuum by an analysis
+of the resonance behavior. RIXS measurements of the dynamical structure factor
+for energies within the continuum show that dynamical spin-spin correlations
+are restricted to nearest neighbors. Notably, these spectroscopic observations
+are also present in the magnetically ordered state for excitation energies
+above the conventional magnon excitations. Phenomenologically, our data agree
+with inelastic neutron scattering results on the related honeycomb compound
+RuCl3, establishing a common ground for a proximate Kitaev spin-liquid regime
+in these materials.",1905.13590v1
+2019-06-18,Dynamical and thermal magnetic properties of the Kitaev spin liquid candidate $α$-RuCl$_3$,"What is the correct low-energy spin Hamiltonian description of
+$\alpha$-RuCl$_3$? The material is a promising Kitaev spin liquid candidate,
+but is also known to order magnetically, the description of which necessitates
+additional interaction terms. The nature of these interactions, their
+magnitudes and even signs, remain an open question. In this work we
+systematically investigate dynamical and thermodynamic magnetic properties of
+proposed effective Hamiltonians. We calculate zero-temperature inelastic
+neutron scattering (INS) intensities using exact diagonalization, and magnetic
+specific heat using a thermal pure quantum states method. We find that no
+single current model satisfactorily explains all observed phenomena of
+$\alpha$-RuCl$_3$. In particular, we find that Hamiltonians derived from first
+principles can capture the experimentally observed high-temperature peak in the
+magnetic specific heat, while overestimating the magnon energy at the zone
+center. In contrast, other models reproduce important features of the INS data,
+but do not adequately describe the magnetic specific heat. To address this
+discrepancy we propose a modified ab initio model that is consistent with both
+magnetic specific heat and low-energy features of INS data.",1906.07579v3
+2019-09-16,Magnetic topology in fluids,"We study the evolution of turbulent magnetic fields from a topological point
+of view, invoking commonplace mathematical tools from general topology and
+dynamical systems theory which connect magnetic field evolution to time
+reversal invariance, entropy increase and the second law of thermodynamics. We
+show that in fact magnetic topology is well-defined only in the phase space
+corresponding to a dynamical system governed by the induction equation. Hence
+the field's topology and stochasticity can be studied in terms of the
+corresponding phase space trajectories rather than the field lines in real
+Euclidean space. In fact, our results suggest that magnetic field lines should
+not be taken too literally because their existence and uniqueness and more
+importantly continuity in time require strong mathematical conditions, hardly
+satisfied in astrophysical systems. As for magnetic topology change, it is
+shown that the phase space topology is preserved in time for a magnetic field
+which, besides satisfying few continuity conditions, solves a time reversal
+invariant induction equation. What breaks the time symmetry in the induction
+equation is the presence of non-ideal plasma effects at small scales such as
+resistivity, which results from random collisions between diffusing electrons
+and other particles. The small scale, stochastic disturbances produced thereby
+are super-linearly amplified by Richardson diffusion in the turbulent cascade,
+which are eventually manifested as large scale reconnection events, somehow
+similar to stretching quantum fluctuations during inflation to seed large scale
+cosmological structures. This suggests that reconnection is rooted in the
+second law of thermodynamics that dictates entropy increase which in turn
+breaks the time symmetry.",1909.07325v4
+2019-12-05,Collective in-plane magnetization in a 2D XY macrospin system within the framework of generalized Ott-Antonsen theory,"The problem of magnetic transitions between the low-temperature (macrospin
+ordered) phases in 2D XY arrays is addressed. The system is modeled as a plane
+structure of identical single-domain particles arranged in a square lattice and
+coupled by the magnetic dipole-dipole interaction; all the particles possess a
+strong easy-plane magnetic anisotropy. The basic state of the system in the
+considered temperature range is an antiferromagnetic (AF) stripe structure,
+where the macrospins (particle magnetic moments) are still involved in
+thermofluctuational motion: the superparamagnetic blocking $T_b$ temperature is
+lower than that ($T_\text{af}$) of the AF transition. The description is based
+on the stochastic equations governing the dynamics of individual magnetic
+moments, where the interparticle interaction is added in the mean field
+approximation. With the technique of a generalized Ott-Antonsen theory, the
+dynamics equations for the order parameters (including the macroscopic
+magnetization and the antiferromagnetic order parameter) and the partition
+function of the system are rigorously obtained and analysed. We show that
+inside the temperature interval of existence of the AF phase, a static external
+field tilted to the plane of the array is able to induce first order phase
+transitions from AF to ferromagnetic state; the phase diagrams displaying
+stable and metastable regions of the system are presented.",1912.02575v1
+2020-07-05,Size and temperature dependent magnetization of iron nanoclusters,"The magnetic behavior of bcc iron nanoclusters, with diameters between 2 and
+8 nm, is investigated by means of spin dynamics (SD) simulations coupled to
+molecular dynamics (MD-SD), using a distance-dependent exchange interaction.
+Finite-size effects in the total magnetization as well as the influence of the
+free surface and the surface/core proportion of the nanoclusters are analyzed
+in detail for a wide temperature range, going beyond the cluster and bulk Curie
+temperatures. Comparison is made with experimental data and with theoretical
+models based on the mean-field Ising model adapted to small clusters, and
+taking into account the influence of low coordinated spins at free surfaces.
+Our results for the temperature dependence of the average magnetization per
+atom M(T), including the thermalization of the transnational lattice degrees of
+freedom, are in very good agreement with available experimental measurements on
+small Fe nanoclusters. In contrast, significant discrepancies with experiment
+are observed if the translational degrees of freedom are artificially frozen.
+The finite-size effects on M(T) are found to be particularly important near the
+cluster Curie temperature. Simulated magnetization above the Curie temperature
+scales with cluster size as predicted by models assuming short-range magnetic
+ordering (SRMO). Analytical approximations to the magnetization as a function
+of temperature and size are proposed.",2007.02230v2
+2020-08-10,"Color, Flavor, Temperature and Magnetic Field Dependence of QCD Phase Diagram: Magnetic Catalysis and its Inverse","We study dynamical chiral symmetry breaking for quarks in the fundamental
+representation of $SU(N_c)$ for $N_f$ number of light quark flavors. We also
+investigate the phase diagram of quantum chromodynamics at finite temperature
+$T$ and/or in the presence of a constant external magnetic field $eB$. The
+unified formalism for this analysis is provided by a symmetry-preserving
+Schwinger-Dyson equations treatment of a vector$\times$vector contact
+interaction model which encodes several well-established features of quantum
+chromodynamics to mimic the latter as closely as possible. Deconfinement and
+chiral symmetry restoration are triggered above a critical value of $N_f$ at
+$T=0=eB$. On the other hand, increasing temperature itself screens strong
+interactions, thus ensuring that a smaller value of $N_f$ is sufficient to
+restore chiral symmetry at higher temperatures. We also observe the well-known
+phenomenon of magnetic catalysis for a strong enough magnetic field. However,
+we note that if the effective coupling strength of the model decreases as a
+function of magnetic field, it can trigger inverse magnetic catalysis in a
+certain window of this functional dependence. Our model allows for the
+simultaneous onset of dynamical chiral symmetry breaking and confinement for
+each case. Qualitative as well as quantitative predictions of our simple but
+effective model are in reasonably satisfactory agreement with lattice results
+and other reliable and refined predictions based upon intricate continuum
+studies of quantum chromodynamics.",2008.03847v1
+2020-09-09,Dynamics of magnetized particles around Einstein-Æther black hole with uniform magnetic field,"This work is devoted to study the effects of Einstein-\AE ther gravity on the
+dynamics of magnetized particles orbiting a static, spherically symmetric and
+uncharged black hole immersed in an external asymptotically uniform magnetic
+field in both comoving and proper observers frames. The analysis is carried out
+by varying the free parameters $c_{13}$ and $c_{14}$ of the Einstein-\AE ther
+theory and noticing their impacts on the particle trajectories, radii of the
+innermost stable circular orbits (ISCOs), and the amount of center-of-mass
+energy produced as a result of the collision. The strength of the magnetic
+field and the location of circular orbits is significantly affected by varying
+the above free parameters. We have also made detailed comparisons between the
+effects of parameters of Einstein-\AE ther and spin of rotating Kerr black
+holes on ISCO followed by magnetized particles and noticed that both black
+holes depict similar behaviour for suitable values of $c_{13}$, $c_{14}$, spin
+and the magnetic coupling parameters which provide exactly the same values for
+the ISCO. Finally, we have analysed the cases when a static \AE ther black hole
+can be described as Schwarzschild black hole in modified gravity (MOG) with the
+corresponding values of the parameters of the black holes.",2009.04898v2
+2020-09-21,Magneto-Elastic Coupling to Coherent Acoustic Phonon Modes in Ferrimagnetic Insulator GdTiO$_3$,"In this work we investigate single crystal GdTiO$_{3}$, a promising candidate
+material for Floquet engineering and magnetic control, using ultrafast optical
+pump-probe reflectivity and magneto-optical Kerr spectroscopy. GdTiO${}_{3}$ is
+a Mott-Hubbard insulator with a ferrimagnetic and orbitally ordered ground
+state (\textit{T${}_{C}$} = 32 K). We observe multiple signatures of the
+magnetic phase transition in the photoinduced reflectivity signal, in response
+to above band-gap 660 nm excitation. Magnetic dynamics measured via Kerr
+spectroscopy reveal optical perturbation of the ferrimagnetic order on
+spin-lattice coupling timescales, highlighting the competition between the
+Gd${}^{3+}$ and Ti${}^{3+}$ magnetic sub-lattices. Furthermore, a strong
+coherent oscillation is present in the reflection and Kerr dynamics,
+attributable to an acoustic strain wave launched by the pump pulse. The
+amplitude of this acoustic mode is highly dependent on the magnetic order of
+the system, growing sharply in magnitude at \textit{T${}_{C}$}, indicative of
+strong magneto-elastic coupling. The driving mechanism, involving
+strain-induced modification of the magnetic exchange interaction, implies an
+indirect method of coupling light to the magnetic degrees of freedom and
+emphasizes the potential of GdTiO${}_{3}$ as a tunable quantum material.",2009.10222v1
+2020-11-19,Topological insulators and semimetals in classical magnetic systems,"Pursuing topological phases in natural and artificial materials is one of the
+central topics in modern physical science and engineering. In classical
+magnetic systems, spin waves (or magnons) and magnetic solitons (such as domain
+wall, vortex, skyrmion, etc) represent two important excitations. Recently, the
+topological insulator and semimetal states in magnon- and soliton-based
+crystals (or metamaterials) have attracted growing attention owing to their
+interesting dynamics and promising applications for designing robust spintronic
+devices. Here, we give an overview of current progress of topological phases in
+structured classical magnetism. We first provide a brief introduction to spin
+wave, and discuss its topological properties including magnon Hall effects,
+topological magnon insulators, and Dirac (Weyl) magnon semimetals. Appealing
+proposal of topological magnonic devices is also highlighted. We then review
+the collective-coordinate approach for describing the dynamics of magnetic
+soliton lattice. Pedagogical topological models such as the
+Su-Schrieffer-Heeger model and the Haldane model and their manifestation in
+magnetic soliton crystals are elaborated. Then we focus on the topological
+properties of magnetic solitons, by theoretically analyzing the first-order
+topological insulating phases in low dimensional systems and higher-order
+topological states in breathing crystals. Finally, we discuss the experimental
+realization and detection of the edge states in both the magnonic and solitonic
+crystals. We remark the challenges and future prospects before concluding this
+article.",2011.09751v1
+2020-12-06,Ultrafast ferromagnetic fluctuations preceding magnetoelastic first-order transitions,"First-order magnetic transitions are of both fundamental and technological
+interest given that a number of emergent phases and functionalities are thereby
+created. Of particular interest are giant magnetocaloric effects, which are
+attributed to first-order magnetic transitions and have attracted broad
+attention for solid-state refrigeration applications. While the conventional
+wisdom is that atomic lattices play an important role in first-order magnetic
+transitions, a coherent microscopic description of the lattice and spin degrees
+of freedom is still lacking. Here, we study the magnetic phase transition
+dynamics on the intermetallic LaFe13-xSix, which is one of the most classical
+giant magnetocaloric systems, in both frequency and time domains utilizing
+neutron scattering and ultrafast X-ray diffraction. We have observed a strong
+magnetic diffuse scattering in the paramagnetic state preceding the first-order
+magnetic transition, corresponding to picosecond ferromagnetic fluctuations.
+Upon photon-excitation, the ferromagnetic state is completely suppressed in 0.9
+ps and recovered in 20 ps. The ultrafast dynamics suggest that the magnetic
+degree of freedom dominates this magnetoelastic transition and ferromagnetic
+fluctuations might be universally relevant for this kind of compounds.",2012.03186v1
+2021-04-01,An energy-conserving dynamical model of GRB afterglows from magnetized forward and reverse shocks,"In the dynamical models of gamma-ray burst (GRB) afterglows, the uniform
+assumption of the shocked region is known as provoking total energy
+conservation problem. In this work we consider shocks originating from
+magnetized ejecta, extend the energy-conserving hydrodynamical model of Yan et
+al. (2007) to the MHD limit by applying the magnetized jump conditions from
+Zhang & Kobayashi (2005). Compared with the non-conservative models, our
+Lorentz factor of the whole shocked region is larger by a factor
+$\lesssim\sqrt{2}$. The total pressure of the forward shocked region is higher
+than the reversed shocked region, in the relativistic regime with a factor of
+about 3 in our interstellar medium (ISM) cases while ejecta magnetization
+degree $\sigma<1$, and a factor of about 2.4 in the wind cases. For $\sigma\le
+1$, the non-conservative model loses $32-42$% of its total energy for ISM
+cases, and for wind cases $25-38$%, which happens specifically in the forward
+shocked region, making the shock synchrotron emission from the forward shock
+less luminous than expected. Once the energy conservation problem is fixed, the
+late time light curves from the forward shock become nearly independent of the
+ejecta magnetization. The reverse shocked region doesn't suffer from the energy
+conservation problem since the changes of the Lorentz factor are recompensed by
+the changes of the shocked particle number density. The early light curves from
+the reverse shock are sensitive to the magnetization of the ejecta, thus are an
+important probe of the magnetization degree.",2104.00509v2
+2021-06-04,Cavitation and charge separation in laser-produced copper and carbon plasma in transverse magnetic field,"In the present work, we report the dynamics and geometrical features of the
+plasma plume formed by the laser ablation of copper and graphite (carbon)
+targets in the presence of different transverse magnetic field. This work
+emphasizes on the effect of atomic mass of the plume species on the diamagnetic
+behaviour and geometrical aspect of the expanding plasma plume in the magnetic
+field. The time-resolved analysis of the simultaneously captured two
+directional images in orthogonal to the expansion axis is carried out for the
+comparative study of projected three-dimensional structure of copper and carbon
+plasma plume. In the presence of magnetic field, sharp differences are observed
+between the copper and carbon plasma plumes in terms of formation of
+diamagnetic cavity and structure formation. An elliptical cavity-like structure
+is observed in case of copper plasma plume which attains the sharp conical
+shape with increasing the time delay or magnetic field strength. On the other
+hand, splitted carbon plasma plume appears as a Y-shape structure in the
+presence of magnetic field where the cavity-like structure is not observed for
+the considered time and magnetic field. Based on the modified energy balance
+relation for the elliptic cylindrical geometry, we have also simulated the
+dynamics of the plume which is in close agreement with observed plasma
+expansion in diamagnetic and non-diamagnetic regions.",2106.02339v1
+2021-06-24,Light Bridges Can Suppress the Formation of Coronal Loops,"A light bridge is a magnetic intrusion into a sunspot, it interacts with the
+main magnetic field and excites a variety of dynamical processes. In the
+letter, we studied magnetic connectivity between a light bridge and coronal
+loops rooted at the sunspot. We used the data of the Atmospheric Imaging
+Assembly onboard the Solar Dynamics Observatory (SDO) to study the features of
+sunspots with light bridges. It is found that if a light bridge anchors at the
+umbra-penumbra boundary, the coronal loops could not be formed around the
+anchoring point. If the a light bridge become detached from the penumbra, the
+coronal loop starts to form again. The vector magnetogram provided by the
+Helioseismic Magnetic Imager onboard SDO shows that the anchoring region of a
+light bridge usually have an accompanying opposite minor-polarities. We
+conjugate that the magnetic field line could connect to these opposite
+polarities and form short-range magnetic loops, and therefore, coronal loops
+that extend to long-range could not be formed. A model of light bridge is
+proposed to explain the magnetic connectivity between a light bridge and the
+coronal loops. This model could explain many physical processes associated with
+light bridges.",2106.12833v1
+2021-08-26,Helical turbulent nonlinear dynamo at large magnetic Reynolds numbers,"The excitation and further sustenance of large-scale magnetic fields in
+rotating astrophysical systems, including planets, stars and galaxies, is
+generally thought to involve a fluid magnetic dynamo effect driven by helical
+magnetohydrodynamic turbulence. While this scenario is appealing on general
+grounds, it however currently remains largely unconstrained, notably because a
+fundamental understanding of the nonlinear asymptotic behaviour of large-scale
+fluid magnetism in the astrophysically-relevant but treacherous regime of large
+magnetic Reynolds number $Rm$ is still lacking. We explore this problem using
+local high-resolution simulations of turbulent magnetohydrodynamics driven by
+an inhomogeneous helical forcing generating a sinusoidal profile of kinetic
+helicity, mimicking the hemispheric distribution of kinetic helicity in
+rotating turbulent fluid bodies. We identify a transition at large $Rm$ to a
+nonlinear state, followed up to $Rm\simeq 3\times 10^3$, consisting of strong,
+saturated small-scale magnetohydrodynamic turbulence and a weaker, travelling
+coherent large-scale field oscillation. This state is characterized by an
+asymptotically small resistive dissipation of magnetic helicity, by its spatial
+redistribution across the equator through turbulent fluxes driven by the
+hemispheric distribution of kinetic helicity, and by the tentative presence in
+the tangled dynamical magnetic field of plasmoids typical of reconnection at
+large $Rm$.",2108.12037v2
+2021-09-02,Giant effective damping of octupole oscillation in an antiferromagnetic Weyl semimetal,"A magnetic Weyl semimetal is a recent focus of extensive research as it may
+exhibit large and robust transport phenomena associated with topologically
+protected Weyl points in momentum space. Since a magnetic texture provides a
+handle for the configuration of the Weyl points and its transport response,
+understanding of magnetic dynamics should form a basis of future control of a
+topological magnet. Mn3Sn is an example of an antiferromagnetic Weyl semimetal
+that exhibits a large response comparable to the one observed in ferromagnets
+despite a vanishingly small magnetization. The non-collinear spin order in
+Mn3Sn can be viewed as a ferroic order of cluster magnetic octupole and breaks
+the time-reversal symmetry, stabilizing Weyl points and the significantly
+enhanced Berry curvature near the Fermi energy. Here we report our first
+observation of time-resolved octupole oscillation in Mn3Sn. In particular, we
+find the giant effective damping of the octupole dynamics, and it is feasible
+to conduct an ultrafast switching at < 10 ps, a hundred times faster than the
+case of spin-magnetization in a ferromagnet. Moreover, high domain wall
+velocity over 10 km/s is theoretically predicted. Our work paves the path
+towards realizing ultrafast electronic devices using the topological
+antiferromagnet.",2109.01223v1
+2021-12-02,Reaching the equilibrium state of frustrated triangular Ising magnet Ca3Co2O6,"Ca3Co2O6 is a frustrated magnet consisting of a triangular arrangement of
+chains of Ising spins. It shows regular magnetization steps vs magnetic field
+every 1.2 T that are metastable with very slow dynamics. This has puzzled the
+community for many years and given rise to numerous potential theories. Here we
+approach the problem by seeking the elusive magnetic equilibrium state at T = 2
+K. To this end, we explore two approaches: (1) bypassing the slow dynamics
+produced by changing fields by instead field-cooling directly to the target
+temperature, and (2) quantum annealing in transverse magnetic fields. While we
+observe no measurable effect of the quantum annealing in fields up to 7 T,
+which is likely due to the large Ising anisotropy of Co spins in this material,
+we find that for the field cooling in longitudinal fields we achieve the
+predicted equilibrium 1/3 magnetization. We perform Monte Carlo simulations of
+the ground state phase diagram and we also simulate the quantum annealing
+process and find good agreement between experiment and theory. Thus we present
+an investigation of the elusive ground state properties of the canonical
+frustrated triangular system Ca3Co2O6.",2112.01356v1
+2021-12-28,"Phonon, Electron, and Magnon Excitations in Antiferromagnetic L1$_{0}$-type MnPt","Antiferromagnetic L1$_{0}$-type MnPt is a material with relatively simple
+crystal and magnetic structure, recently attracting interest due to its high
+N{\'{e}}el temperature and wide usage as a pinning layer in magnetic devices.
+While it is experimentally well characterized, the theoretical understanding is
+much less developed, in part due to the challenging accuracy requirements
+dictated by the small underlying energy scales that govern magnetic ordering in
+antiferromagnetic metals. In this work, we use density functional theory, the
+Korringa-Kohn-Rostoker formalism, and a Heisenberg model to establish a
+comprehensive theoretical description of antiferromagnetic L1$_{0}$-type MnPt,
+along with accuracy limits, by thoroughly comparing to available literature
+data. Our simulations show that the contribution of the magnetic dipole
+interaction to the magnetocrystalline anisotropy energy of $K_{1}$=1.07$\times
+10^{6}$\,J/m$^3$ is comparable in magnitude to the spin-orbit contribution.
+Using our result for the magnetic susceptibility of $5.25\times10^{-4}$, a
+lowest magnon frequency of about 2.02\,THz is predicted, confirming THz spin
+dynamics in this material. From our data for electron, phonon, and magnon
+dispersion we compute the individual contributions to the total heat capacity
+and show that the dominant term at or above 2\,K arises from phonons. From the
+Landau-Lifshitz-Gilbert equation, we compute a N\'{e}el temperature of
+990--1070 K. Finally, we quantify the magnitude of the magneto-optical Kerr
+effect generated by applying an external magnetic field. Our results provide
+insight into the underlying physics, which is critical for a deep understanding
+of fundamental limits of the time scale of spin dynamics, stability of the
+magnetic ordering, and the possibility of magneto-optical detection of
+collective spin motion.",2112.13954v1
+2022-02-09,Dynamics of magnetic flux tubes in accretion disks of Herbig Ae/Be stars,"The dynamics of magnetic flux tubes (MFTs) in the accretion disk of typical
+Herbig Ae/Be star with fossil large-scale magnetic field is modeled taking into
+account the buoyant and drag forces, radiative heat exchange with the
+surrounding gas, and the magnetic field of the disk. The structure of the disk
+is simulated using our magnetohydrodynamic (MHD) model, taking into account the
+heating of the surface layers of the disk with the stellar radiation. The
+simulations show that MFTs periodically rise from the innermost region of the
+disk with speeds up to $10-12$ km s$^{-1}$. MFTs experience decaying magnetic
+oscillations under the action of the external magnetic field near the disk's
+surface. The oscillation period increases with distance from the star and
+initial plasma beta of the MFT, ranging from several hours at $r=0.012$ au up
+to several months at $r=1$ au. The oscillations are characterized by pulsations
+of the MFT's characteristics including its temperature. We argue that the
+oscillations can produce observed IR-variability of Herbig Ae/Be stars, which
+would be more intense than in the case of T Tauri stars, since the disks of
+Herbig Ae/Be stars are hotter, denser and have stronger magnetic field.",2202.04412v1
+2022-02-22,Small moments without long-range magnetic ordering in the zero-temperature ground state of the double-perovskite iridate Ba$_2$YIrO$_6$,"The spin-orbit coupled double perovskite iridate Ba$_2$YIrO$_6$ with $d^4$
+occupancy of Ir is considered as a candidate material for a non-magnetic $J=0$
+ground state. The issue of existence of such a state in Ba$_2$YIrO$_6$ however
+has opened up intense debates both in experimental and theoretical studies. In
+this study, we revisit the issue using \textit{ab-initio} density functional
+combined with dynamical mean-field theory to investigate the magnetic
+properties of Ba$_2$YIrO$_6$ down to zero temperature. To reach the ground
+state, a recently developed impurity solver based on tensor-product states
+working directly at zero temperature is employed. We find that Ba$_2$YIrO$_6$
+has a small instantaneous non-zero magnetic moment, both at $T=0$ K as well as
+at room temperature. We did not observe any evidence of magnetic ordering, not
+even at $T=0$ K. From the calculated local magnetic susceptibility we see that
+the quantum fluctuations are very strong and effective in screening the
+instantaneous moments. This dynamical screening, together with frustration
+effects in the fcc lattice that can lead to almost degenerate magnetic ground
+states, prevents any long-range ordering.",2202.10794v2
+2022-05-04,Cosmic rays and random magnetic traps,"The spatial distribution of cosmic ray (CR) particles in the interstellar
+medium (ISM) is of major importance in radio astronomy, where its knowledge is
+essential for the interpretation of observations, and in theoretical
+astrophysics, where CR contribute to the structure and dynamics of the ISM.
+Local inhomogeneities in interstellar magnetic field strength and structure can
+affect the local diffusivity and ensemble dynamics of the cosmic ray particles.
+Magnetic traps (regions between magnetic mirrors located on the same magnetic
+line) can lead to especially strong and persistent features in the CR spatial
+distribution. Using test particle simulations, we study the spatial
+distribution of an ensemble of CR particles (both protons and electrons) in
+various magnetic field configurations, from an idealized axisymmetric trap to
+those that emerge in intermittent (dynamo-generated) random magnetic fields. We
+demonstrate that both the inhomogeneity in the CR sources and the energy losses
+by the CR particles can lead to persistent local inhomogeneities in the CR
+distribution and that the protons and electrons have different spatial
+distributions. Our results can have profound implications for the
+interpretation of the synchrotron emission from astronomical objects, and in
+particular its random fluctuations.",2205.01986v2
+2022-06-20,Effect of internal magnetic flux on a relativistic spin-1 oscillator in the spinning point source-generated spacetime,"We consider a charged relativistic spin-1 oscillator under the influence of
+an internal magnetic flux in a 2+1 dimensional spacetime induced by a spinning
+point source. In order to analyze the effects of the internal magnetic flux and
+spin of the point source on the relativistic dynamics of such a vector field,
+we seek a non-perturbative solution of the associated spin-1 equation derived
+as an excited state of Zitterbewegung. By performing an analytical solution of
+the resulting equation, we determine exact results for the system in question.
+Accordingly, we analyze the effects of spin of the point source and internal
+magnetic flux on the relativistic dynamics of the considered test field. We see
+that the spin of such a field can be altered by the magnetic flux and this
+means that the considered system may behave as a fermion or boson according to
+the varying values of the magnetic flux, in principle. We observe that the
+internal magnetic flux and the spin of the point source impact on the
+relativistic energy levels and probability density functions. Also, our results
+indicate that the spin of the point source breaks the symmetry of the energy
+levels corresponding to particle-antiparticle states.",2206.09898v3
+2022-06-29,Inertial active Ornstein-Uhlenbeck particle in the presence of magnetic field,"We consider an inertial active Ornstein-Uhlenbeck particle in an athermal
+bath. The particle is charged, constrained to move in a two-dimensional
+harmonic trap, and a magnetic field is applied perpendicular to the plane of
+motion. The steady state correlations and the mean square displacement are
+studied when the particle is confined as well as when it is set free from the
+trap. With the help of both numerical simulation and analytical calculations,
+we observe that inertia plays a crucial role in the dynamics in the presence of
+a magnetic field. In a highly viscous medium where the inertial effects are
+negligible, the magnetic field has no influence on the correlated behaviour of
+position as well as velocity. In the time asymptotic limit, the overall
+displacement of the confined harmonic particle gets enhanced by the presence of
+magnetic field and saturates for a stronger magnetic field. On the other hand,
+when the particle is set free, the overall displacement gets suppressed and
+approaches zero when strength of the field is very high. Interestingly, it is
+seen that in the time asymptotic limit, the confined harmonic particle behaves
+like a passive particle and becomes independent of the activity, especially in
+the presence of a very strong magnetic field. Similarly, for a free particle
+the mean square displacement in the long time limit becomes independent of
+activity even for a longer persistence of noise correlation in the dynamics.",2206.14715v1
+2022-07-07,Thermal spin dynamics of Kitaev magnets $-$ scattering continua and magnetic field induced phases within a stochastic semiclassical approach,"The honeycomb magnet $\alpha-$RuCl$_3$ is a prime candidate material for
+realizing the Kitaev quantum spin liquid (QSL), but it shows long-range
+magnetic order at low temperature. Nevertheless, its broad inelastic neutron
+scattering (INS) response at finite frequency has been interpreted as that of a
+'proximate QSL'. A moderate in-plane magnetic field indeed melts the residual
+zigzag order, giving rise to peculiar intermediate field phases before the
+high-field polarized state. In INS measurements the low-frequency spin waves
+disappear, leading to a broad scattering continuum in the field-induced
+intermediate regime, whose nature is currently under debate. Here, we study the
+magnetic field dependent spin dynamics of the $K-\Gamma-\Gamma'-$model within a
+stochastic semiclassical treatment, which incorporates the effect of
+finite-temperature fluctuations. At temperatures relevant for INS experiments,
+we show how the excitations of the zigzag phase broaden and that the different
+intermediate phases all show a similar continuum response. We discuss the
+implications of our results for experiments and highlight the importance of
+distinguishing finite temperature fluctuations from genuine quantum
+fractionalization signatures in frustrated magnets.",2207.03515v2
+2022-09-12,Holes and magnetic polarons in a triangular lattice antiferromagnet,"The intricate interplay between charge motion and magnetic order in
+geometrically frustrated lattices is central for the properties of many
+two-dimensional quantum materials. The triangular lattice antiferromagnet is a
+canonical example of a frustrated system, and here we analyse the dynamics of a
+hole in such a lattice focusing on observables that have become accessible in a
+new generation of experiments. Using the $t$-$J$ model, we solve the problem
+exactly within linear spin wave theory in the limit of strong magnetic
+interactions, showing that the ground state is described by a coherent state of
+spin waves. The derivation highlights the crucial role played by the
+interaction between a static hole and the neighboring spins, which originates
+in the geometric frustration and has often been omitted in earlier works.
+Furthermore, we show that the non-equilibrium dynamics after a hole has
+abruptly been inserted at a lattice site is given exactly by a coherent state
+with time-dependent oscillatory coefficients. Physically, this describes a
+burst of magnetic frustration propagating through only two-thirds of the
+lattice sites, since a destructive interference of spin waves leaves spins
+parallel to that removed by the hole unperturbed. After the wave has propagated
+through the lattice, the magnetization relaxes to that of the ground state. We
+then use our analytical solution to benchmark the widely used self-consistent
+Born approximation (SCBA), showing that it is very accurate also for a
+triangular lattice. The magnetic polaron spectrum is analysed for general
+magnetic interactions using the SCBA, and we compare our results with those for
+a square lattice.",2209.05131v1
+2022-10-11,The characteristics of flare- and CME-productive solar active regions,"Solar flares and coronal mass ejections (CMEs) cause immediate and adverse
+effects on the interplanetary space and geospace. The deeper understanding of
+the mechanisms that produce them and the construction of efficient prediction
+schemes are of paramount importance. The source regions of flares and CMEs
+exhibit some common morphological characteristics associated with strongly
+sheared magnetic polarity inversion lines, indicative of the complex magnetic
+configurations that store huge amounts of free magnetic energy and helicity.
+This knowledge is transformed into parameters that can help us distinguish
+efficiently between quiet, flare-, and CME-productive active regions.
+Nonetheless, flare and CME prediction still faces a number of challenges. The
+magnetic field information is constrained at the photosphere and accessed only
+from one vantage point of observation; the dynamic behavior of active regions
+is still not fully incorporated into predictions; the stochasticity of flares
+and CMEs renders their prediction probabilistic. To meet these challenges, new
+properties have been put forward to describe different aspects of magnetic
+energy storage mechanisms in active regions and offer the opportunity of
+parametric studies for over an entire solar cycle. This inventory of predictors
+now includes information from flow fields, transition region/coronal
+spectroscopy, data-driven modeling of the coronal magnetic field, as well as
+parameterizations of dynamic effects from time series. Further work towards
+these directions may help alleviate the current limitations in observing the
+magnetic field of higher atmospheric layers. This paper reviews these efforts
+as well as the importance of transforming new knowledge into more efficient
+predictors and including new types of data.",2210.05453v1
+2022-11-10,Static and dynamic magnetic properties of the spin-5/2 triangle lattice antiferromagnet Na3Fe(PO4)2 studied by 31P NMR,"$^{31}$P nuclear magnetic resonance (NMR) measurements have been carried out
+to investigate the magnetic properties and spin dynamics of Fe$^{3+}$ ($S$ =
+5/2) spins in the two-dimensional triangular lattice (TL) compound
+Na$_3$Fe(PO$_4$)$_2$. The temperature ($T$) dependence of nuclear spin-lattice
+relaxation rates ($1/T_1$) shows a clear peak around N\'eel temperature,
+$T_{\rm N} = 10.9$~K, corresponding to an antiferromagnetic (AFM) transition.
+From the temparature dependence of NMR shift ($K$) above $T_{\rm N}$, an
+exchange coupling between Fe$^{3+}$ spins was estimated to be $J/k_{\rm
+B}\simeq 1.9$~K using the spin-5/2 Heisenberg isotropic-TL model. The
+temperature dependence of $1/T_1T$ divided by the magnetic susceptibility
+($\chi$), $1/T_1T\chi$, above $T_{\rm N}$ proves the AFM nature of spin
+fluctuations below $\sim$ 50 K in the paramagnetic state. In the magnetically
+ordered state below $T_{\rm N}$, the characteristic rectangular shape of the
+NMR spectra is observed, indicative of a commensurate AFM state in its ground
+state. The strong temperature dependence of 1/$T_1$ in the AFM state is well
+explained by the two-magnon (Raman) process of the spin waves in a 3D
+antiferromagnet with a spin-anisotropy energy gap of 5.7 K. The temperature
+dependence of sublattice magnetization is also well reproduced by the spin
+waves. Those results indicate that the magnetically ordered state of
+Na$_3$Fe(PO$_4$)$_2$ is a conventional 3D AFM state, and no obvious spin
+frustration effects were detected in its ground state.",2211.05921v1
+2023-03-13,Experimental investigation of the effect of topological insulator on the magnetization dynamics of ferromagnetic metal: $BiSbTe_{1.5}Se_{1.5}$ and $Ni_{80}Fe_{20}$ heterostructure,"We have studied ferromagnetic metal/topological insulator bilayer system to
+understand magnetization dynamics of ferromagnetic metal (FM) in contact with a
+topological insulator (TI). At magnetic resonance condition, the precessing
+magnetization in the metallic ferromagnet ($Ni_{80}Fe_{20}$) injects spin
+current into the topological insulator ($BiSbTe_{1.5}Se_{1.5}$), a phenomenon
+known as spin-pumping. Due to the spin pumping effect, fast relaxation in the
+ferromagnet results in the broadening of ferromagnetic resonance linewidth
+($\Delta H$). We evaluated the parameters like effective Gilbert damping
+coefficient ($\alpha_{eff}$), spin-mixing conductance ($g_{eff}^{\uparrow
+\downarrow}$) and spin current density ($j_S^0$) to confirm a successful spin
+injection due to spin-pumping into the $BiSbTe_{1.5}Se_{1.5}$ layer. TIs embody
+a spin-momentum locked surface state that span the bulk band-gap. It can act
+differently to the FM magnetization than the other normal metals. To probe the
+effect of topological surface state, a systematic low temperature study is
+crucial as surface state of TI dominates at lower temperatures. The exponential
+growth of $\Delta H$ for all different thickness combination of FM/TI bilayers
+and effective Gilbert damping coefficient ($\alpha_{eff}$) with lowering
+temperature confirms the prediction that spin chemical bias generated from
+spin-pumping induces surface current in TI due to spin-momentum locking. The
+hump-like feature of magnetic anisotropy field ($H_K$)of the bilayer around 60K
+suggests that the decrease of interfacial in-plane magnetic anisotropy can
+result from exchange coupling between the TI surface state and the local
+moments of FM layer.",2303.07025v2
+2023-05-03,Catastrophic magnetic flux avalanches in NbTiN superconducting resonators,"Macroscopic superconducting components are an important building block of
+various quantum circuits. Since several of the envisioned applications require
+exposure to magnetic fields, it is of utmost importance to explore the impact
+of magnetic fields on their performance. Here we explore the complex pattern of
+magnetic field penetration and identify its impact on the resonance frequency
+of NbTiN superconducting resonators by combining magneto-optical imaging and
+high-frequency measurements. At temperatures below approximately half of the
+superconducting critical temperature, the development of magnetic flux
+avalanches manifests itself as a noisy response in the field-dependent
+resonance frequency. Magneto-optical imaging reveals different regimes and
+distinguishes the impact of avalanches in the ground plane and resonator. Our
+findings demonstrate that superconducting resonators represent a valuable tool
+to investigate magnetic flux dynamics. Moreover, the current blooming of
+niobium-based superconducting radio-frequency devices makes this report timely
+by unveiling the severe implications of magnetic flux dynamics.",2305.02418v2
+2023-05-24,Manipulation of magnetic solitons under the influence of DMI gradients,"Magnetic solitons are promising for applications due to their intrinsic
+properties such as small size, topological stability, ultralow power
+manipulation and potentially ultrafast operations. To date, research has
+focused on the manipulation of skyrmions, domain walls, and vortices by applied
+currents. The discovery of new methods to control magnetic parameters, such as
+the interfacial Dzyaloshinskii-Moriya interaction (DMI) by strain, geometry
+design, temperature gradients, and applied voltages promises new avenues for
+energetically efficient manipulation of magnetic structures. The latter has
+shown significant progress in 2d material-based technology. In this work, we
+present a comprehensive study using numerical and analytical methods of the
+stability and motion of different magnetic textures under the influence of DMI
+gradients. Our results show that under the influence of linear DMI gradients,
+N\'eel and Bloch-type skyrmions and radial vortex exhibit motion with finite
+skyrmion Hall angle, while the circular vortex undergoes expulsion dynamics.
+This work provides a deeper and crucial understanding of the stability and
+gradient-driven dynamics of magnetic solitons, and paves the way for the design
+of alternative low-power sources of magnetization manipulation in the emerging
+field of 2d materials.",2305.15052v1
+2023-06-28,2.5-MHD models of circumstellar discs around FS~CMa post-mergers : I. Non-stationary accretion stage,"We investigate the dynamic evolution of gaseous region around FS~CMa
+post-mergers. Due to the slow rotation of a central B-type star, the dynamics
+is driven mainly by the magnetic field of the central star. Recent observations
+have allowed us to set a realistic initial conditions such as, the magnetic
+field value ($B_\star\approx6\times10^{3}G$), the mass of the central star
+($M_\star=6M_\odot$), and the initial disc density
+$\rho_{d0}\in[10^{-13}\mathrm{g\,cm^{-3}},10^{-11}\mathrm{g \, cm^{-3}}] $. We
+use the PLUTO code to perform 2.5D-MHD simulations of thin and thick discs
+models. Especially relevant for the interpretation of the observed properties
+of FS~CMa post-mergers are the results for low-density discs, in which we find
+formation of a jet emerging from inner edge of the disc, as well as the
+formation of the so called ""hot plasmoid"" in the corona region. Jets are
+probably detected as discrete absorption components in the resonance lines of
+FS~CMa stars. Moreover, the magnetic field configuration in the low-density
+plasma region, favors the appearance of magnetocentrifugal winds from the disc.
+The currents toward the star created by the magnetic field may explain
+accidentally observed material infall. The disc structure is significantly
+changed due to the presence of the magnetic field. The magnetic field is also
+responsible for the formation of a hot corona as observed in several FS~CMa
+stars through the Raman lines. Our results are valid for all magnetic stars
+surrounded by a low density plasma, i.e., some of stars showing the B[e]
+phenomenon.",2306.16073v1
+2023-07-31,Bioinspired multi-asymmetric magnetized surfaces for tailoring energy-free liquid manipulation and 3-DOF solid transportation,"Through the utilization of smart materials and well-designed structures,
+functional surfaces have been developed to enable small-scale liquid/solid
+manipulation tasks, thereby facilitating crucial applications in the fields of
+microfluidics, soft robotics, and biomedical engineering. However, the design
+of functional systems with flexible, tunable, and multimodal liquid/solid
+manipulation capabilities remains a challenging endeavor. Here, inspired by
+asymmetric structural features in natural plants and metachrony in cross-scale
+biological systems, I report a magnetic-responsive functional surface that can
+achieve rich liquid operations under static magnetic fields, while also
+enabling the transportation of solids with multiple degrees of freedom (DOFs)
+under dynamic magnetic fields. The presence of curvature pillars on the
+surface, combined with their magnetic-driven tilt/gradient arrangement, imparts
+liquids with multi-directional spreading modes based on the asymmetry of
+Laplace pressure. I elucidate the mechanisms governing these liquid spreading
+modes and subsequently develop compelling liquid operations, such as adjustable
+anti-gravity climbing, spontaneous modal shifts in liquid transport, and liquid
+mixing. Furthermore, the dynamic metachronal motion of the magnetic pillars can
+be harnessed for solid object transportation. I illustrate the
+synchronous/asynchronous transport modes of the surface and propose a novel
+strategy for achieving 3-DOF solid transportation by coordinating the
+arrangement of objects and employing magnetic actuation strategies. This study
+presents a new design concept for application-oriented manipulation surfaces,
+which hold significant potential for extensive engineering applications.",2307.16740v2
+2023-08-02,Magnetohydrodynamical torsional oscillations from thermo-resistive instability in hot jupiters,"Hot jupiter atmospheres may be subject to a thermo-resistive instability
+where an increase in the electrical conductivity due to ohmic heating results
+in runaway of the atmospheric temperature. We introduce a simplified
+one-dimensional model of the equatorial sub-stellar region of a hot jupiter
+which includes the temperature-dependence and time-dependence of the electrical
+conductivity, as well as the dynamical back-reaction of the magnetic field on
+the flow. This model extends our previous one-zone model to include the radial
+structure of the atmosphere. Spatial gradients of electrical conductivity
+strongly modify the radial profile of Alfv\'en oscillations, leading to
+steepening and downwards transport of magnetic field, enhancing dissipation at
+depth. We find unstable solutions that lead to self-sustained oscillations for
+equilibrium temperatures in the range $T_\mathrm{eq}\approx 1000$--$1200$~K,
+and magnetic field in the range $\approx 10$--$100$~G. For a given set of
+parameters, self-sustained oscillations occur in a narrow range of equilibrium
+temperatures which allow the magnetic Reynolds number to alternate between
+large and small values during an oscillation cycle. Outside of this temperature
+window, the system reaches a steady state in which the effect of the magnetic
+field can be approximated as a magnetic drag term. Our results show that
+thermo-resistive instability is a possible source of variability in magnetized
+hot jupiters at colder temperatures, and emphasize the importance of including
+the temperature-dependence of electrical conductivity in models of atmospheric
+dynamics.",2308.00892v1
+2023-08-21,Fleeting Small-scale Surface Magnetic Fields Build the Quiet-Sun Corona,"Arch-like loop structures filled with million Kelvin hot plasma form the
+building blocks of the quiet-Sun corona. Both high-resolution observations and
+magnetoconvection simulations show the ubiquitous presence of magnetic fields
+on the solar surface on small spatial scales of $\sim$100\,km. However, the
+question of how exactly these quiet-Sun coronal loops originate from the
+photosphere and how the magnetic energy from the surface is channeled to heat
+the overlying atmosphere is a long-standing puzzle. Here we report
+high-resolution photospheric magnetic field and coronal data acquired during
+the second science perihelion of Solar Orbiter that reveal a highly dynamic
+magnetic landscape underlying the observed quiet-Sun corona. We found that
+coronal loops often connect to surface regions that harbor fleeting weaker,
+mixed-polarity magnetic field patches structured on small spatial scales, and
+that coronal disturbances could emerge from these areas. We suggest that weaker
+magnetic fields with fluxes as low as $10^{15}$\,Mx and/or those that evolve on
+timescales less than 5\,minutes, are crucial to understand the coronal
+structuring and dynamics.",2308.10982v2
+2023-09-05,Ultrafast optical polarimetry in magnetic phases of Kondo semi metal CeSb,"We investigated photoinduced ultrafast transient dynamics in different
+magnetic phases in CeSb by means of the time resolved magneto-optical
+spectroscopy. We observe a distinctive coherent oscillations in the
+ground-state antiferromagnetic (AF) phase and the high-magnetic field
+ferromagnetic (F) phase. While the AF-phase oscillations frequencies match the
+recent Raman scattering findings the F-phase oscillation frequency does not
+correspond to the previously observed magnetic excitation. The large
+spectroscopic factor, g=3.94, and optical polarization properties suggest that
+it corresponds to a previously undetected Ce^{3+} coherent crystal-field state
+excitation. The AF-phase oscillations show no magnetic field dependence so
+their lattice origin cannot be entirely excluded. The non-oscillatory part of
+the transients is qualitatively similar in all investigated magnetic phases
+with a faster sub-picosecond dynamics in the ferromagnetic and
+ferro-para-magnetic phases and is attributed to differences in the electronic
+structure, which affect the photo-excited quasiparticle energy relaxation
+kinetics.",2309.02331v2
+2024-01-16,Anomalous Proximitized Transport in Metal/Quantum Magnet Heterostructure $\rm{Bi_{2}Ir_{2}O_{7}/Yb_{2}Ti_{2}O_{7}}$,"Fluctuations of quantum spins play a crucial role in the emergence of exotic
+magnetic phases and excitations. The lack of the charge degree of freedom in
+insulating quantum magnets, however, precludes such fluctuations from mediating
+electronic transport. Here we show that the quantum fluctuations of a localized
+frustrated magnet induce strong proximitized charge transport of the conduction
+electrons in a synthetic heterostructure comprising an epitaxial
+$\rm{Bi_{2}Ir_{2}O_{7}}$ ultrathin film on the single crystal of
+$\rm{Yb_{2}Ti_{2}O_{7}}$. The proximity effects are evidenced by the scaling
+behavior of the $\rm{Bi_{2}Ir_{2}O_{7}}$ resistance in correspondance with the
+dynamic scaling of the dynamic spin correlation function of
+$\rm{Yb_{2}Ti_{2}O_{7}}$, which is a result of quantum fluctuations near a
+multi-phase quantum critical point. The proximitized transport in
+$\rm{Bi_{2}Ir_{2}O_{7}}$ can be effectively tuned by magnetic field through
+suppressing the quantum spin fluctuations as well as inducing transitions via
+magnetic anisotropy in $\rm{Yb_{2}Ti_{2}O_{7}}$. Our work establishes a new
+pathway for harnessing quantum spin fluctuations in magnetic insulators with
+electric transport, offering exciting prospects for potential applications in
+the realm of quantum spintronics.",2401.08125v1
+2024-01-24,Simplified Shielded MEG-MRI Multimodal System with Scalar-mode Optically Pumped Magnetometers as MEG Sensors,"Magnetoencephalography (MEG) conventionally operates within high-performance
+magnetic shields due to the extremely weak magnetic field signals from the
+measured objects and the narrow dynamic range of the magnetic sensors employed
+for detection. This limitation results in elevated equipment costs and
+restricted usage. Additionally, the information obtained from MEG is functional
+images, and to analyze from which part of the brain the signals are coming, it
+is necessary to capture morphological images separately. When MEG and
+morphological imaging devices are separate, despite their individual high
+measurement accuracies, discrepancies in positional information may arise. In
+response, we have developed a low-field magnetic resonance imaging system that
+incorporates scalar-mode optically pumped magnetometers with a wide dynamic
+range and exceptionally high measurement sensitivity as sensors for MEG.
+Operating at low magnetic fields eliminates the need for superconducting coils
+in magnetic resonance imaging and the high-performance magnetic shields
+essential for MEG, promising a substantial cost reduction compared to
+traditional approaches. We achieved a noise level of about
+$16\,\rm{pT/Hz}^{1/2}$ with a single channel magnetometer, and reached a noise
+level of $367\,\rm{fT/cm/Hz}^{1/2}$ through differential measurements. The
+system successfully conducted MR imaging on a phantom, demonstrating the
+potential of MEG and MRI fusion.",2401.13287v2
+2024-02-15,Emergent topological quasiparticle kinetics in constricted nanomagnets,"The ubiquitous domain wall kinetics under magnetic field or current
+application describes the dynamic properties in nanostructured magnets.
+However, when the geometrical size of a nanomagnetic system is constricted to
+the limiting domain wall length scale, the competing energetics between
+anisotropy, exchange and dipolar interactions can cause emergent kinetics due
+to quasiparticle relaxation, similar to bulk magnets of atomic origin. Here, we
+present a joint experimental and theoretical study to support this argument --
+constricted nanomagnets, made of antiferromagnetic and paramagnetic neodymium
+thin film with honeycomb motif, reveal fast kinetic events at ps time scales
+due to the relaxation of chiral vortex loop-shaped topological quasiparticles
+that persist to low temperature in the absence of any external stimuli. Such
+phenomena are typically found in macroscopic magnetic materials. Our discovery
+is especially important considering the fact that paramagnets or
+antiferromagnets have no net magnetization. Yet, the kinetics in neodymium
+nanostructures is quantitatively similar to that found in ferromagnetic
+counterparts and only varies with the thickness of the specimen. This suggests
+that a universal, topological quasiparticle mediated dynamical behavior can be
+prevalent in nanoscopic magnets, irrespective of the nature of underlying
+magnetic material.",2402.10143v2
+2024-03-14,Large Eddy Simulations of Magnetized Mergers of Black Holes and Neutron Stars,"The LIGO-Virgo-Kagra collaboration has observed gravitational waves
+consistent with the mergers of a black hole and a neutron star, namely GW200105
+and GW200115, providing evidence for such cataclysmic events. Although no
+electromagnetic counterpart was reported for either of these two events, under
+certain conditions black hole--neutron star mergers are expected to form a
+significant accretion disk and to produce both a short gamma ray burst and a
+kilonova, much as observed in the binary neutron star merger GW170817. Here, we
+extend our publicly available code \mhduet to study numerically the merger of a
+magnetized neutron star with a black hole. \mhduet employs Large Eddy
+Simulation techniques to help capture the magnetic field amplification
+resulting from turbulence and other sub-grid scale dynamics in the post-merger
+stage. In particular, we simulate a merger with parameters favorable to
+producing an accretion disk, focusing on the formation and dynamics of the
+turbulent disk and the resulting magnetic field amplification. Following the
+tidal disruption and during the formation of the accretion disk, the magnetic
+field undergoes significant amplification driven by the Kelvin-Helmholtz
+instability, reaching strengths of more than $10^{14}\,\rm{G}$ from a realistic
+initial strength of $10^{11}\,\rm{G}$ in short timescales of approximately
+$20\,\rm{ms}$. At later times in our simulations the magnetic field growth
+occurs at larger scales and is dominated mainly by magnetic winding.",2403.09770v1
+2000-06-22,Solar flare radio pulsations as a signature of dynamic magnetic reconnection,"Decimetric radio observations of the impulsive solar flare on October 5,
+1992, 09:25 UT show a long series of quasi-periodic pulsations deeply
+modulating a continuum in the 0.6-2 GHz range that is slowly drifting toward
+lower frequencies. We propose a model in which the pulsations of the radio flux
+are caused by quasi-periodic particle acceleration episodes that result from a
+dynamic phase of magnetic reconnection in a large-scale current sheet. The
+reconnection is dominated by repeated formation and subsequent coalescence of
+magnetic islands (known as ``secondary tearing'' or ``impulsive bursty'' regime
+of reconnection), while a continuously growing plasmoid is fed by newly
+coalescing islands. Such a model, involving a current sheet and a growing
+plasmoid, is consistent with the Yohkoh observations of the same flare (Ohyama
+& Shibata 1998). We present two-dimensional MHD simulations of dynamic magnetic
+reconnection that support the model. Within the framework of the proposed
+interpretation, the radio observations reveal details of plasmoid formation in
+flares.",0006324v1
+2002-05-22,Dynamics and Structure of Three-Dimensional Trans-Alfvenic Jets. II. The Effect of Density and Winds,"Two three-dimensional magnetohydrodynamical simulations of strongly
+magnetized conical jets, one with a poloidal and one with a helical magnetic
+field, have been performed. In the poloidal simulation a significant sheath
+(wind) of magnetized moving material developed and partially stabilized the jet
+to helical twisting. The fundamental pinch mode was not similarly affected and
+emission knots developed in the poloidal simulation. Thus, astrophysical jets
+surrounded by outflowing winds could develop knotty structures along a straight
+jet triggered by pinching. Where helical twisting dominated the dynamics,
+magnetic field orientation along the line-of-sight could be organized by the
+toroidal flow field accompanying helical twisting. On astrophysical jets such
+structure could lead to a reversal of the direction of Faraday rotation in
+adjacent zones along a jet. Theoretical analysis showed that the different
+dynamical behavior of the two simulations could be entirely understood as a
+result of dependence on the velocity shear between jet and wind which must
+exceed a surface Alfven speed before the jet becomes unstable to helical and
+higher order modes of jet distortion.",0205377v1
+2006-12-07,Dynamics of a magnetized Bianchi I universe with vacuum energy,"We make use of a flat, axisymmetric Bianchi I metric to investigate the
+effects of a magnetic field upon the dynamics of the universe for the case in
+which the accompanying fluid is a cosmological constant and derive two exact
+solutions to the dynamical equations for this situation. We examine the
+behaviour of the scale factor perpendicular and parallel to the field lines,
+A(t) and W(t) respectively, and find the expected behaviour. The field has the
+strongest effect when A(t) is small, decelerating collapse perpendicular to the
+field lines, due to magnetic pressure, and accelerating collapse along the
+field lines, due to magnetic tension, while the vacuum energy dominates at late
+time, driving accelerated expansion.",0612168v2
+1999-04-08,Dynamics of vortex and magnetic lines in ideal hydrodynamics and MHD,"Vortex line and magnetic line representations are introduced for description
+of flows in ideal hydrodynamics and MHD, respectively. For incompressible
+fluids it is shown that the equations of motion for vorticity ${\bf \Omega}$
+and magnetic field with the help of this transformation follow from the
+variational principle. By means of this representation it is possible to
+integrate the system of hydrodynamic type with the Hamiltonian ${\cal{H}}=\int
+|{\bf \Omega}| d{\bf r}$. It is also demonstrated that these representations
+allow to remove from the noncanonical Poisson brackets, defined on the space of
+divergence-free vector fields, degeneracy connected with the vorticity
+frozenness for the Euler equation and with magnetic field frozenness for ideal
+MHD. For MHD a new Weber type transformation is found. It is shown how this
+transformation can be obtained from the two-fluid model when electrons and ions
+can be considered as two independent fluids. The Weber type transformation for
+ideal MHD gives the whole Lagrangian vector invariant. When this invariant is
+absent this transformation coincides with the Clebsch representation analog
+introduced by Zakharov and Kuznetov.",9904015v1
+2000-05-30,Dynamical Properties of Spin-Orbital Chains in a Magnetic Field,"The excitation spectrum of the one-dimensional spin-orbital model in a
+magnetic field is studied, using a recently developed dynamical density matrix
+renormalization group technique. The method is employed on chains with up to 80
+sites, and examined for test cases such as the spin-1/2 antiferromagnetic
+Heisenberg chain, where the excitation spectrum is known exactly from the Bethe
+Ansatz. In the spin-orbital chain, the characteristic dynamical response
+depends strongly on the model parameters and the applied magnetic field. The
+coupling between the spin and orbital degrees of freedom is found to influence
+the incommensuration at finite magnetizations. In the regions of the phase
+diagram with only massive spin and orbital excitations, a finite field is
+required to overcome the spin gap. An incommensurate orbital mode is found to
+become massless in this partially spin-polarized regime, indicating a strong
+coupling between the two degrees of freedom. In the critical region with three
+elementary gapless excitations, a prominent particle-hole excitation is
+observed at higher energies, promoted by the biquadratic term in the model
+Hamiltonian of the spin-orbital chain.",0005526v2
+2001-09-21,"Dynamic spin-glass behavior in a disorder-free, two-component model of quantum frustrated magnets","Motivated by the observation of a spin-glass transition in almost
+disorder-free Kagome antiferromagnets, and by the specific form of the
+effective low-energy model of the S=1/2, trimerized Kagome antiferromagnet, we
+investigate the possibility to obtain a spin-glass behavior in two-component,
+disorder-free models. We concentrate on a toy-model, a modified Ashkin-Teller
+model in a magnetic field that couples only to one species of spins, for which
+we prove that a dynamic spin-glass behavior occurs. The dynamics of the
+magnetization is closely related to that of the underlying Ising model in zero
+field in which spins and pseudo-spins are intimately coupled. The spin-glass
+like history dependence of the magnetization is a consequence of the ageing of
+the underlying Ising model.",0109406v2
+2002-08-06,Spin pumping and magnetization dynamics in metallic multilayers,"We study the magnetization dynamics in thin ferromagnetic films and small
+ferromagnetic particles in contact with paramagnetic conductors. A moving
+magnetization vector causes \textquotedblleft pumping\textquotedblright of
+spins into adjacent nonmagnetic layers. This spin transfer affects the
+magnetization dynamics similar to the Landau-Lifshitz-Gilbert phenomenology.
+The additional Gilbert damping is significant for small ferromagnets, when the
+nonmagnetic layers efficiently relax the injected spins, but the effect is
+reduced when a spin accumulation build-up in the normal metal opposes the spin
+pumping. The damping enhancement is governed by (and, in turn, can be used to
+measure) the mixing conductance or spin-torque parameter of the
+ferromagnet--normal-metal interface. Our theoretical findings are confirmed by
+agreement with recent experiments in a variety of multilayer systems.",0208091v2
+2002-09-03,Terahertz magneto-spectroscopy of transient plasmas in semiconductors,"Using synchronized near-infrared (NIR) and terahertz (THz) lasers, we have
+performed picosecond time-resolved THz spectroscopy of transient carriers in
+semiconductors. Specifically, we measured the temporal evolution of THz
+transmission and reflectivity after NIR excitation. We systematically
+investigated transient carrier relaxation in GaAs and InSb with varying NIR
+intensities and magnetic fields. Using this information, we were able to
+determine the evolution of the THz absorption to study the dynamics of
+photocreated carriers. We developed a theory based on a Drude conductivity with
+time-dependent density and density-dependent scattering lifetime, which
+successfully reproduced the observed plasma dynamics. Detailed comparison
+between experimental and theoretical results revealed a linear dependence of
+the scattering frequency on density, which suggests that electron-electron
+scattering is the dominant scattering mechanism for determining the scattering
+time. In InSb, plasma dynamics was dramatically modified by the application of
+a magnetic field, showing rich magneto-reflection spectra, while GaAs did not
+show any significant magnetic field dependence. We attribute this to the small
+effective masses of the carriers in InSb compared to GaAs, which made the
+plasma, cyclotron, and photon energies all comparable in the density, magnetic
+field, and wavelength ranges of the current study.",0209047v1
+2003-06-12,Nonequilibrium dynamics and magnetoviscosity of moderately concentrated magnetic liquids: A dynamic mean--field study,"A mean-field Fokker-Planck equation approach to the dynamics of ferrofluids
+in the presence of a magnetic field and velocity gradients is proposed that
+incorporates magnetic dipole-dipole interactions of the colloidal particles.
+The model allows to study the combined effect of a magnetic field and dipolar
+interactions on the viscosity of the ferrofluid. It is found that dipolar
+interactions lead to additional non-Newtonian contributions to the stress
+tensor, which modify the behavior of the non-interacting system. The
+predictions of the present model are in qualitative agreement with experimental
+results, such as presence of normal stress differences, enhancement and
+different anisotropy of magnetoviscous effect and the dependence of the
+viscosity on the hydrodynamic volume fraction. A quantitative comparison of the
+concentration dependence of the magnetoviscosity shows good agreement with
+experimental results for low concentrations.",0306313v1
+2005-03-19,"Correlations, spin dynamics, defects: the highly-frustrated Kagomé bilayer","The SrCr$\_{9p}$Ga$\_{12-9p}$O$\_{19}$ and
+Ba$\_{2}$Sn$\_{2}$ZnGa$\_{10-7p}$Cr$\_{7p}$O$\_{22}$ compounds are two
+highly-frustrated magnets possessing a quasi-two-dimensional Kagom\'{e} bilayer
+of spin 3/2 chromium ions with antiferromagnetic interactions. Their magnetic
+susceptibility was measured by local Nuclear Magnetic Resonance and non-local
+(SQUID) techniques, and their low-temperature spin dynamics by Muon Spin
+Resonance. Consistent with the theoretical picture drawn for geometrically
+frustrated systems, the Kagom\'{e} bilayer is shown here to exhibit: (i) short
+range spin-spin correlations down to a temperature much lower than the
+Curie-Weiss temperature, no conventional long-range transition occurring; (ii)
+a Curie contribution to the susceptibility from paramagnetic defects generated
+by spin vacancies; (iii) low-temperature spin fluctuations, at least down to 30
+mK, which are a trademark of a dynamical ground state. These properties point
+to a spin-liquid ground state, possibly built on Resonating Valence Bonds with
+unconfined spinons as the magnetic excitations.",0503496v1
+2005-07-20,All-optical probe of precessional magnetization dynamics in exchange biased NiFe/FeMn bilayers,"An internal anisotropy pulse field is launched by an 8.3 ps short laser
+excitation, which triggers precessional magnetization dynamics of a
+polycrystalline NiFe/FeMn exchange bias system on the picosecond timescale. Due
+to the excitation the unidirectional anisotropy and, thus, the exchange
+coupling across the interface between the ferromagnetic and the
+antiferromagnetic layer is reduced, leading to a fast reduction of the exchange
+bias field and to a dramatic increase of the zero-field susceptibility. The
+fast optical unpinning is followed by a slower recovery of the interfacial
+exchange coupling dominated by spin-lattice and heat flow relaxation with a
+time constant of the order of 160 ps. The measured picosecond time evolution of
+the exchange decoupling and restoration is interpreted as an anisotropy pulse
+field giving rise to fast precessional magnetization dynamics of the
+ferromagnetic layer. The strength of the internal pulse field and even the
+initial magnetization deflection direction from the equilibrium orientation can
+be controlled by the absorbed photons. The dependence of the effective Gilbert
+damping on both small and large angle precessional motion was studied, yielding
+that both cases can be modeled with reasonable accuracy within the
+Landau-Lifshitz and Gilbert framework.",0507475v1
+2006-01-10,Quantum beat phenomenon presence in coherent spin dynamics of spin-2 $^{87}$Rb atoms in a deep optical lattice,"Motivated by the recent experimental work (A. Widera, \textit{et al}, Phys.
+Rev. Lett. 95, 19045), we study the collisional spin dynamics of two spin-2 $%
+^{87}$Rb atoms confined in a deep optical lattice. When the system is
+initialized as $|0,0>$, three different two-particle Zeeman states are involved
+in the time evolution due to the conservation of magnetization. For a large
+magnetic field $B>0.8$ Guass, the spin coherent dynamics reduces to a Rabi-like
+oscillation between the states $|0,0>$ and $% |1,-1>$. However, under a small
+magnetic field, a general three-level coherent oscillation displays. In
+particular, around a critical magnetic field $B_{c}\simeq 0.48$ Guass, the
+probability in the Zeeman states $% |2,-2> $ exhibits a novel quantum beat
+phenomenon, ready to be confirmed in future experiments.",0601188v1
+2006-04-21,Dynamic approach for micromagnetics close to the Curie temperature,"In conventional micromagnetism magnetic domain configurations are calculated
+based on a continuum theory for the magnetization which is assumed to be of
+constant length in time and space. Dynamics is usually described with the
+Landau-Lifshitz-Gilbert (LLG) equation the stochastic variant of which includes
+finite temperatures. Using simulation techniques with atomistic resolution we
+show that this conventional micromagnetic approach fails for higher
+temperatures since we find two effects which cannot be described in terms of
+the LLG equation: i) an enhanced damping when approaching the Curie temperature
+and, ii) a magnetization magnitude that is not constant in time. We show,
+however, that both of these effects are naturally described by the
+Landau-Lifshitz-Bloch equation which links the LLG equation with the theory of
+critical phenomena and turns out to be a more realistic equation for
+magnetization dynamics at elevated temperatures.",0604508v1
+2006-07-03,Slow dynamics at the smeared phase transition of randomly layered magnets,"We investigate a model for randomly layered magnets, viz. a three-dimensional
+Ising model with planar defects. The magnetic phase transition in this system
+is smeared because static long-range order can develop on isolated rare spatial
+regions. Here, we report large-scale kinetic Monte Carlo simulations of the
+dynamical behavior close to the smeared phase transition which we characterize
+by the spin (time) autocorrelation function. In the paramagnetic phase, its
+behavior is dominated by Griffiths effects similar to those in magnets with
+point defects. In the tail region of the smeared transition the dynamics is
+even slower: the autocorrelation function decays like a stretched exponential
+at intermediate times before approaching the exponentially small asymptotic
+value following a power law at late times. Our Monte-Carlo results are in good
+agreement with recent theoretical predictions based on optimal fluctuation
+theory.",0607025v2
+2007-01-11,Dynamical chiral symmetry breaking by a magnetic field and multi-quark interactions,"Catalysis of dynamical symmetry breaking by a constant magnetic field in
+(3+1) dimensions is considered. We use the three flavour Nambu -- Jona-Lasinio
+type model with 't Hooft and eight-quark interaction terms. It is shown that
+the multi-quark interactions introduce new additional features to this
+phenomenon: (a) the local minimum of the effective potential catalyzed by the
+constant magnetic field is smoothed out with increasing strength of the field
+at the characteristic scale H~10^{19} G, (b) the multi-quark forces generate
+independently another local minimum associated with a larger dynamical fermion
+mass. This state may exist even for multi-quark interactions with a subcritical
+set of couplings, and is globally stable with respect to a further increase of
+the magnetic field.",0701090v2
+1996-05-05,The Gross-Neveu Model and the Supersymmetric and Non-Supersymmetric Nambu-Jona-Lasinio Model in a Magnetic Field,"The infrared dynamics in the (3+1)-dimensional supersymmetric and
+non-supersymmetric Nambu-Jona-Lasinio model in a constant magnetic field is
+studied. While at strong coupling the dynamics in these two models is
+essentially different, it is shown that the models become equivalent at weak
+coupling. In particular, at weak coupling, as the strength of the magnetic
+field goes to infinity, both the supersymmetric and non-supersymmetric
+Nambu-Jona-Lasinio models are reduced to a continuum set of independent
+(1+1)-dimensional Gross-Neveu models, labeled by the coordinates in the plane
+perpendicular to the magnetic field. The relevance of these results for
+cosmological models based on supersymmetric dynamics is pointed out.",9605027v4
+1998-02-13,Dynamical Generation of Fermion Mass and Magnetic Field in Three-Dimensional QED with Chern-Simons Term,"We study dynamical symmetry breaking in three-dimensional QED with a
+Chern-Simons (CS) term, considering the screening effect of $N$ flavor
+fermions. We find a new phase of the vacuum, in which both the fermion mass and
+a magnetic field are dynamically generated, when the coefficient of the CS term
+$\kappa$ equals $N e^2/4 \pi$. The resultant vacuum becomes the finite-density
+state half-filled by fermions. For $\kappa=N e^2/2 \pi$, we find the fermion
+remains massless and only the magnetic field is induced. For $\kappa=0$,
+spontaneous magnetization does not occur and should be regarded as an external
+field.",9802101v2
+1998-05-17,Yukawa Interactions and Dynamical Generation of Mass in an External Magnetic Field,"In this work we study the dynamical generation of a fermion mass induced by a
+constant and uniform external magnetic field in an Abelian gauge model with a
+Yukawa term. We show that the Yukawa coupling not only enhances the dynamical
+generation of the mass, but it substantially decreases the magnetic field
+required for the mass to be generated at temperatures comparable to the
+electroweak critical temperature. These results indicate that if large enough
+primordial magnetic fields were present during the early universe evolution,
+the field-induced generation of fermion masses, which in turn corresponds to
+the generation of fermion bound states, may play an important role in the
+electroweak phase transition.",9805103v2
+2001-08-30,Effect of Dynamical SU(2) Gluons to the Gap Equation of Nambu--Jona-Lasinio Model in Constant Background Magnetic Field,"In order to estimate the effect of dynamical gluons to chiral condensate, the
+gap equation of SU(2) gauged Nambu--Jona-Lasinio model, under a constant
+background magnetic field, is investigated up to the two-loop order in 2+1 and
+3+1 dimensions. We set up a general formulation allowing both cases of electric
+as well as magnetic background field. We rely on the proper time method to
+maintain gauge invariance. In 3+1 dimensions chiral symmetry breaking
+($\chi$SB) is enhanced by gluons even in zero background magnetic field and
+becomes much striking as the background field grows larger. In 2+1 dimensions
+gluons also enhance $\chi$SB but whose dependence on the background field is
+not simple: dynamical mass is not a monotone function of background field for a
+fixed four-fermi coupling.",0108225v1
+2000-12-04,Dynamo effect in parity-invariant flow with large and moderate separation of scales,"It is shown that non-helical (more precisely, parity-invariant) flows capable
+of sustaining a large-scale dynamo by the negative magnetic eddy diffusivity
+effect are quite common. This conclusion is based on numerical examination of a
+large number of randomly selected flows. Few outliers with strongly negative
+eddy diffusivities are also found, and they are interpreted in terms of the
+closeness of the control parameter to a critical value for generation of a
+small-scale magnetic field. Furthermore, it is shown that, for parity-invariant
+flows, a moderate separation of scales between the basic flow and the magnetic
+field often significantly reduces the critical magnetic Reynolds number for the
+onset of dynamo action.",0012005v2
+2007-11-04,On connecting the dynamics of the chromosphere and transition region with Hinode SOT and EIS,"We use coordinated Hinode SOT/EIS observations that include high-resolution
+magnetograms, chromospheric and TR imaging and TR/coronal spectra in a first
+test to study how the dynamics of the TR are driven by the highly dynamic
+photospheric magnetic fields and the ubiquitous chromospheric waves. Initial
+analysis shows that these connections are quite subtle and require a
+combination of techniques including magnetic field extrapolations,
+frequency-filtered time-series and comparisons with synthetic chromospheric and
+TR images from advanced 3D numerical simulations. As a first result, we find
+signatures of magnetic flux emergence as well as 3 and 5 mHz wave power above
+regions of enhanced photospheric magnetic field in both chromospheric,
+transition region and coronal emission.",0711.0487v1
+2008-02-01,Ultrafast dynamics of a magnetic antivortex - Micromagnetic simulations,"The antivortex is a fundamental magnetization structure which is the
+topological counterpart of the well-known magnetic vortex. We study here the
+ultrafast dynamic behavior of an isolated antivortex in a patterned Permalloy
+thin-film element. Using micromagnetic simulations we predict that the
+antivortex response to an ultrashort external field pulse is characterized by
+the production of a new antivortex as well as of a temporary vortex, followed
+by an annihilation process. These processes are complementary to the recently
+reported response of a vortex and, like for the vortex, lead to the reversal of
+the orientation of the antivortex core region. In addition to its fundamental
+interest, this dynamic magnetization process could be used for the generation
+and propagation of spin waves for novel logical circuits.",0802.0093v1
+2008-02-11,Dynamic localization of lattice electrons under time dependent electric and magnetic fields,"Applying the method of characteristics leads to wavefunctions and dynamic
+localization conditions for electrons on the one dimensional lattice under
+perpendicular time dependent electric and magnetic fields. Such conditions
+proceed again in terms of sums of products of Bessel functions of the first
+kind. However, this time one deals with both the number of magnetic flux quanta
+times $\pi $ and the quotients between the Bloch frequency and the ones
+characterizing competing fields. Tuning the phases of time dependent
+modulations leads to interesting frequency mixing effects providing an
+appreciable simplification of dynamic localization conditions one looks for.
+The understanding is that proceeding in this manner, the time dependent
+superposition mentioned above gets reduced effectively to the influence of
+individual ac-fields exhibiting mixed frequency quotients. Besides pure field
+limits and superpositions between uniform electric and time dependent magnetic
+fields, parity and periodicity effects have also been discussed.",0802.1449v1
+2008-05-14,Persistent Spin Dynamics in the $S=1/2$ V$_{15}$ Molecular Nano-Magnet,"We present muon spin lattice relaxation measurements in the V15 spin 1/2
+molecular nano-magnet. We find that the relaxation rate in low magnetic fields
+(<5 kG) is temperature independent below ~10 K, implying that the molecular
+spin is dynamically fluctuating down to 12 mK. These measurements show that the
+fluctuation time increases as the temperature is decreased and saturates at a
+value of ~6 nsec at low temperatures. The fluctuations are attributed to V15
+molecular spin dynamics perpendicular to the applied magnetic field direction,
+induced by coupling between the molecular spin and nuclear spin bath in the
+system.",0805.2164v1
+2008-10-06,Dynamics of a self-gravitating magnetized neutron source,"The dynamics of a self-gravitating neutron gas in presence of a magnetic
+field is being studied taking the equation of state of a magnetized neutron gas
+obtained in a previous study [2]. We work in a Bianchi I spacetime
+characterized by a Kasner metric, this metric allow us to take into account the
+anisotropy that introduces the magnetic field. The set of Einstein-Maxwell
+field equations for this gas becomes a dynamical system in a 4-dimensional
+phase space. We get numerical solutions of the system. In particular there is a
+unique point like solution for different initial conditions. Physically this
+singular solution may be associated with the collapse of a local volume of
+neutron material within a neutron star.",0810.1071v2
+2009-01-01,Exact results for the criticality of quench dynamics in quantum Ising models,"Based on the obtained exact results we systematically study the quench
+dynamics of a one-dimensional spin-1/2 transverse field Ising model with zero-
+and finite-temperature initial states. We focus on the magnetization of the
+system after a sudden change of the external field and a coherent
+time-evolution process. With a zero-temperature initial state, the quench
+magnetic susceptibility as a function of the initial field strength exhibits
+strongly similar scaling behaviors to those of the static magnetic
+susceptibility, and the quench magnetic susceptibility as a function of the
+final field strength shows a discontinuity at the quantum critical point. This
+discontinuity remains robust and always occurs at the quantum critical point
+even for the case of finite-temperature initial systems, which indicates a
+great advantage of employing quench dynamics to study quantum phase
+transitions.",0901.0158v2
+2009-11-20,Spin Transfer Dynamics in Spin Valves with Out-of-plane Magnetized CoNi Free Layers,"We have measured spin transfer-induced dynamics in magnetic nanocontact
+devices having a perpendicularly magnetized Co/Ni free layer and an in-plane
+magnetized CoFe fixed layer. The frequencies and powers of the excitations
+agree well with the predictions of the single-domain model and indicate that
+the excited dynamics correspond to precessional orbits with angles ranging from
+zero to 90 degrees as the applied current is increased at a fixed field. From
+measurements of the onset current as a function of applied field strength we
+estimate the magnitude of the spin torque asymmetry parameter lambda ~ 1.5. By
+combining these with spin torque ferromagnetic resonance measurements, we also
+estimate the spin wave radiation loss in these devices.",0911.4077v1
+2010-09-22,Optimal control of magnetization dynamics in ferromagnetic heterostructures by spin--polarized currents,"We study the switching-process of the magnetization in a
+ferromagnetic-normal-metal multilayer system by a spin polarized electrical
+current via the spin transfer torque. We use a spin drift-diffusion equation
+(SDDE) and the Landau-Lifshitz-Gilbert equation (LLGE) to capture the coupled
+dynamics of the spin density and the magnetization dynamic of the
+heterostructure. Deriving a fully analytic solution of the stationary SDDE we
+obtain an accurate, robust, and fast self-consistent model for the
+spin-distribution and spin transfer torque inside general ferromagnetic/normal
+metal heterostructures. Using optimal control theory we explore the switching
+and back-switching process of the analyzer magnetization in a seven-layer
+system. Starting from a Gaussian, we identify a unified current pulse profile
+which accomplishes both processes within a specified switching time.",1009.4296v2
+2011-09-07,The dynamics of azurite Cu$_3$(CO$_3$)$_2$(OH)$_2$ in a magnetic field as determined by neutron scattering,"Azurite, a natural mineral made up of CuO chains, is also an intriguing
+spin-1/2 quantum magnet. There has been much debate as to the 1-dimensional
+(1D) nature of this material by theorists and experimentalists alike. The focus
+of this debate lies in the interactions between Cu-ions within the
+antiferromagnetically ordered state below 1.9 K. We present high-resolution
+inelastic neutron scattering data which highlight the complexity of the
+magnetic ground state of azurite. The application of magnetic fields and
+temperatures were used to probe the excitations revealing important information
+about the dynamics in this system. From this we are able to conclude that the
+1D Heisenberg antiferromagnetic spin chain model is not sufficient to describe
+the dynamics in azurite. Instead additional coupling including interchain
+interactions and an anisotropic staggered field are necessary to fully model
+the observed excitations.",1109.1369v1
+2011-09-30,Charge localization and dynamical spin locking in double quantum dots driven by ac magnetic fields,"We investigate electron localization and dynamical spin locking induced by ac
+magnetic fields in double quantum dots. We demonstrate that by tuning the ac
+magnetic fields parameters, i.e., the field intensity, frequency, and the phase
+difference between the fields within each dot, coherent destruction of
+tunneling (and thus charge localization) can be achieved. We show that in
+contrast with ac electric fields, ac magnetic fields are able to induce spin
+locking, i.e., to freeze the electronic spin, at certain field parameters. We
+show how the symmetry of the Hamiltonian determines the quasienergy spectrum
+which presents degeneracies at certain field parameters, and how it is
+reflected in the charge and spin dynamics.",1109.6934v1
+2011-12-13,Quantum dynamical screening of the local magnetic moment in Fe-based superconductors,"We have calculated the local magnetic susceptibility of one of the
+prototypical Fe-based superconductors (LaFeAsO) by means of the local density
+approximation + dynamical mean field theory as a function of both (imaginary)
+time and real frequencies with and without vertex corrections. Vertex
+corrections are essential for obtaining the correct $\omega$-dependence, in
+particular a pronounced low-energy peak at $\omega \sim 0.2 $eV, which
+constitutes the hallmark of the dynamical screening of a large instantaneous
+magnetic moment on the Fe atoms. In experiments, however, except for the case
+of x-ray absorption spectroscopy (XAS), the magnetic moment or the
+susceptibility represent typically the average over long time scales. In this
+respect, the frequency range of typical neutron experiments would be too
+limited to directly estimate the magnitude of the short-time moment.",1112.3002v2
+2012-02-07,Prediction of Giant Spin Motive Force due to Rashba Spin-Orbit Coupling,"Magnetization dynamics in a ferromagnet can induce a spin-dependent electric
+field through spin motive force. Spin current generated by the spin-dependent
+electric field can in turn modify the magnetization dynamics through
+spin-transfer torque. While this feedback effect is usually weak and thus
+ignored, we predict that in Rashba spin-orbit coupling systems with large
+Rashba parameter $\alpha_{\rm R}$, the coupling generates the spin-dependent
+electric field [$\pm(\alpha_{\rm R}m_e/e\hbar) (\vhat{z}\times \partial
+\vec{m}/\partial t)]$, which can be large enough to modify the magnetization
+dynamics significantly. This effect should be relevant for device applications
+based on ultrathin magnetic layers with strong Rashba spin-orbit coupling.",1202.1406v2
+2013-04-15,Neutron Scattering and Its Application to Strongly Correlated Systems,"Neutron scattering is a powerful probe of strongly correlated systems. It can
+directly detect common phenomena such as magnetic order, and can be used to
+determine the coupling between magnetic moments through measurements of the
+spin-wave dispersions. In the absence of magnetic order, one can detect diffuse
+scattering and dynamic correlations. Neutrons are also sensitive to the
+arrangement of atoms in a solid (crystal structure) and lattice dynamics
+(phonons). In this chapter, we provide an introduction to neutrons and neutron
+sources. The neutron scattering cross section is described and formulas are
+given for nuclear diffraction, phonon scattering, magnetic diffraction, and
+magnon scattering. As an experimental example, we describe measurements of
+antiferromagnetic order, spin dynamics, and their evolution in the
+La(2-x)Ba(x)CuO(4) family of high-temperature superconductors.",1304.4214v1
+2013-09-18,Self-consistent modeling of the dynamic evolution of magnetic island growth in the presence of stabilizing ECCD,"The most promising technique for the control of neoclassical tearing modes in
+tokamak experiments is the compensation of the missing bootstrap current with
+electron-cyclotron current drive. In this frame, the dynamics of magnetic
+islands has been studied extensively in terms of the modified Rutherford
+equation, including the presence of current drive, either analytically
+described or computed by numerical methods. In this article, a self-consistent
+model for the dynamic evolution of the magnetic island and the driven current
+is derived, which takes into account the island's magnetic topology and its
+effect on the current drive. The model combines the modified Rutherford
+equation with a ray-tracing approach to electron-cyclotron wave propagation and
+absorption. Numerical results exhibit a decrease in the time required for
+complete stabilization with respect to the conventional computation (not taking
+into account the island geometry), which increases with increasing initial
+island size and radial misalignment of the deposition.",1309.4571v1
+2013-11-08,Curvature effects in statics and dynamics of a thin magnetic shell,"Equations of the magnetization dynamics are derived for an arbitrary curved
+2D surface. General static solutions are obtained in the limit of a strong
+anisotropy of both signs (easy-surface and easy-normal cases). It is shown that
+the effect of the curvature can be treated as appearance of an effective
+magnetic field which is aligned along the surface normal for the case of
+easy-surface anisotropy and it is tangential to the surface for the case of
+easy-normal anisotropy. In general, the existence of such a field denies the
+solutions strictly tangential as well as strictly normal to the surface. As an
+example we consider static equilibrium solutions and linear dynamics for a cone
+surface magnetization.",1311.2026v2
+2014-01-08,Transport enhancement and suppression in turbulent magnetic reconnection: A self-consistent turbulence model,"Through the enhancement of transport, turbulence is expected to contribute to
+the fast reconnection. However the effects of turbulence are not so
+straightforward. In addition to the enhancement of transport, turbulence under
+some environment shows effects that suppress the transport. In the presence of
+turbulent cross helicity, such a dynamic balance between the transport
+enhancement and suppression occurs. As this result of dynamic balance, the
+region of effective enhanced magnetic diffusivity is confined to a narrow
+region, leading to the fast reconnection. In order to confirm this idea, a
+self-consistent turbulence model for the magnetic reconnection is proposed.
+With the aid of numerical simulations where turbulence effects are incorporated
+in a consistent manner through the turbulence model, the dynamic balance in the
+turbulence magnetic reconnection is confirmed.",1401.1498v1
+2014-01-15,Landau-Stark states and edge-induced Bloch oscillations in topological lattices,"We consider dynamics of a charged particle in a finite along the $x$
+direction square lattice in the presence of normal to the lattice plane
+magnetic field and in-plane electric field aligned with the $y$ axis. For
+vanishing magnetic field this dynamics would be common Bloch oscillations where
+the particle oscillates in the $y$ direction with amplitude inverse
+proportional to the electric field. We show that a non-zero magnetic field
+crucially modifies this dynamics. Namely, the new Bloch oscillations consist of
+time intervals where the particle moves with constant velocity in the $x$
+direction intermitted by intervals where it is accelerated or decelerated along
+the lattice edges. The analysis is done in terms of the Landau-Stark states
+which are eigenstates of a quantum particle in a two-dimensional lattice
+subject to (real or synthetic) electric and magnetic fields.",1401.3411v1
+2014-03-06,Momentum space anisotropy of electronic correlations in Fe and Ni - an analysis of magnetic Compton profiles,"The total and magnetically resolved Compton profiles are analyzed within the
+combined density functional and dynamical mean field theory for the transition
+metal elements Fe and Ni. A rather good agreement between the measured and
+computed magnetic Compton profiles (MCPs) of Fe and Ni is obtained with the
+standard Local Spin Density Approximation (LSDA). By including local but
+dynamic many-body correlations captured by Dynamical Mean Field Theory (DMFT),
+the calculated magnetic Compton profile is further improved when compared with
+experiment. The second moment of the difference of the total Compton profiles
+between LSDA and DMFT, along the same momentum direction, has been used to
+discuss the strength of electronic correlations in Fe and Ni.",1403.1503v1
+2014-03-24,Hyperchaotic Intermittent Convection in a Magnetized Viscous Fluid,"We consider a low-dimensional model of convection in a horizontally
+magnetized layer of a viscous fluid heated from below. We analyze in detail the
+stability of hydromagnetic convection for a wide range of two control
+parameters. Namely, when changing the initially applied temperature difference
+or magnetic field strength, one can see transitions from regular to irregular
+long-term behavior of the system, switching between chaotic, periodic, and
+equilibrium asymptotic solutions. It is worth noting that owing to the induced
+magnetic field a transition to hyperchaotic dynamics is possible for some
+parameters of the model. We also reveal new features of the generalized Lorenz
+model, including both type I and III intermittency.",1403.6169v1
+2014-07-17,Nonlinear mirror instability,"Slow dynamical changes in magnetic-field strength and invariance of the
+particles' magnetic moments generate ubiquitous pressure anisotropies in weakly
+collisional, magnetized astrophysical plasmas. This renders them unstable to
+fast, small-scale mirror and firehose instabilities, which are capable of
+exerting feedback on the macroscale dynamics of the system. By way of a new
+asymptotic theory of the early nonlinear evolution of the mirror instability in
+a plasma subject to slow shearing or compression, we show that the instability
+does not saturate quasilinearly at a steady, low-amplitude level. Instead, the
+trapping of particles in small-scale mirrors leads to nonlinear secular growth
+of magnetic perturbations, $\delta B/B \propto t^{2/3}$. Our theory explains
+recent collisionless simulation results, provides a prediction of the mirror
+evolution in weakly collisional plasmas and establishes a foundation for a
+theory of nonlinear mirror dynamics with trapping, valid up to $\delta B/B
+=O(1)$.",1407.4707v1
+2014-07-23,Modulating spin transfer torque switching dynamics with two orthogonal spin-polarizers by varying the cell aspect ratio,"We study in-plane magnetic tunnel junctions with additional perpendicular
+polarizer for subnanosecond-current-induced switching memories. The
+spin-transfer-torque switching dynamics was studied as a function of the cell
+aspect ratio both experimentally and by numerical simulations using the
+macrospin model. We show that the anisotropy field plays a significant role in
+the dynamics, along with the relative amplitude of the two spin-torque
+contributions. This was confirmed by micromagnetic simulations. Real-time
+measurements of the reversal were performed with samples of low and high aspect
+ratio. For low aspect ratios, a precessional motion of the magnetization was
+observed and the effect of temperature on the precession coherence was studied.
+For high aspect ratios, we observed magnetization reversals in less than 1 ns
+for high enough current densities, the final state being controlled by the
+current direction in the magnetic tunnel junction cell.",1407.6240v2
+2014-08-30,Geometric Quantum Noise of Spin,"The presence of geometric phases is known to affect the dynamics of the
+systems involved. Here we consider a quantum degree of freedom, moving in a
+dissipative environment, whose dynamics is described by a Langevin equation
+with quantum noise. We show that geometric phases enter the stochastic noise
+terms. Specifically, we consider small ferromagnetic particles (nano-magnets)
+or quantum dots close to Stoner instability, and investigate the dynamics of
+the total magnetization in the presence of tunneling coupling to the metallic
+leads. We generalize the Ambegaokar-Eckern-Sch\""on (AES) effective action and
+the corresponding semiclassical equations of motion from the U(1) case of the
+charge degree of freedom to the SU(2) case of the magnetization. The Langevin
+forces (torques) in these equations are strongly influenced by the geometric
+phase. As a first but nontrivial application we predict low temperature quantum
+diffusion of the magnetization on the Bloch sphere, which is governed by the
+geometric phase. We propose a protocol for experimental observation of this
+phenomenon.",1409.0150v2
+2014-09-08,"Dynamics of magnetization and carriers at the onset of the photo-excited precession of magnetization in (Ga,Mn)As","Photo-excited precession of magnetization in (Ga,Mn)As is investigated by
+measuring time-resolved magneto-optical response and transient differential
+reflectivity with pump-and-probe technique. In the time region less than 1 ps,
+rapidly oscillating and spike-like signals are observed, respectively, with
+excitation of below and above the GaAs band gap. Analysis with gyromagnetic
+model and autocorrelation function concludes that those signals are not
+attributed to ultrafast demagnetization but due to interference between pump
+and probe pulses incorporating sub-ps carrier dynamics characteristic of
+low-temperature grown semiconductors. Photo-ionization of Mn ions (Mn2+ ->
+Mn3+) is proposed as a mechanism which dynamically induces orbital angular
+momentum and affects hole-mediated magnetic anisotropy in (Ga,Mn)As.",1409.2209v1
+2014-10-14,Spin precession mapping at ferromagnetic resonance via nuclear resonant scattering,"We probe the spin dynamics in a thin magnetic film at ferromagnetic resonance
+by nuclear resonant scattering of synchrotron radiation at the 14.4 keV
+resonance of $^{57}$Fe. The precession of the magnetization leads to an
+apparent reduction of the magnetic hyperfine field acting at the $^{57}$Fe
+nuclei. The spin dynamics is described in a stochastic relaxation model adapted
+to the ferromagnetic resonance theory by Smit and Beljers to model the decay of
+the excited nuclear state. From the fits of the measured data the shape of the
+precession cone of the spins is determined. Our results open a new perspective
+to determine magnetization dynamics in layered structures with very high depth
+resolution by employing ultrathin isotopic probe layers.",1410.3689v1
+2014-11-13,Transverse dynamical magnetic susceptibilities from regular static density functional theory: Evaluation of damping and g-shifts of spin-excitations,"The dynamical transverse magnetic Kohn-Sham susceptibility calculated within
+time-dependent density functional theory shows a fairly linear behavior for a
+finite energy window. This observation is used to propose a scheme where the
+computation of this quantity is greatly simplified. Regular simulations based
+on static density functional theory can be used to extract the dynamical
+behavior of the magnetic response function. Besides the ability to calculate
+elegantly damping of magnetic excitations, we derive along the way useful
+equations giving the main characteristics of these excitations: effective
+$g$-factors and the resonance frequencies that can be accessed experimentally
+using inelastic scanning tunneling spectroscopy or spin-polarized electron
+energy loss spectroscopy.",1411.3630v1
+2015-02-14,Barkhausen noise in the Random Field Ising Magnet Nd$_2$Fe$_{14}$B,"With sintered needles aligned and a magnetic field applied transverse to its
+easy axis, the rare-earth ferromagnet Nd$_2$Fe$_{14}$B becomes a
+room-temperature realization of the Random Field Ising Model. The transverse
+field tunes the pinning potential of the magnetic domains in a continuous
+fashion. We study the magnetic domain reversal and avalanche dynamics between
+liquid helium and room temperatures at a series of transverse fields using a
+Barkhausen noise technique. The avalanche size and energy distributions follow
+power-law behavior with a cutoff dependent on the pinning strength dialed in by
+the transverse field, consistent with theoretical predictions for Barkhausen
+avalanches in disordered materials. A scaling analysis reveals two regimes of
+behavior: one at low temperature and high transverse field, where the dynamics
+are governed by the randomness, and the second at high temperature and low
+transverse field where thermal fluctuations dominate the dynamics.",1502.04234v1
+2015-02-18,"Dynamics of Electric Currents, Magnetic Field Topology and Helioseismic Response of a Solar Flare","The solar flare on July 30, 2011 was of a modest X-ray class (M9.3), but it
+made a strong photospheric impact and produced a ""sunquake,"" observed with the
+Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics Observatory
+(SDO). In addition to the helioseismic waves (also observed with the SDO/AIA
+instrument), the flare caused a large expanding area of white-light emission
+and was accompanied by substantial restructuring of magnetic fields, leading to
+the rapid formation of a sunspot structure in the flare region. The flare
+produced no significant hard X-ray emission and no coronal mass ejection. This
+indicates that the flare energy release was mostly confined to the lower
+atmosphere. The absence of significant coronal mass ejection rules out magnetic
+rope eruption as a mechanism of helioseismic waves. We discuss the connectivity
+of the flare energy release with the electric currents dynamics and show the
+potential importance of high-speed plasma flows in the lower solar atmosphere
+during the flare energy release.",1502.05190v1
+2015-02-24,Coarsening dynamics driven by vortex-antivortex annihilation in ferromagnetic Bose-Einstein condensates,"In ferromagnetic Bose-Einstein condensates (BECs), the quadratic Zeeman
+effect controls magnetic anisotropy, which affects on magnetic domain pattern
+formation. While the longitudinal magnetization is dominant (similar to the
+Ising model) for a negative quadratic Zeeman energy, the transverse
+magnetization is dominant (similar to the XY model) for a positive one. When
+the quadratic Zeeman energy is positive, the coarsening dynamics is driven by
+vortex-antivortex annihilation in the same way as the XY model. However, due to
+superfluid flow of atoms, there exist several combinations of vortex-antivortex
+pairs in ferromagnetic BECs, which makes the coarsening dynamics more
+complicated than that of the XY model. We propose a revised domain growth law,
+which is based on the growth law of the two-dimensional XY model, for a
+two-dimensional ferromagnetic BEC with a positive quadratic Zeeman energy.",1502.06673v3
+2015-03-24,Far-from-equilibrium dynamics of a strongly coupled non-Abelian plasma with non-zero charge density or external magnetic field,"Using holography, we study the evolution of a spatially homogeneous, far from
+equilibrium, strongly coupled N=4 supersymmetric Yang-Mills plasma with a
+non-zero charge density or a background magnetic field. This gauge theory
+problem corresponds, in the dual gravity description, to an initial value
+problem in Einstein-Maxwell theory with homogeneous but anisotropic initial
+conditions. We explore the dependence of the equilibration process on different
+aspects of the initial departure from equilibrium and, while controlling for
+these dependencies, examine how the equilibration dynamics are affected by the
+presence of a non-vanishing charge density or an external magnetic field. The
+equilibration dynamics are remarkably insensitive to the addition of even large
+chemical potentials or magnetic fields; the equilibration time is set primarily
+by the form of the initial departure from equilibrium. For initial deviations
+from equilibrium which are well localized in scale, we formulate a simple model
+for equilibration times which agrees quite well with our results.",1503.07148v2
+2015-05-01,Spin-charge transport driven by magnetization dynamics on disordered surface of doped topological insulators,"We theoretically study the spin and charge generation along with the electron
+transport on a disordered surface of a doped three-dimensional topological
+insulator/magnetic insulator junction by using Green's function techniques. We
+find that the spin and charge current are induced by not only local but also
+nonlocal magnetization dynamics through nonmagnetic impurity scattering on the
+disordered surface of the doped topological insulator. We also clarify that the
+spin current as well as charge density are induced by spatially inhomogeneous
+magnetization dynamics, and the spin current diffusively propagates on the
+disordered surface. Using these results, we discuss both local and nonlocal
+spin torques before and after the spin and spin current generation on the
+surface, and provide a procedure to detect the spin current.",1505.00106v1
+2015-09-07,Quantum speed limit for a relativistic electron in a uniform magnetic field,"We analyze the influence of relativistic effects on the minimum evolution
+time between two orthogonal states of a quantum system. Defining the initial
+state as an homogeneous superposition between two Hamiltonian eigenstates of an
+electron in a uniform magnetic field, we obtain a relation between the minimum
+evolution time and the displacement of the mean radial position of the electron
+wavepacket. The quantum speed limit time is calculated for an electron dynamics
+described by Dirac and Schroedinger-Pauli equations considering different
+parameters, such as the strength of magnetic field and the linear momentum of
+the electron in the axial direction. We highlight that when the electron
+undergoes a region with extremely strong magnetic field the relativistic and
+non-relativistic dynamics differ substantially, so that the description given
+by Schroedinger-Pauli equation enables the electron traveling faster than c,
+which is prohibited by Einstein's theory of relativity. This approach allows a
+connection between the abstract Hilbert space and the space-time coordinates,
+besides the identification of the most appropriate quantum dynamics used to
+describe the electron motion.",1509.02057v1
+2016-01-21,Magneto--Coriolis waves in a spherical Couette flow experiment,"The dynamics of fluctuations in a fast rotating spherical Couette flow
+experiment in the presence of a strong dipolar magnetic field is investigated
+in detail, through a thorough analysis of the experimental data as well as a
+numerical study. Fluctuations within the conducting fluid (liquid sodium) are
+characterized by the presence of several oscillation modes, identified as
+magneto-Coriolis (MC) modes, with definite symmetry and azimuthal number. A
+numerical simulation provides eigensolutions which exhibit oscillation
+frequencies and magnetic signature comparable to the observation. The main
+characteristics of these hydromagnetic modes is that the magnetic contribution
+has a fundamental influence on the dynamical properties through the Lorentz
+forces, although its importance remains weak in an energetical point of view.
+Another specificity is that the Lorentz forces are confined near the inner
+sphere where the dipolar magnetic field is the strongest, while the Coriolis
+forces are concentrated in the outer fluid volume close to the outer sphere.",1601.05684v1
+2016-06-21,Torsion Effects and LLG Equation,"Based on the non-relativistic regime of the Dirac equation coupled to a
+torsion pseudo-vector, we study the dynamics of magnetization and how it is
+affected by the presence of torsion. We consider that torsion interacting terms
+in Dirac equation appear in two ways one of these is thhrough the covariant
+derivative considering the spin connection and gauge magnetic field and the
+other is through a non-minimal spin torsion coupling. We show within this
+framework, that it is possible to obtain the most general Landau, Lifshitz and
+Gilbert (LLG) equation including the torsion effects, where we refer to torsion
+as a geometric field playing an important role in the spin coupling process. We
+show that the torsion terms can give us two important landscapes in the
+magnetization dynamics: one of them related with damping and the other related
+with the screw dislocation that give us a global effect like a helix damping
+sharped. These terms are responsible for changes in the magnetization
+precession dynamics.",1606.06610v1
+2016-08-12,Dynamic response functions and helical gaps in interacting Rashba nanowires with and without magnetic fields,"A partially gapped spectrum due to the application of a magnetic field is one
+of the main probes of Rashba spin-orbit coupling in nanowires. Such a ""helical
+gap"" manifests itself in the linear conductance, as well as in dynamic response
+functions such as the spectral function, the structure factor, or the
+tunnelling density of states. In this paper, we investigate theoretically the
+signature of the helical gap in these observables with a particular focus on
+the interplay between Rashba spin-orbit coupling and electron-electron
+interactions. We show that in a quasi-one-dimensional wire, interactions can
+open a helical gap even without magnetic field. We calculate the dynamic
+response functions using bosonization, a renormalization group analysis, and
+the exact form factors of the emerging sine-Gordon model. For special
+interaction strengths, we verify our results by refermionization. We show how
+the two types of helical gaps, caused by magnetic fields or interactions, can
+be distinguished in experiments.",1608.03756v3
+2016-08-08,Simulations of Energetic Particles Interacting with Nonlinear Anisotropic Dynamical Turbulence,"We investigate test-particle diffusion in dynamical turbulence based on a
+numerical approach presented before. For the turbulence we employ the nonlinear
+anisotropic dynamical turbulence model which takes into account wave
+propagation effects as well as damping effects. We compute numerically
+diffusion coefficients of energetic particles along and across the mean
+magnetic field. We focus on turbulence and particle parameters which should be
+relevant for the solar system and compare our findings with different
+interplanetary observations. We vary different parameters such as the
+dissipation range spectral index, the ratio of the turbulence bendover scales,
+and the magnetic field strength in order to explore the relevance of the
+different parameters. We show that the bendover scales as well as the magnetic
+field ratio have a strong influence on diffusion coefficients whereas the
+influence of the dissipation range spectral index is weak. The best agreement
+with solar wind observations can be found for equal bendover scales and a
+magnetic field ratio of $\delta$B/B0 = 0.75.",1609.05226v1
+2016-09-27,Steady State and Dynamics of Joule Heating in Magnetic Tunnel Junctions Observed via the Temperature Dependence of RKKY Coupling,"Understanding quantitatively the heating dynamics in magnetic tunnel
+junctions (MTJ) submitted to current pulses is very important in the context of
+spin-transfer-torque magnetic random access memory development. Here we provide
+a method to probe the heating of MTJ using the RKKY coupling of a synthetic
+ferrimagnetic storage layer as a thermal sensor. The temperature increase
+versus applied bias voltage is measured thanks to the decrease of the spin-flop
+field with temperature. This method allows distinguishing spin transfer torque
+(STT) effects from the influence of temperature on the switching field. The
+heating dynamics is then studied in real-time by probing the conductance
+variation due to spin-flop rotation during heating. This approach provides a
+new method for measuring fast heating in spintronic devices, particularly
+magnetic random access memory (MRAM) using thermally assisted or spin transfer
+torque writing.",1609.08385v1
+2016-11-15,Dynamical and Reversible Control of Topological Spin Textures,"Recent observations of topological spin textures brought spintronics one step
+closer to new magnetic memories. Nevertheless, the existence of Skyrmions, as
+well as their stabilization, require very specific intrinsic magnetic
+properties which are usually fixed in magnets. Here we address the possibility
+to dynamically control their intrinsic magnetic interactions by varying the
+strength of a high-frequency laser field. It is shown that drastic changes can
+be induced in the antiferromagnetic exchange interactions and the latter can
+even be reversed to become ferromagnetic, provided the direct exchange is
+already non-negligible in equilibrium as predicted, for example, in Si doped
+with C, Sn, or Pb adatoms. In the presence of Dzyaloshinskii-Moriya
+interactions, this enables us to tune features of ferromagnetic Skyrmions such
+as their radius, making them easier to stabilize. Alternatively, such
+topological spin textures can occur in frustrated triangular lattices. Then, we
+demonstrate that a high-frequency laser field can induce dynamical frustration
+in antiferromagnets, where the degree of frustration can subsequently be tuned
+suitably to drive the material toward a Skyrmionic phase.",1611.05075v2
+2017-02-27,Dynamics of Bound Magnon Pairs in the Quasi-One-Dimensional Frustrated Magnet LiCuVO_4,"We report on the dynamics of the spin-1/2 quasi-one-dimensional frustrated
+magnet LiCuVO$\mathrm{_4}$ measured by nuclear spin relaxation in high magnetic
+fields 10--34 T, in which the ground state has spin-density-wave order. The
+spin fluctuations in the paramagnetic phase exhibit striking anisotropy with
+respect to the magnetic field. The transverse excitation spectrum probed by
+$^{51}$V nuclei has an excitation gap, which increases with field. On the other
+hand, the gapless longitudinal fluctuations sensed by $^7$Li nuclei grow with
+lowering temperature, but tend to be suppressed with increasing field. Such
+anisotropic spin dynamics and its field dependence agree with the theoretical
+predictions and are ascribed to the formation of bound magnon pairs, a
+remarkable consequence of the frustration between ferromagnetic nearest
+neighbor and antiferromagnetic next-nearest-neighbor interactions.",1702.08573v2
+2017-03-17,Dynamic nuclear spin polarization in self-assembled quantum dots under zero magnetic field,"We studied the zero-field dynamic nuclear spin polarization in a single
+In$_{0.75}$Al$_{0.25}$As/Al$_{0.3}$Ga$_{0.7}$As quantum dot. Even without any
+external magnetic field, the positive trion excited by the circularly-polarized
+light generated an Overhauser field of up to $\sim$0.8 T. From the excitation
+power dependences of the Overhauser field and degree of circular polarization
+of the photoluminescence spectra, the relation between the Overhauser field and
+Knight field under zero external magnetic field was revealed clearly. In
+addition, we found that the nuclear depolarization rate decreased as the
+magnitude of the longitudinal magnetic field increased, which seemed to be
+caused by the influence of the quadrupolar interaction of nuclear spins.
+Further, the key parameters describing the dynamics of a coupled
+electron-nuclear spin system, the electron g-factor and the fluctuation of the
+Overhauser field, were evaluated in a typical single InAlAs quantum dot.",1703.06046v1
+2017-03-28,Resonant photoluminescence and dynamics of a hybrid Mn-hole spin in a positively charged magnetic quantum dot,"We analyze, through resonant photoluminescence, the spin dynamics of an
+individual magnetic atom (Mn) coupled to a hole in a semiconductor quantum dot.
+The hybrid Mn-hole spin and the positively charged exciton in a CdTe/ZnTe
+quantum dot forms an ensemble of $\Lambda$ systems which can be addressed
+optically. Auto-correlation of the resonant photoluminescence and resonant
+optical pumping experiments are used to study the spin relaxation channels in
+this multilevel spin system. We identified for the hybrid Mn-hole spin an
+efficient relaxation channel driven by the interplay of the Mn-hole exchange
+interaction and the coupling to acoustic phonons. We also show that the optical
+$\Lambda$ systems are connected through inefficient spin-flips than can be
+enhanced under weak transverse magnetic field. The dynamics of the resonant
+photoluminescence in a p-doped magnetic quantum dot is well described by a
+complete rate equation model. Our results suggest that long lived hybrid
+Mn-hole spin could be obtained in quantum dot systems with large
+heavy-hole/light-hole splitting.",1703.09441v2
+2017-10-02,Multi-scale modelling of current-induced switching in magnetic tunnel junctions using ab initio spin transfer torques,"There exists a significant challenge in developing efficient magnetic tunnel
+junctions with low write currents for non-volatile memory devices. With the aim
+of analysing potential materials for efficient current-operated magnetic
+junctions we have developed a multi-scale methodology combining the ab initio
+calculations of spin-transfer torque with large-scale time-dependent
+simulations using atomistic spin dynamics. In this work we introduce our
+multi-scale approach including a discussion on a number of possible mapping
+schemes the ab initio spin torques into the spin dynamics. We demonstrate this
+methodology on a prototype Co/MgO/Co/Cu tunnel junction showing that the spin
+torques are primarily acting at the interface between the Co free layer and
+MgO. Using spin dynamics we then calculate the reversal switching times for the
+free layer and the critical voltages and currents required for such switching.
+Our work provides an efficient, accurate and versatile framework for designing
+novel current-operated magnetic devices, where all the materials details are
+take into account.",1710.00574v1
+2017-10-10,Electron conduction in solid state via time varying wavevectors,"In this paper, we study electron wavepacket dynamics in electric and magnetic
+fields. We rigorously derive the semiclassical equations of electron dynamics
+in electric and magnetic fields. We do it both for free electron and electron
+in a periodic potential. We do this by introducing time varying wavevectors
+$k(t)$. In the presence of magnetic field, our wavepacket reproduces the
+classical cyclotron orbits once the origin of the Schr\""oedinger equation is
+correctly chosen to be center of cyclotron orbit. In the presence of both
+electric and magnetic fields, our equations for wavepacket dynamics differ from
+classical Lorentz force equations. We show that in a periodic potential, on
+application of electric field, the electron wave function adiabatically follows
+the wavefunction of a time varying Bloch wavevector $k(t)$, with its energies
+suitably shifted with time. We derive the effective mass equation and discuss
+conduction in conductors and insulators.",1710.03480v2
+2017-10-18,Magnetic Dynamics of Phase Separation Domains in GdMn2O5 and Gd0.8Ce0.2Mn2O5 Multiferroics,"Specific features of the magnetic properties and magnetic dynamics of
+isolated phase separation domains in GdMn2O5 and Gd0.8Ce0.2Mn2O5 have been
+investigated. These domains represent 1D superlattices consisting of dielectric
+and conducting layers with the ferromagnetic orientation of their spins. A set
+of ferromagnetic resonances of separate superlattice layers has been studied.
+The properties of the 1D superlattices in GdMn2O5 and Gd0.8Ce0.2Mn2O5 are
+compared with the properties of the previously investigated RMn2O5 (R = Eu, Tb,
+Er, and Bi) series. The similarity of the properties for all the RMn2O5
+compounds with different R ion types is established. Based on the concepts of
+the magnetic dynamics of ferromagnetic multilayers and properties of
+semiconductor superlattices, a 1D model of the superlattices in RMn2O5 is
+built.",1710.06695v1
+2017-11-13,Phases of QCD$_3$ from Non-SUSY Seiberg Duality and Brane Dynamics,"We consider a non-supersymmetric USp Yang-Mills Chern-Simons gauge theory
+coupled to fundamental flavours. The theory is realised in type IIB string
+theory via an embedding in a Hanany-Witten brane configuration which includes
+an orientifold and anti-branes. We argue that the theory admits a magnetic
+Seiberg dual. Using the magnetic dual we identify dynamics in field theory and
+brane physics that correspond to various phases, obtaining a better
+understanding of 3d bosonization and dynamical breaking of flavour symmetry in
+USp QCD$_3$ theory. In field theory both phases correspond to magnetic 'squark'
+condensation. In string theory they correspond to open string tachyon
+condensation and brane reconnection. We also discuss other phases where the
+magnetic 'squark' is massive. Finally, we briefly comment on the case of
+unitary gauge groups.",1711.04832v2
+2018-02-07,Latitudinal structure and dynamic of the photospheric magnetic field,"Analysis of the structure and dynamics of the magnetic field of the Sun is
+fundamental for understanding of the origin of solar activity and variability
+as well as for the study of solar-terrestrial relations. Observations of the
+large scale magnetic field in the photosphere taken at the Wilcox Solar
+Observatory from 1976 up to 2007 have been analysed to deduce its latitudinal
+and longitudinal structures, its differential rotation, and their variability
+in time. This paper is dedicated to the analysis and dynamics of the
+latitudinal structure of the solar magnetic field over three solar cycles 21,
+22, 23. The main results discussed in this paper are the following: the large
+scale latitudinal structure is antisymmetric and composed of four zones with
+boundaries located at the equator, -25 and + 25 degrees, stable over 10-11
+years with a time delay of about 5-6 years in near-equatorial zones. The
+variability and North-South asymmetry of polarity waves running from the
+equator to the poles with 2-3 - year period was studied in detail.",1802.02450v2
+2018-04-22,Magnetic Droplet Soliton Nucleation in Oblique Fields,"We study the auto-oscillating magnetodynamics in orthogonal spin torque
+nano-oscillators (STNOs) as a function of the out-of-plane (OOP) magnetic field
+angle. In perpendicular fields and at OOP field angles down to approximately 50
+degrees we observe the nucleation of a droplet. However, for field angles below
+50 degrees, experiments indicate that the droplet gives way to propagating spin
+waves, in agreement with our micromagnetic simulations. Theoretical
+calculations show that the physical mechanism behind these observations is the
+sign changing of spin-wave nonlinearity (SWN) by angle. In addition, we show
+that the presence of a strong perpendicular magnetic anisotropy (PMA) free
+layer in the system reverses the angular dependence of the SWN and dynamics in
+STNOs with respect to the known behavior determined for the in-plane magnetic
+anisotropy free layer. Our results are of fundamental interest in understanding
+the rich dynamics of nanoscale solitons and spin-wave dynamics in STNOs.",1804.08047v2
+2018-06-01,Dirac-Surface-State Modulated Spin Dynamics in a Ferrimagnetic Insulator at Room Temperature,"This work demonstrates dramatically modified spin dynamics of magnetic
+insulator (MI) by the spin-momentum locked Dirac surface states of the adjacent
+topological insulator (TI) which can be harnessed for spintronic applications.
+As the Bi-concentration x is systematically tuned in 5 nm thick (BixSb1-x)2Te3
+TI film, the weight of the surface relative to bulk states peaks at x = 0.32
+when the chemical potential approaches the Dirac point. At this concentration,
+the Gilbert damping constant of the precessing magnetization in 10 nm thick
+Y3Fe5O12 MI film in the MI/TI heterostructures is enhanced by an order of
+magnitude, the largest among all concentrations. In addition, the MI acquires
+additional strong magnetic anisotropy that favors the in-plane orientation with
+similar Bi-concentration dependence. These extraordinary effects of the Dirac
+surface states distinguish TI from other materials such as heavy metals in
+modulating spin dynamics of the neighboring magnetic layer.",1806.00151v1
+2018-06-18,Stellar dynamics of low mass stars from the surface to the interior measured by CoRoT and Kepler,"Continuous high-precision photometry of stars, provided by space missions
+such as CoRoT, Kepler, and K2, represents a unique way to study stellar
+rotation and magnetism. The coupling of these studies of the surface dynamics
+with asteroseismology is changing our view to surface and internal dynamics. In
+this proceedings I will provide the latest developments in the understanding of
+surface and internal rotation and magnetic fields. I will also discuss the
+possible discovery of strong internal magnetic fields of dynamo origin in the
+convective cores of stars above 1.2-1.4 solar masses. I will finish by
+providing constraints on gyrochronology laws for low-mass stars and put the Sun
+into context of its magnetism when compared to other solar-analog stars.",1806.06642v1
+2018-11-26,Radiative dynamical mass of planar charged fermion in a constant homogeneous magnetic field,"The effective Lagrangian and mass operator are calculated for planar charged
+massive and massless fermions in a constant external homogeneous magnetic field
+in the one-loop approximation of the 2+1 dimensional quantum electrodynamics
+(QED$_{2+1}$). We obtain the renormalizable effective Lagrangian and the
+fermion mass operator for a charged fermion of mass $m$ and then calculate
+these quantities for the massless case. The radiative corrections to the mass
+of charged massless fermion when it occupies the lowest Landau level are found
+for the cases of the pure QED$_{2+1}$ as well as the so-called reduced
+QED$_{3+1}$ on a 2-brane. The fermion masses were found can be generated
+dynamically by an external magnetic field in the pure QED$_{2+1}$ if the
+charged fermion has small bare mass $m_0$ and in the reduced QED$_{3+1}$ on a
+2-brane even at $m_0=0$. The dynamical mass seems to be likely to be revealed
+in monolayer graphene in the presence of constant homogeneous magnetic field
+(normal to the graphene sample).",1811.10414v1
+2019-02-06,Accelerating spin-space sampling by auxiliary spin-dynamics and temperature-dependent spin-cluster expansion,"Atomistic simulations of thermodynamic properties of magnetic materials rely
+on an accurate modelling of magnetic interactions and an efficient sampling of
+the high-dimensional spin space. Recent years have seen significant progress
+with a clear trend from model systems to material specific simulations that are
+usually based on electronic-structure methods. Here we develop a Hamiltonian
+Monte Carlo framework that makes use of auxiliary spin-dynamics and an
+auxiliary effective model, the temperature-dependent spin-cluster expansion, in
+order to efficiently sample the spin space. Our method does not require a
+specific form of the model and is suitable for simulations based on
+electronic-structure methods. We demonstrate fast warm-up and a reasonably
+small dynamical critical exponent of our sampler for the classical Heisenberg
+model. We further present an application of our method to the magnetic phase
+transition in bcc iron using magnetic bond-order potentials.",1902.02116v1
+2019-02-21,Stochastic ejection of nanocontact droplet solitons via drift instability,"The magnetic droplet soliton is a large amplitude, coherently precessing wave
+state that exists in ferromagnetic thin films with perpendicular magnetic
+anisotropy. To effectively sustain a droplet, magnetic damping can be locally
+compensated in a nanocontact region that imparts spin-transfer torque; this has
+been successfully deployed in experiment to directly image the droplet and
+probe its dynamics electrically. However, theory predicts and experiments
+indicate the existence of a drift instability whereby the droplet is ejected
+from the spin-transfer-torque-active region and subsequently decays, an effect
+that may be enhanced or possibly induced by thermal fluctuations. Using soliton
+perturbation theory and large deviation theory, this work determines the
+soliton ejection rate and the most likely path an ejected soliton tracks in the
+presence of thermal fields. These results lead to an effective lower bound on
+the stability of magnetic droplet solitons in spin-transfer torque nanocontact
+devices operating at finite temperature and point to ways in which droplets can
+be made more robust.",1902.09310v1
+2019-03-03,Dynamical mode coupling and coherence in spin Hall nano-oscillator with perpendicular magnetic anisotropy,"We experimentally study the dynamical modes excited by spin current in Spin
+Hall nano-oscillators based on the Pt/[Co/Ni] multilayers with perpendicular
+magnetic anisotropy. Both propagating spin wave and localized solitonic modes
+of the oscillation are achieved and controlled by varying the applied magnetic
+field and current. At room temperature, the generation linewidth broadening
+associated with mode hopping was observed at currents close to the transition
+between different modes and in the mode coexistence regimes. The mode hopping
+was suppressed at cryogenic temperatures, confirming that the coupling between
+modes is mediated by thermal magnons. We also demonstrate that coherent
+single-mode oscillations with linewidth of 5 MHz can be achieved without
+applying external magnetic field. Our results provide insight into the
+mechanisms controlling the dynamical coherence in nanomagnetic oscillators, and
+guidance for optimizing their applications in spin wave-based electronics.",1903.00822v1
+2019-03-07,Interplay between intra- and inter-nanowires dynamic dipolar interactions in the spin wave band structure of Py/Cu/Py nanowires,"We have studied both experimentally and theoretically the reprogrammable spin
+wave band structure in Permalloy(10nm)/Cu(5nm)/Permalloy(30nm) nanowire arrays
+of width w=280 nm and inter-wire separation in the range from 80 to 280 nm. We
+found that, depending on the inter-wire separation, the anti-parallel
+configuration, where the magnetizations of the two Permalloy layers point in
+opposite directions, is stabilized over specific magnetic field ranges thus
+enabling us to directly compare the band structure with that of the parallel
+alignment. We show that collective spin waves of the Bloch type propagate
+through the arrays with different magnonic bandwidths as a consequence of the
+interplay between the intra- and inter-nanowire dynamic dipolar interactions. A
+detailed understanding, e.g. whether they have a stationary or propagating
+character, is achieved by considering the phase relation (in-phase or
+out-of-phase) between the dynamic magnetizations in the two ferromagnetic
+layers and their average value. This work opens the path to magnetic
+field-controlled reconfigurable layered magnonic crystals that can be used for
+future nanoscale magnon spintronic devices.",1903.02935v1
+2019-03-15,Effect of a magnetic field on the thermodynamic uncertainty relation,"The thermodynamic uncertainty relation provides a universal lower bound on
+the product of entropy production and the fluctuations of any current. While
+proven for Markov dynamics on a discrete set of states and for overdamped
+Langevin dynamics, its status for underdamped dynamics is still open. We
+consider a two-dimensional harmonically confined charged particle in a magnetic
+field under the action of an external torque. We show analytically that,
+depending on the sign of the magnetic field, the thermodynamic uncertainty
+relation does not hold for the currents associated with work and heat. A strong
+magnetic field can effectively localize the particle with concomitant bounded
+fluctuations and low dissipation. Numerical results for a three-dimensional
+variant and for further currents suggest that the existence of such a bound
+depends crucially on the specific current.",1903.06480v2
+2019-03-18,Role of excited states in the dynamics of excitons and their spins in diluted magnetic semiconductors,"We theoretically investigate the impact of excited states on the dynamics of
+the exciton ground state in diluted magnetic semiconductor quantum wells.
+Exploiting the giant Zeeman shift in these materials, an external magnetic
+field is used to bring transitions between the exciton ground state and excited
+states close to resonance. It turns out that, when treating the exciton
+dynamics in terms of a quantum kinetic theory beyond the Markov approximation,
+higher exciton states are populated already well below the critical magnetic
+field required to bring the exciton ground state in resonance to an excited
+state. This behavior is explained by exciton-impurity correlations that can
+bridge energy differences on the order of a few meV and require a quantum
+kinetic description beyond the independent-particle picture. Of particular
+interest is the significant spin transfer toward states on the optically dark
+$2p$ exciton parabola which are protected against radiative decay.",1903.07564v2
+2019-04-09,Manipulation of Magnetic Skyrmions by Superconducting Vortices in Ferromagnet-Superconductor Heterostructures,"Dynamics of magnetic skyrmions in hybrid ferromagnetic films harbors novel
+physical phenomena and holds promise for technological applications. In this
+work, we discuss the behavior of magnetic skyrmions when coupled to
+superconducting vortices in a ferromagnet-superconductor heterostructure. We
+use numerical simulations and analytic arguments to reveal broader
+possibilities for manipulating the skyrmion-vortex dynamic correlations in the
+hybrid system, that are not possible in its separated constituents. We explore
+the thresholds of particular dynamic phases, and quantify the phase diagram as
+a function of the relevant material parameters, applied current and induced
+magnetic torques. Finally, we demonstrate the broad and precise tunability of
+the skyrmion Hall-angle in presence of vortices, with respect to currents
+applied to either or both the superconductor and the ferromagnet within the
+heterostructure.",1904.04537v3
+2019-04-28,Effect of magnetic flux advection on the dynamics of shock in accretion flow around a rotating black hole,"We investigate the dynamical behaviour of a magnetized, dissipative,
+accretion flow around a rapidly rotating black hole. We solve the
+magnetohydrodynamic equations and calculate the transonic accretion solutions
+which may contain discontinuous shock transitions. We investigate the effect of
+$\zeta-$ parameter (parametrizing the radial variation of the toroidal magnetic
+flux advection rate) on the dynamical behaviour of shocks. For a rapidly
+rotating black hole and for fixed injection parameters at the outer edge, we
+show that stationary shocks are sustained in the global magnetized accretion
+solutions for a wide range of $\zeta$ and accretion rate ($\dot{m}$). To
+investigate the observational implications, we consider dissipative shocks and
+estimate the maximum accessible energy from the post-shock corona (PSC) for
+nine stellar mass black hole candidates. We compare this with the observed
+radio jet kinetic power reported in the literature, whenever available. We find
+close agreement between the estimated values from our model with those reported
+in the literature.",1904.12296v2
+2019-05-03,Chiral excitations of magnetic droplet solitons driven by their own inertia,"The inertial effects of magnetic solitons play a crucial role in their
+dynamics and stability. Yet governing their inertial effects is a challenge for
+their use in real devices. Here, we show how to control the inertial effects of
+magnetic droplet solitons. Magnetic droplets are strongly nonlinear and
+localized autosolitons than can form in current-driven nanocontacts. Droplets
+can be considered as dynamical particles with an effective mass. We show that
+the dynamical droplet bears a second excitation under its own inertia. These
+excitations comprise a chiral profile, and appear when the droplet resists the
+force induced by the Oersted field of the current injected into the
+nanocontact. We reveal the role of the spin torque on the excitation of these
+chiral modes and we show how to control these modes using the current and the
+field.",1905.01085v2
+2019-05-24,Faraday Rotation Measure Dependence on Galaxy Clusters Dynamics,"We study the magnetic fields in galaxy clusters through Faraday rotation
+measurements crossing systems in different dynamical states. We confirm that
+magnetic fields are present in those systems and analyze the difference between
+relaxed and unrelaxed samples with respect to the dispersion between their
+inherent Faraday Rotation measurements. We found an increase of this RM
+dispersion and a higher RM overlapping frequency for unrelaxed clusters. This
+fact suggests that a large scale physical process is involved in the nature of
+unrelaxed systems and possible depolarization effects are present in the
+relaxed ones. We show that dynamically unrelaxed systems can enhance magnetic
+fields to large coherence lengths. In contrast, the results for relaxed systems
+suggests that small-scale dynamo can be a dominant mechanism for sustaining
+magnetic fields, leading to intrinsic depolarization.",1905.10303v1
+2019-06-11,Effects of the magnetic field direction on the Tsallis statistic,"We extend the use of the Tsallis statistic to measure the differences in gas
+dynamics relative to the mean magnetic field present from natural eddy-type
+motions existing in magnetohydrodynamical (MHD) turbulence. The variation in
+gas dynamics was estimated using the Tsallis parameters on the incremental
+probability distribution function of the observables (intensity and velocity
+centroid) obtained from compressible MHD simulations. We find that the Tsallis
+statistic is susceptible to the anisotropy produce by the magnetic field, even
+when anisotropy is percent the Tsallis statistic can be use to determine MHD
+parameters such as the Sonic Mach number. We quantize the goodness of the
+Tsallis parameters using the coefficient of determination to measure the
+differences in the gas dynamics. These parameters also determine the level of
+magnetization and compressibility of the medium. To further simulate realistic
+spectroscopic observational data we introduced smoothing, noise, and cloud
+boundaries to the MHD simulations.",1906.04821v1
+2019-07-03,Recurrent network classifier for ultrafast skyrmion dynamics,"By using the supervised learning we train a recurrent neural network to
+recognize and classify ultrafast magnetization processes realized in
+two-dimensional nanosystems with Dzyaloshinskii-Moriya interaction. Our focus
+is on the different types of skyrmion dynamics driven by ultrafast magnetic
+pulses. Each process is represented as a sequence of the sorted magnetization
+vectors inputted into the network. The trained network can perform an accurate
+classification of the skyrmionic processes at zero temperature in wide ranges
+of parameters that are the magnetic pulse width and damping factor. The network
+performance is also demonstrated on different types of unseen data including
+finite temperature processes. Our approach can be easily adapted for creating
+an autonomous control system on skyrmion dynamics for experiments or device
+operations.",1907.01814v1
+2019-07-03,Spin wave excitations of magnetic metalorganic materials,"The Organic Materials Database (OMDB) is an open database hosting about
+22,000 electronic band structures, density of states and other properties for
+stable and previously synthesized 3-dimensional organic crystals. The web
+interface of the OMDB offers various search tools for the identification of
+novel functional materials such as band structure pattern matching and density
+of states similarity search. In this work the OMDB is extended to include
+magnetic excitation properties. For inelastic neutron scattering we focus on
+the dynamical structure factor $S(\mathbf{q},\omega)$ which contains
+information on the excitation modes of the material. We introduce a new dataset
+containing atomic magnetic moments and Heisenberg exchange parameters for which
+we calculate the spin wave spectra and dynamic structure factor with linear
+spin wave theory and atomistic spin dynamics. We thus develop the materials
+informatics tools to identify novel functional organic and metalorganic
+magnets.",1907.01817v2
+2019-07-11,Image of dynamic local exchange interactions in the dc magnetoresistance of spin-polarized current through a dopant,"We predict strong, dynamical effects in the dc magnetoresistance of current
+flowing from a spin-polarized electrical contact through a magnetic dopant in a
+nonmagnetic host. Using the stochastic Liouville formalism we calculate
+clearly-defined resonances in the dc magnetoresistance when the applied
+magnetic field matches the exchange interaction with a nearby spin. At these
+resonances spin precession in the applied magnetic field is canceled by spin
+evolution in the exchange field, preserving a dynamic bottleneck for spin
+transport through the dopant. Similar features emerge when the dopant spin is
+coupled to nearby nuclei through the hyperfine interaction. These features
+provide a precise means of measuring exchange or hyperfine couplings between
+localized spins near a surface using spin-polarized scanning tunneling
+microscopy, without any ac electric or magnetic fields, even when the exchange
+or hyperfine energy is orders of magnitude smaller than the thermal energy.",1907.05509v1
+2019-11-07,Electric field effect on spin waves and magnetization dynamics: role of magnetic moment current,"We show that a static electric field $E_x$ gives rise to a shift of the spin
+wave dispersion relation $\omega(q_y-q_E)$ in the direction of the wavenumber
+$q_y$ of the quantity $q_E=-\gamma_LE_x/c^2$. This effect is caused by the
+magnetic moment current carried by the spin wave itself that generates an
+additional phase proportional to the electric field, as in the Aharonov-Casher
+effect. This effect is independent from the possibly present magneto-electric
+effects of insulating ferromagnets and superimposes to them. By extending this
+picture to arbitrary magnetization dynamics, we find that the electric field
+gives rise to a dynamic interaction term which has the same chiral from of the
+Dzyaloshinskii-Moriya interaction but is fully tunable with the applied
+electric field.",1911.02902v1
+2019-12-02,"Quaternionic approach on the Dirac-Maxwell, Bernoulli and Navier-Stokes equations for dyonic fluid plasma","Applying the Hamilton's quaternion algebra, we propose the generalized
+electromagnetic-fluid dynamics of dyons governed by the combination of the
+Dirac-Maxwell, Bernoulli and Navier-Stokes equations. The generalized
+quaternionic hydro-electromagnetic field of dyonic cold plasma consist the
+electrons and the magnetic monopoles in which there exist dual-mass and
+dual-charge species in presence of dyons. We construct the conservation of
+energy and conservation of momentum equations by equating the quaternionic
+scalar and vector parts for generalized hydro-electromagnetic field of dyonic
+cold plasma. We propose the quaternionic form of conservation of energy is
+related to the Bernoulli's like equation while the conservation of momentum is
+related to Navier-Stokes like equation for dynamics of dyonic plasma fluid.
+Further, the continuity equation i.e. the conservation of electric and magnetic
+charges with the dynamics of hydro-electric and hydro-magnetic flow of
+conducting cold plasma fluid is also analyzed. The quaternionic formalism for
+dyonic plasma wave emphasizes that there are two types of waves propagation
+namely the Langmuir like wave propagation due to electrons, and the
+t-Hooft-Polyakov like wave propagation due to magnetic monopoles.",1912.08046v1
+2020-04-20,The role of the quadrupolar interaction in the tunneling dynamics of lanthanide molecular magnets,"Quantum tunneling dominates the low temperature magnetization dynamics in
+molecular magnets and presents features that are strongly system dependent. The
+current discussion is focused on the terbium(III) bis(phtalocyanine)
+([TbPc$_2$]$^{-1}$) complex, that should serve as a prototypical case for
+lanthanide molecular magnets. We analyze numerically the effect of non-axial
+interactions on the magnitude of the intrinsic tunnel splitting and show that
+usual suspects like the transverse ligand field and Zeeman interaction fail to
+explain the experimentally observed dynamics. We then propose through the
+nuclear quadrupolar interaction a viable mechanism that mixes, otherwise
+\textit{almost} degenerate hyperfine states.",2004.09001v1
+2020-05-04,Spin-orbit-torque magnonics,"The field of magnonics, which utilizes propagating spin waves for nano-scale
+transmission and processing of information, has been significantly advanced by
+the advent of the spin-orbit torque. The latter phenomenon can allow one to
+overcome two main drawbacks of magnonic devices - low energy efficiency of
+conversion of electrical signals into spin wave signals, and fast spatial decay
+of spin waves in thin-film waveguiding structures. At first glance, the
+excitation and amplification of spin waves by spin-orbit torques can seem to be
+straightforward. Recent research indicates, however, that the lack of the
+mode-selectivity in the interaction of spin currents with dynamic magnetic
+modes and the onset of dynamic nonlinear phenomena represent significant
+obstacles. Here, we discuss the possible route to overcoming these limitations,
+based on the suppression of nonlinear spin-wave interactions in magnetic
+systems with perpendicular magnetic anisotropy. We show that this approach
+enables efficient excitation of coherent magnetization dynamics and propagating
+spin waves in extended spatial regions, and is expected to enable practical
+implementation of complete compensation of spin-wave propagation losses.",2005.01391v1
+2020-05-15,Multiple magnon modes in spin-1/2 Heisenberg antiferromagnet on simple square lattice in strong magnetic field,"We discuss spin-$\frac12$ Heisenberg antiferromagnet on simple square lattice
+in magnetic field $H$ using recently proposed bond-operator technique. It is
+well known that magnetically ordered phases of quantum magnets are well
+described at least qualitatively by the conventional spin-wave theory that only
+introduces quantum corrections into the classical solution of the problem. We
+observe that quantum fluctuations change drastically dynamical properties of
+the considered model at $H$ close to its saturation value: the dynamical
+structure factor shows anomalies corresponding to Green's function poles which
+have no counterparts in the spin-wave theory. That is, quantum fluctuations
+produce multiple short-wavelength magnon modes not changing qualitatively the
+long-wavelength spin dynamics. Our results are in agreement with previous
+quantum Monte-Carlo simulations and exact diagonalization of finite clusters.",2005.07537v3
+2020-07-20,Dynamical magnetoelectric coupling in axion insulator thin films,"Axion insulator is an exotic magnetic topological insulator with zero Chern
+number but a nonzero quantized Chern-Simons magnetoelectric coupling. A
+conclusive experimental evidence for axion insulators is still lacking due to
+the small signal of topological magnetoelectric effect (TME). Here we show that
+the dynamical magnetoelectric coupling can be induced by the
+\emph{out-of-plane} surface magnetization dynamics in axion insulator thin
+films, which further generates a polarization current in the presence of an
+external magnetic field in the same direction. Such a current is finite in the
+bulk and increases as the film thickness $d$ decreases, in opposite to TME
+current which decreases as $d$ decreases. Remarkably, the current in thin films
+at magnetic resonance is at least ten times larger than that of TME, and thus
+may serve as a smoking gun signature for axion insulators.",2007.09869v1
+2020-08-18,"Survey of 360$^{\circ}$ domain walls in magnetic heterostructures: topology, chirality and current-driven dynamics","Chirality and current-driven dynamics of topologically nontrivial
+360$^{\circ}$ domain walls (360DWs) in magnetic heterostructures (MHs) are
+systematically investigated. For MHs with normal substrates, the static 360DWs
+are N\'{e}el-type with no chirality. While for those with heavy-metal
+substrates, the interfacial Dzyaloshinskii-Moriya interaction (iDMI) therein
+makes 360DWs prefer specific chirality. Under in-plane driving charge currents,
+as the direct result of ""full-circle"" topology a certain 360DW does not undergo
+the ""Walker breakdown""-type process like a well-studied 180$^{\circ}$ domain
+wall as the current density increases. Alternatively, it keeps a fixed
+propagating mode (either steady-flow or precessional-flow, depending on the
+effective damping constant of the MH) until it collapses or changes to other
+types of solition when the current density becomes too high. Similarly, the
+field-like spin-orbit torque (SOT) has no effects on the dynamics of 360DWs,
+while the anti-damping SOT has. For both modes, modifications to the mobility
+of 360DWs by iDMI and anti-damping SOT are provided.",2008.08196v1
+2020-09-16,Dynamical mass generation for ferromagnetic skyrmions in two dimensions,"Magnetic skyrmions are topological magnetization textures that are
+characterized by the homotopy group of two dimensional spheres. Despite years
+of intensive research on skyrmions, the fundamental problem of the inertia of a
+skyrmion in driven motion remains unresolved. By properly taking into account a
+direct coupling between skyrmion motion and the correspondingly excited
+magnons, we identify a dynamical mass for the skyrmion in motion. The direct
+coupling between skyrmion motion and magnons can be employed to engineer
+skyrmion dynamics with magnons through ingenious material and geometry design.",2009.07486v4
+2020-10-27,Vertex Dependent Dynamic Response of a Connected Kagome Artificial Spin Ice,"We present the dynamic response of a connected Kagome artificial spin ice
+with emphasis on the effect of the vertex magnetization configuration on the
+mode characteristics. We use broadband ferromagnetic resonance (FMR)
+spectroscopy and micromagnetic simulations to identify and characterize
+resonant modes. We find the mode frequencies of elongated, single-domain film
+segments not only depend on the orientation of their easy-axis with respect to
+the applied magnetic field, but also depend on the vertex magnetization
+configuration, which suggests control over the FMR mode can be accomplished by
+altering the vertex magnetization. Moreover, we study differences between the
+vertex center mode (VCM) and the localized domain wall (LDW) mode. We show that
+the LDW mode acts as a signature of the domain wall (DW) nucleation process and
+the DW dynamics active during segment reversal events. The results show the VCM
+and LDW modes can be controlled using a field protocol, which has important
+implications for applications in magnonic and spintronic devices.",2010.13965v1
+2020-11-09,Spin-wave dynamics and symmetry breaking in an artificial spin ice,"Artificial spin ices are periodic arrangements of interacting nanomagnets
+successfully used to investigate emergent phenomena in the presence of
+geometric frustration. Recently, it has been shown that artificial spin ices
+can be used as building blocks for creating functional materials, such as
+magnonic crystals, and support a large number of programmable magnetic states.
+We investigate the magnetization dynamics in a system exhibiting anisotropic
+magnetostatic interactions owing to locally broken structural inversion
+symmetry. We find a rich spin-wave spectrum and investigate its evolution in an
+external magnetic field. We determine the evolution of individual modes, from
+building blocks up to larger arrays, highlighting the role of symmetry breaking
+in defining the mode profiles. Moreover, we demonstrate that the mode spectra
+exhibit signatures of long-range interactions in the system. These results
+contribute to the understanding of magnetization dynamics in spin ices beyond
+the kagome and square ice geometries and are relevant for the realization of
+reconfigurable magnonic crystals based on spin ices.",2011.04505v2
+2020-12-11,From one- to two-magnon excitations in the S=3/2 magnet $β$-CaCr$_2$O$_4$,"We apply neutron spectroscopy to measure the magnetic dynamics in the S=3/2
+magnet $\beta$-CaCr$_2$O$_4$ (T$_N$=21 K). The low-energy fluctuations, in the
+ordered state, resemble large-S linear spin-waves from the incommensurate
+ground state. However, at higher energy transfers, these semi-classical and
+harmonic dynamics are replaced by an energy and momentum broadened continuum of
+excitations. Applying kinematic constraints required for energy and momentum
+conservation, sum rules of neutron scattering, and comparison against exact
+diagonalization calculations, we show that the dynamics at high-energy
+transfers resemble low-S one-dimensional quantum fluctuations.
+$\beta$-CaCr$_2$O$_4$ represents an example of a magnet at the border between
+classical N\'eel and quantum phases, displaying dual characteristics.",2012.06314v2
+2021-01-07,Quantum annealing simulation of out-of-equilibrium magnetization in a spin-chain compound,"Geometrically frustrated spin-chain compounds such as Ca3Co2O6 exhibit
+extremely slow relaxation under a changing magnetic field. Consequently, both
+low-temperature laboratory experiments and Monte Carlo simulations have shown
+peculiar out-of-equilibrium magnetization curves, which arise from trapping in
+metastable configurations. In this work we simulate this phenomenon in a
+superconducting quantum annealing processor, allowing us to probe the impact of
+quantum fluctuations on both equilibrium and dynamics of the system. Increasing
+the quantum fluctuations with a transverse field reduces the impact of
+metastable traps in out-of-equilibrium samples, and aids the development of
+three-sublattice ferrimagnetic (up-up-down) long-range order. At equilibrium we
+identify a finite-temperature shoulder in the 1/3-to-saturated phase
+transition, promoted by quantum fluctuations but with entropic origin. This
+work demonstrates the viability of dynamical as well as equilibrium studies of
+frustrated magnetism using large-scale programmable quantum systems, and is
+therefore an important step toward programmable simulation of dynamics in
+materials using quantum hardware.",2101.02769v1
+2021-01-15,Magnetic properties of transition metal dimers probed by inelastic neutron scattering,"The physical characterisation and understanding of molecular magnetic
+materials is one of the most important steps towards the integration of such
+systems in hybrid spintronic devices. Amongst the many characterisation
+techniques employed in such a task, Inelastic Neutron Scattering (INS) stands
+as one of the most powerful and sensitive tools to investigate their spin
+dynamics. Herein, the magnetic properties and spin dynamics of two dinuclear
+complexes, namely [(M(hfacac)$_2$)$_2$(bpym)] (where M = Ni$^{2+}$, Co$^{2+}$,
+abbreviated in the following as Ni$_2$, Co$_2$) are reported. These are model
+systems that could constitute fundamental units of future spintronic devices.
+By exploiting the highly sensitive IN5 Cold INS spectrometer, we are able to
+gain a deep insight into the spin dynamics of Ni$_2$ and to fully obtain the
+microscopic spin Hamiltonian parameters; while for Co$_2$, a multitude of INS
+transitions are observed demonstrating the complexity of the magnetic
+properties of octahedral cobalt-based systems.",2101.06225v1
+2021-09-08,Emergent inductance by dynamical Aharonov-Casher phases,"We propose a mechanism of inductance operation originating from a dynamical
+Aharonov-Casher (AC) phase of an electron in ferromagnets. By taking into
+account spin-orbit coupling effects, we extend the theory of emergent
+inductance, which has recently been discovered in spiral magnets, to arbitrary
+magnetic textures. The inductance of dynamical AC phase origin universally
+arises in the coexistence of magnetism and a spin-orbit coupling, even with
+spatially-uniform magnetization, allowing its stable operation in wide ranges
+of temperature and frequency. Revisiting the widely studied systems, such as
+ferromagnets with spatial inversion asymmetry, with the new perspective offered
+by our work will lead to opening a new paradigm in the study of AC phase
+physics and the spintronics-based power management in ultra-wideband frequency
+range.",2109.03558v1
+2021-09-22,Hopfion Dynamics in Chiral Magnets,"Resonant spin dynamics of topological spin textures are correlated with their
+topological nature, which can be employed to understand this nature. In this
+study, we present resonant spin dynamics of three-dimensional topological spin
+texture, i.e., Neel and Bloch hopfions. Using micromagnetic simulations, we
+stabilize Bloch and Neel hopfions with bulk and interfacial
+Dzyaloshinskii-Moriya interaction (DMI), respectively. We identify the ground
+state spin configuration of both hopfions, effects of anisotropies, geometric
+confinements, and demagnetizing fields. To confirm topological nature, Hopf
+number is calculated for each spin texture. Then, we calculate the resonance
+frequencies and spin-wave modes of spin precessions under multiple magnetic
+fields. Unique resonance frequencies and specific magnetic field dependence can
+help to guide experimental studies to identify the three-dimensional
+topological spin texture of hopfions in functioning chiral magnets when imaging
+is not possible.",2109.10758v1
+2021-12-14,Magnetic properties and pseudogap formation in infinite-layer nickelates: insights from the single-band Hubbard model,"We study the magnetic and spectral properties of a single-band Hubbard model
+for the infinite-layer nickelate compound LaNiO$_2$. As spatial correlations
+turn out to be the key ingredient for understanding its physics, we use two
+complementary extensions of the dynamical mean-field theory to take them into
+account: the cellular dynamical mean-field theory and the dynamical vertex
+approximation. Additionally to the systematic analysis of the doping dependence
+of the non-Curie-Weiss behavior of the uniform magnetic susceptibility, we
+provide insight into its relation to the formation of a pseudogap regime by the
+calculation of the one-particle spectral function and the magnetic correlation
+length. The latter is of the order of a few lattice spacings when the pseudogap
+opens, indicating a strong-coupling pseudogap formation in analogy to cuprates.",2112.07531v1
+2022-03-14,Noncollinear antiferromagnetic textures driven high harmonic generation from magnetic dynamics in the absence of spin-orbit coupling,"We demonstrate the generation of high order harmonics in carrier pumping from
+precessing ferromagnetic or antiferromagnetic orders, excited via magnetic
+resonance, in the presence of topological antiferromagnetic textures. This
+results in an enhancement of the carrier dynamics by orders of magnitude.
+Interestingly, the generation process occurs in an intrinsic manner, and is
+solely governed by the interplay between the s-d exchange coupling underlying
+the noncollinear antiferromagnetic order and the dynamical s-d exchange
+parameter of the magnetic drive. Therefore, the relativistic spin-orbit
+interaction is not required for the emergence of high harmonics in the pumped
+currents. Accordingly, the noncollinear topological antiferromagnetic order is
+presented as an alternative to spin-orbit interaction for the purpose of
+harnessing high harmonic emission in carrier pumping. Our proposal initiates a
+tantalizing perspective for the exploitation of topological magnetic textures
+in the context of the highly active domain of ultrafast spintronics.",2203.07310v2
+2022-03-27,Making a case for femto- phono- magnetism with FePt,"In the field of femtomagnetism magnetic matter is controlled by ultrafast
+laser pulses; here we show that coupling phonon excitations of the nuclei to
+spin and charge leads to femto-phono-magnetism, a powerful route to control
+magnetic order at ultrafast times. With state-of-the-art theoretical
+simulations of coupled spin-, charge-, and lattice-dynamics we identify strong
+non-adiabatic spin-phonon coupled modes that dominate early time spin dynamics.
+Activating these phonon modes we show leads to an additional (up to 40\% extra)
+loss of moment in FePt occurring within 40 femtoseconds of the pump laser
+pulse. Underpinning this enhanced ultrafast loss of spin moment we identify a
+physical mechanism in which minority spin-current drives an enhanced inter-site
+minority charge transfer, in turn promoting increased on-site spin flips. Our
+finding demonstrates that the nuclear system, often assumed to play only the
+role of an energy sink aiding long time re-magnetisation of the spin system,
+can play a profound role in controlling femtosecond spin-dynamics in materials.",2203.14234v1
+2022-06-23,Kramers-Moyal analysis of interplanetary magnetic field fluctuations at sub-ion scales,"In the framework of statistical time series analysis of complex dynamics we
+present a multiscale characterization of solar wind turbulence in the
+near-Earth environment. The data analysis, based on the Markov-process theory,
+is meant to estimate the Kramers-Moyal coefficients associated with the
+measured magnetic field fluctuations. In fact, when the scale-to-scale dynamics
+can be successfully described as a Markov process, first- and second-order
+Kramers-Moyal coefficients provide a complete description of the dynamics in
+terms of Langevin stochastic process. The analysis is carried out by using
+high-resolution magnetic field measurements gathered by Cluster during a fast
+solar wind period on January 20, 2007. This analysis extends recent findings in
+the near-Sun environment with the aim of testing the universality of the
+Markovian nature of the magnetic field fluctuations in the sub-ion/kinetic
+domain.",2206.11498v2
+2022-07-14,Magnetization dynamics in proximity-coupled superconductor-ferromagnet-superconductor multilayers. Part II,"In this work, we study magnetization dynamics in
+superconductor-ferromagnet-superconductor thin-film structures. Results of the
+broad-band ferromagnetic resonance spectroscopy are reported for a large set of
+samples with varied thickness of both superconducting and ferromagnetic layers
+in a wide frequency, field, and temperature ranges. Experimentally the
+one-dimensional anisotropic action of superconducting torque on magnetization
+dynamics is established; its dependence on thickness of layers is revealed. It
+is demonstrated that experimental findings support the recently-proposed
+mechanism of the superconducting torque formation via the interplay between the
+superconducting kinetic inductance and magnetization precession at
+superconductor-ferromagnet interfaces.",2207.06751v2
+2022-09-30,Hybrid magnetization dynamics in $\text{Cu}_\text{2}\text{OSeO}_\text{3}$/$\mathrm{NiFe}$ heterostructures,"We investigate the coupled magnetization dynamics in heterostructures of a
+single crystal of the chiral magnet $\mathrm{Cu_2OSeO_3}$ (CSO) and a
+polycrystalline ferromagnet $\mathrm{NiFe}$ (Py) thin film using broadband
+ferromagnetic resonance (FMR) at cryogenic temperatures. We observe the
+excitation of a hybrid mode (HM) below the helimagnetic transition temperature
+of CSO. This HM is attributed to the spin dynamics at the CSO/Py interface. We
+study the HM by measuring its resonance frequencies for in plane rotations of
+the external magnetic field. We find that the HM exhibits dominantly four-fold
+anisotropy, in contrast to the FMR of CSO and Py.",2210.00897v1
+2022-11-01,Strongly nonlinear antiferromagnetic dynamics in high magnetic fields,"Antiferromagnetic (AFM) materials possess a well-recognized potential for
+ultrafast data processing thanks to their intrinsic ultrafast spin dynamics,
+absence of stray fields, and large spin transport effects. The very same
+properties, however, make their manipulation difficult, requiring frequencies
+in THz range and magnetic fields of tens of Teslas. Switching of AFM order
+implies going into the nonlinear regime, a largely unexplored territory. Here
+we use THz light from a free electron laser to drive antiferromagnetic NiO into
+a highly nonlinear regime and steer it out of nonlinearity with magnetic field
+from a 33-Tesla Bitter magnet. This demonstration of large-amplitude dynamics
+represents a crucial step towards ultrafast resonant switching of AFM order.",2211.00353v1
+2022-12-06,Dynamics of hybrid magnetic skyrmion driven by spin-orbit torque in ferrimagnets,"Magnetic skyrmions are magnetic textures with topological protection, which
+are expected to be information carriers in future spintronic devices. In this
+work, we propose a scheme to implement hybrid magnetic skyrmions (HMS) in
+ferrimagnets, and we study theoretically and numerically the dynamics of the
+HMS driven by spin-orbit torque. It is revealed that the skyrmion Hall effect
+depends on the skyrmion helicity and the net angular momentum ({\delta}s),
+allowing the effective modulation of the HMS motion through tuning
+Dzyaloshinskii-Moriya interaction and {\delta}s. Thus, the Hall effect can be
+suppressed through selecting suitable materials to better control the HMS
+motion. Moreover, Magnus force for finite {\delta}s suppresses the transverse
+motion and enhances the longitudinal propagation, resulting in the HMS dynamics
+in ferrimagnets faster than that in antiferromagnets.",2212.02807v1
+2023-03-29,Universality in relaxation of spin helices under the $XXZ$- spin chain dynamics,"We describe dynamics of transverse spin-helix state (SHS) -- a product state
+with spatially rotating magnetization -- under anisotropic Heisenberg XXZ spin
+chain evolution. Due to experimental relevance we especially focus on
+magnetization dynamics. At long times the $U(1)$ symmetry of the Hamiltonian is
+restored, leading to the decay of transverse magnetization, which can be
+described as an exponential decay of a spatially harmonic profile. We show that
+the dependence of the short and intermediate-time decay timescale, which in
+principle depends on all different parameters, like the wavevector of the
+initial helix, the anisotropy, etc., can be described well by a single scaling
+function. We also briefly discuss the evolution of magnetization current.",2303.16632v2
+2023-05-10,Investigation of Spin-Wave Dynamics in Gyroid Nanostructures,"A new concept in magnonics studies the dynamics of spin waves (SWs) in
+three-dimensional nanosystems. It is a natural evolution from conventionally
+used planar systems to explore magnetization configurations and dynamics in 3D
+nanostructures with lengths near intrinsic magnetic scales. In this work, we
+perform broadband ferromagnetic resonance (BBFMR) measurements and
+micromagnetic simulations of nanoscale magnetic gyroids - a periodic chiral
+structure consisting entirely of chiral triple junctions. Our results show
+unique properties of the network, such as the localization of the SW modes,
+evoking their topological properties, and the substantial sensitivity to the
+direction of the static magnetic field. The presented results open a wide range
+of applications in the emerging field of 3D magnonic crystals and spintronics.",2305.06319v2
+2023-05-23,Current-driven motion of magnetic topological defects in ferromagnetic superconductors,"Recent years have seen a number of instances where magnetism and
+superconductivity intrinsically coexist. Our focus is on the case where
+spin-triplet superconductivity arises out of ferromagnetism, and we make a
+hydrodynamic analysis of the effect of a charge supercurrent on magnetic
+topological defects like domain walls and merons. We find that the emergent
+electromagnetic field that arises out of the superconducting order parameter
+provides a description for not only the physical quantities such as the local
+energy flux density and the interaction between current and defects but also
+the energy dissipation through magnetic dynamics of the Gilbert damping, which
+becomes more prominent compared to the normal state as superconductivity
+attenuates the energy dissipation through the charge sector. In particular, we
+reveal that the current-induced dynamics of domain walls and merons in the
+presence of the Gilbert damping give rise to the nonsingular $4\pi$ and $2\pi$
+phase slips, respectively, revealing the intertwined dynamics of spin and
+charge degrees of freedom in ferromagnetic superconductors.",2305.13564v1
+2023-05-24,Beyond Walker Breakdown through the Resonant Dissipation: Dramatic Enhancement of Magnetic Domain Wall Velocity via Resonant Excitation of Standing Wave Modes of Domain Wall Structure,"The dynamic behaviors of magnetic domain walls have significant implications
+for developing advanced spintronic devices. In this study, we investigate the
+intriguing resonance phenomenon within the magnetic domain wall structure and
+its profound influence on dynamic motion, focusing on the dissipation
+mechanism. By applying a static external magnetic field, we observe a
+remarkable amplification of domain wall velocity, surpassing the limitations of
+the conventional one-dimensional model. To quantify this enhancement, we
+introduce a novel parameter, the distortion variation rate, which captures the
+rapid and pronounced changes occurring within the domain wall structure.
+Through comprehensive micromagnetic simulations, we establish a robust
+relationship between speed and distortion variation rate, thereby validating
+our theoretical framework. Our findings provide crucial insights into the
+underlying mechanisms governing domain wall dynamics while paving the way for
+developing and optimizing next-generation spintronic devices boasting
+unparalleled speed and efficiency.",2305.14868v3
+2023-06-19,Field-free Line Magnetic Particle Imaging: Radon-based Artifact Reduction with Motion Models,"Magnetic particle imaging is a promising medical imaging technique. Applying
+changing magnetic fields to tracer material injected into the object under
+investigation results in a change in magnetization. Measurement of related
+induced voltage signals enables reconstruction of the particle distribution.
+For the field-free line scanner the scanning geometry is similar to the one in
+computerized tomography. We make use of these similarities to derive a forward
+model for dynamic particle concentrations. We validate our theoretical findings
+for synthetic data. By utilizing information about the object's dynamics in
+terms of a diffeomorphic motion model, we are able to jointly reconstruct the
+particle concentration and the corresponding dynamic Radon data without or with
+reduced motion artifacts. Thereby, we apply total variation regularization for
+the concentration and an optional sparsity constraint on the Radon data.",2306.10722v1
+2023-07-25,Lattice structure dependence of laser-induced ultrafast magnetization switching in ferrimagnets,"The experimental discovery of single-pulse ultrafast magnetization switching
+in ferrimagnetic alloys, such as GdFeCo and MnRuGa, opened the door to a
+promising route toward faster and more energy efficient data storage. A recent
+semi-phenomenological theory has proposed that a fast, laser-induced
+demagnetization below a threshold value puts the system into a dynamical regime
+where angular momentum transfer between sublattices dominates. Notably, this
+threshold scales inversely proportional to the number of exchange-coupled
+nearest neighbours considered in the model, which in the simplest case is
+directly linked to the underlying lattice structure. In this work, we study the
+role of the lattice structure on the laser-induced ultrafast magnetization
+switching in ferrimagnets by complementing the phenomenological theory with
+atomistic spin dynamics computer simulations. We consider a spin model of the
+ferrimagnetic GdFeCo alloy with increasing number of exchange-coupled
+neighbours. Within this model, we demonstrate that the laser-induced
+magnetization dynamics and switching depends on the lattice structure. Further,
+we determine that the critical laser energy for switching reduces for
+decreasing number of exchange-coupled neighbours.",2307.13522v1
+2023-08-01,Field and Polarization Dependent Quantum Spin Dynamics in Honeycomb Magnet Na$_2$Co$_2$TeO$_6$: Magnetic Excitations and Continuum,"We report terahertz spectroscopic measurements of quantum spin dynamics in
+the spin-1/2 honeycomb magnet Na$_2$Co$_2$TeO$_6$ as a function of applied
+magnetic field with different terahertz polarizations. Distinct field
+dependencies of the resolved spin dynamics are identified in three regimes,
+which are separated by two critical fields at $B_{c1}\approx 7$ and
+$B_{c2}\approx 10$ T. A polarization selective continuum is observed in the
+intermediate phase, featuring spin fluctuations of a proximate quantum spin
+liquid.",2308.00631v2
+2023-12-13,Kernel Polynomial Method for Linear Spin Wave Theory,"Calculating dynamical spin correlations is essential for matching model
+magnetic exchange Hamiltonians to momentum-resolved spectroscopic measurements.
+A major numerical bottleneck is the diagonalization of the dynamical matrix,
+especially in systems with large magnetic unit cells, such as those with
+incommensurate magnetic structures or quenched disorder. In this paper, we
+demonstrate an efficient scheme based on the kernel polynomial method for
+calculating dynamical correlations of relevance to inelastic neutron scattering
+experiments. This method reduces the scaling of numerical cost from cubic to
+linear in the magnetic unit cell size.",2312.08349v2
+1999-10-26,Spin dynamics simulations of the magnetic dynamics of RbMnF$_3$ and direct comparison with experiment,"Spin-dynamics techniques have been used to perform large-scale simulations of
+the dynamic behavior of the classical Heisenberg antiferromagnet in simple
+cubic lattices with linear sizes $L\leq 60$. This system is widely recognized
+as an appropriate model for the magnetic properties of RbMnF$_3$.
+Time-evolutions of spin configurations were determined numerically from coupled
+equations of motion for individual spins using a new algorithm implemented by
+Krech {\it etal}, which is based on fourth-order Suzuki-Trotter decompositions
+of exponential operators. The dynamic structure factor was calculated from the
+space- and time-displaced spin-spin correlation function. The crossover from
+hydrodynamic to critical behavior of the dispersion curve and spin-wave
+half-width was studied as the temperature was increased towards the critical
+temperature. The dynamic critical exponent was estimated to be $z=(1.43\pm
+0.03)$, which is slightly lower than the dynamic scaling prediction, but in
+good agreement with a recent experimental value. Direct, quantitative
+comparisons of both the dispersion curve and the lineshapes obtained from our
+simulations with very recent experimental results for RbMnF$_3$ are presented.",9910429v1
+2000-12-11,Hysteresis and the dynamic phase transition in thin ferromagnetic films,"Hysteresis and the non-equilibrium dynamic phase transition in thin magnetic
+films subject to an oscillatory external field have been studied by Monte Carlo
+simulation. The model under investigation is a classical Heisenberg spin system
+with a bilinear exchange anisotropy in a planar thin film geometry with
+competing surface fields. The film exhibits a non-equilibrium phase transition
+between dynamically ordered and dynamically disordered phases characterized by
+a critical temperature Tcd, whose location of is determined by the amplitude H0
+and frequency w of the applied oscillatory field. In the presence of competing
+surface fields the critical temperature of the ferromagnetic-paramagnetic
+transition for the film is suppressed from the bulk system value, Tc, to the
+interface localization-delocalization temperature Tci. The simulations show
+that in general Tcd < Tci for the model film. The profile of the time-dependent
+layer magnetization across the film shows that the dynamically ordered and
+dynamically disordered phases coexist within the film for T < Tcd. In the
+presence of competing surface fields, the dynamically ordered phase is
+localized at one surface of the film.",0012190v2
+2004-09-27,A New Measurement of Dynamic Critical exponent of Wolff Algorithm by Dynamic Finite Size Scaling,"In this work we have calculated the dynamic critical exponent $z$ for 2-, 3-
+and 4-dimensional Ising models using the Wolff's algorithm through dynamic
+finite size scaling. We have studied time evolution of the average cluster
+size, the magnetization and higher moments of the magnetization. It is observed
+that dynamic scaling is independent of the algorithm. In this sense,
+universality is established for a wide range of algorithms with their own
+dynamic critical exponents. For scaling, we have used the literature values of
+critical exponents to observe the dynamic finite size scaling and to obtain the
+value of $z$. From the simulation data a very good scaling is observed leading
+to vanishingly small $z$ values for all three dimensions.",0409696v1
+2005-07-11,Critical slowing down in random anisotropy magnets,"We study the purely relaxational critical dynamics with non-conserved order
+parameter (model A critical dynamics) for three-dimensional magnets with
+disorder in a form of the random anisotropy axis. For the random axis
+anisotropic distribution, the static asymptotic critical behaviour coincides
+with that of random site Ising systems. Therefore the asymptotic critical
+dynamics is governed by the dynamical exponent of the random Ising model.
+However, the disorder influences considerably the dynamical behaviour in the
+non-asymptotic regime. We perform a field-theoretical renormalization group
+analysis within the minimal subtraction scheme in two-loop approximation to
+investigate asymptotic and effective critical dynamics of random anisotropy
+systems. The results demonstrate the non-monotonic behaviour of the dynamical
+effective critical exponent $z_{\rm eff}$.",0507241v1
+2012-01-31,Dynamic relaxation of topological defect at Kosterlitz-Thouless phase transition,"With Monte Carlo methods we study the dynamic relaxation of a vortex state at
+the Kosterlitz-Thouless phase transition of the two-dimensional XY model. A
+local pseudo-magnetization is introduced to characterize the symmetric
+structure of the dynamic systems. The dynamic scaling behavior of the
+pseudo-magnetization and Binder cumulant is carefully analyzed, and the
+critical exponents are determined. To illustrate the dynamic effect of the
+topological defect, similar analysis for the the dynamic relaxation with a
+spin-wave initial state is also performed for comparison. We demonstrate that a
+limited amount of quenched disorder in the core of the vortex state may alter
+the dynamic universality class. Further, theoretical calculations based on the
+long-wave approximation are presented.",1201.6423v1
+2021-11-15,Finite-time dynamical phase transition in non-equilibrium relaxation,"We uncover a finite-time dynamical phase transition in the thermal relaxation
+of a mean-field magnetic model. The phase transition manifests itself as a cusp
+singularity in the probability distribution of the magnetisation that forms at
+a critical time. The transition is due to a sudden switch in the dynamics,
+characterised by a dynamical order parameter. We derive a dynamical Landau
+theory for the transition that applies to a range of systems with scalar,
+parity-invariant order parameters. Close to criticalilty, our theory reveals an
+exact mapping between the dynamical and equilibrium phase transitions of the
+magnetic model, and implies critical exponents of mean-field type. We argue
+that interactions between nearby saddle points, neglected at the mean-field
+level, may lead to critical, spatiotemporal fluctuations of the order
+parameter, and thus give rise to novel, dynamical critical phenomena.",2111.07681v2
+2015-09-23,Anomalously slow spin dynamics and short-range correlations in the quantum spin ice systems Yb2Ti2O7 and Yb2Sn2O7,"We report a positive muon spin relaxation and rotation (\muSR) study of the
+quantum spin ice materials Yb2Ti2O7 and Yb2Sn2O7 focusing on the low field
+response. In agreement with earlier reports, data recorded in small
+longitudinal fields evidence anomalously slow spin dynamics in the microsecond
+range below the temperature T_c at which the specific heat displays an intense
+peak, namely T_c = 0.24 K and 0.15 K, respectively, for the two systems. We
+found that slow dynamics extends above T_c up to at least 0.7 K for both
+compounds. The conventional dynamical Gaussian Kubo-Toyabe model describes the
+\muSR spectra recorded above T_c. At lower temperatures a published analytical
+extension of the Gaussian Kubo-Toyabe model provides a good description,
+consistent with the existence of short-range magnetic correlations. While the
+physical response of the two systems is qualitatively the same, Yb2Ti2O7
+exhibits a much larger local magnetic susceptibility than Yb2Sn2O7 below T_c.
+Considering previously reported ac susceptibility, neutron scattering and \muSR
+results, we suggest the existence of anomalously slow spin dynamics to be a
+common physical property of pyrochlore magnetic materials. The possibility of
+molecular spin substructures to be associated to the slow dynamics and
+therefore the short-range correlations is mentioned. The slow spin dynamics
+observed under field does not exclude the presence of much faster dynamics
+detected in extremely low or zero field.",1509.06908v1
+2018-01-29,Temporal organization of magnetospheric fluctuations unveiled by recurrence patterns in the Dst index,"Magnetic storms constitute the most remarkable large-scale phenomena of
+nonlinear magnetospheric dynamics. Studying the dynamical organization of
+macroscopic variability in terms of geomagnetic activity index data by means of
+complexity measures provides a promising approach for identifying the
+underlying processes and associated time-scales. Here, we apply a suite of
+characteristics from recurrence quantification analysis (RQA) and recurrence
+network analysis (RNA) in order to unveil some key nonlinear features of the
+hourly Disturbance storm-time (Dst) index during periods with magnetic storms
+and such of normal variability. Our results demonstrate that recurrence-based
+measures can serve as excellent tracers for changes in the dynamical complexity
+along non-stationary records of geomagnetic activity. In particular, trapping
+time (characterizing the typical length of ""laminar phases"" in the observed
+dynamics) and recurrence network transitivity (associated with the number of
+the system's effective dynamical degrees of freedom) allow for a very good
+discrimination between magnetic storm and quiescence phases. In general, some
+RQA and RNA characteristics distinguish between storm and non-storm times
+equally well or even better than other previously considered nonlinear
+characteristics like Hurst exponent or symbolic dynamics based entropy
+concepts. Our results point to future potentials of recurrence characteristics
+for unveiling temporal changes in the dynamical complexity of the
+magnetosphere.",1802.01426v1
+1993-11-02,Magnetic Activity in Thick Accretion Disks and Associated Observable Phenomena I. Flux Expulsion,"We study the dynamics of toroidal magnetic flux tubes, symmetric about the
+rotation axis, inside non-magnetic thick accretion disks around black holes. We
+present model equations which include effects of gravity, centrifugal force,
+pressure gradient force, Coriolis force, drag, magnetic tension and magnetic
+buoyancy. We solve them assuming the disk to be adiabatic. We show that under a
+wide range of parameters describing the size and the field strength, as well as
+angular momentum distribution inside the disk, buoyant flux tubes, either
+released on the equatorial plane or at the outer edge of the disk, can gather
+in the chimney-like openings near the axis. This behavior makes the chimneys
+magnetically most active and could shed light on the origin and acceleration of
+cosmic jets, as well as the variabilities observed in Blazars.",9311010v1
+2000-02-14,On the Role of Dust Particles in Decoupling of Plasma from Magnetic Field in Laboratory and Space,"The objective of this paper is to apply the recent achievements in
+understanding of the non-MHD effects in plasma (acquired both in laboratory
+experiments, as well as in theory), to the interstellar phenomena. Applied to
+the space plasma, these effects can significantly change the picture of plasma
+dynamics. Charged dust particles are always present in the interstellar medium
+and can easily remain not magnetized, even when the plasma electrons and ions
+are strongly magnetized. In such a medium, the magnetic field can propagate
+with the super-Alfven velocity. This breaks the local ""frozen-in"" law for the
+magnetic field, which can significantly affect the gravitational collapse
+phenomena, the space plasma turbulence spectrum, magnetic dynamo and the rate
+of the Fermi acceleration of cosmic rays.",0002293v1
+2002-01-29,MHD inverse cascade in the early Universe,"We have carried out numerical simulations of freely decaying
+magnetohydrodynamic (MHD) turbulence in three dimensions, which can be applied
+to the evolution of stochastic magnetic fields in the early Universe. For
+helical magnetic fields an inverse cascade effect is observed in which magnetic
+helicity and energy is transfered from smaller scales to larger scales,
+accompanied by power law growth in the characteristic length scale of the
+magnetic field. The magnetic field quickly reaches a scaling regime with
+self-similar evolution, and power law behaviour at high wavenumbers. We also
+find power law decay in the magnetic and kinematic energies.",0201466v1
+2002-02-05,R-modes in the ocean of a magnetic neutron star,"We study the dynamics of r-modes in the ocean of a magnetic neutron star. We
+modeled the star's ocean with a spherical rotating thin shell and assumed that
+the magnetic field symmetry axis is not aligned to the shell's spin axis. In
+the magnetohydrodynamic approximation, we calculate the frequency of $\ell=m$
+r-modes in the shell of an incompressible fluid. Different r-modes with $\ell$
+and $\ell\pm2$ are coupled by the {\it inclined} magnetic field. Kinematical
+secular effects for the motion of a fluid element in the shell undergoing
+$\ell=m=2$ r-mode are studied. The magnetic corrected drift velocity of a given
+fluid element undergoing the $\ell=m$ r-mode oscillations is obtained. The
+magnetic field increases the magnitude of the fluid drift produced by the
+r-mode drift velocity, the high-$\ell$ modes in the ocean fluid will damp
+faster than the low-$\ell$ ones.",0202105v3
+2005-07-16,Magnetohydrodynamics in full general relativity: Formulation and tests,"A new implementation for magnetohydrodynamics (MHD) simulations in full
+general relativity (involving dynamical spacetimes) is presented. In our
+implementation, Einstein's evolution equations are evolved by a BSSN formalism,
+MHD equations by a high-resolution central scheme, and induction equation by a
+constraint transport method. We perform numerical simulations for standard test
+problems in relativistic MHD, including special relativistic magnetized shocks,
+general relativistic magnetized Bondi flow in stationary spacetime, and a
+longterm evolution for self-gravitating system composed of a neutron star and a
+magnetized disk in full general relativity. In the final test, we illustrate
+that our implementation can follow winding-up of the magnetic field lines of
+magnetized and differentially rotating accretion disks around a compact object
+until saturation, after which magnetically driven wind and angular momentum
+transport inside the disk turn on.",0507383v1
+2005-11-09,Solar differential rotation and properties of magnetic clouds,"The most geoeffective solar drivers are magnetic clouds - a subclass of
+coronal mass ejections (CME's) distinguished by the smooth rotation of the
+magnetic field inside the structure. The portion of CME's that are magnetic
+clouds is maximum at sunspot minimum and mimimum at sunspot maximum. This
+portion is determined by the amount of helicity carried away by CME's which in
+turn depends on the amount of helicity transferred from the solar interior to
+the surface, and on the surface differential rotation. The latter can increase
+or reduce, or even reverse the twist of emerging magnetic flux tubes, thus
+increasing or reducing the helicity in the corona, or leading to the violation
+of the hemispheric helicity rule, respectively. We investigate the CME's
+associated with the major geomagnetic storms in the last solar cycle whose
+solar sources have been identified, and find that in 10 out of 12 cases of
+violation of the hemispheric helicity rule or of highly geoeffective CME's with
+no magnetic field rotation, they originate from regions with ""anti-solar"" type
+of surface differential rotation.",0511257v1
+2006-04-21,Modeling the Large Scale Structures of Astrophysical Jets in the Magnetically Dominated Limit,"We suggest a new approach that could be used for modeling both the large
+scale behavior of astrophysical jets and the magnetically dominated explosions
+in astrophysics. We describe a method for modeling the injection of magnetic
+fields and their subsequent evolution in a regime where the free energy is
+magnetically dominated. The injected magnetic fields, along with their
+associated currents, have both poloidal and toroidal components, and they are
+not force free. The dynamic expansion driven by the Lorentz force of the
+injected fields is studied using 3-dimensional ideal magnetohydrodynamic
+simulations. The generic behavior of magnetic field expansion, the interactions
+with the background medium, and the dependence on various parameters are
+investigated.",0604469v1
+2006-07-24,Effect of Rossby and Alfvén waves on the dynamics of the tachocline,"To understand magnetic diffusion, momentum transport, and mixing in the
+interior of the sun, we consider an idealized model of the tachocline, namely
+magnetohydrodynamics (MHD) turbulence on a $\beta$ plane subject to a large
+scale shear (provided by the latitudinal differential rotation). This model
+enables us to self-consistently derive the influence of shear, Rossby and
+Alfv\'{e}n waves on the transport properties of turbulence. In the strong
+magnetic field regime, we find that the turbulent viscosity and diffusivity are
+reduced by magnetic fields only, similarly to the two-dimensional MHD case
+(without Rossby waves). In the weak magnetic field regime, we find a crossover
+scale ($L\_R$) from a Alfv\'{e}n dominated regime (on small scales) to a Rossby
+dominated regime (on large scales). For parameter values typical of the
+tachocline, $L\_R$ is larger that the solar radius so that Rossby waves are
+unlikely to play an important role in the transport of magnetic field and
+angular momentum. This is mainly due to the enhancement of magnetic
+back-reaction by shearing which efficiently generates small scales, thus strong
+currents.",0607545v1
+2006-07-26,Evolution of Collapse Nonuniformity for Rotating Magnetic Interstellar Clouds,"We investigate the formation and evolution of isothermal collapse
+nonuniformity for rotating magnetic interstellar clouds. The initial and
+boundary conditions correspond to the statement of the problem of homogeneous
+cloud contraction from a pressure equilibrium with the external medium. The
+initial uniform magnetic field is collinear with the angular velocity. Fast and
+slow magnetosonic rarefaction waves are shown to be formed and propagate from
+the boundary of the cloud toward its center in the early collapse stages. The
+front of the fast rarefaction wave divides the gas mass into two parts. The
+density, angular velocity, and magnetic field remain uniform in the inner
+region and have nonuniform profiles in the outer region. The rarefaction wave
+front surface can take both prolate and oblate shapes along the rotation axis,
+depending on the relationship between the initial angular velocity and magnetic
+field. We derive a criterion that separates the two regimes of rarefaction wave
+dynamics with the dominant role of electromagnetic and centrifugal forces.
+Based on analytical estimations and numerical calculations, we discuss possible
+scenarios for the evolution of collapse nonuniformity for rotating magnetic
+interstellar clouds.",0607588v1
+2007-01-08,Collapse and Fragmentation of Molecular Cloud Cores. IX. Magnetic Braking of Initially Filamentary Clouds,"The collapse and fragmentation of initially filamentary, magnetic molecular
+clouds is calculated in three dimensions with a gravitational, radiative
+hydrodynamics code. The code includes magnetic field effects in an approximate
+manner: magnetic pressure, tension, braking, and ambipolar diffusion are all
+modelled. Three types of outcomes are observed: direct collapse and
+fragmentation into a multiple protostar system, periodic contraction and
+expansion without collapse, or periodic contraction and expansion leading
+eventually to collapse. While the models begin their evolution at rest except
+for the assumed solid-body rotation, they develop weakly supersonic velocity
+fields as a result of the rebounding prior to collapse. The models show that
+magnetically-supported clouds subject to magnetic braking can undergo dynamic
+collapse leading to protostellar fragmentation on scales of 10 AU to 100 AU,
+consistent with typical binary star separations.",0701210v1
+2007-01-28,"Twist, writhe and energy from the helicity of magnetic perturbed vortex filaments","The twist and writhe numbers and magnetic energy of an orthogonally perturbed
+vortex filaments are obtained from the computation of the magnetic helicity of
+geodesic and abnormal magnetohydrodynamical (MHD) vortex filament solutions.
+Twist is computed from a formula recently derived by Berger and Prior [J. Phys.
+A 39 (2006) 8321] and finally writhe is computed from the theorem that the
+helicity is proportional to the sum of twist and writhe. The writhe number is
+proportional to the total torsion and to integrals of the vector potential. The
+magnetic energy is computed in terms of the integral of the torsion squared
+which allows us to place a bound to energy in in the case of helical filaments
+due to a theorem by Fukumoto [J. Phys. Soc. Japan,(1987)] in fluid vortex
+filaments. It is also shown that filament torsion coincides with the magnetic
+twist in the case under consideration, where a small orthogonal magnetic field
+exist along the thin filament. A new Aharonov-Bohm (AB) phase term is obtained
+in the writhe number expression which is not present in the Moffatt-Ricca (Proc
+Roy Soc London A,1992) computation.",0701796v1
+1996-12-09,Hall Conductivity for Two Dimensional Magnetic Systems,"A Kubo inspired formalism is proposed to compute the longitudinal and
+transverse dynamical conductivities of an electron in a plane (or a gas of
+electrons at zero temperature) coupled to the potential vector of an external
+local magnetic field, with the additional coupling of the spin degree of
+freedom of the electron to the local magnetic field (Pauli Hamiltonian). As an
+example, the homogeneous magnetic field Hall conductivity is rederived. The
+case of the vortex at the origin is worked out in detail. This system happens
+to display a transverse Hall conductivity ($P$ breaking effect) which is
+subleading in volume compared to the homogeneous field case, but diverging at
+small frequency like $1/\omega^2$. A perturbative analysis is proposed for the
+conductivity in the random magnetic impurity problem (Poissonian vortices in
+the plane). At first order in perturbation theory, the Hall conductivity
+displays oscillations close to the classical straight line conductivity of the
+mean magnetic field.",9612080v1
+1997-04-25,Correlated-electron theory of strongly anisotropic metamagnets,"The microscopic origin of metamagnetism and metamagnetic transitions in
+strongly anisotropic antiferromagnets is investigated within a quantum
+mechanical theory of correlated electrons. To this end the Hubbard model with
+staggered magnetization m_st along an easy axis e in a magnetic field H || e is
+studied both analytically and numerically within the dynamical mean field
+theory (DMFT). At intermediate couplings the self-consistent DMFT equations,
+which become exact in the limit of large coordination number, are solved by
+finite temperature Quantum Monte Carlo techniques. The temperature and magnetic
+field dependence of the homogeneous and staggered magnetization are calculated
+and the magnetic phase diagram is constructed. At half filling the metamagnetic
+transitions are found to change from first order at low temperatures to second
+order near the N'eel temperature, implying the existence of a multicritical
+point. Doping with holes or electrons has a strong effect: the system becomes
+metallic, the electronic compressibility increases and the critical
+temperatures and fields decrease. These results are related to known properties
+of insulating metamagnets such as FeBr_2, metallic metamagnets such as UPdGe,
+and the giant and colossal magnetoresistance found in a number of magnetic bulk
+systems.",9704209v1
+2000-10-19,Magnets with strong geometric frustration,"A non-technical introduction to the theory of magnets with strong geometric
+frustration is given, concentrating on magnets on corner-sharing (kagome,
+pyrochlore, SCGO and GGG) lattices. Their rich behaviour is traced back to a
+large ground-state degeneracy in model systems, which renders them highly
+unstable towards perturbations. A systematic classification according to
+properties of their ground states is discussed. Other topics addressed in this
+overview article include a general theoretical framework for thermal order by
+disorder; the dynamics of how the vast regions of phase space accessible at low
+temperature are explored; the origin of the featureless magnetic susceptibility
+fingerprint of geometric frustration; the role of perturbations; and spin ice.
+The rich field of quantum frustrated magnets is also touched on.",0010301v1
+2001-05-24,Electric-Field-Induced Phase Separation and Labyrinthine Patterns in Nanocolloids,"In this paper we report universal labyrinthine patterns observed in
+nanocolloids originated from electric-field-induced phase separation. For
+nanocolloids consisting of magnetic particles (magnetic fluids), the
+labyrinthine pattern as the result of the co-existence of two phases is found
+to be stable against perturbation by an additional magnetic field. The
+relaxation back to the globally disordered pattern after the magnetic field is
+removed clearly shows evolution of ""undulation"" thus demonstrates that
+superimposing magnetic and electric fields can easily manipulate the patterns
+resulted from the phase separation, indicating that a magnetic fluid has an
+advantage in exploring the dynamics of defects that has applications in many
+fields.",0105484v1
+2002-08-26,Tunable Lyapunov exponent in inverse magnetic billiards,"The stability properties of the classical trajectories of charged particles
+are investigated in a two dimensional stadium-shaped inverse magnetic domain,
+where the magnetic field is zero inside the stadium domain and constant
+outside. In the case of infinite magnetic field the dynamics of the system is
+the same as in the Bunimovich billiard, i.e., ergodic and mixing. However, for
+weaker magnetic fields the phase space becomes mixed and the chaotic part
+gradually shrinks. The numerical measurements of the Lyapunov exponent
+(performed with a novel method) and the integrable/chaotic phase space volume
+ratio show that both quantities can be smoothly tuned by varying the external
+magnetic field. A possible experimental realization of the arrangement is also
+discussed.",0208491v1
+2002-09-25,Spin Glass Behavior in RuSr2Gd1.5Ce0.5Cu2O10,"The dynamics of the magnetic properties of polycrystalline
+RuSr2Gd1.5Ce0.5Cu2O10 (Ru-1222) have been studied by ac susceptibility and dc
+magnetization measurements, including relaxation and ageing studies. Ru-1222 is
+a reported magneto-superconductor with Ru spins magnetic ordering at
+temperatures near 100 K and superconductivity in Cu-O2 planes below Tc ~ 40 K.
+The exact nature of Ru spins magnetic ordering is still debated and no
+conclusion has been reached yet. In this work, a frequency-dependent cusp was
+observed in ac susceptibility vs. T measurements, which is interpreted as a
+spin glass transition. The change in the cusp position with frequency follows
+the Vogel-Fulcher law, which is commonly accepted to describe a spin glass with
+magnetically interacting clusters. Such interpretation is supported by
+themoremanaent magnetization (TRM) measurements at T = 60 K. TRM relaxations
+are well described by a stretched exponential relation, and present significant
+ageing effects.",0209593v1
+2003-12-15,The role of dynamical polarization of the ligand to metal charge transfer excitations in {\em ab initio} determination of effective exchange parameters,"The role of the bridging ligand on the effective Heisenberg coupling
+parameters is analyzed in detail. This analysis strongly suggests that the
+ligand-to-metal charge transfer excitations are responsible for a large part of
+the final value of the magnetic coupling constant. This permits to suggest a
+new variant of the Difference Dedicated Configuration Interaction (DDCI)
+method, presently one of the most accurate and reliable for the evaluation of
+magnetic effective interactions. This new method treats the bridging ligand
+orbitals mediating the interaction at the same level than the magnetic orbitals
+and preserves the high quality of the DDCI results while being much less
+computationally demanding. The numerical accuracy of the new approach is
+illustrated on various systems with one or two magnetic electrons per magnetic
+center. The fact that accurate results can be obtained using a rather reduced
+configuration interaction space opens the possibility to study more complex
+systems with many magnetic centers and/or many electrons per center.",0312370v1
+2003-12-30,NMR and LDA evidence for spiral magnetic order in the chain cuprate LiCu2O2,"We report on {6,7}Li nuclear magnetic resonance measurements of the
+spin-chain compound LiCu2O2 in the paramagnetic and magnetically ordered
+states. Below T about 24 K the NMR lineshape presents a clear signature of
+incommensurate (IC) static modulation of the local magnetic field consistent
+with an IC spiral modulation of the magnetic moments. {7}Li NMR reveals strong
+phason-like dynamical fluctuations extending well below 24 K. We hypothesize
+that a series of phase transitions at 24.2, 22.5, and 9 K reflects a ""Devil's
+staircase"" type behavior generic for IC systems. LDA based calculations of
+exchange integrals reveal a large in-chain frustration leading to a magnetical
+spiral.",0312706v1
+2004-05-19,Dynamics of the magnetic and structural a -> e phase transition in Iron,"We have studied the high-pressure iron bcc to hcp phase transition by
+simultaneous X-ray Magnetic Circular Dichroism (XMCD) and X-ray Absorption
+Spectroscopy (XAS) with an X-ray dispersive spectrometer. The combination of
+the two techniques allows us to obtain simultaneously information on both the
+structure and the magnetic state of Iron under pressure. The magnetic and
+structural transitions simultaneously observed are sharp. Both are of first
+order in agreement with theoretical prediction. The pressure domain of the
+transition observed (2.4 $\pm$ 0.2 GPa) is narrower than that usually cited in
+the literature (8 GPa). Our data indicate that the magnetic transition slightly
+precedes the structural one, suggesting that the origin of the instability of
+the bcc phase in iron with increasing pressure is to be attributed to the
+effect of pressure on magnetism as predicted by spin-polarized full potential
+total energy calculations.",0405439v4
+2004-06-18,Spin pumping and magnetization dynamics in ferromagnet-Luttinger liquid junctions,"We study spin transport between a ferromagnet with time-dependent
+magnetization and a conducting carbon nanotube or quantum wire, modeled as a
+Luttinger liquid. The precession of the magnetization vector of the ferromagnet
+due for instance to an outside applied magnetic field causes spin pumping into
+an adjacent conductor. Conversely, the spin injection causes increased
+magnetization damping in the ferromagnet. We find that, if the conductor
+adjacent to the ferromagnet is a Luttinger liquid, spin pumping/damping is
+suppressed by interactions, and the suppression has clear Luttinger liquid
+power law temperature dependence. We apply our result to a few particular
+setups. First we study the effective Landau-Lifshitz-Gilbert (LLG) coupled
+equations for the magnetization vectors of the two ferromagnets in a FM-LL-FM
+junction. Also, we compute the Gilbert damping for a FM-LL and a FM-LL-metal
+junction.",0406437v1
+2004-06-24,Thermal Effects on the Magnetic Field Dependence of Spin Transfer Induced Magnetization Reversal,"We have developed a self-aligned, high-yield process to fabricate CPP
+(current perpendicular to the plane) magnetic sensors of sub 100 nm dimensions.
+A pinned synthetic antiferromagnet (SAF) is used as the reference layer which
+minimizes dipole coupling to the free layer and field induced rotation of the
+reference layer. We find that the critical currents for spin transfer induced
+magnetization reversal of the free layer vary dramatically with relatively
+small changes the in-plane magnetic field, in contrast to theoretical
+predictions based on stability analysis of the Gilbert equations of
+magnetization dynamics including Slonczewski-type spin-torque terms. The
+discrepancy is believed due to thermal fluctuations over the time scale of the
+measurements. Once thermal fluctuations are taken into account, we find good
+quantitative agreement between our experimental results and numerical
+simulations.",0406574v1
+2004-08-17,Vortex state oscillations in soft magnetic cylindrical dots,"We have studied magnetic vortex oscillations in soft sub-micron cylindrical
+dots with variable thickness and diameter by an analytical approach and
+micromagnetic simulations. We have considered two kinds of modes of the vortex
+magnetization oscillations: 1) low-frequency translation mode, corresponding to
+the movement of the vortex as a whole near its equilibrium position; 2)
+high-frequency vortex modes, which correspond to radially symmetric
+oscillations of the vortex magnetization, mainly outside the vortex core. The
+vortex translational eigenmode was calculated numerically in frequency and time
+domains for different dot aspect ratios. To describe the discrete set of vortex
+high-frequency modes we applied the linearized equation of motion of dynamic
+magnetization over the vortex ground state. We considered only radially
+symmetric magnetization oscillations modes. The eigenfrequencies of both kinds
+of excitation modes are determined by magnetostatic interactions. They are
+proportional to the thickness/diameter ratio and lie in the GHz range for
+typical dot sizes.",0408388v1
+2004-10-25,Absence of magnetic moments in plutonium,"Many theories published in the last decade propose that either ordered or
+disordered local moments are present in elemental plutonium at low
+temperatures. We present new experimental data and review previous experimental
+results. None of the experiments provide any evidence for ordered or disordered
+magnetic moments (either static or dynamic) in plutonium at low temperatures,
+in either the alpha- or delta-phases. The experiments presented and discussed
+are magnetic susceptibility,electrical resistivity, NMR, specific heat, and
+both elastic and inelastic neutronscattering. Many recent calculations
+correctly predict experimentally observed atomic volumes, including that of
+delta-Pu. These calculations achieve observed densities by the localization of
+electrons, which then give rise to magnetic moments. However, localized
+magnetic moments have never been observed experimentally in Pu. A theory is
+needed that is in agreement with all the experimental observations. Two
+theories are discussed that might provide understanding of the ensemble of
+unusual properties of Pu, including the absence of experimental evidence for
+localized magnetic moments; an issue that has persisted for over 50 years.",0410634v1
+2005-01-28,Finite-temperature Simulations for Magnetic Nanostructures,"We examine different models and methods for studying finite-temperature
+magnetic hysteresis in nanoparticles and ultrathin films. This includes
+micromagnetic results for the hysteresis of a single magnetic nanoparticle
+which is misaligned with respect to the magnetic field. We present results from
+both a representation of the particle as a one-dimensional array of magnetic
+rotors, and from full micromagnetic simulations. The results are compared with
+the Stoner-Wohlfarth model. Results of kinetic Monte Carlo simulations of
+ultrathin films are also presented. In addition, we discuss other topics of
+current interest in the modeling of magnetic hysteresis in nanostructures,
+including kinetic Monte Carlo simulations of dynamic phase transitions and
+First-Order Reversal Curves.",0501692v2
+2005-02-10,Ultra fast bit addressing in a magnetic memory matrix with crossed wire write line geometry,"An ultra fast bit addressing scheme for magnetic random access memories
+(MRAM) in a crossed wire geometry is proposed. In the addressing scheme a word
+of cells is programmed simultaneously by sub nanosecond field pulses making use
+of the magnetization precession of the free layer. Single spin simulations of
+the free layer dynamics show that the pulse parameters for programming an
+arbitrary word of the array can be chosen such that the magnetization of the
+cells to be written performs either a half or a full precessional turn during
+application of the programming pulse depending on the initial and final
+magnetization orientation of the addressed cells. Such bit addressing scheme
+leads to a suppression of the magnetization ringing in all cells of the memory
+array thereby allowing ultra high MRAM write clock rates above 1 GHz.",0502263v1
+2005-02-28,Magnetization dynamics of two interacting spins in an external magnetic field,"The longitudinal relaxation time of the magnetization of a system of two
+exchange coupled spins subjected to a strong magnetic field is calculated
+exactly by averaging the stochastic Gilbert-Landau-Lifshitz equation for the
+magnetization, i.e., the Langevin equation of the process, over its
+realizations so reducing the problem to a system of linear
+differential-recurrence relations for the statistical moments (averaged
+spherical harmonics). The system is solved in the frequency domain by matrix
+continued fractions yielding the complete solution of the two-spin problem in
+external fields for all values of the damping and barrier height parameters.
+The magnetization relaxation time extracted from the exact solution is compared
+with the inverse relaxation rate from Langer's theory of the decay of
+metastable states, which yields in the high barrier and intermediate-to-high
+damping limits the asymptotic behaviour of the greatest relaxation time.",0502661v2
+2005-08-31,Photon-Induced Magnetization Changes in Single-Molecule Magnets,"Microwave radiation applied to single-molecule magnets can induce large
+magnetization changes when the radiation is resonant with transitions between
+spin levels. These changes are interpreted as due to resonant heating of the
+sample by the microwaves. Pulsed-radiation studies show that the magnetization
+continues to decrease after the radiation has been turned off with a rate that
+is consistent with the spin's characteristic relaxation rate. The measured rate
+increases with pulse duration and microwave power, indicating that greater
+absorbed radiation energy results in a higher sample temperature. We also
+performed numerical simulations that qualitatively reproduce many of the
+experimental results. Our results indicate that experiments aimed at measuring
+the magnetization dynamics between two levels resonant with the radiation must
+be done much faster than the >20-microsecond time scales probed in these
+experiments.",0508774v3
+2005-11-16,Giant magnetoimpedance in composite wires with insulator layer between non-magnetic core and soft magnetic shell,"A method for calculation of the magnetoimpedance in composite wires having an
+insulator layer between non-magnetic core and soft magnetic shell is described.
+It is assumed that the magnetic shell has a helical anisotropy and the driving
+current flows through the core only. The distribution of eddy currents and
+expressions for the impedance are found by means of a solution of Maxwell
+equations taking into account the magnetization dynamics within the shell
+governed by the Landau-Lifshitz equation. The effect of the insulator layer on
+the magnetoimpedance is analyzed.",0511386v1
+2005-11-22,Magnetomechanical Torques in Small Magnetic Cantilevers,"We study the dnamics of small magnetic cantilevers, either made from Si
+covered by a magnetic film or entirely ferromagnetic ones. The
+magnetomechanical torques are found to cause line splittings in ferromagnetic
+resonance spectra and magnetization reversal facilitated by mechanical degrees
+of freedom. We show that the magnetomechanical torques can extend the limits of
+detecting and exciting motion at the nanoscale. A ""nanomotor"" described here
+effectively transforms rf magnetic fields into mechanical oscillations. We
+furthermore propose to integrate mechanical oscillators into magnetoelectronic
+devices that make use of current-induced spin-transfer torques. This opens new
+possibilities for electric transducers of nanomechanical motion.",0511548v1
+2006-01-30,Multiple transfer of angular momentum quanta from a spin-polarized hole to magnetic ions in ZnMnSe/ZnBeSe quantum wells,"The magnetization kinetics in (Zn,Mn)Se/(Zn,Be)Se quantum wells has been
+studied on a ps-time scale after pulsed laser excitation. The magnetization
+induced by an external magnetic field is reduced by up to 30% during ~100 ps
+due to spin and energy transfer from photocarriers to Mn spin system. The giant
+Zeeman splitting leads to a complete spin polarization of the carriers,
+resulting in a strong suppression of flip-flop processes between carriers and
+magnetic ions. Therefore a multiple angular momentum transfer from each
+spin-polarized hole to the Mn ions becomes the dominant mechanism in the
+magnetization dynamics. A model based on spin-momentum coupling in the valence
+band is suggested for explaining this transfer.",0601661v1
+2003-09-17,Asymptotic Regimes of Magnetic Bianchi Cosmologies,"We consider the asymptotic dynamics of the Einstein-Maxwell field equations
+for the class of non-tilted Bianchi cosmologies with a barotropic perfect fluid
+and a pure homogeneous source-free magnetic field, with emphasis on models of
+Bianchi type VII_{0}, which have not been previously studied. Using the
+orthonormal frame formalism and Hubble-normalized variables, we show that, as
+is the case for the previously studied class A magnetic Bianchi models, the
+magnetic Bianchi VII_{0} cosmologies also exhibit an oscillatory approach to
+the initial singularity. However, in contrast to the other magnetic Bianchi
+models, we rigorously establish that typical magnetic Bianchi VII_{0}
+cosmologies exhibit the phenomena of asymptotic self-similarity breaking and
+Weyl curvature dominance in the late-time regime.",0309083v1
+2004-10-03,"Octet, decuplet and antidecuplet magnetic moments in the chiral quark soliton model revisited","We reanalyse the magnetic moments of the baryon octet, decuplet, and
+antidecuplet within the framework of the chiral quark-soliton model, with SU(3)
+symmetry breaking taken into account. We consider the contributions of the
+mixing of higher representations to the magnetic moment operator arising from
+the SU(3) symmetry breaking. Dynamical parameters of the model are fixed by
+experimental data for the magnetic moments of the baryon octet and from the
+masses of the octet, decuplet and of $\Theta^{+}$. The magnetic moment of
+$\Theta^{+}$ depends rather strongly on the pion-nucleon sigma term and reads
+$-1.19 {\rm n.m.}$ to $-0.33 {\rm n.m.}$ for $\Sigma_{\pi N} = 45$ and 75 MeV
+respectively. The recently reported mass of $\Xi^{--}_{\bar{10}}(1862)$ is
+compatible with $\Sigma_{\pi N} = 73$ MeV. As a byproduct the strange magnetic
+moment of the nucleon is obtained with a value of $\mu^{(s)}_N =+0.39$ n.m.",0410042v2
+2004-12-18,Magnetic moments of the pentaquarks,"We present in this talk a recent analysis for the magnetic moments of the
+baryon antidecuplet within the framework of the chiral quark-soliton model with
+linear $m_s$ corrections considered. We take into account the mixing of higher
+representations to the collective magnetic moment operator, which comes from
+the SU(3) symmetry breaking. Dynamical parameters of the model are fixed by
+experimental data for the magnetic moments of the baryon octet as well as by
+the masses of the octet, decuplet and of $\Theta^{+}$. The magnetic moment of
+$\Theta^{+}$ is rather sensitive to the pion-nucleon sigma term and ranges from
+$-1.19 {\rm n.m.}$ to $-0.33 {\rm n.m.}$ as the sigma term is varied from
+$\Sigma_{\pi N} = 45$ to 75 MeV, respectively. On top of them, we obtained that
+the strange magnetic moment of the nucleon has the value of $\mu^{(s)}_N
+=+0.39$ n.m. within this scheme and turns out to be almost independent of the
+sigma term.",0412270v1
+1996-06-10,The Gross-Neveu model on a sphere with a magnetic monopole,"We study, for the first time, the phase structure of the Gross--Neveu model
+with a combination of a (constant) gravitational and a magnetic field. This has
+been made possible by our finding of an exact solution to the problem, namely
+the effective potential for the composite fermions. Then, from the
+corresponding implicit equation the phase diagram for the dynamical fermion
+mass is calculated numerically for some values of the magnetic field. %(what
+can be done with arbitrary precision). For a small magnetic field the phase
+diagram hints to the possibility of a second order phase transition at some
+critical curvature. With growing magnetic field only the phase with broken
+chiral symmetry survives, because the magnetic field prevents the decay of the
+chiral condensate. This result is bound to have important consequences in early
+universe cosmology.",9606051v1
+1996-09-05,Quantum Charged Spinning Particles in a Strong Magnetic Field (a Quantal Guiding Center Theory),"A quantal guiding center theory allowing to systematically study the
+separation of the different time scale behaviours of a quantum charged spinning
+particle moving in an external inhomogeneous magnetic filed is presented. A
+suitable set of operators adapting to the canonical structure of the problem
+and generalizing the kinematical momenta and guiding center operators of a
+particle coupled to a homogenous magnetic filed is constructed. The Pauli
+Hamiltonian rewrites in this way as a power series in the magnetic length $l_B=
+\sqrt{\hbar c/eB}$ making the problem amenable to a perturbative analysis. The
+first two terms of the series are explicitly constructed. The effective
+adiabatic dynamics turns to be in coupling with a gauge filed and a scalar
+potential. The mechanism producing such magnetic-induced geometric-magnetism is
+investigated in some detail.",9609042v1
+2001-07-30,Energy fluxes in helical magnetohydrodynamics and dynamo action,"Renormalized viscosity, renormalized resistivity, and various energy fluxes
+are calculated for helical magnetohydrodynamics using perturbative field
+theory. The calculation is to first-order in perturbation. Kinetic and magnetic
+helicities do not affect the renormalized parameters, but they induce an
+inverse cascade of magnetic energy. The sources for the the large-scale
+magnetic field have been shown to be (1) energy flux from large-scale velocity
+field to large-scale magnetic field arising due to nonhelical interactions, and
+(2) inverse energy flux of magnetic energy caused by helical interactions.
+Based on our flux results, a premitive model for galactic dynamo has been
+constructed. Our calculations yields dynamo time-scale for a typical galaxy to
+be of the order of $10^8$ years. Our field-theoretic calculations also reveal
+that the flux of magnetic helicity is backward, consistent with the earlier
+observations based on absolute equilibrium theory.",0107069v4
+2003-11-26,Simulation of induction at low magnetic Prandtl number,"We consider the induction of magnetic field in flows of electrically
+conducting fluid at low magnetic Prandtl number and large kinetic Reynolds
+number. Using the separation between the magnetic and kinetic diffusive
+lengthscales, we propose a new numerical approach. The coupled magnetic and
+fluid equations are solved using a mixed scheme, where the magnetic field
+fluctuations are fully resolved and the velocity fluctuations at small scale
+are modelled using a Large Eddy Simulation (LES) scheme. We study the response
+of a forced Taylor-Green flow to an externally applied field: tology of the
+mean induction and time fluctuations at fixed locations. The results are in
+remarkable agreement with existing experimental data; a global $1/f$ behavior
+at long times is also evidenced.",0311130v1
+2005-05-03,Magnetization of rotating ferrofluids: predictions of different theoretical models,"We consider a ferrofluid cylinder, that is rotating with constant rotation
+frequency \Omega e_z as a rigid body. A homogeneous magnetic field H_0 e_x is
+applied perpendicular to the cylinder axis e_z. This causes a nonequilibrium
+situation. Therein the magnetization M and the internal magnetic field H are
+constant in time and homogeneous within the ferrofluid. According to the
+Maxwell equations they are related to each other via H = H_0 - M/2. However, H
+and M are not parallel to each other and their directions differ from that of
+the applied field H_0. We have analyzed several different theoretical models
+that provide equations for the magnetization in such a situation. The
+magnetization M is determined for each model as a function of \Omega and H_0 in
+a wide range of frequencies and fields. Comparisons are made of the different
+model results and the differences in particular of the predictions for the
+perpendicular components H_y =-M_y/2 of the fields are analyzed.",0505022v2
+2007-01-12,Fully developed turbulent dynamo at low magnetic Prandtl numbers,"We investigate the dynamo problem in the limit of small magnetic Prandtl
+number ($\Pm$) using a shell model of magnetohydrodynamic turbulence. The model
+is designed to satisfy conservation laws of total energy, cross helicity and
+magnetic helicity in the limit of inviscid fluid and null magnetic diffusivity.
+The forcing is chosen to have a constant injection rate of energy and no
+injection of kinetic helicity nor cross helicity. We find that the value of the
+critical magnetic Reynolds number ($\Rm$) saturates in the limit of small
+$\Pm$. Above the dynamo threshold we study the saturated regime versus $\Rm$
+and $\Pm$. In the case of equipartition, we find Kolmogorov spectra for both
+kinetic and magnetic energy except for wave numbers just below the resistive
+scale. Finally the ratio of both dissipation scales (viscous to resistive)
+evolves as $\Pm^{-3/4}$ for $\Pm < 1$",0701152v1
+2007-05-23,A ferrofluid based neural network: design of an analogue associative memory,"We analyse an associative memory based on a ferrofluid, consisting of a
+system of magnetic nano-particles suspended in a carrier fluid of variable
+viscosity subject to patterns of magnetic fields from an array of input and
+output magnetic pads. The association relies on forming patterns in the
+ferrofluid during a trainingdphase, in which the magnetic dipoles are free to
+move and rotate to minimize the total energy of the system. Once equilibrated
+in energy for a given input-output magnetic field pattern-pair the particles
+are fully or partially immobilized by cooling the carrier liquid. Thus produced
+particle distributions control the memory states, which are read out
+magnetically using spin-valve sensors incorporated in the output pads. The
+actual memory consists of spin distributions that is dynamic in nature,
+realized only in response to the input patterns that the system has been
+trained for. Two training algorithms for storing multiple patterns are
+investigated. Using Monte Carlo simulations of the physical system we
+demonstrate that the device is capable of storing and recalling two sets of
+images, each with an accuracy approaching 100%.",0705.3402v1
+2007-10-24,Criterion of multi-switching stability for magnetic nanoparticles,"We present a procedure to study the switching and the stability of an array
+of magnetic nanoparticles in the dynamical regime. The procedure leads to the
+criterion of multi-switching stability to be satisfied in order to have stable
+switching. The criterion is used to compare various magnetic-field-induced
+switching schemes, either present in the literature or suggested in the present
+work. In particular, we perform micromagnetic simulations to study the
+magnetization trajectories and the stability of the magnetization after
+switching for nanoparticles of elliptical shape. We evaluate the stability of
+the switching as a function of the thickness of the particles and the rise and
+fall times of the magnetic pulses, both at zero and room temperature.
+Furthermore, we investigate the role of the dipolar interaction and its
+influence on the various switching schemes. We find that the criterion of
+multi-switching stability can be satisfied at room temperature and in the
+presence of dipolar interactions for pulses shaped according to CMOS
+specifications, for switching rates in the GHz regime.",0710.4480v1
+2007-10-26,Transport and magnetic properties in YBaCo2O5.45: Focus on the high-temperature transition,"The electronic transport properties and the magnetic susceptibility were
+measured in detail in $YBaCo_2O_{5.45}$. Close to the so-called metal-insulator
+transition, strong effects of resistance relaxation, a clear thermal hysteresis
+and a sudden increase of the resistance noise are observed. This is likely due
+to the first order character of the transition and to the underlying phases
+coexistence. Despite these out of equilibrium features, a positive and linear
+magneto-resistance is also observed, possibly linked to the heterogeneity of
+the state. From a magnetic point of view, the paramagnetic to ordered magnetic
+state transition is observed using non linear susceptibilty. This transition
+shows the characteristics of a continuous transition, and time dependent
+effects can be linked with the dynamics of magnetic domains in presence of
+disorder. Thus, when focusing on the order of the transitions, the electronic
+one and the magnetic one can not be directly associated.",0710.5008v1
+2007-10-30,The Ekman-Hartmann layer in MHD Taylor-Couette flow,"We study magnetic effects induced by rigidly rotating plates enclosing a
+cylindrical MHD Taylor-Couette flow at the finite aspect ratio $H/D=10$. The
+fluid confined between the cylinders is assumed to be liquid metal
+characterized by small magnetic Prandtl number, the cylinders are perfectly
+conducting, an axial magnetic field is imposed $\Ha \approx 10$, the rotation
+rates correspond to $\Rey$ of order $10^2-10^3$. We show that the end-plates
+introduce, besides the well known Ekman circulation, similar magnetic effects
+which arise for infinite, rotating plates, horizontally unbounded by any walls.
+In particular there exists the Hartmann current which penetrates the fluid,
+turns into the radial direction and together with the applied magnetic field
+gives rise to a force. Consequently the flow can be compared with a Taylor-Dean
+flow driven by an azimuthal pressure gradient. We analyze stability of such
+flows and show that the currents induced by the plates can give rise to
+instability for the considered parameters. When designing an MHD Taylor-Couette
+experiment, a special care must be taken concerning the vertical magnetic
+boundaries so they do not significantly alter the rotational profile.",0710.5600v1
+2007-11-12,Enhancing Domain Wall Speed in Nanowires with Transverse Magnetic Fields,"Dynamic micromagnetic simulation studies have been completed to observe the
+motion of a domain wall in a magnetic nanowire in an effort to increase the
+field-driven domain wall speed. Previous studies have shown that the wire
+dimensions place a cap on the maximum speed attainable by a domain wall when
+driven by a magnetic field placed along the direction of the nanowire. Here we
+present data showing a significant increase in the maximum speed of a domain
+wall due to the addition of a magnetic field placed perpendicular to the
+longitudinal driving field. The results are expressed in terms of the relative
+alignment of the transverse field direction with respect to the direction of
+the magnetic moments within the domain wall. In particular, when the transverse
+field is parallel to the magnetic moments within the domain wall, the velocity
+of the wall varies linearly with the strength of the transverse field
+increasing by up to 20%. Further examination of the domain wall structure shows
+that the length of the domain wall also depends linearly on the strength of the
+transverse field. We present a simple model to correlate the effects.",0711.1864v1
+2008-01-25,Effect of External Magnetic Field on Critical Current for the Onset of Virtual Cathode Oscillations in Relativistic Electron Beams,"In this Letter we research the space charge limiting current value at which
+the oscillating virtual cathode is formed in the relativistic electron beam as
+a function of the external magnetic field guiding the beam electrons. It is
+shown that the space charge limiting (critical) current decreases with growth
+of the external magnetic field, and that there is an optimal induction value of
+the magnetic field at which the critical current for the onset of virtual
+cathode oscillations in the electron beam is minimum. For the strong external
+magnetic field the space charge limiting current corresponds to the analytical
+relation derived under the assumption that the motion of the electron beam is
+one-dimensional [High Power Microwave Sources. Artech House Microwave Library,
+1987. Chapter~13]. Such behavior is explained by the characteristic features of
+the dynamics of electron space charge in the longitudinal and radial directions
+in the drift space at the different external magnetic fields.",0801.3960v1
+2008-12-08,Spontaneous magnetization in QCD and non-Fermi-liquid effects,"Magnetic properties of quark matter at finite temperature are discussed by
+evaluating the magnetic susceptibility. Combining the microscopic calculation
+of the self-energy for quarks as well as the screening effects for gluons with
+Fermi-liquid theory in a consistent way, we study the temperature dependence of
+the magnetic susceptibility. The longitudinal gluons have the static screening
+given by the Debye mass, and have a standard temperature dependence of
+$O(T^2)$. An anomalous $T^2\ln T$ term arises in the magnetic susceptibility as
+a novel non-Fermi-liquid effect due to the anomalous self-energy for quarks
+given by the dynamic screening for transverse gluons. We then extract the
+critical(Curie) temperature and present the magnetic phase diagram on the
+density-temperature plane.",0812.1347v2
+2009-01-14,Dynamically dominant magnetic fields in the diffuse interstellar medium,"Observations show that magnetic fields in the interstellar medium (ISM) often
+do not respond to increases in gas density as would be naively expected for a
+frozen-in field. This may suggest that the magnetic field in the diffuse gas
+becomes detached from dense clouds as they form. We have investigated this
+possibility using theoretical estimates, a simple magneto-hydrodynamic model of
+a flow without mass conservation and numerical simulations of a thermally
+unstable flow. Our results show that significant magnetic flux can be shed from
+dense clouds as they form in the diffuse ISM, leaving behind a magnetically
+dominated diffuse gas.",0901.1975v1
+2009-02-08,Magnetic and magnetoelectric studies in pure and cation doped BiFeO3,"We report magnetic and magnetoelectric studies on BiFeO3 and divalent cation
+(A) suvtitute Bi0.7A0.3FeO3 (A = Sr,Ba, and Sr0.5Ba0.5). It is shown that the
+rapid increase of magnetization at the Neel temperature (TN = 642 K) is
+suppressed in the co-doped compound A = Sr0.5Ba0.5. All the divalent subtituted
+compounds show enhanced magnetization and hysteresis loop. Both longitudinal
+and transverse magnetoelectric coefficients were measured using the dynamical
+lock-in technique. The co-doped compound shows the highest magnetoelectric
+coefficient at room temperature although it is not the compound with the
+highest saturation magnetization. It is found that as the size of the A-site
+cation increses, the transverse magnetoelectric coeffient increases and exceeds
+the longitudinal magnetoelectric coefficient. It is suggested that changes in
+magnetic domain structure and magnetostriction are possible reasons for the
+observed changes in the magnetoelectric coefficients.",0902.1283v1
+2009-02-19,Magnetic-field-enhanced incommensurate magnetic order in the underdoped high-temperature superconductor YBa(2)Cu(3)O(6.45),"We present a neutron-scattering study of the static and dynamic spin
+correlations in the underdoped high-temperature superconductor
+YBa(2)Cu(3)O(6.45) in magnetic fields up to 15 T. The field strongly enhances
+static incommensurate magnetic order at low temperatures and induces a
+spectral-weight shift in the magnetic-excitation spectrum. A reconstruction of
+the Fermi surface driven by the field-enhanced magnetic superstructure may thus
+be responsible for the unusual Fermi surface topology revealed by recent
+quantum-oscillation experiments.",0902.3335v2
+2009-02-27,The Magnetic Field of Solar Spicules,"Determining the magnetic field of solar spicules is vital for developing
+adequate models of these plasma jets, which are thought to play a key role in
+the thermal, dynamic, and magnetic structure of the chromosphere. Here we
+report on magnetic spicule properties in a very quiet region of the off-limb
+solar atmosphere, as inferred from new spectropolarimetric observations in the
+HeI 10830 A triplet. We have used a novel inversion code for Stokes profiles
+caused by the joint action of atomic level polarization and the Hanle and
+Zeeman effects (HAZEL) to interpret the observations. Magnetic fields as strong
+as 40G were unambiguously detected in a very localized area of the slit, which
+may represent a possible lower value of the field strength of organized network
+spicules.",0903.0002v1
+2009-05-22,Memory and aging effects in antiferromagnetic nanoparticles,"We investigate slow dynamics of collection of a few antiferromagnetic NiO
+nanoparticles. The zero-field cooled magnetization exhibits size dependent
+fluctuations. We find memory effects in field cooled magnetization, as well as
+aging effects in thermoremenant magnetization of antiferromagnetic
+nanoparticles. The antiferromagnetic nanoparticles show a stronger memory
+effect than the corresponding effect in the ferromagnetic particles, when the
+distribution of particles include very small sizes. The situation reverses for
+bigger sizes. The relaxation of the magnetization after a sudden cooling,
+heating and removal of fields reiterate the memory effects. We also see a weak
+signature of size-dependent magnetization fluctuations in aging effect of
+antiferromagnetic nanoparticles. We find a two-step relaxation of
+thermoremenant magnetization in antiferromagnetic case, which differs
+qualitatively from relaxation of ferromagnetic nanoparticles.",0905.3617v2
+2009-06-12,Magnetic dynamics with spin transfer torques near the Curie temperature,"We use atomistic stochastic Landau-Lifshitz-Slonczewski simulations to study
+the interaction between large thermal fluctuations and spin transfer torques in
+the magnetic layers of spin valves. At temperatures near the Curie temperature
+$T_{\rm C}$, spin currents measurably change the size of the magnetization
+(i.e. there is a {\it longitudinal} spin transfer effect). The change in
+magnetization of the free magnetic layer in a spin valve modifies the
+temperature dependence of the applied field-applied current phase diagram for
+temperatures near $T_{\rm C}$. These atomistic simulations can be accurately
+described by a Landau-Lifshitz-Bloch + Slonczewski equation, which is a
+thermally averaged mean field theory. Both the simulation and the mean field
+theory show that a longitudinal spin transfer effect can be a substantial
+fraction of the magnetization close to $T_{\rm C}$.",0906.2423v1
+2009-08-20,MnSi$_{1.7}$ nanoparticles embedded in Si: Superparamagnetism with a collective behavior,"The doping of Mn in Si is attracting research attentions due to the
+possibility to fabricate Si-based diluted magnetic semiconductors. However, the
+low solubility of Mn in Si favors the precipitation of Mn ions even at
+non-equilibrium growth conditions. MnSi$_{1.7}$ nanoparticles are the common
+precipitates, which show exotic magnetic properties in comparison with the
+MnSi$_{1.7}$ bulk phase. In this paper we present the static and dynamic
+magnetic properties of MnSi$_{1.7}$ nanoparticles. Using the Preisach model, we
+derive the magnetic parameters, such as the magnetization of individual
+particles, the distribution of coercive fields and the inter-particle
+interaction field. Time-dependent magnetization measurements reveal a
+spin-glass behavior of the system.",0908.2906v3
+2009-10-16,Heavy fermion material: Ce versus Yb case,"Heavy fermion compounds are complex systems but excellent materials to study
+quantum criticality with the switch of different ground states. Here a special
+attention is given on the interplay between magnetic and valence instabilities
+which can be crossed or approached by tuning the system by pressure or magnetic
+field. By contrast to conventional rare earth magnetism or classical s wave
+superconductivity, strong couplings may occur with drastic changes in spin or
+charge dynamics. Measurements on Ce materials give already a sound basis with
+clear key factors; they have pointed out that close to a magnetic or a valence
+criticality unexpected phenomena such as unconventional superconductivity, non
+Fermi liquid behaviour and the possibility of re-entrance phenomena under
+magnetic field. Recent progresses in the growth of Yb heavy fermion compounds
+give the perspectives of clear interplays between valence and magnetic
+fluctuations and also the possibility to enter in new situations such as
+valence transitions inside a sole doublet crystal field ground state.",0910.3110v2
+2010-01-13,On the 3D Structure of the Magnetic Field in Regions of Emerging Flux,"We explore the photospheric and chromospheric magnetic field in an emerging
+flux region. An image of the equivalent width of the He I 10830 A red blended
+component shows the presence of filamentary structures that might be
+interpreted as magnetic loops. We point out that the magnetic field strength in
+the chromosphere resembles a smoothed version of that found in the photosphere
+and that it is not correlated at all with the above-mentioned equivalent width
+map. Lacking other diagnostics, this suggests that one cannot discard the
+possibility that the chromospheric field we infer from the observations is
+tracing the lower chromosphere of the active region instead of tracing the
+magnetic field along loops. If the He I line is formed within magnetic loops,
+we point out a potential problem that appears when interpreting observations
+using only one component along the line-of-sight.",1001.2108v1
+2010-03-01,Switchable Hardening of a Ferromagnet at Fixed Temperature,"The intended use of a magnetic material, from information storage to power
+conversion, depends crucially on its domain structure, traditionally crafted
+during materials synthesis. By contrast, we show that an external magnetic
+field applied transverse to the preferred magnetization of a model disordered
+uniaxial ferromagnet is an isothermal regulator of domain pinning. At elevated
+temperatures, near the transition into the paramagnet, modest transverse fields
+increase the pinning, stabilize the domain structure, and harden the magnet,
+until a point where the field induces quantum tunneling of the domain walls and
+softens the magnet. At low temperatures, tunneling completely dominates the
+domain dynamics and provides an interpretation of the quantum phase transition
+in highly disordered magnets as a localization/delocalization transition for
+domain walls. While the energy scales of the rare earth ferromagnet studied
+here restrict the effects to cryogenic temperatures, the principles discovered
+are general and should be applicable to existing classes of highly anisotropic
+ferromagnets with ordering at room temperature or above.",1003.0369v1
+2010-03-04,Local strong parity violation and new possibilities in experimental study of non-perturbative QCD,"Quark interaction with topologically non-trivial gluonic fields, instantons
+and sphalerons, violates \P and \CP symmetry. In the strong magnetic field of a
+non-central nuclear collision such interactions lead to the charge separation
+along the magnetic field, the so called chiral magnetic effect, which manifests
+local parity violations. An experimental observation of the chiral magnetic
+effect would be a direct proof for the existence of such physics. Recent STAR
+results on charge and the reaction plane dependent correlations are consistent
+with theoretical expectations for the chiral magnetic effect. IIn this paper I
+discuss different approaches to experimental study of the local parity
+violation, and propose future measurements which can clarify the picture. In
+particular I propose to use central body-body U+U collisions to disentangle
+correlations due to chiral magnetic effect from possible background
+correlations due to elliptic flow. Further more quantitative studies can be
+performed with collision of isobaric beams.",1003.1127v1
+2010-03-05,Magnetoresistance in nanostructures: the role of nonuniform current,"We developed a method to calculate the magnetoresistance of magnetic
+nanostructures. We discretize a magnetic disk in small cells and numerically
+solve the Landau-Lifshitz-Gilbert (LLG) equation in order to obtain its
+magnetization profile. We consider a anisotropic magnetoresistance (AMR) that
+depends on the local magnetization as the main source of the magnetoresistance.
+We then use it as an input to calculate the resistance and current distribution
+numerically, using a relaxation method. We show how magnetoresistance
+measurements can be useful to obtain information on the magnetic structure.
+Additionally, we obtain non-homogeneous current distributions for different
+magnetic configurations in static and dynamical regimes.",1003.1323v2
+2010-03-17,Chiral Magnetic Spiral,"We argue that the presence of a very strong magnetic field in the chirally
+broken phase induces inhomogeneous expectation values, of a spiral nature along
+the magnetic field axis, for the currents of charge and chirality, when there
+is finite baryon density or an imbalance between left and right chiralities.
+This ""chiral magnetic spiral"" is a gapless excitation transporting the currents
+of (i) charge (at finite chirality), and (ii) chirality (at finite baryon
+density) along the direction of the magnetic field. In both cases it also
+induces in the transverse directions oscillating currents of charge and
+chirality. In heavy ion collisions, the chiral magnetic spiral possibly
+provides contributions both to the out-of-plane and the in-plane dynamical
+charge fluctuations recently observed at RHIC.",1003.3464v1
+2010-04-21,"Effect of pressure on the magnetic, transport, and thermal-transport properties of the electron-doped manganite CaMn$_{1-x}$Sb$_{x}$O$_{3}$","We have demonstrated the effect of hydrostatic pressure on magnetic and
+transport properties, and thermal transport properties in electron-doped
+manganites CaMn$_{1-x}$Sb$_{x}$O$_{3}$. The substitution of Sb$^{5+}$ ion for
+Mn $^{4+}$site of the parent matrix causes one-electron doping with the
+chemical formula CaMn$^{4+}_{1-2x}$Mn$^{3+}_{x}$Sb$^{5+}_{x}$O$_{3}$
+accompanied by a monotonous increase in unit cell volume as a function of $x$.
+Upon increasing the doping level of Sb, the magnitudes of both electrical
+resistivity and negative Seebeck coefficient are suppressed at high
+temperatures, indicating the electron doping. Anomalous diamagnetic behaviors
+at $x=0.05$ and 0.08 are clearly observed in field cooled dc magnetization. The
+effect of hydrostatic pressure on dc magnetization is in contrast to the
+chemical pressure effect due to Sb doping. The dynamical effect of ac magnetic
+susceptibility measurement points to the formation of the magnetically
+frustrated clusters such as FM clusters embedded in canted AFM matrix.",1004.3669v3
+2010-04-20,Wide-range wavevector selectivity of magnon gases in Brillouin light scattering spectroscopy,"Brillouin light scattering spectroscopy is a powerful technique for the study
+of fast magnetization dynamics with both frequency- and wavevector resolution.
+Here, we report on a distinct improvement of this spectroscopic technique
+towards two-dimensional wide-range wavevector selectivity in a backward
+scattering geometry. Spin-wave wavevectors oriented perpendicular to the bias
+magnetic field are investigated by tilting the sample within the magnet gap.
+Wavevectors which are oriented parallel to the applied magnetic field are
+analyzed by turning the entire setup, including the magnet system. The setup
+features a wide selectivity of wavevectors up to 2.04\cdot 10E5 rad/cm for both
+orientations, and allows selecting and measuring wavevectors of dipole- and
+exchange-dominated spin waves of any orientation to the magnetization
+simultaneously.",1005.5084v1
+2010-07-06,Effect of induced magnetic field on peristaltic flow of a micropolar fluid in an asymmetric channel,"Of concern in this paper is an investigation of peristaltic transport of a
+physiological fluid in an asymmetric channel under long wave length and
+low-Reynolds number assumptions. The flow is assumed to be incompressible,
+viscous, electrically conducting micropolar fluid and the effect of induced
+magnetic field is taken into account. Exact analytical solutions obtained for
+the axial velocity, microrotation component, stream line pattern, magnetic
+force function, axial-induced magnetic field as well as the current density
+distribution across the channel. The flow phenomena for the pumping
+characteristics, trapping and reflux are also investigated. The results
+presented reveal that the velocity decreases with the increase of magnetic
+field as well as the coupling parameter. Moreover, the trapping fluid can be
+eliminated by the application of an external magnetic field. Thus, the study
+bears the promise of important applications in physiological systems.",1007.0923v1
+2010-08-14,Scaling the energy conversion rate from magnetic field reconnection to different bodies,"Magnetic field reconnection is often invoked to explain electromagnetic
+energy conversion in planetary magnetospheres, stellar coronae, and other
+astrophysical objects. Because of the huge dynamic range of magnetic fields in
+these bodies, it is important to understand energy conversion as a function of
+magnetic field strength and related parameters. It is conjectured theoretically
+and shown experimentally that the energy conversion rate per unit area in
+reconnection scales as the cube of an appropriately weighted magnetic field
+strength divided by the square root of an appropriately weighted density. With
+this functional dependence, the energy release in flares on the Sun, the large
+and rapid variation of the magnetic flux in the tail of Mercury, and the
+apparent absence of reconnection on Jupiter and Saturn, may be understood.
+Electric fields at the perihelion of the Solar Probe Plus mission may be tens
+of volts/meter.",1008.2454v3
+2010-09-29,Magnetic spectrum of the two-dimensional antiferromagnet La2CoO4 studied by inelastic neutron scattering,"We report measurements of the magnetic excitation spectrum of the layered
+antiferromagnet La2CoO4 by time-of-flight neutron inelastic scattering. In the
+energy range probed in our experiments (0-250 meV) the magnetic spectrum
+consists of spin-wave modes with strong in-plane dispersion extending up to 60
+meV, and a nearly dispersionless peak at 190 meV. The spin-wave modes exhibit a
+small (~1 meV) dispersion along the magnetic zone boundary. We show that the
+magnetic spectrum can be described very well by a model of a Heisenberg
+antiferromagnet that includes the full spin and orbital degrees of freedom of
+Co2+ in an axially-distorted crystal field. The collective magnetic dynamics
+are found to be controlled by dominant nearest-neighbour exchange interactions,
+strong XY-like single-ion anisotropy and a substantial unquenched orbital
+angular momentum.",1009.5913v2
+2010-09-29,Sensitivity of a Babcock-Leighton Flux-Transport Dynamo to Magnetic Diffusivity Profiles,"We study the influence of various magnetic diffusivity profiles on the
+evolution of the poloidal and toroidal magnetic fields in a kinematic flux
+transport dynamo model for the Sun. The diffusivity is a poorly understood
+ingredient in solar dynamo models. We mathematically construct various
+theoretical profiles of the depth-dependent diffusivity, based on constraints
+from mixing length theory and turbulence, and on comparisons of poloidal field
+evolution on the Sun with that from the flux-transport dynamo model.
+  We then study the effect of each diffusivity profile in the cyclic evolution
+of the magnetic fields in the Sun, by solving the mean-field dynamo equations.
+We investigate effects on the solar cycle periods, the maximum tachocline field
+strengths, and the evolution of the toroidal and poloidal field structures
+inside the convection zone, due to different diffusivity profiles.
+  We conduct three experiments: (I) comparing very different magnetic
+diffusivity profiles; (II) comparing different locations of diffusivity
+gradient near the tachocline for the optimal profile; and (III) comparing
+different slopes of diffusivity gradient for an optimal profile.
+  Based on these simulations, we discuss which aspects of depth-dependent
+diffusivity profiles may be most relevant for magnetic flux evolution in the
+Sun, and how certain observations could help improve knowledge of this dynamo
+ingredient.",1009.5965v1
+2010-10-11,"Magnetic fields, winds and X-rays of the massive stars in the Orion Nebula Cluster","In some massive stars, magnetic fields are thought to confine the outflowing
+radiatively-driven wind. Although theoretical models and MHD simulations are
+able to illustrate the dynamics of such a magnetized wind, the impact of this
+wind-field interaction on the observable properties of a magnetic star - X-ray
+emission, photometric and spectral variability - is still unclear. The aim of
+this study is to examine the relationship between magnetism, stellar winds and
+X-ray emission of OB stars, by providing empirical observations and confronting
+theory. In conjunction with the COUP survey of the Orion Nebula Cluster, we
+carried out spectropolarimatric ESPaDOnS observations to determine the magnetic
+properties of massive OB stars of this cluster.",1010.2244v1
+2010-10-29,Magnetic helicity transport in the advective gauge family,"Magnetic helicity fluxes are investigated in a family of gauges in which the
+contribution from ideal magnetohydrodynamics takes the form of a purely
+advective flux. Numerical simulations of magnetohydrodynamic turbulence in this
+advective gauge family exhibit instabilities triggered by the build-up of
+unphysical irrotational contributions to the magnetic vector potential. As a
+remedy, the vector potential is evolved in a numerically well behaved gauge,
+from which the advective vector potential is obtained by a gauge
+transformation. In the kinematic regime, the magnetic helicity density evolves
+similarly to a passive scalar when resistivity is small and turbulent mixing is
+mild, i.e. when the fluid Reynolds number is not too large. In the dynamical
+regime, resistive contributions to the magnetic helicity flux in the advective
+gauge are found to be significant owing to the development of small length
+scales in the irrotational part of the magnetic vector potential.",1010.6177v2
+2010-10-31,Magnetic dynamo action at low magnetic Prandtl numbers,"Amplification of magnetic field due to kinematic turbulent dynamo action is
+studied in the regime of small magnetic Prandtl numbers. Such a regime is
+relevant for planets and stars interiors, as well as for liquid metal
+laboratory experiments. A comprehensive analysis based on the
+Kazantsev-Kraichnan model is reported, which establishes the dynamo threshold
+and the dynamo growth rates for varying kinetic helicity of turbulent
+fluctuations. It is proposed that in contrast with the case of large magnetic
+Prandtl numbers, the kinematic dynamo action at small magnetic Prandtl numbers
+is significantly affected by kinetic helicity, and it can be made quite
+efficient with an appropriate choice of the helicity spectrum.",1011.0202v1
+2010-12-07,"The interplay between magnetism, structure, and strong electron-phonon coupling in binary FeAs under pressure","Unlike the ferropnictide superconductors, which crystallize in a tetragonal
+crystal structure, binary FeAs forms in an orthorhombic crystal structure,
+where the local atomic environment resembles a highly distorted variant of the
+FeAs4 tetrahdedral building block of the ferropnictide superconductors.
+However, like the parent compounds of the ferropnictide superconductors, FeAs
+undergoes magnetic ordering at low temperatures, with no evidence favoring a
+superconducting ground state at ambient pressure. We employ pressure-dependent
+electrical transport and x-ray diffraction measurements using diamond anvil
+cells to characterize the magnetic state and the structure as a function of
+pressure. While the MnP-type structure of FeAs persists up to 25 GPa,
+compressing continuously with no evidence of structural transformations under
+pressure, features in the magnetotransport measurements associated with
+magnetism are not observed for pressures in excess of 11 GPa. Where observable,
+the features associated with magnetic order at ambient pressure show remarkably
+little pressure dependence, and transport measurements suggest that a dynamical
+structural instability coupled to the Fermi surface via a strong
+electron-phonon interaction may play an important role in enabling magnetism in
+FeAs.",1012.1391v1
+2010-12-17,Structural and magnetic properties of Co2MnSi thin films,"Co2MnSi (CMS) films of different thicknesses (20, 50 and 100 nm) were grown
+by radio frequency (RF) sputtering on a-plane sapphire substrates. Our X-rays
+diffraction study shows that, in all the samples, the cubic <110> CSM axis is
+normal to the substrate and that there exist well defined preferential in-plane
+orientations. Static and dynamic magnetic properties were investigated using
+vibrating sample magnetometry (VSM) and micro-strip line ferromagnetic
+resonance (MS-FMR), respectively. From the resonance measurements versus the
+direction and the amplitude of an applied magnetic field we derive most of the
+magnetic parameters: magnetization, gyromagnetic factor, exchange stiffness
+coefficient and magnetic anisotropy terms. The in-plane anisotropy can be
+described as resulting from the superposition of two terms showing a two-fold
+and a four-fold symmetry without necessarily identical principal axes. The
+observed behavior of the hysteresis loops is in agreement with this complex
+form of the in-plane anisotropy",1012.3837v2
+2011-02-13,Magnetization and Lyapunov exponents on a kagome chain with multi-site exchange interaction,"The Ising approximation of the Heisenberg model in a strong magnetic field,
+with two, three and six spin exchange interactions is studied on a kagome
+chain. The kagome chain can be considered as an approximation of the third
+layer of 3He absorbed on the surface of graphite (kagome lattice). By using
+dynamical approach we have found one and multi-dimensional mappings (recursion
+relations) for the partition function. The magnetization diagrams are plotted
+and they show that the kagome chain is separating into four sublattices with
+different magnetizations. Magnetization curves of two sublattices exhibit
+plateaus at zero and 2/3 of the saturation field. The maximal Lyapunov exponent
+for multi-dimensional mapping is considered and it is shown that near the
+magnetization plateaus the maximal Lyapunov exponent also exhibits plateaus.",1102.2589v1
+2011-03-10,Chiral Properties of Strong Interactions in a Magnetic Background,"We investigate the chiral properties of QCD in presence of a magnetic
+background field and in the low temperature regime, by lattice numerical
+simulations of N_f = 2 QCD. We adopt a standard staggered discretization, with
+a pion mass around 200 MeV, and explore a range of magnetic fields (180 MeV)^2
+\leq|e|B \leq (700 MeV)^2, in which we study magnetic catalysis, i.e. the
+increase of chiral symmetry breaking induced by the background field. We
+determine the dependence of the chiral condensate on the external field,
+compare our results with existing model predictions and show that a substantial
+contribution to magnetic catalysis comes from the modified distribution of
+non-Abelian gauge fields, induced by the magnetic field via dynamical quark
+loop effects.",1103.2080v2
+2011-03-11,Interaction of a magnetic dipole with a slowly moving electrically conducting plate,"We report an analytical investigation of the force and torque acting upon a
+magnetic dipole placed in the vicinity of a moving electrically conducting
+nonmagnetic plate. This problem is relevant to contactless electromagnetic flow
+measurement in metallurgy and extends previous theoretical works (Thess et al.
+Phys. Rev. Lett. 96(2006), 164501; New J. Phys. 9(2007), 299) to the case where
+the orientation of the magnetic dipole relative to the plate is arbitrary. It
+is demonstrated that for the case of low magnetic Reynolds number the
+three-dimensional distributions of the induced electric potential, of the eddy
+currents and of the induced magnetic field can be rigorously derived. It is
+also shown that all components of the force and torque can be computed without
+any further approximation. The results of the present work serve as a benchmark
+problem that can be used to verify numerical simulations of more complex
+magnetic field distributions.",1103.2245v1
+2011-04-04,Evolution of magnetic fields through cosmological perturbation theory,"The origin of galactic and extra-galactic magnetic fields is an unsolved
+problem in modern cosmology. A possible scenario comes from the idea of these
+fields emerged from a small field, a seed, which was produced in the early
+universe (phase transitions, inflation, ...) and it evolves in time.
+Cosmological perturbation theory offers a natural way to study the evolution of
+primordial magnetic fields. The dynamics for this field in the cosmological
+context is described by a cosmic dynamo like equation, through the dynamo term.
+In this paper we get the perturbed Maxwell's equations and compute the energy
+momentum tensor to second order in perturbation theory in terms of gauge
+invariant quantities. Two possible scenarios are discussed, first we consider a
+FLRW background without magnetic field and we study the perturbation theory
+introducing the magnetic field as a perturbation. The second scenario, we
+consider a magnetized FLRW and build up the perturbation theory from this
+background. We compare the cosmological dynamo like equation in both scenarios.",1104.0701v4
+2011-04-07,Magnetization hysteresis and time decay measurements in FeSe$_{0.50}$Te$_{0.50}$ : Evidence for fluctuation in mean free path induced pinning,"We present results of magnetic measurements relating to vortex phase diagram
+in a single crystal of FeSe$_{0.5}$Te$_{0.5}$ which displays second
+magnetization peak anomaly for $H \parallel c$. The possible role of the
+crystalline anisotropy on vortex pinning is explored via magnetic torque
+magnetometry. We present evidence in favor of pinning related to spatial
+variations of the charge carrier mean free path leading to small bundle vortex
+pinning by randomly distributed (weak) pinning centers for both $H \parallel c$
+and $H \perp c$. This is further corroborated using magnetization data for $H
+\parallel c$ in a single crystal of FeSe$_{0.35}$Te$_{0.65}$. Dynamical
+response across second magnetization peak (SMP) anomaly in
+FeSe$_{0.5}$Te$_{0.5}$ has been compared with that across the well researched
+phenomenon of peak effect (PE) in a single crystal of CeRu$_2$.",1104.1332v4
+2011-05-05,Wave packet dynamics and valley filter in strained graphene,"The time evolution of a wavepacket in strained graphene is studied within the
+tight-binding model and continuum model. The effect of an external magnetic
+field, as well as a strain-induced pseudo-magnetic field, on the wave packet
+trajectories and zitterbewegung are analyzed. Combining the effects of strain
+with those of an external magnetic field produces an effective magnetic field
+which is large in one of the Dirac cones, but can be practically zero in the
+other. We construct an efficient valley filter, where for a propagating
+incoming wave packet consisting of momenta around the K and K' Dirac points,
+the outgoing wave packet exhibits momenta in only one of these Dirac points,
+while the components of the packet that belong to the other Dirac point are
+reflected due to the Lorentz force. We also found that the zitterbewegung is
+permanent in time in the presence of either external or strain-induced magnetic
+fields, but when both the external and strain-induced magnetic fields are
+present, the zitterbewegung is transient in one of the Dirac cones, whereas in
+the other cone the wave packet exhibits permanent spatial oscillations.",1105.1125v1
+2011-05-06,Magnetism in superconducting EuFe$_2$As$_{1.4}$P$_{0.6}$ single crystals studied by local probes,"We have studied the magnetism in superconducting single crystals of EuFe2
+As1.4 P0.6 by using the local probe techniques of zero-field muon spin
+rotation/relaxation and 151 Eu/57 Fe M\""ossbauer spec- troscopy. All of these
+measurements reveal magnetic hyperfine fields below the magnetic ordering
+temperature TM = 18 K of the Eu2+ moments. The analysis of the data shows that
+there is a coexistence of ferromagnetism, resulting from Eu2+ moments ordered
+along the crystallographic c-axis, and superconductivity below TSC \approx 15
+K. We find indications for a change in the dynamics of the small Fe magnetic
+moments (\sim 0.07 \mu B) at the onset of superconductivity: below TSC the Fe
+magnetic moments seem to be ""frozen"" within the ab-plane.",1105.1201v1
+2011-05-31,Flow-turbulence interaction in magnetic reconnection,"Roles of turbulence in the context of magnetic reconnection are investigated
+with special emphasis on the mutual interaction between flow (large-scale
+inhomogeneous structure) and turbulence. In order to evaluate the effective
+transport due to turbulence, in addition to the {\it intensity} information of
+turbulence represented by the turbulent energy, the {\it structure} information
+represented by pseudoscalar statistical quantities (helicities) is important.
+On the basis of the evolution equation, mechanisms that provide turbulence with
+cross helicity are presented. Magnetic-flux freezing in highly turbulent media
+is considered with special emphasis on the spatial distribution of the
+turbulent cross helicity. The cross-helicity effects in the context of magnetic
+reconnection are also investigated. It is shown that the large-scale flow and
+magnetic-field configurations favorable for the cross-helicity generation is
+compatible with the fast reconnection. In this sense, turbulence and
+large-scale structures promote magnetic reconnection mediated by the turbulent
+cross helicity.",1105.6343v2
+2011-06-14,A dynamo driven by zonal jets at the upper surface: Applications to giant planets,"We present a dynamo mechanism arising from the presence of barotropically
+unstable zonal jet currents in a rotating spherical shell. The shear
+instability of the zonal flow develops in the form of a global Rossby mode,
+whose azimuthal wavenumber depends on the width of the zonal jets. We obtain
+self-sustained magnetic fields at magnetic Reynolds numbers greater than 1000.
+We show that the propagation of the Rossby waves is crucial for dynamo action.
+The amplitude of the axisymmetric poloidal magnetic field depends on the
+wavenumber of the Rossby mode, and hence on the width of the zonal jets. We
+discuss the plausibility of this dynamo mechanism for generating the magnetic
+field of the giant planets. Our results suggest a possible link between the
+topology of the magnetic field and the profile of the zonal winds observed at
+the surface of the giant planets. For narrow Jupiter-like jets, the poloidal
+magnetic field is dominated by an axial dipole whereas for wide Neptune-like
+jets, the axisymmetric poloidal field is weak.",1106.2701v3
+2011-06-16,Synchronous Spatial Oscillation of Electron- and Mn-Spin Polarizations in Dilute-Magnetic-Semiconductor Quantum Wells under Spin-Orbit Effective Magnetic Fields,"In semiconductors, spin-orbit effective magnetic fields, i.e., the Rashba and
+Dresselhaus fields, are used to control electron-spin polarization. This
+operation, however, destroys the electron-spin coherence, and the spin
+polarization is limited to the vicinity of a ferromagnetic source electrode. In
+this paper, we propose the use of dilute magnetic semiconductors to improve the
+coherence of spatially oscillating electron-spin polarization. In dilute
+magnetic semiconductors, the electron-spin polarization near the source
+electrode dynamically induces the local spin polarization of magnetic
+impurities through s-d spin-flip scattering. This impurity-spin polarization
+improves, in turn, the coherence of the electron-spin polarization, and this
+improved electron-spin polarization induces impurity-spin polarization farther
+in the adjacent region. Because of this positive feedback, the coherent and
+synchronized spatial oscillations of electron- and impurity-spin polarizations
+grow cooperatively. A numerical calculation for a CdMnTe quantum well
+demonstrates the validity of this mechanism.",1106.3124v2
+2011-07-04,A Generalized Flux Function for Three-dimensional Magnetic Reconnection,"The definition and measurement of magnetic reconnection in three-dimensional
+magnetic fields with multiple reconnection sites is a challenging problem,
+particularly in fields lacking null points. We propose a generalization of the
+familiar two-dimensional concept of a magnetic flux function to the case of a
+three-dimensional field connecting two planar boundaries. Using hyperbolic
+fixed points of the field line mapping, and their global stable and unstable
+manifolds, we define a unique flux partition of the magnetic field. This
+partition is more complicated than the corresponding (well-known) construction
+in a two-dimensional field, owing to the possibility of heteroclinic points and
+chaotic magnetic regions. Nevertheless, we show how the partition reconnection
+rate is readily measured with the generalized flux function. We relate our
+partition reconnection rate to the common definition of three-dimensional
+reconnection in terms of integrated parallel electric field. An analytical
+example demonstrates the theory, and shows how the flux partition responds to
+an isolated reconnection event.",1107.0594v1
+2011-11-08,Magnetic helicity fluxes and their effect on stellar dynamos,"Magnetic helicity fluxes in turbulently driven alpha^2 dynamos are studied to
+demonstrate their ability to alleviate catastrophic quenching. A
+one-dimensional mean-field formalism is used to achieve magnetic Reynolds
+numbers of the order of 10^5. We study both diffusive magnetic helicity fluxes
+through the mid-plane as well as those resulting from the recently proposed
+alternate dynamic quenching formalism. By adding shear we make a parameter scan
+for the critical values of the shear and forcing parameters for which dynamo
+action occurs. For this $\alpha\Omega$ dynamo we find that the preferred mode
+is antisymmetric about the mid-plane. This is also verified in 3-D direct
+numerical simulations.",1111.2023v2
+2011-11-16,On Simplified Numerical Turbulence Models in Test-particle Simulations,"Using the conventional approach of superposing plane waves, it is not
+possible to create a strictly isotropic turbulent magnetic field structure that
+obeys all physical constraints, which are (i) equal mean of all magnetic field
+components; (ii) isotropy of the wave vectors; and (iii) vanishing divergence
+of the magnetic field. Such magnetic fields are widely implemented in
+test-particle Monte-Carlo simulations, which are used to obtain (i) scattering
+mean free paths of charged particles; (ii) field line diffusion coefficients.
+It is shown that, while the turbulent magnetic field strength plays an
+important role for the results, such does not seem to be the case for a
+non-zero magnetic field divergence and/or the isotropy of the wave vectors.",1111.3780v1
+2012-01-13,Intermediate state switching dynamics in magnetic double layer nanopillars grown by molecular beam epitaxy,"We observe a stable intermediate resistance switching state in the current
+perpendicular to plane geometry for all Co/Cu/Co double layer nanopillar
+junctions grown by molecular beam epitaxy. This novel state has a resistance
+between the resistances of the parallel and antiparallel alignment of both
+Co-layer magnetizations. The state, which originates from an additional
+in-plane magnetic easy axis, can be reached by spin transfer torque switching
+or by an external magnetic field. In addition to spin torque-induced coherent
+small-angle spin wave modes we observe a broad microwave emission spectrum. The
+latter is attributed to incoherent magnetic excitations that lead to a
+switching between the intermediate state and the parallel or antiparallel
+alignment of both ferromagnetic layers. We conclude that the additional
+magnetic easy axis suppresses a stable trajectory of coherent large-angle
+precession, which is not observed in our samples.",1201.2752v1
+2012-03-22,Observation of An Evolving Magnetic Flux Rope Prior To and During A Solar Eruption,"Explosive energy release is a common phenomenon occurring in magnetized
+plasma systems ranging from laboratories, Earth's magnetosphere, the solar
+corona and astrophysical environments. Its physical explanation is usually
+attributed to magnetic reconnection in a thin current sheet. Here we report the
+important role of magnetic flux rope structure, a volumetric current channel,
+in producing explosive events. The flux rope is observed as a hot channel prior
+to and during a solar eruption from the Atmospheric Imaging Assembly (AIA)
+telescope on board the Solar Dynamic Observatory (SDO). It initially appears as
+a twisted and writhed sigmoidal structure with a temperature as high as 10 MK
+and then transforms toward a semi-circular shape during a slow rise phase,
+which is followed by fast acceleration and onset of a flare. The observations
+suggest that the instability of the magnetic flux rope trigger the eruption,
+thus making a major addition to the traditional magnetic-reconnection paradigm.",1203.4859v1
+2012-06-24,Low-Temperature Low-Field Phases of the Pyrochlore Quantum Magnet Tb$_2$Ti$_2$O$_7$,"By means of ac magnetic-susceptibility measurements, we find evidence for a
+new magnetic phase of Tb$_2$Ti$_2$O$_7$ below about 140 mK in zero magnetic
+field. In magnetic fields parallel to [111], this phase---exhibiting frequency-
+and amplitude-dependent susceptibility and an extremely slow spin
+dynamics---extends to about 70 mT, at which it gives way to another phase. The
+field dependence of the susceptibility of this second phase, which extends to
+about 0.6 T, indicates the presence of a weak magnetization plateau below 50
+mK, as has been predicted by a single-tetrahedron four-spin model, giving
+support to the underlying proposal that the disordered low-field ground state
+of Tb$_2$Ti$_2$O$_7$ is a quantum spin ice.",1206.5541v3
+2012-06-24,Chiral Effects and Cosmic Magnetic Fields,"In the presence of cosmic chiral asymmetry, chiral-vorticity and
+chiral-magnetic effects can play an important role in the generation and
+evolution of magnetic fields in the early universe. We include these chiral
+effects in the magnetic field equations and find solutions under simplifying
+assumptions. Our numerical and analytical results show the presence of an
+attractor solution in which chiral effects produce a strong, narrow, Gaussian
+peak in the magnetic spectrum and the magnetic field becomes maximally helical.
+The peak in the spectrum shifts to longer length scales and becomes sharper
+with evolution. We also find that the dynamics may become non-linear for
+certain parameters, pointing to the necessity of a more complete analysis.",1206.5549v1
+2012-08-07,Observation of Coherent Helimagnons and Gilbert damping in an Itinerant Magnet,"We study the magnetic excitations of itinerant helimagnets by applying
+time-resolved optical spectroscopy to Fe0.8Co0.2Si. Optically excited
+oscillations of the magnetization in the helical state are found to disperse to
+lower frequency as the applied magnetic field is increased; the fingerprint of
+collective modes unique to helimagnets, known as helimagnons. The use of
+time-resolved spectroscopy allows us to address the fundamental magnetic
+relaxation processes by directly measuring the Gilbert damping, revealing the
+versatility of spin dynamics in chiral magnets. (*These authors contributed
+equally to this work)",1208.1462v1
+2012-10-25,Strong Competition of Superconducting and Magnetic Order Parameters in Ba1-xNaxFe2As2,"We study the interplay of magnetic and superconducting order in single
+crystalline hole doped Ba1-xNaxFe2As2 using muon spin relaxation. We find
+microscopic coexistence of magnetic order and superconductivity. In a strongly
+underdoped specimen the two forms of order coexist without any measurable
+reduction of the ordered magnetic moment by superconductivity, while in a
+nearly optimally doped sample the ordered magnetic moment is strongly
+suppressed below the superconducting transition temperature. This coupling can
+be well described within the framework of an effective two-band model
+incorporating inter- and intra-band interactions. In optimally doped
+Ba1-xNaxFe2As2 we observe no traces of static or dynamic magnetism and the
+temperature dependence of the superfluid density is consistent with two s-wave
+gaps without nodes.",1210.6881v1
+2012-11-09,An Arecibo Survey for Zeeman Splitting in OH Megamaser Galaxies,"We present the results of a comprehensive survey using the Arecibo
+Observatory for Zeeman splitting of OH lines in OH megamasers (OHMs). A total
+of seventy-seven sources were observed with the Arecibo telescope. Of these,
+maser emission could not be detected for eight sources, and two sources were
+only ambiguously detected. Another twenty-seven sources were detected at low
+signal-to-noise ratios or with interference that prevented placing any useful
+limits on the presence of magnetic fields. In twenty-six sources, it was
+possible to place upper limits on the magnitude of magnetic fields, typically
+between 10-30 mG. For fourteen sources, the Stokes V spectra exhibit features
+consistent with Zeeman splitting. Eleven of these fourteen are new detections,
+and the remaining three are re-detections of Stokes V detections in Robishaw et
+al. (2008). Among confident new detections, we derive magnetic fields
+associated with maser regions with magnitudes ranging from 6.1-27.6 mG. The
+distribution of magnetic field strengths suggests the magnetic fields in OH
+masing clouds in OHMs are larger than those in Galactic OH masers. The results
+are consistent with magnetic fields playing a dynamically important role in OH
+masing clouds in OHMs.",1211.2023v1
+2012-11-13,Magnetization reversal in isolated and interacting single-domain nanoparticles,"Computational and experimental results on the thermally-induced magnetization
+reversal in single-domain magnetic nanoparticles are reported. The simulations
+are based on the direct integration of the Fokker-Planck equation that governs
+the dynamics of the magnetic moment associated with the nanoparticles. A mean
+field approximation is used to account for the influence of the dipolar
+interaction between nanoparticles. It is shown that the interactions can either
+speed up or slow down the reversal process, depending on the angle between the
+external magnetic field and the axis of easy magnetization. The numerical
+results are in good agreement with experimental measurements on cobalt-platinum
+nanoparticles.",1211.3007v1
+2012-11-15,Spin transport and tunable Gilbert damping in a single-molecule magnet junction,"We study time-dependent electronic and spin transport through an electronic
+level connected to two leads and coupled with a single-molecule magnet via
+exchange interaction. The molecular spin is treated as a classical variable and
+precesses around an external magnetic field. We derive expressions for charge
+and spin currents by means of the Keldysh non-equilibrium Green's functions
+technique in linear order with respect to the time-dependent magnetic field
+created by this precession. The coupling between the electronic spins and the
+magnetization dynamics of the molecule creates inelastic tunneling processes
+which contribute to the spin currents. The inelastic spin currents, in turn,
+generate a spin-transfer torque acting on the molecular spin. This back-action
+includes a contribution to the Gilbert damping and a modification of the
+precession frequency. The Gilbert damping coefficient can be controlled by the
+bias and gate voltages or via the external magnetic field and has a
+non-monotonic dependence on the tunneling rates.",1211.3611v2
+2012-11-27,"""Strongly interacting matter in magnetic fields"": an overview","This is an introduction to the volume of Lecture Notes in Physics on
+""Strongly interacting matter in magnetic fields"". The volume combines
+contributions written by a number of experts on different aspects of the
+problem. The response of QCD matter to intense magnetic fields has attracted a
+lot of interest recently. On the theoretical side, this interest stems from the
+possibility to explore the plethora of novel phenomena arising from the
+interplay of magnetic field with QCD dynamics. On the experimental side, the
+interest is motivated by the recent results on the behavior of quark-gluon
+plasma in a strong magnetic field created in relativistic heavy ion collisions
+at RHIC and LHC. The purpose of this introduction is to provide a brief
+overview and a guide to the individual contributions where these topics are
+covered in detail.",1211.6245v2
+2012-12-03,Magnetic effects on nonlinear mechanical properties of a suspended carbon nanotube,"We propose a microscopic model for a nanoelectromechanical system made by a
+radio-frequency driven suspended carbon nanotube (CNT) in the presence of an
+external magnetic field perpendicular to the current. As a main result, we show
+that, when the device is driven far from equilibrium, one can tune the CNT
+mechanical properties by varying the external magnetic field. Indeed, the
+magnetic field affects the CNT bending mode dynamics inducing an enhanced
+damping as well as a noise term due to the electronic phase fluctuations. The
+quality factor, as observed experimentally, exhibits a quadratic dependence on
+external magnetic field strength. Finally, CNT resonance frequencies as a
+function of gate voltage acquire, increasing the magnetic field strength, a
+peculiar dip-peak structure that should be experimentally observed.",1212.0267v3
+2013-01-10,"Magnetization precession induced by quasi-transverse picosecond strain pulses in (311) ferromagnetic (Ga,Mn)As","Quasi-longitudinal and quasi-transverse picosecond strain pulses injected
+into a ferromagnetic (311) (Ga,Mn)As film induce dynamical shear strain in the
+film, thereby modulating the magnetic anisotropy and inducing resonant
+precession of the magnetization at a frequency ~10 GHz. The modulation of the
+out-of-plane magnetization component by the quasitransverse strain reaches
+amplitudes as large as 10% of the equilibrium magnetization. Our theoretical
+analysis is in good agreement with the observed results, thus providing a
+strategy for ultrafast magnetization control in ferromagnetic films by strain
+pulses.",1301.2188v1
+2013-02-04,"Two-flavor color superconductivity at finite temperature, chemical potential and in the presence of strong magnetic fields","Utilizing an extended two-flavor Nambu-Jona Lasinio (NJL) model, we review
+some of the effects of external magnetic fields on two-flavor color
+superconducting phase (2SC) at moderate baryon densities in the QCD phase
+diagram. The effective action of the extended NJL model consists of two mass
+gaps as functions of three intensive quantities, the temperature, the quark
+chemical potential and the external magnetic field. The nonzero values of the
+mass gaps, chiral and diquark condensates, induce spontaneous chiral and color
+symmetry breaking, respectively, and as a result two different phases of quark
+matter appear. We find the transition curves between these phases as well as
+the critical points in the QCD phase diagram in terms of the intensive
+quantities. Imposing a constant strong magnetic field on these two phases, we
+show that the mass gaps increase with the magnetic field and the symmetry
+breaking region in the QCD phase diagram expands even to the larger values of
+temperature and quark chemical potential. This phenomenon is a consequence of
+the magnetic catalysis of dynamical symmetry breaking, which is proven before.",1302.0622v1
+2013-03-03,The inviscid instability in an electrically conducting fluid affected by a parallel magnetic field,"We investigate inviscid instability in an electrically conducting fluid
+affected by a parallel magnetic field. The case of low magnetic
+  Reynolds number in Poiseuille flow is considered. When the magnetic field is
+sufficiently strong, for a flow with low hydrodynamic Reynolds number, it is
+already known that the neutral disturbances are three-dimensional. Our
+investigation shows that at high hydrodynamic Reynolds number(inviscid flow),
+the effect of the strength of the magnetic field on the fastest growing
+perturbations is limited to a decrease of their oblique angle i.e. angle
+between the direction of the wave propagation and the basic flow. The waveform
+remains unchanged. The detailed analysis of the linear instability provided by
+the eigenvalue problem shows that the magnetic field has a stabilizing effect
+on the electrically conducting fluid flow. We find also that at least, the
+unstability appears if the main flow possesses an inflexion point with a
+suitable condition between the velocity of the basic flow and the complex
+stability parameter according to Rayleigh's inflexion point theorem.",1303.0534v1
+2013-04-22,Magnetic anisotropic energy gap and low energy spin wave excitation in antiferromagnetic block phase of K2Fe4Se5,"Neutron scattering experiments were performed to investigate magnetic order
+and magnetic excitations in ternary iron chalcogenide K2Fe4Se5. The formation
+of a superlattice structure below 580 K together with the decoupling between
+the Fe-vacancy order-disorder transition and the antiferromagnetic order
+transition appears to be a common feature in the A2Fe4Se5 family. The study of
+spin dynamics of K2Fe4Se5 reveals two distinct energy gaps at the magnetic
+Brillouin zone center, which indicates the presence of magnetic anisotropy and
+the decrease of local symmetry due to electronic and orbital anisotropy. The
+low-energy spin wave excitations of K2Fe4Se5 can be properly described by
+linear spin wave theory within a Heisenberg model. Compared to iron pnictides,
+K2Fe4Se5 exhibits a more two-dimensional magnetism as characterized by large
+differences not only between out-of-plane and in-plane spin wave velocities,
+but also between out-of-plane and in-plane exchange interactions.",1304.5950v1
+2013-05-22,Fractal multi-scale nature of solar/stellar magnetic field,"An abstract mathematical concept of fractal organization of certain complex
+objects received significant attention in astrophysics during last decades. The
+concept evolved into a broad field including multi-fractality and
+intermittency, percolation theory, self-organized criticality, theory of
+catastrophes, etc. Such a strong mathematical and physical approach provide new
+possibilities for exploring various aspects of astrophysics. In particular, in
+the solar and stellar magnetism, multi-fractal properties of magnetized plasma
+turned to be useful for understanding burst-like dynamics of energy release
+events, conditions for turbulent dynamo action, nature of turbulent magnetic
+diffusivity, and even the dual nature of solar dynamo. In this review, I will
+briefly outline how the ideas of multi-fractality are used to explore the above
+mentioned aspects of solar magnetism.",1305.5282v1
+2013-07-23,Thermodynamic properties of strongly coupled plasma in presence of external magnetic field,"Thermodynamic properties of a Yukawa system consisting of dust particles in
+plasma are studied in presence of an external magnetic field. It is assumed
+that dust particles interact with each other by modified potential in presence
+of magnetic field. Accordingly, a modified expression for internal energy has
+been obtained. A molecular dynamics code is developed to calculate this
+internal energy for the entire system. Based on the values of internal energy
+given by the code Helmholtz free energy and pressure are calculated for the
+system. Our study shows novel kind of behaviour for internal energy in presence
+of magnetic field. Thermodynamic properties are affected significantly by
+magnetic field. The study helps to express internal energy as a function of
+Coulomb coupling parameter and magnetic field.",1307.6088v1
+2013-08-01,Vortex precession frequency and its amplitude-dependent shift in cylindrical nanomagnets,"Frequency of free magnetic vortex precession in circular soft ferromagnetic
+nano-cylinders (magnetic dots) of various sizes is an important parameter, used
+in design of spintronic devices (such as spin-torque microwave
+nano-oscillators) and characterization of magnetic nanostructures. Here, using
+a recently developed collective-variable approach to non-linear dynamics of
+magnetic textures in planar nano-magnets, this frequency and its
+amplitude-dependent shift are computed analytically and plotted for the full
+range of cylinder geometries. The frequency shift is positive in large planar
+dots, but becomes negative in smaller and more elongated ones. At certain dot
+dimensions a zero frequency shift is realized, which can be important for
+enhancing frequency stability of magnetic nano-oscillators.",1308.0240v2
+2013-08-23,Experimental evidence of a collinear antiferromagnetic ordering in the frustrated CoAl2O4 spinel,"Nuclear magnetic resonance (NMR), neutron diffaction (ND), x-ray diffraction,
+magnetic susceptibility and specific heat measurements on the frustrated A-site
+spinel CoAl2O4 compound reveal a collinear antiferromagnetic ordering below Tn
+= 9.8(2) K. A high quality powder sample characterized by x-ray diffraction
+that indicates a relatively low Co-Al inversion parameter x = 0.057(20) in
+(Co1-xAlx)[Al2-xCox]O4, shows a broad maximum around 15 K in magnetic
+susceptibility and a sharp peak at Tn in heat capacity. The average ordered
+magnetic moment of Co^2+ (S = 3/2) ions at the A-site is estimated to be 2.4(1)
+Bohr magneton from NMR and 1.9(5) Bohr magneton from ND which are smaller than
+the expected value of 3 Bohr magneton for S = 3/2 and g = 2. Antiferromagnetic
+spin uctuations and correlations in the paramagnetic state are revealed from
+the magnetic susceptibility, NMR and ND measurements, which are due to spin
+frustration and site inversion effects in the system. The ND data also show
+short-range dynamic magnetic ordering that persists to a temperature that is
+almost twice Tn.",1308.5238v1
+2013-09-05,Nuclear magnetization in gallium arsenide quantum dots at zero magnetic field,"Optical and electrical control of the nuclear spin system allows enhancing
+the sensitivity of NMR applications and spin-based information storage and
+processing. Dynamic nuclear polarization in semiconductors is commonly achieved
+in the presence of a stabilizing external magnetic field. Here we report
+efficient optical pumping of nuclear spins at zero magnetic field in strain
+free GaAs quantum dots. The strong interaction of a single, optically injected
+electron spin with the nuclear spins acts as a stabilizing, effective magnetic
+field (Knight field) on the nuclei. We optically tune the Knight field
+amplitude and direction. In combination with a small transverse magnetic field,
+we are able to control the longitudinal and transverse component of the nuclear
+spin polarization in the absence of lattice strain i.e. nuclear quadrupole
+effects, as reproduced by our model calculations.",1309.1288v1
+2013-09-19,Energy Fluxes during Dynamo Reversals,"Using direct numerical simulations of the equations of magnetohydrodynamics,
+we study reversals of the magnetic field generated by the flow of an
+electrically conducting fluid in a sphere. We show that at low magnetic Prandtl
+numbers, Pm=0.5, the decrease of magnetic energy, ohmic dissipation and power
+of the Lorentz force during a reversal is followed by an increase of the power
+injected by the force driving the flow and an increase of viscous dissipation.
+Cross correlations show that the Lorentz energy flux is in advance with respect
+to the other energy fluxes. We also observe that during a reversal, the maximum
+of the magnetic energy density migrates from one hemisphere to the other and
+comes back to its initial position, in agreement with recent experimental
+observations. For larger magnetic Prandtl numbers (Pm= 1, 2), the magnetic
+field reversals do not display these trends and strongly differ one from
+another.",1309.5062v1
+2013-09-27,Structures and Lagrangian statistics of the Taylor-Green Dynamo,"The evolution of a Taylor-Green forced magnetohydrodynamic (MHD) system
+showing dynamo activity is analyzed via direct numerical simulations. The
+statistical properties of the velocity and magnetic field in Eulerian
+coordinates and along trajectories of fluid elements (Lagrangian coordinates)
+are found to change between the kinematic, non-linear and saturated regime.
+Fluid element (tracer) trajectories change from chaotic quasi-isotropic
+(kinematic phase) to mean magnetic field aligned (saturated phase). The
+probability density functions (PDFs) of the magnetic field change from strongly
+non-Gaussian in the kinematic to quasi-Gaussian PDFs in the saturated regime so
+that their flatness give a precise handle on the definition of the limiting
+points of the three regimes. Also the statistics of the fluctuations of the
+kinetic and magnetic energy along fluid trajectories change. All this goes
+along with a dramatic increase of the correlation time of velocity and magnetic
+field fluctuations experienced by tracers significantly exceeding one turbulent
+large-eddy turn-over time. A remarkable consequence is an intermittent scaling
+regime of the Lagrangian magnetic field structure functions at unusually long
+time scales.",1309.7975v2
+2013-11-15,Electric-field-induced strain-mediated magnetoelectric effect in CoFeB-MgO magnetic tunnel junctions,"Magnetoelectric coupling between magnetic and electric dipoles is one of the
+cornerstones of modern physics towards developing the most energy-efficient
+magnetic data storage. Conventionally, magnetoelectric coupling is achieved in
+single-phase multiferroics or in magnetoelectric composite nanostructures
+consisting of ferromagnetic and ferroelectric/piezoelectric materials. Here, we
+demonstrate an electric-field-induced strain-mediated magnetoelectric effect in
+ultrathin CoFeB/MgO magnetic tunnel junction employing non-piezoelectric
+material, which is a vitally important structure for spintronic devices, by
+using dynamical magnetoelectric and piezoresponse force microscopy measurement
+techniques. We show that the applied electric-field induces strain in a few
+atomic layers of dielectric MgO which is transferred to magnetostrictive CoFeB
+layer, resulting in a magnetoelectric effect of magnitude up to 80.8 V cm-1
+Oe-1 under -0.5 V. The demonstrated strain-mediated magnetoelectric effect with
+an electric field in magnetic tunnel junctions is a significant step towards
+exploring magnetoelectrically controlled spintronic devices for low-power and
+high density magnetic data storage applications.",1311.3794v1
+2013-12-01,Modeling and stabilizability of voltage-actuated piezoelectric beams with magnetic effects,"Models for piezoelectric beams and structures with piezoelectric patches
+generally ignore magnetic effects. This is because the magnetic energy has a
+relatively small effect on the overall dynamics. Piezoelectric beam models are
+known to be exactly observable, and can be exponentially stabilized in the
+energy space by using a mechanical feedback controller. In this paper, a
+variational approach is used to derive a model for a piezoelectric beam that
+includes magnetic effects. It is proven that the partial differential equation
+model is well-posed. Magnetic effects have a strong effect on the
+stabilizability of the control system. For almost all system parameters the
+piezoelectric beam can be strongly stabilized, but is not exponentially
+stabilizable in the energy space. Strong stabilization is achieved using only
+electrical feedback. Furthermore, using the same electrical feedback, an
+exponentially stable closed-loop system can be obtained for a set of system
+parameters of zero Lebesgue measure. These results are compared to those of a
+beam without magnetic effects.",1312.0260v1
+2013-12-30,Transient coherence of an EIT media under strong phase modulation,"A strong phase modulated coupling field leads to an amplitude modulation of a
+probe field in an electromagnetically induced transparency process. Time vs.
+detuning plots for different modulation frequencies reveals a transition
+between an adiabatic regime where a series of smooth pulses are created with a
+global phase dependent upon the detuning, and a non-adiabatic regime where a
+strong transient oscillating response is added to these pulses. In the extreme
+non-adiabatic regime, where the modulation frequency is higher than the
+transient decay time, a coherent interference pattern is revealed. Adding a
+magnetic field lifts the hyperfine level degeneracy, resulting in a separation
+of the original pulse to three pulses. Every pulse has now a different phase
+dependent upon the magnetic field causing an interference effect between the
+different magnetic level transients. We explore the dynamics of the magnetic
+and non magnetic cases and show its resemblance to the Landau-Zener theory. We
+also show that combining the global phase of the pulses with the transient
+interference allows for a wide magnetic sensing range without loosing the
+sensitivity of a single EIT line.",1312.7708v1
+2014-02-13,Unusual spin fluctuations and magnetic frustration in olivine and non-olivine LiCoPO$_4$ detected by $^{31}$P and $^7$Li nuclear magnetic resonance,"We report $^{31}$P and $^{7}$Li nuclear magnetic resonance (NMR) studies in
+new non-olivine LiZnPO$_4$-type LiCoPO$_4^\text{tetra}$ microcrystals, where
+the Co$^{2+}$ ions are tetrahedrally coordinated. Olivine LiCoPO$_4$, which was
+directly transformed from LiCoPO$_4^\text{tetra}$ by an annealing process, was
+also studied and compared. The uniform bulk magnetic susceptibility and the
+$^{31}$P Knight shift obey the Curie-Weiss law for both materials with a high
+spin Co$^{2+}$ ($3d^7$, $S=3/2$), but the Weiss temperature $\Theta$ and the
+effective magnetic moment $\mu_\text{eff}$ are considerably smaller in
+LiCoPO$_4^\text{tetra}$. The spin-lattice relaxation rate $T_1^{-1}$ reveals a
+quite different nature of the spin dynamics in the paramagnetic state of both
+materials. Our NMR results imply that strong geometrical spin frustration
+occurs in tetrahedrally coordinated LiCoPO$_4$, which may lead to the
+incommensurate magnetic ordering.",1402.3082v2
+2014-02-22,LDA+DMFT Approach to Magnetocrystalline Anisotropy of Strong Magnets,"The new challenges posed by the need of finding strong rare-earth free
+magnets demand methods that can predict magnetization and magnetocrystalline
+anisotropy energy (MAE). We argue that correlated electron effects, which are
+normally underestimated in band structure calculations, play a crucial role in
+the development of the orbital component of the magnetic moments. Because
+magnetic anisotropy arises from this orbital component, the ability to include
+correlation effects has profound consequences on our predictive power of the
+MAE of strong magnets. Here we show that incorporating the local effects of
+electronic correlations with dynamical mean-field theory provides reliable
+estimates of the orbital moment, the mass enhancement and the MAE of YCo5.",1402.5543v2
+2014-03-26,Statistics of the inverse-cascade regime in two-dimensional magnetohydrodynamic turbulence,"We present a detailed direct numerical simulation of statistically steady,
+homogeneous, isotropic, two-dimensional magnetohydrodynamic (2D MHD)
+turbulence. Our study concentrates on the inverse cascade of the magnetic
+vector potential. We examine the dependence of the statistical properties of
+such turbulence on dissipation and friction coefficients. We extend earlier
+work sig- nificantly by calculating fluid and magnetic spectra, probability
+distribution functions (PDFs) of the velocity, magnetic, vorticity, current,
+stream-function, and magnetic-vector-potential fields and their increments. We
+quantify the deviations of these PDFs from Gaussian ones by computing their
+flatnesses and hyperflatnesses. We also present PDFs of the Okubo-Weiss
+parameter, which distin- guishes between vortical and extensional flow regions,
+and its magnetic analog. We show that the hyperflatnesses of PDFs of the
+increments of the stream-function and the magnetic vector potential exhibit
+significant scale dependence and we examine the implication of this for the
+multiscaling of structure functions. We compare our results with those of
+earlier studies.",1403.6607v1
+2014-04-15,On the Helicity of Open Magnetic Fields,"We reconsider the topological interpretation of magnetic helicity for
+magnetic fields in open domains, and relate this to the relative helicity.
+Specifically, our domains stretch between two parallel planes, and each of
+these ends may be magnetically open. It is demonstrated that, while the
+magnetic helicity is gauge-dependent, its value in any gauge may be physically
+interpreted as the average winding number among all pairs of field lines with
+respect to some orthonormal frame field. In fact, the choice of gauge is
+equivalent to the choice of reference field in the relative helicity, meaning
+that the magnetic helicity is no less physically meaningful. We prove that a
+particular gauge always measures the winding with respect to a fixed frame, and
+propose that this is normally the best choice. For periodic fields, this choice
+is equivalent to measuring relative helicity with respect to a potential
+reference field. But for aperiodic fields, we show that the potential field can
+be twisted. We prove by construction that there always exists a possible
+untwisted reference field.",1404.3897v1
+2014-05-04,Diffusion of magnetic elements in a supergranular cell,"Small scale magnetic fields (magnetic elements) are ubiquitous in the solar
+photosphere. Their interaction can provide energy to the upper atmospheric
+layers, and contribute to heat the solar corona. In this work, the dynamic
+properties of magnetic elements in the quiet Sun are investigated. The high
+number of magnetic elements detected in a supegranular cell allowed us to
+compute their displacement spectrum $\langle(\Delta
+r)^2\rangle\propto\tau^\gamma$ (being $\gamma>0$, and $\tau$ the time since the
+first detection), separating the contribution of the network (NW) and the
+internetwork (IN) regions. In particular, we found $\gamma=1.27\pm0.05$ and
+$\gamma=1.08\pm0.11$ in NW (at smaller and larger scales, respectively), and
+$\gamma=1.44\pm0.08$ in IN. These results are discussed in light of the
+literature on the topic, as well as the implications for the build up of the
+magnetic network.",1405.0677v1
+2014-07-14,Thermal noise induced stochastic resonance in self organizing Fe nanoparticle system,"The natural world is replete with examples of multistable systems, known to
+respond to periodic modulations and produce a signal, which exhibits resonance
+with noise amplitude. This is a concept not demonstrated in pure materials,
+which involve a measured physical property. In a thermoremanent magnetization
+experiment with a common magnetic material, Fe, in the nanoparticulate form, we
+establish how magnetization in a system of dilute spins during dissipation of
+stored magnetic energy, breaks up into spontaneous oscillatory behavior.
+Starting at 175 K and aided by temperature (stochastic noise) the oscillation
+amplitude goes through a maximum, reminiscent of stochastic resonance. Our
+observation of thermal noise induced coherent resonance is due to intrinsic
+self-organizing magnetic dynamics of the Fe nanoperticle system without
+applying any external periodic force. These results yield new possibilities in
+design of magnetic materials and a platform to understand stochastic
+interference and phase synchronization in neural activity, as models for neural
+communication.",1407.3579v1
+2014-09-18,Storage Ring And Interaction Region Magnets For A μ+μ- Higgs Factory,"A low-energy Muon Collider (MC) offers unique opportunities to study the
+recently found Higgs boson. However, due to a relatively large beam emittance
+with moderate cooling in this machine, large-aperture high- field
+superconducting (SC) magnets are required. The magnets need also an adequate
+margin to operate at a large radiation load from the muon decay showers.
+General specifications of the SC dipoles and quadrupoles for the 125 GeV c.o.m.
+Higgs Factory with an average luminosity of ~2x10**31 cm-2s-1 are formulated.
+Magnet conceptual designs and parameters are reported. The impact of the magnet
+fringe fields on the beam dynamics as well as the IR and lattice magnet
+protection from radiation are also reported and discussed.",1409.5461v1
+2014-10-07,Metamorphosis of helical magnetorotational instability in the presence axial electric current,"This paper presents numerical linear stability analysis of a cylindrical
+Taylor-Couette flow of liquid metal carrying axial electric current in a
+generally helical external magnetic field. Axially symmetric disturbances are
+considered in the inductionless approximation corresponding to zero magnetic
+Prandtl number. Axial symmetry allows us to reveal an entirely new
+electromagnetic instability. First, we show that the electric current passing
+through the liquid can extend the range of helical magnetorotational
+instability (HMRI) indefinitely by transforming it into a purely
+electromagnetic instability. Two different electromagnetic instability
+mechanisms are identified. The first is an internal pinch-type instability,
+which is due to the interaction of the electric current with its own magnetic
+field. Axisymmetric mode of this instability requires a free-space component of
+the azimuthal magnetic field. When the azimuthal component of the magnetic
+field is purely rotational and the axial component is nonzero, a new kind of
+electromagnetic instability emerges. The latter driven by the interaction of
+electric current with a weak collinear magnetic field in a quiescent fluid
+gives rise to a steady meridional circulation coupled with azimuthal rotation.",1410.1750v3
+2014-11-04,Magnetoimpedance effect at the high frequency range for the thin film geometry: Numerical calculation and experiment,"The magnetoimpedance effect is a versatile tool to investigate ferromagnetic
+materials, revealing aspects on the fundamental physics associated to
+magnetization dynamics, broadband magnetic properties, important issues for
+current and emerging technological applications for magnetic sensors, as well
+as insights on ferromagnetic resonance effect at non-saturated magnetic states.
+Here, we perform a theoretical and experimental investigation of the
+magnetoimpedance effect for the thin film geometry in a wide frequency range.
+We calculate the longitudinal magnetoimpedance for single layered, multilayered
+or exchange biased systems from an approach that considers a magnetic
+permeability model for planar geometry and the appropriate magnetic free energy
+density for each structure. From numerical calculations and experimental
+results found in literature, we analyze the magnetoimpedance behavior, and
+discuss the main features and advantages of each structure. To test the
+robustness of the approach, we directly compare theoretical results with
+experimental magnetoimpedance measurements obtained in a wide range of
+frequencies for an exchange biased multilayered film. Thus, we provide
+experimental evidence to confirm the validity of the theoretical approach
+employed to describe the magnetoimpedance in ferromagnetic films, revealed by
+the good agreement between numerical calculations and experimental results.",1411.0971v1
+2014-11-24,Turbulence Reduces Magnetic Diffusivity in a Liquid Sodium Experiment,"The contribution of small scale turbulent fluctuations to the induction of
+mean magnetic field is investigated in our liquid sodium spherical Couette
+experiment with an imposed magnetic field.An inversion technique is applied to
+a large number of measurements at $Rm \approx 100$ to obtain radial profiles of
+the $\alpha$ and $\beta$ effects and maps of the mean flow.It appears that the
+small scale turbulent fluctuations can be modeled as a strong contribution to
+the magnetic diffusivity that is negative in the interior region and positive
+close to the outer shell.Direct numerical simulations of our experiment support
+these results.The lowering of the effective magnetic diffusivity by small scale
+fluctuations implies that turbulence can actually help to achieve
+self-generation of large scale magnetic fields.",1411.6366v2
+2014-11-12,Biological effects of pulsating magnetic fields: role of solitons,"In this paper, we analyze biological effects produced by magnetic fields in
+order to elucidate the physical mechanisms, which can produce them. We show
+that there is a chierarchy of such mechanisms and that the mutual interplay
+between them can result in the synergetic outcome. In particular, we analyze
+the biological effects of magnetic fields on soliton mediated charge transport
+in the redox processes in living organisms. Such solitons are described by
+nonlinear systems of equations and represent electrons that are self-trapped in
+alpha-helical polypeptides due to the moderately strong electron-lattice
+interaction. They represent a particular type of disssipativeless large
+polarons in low-dimensional systems. We show that the effective mass of
+solitons in the is different from the mass of free electrons, and that there is
+a resonant effect of the magnetic fields on the dynamics of solitons, and,
+hence, on charge transport that accompanies photosynthesis and respiration.
+These effects can result in non-thermal resonant effects of magnetic fields on
+redox processes in particular, and on the metabolism of the organism in
+general. This can explain physical mechanisms of therapies based on applying
+magnetic fields.",1411.6576v1
+2014-12-05,Guiding-center transformation of the radiation-reaction force in a nonuniform magnetic field,"In this paper, we present the guiding-center transformation of the
+radiation-reaction force of a classical point charge traveling in a nonuniform
+magnetic field. The transformation is valid as long as the gyroradius of the
+charged particles is much smaller than the magnetic field nonuniformity length
+scale, so that the guiding-center Lie-transform method is applicable.
+Elimination of the gyromotion time scale from the radiation-reaction force is
+obtained with the Poisson bracket formalism originally introduced by [A. J.
+Brizard, Phys. Plasmas 11 4429 (2004)], where it was used to eliminate the fast
+gyromotion from the Fokker-Planck collision operator. The formalism presented
+here is applicable to the motion of charged particles in planetary magnetic
+fields as well as in magnetic confinement fusion plasmas, where the
+corresponding so-called synchrotron radiation can be detected. Applications of
+the guiding-center radiation-reaction force include tracing of charged particle
+orbits in complex magnetic fields as well as kinetic description of plasma when
+the loss of energy and momentum due to radiation plays an important role, e.g.,
+for runaway electron dynamics in tokamaks.",1412.1966v2
+2014-12-26,"Potts models with magnetic field: arithmetic, geometry, and computation","We give a sheaf theoretic interpretation of Potts models with external
+magnetic field, in terms of constructible sheaves and their Euler
+characteristics. We show that the polynomial countability question for the
+hypersurfaces defined by the vanishing of the partition function is affected by
+changes in the magnetic field: elementary examples suffice to see
+non-polynomially countable cases that become polynomially countable after a
+perturbation of the magnetic field. The same recursive formula for the
+Grothendieck classes, under edge-doubling operations, holds as in the case
+without magnetic field, but the closed formulae for specific examples like
+banana graphs differ in the presence of magnetic field. We give examples of
+computation of the Euler characteristic with compact support, for the set of
+real zeros, and find a similar exponential growth with the size of the graph.
+This can be viewed as a measure of topological and algorithmic complexity. We
+also consider the computational complexity question for evaluations of the
+polynomial, and show both tractable and NP-hard examples, using dynamic
+programming.",1412.7925v2
+2015-01-30,Phase diagram and optimal switching induced by spin Hall effect in a perpendicular magnetic layer,"In a ferromagnet/heavy-metal bilayer device with strong spin Hall effect an
+in-plane current excites magnetic dynamics through spin torque. We analyze
+bilayers with perpendicular magnetization and calculate three-dimensional phase
+diagrams describing switching by external magnetic field at a fixed current. We
+then concentrate on the case of a field applied in the plane formed by the film
+normal and the current direction. Here we analytically study the evolution of
+both the conventional ""up""/""down"" magnetic equilibria and the additional
+equilibria created by the spin torque. Expressions for the stability regions of
+all equilibria are derived, and the nature of switching at each critical
+boundary is discussed. The qualitative picture obtained this way predicts
+complex hysteresis patterns that should occur in bilayers. By analyzing the
+phase portraits of the system we show that when the spin torque induced
+equilibrium exists, switching between ""up"" and ""down"" states proceeds through
+it as an intermediate state. Using numeric simulations we analyze the switching
+time and compare it to that of a conventional spin torque device with collinear
+magnetizations of the polarizer and the free layer.",1501.07787v1
+2015-03-16,Persistence of magnetic field driven by relativistic electrons in a plasma,"The onset and evolution of magnetic fields in laboratory and astrophysical
+plasmas is determined by several mechanisms, including instabilities, dynamo
+effects and ultra-high energy particle flows through gas, plasma and
+interstellar-media. These processes are relevant over a wide range of
+conditions, from cosmic ray acceleration and gamma ray bursts to nuclear fusion
+in stars. The disparate temporal and spatial scales where each operates can be
+reconciled by scaling parameters that enable to recreate astrophysical
+conditions in the laboratory. Here we unveil a new mechanism by which the flow
+of ultra-energetic particles can strongly magnetize the boundary between the
+plasma and the non-ionized gas to magnetic fields up to 10-100 Tesla (micro
+Tesla in astrophysical conditions). The physics is observed from the first
+time-resolved large scale magnetic field measurements obtained in a laser
+wakefield accelerator. Particle-in-cell simulations capturing the global plasma
+and field dynamics over the full plasma length confirm the experimental
+measurements. These results open new paths for the exploration and modelling of
+ultra high energy particle driven magnetic field generation in the laboratory.",1503.04696v1
+2015-05-19,Ultrafast Magnetic Light,"We propose a novel concept for efficient dynamic tuning of optical properties
+of a high refractive index subwavelength nanoparticle with a magnetic Mie-type
+resonance by means of femtosecond laser radiation. This concept is based on
+ultrafast generation of electron-hole plasma within such nanoparticle,
+drastically changing its transient dielectric permittivity. This allows to
+manipulate by both electric and magnetic nanoparticle responses, resulting in
+dramatic changes of its extinction cross section and scattering diagram.
+Specifically, we demonstrate the effect of ultrafast switching-on a Huygens
+source in the vicinity of the magnetic dipole resonance. This approach enables
+to design ultrafast and compact optical switchers and modulators based on the
+""ultrafast magnetic light"" concept.",1505.05185v1
+2015-05-25,Magnetism in the three-dimensional layered Lieb lattice: Enhanced transition temperature via flat-band and Van Hove singularities,"We describe the enhanced magnetic transition temperatures $T_c$ of
+two-component fermions in three-dimensional layered Lieb lattices, which are
+created in cold atom experiments. We determine the phase diagram at
+half-filling using the dynamical mean-field theory. The dominant mechanism of
+enhanced $T_c$ gradually changes from the (delta-functional) flat-band to the
+(logarithmic) Van Hove singularity as the interlayer hopping increases. We
+elucidate that the interaction induces an effective flat-band singularity from
+a dispersive flat (or narrow) band. We offer a general analytical framework for
+investigating the singularity effects, where a singularity is treated as one
+parameter in the density of states. This framework provides a unified
+description of the singularity-induced phase transitions, such as magnetism and
+superconductivity, where the weight of the singularity characterizes physical
+quantities. This treatment of the flat-band provides the transition temperature
+and magnetization as a universal form (i.e., including the Lambert function).
+We also elucidate a specific feature of the magnetic crossover in magnetization
+at finite temperatures.",1505.06591v1
+2015-06-09,Spin dynamics in a Curie-switch,"Ferromagnetic resonance properties of F$_1$/f/F$_2$/AF multilayers, where
+weakly ferromagnetic spacer f is sandwiched between strongly ferromagnetic
+layers F$_1$ and F$_2$, with F$_1$ being magnetically soft and F$_2$ -
+magnetically hard due to exchange pinning to antiferromagnetic layer AF, are
+investigated. Spacer-mediated exchange coupling is shown to strongly affect the
+resonance fields of both F$_1$ and F$_2$ layers. Our theoretical calculations
+as well as measurements show that the key magnetic parameters of the spacer,
+which govern the ferromagnetic resonance in F$_1$/f/F$_2$/AF, are the magnetic
+exchange length ($\Lambda$), effective saturation magnetization at $T=0$
+$(m_0)$, and effective Curie temperature ($T_{\text{C}}^{\text{eff}}$). The
+values of these key parameters are deduced from the experimental data for
+multilayers with f = Ni$_x$Cu$_{100-x}$, for the key ranges in Ni-concentration
+($x=54\div70$ at. %) and spacer thickness ($d=3\div 6$ nm). The results
+obtained provide a deeper insight into thermally-controlled spin precession and
+switching in magnetic nanostructures, with potential applications in spin-based
+oscillators and memory devices.",1506.02928v1
+2015-06-15,Neutrino electromagnetic properties: new approach to oscillations in magnetic fields,"Several new and interesting aspects of neutrino oscillations in a magnetic
+field are considered: 1) We develop a standard usually used approach to the
+neutrino spin oscillations in the neutrino mass basis and obtain the effective
+neutrino spin (and ""spin-mass"") oscillation Hamiltonian that can be used for
+description of the neutrino oscillations between different pairs of neutrino
+states with different masses and helicities; 2) We derive the exact solution of
+the Dirac equation for a massive neutrino with nonzero magnetic moment in the
+presence of a constant transversal magnetic field that is rotating along the
+direction of the neutrino propagation (the twisting magnetic field) and on the
+basis of the obtained energy spectrum the neutrino spin oscillation effective
+Hamiltonian is derive; 3) We develop a new approach to neutrino spin
+oscillations that is based on the description of the neutrino spin states with
+the corresponding spin operator that commutes with the neutrino dynamics
+Hamiltonian in the magnetic field. The obtained new results can have important
+phenomenological applications.",1506.05311v1
+2015-07-09,Temperature evolution of superparamagnetic clusters in single-crystal La0.85Sr0.15CoO3 from nonlinear magnetic ac response and neutron depolarization,"The representative measurements of the second harmonic in ac magnetization
+complemented by neutron depolarization have been performed for single-crystal
+La0.85Sr0.15CoO3 in the temperature range 97 K < T < 230 K, where occurrence of
+a small fraction (~ 0.001) of nanoscale ferromagnetic clusters (FMC) has been
+found. Magnetic, geometrical and dynamical parameters of the FMC system have
+been evaluated in the temperature range T < 140 K, where superparamagnetic
+regime installs, by means of the formalism involving the Fokker-Planck equation
+(FPE). With lowering the temperature, the amount of clusters fraction, the
+cluster size and magnetic moment along with its diffusion relaxation time
+strongly increase, each in its own temperature interval. Below 130 K, FMC
+contribute essentially to the total linear magnetic susceptibility. The damping
+factor of the order 0.1 proves the importance of precession in thermal
+relaxation of the cluster magnetic moment. The FMC are a precursor of
+long-range ferromagnetic correlations seen below 100 K with neutron-scattering
+techniques. The employed technique supplemented with FPE-based data-treatment
+formalism is a novel method for studying superparamagnetic systems.",1507.02593v2
+2015-08-17,Magnetization dynamics driven by angle-dependent spin-orbit spin transfer torque,"Spin-orbit spin transfer torque allows an efficient control of magnetization
+by an in-plane current. Recent experiments found that the spin-orbit torque has
+strong dependence on the magnetization angle [Garello et al., Nature
+Nanotechnol. 8, 587 (2013); Qiu et al., Sci. Rep. 4, 4491 (2014)]. We
+theoretically investigate magnetization switching and domain wall motion in a
+perpendicularly magnetized layer, induced by angle-dependent spin-orbit torque.
+We obtain analytic expressions of the switching current and domain wall
+velocity, in agreement with numerical results. Based on the expressions, we
+find that the spin-orbit torque increasing with the polar angle of
+magnetization is beneficial for both switching and domain wall motion. Our
+result will serve as a guideline to design and interpret switching and domain
+wall experiments based on spin-orbit torque.",1508.04067v2
+2015-08-28,Nernst Effect in Magnetized Plasmas,"We present nanosecond timescale Vlasov-Fokker-Planck-Maxwell modeling of
+magnetized plasma transport and dynamics in a hohlraum with an applied external
+magnetic field, under conditions similar to recent experiments. Self-consistent
+modeling of the kinetic electron momentum equation allows for a complete
+treatment of the heat flow equation and Ohm's Law, including Nernst advection
+of magnetic fields. In addition to showing the prevalence of non-local
+behavior, we demonstrate that effects such as anomalous heat flow are induced
+by inverse bremsstrahlung heating. We show magnetic field amplification up to a
+factor of 3 from Nernst compression into the hohlraum wall. The magnetic field
+is also expelled towards the hohlraum axis due to Nernst advection faster than
+frozen-in-flux would suggest. Non-locality contributes to the heat flow towards
+the hohlraum axis and results in an augmented Nernst advection mechanism that
+is included self-consistently through kinetic modeling.",1508.07260v1
+2015-09-06,Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents,"We propose a new mechanism and a related device concept for a robust,
+magnetic field tunable radio-frequency (rf) oscillator using the self
+oscillation of a magnetic domain wall subject to a uniform static magnetic
+field and a spatially non-uniform vertical dc spin current. The self
+oscillation of the domain wall is created as it translates periodically between
+two unstable positions, one being in the region where both the dc spin current
+and the magnetic field are present, and the other, being where only the
+magnetic field is present. The vertical dc spin current pushes it away from one
+unstable position while the magnetic field pushes it away from the other. We
+show that such oscillations are stable under noise and can exhibit a quality
+factor of over 1000. A domain wall under dynamic translation, not only being a
+source for rich physics, is also a promising candidate for advancements in
+nanoelectronics with the actively researched racetrack memory architecture,
+digital and analog switching paradigms as candidate examples. Devising a stable
+rf oscillator using a domain wall is hence another step towards the realization
+of an all domain wall logic scheme.",1509.01791v1
+2015-11-05,Non-Markovian magnetization dynamics for uniaxial nanomagnets,"A stochastic approach for the description of the time evolution of the
+magnetization of nanomagnets is proposed, that interpolates between the
+Landau-Lifshitz-Gilbert and the Landau-Lifshitz-Bloch approximations, by
+varying the strength of the noise. Its finite autocorrelation time, i.e. when
+it may be described as colored, rather than white, is, also, taken into account
+and the consequences, on the scale of the response of the magnetization are
+investigated. It is shown that the hierarchy for the moments of the
+magnetization can be closed, by introducing a suitable truncation scheme, whose
+validity is tested by direct numerical solution of the moment equations and
+compared to the averages obtained from a numerical solution of the
+corresponding colored stochastic Langevin equation. This comparison is
+performed on magnetic systems subject to both an external uniform magnetic
+field and an internal one-site uniaxial anisotropy.",1511.01693v1
+2016-01-06,Primordial magnetic fields from the string network,"Cosmic strings are a type of cosmic defect formed by a symmetry-breaking
+phase transition in the early universe. Individual strings would have gathered
+to build a network, and their dynamical motion would induce scalar--, vector--
+and tensor--type perturbations. In this paper, we focus on the vector mode
+perturbations arising from the string network based on the one scale model and
+calculate the time evolution and the power spectrum of the associated magnetic
+fields. We show that the relative velocity between photon and baryon fluids
+induced by the string network can generate magnetic fields over a wide range of
+scales based on standard cosmology. We obtain the magnetic field spectrum
+before recombination as
+$a^2B(k,z)\sim4\times10^{-16}G\mu/((1+z)/1000)^{4.25}(k/{\rm Mpc}^{-1})^{3.5}$
+Gauss on super-horizon scales, and
+$a^2B(k,z)\sim2.4\times10^{-17}G\mu/((1+z)/1000)^{3.5}(k/{\rm Mpc}^{-1})^{2.5}$
+Gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows
+up to the end of recombination, and has a final amplitude of approximately
+$B\sim10^{-17\sim -18} G\mu$ Gauss at the $k\sim1\ {\rm Mpc}^{-1}$ scale today.
+This field might serve as a seed for cosmological magnetic fields.",1601.01059v1
+2016-02-03,Topological magnetic dipolar interaction and non-local electric magnetization control in topological insulator heterostructures,"The magnetoelectric effect predicted in topological insulators makes
+heterostructures that combine magnetic materials and such insulators promising
+candidates for spintronics applications. Here, we theoretically consider a
+setup that exhibits two well-separated interfaces between a topological
+insulator and a ferromagnetic insulator. We show that there is a topological
+magnetic dipole-dipole interaction stemming from long-range Coulomb
+interactions. We analytically derive the magnetization dynamics at the two
+interfaces and discuss how the long-range coupling can be applied to
+non-locally induce the formation of a magnetic texture at one interface by
+suitably gating the other interface.",1602.01469v4
+2016-02-15,Ferromagnetic Cluster Glass Phase Embedded in a Paramagnetic and Metallic Host in Non-uniform Magnetic System CaRu_{1-x}Sc_{x}O_{3},"We have investigated both static and dynamic magnetic properties of
+polycrystalline CaRu$_{1-x}$Sc$_{x}$O$_{3}$ system in order to clarify the role
+of Sc ions as a disorder for magnetic ordering. We have observed typical
+features of a ferromagnetic cluster glass state below around 40 K: (i) a broad,
+frequency-dependent peak in the ac magnetic susceptibility, (ii) a slow
+relaxation of the magnetization, and (iii) a continuous increase in the dc
+magnetic susceptibility in field cooling process. The composition dependence of
+characteristic parameters for the cluster glass state suggests that chemical
+segregation can hardly explain the clustering mechanism. We propose a possible
+picture that the ferromagnetic clusters are distributed uniformly and form the
+glassy state embedded in the paramagnetic and metallic host of CaRuO$_{3}$.",1602.04647v1
+2016-03-01,Ferromagnetic resonance and magnetic damping in C-doped Mn5Ge3,"Ferromagnetic resonance (FMR) was used to investigate the static and dynamic
+magnetic properties of carbon-doped Mn5Ge3 (C$_{0.1}$ and C$_{0.2}$) thin films
+grown on Ge(111). The temperature dependence of magnetic anisotropy shows an
+increased perpendicular magneto-crystalline contribution at 80K with an
+in-plane easy axis due to the large shape contribution. We find that our
+samples show a small FMR linewidth (corresponding to an intrinsic magnetic
+damping parameter $\alpha$=0.005), which is a measure of the spin relaxation
+and directly related with the magnetic and structural quality of the material.
+In the perpendicular-to-plane geometry, the FMR linewidth shows a minimum at
+around 200K for all the samples, which seems to be not correlated to the
+C-doping. The magnetic relaxation parameters have been determined and indicate
+the two-magnon scattering as the main extrinsic contribution. We observe a
+change in the main contribution from scattering centres in Mn5Ge3C0.2 at low
+temperatures, which could be related to the minimum in linewidth.",1603.00190v1
+2016-03-18,"Structural and Magnetic Characterization of Large Area, Free-Standing Thin Films of Magnetic Ion Intercalated Dichalcogenides Mn0.25TaS2 and Fe0.25TaS2","Free-standing thin films of magnetic ion intercalated transition metal
+dichalcogenides are produced using ultramicrotoming techniques. Films of
+thicknesses ranging from 30nm to 250nm were achieved and characterized using
+transmission electron diffraction and X-ray magnetic circular dichroism.
+Diffraction measurements visualize the long range crystallographic ordering of
+the intercalated ions, while the dichroism measurements directly assess the
+orbital contributions to the total magnetic moment. We thus verify the
+unquenched orbital moment in Fe0.25TaS2 and measure the fully quenched orbital
+contribution in Mn0.25TaS2. Such films can be used in a wide variety of
+ultrafast X-ray and electron techniques that benefit from transmission
+geometries, and allow measurements of ultrafast structural, electronic, and
+magnetization dynamics in space and time.",1603.05921v1
+2016-03-23,Magnetic Flux Cancellation in Ellerman Bombs,"Ellerman Bombs (EBs) are often found co-spatial with bipolar photospheric
+magnetic fields. We use H$\alpha$ imaging spectroscopy along with Fe I 6302.5
+\AA\ spectro-polarimetry from the Swedish 1-m Solar Telescope (SST), combined
+with data from the Solar Dynamic Observatory (SDO) to study EBs and the
+evolution of the local magnetic fields at EB locations. The EBs are found via
+an EB detection and tracking algorithm. We find, using NICOLE inversions of the
+spectro-polarimetric data, that on average (3.43 $\pm$ 0.49) x 10$^{24}$ ergs
+of stored magnetic energy disappears from the bipolar region during the EBs
+burning. The inversions also show flux cancellation rates of 10$^{14}$ -
+10$^{15}$ Mx s$^{-1}$, and temperature enhancements of 200 K at the detection
+footpoints. We investigate near-simultaneous flaring of EBs due to co-temporal
+flux emergence from a sunspot, which shows a decrease in transverse velocity
+when interacting with an existing, stationary area of opposite polarity
+magnetic flux and the EBs are formed. We also show that these EBs can get
+fueled further by additional, faster moving, negative magnetic flux regions.",1603.07100v1
+2016-04-18,Spontaneous Formation of Surface Magnetic Structure from Large-scale Dynamo in Strongly-stratified Convection,"We report the first successful simulation of spontaneous formation of surface
+magnetic structures from a large-scale dynamo by strongly-stratified thermal
+convection in Cartesian geometry. The large-scale dynamo observed in our
+strongly-stratified model has physical properties similar to those in earlier
+weakly-stratified convective dynamo simulations, indicating that the
+$\alpha^2$-type mechanism is responsible for it. Additionally to the
+large-scale dynamo, we find that large-scale structures of the vertical
+magnetic field are spontaneously formed in the convection zone surface only for
+the case of strongly-stratified atmosphere. The organization of the vertical
+magnetic field proceeds in the upper convection zone within tens of convective
+turn-over time and band-like bipolar structures are recurrently-appeared in the
+dynamo-saturated stage. We examine possibilities of several candidates as the
+origin of the surface magnetic structure formation, and then suggest the
+existence of an as-yet-unknown mechanism for the self-organization of the
+large-scale magnetic structure, which should be inherent in the
+strongly-stratified convective atmosphere.",1604.05374v1
+2016-05-13,Integrable magnetic geodesic flows on 2-torus: new example via quasi-linear system of PDEs,"The only one example has been known of magnetic geodesic flow on the 2-torus
+which has a polynomial in momenta integral independent of the Hamiltonian. In
+this example the integral is linear in momenta and corresponds to a one
+parametric group preserving the Lagrangian function of the magnetic flow. In
+this paper the problem of integrability on one energy level is considered. This
+problem can be reduced to a remarkable Semi-hamiltonian system of quasi-linear
+PDEs and to the question of existence of smooth periodic solutions for this
+system. Our main result states that the pair of Liouville metric with zero
+magnetic field on the 2-torus can be analytically deformed to a Riemannian
+metric with small magnetic field so that the magnetic geodesic flow on an
+energy level is integrable by means of a quadratic in momenta integral. Thus
+our construction gives a new example of smooth periodic solution to the
+Semi-hamiltonian (Rich) quasi-linear system of PDEs.",1605.04234v1
+2016-05-31,Correlation effects and orbital magnetism of Co clusters,"Recent experiments on isolated Co clusters have shown huge orbital magnetic
+moments in comparison with their bulk and surface counterparts. These clusters
+hence provide the unique possibility to study the evolution of the orbital
+magnetic moment with respect to the cluster size and how competing interactions
+contribute to the quenching of orbital magnetism. We investigate here different
+theoretical methods to calculate the spin and orbital moments of Co clusters,
+and assess the performances of the methods in comparison with experiments. It
+is shown that density functional theory in conventional local density or
+generalized gradient approximations, or even with a hybrid functional, severely
+underestimates the orbital moment. As natural extensions/corrections we
+considered the orbital polarization correction, the LDA+U approximation as well
+as the LDA+DMFT method. Our theory shows that of the considered methods, only
+the LDA+DMFT method provides orbital moments in agreement with experiment, thus
+emphasizing the importance of dynamic correlations effects for determining
+fundamental magnetic properties of magnets in the nano-size regime.",1605.09547v1
+2016-06-28,Magnetization switching of FePt nanoparticle recording medium by femtosecond laser pulses,"Manipulation of magnetization with ultrashort laser pulses is promising for
+information storage device applications. The dynamic of the magnetization
+response depends on the energy transfer from the photons to the spins during
+the initial laser excitation. A material of special interest for magnetic
+storage is FePt nanoparticles , on which optical writing with optical angular
+momentum was demonstrated recently by Lambert et al., although the mechanism
+remained unclear. Here we investigate experimentally and theoretically the
+all-optical switching of FePt nanoparticles. We show that the magnetization
+switching is a stochastic process. We develop a complete multiscale model which
+allows us to optimize the number of laser shots needed to write the
+magnetization of high anisotropy FePt nanoparticles in our experiments. We
+conclude that only angular momentum induced optically by the inverse Faraday
+effect will provide switching with one single femtosecond laser pulse.",1606.08723v1
+2016-07-22,Constraints on dynamo action in plasmas,"Upper bounds are derived on the amount of magnetic energy that can be
+generated by dynamo action in collisional and collisionless plasmas with and
+without external forcing. A hierarchy of mathematical descriptions is
+considered for the plasma dynamics: ideal MHD, visco-resistive MHD, the
+double-adiabatic theory of Chew, Goldberger and Low (CGL), kinetic MHD, and
+other kinetic models. It is found that dynamo action is greatly constrained in
+models where the magnetic moment of any particle species is conserved. In the
+absence of external forcing, the magnetic energy then remains small at all
+times if it is small in the initial state. In other words, a small ""seed""
+magnetic field cannot be amplified significantly, regardless of the nature of
+flow, as long as the collision frequency and gyroradius are small enough to be
+negligible. A similar conclusion also holds if the system is subject to
+external forcing as long as this forcing conserves the magnetic moment of at
+least one plasma species and does not greatly increase the total energy of the
+plasma (i.e., in practice, is subsonic). Dynamo action therefore always
+requires collisions or some small-scale kinetic mechanism for breaking the
+adiabatic invariance of the magnetic moment.",1607.06637v1
+2016-08-01,Magnetic relaxation phenomena in the Chiral Magnet Fe$_{1-x}$Co$_x$Si: An ac susceptibility study,"We present a systematic study of the ac susceptibility of the chiral magnet
+Fe$_{1-x}$Co$_x$Si with $x$ = 0.30 covering four orders of magnitude in
+frequencies from 0.1 Hz to 1 kHz, with particular emphasis to the pronounced
+history dependence. Characteristic relaxation times ranging from a few
+milliseconds to tens of seconds are observed around the skyrmion lattice
+A-phase, the helical-to-conical transition and in a region above $T_C$. The
+distribution of relaxation frequencies around the A-phase is broad, asymmetric
+and originates from multiple coexisting relaxation processes. The pronounced
+dependence of the magnetic phase diagram on the magnetic history and cooling
+rates as well as the asymmetric frequency dependence and slow dynamics suggest
+more complicated physical phenomena in Fe$_{0.7}$Co$_{0.3}$Si than in other
+chiral magnets.",1608.00404v2
+2016-08-02,Spin dynamics and magnetic interactions of Mn dopants in the topological insulator Bi$_2$Te$_3$,"The magnetic and electronic properties of the magnetically doped topological
+insulator Bi$_{\rm 2-x}$Mn$_{\rm x}$Te$_3$ were studied using electron spin
+resonance (ESR) and measurements of static magnetization and electrical
+transport. The investigated high quality single crystals of Bi$_{\rm
+2-x}$Mn$_{\rm x}$Te$_3$ show a ferromagnetic phase transition for $x\geq 0.04$
+at $T_{C}\approx 12$ K. The Hall measurements reveal a p-type finite
+charge-carrier density. Measurements of the temperature dependence of the ESR
+signal of Mn dopants for different orientations of the external magnetic field
+give evidence that the localized Mn moments interact with the mobile charge
+carriers leading to a Ruderman-Kittel-Kasuya-Yosida-type ferromagnetic coupling
+between the Mn spins of order 2-3 meV. Furthermore, ESR reveals a
+low-dimensional character of magnetic correlations that persist far above the
+ferromagnetic ordering temperature.",1608.00827v2
+2016-10-05,Magnetic reconnection: from MHD to QED,"The paper examines the prospects of using laser plasmas for studying novel
+regimes of the magnetic field line reconnection and charged particle
+acceleration. Basic features of plasma dynamics in the three-dimensional
+configurations relevant to the formation of current sheets in a plasma are
+addressed by analyzing exact self-similar solutions of the
+magneto-hydrodynamics and electron magneto-hydrodynamics equations. Then the
+magnetic field annihilation in the ultrarelativistic limit is considered, when
+the opposite polarity magnetic field is generated in collisionless plasma by
+multiple laser pulses, in the regime with a dominant contribution of the
+displacement current exciting a strong large-scale electric field. This field
+leads to the conversion of the magnetic energy into the kinetic energy of
+accelerated particles inside a thin current sheet. Charged particle
+acceleration during magnetic field reconnection is discussed when radiation
+friction and quantum electrodynamics effects become dominant.",1610.01873v4
+2016-11-19,Inverse Magnetic Catalysis from improved Holographic QCD in the Veneziano limit,"We study the dependence of the chiral condensate on external magnetic field
+in the context of holographic QCD at large number of flavors. We consider a
+holographic QCD model where the flavor degrees of freedom fully backreact on
+the color dynamics. Perturbative QCD calculations have shown that $B$ acts
+constructively on the chiral condensate, a phenomenon called ""magnetic
+catalysis"". In contrast, recent lattice calculations show that, depending on
+the number of flavors and temperature, the magnetic field may also act
+destructively, which is called ""inverse magnetic catalysis"". Here we show that
+the holographic theory is capable of both behaviors depending on the choice of
+parameters. For reasonable choice of the potentials entering the model we find
+qualitative agreement with the lattice expectations. Our results provide
+insight for the physical reasons behind the inverse magnetic catalysis. In
+particular, we argue that the backreaction of the flavors to the background
+geometry decatalyzes the condensate.",1611.06339v1
+2016-12-01,Magnetic field sensitivity and decoherence spectroscopy of an ensemble of narrow-linewidth nitrogen-vacancy centers close to a diamond surface,"We perform pulsed optically detected electron spin resonance to measure the
+DC magnetic field sensitivity and electronic spin coherence time T_2 of an
+ensemble of near-surface, high-density nitrogen-vacancy (NV) centers engineered
+to have a narrow magnetic resonance linewidth. Combining pulsed spectroscopy
+with dynamic nuclear polarization, we obtain the photon-shot-noise-limited DC
+magnetic sensitivity of 35 nT Hz^{-0.5}. We find that T_2 is controlled by
+instantaneous diffusion, enabling decoherence spectroscopy on residual nitrogen
+impurity spins in the diamond lattice and a quantitative determination of their
+density. The demonstrated high DC magnetic sensitivity and decoherence
+spectroscopy are expected to broaden the application range for two-dimensional
+magnetic imaging.",1612.00088v1
+2016-12-01,"A fast spinning magnetic white dwarf in the double-degenerate, super-Chandrasekhar system NLTT 12758","We present an analysis of the close double degenerate NLTT 12758, which is
+comprised of a magnetic white dwarf with a field of about 3.1 MG and an
+apparently non-magnetic white dwarf. We measured an orbital period of 1.154
+days and found that the magnetic white dwarf is spinning around its axis with a
+period of 23 minutes. An analysis of the atmospheric parameters has revealed
+that the cooling ages of the two white dwarfs are comparable, suggesting that
+they formed within a short period of time from each other. Our modelling
+indicates that the non-magnetic white dwarf is more massive (M=0.83 M_sun) than
+its magnetic companion (M=0.69 M_sun) and that the total mass of the system is
+higher than the Chandrasekhar mass. Although the stars will not come into
+contact over a Hubble time, when they do come into contact, dynamically
+unstable mass transfer will take place leading to either an accretion induced
+collapse into a rapidly spinning neutron star or a Type Ia supernova.",1612.00325v1
+2016-12-16,Origin of doping-induced suppression and reemergence of magnetism in LaFeAsO$_{1-x}$H$_x$,"We investigate the evolution of magnetic properties as a function of hydrogen
+doping in iron based superconductor LaFeAsO$_{1-x}$H$_x$ using the dynamical
+mean-field theory combined with the density-functional theory. We find that two
+independent consequences of the doping, the increase of the electron occupation
+and the structural modification, have the opposite effects on the strength of
+electron correlation and magnetism, resulting in the minimum of the calculated
+magnetic moment around the intermediate doping level as a function of $x$. Our
+result provides a natural explanation for the puzzling recent experimental
+discovery of the two separated antiferromagnetic phases at low and high doping
+limits. Furthermore, the increase of orbital occupation and correlation
+strength with the doping results in reduced orbital polarization of $d_{xz/yz}$
+orbitals and the enhanced role of $d_{xy}$ orbital in the magnetism at high
+doping levels, and their possible implications to the superconductivity are
+discussed in line with the essential role of the magnetism.",1612.05520v1
+2016-12-19,Carrier localization due to local magnetic order induced by magnetic impurities in Ba(Fe$_{1-x}$TM$_x$)$_2$As$_2$ (TM = Mn and Cr) as seen via optical spectra,"The charge dynamics of Ba(Fe$_{1-x}$TM$_x$)$_2$As$_2$ (TM = Mn and Cr) has
+been investigated by optical spectroscopy. It was found that in addition to the
+strong suppression of the coherent charge transport, the magnetic impurity
+induces a novel spectral feature related to the carrier localization in the
+far-infrared region above the antiferromagnetic transition temperature. We
+attribute it to the cooperative effect between conduction electrons and local
+magnetic order induced by magnetic impurities. The present results demonstrate
+that Mn and Cr are not conventional magnetic pair-breakers in iron pnictides.",1612.06234v1
+2017-01-09,"Static and Dynamic Magnetic Properties of Spin-1/2 Inequilateral Diamond-Chain Compounds $A_3$Cu$_3$AlO$_2$(SO$_4$)$_4$ ($A$=K, Rb, and Cs)","Spin-1/2 compounds A3Cu3AlO2(SO4)4 (A=K, Rb, and Cs) have one-dimensional
+(1D) inequilateral diamond chains. We analyze the temperature dependence of the
+magnetic susceptibility and determine the magnetic exchange interactions. In
+contrast to the azurite, a dimer is formed on one of the sides of the diamond.
+From numerical analyses of the proposed model, we find that the dimer together
+with a nearly isolated 1D Heisenberg chain characterizes magnetic properties
+including magnetization curve and magnetic excitations. This implies that a
+dimer-monomer composite chain without frustration is a good starting point for
+describing these compounds.",1701.02198v3
+2017-02-09,Magnetic charge injection in spin ice: a new way to fragmentation,"The complexity embedded in condensed matter fertilizes the discovery of new
+states of matter, enriched by ingredients like frustration. Illustrating
+examples in magnetic systems are Kitaev spin liquids, skyrmions phases, or spin
+ices. These unconventional ground states support exotic excitations, for
+example the magnetic charges in spin ices, also called monopoles. Beyond their
+discovery, an important challenge is to be able to control and manipulate them.
+Here, we propose a new mechanism to inject monopoles in a spin ice through a
+staggered magnetic field. We show theoretically, and demonstrate experimentally
+in the Ho$_2$Ir$_2$O$_7$ pyrochlore iridate, that it results in the
+stabilization of a monopole crystal, which exhibits magnetic fragmentation. In
+this new state of matter, the magnetic moment fragments into an ordered part
+and a persistently fluctuating one. Compared to conventional spin ices, the
+different nature of the excitations in this fragmented state opens the way to
+novel tunable field-induced and dynamical behaviors.",1702.02864v1
+2017-02-13,"Coexistence of localized and itinerant magnetism in intercalated iron-selenide (Li,Fe)OHFeSe","The electronic structure and magnetism of a new magnetic intercalation
+compound (Li0.8Fe0.2)OHFeSe are investigated theoretically. The electronic
+structure calculations predict that the Fe in the (Li,Fe)OH intercalated layer
+is in +2 valence state, i.e. there is electron doping to the FeSe layer,
+resulting in the shrinking of the Fermi surface (FS) pocket around Gamma and a
+strong suppression of dynamical spin susceptibility at M in comparison with the
+bulk FeSe compound. The ground state of the FeSe layer is a striped
+antiferromagnetic (SAFM) metal, while the (Li,Fe)OH layer displays a very weak
+localized magnetism, with an interlayer ferromagnetic (FM) coupling between the
+FeSe and intercalated (Li,Fe)OH layers. Moreover, the (Li,Fe)OH is more than a
+block layer; it is responsible for enhancing the antiferromagnetic (AFM)
+correlation in the FeSe layer through interlayer magnetic coupling. We propose
+that the magnetic spacer layer introduces a tuning mechanism for spin
+fluctuations associated with superconductivity in iron-based superconductors.",1702.03845v1
+2017-02-13,Atomic-Scale Magnetometry of Dynamic Magnetization,"The spatial resolution of imaging magnetometers has benefited from scanning
+probe techniques. The requirement that the sample perturbs the scanning probe
+through a magnetic field external to its volume limits magnetometry to samples
+with pre-existing magnetization. We propose a magnetometer in which the
+perturbation is reversed: the probe's magnetic field generates a response of
+the sample, which acts back on the probe and changes its energy. For an NV$^-$
+spin center in diamond this perturbation changes the fine-structure splitting
+of the spin ground state. Sensitive measurement techniques using coherent
+detection schemes then permit detection of the magnetic response of
+paramagnetic and diamagnetic materials. This technique can measure the
+thickness of magnetically dead layers with better than $0.1$ \AA$~$accuracy.",1702.03863v1
+2017-03-27,Spin transfer due to quantum fluctuations of magnetization,"Spin transfer - the transfer of angular momentum from spin-polarized
+electrical current to magnetic materials - has been extensively researched as
+an efficient mechanism for the electronic manipulation of the static and
+dynamic states in nanomagnetic systems, advancing our understanding of
+nanomagnetism and electronic transport, and enabling the development of
+energy-efficient magnetic nanodevices. Our present understanding of spin
+transfer is based on the classical approximation for the magnetization, even
+though the spin-polarized electrons mediating spin transfer are treated
+quantum-mechanically. Here, we utilize a nanoscale magnetic spin-valve
+structure to demonstrate that quantum zero-point fluctuations of magnetization,
+neglected in the existing theories of spin transfer, provide the dominant
+contribution to this effect at cryogenic temperatures, and remain
+non-negligible even at room temperature. The demonstrated quantum spin transfer
+(QST) is distinguished by a non-smooth piecewise-linear dependence of the
+fluctuation intensity on current, and can be driven not only by the directional
+flows of electrons, but also by their thermal motion. This effect can enhance
+current-induced phenomena, overcoming the efficiency limitations that are
+presently perceived as fundamental to the spin transfer mechanism.",1703.09335v2
+2017-04-21,Distribution of eigenstate populations and dissipative beating dynamics in uniaxial single-spin magnets,"Numerical simulations of magnetization reversal of a quantum uniaxial magnet
+under a swept magnetic field [Hatomura, \textit{et al}., \textit{Quantum
+Stoner-Wohlfarth Model}, Phys. Rev. Lett. \textbf{116}, 037203 (2016)] are
+extended. In particular, how the ""wave packet"" describing the time-evolution of
+the system is scattered in the successive avoided level crossings is
+investigated from the viewpoint of the distribution of the eigenstate
+populations. It is found that the peak of the distribution as a function of the
+magnetic field does not depend on spin-size $S$, which indicates that the delay
+of magnetization reversal due to the finite sweeping rate is the same in both
+the quantum and classical cases. The peculiar synchronized oscillations of all
+the spin components result in the beating of the spin-length. Here, dissipative
+effects on this beating are studied by making use of the generalized
+Lindblad-type master equation. The corresponding experimental situations are
+also discussed in order to find conditions for experimental observations.",1704.06466v1
+2017-04-21,"Interplay between particle microstructure, network topology and sample shape in magnetic gels -- A molecular dynamics simulation study","Ferrogels, i.e., hydrogels loaded with magnetic nanoparticles, have the
+ability to deform in external magnetic fields. The precise shape of deformation
+and the alignment of the gel in the field, however, depend on the interplay of
+several factors. In this paper, we introduce a coarse-grained simulation model,
+which takes into account the configuration of magnetic particles in the gel,
+the sample shape, and aspects of the polymer network topology. We use this
+model to show that in gels with an isotropic microstructure, an external
+magnetic field reduces clustering, while this is not the case for uniaxial
+gels, in which the particle configuration is anisotropic due to the presence of
+a magnetic field during cross-linking. For ellipsoidal gels, we find that a
+uniaxial microstructure additionally can override the deformation and alignment
+expected as indicated the demagnetization energy. Finally, we examine to what
+degree gels with different network topologies maintain the particle
+microstructure ``frozen in`` during the cross-linking process.",1704.06578v1
+2017-04-26,Sunspots rotation and magnetic transients associated with flares in NOAA AR 11429,"We analyze sunspots rotation and magnetic transients in NOAA AR 11429 during
+two X-class (X5.4 and X1.3) flares using the data from the Helioseismic and
+Magnetic Imager on board the \emph{Solar Dynamics Observatory}. A large leading
+sunspot with positive magnetic polarity rotated counterclockwise. As expected,
+the rotation was significantly affected by the two flares. The magnetic
+transients induced by the flares were clearly evident in the sunspots with
+negative polarity. They were moving across the sunspots with speed of order
+$3-7\ \rm km \ s^{-1}$. Furthermore, the trend of magnetic flux evolution of
+these sunspots exhibited changes associated with the flares. These results may
+shed light on the understanding of the evolution of sunspots.",1704.08018v2
+2017-07-03,Heavy-mass magnetic modes in pyrochlore iridates due to dominant Dzyaloshinskii-Moriya interaction,"Materials with strong spin-orbit interactions are presently a main target in
+the search for systems with novel magnetic properties. Magnetic anisotropies
+can be very large in such compounds, ranging from strongly frustrated Kitaev
+exchange in honeycomb iridates and the associated spin-liquid states to robust
+antisymmetric couplings in square-lattice Sr_2IrO_4 . Here we predict from ab
+initio quantum chemistry calculations that another highly unusual regime is
+realized in pyrochlore iridium oxides: the nearest-neighbor Heisenberg
+interaction can vanish whilst the antisymmetric Dzyaloshinskii- Moriya exchange
+reaches values as large as 5 meV, a result which challenges common notions and
+existing phenomenological models of magnetic superexchange. The resulting spin
+excitation spectra reveal a very flat magnon dispersion in the Nd- and Tb-based
+pyrochlore iridates, suggesting the possibility of using these modes to store
+magnetic information. Indeed the magnetization dynamics indicates that these
+modes are unable to propagate out of the excitation region.",1707.00500v1
+2017-07-11,Spin switching via quantum dot spin valves,"We develop a theory for spin transport and magnetization dynamics in a
+quantum-dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot.
+Our theory is able to take into account effects of strong correlations. We
+demonstrate that, as a result of these strong correlations, the dot gate
+voltage enables control over the current-induced torques on the magnets, and,
+in particular, enables voltage-controlled magnetic switching. The electrical
+resistance of the structure can be used to read out the magnetic state. Our
+model may be realized by a number of experimental systems, including magnetic
+scanning-tunneling microscope tips and artificial quantum dot systems.",1707.03373v4
+2017-07-21,Decay Rate of Magnetic Dipoles near Non-magnetic Nanostructures,"In this article, we propose a concise theoretical framework based on mixed
+field-susceptibilities to describe the decay of magnetic dipoles induced by
+non--magnetic nanostructures. This approach is first illustrated in simple
+cases in which analytical expressions of the decay rate can be obtained. We
+then show that a more refined numerical implementation of this formalism
+involving a volume discretization and the computation of a generalized
+propagator can predict the dynamics of magnetic dipoles in the vicinity of
+nanostructures of arbitrary geometries. We finally demonstrate the versatility
+of this numerical method by coupling it to an evolutionary optimization
+algorithm. In this way we predict a structure geometry which maximally promotes
+the decay of magnetic transitions with respect to electric emitters.",1707.07006v3
+2017-09-18,Skyrmion morphology in ultrathin magnetic films,"Nitrogen-vacancy magnetic microscopy is employed in quenching mode as a
+non-invasive, high resolution tool to investigate the morphology of isolated
+skyrmions in ultrathin magnetic films. The skyrmion size and shape are found to
+be strongly affected by local pinning effects and magnetic field history.
+Micromagnetic simulations including static disorder, based on a physical model
+of grain-to-grain thickness variations, reproduce all experimental observations
+and reveal the key role of disorder and magnetic history in the stabilization
+of skyrmions in ultrathin magnetic films. This work opens the way to an
+in-depth understanding of skyrmion dynamics in real, disordered media.",1709.06027v2
+2017-09-22,A Co(II)-based Molecular Magnet with a 6 T Coercive Field,"Hard magnets with high coercivity, such as Nd2Fe14B and SmCo5 alloys, can
+maintain magnetisation under a high reverse external magnetic field and have
+therefore become irreplaceable parts in many practical applications. Molecular
+magnets are promising alternatives, owing to their precise and designable
+chemical structures, tuneable functionalities and controllable synthetic
+methods. Here, we demonstrate that an unusually large coercive field can be
+achieved in a single-chain magnet. Systematic characterisations, including
+magnetic susceptibility, heat capacity and neutron diffraction measurements,
+show that the observed giant coercive field originates from the spin dynamics
+along the one-dimensional chain of the compound because of the strong exchange
+coupling between Co(II) centres and radicals.",1709.07697v2
+2017-10-05,Actuated rheology of magnetic micro-swimmers suspensions : emergence of motor and brake states,"We study the effect of magnetic field on the rheology of magnetic
+micro-swimmers suspensions. We use a model of a dilute suspension under simple
+shear and subjected to a constant magnetic field. Particle shear stress is
+obtained for both pusher and puller types of micro-swimmers. In the limit of
+low shear rate, the rheology exhibits a constant shear stress, called actuated
+stress, which only depends on the swimming activity of the particles. This
+stress is induced by the magnetic field and can be positive (brake state) or
+negative (motor state). In the limit of low magnetic fields, a scaling relation
+of the motor-brake effect is derived as a function of the dimensionless
+parameters of the model. In this case, the shear stress is an affine function
+of the shear rate. The possibilities offered by such an active system to
+control the rheological response of a uid are finally discussed.",1710.01954v2
+2017-10-17,"Fast, low-current spin-orbit torque switching of magnetic tunnel junctions through atomic modifications of the free layer interfaces","Future applications of spin-orbit torque will require new mechanisms to
+improve the efficiency for switching nanoscale magnetic tunnel junctions
+(MTJs), while also controlling the magnetic dynamics to achieve fast,
+nanosecond scale performance with low write error rates. Here we demonstrate a
+strategy to simultaneously enhance the interfacial magnetic anisotropy energy
+and suppress interfacial spin memory loss by introducing sub-atomic and
+monatomic layers of Hf at the top and bottom interfaces of the ferromagnetic
+free layer of an in-plane magnetized three-terminal MTJ device. When combined
+with a beta-W spin Hall channel that generates spin-orbit torque, the
+cumulative effect is a switching current density of 5.4 x 106 A/cm2, more than
+a factor of 3 lower than demonstrated in any other spin-orbit-torque magnetic
+memory device at room temperature, and highly reliable switching with current
+pulses only 2 ns long.",1710.06391v1
+2017-12-11,Transition to turbulent dynamo saturation,"While the saturated magnetic energy is independent of viscosity in dynamo
+experiments, it remains viscosity-dependent in state-of-the-art 3D direct
+numerical simulations (DNS). Extrapolating such viscous scaling-laws to
+realistic parameter values leads to an underestimation of the magnetic energy
+by several orders of magnitude. The origin of this discrepancy is that fully 3D
+DNS cannot reach low enough values of the magnetic Prandtl number $Pm$. To
+bypass this limitation and investigate dynamo saturation at very low $Pm$, we
+focus on the vicinity of the dynamo threshold in a rapidly rotating flow: the
+velocity field then depends on two spatial coordinates only, while the magnetic
+field consists of a single Fourier mode in the third direction. We perform
+numerical simulations of the resulting set of reduced equations for $Pm$ down
+to $2\cdot 10^{-5}$. This parameter regime is currently out of reach to fully
+3D DNS. We show that the magnetic energy transitions from a high-$Pm$ viscous
+scaling regime to a low-$Pm$ turbulent scaling regime, the latter being
+independent of viscosity. The transition to the turbulent saturation regime
+occurs at a low value of the magnetic Prandtl number, $Pm \simeq 10^{-3}$,
+which explains why it has been overlooked by numerical studies so far.",1712.03787v1
+2018-01-09,Influence of image forces on the interlayer exchange interaction in magnetic tunnel junctions with ferroelectric barrier,"We study interlayer exchange interaction in magnetic tunnel junctions with
+ferroelectric barrier. We focus on the influence of image forces on the voltage
+dependence of the interlayer magnetic interaction (magneto-electric effect).
+The influence of the image forces is twofold: 1) they significantly enforce
+magneto-electric effect occurring due to the surface charges at the interface
+between ferroelectric and ferromagnets; 2) in combination with voltage
+dependent dielectric constant of the ferroelectric barrier image forces cause
+an additional contribution to the magneto-electric effect in magnetic tunnel
+junctions. This contribution can exceed the one coming from surface charges. We
+compare the interlayer exchange coupling voltage variation with spin transfer
+torque effect and show that for half-metallic electrodes the interlayer
+exchange coupling variation is dominant and defines the magnetic state and
+dynamics of magnetization in the tunnel junction.",1801.03113v1
+2018-01-23,Correlation between Magnetic Properties and Depinning Field in Field-Driven Domain Wall Dynamics in GdFeCo Ferrimagnets,"The influence of temperature on the magnetic-field-driven domain wall (DW)
+motion is investigated in GdFeCo ferrimagnets with perpendicular magnetic
+anisotropy (PMA). We find that the depinning field strongly depends on
+temperature. Moreover, it is also found that the saturation magnetization
+exhibits a similar dependence on temperature to that of depinning field. From
+the creep-scaling criticality, a simple relation between the depinning field
+and the properties of PMA is clearly identified theoretically as well as
+experimentally. Our findings open a way for a better understanding how the
+magnetic properties influence on the depinning field in magnetic system and
+would be valuably extended to depinning studies in other system.",1801.07436v1
+2018-02-26,Small-scale dynamos in simulations of stratified turbulent convection,"Small-scale dynamo action is often held responsible for the generation of
+quiet-Sun magnetic fields. We aim to determine the excitation conditions and
+saturation level of small-scale dynamos in non-rotating turbulent convection at
+low magnetic Prandtl numbers. We use high resolution direct numerical
+simulations of weakly stratified turbulent convection. We find that the
+critical magnetic Reynolds number for dynamo excitation increases as the
+magnetic Prandtl number is decreased, which might suggest that small-scale
+dynamo action is not automatically evident in bodies with small magnetic
+Prandtl numbers as the Sun. As a function of the magnetic Reynolds number
+(${\rm Rm}$), the growth rate of the dynamo is consistent with an ${\rm
+Rm}^{1/2}$ scaling. No evidence for a logarithmic increase of the growth rate
+with ${\rm Rm}$ is found.",1802.09607v1
+2018-03-04,Optimization of Time-Resolved Magneto-optical Kerr Effect Signals for Magnetization Dynamics Measurements,"Recently magnetic storage and magnetic memory have shifted towards the use of
+magnetic thin films with perpendicular magnetic anisotropy (PMA). Understanding
+the magnetic damping in these materials is crucial, but normal Ferromagnetic
+Resonance (FMR) measurements face some limitations. The desire to quantify the
+damping in materials with PMA has resulted in the adoption of Time-Resolved
+Magneto-optical Kerr Effect (TR-MOKE) measurements. In this paper, we discuss
+the angle and field dependent signals in TR-MOKE, and utilize a numerical
+algorithm based on the Landau-Lifshitz-Gilbert (LLG) equation to provide
+information on the optimal conditions to run TR-MOKE measurements.",1803.01280v2
+2018-03-09,Laboratory experiments on dynamo action and magnetically triggered flow instabilities,"Magnetic fields of planets, stars and galaxies are generated by
+self-excitation in moving electrically conducting fluids. Once produced,
+magnetic fields can play an active role in cosmic structure formation by
+destabilizing rotational flows that would be otherwise hydrodynamically stable.
+For a long time, both hydromagnetic dynamo action as well as magnetically
+triggered flow instabilities had been the subject of purely theoretical
+research. Meanwhile, however, the dynamo effect has been observed in
+large-scale liquid sodium experiments in Riga, Karlsruhe and Cadarache. In this
+paper, we summarize the results of liquid metal experiments devoted to the
+dynamo effect and various magnetic instabilities such as the helical and the
+azimuthal magnetorotational instability and the Tayler instability. We discuss
+in detail our plans for a precession-driven dynamo experiment and a large-scale
+Tayler-Couette experiment using liquid sodium, and on the prospects to observe
+magnetically triggered instabilities of flows with positive shear.",1803.03421v1
+2018-03-19,Vegas: Software package for the atomistic simulation of magnetic materials,"We present an open-source software package, Vegas, for the atomistic
+simulation of magnetic materials. Using the classical Heisenberg model and the
+Monte Carlo Metropolis algorithm, Vegas provides the required tools to simulate
+and analyze magnetic phenomena of a great variety of systems. Vegas stores the
+history of the simulation, i.e. the magnetization and energy of the system at
+every time step, allowing to analyze static and dynamic magnetic phenomena from
+results obtained in a single simulation. Also, standardized input and output
+file formats are employed to facilitate the simulation process and the exchange
+and archiving of data. We include results from simulations performed using
+Vegas, showing its applicability to study different magnetic phenomena.",1803.07030v1
+2018-04-10,Magnetometric Mapping of Superconducting RF Cavities,"A scalable mapping system for superconducting RF cavities is presented.
+Currently, it combines local temperature measurement with 3D magnetic field
+mapping along the outer surface of the resonator. This allows for the
+observation of dynamic effects that have an impact on the superconducting
+properties of a cavity, such as the normal to superconducting phase transition
+or a quench. The system was developed for a single cell 1.3 GHz TESLA-type
+cavity, but can be easily adopted to arbitrary other cavity types. A data
+acquisition rate of 500 Hz for all channels simultaneously (i.e.2ms)
+acquisition time for a complete map) and a magnetic field resolution of
+currently up to 14 mA/m/mu0 = 17 nT has been implemented. While temperature
+mapping is a well known technique in SRF research, the integration of magnetic
+field mapping opens the possibility of detailed studies of trapped magnetic
+flux and its impact on the surface resistance. It is shown that magnetic field
+sensors based on the anisotropic magnetoresistance (AMR) effect can be used in
+the cryogenic environment with improved sensitivity compared to room
+temperature. Furthermore, examples of first successful combined temperature and
+magnetic-field maps are presented.",1804.03445v1
+2018-05-07,Phase dynamics of oscillating magnetizations coupled via spin pumping,"A theoretical formalism is developed to simultaneously solve equation of
+motion of the magnetizations in two ferromagnets and the spin-pumping induced
+spin transport equation. Based on the formalism, a coupled motion of the
+magnetizations in a self-oscillation state is studied. The spin pumping is
+found to induce an in-phase synchronization of the magnetizations for the
+oscillation around the easy axis. For an out-of-plane self-oscillation around
+the hard axis, on the other hand, the spin pumping leads to an in-phase
+synchronization in a small current region, whereas an antiphase synchronization
+is excited in a large current region. An analytical theory based on the phase
+equation reveals that the phase difference between the magnetizations in a
+steady state depends on the oscillation direction, clockwise or
+counterclockwise, of the magnetizations.",1805.02766v1
+2018-05-12,"Computational modeling of magnetoconvection: effects of discretization method, grid refinement and grid stretching","The problem of natural convection in a laterally heated three-dimensional
+cubic cavity under the action of an externally imposed magnetic field is
+revisited. Flows at the Rayleigh number Ra=10^6 and the Hartmann number Ha=100,
+and three different orientations of the magnetic field are considered. The
+problem is solved using two independent numerical methods based on the second
+order finite-volume discretization schemes on structured Cartesian grids.
+Convergence toward grid-independent results is examined versus the grid
+refinement and near-wall grid stretching. Converged benchmark-quality results
+are obtained. It is shown that for convection flows with a strong magnetic
+field a steep, sometimes extremely steep, stretching near some of the
+boundaries is needed. Three-dimensional patterns and integral properties of the
+converged flow fields are reported and discussed. It is shown that the
+strongest magnetic suppression is yielded by the field directed along the
+imposed temperature gradient. The horizontal magnetic field perpendicular to
+the imposed temperature gradient stabilizes the main convection roll and leads
+to a flow with higher kinetic energy and heat transfer rate than in the
+non-magnetic case. Applicability of the quasi-two-dimensional model to natural
+convection flows in a box is discussed.",1805.04710v1
+2018-05-15,Control of phase of the magnetization precession excited by circularly polarized fs-laser pulses,"The inverse Faraday effect induced in magnetic films by ultrashort laser
+pulses allows excitation and control of spins at GHz and sub-THz frequencies.
+Frequency of the excited magnetization precession is easily tunable by the
+external magnetic field. On the other hand, phase of the precession hardly
+depends on magnetic field. Here we demonstrate an approach for the control of
+the precession phase by variation of the incidence angle of the laser pulses.
+In particular, theoretical consideration states that the phase increases with
+increase of the incidence angle and for small angles this relation is a direct
+proportionality. Experimental studies confirm this conclusion and provide shift
+of phase by about 4 deg. for the declination of the incidence angle by 15 deg.
+from the normal. This study provides a simple way for additional manipulation
+with optically excited magnetization dynamics, which is of importance for
+different spintronic applications.",1805.05936v1
+2018-06-07,Magnetic domain walls as broadband spin wave and elastic magnetisation wave emitters,"We report on the direct observation of spin wave and elastic wave emission
+from magnetic domain walls in ferromagnetic thin films. Driven by alternating
+homogeneous magnetic fields the magnetic domain walls act as coherent
+magnetisation wave sources. Directional and low damped elastic waves below and
+above the ferromagnetic resonance are excited. The wave vector of the
+magnetoelastically induced acoustic shear waves is linearly tuned by varying
+the excitation frequency. Domain wall emitted magnetostatic surface spin waves
+occur at higher frequencies, which characteristics are confirmed by
+micromagnetic simulations. The distinct modes of magnetisation wave excitation
+from micromagnetic objects are a general physical phenomenon relevant for
+dynamic magnetisation processes in structured magnetic films. Magnetic domain
+walls can act as reconfigurable antennas for spin wave and elastic wave
+generation with control of the wave orientation.",1806.02646v1
+2018-06-08,Metachronal motion of artificial magnetic cilia,"Organisms use hair-like cilia that beat in a metachronal fashion to actively
+transport fluid and suspended particles. Metachronal motion emerges due to a
+phase difference between beating cycles of neighboring cilia and appears as
+traveling waves propagating along ciliary carpet. In this work, we demonstrate
+biomimetic artificial cilia capable of metachronal motion. The cilia are
+micromachined magnetic thin filaments attached at one end to a substrate and
+actuated by a uniform rotating magnetic field. We show that the difference in
+magnetic cilium length controls the phase of the beating motion. We use this
+property to induce metachronal waves within a ciliary array and explore the
+effect of operation parameters on the wave motion. The metachronal motion in
+our artificial system is shown to depend on the magnetic and elastic properties
+of the filaments, unlike natural cilia, where metachronal motion arises due to
+fluid coupling. Our approach enables an easy integration of metachronal
+magnetic cilia in lab-on-a-chip devices for enhanced fluid and particle
+manipulations.",1806.03363v1
+2018-06-14,Magnetic inhomogeneity in the copper pseudochalcogenide CuNCN,"Copper carbodiimide, CuNCN, is a geometrically frustrated nitrogen-based
+analogue of cupric oxide, whose magnetism remains ambiguous. Here, we employ a
+combination of local-probe techniques, including $^{63,\, 65}$Cu nuclear
+quadrupole resonance, $^{13}$C nuclear magnetic resonance and muon spin
+rotation to show that the magnetic ground state of the Cu$^{2+}$ ($S=1/2$)
+spins is frozen and disordered. Moreover, these complementary experiments
+unequivocally establish an onset of intrinsically inhomogeneous magnetic state
+at $T_h=80$ K. Below $T_h$, the low-temperature frozen component coexist with
+the remnant high-temperature dynamical component down to $T_l = 20$ K, where
+the latter finally ceases to exist. Based on a scaling of internal magnetic
+fields of both components we conclude that the two components coexist on a
+microscopic level.",1806.05486v2
+2018-06-27,Site-selective Probe of Magnetic Excitations in Rare-earth Nickelates using Resonant Inelastic X-ray Scattering,"We have used high-resolution resonant inelastic x-ray scattering (RIXS) to
+study a thin film of NdNiO$_3$, a compound whose unusual spin- and bond-ordered
+electronic ground state has been of long-standing interest. Below the magnetic
+ordering temperature, we observe well-defined collective magnon excitations
+along different high-symmetry directions in momentum space. The magnetic
+spectra depend strongly on the incident photon energy, which we attribute to
+RIXS coupling to different local electronic configurations of the expanded and
+compressed NiO$_6$ octahedra in the bond-ordered state. Both the noncollinear
+magnetic ground state and the observed site-dependent magnon excitations are
+well described by a model that assumes strong competition between the
+antiferromagnetic superexchange and ferromagnetic double-exchange interactions.
+Our study provides direct insight into the magnetic dynamics and exchange
+interactions of the rare-earth nickelates, and demonstrates that RIXS can serve
+as a site-selective probe of magnetism in these and other materials.",1806.10499v1
+2018-07-04,Effects of a strong magnetic field on the QCD flux tube,"In this work we investigate the effect of an external magnetic field B on the
+shape of flux tubes in QCD by means of lattice simulations, performed with
+N_f=2+1 flavors of stout improved dynamical staggered quarks with physical
+masses. After having discussed some difficulties in the practical definition of
+the flux tube at B=0, we show that these ambiguities do not affect the
+determination of the flux tube modifications induced by the magnetic field.
+Different results are obtained depending on the relative orientations of the
+flux tube and of the magnetic field: they confirm that the magnetic field acts
+as transverse confinement catalyser and longitudinal confinement inhibitor;
+moreover, the flux tube itself loses its axial symmetry when it is not directed
+along the magnetic background.",1807.01673v2
+2018-09-26,Cavity Optomechanics of Topological Spin Textures in Magnetic Insulators,"Collective dynamics of topological magnetic textures can be thought of as a
+massive particle moving in a magnetic pinning potential. We demonstrate that
+inside a cavity resonator this effective mechanical system can feel the
+electromagnetic radiation pressure from cavity photons through the
+magneto-optical inverse Faraday and Cotton-Mouton effects. We estimate values
+for the effective parameters of the optomechanical coupling for two spin
+textures -- a Bloch domain wall and a chiral magnetic soliton lattice. The
+soliton lattice has magnetic chirality, so that in circularly polarized light
+it behaves like a chiral particle with the sign of the optomechanical coupling
+determined by the helicity of the light and chirality of the lattice. Most
+interestingly, we find a level attraction regime for the soliton lattice, which
+is tunable through an applied magnetic field.",1809.10091v2
+2018-10-05,Ultrafast demagnetization of Pt magnetic moment in L1${}_0$-FePt probed by hard x-ray free electron laser,"We demonstrate ultrafast magnetization dynamics in a 5d transition metal
+using circularly-polarized x-ray free electron laser in the hard x-ray region.
+A decay time of light-induced demagnetization of L1${}_0$-FePt was determined
+to be $\tau_\textrm{Pt} = 0.6\ \textrm{ps}$ using time-resolved x-ray magnetic
+circular dichroism at the Pt L${}_3$ edge, whereas magneto-optical Kerr
+measurements indicated the decay time for total magnetization as
+$\tau_\textrm{total} = 0.1\ \textrm{ps}$. A transient magnetic state with the
+photo-modulated magnetic coupling between the 3d and 5d elements is firstly
+demonstrated.",1810.02551v1
+2018-10-30,Magnetic field sensing with the kinetic inductance of a high-$T_\mathrm{c}$ superconductor,"We carry out an experimental feasibility study of a magnetic field sensor
+based on the kinetic inductance of the high-$T_\mathrm{c}$ superconductor
+yttrium barium copper oxide. We pattern thin superconducting films into
+radio-frequency resonators that feature a magnetic field pick-up loop. At 77 K
+and for film thicknesses down to 75 nm, we observe the persistence of screening
+currents that modulate the loop kinetic inductance. According to the
+experimental results the device concept appears attractive for sensing
+applications in ambient magnetic field environments. We report on a device with
+a magnetic field sensitivity of 4 pT/Hz${}^{1/2}$, an instantaneous dynamic
+range of 11 $\mu$T, and operability in magnetic fields up to 28 $\mu$T.",1810.12725v1
+2018-11-29,Magneto-immutable turbulence in weakly collisional plasmas,"We propose that pressure anisotropy causes weakly collisional turbulent
+plasmas to self-organize so as to resist changes in magnetic-field strength. We
+term this effect ""magneto-immutability"" by analogy with incompressibility
+(resistance to changes in pressure). The effect is important when the pressure
+anisotropy becomes comparable to the magnetic pressure, suggesting that in
+collisionless, weakly magnetized (high-$\beta$) plasmas its dynamical relevance
+is similar to that of incompressibility. Simulations of magnetized turbulence
+using the weakly collisional Braginskii model show that magneto-immutable
+turbulence is surprisingly similar, in most statistical measures, to critically
+balanced MHD turbulence. However, in order to minimize magnetic-field
+variation, the flow direction becomes more constrained than in MHD, and the
+turbulence is more strongly dominated by magnetic energy (a nonzero ""residual
+energy""). These effects represent key differences between pressure-anisotropic
+and fluid turbulence, and should be observable in the $\beta\gtrsim1$ turbulent
+solar wind.",1811.12421v2
+2018-12-26,Time evolution of rotating and magnetized white dwarf stars,"We investigate the evolution of isolated, zero and finite temperature,
+massive, uniformly rotating and highly magnetized white dwarf stars under
+angular momentum loss driven by magnetic dipole braking. We consider the
+structure and thermal evolution of white dwarf isothermal cores taking also
+into account the nuclear burning and neutrino emission processes. We estimate
+the white dwarf lifetime before it reaches the condition either for a type Ia
+supernova explosion or for the gravitational collapse to a neutron star. We
+study white dwarfs with surface magnetic fields from $10^6$ to $10^{9}$~G and
+masses from $1.39$ to $1.46~M_\odot$ and analyze the behavior of the white
+dwarf parameters such as moment of inertia, angular momentum, central
+temperature and magnetic field intensity as a function of lifetime. The
+magnetic field is involved only to slow down white dwarfs, without affecting
+their equation of state and structure. In addition, we compute the
+characteristic time of nuclear reactions and dynamical time scale. The
+astrophysical consequences of the results are discussed.",1812.10543v3
+2019-01-22,Magnetic helicity and fluxes in an inhomogeneous alpha squared dynamo,"Much work on turbulent three-dimensional dynamos has been done using triply
+periodic domains, in which there are no magnetic helicity fluxes. Here we
+present simulations where the turbulent intensity is still nearly homogeneous,
+but now there is a perfect conductor boundary condition on one end and a
+vertical field or pseudo-vacuum condition on the other. This leads to migratory
+dynamo waves. Good agreement with a corresponding analytically solvable alpha^2
+dynamo is found. Magnetic helicity fluxes are studied in both types of models.
+It is found that at moderate magnetic Reynolds numbers, most of the magnetic
+helicity losses occur at large scales. Whether this changes at even larger
+magnetic Reynolds numbers, as required for alleviating the catastrophic dynamo
+quenching problem, remains still unclear.",1901.07552v2
+2019-02-19,Spin-wave mediated interactions for Majority Computation using Skyrmions and Spin-torque Nano-oscillators,"Recent progress in all-electrical nucleation, detection and manipulation of
+magnetic skyrmions has unlocked the tremendous potential of skyrmion-based
+spintronic devices. Here, we show via micromagnetic simulations that the stable
+magnetic oscillations of STNO radiate spin waves (SWs) that can be scattered in
+the presence of skyrmions in the near vicinity. Interference between SWs
+emitted by the STNO and SWs scattered by the skyrmion gives rise to interesting
+dynamics that leads to amplification or attenuation of STNO's magnetic
+oscillations. In the presence of strong Dzyaloshinskii-Moriya interaction
+(DMI), the amplified magnetic oscillations evolve into a new skyrmion. These
+interactions between skyrmions and STNOs are found to be identical for both
+Neel-type and Bloch-type skyrmions, and are not observed between domain walls
+and STNOs. These findings offer a novel perspective in processing information
+using single skyrmions and we propose a 3-bit majority gate for logic
+applications.",1902.06925v2
+2019-02-24,Decoupling of the Kinetic and Magnetic Energy Cascades in MHD Turbulence,"Magnetic and kinetic energy in ideal incompressible MHD are not global
+invariants and, therefore, it had been justified to discuss only the cascade of
+their sum, total energy. We provide a physical argument based on scale-locality
+of the cascade, along with compelling evidence that at high Reynolds numbers,
+magnetic and kinetic energy budgets statistically decouple beyond a
+transitional ""conversion"" range. This arises because magnetic field-line
+stretching is a large-scale process which vanishes on average at intermediate
+and small scales within the inertial-inductive range, thereby allowing each of
+mean kinetic and magnetic energy to cascade conservatively and at an equal
+rate. One consequence is that the turbulent magnetic Prandtl number is unity
+over the ""decoupled range"" of scales.",1902.08983v1
+2019-02-25,Driving magnetization dynamics in an on-demand magnonic crystal by magneto-elastic interaction,"Using spatial light interference of ultrafast laser pulses, we generate a
+lateral modulation in the magnetization profile of an otherwise uniformly
+magnetized film, whose magnetic excitation spectrum is monitored via the
+coherent and resonant interaction with elastic waves. We find an unusual
+dependence of the magnetoelastic coupling as the externally applied magnetic
+field is angle- and field-tuned relative to the wave vector of the
+magnetization modulation, which can be explained by the emergence of spatially
+inhomogeneous spin-wave modes. In this regard, the spatial light interference
+methodology can be seen as a user-configurable, temporally windowed, on-demand
+magnonic crystal, potentially of arbitrary two-dimensional shape, which allows
+control and selectivity of the spatial distribution of spin waves. Calculations
+of spin waves using a variety of methods, demonstrated here using the
+plane-wave method and micromagnetic simulation, can identify the spatial
+distribution and associated energy scales of each excitation, which opens the
+door to a number of excitation methodologies beyond our chosen elastic wave
+excitation.",1902.09186v1
+2019-02-27,Nuclear magnetic resonance spectroscopy as a dynamical structural probe of high pressure hydrogen,"An unambiguous crystallographic structure solution for the observed phases
+II-VI of high pressure hydrogen does not exist due to the failure of standard
+structural probes at extreme pressure. In this work we propose that nuclear
+magnetic resonance spectroscopy provides a complementary structural probe for
+high pressure hydrogen. We show that the best structural models available for
+phases II, III, and IV of high pressure hydrogen exhibit markedly distinct
+nuclear magnetic resonance spectra which could therefore be used to
+discriminate amongst them. As an example, we demonstrate how nuclear magnetic
+resonance spectroscopy could be used to establish whether phase III exhibits
+polymorphism. Our calculations also reveal a strong renormalisation of the
+nuclear magnetic resonance response in hydrogen arising from quantum
+fluctuations, as well as a strong isotope effect. As the experimental
+techniques develop, nuclear magnetic resonance spectroscopy can be expected to
+become a useful complementary structural probe in high pressure experiments.",1902.10721v2
+2019-03-18,Astro2020 Science White Paper: Magnetic Fields and Polarization in the Diffuse Interstellar Medium,"Magnetism is one of the most important forces on the interstellar medium
+(ISM), anisotropically regulating the structure and star formation that drive
+galactic evolution. Recent high dynamic range observations of diffuse gas and
+molecular clouds have revealed new links between interstellar structures and
+the ambient magnetic field. ISM morphology encodes rich physical information,
+but deciphering it requires high-resolution measurements of the magnetic field:
+linear polarization of starlight and dust emission, and Zeeman splitting. These
+measure different components of the magnetic field, and crucially, Zeeman
+splitting is the only way to directly measure the field strength in the ISM. We
+advocate a statistically meaningful survey of magnetic field strengths using
+the 21-cm line in absorption, as well as an observational test of the link
+between structure formation and field strength using the 21-cm line in
+emission. Finally, we report on the serendipitous discovery of linear
+polarization of the 21-cm line, which demands both theoretical and
+observational follow-up.",1903.07671v1
+2019-05-20,Magnetized Gas Collimation of Interstellar Outflow Scaled by Laser-produced Plasma,"Young stellar objects/planetary nebula outflow anisotropies usually involve
+wind-wind interactions and magnetic collimation, but detailed structures of
+wind and magnetic fields inside collimation region remain undetermined. We
+numerically investigated its laboratory counterpart, based on poloidal field
+collimation in magnetocentrifugal launching model. Our analog consist of fast
+wind: Aluminum plasma generated by laser and magnetized ambient: molecular
+Helium and B=5-60 Tesla embedded field. Elevating magnetic field strength or
+decreasing gas density can alter expansion morphology, from sphere to prolonged
+cavity and ultimately to collimated jet. Outflow patterns can be quantitatively
+predicted based on the knowledge of its surroundings through a set of external
+Mach numbers. We conclude that such mixed gas and magnetic field dynamics are
+consistent with astronomical observations of protostars and planetary nebulae
+in certain evolution stages, and here provide a scalable framework allowing
+fitting of flow-field structures in astronomical unresolved regions by assuming
+their possible geometries on a repeatable laboratory platform.",1905.07935v1
+2019-06-19,Stability of a force-free Hall equilibrium and release of magnetic energy,"Conservation of magnetic helicity by the Hall drift does not prevent Hall
+instability of helical fields. This conclusion follows from stability analysis
+of a force-free spatially-periodic Hall equilibrium. The growth rates of the
+instability scale as $\sigma \propto B^{3/4}\eta^{1/4}$ with the field strength
+$B$ and magnetic diffusivity $\eta$ and can be large compared to the rate of
+resistive decay of the background field. The instability deviates the magnetic
+field from the force-free configuration. The unstable eigenmodes include a fine
+spatial structure which evolves into current sheets at the nonlinear stage of
+the instability. The instability catalyses the resistive release of magnetic
+energy. The energy is released in a sequence of spikes, every spike emits
+several percent of the total energy. A numerically defined scaling for the
+energy released in a single spike permits an extrapolation to astrophysically
+relevant values of the Hall number. The instability can be relevant to magnetic
+energy release in a neutron star crust and, possibly, in stellar coronae.",1906.07936v1
+2019-07-01,Spin currents driven by the Higgs mode in magnetic superconductors,"Higgs mode in superconducting materials describes slowly-decaying
+oscillations of the order parameter amplitude. We demonstrate that in magnetic
+superconductors with built-in spin-splitting field Higgs mode is strongly
+coupled to the spin degrees of freedom allowing for the generation of
+time-dependent spin currents.
+  Converting such spin currents to electric signals by spin-filtering elements
+provides a tool for the second-harmonic generation and the electrical detection
+of the Higgs mode generated by the external irradiation. The non-adiabatic spin
+torques generated by these spin currents allow for the magnetic detection of
+the Higgs mode by measuring the precession of magnetic moment in the adjacent
+ferromagnet. We discuss also the reciprocal effect which is the generation of
+the Higgs mode by the magnetic precession. Coupling the collective modes in
+superconductors to light and magnetic dynamics opens the new direction of
+superconducting optospintronics.",1907.00539v1
+2019-07-01,Electrically driven spin torque and dynamical Dzyaloshinskii-Moriya interaction in magnetic bilayer systems,"Efficient control of magnetism with electric means is a central issue of
+current spintronics research, which opens an opportunity to design integrated
+spintronic devices. However, recent well-studied methods are mostly based on
+electric-current injection, and they are inevitably accompanied by considerable
+energy losses through Joule heating. Here we theoretically propose a way to
+exert spin torques into magnetic bilayer systems by application of electric
+voltages through taking advantage of the Rashba spin-orbit interaction. The
+torques resemble the well-known electric-current-induced torques, providing
+similar controllability of magnetism but without Joule-heating energy losses.
+The torques also turn out to work as an interfacial Dzyaloshinskii-Moriya
+interaction which enables us to activate and create noncollinear magnetism like
+skyrmions by electric-voltage application. Our proposal offers an efficient
+technique to manipulate magnetizations in spintronics devices without
+Joule-heating energy losses.",1907.00601v2
+2019-07-02,Prediction of topological Hall effect in a driven magnetic domain wall,"We investigate the possible emergence of topological Hall effect (THE) in a
+driven magnetic DW. Numerical simulation based on the
+Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation shows that the emergent
+magnetic flux appears when the DW is in a non-equilibrium state. The magnitude
+of magnetic flux is modulated by Dzyaloshinskii-Moriya interaction (DMI) or
+in-plane longitudinal magnetic field, providing an experimental test of the
+predicted THE. These results indicate that the THE can be observed even in a
+topologically trivial magnetic DW, and therefore open up new possibility to
+electrically detect the dynamical spin structure.",1907.01648v2
+2019-07-19,A cryogenic memory element based on an anomalous Josephson junction,"We propose a non-volatile memory element based on a lateral ferromagnetic
+Josephson junction with spin-orbit coupling and out-of-plane magnetization. The
+interplay between the latter and the intrinsic exchange field of the
+ferromagnet leads to a magnetoelectric effect that couples the charge current
+through the junction and its magnetization, such that by applying a current
+pulse the direction of the magnetic moment in F can be switched. The two memory
+states are encoded in the direction of the out-of-plane magnetization. With the
+aim to determine the optimal working temperature for the memory element, we
+explore the noise-induced effects on the averaged stationary magnetization by
+taking into account thermal fluctuations affecting both the Josephson phase and
+the magnetic moment dynamics. We investigate the switching process as a
+function of intrinsic parameters of the ferromagnet, such as the Gilbert
+damping and strength of the spin-orbit coupling, and proposed a non-destructive
+readout scheme based on a dc-SQUID. Additionally, we analyze a way to protect
+the memory state from external perturbations by voltage gating in systems with
+a both linear-in-momentum Rashba and Dresselhaus spin-orbit coupling.",1907.08454v2
+2019-09-06,Transverse Force Induced by a Magnetized Wake,"The force on a test charge moving through a strongly magnetized plasma is
+calculated using linear response theory. Strong magnetization is found to
+generate a component of the force perpendicular to the velocity of the particle
+in the plane formed by the velocity and magnetic field vectors. This transverse
+force is generated by an asymmetry with respect to the velocity vector in the
+induced electrostatic wake potential that is associated with the action of the
+Lorentz force on the background plasma. The direction depends on the speed of
+the test charge. If it is faster than a critical speed characteristic of the
+sound speed, it acts to reduce the component of velocity parallel to the
+magnetic field and to increase the gyroradius. In contrast, if the speed is
+below this critical speed, it acts to increase the velocity parallel to the
+magnetic field and to decrease the gyroradius. Because the transverse force is
+perpendicular to the velocity, it does not directly influence the total energy
+of the test charge. Nevertheless, it significantly alters the trajectory on a
+timescale associated with the Coulomb collision time.",1909.03121v1
+2019-10-10,Analytical criteria for magnetization reversal in $\varphi_0$ Josephson junction,"The $\varphi_0$ Josephson junctions formed by ordinary superconductors and a
+magnetic non-centrosymmetric interlayer are studied. We derive an analytical
+solution for the magnetization dynamics induced by an arbitrary current pulse
+and formulate the criteria for magnetization reversal. Using the obtained
+results, the form and duration of the current pulse are optimized. The
+agreement between analytical and numerical investigations is reached in the
+case of a large product of the ratio Josephson to magnetic energy, strength of
+spin-orbit interaction and a minimal value of the current pulse. The obtained
+results allow one to predict magnetization reversal at the chosen system
+parameters.",1910.04419v2
+2019-10-10,Formation of Néel Type Skyrmions in an Antidot Lattice with Perpendicular Magnetic Anisotropy,"Magnetic skyrmions are particle-like chiral spin textures found in a magnetic
+film with out-of-planeanisotropy and are considered to be potential candidates
+as information carriers in next generationdata storage devices. Despite intense
+research into the nature of skyrmions and their dynamic prop-erties, there are
+several key challenges that still need to be addressed. In particular, the
+outstandingissues are the reproducible generation, stabilization and
+confinement of skyrmions at room tempera-ture. Here, we present a method for
+the capture of nanometer sized magnetic skyrmions in an arrayof magnetic
+topological defects in the form of an antidot lattice. With micromagnetic
+simulations,we elucidate the skyrmion formation in the antidot lattice and show
+that the capture is dependenton the antidot lattice parameters. This behavior
+is confirmed with scanning transmission x-ray mi-croscopy measurements. This
+demonstration that a magnetic antidot lattice can be implemented asa host to
+capture skyrmions provides a new platform for experimental investigations of
+skyrmionsand skyrmion based devices.",1910.04515v1
+2019-10-30,Laser-produced magnetic-Rayleigh-Taylor unstable plasma slabs in a 20 T magnetic field,"Magnetized laser-produced plasmas are central to many novel laboratory
+astrophysics and inertial confinement fusion studies, as well as in industrial
+applications. Here we provide the first complete description of the
+three-dimensional dynamics of a laser-driven plasma plume expanding in a 20 T
+transverse magnetic field. The plasma is collimated by the magnetic field into
+a slender, rapidly elongating slab, whose plasma-vacuum interface is unstable
+to the growth of the ""classical"", fluid-like magnetized Rayleigh-Taylor
+instability.",1910.13778v1
+2019-10-31,Ultrafast magnetic dynamics in insulating YBa$_2$Cu$_3$O$_{6+x}$ revealed by time resolved two-magnon Raman Scattering,"Measurement and control of magnetic order and correlations in real time is a
+rapidly developing scientific area relevant for magnetic memory and spintronics
+[1,15]. In these experiments an ultra-short laser pulse (pump) is first
+absorbed by excitations carrying electric dipole moment. These then give their
+energy to the magnetic subsystem monitored by a time-resolved probe. A lot of
+progress has been made in investigations of ferromagnets but antiferromagnets
+are more challenging. Here we introduce time-resolved two-magnon Raman
+scattering as a novel real time probe of magnetic correlations especially
+well-suited for antiferromagnets. Its application to the antiferromagnetic
+charge transfer insulator YBa$_2$Cu$_3$O$_{6+x}$ revealed rapid demagnetization
+within 90fs of photoexcitation. The relaxation back to thermal equilibrium is
+characterized by much slower timescales. We interpret these results in terms of
+slow relaxation of the charge sector and rapid equilibration of the magnetic
+sector to a prethermal state characterized by parameters that change slowly as
+the charge sector relaxes.",1910.14585v3
+2019-11-03,Magnetic damping modulation in $IrMn_{3}/Ni_{80}Fe_{20}$ via the magnetic spin Hall effect,"Non-collinear antiferromagnets can have additional spin Hall effects due to
+the net chirality of their magnetic spin structure, which provides for more
+complex spin-transport phenomena compared to ordinary non-magnetic materials.
+Here we investigated how ferromagnetic resonance of permalloy
+($Ni_{80}Fe_{20}$) is modulated by spin Hall effects in adjacent epitaxial
+$IrMn_{3}$ films. We observe a large dc modulation of the ferromagnetic
+resonance linewidth for currents applied along the [001] $IrMn_{3}$ direction.
+This very strong angular dependence of spin-orbit torques from dc currents
+through the bilayers can be explained by the magnetic spin Hall effect where
+$IrMn_{3}$ provides novel pathways for modulating magnetization dynamics
+electrically.",1911.00943v1
+2019-11-15,Radiative Properties of Magnetically-Arrested Disks,"Magnetically-arrested disks (MADs) appear when accretion flows are supplied
+with a sufficient amount of magnetic flux. In this work, we use results of
+magnetohydrodynamic simulations to set the configuration of the magnetic field
+and investigate the dynamics and radiative properties of the resulting
+accretion flow (i.e., without that of the jet) of MAD. The method developed
+here is applied to both the MAD and the standard and normal evolution (SANE)
+accretion flow with or without large scale magnetic fields. For the radiative
+processes, we include synchrotron, bremsstrahlung and Compton scattering. We
+find that, in general, MAD accretion flows have similar spectra to those of the
+SANE, which complicates the task of distinguishing MADs from SANEs. At the same
+accretion rates, MADs are systematically brighter than SANEs. However, the
+critical accretion rate above which the hot solution ceases to exist is lower
+in MAD. Consequently, the maximum luminosity the MAD can reach is comparable
+but slightly lower than that of SANE, and the dependence on the magnetic flux
+is weak. We then discuss implications of our results for active galactic nuclei
+and accreting black-hole binaries.",1911.06439v1
+2019-11-18,Particle size controlled magnetic loss in magnetite nanoparticles in RF-microwave region,"Frequency dependant complex magnetic permeability is used to understand
+RF-microwave behaviour of magnetic nanoparticles in the frequency range 250 MHz
+to 3 GHz. The stable dispersions of Fe3O4 nanoparticles with mean size varying
+between 11 to 16 nm are prepared for this purpose. The effect of mean particle
+size and external static magnetic field over microwave absorption properties of
+magnetic fluid is studied. It is observed that frequency of ferrimagnetic
+resonance, frequency of maximum absorption, loss tangent and reflection loss
+(RL) can be controlled by modifying mean particle size and strength of applied
+external static magnetic field. This kind of study can be useful for
+radio-microwave devices like tunable attenuator, EM sheilder, and other
+applications like Hyperthermia.",1911.07467v1
+2020-01-10,Unidirectional tilt of domain walls in equilibrium in biaxial stripes with Dzyaloshinskii-Moriya interaction,"The orientation of a chiral magnetic domain wall in a racetrack determines
+its dynamical properties. In equilibrium, magnetic domain walls are expected to
+be oriented perpendicular to the stripe axis. We demonstrate the appearance of
+a unidirectional domain wall tilt in out-of-plane magnetized stripes with
+biaxial anisotropy and Dzyaloshinskii--Moriya interaction (DMI). The tilt is a
+result of the interplay between the in-plane easy-axis anisotropy and DMI. We
+show that the additional anisotropy and DMI prefer different domain wall
+structure: anisotropy links the magnetization azimuthal angle inside the domain
+wall with the anisotropy direction in contrast to DMI, which prefers the
+magnetization perpendicular to the domain wall plane. Their balance with the
+energy gain due to domain wall extension defines the equilibrium magnetization
+the domain wall tilting. We demonstrate that the Walker field and the
+corresponding Walker velocity of the domain wall can be enhanced in the system
+supporting tilted walls.",2001.03408v1
+2020-02-09,Impact of longitudinal bulk viscous effects to heavy quark transport in a strongly magnetized hot QCD medium,"The effects of longitudinal bulk viscous pressure on the heavy quark dynamics
+have been estimated in a strongly magnetized quark-gluon plasma within the
+Fokker-Planck approach. The bulk viscous modification to the momentum
+distribution of bulk degrees of freedom has been obtained in the presence of a
+magnetic field while incorporating the realistic equation of state of the hot
+magnetized QCD medium. As the magnetic field breaks the isotropy of the medium,
+the analysis is done along the directions longitudinal and transverse to the
+field. The longitudinal bulk viscous contribution is seen to have sizable
+effects in the heavy quark momentum diffusion in the magnetized medium. The
+dependence of higher Landau levels and the equation of state on the viscous
+correction to the heavy quark transport has been explored in the analysis.",2002.03325v2
+2020-03-05,Reexaming the ground state and magnetic properties of curium dioxide,"The ground state electronic structure and magnetic behaviors of curium
+dioxide (CmO$_{2}$) are controversial. In general, the formal valence of Cm
+ions in CmO$_{2}$ should be tetravalent. It implies a $5f^{6.0}$ electronic
+configuration and a non-magnetic ground state. However, it is in sharp contrast
+with the large magnetic moment measured by painstaking experiments. In order to
+clarify this contradiction, we tried to study the ground state electronic
+structure of CmO$_{2}$ by means of a combination of density functional theory
+and dynamical mean-field theory. We find that CmO$_{2}$ is a wide-gap charge
+transfer insulator with strong 5$f$ valence state fluctuation. It belongs to a
+mixed-valence compound indeed. The predominant electronic configurations for Cm
+ions are $5f^{6.0}$ and $5f^{7.0}$. The resulting magnetic moment agrees quite
+well with the experimental value. Therefore, the magnetic puzzle in CmO$_{2}$
+can be appropriately explained by the mixed-valence scenario.",2003.02716v2
+2020-03-31,Spin-torque switching mechanisms of perpendicular magnetic tunnel junctions nanopillars,"Understanding the magnetization dynamics induced by spin transfer torques in
+perpendicularly magnetized magnetic tunnel junction nanopillars and its
+dependence on material parameters is critical to optimizing device performance.
+Here we present a micromagnetic study of spin-torque switching in a disk-shaped
+element as a function of the free layer's exchange constant and disk diameter.
+The switching is shown to generally occur by 1) growth of the magnetization
+precession amplitude in the element center; 2) an instability in which the
+reversing region moves to the disk edge, forming a magnetic domain wall; and 3)
+the motion of the domain wall across the element. For large diameters and small
+exchange, step 1 leads to a droplet with a fully reversed core that experiences
+a drift instability (step 2). While in the opposite case (small diameters and
+large exchange), the central region of the disk is not fully reversed before
+step 2 occurs. The origin of the micromagnetic structure is shown to be the
+disk's non-uniform demagnetization field. Faster, more coherence and energy
+efficient switching occur with larger exchange and smaller disk diameters,
+showing routes to increase device performance.",2003.13875v1
+2020-04-13,Density of states and Delocalization for discrete magnetic random Schrödinger operators,"We study discrete magnetic random Schr\""odinger operators on the square and
+honeycomb lattice. For the non-random magnetic operator on the hexagonal
+lattice with any rational magnetic flux, we show that the middle two dispersion
+surfaces exhibit Dirac cones. We then derive an asymptotic expansion for the
+density of states on the honeycomb lattice for oscillations of arbitrary
+rational magnetic flux. This allows us, as a corollary, to rigorously study the
+quantum Hall effect and conclude dynamical delocalization close to the conical
+point under disorder. We obtain similar results for the discrete random
+Schr\""odinger operator on the $\mathbb Z^2$-lattice with weak magnetic fields,
+close to the bottom and top of its spectrum.",2004.06189v2
+2020-05-04,Statistical properties of magnetic structures and energy dissipation during turbulent reconnection in the Earth's magnetotail,"We present the first statistical study of magnetic structures and associated
+energy dissipation observed during a single period of turbulent magnetic
+reconnection, by using the \textit{in-situ} measurements of the Magnetospheric
+Multiscale mission in the Earth's magnetotail on July 26, 2017. The structures
+are selected by identifying a bipolar signature in the magnetic field and
+categorized as plasmoids or current sheets via an automated algorithm which
+examines current density and plasma flow. The size of the plasmoids forms a
+decaying exponential distribution ranging from sub-electron up to ion scales.
+The presence of substantial number of current sheets is consistent with a
+physical picture of dynamic production and merging of plasmoids during
+turbulent reconnection. The magnetic structures are locations of significant
+energy dissipation via electric field parallel to the local magnetic field,
+while dissipation via perpendicular electric field dominates outside of the
+structures. Significant energy also returns from particles to fields.",2005.01226v2
+2020-06-01,Magnetic field effects in peripheral heavy-ion collisions around 1 GeV/nucleon,"Magnetic field effects on free nucleons are studied in peripheral collisions
+of $^{197}$Au + $^{197}$Au at energies ranging from 600 to 1500 MeV/nucleon by
+utilizing an isospin-dependent quantum molecular dynamics (IQMD) model. With
+the help of angular distributions and two-particle angular correlators, the
+magnetic field effect at an impact parameter of 11 fm is found to be more
+obvious than at an impact parameter of 8 fm. Moreover, the results suggest that
+with an increase in the number of peripheral collisions, protons are more
+easily condensed with the magnetic field. Magnetic field effects are further
+investigated by the ratio of free neutrons to free protons as functions of a
+two-particle correlator $C_{2}$, four-particle correlator $C_{4}$ and
+six-particle correlator $C_{6}$ of angle $\phi$, rapidity $Y$ and transverse
+momentum $p_{T}$. The results show that weak magnetic field effects could be
+revealed more clearly by these multiple-particle correlators, with the larger
+number of particle correlators demonstrating a clear signal. The results
+highlight a new method to search for weak signals using multi-particle
+correlators.",2006.00718v1
+2020-06-22,Enhanced x-ray emission arising from laser-plasma confinement by a strong transverse magnetic field,"We analyze, using experiments and 3D MHD numerical simulations, the dynamics
+and radiative properties of a plasma ablated by a laser (1 ns,
+10$^{12}$-10$^{13}$ W/cm$^2$) from a solid target, as it expands into a
+homogeneous, strong magnetic field (up to 30 T) transverse to its main
+expansion axis. We find that as soon as 2 ns after the start of the expansion,
+the plasma becomes constrained by the magnetic field. As the magnetic field
+strength is increased, more plasma is confined close to the target and is
+heated by magnetic compression. We also observe a dense slab that rapidly
+expands into vacuum after ~ 8 ns; however, this slab contains only ~ 2 % of the
+total plasma. As a result of the higher density and increased heating of the
+confined plasma, there is a net enhancement of the total x-ray emissivity
+induced by the magnetization.",2006.12424v1
+2020-07-08,Magnetization around mix jets entering inertial confinement fusion fuel,"Engineering features are known to cause jets of ablator material to enter the
+fuel hot-spot in inertial confinement fusion implosions. The Biermann battery
+mechanism wraps them in self-generated magnetic field. We show that higher-Z
+jets have an additional thermoelectric magnetic source term that is not present
+for hydrogen jets, verified here through a kinetic simulation. It has similar
+magnitude to the Biermann term. We then include this in an extended
+magneto-hydrodynamics approach to post-process an xRAGE radiation-hydrodynamic
+implosion simulation. The simulation includes an accurate model for the capsule
+fill tube, producing a dense carbon jet that becomes wrapped in a 4000T
+magnetic field. A simple spherical carbon mix model shows that this insulates
+the electron heat conduction enough to cause contraction of the jet to an
+optically thick equilibrium. The denser magnetized jet hydrodynamics could
+change its core penetration and therefore the final mix mass, which is known to
+be well correlated with fusion yield degradation. Fully exploring this will
+require self-consistent magneto-hydrodynamic simulations. Experimental
+signatures of this self-magnetization may emerge in the high energy neutron
+spectrum.",2007.04293v1
+2020-07-15,Janus Monolayers of Magnetic Transition Metal Dichalcogenides as an All-in-One Platform for Spin-Orbit Torque,"We theoretically predict that vanadium-based Janus dichalcogenide monolayers
+constitute an ideal platform for spin-orbit-torque memories. Using first
+principles calculations, we demonstrate that magnetic exchange and magnetic
+anisotropy energies are higher for heavier chalcogen atoms, while the broken
+inversion symmetry in the Janus form leads to the emergence of Rashba-like
+spin-orbit coupling. The spin-orbit torque efficiency is evaluated using
+optimized quantum transport methodology and found to be comparable to heavy
+nonmagnetic metals. The coexistence of magnetism and spin-orbit coupling in
+such materials with tunable Fermi-level opens new possibilities for monitoring
+magnetization dynamics in the perspective of non-volatile magnetic random
+access memories.",2007.07579v1
+2020-07-16,Strong surface magnetic field generation in relativistic short pulse laser-plasma interaction with an applied seed magnetic field,"While plasma often behaves diamagnetically, we demonstrate that the laser
+irradiation of a thin opaque target with an embedded target-transverse seed
+magnetic field $B_\mathrm{seed}$ can trigger the generation of an
+order-of-magnitude stronger magnetic field with opposite sign at the target
+surface. Strong surface field generation occurs when the laser pulse is
+relativistically intense and results from the currents associated with the
+cyclotron rotation of laser-heated electrons transiting through the target and
+the compensating current of cold electrons. We derive a predictive scaling for
+this surface field generation, $B_\mathrm{gen} \sim - 2 \pi B_\mathrm{seed}
+\Delta x/\lambda_0$, where $\Delta x$ is the target thickness and $\lambda_0$
+is the laser wavelength, and conduct 1D and 2D particle-in-cell simulations to
+confirm its applicability over a wide range of conditions. We additionally
+demonstrate that both the seed and surface-generated magnetic fields can have a
+strong impact on application-relevant plasma dynamics, for example
+substantially altering the overall expansion and ion acceleration from a
+$\mu$m-thick laser-irradiated target with a kilotesla-level seed magnetic
+field.",2007.08677v1
+2020-07-24,Does elasticity stabilise a magnetic neutron star?,"The configuration of the magnetic field in the interior of a neutron star is
+mostly unknown from observations. Theoretical models of the interior magnetic
+field geometry tend to be oversimplified to avoid mathematical complexity and
+tend to be based on axisymmetric barotropic fluid systems. These static
+magnetic equilibrium configurations have been shown to be unstable on a short
+time scale against an infinitesimal perturbation. Given this instability, it is
+relevant to consider how more realistic neutron star physics affects the
+outcome. In particular, it makes sense to ask if elasticity, which provides an
+additional restoring force on the perturbations, may stabilise the system. It
+is well-known that the matter in the neutron star crust forms an ionic crystal.
+The interactions between the crystallized nuclei can generate shear stress
+against any applied strain. To incorporate the effect of the crust on the
+dynamical evolution of the perturbed equilibrium structure, we study the effect
+of elasticity on the instability of an axisymmetric magnetic star. In
+particular we determine the critical shear modulus required to prevent magnetic
+instability and consider the corresponding astrophysical consequences.",2007.12400v2
+2020-07-28,Quantifying the thermal stability in perpendicularly magnetized ferromagnetic nanodisks with forward flux sampling,"The thermal stability in nanostructured magnetic systems is an important
+issue for applications in information storage. From a theoretical and
+simulation perspective, an accurate prediction of thermally-activated
+transitions is a challenging problem because desired retention times are on the
+order of 10 years, while the characteristic time scale for precessional
+magnetization dynamics is of the order of nanoseconds. Here, we present a
+theoretical study of the thermal stability of magnetic elements in the form of
+perpendicularly-magnetized ferromagnetic disks using the forward flux sampling
+method, which is useful for simulating rare events. We demonstrate how rates of
+thermally-activated switching between the two uniformly-magnetized ``up'' and
+``down'' states, which occurs through domain wall nucleation and propagation,
+vary with the interfacial Dzyaloshinskii-Moriya interaction, which affect the
+energy barrier separating these states. Moreover, we find that the average
+lifetimes differ by several orders of magnitude from estimates based on the
+commonly assumed value of 1 GHz for the attempt frequency.",2007.14382v1
+2020-09-30,Designing of Magnetic MAB Phases for Energy Applications,"Based on high-throughput density functional theory calculations, we performed
+screening for stable magnetic MAB compounds and predicted potential strong
+magnets for permanent magnet and magnetocaloric applications. The
+thermodynamical, mechanical, and dynamical stabilities are systematically
+evaluated, resulting in 21 unreported compounds on the convex hull, and 434
+materials being metastable considering convex hull tolerance to be 100
+meV/atom. Analysis based on the Hume-Rothery rules revealed that the valence
+electron concentration and size factor difference are of significant importance
+in determining the stability, with good correspondence with the local atomic
+bonding. We found 71 compounds with the absolute value of magneto-crystalline
+anisotropy energy above 1.0 MJ/m$^3$ and 23 compounds with a uniaxial
+anisotropy greater than 0.4 MJ/m$^3$, which are potential gap magnets. Based on
+the magnetic deformation proxy, 99 compounds were identified as potential
+materials with interesting magnetocaloric performance.",2009.14543v1
+2020-11-27,Entropic signatures of the skyrmion lattice phase in MnSi1-xAlx and Fe1-yCoySi,"The entropic signatures of magnetic phase transitions in the skyrmion lattice
+host compounds MnSi0.962Al0.038 and Fe0.7Co0.3Si were investigated through low
+field magnetization and ac susceptibility measurements. These data indicate
+that the conical to skyrmion transition that occurs with the application of
+magnetic field in MnSi0.962Al0.038 is characterized by clear discontinuity in
+the magnetic entropy as expected for first order topological phase transition.
+These same magnetoentropic features are negligibly small in isostructural
+Fe0.7Co0.3Si due to the level of chemical substitution related disorder and
+differences in the spin dynamics (range and timescales). Despite the obvious
+similarities in the magnetic structures of these two compounds, the transitions
+between these phases is substantially different indicating a surprising
+non-universality to the magnetic phase transitions in this class of materials.",2011.14025v1
+2020-12-11,Slow Spin Relaxation in Single Endohedral Fullerene Molecules,"Well-protected magnetization, tunable quantum states and long coherence time
+are desired for the use of magnetic molecules in spintronics and quantum
+information technologies. In this work, endohedral fullerene molecules M@C28
+with different transition metal cores were explored through systematic
+first-principles calculations and spin dynamics analyses. Many of them have
+stable magnetization, giant magnetic anisotropy energy and bias-tunable
+structure. In particular, some of them may have coherence time up to several
+milliseconds for their quantum spin states at high temperature (~10K) after
+full consideration of spin-vibration couplings. These results suggest that
+these M@C28 provide a rich pool for the development of single-molecule magnets,
+magnetic molecular junctions, and molecular qubits.",2012.06141v2
+2020-12-20,Probing the internal magnetism of stars using asymptotic magneto-asteroseismology,"Our knowledge of the dynamics of stars has undergone a revolution thanks to
+the simultaneous large amount of high-quality photometric observations
+collected by space-based asteroseismology and ground-based high-precision
+spectropolarimetry. They allowed us to probe the internal rotation of stars and
+their surface magnetism in the whole Hertzsprung-Russell diagram. However, new
+methods should still be developed to probe the deep magnetic fields in those
+stars. Our goal is to provide seismic diagnoses that allow us to sound the
+internal magnetism of stars. Here, we focus on asymptotic low-frequency gravity
+modes and high-frequency acoustic modes. Using a first-order perturbative
+theory, we derive magnetic splittings of their frequencies as explicit
+functions of stellar parameters. As in the case of rotation, we show how
+asymptotic gravity and acoustic modes can allow us to probe the different
+components of the magnetic field in the cavities where they propagate. This
+demonstrates again the high potential of using mixed-modes when this is
+possible.",2012.11050v1
+2020-12-28,Edge magnetic properties of black phosphorene nanoribbons,"The magnetic properties of black phosphorene nanoribbons are investigated
+using static and dynamical mean-field theory. Besides confirming the existence
+of ferromagnetic/antiferromagnetic edge magnetism, our detailed calculations
+using large unit-cells find a phase-transition at weak interaction strength to
+an incommensurate (IC) magnetic phase. A detailed Fourier analysis of the
+magnetization patterns in the IC phase shows the existence of a second critical
+interaction strength, where the incommensurate phase changes to an
+antiferromagnetic (AFM) or ferromagnetic (FM) phase. We demonstrate that the
+difference of the ground state energies of the AFM and FM phase is
+exponentially small, making it possible to switch between both states by a
+small external field. Finally, we analyze the influence of strain and disorder
+on the magnetic properties and show that while the IC phase is robust to
+Anderson type disorder, it is fragile against strain.",2012.14052v2
+2021-01-06,Magnet design optimization of a 100 MeV separated sector medical cyclotron and its injection line,"This paper presents the magnetic design of a 100MeV Separated Sector Medical
+Cyclotron (SSMC) as well as the optimization of the injection line magnets
+where will be used to transport the 14MeV proton beam from the Azimuthally
+Varying Field (AVF) cyclotron to the SSMC. The study demonstrates that the
+isochronous magnetic field with a tolerance around 10-4 T can be obtained all
+along prescribed path by placing three sets of correction trim coils in the
+pole tips. The result of Betatron oscillations is sufficient to verify that the
+focusing forces of the magnetic field can hold particles close to the median
+plane of the magnet. In order to inject the beam by minimum loss from a 14MeV
+Cyclotron to SSMC, it is essential for the beam to fit into the acceptance
+ellipse of the separate sector cyclotron. The characteristics of the beam
+injection system is calculated and optimized by Trace-3D beam dynamic code.",2101.02294v1
+2021-03-07,Phonon Hall Viscosity in Magnetic Insulators,"The Phonon Hall Viscosity is the leading term evincing time-reversal symmetry
+breaking in the low energy description of lattice phonons. It may generate
+phonon Berry curvature, and can be observed experimentally through the acoustic
+Faraday effect and thermal Hall transport. We present a systematic procedure to
+obtain the phonon Hall viscosity induced by phonon-magnon interactions in
+magnetic insulators under an external magnetic field. We obtain a general
+symmetry criterion that leads to non-zero Faraday rotation and Hall
+conductivity, and clarify the interplay between lattice symmetry,
+spin-orbit-coupling, external magnetic field and magnetic ordering. The
+symmetry analysis is verified through a microscopic calculation. By
+constructing the general symmetry-allowed effective action that describes the
+spin dynamics and spin-lattice coupling, and then integrating out the spin
+fluctuations, the leading order time-reversal breaking term in the phonon
+effective action, i.e. the phonon Hall viscosity, can be obtained. The analysis
+of the square lattice antiferromagnet for a cuprate Mott insulator,
+Sr$_2$CuO$_2$Cl$_2$, is presented explicitly, and the procedure described here
+can be readily generalized to other magnetic insulators.",2103.04223v1
+2021-03-25,Observation of magnetic helicoidal dichroism with extreme ultraviolet light vortices,"We report on the experimental evidence of magnetic helicoidal dichroism,
+observed in the interaction of an extreme ultraviolet vortex beam carrying
+orbital angular momentum with a magnetic vortex. Numerical simulations based on
+classical electromagnetic theory show that this dichroism is based on the
+interference of light modes with different orbital angular momenta, which are
+populated after the interaction between the light phase chirality and the
+magnetic topology. This observation gives insight into the interplay between
+orbital angular momentum and magnetism, and sets the framework for the
+development of new analytical tools to investigate ultrafast magnetization
+dynamics.",2103.13697v1
+2021-04-02,Surface plasmon-enhanced photo-magnetic excitation of spin dynamics in Au/YIG:Co magneto-plasmonic crystals,"We report strong amplification of photo-magnetic spin precession in Co-doped
+YIG employing a surface plasmon excitation in a metal-dielectric
+magneto-plasmonic crystal. Plasmonic enhancement is accompanied by the
+localization of the excitation within the 300~nm-thick layer inside the
+transparent dielectric garnet. Experimental results are nicely reproduced by
+numerical simulations of the photo-magnetic excitation. Our findings
+demonstrate the magneto-plasmonic concept of subwavelength localization and
+amplification of the photo-magnetic excitation in dielectric YIG:Co and open up
+a path to all-optical magnetization switching below diffraction limit with
+energy efficiency approaching the fundamental limit for magnetic memories.",2104.01250v1
+2021-04-14,An MHD Modeling of Successive X2.2 and X9.3 Solar Flares of 2017 September 6,"Solar active region 12673 produced two successive X-class flares (X2.2 and
+X9.3) approximately 3 hours apart in September 2017. The X9.3 was the recorded
+largest solar flare in Solar Cycle 24. In this study we perform a
+data-constrained magnetohydrodynamic simulation taking into account the
+observed photospheric magnetic field to reveal the initiation and dynamics of
+the X2.2 and X9.3 flares. According to our simulation, the X2.2 flare is first
+triggered by magnetic reconnection at a local site where at the photosphere the
+negative polarity intrudes into the opposite-polarity region. This magnetic
+reconnection expels the innermost field lines upward beneath which the magnetic
+flux rope is formed through continuous reconnection with external twisted field
+lines. Continuous magnetic reconnection after the X2.2 flare enhances the
+magnetic flux rope, which is lifted up and eventually erupts via the torus
+instability. This gives rise to the X9.3 flare.",2104.06639v1
+2021-05-03,Light-Induced Control of Magnetic Phases in Kitaev Quantum Magnets,"Leveraging coherent light-matter interaction in solids is a promising new
+direction towards control and functionalization of quantum materials, to
+potentially realize regimes inaccessible in equilibrium and stabilize new or
+useful states of matter. We show how driving the strongly spin-orbit coupled
+proximal Kitaev magnet $\alpha$-RuCl$_3$ with circularly-polarized light can
+give rise to a novel ligand-mediated magneto-electric effect that both
+photo-induces a large dynamical effective magnetic field and dramatically
+alters the interplay of competing isotropic and anisotropic exchange
+interactions. We propose that tailored light pulses can nudge the material
+towards the elusive Kitaev quantum spin liquid as well as probe competing
+magnetic instabilities far from equilibrium, and predict that the transient
+competition of magnetic exchange processes can be readily observed via
+pump-probe spectroscopy.",2105.01062v2
+2021-05-20,A hierarchy of multi-moment skyrmion phases in twisted magnetic bilayers,"The recent discovery of two-dimensional (2D) Van der Waals (VdW) magnets is a
+crucial turning point in the quantum magnet research field, since quantum
+fluctuations and experimental difficulties often elude stable magnetic orders
+in 2D. This opens new doors to delve for novel quantum and topological spin
+configurations, which may or may not have direct analogs in bulk counterparts.
+Here we study a twisted bilayer geometry of 2D magnets in which long-range
+spin-spin interactions naturally commence along the inter-layer Heisenberg
+($J_{\perp}$) and dipole-dipole ($J_{\rm D}$) channels. The $J_{\perp}-J_{\rm
+D}$ parameter space unveils a hierarchy of distinct skyrmions phases, ranging
+from point-, rod-, and ring-shaped topological charge distributions.
+Furthermore, we predict a novel topological antiferroelectric phase, where
+oppositely-charged antiskyrmion pairs are formed, and the corresponding
+topological dipole moments become ordered in a N\'eel-like state $-$ hence
+dubbed topological antiferroelectric state. The results indicate that twisted
+magnetic layer provides a new setting to engineer and tune a plethora of novel
+and exotic skyrmion phases and their dynamics.",2105.09521v1
+2021-06-01,Magnetic flux expulsion in a superconducting wire,"An electric current generates a magnetic field, and magnetic fields cannot
+exist in the interior of type I superconductors. As a consequence of these two
+facts, electric currents can only flow near the surface of a type I
+superconducting wire so that the self-field vanishes in the interior. Here we
+examine how an electric current flowing through the entire cross-section of a
+normal conducting wire becomes a surface current when it enters a
+superconducting portion of the wire. This geometry provides insight into the
+dynamics of magnetic flux expulsion that is not apparent in the Meissner effect
+involving expulsion of an externally applied magnetic field. It provides clear
+evidence that the motion of magnetic field lines in superconductors is
+intimately tied to the motion of charge carriers, as occurs in classical
+plasmas (Alfven's theorem) and as proposed in the theory of hole
+superconductivity \cite{holesc}, in contradiction with the conventional
+London-BCS theory of superconductivity.",2106.00262v1
+2021-06-05,Radio afterglow of magnetars' giant flares,"We develop a model for the radio afterglow of the giant flare of SGR 1806-20
+arising due to the interaction of magnetically-dominated cloud, an analogue of
+Solar Coronal Mass Ejections (CMEs), with the interstellar medium (ISM). The
+CME is modeled as a spheromak-like configuration. The CME is first advected
+with the magnetar's wind and later interacts with the ISM, creating a strong
+forward shock and complicated backwards exhaust flow. Using three-dimensional
+magnetohydrodynamic simulations, we study various relative configurations of
+the magnetic field of the CME with respect to the ISM's magnetic field. We show
+that the dynamics of the forward shock mostly follows the Sedov-Taylor
+blastwave, while the internal structure of the shocked medium is considerably
+modified by the back flow, creating a multiple shock configuration. We
+calculate synthetic synchrotron emissivity maps and light curves using two
+assumptions: (i) magnetic field compression; (ii) amplification of the magnetic
+field at the shock.We find that models with magnetic field amplification
+account better for the observed radio emission.",2106.02918v3
+2021-07-01,Van der Waals Magnet based Spin-Valve Devices at Room Temperature,"The discovery of van der Waals (vdW) magnets opened up a new paradigm for
+condensed matter physics and spintronic technologies. However, the operations
+of active spintronic devices with vdW magnets are so far limited to cryogenic
+temperatures, inhibiting its broader practical applications. Here, for the
+first time, we demonstrate room temperature spin-valve devices using vdW
+itinerant ferromagnet Fe5GeTe2 in heterostructures with graphene. The tunnel
+spin polarization of the Fe5GeTe2/graphene vdW interface is detected to be
+significantly large ~ 45 % and negative at room temperature. Lateral spin-valve
+device design enables electrical control of spin signal and realization of
+basic building blocks for device application such as efficient spin injection,
+transport, precession, and detection functionalities. Furthermore, measurements
+with different magnetic orientations provide unique insights into the magnetic
+anisotropy of Fe5GeTe2 and its relation with spin polarization and dynamics in
+the heterostructure. These findings open opportunities for the applications of
+vdW magnet-based all-2D spintronic devices and integrated spin circuits at
+ambient temperatures.",2107.00310v1
+2021-07-09,Spontaneous orbital magnetization of mesoscopic dipole dimers,"Ensembles of gold nanoparticles present a magnetic behavior which is at odds
+with the weakly diamagnetic response of bulk gold. In particular, an unusual
+ferromagnetic order has been unveiled by several experiments. Here we
+investigate if the combined effect of orbital magnetism of conduction electrons
+and interparticle dipolar interaction can lead to magnetic ordering. Using
+different model systems of interacting mesoscopic magnetic dipoles, together
+with a microscopic description of the electron dynamics within the
+nanoparticles, we find that a spontaneous magnetic moment may arise in dimers
+of metallic nanoparticles when the latter are characterized by a large orbital
+paramagnetic susceptibility.",2107.04508v3
+2021-07-15,The Magnetic Mechanism for Hotspot Reversals in Hot Jupiter Atmospheres,"Magnetically-driven hotspot variations (which are tied to atmospheric wind
+variations) in hot Jupiters are studied using non-linear numerical simulations
+of a shallow-water magnetohydrodynamic (SWMHD) system and a linear analysis of
+equatorial SWMHD waves. In hydrodynamic models, mid-to-high latitude
+geostrophic circulations are known to cause a net west-to-east equatorial
+thermal energy transfer, which drives hotspot offsets eastward. We find that a
+strong toroidal magnetic field can obstruct these energy transporting
+circulations. This results in winds aligning with the magnetic field and
+generates westward Lorentz force accelerations in hotspot regions, ultimately
+causing westward hotspot offsets. In the subsequent linear analysis we find
+that this reversal mechanism has an equatorial wave analogy in terms of the
+planetary scale equatorial magneto-Rossby waves. We compare our findings to
+three-dimensional MHD simulations, both quantitively and qualitatively,
+identifying the link between the mechanics of magnetically-driven hotspot and
+wind reversals. We use the developed theory to identify physically-motivated
+reversal criteria, which can be used to place constraints on the magnetic
+fields of ultra-hot Jupiters with observed westward hotspots.",2107.07515v1
+2021-07-28,Transport theory and spin-transfer physics for frustrated magnets,"We study the electron dynamics in magnetic conductors with frustrated
+interactions dominated by isotropic exchange. We present a transport theory for
+itinerant carriers built upon the (single-band) doped Hubbard model and the
+slave-boson formalism, which incorporates the spin-exchange with the
+magnetically frustrated background into the representation of electron
+operators in a clear and controllable way. We also formulate hydrodynamic
+equations for the itinerant charge and spin degrees of freedom, whose currents
+contain new contributions that depend on the spatiotemporal variations of the
+order parameter of the frustrated magnet, which are described by Yang-Mills
+fields. Furthermore, we elucidate the transfer of angular momentum from the
+itinerant charge fluid to the magnet (i.e., the spin-transfer torque) via
+reciprocity arguments. A detailed microscopic derivation of our effective
+theory is also provided for one of the simplest models of frustrated magnetism,
+namely the Heisenberg antiferromagnet on a triangular lattice. Our findings
+point towards the possibility of previously unanticipated Hall physics in these
+frustrated platforms.",2107.13330v2
+2021-08-31,Kinematic dynamos in triaxial ellipsoids,"Planetary magnetic fields are generated by motions of electrically conducting
+fluids in their interiors. The dynamo problem has thus received much attention
+in spherical geometries, even though planetary bodies are non-spherical. To go
+beyond the spherical assumption, we develop an algorithm that exploits a fully
+spectral description of the magnetic field in triaxial ellipsoids to solve the
+induction equation with local boundary conditions (i.e. pseudo-vacuum or
+perfectly conducting boundaries). We use the method to compute the free-decay
+magnetic modes and to solve the kinematic dynamo problem for prescribed flows.
+The new method is thoroughly compared with analytical solutions and standard
+finite-element computations, which are also used to model an insulating
+exterior. We obtain dynamo magnetic fields at low magnetic Reynolds numbers in
+ellipsoids, which could be used as simple benchmarks for future dynamo studies
+in such geometries. We finally discuss how the magnetic boundary conditions can
+modify the dynamo onset, showing that a perfectly conducting boundary can
+strongly weaken dynamo action, whereas pseudo-vacuum and insulating boundaries
+often give similar results.",2109.03232v1
+2021-10-04,Magnetized Ablative Rayleigh-Taylor Instability in 3-D,"3-D extended-MHD simulations of the magnetized ablative Rayleigh-Taylor
+instability are presented for the first time. Previous 2-D simulations claiming
+perturbation suppression by magnetic tension are shown to be misleading, as
+they do not include the most unstable dimension. For perturbation modes along
+the applied field direction, the magnetic field simultaneously reduces ablative
+stabilization and adds magnetic tension stabilization; the stabilizing term is
+found to dominate for applied fields >5T, with both effects increasing in
+importance at short wavelengths. For modes perpendicular to the applied field,
+magnetic tension does not directly stabilize the perturbation, but can result
+in moderately slower growth due to the perturbation appearing 2-D (albeit in a
+different orientation to 2-D ICF simulations). In cases where thermal ablative
+stabilization is dominant the applied field increases the peak bubble-spike
+height. Resistive diffusion is shown to be important for short wavelengths and
+long timescales, reducing the effectiveness of tension stabilization.",2110.01666v1
+2021-10-06,Strong large scale magnetic fields in rotating convection-driven dynamos: the important role of magnetic diffusion,"Natural dynamos such as planets and stars generate global scale magnetic
+field despite the inferred presence of small scale turbulence. Such systems are
+known as large scale dynamos and are typically driven by convection and
+influenced by rotation. Previous numerical studies of rotating dynamos
+generally find that the large scale magnetic field becomes weaker as the flow
+becomes more turbulent. The underlying physical processes necessary for
+sustaining so-called large scale dynamos is therefore still debated. Here we
+use a suite of numerical simulations to show that strong large scale magnetic
+fields can be generated in rotating convective turbulence provided that two
+conditions are satisfied: (1) the flow remains rotationally constrained; and
+(2) magnetic diffusion is important on the small convective length scale. These
+findings are in agreement with previous asymptotic predictions and suggest that
+natural dynamos might satisfy these two conditions.",2110.03086v2
+2021-10-27,Magnetoconductivity of a metal with closed Fermi surface reconstructed by a biaxial density wave,"We investigate quantum dynamics and kinetics of a 2D conductor with closed
+Fermi surface reconstructed by a biaxial density wave, in which electrons move
+along a two-dimensional periodic net of semiclassical trajectories coupled by
+the magnetic breakdown tunnelling under a strong magnetic field. We derive a
+quasi-particle dispersion law and magnetoconductivity tensor. The
+quasi-particle spectrum is found to be the alternating series of
+two-dimensional magnetic energy bands with gaps between them. The longitudinal
+magnetoconductivity shows giant oscillations with change of magnetic field,
+while the Hall coefficient changes sign and is absent in a wide range of the
+magnetic fields in between. Preliminary estimations show that the suggested
+magnetoconductivity mechanism may be the origin of such behaviour of the Hall
+coefficient vs. magnetic field, as observed in experiments in materials with
+analogous topology of the Fermi surface, such as the high-Tc superconducting
+cuprates.",2110.14265v1
+2021-11-23,Pitch Angle Scattering of Fast Particles by Low Frequency Magnetic Fluctuations,"The adiabatic invariance of the magnetic moment during particle motion is of
+fundamental importance to the dynamics of magnetized plasma. The related rate
+of pitch angle scattering is investigated here for fast particles that
+thermally stream through static magnetic perturbations. For a uniform magnetic
+field with a localized perturbation it is found that the curvature parameter
+$\kappa^2=\min(R_c/\rho_L)$ does not predict the level of pitch angle
+scattering. Instead, based on numerical integration of particle orbits in
+prescribed magnetic fields, we derive predictions for the particle scattering
+rates, which can be characterized by the relative perturbation amplitude
+$A\simeq \delta B/B$, and the particle Larmor radius normalized by the
+field-aligned wavelength of the perturbations, $\rho_L/\lambda_{\|}$. Particles
+with $\rho_L/\lambda_{\|}\simeq1$, are subject to strong pitch angle
+scattering, while the level of scattering vanishes for both the limits of
+$\rho_L/\lambda_{\|} \ll 1$ and $\rho_L/\lambda_{\|} \gg 1$. The results are
+summarized in terms of a scattering operator, suitable for including the
+described scattering in basic kinetic models.",2111.11993v1
+2021-12-03,Magnetic field-induced deformation of the spin-density wave microphases in Ca$_3$Co$_2$O$_6$,"The frustrated triangular Ising magnet Ca$_3$Co$_2$O$_6$ has long been known
+for an intriguing combination of extremely slow spin dynamics and peculiar
+magnetic orders, such as the evenly-spaced non-equilibrium metamagnetic
+magnetization steps and the long-wavelength spin density wave (SDW) order, the
+latter of which is essentially an emergent crystal of solitons. Recently, an
+elaborate field-cooling protocol to bypass the low-field SDW phase was proposed
+to overcome the extraordinarily long timescale of spin relaxation that impeded
+previous experimental studies in equilibrium, which may point to a deep
+connection between the low-temperature slow relaxation and the cooling process
+passing through the low-field SDW phase. As the first step to elucidate the
+conjectured connection, we investigate the magnetic field-induced deformation
+of the SDW state and incommensurate-commensurate transitions, thereby mapping
+out the equilibrium in-field phase diagram for a realistic three-dimensional
+lattice spin model by using Monte Carlo simulations. We also discuss
+Ginzburg-Landau theory that includes several Umklapp terms as well as an
+effective sine-Gordon model, which can qualitatively explain the observed
+magnetic field-induced deformation of the SDW microphases.",2112.01701v2
+2021-12-17,Macro-scale fast flow and magnetic field generation in 2-temperature relativistic electron-ion plasmas of astrophysical objects,"We have shown the simultaneous generation of macro-scale fast flows and
+strong magnetic fields in the 2-temperature relativistic electron-ion plasmas
+of astrophysical objects due to Unified Reverse Dynamo/Dynamo mechanism. The
+resulting dynamical magnetic field amplification and/or flow acceleration is
+directly proportional to the initial turbulent kinetic/magnetic (magnetic)
+energy; the process is very sensitive to relativistically hot electron-ion
+fraction temperature and magneto-fluid coupling. It is shown, that for
+realistic physical parameters of White Dwarfs accreting hot astrophysical flow
+/ Binary systems there always exists such a real solution of dispersion
+relation for which the formation of dispersive strong super-Alfv\'enic
+macro-scale flow/outflow with Alfv\'en Mach number $> 10^6$ and/or generation
+of super-strong magnetic fields is guaranteed.",2112.09673v1
+2022-02-01,Magnetic structures and electronic properties of cubic-pyrochlore ruthenates from first principles,"The magnetic ground states of $R_2$Ru$_2$O$_7$ and $A_2$Ru$_2$O$_7$ with $R=$
+Pr, Gd, Ho, and Er, as well as $A=$ Ca, Cd are predicted devising a combination
+of the cluster-multipole (CMP) theory and spin-density-functional theory
+(SDFT). The strong electronic correlation effects are estimated by the
+constrained-random-phase approximation (cRPA) and taken into account within the
+dynamical-mean-field theory (DMFT). The target compounds feature $d$-orbital
+magnetism on Ru$^{4+}$ and Ru$^{5+}$ ions for $R$ and $A$, respectively, as
+well as $f$-orbital magnetism on the $R$ site, which leads to an intriguing
+interplay of magnetic interactions in a strongly correlated system. We find
+CMP+SDFT is capable of describing the magnetic ground states in these
+compounds. The cRPA captures a difference in the screening strength between
+$R_2$Ru$_2$O$_7$ and $A_2$Ru$_2$O$_7$ compounds, which leads to a qualitative
+and quantitative understanding of the electronic properties within DMFT.",2202.00277v1
+2022-02-08,"Spin-Phonon Relaxation in Magnetic Molecules: Theory, Predictions and Insights","Magnetic molecules have played a central role in the development of magnetism
+and coordination chemistry and their study keeps leading innovation in
+cutting-edge scientific fields such as magnetic resonance, magnetism,
+spintronics, and quantum technologies. Crucially, a long spin lifetime well
+above cryogenic temperature is a stringent requirement for all these
+applications. In this chapter we review the foundations of spin relaxation
+theory and provide a detailed overview of first-principles strategies applied
+to the problem of spin-phonon relaxation in magnetic molecules. Firstly, we
+present a rigorous formalism of spin-phonon relaxation based on open quantum
+systems theory. These results are then used to derive classical
+phenomenological relations based on the Debye model. Finally, we provide a
+prescription of how to map the relaxation formalism onto existing electronic
+structure methods to obtain a quantitative picture of spin-phonon relaxation.
+Examples from the literature, including both transition metals and lanthanides
+compounds, will be discussed in order to illustrate how Direct, Orbach and
+Raman relaxation mechanisms can affect spin dynamics for this class of
+compounds.",2202.03776v1
+2022-02-13,Critical-layer instability of shallow water magnetohydrodynamic shear flows,"In this paper, the instability of shallow water shear flow with a sheared
+parallel magnetic field is studied. Waves propagating in such magnetic shear
+flows encounter critical levels where the phase velocity relative to the basic
+flow $c-U(y)$ matches the Alfv\'en wave velocities $\pm B(y)/\sqrt{\mu\rho}$,
+based on the local magnetic field $B(y)$, the magnetic permeability $\mu$ and
+the mass density of the fluid $\rho$. It is shown that when the two critical
+levels are close to each other, the critical layer can generate an instability.
+The instability problem is solved, combining asymptotic solutions at large
+wavenumbers and numerical solutions, and the mechanism of instability explained
+using the conservation of momentum. For the shallow water MHD system, the paper
+gives the general form of the local differential equation governing such
+coalescing critical layers for any generic field and flow profiles, and
+determines precisely how the magnetic field modifies the purely hydrodynamic
+stability criterion based on the potential vorticity gradient in the critical
+layer. The curvature of the magnetic field profile, or equivalently the
+electric current gradient, $J' = - B''/\mu$ in the critical layer is found to
+play a complementary role in the instability.",2202.06272v1
+2022-04-09,Magnetized granular particles running and tumbling on $S^{1}$,"It has been shown that a nonvibrated magnetic granular system, when it is
+feeded by means an altenating magnetic field, behaves with most of the
+distinctive physical features of active matter systems. In this work we focus
+our attention on the simplest granular system composed by a single magnetized
+spherical particle allocated in a quasi one-dimensional circular channel that
+receives energy from a magnetic field reservoir and transduces it into a
+running and tumbling motion. The theoretical analysis based on the run and
+tumble model on a circle of radius R forecasts the existence of a dynamical
+phase transition between an erratic motion (disordered phase) when the
+characteristic persistence length of the run and tumble motion, $\ell_{c} <
+R/2$, to a persistent motion (ordered phase) when $\ell_{c}> R/2$. It is found
+that the limiting behaviours of these phases correspond to a Brownian motion on
+the circle and a simple uniform circular motion, respectively. It is
+qualitatively shown that the lower magnetization of a particle, the larger
+persistence lenght is. It is so at least within the experimental limit of
+validity of our experiments. Our results show a very good agreement between
+theory and experiment.",2204.04552v1
+2022-04-12,Ferrofluid drop impacts and Rosensweig peak formation in a non-uniform magnetic field,"Vertical drop impacts of ferrofluids onto glass slides in a non-uniform
+magnetic field have been studied using high-speed photography. Outcomes have
+been classified based on the motion of the fluid-surface contact lines, and
+formation of peaks (Rosensweig instabilities) which affect the height of the
+spreading drop. The largest peaks are nucleated at the edge of a spreading
+drop, similarly to crown-rim instabilities in drop impacts with conventional
+fluids, and remain there for an extended time. Impact Weber numbers ranged from
+18.0 to 489, and the vertical component of the B-field was varied between 0 and
+0.37 T at the surface by changing the vertical position of a simple disc magnet
+placed below the surface. The falling drop was aligned with the vertical
+cylindrical axis of the 25 mm diameter magnet, and the impacts produced
+Rosensweig instabilities without splashing. At high magnetic field strengths a
+stationary ring of ferrofluid forms approximately above the outer edge of the
+magnet.",2204.05523v1
+2022-04-22,Resistive instabilities in sinusoidal shear flows with a streamwise magnetic field,"We investigate the linear stability of a sinusoidal shear flow with an
+initially uniform streamwise magnetic field in the framework of incompressible
+magnetohydrodynamics (MHD) with finite resistivity and viscosity. This flow is
+known to be unstable to the Kelvin-Helmholtz instability in the hydrodynamic
+case. The same is true in ideal MHD, where dissipation is neglected, provided
+the magnetic field strength does not exceed a critical threshold beyond which
+magnetic tension stabilizes the flow. Here, we demonstrate that including
+viscosity and resistivity introduces two new modes of instability. One of these
+modes, which we call a resistively-unstable Alfv\'en wave due to its connection
+to shear Alfv\'en waves, exists for any nonzero magnetic field strength as long
+as the magnetic Prandtl number $Pm < 1$. We present a reduced model for this
+instability that reveals its excitation mechanism to be the negative eddy
+viscosity of periodic shear flows described by Dubrulle & Frisch (1991).
+Finally, we demonstrate numerically that this mode saturates in a
+quasi-stationary state dominated by counter-propagating solitons.",2204.10875v1
+2022-05-05,$Λ/{\bar Λ}$ Polarization and Splitting Induced by Rotation and Magnetic Field,"The global polarization of $\Lambda/{\bar \Lambda}$ and the splitting of
+${\bar \Lambda}-\Lambda$ polarization induced by rotation and magnetic field
+has been investigated in a dynamical quark model by taking into account the
+axial vector interaction and the anomalous magnetic moment of quarks. It is
+found that the rotation leads to the spin polarization of quarks and
+anti-quarks with the same sign, while the magnetic field to opposite sign,
+which corresponds to the ${\bar \Lambda}-\Lambda$ polarization splitting. The
+combination of the two effects leads to perfect agreement with experiment data.
+Quantitatively, the axial vector spin polarization contributes 30$\%$ of the
+global polarization and the anomalous magnetic moment of quarks contributes
+40$\%$ to the splitting of ${\bar \Lambda}-\Lambda$ polarization. However, at
+$\sqrt{s_{NN}} \leq 7.7 \text{GeV}$, it still remains a challenge to reach
+enough magnitude of the magnetic field at freeze-out.",2205.02420v3
+2022-05-16,Twisting the near-field radiative heat switch in hyperbolic antiferromagnets,"We study the twisted control of the near-field radiative heat transfer
+between two hyperbolic antiferromagnetic insulators under external magnetic
+fields. We show that the near-field heat flux can be affected by both the twist
+angle $\theta$ and the magnitude of the applied magnetic field with different
+broken symmetries. Irrespective of twist angle, the external magnetic field
+causes the radiative heat flux to change nonmonotonically, and the minimum heat
+flux can be found with the magnetic fields of about 1.5 T. Such nonmonotonic
+behavior is due to the fact that the magnetic field can radically change the
+nature of the magnon polaritons with time reversal symmetry breaking. The field
+not only affects the topological structure of surface magnon polaritons, but
+also induces the volume magnon polaritons that progressively dominate the heat
+transfer as the field increases. We further propose a twist-induced thermal
+switch device with inversion symmetry breaking, which can severely regulate
+radiative heat flux through different magnetic fields. Our findings account for
+a characteristic modulation of radiative heat transfer with implications for
+applications in dynamic thermal management.",2205.07648v1
+2022-06-14,Scaling of the Hosking integral in decaying magnetically-dominated turbulence,"The Saffman helicity invariant of Hosking and Schekochihin (2021, PRX 11,
+041005), which we here call the Hosking integral, has emerged as an important
+quantity that may govern the decay properties of magnetically dominated
+nonhelical turbulence. Using a range of different computational methods, we
+confirm that this quantity is indeed gauge-invariant and nearly perfectly
+conserved in the limit of large Lundquist numbers. For direct numerical
+simulations with ordinary viscosity and magnetic diffusivity operators, we find
+that the solution develops in a nearly self-similar fashion. In a diagram
+quantifying the instantaneous decay coefficients of magnetic energy and
+integral scale, we find that the solution evolves along a line that is indeed
+suggestive of the governing role of the Hosking integral. The solution settles
+near a line in this diagram that is expected for a self-similar evolution of
+the magnetic energy spectrum. The solution will settle in a slightly different
+position when the magnetic diffusivity decreases with time, which would be
+compatible with the decay being governed by the reconnection time scale rather
+than the Alfv\'en time.",2206.07513v2
+2022-06-19,Equation of state of fermions in neutron stars,"Employing both the number density and energy density, the equation of state
+of fermions for each microscopic region of a neutron star is derived in the
+presence of various statistical effects. It is computed as functions of
+temperature (T), chemical potential (\mu) and magnetic field (B) based on the
+statistical properties and corresponding phases of neutron stars. It is
+revealed that the measurable properties describing the dynamic behavior of a
+neutron star are determined by the unusual statistical conditions. It is
+demonstrated that, in a strong magnetic field (B larger than\mu), the pressure
+(P) shows a logarithmic dependence on B (P is proportional to logarithm
+of(\mu/B). It is found that the regions with a higher (lower) magnetic field
+(density) have a shorter (longer) life time. Moreover, the relationship between
+the magnetic field and chemical potential confirms that the large magnetic
+field and high density are short lived as compared to low magnetic field and
+low density at the same temperature.",2206.09486v1
+2022-06-28,Impact of magnetic field on giant dipole resonance of $^{40}$Ca using the EQMD model,"By taking into account the magnetic field in the extended quantum molecular
+dynamics model (EQMD), we analyzed its effects on giant dipole resonance (GDR)
+by studying the responses and strengths of the dipole moments. The selected
+system is the $^{40}$Ca nucleus which is excited through the Coulomb
+interaction by $^{16}$O. Particle acceleration term in Li\'enard-Wiechert
+potential is discussed which, however, has small impact on magnetic field. The
+peak energy, strength and width of GDR, temperature, and angular momentum of
+$^{40}$Ca as a function of beam energy are investigated. It is found that the
+magnetic field enhances the peak energy, strength and width of GDR which is not
+only due to the temperature effects but also due to the enhancement of the
+angular momentum of nucleus. At beam energy {E} $>$ 200 MeV/nucleon, magnetic
+field maintains a constant value for the strength of GDR. The work sheds light
+on examining important roles of the magnetic field on nuclear structure in
+low-intermediate energy heavy-ion collisions.",2206.13921v1
+2022-07-05,Noncollinear magnetism in two-dimensional CrTe$_2$,"The discovery of two-dimensional (2D) van der Waals magnets opened
+unprecedented opportunities for the fundamental exploration of magnetism in
+quantum materials and the realization of next generation spintronic devices.
+Here, based on a multiscale modelling approach that combines first-principles
+calculations and a Heisenberg model supplied with ab-initio parameters, we
+report a strong magnetoelastic coupling in a free-standing monolayer of
+CrTe$_2$. We demonstrate that different crystal structures of a single CrTe$_2$
+give rise to non-collinear magnetism through magnetic frustration and emergence
+of the Dzyaloshinskii-Moriya interaction (DMI). Utilizing atomistic spin
+dynamics, we perform a detailed investigation of the complex magnetic
+properties pertaining to this 2D material impacted by the presence of various
+types of structural distortions akin to charge density waves.",2207.01926v2
+2022-07-08,Experimental Evidence of Plasmoids in High-$β$ Magnetic Reconnection,"Magnetic reconnection is a ubiquitous and fundamental process in plasmas by
+which magnetic fields change their topology and release magnetic energy.
+Despite decades of research, the physics governing the reconnection process in
+many parameter regimes remains controversial. Contemporary reconnection
+theories predict that long, narrow current sheets are susceptible to the
+tearing instability and split into isolated magnetic islands (or plasmoids),
+resulting in an enhanced reconnection rate. While several experimental
+observations of plasmoids in the regime of low- to intermediate-$\beta$ (where
+$\beta$ is the ratio of plasma thermal pressure to magnetic pressure) have been
+made, there is a relative lack of experimental evidence for plasmoids in the
+high-$\beta$ reconnection environments which are typical in many space and
+astrophysical contexts. Here, we report the observation of strong experimental
+evidence for plasmoid formation and dynamics in laser-driven high-$\beta$
+reconnection experiments.",2207.04119v1
+2022-07-16,Magnetization Switching of Single Magnetite Nanoparticles Monitored Optically,"Magnetic nanomaterials record information as fast as picoseconds in computer
+memories but retain it for millions of years in ancient rocks. This exceedingly
+broad range of times is covered by hopping over a potential energy barrier
+through temperature, ultrafast optical excitation for demagnetization or
+magnetization manipulation, mechanical stress, or microwaves. As switching
+depends on nanoparticle size, shape, orientation, and material properties, only
+single-nanoparticle studies can eliminate ensemble heterogeneity. Here, we push
+the sensitivity of photothermal magnetic circular dichroism down to individual
+20-nm magnetite nanoparticles. Single-particle magnetization curves display
+superparamagnetic to ferromagnetic behaviors, depending on size, shape, and
+orientation. Some nanoparticles undergo thermally activated switching on time
+scales of milliseconds to minutes. Surprisingly, the switching barrier appears
+to vary in time, leading to dynamical heterogeneity. Our observations will help
+to identify and eventually control the nanoscale parameters influencing the
+switching of magnetic nanoparticles, an important step for applications in many
+fields.",2207.07866v2
+2022-07-18,Nutational switching in ferromagnets and antiferromagnets,"It was demonstrated recently that on ultrashort time scales magnetization
+dynamics does not only exhibit precession but also nutation. Here, we
+investigate how nutation can contribute to spin switching leading towards
+ultrafast data writing. We use analytic theory and atomistic spin simulations
+to discuss the behavior of ferromagnets and antiferromagnets in high-frequency
+magnetic fields. In ferromagnets, linearly polarized fields align the
+magnetization perpendicular to the external field, enabling $90^{\circ}$
+switching. For circularly polarized fields in the $xy$ plane, the magnetization
+tilts to the $z$ direction. During this tilting, it rotates around the $z$
+axis, allowing $180^{\circ}$ switching. In antiferromagnets, external fields
+with frequencies higher than the nutation frequency align the order parameter
+parallel to the field direction, while for lower frequencies it is oriented
+perpendicular to the field. The switching frequency increases with the magnetic
+field strength, and it deviates from the Larmor frequency, making it possible
+to outpace precessional switching in high magnetic fields.",2207.08566v1
+2022-08-15,Tunable Strong Magnetic Anisotropy in Two-Dimensional van der Waals Antiferromagnets,"We show that anisotropic energy of a 2D antiferromagnet is greatly enhanced
+via stacking on a magnetic substrate layer, arising from the
+sublattice-dependent interlayer magnetic interaction that defines an effective
+anisotropic energy. Interestingly, this effective energy couples strongly with
+the interlayer stacking order and the magnetic order of the substrate layer,
+providing unique mechanical and magnetic means to control the antiferromagnetic
+order. These two types of control methods affect distinctly the sublattice
+magnetization dynamics, with a change of the ratio of sublattice precession
+amplitudes in the former and its chirality in the later. In moir\'{e}
+superlattices formed by a relative twist or strain between the layers, the
+coupling with stacking order introduces a landscape of effective anisotropic
+energy across the moir\'{e}, which can be utilized to create nonuniform
+antiferromagnetic textures featuring periodically localized low-energy magnons.",2208.06958v1
+2022-09-18,Observation of axisymmetric standard magnetorotational instability in the laboratory,"We report the first direct evidence for the axisymmetric standard
+magnetorotational instability (SMRI) from a combined experimental and numerical
+study of a magnetized liquid-metal shear flow in a Taylor-Couette cell with
+independently rotating and electrically conducting end caps. When a uniform
+vertical magnetic field $B_i$ is applied along the rotation axis, the measured
+radial magnetic field $B_r$ on the inner cylinder increases linearly with a
+small magnetic Reynolds number $Rm$ due to the magnetization of the residue
+Ekman circulation. Onset of the axisymmetric SMRI is identified from the
+nonlinear increase of $B_r$ beyond a critical $Rm$ in both experiments and
+nonlinear numerical simulations. The axisymmetric SMRI exists only at
+sufficiently large $Rm$ and intermediate $B_i$, a feature consistent with
+theoretical predictions. Our simulations further show that the axisymmetric
+SMRI causes the velocity and magnetic fields to contribute an outward flux of
+axial angular momentum in the bulk region, just as it should in accretion
+disks.",2209.08457v1
+2022-10-24,Reduction of energy cost of magnetization switching in a biaxial nanoparticle by use of internal dynamics,"A solution to energy-efficient magnetization switching in a nanoparticle with
+biaxial anisotropy is presented. Optimal control paths minimizing the energy
+cost of magnetization reversal are calculated numerically as functions of the
+switching time and materials properties, and used to derive energy-efficient
+switching pulses of external magnetic field. Hard-axis anisotropy reduces the
+minimum energy cost of magnetization switching due to the internal torque in
+the desired switching direction. Analytical estimates quantifying this effect
+are obtained based on the perturbation theory. The optimal switching time
+providing a tradeoff between fast switching and energy efficiency is obtained.
+The energy cost of switching and the energy barrier between the stable states
+can be controlled independently in a biaxial nanomagnet. This provides a
+solution to the dilemma between energy-efficient writability and good thermal
+stability of magnetic memory elements.",2210.13514v2
+2022-10-27,Magnetic Solitons due to interfacial chiral interactions,"We study solitons in a zig-zag lattice of magnetic dipoles. The lattice
+comprises two sublattices of parallel chains with magnetic dipoles at their
+vertices. Due to orthogonal easy planes of rotation for dipoles belonging to
+different sublattices, the total dipolar energy of this system is separable
+into a sum of symmetric and chiral long-ranged interactions between the magnets
+where the last takes the form of Dzyaloshinskii-Moriya coupling. For a specific
+range of values of the offset between sublattices, the dipoles realize an
+equilibrium magnetic state in the lattice plane, consisting of one chain
+settled in an antiferromagnetic parallel configuration and the other in a
+collinear ferromagnetic fashion. If the offset grows beyond this value, the
+internal Dzyaloshinskii-Moriya field stabilizes two Bloch domain walls at the
+edges of the antiferromagnetic chain. The dynamics of these solitons is studied
+by deriving the long-wavelength lagrangian density for the easy axis
+antiferromagnet. We find that the chiral couplings between sublattices give
+rise to an effective magnetic field that stabilizes the solitons in the
+antiferromagnet. When the chains displace respect to each other, an emergent
+Lorentz force accelerates the domain walls along the lattice.",2210.15716v2
+2022-11-20,Double Multiple-Relaxation-Time model of Lattice-Boltzmann Magnetohydrodynamics at Low Magnetic Reynolds Numbers,"We develop an improved lattice-Boltzmann numerical scheme to solve
+magnetohydrodynamic (MHD) equations in the regime of low magnetic Reynolds
+numbers, grounded on a manifestly Galilean covariant modeling of the
+Navier-Stokes equations. The simulation of the magnetic induction equation
+within the lattice-Boltzmann approach to MHD has been usually devised along the
+lines of the simplest phenomenological description, the single relaxation time
+(SRT) model. In order to deal with well-known stability difficulties of the SRT
+framework, we introduce, alternatively, a multi-relaxation-time technique for
+the solution of the magnetic induction equation, combined with a novel boundary
+condition method to cope with the subtleties of magnetic Boltzmann-like
+distributions on curved boundaries. As an application, we investigate open
+issues related to the description of transient flow regimes in MHD pipe flows,
+subject to non-uniform magnetic fields.",2211.11005v1
+2022-11-23,Pressure-Strain Interaction: II. Decomposition in Magnetic Field-Aligned Coordinates,"In weakly collisional and collisionless magnetized plasmas, the
+pressure-strain interaction describes the rate of conversion between bulk flow
+and thermal energy density. In this study, we derive an analytical expression
+for the pressure-strain interaction in a coordinate system with an axis aligned
+with the local magnetic field. The result is eight groups of terms
+corresponding to different physical mechanisms that can contribute to the
+pressure-strain interaction. We provide a physical description of each term.
+The results are immediately of interest to weakly collisional and collisionless
+magnetized plasmas and the fundamental processes that happen therein, including
+magnetic reconnection, magnetized plasma turbulence, and collisionless shocks.
+The terms in the field-aligned coordinate decomposition are likely accessible
+to measurement with satellite observations.",2211.13161v1
+2023-01-19,Maple Leaf Antiferromagnet in a Magnetic Field,"We analyze the quantum antiferromagnet on the maple leaf lattice in the
+presence of a magnetic field. Starting from its exact dimer ground state and
+for a magnetic field strength of the order of the local dimer spin exchange
+coupling, we perform a strong coupling expansion and extract an effective
+hardcore boson model. The interplay of effective many-body interactions,
+suppressed single-particle dynamics, and correlated hopping gives way to an
+intriguing series of superfluid to insulator transitions which correspond to
+magnetization plateaux in terms of the maple leaf spin degrees of freedom.
+While we find plateaux at intermediate magnetization to be dominated by bosonic
+density wave order, we conjecture plateau formation from multi-boson bound
+states due to correlated hopping for lower magnetization.",2301.08264v2
+2023-03-20,Free-induction-decay magnetic field imaging with a microfabricated Cs vapor cell,"Magnetic field imaging is a valuable resource for signal source localization
+and characterization. This work reports an optically pumped magnetometer (OPM)
+based on the free-induction-decay (FID) protocol, that implements
+microfabricated cesium (Cs) vapor cell technology to visualize the magnetic
+field distributions resulting from various magnetic sources placed close to the
+cell. The slow diffusion of Cs atoms in the presence of a nitrogen (N$_{2}$)
+buffer gas enables spatially independent measurements to be made within the
+same vapor cell by translating a $175\,\mu$m probe beam over the sensing area.
+For example, the OPM was used to record temporal and spatial information to
+reconstruct magnetic field distributions in one and two dimensions. The optimal
+magnetometer sensitivity was estimated to be 0.43$\,\mathrm{pT/\sqrt{Hz}}$
+within a Nyquist limited bandwidth of $500\,$Hz. Furthermore, the sensor's
+dynamic range exceeds the Earth's field of approximately $50\,\mu$T, which
+provides a framework for magnetic field imaging in unshielded environments.",2303.10915v2
+2023-05-12,Spacetime magnetic hopfions: from internal excitations and braiding of skyrmions,"Spatial topology endows topological solitons, such as skyrmions and hopfions,
+with fascinating dynamics. However, the temporal dimension has so far provided
+a passive stage on which topological solitons evolve. Here we construct
+spacetime magnetic hopfions: magnetic textures in two spatial dimensions that
+when excited by a time-periodic drive develop spacetime topology. We uncover
+two complementary construction routes using skyrmions by braiding their center
+of mass position and by controlling their internal low-energy excitations.
+Spacetime magnetic hopfions can be realized in nanopatterned grids to braid
+skyrmions and in frustrated magnets under an applied AC electric field. Their
+topological invariant, the spacetime Hopf index, can be tuned by the applied
+electric field as demonstrated by our collective coordinate modeling and
+micromagnetic simulations. The principles we have introduced to actively
+control spacetime topology are not limited to magnetic solitons, opening
+avenues to explore spacetime topology of general order parameters and fields.",2305.07589v1
+2023-07-10,Increasing Flips per Second and Speed of p-Computers by Using Dilute Magnetic Semiconductors to Implement Binary Stochastic Neurons,"Probabilistic computing with binary stochastic neurons (BSN) implemented with
+low- or zero-energy barrier nanoscale ferromagnets (LBMs) possessing in-plane
+magnetic anisotropy has emerged as an efficient paradigm for solving
+computationally hard problems. The fluctuating magnetization of an LBM at room
+temperature encodes a p-bit which is the building block of a BSN. Its only
+drawback is that the dynamics of common (transition metal) ferromagnets are
+relatively slow and hence the number of uncorrelated p-bits that can be
+generated per second - the so-called ""flips per second"" (fps) - is
+insufficient, leading to slow computational speed in autonomous co-processing
+with p-computers. Here, we show that a simple way to increase fps is to replace
+commonly used ferromagnets (e.g. Co, Fe, Ni), which have large saturation
+magnetization Ms, with a dilute magnetic semiconductor like GaMnAs with much
+smaller saturation magnetization. The smaller Ms reduces the energy barrier
+within the LBM and increases the fps significantly. It also offers other
+benefits such as increased packing density for increased parallelization and
+reduced device to device variation. This provides a way to realize the hardware
+acceleration and energy efficiency promise of p-computers.",2307.04663v1
+2023-07-26,Symmetry of the emergent inductance tensor exhibited by magnetic textures,"Metals hosting gradually varying spatial magnetic textures are attracting
+attention as a new class of inductor. Under the application of an alternating
+current, the spin-transfer-torque effect induces oscillating dynamics of the
+magnetic texture, which subsequently yields the spin-motive force as a back
+action, resulting in an inductive voltage response. In general, a second-order
+tensor representing a material's response can have an off-diagonal component.
+However, it is unclear what symmetries the emergent inductance tensor has and
+also which magnetic textures can exhibit a transverse inductance response. Here
+we reveal both analytically and numerically that the emergent inductance tensor
+should be a symmetric tensor in the so-called adiabatic limit. By considering
+this symmetric tensor in terms of symmetry operations that a magnetic texture
+has, we further characterize the magnetic textures in which the transverse
+inductance response can appear. This finding provides a basis for exploring the
+transverse response of emergent inductors, which has yet to be discovered.",2307.14542v2
+2023-08-04,Probing the magnetic field strength dependence of the Chiral Magnetic Effect,"The article presents a study aimed at probing the dependence of the Chiral
+Magnetic Effect (CME) on the magnetic field strength using the Anomalous
+Viscous Fluid Dynamics (AVFD) model in Pb--Pb at LHC energies. The results
+demonstrate the quadratic dependence of the correlators used for the study of
+the CME in heavy ion collisions on the number of spectators, a proxy of the
+magnitude of the magnetic field. The article also presents the extension of
+this approach to a two dimensional space, formed by both the aforementioned
+proxy of the magnetic field strength but also a proxy of the final state
+ellipticity, a key ingredient of the background in these measurements, for each
+centrality interval. This provides an exciting possibility to experiments to
+isolate the background contributions from the potential CME signal.",2308.02361v3
+2023-08-16,Quench Detection in a Superconducting Radio Frequency Cavity with Combine Temperature and Magnetic Field Mapping,"Local dissipation of RF power in superconducting radio frequency cavities
+create so called hot spots, primary precursors of cavity quench driven by
+either thermal or magnetic instability. These hot spots are detected by a
+temperature mapping system, and a large increase in temperature on the outer
+surface is detected during cavity quench events. Here, we have used combined
+magnetic and temperature mapping systems using anisotropic magnetoresistance
+(AMR) sensors and carbon resisters to locate the hot spots and areas with high
+trapped flux on a 3.0 GHz single-cell Nb cavity during the RF tests at 2.0 K.
+The quench location and hot spots were detected near the equator when the
+residual magnetic field in the Dewar is kept < 1 mG. The hot spots and quench
+locations moved when the magnetic field is trapped locally, as detected by
+T-mapping system. No significant dynamics of trapped flux is detected by AMR
+sensors, however, change in magnetic flux during cavity quench is detected by a
+flux gate magnetometer, close to the quench location. The result provides the
+direct evidence of hot spots and quench events due to localized trapped
+vortices.",2308.08686v1
+2023-11-06,2D Magnetic Heterostructures: Spintronics and Quantum Future,"The discovery of two-dimensional (2D) magnetism within atomically thin
+structures derived from layered crystals has opened up a new realm for
+exploring magnetic heterostructures. This emerging field provides a
+foundational platform for investigating unique physical properties and
+exquisite phenomena at the nanometer and molecular/atomic scales. By
+engineering 2D interfaces using physical methods and selecting interlayer
+interactions, we unlock the potential for extraordinary exchange dynamics. This
+potential extends to high-performance and high-density magnetic memory
+applications, as well as future advancements in neuromorphic and quantum
+computing. This review delves into recent advances in 2D magnets, elucidates
+the mechanisms behind 2D interfaces, and highlights the development of 2D
+devices for spintronics and quantum information. Particular focus is placed on
+2D magnetic heterostructures with topological properties, promising for a
+resilient and low-error information system. Finally, we discuss the trends of
+2D heterostructures for future electronics, considering the challenges and
+opportunities from physics, material synthesis, and technological prospective.",2311.03505v1
+2023-12-15,Laser Thomson Scattering Measurements around Magnetized Model in Rarefied Argon Arcjet Plume,"To elucidate the role of the Hall effect in magnetohydrodynamic (MHD)
+aerobraking in rarefied flows,we measured the radial distributions of electron
+temperature and density in front of a magnetized model in a rarefied argon
+arcjet wind tunnel using the laser Thomson scattering method. We also developed
+a water-cooled magnetized model to prevent thermal demagnetization during the
+measurement. The measured electron density distributions were in excellent
+agreement with computational fluid dynamics (CFD) predictions. It was also
+found that the magnetic field had little effect on the electron density
+distribution around the model. In the case without the magnetic field, the
+measured electron temperature almost agreed with the CFD prediction. However,
+the measured electron temperature increase caused by applying the magnetic
+field was about 1,000 K less than that of the CFD prediction. This discrepancy
+indicates that the location of an insulating boundary in the plasma is far from
+the model.",2312.09593v2
+2023-12-31,Spinterface Mediated Magnetic Properties of Co20Fe60B20/Alq3 Heterostructures,"Organic semiconductors (OSCs) are suitable materials for spintronics
+applications as they form a spinterface when placed next to a ferromagnet,
+which in turn leads to novel functionalities. The evolution of spinterface can
+tune the global magnetic anisotropy, magnetization reversal, magnetization
+dynamics, etc. Planar tris-(8-hydroxyquinoline)aluminum (Alq3) OSC has shown
+tremendous potential for spintronics applications, thanks to its efficient
+spin-polarized current transport ability. Here, we establish the spinterface
+when the Alq3 molecules are deposited on amorphous ferromagnet
+Co20Fe60B20(CFB). The $\pi$-d hybridization in CFB/Alq3 enhances the coercive
+field and significantly modifies the shape and size of the magnetic domains. A
+$\sim$100% increase in uniaxial anisotropic energies and a reduction in
+magnetic damping are also evident owing to the strong interfacial
+hybridization.",2401.00487v1
+2024-02-12,Continuum of magnetic excitations in the Kitaev honeycomb iridate D$_3$LiIr$_2$O$_6$,"Inelastic neutron scattering (INS) measurements of powder
+D$_3(^{7}$Li)($^{193}$Ir)$_2$O$_6$ reveal low energy magnetic excitations with
+a scattering cross section that is broad in $|Q|$ and consistent with a Kitaev
+spin-liquid (KSL) state. The magnetic nature of the excitation spectrum is
+demonstrated by longitudinally polarized neutron studies. The total magnetic
+moment of 1.7(2)$\mu_B$/Ir inferred from the total magnetic scattering cross
+section is consistent with the effective moment inferred from magnetic
+susceptibility data and expectations for the $J_{\rm eff}=1/2$ single ion
+state. The rise in the dynamic correlation function ${\cal S}(Q,\omega)$ for
+$\hbar\omega<5~$meV can be described by a nearest-neighbor Kitaev model with
+interaction strength $K\approx-13(5)$~meV. Exchange disorder associated with
+the mixed D-Li site could play an important role in stabilizing the low $T$
+quantum fluctuating state.",2402.08083v1
+2024-02-16,Tuning properties of phase-separated magnetic fluid with temperature,"Phase-separated magnetic fluids provide a very strong magnetic response
+($\mu>25$) in a liquid state material. Even small fields can cause a notable
+material response, but this depends on its properties, which are often
+difficult to control. Here, we investigate how temperature affects the
+properties of the system, where phase separation is induced by an increase in
+ionic strength. Following the deformations of individual microscopic droplets,
+we can extract surface tension, magnetic permeability, and viscosity. We find
+that the temperature increase does not affect the surface tension, while the
+magnetic permeability and viscosity increase. Applying this knowledge to induce
+a shape instability for a drop only using temperature shows the potential of
+applicability of our findings.",2402.11117v1
+2024-02-21,Magnetic field and radial velocity fluxes at the initial stages of the evolution of solar active regions based on measurements at the photospheric level,"In this article, the physical processes occurring in the convective layer and
+the photosphere of the Sun and their connection to the formation of active
+regions (ARs) and the development of the corresponding magnetic field are
+explored. Specifically, we test the magnetic flux emergence hypothesis and
+based on the line-of-sight magnetic field and Doppler shift data obtained from
+the Global Oscillation Network Group (GONG) observations. The study encompasses
+the analysis of 24 ARs observed during the period from 2011 to 2022. We find a
+strong correlation between the magnetic flux and the imbalance of radial
+velocity fluxes. The results indicate that the magnetic flux emergence
+hypothesis cannot fully explain the evolution of ARs during their early stages
+of development.",2402.13806v1
+2024-02-26,Oscillatory Hall effect from magnetoelectronic coupling in flexoelectronic silicon,"The magnetoelectronic coupling can be defined as cross-domain coupling
+between electronic and magnetic properties, where modulation in magnetic
+properties changes the electronic properties. In this letter, an explicit
+experimental evidence of magnetoelectronic coupling is presented, which is
+uncovered from oscillatory Hall effect response in Hall measurement. The strain
+gradient in a MgO (1.8 nm)/p-Si (~400 nm) freestanding sample leads to transfer
+of electrons (~5X10^18 cm^-3) from valence to conduction band due to
+flexoelectronic charge separation in the p-Si layer. The resulting
+flexoelectronic polarization gives rise to temporal magnetic moment from
+dynamical multiferroicity. The external magnetic field changes the net temporal
+magnetic moment, which causes modulations in charge carrier concentration and
+oscillatory Hall effect. The period of oscillatory Hall response is 1.12 T,
+which is attributed to the magnitude of temporal magnetic moment. The discovery
+of oscillatory Hall effect adds a new member to the family of Hall effects.",2402.16330v1
+2024-02-26,Discovery of magnetically guided metal accretion onto a polluted white dwarf,"Dynamically active planetary systems orbit a significant fraction of white
+dwarf stars. These stars often exhibit surface metals accreted from debris
+disks, which are detected through infrared excess or transiting structures.
+However, the full journey of a planetesimal from star-grazing orbit to final
+dissolution in the host star is poorly understood. Here, we report the
+discovery that the cool metal polluted star WD0816-310 has cannibalized heavy
+elements from a planetary body similar in size to Vesta, and where accretion
+and horizontal mixing processes have clearly been controlled by the stellar
+magnetic field. Our observations unveil periodic and synchronized variations in
+metal line strength and magnetic field intensity, implying a correlation
+between the local surface density of metals and the magnetic field structure.
+Specifically, the data point to a likely persistent concentration of metals
+near a magnetic pole. These findings demonstrate that magnetic fields may play
+a fundamental role in the final stages of exoplanetary bodies that are recycled
+into their white dwarf hosts.",2402.16526v1
+2024-02-28,Plasma-induced magnetic phase in 3D $\mathrm{Mn^{II}-Nb^{IV}}$ octacyanidometalate with magnetic sponge behavior,"A new magnetic phase with $T_C = 72 \ \mathrm K$ was obtained by exposing the
+three-dimensional $\mathrm{\{ [Mn^{II}(H_2O)_2]_2[Nb^{IV}(CN)_8] \cdot 4H_2O \}
+_n}$ coordination ferrimagnet ($T_C = 49 \ \mathrm K$) to air, oxygen,
+nitrogen, and argon-based plasma. The X-ray powder diffraction pattern revealed
+that the unit cell shrank after plasma treatment, leading to a 20% enhancement
+of the superexchange couplings, as estimated from the mean-field approximation
+(MFA) model. Although no stable dehydrated form was found in the
+thermogravimetric analysis, the observed changes are attributed to the removal
+of crystallization water molecules. The plasma-induced magnetic phase could not
+be obtained by exposing the studied material to 0% relative humidity during
+dynamic vapor sorption. Instead, the material underwent a major structural
+reorganization after dehydration, necessitating an extended MFA model to
+reproduce the magnetic susceptibility. These findings demonstrate that
+plasma-induced changes can create unique magnetic phases in molecule-based
+systems that are otherwise unobtainable.",2402.18195v1
+2024-03-19,Polarization Dynamics in Paramagnet of Charged Quark-Gluon Plasma,"It is commonly understood that the strong magnetic field produced in heavy
+ion collisions is short-lived. The electric conductivity of the quark-gluon
+plasma is unable to significantly extend the life time of magnetic field. We
+propose an alternative scenario to achieve this: with finite baryon density and
+spin polarization by the initial magnetic field, the quark-gluon plasma behaves
+as a paramagnet, which may continue to polarize quark after fading of initial
+magnetic field. We confirm this picture by calculations in both quantum
+electrodynamics and quantum chromodynamics. In the former case, we find a
+splitting in the damping rates of probe fermion with opposite spin component
+along the magnetic field with the splitting parametrically small than the
+average damping rate. In the latter case, we find a similar splitting in the
+damping rates of probe quark with opposite spin components along the magnetic
+field. The splitting is parametrically comparable to the average damping rate,
+providing an efficient way of polarizing strange quarks by the quark-gluon
+plasma paramagnet consisting of light quarks.",2403.12615v1
+2024-04-03,Enhancing Phase Stability and Coercivity of MnAl $τ$-L$1_0$ with Fe and Ni Substitutions: \textit{ab initio} and Micromagnetic Modeling,"The binary manganese aluminium (MnAl) alloy with L$1_0$ crystal structure,
+which exhibits exceptional magnetic properties, is a promising rare earth
+element free permanent magnet material. However, according to experimental
+reports, synthesizing it in a stable bulk form is extremely challenging. Here,
+we propose and theoretically verify an alternative method of stabilizing the
+material by partially substituting Mn and Al sites by Fe and Ni and identify
+its stability, electronic structure, and magnetic properties from density
+functional theory (DFT) calculations. When considering a fixed ($50\%$)-Ni, the
+magnetic anisotropy increases with the increasing Fe content, but the trend is
+opposite in terms of formation energy. The calculated formation energies
+demonstrate that all the binary and quaternary compositions are stable. Through
+the analysis of calculated elastic constants and phonon frequencies, we confirm
+that all compositions are mechanically and dynamically stable. Most
+importantly, both magnetic moment and magnetic anisotropy constant in $50\%$-Fe
+substituted composition (equiatomic phase) increases significantly as compared
+to the MnAl. Predicted coercivity of equiatomic phase is larger than parent
+compound obtained by combining DFT computed parameters with micromagnetic
+simulations.",2404.03051v1
+2020-11-14,Dynamical Effective Field Model for Interacting Ferrofluids: II. The proper relaxation time and effects of dynamic correlations,"The recently proposed dynamical effective field model (DEFM) is
+quantitatively accurate for describing dynamical magnetic response of
+ferrofluids. In paper I it is derived under the framework of dynamical density
+functional theory, via which the original ensemble of bare Brownian particles
+is mapped to an ensemble of dressed particles. However, it remains to clarify
+how the characteristic rotational relaxation time of a dressed particle,
+denoted by $\tau_r$, is quantitatively related to that of a bare particle,
+denoted by $\tau^0_r$. By building macro-micro connections via two different
+routes, I reveal that under some gentle assumptions $\tau_r$ can be identified
+with the long-time rotational self-diffusion time. I further introduce two
+simple but useful integrated correlation factors, describing the effects of
+quasi-static (adiabatic) and dynamic (nonadiabatic) inter-particle
+correlations, respectively. In terms of both correlation factors I reformulate
+the dynamic magnetic susceptibility in an illuminating and elegant form.
+Remarkably, it shows that the macro-micro connection is established via two
+successive steps: a dynamical coarse-graining with nonadiabatic effects
+accounted for by the dynamic factor, followed by equilibrium statistical
+mechanical averaging captured by the static factor. Surprisingly,
+$\tau_r/\tau^0_r$ is found insensitive to changes of particle volume fraction.
+I provide a physical picture to explain it. Furthermore, an empirical formula
+is proposed to characterize the dependence of $\tau_r/\tau^0_r$ on
+dipole-dipole interaction strength. The DEFM supplemented with this formula
+leads to parameter-free predictions in good agreement with results from
+Brownian dynamics simulations. The theoretical developments presented in this
+paper may have important consequences to studies of ferrofluid dynamics in
+particular and other systems modelled by DDFTs in general.",2011.07293v1
+2016-12-07,Effects of uniaxial pressure on the quantum tunneling of magnetization in a high-symmetry Mn12 single-molecule magnet,"The symmetry of single-molecule magnets dictates their spin quantum dynamics,
+influencing how such systems relax via quantum tunneling of magnetization
+(QTM). By reducing a system's symmetry, through the application of a magnetic
+field or uniaxial pressure, these dynamics can be modified. We report
+measurements of the magnetization dynamics of a crystalline sample of the
+high-symmetry [Mn12O12(O2CMe)16(MeOH)4]MeOH single-molecule magnet as a
+function of uniaxial pressure applied either parallel or perpendicular to the
+sample's ""easy"" magnetization axis. At temperatures between 1.8 and 3.3 K,
+magnetic hysteresis loops exhibit the characteristic steplike features that
+signal the occurrence of QTM. After applying uniaxial pressure to the sample in
+situ, both the magnitude and field position of the QTM steps changed. The step
+magnitudes were observed to grow as a function of pressure in both arrangements
+of pressure, while pressure applied along (perpendicular to) the sample's easy
+axis caused the resonant-tunneling fields to increase (decrease). These
+observations were compared with simulations in which the system's Hamiltonian
+parameters were changed. From these comparisons, we determined that parallel
+pressure induces changes to the second-order axial anisotropy parameter as well
+as either the fourth-order axial or fourth-order transverse parameter, or to
+both. In addition, we find that pressure applied perpendicular to the easy axis
+induces a rhombic anisotropy E ~ D/2000 per kbar that can be understood as
+deriving from a symmetry-breaking distortion of the molecule.",1612.02396v3
+2017-11-11,Tunable dynamic moduli of magnetic elastomers: from X-$μ$CT characterization to mesoscopic modeling,"Ferrogels and magnetoelastomers are composite materials obtained by embedding
+magnetic particles of mesoscopic size in a crosslinked polymeric matrix. They
+combine the reversible elastic deformability of polymeric materials with the
+high responsivity of ferrofluids to external magnetic fields. These materials
+stand out, for example, for large magnetostriction as well as significant
+increase of the elastic moduli in the presence of external magnetic fields. By
+means of X-ray micro-computed tomography, position and size of each magnetic
+particle can be measured with a high degree of accuracy. We here use data
+extracted from real magnetoelastic samples as input for coarse-grained
+dipole-spring modeling and calculations to investigate magnetostriction,
+stiffening, and changes in the normal modes spectrum. More precisely, we assign
+to each particle a dipole moment proportional to its volume and set a
+randomized network of springs between them that mimics the behavior of the
+polymeric elastic matrix. Extending our previously developed methods, we
+compute the resulting structural changes in the systems, their overall
+distortions, as well as the frequency-dependent elastic moduli when magnetic
+interactions are turned on. Particularly, with increasing magnetization, we
+observe the formation of chain-like aggregates, resulting in significant
+overall deformations. Interestingly, the static elastic moduli can first show a
+slight decrease with growing amplitude of the magnetic interactions, before a
+pronounced increase appears upon the chain formation. The change of the dynamic
+moduli with increasing magnetization depends on the frequency and can even show
+nonmonotonic behavior. Overall, we demonstrate how theory and experiments can
+complement each other to learn more about the dynamic behavior of this
+interesting class of materials.",1711.04165v1
+2020-08-06,"Magnetic Energy Release, Plasma Dynamics, and Particle Acceleration during Relativistic Turbulent Magnetic Reconnection","In strongly magnetized astrophysical plasma systems, magnetic reconnection is
+believed to be a primary process during which explosive energy release and
+particle acceleration occur, leading to significant high-energy emission. Past
+years have witnessed active development of kinetic modeling of relativistic
+magnetic reconnection, supporting this magnetically dominated scenario. A much
+less explored issue is the consequence of 3D dynamics, where turbulent
+structures are naturally generated as various types of instabilities develop.
+This paper presents a series of 3D, fully-kinetic simulations of relativistic
+turbulent magnetic reconnection (RTMR) in positron-electron plasmas with system
+domains much larger than kinetic scales. Our simulations start from a
+force-free current sheet with several different modes of long wavelength
+magnetic field perturbations, which drive additional turbulence in the
+reconnection region. Because of this, the current layer breaks up and the
+reconnection region quickly evolves into a turbulent layer filled with coherent
+structures such as flux ropes and current sheets. We find that plasma dynamics
+in RTMR is vastly different from their 2D counterparts in many aspects. The
+flux ropes evolve rapidly after their generation, and can be completely
+disrupted due to the secondary kink instability. This turbulent evolution leads
+to superdiffusion behavior of magnetic field lines as seen in MHD studies of
+turbulent reconnection. Meanwhile, nonthermal particle acceleration and
+energy-release time scale can be very fast and do not strongly depend on the
+turbulence amplitude. The main acceleration mechanism is a Fermi-like
+acceleration process supported by the motional electric field, whereas the
+non-ideal electric field acceleration plays a subdominant role. We discuss
+possible observational implications of 3D RTMR in high-energy astrophysics.",2008.02743v2
+2021-07-21,Magnetic field tuning of the spin dynamics in the magnetic topological insulators (MnBi$_{2}$Te$_{4}$)(Bi$_{2}$Te$_{3}$)$_{n}$,"We report a high frequency/high magnetic field electron spin resonance
+(HF-ESR) spectroscopy study in the sub-THz frequency domain of the two
+representatives of the family of magnetic topological insulators
+(MnBi$_{2}$Te$_{4}$)(Bi$_{2}$Te$_{3}$)$_{n}$ with $n = 0$ and 1. The HF-ESR
+measurements in the magnetically ordered state at a low temperature of $T = 4$
+K combined with the calculations of the resonance modes showed that the spin
+dynamics in MnBi$_{\text{4}}$Te$_{\text{7}}$ is typical for an anisotropic
+easy-axis type ferromagnet (FM) whereas MnBi$_{\text{2}}$Te$_{\text{4}}$
+demonstrates excitations of an anisotropic easy-axis type antiferromagnet
+(AFM). However, by applying the field stronger than a threshold value $\sim 6$
+T we observed in MnBi$_{\text{2}}$Te$_{\text{4}}$ a crossover from the AFM
+resonance modes to the FM modes which properties are very similar to the
+ferromagnetic response of MnBi$_{\text{4}}$Te$_{\text{7}}$. We attribute this
+remarkably unusual effect unexpected for a canonical easy-axis AFM, which,
+additionally, can be accurately reproduced by numerical calculations of the
+excitation modes, to the closeness of the strength of the AFM exchange and
+magnetic anisotropy energies which appears to be a very specific feature of
+this compound. Our experimental data evidences that the spin dynamics of the
+magnetic building blocks of these compounds, the Mn-based septuple layers
+(SLs), is inherently ferromagnetic featuring persisting short-range FM
+correlations far above the magnetic ordering temperature as soon as the SLs get
+decoupled either by introducing a nonmagnetic quintuple interlayer, as in
+MnBi$_{\text{4}}$Te$_{\text{7}}$, or by applying a moderate magnetic field, as
+in MnBi$_{\text{2}}$Te$_{\text{4}}$, which may have an effect on the surface
+topological band structure of these compounds.",2107.09929v1
+2021-09-09,Numerical reverse engineering of general spin-wave dispersions: Bridge between numerics and analytics using a dynamic-matrix approach,"Modern problems in magnetization dynamics require more and more the numerical
+determination of the spin-wave spectra and -dispersion in magnetic systems
+where analytic theories are not yet available. Micromagnetic simulations can be
+used to compute the spatial profiles and oscillation frequencies of spin-waves
+in magnetic system with almost arbitrary geometry and different magnetic
+interactions. Although numerical approaches are very versatile, they often do
+not give the same insight and physical understanding as analytical theories.
+For example, it is not always possible to decide whether a certain feature
+(such as dispersion asymmetry, for example) is governed by one magnetic
+interaction or the other. Moreover, since numerical approaches typically yield
+the normal modes of the system, it is not always feasible to disentangle
+hybridized modes. In this manuscript, we build a bridge between numerics and
+analytics by presenting a methodology to calculate the individual contributions
+to general spin-wave dispersions in a fully numerical manner. We discuss the
+general form of any spin-wave dispersion in terms of the effective (stiffness)
+fields produced by the modes. Based on a special type of micromagnetic
+simulations, the numerical dynamic-matrix approach, we show how to calculate
+each stiffness field in the respective dispersion law, separately for each
+magnetic interaction. In particular, it becomes possible to disentangle
+contributions of different magnetic interactions to the dispersion asymmetry in
+systems where non-reciprocity is present. At the same time, dipolar-hybridized
+modes can be easily disentangled. Since this method is independent of the
+geometry or the involved magnetic interactions at hand, we believe it is
+attractive for experimental and theoretical studies of magnetic systems where
+there are no analytics yet, but also to aid the development of new analytical
+theories.",2109.04521v2
+2023-05-19,Secular dipole-dipole stability of magnetic binaries,"The presence of strong large-scale stable magnetic fields in a significant
+portion of early-type stars, white dwarfs, and neutron stars is well
+established. Despite this, the origins of these fields remain unresolved, with
+leading propositions advocating fossil fields, mergers, and shear-driven
+dynamos as the main mechanism. A potential key for further insight could lie in
+the connection with binarity: notably, magnetism can play a role in the
+long-term orbital and rotational dynamics of binaries. In gravitational wave
+astronomy, the advanced sensitivity of upcoming detectors such as LISA and the
+Einstein Telescope will enable the characterisation of the orbital inspirals of
+compact systems, including their magnetic properties. A comprehensive
+understanding of the dynamics of magnetism in these systems is required for the
+interpretation of the gravitational wave signals and to avoid calibration
+biases. Furthermore, this knowledge can be used to create new magnetic
+population models and to provide insight into the nature of their internal
+fields. The aim of this study is to investigate the secular spin precession
+dynamics of binary systems under pure magnetic dipole interactions, focusing on
+stars with strong, stable, dipolar fields. We employ an orbit-averaging
+procedure for the spin equations and obtain an effective secular description.
+By minimising the magnetic energy, we derive the configurations of equilibrium.
+We show that among the four states, only one is stable, consisting of the spin
+and magnetic axes of one star reversed with respect to the companions', and
+orthogonal to the orbital plane. Our long-term stability results disagree with
+usual methods, which tend to neglect orbital motion. Finally, we provide
+analytical solutions for the system out of equilibrium, which can be used to
+derive secular orbital evolution in the context of gravitational wave
+astronomy.",2305.15429v1
+1999-06-29,Magnetic Fields in Clusters: Theory vs. Observations,"It is now well established that the plasma in galaxy clusters is magnetized.
+In some cases, at least, the field is strong enough to be dynamically
+important. Perhaps this is the time to move past simple detection experiments,
+and to work towards a general understanding of the strength, structure and
+maintenance of the cluster field.",9906485v1
+1996-09-24,"Comment on ``Generalized Dynamic Scaling for Critical Relaxation"" [Phys. Rev. Lett. 77, 679 (1996), cond-mat/9607013]","We point out that in nonequilibrium relaxational processes the magnetic field
+of the initial state (instead of the initial magnetization) has to be
+considered as the additional scaling field (related to the initial state).
+Taking this into account the interpretation of the scaling behavior observed in
+the paper by Zheng becomes more straightforward.",9609232v1
+1996-12-27,The magnetic susceptibility of the t-J model at low hole doping,"We compute the dynamical magnetic susceptibility of the t-J model in its
+commensurate flux phase at low hole doping. We compare the calculations with
+experiments and exact diagonalization studies.",9612231v1
+2002-08-21,Re-entrant spin glass and magnetoresistance in Co_{0.2}Zn_{0.8}Fe_{1.6}Ti_{0.4}O_4 spinel oxide,"We have investigated the static and dynamic response of magnetic clusters in
+Co_{0.2}Zn_{0.8}Fe_{1.6}Ti_{0.4}O_4 spinel oxide, where a sequence of magnetic
+phase transitions, i.e., paramagnetic (PM) to ferromagnetic at T_{C} $\leq$
+270K and ferromagnetic to canted spin glass state at T_f$ $\leq$ 125K is
+observed.",0208416v1
+2002-10-31,Dipolar corrections to the static magnetic susceptibility of condensed $^3$He,"We examine the consequences of a recent model describing correlated
+zero-point polarization of the electronic cloud in solid $^3$He. This
+polarization arises from the highly anisotropic and correlated dynamic mixing
+of the $s$ and $p$ electronic levels ($\sim1$%). The magnetic polarization
+introduces a small paramagnetic correction, of $1-0.1$%, to the static
+susceptibility of condensed $^3$He. This correction could explain recent
+measurements in liquid $^3$He.",0210705v1
+2004-03-29,Correlation effects in Co/Cu and Fe/Cr magnetic multilayers,"The electronic structure of Co/Cu(001) and Fe/Cr(001) magnetic multilayers
+has been investigated within the local density approximation combined with
+dynamical mean field theory. Our calculation shows enhanced density of states
+at the Fermi level, suggesting that electronic correlations might play an
+important role in the transport properties of multilayers.",0403685v1
+2005-04-28,To the theory of interaction between electron and nuclear systems,"Coupled electron-nuclear oscillations in antiferromagnetics with anisotropy
+of ""light plane"" type in the strong external magnetic field are under
+consideration. The new mode \epsilon_{2k} of these coupled oscillations is
+obtained for antiferromagnetic systems by using ""u-v""-Bogolubov?s unitary
+transformations. The dynamic shift of the frequency of nuclear magnetic
+resonance concerned with this mode is obtained.",0504759v1
+2005-05-10,Fluctuation-dissipation considerations and damping models for ferromagnetic materials,"The role of fluctuation-dissipation relations (theorems) for the
+magnetization dynamics with Landau-Lifshitz-Gilbert and Bloch-Bloembergen
+damping terms are discussed. We demonstrate that the use of the Callen-Welton
+fluctuation-dissipation theorem that was proven for Hamiltonian systems can
+give an inconsistent result for magnetic systems with dissipation.",0505259v1
+2007-02-05,Rabi oscillations from ultrasound in spin systems,"It is shown that ultrasound in the GHz range can generate space-time Rabi
+oscillations between spin states of molecular magnets. We compute dynamics of
+the magnetization generated by surface acoustic waves and discuss conditions
+under which this novel quantum effect can be observed.",0702116v1
+2002-09-26,Precession of a particle with anomalous magnetic moment in electromagnetic and gravitational pp-wave fields,"We present an exact solution of the Bargmann-Michel-Telegdi (BMT) equations
+for the dynamics of a spin particle in external electromagnetic and
+gravitational pp-wave fields. We demonstrate that an anomalous magnetic moment
+gives rise to an additional spin rotation which is modulated both by the
+electromagnetic and by the gravitational wave periodicities.",0209099v1
+2003-08-26,Precision Measurement of the Anomalous Magnetic Moment of the Muon,"A precision measurement of the anomalous magnetic moment (g-2) of the muon
+has been made by the E821 collaboration at BNL. This paper is a written version
+of a ``hot topics'' talk at ICAP2002 (Cambridge, MA). The principles of the
+experiment are discussed, especially the beam dynamics aspects.",0308064v1
+1997-04-24,Chiral Symmetry Breaking in QED in a Magnetic Field at Finite Temperature,"The catalysis of chiral symmetry breaking in the massless weakly coupled QED
+in a magnetic field at finite temperature is studied. The temperature of the
+symmetry restoration is estimated analytically as $T_c\simeq m_{dyn}$, where
+$m_{dyn}$ is the dynamical mass of a fermion at zero temperature.",9704394v1
+2007-02-01,Progress on chiral symmetry breaking in a strong magnetic field,"The problem of chiral symmetry breaking in QED in a strong magnetic field is
+briefly reviewed. Recent progress on issues regarding the gauge fixing
+independence of the dynamically generated fermion mass is discussed.",0702010v1
+1995-12-15,Chiral Symmetry Breaking by a Magnetic Field in Weak-coupling QED,"Using the nonperturbative Schwinger-Dyson equation, we show that chiral
+symmetry in weak-coupling massless QED is dynamically broken by a constant but
+arbitrarily strong external magnetic field.",9512114v1
+1997-05-26,Magnetic Vortices in a Gauged O(3) Sigma Model with Symmetry Breaking Self-Interaction,"We consider a (2+1) dimensional nonlinear O(3) sigma model with its U(1)
+subgroup gauged along with the inclusion of a self-interaction having symmetry
+breaking minima.The gauge field dynamics is governed by the Maxwell term.The
+model is shown to support topologically stable purely magnetic self-dual
+vortices.",9705196v1
+2004-12-22,Further Investigation on Chiral Symmetry Breaking in a Uniform External Magnetic Field,"We study chiral symmetry breaking in QED when a uniform external magnetic
+field is present. We calculate higher order corrections to the dynamically
+generated fermion mass and find them to be small. In so doing we correct an
+error in the literature regarding the matrix structure of the fermion
+self-energy.",0412278v1
+2004-05-31,The longitudinal KAM-cocycle of a magnetic flow,"Let $M$ be a closed oriented surface of negative Gaussian curvature and let
+$\Omega$ be a non-exact 2-form. Let $\lambda$ be a small positive real number.
+We show that the longitudinal KAM-cocycle of the magnetic flow given by $\la
+\Omega$ is a coboundary if and only if the Gaussian curvature is constant and
+$\Omega$ is a constant multiple of the area form.",0405598v1
+2002-01-08,Spectral cross correlations of magnetic edge states,"We observe strong, non-trivial cross-correlations between the edge states
+found in the interior and the exterior of magnetic quantum billiards. Our
+analysis is based on a novel definition of the edge state spectral density
+which is rigorous, practical and semiclassically accessible.",0201010v1
+2002-11-05,Form Factor of a Quantum Graph in a Weak Magnetic Field,"Using periodic orbit theory, we evaluate the form factor of a quantum graph
+to which a very weak magnetic field is applied. The first correction to the
+diagonal approximation describing the transition between the universality
+classes is shown to be in agreement with Pandey and Mehta's formula of
+parametric random matrix theory.",0211006v1
+2003-06-24,On triple correlations in isotropic electron magnetohydrodynamic turbulence,"The evolution of the correlation characteristics in three-dimensional
+isotropic electron magnetohydrodynamic turbulence is investigated. Universal
+exact relations between the longitudinal and transverse two-point triple
+correlations of the components of the fluctuational magnetic fields and the
+rates of dissipation of the magnetic helicity and energy are obtained in the
+inertial range.",0306045v2
+2004-01-29,Intermittency and the passive nature of the magnitude of the magnetic field,"It is shown that the statistical properties of the magnitude of the magnetic
+field in turbulent electrically conducting media resemble, in the inertial
+range, those of passive scalars in fully developed three-dimensional fluid
+turbulence. This conclusion, suggested by the data from Advanced Composition
+Explorer, is supported by a brief analysis of the appropriate
+magnetohydrodynamic equations.",0401043v2
+2004-09-23,Variational formulations of exact and reduced Vlasov-Maxwell equations,"The foundations of gyrokinetic theory are reviewed with an emphasis on the
+applications of Lagrangian and Hamiltonian methods used in the derivation of
+nonlinear gyrokinetic Vlasov-Maxwell equations. These reduced dynamical
+equations describe the turbulent evolution of low-frequency electromagnetic
+fluctuations in nonuniform magnetized plasmas with arbitrary magnetic geometry.",0409119v1
+2005-03-02,Quantum Magnetohydrodynamics,"The quantum hydrodynamic model for charged particle systems is extended to
+the cases of non zero magnetic fields. In this way, quantum corrections to
+magnetohydrodynamics are obtained starting from the quantum hydrodynamical
+model with magnetic fields. The quantum magnetohydrodynamics model is analyzed
+in the infinite conductivity limit. The conditions for equilibrium in ideal
+quantum magnetohydrodynamics are established. Translationally invariant exact
+equilibrium solutions are obtained in the case of the ideal quantum
+magnetohydrodynamic model.",0503021v1
+2005-06-08,Variational principle for linear stability of moving magnetized plasma,"The variational principle for linear stability of three-dimensional,
+inhomogenious, compressible, moving magnetized plasma is suggested. The
+principle is ``softer'' (easier to be satisfied) than all previously known
+variational stability conditions. The key point of the analysis is a
+conservation in variations of new integrals inherent in the linearized equation
+of the motion that was not earlier discussed in the literature.",0506073v1
+1995-08-22,"Superconducting, magnetic, and charge correlations in the doped two-chain Hubbard model","Superconducting, magnetic, and charge correlation functions and dynamic spin
+correlation functions of the doped two-chain Hubbard model is studied with the
+projector Quantum Monte carlo method and Lanczos recursion method. Of the three
+correlation functions, the interchain singlet superconducting correlation
+function is the most long range. Our data is not consistent with the
+Luther-Emery picture.",9508003v1
+2007-05-11,Measurement of electro-magnetic radiation at PHENIX,"Recent results on direct photons and dileptons from the PHENIX xperiment
+opened up a possibility of landscaping electro-magnetic radiation over various
+kinetic energies in heavy ion collisions. A detail discussion is given based on
+a review of the results.",0705.1711v1
+2008-05-28,Vanishing beta function for Grosse-Wulkenhaar model in a magnetic field,"We prove that the beta function of the Grosse-Wulkenhaar model including a
+magnetic field vanishes at all order of perturbations. We compute the
+renormalization group flow of the relevant dynamic parameters and find a
+non-Gaussian infrared fixed point. Some consequences of these results are
+discussed.",0805.4362v1
+2008-08-29,Closed Magnetic Geodesics on $S^2$,"We give existence results for simple closed curves with prescribed geodesic
+curvature on $S^{2}$, which correspond to periodic orbits of a charge in a
+magnetic field.",0808.4038v4
+2008-11-04,Angular Momentum Loss by Magnetic Braking and Gravitational Radiation in Relativistic Binary Stars,"Angular momentum loss (AML) mechanisms and dynamical evolution owing to
+magnetic braking and gravitational radiation in relativistic binary stars (RBS)
+are studied with use of physical parameters collected from the literature. We
+have calculated and compared AML time scales for the RBS with non-degenerate
+components and double degenerate (DD) systems.",0811.0455v1
+2009-02-17,Chaos at Nonlinear NMR,"The hodographs of magnetization of nonlinear nuclear magnetic resonance are
+investigated in the conditions of resonance on the unshifted frequency. It is
+shown that, depending on the value of amplitude of the variable field and value
+of frequency shift, topologically different hodographs separated from each
+other by separatrix are obtained.",0902.2909v1
+2009-04-28,Meson Spectra and Magnetic Fields in the Sakai-Sugimoto Model,"We continue our study of the dynamics of the flavour sector of the
+Sakai-Sugimoto model in the presence of an external magnetic field, uncovering
+several features of the meson spectrum at high and low temperatures. We employ
+both analytical and numerical methods to study the coupled non-linear equations
+that result from the gravity dual.",0904.4320v1
+2009-09-25,Vorticity Flow Stabilization of Magnetized Plasmas,"Exact solutions of a magnetized plasma in a vorticity containing shear flow
+for constant temperature are presented. This is followed by the modification of
+these solutions by thermomagnetic currents in the presence of temperature
+gradients. It is shown that solutions which are unstable for a subsonic flow,
+are stable if the flow is supersonic.
+  The results are applied to the problem of vorticity shear flow stabilization
+of a linear z-pinch discharge.",0909.4750v2
+2010-03-13,Nonlinear magnetoplasmons in strongly coupled Yukawa plasmas,"The existence of plasma oscillations at multiples of the magnetoplasmon
+frequency in a strongly coupled two-dimensional magnetized Yukawa plasma is
+reported, based on extensive molecular dynamics simulations. These modes are
+the analogues of Bernstein modes which are renormalized by strong interparticle
+correlations. Their properties are theoretically explained by a dielectric
+function incorporating the combined effect of a magnetic field, strong
+correlations and finite temperature.",1003.2721v1
+2010-12-10,Spin relaxation and spin dynamics in semiconductors,"A chapter contribution to book: ""Handbook of Spin Transport and Magnetism"",
+ed. by Evegeny Y. Tsymbal and Igor Zutic (Chapman & Hall/CRC, 2011)
+http://www.crcpress.com/product/isbn/9781439803776 .",1012.2205v1
+2011-08-23,Theory of inverse Faraday effect in disordered metal in THz regime,"We calculate the magnetization dynamics induced by the inverse Faraday effect
+in disordered metals in THz regime by using the diagrammatic method. We find
+that the induced magnetization is proportional to the frequency of circularly
+polarized light.",1108.4522v1
+2011-09-07,Planar approximation for spin transfer systems with application to tilted polarizer devices,"Planar spin-transfer devices with dominating easy-plane anisotropy can be
+described by an effective one-dimensional equation for the in-plane angle. Such
+a description provides an intuitive qualitative understanding of the magnetic
+dynamics. We give a detailed derivation of the effective planar equation and
+use it to describe magnetic switching in devices with tilted polarizer.",1109.1331v1
+2011-09-30,Parker's dynamo and geomagnetic reversals,"Fluctuations of the alpha-effect which break equatorial symmetry of the flow
+in the kinematic Parker's dynamo are considered. We show, that even small (a
+few percents) fluctuation can leed to the substantial assymmetry of the
+magnetic field in the hemispheres as well as the propagation of the dynamo wave
+through the equator plane. We also consider how change of the dynamo number can
+be used to explain different regimes of magnetic field generation in geodynamo.",1109.6889v1
+2012-08-12,On Totally integrable magnetic billiards on constant curvature surface,"We consider billiard ball motion in a convex domain of a constant curvature
+surface influenced by the constant magnetic field. We prove that if the
+billiard map is totally integrable then the boundary curve is necessarily a
+circle. This result is a manifestation of the so-called Hopf rigidity
+phenomenon which was recently obtained for classical billiards on constant
+curvature surfaces.",1208.2455v1
+2012-08-19,Overcoming the Child-Langmuir law via the magnetic mirror effect,"The maximum current in a vacuum tube prescribed by the classical
+Child-Langmuir law can be overcome, when the space-charge effect of the induced
+potential is mitigated by the mirror effect in a spatially varying magnetic
+field. The current could exceed the Child-Langmuir value by as much as a few
+factors. The regime of practical interest is examined.",1208.3898v1
+2013-01-08,Horizon area-angular momentum-charge-magnetic fluxes inequalities in 5D Einstein-Maxwell-dilaton gravity,"In the present paper we consider 5D spacetimes satisfying the
+Einstein-Maxwell-dilaton gravity equations which are $U(1)^2$ axisymmetric but
+otherwise highly dynamical. We derive inequalities between the area, the
+angular momenta, the electric charge and the magnetic fluxes for any smooth
+stably outer marginally trapped surface.",1301.1548v1
+2014-12-30,Stability of the electron cyclotron resonance,"We consider the magnetic AC Stark effect for the quantum dynamics of a single
+particle in the plane under the influence of an oscillating homogeneous
+electric and a constant perpendicular magnetic field. We prove that the
+electron cyclotron resonance is insensitive to impurity potentials.",1501.00038v2
+2015-12-31,Metastability of the two-dimensional Blume-Capel model with zero chemical potential and small magnetic field,"We consider the two-dimensional Blume-Capel model with zero chemical
+potential and small magnetic field evolving on a large but finite torus. We
+obtain sharp estimates for the transition time, we characterize the set of
+critical configurations, and we prove the metastable behavior of the dynamics
+as the temperature vanishes.",1512.09286v1
+2017-03-15,(De)Constructing magnetized dimensions,"We provide an origin of family replications in the standard model of particle
+physics by constructing renormalizable, asymptotically free, four dimensional
+local gauge theories that dynamically generate the fifth and sixth dimensions
+with magnetic fluxes.",1703.05263v1
+2017-11-09,Emergent electromagnetism induced by topological defects created during magnetization reversal in nanowires,"We report that the irreversible magnetization switching process in
+ferromagnetic nanoparticles is governed by the formation and dynamics of
+topological point-defects in the form of hedgehog-antihedgehog pairs. After
+nucleation, these pairs rapidly separate with speeds exceeding domain wall
+velocities, and they generate an emergent electric field of solenoidal
+character and substantial magnitude.",1711.03511v1
+2019-07-23,Dissipative invariants in MHD turbulence,"Role of the dissipative invariants in isotropic homogeneous MHD turbulence
+has been studied using the distributed chaos approach and results of direct
+numerical simulations. Effects of weak imposed mean magnetic field and magnetic
+fields in undisturbed solar photosphere are also briefly discussed in this
+context.",1907.09964v3
+2021-05-18,Computational Micromagnetics based on Normal Modes: bridging the gap between macrospin and full spatial discretization,"The Landau-Lifshitz equation governing magnetization dynamics is written in
+terms of the amplitudes of normal modes associated with the micromagnetic
+system's appropriate ground state. This results in a system of nonlinear
+ordinary differential equations (ODEs), the right-hand side of which can be
+expressed as the sum of a linear term and nonlinear terms with increasing order
+of nonlinearity (quadratic, cubic, etc.). The application of the method to
+nanostructured magnetic systems demonstrates that the accurate description of
+magnetization dynamics requires a limited number of normal modes, which results
+in a considerable improvement in computational speed. The proposed method can
+be used to obtain a reduced-order dynamical description of magnetic
+nanostructures which allows to adjust the accuracy between low-dimensional
+models, such as macrospin, and micromagnetic models with full spatial
+discretization. This new paradigm for micromagnetic simulations is tested for
+three problems relevant to the areas of spintronics and magnonics: directional
+spin-wave coupling in magnonic waveguides, high power ferromagnetic resonance
+in a magnetic nanodot, and injection-locking in spin-torque nano-oscillators.
+The case studies considered demonstrate the validity of the proposed approach
+to systematically obtain an intermediate order dynamical model based on normal
+modes for the analysis of magnetic nanosystems. The time-consuming calculation
+of the normal modes has to be done only one time for the system. These modes
+can be used to optimize and predict the system response for all possible
+time-varying external excitations (magnetic fields, spin currents). This is of
+utmost importance for applications where fast and accurate system simulations
+are required, such as in electronic circuits including magnetic devices.",2105.08829v2
+2021-08-26,Dynamo and the Adiabatic Invariant,"The paper considers dynamo generated by a shallow fluid layer in a celestial
+body (planet or star). This dynamo is based on the extra invariant for
+interacting magnetic Rossby waves. The magnetohydrodynamics (MHD) is linearized
+on the background of strong toroidal magnetic field. The extra invariant is
+used to show that the background field is maintained.",2108.11548v1
+2021-12-31,Demystifying magnetic resonance measurements of the true diffusion propagator,"In a recent work, a method for the magnetic resonance (MR) measurement of the
+true diffusion propagator was introduced, which was subsequently implemented
+and validated for free diffusion on a benchtop MR scanner. Here, we provide a
+brief theoretical description of the method and discuss various experimental
+regimes.",2112.15584v1
+2022-02-22,3D RMHD simulations of jet-wind interactions in High Mass X-ray Binaries,"The interaction of jets in High-Mass X-ray Binaries (HMXBs) with the strong
+winds driven by the hot companion star in the vicinity of the compact object is
+fundamental to understand the jet dynamics, non-thermal emission and long-term
+stability. However, the role of the jet magnetic field in this process is
+unclear. We study the dynamical role of weak and moderate-to-strong toroidal
+magnetic fields during the first hundreds of seconds of jet propagation,
+focusing on the magnetized flow dynamics and the mechanisms of energy
+conversion. We have developed the code L\'ostrego v1.0, a new 3D RMHD code to
+simulate astrophysical plasmas in Cartesian coordinates. Using this tool, we
+performed the first 3D RMHD numerical simulations of relativistic magnetized
+jets propagating through the clumpy stellar wind in a HMXB. The overall
+morphology and dynamics of weakly magnetized jet models is similar to previous
+hydrodynamical simulations, where the jet head generates a strong shock in the
+ambient medium and the initial over-pressure with respect to the stellar wind
+drives one or more recollimation shocks. In the time scales of our simulations,
+these jets are ballistic and seem to be more stable against internal
+instabilities than jets with the same power in the absence of fields. However,
+moderate-to-strong toroidal magnetic fields favour the development of
+current-driven instabilities and the disruption of the jet within the binary. A
+detailed analysis of the energy distribution in the relativistic outflow and
+the ambient medium reveals that both magnetic and internal energies can
+contribute to the effective acceleration of the jet. We certify that the jet
+feedback into the ambient medium is highly dependent on the jet energy
+distribution at injection, where hotter, more dilute and/or more magnetized
+jets are more efficient, as anticipated by feedback studies in the case of jets
+in active galaxies.",2202.11119v1
+2023-10-15,Asymptotic Stability of 3D relativistic Collisionless plasma states in a constant magnetic field with a boundary,"Motivated by solar wind models in the low altitude, we explore a boundary
+problem of the nonlinear relativistic Vlasov-Poisson systems in the 3D half
+space in the presence of a constant vertical magnetic field and strong
+background gravity with the inflow boundary condition. As the main result, we
+construct stationary solutions and establish their nonlinear dynamical
+asymptotic stability.",2310.09865v1
+2024-02-02,The chimera revisited: Wall- and magnetically-bounded turbulent flows,"This paper is a first attempt at bringing together various concepts from
+research on wall- and magnetically-bounded turbulent flows. Brief reviews of
+both fields are provided: The main similarities identified are coherent
+(turbulent) structures, flow generation and transport barriers. Examples are
+provided and discussed.",2402.07918v1
+2009-06-15,Transport of Large Scale Poloidal Flux in Black Hole Accretion,"We report on a global, three-dimensional GRMHD simulation of an accretion
+torus embedded in a large scale vertical magnetic field orbiting a
+Schwarzschild black hole. This simulation investigates how a large scale
+vertical field evolves within a turbulent accretion disk and whether global
+magnetic field configurations suitable for launching jets and winds can
+develop. We find that a ""coronal mechanism"" of magnetic flux motion, which
+operates largely outside the disk body, dominates global flux evolution. In
+this mechanism, magnetic stresses driven by orbital shear create large-scale
+half-loops of magnetic field that stretch radially inward and then reconnect,
+leading to discontinuous jumps in the location of magnetic flux. In contrast,
+little or no flux is brought in directly by accretion within the disk itself.
+The coronal mechanism establishes a dipole magnetic field in the evacuated
+funnel around the orbital axis with a field intensity regulated by a
+combination of the magnetic and gas pressures in the inner disk. These results
+prompt a reevaluation of previous descriptions of magnetic flux motion
+associated with accretion. Local pictures are undercut by the intrinsically
+global character of magnetic flux. Formulations in terms of an ""effective
+viscosity"" competing with an ""effective resistivity"" are undermined by the
+nonlinearity of of the magnetic dynamics and the fact that the same turbulence
+driving mass motion (traditionally identified as ""viscosity"") can alter
+magnetic topology.",0906.2784v2
+2012-09-24,Droplet microfluidics to prepare magnetic polymer vesicles and to confine the heat in magnetic hyperthermia,"In this work, we present two types of microfluidic chips involving magnetic
+nanoparticles dispersed in cyclohexane with oleic acid. In the first case, the
+hydrophobically coated nanoparticles are self-assembled with an amphiphilic
+diblock copolymer by a double-emulsion process in order to prepare giant
+magnetic vesicles (polymersomes) in one step and at a high throughput. It was
+shown in literature that such diblock copolymer W/O/W emulsion droplets can
+evolve into polymersomes made of a thin (nanometric) magnetic membrane through
+a dewetting transition of the oil phase from the aqueous internal cores usually
+leading to ""acorn-like"" structures (polymer excess) sticking to the membranes.
+To address this issue and greatly speed up the process, the solvent removal by
+evaporation was replaced by a ""shearing-off"" of the vesicles in a simple PDMS
+chip designed to exert a balance between a magnetic gradient and viscous shear.
+In the second example, a simple oil-in-oil emulsion chip is used to obtain
+regular trains of magnetic droplets that circulate inside an inductor coil
+producing a radio-frequency magnetic field. We evidence that the heat produced
+by magnetic hyperthermia can be converted into a temperature rise even at the
+scale of nL droplets. The results are compared to heat transfer models in two
+limiting cases: adiabatic vs. dissipative. The aim is to decipher the delicate
+puzzle about the minimum size required for a tumor ""phantom"" to be heated by
+radio-frequency hyperthermia in a general scope of anticancer therapy.",1209.5249v5
+2013-10-02,Magnetic Field Amplification in Young Galaxies,"The Universe at present is highly magnetized, with fields of the order of a
+few 10^-5 G and coherence lengths larger than 10 kpc in typical galaxies like
+the Milky Way. We propose that the magnetic field was amplified to this values
+already during the formation and the early evolution of the galaxies.
+Turbulence in young galaxies is driven by accretion as well as by supernova
+(SN) explosions of the first generation of stars. The small-scale dynamo can
+convert the turbulent kinetic energy into magnetic energy and amplify very weak
+primordial magnetic seed fields on short timescales. The amplification takes
+place in two phases: in the kinematic phase the magnetic field grows
+exponentially, with the largest growth on the smallest non-resistive scale. In
+the following non-linear phase the magnetic energy is shifted towards larger
+scales until the dynamo saturates on the turbulent forcing scale. To describe
+the amplification of the magnetic field quantitatively we model the
+microphysics in the interstellar medium (ISM) of young galaxies and determine
+the growth rate of the small-scale dynamo. We estimate the resulting saturation
+field strengths and dynamo timescales for two turbulent forcing mechanisms:
+accretion-driven turbulence and SN-driven turbulence. We compare them to the
+field strength that is reached, when only stellar magnetic fields are
+distributed by SN explosions. We find that the small-scale dynamo is much more
+efficient in magnetizing the ISM of young galaxies. In the case of
+accretion-driven turbulence a magnetic field strength of the order of 10^-6 G
+is reached after a time of 24-270 Myr, while in SN-driven turbulence the dynamo
+saturates at field strengths of typically 10^-5 G after only 4-15 Myr. This is
+considerably shorter than the Hubble time. Our work can help to understand why
+present-day galaxies are highly magnetized.",1310.0853v2
+2016-07-06,"Binary Neutron Star Mergers and Short Gamma-Ray Bursts: Effects of Magnetic Field Orientation, Equation of State, and Mass Ratio","We present fully GRMHD simulations of the merger of binary neutron star (BNS)
+systems. We consider BNSs producing a hypermassive neutron star (HMNS) that
+collapses to a spinning black hole (BH) surrounded by a magnetized accretion
+disk in a few tens of ms. We investigate whether such systems may launch
+relativistic jets and power short gamma-ray bursts. We study the effects of
+different equations of state (EOSs), different mass ratios, and different
+magnetic field orientations. For all cases, we present a detailed investigation
+of the matter dynamics and of the magnetic field evolution, with particular
+attention to its global structure and possible emission of relativistic jets.
+The main result of this work is that we found the formation of an organized
+magnetic field structure. This happens independently of EOS, mass ratio, and
+initial magnetic field orientation. We also show that those models that produce
+a longer-lived HMNS lead to a stronger magnetic field before collapse to BH.
+Such larger fields make it possible, for at least one of our models, to resolve
+the MRI and hence further amplify the magnetic field. However, by the end of
+our simulations, we do not observe a magnetically dominated funnel and hence
+neither a relativistic outflow. With respect to the recent simulations of Ruiz
+et al 2016, we evolve models with lower and more realistic initial magnetic
+field strengths and, because of computational reasons, we do not evolve the
+accretion disk for the long timescales that seem to be required in order to see
+a relativistic outflow. Since all our models produce a similar ordered magnetic
+field structure, we expect that the results found in Ruiz et al 2016, where
+they only considered an equal-mass system with an ideal fluid EOS, should be
+general and, at least from a qualitative point of view, independent from
+mass-ratio, magnetic field orientation, and EOS.",1607.01791v2
+2016-09-22,Ambipolar diffusion regulated collapse of filaments threaded by perpendicular magnetic fields,"We numerically reproduce the density profiles for filaments that are in
+magnetohydrostatic and pressure equilibrium with their surroundings obtained in
+Tomisaka (2014) and show that these equilibria are dynamically stable. If the
+effect of ambipolar diffusion is considered, these filaments lose magnetic
+support initiating cloud collapse. The filaments do not lose magnetic flux.
+Rather the magnetic flux is redistributed within the filament from the centre
+towards the envelope.
+  The rate of the collapse is inversely proportional to the fractional
+ionisation and two gravitationally-driven ambipolar diffusion regimes for the
+collapse are observed as predicted in Mouschovias & Morton (1991). For high
+values of the ionisation coefficient, that is $X \geq 10^{-7}$, the gas is
+strongly coupled to the magnetic field and the Jeans length is larger than the
+ambipolar diffusion length scale. Then the collapse is governed by
+magnetically-regulated ambipolar diffusion. For $X \lesssim 10^{-8}$, the gas
+is weakly coupled to the magnetic field and the magnetic support is removed by
+gravitationally-dominated ambipolar diffusion. Here, neutrals and ions only
+collide sporadically, that is the ambipolar diffusion length scale is larger
+than the Jeans length.
+  When decaying turbulence is included, additional support is provided to the
+filament. This slows down the collapse of the filament even in the absence of a
+magnetic field. When a magnetic field is present, the collapse rate increases
+by a ratio smaller than for the non-magnetic case. This is because of a
+speed-up of the ambipolar diffusion due to larger magnetic field gradients
+generated by the turbulence and because the ambipolar diffusion aids the
+dissipation of turbulence below the ambipolar diffusion length scale. The
+highest increase in the rate is observed for the lowest ionisation coefficient
+and the highest turbulent intensity.",1609.06879v1
+2018-02-13,Estimating the coronal and chromospheric magnetic fields of solar active regions as observed with the Nobeyama Radioheliograph Compared with the Extrapolated Linear Force-Free Field,"Adopting the thermal free-free emission mechanism, the coronal and
+chromospheric magnetic fields are derived from the polarization and spectral
+observations with the Nobeyama Radioheliograph at 1.76 cm. The solar active
+regions (AR) located near the disk center observed on January 8, 2015 (AR
+12257) and December 4, 2016 (AR 12615) are used for the estimate of the
+chromospheric and coronal magnetic fields with the microwave radio
+observations. We compare solar radio maps of active regions for both intensity
+and circularly polarized component with the optical maps from observations with
+the Helioseismic and Magnetic Imager and the chromosphere and corona transition
+region images obtained with the Atmospheric Imaging Assembly instrument, on
+board the Solar Dynamic Observatory. We notice from the comparison between
+radio maps of both AR that the circular polarization degree in the AR 12257 is
+about 2 percent, but the AR 12615 has a higher existent value by 3 percent.
+Radio observations provide us for direct measurements of magnetic fields in the
+chromospheric and coronal layers. We estimate the coronal magnetic fields using
+the Atmospheric Imaging Assembly observations by adopting magnetic loops in the
+corona over some patches with weak photospheric magnetic fields. The coronal
+magnetic field derived from the Atmospheric Imaging Assembly data was from 90
+to 240 Gauss. We also study the coronal magnetic fields based on the structure
+of the extrapolated field, where the result of the magnetic fields was in the
+range from 35 to 145 Gauss, showing that the difference in the coronal magnetic
+fields between both results is attributed to the assumption of the force-free
+approximation.",1802.04598v1
+2018-06-28,"Fluctuation Dynamo in a Collisionless, Weakly Magnetized Plasma","Results from a numerical study of fluctuation dynamo in a collisionless,
+weakly magnetized plasma are presented. The key difference between this dynamo
+and its magnetohydrodynamic (MHD) counterpart is the adiabatic production of
+magnetic-field-aligned pressure anisotropy by the amplification of a weak seed
+field. This in turn drives kinetic instabilities on the ion-Larmor
+scale---namely, firehose and mirror---which sever the adiabatic link between
+the thermal and magnetic pressures, thereby allowing the dynamo to proceed.
+After an initial phase of rapid growth driven by these instabilities, the
+magnetic energy grows exponentially and exhibits a $k^{3/2}$ spectrum that
+peaks near the resistive scale, similar to the large-magnetic-Prandtl-number
+($\mathrm{Pm}\gg{1}$) MHD dynamo. The magnetic field self-organizes into a
+folded-sheet topology, with direction reversals at the resistive scale and
+field lines curved at the parallel scale of the flow. The effective
+$\mathrm{Pm}$ is determined by whether the ion-Larmor scale is above or below
+the field-reversing scale: in the former case, particles undergo Bohm-like
+diffusion; in the latter case, particles scatter primarily off firehose
+fluctuations residing at the ends of the magnetic folds, and the viscosity
+becomes anisotropic. The magnetic field ultimately saturates at dynamical
+strengths, with its spectral peak migrating towards larger scales. This
+feature, along with an anti-correlation of magnetic-field strength and
+field-line curvature and a gradual thinning of magnetic sheets into ribbons,
+resemble the saturated state of the large-$\mathrm{Pm}$ dynamo, the primary
+differences manifesting in firehose/mirror-unstable regions. These results have
+implications for magnetic-field growth in the weakly collisional intracluster
+medium of galaxy clusters.",1806.11162v3
+2019-08-20,Magnetic fields in heavy ion collisions: flow and charge transport,"At the earliest times after a heavy-ion collision, the magnetic field created
+by the spectator nucleons will generate an extremely strong, albeit rapidly
+decreasing in time, magnetic field. The impact of this magnetic field may have
+detectable consequences, and is believed to drive anomalous transport effects
+like the Chiral Magnetic Effect (CME). We detail an exploratory study on the
+effects of a dynamical magnetic field on the hydrodynamic medium created in the
+collisions of two ultrarelativistic heavy-ions, using the framework of
+numerical ideal MagnetoHydroDynamics (MHD) with the ECHO-QGP code. In this
+study, we consider a magnetic field captured in a conducting medium, where the
+conductivity can receive contributions from the electromagnetic conductivity
+$\sigma$ and the chiral magnetic conductivity $\sigma_{\chi}$. We first study
+the elliptic flow of pions, which we show is relatively unchanged by the
+introduction of a magnetic field. However, by increasing the magnitude of the
+magnetic field, we find evidence for an enhancement of the elliptic flow in
+peripheral collisions. Next, we explore the impact of the chiral magnetic
+conductivity on electric charges produced at the edges of the fireball. This
+initial $\sigma_\chi$ can be understood as a long-wavelength effective
+description of chiral fermion production. We then demonstrate that this chiral
+charge, when transported by the MHD medium, produces a charge dipole
+perpendicular to the reaction plane which extends a few units in rapidity.
+Assuming charge conservation at the freeze-out surface, we show that the
+produced charge imbalance can have measurable effects on some experimental
+observables, like $v_1$ or $\langle \sin \phi \rangle$. This demonstrates the
+ability of a MHD fluid to transport the signature of the initial chiral
+magnetic fields to late times.",1908.07605v2
+2020-02-25,Investigation of the magnetic ground state of the ordered double perovskite Sr2YbRuO6: a tale of two transitions,"Comprehensive muon spin rotation/relaxation (muSR) and neutron powder
+diffraction (NPD) studies supported via bulk measurements have been performed
+on the ordered double perovskite Sr2YbRuO6 to investigate the nature of the
+magnetic ground state. Two sharp transitions at TN1 ~ 42 K and TN2 ~ 36 K have
+been observed in the static and dynamic magnetization measurements, coinciding
+with the heat capacity data. In order to confirm the origin of the observed
+phase transitions and the magnetic ground state, microscopic evidences are
+presented here. An initial indication of long-range magnetic ordering comes
+from a sharp drop in the muon initial asymmetry and a peak in the relaxation
+rate near TN1. NPD confirms that the magnetic ground state of Sr2YbRuO6
+consists of an antiferromagnetic (AFM) structure with interpenetrating lattices
+of parallel Yb3+ and Ru5+ moments lying in the ab-plane and adopting a A-type
+AFM structure. Intriguingly, a small but remarkable change is observed in the
+long-range ordering parameters at TN2 confirming the presence of a weak spin
+reorientation (i.e. change in spin configuration) transition of Ru and Yb
+moments, as well as a change in the magnetic moment evolution of the Yb3+ spins
+at TN2. The temperature dependent behaviour of the Yb3+ and Ru5+ moments
+suggests that the 4d-electrons of Ru5+ play a dominating role in stabilizing
+the long range ordered magnetic ground state in the double perovskite Sr2YbRuO6
+whereas only the Yb3+ moments show an arrest at TN2. The observed magnetic
+structure and the presence of a ferromagnetic interaction between Ru- and Yb-
+ions are explained with use of the Goodenough-Kanamori-Anderson (GKA) rules.
+Possible reasons for the presence of the second magnetic phase transition and
+of a compensation point in the magnetization data are linked to competing
+mechanisms of magnetic anisotropy.",2002.10985v3
+2020-03-09,Distinguishing between Flaring and Non-Flaring Active Regions: A Machine Learning Perspective,"Large scale solar eruptions significantly impact space weather and damages
+space-based human infrastructures. It is necessary to predict large scale solar
+eruptions, which will enable us to protect our vulnerable infrastructures of
+modern society. We aim to investigate the difference between flaring and
+non-flaring active regions. We use photospheric vector magnetogram data from
+Solar Dynamic Observatory's Helioseismic Magnetic Imager to study the time
+evolution of photospheric magnetic parameters on the solar surface. We build a
+database of flaring and non-flaring active region observed on the solar surface
+from the years 2010 to 2017. We train the machine learning algorithm by the
+time evolution of these active region parameters. Finally, we estimate the
+performance obtained from this machine learning algorithm. We find the strength
+of some magnetic parameters namely total unsigned magnetic flux, total unsigned
+magnetic helicity, total unsigned vertical current and total photospheric
+magnetic energy density in flaring active regions are much higher compared to
+the non-flaring ones. These magnetic parameters in the flaring active region
+are highly evolving and complex. We are able to obtain good forecasting
+capability with a relatively high value of true skill statistic (TSS). We also
+find that time evolution of total unsigned magnetic helicity and total unsigned
+magnetic flux have very high ability to distinguish flaring and non-flaring
+active regions. It is possible to distinguish flaring active region from the
+non-flaring one with good accuracy. We confirm that there is no single common
+parameter which can distinguish all flaring active regions from the non flaring
+one. However, time evolution of top few magnetic parameters namely total
+unsigned magnetic flux and total unsigned magnetic helicity have very high
+distinguishing capability.",2003.03878v1
+2023-04-26,Exploring magnetic field properties at the boundary of solar pores: A comparative study based on SDO-HMI observations,"The Sun's magnetic fields play an important role in various solar phenomena.
+Solar pores are regions of intensified magnetic field strength compared to the
+surrounding photospheric environment, and their study can help us better
+understand the properties and behaviour of magnetic fields in the Sun. Up to
+now, there exists only a single study on magnetic field properties at the
+boundary region of a pore. Therefore, the main goal of this work is to increase
+the statistics of magnetic properties determining the pore boundary region. We
+analyse six solar pores using data from the Helioseismic and Magnetic Imager
+instrument on board the Solar Dynamics Observatory. We apply image processing
+techniques to extract the relevant features of the solar pores and determine
+the boundary conditions of the magnetic fields. We find the maximal vertical
+magnetic field values on the boundaries of the studied solar pores to range
+from 1400~G to 1600~G, with a standard deviation between 7.8\% and 14.8\%.
+These values are lower than those reported in the mentioned preceding study.
+However, this can be explained by differences in spatial resolution as well as
+the type of data we used. The vertical magnetic field is an important factor in
+determining the boundary of solar pores, and it plays a more relevant role than
+the intensity gradient. The obtained information will be useful for future
+studies on the formation and evolution of magnetic structures of the Sun.
+Additionally, this study highlights the importance of high spatial resolution
+data for the purpose of accurately characterising the magnetic properties of
+solar pores.",2304.13212v1
+2023-07-18,The effect of pressure-anisotropy-driven kinetic instabilities on magnetic field amplification in galaxy clusters,"The intracluster medium (ICM) is the low-density diffuse magnetized plasma in
+galaxy clusters, which reaches virial temperatures of up to 10^8 K. Under these
+conditions, the plasma is weakly collisional and therefore has an anisotropic
+pressure tensor with respect to the local direction of the magnetic field. This
+triggers very fast, Larmor-scale, pressure-anisotropy-driven kinetic
+instabilities that alter magnetic field amplification. We study magnetic field
+amplification through a turbulent small-scale dynamo, including the effects of
+the kinetic instabilities, during the evolution of a typical massive galaxy
+cluster. A specific aim of this work is to establish a redshift limit from
+which a dynamo has to start to amplify the magnetic field up to equipartition
+with the turbulent velocity field at redshift z=0. We implemented 1D radial
+profiles for various plasma quantities for merger trees generated with the
+Modified GALFORM algorithm. We assume that turbulence is driven by successive
+mergers of dark matter halos and construct effective models for the Reynolds
+number Re_eff dependence on the magnetic field in three different magnetization
+regimes, including the effects of kinetic instabilities. The magnetic field
+growth rate is calculated for the different Re_eff models. The model results in
+a higher magnetic field growth rate at higher redshift. For all scenarios
+considered, to reach equipartition at z=0, the amplification of the magnetic
+field has to start at redshift z_start=1.5 and above. The time to reach
+equipartition can be significantly shorter, in cases with systematically
+smaller turbulent forcing scales, and for the highest Re_eff models. Merger
+trees are useful tools for studying the evolution of magnetic fields in weakly
+collisional plasmas. They could also be used to constrain the different stages
+of the dynamo that could be observed by future radio telescopes.",2307.09451v2
+2023-10-02,Control of the magnetic anisotropy in multi-repeat Pt/Co/Al heterostructures using magneto-ionic gating,"Controlling magnetic properties through the application of an electric field
+is a significant challenge in modern nanomagnetism. In this study, we
+investigate the magneto-ionic control of magnetic anisotropy in the topmost Co
+layer in Ta/Pt/[Co/Al/Pt]$_n$/Co/Al/AlO$_\text{x}$ multilayer stacks comprising
+$n +1$ Co layers and its impact on the magnetic properties of the multilayers.
+We demonstrate that the perpendicular magnetic anisotropy can be reversibly
+quenched through gate-driven oxidation of the intermediary Al layer between Co
+and AlO$_\text{x}$, enabling dynamic control of the magnetic layers
+contributing to the out-of-plane remanence - varying between $n$ and $n +1$.
+For multilayer configurations with $n = 2$ and $n = 4$, we observe reversible
+and non-volatile additions of 1/3 and 1/5, respectively, to the anomalous Hall
+effect amplitude based on the applied gate voltage. Magnetic imaging reveals
+that the gate-induced spin-reorientation transition occurs through the
+propagation of a single 90$^{\circ}$ magnetic domain wall separating the
+perpendicular and in-plane anisotropy states. In the 5-repetition multilayer,
+the modification leads to a doubling of the period of the magnetic domains at
+remanence. These results demonstrate that the magneto-ionic control of the
+anisotropy of a single magnetic layer can be used to control the magnetic
+properties of coupled multilayer systems, extending beyond the gating effects
+on a single magnetic layer.",2310.01623v1
+2024-01-11,The Decay Process of an α-configuration Sunspot,"The decay of sunspot plays a key role in magnetic flux transportation in
+solar active regions (ARs). To better understand the physical mechanism of the
+entire decay process of a sunspot, an {\alpha}-configuration sunspot in AR NOAA
+12411 was studied. Based on the continuum intensity images and vector magnetic
+field data with stray light correction from Solar Dynamics
+Observatory/Helioseismic and Magnetic Imager, the area, vector magnetic field
+and magnetic flux in the umbra and penumbra are calculated with time,
+respectively. Our main results are as follows: (1) The decay curves of the
+sunspot area in its umbra, penumbra, and whole sunspot take the appearance of
+Gaussian profiles. The area decay rates of the umbra, penumbra and whole
+sunspot are -1.56 MSH/day, -12.61 MSH/day and -14.04 MSH/day, respectively; (2)
+With the decay of the sunspot, the total magnetic field strength and the
+vertical component of the penumbra increase, and the magnetic field of the
+penumbra becomes more vertical. Meanwhile, the total magnetic field strength
+and vertical magnetic field strength for the umbra decrease, and the
+inclination angle changes slightly with an average value of about 20{\deg}; (3)
+The magnetic flux decay curves of the sunspot in its umbra, penumbra, and whole
+sunspot exhibit quadratic patterns, their magnetic flux decay rates of the
+umbra, penumbra and whole sunspot are -9.84 * 10^19 Mx/day, -1.59 * 10^20
+Mx/day and -2.60 * 10^20 Mx/day , respectively. The observation suggests that
+the penumbra may be transformed into the umbra, resulting in the increase of
+the average vertical magnetic field strength and the reduction of the
+inclination angle in the penumbra during the decay of the sunspot.",2401.05688v1
+2012-10-29,Spin-Transfer Torque Magnetization Reversal in Uniaxial Nanomagnets with Thermal Noise,"We consider the general Landau-Lifshitz-Gilbert (LLG) dynamical theory
+underlying the magnetization switching rates of a thin film uniaxial magnet
+subject to spin-torque effects and thermal fluctuations (thermal noise). After
+discussing the various dynamical regimes governing the switching phenomena, we
+present analytical results for the mean switching time behavior. Our approach,
+based on explicitly solving the first passage time problem, allows for a
+straightforward analysis of the thermally assisted, low spin-torque, switching
+asymptotics of thin film magnets. To verify our theory, we have developed an
+efficient GPU-based micromagnetic code to simulate the stochastic LLG dynamics
+out to millisecond timescales. We explore the effects of geometrical tilts
+between the spin-current and uniaxial anisotropy axes on the thermally assisted
+dynamics. We find that even in the absence of axial symmetry, the switching
+times can be functionally described in a form virtually identical to the
+collinear case. We further verify that asymptotic behavior is reached fairly
+slowly, thus quantifying the role of thermal noise in the crossover regime
+linking deterministic to thermally assisted magnetization reversal.",1210.7675v3
+2013-08-09,The contact property for nowhere vanishing magnetic fields on the two-sphere,"In this paper we give some positive and negative results about the contact
+property for the energy levels $\Sigma_c$ of a symplectic magnetic field on
+$S^2$. In the first part we focus on the case of the area form on a surface of
+revolution. We state a sufficient condition for an energy level to be of
+contact type and give an example where the contact property fails. If the
+magnetic curvature is positive, the dynamics and the action of invariant
+measures can be numerically computed. This hints at the conjecture that an
+energy level of a symplectic magnetic field with positive magnetic curvature
+should be of contact type. In the second part we show that, for small energies,
+there exists a convex hypersurface $N_c$ in $\mathbb C^2$ and a covering map
+$p_c:N_c \rightarrow \Sigma_c$ such that the pull-back via $p_c$ of the
+characteristic distribution on $\Sigma_c$ is the standard characteristic
+distribution on $N_c$. As a corollary we prove that there are either two or
+infinitely many periodic orbits on $\Sigma_c$. The second alternative holds if
+there exists a contractible prime periodic orbit.",1308.2128v2
+2015-09-21,Isotropic and Anisotropic Regimes of the Field-Dependent Spin Dynamics in Sr2IrO4: Raman Scattering Studies,"A major focus of experimental interest in Sr2IrO4 has been to clarify how the
+magnetic excitations of this strongly spin-orbit coupled system differ from the
+predictions of anisotropic 2D spin-1/2 Heisenberg model and to explore the
+extent to which strong spin-orbit coupling affects the magnetic properties of
+iridates. Here, we present a high-resolution inelastic light (Raman) scattering
+study of the low energy magnetic excitation spectrum of Sr2IrO4 and doped
+Eu-doped Sr2IrO4 as functions of both temperature and applied magnetic field.
+We show that the high-field (H>1.5 T) in-plane spin dynamics of Sr2IrO4 are
+isotropic and governed by the interplay between the applied field and the small
+in-plane ferromagnetic spin components induced by the Dzyaloshinskii-Moriya
+interaction. However, the spin dynamics of Sr2IrO4 at lower fields (H<1.5 T)
+exhibit important effects associated with interlayer coupling and in-plane
+anisotropy, including a spin-flop transition at Hc in Sr2IrO4 that occurs
+either discontinuously or via a continuous rotation of the spins, depending
+upon the in-plane orientation of the applied field. These results show that
+in-plane anisotropy and interlayer coupling effects play important roles in the
+low-field magnetic and dynamical properties of Sr2IrO4.",1509.06409v1
+2016-07-11,Magnetorotational dynamo chimeras. The missing link to turbulent accretion disk dynamo models?,"In Keplerian accretion disks, turbulence and magnetic fields may be jointly
+excited through a subcritical dynamo process involving the magnetorotational
+instability (MRI). High-resolution simulations exhibit a tendency towards
+statistical self-organization of MRI dynamo turbulence into large-scale cyclic
+dynamics. Understanding the physical origin of these structures, and whether
+they can be sustained and transport angular momentum efficiently in
+astrophysical conditions, represents a significant theoretical challenge. The
+discovery of simple periodic nonlinear MRI dynamo solutions has recently proven
+useful in this respect, and has notably served to highlight the role of
+turbulent magnetic diffusion in the seeming decay of the dynamics at low
+magnetic Prandtl number Pm (magnetic diffusivity larger than viscosity), a
+common regime in accretion disks. The connection between these simple
+structures and the statistical organization reported in turbulent simulations
+remained elusive, though. Here, we report the numerical discovery in moderate
+aspect ratio Keplerian shearing boxes of new periodic, incompressible,
+three-dimensional nonlinear MRI dynamo solutions with a larger dynamical
+complexity reminiscent of such simulations. These ""chimera"" cycles are
+characterized by multiple MRI-unstable dynamical stages, but their basic
+physical principles of self-sustainment are nevertheless identical to those of
+simpler cycles found in azimuthally elongated boxes. In particular, we find
+that they are not sustained at low Pm either due to subcritical turbulent
+magnetic diffusion. These solutions offer a new perspective into the transition
+from laminar to turbulent instability-driven dynamos, and may prove useful to
+devise improved statistical models of turbulent accretion disk dynamos.",1607.02903v1
+2016-10-13,Dynamic Domains of DTS: Simulations of a Spherical Magnetized Couette Flow,"The Derviche Tourneur Sodium experiment, a spherical Couette
+magnetohydrodynamics experiment with liquid sodium as the medium and a dipole
+magnetic field imposed from the inner sphere, recently underwent upgrades to
+its diagnostics to better characterize the flow and induced magnetic fields
+with global rotation. In tandem with the upgrades, a set of direct numerical
+simulations were run with the xshells code to give a more complete view of the
+fluid and magnetic dynamics at various rotation rates of the inner and outer
+spheres. These simulations reveal several dynamic regimes, determined by the
+Rossby number. At positive differential rotation there is a regime of
+quasigeostrophic flow, with low levels of fluctuations near the outer sphere.
+Negative differential rotation shows a regime of what appear to be saturated
+hydrodynamic instabilities at low negative differential rotation, followed by a
+regime where filamentary structures develop at low latitudes and persist over
+five to ten differential rotation periods as they drift poleward. We emphasize
+that all these coherent structures emerge from turbulent flows. At least some
+of them seem to be related to linear instabilities of the mean flow. The
+simulated flows can produce the same measurements as those that the physical
+experiment can take, with signatures akin to those found in the experiment.
+This paper discusses the relation between the internal velocity structures of
+the flow and their magnetic signatures at the surface.",1610.03964v4
+2016-11-15,Dynamics of Coronal-Hole Boundaries,"Remote and in-situ observations strongly imply that the slow solar wind
+consists of plasma from the hot, closed-field corona that is released onto open
+magnetic field lines. The Separatrix Web (S-Web) theory for the slow wind
+proposes that photospheric motions, at the scale of supergranules, are
+responsible for generating dynamics at coronal-hole boundaries, which result in
+the closed plasma release. We use three-dimensional magnetohydrodynamic (3D
+MHD) simulations to determine the effect of photospheric flows on the open and
+closed magnetic flux of a model corona with a dipole magnetic field and an
+isothermal solar wind. A rotational surface motion is used to approximate
+photospheric supergranular driving and is applied at the boundary between the
+coronal hole and helmet streamer. The resulting dynamics consist primarily of
+prolific and efficient interchange reconnection between open and closed flux.
+Magnetic flux near the coronal-hole boundary experiences multiple interchange
+events, with some flux interchanging over fifty times in one day. Additionally,
+we find that the interchange reconnection occurs all along the coronal-hole
+boundary, even producing a lasting change in magnetic-field connectivity in
+regions that were not driven by the applied motions. Our results show that
+these dynamics should be ubiquitous in the Sun and heliosphere. We discuss the
+implications of our simulations for understanding the observed properties of
+the slow solar wind, with particular focus on the global-scale consequences of
+interchange reconnection.",1611.04968v2
+2017-06-07,Cosmological dynamics of magnetic Bianchi I in viable $f(R)$ models of gravity,"Standard dynamical system analysis of Einstein-Maxwell equation in $f(R)$
+theories is considered in this work. We investigate cosmological dynamics of a
+uniform magnetic field in the Orthogonal Spatially Homogeneous (OSH) Bianchi
+type I universe with viable $f(R)$ models of gravity. In this work, the $f(R) =
+R -\alpha R^n$ and $f(R) = \left( R^b - \Lambda\right)^c$ models are examined
+by using our dynamical system analysis. Our results show that both of two
+$f(R)$ models have a viable cosmological consequence identical to the analysis
+present in Ref.\cite{Amendola:2007nt} for the FLRW background. Contrary to
+Ref.\cite{Amendola:2007nt}, we discover in our models that there is an
+additional anisotropic and non-zero cosmological magnetic fields fixed point
+emerging before the present of the standard matter epoch. This means that the
+universe has initially isotropic stage with the intermediated epoch as the
+anisotropic background and it ends up with the isotropic late-time
+acceleration. The primordial magnetic fields play a crucial role of the shear
+evolutions obtained from these two models which have the same scaling of the
+cosmic time as $\sigma\sim t^{-\frac13}$, instead of $\sigma\sim t^{-1}$ for
+the absence of the primordial magnetic cases.",1706.02279v2
+2018-07-10,Dynamic Response of Tunable Phononic Crystals and New Homogenization Approaches in Magnetoactive Composites,"This research investigates dynamic response of tunable periodic structures
+and homogenization methods in magnetoelastic composites (MECs). The research on
+tunable periodic structures is focused on the design, modeling and
+understanding of wave propagation phenomena and the dynamic response of smart
+phononic crystals. High amplitude wrinkle formation is employed to study a
+one-dimensional phononic crystal slab consists of a thin film bonded to a thick
+compliant substrate. Buckling induced surface instability generates a wrinkly
+structure triggered by a compressive strain. It is demonstrated that surface
+periodic pattern and the corresponding large deformation can control elastic
+wave propagation in the low thickness composite slab. Simulation results show
+that the periodic wrinkly structure can be used as a smart phononic crystal
+which can switch band diagrams of the structure in a transformative manner. A
+magnetoactive phononic crystal is proposed which its dynamic properties are
+controlled by combined effects of large deformations and an applied magnetic
+field. Finite deformations and magnetic induction influence phononic
+characteristics of the periodic structure through geometrical pattern
+transformation and material properties. A magnetoelastic energy function is
+proposed to develop constitutive laws considering large deformations and
+magnetic induction in the periodic structure. Analytical and finite element
+methods are utilized to compute dispersion relation and band structure of the
+phononic crystal for different cases of deformation and magnetic loadings. It
+is demonstrated that magnetic induction not only controls the band diagram of
+the structure but also has a strong effect on preferential directions of wave
+propagation. Moreover, a thermally controlled phononic crystal is designed
+using ligaments of bi-materials in the structure.",1810.05678v1
+2019-02-18,Dynamics of frequency-swept nuclear spin optical pumping in powdered diamond at low magnetic fields,"A broad effort is underway to improve the sensitivity of nuclear magnetic
+resonance through the use of dynamic nuclear polarization. Nitrogen-vacancy
+(NV) centers in diamond offer an appealing platform because these paramagnetic
+defects can be optically polarized efficiently at room temperature. However,
+work thus far has been mainly limited to single crystals because most
+polarization transfer protocols are sensitive to misalignment between the NV
+and magnetic field axes. Here we study the spin dynamics of NV-13C pairs in the
+simultaneous presence of optical excitation and microwave frequency sweeps at
+low magnetic fields. We show that a subtle interplay between illumination
+intensity, frequency sweep rate, and hyperfine coupling strength leads to
+efficient, sweep-direction-dependent 13C spin polarization over a broad range
+of orientations of the magnetic field. In particular, our results strongly
+suggest that finely-tuned, moderately coupled nuclear spins are key to the
+hyperpolarization process, which makes this mechanism distinct from other known
+dynamic polarization channels. These findings pave the route to applications
+where powders are intrinsically advantageous, including the hyper-polarization
+of target fluids in contact with the diamond surface or the use of
+hyperpolarized particles as contrast agents for in-vivo imaging.",1902.06805v1
+2019-07-25,Magnetic memory effect in ensembles of interacting anisotropic magnetic nanoparticles,"We explore the influence of demagnetization interaction on magnetic memory
+effect by varying organization geometry of anisotropic ZnFe$_2$O$_4$
+nanoparticles in an ensemble. The static and dynamic behaviour of two
+differently organized ensembles, compact ensemble (CE) and hollow core ensemble
+(HCE), are extensively studied by both dc and ac susceptibility, magnetic
+memory effect and spin relaxation. The frequency-dependence peak shifting of
+freezing temperature in both the systems is analyzed properly with the help of
+two dynamic scaling models: Vogel-Fulcher law and power law. Presence of
+cluster spin-glass phase is reflected from Vogel-Fulcher temperature $T_0$
+$\simeq$ 142.58 K for CE, $\simeq$ 97 K for HCE and characteristic time
+constant $\tau_0$ $\simeq$ $8.85\times10^{-9}$ s for CE, $\simeq$
+$3.8\times10^{-10}$ s for HCE; along with $\delta$T$_{Th}$ $\sim$ 0.1 for CE
+and 0.2 for HCE. The power law fitting with dynamic exponent $zv'$ = 6.2 $\pm$
+1.1 for CE, 6.3 $\pm$ 0.5 for HCE and single spin flip $\tau^*$ $\simeq$
+$7.7\times10^{-11}$ s for CE, $\simeq$ $1.3\times10^{-10}$ s for HCE provide
+firm confirmation of cluster spin-glass phase. The progressive spin freezing
+across multiple metastable states with prominent memory effects is reflected in
+both the systems via nonequilibrium dynamics study. The hollow core geometry
+with anisotropic nanoparticles on surface with closer proximity leads to
+complex anisotropy energy landscape with enhanced demagnetizing field resulting
+highly frustrated surface spins. As a consequence, more prominent magnetic
+memory effect is observed in HCE with higher activation energy, reduced
+blocking temperature and enhanced coercivity than that of CE.",1907.11116v2
+2020-07-18,The dynamics of 3-minute wavefronts and their relation to sunspot magnetic fields,"We present a study of wave processes occurring in solar active region NOAA
+11131 on 2010 December 10, captured by the Solar Dynamics Observatory in the
+1600A, 304A, and 171A channels. For spectral analysis we employed pixelised
+wavelet filtering together with a developed digital technique based on
+empirical mode decomposition. We studied the 3-minute wave dynamics to obtain
+relationships with the magnetic structuring of the underlying sunspot. We found
+that during development of wave trains the motion path occurred along a
+preferential direction, and that the broadband wavefronts can be represented as
+a set of separate narrowband oscillation sources. These sources become visible
+as the waves pass through the umbral inhomogeneities caused by the differing
+magnetic field inclination angles. We found the spatial and frequency
+fragmentation of wavefronts, and deduced that the combination of narrowband
+spherical and linear parts of the wavefronts provide the observed spirality.
+Maps of the magnetic field inclination angles confirm this assumption. We
+detect the activation of umbral structures as the increasing of oscillations in
+the sources along the front ridge. Their temporal dynamics are associated with
+the occurrence of umbral flashes. Spatial localisation of the sources is stable
+over time and depends on the oscillation period. We propose that these sources
+are the result of wave paths along the loops extending outwards from the
+magnetic bundles of the umbra.",2007.09369v1
+2020-11-20,An ac-susceptibility study of magnetic relaxation phenomena in the antiskyrmion hosting tetragonal Mn-Pt(Pd)-Sn system,"Here, we report an exhaustive study of the frequency-dependent ac-magnetic
+susceptibility of the $D_{2d}$ symmetric Heusler system Mn-Pt(Pd)-Sn that hosts
+antiskyrmions over a wide temperature range. Magnetic relaxation studies using
+Cole-Cole formalism reveal a Debye-type relaxation with a nearly negligible
+distribution in relaxation times. In contrast to the archetypical skyrmion
+hosts, the high Curie temperature ($ T_C $) of the present system ensures
+shorter switching times, and, correspondingly, higher frequencies are required
+to probe the relaxation dynamics. We find a non-monotonic variation in the
+characteristic relaxation time with distinct maxima at the phase boundaries
+\textit{via} helical $\longrightarrow$ antiskyrmion $\longrightarrow$
+field-polarized states, indicating slower magnetization dynamics over the
+region of phase coexistence. The temperature-dependent relaxation time across
+different phases is of the order of $ 10^{-5} - 10^{-4} $ s and follows the
+well-known Arrhenius law with reasonable values of the energy barriers. The
+present study concerning the magnetization dynamics in the antiskyrmion host
+tetragonal Heusler system is an important contribution towards the basic
+understanding of the dynamical aspects of antiskyrmions for their potential
+applications.",2011.10229v1
+2021-05-28,Influence of magnetic fields on ultrafast laser-induced switching dynamics in Co/Gd bilayers,"Recently it has been shown that not only GdFeCo alloys exhibit single-pulse
+helicity-independent all-optical switching (HI-AOS), but that this effect is
+also seen in Co/Gd bilayers. However, there have been no reports on the
+explicit time dynamics of the switching process in these bilayers as of yet.
+Furthermore, time-resolved measurements of switching of other materials are
+typically done with a constant applied field to reset the magnetization between
+consecutive pulses and thus ensure repeatable behavior. In this paper we
+experimentally resolve the explicit dynamics of the switching process in Co/Gd,
+and the influence of applied magnetic fields on the switching process. We
+observe that after a switch within several picoseconds, the magnetization
+switches back at a timescale of hundreds of picoseconds. This backswitch
+includes a strong dependence on the magnetic field strength even at sub-tesla
+fields, significantly smaller than the exchange fields that govern the
+switching dynamics. This surprising behaviour is explained by a combination of
+longitudinal switching (on a picosecond timescale), precessional switching (on
+a nanosecond timescale) and domain-wall motion (on a timescale of 10 ns and
+beyond). We discuss these different switching regimes and their relative
+importance using simple model calculations.",2105.13862v1
+2021-11-05,Ultrafast optical excitation of magnetic dynamics in van der Waals magnets: Coherent magnons and BKT dynamics in NiPS$_3$,"Optical pump-probe experiments carried out in the time domain reveal both the
+intrinsic low energy dynamics and its connections to higher energy excitations
+in correlated electron systems. In this work, we propose two microscopic
+mechanisms for the optical generation of coherent magnetic modes in van der
+Waals magnets, and derive the corresponding effective light-spin interactions:
+either through pumping atomic orbital excitations resonantly or via a
+light-induced Floquet spin Hamiltonian, the ground state of the system is
+driven out of equilibrium. The subsequent long-time relaxational dynamics can
+then be probed using, e.g. the magneto-optical Kerr effect or transient grating
+spectroscopy. As an example, we apply our framework to NiPS$_3$, which is
+magnetically ordered in the bulk, and is conjectured to realize the XY model in
+the monolayer limit. Our theory makes explicit how the material's low-energy
+response depends sensitively on the microscopic details of the light-spin
+coupling as well as pump fluence, frequency and polarization. For the case of
+bulk NiPS$_3$, we find quantitative agreement with recent experiments by
+Afanasiev et al. [Science Advances 7, abf3096 (2021)]. We further propose
+pump-probe experiments for monolayer NiPS$_3$ and detail how anomalous
+relaxational behaviour may reveal excitations of a (proximate) BKT phase in a
+proposed effective XY model.",2111.03674v2
+2021-12-31,Spin-injection-generated shock waves and solitons in a ferromagnetic thin film: the spin piston problem,"The unsteady, nonlinear magnetization dynamics induced by spin injection in
+an easy-plane ferromagnetic channel subject to an external magnetic field are
+studied analytically. Leveraging a dispersive hydrodynamic description, the
+Landau-Lifshitz equation is recast in terms of hydrodynamic-like variables for
+the magnetization's perpendicular component (spin density) and azimuthal phase
+gradient (fluid velocity). Spin injection acts as a moving piston that
+generates nonlinear, dynamical spin textures in the ferromagnetic channel with
+downstream quiescent spin density set by the external field. In contrast to the
+classical problem of a piston accelerating a compressible gas, here, variable
+spin injection and field lead to a rich variety of nonlinear wave phenomena
+from oscillatory spin shocks to solitons and rarefaction waves. A full
+classification of solutions is provided using nonlinear wave modulation theory
+by identifying two key aspects of the fluid-like dynamics: subsonic/supersonic
+conditions and convex/nonconvex hydrodynamic flux. Familiar waveforms from the
+classical piston problem such as rarefaction (expansion) waves and shocks
+manifest in their spin-based counterparts as smooth and highly oscillatory
+transitions, respectively. The spin shock is an example of a dispersive shock
+wave, which arises in many physical systems. New features without a gas
+dynamics counterpart include composite wave complexes with ""contact"" spin
+shocks and rarefactions. Magnetic supersonic conditions lead to two pronounced
+piston edge behaviors including a stationary soliton and an oscillatory
+wavetrain. These coherent wave structures have physical implications for the
+generation of high frequency spin waves from pulsed injection and persistent,
+stable stationary and/or propagating solitons in the presence of magnetic
+damping. The analytical results are favorably compared with numerical
+simulations.",2112.15301v2
+2022-02-17,Escape Dynamics in an Anisotropically Driven Brownian Magneto-System,"Thermally activated escape of a Brownian particle over a potential barrier is
+well understood within Kramers theory. When subjected to an external magnetic
+field, the Lorentz force slows down the escape dynamics via a rescaling of the
+diffusion coefficient without affecting the exponential dependence on the
+barrier height. Here, we study the escape dynamics of a charged Brownian
+particle from a two-dimensional truncated harmonic potential under the
+influence of Lorentz force due to an external magnetic field. The particle is
+driven anisotropically by subjecting it to noises with different strengths
+along different spatial directions. We show that the escape time can largely be
+tuned by the anisotropic driving. While the escape process becomes anisotropic
+due to the two different noises, the spatial symmetry is restored in the limit
+of large magnetic fields. This is attributed to the Lorentz force induced
+coupling between the spatial degrees of freedom which makes the difference
+between two noises irrelevant at high magnetic fields. The theoretical
+predictions are verified by Brownian dynamics simulations. In principle, our
+predictions can be tested by experiments with a Brownian gyrator in the
+presence of a magnetic field.",2202.08559v3
+2022-11-09,Electron dynamics in planar radio frequency magnetron plasmas: I. The mechanism of Hall heating and the μ-mode,"The electron dynamics and the mechanisms of power absorption in
+radio-frequency (RF) driven, magnetically enhanced capacitively coupled plasmas
+(MECCPs) at low pressure are investigated. The device in focus is a
+geometrically asymmetric cylindrical magnetron with a radially nonuniform
+magnetic field in axial direction and an electric field in radial direction.
+The dynamics is studied analytically using the cold plasma model and a
+single-particle formalism, and numerically with the inhouse energy and charge
+conserving particle-in-cell/Monte Carlo collisions code ECCOPIC1S-M. It is
+found that the dynamics differs significantly from that of an unmagnetized
+reference discharge. In the magnetized region in front of the powered
+electrode, an enhanced electric field arises during sheath expansion and a
+reversed electric field during sheath collapse. Both fields are needed to
+ensure discharge sustaining electron transport against the confining effect of
+the magnetic field. The corresponding azimuthal ExB-drift can accelerate
+electrons into the inelastic energy range which gives rise to a new mechanism
+of RF power dissipation. It is related to the Hall current and is different in
+nature from Ohmic heating, as which it has been classified in previous
+literature. The new heating is expected to be dominant in many magnetized
+capacitively coupled discharges. It is proposed to term it the ""{\mu}-mode"" to
+separate it from other heating modes.",2211.04805v1
+2023-03-10,Field-driven collapsing dynamics of skyrmions in magnetic multilayers,"Magnetic skyrmions are fascinating topological particle-like textures
+promoted by a trade-off among interfacial properties (perpendicular anisotropy
+and Dzyaloshinskii-Moriya interaction (DMI)) and dipolar interactions.
+Depending on the dominant interaction, complex spin textures, including pure
+N\'eel and hybrid skyrmions have been observed in multilayer heterostructures.
+A quantification of these different spin textures typically requires a
+depth-reoslved magnetic imaging or scattering techniques. In the present work,
+we will show qualitatively different collapsing dynamics for pure N\'eel and
+hybrid skyrmions induced by a perpendicular magnetic field in two
+representative systems, [Pt/Co/Ir]15 and [Ta/CoFeB/MgO]15 multilayers.
+Skyrmions in the former stack undergo two morphological transitions, upon
+reversing the perpendicular field direction. Skyrmions in [Ta/CoFeB/MgO]15
+multilayers exhibit a continuous transition, which is mainly linked to a
+reversible change of the skyrmion size. A full micromagnetic phase diagram is
+presented to identify these two collapsing mechanisms as a function of material
+parameters. Since the two distinct collapsing dynamics rely on the detailed
+layer-dependent spin structures of skyrmions, they could be used as potential
+fingerprints for identifying the skyrmion type in magnetic multilayers. Our
+work suggests the employment of pure and hybrid skyrmions for specific
+applications, due to the strong correlation between the skyrmion dynamics and
+3-dimentional spin profiles.",2303.05988v1
+2024-03-11,Topological solitons stabilized by a background gauge field and soliton-anti-soliton asymmetry,"We study topological lumps supported by the second homotopy group $\pi_2(S^2)
+\simeq {\mathbb Z}$ in a gauged $O(3)$ model without any potential term coupled
+with a (non)dynamical $U(1)$ gauge field. It is known that gauged-lumps are
+stable with an easy-plane potential term but are unstable to expand if the
+model has no potential term. In this paper, we find that these gauged lumps
+without a potential term can be made stable by putting them in a uniform
+magnetic field, irrespective of whether the gauge field is dynamical or not. In
+the case of the non-dynamical gauge field, only either of lumps or anti-lumps
+stably exists depending on the sign of the background magnetic field, and the
+other is unstable to shrink to be singular. We also construct coaxial multiple
+lumps whose size and mass exhibit a behaviour of droplets. In the case of the
+dynamical gauge field, both the lumps and anti-lumps stably exist with
+different masses; the lighter (heavier) one corresponds to the (un)stable one
+in the case of the nondynamical gauge field. We find that a lump behaves as a
+superconducting ring and traps magnetic field in its inside, with the total
+magnetic field reduced from the background magnetic field.",2403.06778v1
+2015-01-21,Observations of an Energetically Isolated Quiet Sun Transient: Evidence of Quasi-Steady Coronal Heating,"Increasing evidence for coronal heating contributions from cooler solar
+atmospheric layers, notably quiet Sun (QS) conditions, challenges standard
+solar atmospheric descriptions of bright transition region (TR) emission. As
+such, questions to the role of dynamic QS transients in contributing to the
+total coronal energy budget are elevated. Using observations from the {\it
+Atmospheric Imaging Assembly} and {\it Heliosemic Magnetic Imager} on board the
+{\it Solar Dynamics Observatory}, and numerical model extrapolations of coronal
+magnetic fields, we investigate a dynamic QS transient energetically isolated
+to the TR and extruding from a common footpoint shared with two heated loop
+arcades. A non-casual relationship is established between episodic heating of
+the QS transient and wide-spread magnetic field re-organization events, while
+evidence is found favoring a magnetic topology typical of eruptive processes.
+Quasi-steady interchange reconnection events are implicated as a source of the
+transient's visibly bright radiative signature. We consider the QS transient's
+temporally stable ($\approx$\,35\,min) radiative nature occurs as a result of
+the large-scale magnetic field geometries of the QS and/or relatively quiet
+nature of the magnetic photosphere, which possibly act to inhibit energetic
+buildup processes required to initiate a catastrophic eruption phase. This work
+provides insight to the QS's thermodynamic and magnetic relation to eruptive
+processes quasi-steadily heating a small-scale dynamic and TR transient. This
+work elevates arguments of non-negligible coronal heating contributions from
+cool atmospheric layers in QS conditions, and increases evidence for solar wind
+mass feeding of dynamic transients therein.",1501.05211v4
+2018-06-24,Dynamics of Insufflated Abdominal Wall Tissue for Magnetically Anchored Surgical Instruments,"Magnetically-anchored surgical devices have recently gained attention in
+abdominal surgery, with the use of magnets to anchor surgical devices onto the
+insufflated abdominal wall. These anchors have been used to secure passive and
+active devices, where active device such as robotic manipulators produce
+motions that would excite the dynamics of the non-rigid abdominal wall. Hence,
+there is a need to investigate the mechanical dynamics of the abdominal wall
+tissue in insufflated state, combined with magnetic anchoring, specifically its
+response to mechanical excitations and the expected disturbances to the
+operation of the anchored devices. In this paper, loading and unloading tests
+are performed on a corresponding porcine specimen for dynamics identification.
+The experiment setup was constructed to emulate the insufflated state of the
+abdomen with the magnetically anchored mechanism. The tissue responses during
+unloading are captured and approximated with a general numerical model, which
+is in turn used for the dynamic analysis of the tissue using Bode plot. The
+results showed that in such stretched and compressed state, the steady state
+displacement of the tissue is approximately zero. The maximum transient error
+was found to be 1mm in displacement using a high magnetic anchoring force.
+Significant attenuation of the disturbances due to the high stiffness and
+damping of the abdominal wall, was observed from 100rad/s in the frequency
+response. If a robotic manipulator was attached to the anchoring device, the
+typical operating frequency of movements would still produce unattenuated
+disturbances. It is expected that some error compensation through suitable
+control strategies is required. These outcomes establish the basis for the
+controller design and the design specification of the active
+magnetically-anchored surgical devices for minimal disturbance impact onto the
+abdominal wall tissue.",1806.09067v1
+2021-11-26,Magnetic correlations in infinite-layer nickelates: an experimental and theoretical multi-method study,"We report a comprehensive study of magnetic correlations in LaNiO$_{2}$, a
+parent compound of the recently discovered family of infinite-layer (IL)
+nickelate superconductors, using multiple experimental and theoretical methods.
+Our specific heat, muon-spin rotation ($\mu$SR), and magnetic susceptibility
+measurements on polycrystalline LaNiO$_{2}$ show that long-range magnetic order
+remains absent down to 2 K. Nevertheless, we detect residual entropy in the
+low-temperature specific heat, which is compatible with a model fit that
+includes paramagnon excitations. The $\mu$SR and low-field static and dynamic
+magnetic susceptibility measurements indicate the presence of short-range
+magnetic correlations and glassy spin dynamics, which we attribute to local
+oxygen non-stoichiometry in the average infinite-layer crystal structure. This
+glassy behavior can be suppressed in strong external fields, allowing us to
+extract the intrinsic paramagnetic susceptibility. Remarkably, we find that the
+intrinsic susceptibility shows non-Curie-Weiss behavior at high temperatures,
+in analogy to doped cuprates that possess robust non-local spin fluctuations.
+The distinct temperature dependence of the intrinsic susceptibility of
+LaNiO$_{2}$ can be theoretically understood by a multi-method study of the
+single-band Hubbard model in which we apply complementary cutting-edge quantum
+many-body techniques (dynamical mean-field theory, cellular dynamical
+mean-field theory and the dynamical vertex approximation) to investigate the
+influence of both short- and long-ranged correlations. Our results suggest a
+profound analogy between the magnetic correlations in parent (undoped) IL
+nickelates and doped cuprates.",2111.13668v1
+2017-08-01,Influence of a dispersion of magnetic and nonmagnetic nanoparticles on the magnetic Fredericksz transition of the liquid crystal 5CB,"A long time ago, Brochard and de Gennes predicted the possibility of
+significantly decreasing the critical magnetic field of the Fredericksz
+transition (the magnetic Fredericksz threshold) in a mixture of nematic liquid
+crystals and ferromagnetic particles, the so-called ferronematics. This
+phenomenon has rarely been measured, usually due to soft homeotropic anchoring
+induced at the nanoparticle surface. Here we present an optical study of the
+magnetic Fredericksz transition combined with a light scattering study of the
+classical nematic liquid crystal, 5CB, doped with 6 nm diameter magnetic and
+non-magnetic nanoparticles. Surprisingly, for both nanoparticles, we observe at
+room temperature a net decrease of the threshold field of the Fredericksz
+transition at low nanoparticle concentrations, which appears associated with a
+coating of the nanoparticles by a brush of polydimethylsiloxane copolymer
+chains inducing planar anchoring of the director on the nanoparticle surface.
+Moreover the magnetic Fredericksz threshold exhibits non-monotonic behaviour as
+a function of the nanoparticle concentration for both types of nanoparticles,
+first decreasing down to a value from 23\% to 31\% below that of pure 5CB, then
+increasing with a further increase of nanoparticle concentration. This is
+interpreted as an aggregation starting at around 0.02 weight fraction that
+consumes more isolated nanoparticles than those introduced when the
+concentration is increased above $c = 0.05$ weight fraction (volume fraction
+$3.5 \times 10^{-2}$). This shows the larger effect of isolated nanoparticles
+on the threshold with respect to aggregates. From dynamic light scattering
+measurements we deduced that, if the decrease of the magnetic threshold when
+the nanoparticle concentration increases is similar for both kinds of
+nanoparticles, the origin of this decrease is different for magnetic and
+non-magnetic nanoparticles. For non-magnetic nanoparticles, the behavior may be
+associated with a decrease of the elastic constant due to weak planar
+anchoring. For magnetic nanoparticles there are non-negligible local magnetic
+interactions between liquid crystal molecules and magnetic nanoparticles,
+leading to an increase of the average order parameter. This magnetic
+interaction thus favors an easier liquid crystal director rotation in the
+presence of external magnetic field, able to reorient the magnetic moments of
+the nanoparticles along with the molecules.",1708.00286v1
+2006-11-24,Internal shocks in relativistic outflows: collisions of magnetized shells,"(Abridged): We study the collision of magnetized irregularities (shells) in
+relativistic outflows in order to explain the origin of the generic
+phenomenology observed in the non-thermal emission of both blazars and
+gamma-ray bursts. We focus on the influence of the magnetic field on the
+collision dynamics, and we further investigate how the properties of the
+observed radiation depend on the strength of the initial magnetic field and on
+the initial internal energy density of the flow. The collisions of magnetized
+shells and the radiation resulting from these collisions are calculated using
+the 1D relativistic magnetohydrodynamics code MRGENESIS. The interaction of the
+shells with the external medium prior to their collision is also determined
+using an exact solver for the corresponding 1D relativistic magnetohydrodynamic
+Riemann problem. Our simulations show that two magnetization parameters - the
+ratio of magnetic energy density and thermal energy density, \alpha_B, and the
+ratio of magnetic energy density and mass-energy density, \sigma - play an
+important role in the pre-collision phase, while the dynamics of the collision
+and the properties of the light curves depend mostly on the magnetization
+parameter \sigma. The interaction of the shells with the external medium
+changes the flow properties at their edges prior to the collision. For
+sufficiently dense shells moving at large Lorentz factors (\simgt 25) these
+properties depend only on the magnetization parameter \sigma. Internal shocks
+in GRBs may reach maximum efficiencies of conversion of kinetic into thermal
+energy between 6% and 10%, while in case of blazars, the maximum efficiencies
+are \sim 2%.",0611765v3
+2005-10-07,Magnetic and Charge Correlations in La{2-x-y}Nd_ySr_xCuO_4: Raman Scattering Study,"Two aspects in connection with the magnetic properties of
+La_{2-x-y}Nd_ySr_xCuO_4 single crystals are discussed. The first is related to
+long wavelength magnetic excitations in x = 0, 0.01, and 0.03 La_{2-x}Sr_xCuO_4
+detwinned crystals as a function of doping, temperature and magnetic field. Two
+magnetic modes were observed within the AF region of the phase diagram. The one
+at lower energies was identified with the spin-wave gap induced by the
+antisymmetric DM interaction and its anisotropic properties in magnetic field
+could be well explained using a canonical form of the spin Hamiltonian. A new
+finding was a magnetic field induced mode whose dynamics allowed us to discover
+a spin ordered state outside the AF order which was shown to persist in a 9 T
+field as high as 100 K above the N\'eel temperature T_N for x = 0.01. For these
+single magnon excitations we map out the Raman selection rules in magnetic
+fields and demonstrate that their temperature dependent spectral weight is
+peaked at the N\'eel temperature. The second aspect is related to phononic and
+magnetic Raman scattering in La_{2-x-y}Nd_ySr_xCuO_4 with three doping
+concentrations: x = 1/8, y = 0; x = 1/8, y = 0.4; and x = 0.01, y = 0. We
+observed that around 1/8 Sr doping and independent of Nd concentration there
+exists substantial disorder in the tilt pattern of the CuO_6 octahedra in both
+the orthorhombic and tetragonal phases which persist down to 10 K and are
+coupled to bond disorder in the cation layers. The weak magnitude of existing
+charge/spin modulations in the Nd doped structure did not allow us to detect
+specific Raman signatures on lattice dynamics or two-magnon scattering around
+2200 cm-1.",0510191v1
+2009-08-25,Methanol masers probing the ordered magnetic field of W75N,"The role of magnetic fields during the protostellar phase of high-mass
+star-formation is a debated topic. In particular, it is still unclear how
+magnetic fields influence the formation and dynamic of disks and outflows. Most
+current information on magnetic fields close to high-mass protostars comes from
+H2O and OH maser observations. Recently, the first 6.7 GHz methanol maser
+polarization observations were made, and they reveal strong and ordered
+magnetic fields. The morphology of the magnetic field during high-mass
+star-formation needs to be investigated on small scales, which can only be done
+using very long baseline interferometry observations. The massive star-forming
+regionW75N contains three radio sources and associated masers, while a
+large-scale molecular bipolar outflow is also present. Polarization
+observations of the 6.7 GHz methanol masers at high angular resolution probe
+the strength and structure of the magnetic field and determine its relation to
+the outflow. Eight of the European VLBI network antennas were used to measure
+the linear polarization and Zeeman-splitting of the 6.7 GHz methanol masers in
+the star-forming region W75N. We detected 10 methanol maser features, 4 of
+which were undetected in previous work. All arise near the source VLA1 of W75N.
+The linear polarization of the masers reveals a tightly ordered magnetic field
+over more than 2000 AU around VLA1 that is exactly aligned with the large-scale
+molecular outflow. This is consistent with the twisted magnetic field model
+proposed for explaining dust polarization observations. The Zeeman-splitting
+measured on 3 of the maser features indicates a dynamically important magnetic
+field in the maser region of the order of 50mG. We suggest VLA1 is the powering
+sources of the bipolar outflow.",0908.3585v1
+2011-01-10,The structure of the magnetic field in the massive star-forming region W75N,"A debated topic in star formation theory is the role of magnetic fields
+during the protostellar phase of high-mass stars. It is still unclear how
+magnetic fields influence the formation and dynamics of massive disks and
+outflows. Most current information on magnetic fields close to high-mass
+protostars comes from polarized maser emissions, which allows us to investigate
+the magnetic field on small scales by using very long-baseline interferometry.
+The massive star-forming region W75N contains three radio continuum sources
+(VLA1, VLA2, and VLA3), at three different evolutionary stages, and associated
+masers, while a large-scale molecular bipolar outflow is also present. Very
+recently, polarization observations of the 6.7 GHz methanol masers at
+milliarsecond resolution have been able to probe the strength and structure of
+the magnetic field over more than 2000 AU around VLA1. The magnetic field is
+parallel to the outflow, suggesting that VLA1 is its powering source. The
+observations of water masers at 22 GHz can give more information about the gas
+dynamics and the magnetic fields around VLA1 and VLA2. The NRAO Very Long
+Baseline Array was used to measure the linear polarization and the
+Zeeman-splitting of the 22 GHz water masers in the star-forming region W75N. We
+detected 124 water masers, 36 around VLA1 and 88 around VLA2 of W75N, which
+indicate two different physical environments around the two sources, where VLA1
+is in a more evolved state. The linear polarization of the masers confirms the
+tightly ordered magnetic field around VLA1, which is aligned with the
+large-scale molecular outflow, and also reveals an ordered magnetic field
+around VLA2, which is not parallel to the outflow. [abridged]",1101.1956v1
+2011-11-22,Observation of spin glass state in weakly ferromagnetic Sr$_2$FeCoO$_6$ double perovskite,"We report the observation of spin glass state in the double perovskite oxide
+Sr$_{2}$FeCoO$_{6}$ prepared through sol-gel technique. Initial structural
+studies using x rays reveal that the compound crystallizes in tetragonal $I
+4/m$ structure with lattice parameters, $a$ = 5.4609(2) \AA and $c$ = 7.7113(7)
+\AA. The temperature dependent powder x ray studies reveal no structural phase
+transition in the temperature range 10 -- 300 K. However, the unit cell volume
+shows an anomaly coinciding with the magnetic transition temperature thereby
+suggesting a close connection between lattice and magnetism. Neutron
+diffraction studies and subsequent bond valence sums analysis show that in
+Sr$_{2}$FeCoO$_{6}$, the $B$ site is randomly occupied by Fe and Co in the
+mixed valence states of Fe$^{3+}$/Fe$^{4+}$ and Co$^{3+}$/Co$^{4+}$. The random
+occupancy and mixed valence sets the stage for inhomogeneous magnetic exchange
+interactions and in turn, for the spin glass like state in this double
+perovskite which is observed as an irreversibility in temperature dependent dc
+magnetization at $T_f\sim$ 75 K. Thermal hysteresis observed in the
+magnetization profile of Sr$_{2}$FeCoO$_{6}$ is indicative of the mixed
+magnetic phases present. The dynamic magnetic susceptibility displays
+characteristic frequency dependence and confirms the spin glass nature of this
+material. Dynamical scaling analysis of $\chi'(T)$ yields a critical
+temperature $T_{ct}$ = 75.14(8) K and an exponent $z\nu$ = 6.2(2) typical for
+spin glasses. The signature of presence of mixed magnetic interactions is
+obtained from the thermal hysteresis in magnetization of Sr$_{2}$FeCoO$_{6}$.
+Combining the neutron and magnetization results of Sr$_2$FeCoO$_6$, we deduce
+the spin states of Fe to be in low spin while that of Co to be in low spin and
+intermediate spin.",1111.5136v1
+2013-02-22,The Post-Merger Magnetized Evolution of White Dwarf Binaries: The Double-Degenerate Channel of Sub-Chandrasekhar Type Ia Supernovae and the Formation of Magnetized White Dwarfs,"Type Ia supernovae (SNe Ia) play a crucial role as standardizable
+cosmological candles, though the nature of their progenitors is a subject of
+active investigation. Recent observational and theoretical work has pointed to
+merging white dwarf binaries, referred to as the double-degenerate channel, as
+the possible progenitor systems for some SNe Ia. Additionally, recent
+theoretical work suggests that mergers which fail to detonate may produce
+magnetized, rapidly-rotating white dwarfs. In this paper, we present the first
+multidimensional simulations of the post-merger evolution of white dwarf
+binaries to include the effect of the magnetic field. In these systems, the two
+white dwarfs complete a final merger on a dynamical timescale, and are tidally
+disrupted, producing a rapidly-rotating white dwarf merger surrounded by a hot
+corona and a thick, differentially-rotating disk. The disk is strongly
+susceptible to the magnetorotational instability (MRI), and we demonstrate that
+this leads to the rapid growth of an initially dynamically weak magnetic field
+in the disk, the spin-down of the white dwarf merger, and to the subsequent
+central ignition of the white dwarf merger. Additionally, these magnetized
+models exhibit new features not present in prior hydrodynamic studies of white
+dwarf mergers, including the development of MRI turbulence in the hot disk,
+magnetized outflows carrying a significant fraction of the disk mass, and the
+magnetization of the white dwarf merger to field strengths $\sim 2 \times 10^8$
+G. We discuss the impact of our findings on the origins, circumstellar media,
+and observed properties of SNe Ia and magnetized white dwarfs.",1302.5700v2
+2014-05-03,3D MHD simulation of linearly polarised Alfven wave dynamics in Arnold-Beltrami-Childress magnetic field,"Previous studies [Malara et al ApJ, 533, 523 (2000)] considered
+small-amplitude Alfven wave (AW) packets in Arnold-Beltrami-Childress (ABC)
+magnetic field using WKB approximation. In this work linearly polarised Alfven
+wave dynamics in ABC magnetic field via direct 3D MHD numerical simulation is
+studied for the first time. Gaussian AW pulse with length-scale much shorter
+than ABC domain length and harmonic AW with wavelength equal to ABC domain
+length are studied for four different resistivities. While it is found that AWs
+dissipate quickly in the ABC field, surprisingly, AW perturbation energy
+increases in time. In the case of the harmonic AW perturbation energy growth is
+transient in time, attaining peaks in both velocity and magnetic perturbation
+energies within timescales much smaller than resistive time. In the case of the
+Gaussian AW pulse velocity perturbation energy growth is still transient in
+time, attaining a peak within few resistive times, while magnetic perturbation
+energy continues to grow. It is also shown that the total magnetic energy
+decreases in time and this is governed by the resistive evolution of the
+background ABC magnetic field rather than AW damping. On contrary, when
+background magnetic field is uniform, the total magnetic energy decrease is
+prescribed by AW damping, because there is no resistive evolution of the
+background. By considering runs with different amplitudes and by analysing
+perturbation spectra, possible dynamo action by AW perturbation-induced
+peristaltic flow and inverse cascade of magnetic energy have been excluded.
+Therefore, the perturbation energy growth is attributed to a new instability.
+The growth rate appears to be dependent on the value of the resistivity and
+spatial scale of the AW disturbance. Thus, when going beyond WKB approximation,
+AW damping, described by full MHD equations, does not guarantee decrease of
+perturbation energy.",1405.0587v1
+2015-04-24,Small-scale magnetic islands in the solar wind and their role in particle acceleration. Part 1: Dynamics of magnetic islands near the heliospheric current sheet,"Increases of ion fluxes in the keV-MeV range are sometimes observed near the
+heliospheric current sheet (HCS) during periods when other sources are absent.
+These resemble solar energetic particle (SEP) events, but the events are weaker
+and apparently local. Conventional explanations based on either shock
+acceleration of charged particles or particle acceleration due to magnetic
+reconnection at interplanetary current sheets are not persuasive. We suggest
+instead that recurrent magnetic reconnection occurs at the HCS and smaller
+current sheets in the solar wind (Zharkova & Khabarova 2012), of which a
+consequence is particle energization by the dynamically evolving secondary
+current sheets and magnetic islands (Zank et al. 2014; Drake et al. 2006a). The
+effectiveness of the trapping and acceleration process associated with magnetic
+islands depends in part on the topology of the HCS. We show that the HCS
+possesses ripples superimposed on the large-scale flat or wavy structure. We
+conjecture that the ripples can efficiently confine plasma and provide
+tokamak-like conditions that are favorable for the appearance of small-scale
+magnetic islands that merge and/or contract. Particles trapped in the vicinity
+of merging islands and experiencing multiple small-scale reconnection events
+are accelerated by the induced electric field, and experience first-order Fermi
+acceleration in contracting magnetic islands (Zank et al. 2014). We present
+multi-spacecraft observations of magnetic island merging and particle
+energization in the absence of other sources, providing support for theory and
+simulations that show particle energization by reconnection related processes
+of magnetic island merging and contraction.",1504.06616v2
+2016-04-18,Full particle orbit effects in regular and stochastic magnetic fields,"We present a numerical study of charged particle motion in a time-independent
+magnetic field in cylindrical geometry. The magnetic field model consists of an
+unperturbed reversed-shear helical part and a perturbation consisting of a
+superposition of modes. Contrary to most of the previous studies, the particle
+trajectories are computed by directly solving the full Lorentz force equations
+of motion in a six-dimensional phase space using a sixth-order, implicit,
+symplectic Gauss-Legendre method. The level of stochasticity in the particle
+orbits is diagnosed using averaged, effective Poincare sections. It is shown
+that when only one mode is present the particle orbits can be stochastic even
+though the magnetic field line orbits are not stochastic. The lack of
+integrability of the particle orbits in this case is related to separatrix
+crossing and the breakdown of the global conservation of the magnetic moment.
+Some perturbation consisting of two modes creates resonance overlapping,
+leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits
+exhibit a nontrivial dynamics depending on their energy and pitch angle. It is
+shown that the regions where the particle motion is stochastic decrease as the
+energy increases. The non-monotonicity of the $q$-profile implies the existence
+of magnetic ITBs which correspond to shearless flux surfaces located in the
+vicinity of the $q$-profile minimum. It is shown that depending on the energy,
+these magnetic ITBs might or might not confine particles. That is, magnetic
+ITBs act as an energy-dependent particle confinement filter. Magnetic field
+lines in reversed-shear configurations exhibit topological bifurcations due to
+separatrix reconnection. We show that a similar but more complex scenario
+appears in the case of particle orbits that depends in a non-trivial way on the
+energy and pitch angle of the particles.",1604.05112v2
+2016-08-16,"Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu$_{2}$(Si$_{x}$Ge$_{1-x}$)$_{2}$","In mixed-valence or heavy-fermion systems, the hybridization between local
+$f$ orbitals and conduction band states can cause the suppression of long-range
+magnetic order, which competes with strong spin fluctuations. Ce- and Yb-based
+systems have been found to exhibit fascinating physical properties
+(heavy-fermion superconductivity, non-Fermi-liquid states, etc.) when tuned to
+the vicinity of magnetic quantum critical points by use of various external
+control parameters (temperature, magnetic field, chemical composition).
+Recently, similar effects (mixed-valence, Kondo fluctuations, heavy Fermi
+liquid) have been reported to exist in some Eu-based compounds. Unlike Ce (Yb),
+Eu has a multiple electron (hole) occupancy of its $4f$ shell, and the magnetic
+Eu$^{2+}$ state ($4f^7$) has no orbital component in the usual $LS$ coupling
+scheme, which can lead to a quite different and interesting physics. In the
+EuCu$_{2}$(Si$_{x}$Ge$_{1-x}$)$_{2}$ series, where the valence can be tuned by
+varying the Si/Ge ratio, it has been reported that a significant valence
+fluctuation can exist even in the magnetic order regime. This paper presents a
+detailed study of the latter material using different microscopic probes
+(XANES, M\""ossbauer spectroscopy, elastic and inelastic neutron scattering), in
+which the composition dependence of the magnetic order and dynamics across the
+series is traced back to the change in the Eu valence state. In particular, the
+results support the persistence of valence fluctuations into the
+antiferromagnetic state over a sizable composition range below the critical Si
+concentration $x_c \approx 0.65$. The sequence of magnetic ground states in the
+series is shown to reflect the evolution of the magnetic spectral response.",1608.04687v2
+2017-06-20,"Filament formation in wind-cloud interactions. II. Clouds with turbulent density, velocity, and magnetic fields","We present a set of numerical experiments designed to systematically
+investigate how turbulence and magnetic fields influence the morphology,
+energetics, and dynamics of filaments produced in wind-cloud interactions. We
+cover 3D magnetohydrodynamic systems of supersonic winds impacting clouds with
+turbulent density, velocity, and magnetic fields. We find that log-normal
+density distributions aid shock propagation through clouds, increasing their
+velocity dispersion and producing filaments with expanded cross sections and
+highly-magnetised knots and sub-filaments. In self-consistently turbulent
+scenarios the ratio of filament to initial cloud magnetic energy densities is
+~1. The effect of Gaussian velocity fields is bound to the turbulence Mach
+number: Supersonic velocities trigger a rapid cloud expansion; subsonic
+velocities only have a minor impact. The role of turbulent magnetic fields
+depends on their tension and is similar to the effect of radiative losses: the
+stronger the magnetic field or the softer the gas equation of state, the
+greater the magnetic shielding at wind-filament interfaces and the suppression
+of Kelvin-Helmholtz instabilities. Overall, we show that including turbulence
+and magnetic fields is crucial to understanding cold gas entrainment in
+multi-phase winds. While cloud porosity and supersonic turbulence enhance the
+acceleration of clouds, magnetic shielding protects them from ablation and
+causes Rayleigh-Taylor-driven sub-filamentation. Wind-swept clouds in turbulent
+models reach distances ~15-20 times their core radius and acquire bulk speeds
+~0.3-0.4 of the wind speed in one cloud-crushing time, which are three times
+larger than in non-turbulent models. In all simulations the ratio of turbulent
+magnetic to kinetic energy densities asymptotes at ~0.1-0.4, and convergence of
+all relevant dynamical properties requires at least 64 cells per cloud radius.",1706.06607v1
+2018-01-19,Polarized-neutron investigation of magnetic ordering and spin dynamics in BaCo$_2$(AsO$_4$)$_2$ frustrated honeycomb-lattice magnet,"The magnetic properties of the cobaltite {\BCAO}, a good realization of the
+quasi two-dimensional frustrated honeycomb-lattice system with strong planar
+anisotropy, have been reinvestigated by means of spherical neutron polarimetry
+with CRYOPAD. From accurate measurements of polarization matrices both on
+elastic and inelastic contributions as a function of the scattering vector
+{\bf{Q}}, we have been able to determine the low-temperature magnetic structure
+of {\BCAO} and reveal its puzzling in-plane spin dynamics. Surprisingly, the
+ground-state structure (described by an incommensurate propagation vector
+${\bf{k}}_{1}=(k_{x}, 0, k_{z}$), with $k_{x}=0.270{\pm}0.005$ and $k_{z}
+\approx -1.31$) appears to be a quasi-collinear structure, and not a simple
+helix, as previously determined. In addition, our results have revealed the
+existence of a non-negligible out-of-plane moment component $ \approx
+0.25{\mu}_{B}$/Co$^{2+}$, representing about 10\% of the in-plane component, as
+demonstrated by the presence of finite off-diagonal elements $P_{yz}$ and
+$P_{zy}$ of the polarization matrix, both on elastic and inelastic magnetic
+contributions. Despite a clear evidence of the existence of a slightly
+inelastic contribution of structural origin superimposed to the magnetic
+excitations at the scattering vectors ${\bf{Q}}=(0.27, 0, 3.1)$ and
+${\bf{Q}}=(0.73, 0, 0.8)$ (energy transfer ${\Delta}E \approx 2.3$ meV), no
+strong inelastic nuclear-magnetic interference terms could be detected so far,
+meaning that the nuclear and magnetic degrees of freedom have very weak
+cross-correlations. The strong inelastic $P_{yz}$ and $P_{zy}$ matrix elements
+can be understood by assuming that the magnetic excitations in {\BCAO} are spin
+waves associated with trivial anisotropic precessions of the magnetic moments
+involved in the canted incommensurate structure.",1801.06588v1
+2018-10-25,Time-retarded damping and magnetic inertia in the Landau-Lifshitz-Gilbert equation self-consistently coupled to electronic time-dependent nonequilibrium Green functions,"The conventional Landau-Lifshitz-Gilbert (LLG) equation is a widely used tool
+to describe dynamics of local magnetic moments, viewed as classical vectors of
+fixed length, with their change assumed to take place simultaneously with the
+cause. Here we demonstrate that recently developed [M. D. Petrovi\'{c} {\em et
+al.}, {\tt arXiv:1802.05682}] self-consistent coupling of the LLG equation to
+time-dependent quantum-mechanical description of electrons microscopically
+generates time-retarded damping in the LLG equation described by a memory
+kernel which is also spatially dependent. For sufficiently slow dynamics of
+local magnetic moments, the memory kernel can be expanded to extract the
+Gilbert damping (proportional to first time derivative of magnetization) and
+magnetic inertia (proportional to second time derivative of magnetization)
+terms whose parameters, however, are time-dependent in contrast to
+time-independent parameters used in the conventional LLG equation. We use
+examples of single or multiple magnetic moments precessing in an external
+magnetic field, as well as field-driven motion of a magnetic domain wall (DW),
+to quantify the difference in their time evolution computed from conventional
+LLG equation vs. TDNEGF+LLG quantum-classical hybrid approach. The faster DW
+motion predicted by TDNEGF+LLG approach reveals that important quantum effects,
+stemming from finite amount of time which it takes for conduction electron spin
+to react to the motion of classical local magnetic moments, are missing from
+conventional classical micromagnetics simulations. We also demonstrate large
+discrepancy between TDNEGF+LLG-computed numerically exact and, therefore,
+nonperturbative result for charge current pumped by a moving DW and the same
+quantity computed by perturbative spin motive force formula combined with the
+conventional LLG equation.",1810.11016v2
+2019-11-22,Anisotropic electrical conductivity of magnetized hot quark matter,"We studied the effect of a strong magnetic field ($B$) on the electrical
+conductivity of hot quark matter. The electrical conductivity is a key
+transport coefficient determining the time dependence and strength of magnetic
+fields generated in a relativistic heavy-ion collision. A~magnetic field
+induces Hall anisotropic conduction, phase-space Landau-level quantization and,
+if sufficiently strong, interferes with prominent QCD phenomena such as
+dynamical quark mass generation, likely affecting the quark matter electrical
+conductivity, which depends strongly on the quark masses. To address these
+issues, we used a quasi-particle description of quark matter in which the
+electric charge carriers are constituent quarks with temperature- and
+magnetic-field-dependent masses predicted by a Nambu--Jona-Lasinio model. The
+model accurately describes recent lattice QCD results showing magnetic
+catalysis at low temperatures and inverse magnetic catalysis at temperatures
+close to the pseudo-critical temperature ($T_{\rm pc}$) of the QCD phase
+transition. We found that the magnetic field increases the conductivity
+component parallel to it and decreases the transverse component, in qualitative
+agreement with recent lattice QCD results. In addition, we found that: (1)~the
+space anisotropy of the conductivity increases with~$B$, (2)~the longitudinal
+conductivity increases due to phase-space Landau-level quantization, (3)~a
+lowest Landau level approximation behaves poorly for temperatures close to
+$T_{\rm pc}$, and (5)~inverse magnetic catalysis leaves a distinctive signal in
+all components of the conductivity, a prominent peak at $T_{\rm pc}$. Our study
+adds to the existing body of work on the hot quark matter electrical
+conductivity by incorporating nontrivial temperature and magnetic field effects
+on dynamical mass generation.",1911.10005v2
+2020-06-22,A dynamo amplifies the magnetic field of a Milky-Way-like galaxy,"The magnetic fields of spiral galaxies are so strong that they cannot be
+primordial. Their typical values are over one billion times higher than any
+value predicted for the early Universe. Explaining this immense growth and
+incorporating it in galaxy evolution theories is one of the long-standing
+challenges in astrophysics. So far, the most successful theory for the
+sustained growth of the galactic magnetic field is the alpha-omega dynamo. This
+theory predicts a characteristic dipolar or quadrupolar morphology for the
+galactic magnetic field, which has been observed in external galaxies. However,
+so far, there has been no direct demonstration of a mean-field dynamo operating
+in direct, multi-physics simulations of spiral galaxies. We do so in this work.
+We employ numerical models of isolated, star-forming spiral galaxies that
+include a magnetized gaseous disk, a dark matter halo, stars, and stellar
+feedback. Naturally, the resulting magnetic field has a complex morphology that
+includes a strong random component. Using a smoothing of the magnetic field on
+small scales, we are able to separate the mean from the turbulent component and
+analyze them individually. We find that a mean-field dynamo naturally occurs as
+a result of the dynamical evolution of the galaxy and amplifies the magnetic
+field by an order of magnitude over half a Gyr. Despite the highly dynamical
+nature of these models, the morphology of the mean component of the field is
+identical to analytical predictions. This result underlines the importance of
+the mean-field dynamo in galactic evolution. Moreover, by demonstrating the
+natural growth of the magnetic field in a complex galactic environment, it
+brings us a step closer to understanding the cosmic origin of magnetic fields.",2006.12574v1
+2021-02-01,Temporal evolution of small-scale internetwork magnetic fields in the solar photosphere,"While the longitudinal field that dominates photospheric network regions has
+been studied extensively, small scale transverse fields have recently been
+found to be ubiquitous in the quiet internetwork photosphere. Few observations
+have captured how this field evolves. We aim to statistically characterise the
+magnetic properties and observe the temporal evolution of small scale magnetic
+features. We present two high spatial/temporal resolution observations that
+reveal the dynamics of two disk centre internetwork regions taken by the new
+GRIS/IFU (GREGOR Infrared Spectrograph Integral Field Unit) with the highly
+magnetically sensitive Fe I line pair at 15648.52 {\AA} and 15652.87 {\AA}.
+With the SIR code, we consider two inversion schemes: scheme 1 (S1), where a
+magnetic atmosphere is embedded in a field free medium, and scheme 2 (S2), with
+two magnetic models and a fixed stray light component. S1 inversions returned a
+median magnetic field strength of 200 and 240 G for the two datasets,
+respectively. We consider the median transverse (horizontal) component, among
+pixels with Stokes Q or U, and the median unsigned longitudinal (vertical)
+component, among pixels with Stokes V, above a noise threshold. We determined
+the former to be 263 G and 267 G, and the latter to be 131 G and 145 G, for the
+two datasets, respectively. We present three regions of interest (ROIs),
+tracking the dynamics of small scale magnetic features. We apply S1 and S2
+inversions to specific profiles, and find S2 produces better approximations
+when there is evidence of mixed polarities. We find patches of linear
+polarization with magnetic flux density between 130 and 150 G, appearing
+preferentially at granule/intergranular lane (IGL) boundaries. The weak hG
+magnetic field appears to be organised in terms of complex loop structures,
+with transverse fields often flanked by opposite polarity longitudinal fields.",2102.00942v4
+2021-11-10,Influence of the Magnetic Sub-Lattices in the Double Perovskite Compound LaCaNiReO$_6$,"The magnetism of double perovskites is a complex phenomenon, determined from
+intra- or interatomic magnetic moment interactions, and strongly influenced by
+geometry. We take advantage of the complementary length and time scales of the
+muon spin rotation, relaxation and resonance ($\mu^+$SR) microscopic technique
+and bulk AC/DC magnetic susceptibility measurements to study the magnetic
+phases of the LaCaNiReO$_6$ double perovskite. As a result we are able to
+discern and report a newly found dynamic phase transition and the formation of
+magnetic domains below and above the known magnetic transition of this compound
+at T$_N$ = 103 K. $\mu^+$SR, serving as a local probe at crystallographic
+interstitial sites, reveals a transition from a metastable ferrimagnetic
+ordering below T = 103 K to a stable one below T = 30 K. The fast and slow
+collective dynamic state of this system are investigated. Between 103 K < T <
+230 K, the following two magnetic environments appear, a dense spin region and
+a static-dilute spin region. The paramagnetic state is obtained only above T >
+270 K. An evolution of the interaction between Ni and Re magnetic sublattices
+in this geometrically frustrated fcc perovskite structure, is revealed as a
+function of temperature and magnetic field, through the critical behaviour and
+thermal evolution of microscopic and macroscopic physical quantities.",2111.05920v2
+2022-08-31,Magnetic signatures on mixed-mode frequencies. II. Period spacings as a probe of the internal magnetism of red giants,"Theoretical works have looked into the various topologies and amplitudes, as
+well as the stability of the magnetic field that is expected to be present in
+the radiative interior of stars evolving after the main sequence. Such internal
+magnetic fields have never been observed in evolved stars. As a result, there
+is a major piece missing from our global picture of stars as dynamical bodies.
+Asteroseismology opened a window onto stellar internal dynamics, as oscillation
+frequencies, amplitudes, and lifetimes are affected by processes that are
+taking place inside the star. In this scope, magnetic signatures on mixed-mode
+frequencies have recently been characterized, but the task of detection remains
+challenging as the mixed-mode frequency pattern is highly complex and affected
+by rotational effects, while modes of different radial orders are often
+intertwined. In this work, we aim to build a bridge between theoretical
+prescriptions and complex asteroseismic data analysis to facilitate a future
+search and characterization of internal magnetism with asteroseismology. We
+investigate the effect of magnetic fields inside evolved stars with solar-like
+oscillations on the estimation of the period spacing of gravity-mode components
+of simulated mixed gravito-acoustic modes. We derived a new corrected
+stretching function of the power spectrum density to account for the presence
+of magnetic signatures on their frequencies. We demonstrate that the strong
+dependency of the amplitude of the magnetic signature with mixed-mode
+frequencies leads to biased estimates of period spacings towards lower values.
+We also show that a careful analysis of the oscillation frequency pattern
+through various period spacing estimates and across a broad frequency range
+might lead to the first detection of magnetic fields inside red giants and at
+the same time, we adjust the measured value of gravity-mode period spacing.",2208.14954v1
+1994-05-09,Fragmentation of a Magnetized Filamentary Molecular Cloud Rotating around its Axis,"The dynamical instability of a self-gravitating magnetized filamentary cloud
+was investigated while taking account of rotation around its axis. The
+filamentary cloud of our model is supported against self-gravity in part by
+both a magnetic field and rotation. The density distribution in equilibrium was
+assumed to be a function of the radial distance from the axis, $ \rho _0 (r) \,
+= \, \rho _{\rm c} \, ( 1 \, + \, r ^2 / 8 H ^2 ) ^{-2} $, where $ \rho _{\rm
+c} $ and $ H $ are model parameters specifying the density on the axis and the
+length scale, respectively; the magnetic filed was assumed to have both
+longitudinal ($z$-) and azimuthal ($\varphi$-) components with a strength of $
+B _0 (r) \, \propto \, \sqrt{ \rho _0 (r) } $. The rotation velocity was
+assumed to be $ v _{0\varphi} \, = \, \Omega _{\rm c} \, r \, (1 \, + \, r ^2 /
+8 H ^2 ) ^{-1/2} $. We obtained the growth rate and eigenfunction numerically
+for (1) axisymmetric $ ( m \, = \, 0 ) $ perturbations imposed on a rotating
+cloud with a longitudinal magnetic field, (2) non-axisymmetric $ ( m \, = \, 1
+) $ perturbations imposed on a rotating cloud with a longitudinal magnetic
+filed, and (3) axisymmetric perturbations imposed on a rotating cloud with a
+helical magnetic field. The fastest growing perturbation is an axisymmetric one
+for all of the model clouds studied. Its wavelength is $ \lambda _{\rm max} \,
+\le \, 11.14 \, H $ for a non-rotating cloud without a magnetic field, and is
+shorter",9405019v1
+1995-10-23,The MHD Kelvin-Helmholtz Instability: A Two-Dimensional Numerical Study,"Using a new numerical code we have carried out two-dimensional simulations of
+the nonlinear evolution of unstable sheared magnetohydrodynamic flows. We
+considered two cases: a strong magnetic field (Alfven Mach number, M_a = 2.5)
+and a weak field (M_a =5). Each flow rapidly evolves until it reaches a nearly
+steady condition, which is fundamentally different from the analogous
+gasdynamic state. Both MHD flows relax to a stable, laminar flow on timescales
+less than or of the order of 15 linear growth times, measured from saturation
+of the instability. That timescale is several orders of magnitude less than the
+nominal dissipation time for these simulated flows, so this condition
+represents an quasi-steady relaxed state. The strong magnetic field case
+reaches saturation as magnetic tension in the displaced flow boundary becomes
+sufficient to stabilize it. That flow then relaxes in a straightforward way to
+the steady, laminar flow condition. The weak magnetic field case, on the other
+hand, begins development of the vortex expected for gasdynamics, but that
+vortex is destroyed by magnetic stresses that locally become strong. Magnetic
+topologies lead to reconnection and dynamical alignment between magnetic and
+velocity fields. Together these processes produce a sequence of intermittent
+vortices and subsequent relaxation to a nearly laminar flow condition in which
+the magnetic cross helicity is nearly maximized. Remaining irregularities
+consist of a pair of flux tubes straddling the shear layer. Fluctuations within
+those features are closely aligned, representing Alfv\'en waves propagating
+locally downstream.",9510115v1
+1996-10-22,The galactic dynamo effect due to Parker-shearing instability of magnetic flux tubes. I. General formalism and the linear approximation,"In this paper we investigate the idea of Hanasz & Lesch 1993 that the
+galactic dynamo effect is due to the Parker instability of magnetic flux tubes.
+In addition to the former approach, we take into account more general physical
+conditions in this paper, by incorporating cosmic rays and differential forces
+due to the axisymmetric differential rotation and the density waves as well. We
+present the theory of slender magnetic flux tube dynamics in the thin flux tube
+approximation and the Lagrange description. This is the application of the
+formalism obtained for solar magnetic flux tubes by Spruit (1981), to the
+galactic conditions. We perform a linear stability analysis for the
+Parker-shearing instability of magnetic flux tubes in galactic discs and then
+calculate the dynamo coefficients. We present a number of new effects which are
+very essential for cosmological and contemporary evolution of galactic magnetic
+fields. First of all we demonstrate that a very strong dynamo $\alpha$-effect
+is possible in the limit of weak magnetic fields in presence of cosmic rays.
+Second, we show that the differential force resulting from axisymmetric
+differential rotation and the linear density waves causes that the
+$\alpha$-effect is essentially magnified in galactic arms and switched off in
+the interarm regions. Moreover, we predict a non-uniform magnetic field in
+spiral arms and well aligned one in interarm regions. These properties are well
+confirmed by recent observational results by Beck & Hoernes (1996)",9610167v2
+2000-02-03,Fast Turbulent Reconnection,"Reconnection is the process by which magnetic fields in a conducting fluid
+change their topology. This process is essential for understanding a wide
+variety of astrophysical processes, including stellar and galactic dynamos and
+astrophysical turbulence. To account for solar flares, solar cycles and the
+structure of the galactic magnetic field reconnection must be fast, propagating
+with a speed close to the Alfven speed. We show that the presence of a random
+magnetic field component substantially enhances the reconnection rate and
+enables fast reconnection, i.e. reconnection that does not depend on fluid
+resistivity. The enhancement of the reconnection rate is achieved via a
+combination of two effects. First of all, only small segments of magnetic field
+lines are subject to direct Ohmic annihilation. Thus the fraction of magnetic
+energy that goes directly into fluid heating goes to zero as fluid resistivity
+vanishes. However, the most important enhancement comes from the fact that
+unlike the laminar fluid case where reconnection is constrained to proceed line
+by line, the presence of turbulence enables many magnetic field lines to enter
+the reconnection zone simultaneously. A significant fraction of magnetic energy
+goes into MHD turbulence and this enhances reconnection rates through an
+increase in the field stochasticity. In this way magnetic reconnection becomes
+fast when field stochasticity is accounted for. As a consequence solar and
+galactic dynamos are also fast, i.e. do not depend on fluid resistivity.",0002067v1
+2002-01-07,Magnetic fields and radio polarization of barred galaxies - 3D dynamo simulations,"A three-dimensional (3D) MHD model is applied to simulate the evolution of a
+large-scale magnetic field in a barred galaxy possessing a gaseous halo
+extending to about 2.8 kpc above the galactic plane. As the model input we use
+a time-dependent velocity field of molecular gas resulting from self-consistent
+3D N-body simulations of a galactic disk. We assume that the gaseous halo
+rotates differentially co-rotating with the disk or decreasing its velocity in
+the Z direction. The dynamo process included in the model yields the
+amplification of the magnetic field as well as the formation of field
+structures high above the galactic disk. The simulated magnetic fields are used
+to construct the models of a high-frequency (Faraday rotation-free) polarized
+radio emission that accounts for effects of projection and limited resolution,
+and is thus suitable for direct comparison with observations. We found that the
+resultant magnetic field correctly reproduces the observed structures of
+polarization B-vectors, forming coherent patterns well aligned with spiral arms
+and with the bar. The process initializing a wave-like behavior of the magnetic
+field, which efficiently forms magnetic maxima between the spiral arms, is
+demonstrated. The inclusion of the galactic halo constitutes a step towards a
+realistic model of galactic magnetic fields that includes as many dynamical
+components as needed for a realistic description.",0201083v2
+2003-06-23,High resolution simulations of nonhelical MHD turbulence,"According to the kinematic theory of nonhelical dynamo action the magnetic
+energy spectrum increases with wavenumber and peaks at the resistive cutoff
+wavenumber. It has previously been argued that even in the dynamical case the
+magnetic energy peaks at the resistive scale. Using high resolution simulations
+(up to 1024^3 meshpoints) with no large scale imposed field we show that the
+magnetic energy peaks at a wavenumber that is independent of the magnetic
+Reynolds number and about 5 times larger than the forcing wavenumber.
+Throughout the inertial range the spectral magnetic energy exceeds the kinetic
+energy by a factor of 2 to 3. Both spectra are approximately parallel. The
+total energy spectrum seems to be close to k^{-3/2}, but there is a strong
+bottleneck effect and it is suggested that the asymptotic spectrum is instead
+k^{-5/3}. This is supported by the value of the second order structure function
+exponent that is found to be zeta_2=0.70, suggesting a k^{-1.70} spectrum. The
+third order structure function scaling exponent is very close to unity, in
+agreement with Goldreich-Sridhar theory.
+  Adding an imposed field tends to suppress the small scale magnetic field. We
+find that at large scales the magnetic power spectrum follows then a k^{-1}
+slope. When the strength of the imposed field is of the same order as the
+dynamo generated field, we find almost equipartition between the magnetic and
+kinetic power spectra.",0306453v1
+2003-10-07,The Effects of Magnetic Fields on Line-Driven Hot-Star Winds,"This talk summarizes results from recent MHD simulations of the role of a
+dipole magnetic field in inducing large-scale structure in the line-driven
+stellar winds of hot, luminous stars. Unlike previous fixed-field analyses, the
+MHD simulations here take full account of the dynamical competition between the
+field and the flow. A key result is that the overall degree to which the wind
+is influenced by the field depends largely on a single, dimensionless `wind
+magnetic confinement parameter', $\eta_\ast (= B_{eq}^2 R_{\ast}^2/\dot{M}
+v_\infty$), which characterizes the ratio between magnetic field energy density
+and kinetic energy density of the wind. For weak confinement, $\eta_\ast \le
+1$, the field is fully opened by wind outflow, but nonetheless, for confinement
+as small as $\eta_\ast=1/10$ it can have significant back-influence in
+enhancing the density and reducing the flow speed near the magnetic equator.
+For stronger confinement, $\eta_\ast > 1$, the magnetic field remains closed
+over limited range of latitude and height above the equatorial surface, but
+eventually is opened into nearly radial configuration at large radii. Within
+the closed loops, the flow is channeled toward loop tops into shock collisions
+that are strong enough to produce hard X-rays. Within the open field region,
+the equatorial channeling leads to oblique shocks that are again strong enough
+to produce X-rays and also lead to a thin, dense, slowly outflowing ``disk'' at
+the magnetic equator.",0310180v1
+2003-10-10,Magnetic Braking and Viscous Damping of Differential Rotation in Cylindrical Stars,"Differential rotation in stars generates toroidal magnetic fields whenever an
+initial seed poloidal field is present. The resulting magnetic stresses, along
+with viscosity, drive the star toward uniform rotation. This magnetic braking
+has important dynamical consequences in many astrophysical contexts. For
+example, merging binary neutron stars can form ""hypermassive"" remnants
+supported against collapse by differential rotation. The removal of this
+support by magnetic braking induces radial fluid motion, which can lead to
+delayed collapse of the remnant to a black hole. We explore the effects of
+magnetic braking and viscosity on the structure of a differentially rotating,
+compressible star, generalizing our earlier calculations for incompressible
+configurations. The star is idealized as a differentially rotating, infinite
+cylinder supported initially by a polytropic equation of state. The gas is
+assumed to be infinitely conducting and our calculations are performed in
+Newtonian gravitation. Though highly idealized, our model allows for the
+incorporation of magnetic fields, viscosity, compressibility, and shocks with
+minimal computational resources in a 1+1 dimensional Lagrangian MHD code. Our
+evolution calculations show that magnetic braking can lead to significant
+structural changes in a star, including quasistatic contraction of the core and
+ejection of matter in the outermost regions to form a wind or an ambient disk.
+These calculations serve as a prelude and a guide to more realistic MHD
+simulations in full 3+1 general relativity.",0310304v1
+2004-02-24,Distribution of Faraday Rotation Measure in Jets from Active Galactic Nuclei II. Prediction from our Sweeping Magnetic Twist Model for the Wiggled Parts of AGN Jets and Tails,"Distributions of Faraday rotation measure (FRM) and the projected magnetic
+field derived by a 3-dimensional simulation of MHD jets are investigated based
+on our ""sweeping magnetic twist model"". FRM and Stokes parameters were
+calculated to be compared with radio observations of large scale wiggled AGN
+jets on kpc scales. We propose that the FRM distribution can be used to discuss
+the 3-dimensional structure of magnetic field around jets and the validity of
+existing theoretical models, together with the projected magnetic field derived
+from Stokes parameters. In the previous paper, we investigated the basic
+straight part of AGN jets by using the result of a 2-dimensional axisymmetric
+simulation. The derived FRM distribution has a general tendency to have a
+gradient across the jet axis, which is due to the toroidal component of the
+magnetic field generated by the rotation of the accretion disk. In this paper,
+we consider the wiggled structure of the AGN jets by using the result of a
+3-dimensional simulation. Our numerical results show that the distributions of
+FRM and the projected magnetic field have a clear correlation with the large
+scale structure of the jet itself, namely, 3-dimensional helix. Distributions,
+seeing the jet from a certain direction, show a good matching with those in a
+part of 3C449 jet. This suggests that the jet has a helical structure and that
+the magnetic field (especially the toroidal component) plays an important role
+in the dynamics of the wiggle formation because it is due to a current-driven
+helical kink instability in our model.",0402545v1
+2004-08-10,Alignment of Dust in Molecular Clouds,"Polarimetry is one of the most informative techniques of studying magnetic
+fields in molecular clouds. How reliable the interpretation of the polarization
+maps in terms of magnetic fields is the issue that the grain alignment theory
+addresses.
+  We show that grain alignment involves several processes acting
+simultaneously, but on different time-scales. We explain that rotating dust
+grains get substantial magnetic moment that allows them precess fast about
+magnetic field lines. As the result, grains preserve their orientation to
+magnetic field when the magnetic field direction fluctuates. We point out to
+the importance of internal alignment, i.e. the process forces grain axes to be
+aligned in respect to the grain angular momentum. We show that subtle quantum
+effects, in particular relaxation related to nuclear magnetic moments of atoms
+composing the grain, brings to live complex grain motions, e.g. flips. These
+flips substantially alter the dynamics of grain and limit the applicability of
+earlier theories that did not account for them. We also briefly review basic
+physical processes involved in the alignment of grain angular momentum in
+respect to interstellar magnetic field. We claim that the bulk of existing
+observational data is consistent with the radiative torque alignment mechanism.
+In particular, we show that large grains that are known to exist in the cores
+of molecular clouds may be aligned by the attenuated external interstellar
+radiation field.",0408174v1
+2006-01-26,The magnetic field and confined wind of the O star $θ^1$~Orionis~C,"In this paper we confirm the presence of a globally-ordered, kG-strength
+magnetic field in the photosphere of the young O star $\theta^1$~Orionis~C, and
+examine the properties of its optical line profile variations. A new series of
+high-resolution MuSiCoS Stokes $V$ and $I$ spectra has been acquired which
+samples approximately uniformly the rotational cycle of $\theta^1$~Orionis~C.
+Using the Least-Squares Deconvolution (LSD) multiline technique, we have
+succeeded in detecting variable Stokes $V$ Zeeman signatures associated with
+the LSD mean line profile. These signatures have been modeled to determine the
+magnetic field geometry. We have furthermore examined the profi le variations
+of lines formed in both the wind and photosphere using dynamic spectra. Based
+on spectrum synthesis fitting of the LSD profiles, we determine that the polar
+strength of the magnetic dipole component is $1150 \la B_{\rm d}\la 1800$~G and
+that the magnetic obliquity is $27\degr \la \beta \la 68\degr$, assuming
+$i=45\pm 20\degr$. The best-fit values for $i=45\degr$ are $B_{\rm d} = 1300
+\pm 150 (1\sigma)$~G and $\beta = 50\degr \pm 6\degr (1\sigma)$. Our data
+confirm the previous detection of a magnetic field in this star, and
+furthermore demonstrate the sinusoidal variability of the longitudinal field
+and accurately determine the phases and intensities of the magnetic extrema.
+The analysis of ``photospheric'' and ``wind'' line profile variations supports
+previous reports of the optical spectroscopic characteristics, and provides
+evidence for infall of material within the magnetic equatorial plane.",0601623v1
+2007-02-21,Polarimetry toward the IRAS Vela Shell. II. Extinction and Magnetic Fields,"We explore correlations between visual extinction and polarization along the
+western side of the IRAS Vela Shell using a published polarimetric catalog of
+several hundreds of objects. Our extinction maps along this ionization front
+(I-front) find evidence of clumpy structure with typical masses between 1.5 and
+6 solar masses and a mean length scale L ~ 0.47pc. The polarimetric data
+allowed us to investigate the distribution of the local magnetic field in small
+(~pc) scales across the I-front. Using the dispersion of polarization position
+angles, we find variations in the kinetic-to-magnetic energy density ratio of,
+at least, one order of magnitude along the I-front, with the magnetic pressure
+generally dominating over the turbulent motions. These findings suggest that
+the magnetic component has a significant contribution to the dynamical balance
+of this region. Along the I-front, the mean magnetic field projected on the sky
+is [0.018 +/- 0.013]mG. The polarization efficiency seems to change along the
+I-front. We attribute high polarization efficiencies in regions of relatively
+low extinction to an optimum degree of grain alignment. Analysis of the
+mass-to-magnetic flux ratio shows that this quantity is consistent with the
+subcritical regime (lambda < 1), showing that magnetic support is indeed
+important in the region. Our data extend the overall lambda-N(H2) relation
+toward lower density values and show that such trend continues smoothly toward
+low N(H2) values. This provides general support for the evolution of initially
+subcritical clouds to an eventual supercritical stage.",0702550v1
+2005-11-16,"Dynamic relaxation of magnetic clusters in a ferromagnetic (Ga,Mn)As epilayer","A new scenario of the mechanism of intriguing ferromagnetic properties in
+Mn-doped magnetic semiconductor (Ga,Mn)As is examined in detail. We find that
+magnetic features seen in zero-field cooled and field cooled magnetizations are
+not interpreted with a single domain model [Phys. Rev. Lett. 95, 217204
+(2005)], and the magnetic relaxation, which is similar to that seen in magnetic
+particles and granular systems, is becoming significant at temperatures above
+the lower-temperature peak in the temperature dependence of ac susceptibility,
+supporting the cluster/matrix model reported in our previous work [Phys. Rev.
+Lett. 94, 147203 (2005)]. Cole-Cole analysis reveals that magnetic interactions
+between such (Ga,Mn)As clusters are significant at temperatures below the
+higher-temperature peak in the temperature dependent ac susceptibility. The
+magnetizations of these films disappear above the temperature showing the
+higher-temperature peak, which is generally referred to as the Curie
+temperature. However, we suggest that these combined results are evidence that
+the temperature is actually the blocking temperature of (Ga,Mn)As clusters with
+a relatively high hole concentration compared to the (Ga,Mn)As matrix.",0511392v2
+2007-04-25,Orbital magnetization and its effects in spin-chiral ferromagnetic Kagome lattice,"Recently, Berry phase in the semiclassical dynamical of Bloch electrons has
+been found to make a correction to the phase-space density of states and a
+general multi-band formula for finite-temperature orbital magnetization has
+been given [Phys. Rev. Lett. \textbf{97}, 026603 (2006)], where the orbital
+magnetization $\mathcal{M}$ consists of two parts, i.e., the conventional part
+$M_{c}$ and the Berry-phase correction part $M_{\Omega}$. Using this general
+formula, we theoretically investigate the orbital magnetization and its effects
+on thermoelectric transport and magnetic susceptibility properties of the
+two-dimensional \textit{kagom\'{e}} lattice with spin anisotropies included.
+The study in this paper is highly interesting by the occurrence of nonzero
+Chern number in the lattice. The spin chirality parameter $\phi$ (see text)
+results in profound effects on the orbital magnetization properties. It is
+found that the two parts in orbital magnetization opposite each other. In
+particular, we show that $M_{c}$ and $M_{\Omega}$ yield the paramagnetic and
+diamagnetic responses, respectively. It is further shown that the orbital
+magnetization displays fully different behavior in the metallic and insulating
+regions, which is due to the different roles $M_{c}$ and $M_{\Omega}$ play in
+these two regions. The anomalous Nernst conductivity is also calculated, which
+displays a peak-valley structure as a function of the electron Fermi energy.",0704.3305v1
+2007-05-13,Recent progresses in the simulation of small-scale magnetic fields,"New high-resolution observations reveal that small-scale magnetic flux
+concentrations have a delicate substructure on a spatial scale of 0.1''. Its
+basic structure can be interpreted in terms of a magnetic flux sheet or tube
+that vertically extends through the ambient weak-field or field-free atmosphere
+with which it is in mechanical equilibrium. A more refined interpretation comes
+from new three-dimensional magnetohydrodynamic simulations that are capable of
+reproducing the corrugated shape of magnetic flux concentrations and their
+signature in the visible continuum. Furthermore it is shown that the
+characteristic asymmetric shape of the contrast profile of facular granules is
+an effect of radiative transfer across the rarefied atmosphere of the magnetic
+flux concentration. I also discuss three-dimensional radiation
+magnetohydrodynamic simulations of the integral layers from the top of the
+convection zone to the mid-chromosphere. They show a highly dynamic
+chromospheric magnetic field, marked by rapidly moving filaments of stronger
+than average magnetic field that form in the compression zone downstream and
+along propagating shock fronts. The simulations confirm the picture of flux
+concentrations that strongly expand through the photosphere into a more
+homogeneous, space filling chromospheric field. Future directions in the
+simulation of small-scale magnetic fields are indicated by a few examples of
+very recent work.",0705.1848v1
+2008-01-09,Fluctuation-dissipation relations in critical coarsening: crossover from unmagnetized to magnetized initial states,"We study the non-equilibrium dynamics of the spherical ferromagnet quenched
+to its critical temperature, as a function of the magnetization of the initial
+state. The two limits of unmagnetized and fully magnetized initial conditions
+can be understood as corresponding to times that are respectively much shorter
+and much longer than a magnetization timescale, as in a recent field
+theoretical analysis of the $n$-vector model. We calculate exactly the
+crossover functions interpolating between these two limits, for the
+magnetization correlator and response and the resulting fluctuation-dissipation
+ratio (FDR). For $d>4$ our results match those obtained recently from a
+Gaussian field theory. For $d<4$, non-Gaussian fuctuations arising from the
+spherical constraint need to be accounted for. We extend our framework from the
+fully magnetized case to achieve this, providing an exact solution for the
+relevant integral kernel. The resulting crossover behaviour is very rich, with
+the asymptotic FDR $X^\infty$ depending non-monotonically on the scaled age of
+the system. This is traced back to non-monotonicities of the two-time
+correlator, themselves the consequence of large magnetization fluctuations on
+the crossover timescale. We correct a trivial error in our earlier calculation
+for fully magnetized initial states; the corrected FDR is {\em consistent} with
+renormalization group expansions to first order in $4-d$ for the longitudinal
+fluctuations of the O(n) model in the limit $n\to\infty$.",0801.1381v1
+2008-01-29,"Viscous, Resistive Magnetorotational Modes","We carry out a comprehensive analysis of the behavior of the
+magnetorotational instability (MRI) in viscous, resistive plasmas. We find
+exact, non-linear solutions of the non-ideal magnetohydrodynamic (MHD)
+equations describing the local dynamics of an incompressible, differentially
+rotating background threaded by a vertical magnetic field when disturbances
+with wavenumbers perpendicular to the shear are considered. We provide a
+geometrical description of these viscous, resistive MRI modes and show how
+their physical structure is modified as a function of the Reynolds and magnetic
+Reynolds numbers. We demonstrate that when finite dissipative effects are
+considered, velocity and magnetic field disturbances are no longer orthogonal
+(as it is the case in the ideal MHD limit) unless the magnetic Prandtl number
+is unity. We generalize previous results found in the ideal limit and show that
+a series of key properties of the mean Reynolds and Maxwell stresses also hold
+for the viscous, resistive MRI. In particular, we show that the Reynolds stress
+is always positive and the Maxwell stress is always negative. Therefore, even
+in the presence of viscosity and resistivity, the total mean angular momentum
+transport is always directed outwards. We also find that, for any combination
+of the Reynolds and magnetic Reynolds numbers, magnetic disturbances dominate
+both the energetics and the transport of angular momentum and that the total
+mean energy density is an upper bound for the total mean stress responsible for
+angular momentum transport. The ratios between the Maxwell and Reynolds
+stresses and between magnetic and kinetic energy densities increase with
+decreasing Reynolds numbers for any magnetic Reynolds number; the lowest limit
+of both ratios is reached in the ideal MHD regime.",0801.4570v1
+2008-01-31,"Glassy behavior in the ferromagnetic and the non-magnetic insulating states of the rare earth manganates, Ln0.7Ba0.3MnO3 (Ln = Nd or Gd)","While La0.7Ba0.3MnO3 is a ferromagnetic metal (TC = 340 K) with longrange
+ordering, Nd0.7Ba0.3MnO3 shows a transition around 150 K with a small increase
+in magnetization, but remains an insulator at all temperatures. Gd0.7Ba0.3MnO3
+is non-magnetic and insulating at all temperatures. Low field dc magnetization
+and ac susceptibility measurements reveal the presence of a transition at
+around 150 K in Nd0.7Ba0.3MnO3, and a complex behavior with different
+ordering/freezing transitions at 62, 46 and 36 K in the case of Gd0.7Ba0.3MnO3,
+the last one being more prominent. The nature of the field dependence of the
+magnetization, combined with the slow magnetic relaxation, ageing and memory
+effects, suggests that Nd0.7Ba0.3MnO3 is a cluster glass below 150 K, a
+situation similar to that found for La_{1-x}SrxCoO3. Gd0.7Ba0.3MnO3, however,
+shows non-equilibrium dynamics characteristic of spin glasses, below 36 K. The
+difference in nature of the glassy behavior between Gd0.7Ba0.3MnO3 and
+Nd0.7Ba0.3MnO3 probably arises because of the larger disorder arising from the
+mismatch between the sizes of the A-site cations in the former. Our results on
+Nd0.7Ba0.3MnO3 and Gd0.7Ba0.3MnO3 suggest that the magnetic insulating states
+often reported for rare earth manganates of the type Ln1-xAxMnO3 (Ln = rare
+earth, A = alkaline earth) are likely to be associated with glassy magnetic
+behavior.",0802.0018v1
+2008-06-13,Testing magnetically confined wind shock models for Beta Cep using XMM-Newton and Chandra phase-resolved X-ray observations,"(abridged) We have performed a set of phase-resolved X-ray observations of
+the magnetic B star Beta Cep, for which theoretical models predict the presence
+of a confined wind emitting X-rays from stationary shocks.
+  We obtained four observations spaced in rotational phase with XMM-Newton and
+with Chandra. A detailed analysis of the data was performed to derive both
+photometric and spectral parameters from the EPIC data, searching for
+rotational modulation, and to derive the location of the X-ray plasma from the
+line ratios in the He-like triplets of N, O and Ne from the RGS data. The LETG
+data were used to constrain the presence of bulk motions in the plasma.
+  The strong rotational modulation predicted by the early, static magnetically
+confined wind model for the X-ray emission is not observed in Beta Cep. The
+small modulation present goes in the opposite direction, pointing to the
+absence of any optically thick disk of neutral material, and showing a
+modulation consistent with the later, dynamic models of magnetically confined
+wind models in B stars. The lack of observed bulk motion points to the plasma
+being confined by a magnetic field, but the low plasma temperature and lack of
+any flaring show that the plasma is not heated by magnetic reconnection.
+Therefore, the observations point to X-ray emission from shocks in a
+magnetically confined wind, with no evidence of an optically thick, dense disk
+at the magnetic equator",0806.2275v1
+2008-10-16,Deceleration of arbitrarily magnetized GRB ejecta: the complete evolution,"(Abridged) We aim to quantitatively understand the dynamical effect and
+observational signatures of magnetization of the GRB ejecta on the onset of the
+afterglow. We perform ultrahigh-resolution one-dimensional relativistic MHD
+simulations of the interaction of a radially expanding, magnetized ejecta with
+the interstellar medium. The need of ultrahigh numerical resolution derives
+from the extreme jump conditions in the region of interaction between the
+ejecta and the circumburst medium. We study the evolution of an
+ultrarelativistic shell all the way to a the self-similar asymptotic phase. Our
+simulations show that the complete evolution can be characterized in terms of
+two parameters, namely, the \xi parameter introduced by Sari & Piran (1995) and
+the magnetization \sigma_0. We exploit this property by producing numerical
+models where the shell Lorentz factor is \gamma_0 ~ tens and rescaling the
+results to arbitrarily large \gamma_0. We find that the reverse shock is
+typically very weak or absent for ejecta characterized by \sigma_0 >~ 1. The
+onset of the forward shock emission is strongly affected by the magnetization.
+On the other hand, the magnetic energy of the shell is transfered to the
+external medium on a short timescale (~several times the duration of the
+burst). The later forward shock emission does not contain information for the
+initial magnetization of the flow. The asymptotic evolution of strongly
+magnetized shells, after they have suffred a substantial deceleration,
+resembles that of hydrodynamic shells, i.e., they fully enter in the
+Blandford-McKee self-similar regime.",0810.2961v2
+2008-11-14,An 84 microGauss Magnetic Field in a Galaxy at Redshift z=0.692,"The magnetic field pervading our Galaxy is a crucial constituent of the
+interstellar medium: it mediates the dynamics of interstellar clouds, the
+energy density of cosmic rays, and the formation of stars. The field associated
+with ionized interstellar gas has been determined through observations of
+pulsars in our Galaxy. Radio-frequency measurements of pulse dispersion and the
+rotation of the plane of linear polarization, i.e., Faraday rotation, yield an
+average value B ~ 3 microGauss. The possible detection of Faraday rotation of
+linearly polarized photons emitted by high-redshift quasars suggests similar
+magnetic fields are present in foreground galaxies with redshifts z > 1. As
+Faraday rotation alone, however, determines neither the magnitude nor the
+redshift of the magnetic field, the strength of galactic magnetic fields at
+redshifts z > 0 remains uncertain. Here we report a measurement of a magnetic
+field of B ~ 84 microGauss in a galaxy at z =0.692, using the same
+Zeeman-splitting technique that revealed an average value of B = 6 microGauss
+in the neutral interstellar gas of our Galaxy. This is unexpected, as the
+leading theory of magnetic field generation, the mean-field dynamo model,
+predicts large-scale magnetic fields to be weaker in the past rather than
+stronger.",0811.2408v1
+2008-12-03,Growth of Magnetic Fields Induced by Turbulent Motions,"We present numerical simulations of driven magnetohydrodynamic (MHD)
+turbulence with weak/moderate imposed magnetic fields. The main goal is to
+clarify dynamics of magnetic field growth. We also investigate the effects of
+the imposed magnetic fields on the MHD turbulence, including, as a limit, the
+case of zero external field. Our findings are as follows. First, when we start
+off simulations with weak mean magnetic field only (or with small scale random
+field with zero imposed field), we observe that there is a stage at which
+magnetic energy density grows linearly with time. Runs with different numerical
+resolutions and/or different simulation parameters show consistent results for
+the growth rate at the linear stage. Second, we find that, when the strength of
+the external field increases, the equilibrium kinetic energy density drops by
+roughly the product of the rms velocity and the strength of the external field.
+The equilibrium magnetic energy density rises by roughly the same amount.
+Third, when the external magnetic field is not very strong (say, less than ~0.2
+times the rms velocity when measured in the units of Alfven speed), the
+turbulence at large scales remains statistically isotropic, i.e. there is no
+apparent global anisotropy of order B_0/v. We discuss implications of our
+results on astrophysical fluids.",0812.0817v1
+2009-01-06,On the analogy between streamlined magnetic and solid obstacles,"Analogies are elaborated in the qualitative description of two systems: the
+magnetohydrodynamic (MHD) flow moving through a region where an external local
+magnetic field (magnetic obstacle) is applied, and the ordinary hydrodynamic
+flow around a solid obstacle. The former problem is of interest both
+practically and theoretically, and the latter one is a classical problem being
+well understood in ordinary hydrodynamics. The first analogy is the formation
+in the MHD flow of an impenetrable region -- core of the magnetic obstacle --
+as the interaction parameter $N$, i.e. strength of the applied magnetic field,
+increases significantly. The core of the magnetic obstacle is streamlined both
+by the upstream flow and by the induced cross stream electric currents, like a
+foreign insulated insertion placed inside the ordinary hydrodynamic flow. In
+the core, closed streamlines of the mass flow resemble contour lines of
+electric potential, while closed streamlines of the electric current resemble
+contour lines of pressure. The second analogy is the breaking away of attached
+vortices from the recirculation pattern produced by the magnetic obstacle when
+the Reynolds number $Re$, i.e. velocity of the upstream flow, is larger than a
+critical value. This breaking away of vortices from the magnetic obstacle is
+similar to that occurring past a real solid obstacle. Depending on the inlet
+and/or initial conditions, the observed vortex shedding can be either symmetric
+or asymmetric.",0901.0685v3
+2009-01-28,Spin canting in a Dy-based Single-Chain Magnet with dominant next-nearest neighbor antiferromagnetic interactions,"We investigate theoretically and experimentally the static magnetic
+properties of single crystals of the molecular-based Single-Chain Magnet (SCM)
+of formula [Dy(hfac)$_{3}$NIT(C$_{6}$H$_{4}$OPh)]$_{\infty}$ comprising
+alternating Dy$^{3+}$ and organic radicals. A peculiar inversion between maxima
+and minima in the angular dependence of the magnetic molar susceptibility
+$\chi_{M}$ occurs on increasing temperature. Using information regarding the
+monomeric building block as well as an {\it ab initio} estimation of the
+magnetic anisotropy of the Dy$^{3+}$ ion, this anisotropy-inversion phenomenon
+can be assigned to weak one-dimensional ferromagnetism along the chain axis.
+This indicates that antiferromagnetic next-nearest-neighbor interactions
+between Dy$^{3+}$ ions dominate, despite the large Dy-Dy separation, over the
+nearest-neighbor interactions between the radicals and the Dy$^{3+}$ ions.
+Measurements of the field dependence of the magnetization, both along and
+perpendicularly to the chain, and of the angular dependence of $\chi_{M}$ in a
+strong magnetic field confirm such an interpretation. Transfer matrix
+simulations of the experimental measurements are performed using a classical
+one-dimensional spin model with antiferromagnetic Heisenberg exchange
+interaction and non-collinear uniaxial single-ion anisotropies favoring a
+canted antiferromagnetic spin arrangement, with a net magnetic moment along the
+chain axis. The fine agreement obtained with experimental data provides
+estimates of the Hamiltonian parameters, essential for further study of the
+dynamics of rare-earths based molecular chains.",0901.4409v1
+2009-09-27,Space-time symmetry violation of the fields in quasi-2D ferrite particles with magnetic-dipolar-mode oscillations,"In magnetic systems with reduced dimensionality, the effects of dipolar
+interactions allow the existence of long-range ordered phases. Long-range
+magnetic-dipolar interactions are at the heart of the explanation of many
+peculiar phenomena observed in nuclear magnetic resonance, ferromagnetic
+resonance, and Bose-Einstein-condensate structures. In this paper we show that
+magnetic-dipolar-modes (MDMs) in quasi-2D ferrite disks are characterized by
+symmetry breaking effects. Our analysis is based on postulates about a physical
+meaning of the magnetostatic-potential function as a complex scalar wave
+function, which presumes the long-range phase correlations. An important
+feature of the MDM oscillations in a ferrite disk concerns the fact that a
+structure with symmetric parameters and symmetric basic equations goes into
+eigenstates that are not space-time symmetric. The proper solutions are found
+based on an analysis of magnetostatic-wave propagation in a helical coordinate
+system. For a ferrite disk, we show that while a composition of two helical
+waves may acquire a geometrical phase over-running of during a period, every
+separate helical wave has a dynamical phase over-running of and so behaves as a
+double-valued function. We demonstrate that unique topological structures of
+the fields in a ferrite disk are intimately related to the symmetry breaking
+properties of MDM oscillations. The solutions give the MDM power-flow-density
+vortices with cores at the disk center and azimuthally running waves of
+magnetization. One can expect that the proposed models of long-range ordered
+phases and space-time violation properties of magnetic-dipolar interactions can
+be used in other magnetic structures, different from the
+ferromagnetic-resonance system with reduced dimensionality.",0909.4920v1
+2010-04-08,CMB temperature anisotropy at large scales induced by a causal primordial magnetic field,"We present an analytical derivation of the Sachs Wolfe effect sourced by a
+primordial magnetic field. In order to consistently specify the initial
+conditions, we assume that the magnetic field is generated by a causal process,
+namely a first order phase transition in the early universe. As for the
+topological defects case, we apply the general relativistic junction conditions
+to match the perturbation variables before and after the phase transition which
+generates the magnetic field, in such a way that the total energy momentum
+tensor is conserved across the transition and Einstein's equations are
+satisfied. We further solve the evolution equations for the metric and fluid
+perturbations at large scales analytically including neutrinos, and derive the
+magnetic Sachs Wolfe effect. We find that the relevant contribution to the
+magnetic Sachs Wolfe effect comes from the metric perturbations at
+next-to-leading order in the large scale limit. The leading order term is in
+fact strongly suppressed due to the presence of free-streaming neutrinos. We
+derive the neutrino compensation effect dynamically and confirm that the
+magnetic Sachs Wolfe spectrum from a causal magnetic field behaves as
+l(l+1)C_l^B \propto l^2 as found in the latest numerical analyses.",1004.1405v2
+2010-06-18,Probing the magnetic state by linear and non linear ac magnetic susceptibility measurements in under doped manganite Nd0.8Sr0.2MnO3,"We have thoroughly investigated the entire magnetic states of under doped
+ferromagnetic insulating manganite Nd0.8Sr0.2MnO3 through temperature dependent
+linear and non linear complex ac magnetic susceptibility measurements. This
+ferromagnetic insulating manganite is found to have frequency independent
+ferromagnetic to paramagnetic transition temperature at around 140 K. At around
+90 K (\approx T_f) the sample shows a second frequency dependent re - entrant
+magnetic transition as explored through complex ac susceptibility measurements.
+Non linear ac susceptibility measurements (higher harmonics of ac
+susceptibility) have also been performed (with and without the superposition of
+a dc magnetic field) to further investigate the origin of this frequency
+dependence (dynamic behavior at this re-entrant magnetic transition).
+Divergence of 3rd order susceptibility in the limit of zero exciting field
+indicates a spin glass like freezing phenomena. However, large value of spin
+relaxation time (?0= 10-8 s) and small value of coercivity (~22 Oe) obtained at
+low temperature (below T_f) from critical slowing down model and dc magnetic
+measurements, respectively, are in contrast with what generally observed in a
+canonical spin glass (?0 = 10-12 - 10-14 s and very large value of coercivity
+below freezing temperature). We have attributed our observation to the
+formation of finite size ferromagnetic clusters which are formed as consequence
+of intrinsic separation and undergo cluster glass like freezing below certain
+temperature in this under doped manganite. The results are supported by the
+electronic - and magneto - transport data.",1006.3733v1
+2010-06-29,"Systematics of the magnetic-Prandtl-number dependence of homogeneous, isotropic magnetohydrodynamic turbulence","We present the results of our detailed pseudospectral direct numerical
+simulation (DNS) studies, with up to $1024^3$ collocation points, of
+incompressible, magnetohydrodynamic (MHD) turbulence in three dimensions,
+without a mean magnetic field. Our study concentrates on the dependence of
+various statistical properties of both decaying and statistically steady MHD
+turbulence on the magnetic Prandtl number ${\rm Pr_M}$ over a large range,
+namely, $0.01 \leq {\rm Pr_M} \leq 10$. We obtain data for a wide variety of
+statistical measures such as probability distribution functions (PDFs) of
+moduli of the vorticity and current density, the energy dissipation rates, and
+velocity and magnetic-field increments, energy and other spectra, velocity and
+magnetic-field structure functions, which we use to characterise intermittency,
+isosurfaces of quantities such as the moduli of the vorticity and current, and
+joint PDFs such as those of fluid and magnetic dissipation rates. Our
+systematic study uncovers interesting results that have not been noted
+hitherto. In particular, we find a crossover from larger intermittency in the
+magnetic field than in the velocity field, at large ${\rm Pr_M}$, to smaller
+intermittency in the magnetic field than in the velocity field, at low ${\rm
+Pr_M}$. Furthermore, a comparison of our results for decaying MHD turbulence
+and its forced, statistically steady analogue suggests that we have strong
+universality in the sense that, for a fixed value of ${\rm Pr_M}$, multiscaling
+exponent ratios agree, at least within our errorbars, for both decaying and
+statistically steady homogeneous, isotropic MHD turbulence.",1006.5585v1
+2011-04-22,Can nothing be a superconductor and a superfluid?,"A superconductor is a material that conducts electric current with no
+resistance. Superconductivity and magnetism are known to be antagonistic
+phenomena: superconductors expel weak external magnetic field (the Meissner
+effect) while a sufficiently strong magnetic field, in general, destroys
+superconductivity. In a seemingly contradictory statement, we show that a very
+strong magnetic field can turn an empty space into a superconductor. The
+external magnetic field required for this effect should be about 10^{16} Tesla
+(eB ~ 1 GeV^2). The physical mechanism of the exotic vacuum superconductivity
+is as follows: in strong magnetic field the dynamics of virtual quarks and
+antiquarks is effectively one-dimensional because these electrically charged
+particles tend to move along the lines of the magnetic field. In one spatial
+dimension a gluon-mediated attraction between a quark and an antiquark of
+different flavors inevitably leads to formation of a colorless spin-triplet
+bound state (a vector analogue of the Cooper pair) with quantum numbers of an
+electrically charged rho meson. Such quark-antiquark pairs condense to form an
+anisotropic inhomogeneous superconducting state similar to the Abrikosov vortex
+lattice in a type-II superconductor. The onset of the superconductivity of the
+charged rho mesons should also induce an inhomogeneous superfluidity of the
+neutral rho mesons. The vacuum superconductivity should survive at very high
+temperatures of typical Quantum Chromodynamics (QCD) scale of 10^{12} K (T ~
+100 MeV). We propose the phase diagram of QCD in the plane ""magnetic field -
+temperature"".",1104.4404v1
+2011-09-25,Study of the mixed state of La_{1.83}Sr_{0.17}CuO_{4} by means of muon-spin rotation and magnetization experiments in a low magnetic field,"Muon-spin rotation (muSR) experiments are often used to study the magnetic
+field distribution in type-II superconductors in the vortex state. Based on the
+determination of the magnetic penetration depth it is frequently
+speculated---also controversially---about the order-parameter symmetry of the
+studied superconductors. This article reports on a combined muSR and
+magnetization study of the mixed state in the cuprate high-temperature
+superconductor La_{1.83}Sr_{0.17}CuO_{4} in a low magnetic field of 20 mT
+applied along the c axis of a single crystal. The macroscopic magnetization
+measurements reveal substantial differences for various cooling procedures.
+Yet, indicated changes in the vortex dynamics between different temperature
+regions as well as the results of the microscopic muSR experiments are
+virtually independent of the employed cooling cycles. Additionally, it is found
+that the mean magnetic flux density, locally probed by the muons, strongly
+increases at low temperatures. This can possibly be explained by a non-random
+sampling of the spatial field distribution of the vortex lattice in this
+cuprate superconductor caused by intensified vortex pinning.",1109.5367v2
+2011-10-18,Lagrangian coherent structures in photospheric flows and their implications for coronal magnetic structure,"Aims. We show how the build-up of magnetic gradients in the Sun's corona may
+be inferred directly from photospheric velocity data. This enables computation
+of magnetic connectivity measures such as the squashing factor without recourse
+to magnetic field extrapolation.
+  Methods.Assuming an ideal evolution in the corona, and an initially uniform
+magnetic field, the subsequent field line mapping is computed by integrating
+trajectories of the (time-dependent) horizontal photospheric velocity field.
+The method is applied to a 12 hour high-resolution sequence of photospheric
+flows derived from Hinode/SOT magnetograms.
+  Results. We find the generation of a network of quasi-separatrix layers in
+the magnetic field, which correspond to Lagrangian coherent structures in the
+photospheric velocity. The visual pattern of these structures arises primarily
+from the diverging part of the photospheric flow, hiding the effect of the
+rotational flow component: this is demonstrated by a simple analytical model of
+photospheric convection. We separate the diverging and rotational components
+from the observed flow and show qualitative agreement with purely diverging and
+rotational models respectively. Increasing the flow speeds in the model
+suggests that our observational results are likely to give a lower bound for
+the rate at which magnetic gradients are built up by real photospheric flows.
+Finally, we construct a hypothetical magnetic field with the inferred topology,
+that can be used for future investigations of reconnection and energy release.",1110.3957v2
+2011-11-03,Scattering of Scalar Waves by Schwarzschild Black Hole Immersed in Magnetic Field,"The magnetic field is one of the most important constituents of the cosmic
+space and one of the main sources of the dynamics of interacting matter in the
+universe. The astronomical observations imply the existence of a strong
+magnetic fields of up to $10^4-10^8G$ near supermassive black holes in the
+active galactic nuclei and even around stellar mass black holes. In this paper,
+with the quantum scattering theory, we analysis the Schr\""{o}edinger-type
+scalar wave equation of black hole immersed in magnetic field and numerically
+investigate its absorption cross section and scattering cross section. We find
+that the absorption cross sections oscillate about the geometric optical value
+in the high frequency regime. Furthermore in low frequency regime, the magnetic
+field makes the absorption cross section weaker and this effect is more
+obviously on lower frequency brand. On the other hand, for the effects of
+scattering cross sections for the black hole immersed in magnetic field, we
+find that the magnetic field makes the scattering flux weaker and its width
+narrower in the forward direction. We find that there also exists the glory
+phenomenon along the backforward direction. At fixed frequency, the glory peak
+is higher and the glory width becomes narrower due to the black hole immersed
+in magnetic field.",1111.0825v1
+2011-12-16,Growth rate of small-scale dynamo at low magnetic Prandtl numbers,"In this study we discuss two key issues related to a small-scale dynamo
+instability at low magnetic Prandtl numbers and large magnetic Reynolds
+numbers, namely: (i) the scaling for the growth rate of small-scale dynamo
+instability in the vicinity of the dynamo threshold; (ii) the existence of the
+Golitsyn spectrum of magnetic fluctuations in small-scale dynamos. There are
+two different asymptotics for the small-scale dynamo growth rate: in the
+vicinity of the threshold of the excitation of the small-scale dynamo
+instability, $\lambda \propto \ln({\rm Rm}/ {\rm Rm}^{\rm cr})$, and when the
+magnetic Reynolds number is much larger than the threshold of the excitation of
+the small-scale dynamo instability, $\lambda \propto {\rm Rm}^{1/2}$, where
+${\rm Rm}^{\rm cr}$ is the small-scale dynamo instability threshold in the
+magnetic Reynolds number ${\rm Rm}$. We demonstrated that the existence of the
+Golitsyn spectrum of magnetic fluctuations requires a finite correlation time
+of the random velocity field. On the other hand, the influence of the Golitsyn
+spectrum on the small-scale dynamo instability is minor. This is the reason why
+it is so difficult to observe this spectrum in direct numerical simulations for
+the small-scale dynamo with low magnetic Prandtl numbers.",1112.3926v2
+2012-03-27,General Relativistic Simulations of Magnetized Plasmas around Merging Supermassive Black Holes,"Coalescing supermassive black hole binaries are produced by the mergers of
+galaxies and are the most powerful sources of gravitational waves accessible to
+space-based gravitational observatories. Some such mergers may occur in the
+presence of matter and magnetic fields and hence generate an electromagnetic
+counterpart. In this Letter, we present the first general relativistic
+simulations of magnetized plasma around merging supermassive black holes using
+the general relativistic magnetohydrodynamic code Whisky. By considering
+different magnetic field strengths, going from non-magnetically dominated to
+magnetically dominated regimes, we explore how magnetic fields affect the
+dynamics of the plasma and the possible emission of electromagnetic signals. In
+particular we observe a total amplification of the magnetic field of ~2 orders
+of magnitude which is driven by the accretion onto the binary and that leads to
+much stronger electromagnetic signals, more than a factor of 10^4 larger than
+comparable calculations done in the force-free regime where such amplifications
+are not possible.",1203.6108v2
+2012-05-29,Magnetic Interactions in Coalescing Neutron Star Binaries,"It is expected on both evolutionary and empirical grounds that many merging
+neutron star (NS) binaries are composed of a highly magnetized NS in orbit with
+a relatively low magnetic field NS. I study the magnetic interactions of these
+binaries using the framework of a unipolar inductor model. The e.m.f. generated
+across the non-magnetic NS as it moves through the magnetosphere sets up a
+circuit connecting the two stars. The exact features of this circuit depend on
+the uncertain resistance in the space between the stars R_space. Nevertheless,
+I show that there are interesting observational and/or dynamical effects
+irrespective of its exact value. When R_space is large, electric dissipation as
+great as ~10^{46} erg/s (for magnetar-strength fields) occurs in the
+magnetosphere, which would exhibit itself as a hard X-ray precursor in the
+seconds leading up to merger. With less certainty, there may also be an
+associated radio transient, but this would be observed well past merger (~hrs)
+because of interstellar dispersion. When R_space is small, electric dissipation
+largely occurs in the surface layers of the magnetic NS. This can reach
+~10^{49} erg/s during the final ~1 sec before merger, similar to the energetics
+and timescales of short gamma-ray bursts. In addition, for dipole fields
+greater than ~10^{12} G and a small R_space, magnetic torques spin up the
+magnetized NS. This drains angular momentum from the binary and accelerates the
+inspiral. A faster coalescence results in less orbits occurring before merger,
+which would impact matched-filtering gravitational-wave searches by
+ground-based laser interferometers and could create difficulties for studying
+alternative theories of gravity with compact inspirals.",1205.6482v1
+2012-06-18,Impact of Dynamic Orbital Correlations on Magnetic Excitations in the Normal State of Iron-Based Superconductors,"We show here that orbital degrees of freedom produce a distinct signature in
+the magnetic excitation spectrum of iron-based superconductors above the
+magnetic ordering temperature. Because $d_{xz}$ and $d_{yz}$ orbitals are
+strongly connected with the Fermi surface topology, the nature of magnetic
+excitations can be modified significantly due to the presence of either static
+or fluctuating orbital correlations. Within a five-orbital itinerant model, we
+show that static orbital order generally leads to an enhancement of
+commensurate magnetic excitations even when the original Fermi surface lacks
+nesting at $(\pi,0)$ or $(0,\pi)$. When long-range orbital order is absent,
+Gaussian fluctuations beyond the standard random-phase approximation (RPA)
+capture the effects of fluctuating orbital correlations on the magnetic
+excitations. We find that commensurate magnetic excitations can also be
+enhanced if the orbital correlations are strong. Our results offer a natural
+explanation for the incommensurate-to-commensurate transformation observed in a
+recent neutron scattering measurement (Z. Xu, et. al., arXiv:1201.4404), and we
+propose that this unusual transformation is an important signature to
+distinguish orbital from spin physics in the normal state of the pnictides.
+Implications for the magnetic and superconducting states are discussed.",1206.4095v2
+2012-06-29,Laser spectroscopy of finite size and covering effects in magnetite nanoparticles,"The experiments on the impact of the size of magnetite clusters on various
+magnetic properties (magnetic moment, Curie temperature, blocking temperature
+etc.) have been carried out. The methods of magnetic separation, centrifuging
+of water suspensions of biocompatible iron oxide nanoparticles (NPs) allow
+producing fractions with diameter of nanoparticles in the range of 4{\div}22
+nm. The size of NPs are controlled by the methods of dynamic light scattering
+(DLS), transmission electron microscopy (TEM) and atomic force microscopy
+(AFM). For the first time the DLS method is applied in real time to control the
+size during the process of the separation of the NPs in aqueous suspensions.
+The changes of the size of NPs cause a shift in the Curie temperature and in
+the changes in the specific magnetic properties of the iron NPs. The
+experimental data is interpreted on the basis of Monte Carlo simulations for
+the classical Heisenberg model with different bulk and surface magnetic
+moments. It is demonstrated experimentally and by theoretical modeling that
+magnetic properties of magnetite NPs are determined not only by their sizes,
+but also by the their surface spin states, while both growing and falling
+dependences of the magnetic moment (per Fe3O4 formula unit) being possible,
+depending on the number of magnetic atoms in the nanoparticle. Both NPs clean
+and covered with a bioresorbable layer clusters have been investigated.",1206.6985v5
+2012-09-02,Nanoscale magnetic imaging of a single electron spin under ambient conditions,"The detection of ensembles of spins under ambient conditions has
+revolutionized the biological, chemical, and physical sciences through magnetic
+resonance imaging and nuclear magnetic resonance. Pushing sensing capabilities
+to the individual-spin level would enable unprecedented applications such as
+single molecule structural imaging; however, the weak magnetic fields from
+single spins are undetectable by conventional far-field resonance techniques.
+In recent years, there has been a considerable effort to develop nanoscale
+scanning magnetometers, which are able to measure fewer spins by bringing the
+sensor in close proximity to its target. The most sensitive of these
+magnetometers generally require low temperatures for operation, but measuring
+under ambient conditions (standard temperature and pressure) is critical for
+many imaging applications, particularly in biological systems. Here we
+demonstrate detection and nanoscale imaging of the magnetic field from a single
+electron spin under ambient conditions using a scanning nitrogen-vacancy (NV)
+magnetometer. Real-space, quantitative magnetic-field images are obtained by
+deterministically scanning our NV magnetometer 50 nanometers above a target
+electron spin, while measuring the local magnetic field using dynamically
+decoupled magnetometry protocols. This single-spin detection capability could
+enable single-spin magnetic resonance imaging of electron spins on the nano-
+and atomic scales and opens the door for unique applications such as mechanical
+quantum state transfer.",1209.0203v1
+2012-10-01,Magnetic Field Structures Triggering Solar Flares and Coronal Mass Ejections,"Solar flares and coronal mass ejections (CMEs), the most catastrophic
+eruptions in our solar system, have been known to affect terrestrial
+environments and infrastructure. However, because their triggering mechanism is
+still not sufficiently understood, our capacity to predict the occurrence of
+solar eruptions and to forecast space weather is substantially hindered. Even
+though various models have been proposed to determine the onset of solar
+eruptions, the types of magnetic structures capable of triggering these
+eruptions are still unclear. In this study, we solved this problem by
+systematically surveying the nonlinear dynamics caused by a wide variety of
+magnetic structures in terms of three-dimensional magnetohydrodynamic
+simulations. As a result, we determined that two different types of small
+magnetic structures favor the onset of solar eruptions. These structures, which
+should appear near the magnetic polarity inversion line (PIL), include magnetic
+fluxes reversed to the potential component or the nonpotential component of
+major field on the PIL. In addition, we analyzed two large flares, the X-class
+flare on December 13, 2006 and the M-class flare on February 13, 2011, using
+imaging data provided by the Hinode satellite, and we demonstrated that they
+conform to the simulation predictions. These results suggest that forecasting
+of solar eruptions is possible with sophisticated observation of a solar
+magnetic field, although the lead time must be limited by the time scale of
+changes in the small magnetic structures.",1210.0598v1
+2012-10-08,Chiral Magnetic Effect in Hydrodynamic Approximation,"We review derivations of the chiral magnetic effect (ChME) in hydrodynamic
+approximation. The reader is assumed to be familiar with the basics of the
+effect. The main challenge now is to account for the strong interactions
+between the constituents of the fluid. The main result is that the ChME is not
+renormalized: in the hydrodynamic approximation it remains the same as for
+non-interacting chiral fermions moving in an external magnetic field. The key
+ingredients in the proof are general laws of thermodynamics and the
+Adler-Bardeen theorem for the chiral anomaly in external electromagnetic
+fields. The chiral magnetic effect in hydrodynamics represents a macroscopic
+manifestation of a quantum phenomenon (chiral anomaly). Moreover, one can argue
+that the current induced by the magnetic field is dissipation free and talk
+about a kind of ""chiral superconductivity"". More precise description is a
+ballistic transport along magnetic field taking place in equilibrium and in
+absence of a driving force. The basic limitation is exact chiral limit while
+the temperature--excitingly enough- does not seemingly matter. What is still
+lacking, is a detailed quantum microscopic picture for the ChME in
+hydrodynamics. Probably, the chiral currents propagate through
+lower-dimensional defects, like vortices in superfluid. In case of superfluid,
+the prediction for the chiral magnetic effect remains unmodified although the
+emerging dynamical picture differs from the standard one.",1210.2186v1
+2012-12-11,A mean field dynamo from negative eddy diffusivity,"Using direct numerical simulations, we verify that ""flow IV"" of Roberts
+(1972) exhibits dynamo action dominated by horizontally averaged large-scale
+magnetic field. With the test-field method we compute the turbulent magnetic
+diffusivity and find that it is negative and overcomes the molecular
+diffusivity, thus explaining quantitatively the large-scale dynamo for magnetic
+Reynolds numbers above $\approx8$. As expected for a dynamo of this type, but
+contrary to $\alpha$-effect dynamos, the two horizontal field components grow
+independently of each other and have arbitrary amplitude ratios and phase
+differences. Small length scales of the mean magnetic field are shown to be
+stabilized by the turbulent magnetic diffusivity becoming positive at larger
+wavenumbers. Oscillatory decaying or growing solutions have also been found in
+certain wavenumber intervals and sufficiently large values of the magnetic
+Reynolds number. For magnetic Reynolds numbers below $\approx0.5$ the turbulent
+magnetic diffusivity is confirmed to be positive, as expected for all
+incompressible flows. Earlier claims of a dynamo driven by a modified
+Taylor-Green flow through negative eddy diffusivity could not be confirmed.",1212.2626v3
+2014-03-04,Oscillations in solar Jets Observed with the SOT of Hinode: Viscous Effects during Reconnection,"Transverse oscillatory motions and recurrence behavior in the chromospheric
+jets observed by Hinode/SOT are studied. A comparison is considered with the
+behavior that was noticed in coronal X-ray jets observed by Hinode/XRT. A jet
+like bundle observed at the limb in Ca II H line appears to show a magnetic
+topology that is similar to X-ray jets (i.e., the Eiffel tower shape). The
+appearance of such magnetic topology is usually assumed to be caused by
+magnetic reconnection near a null point. Transverse motions of the jet axis are
+recorded but no clear evidence of twist is appearing from the highly processed
+movie. The aim is to investigate the dynamical behavior of an incompressible
+magnetic X-point occurring during the magnetic reconnection in the jet
+formation region. The viscous effect is specially considered in the closed
+line-tied magnetic X-shape nulls. We perform the MHD numerical simulation in
+2-D by solving the visco-resistive MHD equations with the tracing of velocity
+and magnetic field. A qualitative agreement with Hinode observations is found
+for the oscillatory and non-oscillatory behaviors of the observed solar jets in
+both the chromosphere and the corona. Our results suggest that the viscous
+effect contributes to the excitation of the magnetic reconnection by generating
+oscillations that we observed at least inside this Ca II H line cool solar jet
+bundle.",1403.0814v2
+2014-03-13,Ribbons characterize magnetohydrodynamic magnetic fields better than lines: a lesson from dynamo theory,"Blackman & Brandenburg argued that magnetic helicity conservation in dynamo
+theory can in principle be captured by diagrams of mean field dynamos when the
+magnetic fields are represented by ribbons or tubes, but not by lines. Here we
+present such a schematic ribbon diagram for the $\alpha^2$ dynamo that tracks
+magnetic helicity and provides distinct scales of large scale magnetic
+helicity, small scale magnetic helicity, and kinetic helicity involved in the
+process. This also motivates our construction of a new ""2.5 scale"" minimalist
+generalization of the helicity-evolving equations for the \alpha^2 dynamo that
+separately allows for these three distinct length scales while keeping only two
+dynamical equations. We solve these equations and, as in previous studies, find
+that the large scale field first grows at a rate independent of the magnetic
+Reynolds number R_M before quenching to an R_M dependent regime. But we also
+show that the larger the ratio of the wavenumber where the small scale current
+helicity resides to that of the forcing scale, the earlier the non-linear
+dynamo quenching occurs, and the weaker the large scale field is at the turnoff
+from linear growth. The harmony between the theory and the schematic diagram
+exemplifies a general lesson that magnetic fields in MHD are better visualized
+as two-dimensional ribbons (or pairs of lines) rather than single lines.",1403.3445v2
+2014-04-07,The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches,"A new data product from the Helioseismic and Magnetic Imager (HMI) onboard
+the Solar Dynamics Observatory (SDO) called Space-weather HMI Active Region
+Patches (SHARPs) is now available. SDO/HMI is the first space-based instrument
+to map the full-disk photospheric vector magnetic field with high cadence and
+continuity. The SHARP data series provide maps in patches that encompass
+automatically tracked magnetic concentrations for their entire lifetime; map
+quantities include the photospheric vector magnetic field and its uncertainty,
+along with Doppler velocity, continuum intensity, and line-of-sight magnetic
+field. Furthermore, keywords in the SHARP data series provide several
+parameters that concisely characterize the magnetic-field distribution and its
+deviation from a potential-field configuration. These indices may be useful for
+active-region event forecasting and for identifying regions of interest. The
+indices are calculated per patch and are available on a twelve-minute cadence.
+Quick-look data are available within approximately three hours of observation;
+definitive science products are produced approximately five weeks later. SHARP
+data are available at http://jsoc.stanford.edu and maps are available in either
+of two different coordinate systems. This article describes the SHARP data
+products and presents examples of SHARP data and parameters.",1404.1879v1
+2014-06-11,Dynamic behavior of magnetic avalanches in the spin-ice compound Dy$_2$Ti$_2$O$_7$,"Avalanches of the magnetization, that is to say an abrupt reversal of the
+magnetization at a given field, have been previously reported in the spin-ice
+compound Dy$_{2}$Ti$_{2}$O$_{7}$. This out-of-equilibrium process, induced by
+magneto-thermal heating, is quite usual in low temperature magnetization
+studies. A key point is to determine the physical origin of the avalanche
+process. In particular, in spin-ice compounds, the origin of the avalanches
+might be related to the monopole physics inherent to the system. We have
+performed a detailed study of the avalanche phenomena in three single crystals,
+with the field oriented along the [111] direction, perpendicular to [111] and
+along the [100] directions. We have measured the changing magnetization during
+the avalanches and conclude that avalanches in spin ice are quite slow compared
+to the avalanches reported in other systems such as molecular magnets. Our
+measurements show that the avalanches trigger after a delay of about 500 ms and
+that the reversal of the magnetization then occurs in a few hundreds of
+milliseconds. These features suggest an unusual propagation of the reversal,
+which might be due to the monopole motion. The avalanche fields seem to be
+reproducible in a given direction for different samples, but they strongly
+depend on the initial state of magnetization and on how the initial state was
+achieved.",1406.2954v1
+2014-08-09,Direct observations of magnetic flux rope formation during a solar coronal mass ejection,"Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in
+the solar atmosphere. It is generally accepted that CMEs are results of
+eruptions of magnetic flux ropes (MFRs). However, a heated debate is on whether
+MFRs pre-exist before the eruptions or they are formed during the eruptions.
+Several coronal signatures, \textit{e.g.}, filaments, coronal cavities, sigmoid
+structures and hot channels (or hot blobs), are proposed as MFRs and observed
+before the eruption, which support the pre-existing MFR scenario. There is
+almost no reported observation about MFR formation during the eruption. In this
+letter, we present an intriguing observation of a solar eruptive event occurred
+on 2013 November 21 with the Atmospheric Imaging Assembly on board the
+\textit{Solar Dynamic Observatory}, which shows a detailed formation process of
+the MFR during the eruption. The process started with the expansion of a
+low-lying coronal arcade, possibly caused by the flare magnetic reconnection
+underneath. The newly-formed ascending loops from below further pushed the
+arcade upward, stretching the surrounding magnetic field. The arcade and
+stretched magnetic field lines then curved-in just below the arcade vertex,
+forming an X-point. The field lines near the X-point continued to approach each
+other and a second magnetic reconnection was induced. It is this high-lying
+magnetic reconnection that led to the formation and eruption of a hot blob
+($\sim$ 10 MK), presumably a MFR, producing a CME. We suggest that two
+spatially-separated magnetic reconnections occurred in this event, responsible
+for producing the flare and the hot blob (CME), respectively.",1408.2000v1
+2015-01-20,Evolution of field line helicity during magnetic reconnection,"We investigate the evolution of field line helicity for magnetic fields that
+connect two boundaries without null points, with emphasis on localized finite-B
+magnetic reconnection. Total (relative) magnetic helicity is already recognized
+as an important topological constraint on magnetohydrodynamic processes. Field
+line helicity offers further advantages because it preserves all topological
+information and can distinguish between different magnetic fields with the same
+total helicity. Magnetic reconnection changes field connectivity and field line
+helicity reflects these changes; the goal of this paper is to characterize that
+evolution. We start by deriving the evolution equation for field line helicity
+and examining its terms, also obtaining a simplified form for cases where
+dynamics are localized within the domain. The main result, which we support
+using kinematic examples, is that during localized reconnection in a complex
+magnetic field, the evolution of field line helicity is dominated by a
+work-like term that is evaluated at the field line endpoints, namely the scalar
+product of the generalized field line velocity and the vector potential.
+Furthermore, the flux integral of this term over certain areas is very small
+compared to the integral of the unsigned quantity, which indicates that changes
+of field line helicity happen in a well-organized pairwise manner. It follows
+that reconnection is very efficient at redistributing helicity in complex
+magnetic fields despite having little effect on the total helicity.",1501.04856v2
+2015-06-22,"The structure of steady, relativistic, magnetised jets with rotation","We present equilibrium models of relativistic magnetised, infinite,
+axisymmetric jets with rotation propagating through an homogeneous,
+unmagnetised ambient medium at rest. The jet models are characterised by six
+functions defining the radial profiles of density, pressure, and the toroidal
+and axial components of velocity and magnetic field. Fixing the ambient
+pressure and the jet rest-mass density and axial components of the flow
+velocity and magnetic field, we analyze the influence of the toroidal magnetic
+field and several rotation laws on the structure of the equilibrium models. Our
+approach excludes by construction the analysis of the self-consistently
+magnetically launched jet models or the force-free equilibrium solutions.
+Several forbidden regions in the magnetic pitch angle/magnetization plane are
+found where models of the class considered in our study could not be settled.
+These forbidden regions are associated with the existence of maximum axial and
+toroidal magnetic field components compatible with the prescribed equilibrium
+condition at the jet surface, and/or an excess of centrifugal force producing
+gaps with negative pressures in the jet. The present study can be easily
+extended to jet models with different transversal profiles and magnetic field
+configurations.
+  In the last part of the paper, we test the ability of our RMHD code to
+maintain steady equilibrium models of axisymmetric RMHD jets in one and two
+spatial dimensions. The one dimensional numerical simulations serve also as a
+consistency proof of the fidelity of the analytical steady solutions discussed
+in the first part of the paper. The present study allows us to build initial
+equilibrium jet models with selected properties for dynamical (and emission)
+simulations of magnetised relativistic jets with rotation.",1506.06519v1
+2015-08-10,On the distribution of particle acceleration sites in plasmoid-dominated relativistic magnetic reconnection,"We investigate the distribution of particle acceleration sites, independently
+of the actual acceleration mechanism, during plasmoid-dominated, relativistic
+collisionless magnetic reconnection by analyzing the results of a
+particle-in-cell numerical simulation. The simulation is initiated with
+Harris-type current layers in pair plasma with no guide magnetic field,
+negligible radiative losses, no initial perturbation, and using periodic
+boundary conditions. We find that the plasmoids develop a robust internal
+structure, with colder dense cores and hotter outer shells, that is recovered
+after each plasmoid merger on a dynamical time scale. We use spacetime diagrams
+of the reconnection layers to probe the evolution of plasmoids, and in this
+context we investigate the individual particle histories for a representative
+sample of energetic electrons. We distinguish three classes of particle
+acceleration sites associated with (1) magnetic X-points, (2) regions between
+merging plasmoids, and (3) the trailing edges of accelerating plasmoids. We
+evaluate the contribution of each class of acceleration sites to the final
+energy distribution of energetic electrons -- magnetic X-points dominate at
+moderate energies, and the regions between merging plasmoids dominate at higher
+energies. We also identify the dominant acceleration scenarios, in order of
+decreasing importance -- (1) single acceleration between merging plasmoids, (2)
+single acceleration at a magnetic X-point, and (3) acceleration at a magnetic
+X-point followed by acceleration in a plasmoid. Particle acceleration is absent
+only in the vicinity of stationary plasmoids. The effect of magnetic mirrors
+due to plasmoid contraction does not appear to be significant in relativistic
+reconnection.",1508.02392v2
+2015-09-18,Active region upflows: 2. Data driven MHD modeling,"Context. Observations of many active regions show a slow systematic
+outflow/upflow from their edges lasting from hours to days. At present no
+physical explanation has been proven, while several suggestions have been put
+forward. Aims. This paper investigates one possible method for maintaining
+these upflows assuming that convective motions drive the magnetic field to
+initiate them through magnetic reconnection. Methods. We use Helioseismic and
+Magnetic Imager (HMI) data to provide an initial potential three dimensional
+magnetic field of the active region NOAA 11123 on 2010 November 13 where the
+characteristic upflow velocities are observed. A simple one-dimensional
+hydrostatic atmospheric model covering the region from the photosphere to the
+corona is derived. Local Correlation Tracking of the magnetic features in the
+HMI data is used to derive a proxy for the time dependent velocity field. The
+time dependent evolution of the system is solved using a resistive
+three-dimensional MagnetoHydro-Dynamic code. Results. The magnetic field
+contains several null points located well above the photosphere, with their fan
+planes dividing the magnetic field into independent open and closed flux
+domains. The stressing of the interfaces between the different flux domains is
+expected to provide locations where magnetic reconnection can take place and
+drive systematic flows. In this case, the region between the closed and open
+flux is identified as the region where observations find the systematic
+upflows. Conclusions. In the present experiment, the driving only initiates
+magneto-acoustic waves, without driving any systematic upflows at any of the
+flux interfaces.",1509.05639v1
+2015-11-11,A global galactic dynamo with a corona constrained by relative helicity,"We present a model for a global axisymmetric turbulent dynamo operating in a
+galaxy with a corona which treats the supernovae (SNe) and magneto-rotational
+instability (MRI) driven turbulence parameters under a common formalism. The
+nonlinear quenching of the dynamo is alleviated by inclusion of small-scale
+advective and diffusive magnetic helicity fluxes, which allow the gauge
+invariant magnetic helicity to be transferred outside the disk and consequently
+build up a corona during the course of dynamo action. The time-dependent dynamo
+equations are expressed in a separable form and solved through an eigenvector
+expansion constructed using the steady-state solutions of the dynamo equation.
+The parametric evolution of the dynamo solution allows us to estimate the final
+structure of the global magnetic field and the saturated value of the
+turbulence parameter $\alpha_m$, even before solving the dynamical equations
+for evolution of magnetic fields in the disk and the corona, along with
+$\alpha$-quenching. We then solve these equations simultaneously to study the
+saturation of large-scale magnetic field, its dependence on the small-scale
+magnetic helicity fluxes and corresponding evolution of the force-free field in
+the corona. The quadrupolar large-scale magnetic field in the disk is found to
+reach equipartition strength within a timescale of 1 Gyr. The large-scale
+magnetic field in the corona obtained is much weaker in strength compared to
+the field inside the disk and has only a weak impact on the dynamo operation.",1511.03392v2
+2016-01-12,Solar Atmospheric Magnetic Energy Coupling: Broad Plasma Conditions and Spectrum Regimes,"Solar variability investigations that include magnetic energy coupling are
+paramount to solving many key solar/stellar physics problems, particularly for
+understanding the temporal variability of magnetic energy redistribution and
+heating processes. Using three years of observations from the {\it Solar
+Dynamics Observatory's} Atmospheric Imaging Assembly and Heliosemic Magnetic
+Imager; radiative and magnetic fluxes were measured from gross features and at
+full-disk scales, respectively. Magnetic energy coupling analyses support
+radiative flux descriptions via a plasma heating connectivity of dominant
+(magnetic) and diffuse components, specifically of the predominantly closed
+field corona. Our work shows that this relationship favors an energetic
+redistribution efficiency across large temperature gradients, and potentially
+sheds light on the long withstanding issue of diffuse unresolved low corona
+emission. The intimacy of magnetic energy redistribution and plasma conditions
+revealed by this work holds significant insight for the field of stellar
+physics, as we have provided possible means for probing distant sources in
+currently limited and/or undetectable radiation distributions.",1601.02986v6
+2016-01-26,N-body model of magnetic flux tubes reconnecting in the solar atmosphere,"The investigation of dynamics of the small scale magnetic field on the Sun
+photosphere is necessary to understand the physical processes occurring in the
+higher layers of solar atmosphere due to the magnetic coupling between the
+photosphere and the corona. We present a simulation able to address these
+phenomena investigating the statistics of magnetic loops reconnections. The
+simulation is based on N-body model approach and is divided in two
+computational layers. We simplify the convection problem, interpreting the
+larger convective scale, mesogranulation, as the result of the collective
+interaction of convective downflow of granular scale. The N-body advection
+model is the base to generate a synthetic time series of nanoflares produced by
+interacting magnetic loops. The reconnection of magnetic field lines is the
+result of the advection of the magnetic footpoints following the velocity field
+generated by the interacting downflows. The model gives a quantitative idea of
+how much energy is expected to be released by the reconfiguration of magnetic
+loops in the quiet Sun.",1601.07105v1
+2016-02-24,Nonaxisymmetric MHD instabilities of Chandrasekhar states in Taylor-Couette geometry,"We consider axially periodic Taylor-Couette geometry with insulating boundary
+conditions. The imposed basic states are so-called Chandrasekhar states, where
+the azimuthal flow $U_\phi$ and magnetic field $B_\phi$ have the same radial
+profiles. Mainly three particular profiles are considered: the Rayleigh limit,
+quasi-Keplerian, and solid-body rotation. In each case we begin by computing
+linear instability curves and their dependence on the magnetic Prandtl number
+Pm. For the azimuthal wavenumber m=1 modes, the instability curves always scale
+with the Reynolds number and the Hartmann number. For sufficiently small Pm
+these modes therefore only become unstable for magnetic Mach numbers less than
+unity, and are thus not relevant for most astrophysical applications. However,
+modes with m>10 can behave very differently. For sufficiently flat profiles,
+they scale with the magnetic Reynolds number and the Lundquist number, thereby
+allowing instability also for the large magnetic Mach numbers of astrophysical
+objects. We further compute fully nonlinear, three-dimensional equilibration of
+these instabilities, and investigate how the energy is distributed among the
+azimuthal (m) and axial (k) wavenumbers. In comparison spectra become steeper
+for large m, reflecting the smoothing action of shear. On the other hand
+kinetic and magnetic energy spectra exhibit similar behavior: if several
+azimuthal modes are already linearly unstable they are relatively flat, but for
+the rigidly rotating case where m=1 is the only unstable mode they are so steep
+that neither Kolmogorov nor Iroshnikov-Kraichnan spectra fit the results. The
+total magnetic energy exceeds the kinetic energy only for large magnetic
+Reynolds numbers Rm>100.",1602.07436v1
+2016-04-26,Quantifying the Topology and Evolution of a Magnetic Flux Rope Associated with Multi-flare Activities,"Magnetic flux rope (MFR) plays an important role in solar activities. A
+quantitative assessment of the topology of an MFR and its evolution is crucial
+for a better understanding of the relationship between the MFR and the
+associated activities. In this paper, we investigate the magnetic field of
+active region 12017 from 2014 March 28 to 29, where 12 flares were triggered by
+the intermittent eruptions of a filament (either successful or confined). Using
+the vector magnetic field data from the Helioseismic and Magnetic Imager on
+board the \textit{Solar Dynamics Observatory}, we calculate the magnetic energy
+and helicity injection in the active region, and extrapolate the 3D magnetic
+field with a nonlinear force-free field model. From the extrapolations, we find
+an MFR that is cospatial with the filament. We further determine the
+configuration of this MFR by a closed quasi-separatrix layer (QSL) around it.
+Then, we calculate the twist number and the magnetic helicity for the field
+lines composing the MFR. The results show that the closed QSL structure
+surrounding the MFR gets smaller as a consequence of the flare occurrence. We
+also find that the flares in our sample are mainly triggered by kink
+instability. Moreover, the twist number varies more sensitively than other
+parameters to the occurrence of flares.",1604.07502v1
+2016-04-26,"Quark-hadron phase structure, thermodynamics and magnetization of QCD matter","SU($3$) Polyakov linear-sigma model (PLSM) is systematically implemented to
+characterize the quark-hadron phase structure and to determine various
+thermodynamic quantities and magnetization of the QCD matter. In mean-field
+approximation, the dependence of the chiral order-parameter on finite magnetic
+field is also calculated. In a wide range of temperatures and magnetic field
+strengths, various thermodynamic quantities including trace anomaly, speed of
+sound squared, entropy density, specific heat are presented and some magnetic
+properties are described, as well. Wherever available these results are
+confronted to recent lattice QCD calculations. The temperature dependence of
+these quantities confirms our previous result that the transition temperature
+is reduced with the increase in the magnetic field strength, i.e. QCD matter is
+to be characterized by an inverse magnetic catalysis. Furthermore, the
+temperature dependence of the magnetization shows that the conclusion that the
+QCD matter has paramagnetic properties slightly below and far above the
+pseudo-critical temperature, is confirmed, as well. The excellent agreement
+with recent lattice calculations proves that our QCD-like approach (PLSM) seems
+to possess the correct degrees-of-freedom in both hadronic and partonic phases
+and describes well the dynamics deriving confined hadrons to deconfined
+quark-gluon plasma.",1604.08174v2
+2016-05-04,"Insight into the magnetism of a distorted Kagome lattice, Dy3Ru4Al12, based on polycrystalline studies","The layered compound with distorted Kagome nets, Dy3Ru4Al12, was previously
+reported to undergo antiferromagnetic ordering below (TN=) 7 K, based on
+investigations on single crystals. Here, we report the results of our
+investigation of ac and dc magnetic susceptibility (\c{hi}), isothermal remnant
+magnetization (MIRM), heat-capacity, magnetocaloric effect and
+magnetoresistance measurements on polycrystals. The present results reveal that
+there is an additional magnetic anomaly around 20 K, as though the N\'eel order
+is preceded by the formation of ferromagnetic clusters. We attribute this
+feature to geometric frustration of magnetism. In view of the existence of this
+phase, the interpretation of the linear-term in the heat-capacity in terms of
+spin-fluctuations from the Ru 4d band needs to be revisited. Additionally, in
+the vicinity of TN, AC \c{hi} shows a prominent frequency dependence and, below
+TN, MIRM exhibits a slow decay with time. This raises a question whether the
+antiferromagnetic structure in this compound is characterized by
+spin-glass-like dynamics. In contrast to what was reported earlier, there is a
+change in the sign of the magnetoresistance (MR) at the metamagnetic
+transition. A butter-fly-shaped (isothermal) MR loop (interestingly spanning
+over all the four quadrants) is observed at 2 K with distinct evidence for the
+magnetic phase co-existence phenomenon in zero field after travelling through
+metamagnetic transition field. The results on polycrystals thus provide
+additional information about the magnetism of this compound, revealing that the
+magnetism of this compound is more complex than what is believed, due to
+geometric frustration intrinsic to Kagome net.",1605.01147v1
+2016-07-13,Comparison of magnetic properties in a magnetic cloud and its solar source on April 11-14 2013,"In the context of Sun-Earth connection of coronal mass ejections and magnetic
+flux ropes (MFRs), we studied the solar active region (AR) and the magnetic
+properties of magnetic cloud (MC) event during April 14-15, 2013. We use
+in-situ observations from the Advanced Composition Explorer and source AR
+measurements from the Solar Dynamic Observatory. The MCs magnetic structure is
+reconstructed from the Grad-Shafranov method which reveals a northern component
+of the axial field with left-handed helicity. The MC invariant axis is highly
+inclined to the ecliptic plane pointing northward and is rotated by $117^o$
+with respect to the source region PIL. The net axial flux and current in the MC
+are comparatively higher than from the source region. Linear force-free alpha
+distribution ($10^{-7}-10^{-6}$ m$^{-1}$) at the sigmoid leg matches the range
+of twist number in the MC of 1-2 AU MFR. The MFR is non-linear force-free with
+decreasing twist from the axis (9 turns/AU) towards the edge. Therefore
+Gold-Hoyle (GH) configuration, assuming a constant twist, is more consistent
+with the MC structure than the Lundquist configuration of increasing twist from
+the axis to boundary. As an indication to that, the GH configuration yields
+better fitting to the global trend of in-situ magnetic field components, in
+terms of rms, than the Lundquist model. These cylindrical configurations
+improved the MC fitting results when considered the effect of self-similar
+expansion of MFR. For such twisting behaviour, this study suggests an
+alternative fitting procedure to better characterise the MC magnetic structure
+and its source region links.",1607.03811v1
+2016-09-01,Magnetic Field Induced Vortex Lattice Transition in HgBa$_{2}$CuO$_{4+δ}$,"Measurements of the $^{17}$O nuclear magnetic resonance (NMR) quadrupolar
+spectrum of apical oxygen in HgBa$_{2}$CuO$_{4+\delta}$ were performed over a
+range of magnetic fields from 6.4 to 30\,T in the superconducting state. Oxygen
+isotope exchanged single crystals were investigated with doping corresponding
+to superconducting transition temperatures from 74\,K underdoped, to 78\,K
+overdoped. The apical oxygen site was chosen since its NMR spectrum has narrow
+quadrupolar satellites that are well separated from any other resonance.
+Non-vortex contributions to the spectra can be deconvolved in the time domain
+to determine the local magnetic field distribution from the vortices. Numerical
+analysis using Brandt's Ginzburg-Landau theory was used to find structural
+parameters of the vortex lattice, penetration depth, and coherence length as a
+function of magnetic field in the vortex solid phase. From this analysis we
+report a vortex structural transition near 15\,T from an oblique lattice with
+an opening angle of $73^{\circ}$ at low magnetic fields to a triangular lattice
+with $60^{\circ}$ stabilized at high field. The temperature for onset of vortex
+dynamics has been identified with vortex lattice melting. This is independent
+of the magnetic field at sufficiently high magnetic field similar to that
+reported for YBa$_2$Cu$_3$O$_7$ and Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$
+and is correlated with mass anisotropy of the material. This behavior is
+accounted for theoretically only in the limit of very high anisotropy.",1609.00414v1
+2016-09-22,Magnetization oscillations and waves driven by pure spin currents,"Recent advances in the studies of pure spin currents - flows of angular
+momentum (spin) not accompanied by the electric currents - have opened new
+horizons for the emerging technologies based on the electron's spin degree of
+freedom, such as spintronics and magnonics. The main advantage of pure spin
+current, as compared to the spin-polarized electric current, is the possibility
+to exert spin transfer torque on the magnetization in thin magnetic films
+without electrical current flow through the material. In addition to minimizing
+Joule heating and electromigration effects, this characteristic enables the
+implementation of spin torque devices based on the low-loss insulating magnetic
+materials, and offers an unprecedented geometric flexibility. Here we review
+the recent experimental achievements in investigations of magnetization
+oscillations excited by pure spin currents in different magnetic nanosystems
+based on metallic and insulating magnetic materials. We discuss the spectral
+properties of spin-current nano-oscillators, and relate them to the spatial
+characteristics of the excited dynamic magnetic modes determined by the
+spatially-resolved measurements. We also show that these systems support
+locking of the oscillations to external microwave signals, as well as their
+mutual synchronization, and can be used as efficient nanoscale sources of
+propagating spin waves.",1609.06899v1
+2016-10-10,Study on creation and destruction of transport barriers via effective safety factors for energetic particles,"Charged particles with low kinetic energy move along magnetic field lines,
+but so do not energetic particles. We investigate the topological structure
+changes in the phase space of energetic particles with respect to the magnetic
+one. For this study cylindrical magnetic fields with non-monotonic safety
+factors that induce the magnetic internal transport barrier are considered. We
+show that the topological structure of the magnetic field line and of the
+particle trajectories can be quite different. We explain this difference using
+the concept of effective particle $q$-profile. Using this notion we can
+investigate the location and existence of resonances for particle orbits that
+are different from the magnetic ones. These are examined both numerically by
+integrating an equation of motion and theoretically by use of Alfv\'en's
+guiding center theory and by use of the effective reduced Hamiltonian for the
+integrable unperturbed system. It is clarified that, for the energetic
+particles, the grad $B$ drift effect shifts the resonances and the drift
+induced by curvature of the magnetic field line leads to the vanishing of the
+resonances. As a result, we give two different mechanisms that lead to the
+creation of transport barriers for energetic particles in the region where the
+magnetic field line is chaotic.",1610.02867v1
+2016-10-26,Magnetic field amplification in turbulent astrophysical plasmas,"Magnetic fields play an important role in astrophysical accretion discs, and
+in the interstellar and intergalactic medium. They drive jets, suppress
+fragmentation in star-forming clouds and can have a significant impact on the
+accretion rate of stars. However, the exact amplification mechanisms of cosmic
+magnetic fields remain relatively poorly understood. Here I start by reviewing
+recent advances in the numerical and theoretical modelling of the 'turbulent
+dynamo', which may explain the origin of galactic and inter-galactic magnetic
+fields. While dynamo action was previously investigated in great detail for
+incompressible plasmas, I here place particular emphasis on highly compressible
+astrophysical plasmas, which are characterised by strong density fluctuations
+and shocks, such as the interstellar medium. I find that dynamo action works
+not only in subsonic plasmas, but also in highly supersonic, compressible
+plasmas, as well as for low and high magnetic Prandtl numbers. I further
+present new numerical simulations from which I determine the growth of the
+turbulent (un-ordered) magnetic field component ($B_\mathrm{turb}$) in the
+presence of weak and strong guide fields ($B_0$). I vary $B_0$ over 5 orders of
+magnitude and find that the dependence of $B_\mathrm{turb}$ on $B_0$ is
+relatively weak, and can be explained with a simple theoretical model in which
+the turbulence provides the energy to amplify $B_\mathrm{turb}$. Finally, I
+discuss some important implications of magnetic fields for the structure of
+accretion discs, the launching of jets, and the star formation rate of
+interstellar clouds.",1610.08132v2
+2016-10-26,Skyrmion production on demand by homogeneous DC currents,"Topological magnetic textures - like skyrmions - have become a major player
+in the design of next-generation magnetic storage technology due to their
+stability and the control of their motion by ultra-low current densities. A
+major challenge to develop this new skyrmion-based technology is to achieve the
+controlled and deterministic creation of magnetic skyrmions without the need of
+complex setups. We demonstrate a solution to this challenge by showing how to
+create skyrmions and other magnetic textures in ferromagnetic thin films by
+means of a homogeneous DC current and without requiring Dzyaloshinskii-Moriya
+interactions. This is possible by exploiting a static loss of stability arising
+from the interplay of current-induced spin-transfer torque and a spatially
+inhomogeneous magnetization, which can be achieved, e.g., by locally
+engineering the anisotropy, the magnetic field, or other magnetic interactions.
+The magnetic textures are created controllably, efficiently, and periodically
+with a period that can be tuned by the applied current strength. We propose
+specific experimental setups realizable with simple materials, such as cobalt
+based materials, to observe the periodic formation of skyrmions. We show that
+adding chiral interactions will not influence the basics of the generations but
+then influence the consequent dynamics with respect to the stabilization of
+topological textures. Our findings allow for the production of skyrmions on
+demand in simple ferromagnetic thin films by homogeneous DC currents.",1610.08313v2
+2017-01-13,The role of magnetic fields in the structure and interaction of supershells,"Large-scale shocks formed by clustered feedback of young OB stars are
+considered an important source of mechanical energy for the ISM and a trigger
+of molecular cloud formation. Their interaction sites are locations where
+kinetic energy and magnetic fields are redistributed between ISM phases. In
+this work we study the effect of the magnetic field on the expansion and
+fragmentation of supershells and look for the signatures of supershell
+collisions on dense structures and on the kinetic and magnetic energy
+distribution of the ISM. We performed a series of high-resolution,
+three-dimensional simulations of colliding supershells. The shocks are created
+by time-dependent feedback and evolve in a diffuse turbulent environment that
+is either unmagnetized or has different initial magnetic field configurations.
+In the hydrodynamical situation, the expansion law of the superbubbles is
+consistent with the radius-time relation that is theoretically predicted for
+wind-blown bubbles. The supershells fragment over their entire surface into
+small dense clumps that carry more than half of the total kinetic energy in the
+volume. However, this is not the case when a magnetic field is introduced,
+either in the direction of the collision or perpendicular to the collision. In
+magnetized situations, the shell surfaces are more stable to dynamical
+instabilities. When the magnetic field opposes the collision, the expansion law
+of the supershells also becomes significantly flatter than in the
+hydrodynamical case. Although a two-phase medium arises in all cases, in the
+MHD simulations the cold phase is limited to lower densities.",1701.03696v1
+2017-01-29,Observational Evidence of Magnetic Reconnection for Brightenings and Transition Region Arcades in IRIS observations,"By using a new method of forced-field extrapolation, we study the emerging
+flux region AR 11850 observed by the Interface Region Imaging Spectrograph
+(IRIS) and Solar Dynamical Observatory (SDO). Our results suggest that the
+bright points (BPs) in this emerging region have responses in lines formed from
+the upper photosphere to the transition region, with a relatively similar
+morphology. They have an oscillation of several minutes according to the
+Atmospheric Imaging Assembly (AIA) data at 1600 and 1700 A . The ratio between
+the BP intensities measured in 1600 A and 1700 A filtergrams reveals that these
+BPs are heated differently. Our analysis of the Helioseismic and Magnetic
+Imager (HMI) vector magnetic field and the corresponding topology in AR11850
+indicates that the BPs are located at the polarity inversion line (PIL) and
+most of them related with magnetic reconnection or cancelation. The heating of
+the BPs might be different due to different magnetic topology. We find that the
+heating due to the magnetic cancelation would be stronger than the case of bald
+patch reconnection. The plasma density rather than the magnetic field strength
+could play a dominant role in this process. Based on physical conditions in the
+lower atmosphere, our forced-field extrapolation shows consistent results
+between the bright arcades visible in slit-jaw image (SJI) 1400 A and the
+extrapolated field lines that pass through the bald patches. It provides a
+reliable observational evidence for testing the mechanism of magnetic
+reconnection for the BPs and arcades in emerging flux region, as proposed in
+simulation works.",1701.08356v1
+2017-02-16,Plasma Brightenings in a Failed Solar Filament Eruption,"Failed filament eruptions are solar eruptions that are not associated with
+coronal mass ejections. In a failed filament eruption, the filament materials
+usually show some ascending and falling motions as well as generate bright EUV
+emissions. Here we report a failed filament eruption that occurred in a
+quiet-Sun region observed by the Atmospheric Imaging Assembly on board the
+Solar Dynamics Observatory. In this event, the filament spreads out but gets
+confined by the surrounding magnetic field. When interacting with the ambient
+magnetic field, the filament material brightens up and flows along the magnetic
+field lines through the corona to the chromosphere. We find that some materials
+slide down along the lifting magnetic structure containing the filament and
+impact the chromosphere to cause two ribbon-like brightenings in a wide
+temperature range through kinetic energy dissipation. There is evidence
+suggesting that magnetic reconnection occurs between the filament magnetic
+structure and the surrounding magnetic fields where filament plasma is heated
+to coronal temperatures. In addition, thread-like brightenings show up on top
+of the erupting magnetic fields at low temperatures, which might be produced by
+an energy imbalance from a fast drop of radiative cooling due to plasma
+rarefaction. Thus, this single event of failed filament eruption shows
+existence of a variety of plasma brightenings that may be caused by completely
+different heating mechanisms.",1702.05136v1
+2017-04-27,Magnetorotational Dynamo Action in the Shearing Box,"Magnetic dynamo action caused by the magnetorotational instability is studied
+in the shearing-box approximation with no imposed net magnetic flux. Consistent
+with recent studies, the dynamo action is found to be sensitive to the aspect
+ratio of the box: it is much easier to obtain in tall boxes (stretched in the
+direction normal to the disk plane) than in long boxes (stretched in the radial
+direction). Our direct numerical simulations indicate that the dynamo is
+possible in both cases, given a large enough magnetic Reynolds number. To
+explain the relatively larger effort required to obtain the dynamo action in a
+long box, we propose that the turbulent eddies caused by the instability most
+efficiently fold and mix the magnetic field lines in the radial direction. As a
+result, in the long box the scale of the generated strong azimuthal
+(stream-wise directed) magnetic field is always comparable to the scale of the
+turbulent eddies. In contrast, in the tall box the azimuthal magnetic flux
+spreads in the vertical direction over a distance exceeding the scale of the
+turbulent eddies. As a result, different vertical sections of the tall box are
+permeated by large-scale nonzero azimuthal magnetic fluxes, facilitating the
+instability. In agreement with this picture, the cases when the dynamo is
+efficient are characterized by a strong intermittency of the local azimuthal
+magnetic fluxes.",1704.08636v1
+2017-07-26,Stabilizing isolated skyrmions at low magnetic fields exploiting vanishing magnetic anisotropy,"Skyrmions are topologically protected non-collinear magnetic structures.
+Their stability and dynamics, arising from their topological character, have
+made them ideal information carriers e.g. in racetrack memories. The success of
+such a memory critically depends on the ability to stabilize and manipulate
+skyrmions at low magnetic fields. The driving force for skyrmion formation is
+the non-collinear Dzyaloshinskii-Moriya exchange interaction (DMI) originating
+from spin-orbit coupling (SOC). It competes with both the nearest neighbour
+Heisenberg exchange interaction and the magnetic anisotropy, which favour
+collinear states. While skyrmion lattices might evolve at vanishing magnetic
+fields, the formation of isolated skyrmions in ultra-thin films so far required
+the application of an external field which can be as high as several T. Here,
+we show that isolated skyrmions in a monolayer (ML) of Co epitaxially grown on
+a Ru(0001) substrate can be stabilized at magnetic fields as low as 100 mT.
+Even though SOC is weak in the 4d element Ru, a homochiral spin spiral ground
+state and isolated skyrmions could be detected and laterally resolved using a
+combination of tunneling and anisotropic tunneling magnetoresistance effect in
+spin-sensitive scanning tunneling microscopy (STM). Density functional theory
+(DFT) calculations confirm these chiral magnetic textures, even though the
+stabilizing DMI interaction is weak. We find that the key factor is the absence
+of magnetocristalline anisotropy in this system which enables non-collinear
+states to evolve in spite of weak SOC, opening up a wide choice of materials
+beyond 5d elements.",1707.08519v1
+2017-09-25,On magnetic field amplification and particle acceleration near non-relativistic astrophysical shocks: Particles in MHD Cells simulations,"We present simulations of magnetized astrophysical shocks taking into account
+the interplay between the thermal plasma of the shock and supra-thermal
+particles. Such interaction is depicted by combining a grid-based
+magneto-hydrodynamics description of the thermal fluid with particle in cell
+techniques devoted to the dynamics of supra-thermal particles. This approach,
+which incorporates the use of adaptive mesh refinement features, is potentially
+a key to simulate astrophysical systems on spatial scales that are beyond the
+reach of pure particle-in-cell simulations. We consider in this study
+non-relativistic shocks with various Alfvenic Mach numbers and magnetic field
+obliquity. We recover all the features of both magnetic field amplification and
+particle acceleration from previous studies when the magnetic field is parallel
+to the normal to the shock. In contrast with previous particle-in-cell-hybrid
+simulations, we find that particle acceleration and magnetic field
+amplification also occur when the magnetic field is oblique to the normal to
+the shock but on larger timescales than in the parallel case. We show that in
+our simulations, the supra-thermal particles are experiencing acceleration
+thanks to a pre-heating process of the particle similar to a shock drift
+acceleration leading to the corrugation of the shock front. Such oscillations
+of the shock front and the magnetic field locally help the particles to enter
+the upstream region and to initiate a non-resonant streaming instability and
+finally to induce diffuse particle acceleration.",1709.08482v2
+2017-11-22,Dynamical onset of superconductivity and retention of magnetic fields in cooling neutron stars,"A superconductor of paired protons is thought to form in the core of neutron
+stars soon after their birth. Minimum energy conditions suggest magnetic flux
+is expelled from the superconducting region due to the Meissner effect, such
+that the neutron star core is largely devoid of magnetic fields for some
+nuclear equation of state and proton pairing models. We show via neutron star
+cooling simulations that the superconducting region expands faster than flux is
+expected to be expelled because cooling timescales are much shorter than
+timescales of magnetic field diffusion. Thus magnetic fields remain in the bulk
+of the neutron star core for at least 10^6-10^7 yr. We estimate the size of
+flux free regions at 10^7 yr to be <~ 100 m for a magnetic field of 10^11 G and
+possibly smaller for stronger field strengths. For proton pairing models that
+are narrow, magnetic flux may be completely expelled from a thin shell of
+approximately the above size after 10^5 yr. This shell may insulate lower
+conductivity outer layers, where magnetic fields can diffuse and decay faster,
+from fields maintained in the highly conducting deep core.",1711.08480v1
+2017-11-23,A Statistical Study of Photospheric Magnetic Field Changes During 75 Solar Flares,"Abrupt and permanent changes of photospheric magnetic fields have been
+observed during solar flares. The changes seem to be linked to the
+reconfiguration of magnetic fields, but their origin is still unclear. We
+carried out a statistical analysis of permanent line-of-sight magnetic field
+($B_{\rm LOS}$) changes during 18 X-, 37 M-, 19 C- and 1 B-class flares using
+data from Solar Dynamics Observatory/Helioseismic and Magnetic Imager. We
+investigated the properties of permanent changes, such as frequency, areas, and
+locations. We detected changes of $B_{\rm LOS}$ in 59/75 flares. We find that
+strong flares are more likely to show changes, with all flares $\ge$ M1.6
+exhibiting them. For weaker flares, permanent changes are observed in 6/17
+C-flares. 34.3\% of the permanent changes occurred in the penumbra and 18.9\%
+in the umbra. Parts of the penumbra appeared or disappeared in 23/75 flares.
+The area where permanent changes occur is larger for stronger flares. Strong
+flares also show a larger change of flux, but there is no dependence of the
+magnetic flux change on the heliocentric angle. The mean rate of change of
+flare-related magnetic field changes is 20.7 Mx cm$^{-2}$ min$^{-1}$. The
+number of permanent changes decays exponentially with distance from the
+polarity inversion line. The frequency of the strength of permanent changes
+decreases exponentially, and permanent changes up to 750 Mx cm$^{-2}$ were
+observed. We conclude that permanent magnetic field changes are a common
+phenomenon during flares, and future studies will clarify their relation to
+accelerated electrons, white light emission, and sunquakes to further
+investigate their origin.",1711.08631v2
+2017-12-17,"Low temperature ferromagnetic properties, magnetic field induced spin order and random spin freezing effect in Ni1.5Fe1.5O4 ferrite; prepared at different pH values and annealing temperatures","We present the low temperature magnetic properties in Ni1.5Fe1.5O4 ferrite as
+the function of pH at which the material was prepared by chemical route and
+post annealing temperature. The material is a ferri or ferromagnet, but showed
+magnetic blocking and random spin freezing process on lowering the measurement
+temperature down to 5 K. The sample prepared at pH =12 and annealed at 800 ^C
+showed a sharp magnetization peak at 105 K, the superparamagnetic blocking
+temperature of the particles. The magnetization peak remained incomplete within
+measurement temperature up to 350 K for rest of the samples, although peak
+temperature was brought down by increasing applied dc field. The fitting of
+temperature dependence of coercivity data according to Kneller law suggested
+random orientation of ferromagnetic particles. The fitting of saturation
+magnetization according to Bloch law provided the exponent that largely
+deviated from 1.5, a typical value for long ranged ferromagnet. An abrupt
+increase of saturation magnetization below 50 K suggested the active role of
+frozen surface spins in low temperature magnetic properties. AC susceptibility
+data elucidated the low temperature spin freezing dynamics and exhibited the
+characters of cluster spin glass in the samples depending on pH value and
+annealing temperature.",1712.06114v1
+2018-02-28,Magnetically regulated collapse in the B335 protostar ? I. ALMA observations of the polarized dust emission,"The role of the magnetic field during protostellar collapse is poorly
+constrained from an observational point of view, although it could be
+significant if we believe state-of-the-art models of protostellar formation. We
+present polarimetric observations of the 233 GHz thermal dust continuum
+emission obtained with ALMA in the B335 Class 0 protostar. Linearly polarized
+dust emission arising from the circumstellar material in the envelope of B335
+is detected at all scales probed by our observations, from radii of 50 to 1000
+au. The magnetic field structure producing the dust polarization has a very
+ordered topology in the inner envelope, with a transition from a large-scale
+poloidal magnetic field, in the outflow direction, to strongly pinched in the
+equatorial direction. This is probably due to magnetic field lines being
+dragged along the dominating infall direction since B335 does not exhibit
+prominent rotation. Our data and their qualitative comparison to a family of
+magnetized protostellar collapse models show that, during the magnetized
+collapse in B335, the magnetic field is maintaining a high level of
+organization from scales 1000 au to 50 au: this suggests the field is
+dynamically relevant and capable of influencing the typical outcome of
+protostellar collapse, such as regulating the disk size in B335.",1803.00028v1
+2018-03-27,Generation and annihilation time of magnetic droplet solitons,"Magnetic droplet solitons were first predicted to occur in materials with
+uniaxial magnetic anisotropy due to a long-range attractive interaction between
+elementary magnetic excitations, magnons. A non-equilibrium magnon population
+provided by a spin-polarized current in nanocontacts enables their creation and
+there is now clear experimental evidence for their formation, including direct
+images obtained with scanning x-ray transmission microscopy. Interest in
+magnetic droplets is associated with their unique magnetic dynamics that can
+lead to new types of high frequency nanometer scale oscillators of interest for
+information processing, including in neuromorphic computing. However, there are
+no direct measurements of the time required to nucleate droplet solitons or
+their lifetime---experiments to date only probe their steady-state
+characteristics, their response to dc spin currents. Here we determine the
+timescales for droplet annihilation and generation using current pulses.
+Annihilation occurs in a few nanoseconds while generation can take several
+nanoseconds to a microsecond depending on the pulse amplitude. Micromagnetic
+simulations show that there is an incubation time for droplet generation that
+depends sensitively on the initial magnetic state of the nanocontact. An
+understanding of these processes is essential to utilizing the unique
+characteristics of magnetic droplet solitons oscillators, including their high
+frequency, tunable and hysteretic response.",1803.10334v1
+2018-04-26,Particle acceleration in explosive relativistic reconnection events and Crab Nebula gamma-ray flares,"We develop a model of gamma-ray flares of the Crab Nebula resulting from the
+magnetic reconnection events in highly-magnetized relativistic plasma. We first
+discuss physical parameters of the Crab nebula and review the theory of pulsar
+winds and termination shocks. We also review the principle points of particle
+acceleration in explosive reconnection events (Lyutikov et al. 2017a,b).
+  It is required that particles producing flares are accelerated in highly
+magnetized regions of the nebula. Flares originate from the poleward regions at
+the base of Crab's polar outflow, where both the magnetization and the magnetic
+field strength are sufficiently high. The post-termination shock flow develops
+macroscopic (not related to the plasma properties on the skin-depth scale)
+kink-type instabilities. The resulting large-scales magnetic stresses drive
+explosive reconnection events on the light-crossing time of the reconnection
+region. Flares are produced at the initial stage of the current sheet
+development, during the X-point collapse. The model has all the ingredients
+needed for Crab flares: natural formation of highly magnetized regions,
+explosive dynamics on light travel time, development of high electric fields on
+macroscopic scales and acceleration of particles to energies well exceeding the
+average magnetic energy per particle.",1804.10291v2
+2018-05-14,Optically Pumped Floquet States of Magnetization in Ferromagnets,"Floquet states have been subject of great research interest since
+Zel'dovich's pioneering work on the quasienergy of a quantum system subject to
+a temporally periodic action. Nowadays periodic modulation of the system
+Hamiltonian is mostly achieved by microwaves leading to novel exciting
+phenomena in condensed matter physics: Floquet topological insulators, chiral
+edge states etc. On the other hand, nonthermal optical control of magnetization
+at picosecond time scales is currently a highly appealing research topic for
+potential applications in magnetic data storage. Here we combine these two
+concepts to investigate Floquet states in the system of exchange-coupled spins
+in a ferromagnet. We periodically perturb the magnetization of an iron-garnet
+film by a train of circularly-polarized femtosecond laser pulses hitting the
+sample at 1 GHz repetition rate and monitor the magnetization dynamics behaving
+like a Floquet state. An external magnetic field allows tuning of the Floquet
+states leading to a pronounced increase of the precession amplitude by one
+order of magnitude at the center of the Brillouin zone, i.e. when the
+precession frequency is a multiple of the laser pulse repetition rate. Floquet
+states might potentially allow for parametric generation of magnetic
+oscillations. The observed phenomena expand the capabilities of coherent
+ultrafast optical control of magnetization and pave a way for their application
+in quantum computation or data processing.",1805.05822v1
+2018-05-18,Transport coefficients of hot magnetized QCD matter beyond the lowest Landau level approximation,"In this article, shear viscosity, bulk viscosity, and thermal conductivity of
+a hot QCD medium have been studied in the presence of a strong magnetic field.
+To model the hot magnetized QCD matter, an extended quasi-particle description
+of the hot QCD equation of state in the presence of the magnetic field has been
+adopted. The effects of higher Landau levels on the temperature dependence of
+viscous coefficients (bulk and shear viscosities) and thermal conductivity have
+been obtained by considering the $1\rightarrow 2$ processes in the presence of
+the strong magnetic field. An effective covariant kinetic theory has been set
+up in (1+1)-dimensional that includes mean field contributions in terms of
+quasi-particle dispersions and magnetic field to describe the Landau level
+dynamics of quarks. The sensitivity of these parameters to the magnitude of the
+magnetic field has also been explored. Both the magnetic field and mean field
+contributions have seen to play a significant role in obtaining the temperature
+behaviour of the transport coefficients of hot QCD medium.",1805.07313v2
+2018-06-25,On the sensitivity of magnetic cycles in global simulations of solar-like stars,"The periods of magnetic activity cycles in the Sun and solar-type stars do
+not exhibit a simple or even single trend with respect to rotation rate or
+luminosity. Dynamo models can be used to interpret this diversity, and can
+ultimately help us understand why some solar-like stars do not exhibit a
+magnetic cycle, whereas some do, and for the latter what physical mechanisms
+set their magnetic cycle period. Three-dimensional non-linear
+magnetohydrodynamical simulations present the advantage of having only a small
+number of tunable parameters, and produce in a dynamically self-consistent
+manner the flows and the dynamo magnetic fields pervading stellar interiors. We
+conducted a series of such simulations within the EULAG-MHD framework, varying
+the rotation rate and luminosity of the modeled solar-like convective
+envelopes. We find decadal magnetic cycles when the Rossby number near the base
+of the convection zone is moderate (typically between 0.25 and 1). Secondary,
+shorter cycles located at the top of the convective envelope close to the
+equator are also observed in our numerical experiments, when the local Rossby
+number is lower than 1. The deep-seated dynamo sustained in these numerical
+experiments is fundamentally non-linear, in that it is the feedback of the
+large-scale magnetic field on the large-scale differential rotation that sets
+the magnetic cycle period. The cycle period is found to decrease with the
+Rossby number, which offers an alternative theoretical explanation to the
+variety of activity cycles observed in solar-like stars.",1806.09484v1
+2018-07-04,A Study of Magnetic Field Characteristics of Flaring Active Region Based on Nonlinear Force-free Field Extrapolation,"Coronal magnetic fields are responsible for the onset of solar flares and
+solar eruptions. However, the type of magnetic field parameters that can be
+used to measure the critical condition for a solar eruption is still unclear.
+As an effort to understand the possible condition for a solar flare, we have
+examined the non-dimensional parameter $\kappa$ introduced by Ishiguro & Kusano
+(2017), which contains information about magnetic twist distribution and
+magnetic flux in an active region (AR). We introduce a new parameter
+$\kappa^\ast$, as a proxy for $\kappa$, and we have analyzed the evolution of
+$\kappa^\ast$ during the flaring period of an AR using the nonlinear force-free
+field (NLFFF) extrapolated from the photospheric vector magnetic field data.
+Using data from the Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic
+Imager (HMI), we have calculated $\kappa^\ast$ for the AR NOAA 11158 during its
+three-day flaring period. We found that $\kappa^\ast$ increased to a certain
+level before two large flares and decreased significantly after their onset.
+The results suggest that $\kappa^\ast$ may be used as an indicator of the
+necessary condition for the onset of a solar eruption in the AR. Based on this
+result, we propose a new method to assess the possibility of a large solar
+eruption from an AR by combining the parameter $\kappa^\ast$ and information
+about the magnetic energy of the AR.",1807.01436v1
+2018-07-12,Effect of the exoplanet magnetic field topology on its magnetospheric radio emission,"The magnetized wind from stars that impact exoplanets should lead to radio
+emissions. According to the scaling laws derived in the solar system, the radio
+emission should depend on the stellar wind, interplanetary magnetic field, and
+topology of the exoplanet magnetosphere. The aim of this study is to calculate
+the dissipated power and subsequent radio emission from exoplanet
+magnetospheres with different topologies perturbed by the interplanetary
+magnetic field and stellar wind, to refine the predictions from scaling laws,
+and to prepare the interpretation of future radio detections. We use the
+magnetohydrodynamic (MHD) code PLUTO in spherical coordinates to analyze the
+total radio emission level resulting from the dissipation of the kinetic and
+magnetic (Poynting flux) energies inside the exoplanet's magnetospheres. We
+apply a formalism to infer the detailed contribution in the exoplanet radio
+emission on the exoplanet's day side and magnetotail. The model is based on
+Mercury-like conditions, although the study results are extrapolated to
+exoplanets with stronger magnetic fields, providing the lower bound of the
+radio emission. The predicted dissipated powers and resulting radio emissions
+depends critically on the exoplanet magnetosphere topology and interplanetary
+magnetic field (IMF) orientation. The radio emission on the exoplanet's night
+and day sides should thus contain information on the exoplanet magnetic field
+topology. In addition, if the topology of an exoplanet magnetosphere is known,
+the radio emission measurements can be used as a proxy of the instantaneous
+dynamic pressure of the stellar wind, IMF orientation, and intensity.",1807.04417v1
+2018-07-12,First-Principles-Based Strain and Temperature Dependent Ferroic Phase Diagram of SrMnO$_3$,"Perovskite structure SrMnO$_3$ is a rare example of a multiferroic material
+where strain-tuning and/or cation substitution could lead to coinciding
+magnetic and ferroelectric ordering temperatures, which would then promise
+strong magnetoelectric coupling effects. Here, we establish the temperature and
+strain dependent ferroic phase diagram of SrMnO$_3$ using
+first-principles-based effective Hamiltonians. All parameters of these
+Hamiltonians are calculated using density functional theory, i.e., no fitting
+to experimental data is required. Temperature dependent properties are then
+obtained from Monte Carlo and molecular dynamics simulations. We observe a
+sequence of several magnetic transitions under increasing tensile strain, with
+a moderate variation of the corresponding critical temperatures. In contrast,
+the ferroelectric Curie temperature increases strongly after its onset around
+2.5\,\% strain, and indeed crosses the magnetic transition temperature just
+above 3\,\% strain. Our results indicate pronounced magnetoelectric coupling,
+manifested in dramatic changes of the magnetic ordering temperatures and
+different magnetic ground states as function of the ferroelectric distortion.
+In addition, coexisting ferroelectric and ferromagnetic order is obtained for
+strains above 4\,\%. Our calculated phase diagram suggests the possibility to
+control the magnetic properties of SrMnO$_3$ through an applied electric field,
+significantly altering the magnetic transition temperatures, or even inducing
+transitions between different magnetic states.",1807.04777v1
+2018-08-14,Magnetic nanowires and nanotubes,"We propose a review of the current knowledge about the synthesis, magnetic
+properties and applications of magnetic cylindrical nanowires and nanotubes. By
+""nano"" we consider diameters reasonably smaller than a micrometer. At this
+scale, comparable to micromagnetic and transport length scales, novel
+properties appear. At the same time, this makes the underlying physics easier
+to understand due to the limiter number of degrees of freedom involved. The
+three-dimensional nature and the curvature of these objects contribute also to
+their specific properties, compared to patterns flat elements. While the topic
+of nanowires and later nanotubes started now decades ago, it is nevertheless
+flourishing, thanks to the progress of synthesis, theory and characterization
+tools. These give access to ever more complex and thus functional structures,
+and also shifting the focus from material-type measurements of large
+assemblies, to single-object investigations. We first provide an overview of
+common fabrication methods yielding nanowires, nanotubes and structures
+engineered in geometry~(change in diameter, shape) or material (segments,
+core-shell structures), shape or core-shell. We then review their magnetic
+properties: global measurements, magnetization states and switching, single
+domain wall statics and dynamics, and spin waves. For each aspect, both theory
+and experiments are surveyed. We also mention standard characterization
+techniques useful for these. We finally mention emerging applications of
+magnetic nanowires and nanotubes, along with the foreseen perspectives in the
+topic.",1808.04656v1
+2018-09-04,Chiral magnetic interlayer coupling in synthetic antiferromagnets,"The exchange coupling underlies ferroic magnetic coupling and is thus the key
+element that governs statics and dynamics of magnetic systems. This fundamental
+interaction comes in two flavors - symmetric and antisymmetric coupling. While
+symmetric coupling leads to ferro- and antiferromagnetism, antisymmetric
+coupling has attracted significant interest owing to its major role in
+promoting topologically non-trivial spin textures that promise high-speed and
+energy-efficient devices. So far, the antisymmetric exchange coupling rather
+short-ranged and limited to a single magnetic layer has been demonstrated,
+while the symmetric coupling also leads to long-range interlayer exchange
+coupling. Here, we report the missing component of the long-range antisymmetric
+interlayer exchange coupling in perpendicularly magnetized synthetic
+antiferromagnets with parallel and antiparallel magnetization alignments.
+Asymmetric hysteresis loops under an in-plane field unambiguously reveal a
+unidirectional and chiral nature of this novel interaction, which cannot be
+accounted for by existing coupling mechanisms, resulting in canted
+magnetization alignments. This can be explained by spin-orbit coupling combined
+with reduced symmetry in multilayers. This new class of chiral interaction
+provides an additional degree of freedom for engineering magnetic structures
+and promises to enable a new class of three-dimensional topological structures.",1809.01080v2
+2019-01-21,Paramagnetic squeezing of a uniformly expanding quark-gluon plasma in and out of equilibrium,"The plasma of quarks and gluons created in ultrarelativistic heavy-ion
+collisions turns out to be paramagnetic. In the presence of a background
+magnetic field, this paramagnetism thus leads to a pressure anisotropy, similar
+to anisotropies appearing in a viscous fluid. In the present paper, we use this
+analogy, and develop a framework similar to anisotropic hydrodynamics, to take
+the pressure anisotropy caused, in particular, by the nonvanishing
+magnetization of a plasma of quarks and gluons into account. We consider the
+first two moments of the classical Boltzmann equation in the presence of an
+electromagnetic source in the relaxation-time approximation, and derive a set
+of coupled differential equations for the anisotropy parameter $\xi_0$ and the
+effective temperature $\lambda_0$ of an ideal fluid with nonvanishing
+magnetization. We also extend this method to a dissipative fluid with finite
+magnetization in the presence of a strong and dynamical magnetic field. We
+present a systematic method leading to the one-particle distribution function
+of this magnetized dissipative medium in a first-order derivative expansion,
+and arrive at analytical expressions for the shear and bulk viscosities in
+terms of the anisotropy parameter $\xi$ and effective temperature $\lambda$. We
+then solve the corresponding differential equations for $(\xi_0,\lambda_0)$ and
+$(\xi,\lambda)$ numerically, and determine, in this way, the proper time and
+temperature dependence of the energy density, directional pressures, speed of
+sound, and the magnetic susceptibility of a longitudinally expanding magnetized
+quark-gluon plasma in and out of equilibrium.",1901.06928v2
+2019-02-14,High-speed domain wall racetracks in a magnetic insulator,"Recent reports of current-induced switching of ferrimagnetic oxides coupled
+to a heavy metal layer have opened realistic prospects for implementing
+magnetic insulators into electrically addressable spintronic devices. However,
+key aspects such as the configuration and dynamics of magnetic domain walls
+driven by electrical currents in insulating oxides remain unexplored. Here, we
+investigate the internal structure of the domain walls in Tm3Fe5O12 (TmIG) and
+TmIG/Pt bilayers and demonstrate their efficient manipulation by spin-orbit
+torques with velocities of up to 400 m s$^{-1}$ and minimal current threshold
+for domain wall flow of 5 x 10$^{6}$ A cm$^{-2}$. Domain wall racetracks
+embedded in TmIG are defined by the deposition of Pt current lines, which allow
+us to control the domain propagation and magnetization switching in selected
+regions of an extended magnetic layer. Scanning nitrogen-vacancy magnetometry
+reveals that the domain walls of thin TmIG films are N\'eel walls with
+left-handed chirality, with the domain wall magnetization rotating towards an
+intermediate N\'eel-Bloch configuration upon deposition of Pt. These results
+indicate the presence of a sizable interfacial Dzyaloshinskii-Moriya
+interaction in TmIG, which leads to novel possibilities to control the
+formation of chiral spin textures in magnetic insulators. Ultimately, domain
+wall racetracks provide an efficient scheme to pattern the magnetic landscape
+of TmIG in a fast and reversible way",1902.05639v1
+2019-02-25,Strong deformation of ferrofluid-filled elastic alginate capsules in inhomogenous magnetic fields,"We present a new system based on alginate gels for the encapsulation of a
+ferrofluid drop, which allows us to create millimeter-sized elastic capsules
+that are highly deformable by inhomogeneous magnetic fields. We use a
+combination of experimental and theoretical work in order to characterize and
+quantify the deformation behavior of these ferrofluid-filled capsules. We
+introduce a novel method for the direct encapsulation of unpolar liquids by
+sodium alginate. The addition of polar alcohol molecules allows us to
+encapsulate a ferrofluid as a single phase. This encapsulation method increases
+the amount of encapsulated magnetic nanoparticles resulting in high
+deformations and offers possible applications of capsules as actuators,
+switches, or valves in confined spaces like microfluidic devices. We determine
+both elastic moduli of the capsule shell, Young's modulus and Poisson's ratio,
+by employing two independent mechanical methods, spinning capsule measurements
+and capsule compression between parallel plates. We then show that the observed
+magnetic deformation can be fully understood from magnetic forces exerted by
+the ferrofluid on the capsule shell if the magnetic field distribution and
+magnetization properties of the ferrofluid are known. Using an iterative
+solution scheme that couples a finite element / boundary element method for the
+magnetic field calculation to the solution of the elastic shape equations, we
+achieve quantitative agreement between theory and experiment for deformed
+capsule shapes using the Young modulus from mechanical characterization and the
+surface Poisson ratio as a fit parameter. This detailed analysis confirms the
+results from mechanical characterization that the surface Poisson ratio of the
+alginate shell is close to unity, that is, deformations of the alginate shell
+are almost area conserving.",1902.09389v1
+2019-04-04,Topological-chiral magnetic interactions driven by emergent orbital magnetism,"Two hundred years ago, Andr\'e-Marie Amp\`ere discovered that electric loops
+in which currents of electrons are generated by a penetrating magnetic field
+can interact with each other. Here we show that Amp\`ere's observation can be
+transferred to the quantum realm of interactions between triangular plaquettes
+of spins on a lattice, where the electrical currents at the atomic scale are
+associated with a peculiar type of the orbital motion of electrons in response
+to the non-coplanarity of neighbouring spins playing the role of a magnetic
+field. The resulting topological orbital moment underlies the relation of the
+orbital dynamics with the topology of the spin structure. We demonstrate that
+the interactions of the topological orbital moments with each other and with
+the spins of the underlying lattice give rise to a new class of magnetic
+interactions $-$ topological chiral interactions $-$ which can dominate over
+the celebrated Dzyaloshinskii-Moriya interaction, thus opening a path for the
+realization of new classes of chiral magnetic materials with three-dimensional
+magnetization textures such as magnetic hopfions.",1904.02369v3
+2019-04-12,Data-Optimized Coronal Field Model: I. Proof of Concept,"Deriving the strength and direction of the three-dimensional (3D) magnetic
+field in the solar atmosphere is fundamental for understanding its dynamics.
+Volume information on the magnetic field mostly relies on coupling 3D
+reconstruction methods with photospheric and/or chromospheric surface vector
+magnetic fields. Infrared coronal polarimetry could provide additional
+information to better constrain magnetic field reconstructions. However,
+combining such data with reconstruction methods is challenging, e.g., because
+of the optical-thinness of the solar corona and the lack and limitations of
+stereoscopic polarimetry. To address these issues, we introduce the
+Data-Optimized Coronal Field Model (DOCFM) framework, a model-data fitting
+approach that combines a parametrized 3D generative model, e.g., a magnetic
+field extrapolation or a magnetohydrodynamic model, with forward modeling of
+coronal data. We test it with a parametrized flux rope insertion method and
+infrared coronal polarimetry where synthetic observations are created from a
+known ""ground truth"" physical state. We show that this framework allows us to
+accurately retrieve the ground truth 3D magnetic field of a set of force-free
+field solutions from the flux rope insertion method. In observational studies,
+the DOCFM will provide a means to force the solutions derived with different
+reconstruction methods to satisfy additional, common, coronal constraints. The
+DOCFM framework therefore opens new perspectives for the exploitation of
+coronal polarimetry in magnetic field reconstructions and for developing new
+techniques to more reliably infer the 3D magnetic fields that trigger solar
+flares and coronal mass ejections.",1904.06308v1
+2019-09-07,A Coupled A-H Formulation for Magneto-Thermal Transients in High-Temperature Superconducting Magnets,"The application of high-temperature superconductors to accelerator magnets
+for future particle colliders is under study. Numerical methods are crucial for
+an accurate evaluation of the complex dynamical behavior of the magnets,
+especially concerning the magnetic field quality and thermal behavior. We
+present a coupled $\textbf{A}$-$\textbf{H}$ field formulation for the analysis
+of magneto-thermal transients in accelerator magnets. The magnetic field
+strength $\textbf{H}$ accounts for the eddy current problem in the source
+regions containing the superconducting domains, while the magnetic vector
+potential $\textbf{A}$ represents the magnetoquasistatic problem in the normal
+and non-conducting domains. Furthermore, we include a slab approximation for
+the source regions, making the formulation suitable for large scale models
+composed of thousands of tapes. In this work, the relevant equations are
+derived and discussed, with emphasis on the coupling conditions. The weak
+formulation is derived, and numerical results are provided in order to both,
+verify the formulation and scale it to the size of an accelerator magnet.",1909.03312v3
+2019-12-10,Dynamical resilience to disorder: the dilute Hubbard model on the Lieb lattice,"In itinerant systems, electron-electron interactions may lead to the
+formation of local magnetic moments and their effective exchange coupling,
+which in turn gives rise to long-range magnetic order. Therefore, when moment
+formation is weakened, such as in the single-band Hubbard model on a square
+lattice with the on-site repulsion being randomly switched off on a fraction
+$x$ of sites, magnetic order is suppressed beyond some critical $x_c$, which
+was found to lie below the classical percolation threshold,
+$x_c^\text{(perc,sq)}$. Here we study dilute magnetism in flat band systems,
+namely in the Hubbard model on a `Lieb' lattice. Interestingly, we show that
+magnetic order persists to $x$ almost twice as large as the classical
+percolation threshold for the lattice, thus emphasizing the central role of
+electron itinerancy to the magnetic response. The analysis of the
+orbital-resolved order parameters reveals that the contribution of the
+four-fold coordinated `d' sites to magnetism is dramatically affected by
+dilution, while the localized `p' states of the flat band provide the dominant
+contribution to long-range correlations. We also examine the transport
+properties, which suggest the existence of an insulator-to-metal transition in
+the same range of the critical magnetic dilution.",1912.04918v3
+2020-01-08,Effect of collisions on the plasma sheath in the presence of an inhomogeneous magnetic field,"A low-pressure magnetized plasma is studied to find the dependency of sheath
+properties on ion-neutral collisions in presence of an inhomogeneous magnetic
+field. A self-consistent one-dimensional two-fluid hydrodynamic model is
+considered, and the system of equations is solved numerically. The study
+reveals that the width of the plasma sheath expands and space charge increases
+with collisions. The ion-neutral collisions and the inhomogeneous magnetic
+field restrict the ions to move towards the surface. The movement of the ions
+towards the wall can be controlled by choosing a suitable configuration of the
+magnetic field and ion-neutral collision frequency. A comparison between two
+different magnetic field configurations has been presented alongside to
+differentiate the commonly found scenarios in the field. The outcome of the
+study is supposed to help in understanding the complex dynamics of ions in
+plasma confinement and plasma processing of materials. Furthermore, the present
+work seeks to create a framework for two-fluid modeling of magnetized plasmas
+with any arbitrary magnetic field profiles. The analysis provided here is
+supposed to act as a basis for any future work in the respective field.",2001.02389v3
+2020-02-12,Hyperfine and quadrupole interactions for Dy isotopes in DyPc$_2$ molecules,"Nuclear spin levels play an important role in understanding magnetization
+dynamics and implementation and control of quantum bits in lanthanide-based
+single-molecule magnets. We investigate the hyperfine and nuclear quadrupole
+interactions for $^{161}$Dy and $^{163}$Dy nucleus in anionic DyPc$_2$
+(Pc=phthalocyanine) single-molecule magnets, using multiconfigurational
+ab-initio methods (beyond density-functional theory) including spin-orbit
+interaction. The two isotopes of Dy are chosen because the others have zero
+nuclear spin. Both isotopes have the nuclear spin $I=5/2$, although the
+magnitude and sign of the nuclear magnetic moment differ from each other. The
+large energy gap between the electronic ground and first-excited Kramers
+doublets, allows us to map the microscopic hyperfine and quadrupole interaction
+Hamiltonian onto an effective Hamiltonian with an electronic pseudo-spin
+$S_{\rm eff}=1/2$ that corresponds to the ground Kramers doublet. Our ab-initio
+calculations show that the coupling between the nuclear spin and electronic
+orbital angular momentum contributes the most to the hyperfine interaction and
+that both the hyperfine and nuclear quadrupole interactions for $^{161}$Dy and
+$^{163}$Dy nucleus are much smaller than those for $^{159}$Tb nucleus in
+TbPc$_2$ single-molecule magnets. The calculated separations of the
+electronic-nuclear levels are comparable to experimental data reported for
+$^{163}$DyPc$_2$. We demonstrate that hyperfine interaction for Dy Kramers ion
+leads to tunnel splitting (or quantum tunneling of magnetization) at zero
+field. This effect does not occur for TbPc$_2$ single-molecule magnets. The
+magnetic field values of the avoided level crossings for $^{161}$DyPc$_2$ and
+$^{163}$DyPc$_2$ are found to be noticeably different, which can be observed
+from experiment.",2002.05134v1
+2020-03-31,Skyrmions in antiferromagnets: thermal stability and the effect of external field and impurities,"Calculations of skyrmions in antiferromagnets (AFMs) are presented, and their
+properties compared with skyrmions in corresponding ferromagnets (FMs). The
+rates of skyrmion collapse and escape through the boundary of a track, as well
+as the binding to and collapse at a non-magnetic impurity, are calculated as a
+function of applied magnetic field. The activation energy for skyrmion
+annihilation is the same in AFMs and corresponding FMs in the absence of an
+applied magnetic field. The pre-exponential factor in the Arrhenius rate law
+is, however, different because skyrmion dynamics is different in the two
+systems. An applied magnetic field has opposite effects on skyrmions in the two
+types of materials. In AFMs the rate of collapse of skyrmions as well as the
+rate of escape through the edge of a magnetic strip decreases slightly with
+increasing field, while these rates increase strongly for a skyrmion in the
+corresponding FMs when the field is directed antiparallel to the magnetization
+in the center of the skyrmion. A non-magnetic impurity is less likely to trap a
+skyrmion in AFMs especially in the presence of a magnetic field. This, together
+with the established fact that a spin polarized current moves skyrmions in AFMs
+in the direction of the current, while in FMs skyrmions move at an angle to the
+current, demonstrates that skyrmions in AFMs have several advantageous
+properties over skyrmions in FMs for memory and spintronic devices.",2004.00095v2
+2020-04-07,Laser-induced magnetization precession in individual magnetoelastic domains of a multiferroic CoFeB/BaTiO$_3$ composite,"Using a magneto-optical pump-probe technique with micrometer spatial
+resolution we show that magnetization precession can be launched in individual
+magnetic domains imprinted in a Co$_{40}$Fe$_{40}$B$_{20}$ (CoFeB) layer by
+elastic coupling to ferroelectric domains in a BaTiO$_{3}$ substrate. The
+dependence of the precession parameters on external magnetic field strength and
+orientation reveal that by laser-induced ultrafast partial quenching of the
+magnetoelastic coupling parameter of CoFeB by $\approx$27% along with 10%
+ultrafast demagnetization trigger the magnetization precession. The relation
+between the laser-induced reduction of the magnetoelastic coupling and the
+demagnetization is approximated by the $n(n+1)/2$-law with n$\approx$2. This
+correspondence confirms the thermal origin of the laser-induced anisotropy
+change. Based on the analysis and modeling of the excited precession we find
+signatures of laser-induced precessional switching, which occurs when the
+magnetic field is applied along the hard magnetization axis and its value is
+close to the effective magnetoelastic anisotropy field. The precession
+excitation process in an individual magnetoelastic domain is found to be
+unaffected by neighboring domains. This makes laser-induced changes of
+magnetoelastic anisotropy a promising tool for driving magnetization dynamics
+and switching in composite multiferroics with spatial selectivity.",2004.03566v5
+2020-05-07,Spin caloritronics in a CrBr$_3$-based magnetic van der Waals heterostructure,"The recently reported magnetic ordering in insulating two-dimensional (2D)
+materials, such as chromium triiodide (CrI$_3$) and chromium tribromide
+(CrBr$_3$), opens new possibilities for the fabrication of magneto-electronic
+devices based on 2D systems. Inevitably, the magnetization and spin dynamics in
+2D magnets are strongly linked to Joule heating. Therefore, understanding the
+coupling between spin, charge and heat, i.e. spin caloritronic effects, is
+crucial. However, spin caloritronics in 2D ferromagnets remains mostly
+unexplored, due to their instability in air. Here we develop a fabrication
+method that integrates spin-active contacts with 2D magnets through hBN
+encapsulation, allowing us to explore the spin caloritronic effects in these
+materials. The angular dependence of the thermal spin signal of the CrBr$_3$/Pt
+system is studied, for different conditions of magnetic field and heating
+current. We highlight the presence of a significant magnetic proximity effect
+from CrBr$_3$ on Pt revealed by an anomalous Nernst effect in Pt, and suggest
+the contribution of the spin Seebeck effect from CrBr$_3$. These results pave
+the way for future magnonic devices using air-sensitive 2D magnetic insulators.",2005.03561v1
+2020-08-03,Magnetofluidic mixing of a ferrofluid droplet under the influence of time-dependent external field,"We report the experimental investigations on the mixing of a ferrofluid
+droplet with a non-magnetic fluid in the presence of a time-dependent magnetic
+field on an open surface microfluidic platform. The bright field visualization
+technique, in combination with the micro-PIV analysis, is carried out to
+explore the internal hydrodynamics of the ferrofluid droplet. Also, using the
+Laser-induced fluorescence (micro-LIF) technique, we quantify the mass transfer
+occurring between the two droplets, which in effect, determines the underlying
+mixing performance under the modulation of the frequency of the applied
+magnetic field. We show that the magnetic nanoparticles exhibit complex
+spatio-temporal movement inside the ferrofluid droplet domain under the
+influence of a time-dependent magnetic field, which, in turn, promotes the
+mixing efficiency in the convective mixing regime. Our analysis establishes
+that the movement of magnetic nanoparticles in presence of the time-periodic
+field strengthens the interfacial instability, which acts like a sparking agent
+to initiate an augmented mixing in the present scenario. By performing
+numerical simulations, we also review the onset of interfacial instability,
+mainly stemming from the susceptibility mismatch between the magnetic and
+non-magnetic fluids. Inferences of the present analysis, which focuses on the
+simple, wireless, robust, and low-cost open surface micromixing mechanism, will
+provide a potential solution for rapid droplets mixing without requiring pH
+level or ion concentration dependency of the fluids.",2008.00678v1
+2020-08-17,Multiphase Circumnuclear Gas in a Low-$β$ Disk: Turbulence and Magnetic Field Reversals,"We studied the magnetic field structures and dynamics of magnetized
+multiphase gas on parsec scales around supermassive black holes by using global
+3D magnetohydrodynamics (MHD) simulations. We considered the effect of
+radiative cooling and X-ray heating due to active galactic nuclei (AGNs). The
+gas disk consists of a multiphase gas with (1) cold ($\leq 10^3$ K) and thin,
+and (2) warm ($\sim 10^4$ K) and thick components with a wide range of number
+densities. The turbulent magnetic energy at maximum is comparable to the
+thermal and turbulent kinetic energies in the turbulent motion. We confirmed
+that the turbulent velocity of the warm gas in the ambient cold gas is caused
+by magnetoconvective instability. The turbulent magnetic field due to
+magnetorotational instability (MRI) is developed in the disk, but the mean
+toroidal magnetic field dominates and supports in a quasi-steady state, where
+the plasma-$\beta$, the ratio between gas pressure and magnetic pressure, is
+low ($\beta < 1$). As often seen in adiabatic MHD simulations of rotating
+disks, the direction of the mean toroidal field periodically reverses with time
+even in multiphase gas structures. The direction reversal is caused by magnetic
+flux vertically escaping from the disk and by the combination of the MRI and
+the Parker instability.",2008.07050v4
+2020-09-22,Magnon-mediated spin currents in Tm3Fe5O12/Pt with perpendicular magnetic anisotropy,"The control of pure spin currents carried by magnons in magnetic insulator
+(MI) garnet films with a robust perpendicular magnetic anisotropy (PMA) is of
+great interest to spintronic technology as they can be used to carry, transport
+and process information. Garnet films with PMA present labyrinth domain
+magnetic structures that enrich the magnetization dynamics, and could be
+employed in more efficient wave-based logic and memory computing devices. In
+MI/NM bilayers, where NM being a normal metal providing a strong spin-orbit
+coupling, the PMA benefits the spin-orbit torque (SOT) driven magnetization's
+switching by lowering the needed current and rendering the process faster,
+crucial for developing magnetic random-access memories (SOT-MRAM). In this
+work, we investigated the magnetic anisotropies in thulium iron garnet (TIG)
+films with PMA via ferromagnetic resonance measurements, followed by the
+excitation and detection of magnon-mediated pure spin currents in TIG/Pt driven
+by microwaves and heat currents. TIG films presented a Gilbert damping constant
+{\alpha}~0.01, with resonance fields above 3.5 kOe and half linewidths broader
+than 60 Oe, at 300 K and 9.5 GHz. The spin-to-charge current conversion through
+TIG/Pt was observed as a micro-voltage generated at the edges of the Pt film.
+The obtained spin Seebeck coefficient was 0.54 {\mu}V/K, confirming also the
+high interfacial spin transparency.",2009.10299v1
+2021-03-04,Fitting an Analytic Magnetic Field to a Prestellar Core,"We deploy and demonstrate the capabilities of the magnetic field model
+developed by Ewertowski & Basu (2013) by fitting observed polarimetry data of
+the prestellar core FeSt 1-457. The analytic hourglass magnetic field function
+derived directly from Maxwell's equations yields a central-to-surface magnetic
+field strength ratio in the equatorial plane, as well as magnetic field
+directions with relative magnitudes throughout the core. This fit emerges from
+a comparison of a single plane of the model with the polarization map that
+results from the integrated properties of the magnetic field and dust
+throughout the core. Importantly, our fit is independent of any assumed density
+profile of the core. We check the robustness of the fit by using the POLARIS
+code to create synthetic polarization maps that result from the integrated
+scattering and emission properties of the dust grains and their radiative
+transfer, employing an observationally-motivated density profile. We find that
+the synthetic polarization maps obtained from the model also provides a good
+fit to the observed polarimetry. Our model fits the striking feature of
+significant curvature of magnetic field lines in the outer part of FeSt 1-457.
+Combined with independent column density estimates, we infer that the core of
+size $R_{\rm gas}$ has a mildly supercritical mass-to-flux ratio and may have
+formed through dynamical motions starting from a significantly larger radius
+$R$. A breakdown of flux-freezing through neutral-ion slip (ambipolar
+diffusion) could be responsible for effecting such a transition from a
+large-scale magnetic field structure to a more compact gas structure.",2103.03324v1
+2021-04-28,Statistical description of coalescing magnetic islands via magnetic reconnection,"The physical picture of interacting magnetic islands provides a useful
+paradigm for certain plasma dynamics in a variety of physical environments,
+such as the solar corona, the heliosheath, and the Earth's magnetosphere. In
+this work, we derive an island kinetic equation to describe the evolution of
+the island distribution function (in area and in flux of islands) subject to a
+collisional integral designed to account for the role of magnetic reconnection
+during island mergers. This equation is used to study the inverse transfer of
+magnetic energy through the coalescence of magnetic islands in 2D. We solve our
+island kinetic equation numerically for three different types of initial
+distribution: delta-distribution, Gaussian and power-law distribution. The time
+evolution of several key quantities is found to agree well with our analytical
+predictions: magnetic energy decays as $\tilde t^{-1}$, the number of islands
+decreases as $\tilde t^{-1}$, and the averaged area of islands grows as $\tilde
+t$, where $\tilde t$ is the time normalized to the characteristic reconnection
+time scale of islands. General properties of the distribution function and the
+magnetic energy spectrum are also studied.",2104.13757v2
+2021-10-16,Annihilation of Magnetic Islands at the Top of Solar Flare Loops,"The dynamics of magnetic reconnection in the solar current sheet (CS) is
+studied by high-resolution 2.5-dimensional MHD simulation. With the commence of
+magnetic reconnection, a number of magnetic islands are formed intermittently
+and move quickly upward and downward along the CS. When colliding with the
+semi-closed flux of flare loops, the downflow islands cause a second
+reconnection with a rate even comparable with that in the main CS. Though the
+time-integrated magnetic energy release is still dominated by the reconnection
+in main CS, the second reconnection can release substantial magnetic energy,
+annihilating the main islands and generating secondary islands with various
+scales at the flare loop top. The distribution function of the flux of the
+second islands is found to follow a power-law varying from
+$f\left(\psi\right)\sim\psi^{-1}$ (small scale) to $\psi^{-2}$ (large scale),
+which seems to be independent with background plasma $\beta$ and if including
+thermal conduction. However, the spatial scale and the strength of the
+termination shocks driven by main reconnection outflows or islands decrease if
+$\beta$ increases or thermal conduction is included. We suggest that the
+annihilation of magnetic islands at the flare loop top, which is not included
+in the standard flare model, plays a non-negligible role in releasing magnetic
+energy to heat flare plasma and accelerate particles.",2110.08526v3
+2022-01-06,Magnetic fields in the formation of the first stars.--II Results,"Beginning with cosmological initial conditions at z=100, we simulate the
+effects of magnetic fields on the formation of Population III stars and compare
+our results with the predictions of Paper I. We use Gadget-2 to follow the
+evolution of the system while the field is weak. We introduce a new method for
+treating kinematic fields by tracking the evolution of the deformation tensor.
+The growth rate in this stage of the simulation is lower than expected for
+diffuse astrophysical plasmas, which have a very low resistivity (high magnetic
+Prandtl number); we attribute this to the large numerical resistivity in
+simulations, corresponding to a magnetic Prandtl number of order unity. When
+the magnetic field begins to be dynamically significant in the core of the
+minihalo at z=27, we map it onto a uniform grid and follow the evolution in an
+adaptive mesh refinement, MHD simulation in Orion2. The nonlinear evolution of
+the field in the Orion2 simulation violates flux-freezing and is consistent
+with the theory proposed by Xu & Lazarian. The fields approach equipartition
+with kinetic energy at densities ~ 10^10 - 10^12 cm^-3. When the same
+calculation is carried out in Orion2 with no magnetic fields, several
+protostars form, ranging in mass from ~ 1 to 30 M_sol with magnetic fields,
+only a single ~ 30 M_sol protostar forms by the end of the simulation. Magnetic
+fields thus suppress the formation of low-mass Pop III stars, yielding a
+top-heavy Pop III IMF and contributing to the absence of observed Pop III
+stars.",2201.02225v2
+2022-01-27,Jet Formation in 3D GRMHD Simulations of Bondi-Hoyle-Lyttleton Accretion,"A black hole (BH) travelling through a uniform, gaseous medium is described
+by Bondi-Hoyle-Lyttleton (BHL) accretion. If the medium is magnetized, then the
+black hole can produce relativistic outflows. We performed the first 3D,
+general-relativistic magnetohydrodynamics simulations of BHL accretion onto
+rapidly rotating black holes using the code H-AMR, where we mainly varied the
+strength of a background magnetic field that threads the medium. We found that
+the ensuing accretion continuously drags to the BH the magnetic flux, which
+accumulates near the event horizon until it becomes dynamically important.
+Depending on the strength of the background magnetic field, the BHs can
+sometimes launch relativistic jets with high enough power to drill out of the
+inner accretion flow, become bent by the headwind, and escape to large
+distances. While for stronger background magnetic fields the jets are
+continuously powered, at weaker field strengths they are intermittent, turning
+on and off depending on the fluctuating gas and magnetic flux distributions
+near the event horizon. We find that our jets reach extremely high efficiencies
+of $\sim100-300\%$, even in the absence of an accretion disk. We also
+calculated the drag forces exerted by the gas onto to the BH, finding that the
+presence of magnetic fields causes drag forces to be much less efficient than
+in unmagnetized BHL accretion, and sometimes become negative, accelerating the
+BH rather than slowing it down. Our results extend classical BHL accretion to
+rotating BHs moving through magnetized media and demonstrate that accretion and
+drag are significantly altered in this environment.",2201.11753v2
+2022-02-07,Coulomb correlations and magnetic properties of L1$_0$ FeCo: a DFT+DMFT study,"We consider electronic correlation effects and their impact on magnetic
+properties of tetragonally distorted chemically ordered FeCo alloys (L1$_0$
+structure) being a promising candidate for rare-earth-free permanent magnets.
+We employ a state-of-the-art method combining density functional and dynamical
+mean-field theory. According to our results, the predicted Curie temperature
+reduces with increase of lattice parameters ratio $c/a$ and reaches nearly 850
+K at ${c/a=1.22}$. For all considered $c/a$ from 1 to $\sqrt{2}$, we find
+well-localized magnetic moments on Fe sites, which are formed due to strong
+correlations originating from Hund's coupling. At the same time, magnetism of
+Co sites is more itinerant with a much less lifetime of local magnetic moments.
+However, these short-lived local moments are also formed due to Hund's
+exchange. Electronic states at Fe sites are characterized by a
+non-quasiparticle form of self-energies, while the ones for Co sites are found
+to have a Fermi-liquid-like shape with quasiparticle mass enhancement factor
+${m^*/m\sim 1.4}$, corresponding to moderately correlated metal. The strong
+electron correlations on Fe sites leading to Hund's metal behaviour can be
+explained by peculiarities of the density of states, which has pronounced peaks
+near the Fermi level, while weaker many-body effects on Co sites can be caused
+by stronger deviation from half-filling of their $3d$ states. The obtained
+momentum dependence of magnetic susceptibility suggests that the ferromagnetic
+ordering is the most favourable one except for the near vicinity of the fcc
+structure and the magnetic exchange is expected to be of RKKY type.",2202.03205v2
+2022-02-10,Magnetic phase diagram and cluster glass-like properties of stage-1 graphite intercalated FeCl$_3$,"We present a comprehensive investigation of the magnetic properties of
+stage-1 graphite intercalated FeCl$_3$ using a combination of DC and AC
+magnetic susceptibility, thermoremanent magnetization and field dependent
+magnetization measurements. This van der Waals system, with a centrosymmetric
+honeycomb lattice, combines frustration and disorder, due to intercalation, and
+may be hosting topologically non-trivial magnetic phases. Our study identifies
+two magnetic phase transitions at $T_{f1} \approx $ 4.2 K and at $T_{f2}
+\approx $ 2.7 K. We find that the paramagnetic state, for $T > T_{f1}$, is
+dominated by short-range ferromagnetic correlations. These build up well above
+$T_{f1}$ and lead to a significant change in magnetic entropy, which reaches
+$\Delta S_M^{Pk} = $ -5.52 J kg$^{-1}$ K$^{-1}$ at 7 T. Between $T_{f1}$ and
+$T_{f2}$ we observe slow spin dynamics characteristic of a cluster glass-like
+state, whereas for $T$ $ < $ $T_{f2}$ our results indicate the onset of a low
+temperature long range ordered state. The analysis of the experimental results
+leads to a complex phase diagram, which may serve as a reference for future
+investigations searching for topological non-trivial phases in this system.",2202.04983v1
+2022-02-16,Magnetic support for neutrino-driven explosion of 3D non-rotating core-collapse supernova models,"The impact of the magnetic field on postbounce supernova dynamics of
+non-rotating stellar cores is studied by performing three-dimensional
+magnetohydrodynamics simulations with spectral neutrino transport. The
+explodability of strongly and weakly magnetized models of $20$ and $27$
+$M_{\odot}$ pre-supernova progenitors are compared. We find that although the
+efficiency for the conversion of the neutrino heating into turbulent energy
+including magnetic fields in the gain region is not significantly different
+between the strong and weak field models, the amplified magnetic field due to
+the neutrino-driven convection on large hot bubbles just behind stalled shock
+results in a faster and more energetic explosion in the strongly magnetized
+models. In addition, by comparing the difference between the 2nd- and 5th-order
+spatial accuracy of the simulation in the strong field model for $27$
+$M_{\odot}$ progenitor, we also find that the higher order accuracy in space is
+beneficial to the explosion because it enhances the growth of neutrino-driven
+convection in the gain region. Based on our results of core-collapse supernova
+simulations for the non-rotating model, a new possibility for the origin of the
+magnetic field of the protoneutron star (PNS) is proposed. The magnetic field
+is accumulated and amplified to magnetar level, that is, $\mathcal{O}(10^{14})$
+G, in the convectively stable shell near the PNS surface.",2202.07967v2
+2022-03-21,Magnetic fields in star formation: from clouds to cores,"In this chapter we review recent advances in understanding the roles that
+magnetic fields play throughout the star formation process, gained through
+observations and simulations of molecular clouds, the dense, star-forming phase
+of the magnetised, turbulent interstellar medium (ISM). Recent results broadly
+support a picture in which the magnetic fields of molecular clouds transition
+from being gravitationally sub-critical and near equipartition with turbulence
+in low-density cloud envelopes, to being energetically sub-dominant in dense,
+gravitationally unstable star-forming cores. Magnetic fields appear to play an
+important role in the formation of cloud substructure by setting preferred
+directions for large-scale gas flows in molecular clouds, and can direct the
+accretion of material onto star-forming filaments and hubs. Low-mass star
+formation may proceed in environments close to magnetic criticality; high-mass
+star formation remains less well-understood, but may proceed in more
+supercritical environments. The interaction between magnetic fields and
+(proto)stellar feedback may be particularly important in setting star formation
+efficiency. We also review a range of widely-used techniques for quantifying
+the dynamic importance of magnetic fields, concluding that better-calibrated
+diagnostics are required in order to use the spectacular range of forthcoming
+observations and simulations to quantify our emerging understanding of how
+magnetic fields influence the outcome of the star formation process.",2203.11179v1
+2022-04-27,The Rise of Buoyant Magnetic Structures through Convection with a Background Magnetic Field,"Inspired by observations of sunspots embedded in active regions, it is often
+assumed that large-scale, strong magnetic flux emerges from the Sun's deep
+interior in the form of arched, cylindrical structures, colloquially known as
+flux tubes. Here, we continue to examine the different dynamics encountered
+when these structures are considered as concentrations in a volume-filling
+magnetic field rather than as isolated entities in a field-free background. Via
+2.5D numerical simulations, we consider the buoyant rise of magnetic flux
+concentrations from a radiative zone through an overshooting convection zone
+that self-consistently (via magnetic pumping) arranges a volume-filling
+large-scale background field. This work extends earlier papers that considered
+the evolution of such structures in a purely adiabatic stratification with an
+assumed form of the background field. This earlier work established the
+existence of a bias that created an increased likelihood of successful rise for
+magnetic structures with one (relative) orientation of twist and a decreased
+likelihood for the other. When applied to the solar context, this bias is
+commensurate with the solar hemispherical helicity rules (SHHR). This paper
+establishes the robustness of this selection mechanism in a model incorporating
+a more realistic background state, consisting of overshooting convection and a
+turbulently-pumped mean magnetic field. Ultimately, convection only weakly
+influences the selection mechanism, since it is enacted at the initiation of
+the rise, at the edge of the overshoot zone. Convection does however add
+another layer of statistical fluctuations to the bias, which we investigate in
+order to explain variations in the SHHR.",2204.13078v1
+2022-04-29,Novel magnetic ordering in LiYbO2 probed by muon spin relaxation,"The stretched diamond lattice material LiYbO2 has recently been reported to
+exhibit two magnetic transitions ($T_{N1} = 1.1 K$, $T_{N2} = 0.45 K$) via
+specific heat, magnetization, and neutron scattering measurements [Bordelon et
+al., Phys. Rev. B 103, 014420 (2021)]. Here we report complementary magnetic
+measurements down to T = 0.28 K via the local probe technique of muon spin
+relaxation. While we observe a rapid increase in the zero-field muon
+depolarization rate at $T_{N1}$, we do not observe any spontaneous muon
+precession for $T < T_{N1}$, which is typically associated with long-range
+magnetic ordering. The depolarization rate in the ordered state shows a
+surprising sensitivity to magnetic fields applied along the initial spin
+polarization direction. Using a simple one-dimensional model, we show that
+these results are consistent with the unusual random-phase bipartite
+incommensurate magnetic structure proposed by Bordelon et al. for the
+intermediate temperature range $T_{N2} < T < T_{N1}$. We also find evidence for
+temperature-independent magnetic fluctuations persisting to our lowest
+temperatures, but no obvious signature of the transition or spontaneous muon
+precession at and below TN2, respectively. This result is suggestive of quantum
+dynamics within a highly degenerate ground state.",2205.00052v2
+2022-05-24,Electronic structure of the frustrated diamond lattice magnet NiRh$_2$O$_4$,"The $A$-site spinel NiRh$_2$O$_4$ is the only known realization of a spin-1
+diamond lattice magnet and is predicted to host unconventional magnetic
+phenomena driven by frustrated nearest and next-nearest neighbor exchange as
+well as orbital degeneracy. Previous works found no sign of magnetic order but
+found a gapped dispersive magnetic excitation indicating a possible valence
+bond magnetic ground state. However, the presence of many competing low energy
+degrees of freedom and limited empirical microscopic constraints complicates
+further analysis. Here, we carry out resonant inelastic x-ray scattering (RIXS)
+and x-ray absorption spectroscopy (XAS) to characterize the local electronic
+structure of NiRh$_2$O$_4$. The RIXS data can be partly described by a
+single-ion model for tetrahedrally coordinated Ni$^{2+}$ and indicates a
+tetragonal distortion $\Delta t_2\!=\!70$ meV that splits the $t_2$ orbitals
+into a high energy orbital singlet and lower energy orbital doublet. We
+identify features of the RIXS spectra that are consistent with a Rh-Ni two-site
+excitation indicating strong metal-metal hybridization mediated by oxygen in
+NiRh$_2$O$_4$. We also identify signatures of electron-phonon coupling through
+the appearance of phonon sidebands that dress crystal field excitations. These
+results establish the key energy scales relevant to the magnetism in
+NiRh$_2$O$_4$ and further demonstrate that covalency and lattice dynamics play
+essential roles in controlling the magnetic ground states of $A$-site spinels.",2205.12296v1
+2022-05-29,"Quantum Scattering Theory of Spin Transfer Torque, Spin Pumping and Fluctuations","Spin transfer torque and spin pumping are central reciprocal phenomena in
+spintronics. These phenomena occur in hybrid systems of normal metals and
+magnets. Spin transfer is the conversion of spin currents in metals to a torque
+on the magnetization of magnets. Spin pumping is the emission of spin currents
+from precessing magnets. Here, we demonstrate a general way to understand these
+effects within a quantum out-of-equilibrium path-integral model. Our results
+agree with known expressions for spin transfer and spin pumping in terms of
+transverse (mixing) conductances when there are no fluctuations. However, at a
+finite temperature, frequency or spin accumulation, the magnet also experiences
+fluctuating torques. In the classical regime, when the thermal energy is larger
+than the bias voltage and precession frequency, we reproduce the classical
+Brownian-Langevin forces associated with spin transfer and spin pumping. At low
+temperatures, in the quantum regime, we demonstrate that magnetization
+fluctuations differ in the elastic and inelastic electron transport regimes.
+Furthermore, we show how additional transport coefficients beyond the mixing
+conductance govern the fluctuations. Some of these coefficients are related to
+electron shot noise because of the discrete spin angular momentum of electrons.
+We estimate the fluctuation coefficients of clean, tunnel, and disordered
+junctions and in the case of an insulating magnet. Our results open a path for
+exploring low-temperature magnetization dynamics and spin caloritronics.",2205.14672v2
+2022-07-02,Spin excitations in the quantum dipolar magnet Yb(BaBO$_3$)$_3$,"We report results of magnetization, specific-heat and muon-spin relaxation
+measurements on single crystals of disorder-free Yb$^{3+}$ triangular lattice
+Yb(BaBO$_3$)$_3$. The magnetization experiments show anisotropic magnetic
+properties with Curie-Weiss temperatures $\theta_{\perp}=-1.40$~K ($H \perp c$)
+and $\theta_{\parallel}=-1.16$~K ($H \parallel c$) determined from low
+temperature data. The absence of both long-range antiferromagnetic order and
+spin freezing is confirmed down to 0.27 K at zero field. A two-level Schottky
+anomaly due to the opening of the ground-state Kramers doublet is observed from
+the low-temperature specific-heat measurements when the applied magnetic fields
+$\mu_0H >0.7$~T. At zero field, the increase of both $C_{\rm mag}/T$ and the
+muon spin relaxation rate $\lambda$ below 1~K is due to the electronic spin
+excitations, which often exist in quantum magnets where dipole-dipole
+interaction creates an anisotropy of magnetic properties. The spin excitation
+is also supported by the unusual maximum of field dependence of $\lambda$ due
+to the field-induced increase of the density of excitations. We argue that
+dipolar interaction is dominant and induces the spin dynamics in the quantum
+magnet Yb(BaBO$_3$)$_3$.",2207.00702v1
+2022-08-11,"Trion magnetic polarons in (Cd,Mn)Te/(Cd,Mn,Mg)Te quantum wells","A trion magnetic polaron formed by the exchange interaction of a positively
+charged exciton (trion) with localized spins of Mn$^{2+}$ ions is found
+experimentally in a 4\,nm wide
+Cd$_{0.98}$Mn$_{0.02}$Te/Cd$_{0.78}$Mn$_{0.02}$Mg$_{0.2}$Te quantum well
+containing resident holes. The experiment is performed at a temperature of 1.6
+K using resonant excitation of the trion with circularly polarized light. The
+trion is formed from a resident hole, which is in a hole magnetic polaron
+state, and a photogenerated electron-hole pair. The dynamical evolution from
+the hole magnetic polaron to the trion magnetic polaron is accompanied by a
+spin-flip of the electron, which results in negative circular polarization of
+the photoluminescence. The degree of circular polarization reaches $-8\%$ at
+zero magnetic field and strongly decreases in transverse magnetic fields
+exceeding 0.2 T. Our model considerations show that different localization
+sizes of the resident and photogenerated holes and the resulting difference in
+their exchange interaction with the Mn$^{2+}$ spins maintains Mn spin
+polarization. The resulting exchange field of Mn acting on the electron
+provides a robust spin polarization of the trion magnetic polaron. We evaluate
+the electron exchange energy in the T$^+$MP to be 0.19~meV, and the T$^+$MP
+binding energy to be about 0.5 - 1 meV.",2208.05943v1
+2022-10-18,Spin re-orientation induced anisotropic magnetoresistance switching in LaCo$_{0.5}$Ni$_{0.5}$O$_{3-δ}$ thin films,"Realization of novel functionalities by tuning magnetic interactions in rare
+earth perovskite oxide thin films opens up exciting technological prospects.
+Strain-induced tuning of magnetic interactions in rare earth cobaltates and
+nickelates is of central importance due to their versatility in electronic
+transport properties. Here we reported the spin re-orientation induced
+switching of anisotropic magnetoresistance (AMR) and its tunability with strain
+in epitaxial LaCo$_{0.5}$Ni$_{0.5}$O$_{3-\delta}$ thin films across the
+ferromagnetic transition. Moreover, with strain tuning, we could observe a
+two-fold to four-fold symmetry crossover in AMR across the magnetic transition
+temperature. The magnetization measurements revealed an onset of ferromagnetic
+transition around 50 K, and a further reduction in temperature showed a subtle
+change in the magnetization dynamics, which reduced the ferromagnetic
+long-range ordering and introduced glassiness in the system. X-ray absorption
+and X-ray magnetic circular dichroism spectroscopy measurements over Co and Ni
+L edges revealed the Co spin state transition below the magnetic transition
+temperature leading to the AMR switching and also the presence of Ni$^{2+}$ and
+Co$^{4+}$ ions evidencing the charge transfer from Ni to Co ions. Our work
+demonstrated the tunability of magnetic interactions mediated electronic
+transport in cobaltate-nickelate thin films, which is relevant in understanding
+Ni-Co interactions in oxides for their technological applications such as in
+AMR sensors.",2210.09608v3
+2022-10-27,Dynamics of a relativistic jet through magnetized media,"The merger of two neutron stars (NSs) produces the emission of gravitational
+waves, the formation of a compact object surrounded by a dense and magnetized
+environment, and the launching of a collimated and relativistic jet, which will
+eventually produce a short gamma-ray burst (SGRB). The interaction of the jet
+with the environment has been shown to play a major role in shaping the
+structure of the outflow that eventually powers the gamma-ray emission. In this
+paper, we present a set of 2.5 dimensional RMHD simulations that follow the
+evolution of a relativistic non-magnetized jet through a medium with different
+magnetization levels, as produced after the merger of two NSs. We find that the
+predominant consequence of a magnetized ambient medium is that of suppressing
+instabilities within the jet, and preventing the formation of a series of
+collimation shocks. One implication of this is that internal shocks lose
+efficiency, causing bursts with low-luminosity prompt emission. On the other
+hand, the jet-head velocity and the induced magnetization within the jet are
+fairly independent from the magnetization of the ambient medium. Future
+numerical studies with a larger domain are necessary to obtain light curves and
+spectra in order to better understand the role of magnetized media.",2210.15698v1
+2023-01-12,Shear-driven magnetic buoyancy in the solar tachocline: The mean electromotive force due to rotation,"The leading theoretical paradigm for the Sun's magnetic cycle is an
+$\alpha\omega$-dynamo process, in which a combination of differential rotation
+and turbulent, helical flows produces a large-scale magnetic field that
+reverses every 11 years. Most $\alpha\omega$ solar dynamo models rely on
+differential rotation in the solar tachocline to generate a strong toroidal
+field. The most problematic part of such models is then the production of the
+large-scale poloidal field, via a process known as the $\alpha$-effect. Whilst
+this is usually attributed to small-scale convective motions under the
+influence of rotation, the efficiency of this regenerative process has been
+called into question by some numerical simulations. Motivated by likely
+conditions within the tachocline, the aim of this paper is to investigate an
+alternative mechanism for the poloidal field regeneration, namely the magnetic
+buoyancy instability in a shear-generated, rotating magnetic layer. We use a
+local, fully compressible model in which an imposed vertical shear winds up an
+initially vertical magnetic field. The field ultimately becomes buoyantly
+unstable, and we measure the resulting mean electromotive force (EMF). For
+sufficiently rapid rotation, we find that a significant component of the mean
+EMF is aligned with the direction of the mean magnetic field, which is the
+characteristic feature of the classical $\alpha\omega$-dynamo model. Our
+results therefore suggest that magnetic buoyancy could contribute directly to
+the generation of large-scale poloidal field in the Sun.",2301.05067v1
+2023-01-19,Stereoscopic Observation of Simultaneous Longitudinal and Transverse Oscillations in a Single Filament Driven by Two-sided-loop Jet,"We report the first observations of simultaneous large-amplitude longitudinal
+and transverse oscillations of a quiescent filament trigged by a two-sided-loop
+jet formed by the magnetic reconnection between the filament and an emerging
+loop in the filament channel, recorded by the Solar Dynamics Observatory and
+the Solar TErrestrial RElations Observatory. The north arm of the jet firstly
+pushed the filament mass moving northwardly along the magnetic field lines
+consisting of the coronal cavity, then some elevated filament mass fell back
+and started to oscillate longitudinally at the bottom of the cavity (i.e., the
+magnetic dip). The northernmost part of the filament also showed transverse
+oscillation simultaneously. The amplitude and period of the longitudinal
+(transverse) oscillation are 12.96 (2.99) Mm and 1.18 (0.33) hours,
+respectively. By using the method of filament seismology, the radius of
+curvature of the magnetic dip is about 151 Mm, consistent with that obtained by
+the 3D reconstruction (166 Mm). Using different physical parameters of the
+observed longitudinal and transverse oscillations, the magnetic field strength
+of the filament is estimated to be about 23 and 21 Gauss, respectively. By
+calculating the energy of the moving filament mass, the minimum energy of the
+jet is estimated to be about 1.96 x 10^28 erg. We conclude that the newly
+formed jet can not only trigger simultaneous longitudinal and transverse
+oscillations in a single filament, but also can be used as a seismology tool
+for diagnosing filament information, such as the magnetic structure, magnetic
+field strength, and magnetic twists.",2301.07989v1
+2023-02-14,Structural and spin-glass properties of single crystal $J_{eff}$ = 1/2 pyrochlore antiferromagnet NaCdCo$_2$F$_7$ : correlating $T_f$ with magnetic-bond-disorder,"Weak bond disorder disrupts the expected spin-liquid ground-state of the
+ideal $S$ = 1/2 Heisenberg pyrochlore antiferromagnet. Here we introduce a
+single crystal study of the structural and magnetic properties of the
+bond-disordered pyrochlore NaCdCo$_2$F$_7$. The magnetic susceptibility appears
+isotropic, with a large negative Curie-Weiss temperature ($\theta_{CW}$ =
+-108(1) K), however no magnetic order is observed on cooling until a spin-glass
+transition at $T_f$ = 4.0 K. AC-susceptibility measurements show a
+frequency-dependent shift of the associated cusp in $\chi$ at $T_f$, that can
+be fitted well by the empirical Vogel-Fulcher law. The magnetic moment of
+$\mu_{eff}$ = 5.4(1) $\mu_{B}$/Co$^{2+}$ indicates a significant orbital
+contribution and heat capacity measurements show that down to 1.8 K, well below
+$T_f$, only $S_{mag}$ ~2/3 Rln(2) of the magnetic entropy is recovered,
+suggestive of residual continued dynamics. Structural and magnetism comparisons
+are made with the other known members of the Na$A$Co$_2$F$_7$ family ($A$ =
+Ca$^{2+}$, Sr$^{2+}$), confirming the expected relationship between spin-glass
+freezing temperature, and extent of magnetic bond disorder brought about by the
+size mismatch between A-site ions.",2302.06919v2
+2023-02-21,Coronal Magnetic Fields derived with Images acquired during the 21 August 2017 Total Solar Eclipse,"The coronal magnetic field, despite its overwhelming importance to the
+physics and dynamics of the corona, has only rarely been measured. Here, the
+electron density maps derived from images acquired during the total solar
+eclipse of August 21st, 2017 are employed to demonstrate a new technique to
+measure the coronal magnetic fields. The strength of the coronal magnetic
+fields is derived with a semiempirical formula relating the plasma magnetic
+energy density to the gravitational potential energy. The resulting values are
+compared with those provided by more advanced coronal field reconstruction
+methods based on MHD simulations of the whole corona starting from photospheric
+field measurements, finding a very good agreement. Other parameters such as the
+plasma-$\beta$ and Alfv\'en velocity are also derived and compared with those
+of MHD simulations. Moreover, the plane-of-sky (POS) orientation of the coronal
+magnetic fields is derived from the observed inclination of the coronal
+features in the filtered images, also finding a close agreement with magnetic
+field reconstructions. Hence, this work demonstrates for the first time that
+the 2D distribution of coronal electron densities measured during total solar
+eclipses is sufficient to provide the coronal magnetic field strengths and
+inclinations projected on the POS. These are among the main missing pieces of
+information that limited so far our understanding of physical phenomena going
+on in the solar corona.",2302.10647v1
+2023-05-03,Correlation Induced Magnetic Topological Phases in Mixed-Valence Compound SmB6,"SmB6 is a mixed-valence compound with flat f-electron bands that have a
+propensity to magnetism. Here, using a realistic Gamma8 quartet model, we
+investigate the dynamical spin susceptibility and describe the in-gap
+collective mode observed in neutron scattering experiments. We show that as the
+Sm valence increases with pressure, the magnetic correlations enhance and SmB6
+undergoes a first-order phase transition into a metallic antiferromagnetic
+state, whose symmetry depends on the model parameters. The magnetic orderings
+give rise to distinct band topologies: while the A-type order leads to an
+overlap between valence and conduction bands in the form of Dirac nodal lines,
+the G-type order has a negative indirect gap with weak Z2 indices. We also
+consider the spin polarized phase under a strong magnetic field, and find that
+it exhibits Weyl points as well as nodal lines close to the Fermi level. The
+magnetic phases show markedly different surface states and tunable bulk
+transport properties, with important implications for experiments. Our theory
+predicts that a magnetic order can be stabilized also by lifting the Gamma8
+cubic symmetry, thus explaining the surface magnetism reported in SmB6.",2305.02454v2
+2023-06-05,Stockmayer supracolloidal magnetic polymers under the influence of an applied magnetic field and a shear flow,"The idea of creating magnetically controllable colloids whose rheological
+properties can be finely tuned on the nano- or micro-scale has caused a lot of
+experimental and theoretical effort. The latter resulted in systems whose
+building blocks are ranging between single magnetic nanoparticles to complexes
+of such nanoparticles bound together by various mechanisms. The binding can be
+either chemical or physical, reversible or not. One way to create a system that
+is physically bound is to let the precrosslinked supracolloidal magnetic
+polymers (SMPs) to cluster due to both magnetic and Van-der-Waals-type forces.
+The topology of the SMPs in this case can be used to tune both magnetic and
+rheological properties of the resulting clusters as we show in this work. We
+employ Molecular Dynamics computer simulations coupled with explicit solvent
+modelled by Lattice-Boltzmann method in order to model the behaviour of the
+clusters formed by chains, rings, X- and Y-shaped SMPs in a shear flow with
+externally applied magnetic field. We find that the shear stabilises the shape
+of the clusters not letting them extend in the direction of the field and
+disintegrate. The clusters that show the highest response to an applied field
+and higher shape stability are those made of Y- and X-like SMPs.",2306.03005v1
+2023-06-16,Synchrotron Intensity Gradient Revealing Magnetic Fields in Galaxy Clusters,"Magnetic fields and their dynamical interplay with matter in galaxy clusters
+contribute to the physical properties and evolution of the intracluster medium.
+However, the current understanding of the origin and properties of cluster
+magnetic fields is still limited by observational challenges. In this article,
+we map the magnetic fields at hundreds-kpc scales of five clusters RXC J1314.4
+-2515, Abell 2345, Abell 3376, MCXC J0352.4 -7401, and El Gordo using the
+innovative synchrotron intensity gradient technique in conjunction with
+high-resolution radio observations from JVLA and MeerKAT. We demonstrate that
+magnetic field orientation of radio relics derived from synchrotron intensity
+gradients is in very good agreement with that obtained with synchrotron
+polarization. Most important, synchrotron intensity gradients is not limited by
+Faraday depolarization in the cluster central regions and allows us to map
+magnetic fields in the radio halos of RXC J1314.4 -2515 and El Gordo. We find
+that magnetic fields in radio halos exihibit a preferential direction along the
+major merger axis and show turbulent structures at higher angular resolution.
+Results are consistent with expectations from numerical simulations which
+predict turbulent magnetic fields in cluster mergers that are stirred and
+amplified by matter motions.",2306.10011v2
+2023-07-11,"Magnetic and quadrupole moments of the $Z_{c}(4020)^+$, $Z_{c}(4050)^+$, and $Z_{c}(4600)^{+}$ states in the diquark-antidiquark picture","The magnetic and quadrupole moments of the $Z_{c}(4020)^+$, $Z_{c}(4050)^+$
+and $Z_{c}(4600)^{+}$ states are calculated within the QCD light-cone sum
+rules. The compact diquark-antidiquark interpolating currents and the
+distribution amplitudes of the on-shell photon are used to extract the magnetic
+and quadrupole moments of these states. The magnetic moments are acquired as
+$\mu_{Z_{c}} = 0.50 ^{+0.22}_{-0.22}~\mu_N$, $\mu_{Z^{1}_{c}}=1.22
+^{+0.34}_{-0.32}~\mu_N$, and $\mu_{Z^2_{c}}=2.40 ^{+0.53}_{-0.48}~\mu_N$ for
+the $Z_{c}(4020)^+$, $Z_{c}(4050)^+$ and $Z_{c}(4600)^{+}$ states,
+respectively. The magnetic moments evaluated for the $Z_{c}4020)^+$,
+$Z_{c}(4050)^+$ and $Z_{c}(4600)^{+}$ states are sufficiently large to be
+experimentally measurable. The magnetic moment is an excellent platform for
+studying the internal structure of hadrons governed by the quark-gluon dynamics
+of QCD because it is the leading-order response of a bound system to a weak
+external magnetic field. The quadrupole moment results are
+$\mathcal{D}_{Z_c}=(0.20 ^{+0.05}_{-0.04}) \times 10^{-3}~\mbox{fm}^2 $,
+$\mathcal{D}_{Z_c^1}=(0.57 ^{+0.07}_{-0.08}) \times 10^{-3}~\mbox{fm}^2 $, and
+$\mathcal{D}_{Z_c^2}=(0.30 ^{+0.05}_{-0.04}) \times 10^{-3}~\mbox{fm}^2 $ for
+the $Z_{c}(4020)^+$, $Z_{c}(4050)^+$ and $Z_{c}(4600)^{+}$ states,
+respectively. We obtain a non-zero, but small, value for the quadrupole moments
+of the $Z_c$ states, which indicates a non-spherical charge distribution. The
+nature and internal structure of these states can be elucidated by comparing
+future experimental data on the magnetic and quadrupole moments of the
+$Z_{c}(4020)^+$, $Z_{c}(4050)^+$, and $Z_{c}(4600)^{+}$ states with the results
+of the present study.",2307.05028v3
+2023-10-20,X-Type Antiferromagnets,"Magnetically ordered materials reveal various types of magnetic moment
+alignment that affects their functional properties. This makes the exploration
+of unconventional magnetic orderings promising for the discovery of new
+physical phenomena and spintronic applications. Here, we introduce cross-chain
+antiferromagnets, dubbed X-type antiferromagnets, as an uncharted class of
+magnetically ordered crystals, where the stacking of two magnetic sublattices
+form an orthogonal pattern of intersecting atomic chains. These largely
+unexplored X-type antiferromagnets reveal unique spin-dependent transport
+properties that are not present in conventional magnets. Using $\beta$-Fe2PO5
+as a representative example of such X-type antiferromagnets, we predict the
+emergence of sublattice-selective spin-polarized transport, where one magnetic
+sublattice is conducting, while the other is not. As a result, spin torque can
+be exerted solely on a single sublattice, leading to unconventional ultrafast
+dynamics of the N\`eel vector capable of deterministic switching of the
+antiferromagnetic domains. Our work uncovers a previously overlooked type of
+magnetic moment alignment in antiferromagnets and reveals sublattice-selective
+physical properties promising for high-performance spintronic applications.",2310.13271v1
+2023-11-01,Generation of Strong Fields to Study the Phase Transitions of Magnetized Warm Dense Matter,"Warm dense matter is a regime where Fermi degenerate electrons take an
+important role in the macroscopic properties of a material. While recent
+experiments hinged us closer to better understanding the unmagnetized processes
+in such dense materials, their magnetized counterpart has been more difficult
+to study since kilo-Tesla order magnetic fields are required. Although there
+are examples of field compression generating such fields by compressing
+pre-magnetized targets, this approach uses a closed configuration, where a
+converging liner compresses the magnetic flux dynamically. The plasma produced
+to compress the field is so dense that the fast-heating laser beam required to
+form warm dense matter cannot penetrate where the field is the highest. In this
+paper, numerical simulations are used to show that magnetic field compression
+is also possible by shining the laser beams onto the inner surface of the
+target, rather than on the outer surface. This approach relies on field
+compression done by a low-density high-temperature plasma, rather than a
+high-density low-temperature plasma, used in the more conventional approach.
+With this novel configuration, the region of the large magnetic field is now
+mostly free of plasma so the heating beam can reach the sample, located where
+the magnetic field is the strongest.",2311.00879v2
+2023-11-06,Controlling effective field contributions to laser-induced magnetization precession by heterostructure design,"Nanoscale heterostructure design can control laser-induced heat dissipation
+and strain propagation as well as their efficiency for driving magnetization
+precession. We use insulating MgO layers incorporated into metallic Pt-Cu-Ni
+heterostructures to block the propagation of hot electrons. Ultrafast x-ray
+diffraction (UXRD) experiments quantify how this enables controlling the
+spatio-temporal shape of the transient heat and strain, which drive the
+magnetization dynamics in the Ni layer. The frequency of the magnetization
+precession observed by the time-resolved magneto-optical Kerr effect (MOKE) in
+polar geometry is systematically tuned by the magnetic field orientation. The
+combined experimental analysis (UXRD and MOKE) and modeling of transient
+strain, heat and magnetization uniquely highlights the importance of
+quasi-static strain as a driver of precession, when the magnetic material is
+rapidly heated via electrons. The concomitant effective field change
+originating from demagnetization partially compensates the change induced by
+quasi-static strain. Tailored strain pulses shaped via the nanoscale
+heterostructure design provide an equally efficient, phase-matched driver of
+precession, paving the way for opto-magneto-acoustic devices with low heat
+energy deposited in the magnetic layer.",2311.03158v2
+2023-11-11,Double-Free-Layer Stochastic Magnetic Tunnel Junctions with Synthetic Antiferromagnets,"Stochastic magnetic tunnel junctions (sMTJ) using low-barrier nanomagnets
+have shown promise as fast, energy-efficient, and scalable building blocks for
+probabilistic computing. Despite recent experimental and theoretical progress,
+sMTJs exhibiting the ideal characteristics necessary for probabilistic bits
+(p-bit) are still lacking. Ideally, the sMTJs should have (a) voltage bias
+independence preventing read disturbance (b) uniform randomness in the
+magnetization angle between the free layers, and (c) fast fluctuations without
+requiring external magnetic fields while being robust to magnetic field
+perturbations. Here, we propose a new design satisfying all of these
+requirements, using double-free-layer sMTJs with synthetic antiferromagnets
+(SAF). We evaluate the proposed sMTJ design with experimentally benchmarked
+spin-circuit models accounting for transport physics, coupled with the
+stochastic Landau-Lifshitz-Gilbert equation for magnetization dynamics. We find
+that the use of low-barrier SAF layers reduces dipolar coupling, achieving
+uncorrelated fluctuations at zero-magnetic field surviving up to diameters
+exceeding ($D\approx 100$ nm) if the nanomagnets can be made thin enough
+($\approx 1$-$2$ nm). The double-free-layer structure retains bias-independence
+and the circular nature of the nanomagnets provides near-uniform randomness
+with fast fluctuations. Combining our full sMTJ model with advanced transistor
+models, we estimate the energy to generate a random bit as $\approx$ 3.6 fJ,
+with fluctuation rates of $\approx$ 3.3 GHz per p-bit. Our results will guide
+the experimental development of superior stochastic magnetic tunnel junctions
+for large-scale and energy-efficient probabilistic computation for problems
+relevant to machine learning and artificial intelligence.",2311.06642v2
+2023-12-07,Evolution of the magnetic field and flows of solar active regions with persistent magnetic bipoles before emergence,"Magnetic active regions on the Sun are harbingers of space weather events.
+Understanding the physics of how they form and evolve will improve space
+weather forecasting. Our aim is to characterise the surface magnetic field and
+flows for a sample of active regions with persistent magnetic bipoles prior to
+emergence. We identified 42 emerging active regions (EARs), in the Solar
+Dynamics Observatory Helioseismic Emerging Active Region survey (Schunker et
+al. 2016), associated with small magnetic bipoles at least one day before the
+time of emergence. We then identified a contrasting sample of 42 EARs that
+emerge more abruptly without bipoles before emergence. We computed the
+supergranulation scale surface flows using helioseismic holography. We averaged
+the flow maps and magnetic field maps over all active regions in each sample at
+each time interval from 2 days before emergence to 1 day after. We found that
+EARs associated with a persistent pre-emergence bipole evolve to be, on
+average, lower flux active regions than EARs that emerge more abruptly.
+Further, we found that the EARs that emerge more abruptly do so with a
+diverging flow of $(3\pm 0.6) \times 10^{-6}$ s$^{-1}$ on the order of 50-100
+ms$^{-1}$. Our results suggest that there is a statistical dependence of the
+surface flow signature throughout the emergence process on the maximum magnetic
+flux of the active region.",2312.04157v1
+2023-12-08,"Sub-Alfvenic Turbulence: Magnetic to Kinetic Energy Ratio, Modification of Weak Cascade and Implications for Magnetic Field Strength Measurement","We study the properties of sub-Alfvenic magnetohydrodynamic (MHD) turbulence,
+i.e., turbulence with Alfven Mach number $M_A=V_L/V_A<1$, where $V_L$ is the
+velocity at the injection scale and $V_A$ is the Alfven velocity. We
+demonstrate that weak turbulence can have different regimes depending on
+whether it is driven by velocity or magnetic fluctuations. If the turbulence is
+driven by isotropic bulk forces, i.e. velocity-driven, in an incompressible
+conducting fluid, we predict that the kinetic energy is $M_A^{-2}$ times larger
+than the energy of magnetic fluctuations. This effect arises from the long
+parallel wavelength tail of the forcing, which excites modes with $k_\|/k_\perp
+< M_A$. We also predict that as the turbulent cascade reaches the strong regime
+the energy of slow modes exceeds the energy of Alfven modes by a factor
+$M_A^{-1}$. These effects are absent if the turbulence is magnetically driven
+at the injection scale. We confirm these predictions with numerical
+simulations. As the assumption of magnetic and kinetic energy equipartition is
+at the core of the Davis-Chandrasekhar-Fermi (DCF) approach to measuring
+magnetic field strength in sub-Alfvenic turbulence, we conclude that the DCF
+technique is not universally applicable. In particular, we suggest that the
+dynamical excitation of long azimuthal wavelength modes in the galactic disk
+may compromise the use of the DCF technique. We discuss alternative expressions
+that can be used to obtain magnetic field strength from observations.",2312.05399v1
+2023-12-14,On statistical zonostrophic instability and the effect of magnetic fields,"Zonal flows are mean flows in the east-west direction, which are ubiquitous
+on planets, and can be formed through 'zonostrophic instability': within
+turbulence or random waves, a weak large-scale zonal flow can grow
+exponentially to become prominent. In this paper, we study the statistical
+behaviour of the zonostrophic instability and the effect of magnetic fields. We
+use a stochastic white noise forcing to drive random waves, and study the
+growth of a mean flow in this random system. The dispersion relation for the
+growth rate of the expectation of the mean flow is derived, and properties of
+the instability are discussed. In the limits of weak and strong magnetic
+diffusivity, the dispersion relation reduces to manageable expressions, which
+provide clear insights into the effect of the magnetic field and scaling laws
+for the threshold of instability. The magnetic field mainly plays a stabilising
+role and thus impedes the formation of the zonal flow, but under certain
+conditions it can also have destabilising effects. Numerical simulation of the
+stochastic flow is performed to confirm the theory. Results indicate that the
+magnetic field can significantly increase the randomness of the zonal flow. It
+is found that the zonal flow of an individual realisation may behave very
+differently from the expectation. For weak magnetic diffusivity and moderate
+magnetic field strengths, this leads to considerable variation of the outcome,
+that is whether zonostrophic instability takes place or not in individual
+realisations.",2312.08905v1
+2023-12-15,Topological magnon gap engineering in van der Waals CrI$_3$ ferromagnets,"The microscopic origin of the topological magnon band gap in CrI$_3$
+ferromagnets has been a subject of controversy for years since two main models
+with distinct characteristics, i.e., Dzyaloshinskii-Moriya (DM) and Kitaev,
+provided possible explanations with different outcome implications. Here we
+investigate the angular magnetic field dependence of the magnon gap of CrI$_3$
+by elucidating what main contributions play a major role in its generation. We
+implement stochastic atomistic spin dynamics simulations to compare the impact
+of these two spin interactions on the magnon spectra. We observe three distinct
+magnetic field dependencies between these two gap opening mechanisms. First, we
+demonstrate that the Kitaev-induced magnon gap is influenced by both the
+direction and amplitude of the applied magnetic field, while the DM-induced gap
+is solely affected by the magnetic field direction. Second, the position of the
+Dirac cones within the Kitaev-induced magnon gap shifts in response to changes
+in the magnetic field direction, whereas they remain unaffected by the magnetic
+field direction in the DM-induced gap scenario. Third, we find a
+direct-indirect magnon band-gap transition in the Kitaev model by varying the
+applied magnetic field direction. These differences may distinguish the origin
+of topological magnon gaps in CrI$_3$ and other van der Waals magnetic layers.
+Our findings pave the way for exploration and engineering topological gaps in
+van der Waals materials.",2312.09903v1
+2024-02-21,Switchback Patches Evolve into Microstreams via Magnetic Relaxation,"Magnetic switchbacks are distinct magnetic structures characterized by their
+abrupt reversal in the radial component of the magnetic field within the
+pristine solar wind. Switchbacks are believed to lose magnetic energy with
+heliocentric distance. To investigate this switchbacks originating from similar
+solar source regions are identified during a radial alignment of the Parker
+Solar Probe (PSP; 25.8 solar radii) and Solar Orbiter (SolO; 152 solar radii).
+We found that 1) the dynamic and thermal pressures decrease at the switchback
+boundaries by up to 20% at PSP and relatively unchanged at SolO and magnetic
+pressure jump across the boundary remains negligible at both distances, and 2)
+bundles of switchbacks are often observed in switchback patches near the Sun,
+and in microstreams farther away. Background proton velocity (vp) is 10%
+greater than the pristine solar wind (vsw) in microstreams, whereas vp ~ vsw in
+switchback patches. Microstreams contain an average of 30% fewer switchbacks
+than switchback patches. It is concluded that switchbacks likely relax
+magnetically and equilibrate their plasma with the surrounding environment with
+heliocentric distance. Switchback relaxation can, in turn, accelerate the
+surrounding plasma. Therefore, it is hypothesized that magnetic relaxation of
+switchbacks may cause switchback patches to evolve into microstreams with
+heliocentric distance. Statistical analysis of PSP and SolO switchbacks is
+underway to further test our hypothesis.",2402.13964v1
+2024-03-07,Relative alignment between gas structures and magnetic field in Orion A at different scales using different molecular gas tracers,"Context: Magnetic fields can play crucial roles in high-mass star formation.
+Nonetheless, the significance of magnetic fields at various scales and their
+relationship with gas structures is largely overlooked. Aims: Our goal is to
+examine the relationship between the magnetic field and molecular gas
+structures within the Orion A giant molecular cloud at different scales and
+density regimes. Methods: We assess the gas intensity structures and column
+densities in Orion A by utilizing $^{12}$CO, $^{13}$CO, and C$^{18}$O from
+Nobeyama observations. Through comparing Nobeyama observations with
+{\it{Planck}} polarization observations on large scales ($\sim0.6$ pc) and JCMT
+polarization observations on small scales ($\sim0.04$ pc), we investigate how
+the role of magnetic fields change with scale and density. Results: We find a
+similar trend from parallel to perpendicular alignment with increasing column
+densities in Orion A at both large and small spatial scales. Besides, when
+changing from low-density to high-density tracers, the relative orientation
+preference changes from random to perpendicular. The self-similar results at
+different scales indicate that magnetic fields are dynamically important in
+both cloud formation and filament formation. However, magnetic fields
+properties at small scales are relative complicated, and the interplay between
+magnetic field and star-forming activities needs to be discussed case-by-case.",2403.04274v1
+1995-05-30,On the dynamics of a spherical spin-glass,"We carry out an analysis of the effect of a quenched magnetic field on the
+dynamics of the spherical Sherrington-Kirkpatrick spin-glass model. We show
+that there is a characteristic time introduced by the presence of the field.
+Firstly, for times sufficiently small the dynamic scenario of the zero field
+case - with aging effects - is reproduced. Secondly, for times larger than the
+characteristic time one sees equilibrium dynamics. This dynamical behaviour is
+reconciled with the geometry of the energy landscape of the model. We compare
+this behaviour with experimental observations at a finite applied field.",9505149v1
+2000-03-29,Ultrafast spin dynamics and critical behavior in half-metallic ferromagnet : Sr_2FeMoO_6,"Ultrafast spin dynamics in ferromagnetic half-metallic compound Sr_2FeMoO_6
+is investigated by pump-probe measurements of magneto-optical Kerr effect.
+Half-metallic nature of this material gives rise to anomalous thermal
+insulation between spins and electrons, and allows us to pursue the spin
+dynamics from a few to several hundred picoseconds after the optical
+excitation. The optically detected magnetization dynamics clearly shows the
+crossover from microscopic photoinduced demagnetization to macroscopic critical
+behavior with universal power law divergence of relaxation time for wide
+dynamical critical region.",0003467v3
+2002-06-29,"Dynamical Decimation Renormalization-Group Technique: Kinetic Gaussian Model on Non-Branching, Braching and Multi-branching Koch Curve","A generalizing formulation of dynamical real-space renormalization that suits
+for arbitrary spin systems is suggested. The new version replaces the
+single-spin flipping Glauber dynamics with the single-spin transition dynamics.
+As an application, in this paper we mainly investigate the critical slowing
+down of the Gaussian spin model on three fractal lattices, including
+nonbranching, branching and multibranching Koch Curve. The dynamical critical
+exponent $z$ is calculated for these lattices using an exact decimation
+renormalization transformation in the assumption of the magnetic-like
+perturbation, and a universal result $z=1/\nu $ is found.",0207008v1
+2001-12-19,Pseudochaos,"A family of the billiard-type systems with zero Lyapunov exponent is
+considered as an example of dynamics which is between the regular one and
+chaotic mixing. This type of dynamics is called ``pseudochaos''. We demonstrate
+how the fractional kinetic equation can be introduced for the pseudochaos and
+how the main critical exponents of the fractional kinetics can be evaluated
+from the dynamics. Problems related to pseudochaos are discussed: Poincare
+recurrences, continued fractions, log-periodicity, rhombic billiards, and
+others. Pseudochaotic dynamics and fractional kinetics can be applied to
+streamlines or magnetic field lines behavior.",0112033v2
+1999-04-21,Nonlinear Accelerator Problems via Wavelets: 2. Orbital Dynamics in General Multipolar Field,"In this series of eight papers we present the applications of methods from
+wavelet analysis to polynomial approximations for a number of accelerator
+physics problems. In this part we consider orbital motion in transverse plane
+for a single particle in a circular magnetic lattice in case when we take into
+account multipolar expansion up to an arbitrary finite number. We reduce
+initial dynamical problem to the finite number (equal to the number of n-poles)
+of standard algebraical problem and represent all dynamical variables via an
+expansion in the base of periodical wavelets.",9904040v1
+1999-04-21,Nonlinear Accelerator Problems via Wavelets: 3. Effects of Insertion Devices on Beam Dynamics,"In this series of eight papers we present the applications of methods from
+wavelet analysis to polynomial approximations for a number of accelerator
+physics problems. In this part, assuming a sinusoidal field variation, we
+consider the analytical treatment of the effects of insertion devices on beam
+dynamics. We investigate via wavelet approach a dynamical model which has
+polynomial nonlinearities and variable coefficients. We construct the
+corresponding wavelet representation. As examples we consider wigglers and
+undulator magnets. We consider the further modification of our variational
+approach which may be applied in each scale.",9904041v1
+2007-09-25,Chaotic Dynamics of Spin-Valve Oscillators,"Recent experimental and theoretical studies on the magnetization dynamics
+driven by an electric current have uncovered a number of unprecedented rich
+dynamic phenomena. We predict an intrinsic chaotic dynamics that has not been
+previously anticipated. We explicitly show that the transition to chaotic
+dynamics occurs through a series of period doubling bifurcations. In chaotic
+regime, two dramatically different power spectra, one with a well-defined peak
+and the other with a broadly distributed noise, are identified and explained.",0709.4045v1
+2011-07-04,Moderate Deviations for a Curie-Weiss model with dynamical external field,"In the present paper we prove moderate deviations for a Curie-Weiss model
+with external magnetic field generated by a dynamical system, as introduced by
+Dombry and Guillotin-Plantard. The results extend those already obtained in the
+case of a constant external field by Eichelsbacher and L\""owe. The Curie-Weiss
+model with dynamic external field is related to the so called dynamic Z-random
+walks. We also prove a moderate deviation result for the dynamic Z-random walk,
+completing the list of limit theorems for this object.",1107.0671v1
+2015-10-13,Taming the dynamical sign problem in real-time evolution of quantum many-body problems,"Current nonequilibrium Monte Carlo methods suffer from a dynamical sign
+problem that makes simulating real-time dynamics for long times exponentially
+hard. We propose a new `Inchworm Algorithm', based on iteratively reusing
+information obtained in previous steps to extend the propagation to longer
+times. The algorithm largely overcomes the dynamical sign problem, changing the
+scaling from exponential to quadratic. We use the method to solve the Anderson
+impurity model in the Kondo and mixed valence regimes, obtaining results both
+for quenches and for spin dynamics in the presence of an oscillatory magnetic
+field.",1510.03534v1
+2013-08-05,Revisiting linear dynamics of non-axisymmetric perturbations in weakly magnetized accretion discs,"We investigate linear dynamics of non-axisymmetric perturbations in
+incompressible, vertically stratified Keplerian discs with a weak vertical
+magnetic field in the shearing box approximation. Perturbations are decomposed
+into shearing waves whose evolution is followed via numerical integration of
+the linearized ideal MHD equations. There are two basic modes in the system --
+inertia-gravity waves and magnetic mode, which displays the magnetorotational
+instability (MRI). As distinct from previous studies, we introduce
+`eigenvariables' characterizing each (counter-propagating) component of the
+inertia-gravity and magnetic modes, which are governed by a set of four first
+order coupled ordinary differential equations. This allowed us to identify a
+new process of linear coupling of the two above non-axisymmetric modes due to
+the disc's differential rotation. We did a comparative analysis of the dynamics
+of non-axisymmetric and axisymmetric magnetic mode perturbations. It is shown
+that the growth of optimal and close-to-optimal non-axisymmetric harmonics of
+this mode, having transient nature, can prevail over the exponential growth of
+axisymmetric ones (i.e., over the axisymmetric MRI) during dynamical time. A
+possible implication of this result for axisymmetric channel solutions is
+discussed. Specifically, the formation of the channel may be affected/impeded
+by non-axisymmetric modes already at the early linear stage leading to its
+untimely disruption -- the outcome strongly depends on the amplitude and
+spectrum of initial perturbation. So, this competition may result in an
+uncertainty in the magnetic mode's non-linear dynamics. It is also shown that a
+maximum non-axisymmetric growth is at vertical wavelengths close to the
+scale-height for which compressibility effects are important. This indirectly
+suggests that compressibility plays a role in the dynamics of the
+non-axisymmetric MRI.",1308.1058v1
+2017-02-08,Meridional Circulation Dynamics in a Cyclic Convective Dynamo,"Surface observations indicate that the speed of the solar meridional
+circulation in the photosphere varies in anti-phase with the solar cycle. The
+current explanation for the source of this variation is that inflows into
+active regions alter the global surface pattern of the meridional circulation.
+When these localized inflows are integrated over a full hemisphere, they
+contribute to the slow down of the axisymmetric poleward horizontal component.
+The behavior of this large scale flow deep inside the convection zone remains
+largely unknown. Present helioseismic techniques are not sensitive enough to
+capture the dynamics of this weak large scale flow. Moreover, the large time of
+integration needed to map the meridional circulation inside the convection
+zone, also masks some of the possible dynamics on shorter timescales. In this
+work we examine the dynamics of the meridional circulation that emerges from a
+3D MHD global simulation of the solar convection zone. Our aim is to assess and
+quantify the behavior of meridional circulation deep inside the convection
+zone, where the cyclic large-scale magnetic field can reach considerable
+strength. Our analyses indicate that the meridional circulation morphology and
+amplitude are both highly influenced by the magnetic field, via the impact of
+magnetic torques on the global angular momentum distribution. A dynamic feature
+induced by these magnetic torques is the development of a prominent upward flow
+at mid latitudes in the lower convection zone that occurs near the equatorward
+edge of the toroidal bands and that peaks during cycle maximum. Globally, the
+dynamo-generated large-scale magnetic field drives variations in the meridional
+flow, in stark contrast to the conventional kinematic flux transport view of
+the magnetic field being advected passively by the flow.",1702.02421v2
+2006-08-31,Using the Galactic Dynamics of M7 Dwarfs to Infer the Evolution of Their Magnetic Activity,"We present a spectroscopic study and dynamical analysis of ~2600 M7 dwarfs.
+We confirm our previous finding that the fraction of magnetically active stars
+decreases with vertical distance from the Galactic plane. We also show that the
+mean luminosity of the H-alpha emission has a small but statistically
+significant decrease with distance. Using space motions for ~1300 stars and a
+simple one-dimensional dynamical simulation, we demonstrate that the drop in
+the activity fraction of M7 dwarfs can be explained by thin disk dynamical
+heating and a rapid decrease of magnetic activity at a mean stellar age of ~6-7
+Gyr.",0609001v1
+1995-11-27,Topology and dynamics in ferromagnetic media,"A direct link between the topological complexity of ferromagnetic media and
+their dynamics has recently been established through the construction of
+unambiguous conservation laws as moments of a topological vorticity. In the
+present paper we carry out this program under completely realistic conditions,
+with due account of the long-range magnetostatic field and related boundary
+effects. In particular, we derive unambiguous expressions for the linear and
+angular momentum in a ferromagnetic film which are then used to study the
+dynamics of magnetic bubbles under the influence of an applied magnetic-field
+gradient. The semi-empirical golden rule of bubble dynamics is verified in its
+gross features but not in its finer details. A byproduct of our analysis is a
+set of virial theorems generalizing Derrick's scaling relation as well as a
+detailed recalculation of the fundamental magnetic bubble.",9511126v2
+1996-04-16,Dynamics of Domains in Diluted Antiferromagnets,"We investigate the dynamics of two-dimensional site-diluted Ising
+antiferromagnets. In an external magnetic field these highly disordered
+magnetic systems have a domain structure which consists of fractal domains with
+sizes on a broad range of length scales. We focus on the dynamics of these
+systems during the relaxation from a long-range ordered initial state to the
+disordered fractal-domain state after applying an external magnetic field. The
+equilibrium state with applied field consists of fractal domains with a size
+distribution which follows a power law with an exponential cut-off. The
+dynamics of the system can be understood as a growth process of this
+fractal-domain state in such a way that the equilibrium distribution of domains
+develops during time. Following these ideas quantitatively we derive a simple
+description of the time dependence of the order parameter. The agreement with
+simulations is excellent.",9604094v1
+1997-05-22,Monte Carlo Simulation of the Short-time Behaviour of the Dynamic XY Model,"Dynamic relaxation of the XY model quenched from a high temperature state to
+the critical temperature or below is investigated with Monte Carlo methods.
+When a non-zero initial magnetization is given, in the short-time regime of the
+dynamic evolution the critical initial increase of the magnetization is
+observed. The dynamic exponent $\theta$ is directly determined. The results
+show that the exponent $\theta$ varies with respect to the temperature.
+Furthermore, it is demonstrated that this initial increase of the magnetization
+is universal, i.e. independent of the microscopic details of the initial
+configurations and the algorithms.",9705236v1
+2001-02-07,Finite-temperature dynamical magnetic susceptibility of quasi-one-dimensional frustrated spin-1/2 Heisenberg antiferromagnets,"We study the dynamical response of frustrated, quasi-one-dimensional spin-1/2
+Heisenberg antiferromagnets at finite temperatures. We allow for the presence
+of a Dzyaloshinskii-Moriya interaction. We concentrate on a model of weakly
+coupled planes of anisotropic triangular lattices. Combining exact results for
+the dynamical response of one dimensional Heisenberg chains with a Random Phase
+Approximation (RPA) in the frustrated interchain couplings, we calculate the
+dynamical susceptibility in the disordered phase. We investigate the
+instability of the disordered phase to the formation of collective modes. We
+find a very weak instability to the formation of incommensurate magnetic order
+and determine the ordering temperature and wave vector. We also determine the
+effects of uniform magnetic fields on the ordering transition.",0102138v2
+2001-09-20,Spin dynamics of a one-dimensional spin-1/2 fully anisotropic Ising-like antiferromagnet in a transverse magnetic field,"We consider the one-dimensional Ising-like fully anisotropic S=1/2 Heisenberg
+antiferromagnetic Hamiltonian and study the dynamics of domain wall excitations
+in the presence of transverse magnetic field $h_x$. We obtain dynamical spin
+correlation functions along the magnetic field $S^{xx}(q,\omega)$ and
+perpendicular to it $S^{yy}(q,\omega)$. It is shown that the line shapes of
+$S^{xx}(q,\omega)$ and $S^{yy}(q,\omega)$ are purely symmetric at the
+zone-boundary. It is observed in $S^{yy}(q,\omega)$ for $\pi/2<q<\pi$ that the
+spectral weight moves toward low energy side with the increase of $h_x$. This
+model is applicable to study the spin dynamics of CsCoCl$_3$ in the presence of
+weak interchain interactions.",0109364v1
+2004-04-02,Quantum Spin Dynamics in Single-Molecule Magnets,"This thesis contains a thorough investigation of the quantum spin dynamics in
+Mn12-ac and Mn6 Single-molecule magnets. In particular, we have investigated
+the interplay between quantum tunneling of magnetization and nuclear spin
+dynamics in Mn12-ac by ultra-low temperature NMR experiments. We discuss the
+effect of quantum tunneling on the nuclear spin-lattice relaxation, the nuclear
+spin diffusion, the thermalization of the nuclear spins, the isotope effect,
+the influence of strong perpendicular fields, and we propose a model to unify
+all our observations. For the isotropic Mn6 molecule, we report the observation
+of long-range ferromagentic ordering of the cluster spins, due to dipolar
+interactions only. The nuclear spin dynamics provides an interesting comparison
+with the case of Mn12-ac. Two large introductory chapters describe the design
+of our ultra-low temperature setups, and the theoretical background necessary
+to understand the interplay between nuclear spins and quantum tunneling, with
+emphasis on the Prokof'ev-Stamp theory of the ""spin-bath"".",0404049v1
+2004-11-18,Optoelectronic control of spin dynamics at near-THz frequencies in magnetically doped quantum wells,"We use time-resolved Kerr rotation to demonstrate the optical and electronic
+tuning of both the electronic and local moment (Mn) spin dynamics in
+electrically gated parabolic quantum wells derived from II-VI diluted magnetic
+semiconductors. By changing either the electrical bias or the laser energy, the
+electron spin precession frequency is varied from 0.1 to 0.8 THz at a magnetic
+field of 3 T and at a temperature of 5 K. The corresponding range of the
+electrically-tuned effective electron g-factor is an order of magnitude larger
+compared with similar nonmagnetic III-V parabolic quantum wells. Additionally,
+we demonstrate that such structures allow electrical modulation of local moment
+dynamics in the solid state, which is manifested as changes in the amplitude
+and lifetime of the Mn spin precession signal under electrical bias. The large
+variation of electron and Mn-ion spin dynamics is explained by changes in
+magnitude of the sp&#8722;d exchange overlap.",0411492v1
+2006-02-22,Soliton pair dynamics in patterned ferromagnetic ellipses,"Confinement alters the energy landscape of nanoscale magnets, leading to the
+appearance of unusual magnetic states, such as vortices, for example. Many
+basic questions concerning dynamical and interaction effects remain unanswered,
+and nanomagnets are convenient model systems for studying these fundamental
+physical phenomena. A single vortex in restricted geometry, also known as a
+non-localized soliton, possesses a characteristic translational excitation mode
+that corresponds to spiral-like motion of the vortex core around its
+equilibrium position. Here, we investigate, by a microwave reflection
+technique, the dynamics of magnetic soliton pairs confined in lithographically
+defined, ferromagnetic Permalloy ellipses. Through a comparison with
+micromagnetic simulations, the observed strong resonances in the subgigahertz
+frequency range can be assigned to the translational modes of vortex pairs with
+parallel or antiparallel core polarizations. Vortex polarizations play a
+negligible role in the static interaction between two vortices, but their
+effect dominates the dynamics.",0602509v1
+2000-09-12,"Confinement, magnetic Z(N) symmetry and low energy effective theory of gluodynamics","In these notes I explain the idea how one could understand confinement by
+studying the low energy effective dynamics of non Abelian gauge theories. I
+argue that under some mild assumptions, the low energy dynamics is determined
+universally by the spontaneous breaking of the magnetic symmetry introduced by
+'t Hooft more than 20 years ago. The degrees of freedom in the effective theory
+are magnetic vortices. They play a similar role in confining dynamics to the
+role played by pions and sigma in the chiral symmetry breaking dynamics.
+  I give explicit derivation of the effective theory in 2+1 dimensional weekly
+coupled confining models and give arguments that it remains qualitatively the
+same in strongly coupled 2+1 dimensional gluodynamics. Confinement in this
+effective theory is a very simple classical statement about long range
+interaction between topological solitons, which follows by a simple direct
+classical calculation from the structure of the effective Lagrangian. I discuss
+the elements of this picture which generalize to 3+1 dimensions and point to
+the open questions still remaining.",0009138v2
+2002-04-17,Electron Mass Operator in a Strong Magnetic Field and Dynamical Chiral Symmetry Breaking,"The electron mass operator in a strong magnetic field is calculated. The
+contribution of higher Landau levels of virtual electrons, along with the
+ground Landau level, is shown to be essential in the leading log approximation.
+The effect of the electron dynamical mass generation by a magnetic field is
+investigated. In a model with N charged fermions, it is shown that some
+critical number N_{cr} exists for any value of the electromagnetic coupling
+constant alpha, such that the fermion dynamical mass is generated with a
+doublet splitting for N < N_{cr}, and the dynamical mass does not arise at all
+for N > N_{cr}, thus leaving the chiral symmetry unbroken.",0204201v1
+2002-05-31,Magnetic catalysis and anisotropic confinement in QCD,"The expressions for dynamical masses of quarks in the chiral limit in QCD in
+a strong magnetic field are obtained. A low energy effective action for the
+corresponding Nambu-Goldstone bosons is derived and the values of their decay
+constants as well as the velocities are calculated. The existence of a
+threshold value of the number of colors $N^{thr}_c$, dividing the theories with
+essentially different dynamics, is established. For the number of colors $N_c
+\ll N^{thr}_c$, an anisotropic dynamics of confinement with the confinement
+scale much less than $\Lambda_{QCD}$ and a rich spectrum of light glueballs is
+realized. For $N_c$ of order $N^{thr}_c$ or larger, a conventional confinement
+dynamics takes place. It is found that the threshold value $N^{thr}_c$ grows
+rapidly with the magnetic field [$N^{thr}_c \gtrsim 100$ for $|eB| \gtrsim
+(1{GeV})^2$]. In contrast to QCD with a nonzero baryon density, there are no
+principal obstacles for checking these results and predictions in lattice
+computer simulations.",0205348v3
+1996-03-23,RG analysis of magnetic catalysis in Dynamical symmetry breaking,"We perform the renormalization group analysis on the dynamical symmetry
+breaking under strong external magnetic field, studied recently by Gusynin,
+Miransky and Shovkovy. We find that any attractive four-Fermi interaction
+becomes strong in the low energy, thus leading to dynamical symmetry breaking.
+When the four-Fermi interaction is absent, the $\beta$-function for the
+electromagnetic coupling vanishes in the leading order in $1/N$. By solving the
+Schwinger-Dyson equation for the fermion propagator, we show that in $1/N$
+expansion, for any electromagnetic coupling, dynamical symmetry breaking occurs
+due to the presence of Landau energy gap by the external magnetic field.",9603157v1
+2000-09-15,Exact time-correlation functions of quantum Ising chain in a kicking transversal magnetic field,"Spectral analysis of the {\em adjoint} propagator in a suitable Hilbert space
+(and Lie algebra) of quantum observables in Heisenberg picture is discussed as
+an alternative approach to characterize infinite temperature dynamics of
+non-linear quantum many-body systems or quantum fields, and to provide a bridge
+between ergodic properties of such systems and the results of classical ergodic
+theory. We begin by reviewing some recent analytic and numerical results along
+this lines. In some cases the Heisenberg dynamics inside the subalgebra of the
+relevant quantum observables can be mapped explicitly into the (conceptually
+much simpler) Schr\"" odinger dynamics of a single one-(or few)-dimensional
+quantum particle. The main body of the paper is concerned with an application
+of the proposed method in order to work out explicitly the general spectral
+measures and the time correlation functions in {\em a quantum Ising spin 1/2
+chain in a periodically kicking transversal magnetic field}, including the
+results for the simpler autonomous case of a static magnetic field in the
+appropriate limit. The main result, being a consequence of a purely continuous
+non-trivial part of the spectrum, is that the general time-correlation
+functions decay to their saturation values as $t^{-3/2}$.",0009031v1
+2007-04-06,Model C critical dynamics of random anisotropy magnets,"We study the relaxational critical dynamics of the three-dimensional random
+anisotropy magnets with the non-conserved n-component order parameter coupled
+to a conserved scalar density. In the random anisotropy magnets the structural
+disorder is present in a form of local quenched anisotropy axes of random
+orientation. When the anisotropy axes are randomly distributed along the edges
+of the n-dimensional hypercube, asymptotical dynamical critical properties
+coincide with those of the random-site Ising model. However structural disorder
+gives rise to considerable effects for non-asymptotic critical dynamics. We
+investigate this phenomenon by a field-theoretical renormalization group
+analysis in the two-loop order. We study critical slowing down and obtain
+quantitative estimates for the effective and asymptotic critical exponents of
+the order parameter and scalar density. The results predict complex scenarios
+for the effective critical exponent approaching an asymptotic regime.",0704.0896v1
+2007-08-03,Local dynamics and gravitational collapse of a self-gravitating magnetized Fermi gas,"We use the Bianchi-I spacetime to study the local dynamics of a magnetized
+self-gravitating Fermi gas. The set of Einstein-Maxwell field equations for
+this gas becomes a dynamical system in a 4-dimensional phase space. We consider
+a qualitative study and examine numeric solutions for the degenerate zero
+temperature case. All dynamic quantities exhibit similar qualitative behavior
+in the 3-dimensional sections of the phase space, with all trajectories
+reaching a stable attractor whenever the initial expansion scalar H_{0} is
+negative. If H_{0} is positive, and depending on initial conditions, the
+trajectories end up in a curvature singularity that could be isotropic(singular
+""point"") or anisotropic (singular ""line""). In particular, for a sufficiently
+large initial value of the magnetic field it is always possible to obtain an
+anisotropic type of singularity in which the ""line"" points in the same
+direction of the field.",0708.0593v2
+2008-08-18,Dynamics of driven vortex-antivortex matter in superconducting films with a magnetic dipole array,"We investigate theoretically vortex-antivortex (v-av) matter moving in thin
+superconducting films with a regular array of in-plane magnetic dipoles. Our
+model considers v-av pair creation induced by the local current density
+generated by the magnetic texture and the transport current and simulates the
+dynamics of vortices and antivortices by numerical integration of the Langevin
+equation of motion. Calculations of the transport properties at zero applied
+field show a strong dependence of the v-av dynamics on the current intensity
+and direction. The dynamics of the v-av matter is characterized by a series of
+creation and annihilation processes, which reflect on the time dependence of
+the electrical field, and by guided motion, resulting in a zero-field
+transverse resistance.",0808.2421v1
+2008-10-20,"Gas-dynamic shock heating of post-flare loops due to retraction following localized, impulsive reconnection","We present a novel model in which shortening of a magnetic flux tube
+following localized, three-dimensional reconnection generates strong
+gas-dynamic shocks around its apex. The shortening releases magnetic energy by
+progressing away from the reconnection site at the Alfven speed. This launches
+inward flows along the field lines whose collision creates a pair of
+gas-dynamic shocks. The shocks raise both the mass density and temperature
+inside the newly shortened flux tube. Reconnecting field lines whose initial
+directions differ by more that 100 degrees can produce a concentrated knot of
+plasma hotter that 20 MK, consistent with observations. In spite of these high
+temperatures, the shocks convert less than 10% of the liberated magnetic energy
+into heat - the rest remains as kinetic energy of bulk motion. These
+gas-dynamic shocks arise only when the reconnection is impulsive and localized
+in all three dimensions; they are distinct from the slow magnetosonic shocks of
+the Petschek steady-state reconnection model.",0810.3661v2
+2008-11-12,Spin-Dynamics of the antiferromagnetic S=1/2-Chain at finite magnetic Fields and intermediate Temperatures,"We present a study of the dynamic structure factor of the antiferromagnetic
+spin-1/2 Heisenberg chain at finite temperatures and finite magnetic fields.
+Using Quantum-Monte-Carlo based on the stochastic series expansion and
+Maximum-Entropy methods we evaluate the longitudinal and the transverse dynamic
+structure factor from vanishing magnetic fields up to and above the threshold
+$B_c$ for ferromagnetic saturation, as well as for high and for intermediate
+temperatures. We study the field-induced redistribution of spectral weight
+contrasting longitudinal versus transverse excitations. At finite fields below
+saturation incommensurate low-energy modes are found consistent with zero
+temperature Bethe-Ansatz. The crossover between the field induced ferromagnet
+above $B_c$ and the Luttinger liquid below $B_c$ is analyzed in terms of the
+transverse spin-dynamics. Evaluating sum-rules we assess the quality of the
+analytic continuation and demonstrate excellent consistency of the
+Maximum-Entropy results.",0811.1956v2
+2009-04-07,Spin dynamics and structure formation in a spin-1 condensate in a magnetic field,"We study the dynamics of a trapped spin-1 condensate in a magnetic field.
+First, we analyze the homogeneous system, for which the dynamics can be
+understood in terms of orbits in phase space. We analytically solve for the
+dynamical evolution of the populations of the various Zeeman components of the
+homogeneous system. This result is then applied via a local density
+approximation to trapped quasi-1D condensates. Our analysis of the trapped
+system in a magnetic field shows that both the mean-field and Zeeman regimes
+are simultaneously realized, and we argue that the border between these two
+regions is where spin domains and phase defects are generated. We propose a
+method to experimentally tune the position of this border.",0904.1160v2
+2009-11-30,Small-scale structure and dynamics of the chromospheric magnetic field,"Recent advances in observational performance and numerical simulations have
+revolutionised our understanding of the solar chromosphere. This concerns in
+particular the structure and dynamics on small spatial and temporal scales. As
+a result, the picture of the solar chromosphere changed from an idealised
+static and plane-parallel stratification to a complex compound of intermittent
+domains, which are dynamically coupled to the layers below and above. In this
+picture, the chromosphere in a stricter sense is associated with the typical
+fibrillar structure shaped by magnetic fields like it is known from images
+taken in the H alpha line core. In internetwork regions below this layer, there
+exists a domain with propagating shock waves and weak magnetic fields, which
+both probably interact with the overlying large scale field. The existence of
+such a sub-canopy domain certainly depends on the properties of the overlying
+field. Details of the structure of the lower atmosphere can therefore be
+expected to vary significantly from location to location. Here, high-resolution
+observations, which were obtained with the CRISP filter at the Swedish Solar
+Telescope, are used to derive qualitative constraints for the atmospheric
+structure of quiet Sun regions.",0911.5639v1
+2010-07-05,Laser-induced Spin Dynamics in Metallic Multilayers,"Electronic excitations in a ferromagnet can trigger ultrafast spin dynamics
+with potential applications in a speed increase in magnetic recording. The
+project investigates ultrafast magnetization dynamics, which is driven in
+metallic layers by ballistic hot electrons. In a ferromagnet these electrons
+induce a change in the absolute value of the magnetization M through
+spin-dependent scattering. If the electrons are spin-polarized, scattering at
+the interface of a noble metal and a ferromagnet results in spin-transfer
+torque and hence modifies the direction of M. To reveal the underlying
+mechanisms, we study model systems, which are realized by layers of Au with its
+large ballistic mean free path and Fe as an itinerant ferromagnet. We aim at
+understanding ultrafast demagnetization and femtosecond all-optical generation
+of spin transfer torque effects (excitation of hot electrons with a femtosecond
+laser). The launched dynamics are probed by magneto-optics in a time-resolved
+experiment.",1007.0726v1
+2012-04-20,Magnetic order and spin dynamics in the proximity of a ferromagnetic quantum critical point: A μSR study of YbNi4P2,"The local 4f-electronic spin dynamics and magnetic order in YbNi4P2 were
+studied by means of muon-spin relaxation measurements. Zero-field muon-spin
+relaxation proves static magnetic order with a strongly reduced ordered Yb3+
+moment of (2.5-4.6) \times 10-2{\mu}B, below TC = 140 mK. Above TC, the
+muon-spin polarization P(t,B) is dominated by quasihomogeneous spin
+fluctuations and exhibits a time-field scaling relation P(t,B) =
+P(t/B{\gamma}), indicating cooperative critical spin dynamics in the system. At
+T = 190 mK, slightly above TC, {\gamma} = 0.81(5), suggesting time-scale
+invariant power-law behavior for the dynamic electronic spin-spin
+autocorrelation function.",1204.4632v1
+2012-07-20,Measurement of the dynamical dipolar coupling in a pair of magnetic nano-disks using a Ferromagnetic Resonance Force Microscope,"We perform an extensive experimental spectroscopic study of the collective
+spin-wave dynamics occurring in a pair of magnetic nano-disks coupled by the
+magneto-dipolar interaction. For this, we take advantage of the stray field
+gradient produced by the magnetic tip of a ferromagnetic resonance force
+microscope (f-MRFM) to continuously tune and detune the relative resonance
+frequencies between two adjacent nano-objects. This reveals the anti-crossing
+and hybridization of the spin-wave modes in the pair of disks. At the exact
+tuning, the measured frequency splitting between the binding and anti-binding
+modes precisely corresponds to the strength of the dynamical dipolar coupling
+$\Omega$. This accurate f-MRFM determination of $\Omega$ is measured as a
+function of the separation between the nano-disks. It agrees quantitatively
+with calculations of the expected dynamical magneto-dipolar interaction in our
+sample.",1207.4919v1
+2013-02-07,Three-dimensional artificial neural network model of the dayside magnetopause,"Artificial Neural Networks (ANN) from package NeuroShell 2 are applied for
+modeling of dayside magnetopause. The model data set is based on the
+magnetopause crossings and on the corresponding hour-averaged measurements of
+solar wind plasma and interplanetary magnetic field. ANN model represents 3D
+shape and size of the dayside magnetopause in dependence on solar wind dynamic
+pressure, Bz and By components of interplanetary magnetic field. The model
+permits firstly to describe dynamics of the magnetic cusp and global asymmetry
+of the dayside magnetopause under wide range of the external conditions.
+Slightly change of the magnetopause size with change of By absolute value is
+presented quantitatively in the form of analytical expression. ANN model shows
+three regimes of the magnetopause dynamics that controlled by Bz component:
+pressure balance regime (Bz>0 nT), reconnection regime (0>Bz>-10 nT) and regime
+of reconnection saturation (Bz<-10 nT). Three different regimes of magnetopause
+dynamics at the subsolar point are described by modified pressure balance
+equation obtained from ANN model.",1302.1704v1
+2013-04-02,Structures and dynamics of small scales in decaying magnetohydrodynamic turbulence,"The topological and dynamical features of small scales are studied in the
+context of decaying magnetohydrodynamic turbulent flows using direct numerical
+simulations. Joint probability density functions (PDFs) of the invariants of
+gradient quantities related to the velocity and the magnetic fields demonstrate
+that structures and dynamics at the time of maximum dissipation depend on the
+large scale initial conditions. This is evident in particular from the fact
+that each flow has a different shape for the joint PDF of the invariants of the
+velocity gradient in contrast to the universal teardrop shape of hydrodynamic
+turbulence. The general picture that emerges from the analysis of the
+invariants is that regions of high vorticity are correlated with regions of
+high strain rate $\bm S$ also in contrast to hydrodynamic turbulent flows.
+Magnetic strain dominated regions are also well correlated with region of high
+current density $\bm j$. Viscous dissipation ($\propto \bm S^2$) as well as
+Ohmic dissipation ($\propto \bm j^2$) reside in regions where strain and
+rotation are locally almost in balance. The structures related to the velocity
+gradient possess different characteristics than those associated with the
+magnetic field gradient with the latter being locally more quasi-two
+dimensional.",1304.0695v1
+2013-07-05,Instabilities of rotational flows in azimuthal magnetic fields of arbitrary radial dependence,"Using the WKB approximation we perform a linear stability analysis for a
+rotational flow of a viscous and electrically conducting fluid in an external
+azimuthal magnetic field that has an arbitrary radial profile B_{phi}(R). In
+the inductionless approximation, we find the growth rate of the
+three-dimensional perturbation in a closed form and demonstrate in particular
+that it can be positive when the velocity profile is Keplerian and the magnetic
+field profile is slightly shallower than R^{-1}.",1307.1576v2
+2013-10-19,Stochastic Resonance and Dynamic First-Order Pseudo-Phase Transitions in the Irreversible Growth of Thin Films under Spatially Periodic Magnetic Fields,"We study the irreversible growth of magnetic thin films under the influence
+of spatially periodic fields by means of extensive Monte Carlo simulations. We
+find first-order pseudo-phase transitions that separate a dynamically
+disordered phase from a dynamically ordered phase. By analogy with
+time-dependent oscillating fields applied to Ising-type models, we
+qualitatively associate this dynamic transition with the
+localization/delocalization transition of ""spatial hysteresis"" loops. Depending
+on the relative width of the magnetic film, $L$, compared to the wavelength of
+the external field, $\lambda$, different transition regimes are observed. For
+small systems ($L<\lambda$), the transition is associated with the Standard
+Stochastic Resonance regime, while, for large systems ($L>\lambda$), the
+transition is driven by Anomalous Stochastic Resonance. The origin of the
+latter is identified as due to the emergence of an additional relevant
+lengthscale, namely the roughness of the spin domain switching interface. The
+distinction between different stochastic resonance regimes is discussed at
+length, both qualitatively by means of snapshot configurations, as well as
+quantitatively via residence-length and order-parameter probability
+distributions.",1310.5259v1
+2014-03-19,Vibrational free energy and phase stability of paramagnetic and antiferromagnetic CrN from ab-initio molecular dynamics,"We present a theoretical first-principles method to calculate the free energy
+of a magnetic system in its high-temperature paramagnetic phase, including
+vibrational, electronic, and magnetic contributions. The method for calculating
+free energies is based on ab-initio molecular dynamics and combines a treatment
+of disordered magnetism using disordered local moments molecular dynamics
+(DLM-MD) with the temperature dependent effective potential (TDEP) method to
+obtain the vibrational contribution to the free energy. We illustrate the
+applicability of the method by obtaining the anharmonic free energy for the
+paramagnetic cubic and the antiferromagnetic orthorhombic phases of chromium
+nitride. The influence of lattice dynamics on the transition between the two
+phases is demonstrated by constructing the temperature-pressure phase diagram.",1403.4766v1
+2015-01-22,Topologically Protected Dynamics of Spin Textures,"We study current-induced dynamics of spin textures in thin magnetic
+nanowires. We derive effective equations of motion describing the dynamics of
+the domain-wall soft modes associated with topological defects. Because the
+magnetic domain walls are topological objects, these equations are universal
+and depend only on a few parameters. We obtain spin spiral domain-wall
+structure in ferromagnetic wires with Dzyaloshinskii-Moriya interaction and
+critical current dependence on this interaction. We also find the most
+efficient way to move the domain walls by resonant current pulses and propose a
+procedure to determine their dynamics by measuring the voltage induced by a
+moving domain wall. Based on translationally non-invariant nanowires, we show
+how to make prospective magnetic memory nanodevices much more energy efficient.",1501.05366v1
+2015-03-08,Antiferromagnetic order and spin dynamics in iron-based superconductors,"High-transition temperature (high-$T_c$) superconductivity in the iron
+pnictides/chalcogenides emerges from the suppression of the static
+antiferromagnetic order in their parent compounds, similar to copper oxides
+superconductors. This raises a fundamental question concerning the role of
+magnetism in the superconductivity of these materials. Neutron scattering, a
+powerful probe to study the magnetic order and spin dynamics, plays an
+essential role in determining the relationship between magnetism and
+superconductivity in high-$T_c$ superconductors. The rapid development of
+modern neutron time-of-flight spectrometers allows a direct determination of
+the spin dynamical properties of iron-based superconductors throughout the
+entire Brillouin zone. In this review, we present an overview of the neutron
+scattering results on iron-based superconductors, focusing on the evolution of
+spin excitation spectra as a function of electron/hole-doping and isoelectronic
+substitution. We compare spin dynamical properties of iron-based
+superconductors with those of copper oxide and heavy fermion superconductors,
+and discuss the common features of spin excitations in these three families of
+unconventional superconductors and their relationship with superconductivity.",1503.02340v2
+2015-04-22,Chromatic and Dispersive Effects in Nonlinear Integrable Optics,"Proton accumulator rings and other circular hadron accelerators are
+susceptible to intensity-driven parametric instabilities because the
+zero-current charged particle dynamics are characterized by a single tune.
+Landau damping can suppress these instabilities, which requires energy spread
+in the beam or introducing nonlinear magnets such as octupoles. However, this
+approach reduces dynamic aperture. Nonlinear integrable optics can suppress
+parametric instabilities independent of energy spread in the distribution,
+while preserving the dynamic aperture. This novel approach promises to reduce
+particle losses and enable order-of-magnitude increases in beam intensity. In
+this paper we present results, obtained using the Lie operator formalism, on
+how chromaticity and dispersion affect particle orbits in integrable optics. We
+conclude that chromaticity in general breaks the integrability, unless the
+vertical and horizontal chromaticities are equal. Because of this, the
+chromaticity correcting magnets can be weaker and fewer correcting magnet
+families are required, thus minimizing the impact on dynamic aperture.",1504.05981v2
+2015-06-16,Stochastic approximation of dynamical exponent at quantum critical point,"We have developed a unified finite-size scaling method for quantum phase
+transitions that requires no prior knowledge of the dynamical exponent $z$.
+During a quantum Monte Carlo simulation, the temperature is automatically tuned
+by the Robbins-Monro stochastic approximation method, being proportional to the
+lowest gap of the finite-size system. The dynamical exponent is estimated in a
+straightforward way from the system-size dependence of the temperature. As a
+demonstration of our novel method, the two-dimensional $S=1/2$ quantum $XY$
+model in uniform and staggered magnetic fields is investigated in the
+combination of the world-line quantum Monte Carlo worm algorithm. In the
+absence of the uniform magnetic field, we obtain the fully consistent result
+with the Lorentz invariance at the quantum critical point, $z=1$, i.e., the
+three-dimensional classical $XY$ universality class. Under a finite uniform
+magnetic field, on the other hand, the dynamical exponent becomes two, and the
+mean-field universality with effective dimension $(2+2)$ governs the quantum
+phase transition.",1506.04837v1
+2015-07-29,Taub-NUT Dynamics with a Magnetic Field,"We study classical and quantum dynamics on the Euclidean Taub-NUT geometry
+coupled to an abelian gauge field with self-dual curvature and show that, even
+though Taub-NUT has neither bounded orbits nor quantum bound states, the
+magnetic binding via the gauge field produces both. The conserved Runge-Lenz
+vector of Taub-NUT dynamics survives, in a modified form, in the gauged model
+and allows for an essentially algebraic computation of classical trajectories
+and energies of quantum bound states. We also compute scattering cross sections
+and find a surprising electric-magnetic duality. Finally, we exhibit the
+dynamical symmetry behind the conserved Runge-Lenz and angular momentum vectors
+in terms of a twistorial formulation of phase space.",1507.08165v1
+2015-08-07,Spin Dynamics in Driven Composite Multiferroics,"A spin dynamics approach has been used to study the behavior of the magnetic
+spins and the electric pseudo-spins in a 1-D composite multiferroic chain with
+a linear magneto-electric coupling at the interface. The response is
+investigated with either external magnetic or electric fields driving the
+system. The spin dynamics is based on the Landau-Lifshitz-Gilbert equation. A
+Gaussian white noise is later added into the dynamic process to include the
+thermal effects. The interface requires a closer inspection of the
+magneto-electric effects. Thus, we construct a 2-D ladder model to describe the
+behavior of the magnetic spins and the electric pseudo-spins with different
+magneto-electric couplings.",1508.01584v2
+2015-11-19,Novel considerations about the non-equilibrium regime of the tricritical point in a metamagnetic model: localization and tricritical exponents,"We have investigated the time-dependent regime of a two-dimensional
+metamagnetic model at its tricritical point via Monte Carlo simulations. First
+of all, we obtained the temperature and magnetic field corresponding to the
+tricritical point of the model by using a refinement process based on
+optimization of the coefficient of determination in the log-log fit of
+magnetization decay as function of time. With these estimates in hand, we
+obtained the dynamic tricritical exponents $\theta $ and $z$ and the static
+tricritical exponents $\nu $ and $\beta $ by using the universal power-law
+scaling relations for the staggered magnetization and its moments at early
+stage of the dynamic evolution. Our results at tricritical point confirm that
+this model belongs to the two-dimensional Blume-Capel model universality class
+for both static and dynamic behaviors, and also they corroborate the conjecture
+of Janssen and Oerding for the dynamics of tricritical points.",1511.06377v1
+2016-01-06,All-electrical detection of spin dynamics in magnetic antidot lattices by the inverse spin Hall effect,"The understanding of spin dynamics in laterally confined structures on
+sub-micron length scales has become a significant aspect of the development of
+novel magnetic storage technologies. Numerous ferromagnetic resonance
+measurements, optical characterization by Kerr microscopy and Brillouin light
+scattering spectroscopy and x-ray studies were carried out to detect the
+dynamics in patterned magnetic antidot lattices. Here, we investigate
+Oersted-field driven spin dynamics in rectangular Ni80Fe20/Pt antidot lattices
+with different lattice parameters by electrical means and compare them to
+micromagnetic simulations. When the system is driven to resonance, a dc voltage
+across the length of the sample is detected that changes its sign upon field
+reversal, which is in agreement with a rectification mechanism based on the
+inverse spin Hall effect. Furthermore, we show that the voltage output scales
+linearly with the applied microwave drive in the investigated range of powers.
+Our findings have direct implications on the development of engineered
+magnonics applications and devices.",1601.01221v1
+2017-02-16,Visualization of the global flow structure in a modified Rayleigh-Benard setup using contactless inductive flow tomography,"Rayleigh-Benard convection is not only a classical problem in fluid dynamics
+but plays also an important role in many metallurgical and crystal growth
+applications. The measurement of the flow field and of the dynamics of the
+emerging large-scale circulation in liquid metals is a challenging task due to
+the opaqueness and the high temperature of the melts. Contactless inductive
+flow tomography is a technique to visualize the mean three-dimensional flow
+structure in liquid metals by measuring the flow induced magnetic field
+perturbations under the influence of one or several applied magnetic fields. In
+this paper, we present first measurements of the flow induced magnetic field in
+a Rayleigh-Benard setup, which are also used to investigate the dynamics of the
+large-scale circulation. Additionally, we investigate numerically the quality
+of the reconstruction of the three-dimensional flow field for different sensor
+configurations.",1702.04880v1
+2017-04-24,Magnetic field fluctuations analysis for the ion trap implementation of the quantum Rabi model in the the deep strong coupling regime,"The dynamics of the quantum Rabi model in the deep strong coupling regime is
+theoretically analyzed in a trapped-ion setup. Recognizably, the main hallmark
+of this regime is the emergence of collapses and revivals, whose faithful
+observation is hindered under realistic magnetic dephasing noise. Here we
+discuss how to attain a faithful implementation of the quantum Rabi model in
+the deep strong coupling regime which is robust against magnetic field
+fluctuations and at the same time provides a large tunability of the simulated
+parameters. This is achieved by combining standing wave laser configuration
+with continuous dynamical decoupling. In addition, we study the role that
+amplitude fluctuations play to correctly attain the quantum Rabi model using
+the proposed method. In this manner the present work further supports the
+suitability of continuous dynamical decoupling techniques in trapped-ion
+settings to faithfully realize different interacting dynamics.",1704.07303v2
+2017-07-07,Magnetoelectric antiferromagnets as platforms for the manipulation of solitons,"We study the magnetic dynamics of magnetoelectric antiferromagnetic thin
+films, where an unconventional boundary ferromagnetism coexists with the bulk
+N\'{e}el phase below the N\'{e}el temperature. The spin exchange between the
+two order parameters yields an effective low-energy theory that is formally
+equivalent to that of a ferrimagnet. Dynamics of domain walls and skyrmions are
+analyzed within the collective variable approach, from which we conclude that
+they behave as massive particles moving in a viscous medium subjected to a
+gyrotropic force. We find that the film thickness can be used as a control
+parameter for the motion of these solitons. In this regard, it is shown that an
+external magnetic field can drive the dynamics of domain walls, whose terminal
+velocity is tunable with the sample thickness. Furthermore, the classification
+of the skyrmion dynamics is sensitive to the spatial modulation of the sample
+thickness, which can be easily engineered with the present (thin-film)
+deposition techniques. Current-driven spin transfer can trigger drifting orbits
+of skyrmions, which can be utilized as racetracks for these magnetic textures.",1707.02374v1
+2017-08-21,Relaxation of Compressible Euler Flow in a Toroidal Domain,"It is shown that the universal steady Euler flow field, independent of
+boundary shape or symmetry, in a toroidal domain with fixed boundary obeys a
+nonlinear Beltrami equation, with the nonlinearity arising from a
+Boltzmann-like, velocity-dependent factor. Moreover, this is a relaxed velocity
+field, in the sense that it extremizes the total kinetic energy in the domain
+under free variations of the velocity field, constrained only by tangential
+velocity and vorticity boundary conditions and conservation of total fluid
+helicity and entropy. This is analogous to Woltjer-Taylor relaxation of plasma
+magnetic field to a stationary state. However, unlike the magnetic field case,
+attempting to derive slow, quasi-relaxed dynamics from Hamilton's action
+principle, with constant total fluid helicity as a constraint, fails to agree,
+in the static limit, with the nonlinear Beltrami solution of the Euler
+equations. Nevertheless, an action principle that gives a quasi-relaxed
+dynamics that does agree can be formulated, by introducing a potential
+representation of the velocity field and defining an analogue of the magnetic
+helicity as a new constraint. A Hamiltonian form of quasi-relaxed fluid
+dynamics is also given.",1708.06193v1
+2017-10-10,Dynamical regimes of vortex flow in type-II superconductors with parallel twin boundaries,"We explore the dynamics of driven magnetic flux lines in disordered type-II
+superconductors in the presence of twin boundaries oriented parallel to the
+direction of the applied magnetic field, using a three-dimensional elastic line
+model simulated with Langevin molecular dynamics. The lines are driven
+perpendicular to the planes to model the effect of an electric current applied
+parallel to the planes and perpendicular to the magnetic field. A study of the
+long-time non-equilibrium steady states for varying sample orientation and
+thickness reveals a rich collection of dynamical regimes spanning the depinning
+crossover region that separates the pinned and moving-lattice states of vortex
+matter. We observe the emergence of a preferred direction for the ordering of
+the Abrikosov lattice in the free-flowing vortex regime due to asymmetric
+pinning by the planar defects. We have performed novel direct measurements of
+flux line excitations such as half-loops and double kinks to aid the
+characterization of the topologically rich flux flow profile.",1710.03679v2
+2018-03-01,Aging dynamics in quenched noisy long-range quantum Ising models,"We consider the $d$-dimensional transverse-field Ising model with power-law
+interactions $J/r^{d+\sigma}$ in the presence of a noisy longitudinal field
+with zero average. We study the longitudinal-magnetization dynamics of an
+initial paramagnetic state after a sudden switch-on of both the interactions
+and the noisy field. While the system eventually relaxes to an
+infinite-temperature state with vanishing magnetization correlations, we find
+that two-time correlation functions show aging at intermediate times. Moreover,
+for times shorter than the inverse noise strength $\kappa$ and distances longer
+than $a(J/\kappa)^{2/\sigma}$ with $a$ being the lattice spacing, we find a
+critical scaling regime of correlation and response functions consistent with
+the model A dynamical universality class with an initial-slip exponent
+$\theta=1$ and dynamical critical exponent $z=\sigma/2$. We obtain our results
+analytically by deriving an effective action for the magnetization field
+including the noise in a non-perturbative way. The above scaling regime is
+governed by a non-equilibrium fixed point dominated by the noise fluctuations.",1803.00280v2
+2018-03-05,Off-resonant all-optical switching dynamics in a ferromagnetic model system,"We present a theoretical study of the the effects of off-resonant polarized
+optical fields on a ferromagnetic model system. We determine the light-induced
+dynamics of itinerant carriers in a system that includes magnetism at the
+mean-field level and spin-orbit coupling. We investigate an all-optical
+switching process for ferromagnets, which is close to the one proposed by
+Qaiumzadeh et al. [Phys. Rev. B 88, 064416] for the inverse Faraday effect. By
+computing the optically driven coherent dynamics together with incoherent
+scattering mechanisms we go beyond a perturbation expansion in powers of the
+optical field. We find an important contribution of a dynamic Stark effect
+coupling of the Raman type between the magnetic bands, which leads to a
+polarization-dependent effect on the magnetization that may support or oppose
+switching, but also contributes to demagnetization via an increase in
+electronic energy.",1803.01924v1
+2018-04-24,Coupling between dynamic magnetic and charge-order correlations in the cuprate superconductor Nd$_{2-x}$Ce$_{x}$CuO$_4$,"Charge order has now been observed in several cuprate high-temperature
+superconductors. We report a resonant inelastic x-ray scattering experiment on
+the electron-doped cuprate Nd$_{2-x}$Ce$_{x}$CuO$_4$ that demonstrates the
+existence of dynamic correlations at the charge order wave vector. Upon cooling
+we observe a softening in the electronic response, which has been predicted to
+occur for a d-wave charge order in electron-doped cuprates. At low
+temperatures, the energy range of these excitations coincides with that of the
+dispersive magnetic modes known as paramagnons. Furthermore, measurements where
+the polarization of the scattered photon is resolved indicate that the dynamic
+response at the charge order wave vector primarily involves spin-flip
+excitations. Overall, our findings indicate a coupling between dynamic magnetic
+and charge-order correlations in the cuprates.",1804.09185v1
+2018-07-26,Reversal Time of Jump-Noise Dynamics for Large Nucleation,"The jump-noise is a phenomenological stochastic process used to model the
+thermal fluctuation of magnetization in nanomagnets. In this work, the large
+nucleation regime of jump-noise dynamics is studied, and its reversal time is
+characterized from Monte Carlo simulations and analysis. Results show that the
+reversal time of jump-noise dynamics for large nucleation is asymptotically
+equal to the time constant associated with a single jump-noise scattering event
+from the energy minimum in the energy landscape of the magnetization. The
+reversal time for large nucleation depends linearly on the height of the energy
+barrier for large barriers. The significance of the large nucleation regime of
+jump-noise dynamics to phenomenologically explain the magnetoelectric switching
+of antiferromagnetic order parameter is also prospected.",1807.09922v1
+2018-08-17,Director switching dynamics of ferromagnetic nematic liquid crystals,"Successful realization of ferromagnetic nematic liquid crystals has opened up
+the possibility to experimentally study a completely new set of fundamental
+physical phenomena. In this contribution we present a detailed investigation of
+some aspects of the static response and the complex dynamics of ferromagnetic
+liquid crystals under the application of an external magnetic field.
+Experimental results are then compared with a macroscopic model. Dynamics of
+the director were measured by optical methods and analyzed in terms of a
+theoretical macroscopic model. A dissipative cross-coupling coefficient
+describing the dynamic coupling between the two system order parameters, the
+magnetization and the nematic director, is needed to explain the results. In
+this contribution we examine the dependency of this coefficient on material
+parameters and the saturation magnetization and the liquid crystal host.
+Despite the complexity of the system, the theoretical description allows for a
+proper interpretation of the results and is connected to several microscopic
+aspects of the colloidal suspension.",1808.05843v1
+2018-11-10,Spin dynamics in lattices of spinor atoms with quadratic Zeeman effect,"A lattice system of spinor atoms or molecules experiencing quadratic Zeeman
+effect is considered. This can be an optical lattice with sufficiently deep
+wells at lattice sites, so that the system is in an isolating state, where
+atoms are well localized. But their effective spins can move in the presence of
+external magnetic fields. The dynamics of spins, starting from an initial
+nonequilibrium state, is investigated. The system is immersed into a magnetic
+coil of an electric circuit, creating a magnetic feedback field. Two types of
+quadratic Zeeman effect are treated, a nonresonant, so-called static-current
+quadratic Zeeman effect and a quasi-resonant alternating-current quadratic
+Zeeman effect. Spin dynamics in these conditions is highly nonlinear. Different
+regimes of spin dynamics, starting from a strongly nonequilibrium state, are
+studied. Conditions for realizing fast spin reversal are found, which can be
+used in quantum information processing and spintronics.",1811.04271v1
+2018-11-21,Metastable hard-axis polar state of a spinor Bose-Einstein condensate under a magnetic field gradient,"We investigate the stability of a hard-axis polar state in a spin-1
+antiferromagnetic Bose-Einstein condensate under a magnetic field gradient,
+where the easy-plane spin anisotropy is controlled by a negative quadratic
+Zeeman energy $q<0$. In a uniform magnetic field, the axial polar state is
+dynamically unstable and relaxes into the planar polar ground state. However,
+under a field gradient $B'$, the excited spin state becomes metastable down to
+a certain threshold $q_{th}$ and as $q$ decreases below $q_{th}$, its intrinsic
+dynamical instability is rapidly recalled. The incipient spin excitations in
+the relaxation dynamics appear with stripe structures, indicating the
+rotational symmetry breaking by the field gradient. We measure the dependences
+of $q_{th}$ on $B'$ and the sample size, and we find that $q_{th}$ is highly
+sensitive to the field gradient in the vicinity of $B'=0$, exhibiting power-law
+behavior of $|q_{th}|\propto B'^{\alpha}$ with $\alpha \sim 0.5$. Our results
+demonstrate the significance of the field gradient effect in the quantum
+critical dynamics of spinor condensates.",1811.08544v1
+2019-01-23,The near and far of a pair of magnetic capillary disks,"Control on microscopic scales depends critically on our ability to manipulate
+interactions with different physical fields. The creation of micro-machines
+therefore requires us to understand how multiple fields, such as surface
+capillary or electro-magnetic, can be used to produce predictable behaviour.
+Recently, a spinning micro-raft system was developed that exhibited both static
+and dynamic self-assembly [Wang et al. (2017) Sci. Adv. 3, e1602522]. These
+rafts employed both capillary and magnetic interactions and, at a critical
+driving frequency, would suddenly change from stable orbital patterns to static
+assembled structures. In this paper, we explain the dynamics of two interacting
+micro-rafts through a combination of theoretical models and experiments. This
+is first achieved by identifying the governing physics of the orbital patterns,
+the assembled structures, and the collapse separately. We find that the orbital
+patterns are determined by the short range capillary interactions between the
+disks, while the explanations of the other two behaviours only require the
+capillary far field. Finally we combine the three models to explain the
+dynamics of a new micro-raft experiment.",1901.09703v1
+2019-02-08,Simulation of the Magnetization Dynamics of a Single Domain BiFeO$_3$ Thin Film,"The switching dynamics of a single-domain BiFeO$_3$ thin films is
+investigated through combining the dynamics of polarization and Neel vector.
+The evolution of the ferroelectric polarization is described by the
+Landau-Khalatnikov (LK) equation, and the Landau-Lifshitz-Gilbert (LLG)
+equations for spins in two sublattices to model the time evolution of the
+antiferromagnetic order (Neel vector) in a G-type antiferromagnet. This work
+theoretically demonstrates that due to the rotation of the magnetic hard axis
+following the polarization reversal, the Neel vector can be switched by 180
+degrees, while the weak magnetization can remain unchanged. The simulation
+results are consistent with the ab initio calculation, where the Neel vector
+rotates during polarization rotation, and also match our calculation of the
+dynamics of order parameter using Landau-Ginzburg theory. We also find that the
+switching time of the Neel vector is determined by the speed polarization
+switching and is predicted to be as short as 30 ps.",1902.03330v1
+2019-08-01,Theory of current-driven dynamics of spin textures on a surface of topological insulators,"Spin-transfer torque is one of the important physical quantities to
+understand for successful application of topological insulators to spintronics.
+In this paper, we present analytical expressions of the spin-transfer torques
+on a surface of a magnetic topological insulator by including the higher-order
+contributions of momentum, $k^2$-term and the hexagonal warping. We obtain six
+different types of the spin-transfer torque including both the field-like and
+the damping-like torques; the four of them appear only when the higher-order
+momentum contributions are included. In addition, we discuss the dynamics of
+magnetic skyrmions driven by the spin-transfer torques on the surface of the
+topological insulator. Unlike the skyrmion dynamics in conventional metals, we
+find that the dynamics significantly depends on the internal structure of
+magnetic textures.",1908.00152v1
+2019-08-13,Ultrafast spin dynamics in the proximate quantum spin liquid α-RuCl3,"{\alpha}-RuCl3 is a Kitaev material suggested to be a proximate quantum spin
+liquid in a certain temperature and magnetic field range. Nonequilibrium
+measurements of transient dynamics have been proposed to detect fractionalized
+particles that emerge in the spin liquid and to possibly drive the system into
+novel photoinduced magnetic states that cannot be accessed by conventional
+equilibrium probes. Here we study ultrafast spin dynamics of photoinduced
+excitations in {\alpha}-RuCl3 using pump-probe transient grating spectroscopy.
+In the real part of the complex transient reflectance change {\Delta}R/R, we
+observe the long-range antiferromagnetic correlation near the N\'eel
+temperature. Most intriguingly, above the N\'eel temperature in the Kitaev
+paramagnetic phase, we reveal a photoexcitation component sensitive to the
+in-plane magnetic field in the imaginary part of {\Delta}R/R. This component
+exhibits two distinct lifetimes of about tens of picoseconds. This
+photoexcitation component may be connected to novel photoexcited states in the
+Kitaev quantum spin liquid, and its lifetimes likely reflect the dynamics of
+unconventional spin excitations in the Kitaev model.",1908.04807v2
+2019-11-08,Magnetic Field Effect on Dynamics of Entanglement for Time-dependent Harmonic Oscillator,"We investigate the dynamics of entanglement, uncertainty and mixedness by
+solving time dependent Schr\""{o}dinger equation for two-dimensional harmonic
+oscillator with time dependent frequency and coupling parameter subject to a
+static magnetic field. We compute the purities (global/marginal) and then
+calculate explicitly the linear entropy $S_{L}$ as well as logarithmic
+negativity $\mathcal{N}$ using the symplectic parametrization of vacuum state.
+We introduce the spectral decomposition to diagonalize the marginal state and
+get the expression of von Neumann entropy $S_{von}$ and establish its link with
+$S_{L}$. We use the Wigner formalism to derive the Heisenberg uncertainties and
+{show their dependencies on both $S_{L}$ and the coupling parameters
+$\gamma_{i}$ $ (i=1,2)$ of the quadrature term $x_{i}p_{i}$.} We graphically
+study the dynamics of the three features (entanglement, uncertainty, mixedness)
+and present the similar topology with respect to time. We show the effects of
+the magnetic field and quenched values of $J(t)$ and $\omega_{2}(t)$ on these
+three dynamics, which lead eventually to control and handle them.",1911.03153v2
+2020-02-27,Ultrafast magnetization dynamics in half-metallic Co$_2$FeAl Heusler alloy,"We report on optically induced, ultrafast magnetization dynamics in the
+Heusler alloy $\mathrm{Co_{2}FeAl}$, probed by time-resolved magneto-optical
+Kerr effect. Experimental results are compared to results from electronic
+structure theory and atomistic spin-dynamics simulations. Experimentally, we
+find that the demagnetization time ($\tau_{M}$) in films of
+$\mathrm{Co_{2}FeAl}$ is almost independent of varying structural order, and
+that it is similar to that in elemental 3d ferromagnets. In contrast, the
+slower process of magnetization recovery, specified by $\tau_{R}$, is found to
+occur on picosecond time scales, and is demonstrated to correlate strongly with
+the Gilbert damping parameter ($\alpha$). Our results show that
+$\mathrm{Co_{2}FeAl}$ is unique, in that it is the first material that clearly
+demonstrates the importance of the damping parameter in the remagnetization
+process. Based on these results we argue that for $\mathrm{Co_{2}FeAl}$ the
+remagnetization process is dominated by magnon dynamics, something which might
+have general applicability.",2002.12255v1
+2020-06-19,Spin-glass thermo-remanent magnetization revisited: a numerical and analytical study,"Thermoremanent magnetization data for the 3D Edwards-Anderson spin glass are
+generated using the Waiting Time Method as simulational tool and interpreted
+using Record Dynamics. We verify that clusters of contiguous spins are
+overturned by quakes, non-equilibrium events linked to record sized energy
+fluctuations and show that quaking is a log-Poisson process, i.e. a Poisson
+process whose average depends on the logarithm of the system age, counted from
+the initial quench. Our results compare favorably with experimental
+thermoremanent magnetization findings and with the spontaneous fluctuation
+dynamics of the E-A model.
+  The logarithm growth of the size of overturned clusters is related to similar
+experimental results and to the growing length scale of the spin-spin spatial
+correlation function. The analysis buttresses the applicability of the Waiting
+Time Method as a simulational tool and of Record Dynamics as coarse-graining
+method for aging dynamics.",2006.11214v2
+2020-06-23,Experimental Observation of Quantum Many-Body Excitations of $E_8$ Symmetry in the Ising Chain Ferromagnet CoNb$_2$O$_6$,"Close to the quantum critical point of the transverse-field Ising spin-chain
+model, an exotic dynamic spectrum was predicted to emerge upon a perturbative
+longitudinal field. The dynamic spectrum consists of eight particles and is
+governed by the symmetry of the $E_8$ Lie algebra. Here we report on
+high-resolution terahertz spectroscopy of quantum spin dynamics in the
+ferromagnetic Ising-chain material CoNb$_2$O$_6$. At 0.25 K in the magnetically
+ordered phase we identify characteristics of the first six $E_8$ particles,
+$\mathbf{m}_1$ to $\mathbf{m}_6$, and the two-particle
+($\mathbf{m}_1+\mathbf{m}_2$) continuum in an applied transverse magnetic field
+of $B_c^{1D}=4.75$ T, before the three-dimensional magnetic order is suppressed
+above $B_c^{3D}\approx 5.3$ T. The observation of the higher-energy particles
+($\mathbf{m}_3$ to $\mathbf{m}_6$) above the low-energy two-particle continua
+features quantum many-body effects in the exotic dynamic spectrum.",2006.12956v2
+2020-07-30,Dynamical torques from Shiba states in $s$-wave superconductors,"Magnetic impurities inserted in a $s$-wave superconductor give rise to
+spin-polarized in-gap states called Shiba states. We study the back-action of
+these induced states on the dynamics of the classical moments. We show that the
+Shiba state pertains to both reactive and dissipative torques acting on the
+precessing classical spin that can be detected through ferromagnetic resonance
+measurements. Moreover, we highlight the influence of the bulk states as well
+as the effect of the finite linewidth of the Shiba state on the magnetization
+dynamics. Finally, we demonstrate that the torques are a direct measure of the
+even and odd frequency triplet pairings generated by the dynamics of the
+magnetic impurity. Our approach offers non-invasive alternative to the STM
+techniques used to probe the Shiba states.",2007.15392v2
+2020-08-29,Frequency analysis and dynamic aperture studies in ELENA with realistic 3D magnetic fields,"We briefly present recent progress with our algorithm and its implementation
+called SIMPA described in a previous paper. The algorithm has a new and unique
+approach to long-term 4D tracking of charged particles in arbitrary static
+electromagnetic fields. Using the improvements described in this paper, we made
+frequency analysis and dynamic aperture studies in ELENA. The effect of the end
+fields and the perturbation introduced by the magnetic system of the electron
+cooler on dynamic aperture is shown. A special feature of this study is that we
+have not introduced any multipole errors into the model. The dynamic aperture
+calculated in this paper is the direct consequence of the geometry of the
+magnetic elements. Based on the results, we make a few suggestions to reduce
+the losses during the deceleration of the beam.",2008.12945v1
+2021-04-13,Spin dynamics of the director state in frustrated hyperkagome systems,"We present an experimental study of the magnetic structure and dynamics of
+two frustrated hyperkagome compounds, Gd3Ga5O12 and Gd3Al5O12. It has
+previously been shown that Gd3Ga5O12 exhibits long-range correlations of
+multipolar directors, that are formed from antiferromagnetic spins on loops of
+ten ions. Using neutron diffraction and Reverse Monte Carlo simulations we
+prove the existence of similar magnetic correlations in Gd3Al5O12, showing the
+ubiquity of these complex structures in frustrated hyperkagome materials.
+  Using inelastic neutron scattering we shed further light on the director
+state and the associated low lying magnetic excitations. In addition we have
+measured quasielastic dynamics that show evidence of spin diffusion. Finally,
+we present AC susceptibility measurements on both Gd3Ga5O12 and Gd3Al5O12,
+revealing a large difference in the low frequency dynamics between the two
+otherwise similar compounds.",2104.05987v2
+2021-06-21,Resonant Measurement of Non-Reorientable Spin-Orbit Torque from a Ferromagnetic Source Layer Accounting for Dynamic Spin Pumping,"Using a multilayer structure containing (cobalt detector layer)/(copper
+spacer)/(Permalloy source layer), we show experimentally how the
+non-reorientable spin-orbit torque generated by the Permalloy source layer (the
+component of spin-orbit torque that does not change when the Permalloy
+magnetization is rotated) can be measured using spin-torque ferromagnetic
+resonance (ST-FMR) with lineshape analysis. We find that dynamic spin pumping
+between the magnetic layers exerts torques on the magnetic layers as large or
+larger than the spin-orbit torques, so that if dynamic spin pumping is
+neglected the result would be a large overestimate of the spin-orbit torque.
+Nevertheless, the two effects can be separated by performing ST-FMR as a
+function of frequency. We measure a non-reorientable spin torque ratio
+$\xi_{\text{Py}} = 0.04 \pm 0.01$ for spin current flow from Permalloy through
+an 8 nm Cu spacer to the Co, and a strength of dynamic spin pumping that is
+consistent with previous measurements by conventional ferromagnetic resonance.",2106.11127v1
+2021-09-06,Applying explicit symplectic integrator to study chaos of charged particles around magnetized Kerr black hole,"In a recent work of Wu, Wang, Sun and Liu, a second-order explicit symplectic
+integrator was proposed for the integrable Kerr spacetime geometry. It is still
+suited for simulating the nonintegrable dynamics of charged particles moving
+around the Kerr black hole embedded in an external magnetic field. Its
+successful construction is due to the contribution of a time transformation.
+The algorithm exhibits a good long-term numerical performance in stable
+Hamiltonian errors and computational efficiency. As its application, the
+dynamics of order and chaos of charged particles is surveyed. In some
+circumstances, an increase of the dragging effects of the spacetime seems to
+weaken the extent of chaos from the global phase-space structure on Poincare
+sections. However, an increase of the magnetic parameter strengthens the
+chaotic properties. On the other hand, fast Lyapunov indicators show that there
+is no universal rule for the dependence of the transition between different
+dynamical regimes on the black hole spin. The dragging effects of the spacetime
+do not always weaken the extent of chaos from a local point of view.",2109.02295v1
+2021-11-10,Periodicities in a multiply connected geometry from quenched dynamics,"Exploring the lowest energy configurations of a quantum system is consistent
+with the counting statistics of the frequently appeared states from quenching
+dynamics. By studying the Little-Parks periodicities in a multiply-connected
+ring-shaped geometry from the holographic technique, it is found that the
+frequently appeared states from dynamics incline to have lower free energies.
+In particular, the resulting winding numbers from quenched dynamics are
+constrained in a normal distribution for a fixed magnetic flux threading the
+ring. Varying the magnetic fluxes, Little-Parks periodicities will take place
+with periods identical to the flux quantum $\Phi_0$. Favorable solutions with
+lowest free energies perform first order phase transitions which transform
+between distinct winding numbers as the magnetic flux equals half-integers
+multiplying $\Phi_0$.",2111.05568v3
+2021-12-08,Skyrmion Dynamics in the Presence of Deformation,"Magnetic skyrmions are topological spin textures promising for future
+high-density and nonvolatile memory. It is crucial to understand the
+current-driven skyrmion dynamics in the presence of deformation, of which an
+analytical model, however, remains elusive. Here we extend Thiele's model by
+considering both the radial and tangential forces. Our model attributes the
+skyrmion deformation to the current-induced rotational symmetry breaking, which
+includes magnetization canting and domain wall width variation. Our predictions
+of skyrmion radius and nonlinear dynamics are consistent with micromagnetic
+simulation results. Besides, we show that by applying an in-plane magnetic
+field, the deformation of a skyrmion can be suppressed, and even the
+compression of a skyrmion can be achieved. Our model provides a generic way to
+analyze the skyrmion deformation and may inspire applications based on
+nonlinear skyrmion dynamics.",2112.04073v1
+2021-12-13,Selective quantum Zeno effect of ultracold atom-molecule scattering in dynamic magnetic fields,"We demonstrated that final states of ultracold scattering between atom and
+molecule can be selectively produced using dynamic magnetic fields of multiple
+frequencies. The mechanism of the dynamic magnetic field control is based on a
+generalized quantum Zeno effect for the selected scattering channels. In
+particular, we use an atom-molecule spin flip scattering to show that the
+transition to the selected final spin projection of the molecule in the
+inelastic scattering can be suppressed by dynamic modulation of coupling
+between the Floquet engineered initial and final states.",2112.06481v2
+2022-03-09,Nonequilibrium Hole Dynamics in Antiferromagnets: Damped Strings and Polarons,"We develop a nonperturbative theory for hole dynamics in antiferromagnetic
+spin lattices, as described by the $t$-$J$ model. This is achieved by
+generalizing the selfconsistent Born approximation to nonequilibrium systems,
+making it possible to calculate the full time-dependent many-body wave
+function. Our approach reveals three distinct dynamical regimes, ultimately
+leading to the formation of magnetic polarons. Following the initial ballistic
+stage of the hole dynamics, coherent formation of string excitations gives rise
+to characteristic oscillations in the hole density. Their damping eventually
+leaves behind magnetic polarons that undergo ballistic motion with a greatly
+reduced velocity. The developed theory provides a rigorous framework for
+understanding nonequilibrium physics of defects in quantum magnets and
+quantitatively explains recent observations from cold-atom quantum simulations
+in the strong coupling regime.",2203.04789v2
+2022-05-18,Dynamical magnetic response in superconductors with finite momentum pairs,"We derive the dynamical magnetic response functions in the Fulde-Ferrell (FF)
+state of a superconductor with inversion symmetry. The pair momentum 2q is
+obtained by minimization of the condensation energy and the resulting
+quasiparticle states and spectral functions exhibit the segmentation into
+paired and unpaired regions due to the finite q. The dynamical magnetic
+susceptibility is then calculated in linear response formalism in the FF state
+with finite-q condensate resulting from s-wave or d-wave pairing. We show that
+quasiparticle excitations inside as well as between paired and unpaired
+segments contribute to the dynamical response. We discuss its dependence on
+frequency and momentum transfer which develops a characteristic
+symmetry-breaking parallel to q. Furthermore, we investigate the possible
+influence on Knight shift and in the case of d-wave pairing on the spin
+resonance formation in the FF state.",2205.09207v1
+2022-06-22,Direct optical probing of ultrafast spin dynamics in a magnetic semiconductor,"We uncovered for the first time the spin dynamics involved in the birth and
+growth of giant spin polarons in a magnetic semiconductor. For this purpose, we
+developed a new measurement technique, which for the first time provides direct
+access to the spin dynamics, irrespective of phonons and carriers involved in
+the process. Moreover, we solved for the first time the Landau-Liftshitz
+equation in the specific scenario of spin polarons, which fits our data
+excellently, and demonstrates for the first time that the spin polaron growth
+slows down dramatically when the sample is cooled in the paramagnetic phase.
+Finally, temperature dependent Monte Carlo simulations were performed, which
+are in excellent agreement with the observed slowdown, which demonstrates for
+the first time that fluctuations in the Weiss field play a decisive role in
+spin coherence generation induced by light in magnetic materials. These results
+offer a new tool and new insight for spin dynamics investigations.",2206.10933v1
+2022-09-21,Manipulating THz Spin Current Dynamics by the Dzyaloshinskii-Moriya Interaction in Antiferromagnetic Hematite,"An important vision of modern magnetic research is to use antiferromagnets as
+controllable and active ultrafast components in spintronic devices. Hematite is
+a promising model material in this respect because its pronounced
+Dzyaloshinskii-Moriya interaction leads to the coexistence of
+antiferromagnetism and weak ferromagnetism. Here, we use femtosecond laser
+pulses to drive terahertz spin currents from hematite into an adjacent Pt
+layer. We find two contributions to the generation of the spin current with
+distinctly different dynamics: the impulsive stimulated Raman scatting that
+relies on the antiferromagnetic order and the ultrafast spin Seebeck effect
+that relies on the net magnetization. The total THz spin current dynamics can
+thus be manipulated by a medium-strength magnetic field. The controllability of
+the THz spin current achieved in hematite opens the pathway toward controlling
+the exact spin current dynamics from ultrafast antiferromagnetic spin sources.",2209.10175v1
+2023-01-26,"Optical orientation of excitons in a longitudinal magnetic field in indirect band gap (In,Al)As/AlAs quantum dots with type-I band alignment","The exciton recombination and spin dynamics in (In,Al)As/AlAs quantum dots
+(QDs) with indirect band gap and type-I band alignment are studied. The
+negligible (less than $0.2~\mu$eV) value of the anisotropic exchange
+interaction in these QDs prevents a mixing of the excitonic basis states with
+pure spin and allows for the formation of spin polarized bright excitons for
+quasi-resonant circularly polarized excitation. In a longitudinal magnetic
+field, the recombination and spin dynamics of the excitons are controlled by
+the hyperfine interaction between the electron and nuclear spins. A QD blockade
+by dark excitons is observed in magnetic field eliminating the impact of the
+nuclear spin fluctuations. A kinetic equation model, which accounts for the
+population dynamics of the bright and dark exciton states as well as for the
+spin dynamics, has been developed, which allows for a quantitative description
+of the experimental data.",2301.11138v1
+2023-03-05,Electrical detection of antiferromagnetic dynamics in Gd-Co thin films by using a 154-GHz gyrotron irradiation,"THz magnetization dynamics is a key property of antiferromagnets as well as
+ferrimagnets that could harness the THz forefront and spintronics. While most
+of the present THz measurement techniques are for bulk materials whose
+sensitivities rely on the volume of the material, measurement techniques
+suitable for thin films are quite limited. In this study, we explored and
+demonstrated electrical detection of the antiferromagnetic dynamics in
+ferrimagnetic Gd-Co thin films by using a 154 GHz gyrotron, a high-power
+electromagnetic wave source. Captured resonant modes allow us to characterize
+the peculiar magnetization dynamics of the Gd-Co around the net angular
+momentum compensation. As the gyrotron frequency is scalable up to THz, our
+demonstration can be an important milestone toward the THz measurements for
+antiferro- and ferri- magnetic thin films.",2303.02639v1
+2023-04-25,Vortex dynamics induced by scanning SQUID susceptometry,"We measured the local magnetic response of a niobium thin film by applying a
+millitesla-scale AC magnetic field using a micron-scale field coil and
+detecting the response with a micron-scale pickup loop in a scanning
+superconducting quantum interference device (SQUID) susceptometry measurement.
+Near the film's critical temperature, we observed a step-like nonlinear and
+dissipative magnetic response due to the dynamics of a small number of
+vortex-antivortex pairs induced in the film by the local applied AC field. We
+modeled the dynamics of the measurement using a combined two-dimensional
+London-Maxwell and time-dependent Ginzburg-Landau approach, allowing us to
+construct a detailed real-space picture of the vortex motion causing the
+observed dissipative response. This work pushes scanning SQUID susceptometry of
+two-dimensional superconductors beyond the regime of linear response and lays
+the foundation for microscopic studies of vortex dynamics and pinning in
+superconducting devices and more exotic materials systems.",2304.13093v2
+2023-06-20,Dynamic image reconstruction with motion priors in application to 3D magnetic particle imaging,"Various imaging modalities allow for time-dependent image reconstructions
+from measurements where its acquisition also has a time-dependent nature.
+Magnetic particle imaging (MPI) falls into this class of imaging modalities and
+it thus also provides a dynamic inverse problem. Without proper consideration
+of the dynamic behavior, motion artifacts in the reconstruction become an
+issue. More sophisticated methods need to be developed and applied to the
+reconstruction of the time-dependent sequences of images. In this context, we
+investigate the incorporation of motion priors in terms of certain
+flow-parameter-dependent PDEs in the reconstruction process of time-dependent
+3D images in magnetic particle imaging. The present work comprises the method
+development for a general 3D+time setting for time-dependent linear forward
+operators, analytical investigation of necessary properties in the MPI forward
+operator, modeling aspects in dynamic MPI, and extensive numerical experiments
+on 3D+time imaging including simulated data as well as measurements from a
+rotation phantom and in-vivo data from a mouse.",2306.11625v1
+2020-04-26,Dynamical crossover in the transient quench dynamics of short-range transverse field Ising models,"Dynamical detection of quantum phases and phase transitions (QPT) in quenched
+systems with experimentally convenient initial states is a topic of interest
+from both theoretical and experimental perspectives. Quenched from polarized
+states, longitudinal magnetization decays exponentially to zero in time for the
+short-range transverse-field Ising model (TFIM) and hence, has a featureless
+steady state regime, which prevents it from exhibiting dynamical phase
+transitions of type-I. In this paper, we ask whether the transient regimes of
+such non-equilibrium processes probed by single-site observables, that is
+magnetization per site, could encode information about the underlying QPT. The
+decay rates of time-dependent and single-site observables exhibit a dynamical
+crossover that separates two dynamical regions, ordered and disordered, both of
+which have distinct nonequilibrium responses. We construct a dynamical order
+parameterlike quantity that exhibits a scaling law at the vicinity of the
+crossover. Our results reveal that scaling law exponent in short times at the
+close vicinity of the dynamical crossover is significantly different than the
+one predicted by analytical theory for long times. When integrability is
+strongly broken, the crossover boundary turns into a region that separates two
+other dynamical regions that act like dynamically-ordered and -disordered
+regimes.",2004.12287v5
+2024-01-05,Solutions to the Landau-Lifshitz-Gilbert equation in the frequency space: Discretization schemes for the dynamic-matrix approach,"The dynamic matrix method addresses the Landau-Lifshitz-Gilbert (LLG)
+equation in the frequency domain by transforming it into an eigenproblem.
+Subsequent numerical solutions are derived from the eigenvalues and
+eigenvectors of the dynamic matrix. In this work we explore discretization
+methods needed to obtain a matrix representation of the dynamic operator, a
+fundamental counterpart of the dynamic matrix. Our approach opens a new set of
+linear algebra tools for the dynamic matrix method and expose the
+approximations and limitations intrinsic to it. Moreover, our discretization
+algorithms can be applied to various discretization schemes, extending beyond
+micromagnetism problems. We present some application examples, including a
+technique to obtain the dynamic matrix directly from the magnetic free energy
+function of an ensemble of macrospins, and an algorithmic method to calculate
+numerical micromagnetic kernels, including plane wave kernels. We also show how
+to exploit symmetries and reduce the numerical size of micromagnetic
+dynamic-matrix problems by a change of basis. This procedure significantly
+reduces the size of the dynamic matrix by several orders of magnitude while
+maintaining high numerical precision. Additionally, we calculate analytical
+approximations for the dispersion relations in magnonic crystals. This work
+contributes to the understanding of the current magnetization dynamics methods,
+and could help the development and formulations of novel analytical and
+numerical methods for solving the LLG equation within the frequency domain.",2401.02933v2
+2005-06-27,The dynamical disconnection of sunspots from their magnetic roots,"After a dynamically active emergence phase, magnetic flux at the solar
+surface soon ceases to show strong signs of the subsurface dynamics of its
+parent magnetic structure. This indicates that some kind of disconnection of
+the emerged flux from its roots in the deep convection zone should take place.
+We propose a mechanism for the dynamical disconnection of the surface flux
+based upon the buoyant upflow of plasma along the field lines. Such flows arise
+in the upper part of a rising flux loop during the final phases of its buoyant
+ascent towards the surface. The combination of the pressure buildup by the
+upflow and the cooling of the upper layers of an emerged flux tube by radiative
+losses at the surface lead to a progressive weakening of the magnetic field in
+several Mm depth. When the field strength has become sufficiently low,
+convective motions and the fluting instability disrupt the flux tube into thin,
+passively advected flux fragments, thus providing a dynamical disconnection of
+the emerged part from its roots. We substantiate this scenario by considering
+the quasi-static evolution of a sunspot model under the effects of radiative
+cooling, convective energy transport, and pressure buildup by a prescribed
+inflow at the bottom of the model. For inflow speeds in the range shown by
+simulations of thin flux tubes, we find that the disconnection takes place in a
+depth between 2 and 6 Mm for disconnection times up to 3 days.",0506654v1
+2002-05-08,Quasiparticles governing the zero-temperature dynamics of the 1D spin-1/2 Heisenberg antiferromagnet in a magnetic field,"The T=0 dynamical properties of the one-dimensional (1D) $s=1/2$
+  Heisenberg antiferromagnet in a uniform magnetic field are studied via Bethe
+ansatz for cyclic chains of $N$ sites. The ground state at magnetization
+$0<M_z<N/2$, which can be interpreted as a state with $2M_z$ spinons or as a
+state of $M_z$ magnons, is reconfigured here as the vacuum for a different
+species of quasiparticles, the {\em psinons} and {\em antipsinons}. We
+investigate three kinds of quantum fluctuations, namely the spin fluctuations
+parallel and perpendicular to the direction of the applied magnetic field and
+the dimer fluctuations. The dynamically dominant excitation spectra are found
+to be sets of collective excitations composed of two quasiparticles excited
+from the psinon vacuum in different configurations. The Bethe ansatz provides a
+framework for (i) the characterization of the new quasiparticles in relation to
+the more familiar spinons and magnons, (ii) the calculation of spectral
+boundaries and densities of states for each continuum, (iii) the calculation of
+transition rates between the ground state and the dynamically dominant
+collective excitations, (iv) the prediction of lineshapes for dynamic structure
+factors relevant for experiments performed on a variety of quasi-1D
+antiferromagnetic compounds, including KCuF$_3$,
+  Cu(C$_4$H$_4$N$_2)(NO_3)_2$, and CuGeO$_3$.",0205142v1
+2004-02-16,Low energy excitations and dynamic Dzyaloshinskii-Moriya interaction in $α'$-NaV$_2$O$_5$ studied by far infrared spectroscopy,"We have studied far infrared transmission spectra of alpha'-NaV2O5 between 3
+and 200cm-1 in polarizations of incident light parallel to a, b, and c
+crystallographic axes in magnetic fields up to 33T. The triplet origin of an
+excitation at 65.4cm-1 is revealed by splitting in the magnetic field. The
+magnitude of the spin gap at low temperatures is found to be magnetic field
+independent at least up to 33T. All other infrared-active transitions appearing
+below Tc are ascribed to zone-folded phonons. Two different dynamic
+Dzyaloshinskii-Moriya (DM) mechanisms have been discovered that contribute to
+the oscillator strength of the otherwise forbidden singlet to triplet
+transition. 1. The strongest singlet to triplet transition is an electric
+dipole transition where the polarization of the incident light's electric field
+is parallel to the ladder rungs, and is allowed by the dynamic DM interaction
+created by a high frequency optical a-axis phonon. 2. In the incident light
+polarization perpendicular to the ladder planes an enhancement of the singlet
+to triplet transition is observed when the applied magnetic field shifts the
+singlet to triplet resonance frequency to match the 68cm-1 c-axis phonon
+energy. The origin of this mechanism is the dynamic DM interaction created by
+the 68cm-1 c-axis optical phonon. The strength of the dynamic DM is calculated
+for both mechanisms using the presented theory.",0402419v2
+2004-06-23,Aging and Memory Effects in Superparamagnets and Superspin Glasses,"Many dense magnetic nanoparticle systems exhibit slow dynamics which is
+qualitatively indistinguishable from that observed in atomic spin glasses and
+its origin is attributed to dipole interactions among particle moments (or
+superspins). However, even in dilute nanoparticle systems where the dipole
+interactions are vanishingly small, slow dynamics is observed and is attributed
+solely to a broad distribution of relaxation times which in turn comes from
+that of the anisotropy energy barriers. To clarify characteristic differences
+between the two types of slow dynamics, we study a simple model of a
+non-interacting nanoparticle system (a superparamagnet) analytically as well as
+ferritin (a superparamagnet) and a dense Fe-N nanoparticle system (a superspin
+glass) experimentally. It is found that superparamagnets in fact show aging (a
+waiting time dependence) of the thermoremanent-magnetization as well as various
+memory effects. We also find some dynamical phenomena peculiar only to
+superspin glasses such as the flatness of the field-cooled magnetization below
+the critical temperature and memory effects in the zero-field-cooled
+magnetization. These dynamical phenomena are qualitatively reproduced by the
+random energy model, and are well interpreted by the so-called droplet theory
+in the field of the spin-glass study.",0406546v2
+2005-08-03,Nonequilibrium multicritical behavior in anisotropic Heisenberg ferromagnet driven by oscillating magnetic field,"The Heisenberg ferromagnet (uniaxially anisotropic along z-direction), in the
+presence of time dependent (but uniform over space) magnetic field, is studied
+by Monte Carlo simulation. The time dependent magnetic field was taken as
+elliptically polarised in such a way that the resulting field vector rotates in
+the XZ plane. In the limit of low anisotropy, the dynamical responses of the
+system are studied as functions of temperature and the amplitudes of the
+magnetic field. As the temperature decreases, it aws found that the system
+undergoes multiple dynamical phase transitions. In this limit, the multiple
+transitions were studied in details and the phase diagram for this observed
+multicritical behaviour was drawn in the field amplitude and temperature
+palne.The natures (continuous/discontinuous) of the transitions are determined
+by the temperature variations of fourth order Binder cumulant ratio and the
+distributions of the order parameter near the transition points. The
+transitions are supported by finite size study. The temperature variations of
+the variances of dynamic order parameter components (for different system
+sizes) indicate the existence of diverging length scale near the dynamic
+transition points. The frequency dependences of the transition temperatures of
+the multiple dynamic transition are also studied briefly.",0508103v2
+2009-11-20,Magnetisation dynamics in exchange coupled spring systems with perpendicular anisotropy,"Magnetisation dynamics in exchange spring magnets have been studied using
+simulations of the FePt/Fe bilayer system. The FePt hard layer exhibits strong
+perpendicular magnetocrystalline anisotropy, while the soft (Fe) layer has
+negligible magnetocrystalline anisotropy. The variation of the local spin
+orientation in the Fe layer is determined by the competition of the exchange
+coupling interaction with the hard layer and the magnetostatic energy which
+favours in-plane magnetisation. Dynamics were studied by monitoring the
+response of the Fe layer magnetisation after the abrupt application of a
+magnetic field which causes the systems to realign via precessional motion.
+This precessional motion allows us to obtain the frequency spectrum and hence
+examine the dynamical magnetisation motion. Since the rotation of the spins in
+the soft layer does not have a well defined magnetic anisotropy, the system
+does not present the usual frequency field characteristics for a thin film.
+Additionally we obtain multi-peaked resonance spectra for the application of
+magnetic fields perpendicular to the film plane, though we discount the
+existence of spin wave modes and propose that this arises due to variations in
+the local effective field across the Fe layer. The dynamic response is only
+considered in the Fe layer, with the FePt layer held fixed in the perpendicular
+orientation.",0911.4137v2
+2014-05-25,Proton spin dynamics in polymer melts: new perspectives for experimental investigations of polymer dynamics,"Significant progress was made in recent years in the understanding of the
+proton spin kinetics in polymer melts. Generally, the proton spin kinetics is
+determined by intramolecular and intermolecular magnetic dipole-dipole
+contributions of proton spins. During many decades it was postulated that the
+main contribution is a result of intramolecular magnetic dipole-dipole
+interactions of protons belonging to the same polymer segment. It appears that
+this postulate is far from reality. The relative weights of intra- and
+intermolecular contributions are time dependent and sensitive to details of
+polymer chain dynamics. It is shown that for isotropic models of polymer
+dynamics the influence of the intermolecular magnetic dipole-dipole
+interactions increases faster with increasing evolution time (i.e. decreasing
+frequency) than the corresponding influence of the intramolecular counterpart.
+On the other hand, an inverted situation is predicted by the tube-reptation
+model: here the influence of the intramolecular magnetic dipole-dipole
+interactions increases faster with time than the contribution from
+intermolecular interactions. The intermolecular contribution in the proton
+relaxation of polymer melts can experimentally be isolated using the isotope
+dilution technique and this opens a new perspective for experimental
+investigations of polymer dynamics by proton NMR.",1405.6366v1
+2017-04-26,Anomalous lattice dynamics in a sigma-Fe60V40 alloy: Mossbauer spectroscopic study,"Lattice dynamics in a sigma-Fe60V40 compound, which shows a re-entrant
+magnetism and orders ferromagnetic ally at ca. 170K, was investigated with the
+Mossbauer spectroscopy in the temperature interval of 5-300 K. Two relevant
+spectral parameters viz. the average center shift, <CS>, and the relative
+recoil-free fraction, f/fo, were explored. The former yielded the Debye
+temperature, T_D1, and the mean-square velocity of vibration, <v^2>, while the
+latter T_D2 and the mean-square amplitude of vibrations, <x^2>. Significant
+differences in the lattice-dynamical behaviors in the magnetic and paramagnetic
+phases were revealed. In particular, the values of T_D were notably lower and
+those of f/fo greatly higher in the former. This anomalous result has likely
+its origin in a remarkably high inharmonic contribution to the vibrations found
+for the ground magnetic state (spin-glass). Especially anomalous behavior vs.
+temperature exhibits <x^2> where four well defined ranges could have been
+identified and ascribed to the paramagnetic, ferromagnetic and two spin-glass
+phases. Linear correlations between <v^2>-<x^2> were found within each of the
+four ranges. They enabled determination of force constants, hence a change of
+the potential energy, Ep, in each of the ranges. The total change of Ep=30 meV
+while the corresponding one of the kinetic energy, determined from the
+knowledge of <v^2>, was Ek=21 meV. The lack of balance between Ep and Ek
+follows from the anharmonic lattice-dynamical behavior observed in the
+spin-glass state. The results give a strong evidence that magnetism can
+significantly affect the lattice dynamics.",1704.08054v1
+2020-11-25,Spin dynamics in bulk MnNiGa and Mn$_{1.4}$Pt$_{0.9}$Pd$_{0.1}$Sn investigated by muon spin relaxation,"We report muon spin relaxation and magnetometry studies of bulk
+Mn$_{1.4}$Pt$_{0.9}$Pd$_{0.1}$Sn and MnNiGa, two materials which have recently
+been proposed to host topological magnetic states in thin lamella
+(antiskyrmions for Mn$_{1.4}$Pt$_{0.9}$Pd$_{0.1}$Sn and biskyrmions for
+MnNiGa), and show spin reorientation transitions in bulk. These measurements
+shed light on the magnetic dynamics surounding the two magnetic phase
+transitions in each material. In particular, we demonstrate that the behaviour
+approaching the higher temperature transition in both samples is best
+understood by considering a slow decrease in the frequency of dynamics with
+temperature, rather than the sharp critical slowing down typical of second
+order transitions. Furthermore, at low temperatures the two samples both show
+spin dynamics over a broad range of frequencies that persist below the spin
+reorienation transition. The dynamic behavior we identify gives new insight
+into the bulk magnetism of these materials that may help underpin the
+stabilization of the topologically non-trivial phases that are seen in thin
+lamellae.",2011.12994v2
+2021-04-30,Ab-Initio Molecular Dynamics with Screened Lorentz Forces. Part I. Calculation and Atomic Charge Interpretation of Berry Curvature,"The dynamics of a molecule in a magnetic field is significantly different
+form its zero-field counterpart. One important difference in the presence of a
+field is the Lorentz force acting on the nuclei, which can be decomposed as the
+sum of the bare nuclear Lorentz force and a screening force due to the
+electrons. This screening force is calculated from the Berry curvature and can
+change the dynamics qualitatively. It is therefore important to include the
+contributions from the Berry curvature in molecular dynamics simulations in a
+magnetic field. In this work, we present a scheme for calculating the Berry
+curvature numerically, by a finite-difference technique, addressing challenges
+related to the arbitrary global phase of the wave function. The Berry curvature
+is calculated as a function of bond distance for H$_2$ at the restricted and
+unrestricted Hartree--Fock levels of theory and for CH$^{+}$ as a function of
+the magnetic field strength at the restricted Hartree--Fock level of theory.
+The calculations are carried out using basis sets of contracted Gaussian
+functions equipped with London phase factors (London orbitals) to ensure
+gauge-origin invariance. In the paper, we also interpret the Berry curvature in
+terms of atomic charges and discuss its convergence in basis sets with and
+without London phase factors. Calculation of the Berry curvature allows for its
+inclusion in \textit{ab initio} molecular dynamics simulations in a magnetic
+field.",2104.14861v1
+2021-05-10,Ab-Initio Molecular Dynamics with Screened Lorentz Forces. Part II. Efficient Propagators and Rovibrational Spectra in Strong Magnetic Fields,"Strong magnetic fields have a large impact on the dynamics of molecules. In
+addition to the changes of the electronic structure, the nuclei are exposed to
+the Lorentz force with the magnetic field being screened by the electrons. In
+this work, we explore these effects using ab-initio molecular dynamics
+simulations based on an effective Hamiltonian calculated at the Hartree-Fock
+level of theory. To correctly include these non-conservative forces in the
+dynamics, we have designed a series of novel propagators that show both good
+efficiency and stability in test cases. As a first application, we analyze
+simulations of He and H$_2$ at two field strengths characteristic of magnetic
+white dwarfs (0.1 $B_0 = 2.35 \times 10^4$ T and $B_0 = 2.35 \times 10^5$ T).
+While the He simulations clearly demonstrate the importance of electron
+screening of the Lorentz force in the dynamics, the extracted rovibrational
+spectra of H$_2$ reveal a number of fascinating features not observed in the
+field-free case: couplings of rotations/vibrations with the cyclotron rotation,
+overtones with unusual selection rules, and hindered rotations that transmute
+into librations with increasing field strength. We conclude that our presented
+framework is a powerful tool to investigate molecules in these extreme
+environments.",2105.04225v1
+2021-11-01,Dynamics of position disordered Ising spins with a soft-core potential,"We theoretically study magnetization relaxation of Ising spins distributed
+randomly in a $d$-dimension homogeneous and Gaussian profile under a soft-core
+two-body interaction potential $\propto1/[1+(r/R_c)^\alpha]$ ($\alpha\ge d$),
+where $r$ is the inter-spin distance and $R_c$ is the soft-core radius. The
+dynamics starts with all spins polarized in the transverse direction. In the
+homogeneous case, an analytic expression is derived at the thermodynamic limit,
+which starts as $\propto\exp(-t^2)$ and follows a stretched-exponential law
+asymptotically at long time with an exponent $\beta=d/\alpha$. In between an
+oscillating behaviour is observed with a damping amplitude. For Gaussian
+samples, the degree of disorder in the system can be controlled by the ratio
+$l_\rho/R_c$ with $l_\rho$ the mean inter-spin distance and the magnetization
+dynamics is investigated numerically. In the limit of $l_\rho/R_c\ll1$, a
+coherent many-body dynamics is recovered for the total magnetization despite of
+the position disorder of spins. In the opposite limit of $l_\rho/R_c\gg1$, a
+similar dynamics as that in the homogeneous case emerges at later time after a
+initial fast decay of the magnetization. We obtain a stretched exponent of
+$\beta\approx0.18$ for the asymptotic evolution with $d=3, \alpha=6$, which is
+different from that in the homogeneous case ($\beta=0.5$).",2111.00779v1
+2021-11-09,Dynamics of charged particles moving around Kerr black hole with inductive charge and external magnetic field,"We mainly focus on the effects of small changes of parameters on the dynamics
+of charged particles around the Kerr black hole surrounded by an external
+magnetic field, which can be considered as a tidal environment. The radial
+motions of charged particles on the equatorial plane are studied via an
+effective potential. It is found that the particle energies at the local maxima
+values of the effective potentials increase with an increase of the black hole
+spin and the particle angular momenta, but decrease with an increase of one of
+the inductive charge parameter and magnetic field parameter. The radii of
+stable circular orbits on the equatorial plane also increase, whereas those of
+the innermost stable circular orbits decrease. On the other hand, the effects
+of small variations of the parameters on the orbital regular and chaotic
+dynamics of charged particles on the non-equatorial plane are traced by means
+of a time-transformed explicit symplectic integrator, Poincar\'{e} sections and
+fast Lyapunov indicators. It is shown that the dynamics sensitively depends on
+small variations of the inductive charge parameter, magnetic field parameter,
+energy and angular momentum. Chaos occurs easily as each of the dynamical
+parameters increases. When the dragging effects of the spacetime increase, the
+chaotic properties are not always weakened under some circumstances.",2111.04900v1
+2022-04-30,Electron dynamics in small magnetospheres: insights from global fully-kinetic plasma simulations of planet Mercury,"The planet Mercury possesses a small but highly dynamic magnetosphere in
+which the role and dynamics of electrons are still largely unknown. We aim at
+modeling the global dynamics of solar wind electrons impinging on Mercury's
+magnetosphere. Particular relevance is given to local acceleration processes
+and the global circulation patterns. The goals of this work are pursued by
+means of three-dimensional, fully kinetic particle-in-cell simulations modeling
+the interaction of the solar wind with the Hermean magnetosphere. This method
+allows a self-consistent representation of the plasma dynamics from the large
+planetary scale down to the electron kinetic scale. Numerical simulations are
+carried out using two different solar wind conditions: purely northward or
+purely southward interplanetary magnetic field direction. We find a high plasma
+current (of the order of few $\mu$A/m2) flowing at the magnetospheric
+boundaries (bow shock and magnetopause) dominated by electrons. This current is
+driven by the small-scale electron physics resolved in our model. Furthermore,
+we observe strong electron acceleration up to tens of keV as a consequence of
+magnetic reconnection when the interplanetary magnetic field is directed
+southward. Such energetic electrons are partially trapped in the dipolar
+magnetic field of the planet mainly at nightside. Finally, by studying the
+distribution of electrons in our simulations along Mariner10 and BepiColombo
+first-Mercury-flyby trajectories, we propose that both spacecraft observed this
+energetic quasi-trapped electron population around closest approach.",2205.00229v1
+2022-08-12,Dynamic Sensor Matching based on Geomagnetic Inertial Navigation,"Optical sensors can capture dynamic environments and derive depth information
+in near real-time. The quality of these digital reconstructions is determined
+by factors like illumination, surface and texture conditions, sensing speed and
+other sensor characteristics as well as the sensor-object relations.
+Improvements can be obtained by using dynamically collected data from multiple
+sensors. However, matching the data from multiple sensors requires a shared
+world coordinate system. We present a concept for transferring multi-sensor
+data into a commonly referenced world coordinate system: the earth's magnetic
+field. The steady presence of our planetary magnetic field provides a reliable
+world coordinate system, which can serve as a reference for a position-defined
+reconstruction of dynamic environments. Our approach is evaluated using
+magnetic field sensors of the ZED 2 stereo camera from Stereolabs, which
+provides orientation relative to the North Pole similar to a compass. With the
+help of inertial measurement unit informations, each camera's position data can
+be transferred into the unified world coordinate system. Our evaluation reveals
+the level of quality possible using the earth magnetic field and allows a basis
+for dynamic and real-time-based applications of optical multi-sensors for
+environment detection.",2208.06233v2
+2022-09-08,Effects of the rf current and bias field direction on the transition from linear to non-linear gyrotropic dynamics in magnetic vortex structures,"We present a frequency-domain study of the dynamic behavior of a magnetic
+vortex core within a single Permalloy disk by means of electrical detection and
+micromagnetic simulations. When exciting the vortex core dynamics in a
+non-linear regime, the lineshape of the rectified dc signal reveals a resonance
+peak splitting which depends on the excitation amplitude. Using micromagnetic
+simulations, we show that at high excitation power the peak splitting
+originates from the nanosecond time scale quasi-periodic switching of the
+vortex core polarity. Using lock-in detection, the rectified voltage is
+integrated over a ms time scale, so that the net signal detected between the
+two resonant peaks for a given range of parameters cancels out. The results are
+in agreement with the reported effects of the in-plane static field magnitude
+on the gyration dynamics, and complement them by detailed analysis of the
+effects of the rf current amplitude and the azimuthal angle of the in-plane
+bias magnetic field. Systematic characterization shows that a transition from
+linear to nonlinear dynamical regime can be controlled by rf current as well as
+by varying the magnitude and the direction of the bias magnetic field.",2209.03701v2
+2023-07-30,Spin dynamics in ordered phases of anisotropic triangular-lattice antiferromagnet Cs2CoBr4,"We study spin dynamics of ordered phases of Cs2CoBr4 in a magnetic field
+using electron spin resonance (ESR) technique and theoretical analysis. This
+material hosts weakly interacting distorted-triangular-lattice planes of
+spin-3/2 Co(2+) ions which can be viewed as spin chains coupled by frustrating
+interactions. Strong single-ion anisotropy allows to describe the low-energy
+spin dynamics of this system by an effective strongly anisotropic
+pseudospin-1/2 model. Our ESR data show up to seven branches of magnetic
+resonance in four magnetic phases arising due to subtle interplay of
+frustration, low dimensionality and strong anisotropy. In particular, in the
+low-field collinear stripe phase, the field evolution of modes lying below 200
+GHz is described reasonably good by spectra of spin-1 and spin-0 quasiparticles
+which we obtain using the bond-operator technique. These well-defined
+excitations can be treated as conventional magnons and bound states of two
+magnons, respectively. In contrast, numerous excitations lying above 200 GHz
+are not captured by our theory due to pronounced one-dimensional correlations
+inside spin chains which govern the spin dynamics at high enough energies. As
+it was shown before, these modes can be most naturally interpreted as bound
+states of domain walls in individual chains and their sequence resembles the
+so-called ""Zeeman ladder"" in anisotropic Ising-like spin chains. Thus, Cs2CoBr4
+is a system showing spin-dynamics in ordered state characteristic of both
+two-dimensional and one-dimensional magnets.",2307.16251v1
+2023-08-29,Wall mode dynamics and transition to chaos in magnetoconvection with a vertical magnetic field,"Quasistatic magnetoconvection of a low Prandtl number fluid
+($\textrm{Pr}=0.025)$ with a vertical magnetic field is considered in a unit
+aspect ratio box with no-slip boundaries. At high relative magnetic field
+strengths, given by the Hartmann number $\textrm{Ha}$, the onset of convection
+is known to result from a sidewall instability giving rise to the wall mode
+regime. Here, we carry out 3D direct numerical simulations of unprecedented
+length to map out the parameter space at $\textrm{Ha} = 200, 500, 1000$,
+varying the Rayleigh number ($\textrm{Ra}$) between $6\times10^5 \lesssim
+\textrm{Ra} \lesssim 5\times 10^8$. We track the development of stable
+equilibria produced by this primary instability, identify bifurcations leading
+to limit cycles, and eventually to chaotic dynamics. At {$\textrm{Ha}=200$},
+the steady wall mode solution undergoes a symmetry-breaking bifurcation
+producing a state featuring a coexistence between wall modes and a large-scale
+roll in the centre of the domain which persists to higher $\textrm{Ra}$.
+However, under a stronger magnetic field at $\textrm{Ha}=1000$, the steady wall
+mode solution undergoes a Hopf bifurcation producing a limit cycle which
+further develops to solutions that shadow an orbit homoclinic to a saddle
+point. Upon a further increase in $\textrm{Ra}$, the system undergoes a
+subsequent symmetry break producing a coexistence between wall modes and a
+large-scale roll, although the large-scale roll exists only for a small range
+of $\textrm{Ra}$, and chaotic dynamics primarily arise due to a mixture of
+chaotic wall mode dynamics and arrays of cellular structures.",2308.15165v2
+2024-01-22,Time-Resolved Imaging Reveals Transiently Chaotic Spin-Orbit-Torque-Driven Dynamics Under Controlled Conditions,"Spin-orbit torques (SOTs) act as efficient drivers for nanoscale magnetic
+systems, such as in magnetic tunnel junctions, nano-oscillators and racetrack
+geometries. In particular, in combination with materials exhibiting high
+Dzyaloshinskii--Moriya interaction, SOTs are considered to result in
+well-controlled deterministic magnetisation dynamics and are, therefore, used
+as robust drives to move and create magnetic skyrmions. In contrast to these
+expectations, we here find unpredictable, transiently chaotic dynamics induced
+by SOT at an artificial anisotropy-engineered defect in a magnetic racetrack.
+Based on these controlled conditions, we directly observe the nanoscale
+dynamics with holography-based, time-resolved x-ray imaging. In concert with
+micromagnetic simulations, we disclose a regime of violent picosecond
+fluctuations, including topological instabilities that, remarkably, result in
+deterministic final configurations. In addition, our images expose previously
+unseen skyrmion shedding and highlight the potential of transiently chaotic
+pathways for topological switching. Our approach offers new perspectives for
+the investigation and application of highly non-linear SOT dynamics in
+spintronics materials.",2401.12130v1
+2024-02-16,Live magnetic observation of parahydrogen hyperpolarization dynamics,"Nuclear spin hyperpolarization is used in physics, chemistry, and medicine to
+produce strong magnetization unachievable by equilibrium polarization
+techniques. Hyperpolarization enables magnetic resonance spectroscopy and
+imaging with minute samples, and is used to produce MRI spin-tracers and
+polarized physics targets. Although widely used, the dynamics of the
+hyperpolarization process have never been studied `live' due to the extremely
+low (Hz-band) frequencies involved, and/or detector saturation by the driving
+fields used. Here, we use an atomic magnetometer with sub-pT sensitivity to
+observe, in real time, the complex dynamics of hyperpolarization, without
+disturbing or disrupting the process. We start by examining
+parahydrogen-induced $^1$H and $^{13}$C magnetization build-up during adiabatic
+eigenbasis transformations in the $\mu$T-field avoided state crossings at the
+heart of the process; we see live hyperpolarization dynamics including coherent
+oscillations, leakage mechanisms and dipolar shifts that would be challenging
+or impossible to observe by post hoc measurement. We then extend the methods to
+observe the chemical-exchange-driven $^{13}$C hyperpolarization of
+[1-$^{13}$C]-pyruvate -- the most important spin tracer for clinical metabolic
+imaging. Beyond the interests of hyperpolarization, the observation of
+adiabatic transitions in real-time is a fundamentally new approach to NMR,
+reveals previously hidden nuclear spin dynamics and enables quantum control and
+live process optimization in a variety of chemical scenarios.",2402.10766v1
+2012-05-14,Tuning the phase transition dynamics by variation of cooling field and metastable phase fraction in Al doped Pr$_{0.5}$Ca$_{0.5}$MnO$_3$,"We report the effect of field, temperature and thermal history on the time
+dependence in resistivity and magnetization in the phase separated state of Al
+doped Pr$_{0.5}$Ca$_{0.5}$MnO$_3$. The rate of time dependence in resistivity
+is much higher than that of magnetization and it exhibits a different cooling
+field dependence due to percolation effects. Our analysis show that the time
+dependence in physical properties depends on the phase transition dynamics
+which can be effectively tuned by variation of temperature, cooling field and
+metastable phase fraction. The phase transition dynamics can be broadly divided
+into the arrested and un-arrested regimes, and in the arrested regime, this
+dynamics is mainly determined by time taken in the growth of critical nuclei.
+An increase in cooling field and/or temperature shifts this dynamics from
+arrested to un-arrested regime, and in this regime, this dynamics is determined
+by thermodynamically allowed rate of formation of critical nuclei which in turn
+depends on the cooling field and available metastable phase fraction. At a
+given temperature, a decrease in metastable phase fraction shifts the crossover
+from arrested to un-arrested regimes towards lower cooling field. It is rather
+significant that inspite of the metastable phase fraction calculated from
+resistivity being somewhat off from that of magnetization, their cooling field
+dependence exhibits a striking similarity which indicate that the dynamics in
+arrested and un-arrested regimes are so different that it comes out vividly
+provided that the measurements are done around percolation threshold.",1205.3040v1
+2019-05-24,"Fluid Dynamics of Earth's core: geodynamo, inner core dynamics, core formation","This chapter is build from three 1.5 hours lectures given in Udine in april
+2018 on various aspects of Earth's core dynamics. The chapter starts with a
+short historical note on the discovery of Earth's magnetic field and core
+(section 1). We then turn to an introduction of magnetohydrodynamics (section
+2), introducing and discussing the induction equation and the form and effects
+of the Lorentz force. Section 3 is devoted to the description of Earth's
+magnetic field, introducing its spherical harmonics description and showing how
+it can be used to demonstrate the internal origin of the geomagnetic origin. We
+then move to an introduction of the convection-driven model of the geodynamo
+(section 4), discussing our current understanding of the dynamics of Earth's
+core, obtaining heuristically the Ekman dependency of the critical Rayleigh
+number for natural rotating convection, and introducing the equations and
+non-dimensional parameters used to model a convectively driven dynamo. The
+following section deals with the energetics of the geodynamo (section 5). The
+final two section deal with the dynamics of the inner core, focusing on the
+effect of the magnetic field (section 6), and with the formation of the core
+(section 7). Given the wide scope of this chapter and the limited time
+available, this introduction to Earth's core dynamics is by no means intended
+to be comprehensive. For more informations, the interested reader may refer to
+Jones (2011), Olson (2013), or Christensen and Wicht (2015) on the geomagnetic
+field and the geodynamo, to Sumita and Bergman (2015), Deguen (2012) and
+Lasbleis and Deguen (2015) on the dynamics of the inner core, and to Rubie et
+al. (2015) on core formation.",1905.10416v1
+2022-04-23,Critical Dynamics of the Antiferromagnetic $O(3)$ Nonlinear Sigma Model with Conserved Magnetization,"We study the near-equilibrium critical dynamics of the $O(3)$ nonlinear sigma
+model describing isotropic antiferromagnets with non-conserved order parameter
+reversibly coupled to the conserved total magnetization. To calculate response
+and correlation functions, we set up a description in terms of Langevin
+stochastic equations of motion, and their corresponding Janssen--De~Dominicis
+response functional. We find that in equilibrium, the dynamics is
+well-separated from the statics, at least to one-loop order in a perturbative
+treatment with respect to the static and dynamical nonlinearities. Since the
+static nonlinear sigma model must be analyzed in a dimensional $d = 2 +
+\varepsilon$ expansion about its lower critical dimension $d_\textrm{lc} = 2$,
+whereas the dynamical mode-coupling terms are governed by the upper critical
+dimension $d_c = 4$, a simultaneous perturbative dimensional expansion is not
+feasible, and the reversible critical dynamics for this model cannot be
+accessed at the static critical renormalization group fixed point. However, in
+the coexistence limit addressing the long-wavelength properties of the
+low-temperature ordered phase, we can perform an $\epsilon = 4 - d$ expansion
+near $d_c$. This yields anomalous scaling features induced by the massless
+Goldstone modes, namely sub-diffusive relaxation for the conserved
+magnetization density with asymptotic scaling exponent $z_\Gamma = d - 2$ which
+may be observable in neutron scattering experiments. Intriguingly, if
+initialized near the critical point, the renormalization group flow for the
+effective dynamical exponents recovers their universal critical values $z_c = d
+/ 2$ in an intermediate crossover region.",2204.11145v2
+2022-11-06,Dynamical singularity of the rate function for quench dynamics in finite-size quantum systems,"The dynamical quantum phase transition is characterized by the emergence of
+nonanalytic behaviors in the rate function, corresponding to the occurrence of
+exact zero points of the Loschmidt echo in the thermodynamical limit. In
+general, exact zeros of the Loschmidt echo are not accessible in a finite-size
+quantum system except for some fine-tuned quench parameters. In this work, we
+study the realization of the dynamical singularity of the rate function for
+finite-size systems under the twist boundary condition, which can be introduced
+by applying a magnetic flux. By tuning the magnetic flux, we illustrate that
+exact zeros of the Loschmidt echo can be always achieved when the postquench
+parameter is across the underlying equilibrium phase transition point, and thus
+the rate function of a finite-size system is divergent at a series of critical
+times. We demonstrate our theoretical scheme by calculating the
+Su-Schrieffer-Heeger model and the Creutz model in detail and exhibit its
+applicability to more general cases. Our result unveils that the emergence of
+dynamical singularity in the rate function can be viewed as a signature for
+detecting dynamical quantum phase transition in finite-size systems. We also
+unveil that the critical times in our theoretical scheme are independent on the
+systems size, and thus it provides a convenient way to determine the critical
+times by tuning the magnetic flux to achieve the dynamical singularity of the
+rate function.",2211.03135v2
+2022-11-17,As a matter of dynamical range -- scale dependent energy dynamics in MHD turbulence,"Magnetized turbulence is ubiquitous in many astrophysical and terrestrial
+plasmas but no universal theory exists. Even the detailed energy dynamics in
+magnetohydrodynamic (MHD) turbulence are still not well understood. We present
+a suite of subsonic, super-Alfv\'enic, high plasma-beta MHD turbulence
+simulations that only vary in their dynamical range, i.e., in their separation
+between the large-scale forcing and dissipation scales, and their dissipation
+mechanism (implicit large eddy simulation, ILES, versus and direct numerical
+simulation, DNS). Using an energy transfer analysis framework we calculate the
+effective, numerical viscosities and resistivities and demonstrate and that all
+ILES calculations of MHD turbulence are resolved and correspond to an
+equivalent visco-resistive MHD turbulence calculation. Increasing the number of
+grid points used in an ILES corresponds to lowering the dissipation
+coefficients, i.e., larger (kinetic and magnetic) Reynolds numbers for a
+constant forcing scale. Independently, we use this same framework to
+demonstrate that -- contrary to hydrodynamic turbulence -- the cross-scale
+energy fluxes are not constant in MHD turbulence. This applies both to
+different mediators (such as cascade processes or magnetic tension) for a given
+dynamical range as well as to a dependence on the dynamical range itself, which
+determines the physical properties of the flow. We do not observe any
+indication of convergence even at the highest resolution (largest Reynolds
+numbers) simulation at $2{,}048^3$ cells, calling into question whether an
+asymptotic regime in MHD turbulence exists, and, if so, what it looks like.",2211.09750v1
+1998-12-09,Nonlinear dynamic susceptibilities of interacting and noninteracting nanoparticle systems,"The linear and cubic dynamic susceptibilities of solid dispersions of
+nano-sized maghemite particles have been measured for three samples with a
+volume concentration of magnetic particles ranging from 0.3 % to 17 %, in order
+to study the effect of dipole-dipole interactions. Significant differences
+between the dynamic response of the three samples are observed. The dynamic
+susceptibilities of the most dilute sample compare reasonably well with an
+existing theory for the linear and cubic dynamic susceptibilities of an
+assembly of noninteracting, uniaxial magnetic particles. The nonlinear dynamic
+response of the most concentrated sample exhibits at low temperatures some of
+the features observed in a Ag(11 at.% Mn) spin glass.",9812143v2
+2003-08-23,On the universality of the fluctuation-dissipation ratio in non-equilibrium critical dynamics,"The two-time nonequilibrium correlation and response functions in 1D kinetic
+classical spin systems with non-conserved dynamics and quenched to their
+zero-temperature critical point are studied. The exact solution of the kinetic
+Ising model with Glauber dynamics for a wide class of initial states allows for
+an explicit test of the universality of the non-equilibrium limit
+fluctuation-dissipation ratio X_{\infty}. It is shown that the value of
+X_{\infty} depends on whether the initial state has finitely many domain walls
+or not and thus two distinct dynamic universality classes can be identified in
+this model. Generic 1D kinetic spin systems with non-conserved dynamics fall
+into the same universality classes as the kinetic Glauber-Ising model provided
+the dynamics is invariant under the C-symmetry of simultaneous spin and
+magnetic-field reversal. While C-symmetry is satisfied for magnetic systems, it
+need not be for lattice gases which may therefore display hitherto unexplored
+types of non-universal kinetics.",0308466v2
+2003-09-26,Spin Glasses: Model systems for non-equilibrium dynamics,"Spin glasses are frustrated magnetic systems due to a random distribution of
+ferro- and antiferromagnetic interactions. An experimental three dimensional
+(3d) spin glass exhibits a second order phase transition to a low temperature
+spin glass phase regardless of the spin dimensionality. In addition, the low
+temperature phase of Ising and Heisenberg spin glasses exhibits similar
+non-equilibrium dynamics and an infinitely slow approach towards a
+thermodynamic equilibrium state. There are however significant differences in
+the detailed character of the dynamics as to memory and rejuvenation phenomena
+and the influence of critical dynamics on the behaviour. In this article, some
+aspects of the non-equilibrium dynamics of an Ising and a Heisenberg spin glass
+are briefly reviewed and some comparisons are made to other glassy systems that
+exhibit magnetic non-equilibrium dynamics.",0309602v1
+2004-09-04,Stochastic dynamic simulations of fast remagnetization processes: recent advances and applications,"Numerical simulations of fast remagnetization processes using the stochastic
+dynamics are widely used to study various magnetic systems. In this paper we
+first address several crucial methodological problems of such simulations: (i)
+the influence of the finite-element discretization on the simulated dynamics,
+(ii) choice between Ito and Stratonovich stochastic calculi by the solution of
+micromagnetic stochastic equations of motion and (iii) non-trivial correlation
+properties of the random (thermal) field. Next we discuss several examples to
+demonstrate the great potential of the Langevin dynamics for studying fast
+remagnetization processes in technically relevant applications: we present
+numerical analysis of equilibrium magnon spectra in patterned structures, study
+thermal noise effects on the magnetization dynamics of nanoelements in pulsed
+fields and show some results for a remagnetization dynamics induced by a
+spin-polarized current.",0409098v1
+2006-10-05,Dynamic dipole and quadrupole phase transitions in the kinetic spin-1 model,"The dynamic phase transitions have been studied, within a mean-field
+approach, in the kinetic spin-1 Ising model Hamiltonian with arbitrary bilinear
+and biquadratic pair interactions in the presence of a time varying
+(sinusoidal) magnetic field by using the Glauber-type stochastic dynamics. The
+nature (first- or second-order) of the transition is characterized by
+investigating the behavior of the thermal variation of the dynamic order
+parameters. The dynamic phase transitions (DPTs) are obtained and the phase
+diagrams are constructed in the temperature and magnetic field amplitude plane
+and found six fundamental types of phase diagrams. Phase diagrams exhibit one
+or two dynamic tricritical points depending on the biquadratic interaction (K).
+Besides the disordered (D) and ferromagnetic (F) phases, the FQ + D, F + FQ and
+F + D coexistence phase regions also exist in the system and the F and F + D
+phases disappear for high values of K.",0610149v1
+2010-05-04,Critical Slowing Down Along the Dynamic Phase Boundary in Ising Meanfield Dynamics,"We studied the dynamical phase transition in kinetic Ising ferromagnets
+driven by oscillating magnetic field in meanfield approximation. The meanfield
+differential equation was solved by sixth order Runge-Kutta-Felberg method. The
+time averaged magnetisation plays the role of the dynamic order parameter. We
+studied the relaxation behaviour of the dynamic order parameter close to the
+transition temperature, which depends on the amplitude of the applied magnetic
+field. We observed the critical slowing down along the dynamic phase boundary.
+We proposed a power law divergence of the relaxation time and estimated the
+exponent. We also found its dependence on the field amplitude and compared the
+result with the exact value in limiting case.",1005.0565v1
+2010-12-11,Monte Carlo study of dynamic phase transition in Ising metamagnet driven by oscillating magnetic field,"The dynamical responses of Ising metamagnet (layered antiferromagnet) in the
+presence of a sinusoidally oscillating magnetic field are studied by Monte
+Carlo simulation. The time average staggered magnetisation plays the role of
+dynamic order parameter. A dynamical phase transition was observed and a phase
+diagram was plotted in the plane formed by field amplitude and temperature. The
+dynamical phase boundary is observed to shrink inward as the relative
+antiferromagnetic strength decreases. The results are compared with that
+obtained from pure ferromagnetic system. The shape of dynamic phase boundary
+observed to be qualitatively similar to that obtained from previous meanfield
+calculations.",1012.2457v2
+2012-01-30,Universal dynamical phase diagram of lattice spin models and strongly correlated ultracold atoms in optical lattices,"We study semiclassical dynamics of anisotropic Heisenberg models in two and
+three dimensions. Such models describe lattice spin systems and hard core
+bosons in optical lattices. We solve numerically Landau-Lifshitz type equations
+on a lattice and show that in the phase diagram of magnetization and
+interaction anisotropy, one can identify several distinct regimes of dynamics.
+These regions can be distinguished based on the character of one dimensional
+solitonic excitations, and stability of such solitons to transverse modulation.
+Small amplitude and long wavelength perturbations can be analyzed analytically
+using mapping of non-linear hydrodynamic equations to KdV type equations.
+Numerically we find that properties of solitons and dynamics in general remain
+similar to our analytical results even for large amplitude and short distance
+inhomogeneities, which allows us to obtain a universal dynamical phase diagram.
+As a concrete example we study dynamical evolution of the system starting from
+a state with magnetization step and show that formation of oscillatory regions
+and their stability to transverse modulation can be understood from the
+properties of solitons. In regimes unstable to transverse modulation we observe
+formation of lump type solutions with modulation in all directions. We discuss
+implications of our results for experiments with ultracold atoms.",1201.6400v1
+2014-08-05,Dynamics of a Mn spin coupled to a single hole confined in a quantum dot,"Using the emission of the positively charged exciton as a probe, we analyze
+the dynamics of the optical pumping and the dynamics of the relaxation of a Mn
+spin exchange-coupled with a confined hole spin in a II-VI semiconductor
+quantum dot. The hole-Mn spin can be efficiently initialized in a few tens of
+$ns$ under optical injection of spin polarized carriers. We show that this
+optical pumping process and its dynamics are controlled by electron-Mn
+flip-flops within the positively charged exciton-Mn complex. The pumping
+mechanism and its magnetic field dependence are theoretically described by a
+model including the dynamics of the electron-Mn complex in the excited state
+and the dynamics of the hole-Mn complex in the ground state of the positively
+charged quantum dot. We measure at zero magnetic field a spin relaxation time
+of the hole-Mn spin in the $\mu s$ range or shorter. This hole-Mn spin
+relaxation is induced by the presence of valence band mixing in self-assembled
+quantum dots.",1408.0930v2
+2014-11-14,Dynamical instabilities and transient short-range order in the fermionic Hubbard model,"We study the dynamics of magnetic correlations in the half-filled fermionic
+Hubbard model following a fast ramp of the repulsive interaction. We use
+Schwinger-Keldysh self-consistent second-order perturbation theory to
+investigate the evolution of single-particle Green's functions and solve the
+non-equilibrium Bethe-Salpeter equation to study the dynamics of magnetic
+correlations. This approach gives us new insights into the interplay between
+single-particle relaxation dynamics and the growth of antiferromagnetic
+correlations. Depending on the ramping time and the final value of the
+interaction, we find different dynamical behavior which we illustrate using a
+dynamical phase diagram. Of particular interest is the emergence of a transient
+short-range ordered regime characterized by the strong initial growth of
+antiferromagnetic correlations followed by a decay of correlations upon
+thermalization. The discussed phenomena can be probed in experiments with
+ultracold atoms in optical lattices.",1411.4049v1
+2015-07-06,Bose-Hubbard ladder subject to effective magnetic field: quench dynamics in a harmonic trap,"Motivated by a recent experiment with optical lattices that has realized a
+ladder geometry with an effective magnetic field (Atala et al., Nature Physics
+\textbf{10}, 588 (2014)), we study the dynamics of bosons on a tight-binding
+two-leg ladder with complex hopping amplitudes. This system displays a quantum
+phase transition even without interactions. We study the non-equilibrium
+dynamics without and with interactions, in the presence of a harmonic trapping
+potential. In particular we consider dynamics induced by quenches of the
+trapping potential and of the magnitude of the rung hopping. We present a
+striking ""slowing down"" effect in the collective mode dynamics near the phase
+transition. This manifestation of a slowing down phenomenon near a quantum
+phase transition can be visualized unusually directly: the collective mode
+dynamics can be followed experimentally in real time and real space by imaging
+the atomic cloud.",1507.01402v1
+2016-02-09,Dynamics of cholesteric liquid crystals in the presence of random magnetic fields,"Based on dynamic renormalization group techniques, this letter analyzes the
+effects of external stochastic perturbations on the dynamical properties of
+cholesteric liquid crystals, studied in presence of a random magnetic field.
+Our analysis quantifies the nature of the temperature dependence of the
+dynamics; the results also highlight a hitherto unexplored regime in
+cholesteric liquid crystal dynamics. We show that stochastic fluctuations drive
+the system to a second-ordered Kosterlitz-Thouless phase transition point,
+eventually leading to a Kardar-Parisi-Zhang (KPZ) universality class. The
+results go beyond quasi-first order mean-field theories, and provides the first
+theoretical understanding of a KPZ phase in distorted nematic liquid crystal
+dynamics.",1602.03219v1
+2016-11-03,Spatio-temporal Dynamics of Intrinsic Networks in Functional Magnetic Imaging Data Using Recurrent Neural Networks,"We introduce a novel recurrent neural network (RNN) approach to account for
+temporal dynamics and dependencies in brain networks observed via functional
+magnetic resonance imaging (fMRI). Our approach directly parameterizes temporal
+dynamics through recurrent connections, which can be used to formulate blind
+source separation with a conditional (rather than marginal) independence
+assumption, which we call RNN-ICA. This formulation enables us to visualize the
+temporal dynamics of both first order (activity) and second order (directed
+connectivity) information in brain networks that are widely studied in a static
+sense, but not well-characterized dynamically. RNN-ICA predicts dynamics
+directly from the recurrent states of the RNN in both task and resting state
+fMRI. Our results show both task-related and group-differentiating directed
+connectivity.",1611.00864v2
+2017-01-27,Collective dynamics in atomistic models with coupled translational and spin degrees of freedom,"Using an atomistic model that simultaneously treats the dynamics of
+translational and spin degrees of freedom, we perform combined molecular and
+spin dynamics simulations to investigate the mutual influence of the phonons
+and magnons on their respective frequency spectra and lifetimes in
+ferromagnetic bcc iron. By calculating the Fourier transforms of the space- and
+time-displaced correlation functions, the characteristic frequencies and the
+linewidths of the vibrational and magnetic excitation modes were determined.
+Comparison of the results with that of the stand-alone molecular dynamics and
+spin dynamics simulations reveals that the dynamic interplay between the
+phonons and magnons leads to a shift in the respective frequency spectra and a
+decrease in the lifetimes. Moreover, in the presence of lattice vibrations,
+additional longitudinal magnetic excitations were observed with the same
+frequencies as the longitudinal phonons.",1701.07906v1
+2019-03-24,"Synchronized, periodic, and chaotic dynamics in spin torque oscillator with two free layers","A phase diagram of the magnetization dynamics is studied by numerically
+solving the Landau-Lifshitz-Gilbert (LLG) equation in a spin torque oscillator
+consisting of asymmetric two free layers that are magnetized in in-plane
+direction. We calculated the dynamics for a wide range of current density for
+both low and high field cases, and found many dynamical phases such as
+synchronization, auto-oscillation with different frequencies, and chaotic
+dynamics. The observation of the synchronization indicates the presence of a
+dynamical phase which has not been found experimentally by using the
+conventional electrical detection method. The auto-oscillations with different
+frequencies lead to an oscillation of magnetoresistance with a high frequency,
+which can be measured experimentally. The chaotic and/or periodic behavior of
+magnetoresistance in a high current region, on the other hand, leads to a
+discontinuous change of the peak frequency in Fourier spectrum.",1903.09938v2
+2019-07-18,Dynamical formation of a magnetic polaron in a two-dimensional quantum antiferromagnet,"We numerically study the real-time dynamics of a single hole created in the
+$t-J$ model on a square lattice. Initially, the hole spreads ballistically with
+a velocity proportional to the hopping matrix element. At intermediate to long
+times, the dimensionality as well as the spin background determine the hole
+dynamics. A hole created in the ground state of a two dimensional quantum
+antiferromagnet propagates again ballistically at long times but with a
+velocity proportional to the spin exchange coupling, showing the formation of a
+magnetic polaron. We provide an intuitive explanation of this dynamics in terms
+of a parton construction, which leads to a good quantitative agreement with the
+numerical simulations. In the limit of infinite temperature and no spin
+exchange couplings, the dynamics can be approximated by a quantum random walk
+on the Bethe lattice. Adding Ising interactions corresponds to an effective
+disordered potential, which can dramatically slow down the hole propagation,
+consistent with subdiffusive dynamics.",1907.08214v1
+2020-05-13,Manipulation of heteronuclear spin dynamics with microwave and vector light shift,"We report the observation and manipulation of heteronuclear spin dynamics in
+a spin-1 mixture of ultracold $^{87}$Rb and $^{23}$Na atoms. The dynamics is
+driven by the interspecies spin-dependent interaction and shows a pronounced
+dependence on magnetic fields with influences from both linear and quadratic
+Zeeman shifts. Similar to the well-studied homonuclear cases, the interspecies
+spin dynamics can be controlled by tuning the quadratic Zeeman shift with
+far-detuned microwave fields. In addition, we successfully realize spin
+dynamics control with vector light shifts which act as a species-selective
+effective magnetic field on $^{87}$Rb atoms. Both methods show negligible loss
+of atoms thus will be powerful techniques for investigating spin dynamics with
+fast temporal and high spatial resolutions.",2005.06098v1
+2021-03-02,Open Quantum-System Simulation of Faraday's Induction Law via Dynamical Instabilities,"We propose a novel type of a Bose-Hubbard ladder model based on an open
+quantum-gas--cavity-QED setup to study the physics of dynamical gauge
+potentials. Atomic tunneling along opposite directions in the two legs of the
+ladder is mediated by photon scattering from transverse pump lasers to two
+distinct cavity modes. The resulting interplay between cavity photon
+dissipation and the optomechanical atomic back-action then induces an
+average-density-dependent dynamical gauge field. The dissipation-stabilized
+steady-state atomic motion along the legs of the ladder leads either to a pure
+chiral current, screening the induced dynamical magnetic field as in the
+Meissner effect, or generates simultaneously chiral and particle currents. For
+sufficiently strong pump the system enters into a dynamically unstable regime
+exhibiting limit-cycle and period-doubled oscillations. Intriguingly, an
+electromotive force is induced in this dynamical regime as expected from an
+interpretation based on Faraday's law of induction for the time-dependent
+synthetic magnetic flux.",2103.01979v2
+2021-07-02,Vortex Dynamics in Amorphous MoSi Superconducting Thin Films,"Vortex dynamics in superconductors have received a great deal of attention
+from both fundamental and applied researchers over the past few decades.
+Because of its critical role in the energy relaxation process of type II
+superconductors, vortex dynamics have been deemed a key factor for the emerging
+superconducting devices, but the effect of irradiation on vortex dynamics
+remains unclear. With the support of electrical transport measurements under
+external magnetic fields and irradiation, photon effect on vortex dynamics in
+amorphous MoSi (a MoSi) superconducting thin films are investigated in this
+work. The magnetic field dependent critical vortex velocity v* derived from the
+Larkin Ovchinnikov model is not significantly affected by irradiation. However,
+vortex depinning is found to be enhanced by photon-induced reduction in
+potential barrier, which mitigates the adverse effect of film inhomogeneity on
+superconductivity in the a MoSi thin films. The thorough understanding of the
+vortex dynamics in a MoSi thin films under the effect of external stimuli is of
+paramount importance for both further fundamental research in this area and
+optimization of future superconducting devices.",2107.01046v2
+2022-01-04,Quantum dynamics of Gaudin magnets,"Quantum dynamics of many-body systems is a fascinating and significant
+subject for both theory and experiment. The question of how an isolated
+many-body system evolves to its steady state after a sudden perturbation or
+quench still remains challenging. In this paper, using the Bethe ansatz wave
+function, we study the quantum dynamics of an inhomogeneous Gaudin magnet. We
+derive explicit analytical expressions for various local dynamic quantities
+with an arbitrary number of flipped bath spins, such as: the spin distribution
+function, the spin-spin correlation function, and the Loschmidt echo. We also
+numerically study the relaxation behavior of these dynamic properties, gaining
+considerable insight into coherence and entanglement between the central spin
+and the bath. In particular, we find that the spin-spin correlations relax to
+their steady value via a nearly logarithmic scaling, whereas the Loschmidt echo
+shows an exponential relaxation to its steady value. Our results advance the
+understanding of relaxation dynamics and quantum correlations of long-range
+interacting models of Gaudin type.",2201.01025v1
+2022-11-07,Simulation of the Einstein-de Haas effect combining molecular and spin dynamics,"The spin and lattice dynamics of a ferromagnetic nanoparticle are studied via
+molecular dynamics and with semi-classical spin dynamics simulations where spin
+and lattice degrees of freedom are coupled via a dynamic uniaxial anisotropy
+term. We show that this model conserves total angular momentum, whereas spin
+and lattice angular momentum are not conserved. We carry out simulations of the
+the Einstein-de Haas effect for a Fe nanocluster with more than 500 atoms that
+is free to rotate, using a modified version of the open-source spinlattice
+dynamics code (SPILADY). We show that the rate of angular momentum transfer
+between spin and lattice is proportional to the strength of the magnetic
+anisotropy interaction. The addition of the anisotropy allows full spin-lattice
+relaxation to be achieved on previously reported timescales of \sim 100 ps and
+for tight-binding magnetic anisotropy energies comparable to those of small Fe
+nanoclusters.",2211.03706v1
+2024-02-08,Absence of breakdown of ferrodark solitons exhibiting snake instability,"We investigate the dynamical stability and real time dynamics of the
+two-types of ferrodark solitons (FDSs) which occur as topological magnetic
+domain walls in the easy-plane phase of a quasi-two-dimensional (2D)
+ferromagnetic spin-1 Bose-Einstein condensate. The type-I FDS has positive
+inertial mass and exhibits a single dynamical instability that generates in
+plane spin winding, causing polar-core spin vortex dipoles. The positive
+inertial mass leads to the elastic oscillations of the soliton under transverse
+perturbations. The type-II FDS has negative inertial mass and exhibits a snake
+instability and a spin-twist instability, with the latter involving the
+generation of out of plane spin winding. Distinct from the normal dynamics of
+negative mass solitons under long wave length transverse perturbations, the
+snake instability does not lead to the type-II FDS breaking down. Instead,
+segments of the type-II FDS convert to type-I and mass vortex dipoles are
+produced. The resulting hybridized-chain of the two soliton types and vortices
+exhibits complex 2D soliton dynamics at long times while the vortices remain
+confined and the topological structure of a magnetic domain wall is preserved.",2402.05351v1
+2010-04-20,"Near-Infrared Imaging Polarimetry of the Serpens Cloud Core: Magnetic Field Structure, Outflows, and Inflows in A Cluster Forming Clump","We made deep NIR imaging polarimetry toward the Serpens cloud core. The
+polarization vector maps enable us to newly detect 24 small IR reflection
+nebulae with YSOs. Polarization measurements of NIR point sources indicate an
+hourglass-shaped magnetic field, of which symmetry axis is nearly perpendicular
+to the elongation of the C18O (J=1-0) or submillimeter continuum emission. The
+bright part of C18O (J=1-0), submillimeter continuum cores as well as many
+class 0/I objects are located just toward the constriction region of the
+hourglass-shaped magnetic field. Applying the CF method, the magnetic field
+strength was estimated to be ~100 muG, suggesting that the ambient region of
+the Serpens cloud core is moderately magnetically supercritical. These suggest
+that the Serpens cloud core first contracted along the magnetic field to be an
+elongated cloud, which is perpendicular to the magnetic field, and that then
+the central part contracted cross the magnetic field due to the high density in
+the central region of the cloud core, where star formation is actively
+continuing. Comparison of this magnetic field with the previous observations of
+molecular gas and large-scale outflows suggests a possibility that the cloud
+dynamics is controlled by the magnetic field, protostellar outflows and
+gravitational inflows. This appears to be in good agreement with the
+outflow-driven turbulence model and implies the importance of the magnetic
+field to continuous star formation in the center region of the cluster forming
+region.",1004.3409v1
+2011-04-20,Magnetic fields in supernova remnants and pulsar-wind nebulae,"We review the observations of supernova remnants (SNRs) and pulsar-wind
+nebulae (PWNe) that give information on the strength and orientation of
+magnetic fields. Radio polarimetry gives the degree of order of magnetic
+fields, and the orientation of the ordered component. Many young shell
+supernova remnants show evidence for synchrotron X-ray emission. The spatial
+analysis of this emission suggests that magnetic fields are amplified by one to
+two orders of magnitude in strong shocks. Detection of several remnants in TeV
+gamma rays implies a lower limit on the magnetic-field strength (or a
+measurement, if the emission process is inverse-Compton upscattering of cosmic
+microwave background photons). Upper limits to GeV emission similarly provide
+lower limits on magnetic-field strengths. In the historical shell remnants,
+lower limits on B range from 25 to 1000 microGauss. Two remnants show
+variability of synchrotron X-ray emission with a timescale of years. If this
+timescale is the electron-acceleration or radiative loss timescale, magnetic
+fields of order 1 mG are also implied. In pulsar-wind nebulae, equipartition
+arguments and dynamical modeling can be used to infer magnetic-field strengths
+anywhere from about 5 microGauss to 1 mG. Polarized fractions are considerably
+higher than in SNRs, ranging to 50 or 60% in some cases; magnetic-field
+geometries often suggest a toroidal structure around the pulsar, but this is
+not universal. Viewing-angle effects undoubtedly play a role. MHD models of
+radio emission in shell SNRs show that different orientations of upstream
+magnetic field, and different assumptions about electron acceleration, predict
+different radio morphology. In the remnant of SN 1006, such comparisons imply a
+magnetic-field orientation connecting the bright limbs, with a non-negligible
+gradient of its strength across the remnant.",1104.4047v2
+2011-07-25,Modelling interaction of relativistic and non-relativistic winds in binary system PSR B1259-63/SS2883 - II. Impact of magnetization and anisotropy of the pulsar wind,"In this paper, we present a numerical study of the properties of the flow
+produced by the collision of a magnetized anisotropic pulsar wind with its
+environment in binary system. We compare the impact of both the magnetic field
+and the wind anisotropy to the benchmark case of a purely hydrodynamical (HD)
+interaction of isotropic winds, which has been studied in detail by Bogovalov
+et al. (2008). We consider the interaction in axisymmetric approximation, i.e.
+the pulsar rotation axis is assumed to be oriented along the line between the
+pulsar and the optical star and the effects related to the pulsar orbiting are
+neglected. The impact of the magnetic field is studied for the case of weak
+magnetization (with magnetization parameter $\sigma<0.1$), which is consistent
+with conventional models of pulsar winds. The effects related to anisotropy in
+pulsar winds are modeled assuming that the kinetic energy flux in a
+non-magnetized pulsar wind is strongly anisotropic, with the minimum at the
+pulsar rotation axis and the maximum in the perpendicular direction. We show
+that, although both considered effects change the shape of the region occupied
+by the terminated pulsar wind, their impact appears to be small. In particular,
+for the magnetization of the pulsar wind below 0.1, the magnetic field pressure
+remains well below the plasma pressure in the post-shock region. Thus, in the
+case of interaction of a pulsar with the stellar wind environment (opposite to
+the case of plerions, i.e. the pulsar interaction with the interstellar medium,
+when the magnetic field becomes dynamically important independently on the wind
+magnetization) the HD approach represents a feasible approximation for
+numerical modelling.",1107.4831v1
+2011-10-31,Linear stability of magnetohydrodynamic flow in a perfectly conducting rectangular duct,"We analyse numerically the linear stability of a liquid metal flow in a
+rectangular duct with perfectly electrically conducting walls subject to a
+uniform transverse magnetic field. A non-standard three dimensional vector
+stream function/vorticity formulation is used with Chebyshev collocation method
+to solve the eigenvalue problem for small-amplitude perturbations. A relatively
+weak magnetic field is found to render the flow linearly unstable as two weak
+jets appear close to the centre of the duct at the Hartmann number Ha \approx
+9.6. In a sufficiently strong magnetic field, the instability following the
+jets becomes confined in the layers of characteristic thickness \delta \sim
+Ha^{-1/2} located at the walls parallel to the magnetic field. In this case the
+instability is determined by \delta, which results in both the critical
+Reynolds and wavenumbers numbers scaling as \sim \delta^{-1}. Instability modes
+can have one of the four different symmetry combinations along and across the
+magnetic field. The most unstable is a pair of modes with an even distribution
+of vorticity along the magnetic field. These two modes represent strongly
+non-uniform vortices aligned with the magnetic field, which rotate either in
+the same or opposite senses across the magnetic field. The former enhance while
+the latter weaken one another provided that the magnetic field is not too
+strong or the walls parallel to the field are not too far apart. In a strong
+magnetic field, when the vortices at the opposite walls are well separated by
+the core flow, the critical Reynolds and wavenumbers for both of these
+instability modes are the same: Re_c \approx 642Ha^{1/2}+8.9x10^3Ha^{-1/2} and
+k_c \approx 0.477Ha^{1/2}. The other pair of modes, which differs from the
+previous one by an odd distribution of vorticity along the magnetic field, is
+more stable with approximately four times higher critical Reynolds number.",1111.0036v2
+2011-11-29,Magnetic properties and spin dynamics of 3d-4f molecular complexes,"We present the magnetic properties of three recently synthesized binuclear
+molecular complexes [NiNd], [NiGd] and [ZnGd] investigated by dc magnetization
+and proton nuclear magnetic resonance (NMR) measurements. The high-temperature
+magnetic properties are related to the independent paramagnetic behavior of the
+two magnetic metal ions within the binuclear entities both in [NiNd] and
+[NiGd]. On lowering the temperature, the formation of a magnetic dimer, with a
+low-spin ground state due to antiferromagnetic interaction (J/kB = -25 K)
+between Ni2+ and Nd3+, is found in the case of [NiNd], while in [NiGd] a
+ferromagnetic interaction (J/kB = 3.31 K) between the magnetic ions leads to a
+high-spin (S = 9/2) ground state. The temperature dependence of the proton
+nuclear spin lattice relaxation rate 1/T1 in [NiNd] is driven by the
+fluctuation of the hyperfine field at the nuclear site due to relaxation of the
+magnetization. At high temperature the independent Ni2+ and Nd3+ spins
+fluctuate fast while at low temperature we observe a slowing down of the
+fluctuation of the total magnetization of the dimer because of the insurgence
+of antiferromagnetic spin correlations. The relaxation mechanism in [NiNd] at
+low temperature is interpreted by a single, temperature dependent, correlation
+frequency wc\simT^3.5, which reflects the life time broadening of the exchange
+coupled spins via spin-phonon interaction. The proton NMR signal in [NiGd]
+could be detected just at room temperature, due to the shortening of relaxation
+times when T is decreased. The magnetic properties of [ZnGd] are the ones
+expected from a weakly interacting assembly of isolated moments except for
+anomalies in the susceptibility and NMR results below 15 K which currently
+cannot be explained.",1111.7008v1
+2012-08-03,"Spin dynamics, short-range order and superparamagnetism in superconducting ferromagnet RuSr2Gd1.4Ce0.6Cu2O10-δ","We report structural, detailed DC and linear/non-linear AC, isothermal and
+thermoremanent magnetization study of the rutheno-cuprate superconducting
+ferromagnet RuSr2Gd1.4Ce0.6Cu2O10-{\delta} (GdRu-1222). Structural analysis, by
+employing Rietveld refinement of X-ray diffraction pattern, reveals that
+GdRu-1222 crystallizes in tetragonal phase with I4/mmm space group. GdRu-1222
+is a reported superconducting ferromagnet with Ru spins magnetic ordering at
+around 110 K and superconductivity below 40 K in Cu-O2 planes. Detailed
+linear/non-linear first and higher order harmonic of AC susceptibility studies
+unveiled the complex magnetism of GdRu-1222. A frequency dependent cusp is
+observed in AC susceptibility ({\chi}ac) vs. T measurements. The change in cusp
+position with applied frequency followed the well known Vogel-Fulcher law,
+which is a feature to describe a spin-glass (SG) system with possibility of
+embedded homogeneous/non-homogeneous magnetically interacting/non-interacting
+ferromagnetic clusters. Such an interpretation is also supported by
+thermoremanent magnetization (TRM) study at T = 60 K. Detailed interpretation
+of AC magnetization results revealed the formation of magnetic (ferromagnetic)
+homogenous/non-homogenous clusters of different sizes embedded in spin-glass
+(SG) matrix. The magnetization vs. applied field loops do not saturate, even at
+high applied fields (50 kOe), resulting in the short-range magnetic ordering in
+the system, which causes the formation of clusters that freeze at low
+temperatures. Temperature variation of first- and third-order susceptibility
+harmonics show good agreement with Wohlfarth's model (WM), leading to the
+superparamagnetism (SPM) state. Detailed magnetization (DC and AC both) results
+and their analysis helped in explaining the temperature dependent magnetism of
+the GdRu-1222 system.",1208.0760v2
+2013-05-15,The plasmoid instability during asymmetric inflow magnetic reconnection,"Theoretical studies of the plasmoid instability generally assume that the
+reconnecting magnetic fields are symmetric. We relax this assumption by
+performing two-dimensional resistive magnetohydrodynamic simulations of the
+plasmoid instability during asymmetric inflow magnetic reconnection. Magnetic
+asymmetry modifies the onset, scaling, and dynamics of this instability.
+Magnetic islands develop preferentially into the weak magnetic field upstream
+region. Outflow jets from individual X-points impact plasmoids obliquely rather
+than directly as in the symmetric case. Consequently, deposition of momentum by
+the outflow jets into the plasmoids is less efficient, the plasmoids develop
+net vorticity, and shear flow slows down secondary merging between islands.
+Secondary merging events have asymmetry along both the inflow and outflow
+directions. Downstream plasma is more turbulent in cases with magnetic
+asymmetry because islands are able to roll around each other after exiting the
+current sheet. As in the symmetric case, plasmoid formation facilitates faster
+reconnection for at least small and moderate magnetic asymmetries. However,
+when the upstream magnetic field strengths differ by a factor of four, the
+reconnection rate plateaus at a lower value than expected from scaling the
+symmetric results. We perform a parameter study to investigate the onset of the
+plasmoid instability as a function of magnetic asymmetry and domain size. There
+exist domain sizes for which symmetric simulations are stable but asymmetric
+simulations are unstable, suggesting that moderate magnetic asymmetry is
+somewhat destabilizing. We discuss the implications for plasmoid and flux rope
+formation in solar eruptions, laboratory reconnection experiments, and space
+plasmas. The differences between symmetric and asymmetric simulations provide
+some hints regarding the nature of the three-dimensional plasmoid instability.",1305.3646v1
+2014-10-23,The 2014 Magnetism Roadmap,"Magnetism is a very fascinating and dynamic field. Especially in the last 30
+years it has experienced many major advances in the full range from novel
+fundamental phenomena to new products. Applications such as hard disk drives
+and magnetic sensors are part of our daily life, and new applications, such as
+in non-volatile computer random access memory, are expected to surface shortly.
+Thus it is timely for describing the current status, and current and future
+challenges in the form of a Roadmap article. This 2014 Magnetism Roadmap
+provides a view on several selected, currently very active innovative
+developments. It consists of 12 sections, each written by an expert in the
+field and addressing a specific subject, with strong emphasize on future
+potential. This Roadmap cannot cover the entire field. We have selected several
+highly relevant areas without attempting to provide a full review - a future
+update will have room for more topics. The scope covers mostly nano-magnetic
+phenomena and applications, where surfaces and interfaces provide additional
+functionality. New developments in fundamental topics such as interacting
+nano-elements, novel magnon-based spintronics concepts, spin-orbit torques and
+spin-caloric phenomena are addressed. New materials, such as organic magnetic
+materials and permanent magnets are covered. New applications are presented
+such as nano-magnetic logic, non-local and domain-wall based devices,
+heat-assisted magnetic recording, magnetic random access memory, and
+applications in biotechnology. May the Roadmap serve as a guideline for future
+emerging research directions in modern magnetism.",1410.6404v1
+2014-11-24,B fields in OB stars (BOB): on the detection of weak magnetic fields in the two early B-type stars beta CMa and epsilon CMa,"Within the context of the ""B fields in OB stars (BOB)"" collaboration, we used
+the HARPSpol spectropolarimeter to observe the early B-type stars beta CMa
+(HD44743; B1 II/III) and epsilon CMa (HD52089; B1.5 II). For both stars, we
+consistently detected the signature of a weak (<30 G in absolute value)
+longitudinal magnetic field. We determined the physical parameters of both
+stars and characterise their X-ray spectrum. For beta CMa, our mode
+identification analysis led to determining a rotation period of 13.6+/-1.2 days
+and of an inclination angle of the rotation axis of 57.6+/-1.7 degrees, with
+respect to the line of sight. On the basis of these measurements and assuming a
+dipolar field geometry, we derived a best fitting obliquity of ~22 degrees and
+a dipolar magnetic field strength (Bd) of ~100 G (60<Bd<230 G within 1 sigma),
+below what is typically found for other magnetic massive stars. For epsilon CMa
+we could only determine a lower limit on the dipolar magnetic field strength of
+13 G. For this star, we determine that the rotation period ranges between 1.3
+and 24 days. Both stars are expected to have a dynamical magnetosphere. We also
+conclude that both stars are most likely core hydrogen burning and that they
+have spent more than 2/3 of their main sequence lifetime. A histogram of the
+distribution of the dipolar magnetic field strength for the magnetic massive
+stars known to date does not show the magnetic field ""desert"" observed instead
+for intermediate-mass stars. The biases involved in the detection of (weak)
+magnetic fields in massive stars with the currently available instrumentation
+and techniques imply that weak fields might be more common than currently
+observed. Our results show that, if present, even relatively weak magnetic
+fields are detectable in massive stars and that more observational effort is
+probably still needed to properly access the magnetic field incidence.",1411.6490v1
+2016-02-15,Magnetic field and early evolution of circumstellar disks,"The magnetic field plays a central role in the formation and evolution of
+circumstellar disks. The magnetic field connects the rapidly rotating central
+region with the outer envelope and extracts angular momentum from the central
+region during gravitational collapse of the cloud core. This process is known
+as magnetic braking. Both analytical and multidimensional simulations have
+shown that disk formation is strongly suppressed by magnetic braking in
+moderately magnetized cloud cores in the ideal magnetohydrodynamic limit. On
+the other hand, recent observations have provided growing evidence of a
+relatively large disk several tens of astronomical units in size existing in
+some Class 0 young stellar objects. This introduces a serious discrepancy
+between the theoretical study and observations. Various physical mechanisms
+have been proposed to solve the problem of catastrophic magnetic braking, such
+as misalignment between the magnetic field and the rotation axis, turbulence,
+and non-ideal effect. In this paper, we review the mechanism of magnetic
+braking, its effect on disk formation and early evolution, and the mechanisms
+that resolve the magnetic braking problem. In particular, we emphasize the
+importance of non-ideal effects. The combination of magnetic diffusion and
+thermal evolution during gravitational collapse provides a robust formation
+process for the circumstellar disk at the very early phase of protostar
+formation. The rotation induced by the Hall effect can supply a sufficient
+amount of angular momentum for typical circumstellar disks around T Tauri
+stars. By examining the combination of the suggested mechanisms, we conclude
+that the circumstellar disks commonly form in the very early phase of protostar
+formation.",1602.04538v2
+2017-04-25,Measuring surface magnetic fields of red supergiant stars,"RSG stars are very massive cool evolved stars. Recently, a weak magnetic
+field was measured at the surface of $\alpha$ Ori and this is so far the only
+M-type supergiant for which a direct detection of a surface magnetic field has
+been reported. By extending the search for surface magnetic field in a sample
+of late-type supergiants, we want to determine whether the surface magnetic
+field detected on $\alpha$ Ori is a common feature among the M-type
+supergiants. With the spectropolarimeter Narval at TBL we undertook a search
+for surface magnetic fields in a sample of cool supergiant stars, and we
+analysed circular polarisation spectra using the least-squares deconvolution
+technique. We detect weak Zeeman signatures of stellar origin in the targets CE
+Tau, $\alpha^1$ Her and $\mu$ Cep. For the latter star, we also show that
+cross-talk from the strong linear polarisation signals detected on this star
+must be taken into account. For CE Tau and $\mu$ Cep, the longitudinal
+component of the detected surface fields is at the Gauss-level, such as in
+$\alpha$~Ori. We measured a longitudinal field almost an order of magnitude
+stronger for $\alpha^1$ Her. We also report variability of the longitudinal
+magnetic field of CE Tau and $\alpha^1$ Her, with changes in good agreement
+with the typical atmospheric dynamics time-scales. We also report a
+non-detection of magnetic field at the surface of the yellow supergiant star
+$\rho$ Cas. The two RSG stars of our sample, CE Tau and $\mu$ Cep, display
+magnetic fields very similar to that of $\alpha$ Ori. The non-detection of a
+magnetic field on the post-RSG star $\rho$ Cas suggests that the magnetic field
+disappears, or at least becomes undetectable with present methods, at later
+evolutionary stages. Our analysis of $\alpha^1$ Her supports the proposed
+reclassification of the star as an AGB star.",1704.07761v2
+2017-08-05,Proton imaging of stochastic magnetic fields,"Recent laser-plasma experiments report the existence of dynamically
+significant magnetic fields, whose statistical characterisation is essential
+for understanding the physical processes these experiments are attempting to
+investigate. In this paper, we show how a proton imaging diagnostic can be used
+to determine a range of relevant magnetic field statistics, including the
+magnetic-energy spectrum. To achieve this goal, we explore the properties of an
+analytic relation between a stochastic magnetic field and the image-flux
+distribution created upon imaging that field. We conclude that features of the
+beam's final image-flux distribution often display a universal character
+determined by a single, field-scale dependent parameter - the contrast
+parameter - which quantifies the relative size of the correlation length of the
+stochastic field, proton displacements due to magnetic deflections, and the
+image magnification. For stochastic magnetic fields, we establish the existence
+of four contrast regimes - linear, nonlinear injective, caustic and diffusive -
+under which proton-flux images relate to their parent fields in a qualitatively
+distinct manner. As a consequence, it is demonstrated that in the linear or
+nonlinear injective regimes, the path-integrated magnetic field experienced by
+the beam can be extracted uniquely, as can the magnetic-energy spectrum under a
+further statistical assumption of isotropy. This is no longer the case in the
+caustic or diffusive regimes. We also discuss complications to the
+contrast-regime characterisation arising for inhomogeneous, multi-scale
+stochastic fields, as well as limitations currently placed by experimental
+capabilities on extracting magnetic field statistics. The results presented in
+this paper provide a comprehensive description of proton images of stochastic
+magnetic fields, with applications for improved analysis of given proton-flux
+images.",1708.01738v1
+2018-07-26,Is there a left-handed magnetic field in the solar neighborhood? Exploring helical magnetic fields in the interstellar medium through dust polarization power spectra,"The full-sky Planck polarization data at 850um revealed unexpected properties
+of the E and B mode power spectra of dust emission in the interstellar medium
+(ISM). The positive cross-correlation between the total dust intensity, T, with
+the B modes has raised new questions about the physical mechanisms that affect
+dust polarization, such as the Galactic magnetic-field structure. This is key
+both to better understanding ISM dynamics and to accurately describing Galactic
+foregrounds to the polarization of the Cosmic Microwave Background (CMB). In
+this theoretical paper we investigate the possibility that the observed
+cross-correlations in the dust polarization power spectra, and specifically
+between T and B, can be related to a parity-odd quantity in the ISM such as the
+magnetic helicity. We produce synthetic dust polarization data, derived from 3D
+analytical toy models of density structures and helical magnetic fields, to
+compare with the E and B modes of observations. Focusing on the observed T-B
+correlation, we propose a new line of interpretation of the Planck observations
+based on a large-scale helical component of the Galactic magnetic field in the
+solar neighborhood. Our analysis shows that: I) the sign of magnetic helicity
+does not affect E and B modes for isotropic magnetic-field configurations; II)
+helical magnetic fields threading interstellar filaments cannot reproduce the
+Planck results; III) a weak helical left-handed magnetic field structure in the
+solar neighborhood may explain the T-B correlation seen in the Planck data.
+This work suggests a new perspective for the interpretation of the dust
+polarization power spectra, which strongly supports the imprint of a
+large-scale structure of the Galactic magnetic field in the solar neighborhood.",1807.10188v3
+2018-10-25,"Magnetic Properties of Dust Grains, Effect of Precession and Radiative Torque Alignment","Alignment of dust grains in astrophysical environments results in the
+polarization of starlight as well as the polarization of radiation emitted by
+dust. We demonstrate the advances in grain alignment theory allow the use of
+linear and circular polarization to probe not only the magnetic field, but also
+dust composition, the dust environment, etc. We revisit the process of grain
+alignment by Radiative Torques (RATs) and focus on constraining magnetic
+susceptibility of grains via observations. We discuss the possibility of
+observational testing of the magnetic properties of grains as the alignment
+changes from being in respect to the magnetic field to being in respect to the
+radiation direction. This opens both a possibility of constraining the
+uncertain parameters of the RATs theory and provides a new way of measuring
+magnetic fields in interstellar medium and circumstellar regions. We provide a
+detailed discussion of the precession induced both by the magnetic field and
+the anisotropic radiation and revisit a number of key processes related to
+magnetic response of the grains. We consider various effects that increase the
+rate of magnetic relaxation both in silicate and carbonaceous grains. In
+particular, we find a new relaxation process related to the change of the
+amplitude of internal magnetization within a wobbling triaxial grain and
+identify a range of grain sizes in which this effect can dominate the internal
+alignment of angular momentum within grain axes. We show that these relaxation
+processes significantly change the dynamics of grains in the presence of RATs.
+We apply our analysis for observed grain alignment in special environments to
+put constraints on the enhanced magnetic properties of dust grains in the cloud
+near supernovae, in cometary coma, and protoplanetary disks.",1810.10686v2
+2019-01-14,Magneto-structural and dynamic susceptibility studies on rare-earth rich intermetallic compound,"Complex magneto structural behaviour of rare rich intermetallic Tb$_3$Co is
+reported in this study. Below the 84K (T$_N$), it undergoes a first order
+magnetic transition 72K confirmed from specific heat and magnetization
+measurements. Detailed study using magnetization, specific heat, neuron
+diffraction and ac-susceptibility measurements suggests that the compound in
+the question possesses canted magnetic structure. Neutron diffraction reveals
+that Tb moments are aligned antiferromagnetically (AFM) in ab plane and
+ferromagnetically (FM) along c direction. This study focusses on the
+temperature evolution of magnetic order at low temperatures. Neutron
+Diffraction clearly shows that magnetic structure remains more or less same up
+to 70K although low field magnetization exhibits a transition like feature
+around 30K. Field dependent neutron diffraction suggests that a strong
+spin-lattice coupling is present at lower temperature region (below 20K)
+compared to that for T above 40K. This is responsible for the observed drop in
+ZFC magnetization around 30K and is not due to any change in magnetic
+structure. Another important but surprising result that observed is the
+signature of magnetic glass below 72K in frequency dependent ac susceptibility
+measurements. Real part of ac-susceptibility data shows dispersion with
+frequency which on detailed analysis provides evidence for spin glass behaviour
+in the compound riding on top of non-collinear AFM order. Higher order
+harmonics in ac non-linear) susceptibilities, which are expected to show a
+well-defined behaviour for pure FM or AFM or spin glass or cluster glass
+systems, were also measured. However, the non-linear susceptibilities do not
+exhibit any well-known variation but show complex behaviour thus indicating
+Tb$_3$Co is neither a pure AFM or FM or spin glass system but provides another
+evidence for non-collinear magnetic structure.",1901.04191v1
+2019-08-25,"Electric and magnetic axion quark nuggets, their stability and their detection","The present work studies the dynamics of axion quark nuggets introduced in
+\cite{zhitnitsky} and exploited in the works
+\cite{zhitnitsky2}-\cite{zhitnitsky13}. The new feature considered here is the
+possibility that these nuggets become ferromagnetic. This possibility was
+pointed out in \cite{tatsumi}, although ferromagnetism may also take place due
+some anomaly terms found in \cite{son}-\cite{son2}. The purpose of the present
+letter however, is not to give evidence in favor or against these statements.
+Instead, it is focused in some direct consequences of this ferromagnetic
+behavior, if it exists. The first is that the nugget magnetic field induces an
+electric field due to the axion wall, which may induce pair production by
+Schwinger effect. Depending on the value of the magnetic field, the pair
+production can be quite large. A critical value for such magnetic field at the
+surface of the nugget is obtained, and it is argued that the value of the
+magnetic field of \cite{tatsumi} is at the verge of stability and may induce
+large pair production. The consequences of this enhanced pair production may be
+unclear. It may indicate that the the nugget evaporates, but on the other hand
+it may be just an indication that the intrinsic magnetic field disappears and
+the nuggets evolves to a non magnetized state such as
+\cite{zhitnitsky}-\cite{zhitnitsky13}. The interaction of such magnetic and
+electric nugget with the troposphere of the earth is also analyzed. However, if
+the magnetic field does not decay before the actual universe, then this would
+lead to high energy electron flux due to its interaction with the electron
+gases of the Milky Way. This suggests that these magnetized quarks may be a
+considerably part of dark matter, but only if their hypothetical magnetic and
+electric fields are evaporated.",1908.09409v5
+2019-11-05,The nature of mean-field generation in three classes of optimal dynamos,"In recent years, several optimal dynamos have been discovered. They minimize
+the magnetic energy dissipation or, equivalently, maximize the growth rate at a
+fixed magnetic Reynolds number. In the optimal dynamo of Willis (2012, Phys.
+Rev. Lett. 109, 251101), we find mean-field dynamo action for planar averages.
+One component of the magnetic field grows exponentially while the other decays
+in an oscillatory fashion near onset. This behavior is different from that of
+an alpha^2 dynamo, where the two non-vanishing components of the planar
+averages are coupled and have the same growth rate. For the Willis dynamo, we
+find that the mean field is excited by a negative turbulent magnetic
+diffusivity, which has a non-uniform spatial profile near onset. The temporal
+oscillations in the decaying component are caused by the corresponding
+component of the diffusivity tensor being complex when the mean field is
+decaying and, in this way, time-dependent. The growing mean field can be
+modeled by a negative magnetic diffusivity combined with a positive magnetic
+hyperdiffusivity. In two other classes of optimal dynamos of Chen et al. (2015,
+J. Fluid Mech. 783, 23), we find, to some extent, similar mean-field dynamo
+actions. When the magnetic boundary conditions are mixed, the two components of
+the planar averaged field grow at different rates when the dynamo is 15%
+supercritical. When the mean magnetic field satisfies homogeneous boundary
+conditions (where the magnetic field is tangential to the boundary), mean-field
+dynamo action is found for one-dimensional averages, but not for planar
+averages. Despite having different spatial profiles, both dynamos show negative
+turbulent magnetic diffusivities. Our finding suggests negative turbulent
+magnetic diffusivities may support a broader class of dynamos than previously
+thought, including these three optimal dynamos.",1911.01712v2
+2020-01-03,"3D Turbulent Reconnection: Theory, Tests and Astrophysical Implications","Magnetic reconnection, topological change in magnetic fields, is a
+fundamental process in magnetized plasmas. It is associated with energy release
+in regions of magnetic field annihilation, but this is only one facet of this
+process. Astrophysical flows normally have very large Reynolds numbers and are
+expected to be turbulent, in agreement with observations. In strong turbulence
+magnetic lines constantly reconnect everywhere at all scales, making magnetic
+reconnection an intrinsic part of turbulent cascade. We note that this is
+inconsistent with the usual practice of regarding magnetic lines as persistent
+dynamical elements. A number of theoretical, numerical, and observational
+studies, starting with Lazarian & Vishniac (1999), demonstrated that 3D
+turbulence makes magnetic reconnection fast and that these two processes are
+intrinsically connected. We discuss the dramatic violation of the textbook
+concept of magnetic flux-freezing in the presence of turbulence and demonstrate
+that in the presence of turbulence the plasma effects are subdominant to
+turbulence as far as the magnetic reconnection is concerned. This justifies an
+MHD-like treatment of magnetic reconnection at scales much larger than the
+relevant plasma scales. We discuss numerical and observational evidences
+supporting the turbulent reconnection model. In particular, we show that
+tearing reconnection is suppressed in 3D and, unlike the 2D case, the 3D
+reconnection induces turbulence that makes reconnection independent of
+resistivity. We show that turbulent reconnection dramatically affects the key
+astrophysical processes, e.g., star formation, turbulent dynamo, acceleration
+of cosmic rays. We provide criticism of the concept of ""reconnection-mediated
+turbulence"" and explain why turbulent reconnection is very different from
+enhanced turbulent resistivity and hyper-resistivity, and why the latter has
+fatal conceptual flaws.",2001.00868v1
+2020-01-29,Helicity proxies from linear polarisation of solar active regions,"The alpha effect is believed to play a key role in the generation of the
+solar magnetic field. A fundamental test for its significance in the solar
+dynamo is to look for magnetic helicity of opposite signs in the two
+hemispheres, and at small and large scales. However, measuring magnetic
+helicity is compromised by the inability to fully infer the magnetic field
+vector from observations of solar spectra, caused by what is known as the ""pi
+ambiguity"" of spectropolarimetric observations. We decompose linear
+polarisation into parity-even and parity-odd E and B polarisations, which are
+not affected by the ""pi ambiguity"". Furthermore, we study whether the
+correlations of spatial Fourier spectra of B and parity-even quantities such as
+E or temperature T are a robust proxy for magnetic helicity of solar magnetic
+fields. We analyse polarisation measurements of active regions observed by the
+Helioseismic and Magnetic Imager on board the Solar Dynamics observatory.
+Theory predicts the magnetic helicity of active regions to have, statistically,
+opposite signs in the two hemispheres. We then compute the parity-odd E B and T
+B correlations, and test for systematic preference of their sign based on the
+hemisphere of the active regions. We find that: (i) E B and T B correlations
+are a reliable proxy for magnetic helicity, when computed from linear
+polarisation measurements away from spectral line cores, and (ii) E
+polarisation reverses its sign close to the line core. Our analysis reveals
+Faraday rotation to not have a significant influence on the computed parity-odd
+correlations. The EB decomposition of linear polarisation appears to be a good
+proxy for magnetic helicity independent of the ""pi ambiguity"". This allows us
+to routinely infer magnetic helicity directly from polarisation measurements.",2001.10884v2
+2020-12-07,Predicting the Evolution of Photospheric Magnetic Field in Solar Active Regions Using Deep Learning,"The continuous observation of the magnetic field by Solar Dynamics
+Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) produces numerous
+image sequences in time and space. These sequences provide data support for
+predicting the evolution of photospheric magnetic field. Based on the
+spatiotemporal long short-term memory(LSTM) network, we use the preprocessed
+data of photospheric magnetic field in active regions to build a prediction
+model for magnetic field evolution. Because of the elaborate learning and
+memory mechanism, the trained model can characterize the inherent relationships
+contained in spatiotemporal features. The testing results of the prediction
+model indicate that (1) the prediction pattern learned by the model can be
+applied to predict the evolution of new magnetic field in the next 6 hour that
+have not been trained, and predicted results are roughly consistent with real
+observed magnetic field evolution in terms of large-scale structure and
+movement speed; (2) the performance of the model is related to the prediction
+time; the shorter the prediction time, the higher the accuracy of the predicted
+results; (3) the performance of the model is stable not only for active regions
+in the north and south but also for data in positive and negative regions.
+Detailed experimental results and discussions on magnetic flux emergence and
+magnetic neutral lines finally show that the proposed model could effectively
+predict the large-scale and short-term evolution of the photospheric magnetic
+field in active regions. Moreover, our study may provide a reference for the
+spatiotemporal prediction of other solar activities.",2012.03584v1
+2021-01-15,Direct evidence for magnetic reconnection at the boundaries of magnetic switchbacks with Parker Solar Probe,"Parker Solar Probe's first encounters with the Sun revealed the presence of
+ubiquitous localised magnetic deflections in the inner heliosphere; these
+structures, often called switchbacks, are particularly striking in solar wind
+streams originating from coronal holes. We report the direct evidence for
+magnetic reconnection occuring at the boundaries of three switchbacks crossed
+by Parker Solar Probe (PSP) at a distance of 45 to 48 solar radii of the Sun
+during its first encounter. We analyse the magnetic field and plasma parameters
+from the FIELDS and SWEAP instruments. The three structures analysed all show
+typical signatures of magnetic reconnection. The ion velocity and magnetic
+field are first correlated and then anti-correlated at the inbound and outbound
+edges of the bifurcated current sheets with a central ion flow jet. Most of the
+reconnection events have a strong guide field and moderate magnetic shear but
+one current sheet shows indications of quasi anti-parallel reconnection in
+conjunction with a magnetic field magnitude decrease by $90\%$. Given the
+wealth of intense current sheets observed by PSP, reconnection at switchbacks
+boundaries appears to be rare. However, as the switchback boundaries accomodate
+currents one can conjecture that the geometry of these boundaries offers
+favourable conditions for magnetic reconnection to occur. Such a mechanism
+would thus contribute in reconfiguring the magnetic field of the switchbacks,
+affecting the dynamics of the solar wind and eventually contributing to the
+blending of the structures with the regular wind as they propagate away from
+the Sun.",2101.06279v2
+2021-01-28,Phase diagram for strongly interacting matter in the presence of a magnetic field using the Polyakov-Nambu-Jona-Lasinio model with magnetic field dependent coupling strengths,"We study the phase diagram for strongly interacting matter using the 't Hooft
+determinant extended Nambu--Jona-Lasinio model with a Polyakov loop in the
+light and strange quark sectors (\emph{up}, \emph{down} and \emph{strange})
+focusing on the effect of a magnetic field dependence of the coupling strengths
+of these interactions. This dependence was obtained so as to reproduce recent
+lattice QCD results for the magnetic field dependence of the quarks dynamical
+masses.
+  A finite magnetic field is known to induce several additional first-order
+phase transition lines with the respective Critical End Points (CEP) in the
+temperature-quark chemical potential phase diagram when compared to the zero
+magnetic field case. A study of the magnetic field dependence in the range
+$eB=0-0.6~\mathrm{GeV}^2$ of the location of these CEPs reveals that the
+initial one as well as several of the new ones only survive up to a critical
+magnetic field. Only two remain in the upper limit of the studied magnetic
+field strength. A comparison of the results obtained with versions of the model
+with and without Polyakov loop is also done.
+  We also found that the inclusion of the magnetic field dependence on the
+coupling strengths, while not changing the qualitative features of the phase
+diagram, affects the location of these CEPs. The comparison of results with and
+without a regularization cutoff in the medium part of the integrals does not
+show a significant change.",2101.12004v2
+2024-02-26,Black hole in a combined magnetic field: ionized accretion disks in the jetlike and looplike configurations,"Magnetic fields surrounding black holes are responsible for various
+astrophysical phenomena related to accretion processes and relativistic jets.
+Depending on the source, the configuration of the field lines may differ
+significantly, affecting the trajectories of charged particles and the
+corresponding observables. Usually, the magnetic fields around black holes are
+modeled within a single source or current generating the field. However,
+magnetic fields can have more than a single origin, being a combination of
+different fields, such as, e.g., that of an accretion disk and external
+large-scale or Galactic ones. In this paper, we propose a combined magnetic
+field solution given by the superposition of the uniform and Blandford-Znajek
+split-monopole magnetic fields in a strong gravity regime of the Schwarzschild
+black hole. We show that when the combined magnetic field components are
+aligned, the resulting field is of a paraboloidal jetlike shape. Such a
+configuration is supported by relativistic jet observations and is often
+utilized in general relativistic magnetohydrodynamical simulations. In the
+opposite orientation of the two field components, we observe looplike field
+structures magnetically connecting the black hole with an accretion disk and
+the magnetic null points, which can be related to the regions of magnetic
+reconnection. In the combined magnetic field configurations, we analyze the
+dynamics of charged particles, study their stability conditions, and find the
+locations of stable off-equatorial structures close to the symmetry axis. We
+consider an ionization of Keplerian accretion disk as a particular scenario of
+particle scattering. From the numerical experiments, we conclude that charged
+particles in the jetlike combination show a strong tendency to escape from the
+black hole. In contrast, the looplike combination supports accretion of charged
+particles into the black hole.",2402.16529v1
+2000-12-01,Two-dimensional disk dynamos with vertical outflows into a halo,"We study the effects of vertical outflows on mean-field dynamos in disks.
+These outflows could be due to thermal winds or magnetic buoyancy. We analyse
+numerical solutions of the nonlinear mean-field dynamo equations using a
+two-dimensional finite-difference model. Contrary to expectations, a modest
+vertical velocity can enhance dynamo action. This can lead to super-exponential
+growth of the magnetic field and to higher magnetic energies at saturation in
+the nonlinear regime.",0012013v1
+2000-12-05,The inverse cascade in turbulent dynamos,"The emergence of a large scale magnetic field from randomly forced isotropic
+strongly helical flows is discussed in terms of the inverse cascade of magnetic
+helicity and the alpha-effect. In simulations of such flows the maximum field
+strength exceeds the equipartition field strength for large scale separation.
+However, helicity conservation controls the speed at which this final state is
+reached. In the presence of open boundaries magnetic helicity fluxes out of the
+domain are possible. This reduces the timescales of the field growth, but it
+also tends to reduce the maximum attainable field strength.",0012112v1
+2001-05-21,A Solvable Model for Nonlinear Mean Field Dynamo,"We formulate a solvable model that describes generation and saturation of
+mean magnetic field in a dynamo with kinetic helicity, in the limit of large
+magnetic Prandtl number. This model is based on the assumption that the
+stochastic part of the velocity field is Gaussian and white in time (the
+Kazantsev-Kraichnan ensemble), while the regular part describing the back
+reaction of the magnetic field is chosen from balancing the viscous and Lorentz
+stresses in the MHD Navier-Stokes equation. The model provides an analytical
+explanation for previously obtained numerical results.",0105354v1
+2001-12-15,Grain Dynamics In Magnetized Interstellar Gas,"Interstellar medium is turbulent and this induces relative motions of dust
+grains. We calculate relative velocities of charged grains in a partially
+ionized magnetized gas. We account for anisotropy of magnetohydrodynamic (MHD)
+turbulence, grain coupling with magnetic field, and the turbulence cutoff
+arising from the ambipolar drag. We obtain grain velocities for turbulence with
+parameters consistent with those in HI and dark clouds. Those velocities are
+smaller than those in earlier papers, where MHD effects were disregarded.
+Finally, we compare grain velocities arising from photoelectric emission,
+radiation pressure and thrusts from molecular hydrogen formation. We conclude
+that turbulence should prevent segregation of grains of different sizes.",0112365v2
+2003-12-09,Early Disk Evolution,"A variety of processes play a role in the evolution of protostellar disks.
+Here I focus on the uncertain issue of magnetic field-disk coupling and its
+implications for magnetically-driven turbulence and disk-driven winds. At
+present it is clear that the magnetic field plays a crucial role in disk
+evolution, but detailed conclusions cannot be drawn because the complicated
+interplay between dynamics and the evolution of the grain population remains to
+be explored.",0312220v1
+2004-03-14,Nearly Minimal Magnetogenesis,"We propose a new mechanism for magnetic field generation from inflation, by
+which strong magnetic fields can be generated on cosmological scales. These
+fields may be observable by cosmic microwave background radition measurements,
+and may have a dynamical impact on structure formation. The mechanism is based
+on the observation that a light nearly minimally coupled charged scalar may be
+responsible for the creation of a negative photon mass-squared (provided the
+scalar field coupling to the curvature scalar is small but negative), which in
+turn results in abundant photon production - and thus in growing magnetic
+fields - during inflation.",0403335v1
+2004-09-06,Chiral Symmetry Breaking in Presence of Strong Quantizing Magnetic Fields- A Nambu-Jona-Lasino Model with Semi-Classical Approximation,"The breaking of chiral symmetry of light quarks at zero temperature in
+presence of strong quantizing magnetic field is studied using
+Nambu-Jona-Lasinio (NJL) model with Thomas-Fermi type semi-classical formalism.
+It is found that the dynamically generated light quark mass can never become
+zero if the Landau levels are populated and increases with the increase of
+magnetic field strength.",0409109v2
+2005-03-23,"Comment on ""Gamma-ray burst early afterglows: reverse shock emission from an arbitrarily magnetized ejecta"" by Zhang and Kobayashi (2004)","Zhang and Kobayashi (2004) attempted to calculate early afterglow emission
+from a system of forward and reverse shocks in GRB outflows for the case of
+magnetized ejecta. We point out a fundamental error in the underlying dynamical
+model. According to the authors, energy and momentum carried by the magnetic
+field of the ejecta are not transfered to the forward shock. This is an
+incorrect assumption that invalidates the results.",0503505v1
+2006-08-02,"Grain Alignment, Polarization and Magnetic Fields","Aligned non-spherical dust particles polarize starlight passing through the
+dust cloud. They also emit polarized far infrared and sub-mm radiation.
+Substantial progress in understanding of grain alignment theory makes the
+interpretation of the polarized radiation in terms of underlying magnetic
+fields much more reliable. I discuss a number of fundamental processes that
+affect grain alignment. In particular, I shall discuss how subtle effects
+related to nuclear spins of the atoms alter the dynamics of dust grains. I
+shall discuss how the theory explains the existing observational data and
+demonstrate when the polarization can and cannot be interpreted in terms of the
+underlying magnetic fields.",0608049v1
+2007-02-08,Sunspot models with bright rings,"A theoretical sunspot model is provided including magnetic suppression of the
+diffusivities and also a strong stratification of density and temperature. Heat
+diffusion alone with given magnetic field and zero mean flow only produces
+(after a very long relaxation time) dark spots without any bright ring. Models
+with full dynamics of both field and flow, however, provide rings and also the
+observed correlation of ring temperature excess and the spot size. The rings
+are formed as the result of heat transport by the resulting flow system and
+increased thermal diffusivity due to reduced magnetic quenching around spots.",0702232v2
+1992-09-05,Aspects of Spin Dynamics in the Cuprate Superconductors,"One of the interesting aspects of the CuO superconductors is that
+superconductivity is happening so close to the antiferromagnetic state. The
+nuclear magnetic resonance and the recent neutron scattering experiments
+clearly indicate that magnetic correlations persist in to the heavily doped
+regime. In this paper we will discuss some of the details of the coupling of
+the nuclear magnetic spin to the conduction electron spins. Furthermore we will
+show that a simple band structure can explain the recent neutron scattering
+data in the \LaSrCuO material for the optimal concentration of $x\approx 0.15$
+if the lifetime effects are included.",9209005v1
+1996-10-07,Self similar Barkhausen noise in magnetic domain wall motion,"A model for domain wall motion in ferromagnets is analyzed. Long-range
+magnetic dipolar interactions are shown to give rise to self-similar dynamics
+when the external magnetic field is increased adiabatically. The power spectrum
+of the resultant Barkhausen noise is of the form $1/\omega^\alpha$, where
+$\alpha\approx 1.5$ can be estimated from the critical exponents for interface
+depinning in random media.",9610053v2
+1996-11-13,Dramatic Switching of Magnetic Exchange in a Classic Transition Metal Oxide: Evidence for Orbital Ordering,"Spin correlations in metallic and insulating phases of $V_2O_3$ and its
+derivatives are investigated using magnetic neutron scattering. Metallic
+samples have incommensurate spin correlations varying little with hole doping.
+Paramagnetic insulating samples have spin correlations only among near
+neighbors. The transition from either of these phases into the low temperature
+insulating antiferromagnetic phase is accompanied by an abrupt change of
+dynamic magnetic short range order. Our results support the idea that the
+transition into the antiferromagnetic insulator is also an orbital ordering
+transition.",9611109v1
+1997-07-10,Incommensurate Magnetic Fluctuations in YBa2Cu3O6.6,"We use inelastic neutron scattering to demonstrate that at low temperatures,
+the low frequency magnetic fluctuations in YBa_2Cu_3O_{6.6} ($T_c=62.7$ K) are
+incommensurate, being found at positions displaced by $\pm\delta$ ($0.057\pm
+0.006$ r.l.u.) along the $[\pi,\pi]$ direction from the wave vector $(\pi,\pi)$
+associated with the antiferromagnetic order of the parent insulator,
+YBa_2Cu_3O_{6}. The dynamical susceptibility $\chi''(q,\omega)$ at the
+incommensurate positions increases on cooling below $T_c$, accompanied by a
+suppression of magnetic fluctuations at the commensurate points.",9707112v1
+1997-10-01,Semiclassical Approach to Orbital Magnetism of Interacting Diffusive Quantum Systems,"We study interaction effects on the orbital magnetism of diffusive mesoscopic
+quantum systems. By combining many-body perturbation theory with semiclassical
+techniques, we show that the interaction contribution to the ensemble averaged
+quantum thermodynamic potential can be reduced to an essentially classical
+operator. We compute the magnetic response of disordered rings and dots for
+diffusive classical dynamics. Our semiclassical approach reproduces the results
+of previous diagrammatic quantum calculations.",9710014v1
+1997-11-13,On the Dynamics of the 4d Spin Glass in a magnetic field,"We study the four dimensional Gaussian spin glass in presence of a magnetic
+field. Using off-equilibrium numerical simulations we have found that the
+probability distribution of the overlaps is built in the same way as that of
+the Mean Field approximation with replica symmetry breaking. Finally we have
+studied the violation of the fluctuation-dissipation theorem in presence of
+magnetic field.",9711122v1
+1998-04-22,A magnetic model for the incommensurate I phase of spin-Peierls systems,"A magnetic model is proposed for describing the incommensurate I phase of
+spin-Peierls systems. Based on the harmonicity of the lattice distortion, its
+main ingredient is that the distortion of the lattice adjusts to the average
+magnetization such that the system is always gapful. The presence of dynamical
+incommensurabilities in the fluctuation spectra is also predicted. Recent
+experimental results for CuGeO_3 obtained by NMR, ESR and light scattering
+absorption are well understood within this model.",9804242v1
+1998-04-23,Response in kinetic Ising model to oscillating magnetic fields,"Ising models obeying Glauber dynamics in a temporally oscillating magnetic
+field are analyzed. In the context of stochastic resonance, the response in the
+magnetization is calculated by means of both a mean-field theory with
+linear-response approximation, and the time-dependent Ginzburg-Landau equation.
+Analytic results for the temperature and frequency dependent response,
+including the resonance temperature, compare favorably with simulation data.",9804251v1
+1998-07-14,Non-adiabatic scattering of a classical particle in an inhomogeneous magnetic field,"We study the violation of the adiabaticity of the electron dynamics in a
+slowly varying magnetic field. We formulate and solve exactly a non-adiabatic
+scattering problem. In particular, we consider scattering on a magnetic field
+inhomogeneity which models scatterers in the composite-fermion theory of the
+half-filled Landau level. The calculated non-adiabatic shift of the guiding
+center is exponentially small and exhibits an oscillatory behavior related to
+the ""self-commensurability"" of the drifting cyclotron orbit. The analytical
+results are complemented with a numerical simulation.",9807213v1
+1998-12-28,The Kronig-Penney-Ising picture of the colossal magnetoresistance,"From general arguments, it is shown that a magnetic Kronig-Penney model based
+on the thermodynamics of an Ising model can be used for describing the Colossal
+Magnetoresistance (CMR) phenomenon. The model considers a tunneling-like
+transmission process of hopping electrons through a dynamic lattice
+characterized by evolving magnetic clusters. In this model, correlations
+between the magnetic states are considered to be more relevant than the lattice
+strain effects for obtaining the CMR features. Physical arguments lead to the
+theoretical description of the intrinsic temperature and field dependences of
+the CMR observed in typical manganite materials.",9812406v1
+1999-01-26,Antiferromagnetism in doped anisotropic two-dimensional spin-Peierls systems,"We study the formation of antiferromagnetic correlations induced by impurity
+doping in anisotropic two-dimensional spin-Peierls systems. Using a mean-field
+approximation to deal with the inter-chain magnetic coupling, the intra-chain
+correlations are treated exactly by numerical techniques. The magnetic coupling
+between impurities is computed for both adiabatic and dynamical lattices and is
+shown to have an alternating sign as a function of the impurity-impurity
+distance, hence suppressing magnetic frustration. An effective model based on
+our numerical results supports the coexistence of antiferromagnetism and
+dimerization in this system.",9901286v2
+2000-01-10,Irreversibility temperature from magnetic relaxation,"Simulation of the magnetic relaxation in a model of hard superconductor
+reveals a new time scale below the irreversibility temperature. The relaxation
+in this new time scale, which appears in an intermediate time window, is a
+power law and is related to self organization of the magnetic flux around the
+critical current density J_c during the relaxation. Emergence of a new time
+scale which along with the time scale for long time relaxation due to thermally
+activated process dynamically identifies the irreversibility temperature.",0001096v1
+2000-02-14,Magnetization Switching in Nanowires: Monte Carlo Study with Fast Fourier Transformation for Dipolar Fields,"For the investigations of thermally activated magnetization reversal in
+systems of classical magnetic moments numerical methods are desirable. We
+present numerical studies which base on time quantified Monte Carlo methods
+where the long-range dipole-dipole interaction is calculated with the aid of
+fast Fourier transformation. As an example, we study models for ferromagnetic
+nanowires comparing our numerical results for the characteristic time of the
+reversal process also with numerical data from Langevin dynamics simulations
+where the fast Fourier transformation method is well established. Depending on
+the system geometry different reversal mechanism occur like coherent rotation,
+nucleation, and curling.",0002201v1
+2000-04-17,Formation of Directed Beams from Atom Lasers,"The problem of creating well-collimated beams of atoms escaping from a trap
+is studied. This problem is of high importance for the realization of atom
+lasers. Nonadiabatic dynamics of neutral atoms in nonuniform magnetic fields,
+typical of quadrupole magnetic traps, has been considered. The main result of
+this report is that an unusual semiconfining regime of motion is found, when
+atoms are confined from one side of an axis but are not confined from another
+side. This regime can be achieved by means of only magnetic fields. The formed
+atomic beam can be forwarded in arbitrary direction.",0004267v1
+2001-05-31,Quantum transport in parallel magnetic fields: A realization of the Berry-Robnik symmetry phenomenon,"We analyze the magnetoconductance of two-dimensional electron and hole gases
+(2DEGs) subject to a parallel magnetic field. It is shown that, for confining
+potential wells which are symmetric with respect to spatial inversion, a
+temperature-dependent weak localization signal exists even in the presence of a
+magnetic field. Deviations from this symmetry lead to magnetoconductance
+profiles that contain information on both, the geometry of the confining
+potential and characteristics of the disorder.",0105623v1
+2001-06-08,Droplets in Disordered Metallic Quantum Critical Systems,"We present a field theory for a structurally disordered magnetic system
+coupled to a metallic environment near a quantum critical point. We show that
+close to the magnetic quantum critical point droplets are formed due to the
+disorder and undergo dissipative quantum dynamics. We show that the problem has
+a characteristic energy scale, the droplet Kondo temperature, that determines
+the crossover energy scale from weak to strong coupling. Our results have
+direct significance for the Griffiths-McCoy singularities of itinerant magnets.",0106176v1
+2001-06-14,Magnetic field-induced insulating behavior in highly oriented pyrolitic graphite,"We propose an explanation for the apparent semimetal-insulator transition
+observed in highly oriented pyrolitic graphite in the presence of magnetic
+field perpendicular to the layers. We show that the magnetic field opens an
+excitonic gap in the linear spectrum of the Coulomb interacting quasiparticles,
+in a close analogy with the phenomenon of dynamical chiral symmetry breaking in
+the relativistic theories of the 2+1-dimensional Dirac fermions. Our
+strong-coupling appoach allows for a non-perturbative description of the
+corresponding critical behavior.",0106261v3
+2001-06-19,Observation of Convergent Oscillations of the Flux Line Lattice as a Result of Magnetic Flux Jumping in Hard Superconductors,"We have monitored new peculiarities of the dynamics of catastrophic
+avalanches of the magnetic flux in superconducting Nb, Nb-Ti, and YBaCuO
+samples: i) convergent oscillations of the magnetic flux; ii) a threshold for
+entering the huge flux avalanches in the shielding experiments; iii) a
+threshold for the exit of a residual flux in the trapping experiments. The
+observed phenomena are interpreted in terms of a theoretical model which takes
+into account the inertial properties of the vortex matter.",0106379v2
+2001-06-26,Fragility of the spin-glass-like collective state to a magnetic field in an interacting Fe-C nanoparticle system,"The effect of applied magnetic fields on the collective nonequilibrium
+dynamics of a strongly interacting Fe-C nanoparticle system has been
+investigated. It is experimentally shown that the magnetic aging diminishes to
+finally disappear for fields of moderate strength. The field needed to remove
+the observable aging behavior increases with decreasing temperature. The same
+qualitative behavior is observed in an amorphous metallic spin glass
+(Fe_{0.15}Ni_{0.85})_{75}P_{16}B_6Al_3.",0106530v1
+2002-03-18,Relaxation of Shallow Donor Electron Spin due to Interaction with Nuclear Spin Bath,"We study the low-temperature dynamics of a shallow donor, e.g., $^{31}$P,
+impurity electron spin in silicon, interacting with the bath of nuclear spins
+of the $^{29}$Si isotope. For small applied magnetic fields, the electron spin
+relaxation is controlled by the steady state distribution of the nuclear spins.
+We calculate the relaxation times $T_1$ and $T_2$ as functions of the external
+magnetic field, and conclude that nuclear spins play an important role in the
+donor electron spin decoherence in Si:P at low magnetic fields.",0203362v1
+2002-06-19,Magnetic-field induced triplet superconductivity in the Hubbard model on a triangular lattice,"We propose theoretically that a magnetic field can realize spin-triplet
+superconductivity in repulsively interacting electron systems having strong
+ferromagnetic spin fluctuations. We confirm the general idea for the
+low-density Hubbard model on a triangular lattice, whose Fermi surface consists
+of disconnected pieces, by calculating the pairing susceptibility in a moderate
+magnetic field with the quantum Monte-Carlo method combined with the dynamical
+cluster approximation.",0206358v1
+2002-08-25,Spin dynamics of a tetrahedral cluster magnet,"We study the magnetism of a lattice of coupled tetrahedral spin-1/2 clusters
+which might be of relevance to the tellurate compounds Cu2Te2O5X2, with X=Cl,
+Br. Using the flow equation method we perform a series expansion in terms of
+the inter-tetrahedral exchange couplings starting from the quadrumer limit.
+Results will be given for the magnetic instabilities of the quadrumer phase and
+the dispersion of elementary triplet excitations. In limiting cases of our
+model of one- or two dimensional character we show our results to be consistent
+with findings on previously investigated decoupled tetrahedral chains and the
+Heisenberg model on the 1/5-depleted square lattice.",0208472v1
+2002-10-16,Quantum dynamics of crystals of molecular nanomagnets inside a resonant cavity,"It is shown that crystals of molecular nanomagnets exhibit enhanced magnetic
+relaxation when placed inside a resonant cavity. Strong dependence of the
+magnetization curve on the geometry of the cavity has been observed, providing
+evidence of the coherent microwave radiation by the crystals. A similar
+dependence has been found for a crystal placed between Fabry-Perot
+superconducting mirrors. These observations open the possibility of building a
+nanomagnetic microwave laser pumped by the magnetic field.",0210340v1
+2002-10-17,Magnetization reversal times in the 2D Ising model,"We present a theoretical framework which is generally applicable to the study
+of time scales of activated processes in systems with Brownian type dynamics.
+This framework is applied to a prototype system: magnetization reversal times
+in the 2D Ising model. Direct simulation results for the magnetization reversal
+times, spanning more than five orders of magnitude, are compared with
+theoretical predictions; the two agree in most cases within 20%.",0210370v1
+2002-11-12,Putting hydrodynamic interactions to work: tagged particle separation,"Separation of magnetically tagged cells is performed by attaching markers to
+a subset of cells in suspension and applying fields to pull from them in a
+variety of ways. The magnetic force is proportional to the field gradient, and
+the hydrodynamic interactions play only a passive, adverse role. Here we
+propose using a homogeneous rotating magnetic field only to make tagged
+particles rotate, and then performing the actual separation by means of
+hydrodynamic interactions, which thus play an active role. The method, which we
+explore here theoretically and by means of numerical simulations, lends itself
+naturally to sorting on large scales.",0211243v2
+2002-12-03,Thermal stability of coupled ferromagnetic and superparamagnetic particles,"We consider a single-domain ferromagnetic particle with uniaxial anisotropy
+coupled to a single-domain soft ferromagnetic particle (superparamagnetic
+particle). The problem of thermally agitated magnetization reversal in this
+case can be reduced to the random magnetization dynamics of the first particle
+with an effectively larger anisotropy field. The magnetic external field is
+also altered in a manner that depends on the sign of the coupling and can be
+either enhanced or suppressed.",0212041v1
+2003-03-04,Field-tuned quantum tunneling in a supramolecule dimer $[Mn_4]_2$,"Field-tuned quantum tunneling in two single-molecule magnets coupled
+antiferromagnetically and formed a supramolecule dimer is studied. We obtain
+step-like magnetization curves by means of the numerically exact solution of
+the time-dependent Schr\H{o}dinger equation. The steps in magnetization curves
+show the phenomenon of quantum resonant tunneling quantitatively. The effects
+of the sweeping rate of applied field is discussed. These results obtained from
+quantum dynamical evolution well agree with the recent experiment[W.Wernsdorfer
+et al. Nature 416(2002)406].",0303048v1
+2003-04-11,Quantum dynamics of exchange biased Single Molecule Magnets,"We present a new family of exchange biased Single Molecule Magnets in which
+antiferromagnetic coupling between the two components results in quantum
+behaviour different from that of the individual SMMs. Our experimental
+observations and theoretical analysis suggest a means of tuning the quantum
+tunnelling of magnetization in SMMs. See also: W. Wernsdorfer, N.
+Aliaga-Alcalde, D. Hendrickson, G. Christou, Nature 416 (2002) 406.",0304279v1
+2003-07-21,Nuclear Magnetic Resonance in a Ferromagnet-Semiconductor Heterostructure,"We report the observation of nuclear magnetic resonance (NMR) in a
+ferromagnet-semiconductor heterostructure in the presence of a spin-polarized
+current. Spin-polarized electrons injected from a metallic ferromagnet generate
+a large nuclear spin population in a GaAs quantum well by dynamic polarization.
+The characteristic time for the polarization process is approximately 20 sec,
+and the nuclear polarization can persist for several minutes after the current
+is turned off. Resonant depolarization is observed in the presence of an AC
+magnetic field or when the injection current is modulated at the NMR frequency.",0307512v1
+2004-04-01,Temperature dependence of spin-transfer-induced switching of nanomagnets,"We measure the temperature, magnetic-field, and current dependence for the
+switching of nanomagnets by a spin-polarized current. Depending on current
+bias, switching can occur between either two static magnetic states or a static
+state and a current-driven precessional mode. In both cases, the switching is
+thermally activated and governed by the sample temperature, not a higher
+effective magnetic temperature. The activation barriers for switching between
+static states depend linearly on current, with a weaker dependence for dynamic
+to static switching.",0404003v1
+2004-05-26,Nonequilibrium Extension of the Landau-Lifshitz-Gilbert Equation for Magnetic Systems,"Using the invariant operator method for an effective Hamiltonian including
+the radiation-spin interaction, we describe the quantum theory for
+magnetization dynamics when the spin system evolves nonadiabatically and out of
+equilibrium, $d \hat{\rho}/dt \neq 0$. It is shown that the vector parameter of
+the invariant operator and the magnetization defined with respect to the
+density operator, both satisfying the quantum Liouville equation, still obey
+the Landau-Lifshitz-Gilbert equation.",0405599v1
+2004-06-21,"Magnetic susceptibility, exchange interactions and spin-wave spectra in the local spin density approximation","Starting from exact expression for the dynamical spin susceptibility in the
+time-dependent density functional theory a controversial issue about exchange
+interaction parameters and spin-wave excitation spectra of itinerant electron
+ferromagnets is reconsidered. It is shown that the original expressions for
+exchange integrals based on the magnetic force theorem (J. Phys. F14 L125
+(1984)) are optimal for the calculations of the magnon spectrum whereas static
+response function is better described by the ``renormalized'' magnetic force
+theorem by P. Bruno (Phys. Rev. Lett. 90, 087205 (2003)). This conclusion is
+confirmed by the {\it ab initio} calculations for Fe and Ni.",0406488v1
+2004-07-23,Low-Temperature Glassy Response of Ultrathin Manganite Films to Electric and Magnetic Fields,"The glassy response of thin films of La0.8Ca0.2MnO3 to external magnetic and
+gated electrostatic fields in a field-effect geometry has been studied at low
+temperatures. A hierarchical response with irreversible memory effects,
+non-ergodic time evolution, aging and annealing behavior of the resistance
+suggest that the dynamics are governed by strain relaxation for both electronic
+and magnetic perturbations. Cross-coupling of charge, spin, and strain have
+been exploited to tune the coercivity of an ultrathin manganite film by
+electrostatic gating.",0407607v1
+2005-06-04,Magnetic Soliton and Soliton Collisions of Spinor Bose-Einstein Condensates in an Optical Lattice,"We study the magnetic soliton dynamics of spinor Bose-Einstein condensates in
+an optical lattice which results in an effective Hamiltonian of anisotropic
+pseudospin chain. A modified Landau-Lifshitz equation is derived and exact
+magnetic soliton solutions are obtained analytically. Our results show that the
+time-oscillation of the soliton size can be controlled in practical experiment
+by adjusting of the light-induced dipole-dipole interaction. Moreover, the
+elastic collision of two solitons is investigated.",0506101v1
+2005-09-22,Current-induced motion of a domain wall in magnetic nanowires,"The dynamics of current-induced motion of a magnetic domain wall in a
+quasi-one-dimensional ferromagnet with both easy-axis and easy-plane
+anisotropy, is studied. We pay a special attention to the case of a sharp
+domain wall, and calculate the spin torque created by the electric current. The
+torque has two components, one of which is acting as a driving force for the
+motion of the domain wall while the other distorts its shape, forcing thus the
+magnetic moments to deviate from the easy plane.",0509574v1
+2006-01-15,Self-Induced Quasistationary Magnetic Fields,"The interaction of electromagnetic radiation with temporally dispersive
+magnetic solids of small dimensions may show very special resonant behaviors.
+The internal fields of such samples are characterized by
+magnetostatic-potential scalar wave functions. The oscillating modes have the
+energy orthogonality properties and unusual pseudo-electric (gauge) fields.
+Because of a phase factor, that makes the states single valued, a persistent
+magnetic current exists. This leads to appearance of an eigen-electric moment
+of a small disk sample. One of the intriguing features of the mode fields is
+dynamical symmetry breaking.",0601319v1
+2006-02-04,Spin-transfer-driven ferromagnetic resonance of individual nanomagnets,"We demonstrate a technique that enables ferromagnetic resonance (FMR)
+measurements of the normal modes for magnetic excitations in individual
+nanoscale ferromagnets, smaller in volume by a factor of 1000 than can be
+probed by other methods. The measured peak shapes indicate two regimes of
+response: simple FMR and phase locking. Studies of the resonance frequencies,
+amplitudes, and linewidths as a function of microwave power, DC current, and
+magnetic field provide detailed new information about the exchange, damping,
+and spin-transfer torques that govern the dynamics in magnetic nanostructures.",0602105v1
+2006-02-17,Andreev drag effect via magnetic quasiparticle focusing in normal-superconductor nanojunctions,"We study a new hybrid normal-superconductor (NS) pi-junction in which the
+non-local current can be orders of magnitude larger than that in earlier
+proposed systems. We calculate the electronic transport of this NS hybrid when
+an external magnetic field is applied. It is shown that the non-local current
+exhibits oscillations as a function of the magnetic field, making the effect
+tunable with the field. The underlying classical dynamics is qualitatively
+discussed.",0602423v2
+2006-05-08,Microscopic Calculation of Spin Torques in Disordered Ferromagnets,"Effects of conduction electrons on magnetization dynamics, represented by
+spin torques, are calculated microscopically in the first order in spatial
+gradient and time derivative of magnetization. Special attention is paid to the
+so-called $\beta$-term and the Gilbert damping, $\alpha$, in the presence of
+electrons' spin-relaxation processes, which are modeled by quenched magnetic
+(and spin-orbit) impurities. The obtained results such as $\alpha \ne \beta$
+hold for localized as well as itinerant ferromagnetism.",0605186v1
+2006-06-21,Quantum Dynamics of Spin Wave Propagation Through Domain Walls,"Through numerical solution of the time-dependent Schrodinger equation, we
+demonstrate that magnetic chains with uniaxial anisotropy support stable
+structures, separating ferromagnetic domains of opposite magnetization. These
+structures, domain walls in a quantum system, are shown to remain stable if
+they interact with a spin wave. We find that a domain wall transmits the
+longitudinal component of the spin excitations only. Our results suggests that
+continuous, classical spin models described by LLG equation cannot be used to
+describe spin wave-domain wall interaction in microscopic magnetic systems.",0606549v1
+2006-06-25,Quantum chaos and fluctuations in isolated nuclear spin systems,"Using numerical simulations we investigate dynamical quantum chaos in
+isolated nuclear spin systems. We determine the structure of quantum states,
+investigate the validity of the Curie law for magnetic susceptibility and find
+the spectrum of magnetic noise. The spectrum is the same for positive and
+negative temperatures. The study is motivated by recent interest in
+condensed-matter experiments for searches of fundamental parity- and
+time-reversal-invariance violations. In these experiments nuclear spins are
+cooled down to microkelvin temperatures and are completely decoupled from their
+surroundings. A limitation on statistical sensitivity of the experiments arises
+from the magnetic noise.",0606635v1
+2006-06-26,Self Consistent NEGF-LLG Model for Spin-Torque Based Devices,"We present here a self consistent solution of quantum transport, using the
+Non Equilibrium Green's Function (NEGF) method, and magnetization dynamics,
+using the Landau-Lifshitz-Gilbert (LLG) formulation. We have applied this model
+to study current induced magnetic switching due to `spin torque' in a device
+where the electronic transport is ballistic and the free magnetic layer is
+sandwiched between two anti-parallel ferromagnetic contacts. The device shows
+clear hysteretic current-voltage characteristics, at room temperature, with a
+sharp transition between the bistable states and hence can be used as a
+non-volatile memory. We show that the proposed design may allow reducing the
+switching current by an order of magnitude.",0606648v2
+2006-06-27,Magnetic Susceptibility of the Double-Exchange Model in the RKKY Limit,"The magnetic susceptibility and Edwards-Anderson order parameter q of the
+spin-glass-like (SGL) phase of the double-exchange model are evaluated in the
+weak-coupling or RKKY limit. Dynamical mean-field theory is used to show that
+q=M(T/Tsg)^2, where M is the classical Brillouin function and Tsg is the SGL
+transition temperature. The correlation length of the SGL phase is determined
+by a correlation parameter Q that maximizes Tsg and minimizes the free energy.
+The magnetic susceptibility has a cusp at Tsg and reaches a nonzero value as T
+goes to zero.",0606699v1
+2006-08-19,Spin dynamics in molecular ring nanomagnets: Significant effect of acoustic phonons and magnetic anisotropies,"The nuclear spin-lattice relaxation rate 1/T_1_ is calculated for magnetic
+ring clusters by fully diagonalizing their microscopic spin Hamiltonians.
+Whether the nearest-neighbor exchange interaction J is ferromagnetic or
+antiferromagnetic, 1/T_1_ versus temperature T in ring nanomagnets may be
+peaked at around k_B_T=|J| provided the lifetime broadening of discrete energy
+levels is in proportion to T^3^. Experimental findings for ferromagnetic and
+antiferromagnetic Cu^II^ rings are reproduced with crucial contributions of
+magnetic anisotropies as well as acoustic phonons.",0608438v1
+2006-08-22,Clustering induced suppression of ferromagnetism in diluted magnets,"Ferromagnetism in diluted magnets in the compensated regime p << x is shown
+to be suppressed by the formation of impurity spin clusters. The majority bulk
+spin couplings are shown to be considerably weakened by the preferential
+accumulation of holes in spin clusters, resulting in low-energy magnon
+softening and enhanced low-temperature decay of magnetic order. A locally
+self-consistent magnon renormalization analysis of spin dynamics shows that
+although strong intra-cluster correlations tend to prolong global order, T_c is
+still reduced compared to the ordered case.",0608474v2
+2006-08-31,Magnetic correlations around the Mott transition in the Kagomé lattice Hubbard model,"We study the magnetic properties around the Mott transition in the Kagom\'e
+lattice Hubbard model by the cellular dynamical mean field theory combined with
+quantum Monte Carlo simulations. By investigating the q-dependence of the
+susceptibility, we find a dramatic change of the dominant spin fluctuations
+around the Mott transition. The spin fluctuations in the insulating phase favor
+down to the lowest temperature a spatial spin configuration in which
+antiferromagnetic correlations are strong only in one chain direction but
+almost vanishing in the others.",0608699v1
+2006-09-19,Spin echo without an external permanent magnetic field,"The spin echo techniques aim at the elimination of the effect of a random
+magnetic field on the spin evolution. These techniques conventionally utlize
+the application of a permanent field which is much stronger than the random
+one. The strong field, however, may also modify the magnetic response of the
+medium containing the spins, thus altering their ``natural'' dynamics. We
+suggest an iterative scheme for generating a sequence of pulses which create an
+echo without an external permanent field. The approximation to the ideal echo
+improves with the sequence length.",0609490v1
+2006-09-20,Coherent spin dynamics in quantum wells in quantizing magnetic field,"We investigate theoretically the coherent longitudinal and transversal spin
+relaxation of photoexcited electrons in quantum wells in quantized magnetic
+fields. We find the relaxation time for typical quantum well parameters between
+100 and 1000 ps. For a realistic random potential the relaxation process
+depends on the electron energy and g-factor, demonstrating oscillations in the
+spin polarization accompanying the spin relaxation. The dependence of spin
+relaxation on applied field, and thus on the corresponding ""magnetic"" length,
+can be used to characterize the spatial scale of disorder in quantum wells.",0609522v1
+2007-01-17,Flux-biased mesoscopic rings,"Kinetics of magnetic flux in a thin mesoscopic ring biased by a strong
+external magnetic field is described equivalently by dynamics of a Brownian
+particle in a tilted washboard potential. The 'flux velocity', i.e. the
+averaged time derivative of the total magnetic flux in the ring, is a candidate
+for a novel characteristics of mesoscopic rings. Its global properties reflect
+the possibility of accommodating persistent currents in the ring.",0701403v2
+2007-02-02,Current-induced magnetic vortex core switching in a Permalloy nanodisk,"We report on the switching of a magnetic vortex core in a sub-micron
+Permalloy disk, induced by a short current pulse applied in the film plane.
+Micromagnetic simulations including the adiabatic and non-adiabatic spin-torque
+terms are used to investigate the current-driven magnetization dynamics. We
+predict that a core reversal can be triggered by current bursts a tenth of a
+nanosecond long. The vortex core reversal process is found to be the same as
+when an external field pulse is applied. The control of a vortex core's
+orientation using current pulses introduces the technologically relevant
+possibility to address individual nanomagnets within dense arrays.",0702048v1
+2001-09-25,Magnetic Brane-worlds,"We investigate brane-worlds with a pure magnetic field and a perfect fluid.
+We extend earlier work to brane-worlds, and find new properties of the Bianchi
+type I brane-world. We find new asymptotic behaviours on approach to the
+singularity and classify the critical points of the dynamical phase space. It
+is known that the Einstein equations for the magnetic Bianchi type I models are
+in general oscillatory and are believed to be chaotic, but in the brane-world
+model this chaotic behaviour does not seem to be possible.",0109084v2
+2002-10-22,Bianchi type I universes with dilaton and magnetic fields,"We consider the dynamics of a Bianchi type I spacetime in the presence of
+dilaton and magnetic fields. The general solution of the Einstein-Maxwell
+dilaton field equations can be obtained in an exact parametric form. Depending
+on the numerical values of the parameters of the model there are three distinct
+classes of solutions. The time evolution of the mean anisotropy, shear and
+deceleration parameter is considered in detail and it is shown that a
+magnetic-dilaton anisotropic Bianchi type I geometry does not isotropize, the
+initial anisotropy being present in the universe for all times.",0210073v1
+1997-04-18,"Comment on ""Cherenkov Radiation by Neutrinos in a Supernova Core""","Mohanty and Samal have shown that the magnetic-moment interaction with
+nucleons contributes significantly to the photon dispersion relation in a
+supernova core, and with an opposite sign relative to the usual plasma effect.
+Because of a numerical error they overestimated the magnetic-moment term by two
+orders of magnitude, but it is still of the same order as the plasma effect. It
+appears that the Cherenkov processes gamma+nu -> nu and nu -> nu+gamma remain
+forbidden, but a final verdict depends on a more detailed investigation of the
+dynamical magnetic susceptibility of a hot nuclear medium.",9704352v1
+2000-09-26,External Magnetic Fields in QFT: A Non-Perturbative Approach,"A discussion of the influence of boundaries and scalar field interactions in
+the non-perturbative dynamics of fermions in an external magnetic field, along
+with their possible applications to condensed matter and cosmology, is briefly
+presented. The significance of the results for electroweak baryogenesis in the
+presence of an external magnetic field is indicated.",0009303v1
+2002-03-26,Magnetic moments of the Lambda(1405) and Lambda(1670) resonances,"By using techniques of unitarized chiral perturbation theory, where the
+$\Lambda(1405)$ and $\Lambda(1670)$ resonances are dynamically generated, we
+evaluate the magnetic moments of these resonances and their transition magnetic
+moment. The results obtained here differ appreciably from those obtained with
+existing quark models. The width for the $\Lambda(1670) \to \Lambda(1405)
+\gamma$ transition is also evaluated leading to a branching ratio of the order
+of $2 \times 10^{-6}$.",0203248v1
+1997-01-29,Chiral Symmetry Breaking in a Uniform External Magnetic Field,"Using the nonperturbative Schwinger-Dyson equation, we show that chiral
+symmetry is dynamically broken in QED at weak couplings when an external
+magnetic field is present, and that chiral symmetry is restored at temperatures
+above $T_c \simeq \alpha\pi^2/\sqrt{2 \pi |eH|}$, where $\alpha$ is the fine
+structure constant and $H$ is the magnetic field strength.",9701172v1
+1998-10-19,The effective potential of composite fields in weakly coupled QED in a uniform external magnetic field,"The effective potential for the composite fields responsible for chiral
+symmetry breaking in weakly coupled QED in a magnetic field is derived. The
+global minimum of the effective potential is found to acquire a non-vanishing
+expectation value of the composite fields that leads to generating the
+dynamical fermion mass by an external magnetic field. The results are compared
+with those for the Nambu-Jona-Lasinio model.",9810144v1
+1998-10-22,The Aharonov-Bohm Problem Revisited,"The properties of a nonrelativistic charged particle in two dimensions in the
+presence of an arbitrary number of nonquantized magnetic fluxes are
+investigated in free space as well as in a uniform magnetic field. The fluxes
+are represented mathematically as branch points in one of the complex
+coordinates. It is found that in order to construct solutions, the fluxes have
+to be treated in general as dynamical objects dual to the charges. A medium
+made up of fluxes acts like an anti-magnetic field and tends to expel the
+charges.",9810182v2
+1999-09-06,Dynamical Symmetry Breaking in Planar QED,"We investigate (2+1)-dimensional QED coupled with Dirac fermions both at zero
+and finite temperature. We discuss in details two-components (P-odd) and
+four-components (P-even) fermion fields. We focus on P-odd and P-even Dirac
+fermions in presence of an external constant magnetic field. In the spontaneous
+generation of the magnetic condensate survives even at infinite temperature. We
+also discuss the spontaneous generation of fermion mass in presence of an
+external magnetic field.",9909029v2
+2002-07-17,Non Abelian Magnetic Monopoles and Dynamics of Confinement,"Magnetic monopoles having non-Abelian charges have been found recently to
+play a crucial role in the infrared in a class of supersymmetric gauge
+theories. We argue that these ""dual quarks"" can naturally be identified with
+the non-Abelian magnetic monopoles of the type first discussed by Goddard,
+Nuyts and Olive. Our argument is based on a few simple observations as regards
+to their charge structure, flavor quantum numbers, and some general properties
+of electromagnetic duality.",0207161v1
+2005-10-17,Stable Monopole-Antimonopole String Background in SU(2) QCD,"Motivated by the instability of the Savvidy-Nielsen-Olesen vacuum we make a
+systematic search for a stable magnetic background in pure SU(2) QCD. It is
+shown that a pair of axially symmetric monopole and antimonopole strings is
+stable, provided that the distance between the two strings is less than a
+critical value. The existence of a stable monopole-antimonopole string
+background strongly supports that a magnetic condensation of
+monopole-antimonopole pairs can generate a dynamical symmetry breaking, and
+thus the magnetic confinement of color in QCD.",0510140v1
+1999-02-02,Rigidity for periodic magnetic fields,"We study the motion of a charge on a conformally flat Riemannian torus in the
+presence of magnetic field. We prove that for any non-zero magnetic field there
+always exist orbits of this motion which have conjugate points. We conjecture
+that the restriction of conformal flatness of the metric is not essential for
+this result. This would provide a ``twisted'' version of the recent
+generalisation of Hopf's rigidity result obtained by Burago and Ivanov.",9902013v1
+2002-04-15,Thresholds to Chaos and Ionization for the Hydrogen Atom in Rotating Fields,"We analyze the classical phase space of the hydrogen atom in crossed magnetic
+and circularly polarized microwave fields in the high frequency regime, using
+the Chirikov resonance overlap criterion and the renormalization map. These
+methods are used to compute thresholds to large scale chaos and to ionization.
+The effect of the magnetic field is a strong stabilization of a set of
+invariant tori which bound the trajectories and prevent stochastic ionization.
+In order to ionize, larger amplitudes of the microwave field are necessary in
+the presence of a magnetic field.",0204033v1
+2003-01-30,Local amplitude equation from non-local dynamics,"We derive a closed equation for the shape of the free surface of a magnetic
+fluid subject to an external magnetic field. The equation is strongly non-local
+due to the long range character of the magnetic interaction. We develop a
+systematic multiple scale perturbation expansion in which the non-locality is
+reduced to the occurrence of the Hilbert transform of the surface profile. The
+resulting third order amplitude equation describing the slow modulation of the
+basic pattern is shown to be purely local.",0301046v1
+2000-06-17,Time-odd mean fields in the rotating frame: microscopic nature of nuclear magnetism,"The microscopic role of nuclear magnetism in rotating frame is investigated
+for the first time in the framework of the cranked relativistic mean field
+theory. It is shown that nuclear magnetism modifies the expectation values of
+single-particle spin, orbital and total angular momenta along the rotational
+axis effectively creating additional angular momentum. This effect leads to the
+increase of kinematic and dynamic moments of inertia at given rotational
+frequency and has an impact on effective alignments.",0006034v1
+2001-06-27,The Kraichnan-Kazantsev dynamo,"The problem of the dynamo effect for a Kraichnan incompressible helicity-free
+velocity field is considered. Exploiting a quantum formalism first introduced
+by Kazantsev (A.P. Kazantsev, Sov. Phys. JETP 26, 1031-1034 (1968)), we show
+that a critical magnetic Reynolds number exists for the presence of dynamo. The
+value of the Prandtl number influences the spatial distribution of the magnetic
+field and its growth in time. The magnetic field correlation length is always
+the largest between the diffusive scale and the viscous scale of the flow. In
+the same way the field growth is characterized by a time scale that corresponds
+to the largest between the diffusive and the viscous characteristic time.",0106090v1
+2001-06-28,Preferential Acceleration of Coherent Magnetic Structures and Bursty Bulk Flows in Earth's Magnetotail,"Observations indicate that the magnetotail convection is turbulent and
+bi-modal, consisting of fast bursty bulk flows (BBF) and a nearly stagnant
+background. We demonstrate that this observed phenomenon may be understood in
+terms of the intermittent interactions, dynamic mergings and preferential
+accelerations of coherent magnetic structures under the influence of a
+background magnetic field geometry that is consistent with the development of
+an X-point mean-field structure.",0106098v1
+2003-06-05,Statistical anisotropy of magnetohydrodynamic turbulence,"Direct numerical simulations of decaying and forced magnetohydrodynamic (MHD)
+turbulence without and with mean magnetic field are analyzed by higher-order
+two-point statistics. The turbulence exhibits statistical anisotropy with
+respect to the direction of the local magnetic field even in the case of global
+isotropy. A mean magnetic field reduces the parallel-field dynamics while in
+the perpendicular direction a gradual transition towards two-dimensional MHD
+turbulence is observed with $k^{-3/2}$ inertial-range scaling of the
+perpendicular energy spectrum. An intermittency model based on the Log-Poisson
+approach, $\zeta_p=p/g^2 +1 -(1/g)^{p/g}$, is able to describe the observed
+structure function scalings.",0306045v1
+2004-05-06,Fluid pumped by magnetic stress,"A magnetic field rotating on the free surface of a ferrofluid layer is shown
+to induce considerable fluid motion toward the direction the field is rolling.
+The measured flow velocity i) increases with the square of the magnetic field
+amplitude, ii) is proportional to the thickness of the fluid layer, and iii)
+has a maximum at a driving frequency of about 3 kHz. The pumping speed can be
+estimated with a two-dimensional flow model.",0405025v2
+2004-11-21,Plateau Instability of Liquid Crystalline Cylinder in Magnetic Field,"The capillary instability of a LC cylinder in magnetic field is considered
+using an energy approach. The boundary problem is solved in the linear
+approximation of the anisotropy $\chi_a$ of the magnetic susceptibility $\chi$.
+The effect of anisotropy, in the region $1\gg|\chi|>|\chi_a|\gg \chi^2$, can be
+strong enough to counteract and even reverse the tendency of the field to
+enhance stabilization by enlarging the cut--off wave number $k_s$ beyond the
+conventional one set by Rayleigh.",0411200v1
+2005-01-07,Anharmonic mixing in a magnetic trap,"We have experimentally observed re-equilibration of a magnetically trapped
+cloud of metastable neon atoms after it was put in a non-equilibrium state.
+Using numerical simulations we show that anharmonic mixing, equilibration due
+to the collisionless dynamics of atoms in a magnetic trap, is the dominant
+process in this equilibration. We determine the dependence of its time on trap
+parameters and atom temperature. Furthermore we observe in the simulations a
+resonant energy exchange between the radial and axial trap dimensions at a
+ratio of trap frequencies \omega_r / \omega_z = 3/2. This resonance is
+explained by a simple oscillator model.",0501033v1
+2005-06-01,Multi-electron giant dipole resonances of atoms in crossed electric and magnetic fields,"Multi-electron giant dipole resonances of atoms in crossed electric and
+magnetic fields are investigated. Stationary configurations corresponding to a
+highly symmetric arrangement of the electrons on a decentered circle are
+derived, and a normal-mode stability analysis is performed. A classification of
+the various modes, which are dominated either by the magnetic or Coulomb
+interactions, is provided. A six-dimensional wave-packet dynamical study, based
+on the MCTDH approach, is accomplished for the two-electron resonances,
+yielding in particular lifetimes of more than 0.1 $\mu$s for strong electric
+fields.",0506007v1
+2005-08-02,N-Electron Giant Dipole States in Crossed Electric and Magnetic Fields,"Multi-electron giant dipole resonances of atoms in crossed electric and
+magnetic fields are investigated. Stationary configurations corresponding to a
+highly symmetric arrangement of the electrons on a decentered circle are
+derived, and a normal-mode and stability analysis are performed. A
+classification of the various modes, which are dominated by the magnetic field
+or the Coulomb interactions, is provided. Based on the MCTDH approach, we carry
+out a six-dimensional wave-packet dynamical study for the two-electron
+resonances, yielding in particular lifetimes of more than 0.1 $\mu$s for strong
+electric fields.",0508021v1
+2001-06-28,Trapped-Atom-Interferometer in a Magnetic Microtrap,"We propose a configuration of a magnetic microtrap which can be used as an
+interferometer for three-dimensionally trapped atoms. The interferometer is
+realized via a dynamic splitting potential that transforms from a single well
+into two separate wells and back. The ports of the interferometer are
+neighboring vibrational states in the single well potential. We present a
+one-dimensional model of this interferometer and compute the probability of
+unwanted vibrational excitations for a realistic magnetic potential. We
+optimize the speed of the splitting process in order suppress these excitations
+and conclude that such interferometer device should be feasible with currently
+available microtrap technique.",0106162v1
+2002-10-07,Single-Spin Measurement and Decoherence in Magnetic Resonance Force Microscopy,"We consider a simple version of a cyclic adiabatic inversion (CAI) technique
+in magnetic resonance force microscopy (MRFM). We study the problem: What
+component of the spin is measured in the CAI MRFM? We show that the
+non-destructive detection of the cantilever vibrations provides a measurement
+of the spin component along the effective magnetic field. This result is based
+on numerical simulations of the Hamiltonian dynamics (the Schrodinger equation)
+and the numerical solution of the master equation.",0210043v1
+2005-03-18,On decoherence in noncommutative plane with perpendicular magnetic field,"In the last years noncommutative quantum mechanics has been investigated
+intensively. We consider the influence of magnetic field on decoherence of a
+system in the noncommutative quantum plane. Particularly, we point out a model
+in which the magnetic field allows {\it in situ} dynamical control of
+decoherence as well as, in principle, observation of noncommutativity.",0503163v1
+2007-04-27,Constrained flow around a magnetic obstacle,"Many practical applications exploit an external local magnetic field --
+magnetic obstacle -- as an essential part of their constructions. Recently, it
+has been demonstrated that the flow of an electrically conducting fluid
+influenced by an external field can show several kinds of recirculation. The
+present paper reports a 3D numerical study whose some results are compared with
+an experiment about such a flow in a rectangular duct.",0704.3700v2
+2007-05-14,On the Enhanced Reverse Beta Processes in Graphene-Iron Composite Nanostructures at High Temperatures in Strong Magnetic Field,"Strong dense many-spin interactions have been proposed to organize novel
+orbital dynamics (the Little Effect) for novel chemical and catalytic
+phenomena. The recent determinations of the relativistic and quantum Hall
+effects of carriers in graphene under strong magnetic confinement have
+substantiated the Little Effect. Moreover such nonclassical phenomena under the
+stronger magnetic confinement of ferro-nanocatalysts are here shown to organize
+reverse beta processes and possibly pycnonuclear reactions under high
+temperature and high-pressure conditions. Such processes have implications for
+reverse beta reactions and nuclear reactions within the interior of the earth
+and new technologies for carbon nanotube-ferrometal and nanographene-ferrometal
+composites.",0705.1909v1
+2007-06-12,Theory of nonlinear particle acceleration at shocks and self-generation of the magnetic field,"We present some recent developments in the theory of particle acceleration at
+shock fronts in the presence of dynamical reaction of the accelerated particles
+and self-generation of magnetic field due to streaming instability. The spectra
+of accelerated particles, the velocity, magnetic field and temperature profiles
+can be calculated in this approach anywhere in the precursor and in the
+downstream region. The implications for the origin of cosmic rays and for the
+phenomenology of supernova remnants will be discussed.",0706.1714v1
+2007-07-14,Nonequilibrium Work distributions for a trapped Brownian particle in a time dependent magnetic field,"We study the dynamics of a trapped, charged Brownian particle in presence of
+a time dependent magnetic field. We calculate work distributions for different
+time dependent protocols. In our problem thermodynamic work is related to
+variation of vector potential with time as opposed to the earlier studies where
+the work is related to time variation of the potentials which depends only on
+the coordinates of the particle. Using Jarzynski identity and Crook's equality
+we show that the free energy of the particle is independent of the magnetic
+field, thus complementing the Bohr-van Leeuwen theorem. We also show that our
+system exhibits a parametric resonance in certain parameter space.",0707.2131v1
+2007-08-14,Circumstellar Magnetic Field Diagnostics from Line Polarization,"Given that dynamically significant magnetic fields in at least some massive
+stars have now been measured, our contribution addresses the question, to what
+extent can fields be directly detected in circumstellar gas? The question
+speaks directly to the very interesting topic of line-driving physics coupled
+with magnetized plasmas, and how this coupling produces structure in the wind
+flow. We focus our attention on weak-field diagnostics. These come in two main
+types: the Hanle effect, which pertains to coherence effects for linear
+polarization from line scattering, and the weak longitudinal Zeeman effect,
+which pertains to circular polarization in lines.",0708.1942v2
+2007-08-31,Increasing the Efficiency of Energy Scavengers,"In this paper, a methodology for designing efficient energy scavengers is
+proposed. The scavenger consists of a cantilever beam on which piezoelectric
+films and a mass are mounted. The mass at the tip of the beam is known as the
+proof mass and the device is called either an energy scavenger or a beam-mass
+system. The proof mass is a permanent magnet, where in its vicinity attracting
+permanent magnets are placed. It is shown that when the magnets have
+appropriate strengths and are placed appropriately, the vibration of the
+beam-mass system can be amplified, thereby the scavenged energy is increased.
+Examples are given throughout the paper.",0708.4412v2
+2007-09-06,Magnetogenesis from Rotating Cosmic String Loops,"We present a mechanism to create vortices in a plasma via gravitational
+dragging behind rotating cosmic string loops. The vortical motions create
+magnetic fields by means of the Harrison-Rees mechanism; the fields are further
+enhanced through galactic collapse and dynamo amplification. Employing the
+Velocity dependent One Scale model (VOS) for the string network and
+incorporating loop dynamics, we compute the magnetic fields generated around
+the time of decoupling: these are just strong and coherent enough to account
+for presently observed magnetic fields in spiral galaxies if efficient dynamos
+with $\Gamma_{dy}^{-1}\approx 0.3$ Gyr are present.",0709.0735v1
+2007-09-07,Theory of Electromotive Force Induced by Domain Wall Motion,"We formulate a theory on the dynamics of conduction electrons in the presence
+of moving magnetic textures in ferromagnetic materials. We show that the
+variation of local magnetization in both space and time gives rise to
+topological fields, which induce electromotive forces on the electrons.
+Universal results are obtained for the emf induced by both transverse and
+vortex domain walls traveling in a magnetic film strip, and their measurement
+may provide clear characterization on the motion of such walls.",0709.1117v3
+2007-10-02,Harmonic oscillator model for current- and field-driven magnetic vortices,"In experiments the distinction between spin-torque and Oersted-field driven
+magnetization dynamics is still an open problem. Here, the gyroscopic motion of
+current- and field-driven magnetic vortices in small thin-film elements is
+investigated by analytical calculations and by numerical simulations. It is
+found that for small harmonic excitations the vortex core performs an
+elliptical rotation around its equilibrium position. The global phase of the
+rotation and the ratio between the semi-axes are determined by the frequency
+and the amplitude of the Oersted field and the spin torque.",0710.0532v1
+2007-11-07,"Comment on Effects of transverse magnetic field on mixed convection in wall plume of power-law fluids, by Gorla, Lee, Nakamura and Pop, IJES, 1993","Comment on Effects of transverse magnetic field on mixed convection in wall
+plume of power-law fluids, by Rama Subba Reddy Gorla, Jin Kook Lee, Shoichiro
+Nakamura and Ioan Pop [International Journal of Engineering Science, 31 (1993)
+1035-1045]. In the above paper the authors treat the boundary layer mixed
+convection flow of a power-law fluid along a vertical adiabatic surface in a
+transverse magnetic field with a steady thermal source at the leading edge. The
+governing non-similar equations are solved by means of a novel finite
+difference scheme. However, there are two fundamental errors in this paper and
+the presented results do not have any practical value.",0711.1015v1
+2007-11-19,Nonlinear mode conversion in monodomain magnetic squares,"Modifications of spatial distributions of dynamic magnetization corresponding
+to spinwave eigenmodes of magnetic squares subjected to a strong microwave
+excitation field have been studied experimentally and theoretically. We show
+that an increase of the excitation power leads to a nonlinear generation of
+long-wavelength spatial harmonics caused by the nonlinear cross coupling
+between the eigenmodes. The analysis of the experimental data shows that this
+process is mainly governed by the action of the nonlinear spin-wave damping.
+This conclusion is further supported by the numerical calculations based on the
+complex Ginzburg-Landau equation phenomenologically taking into account the
+nonlinear damping.",0711.2872v1
+2008-01-15,Broadband ferromagnetic resonance of Ni81Fe19 wires using a rectifying effect,"The broadband ferromagnetic resonance measurement using the rectifying effect
+of Ni81Fe19 wire has been investigated. One wire is deposited on the center
+strip line of the coplanar waveguide (CPW) and the other one deposited between
+two strip lines of CPW. The method is based on the detection of the
+magnetoresistance oscillation due to the magnetization dynamics induced by the
+radio frequency field. The magnetic field dependences of the resonance
+frequency and the rectification spectrum are presented and analytically
+interpreted on the standpoint of a uniform magnetization precession model.",0801.2203v1
+2008-02-06,Self-organized plane arrays of metallic magnetic elements,"We studied the dynamic magnetic properties of plane periodical arrays of
+circular permalloy nano-dots fabricated using a self-organized mask formed by
+polysterene nanospheres on the surface of a Permalloy film. Conventional
+(microwave cavity) and broadband coplanar-line ferromagnetic resonance setups
+were used for the measurements. We found several well resolved resonance peaks.
+This result shows that the self-organized mask fabrication technique is able to
+produce high-quality samples with small dispersion of geometrical and magnetic
+parameters.",0802.0731v1
+2008-02-25,Tunnel barrier enhanced voltage signals generated by magnetization precession of a single ferromagnetic layer,"We report the electrical detection of magnetization dynamics in an
+Al/AlOx/Ni80Fe20/Cu tunnel junction, where a Ni80Fe20 ferromagnetic layer is
+brought into precession under the ferromagnetic resonance (FMR) conditions. The
+dc voltage generated across the junction by the precessing ferromagnet is
+enhanced about an order of magnitude compared to the voltage signal observed
+when the contacts in this type of multilayered structure are ohmic. We discuss
+the relation of this phenomenon to magnetic spin pumping and speculate on other
+possible underlying mechanisms responsible for the enhanced electrical signal.",0802.3646v1
+2008-03-18,Quantum mechanics on curved 2D systems with electric and magnetic fields,"We derive the Schroedinger equation for a spinless charged particle
+constrained to a curved surface with electric and magnetics fields applied. The
+particle is confined on the surface using a thin-layer procedure, giving rise
+to the well-known geometric potential. The electric and magnetic fields are
+included via the four-potential. We find that there is no coupling between the
+fields and the surface curvature and that, with a proper choice of the gauge,
+the surface and transverse dynamics are exactly separable. Finally, the
+Hamiltonian for the cylinder, sphere and torus are analytically derived.",0803.2670v1
+2008-04-18,Magnetic Component of Quark-Gluon Plasma,"We describe recent developments of the ""magnetic scenario"" of sQGP. We show
+that at $T=(0.8-1.3)T_c$ there is a dense plasma of monopoles, capable of
+supporting metastable flux tubes. Their existence allows to quantitatively
+explained the non-trivial $T$-dependence of the static $\bar Q Q$ potential
+energy calculated on the lattice. By molecular dynamics simulation we derived
+transport properties (shear viscosity and diffusion constant) and showed that
+the best liquid is given by most symmetric plasma, with 50%-50% of electric and
+magnetic charges. The results are close to those of the ``perfect liquid''
+observed at RHIC.",0804.3102v1
+2008-05-15,Spin polarizations and spin Hall currents in a two-dimensional electron gas with magnetic impurities,"We consider a two-dimensional electron gas in the presence of Rashba
+spin-orbit coupling, and study the effects of magnetic s-wave impurities and
+long-range non-magnetic disorder on the spin-charge dynamics of the system. We
+focus on voltage induced spin polarizations and their relation to spin Hall
+currents. Our results are obtained using the quasiclassical Green function
+technique, and hold in the full range of the disorder parameter $\alpha
+p_F\tau$.",0805.2346v2
+2008-05-27,Self-sustained magnetoelectric oscillations in magnetic resonant tunneling structures,"The dynamic interplay of transport, electrostatic, and magnetic effects in
+the resonant tunneling through ferromagnetic quantum wells is theoretically
+investigated. It is shown that the carrier-mediated magnetic order in the
+ferromagnetic region not only induces, but also takes part in intrinsic,
+robust, and sustainable high-frequency current oscillations over a large window
+of nominally steady bias voltages. This phenomenon could spawn a new class of
+quantum electronic devices based on ferromagnetic semiconductors.",0805.4068v1
+2008-06-04,External magnetic field effects on a distorted kagome antiferromagnet,"We report bulk magnetization, and elastic and inelastic neutron scattering
+measurements under an external magnetic field, $H$, on the weakly coupled
+distorted kagome system, Cu_{2}(OD)_3Cl. Our results show that the ordered
+state below 6.7 K is a canted antiferromagnet and consists of large
+antiferromagnetic $ac$-components and smaller ferromagnetic $b$-components. By
+first-principle calculations and linear spin wave analysis, we present a simple
+spin hamiltonian with non-uniform nearest neighbor exchange interactions
+resulting in a system of coupled spin trimers with a single-ion anisotropy that
+can qualitatively reproduce the spin dynamics of Cu_{2}(OD)_3Cl.",0806.0767v1
+2008-06-04,Electric Field Induced Transformation of Magnetic Domain Structure in Magnetoelectric Iron Garnet Films,"The room temperature magnetoelectric effect was observed in epitaxial iron
+garnet films that appeared as magnetic domain wall motion induced by electric
+field. The films grown on gadolinium-gallium garnet substrates with various
+crystallographic orientations were examined. The effect was observed in (210)
+and (110) films and was not observed in (111) films. Dynamic observation of the
+domain wall motion in 400 V voltage pulses gave the value of domain wall
+velocity in the range 30-50 m/s. The same velocity was achieved in magnetic
+field pulse about 50 Oe.",0806.0811v1
+2008-07-27,Magnetic-dipolar and electromagnetic vortices in quasi-2D ferrite disks,"Magnetic-dipolar-mode (MDM) oscillations in a quasi-2D ferrite disk show
+unique dynamical symmetry properties resulting in appearance of topologically
+distinct structures. Based on the magnetostatic (MS) spectral problem
+solutions, in this paper we give an evidence for eigen MS power-flow-density
+vortices in a ferrite disk. Due to these circular eigen power flows, the MDMs
+are characterized by MS energy eigen states. It becomes evident that the reason
+of stability of the vortex configurations in saturated ferrite samples is
+completely different from the nature of stability in magnetically soft
+cylindrical dots. We found a clear correspondence between analytically derived
+MDM vortex states and numerically modeled electromagnetic vortices in quasi-2D
+ferrite disks.",0807.4281v1
+2008-07-31,Scattering Theory of Gilbert Damping,"The magnetization dynamics of a single domain ferromagnet in contact with a
+thermal bath is studied by scattering theory. We recover the
+Landau-Liftshitz-Gilbert equation and express the effective fields and Gilbert
+damping tensor in terms of the scattering matrix. Dissipation of magnetic
+energy equals energy current pumped out of the system by the time-dependent
+magnetization, with separable spin-relaxation induced bulk and spin-pumping
+generated interface contributions. In linear response, our scattering theory
+for the Gilbert damping tensor is equivalent with the Kubo formalism.",0807.5009v1
+2008-09-09,Finite Volume Study of the Delta Magnetic Moments Using Dynamical Clover Fermions,"We calculate the magnetic dipole moment of the Delta baryon using a
+background magnetic field on 2+1-flavors of clover fermions on anisotropic
+lattices. We focus on the finite volume effects that can be significant in
+background field studies, and thus we use two different spatial volumes in
+addition to several quark masses.",0809.1629v1
+2008-10-05,Electric Field Driven Magnetic Domain Wall Motion in Iron Garnet Film,"The dynamic observation of domain wall motion induced by electric field in
+magnetoelectric iron garnet film is reported. Measurements in 800 kV/cm
+electric field pulses gave the domain wall velocity ~45 m/s. Similar velocity
+was achieved in magnetic field pulse about 50 Oe. Reversible and irreversible
+micromagnetic structure transformation is demonstrated. These effects are
+promising for applications in spintronics and magnetic memory.",0810.0850v1
+2008-10-24,Dynamical view of pair creation in uniform electric and magnetic fields,"Pair creation in a uniform classical electromagnetic field (Schwinger
+mechanism) is studied focusing on the time evolution of the distribution of
+created particles. The time evolution of the distribution in time-dependent
+fields is also presented as well as effects of back reaction. Motivated by the
+Glasma flux tube, which may be formed at the initial stage of heavy-ion
+collisions, we investigate effects of a magnetic field parallel to an electric
+field, and find that the magnetic field makes the evolution of a fermion system
+faster.",0810.4429v2
+2008-10-28,Ferroplasmas: Magnetic Dust Dynamics in a Conducting Fluid,"We consider a dusty plasma, in which the dust particles have a magnetic
+dipole moment. A Hall-MHD type of model, generalized to account for the
+intrinsic magnetization, is derived. The model is shown to be energy
+conserving, and the energy density and flux is derived. The general dispersion
+relation is then derived, and we show that kinetic Alfv\'en waves exhibit an
+instability for a low temperature and high density plasma. We discuss the
+implication of our results.",0810.5005v2
+2008-11-06,Large-scale intermittency of liquid-metal channel flow in a magnetic field,"We predict a novel flow regime in liquid metals under the influence of a
+magnetic field. It is characterised by long periods of nearly steady,
+two-dimensional flow interrupted by violent three-dimensional bursts. Our
+prediction has been obtained from direct numerical simulations in a channel
+geometry at low magnetic Reynolds number and translates into physical
+parameters which are amenable to experimental verification under laboratory
+conditions. The new regime occurs in a wide range of parameters and may have
+implications for metallurgical applications.",0811.0912v1
+2008-11-16,Soliton dynamics for the nonlinear Schrödinger equation with magnetic field,"The semiclassical limit of a nonlinear focusing Schr\""odinger equation in
+presence of nonconstant electric and magnetic potentials V,A is studied by
+taking as initial datum the ground state solution of an associated autonomous
+elliptic equation. The concentration curve of the solutions is a
+parameterization of the solutions of a Newton ODE involving the electric force
+as well as the magnetic force via the Lorenz law of electrodynamics.",0811.2584v4
+2008-11-26,Coherent Activation of Zero-Field Fiske Modes in Arrays of Josephson Junctions,"Series arrays of Josephson junctions show evidence of a mode in which all the
+junctions oscillate in synchronism on voltage resonances appearing, in zero
+external magnetic field, at multiples of the fundamental Fiske step spacing.
+The measurements show that the current amplitude of the resonances increases
+linearly as their voltages are summed. Investigation of the nature of the
+coherent mode by magnetic field responses of arrays and isolated juctions
+reveals that the oscillations take place in a parameter plane region where dc
+magnetic fields only activate boundary current and flux-quanta dynamics can
+take place.",0811.4317v1
+2008-12-14,"Magnetic resonance in the cuprates -- exciton, plasmon, or π-mode","We re-analyzed the issue whether the resonance peak observed in neutron
+scattering experiments on the cuprates is an exciton, a \pi-resonance, or a
+magnetic plasmon. We considered a toy model with on-cite Hubbard U and
+nearest-neighbor interactions in both charge and spin channels. We found that
+the resonance is predominantly an exciton, even if magnetic interaction is
+absent and d-wave pairing originates from attractive density-density
+interaction. Our results indicate that one cannot distinguish between spin and
+charge-mediated pairing interactions by just looking at the resonance peak in
+the dynamic spin susceptibility.",0812.2697v1
+2009-02-03,Electromagnon Resonances in the Optical Response of Spiral Magnets,"The optical response of spiral magnets is studied, with special attention to
+its electromagnon features. We show that these features trace back to the
+resonant magnetoelectric response resulting from the spiral ordering
+(irrespective of any concomitant ferroelectricity). This response, being
+magnetoelectric in nature, not always can be reduced to an effective electric
+permittivity. We argue that electromagnons in spiral magnets can produce, in
+addition to the observed peaks in the optical absorption of multiferroics, a
+(dynamically enhanced) optical rotation and a negative refractive index
+behavior.",0902.0495v2
+2009-02-23,Magnetic field variations and the seismicity of solar active regions,"Dynamical changes in the solar corona have proven to be very important in
+inducing seismic waves into the photosphere. Different mechanisms for their
+generation have been proposed. In this work, we explore the magnetic field
+forces as plausible mechanisms to generate sunquakes as proposed by Hudson,
+Fisher and Welsch. We present a spatial and temporal analysis of the
+line-of-sight magnetic field variations induced by the seismically active 2003
+October 29 and 2005 January 15 solar flares and compare these results with
+other supporting observations.",0902.3856v2
+2009-03-21,Analytical results on the magnetization of the Hamiltonian Mean Field model,"The violent relaxation and the metastable states of the Hamiltonian
+Mean-Field model, a paradigmatic system of long-range interactions, is studied
+using a Hamiltonian formalism. Rigorous results are derived algebraically for
+the time evolution of selected macroscopic observables, e.g., the global
+magnetization. The high and low energy limits are investigated and the
+analytical predictions are compared with direct $N$-body simulations. The
+method we use enables us to re-interpret the out-of-equilibrium phase
+transition separating magnetized and (almost) unmagnetized regimes.",0903.3641v1
+2009-04-01,Current-induced microwave excitation of a domain wall confined in a magnetic wire with bi-axial anisotropy,"We studied the current-induced magnetization dynamics of a domain wall
+confined in a magnetic wire with bi-axial anisotropy. We showed that above the
+threshold current density, breathing-mode excitation, where the thickness of
+the domain wall oscillates, is induced by spin-transfer torque. We found that
+the breathing-mode can be applied as a source of microwave oscillation because
+the resistance of the domain wall is a function of the domain wall thickness.
+In a current sweep simulation, the frequency of the breathing-mode exhibits
+hysteresis because of the confinement.",0904.0044v1
+2009-05-27,NMR and muSR in Highly Frustrated Magnets,"We present a brief overview on some of the most significant achievements
+obtained by means of NMR and muSR techniques in highly frustrated magnets.
+First the basic quantities measured by the two techniques will be presented and
+their connection to the microscopic static and dynamical spin susceptibility
+recalled. Then the main findings will be outlined, starting from the most
+simple frustrated units, the molecular nanomagnets, to artificially built
+frustrated systems as $^{3}$He on graphite, to magnets with a macroscopically
+degenerate ground-state as the ones on a pyrochlore or kagom\'e lattices.",0905.4414v1
+2009-06-14,Magneto-optical imaging of magnetic deflagration in Mn12-Acetate,"For the first time, the morphology and dynamics of spin avalanches in
+Mn12-Acetate crystals using magneto-optical imaging has been explored. We
+observe an inhomogeneous relaxation of the magnetization, the spins reversing
+first at one edge of the crystal and a few milliseconds later at the other end.
+Our data fit well with the theory of magnetic deflagration, demonstrating that
+very slow deflagration rates can be obtained, which makes new types of
+experiments possible.",0906.2562v1
+2009-06-20,A numerical model of the VKS experiment,"We present numerical simulations of the magnetic field generated by the flow
+of liquid sodium driven by two counter-rotating impellers (VKS experiment).
+Using a dynamo kinematic code in cylindrical geometry, it is shown that
+different magnetic modes can be generated depending on the flow configuration.
+While the time averaged axisymmetric mean flow generates an equatorial dipole,
+our simulations show that an axial field of either dipolar or quadrupolar
+symmetry can be generated by taking into account non-axisymmetric components of
+the flow. Moreover, we show that by breaking a symmetry of the flow, the
+magnetic field becomes oscillatory. This leads to reversals of the axial dipole
+polarity, involving a competition with the quadrupolar component.",0906.3792v1
+2009-06-29,Performance of Magnetic Quantum Cellular Automata and Limitations due to Thermal Noise,"Operation parameters of magnetic quantum cellular automata are evaluated for
+the purposes of reliable logic operation. The dynamics of the nanomagnets is
+simulated via the Landau-Lifshitz-Gilbert equations with a stochastic magnetic
+field corresponding to thermal fluctuations. It is found that in the macrospin
+approximation the switching speed does not change under scaling of both size
+and distances between nanomagnets. Thermal fluctuations put a limitation on the
+size of nanomagnets, since the gate error rate becomes excessive for
+nanomagnets smaller than 200nm at room temperature.",0906.5172v1
+2009-07-05,Magnetic quantum tunnelling in Fe8 with excited nuclei,"We investigate the effect of dynamic nuclear spin fluctuation on quantum
+tunneling of the magnetization (QTM) in the molecular magnet Fe8 by increasing
+the nuclei temperature using radio frequency (RF) pulses before the hysteresis
+loop measurements. The RF pulses do not change the electrons spin temperature.
+Independently we show that the nuclear spin-spin relaxation time T2 has strong
+temperature dependence. Nevertheless, we found no effect of the nuclear spin
+temperature on the tunneling probability. This suggests that in our
+experimental conditions only the hyperfine field strength is relevant for QTM.
+We demonstrate theoretically how this can occur.",0907.0844v1
+2009-07-16,Long-lived spin memory in Mn-doped GaAs: Time resolved study,"We study the electron spin dynamics in p-type GaAs doped with magnetic Mn
+acceptors by means of time-resolved pump-probe and photoluminescence
+techniques. Measurements in transverse magnetic fields show a long spin
+relaxation time of 20 ns that can be uniquely related to electrons. Application
+of weak longitudinal magnetic fields above 100 mT extends the spin relaxation
+times up to microseconds which is explained by suppression of the
+Bir-Aronov-Pikus spin relaxation for the electron on the Mn acceptor.",0907.2851v1
+2009-08-20,Theory of anisotropic exchange in laterally coupled quantum dots,"The effects of spin-orbit coupling on the two-electron spectra in lateral
+coupled quantum dots are investigated analytically and numerically. It is
+demonstrated that in the absence of magnetic field the exchange interaction is
+practically unaffected by spin-orbit coupling, for any interdot coupling,
+boosting prospects for spin-based quantum computing. The anisotropic exchange
+appears at finite magnetic fields. A numerically accurate effective spin
+Hamiltonian for modeling spin-orbit-induced two-electron spin dynamics in the
+presence of magnetic field is proposed.",0908.2961v2
+2009-10-14,Multiple eruptions from magnetic flux emergence,"In this paper we study the effects of a toroidal magnetic flux tube emerging
+into a magnetized corona, with an emphasis on large-scale eruptions. The
+orientation of the fields is such that the two flux systems are almost
+antiparallel when they meet. We follow the dynamic evolution of the system by
+solving the 3D MHD equations using a Lagrangian remap scheme. Multiple
+eruptions are found to occur. The physics of the trigger mechanisms are
+discussed and related to well-known eruption models.",0910.2616v1
+2009-10-14,Note on a non-critical holographic model with a magnetic field,"We consider a noncritical holographic model constructed from an intersecting
+brane configuration D4/$\bar{\rm{D4}}$-D4 with an external magnetic field. We
+investigate the influences of this magnetic field on strongly coupled dynamics
+by the gauge/gravity correspondence.",0910.2661v5
+2009-10-23,Chiral symmetry restoration and strong CP violation in a strong magnetic background,"Motivated by the phenomenological scenario of the chiral magnetic effect that
+can be possibly found in high-energy heavy ion collisions, we study the role of
+very intense magnetic fields and strong CP violation in the phase structure of
+strong interactions and, more specifically, their influence on the nature of
+the chiral transition. Direct implications for the dynamics of phase conversion
+and its time scales are briefly discussed. Our results can also be relevant in
+the case of the early universe.",0910.4525v1
+2009-12-09,Single magnetic molecule between conducting leads: Effect of mechanical rotations,"We study spin-rotation effects in a magnetic molecule bridged between two
+conducting leads. Dynamics of the total angular momentum couples spin tunneling
+to the mechanical rotations. Landau-Zener spin transition produced by the
+time-dependent magnetic field generates a unique pattern of mechanical
+oscillations that can be detected by measuring the electronic tunneling current
+through the molecule.",0912.1882v1
+2009-12-12,Induction in a von Karman flow driven by ferromagnetic impellers,"We study magnetohydrodynamics in a von K\'arm\'an flow driven by the rotation
+of impellers made of material with varying electrical conductivity and magnetic
+permeability. Gallium is the working fluid and magnetic Reynolds numbers of
+order unity are achieved. We find that specific induction effects arise when
+the impeller's electric and magnetic characteristics differ from that of the
+fluid. Implications in regards to the VKS dynamo are discussed.",0912.2429v1
+2010-01-24,Stability problem in dynamo,"It is shown, that the saturated $\alpha$-effect taken from the nonlinear
+dynamo equations for the thin disk can still produce exponentially growing
+magnetic field in the case, when this field does not feed back on the $\alpha$.
+For negative dynamo number (stationary regime) stability is defined by the
+structure of the spectra of the linear problem for the positive dynamo numbers.
+Stability condition for the oscillatory solution (positive dynamo number) is
+also obtained and related to the phase shift of the original magnetic field,
+which produced saturated $\alpha$ and magnetic field in the kinematic regime.
+Results can be used for explanation of the similar effect observed in the shell
+models simulations as well in the 3D dynamo models in the plane layer and
+sphere.",1001.4234v1
+2010-04-23,Magnetic traveling-stripe-forcing: enhanced transport in the advent of the Rosensweig instability,"A new kind of contactless pumping mechanism is realized in a layer of
+ferrofluid via a spatio-temporally modulated magnetic field. The resulting
+pressure gradient leads to a liquid ramp, which is measured by means of X-rays.
+The transport mechanism works best if a resonance of the surface waves with the
+driving is achieved. The behavior can be understood semi-quantitatively by
+considering the magnetically influenced dispersion relation of the fluid.",1004.4151v1
+2010-05-10,Direct and inverse cascades in the geodynamo,"The rapid rotation of planets causes cyclonic thermal turbulence in their
+cores which may generate the large-scale magnetic fields observed outside the
+planets. We consider the model which enables us reproduce the typical features
+of small-scale geostrophic flows in physical and wave spaces. We present
+estimates of kinetic and magnetic energy fluxes as a function of the wave
+number. The joint existence of forward and inverse cascades are demonstrated.
+We also consider the mechanism of magnetic field saturation at the end of the
+kinematic dynamo regime.",1005.1546v1
+2010-05-31,Atomic levels in superstrong magnetic fields and D=2 QED of massive electrons: screening,"The photon polarization operator in superstrong magnetic fields induces the
+dynamical photon ""mass"" which leads to screening of Coulomb potential at small
+distances $z\ll 1/m$, $m$ is the mass of an electron. We demonstrate that this
+behaviour is qualitatively different from the case of D=2 QED, where the same
+formula for a polarization operator leads to screening at large distances as
+well. Because of screening the ground state energy of the hydrogen atom at the
+magnetic fields $B \gg m^2/e^3$ has the finite value $E_0 = -me^4/2
+\ln^2(1/e^6)$.",1005.5695v1
+2010-06-29,Supertransient magnetohydrodynamic turbulence in Keplerian shear flows,"A subcritical transition to turbulence in magnetized Keplerian shear flows is
+investigated using a statistical approach. Three-dimensional numerical
+simulations of the shearing box equations with zero net magnetic flux are
+employed to determine the transition from decaying to sustained turbulence as a
+function of the magnetic Reynolds number Rm. The results reveal no clear
+transition to sustained turbulence as the average lifetime of the transients
+grows as an exponential function of Rm, in accordance with a type-II
+supertransient law.",1006.5669v1
+2010-07-22,Neutron magnetic form factor in strongly correlated materials,"We introduce a formalism to compute the neutron magnetic form factor Fm(q)
+within a first-principles Density Functional Theory (DFT) + Dynamical Mean
+Field Theory (DMFT). The approach treats spin and orbital interactions on the
+same footing and reduces to earlier methods in the fully localized or the fully
+itinerant limit. We test the method on various actinides of current interest
+NpCoGa5, PuSb and PuCoGa5; we show that PuCoGa5 is in mixed valent state, which
+naturally explains the measured magnetic form factor.",1007.3997v2
+2010-08-02,Chern number spins of Mn acceptor magnets in GaAs,"We determine the effective total spin $J$ of local moments formed from
+acceptor states bound to Mn ions in GaAs by evaluating their magnetic Chern
+numbers. We find that when individual Mn atoms are close to the sample surface,
+the total spin changes from $J = 1$ to $J = 2$, due to quenching of the
+acceptor orbital moment. For Mn pairs in bulk, the total $J$ depends on the
+pair orientation in the GaAs lattice and on the separation between the Mn
+atoms. We point out that Berry curvature variation as a function of local
+moment orientation can profoundly influence the quantum spin dynamics of these
+magnetic entities.",1008.0275v1
+2010-08-17,Anisotropic magnetic fluctuations in the ferromagnetic superconductor UCoGe studied by angle-resolved ^{59}Co NMR,"We have carried out direction-dependent ^{59}Co NMR experiments on a single
+crystal sample of the ferromagnetic superconductor UCoGe in order to study the
+magnetic properties in the normal state. The Knight shift and nuclear
+spin-lattice relaxation rate measurements provide microscopic evidence that
+both static and dynamic susceptibilities are ferromagnetic with strong Ising
+anisotropy. We discuss that superconductivity induced by these magnetic
+fluctuations prefers spin-triplet pairing state.",1008.2837v1
+2010-09-24,Parametric excitation of a magnetic nanocontact by a microwave field,"We demonstrate that magnetic oscillations of a current-biased magnetic
+nanocontact can be parametrically excited by a microwave field applied at twice
+the resonant frequency of the oscillation. The threshold microwave amplitude
+for the onset of the oscillation decreases with increasing bias current, and
+vanishes at the transition to the auto-oscillation regime. The parametrically
+excited oscillation mode is the same as the one in the auto-oscillation regime,
+enabling studies of both the passive and the active dynamics of the oscillator.
+Theoretical analysis shows that measurements of parametric excitation provide
+quantitative information about the relaxation rate, the spin transfer
+efficiency, and the nonlinearity of the nanomagnetic system.",1009.4837v1
+2010-11-01,Optical control of magnetization of micron-size domains in antiferromagnetic NiO single crystals,"We propose Raman-induced collinear difference-frequency generation (DFG) as a
+method to manipulate dynamical magnetization. When a fundamental beam
+propagates along a threefold rotational axis, this coherent second-order
+optical process is permitted by angular momentum conservation through the
+rotational analogue of the Umklapp process. As a demonstration, we
+experimentally obtained polarization properties of collinear magnetic DFG along
+a [111] axis of a single crystal of antiferromagnetic NiO with micro
+multidomain structure, which excellently agreed with the theoretical
+prediction.",1011.0327v1
+2010-11-10,Macrospin Tunneling and Magnetopolaritons with Nanomechanical Interference,"We theoretically address the quantum dynamics of a nanomechanical resonator
+coupled to the macrospin of a magnetic nanoparticle by both instanton and
+perturbative approaches. We demonstrate suppression of the tunneling between
+opposite magnetizations by nanomechanical interference. By approximating the
+macrospin as a two-level system, we describe magnetopolaritons and their
+destruction by interference. The predictions can be verified experimentally by
+a molecular magnet attached to a nanomechanical bridge.",1011.2242v2
+2010-11-17,Generalized Split-Octonion Electrodynamics,"Starting with the usual definitions of octonions and split octonions in terms
+of Zorn vector matrix realization, we have made an attempt to write the
+consistent form of generalized Maxwell's equations in presence of electric and
+magnetic charges (dyons). We have thus written the generalized potential,
+generalized field, and generalized current of dyons in terms of split octonions
+and accordingly the split octonion forms of generalized Dirac Maxwell's
+equations are obtained in compact and consistent manner. This theory reproduces
+the dynamic of electric (magnetic) in the absence of magnetic (electric)
+charges.",1011.3922v1
+2011-01-05,Effects of La non-magnetic impurities on the spin resonance of CeCoIn$_{5}$,"The influence of La non magnetic impurities on the spin dynamics of
+CeCoIn$_{5}$ was studied by inelastic neutron scattering. In La-substituted
+systems, the spin resonance peak (observed at $\Omega_{res}=0.55 meV$ in the
+pure system) is shifted to lower energies but the ratio
+$\Omega_{res}/k_{B}T_{c}$ remains unchanged. The excitation broadens till it
+reaches 0.3 meV equal to the value of the quasi-elastic signal in the normal
+state. The evolution of La substitution is compared with the evolution of the
+magnetic resonance in Ni and Zn substituted YBa$_{2}$Cu$_{3}$O$_{7}$.",1101.1018v1
+2011-01-17,Alleviation of catastrophic quenching in solar dynamo model with nonlocal alpha-effect,"The nonlocal alpha-effect of Babcock-Leighton type is not prone to the
+catastrophic quenching due to conservation of magnetic helicity. This is shown
+with a dynamo model, which jointly applies the nonlocal alpha-effect, the
+diamagnetic pumping, and dynamical equation for the magnetic alpha-effect. The
+same model shows catastrophic quenching when the alpha-effect is changed to its
+local formulation. The nonlocal model shows the preferred excitation of
+magnetic fields of dipolar symmetry, which oscillate with a period of about ten
+years and have a toroidal-to-polar fields ratio of about a thousand.",1101.3115v1
+2011-01-21,Global fluctuations in magnetohydrodynamic dynamos,"The spectrum of temporal fluctuations of total magnetic energy for several
+dynamo models is different from white noise at frequencies smaller than the
+inverse of the turnover time of the underlying turbulent velocity field.
+Examples for this phenomenon are known from previous work and we add in this
+paper simulations of the G.O. Roberts dynamo and of convectively driven dynamos
+in rotating spherical shells. The appearance of colored noise in the magnetic
+energy is explained by simple phenomenological models. The Kolmogorov theory of
+turbulence is used to predict the spectrum of kinetic and magnetic energy
+fluctuations in the inertial range.",1101.4141v1
+2011-01-25,Onset and saturation of ion heating by odd-parity rotating-magnetic-fields in a field-reversed configuration,"Heating of figure-8 ions by odd-parity rotating magnetic fields ($RMF_o$)
+applied to an elongated field-reversed configuration (FRC) is investigated. The
+largest energy gain occurs at resonances ($s \equiv \omega_R/ \omega$) of the
+$RMF_o$ frequency, $\omega_R$, with the figure-8 orbital frequency, $\omega$,
+and is proportional to $s^2$ for $s-even$ resonances and to $s$ for $s-odd$
+resonances. The threshold for the transition from regular to stochastic orbits
+explains both the onset and saturation of heating. The FRC magnetic geometry
+lowers the threshold for heating below that in the tokamak by an order of
+magnitude.",1101.4774v1
+2011-03-24,Effect of nonadiabatic spin transfer torque on domain wall resonance frequency and mass,"The dynamics of a magnetic domain wall in a semi circular nanowire loop is
+studied by an analytical model and micromagnetic simulations. We find a damped
+sinusoidal oscillation of the domain wall for small displacement angles around
+its equilibrium position under an external magnetic field in the absence of
+currents. By studying the effect of current induced nonadiabatic spin transfer
+torque on the magnetic domain wall resonance frequency and mass, a red shift is
+found in the resonance frequency and domain wall mass increases by increasing
+the ratio of nonadiabatic spin torque to adiabatic contribution above 1.",1103.4670v1
+2011-04-22,Stochastic Resonance in a simple model of magnetic reversals,"We discuss the effect of stochastic resonance in a simple model of magnetic
+reversals. The model exhibits statistically stationary solutions and bimodal
+distribution of the large scale magnetic field. We observe a non trivial
+amplification of stochastic resonance induced by turbulent fluctuations, i.e.
+the amplitude of the external periodic perturbation needed for stochastic
+resonance to occur is much smaller than the one estimated by the equilibrium
+probability distribution of the unperturbed system. We argue that similar
+amplifications can be observed in many physical systems where turbulent
+fluctuations are needed to maintain large scale equilibria.",1104.4417v1
+2011-06-03,Spectral scaling laws in MHD turbulence simulations and in the solar wind,"The question is addressed to what extent incompressible magnetohydrodynamics
+(MHD) can describe random magnetic and velocity fluctuations measured in the
+solar wind. It is demonstrated that distributions of spectral indices for the
+velocity, magnetic field, and total energy obtained from high resolution
+numerical simulations are qualitatively and quantitatively similar to solar
+wind observations at 1 AU. Both simulations and observations show that in the
+inertial range the magnetic field spectrum E_b is steeper than the velocity
+spectrum E_v with E_b >~ E_v and that the residual energy E_R = E_b-E_v
+decreases nearly following a k_perp^-2 scaling.",1106.0700v1
+2011-06-20,A note on the magnetic spatial forcing of a ferrofluid layer,"We report on the response of a thin layer of ferrofluid to a spatially
+modulated magnetic field. This field is generated by means of a constant
+current in a special arrangement of aluminum wires. The full surface profile of
+the liquid layer is recorded by means of the absorption of X-rays. The outcome
+is analyzed particularly with regard to the magnetic self focusing effect under
+a deformable fluid layer.",1106.3857v1
+2011-06-22,Electric spectroscopy of vortex states and dynamics in magnetic disks,"Spin-polarized radio frequency (RF) currents and RF-Oersted fields resonantly
+excite a magnetic vortex core confined in a micron-scale soft magnetic disk. In
+this study, we measured the rectifying voltage spectra caused by the
+anisotropic magnetoresistance oscillation due to the gyration of the vortex
+with different polarity and chirality. The measured spectra are presented such
+that we can determine the vortex properties and strength of the spin torques
+and Oersted field accurately and directly through analytical calculation.",1106.4516v2
+2011-06-23,Landau quantization effects in ultracold atom-ion collisions,"We study ultracold atom-ion collisions in the presence of an external
+magnetic field. At low collision energy the field can drastically modify the
+translational motion of the ion, which follows quantized cyclotron orbits. We
+present a rigorous theoretical approach for the calculation of quantum
+scattering amplitudes in these conditions. Collisions in different magnetic
+field regimes, identified by the size of the cyclotron radius with respect to
+the range of the interaction potential, are investigated. Our results are
+important in cases where use of a magnetic field to control the atom-ion
+collision dynamics is envisioned.",1106.4672v1
+2011-09-20,Hysteresis for ferromagnetism: asymptotics of some 2-scale Landau-Lifshitz model,"We study a 2-scale version of the Landau-Lifshitz system of ferromagnetism,
+introduced by Starynkevitch to modelize hysteresis: the response of the
+magnetization is fast compared to a slowly varying applied magnetic fi eld.
+Taking the exchange term into account, in space dimension 3, we prove that,
+under some natural stability assumption on the equilibria of the system, the
+strong solutions follow the dynamics of these equilibria. We also give explicit
+examples of relevant equilibria and exterior magnetic fields, when the
+ferromagnetic medium occupies some ellipsoidal domain.",1109.4352v1
+2011-09-22,Bistability and chaos in Taylor-Green dynamo,"Using direct numerical simulations we study dynamo action under the
+Taylor-Green forcing with Prandtl number less than one. We observe bistability
+with a weak magnetic field branch and a strong magnetic field branch. Both the
+dynamo branches undergo subcritical dynamo transition. We also observe host of
+dynamo states including constant, periodic, quasiperiodic, and chaotic magnetic
+fields. One of the chaotic state originates through a quasiperiodic route with
+phase locking, while another chaotic attractor appears to follow
+Newhouse-Ruelle-Takens route to chaos. We also observe intermittent transitions
+among quasiperiodic and chaotic states for a given Taylor-Green forcing.",1109.4894v1
+2011-09-27,Ferroelectric charge order stabilized by antiferromagnetism in multiferroic LuFe2O4,"Neutron diffraction measurements on multiferroic LuFe2O4 show changes in the
+antiferromagnetic (AFM) structure characterized by wavevector q = (1/3 1/3 1/2)
+as a function of electric field cooling procedures. The increase of intensity
+from all magnetic domains and the decrease in the 2D magnetic order observed
+below the Neel temperature are indicative of increased ferroelectric charge
+order. The AFM order changes the dynamics of the CO state, and stabilizes it.
+It is determined that the increase in electric polarization observed at the
+magnetic ordering temperature is due to a transition from paramagnetic 2D
+charge order to AFM 3D charge order.",1109.5762v1
+2011-09-29,Lattice Planar QED in external magnetic field,"We investigate planar Quantum ElectroDynamics (QED) with two degenerate
+staggered fermions in an external magnetic field on the lattice. Our
+preliminary results indicate that in external magnetic fields there is
+dynamical generation of mass for two-dimensional massless Dirac fermions in the
+weak coupling region. We comment on possible implications to the quantum Hall
+effect in graphene.",1109.6549v1
+2011-10-13,Vertically Self-Gravitating ADAFs in the Presence of Toroidal Magnetic Field,"Force due to the self-gravity of the disc in the vertical direction is
+considered to study its possible effects on the structure of a magnetized
+advection-dominated accretion disc. We present steady-sate self similar
+solutions for the dynamical structure of such a type of the accretion flows.
+Our solutions imply reduced thickness of the disc because of the self-gravity.
+It also imply that the thickness of the disc will increase by adding the
+magnetic field strength.",1110.2941v1
+2011-12-06,Three-magnetic fields,"A completely new mechanism to generate the observed amount of large-scale
+cosmological magnetic fields is introduced in the context of three-form
+inflation. The amplification of the fields occurs via fourth order dynamics of
+the vector perturbations and avoids the backreaction problem that plagues most
+previously introduced mechanisms.",1112.1356v2
+2011-12-28,Spectral signatures of magnetic Bloch oscillations in one-dimensional easy-axis ferromagnets,"Domain walls in a one-dimensional gapped easy-axis ferromagnet can exhibit
+Bloch oscillations in an applied magnetic field. We investigate how exchange
+couplings modify this behavior within an approximation based on noninteracting
+domain-wall bound states. In particular, we obtain analytical results for the
+spectrum and the dynamic structure factor, and show where in momentum space to
+expect equidistant energy levels, the Wannier-Zeeman ladder, which is the
+spectral signature of magnetic Bloch oscillations. We compare our results to
+previous calculations employing a single domain-wall approximation, and make
+predictions relevant for the material $CoCl2\cdot2H2O$.",1112.6195v2
+2012-01-17,Spin wave excitation in magnetic insulators by spin-transfer torque,"We study the excitation of spin waves in magnetic insulators by the
+current-induced spin-transfer torque. We predict preferential excitation of
+surface spin waves induced by an easy-axis surface anisotropy with critical
+current inversely proportional to the penetration depth and surface anisotropy.
+The surface modes strongly reduce the critical current and enhance the
+excitation power of the current-induced magnetization dynamics.",1201.3442v1
+2012-02-06,Mean-field quantum dynamics with magnetic fields,"We consider a system of $N$ bosons in three dimensions interacting through a
+mean-field Coulomb potential in an external magnetic field. For initially
+factorized states we show that the one-particle density matrix associated with
+the solution of the $N$-body Schr\""odinger equation converges to the projection
+onto the solution of the magnetic Hartree equation in trace norm and in energy
+as $N \rightarrow \infty$. Estimates on the rate of convergence are provided.",1202.1065v2
+2012-03-07,3D Simulations of Magnetic Massive Star Winds,"Due to computational requirements and numerical difficulties associated with
+coordinate singularity in spherical geometry, fully dynamic 3D
+magnetohydrodynamic (MHD) simulations of massive star winds are not readily
+available. Here we report preliminary results of the first such a 3D simulation
+using $\theta^1$ Ori C (O5.5 V) as a model. The oblique magnetic rotator
+$\theta^1$ Ori C is a source of hard X-ray emitting plasma in its circumstellar
+environment. Our numerical model can explain both the hardness and the location
+of the X-ray emission from this star confirming that magnetically confined wind
+shock (MCWS) is the dominating mechanism for hard Xrays in some massive stars.",1203.1523v1
+2012-03-29,The role of large-scale magnetic field in the morphology and evolution of extragalactic radio sources,"We discuss a model of formation of extragalactic radio sources when the
+parent optical galaxy has a large-scale dipolar magnetic field. The study of
+dynamics of ejected from the central part of optical galaxy clouds of
+relativistic particles in dipolar magnetic field gives a possibility to explain
+main morphological features and physical properties of formed extragalactic
+radio sources. We bring some results of statistical analyses and correlations
+between physical parameters for more than 500 radio sources. In appendix we
+present the data of all used extragalactic radio sources with the references
+for them.",1203.6549v1
+2012-04-24,"Magnetostatic Spin Waves and Magnetic-Wave Chaos in Ferromagnetic Films. III. Numeric Simulations of Microwave-Band Magnetic Chaos, Its Synchronization and Application to Secure Communication","Selected results of original numeric simulations of non-linear magnetostatic
+spin waves and microwave-frequency magnetic chaos in ferrite films are
+expounded, as third part of the work whose first two parts are recent arXive
+preprints 1204.0200 and 1204.2423 . Especially we consider crucial role of
+parametric processes in creating the chaos and simultaneously obstacles to its
+synchronization, and examine some possibilities of good enough synchronization
+(to an extent allowing its use for direct secure communication in microwave
+band).",1204.5410v1
+2012-04-27,Chiral Symmetry Breaking in Planar QED in External Magnetic Fields,"We investigate planar quantum electrodynamics (QED) with two degenerate
+staggered fermions in an external magnetic field on the lattice. We argue that
+in external magnetic fields there is dynamical generation of mass for
+two-dimensional massless Dirac fermions in the weak-coupling region. We
+extrapolate our lattice results to the quantum Hall effect in graphene.",1204.6112v1
+2012-05-16,The magnetic fields and magnetospheres of hot stars,"Strong advances in direct evidence of magnetic fields in hot massive stars
+have been possible thanks to the new generation of high-resolution
+spectropolarimeters such as ESPaDOnS (on the Canada-France-Hawaii Telescope) or
+HARPSpol (on the 3.6m ESO telescope). UV and optical high-resolution
+spectroscopy has also been very useful to study the magnetospheres of massive
+stars. In this contribution I review the observing tools and our current
+knowledge concerning the detection and characterisation of the magnetic fields
+and magnetospheres in hot stars.",1205.3603v1
+2012-06-20,Magnetoelectric nature of skyrmions in a chiral magnetic insulator Cu2OSeO3,"Dielectric properties were investigated under various magnitudes and
+directions of magnetic field (H) for a chiral magnetic insulator Cu2OSeO3. We
+found that the skyrmion crystal induces electric polarization (P) along either
+in-plane or out-of-plane direction of the spin vortices depending on the
+applied H-direction. The observed H-dependence of P in ferrimagnetic,
+helimagnetic, and skyrmion crystal state can be consistently described by the
+d-p hybridization model, highlighting an important role of relativistic
+spin-orbit interaction in the magnetoelectric coupling in Cu2OSeO3. Our
+analysis suggests that each skyrmion particle can locally carry electric dipole
+or quadrupole, which implies that the dynamics of skyrmions are controllable by
+the external electric field.",1206.4404v1
+2012-06-26,Entanglement and Sources of Magnetic Anisotropy in Radical Pair-Based Avian Magnetoreceptors,"One of the principal models of magnetic sensing in migratory birds rests on
+the quantum spin-dynamics of transient radical pairs created photochemically in
+ocular cryptochrome proteins. We consider here the role of electron spin
+entanglement and coherence in determining the sensitivity of a radical
+pair-based geomagnetic compass and the origins of the directional response. It
+emerges that the anisotropy of radical pairs formed from spin-polarized
+molecular triplets could form the basis of a more sensitive compass sensor than
+one founded on the conventional hyperfine-anisotropy model. This property
+offers new and more flexible opportunities for the design of biologically
+inspired magnetic compass sensors.",1206.5946v1
+2012-07-18,"Comment on ""Geometric phase of the gyromotion for charged particles in a time-dependent magnetic field"" [Phys. Plasmas 18, 072505 (2011)]","The geometric analysis of the gyromotion for charged particles in a
+time-dependent magnetic field by J. Liu and H. Qin [Phys. Plasmas 18, 072505
+(2011)] is reformulated in terms of the spatial angles that represent the
+instantaneous orientation of the magnetic field. This new formulation, which
+includes the equation of motion for the pitch angle, clarifies the
+decomposition of the gyroangle-averaged equation of motion for the gyrophase
+into its dynamic and geometric contributions.",1207.4356v1
+2012-08-02,"Magnetic moments of the low-lying $J^P=\,1/2^-$, $3/2^-$ $Λ$ resonances within the framework of the chiral quark model","The magnetic moments of the low-lying spin-parity $J^P=$ $1/2^-$, $3/2^-$
+$\Lambda$ resonances, like, for example, $\Lambda(1405)$ $1/2^-$,
+$\Lambda(1520)$ $3/2^-$, as well as their transition magnetic moments, are
+calculated using the chiral quark model. The results found are compared with
+those obtained from the nonrelativistic quark model and those of unitary chiral
+theories, where some of these states are generated through the dynamics of two
+hadron coupled channels and their unitarization.",1208.0477v1
+2012-09-03,Pressure induced ferromagnetism in antiferromagnetic Fe_1.03Te,"The magnetic properties of Fe1.03Te under hydrostatic pressure up to p ~ 5.7
+GPa were investigated by means of muon spin rotation, dc magnetization, and
+neutron depolarization measurements. With increasing pressure the
+antiferromagnetic ordering temperature TN decreases continuously from 70 K at
+ambient pressure towards higher pressures. Surprisingly, the commensurate
+antiferromagnetic order of FeTe enters a region of incommensurate and dynamical
+magnetic order before at p ~ 1.7 GPa the system turns ferromagnetic. The
+ferromagnetic ordering temperature TC increases with increasing pressure.",1209.0383v1
+2012-09-17,Electrical excitation and detection of magnetic dynamics with impedance matching,"Motivated by the prospects of increased measurement bandwidth, improved
+signal to noise ratio and access to the full complex magnetic susceptibility we
+develop a technique to extract microwave voltages from our high resistance (10
+k{\Omega}) (Ga,Mn)As microbars. We drive magnetization precession with
+microwave frequency current, using a mechanism that relies on the spin orbit
+interaction. A capacitively coupled lambda/2 microstrip resonator is employed
+as an impedance matching network, enabling us to measure the microwave voltage
+generated during magnetisation precession.",1209.3643v2
+2012-10-04,All Spin Nano-magnetic State Elements,"We propose an all spin state element to enable all spin state machines using
+spin currents and nanomagnets. We demonstrate via numerical simulations the
+operation of a state element a critical building block for synchronous,
+sequential logic computation. The numerical models encompass
+Landau-Lifshitz-Gilbert (LLG) nanomagnet dynamics with stochastic models and
+vector spin-transport in metallic magnetic and non-magnetic channels. Combined
+with all spin combinatorial logic, the state elements can enable synchronous
+and asynchronous computing elements.",1210.1613v1
+2012-11-18,Controlling the Spin Torque Efficiency with Ferroelectric Barriers,"Non-equilibrium spin-dependent transport in magnetic tunnel junctions
+comprising a ferroelectric barrier is theoretically investigated. The exact
+solutions of the free electron Schr\""odinger equation for electron tunneling in
+the presence of interfacial screening are obtained by combining Bessel and Airy
+functions. We demonstrate that the spin transfer torque efficiency, and more
+generally the bias-dependence of tunneling magneto- and electroresistance, can
+be controlled by switching the ferroelectric polarization of the barrier. This
+effect provides a supplementary way to electrically control the current-driven
+dynamic states of the magnetization and related magnetic noise in spin transfer
+devices.",1211.4196v1
+2012-11-29,Pumping $ac$ Josephson current in the Single Molecular Magnets by spin nutation,"We demonstrate that an {\it ac} Josephson current is pumped through the
+Single Molecular Magnets (SMM) by the spin nutation. The spin nutation is
+generated by applying a time dependent magnetic field to the SMM. We obtain the
+flowing charge current through the junction by working in the tunneling limit
+and employing Green's function technique. At the resonance conditions some
+discontinuities and divergencies are appeared in the normal and Josephson
+currents, respectively. Such discontinuities and divergencies reveal themselves
+when the absorbed/emitted energy, owing to the interaction of the
+quasiparticles with the spin dynamics are in the range of the superconducting
+gap.",1211.6879v1
+2012-12-19,Nanomagnetic Logic and Magnetization Switching Dynamics in Spin Torque Majority Gates,"Spin torque majority gates are modeled and several regimes of magnetization
+switching (some leading to failure) are discovered. The switching speed and
+noise margins are determined for STMGs and an adder based on it. With switching
+time of 3ns at current of 80uA, the adder computational throughput is
+comparable to that of a CMOS adder.",1212.4547v1
+2013-01-08,Magnetic chirality as probed by neutron scattering,"We review the concept of chirality, at first briefly in a general context
+then in the specific framework of the spin networks. We next discuss to what
+extent neutron scattering appears as an unconvertible tool to probe magnetic
+chirality in the static and dynamical regimes of the spins. The remarkable
+chiral ground state and excitations of the Fe-langasite compound finally serves
+to illustrate the use of neutron polarimetry in the experimental studies of the
+magnetic chirality.",1301.1616v1
+2013-01-10,Application of Harmonic Maps $CP^{(N-1)}$ on SU(N) Bogomolny Equation for BPS Magnetic Monopoles,"In this thesis we study dynamic of magnetic monopoles from Lagrangian density
+in Yang-Mills-Higgs field theory. In particular, we discuss BPS (Bogomolny
+Prasad Sommerfield) magnetic monopoles, described by SU(N) Bogomolny equations,
+which has field equations in form of non-linear coupled matrix field equations.
+One of the methods to simplify SU(N) Bogomolny equations is by using harmonic
+maps $CP^{(N-1)}$. This method has relation with $Gr(n,N)} \sigma$-model and
+can transform SU(N) Bogomolny equation into more simple scalar field equations
+that depends only on one variable. As an example, we consider the case of SU(2)
+Bogomolny equation.",1301.2017v1
+2013-03-21,Magneto-optics of monolayer and bilayer graphene,"The optical conductivity of graphene and bilayer graphene in quantizing
+magnetic fields is studied. Both dynamical conductivities, longitudinal and
+Hall's, are analytically evaluated. The conductivity peaks are explained in
+terms of electron transitions. Correspondences between the transition
+frequencies and the magneto-optical features are established using the
+theoretical results. The main optical transitions obey the selection rule with
+$\Delta n=1$ for the Landau number $n$. The Faraday rotation and light
+transmission in the quantizing magnetic fields are calculated. The effects of
+temperatures and magnetic fields on the chemical potential are considered.
+\pacs{71.20.Nr, 78.20.Ci, 78.20.Bh}",1303.5214v1
+2013-04-23,Intermittency in spherical Couette dynamos,"We investigate dynamo action in three-dimensional numerical simulations of
+turbulent spherical Couette flows. Close to the onset of dynamo action, the
+magnetic field exhibits an intermittent behavior, characterized by a series of
+short bursts of the magnetic energy separated by low-energy phases. We show
+that this behavior corresponds to the so-called on-off intermittency. This
+behavior is here reported for dynamo action with realistic boundary conditions.
+We investigate the role of magnetic boundary conditions in this phenomenon.",1304.6212v1
+2013-06-06,The origins of $k^{-2}$ spectrum in the decaying Taylor-Green magnetohydrodynamic turbulent flows,"We investigate the origins of $k^{-2}$ spectrum in a decaying Taylor-Green
+magnetohydrodynamic flow with zero large scale magnetic flux that was reported
+in Lee et al. (2010). A possible candidate for this scaling exponent has been
+the weak turbulence phenomenology. From our numerical simulations, we observe
+that current sheets in the magnetic Taylor-Green flow are formed in regions of
+magnetic discontinuities. Based on this observation and by studying the
+influence of the current sheets on the energy spectrum, using a filtering
+technique, we argue that the discontinuities are responsible for the $-2$ power
+law scaling of the energy spectra of this flow.",1306.1380v1
+2013-07-11,Ultra-Low-Intensity Magneto-Optical and Mechanical Effects in Metal Nanocolloids,"We theoretically and numerically investigate the linear and nonlinear
+magneto-optical contributions to the refractive index of metal nanospheres. The
+analysis is in good agreement with the experimental extinction spectra of gold
+nanocolloid solutions, with threshold magnetic fields less than 1 mT when
+illuminated with light intensities less than 1 W/cm^2. Plasmonic current loops
+and vortex power flows provide a new framework for the dynamical interaction
+between material magnetization, light polarization and nano-surfaces. The
+photo-induced magneto-optical interaction of non-magnetic metal nanocolloids
+imparts significant, non-negligible torque forces in nanofluids.",1307.3188v1
+2013-07-22,Analytical expression for the harmonic Hall voltages in evaluating spin orbit torques,"Solid understanding of current induced torques is key to the development of
+current and voltage controlled magnetization dynamics in ultrathin magnetic
+heterostructures. A versatile technique is needed to evaluate such torques in
+various systems. Here we examine the adiabatic (low frequency) harmonic Hall
+voltage measurement that has been recently developed to study current induced
+effective field that originate from the spin orbit effects. We analytically
+derive a form that can be used to evaluate the harmonic Hall voltages and
+extract relevant parameters in two representative systems, i.e. out of plane
+and in-plane magnetized systems. Contributions from the anomalous Hall and
+planar Hall effects are considered.",1307.5603v1
+2013-08-21,Thermal transport due to quantum interference in magnetic tunnel junctions,"We study the thermal transport in magnetic tunnel junctions. Thermal
+gradients across the tunneling barrier appear around the Fowler-Nordheim
+tunneling regime, due to the current-induced heat caused by quantum
+interference. Both thermovoltage and thermal temperature follow a linear
+response with the applied current, which is an evidence for a thermoelectric
+effect. By increasing the barrier transparency, the dynamics of thermoelectric
+properties is observed with the current. Accordingly, a large range of the
+Seebeck coefficient, 10 - 1000 {\mu}V/K, has been obtained in magnetic tunnel
+junctions.",1308.4483v1
+2013-09-16,Fundamental solutions of MHD Stokes flow,"A simple analytical solution is obtained for the MHD stokeslet in a
+homogeneous magnetic field. This solution represents the flow past a small
+particle and can also be interpreted as the flow sufficiently far away from a
+body of finite size. Fundamental solutions are found in terms of velocity,
+pressure and scalar potential distributions for the flows due to either a
+concentrated force or a current source. The former consists of two basic
+solutions for the force parallel and transverse to the magnetic field,
+respectively. All fundamental solutions have the characteristic length scale of
+the Hartmann boundary layer and two parabolic wakes developing along the
+magnetic field.",1309.3886v1
+2013-09-19,Neutrino oscillations in the presence of the crust magnetization,"It is noted that the crustal magnetic spectrum exhibits the signal from the
+partly correlated domain dipoles on the space-scale up to approximately 500 km.
+This suggests the nonzero correlation among the dynamical variables of the
+ferromagnetic magnetization phenomenon on the small domain scale inside the
+earth's crust also. Therefore the influence of the mean of the zero component
+of the polarization on the CP matter-induced violation indexes is discussed.",1309.5115v1
+2013-09-25,Magnetoplasmons in rotating dusty plasmas,"A rotating dusty plasma apparatus was constructed to provide the possibility
+of experimental emulation of extremely high magnetic fields by means of the
+Coriolis force, observable in a co-rotating measurement frame. We present
+collective excitation spectra for different rotation rates with a magnetic
+induction equivalent of up to 3200 Tesla. We identify the onset of
+magnetoplasmon-equivalent mode dispersion in the rotating macroscopic
+two-dimensional single-layer dusty plasma. The experimental results are
+supported by molecular dynamics simulations of 2D magnetized Yukawa systems.",1309.6416v1
+2013-10-08,Single-file and normal diffusion of magnetic colloids in modulated channels,"Diffusive properties of interacting magnetic dipoles confined in a parabolic
+narrow channel and in the presence of a periodic modulated (corrugated)
+potential along the unconfined direction are studied using Brownian dynamics
+simulations. We compare our simulation results with the analytical result for
+the effective diffusion coefficient of a single-particle by Festa and d'Agliano
+[Physica A \textbf{90}, 229 (1978)] and show the importance of inter-particle
+interaction on the diffusion process. We present results for the diffusion of
+magnetic dipoles as a function of linear density, strength of the periodic
+modulation and commensurability factor.",1310.2153v1
+2013-10-09,Constants of motion for the magnetic force: the angular momentum and the Laplace-Runge-Lenz vector,"It is well-known that an electric charge under a uniform magnetic field has a
+bidimensional motion if its initial position and velocity are perpendicular to
+this magnetic field. Although some constants of motion, as the energy and
+angular momentum, have been identified for this system, its features hide
+others. In this work, we build generalizations of the angular momentum and the
+Laplace-Runge-Lenz vector and show that these vectors are constants of motion.
+Moreover, from them, we find four dynamically independent conserved qualities.",1310.2591v3
+2013-10-10,Phenomenology of current-skyrmion interactions in thin films with perpendicular magnetic anisotropy,"We study skyrmions in magnetic thin films with structural inversion asymmetry
+perpendicular to the film plane. We determine the magnetization texture of a
+single skyrmion and its dependence on the strength of the Dzyaloshinskii-Moriya
+interaction relative to the magnetostatic energy. Furthermore, we construct a
+phenomenological model that describes the interaction between the motion of
+skyrmions and electric currents to lowest order in spin-orbit coupling. We
+estimate the experimental verifiable velocities for current-driven motion of
+skyrmion textures based on available results obtained from domain walls
+dynamics.",1310.2850v2
+2013-11-12,Photonic de Haas-van Alphen effect,"Based on the recently proposed concept of effective gauge potential and
+magnetic field for photons, we numerically demonstrate a photonic de Haas-van
+Alphen effect. We show that in a dynamically modulated photonic resonator
+lattice exhibiting an effect magnetic field, the trajectories of the light beam
+at a given frequency have the same shape as the constant energy contour for the
+photonic band structure of the lattice in the absence of the effective magnetic
+field.",1311.2860v1
+2013-11-18,On the range of the attenuated magnetic ray transform for connections and Higgs fields,"For a two-dimensional simple magnetic system, we study the attenuated
+magnetic ray transform $I_{A,\Phi}$, with attenuation given by a unitary
+connection $A$ and a skew-Hermitian Higgs field $\Phi$. We give a description
+for the range of $I_{A,\Phi}$ acting on $\mathbb C^n$-valued tensor fields.",1311.4582v2
+2013-12-18,Interplay between chromoelectric and chromomagnetic gluons in Yang-Mills thermodynamics,"We propose an effective theory of SU(3) gluonic matter where interactions
+between color-electric and color-magnetic gluons are constrained by the center
+and scale symmetries. Through matching to the dimensionally-reduced magnetic
+theories, the magnetic gluon condensate qualitatively changes its thermal
+behavior above the critical temperature. We argue its phenomenological
+consequences for the thermodynamics, in particular the dynamical breaking of
+scale invariance.",1312.5245v1
+2013-12-23,Acoustic parametric pumping of spin waves,"Recent experiments demonstrated generation of spin currents by ultrasound. We
+can understand this acoustically induced spin pumping in terms of the coupling
+between magnetization and lattice waves. Here we study the parametric
+excitation of magnetization by longitudinal acoustic waves and calculate the
+acoustic threshold power. The induced magnetization dynamics can be detected by
+the spin pumping into an adjacent normal metal that displays the inverse spin
+Hall effect.",1312.6499v1
+2014-02-14,Thermodynamically self-consistent non-stochastic micromagnetic model for the ferromagnetic state,"In this work, a self-consistent thermodynamic approach to micromagnetism is
+presented. The magnetic degrees of freedom are modeled using the
+Landau-Lifshitz-Baryakhtar theory, that separates the different contributions
+to the magnetic damping, and thereby allows them to be coupled to the electron
+and phonon systems in a self-consistent way. We show that this model can
+quantitatively reproduce ultrafast magnetization dynamics in Nickel.",1402.3487v3
+2014-02-17,Photon Polarization Precession Spectroscopy for High-Resolution Studies of Spinwaves,"A new type of spectroscopy for high-resolution studies of spin waves that
+relies on resonant scattering of hard x-rays is introduced. The energy transfer
+in the scattering process is encoded in the precession of the polarization
+vector of the scattered photons. Thus, the energy resolution of such a
+spectroscopy is independent of the bandwidth of the probing radiation. The
+measured quantity resembles the intermediate scattering function of the
+magnetic excitations in the sample. At pulsed x-ray sources, especially x-ray
+lasers, the proposed technique allows to take single-shot spectra of the
+magnetic dynamics. The method opens new avenues to study low-energy
+non-equilibrium magnetic processes in a pump-probe setup.",1402.4795v1
+2014-03-04,Ultrafast switching of the electric polarization and magnetic chirality in BiFeO3 by an electric field,"Using a first-principles-based effective Hamiltonians within molecular
+dynamics simulations, we discover that applying an electric field that is
+opposite to the initial direction of the polarization results in a switching of
+both the polarization and the magnetic chirality vector of multiferroic BiFeO3
+at an ultrafast pace (namely of the order of picoseconds). We discuss the
+origin of such a double ultrafast switching, which is found to involve original
+intermediate magnetic states and may hold promise for designing various
+devices.",1403.0671v1
+2014-03-24,Skyrmionic spin Seebeck effect via dissipative thermomagnonic torques,"We derive thermomagnonic torque and its ""$\beta$-type"" dissipative correction
+from the stochastic Landau-Lifshitz-Gilbert equation. The ""$\beta$-type""
+dissipative correction describes viscous coupling between magnetic dynamics and
+magnonic current and it stems from spin mistracking of the magnetic order. We
+show that thermomagnonic torque is important for describing temperature
+gradient induced motion of skyrmions in helical magnets while dissipative
+correction plays an essential role in generating transverse Magnus force. We
+propose to detect such skyrmionic motion by employing the transverse spin
+Seebeck effect geometry.",1403.6160v2
+2014-04-11,Utilizing Nitrogen Vacancy Centers to measure oscillating magnetic fields,"We show how nitrogen vacancy (NV) centers can be used to determine the
+amplitude, phase and frequency of unknown weak monochromatic and multichromatic
+oscillating magnetic fields using only the periodic dynamical decoupling (PDD)
+and Carr-Purcell-Meiboom-Gill (CPMG) sequences. The effect of decoherence on
+the measurement of the magnetic field parameters is explicitly analyzed, and we
+take into account the fact that different pulse sequences suppress decoherence
+to different extents. Since the sensitivity increases with increasing sensing
+time while it decreases due to decoherence, we use the Fisher information
+matrix in order to optimize the number of pulses that should be used.",1404.3133v1
+2014-08-05,Vinamax: a macrospin simulation tool for magnetic nanoparticles,"We present Vinamax, a simulation tool for nanoparticles that aims at
+simulating magnetization dynamics on very large timescales. To this end, each
+in dividual nanoparticle is approximated by a macrospin. Vinamax numerically
+solves the Landau-Lifshitz equation by adopting a dipole approximation method,
+while temperature effects can be taken into account with two stochastic
+methods. It describes the influence of demagnetizing and anisotropy fields on
+magnetic nanoparticles at finite temperatures in a space and time-dependent
+externally applied field. Vinamax can be used in biomedical research where
+nanoparticle imaging techniques are under developement.",1408.0908v1
+2014-09-15,Enhanced synchronization in an array of spin torque nano oscillators in the presence of oscillating external magnetic field,"We demonstrate that the synchronization of an array of electrically coupled
+spin torque nano-oscillators (STNO) modelled by
+Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation can be enhanced appreciably
+in the presence of a common external microwave magnetic field. The applied
+microwave magnetic field stabilizes and enhances the regions of synchronization
+in the parameter space of our analysis, where the oscillators are exhibiting
+synchronized oscillations thereby emitting improved microwave power. To
+characterize the synchronized oscillations we have calculated the locking range
+in the domain of external source frequency.",1409.4384v2
+2014-09-21,Effective potential energy for relativistic particles in the field of inclined rotating magnetized sphere,"The dynamics of a charged relativistic particle in electromagnetic field of a
+rotating magnetized celestial body with the magnetic axis inclined to the axis
+of rotation is studied. The covariant Lagrangian function in the rotating
+reference frame is found. Effective potential energy is defined on the base of
+the first integral of motion. The structure of the equipotential surfaces for a
+relativistic charged particle is studied and depicted for different values of
+the dipole moment. It is shown that there are trapping regions for the
+particles of definite energies.",1409.5976v1
+2014-12-14,Landau levels for discrete-time quantum walks in artificial magnetic fields,"A new family of 2D discrete-time quantum walks (DTQWs) is presented and shown
+to coincide, in the continuous limit, with the Dirac dynamics of a spin 1/2
+fermion coupled to a constant and uniform magnetic field. Landau levels are
+constructed, not only in the continuous limit, but also for the DTQWs i.e. for
+finite non-vanishing values of the time- and position-step, by a perturbative
+approach in the step. Numerical simulations support the above results and
+suggest that the magnetic interpretation is valid beyond the scope of the
+continuous limit. The possibility of quantum simulation of condensed-matter
+systems by DTQWs is also discussed.",1412.4337v2
+2014-12-15,Nonequilibrium spin current through interacting quantum dots,"We develop a theory for charge and spin current between two canted magnetic
+leads flowing through a quantum dot with an arbitrary local interaction. For a
+noncollinear magnetic configuration, we calculate equilibrium and
+nonequilibrium current biased by voltage or temperature difference or pumped by
+magnetic dynamics. We are able to explicitly separate the equilibrium and
+nonequilibrium contributions to the current, both of which can be written in
+terms of the full retarded Green's function on the dot. Taking the specific
+example of a single-level quantum dot with a large on-site Coulomb interaction,
+we calculate the total spin current near the Kondo regime, which we find to be
+generally enhanced in magnitude as compared to the noninteracting case.",1412.4663v1
+2014-12-18,Coherent elastic excitation of spin waves,"We model the injection of elastic waves into a ferromagnetic film (F) by a
+non-magnetic transducer (N). We compare the configurations in which the
+magnetization is normal and parallel to the wave propagation. The lack of axial
+symmetry in the former results in the emergence of evanescent interface states.
+We compute the energy-flux transmission across the N$|$F interface and
+sound-induced magnetization dynamics in the ferromagnet. We predict efficient
+acoustically induced pumping of spin current into a metal contact attached to
+F.",1412.5820v2
+2015-01-30,Memory functions of magnetic skyrmions,"Magnetic skyrmion, a swirling spin texture, in chiral magnets is
+characterized by (i) nano-scale size ($\sim$1nm -- 100nm), (ii) topological
+stability, and (iii) gyro-dynamics. These features are shown to be advantageous
+for (a) high-density data-storage, (b) nonvolatile memory, and (c) ultra-low
+current and energy cost manipulation, respectively. By the numerical
+simulations of Landau-Lifshitz-Gilbert equation, the elementary functions of
+skyrmions are demonstrated aiming at the design principles of skyrmionic memory
+devices.",1501.07650v1
+2015-02-14,Energy dissipation in single-domain ferromagnetic nanoparticles: Dynamical approach,"We study, both analytically and numerically, the phenomenon of energy
+dissipation in single-domain ferromagnetic nanoparticles driven by an
+alternating magnetic field. Our interest is focused on the power loss resulting
+from the Landau-Lifshitz-Gilbert equation, which describes the precessional
+motion of the nanoparticle magnetic moment. We determine the power loss as a
+function of the field amplitude and frequency and analyze its dependence on
+different regimes of forced precession induced by circularly and linearly
+polarized magnetic fields. The conditions to maximize the nanoparticle heating
+are also analyzed.",1502.04222v1
+2015-03-16,Detection of spin waves in permalloy using planar Hall effect,"Rectification of microwave oscillations of magnetization in a permalloy film
+is realized using planar Hall effect. Two different rectified signals are
+obtained: a signal from the linearly excited uniform magnetization precession
+at the frequency of the external pumping and a signal from the pairs of
+contra-propagating short-wavelength spin waves parametrically generated at a
+half of the pumping frequency. The second, most unusual, rectified signal is
+caused by the uniform component of the dynamic magnetization created due to the
+interference of the phase correlated pairs of parametric spin waves.",1503.04638v1
+2015-03-23,Quantum Stoner-Wohlfarth model,"The quantum mechanical counterpart of the famous Stoner-Wohlfarth model -- an
+easy-axis magnet in a tilted magnetic field -- is studied theoretically and
+through simulations, as a function of the spin-size $S$ in a sweeping
+longitudinal field. Beyond the classical Stoner-Wohlfarth transition, the
+sweeping field-induced adiabatic change of states slows down as $S$ increases,
+leading to a dynamical quantum phase transition. This result is described as a
+critical phenomenon associated with Landau-Zener tunneling gaps at metastable
+quasi-avoided crossings. Furthermore, a beating of the magnetization is
+discovered after the Stoner-Wohlfarth transition. The period of the beating,
+obtained analytically, arises from a new type of quantum phase factor.",1503.06658v1
+2015-03-31,On the existence of periodic orbits for magnetic systems on the two-sphere,"We prove that there exist periodic orbits on almost all compact regular
+energy levels of a Hamiltonian function defined on a twisted cotangent bundle
+over the two-sphere. As a corollary, given any Riemannian two-sphere and a
+magnetic field on it, there exists a closed magnetic geodesic for almost all
+kinetic energy levels.",1503.09035v2
+2015-04-17,Critical analysis and remedy of switching failures in straintronic logic using Bennett clocking in the presence of thermal fluctuations,"Straintronic logic is a promising platform for beyond Moore's law computing.
+Using Bennett clocking mechanism, information can propagate through an array of
+strain-mediated multiferroic nanomagnets exploiting the dipolar coupling
+between the magnets without having to physically interconnect them. Here we
+perform a critical analysis of switching failures, i.e., error in information
+propagation due to thermal fluctuations through a chain of such straintronic
+devices. We solved stochastic Landau-Lifshitz-Gilbert equation considering
+room-temperature thermal perturbations and show that magnetization switching
+may fail due to inherent magnetization dynamics accompanied by thermally
+broadened switching delay distribution. Avenues available to circumvent such
+issue are proposed.",1504.04618v1
+2015-06-05,Spin dynamics in pressure-induced magnetically-ordered phases in PHCC,"We present inelastic neutron scattering experiments on the $S=1/2$ frustrated
+gapped quantum magnet piperazinium hexachlorodicuprate under applied
+hydrostatic pressure. These results show that at 9 kbar the magnetic triplet
+excitations in the system are gapless, contrary to what was previously
+reported. We show that the changes in the excitation spectrum can be primarily
+attributed to the change in a single exchange pathway.",1506.01876v1
+2015-06-11,The Effect of Correlations on the Heat Transport in a Magnetized Plasma,"In a classical ideal plasma, a magnetic field is known to reduce the heat
+conductivity perpendicular to the field whereas it does not alter the one along
+the field. Here we show that, in strongly correlated plasmas that are observed
+at high pressure or/and low temperature, a magnetic field reduces the
+perpendicular heat transport much less and even {\it enhances} the parallel
+transport. These surprising observations are explained by the competition of
+kinetic, potential and collisional contributions to the heat conductivity. Our
+results are based on first principle molecular dynamics simulations of a
+one-component plasma.",1506.03605v1
+2015-08-11,"Disks and Jets - Gravity, Rotation and Magnetic Fields","Magnetic fields are fundamental to the dynamics of both accretion disks and
+the jets that they often drive. We review the basic physics of these phenomena,
+the past and current efforts to model them numerically with an emphasis on the
+jet-disk connection, and the observational constraints on the role of magnetic
+fields in the jets of active galaxies on all scales.",1508.02546v1
+2015-09-14,Spin Transport in Antiferromagnetic Insulators Mediated by Magnetic Correlations,"We report a systematic study of spin transport in antiferromagnetic (AF)
+insulators having a wide range of ordering temperatures. Spin current is
+dynamically injected from Y3Fe5O12 (YIG) into various AF insulators in
+Pt/insulator/YIG trilayers. Robust, long-distance spin transport in the AF
+insulators is observed, which shows strong correlation with the AF ordering
+temperatures. We find a striking linear relationship between the spin decay
+length in the AFs and the damping enhancement in YIG, suggesting the critical
+role of magnetic correlations in the AF insulators as well as at the AF/YIG
+interfaces for spin transport in magnetic insulators.",1509.04336v1
+2015-11-05,Force law in material media and quantum phases,"We show that the known expressions for the force on a point-like dipole are
+incompatible with the relativistic transformation of force, and in this respect
+we apply the Lagrangian approach to the derivation of the correct equation for
+force on a small electric/magnetic dipole. The obtained expression for the
+generalized momentum of a moving dipole predicts two novel quantum effects with
+non-topological and non-dynamic phases, when an electric dipole is moving in an
+electric field, and when a magnetic dipole is moving in a magnetic field,
+correspondingly. The implications of the obtained results are discussed.",1511.04341v1
+2015-11-14,Parametric resonance induced chaos in magnetic damped driven pendulum,"A damped driven pendulum with a magnetic driving force, appearing from a
+solenoid, where ac current flows is considered. The solenoid acts on the
+magnet, which is located at the free end of the pendulum. In this system, the
+existence and interrelation of chaos and parametric resonance is theoretically
+examined. Derived analytical results are supported by numerical simulations and
+conducted experiments.",1511.04593v2
+2016-01-16,On the integrable magnetic geodesic flow on a 2-torus,"In this paper the magnetic geodesic flow on a 2-torus is considered. We study
+a semi-hamiltonian quasi-linear PDEs which is equivalent to the existence of
+polynomial in momenta first integral of magnetic geodesic flow on fixed energy
+level. It is known that diagonal metric associated with this system is Egorov
+one if degree of the first integral is equal to 2 or 3. In this paper we prove
+this fact in the case of existence of the first integral of any degree.",1601.04160v1
+2016-03-16,Magnetic properties of a two-dimensional electron gas strongly coupled to light,"Considering the quantum dynamics of 2DEG exposed to both a stationary
+magnetic field and an intense high-frequency electromagnetic wave, we found
+that the wave decreases the scattering-induced broadening of Landau levels.
+Therefore, various magnetoelectronic properties of two-dimensional
+nanostructures (density of electronic states at Landau levels,
+magnetotransport, etc) are sensitive to the irradiation by light. Thus, the
+elaborated theory paves a way to optical controlling magnetic properties of
+2DEG.",1603.04965v2
+2016-04-02,Fluctuations of electrical conductivity: a new source for astrophysical magnetic fields,"We consider the generation of magnetic field by the flow of a fluid for which
+the electrical conductivity is nonuniform. A new amplification mechanism is
+found which leads to dynamo action for flows much simpler than those considered
+so far. In particular, the fluctuations of the electrical conductivity provide
+a way to bypass anti-dynamo theorems. For astrophysical objects, we show
+through three-dimensional global numerical simulations that the
+temperature-driven fluctuations of the electrical conductivity can amplify an
+otherwise decaying large scale equatorial dipolar field. This effect could play
+a role for the generation of the unusually tilted magnetic field of the iced
+giants Neptune and Uranus.",1604.00469v1
+2016-04-13,Dipolar Rings of Microscopic Ellipsoids: Magnetic Manipulation and Cell Entrapment,"We study the formation and dynamics of dipolar rings composed by microscopic
+ferromagnetic ellipsoids, which self-assemble in water by switching the
+direction of the applied field. We show how to manipulate these fragile
+structures and control their shape via application of external static and
+oscillating magnetic fields. We introduce a theoretical framework which
+describes the ring deformation under an applied field, allowing to understand
+the underlying physical mechanism. Our microscopic rings are finally used to
+capture, entrap and later release a biological cell via magnetic command, i.e.
+performing a simple operation which can be implemented in other microfluidic
+devices which make use of ferromagnetic particles.",1604.03895v2
+2016-04-20,Magnetic monopoles in noncommutative quantum mechanics,"We discuss certain generalization of the Hilbert space of states in
+noncommutaive quantum mechanics that, as we show, introduces magnetic monopoles
+into the theory. Such generalization arises very naturally in the considered
+model, but can be easily reproduced in ordinary quantum mechanics as well. This
+approach offers a different viewpoint on the Dirac quantization condition and
+other important relations for magnetic monopoles. We focus mostly on the
+kinematic structure of the theory, but investigate also a dynamical problem
+(with the Coulomb potential).",1604.05968v3
+2016-05-04,Parker's model in geodynamo,"We consider how information on geostrophic flows in the planetary cores,
+taken from 3D simulations in the sphere, can be used in 2D Parker's geodynamo
+model with the simple forms of the $\alpha$-quenching. Using cluster computer
+systems dependence of dynamo equations solution on the magnitudes of $\alpha$-
+and $\omega$-effects is studied. We show that geostrophical flow can produce
+the well-known Z-structure of the poloidal magnetic field without the feed-back
+of the magnetic field onto the large-scale velocity field. The influence of
+fluctuations of $\alpha$-effect on magnetic field generation, its spectral
+properties, in respect to the geodynamo applications, is also discussed.",1605.01321v1
+2016-06-11,Chiral magnetic effect by synthetic gauge fields,"We study the dynamical generation of the chiral chemical potential in a Weyl
+metal constructed from a three-dimensional optical lattice and subject to
+synthetic gauge fields. By numerically solving the Boltzmann equation with the
+Berry curvature in the presence of parallel synthetic electric and magnetic
+fields, we find that the spectral flow and the ensuing chiral magnetic current
+emerge. We show that the spectral flow and the chiral chemical potential can be
+probed by time-of-flight imaging.",1606.03589v1
+2016-07-18,Heat transfer in MHD flow due to a linearly stretching sheet with induced magnetic field,"The full MHD problem of the flow and heat transfer due to a linearly
+stretching sheet in the presence of a transverse magnetic field is put in a
+self-similar form. Traditionally ignored physical processes such as induced
+magnetic field, viscous dissipation, Joule heating, and work shear are included
+and their importance is established. Cases of prescribed surface temperature,
+prescribed heat flux, surface feed (injection or suction), velocity slip, and
+thermal slip are also considered. The problem is shown to admit self
+similarity. Sample numerical solutions are obtained for chosen combinations of
+the flow parameters.",1607.05720v2
+2016-10-26,On the motion of free interface in two-dimensional ideal incompressible MHD,"For the free boundary problem of the plasma-vacuum interface to ideal
+incompressible magnetohydrodynamics (MHD) in two-dimensional space, the a
+priori estimates of solutions are proved in Sobolev norms by adopting a
+geometrical point of view. In the vacuum region, the magnetic field is
+described by the div-curl system of pre-Maxwell dynamics, while at the
+interface the total pressure is continuous and the magnetic field is tangent to
+the boundary. We prove that the $L^2$ norms of any order covariant derivatives
+of the magnetic field in vacuum and on the boundaries are bounded in terms of
+initial data and the second fundamental forms of the free interface and the
+rigid wall.",1610.08285v2
+2016-11-05,Averaging of nonlinear Schrödinger equations with strong magnetic confinement,"We consider the dynamics of nonlinear Schr\""odinger equations with strong
+constant magnetic fields. In an asymptotic scaling limit the system exhibits a
+purely magnetic confinement, based on the spectral properties of the Landau
+Hamiltonian. Using an averaging technique we derive an associated effective
+description via an averaged model of nonlinear Schr\""odinger type. In a special
+case this also yields a derivation of the LLL equation.",1611.01574v2
+2016-11-07,Purcell magneto-elastic swimmer controlled by an external magnetic field,"This paper focuses on the mechanism of propulsion of a Purcell swimmer whose
+segments are magnetized and react to an external magnetic field applied into
+the fluid. By an asymptotic analysis, we prove that it is possible to steer the
+swimmer along a chosen direction when the control functions are prescribed as
+an oscillating field. Moreover, we discuss what are the main obstructions to
+overcome in order to get classical controllability result for this system.",1611.02020v1
+2016-11-26,Growth of the inner core in the mean-field dynamo model,"Application of Parker's dynamo model to the geodynamo with the growing inner
+core is considered. It is shown that decrease of the inner core size, where
+intensive magnetic field generation takes place, leads to the multi-polar
+magnetic field in the past. This effect reflects the decrease of the region of
+the effective magnetic field generation. The process is accompanied by increase
+of the reversals number and decrease of intensity of the geomagnetic field. The
+constraints on the mechanisms of convection in the liquid core are discussed.",1611.08652v1
+2016-11-29,Investigation of thermalization in giant-spin models by different Lindblad schemes,"The theoretical understanding of time-dependence in magnetic quantum systems
+is of great importance in particular for cases where a unitary time evolution
+is accompanied by relaxation processes. A key example is given by the dynamics
+of single-molecule magnets where quantum tunneling of the magnetization
+competes with thermal relaxation over the anisotropy barrier. In this article
+we investigate how good a Lindblad approach describes the relaxation in giant
+spin models and how the result depends on the employed operator that transmits
+the action of the thermal bath.",1611.09695v1
+2016-12-27,Reinventing atomistic magnetic simulations with spin-orbit coupling,"We propose a powerful extension to combined molecular and spin dynamics that
+fully captures the coupling between the atomic and spin subsystems via
+spin-orbit interactions. Its foundation is the inclusion of the local magnetic
+anisotropies that arise as a consequence of the lattice symmetry breaking due
+to phonons or defects. We demonstrate that our extension enables the exchange
+of angular momentum between the atomic and spin subsystems, which is critical
+to the challenges arising in the study of fluctuations and non-equilibrium
+processes in complex, natural, and engineered magnetic materials.",1612.08503v1
+2017-01-09,Quantum Ring in Gapped Graphene Layer with Wedge Disclination in the Presence of an Uniform Magnetic Field,"In this paper we investigate the relativistic quantum dynamics of a massive
+excitation in a graphene layer with a wedge disclination in the presence of an
+uniform magnetic field. We use a Dirac oscillator type coupling to introduce
+the confining potential for massive fermions in this system. We obtain the
+energy spectrum and eigenfunctions for the quantum ring pierced by
+Aharonov-Bohm flux resulting in appearance of persistent current and
+spontaneous magnetization.",1701.02051v2
+2017-01-11,Theory of Quantum Oscillations of Magnetization in Kondo Insulators,"The Kondo lattice model of spin-1/2 local moments coupled to the conduction
+electrons at half-filling is studied for its orbital response to magnetic field
+on bipartite lattices. Through an effective charge dynamics, in a canonical
+representation of electrons that appropriately describes the Kondo insulating
+ground state, the magnetization is found to show de Haas-van Alphen
+oscillations from intermediate to weak Kondo coupling. These oscillations are
+ascribed to Lifshitz-like inversion of a dispersion of the gapped
+quasiparticles, whose chemical potential surface is measured by the oscillation
+frequency. Such oscillations are also predicted to occur in spin-density wave
+insulators.",1701.02825v2
+2017-01-24,Accelerated Magnetic Resonance Spectroscopy with Vandermonde Factorization,"Multi-dimensional magnetic resonance spectroscopy is an important tool for
+studying molecular structures, interactions and dynamics in bio-engineering.
+The data acquisition time, however, is relatively long and non-uniform sampling
+can be applied to reduce this time. To obtain the full spectrum,a
+reconstruction method with Vandermonde factorization is proposed.This method
+explores the general signal property in magnetic resonance spectroscopy: Its
+time domain signal is approximated by a sum of a few exponentials. Results on
+synthetic and realistic data show that the new approach can achieve faithful
+spectrum reconstruction and outperforms state-of-the-art low rank Hankel matrix
+method.",1701.07017v1
+2017-04-13,The hottest hot Jupiters may host Atmospheric Dynamos,"Hot Jupiters have proven themselves to be a rich class of exoplanets which
+test our theories of planetary evolution and atmospheric dynamics under extreme
+conditions. Here, we present three-dimensional magnetohydrodynamic simulations
+and analytic results which demonstrate that a dynamo can be maintained in the
+thin, stably-stratified atmosphere of a hot Jupiter, independent of the
+presumed deep-seated dynamo. This dynamo is maintained by conductivity
+variations arising from strong asymmetric heating from the planets' host star.
+The presence of a dynamo significantly increases the surface magnetic field
+strength and alters the overall planetary magnetic field geometry, possibly
+affecting star-planet magnetic interactions.",1704.04197v1
+2017-05-31,Topological lattice using multi-frequency radiation,"We describe a novel technique for creating an artificial magnetic field for
+ultra-cold atoms using a periodically pulsed pair of counter propagating Raman
+lasers that drive transitions between a pair of internal atomic spin states: a
+multi-frequency coupling term. In conjunction with a magnetic field gradient,
+this dynamically generates a rectangular lattice with a non-staggered magnetic
+flux. For a wide range of parameters, the resulting Bloch bands have
+non-trivial topology, reminiscent of Landau levels, as quantified by their
+Chern numbers.",1705.11101v2
+2017-07-26,Interfacial exchange interactions and magnetism of Ni2MnAl/Fe bilayers,"Based on a multi-scale calculations, combining ab-initio methods with spin
+dynamics simulations, we perform a detailed study of the magnetic behavior of
+Ni2MnAl/Fe bilayers. Our simulations show that such a bilayer exhibits a small
+exchange bias effect when the Ni2MnAl Heusler alloy is in a disordered B2
+phase. Additionally, we present an effective way to control the magnetic
+structure of the Ni2MnAl antiferromagnet, in the pseudo-ordered B2-I as well as
+the disordered B2 phases, via a spin-flop coupling to the Fe layer.",1707.08651v1
+2017-08-03,Interaction of ultracold non-ideal ion-electron plasma with a uniform magnetic field,"The method of molecular dynamics is used to study behavior of a ultracold
+non-ideal ion-electron Be plasma in a uniform magnetic field. Our simulations
+yield an estimate for the rate of electron-ion collisions which is
+non-monotonicallydependent on the magnetic field magnitude. Also they
+explicitly show that there are two types of diffusion: classical one,
+corresponding to Brownian motion of particles, and Bohm diffusion when the
+trajectory of particles (guiding centers) includes substantial lengths of drift
+motion.",1708.00990v4
+2017-08-21,Dynamo transition in a five-mode helical model,"We construct a five-mode helical dynamo model containing three velocity and
+two magnetic modes and solve it analytically. This model exhibits dynamo
+transition via supercritical pitchfork bifurcation. We show that the critical
+magnetic Reynolds number for dynamo transition ($\mathrm{Rm}_c$) asymptotes to
+constant values for very low and very high magnetic Prandtl numbers
+($\mathrm{Pm}$). Beyond dynamo transition, secondary bifurcations lead to
+periodic, quasi-periodic, and chaotic dynamo states as the forcing amplitude is
+increased and chaos appears through a quasi-periodic route.",1708.06124v1
+2017-10-19,Optically Pumped Magnetometry in Arbitrarily Oriented Magnetic Fields,"Optically pumped atomic magnetometers (OPMs) offer highly sensitive magnetic
+measurements using compact hardware, offering new possibilities for practical
+precision sensors. Double-resonance OPM operation is well suited to unshielded
+magnetometry, due to high sensor dynamic range. However, sensor response is
+highly anisotropic with variation in the orientation of the magnetic field. We
+present data quantifying these effects and discuss implications for the design
+of practical sensors.",1710.07024v1
+2017-10-24,Equilibrium properties of magnetic filament suspensions,"Langevin dynamics is used to study equilibrium properties of the suspension
+of magnetic filaments (chains of nanoparticles permanently crosslinked with
+polymers). It is shown that the filament suspension generally has a larger
+magnetic susceptibility than the system of unlinked nanoparticles with the same
+average particle concentration. However, actual susceptibility gain strongly
+depends on length and flexibility of filaments. It is also shown that in a
+strong gravitational (centrifugal) field sedimentation profiles of filaments
+are less homogeneous than that of unlinked particles. The spatial distribution
+of filaments weakly depends on the intensity of interparticle dipole-dipole
+interactions.",1710.08956v2
+2017-11-17,Electron heating in the laser and static electric and magnetic fields,"A 2D slab approximation of the interactions of electrons with intense
+linearly polarized laser radiation and static electric and magnetic fields is
+widely used for both numerical simulations and simplified semi-analytical
+models. It is shown that in this case electron dynamics can be conveniently
+described in the framework of 3/2 dimensional Hamiltonian approach. The
+electron acceleration beyond a standard ponderomotive scaling, caused by the
+synergistic effects of the laser and static electro-magnetic fields, is due to
+an onset of stochastic electron motion.",1711.06714v4
+2018-02-02,Nonequilibrium Kondo-vs-RKKY Scenarios in Nanoclusters,"Ultrafast manipulations of magnetic phases are eliciting increasing attention
+from the scientific community, because potentially relevant to the
+understanding of nonequilibrium phase transitions and to novel technologies.
+Here, we focus on manipulations applied to magnetic impurities in metallic
+hosts. By considering small nanoring geometries, we show how currents can
+induce a dynamical switching between different types of exchange interactions
+in these systems. Our work thus opens a study window on nonequilibrium
+Doniach's magnetic phase diagrams, and time-dependent Kondo-vs-RKKY scenarios.",1802.00838v2
+2018-02-19,Algebraic non-integrability of magnetic billiards on the Sphere and Hyperbolic plane,"We consider billiard ball motion in a convex domain on a constant curvature
+surface influenced by the constant magnetic field. We examine the existence of
+integral of motion which is polynomial in velocities. We prove that if such an
+integral exists then the boundary curve of the domain determines an algebraic
+curve in $\mathbf{C}^3$ which must be nonsingular. Using this fact we deduce
+that for any domain different from round disc for all but finitely many values
+of the magnitude of the magnetic field billiard motion does not have Polynomial
+in velocities integral of motion.",1802.06582v1
+2018-04-27,Angular Dependent Magnetization Dynamics with Mirror-symmetric Excitations in Artificial Quasicrystalline Nanomagnet Lattices,"We report angle-dependent spin-wave spectroscopy on aperiodic
+quasicrystalline magnetic lattices, i.e., Ammann, Penrose P2 and P3 lattices
+made of large arrays of interconnected Ni$_{80}$Fe$_{20}$ nanobars. Spin-wave
+spectra obtained in the nearly saturated state contain distinct sets of
+resonances with characteristic angular dependencies for applied in-plane
+magnetic fields. Micromagnetic simulations allow us to attribute detected
+resonances to mode profiles with specific mirror symmetries. Spectra in the
+reversal regime show systematic emergence and disappearance of spin wave modes
+indicating reprogrammable magnonic characteristics.",1804.10630v1
+2018-07-18,Concentration phenomena for a fractional Choquard equation with magnetic field,"We consider the following nonlinear fractional Choquard equation $$
+\varepsilon^{2s}(-\Delta)^{s}_{A/\varepsilon} u + V(x)u =
+\varepsilon^{\mu-N}\left(\frac{1}{|x|^{\mu}}*F(|u|^{2})\right)f(|u|^{2})u
+\mbox{ in } \mathbb{R}^{N}, $$ where $\varepsilon>0$ is a parameter, $s\in (0,
+1)$, $0<\mu<2s$, $N\geq 3$, $(-\Delta)^{s}_{A}$ is the fractional magnetic
+Laplacian, $A:\mathbb{R}^{N}\rightarrow \mathbb{R}^{N}$ is a smooth magnetic
+potential, $V:\mathbb{R}^{N}\rightarrow \mathbb{R}$ is a positive potential
+with a local minimum and $f$ is a continuous nonlinearity with subcritical
+growth. By using variational methods we prove the existence and concentration
+of nontrivial solutions for $\varepsilon>0$ small enough.",1807.07442v1
+2018-08-27,Hamiltonian Nature of Monopole Dynamics,"Classical electromagnetism with magnetic monopoles is not a Hamiltonian field
+theory because the Jacobi identity for the Poisson bracket fails. The Jacobi
+identity is recovered only if all of the species have the same ratio of
+electric to magnetic charge or if an electron and a monopole can never collide.
+Without the Jacobi identity, there are no local canonical coordinates or
+Lagrangian action principle. To build a quantum theory of magnetic monopoles,
+we either must explain why the positions of electrons and monopoles can never
+coincide or we must resort to new quantization techniques.",1808.08689v3
+2018-10-11,Observation of magnetic structural universality using transverse NMR relaxation,"Transverse NMR relaxation from spins diffusing through a random magnetic
+medium is sensitive to its structure on a mesoscopic scale. In particular, this
+results in the time-dependent relaxation rate. We show analytically and
+numerically that this rate approaches the long-time limit in a power-law
+fashion, with the exponent reflecting the disorder class of mesoscopic magnetic
+structure. The spectral line shape acquires a corresponding non-analytic power
+law singularity at zero frequency. We experimentally detect a change in the
+dynamical exponent as a result of the transition into a maximally random jammed
+state characterized by hyperuniform correlations.",1810.04847v1
+2018-11-05,Surface acoustic wave coupled to magnetic resonance on a multiferroic CuB$_2$O$_4$,"We observed surface acoustic wave (SAW) propagation on a multiferroic
+material CuB$_2$O$_4$ with use of two interdigital transducers (IDTs). The
+period of IDT fingers is as short as 1.6 $\mu$m so that the frequency of SAW is
+3 GHz, which is comparable with that of magnetic resonance. In
+antiferromagnetic phase, the SAW excitation intensity varied with the magnitude
+and direction of the magnetic field, owing to the dynamical coupling between
+SAWs and antiferromagnetic resonance of CuB$_2$O$_4$. The microscopic mechanism
+is discussed based on the symmetrically allowed magentoelastic coupling.",1811.01527v1
+2018-11-29,Extended statistical analysis of emerging solar active regions,"We use observations of line-of-sight magnetograms from Helioseismic and
+Magnetic Imager (HMI) on board of Solar Dynamics Observatory (SDO) to
+investigate polarity separation, magnetic flux, flux emergence rate, twist and
+tilt of solar emerging active regions. Functional dependence of polarity
+separation and maximum magnetic flux of an active region is in agreement with a
+simple model of flux emergence as the result of buoyancy forces. Our
+investigation did not reveal any strong dependence of emergence rate on twist
+properties of active regions.",1811.12089v1
+2018-12-04,Polynomial integrals of magnetic geodesic flows on the 2-torus on several energy levels,"In this paper the geodesic flow on a 2-torus in a non-zero magnetic field is
+considered. Suppose that this flow admits an additional first integral $F$ on
+$N+2$ different energy levels which is polynomial in momenta of arbitrary
+degree $N$ with analytic periodic coefficients. It is proved that in this case
+the magnetic field and metrics are functions of one variable and there exists a
+linear in momenta first integral on all energy levels.",1812.01290v1
+2018-12-05,Magnetic control of polariton spin transport,"We show the full control of the polarization dynamics of a propagating
+exciton-polariton condensate in a planar microcavity by using a magnetic field
+applied in the Voigt geometry. The change of the spin-beat frequency, the
+suppression of the optical spin Hall effect and the rotation of the
+polarization pattern by the magnetic field are theoretically reproduced by
+accounting for the magneto-induced mixing of exciton-polariton and dark, spin
+forbidden, exciton states.",1812.01919v1
+2019-01-04,Hydrodynamics of three-dimensional skyrmions in frustrated magnets,"We study the nucleation and collective dynamics of Shankar skyrmions [R.
+Shankar, Journal de Physique 38, 1405 (1977)] in the class of frustrated
+magnetic systems described by an SO(3) order parameter, including multi-lattice
+antiferromagnets and amorphous magnets. We infer the expression for the
+spin-transfer torque that injects skyrmion charge into the system and the
+Onsager-reciprocal pumping force that enables its detection by electrical
+means. The thermally-assisted flow of topological charge gives rise to an
+algebraically decaying drag signal in nonlocal transport measurements. We
+contrast our findings to analogous effects mediated by spin supercurrents.",1901.01208v1
+2019-01-10,An upper limit on primordial magnetic fields from ultra-faint dwarf galaxies,"The presence of primordial magnetic fields increases the minimum halo mass in
+which star formation is possible at high redshifts. Estimates of the dynamical
+mass of ultra-faint dwarf galaxies (UFDs) within their half-light radius
+constrain their virialized halo mass before their infall into the Milky Way.
+The inferred halo mass and formation redshift of the UFDs place upper bounds on
+the primordial comoving magnetic field, $B_0$. We derive an upper limit of
+$0.50\pm 0.086$ ($0.31\pm 0.04$) nG on $B_0~$ assuming the average formation
+redshift of the UFD host halos is $z_{\rm form}=$ 10 (20), respectively.",1901.03341v2
+2019-01-28,Hölder Stable Recovery of Time-Dependent Electromagnetic Potentials Appearing in a Dynamical Anisotropic Schrödinger Equation,"We consider the inverse problem of H\""oldder-stably determining the time- and
+space-dependent coefficients of the Schr\""odinger equation on a simple
+Riemannian manifold with boundary of dimension $n\geq2$ from knowledge of the
+Dirichlet-to-Neumann map. Assuming the divergence of the magnetic potential is
+known, we show that the electric and magnetic potentials can be H\""older-stably
+recovered from these data. Here we also remove the smallness assumption for the
+solenoidal part of the magnetic potential present in previous results.",1901.09728v1
+2019-03-21,Magnetic Skyrmions in Atomic Thin CrI$_3$ Monolayer,"In this letter, we report the visualization of topologically protected spin
+textures, in the form of magnetic skyrmions, in recently discovered
+monoatomic-thin two-dimensional CrI$_3$. By combining density functional theory
+and atomistic spin dynamic simulation, we demonstrate that an application of
+out-of-plane electric field to CrI$_3$ lattice favors the formation of sub-10
+nm skyrmions at 0 K temperature. The spin texture arises due to a strong
+correlation between magneto-crystalline anisotropy, Dzyaloshinskii-Moriya
+interaction and the vertical electric field, whose shape and size could be
+tuned with the magnetic field. Such finding will open new avenues for
+atomic-scale quantum engineering and precision sensing.",1903.08797v1
+2019-04-25,Scale-invariant Helical Magnetic Fields from Inflation,"We discuss a model which can generate scale-invariant helical magnetic fields
+on large scales ($\lesssim 1$Mpc) in the primordial universe. It is also shown
+that the electric conductivity becomes significant and terminates
+magnetogenesis even before reheating is completed. By solving the
+electromagnetic dynamics taking conductivity into account, we find that
+magnetic fields with amplitude $B\simeq 10^{-15}{\rm G}$ at present can be
+generated without encountering a backreaction or strong coupling problem.",1904.11428v1
+2019-06-17,Electronic structure and Magneto-transport in MoS$_2$/Phosphorene van der Waals heterostructure,"The time-dependent spin current mediated spin transfer torque behaviour has
+been investigated via scattering formalism within density functional theory
+framework supported by Green's function. Quantum magnetotransport
+characteristics have been revealed in a model semiconducting
+MoS$_2$/phosphorene van der Waals heterostructure. The dynamics of spin current
+channelized heterolayer transport has been studied with rotational variation in
+magnetization angle. It is observed that the time-dependent spin transport
+torque remains invariant irrespective of magnetization angle direction. The
+polarized spin-current is persistent with the external magnetic field for
+potential applicability towards spintronics.",1906.09187v1
+2019-06-22,Effects of a quadrupolar magnetic term in a Generalized Störmer problem,"A new generalized St\""ormer problem is proposed. The charged particles motion
+around a rotating axisymmetric magnetic planet is studied using various
+conditions mainly in planetary magnetospheres. It is shown that the existence
+of specific trajectories is due to the quadrupolar and dipolar magnetic terms.
+Moreover, the equilibrium and stability behaviors and the corresponding orbital
+frequencies for various kinds of charged dust grains are treated giving rise to
+a new model describing the dynamical system and leading to more interesting
+results.",1906.09481v1
+2019-07-01,Determination of energy flux rate in homogeneous ferrohydrodynamic turbulence using two-point statistics,"In ferrofluids the suspended ferromagnetic particles agglomerate due to the
+interaction between the particle magnetic moment and the external magnetic
+field, which in turn, influences the turbulence and relaxation time. The
+relaxation time becomes large when we are considering turbulence drag force
+instead of viscous drag force in Brownian motion. We investigate that the total
+energy conservation in ferrofluids taking into interaction between the external
+magnetic field and the ferrofluid.",1907.00604v1
+2019-10-09,Scattering of exchange spin waves from regions of modulated magnetization,"We investigate the reflection coefficient of spin waves propagating in an
+ultra-thin ferromagnetic film with regions where saturation magnetization is
+modulated. We find analytically and using micromagnetic simulations that there
+are transmission resonances that depend on the width of the regions and on the
+energy of excitation. Our results resemble the quantum mechanical
+Ramsauer-Townsend effect in which an electron with certain energies can
+propagate above a potential field without scattering. Our findings are useful
+for reconfigurable magnonic devices where the saturation magnetization can be
+dynamically controlled via a thermal landscape.",1910.04303v1
+2019-10-28,Taylor state merging at SSX: experiment and simulation,"We describe experiments and simulations of dynamical merging with two Taylor
+state plasmas in the SSX device. Taylor states are formed by magnetized plasma
+guns at opposite ends of the device. We have performed experiments with Taylor
+states of either sense of magnetic helicity (right-handed twist or left-handed
+twist). We present results of both counter-helicity merging (one side
+left-handed, the other right-handed) and co-helicity merging (both sides
+left-handed). Experiments show significant ion heating, consistent with
+magnetic reconnection. Magnetohydrodynamic simulations of these experiments
+reveal the structure of the final relaxed, merged state.",1910.13861v1
+2019-11-07,Optimal Actuation of Flagellar Magnetic Micro-Swimmers,"We present an automated procedure for the design of optimal actuation for
+flagellar magnetic microswimmers based on numerical optimization. Using this
+method, a new magnetic actuation method is provided which allows these devices
+to swim significantly faster compared to the usual sinusoidal actuation. This
+leads to a novel swimming strategy which makes the swimmer perform a 3D
+figure-8 trajectory. This shows that a faster propulsion is obtained when the
+swimmer is allowed to go out-of-plane. This approach is experimentally
+validated on a scaled-up flexible swimmer.",1911.02805v1
+2019-11-07,On the Complexity of a Charged Quantum Oscillator,"In this paper, we study the effect of both the electric and the magnetic
+fields on the rate of complexity growth. Our system is a charged quantum
+oscillator and over a period of time, we study the maximum dynamic evolution of
+quantum states which might lead to a strong bound on the rate of computation.
+We show that by turning on the electric field, the rate of complexity decreases
+whereas this rate has increasing behavior when the magnetic field is turned on.
+In this regard, we also find a critical value of the magnetic field, beyond
+which this rate changes its behavior drastically.",1911.08886v2
+2019-12-19,On the effect of time-dependent inhomogeneous magnetic fields on the particle momentum spectrum in electron-positron pair production,"Electron-positron pair production in spatially and temporally inhomogeneous
+electric and magnetic fields is studied within the Dirac-Heisenberg-Wigner
+formalism (quantum kinetic theory) through computing the corresponding Wigner
+functions. The focus is on discussing the particle momentum spectrum regarding
+signatures of Schwinger and multiphoton pair production. Special emphasis is
+put on studying the impact of a strong dynamical magnetic field on the particle
+distribution functions. As the equal-time Wigner approach is formulated in
+terms of partial integro-differential equations an entire section of the
+manuscript is dedicated to present numerical solution techniques applicable to
+Wigner function approaches in general.",1912.09359v1
+2020-02-21,Rayleigh-Bénard Convection in Strong Vertical Magnetic Field: Flow Structure and Verification of Numerical Method,"Direct numerical simulations are performed to study turbulent
+Rayleigh-B\'{e}nard convection in a vertical cylindrical cavity with uniform
+axial magnetic field. Flows at high Hartmann and Rayleigh numbers are
+considered. The calculations reveal that, similarly to the behavior observed in
+Rayleigh-B\'{e}nard convection with strong rotation, flows at strong magnetic
+field develop a central vortex, while the heat transfer is suppressed.",2002.09404v2
+2020-03-02,Chirality transfer & chiral turbulence in gauge theories,"Chirality transfer between fermions and gauge fields plays a crucial role for
+understanding the dynamics of anomalous transport phenomena such as the Chiral
+Magnetic Effect. In this proceeding we present a first principles study of
+these processes based on classical-statistical real-time lattice simulations of
+strongly coupled QED $(e^2N_f=64)$. Our simulations demonstrate that a
+chirality imbalance in the fermion sector triggers chiral plasma instabilities
+in the gauge field sector, which ultimately lead to the generation of long
+range helical magnetic fields via a self-similar turbulent cascade of the
+magnetic helicity.",2003.00763v1
+2020-04-13,Reduction of divisors for classical superintegrable $GL(3)$ magnetic chain,"Variables of separation for classical $GL(3)$ magnetic chain obtained by
+Sklyanin form a generic positive divisor $D$ of degree $n$ on a genus $g$
+non-hyperelliptic algebraic curve. Because $n>g$ this divisor $D$ has unique
+representative $\rho(D)$ in the Jacobian which can be constructed by using
+dim$|D|=n-g$ steps of Abel's algorithm. We study properties of the
+corresponding chain of divisors and prove that the classical $GL(3)$ magnetic
+chain is a superintegrable system with dim$|D|=2$ superintegrable Hamiltonians.",2004.05775v2
+2020-04-20,Decoherence measurements in crystals of molecular magnets,"Decoherence processes in crystals of molecular magnets are prototypical for
+interacting electronic spin systems. We analyze the Landau-Zener dynamics of
+the archetypical TbPc$_2$ complex diluted in a diamagnetic monocrystal. The
+dependence of the tunneling probability on the field sweep rate is evaluated in
+the framework of the recently proposed master equation in which the decoherence
+processes are described through a phenomenological Lindblad operator. Thus, we
+showcase low temperature magnetic measurements that complement resonant
+techniques in determining small tunnel splittings and dephasing times.",2004.09011v1
+2020-05-30,A phenomenological model for the spontaneous exchange bias effect,"In this work we propose an alternative model to explain the spontaneous
+exchange bias (SEB) effect observed in spin glass (SG)-like systems. As in a
+previously proposed model (Ref. 1), it is based on the unconventional dynamics
+of the SG-like moments at the magnetic hysteresis cycle. However, using a
+reliable estimate of the amount of SG-spins that are relaxing during the cycle,
+the new model can correctly describe the changes in the SEB observed for
+measurements performed at different temperatures and different maximum applied
+fields.",2006.00230v1
+2020-05-29,Investigation of spin-$0$ massive charged particle subject to a homogeneous magnetic field with potentials in a topologically trivial flat class of Gödel-type space-time,"In this paper, we investigate relativistic quantum dynamics of spin- $0$
+massive charged particle subject to a homogeneous magnetic field in the
+G\""{o}del-type space-time with potentials. We solve the Klein-Gordon equation
+subject to a homogeneous magnetic field in a topologically trivial flat class
+of G\""{o}del-type space-time in the presence of a Cornell-type scalar and
+Coulomb-type vector potentials and analyze the effects on the energy
+eigenvalues and eigenfunctions.",2006.00907v1
+2020-06-15,Low MHD turbulence: the role of boundaries,"In this short review, we present the main known features of MHD Turbulence at
+Low Magnetic Reynolds number, for which the flow isn't intense nor electrically
+conductive enough to disturb an externally applied magnetic field. The emphasis
+is deliberately placed on the very specific physical mechanisms of these flows,
+rather than their numerical modelling. We also focus on homogeneous magnetic
+fields which have received most attention. Since the basic properties of these
+flows have been thoroughly reviewed a number of times, this review is
+deliberately biased towards flows in bounded domains, in which the tendency to
+two-dimensionality observed in MHD flows casts the boundaries of the domain
+into a leading role.",2006.08187v1
+2020-08-25,Friction Force in Strongly Magnetized Plasmas,"A charged particle moving through a plasma experiences a friction force that
+commonly acts antiparallel to its velocity. It was recently predicted that in
+strongly magnetized plasmas, in which the plasma particle gyro-frequency
+exceeds the plasma frequency, the friction also includes a transverse component
+that is perpendicular to both the velocity and Lorentz force. Here, this
+prediction is confirmed using molecular dynamics simulations, and it is shown
+that the relative magnitude of the transverse component increases with plasma
+coupling strength. This result influences single particle motion and
+macroscopic transport in strongly magnetized plasmas found in a broad range of
+applications.",2008.11126v1
+2020-09-07,Anomalous In-plane Magnetic Anisotropy in Strain-mediated Converse Magnetoelectric Coupling,"Magnetic axis rotation (MAR) in ferromagnetic (FM) layers is crucial for
+strain-mediated converse magnetoelectric coupling. Employing the density
+functional theory (DFT), we computationally study the magnetic anisotropy of
+selected deformed FM materials such as body-centered iron. The results show
+that the short axis is more energy-favorable at high in-plane strain difference
+than previously predicted phenomenologically. This anomalous trend and the
+complex energy behaviors at different strain conditions explain why
+spin-lattice dynamics (SLD) simulation does not produce in-plane MAR and imply
+couplings between different energy terms together with high order coefficient
+contributions.",2009.03045v2
+2020-09-07,Aharonov-Bohm effect on spin-$0$ scalar massive charged particle with a uniform magnetic field in Som-Raychaudhuri space-time with a cosmic string,"We study the relativistic quantum dynamics of spin-$0$ massive charged
+particle in a G\""{o}del-type space-time with electromagnetic interactions. We
+solve the Klein-Gordon equation subject to a uniform magnetic field in the
+Som-Raychaudhuri space-time with a cosmic string. In addition, we include a
+magnetic quantum flux into the relativistic quantum system obtain the energy
+eigenvalues and analyze an analogue of the Aharonov-Bohm (AB) effect.",2009.07080v2
+2020-11-11,Reduction of back switching by large damping ferromagnetic material,"Recent studies on magnetization dynamics induced by spin-orbit torque have
+revealed a weak dependence of the critical current for magnetization switching
+on the damping constant of a ferromagnetic free layer. This study, however,
+reveals that the damping constant nevertheless plays a key role in
+magnetization switching induced by spin-orbit torque. An undesirable switching,
+returning to an initial state, named as back switching, occurs in a ferromagnet
+with an easy axis parallel to the current direction. Numerical and theoretical
+analyses reveal that back switching is strongly suppressed when the damping
+constant of the ferromagnet is large.",2011.05566v1
+2021-04-11,Orbital dynamics in 2D topological and Chern insulators,"Within a relativistic quantum formalism we examine the role of second-order
+corrections caused by the application of magnetic fields in two-dimensional
+topological and Chern insulators. This allows to reach analytical expressions
+for the change of the Berry curvature, orbital magnetic moment, density of
+states and energy determining their canonical grand potential and transport
+properties. The present corrections, which become relevant at relatively low
+fields due to the small gap characterizing these systems, unveil a zero-field
+diamagnetic susceptibility which can be tuned by the external magnetic field.",2104.05126v1
+2021-04-30,Micromagnetic modeling of magnon coherent states in a nonuniform magnetic field,"The study of the dynamics of magnetically ordered states in strong excitation
+through micromagnetic modeling has become relevant due to the observation of
+magnon Bose condensation. In particular, the question has arisen about the
+possibility of describing the coherent quantum state by the quasi-classical
+Landau-Lifshitz-Gilbert equations. We performed micromagnetic simulations of
+magnetization precession with a high angle of deviation in an out-of-plane
+nonuniform dc field. Our results confirm the formation of coherent magnon state
+under conditions of high excitation. This coherent state extends over long
+distances and described by a spatially inhomogeneous amplitude and a
+homogeneous precession phase.",2104.14804v1
+2021-06-03,Magnon spin transport around the compensation magnetic field in easy-plane antiferromagnetic insulators,"In this work, we theoretically study the magnon spin transport in easy-plane
+antiferromagnetic insulators in the presence of an in-plane magnetic field. By
+exactly calculating the magnon spectrum, we find the band splitting due to the
+magnetic anisotropy can be fully compensated by the external field at a
+particular strength, which makes its dynamics nearly equivalent to an easy-axis
+antiferromagnet. As a result, the intrinsic magnon spin Hall effect due to the
+dipole-dipole interaction, previously predicted in easy-axis antiferromagnets
+is activated in easy-plane antiferromagnets. The compensation feature also
+allows the field control of magnon spin lifetime and hence the spin diffusion
+length. The compensation feature is robust against the biaxial anisotropy.",2106.02178v1
+2021-07-14,Transitionless quantum driving in spin echo,"Spin echo can be used to refocus random dynamical phases caused by
+inhomogeneities in control fields and thereby retain the purity of a spatial
+distribution of quantum spins. This technique for accurate spin control is an
+essential ingredient in many applications, such as nuclear magnetic resonance,
+magnetic resonance imaging, and quantum information processing. Here, we show
+how all the elements of a spin echo sequence can be performed at high speed by
+means of transitionsless quantum driving. This technique promises accurate
+control of rapid quantum spin evolution. We apply the scheme to universal
+nonadiabatic geometric single- and two-qubit gates in a nuclear magnetic
+resonance setting.",2107.06598v2
+2021-11-30,Global weak solutions for the Landau-Lifshitz-Gilbert-Vlasov-Maxwell system coupled via emergent electromagnetic fields,"Motivated by recent models of current driven magnetization dynamics, we
+examine the coupling of the Landau-Lifshitz-Gilbert equation and classical
+electron transport governed by the Vlasov-Maxwell system. The interaction is
+based on space-time gyro-coupling in the form of emergent electromagnetic
+fields of quantized helicity that add up to the conventional Maxwell fields. We
+construct global weak solutions of the coupled system in the framework of
+frustrated magnets with competing first and second order gradient interactions
+known to host topological solitons such as magnetic skyrmions and hopfions.",2111.15482v1
+2021-12-20,Thermal Coherence of Heisenberg Model With Dipole Interaction and Magnetic External Field,"The dynamics of coherence in a two-qubit Heisenberg XXX model with magnetic
+field in the presence of the intrinsic decoherence is investigated. We discuss
+the influence of dipole parameter, spin distance, magnetic field and initial
+state parameter on coherence of the long time limit situation. Then, we discuss
+how decoherence changes with time with the initial state parameter and the
+decoherence parameter.",2112.10341v1
+2021-12-30,Estimations and scaling laws for stellar magnetic fields,"In rapidly rotating turbulence (Rossby number much less than unity), the
+standard mixing length theory for turbulent convection breaks and Coriolis
+force enters the force balance such that magnetic field eventually depends on
+rotation. By simplifying the self-sustained magnetohydrodynamics dynamo
+equations of electrically conducting fluid motion, with the aid of theory of
+isotropic non-rotating or anisotropic rotating turbulence driven by thermal
+convection, we make estimations and derive scaling laws for stellar magnetic
+fields with slow and fast rotation. Our scaling laws are in good agreement with
+the observations.",2112.15103v3
+2022-03-10,Study of the Kramers-Fokker-Planck quadratic operator with a constant magnetic field,"We study the quadratic Kramers-Fokker-Planck operator with a constant
+magnetic field and with a quadratic potential. We describe the exact expression
+of the norm of the semi-group associated to the operator near the equilibrium.
+At this level, explicit and accurate estimates of this norm are shown in small
+and long times as well as uniform-in-time estimates when the magnetic parameter
+$b$ tends to infinity.",2203.05273v1
+2022-05-28,Magnetoclinicity Instability,"In strongly compressible magnetohydrodynamic turbulence, obliqueness between
+the large-scale density gradient and magnetic field gives an electromotive
+force mediated by density variance (intensity of density fluctuation). This
+effect is named ``magnetoclinicity'', and is expected to play an important role
+in large-scale magnetic-field generation in astrophysical compressible
+turbulent flows. Analysis of large-scale instability due to the
+magnetoclinicity effect shows that the mean magnetic-field perturbation is
+destabilised at large scales in the vicinity of strong mean density gradient in
+the presence of density variance.",2205.14453v1
+2022-06-15,Twisted light affects ultrafast demagnetization,"Irradiation with an ultrashort laser pulse can completely destroy the
+magnetic order of ferromagnetic thin films on the femtosecond timescale. This
+phenomenon holds great potential for ultrafast spintronics and information
+processing and is an active field of research. It is still an open question if
+the angular momentum of light can support this effect. While it has been shown
+that the spin of light only has a negligible influence, we experimentally
+demonstrate the influence of ultrashort laser pulses with orbital angular
+momentum (OAM) on the magnetization dynamics of a thin nickel film. Our results
+reveal that the photonic OAM affects the demagnetization behavior within the
+first hundreds of femtoseconds depending on the handedness of the OAM with
+respect to the direction of the sample magnetization.",2206.07502v1
+2022-06-28,Meaning of the splitting process for the transition to self-sustained turbulence in a magnetized cylindrical plasma,"When turbulent structures split more frequently before they decay, persistent
+turbulence forms in neutral fluid shear flows. Whether this concept can be
+extended to linear magnetized plasmas is investigated here and compared to the
+behavior of the pipe flow. With increasing control parameter the dynamics in
+the magnetized plasmas is known to undergo several changes from a quasiperiodic
+to a phase locked to a weakly turbulent regime. When the phase-locked regime
+breaks down, the splitting time approaches the decreasing lifetime reflecting
+self-sustained turbulence, as known from the pipe flow.",2206.14038v1
+2022-07-26,Rectification of the spin Seebeck current in noncollinear antiferromagnets,"In the absence of an external magnetic field and a spin-polarized charge
+current, an antiferromagnetic system supports two degenerate magnon modes. An
+applied thermal bias activates the magnetic dynamics, leading to a magnon flow
+from the hot to the cold edge (magnonic spin Seebeck current). Both degenerate
+bands contribute to the magnon current but the orientations of the magnetic
+moments underlying the magnons are opposite in different bands. Therefore,
+while the magnon current is nonzero, the net spin current is zero.",2207.12890v1
+2022-10-05,Nonlinear effective dynamics of Brownian particle in magnetized plasma,"An effective description is presented for a Brownian particle in a magnetized
+plasma. In order to systematically capture various corrections to linear
+Langevin equation, we construct effective action for the Brownian particle, to
+quartic order in its position. The effective action is first derived within
+non-equilibrium effective field theory formalism, and then confirmed via a
+microscopic holographic model consisting of an open string probing magnetic
+AdS$_5$ black brane. For practical usage, the non-Gaussian effective action is
+converted into Fokker-Planck type equation, which is an Euclidean analog of
+Schr$\ddot{\rm o}$dinger equation and describes time evolution of probability
+distribution for particle's position and velocity.",2210.02274v1
+2022-10-28,Magnetorheological Axisymmetric Actuator with Permanent Magnet,"This study examines the concept of axisymmetric actuator based on the
+magnetorheological membrane, electromagnet and permanent magnet. The
+construction of the actuator enables its application in wide range of practical
+devices like pumping, loudspeaker or varying-stiffness button. This work will
+highlight its working principle especially the influence of permanent magnet.
+Furthermore, the model of devices will be defined relaying on the Hammerstein
+model. To show the properties of the actuator and to perform the model
+identification, the set of experiments was run taking into account static and
+dynamic working conditions.",2210.15968v1
+2022-12-02,Energy pathways in large- and small-scale convection-driven dynamos,"We investigate the energy pathways between the velocity and the magnetic
+fields in a rotating plane layer dynamo driven by Rayleigh-B\'enard convection
+using direct numerical simulations. The kinetic and magnetic energies are
+divided into mean and turbulent components to study the production, transport,
+and dissipation associated with large and small-scale dynamos. This energy
+balance-based characterization reveals distinct mechanisms for large- and
+small-scale magnetic field generation in dynamos, depending on the nature of
+the velocity field and the conditions imposed at the boundaries.",2212.00969v2
+2023-02-14,Particle and guiding-center orbits in crossed electric and magnetic fields,"The problem of the charged-particle motion in crossed electric and magnetic
+fields is investigated, and the validity of the guiding-center representation
+is assessed in comparison with the exact particle dynamics. While the magnetic
+field is considered to be straight and uniform, the (perpendicular) radial
+electric field is nonuniform. The Hamiltonian guiding-center theory of
+charged-particle motion is presented for arbitrary radial electric fields, and
+explicit examples are provided for the case of a linear radial electric field.",2302.07119v2
+2023-03-06,On the topology of the magnetic lines of solutions of the MHD equations,"We construct examples of smooth periodic solutions to the Magnetohydrodynamic
+equations in dimension 2 with positive resistivity for which the topology of
+the magnetic lines changes under the flow. By Alfv\'en's theorem this is known
+to be impossible in the ideal case (resistivity = 0). In the resistive case the
+reconnection of the magnetic lines is known to occur and has deep physical
+implications, being responsible for many dynamic phenomena in astrophysics. The
+construction is a simplified proof of [3] and in addition we consider the case
+of the forced system.",2303.02999v1
+2023-03-07,Four-thirds law of energy and magnetic helicity in electron and Hall magnetohydrodynamic fluids,"In this paper, by exploiting the feature of the Hall term, we establish some
+local version four-thirds laws for the dissipation rates of energy and magnetic
+helicity in both electron and Hall magnetohydrodynamic equations in the sense
+of Duchon-Robert type. New 4/3 laws for the dissipation rates of magnetic
+helicity in these systems are first observed and four-thirds law involving the
+dissipation rates of energy for the Hall magnetohydrodynamic equations
+generalizes the work of Galtier.",2303.04290v1
+2023-04-19,Regions without flux surfaces of given class for magnetic fields in toroidal geometry,"A Converse KAM method for 3D vector fields, establishing regions through
+which pass no invariant 2-tori transverse to a given direction field, is tested
+on some helical perturbations of an axisymmetric magnetic field in toroidal
+geometry. It finds regions corresponding to magnetic islands and chaos for the
+fieldline flow. Minimization of these regions is proposed as a tool to help in
+the design of plasma confinement devices of tokamak and stellarator type.",2304.09613v3
+2023-07-10,Coexistence of self-similar and anomalous scalings in turbulent small-scale solar magnetic fields,"We report an evidence that self-similar and anomalous scalings coexist in a
+turbulent medium, particularly in fluctuations of the magnetic field flux
+density in magnetized plasma of the solar photosphere. The structure function
+scaling exponents in the inertial range have been analyzed for fluctuations
+grouped according to the sign of the path-dependent stochastic entropy
+production. It is found that the scaling exponents for fluctuations with the
+positive entropy production follow the phenological linear dependence for the
+magnetohydrodynamic turbulence. For fluctuations with the negative entropy
+production, the scaling is anomalous.",2307.04703v1
+2023-07-13,Chiral magnetovortical instability,"We demonstrate that in a chiral plasma subject to an external magnetic field,
+the chiral vortical effect can induce a new type of magnetohydrodynamic
+instability which we refer to as the {\it chiral magnetovortical instability}.
+This instability arises from the mutual evolution of the magnetic and vortical
+fields. It can cause a rapid amplification of the magnetic fields by
+transferring the chirality of the constituent particles to the cross helicity
+of the plasma.",2307.06746v1
+2023-07-18,"Propagation of Coupled Acoustic, Electromagnetic and Spin Waves in Saturated Ferromagnetoelastic Solids","We study the propagation of plane waves in an unbounded body of a saturated
+ferromagnetoelastic solid. The equations by Tiersten for small fields
+superposed on finite initial fields in a saturated ferromagnetoelastic material
+are employed, with their quasistatic magnetic field extended to dynamic
+electric and magnetic fields for electromagnetic waves. Dispersion relations of
+the plane waves are obtained. The cutoff frequencies and long wave
+approximation of the dispersion curves are determined. Results show that
+acoustic, electromagnetic and magnetic spin waves are coupled in such a
+material. For YIG which is a cubic crystal without piezoelectric coupling, the
+acoustic and electromagnetic waves are not directly coupled but they can still
+interact indirectly through spin waves.",2307.09171v1
+2023-07-27,Newton's Off-Center Circular Orbits and the Magnetic Monopole,"Introducing a radially dependent magnetic field into Newton's off-center
+circular orbits potential so as to preserve the $E=0$ dynamical symmetry leads
+to a unique choice of field that can be identified as the inclusion of a
+magnetic monopole in the inverse stereographically projected problem. One finds
+also a phenomenological correspondence with that of the linearly damped Kepler
+model. The presence of the monopole field deforms the symmetry algebra by a
+central extension, and the quantum mechanical version of this algebra reveals a
+number of zero modes equal to that counted using the index theorem of elliptic
+operators.",2307.15222v2
+2023-09-01,Multichannel quantum defect theory with a frame transformation for ultracold molecular collisions in magnetic fields,"We extend the powerful formalism of multichannel quantum defect theory
+combined with a frame transformation (MQDT-FT) to ultracold molecular
+collisions in magnetic fields. By solving the coupled-channel equations with
+hyperfine and Zeeman interactions omitted at short range, MQDT-FT enables a
+drastically simplified description of the intricate quantum dynamics of
+ultracold molecular collisions in terms of a small number of short-range
+parameters. We apply the formalism to ultracold Mg + NH collisions in a
+magnetic field, achieving a 10$^4$-fold reduction in computational effort.",2309.00263v1
+2023-09-18,Tuning domain wall oscillation frequency in bent nanowires through a mechanical analogy,"In this work, we present a theoretical model for domain wall (DW)
+oscillations in a curved magnetic nanowire with a constant curvature under the
+action of a uniaxial magnetic field. Our results show that the DW dynamics can
+be described as that of the mechanical pendulum, and both the NW curvature and
+the external magnetic field influence its oscillatory frequency. A comparison
+between our theoretical approach and experimental data in the literature shows
+an excellent agreement. The results presented here can be used to design
+devices demanding the proper control of the DW oscillatory motion in NWs.",2309.10051v1
+2023-10-22,Suppressing Rayleigh-Plateau Instability with a Magnetic Force Field for Deformable Interfaces Engineering,"The Rayleigh-Plateau instability (RPI) is a classical hydrodynamics
+phenomenon that prevents a jet of liquid to flow indefinitely within air or
+another liquid. Here, we show how adding a magnetic force field makes possible
+its suppression. Enclosing the jet in a ferrofluid held by magnetic forces
+allows flow focusing without sheath flow, which completely avoids dripping
+failure at small flow rates and provides conditional stability for a continuous
+fluid jet. Highly deformable liquid interfaces withstanding spatial and time
+varying flow conditions within a large parameter space can be realized.",2310.14280v1
+2023-10-25,Variational Gaussian approximation for the magnetic Schrödinger equation,"In the present paper we consider the semiclassical magnetic Schr\""odinger
+equation, which describes the dynamics of particles under the influence of a
+magnetic field. The solution of the time-dependent Schr\""odinger equation is
+approximated by a single Gaussian wave packet via the time-dependent
+Dirac--Frenkel variational principle. For the approximation we derive ordinary
+differential equations of motion for the parameters of the variational
+solution. Moreover, we prove $L^2$-error bounds and observable error bounds for
+the approximating Gaussian wave packet.",2310.16734v1
+2023-10-31,Annihilation of electroweak dumbbells,"We study the annihilation of electroweak dumbbells and the dependence of
+their dynamics on initial dumbbell length and twist. Untwisted dumbbells decay
+rapidly while maximally twisted dumbbells collapse to form a compact
+sphaleron-like object, before decaying into radiation. The decay products of a
+dumbbell include electromagnetic magnetic fields with energy that is a few
+percent of the initial energy. The magnetic field from the decay of twisted
+dumbbells carries magnetic helicity with magnitude that depends on the twist,
+and handedness that depends on the decay pathway.",2311.00026v1
+2023-12-03,Thermally Averaged Magnetic Anisotropy Tensors via Machine Learning Based on Gaussian Moments,"We propose a machine learning method to model molecular tensorial quantities,
+namely the magnetic anisotropy tensor, based on the Gaussian-moment
+neural-network approach. We demonstrate that the proposed methodology can
+achieve an accuracy of 0.3--0.4 cm$^{-1}$ and has excellent generalization
+capability for out-of-sample configurations. Moreover, in combination with
+machine-learned interatomic potential energies based on Gaussian moments, our
+approach can be applied to study the dynamic behavior of magnetic anisotropy
+tensors and provide a unique insight into spin-phonon relaxation.",2312.01415v1
+2023-12-11,A local study of dynamo action driven by precession,"We demonstrate an efficient magnetic dynamo due to precession-driven
+hydrodynamic turbulence in the local model. Dynamo growth rate increases with
+Poincar\'{e} and magnetic Prandtl numbers. Spectral analysis shows that the
+dynamo acts over a broad range of scales: at large (system size) and
+intermediate scales it is driven by 2D vortices and shear of the background
+precessional flow, while at smaller scales it is mainly driven by 3D inertial
+waves. These results are important for understanding magnetic field generation
+and amplification in precessing planets and stars.",2312.06835v1
+2023-12-14,Magnetic Taylor-Proudman constraint explains the flow into Tangent Cylinders,"Our understanding of planetary dynamos and liquid cores relies on the
+existence of a Tangent Cylinder (TC). This imaginary surface that physically
+separates polar and equatorial regions stems from Taylor-Proudman's Constraint
+(TPC) due to planetary rotation only. Here we establish mathematically and
+verify experimentally that a magnetic field aligned with the rotation incurs a
+flow \emph{into} the TC, linked to the flow along it by a \emph{magnetic} TPC.
+This constraint sheds new light on flows in planetary cores and flows subject
+to both magnetic fields and rotation in general.",2312.08840v1
+2023-12-25,Fermion-antifermion pairs in Bonnor-Melvin magnetic space-time with non-zero cosmological constant,"We study the relativistic dynamics of fermion-antifermion pairs in the
+Bonnor-Melvin magnetic (BMM) spacetime in non-zero cosmology. We focus on the
+$(1+2)$-dimensional cylindrically symmetric BMM-spacetime background. Within
+the context of such a magnetized universe, we rigorously investigate the
+fully-covariant two-body Dirac equation. We derive the corresponding radial
+part of the equation and obtain an exact closed form analytical solution for
+the problem at hand. Moreover, we report some intriguing parallels with
+relativistic and non-relativistic quantum oscillators in flat spaces. Notably,
+our findings suggest a compelling correlation between the cosmological constant
+and the energy spectrum of fermion-antifermion systems, hinting at profound
+connections between quantum realms and cosmology.",2401.02441v1
+2024-01-16,Singular vortex pairs follow magnetic geodesics,"We consider pairs of point vortices having circulations $\Gamma_1$ and
+$\Gamma_2$ and confined to a two-dimensional surface $S$. In the limit of zero
+initial separation $\varepsilon$, we prove that they follow a magnetic geodesic
+in unison, if properly renormalized. Specifically, the ``singular vortex pair""
+moves as a single charged particle on the surface with a charge of order
+$1/\varepsilon^2$ in a magnetic field $B$ which is everywhere normal to the
+surface and of strength $|B|=\Gamma_1 +\Gamma_2$. In the case
+$\Gamma_1=-\Gamma_2$, this gives another proof of Kimura's conjecture (Kimura
+1999) that singular dipoles follow geodesics.",2401.08512v1
+2024-01-30,Coherent and dissipative coupling in a magneto-mechanical system,"Hybrid elastic and spin waves hold promises for energy-efficient and
+versatile generation and detection of magnetic signals, with potentially long
+coherence times. Here we report on the combined elastic and magnetic dynamics
+in a one-dimensional magneto-mechanical crystal composed of an array of
+magnetic nanowires. Phononic and magnonic modes are impulsively excited by an
+optical ultrafast trigger and their decay is monitored by time resolved Magneto
+Optical Kerr Effect, with complementary Brillouin Light Scattering measurements
+and micromagnetic simulations. The strength and degree of mixing of coherent
+and dissipative coupling of the quasi-particles is determined quantitatively.",2401.16994v1
+2024-02-01,Investigating the magnetism of Ni from a momentum space perspective,"For more than three decades, clear discrepancies have existed between spin
+densities in momentum space revealed by Magnetic Compton scattering experiments
+and theoretical calculations based on density functional theory (DFT). Here by
+making a wide comparison between different theoretical methods, including DFT,
+DFT combined with dynamical mean field theory, and Hedin's $GW$ approximation,
+we discover how the magnetic Compton profiles of Ni can be predicted remarkably
+well. We find that the essential ingredients missing in DFT are (i) local spin
+fluctuations and (ii) a non-local treatment of electron correlations.",2402.00799v1
+2024-03-04,Carroll Strings with an Extended Symmetry Algebra,"Starting from the Polyakov action we consider two distinct Carroll limits in
+target space, keeping the string worldsheet relativistic. The resulting
+magnetic and chiral Carroll string models exhibit different symmetries and
+dynamics. Both models have an infinite dimensional symmetry algebra with
+Carroll symmetry included in a finite dimensional subalgebra. For the magnetic
+model, this is the so-called string Carroll algebra. The chiral model realises
+an extended version of the string Carroll algebra. The magnetic model does not
+have any transverse string excitations. The chiral model is less restrictive
+and includes arbitrary left-moving modes that carry transverse momentum but do
+not contribute to the energy in target space.",2403.01984v1
+2024-03-04,All-optical control of skyrmion configuration in CrI$_3$ monolayer,"The potential for manipulating characteristics of skyrmions in a CrI$_3$
+monolayer using circularly polarised light is explored. The effective
+skyrmion-light interaction is mediated by bright excitons whose magnetization
+is selectively influenced by the polarization of photons. The light-induced
+skyrmion dynamics is illustrated by the dependencies of the skyrmion size and
+the skyrmion lifetime on the intensity and polarization of the incident light
+pulse. Two-dimensional magnets hosting excitons thus represent a promising
+platform for the control of topological magnetic structures by light.",2403.02223v1
+2024-03-18,Nonlinear Pulse Dynamics in a Magnetized and Nonextensive Quark-Gluon Plasma,"We investigate the propagation of nonlinear energy density waves in a
+nonextensive quark-gluon plasma under the influence of a magnetic field using
+the reductive perturbation technique. For a nonextensive MIT bag equation of
+state, we obtain the governing equation for the first order perturbation of the
+energy density. We observe that an increase in the strength of the magnetic
+field results in the localization of the waves.",2403.11630v1
+2024-03-28,Gyrokinetic limit of the 2D Hartree equation in a large magnetic field,"We study the dynamics of two-dimensional interacting fermions submitted to a
+homogeneous transverse magnetic field. We consider a large magnetic field
+regime, with the gap between Landau levels set to the same order as that of
+potential energy contributions. Within the mean-field approximation, i.e.
+starting from Hartree's equation for the first reduced density matrix, we
+derive a drift equation for the particle density. We use vortex coherent states
+and the associated Husimi function to define a semi-classical density almost
+satisfying the limiting equation. We then deduce convergence of the density of
+the true Hartree solution by a Dobrushin-type stability estimate for the
+limiting equation.",2403.19226v1
+2013-04-01,Two Dimensional Incommensurate and Three Dimensional Commensurate Magnetic Order and Fluctuations in $La_{2-x}Ba_{x}CuO_{4}$,"We present neutron scattering measurements on single crystals of lightly
+doped $La_{2-x}Ba_{x}CuO_{4}$, with $0 \leq x \leq? 0.035$. These reveal the
+evolution of the magnetism in this prototypical doped Mott insulator from a
+three dimensional (3D) commensurate (C) antiferromagnetic ground state, which
+orders at a relatively high TN, to a two dimensional (2D) incommensurate (IC)
+ground state with finite ranged static correlations, which appear below a
+relatively low effective TN. At low temperatures, the 2D IC magnetism co-exists
+with the 3D C magnetism for doping concentrations as low as ? 0.0125. We find
+no signal of a 3D C magnetic ground state by x $\sim$? 0.025, consistent with
+the upper limit of x $\sim$? 0.02 observed in the sister family of doped Mott
+insulators, $La_{2-x}Sr_{x}CuO_{4}$. The 2D IC ground states observed for
+$0.0125 \leq x \leq 0.035$ are diagonal, and are rotated by 45 degrees within
+the orthorhombic basal plane compared with those previously reported for
+samples with superconducting ground states: $La_{2-x}Ba_{x}CuO_{4}$, with $0.05
+\leq? x \leq? 0.095. We construct a phase diagram based solely on magnetic
+order parameter measurements, which displays much of the complexity of standard
+high temperature superconductivity phase diagrams discussed in the literature.
+Analysis of high energy-resolution inelastic neutron scattering at moderately
+low temperatures shows a progressive depletion of the very low energy dynamic
+magnetic susceptibility as x increases from 0.0125 to 0.035. This low energy,
+dynamic susceptibility falls off? with increasing temperature on a scale much
+higher than the effective 2D IC TN appropriate to these materials. Appreciable
+dynamic 2D IC magnetic fluctuations inhabit much of the ""pseudogap"" regime of
+the phase diagram.",1304.0362v1
+2013-04-02,Modeling Multi-Magnet Networks Interacting Via Spin Currents,"The significant experimental advances of the last few decades in dealing with
+the interaction of spin currents and nanomagnets, at the device level, has
+allowed envisioning a broad class of devices that propose to implement
+information processing using spin currents and nanomagnets. To analyze such
+spin-magnet logic circuits, in general, we have developed a coupled
+spin-transport/ magnetization-dynamics simulation framework that could be
+broadly applicable to various classes of spin-valve/ spin-torque devices.
+Indeed, the primary purpose of this chapter is to describe in detail, the
+overall approach we have developed to include a description of spin transport
+coupled with magnetization dynamics and to show how it was benchmarked against
+available data on experiments.
+  We address non-collinear spin-transport in Section-2 using a lumped
+""4-component spin-circuit formalism"" that describes the interaction of
+non-collinear magnets (required for modeling spin torque), by computing
+4-component currents and voltages at every node of a ""circuit"". For modeling
+the magnetization dynamics, we use the standard Landau-Lifshitz-Gilbert (LLG)
+equation with the Slonczewski and the field-like terms included for spin
+torque. Section-3 describes how this LLG model is coupled with the spin
+transport model to analyze spin-torque experiments and spin-magnet circuits in
+general.
+  We include MATLAB codes in the Appendix to facilitate a ""hands-on""
+understanding of our model and hope it will enable interested readers to
+conveniently analyze their own experiments, develop a deeper insight into
+spin-magnet circuits or come up with their own creative designs.",1304.0742v3
+2013-05-09,Flux emergence in a magnetized convection zone,"We study the influence of a dynamo magnetic field on the buoyant rise and
+emergence of twisted magnetic flux-ropes, and their influence on the global
+external magnetic field. We ran 3D MHD numerical simulations using the ASH code
+and analysed the dynamical evolution of such buoyant flux-ropes from the bottom
+of the convection zone until the post-emergence phases. The global nature of
+this model represents very crudely and inaccurately the local dynamics of the
+buoyant rise, but allows to study the influence of global effects such as
+self-consistently generated differential rotation, meridional circulation and
+Coriolis forces. Although motivated by the solar context, this model cannot be
+thought of as a realistic model of the rise of magnetic structures and their
+emergence in the Sun where the local dynamics are completely different. The
+properties of initial phases of the buoyant rise in good agreement with
+previous studies. However, the effects of the interaction of the background
+dynamo field become increase as the flux-ropes evolve. During the buoyant rise
+across the CZ, the flux-rope's magnetic field strength and scales as $rho^a$,
+with $a\lesssim 1$. An increase of velocity, density and current precedes flux
+emergence at all longitudes. The geometry, latitude and relative orientation of
+the flux-ropes with respect to the background magnetic field influences the
+rise speeds, zonal flow amplitudes (which develop within the flux-ropes) and
+the corresponding surface signatures. This influences the morphology, duration
+and amplitude of the associated surface shearing and Poynting flux. The emerged
+flux influences the system's global polarity, leading in some cases to a
+polarity reversal while inhibiting background dynamo from doing so in some
+others. The emerged magnetic flux is slowly advected poleward, while being
+diffused and assimilated by the background dynamo field.",1305.2159v1
+2014-07-08,Effect of divalent Ba cation substitution with Sr on coupled multiglass state in the magnetoelectric multiferroic compound Ba3NbFe3Si2O14,"(Ba/Sr)3NbFe3Si2O14 is a magnetoelectric multiferroic with an incommensurate
+antiferromagnetic spiral magnetic structure which induces electric polarization
+at 26 K. The structure, as revealed by x-rays and neutrons, as well as static
+and dynamic magnetic and dielectric properties of these compounds have been
+studied down to 6 K under different conditions. Both the compounds have similar
+crystal structure but with different lattice constants down to 6 K. The Ba-and
+Sr-compounds exhibit a transition at 26 K and 25 K respectively, as indicated
+by the specific heat capacity and dc specific magnetization, into an
+antiferromagnetic state. Although Ba and Sr are isovalent, they exhibit very
+different static and dynamic magnetic behavior. The Ba-compound exhibits both
+thermal and magnetic field hysteresis with the thermal hysteresis decreasing
+with increasing magnetic field, a behavior typical of glasses. The glassy
+behavior is also clearly seen in the ac susceptibility studies which show a
+dispersive peak in the range 40 K to 90 K in the frequency range 10^1 Hz to
+10^4 Hz. The dispersive behavior follows a cluster glass critical slowing
+dynamics with a freezing temperature of 35 K and a critical exponent of 3.9, a
+value close to the 3-D Ising model. The Sr-compound however does not exhibit
+any dispersive behavior except for the invariant transition at 25 K in ac
+susceptibility with no magnetic field hysteresis at all temperatures. The
+dielectric constant studied in the frequency range 10^1 Hz to 10^6 Hz also
+reflects the magnetic behavior of the two compounds. The Ba-compound has two
+distinct dispersive peaks near TN and in the range 40 K to 125 K while the
+Sr-compound has a single dispersive peak in the range 40 K to 80 K. The
+activation energy of the high temperature dispersive peak in both compounds
+however is found to be similar, 71 meV and 65 meV respectively for Ba- and
+Sr-compounds.",1407.2049v1
+2018-10-09,Cluster spin-glass behaviour and memory effect in Cr$_{0.5}$Fe$_{0.5}$Ga,"We report the structural, static, and dynamic properties of
+Cr$_{0.5}$Fe$_{0.5}$Ga by means of powder x-ray diffraction, magnetization,
+heat capacity, magnetic relaxation, and magnetic memory effect measurements. DC
+magnetization and AC susceptibility studies reveal a spin-glass transition at
+around $T_{\rm f} \simeq 22$~K. An intermediate value of the relative shift in
+freezing temperature $\delta T_{\rm f} \simeq 0.017$, obtained from the AC
+susceptibility data reflects the formation of cluster spin-glass states. The
+frequency dependence of $T_{\rm f}$ is also analyzed within the framework of
+dynamic scaling laws. The analysis using power law yields a time constant for a
+single spin flip $\tau* \simeq 1.1\times10^{-10}$~s and critical exponent
+$z\nu^{\prime}=4.2\pm0.2$. On the other hand, the Vogel-Fulcher (VF) law yields
+the time constant for a single spin flip $\tau_0 \simeq 6.6\times10^{-9}$~s, VF
+temperature $T_{\rm 0}=21.1\pm0.1$~K, and an activation energy $E_{\rm
+a}/k_{\rm B} \simeq 16$~K. The value of $\tau*$ and $\tau_0$ along with a
+non-zero value of $T_{\rm 0}$ provide further evidence for the cluster
+spin-glass behaviour. The magnetic field dependent $T_{\rm f}$ follows the de
+Almeida-Thouless line with a non-mean-field type instability, reflecting either
+a different universality class or strong anisotropy in the spin system. A
+detailed non-equilibrium dynamics study via relaxation and memory effect
+experiments demonstrates striking memory effects. All the above observations
+render a cluster spin-glass behaviour which is triggered by magnetic
+frustration due to competing antiferromagnetic and ferromagnetic interactions
+and magnetic site disorder. Moreover, the asymmetric response of magnetic
+relaxation with respect to the change in temperature, below $T_{\rm f}$ can be
+explained by the hierarchical model.",1810.03890v1
+2020-07-06,Magnetic field amplification in accretion discs around the first stars: implications for the primordial IMF,"Magnetic fields play an important role in the dynamics of present-day
+molecular clouds. Recent work has shown that magnetic fields are equally
+important for primordial clouds, which form the first stars in the Universe.
+While the primordial magnetic field strength on cosmic scales is largely
+unconstrained, theoretical models strongly suggest that a weak seed field
+existed in the early Universe. We study how the amplification of such a weak
+field can influence the evolution of accretion discs around first stars, and
+thus affect the primordial initial mass function (IMF). We perform a suite of
+3D ideal magneto-hydrodynamic (MHD) simulations with different initial field
+strengths and numerical resolutions. We find that, in simulations with
+sufficient spatial resolution to resolve the Jeans scale during the collapse,
+even initially weak magnetic fields grow exponentially to become dynamically
+important due to both the so-called 'small-scale turbulent dynamo' and the
+'large-scale mean-field dynamo'. Capturing the small-scale dynamo action
+depends primarily on how well we resolve the Jeans length, while capturing the
+large-scale dynamo depends on the Jeans resolution as well as the maximum
+absolute resolution. Provided enough resolution, we find that fragmentation
+does not depend strongly on the initial field strength, because even weak
+fields grow to become strong. However, fragmentation in runs with magnetic
+fields differs significantly from those without magnetic fields. We conclude
+that the development of dynamically strong magnetic fields during the formation
+of the first stars is likely inevitable, and that these fields had a
+significant impact on the primordial IMF.",2007.02678v2
+2021-01-22,Spin dynamics in NaFeAs and NaFe$_{0.53}$Cu$_{0.47}$As probed by resonant inelastic X-ray scattering,"The parent compounds of iron-based superconductors are magnetically-ordered
+bad metals, with superconductivity appearing near a putative magnetic quantum
+critical point. The presence of both Hubbard repulsion and Hund's coupling
+leads to rich physics in these multiorbital systems, and motivated descriptions
+of magnetism in terms of itinerant electrons or localized spins. The
+NaFe$_{1-x}$Cu$_x$As series consists of magnetically-ordered bad metal ($x=0$),
+superconducting ($x\approx0.02$) and magnetically-ordered
+semiconducing/insulating ($x\approx0.5$) phases, providing a platform to
+investigate the connection between superconductivity, magnetism and electronic
+correlations. Here we use X-ray absorption spectroscopy and resonant inelastic
+X-ray scattering to study the valence state of Fe and spin dynamics in two
+NaFe$_{1-x}$Cu$_x$As compounds ($x=0$ and 0.47). We find that magnetism in both
+compounds arises from Fe$^{2+}$ atoms, and exhibits underdamped dispersive spin
+waves in their respective ordered states. The dispersion of spin excitations in
+NaFe$_{0.53}$Cu$_{0.47}$As is consistent with being quasi-one-dimensional.
+Compared to NaFeAs, the band top of spin waves in NaFe$_{0.53}$Cu$_{0.47}$As is
+slightly softened with significantly more spectral weight of the spin
+excitations. Our results indicate the spin dynamics in
+NaFe$_{0.53}$Cu$_{0.47}$As arise from localized magnetic moments and suggest
+the iron-based superconductors are proximate to a correlated insulating state
+with localized iron moments.",2101.08948v1
+2022-11-07,Quantum-classical approach to spin and charge pumping and the ensuing radiation in THz spintronics: Example of ultrafast-light-driven Weyl antiferromagnet Mn$_3$Sn,"The interaction of fs light pulses with magnetic materials has been intensely
+studied for more than two decades in order to understand ultrafast
+demagnetization in single magnetic layers or THz emission from their bilayers
+with nonmagnetic spin-orbit (SO) materials. Here we develop a multiscale
+quantum-classical formalism -- where conduction electrons are described by
+quantum master equation of the Lindblad type; classical dynamics of local
+magnetization is described by the Landau-Lifshitz-Gilbert (LLG) equation; and
+incoming light is described by classical vector potential while outgoing
+electromagnetic radiation is computed using Jefimenko equations for retarded
+electric and magnetic fields -- and apply it a bilayer of antiferromagnetic
+Weyl semimetal Mn$_3$Sn with noncollinear local magnetization in contact with
+SO-coupled nonmagnetic material. Our QME+LLG+Jefimenko scheme makes it possible
+to understand how fs light pulse generates directly spin and charge pumping and
+electromagnetic radiation by the latter, including both odd and even high
+harmonics (of the pulse center frequency) up to order $n \le 7$. The directly
+pumped spin current then exert spin torque on local magnetization whose
+dynamics, in turn, pumps additional spin and charge currents radiating in the
+THz range. By switching on and off LLG dynamics and SO couplings, we unravel
+which microscopic mechanism contribute the most to emitted THz radiation --
+charge pumping by local magnetization of Mn$_3$Sn in the presence of its
+intrinsic SO coupling is far more important than standardly assumed (for other
+types of magnetic layers) spin pumping and subsequent spin-to-charge conversion
+within the neighboring nonmagnetic SO-coupled material.",2211.03645v3
+2019-05-14,Dynamics of an itinerant spin-3 atomic dipolar gas in an optical lattice,"Arrays of ultra-cold dipolar gases loaded in optical lattices are emerging as
+powerful quantum simulators of the many-body physics associated with the rich
+interplay between long-range dipolar interactions, contact interactions,
+motion, and quantum statistics. In this work we report on our investigation of
+the quantum many-body dynamics of a large ensemble of bosonic magnetic chromium
+atoms with spin S = 3 in a three-dimensional lattice as a function of lattice
+depth. Using extensive theory and experimental comparisons we study the
+dynamics of the population of the different Zeeman levels and the total
+magnetization of the gas across the superfluid to the Mott insulator
+transition. We are able to identify two distinct regimes: At low lattice
+depths, where atoms are in the superfluid regime, we observe that the spin
+dynamics is strongly determined by the competition between particle motion,
+onsite interactions and external magnetic field gradients. Contact spin
+dependent interactions help to stabilize the collective spin length, which sets
+the total magnetization of the gas. On the contrary, at high lattice depths,
+transport is largely frozen out. In this regime, while the spin populations are
+mainly driven by long range dipolar interactions, magnetic field gradients also
+play a major role in the total spin demagnetization. We find that dynamics at
+low lattice depth is qualitatively reproduced by mean-field calculations based
+on the Gutzwiller ansatz; on the contrary, only a beyond mean-field theory can
+account for the dynamics at large lattice depths. While the cross-over between
+these two regimes does not correspond to sharp features in the observed
+dynamical evolution of the spin components, our simulations indicate that it
+would be better revealed by measurements of the collective spin length.",1905.06123v1
+2020-09-22,Bethe strings in the dynamical structure factor of the spin-1/2 Heisenberg XXX chain,"Recently there has been a renewed interest in the spectra and role in
+dynamical properties of excited states of the spin-1/2 Heisenberg
+antiferromagnetic chain in longitudinal magnetic fields associated with Bethe
+strings. The latter are bound states of elementary magnetic excitations
+described by Bethe-ansatz complex non-real rapidities. Previous studies on this
+problem referred to finite-size systems. Here we consider the thermodynamic
+limit and study it for the isotropic spin-1/2 Heisenberg XXX chain in a
+longitudinal magnetic field. We confirm that also in that limit the most
+significant spectral weight contribution from Bethe strings leads to gapped
+continua in the spectra of the spin +- and xx dynamical structure factors. The
+contribution of Bethe strings to the zz dynamical structure factor is found to
+be small at low spin densities and to become negligible upon increasing that
+density above 0.317. For the -+ dynamical structure factor, that contribution
+is found to be negligible at finite magnetic field. We derive analytical
+expressions for the line shapes of the +-, xx, and zz dynamical structure
+factors valid in the vicinity of singularities located at and just above the
+gapped lower thresholds of the Bethe-string states's spectra. As a side result
+and in order to provide an overall physical picture that includes the relative
+location of all spectra with a significant amount of spectral weight, we
+revisit the general problem of the line-shape of the transverse and
+longitudinal spin dynamical structure factors at finite magnetic field and
+excitation energies in the vicinity of other singularities. This includes those
+located at and just above the lower thresholds of the spectra that stem from
+excited states described by only real Bethe-ansatz rapidities.",2009.10499v1
+2016-02-02,Carrier-impurity spin transfer dynamics in paramagnetic II-VI diluted magnetic semiconductors in the presence of a wave-vector-dependent magnetic field,"Quantum kinetic equations of motion for carrier and impurity spins in
+paramagnetic II-VI diluted magnetic semiconductors in a $\mathbf{k}$-dependent
+effective magnetic field are derived, where the carrier-impurity correlations
+are taken into account. In the Markov limit, rates for the electron-impurity
+spin transfer can be derived for electron spins parallel and perpendicular to
+the impurity spins corresponding to measurable decay rates in Kerr experiments
+in Faraday and Voigt geometry. Our rigorous microscopic quantum kinetic
+treatment automatically accounts for the fact that, in an individual spin
+flip-flop scattering process, a spin flip of an electron is necessarily
+accompanied by a flop of an impurity spin in the opposite direction and the
+corresponding change of the impurity Zeeman energy influences the final energy
+of the electron after the scattering event. This shift in the electron energies
+after a spin flip-flop scattering processes, which usually has been overlooked
+in the literature, turns out to be especially important in the case of
+extremely diluted magnetic semiconductors in an external magnetic field. As a
+specific example for a $\mathbf{k}$-dependent effective magnetic field the
+effects of a Rashba field on the dynamics of the carrier-impurity correlations
+in a Hg$_{1-x-y}$Cd$_y$Mn$_x$Te quantum well are described. It is found that,
+although accounting for the Rashba interaction in the dynamics of the
+correlations leads to a modified $\mathbf{k}$-space dynamics, the time
+evolution of the total carrier spin is not significantly influenced.
+Furthermore, a connection between the present theory and the description of
+collective carrier-impurity precession modes is presented.",1602.00911v2
+2019-09-06,Magnetically actuated artificial microswimmers as mobile microparticle manipulators,"Micro-scale swimming robots have been envisaged for many medical applications
+such as targeted drug delivery, where the microrobot will be expected to
+navigate in a fluid through channels carrying a payload. Alternatively, in many
+cases, such a payload does not have to be physically bound to the swimmer, but
+may be instead manipulated and steered through the channel by the microrobot.
+We investigate this problem of contactless manipulation of a microparticle by
+mobile microswimmer in a fluid at low Reynolds number. We consider a model of a
+magnetically actuated artificial microswimmer, whose locomotion through a fluid
+induces a disturbance velocity field in the fluid, that then acts to propel a
+cargo particle in its vicinity. The problem investigated in this paper is
+therefore one of coupled locomotion-manipulation of two bodies in a fluid. The
+magnetic swimmer's motion is actuated by an externally applied magnetic field
+of constant strength but whose direction rotates at a constant rate in a plane.
+The swimmer propels itself in the direction perpendicular to this plane if the
+frequency associated with the periodic magnetic field is above a critical
+frequency. Below this critical frequency, the swimmer tumbles in place without
+net locomotion. The coupled fluid-swimmer-cargo particle dynamics are solved
+numerically using the method of Stokesian dynamics. The induced motion of the
+cargo particle is shown to be controllable. This is achieved by switching the
+planes of rotation of the magnetic field and switching frequency of the
+magnetic field above and below the critical frequency. While a swimmer with a
+specific geometry has been used in the model, the results of this paper are
+applicable to swimmers with other geometries and means of propulsion. The
+results of this paper show that microswimmers can be utilized as mobile
+manipulators of microparticles in a fluid.",1909.05646v1
+2019-12-11,Robust cycloid crossover driven by anisotropy in the skyrmion host GaV$_\mathbf{4}$S$_\mathbf{8}$,"We report on the anomalous magnetization dynamics of the
+cycloidally-modulated spin textures under the influence of uniaxial anisotropy
+in multiferroic $\mathrm{GaV_4S_8}$. The temperature and field dependence of
+the linear ac susceptibility [$\chi_{1\omega}^{\prime}(T,H)$], ac magnetic loss
+[$\chi_{1\omega}^{\prime\prime}(T,H)$], and nonlinear ac magnetic response
+[$M_{3\omega}(T,H)$] are examined across the magnetic phase diagram in the
+frequency range $f = 10-10000$ Hz. According to recent theory, skyrmion
+vortices under axial crystal symmetry are confined along specific orientations,
+resulting in enhanced robustness against oblique magnetic fields and altered
+spin dynamics. We characterize the magnetic response of each spin texture and
+find that the dynamic rigidity of the N\'eel skyrmion lattice appears enhanced
+compared to Bloch-type skyrmions in cubic systems, even in the multidomain
+state. Anomalous $M_{3\omega}$ and strong dissipation emerge over the same
+phase regime where strong variations in the cycloid pitch were observed on
+lowering temperature in recent small-angle neutron scattering experiments
+[White et al., Phys. Rev. B 97, 020401(R) (2018)]. Here, we show that strong
+anisotropy also drives an extended crossover of the zero-field cycloid texture
+in $\mathrm{GaV_4S_8}$. The frequency dependence of these dynamic signatures is
+consistent with that of a robust anharmonic spin texture exhibiting a
+correlated domain arrangement. The results underpin the essential role of
+magnetic anisotropy in enhancing the rigidity of topological spin textures for
+diverse applications.",1912.05367v2
+2020-11-15,Adiabaticity of spin dynamics in diamond nitrogen vacancy centers in time-dependent magnetic fields,"We study the spin dynamics of diamond nitrogen vacancy (NV) centers in an
+oscillating magnetic field along the symmetry axis of the NV in the presence of
+transverse magnetic fields. It is well-known that the coupling between the
+otherwise degenerate Zeeman levels $|M_S=\pm1\rangle$ due to strain and
+electric fields is responsible for a Landau-Zener process near the
+pseudo-crossing of the adiabatic energy levels when the axial component of the
+oscillating magnetic field changes sign. We derive an effective two-level
+Hamiltonian for the NV system that includes coupling between the two levels via
+virtual transitions into the third far-detuned level $|M_S=0\rangle$ induced by
+transverse magnetic fields. This coupling adds to the coupling due to strain
+and electric fields, with a phase that depends on the direction of the
+transverse field in the plane perpendicular to the NV axis. Hence, the {\em
+total coupling} of the Zeeman levels can be tuned to control the adiabaticity
+of spin dynamics by fully or partially compensating the effect of the strain
+and electric fields, or by enhancing it. Moreover, by varying the strength and
+direction of the transverse magnetic fields, one can determine the strength and
+direction of the local strain and electric fields at the position of the NV
+center, and even the {\em external} stress and electric field. The nuclear spin
+hyperfine interaction is shown to introduce a nuclear spin dependent offset of
+the axial magnetic field for which the pseudo-crossing occurs, while the
+adiabaticity remains unaffected by the nuclear spin. If the NV center is
+coupled to the environment, modeled by a bath with a Gaussian white noise
+spectrum, as appropriate for NVs near the diamond surface, then the spin
+dynamics is accompanied by relaxation of the Zeeman level populations and
+decoherence with a non-monotonic decrease of the purity of the system.",2011.07609v3
+2022-10-26,Phase stability of Fe from first-principles: atomistic spin dynamics coupled with ab initio molecular dynamics simulations and thermodynamic integration,"The calculation of free energies from first principles in materials is a
+formidable task which enables the prediction of phase stability with high
+accuracy; these calculations are complicated in magnetic materials by the
+interplay of electronic, magnetic, and vibrational degrees of freedom. In this
+work, we show the feasibility and accuracy of the calculation of phase
+stability in magnetic systems with ab initio methods and thermodynamic
+integration by sampling the magnetic and vibrational phase space with coupled
+atomistic spin dynamics-ab initio molecular dynamics (ASD-AIMD) simulations
+[Stockem et al., PRL 121, 125902 (2018)], where energies and interatomic forces
+are calculated with density functional theory (DFT). We employ the method to
+calculate the phase stability of Fe at ambient pressure from 800 K up to 1800
+K. The Gibbs free energy difference between fcc and bcc Fe at zero pressure as
+a function of temperature is calculated carrying out thermodynamic integration
+over temperature on the energies at the DFT level from ASD-AIMD, using a
+reference free energy difference calculated in the paramagnetic state at
+temperatures much higher than the magnetic transition temperatures with
+thermodynamic integration over stress-strain variables with disordered local
+moment (DLM)-AIMD simulations. We show the importance of the magnetic ordering
+temperature of bcc Fe on the $\alpha$ to $\gamma$ structural transition
+temperature, whereas the $\gamma$ to $\delta$ transition is well reproduced
+independently of the exchange interactions. The Gibbs free energy difference
+between the two structures is within 5 meV/atom from the CALPHAD estimate, and
+both transition temperatures are reproduced within 150 K. The present work
+paves the way to free energy calculations in magnetic materials from first
+principles with accuracy in the order of 1 meV/atom.",2210.14718v2
+2024-03-01,Dichotomous Dynamics of Magnetic Monopole Fluids,"A recent advance in the study of emergent magnetic monopoles was the
+discovery that monopole motion is restricted to dynamical fractal trajectories
+(J. Hall\'en et al, Science 378, 1218 (2022)) thus explaining the
+characteristics of magnetic monopole noise spectra (Dusad, R. et al. Nature
+571, 234 (2019); Samarakoon, A. M. et al. Proc. Natl. Acad. Sci. 119,
+e2117453119 (2022)). Here we apply this new theory to explore the dynamics of
+field-driven monopole currents, finding them comprised of two quite distinct
+transport processes: initially swift fractal rearrangements of local monopole
+configurations followed by conventional monopole diffusion. This theory also
+predicts a characteristic frequency dependence of the dissipative loss-angle
+for AC-field-driven currents. To explore these novel perspectives on monopole
+transport, we introduce simultaneous monopole current control and measurement
+techniques using SQUID-based monopole current sensors. For the canonical
+material Dy2Ti2O7, we measure ${\Phi}(t)$, the time-dependence of magnetic flux
+threading the sample when a net monopole current $J(t) = \dot{\Phi}(t)/\mu_0$
+is generated by applying an external magnetic field $B_0(t)$. These experiments
+find a sharp dichotomy of monopole currents, separated by their distinct
+relaxation time-constants before and after $t \approx 600 {\mu}s$ from monopole
+current initiation. Application of sinusoidal magnetic fields $B_0(t) =
+Bcos({\omega}t)$ generates oscillating monopole currents whose loss angle
+${\theta}(f)$ exhibits a characteristic transition at frequency $f \approx 1.8$
+kHz over the same temperature range. Finally, the magnetic noise power is also
+dichotomic, diminishing sharply after $t \approx 600 {\mu}s$. This complex
+phenomenology represents a new form of heterogeneous dynamics generated by the
+interplay of fractionalization and local spin configurational symmetry.",2403.00726v1
+1999-06-28,Does magnetic pressure affect the ICM dynamics?,"A possible discrepancy found in the determination of mass from gravitational
+lensing data, and from X-rays observations, has been largely discussed in the
+latest years (for instance, Miralda-Escude & Babul (1995)). Another important
+discrepancy related to these data is that the dark matter is more centrally
+condensed than the X-ray-emitting gas, and also with respect to the galaxy
+distribution (Eyles et al. 1991). Could these discrepancies be consequence of
+the standard description of the ICM, in which it is assumed hydrostatic
+equilibrium maintained by thermal pressure? We follow the evolution of the ICM,
+considering a term of magnetic pressure, aiming at answering the question
+whether or not these discrepancies can be explained via non-thermal terms of
+pressure. Our results suggest that the magnetic pressure could only affect the
+dynamics of the ICM on scales as small as < 1kpc. Our models are constrained by
+the observations of large and small scale fields and we are successful at
+reproducing available data, for both Faraday rotation limits and inverse
+Compton limits for the magnetic fields. In our calculations the radius (from
+the cluster center) in which magnetic pressure reaches equipartition is smaller
+than radii derived in previous works, as a consequence of the more realistic
+treatment of the magnetic field geometry and the consideration of a sink term
+in the cooling flow.",9906453v2
+2001-05-18,Structure of Small-Scale Magnetic Fields in the Kinematic Dynamo Theory,"A weak fluctuating magnetic field embedded into a turbulent conducting medium
+grows exponentially while its characteristic scale decays. In the ISM and
+protogalactic plasmas, the magnetic Pr is very large, so a broad spectrum of
+growing magnetic fluctuations is excited at subviscous scales. We study the
+statistical correlations that are set up in the field pattern and show that the
+magnetic-field lines possess a folding structure, where most of the scale
+decrease is due to rapid transverse field direction reversals, while the scale
+of the field variation along itself stays approximately constant. Specifically,
+we find that the field strength and the field-line curvature are
+anticorrelated, and the curvature possesses a stationary limiting distribution
+with the bulk located at the values of curvature comparable to the
+characteristic wave number of the velocity field and a power tail extending to
+large values of curvature. The regions of large curvature, therefore, occupy
+only a small fraction of the total volume of the system. Our theoretical
+results are corroborated by direct numerical simulations. The implication of
+the folding effect is that the advent of the Lorentz back reaction occurs when
+the magnetic energy approaches that of the smallest turbulent eddies. Our
+results also directly apply to the problem of statistical geometry of the
+material lines in a random flow.",0105322v3
+2002-06-30,Self-Gravitating Magnetically-Supported Protostellar Disks and the Formation of Substellar Companions,"Isolated low-mass stars are formed, in the standard picture, from the
+collapse of dense cores condensed out of strongly magnetized molecular clouds.
+The dynamically collapsing inflow traps nearly half of the critical magnetic
+flux needed for the core support and deposits it in a small region surrounding
+the protostar. It has been argued previously that the deposited flux can slow
+down the inflow, allowing matter to pile up and settle along field lines into a
+magnetically supported, circumstellar disk. Here we show that the disk
+typically contains $\sim 10%$ of the stellar mass, and that it could become
+self-gravitating under plausible conditions during the rapidly accreting,
+``Class 0'' phase of star formation. Subsequent fragmentation of the
+self-gravitating, magnetically subcritical disk, driven by magnetic diffusion,
+could produce fragments of substellar masses, which collapse to form brown
+dwarfs and possibly massive planets. This scenario predicts substellar object
+formation at distances of order 100 AU from the central star, although orbital
+evolution is possible after formation. It may provide an explanation for the
+small, but growing, number of brown dwarf companions found around nearby stars
+by direct imaging. The relatively large formation distances make the substellar
+companions vulnerable to dynamic ejection, particularly in binary (multiple)
+systems and dense clusters. Those ejected may account for, at least in part,
+the isolated brown dwarfs and perhaps free-floating planetary mass objects.",0207014v1
+2003-04-28,Dynamics of magnetic flux tubes in close binary stars II. Nonlinear evolution and surface distributions,"Observations of magnetically active close binaries with orbital periods of a
+few days reveal the existence of starspots at preferred longitudes (with
+respect to the direction of the companion star). We numerically investigate the
+non-linear dynamics and evolution of magnetic flux tubes in the convection
+zoneof a fast-rotating component of a close binary system and explore whether
+the tidal effects are able to generate non-uniformities in the surface
+distribution of erupting flux tubes. Assuming a synchronised system with a
+rotation period of two days and consisting of two solar-type components, both
+the tidal force and the deviation of the stellar structure from spherical shape
+are considered in lowest-order perturbation theory. The magnetic field is
+initially stored in the form of toroidal magnetic flux rings within the stably
+stratified overshoot region beneath the convection zone. Once the field has
+grown sufficiently strong, instabilities initiate the formation of rising flux
+loops, which rise through the convection zone and emerge at the stellar
+surface. We find that although the magnitude of tidal effects is rather small,
+they nevertheless lead to the formation of clusters of flux tube eruptions at
+preferred longitudes on opposite sides of the star, which result from the
+cumulative and resonant character of the action of tidal effects on rising flux
+tubes. The longitude distribution of the clusters depends on the initial
+parameters of flux tubes in the overshoot region like magnetic field strength
+and latitude, implying that there is no globally unique preferred longitude
+along a fixed direction.",0304498v1
+2003-12-03,Ultra-Relativistic Magneto-Hydro-Dynamic Jets in the context of Gamma Ray Bursts,"We present a detailed numerical study of the dynamics and evolution of
+ultrarelativistic magnetohydrodynamic jets in the black hole-disk system under
+extreme magnetization conditions. We find that Lorentz factors of up to 3000
+are achieved and derived a modifiedMichel scaling (Gamma ~ sigma) which allows
+for a wide variation in the flow Lorentz factor. Pending contamination induced
+by mass-entrainment, the linear Michel scaling links modulations in the
+ultrarelativistic wind to variations in mass accretion in the disk for a given
+magnetization. The jet is asymptotically dominated by the toroidal magnetic
+field allowing for efficient collimation. We discuss our solutions (jets) in
+the context of Gamma ray bursts and describe the relevant features such as the
+high variability in the Lorentz factor and how high collimation angles (~ 0-5
+degrees), or cylindrical jets, can be achieved. We isolate a jet instability
+mechanism we refer to as the ""bottle-neck"" instability which essentially relies
+on a high magnetization and a recollimation of the magnetic flux surfaces. The
+instability occurs at large radii where any dissipation of the magnetic energy
+into radiation would in principle result in an optically thin emission.",0312090v1
+2004-08-24,Magnetorotational instability in protoplanetary discs,"We investigate the linear growth and vertical structure of the
+magnetorotational instability (MRI) in weakly ionised, stratified accretion
+discs. The magnetic field is initially vertical and dust grains are assumed to
+have settled towards the midplane, so charges are carried by electrons and ions
+only. Solutions are obtained at representative radial locations from the
+central protostar for different choices of the initial magnetic field strength,
+sources of ionisation, and disc surface density.
+  The MRI is active over a wide range of magnetic field strengths and fluid
+conditions in low conductivity discs. For the minimum-mass solar nebula model,
+incorporating cosmic ray ionisation, perturbations grow at 1 AU for B < 8 G.
+For a significant subset of these strengths (0.2 - 5 G), the growth rate is of
+order the ideal MHD rate (0.75 Omega). Similarly, when cosmic rays are assumed
+to be excluded from the disc by the winds emitted by the magnetically active
+protostar, unstable modes grow at this radius for B less than about 2 G.
+  This study shows that, despite the low magnetic coupling, the magnetic field
+is dynamically important for a large range of fluid conditions and field
+strengths in protostellar discs. Hall diffusion largely determines the
+structure and growth rate of these perturbations for all studied radii. At
+radii of order 1 AU, in particular, it is crucial to incorporate the full
+conductivity tensor in studies of the dynamics of astrophysical discs.
+(Abridged)",0408427v1
+1998-04-29,"Magnetic correlations and quantum criticality in the insulating antiferromagnetic, insulating spin liquid, renormalized Fermi liquid, and metallic antiferromagnetic phases of the Mott system V_2O_3","Magnetic correlations in all four phases of pure and doped vanadium
+sesquioxide V_2O_3 have been examined by magnetic thermal neutron scattering.
+While the antiferromagnetic insulator can be accounted for by a Heisenberg
+localized spin model, the long range order in the antiferromagnetic metal is an
+incommensurate spin-density-wave, resulting from a Fermi surface nesting
+instability. Spin dynamics in the strongly correlated metal are dominated by
+spin fluctuations in the Stoner electron-hole continuum. Furthermore, our
+results in metallic V_2O_3 represent an unprecedentedly complete
+characterization of the spin fluctuations near a metallic quantum critical
+point, and provide quantitative support for the SCR theory for itinerant
+antiferromagnets in the small moment limit. Dynamic magnetic correlations for
+energy smaller than k_BT in the paramagnetic insulator carry substantial
+magnetic spectral weight. However, the correlation length extends only to the
+nearest neighbor distance. The phase transition to the antiferromagnetic
+insulator introduces a sudden switching of magnetic correlations to a different
+spatial periodicity which indicates a sudden change in the underlying spin
+Hamiltonian. To describe this phase transition and also the unusual short range
+order in the paramagnetic state, it seems necessary to take into account the
+orbital degrees of freedom associated with the degenerate d-orbitals at the
+Fermi level in V_2O_3.",9804320v3
+2001-11-24,Static Correlation and Dynamical Properties of Tb3+-moments in Tb2Ti2O7 -Neutron Scattering Study-,"Static and dynamical properties of the magnetic moment system of pyrochlore
+compound Tb2Ti2O7 with strong magnetic frustration, have been investigated down
+to the temperature T=0.4 K by neutron scattering on a single crystal sample.
+The scattering vector (Q)-dependence of the magnetic scattering intensity
+becomes appreciable with decreasing T at around 30 K, indicating the
+development of the magnetic correlation. From the observed energy profiles, the
+elastic, quasi elastic and inelastic components have been separately obtained.
+The quasi elastic component corresponds to the diffusive motion of the magnetic
+moments within the lowest states, which are formed of the lowest energy levels
+of Tb3+ ions. Magnetic correlation pattern which can roughly reproduce the
+Q-dependence of the scattering intensities of the elastic and quasi elastic
+component is discussed based on the trial calculations for clusters of 7
+moments belonging to two corner-sharing tetrahedra. A possible origin of the
+glassy state, which develops at around 1.5 K with decreasing T is discussed.",0111466v3
+2005-08-18,Probing spin dynamics and quantum relaxation in LiY0.998Ho0.002F4 via 19F NMR,"We report measurements of 19F nuclear spin-lattice relaxation 1/T1 as a
+function of temperature and external magnetic field in LiY0.998Ho0.002F4 single
+crystal, a single-ion magnet exhibiting interesting quantum effects. The 19F
+1/T1 is found to depend on the coupling with the diluted rare-earth (RE)
+moments. Depending on the temperature range, a fast spin diffusion regime or a
+diffusion limited regime is encountered. In both cases we find it possible to
+use the 19F nucleus as a probe of the rare-earth spin dynamics. The results for
+1/T1 show a behavior similar to that observed in molecular nanomagnets, a
+result which we attribute to the discreteness of the energy levels in both
+cases. At intermediate temperatures the lifetime broadening of the crystal
+field split RE magnetic levels follows a T3 power law. At low temperature the
+field dependence of 1/T1 shows peaks in correspondence to the critical magnetic
+fields for energy level crossings (LC). The results can be explained by
+inelastic scattering between the fluorine nuclear spins and the RE magnetic
+levels. A key result of this study is that the broadening of the levels at LC
+is found to be become extremely small at low temperatures, about 1.7 mT, a
+value which is comparable to the weak dipolar fields at the RE lattice
+positions. Thus, unlike the molecular magnets, decoherence effects are strongly
+suppressed, and it may be possible to measure directly the level repulsions at
+avoided level crossings.",0508406v1
+2005-11-30,"A Novel ""Magnetic"" Field And Its Dual Non-Commutative Phase Space","In this paper we have studied a new form of Non-Commutative (NC) phase space
+with an operatorial form of noncommutativity. A point particle in this space
+feels the effect of an interaction with an ""{\it{internal}}"" magnetic field,
+that is singular at a specific position $\theta^{-1}$. By ""internal"" we mean
+that the effective magnetic fields depends essentially on the particle
+properties and modifies the symplectic structure. Here $\theta $ is the NC
+parameter and induces the coupling between the particle and the ""internal""
+magnetic field. The magnetic moment of the particle is computed. Interaction
+with an {\it{external}} physical magnetic field reveals interesting features
+induced by the inherent fuzziness of the NC phase space: introduction of
+non-trivial structures into the charge and mass of the particle and possibility
+of the particle dynamics collapsing to a Hall type of motion. The dynamics is
+studied both from Lagrangian and symplectic (Hamiltonian) points of view. The
+canonical (Darboux) variables are also identified. We briefly comment, that the
+model presented here, can play interesting role in the context of (recently
+observed) {\it{real}} space Berry curvature in material systems.",0511302v4
+2007-05-30,Magnetic fluctuations in n-type high-$T_c$ superconductors reveal breakdown of fermiology,"By combining experimental measurements of the quasiparticle and dynamical
+magnetic properties of optimally electron-doped Pr$_{0.88}$LaCe$_{0.12}$CuO$_4$
+with theoretical calculations we demonstrate that the conventional fermiology
+approach cannot possibly account for the magnetic fluctuations in these
+materials. In particular, we perform tunneling experiments on the very same
+sample for which a dynamical magnetic resonance has been reported recently and
+use photoemission data by others on a similar sample to characterize the
+fermionic quasiparticle excitations in great detail. We subsequently use this
+information to calculate the magnetic response within the conventional
+fermiology framework as applied in a large body of work for the hole-doped
+superconductors to find a profound disagreement between the theoretical
+expectations and the measurements: this approach predicts a step-like feature
+rather than a sharp resonance peak, it underestimates the intensity of the
+resonance by an order of magnitude, it suggests an unreasonable temperature
+dependence of the resonance, and most severely, it predicts that most of the
+spectral weight resides in incommensurate wings which are a key feature of the
+hole-doped cuprates but have never been observed in the electron-doped
+counterparts. Our findings strongly suggest that the magnetic fluctuations
+reflect the quantum-mechanical competition between antiferromagnetic and
+superconducting orders.",0705.4424v1
+2008-02-14,Extragalactic jets with helical magnetic fields: relativistic MHD simulations,"Extragalactic jets are inferred to harbor dynamically important, organized
+magnetic fields which presumably aid in the collimation of the relativistic jet
+flows. We here explore by means of grid-adaptive, high resolution numerical
+simulations the morphology of AGN jets pervaded by helical field and flow
+topologies. We concentrate on morphological features of the bow shock and the
+jet beam behind the Mach disk, for various jet Lorentz factors and magnetic
+field helicities. We investigate the influence of helical magnetic fields on
+jet beam propagation in overdense external medium. We use the AMRVAC code,
+employing a novel hybrid block-based AMR strategy, to compute ideal plasma
+dynamics in special relativity. The helicity of the beam magnetic field is
+effectively transported down the beam, with compression zones in between
+diagonal internal cross-shocks showing stronger toroidal field regions. In
+comparison with equivalent low-relativistic jets which get surrounded by
+cocoons with vortical backflows filled by mainly toroidal field, the high speed
+jets demonstrate only localized, strong toroidal field zones within the
+backflow vortical structures. We find evidence for a more poloidal, straight
+field layer, compressed between jet beam and backflows. This layer decreases
+the destabilizing influence of the backflow on the jet beam. In all cases, the
+jet beam contains rich cross-shock patterns, across which part of the kinetic
+energy gets transferred. For the high speed reference jet considered here,
+significant jet deceleration only occurs beyond distances exceeding ${\cal
+O}(100 R_j)$, as the axial flow can reaccelerate downstream to the internal
+cross-shocks. This reacceleration is magnetically aided, due to field
+compression across the internal shocks which pinch the flow.",0802.2034v1
+2008-03-03,Slipping friction of an optically and magnetically manipulated microsphere rolling at a glass-water interface,"The motion of submerged magnetic microspheres rolling at a glass-water
+interface has been studied using magnetic rotation and optical tweezers
+combined with bright-field microscopy particle tracking techniques. Individual
+microspheres of varying surface roughness were magnetically rotated both in and
+out of an optical trap to induce rolling, along either plain glass cover slides
+or glass cover slides functionalized with polyethylene glycol. It has been
+observed that the manipulated microspheres exhibited nonlinear dynamic
+rolling-while-slipping motion characterized by two motional regimes: At low
+rotational frequencies, the speed of microspheres free-rolling along the
+surface increased proportionately with magnetic rotation rate; however, a
+further increase in the rotation frequency beyond a certain threshold revealed
+a sharp transition to a motion in which the microspheres slipped with respect
+to the external magnetic field resulting in decreased rolling speeds. The
+effects of surface-microsphere interactions on the position of this threshold
+frequency are posed and investigated. Similar experiments with microspheres
+rolling while slipping in an optical trap showed congruent results.",0803.0328v1
+2008-03-27,Spherically Symmetric Accretion Flows: Minimal Model with MHD Turbulence,"The first spherical accretion model was developed 55 years ago, but the
+theory is yet far from being complete. The real accretion flow was found to be
+time-dependent and turbulent. This paper presents the minimal MHD spherical
+accretion model that separately deals with turbulence. Treatment of turbulence
+is based on simulations of several regimes of collisional MHD. The effects of
+freezing-in amplification, dissipation, dynamo action, isotropization, and
+constant magnetic helicity are self-consistently included. The assumptions of
+equipartition and magnetic field isotropy are released. Correct dynamics of
+magnetized flow is calculated. Diffusion, convection, and radiation are not
+accounted for. Two different types of Radiatively Inefficient accretion flows
+are found: a transonic non-rotating flow (I), a flow with effective transport
+of angular momentum outward (II). Non-rotating flow has an accretion rate
+several times smaller than Bondi rate, because turbulence inhibits accretion.
+Flow with angular momentum transport has accretion rate about 10-100 times
+smaller than Bondi rate. The effects of highly helical turbulence, states of
+outer magnetization, and different equations of state are discussed. The flows
+were found to be convectively stable on average, despite gas entropy increases
+inward. The proposed model has a small number of free parameters and the
+following attractive property. Inner density in the non-rotating magnetized
+flow was found to be several times lower than density in a non-magnetized
+accretion. Still several times lower density is required to explain the
+observed low IR luminosity and low Faraday rotation measure of accretion onto
+Sgr A*.",0803.3909v1
+2008-07-12,Time-Dependent of Accretion Flow with Toroidal Magnetic Field,"In the present study time evolution of quasi-spherical polytropic accretion
+flow with toroidal magnetic field is investigated. The study especially focused
+the astrophysically important case in which the adiabatic exponent
+$\gamma=5/3$. In this scenario, it was assumed that the angular momentum
+transport is due to viscous turbulence and used $\alpha$-prescription for
+kinematic coefficient of viscosity. The equations of accretion flow are solved
+in a simplified one-dimensional model that neglects the latitudinal dependence
+of the flow. In order to solve the integrated equations which govern the
+dynamical behavior of the accretion flow, self-similar solution was used. The
+solution provides some insight into the dynamics of quasi-spherical accretion
+flow and avoids many of the strictures of the steady self-similar solution. The
+effect of the toroidal magnetic field is considered with additional variable
+$\beta[=p_{mag}/p_{gas}]$, where $p_{mag}$ and $p_{gas}$ are the magnetic and
+gas pressure, respectively. The solution indicates a transonic point in the
+accretion flow, that this point approaches to central object by adding strength
+of the magnetic field. Also, by adding strength of the magnetic field, the
+radial-thickness of the disk decreases and the disk compresses. It was
+analytically indicated that the radial velocity is only a function of Alfv'en
+velocity. The model implies that the flow has differential rotation and is
+sub-Keplerian at all radii.",0807.1983v2
+2009-02-13,Mesoscale dynamics on the Sun's surface from HINODE observations,"Aims: The interactions of velocity scales on the Sun's surface, from
+granulation to supergranulation are still not understood, nor are their
+interaction with magnetic fields. We thus aim at giving a better description of
+dynamics in the mesoscale range which lies between the two scales mentioned
+above. Method: We analyse a 48h high-resolution time sequence of the quiet Sun
+photosphere at the disk center obtained with the Solar Optical Telescope
+onboard Hinode. The observations, which have a field of view of 100
+\arcsec$\times$ 100 \arcsec, typically contain four supergranules. We monitor
+in detail the motion and evolution of granules as well as those of the radial
+magnetic field. Results: This analysis allows us to better characterize Trees
+of Fragmenting Granules issued from repeated fragmentation of granules,
+especially their lifetime statistics. Using floating corks advected by measured
+velocity fields, we show their crucial role in the advection of the magnetic
+field and in the build up of the network. Finally, thanks to the long duration
+of the time series, we estimate that the turbulent diffusion coefficient
+induced by horizontal motion is approximately $430 \mathrm{km}^2
+\mathrm{s}^{-1}$. Conclusions: These results demonstrate that the long living
+families contribute to the formation of the magnetic network and suggest that
+supergranulation could be an emergent length scale building up as small
+magnetic elements are advected and concentrated by TFG flows. Our estimate for
+the magnetic diffusion associated with this horizontal motion might provide a
+useful input for mean-field dynamo models.",0902.2299v1
+2009-06-29,Generation of a symmetric magnetic field by thermal convection in a plane rotating layer,"We investigate numerically magnetic field generation by thermal convection
+with square periodicity cells in a rotating horizontal layer of
+electrically-conducting fluid with stress-free electrically perfectly
+conducting boundaries for Rayleigh numbers in the interval 5100\le R\le 5800.
+Dynamos of three kinds, apparently not encountered before, are presented: 1)
+Steady and time-periodic regimes, where the flow and magnetic field are
+symmetric about a vertical axis. In regimes with this symmetry, the global
+alpha-effect is insignificant, and the complex structure of the system of
+amplitude equations controlling weakly nonlinear stability of the system to
+perturbations with large spatial and temporal scales suggests that the
+perturbations are likely to exhibit uncommon complex patterns of behaviour, to
+be studied in the future work. 2) Periodic in time regimes, where magnetic
+field is always concentrated in the interior of the convective layer, in
+contrast to the behaviour first observed by St Pierre (1993) and often
+perceived as generic for electrically infinitely conducting boundaries. 3) A
+dynamo exhibiting chaotic behaviour of heteroclinic nature, where a sample
+trajectory enjoys excursions between a periodic magnetohydrodynamic regime and
+rolls. The rolls are amagnetic, but generate magnetic field kinematically. As a
+result, magnetic energy falls off almost to zero, while the rolls are
+approached.",0906.5380v2
+2010-05-12,Using Faraday Rotation to Probe MHD Instabilities in Intracluster Media,"It has recently been suggested that conduction-driven magnetohydrodynamic
+(MHD) instabilities may operate at all radii within an intracluster medium
+(ICM), and profoundly affect the structure of a cluster's magnetic field. Where
+MHD instabilities dominate the dynamics of an ICM, they will re-orient magnetic
+field lines perpendicular to the temperature gradient inside a cooling core, or
+parallel to the temperature gradient outside it. This characteristic structure
+of magnetic field could be probed by measurements of polarized radio emission
+from background sources. Motivated by this possibility we have constructed 3-d
+models of a magnetized cooling core cluster and calculated Faraday rotation
+measure (RM) maps in the plane of the sky under realistic observing conditions.
+We compare a scenario in which magnetic field geometry is characterized by
+conduction driven MHD instabilities to that where it is determined by isotropic
+turbulent motions. We find that future high-sensitivity spectro-polarimetric
+measurements of RM, such as will be enabled by the Expanded Very Large Array
+and Square Kilometer Array can distinguish between these two cases with
+plausible exposure times. Such observations will test the existence of
+conduction-driven MHD instabilities in dynamically relaxed cooling core
+clusters. More generally, our findings imply that observations of Faraday RM
+should be able to discern physical mechanisms that result in qualitatively
+different magnetic field topologies, without a priori knowledge about the
+nature of the processes.",1005.2193v2
+2010-06-11,Power-Law NLED-Based Magnetic Universe Can Mimic Phantom Behavior,"We study the cosmic dynamics of a magnetic universe supported by non-linear
+electrodynamics (NLED) Lagrangeans that are proportional to powers of the
+electromagnetic invariant $\propto F^{1/(1-m)}$ ($m$ is an overall constant).
+For simplicity we focus in the case when $F$ depends on the magnetic field
+alone, a case dubbed in the bibliography as ''magnetic universe''. Our results
+demonstrate that, depending on the values of the free parameter $m$, the
+magnetic field can mimic phantom field behavior, an effect previously found in
+other contexts. It is demonstrated that, since there are found equilibrium
+points in the phase space of these models that can be associated with
+magnetic-dominated past and future attractors, a combination of positive and
+negative powers of $F$ may lead to interesting cosmological behavior. In
+particular, a cosmological scenario where the universe might evolve from a past
+NLED-driven (non-inflationary) state into a future (late-time) -- also
+NLED-driven -- inflationary stage, transiting through a matter-dominated
+solution, is envisioned. The impact of braneworld gravity on the dynamics
+driven by such NLED Lagrangeans is also investigated. It is demonstrated that,
+due to phantom property at late times, the non-linear electromagnetic effects
+may play an important role in deciding the fate of the cosmic evolution.
+Randall-Sundrum brane effects, in particular, modify the nature of the starting
+point of the cosmic evolution, as well as the fate of the expansion: both, the
+big bang singularity and the big rip event -- inherent in general relativity
+with phantom matter source --, may be avoided.",1006.2274v2
+2010-07-07,Magnetic Quenching of Turbulent Diffusivity: Reconciling Mixing-length Theory Estimates with Kinematic Dynamo Models of the Solar Cycle,"The turbulent magnetic diffusivity in the solar convection zone is one of the
+most poorly constrained ingredients of mean-field dynamo models. This lack of
+constraint has previously led to controversy regarding the most appropriate set
+of parameters, as different assumptions on the value of turbulent diffusivity
+lead to radically different solar cycle predictions. Typically, the dynamo
+community uses double step diffusivity profiles characterized by low values of
+diffusivity in the bulk of the convection zone. However, these low diffusivity
+values are not consistent with theoretical estimates based on mixing-length
+theory -- which suggest much higher values for turbulent diffusivity. To make
+matters worse, kinematic dynamo simulations cannot yield sustainable magnetic
+cycles using these theoretical estimates. In this work we show that magnetic
+cycles become viable if we combine the theoretically estimated diffusivity
+profile with magnetic quenching of the diffusivity. Furthermore, we find that
+the main features of this solution can be reproduced by a dynamo simulation
+using a prescribed (kinematic) diffusivity profile that is based on the
+spatiotemporal geometric-average of the dynamically quenched diffusivity. Here,
+we provide an analytic fit to the dynamically quenched diffusivity profile,
+which can be used in kinematic dynamo simulations. Having successfully
+reconciled the mixing-length theory estimated diffusivity profile with
+kinematic dynamo models, we argue that they remain a viable tool for
+understanding the solar magnetic cycle.",1007.1262v1
+2010-10-12,Differential Rotation and Magnetism in Simulations of Fully Convective Stars,"Stars of sufficiently low mass are convective throughout their interiors, and
+so do not possess an internal boundary layer akin to the solar tachocline.
+Because that interface figures so prominently in many theories of the solar
+magnetic dynamo, a widespread expectation had been that fully convective stars
+would exhibit surface magnetic behavior very different from that realized in
+more massive stars. Here I describe how recent observations and theoretical
+models of dynamo action in low-mass stars are partly confirming, and partly
+confounding, this basic expectation. In particular, I present the results of
+3--D MHD simulations of dynamo action by convection in rotating spherical
+shells that approximate the interiors of 0.3 solar-mass stars at a range of
+rotation rates. The simulated stars can establish latitudinal differential
+rotation at their surfaces which is solar-like at ``rapid'' rotation rates
+(defined within) and anti-solar at slower rotation rates; the differential
+rotation is greatly reduced by feedback from strong dynamo-generated magnetic
+fields in some parameter regimes. I argue that this ``flip'' in the sense of
+differential rotation may be observable in the near future. I also briefly
+describe how the strength and morphology of the magnetic fields varies with the
+rotation rate of the simulated star, and show that the maximum magnetic
+energies attained are compatible with simple scaling arguments.",1010.2509v1
+2010-11-12,"Magnetization Dynamics, Bennett Clocking and Associated Energy Dissipation in Multiferroic Logic","It has been recently shown that multiferroic logic - where logic bits are
+encoded in the magnetization orientation of a nanoscale magnetostrictive layer
+elastically coupled to a piezoelectric layer - can be Bennett clocked with
+small electrostatic potentials of few tens of mV applied to the piezoelectric
+layer. The potential generates stress in the magnetostrictive layer and rotates
+its magnetization by a large angle to carry out Bennett clocking. This method
+of clocking is far more energy-efficient than using spin transfer torque. In
+order to assess if such a clocking scheme can be also reasonably fast, we have
+studied the magnetization dynamics of a multiferroic logic array with nearest
+neighbor dipole coupling using the Landau-Lifshitz-Gilbert (LLG) equation. We
+find that switching delays of ~ 3 ns (clock rates of 0.33 GHz) can be achieved
+with proper design provided we clock non-adiabatically and dissipate ~48,000 kT
+(at room temperature) of energy per clock cycle per bit flip in the clocking
+circuit. This dissipation far exceeds the energy barrier separating the two
+logic states, which we assumed to be 32 kT to yield a bit error probability of
+. Had we used spin transfer torque to switch with the same ~ 3 ns delay, the
+energy dissipation would have been much larger (~ $6 \times 106$ kT). This
+shows that spin transfer torque, widely used in magnetic random access memory,
+is an inefficient way to switch a magnet, and multiferroic logic clocked with
+voltage-induced stress is a superior nanomagnetic logic scheme.",1011.2914v2
+2011-10-10,Magnetar Oscillations II: spectral method,"The seismological dynamics of magnetars is largely determined by a strong
+hydro-magnetic coupling between the solid crust and the fluid core. In this
+paper we set up a ""spectral"" computational framework in which the magnetar's
+motion is decomposed into a series of basis functions which are associated with
+the crust and core vibrational eigenmodes. A general-relativistic formalism is
+presented for evaluation of the core Alfven modes in the magnetic-flux
+coordinates, as well for eigenmode computation of a strongly magnetized crust
+of finite thickness. By considering coupling of the crustal modes to the
+continuum of Alfven modes in the core, we construct a fully relativistic
+dynamical model of the magnetar which allows: i) Fast and long simulations
+without numerical dissipation. ii) Very fine sampling of the stellar structure.
+We find that the presence of strong magnetic field in the crust results in
+localizing of some high-frequency crustal elasto-magnetic modes with the radial
+number n>1 to the regions of the crust where the field is nearly horizontal.
+While the hydro-magnetic coupling of these localized modes to the Alfven
+continuum in the core is reduced, their energy is drained on a time-scale much
+less than 1 second. Therefore the puzzle of the observed QPOs with frequencies
+larger than 600 Hz still stands.",1110.2107v1
+2011-11-17,Non-Equilibrium Chemistry of Dynamically Evolving Prestellar Cores: II. Ionization and Magnetic Field,"We study the effect that non-equilibrium chemistry in dynamical models of
+collapsing molecular cloud cores has on measurements of the magnetic field in
+these cores, the degree of ionization, and the mean molecular weight of ions.
+We find that OH and CN, usually used in Zeeman observations of the
+line-of-sight magnetic field, have an abundance that decreases toward the
+center of the core much faster than the density increases. As a result, Zeeman
+observations tend to sample the outer layers of the core and consistently
+underestimate the core magnetic field. The degree of ionization follows a
+complicated dependence on the number density at central densities up to 10^5
+cm^{-3} for magnetic models and 10^6 cm^{-3} in non-magnetic models. At higher
+central densities the scaling approaches a power-law with a slope of -0.6 and a
+normalization which depends on the cosmic-ray ionization rate {\zeta} and the
+temperature T as ({\zeta}T)^1/2. The mean molecular weight of ions is
+systematically lower than the usually assumed value of 20 - 30, and, at high
+densities, approaches a value of 3 due to the asymptotic dominance of the H3+
+ion. This significantly lower value implies that ambipolar diffusion operates
+faster.",1111.4218v2
+2012-01-18,Statics and dynamics of weakly coupled antiferromagnetic spin-1/2 ladders in a magnetic field (PhD thesis),"We investigate weakly coupled spin-1/2 ladders in a magnetic field. The work
+is motivated by recent experiments on the compound
+$\mathrm{(C_5H_{12}N)_2CuBr_4}$ (BPCB). We use a combination of numerical and
+analytical methods, in particular the density matrix renormalization group
+(DMRG) technique, to explore the phase diagram and the excitation spectra of
+such a system. We give detailed results on the temperature dependence of the
+magnetization and the specific heat, and the magnetic field dependence of the
+nuclear magnetic resonance (NMR) relaxation rate of single ladders. For coupled
+ladders, treating the weak interladder coupling within a mean field approach,
+we compute the transition temperature of triplet condensation and its
+corresponding antiferromagnetic order parameter. Existing experimental
+measurements are discussed and compared to our theoretical results. Furthermore
+we compute, using time dependent DMRG, the dynamical correlations of a single
+spin ladder. Our results allow to directly describe the inelastic neutron
+scattering cross section up to high energies. We focus on the evolution of the
+spectra with the magnetic field and compare their behavior for different
+couplings. The characteristic features of the spectra are interpreted using
+different analytical approaches such as the mapping onto a spin chain, a
+Luttinger liquid (LL) or onto a t-J model. For values of parameters for which
+such measurements exist, we compare our results to inelastic neutron scattering
+experiments on the compound BPCB and find excellent agreement. We make
+additional predictions for the high energy part of the spectrum that are
+potentially testable in future experiments.",1201.5276v1
+2012-04-03,The Small-Scale Dynamo and Non-Ideal MHD in Primordial Star Formation,"We study the amplification of magnetic fields during the formation of
+primordial halos. The turbulence generated by gravitational infall motions
+during the formation of the first stars and galaxies can amplify magnetic
+fields very efficiently and on short timescales up to dynamically significant
+values. Using the Kazantsev theory, which describes the so-called small-scale
+dynamo - a magnetohydrodynamical process converting kinetic energy from
+turbulence into magnetic energy - we can then calculate the growth rate of the
+small-scale magnetic field. Our calculations are based on a detailed chemical
+network and we include non-ideal magnetohydrodynamical effects such as
+ambipolar diffusion and Ohmic dissipation. We follow the evolution of the
+magnetic field up to larger scales until saturation occurs on the Jeans scale.
+Assuming a weak magnetic seed field generated by the Biermann battery process,
+both Burgers and Kolmogorov turbulence lead to saturation within a rather small
+density range. Such fields are likely to become relevant after the formation of
+a protostellar disk and, thus, could influence the formation of the first stars
+and galaxies in the Universe.",1204.0658v2
+2012-10-12,Distribution of Magnetic Discontinuities in the Solar Wind and in MHD Turbulence,"The statistical properties of magnetic discontinuities in the solar wind are
+investigated by measuring fluctuations in the magnetic field direction, given
+by the rotation Delta theta that the magnetic field vector undergoes during
+time interval Delta t. We show that the probability density function for
+rotations, P(Delta theta), can be described by a simple model in which the
+magnetic field vector rotates with a relative increment (Delta B)/B that is
+lognormally distributed. We find that the probability density function of
+increments, P((Delta B)/B), has a remarkable scaling property: the normalized
+variable x=[(Delta B)/B]*[(Delta t)/(Delta t_0)]^-a has a universal lognormal
+distribution for all time intervals Delta t. We then compare measurements from
+the solar wind with those from direct numerical simulations of
+magnetohydrodynamic (MHD) turbulence. We find good agreement for P(Delta theta)
+obtained in the two cases when the magnetic guide-field to fluctuations ratio
+B_0/b_rms is chosen accordingly. However, the scale invariance of P((Delta
+B)/B) is broken in the MHD simulations with relatively limited inertial
+interval, which causes P(Delta theta) to scale with measurement interval
+differently than in the solar wind.",1210.3613v1
+2012-11-13,Tracing Electron Beams in the Sun's Corona with Radio Dynamic Imaging Spectroscopy,"We report observations of type III radio bursts at decimeter wavelengths
+(type IIIdm bursts) -- signatures of suprathermal electron beams propagating in
+the low corona -- using the new technique of radio dynamic imaging spectroscopy
+provided by the recently upgraded Karl G. Jansky Very Large Array (VLA). For
+the first time, type IIIdm bursts were imaged with high time and frequency
+resolution over a broad frequency band, allowing electron beam trajectories in
+the corona to be deduced. Together with simultaneous hard X-ray (HXR) and
+extreme ultraviolet (EUV) observations, we show these beams emanate from an
+energy release site located in the low corona at a height below ~15 Mm, and
+propagate along a bundle of discrete magnetic loops upward into the corona. Our
+observations enable direct measurements of the plasma density along the
+magnetic loops, and allow us to constrain the diameter of these loops to be
+less than 100 km. These over-dense and ultra-thin loops reveal the
+fundamentally fibrous structure of the Sun's corona. The impulsive nature of
+the electron beams, their accessibility to different magnetic field lines, and
+the detailed structure of the magnetic release site revealed by the radio
+observations indicate that the localized energy release is highly fragmentary
+in time and space, supporting a bursty reconnection model that involves
+secondary magnetic structures for magnetic energy release and particle
+acceleration.",1211.3058v2
+2013-01-18,Collapse and Fragmentation of Magnetic Molecular Cloud Cores with the Enzo AMR MHD Code. I. Uniform Density Sphere,"Magnetic fields are important contributers to the dynamics of collapsing
+molecular cloud cores, and can have a major effect on whether collapse results
+in a single protostar or fragmentation into a binary or multiple protostar
+system. New models are presented of the collapse of magnetic cloud cores using
+the adaptive mesh refinement (AMR) code Enzo2.0. The code was used to calculate
+the ideal magnetohydrodynamics (MHD) of initially spherical, uniform density
+and rotation clouds with density perturbations, i.e., the Boss and Bodenheimer
+(1979) standard isothermal test case for three dimensional (3D) hydrodynamics
+(HD) codes. After first verifying that Enzo reproduces the binary fragmentation
+expected for the non-magnetic test case, a large set of models was computed
+with varied initial magnetic field strengths and directions with respect to the
+cloud core axis of rotation (parallel or perpendicular), density perturbation
+amplitudes, and equations of state. Three significantly different outcomes
+resulted: (1) contraction without sustained collapse, forming a denser cloud
+core, (2) collapse to form a single protostar with significant spiral arms, and
+(3) collapse and fragmentation into binary or multiple protostar systems, with
+multiple spiral arms. Comparisons are also made with previous MHD calculations
+of similar clouds with barotropic equations of state. These results for the
+collapse of initially uniform density spheres illustrate the central importance
+of both magnetic field direction and field strength for determining the outcome
+of dynamic protostellar collapse.",1301.4495v1
+2014-01-08,Dynamical quark mass generation in a strong external magnetic field,"We investigate the effect of a strong magnetic field on dynamical chiral
+symmetry breaking in quenched and unquenched QCD. To this end we apply the
+Ritus formalism to the coupled set of (truncated) Dyson-Schwinger equations for
+the quark and gluon propagator under the presence of an external constant
+Abelian magnetic field. We work with an approximation that is trustworthy for
+large fields eH > \Lambda_{QCD}^2 but is not restricted to the lowest Landau
+level. We confirm the linear rise of the quark condensate with large external
+field previously found in other studies and observe the transition to the
+asymptotic power law at extremely large fields. We furthermore quantify the
+validity of the lowest Landau level approximation and find substantial
+quantitative differences to the full calculation even at very large fields. We
+discuss unquenching effects in the strong field propagators, condensate and the
+magnetic polarization of the vacuum. We find a significant weakening of
+magnetic catalysis caused by the back reaction of quarks on the Yang-Mills
+sector. Our results support explanations of the inverse magnetic catalysis
+found in recent lattice studies due to unquenching effects.",1401.1647v2
+2014-12-04,Cross-correlation Aided Transport in Stochastically Driven Accretion Flows,"Origin of linear instability resulting in rotating sheared accretion flows
+has remained a controversial subject for long. While some explanations of such
+non-normal transient growth of disturbances in the Rayleigh stable limit were
+available for magnetized accretion flows, similar instabilities in absence of
+magnetic perturbations remained unexplained. This dichotomy was resolved in two
+recent publications by Chattopadhyay, {\it et al} where it was shown that such
+instabilities, especially for non-magnetized accretion flows, were introduced
+through interaction of the inherent stochastic noise in the system (even a
+\enquote{cold} accretion flow at 3000K is too \enquote{hot} in the statistical
+parlance and is capable of inducing strong thermal modes) with the underlying
+Taylor-Couette flow profiles. Both studies, however, excluded the additional
+energy influx (or efflux) that could result from nonzero cross-correlation of a
+noise perturbing the velocity flow, say, with the noise that is driving the
+vorticity flow (or equivalently the magnetic field and magnetic vorticity flow
+dynamics). In this article we show that nonzero noise cross-correlations
+essentially renormalize the strength of temporal correlations. Apart from an
+overall boost in the energy rate (both for spatial and temporal correlations,
+and hence in the ensemble averaged energy spectra), this results in mutual
+competition in growth rates of affected variables often resulting in
+suppression of oscillating Alfven waves at small times while leading to faster
+saturations at relatively longer time scales. The effects are seen to be more
+pronounced with magnetic field fluxes where the noise cross-correlation
+magnifies the strength of the field concerned.",1412.1752v1
+2015-01-18,Dynamics of Dirac strings and monopole-like excitations in chiral magnets under a current drive,"Skyrmion lines in metallic chiral magnets carry an emergent magnetic field
+experienced by the conduction electrons. The inflow and outflow of this field
+across a closed surface is not necessarily equal, thus it allows for the
+existence of emergent monopoles. One example is a segment of skyrmion line
+inside a crystal, where a monopole and antimonopole pair is connected by the
+emergent magnetic flux line. This is a realization of Dirac string-like
+excitations. Here we study the dynamics of monopoles in chiral magnets under an
+electric current. We show that in the process of creation of skyrmion lines,
+skyrmion line segments are first created via the proliferation of monopoles and
+antimonopoles. Then these line segments join and span the whole system through
+the annihilation of monopoles. The skyrmion lines are destroyed via the
+proliferation of monopoles and antimonopoles at high currents, resulting in a
+chiral liquid phase. We also propose to create the monopoles in a controlled
+way by applying an inhomogenous current to a crystal. Remarkably, an electric
+field component in the magnetic field direction proportional to the current
+squared in the low current region is induced by the motion of distorted
+skyrmion lines, in addition to the Hall and longitudinal voltage. The existence
+of monopoles can be inferred from transport or imaging measurements.",1501.04356v2
+2015-02-10,Magnetic-field and doping dependence of low-energy spin fluctuations in the antiferroquadrupolar compound Ce(1-x)La(x)B(6),"CeB(6) is a model compound exhibiting antiferroquadrupolar (AFQ) order, its
+magnetic properties being typically interpreted within localized models. More
+recently, the observation of strong and sharp magnetic exciton modes forming in
+its antiferromagnetic (AFM) state at both ferromagnetic and AFQ wave vectors
+suggested a significant contribution of itinerant electrons to the spin
+dynamics. Here we investigate the evolution of the AFQ excitation upon the
+application of an external magnetic field and the substitution of Ce with
+non-magnetic La, both parameters known to suppress the AFM phase. We find that
+the exciton energy decreases proportionally to T_N upon doping. In field, its
+intensity is suppressed, while its energy remains constant. Its disappearance
+above the critical field of the AFM phase is preceded by the formation of two
+modes, whose energies grow linearly with magnetic field upon entering the AFQ
+phase. These findings suggest a crossover from itinerant to localized spin
+dynamics between the two phases, the coupling to heavy-fermion quasiparticles
+being crucial for a comprehensive description of the magnon spectrum.",1502.03139v2
+2015-04-13,The Evolution and Impacts of Magnetorotational Instability in Magnetized Core-Collapse Supernovae,"We carried out 2D-axisymmetric MHD simulations of core-collapse supernovae
+for rapidly-rotating magnetized progenitors. By changing both the strength of
+the magnetic field and the spatial resolution, the evolution of the
+magnetorotational instability (MRI) and its impacts upon the dynamics are
+investigated. We found that the MRI greatly amplifies the seed magnetic fields
+in the regime where not the Alfv\'en mode but the buoyant mode plays a primary
+role in the exponential growth phase. The MRI indeed has a powerful impact on
+the supernova dynamics. It makes the shock expansion faster and the explosion
+more energetic, with some models being accompanied by the collimated-jet
+formations. These effects, however, are not made by the magnetic pressure
+except for the collimated-jet formations. The angular momentum transfer induced
+by the MRI causes the expansion of the heating region, by which the accreting
+matter gain an additional time to be heated by neutrinos. The MRI also drifts
+low-$Y_p$ matter from the deep inside of the core to the heating region, which
+makes the net neutrino heating rate larger by the reduction of the cooling due
+to the electron capture. These two effects enhance the efficiency of the
+neutrino heating, which is found to be the key to boost the explosion. Indeed
+we found that our models explode far more weakly when the net neutrino heating
+is switched off. The contribution of the neutrino heating to the explosion
+energy could reach 60\% even in the case of strongest magnetic field in the
+current simulations.",1504.03035v2
+2015-05-21,Exact two-dimensionalization of low-magnetic-Reynolds-number flows subject to a strong magnetic field,"We investigate the behavior of flows, including turbulent flows, driven by a
+horizontal body-force and subject to a vertical magnetic field, with the
+following question in mind: for very strong applied magnetic field, is the flow
+mostly two-dimensional, with remaining weak three-dimensional fluctuations, or
+does it become exactly 2D, with no dependence along the vertical?
+  We first focus on the quasi-static approximation, i.e. the asymptotic limit
+of vanishing magnetic Reynolds number Rm << 1: we prove that the flow becomes
+exactly 2D asymptotically in time, regardless of the initial condition and
+provided the interaction parameter N is larger than a threshold value. We call
+this property ""absolute two-dimensionalization"": the attractor of the system is
+necessarily a (possibly turbulent) 2D flow.
+  We then consider the full-magnetohydrodynamic equations and we prove that,
+for low enough Rm and large enough N, the flow becomes exactly two-dimensional
+in the long-time limit provided the initial vertically-dependent perturbations
+are infinitesimal. We call this phenomenon ""linear two-dimensionalization"": the
+(possibly turbulent) 2D flow is an attractor of the dynamics, but it is not
+necessarily the only attractor of the system. Some 3D attractors may also exist
+and be attained for strong enough initial 3D perturbations.
+  These results shed some light on the existence of a dissipation anomaly for
+magnetohydrodynamic flows subject to a strong external magnetic field.",1505.05662v1
+2015-06-02,Respective influence of in-plane and out-of-plane spin-transfer torques in magnetization switching of perpendicular magnetic tunnel junctions,"The relative contributions of in-plane (damping-like) and out-of-plane
+(field-like) spin-transfer-torques in the magnetization switching of
+out-of-plane magnetized magnetic tunnel junctions (pMTJ) has been theoretically
+analyzed using the transformed Landau-Lifshitz (LL) equation with the STT
+terms. It is demonstrated that in a pMTJ structure obeying macrospin dynamics,
+the out-of-plane torque influences the precession frequency but it does not
+contribute significantly to the STT switching process (in particular to the
+switching time and switching current density), which is mostly determined by
+the in-plane STT contribution. This conclusion is confirmed by finite
+temperature and finite writing pulse macrospin simulations of the current-field
+switching diagrams. It contrasts with the case of STT-switching in in-plane
+magnetized MTJ in which the field-like term also influences the switching
+critical current. This theoretical analysis was successfully applied to the
+interpretation of voltage-field STT switching diagrams experimentally measured
+on perpendicular MTJ pillars 36 nm in diameter, which exhibit macrospin-like
+behavior. The physical nonequivalence of Landau and Gilbert dissipation terms
+in presence of STT-induced dynamics is also discussed.",1506.00780v2
+2015-06-18,Dynamical mean-field study of partial Kondo screening in the periodic Anderson model on the triangular lattice,"The competition between Kondo screening and indirect magnetic exchange is
+studied for a system with geometrical frustration using dynamical mean-field
+theory (DMFT). We systematically scan the weak- to strong-coupling regime of
+the periodic Anderson model on the triangular lattice for a wide range of
+fillings n. The magnetic phase diagram is derived using a site-dependent DMFT
+approach by self-consistent mapping onto three independent single-impurity
+models corresponding to the three correlated f orbitals in the unit cell. At
+half-filling, the system is a non-magnetic Kondo insulator for all considered
+interaction strengths U>0 which immediately develops into a non-magnetic
+metallic Kondo-singlet phase for fillings slightly below half-filling. On the
+other hand, indirect magnetic exchange between the f moments results in
+antiferromagnetic order at lower fillings. The antiferromagnetic and the
+Kondo-singlet phases are separated in the U-n phase diagram by an extended
+region of partial Kondo screening, i.e., a phase where the magnetic moment at
+one site in the unit cell is Kondo screened while the remaining two are coupled
+antiferromagnetically. At even lower fillings the system crosses over from a
+local-moment to a mixed-valence regime where the minimization of the kinetic
+energy in a strongly correlated system gives rise to a metallic and partially
+polarized ferromagnetic state.",1506.05755v2
+2015-06-22,Analytic Bjorken flow in one-dimensional relativistic magnetohydrodynamics,"In the initial stage of relativistic heavy-ion collisions, strong magnetic
+fields appear due to the large velocity of the colliding charges. The evolution
+of these fields appears as a novel and intriguing feature in the
+fluid-dynamical description of heavy-ion collisions. In this work, we study
+analytically the one-dimensional, longitudinally boost-invariant motion of an
+ideal fluid in the presence of a transverse magnetic field. Interestingly, we
+find that, in the limit of ideal magnetohydrodynamics, i.e., for infinite
+conductivity, and irrespective of the strength of the initial magnetization,
+the decay of the fluid energy density $e$ with proper time $\tau$ is the same
+as for the time-honored ""Bjorken flow"" without magnetic field. Furthermore,
+when the magnetic field is assumed to decay $\sim \tau^{-a}$, where $a$ is an
+arbitrary number, two classes of analytic solutions can be found depending on
+whether $a$ is larger or smaller than one. In summary, the analytic solutions
+presented here highlight that the Bjorken flow is far more general than
+formerly thought. These solutions can serve both to gain insight on the
+dynamics of heavy-ion collisions in the presence of strong magnetic fields and
+as testbeds for numerical codes.",1506.06620v2
+2015-08-11,Anisotropic Formation of Magnetized Cores in Turbulent Clouds,"In giant molecular clouds (GMCs), shocks driven by converging turbulent flows
+create high-density, strongly-magnetized regions that are locally sheetlike. In
+previous work, we showed that within these layers, dense filaments and embedded
+self-gravitating cores form by gathering material along the magnetic field
+lines. Here, we extend the parameter space of our three-dimensional, turbulent
+MHD core formation simulations. We confirm the anisotropic core formation model
+we previously proposed, and quantify the dependence of median core properties
+on the pre-shock inflow velocity and upstream magnetic field strength. Our
+results suggest that bound core properties are set by the total dynamic
+pressure (dominated by large-scale turbulence) and thermal sound speed c_s in
+GMCs, independent of magnetic field strength. For models with Mach number
+between 5 and 20, the median core masses and radii are comparable to the
+critical Bonnor-Ebert mass and radius defined using the dynamic pressure for
+P_ext. Our results correspond to M_core = 1.2 c_s^4/sqrt(G^3 rho_0 v_0^2) and
+R_core = 0.34 c_s^2/sqrt(G rho_0 v_0^2) for rho_0 and v_0 the large-scale mean
+density and velocity. For our parameter range, the median M_core ~ 0.1-1 M_sun,
+but a very high pressure cloud could have lower characteristic core mass. We
+find cores and filaments form simultaneously, and filament column densities are
+a factor ~2 greater than the surrounding cloud when cores first collapse. We
+also show that cores identified in our simulations have physical properties
+comparable to those observed in the Perseus cloud. Superthermal cores in our
+models are generally also magnetically supercritical, suggesting that the same
+may be true in observed clouds.",1508.02710v1
+2015-08-14,Numerical MHD Simulation of the Coupled Evolution of Collisional Plasma and Magnetic Field in the Solar Chromosphere. I. Gradual and Impulsive Energisation,"The dynamical coupling between the solar chromospheric plasma and magnetic
+field is investigated by numerically solving a fully self-consistent,
+two-dimensional initial-value problem for the nonlinear collisional MHD
+equations including electric resistivity, thermal conduction, and, in some
+cases, gas-dynamic viscosity. The processes in the contact zone between two
+horizontal magnetic fields of opposite polarities are considered. The plasma is
+assumed to be initially motionless and having a temperature of 50,000 K uniform
+throughout the plasma volume; the characteristic magnetic field corresponds to
+a plasma $\beta\gtrsim 1$. In a physical-time interval of 17~seconds typically
+covered by a computational run, the plasma temperature gradually increases by a
+factor of two to three. Against this background, an impulsive (in 0.1 seconds
+or less) increase in the current-aligned plasma velocity occurs at the site of
+the current-layer thinning (sausage-type deformation, or $m=0$ pinch
+instability). Such a ""velocity burst"" can be interpreted physically as an event
+of suprathemal-proton generation. Further development of the sausage
+instability results in an increase in the kinetic temperature of the protons to
+high values, even to those observed in flares. The form of our system of MHD
+equations indicates that such increases are a property of the exact solution of
+the system at an appropriate choice of the parameters. Magnetic reconnection
+does not manifest itself in this solution: it would generate flows forbidden by
+the chosen geometry. Therefore, the pinch-sausage effect can act as an
+energiser of the upper chromosphere and be an alternative to the
+magnetic-reconnection process as the producer of flares.",1508.03626v1
+2015-12-18,Electronic Correlation and Magnetism in the Ferromagnetic Metal Fe3GeTe2,"Motivated by the search for design principles of rare-earth-free strong
+magnets, we present a study of electronic structure and magnetic properties of
+the ferromagnetic metal Fe3GeTe2 within local density approximation (LDA) of
+the density functional theory, and its combination with dynamical mean-field
+theory (DMFT). For comparison to these calculations, we have measured magnetic
+and thermodynamic properties as well as X-ray magnetic circular dichroism and
+the photoemission spectrum of single crystal Fe3GeTe2. We find that the
+experimentally determined Sommerfeld coefficient is enhanced by an order of
+magnitude with respect to the LDA value. This enhancement can be partially
+explained by LDA+DMFT. In addition, the inclusion of dynamical electronic
+correlation effects provides the experimentally observed magnetic moments, and
+the spectral density is in better agreement with photoemission data. These
+results establish the importance of electronic correlations in this
+ferromagnet.",1512.05847v2
+2016-04-25,Frequency-based nanoparticle sensing over large field ranges using the ferromagnetic resonances of a magnetic nanodisc,"Using finite element micromagnetic simulations, we study how resonant
+magnetisation dynamics in thin magnetic discs with perpendicular anisotropy are
+influenced by magnetostatic coupling to a magnetic nanoparticle. We identify
+resonant modes within the disc using direct magnetic eigenmode calculations and
+study how their frequencies and profiles are changed by the nanoparticle's
+stray magnetic field. We demonstrate that particles can generate shifts in the
+resonant frequency of the disc's fundamental mode which exceed resonance
+linewidths in recently studied spin torque oscillator devices. Importantly, it
+is shown that the simulated shifts can be maintained over large field ranges
+(here up to 1T). This is because the resonant dynamics (the basis of
+nanoparticle detection here) respond directly to the nanoparticle stray field,
+i.e. detection does not rely on nanoparticle-induced changes to the magnetic
+ground state of the disk. A consequence of this is that in the case of small
+disc-particle separations, sensitivities to the particle are highly mode- and
+particle-position-dependent, with frequency shifts being maximised when the
+intense stray field localised directly beneath the particle can act on a large
+proportion of the disc's spins that are undergoing high amplitude precession.",1604.07277v2
+2016-05-06,Nanosecond-timescale low error switching of in-plane magnetic tunnel junctions through dynamic Oersted-field assisted spin-Hall effect,"We investigate fast-pulse switching of in-plane-magnetized magnetic tunnel
+junctions (MTJs) within 3-terminal devices in which spin-transfer torque is
+applied to the MTJ by the giant spin Hall effect. We measure reliable
+switching, with write error rates down to $10^{-5}$, using current pulses as
+short as just 2 ns in duration. This represents the fastest reliable switching
+reported to date for any spin-torque-driven magnetic memory geometry, and
+corresponds to a characteristic time scale that is significantly shorter than
+predicted possible within a macrospin model for in-plane MTJs subject to
+thermal fluctuations at room temperature. Using micromagnetic simulations, we
+show that in the 3-terminal spin-Hall devices the Oersted magnetic field
+generated by the pulse current strongly modifies the magnetic dynamics excited
+by the spin-Hall torque, enabling this unanticipated performance improvement.
+Our results suggest that in-plane MTJs controlled by Oersted-field-assisted
+spin-Hall torque are a promising candidate for both cache memory applications
+requiring high speed and for cryogenic memories requiring low write energies.",1605.02104v2
+2017-01-05,Collective vortex pinning and crossover between second order to first order transition in optimally doped Ba1-xKxBiO3 single crystals,"Measurements on magnetization and relaxation have been carried out on an
+optimally doped Ba$_{0.59}$K$_{0.47}$BiO$_{3+\delta}$ single crystal with $T_c$
+= 31.3 K. Detailed analysis is undertaken on the data. Both the dynamical
+relaxation and conventional relaxation have been measured leading to the
+self-consistent determination of the magnetization relaxation rate. It is found
+that the data are well described by the collective pinning model leading to the
+glassy exponent of about $\mu\approx$ 1.64 to 1.68 with the magnetic fields of
+1 and 3 T. The analysis based on Maley's method combining with the conventional
+relaxation data allows us to determine the current dependent activation energy
+$U$ which yields a $\mu$ value of about 1.23 to 1.29 for the magnetic fields of
+1 and 3 T. The second magnetization peaks appear in wide temperature region
+from 2 K to 24 K. The separation between the second peak field and the
+irreversibility field becomes narrow when temperature is increased. When the
+two fields are close to each other, we find that the second peak evolves into a
+step like transition of magnetization, suggesting a crossover from the second
+order to first order transition. Finally, we present a vortex phase diagram and
+demonstrate that the vortex dynamics in Ba$_{1-x}$K$_x$BiO$_3$ can be used as a
+model system for studying the collective vortex pining.",1701.01346v1
+2017-07-09,Signatures of pairing in the magnetic excitation spectrum of strongly correlated ladders,"Magnetic interactions are widely believed to play a crucial role in the
+microscopic mechanism leading to high critical temperature superconductivity.
+It is therefore important to study the signatures of pairing in the magnetic
+excitation spectrum of simple models known to show unconventional
+superconducting tendencies. Using the Density Matrix Renormalization Group
+technique, we calculate the dynamical spin structure factor $S({\bf k},\omega)$
+of a generalized $t-U-J$ Hubbard model away from half-filling in a two-leg
+ladder geometry. The addition of $J$ enhances pairing tendencies. We analyze
+quantitatively the signatures of pairing in the magnetic excitation spectra. We
+found that the superconducting pair-correlation strength, that can be estimated
+independently from ground state properties, is closely correlated with the
+integrated low-energy magnetic spectral weight in the vicinity of $(\pi,\pi)$.
+In this wave-vector region, robust spin incommensurate features develop with
+increasing doping. The branch of the spectrum with rung direction wave-vector
+$k_{rung}=0$ does not change substantially with doping where pairing dominates,
+and thus plays a minor role. We discuss the implications of our results for
+neutron scattering experiments, where the spin excitation dynamics of
+hole-doped quasi-one dimensional magnetic materials can be measured, and also
+address implications for recent resonant inelastic X-ray scattering
+experiments.",1707.02626v1
+2017-10-17,Observation of superparamagnetism in coexistence with quantum anomalous Hall C=$\pm$1 and C=0 Chern states,"Simultaneous transport and scanning nanoSQUID-on-tip magnetic imaging studies
+in Cr-(Bi,Sb)$_2$Te$_3$ modulation-doped films reveal the presence of
+superparamagnetic order within the quantum anomalous Hall regime. In contrast
+to the expectation that a long-range ferromagnetic order is required for
+establishing the quantum anomalous Hall state, superparamagnetic dynamics of
+weakly interacting nanoscale magnetic islands is observed both in the plateau
+transition regions as well as within the fully quantized C=$\pm$1 Chern
+plateaus. Modulation doping of the topological insulator films is found to give
+rise to significantly larger superparamagnetic islands as compared to uniform
+magnetic doping, evidently leading to enhanced robustness of the quantum
+anomalous Hall effect. Nonetheless, even in this more robust quantum state,
+attaining full quantization of transport coefficients requires magnetic
+alignment of at least 95% of the superparamagnetic islands. The
+superparamagnetic order is also found within the incipient C=0 zero Hall
+plateau, which may host an axion state if the top and bottom magnetic layers
+are magnetized in opposite directions. In this regime, however, a significantly
+lower level of island alignment is found in our samples, hindering the
+formation of the axion state. Comprehension and control of superparamagnetic
+dynamics is thus a key factor in apprehending the fragility of the quantum
+anomalous Hall state and in enhancing the endurance of the different quantized
+states to higher temperatures for utilization of robust topological protection
+in novel devices.",1710.06446v1
+2017-10-20,Transverse instabilities of stripe domains in magnetic thin films with perpendicular magnetic anisotropy,"Stripe domains are narrow, elongated, reversed regions that exist in magnetic
+materials with perpendicular magnetic anisotropy. Stripe domains appear as a
+pair of domain walls that can exhibit topology with a nonzero chirality. Recent
+experimental and numerical investigations identify an instability of stripe
+domains in the long direction as a means of nucleating isolated magnetic
+skyrmions. Here, the onset and nonlinear evolution of transverse instabilities
+for a dynamic stripe domain known as the bion stripe are investigated. Both
+non-topological and topological variants of the bion stripe are shown to
+exhibit a long-wavelength transverse instability with different characteristic
+features. In the former, small transverse variations in the stripe's width lead
+to a neck instability that eventually pinches the non-topological stripe into a
+chain of two-dimensional breathers composed of droplet soliton pairs. In the
+latter case, small variations in the stripe's center results in a snake
+instability whose topological structure leads to the nucleation of dynamic
+magnetic skyrmions and antiskyrmions as well as perimeter-modulated droplets.
+Quantitative, analytical predictions for both the early, linear evolution and
+the long-time, nonlinear evolution are achieved using an averaged Lagrangian
+approach that incorporates both exchange (dispersion) and anisotropy
+(nonlinearity). The method of analysis is general and can be applied to other
+filamentary structures.",1710.07718v1
+2017-11-03,Geometric theory of the natural optical activity in noncentrosymmetric metals,"This is a PhD dissertation. Ignited by the chiral anomaly of recently
+discovered Weyl (semi-)metals, we study the chiral magnetic effect and the
+natural optical activity of noncentrosymmetric metals. Both phenomena are
+related to the linear-in-$\mathbf{q}$ spatial dispersion of the optical
+conductivity tensor, and can be calculated within the formalism of the
+semiclassical kinetic equation. Therefore, we calculate the dispersion of
+optical conductivity up to the linear order of the wave vector, in the low
+frequency regime, with both the semiclassical Boltzmann equation and the Kubo
+formula. The two different methods of calculation provide us the same result.
+In this result, the static and dynamic chiral magnetic effects are revealed to
+have different origin: one comes from topology, related to Berry monopoles, and
+the other has a geometric origin, which is determined by the orbital magnetic
+moment. The Faraday rotation of the polarization of light transmitted through a
+slab of the sample provides us the most direct way to measure the magnitude of
+dynamic chiral magnetic effect. We develop an effective medium theory for
+electromagnetic wave propagating through gapless nonuniform systems, to
+calculate macroscopic sample inhomogeneities induced corrections to the chiral
+magnetic conductivity. We show that, in metals with low carrier density, the
+way in which macroscopic fluctuations of the local conductivity affect the
+frequency dependent of the measured optical polarization rotation angle: by
+creating a sharp feature near the plasma edge, which can be detected by
+experiments. Then we narrow down our research a bit further to the current
+induced magnetization.",1711.01289v2
+2018-01-11,Occurrence and persistence of magnetic elements in the quiet Sun,"Turbulent convection efficiently transports energy up to the solar
+photosphere, but its multi-scale nature and dynamic properties are still not
+fully understood. Several works in the literature have investigated the
+emergence of patterns of convective and magnetic nature in the quiet Sun at
+spatial and temporal scales from granular to global. Aims. To shed light on the
+scales of organisation at which turbulent convection operates, and its
+relationship with the magnetic flux therein, we studied characteristic spatial
+and temporal scales of magnetic features in the quiet Sun. Methods. Thanks to
+an unprecedented data set entirely enclosing a supergranule, occurrence and
+persistence analysis of magnetogram time series were used to detect spatial and
+long-lived temporal correlations in the quiet Sun and to investigate their
+nature. Results. A relation between occurrence and persistence representative
+for the quiet Sun was found. In particular, highly recurrent and persistent
+patterns were detected especially in the boundary of the supergranular cell.
+These are due to moving magnetic elements undergoing motion that behaves like a
+random walk together with longer decorrelations ($\sim2$ h) with respect to
+regions inside the supergranule. In the vertices of the supegranular cell the
+maximum observed occurrence is not associated with the maximum persistence,
+suggesting that there are different dynamic regimes affecting the magnetic
+elements.",1801.03871v1
+2018-05-04,Selective measurements of intertwined multipolar orders: non-Kramers doublets on a triangular lattice,"Motivated by the rapid experimental progress on the spin-orbit-coupled Mott
+insulators, we propose and study a generic spin model that describes the
+interaction between the non-Kramers doublets on a triangular lattice and is
+relevant for triangular lattice rare-earth magnets. We predict that the system
+supports both pure quadrupolar orders and intertwined multipolar orders in the
+phase diagram. Besides the multipolar orders, we explore the magnetic
+excitations to reveal the dynamic properties of the systems. Due to the
+peculiar properties of the non-Kramers doublets and the selective coupling to
+the magnetic field, we further study the magnetization process of the system in
+the magnetic field. We point out the selective measurements of the static and
+dynamic properties of the intertwined multipolarness in the neutron scattering,
+NMR and $\mu$SR probes and predict the experimental consequences. The relevance
+to the existing materials such as TmMgGaO$_{4}$, Pr-based and Tb-based magnets,
+and many ternary chalcogenides is discussed. Our results illustrate the rich
+physics and the promising direction in the interplay between strong
+spin-orbit-entangled multipole moments and the geometrical frustration.",1805.01865v3
+2018-06-01,"Magnetic phases of skyrmion-hosting GaV$_4$S$_{8-y}$Se$_{y}$ ($y = 0, 2, 4, 8$) probed with muon spectroscopy","We present the results of a muon-spin spectroscopy investigation of
+GaV$_4$S$_{8-y}$Se$_{y}$ with $y=0, 2, 4$ and 8. Zero-field measurements
+suggest that GaV$_{4}$Se$_{8}$ and GaV$_{4}$S$_{8}$ have distinct magnetic
+ground states, with the latter material showing an anomalous
+temperature-dependence of the local magnetic field. It is not possible to
+evolve the magnetic state continuously between these two systems, with the
+intermediate $y=2$ and $4$ materials showing glassy magnetic behaviour at low
+temperature. The skyrmion lattice (SkL) phase is evident in the $y=0$ and 8
+materials through an enhanced response of the muon-spin relaxation to the
+emergent dynamics that accompany the SkL. For our polycrystalline samples of
+GaV$_4$Se$_{8}$, this enhanced dynamic response is confined to a smaller region
+of the magnetic field-temperature phase diagram than the previous reports of
+the SkL in single crystals.",1806.00412v3
+2018-06-14,Selection of axial dipole from a seed magnetic field in rapidly rotating dynamo models,"In this study, we investigate preferences of dipolar magnetic structure from
+a seed magnetic field in the rapidly rotating spherical shell dynamo models. In
+this study, we set up a realistic model to show the effect of the Lorentz force
+in the polarity selection. The important results that has come out from our
+study is that the magnetic field acts on the flow much before the saturation.
+Our study suggests that the growth of the magnetic field is not a kinematic
+effect as one might think off, rather a dynamic effect. This dynamic effect
+grows as the field generated with time and finally brings the saturation to the
+dynamo action. Previous studies show that Lorentz force effect the flow when
+Elsasser number more or less 1 and the studies were focused on the saturation
+by looking at the time-averaged quantities. However, in this study, we show a
+clear effect of the Lorentz force even at Elsasser number of $0.3-0.4$. To show
+the effect of the Lorentz force, we did two different simulations, one is a
+nonlinear model and another is kinematic model and shows that how a magnetic
+field can change the flow structure and by doing that the generated field
+changes, while this kind of behavior is not observed in kinematic dynamo
+models. This study shows a scale dependent behaviour of the kinetic helicity at
+two different spectral range.",1806.05368v1
+2018-08-21,Pseudospin-lattice coupling in the spin-orbit Mott insulator Sr2IrO4,"Spin-orbit entangled magnetic dipoles, often referred to as pseudospins,
+provide a new avenue to explore novel magnetism inconceivable in the weak
+spin-orbit coupling limit, but the nature of their low-energy interactions
+remains to be understood. We present a comprehensive study of the static
+magnetism and low-energy pseudospin dynamics in the archetypal spin-orbit Mott
+insulator Sr2IrO4. We find that in order to understand even basic magnetization
+measurements, a formerly overlooked in-plane anisotropy is fundamental. In
+addition to magnetometry, we use neutron diffraction, inelastic neutron
+scattering and resonant elastic and inelastic x-ray scattering to identify and
+quantify the interactions that determine the global symmetry of the system and
+govern the linear responses of pseudospins to external magnetic felds and their
+low-energy dynamics. We find that a pseudospin-only Hamiltonian is insufficient
+for an accurate description of the magnetism in Sr2IrO4 and that
+pseudospin-lattice coupling is essential. This finding should be generally
+applicable to other pseudospin systems with sizable orbital moments sensitive
+to anisotropic crystalline environments.",1808.06920v2
+2018-09-12,Low-Temperature and Dynamic Magnetism of Highly Frustrated 5d2 Li4MgOsO6 Polymorphs in Comparison with 5d3 Li3Mg2OsO6,"Geometric magnetic frustration (GMF) has attracted substantial interest due
+to the exotic physics and rich phase diagrams revealed by the cancellation of
+normally-dominant magnetic interactions, giving impetus for the search for
+novel frustrated systems, most often based on antiferromagnetic correlations
+between magnetic ions decorating triangular or tetrahedral lattices. We report
+here low-temperature magnetic susceptibility and muon spin relaxation results
+on Li4MgOsO6 and Li3Mg2OsO6, members of the A5BO6 ""rock salt ordered"" family of
+frustrated materials. In Li3Mg2OsO6 we find spin freezing below 12K. In
+Li4MgOsO6, which can crystallize into either orthorhombic Fddd or monoclinic
+C2/m crystal symmetries depending on synthesis conditions, we find magnetism
+consistent with glassy-like behavior dominating below 2K, with partial ordering
+and evidence for dynamics at somewhat higher temperatures.",1809.04687v3
+2018-10-19,Effect of Meissner screening and trapped magnetic flux on magnetization dynamics in thick Nb/Ni80Fe20/Nb trilayers,"We investigate the influence of Meissner screening and trapped magnetic flux
+on magnetization dynamics for a Ni80Fe20 film sandwiched between two thick Nb
+layers (100 nm) using broadband (5-20 GHz) ferromagnetic resonance (FMR)
+spectroscopy. Below the superconducting transition Tc of Nb, significant
+zero-frequency line broadening (5-6 mT) and DC resonance field shift (50 mT) to
+a low field are both observed if the Nb thickness is comparable to the London
+penetration depth of Nb films (>= 100 nm). We attribute the observed peculiar
+behaviors to the increased incoherent precession near the Ni80Fe20/Nb interface
+and the effectively focused magnetic flux in the middle Ni80Fe20 caused by
+strong Meissner screening and (defect-)trapped flux of the thick adjacent Nb
+layers. This explanation is supported by static magnetic properties of the
+samples and comparison with FMR data on thick Nb/Ni80Fe20 bilayers. Great care
+should therefore be taken in the analysis of FMR response in ferromagnetic
+Josephson structures with thick superconductors, a fundamental property for
+high-frequency device applications of spin-polarized supercurrents.",1810.08443v2
+2018-11-21,Does magnetic field modify tidal dynamics in the convective envelope of Solar mass stars?,"The energy dissipation of wave-like tidal flows in the convective envelope of
+low-mass stars is one of the key physical mechanisms that shape the orbital and
+rotational dynamics of short-period planetary systems. Tidal flows, and the
+excitation, propagation, and dissipation of tidally-induced inertial waves can
+be modified by stellar magnetic fields (e.g., Wei 2016, 2018, Lin and Ogilvie
+2018). It is thus important to assess for which stars, at which location of
+their internal structure, and at which phase of their evolution, one needs to
+take into account the effects of magnetic fields on tidal waves. Using scaling
+laws that provide the amplitude of dynamo-generated magnetic fields along the
+rotational evolution of these stars (e.g., Christensen et al. 2009, Brun et al.
+2015), combined with detailed grids of stellar rotation models (e.g., Amard et
+al. 2016), we examine the influence of a magnetic field on tidal forcing and
+dissipation near the tachocline of solar-like stars. We show that full
+consideration of magnetic fields is required to compute tidal dissipation, but
+not necessarily for tidal forcing.",1811.08649v1
+2018-12-06,Finite Dissipation in Anisotropic Magnetohydrodynamic Turbulence,"In presence of an externally supported, mean magnetic field a turbulent,
+conducting medium, such as plasma, becomes anisotropic. This mean magnetic
+field, which is separate from the fluctuating, turbulent part of the magnetic
+field, has considerable effects on the dynamics of the system. In this paper,
+we examine the dissipation rates for decaying incompressible
+magnetohydrodynamic (MHD) turbulence with increasing Reynolds number, and in
+the presence of a mean magnetic field of varying strength. Proceeding
+numerically, we find that as the Reynolds number increases, the dissipation
+rate asymptotes to a finite value for each magnetic field strength, confirming
+the K\'arm\'an-Howarth hypothesis as applied to MHD. The asymptotic value of
+the dimensionless dissipation rate is initially suppressed from the
+zero-mean-field value by the mean magnetic field but then approaches a constant
+value for higher values of the mean field strength. Additionally, for
+comparison, we perform a set of two-dimensional (2DMHD) and a set of reduced
+MHD (RMHD) simulations. We find that the RMHD results lie very close to the
+values corresponding to the high mean-field limit of the three-dimensional runs
+while the 2DMHD results admit distinct values far from both the zero mean field
+cases and the high mean field limit of the three-dimensional cases. These
+findings provide firm underpinnings for numerous applications in space and
+astrophysics wherein von K\'arm\'an decay of turbulence is assumed.",1812.02379v1
+2018-12-28,High-order two-fluid plasma solver for direct numerical simulations of plasma flows with full transport phenomena,"The two-fluid plasma equations for a single ion species, with full transport
+terms, including temperature and magnetic field dependent ion and electron
+viscous stresses and heat fluxes, frictional drag force, and ohmic heating term
+have been implemented in the CFDNS code and solved by using sixth-order
+non-dissipative compact finite differences for plasma flows in several
+different regimes. In order to be able to fully resolve all the dynamically
+relevant time and length scales, while maintaining computational feasibility,
+the assumptions of infinite speed of light and negligible electron inertia have
+been made. Non-dimensional analysis of the two-fluid plasma equations shows
+that, by varying the characteristic/background number density, length scale,
+temperature, and magnetic strength, the corresponding Hall, resistive, and
+ideal magnetohydrodynamics (MHD) equations can be recovered as limiting cases.
+The accuracy and robustness of this two-fluid plasma solver in handling plasma
+flows in different regimes have been validated against four canonical problems:
+Alfven and whistler dispersion relations, electromagnetic plasma shock, and
+magnetic reconnection. For all test cases, by using physical dissipation and
+diffusion, with negligible numerical dissipation/diffusion, fully converged
+Direct Numerical Simulations (DNS)-like solutions are obtained when the ion
+Reynolds number based on grid size is smaller than a threshold value which is
+about 2.3 in this study. For the magnetic reconnection problem, the results
+show that the magnetic flux saturation time and value converge when the ion and
+magnetic Reynolds numbers are large enough. Thus, the DNS-like results become
+relevant to practical problems with much larger Reynolds numbers.",1812.11237v1
+2019-01-05,Generation and transport of magnetic flux in accretion-ejection flows,"Astrophysical accretion flows are associated with energetic emission of
+radiation and outflows (winds and jets). Extensive observations of these two
+processes in X-ray binary outbursts are available. A convincing understanding
+of their dynamics remains, however, elusive. The main agent that controls the
+dynamics is believed to be a large scale magnetic field that threads the
+system. We propose that during the quiescent state, the field is held in place
+by a delicate balance between inward advection and outward diffusion through
+the accreting matter. We also propose that the source of the field is a growing
+toroidal electric current generated by the aberrated radiation pressure on the
+innermost plasma electrons in orbit around the central black hole. This is the
+astrophysical mechanism of the Cosmic Battery. When the return magnetic field
+outside the toroidal electric current diffuses through the surrounding disk,
+the disk magnetic field and its associated accretion rate gradually increase,
+thus leading the system to an outburst. After the central accretion flow
+approaches equipartition with radiation, it is disrupted, and the Cosmic
+Battery ceases to operate. The outward field diffusion is then reversed,
+magnetic flux reconnects with the flux accumulated around the central black
+hole and disappears. The magnetic field and the associated accretion rate
+slowly decrease, and the system is gradualy driven back to quiescence. We
+conclude that the action (or inaction) of the Cosmic Battery may be the missing
+key that will allow us to understand the long-term evolution of astrophysical
+accretion-ejection flows.",1901.01404v3
+2019-03-26,Astro2020 Science White Paper: Probing Magnetic Reconnection in Solar Flares - New Perspectives from Radio Dynamic Imaging Spectroscopy,"Magnetic reconnection is a fundamental physical process in many laboratory,
+space, and astrophysical plasma contexts. Solar flares serve as an outstanding
+laboratory to study the magnetic reconnection and the associated energy release
+and conversion processes under plasma conditions difficult to reproduce in the
+laboratory, and with considerable spatiotemporal details not possible elsewhere
+in astrophysics. Here we emphasize the unique power of remote-sensing
+observations of solar flares at radio wavelengths. In particular, we discuss
+the transformative technique of broadband radio dynamic imaging spectroscopy in
+making significant contributions to addressing several outstanding challenges
+in magnetic reconnection, including the capability of pinpointing magnetic
+reconnection sites, measuring the time-evolving reconnecting magnetic fields,
+and deriving the spatially and temporally resolved distribution function of
+flare-accelerated electrons.",1903.11192v1
+2019-03-28,Magnetic filed dynamics and varying plasma emission in large coronal loops,"In this study we report detailed observations of magnetic environment at four
+footpoints of two warm coronal loops observed on 5 May 2016 in NOAA AR 12542
+(Loop I) and 17 Dec 2015 in NOAA AR 12470 (Loop II). These loops were
+connecting a plage region with sunspot periphery (Loop I) and a sunspot umbra
+(Loop II). We used Solar Dynamics Observatory (SDO) and Goode Solar Telescope
+(GST) data to describe the phenomenon and understand its causes. The study
+indicates loop brightening episodes were associated with magnetic flux
+emergence and cancellation processes observed in SDO's Helioseismic and
+Magnetic Imager (HMI) and GST's Near InfraRed Imaging Spectrapolarimeter
+(NIRIS) data. The observed activity was driven by magnetic reconnection between
+small-scale emerging dipoles and large-scale pre-existing fields, suggesting
+that the reconnection occurred in the lower chromosphere at the edge of an
+extended plage region, where the loops were rooted. We suggest that plasma,
+evaporated during these reconnection events, gradually filled the loops and as
+it cooled the visible density front propagated from one footpoint of the loop
+to another at a rate of 90-110 km s$^{-1}$. This study also indicates that at
+least some of the bright loops seen in SDO Atmospheric Imaging Assembly images
+rooted in sunspot umbra may be heated due to magnetic activity taking place at
+the remote (non-sunspot) footpoint.",1903.12148v1
+2019-04-11,FSRQ/BL Lac dichotomy as the magnetized advective accretion process around black holes: a unified classification of blazars,"The $Fermi$ blazar observations show a strong correlation between
+$\gamma$-ray luminosities and spectral indices. BL Lac objects are less
+luminous with harder spectra than flat-spectrum radio quasars (FSRQs).
+Interestingly FSRQs are evident to exhibit a Keplerian disc component along
+with a powerful jet. We compute the jet intrinsic luminosities by beaming
+corrections determined by different cooling mechanisms. Observed $\gamma$-ray
+luminosities and spectroscopic measurements of broad emission lines suggest a
+correlation of the accretion disc luminosity with jet intrinsic luminosity.
+Also, theoretical and observational inferences for these jetted sources
+indicate a signature of hot advective accretion flow and a dynamically dominant
+magnetic field at jet-footprint. Indeed it is difficult to imagine the powerful
+jet launching from a geometrically thin Keplerian disc. We propose a
+magnetized, advective disc-outflow symbiosis with explicit cooling to address a
+unified classification of blazars by controlling both the mass accretion rate
+and magnetic field strength. The large scale strong magnetic fields influence
+the accretion dynamics, remove angular momentum from the infalling matter, help
+in the formation of strong outflows/jets, and lead to synchrotron emissions
+simultaneously. We suggest that the BL Lacs are more optically thin and
+magnetically dominated than FSRQs at the jet-footprint to explain their
+intrinsic $\gamma$-ray luminosities.",1904.05898v1
+2019-04-21,Spectropolarimetric analysis of an active region filament. I. Magnetic and dynamical properties from single component inversions,"The determination of the magnetic filed vector in solar filaments is possible
+by interpreting the Hanle and Zeeman effects in suitable chromospheric spectral
+lines like those of the He I multiplet at 10830 A. We study the vector magnetic
+field of an active region filament (NOAA 12087). Spectropolarimetric data of
+this active region was acquired with the GRIS instrument at the GREGOR
+telescope and studied simultaneously in the chromosphere with the He I 10830 A
+multiplet and in the photosphere with the Si I 10827 A line. As it is usual
+from previous studies, only a single component model is used to infer the
+magnetic properties of the filament. The results are put into a solar context
+with the help of the Solar Dynamic Observatory images. Some results clearly
+point out that a more complex inversion had to be done. Firstly, the Stokes $V$
+map of He I does not show any clear signature of the presence of the filament.
+Secondly, the local azimuth map follows the same pattern than Stokes $V$ as if
+the polarity of Stokes $V$ were conditioning the inference to very different
+magnetic field even with similar linear polarization signals. This indication
+suggests that the Stokes $V$ could be dominated by the below magnetic field
+coming from the active region, and not, from the filament itself. Those and
+more evidences will be analyzed in depth and a more complex inversion will be
+attempted in the second part of this series.",1904.09593v1
+2019-06-18,The structure of magnetic turbulence in the heliosheath region observed by Voyager 2 at 106 AU,"It is currently believed that the turbulent fluctuations pervade the
+outermost heliosphere. Turbulence, magnetic reconnection, and their link may be
+responsible for magnetic energy conversion in these regions. The governing
+mechanisms of such anisotropic and compressible magnetic turbulence in the
+inner heliosheath (IHS) and in the local interstellar medium (LISM) still lack
+a thorough description. The present literature mainly concerns large scales
+which are not representative of the inertial-cascade dynamics of turbulence.
+Moreover, lack of broadband spectral analysis makes the IHS dynamics critically
+understudied. Our recent study shows that 48 s magnetic-field data from the
+Voyager mission are appropriate for a spectral analysis over a frequency range
+of six decades, from 5 x 10-8 Hz to 10-2 Hz. Here, focusing on the Voyager 2
+observation interval from 2013.824 to 2016.0, we describe the structure of
+turbulence in a sector zone of the IHS. A spectral break around 7 x 10-7 Hz
+(magnetic structures with size l~1.3 Astronomical Units) separates the
+energy-injection regime from the inertial-cascade regime of turbulence. A
+second scale is observed around 6 x 10-5 Hz (l~ 0.017 AU) and corresponds to a
+peak of compressibility and intermittency of fluctuations.",1906.07520v1
+2019-07-18,Kosterlitz-Thouless Melting of Magnetic Order in the Triangular Quantum Ising Material TmMgGaO$_4$,"Frustrated magnets host the promises of material realizations of new paradigm
+of quantum matter, while direct comparison of unbiased model calculations with
+experimental measurements is still very challenging. Here, we design and
+implement a protocol of employing many-body computation methodologies for
+accurate model calculation -- both equilibrium and dynamical properties -- of a
+frustrated rare-earth magnet TmMgGaO$_4$ (TMGO), which perfectly explains the
+corresponding experimental findings. Our results confirm TMGO is an ideal
+realization of triangular-lattice Ising model with an intrinsic transverse
+field. The magnetic order of TMGO is predicted to melt through two successive
+Kosterlitz-Thouless (KT) phase transitions, with a floating KT phase in
+between. The dynamical spectra calculated suggest remnant images of a vanishing
+magnetic stripe order that represent vortex-antivortex pairs, resembling rotons
+in a superfluid helium film. TMGO therefore constitutes a rare quantum magnet
+for realizing KT physics and we further propose experimental detections of its
+intriguing properties.",1907.08173v3
+2019-10-17,3-Dimensional Dusty Plasma in a Strong Magnetic Field: Observation of Rotating Dust Tori,"The paper reports on the dynamics of a 3-dimensional dusty plasma in a strong
+magnetic field. An electrostatic potential well created by a conducting or
+non-conducting ring in the rf discharge confines the charged dust particles. In
+the absence of the magnetic field, dust grains exhibit a thermal motion about
+their equilibrium position. As the magnetic field crosses a threshold value (B
+$>$ 0.02 T), the edge particles start to rotate and form a vortex in the
+vertical plane. At the same time, the central region particles either exhibit
+thermal motion or $\vec{E} \times \vec{B}$ motion in the horizontal plane. At B
+$>$ 0.15 T, the central region dust grains start to rotate in the opposite
+direction resulting in a pair of counter-rotating vortices in the vertical
+plane. The characteristics of the vortex pair change with increasing the
+strength of the magnetic field (B $\sim$ 0.8 T). At B $>$ 0.8 T, dust grains
+exhibit very complex motion in the rotating torus. The angular frequency
+variation of rotating particles indicates a differential or sheared dust
+rotation in a vortex. The angular frequency increases with increasing the
+magnetic field from 0.05 T to 0.8 T. The ion drag force and dust charge
+gradient along with the E-field are considered as possible energy sources for
+driving the edge vortex flow and central region vortex motion, respectively.
+The directions of rotation also confirm the different energy sources
+responsible for the vortex motion.",1910.07846v2
+2019-11-25,Quantum field theory of topological spin dynamics,"We develop a field theory of quantum magnets and magnetic (semi)metals, which
+is suitable for the analysis of their universal and topological properties. The
+systems of interest include collinear, coplanar and general non-coplanar
+magnets. At the basic level, we describe the dynamics of magnetic moments using
+smooth vector fields in the continuum limit. Dzyaloshinskii-Moriya interaction
+is captured by a non-Abelian vector gauge field, and chiral spin couplings
+related to topological defects appear as higher-rank antisymmetric tensor gauge
+fields. We distinguish type-I and type-II magnets by their equilibrium response
+to the non-Abelian gauge flux, and characterize the resulting lattices of
+skyrmions and hedgehogs, the spectra of spin waves, and the chiral response to
+external perturbations. The general spin-orbit coupling of electrons is
+similarly described by non-Abelian gauge fields, including higher-rank tensors
+related to the electronic Berry flux. Itinerant electrons and local moments
+exchange their gauge fluxes through Kondo and Hund interactions. Hence, by
+utilizing gauge fields, this theory provides a unifying physical picture of
+``intrinsic'' and ``topological'' anomalous Hall effects, spin-Hall effects,
+and other correlations between the topological properties of electrons and
+moments. We predict ``topological'' magnetoelectric effect in materials prone
+to hosting hedgehogs. Links to experiments and model calculations are provided
+by deriving the couplings and gauge fields from generic microscopic models,
+including the Hubbard model with spin-orbit interactions. We establish the
+possible existence of novel quantum spin liquids that exhibit a fractional
+magnetoelectric effect, and discuss a few applications to topological magnetic
+conductors like Mn$_3$Sn and Pr$_2$Ir$_2$O$_7$.",1911.11155v2
+2020-01-13,The Surprisingly Small Impact of Magnetic Fields On The Inner Accretion Flow of Sagittarius A* Fueled By Stellar Winds,"We study the flow structure in 3D magnetohydrodynamic (MHD) simulations of
+accretion onto Sagittarius A* via the magnetized winds of the orbiting
+Wolf-Rayet stars. These simulations cover over 3 orders of magnitude in radius
+to reach $\approx$ 300 gravitational radii, with only one poorly constrained
+parameter (the magnetic field in the stellar winds). Even for winds with
+relatively weak magnetic fields (e.g., plasma $\beta$ $\sim$ $10^6$), flux
+freezing/compression in the inflowing gas amplifies the field to $\beta$ $\sim$
+few well before it reaches the event horizon. Overall, the dynamics, accretion
+rate, and spherically averaged flow profiles (e.g., density, velocity) in our
+MHD simulations are remarkably similar to analogous hydrodynamic simulations.
+We attribute this to the broad distribution of angular momentum provided by the
+stellar winds, which sources accretion even absent much angular momentum
+transport. We find that the magneto-rotational instability is not important
+because of i) strong magnetic fields that are amplified by flux
+freezing/compression, and ii) the rapid inflow/outflow times of the gas and
+inefficient radiative cooling preclude circularization. The primary effect of
+magnetic fields is that they drive a polar outflow that is absent in
+hydrodynamics. The dynamical state of the accretion flow found in our
+simulations is unlike the rotationally supported tori used as initial
+conditions in horizon scale simulations, which could have implications for
+models being used to interpret Event Horizon Telescope and GRAVITY observations
+of Sgr A*.",2001.04469v1
+2020-02-19,Linear and nonlinear hydromagnetic stability in laminar and turbulent flows,"We consider the evolution of arbitrarily large perturbations of a prescribed
+pure hydrodynamical flow of an electrically conducting fluid. We study whether
+the flow perturbations as well as the generated magnetic fields decay or grow
+with time and constitute a dynamo process. For that purpose we derive a
+generalized Reynolds-Orr equation for the sum of the kinetic energy of the
+hydrodynamic perturbation and the magnetic energy. The flow is confined in a
+finite volume so the normal component of the velocity at the boundary is zero.
+The tangential component is left arbitrary in contrast with previous works. For
+the magnetic field we mostly employ the classical boundary conditions where the
+field extends in the whole space. We establish critical values of hydrodynamic
+and magnetic Reynolds numbers below which arbitrarily large initial
+perturbations of the hydrodynamic flow decay. This involves generalization of
+the Rayleigh-Faber-Krahn inequality for the smallest eigenvalue of an elliptic
+operator. For high Reynolds number turbulence we provide an estimate of
+critical magnetic Reynolds number below which arbitrarily large fluctuations of
+the magnetic field decay.",2002.08275v2
+2020-05-15,Diffusion of large-scale magnetic fields by reconnection in MHD turbulence,"The rate of magnetic field diffusion plays an essential role in several
+astrophysical plasma processes. It has been demonstrated that the omnipresent
+turbulence in astrophysical media induces fast magnetic reconnection, which
+consequently leads to large-scale magnetic flux diffusion at a rate independent
+of the plasma microphysics. This process is called ``reconnection diffusion''
+(RD) and allows for the diffusion of fields which are dynamically important.
+The current theory describing RD is based on incompressible magnetohydrodynamic
+(MHD) turbulence. In this work, we have tested quantitatively the predictions
+of the RD theory when magnetic forces are dominant in the turbulence dynamics
+(Alfv\'{e}nic Mach number $M_A < 1$). We employed the \textsc{Pencil Code} to
+perform numerical simulations of forced MHD turbulence, extracting the values
+of the diffusion coefficient $\eta_{RD}$ using the Test-Field method. Our
+results are consistent with the RD theory ($\eta_{RD} \sim M_A^{3}$ for $M_A <
+1$) when turbulence approaches the incompressible limit (sonic Mach number $M_S
+\lesssim 0.02$), while for larger $M_S$ the diffusion is faster ($\eta_{RD}
+\sim M_A^{2}$). This work shows for the first time simulations of compressible
+MHD turbulence with the suppression of the cascade in the direction parallel to
+the mean magnetic field, which is consistent with incompressible weak
+turbulence theory. We also verified that in our simulations the energy
+cascading time does not follow the scaling with $M_A$ predicted for the weak
+regime, in contradiction with the RD theory assumption. Our results generally
+support and expand the RD theory predictions.",2005.07775v2
+2020-06-19,X-ray detection of ultrashort spin current pulses in synthetic antiferromagnets,"We explore the ultrafast generation of spin currents in magnetic multilayer
+samples by applying fs laser pulses to one layer and measuring the magnetic
+response in the other layer by element-resolved x-ray spectroscopy. In
+Ni(5~nm)/Ru(2~nm)/Fe(4~nm), the Ni and Fe magnetization directions couple
+antiferromagnetically due to the RKKY interaction, but may be oriented parallel
+through an applied magnetic field. After exciting the top Ni layer with a fs
+laser pulse, we find that also the Fe layer underneath demagnetizes, with a
+$4.1 \pm 1.9$\% amplitude difference between parallel and antiparallel
+orientation of the Ni and Fe magnetizations. We attribute this difference to
+the influence of a spin current generated by the fs laser pulse that transfers
+angular momentum from the Ni into the Fe layer. Our results confirm that
+superdiffusive spin transport plays a role in determining the sub-ps
+demagnetization dynamics of synthetic antiferromagnetic layers, but also
+evidence large depolarization effects due to hot electron dynamics, which are
+independent of the relative alignment of the magnetization in Ni and Fe.",2006.11030v1
+2020-08-07,Spin dynamics under the influence of elliptically rotating fields: Extracting the field topology from time-averaged quantities,"We focus on quantum systems that can be effectively described as a localized
+spin-$s$ particle subject to a static magnetic field coplanar to a coexisting
+elliptically rotating time-periodic field. Depending on the values taken on by
+the static and rotating components, the total magnetic field shows two regimes
+with different topological properties. Along the boundary that separates these
+two regimes, the total magnetic field vanishes periodically in time and the
+system dynamics becomes highly nonadiabatic. We derive a relation between two
+time-averaged quantities of the system which is linked to the topology of the
+applied magnetic field. Based on this finding, we propose a measurable quantity
+that has the ability to indicate the topology of the total magnetic field
+without knowing a priori the value of the static component. We also propose a
+possible implementation of our approach by a trapped-ion quantum system. The
+results presented here are independent of the initial state of the system. In
+particular, when the system is initialized in a Floquet state, we find some
+interesting properties of the quasienergy spectrum which are linked to the
+topological change of the total magnetic field. Throughout the paper, the
+theoretical results are illustrated with numerical simulations for the case of
+a two-level quantum system.",2008.03078v2
+2020-08-11,Near-horizon structure of escape zones of electrically charged particles around weakly magnetized rotating black hole. II. Acceleration and escape in the oblique magnetosphere,"Strong gravity and magnetic fields are key ingredients that power processes
+of accretion and ejection near compact objects. While the particular mechanisms
+that operate here are still discussed, it seems that the presence of an ordered
+magnetic field is crucial for the acceleration and collimation of relativistic
+jets of electrically charged particles on superhorizon length scales. In this
+context, we further study the effect of a large-scale magnetic field on the
+dynamics of charged particles near a rotating black hole. We consider a
+scenario in which the initially neutral particles on regular geodesic orbits in
+the equatorial plane are destabilized by a charging process (e.g., by
+photoionization). Some charged particles are accelerated out of the equatorial
+plane, and they follow jetlike trajectories with relativistic velocities. In
+our previous paper, we investigated this scenario for the case of perfect
+alignment of the magnetic field with the axis of rotation; i.e., the system was
+considered axisymmetric. Here we relax this assumption and investigate
+nonaxisymmetric systems in which the magnetic field is arbitrarily inclined
+with respect to the black hole spin. We study the system numerically in order
+to locate the zones of escaping trajectories and compute the maximum (terminal)
+escape velocity. It appears that breaking the axial symmetry (even by small
+inclination angles) substantially increases the fraction of escaping orbits and
+allows the acceleration to ultrarelativistic velocities that were excluded in
+the axisymmetric setup. The presence of transient chaotic dynamics in the
+launching region of the relativistic outflow is confirmed with chaotic
+indicators.",2008.04630v2
+2020-08-19,Dynamics of Composite Domain Walls in Multiferroics in Magnetic Field and Their Instability,"We study theoretically the dynamics of composite domain walls (DW) in
+multiferroic material GdFeO${}_3$ driven by magnetic field $H$. Two
+antiferromagnetic orders of Fe and Gd spins interact Gd-ion displacement in
+this system with coupling $c$ at low temperatures, and we have numerically
+simulated the corresponding time-dependent Ginzburg-Landau equations in which
+magnetic field $H$ couples to Fe-spin order parameter. We vary $H$ and $c$
+systematically and calculate velocity $v$ and inner structure in a stationary
+state for magnetic DW and magneto-electric DW. DW mobility $v/H$ increases with
+$H$ and decreases with $c$ for both DWs, but their characteristics differ
+between the two. We have also studied analytically the smooth characteristics
+of magneto-electric DW by perturbation theory. Another finding is a splitting
+instability at large H. A magneto-electric DW splits into a pair of magnetic DW
+and electric DW when $c$ is large, while a magnetic DW splits when $c$ is
+small. Internal structure of composite DW deforms with increasing $c$ and $H$,
+and modulations in different order parameters separate in space. Their relative
+distances show a noticeable enhancement with approaching the splitting
+instability.",2008.08600v1
+2020-09-22,Dynamic $^{14}\rm N$ nuclear spin polarization in nitrogen-vacancy centers in diamond,"We studied the dynamic nuclear spin polarization of nitrogen in negatively
+charged nitrogen-vacancy (NV) centers in diamond both experimentally and
+theoretically over a wide range of magnetic fields from 0 to 1100 G covering
+both the excited-state level anti-crossing and the ground-state level
+anti-crossing magnetic field regions. Special attention was paid to the less
+studied ground-state level anti-crossing region. The nuclear spin polarization
+was inferred from measurements of the optically detected magnetic resonance
+signal. These measurements show that a very large (up to $96 \pm 2\%$) nuclear
+spin polarization of nitrogen can be achieved over a very broad range of
+magnetic field starting from around 400 G up to magnetic field values
+substantially exceeding the ground-state level anti-crossing at 1024 G. We
+measured the influence of angular deviations of the magnetic field from the NV
+axis on the nuclear spin polarization efficiency and found that, in the
+vicinity of the ground-state level anti-crossing, the nuclear spin polarization
+is more sensitive to this angle than in the vicinity of the excited-state level
+anti-crossing. Indeed, an angle as small as a tenth of a degree of arc can
+destroy almost completely the spin polarization of a nitrogen nucleus. In
+addition, we investigated theoretically the influence of strain and optical
+excitation power on the nuclear spin polarization.",2009.10516v1
+2020-12-21,Electronic correlations and magnetic interactions in infinite-layer NdNiO$_2$,"The large antiferromagnetic exchange coupling in the parent high-$T_{\rm c}$
+cuprate superconductors is believed to play a crucial role in pairing the
+superconducting carriers. The recent observation of superconductivity in
+hole-doped infinite-layer (IL-) NdNiO$_2$ brings to the fore the relevance of
+magnetic coupling in high-$T_{\rm c}$ superconductors, particularly because no
+magnetic ordering is observed in the undoped IL-NdNiO$_2$ unlike in parent
+copper oxides. Here, we investigate the electronic structure and the nature of
+magnetic exchange in IL-NdNiO$_2$ using state-of-the-art many-body quantum
+chemistry methods. From a systematic comparison of the electronic and magnetic
+properties with isostructural cuprate IL-CaCuO$_2$, we find that the on-site
+dynamical correlations are significantly stronger in IL-NdNiO$_2$ compared to
+the cuprate analog. These dynamical correlations play a critical role in the
+magnetic exchange resulting in an unexpectedly large antiferromagnetic nearest
+neighbor isotropic $J$ of 77 meV between the Ni$^{1+}$ ions within the
+$ab$-plane. While we find many similarities in the electronic structure between
+the nickelate and the cuprate, the role of electronic correlations is
+profoundly different in the two. We further discuss the implications of our
+findings in understanding the origin of superconductivity in nickelates.",2012.11179v1
+2021-02-16,Lifshitz scaling effects on the holographic paramagnetic-ferromagnetic phase transition,"We disclose the effects of Lifshitz dynamical exponent $z$ on the properties
+of holographic paramagnetic-ferromagnetic phase transition in the background of
+Lifshitz spacetime. To preserve the conformal invariance in higher dimensions,
+we consider the Power-Maxwell (PM) electrodynamics as our gauge field. We
+introduce a massive $2$-form coupled to the PM field and perform the numerical
+shooting method in the probe limit by assuming the PM and the $2$-form fields
+do not back-react on the background geometry. The obtained results indicate
+that the critical temperature decreases with increasing the strength of the
+power parameter $q$ and dynamical exponent $z$. Besides, the formation of the
+magnetic moment in the black hole background is harder in the absence of an
+external magnetic field. At low temperatures, and in the absence of an external
+magnetic field, our result show the spontaneous magnetization and the
+ferromagnetic phase transition. We find that the critical exponent takes the
+universal value $\beta= 1/2$ regardless of the parameters $q, z, d$, which is
+in agreement with the mean field theory. In the presence of an external
+magnetic field, the magnetic susceptibility satisfies the Curie-Weiss law.",2102.08047v3
+2021-03-03,Emergence of internetwork magnetic fields through the solar atmosphere,"Internetwork (IN) magnetic fields are highly dynamic, short-lived magnetic
+structures that populate the interior of supergranular cells. Since they emerge
+all over the Sun, these small-scale fields bring a substantial amount of flux,
+and therefore energy, to the solar surface. Because of this, IN fields are
+crucial for understanding the quiet Sun (QS) magnetism. However, they are weak
+and produce very small polarization signals, which is the reason why their
+properties and impact on the energetics and dynamics of the solar atmosphere
+are poorly known. Here we use coordinated, high-resolution, multiwavelength
+observations obtained with the Swedish 1-m Solar Telescope (SST) and the
+\textit{Interface Region Imaging Spectrograph} (IRIS) to follow the evolution
+of IN magnetic loops as they emerge into the photosphere and reach the
+chromosphere and transition region. We studied in this paper three flux
+emergence events having total unsigned magnetic fluxes of $1.9\times10^{18}$,
+$2.5\times10^{18}$, and $5.3\times10^{18}$~Mx. The footpoints of the emerging
+IN bipoles are clearly seen to appear in the photosphere and to rise up through
+the solar atmosphere, as observed in \ion{Fe}{1} 6173 \AA\/ and \ion{Mg}{1}
+b$_2$ 5173 \AA\/ magnetograms, respectively. For the first time, our
+polarimetric measurements taken in the chromospheric \ion{Ca}{2} 8542 \AA\/
+line provide direct observational evidence that IN fields are capable of
+reaching the chromosphere. Moreover, using IRIS data, we study the effects of
+these weak fields on the heating of the chromosphere and transition region.",2103.02213v1
+2021-04-23,A Kinetic Model of Friction in Strongly Coupled Strongly Magnetized Plasmas,"Plasmas that are strongly magnetized in the sense that the gyrofrequency
+exceeds the plasma frequency exhibit novel transport properties that are not
+well understood. As a representative example, we compute the friction force
+acting on a massive test charge moving through a strongly coupled and strongly
+magnetized one-component plasma using a generalized Boltzmann kinetic theory.
+Recent works studying the weakly coupled regime have shown that strong
+magnetization leads to a transverse component of the friction force that is
+perpendicular to both the Lorentz force and velocity of the test charge; in
+addition to the stopping power component aligned antiparallel to the velocity.
+Recent molecular dynamics simulations have also shown that strong Coulomb
+coupling in addition to strong magnetization gives rise to a third component of
+the friction force in the direction of the Lorentz force. Here, we show that
+the generalized Boltzmann kinetic theory captures these effects, and generally
+agrees well with the molecular dynamics simulations over a broad range of
+Coulomb coupling and magnetization strength regimes. The theory is also used to
+show that a ""gyro"" component of the friction in the direction of the Lorentz
+force arises due to asymmetries associated with gyromotion during short-range
+collisions. Computing the average motion of the test charge through the
+background plasma, the transverse force is found to strongly influence the
+trajectory by changing the gyroradius and the gyro friction force is found to
+slightly change the gyrofrequency of the test charge resulting in a phase
+shift.",2104.11718v1
+2021-06-27,Hadron gas in the presence of a magnetic field using non-extensive statistics: A transition from diamagnetic to paramagnetic system,"Non-central heavy-ion collisions at ultra-relativistic energies are unique in
+producing magnetic fields of the largest strength in the laboratory. Such
+fields being produced at the early stages of the collision could affect the
+properties of Quantum Chromodynamics (QCD) matter formed in the relativistic
+heavy-ion collisions. The transient magnetic field leaves its reminiscence,
+which in principle, can affect the thermodynamic and transport properties of
+the final state dynamics of the system. In this work, we study the
+thermodynamic properties of a hadron gas in the presence of an external static
+magnetic field using a thermodynamically consistent non-extensive Tsallis
+distribution function. Various thermodynamical observables such as energy
+density ($\epsilon$), entropy density ($s$), pressure ($P$) and speed of sound
+($c_{\rm s}$) are studied. Investigation of magnetization ($M$) is also
+performed and this analysis reveals an interplay of diamagnetic and
+paramagnetic nature of the system in the presence of a magnetic field of
+varying strength. Further, to understand the system dynamics under equilibrium
+and non-equilibrium conditions, the effect of the non-extensive parameter ($q$)
+on the above observables is also studied.",2106.14297v2
+2021-10-14,Long-Term Evolution of Magnetic Fields in Flaring Active Region NOAA 12673,"During the lifetime of AR 12673, its magnetic field evolved drastically and
+produced numerous large flares. In this study, using full maps of the Sun
+observed by the Solar Dynamics Observatory and the Solar Terrestrial Relations
+Observatory, we identified that AR 12673 emerged in decayed AR 12665, which had
+survived for two solar rotations. Although both ARs emerged at the same
+location, they possessed different characteristics and different flare
+productivities. Therefore, it is important to study the long-term magnetic
+evolution of both ARs to identify the distinguishing characteristics of an AR
+that can produce large solar flares. We used the Spaceweather Helioseismic and
+Magnetic Imager Active Region Patch data to investigate the evolution of the
+photospheric magnetic field and other physical properties of the recurring ARs
+during five Carrington rotations. All these investigated parameters dynamically
+evolved through a series of solar rotations. We compared the long-term
+evolution of AR 12665 and AR 12673 to understand the differences in their
+flare-producing properties. We also studied the relation of the long-term
+evolution of these ARs with the presence of active longitude. We found that the
+magnetic flux and complexity of AR 12673 developed much faster than those of AR
+12665. Our results confirmed that a strong emerging flux that emerged in the
+pre-existing AR near the active longitude created a very strong and complex AR
+that produced large flares.",2110.07369v1
+2021-11-30,The dynamical structure of the outflows driven by a large-scale magnetic field,"Large-scale magnetic field is crucial in launching and collimating the
+jets/outflows. It is found that the magnetic flux can be efficiently
+transported inward by the fast moving corona above a thin disk. In this work we
+investigate the dynamical structure of the outflows driven by the large-scale
+magnetic field advected by the hot corona. With derived large-scale magnetic
+field, the outflow solution along every field line is obtained by solving a set
+of magneto-hydrodynamical (MHD) Equations self-consistently with boundary
+conditions at the upper surface of the corona. We find that the terminal speeds
+of the outflows driven from the inner region of the disk are $\sim 0.01c-0.1c$.
+The temperatures of the outflows at the large distance from the black hole are
+still as high as several ten keV. The properties of the magnetic outflows
+derived in this work are roughly consistent with the fast outflows detected in
+some luminous quasars and X-ray binaries. The total mass loss rate in the
+outflows from the corona is about $7\%-12\%$ of the mass accretion rate of the
+disk. The three dimension field geometry, the velocity, temperature and density
+of the outflows derived in this work can be used for calculating the emergent
+spectra and their polarization of the accretion disk/corona/outflow systems.
+Our results may help understand the features of the observed spectra of X-ray
+binaries and active galactic nuclei.",2111.15115v2
+2022-02-08,Ultrafast Emergence of Ferromagnetism in Antiferromagnetic FeRh in High Magnetic Fields,"Ultrafast heating of FeRh by a femtosecond laser pulse launches a
+magneto-structural phase transition from an antiferromagnetic to a
+ferromagnetic state. Aiming to reveal the ultrafast kinetics of this
+transition, we studied magnetization dynamics with the help of the
+magneto-optical Kerr effect in a broad range of temperatures (from 4 K to 400
+K) and magnetic fields (up to 25 T). Three different types of ultrafast
+magnetization dynamics were observed and, using a numerically calculated H-T
+phase diagram, the differences were explained by different initial states of
+FeRh corresponding to a (i) collinear antiferromagnetic, (ii) canted
+antiferromagnetic and (iii) ferromagnetic alignment of spins. We argue that
+ultrafast heating of FeRh in the canted antiferromagnetic phase launches
+practically the fastest possible emergence of magnetization in this material.
+The magnetization emerges on a time scale of 2 ps, which corresponds to the
+earlier reported time-scale of the structural changes during the phase
+transition.",2202.03931v4
+2022-02-16,Turbulent dynamo in the two-phase interstellar medium,"Magnetic fields are a dynamically important component of the turbulent
+interstellar medium (ISM) of star-forming galaxies. These magnetic fields are
+due to a dynamo action, which is a process of converting turbulent kinetic
+energy to magnetic energy. A dynamo that acts at scales less than the turbulent
+driving scale is known as the turbulent dynamo. The ISM is a multiphase medium
+and observations suggest that the properties of magnetic fields differ with the
+phase. Here, we aim to study how the properties of the turbulent dynamo depend
+on the phase. We simulate the non-isothermal turbulent dynamo in a two-phase
+medium (most previous work assumes an isothermal gas). We show that the warm
+phase ($T\ge10^3~{\rm K}$) is transsonic and the cold phase ($T<10^3~{\rm K}$)
+is supersonic. We find that the growth rate of magnetic fields in the
+exponentially growing stage is similar in both phases. We compute the terms
+responsible for amplification and destruction of vorticity and show that in
+both phases vorticity is amplified due to turbulent motions, further amplified
+by the baroclinic term in the warm phase, and destroyed by the term for viscous
+interactions in the presence of logarithmic density gradients in the cold
+phase. We find that the final ratio of magnetic to turbulent kinetic energy is
+lower in the cold phase due to a stronger Lorentz force. We show that the
+non-isothermal turbulent dynamo is significantly different from its isothermal
+counterpart and this demonstrates the need for studying the turbulent dynamo in
+a multiphase medium.",2202.08324v2
+2022-03-06,Spin-Dependent Graph Neural Network Potential for Magnetic Materials,"The development of machine learning interatomic potentials has immensely
+contributed to the accuracy of simulations of molecules and crystals. However,
+creating interatomic potentials for magnetic systems that account for both
+magnetic moments and structural degrees of freedom remains a challenge. This
+work introduces SpinGNN, a spin-dependent interatomic potential approach that
+employs the graph neural network (GNN) to describe magnetic systems. SpinGNN
+consists of two types of edge GNNs: Heisenberg edge GNN (HEGNN) and
+spin-distance edge GNN (SEGNN). HEGNN is tailored to capture Heisenberg-type
+spin-lattice interactions, while SEGNN accurately models multi-body and
+high-order spin-lattice coupling. The effectiveness of SpinGNN is demonstrated
+by its exceptional precision in fitting a high-order spin Hamiltonian and two
+complex spin-lattice Hamiltonians with great precision. Furthermore, it
+successfully models the subtle spin-lattice coupling in BiFeO3 and performs
+large-scale spin-lattice dynamics simulations, predicting its antiferromagnetic
+ground state, magnetic phase transition, and domain wall energy landscape with
+high accuracy. Our study broadens the scope of graph neural network potentials
+to magnetic systems, serving as a foundation for carrying out large-scale
+spin-lattice dynamic simulations of such systems.",2203.02853v2
+2022-04-12,Three-dimensional close-to-substrate trajectories of magnetic microparticles in dynamically changing magnetic field landscapes,"The transport of magnetic nano- or microparticles in microfluidic devices
+using artificially designed magnetic field landscapes (MFL) is promising for
+the implementation of key functionalities in Lab-on-a-chip (LOC) systems. A
+close-to-substrate transport is hereby instrumental to use changing
+particle-substrate interactions upon analyte binding for analytics and
+diagnostics. Here, we present an essential prerequisite for such an
+application, namely the label-free quantitative experimental determination of
+the three-dimensional trajectories of superparamagnetic particles (SPP)
+transported by a dynamically changing MFL above a topographically flat
+substrate. The evaluation of the SPP sharpness within defocused video-recorded
+images, acquired by an optical bright-field microscope, was employed to obtain
+a vertical z-coordinate. This method applied to a prototypical transport
+scheme, using the static MFL of parallel-stripe domains superposed by a
+particular magnetic field pulse sequence, revealed a hopping-like motion of the
+magnetic particles, previously predicted by theory. Maximum vertical particle
+jumps of several micrometers have been observed experimentally, corroborating
+theoretical estimates for the particle-substrate distance. As our findings pave
+the way towards precise quantification of particle-substrate separations in the
+discussed transport system, they bear deep implications for future LOC
+detection schemes using only optical microscopy.",2204.05958v1
+2022-05-30,Skyrmion-Magnetic Tunnel Junction Synapse with Mixed Synaptic Plasticity for Neuromorphic Computing,"Magnetic skyrmion-based data storage and unconventional computing devices
+have gained increasing attention due to their topological protection, small
+size, and low driving current. However, skyrmion creation, deletion, and motion
+are still being studied. In this study, we propose a skyrmion-based
+neuromorphic magnetic tunnel junction (MTJ) device with both long- and
+short-term plasticity (LTP and STP) (mixed synaptic plasticity). We showed that
+plasticity could be controlled by magnetic field, spin-orbit torque (SOT), and
+the voltage-controlled magnetic anisotropy (VCMA) switching mechanism. LTP
+depends on the skyrmion density and is manipulated by the SOT and magnetic
+field while STP is controlled by the VCMA. The LTP property of the device was
+utilized for static image recognition. By incorporating the STP feature, the
+device gained additional temporal filtering ability and could adapt to a
+dynamic environment. The skyrmions were conserved and confined to a nanotrack
+to minimize the skyrmion nucleation energy. The synapse device was trained and
+tested for emulating a deep neural network. We observed that when the skyrmion
+density was increased, the inference accuracy improved: 90% accuracy was
+achieved by the system at the highest density. We further demonstrated the
+dynamic environment learning and inference capabilities of the proposed device.",2205.14915v1
+2022-06-16,Compressible two-dimensional turbulence: cascade reversal and sensitivity to imposed magnetic field,"We study the impact of compressibility on two-dimensional turbulent flows,
+such as those modeling astrophysical disks. We demonstrate that the direction
+of cascade undergoes continuous transition as the Mach number Ma increases,
+from inverse at zero Ma, to direct at infinite Ma. Thus, at Ma of order one
+comparable amounts of energy flow from the scale of the pumping to large and
+small scales, in accord with previous data. For supersonic turbulence with
+large Ma, the cascade is direct, as in three dimensions, which results in
+multifractal density field. For compressible flows of conducting fluids,
+imposing external magnetic field allows to manipulate the flow producing
+possibly large changes even at small Mach number. Thus Zeldovich antidynamo
+theorem, by which at zero Ma the magnetic field is zero in the steady state,
+must be used with caution. Real flows have finite Ma and, however small it is,
+for large magnetic flux through the disk, the magnetic field changes the flow
+appreciably, or rearranges it completely. For large Ma, relevant for
+astrophysical disks, the magnetic field energy is enhanced by a large factor as
+compared to estimates based on the mean field. We propose to use
+two-dimensional Burgers turbulence, whose three-dimensional counterpart is used
+for studies of the large-scale structure of the Universe, as a model for
+supersonic thin accretion disks.",2206.10367v2
+2022-08-08,Van der Waals engineering of ultrafast carrier dynamics in magnetic heterostructures,"Heterostructures composed of the intrinsic magnetic topological insulator
+MnBi$_2$Te$_4$ and its non-magnetic counterpart Bi$_2$Te$_3$ host distinct
+surface band structures depending on the stacking order and exposed
+termination, allowing fine control of their magnetic, electronic and optical
+properties. Here, we probe the ultrafast dynamical response of MnBi$_2$Te$_4$
+and MnBi$_4$Te$_7$ following near-infrared optical excitation using time- and
+angle-resolved photoemission spectroscopy. We gain access to the
+out-of-equilibrium surface electronic structure of both MnBi$_2$Te$_4$ and
+Bi$_2$Te$_3$ surface terminations of MnBi$_4$Te$_7$, revealing an instantaneous
+occupation of states that are resonant with the optical excitation in the
+Bi$_2$Te$_3$ layer followed by carrier extraction into the adjacent
+MnBi$_2$Te$_4$ layers with a laser fluence-tunable delay of up to 350 fs. The
+ensuing thermal relaxation processes are driven by in-plane phonon scattering
+with significantly slower relaxation times in the magnetic MnBi$_2$Te$_4$
+septuple layers. The competition of interlayer charge transfer and intralayer
+phonon scattering establishes MnBi$_2$Te$_4$-based compounds as a platform for
+controlling ultrafast charge transfer processes in combination with magnetism
+and topology in van der Waals heterostructures.",2208.04098v1
+2022-12-21,Charge transfer and disorder-induced spin relaxation in La2NiMnO6 crystallites,"Investigation of the electronic and spin structure in double perovskites is
+recently attracting significant attention, mainly driven by their unique
+multifunctional properties and other underlying charge and spin dynamics.
+Herein, using X-ray photoelectron spectroscopy (XPS), we explore the influence
+of variable fractions of Mn3+/Mn4+ cation in different crystallite sizes of
+La2NiMnO6 that control the various completing exchange interactions of Ni/Mn
+cations responsible for multiple magnetic transitions. The enhanced itinerant
+electron due to Mn4+ + Ni2+ to Mn3+ + Ni3+ charge transfer emerged as a
+shoulder like characteristics at the low binding energy in the Mn-2P core-level
+spectrum. The various approaches such as difference in saturation
+magnetization, presence of multiple charge valance, and magnetic entropy
+calculations confirm the presence of antisites disorder and it varies as a
+function of milling. As milling provides excess energy that helps with
+nucleation or cation ordering. Competing magnetic interactions driven by mixed
+valences and disorder were established across a cluster glassy phase in the
+crystallites. Electron spin resonance spectroscopy (ESR) was utilized to probe
+the temperature-driven ferromagnetic-cluster spin-glass transition with
+modified g-factor ranging from 2.050 to 2.037. The line width of the ESR
+signals increases across the ferromagnetic to cluster-glass phase transition
+due to spin freezing. This phase transition is further characterized by
+temperature-dependent ac-magnetic susceptibility measurements. Argand diagram
+for the ac-susceptibility of the interacting crystallites suggests a collective
+magnetization relaxation dynamic in the proximity of spin-glass freezing
+temperature of La2NiMnO6.",2212.10845v2
+2023-03-28,Generation of third-harmonic spin oscillation from strong spin precession induced by terahertz magnetic near fields,"The ability to drive a spin system to state far from the equilibrium is
+indispensable for investigating spin structures of antiferromagnets and their
+functional nonlinearities for spintronics. While optical methods have been
+considered for spin excitation, terahertz (THz) pulses appear to be a more
+convenient means of direct spin excitation without requiring coupling between
+spins and orbitals or phonons. However, room-temperature responses are usually
+limited to small deviations from the equilibrium state because of the
+relatively weak THz magnetic fields in common approaches. Here, we studied the
+magnetization dynamics in a HoFeO3 crystal at room temperature. A custom-made
+spiral-shaped microstructure was used to locally generate a strong multicycle
+THz magnetic near field perpendicular to the crystal surface; the maximum
+magnetic field amplitude of about 2 T was achieved. The observed time-resolved
+change in the Faraday ellipticity clearly showed second- and third-order
+harmonics of the magnetization oscillation and an asymmetric oscillation
+behaviour. Not only the ferromagnetic vector M but also the antiferromagnetic
+vector L plays an important role in the nonlinear dynamics of spin systems far
+from equilibrium.",2303.16016v1
+2023-05-16,Impact of radiative cooling on the magnetised geometrically thin accretion disk around Kerr black hole,"It is believed that the spectral state transitions of the outbursts in X-ray
+binaries (XRBs) are triggered by the rise of the mass accretion rate due to
+underlying disc instabilities. Recent observations found that characteristics
+of disc winds are probably connected with the different spectral states, but
+the theoretical underpinnings of it are highly ambiguous. To understand the
+correlation between disc winds and the dynamics of the accretion flow, we have
+performed General Relativistic Magneto-hydrodynamic (GRMHD) simulations of an
+axisymmetric thin accretion disc with different accretion rates and magnetic
+field strengths. Our simulations have shown that the dynamics and the
+temperature properties depend on both accretion rates and magnetic field
+strengths. We later found that these properties greatly influence spectral
+properties. We calculated the average coronal temperature for different
+simulation models, which is correlated with high-energy Compton emission. Our
+simulation models reveal that the average coronal temperature is
+anti-correlated with the accretion rates, which is correlated with the magnetic
+field strengths. We also found that the structured component of the disc winds
+(Blandford-Payne disc wind) predominates as the accretion rates and magnetic
+field strengths increase. In contrast, the turbulent component of the disc
+winds ($B_{\rm tor}$ disc wind) predominates as the accretion rates and
+magnetic field strengths decrease. Our results suggest that the disc winds
+during an outburst in XRBs can only be understood if the magnetic field
+contribution varies over time (e.g., MAXI J1820+070).",2305.09698v1
+2023-05-24,Charged spinning and magnetized test particles orbiting quantum improved charged black holes,"In the present work, we aimed to investigate the dynamics of spinning charged
+and magnetized test particles around both electrically and magnetically charged
+quantum-improved black holes. We derive the equations of motion for charged
+spinning test particles using the Mathisson-Papapetrou-Dixon equations with the
+Lorentz coupling term. The radius of innermost stable circular orbits (ISCOs),
+specific angular momentum, and energy for charged spinless, uncharged spinning,
+and charged spinning test particles around the charged and non-charged
+quantum-improved black holes are analyzed separately. We found that the quantum
+parameter increases the maximum spin value, $s_\text{max}$, which leads to the
+nonphysical motion (superluminal motion) of the charged spinning test particle,
+whereas the black hole charge decreases its value. We also found that, in
+contrast to the Reissner Nordstr\""om black hole, spinning charged test
+particles in the quantum-improved charged black hole have higher
+$s_\text{max}$; moreover, positively charged spinning particles can have higher
+values of $s_\text{max}$ near the extreme black hole cases when compared with
+uncharged spinning particles. Finally, we investigate the magnetized test
+particle's dynamics around a quantum-improved magnetically charged black hole
+in Quantum Einstein Gravity using the Hamilton-Jacobi equation. We show that
+the presence of $\omega$ increases the maximum value of the effective potential
+and decreases the minimum energy and angular momentum of magnetized particles
+at their circular orbits. We found an upper constraint in the black hole charge
+at the ISCO.",2305.15350v1
+2023-06-27,MHD Simulation in Galactic Center Region with Radiative Cooling and Heating,"We investigate the role of magnetic field on the gas dynamics in a galactic
+bulge region by three dimensional simulations with radiative cooling and
+heating. While high-temperature corona with $T>10^6\ {\rm K}$ is formed in the
+halo regions, the temperature near the mid-plane is $\lesssim 10^4\ {\rm K}$
+following the thermal equilibrium curve determined by the radiative cooling and
+heating. Although the thermal energy of the interstellar gas is lost by
+radiative cooling, the saturation level of the magnetic field strength does not
+significantly depend on the radiative cooling and heating. The magnetic field
+strength is amplified to $10\ {\rm \mu G}$ on average, and reaches several
+hundred ${\rm \mu G}$ locally. We find the formation of magnetically dominated
+regions at mid-latitudes in the case with the radiative cooling and heating,
+which is not seen in the case without radiative effect. The vertical thickness
+of the mid-latitude regions is $50-150\ {\rm pc}$ at the radial location of
+$0.4-0.8\ {\rm kpc}$ from the galactic center, which is comparable to the
+observed vertical distribution of neutral atomic gas. When we take the average
+of different components of energy density integrated over the galactic bulge
+region, the magnetic energy is comparable to the thermal energy. We conclude
+that the magnetic field plays a substantial role in controlling the dynamical
+and thermal properties of the galactic bulge region.",2306.15761v2
+2023-07-05,Dynamical Effects of Magnetic Opacity in Neutron Star Accretion Columns,"We present relativistic, radiation magnetohydrodynamic simulations of
+supercritical neutron star accretion columns in Cartesian geometry, including
+temperature-dependent, polarization-averaged Rosseland mean opacities
+accounting for classical electron scattering in a magnetic field. Just as in
+our previous pure Thomson scattering simulations, vertical oscillations of the
+accretion shock and horizontally propagating entropy waves (photon bubbles) are
+present in all our simulations. However, at high magnetic fields
+$\gtrsim10^{12}$~G, the magnetic opacities produce significant differences in
+the overall structure and dynamics of the column. At fixed accretion rate,
+increasing the magnetic field strength results in a shorter accretion column,
+despite the fact that the overall opacity within the column is larger.
+Moreover, the vertical oscillation amplitude of the column is reduced.
+Increasing the accretion rate at high magnetic fields restores the height of
+the column. However, a new, slower instability takes place at these field
+strengths because they are in a regime where the opacity increases with
+temperature. This instability causes both the average height of the column and
+the oscillation amplitude to substantially increase on a time scale of
+$\sim10$~ms. We provide physical explanations for these results, and discuss
+their implications for the observed properties of these columns, including
+mixed fan-beam/pencil-beam emission patterns caused by the oscillations.",2307.02410v1
+2023-08-16,A New Magneto-Micropolar Boundary Layer Model for Liquid Flows -- Effect of Micromagnetorotation (MMR),"In this paper, we present a micropolar continuum model based on the theory of
+magnetohydrodynamics. In particular, the effect of micromagnetorotation (MMR)
+is taken into account in the derivation of an initial-boundary value problem
+(i-bvp) within magneto-micorpolar flows. MMR is a phenomenon that is related to
+the micromotions of the magnetic liquid particles in the presence of externally
+applied magnetic field. In all previous investigations magnetization was
+supposed to be parallel to applied magnetic field therefore its effect in the
+lateral direction is neglected. This assumption is not correct in
+magnetic-micropolar flows. Since, magnetic-micropolar flows are anisotropic in
+nature. Here, we present a model accounting for this MMR effect. The
+constitutive equation for the MMR is described and the governing system of flow
+dynamics is described in the form of PDEs. Boundary layer flow assumptions are
+used to derive an initial-boundary value problem in ODEs. As a consequence, two
+newly defined parameters arises that are related to the MMR. The effects of
+these parameters on the flow characteristics are investigated. The developed
+i-bvp is solved through the shooting method using MATLAB routines. Effects of
+MMR are analyzed on the miro-rotational and hydrodynamic velocities profiles.
+Some interesting features of the flow are observed. Results are presented
+through graphs and discussed in detail. It is worth mentioning that the model
+presented is first of its kind in the literature and has a great potential in
+investigating boundary layer flows within micropolar continuum with other
+physical aspects of the flow pertinent to engineering and biomedical
+applications.",2308.08457v1
+2023-11-12,Emergence of magnetic structure in supersonic isothermal magnetohydrodynamic turbulence,"The inverse transfer of magnetic helicity is a fundamental process which may
+explain large scale magnetic structure formation and sustainement. Until very
+recently, direct numerical simulations (DNS) of the inverse transfer in
+magnetohydrodynamics (MHD) turbulence have been done in incompressible MHD or
+at low Mach numbers only. We review first results obtained through DNS of the
+isothermal MHD equations at Mach numbers ranging from subsonic to about 10. The
+spectral exponent of the magnetic helicity spectrum becomes flatter with
+increasing compressibility. When considering the Alfv\'en velocity in place of
+the magnetic field however, results found in incompressible MHD, including a
+dynamic balance between shear and twist, can be extended to supersonic MHD. In
+the global picture of an inverse transfer of magnetic helicity, three phenomena
+are at work: a local direct transfer mediated by the large scale velocity
+field, a local inverse transfer mediated by the intermediate scale velocity
+field and a nonlocal inverse transfer mediated by the small scale velocity
+field. The compressive part of the velocity field is geometrically favored in
+the local direct transfer and contributes to the nonlocal inverse transfer, but
+plays no role in the local inverse transfer.",2311.06803v1
+2023-11-27,Quantum magnetometry using discrete-time quantum walk,"Quantum magnetometry uses quantum resources to measure magnetic fields with
+precision and accuracy that cannot be achieved by its classical counterparts.
+In this paper, we propose a scheme for quantum magnetometry using discrete-time
+quantum walk (DTQW) where multi-path interference plays a central role. The
+dynamics of a spin-half particle implementing DTQW on a one-dimensional lattice
+gets affected by magnetic fields, and the controlled dynamics of DTQW help in
+estimating the fields' strength. To gauge the effects of the field, we study
+the variance of the particle's position probability distribution (PD) and use
+it to determine the direction of the magnetic field maximally affecting the
+quantum walk. We then employ statistical tools like quantum Fisher information
+(QFI) and Fisher information (FI) of the particle's position and spin
+measurements to assess the system's sensitivity to the magnetic fields. We find
+that one can use the position and spin measurements to estimate the strengths
+of the magnetic fields. Calculations for an electron implementing quantum walk
+of fifty time steps show that the estimate had a root-mean-square error of the
+order of 0.1 picoTesla. Moreover, the sensitivity of our system can be tuned to
+measure any desired magnetic field. Our results indicate that the system can be
+used as a tool for optimal quantum magnetometry.",2311.15801v2
+2024-01-03,Spin-Transfer-Torque Induced Spatially Nonuniform Switching in Ferrimagnets,"Ferrimagnet (FiM), (FeCo)1-xGdx, attracts research attention due to its
+ultrafast magnetic dynamics and finite net magnetization. Incorporating FiM
+into the magnetic tunnel junction will be beneficial to further improve the
+writing speed of magnetic random access memory (MRAM). It is commonly assumed
+that the FeCo and Gd atoms are switched together due to the strong exchange
+coupling, which remains valid even if one performs the two-sublattice macrospin
+simulation. Interestingly, using the atomistic model developed by our group, it
+is clearly seen that different atoms are not switched together. In addition,
+our study reveals that the nature of switching is spatially nonuniform even in
+the small sample with the dimension of 20 nm-20 nm. Furthermore, the
+characteristics of nonuniformity are completely different for samples with
+different Gd composition (x). When x is close to the magnetization compensation
+point, successful switching cannot be obtained, but is accompanied by the
+stable oscillation. The atom type that dominates the oscillation is different
+from that predicted by the two-sublattice macrospin model. In addition, the
+size of singular region is a non-monotonic function of current density. All
+these results can only be understood by considering the spatial nonuniform
+magnetization dynamics.",2401.01741v1
+2024-03-18,Coarsening of chiral domains in itinerant electron magnets: A machine learning force field approach,"Frustrated itinerant magnets often exhibit complex noncollinear or
+noncoplanar magnetic orders which support topological electronic structures. A
+canonical example is the anomalous quantum Hall state with a chiral spin order
+stabilized by electron-spin interactions on a triangular lattice. While a
+long-range magnetic order cannot survive thermal fluctuations in two
+dimensions, the chiral order which results from the breaking of a discrete
+Ising symmetry persists even at finite temperatures. We present a scalable
+machine learning (ML) framework to model the complex electron-mediated
+spin-spin interactions that stabilize the chiral magnetic domains in a
+triangular lattice. Large-scale dynamical simulations, enabled by the ML
+force-field models, are performed to investigate the coarsening of chiral
+domains after a thermal quench. While the chiral phase is described by a broken
+$Z_2$ Ising-type symmetry, we find that the characteristic size of chiral
+domains increases linearly with time, in stark contrast to the expected
+Allen-Cahn domain growth law for a non-conserved Ising order parameter field.
+The linear growth of the chiral domains is attributed to the orientational
+anisotropy of domain boundaries. Our work also demonstrates the promising
+potential of ML models for large-scale spin dynamics of itinerant magnets.",2403.11705v1
+2008-10-22,Phonon Control of Magnetic Relaxation in the Pyrochlore Slab Compounds SCGO and BSZCGO,"We are interested in the phonon response in the frustrated magnets
+SrCr$_{9x}$Ga$_{12-9x}$O$_{19}$ (SCGO) and
+Ba$_{2}$Sn$_{2}$ZnCr$_{7x}$Ga$_{10-7x}$O$_{22}$ (BSZCGO). The motivation of the
+study is the recently discovered, phonon-driven, magnetic relaxation in the
+SCGO compound [Mutka et al. PRL {\bf 97} 047203 (2006)] pointing out the
+importance of a low-energy ($\hbar\omega\sim$7 meV) phonon mode. In neutron
+scattering experiments on these compounds the phonon signal is partly masked by
+the magnetic signal from the Cr moments and we have therefore examined in
+detail the non-magnetic isostructural counterparts SrGa$_{12}$O$_{19}$ (SGO)
+and Ba$_{2}$Sn$_{2}$ZnGa$_{10}$O$_{22}$ (BSZGO). Our {\it ab-initio} lattice
+dynamics calculations on SGO reveal a peak in the vibrational density of states
+matching with the neutron observations on SGO and SCGO. A strong contribution
+in the vibrational density of states comes from the partial contribution of the
+Ga atoms on the 2b and 12k sites, involving modes at the M--point of the
+hexagonal system. These modes comprise dynamics of the kagom\'e planes of the
+pyrochlore slab magnetic sub-lattice, 12k sites, and therefore can drive
+magnetic relaxation via spin-phonon coupling. Both BSZCGO and BSZGO show a
+similar low-energy Raman peak but no corresponding peak in the neutron
+determined density of states of BSZGO is seen. However, a strong non-Debye
+enhancement of low-energy phonon response is observed. We attribute this
+particular feature to the Zn/Ga disorder on the 2$d$ -site, already evoked
+earlier to affect the magnetic properties of BSZCGO. We propose that this
+disorder-induced phonon response explains the absence of a characteristic
+energy scale and the much faster magnetic relaxation observed in BSZCGO.",0810.3941v2
+2012-03-30,The magnetic field of IRAS 16293-2422 as traced by shock-induced H2O masers,"Shock-induced H2O masers are important magnetic field tracers at very high
+density gas. Water masers are found in both high- and low-mass star-forming
+regions, acting as a powerful tool to compare magnetic field morphologies in
+both mass regimes. In this paper, we show one of the first magnetic field
+determinations in the low-mass protostellar core IRAS 16293-2422 at volume
+densities as high as 10^(8-10) cm^-3. Our goal is to discern if the collapsing
+regime of this source is controlled by magnetic fields or other factors like
+turbulence. We used the Very Large Array (VLA) to carry out
+spectro-polarimetric observations in the 22 GHz Zeeman emission of H2O masers.
+From the Stokes V line profile, we can estimate the magnetic field strength in
+the dense regions around the protostar. A blend of at least three maser
+features can be inferred from our relatively high spatial resolution data set
+(~ 0.1""), which is reproduced in a clear non-Gaussian line profile. The
+emission is very stable in polarization fraction and position angle across the
+channels. The maser spots are aligned with some components of the complex
+outflow configuration of IRAS 16293-2422, and they are excited in zones of
+compressed gas produced by shocks. The post-shock particle density is in the
+range of 1-3 x 10^9 cm^-3, consistent with typical water masers pumping
+densities. Zeeman emission is produced by a very strong line-of-sight magnetic
+field (B ~ 113 mG). The magnetic field pressure derived from our data is
+comparable to the ram pressure of the outflow dynamics. This indicates that the
+magnetic field is energetically important in the dynamical evolution of IRAS
+16293-2422.",1204.0004v1
+2014-01-29,Analytical Models of Exoplanetary Atmospheres. I. Atmospheric Dynamics via the Shallow Water System,"Within the context of exoplanetary atmospheres, we present a comprehensive
+linear analysis of forced, damped, magnetized shallow water systems, exploring
+the effects of dimensionality, geometry (Cartesian, pseudo-spherical and
+spherical), rotation, magnetic tension and hydrodynamic and magnetic sources of
+friction. Across a broad range of conditions, we find that the key governing
+equation for atmospheres and quantum harmonic oscillators are identical, even
+when forcing (stellar irradiation), sources of friction (molecular viscosity,
+Rayleigh drag and magnetic drag) and magnetic tension are included. The global
+atmospheric structure is largely controlled by a single, key parameter that
+involves the Rossby and Prandtl numbers. This near-universality breaks down
+when either molecular viscosity or magnetic drag acts non-uniformly across
+latitude or a poloidal magnetic field is present, suggesting that these effects
+will introduce qualitative changes to the familiar chevron-shaped feature
+witnessed in simulations of atmospheric circulation. We also find that
+hydrodynamic and magnetic sources of friction have dissimilar phase signatures
+and affect the flow in fundamentally different ways, implying that using
+Rayleigh drag to mimic magnetic drag is inaccurate. We exhaustively lay down
+the theoretical formalism (dispersion relations, governing equations and
+time-dependent wave solutions) for a broad suite of models. In all situations,
+we derive the steady state of an atmosphere, which is relevant to interpreting
+infrared phase and eclipse maps of exoplanetary atmospheres. We elucidate a
+pinching effect that confines the atmospheric structure to be near the equator.
+Our suite of analytical models may be used to decisively develop physical
+intuition and as a reference point for three-dimensional, magnetohydrodynamic
+(MHD) simulations of atmospheric circulation.",1401.7571v2
+2014-01-30,Mixing in Magnetized Turbulent Media,"Turbulent motions are essential to the mixing of entrained fluids and are
+also capable of amplifying weak initial magnetic fields by small-scale dynamo
+action. Here we perform a systematic study of turbulent mixing in magnetized
+media, using three-dimensional magnetohydrodynamic simulations that include a
+scalar concentration field. We focus on how mixing depends on the magnetic
+Prandtl number, Pm, from 1 to 4 and the Mach number, M}, from 0.3 to 2.4. For
+all subsonic flows, we find that the velocity power spectrum has a k^-5/3 slope
+in the early, kinematic phase, but steepens due to magnetic back reactions as
+the field saturates. The scalar power spectrum, on the other hand, flattens
+compared to k^-5/3 at late times, consistent with the Obukohov-Corrsin picture
+of mixing as a cascade process. At higher Mach numbers, the velocity power
+spectrum also steepens due to the presence of shocks, and the scalar power
+spectrum again flattens accordingly. Scalar structures are more intermittent
+than velocity structures in subsonic turbulence while for supersonic
+turbulence, velocity structures appear more intermittent than the scalars only
+in the kinematic phase. Independent of the Mach number of the flow, scalar
+structures are arranged in sheets in both the kinematic and saturated phases of
+the magnetic field evolution. For subsonic turbulence, scalar dissipation is
+hindered in the strong magnetic field regions, probably due to Lorentz forces
+suppressing the buildup of scalar gradients, while for supersonic turbulence,
+scalar dissipation increases monotonically with increasing magnetic field
+strength. At all Mach numbers, mixing is significantly slowed by the presence
+of dynamically-important small-scale magnetic fields, implying that mixing in
+the interstellar medium and in galaxy clusters is less efficient than modeled
+in hydrodynamic simulations.",1401.8001v2
+2015-11-16,Determination of intrinsic damping of perpendicularly magnetized ultrathin films from time resolved precessional magnetization measurements,"Magnetization dynamics are strongly influenced by damping. An effective
+damping constant {\alpha}eff is often determined experimentally from the
+spectral linewidth of the free induction decay of the magnetization after the
+system is excited to its non-equilibrium state. Such an {\alpha}eff, however,
+reflects both intrinsic damping as well as inhomogeneous broadening. In this
+paper we compare measurements of the magnetization dynamics in ultrathin
+non-epitaxial films having perpendicular magnetic anisotropy using two
+different techniques, time-resolved magneto optical Kerr effect (TRMOKE) and
+hybrid optical-electrical ferromagnetic resonance (OFMR). By using an external
+magnetic field that is applied at very small angles to the film plane in the
+TRMOKE studies, we develop an explicit closed-form analytical expression for
+the TRMOKE spectral linewidth and show how this can be used to reliably extract
+the intrinsic Gilbert damping constant. The damping constant determined in this
+way is in excellent agreement with that determined from the OFMR method on the
+same samples. Our studies indicate that the asymptotic high-field approach that
+is often used in the TRMOKE method to distinguish the intrinsic damping from
+the effective damping may result in significant error, because such high
+external magnetic fields are required to make this approach valid that they are
+out of reach. The error becomes larger the lower is the intrinsic damping
+constant, and thus may account for the anomalously high damping constants that
+are often reported in TRMOKE studies. In conventional ferromagnetic resonance
+(FMR) studies, inhomogeneous contributions can be readily distinguished from
+intrinsic damping contributions from the magnetic field dependence of the FMR
+linewidth. Using the analogous approach, we show how reliable values of the
+intrinsic damping can be extracted from TRMOKE.",1511.04802v1
+2016-06-07,A moving mesh unstaggered constrained transport scheme for magnetohydrodynamics,"We present a constrained transport (CT) algorithm for solving the 3D ideal
+magnetohydrodynamic (MHD) equations on a moving mesh, which maintains the
+divergence-free condition on the magnetic field to machine-precision. Our CT
+scheme uses an unstructured representation of the magnetic vector potential,
+making the numerical method simple and computationally efficient. The scheme is
+implemented in the moving mesh code Arepo. We demonstrate the performance of
+the approach with simulations of driven MHD turbulence, a magnetized disc
+galaxy, and a cosmological volume with primordial magnetic field. We compare
+the outcomes of these experiments to those obtained with a previously
+implemented Powell divergence-cleaning scheme. While CT and the Powell
+technique yield similar results in idealized test problems, some differences
+are seen in situations more representative of astrophysical flows. In the
+turbulence simulations, the Powell cleaning scheme artificially grows the mean
+magnetic field, while CT maintains this conserved quantity of ideal MHD. In the
+disc simulation, CT gives slower magnetic field growth rate and saturates to
+equipartition between the turbulent kinetic energy and magnetic energy, whereas
+Powell cleaning produces a dynamically dominant magnetic field. Such difference
+has been observed in adaptive-mesh refinement codes with CT and
+smoothed-particle hydrodynamics codes with divergence-cleaning. In the
+cosmological simulation, both approaches give similar magnetic amplification,
+but Powell exhibits more cell-level noise. CT methods in general are more
+accurate than divergence-cleaning techniques, and, when coupled to a moving
+mesh can exploit the advantages of automatic spatial/temporal adaptivity and
+reduced advection errors, allowing for improved astrophysical MHD simulations.",1606.02310v2
+2016-07-02,Interface-Induced Phenomena in Magnetism,"This article reviews static and dynamic interfacial effects in magnetism,
+focusing on interfacially-driven magnetic effects and phenomena associated with
+spin-orbit coupling and intrinsic symmetry breaking at interfaces. It provides
+a historical background and literature survey, but focuses on recent progress,
+identifying the most exciting new scientific results and pointing to promising
+future research directions. It starts with an introduction and overview of how
+basic magnetic properties are affected by interfaces, then turns to a
+discussion of charge and spin transport through and near interfaces and how
+these can be used to control the properties of the magnetic layer. Important
+concepts include spin accumulation, spin currents, spin transfer torque, and
+spin pumping. An overview is provided to the current state of knowledge and
+existing review literature on interfacial effects such as exchange bias,
+exchange spring magnets, spin Hall effect, oxide heterostructures, and
+topological insulators. The article highlights recent discoveries of
+interface-induced magnetism and non-collinear spin textures, non-linear
+dynamics including spin torque transfer and magnetization reversal induced by
+interfaces, and interfacial effects in ultrafast magnetization processes.",1607.00439v4
+2016-11-02,Topological insulator in a helicoidal magnetization field,"A key feature of topological insulators is the robustness of the electron
+energy spectrum. At a surface of a topological insulator, Dirac point is
+protected by the characteristic symmetry of the system. The breaking of the
+symmetry opens a gap in the energy spectrum. Therefore, topological insulators
+are very sensitive to magnetic fields, which can open a gap in the electronic
+spectrum. Concerning ""internal"" magnetic effects, for example the situation
+with doped magnetic impurities, is not trivial. A single magnetic impurity is
+not enough to open the band gap, while in the case of a ferromagnetic chain of
+deposited magnetic impurities the Dirac point is lifted. However, a much more
+interesting case is when localized magnetic impurities form a chiral spin
+order. Our first principle density functional theory calculations have shown
+that this is the case for Fe deposited on the surface of Bi2Se3 topological
+insulator. But not only magnetic impurities can form a chiral helicoidal spin
+texture. An alternative way is to use chiral multiferroics (prototype material
+is LiCu2O2) that induce a proximity effect. The theoretical approach we present
+here is valid for both cases. We observed that opposite to a ferromagnetically
+ordered case, a chiral spin order does not destroy the Dirac point. We also
+observed that the energy gap appears at the edges of the new Brillouin zone.
+Another interesting result concerns the spin dynamics. We derived an equation
+for the spin density dynamics with a spin current and relaxation terms. We have
+shown that the motion of the conductance electron generates a magnetic torque
+and exerts a certain force on the helicoidal texture.",1611.00642v1
+2017-01-05,Magnetic switching in granular FePt layers promoted by near-field laser enhancement,"Light-matter interaction at the nanoscale in magnetic materials is a topic of
+intense research in view of potential applications in next-generation
+high-density magnetic recording. Laser-assisted switching provides a pathway
+for overcoming the material constraints of high-anisotropy and high-packing
+density media, though much about the dynamics of the switching process remains
+unexplored. We use ultrafast small-angle x-ray scattering at an x-ray
+free-electron laser to probe the magnetic switching dynamics of FePt
+nanoparticles embedded in a carbon matrix following excitation by an optical
+femtosecond laser pulse. We observe that the combination of laser excitation
+and applied static magnetic field, one order of magnitude smaller than the
+coercive field, can overcome the magnetic anisotropy barrier between ""up"" and
+""down"" magnetization, enabling magnetization switching. This magnetic switching
+is found to be inhomogeneous throughout the material, with some individual FePt
+nanoparticles neither switching nor demagnetizing. The origin of this behavior
+is identified as the near-field modification of the incident laser radiation
+around FePt nanoparticles. The fraction of not-switching nanoparticles is
+influenced by the heat flow between FePt and a heat-sink layer.",1701.01237v1
+2017-04-13,Low energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu$_2$OSeO$_3$,"In this work, we present a comprehensive study of the low energy optical
+magnetic response of the skyrmionic Mott insulator Cu$_2$OSeO$_3$ via high
+resolution time-domain THz spectroscopy. In zero field, a new magnetic
+excitation not predicted by spin-wave theory with frequency $f$ = 2.03 THz is
+observed and shown, with accompanying time-of-flight neutron scattering
+experiments, to be a zone folded magnon from the $\mathrm{R}$ to
+$\mathrm{\Gamma}$ points of the Brillouin zone. Highly sensitive polarimetry
+experiments performed in weak magnetic fields, $\mu_0$H $<$ 200 mT, observe
+Faraday and Kerr rotations which are proportional to the sample magnetization,
+allowing for optical detection of the skyrmion phase and construction of a
+magnetic phase diagram. From these measurements, we extract a critical exponent
+of $\beta$ = 0.35 $\pm$ 0.04, in good agreement with the expected value for the
+3D Heisenberg universality class of $\beta$ = 0.367. In large magnetic fields,
+$\mu_0$H $>$ 5 T, we observe the magnetically active uniform mode of the
+ferrimagnetic field polarized phase whose dynamics as a function of field and
+temperature are studied. In addition to extracting a $g_\text{eff}$ = 2.08
+$\pm$ 0.03, we observe the uniform mode to decay through a non-Gilbert damping
+mechanism and to possesses a finite spontaneous decay rate, $\Gamma_0$
+$\approx$ 25 GHz, in the zero temperature limit. Our observations are
+attributed to Dzyaloshinkii-Moriya interactions, which have been proposed to be
+exceptionally strong in Cu$_2$OSeO$_3$ and are expected to impact the low
+energy magnetic response of such chiral magnets.",1704.04228v1
+2017-06-27,The pulsating magnetosphere of the extremely slowly rotating magnetic $β$ Cep star $ξ^1$ CMa,"$\xi^1$ CMa is a monoperiodically pulsating, magnetic $\beta$ Cep star with
+magnetospheric X-ray emission which, uniquely amongst magnetic stars, is
+clearly modulated with the star's pulsation period. The rotational period
+$P_{\rm rot}$ has yet to be identified, with multiple competing claims in the
+literature. We present an analysis of a large ESPaDOnS dataset with a 9-year
+baseline. The longitudinal magnetic field $\langle B_{\rm Z}\rangle$ shows a
+significant annual variation, suggesting that $P_{\rm rot}$ is at least on the
+order of decades. The possibility that the star's H$\alpha$ emission originates
+around a classical Be companion star is explored and rejected based upon VLTI
+AMBER and PIONIER interferometry, indicating that the emission must instead
+originate in the star's magnetosphere and should therefore also be modulated
+with $P_{\rm rot}$. Period analysis of H$\alpha$ equivalent widths measured
+from ESPaDOnS and CORALIE spectra indicates $P_{\rm rot} > 30$ yr. All evidence
+thus supports that $\xi^1$ CMa is a very slowly rotating magnetic star hosting
+a dynamical magnetosphere. H$\alpha$ also shows evidence for modulation with
+the pulsation period, a phenomenon which we show cannot be explained by
+variability of the underlying photospheric line profile, i.e. it may reflect
+changes in the quantity and distribution of magnetically confined plasma in the
+circumstellar environment. In comparison to other magnetic stars with similar
+stellar properties, $\xi^1$ CMa is by far the most slowly rotating magnetic
+B-type star, is the only slowly rotating B-type star with a magnetosphere
+detectable in H$\alpha$ (and thus, the coolest star with an optically
+detectable dynamical magnetosphere), and is the only known early-type magnetic
+star with H$\alpha$ emission modulated by both pulsation and rotation.",1706.08820v1
+2017-09-14,Origin and evolution of magnetic fields in PMS stars : influence of rotation and structural changes,"During stellar evolution, especially in the PMS, stellar structure and
+rotation evolve significantly causing major changes in the dynamics and global
+flows of the star. We wish to assess the consequences of these changes on
+stellar dynamo, internal magnetic field topology and activity level. To do so,
+we have performed a series of 3D HD and MHD simulations with the ASH code. We
+choose five different models characterized by the radius of their radiative
+zone following an evolutionary track computed by a 1D stellar evolution code.
+These models characterized stellar evolution from 1 Myr to 50 Myr. By
+introducing a seed magnetic field in the fully convective model and spreading
+its evolved state through all four remaining cases, we observe systematic
+variations in the dynamical properties and magnetic field amplitude and
+topology of the models. The five MHD simulations develop strong dynamo field
+that can reach equipartition state between the kinetic and magnetic energy and
+even super- equipartition levels in the faster rotating cases. We find that the
+magnetic field amplitude increases as it evolves toward the ZAMS. Moreover the
+magnetic field topology becomes more complex, with a decreasing axisymmetric
+component and a non-axisymmetric one becoming predominant. The dipolar
+components decrease as the rotation rate and the size of the radiative core
+increase. The magnetic fields possess a mixed poloidal-toroidal topology with
+no obvious dominant component. Moreover the relaxation of the vestige dynamo
+magnetic field within the radiative core is found to satisfy MHD stability
+criteria. Hence it does not experience a global reconfiguration but slowly
+relaxes by retaining its mixed stable poloidal-toroidal topology.",1709.04667v1
+2019-06-09,Spin dynamics and unconventional magnetism in insulating La$_{(1-2x)}$Sr$_{2x}$Co$_{(1-x)}$Nb$_{x}$O$_3$,"We study the structural, magnetic, transport and electronic properties of
+LaCoO$_3$ with Sr/Nb co-substitution, i.e.,
+La$_{(1-2x)}$Sr$_{2x}$Co$_{(1-x)}$Nb$_{x}$O$_3$ using x-ray and neutron
+diffraction, dc and ac-magnetization, neutron depolarization, dc-resistivity
+and photoemission measurements. The powder x-ray and neutron diffraction data
+were fitted well with the rhombohedral crystal symmetry (space group
+\textit{R$\bar{3}$c}) in Rietveld refinement analysis. The calculated effective
+magnetic moment ($\approx$3.85~$\mu_B$) and average spin ($\approx$1.5) of Co
+ions from the analysis of magnetic susceptibility data are consistent with 3+
+state of Co ions in intermediate-spin (IS) and high-spin (HS) states in the
+ratio of $\approx$50:50, i.e., spin-state of Co$^{3+}$ is preserved at least up
+to $x=$ 0.1 sample. Interestingly, the magnetization values were significantly
+increased with respect to the $x=$ 0 sample, and the M-H curves show
+non-saturated behavior up to an applied maximum magnetic field of $\pm$70 kOe.
+The ac-susceptibility data show a shift in the freezing temperature with
+excitation frequency and the detailed analysis confirm the slower dynamics and
+a non-zero value of the Vogel-Fulcher temperature T$_0$, which suggests for the
+cluster spin glass. The unusual magnetic behavior indicates the presence of
+complex magnetic interactions at low temperatures. The dc-resistivity
+measurements show the insulating nature in all the samples. However, relatively
+large density of states $\approx$10$^{22}$ eV$^{-1}$cm$^{-3}$ and low
+activation energy $\approx$130~meV are found in $x=$ 0.05 sample. Using x-ray
+photoemission spectroscopy, we study the core-level spectra of La 3$d$, Co
+2$p$, Sr 3$d$, and Nb 3$d$ to confirm the valence state.",1906.03659v1
+2022-06-11,Field evolution of magnetic phases and spin dynamics in the honeycomb lattice magnet Na2Co2TeO6: 23Na NMR study,"We report on the results of 23Na NMR in the honeycomb lattice magnet
+Na2Co2TeO6 which has been nominated as a Kitaev material. Measurements of
+magnetic shift and width of the NMR line as functions of temperature and
+magnetic field show that a spin-disordered phase does not appear up to a field
+of 9 T. In the antiferromagnetic phase just below the Neel temperature TN, we
+find a temperature region extending down to ~TN/2 where the nuclear
+spin-lattice relaxation rate 1/T1 remains enhanced and is further increased by
+a magnetic field. This region crosses over to a low temperature region
+characterized by the rapidly decreasing 1/T1 which is less field-sensitive.
+These observations suggest incoherent spin excitations with a large spectral
+weight at low energies in the intermediate temperature region transforming to
+more conventional spin-wave excitations at low temperatures. The drastic change
+of the low-energy spin dynamics is likely caused by strong damping of spin
+waves activated only in the intermediate temperature region, which may be
+realized for triple-q magnetic order possessing partially-disordered moments as
+scattering centers of spin waves. In the paramagnetic phase near TN, dramatic
+field suppression of 1/T1 is observed. From analysis of the temperature
+dependence of 1/T1 based on the renormalized-classical description of a
+two-dimensional quantum antiferromagnet, we find the field-dependent spin
+stiffness constant that scales with TN as a function of magnetic field. This
+implies field suppression of the energy scale characterizing both
+two-dimensional spin correlations and three-dimensional long-range order, which
+may be associated with an increasing effect of frustration in magnetic fields.",2206.05409v3
+2023-04-14,Magnetic properties of a spin-orbit entangled Jeff=1/2 three-dimensional frustrated rare-earth hyperkagome,"The interplay between competing degrees of freedom can stabilize non-trivial
+magnetic states in correlated electron materials. Frustration-induced strong
+quantum fluctuations can evade long-range magnetic ordering leading to exotic
+quantum states such as spin liquids in two-dimensional spin-lattices such as
+triangular and kagome structures. However, the experimental realization of
+dynamic and correlated quantum states is rare in three-dimensional (3D)
+frustrated magnets wherein quantum fluctuations are less prominent. Herein, we
+report the crystal structure, magnetic susceptibility, electron spin resonance
+(ESR) and specific heat studies accompanied by crystal electric field (CEF)
+calculations on a 3D frustrated magnet Yb3Sc2Ga3O12. In this material, Yb3+
+ions form a three-dimensional network of corner-sharing triangles known as
+hyperkagome lattice without any detectable anti-site disorder. Our results
+reveal a low energy state with Jeff = 1/2 degrees of freedom in the Kramers
+doublet state. The zero field-cooled and field cooled magnetic susceptibility
+taken in 0.001 T rules out the presence of spin-freezing down to 1.8K. The
+Curie-Weiss (CW) fit to low-T susceptibility data yields a small and negative
+CW temperature indicating the presence of a weak antiferromagnetic interaction
+between Jeff = 1/2 (Yb3+) moments. The Yb-ESR displays a broad line of
+non-Lorentzian shape that suggests considerable magnetic anisotropy in
+Yb3Sc2Ga3O12. The CEF calculations suggest that the ground state is well
+separated from the excited states, which are in good agreement with
+experimental results. The absence of long-range magnetic ordering indicates a
+dynamic liquid-like ground state at least down to 130 mK. Furthermore, zero
+field specific heat shows a broad maximum around 200 mK suggesting the presence
+of short-range spin correlations in this 3D frustrated antiferromagnet.",2304.07350v2
+2024-01-16,Critical magnetic Reynolds number of the turbulent dynamo in collisionless plasmas,"The intracluster medium of galaxy clusters is an extremely hot and diffuse,
+nearly collisionless plasma, which hosts dynamically important magnetic fields
+of $\sim \mu {\rm G}$ strength. Seed magnetic fields of much weaker strength of
+astrophysical or primordial origin can be present in the intracluster medium.
+In collisional plasmas, which can be approximated in the magneto-hydrodynamical
+(MHD) limit, the turbulent dynamo mechanism can amplify weak seed fields to
+strong dynamical levels efficiently by converting turbulent kinetic energy into
+magnetic energy. However, the viability of this mechanism in weakly collisional
+or completely collisionless plasma is much less understood. In this study, we
+explore the properties of the collisionless turbulent dynamo by using
+three-dimensional hybrid-kinetic particle-in-cell simulations. We explore the
+properties of the collisionless turbulent dynamo in the kinematic regime for
+different values of the magnetic Reynolds number, ${\rm Rm}$, initial
+magnetic-to-kinetic energy ratio, $(E_{\rm{mag}}/E_{\rm{kin}})_{\rm{i}}$, and
+initial Larmor ratio, $(r_{\rm Larmor}/L_{\rm box})_{\rm i}$, i.e., the ratio
+of the Larmor radius to the size of the turbulent system. We find that in the
+`un-magnetised' regime, $(r_{\rm Larmor}/L_{\rm box})_{\rm i} > 1$, the
+critical magnetic Reynolds number for the dynamo action ${\rm Rm}_{\rm crit}
+\approx 107 \pm 3$. In the `magnetised' regime, $(r_{\rm Larmor}/L_{\rm
+box})_{\rm i} \lesssim 1$, we find a marginally higher ${\rm Rm}_{\rm crit} =
+124 \pm 8$. We find that the growth rate of the magnetic energy does not depend
+on the strength of the seed magnetic field when the initial magnetisation is
+fixed. We also study the distribution and evolution of the pressure anisotropy
+in the collisionless plasma and compare our results with the MHD turbulent
+dynamo.",2401.08499v1
+2024-03-06,Dark Dragon Breaks Magnetic Chain: Dynamical Substructures of IRDC G28.34 Form in Supported Environments,"We have comprehensively studied the multi-scale physical properties of the
+infrared dark cloud (IRDC) G28.34 (the Dragon cloud) with dust polarization and
+molecular line data from Planck, FCRAO-14m, JCMT, and ALMA. We find that the
+averaged magnetic fields of clumps tend to be either parallel with or
+perpendicular to the cloud-scale magnetic fields, while the cores in clump MM4
+tend to have magnetic fields aligned with the clump fields. Implementing the
+relative orientation analysis (for magnetic fields, column density gradients,
+and local gravity), Velocity Gradient Technique (VGT), and modified
+Davis-Chandrasekhar-Fermi (DCF) analysis, we find that: G28.34 is located in a
+trans-to-sub-Alfv\'{e}nic environment ($\mathcal{M}_{A}=0.74$ within $r=15$
+pc); the magnetic field is effectively resisting gravitational collapse in
+large-scale diffuse gas, but is distorted by gravity within the cloud and
+affected by star formation activities in high-density regions; and the
+normalized mass-to-flux ratio tends to increase with increasing density and
+decreasing radius. Considering the thermal, turbulent, and magnetic supports,
+we find that the environmental gas of G28.34 is in a super-virial (supported)
+state, the infrared dark clumps may be in a near-equilibrium state, and core
+MM4-core4 is in a sub-virial (gravity-dominant) state. In summary, we suggest
+that magnetic fields dominate gravity and turbulence in the cloud environment
+at large scales, resulting in relatively slow cloud formation and evolution
+processes. Within the cloud, gravity could overwhelm magnetic fields and
+turbulence, allowing local dynamical star formation to happen.",2403.03437v2
+1997-03-21,"Star Formation in Cold, Spherical, Magnetized Molecular Clouds","We present an idealized, spherical model of the evolution of a magnetized
+molecular cloud due to ambipolar diffusion. This model allows us to follow the
+quasi-static evolution of the cloud's core prior to collapse and the subsequent
+evolution of the remaining envelope. By neglecting the thermal pressure
+gradients in comparison with magnetic stresses and by assuming that the ion
+velocity is small compared with the neutral velocity, we are able to find exact
+analytic solutions to the MHD equations. We show that, in the case of a
+centrally condensed cloud, a core of finite mass collapses into the origin
+leaving behind a quasi-static envelope, whereas initially homogeneous clouds
+never develop any structure in the absence of thermal stresses, and collapse as
+a whole. Prior to the collapse of the core, the cloud's evolution is
+characterized by two phases: a long, quasi-static phase where the relevant
+timescale is the ambipolar diffusion time (treated in this paper), and a short,
+dynamical phase where the characteristic timescale is the free-fall time. The
+collapse of the core is an ""outside-in"" collapse. The quasi-static evolution
+terminates when the cloud becomes magnetically supercritical; thereafter its
+evolution is dynamical, and a singularity develops at the origin-a protostar.
+After the initial formation of the protostar, the outer envelope continues to
+evolve quasi-statically, while the region of dynamical infall grows with
+time-an ""inside-out"" collapse. We use our solution to estimate the magnetic
+flux trapped in the collapsing core and the mass accretion rate onto the newly
+formed protostar. Our results agree, within factors of order unity, with the
+numerical results of Fiedler & Mouschovias (1992) for the physical quantities
+in the midplane of",9703144v1
+2002-11-14,Collapse of a Magnetized Star to a Black Hole,"We study of the collapse of a magnetized spherical star to a black hole in
+general relativity theory. The matter and gravitational fields are described by
+the exact Oppenheimer-Snyder solution for the collapse of a spherical,
+homogeneous dust ball. We adopt a ``dynamical Cowling approximation'' whereby
+the matter and the geometry (metric), while highly dynamical, are unaffected by
+the electromagnetic fields. The matter is assumed to be perfectly conducting
+and threaded by a dipole magnetic field at the onset of collapse. We determine
+the subsequent evolution of the magnetic and electric fields without
+approximation; the fields are determined analytically in the matter interior
+and numerically in the vacuum exterior. We apply junction conditions to match
+the electromagnetic fields across the stellar surface. We use this model to
+experiment with several coordinate gauge choices for handling spacetime
+evolution characterized by the formation of a black hole and the associated
+appearance of singularities. These choices range from ``singularity avoiding''
+time coordinates to ``horizon penetrating'' time coordinates accompanied by
+black hole excision. The later choice enables us to integrate the
+electromagnetic fields arbitrarily far into the future. At late times the
+longitudinal magnetic field in the exterior has been transformed into a
+transverse electromagnetic wave; part of the electromagnetic radiation is
+captured by the hole and the rest propagates outward to large distances. The
+solution we present for our simple scenario can be used to test codes designed
+to treat more general evolutions of relativistic MHD fluids flowing in strong
+gravitational fields in dynamical spacetimes.",0211339v1
+1999-04-01,Pauli principle and chaos in a magnetized disk,"We present results of a detailed quantum mechanical study of a gas of $N$
+noninteracting electrons confined to a circular boundary and subject to
+homogeneous dc plus ac magnetic fields $(B=B_{dc}+B_{ac}f(t)$, with
+$f(t+2\pi/\omega_0)=f(t)$). We earlier found a one-particle {\it classical}
+phase diagram of the (scaled) Larmor frequency
+$\tilde\omega_c=omega_c/\omega_0$ {\rm vs} $\epsilon=B_{ac}/B_{dc}$ that
+separates regular from chaotic regimes. We also showed that the quantum
+spectrum statistics changed from Poisson to Gaussian orthogonal ensembles in
+the transition from classically integrable to chaotic dynamics. Here we find
+that, as a function of $N$ and $(\epsilon,\tilde\omega_c)$, there are clear
+quantum signatures in the magnetic response, when going from the
+single-particle classically regular to chaotic regimes. In the quasi-integrable
+regime the magnetization non-monotonically oscillates between diamagnetic and
+paramagnetic as a function of $N$. We quantitatively understand this behavior
+from a perturbation theory analysis. In the chaotic regime, however, we find
+that the magnetization oscillates as a function of $N$ but it is {\it always}
+diamagnetic. Equivalent results are also presented for the orbital currents. We
+also find that the time-averaged energy grows like $N^2$ in the
+quasi-integrable regime but changes to a linear $N$ dependence in the chaotic
+regime. In contrast, the results with Bose statistics are akin to the
+single-particle case and thus different from the fermionic case. We also give
+an estimate of possible experimental parameters were our results may be seen in
+semiconductor quantum dot billiards.",9904024v1
+2006-07-25,Spin dynamics in the diluted ferromagnetic Kondo lattice model,"The interplay of disorder and competing interactions is investigated in the
+carrier-induced ferromagnetic state of the Kondo lattice model within a
+numerical finite-size study in which disorder is treated exactly. Competition
+between impurity spin couplings, stability of the ferromagnetic state, and
+magnetic transition temperature are quantitatively investigated in terms of
+magnon properties for different models including dilution, disorder, and
+weakly-coupled spins. A strong optimization is obtained for T_c at hole doping
+p << x, highlighting the importance of compensation in diluted magnetic
+semiconductors. The estimated T_c is in good agreement with experimental
+results for Ga_{1-x}Mn_x As for corresponding impurity concentration, hole
+bandwidth, and compensation. Finite-temperature spin dynamics is quantitatively
+studied within a locally self-consistent magnon renormalization scheme, which
+yields a substantial enhancement in T_c due to spin clustering, and highlights
+the nearly-paramagnetic spin dynamics of weakly-coupled spins. The large
+enhancement in density of low-energy magnetic excitations due to disorder and
+competing interactions results in a strong thermal decay of magnetization,
+which fits well with the Bloch form M_0(1-BT^{3/2}) at low temperature, with B
+of same order of magnitude as obtained in recent squid magnetization
+measurements on Ga_{1-x}Mn_x As samples.",0607633v1
+2006-12-17,Phase separation and suppression of critical dynamics at quantum transitions of itinerant magnets: MnSi and (Sr$_{1-x}$Ca$_{x}$)RuO$_{3}$,"Quantum phase transitions (QPTs) have been studied extensively in correlated
+electron systems. Characterization of magnetism at QPTs has, however, been
+limited by the volume-integrated feature of neutron and magnetization
+measurements and by pressure uncertainties in NMR studies using powderized
+specimens. Overcoming these limitations, we performed muon spin relaxation
+($\mu$SR) measurements which have a unique sensitivity to volume fractions of
+magnetically ordered and paramagnetic regions, and studied QPTs from itinerant
+heli/ferro magnet to paramagnet in MnSi (single-crystal; varying pressure) and
+(Sr$_{1-x}$Ca$_{x}$)RuO$_{3}$ (ceramic specimens; varying $x$). Our results
+provide the first clear evidence that both cases are associated with
+spontaneous phase separation and suppression of dynamic critical behavior,
+revealed a slow but dynamic character of the ``partial order'' diffuse spin
+correlations in MnSi above the critical pressure, and, combined with other
+known results in heavy-fermion and cuprate systems, suggest a possibility that
+a majority of QPTs involve first-order transitions and/or phase separation.",0612437v1
+2009-10-19,Flux dynamics and vortex phase diagram in $Ba(Fe_{1-x}Co_x)_2As_2$ single crystals revealed by magnetization and its relaxation,"Magnetization and its relaxation have been measured in
+$Ba(Fe_{1-x}Co_x)_2As_2$ single crystals at various doping levels ranging
+fromvery underdoped to very overdoped regimes. Sizable magnetization relaxation
+rate has been observed in all samples, indicating a moderate vortex motion and
+relatively small characteristic pinning energy. Detailed analysis leads to the
+following conclusions: (1) A prominent second-peak (SP) effect was observed in
+the samples around the optimal doping level (x $\approx$ 0.08), but it becomes
+invisible or very weak in the very underdoped and overdoped samples; (2) The
+magnetization relaxation rate is inversely related to the transient
+superconducting current density revealing the non-monotonic field and
+temperature dependence through the SP region; (3) A very sharp magnetization
+peak was observed near zero field which corresponds to a much reduced
+relaxation rate; (4) A weak temperature dependence of relaxation rate or a
+plateau was found in the intermediate temperature region. Together with the
+treatment of the Generalized-Inversion-Scheme, we suggest that the vortex
+dynamics is describable by the collective pinning model. Finally, vortex phase
+diagrams were drawn for all the samples showing a systematic evolution of
+vortex dynamics.",0910.3600v2
+2011-02-16,Experimental characterization of coherent magnetization transport in a one-dimensional spin system,"We experimentally characterize the non-equilibrium, room-temperature
+magnetization dynamics of a spin chain evolving under an effective
+double-quantum Hamiltonian. We show that the Liouville space operators
+corresponding to the magnetization and the two-spin correlations evolve 90
+degrees out of phase with each other, and drive the transport dynamics. For a
+nearest-neighbor-coupled N-spin chain, the dynamics are found to be restricted
+to a Liouville operator space whose dimension scales only as N^2, leading to a
+slow growth of multi-spin correlations. Even though long-range couplings are
+present in the real system, we find excellent agreement between the analytical
+predictions and our experimental results, confirming that leakage out of the
+restricted Liouville space is slow on the timescales investigated. Our results
+indicate that the group velocity of the magnetization is 6.04 +/- 0.38 um/s,
+corresponding to a coherent transport over N ~ 26 spins on the experimental
+timescale. As the double-quantum Hamiltonian is related to the standard
+one-dimensional XX Hamiltonian by a similarity transform, our results can be
+directly extended to XX quantum spin chains, which have been extensively
+studied in the context of both quantum magnetism and quantum information
+processing.",1102.3400v2
+2013-08-01,Simulation of the dynamics in the magnetotail current sheet,"The dynamics in the magnetosphere current sheet was simulated following
+transformations to the rectangular NxM array of cells (cellular automaton)
+originally proposed by Koselov and Koselova (2002). The magnetosphere part of
+the modeling system was organized as a rectangular arrangement of cells with a
+stored energy, a local redistribution of the energy will exist when a value
+threshold is exceeded in one of the cells. We assume that the threshold value
+in each cell depends on external control parameter which influences the long
+boundaries of the rectangular array (40x80). The model dynamics controlled by
+the z-component of the interplanetary magnetic field (Bz) as well as analogies
+between the model transient processes and the observed substorm auroral
+activations are discussed. The Bz correspond to temporary windows of the solar
+wind for a group of magnetic clouds and plasmoids. The model simulates
+organized patterns in the energy distribution. The function of distribution of
+probability (or PDF) of the size of the avalanches have a power-law form,
+showing evidences of a system with Self-Organized Criticality (SOC). The
+occurrence of big avalanches in the model is related with the activation of
+some intense magnetic substorm. The arrival to the terrestrial magnetopause of
+a solar wind with Bz negative is a fundamental condition of occurrence of
+magnetic substorms. While more negative it is the Bz IMF component bigger it is
+the value of the AE index and trigger a strong magnetic substorm.",1308.0350v1
+2013-12-10,On the alignment of PNe and local magnetic field at the galactic centre: MHD numerical simulations,"For the past decade observations of the alignement of PNe symmetries with
+respect to the galactic disk have led to conflicting results. Recently
+observational evidence for alignment between PNe and local interstellar
+magnetic fields in the central part of the Galaxy ($b < 5^\circ$) has been
+found. We studied the role of the interstellar magnetic field on the dynamical
+evolution of a PN by means of an analytical model and from 3D MHD numerical
+simulations. We test under what conditions typical ejecta would have their
+dynamics severely modified by an interstellar magnetic field. We found that
+uniform fields of $> 100\mu$G are required in order to be dynamically dominant.
+This is found to occur only at later evolutionary stages, therefore being
+unable to change the general morphology of the nebula. However, the symmetry
+axis of bipolar and elliptical nebulae end up aligned to the external field.
+This result can explain why different samples of PNe result in different
+conclusions regarding the alignment of PNe. Objects located at high galactic
+latitudes, or at large radii, should present no preferential alignment with
+respect to the galactic plane. PNe located at the galactic centre and low
+latitudes would, on the other hand, be preferentiably aligned to the disk.
+Finally, we present synthetic polarization maps of the nebulae to show that the
+polarization vectors, as well as the field lines at the expanding shell, are
+not uniform even in the strongly magnetized case, indicating that polarization
+maps of nebulae are not adequate in probing the orientation, or intensity, of
+the dominant external field.",1312.2910v1
+2014-01-23,Electron-spin dynamics induced by photon spins,"Strong rotating magnetic fields may cause a precession of the electron's spin
+around the rotation axis of the magnetic field. The superposition of two
+counterpropagating laser beams with circular polarization and opposite helicity
+features such a rotating magnetic field component but also carries spin. The
+laser's spin density, that can be expressed in terms of the lase's
+electromagnetic fields and potentials, couples to the electron's spin via a
+relativistic correction to the Pauli equation. We show that the quantum
+mechanical interaction of the electron's spin with the laser's rotating
+magnetic field and with the laser's spin density counteract each other in such
+a way that a net spin rotation remains with a precession frequency that is much
+smaller than the frequency one would expect from the rotating magnetic field
+alone. In particular, the frequency scales differently with the laser's
+electric field strength depending on if relativistic corrections are taken into
+account or not. Thus, the relativistic coupling of the electron's spin to the
+laser's spin density changes the dynamics not only quantitatively but also
+qualitatively as compared to the nonrelativistic theory. The electron's spin
+dynamics is a genuine quantum mechanical relativistic effect.",1401.5976v2
+2014-02-05,Magnetization dynamics: path-integral formalism for the stochastic Landau-Lifshitz-Gilbert equation,"We construct a path-integral representation of the generating functional for
+the dissipative dynamics of a classical magnetic moment as described by the
+stochastic generalization of the Landau-Lifshitz-Gilbert equation proposed by
+Brown, with the possible addition of spin-torque terms. In the process of
+constructing this functional in the Cartesian coordinate system, we critically
+revisit this stochastic equation. We present it in a form that accommodates for
+any discretization scheme thanks to the inclusion of a drift term. The
+generalized equation ensures the conservation of the magnetization modulus and
+the approach to the Gibbs-Boltzmann equilibrium in the absence of non-potential
+and time-dependent forces. The drift term vanishes only if the mid-point
+Stratonovich prescription is used. We next reset the problem in the more
+natural spherical coordinate system. We show that the noise transforms
+non-trivially to spherical coordinates acquiring a non-vanishing mean value in
+this coordinate system, a fact that has been often overlooked in the
+literature. We next construct the generating functional formalism in this
+system of coordinates for any discretization prescription. The functional
+formalism in Cartesian or spherical coordinates should serve as a starting
+point to study different aspects of the out-of-equilibrium dynamics of magnets.
+Extensions to colored noise, micro-magnetism and disordered problems are
+straightforward.",1402.1200v2
+2014-06-19,"Neutrino Magnetic Moment, CP Violation and Flavor Oscillations in Matter","We consider collective oscillations of neutrinos, which are emergent
+nonlinear flavor evolution phenomena instigated by neutrino-neutrino
+interactions in astrophysical environments with sufficiently high neutrino
+densities. We investigate the symmetries of the problem in the full three
+flavor mixing scheme and in the exact many-body formulation by including the
+effects of CP violation and neutrino magnetic moment. We show that, similar to
+the two flavor scheme, several dynamical symmetries exist for three flavors in
+the single-angle approximation if the net electron background in the
+environment and the effects of the neutrino magnetic moment are negligible.
+Moreover, we show that these dynamical symmetries are present even when the CP
+symmetry is violated in neutrino oscillations. We explicitly write down the
+constants of motion through which these dynamical symmetries manifest
+themselves in terms of the generators of the SU(3) flavor transformations. We
+also show that the effects due to the CP-violating Dirac phase factor out of
+the many-body evolution operator and evolve independently of nonlinear flavor
+transformations if neutrino electromagnetic interactions are ignored. In the
+presence of a strong magnetic field, CP-violating effects can still be
+considered independently provided that an effective definition for neutrino
+magnetic moment is used.",1406.5489v1
+2014-06-24,Dynamic Topology and Flux Rope Evolution During Non-linear Tearing of 3D Null Point Current Sheets,"In this work the dynamic magnetic field within a tearing-unstable
+three-dimensional (3D) current sheet about a magnetic null point is described
+in detail. We focus on the evolution of the magnetic null points and flux ropes
+that are formed during the tearing process. Generally, we find that both
+magnetic structures are created prolifically within the layer and are
+non-trivially related. We examine how nulls are created and annihilated during
+bifurcation processes, and describe how they evolve within the current layer.
+The type of null bifurcation first observed is associated with the formation of
+pairs of flux ropes within the current layer. We also find that new nulls form
+within these flux ropes, both following internal reconnection and as adjacent
+flux ropes interact. The flux ropes exhibit a complex evolution, driven by a
+combination of ideal kinking and their interaction with the outflow jets from
+the main layer. The finite size of the unstable layer also allows us to
+consider the wider effects of flux rope generation. We find that the unstable
+current layer acts as a source of torsional MHD waves and dynamic braiding of
+magnetic fields. The implications of these results to several areas of
+heliophysics are discussed.",1406.6120v1
+2014-08-14,Structural stability and thermodynamics of CrN magnetic phases from ab initio and experiment,"The dynamical and thermodynamic phase stabilities of the stoichiometric
+compound CrN including different structural and magnetic configurations are
+comprehensively investigated using a first-principles density-functional-theory
+(DFT) plus U approach in conjunction with experimental measurements of the
+thermal expansion. Comparing DFT and DFT+U results with experimental data
+reveals that the treatment of electron correlations using methods beyond
+standard DFT is crucial. The non-magnetic face-centered cubic B1-CrN phase is
+both, elastically and dynamically unstable, even under high pressure, while CrN
+phases with non-zero local magnetic moments are predicted to be dynamically
+stable within the framework of the DFT+U scheme. Furthermore, the impact of
+different treatments for the exchange-correlation (xc)-functional is
+investigated by carrying out all computations employing the local density
+approximation and generalized gradient approximation. To address
+finite-temperature properties, both, magnetic and vibrational contributions to
+the free energy have been computed employing our recently developed spin-space
+averaging method. The calculated phase transition temperature between
+low-temperature antiferromagnetic and high-temperature paramagnetic (PM) CrN
+variants is in excellent agreement with experimental values and reveals the
+strong impact of the choice of the xc-functional. The temperature-dependent
+linear thermal expansion coefficient of CrN is experimentally determined by the
+wafer curvature method from a reactive magnetron sputter deposited single-phase
+B1-CrN thin film with dense film morphology. A good agreement is found between
+experimental and ab initio calculated linear thermal expansion coefficients of
+PM B1-CrN. Other thermodynamic properties, such as the specific heat capacity,
+have been computed as well and compared to previous experimental data.",1408.3201v1
+2015-01-06,Exciton spin dynamics and photoluminescence polarization of CdSe/CdS dot-in-rod nanocrystals in high magnetic fields,"The exciton spin dynamics and polarization properties of the related emission
+are investigated in colloidal CdSe/CdS dot-in-rod (DiR) and spherical
+core/shell nanocrystal (NC) ensembles by magneto-optical photoluminescence (PL)
+spectroscopy in magnetic fields up to 15 T. It is shown that the degree of
+circular polarization (DCP) of the exciton emission induced by the magnetic
+field is affected by the NC geometry as well as the exciton fine structure and
+can provide information on nanorod orientation. A theory to describe the
+circular and linear polarization properties of the NC emission in magnetic
+field is developed. It takes into account phonon mediated coupling between the
+exciton fine structure states as well as the dielectric enhancement effect
+resulting from the anisotropic shell of DiR NCs. This theoretical approach is
+used to model the experimental results and allows us to explain most of the
+measured features. The spin dynamics of the dark excitons is investigated in
+magnetic fields by time-resolved photoluminescence. The results highlight the
+importance of confined acoustic phonons in the spin relaxation of dark
+excitons. The bare core surface as well as the core/shell interface give rise
+to an efficient spin relaxation channel, while the surface of core/shell NCs
+seems to play only a minor role.",1501.01169v1
+2015-10-08,Elliptic Annular Josephson Tunnel Junctions in an external magnetic field: The dynamics,"We analyze the dynamics of a magnetic flux quantum (current vortex) trapped
+in a current-biased long planar elliptic annular Josephson tunnel junction. The
+system is modeled by a perturbed sine-Gordon equation that determines the
+spatial and temporal behavior of the phase difference across the tunnel barrier
+separating the two superconducting electrodes. In the absence of an external
+magnetic field the fluxon dynamics in an elliptic annulus does not differ from
+that of a circular annulus where the stationary fluxon speed merely is
+determined by the system losses. The interaction between the vortex magnetic
+moment and a spatially homogeneous in-plane magnetic field gives rise to a
+tunable periodic non-sinusoidal potential which is strongly dependent on the
+annulus aspect ratio. We study the escape of the vortex from a well in the
+tilted potential when the bias current exceeds the depinning current. The
+smallest depinning current as well as the lowest sensitivity of the annulus to
+the external field is achieved when the eccentricity is equal to -1. The
+presented extensive numerical results are in good agreement with the findings
+of the perturbative approach. We also probe the rectifying properties of an
+asymmetric potential implemented with an egg-shaped annulus formed by two
+semi-elliptic arcs.",1510.02254v1
+2015-12-02,Investigation of intergranular bright points from the New Vacuum Solar Telescope,"Six high-resolution TiO-band image sequences from the New Vacuum Solar
+Telescope (NVST) are used to investigate the properties of intergranular bright
+points (igBPs). We detect the igBPs using a Laplacian and morphological
+dilation algorithm (LMD) and track them using a three-dimensional segmentation
+algorithm automatically, and then investigate the morphologic, photometric and
+dynamic properties of igBPs, in terms of equivalent diameter, the intensity
+contrast, lifetime, horizontal velocity, diffusion index, motion range and
+motion type. The statistical results confirm the previous studies based on
+G-band or TiO-band igBPs from the other telescopes. It illustrates that the TiO
+data from the NVST have a stable and reliable quality, which are suitable for
+studying the igBPs. In addition, our method is feasible to detect and track the
+igBPs in the TiO data from the NVST. With the aid of the vector magnetograms
+obtained from the Solar Dynamics Observatory /Helioseismic and Magnetic Imager,
+the properties of igBPs are found to be influenced by their embedded magnetic
+environments strongly. The area coverage, the size and the intensity contrast
+values of igBPs are generally larger in the regions with higher magnetic flux.
+However, the dynamics of igBPs, including the horizontal velocity, the
+diffusion index, the ratio of motion range and the index of motion type are
+generally larger in the regions with lower magnetic flux. It suggests that the
+absence of strong magnetic fields in the medium makes it possible for the igBPs
+to look smaller and weaker, diffuse faster, move faster and further in a
+straighter path.",1512.00737v1
+2016-05-08,Decay of isotropic flow and anisotropic flow with rotation or magnetic field or both in a weakly nonlinear regime,"We investigate numerically the decay of isotropic, rotating,
+magnetohydrodynamic (MHD), and rotating MHD flows in a periodic box. The
+Reynolds number $Re$ defined with the box size and the initial velocity is
+$100$ at which the flows are in a weakly nonlinear regime, i.e. not laminar but
+far away from the fully turbulent state. The decay of isotropic flow has two
+stages, the first stage for the development of small scales and the second
+stage for the viscous dissipation. In the rapidly rotating flow, fast rotation
+induces the inertial wave and causes the large-scale structure to inhibit the
+development of the first stage and retard the flow decay. In the MHD flow, the
+imposed field also causes the large-scale structure but facilitates the flow
+decay in the first stage because of the energy conversion from flow to magnetic
+field. Magnetic Reynolds number $Rm$ is important for the dynamics of the MHD
+flow, namely a high $Rm$ induces the Alfv\'en wave but a low $Rm$ cannot. In
+the rotating MHD flow, slower rotation tends to convert more kinetic energy to
+magnetic energy. The orientation between the rotational and magnetic axes is
+important for the dynamics of the rotating MHD flow, namely the energy
+conversion is more efficient and the stronger wave is induced when the two axes
+are not parallel than when they are parallel.",1605.02267v1
+2017-01-31,Flux Accretion and Coronal Mass Ejection Dynamics,"Coronal mass ejections (CMEs) are the primary drivers of severe space weather
+disturbances in the heliosphere. Models of CME dynamics have been proposed that
+do not fully include the effects of magnetic reconnection on the forces driving
+the ejection. Both observations and numerical modeling, however, suggest that
+reconnection likely plays a major role in most, if not all, fast CMEs. Here, we
+theoretically investigate the accretion of magnetic flux onto a rising ejection
+by reconnection involving the ejection's background field. This reconnection
+alters the magnetic structure of the ejection and its environment, thereby
+modifying the forces acting upon the ejection, generically increasing its
+upward acceleration. The modified forces, in turn, can more strongly drive the
+reconnection. This feedback process acts, effectively, as an instability, which
+we refer to as a reconnective instability. Our analysis implies that CME models
+that neglect the effects of reconnection cannot accurately describe observed
+CME dynamics. Our ultimate aim is to understand changes in CME acceleration in
+terms of observable properties of magnetic reconnection, such as the amount of
+reconnected flux. This flux can be estimated from observations of flare ribbons
+and photospheric magnetic fields.",1701.09082v5
+2017-02-27,Current Induced Damping of Nanosized Quantum Moments in the Presence of Spin-Orbit Interaction,"Motivated by the need to understand current-induced magnetization dynamics at
+the nanoscale, we have developed a formalism, within the framework of Keldysh
+Green function approach, to study the current-induced dynamics of a
+ferromagnetic (FM) nanoisland overlayer on a spin-orbit-coupling (SOC) Rashba
+plane. In contrast to the commonly employed classical micromagnetic LLG
+simulations the magnetic moments of the FM are treated {\it quantum
+mechanically}. We obtain the density matrix of the whole system consisting of
+conduction electrons entangled with the local magnetic moments and calculate
+the effective damping rate of the FM. We investigate two opposite limiting
+regimes of FM dynamics: (1) The precessional regime where the magnetic
+anisotropy energy (MAE) and precessional frequency are smaller than the
+exchange interactions, and (2) The local spin-flip regime where the MAE and
+precessional frequency are comparable to the exchange interactions. In the
+former case, we show that due to the finite size of the FM domain, the
+\textquotedblleft Gilbert damping\textquotedblright does not diverge in the
+ballistic electron transport regime, in sharp contrast to Kambersky's breathing
+Fermi surface theory for damping in metallic FMs. In the latter case, we show
+that above a critical bias the excited conduction electrons can switch the
+local spin moments resulting in demagnetization and reversal of the
+magnetization. Furthermore, our calculations show that the bias-induced
+antidamping efficiency in the local spin-flip regime is much higher than that
+in the rotational excitation regime.",1702.08408v2
+2017-03-30,Structure distribution and turbulence in self-consistently supernova-driven ISM of multiphase magnetized galactic discs,"Galaxy evolution and star formation are two multi-scale problems tightly
+linked to each other. To understand the interstellar cycle, which triggers
+galaxy evolution, it is necessary to describe simultaneously the large-scale
+evolution widely induced by the feedback processes and the details of the gas
+dynamics that controls the star formation process through gravitational
+collapse. We perform a set of three-dimensional high-resolution numerical
+simulations of a turbulent, self-gravitating and magnetized interstellar medium
+within a $1\ \mathrm{kpc}$ stratified box with supernova feedback correlated
+with star-forming regions. In particular, we focus on the role played by the
+magnetic field and the feedback on the galactic vertical structure, the star
+formation rate (SFR) and the flow dynamics. For this purpose we vary their
+respective intensities. We extract properties of the dense clouds arising from
+the turbulent motions and compute power spectra of various quantities. Using a
+distribution of supernovae sufficiently correlated with the dense gas, we find
+that supernova explosions can reproduce the observed SFR, particularly if the
+magnetic field is on the order of a few $\mu G$. The vertical structure, which
+results from a dynamical and an energy equilibrium is well reproduced by a
+simple analytical model, which allows us to estimate the coupling between the
+gas and the supernovae. We found the coupling to be rather low and on the order
+of 1.5$\%$. Strong magnetic fields may help to increase this coupling by a
+factor of about 2-3. To characterize the flow we compute the power spectra of
+various quantities in 3D but also in 2D in order to account for the
+stratification of the galactic disc.",1703.10421v1
+2017-12-04,Effect of FePd alloy composition on the dynamics of artificial spin ice,"Artificial spin ices (ASI) are arrays of single domain nano-magnetic islands,
+arranged in geometries that give rise to frustrated magnetostatic interactions.
+It is possible to reach their ground state via thermal annealing. We have made
+square ASI using different FePd alloys to vary the magnetization via
+co-sputtering. From a polarized state the samples were incrementally heated and
+we measured the vertex population as a function of temperature using magnetic
+force microscopy. For the higher magnetization FePd sample, we report an onset
+of dynamics at $T = 493$ K, with a rapid collapse into $>90\%$ ground state
+vertices. In contrast, the low magnetization sample started to fluctuate at
+lower temperatures, $T = 393$ K and over a wider temperature range but only
+reached a maximum of $25\%$ of ground state vertices. These results indicate
+that the interaction strength, dynamic temperature range and pathways can be
+finely tuned using a simple co-sputtering process. In addition we have compared
+our experimental values of the blocking temperature to those predicted using
+the simple N\'{e}el-Brown two-state model and find a large discrepancy which we
+attribute to activation volumes much smaller than the island volume.",1712.02404v1
+2018-03-01,Quantum Interference Controls the Electron Spin Dynamics in n-GaAs,"Manifestations of quantum interference effects in macroscopic objects are
+rare. Weak localization is one of the few examples of such effects showing up
+in the electron transport through solid state. Here we show that weak
+localization becomes prominent also in optical spectroscopy via detection of
+the electron spin dynamics. In particular, we find that weak localization
+controls the free electron spin relaxation in semiconductors at low
+temperatures and weak magnetic fields by slowing it down by almost a factor of
+two in $n$-doped GaAs in the metallic phase. The weak localization effect on
+the spin relaxation is suppressed by moderate magnetic fields of about 1 T,
+which destroy the interference of electron trajectories, and by increasing the
+temperature. The weak localization suppression causes an anomalous decrease of
+the longitudinal electron spin relaxation time $T_1$ with magnetic field, in
+stark contrast with well-known magnetic field induced increase in $T_1$. This
+is consistent with transport measurements which show the same variation of
+resistivity with magnetic field. Our discovery opens a vast playground to
+explore quantum magneto-transport effects optically in the spin dynamics.",1803.00352v2
+2018-04-18,"Onset of Photospheric Impacts and Helioseismic Waves in X9.3 Solar Flare of September 6, 2017","The X9.3 flare of September 6, 2017, was the most powerful flare of Solar
+Cycle 24. It generated strong white-light emission and multiple helioseismic
+waves (sunquakes). By using data from Helioseismic and Magnetic Imager (HMI)
+onboard the Solar Dynamics Observatory (SDO) as well as hard X-ray data from
+KONUS instrument onboard WIND spacecraft, and Anti-Coincidence System (ACS)
+onboard the INTERGRAL space observatory, we investigate spatio-temporal
+dynamics of photospheric emission sources, identify sources of helioseismic
+waves and compare the flare photospheric dynamics with the hard X-ray (HXR)
+temporal profiles. The results show that the photospheric flare impacts started
+to develop in compact regions in close vicinity of the magnetic polarity
+inversion line (PIL) in the pre-impulsive phase before detection of the HXR
+emission. The initial photospheric disturbances were localized in the region of
+strong horizontal magnetic field of the PIL, and, thus, are likely associated
+with a compact sheared magnetic structure elongated along the PIL. The acoustic
+egression power maps revealed two primary sources of generation of sunquakes,
+which were associated with places of the strongest photospheric impacts in the
+pre-impulsive phase and the early impulsive phase. This can explain the two
+types of helioseismic waves observed in this flare. Analysis of the
+high-cadence HMI filtergrams suggests that the flare energy release developed
+in the form of sequential involvement of compact low-lying magnetic loops that
+were sheared along the PIL.",1804.06565v1
+2018-09-07,Magnetohydrodynamic Modeling of a Solar Eruption Associated with X9.3 Flare Observed in Active Region 12673,"On SOL2017-09-06 solar active region 12673 produced an X9.3 flare which is
+regarded as largest to occur in solar cycle 24. In this work we have preformed
+a magnetohydrodynamic (MHD) simulation in order to reveal the three-dimensional
+(3D) dynamics of the magnetic fields associated with the X9.3 solar flare. We
+first performed an extrapolation of the 3D magnetic field based on the observed
+photospheric magnetic field prior to the flare and then used it as the initial
+condition for an MHD simulation. Consequently, the simulation showed a dramatic
+eruption. In particular, we found that a large coherent flux rope composed of
+highly twisted magnetic field lines is formed during the eruption. A series of
+small flux ropes are found to lie along a magnetic polarity inversion line
+prior to the flare. Reconnection occurring between each small flux rope during
+the early stages of the eruption forms the large and highly twisted flux
+rope.Furthermore, we found a writhing motion of the erupting flux rope. The
+understanding of these dynamics is important in increasing the accuracy of
+space weather forecasting. We report on the detailed dynamics of the 3D
+eruptive flux rope and discuss the possible mechanisms of the writhing motion.",1809.02309v1
+2018-12-18,Petahertz Spintronics,"The enigmatic coupling between electronic and magnetic phenomena was one of
+the riddles propelling the development of modern electromagnetism. Today, the
+fully controlled electric field evolution of ultrashort laser pulses permits
+the direct and ultrafast control of electronic properties of matter and is the
+cornerstone of light-wave electronics. In sharp contrast, because there is no
+first order interaction between light and spins, the magnetic properties of
+matter can only be affected indirectly on the much slower tens-of-femtosecond
+timescale in a sequence of optical excitation followed by the rearrangement of
+the spin structure. Here we record an orders of magnitude faster magnetic
+switching with sub-femtosecond response time by initiating optical excitations
+with near-single-cycle laser pulses in a ferromagnetic layer stack. The
+unfolding dynamics are tracked in real-time by a novel attosecond time-resolved
+magnetic circular dichroism (atto-MCD) detection scheme revealing optically
+induced spin and orbital momentum transfer (OISTR) in synchrony with light
+field driven charge relocation. In tandem with ab-initio quantum dynamical
+modelling, we show how this mechanism provides simultaneous control over
+electronic and magnetic properties that are at the heart of spintronic
+functionality. This first incarnation of attomagnetism observes light field
+coherent control of spin-dynamics in the initial non-dissipative temporal
+regime and paves the way towards coherent spintronic applications with
+Petahertz clock rates.",1812.07420v1
+2019-04-26,Non perturbative and thermal dynamics of confined fields in dual QCD,"In order to study the detailed dynamics and associated non-perturbative
+features of QCD, a dual version of the color gauge theory based on the
+topologically viable homogeneous fiber bundle approach has been analysed taking
+into account its magnetic symmetry structure. In the dynamically broken phase
+of magnetic symmetry, the associated flux tube structure on a S 2 -sphere in
+the magnetically condensed state of the dual QCD vacuum has been analyzed for
+the profiles of the color electric field using flux quantization and stability
+conditions. The color electric field has its intimate association with the
+vector mode of the magnetically condensed QCD vacuum and such field
+configurations have been analyzed to show that the color electric flux gets
+localized towards the poles for a large sphere case while it gets uniformly
+distributed for the small sphere case in the infrared sector of QCD. The
+critical flux tube densities have been computed for various couplings and are
+shown to be in agreement with that for lead-ion central collisions in the near
+infrared sector of QCD. The possible annihilation/unification of flux tubes
+under some typical flux tube density and temperature conditions in the magnetic
+symmetry broken phase of QCD has also been analyzed and shown to play an
+important role in the process of QGP formation. The thermal variation of the
+profiles of the color electic field is further investigated which indicates the
+survival of flux tubes even in the thermal domain that leads the possibility of
+the formation of some exotic states like QGP in the intermedate regime during
+the quark-hadron phase transition.",1904.11714v1
+2019-06-05,The formation and dissipation of current sheets and shocks due to compressive waves in a stratified atmosphere containing a magnetic null,"We study the propagation and dissipation of magnetohydrodynamic waves in a
+set of numerical models that each include a solar--like stratified atmosphere
+and a magnetic field with a null point. All simulations have the same magnetic
+field configuration but different transition region heights. Compressive wave
+packets introduced in the photospheric portion of the simulations refract
+towards the null and collapse it into a current sheet, which then undergoes
+reconnection. The collapsed null forms a current sheet due to a strong magnetic
+pressure gradient caused by the inability of magnetic perturbations to cross
+the null. Although the null current sheet undergoes multiple reconnection
+episodes due to repeated reflections off the lower boundary, we find no
+evidence of oscillatory reconnection arising from the dynamics of the null
+itself. Wave mode conversion around the null generates a series of slow mode
+shocks localized near each separatrix. The shock strength is asymmetric across
+each separatrix, and subsequent shock damping therefore creates a tangential
+discontinuity across each separatrix, with long--lived current densities. A
+parameter study of the injected wave energy to reach the null confirms our
+previous WKB estimates. Finally, using current estimates of the photospheric
+acoustic power, we estimate that the shock and Ohmic heating we describe may
+account for $\approx1-10\%$ of the radiative losses from coronal bright points
+with similar topologies, and are similarly insufficient to account for losses
+from larger structures such as ephemeral regions. At the same time, the
+dynamics are comparable to proposed mechanisms for generating type--II
+spicules.",1906.02317v1
+2019-09-20,Impact of disorder on dynamics and ordering in the honeycomb lattice iridate Na$_2$IrO$_3$,"Kitaev's honeycomb spin-liquid model and its proposed realization in
+materials such as $\alpha$-RuCl$_3$, Li$_2$IrO$_3$ and Na$_2$IrO$_3$ continue
+to present open questions about how the dynamics of a spin-liquid are modified
+in the presence of non-Kitaev interactions as well as the presence of
+inhomogeneities. Here we use $^{23}$Na nuclear magnetic resonance to probe both
+static and dynamical magnetic properties in single crystal Na$_2$IrO$_3$. We
+find that the NMR shift follows the bulk susceptibility above 30 K but deviates
+from it below; moreover below $T_N$ the spectra show a broad distribution of
+internal magnetic fields. Both of these results provide evidence for
+inequivalent magnetic sites at low temperature, suggesting inhomogeneities are
+important for the magnetism. The spin-lattice relaxation rate is isotropic and
+diverges at $T_N$, suggesting that the Kitaev cubic axes may control the
+critical quantum spin fluctuations. In the ordered state, we observe gapless
+excitations, which may arise from site substitution, emergent defects from
+milder disorder, or possibly be associated with nearby quantum paramagnetic
+states distinct from the Kitaev spin liquid.",1909.09356v2
+2020-01-31,Coupling large eddies and waves in turbulence: Case study of magnetic helicity at the ion inertial scale,"In turbulence, for neutral or conducting fluids, a large ratio of scales is
+excited because of the possible occurrence of inverse cascades to large, global
+scales together with direct cascades to small, dissipative scales, as observed
+in the atmosphere and oceans, or in the solar environment. In this context,
+using direct numerical simulations with forcing, we analyze scale dynamics in
+the presence of magnetic fields with a generalized Ohm's law including a Hall
+current. The ion inertial length epsilon_H serves as the control parameter at
+fixed Reynolds number. Both the magnetic and generalized helicity -- invariants
+in the ideal case -- grow linearly with time, as expected from classical
+arguments. The cross-correlation between the velocity and magnetic field grows
+as well, more so in relative terms for a stronger Hall current. We find that
+the helical growth rates vary exponentially with epsilon_H, provided the ion
+inertial scale resides within the inverse cascade range. These exponential
+variations are recovered phenomenologically using simple scaling arguments.
+They are directly linked to the wavenumber power-law dependence of generalized
+and magnetic helicity, k^(-2), in their inverse ranges. This illustrates and
+confirms the important role of the interplay between large and small scales in
+the dynamics of turbulent flows.",2001.11625v1
+2020-03-09,Magnetic connectivity between the light bridge and penumbra in a sunspot,"A light bridge is a prominent structure commonly observed within a sunspot.
+Its presence usually triggers a wealth of dynamics in a sunspot, and has a
+lasting impact on sunspot evolution. However, the fundamental structure of
+light bridges is still not well understood. In this study, we used the
+high-resolution spectropolarimetry data obtained by the Solar Optical Telescope
+onboard the Hinode satellite to analyze the magnetic and thermal structure of a
+light bridge at \AR. We also combined the high-cadence $1700\unit{\AA}$ channel
+data provided by the Atmospheric Imaging Assembly onboard the Solar Dynamic
+Observatory to study the dynamics on this bridge. We found that a pair of blue
+and red Doppler shift patches at two ends of this bridge, this pattern appears
+to be the convective motion directed by the horizontal component of the
+magnetic field aligned with the spine of this bridge. Paired upward and
+downward motions implies that the light bridge could have a two-legged or
+undulate magnetic field. Significant four minute oscillations in the emission
+intensity of the $1700\unit{\AA}$ bandpass were detected at two ends, which had
+overlap with the paired blue and red shift patches. The oscillatory signals at
+the light bridge and the penumbra were highly correlated with each other.
+Although they are separated in space at the photosphere, the periodicity seems
+to have a common origin from the underneath. Therefore, we infer that the light
+bridge and penumbra could share a common magnetic source and become fragmented
+at the photosphere by magneto-convection.",2003.03976v1
+2020-06-29,Long term time dependent frequency analysis of chaotic waves in the weakly magnetized spherical Couette system,"The long therm behavior of chaotic flows is investigated by means of time
+dependent frequency analysis. The system under test consists of an electrically
+conducting fluid, confined between two differentially rotating spheres. The
+spherical setup is exposed to an axial magnetic field. The classical Fourier
+Transform method provides a first estimation of the time dependence of the
+frequencies associated to the flow, as well as its volume-averaged properties.
+It is however unable to detect strange attractors close to regular solutions in
+the Feigenbaum as well as Newhouse-Ruelle-Takens bifurcation scenarios. It is
+shown that Laskar's frequency algorithm is sufficiently accurate to identify
+these strange attractors and thus is an efficient tool for classification of
+chaotic flows in high dimensional dynamical systems. Our analysis of several
+chaotic solutions, obtained at different magnetic field strengths, reveals a
+strong robustness of the main frequency of the flow. This frequency is
+associated to an azimuthal drift and it is very close to the frequency of the
+underlying unstable rotating wave. In contrast, the main frequency of
+volume-averaged properties can vary almost one order of magnitude as the
+magnetic forcing is decreased. We conclude that, at the moderate differential
+rotation considered, unstable rotating waves provide a good description of the
+variation of the main time scale of any flow with respective variations in the
+magnetic field.",2006.15145v2
+2020-10-29,Domain wall dynamics in antiferromagnetically-coupled double-lattice systems,"In ferromagnetic materials, the rich dynamics of magnetic domain walls (DWs)
+under magnetic field or current have been successfully described using the
+well-known q-{\phi} analytical model. We demonstrate here that this simple
+unidimensional model holds for multiple-sublattice materials such as
+ferrimagnetic alloys or synthetic antiferromagnets (SAF) by using effective
+parameters, and is in excellent agreement with double-lattice micromagnetic
+simulations. We obtain analytical laws for the DW velocity and internal
+precession angle as a function of net magnetisation for different driving
+forces (magnetic field, spin transfer and spin-orbit torques) and different
+propagation regimes in ferrimagnetic alloys and SAFs. The model predicts that
+several distinctive dynamical features occur near or at the magnetic and the
+angular compensation points when the net magnetization or the net angular
+momentum of the system vanishes, and we discuss the experimental observations
+that have been reported for some of them. Using a higher degree-of-freedom
+analytical model that accounts for inter-sublattice distortions, we give
+analytical expressions for these distortions that agree with the micromagnetic
+simulations. This model shows that the DW velocity and precession rate are
+independent of the strength of the inter-sublattice exchange coupling, and
+justifies the use of the simpler effective parameters model.",2010.15443v1
+2021-02-16,Dynamic symmetry breaking in chiral magnetic systems,"The Dzyaloshinskii-Moriya interaction (DMI) in magnetic systems stabilizes
+spin textures with preferred chirality, applicable to next-generation memory
+and computing architectures. In perpendicularly magnetized
+heavy-metal/ferromagnet films, the interfacial DMI originating from structural
+inversion asymmetry and strong spin-orbit coupling favors chiral N\'eel-type
+domain walls (DWs) whose energetics and mobility remain at issue. Here, we
+characterize a new effect in which domains expand unidirectionally in response
+to a combination of out-of-plane and in-plane magnetic fields, with the growth
+direction controlled by the in-plane field strength. These growth
+directionalities and symmetries with applied fields cannot be understood from
+static treatments alone. We theoretically demonstrate that perpendicular field
+torques stabilize steady-state magnetization profiles highly asymmetric in
+elastic energy, resulting in a dynamic symmetry breaking consistent with the
+experimental findings. This phenomenon sheds light on the mechanisms governing
+the dynamics of N\'eel-type DWs and expands the utility of field-driven DW
+motion to probe and control chiral DWs.",2102.07909v4
+2021-10-24,$^{139}$La-NMR study of spin-dynamics coupled with hole mobility in $T$*-type La$_{0.86}$Eu$_{0.86}$Sr$_{0.28}$CuO$_{4-δ}$,"In $T$*-type cuprate oxides with five oxygen coordination, little is known
+about the relationship between the spin correlations and dope carriers. We
+performed $^{139}$La-nuclear magnetic resonance (NMR) and electrical
+resistivity measurements on an as-sintered (AS) and oxidation annealed (OA)
+polycrystalline $T$*-type La$_{0.86}$Eu$_{0.86}$S$_{0.28}$CuO$_4$ (LESCO) to
+investigate its magnetic and superconducting (SC) properties. Upon cooling, the
+NMR spectrum of AS LESCO broadened below 3 K, at which the nuclear spin-lattice
+relaxation rate $1/T_1$ against the temperature exhibited a maximum, thereby
+indicating the appearance of static magnetism. The temperature dependence of
+$1/T_1$ between 3 K and 20 K was similar to that of the resistivity displaying
+the semiconducting behavior. Furthermore, the energy scale of the transport gap
+and spin-dynamics estimated was found to be comparable. These results suggest a
+close connection between the mobility of the doped carriers and low-energy
+spin-dynamics, as reported for lightly doped $T$-type La$_{2-x}$Sr$_x$CuO$_4$.
+In the OA SC sample, we confirmed the absence of a magnetic order and the
+Korringa relation above 10 K. Therefore, in the $T$*-type LESCO with $x$ =
+0.28, the magnetic state coupled with holes drastically turns to the weakly
+correlated metallic state by oxidation annealing.",2110.12333v1
+2021-11-29,Quantifying the Computational Capability of a Nanomagnetic Reservoir Computing Platform with Emergent Magnetization Dynamics,"Devices based on arrays of interconnected magnetic nano-rings with emergent
+magnetization dynamics have recently been proposed for use in reservoir
+computing applications, but for them to be computationally useful it must be
+possible to optimise their dynamical responses. Here, we use a phenomenological
+model to demonstrate that such reservoirs can be optimised for classification
+tasks by tuning hyperparameters that control the scaling and input rate of data
+into the system using rotating magnetic fields. We use task-independent metrics
+to assess the rings' computational capabilities at each set of these
+hyperparameters and show how these metrics correlate directly to performance in
+spoken and written digit recognition tasks. We then show that these metrics,
+and performance in tasks, can be further improved by expanding the reservoir's
+output to include multiple, concurrent measures of the ring arrays magnetic
+states.",2111.14603v2
+2022-03-18,Semi-classical simulation of spin-1 magnets,"Theoretical studies of magnets have traditionally concentrated on either
+classical spins, or the extreme quantum limit of spin-1/2. However, magnets
+built of spin-1 moments are also intrinsically interesting, not least because
+they can support quadrupole, as well as dipole moments, on a single site. For
+this reason, spin-1 models have been extensively studied as prototypes for
+quadrupolar (spin-nematic) order in magnetic insulators, and Fe-based
+superconductors. At the same time, because of the presence of quadrupoles, the
+classical limit of a spin-1 moment is not an $O(3)$ vector, a fact which must
+be taken into account in describing their properties. In this Article we
+develop a method to simulate spin-1 magnets based on a $u(3)$ algebra which
+treats both dipole and quadrupole moments on equal footing. This approach is
+amenable to both classical and quantum calculations, and we develop the
+techniques needed to calculate thermodynamic properties through Monte Carlo
+simulations and classical low-temperature expansion, and dynamical properties,
+through ""molecular dynamics"" simulations and a multiple-boson expansion. As a
+case study, we present detailed analytic and numerical results for the
+thermodynamic properties of ferroquadrupolar order on the triangular lattice,
+and its associated dynamics. At low temperatures, we show that it is possible
+to ""correct"" for the effects of classical statistics in simulations, and
+extrapolate to the zero-temperature quantum results found in flavour-wave
+theory.",2203.09819v3
+2022-03-22,Quantum sensing and imaging of spin-orbit-torque-driven spin dynamics in noncollinear antiferromagnet Mn3Sn,"Novel noncollinear antiferromagnets with spontaneous time-reversal symmetry
+breaking, nontrivial band topology, and unconventional transport properties
+have received immense research interest over the past decade due to their rich
+physics and enormous promise in technological applications. One of the central
+focuses in this emerging field is exploring the relationship between the
+microscopic magnetic structure and exotic material properties. Here, the
+nanoscale imaging of both spin-orbit-torque-induced deterministic magnetic
+switching and chiral spin rotation in noncollinear antiferromagnet Mn3Sn films
+using nitrogen-vacancy (NV) centers is reported. Direct evidence of the
+off-resonance dipole-dipole coupling between the spin dynamics in Mn3Sn and
+proximate NV centers is also demonstrated with NV relaxometry measurements.
+These results demonstrate the unique capabilities of NV centers in accessing
+the local information of the magnetic order and dynamics in these emergent
+quantum materials and suggest new opportunities for investigating the interplay
+between topology and magnetism in a broad range of topological magnets.",2203.11465v1
+2022-04-04,Study of general relativistic magnetohydrodynamic accretion flow around black holes,"We present a novel approach to study the global structure of steady,
+axisymmetric, advective, geometrically thin, magnetohydrodynamic (MHD)
+accretion flow around black holes in full general relativity (GR). Considering
+ideal MHD conditions and relativistic equation of state (REoS), we solve the
+governing equations to obtain all possible smooth global accretion solutions.
+We examine the dynamical and thermodynamical properties of accreting matter in
+terms of the flow parameters, namely energy (${\cal E}$), angular momentum
+(${\cal L}$), and local magnetic fields. For a thin GRMHD flow, we observe that
+toroidal component ($b^\phi$) of the magnetic fields generally dominates over
+radial component ($b^r$) at the disk equatorial plane. This evidently suggests
+that toroidal magnetic field indeed plays important role in regulating the disk
+dynamics. We further notice that the disk remains mostly gas pressure ($p_{\rm
+gas}$) dominated ($\beta = p_{\rm gas}/p_{\rm mag} > 1$, $p_{\rm mag}$ refers
+magnetic pressure) except at the near horizon region, where magnetic fields
+become dynamically important ($\beta \sim 1$). We observe that Maxwell stress
+is developed that eventually yields angular momentum transport inside the disk.
+Towards this, we calculate the viscosity parameter ($\alpha$) that appears to
+be radially varying. In addition, we examine the underlying scaling relation
+between $\alpha$ and $\beta$, which clearly distinguishes two domains coexisted
+along the radial extent of the disk. Finally, we discuss the utility of the
+present formalism in the realm of GRMHD simulation studies.",2204.01412v2
+2022-04-13,"Chaos, complexity, and intermittent turbulence in space plasmas","Intermittent turbulence is key for understanding the stochastic nonlinear
+dynamics of space, astrophysical, and laboratory plasmas. We review the
+observation and theory of chaos and complexity in plasmas, and elucidate their
+links to intermittent plasma turbulence. First, we present evidence of magnetic
+reconnection and intermittent magnetic turbulence in coronal mass ejections in
+the solar corona and solar wind via remote and in situ observations. The
+signatures of turbulent magnetic reconnection, i.e., bifurcated current sheet,
+reconnecting jet, parallel/anti-parallel Alfv\'en waves, and spiky dynamical
+pressure pulse, as well as fully-developed Kolmogorov intermittent turbulence,
+are detected at the leading edge of an interplanetary coronal mass ejection and
+the interface region of two interplanetary magnetic flux ropes. Methods for
+quantifying the degree of coherence, amplitude-phase synchronization, and
+multifractality of nonlinear multiscale fluctuations are discussed. The
+stochastic chaotic nature of Alfv\'en intermittent structures driven by
+magnetic reconnection is determined by a complexity-entropy analysis. Next, we
+discuss the theory of chaos, intermittency, and complexity for nonlinear
+Alfv\'en waves, and parametric decay and modulational wave-wave interactions,
+in the absence/presence of noise. The transition from order to chaos is studied
+using the bifurcation diagram. Two types of plasma chaos are considered: type-I
+Pomeau-Manneville intermittency and crisis-induced intermittency. The role of
+transient structures known as chaotic saddles in deterministic and stochastic
+chaos in plasmas is investigated. Alfv\'en complexity associated with
+noise-induced intermittency, in the presence of multistability, is studied.",2204.06133v1
+2022-06-30,Origin and dynamics of umbrella states in rare-earth iron garnets,"Rare-earth iron garnets $R_{3}$Fe$_{5}$O$_{12}$ are fascinating insulators
+with very diverse magnetic phases. Their strong potential in spintronic devices
+has encouraged a renewal of interest in the study of their low temperature spin
+structures and spin wave dynamics. A striking feature of rare-earth garnets
+with $R$-ions exhibiting strong crystal-field effects like Tb-, Dy-, Ho-, and
+Er-ions is the observation of low-temperature non-collinear magnetic structures
+featuring ""umbrella-like"" arrangements of the rare-earth magnetic moments. In
+this study, we demonstrate that such umbrella magnetic states are naturally
+emerging from the crystal-field anisotropies of the rare-earth ions. By means
+of a general model endowed with only the necessary elements from the crystal
+structure, we show how umbrella-like spin structures can take place and
+calculate the canting-angle as a result of the competition between the
+exchange-interaction of the rare-earth and the iron ions as well as the
+crystal-field anisotropy. Our results are compared to experimental data, and a
+study of the polarised spin wave dynamics is presented. Our study improves the
+understanding of umbrella-like spin structures and paves the way for more
+complex spin wave calculations in rare-earth iron garnets with non-collinear
+magnetic phases.",2207.00017v2
+2022-11-14,Heavily Damped Precessional Switching with Very Low Write-error Rate in Elliptical-cylinder Magnetic Tunnel Junction,"Voltage-induced dynamic switching in magnetic tunnel junctions (MTJs) is a
+writing technique for voltage-controlled magnetoresistive random access memory
+(VCMRAM), which is expected to be an ultimate non-volatile memory with
+ultra-low power consumption. In conventional dynamic switching, the width of
+sub-nanosecond write voltage pulses must be precisely controlled to achieve a
+sufficiently low write-error rate (WER). This very narrow tolerance of pulse
+width is the biggest technical difficulty in developing VCMRAM. Heavily damped
+precessional switching is a writing scheme for VCMRAM with a substantially high
+tolerance of pulse width although the minimum WER has been much higher than
+that of conventional dynamic switching with an optimum pulse width. In this
+study, we theoretically investigate the effect of MTJ shape and the direction
+of the applied magnetic field on the WER of heavily damped precessional
+switching. The results show that the WER in elliptical-cylinder MTJ can be
+several orders of magnitude smaller than that in usual circular-cylinder MTJ
+when the external magnetic field is applied parallel to the minor axis of the
+ellipse. The reduction in WER is due to the fact that the demagnetization field
+narrows the component of the magnetization distribution perpendicular to the
+plane direction immediately before the voltage is applied.",2211.07148v1
+2023-01-18,Emergence of field-induced memory effect in spin ices,"Out-of-equilibrium investigation of strongly correlated materials deciphers
+the hidden equilibrium properties. Herein, we have investigated the
+out-of-equilibrium magnetic properties of polycrystalline Dy2Ti2O7 and Ho2Ti2O7
+spin ices. The experimental results show the emergence of magnetic
+field-induced anomalous hysteresis observed only in temperature/magnetic
+field-dependent ac susceptibility measurements. The observed memory effect
+(anomalous thermomagnetic hysteresis) strongly depends on the driving thermal
+and non-thermal variables. Contrary, in the absence of the magnetic field,
+dipolar interaction induced Ising paramagnetic to spin ice crossover develops a
+liquid-gas transition type hysteresis below 4 K. Unlike field-induced
+hysteresis, it shows weak dependency on thermal and non-thermal variables. Due
+to the non-colinear spin structure, the applied dc bias magnetic field produces
+quench disorder sites in the cooperative Ising spin matrix and suppresses the
+spin-phonon coupling. These quench disorders create dynamic spin correlations
+governed by quantum fluctuations, having slow spin relaxation and quick decay
+times, which additionally contribute to ac susceptibility. The initial
+conditions and measurement protocol decide the magnitude and sign of this
+dynamical term contributing to ac susceptibility. It has been suggested that
+such kind of out-of-equilibrium properties emerge by the cumulative effect of
+geometric frustration, disorder, quantum fluctuations, and the cooperative
+nature of spin dynamics of these materials.",2301.07741v1
+2023-05-04,Impact of electric charges on chaos in magnetized $Reissner-Nordström$ spacetimes,"We consider the motion of test particles around a $Reissner-Nordstr\""{o}m$
+black hole immersed into a strong external magnetic field modifying the
+spacetime structure. When the particles are neutral, their dynamics are
+nonintegrable because the magnetic field acts as a gravitational effect, which
+destroys the existence of a fourth motion constant in the
+$Reissner-Nordstr\""{o}m$ spacetime. A time-transformed explicit symplectic
+integrator is used to show that the motion of neutral particles can be chaotic
+under some circumstances. When test particles have electric charges, their
+motions are subject to an electromagnetic field surrounding the black hole as
+well as the gravitational forces from the black hole and the magnetic field. It
+is found that increasing both the magnetic field and the particle energy or
+decreasing the particle angular momentum can strengthen the degree of chaos
+regardless of whether the particles are neutral or charged. The effect of
+varying the black hole positive charge on the dynamical transition from order
+to chaos is associated with the electric charges of particles. The dynamical
+transition of neutral particles has no sensitive dependence on a change of the
+black hole charge. An increase of the black hole charge weakens the chaoticity
+of positive charged particles, whereas enhances the chaoticity of negative
+charged particles. With the magnitude of particle charge increasing, chaos
+always gets stronger.",2305.02702v1
+2023-08-22,Dynamics of K$_2$Ni$_2$(SO$_4$)$_3$ governed by proximity to a 3D spin liquid model,"Quantum spin liquids (QSLs) have become a key area of research in magnetism
+due to their remarkable properties, such as long-range entanglement, fractional
+excitations, pinch-point singularities, and topologically protected phenomena.
+In recent years, the search for QSLs has expanded into the three-dimensional
+world, where promising features have been found in materials that form
+pyrochlore and hyper-kagome lattices, despite the suppression of quantum
+fluctuations due to high dimensionality. One such material is the $S = 1$
+K$_2$Ni$_2$(SO$_4$)$_3$ compound, which belongs to the langbeinite family
+consisting of two interconnected trillium lattices. Although magnetically
+ordered, K$_2$Ni$_2$(SO$_4$)$_3$ has been found to exhibit a highly dynamical
+and correlated state which can be driven into a pure quantum spin liquid under
+magnetic fields of only $B \simeq 4$~T. In this article, we combine inelastic
+neutron scattering measurements with pseudo-fermion functional renormalization
+group (PFFRG) and classical Monte Carlo (cMC) calculations to study the
+magnetic properties of K$_2$Ni$_2$(SO$_4$)$_3$, revealing a high level of
+agreement between the experiment and theory. We further reveal the origin of
+the dynamical state in K$_2$Ni$_2$(SO$_4$)$_3$ by studying a larger set of
+exchange parameters, uncovering an `island of liquidity' around a focal point
+given by a magnetic network composed of tetrahedra on a trillium lattice.",2308.11746v1
+2023-10-10,A numerical investigation of quasi-static magnetoconvection with an imposed horizontal magnetic field,"Quasi-static Rayleigh-B\'enard convection with an imposed horizontal magnetic
+field is investigated numerically for Chandrasekhar numbers up to $Q=10^6$ with
+stress free boundary conditions. Both $Q$ and the Rayleigh number ($Ra$) are
+varied to identify the various dynamical regimes that are present in this
+system. We find three primary regimes: (I) a two-dimensional (2D) regime in
+which the axes of the convection rolls are oriented parallel to the imposed
+magnetic field; (II) an anisotropic three-dimensional (3D) regime; and (III) a
+mean flow regime characterized by a large scale horizontal flow directed
+transverse to the imposed magnetic field. The transition to 3D dynamics is
+preceded by a series of 2D transitions in which the number of convective rolls
+decreases as $Ra$ is increased. For sufficiently large $Q$, there is an
+eventual transition to two rolls just prior to the 2D/3D transition. The 2D/3D
+transition occurs when inertial forces become comparable to the Lorentz force,
+i.e. when $\sqrt{Q}/Re = O(1)$; 2D, magnetically constrained states persist
+when $\sqrt{Q}/Re \gtrsim O(1)$. Within the 2D regime we find heat and momentum
+transport scalings that are consistent with the hydrodynamic asymptotic
+predictions of Chini and Cox [Phys. Fluids \textbf{21}, 083603 (2009)]: the
+Nusselt number ($Nu$) and Reynolds number ($Re$) scale as $Nu \sim Ra^{1/3}$
+and $Re \sim Ra^{2/3}$, respectively. For $Q=10^6$, we find that the scaling
+behavior of $Nu$ and $Re$ breaks down at large values of $Ra$ due to a sequence
+of bifurcations and the eventual manifestation of mean flows.",2310.06683v1
+2024-02-05,Inferring Fundamental Properties of the Flare Current Sheet Using Flare Ribbons: Oscillations in the Reconnection Flux Rates,"Magnetic reconnection is understood to be the main physical process that
+facilitates the transformation of magnetic energy into heat, motion, and
+particle acceleration during solar eruptions. Yet, observational constraints on
+reconnection region properties and dynamics are limited due to lack of
+high-cadence and high-spatial-resolution observations. By studying the
+evolution and morphology of post-reconnected field-lines footpoints, or flare
+ribbons and vector photospheric magnetic field, we estimate the magnetic
+reconnection flux and its rate of change with time to study the flare
+reconnection process and dynamics of the current sheet above. We compare
+high-resolution imaging data to study the evolution of the fine structure in
+flare ribbons as ribbons spread away from the polarity inversion line. Using
+data from two illustrative events (one M- and X-class flare), we explore the
+relationship between the ribbon-front fine structure and the temporal
+development of bursts in the reconnection region. Additionally, we use the
+RibbonDB database to perform statistical analysis of 73 (C- to X-class) flares
+and identify QPP's properties using the Wavelet Transform. Our main finding is
+the discovery of quasi-periodic pulsations (QPP) signatures in the derived
+magnetic reconnection rates in both example events and the large flare sample.
+We find that the oscillations' periods range from one to four minutes.
+Furthermore, we find nearly co-temporal bursts in Hard X-ray (HXR) emission
+profiles. We discuss how dynamical processes in the current sheet involving
+plasmoids can explain the nearly-co-temporal signatures of quasi periodicity in
+the reconnection rates and HXR emission.",2402.03567v1
+2024-03-17,Merons and magnetoelectric switching in centrosymmetric spiral magnets,"Spiral multiferroics exhibit a strong coupling between magnetic and
+ferroelectric orders, allowing cross-control. Since the seminal work of Kimura
+et al. in 2003, these materials have attracted great interest galvanized by the
+prospect of new high-efficiency memory devices, where magnetic (electric) bits
+are switched via an external electric (magnetic) field. Nevertheless, the
+mechanism underlying such a switching process - the electric field-driven
+dynamics of domain walls (DWs) - is still poorly understood. We address this
+problem for meron DWs, which represent one of the main DW types in spiral
+multiferroics and consist of an array of meron (half-skyrmion) strings. Minimum
+energy walls feature merons with alternating topological charges and move as
+relativistic massive particles, with the limiting velocity set by magnon speed.
+Low-energy defects in this alternating charge sequence, which appear during
+domain nucleation, can lead to DWs with net topological charge. This induces a
+peculiar non-local dynamics where all the spins in the system rotate, merons
+translate within the wall, and the DW mobility is suppressed. The topological
+charge of the wall and the meron helicity can be easily modified via an
+external magnetic and electric field, respectively, offering fine control over
+DW dynamics. Defects within the meron strings, analogous to Bloch points, have
+hedgehog-like spin texture and are strongly pinned to the lattice. The
+fascinating interplay between domain wall motion, translation of merons within
+the wall, and precession of spins in the entire domains opens a new playground
+for the electric manipulation of topological spin textures.",2403.11195v1
+2016-03-04,Novel Dynamical Phenomena in Magnetic systems,"Dynamics of Ising models is a much studied phenomenon and has emerged as a
+rich field of present-day research. An important dynamical feature commonly
+studied is the quenching phenomenon below the critical temperature. In this
+thesis we have studied the zero temperature quenching dynamics of different
+Ising spin systems. First we have studied the zero temperature quenching
+dynamics of two dimensional Ising spin system with competating interactions.
+Then we have studied the effect of randomness or disorder on the quenching
+dynamics of Ising spin system. We have studied the effect of the nature of
+randomness on zero temperature quenching dynamics of one dimensional Ising
+model on two type of complex networks. A model for opinion dynamics also has
+been proposed in this thesis, in which the binary opinions of the individuals
+are determined according to the size of their neighboring domains. This model
+can be equivalently defined in terms of Ising spin variables and the various
+quantities studied have one to one correspondence with magnetic systems.
+Introducing disorder in this model through a parameter called rigidity
+parameter $\rho$ (probability that people are completely rigid and never change
+their opinion), the transition to a heterogeneous society at $\rho = 0^{+}$ is
+obtained. The Model (Model I) has been generalized introducing a parameter
+named as size sensitivity parameter to modify the dynamics of the proposed
+model and a macroscopic crossover in time is observed for the intermediate
+values of this parameter.",1603.01646v1
+2017-02-07,One-dimensional Quantum Spin Dynamics of Bethe String States,"Quantum dynamics of strongly correlated systems is a challenging problem.
+Although the low energy fractional excitations of one dimensional integrable
+models are often well-understood, exploring quantum dynamics in these systems
+remains challenging in the gapless regime, especially at intermediate and high
+energies. Based on the algebraic Bethe ansatz formalism, we study spin dynamics
+in a representative one dimensional strongly correlated model, {\it i.e. }, the
+antiferromagnetic spin-$\frac{1}{2}$ XXZ chain with the Ising anisotropy, via
+the form-factor formulae. Various excitations at different energy scales are
+identified crucial to the dynamic spin structure factors under the guidance of
+sum rules. At small magnetic polarizations, gapless excitations dominate the
+low energy spin dynamics arising from the magnetic-field-induced
+incommensurability. In contrast, spin dynamics at intermediate and high
+energies is characterized by the two- and three-string states, which are
+multi-particle excitations based on the commensurate N\'eel ordered background.
+Our work is helpful for experimental studies on spin dynamics in both condensed
+matter and cold atom systems beyond the low energy effective Luttinger liquid
+theory. Based on an intuitive physical picture, we speculate that the dynamic
+feature at high energies due to the multi-particle anti-bound state excitations
+can be generalized to non-integrable spin systems.",1702.01854v2
+2019-03-21,Emergent topology and symmetry-breaking order in correlated quench dynamics,"Quenching a quantum system involves three basic ingredients: the initial
+phase, the post-quench target phase, and the non-equilibrium dynamics which
+carries the information of the former two. Here we propose a dynamical theory
+to characterize both the topology and symmetry-breaking order in correlated
+quantum system, through quenching the Haldane-Hubbard model from an initial
+magnetic phase to topologically nontrivial regime. The equation of motion for
+the complex pseudospin dynamics is obtained with the flow equation method, with
+the pseudospin evolution shown to obey a microscopic
+Landau-Lifshitz-Gilbert-Bloch equation. We find that the correlated quench
+dynamics exhibit robust universal behaviors on the so-called band-inversion
+surfaces (BISs), from which the nontrivial topology and magnetic order can be
+extracted. In particular, the topology of the post-quench regime can be
+characterized by an emergent dynamical topological pattern of quench dynamics
+on BISs, which is robust against dephasing and heating induced by interactions;
+the pre-quench symmetry-breaking orders is read out from a universal scaling
+behavior of the quench dynamics emerging on the BIS, which is valid beyond the
+mean-field regime. This work opens a way to characterize both the topology and
+symmetry-breaking orders by correlated quench dynamics.",1903.09144v3
+2001-07-12,Magnetic fields in barred galaxies. II. Dynamo models,"We study the generation and maintenance of large-scale magnetic fields in
+barred galaxies. We take a velocity field (with strong noncircular components)
+from a published gas dynamical simulation of Athanassoula (1992), and use this
+as input to a galactic dynamo calculation. Our work is largely motivated by
+recent high quality VLA radio observations of the barred galaxy NGC 1097, and
+we compare our results in detail with the regular magnetic fields deduced from
+these observations. We are able to reproduce most of the conspicuous
+large-scale features of the observed regular field, including the field
+structure in the central regions, by using a simple mean-field dynamo model in
+which the intensity of interstellar turbulence (more precisely, the turbulent
+diffusivity) is enhanced by a factor of 2-6 in the dust lanes and near the
+circumnuclear ring. We argue that magnetic fields can be dynamically important,
+and therefore should be included in models of gas flow in barred galaxies.",0107214v2
+2001-10-08,The effect of hyperdiffusivity on turbulent dynamos with helicity,"In numerical studies of turbulence, hyperviscosity is often used as a tool to
+extend the inertial subrange and to reduce the dissipative subrange. By
+analogy, hyperdiffusivity (or hyperresistivity) is sometimes used in
+magnetohydrodynamics. The underlying assumption is that only the small scales
+are affected by this manipulation. In the present paper, possible side effects
+on the evolution of the large scale magnetic field are investigated. It is
+found that for turbulent flows with helicity, hyperdiffusivity causes the
+dynamo-generated magnetic field to saturate at a higher level than normal
+diffusivity. This result is successfully interpreted in terms of magnetic
+helicity conservation, which also predicts that full saturation is only reached
+after a time comparable to the large scale magnetic (hyper)diffusion time.",0110171v1
+2001-11-16,Dynamics of Walls: Fermion Scattering in Magnetic Field,"We investigate the scattering of fermions off walls in the presence of a
+magnetic field. We consider both the bubble wall and the kink domain wall. By
+solving the Dirac equation for fermions in the presence of a domain wall in an
+external magnetic field, we investigate the dependence on the magnetic field of
+the transmission and reflection coefficients. In the case of kink domain wall,
+we also consider the solutions localized on the wall. The possibile role of the
+ferromagnetic domain walls in the dynamics of the early Universe is also
+discussed.",0111327v1
+2002-10-09,Dynamics of relativistic reconnection,"The dynamics of the steady-state Sweet--Parker-type reconnection is analyzed
+in relativistic regime when energy density in the inflowing region is dominated
+by magnetic field. The structure of reconnection layer (its thickness, inflow
+and outflow velocities) depends on the ratio of two large dimensionless
+parameters of the problem - magnetization parameter $\sigma \gg 1$ (the ratio
+of the magnetic to particle energy-densities in the inflowing region) and the
+Lundquist number $S$. The inflow velocity may be relativistic (for $ S<
+\sigma$) or non-relativistic (for $ S > \sigma$), while the outflowing plasma
+is moving always relativisticly. For extremely magnetized plasmas with $\sigma
+\geq S^2$, the inflow four-velocity becomes of the order of the \Alfven
+four-velocity.",0210206v1
+2003-02-06,Magnetic Protoneutron Star Winds and r-Process Nucleosynthesis,"Because of their neutron-richness and association with supernovae,
+post-explosion protoneutron star winds are thought to be a likely astrophysical
+site for rapid neutron capture nucleosynthesis (the r-process). However, the
+most recent models of spherical neutrino-driven protoneutron star winds do not
+produce robust r-process nucleosynthesis for `canonical' neutron stars with a
+gravitational mass of 1.4M_sun and coordinate radius of 10km. These models fail
+variously; either the flow entropy is too low, the electron fraction is too
+high, or the dynamical expansion timescale is too long. To date, no models have
+included the effects of an ordered dipole magnetic field. We show that a strong
+magnetic field can trap the outflow in the neutrino heating region, thus
+leading to much higher matter entropy. We estimate both the trapping timescale
+and the resulting entropy amplification. For sufficiently large energy
+deposition rates, the trapped matter emerges dynamically from the region of
+closed magnetic field lines and escapes to infinity. We find that ordered
+dipoles with surface fields of greater than 6 times 10^14 Gauss increase the
+asymptotic entropy sufficiently for robust r-process nucleosynthesis.",0302132v1
+2004-01-09,Two Dimensional Poynting Flux Dominated Flow onto a Schwarzschild Black Hole,"We discuss the dynamics of the accretion flow onto a black hole driven by
+Poynting flux in a simplified model of a two-dimensional accretion disk. In
+this simplified model, the condition of the stationary accretion flow is found
+to impose a nontrivial constraint on the magnetic field configuration. The
+effect of the magnetic field on the accretion flow is discussed in detail using
+the paraboloidal and hyperboloidal type configuration for the poloidal
+structure suggested by Blandford in 1976. It is demonstrated explicitly that
+the angular velocity of the disk, $\Omega_D$, deviates from the Keplerian
+angular velocity. The angular velocity of the rigidly-rotating magnetic
+surface, $\Omega_F$, does not have to be the same as the angular velocity of
+the disk for the paraboloidal type configuration. But for the hyperboloidal
+type configuration, it is found that we can set $\Omega_F = \Omega_D$, which
+corresponds to an accretion disk of perfect conductor. We discuss the numerical
+solutions of the stream equation for stationary accretion flow in the
+Schwarzschild background using a paraboloidal type configuration. The dynamics
+of the accretion disk is found to depend strongly on the ratio of the accretion
+rate to the magnetic field strength.",0401143v1
+2004-06-07,Magnetic Effects Change Our View of the Heliosheath,"There is currently a controversy as to whether Voyager 1 has already crossed
+the Termination Shock, the first boundary of the Heliosphere. The region
+between the Termination Shock and the Heliopause, the Helisheath, is one of the
+most unknown regions theoretically. In the Heliosheath magnetic effects are
+crucial, as the solar magnetic field is compressed at the Termination Shock by
+the slowing flow. Recently, our simulations showed that the Heliosheath
+presents remarkable dynamics, with turbulent flows and the presence of a jet
+flow at the current sheet that is unstable due to magnetohydrodynamic
+instabilities \cite{opher,opher1}. In this paper we review these recent
+results, and present an additional simulation with constant neutral atom
+background. In this case the jet is still present but with reduced intensity.
+Further study, e.g., including neutrals and the tilt of the solar rotation from
+the magnetic axis, is required before we can definitively address how the
+Heliosheath behaves. Already we can say that this region presents remarkable
+dynamics, with turbulent flows, indicating that the Heliosheath might be very
+different from what we previously thought.",0406184v1
+2005-04-19,Reply to Lyutikov's comments on Zhang & Kobayashi (2005),"Lyutikov (astro-ph/0503505) raised a valid point that for shock deceleration
+of a highly magnetized outflow, the fate of the magnetic fields after shock
+crossing should be considered. However, his comment that the deceleration
+radius should be defined by the total energy rather than by the baryonic
+kinetic energy is incorrect. As strictly derived from the shock jump conditions
+in Zhang & Kobayashi (2005), during the reverse shock crossing process the
+magnetic energy is not tapped. As a result, the fireball deceleration radius is
+defined by the baryonic energy only. The magnetic energy is expected to be
+transferred to the circumburst medium after the reverse shock disappears. The
+evolution of the system then mimicks a continuously-fed fireball. As a result,
+Lyutikov's naive conclusion that the forward shock dynamics is independent on
+the ejecta content is also incorrect. The shock deceleration dynamics and the
+reverse shock calculation presented in Zhang & Kobayashi (2005) are robust and
+correct.",0504425v1
+1999-03-19,Anisotropic non-perturbative zero modes for passively advected magnetic fields,"A first analytic assessment of the role of anisotropic corrections to the
+isotropic anomalous scaling exponents is given for the $d$-dimensional
+kinematic magneto-hydrodynamics problem in the presence of a mean magnetic
+field. The velocity advecting the magnetic field changes very rapidly in time
+and scales with a positive exponent $\xi$. Inertial-range anisotropic
+contributions to the scaling exponents, $\zeta_j$, of second-order magnetic
+correlations are associated to zero modes and have been calculated
+non-perturbatively. For $d=3$, the limit $\xi\mapsto 0$ yields
+$\protect{\zeta_j=j-2+ \xi (2j^3 +j^2 -5 j - 4)/[2(4 j^2 - 1)]} $ where $j$
+($j\geq 2$) is the order in the Legendre polynomial decomposition applied to
+correlation functions. Conjectures on the fact that anisotropic components
+cannot change the isotropic threshold to the dynamo effect are also made.",9903026v2
+1999-09-14,Nonperturbative Spectrum of Anomalous Scaling Exponents in the Anisotropic Sectors of Passively Advected Magnetic Fields,"We address the scaling behavior of the covariance of the magnetic field in
+the three-dimensional kinematic dynamo problem when the boundary conditions
+and/or the external forcing are not isotropic. The velocity field is gaussian
+and $\delta$-correlated in time, and its structure function scales with a
+positive exponent $\xi$. The covariance of the magnetic field is naturally
+computed as a sum of contributions proportional to the irreducible
+representations of the SO(3) symmetry group. The amplitudes are non-universal,
+determined by boundary conditions. The scaling exponents are universal, forming
+a discrete, strictly increasing spectrum indexed by the sectors of the symmetry
+group. When the initial mean magnetic field is zero, no dynamo effect is found,
+irrespective of the anisotropy of the forcing. The rate of isotropization with
+decreasing scales is fully understood from these results.",9909020v1
+1997-02-02,Effect of spin-glass order on magnetic polarons in semimagnetic semiconductors,"A theory accounting for the specific features of magnetic polarons (MP) in
+the presence of spin glass order is presented. We derive and solve
+selfconsistent equations for i) the polaron magnetisation, ii) the
+thermodynamically averaged carrier--spin, and iii) for the spin glass order
+parameter. The temperature dependence of these quantities is analysed in
+detail. The modification of the spin glass phase due to the presence of the
+exchange field of the carrier inside the magnetic polaron volume is
+investigated. The onset of spin glass order leads to a plateau--like flattening
+in the temperature dependence of the MP energy at low temperatures. It is found
+that solutions of spin glass equations are needed to optimally fit the
+experimental data of the temperature dependence of the exciton magnetic polaron
+(EMP) energy in (Cd,Mn)Te. Moreover, the dynamical aspects of the MP formation
+are discussed. Our model predicts qualitatively different temperature
+dependences of the MP formation time in different dynamical scenarios.",9702013v1
+1998-05-05,Thermally Activated Resonant Magnetization Tunneling in Molecular Magnets: Mn_12Ac and others,"The dynamical theory of thermally activated resonant magnetization tunneling
+in uniaxially anisotropic magnetic molecules such as Mn_12Ac (S=10) is
+developed.The observed slow dynamics of the system is described by master
+equations for the populations of spin levels.The latter are obtained by the
+adiabatic elimination of fast degrees of freedom from the density matrix
+equation with the help of the perturbation theory developed earlier for the
+tunneling level splitting [D. A. Garanin, J. Phys. A, 24, L61 (1991)]. There
+exists a temperature range (thermally activated tunneling) where the escape
+rate follows the Arrhenius law, but has a nonmonotonic dependence on the bias
+field due to tunneling at the top of the barrier. At lower temperatures this
+regime crosses over to the non-Arrhenius law (thermally assisted tunneling).
+The transition between the two regimes can be first or second order, depending
+on the transverse field, which can be tested in experiments. In both regimes
+the resonant maxima of the rate occur when spin levels in the two potential
+wells match at certain field values. In the thermally activated regime at low
+dissipation each resonance has a multitower self-similar structure with
+progressively narrowing peaks mounting on top of each other.",9805057v1
+1999-12-09,Dynamics of the Local Moment Induced by Nonmagnetic Defects in Cuprates,"We present a study of the spin dynamics of magnetic defects induced by Li
+substitution of the plane Cu in the normal state of YBa$_2$Cu$_3$O$_{6+x}$. The
+fluctuations of the coupled Cu magnetic moments in the vicinity of Li are
+probed by near-neighbour $^{89}$Y {\it and} $^7$Li NMR spin lattice relaxation.
+The data indicates that the magnetic perturbation fluctuates as a single entity
+with a correlation time $\tau$ which scales with the local static
+susceptibility. This behaviour is reminiscent of the low $T$ Kondo state of
+magnetic impurities in conventional metals. Surprisingly it extends well above
+the ``Kondo'' temperature for the underdoped pseudogapped case.",9912165v2
+2000-11-22,Fractal Structure of the Harper Map Phase Diagram from Topological Hierarchical Classification,"It is suggested a topological hierarchical classification of the infinite
+many Localized phases figuring in the phase diagram of the Harper equation for
+anisotropy parameter $\epsilon$ versus Energy $E$ with irrational magnetic flux
+$\omega$. It is also proposed a rule that explain the fractal structure of the
+phase diagram. Among many other applications, this system is equivalent to the
+Semi-classical problem of Bloch electrons in a uniform magnetic field, the
+Azbel-Hofstadter model, where the discrete magnetic translations operators
+constitute the quantum algebra $U_q(sl_2)$ with $q^2=e^{i2\pi\omega}$. The
+magnetic flux is taken to be the golden mean $\omega^*=(\sqrt{5}-1)/2$ and is
+obtained by successive rational approximants $\omega_m=F_{m-1}/F_m$ with $F_m$
+given by the Fibonacci sequence $F_m$.[OUTP-00-08S, \texttt{cond-mat/0011396}]",0011396v2
+2001-03-25,Dynamical turbulent flow on the Galton board with friction and magnetic field,"We study numerically and analytically the dynamics of charged particles on
+the Galton board, a regular lattice of disc scatters, in the presence of
+constant external force, magnetic field and friction. It is shown that under
+certain conditions friction leads to the appearance of a strange chaotic
+attractor. In this regime the average velocity and direction of particle flow
+can be effectively affected by electric and magnetic fields. We discuss the
+applications of these results to the charge transport in antidot superlattices
+and stream of suspended particles in a viscous flow through scatters.",0103515v1
+2001-11-14,Ultrafast Spin Dynamics in GaAs/GaSb/InAs Heterostructures Probed by Second Harmonic Generation,"We report the first application of pump-probe second harmonic generation
+(SHG) measurements to characterize optically-induced magnetization in
+non-magnetic multilayer semiconductors. In the experiment, coherent spins are
+selectively excited by a pump beam in the GaAs layer of GaAs/GaSb/InAs
+structures. However, the resulting net magnetization manifests itself through
+the induced SHG probe signal from the GaSb/InAs interface, thus indicating a
+coherent spin transport across the heterostructure. We find that the
+magnetization dynamics is governed by an interplay between the spin density
+evolution at the interfaces and the spin dephasing.",0111266v1
+2002-07-30,Microscopic relaxation mechanisms and linear magnetization dynamics,"Linear magnetization dynamics in the presense of a thermal bath is analyzed
+for two general classes of microscopic damping mechanisms. The resulting
+stochastic differential equations are always in the form of a damped harmonic
+oscillator driven by a thermal field. The damping term contains both the
+interaction mechanisms and the symmetry of the magnetic system. Back
+transformation from the oscillator coordinates to the magnetization variables
+results in a macroscopic tensor form of damping that reflects the system
+anisotropy. Scalar Landau-Lifshitz-Gilbert damping term is valid only for
+systems with axial symmetry. Analysis of FMR linewith measurements versus
+frequency, temperature, and film thickness in NiFe films shows good agreement
+with a combination of slow-relaxing impurity and magnon-electron confluence
+processes.",0207721v1
+2002-08-13,Electron Spin Dynamics in Semiconductors without Inversion Symmetry,"We present a microscopic analysis of electron spin dynamics in the presence
+of an external magnetic field for non-centrosymmetric semiconductors in which
+the D'yakonov-Perel' spin-orbit interaction is the dominant spin relaxation
+mechanism. We implement a fully microscopic two-step calculation, in which the
+relaxation of orbital motion due to electron-bath coupling is the first step
+and spin relaxation due to spin-orbit coupling is the second step. On this
+basis, we derive a set of Bloch equations for spin with the relaxation times
+T_1 and T_2 obtained microscopically. We show that in bulk semiconductors
+without magnetic field, T_1 = T_2, whereas for a quantum well with a magnetic
+field applied along the growth direction T_1 = T_2/2 for any magnetic field
+strength.",0208261v1
+2002-09-07,Neural network analysis of the magnetization reversal in magnetic dot arrays,"We simulated the remagnetization dynamics of the ultra-dense and ultra-thin
+magnetic dot array system with dipole-dipole and exchange coupling
+interactions. Within the proposed 2D XY superlattice model, the square dots are
+modeled by the spatially modulated exchange-couplings. The dipole-dipole
+interactions were approximated by the hierarchical sums and dynamics was
+reduced to damping term of the Landau-Lifshitz-Gilbert equation. The simulation
+of 40 000 spin system leads to nonequilibrium nonuniform configurations with
+soliton-antisoliton pairs detected at intra-dot and inter-dot scales. The
+classification of intra-dot magnetic configurations was performed using the
+self-adaptive neural networks with varying number of neurons.",0209186v1
+2003-01-17,Current-Induced Magnetization Reversal in High Magnetic Fields in Co/Cu/Co Nanopillars,"Current-induced magnetization dynamics in Co/Cu/Co trilayer nanopillars
+(~100nm in diameter) has been studied experimentally for large applied fields
+perpendicular to the layers. An abrupt and hysteretic increase in dynamic
+resistance is observed at high current densities for one polarity of the
+current, comparable to the giant magnetoresistance effect observed at low
+fields. A micromagnetic model, that includes a spin-transfer torque, suggests
+that the current induces a complete reversal of the thin Co layer to alignment
+antiparallel to the applied field-that is, to a state of maximum magnetic
+energy.",0301324v4
+2003-09-24,Magnetic susceptibilities of diluted magnetic semiconductors and anomalous Hall-voltage noise,"The carrier spin and impurity spin densities in diluted magnetic
+semiconductors are considered using a semiclassical approach. Equations of
+motions for the spin densities and the carrier spin current density in the
+paramagnetic phase are derived, exhibiting their coupled diffusive dynamics.
+The dynamical spin susceptibilities are obtained from these equations. The
+theory holds for p-type and n-type semiconductors doped with magnetic ions of
+arbitrary spin quantum number. Spin-orbit coupling in the valence band is shown
+to lead to anisotropic spin diffusion and to a suppression of the Curie
+temperature in p-type materials. As an application we derive the Hall-voltage
+noise in the paramagnetic phase. This quantity is critically enhanced close to
+the Curie temperature due to the contribution from the anomalous Hall effect.",0309547v1
+2004-02-10,Magnetism in semiconductors: A dynamical mean field study of ferromagnetism in Ga_{1-x}Mn_xAs,"We employ the dynamical mean field approximation to perform a systematic
+study of magnetism in Ga_{1-x}Mn_xAs. Our model incorporates the effects of the
+strong spin-orbit coupling on the J=3/2 GaAs valence bands and of the exchange
+interaction between the randomly distributed magnetic ions and the itinerant
+holes. The ferromagnetic phase transition temperature T_c is obtained for
+different values of the impurity-hole coupling J_c and of the hole
+concentration n_h at the Mn doping of x=0.05. We also investigate the
+temperature dependence of the local magnetization and spin polarization of the
+holes. By comparing our results with those for a single band Hamiltonian in
+which the spin-orbit coupling is switched off, we conclude that the spin-orbit
+coupling in Ga_{1-x}Mn_xAs gives rise to frustration in the ferromagnetic
+order, strengthening recent findings by Zarand and Janko (Phys. Rev. Lett. 89,
+047201 (2002)).",0402289v1
+2004-03-02,Vortex configurations and metastability in mesoscopic superconductors,"The vortex dynamics in mesoscopic superconducting cylinders with rectangular
+cross section under an axially applied magnetic field is investigated in the
+multivortex London regime. The rectangles considered range from a square up to
+an infinite slab. The flux distribution and total flux carried by a vortex
+placed in an arbitrary position of the sample is calculated analytically by
+assuming Clem's solution for the vortex core. The Bean-Livingston energy
+barrier is also analytically calculated in this framework. A Langevin algorithm
+simulates the flux penetration and dynamical evolution of the vortices as the
+external field is slowly cycled. The simulated magnetization process is
+governed by metastable states. The magnetization curves are hysteretic, with
+paramagnetic response in part of the downward branch, and present a series of
+peaks corresponding to the entry or expulsion of a single vortex. For elongated
+rectangles, the vortices arrange themselves into parallel vortex chains and an
+additional modulation of the magnetization, corresponding to creation or
+destruction of a vortex chain, comes out.",0403077v1
+2004-03-25,Ab-initio spin dynamics applied to nanoparticles: canted magnetism of a finite Co chain along a Pt(111) surface step edge,"In order to search for the magnetic ground state of surface nanostructures we
+extended first principles adiabatic spin dynamics to the case of fully
+relativistic electron scattering. Our method relies on a constrained density
+functional theory whereby the evolution of the orientations of the spin-moments
+results from a semi-classical Landau-Lifshitz equation. This approach is
+applied to a study of the ground state of a finite Co chain placed along a step
+edge of a Pt(111) surface. As far as the ground state spin orientation is
+concerned we obtain excellent agreement with the experiment. Furthermore we
+observe noncollinearity of the atom-resolved spin and orbital moments. In terms
+of magnetic force theorem calculations we also demonstrate how a reduction of
+symmetry leads to the existence of canted magnetic states.",0403637v1
+2004-04-05,"Large-angle, gigahertz-rate random telegraph switching induced by spin-momentum transfer","We show that spin-polarized dc current passing through a small magnetic
+element induces two-state, random telegraph switching of the magnetization via
+the spin-momentum transfer effect. The resistances of the states differ by up
+to 50% of the change due to complete magnetization reversal. Fluctuations are
+seen for a wide range of currents and magnetic fields, with rates that can
+exceed 2 GHz, and involve collective motion of a large volume (10^4 nm^3) of
+spins. Switching rate trends with field and current indicate that increasing
+temperature alone cannot explain the dynamics. The rates approach a stochastic
+regime wherein dynamics are governed by both precessional motion and thermal
+perturbations.",0404109v1
+2004-04-07,The Effect of Columnar Disorder on the Superconducting Transition of a Type-II Superconductor in Zero Applied Magnetic Field,"We investigate the effect of random columnar disorder on the superconducting
+phase transition of a type-II superconductor in zero applied magnetic field
+using numerical simulations of three dimensional XY and vortex loop models. We
+consider both an unscreened model, in which the bare magnetic penetration
+length is approximated as infinite, and a strongly screened model, in which the
+magnetic penetration length is of order the vortex core radius. We consider
+both equilibrium and dynamic critical exponents. We show that, as in the
+disorder free case, the equilibrium transitions of the unscreened and strongly
+screened models lie in the same universality class, however scaling is now
+anisotropic. We find for the correlation length exponent $\nu=1.2\pm 0.1$, and
+for the anisotropy exponent $\zeta=1.3\pm 0.1$. We find different dynamic
+critical exponents for the unscreened and strongly screened models.",0404179v1
+2004-05-31,Electron Dynamics in a Coupled Quantum Point Contact Structure with a Local Magnetic Moment,"We develop a theoretical model for the description of electron dynamics in
+coupled quantum wires when the local magnetic moment is formed in one of the
+wires. We employ a single-particle Hamiltonian that takes account of the
+specific geometry of potentials defining the structure as well as electron
+scattering on the local magnetic moment. The equations for the wave functions
+in both wires are derived and the approach for their solution is discussed. We
+determine the transmission coefficient and conductance of the wire having the
+local magnetic moment and show that our description reproduces the
+experimentally observed features.",0405705v1
+2004-06-21,Basic considerations for magnetization dynamics in the combined presence of spin-transfer torques and thermal fluctuations,"This article reviews basic theoretical features of Gilbert magnetization
+dynamics of a single domain magnetic film in the presence of Slonczewski
+spin-transfer torques, with and without thermal fluctuations taken into
+account. Rather than showing results of detailed numerical calculations, the
+discussion here is restricted to basic analytical results and conclusions which
+can mostly be derived from simply the form of the equations of motion, as well
+as elementary considerations based on classical stability analysis and the
+fluctuation-dissipation theorem. The presents work describes how interesting
+features of spin-transfer may be viewed as arising from non-equilibrium
+thermodynamics that are a direct consequence of the nonreciprocal nature of
+spin-transfer torques. The present article discusses fairly general results for
+spin-torque induced instability without thermal fluctuations, as well as the
+case of thermally activated magnetization reversal in uniaxial devices in the
+combined presence of external fields, thermal fluctuations, and spin-transfer
+torques. The results will be discussed and briefly compared and contrasted with
+that of prior work.",0406486v1
+2004-07-27,Study of Gas-Fluidization Dynamics with Laser-Polarized 129Xe,"We report initial NMR studies of gas dynamics in a particle bed fluidized by
+laser-polarized xenon (129Xe) gas. We have made preliminary measurements of two
+important characteristics: gas exchange between the bubble and emulsion phases;
+and the gas velocity distribution in the bed. We used T2* contrast to
+differentiate the bubble and emulsion phases by choosing solid particles with
+large magnetic susceptibility, in order. Experimental tests demonstrated that
+this method was successful in eliminating 129Xe magnetization in the emulsion
+phase, which enabled us to observe the time-dependence of the bubble
+magnetization. By employing the pulsed field gradient method, we also measured
+the gas velocity distribution within the bed. These results clearly show the
+onset of bubbling and can be used to deduce information about gas and particle
+motion in the fluidized bed.",0407708v1
+2004-11-10,Dynamical nuclear polarization and nuclear magnetic fields in semiconductor nanostructures,"We investigate the dynamic nuclear polarization from the hyperfine
+interaction between nonequilibrium electronic spins and nuclear spins coupled
+to them in semiconductor nanostructures. We derive the time and position
+dependence of the induced nuclear spin polarization and dipolar magnetic
+fields. In GaAs/AlGaAs parabolic quantum wells the nuclear spin polarization
+can be as high as 80% and the induced nuclear magnetic fields can approach a
+few gauss with an associated nuclear resonance shift of the order of kHz when
+the electronic system is 100% spin polarized. These fields and shifts can be
+tuned using small electric fields. We discuss the implications of such control
+for optical nuclear magnetic resonance experiments in low-dimensional
+semiconductor nanostructures.",0411277v1
+2004-11-11,Dynamical breakdown of the Ising spin-glass order under a magnetic field,"The dynamical magnetic properties of an Ising spin glass
+Fe$_{0.55}$Mn$_{0.45}$TiO$_3$ are studied under various magnetic fields. Having
+determined the temperature and static field dependent relaxation time
+$\tau(T;H)$ from ac magnetization measurements under a dc bias field by a
+general method, we first demonstrate that these data provide evidence for a
+spin-glass (SG) phase transition only in zero field. We next argue that the
+data $\tau(T;H)$ of finite $H$ can be well interpreted by the droplet theory
+which predicts the absence of a SG phase transition in finite fields.",0411291v2
+2004-12-22,Topology and spin dynamics in magnetic molecules,"We investigate the role of topology and distortions in the quantum dynamics
+of magnetic molecules, using a cyclic spin system as reference. We consider
+three variants of antiferromagnetic molecular ring, i.e. Cr$_8$, Cr$_7$Zn and
+Cr$_7$Ni, characterized by low lying states with different total spin $S$. We
+theoretically and experimentally study the low-temperature behavior of the
+magnetic torque as a function of the applied magnetic field. Near level
+crossings, this observable selectively probes quantum fluctuations of the total
+spin (''$S$ mixing"") induced by lowering of the ideal ring symmetry. We show
+that while a typical distortion of a model molecular structure is very
+ineffective in opening new $S$-mixing channels, the spin topology is a major
+ingredient to control the degree of $S$ mixing. This conclusion is further
+substantiated by low-temperature heat capacity measurements.",0412628v1
+2005-07-19,Energy-resolved inelastic electron scattering off a magnetic impurity,"We study inelastic scattering of energetic electrons off a Kondo impurity. If
+the energy E of the incoming electron (measured from the Fermi level) exceeds
+significantly the Kondo temperature T_K, then the differential inelastic
+cross-section \sigma (E,w), i.e., the cross-section characterizing scattering
+of an electron with a given energy transfer w, is well-defined. We show that
+\sigma (E,w) factorizes into two parts. The E-dependence of \sigma (E,w) is
+logarithmically weak and is due to the Kondo renormalization of the effective
+coupling. We are able to relate the w-dependence to the spin-spin correlation
+function of the magnetic impurity. Using this relation, we demonstrate that in
+the absence of magnetic field the dynamics of the impurity spin causes the
+electron scattering to be inelastic at any temperature. Quenching of the spin
+dynamics by an applied magnetic field results in a finite elastic component of
+the electron scattering cross-section. The differential scattering
+cross-section may be extracted from the measurements of relaxation of hot
+electrons injected in conductors containing localized spins.",0507431v2
+2006-01-27,Dynamics of thin-film spin-flip transistors with perpendicular source-drain magnetizations,"A ""spin-flip transistor"" is a lateral spin valve consisting of ferromagnetic
+source drain contacts to a thin-film normal-metal island with an electrically
+floating ferromagnetic base contact on top. We analyze the
+\emph{dc}-current-driven magnetization dynamics of spin-flip transistors in
+which the source-drain contacts are magnetized perpendicularly to the device
+plane by magnetoelectronic circuit theory and the macrospin
+Landau-Lifshitz-Gilbert equation. Spin flip scattering and spin pumping effects
+are taken into account. We find a steady-state rotation of the base
+magnetization at GHz frequencies that is tuneable by the source-drain bias. We
+discuss the advantages of the lateral structure for high-frequency generation
+and actuation of nanomechanical systems over recently proposed nanopillar
+structures.",0601630v1
+2006-02-07,Dynamics of magnetic domain wall motion after nucleation: Dependence on the wall energy,"The dynamics of magnetic domain wall motion in the FeNi layer of a
+FeNi/Al2O3/Co trilayer has been investigated by a combination of x-ray magnetic
+circular dichroism, photoelectron emission microscopy, and a stroboscopic
+pump-probe technique. The nucleation of domains and subsequent expansion by
+domain wall motion in the FeNi layer during nanosecond-long magnetic field
+pulses was observed in the viscous regime up to the Walker limit field. We
+attribute an observed delay of domain expansion to the influence of the domain
+wall energy that acts against the domain expansion and that plays an important
+role when domains are small.",0602174v1
+2006-07-25,The magnetization-driven random field Ising model at T=0,"We study the hysteretic evolution of the random field Ising model (RFIM) at
+T=0 when the magnetization M is controlled externally and the magnetic field H
+becomes the output variable. The dynamics is a simple modification of the
+single-spin-flip dynamics used in the H-driven situation and consists in
+flipping successively the spins with the largest local field. This allows to
+perform a detailed comparison between the microscopic trajectories followed by
+the system with the two protocols. Simulations are performed on random graphs
+with connectivity z=4 (Bethe lattice) and on the 3-D cubic lattice. The same
+internal energy U(M)is found with the two protocols when there is no
+macroscopic avalanche and it does not depend on whether the microscopic states
+are stable or not. On the Bethe lattice, the energy inside the macroscopic
+avalanche also coincides with the one that is computed analytically with the
+H-driven algorithm along the unstable branch of the hysteresis loop. The output
+field, defined here as dU/dM, exhibits very large fluctuations with the
+magnetization and is not self-averaging. Relation to the experimental situation
+is discussed.",0607644v1
+2006-11-29,Irregular Spin Tunnelling for Spin-1 Bose-Einstein Condensates in a Sweeping Magnetic Field,"We investigate the spin tunnelling of spin-1 Bose-Einstein condensates in a
+linearly sweeping magnetic field with a mean-field treatment. We focus on the
+two typical alkali Bose atoms $^{87}Rb$ and $^{23}Na$ condensates and study
+their tunnelling dynamics according to different sweeping rates of external
+magnetic fields. In the adiabatic (i.e., slowly sweeping) and sudden (i.e.,
+fast sweeping) limits, no tunnelling is observed. For the case of moderate
+sweeping rates, the tunnelling dynamics is found to be very sensitive on the
+sweeping rates with showing a chaotic-like tunnelling regime. With magnifying
+the regime, however, we find interestedly that the plottings become resolvable
+under a resolution of $10^{-4}$ G/s where the tunnelling probability with
+respect to the sweeping rate shows a regular periodic-like pattern. Moreover, a
+conserved quantity standing for the magnetization in experiments is found can
+dramatically affect the above picture of the spin tunnelling. Theoretically we
+have given a reasonable interpretation to the above findings and hope our
+studies would bring more attention to spin tunnelling experimentally.",0611734v1
+1999-09-14,Dynamics of magnetic Bianchi VI_0 cosmologies,"Methods of dynamical systems analysis are used to show rigorously that the
+presence of a magnetic field orthogonal to the two commuting Killing vector
+fields in any spatially homogeneous Bianchi type VI_0 vacuum solution to
+Einstein's equation changes the evolution toward the singularity from
+convergent to oscillatory. In particular, it is shown that the alpha-limit set
+(for time direction that puts the singularity in the past) of any of these
+magnetic solutions contains at least two sequential Kasner points of the BKL
+sequence and the orbit of the transition solution between them. One of the
+Kasner points in the alpha-limit set is non-flat, which leads to the result
+that each of these magnetic solutions has a curvature singularity.",9909043v4
+1998-03-21,Magnetohydrodynamics of the Early Universe and the Evolution of Primordial Magnetic Fields,"We show that the decaying magnetohydrodynamic turbulence leads to a more
+rapid growth of the correlation length of a primordial magnetic field than that
+caused by the expansion of the Universe. As an example, we consider the
+magnetic fields created during the electroweak phase transition. The expansion
+of the universe alone would yield a correlation length at the present epoch of
+1 AU, whereas we find that the correlation length is likely of order 100 AU,
+and cannot possibly be longer than $10^4$ AU for non-helical fields. If the
+primordial field is strongly helical, the correlation length can be much
+larger, but we show that even in this case it cannot exceed 100 pc. All these
+estimates make it hard to believe that the observed galactic magnetic fields
+can result from the amplification of seed fields generated at the electroweak
+phase transition by the standard galactic dynamo.",9803412v2
+1998-02-08,Abelianization of SU(N) Gauge Theory with Gauge Invariant Dynamical Variables and Magnetic Monopoles,"It is shown that SU(N) gauge theory coupled to adjoint Higgs can be
+explicitly re-written in terms of SU(N) gauge invariant dynamical variables
+with local physical interactions. The resultant theory has a novel compact
+abelian $U(1)^{(N - 1)}$ gauge invariance. The above abelian gauge invariance
+is related to the adjoint Higgs field and not to the gauge group SU(N). In this
+abelianized version the magnetic monopoles carrying the magnetic charges of
+$(N-1)$ types have a natural origin and therefore appear explicitly in the
+partition function as Dirac monopoles along with their strings. The gauge
+invariant electric and magnetic charges with respect to $U(1)^{(N-1)}$ gauge
+groups are shown to be vectors in root and co-root lattices of SU(N)
+respectively. Therefore, the Dirac quantization condition corresponds to SU(N)
+Cartan matrix elements being integers. We also study the effect of the $\theta$
+term in the abelian version of the theory.",9802050v1
+2000-06-13,"Microscopic Pictures of Dynamical Symmetry Breaking in Supersymmetric $SU(n_c)$, $USp(2n_c)$ and $SO(n_c)$ Theories","Several distinct mechanisms of confinement and dynamical symmetry breaking
+(DSB) are identified, in a class of supersymmetric $SU(n_c)$, $USp(2n_c)$ and
+$SO(n_c)$ gauge theories. In some of the vacua, the magnetic monopoles carrying
+nontrivial flavor quantum numbers condense, causing confinement and symmetry
+breaking simultaneously. In more general classes of vacua, however, the
+effective low-energy degrees of freedom are found to be constituents of the
+monopoles - dual (magnetic) quarks. These magnetic quarks condense and give
+rise to confinement and DSB. We find two more important classes of vacua, one
+is in various universality classes of nontrivial superconformal theories
+(SCFT), another in free-magnetic phase.",0006086v1
+2007-02-17,Magneto-electrostatic trapping of ground state OH molecules,"We report the magnetic confinement of neutral, ground state hydroxyl radicals
+(OH) at a density of $\sim3\times10^{3}$ cm$^{-3}$ and temperature of $\sim$30
+mK. An adjustable electric field of sufficient magnitude to polarize the OH is
+superimposed on the trap in either a quadrupole or homogenous field geometry.
+The OH is confined by an overall potential established via molecular state
+mixing induced by the combined electric and magnetic fields acting on the
+molecule's electric dipole and magnetic dipole moments, respectively. An
+effective molecular Hamiltonian including Stark and Zeeman terms has been
+constructed to describe single molecule dynamics inside the trap. Monte Carlo
+simulation using this Hamiltonian accurately models the observed trap dynamics
+in various trap configurations. Confinement of cold polar molecules in a
+magnetic trap, leaving large, adjustable electric fields for control, is an
+important step towards the study of low energy dipole-dipole collisions.",0702146v1
+2005-01-27,Tunnelling of condensate magnetization in a double-well potential,"We study quantum dynamical properties of a spin-1 atomic Bose-Einstein
+condensate in a double-well potential. Adopting a mean field theory and single
+spatial mode approximation, we characterize our model system as two coupled
+spins. For certain initial states, we find full magnetization oscillations
+between wells not accompanied by mass (or atom numbers) exchange. We identify
+dynamic regimes of collective spin variables arising from nonlinear
+self-interactions that are different from the usual Josephson oscillations. We
+also discuss magnetization beats and incomplete oscillations of collective spin
+variables other than the magnetization. Our study points to an alternative
+approach to observe coherent tunnelling of a condensate through a (spatial)
+potential barrier.",0501165v1
+2007-03-31,Formation of quasi-solitons in transverse confined ferromagnetic film media,"The formation of quasi-2D spin-wave waveforms in longitudinally magnetized
+stripes of ferrimagnetic film was observed by using time- and space-resolved
+Brillouin light scattering technique. In the linear regime it was found that
+the confinement decreases the amplitude of dynamic magnetization near the
+lateral stripe edges. Thus, the so-called effective dipolar pinning of dynamic
+magnetization takes place at the edges.
+  In the nonlinear regime a new stable spin wave packet propagating along a
+waveguide structure, for which both transversal instability and interaction
+with the side walls of the waveguide are important was observed. The
+experiments and a numerical simulation of the pulse evolution show that the
+shape of the formed waveforms and their behavior are strongly influenced by the
+confinement.",0704.0024v1
+2007-04-24,Element-resolved x-ray ferrimagnetic and ferromagnetic resonance spectroscopy,"We report on the measurement of element-specific magnetic resonance spectra
+at gigahertz frequencies using x-ray magnetic circular dichroism (XMCD). We
+investigate the ferrimagnetic precession of Gd and Fe ions in Gd-substituted
+Yttrium Iron Garnet, showing that the resonant field and linewidth of Gd
+precisely coincide with Fe up to the nonlinear regime of parametric
+excitations. The opposite sign of the Gd x-ray magnetic resonance signal with
+respect to Fe is consistent with dynamic antiferromagnetic alignment of the two
+ionic species. Further, we investigate a bilayer metal film,
+Ni$_{80}$Fe$_{20}$(5 nm)/Ni(50 nm), where the coupled resonance modes of Ni and
+Ni$_{80}$Fe$_{20}$ are separately resolved, revealing shifts in the resonance
+fields of individual layers but no mutual driving effects. Energy-dependent
+dynamic XMCD measurements are introduced, combining x-ray absorption and
+magnetic resonance spectroscopies.",0704.3139v2
+2007-05-24,Local spin dynamic arising from the non-perturbative SU(2) gauge field of the spin orbit effect,"We use the non-perturbative gauge field approach to study the effects of spin
+orbit coupling on the dynamic of magnetic moment. We present a general equation
+of motion (EOM) which unifies i) the spin orbit coupling effect derived from
+the SU(2) spin gauge field, and ii) the moment chirality effect previously
+derived from the topological U(1)xU(1) rotation gauge under the adiabatic
+condition. We present a modified Landau-Liftshitz-Gilbert equation and discuss
+the implication of the modified EOM in various technological applications, such
+as current-induced switching and trajectory of magnetic moments in spin-valve
+multilayers, magnetic memory and diluted magnetic semiconductor.",0705.3502v1
+2007-05-30,Two Modes of Magnetization Switching in a Simulated Iron Nanopillar in an Obliquely Oriented Field,"Finite-temperature micromagnetics simulations are employed to study the
+magnetization-switching dynamics driven by a field applied at an angle to the
+long axis of an iron nanopillar. A bi-modal distribution in the switching times
+is observed, and evidence for two competing modes of magnetization-switching
+dynamics is presented. For the conditions studied here, temperature $T = 20$ K
+and the reversal field 3160 Oe at an angle of 75$^\circ$ to the long axis,
+approximately 70% of the switches involve unstable decay (no free-energy
+barrier) and 30% involve metastable decay (a free-energy barrier is crossed).
+The latter are indistinguishable from switches which are constrained to start
+at a metastable free-energy minimum. Competition between unstable and
+metastable decay could greatly complicate applications involving magnetization
+switches near the coercive field.",0705.4454v1
+2007-05-30,Weather in stellar atmosphere: the dynamics of mercury clouds in alpha Andromedae,"The formation of long-lasting structures at the surfaces of stars is commonly
+ascribed to the action of strong magnetic fields. This paradigm is supported by
+observations of evolving cool spots in the Sun and active late-type stars, and
+stationary chemical spots in the early-type magnetic stars. However, results of
+our seven-year monitoring of mercury spots in non-magnetic early-type star
+alpha Andromedae show that the picture of magnetically-driven structure
+formation is fundamentally incomplete. Using an indirect stellar surface
+mapping technique, we construct a series of 2-D images of starspots and
+discover a secular evolution of the mercury cloud cover in this star. This
+remarkable structure formation process, observed for the first time in any
+star, is plausibly attributed to a non-equilibrium, dynamical evolution of the
+heavy-element clouds created by atomic diffusion and may have the same
+underlying physics as the weather patterns on terrestrial and giant planets.",0705.4469v1
+2007-06-04,Sum-rules for electron energy-loss near-edge spectra,"We derive four sum-rule expressions for spectra measured in electron
+energy-loss near edge structure experiments. These sum-rules permit the
+determination spin and orbital magnetic moments, spin-orbit interaction and
+number of states, analogously to the sum rules of x-ray magnetic circular
+dichroism. The derivation of the sum-rules is based on dynamical electron
+diffraction theory and the properties of the mixed dynamic form-factor. The
+accuracy of the sum-rules is tested by a complete evaluation of the thickness
+dependent electron energy-loss spectra for iron, cobalt, and nickel crystals.
+We find that the sum-rules reproduce both spin and orbital moments with very
+good accuracy. Our results provide a foundation for the use of the energy loss
+magnetic chiral dichroism technique as a quantitative probe of element specific
+magnetic properties.",0706.0402v2
+2007-09-18,Theory of current-driven magnetization dynamics in inhomogeneous ferromagnets,"We give a brief account of recent developments in the theoretical
+understanding of the interaction between electric currents and inhomogeneous
+ferromagnetic order parameters. We start by discussing the physical origin of
+the spin torques responsible for this interaction and construct a
+phenomenological description. We then consider the electric current-induced
+ferromagnetic instability and domain-wall motion. Finally, we present a
+microscopic justification of the phenomenological description of current-driven
+magnetization dynamics, with particular emphasis on the dissipative terms, the
+so-called Gilbert damping $\alpha$ and the $\beta$ component of the adiabatic
+current-driven torque.",0709.2937v2
+2007-12-12,Anisotropic turbulent model for solar coronal heating,"Context : We present a self-consistent model of solar coronal heating,
+originally developed by Heyvaert & Priest (1992), in which we include the
+dynamical effect of the background magnetic field along a coronal structure by
+using exact results from wave MHD turbulence (Galtier et al. 2000). Aims : We
+evaluate the heating rate and the microturbulent velocity for comparison with
+observations in the quiet corona, active regions and also coronal holes.
+Methods :The coronal structures are assumed to be in a turbulent state
+maintained by the slow erratic motions of the magnetic footpoints. A
+description for the large-scale and the unresolved small-scale dynamics are
+given separately. From the latter, we compute exactly (or numerically for
+coronal holes) turbulent viscosites that are finally used in the former to
+close self-consistently the system and derive the heating flux expression.
+Results : We show that the heating rate and the turbulent velocity compare
+favorably with coronal observations. Conclusions : Although the Alfven wave
+turbulence regime is strongly anisotropic, and could reduce a priori the
+heating efficiency, it provides an unexpected satisfactory model of coronal
+heating for both magnetic loops and open magnetic field lines.",0712.2029v2
+2008-01-28,Switching phenomena in magnetic vortex dynamics,"A magnetic nanoparticle in a vortex state is a promising candidate for the
+information storage. One bit of information corresponds to the upward or
+downward magnetization of the vortex core (vortex polarity). Generic properties
+of the vortex polarity switching are insensitive of the way how the vortex
+dynamics was excited: by an AC magnetic field, or by an electrical current. We
+study theoretically the switching process and describe in detail its mechanism,
+which involves the creation and annihilation of an intermediate
+vortex-antivortex pair.",0801.4045v2
+2008-05-14,Bypassing Cowling's theorem in axisymmetric fluid dynamos,"We present a numerical study of the magnetic field generated by an
+axisymmetrically forced flow in a spherical domain. At small enough Reynolds
+number, Re, the flow is axisymmetric and generates an equatorial dipole above a
+critical magnetic Reynolds number Rmc . The magnetic field thus breaks
+axisymmetry, in agreement with Cowling's theorem. This structure of the
+magnetic field is however replaced by a dominant axial dipole when Re is larger
+and allows non axisymmetric fluctuations in the flow. We show here that even in
+the absence of such fluctuations, an axial dipole can also be generated, at low
+Re, through a secondary bifurcation, when Rm is increased above the dynamo
+threshold. The system therefore always find a way to bypass the constraint
+imposed by Cowling's theorem. We understand the dynamical behaviors that result
+from the interaction of equatorial and axial dipolar modes using simple model
+equations for their amplitudes derived from symmetry arguments.",0805.2123v1
+2008-09-05,MHD turbulence in a channel with spanwise magnetic field,"The effect of a uniform spanwise magnetic field on a turbulent channel flow
+is investigated for the case of low magnetic Reynolds number. DNS and LES
+computations are performed for two values of the hydrodynamic Reynolds number
+(10^4 and 2\times 10^4) and the Hartmann number varying in a wide range. It is
+shown that the main effect of the magnetic field is the suppression of
+turbulent velocity fluctuations and momentum transfer in the wall-normal
+direction. This leads to drag reduction and transformation of the mean flow
+profile. The centerline velocity grows, the mean velocity gradients near the
+wall decrease, and the typical horizontal dimensions of the coherent structures
+enlarge upon increasing the Hartmann number. Comparison between LES and DNS
+results shows that the dynamic Smagorinsky model accurately reproduces the flow
+transformation.",0809.0964v1
+2008-10-03,Dilution effects in Ho$_{2-x}$Y$_x$Sn$_2$O$_7$: from the Spin Ice to the single-ion magnet,"A study of the modifications of the magnetic properties of
+Ho$_{2-x}$Y$_x$Sn$_2$O$_7$ upon varying the concentration of diamagnetic
+Y$^{3+}$ ions is presented. Magnetization and specific heat measurements show
+that the Spin Ice ground-state is only weakly affected by doping for $x\leq
+0.3$, even if non-negligible changes in the crystal field at Ho$^{3+}$ occur.
+In this low doping range $\mu$SR relaxation measurements evidence a
+modification in the low-temperature dynamics with respect to the one observed
+in the pure Spin Ice. For $x\to 2$, or at high temperature, the dynamics
+involve fluctuations among Ho$^{3+}$ crystal field levels which give rise to a
+characteristic peak in $^{119}$Sn nuclear spin-lattice relaxation rate. In this
+doping limit also the changes in Ho$^{3+}$ magnetic moment suggest a variation
+of the crystal field parameters.",0810.0608v1
+2008-11-17,Magnetic Moments of Delta and Omega^- Baryons with Dynamical Clover Fermions,"We calculate the magnetic dipole moment of the Delta(1232) and Omega^-
+baryons with 2+1-flavors of clover fermions on anisotropic lattices using a
+background magnetic field. This is the first dynamical calculation of these
+magnetic moments using a background field technique. The calculation for
+Omega^- is done at the physical strange quark mass, with the result in units of
+the physical nuclear magneton mu_Omega^-= -1.93(8)(12) (where the first error
+is statistical and the second is systematic) compared to the experimental
+number: -2.02(5). The Delta has been studied at three unphysical quark masses,
+corresponding to pion mass m_pi = 366, 438, and 548 MeV. The pion mass
+dependence is compared with the behavior obtained from chiral effective field
+theory.",0811.2440v1
+2008-11-25,Electronic theory of ultrafast spin dynamics,"NiO is a good candidate for ultrafast magnetic switching because of its large
+spin density, antiferromagnetic order, and clearly separated intragap states.
+In order to detect and monitor the switching dynamics, we develop a systematic
+approach to study optical second harmonic generation (SHG) in NiO, both at the
+(001) surface and in the bulk. In our calculations NiO is modeled as a doubly
+embedded cluster. All intragap \emph{d}-states of the bulk and the (001)
+surface are obtained with highly-correlational quantum chemistry and propagated
+in time under the influence of a static magnetic field and a laser pulse. We
+find that demagnetization and switching can be best achieved in a subpicosecond
+regime with linearly rather than circularly polarized light. We also show the
+importance of including an external magnetic field in order to distinguish
+spin-up and spin-down states and the necessity of including magnetic-dipole
+transitions in order to realize the $\Lambda$-process in the centrosymmetric
+bulk. Having already shown the effects of phonons in the SHG for the bulk NiO
+within the frozen-phonon approximation, and following the same trail of
+thoughts, we discuss the role of phonons in a fully quantized picture as a
+symmetry-lowering mechanism in the switching scenario and investigate the
+electronic and lattice temperature effects.",0811.4042v1
+2009-01-13,Spinor condensate of $^{87}$Rb as a dipolar gas,"We consider a spinor condensate of $^{87}$Rb atoms in F=1 hyperfine state
+confined in an optical dipole trap. Putting initially all atoms in $m_F=0$
+component we find that the system evolves towards a state of thermal
+equilibrium with kinetic energy equally distributed among all magnetic
+components. We show that this process is dominated by the dipolar interaction
+of magnetic spins rather than spin mixing contact potential. Our results show
+that because of a dynamical separation of magnetic components the spin mixing
+dynamics in $^{87}$Rb condensate is governed by dipolar interaction which plays
+no role in a single component rubidium system in a magnetic trap.",0901.1763v2
+2009-02-16,Nature-inspired microfluidic propulsion using magnetic actuation,"In this work we mimic the efficient propulsion mechanism of natural cilia by
+magnetically actuating thin films in a cyclic but non-reciprocating manner. By
+simultaneously solving the elasto-dynamic, magnetostatic and fluid mechanics
+equations, we show that the amount of fluid propelled is proportional to the
+area swept by the cilia. By using the intricate interplay between film
+magnetization and applied field we are able to generate a pronounced asymmetry
+and associated flow. We delineate the functional response of the system in
+terms of three dimensionless parameters that capture the relative contribution
+of elastic, inertial, viscous and magnetic forces.",0902.2632v1
+2009-03-06,Structure and Dynamics of Sunspots,"The physics of Sunspots is a fascinating and demanding field of research in
+solar astronomy. Interaction of magnetic fields and plasma flows takes place in
+a tangled magnetic geometry and occurs on spatial scales that pose a continuous
+challenge for existing instrumentation and for the unambiguous interpretation
+of spectropolarimetric observations. Thus, the main properties of sunspots are
+well established but its fine structure is not yet fully understood.
+  In this contribution we summarize the current knowledge of the magnetic and
+dynamic properties of sunspots at the photospheric level based on selected
+observations featuring the highest possible spatial and spectral resolution. We
+concentrate on light bridges, umbral dots, penumbral filaments and the
+notorious dark cores in penumbral filaments. We report on the morphology of the
+fine structure elements but mostly focus on observations of their line-of-sight
+velocities and magnetic field parameters. We briefly comment on results from
+recent radiative MHD simulations and more schematic model ideas that attempt to
+rationalize observations of the penumbra.",0903.1300v1
+2009-04-05,Static and Dynamic Magnetism in Underdoped Superconductor BaFe$_{1.92}$Co$_{0.08}$As$_2$,"We report neutron scattering measurements on single crystals of
+BaFe$_{1.92}$Co$_{0.08}$As$_2$. The magnetic Bragg peak intensity is reduced by
+6 % upon cooling through T$_C$. The spin dynamics exhibit a gap of 8 meV with
+anisotropic three-dimensional (3d) interactions. Below T$_C$ additional
+intensity appears at an energy of $\sim$4.5(0.5) meV similar to previous
+observations of a spin resonance in other Fe-based superconductors. No further
+gapping of the spin excitations is observed below T$_C$ for energies down to 2
+meV. These observations suggest the redistribution of spectral weight from the
+magnetic Bragg position to a spin resonance demonstrating the direct
+competition between static magnetic order and superconductivity.",0904.0767v1
+2009-06-05,One-dimensional stability of parallel shock layers in isentropic magnetohydrodynamic,"Extending investigations of Barker, Humpherys, Lafitte, Rudd, and Zumbrun for
+compressible gas dynamics and Freist\""uhler and Trakhinin for compressible
+magnetohydrodynamics, we study by a combination of asymptotic ODE estimates and
+numerical Evans function computations the one-dimensional stability of parallel
+isentropic magnetohydrodynamic shock layers over the full range of physical
+parameters (shock amplitude, strength of imposed magnetic field, viscosity,
+magnetic permeability, and electrical resistivity) for a $\gamma$-law gas with
+$\gamma\in [1,3]$. Other $\gamma$-values may be treated similarly, but were not
+checked numerically. Depending on magnetic field strength, these shocks may be
+of fast Lax, intermediate (overcompressive), or slow Lax type; however, the
+shock layer is independent of magnetic field, consisting of a purely
+gas-dynamical profile. In each case, our results indicate stability.
+Interesting features of the analysis are the need to renormalize the Evans
+function in order to pass continuously across parameter values where the shock
+changes type or toward the large-amplitude limit at frequency $\lambda=0$ and
+the systematic use of winding number computations on Riemann surfaces.",0906.1208v1
+2009-06-13,On the lack of universality in decaying magnetohydrodynamic turbulence,"Using computations of three-dimensional magnetohydrodynamic (MHD) turbulence
+with a Taylor-Green flow, whose inherent time-independent symmetries are
+implemented numerically, and in the absence of either a forcing function or an
+imposed uniform magnetic field, we show that three different inertial ranges
+for the energy spectrum may emerge for three different initial magnetic fields,
+the selecting parameter being the ratio of the Alfven to the eddy turnover
+time. Equivalent computational grids range from 128^3 to 2048^3 points with a
+unit magnetic Prandtl number and a Taylor Reynolds number of up to 1500 at the
+peak of dissipation. We also show convergence of our results with Reynolds
+number. Our study is consistent with previous findings of a variety of energy
+spectra in MHD turbulence by studies performed in the presence of both a
+forcing term with a given correlation time and a strong, uniform magnetic
+field. In contrast to the previous studies, however, the ratio of
+characteristic time scales here can only be ascribed to the intrinsic nonlinear
+dynamics of the flows under study.",0906.2506v1
+2009-09-03,Spontaneous Magnetic Ordering in a Ferromagnetic Spinor Dipolar Bose-Einstein Condensate,"We study the spin dynamics in a spin-1 ferromagnetic Bose-Einstein condensate
+with magnetic dipole-dipole interaction (MDDI) based on the Gross-Pitaevskii
+and Bogoliubov theories. We find that various magnetic structures such as
+checkerboards and stripes emerge in the course of the dynamics due to the
+combined effects of spin-exchange interaction, MDDI, quadratic Zeeman and
+finite-size effects, and non-stationary initial conditions. However, the
+short-range magnetic order observed by the Berkeley group [Phys. Rev. Lett.
+{\bf 100}, 170403 (2008)] is not fully reproduced in our calculations; the
+periodicity of the order differs by a factor of three and the checkerboard
+pattern eventually dissolves in our numerical simulations. Possible reasons for
+the discrepancy are discussed.",0909.0565v2
+2009-09-03,Simulation of the current dynamics in superconductors: Application to magnetometry measurements,"A simple model for simulating the current dynamics and the magnetic
+properties of superconductors is presented. Short simulation times are achieved
+by solving the differential form of Maxwell's equations inside the sample,
+whereas integration is only required at the surface to meet the exact boundary
+conditions. The procedure reveals the time and position dependence of the
+current density and the magnetic induction (B) making it very convenient to
+apply field dependent material parameters for the simulation of magnetization
+loops, relaxation measurements, etc. Two examples, which are important for
+standard magnetometry experiments, are discussed. Firstly, we prove that
+evaluating the critical current density (J_c) from experiment by applying
+Bean's model reveals almost the exact J_c(B) behavior, if the evaluation is
+corrected by a simple numerical expression. Secondly, we show that the
+superconducting volume fraction of a sample can be directly determined from
+magnetization loops by carefully comparing experiment and simulation in the
+field range, where the current loops are differently oriented within the
+sample.",0909.0597v1
+2009-09-30,Two-Dimensional Spin Dynamics in the Itinerant Ferromagnet LaCoPO Revealed by Magnetization and $^{31}$P-NMR Measurements,"We have performed magnetization and $^{31}$P-NMR measurements on the
+itinerant ferromagnet LaCoPO (Curie temperature $T_{\rm Curie}\sim 44$ K) with
+a layered structure in order to investigate spin dynamics in the paramagnetic
+state. The linear scaling between the Knight shift $K$ at the P site and the
+bulk susceptibility $\chi$ above $T_{\rm Curie}$ indicates that the P nucleus
+is suitable for investigating magnetic properties. The temperature and magnetic
+field dependences of the nuclear spin-lattice relaxation rate divided by the
+temperature $1/T_1T$ at the P site show characteristic features of itinerant
+ferromagnets, such as ZrZn$_2$ and Y(Co$_{1-x}$Al$_x$)$_2$. In addition, the
+relationship between $1/T_1T$ and $\chi$ above $T_{\rm Curie}$ suggests that
+ferromagnetic fluctuations possess a two-dimensional (2D) characteristic. The
+present data show that LaCoPO is a unique ferromagnet, where the 2D
+fluctuations anticipated from the crystal structure are predominant down to
+almost $T_{\rm Curie}$.",0909.5641v1
+2009-10-06,Effect of dipolar interactions for domain wall dynamics in magnetic thin films,"We study the effect of long range dipolar forces on the dynamics and
+morphology of domain walls in magnetic thin films by numerical simulations of
+the spin-1 random field Ising model. By studying the size distribution of
+avalanches of domain wall motion arising as a response to quasistatic external
+driving, we observe a cross-over from the case dominated by short range
+interactions to another universality class where the long range dipolar forces
+become important. This crossover is accompanied with a change of the domain
+wall morphology from a rough wall to walls with zigzag structure.",0910.1040v1
+2009-11-12,An ac field probe for the magnetic ordering of magnets with random anisotropy,"A Monte Carlo simulation is carried out to investigate the magnetic ordering
+in magnets with random anisotropy (RA). Our results show peculiar similarities
+to recent experiments that the real part of ac susceptibility presents two
+peaks for weak RA and only one for strong RA regardless of glassy critical
+dynamics manifested for them. We demonstrate that the thermodynamic nature of
+the low-temperature peak is a ferromagnetic-like dynamic phase transition to
+quasi-long range order (QLRO) for the former. Our simulation, therefore, is
+able to be incorporated with the experiments to help clarify the existence of
+the QLRO theoretically predicted so far.",0911.2352v1
+2009-11-20,On Chern-Simons corrections to magnetohydrodynamics equations,"We study the effect of a (3+1)-dimensional Chern-Simons electrodynamics on
+the equations governing the dynamics of magnetized plasma and fields. In this
+model, the Chern-Simons (CS) part consists of a dynamical pseudo-scalar field
+whose space-time derivatives couple with the electromagnetic field. We explore
+the CS corrections to the evolution equation for the magnetic field in a plasma
+with non-zero electrical resistivity. We revisit Cowling's theorem in this
+context and observe that the CS corrections lead to possibly small but non-zero
+source terms for axisymmetric magnetic field. The scalar product of electric
+and magnetic fields play the role of source of the pseudo-scalar field, and
+therefore, pulsars and magnetars are likely astrophysical candidates to
+generate propagating pseudo-scalar waves. Although aligned electric field gets
+shorted out by flowing charges in large parts of the magnetosphere, there are
+vacuum gaps in the vicinity of pulsars where strong $\vec E. \vec B$ is
+expected to be present. We derive a wave solution for the pseudo-scalar field
+generated by the time-varying $\vec E. \vec B$ associated with a pulsar.",0911.3967v1
+2009-11-27,Multiple vortex-antivortex pair generation in magnetic nanodots,"The interaction of a magnetic vortex with a rotating magnetic field causes
+the nucleation of a vortex--antivortex pair leading to a vortex polarity
+switching. The key point of this process is the creation of a dip, which can be
+interpreted as a nonlinear resonance in the system of certain magnon modes with
+nonlinear coupling. The usually observed single-dip structure is a particular
+case of a multidip structure. The dynamics of the structure with $n$ dips is
+described as the dynamics of nonlinearly coupled modes with azimuthal numbers
+$m=0,\pm n,\pm 2n$. The multidip structure with arbitrary number of vortex
+antivortex pairs can be obtained in vortex-state nanodisk using a space- and
+time-varying magnetic field. A scheme of a possible experimental setup for
+multidip structure generation is proposed.",0911.5353v2
+2009-12-01,Trapping ultracold dysprosium: a highly magnetic gas for dipolar physics,"Ultracold dysprosium gases, with a magnetic moment ten times that of alkali
+atoms and equal only to terbium as the most magnetic atom, are expected to
+exhibit a multitude of fascinating collisional dynamics and quantum dipolar
+phases, including quantum liquid crystal physics. We report the first laser
+cooling and trapping of half a billion Dy atoms using a repumper-free
+magneto-optical trap (MOT) and continuously loaded magnetic confinement, and we
+characterize the trap recycling dynamics for bosonic and fermionic isotopes.
+The first inelastic collision measurements in the few partial wave, 100 uK to 1
+mK, regime are made in a system possessing a submerged open electronic f-shell.
+In addition, we observe unusual stripes of intra-MOT <10 uK sub-Doppler cooled
+atoms.",0912.0050v3
+2010-05-12,Parametric amplification of matter waves in dipolar spinor Bose-Einstein condensates,"Spin-changing collisions may lead under proper conditions to the parametric
+amplification of matter waves in spinor Bose-Einstein condensates. Magnetic
+dipole-dipole interactions, although typically very weak in alkaline atoms, are
+shown to play a very relevant role in the amplification process. We show that
+these interactions may lead to a strong dependence of the amplification
+dynamics on the angle between the trap axis and the magnetic-field orientation.
+We analyze as well the important role played by magnetic-field gradients, which
+modify also strongly the amplification process. Magnetic-field gradients must
+be hence carefully controlled in future experiments, in order to observe
+clearly the effects of the dipolar interactions in the amplification dynamics.",1005.2011v1
+2010-05-12,Ca II K Spectral Study of an Emerging Flux Region using Domeless Solar Telescope in Hida Observatory,"A cooperative observation with Hida observatory and Hinode satellite was
+performed on an emerging flux region. The successive Ca II K spectro-heliograms
+of the emerging flux region were taken by the Domeless Solar Telescope of Hida
+observatory. Hinode observed the emerging flux region with Ca II H and Fe I
+Stokes IQUV filtergrams. In this study, detailed dynamics and temporal
+evolution of the magnetic flux emergence was studied observationally. The event
+was first detected in the photospheric magnetic field signals. 3 minutes later,
+the horizontal expansion of the dark area was detected. And then, 7 minutes
+later than the horizontal expansion, the emerging loops were detected with the
+maximal rise speed of 2.1 km/s at chromospheric heights. The observed dynamics
+of emerging magnetic flux from the photosphere to the upper chromosphere is
+well consistent with the results of previous simulation works. The gradual
+rising phase of flux tubes with a weak magnetic strength was confirmed by our
+observation.",1005.2025v1
+2010-06-08,Linear-Temperature Dependence of Static Magnetic Susceptibility in LaFeAsO from Dynamical Mean-Field Theory,"In this Letter we report the LDA+DMFT (method combining Local Density
+Approximation with Dynamical Mean-Field Theory) results for magnetic properties
+of parent superconductor LaFeAsO in paramagnetic phase. Calculated uniform
+magnetic susceptibility shows linear dependence at intermediate temperatures in
+agreement with experimental data. For high temperatures ($>$1000 K)
+calculations show saturation and then susceptibility decreases with
+temperature. Contributions to temperature dependence of the uniform
+susceptibility are strongly orbitally dependent. It is related to the form of
+the orbitally-resolved spectral functions near the Fermi energy with strong
+temperature dependent narrow peaks for some of the orbitals. Our results
+demonstrate that linear-temperature dependence of static magnetic
+susceptibility in pnictide superconductors can be reproduced without invoking
+antiferromagnetic fluctuations.",1006.1509v2
+2010-07-02,Interaction of a Nanomagnet with a Weak Superconducting Link,"We study electromagnetic interaction of a nanomagnet with a weak
+superconducting link. Equations that govern coupled dynamics of the two systems
+are derived and investigated numerically. We show that the presence of a small
+magnet in the proximity of a weak link may be detected through Shapiro-like
+steps caused by the precession of the magnetic moment. Despite very weak
+magnetic field generated by the weak link, a time-dependent bias voltage
+applied to the link can initiate a non-linear dynamics of the nanomagnet that
+leads to the reversal of its magnetic moment. We also consider quantum problem
+in which a nanomagnet interacting with a weak link is treated as a two-state
+spin system due to quantum tunneling between spin-up and spin-down states.",1007.0416v2
+2010-07-20,Evidence for Dynamically Important Magnetic Fields in Molecular Clouds,"Recent observational evidence that magnetic fields are dynamically important
+in molecular clouds, compared to self-gravity and turbulence, is reviewed and
+illustrated with data from the NGC 2024 region. One piece of evidence,
+turbulence anisotropy, was found in the diffuse envelope of a cloud (Av~1;
+Heyer et al. 2008); our data further suggests turbulence anisotropy in the
+cloud (Av >7) and even near the cloud core (Av~100). The data also shows that
+magnetic fields can channel gravitational contraction even for a region with
+super-critical N(H2)/2Blos ratio (the ratio between the observed column density
+and two times the line-of-sight observed field strength), a parameter which has
+been widely used by observers to estimate core mass-to-flux ratios. Although
+the mass-to-flux ratio is constant under the flux-freezing condition, we show
+that N(H2)/2Blos grows with time if gravitational contraction is anisotropic
+due to magnetic fields.",1007.3312v2
+2010-07-22,Theory of the power spectrum of spin-torque nanocontact vortex oscillators,"Spin-transfer torques in magnetic nanocontacts can lead to self-sustained
+magnetization oscillations that involve large-amplitude gyrotropic vortex
+motion. This dynamics consists of a steady state orbit around the nanocontact,
+which is made possible because the intrinsic magnetic damping is compensated by
+spin torques. In this article, we present an analytical theory of the power
+spectrum of these oscillations based on a rigid-vortex model. The appearance of
+vortex oscillations in nanocontacts is not associated with a Hopf bifurcation:
+there is no critical current and the only precondition for steady-state
+oscillations at finite currents is the existence of a vortex in the system, in
+contrast with conventional spin-torque oscillators that involve large-angle
+magnetization precession. The oscillation frequency is found to depend linearly
+on the applied current and inversely proportional to the orbital radius. By
+solving the associated Langevin problem for the vortex dynamics, the lineshape
+and linewidth for the power spectrum are also obtained. Under typical
+experimental conditions, a Lorentzian lineshape with a current-independent
+linewidth is predicted. Good quantitative agreement between the theory and
+recent experiments is shown.",1007.3859v1
+2010-09-22,Temperature- and Magnetic-Field-Dependent Optical Properties of Heavy Quasiparticles in YbIr2Si2,"We report the temperature- and magnetic-field-dependent optical conductivity
+spectra of the heavy electron metal YbIr$_2$Si$_2$. Upon cooling below the
+Kondo temperature ($T_{\rm K}$), we observed a typical charge dynamics that is
+expected for a formation of a coherent heavy quasiparticle state. We obtained a
+good fitting of the Drude weight of the heavy quasiparticles by applying a
+modified Drude formula with a photon energy dependence of the quasiparticle
+scattering rate that shows a similar power-law behavior as the temperature
+dependence of the electrical resistivity. By applying a magnetic field of 6T
+below $T_{\rm K}$, we found a weakening of the effective dynamical mass
+enhancement by about 12% in agreement with the expected decrease of the
+$4f$-conduction electron hybridization on magnetic field.",1009.4290v2
+2010-11-01,Decay of trefoil and other magnetic knots,"Two setups with interlocked magnetic flux tubes are used to study the
+evolution of magnetic energy and helicity on magnetohydrodynamical (MHD)
+systems like plasmas. In one setup the initial helicity is zero while in the
+other it is finite. To see if it is the actual linking or merely the helicity
+content that influences the dynamics of the system we also consider a setup
+with unlinked field lines as well as a field configuration in the shape of a
+trefoil knot. For helical systems the decay of magnetic energy is slowed down
+by the helicity which decays slowly. It turns out that it is the helicity
+content, rather than the actual linking, that is significant for the dynamics.",1011.0417v3
+2010-12-13,"Comment on paper by L. M. Malyshkin and S. Boldyrev, ""Magnetic dynamo action at low magnetic Prandtl numbers"", PRL 105, 215002 (2010)","Is the scaling, \lambda \sim Rm^{1/2}, for the growth rate of small-scale
+dynamo instability at low magnetic Prandtl numbers and large magnetic Reynolds
+numbers, Rm, valid in the vicinity of the threshold? Our analysis and even
+numerical solution (Malyshkin and Boldyrev, 2010) of the dynamo equations for a
+Gaussian white-noise velocity field (the Kazantsev-Kraichnan model) imply that
+the answer is negative. Contrary to the claim by Malyshkin and Boldyrev (2010),
+there are two different asymptotics for the dynamo growth rate: in the vicinity
+of the threshold and far from the threshold.",1012.2773v1
+2010-12-14,Constraints on the Galactic Magnetic Field from the Canadian Galactic Plane Survey,"The Galactic magnetic field is important in the dynamics of our Galaxy. It is
+believed to play a role in star formation and influence the structure of the
+Galaxy. In order to understand how the Galactic magnetic field originally
+formed or how it is evolving, we must first determine its present topology. To
+this end, we have used observations from the Canadian Galactic Plane Survey
+(CGPS) to calculate the highest source density of rotation measures (RM) to
+date in the disk of the Galaxy. Using these data, we estimate the Galactic
+longitude of the RM null point in the outer Galaxy (where the RMs of
+extragalactic sources are observed to pass through zero, on average, with
+increasing Galactic longitude). We have also examined the RM scale height using
+the CGPS latitude extension. The values of these parameters offer critical
+constraints for modeling the large-scale magnetic field in the Galactic disk.",1012.2934v1
+2011-01-10,Dynamical Signatures of Edge-State Magnetism on Graphene Nanoribbons,"We investigate the edge-state magnetism of graphene nanoribbons using
+projective quantum Monte Carlo simulations and a self-consistent mean-field
+approximation of the Hubbard model. The static magnetic correlations are found
+to be short ranged. Nevertheless, the correlation length increases with the
+width of the ribbon such that already for ribbons of moderate widths we observe
+a strong trend towards mean-field-type ferromagnetic correlations at a zigzag
+edge. These correlations are accompanied by a dominant low-energy peak in the
+local spectral function and we propose that this can be used to detect
+edge-state magnetism by scanning tunneling microscopy. The dynamic spin
+structure factor at the edge of a ribbon exhibits an approximately linearly
+dispersing collective magnonlike mode at low energies that decays into Stoner
+modes beyond the energy scale where it merges into the particle-hole continuum.",1101.1882v2
+2011-03-08,Slow dynamics of interacting antiferromagnetic nanoparticles,"We study magnetic relaxation dynamics, memory and aging effects in
+interacting polydisperse antiferromagnetic NiO nanoparticles by solving a
+master equation using a two-state model. We investigate the effects of
+interactions using dipolar, Nearest-Neighbour Short-Range (NNSR) and Long-Range
+Mean-Field (LRMF) interactions. The magnetic relaxation of the nanoparticles in
+a time-dependent magnetic field has been studied using LRMF interaction. The
+size-dependent effects are suppressed in the ac-susceptibility, as the
+frequency is increased. We find that the memory dip, that quantifies the memory
+effect is about the same as that of non-interacting nanoparticles for the NNSR
+case. There is a stronger memory-dip for LRMF, and a weaker memory-dip for the
+dipolar interactions. We have also shown a memory effect in the
+Zero-field-cooled magnetization for the dipolar case, a signature of glassy
+behaviour, from Monte-Carlo studies.",1103.1667v1
+2011-03-19,Magnetic dynamics of single domain Ni nanoparticles,"The dynamic magnetic properties of Ni nanoparticles diluted in an amorphous
+SiO2 matrix prepared from a modified sol-gel method have been studied by the
+frequency f dependence of the ac magnetic susceptibility \c{hi}(T). For samples
+with similar average radii ~ 3-4 nm, an increase of the blocking temperature
+from TB ~ 20 to ~ 40 K was observed for Ni concentrations of ~ 1.5 and 5 wt.%,
+respectively, assigned to the effects of dipolar interactions. Both the
+in-phase \c{hi}'(T) and the out-of-phase \c{hi}""(T) maxima follow the
+predictions of the thermally activated N\'eel-Arrhenius model. The effective
+magnetic anisotropy constant Keff inferred from \c{hi}""(T) versus f data for
+the 1.5 wt.% Ni sample is close to the value of the magnetocrystalline
+anisotropy of bulk Ni, suggesting that surface effects are negligible in the
+present samples. In addition, the contribution from dipolar interactions to the
+total anisotropy energy Ea in specimens with 5 wt.% Ni was found to be
+comparable to the intrinsic magnetocrystalline anisotropy barrier.",1103.3783v1
+2011-04-18,Entanglement dynamics of one-dimensional driven spin systems in time-varying magnetic fields,"We study the dynamics of entanglement for a one-dimensional spin chain with a
+nearest neighbor time dependent Heisenberg coupling J(t) between the spins in
+presence of a time dependent external magnetic field h(t) at zero and finite
+temperatures. We consider different forms of time dependence for the coupling
+and magnetic field; exponential, hyperbolic and periodic. We examined the
+system size effect on the entanglement asymptotic value. It was found that for
+a small system size the entanglement starts to fluctuate within a short period
+of time after applying the time dependent coupling. The period of time
+increases as the system size increases and disappears completely as the size
+goes to infinity. We also found that when J(t) is periodic the entanglement
+shows a periodic behavior with the same period, which disappears upon applying
+periodic magnetic field with the same frequency. Solving the particular case
+where J(t) and h(t) are proportional exactly, we showed that the asymptotic
+value of entanglement depends only on the initial conditions regardless of the
+form of J(t) and h(t) applied at t > 0.",1104.3521v1
+2011-05-06,Chiral transition in a magnetic field and at finite baryon density,"We consider the quark-meson model with two quark flavors in a constant
+external magnetic field $B$ at finite temperature $T$ and finite baryon
+chemical potential $\mu_B$. We calculate the full renormalized effective
+potential to one-loop order in perturbation theory. We study the system in the
+large-$N_c$ limit, where we treat the bosonic modes at tree level. It is shown
+that the system exhibits dynamical chiral symmetry breaking, i. e. that an
+arbitrarily weak magnetic field breaks chiral symmetry dynamically, in
+agreement with earlier calculations using the NJL model. We study the influence
+on the phase transition of the fermionic vacuum fluctuations. For strong
+magnetic fields, $|qB|\sim5m_{\pi}^2$ and in the chiral limit, the transition
+is first order in the entire $\mu_B-T$ plane if vacuum fluctuations are not
+included and second order if they are included. At the physical point, the
+transition is a crossover for $\mu_B=0$ with and without vacuum fluctuations.",1105.1290v3
+2011-08-30,Residual energy in magnetohydrodynamic turbulence and in the solar wind,"Recent observations indicate that kinetic and magnetic energies are not in
+equipartition in the solar wind turbulence. Rather, magnetic fluctuations are
+more energetic and have somewhat steeper energy spectrum compared to the
+velocity fluctuations. This leads to the presence of the so-called residual
+energy E_r=E_v-E_b in the inertial interval of turbulence. This puzzling effect
+is addressed in the present paper in the framework of weak turbulence theory.
+Using a simple model of weakly colliding Alfv\'en waves, we demonstrate that
+the kinetic-magnetic equipartition indeed gets broken as a result of nonlinear
+interaction of Alfv\'en waves. We establish that magnetic energy is indeed
+generated more efficiently as a result of these interactions, which proposes an
+explanation for the solar wind observations.",1108.6072v1
+2011-09-02,Angle-resolved NMR: quantitative theory of 75As T1 relaxation rate in BaFe2As2,"While NMR measurements of nuclear energy spectra are routinely used to
+characterize the static properties of quantum magnets, the dynamical
+information locked in NMR 1/T1 relaxation rates remains notoriously difficult
+to interpret. The difficulty arises from the fact that information about all
+possible low-energy spin excitations of the electrons, and their coupling to
+the nuclear moments, is folded into a single number, 1/T1. Here we develop a
+quantitative theory of the NMR 1/T1 relaxation rate in a collinear
+antiferromagnet, focusing on the specific example of BaFe2As2. One of the most
+striking features of magnetism in BaFe2As2 is a strong dependence of 1/T1 on
+the orientation of the applied magnetic field. By careful analysis of the
+coupling between the nuclear and electronic moments, we show how this
+anisotropy arises from the ""filtering"" of spin fluctuations by the form-factor
+for transferred hyperfine interactions. This allows us to make convincing,
+quantitative, fits to experimental 1/T1 data for BaFe2As2, for different field
+orientations. We go on to show how a quantitative, angle-dependent theory for
+the relaxation rate leads to new ways of measuring the dynamical parameters of
+magnetic systems, in particular the spin wave velocities.",1109.0384v2
+2011-10-24,Pressure balance at the magnetopause: Experimental studies,"The pressure balance at the magnetopause is formed by magnetic field and
+plasma in the magnetosheath, on one side, and inside the magnetosphere, on the
+other side. In the approach of dipole earth's magnetic field configuration and
+gas-dynamics solar wind flowing around the magnetosphere, the pressure balance
+predicts that the magnetopause distance R depends on solar wind dynamic
+pressure Pd as a power low R ~ Pd^alpha, where the exponent alpha=-1/6. In the
+real magnetosphere the magnetic filed is contributed by additional sources:
+Chapman-Ferraro current system, field-aligned currents, tail current, and
+storm-time ring current. Net contribution of those sources depends on
+particular magnetospheric region and varies with solar wind conditions and
+geomagnetic activity. As a result, the parameters of pressure balance,
+including power index alpha, depend on both the local position at the
+magnetopause and geomagnetic activity. In addition, the pressure balance can be
+affected by a non-linear transfer of the solar wind energy to the
+magnetosheath, especially for quasi-radial regime of the subsolar bow shock
+formation proper for the interplanetary magnetic field vector aligned with the
+solar wind plasma flow.",1110.5209v1
+2011-10-24,Dynamically configurable and optimizable Zeeman slower using permanent magnets and servomotors,"We report on the implementation of a dynamically configurable, servomotor-
+controlled, permanent magnet Zeeman slower for quantum optics experiments with
+ultracold atoms and molecules. This atom slower allows for switching between
+magnetic field profiles that are designed for different atomic species.
+Additionally, through feedback on the atom trapping rate, we demonstrate that
+computer-controlled genetic optimization algorithms applied to the magnet
+positions can be used in situ to obtain field profiles that maximize the
+trapping rate for any given experimental conditions. The device is lightweight,
+remotely controlled, and consumes no power in steady state; it is a step toward
+automated control of quantum optics experiments.",1110.5351v2
+2011-11-28,Structural and magnetic dynamics of a laser induced phase transition in FeRh,"We use time-resolved x-ray diffraction and magnetic optical Kerr effect to
+study the laser induced antiferromagnetic to ferromagnetic phase transition in
+FeRh. The structural response is given by the nucleation of independent
+ferromagnetic domains (\tau_1 ~ 30ps). This is significantly faster than the
+magnetic response (\tau_2 ~ 60ps) given by the subsequent domain realignment.
+X-ray diffraction shows that the two phases co-exist on short time-scales and
+that the phase transition is limited by the speed of sound. A nucleation model
+describing both the structural and magnetic dynamics is presented.",1111.6435v2
+2011-12-05,Phase transitions of quasistationary states in the Hamiltonian Mean Field model,"The out-of-equilibrium dynamics of the Hamiltonian Mean Field (HMF) model is
+studied in presence of an externally imposed magnetic field h. Lynden-Bell's
+theory of violent relaxation is revisited and shown to adequately capture the
+system dynamics, as revealed by direct Vlasov based numerical simulations in
+the limit of vanishing field. This includes the existence of an
+out-of-equilibrium phase transition separating magnetized and non magnetized
+phases. We also monitor the fluctuations in time of the magnetization, which
+allows us to elaborate on the choice of the correct order parameter when
+challenging the performance of Lynden-Bell's theory. The presence of the field
+h removes the phase transition, as it happens at equilibrium. Moreover, regions
+with negative susceptibility are numerically found to occur, in agreement with
+the predictions of the theory.",1112.1101v1
+2011-12-20,Magnetic catalysis with massive dynamical flavours,"Within gauge/gravity duality, we construct a backreacted supergravity
+background dual to SU(Nc) N=4 SYM coupled to Nf massive fundamental flavours in
+the presence of an external magnetic field. Our solution is perturbative in a
+parameter that counts the number of the internal flavour loops. The background
+has a hollow cavity in the bulk of the geometry, where it is similar to the
+supergravity dual of a non-commutative SYM. The radius of this cavity is
+related to the dynamically generated mass of the fundamental fields. We apply
+our construction to study the effect of magnetic catalysis and develop an
+appropriate renormalization scheme to compute the free energy and the
+fundamental condensate of the dual gauge theory as a function of the bare mass.
+While at leading order in the expansion of the perturbative parameter, the free
+energy and the fundamental condensate agree with the results obtained in the
+quenched approximation, at next order we show that the effect of magnetic
+catalysis is enhanced and the contribution to the condensate of the theory from
+internal fundamental loops runs logarithmically with the finite cutoff
+Lambda_UV.",1112.4807v1
+2012-01-04,Quasiparticles of string solutions in the spin-1/2 antiferromagnetic Heisenberg chain in a magnetic field,"Spectral properties of the spin-1/2 antiferromagnetic Heisenberg chain in a
+magnetic field are investigated by using exact Bethe-ansatz solutions. We argue
+that not only quasiparticles called psinon and antipsinon but also a
+quasiparticle representing a 2-string in the Bethe ansatz plays an important
+role for dynamical properties in a magnetic field. Combined with psinon and
+antipsinon, the quasiparticle for a 2-string forms a continuum in the
+high-energy regime for transverse dynamical structure factor
+$S^{+-}(k,\omega)$. In the zero-field limit, the continuum is located on the
+mode of the lowest excited states in zero field called the des
+Cloizeaux-Pearson mode. In a magnetic field, the continuum separates from other
+low-energy continua, and reduces to the mode of bound states of overturned
+spins from the fully polarized state near the saturation field. We confirm the
+relevance through comparisons with available experimental results on the
+quasi-one-dimensional antiferromagnet CuCl$_2\cdot$2N(C$_5$D$_5$).",1201.0844v1
+2012-01-04,Low-temperature magnetization in geometrically frustrated Tb2Ti2O7,"The nature of the low temperature ground state of the pyrochlore compound
+Tb2Ti2O7 remains a puzzling issue. Dynamic fluctuations and short-range
+correlations persist down to 50 mK, as evidenced by microscopic probes. In
+parallel, magnetization measurements show irreversibilities and glassy behavior
+below 200 mK. We have performed magnetization and AC susceptibility
+measurements on four single crystals down to 57 mK. We did not observe a clear
+plateau in the magnetization as a function of field along the [111] direction,
+as suggested by the quantum spin ice model. In addition to a freezing around
+200 mK, slow dynamics are observed in the AC susceptibility up to 4 K. The
+overall frequency dependence cannot be described by a canonical spin-glass
+behavior.",1201.0859v2
+2012-01-20,Lagrangian chaos in an ABC--forced nonlinear dynamo,"The Lagrangian properties of the velocity field in a magnetized fluid are
+studied using three-dimensional simulations of a helical magnetohydrodynamic
+dynamo. We compute the attracting and repelling Lagrangian coherent structures,
+which are dynamic lines and surfaces in the velocity field that delineate
+particle transport in flows with chaotic streamlines and act as transport
+barriers. Two dynamo regimes are explored, one with a robust coherent mean
+magnetic field and one with intermittent bursts of magnetic energy. The
+Lagrangian coherent structures and the statistics of finite--time Lyapunov
+exponents indicate that the stirring/mixing properties of the velocity field
+decay as a linear function of the magnetic energy. The relevance of this study
+for the solar dynamo problem is discussed.",1201.4324v1
+2012-02-10,The Chern-Simons diffusion rate in strongly coupled N=4 SYM plasma in an external magnetic field,"We calculate the Chern-Simons diffusion rate in a strongly coupled N=4 SUSY
+Yang-Mills plasma in the presence of a constant external $U(1)_R$ magnetic flux
+via the holographic correspondence. Due to the strong interactions between the
+charged fields and non-Abelian gauge fields, the external Abelian magnetic
+field affects the thermal Yang-Mills dynamics and increases the diffusion rate,
+regardless of its strength. We obtain the analytic results for the Chern-Simons
+diffusion rate both in the weak and strong magnetic field limits. In the latter
+limit, we show that the diffusion rate scales as $B\times T^2$ and this can be
+understood as a result of a dynamical dimensional reduction.",1202.2161v2
+2012-03-05,Frequency generation by a magnetic vortex-antivortex dipole in spin-polarized current,"A vortex-antivortex (VA) dipole may be generated due to a spin-polarized
+current flowing through a nano-aperture in a magnetic element. We study the
+vortex dipole dynamics using the Landau-Lifshitz equation in the presence of an
+in-plane applied magnetic field and a Slonczewski spin-torque term with
+in-plane polarization. We establish that the vortex dipole is set in steady
+state rotational motion. The frequency of rotation is due to two independent
+forces: the interaction between the two vortices and the external magnetic
+field. The nonzero skyrmion number of the dipole is responsible for both forces
+giving rise to rotational dynamics. The spin-torque acts to stabilize the
+vortex dipole motion at a definite vortex-antivortex separation distance. We
+give analytical and numerical results for the angular frequency of rotation and
+VA dipole features as functions of the parameters.",1203.0880v1
+2012-05-29,Thermally-Assisted Spin-Transfer Torque Magnetization Reversal in Uniaxial Nanomagnets,"We simulate the stochastic Landau-Lifshitz-Gilbert (LLG) dynamics of a
+uniaxial nanomagnet out to sub-millisecond timescales using a graphical
+processing unit based micromagnetic code and determine the effect of
+geometrical tilts between the spin-current and uniaxial anisotropy axes on the
+thermally assisted reversal dynamics. The asymptotic behavior of the switching
+time ($I\rightarrow 0$, $<\tau>\propto\exp(-\xi(1-I)^2)$) is approached
+gradually, indicating a broad crossover regime between ballistic and thermally
+assisted spin transfer reversal. Interestingly, the mean switching time is
+shown to be nearly independent of the angle between the spin current and
+magnet's uniaxial axes. These results have important implications for modeling
+the energetics of thermally assisted magnetization reversal of spin transfer
+magnetic random access memory bit cells.",1205.6509v1
+2012-08-31,Cosmological Ohm's law and dynamics of non-minimal electromagnetism,"The origin of large-scale magnetic fields in cosmic structures and the
+intergalactic medium is still poorly understood. We explore the effects of
+non-minimal couplings of electromagnetism on the cosmological evolution of
+currents and magnetic fields. In this context, we revisit the mildly non-linear
+plasma dynamics around recombination that are known to generate weak magnetic
+fields. We use the covariant approach to obtain a fully general and non-linear
+evolution equation for the plasma currents and derive a generalised Ohm law
+valid on large scales as well as in the presence of non-minimal couplings to
+cosmological (pseudo-)scalar fields. Due to the sizeable conductivity of the
+plasma and the stringent observational bounds on such couplings, we conclude
+that modifications of the standard (adiabatic) evolution of magnetic fields are
+severely limited in these scenarios. Even at scales well beyond a Mpc, any
+departure from flux freezing behaviour is inhibited.",1208.6547v2
+2012-09-21,Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillars,"Broadband magnetization response of coupled vortex state magnetic dots in
+layered nanopillars was explored as a function of in-plane magnetic field and
+interlayer separation. For dipolarly coupled circular Py(25 nm)/Cu(20 nm)/Py(25
+nm) nanopillars of 600 nm diameter, a small in-plane field splits the
+eigenfrequencies of azimuthal spin wave modes inducing an abrupt transition
+between in-phase and out-of-phase kinds of the low-lying coupled spin wave
+modes. The critical field for this splitting is determined by antiparallel
+chiralities of the vortices in the layers. Qualitatively similar (although more
+gradual) changes occur also in the exchange coupled Py(25 nm)/Cu(1 nm)/Py(25
+nm) tri-layer nanopillars. These findings are in qualitative agreement with
+micromagnetic dynamic simulations.",1209.4822v1
+2012-10-23,Averaged equation for energy diffusion on a graph reveals bifurcation diagram and thermally assisted reversal times in spin-torque driven nanomagnets,"Driving nanomagnets by spin-polarized currents offers exciting prospects in
+magnetoelectronics, but the response of the magnets to such currents remains
+poorly understood. We show that an averaged equation describing the diffusion
+of energy on a graph captures the low-damping dynamics of these systems. From
+this equation we obtain the bifurcation diagram of the magnets, including the
+critical currents to induce stable precessional states and magnetization
+switching, as well as the mean times of thermally assisted magnetization
+reversal in situations where the standard reaction rate theory of Kramers is no
+longer valid. These results match experimental observations and give a
+theoretical basis for a N\'eel-Brown-type formula with an effective energy
+barrier for the reversal times.",1210.6253v3
+2012-11-26,Low temperature dynamic freezing and the fragility of ordering in Tb2Sn2O7,"We have probed the low temperature magnetic behavior of the ordered spin ice
+material Tb2Sn2O7 through ac magnetic susceptibility measurements of both the
+pure material and samples with small percentages of Ti substituted on the Sn
+sublattice. We observe a clear signature for the previously reported ordering
+transition at TC = 850 mK, as well as evidence for dynamic freezing at
+temperatures well below TC, confirming the persistence of significant magnetic
+fluctuations deep in the spin-ordered regime. The long range ordering
+transition was completely suppressed with as little as 5% Ti for Sn
+substitution, and 10% Ti substitution resulted in a spin-glass-like spin
+freezing transition near 250 mK. The results demonstrate that the long range
+magnetic ordering is surprisingly fragile in this system.",1211.6047v1
+2012-12-13,Real-time MOKE microscopy made simple,"We present a simple and effective instrument for simultaneous real-time
+imaging and hysteresis of the anisotropic magnetic domain dynamics in thin
+films using the Magneto-Optical Kerr Effect (MOKE). We furthermore illustrate
+that magnetic imaging allows a more accurate interpretation of the
+magnetization reversal processes than the conventional hysteresis
+characterization. In particular, we present a case where the onset of a
+double-step reversal observed in imaging remains invisible in the spatially
+integrated hysteresis loops. When complemented by precise tuning of the
+external magnetic field orientation, our system reveals the singular
+anisotropic variations of the domain dynamics near the hard-axis in epitaxial
+thin films, thus shedding light on the reported, but as yet unexplained, hard
+axis coercivity behavior.",1212.3259v1
+2012-12-31,Forced MHD turbulence in three dimensions using Taylor-Green symmetries,"We examine the scaling laws of MHD turbulence for three different types of
+forcing functions and imposing at all times the four-fold symmetries of the
+Taylor-Green (TG) vortex generalized to MHD; no uniform magnetic field is
+present and the magnetic Prandtl number is equal to unity. We also include a
+forcing in the induction equation, and we take the three configurations studied
+in the decaying case in [E. Lee et al. Phys. Rev.E {\bf 81}, 016318 (2010)]. To
+that effect, we employ direct numerical simulations up to an equivalent
+resolution of $2048^3$ grid points. We find that, similarly to the case when
+the forcing is absent, different spectral indices for the total energy spectrum
+emerge, corresponding to either a Kolmogorov law, an Iroshnikov-Kraichnan law
+that arises from the interactions of turbulent eddies and Alfv\'en waves, or to
+weak turbulence when the large-scale magnetic field is strong. We also examine
+the inertial range dynamics in terms of the ratios of kinetic to magnetic
+energy, and of the turn-over time to the Alfv\'en time, and analyze the
+temporal variations of these quasi-equilibria.",1212.6902v2
+2013-02-01,Vortex mechanics in planar nano-magnets,"A collective-variable approach for the study of non-linear dynamics of
+magnetic textures in planar nano-magnets is proposed. The variables are just
+arbitrary parameters (complex or real) in the specified analytical function of
+a complex variable, describing the texture in motion. Starting with such a
+function, a formal procedure is outlined, allowing a (non-linear) system of
+differential equations of motion to be obtained for the variables. The
+resulting equations are equivalent to Landau-Lifshitz-Gilbert dynamics as far
+as the definition of collective variables allows it. Apart from the
+collective-variable specification, the procedure does not involve any
+additional assumptions (such as translational invariance or steady-state
+motion). As an example, the equations of weakly non-linear motion of a magnetic
+vortex are derived and solved analytically. A simple formula for the dependence
+of the vortex precession frequency on its amplitude is derived. The results are
+verified against special cases from the literature and agree quantitatively
+with experiments and simulations.",1302.0222v3
+2013-03-02,Two-band effect on the vortex dynamics and critical current density in an anisotropic MgB$_2$ thin film,"We report the influence of intrinsic superconducting parameters on the vortex
+dynamics and the critical current densities of a MgB$_2$ thin film. The small
+magnetic penetration depth of \lambda = 50 nm at T=4 K is related to a clean
+\pi-band, and transport and magnetization data show an upper critical field
+similar to those reported in clean single crystals. We find a high self-field
+critical current density Jc, which is strongly reduced with applied magnetic
+field, and attribute this to suppression of the superconductivity in the
+\pi-band. The temperature dependence of the creep rate S(T) at low magnetic
+field can be explained by a simple Anderson-Kim mechanism. The system shows
+high pinning energies at low field that are strongly suppressed by high field,
+which is consistent with a two-band contribution.",1303.0352v1
+2013-05-16,Topics in microphysics of relativistic plasmas,"Astrophysical plasmas can have parameters vastly different from the more
+studied laboratory and space plasmas. In particular, the magnetic fields can be
+the dominant component of the plasma, with energy-density exceeding the
+particle rest-mass energy density. Magnetic fields then determine the plasma
+dynamical evolution, energy dissipation and acceleration of non-thermal
+particles. Recent data coming from astrophysical high energy missions, like
+magnetar bursts and Crab nebula flares, point to the importance of magnetic
+reconnection in these objects.
+  In this review we outline a broad spectrum of problems related to the
+astrophysical relevant processes in magnetically dominated relativistic
+plasmas. We discuss the problems of large scale dynamics of relativistic
+plasmas, relativistic reconnection and particle acceleration at reconnecting
+layers, turbulent cascade in force-fee plasmas. A number of astrophysical
+applications are also discussed.",1305.3838v1
+2013-06-12,Non-equilibrium quantum magnetism in a dipolar lattice gas,"Research on quantum magnetism with ultra-cold gases in optical lattices is
+expected to open fascinating perspectives for the understanding of fundamental
+problems in condensed-matter physics. Here we report on the first realization
+of quantum magnetism using a degenerate dipolar gas in an optical lattice. In
+contrast to their non-dipolar counterparts, dipolar lattice gases allow for
+inter-site spin-spin interactions without relying on super-exchange energies,
+which constitutes a great advantage for the study of spin lattice models. In
+this paper we show that a chromium gas in a 3D lattice realizes a lattice model
+resembling the celebrated t-J model, which is characterized by a
+non-equilibrium spinor dynamics resulting from inter-site Heisenberg-like
+spin-spin interactions provided by non-local dipole-dipole interactions.
+Moreover, due to its large spin, chromium lattice gases constitute an excellent
+environment for the study of quantum magnetism of high-spin systems, as
+illustrated by the complex spin dynamics observed for doubly-occupied sites.",1306.2754v2
+2013-07-23,Engineering Weyl nodes in Dirac semimetals by a magnetic field,"We study the phase diagram of a Dirac semimetal in a magnetic field at a
+nonzero charge density. It is shown that there exists a critical value of the
+chemical potential at which a first-order phase transition takes place. At
+subcritical values of the chemical potential the ground state is a gapped state
+with a dynamically generated Dirac mass and a broken chiral symmetry. The
+supercritical phase is the normal (gapless) phase with a nontrivial chiral
+structure: it is a Weyl semimetal with a pair of Weyl nodes for each of the
+original Dirac points. The nodes are separated by a dynamically induced chiral
+shift. The direction of the chiral shift coincides with that of the magnetic
+field and its magnitude is determined by the quasiparticle charge density, the
+strength of the magnetic field, and the strength of the interaction. The
+rearrangement of the Fermi surface accompanying this phase transition is
+described.",1307.6230v2
+2013-07-25,Geometrical crossover in two-body systems in a magnetic field,"An algebraic approach is formulated in the harmonic approximation to describe
+a dynamics of two-fermion systems, confined in three-dimensional axially
+symmetric parabolic potential, in an external magnetic field. The fermion
+interaction is considered in the form U_(M)(r)= alpha_(M)r^{-M} (alpha_(M)>0,
+M>0). The formalism of a semi-simple Lie group is applied to analyse symmetries
+of the considered system. Explicit algebraic expressions are derived in terms
+of system's parameters and the magnetic field strength to trace the evolution
+of the equilibrium shape. It is predicted that the interplay of classical and
+quantum correlations may lead to a quantum shape transition from a lateral to a
+vertical localization of fermions in the confined system. The analytical
+results demonstrate a good agreement with numerical results for two-electron
+quantum dots in the magnetic field, when classical correlations dominate in the
+dynamics.",1307.6833v2
+2013-09-14,Electric-field induced domain-wall dynamics: depinning and chirality switching,"We theoretically study the equilibrium and dynamic properties of nanoscale
+magnetic tunnel junctions (MTJs) and magnetic wires, in which an electric field
+controls the magnetic anisotropy through spin-orbit coupling. By performing
+micromagnetic simulations, we construct a rich phase diagram and find that, in
+particular, the equilibrium magnetic textures can be tuned between Neel and
+Bloch domain walls in an elliptical MTJ. Furthermore, we develop a
+phenomenological model of a quasi-one-dimensional domain wall confined by a
+parabolic potential and show that, near the Neel-to-Bloch-wall transition, a
+pulsed electric field induces precessional domain-wall motion which can be used
+to reverse the chirality of a Neel wall and even depin it. This domain-wall
+motion controlled by electric fields, in lieu of applied current, may provide a
+model for ultra-low-power domain-wall memory and logic devices.",1309.3693v1
+2013-10-09,Chargeless spin current for switching and coupling of domain walls in magnetic nanowires,"The demonstration of the generation and control of a pure spin current
+(without net charge flow) by electric fields and/or temperature gradient has
+been an essential leap in the quest for low-power consumption electronics. The
+key issue of whether and how such a current can be utilized to drive and
+control information stored in magnetic domain walls (DWs) is still outstanding
+and is addressed here. We demonstrate that pure spin current acts on DWs in a
+magnetic stripe with an effective spin-transfer torque resulting in a mutual
+DWs separation dynamics and picosecond magnetization reversal. In addition,
+long-range ($\sim$ mm) antiferromagnetic DWs coupling emerges. If one DW is
+pinned by geometric constriction, the spin current induces a dynamical spin
+orbital interaction that triggers an internal electric field determined by
+$\vec{E} \sim \hat{e}_{x} \cdot (\vec{n}_{1} \times \vec{n}_{2})$ where
+$\vec{n}_{1/2}$ are the effective DWs orientations and $\hat{e}_{x} $ is their
+spatial separation vector. This leads to charge accumulation or persistent
+electric current in the wire. As DWs are routinely realizable and tuneable, the
+predicted effects bear genuine potential for power-saving spintronics devices.",1310.2331v1
+2013-12-05,Zero modes in magnetic systems: general theory and an efficient computational scheme,"The presence of topological defects in magnetic media often leads to normal
+modes with zero frequency (zero modes). Such modes are crucial for long-time
+behavior, describing, for example, the motion of a domain wall as a whole.
+Conventional numerical methods to calculate the spin-wave spectrum in magnetic
+media are either inefficient or they fail for systems with zero modes. We
+present a new efficient computational scheme that reduces the magnetic
+normal-mode problem to a generalized Hermitian eigenvalue problem also in the
+presence of zero modes. We apply our scheme to several examples, including
+two-dimensional domain walls and Skyrmions, and show how the effective masses
+that determine the dynamics can be calculated directly. These systems highlight
+the fundamental distinction between the two types of zero modes that can occur
+in spin systems, which we call special and inertial zero modes. Our method is
+suitable for both conservative and dissipative systems. For the latter case, we
+present a perturbative scheme to take into account damping, which can also be
+used to calculate dynamical susceptibilities.",1312.1503v1
+2013-12-19,Deconfinement transition in two-flavour lattice QCD with dynamical overlap fermions in an external magnetic field,"We study the influence of an external magnetic field on the deconfinement
+transition in two-flavour lattice QCD with physical quark charges. We use
+dynamical overlap fermions without any approximation such as fixed topology and
+perform simulations on a $16^3 \times 6$ lattice and at a pion mass around
+$500MeV$. The pion mass (as well as the lattice spacing) was determined in
+independent runs on $12^3 \times 24$ lattices. We consider two temperatures,
+one of which is close to the deconfinement transition and one which is above.
+Within our limited statistics the dependence of the Polyakov loop and chiral
+condensate on the magnetic field supports the ""inverse magnetic catalysis""
+scenario in which the transition temperature decreases as the field strength
+grows for temperature not to far above the critical temperature.",1312.5628v2
+2013-12-24,Two driven coupled qubits in a time varying magnetic field: exact and approximate solutions,"We study the dynamics of a two-qubit system coupled through time dependent
+anisotropic $XYZ$ Heisenberg interaction in presence of a time varying
+non-uniform external magnetic field. Exact results are presented for the time
+evolution of the system under certain integrability conditions. Furthermore,
+the corresponding entanglement of the system is studied for different values of
+the involved parameters. We found that the time evolution and different
+properties of entanglement such as amplitude, frequency and profile can be
+finely tuned by the interplay of the characteristics of the time-dependent
+magnetic field and exchange coupling. Also we show how the discrete symmetries
+of the system Hamiltonian, which splits its Hilbert space into two distinct
+subspaces, can be utilized to deduce the dynamics in one of its two distinct
+subspaces from the other one. Moreover, approximate results for the time
+evolution are provided utilizing the rotating wave as well as the perturbation
+approximations for the special case of either static magnetic field or exchange
+coupling. We compare the range of validity of the two approximation methods and
+their effectiveness in treating the considered system and determine their
+critical parameters.",1312.6883v1
+2014-01-17,Exact scattering matrix of graphs in magnetic field and quantum noise,"We consider arbitrary quantum wire networks modelled by finite, noncompact,
+connected quantum graphs in the presence of an external magnetic field.
+  We find a general formula for the total scattering matrix of the network in
+terms of its local scattering properties and its metric structure. This is
+applied to a quantum ring with $N$ external edges. Connecting the external
+edges of the ring to heat reservoirs, we study the quantum transport on the
+graph in ambient magnetic field. We consider two types of dynamics on the ring:
+the free Schr\""odinger and the free massless Dirac equations. For each case, a
+detailed study of the thermal noise is performed analytically.
+  Interestingly enough, in presence of a magnetic field, the standard linear
+Johnson-Nyquist law for the low temperature behaviour of the thermal noise
+becomes nonlinear. The precise regime of validity of this effect is discussed
+and a typical signature of the underlying dynamics is observed.",1401.4967v1
+2014-04-17,Wave packet dynamics in monolayer MoS$_2$ with and without a magnetic field,"We study the dynamics of electrons in monolayer Molybdenum Disulfide
+(MoS$_2$), in the absence as well as presence of a transverse magnetic field.
+Considering the initial electronic wave function to be a Gaussian wave packet,
+we calculate the time dependent expectation value of position and velocity
+operators. In the absence of the magnetic field, the time dependent average
+values of position and velocity show damped oscillations dependent on the width
+of the wave packet. In the presence of a transverse magnetic field, the wave
+packet amplitude shows oscillatory behaviour over short timescales associated
+with classical cyclotron orbit, followed by the phenomena of spontaneous
+collapse and revival over larger timescales. We relate the timescales of these
+effects and our results can be useful for the interpretation of experiments
+with trapped ions.",1404.4534v2
+2014-05-22,Giant magnetoelectric effect in magnetic tunnel junctions coupled to an electromagnetic environment,"We study the magnetization dynamics in
+ferromagnet$\mid$insulator$\mid$ferromagnet and
+ferromagnet$\mid$insulator$\mid$normal metal ultra-small tunnel junctions, and
+the associated voltage drop in the presence of an electromagnetic environment
+assisting the tunneling processes. We show that the environment strongly
+affects the resulting voltage, which becomes a highly non-linear function of
+the precession cone angle $\theta$. We find that voltages comparable to the
+driving frequency $\omega$ can be reached even for small precession cone angles
+$\theta$, in stark contrast to the case where the environment is absent. Such
+an effect could be useful for the detection local magnetization precessions in
+textured ferromagnets or, conversely, for probing the environment via the
+magnetization dynamics.",1405.5744v2
+2014-05-26,Structural and Magnetic Dynamics in the Magnetic Shape Memory Alloy Ni$_2$MnGa,"Magnetic shape memory Heusler alloys are multiferroics stabilized by the
+correlations between electronic, magnetic and structural order. To study these
+correlations we use time resolved x-ray diffraction and magneto-optical Kerr
+effect experiments to measure the laser induced dynamics in a Heusler alloy
+Ni$_2$MnGa film and reveal a set of timescales intrinsic to the system. We
+observe a coherent phonon which we identify as the amplitudon of the modulated
+structure and an ultrafast phase transition leading to a quenching of the
+incommensurate modulation within 300~fs with a recovery time of a few ps. The
+thermally driven martensitic transition to the high temperature cubic phase
+proceeds via nucleation within a few ps and domain growth limited by the speed
+of sound. The demagnetization time is 320~fs, which is comparable to the
+quenching of the structural modulation.",1405.6534v1
+2014-10-16,Nonlinear dynamics of Josephson vortices in a film screen under dc and ac magnetic fields,"We present detailed numerical simulations of Josephson vortices in a long
+Josephson junction perpendicular to a thin film screen under strong dc and ac
+magnetic fields. By solving the sine-Gordon equation, we calculated the
+threshold magnetic field for penetration of fluxons as a function of frequency,
+and the power dissipated by oscillating fluxons as functions of the ac field
+amplitude and frequency. We considered the effects of superimposed ac and dc
+fields, and a bi-harmonic magnetic field resulting in a vortex ratchet
+dynamics. The results were used to evaluate the contribution of weak-linked
+grain boundaries to the nonlinear surface resistance of polycrystalline
+superconductors under strong electromagnetic fields, particularly thin film
+screens and resonator cavities.",1410.4606v1
+2014-11-03,Curvature effects in statics and dynamics of low dimensional magnets,"We develop an approach to treat magnetic energy of a ferromagnet for
+arbitrary curved wires and shells on the assumption that the anisotropy
+contribution much exceeds the dipolar and other weak interactions. We show that
+the curvature induces two effective magnetic interactions: effective magnetic
+anisotropy and effective Dzyaloshinskii-like interaction. We derive an equation
+of magnetisation dynamics and propose a general static solution for the limit
+case of strong anisotropy. To illustrate our approach we consider the
+magnetisation structure in a ring wire and a cone surface: ground states in
+both systems essentially depend on the curvature excluding strictly tangential
+solutions even in the case of strong anisotropy. We derive also the spectrum of
+spin waves in such systems.",1411.0646v2
+2014-11-12,Quantum magnetism and topological ordering via enhanced Rydberg-dressing near Förster-resonances,"We devise a cold-atom approach to realizing a broad range of bi-linear
+quantum magnets. Our scheme is based on off-resonant single-photon excitation
+of Rydberg $P$-states (Rydberg-dressing), whose strong interactions are shown
+to yield controllable XYZ-interactions between effective spins, represented by
+different atomic ground states. The distinctive features of F\""orster-resonant
+Rydberg atom interactions are exploited to enhance the effectiveness of
+Rydberg-dressing and, thereby, yield large spin-interactions that greatly
+exceed corresponding decoherence rates. We illustrate the concept on a spin-1
+chain implemented with cold Rubidium atoms, and demonstrate that this permits
+the dynamical preparation of topological magnetic phases. Generally, the
+described approach provides a viable route to exploring quantum magnetism with
+dynamically tuneable (an)isotropic interactions as well as variable space- and
+spin-dimensions in cold-atom experiments.",1411.3118v2
+2014-11-19,Thermally driven classical Heisenberg chain with a spatially varying magnetic field: Thermal rectification and Negative differential thermal resistance,"Thermal rectification and negative differential thermal resistance are two
+important features that have direct technological relevance. In this paper, we
+study the classical one dimensional Heisenberg model, thermally driven by heat
+baths attached at the two ends of the system, and in presence of an external
+magnetic field that varies monotonically in space. Heat conduction in this
+system is studied using a local energy conserving dynamics. It is found that,
+by suitably tuning the spatially varying magnetic field, the homogeneous
+symmetric system exhibits both thermal rectification and negative differential
+thermal resistance. Thermal rectification, in some parameter ranges, shows
+interesting dependences on the average temperature T and the system size N -
+rectification improves as T and N is increased. Using the microscopic dynamics
+of the spins we present a physical picture to explain the features observed in
+rectification as exhibited by this system and provide supporting numerical
+evidences. Emergence of NDTR in this system can be controlled by tuning the
+external magnetic field alone which can have possible applications in the
+fabrication of thermal devices.",1411.5200v1
+2015-02-20,Magneto-Plasmonics and Resonant Interaction of Light with Dynamic Magnetisation in Metallic and All-Dielectric Nanostructures (Review),"A significant interest in combining plasmonics and magnetism at the nanoscale
+gains momentum in both photonics and magnetism sectors that are concerned with
+the resonant enhancement of light-magnetic-matter interaction in
+nanostructures. These efforts result in a considerable amount of literature,
+which is difficult to collect and digest in limited time. Furthermore, there is
+insufficient exchange of results between the two research sectors.
+Consequently, the goal of this review paper is to bridge this gap by presenting
+an overview of recent progress in the field of magneto-plasmonics from two
+different points of view: magneto-plasmonics, and magnonics and magnetisation
+dynamics. It is expected that this presentation style will make this review
+paper of particular interest to both general physical audience and specialists
+conducting research on photonics, plasmonics, Brillouin light scattering
+spectroscopy of magnetic nanostructures and magneto-optical Kerr effect
+magnetometry, as well as ultrafast all-optical and THz-wave excitation of spin
+waves. Moreover, readers interested in a new, rapidly emerging field of
+all-dielectric nanophotonics will find a section about all-magneto-dielectric
+nanostructures.",1502.05783v1
+2015-02-25,Magnetic Flux Dynamics in Horizontally Cooled Superconducting Cavities,"Previous studies on magnetic flux expulsion as a function of cooling details
+have been performed for superconducting niobium cavities with the cavity beam
+axis placed parallel respect to the helium cooling flow, and findings showed
+that for sufficient cooling thermogradients all magnetic flux could be expelled
+and very low residual resistance could be achieved. In this paper we
+investigate the flux trapping and its impact on radio frequency surface
+resistance when the resonators are positioned perpendicularly to the helium
+cooling flow, which is representative of how superconducting radio-frequency
+(SRF) cavities are cooled in an accelerator. We also extend the studies to
+different directions of applied magnetic field surrounding the resonator.
+Results show that in the cavity horizontal configuration there is a different
+impact of the various field components on the final surface resistance, and
+that several parameters have to be considered to understand flux dynamics. A
+newly discovered phenomenon of concentration of flux lines at the cavity top
+leading to cavity equator temperature rise is presented.",1502.07291v3
+2015-03-10,Microwave-induced dynamic switching of magnetic skyrmion cores in nanodots,"The nonlinear dynamic behavior of a magnetic skyrmion in circular nanodots
+was studied numerically by solving the Landau-Lifshitz-Gilbert equation with a
+classical spin model. We show that a skyrmion core reversal can be achieved
+within nanoseconds using a perpendicular oscillating magnetic field. Two
+symmetric switching processes that correspond to excitations of the breathing
+mode and the mixed mode (combination of the breathing mode and a radial
+spin-wave mode) are identified. For excitation of the breathing mode, the
+skyrmion core switches through nucleation of a new core from a transient
+uniform state. In the mixed mode, the skyrmion core reverses with the help of
+spins excited both at the edge and core regions. Unlike the magnetic vortex
+core reversal, the excitation of radial spin waves does not dominate the
+skyrmion core reversal process.",1503.02869v1
+2015-04-30,Optical diode effect in the room-temperature multiferroic BiFeO$_3,"Multiferroics permit the magnetic control of the electric polarization and
+electric control of the magnetization. These static magnetoelectric (ME)
+effects are of enormous interest: The ability to read and write a magnetic
+state current-free by an electric voltage would provide a huge technological
+advantage. Dynamic or optical ME effects are equally interesting because they
+give rise to unidirectional light propagation as recently observed in
+low-temperature multiferroics. This phenomenon, if realized at room
+temperature, would allow the development of optical diodes which transmit
+unpolarized light in one, but not in the opposite direction. Here, we report
+strong unidirectional transmission in the room-temperature multiferroic
+BiFeO$_3$ over the gigahertz--terahertz frequency range. Supporting theory
+attributes the observed unidirectional transmission to the spin-current driven
+dynamic ME effect. These findings are an important step toward the realization
+of optical diodes, supplemented by the ability to switch the transmission
+direction with a magnetic or electric field.",1505.00033v1
+2015-06-08,Demagnetization dynamics of non-interacting trapped fermions,"Motivated by several experimental efforts to understand spin diffusion and
+transport in ultracold fermionic gases, we study the spin dynamics of initially
+spin-polarized ensembles of harmonically trapped non-interacting spin-1/2
+fermionic atoms, subjected to a magnetic field gradient. We obtain simple
+analytic expressions for spin observables in the presence of both constant and
+linear magnetic field gradients, with and without a spin-echo pulse, and at
+zero and finite temperatures. The analysis shows the relevance of spin-motional
+coupling in the non-interacting regime where the demagnetization decay rate at
+short times can be faster than the experimentally measured rates in the
+strongly interacting regime under similar trapping conditions. Our calculations
+also show that particle motion limits the ability of a spin-echo pulse to
+remove the effect of magnetic field inhomogeneity, and that a spin-echo pulse
+can instead lead to an increased decay of magnetization at times comparable to
+the trapping period.",1506.02353v1
+2015-06-15,Detection of topological states in two-dimensional Dirac systems by the dynamic spin susceptibility,"We discuss dynamic spin susceptibility (DSS) in two-dimensional (2D) Dirac
+electrons with spin-orbit interactions to characterize topological insulators.
+The imaginary part of the DSS appears as an absorption rate in response to a
+transverse ac magnetic field, just as in an electron spin resonance experiment
+for localized spin systems. We found that when the system is in a static
+magnetic field, the topological state can be identified by an anomalous
+resonant peak of the imaginary part of the DSS as a function of the frequency
+of the transverse magnetic field $\omega$. In the absence of a static magnetic
+field, the imaginary part of the DSS becomes a continuous function of $\omega$
+with a threshold frequency $\omega_{\rm c}$. In this case, the topological and
+the trivial phases can also be distinguished by the values of $\omega_{\rm c}$
+and by the line shapes. Thus the DSS is an experimentally observable physical
+quantity to characterize a topological insulator directly from bulk properties,
+without observing a topological transition.",1506.04691v2
+2015-09-11,Comparison between a quantum kinetic theory of spin transfer dynamics in Mn doped bulk semiconductors and its Markov limit for non-zero Mn magnetization,"We investigate the transfer between carrier and Mn spins due to the
+s-d-exchange interaction in a Mn doped bulk semiconductor within a microscopic
+quantum kinetic theory. We demonstrate that the spin transfer dynamics is
+qualitatively different for components of the carrier spin parallel and
+perpendicular to the Mn magnetization. From our quantum kinetic equations we
+have worked out the corresponding Markov limit which is equivalent to rate
+equations based on Fermi's golden rule. The resulting equations resemble the
+widely used Landau-Lifshitz-Gilbert-equations, but also describe genuine spin
+transfer due to quantum corrections. Although it is known that the Markovian
+rate description works well for bulk systems when the initial Mn magnetization
+is zero, we find large qualitative deviations from the full quantum kinetic
+theory for finite initial Mn magnetizations. These deviations mainly reflect
+corrections of higher than leading order in the interaction which are not
+accounted for in golden rule-type rates.",1509.03479v1
+2015-10-02,Evidence for unidimensional low-energy excitations as the origin of persistent spin dynamics in geometrically frustrated magnets,"We report specific heat, magnetic, and muon spin relaxation measurements
+performed on a polycrystalline sample of the normal spinel CdHo2S4. The
+rare-earth ions sit on a lattice of corner-sharing regular tetrahedra as in
+pyrochlore compounds. Magnetic ordering is detected at Tc ~ 0.87 K. From
+spin-lattice relaxation rate measurements on both sides of Tc we uncover
+similar magnetic excitation modes driving the so-called persistent spin
+dynamics at T < Tc. Unidimensional excitations are argued to be at its origin.
+Often observed spin loop structures are suggested to support these excitations.
+The possibility of a generic mechanism for their existence is discussed.",1510.00544v1
+2015-10-20,Nonaxisymmetric linear instability of cylindrical magnetohydrodynamic Taylor-Couette flow,"We consider the nonaxisymmetric modes of instability present in
+Taylor-Couette flow under the application of helical magnetic fields, mainly
+for magnetic Prandtl numbers close to the inductionless limit, and conduct a
+full examination of marginal stability in the resulting parameter space. We
+allow for the azimuthal magnetic field to be generated by a combination of
+currents in the inner cylinder and fluid itself, and introduce a parameter
+governing the relation between the strength of these currents. A set of
+governing eigenvalue equations for the nonaxisymmetric modes of instability are
+derived and solved by spectral collocation with Chebyshev polynomials over the
+relevant parameter space, with the resulting instabilities examined in detail.
+We find that by altering the azimuthal magnetic field profiles the azimuthal
+magnetorotational instability, nonaxisymmetric helical magnetorotational
+instability, and Tayler instability yield interesting dynamics, such as
+different preferred mode types, and modes with azimuthal wave number $m>1$.
+Finally, a comparison is given to the recent WKB analysis performed by Kirillov
+$et$ $al$. [Kirillov, Stefani, and Fukumoto, J. Fluid Mech. 760, 591 (2014)]
+and its validity in the linear regime.",1510.05932v1
+2015-11-25,Three-dimensional magnetic cloak working from DC to 250 kHz,"Invisible cloaking is one of major outcomes of the metamaterial research, but
+the practical potential, in particular for high frequencies (e.g., microwave to
+visible light), is fatally challenged by the complex material properties they
+usually demand. On the other hand, it will be advantageous and also
+technologically instrumental to design cloaking devices for applications at low
+frequencies where electromagnetic components are favorably uncoupled. In this
+work, we vastly develop the bilayer approach to create a three-dimensional
+magnetic cloak able to work in both static and dynamic fields. Under the
+quasi-static approximation, we demonstrate a perfect magnetic cloaking device
+with a large frequency band from zero to 250 kHz. The practical potential of
+our device is experimentally verified by using a commercial metal detector,
+which may lead us to having a real cloaking application where the dynamic
+magnetic field can be manipulated in desired ways.",1511.08005v1
+2015-12-01,Competition of static magnetic and dynamic photon forces in electronic transport through a quantum dot,"We investigate theoretically the balance of the static magnetic and the
+dynamical photon forces in the electron transport through a quantum dot in a
+photon cavity with a single photon mode. The quantum dot system is connected to
+external leads and the total system is exposed to a static perpendicular
+magnetic field. We explore the transport characteristics through the system by
+tuning the ratio, $\hbar\omega_{\gamma} / \hbar\omega_c$, between the photon
+energy, $\hbar\omega_{\gamma}$, and the cyclotron energy, $\hbar\omega_c$.
+Enhancement in the electron transport with increasing electron-photon coupling
+is observed when $\hbar\omega_{\gamma} / \hbar\omega_c > 1$. In this case the
+photon field dominates and stretches the electron charge distribution in the
+quantum dot, extending it towards the contacts area for the leads. Suppression
+in the electron transport is found when $\hbar\omega_{\gamma} / \hbar\omega_c <
+1$, as the external magnetic field causes circular confinement of the charge
+density around the dot.",1512.00392v1
+2016-01-07,Driving Skyrmions on a Composite Multiferroic Lattice,"Magnetic skyrmions and multiferroics are the most interesting objects in
+nanostructure science that have great potential in future spin-electronic
+technology. The study of the multiferroic skyrmions has attracted much interest
+in recent years. This paper reports on the magnetic skyrmions induced by an
+electric driving field on a composite multiferroic lattice. By using the spin
+dynamics method, we use a classical magnetic spin model and an electric
+pseudospin model, which are coupled by a strong magnetoelectric coupling in the
+dynamical simulations. Interestingly, we observe some skyrmion-like objects on
+the electric component during the switching process, which is due to the
+connection between the electric and the magnetic structures.",1601.01383v1
+2016-02-03,Dynamic Error in Strain Induced Magnetization Reversal of Nanomagnets due to Incoherent Switching and Formation of Metastable States: A Size-dependent Study,"Modulation of stress anisotropy of magnetostrictive nanomagnets with strain
+offers an extremely energy-efficient method of magnetization reversal. The
+reversal process, however, is often incoherent and hence error-prone in the
+presence of thermal noise at room temperature. Occurrence of incoherent
+metastable states in the potential landscape of the nanomagnet can further
+exacerbate the error. Stochastic micromagnetic simulations at room temperature
+are used to understand and calculate energy dissipations and switching error
+probabilities in this important magnetization switching methodology. We find
+that these quantities have an intriguing dependence on nanomagnet size: small
+nanomagnets perform better owing to the fact that they are more resilient to
+the formation of metastable states and magnetization dynamics in them is more
+coherent. However, for a fixed stress anisotropy energy density, smaller
+nanomagnets will also have poorer resilience against thermal instability. Thus,
+the challenge in straintronics is to maximize the stress anisotropy energy
+density by developing materials and processes that yield the largest
+magnetostriction.",1602.01491v2
+2016-02-12,Mass Effect on Axial Charge Dynamics,"We studied effect of finite quark mass on the dynamics of axial charge using
+the D3/D7 model in holography. The mass term in axial anomaly equation affects
+both the fluctuation (generation) and dissipation of axial charge. We studied
+the dependence of the effect on quark mass and external magnetic field. For
+axial charge generation, we calculated the mass diffusion rate, which
+characterizes the helicity flipping rate. The rate is a non-monotonous function
+of mass and can be significantly enhanced by the magnetic field. The diffusive
+behavior is also related to a divergent susceptibility of axial charge. For
+axial charge dissipation, we found that in the long time limit, the mass term
+dissipates all the charge effectively generated by parallel electric and
+magnetic fields. The result is consistent with a relaxation time approximation.
+The rate of dissipation through mass term is a monotonous increasing function
+of both quark mass and magnetic field.",1602.03952v2
+2016-02-25,Orbital magnetism of ultracold fermionic gases in a lattice: dynamical mean-field approach,"We study finite-temperature properties of ultracold four-component mixtures
+of alkaline-earth-like atoms in optical lattices that can be effectively
+described by the two-band spin-$1/2$ Hubbard model including the Hund's
+exchange coupling term. Our main goal is to investigate the effect of exchange
+interactions on finite-temperature magnetic phases for a wide range of lattice
+fillings. We use the dynamical mean-field theory approach and its real-space
+generalization to obtain finite-temperature phase diagrams including
+transitions to magnetically-ordered phases. It allows to determine optimal
+experimental regimes for approaching long-range ferromagnetic ordering in
+ultracold gases. We also calculate the entropy in the vicinity of
+magnetically-ordered phases, which provides quantitative predictions for
+on-going and future experiments aiming at approaching and studying long-range
+ordered states in optical lattices.",1602.08031v2
+2016-04-05,Domain wall-gated skyrmion logic,"Skyrmions and domain walls are typical spin textures of significant
+technological relevance to magnetic memory and logic applications, where they
+are used as carriers of information. The unique topology of skyrmions makes
+them to display distinct dynamical properties compared to domain walls. Some
+studies have demonstrated that the two topologically inequivalent magnetic
+objects could be interconverted by cleverly designed geometric structures.
+Here, we numerically address the skyrmion-domain wall collision in a magnetic
+racetrack by introducing relative motion between the two objects based on a
+specially designed junction. An electric current serves as the driving force
+that moves a skyrmion toward a trapped domain-wall pair. We observe different
+types of collision dynamics by changing the driving parameters. Most
+importantly, the domain wall modulation of skyrmion transport is realized in
+this system, allowing a set of domain wall-gated logical NOT, NAND, and NOR
+gates to be constructed. By providing a promising logic architecture that is
+fully compatible with racetrack memories, this work is expected to speed up the
+development of skyrmion-based magnetic computation.",1604.01310v1
+2016-04-22,First evidence for a Sm$^{3+}$-type contribution to the magnetic form factor in the quasielastic spectral response of intermediate valence SmB$_{6}$,"The momentum transfer dependence of the magnetic form factor associated with
+the quasielastic spectral component in the dynamic magnetic response of
+intermediate valence SmB$_{6}$ has been measured using inelastic neutron
+scattering on a double-isotope ($^{154}$Sm, $^{11}$B) single crystal. The
+experimental dependence differs qualitatively from those obtained earlier for
+the inelastic signals, as well as from the field-induced magnetic form factor
+of SmB$_{6}$ obtained by polarized neutron diffraction. This observation is
+interpreted by specifically considering the Curie-type contributions to the
+dynamic susceptibility, which arise from the mixing of 4f$^{5}$ and 4f$^{6}$
+J-multiplets into the intermediate valence state wave function.",1604.06717v1
+2016-05-07,Persistence of slow dynamics in Tb(OETAP)$_2$ single molecule magnets embedded in conducting polymers,"The spin dynamics of Tb(OETAP)$_2$ single ion magnets was investigated by
+means of muon spin resonance ($\mu$SR) both in the bulk material as well as
+when the system is embedded into PEDOT:PSS polymer conductor. The
+characteristic spin fluctuation time is characterized by a high temperature
+activated trend, with an energy barrier around 320 K, and by a low temperature
+tunneling regime. When the single ion magnet is embedded into the polymer the
+energy barrier only slightly decreases and the fluctuation time remains of the
+same order of magnitude even at low temperature. This finding shows that these
+single molecule magnets preserve their characteristics which, if combined with
+those of the conducting polymer, result in a hybrid material of potential
+interest for organic spintronics.",1605.02148v1
+2016-05-27,A reduced model for precessional switching of thin-film nanomagnets under the influence of spin-torque,"We study the magnetization dynamics of thin-film magnetic elements with
+in-plane magnetization subject to a spin-current flowing perpendicular to the
+film plane. We derive a reduced partial differential equation for the in-plane
+magnetization angle in a weakly damped regime. We then apply this model to
+study the experimentally relevant problem of switching of an elliptical element
+when the spin-polarization has a component perpendicular to the film plane,
+restricting the reduced model to a macrospin approximation. The macrospin
+ordinary differential equation is treated analytically as a weakly damped
+Hamiltonian system, and an orbit-averaging method is used to understand
+transitions in solution behaviors in terms of a discrete dynamical system. The
+predictions of our reduced model are compared to those of the full
+Landau--Lifshitz--Gilbert--Slonczewski equation for a macrospin.",1605.08698v1
+2016-05-31,Electric field control of magnon-induced magnetization dynamics in multiferroics,"We consider theoretically the effect of an inhomogeneous magnetoelectric
+coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated
+magnetoelectric torque affects both the homogeneous magnetization and
+magnon-driven domain wall motion. In the domains, we predict a reorientation of
+the magnetization, controllable by the applied electric field, which is almost
+an order of magnitude larger than that observed in other physical systems via
+the same mechanism. The applied electric field can also be used to tune the
+domain wall speed and direction of motion in a linear fashion, producing domain
+wall velocities several times the zero field velocity. These results show that
+multiferroic systems offer a promising arena to achieve low-dissipation
+magnetization rotation and domain wall motion by exciting spin-waves.",1606.00007v2
+2016-06-13,Dynamo generated by the centrifugal instability,"We present a new scenario for magnetic field amplification where an
+electrically conducting fluid is confined in a differentially rotating,
+spherical shell with thin aspect-ratio. When the angular momentum sufficiently
+decreases outwards, an hydrodynamic instability develops in the equatorial
+region, characterised by pairs of counter-rotating toroidal vortices similar to
+those observed in cylindrical Couette flow. These spherical Taylor-Couette
+vortices generate a subcritical dynamo magnetic field dominated by
+non-axisymmetric components. We show that the critical magnetic Reynolds number
+seems to reach a constant value at large Reynolds number and that the global
+rotation can strongly decrease the dynamo onset. Our numerical results are
+understood within the framework of a simple dynamical system, and we propose a
+low-dimensional model for subcritical dynamo bifurcations. Implications for
+both laboratory dynamos and astrophysical magnetic fields are finally
+discussed.",1606.04078v1
+2016-06-29,"Kinetics of local $""$magnetic$""$ moment and non-stationary spin-polarized current in the single impurity Anderson-model","We perform theoretical investigation of the localized state dynamics in the
+presence of interaction with the reservoir and Coulomb correlations. We analyze
+kinetic equations for electron occupation numbers with different spins taking
+into account high order correlation functions for the localized electrons. We
+reveal that in the stationary state electron occupation numbers with the
+opposite spins always have the same value - the stationary state is a
+$""$paramagnetic$""$ one. $""$Magnetic$""$ properties can appear only in the
+non-stationary characteristics of the single-impurity Anderson model and in the
+dynamics of the localized electrons second order correlation functions. We
+found, that for deep energy levels and strong Coulomb correlations, relaxation
+time for initial $""$magnetic$""$ state can be several orders larger than for
+$""$paramagnetic$""$ one. So, long-living $""$magnetic$""$ moment can exist in the
+system. We also found non-stationary spin polarized currents flowing in
+opposite directions for the different spins in the particular time interval.",1606.08975v1
+2016-07-29,Exchange interaction-driven dynamic nuclear polarization in Mn-doped InGaAs/GaAs quantum dots,"We investigated optical spin orientation and dynamic nuclear polarization
+(DNP) in individual self-assembled InGaAs/GaAs quantum dots (QDs) doped by a
+single Mn atom, a magnetic impurity providing a neutral acceptor A$^0$ with an
+effective spin $J=1$. We find that the spin of an electron photo-created in
+such a quantum dot can be efficiently oriented by a quasi-resonant
+circularly-polarized excitation. For the electron spin levels which are made
+quasi-degenerate by a magnetic field compensating the exchange interaction
+$\Delta_e$ with A$^0$, there is however a full depolarization due the
+anisotropic part of the exchange. Still, in most studied QDs, the spin
+polarized photo-electrons give rise to a pronounced DNP which grows with a
+longitudinal magnetic field until a critical field where it abruptly vanishes.
+For some QDs, several replica of such DNP sequence are observed at different
+magnetic fields. This striking behavior is qualitatively discussed as a
+consequence of different exchange interactions experienced by the electron,
+driving the DNP rate via the energy cost of electron-nucleus spin flip-flops.",1607.08870v2
+2016-08-29,Impurity effects on spin dynamics in magnetic and superconducting iron pnictides and chalcogenides,"In this paper we summarize the effects of magnetic and nonmagnetic impurities
+on the spin dynamics in Febased superconductors and their parent compounds. The
+effects of chemical substitution, vacancies, and disorder on the suppression or
+stabilization of superconductivity and spin-density-wave phases are reviewed in
+the context of recent neutron-spectroscopy measurements of spin excitations. We
+also present new results on the structure of magnetic fluctuations in BaFe2As2
+single crystals doped with Mn local moments and discuss them in relationship to
+the previously reported (pi, pi) branch of checkerboard magnetic excitations.",1608.08123v4
+2016-08-30,Quantum speed limit time in a magnetic resonance,"A visualization for dynamics of a qudit spin vector in a time-dependent
+magnetic field is realized by means of mapping a solution for a spin vector on
+the three-dimensional spherical curve (vector hodograph). The obtained results
+obviously display the quantum interference of precessional and nutational
+effects on the spin vector in the magnetic resonance. For any spin the bottom
+bounds of the quantum speed limit time (QSL) are found. It is shown that the
+bottom bound goes down when using multilevel spin systems. Under certain
+conditions the non-nil minimal time, which is necessary to achieve the
+orthogonal state from the initial one, is attained at spin S=2. An estimation
+of the product of two and three standard deviations of the spin components are
+presented. We discuss the dynamics of the mutual uncertainty, conditional
+uncertainty and conditional variance in terms of spin standard deviations. The
+study can find practical applications in the magnetic resonance, 3D
+visualization of computational data and in designing of optimized information
+processing devices for quantum computation and communication.",1608.08537v3
+2016-09-07,Cu nuclear magnetic resonance study of charge and spin stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$,"We present a Cu nuclear magnetic/quadrupole resonance study of the charge
+stripe ordered phase of LBCO, with detection of previously unobserved
+('wiped-out') signal. We show that spin-spin and spin-lattice relaxation rates
+are strongly enhanced in the charge ordered phase, explaining the apparent
+signal decrease in earlier investigations. The enhancement is caused by
+magnetic, rather than charge fluctuations, conclusively confirming the
+long-suspected assumption that spin fluctuations are responsible for the
+wipeout effect. Observation of the full Cu signal enables insight into the spin
+and charge dynamics of the stripe-ordered phase, and measurements in external
+magnetic fields provide information on the nature and suppression of spin
+fluctuations associated with charge order. We find glassy spin dynamics, in
+agreement with previous work, and incommensurate static charge order with
+charge modulation amplitude similar to other cuprate compounds, suggesting that
+the amplitude of charge stripes is universal in the cuprates.",1609.02162v1
+2016-09-12,Currentless reversal of Néel vector in antiferromagnets,"The bias driven perpendicular magnetic anisotropy is a magneto-electric
+effect that can realize 90$^\circ$ magnetization rotation and even 180$% ^\circ
+$ flip along the easy axis in the ferromagnets with a minimal energy
+consumption. This study theoretically demonstrates a similar phenomenon of the
+N\'{e}el vector reversal via a short electrical pulse that can mediate
+perpendicular magnetic anisotropy in the antiferromagnets. The analysis based
+on the dynamical equations as well as the micro-magnetic simulations reveals
+the important role of the inertial behavior in the antiferromagnets that
+facilitates the N\'{e}el vector to overcome the barrier between two free-energy
+minima of the bistable states along the easy axis. In contrast to the
+ferromagnets, this N\'{e}el vector reversal does not accompany angular moment
+transfer to the environment, leading to acceleration in the dynamical response
+by a few orders of magnitude. Further, a small switching energy requirement of
+a few attojoules illustrates an added advantage of the phenomenon in low-power
+spintronic applications.",1609.03454v2
+2016-09-26,Relativistic theory of spin relaxation mechanisms in the Landau-Lifshitz-Gilbert equation of spin dynamics,"Starting from the Dirac-Kohn-Sham equation we derive the relativistic
+equation of motion of spin angular momentum in a magnetic solid under an
+external electromagnetic field. This equation of motion can be written in the
+form of the well-known Landau-Lifshitz-Gilbert equation for a harmonic external
+magnetic field, and leads to a more general magnetization dynamics equation for
+a general time-dependent magnetic field. In both cases with an electronic
+spin-relaxation term which stems from the spin-orbit interaction. We thus
+rigorously derive, from fundamental principles, a general expression for the
+anisotropic damping tensor which is shown to contain an isotropic Gilbert
+contribution as well as an anisotropic Ising-like and a chiral,
+Dzyaloshinskii-Moriya-like contribution. The expression for the spin relaxation
+tensor comprises furthermore both electronic interband and intraband
+transitions. We also show that when the externally applied electromagnetic
+field possesses spin angular momentum, this will lead to an optical spin torque
+exerted on the spin moment.",1609.07901v1
+2016-11-03,Magnetic avalanches in granular ferromagnets: Thermal activated collective behavior,"We present a numerical study on the thermal activated avalanche dynamics in
+granular materials composed of ferromagnetic clusters embedded in a
+non-magnetic matrix. A microscopic dynamical simulation based on the
+reaction-diffusion process is developed to modeling the magnetization process
+of such systems. The large-scale simulations presented here explicitly
+demonstrate inter-granular collective behavior induced by thermal activation of
+spin tunneling. In particular, we observe an intriguing criticality controlled
+by the rate of energy dissipation. We show that thermal activated avalanches
+can be understood in the framework of continuum percolation and the emergent
+dissipation induced criticality is in the universality class of
+three-dimensional percolation transition. Implications of these results to the
+phase-separated states of colossal magnetoresistance materials and other
+artificial granular magnetic systems are also~discussed.",1611.01098v1
+2016-12-06,Quantum Dynamics of Skyrmions in Chiral Magnets,"We study the quantum propagation of a Skyrmion in chiral magnetic insulators
+by generalizing the micromagnetic equations of motion to a finite-temperature
+path integral formalism, using field theoretic tools. Promoting the center of
+the Skyrmion to a dynamic quantity, the fluctuations around the Skyrmionic
+configuration give rise to a time-dependent damping of the Skyrmion motion.
+From the frequency dependence of the damping kernel, we are able to identify
+the Skyrmion mass, thus providing a microscopic description of the kinematic
+properties of Skyrmions. When defects are present or a magnetic trap is
+applied, the Skyrmion mass acquires a finite value proportional to the
+effective spin, even at vanishingly small temperature. We demonstrate that a
+Skyrmion in a confined geometry provided by a magnetic trap behaves as a
+massive particle owing to its quasi-one-dimensional confinement. An additional
+quantum mass term is predicted, independent of the effective spin, with an
+explicit temperature dependence which remains finite even at zero temperature.",1612.01885v2
+2017-01-10,Capturing ultrafast magnetic dynamics by time-resolved soft x-ray magnetic circular dichroism,"Experiments of time-resolved x-ray magnetic circular dichroism (Tr-XMCD) and
+resonant x-ray scattering at a beamline BL07LSU in SPring-8 with a
+time-resolution of under 50 ps are presented. A micro-channel plate is utilized
+for the Tr-XMCD measurements at nearly normal incidence both in the partial
+electron and total fluorescence yield (PEY and TFY) modes at the L2,3
+absorption edges of the 3d transition-metals in the soft x-ray region. The
+ultrafast photo-induced demagnetization within 50 ps is observed on the
+dynamics of a magnetic material of FePt thin film, having a distinct threshold
+of the photon density. The spectrum in the PEY mode is less-distorted both at
+the L2,3 edges compared with that in the TFY mode and has the potential to
+apply the sum rule analysis for XMCD spectra in pump-probed experiments.",1701.03156v2
+2017-01-19,Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of Fe$_{1-x}$Co$_x$Si,"We present a comprehensive Small Angle Neutron Scattering (SANS) and Neutron
+Spin Echo Spectroscopy (NSE) study of the structural and dynamical aspects of
+the helimagnetic transition in Fe$_{1-x}$Co$_x$Si with $x$ = 0.30. In contrast
+to the sharp transition observed in the archetype chiral magnet MnSi, the
+transition in Fe$_{1-x}$Co$_x$Si is gradual and long-range helimagnetic
+ordering coexists with short-range correlations over a wide temperature range.
+The dynamics are more complex than in MnSi and involve long relaxation times
+with a stretched exponential relaxation which persists even under magnetic
+field. These results in conjunction with an analysis of the hierarchy of the
+relevant length scales show that the helimagnetic transition in
+Fe$_{1-x}$Co$_x$Si differs substantially from the transition in MnSi and
+question the validity of a universal approach to the helimagnetic transition in
+chiral magnets.",1701.05448v2
+2017-02-03,A dynamic analysis of magnetized plasma sheath in a collisionless scenario with ion sources,"In this paper, the central concern is to analyze the influence of the forces
+that controls the ion dynamics inside a magnetized plasma sheath under
+collisionless conditions. The ionization effects are considered within the
+sheath. The magnetic field is tilted in x-z plane and makes an angle with the
+x-axis. The motivation of the paper is to see the effect of both field strength
+variation and the variation of the inclination angle on the force fields inside
+the sheath. The pitch length and pitch angle for the particle velocity field is
+also calculated and has been found to vary widely with the inclination angle
+and the strength of the magnetic field. The role of the Lorentz force and
+energy acquired by the ions while moving towards the wall is highlighted. A
+comparison between two different ion sources has also been foregrounded.",1702.00944v2
+2017-03-22,Skyrmion dynamics in a frustrated ferromagnetic film and current-induced helicity locking-unlocking transition,"The helicity-orbital coupling is an intriguing feature of magnetic skyrmions
+in frustrated magnets. Here, we explore the skyrmion dynamics in a frustrated
+magnet based on the $J_{1}$-$J_{2}$-$J_{3}$ classical Heisenberg model
+explicitly by including the dipole-dipole interaction. The skyrmion energy
+acquires a helicity dependence due to the dipole-dipole interaction, resulting
+in the current-induced translational motion with a fixed helicity. The lowest
+energy states are the degenerate Bloch-type states, which can be used for
+building the binary memory. By increasing the driving current, the helicity
+locking-unlocking transition occurs, where the translational motion changes to
+the rotational motion. Furthermore, we demonstrate that two skyrmions can
+spontaneously form a bound state. The separation of the bound state forced by a
+driving current is also studied. In addition, we show the annihilation of a
+pair of skyrmion and antiskyrmion. Our results reveal the distinctive
+frustrated skyrmions may enable viable applications in topological magnetism.",1703.07501v3
+2017-04-13,Simulating chiral magnetic effect and anomalous transport phenomena in the pre-equilibrium stages of heavy-ion collisions,"We present a first principles approach to study the Chiral Magnetic Effect
+during the pre-equilibrium stage of a heavy-ion collision. We discuss the
+dynamics of the Chiral Magnetic Effect and Chiral Magnetic Wave based on
+real-time lattice simulations with dynamical (Wilson and Overlap) fermions
+simultaneously coupled to color and electromagnetic fields. While for light
+quarks we observe a dissipation-less transport of charges as in anomalous
+hydrodynamics, we demonstrate that for heavier quarks the effects of explicit
+chiral symmetry breaking lead to a significant reduction of the associated
+currents.",1704.05887v2
+2017-04-30,Modelling the Lagrangian of magnetized plasmas with low-frequency magnetic perturbations by a gyrokinetic Ampere-Poisson model,"Following the method in Ref.(1), this paper introduces a fundamental
+Lagrangian 1-form on the particle's coordinates, which determines the dynamics
+of all ions and electrons of the magnetized plasma with low-frequency magnetic
+perturbations. An Ampere-Vlasov model is utilized to model this fundamental
+Lagrangian 1-form based on a kind of coarse-grained scheme. With the
+Cary-Littlejohn single-parameter Lie transform method, a new fundamental
+Lagrangian 1-form on the gyrocenter coordinates is derived through transforming
+the one on particle's coordinates. This new 1-form determines the dynamics of
+all ions and electrons on the gyrocenter coordinates. A new Ampere-Vlasov model
+totally defined on the gyrocenter coordinates is developed to model the new
+Lagrangian 1-form. By incorporating the electrostatic perturbation into the
+Lagrangian 1-form, we eventually derived an Ampere-Poisson-Vlasov model defined
+on the gyrocenter coordinates.",1705.00282v1
+2017-05-11,Spin Dynamics and Magnetoelectric Coupling Mechanism of Co4Nb2O9,"Neutron powder diffraction experiments reveal that Co4Nb2O9 forms a
+noncollinear in-plane magnetic structure with Co2+ moments lying in the ab
+plane. The spin-wave excitations of this magnet were measured by using
+inelastic neutron scattering and soundly simulated by a dynamic model involving
+nearest and next-nearest neighbour exchange interactions, in-plane anisotropy
+and the Dzyaloshinskii-Moriya interaction. The in-plane magnetic structure of
+Co4Nb2O9 is attributed to the large in-plane anisotropy while the
+noncollinearity of the spin configuration is attributed to the
+Dzyaloshinskii-Moriya interaction. The high magnetoelectric coupling effect of
+Co4Nb2O9 in fields can be explained by its special in-plane magnetic structure.",1705.04017v3
+2017-05-16,Characterizing the ionospheric current pattern response to southward and northward IMF turnings with dynamical SuperMAG correlation networks,"We characterize the response of the quiet time (no substorms or storms)
+large-scale ionospheric transient equivalent currents to north-south and
+south-north IMF turnings by using a dynamical network of ground-based
+magnetometers. Canonical correlation between all pairs of SuperMAG magnetometer
+stations in the Northern Hemisphere (magnetic latitude (MLAT) 50-82$^{\circ}$)
+is used to establish the extent of near-simultaneous magnetic response between
+regions of magnetic local time-MLAT. Parameters and maps that describe
+spatial-temporal correlation are used to characterize the system and its
+response to the turnings aggregated over several hundred events. We find that
+regions that experience large increases in correlation post turning coincide
+with typical locations of a two-cell convection system and are influenced by
+the interplanetary magnetic field $\mathit{B}_{y}$. The time between the
+turnings reaching the magnetopause and a network response is found to be
+$\sim$8-10 min and correlation in the dayside occurs 2-8 min before that in the
+nightside.",1705.05698v1
+2017-05-16,How does an asymmetric magnetic field change the vertical structure of a hot accretion flow?,"This paper explores the effects of large-scale magnetic fields in hot
+accretion flows for asymmetric configurations with respect to the equatorial
+plane. The solutions that we have found show that the large-scale asymmetric
+magnetic field can significantly affect the dynamics of the flow and also cause
+notable outflows in the outer parts. Previously, we treated a viscous resistive
+accreting disc in the presence of an odd symmetric $\textbf{B-}$ field about
+the equatorial plane. Now we extend our earlier work by taking into account
+another configuration of large-scale magnetic field which is no longer
+symmetric. We provide asymmetric field structures with small deviations from
+even and odd symmetric $\textbf{B-}$field. Our results show that the disc's
+dynamics and appearance become different above and below the equatorial plane.
+The set of solutions also predicts that even a small deviation in a symmetric
+field causes the disc to compress on one side and expand on the other. In some
+cases, our solution represents a very strong outflow from just one side of the
+disc. Therefore, the solution may potentially explain the origin of one-sided
+jets in radio galaxies.",1705.07190v2
+2017-06-05,Dynamic anisotropy in MHD turbulence induced by mean magnetic field,"In this paper, we study the development of anisotropy in strong MHD
+turbulence in the presence of a large scale magnetic field B 0 by analyzing the
+results of direct numerical simulations. Our results show that the developed
+anisotropy among the different components of the velocity and magnetic field is
+a direct outcome of the inverse cascade of energy of the perpendicular velocity
+components u? and a forward cascade of the energy of the parallel component u k
+. The inverse cascade develops for a strong B0, where the flow exhibits a
+strong vortical structure by the suppression of fluctuations along the magnetic
+field. Both the inverse and the forward cascade are examined in detail by
+investigating the anisotropic energy spectra, the energy fluxes, and the shell
+to shell energy transfers among different scales.",1706.01250v2
+2017-06-09,Localization of a magnetic moment using a two-qubit probe,"A nanomagnet precessing in an external magnetic field can be treated as a
+source of narrow-bandwidth magnetic noise, that leaves characteristic
+fingerprints in decoherence of a nearby spin qubit undergoing dynamical
+decoupling. We show how, by measurements of two-qubit coherence, a noise sensor
+composed of qubit pair can be used to reconstruct the position of the
+nanomagnet. Such localization of noise source is possible with only two qubit
+probes, because the course of coherence decay under appropriately designed
+dynamical decoupling sequences contain information not only about noises
+experienced by each qubit, but also about their cross-correlations. We test the
+applicability of the proposed protocol on an example of two qubits coupled to
+the nanomagnet via dipolar interaction. We also show how, using a two-qubit
+sensor possessing a particular symmetry, one can localize the nanomagnet even
+when the sensor-magnet coupling law is unknown.",1706.02948v2
+2017-07-11,Putative spin liquid in the triangle-based iridate Ba$_3$IrTi$_2$O$_9$,"We report on thermodynamic, magnetization, and muon spin relaxation
+measurements of the strong spin-orbit coupled iridate Ba$_3$IrTi$_2$O$_9$,
+which constitutes a new frustration motif made up a mixture of edge- and
+corner-sharing triangles. In spite of strong antiferromagnetic exchange
+interaction of the order of 100~K, we find no hint for long-range magnetic
+order down to 23 mK. The magnetic specific heat data unveil the $T$-linear and
+-squared dependences at low temperatures below 1~K. At the respective
+temperatures, the zero-field muon spin relaxation features a persistent spin
+dynamics, indicative of unconventional low-energy excitations. A comparison to
+the $4d$ isostructural compound Ba$_3$RuTi$_2$O$_9$ suggests that a concerted
+interplay of compass-like magnetic interactions and frustrated geometry
+promotes a dynamically fluctuating state in a triangle-based iridate.",1707.03140v1
+2017-08-17,Front dynamics and entanglement in the XXZ chain with a gradient,"We consider the XXZ spin chain with a magnetic field gradient and study the
+profiles of the magnetization as well as the entanglement entropy. For a slowly
+varying field it is shown that, by means of a local density approximation, the
+ground-state magnetization profile can be obtained with standard Bethe ansatz
+techniques. Furthermore, it is argued that the low-energy description of the
+theory is given by a Luttinger liquid with slowly varying parameters. This
+allows us to obtain a very good approximation of the entanglement profile using
+a recently introduced technique of conformal field theory in curved spacetime.
+Finally, the front dynamics is also studied after the gradient field has been
+switched off, following arguments of generalized hydrodynamics for integrable
+systems. While for the XX chain the hydrodynamic solution can be found
+analytically, the XXZ case appears to be more complicated and the magnetization
+profiles are recovered only around the edge of the front via an approximate
+numerical solution.",1708.05187v2
+2017-08-29,Magnetic field generation by pointwise zero-helicity three-dimensional steady flow of incompressible electrically conducting fluid,"We introduce six families of three-dimensional space-periodic steady
+solenoidal flows, whose kinetic helicity density is zero at any point. Four
+families are analytically defined. Flows in four families have zero helicity
+spectrum. Sample flows from five families are used to demonstrate numerically
+that neither zero kinetic helicity density, nor zero helicity spectrum prohibit
+generation of large-scale magnetic field by the two most prominent dynamo
+mechanisms: the magnetic $\alpha$-effect and negative eddy diffusivity. Our
+computations also attest that such flows often generate small-scale field for
+sufficiently small magnetic molecular diffusivity. These findings indicate that
+kinetic helicity and helicity spectrum are not the quantities controlling the
+dynamo properties of a flow regardless of whether scale separation is present
+or not.",1708.08770v4
+2017-08-29,Element-resolved ultrafast demagnetization rates in ferrimagnetic CoDy,"Femtosecond laser induced ultrafast magnetization dynamics have been studied
+in multisublattice CoxDy1-x alloys. By performing element and time-resolved
+X-ray spectroscopy, we distinguish the ultrafast quenching of Co3d and Dy4f
+magnetic order when the initial temperatures are below (T=150K) or above
+(T=270K) the temperature of magnetic compensation (Tcomp). In accordance with
+former element-resolved investigations and theoretical calculations, we observe
+different dynamics for Co3d and Dy4f spins. In addition we observe that, for a
+given laser fluence, the demagnetization amplitudes and demagnetization times
+are not affected by the existence of a temperature of magnetic compensation.
+However, our experiment reveals a twofold increase of the ultrafast
+demagnetization rates for the Dy sublattice at low temperature. In parallel, we
+measure a constant demagnetization rate of the Co3d sublattice above and below
+Tcomp. This intriguing difference between the Dy4f and Co3d sublattices calls
+for further theoretical and experimental investigations.",1708.08918v2
+2017-09-29,Designing Magnetic Droplet Soliton Nucleation Employing Spin Polarizer,"We show by means of micromagnetic simulations that spin polarizer in
+nano-contact spin torque oscillators (NC-STOs) as the representative of the
+fixed layer in an orthogonal pseudo-spin valve (P-SV) can be employed to design
+and to control magnetic droplet soliton nucleation and dynamics. We found that
+using a tilted spin polarizer layer decreases the droplet nucleation time which
+is more suitable for high speed applications. However, a tilted spin polarizer
+increases the nucleation current and decreases the frequency stability of the
+droplet. Additionally, by driving the magnetization inhomogenously at the
+nano-contact region, it is found that a tilted spin polarizer reduces the
+precession angle of the droplet and through an interplay with the Oersted field
+of the DC current, it breaks the spatial symmetry of the droplet profile. Our
+findings explore fundamental insight into nano-scale magnetic droplet soliton
+dynamics with potential tunability parameters for future microwave electronics.",1709.10325v3
+2017-10-12,Magnetic droplet solitons generated by pure spin currents,"Magnetic droplets are dynamical solitons that can be generated by locally
+suppressing the dynamical damping in magnetic films with perpendicular
+anisotropy. To date, droplets have been observed only in nanocontact
+spin-torque oscillators operated by spin-polarized electrical currents. Here,
+we experimentally demonstrate that magnetic droplets can be nucleated and
+sustained by pure spin currents in nanoconstriction-based spin Hall devices.
+Micromagnetic simulations support our interpretation of the data, and indicate
+that in addition to the stationary droplets, propagating solitons can be also
+generated in the studied system, which can be utilized for the information
+transmission in spintronic applications.",1710.04430v1
+2017-10-13,Mode-Dependent Damping in Metallic Antiferromagnets Due to Inter-Sublattice Spin Pumping,"Damping in magnetization dynamics characterizes the dissipation of magnetic
+energy and is essential for improving the performance of spintronics-based
+devices. While the damping of ferromagnets has been well studied and can be
+artificially controlled in practice, the damping parameters of
+antiferromagnetic materials are nevertheless little known for their physical
+mechanisms or numerical values. Here we calculate the damping parameters in
+antiferromagnetic dynamics using the generalized scattering theory of
+magnetization dissipation combined with the first-principles transport
+computation. For the PtMn, IrMn, PdMn and FeMn metallic antiferromagnets, the
+damping coefficient associated with the motion of magnetization ($\alpha_m$) is
+one to three orders of magnitude larger than the other damping coefficient
+associated with the variation of the N\'eel order ($\alpha_n$), in sharp
+contrast to the assumptions made in the literature.",1710.04766v1
+2017-10-27,Semiconducting double-dot exchange-only qubit dynamics in presence of magnetic and charge noises,"The effects of magnetic and charge noises on the dynamical evolution of the
+double-dot exchange-only qubit (DEOQ) is theoretically investigated. The DEOQ
+consisting of three electrons arranged in an electrostatically defined double
+quantum dot deserves special interest in quantum computation applications due
+to its advantages in terms of fabrication, control and manipulation in view of
+implementation of fast single and two qubit operations through only electrical
+tuning. The presence of the environmental noise due to nuclear spins and charge
+traps, in addition to fluctuations in the applied magnetic field and charge
+fluctuations on the electrostatic gates adopted to confine the electrons, is
+taken into account including random magnetic field and random coupling terms in
+the Hamiltonian. The behavior of the return probability as a function of time
+for initial conditions of interest is presented. Moreover, through an
+envelope-fitting procedure on the return probabilities, coherence times are
+extracted when model parameters take values achievable experimentally in
+semiconducting devices.",1710.10032v2
+2017-10-28,High frequency dynamics modulated by collective magnetization reversal in artificial spin ice,"Spin-torque ferromagnetic resonance (ST-FMR) arises in heavy
+metal/ferromagnet heterostructures when an alternating charge current is passed
+through the bilayer stack. The methodology to detect the resonance is based on
+the anisotropic magnetoresistance, which is the change in the electrical
+resistance due to different orientations of the magnetization. In connected
+networks of ferromagnetic nanowires, known as artificial spin ice, the
+magnetoresistance is rather complex owing to the underlying collective behavior
+of the geometrically frustrated magnetic domain structure. Here, we demonstrate
+ST-FMR investigations in a square artificial spin-ice system and correlate our
+observations to magnetotransport measurements. The experimental findings are
+described using a simulation approach that highlights the importance of the
+correlated dynamics response of the magnetic system. Our results open the
+possibility of designing reconfigurable microwave oscillators and
+magnetoresistive devices based on connected networks of nanomagnets.",1710.10534v1
+2017-11-08,Magnetic skyrmion bubble motion driven by surface acoustic waves,"We study the dynamical control of a magnetic skyrmion bubble by using
+counter-propagating surface acoustic waves (SAWs) in a ferromagnet. First, we
+determine the bubble mass and derive the force due to SAWs acting on a magnetic
+bubble using Thiele's method. The force that pushes the bubble is proportional
+to the strain gradient for the major strain component. We then study the
+dynamical pinning and motion of magnetic bubbles by SAWs in a nanowire. In a
+disk geometry, we propose a SAWs-driven skyrmion bubble oscillator with two
+resonant frequencies.",1711.03041v3
+2017-11-14,Temperature effects on drift of suspended single-domain particles induced by the Magnus force,"We study the temperature dependence of the drift velocity of single-domain
+ferromagnetic particles induced by the Magnus force in a dilute suspension. A
+set of stochastic equations describing the translational and rotational
+dynamics of particles is derived, and the particle drift velocity that depends
+on components of the average particle magnetization is introduced. The
+Fokker-Planck equation for the probability density of magnetization
+orientations is solved analytically in the limit of strong thermal fluctuations
+for both the planar rotor and general models. Using these solutions, we
+calculate the drift velocity and show that the out-of-plane fluctuations of
+magnetization, which are not accounted for in the planar rotor model, play an
+important role. In the general case of arbitrary fluctuations, we investigate
+the temperature dependence of the drift velocity by numerically simulating a
+set of effective stochastic differential equations for the magnetization
+dynamics.",1711.05338v1
+2017-11-16,Transient dynamics of nonlinear magneto-optical rotation,"We analyze nonlinear magneto-optical rotation (NMOR) in rubidium vapor
+subjected to continuously-scanned magnetic field. By varying magnetic-field
+sweep rate, a transition from traditionally-observed dispersive-like NMOR
+signals (low sweep rate) to oscillating signals (higher sweep rates) is
+demonstrated. The transient oscillatory behavior is studied versus light and
+magnetic-field parameters, revealing a strong dependence of the signals on
+magnetic-sweep rate and light intensity. The experimental results are supported
+with density-matrix calculations, which enable quantitative analysis of the
+effect. Fitting of the signals simulated versus different parameters with a
+theoretically-motivated curve reveals presence of oscillatory and static
+components in the signals. The components depend differently on the system
+parameters, which suggests their distinct nature. The investigations provide
+insight into dynamics of ground-state coherence generation and enable
+application of NMOR in detection of transient spin couplings.",1711.06028v1
+2017-12-28,Theory of magnetic skyrmion glass,"Skyrmions and skyrmion crystal (SkX) discovered in chiral magnets show unique
+physical properties due to their nontrivial topology such as the stability
+against the annihilation and the motion driven by the ultralow current density,
+which can be advantageous for the device applications such as magnetic
+memories. Especially, the chiral dynamics, i.e., the velocity perpendicular to
+the force acting on a skyrmion, is a key to avoid the impurity potential and
+enhances its mobility. However, the collective pinning of SkX occurs by the
+disorder, which is crucial for its low energy properties. Here, we study
+theoretically the low energy dynamics of SkX in the presence of disorder
+effects in terms of replica field theory, and reveal nonreciprocal collective
+modes and their electromagnetic responses along the direction of external
+magnetic field. The physical quantities such as the relaxation rate of
+$\mu$SR/NMR and the pinning frequency show a dramatic change associated with
+the topological phase transition from the helical state to SkX. These results
+provide a firm basis to explore the glassy state of SkX.",1712.09782v1
+2018-01-10,Spin and motion dynamics with zigzag ion crystals in transverse magnetic field gradients,"We investigate the dynamics of ion crystals in zigzag configuration in
+transverse magnetic field gradients. A surface-electrode Paul trap is employed
+to trap $^{40}$Ca$^+$ ions and features submerged wires to generate magnetic
+field gradients of up to 16.3(9) T/m at the ions position. With the gradient
+aligned in the direction perpendicular to the axis of weakest confinement,
+along which linear ion crystals are formed, we demonstrate magnetic field
+gradient induced coupling between the spin and ion motion. For crystals of
+three ions across their linear-to-zigzag structural transition we perform
+sideband spectroscopy upon directly driving the spins with a radiofrequency
+field. Furthermore, we observe the rich excitation spectrum of vibrational
+modes in a planar crystal comprised of four ions.",1801.03391v2
+2018-01-17,Mimicking inflation with 2-fluid systems in a strong gradient magnetic field,"In the standard cosmological picture the Universe underwent a brief period of
+near-exponential expansion, known as Inflation. This provides an explanation
+for structure formation through the amplification of perturbations by the rapid
+expansion of the fabric of space. Although this mech- anism is theoretically
+well understood, it cannot be directly observed in nature. We propose a novel
+experiment combining fluid dynamics and strong magnetic field physics to
+simulate cosmo- logical inflation. Our proposed system consists of two
+immiscible, weakly magnetised fluids moving through a strong magnetic field in
+the bore of a superconducting magnet. By precisely controlling the propagation
+speed of the interface waves, we can capture the essential dynamics of
+inflation- ary fluctuations: interface perturbations experience a shrinking
+effective horizon and are shown to transition from oscillatory to squeezed and
+frozen regimes at horizon crossing.",1801.05843v1
+2018-01-18,Axion-plasmon polaritons in strongly magnetized plasmas,"Axions are hypothetical particles related to the violation of the
+charge-parity symmetry, being the most prone candidates for dark matter.
+Multiple attempts to prove their existence are currently performed in different
+physical systems. Here, we anticipate the possibility of the axions coupling to
+the electrostatic (Langmuir) modes of a strongly magnetized plasma, by showing
+that a new quasi-particle can be defined, the axion-plasmon polariton. The
+excitation of axions can be inferred from the pronounced modification of the
+dispersion relation of the Langmuir waves, a feature that we estimate to be
+accessible in state-of-the-art plasma-based experiments. We further show that,
+under extreme density and magnetic field conditions (e.g. at the interior of
+dense neutron stars), the axion-plasmon polariton becomes dynamically unstable,
+similarly to the case of the Jeans instability occurring in self-gravitating
+fluids. This latter result anticipates a plausible mechanism to the creation of
+axion-like particles in the universe.",1801.06254v1
+2018-02-12,Dynamics of a magnetic skyrmionium driven by spin waves,"The magnetic skyrmionium is a skyrmion-like structure but carries a zero net
+skyrmion number, which can be used as a building block for non-volatile
+information processing devices. Here, we study the dynamics of a magnetic
+skyrmionium driven by propagating spin waves. It is found that the skyrmionium
+can be effectively driven into motion by spin waves showing tiny skyrmion Hall
+effect, of which the mobility is much better than that of the skyrmion at the
+same condition. We also show that the skyrmionium mobility depends on the
+nanotrack width and damping coefficient, and can be controlled by an external
+out-of-plane magnetic field. Besides, we demonstrate the skyrmionium motion
+driven by spin waves is inertial. Our results indicate that the skyrmionium is
+a promising building block for building spin-wave spintronic devices.",1802.03868v2
+2018-02-20,Magnetic exchange and susceptibilities in fcc iron: A supercell dynamical mean-field theory study,"We study the momentum- and temperature dependencies of magnetic
+susceptibilities and magnetic exchange in paramagnetic fcc iron by a
+combination of density functional theory and supercell dynamical mean-field
+theory (DFT+DMFT). We find that in agreement with experimental results the
+antiferromagnetic correlations with the wave vector close to $(0,0,2\pi)$
+dominate at low temperatures (as was also obtained previously theoretically),
+while the antiferromagnetic and ferromagnetic correlations closely compete at
+the temperatures $T\sim 1000$ K, where $\gamma$-iron exists in nature. Inverse
+staggered susceptibility has linear temperature dependence at low temperatures,
+with negative Weiss temperature $\theta_{\rm stagg} \approx -340$ K; the
+inverse local susceptibility is also linear at not too low temperatures,
+showing well formed local moments. Analysis of magnetic exchange shows that the
+dominant contribution comes from first two coordination spheres. In agreement
+with the analysis of the susceptibility, the nearest-neighbor exchange is found
+to be antiferromagnetic at low temperatures, while at temperature of the
+$\alpha$-$\gamma$ structural phase transition its absolute value becomes small,
+and the system appears on the boundary between the regimes with strongest
+antiferro- and ferromagnetic correlations.",1802.07061v2
+2018-02-26,Devil's Staircases in SFS Josephson Junctions,"We study the effect of coupling between the superconducting current and
+magnetization in the superconductor/ferromagnet/superconductor Josephson
+junction under an applied circularly polarized magnetic field. Manifestation of
+ferromagnetic resonance in the frequency dependence of the amplitude of the
+magnetization and the average critical current density is demonstrated
+numerically. The IV-characteristics show subharmonic steps that form devil's
+staircases, following a continued fraction algorithm. The origin of the found
+steps is related to the effect of the magnetization dynamics on the phase
+difference in the Josephson junction. The dynamics of our system is described
+by a generalized RCSJ model coupled to the Landau-Lifshitz-Gilbert equation. In
+the suplement we justify analytically the appearance of the fractional steps in
+IV-characteristics of the superconductor/ferromagnet/superconductor Josephson
+junction.",1802.09212v2
+2018-03-01,Coupling of phonons with orbital dynamics and magnetism in CuSb$_2$O$_6$,"Strongly interacting phonons and orbital excitations are observed in the same
+energy range for CuSb$_2$O$_6$, unlocking a so-far unexplored type of
+electron-phonon interaction. An orbital wave at $\sim 550$ cm$^{-1}$ softens on
+warming and strongly interferes with a phonon at $\sim 500$ cm$^{-1}$, giving
+rise to a merged excitation of mixed character. An electronic continuum grows
+on warming to the orbital ordering temperature $T_{OO}$=400 K, generating an
+important phonon decay channel. This direct and simultaneous observation of
+orbital and vibrational excitations reveals details of their combined dynamics.
+In addition, phonon frequency anomalies due to magnetic correlations are
+observed below $\sim 150$ K, much above the three-dimensional magnetic ordering
+temperature $T_N^{3D}=8.5$ K, confirming one-dimensional magnetic correlations
+along Cu-O-O-Cu linear chains in the paramagnetic state.",1803.00559v3
+2018-04-05,Stochastic ferrimagnetic Landau-Lifshitz-Bloch equation for finite magnetic structures,"Precise modeling of the magnetization dynamics of nanoparticles with finite
+size effects at fast varying temperatures is a computationally challenging
+task. Based on the Landau-Lifshitz-Bloch (LLB) equation we derive a coarse
+grained model for disordered ferrimagnets, which is both fast and accurate.
+First, we incorporate stochastic fluctuations to the existing ferrimagnetic LLB
+equation. Further, we derive a thermodynamic expression for the temperature
+dependent susceptibilities, which is essential to model finite size effects.
+Together with the zero field equilibrium magnetization the susceptibilities are
+used in the stochastic ferrimagnetic LLB to simulate a $5\times10$ nm$^2$
+ferrimagnetic GdFeCo particle with 70 % FeCo and 30 % Gd under various external
+applied fields and heat pulses. The obtained trajectories agree well with those
+of an atomistic model, which solves the stochastic Landau-Lifshitz-Gilbert
+equation for each atom. Additionally, we derive an expression for the
+intergrain exchange field which couple the ferromagnetic sublattices of a
+ferrimagnet. A comparison of the magnetization dynamics obtained from this
+simpler model with those of the ferrimagnetic LLB equation shows a perfect
+agreement.",1804.01724v1
+2018-04-27,Two-Dimensional Computation of Pulsed Magnetic Field Diffusion Dynamics in Gold Cone with Consideration of Inductive Heating and Temperature Dependence of Electrical Conductivity,"Application of an external kilo-tesla-level magnetic field, which can be
+generated using high-intensity laser, to a target is a promising scheme to
+reduce spray angle of a laser-driven relativistic electron beam (REB) for
+enhancing the isochoric heating of a dense plasma with the laser-driven REB.
+Here we have developed a two-dimensional electro-magnetic dynamics (2D-EMD)
+simulation code to solve Maxwell equations with considerations of the inductive
+heating and temperature-dependence of electrical conductivity of a material for
+calculating temporally and spatially resolved two-dimensional profile of the
+externally applied magnetic field in a gold-cone-attached target.",1804.10410v1
+2018-05-19,Optically driven spin pumping mediating collective magnetization dynamics in a spin valve structure,"We demonstrate spin pumping, i.e. the generation of a pure spin current by
+precessing magnetization, without application of microwave radiation commonly
+used in spin pumping experiments. We use femtosecond laser pulses to
+simultaneously launch the magnetization precession in each of two ferromagnetic
+layers of a Galfenol-based spin valve and monitor the temporal evolution of the
+magnetizations. The spin currents generated by the precession cause a dynamic
+coupling of the two layers. This coupling has dissipative character and is
+especially efficient when the precession frequencies in the two layers are in
+resonance, where coupled modes with strongly different decay rates are formed.",1805.07669v1
+2018-05-22,Solar coronal loop dynamics near the null point above active region NOAA 2666,"We analyse observations of a saddle-like structure in the corona above the
+western limb of the Sun on 2017 July 18. The structure was clearly outlined by
+coronal loops with typical coronal temperature no more than 1 MK. The dynamics
+of loops showed convergence toward the centre of the saddle in the vertical
+direction and divergence in the horizontal direction. The event is a clear
+example of smooth coronal magnetic field reconnection. No heating
+manifestations in the reconnection region or magnetically connected areas were
+observed. Potential magnetic field calculations, which use as the boundary
+condition the SDO/HMI magnetogram taken on July 14, showed the presence of a
+null point at the height of 122"" above the photosphere just at the centre of
+the saddle structure. The shape of field lines fits the fan-spine magnetic
+configuration above NOAA 2666.",1805.08540v1
+2018-05-25,Macromagnetic simulation for reservoir computing utilizing spin dynamics in magnetic tunnel junctions,"The figures-of-merit for reservoir computing (RC), using spintronics devices
+called magnetic tunnel junctions (MTJs), are evaluated. RC is a type of
+recurrent neural network. The input information is stored in certain parts of
+the reservoir, and computation can be performed by optimizing a linear
+transform matrix for the output. While all the network characteristics should
+be controlled in a general recurrent neural network, such optimization is not
+necessary for RC. The reservoir only has to possess a non-linear response with
+memory effect. In this paper, macromagnetic simulation is conducted for the
+spin-dynamics in MTJs, for reservoir computing. It is determined that the
+MTJ-system possesses the memory effect and non-linearity required for RC. With
+RC using 5-7 MTJs, high performance can be obtained, similar to an echo-state
+network with 20-30 nodes, even if there are no magnetic and/or electrical
+interactions between the magnetizations.",1805.09977v3
+2018-05-30,Magnonic band gap and mode hybridization in continuous Permalloy film induced by vertical coupling with an array of Permalloy ellipses,"We investigate magnonic band structure in thin homogeneous permalloy film
+decorated with periodic array of elliptically shaped permalloy dots and
+separated by non-magnetic Pt spacer. We demonstrated experimentally formation
+of the magnonic band structure for Damon-Eshbach wave propagating in permalloy
+film with the band gap opened at the Brillouin zone border and band splitting
+at smaller wavenumbers, due to the Bragg interference and interaction of
+propagating wave of the continuous film with a standing resonant mode of the
+nano-ellipses, respectively. The shape anisotropy of the permalloy nanodots
+allows to control the spin wave dynamics through the switch between two states
+of the magnetization with respect to the underneath film magnetization, thus
+enabling magnonic band structure reprogrammability. With numerical analysis we
+show, that predominant role in formation of the magnonic band structure is
+played by a vertical dynamic coupling between propagating wave in the film and
+magnetization oscillations in the nanodots.",1805.12178v2
+2018-06-30,Scalable Dissolution-Dynamic Nuclear Polarization with Rapid Transfer of a Polarized Solid,"In dissolution-dynamic nuclear polarization, nuclear spins are hyperpolarized
+at cryogenic temperatures using radicals and microwave irradiation. The
+hyperpolarized solid is dissolved with hot solvent and the solution is
+transferred to a secondary magnet where strongly enhanced magnetic resonance
+signals are observed. Here we present a method for transferring the
+hyperpolarized solid. A bullet containing the frozen, hyperpolarized sample is
+ejected using pressurized helium gas, and shot into a receiving structure in
+the secondary magnet, where the bullet is retained and the polarized solid is
+dissolved rapidly. The transfer takes approximately 70 ms. A solenoid, wound
+along the entire transfer path ensures adiabatic transfer and limits
+radical-induced low-field relaxation. The method is fast and scalable towards
+small volumes suitable for high-resolution nuclear magnetic resonance
+spectroscopy while maintaining high concentrations of the target molecule.
+Polarization levels of approximately 30% have been observed for 1-$^{\sf
+13}$C-labelled pyruvic acid in solution.",1807.00223v2
+2018-08-03,Magnetic reconnection detonation in supernova remnants,"As a key process that refreshes the interstellar medium, the dynamics and
+radiative properties of the supernova remnant (SNR) expansion front not only
+reflect the physical environment of the old interstellar medium (ISM)
+surrounding the supernova, but they also provide information about the
+refreshed ISM. However the expansion dynamics of SNRs cannot be simply
+explained by the conventional law of spherical shock wave propagation; on the
+other hand, the high energy radiation requires an additional electron
+acceleration mechanism in the shock front beyond thermal collision. We consider
+herein the detonation wave description of the SNR expansion, in which magnetic
+reconnection follows the shock front and transfers the SNR magnetic field
+energy to both fluid thermal energy and particle kinetic energy. The structure
+of the magnetic reconnection detonation (MRD) is identified based on scaling
+analysis in this paper. By applying the MRD description of the SNR expansion
+shock to the example of the Crab Nebula, this paper shows that the MRD
+description can explain both the accelerative expansion of the nebula as well
+as the origin of the luminous expanding shell.",1808.01089v1
+2018-08-17,Laser-induced antiferromagnetic-like resonance in amorphous ferrimagnets,"The magnetization dynamics for ferrimagnets at the angular momentum
+compensation temperature T_A is believed to be analogous to that for
+antiferromagnets. We investigated the pulsed-laser-induced magnetization
+dynamics in amorphous rare-earth transition-metal ferrimagnet films with a T_A
+just above room temperature. For a low pulse fluence, the magnetization
+precession frequency decreases as the applied magnetic field increases, whereas
+for a higher pulse fluence, it increases as the applied field increases. The
+result was well explained by the left-handed and right-handed precession modes
+of the antiferromagnetic-like resonance at temperatures below and above T_A,
+respectively, and the data were in agreement with the theoretical simulation.
+The study demonstrated the experimental route to achieving antiferromagnetic
+resonance in ferrimagnets using a pulsed laser.",1808.05707v1
+2018-10-04,Magnetic moment generation in small gold nanoparticles via the plasmonic inverse Faraday effect,"We theoretically investigate the creation of a magnetic moment in gold
+nanoparticles by circularly polarized laser light. To this end, we describe the
+collective electron dynamics in gold nanoparticles using a semiclassical
+approach based on a quantum hydrodynamic model that incorporates the prin-
+cipal quantum many-body and nonlocal effects, such as the electron spill-out,
+the Hartree potential, and the exchange and correlation effects. We use a
+variational approach to investigate the breathing and the dipole dynamics
+induced by an external electric field. We show that gold nanoparticles can
+build up a static magnetic moment through the interaction with a circularly
+polarized laser field. We analyze that the responsible physical mechanism is a
+plasmonic, orbital inverse Faraday effect, which can be understood from the
+time-averaged electron current that contains currents rotating on the
+nanoparticles surface. The computed laser-induced magnetic moments are
+sizeable, of about 0.35 muB/atom for a laser intensity of 450 GW/cm2 at plasmon
+resonance.",1810.02097v1
+2018-11-02,A two-step symmetric method for charged-particle dynamics in a normal or strong magnetic feld,"The study of the long time conservation for numerical methods poses
+interesting and challenging questions from the point of view of geometric
+integration. In this paper, we analyze the long time energy and magnetic moment
+conservations of two-step symmetric methods for charged-particle dynamics. A
+two-step symmetric method is proposed and its long time behaviour is shown not
+only in a normal magnetic feld but also in a strong magnetic feld. The
+approaches to dealing with these two cases are based on the backward error
+analysis and modulated Fourier expansion, respectively. It is obtained from the
+analysis that the method has better long time conservations than the
+variational method which was researched recently in the literature.",1811.01060v2
+2018-11-30,Influence of Landau levels in the phonon dispersion of Weyl semimetals,"Weyl semimetals display unusual electronic transport properties when placed
+under magnetic fields. Here, we investigate how magnetic fields alter the
+dynamics of long wavelength lattice vibrations in these materials. To that end,
+we develop a theory for the phonon dispersion, which incorporates contributions
+from chiral and nonchiral Landau levels, electron-phonon interactions,
+electron-electron interactions, and disorder. We predict (i) a
+magnetic-field-induced hybridization between optical phonons and plasmons, (ii)
+avoided crossings between pseudoscalar optical phonons and electronic
+excitations originating from nonchiral Landau levels, (iii) a sharp dependence
+of the sound velocity on the relative angle between the sound propagation and
+the magnetic field. We compare our results to recent theoretical studies on the
+signatures of the chiral anomaly in phonon dynamics.",1811.12899v2
+2018-12-06,Multistep Bloch-line-mediated Walker breakdown in ferromagnetic strips,"A well-known feature of magnetic field driven dynamics of domain walls in
+ferromagnets is the existence of a threshold driving force at which the
+internal magnetization of the domain wall starts to precess -- a phenomenon
+known as the Walker breakdown -- resulting in an abrupt drop of the domain wall
+propagation velocity. Here, we report on micromagnetic simulations of magnetic
+field driven domain wall dynamics in thin ferromagnetic strips with
+perpendicular magnetic anisotropy which demonstrate that in wide enough strips
+Walker breakdown is a multistep process: It consists of several distinct
+velocity drops separated by short linear parts of the velocity vs field curve.
+These features originate from the repeated nucleation, propagation and
+annihilation of an increasing number of Bloch lines within the domain wall as
+the driving field magnitude is increased. This mechanism arises due to
+magnetostatic effects breaking the symmetry between the two ends of the domain
+wall.",1812.02545v2
+2019-01-14,Inducing out-of-plane precession of magnetization for microwave assisted magnetic recording using an oscillating polarizer in spin torque oscillator,"We investigated the dynamics of a novel design of spin torque oscillator
+(STO) for microwave assisted magnetic recording. Using Ni$_{80}$Fe$_{20}$
+(NiFe) as the polarizer and Fe$_{67}$Co$_{33}$ (FeCo) as the field generating
+layer, we experimentally observed the magnetization reversal of NiFe, followed
+by multiple signals in the power spectra as the bias voltage increased. The
+signals reflected the out-of-plane precession (OPP) mode oscillation of both
+FeCo and NiFe, as well as the magnetoresistance effect of the STO device, which
+had the frequency equal to the difference between the oscillation frequency of
+NiFe and FeCo. Such dynamics were reproduced by micromagnetic simulation. In
+addition to the merit of realizing the OPP mode oscillation with a simple and
+thin structure suitable for a narrow gap recording head, the experimental
+results using this design suggested that a large cone angle of $\sim$
+70$^{\circ}$ for the OPP mode oscillation of FeCo was achieved, which was
+estimated based on the macrospin model.",1901.04208v1
+2019-03-19,Spin Dynamics of CPMG sequence in time-dependent magnetic fields,"We analyze the effects of time dependent magnetic and RF fields on the spin
+dynamics of the Carr-Purcell-Meiboom-Gill (CPMG) sequence. The analysis is
+based on the decomposition of the magnetization into the eigenmodes of the
+propagator of a single refocusing cycle. For sufficiently slow changes in the
+external fields, the magnetization follows the changing eigenmodes
+adiabatically. This results in echo amplitudes that show regular modulations
+with time. Faster field changes can induce transitions between the eigenmodes.
+Such non-adiabatic behavior occurs preferentially at particular offsets of the
+Larmor frequency from the RF frequency where the eigenmodes become nearly
+degenerate. We introduce the instantaneous adiabaticity parameter ${\cal A}(t)$
+that accurately predicts the crossover from the adiabatic to the non-adiabatic
+regime and allows the classification of field fluctuations. ${\cal A}(t)$ is
+determined solely by the properties of a single refocusing cycle under static
+conditions and the instantaneous value of the field offset and its temporal
+derivative. The analytical results are compared with numerical simulations.",1903.08006v1
+2019-04-19,Sub-terahertz ferrimagnetic spin-transfer torque oscillator,"A theory of magnetization dynamics in ferrimagnetic materials with
+antiparallel aligned spin sub-lattices under action of spin-transfer torques
+(STT) is developed. We consider magnetization dynamics in GdFeCo layers in two
+cases of magnetic anisotropy: easy plane and easy axis. We demonstrate that,
+(i) for the easy plane anisotropy the precession of the N\'{e}el vector is
+conical and the cone angle depends on the STT strength and the value of spin
+non-compensation, while the frequency of precession can reach sub-THz
+frequencies; (ii) for the easy axis anisotropy two regimes are possible:
+deterministic switching of the net magnetization and a conical sub-THz
+precession depending on the STT strength.",1904.09341v1
+2019-05-03,Generalized quenching of large-scale magnetic dynamos in anisotropic flows,"The buildup of small-scale magnetic helicity which accompanies the oppositely
+signed growth on large scales is central to conventional dynamical quenching
+theories of mean-field dynamos. However, the conventional formalism presumes
+isotropic turbulence and thereby excludes part of the magnetic Lorentz
+back-reaction. This renders it insufficient to predict the full quenching for
+general anisotropic flows. To overcome this deficiency, we derive a new
+generalized quenching formalism that includes the full back-reacting Lorentz
+force, and a new ""selective-damping-$\tau$"" closure which conserves magnetic
+helicity. We apply the formalism to examples of $\bm\alpha^2$ dynamos and show
+its predicted quenching for different cases of turbulence---isotropic helical,
+anisotropic helical, and anisotropic non-helical. It predicts
+stronger-than-conventional quenching in general, but reduces to the
+conventional case in the helical isotropic limit.",1905.01256v4
+2019-05-24,Inverse cascade of hybrid helicity in $B Ω$-MHD turbulence,"We investigate the impact of a solid-body rotation $\Omega_0$ on the
+large-scale dynamics of an incompressible magnetohydrodynamic turbulent flow in
+presence of a background magnetic field $\bf B_0$ and at low Rossby number.
+Three-dimensional direct numerical simulations are performed in a periodic box,
+at unit magnetic Prandtl number and with a forcing at intermediate wavenumber
+$k_f=20$. When $\Omega_0$ is aligned with $\bf B_0$ (i.e. $\theta \equiv
+\widehat{\left(\Omega_{0}, \bf B_0 \right)} = 0$), inverse transfer is found
+for the magnetic spectrum at $k<k_f$. This transfer is stronger when the
+forcing excites preferentially right-handed (rather than left-handed)
+fluctuations; it is smaller when $\theta>0$ and becomes weak when $\theta \ge
+35^o$. These properties are understood as the consequence of an inverse cascade
+of hybrid helicity which is an inviscid/ideal invariant of this system when
+$\theta=0$. Hybrid helicity emerges, therefore, as a key element for
+understanding rotating dynamos. Implication of these findings on the origin of
+the alignment of the magnetic dipole with the rotation axis in planets and
+stars is discussed.",1905.10250v1
+2019-06-11,"Vortex dynamic, pinning and irreversibility field investigation in EuRbFe4As4 superconductor","We performed systematic AC susceptibility and magnetic moment measurements to
+investigate the vortex dynamics and pinning in the $EuRbFe_4As_4$ single
+crystal as a function of temperature, frequency, and DC magnetic field. The
+vortex solid-liquid line was determined and it fits well with
+$H(T_p)=H_0(1-t_p)^\beta$ using $\beta$=1.74-1.91, for $H\parallel ab$. It
+indicates a rather high pinning strength of the vortex system. The activation
+energy $U_0$ was determined from thermally activated flux creep theory and
+reached 6700 K at low fields, suggesting strong vortex pinning. A field
+dependence of $U_0(H\parallel ab)\sim H^a$ with $a=0.47$ suggests thermally
+activated plastic pinning or caused by planar defects. Magnetic moment
+measurements also confirmed strong pinning in a $EuRbFe_4As_4$ superconductor
+and the superconducting response gives the main contribution to the $M(H)$
+hysteresis. Additionally, we found evidence of long-range magnetic interactions
+in $Eu^{2+}$ sublattice and the FM-like nature of $Eu^{2+}$ atoms ordering.",1906.04597v2
+2019-06-25,Melting of Spin Ice state through structural disorder in Dy2Zr2O7,"Neutron scattering, a.c. magnetic susceptibility and specific heat studies
+have been carried out on polycrystalline Dy2Zr2O7. Unlike the pyrochlore spin
+ice Dy2Ti2O7, Dy2Zr2O7 crystallizes into the fluorite structure and the
+magnetic Dy3+ moments randomly reside on the corner-sharing tetrahedral
+sublattice with non-magnetic Zr ions. Antiferromagnetic spin correlations
+develop below 10 K but remain dynamic down to 40 mK. These correlations extend
+over the length of two tetrahedra edges and grow to 6 nearest neighbors with
+the application of a 20 kOe magnetic field. No Pauling's residual entropy was
+observed and by 8 K the full entropy expected for a two level system is
+released. We propose that the disorder melts the spin ice state seen in the
+chemically ordered Dy2Ti2O7 compound, but the spins remain dynamic in a
+disordered, liquid-like state and do not freeze into a glass-like state that
+one might intuitively expect.",1906.10738v1
+2019-07-04,Domain wall dynamics due to femtosecond laser-induced superdiffusive spin transport,"Manipulation of magnetic domain walls via a helicity-independent laser pulse
+has recently been experimentally demonstrated and various physical mechanisms
+leading to domain wall dynamics have been discussed. Spin-dependent
+superdiffusive transport of hot electrons has been identified as one of the
+possible ways how to affect a magnetic domain wall. Here, we develop a model
+based on superdiffusive spin-dependent transport to study the laser-induced
+transport of hot electrons through a smooth magnetic domain wall. We show that
+the spin transfer between neighboring domains can enhance ultrafast
+demagnetization in the domain wall. More importantly, our calculations reveal
+that when the laser pulse is properly focused on to the vicinity of the domain
+wall, it can excite sufficiently strong spin currents to generate a
+spin-transfer torque that can rapidly move the magnetic domain wall by several
+nanometers in several hundreds of femtoseconds, leading to a huge
+nonequilibrium domain wall velocity.",1907.02419v1
+2019-08-31,Dispersions of Many-Body Bethe strings,"Complex bound states of magnetic excitations, known as Bethe string, were
+predicted almost a century ago to exist in one-dimensional quantum magnets 1.
+The dispersions of the string states have so far remained the subject of
+intensive theoretical studies 2-7. By performing neutron scattering experiments
+on the one-dimensional Heisenberg-Ising antiferromagnet SrCo2V2O8 in high
+longitudinal magnetic fields, we reveal in detail the dispersion relations of
+the string states over the full Brillouin zone, as well as their magnetic field
+dependences. Furthermore the characteristic energy, the scattering intensity
+and linewidth of the observed string states exhibit excellent agreement with
+our precise Bethe Ansatz calculations. Our results establish the important role
+of string states in the quantum spin dynamics of one-dimensional systems, and
+will invoke studies of their dynamical properties in more general many-body
+systems.",1909.00146v1
+2019-09-12,Perspectives on spin hydrodynamics in ferromagnetic materials,"The field of spin hydrodynamics aims to describe magnetization dynamics from
+a fluid perspective. For ferromagnetic materials, there is an exact mapping
+between the Landau-Lifshitz equation and a set of dispersive hydrodynamic
+equations. This analogy provides ample opportunities to explore novel
+magnetization dynamics and magnetization states that can lead to applications
+relying entirely upon magnetic materials, for example, long-distance transport
+of information. This article provides an overview of the theoretical
+foundations of spin hydrodynamics and their physical interpretation in the
+context of spin transport. We discuss other proposed applications for spin
+hydrodynamics as well as our view on challenges and future research directions.",1909.05756v1
+2019-09-27,Dynamics of longitudinal magnetization in transverse-field quantum Ising model: from symmetry-breaking gap to Kibble-Zurek mechanism,"We show that the symmetry-breaking gap of the quantum Ising model in the
+transverse field can be extracted from free evolution of the longitudinal
+magnetization taking place after a gradual quench of the magnetic field. We
+perform for this purpose numerical simulations of the Ising chains with either
+periodic or open boundaries. We also study the condition for adiabaticity of
+evolution of the longitudinal magnetization finding excellent agreement between
+our simulations and the prediction based on the Kibble-Zurek theory of
+non-equilibrium phase transitions. Our results should be relevant for ongoing
+cold atom and ion experiments targeting either equilibrium or dynamical aspects
+of quantum phase transitions. They could be also useful for benchmarking D-Wave
+machines.",1909.12853v3
+2019-10-11,Investigation of spin orbit torque driven dynamics in ferromagnetic heterostructures,"We use time-resolved (TR) measurements based on the polar magneto-optical
+Kerr effect (MOKE) to study the magnetization dynamics excited by spin orbit
+torques in Py (Permalloy)/Pt and Ta/CoFeB bilayers. The analysis reveals that
+the field-like (FL) spin orbit torque (SOT) dominates the amplitude of the
+first oscillation cycle of the magnetization precession and the damping-like
+(DL) torque determines the final steady-state magnetization. In our bilayer
+samples, we have extracted the effective fields, hFL and hDL, of the two SOTs
+from the time-resolved magnetization oscillation spectrum. The extracted values
+are in good agreement with those extracted from time-integrated DCMOKE
+measurements, suggesting that the SOTs do not change at high frequencies. We
+also find that the amplitude ratio of the first oscillation to steady state is
+linearly proportional to the ratio hFL/hDL. The first oscillation amplitude is
+inversely proportional to, whereas the steady state value is independent of,
+the applied external field along the current direction.",1910.04945v1
+2019-12-01,On the Chaplygin sphere in a magnetic field,"We consider the possibility of using Dirac's ideas of the deformation of
+Poisson brackets in nonholonomic mechanics. As an example, we analyze the
+composition of external forces that do no work and reaction forces of
+nonintegrable constraints in the model of a nonholonomic Chaplygin sphere on a
+plane. We prove that, when a solenoidal field is applied, the general
+mechanical energy, the invariant measure and the conformally Hamiltonian
+representation of the equations of motion are preserved. In addition, we
+consider the case of motion of the nonholonomic Chaplygin sphere in a constant
+magnetic field taking dielectric and ferromagnetic (superconducting) properties
+of the sphere into account. As a by-product we also obtain two new integrable
+cases of the Hamiltonian rigid body dynamics in a constant magnetic field
+taking the magnetization by rotation effect into account.",1912.00373v1
+2019-12-11,Lyapunov exponents and entanglement entropy transition on the noncommutative hyperbolic plane,"We study quantum dynamics on noncommutative spaces of negative curvature,
+focusing on the hyperbolic plane with spatial noncommutativity in the presence
+of a constant magnetic field. We show that the synergy of noncommutativity and
+the magnetic field tames the exponential divergence of operator growth caused
+by the negative curvature of the hyperbolic space. Their combined effect
+results in a first-order transition at a critical value of the magnetic field
+in which strong quantum effects subdue the exponential divergence for {\it all}
+energies, in stark contrast to the commutative case, where for high enough
+energies operator growth always diverge exponentially. This transition
+manifests in the entanglement entropy between the `left' and `right' Hilbert
+spaces of spatial degrees of freedom. In particular, the entanglement entropy
+in the lowest Landau level vanishes beyond the critical point. We further
+present a non-linear solvable bosonic model that realizes the underlying
+algebraic structure of the noncommutative hyperbolic plane with a magnetic
+field.",1912.10805v3
+2020-03-10,Collective Transport of Magnetic Microparticles at a Fluid Interface through Dynamic Self-Assembled Lattices,"The transport of motile entities across modulated energy landscapes plays an
+important role in a range of phenomena in biology, colloidal science and
+solid-state physics. Here, an easily implementable strategy that allows for the
+collective and monitored transport of microparticles at fluid-fluid interfaces
+is introduced. Adsorbed magnetic microparticles are carried on time-dependent
+magnetic potentials, generated by a dynamic self-assembled lattice of
+different-sized magnetic particles. In such binary systems, the sudden
+reorientation of the applied field triggers the rapid exchange between
+attractive and repulsive configurations, enabling for the ballistic transfer of
+the carriers through the lattice. As the number of motile entities increases,
+the induced current increases, before reaching a maximum, while the loaded
+interface gradually displays bidirectional transport. The described methodology
+can be tuned through the applied field and exploited for the monitored guidance
+of adsorbed molecules on liquid surfaces, the segregation of colloidal
+mixtures, the induced motion of defects in photonic crystals or the design of
+new self-assembled microrobots.",2003.04594v1
+2020-05-31,Ultrafast dynamics of light-induced spin crossovers under high pressure,"Within the multielectron model of magnetic insulator with spin crossover
+under high pressure we have studied the mean field phase diagrams in pressure
+temperature plane and dynamics of a sudden excited non equilibrium spin state.
+We obtain the different relaxation of the magnetization, high spin/low spin
+occupation numbers, and the metal oxygen bond length for different values of
+the external pressure. We found the long living oscillations of magnetization
+without pressure and at small external pressure. Close to crossover pressure
+the smooth relaxation is accompanied with a set of sharp strongly non linear
+oscillations of magnetization and HS/LS occupation numbers that are accompanied
+by the Franck Condon resonances.",2006.00539v1
+2020-08-03,"Energy Transfer by Nonlinear Alfvén Waves in the Solar Chromosphere, and Its Effect on Spicule Dynamics, Coronal Heating, and Solar Wind Acceleration","Alfv\'en waves are responsible for the transfer of magnetic energy in the
+magnetized plasma. They are involved in heating solar atmosphere and driving
+solar wind through various nonlinear processes. Since the magnetic field
+configurations directly affect the nonlinearity of Alfv\'en waves, it is
+important to investigate how they relate to the solar atmosphere and wind
+structure through the nonlinear propagation of Alfv\'en waves. In this study,
+we carried out the one-dimensional magnetohydrodynamic simulations to realize
+the above relation. The results show that when the nonlinearity of Alfv\'en
+waves in the chromosphere exceeds a critical value, the dynamics of the solar
+chromosphere (e.g., spicule) and the mass loss rate of solar wind tend to be
+independent of the energy input from the photosphere. In a situation where the
+Alfv\'en waves are highly nonlinear, the strong shear torsional flow generated
+in the chromosphere ``fractures'' the magnetic flux tube. This corresponds to
+the formation of chromospheric intermediate shocks, which limit the
+transmission of the Poynting flux into the corona by Alfv\'en waves and also
+inhibits the propagation of chromospheric slow shock.",2008.00643v1
+2020-08-03,Small-Scale Dynamo in Stably Stratified Turbulence,"We present numerical investigations into three principal properties of the
+small-scale dynamo in stably stratified turbulence: the onset criterion, the
+growth rate, and the nature of the magnetic field anisotropy in the kinematic
+regime. The results suggest that all three dynamo properties are controlled by
+the scale separation between the Ozmidov scale and the viscous or resistive
+scale. In addition to the critical magnetic Reynolds number, this allows for
+the definition of critical buoyancy and magnetic buoyancy Reynolds numbers for
+stratified small-scale dynamo onset in the high and low magnetic Prandtl number
+regimes, respectively. The presence of a small-scale dynamo in stellar
+radiative zones could affect dynamics through resulting Maxwell stresses and/or
+influence large-scale dynamo mechanisms in regions of differential rotation.
+Taking the solar radiative zone as a representative example and applying the
+onset criterion, we find that the stratification is strong enough to make the
+small-scale dynamo marginally active in the stably stratified turbulence of the
+solar tachocline.",2008.01025v3
+2020-09-07,As a matter of tension -- kinetic energy spectra in MHD turbulence,"Magnetized turbulence is ubiquitous in many astrophysical and terrestrial
+systems but no complete, uncontested theory even in the simplest form,
+magnetohydrodynamics (MHD), exists. Many theories and phenomenologies focus on
+the joint (kinetic and magnetic) energy fluxes and spectra. We highlight the
+importance of treating kinetic and magnetic energies separately to shed light
+on MHD turbulence dynamics. We conduct an implicit large eddy simulation of
+subsonic, super-Alfv\'enic MHD turbulence and analyze the scale-wise energy
+transfer over time. Our key finding is that the kinetic energy spectrum
+develops a scaling of approximately $k^{-4/3}$ in the stationary regime as the
+kinetic energy cascade is suppressed by magnetic tension. This motivates a
+reevaluation of existing MHD turbulence theories with respect to a more
+differentiated modeling of the energy fluxes.",2009.03342v1
+2020-09-17,Magnetic Gradient Fluctuations from Quadrupolar $^{73}$Ge in Si/SiGe Exchange-Only Qubits,"We study the time-fluctuating magnetic gradient noise mechanisms in pairs of
+Si/SiGe quantum dots using exchange echo noise spectroscopy. We find through a
+combination of spectral inversion and correspondence to theoretical modeling
+that quadrupolar precession of the $^{73}$Ge nuclei play a key role in the
+spin-echo decay time $T_2$, with a characteristic dependence on magnetic field
+and the width of the Si quantum well. The $^{73}$Ge noise peaks appear at the
+fundamental and first harmonic of the $^{73}$Ge Larmor resonance, superimposed
+over $1/f$ noise due to $^{29}$Si dipole-dipole dynamics, and are dependent on
+material epitaxy and applied magnetic field. These results may inform the needs
+of dynamical decoupling when using Si/SiGe quantum dots as qubits in quantum
+information processing devices.",2009.08079v1
+2020-09-20,Non-classical spin transfer effects in an antiferromagnet,"We simulate scattering of electrons by a chain of antiferromagnetically
+coupled quantum Heisenberg spins, to analyze spin-transfer effects not
+described by the classical models of magnetism. Our simulations demonstrate
+efficient excitation of dynamical states that would be forbidden by the
+semiclassical symmetries, such as generation of multiple magnetic excitation
+quanta by a single electron. Furthermore, quantum interference of spin
+wavefunctions enables generation of magnetization dynamics with amplitudes
+exceeding the transferred magnetic moment. The efficiency of excitation is
+almost independent of the electron spin polarization, and is governed mainly by
+the transfer of energy. Non-classical spin transfer may thus enable efficient
+electronic control of antiferromagnets not limited by the classical
+constraints.",2009.09540v2
+2020-09-30,Electronic structure and finite temperature magnetism of yttrium iron garnet,"Yttrium iron garnet is a complex ferrimagnetic insulator with 20 magnon modes
+which is used extensively in fundamental experimental studies of magnetisation
+dynamics. As a transition metal oxide with moderate gap (2.8 eV), yttrium iron
+garnet requires a careful treatment of electronic correlation. We have applied
+quasiparticle self-consistent GW to provide a fully ab initio description of
+the electronic structure and resulting magnetic properties, including the
+parameterisation of a Heisenberg model for magnetic exchange interactions.
+Subsequent spin dynamical modelling with quantum statistics extends our
+description to the magnon spectrum and thermodynamic properties such as the
+Curie temperature, finding favourable agreement with experimental measurements.
+This work provides a snapshot of the state-of-the art in modelling of complex
+magnetic insulators.",2009.14601v1
+2020-10-09,"A Magnetized, Moon-Forming Giant Impact","The Moon is believed to have formed in the aftermath of a giant impact
+between a planetary mass body and the proto-Earth. In a typical giant impact
+scenario, a disk of vapor, liquid, and solid debris forms around the
+proto-Earth and--after possibly decades of evolution--condenses to form the
+Moon. Using state-of-the-art numerical simulations, we investigate the
+dynamical effects of magnetic fields on the Moon-forming giant impact. We show
+that turbulence generated by the collision itself, shear in the boundary layer
+between the post-impact debris field and the proto-Earth, and turbulence in the
+vapor component of the disk amplify the field to dynamically significant
+strengths. Magnetically driven turbulence promotes angular momentum transport
+in the protolunar disk. Debris material is accreted onto the proto-Earth,
+making Moon formation less efficient, while the disk is forced to spread to
+larger radii, cooling at its outer edge. Magnetic fields speed the evolution of
+the vapor component of the protolunar disk and hasten the formation of the
+Moon.",2010.04798v1
+2020-11-03,Driving spin chirality by electron dynamics in laser-excited antiferromagnets,"Optical generation of complex spin textures is one of the most exciting
+challenges of modern spintronics. Here, we uncover a distinct physical
+mechanism for imprinting spin chirality into collinear magnets with short laser
+pulses. By simultaneously treating the laser-ignited evolution of electronic
+structure and magnetic order, we show that their intertwined dynamics can
+result in an emergence of quasi-stable chiral states. We find that laser-driven
+chirality does not require any auxiliary external fields or intrinsic
+spin-orbit interaction to exist, and it can survive on the time scale of
+nanoseconds even in the presence of thermal fluctuations, which makes the
+uncovered mechanism relevant for understanding various optical experiments on
+magnetic materials. Our findings open a new perspective at the interaction of
+complex chiral magnetism with light.",2011.01670v3
+2020-11-23,New approach to describe two coupled spins in a variable magnetic field,"We propose a method to describe the evolution of two spins coupled by
+hyperfine interaction in an external time-dependent magnetic field. We apply
+the approach to the case of hyperfine interaction with axial symmetry, which
+can be solved exactly in a constant, appropriately oriented magnetic field. In
+order to treat the nonstationary dynamical problem, we modify the
+time-dependent Schr\""odinger equation through a change of representation that,
+by exploiting an instantaneous (adiabatic) basis makes the time-dependent
+Hamiltonian diagonal at any time instant. The solution of the transformed
+time-dependent Schr\""odinger in the form of chronologically ordered exponents
+with transparent pre-exponential coefficients is reported. This solution is
+highly simplified when an adiabatically varying magnetic field perturbs the
+system. The approach here proposed may be used for the perturbative treatment
+of other dynamical problems with no exact solution.",2011.11569v1
+2020-12-16,Magnetic Compton profiles of Ni beyond the one-particle picture: numerically exact and perturbative solvers of dynamical mean-field theory,"We calculated the magnetic Compton profiles (MCPs) of Ni using density
+functional theory supplemented by electronic correlations treated within
+dynamical mean-field theory (DMFT). We present comparisons between the
+theoretical and experimental MCPs. The theoretical MCPs were calculated using
+the KKR method with the perturbative spin-polarized T-matrix fluctuation
+exchange approximation DMFT solver, as well as with the full potential linear
+augmented planewave method with the numerically exact continuous-time quantum
+Monte Carlo DMFT solver. We show that the total magnetic moment decreases with
+the intra-atomic Coulomb repulsion $U$, which is also reflected in the
+corresponding MCPs. The total magnetic moment obtained in experimental
+measurements can be reproduced by intermediate values of $U$. The spectral
+function reveals that the minority X$_2$ Fermi surface pocket shrinks and gets
+shallower with respect to the density functional theory calculations.",2012.08812v2
+2021-01-04,Importance of magnetic fields in highly eccentric discs with applications to tidal disruption events,"Whether tidal disruption events (TDEs) circularise or accrete directly as a
+highly eccentric disc is the subject of current research and appears to depend
+sensitively on the disc thermodynamics. In a previous paper we applied the
+theory of eccentric discs to TDE discs using an $\alpha-$prescription for the
+disc stress, which leads to solutions that exhibit extreme, potentially
+unphysical, behaviour. In this paper we further explore the dynamical vertical
+structure of highly eccentric discs using alternative stress models that are
+better motivated by the behaviour of magnetic fields in eccentric discs. We
+find that the presence of a coherent magnetic field has a stabilising effect on
+the dynamics and can significantly alter the behaviour of highly eccentric
+radiation dominated discs. We conclude that magnetic fields are important for
+the evolution of TDE discs.",2101.01221v1
+2021-01-20,Dynamic mitigation of filamentation instability and magnetic reconnection in sheet-current sustained plasma,"Dynamic mitigation is presented for filamentation instability and magnetic
+reconnection in a plasm driven by a wobbling electron sheet current. The
+wobbling current introduces an oscillating perturbation and smooths the
+perturbation. The sheet current creates an anti-parallel magnetic field in
+plasma. The initial small perturbation induces the electron beam filamentation
+and the magnetic reconnection. When the wobbling or oscillation motion is added
+to the sheet electron beam along the sheet current surface, the perturbation
+phase is mixed and consequently the instability growth is delayed remarkably.
+Normally plasma instabilities are discussed by the growth rate, because it
+would be difficult to measure or detect the phase of the perturbations in
+plasmas. However, the phase of perturbation can be controlled externally, for
+example, by the driver wobbling motion. The superimposition of perturbations
+introduced actively results in the perturbation smoothing, and the instability
+growth can be reduced, like feed-forward control.",2101.07939v1
+2021-01-26,Hydrodynamical study of Terahertz emission in magnetized graphene field-effect transistors,"Several hydrodynamic descriptions of charge transport in graphene have been
+presented in the late years. We discuss a general hydrodynamic model governing
+the dynamics of a two-dimensional electron gas in a magnetized field-effect
+transistor in the slow drift regime. The Dyakonov--Shur instability is
+investigated including the effect of weak magnetic fields (i.e. away from
+Landau levels). We show that the gap on the dispersion relation prevents the
+instability to reach the lower frequencies thus imposing a limit on the Mach
+number of the electronic flow. Furthermore, we discuss that the presence of the
+external magnetic field decreases the growth rate of the instability, as well
+as the saturation amplitude. The numerical results from our simulations and the
+presented higher order dynamic mode decomposition support such reasoning.",2101.10786v2
+2021-05-03,Three-dimensional core-collapse supernovae with complex magnetic structures: I. Explosion dynamics,"Magnetic fields can play a major role in the dynamics of outstanding
+explosions associated to violent events such as GRBs and hypernovae, since they
+provide a natural mechanism to harness the rotational energy of the central
+proto-neutron star and power relativistic jets through the stellar progenitor.
+As the structure of such fields is quite uncertain, most numerical models of
+MHD-driven core-collapse supernovae consider an aligned dipole as initial
+magnetic field, while the field's morphology can actually be much more complex.
+We present three-dimensional simulations of core-collapse supernovae with more
+realistic magnetic structures, such as quadrupolar fields and, for the first
+time, an equatorial dipolar field. Configurations other than an aligned dipole
+produce weaker explosions and less collimated outflows, but can at the same
+time be more efficient in extracting the rotational energy from the PNS. This
+energy is then stored in the surroundings of the PNS, rather than powering the
+polar jets. A significant axial dipolar component is also produced by models
+starting with a quadrupolar field, pointing to an effective dynamo mechanism
+operating in proximity of the PNS surface.",2105.00665v2
+2021-07-22,Are GRMHD Mean-Field Dynamo Models of Thick Accretion Disks SANE?,"The remarkable results by the Event Horizon Telescope collaboration
+concerning the emission from M87* and, more recently, its polarization
+properties, require an increasingly accurate modeling of the plasma flows
+around the accreting black hole. Radiatively inefficient sources such as M87*
+and Sgr A* are typically modeled with the SANE (standard and normal evolution)
+paradigm, if the accretion dynamics is smooth, or with the MAD (magnetically
+arrested disk) paradigm, if the black hole's magnetosphere reacts by halting
+the accretion sporadically, resulting in a highly dynamical process. While the
+recent polarization studies seem to favor MAD models, this may not be true for
+all sources, and SANE accretion surely still deserves attention. In this work,
+we investigate the possibility of reaching the typical degree of magnetization
+and other accretion properties expected for SANE disks by resorting to the
+mean-field dynamo process in axisymmetric GRMHD simulations, which are supposed
+to mimic the amplifying action of an unresolved magnetorotational
+instability-driven turbulence. We show that it is possible to reproduce the
+main diagnostics present in the literature by starting from very unfavorable
+initial configurations, such as a purely toroidal magnetic field with
+negligible magnetization.",2107.10630v1
+2021-07-27,"Dipolar Ising Model: Phases, Growth Laws and Universality","The behavior of many magnetic and dielectric solids, and the more
+contemporary magnetic super-lattices, is governed by dipolar interactions. They
+are anisotropic and long-ranged, having varied consequences ranging from ground
+states with complicated magnetic order to the presence of glassy dynamics
+characterised by a plethora of relaxation times.These systems are well-captured
+by the dipolar Ising model (DIM) with nearest-neighbor exchange interactions
+(J) and long-range dipolar interactions (D). Depending on the relative
+interaction strength {\Gamma} =J/D, there are four phases of distinct magnetic
+order and symmetry. Using Monte Carlo simulations, we perform deep quenches to
+study domain growth or coarsening in the d= 3 DIM. This important
+non-equilibrium phenomenon has not been addressed as dipolar interactions are
+notoriously difficult to handle theoretically. Our study reveals that, in spite
+of the anisotropy in interactions and diversity in ground state configurations,
+we observe universality in the ordering dynamics of all phases.",2107.12803v1
+2021-08-11,Optical excitation and probing of the antiferromagnetic modes with non-uniform in-depth distribution in birefringent antiferromagnetic crystals,"Optical pump-probe setups are commonly used for excitation and investigation
+of the spin dynamics in various types of magnetic materials. However, usually
+the spatially homogeneous excitation is considered. In the present study we
+describe an approach for optical excitation of the nonuniform THz spin dynamics
+and for probing its spatial distribution inside a magnetic crystal. We propose
+to illuminate a crystal with laser pulses of properly adjusted polarization to
+benefit from a strong optical birefringence inherent to the crystal. It results
+in an unusual behavior of the effective magnetic field generated by the pulses
+due to the inverse Faraday effect and the peculiar sign-changing dependence of
+the direct Faraday effect inside the crystal. The study is performed exemplary
+for yttrium orthoferrite crystal although the proposed approach is applicable
+for various magnetic materials with optical anisotropy.",2108.05443v2
+2021-08-16,Bell-state generation for spin qubits via dissipative coupling,"We theoretically investigate the dynamics of two spin qubits interacting with
+a magnetic medium. A systematic formal framework for this qubit-magnet hybrid
+system is developed in terms of the steady-state properties of the magnetic
+medium. Focusing on the induced dissipative coupling between the spin qubits,
+we show how a sizable long-lived entanglement can be established via the
+magnetic environment, in the absence of any coherent coupling. Moreover, we
+demonstrate that maximally-entangled two-qubit states (Bell states) can be
+achieved in this scheme when complemented by proper postselection. In this
+situation, the time evolution of the entanglement is governed by a
+non-Hermitian Hamiltonian, where dynamical phases are separated by an
+exceptional point. The resultant Bell state is robust against weak random
+perturbations and does not require the preparation of a particular initial
+state. Our study may find applications in quantum information science, quantum
+spintronics, and for sensing of nonlocal quantum correlations.",2108.07365v2
+2021-09-01,Collective hydrodynamic transport of magnetic microrollers,"We investigate the collective transport properties of microscopic magnetic
+rollers that propel close to a surface due to a circularly polarized, rotating
+magnetic field. The applied field exerts a torque to the particles, which
+induces a net rolling motion close to a surface. The collective dynamics of the
+particles result from the balance between magnetic dipolar interactions and
+hydrodynamic ones. We show that, when hydrodynamics dominate, i.e. for high
+particle spinning, the collective mean velocity linearly increases with the
+particle density. In this regime we analyse the clustering kinetics, and find
+that hydrodynamic interactions between the anisotropic, elongated particles,
+induce preferential cluster growth along a direction perpendicular to the
+driving one, leading to dynamic clusters that easily break and reform during
+propulsion.",2109.00289v2
+2021-09-28,Radical pairs may play a role in microtubule reorganization,"The exact mechanism behind general anesthesia remains an open question in
+neuroscience. It has been proposed that anesthetics selectively prevent
+consciousness and memory via acting on microtubules (MTs). It is known that the
+magnetic field modulates MT organization. A recent study shows that a radical
+pair model can explain the isotope effect in xenon-induced anesthesia and
+predicts magnetic field effects on anesthetic potency. Further, reactive oxygen
+species are also implicated in MT stability and anesthesia. Based on a simple
+radical pair mechanism model and a simple mathematical model of MT
+organization, we show that magnetic fields can modulate spin dynamics of
+naturally occurring radical pairs in MT. We show that the spin dynamics
+influence a rate in the reaction cycle, which translates into a change in the
+MT density. We can reproduce magnetic field effects on the MT concentration
+that have been observed. Our model also predicts additional effects at slightly
+higher fields. Our model further predicts that the effect of zinc on the MT
+density exhibits isotopic dependence. The findings of this work make a
+connection between microtubule-based and radical pair-based quantum theories of
+consciousness.",2109.14055v1
+2021-10-28,The dynamic chirality flips of Skyrmion bubbles,"Magnetic skyrmion, a topological magnetic domain with complex non-coplanar
+spin texture, appears a disk-like structure in two dimensions. Exploring
+three-dimensional spin texture and related chirality switching has drawn
+enormous interests from the perspective of fundamental research. Here, the
+three-dimensional magnetic moment of the skyrmion bubbles in centrosymmetric
+Mn-Ni-Ga were reconstructed with the vector field tomography approach via
+Lorentz transmission electron microscopy. The type of the bubbles was
+determined from investigating the magnetic vectors in entire space. We found
+that the bubbles switched their chirality easily but still keep the polarity to
+remain the singularity of the bubbles within the material. Our results offer
+valuable insights into the fundamental mechanisms underlying the spin chirality
+flips dynamics of skyrmion bubbles.",2110.14898v1
+2021-11-24,A generalized model of magnon kinetics and subgap magnetic noise,"Magnetic noise spectroscopy provides a noninvasive probe of spin dynamics in
+magnetic materials. We consider two-dimensional magnetically ordered insulators
+with magnon excitations, especially those supporting long-distance magnon
+transport, where nitrogen-vacancy (NV) centers enable the access to (nearly)
+ballistic transport regime of magnons. We develop a generalized theory to
+describe the magnon transport across a wide range of length scales. The
+longitudinal dynamic spin susceptibility is derived from the Boltzmann equation
+and extended to a Lindhard form, which is modified by both the spin-conserving
+magnon collisions and spin relaxation. Our result is consistent with the
+diffusive (ballistic) model for the length scale much larger (smaller) than the
+magnon mean free path, and provides a description for the intermediate regime.
+We also give a prediction for the NV transition rate in different magnon
+transport regimes.",2111.12613v2
+2021-12-16,Geometric continuous-stage exponential energy-preserving integrators for charged-particle dynamics in a magnetic field from normal to strong regimes,"This paper is concerned with geometric exponential energy-preserving
+integrators for solving charged-particle dynamics in a magnetic field from
+normal to strong regimes. We firstly formulate the scheme of the methods for
+the system in a uniform magnetic field by using the idea of continuous-stage
+methods, and then discuss its energy-preserving property. Moreover, symmetric
+conditions and order conditions are analysed. Based on those conditions, we
+propose two practical symmetric continuous-stage exponential energy-preserving
+integrators of order up to four. Then we extend the obtained methods to the
+system in a nonuniform magnetic field and derive their properties including the
+symmetry, convergence and energy conservation. Numerical experiments
+demonstrate the efficiency of the proposed methods in comparison with some
+existing schemes in the literature.",2112.08576v1
+2021-12-29,Harnessing re-programmable phase transitions to control the propagation of sound waves,"Metamaterials can enable peculiar static and dynamic behavior (such as
+negative effective mass density, dynamical stiffness, and Poisson's ratio) due
+to their geometry rather than their chemical composition. The geometry of these
+metamaterials can be thought of as the phase of the material, which is usually
+fixed once the material is fabricated. While there exist many theoretical and
+numerical studies of metamaterials that can change phase, or re-program,
+experimental realizations remain limited due to challenges in
+manufacturability, the destructive nature of the re-programming and inherent
+non-linearities. Through a combination of analytical, numerical and
+experimental analyses, we utilize tunable, self-assembled, nonlinear magnetic
+lattices to realize metamaterials with reversible phase transitions. Our
+metamaterials are composed of free-floating disks, with embedded permanent
+magnets, confined within magnetic boundaries. We exploit the non-destructive
+nature of the adjustable magnetic boundaries to create a set of re-programmable
+metamaterials to control the propagation of sound waves. Furthermore, we
+demonstrate a robust, real-time tunable wave filter at ultra-low frequencies.
+Our findings can expand the metamaterials horizon into functional and tunable
+devices.",2112.14787v1
+2021-12-30,Spin Torque Oscillations Triggered by In-plane Field,"We study the dynamics of a spin torque nano oscillator that consists of
+parallelly magnetized free and pinned layers by numerically solving the
+associated Landau-Lifshitz-Gilbert-Slonczewski equation in the presence of a
+field-like torque. We observe that an in-plane magnetic field which is applied
+for a short interval of time ($<$1ns) triggers the magnetization to exhibit
+self-oscillations from low energy initial magnetization state. Also, we confirm
+that the frequency of oscillations can be tuned over the range $\sim$25 GHz to
+$\sim$72 GHz by current, even in the absence of field-like torque. We find the
+frequency enhancement up to 10 GHz by the presence of field-like torque. We
+determine the Q-factor for different frequencies and show that it increases
+with frequency. Our analysis with thermal noise confirms that the system is
+stable against thermal noise and the dynamics is not altered appreciably by it.",2112.15004v1
+2022-01-05,Topological characterization of dynamic chiral magnetic textures using machine learning,"Recently proposed spintronic devices use magnetic skyrmions as bits of
+information. The reliable detection of those chiral magnetic objects is an
+indispensable requirement. Yet, the high mobility of magnetic skyrmions leads
+to their stochastic motion at finite temperatures, which hinders the precise
+measurement of the topological numbers. Here, we demonstrate the successful
+training of artificial neural networks to reconstruct the skyrmion number in
+confined geometries from time-integrated, dimensionally reduced data. Our
+results prove the possibility to recover the topological charge from a
+time-averaged measurement and hence smeared dynamic skyrmion ensemble, which is
+of immediate relevance to the interpretation of experimental results,
+skyrmion-based computing, and memory concepts",2201.01629v2
+2022-02-07,Magnetization dynamics affected by phonon pumping,"""Pumping"" of phonons by a dynamic magnetization promises to extend the range
+and functionality of magnonic devices. We explore the impact of phonon pumping
+on room-temperature ferromagnetic resonance (FMR) spectra of bilayers of thin
+yttrium iron garnet (YIG) films on thick gadolinium gallium garnet substrates
+over a wide frequency range. At low frequencies the Kittel mode hybridizes
+coherently with standing ultrasound waves of a bulk acoustic resonator to form
+magnon polarons that induce rapid oscillations of the magnetic susceptibility,
+as reported before. At higher frequencies, the phonon resonances overlap,
+merging into a conventional FMR line, but with an increased line width. The
+frequency dependence of the increased line broadening follows the predictions
+from phonon pumping theory in the thick substrate limit. In addition, we find
+substantial magnon-phonon coupling of a perpendicular standing spin wave (PSSW)
+mode. This evidences the importance of the mode overlap between the acoustic
+and magnetic modes, and provides a route towards engineering the magnetoelastic
+mode coupling.",2202.03331v1
+2022-02-10,Dimensional reduction and the generalized pion in a magnetic field within the NJL model,"In this work, the mass of the neutral pion is investigated in the presence of
+background magnetic fields in the framework of the Nambu--Jona-Lasinio model.
+Taking into account the anisotropic four-fermion interactions, a tensor current
+arises in the magnetized QCD system, which forms an anomalous magnetic moment
+(AMM) coupling in the Dirac equation for the quarks. By solving the gap
+equations, we find that the sign of the dynamically generated AMM is opposite
+to the sign of the quark's charge and its magnitude is definitely smaller than
+the constituent mass. We construct two generalized Nambu-Goldstone pions, which
+emerge as combinations of the quantum fluctuations around the conventional
+scalar and the emergent tensor chiral condensates. We analytically demonstrate
+that the Goldstone nature has been spoiled by the dimensional reduction in the
+two-particle state and the corresponding decreasing mass of the lighter
+generalized pionic mode is a remnant of the infrared dynamics.",2202.05090v2
+2022-03-03,Beam dynamics corrections to the Run-1 measurement of the muon anomaly $a_μ$ at Fermilab,"The Fermi National Accelerator Laboratory (FNAL) Muon $g-2$ Experiment has
+measured the positive muon magnetic anomaly $a_{\mu} \equiv (g_{\mu}-2)/2$ with
+a precision of 0.46 parts per million, with data collected during its first
+physics run in 2018. The experimental result combined with the measurement from
+the former experiment at Brookhaven National Laboratory increases the tension
+with the Standard Model expectation to $4.2\sigma$, thus strengthening evidence
+for new physics. The magnetic anomaly is determined from the precision
+measurements of the muon spin precession frequency, relative to the muon
+momentum, and the average magnetic field seen by the beam. In an ideal case
+with muons orbiting in a horizontal plane with a uniform vertical magnetic
+field, the anomalous precession frequency $\omega_a$ is given by the difference
+between the spin~($s$) and cyclotron~($c$) frequencies, $\omega_a = \omega_s -
+\omega_c$. The observable $\omega_a$ is proportional to $a_{\mu}$. This
+proceeding presents the beam dynamics systematic corrections that are required
+to adjust the measured muon precession frequency $\omega^{m}_{a}$ to its true
+physical value $\omega_{a}$.",2203.02021v1
+2022-03-22,Intrinsic ferromagnetism and restrictive thermodynamic stability in MA$_2$N$_4$ and Janus VSiGeN$_4$ monolayers,"The seminal experimental discovery of the remarkably stable MoSi$_2$N$_4$
+monolayer has led to a handful of predicted magnetic two-dimensional (2D)
+materials in the MA$_2$Z$_4$ family (M = transition metals, A = Si, Ge, and Z =
+N, P, As). These magnetic monolayers were predicted to be dynamically stable,
+but none of them has been synthesized to date. In this Research Letter, from
+first-principles thermodynamic stability analysis, we demonstrate that only the
+nitrides are thermodynamically stable and this occurs under N-rich conditions.
+Based on this finding, we propose two ferromagnetic, semiconducting Janus
+monolayers in the family: VSiGeN$_4$ and VSiSnN$_4$. They are both dynamically
+and thermally stable, but only the former is thermodynamically stable.
+Intriguingly, Janus VSiGeN$_4$ and VSiSnN$_4$ monolayers show weak in-plane
+anisotropy compared with the VSi$_2$N$_4$ monolayer. These two emerging Janus
+magnetic semiconductors offer opportunities for studying 2D magnetism and spin
+control for spintronics applications.",2203.11605v3
+2022-04-03,Zero absolute vorticity plane Couette flow as an hydrodynamic representation of quantum energy states under perpendicular magnetic field,"Here we extend the Madelung transformation of the Schr\""{o}dinger equation
+into a fluid-like form to include the influence of an external electromagnetic
+field on a charged particle. The vorticity of the Madelung fluid is then in the
+opposite direction to the imposed magnetic field and equal in magnitude to the
+cyclotron angular frequency. When the particle motion is confined to a plane,
+perpendicular to an imposed magnetic field, the equivalent flow dynamics is
+that of zero absolute vorticity obtained in a quasi 2D rotating frame, where
+the cyclotron frequency plays a role equivalent to that of the Coriolis
+frequency in a rotating frame. We show how the Landau levels and the extended
+modes in the integer quantum Hall effect are all mapped into such zero absolute
+vorticity-like plane Couette flows, where the latter exhibit a geostrophic-like
+balance between the magnetic force and the gradients of the quantum (Bohm)
+potential and the electric force.",2204.01013v1
+2022-05-23,Three-dimensional direct numerical simulation of free-surface magnetohydrodynamic wave turbulence,"We report on three-dimensional direct numerical simulation of wave turbulence
+on the free surface of a magnetic fluid subjected to an external horizontal
+magnetic field. A transition from capillarywave turbulence to anisotropic
+magneto-capillary wave turbulence is observed for an increasing field. At high
+enough field, wave turbulence becomes highly anisotropic, cascading mainly
+perpendicularly to the field direction, in good agreement with the prediction
+of a phenomenological model, and with anisotropic Alfv{\'e}n wave turbulence.
+Although surface waves on a magnetic fluid are different from Alfv{\'e}n waves
+in plasma, a strong analogy is found with similar wave spectrum scalings and
+similar magnetic-field dependent dispersionless wave velocities.",2205.11516v1
+2022-07-25,Local fluxes in MHD Turbulence,"Using highly resolved direct numerical simulations we examine the statistical
+properties of the local energy flux rate $\Pi_\ell(x)$ towards small scales for
+three isotropic turbulent magnetohydrodynamic flows, which differ in strength
+and structure of the magnetic field. We analyse the cascade process both in the
+kinetic and magnetic energy, disentangling the different flux contributions to
+the overall energy dynamics. The results show that the probability distribution
+of the local energy flux develops long tails related to extreme events, similar
+to the hydrodynamic case. The different terms of the energy flux display
+different properties and show sensitivity on the type of the flow examined. We
+further examine the joint pdf between the local energy flux and the gradients
+of the involved fields. The results point out a correlation with the magnetic
+field gradients, showing however a dispersion much stronger than what is
+observed in hydrodynamic flows. Finally, it is also shown that the local energy
+flux shows some dependence on the local amplitude of the magnetic field. The
+present results have implications for subgrid scale models that we discuss.",2207.12335v1
+2022-07-28,Dynamical chiral magnetic current and instability in Weyl semimetals,"Weyl semimetals realize massless relativistic fermions with two Weyl nodes
+separated in energy and momentum space, whose low-energy physics is described
+by Dirac fermions with an axial gauge constant. Here, we study their
+electromagnetic linear responses based on the effective field theory and on the
+chiral kinetic theory. Although the static chiral magnetic effect is canceled
+by the Chern-Simons current under the Pauli-Villars regularization, a dynamical
+magnetic field is found capable of driving an electric current along its
+direction, with the total transported charge being independent of temperature
+and chemical potential for a uniform field. We also incorporate dissipation in
+the relaxation-time approximation and study collective excitations coupled with
+Maxwell electromagnetic fields when Weyl node populations deviate from
+equilibrium. Their dispersion relations at low frequency and long wavelength
+are determined only by electric, chiral magnetic, and anomalous Hall
+conductivities, which predict unstable modes leading to anisotropic generation
+of electromagnetic waves oriented to the direction of Weyl node separation.",2207.14272v3
+2022-09-06,Magnetic-induced Spontaneous Scalarization in Dynamcial Chern-Simons Gravity,"In the framework of the dynamical Chern-Simons gravity, we study the scalar
+field perturbations of the Reissner-Nordstr\""{o}m-Melvin spacetime, which
+describes a charged black hole permeated by a uniform magnetic field. In the
+presence of the magnetic field, the scalar field acquires an effective mass
+whose square takes negative value in the half domain of the angular direction.
+This inevitably introduces the tachyonic instability and associated spontaneous
+scalarization as long as the coupling constant between the scalar field and the
+Chern-Simons invariant exceeds a threshold value. We study the object pictures
+of the time evolutions of the scalar field perturbations at the linear level,
+and find that the presence of the magnetic field will dramatically change the
+waveforms and associated ringdown modes. Nonlinear evolutions for the unstable
+perturbations are also performed in the decoupling limit, which demonstrate the
+scalar cloud as the final fate. Influences of the coupling constant and the
+black hole charge on the wave dynamics are also studied.",2209.02268v2
+2022-12-19,Multi-Meron Interactions and Statistics in Two-Dimensional Materials,"As a fundamental type of topological spin textures in two-dimensional (2D)
+magnets, a magnetic meron carries half-integer topological charge and forms a
+pair with its antithesis to keep the stability in materials. However, it is
+challenging to quantitatively calculate merons and their dynamics by using the
+widely used continuum model because of the characteristic highly inhomogeneous
+spin textures. In this work, we develop a discrete method to address the
+concentrated spin structures around the core of merons. We reveal a
+logarithmic-scale interaction between merons when their distance is larger than
+twice their core size and obtain subsequent statistics of meron gas. The model
+also predicts how these properties of single and paired merons evolve with
+magnetic exchange interactions, and the results are in excellent agreement with
+the Monte Carlo simulations using the parameters of real 2D van der Waals
+magnetic materials. This discrete approach not only shows equilibrium static
+statistics of meron systems but also is useful to further explore the dynamic
+properties of merons through the quantified pairing interactions.",2212.09698v1
+2022-12-29,Non-volatile Electric Control of Magnetic and Topological Properties of MnBi2Te4 Thin Films,"In this letter, we propose a mechanism to control the magnetic properties of
+topological quantum material (TQM) by using magnetoelectric coupling: this
+mechanism uses a heterostructure of TQM with two-dimensional (2D) ferroelectric
+material, which can dynamically control the magnetic order by changing the
+polarization of the ferroelectric material and induce possible topological
+phase transitions. This concept is demonstrated using the example of the
+bilayer MnBi2Te4 on ferroelectric In2Se3 or In2Te3, where the polarization
+direction of the 2D ferroelectrics determines the interfacial band alignment
+and consequently the direction of the charge transfer. This charge transfer, in
+turn, enhances the stability of the ferromagnetic state of MnBi2Te4 and leads
+to a possible topological phase transition between the quantum anomalous Hall
+(QAH) effect and the zero plateau QAH. Our work provides a route to dynamically
+alter the magnetic ordering of TQMs and could lead to the discovery of new
+multifunctional topological heterostructures.",2212.14331v1
+2022-12-30,Unique determination of localized basis in molecular spin,"Localized basis plays an important role in comprehending the magnetic
+dynamics in molecular spins from a physics perspective. Nonetheless, the
+uniqueness and rigor of its determination have received limited attention. In
+this study, we propose a new determination of the localized basis applicable to
+both non-Kramers and Kramers molecular spin systems, leveraging the
+time-reversal symmetry of the spin Hamiltonian and the molecular spin's main
+magnetic axis. By introducing this, we establish a distinct and practical means
+of determining the localized basis, enabling the association of a molecular
+spin wave function with either an ""up"" or ""down"" magnetic moment orientation in
+molecular spins. This finding facilitates a comprehensive interpretation of
+magnetic dynamics and simplifies the construction of theoretical models for
+materials analysis.",2212.14639v3
+2023-01-12,Identification of Magnetic Field Errors in Synchrotrons based on Deep Lie Map Networks,"Magnetic field errors pose a limitation in the performance of synchrotrons,
+as they excite non-systematic resonances, reduce dynamic aperture and may
+result in beam loss. Their effect can be compensated assuming knowledge of
+their location and strength. Established identification procedures are based on
+orbit response matrices or resonance driving terms. While they sequentially
+build a field error model for subsequent accelerator sections, a method
+detecting field errors in parallel could save valuable beam time. We introduce
+deep Lie map networks, which enable construction of an accelerator model
+including multipole components for the magnetic field errors by linking charged
+particle dynamics with machine learning methodology in a data-driven approach.
+Based on simulated beam-position-monitor readings for the example case of SIS18
+at GSI, we demonstrate inference of location and strengths of gradient and
+sextupole errors for all accelerator sections in parallel. The obtained refined
+accelerator model may support setup of corrector magnets in operation to allow
+more precise control over tunes, chromaticities and resonance compensation.",2301.04914v2
+2023-03-24,Magnetic and antimagnetic rotational bands data tables,"The experimental results of 252 magnetic rotational bands reported in 123
+nuclei and 38 antimagnetic rotational bands reported in 27 nuclei are collected
+and listed in the present work, including energy, spin, parity, magnetic dipole
+reduced transition probability B(M1), electric quadrupole reduced transition
+probability B(E2), B(M1)/B(E2) ratio, and the ratio of the dynamic moment of
+inertia to the electric quadrupole reduced transition probability J(2)/B(E2).
+Following the presentation of the kinematic moment of inertia J(1), dynamic
+moment of inertia J(2), and I versus rotational frequency, as well as energy
+staggering parameter S(I), B(M1), B(E2), B(M1)/B(E2), and J(2)/B(E2) versus I
+in A 60, 80, 110, 140, and 190 mass regions, a brief discussion is provided.
+Based on the systematic studies, some nuclei are predicted to be candidates for
+magnetic or antimagnetic rotation.",2303.13849v1
+2023-04-26,Confining and escaping magnetic field lines in Tokamaks: Analysis via symplectic map,"In magnetically confined plasma, it is possible to qualitatively describe the
+magnetic field configuration via phase spaces of suitable symplectic maps.
+These phase spaces are of mixed type, where chaos coexists with regular motion,
+and the complete understanding of the chaotic transport is a challenge that,
+when overcome, may provide further knowledge into the behaviour of confined
+fusion plasma. This work presents two numerical investigations into
+characteristics of mixed phase spaces which model distinct magnetic
+configurations in tokamaks under different perturbation regimes. The first
+approach relies on a recurrence-based analysis of ensembles of chaotic
+trajectories to detect open field lines that widely differ from the average.
+The second focuses on the transient dynamical behaviour of field lines before
+they escape the systems. These two methods provide insights into the influence
+of stickiness and invariant manifolds on the evolution of chaotic trajectories,
+improving our understanding of how these features affect the chaotic transport
+and diffusion properties in mixed phase spaces. These theoretical and numerical
+approaches may enhance our comprehension of confined plasma behaviour and
+plasma-wall interactions.",2304.13810v1
+2023-05-03,"Impacts of the half-skyrmion spin topology, spin-orbit torque, and dynamic symmetry breaking on the growth of magnetic stripe domains","We have performed an experimental and modeling-based study of the spin-orbit
+torque-induced growth of magnetic stripe domains in heavy metal/ferromagnet
+thin-film heterostructures that possess chiral N\'eel-type domain walls due to
+an interfacial Dzyaloshinskii-Moriya interaction. In agreement with previous
+reports, the stripe domains stabilized in these systems exhibit a significant
+transverse growth velocity relative to the applied current axis. This behavior
+has previously been attributed to the Magnus force-like skyrmion Hall effect of
+the stripe domain spin topology, which is analogous to that of a half-skyrmion.
+However, through analytic modeling of the in-plane torques generated by
+spin-orbit torque, we find that a dynamical reconfiguration of the domain wall
+magnetization profile is expected to occur - promoting motion with similar
+directionality and symmetry as the skyrmion Hall effect. These results further
+highlight the sensitivity of spin-orbit torque to the local orientation of the
+domain wall magnetization profile and its contribution to domain growth
+directionality.",2305.02181v1
+2023-05-29,Phase transition of three-dimensional finite-sized charged dust clusters in a plasma environment,"The dynamics of a harmonically trapped three-dimensional Yukawa ball of
+charged dust particles immersed in plasma is investigated as function of
+external magnetic field and Coulomb coupling parameter using molecular dynamics
+simulation. It is shown that the harmonically trapped dust particles organize
+themselves into nested spherical shells. The particles start rotating in a
+coherent order as the magnetic field reaches a critical value corresponding to
+the coupling parameter of the system of dust particles. The magnetically
+controlled charged dust cluster of finite size undergoes a first-order phase
+transition from disordered to ordered phase. At sufficiently high coupling and
+strong magnetic field, the vibrational mode of this finite-sized charged dust
+cluster freezes, and the system retains only rotational motion.",2305.17902v1
+2023-07-13,Magnon-magnon coupling in synthetic ferrimagnets,"Magnetic multilayers with interlayer exchange coupling have been widely
+studied for both static and dynamic regimes. Their dynamical responses depend
+on the exchange coupling strength and magnetic properties of individual layers.
+Magnetic resonance spectra in such systems are conveniently discussed in terms
+of coupling of acoustic and optical modes. At a certain value of applied
+magnetic field, the two modes come close to being degenerate and the spectral
+gap indicates the strength of mode hybridisation. In this work, we
+theoretically and experimentally study the mode hybridisation of
+interlayer-exchange-coupled moments with dissimilar magnetisation and thickness
+of two ferromagnetic layers. In agreement with symmetry analysis for
+eigenmodes, our low-symmetry multilayers exhibit sizable spectral gaps for all
+experimental conditions. The spectra agree well with the predictions from the
+Landau-Lifshitz-Gilbert equation at the macrospin limit whose parameters are
+independently fixed by static measurements.",2307.06888v2
+2023-07-20,Dynamical Energy Dissipation of Relativistic Magnetic Bullets,"To demonstrate the magnetic energy dissipation via relativistic shocks, we
+carry out spherically symmetrical one-dimensional special relativistic
+magneto-hydrodynamic simulations of highly magnetised outflows with an adaptive
+mesh refinement method. We first investigate the detail of the dynamical energy
+dissipation via interaction between a single ejecta and an external medium. The
+energy dissipation timescales, which affect the early behaviour of the
+afterglow emission in gamma-ray bursts, are estimated for a wide range of
+magnetisation. In addition, we demonstrate the internal shock dissipation in
+multiple interactions between magnetically dominated relativistic ejecta and
+kinetically dominated non-relativistic winds. Our numerical results show that
+almost 10% of the magnetic energy in the ejecta can be converted into the
+thermal energy of the relativistic and low-magnetised outflows via shocks in
+the rarefaction waves or the winds. Such hot and less magnetised outflows are
+relevant for observed non-thermal emissions in blazars or gamma-ray bursts.",2307.10576v1
+2023-08-24,Stability threshold of the 2D Couette flow in a homogeneous magnetic field using symmetric variables,"We consider a 2D incompressible and electrically conducting fluid in the
+domain $\mathbb{T}\times\mathbb{R}$. The aim is to quantify stability
+properties of the Couette flow $(y,0)$ with a constant homogenous magnetic
+field $(\beta,0)$ when $|\beta|>1/2$. The focus lies on the regime with small
+fluid viscosity $\nu$, magnetic resistivity $\mu$ and we assume that the
+magnetic Prandtl number satisfies
+$\mu^2\lesssim\mathrm{Pr}_{\mathrm{m}}=\nu/\mu\leq 1$. We establish that small
+perturbations around this steady state remain close to it, provided their size
+is of order $\varepsilon\ll\nu^{2/3}$ in $H^N$ with $N$ large enough.
+Additionally, the vorticity and current density experience a transient growth
+of order $\nu^{-1/3}$ while converging exponentially fast to an $x$-independent
+state after a time-scale of order $\nu^{-1/3}$. The growth is driven by an
+inviscid mechanism, while the subsequent exponential decay results from the
+interplay between transport and diffusion, leading to the dissipation
+enhancement. A key argument to prove these results is to reformulate the system
+in terms of symmetric variables, inspired by the study of inhomogeneous fluid,
+to effectively characterize the system's dynamic behavior.",2308.12589v1
+2023-08-24,Effect of magnetic field on the long-time dynamics of two charged coupled harmonic oscillators in the presence of a common heat bath,"In this paper, the moderately long-time behaviours of the position
+autocorrelation, position velocity correlation and velocity autocorrelation
+functions for two charged coupled harmonic oscillators connected to a heat bath
+are derived in the presence of a magnetic field via the Quantum Langevin
+equation. It is seen that at long times the correlation functions at T->0
+exhibit a power law decay with the coefficients of the power laws being
+completely different for the two masses that affect the overall trends of the
+decays of the correlation functions. The effect of the bath-induced force on
+mass m1 mediated by the interaction of m2 with the common heat bath is studied
+and the results are highlighted in the presence of an external magnetic field.
+This brings out the distinctness of the coupled oscillator scenario from the
+independent single oscillator model studied earlier in the literature. The
+results in the absence of a magnetic field are also presented, which are
+extremely important for analyzing the dynamics of atoms in protein molecules at
+low temperatures.",2308.12668v1
+2023-09-14,Paramagnon Heat Capacity and Anomalous Thermopower in Anisotropic Magnetic Systems: Understanding Inter-Layer Spin Correlations in a Magnetically Disordered Phase,"The interplay between entropy transport and charge carriers-paramagnon
+interaction in the Onsager linear system has been a subject of debate due to
+the limited theoretical and experimental understanding of paramagnon heat
+capacity. In this study, we investigate this interplay in an anisotropic
+layered magnetic system using cluster mean-field theory with spin quantum
+correlations. By examining spin correlation functions between different spins
+with various types of clustering, we derive the spin correlation function as a
+function of distance and temperature for the inter-layer clusters both below
+and above the magnetic order phase transition. Our analysis reveals that
+paramagnons characterized by pronounced spin correlations among inter-layer
+nearest-neighbor spins exhibit a non-zero heat capacity, providing valuable
+insights into the dynamics of entropy transport. The findings align with
+experimental observations, lending strong support to the validity of the
+paramagnon drag thermopower concept. This study sheds light on the intricate
+dynamics and thermodynamic properties of paramagnons, advancing our
+understanding of entropy transport in complex systems.",2309.07646v1
+2023-11-24,Light--absorbed orbital angular momentum in the linear response regime,"In exploring the light-induced dynamics within the linear response regime,
+this study investigates the induced orbital angular momentum on a wide variety
+of electronic structures. We derive a general expression for the torque induced
+by light on different electronic systems based on their characteristic
+dielectric tensor. We demonstrate that this phenomenon diverges from the
+inverse Faraday effect as it produces an orbital magnetization persistent
+post-illumination. Indeed, our results reveal that, while isotropic
+non-dissipative materials do not absorb orbital angular momentum from
+circularly polarized light, any symmetry-breaking arrangement of matter, be it
+spatial or temporal, introduces novel channels for the absorption of orbital
+angular momentum, or magnetization. Most notably, in dissipative materials,
+circularly polarized light imparts a torque corresponding to a change in
+orbital angular momentum of $\hbar$ per absorbed photon. The potential of these
+mechanisms to drive helicity-dependent magnetic phenomena paves the way for a
+deeper understanding of light-matter interactions. Notably, the application of
+pump-probe techniques in tandem with our findings allows experimentalists to
+quantitatively assess the amount of orbital angular momentum transferred to
+electrons in matter, thus hopefully enhancing our ability to steer ultrafast
+light-induced magnetization dynamics.",2311.14774v1
+2023-11-30,Two-scale exponential integrators with uniform accuracy for three-dimensional charged-particle dynamics under strong magnetic field,"The numerical simulation of three-dimensional charged-particle dynamics (CPD)
+under strong magnetic field is challenging. In this paper, we introduce a new
+methodology to design two-scale exponential integrators for three-dimensional
+CPD whose magnetic field's strength is inversely proportional to a
+dimensionless parameter $0<\varepsilon \ll 1$. By dealing with the transformed
+form of three-dimensional CPD, we linearize the magnetic field and put the rest
+part in a nonlinear function which can be shown to be small. Based on which and
+the proposed two-scale exponential integrators, a class of novel integrators is
+formulated. The corresponding uniform accuracy over
+$\mathcal{O}(1/\varepsilon^{\beta})$ time interval is
+$\mathcal{O}(\varepsilon^{r\beta} h^r)$ for the $r$-th order integrator with
+the time stepsize $h$, $r=1,2,3,4$ and $0<\beta<1$. A rigorous proof of this
+error bound is presented and a numerical test is performed to illustrate the
+error behaviour of the proposed integrators.",2311.18615v1
+2023-12-15,Dynamic behavior of a magnetic system driven by an oscillatory external temperature,"The dynamic effects on a magnetic system exposed to a time-oscillating
+external temperature are studied using Monte Carlo simulations on the classic
+2D Ising Model.
+  The time dependence of temperature is defined as $T(t)=T_0 + A \cdot
+\sin(2\pi t/\tau)$. Magnetization $M(t)$ and period-averaged magnetization
+$\langle Q\rangle$ are analyzed to characterize out-of-equilibrium phenomena.
+Hysteresis-like loops in $M(t)$ are observed as a function of $T(t)$. The area
+of the loops is well-defined outside the critical Ising temperature ($T_c$) but
+takes more time to close it when the system crosses the critical curve. Results
+show a power-law dependence of $\langle Q\rangle$ (the averaged area of loops)
+on both $L$ and $\tau$, with exponents $\alpha=1.0(1)$ and $\beta=0.70(1)$,
+respectively.
+  Furthermore, the impact of shifting the initial temperature $T_0$ on $\langle
+Q\rangle$ is analyzed, suggesting the existence of an effective
+$\tau$-dependent critical temperature $T_c(\tau)$. A scaling law behavior for
+$\langle Q\rangle$ is found on the base of this $\tau$-dependent critical
+temperature.",2312.10164v1
+2023-12-20,Modelling of impurity heating during reconnections in a Reverse Field Pinch device as due to parallel electric field acceleration and chaos-induced thermalization,"The ion temperature during magnetic reconnections measured along the
+direction of the magnetic field at the MST Reverse Field Pinch has not yet
+received a satisfactory theoretical explanation. In this work we argue that it
+is consistent with a picture of ion energization by the parallel electric
+fields generated by the plasma during reconnection, and thermalization due to
+the chaotic ion dynamics. Three possible sources of randomness are pointed out:
+particle motion along static stochastic magnetic field lines, breakup of the
+adiabatic ion dynamics caused by the strong gradient nonlinearity of the
+magnetic field, parallel acceleration along stochastic time-dependent electric
+fields. The three mechanisms are likely operative simultaneously; regardless
+the specific mechanism active, the correct scaling laws with ion parameters are
+recovered. Furthermore, we argue that quantitative agreement can be obtained by
+feeding the model with realistic values for the plasma conditions.",2312.13067v1
+2023-12-21,Pseudo-spectral Landau-Lifshitz description of magnetization dynamics,"Magnetic materials host a wealth of nonlinear dynamics, textures, and
+topological defects. This is possible due to the competition between strong
+nonlinearity and dispersion that act at the atomic scale as well as long-range
+interactions. However, these features are difficult to analytically and
+numerically study because of the vastly different temporal and spatial scales
+involved. Here, we present a pseudo-spectral approach for the Landau-Lifshitz
+equation that invokes energy and momentum conservation embodied in the magnon
+dispersion relation to accurately describe both atomic and continuum limits.
+Furthermore, this approach enables analytical study at every scale. We show the
+applicability of this model in both the continuum and atomic limit by
+investigating modulational instability and ultrafast evolution of magnetization
+due to transient grating, respectively, in a 1D ferromagnetic chain with
+perpendicular magnetic anisotropy. This model provides the possibility of
+grid-independent multiscale numerical approaches that will enable the
+description of singularities within a single framework.",2312.14068v1
+2023-12-23,Pulse-driven depinning of magnetic gap modes in ferromagnetic films,"Manipulation of magnons in artificial magnonic crystals (MCs) leads to
+fascinating nonlinear wave phenomena such as the generation of gap solitons,
+which has been mostly limited to one-dimensional systems. Here, we propose a
+model system for the magnetization in two-dimensional MCs subjected to a
+periodic external magnetic field, describing the dynamics of magnetic gap
+solitons (MGSs) formed by nonlinear self-trapping. We show the formation,
+stability, and dynamics for various two-dimensional gap modes, including gap
+solitons and vortical ones. Their existence regions depend on the anisotropic
+axis orientation of the ferromagnetic film. The Bloch oscillation and depinning
+propagation of MGSs under constant spin-current injections are discovered and
+characterized. We design a scheme of pulse current injection to achieve
+distortionless propagation of MGSs. These findings show that the 2D magnonic
+crystals can be viewed as a building block for MGSs-based storage and
+transmission, where the propagation and localization are variously controlled
+and reconfigurable.",2312.15200v1
+2024-02-03,Numerical MHD simulations of solar flares and their associated small-scale structures,"Using numerical simulations, we study the formation and dynamics of
+post-flare loops in a local region of the solar atmosphere. The MHD equations
+rule the post-flare structures' dynamic evolution, including space-dependent
+magnetic resistivity and highly anisotropic thermal conduction on a 2.5 D
+slice. We use an initial magnetic configuration consisting of a vertical
+current sheet, which helps trigger the magnetic reconnection process.
+Specifically, we study two scenarios, one with only resistivity and the second
+with resistivity plus thermal conduction. Numerical simulations show
+differences in the global morphology of the post-flare substructures in both
+cases. In particular, localized resistivity produces more substructure on the
+loops related to a Ritchmyer-Meshkov Instability (RMI). On the other hand, in
+the scenario with resistivity plus thermal conduction, the post-flare loops are
+smooth, and no apparent substructures develop. Besides, in the $z-$component of
+the current density for the Res+TC scenario, we observe the development of
+multiple small magnetic islands along the current sheet.",2402.02161v1
+2024-02-05,Transition to chaos and magnetic field generation in rotating Rayleigh-Bénard convection,"Hydrodynamic and magnetohydrodynamic convective attractors in
+three-dimensional rotating Rayleigh-B\'enard convection are studied numerically
+by varying the Taylor and Rayleigh numbers as control parameters. First, an
+analysis of hydrodynamic attractors and their bifurcations is conducted, where
+routes to chaos via quasiperiodicity are identified. Second, the behaviour of
+the magnetohydrodynamic system is investigated by introducing a seed magnetic
+field and measuring its growth or decay as a function of the Taylor number,
+while keeping the Rayleigh number fixed. Analysis of the attractors shows that
+rotation has a significant impact on magnetic field generation in
+Rayleigh-B\'enard convection, with the critical magnetic Prandtl number
+changing nonmonotonically with the rotation rate. It is argued that a
+nonhysteretic blowout bifurcation with on-off intermittency is responsible for
+the transitions to dynamo.",2402.02908v1
+2024-02-07,Macroscopic Magnetic Dynamics,"Ferromagnetic metals and spin-polarized $^{3}$He are spin 1/2 systems with
+the same macroscopic symmetry, and thus should have macroscopic magnetic
+dynamics with the same structure. Using Onsager's irreversible thermodynamics,
+we develop a theory for these systems that contains two relaxation times (one
+for the magnetization $\vec{M}$ and the other for the spin current
+$\vec{J}_{i}$), a magnetic compressibility, and a mean-field parameter.
+Currently spintronics data on metallic ferromagnets are analyzed using a
+complex decay length from a theory employing a diffusion constant, a lifetime,
+and a mean-field parameter. The present theory leads to a complex decay length
+with the same structure. On neglecting decay of $\vec{M}$, the present theory
+applies to liquids and gases. For macroscopic equations the particle statistics
+is not relevant, so the theory also applies to bosons. The theory predicts a
+longitudinal spin wave whose velocity we estimate for liquid $^{3}$He and for
+paramagnetic metals; but such a wave should also occur for ferromagnets and for
+gases.",2402.04639v1
+2024-02-16,Spin projection noise and the magnetic sensitivity of optically pumped magnetometers,"Present protocols for obtaining the ultimate magnetic sensitivity of
+optically pumped magnetometers (OPMs) utilizing alkali-metal ensembles rely on
+uncorrelated atoms in stretched states. A new approach for calculating the spin
+projection noise (SPN)-limited signal to noise ratio (SNR) and the magnetic
+sensitivity of OPMs is proposed. Our model is based solely on the mean-field
+density matrix dynamics and in contrast to previous models, it applies to both
+low and high field regimes, it takes into account the degree of spin
+polarization, the intra- and interhyperfine correlations, the decoherence
+processes, the atom-light coupling and the effects of the spin dynamics on the
+spin-noise spectra. Fine tuning of the probe frequency allow us to explore
+different hyperfine states and ground-state correlations. Especially in the
+spin-exchange-relaxation-free (SERF) regime, alongside the magnetic resonance
+narrowing and the increased number density, hallmarks of SERF magnetometers, we
+report on a new SERF feature; the reduction of spin-projection noise at the
+spin precession frequency as a consequence of strongly-correlated hyperfine
+spins that attenuate and redistribute SPN when properly probed.",2402.10746v2
+2024-03-06,"Buzdin, Shapiro and Chimera Steps in $\varphi_0$ Josephson Junctions. II. Bifurcation, Switching, and Hysteresis","The dynamics of magnetization and current-voltage characteristics of the
+superconductor-ferromagnet-superconductor $\varphi_0$ Josephson junction in the
+presence of external electromagnetic radiation have been studied. Effects of
+radiation magnetic component are investigated in the frameworks of one- and
+two-signal models. The implementation of two types of dynamical states of
+magnetization is demonstrated. These states have a phase shift of $\pi$ in the
+synchronization region of magnetic precession and Josephson oscillations and
+differ in the nature of their time dependence. Transitions between these states
+with increasing and decreasing bias current show hysteresis, which is reflected
+in the bifurcation diagram and the current-voltage characteristics. We also
+provide an experimental way to test the obtained results by measuring the phase
+shift in voltage temporal dependence at fixed current value for both sweeping
+directions. The results obtained can find application in various fields of
+superconducting spintronics and quantum computing.",2403.03621v1
+1997-11-01,The dissipative effect of thermal radiation loss in high-temperature dense plasmas,"A dynamical model based on the two-fluid dynamical equations with energy
+generation and loss is obtained and used to investigate the self-generated
+magnetic fields in high-temperature dense plasmas such as the solar core. The
+self-generation of magnetic fields might be looked at as a
+self-organization-type behavior of stochastic thermal radiation fields, as
+expected for an open dissipative system according to Prigogine's theory of
+dissipative structures.",9711002v1
+2005-03-26,On Quasilinear Perpendicular Diffusion,"Quasilinear perpendicular diffusion of charged particles in fluctuating
+electromagnetic fields is the focus of this paper. A general transport
+parameter for perpendicular diffusion is presented being valid for an arbitrary
+turbulence geometry and a plasma wave dispersion relation varying arbitrarily
+in wavevector. The new diffusion coefficient is evaluated in detail for slab
+turbulence geometry for two special cases: (1) Alfv\'enic turbulence and (2)
+dynamical magnetic turbulence. Furthermore, perpendicular diffusion in 2D
+geometry is considered for a purely dynamical magnetic turbulence. The
+derivations and numerical calculations presented here cast serious doubts on
+the applicability of quasilinear theory for perpendicular diffusion.
+Furthermore, they emphasize that nonlinear effects play a crucial role in the
+context of perpendicular diffusion.",0503576v1
+1995-09-05,Computation of Kolmogorov's Constant in Magnetohydrodynamic Turbulence,"In this paper we calculate Kolmogorov's constant for magnetohydrodynamic
+turbulence to one loop order in perturbation theory using the direct
+interaction approximation technique of Kraichnan. We have computed the
+constants for various $E^u(k)/E^b(k)$, i.e., fluid to magnetic energy ratios
+when the normalized cross helicity is zero. We find that $K$ increases from
+1.47 to 4.12 as we go from fully fluid case $(E^b=0)$ to a situation when $%
+E^u/E^b=0.5$, then it decreases to 3.55 in a fully magnetic limit $(E^u=0)$.
+When $E^u/E^b=1$, we find that $K=3.43$.",9509001v1
+1996-07-29,On developed turbulence in a weak compressibile conductive fluid,"A method of construction of decomposition of correlation functions of
+developed turbulence in a compressible fluid on Mach number {\em Ma} is
+generalized now for a model of stochastic magnetic hydrodynamics. With the help
+of the field theory renormalization group method the composite operators of
+transversal fields are studied. It is shown, that in the case of hydrodynamical
+interaction of fluid flows is prevalent the compressible effects are essential
+in inertial range. On the contrary the corrections to developed turbulent
+spectra due to compressibility are insignificant if the magnetic interaction of
+flows is more important one.",9607015v1
+1999-01-20,The Effect of Radiation on the Stochastic Web,"A charged particle circling in a uniform magnetic field and kicked by an
+electric field is considered. Under the assumption of small magnetic field, an
+iterative map is developed. Comparison between the (relativistic) non-radiative
+case and the (relativistic) radiative case shows that in both cases one can
+observe a stochastic web structure, and that both cases are qualitatively
+similar.",9901015v1
+1999-10-11,Decaying magnetohydrodynamics: effects of initial conditions,"We study the effects of homogenous and isotropic initial conditions on
+decaying Magnetohydrodynamics (MHD). We show that for an initial distribution
+of velocity and magnetic field fluctuations, appropriately defined structure
+functions decay as power law in time. We also show that for a suitable choice
+of initial cross-correlations between velocity and magnetic fields even order
+structure functions acquire anomalous scaling in time where as scaling
+exponents of the odd order structure functions remain unchanged. We discuss our
+results in the context of fully developed MHD turbulence.",9910017v1
+1993-03-26,Nonequilibrium Dynamics and Aging in the Three--Dimensional Ising Spin Glass Model,"The low temperature dynamics of the three dimensional Ising spin glass in
+zero field with a discrete bond distribution is investigated via MC
+simulations. The thermoremanent magnetization is found to decay algebraically
+and the temperature dependent exponents agree very well with the experimentally
+determined values. The nonequilibrium autocorrelation function $C(t,t_w)$ shows
+a crossover at the waiting (or {\em aging}) time $t_w$ from algebraic {\em
+quasi-equilibrium} decay for times $t$$\ll$$t_w$ to another, faster algebraic
+decay for $t$$\gg$$t_w$ with an exponent similar to one for the remanent
+magnetization.",9303048v1
+1993-08-27,Phase Transition Study of Superconducting Microstructures,"The presented results are part of a feasibility study of superheated
+superconducting microstructure detectors. The microstructures (dots) were
+fabricated using thin film patterning techniques with diameters ranging from
+$50\mu$m up to $500\mu$m and thickness of $1\mu$m. We used arrays and single
+dots to study the dynamics of the superheating and supercooling phase
+transitions in a magnetic field parallel to the dot surface. The phase transi-
+tions were produced by either varying the applied magnetic field strength at a
+constant temperature or changing the bath temperature at a constant field.
+Preliminary results on the dynamics of the phase transitions of arrays and
+single indium dots will be reported.",9308033v1
+1995-04-26,Chaos in Andreev Billiards,"A new type of classical billiard - the Andreev billiard - is investigated
+using the tangent map technique. Andreev billiards consist of a normal region
+surrounded by a superconducting region. In contrast with previously studied
+billiards, Andreev billiards are integrable in zero magnetic field, {\it
+regardless of their shape}. A magnetic field renders chaotic motion in a
+generically shaped billiard, which is demonstrated for the Bunimovich stadium
+by examination of both Poincar\'e sections and Lyapunov exponents. The issue of
+the feasibility of certain experimental realizations is addressed.",9504110v1
+1996-07-24,Long Wavelength Anomalous Diffusion Mode in the 2D XY Dipole Magnet,"In 2D XY ferromagnet the dipole force induces a strong interaction between
+spin-waves in the long-wavelength limit. The major effect of this interaction
+is the transformation of a propagating spin-wave into a diffusion mode. We
+study the anomalous dynamics of such diffusion modes. We find that the
+Janssen-De Dominics functional, which governs this dynamics, approaches the
+non-Gaussian fixed-point. A spin-wave propagates by an anomalous anisotropic
+diffusion with the dispersion relation: $i\omega{\sim}k_{y}^{\Delta_y}$ and
+$i\omega{\sim}k_{x}^{\Delta_x}$, where ${\Delta_y}=47/27$ and
+${\Delta_x}=47/36$. The low-frequency response to the external magnetic field
+is found.",9607168v1
+1997-01-15,Spin dynamics of the spin-Peierls compound CuGeO_3 under magnetic field,"The magnetic field--driven transition in the spin-Peierls system CuGeO_3
+associated with the closing of the spin gap is investigated numerically. The
+field dependence of the spin dynamical structure factor (seen by inelastic
+neutron scattering) and of the momentum dependent static susceptibility are
+calculated. In the dimerized phase (H<H_c), we suggest that the strong field
+dependence of the transverse susceptibility could be experimentally seen from
+the low temperature spin-echo relaxation rate 1/T_{2G} or the second moment of
+the NMR spectrum. Above H_c low energy spin excitations appear at
+incommensurate wave vectors where the longitudinal susceptibility chi_{zz}(q)
+peaks.",9701107v1
+1997-02-12,Quantum internal modes of solitons in 1d easy-plane antiferromagnet in strong magnetic field,"In presence of a strong external magnetic field the dynamics of solitons in a
+one-dimensional easy-plane Heisenberg antiferromagnet exhibits a number of
+peculiarities. Dynamics of internal soliton degrees of freedom is essentially
+quantum, and they are strongly coupled to the ""translational"" mode of soliton
+movement. These peculiarities lead to considerable changes in the response
+functions of the system which can be detected experimentally.",9702114v1
+1997-05-16,Origin of strong scarring of wavefunctions in quantum wells in a tilted magnetic field,"The anomalously strong scarring of wavefunctions found in numerical studies
+of quantum wells in a tilted magnetic field is shown to be due to special
+properties of the classical dynamics of this system. A certain subset of
+periodic orbits are identified which are nearly stable over a very large
+interval of variation of the classical dynamics; only this subset are found to
+exhibit strong scarring. Semiclassical arguments shed further light on why
+these orbits dominate the experimentally observed tunneling spectra.",9705167v1
+1997-06-13,Dynamic instabilities in resonant tunneling induced by a magnetic field,"We show that the addition of a magnetic field parallel to the current induces
+self sustained intrinsic current oscillations in an asymmetric double barrier
+structure. The oscillations are attributed to the nonlinear dynamic coupling of
+the current to the charge trapped in the well, and the effect of the external
+field over the local density of states across the system. Our results show that
+the system bifurcates as the field is increased, and may transit to chaos at
+large enough fields.",9706144v1
+1997-08-05,Dynamical properties of the pinned Wigner crystal,"We study various dynamical properties of the weakly pinned Wigner crystal in
+a high magnetic field. Using a Gaussian variational method we can compute the
+full frequency and field dependence of the real and imaginary parts of the
+diagonal and Hall conductivities. The zero temperature Hall resistivity is
+independent of frequency and remains unaffected by disorder at its classical
+value. We show that, depending on the inherent length scales of the system, the
+pinning peak and the threshold electric field exhibit strikingly different
+magnetic field dependences.",9708034v2
+1998-10-23,Bloch Electrons in a Magnetic Field - Why Does Chaos Send Electrons the Hard Way?,"We find that a 2D periodic potential with different modulation amplitudes in
+x- and y-direction and a perpendicular magnetic field may lead to a transition
+to electron transport along the direction of stronger modulation and to
+localization in the direction of weaker modulation. In the experimentally
+accessible regime we relate this new quantum transport phenomenon to avoided
+band crossing due to classical chaos.",9810313v3
+1998-12-06,The dynamo effect - A dynamic renormalisation group approach,"The Dynamo effect is used to describe the generation of magnetic fields in
+astrophysical objects. However, no rigorous derivation of the dynamo equation
+is available. We justify the form of the equation using an Operator Product
+Expansion (OPE) of the relevant fields. We also calculate the coefficients of
+the OPE series using a dynamic renormalisation group approach and discuss the
+time evolution of the initial conditions on the initial seed magnetic field.",9812090v1
+1998-12-17,Magnetic Field Induced Phase Transitions in YBa2Cu4O8,"The $c$-axis resistivity measurements in YBa_2Cu_4O_8 from Hussey et al. for
+magnetic field orientations along the c-axis as well as within the ab-plane are
+analyzed and interpreted using the scaling theory for static and dynamic
+classical critical phenomena. We identify a superconductor to normal conductor
+transition for both field orientations as well as a normal conductor to
+insulator transition at a critical field H_c||a with dynamical critical
+exponent z=1, leading to a multicritical point where superconducting, normal
+conducting and insulating phases coexist.",9812301v1
+1999-01-05,A low-temperature dynamic mode scanning force microscope operating in high magnetic fields,"A scanning force microscope was implemented operating at temperatures below
+4.2K and in magnetic fields up to 8T. Piezoelectric quartz tuning forks were
+employed for non optical tip-sample distance control in the dynamic operation
+mode. Fast response was achieved by using a phase-locked loop for driving the
+mechanical oscillator. Possible applications of this setup for various scanning
+probe techniques are discussed.",9901023v1
+2000-02-09,Vortex Pinning and Dynamics in Layerd Superconductors with Periodic Pinning Arrays,"We examine vortex dynamics and pinning in layered superconductors using
+three-dimensional molecular dyanmics simulations of magnetically interacting
+pancake vortices. Our model treats the magnetic interactions of the pancakes
+exactly, with longe-range logarithmic interactions both within and between
+planes. At the matching field the vortices are aligned with the pinning array.
+As a function of tilt angle for the pinning arrays a series of commensuration
+effects occur, seen as peaks in the critical current, due to pancakes finding a
+favorable alignment.",0002123v1
+2000-06-06,A critical examination of the spin dynamics in high-$T_C$ cuprates,"A critical examination of the spin dynamics in high-$T_C$ cuprates is made on
+the light of inelastic neutron scattering results obtained by different groups.
+Recent neutron data show that incommensurate magnetic peaks in YBCO belong to
+the same excitation as the resonance peak observed at $(\pi/a,\pi/a)$. Being
+only observed in the superconducting state, the incommensurability is then
+rather difficult to reconcile with a stripe picture. We also discuss the link
+between the resonance peak spectral weight and the superconducting condensation
+energy.",0006085v2
+2000-07-24,rf susceptibility of La_{1-x}Sr_{x}MnO_{3} single crystals : magnetic signatures of structural changes,"A sensitive tunnel diode oscillator (TDO) operating at 4MHz is used to probe
+the dynamic response of La_{1-x}Sr_{x}MnO_{3} single crystals for
+x=0.125,0.175,0.28 and 0.33 doping. Systematics of the measured change in
+reactance as a function of temperature (30K<T<320K) and DC magnetic field
+(0<H<6kOe) reveal distinct temperature and field scales associated with the
+dynamic response of spin. It is notable that these features are far more
+striking than the corresponding features in static measurements. The results
+are discussed in the context of structural changes leading to polaron ordering.",0007377v1
+2000-09-21,Dynamics of spin correlations in the spin-1/2 isotropic XY chain in a transverse field,"Dynamic xx spin pair correlation functions for the isotropic spin-1/2 XY
+chain are calculated numerically for long open chains in the presence of a
+transverse magnetic field at finite temperature. As an application we discuss
+the temperature dependence of the spin-spin relaxation time in PrCl_3.",0009334v1
+2000-10-05,Critical dynamics of an interacting magnetic nanoparticle system,"Effects of dipole-dipole interactions on the magnetic relaxation have been
+investigated for three Fe-C nanoparticle samples with volume concentrations of
+0.06, 5 and 17 vol%. While both the 5 and 17 vol% samples exhibit collective
+behavior due to dipolar interactions, only the 17 vol% sample displays critical
+behavior close to its transition temperature. The behaviour of the 5 vol%
+sample can be attributed to a mixture of collective and single particle
+dynamics.",0010090v2
+2000-12-06,A macroscopically frustrated Ising model,"A disordered spin glass model where both static and dynamical properties
+depend on macroscopic magnetizations is presented. These magnetizations
+interact via random couplings and, therefore, the typical quenched realization
+of the system exhibit a macroscopic frustration. The model is solved by using a
+revisited replica approach, and the broken symmetry solution turns out to
+coincide with the symmetric solution. Some dynamical aspects of the model are
+also discussed, showing how it could be a useful tool for describing some
+properties of real systems as, for example, natural ecosystems or human social
+systems.",0012089v1
+2001-04-29,"Driven Heisenberg Magnets: Nonequilibrium Criticality, Spatiotemporal Chaos and Control","We drive a $d$-dimensional Heisenberg magnet using an anisotropic current.
+The continuum Langevin equation is analysed using a dynamical renormalization
+group and numerical simulations. We discover a rich steady-state phase diagram,
+including a critical point in a new nonequilibrium universality class, and a
+spatiotemporally chaotic phase. The latter may be `controlled' in a robust
+manner to target spatially periodic steady states with helical order.",0104566v2
+2001-05-08,Glassy dynamics of the inhomogeneous metallic phase in La1-xCaxMnO3,"The anelastic spectra (elastic energy loss and dynamic modulus versus
+temperature) of La1-xCaxMnO3 have been measured for 0.33< x < 0.5. A peak in
+the imaginary part of the elastic susceptibility is found slightly below the
+Curie temperature, whose temperature and frequency dependences are typical of
+the dielectric and magnetic susceptibilities of relaxor ferroelectrics, spin
+glasses and other inhomogeneous frustrated systems. The fluctuations can be
+associated with the magnetic clusters which are observed by several techniques
+or with charge-ordered insulating domains in the low temperature inhomogeneous
+phase. The temperature dependent distribution function of the fluctuation
+energy barriers has been extracted by the analysis of the experimental curves.",0105159v1
+2001-08-11,Spin dynamics from time-dependent spin density-functional theory,"We derive the spin-wave dynamics of a magnetic material from the
+time-dependent spin density functional theory in the linear response regime.
+The equation of motion for the magnetization includes, besides the static spin
+stiffness, a ""Berry curvature"" correction and a damping term. A gradient
+expansion scheme based on the homogeneous spin-polarized electron gas is
+proposed for the latter two quantities, and the first few coefficients of the
+expansion are calculated to second order in the Coulomb interaction.",0108193v1
+2001-11-26,Ferromagnetic transition in a double-exchange system containing impurities in the Dynamical Mean Field Approximation,"We formulate the Dynamical Mean Field Approximation equations for the
+double-exchange system with quenched disorder for arbitrary relation between
+Hund exchange coupling and electron band width. Close to the
+ferromagnetic-paramagnetic transition point the DMFA equations can be reduced
+to the ordinary mean field equation of Curie-Weiss type. We solve the equation
+to find the transition temperature and present the magnetic phase diagram of
+the system.",0111491v4
+2002-04-28,Dynamical density correlation function of 1D Mott insulators in a magnetic field,"We consider the one dimensional (1D) extended Hubbard model at half filling
+in the presence of a magnetic field. Using field theory techniques we calculate
+the dynamical density-density correlation function $\chi_{nn}(\omega,q)$ in the
+low-energy limit. When excitons are formed, a singularity appears in
+$\chi_{nn}(\omega,q)$ at a particular energy and momentum transfer.",0204594v1
+2002-08-21,The spin angular gradient approximation in the density functional theory,"A spin angular gradient approximation for the exchange correlation magnetic
+field in the density functional formalism is proposed. The usage of such
+corrections leads to a consistent spin dynamical approach beyond the local
+approximation. The proposed technique does not contain any approximations for
+the form of potential and can be used in modern full potential band structure
+methods. The obtained results indicate that the direct 'potential' exchange in
+3d magnets is rather small compared to the indirect 'kinetic' exchange, thus
+justifies the dynamical aspect of the local density approximation in 3d metals.",0208420v1
+2002-10-26,Dynamic exchange coupling in magnetic bilayers,"A long-ranged dynamic interaction between ferromagnetic films separated by
+normal-metal spacers is reported, which is communicated by nonequilibrium spin
+currents. It is measured by ferromagnetic resonance (FMR) and explained by an
+adiabatic spin-pump theory. In FMR the spin-pump mechanism of spatially
+separated magnetic moments leads to an appreciable increase in the FMR line
+width when the resonance fields are well apart, and results in a dramatic
+line-width narrowing when the FMR fields approach each other.",0210588v2
+2003-04-22,"Dynamical Systems, Topology and Conductivity in Normal Metals","New observable integer-valued numbers of the topological origin were revealed
+by the present authors studying the conductivity theory of single crystal 3D
+normal metals in the reasonably strong magnetic field ($B \leq 10^{3} Tl$). Our
+investigation is based on the study of dynamical systems on Fermi surfaces for
+the motion of semi-classical electron in magnetic field. All possible
+asymptotic regimes are also found for $B \to \infty$ based on the topological
+classification of trajectories.",0304471v2
+2003-05-15,Inhomogeneous Ferromagnetism and Unconventional Charge Dynamics in Disordered Double Exchange Magnets,"We solve the double exchange model in the presence of arbitrary
+substitutional disorder by using a self consistently generated effective
+Hamiltonian for the spin degrees of freedom. The magnetic properties are
+studied through classical Monte Carlo while the effective exchange, $D_{ij}$,
+are calculated by solving the disordered fermion problem, and renormalised
+self-consistently with increasing temperature. We present exact results on the
+conductivity, magnetoresistance, optical response and `real space' structure of
+the inhomogeneous ferromagnetic state, and compare our results with charge
+dynamics in disordered La_{1-x}Sr_xMnO_3. The large sizes, ${\cal O} (10^3)$,
+accessible within our method allows a complete, controlled calculation on the
+disordered strongly interacting problem.",0305352v1
+2003-06-13,Scaling of the magnetic response in doped antiferromagnets,"A theory of the anomalous $\omega/T$ scaling of the dynamic magnetic response
+in cuprates at low doping is presented. It is based on the memory function
+representation of the dynamical spin suceptibility in a doped antiferromagnet
+where the damping of the collective mode is constant and large, whereas the
+equal-time spin correlations saturate at low $T$. Exact diagonalization results
+within the t-J model are shown to support assumptions. Consequences, both for
+the scaling function and the normalization amplitude, are well in agreement
+with neutron scattering results.",0306366v2
+2003-06-19,Griffiths phase in diluted magnetic semiconductors,"We study the effects of disorder in the vicinity of the ferromagnetic
+transition in a diluted magnetic semiconductor in the strongly localized
+regime. We derive an effective polaron Hamiltonian, which leads to the
+Griffiths phase above the ferromagnetic transition point. The Griffiths-McCoy
+effects yield non-perturbative contributions to the dynamic susceptibility. We
+explicitly derive the long-time susceptibility, which has a pseudo-scaling
+form, with the dynamic critical exponent being expressed through the
+percolation indices.",0306488v2
+2003-07-16,"The quantum dynamics of atomic magnets, co-tunneling and dipolar-biased tunneling","Multi-spins tunneling cross-relaxations in an ensemble of weakly-coupled
+Ho$^{3+}$ ions, mediated by weak anisotropic dipolar interactions, can be
+evidenced by ac-susceptibility measurements in a high temperature regime. Based
+on a four-body representation, including the rare-earth nuclear spin, two-ions
+tunneling mechanisms can be attributed to both dipolar-biased tunneling and
+co-tunneling processes. The co-reversal involving entangled pairs of magnetic
+moments is discussed with a particular emphasis, giving new evidences to
+elucidate the many-body quantum dynamics.",0307405v1
+2003-11-14,Magnetization reversal and spin dynamics exchange in biased F/AF bilayers probed with complex permeability spectra,"The spin dynamics of the ferromagnetic pinned layer of
+ferro-antiferromagnetic coupled NiFe/MnNi bilayers is investigated in a broad
+frequency range (30 MHz-6 GHz). A phenomenological model based on the
+Landau-Lifshitz equation for the complex permeability of the F/AF bilayer is
+proposed. The experimental results are compared to theoretical predictions. We
+show that the resonance frequencies, measured during the magnetization, are
+likewise hysteretic.",0311338v1
+2003-11-14,Dynamic roughening and fluctuations of dipolar chains,"Nonmagnetic particles in a carrier ferrofluid acquire an effective dipolar
+moment when placed in an external magnetic field. This fact leads them to form
+chains that will roughen due to Brownian motion when the magnetic field is
+decreased. We study this process through experiments, theory and simulations,
+three methods that agree on the scaling behavior over 5 orders of magnitude.
+The RMS width goes initially as $t^{1/2}$, then as $t^{1/4}$ before it
+saturates. We show how these results complement existing results on polymer
+chains, and how the chain dynamics may be described by a recent non-Markovian
+formulation of anomalous diffusion.",0311340v1
+2004-02-12,Spin Dynamics of Double-Exchange Manganites with Magnetic Frustration,"This work examines the effects of magnetic frustration due to competing
+ferromagnetic and antiferromagnetic Heisenberg interactions on the spin
+dynamics of the double-exchange model. When the local moments are non-colinear,
+a charge-density wave forms because the electrons prefer to sit on lines of
+sites that are coupled ferromagnetically. With increasing hopping energy, the
+local spins become aligned and the average spin-wave stiffness increases. Phase
+separation is found only within a narrow range of hopping energies. Results of
+this work are applied to the field-induced jump in the spin-wave stiffness
+observed in the manganite Pr$_{1-x}$Ca$_x$MnO$_3$ with $0.3 \le x \le 0.4$.",0402344v1
+2004-02-25,Spin Dynamics of a Canted Antiferromagnet in a Magnetic Field,"The spin dynamics of a canted antiferromagnet with a quadratic spin-wave
+dispersion near $\vq =0$ is shown to possess a unique signature. When the
+anisotropy gap is negligible, the spin-wave stiffness $\dsw (\vq, B) =
+(\omega_{\vq}-B)/q^2$ depends on whether the limit of zero field or zero
+wavevector is taken first. Consequently, $\dsw $ is a strong function of
+magnetic field at a fixed wavevector. Even in the presence of a sizeable
+anisotropy gap, the field dependence of both $\dsw $ and the gap energy
+distinguishes a canted antiferromagnet from a phase-separated mixture
+containing both ferromagnetic and antiferromagnetic regions.",0402633v2
+2004-04-01,Semiclassical dynamics of domain walls in the one-dimensional Ising ferromagnet in a transverse field,"We investigate analytically and numerically the dynamics of domain walls in a
+spin chain with ferromagnetic Ising interaction and subject to an external
+magnetic field perpendicular to the easy magnetization axis (transverse field
+Ising model). The analytical results obtained within the continuum
+approximation and numerical simulations performed for discrete classical model
+are used to analyze the quantum properties of domain walls using the
+semiclassical approximation. We show that the domain wall spectrum shows a band
+structure consisting of 2$S$ non-intersecting zones.",0404014v1
+2004-12-24,"""Glassy Dynamics"" in Ising Spin Glasses -- Experiment and Simulation","The field-cooled magnetization (FCM) processes of Ising spin glasses under
+relatively small fields are investigated by experiment on
+Fe_{0.55}Mn_{0.45}TiO_3 and by numerical simulation on the three-dimensional
+Edwards-Anderson model. Both results are explained in a unified manner by means
+of the droplet picture. In particular, the cusp-like behavior of the FCM is
+interpreted as evidence, not for an equilibrium phase transition under a finite
+magnetic field, but for a dynamical (`blocking') transition frequently observed
+in glassy systems.",0412674v2
+2005-02-24,Lifetime Widths of Surface States on Magnetic Lanthanide Metals,"Low-temperature scanning tunneling spectroscopy is used to study electronic
+structure and dynamics of d-like surface states of trivalent lanthanide metals
+from La to Lu. The magnetic exchange splitting of these states is found to
+scale with the 4f spin multiplied by an effective exchange-coupling constant
+that increases with 4f occupancy in an approximately linear way. The dynamics
+of the surfaces states, as revealed by the lifetime width, is dominated by
+electron-phonon scattering in the occupied region and by electron-magnon
+scattering in the unoccupied region, respectively.",0502581v1
+2005-06-24,Dynamics of Dipolar Spinor Condensates,"We study the semiclassical dynamics of a spinor condensate with the magnetic
+dipole-dipole interaction included. The time evolution of the population
+imbalance and the relative phase among different spin components depends
+greatly on the relative strength of interactions as well as on the initial
+conditions. The interplay of spin exchange and dipole-dipole interaction makes
+it possible to manipulate the atomic population on different components,
+leading to the phenomena of spontaneous magnetization and Macroscopic Quantum
+Self Trapping. Simple estimate demonstrates that these effects are accessible
+and controllable by modifying the geometry of the trapping potential.",0506630v1
+2005-08-30,Current induced transverse spin-wave instability in thin ferromagnets: beyond linear stability analysis,"A sufficiently large unpolarized current can cause a spin-wave instability in
+thin nanomagnets with asymmetric contacts. The dynamics beyond the instability
+is understood in the perturbative regime of small spin-wave amplitudes, as well
+as by numerically solving a discretized model. In the absence of an applied
+magnetic field, our numerical simulations reveal a hierarchy of instabilities,
+leading to chaotic magnetization dynamics for the largest current densities we
+consider.",0508732v1
+2005-12-02,Exchange enhanced anisotropy in ferromagnetic/antiferromagnetic multilayers: dynamic consequences,"The phenomena of exchange anisotropy is well known in terms of static
+magnetization properties such as enhanced coercivity and magnetization loop
+shifts. These effects are primarily associated with effective anisotropies
+introduced into the ferromagnet by exchange coupling with a strongly
+anisotropic antiferromagnet. These effective anisotropies can be understood as
+manifestations of a more fundamental exchange induced susceptibility. We show
+that a consequence of this view is that a class of unusual dynamic effects
+associated with the exchange susceptibility should also exist. The effects
+become apparent near the ordering temperature of the antiferromagnet and affect
+domain wall velocities, domain wall resonances, and precessional switching of
+the ferromagnet.",0512034v1
+2005-12-08,Nature of non-magnetic strongly-correlated state in delta-plutonium,"Ab-initio relativistic dynamical mean-field theory is applied to resolve the
+long-standing controversy between theory and experiment in the ""simple""
+face-centered cubic phase of plutonium called delta-Pu. In agreement with
+experiment, neither static nor dynamical magnetic moments are predicted. In
+addition, the quasiparticle density of states reproduces not only the peak
+close to the Fermi level, which explains the large coefficient of electronic
+specific heat, but also main 5f features observed in photoelectron
+spectroscopy.",0512185v1
+2006-04-10,Transport of magnetic vortices by surface acoustic waves,"In a thin film of superconducting YBCO the impact of surface acoustic waves
+(SAWs) traveling on the piezoelectric substrate is investigated. A pronounced
+interaction between the ultrasonic waves and the vortex system in the type II
+superconductor is observed. The occurrence of a SAW-induced dc voltage
+perpendicular to the sound path is interpreted as {\em dynamic pinning} of
+vortices by the piezoacoustic SAW, which acts as a conveyor for the fluxquanta.
+Its antisymmetry with respect to the magnetic field directly evidences the
+induced, directed flux motion.This dynamic manipulation of vortices can be seen
+as an important step towards flux-based electronic devices.",0604254v1
+2006-07-21,Magnetic quantum phase transition in an anisotropic Kondo lattice,"The quantum phase transition between paramagnetic and antiferromagnetic
+phases of the Kondo lattice model with Ising anisotropy in the intersite
+exchange is studied within the framework of extended dynamical mean-field
+theory. Nonperturbative numerical solutions at zero temperature point to a
+continuous transition for both two- and three-dimensional magnetism. In the
+former case, the transition is associated with critical local physics,
+characterized by a vanishing Kondo scale and by an anomalous exponent in the
+dynamics close in value to that measured in heavy-fermion CeCu_{5.9}Au_{0.1}.",0607566v3
+2006-09-08,Quantum Dynamics of Molecular Nanomagnets in a Resonant Cavity and the Maser Effect,"We study the dynamics of molecular nanomagnets through a fully quantum
+mechanical model describing high-spin and high-anisotropy magnetic molecules
+subjected to a time-dependent magnetic field along the quantization axis, which
+continuously inverts the population of spin states. Crystals of molecular
+nanomagnets placed inside a resonant cavity interact with a quantized
+electromagnetic field. Relaxation of excited states takes place by means of
+spin-photon interaction, allowing stimulated emission of radiation and creating
+a maser effect.",0609205v1
+2006-09-12,Nonlinear dynamics of quantum dot nuclear spins,"We report manifestly nonlinear dependence of quantum dot nuclear spin
+polarization on applied magnetic fields. Resonant absorption and emission of
+circularly polarized radiation pumps the resident quantum dot electron spin,
+which in turn leads to nuclear spin polarization due to hyperfine interaction.
+We observe that the resulting Overhauser field exhibits hysteresis as a
+function of the external magnetic field. This hysteresis is a consequence of
+the feedback of the Overhauser field on the nuclear spin cooling rate. A
+semi-classical model describing the coupled nuclear and electron spin dynamics
+successfully explains the observed hysteresis but leaves open questions for the
+low field behaviour of the nuclear spin polarization.",0609291v1
+2006-11-25,Dynamics of Vortex Core Switching in Ferromagnetic Nanodisks,"Dynamics of magnetic vortex core switching in nanometer-scale permalloy disk,
+having a single vortex ground state, was investigated by micromagnetic
+modeling. When an in-plane magnetic field pulse with an appropriate strength
+and duration is applied to the vortex structure, additional two vortices, i.e.,
+a circular- and an anti-vortex, are created near the original vortex core.
+Sequentially, the vortex-antivortex pair annihilates. A spin wave is created at
+the annihilation point and propagated through the entire element; the relaxed
+state for the system is the single vortex state with a switched vortex core.",0611640v1
+2007-03-27,Gauge Field Formulation of Adiabatic Spin Torques,"Previous calculation of spin torques for small-amplitude magnetization
+dynamics around a uniformly magnetized state [J. Phys. Soc. Jpn. {\bf 75}
+(2006) 113706] is extended here to the case of finite-amplitude dynamics. This
+is achieved by introducing an `` adiabatic'' spin frame for conduction
+electrons, and the associated SU(2) gauge field. In particular, the Gilbert
+damping is shown to arise from the time variation of the spin-relaxation source
+terms in this new frame, giving a new physical picture of the damping. The
+present method will allow a `` first-principle'' derivation of spin torques
+without any assumptions such as rotational symmetry in spin space.",0703705v1
+1993-03-26,Nonequilibrium Dynamics and Aging in the Three--Dimensional Ising Spin Glass Model,"The low temperature dynamics of the three dimensional Ising spin glass in
+zero field with a discrete bond distribution is investigated via MC
+simulations. The thermoremanent magnetization is found to decay algebraically
+and the temperature dependent exponents agree very well with the experimentally
+determined values. The nonequilibrium autocorrelation function $C(t,t_w)$ shows
+a crossover at the waiting (or {\em aging}) time $t_w$ from algebraic {\em
+quasi-equilibrium} decay for times $t$$\ll$$t_w$ to another, faster algebraic
+decay for $t$$\gg$$t_w$ with an exponent similar to one for the remanent
+magnetization.",9303013v1
+1997-04-11,Electroweak properties of light mesons in relativistic hamiltonian dynamics,"The calculation of lepton decay constants and electromagnetic form factors of
+pion and kaon is performed in the framework of relativistic hamiltonian
+dynamics. The different model wave function is used. Wave function parameters
+are fixed from fit of mean square radius of meson. The internal quark structure
+is taken into account by electromagnetic quark form factor and quark anomalous
+magnetic moment. The pion and kaon form factors depend only weakly on model
+wave function. Strong dependence of these values on quark anomalous magnetic
+moment is obtained in the transfer momentum region of CEBAF experiments.",9704293v1
+2000-06-20,Magnetic string contribution to hadron dynamics in QCD,"Dynamics of a light quark in the field of static source (heavy-light meson)
+is studied using the nonlinear Dirac equation, derived recently. Special
+attention is paid to the contribution of magnetic correlators and it is found
+that it yields a significant increase of string tension at intermediate
+distances. The spectrum of heavy-light mesons is computed with account of this
+contribution and compared to experimental and lattice data.",0006237v1
+2006-05-02,"Comment on ""Dynamical mass generation in strongly coupled quantum electrodynamics with weak magnetic fields""","In a recent article, Ayala et al. [Phys. Rev. D 73, 105009 (2006)] have
+studied the dynamical generation of masses for fundamental fermions in strongly
+coupled QED in the presence of weak magnetic fields. We argue that the results
+and conclusions of the article are not reliable as they are subject to gauge
+dependent artifacts resulting from an inconsistent truncation of the
+Schwinger-Dyson equations.",0605027v2
+2007-03-29,Nonperturbative dynamics in the colour-magnetic QCD vacuum,"In the deconfinement phase of QCD quarks and gluons interact with the dense
+stochastic colour-magnetic vacuum. We consider the dynamics of quarks in this
+deconfinement phase using the Field Correlators Method and derive an effective
+nonperturbative inter-quark potential, in addition to the usual perturbative
+short-ranged interaction. We find the resulting angular-momentum-dependent
+interaction to be attractive enough to maintain bound states and, for light
+quarks (and gluons), to cause emission of quark and gluon pairs. Possible
+consequences for the strong interacting quark--gluon plasma are briefly
+discussed.",0703306v1
+1998-11-09,Dynamical Chiral Symmetry Breaking in QED in a Magnetic Field: Toward Exact Results,"We describe a (first, to the best of our knowledge) essentially soluble
+example of dynamical symmetry breaking phenomenon in a 3+1 dimensional gauge
+theory without fundamental scalar fields: QED in a constant magnetic field.",9811079v3
+2001-12-14,Supersymmetry-based Approach to Quantum Particle Dynamics,"We present the N=2 supersymmetric formulation for the classical and quantum
+dynamics of a nonrelativistic charged particle on a curved surface in the
+presence of a perpendicular magnetic field. For a particle moving on a
+constant-curvature surface in a constant magnetic field, our Hamiltonian
+possesses the shape-invariance property in addition. On the surface of a sphere
+and also on the hyperbolic plane, we exploit the supersymmetry and
+shape-invariance properties to obtain complete solutions to the corresponding
+quantum mechanical problems.",0112120v1
+2004-07-20,Noncommuting spherical coordinates,"Restricting the states of a charged particle to the lowest Landau level
+introduces a noncommutativity between Cartesian coordinate operators. This idea
+is extended to the motion of a charged particle on a sphere in the presence of
+a magnetic monopole. Restricting the dynamics to the lowest energy level
+results in noncommutativity for angular variables and to a definition of a
+noncommuting spherical product. The values of the commutators of various
+angular variables are not arbitrary but are restricted by the discrete
+magnitude of the magnetic monopole charge. An algebra, isomorphic to angular
+momentum, appears. This algebra is used to define a spherical star product.
+Solutions are obtained for dynamics in the presence of additional angular
+dependent potentials.",0407177v1
+2003-12-23,An example of a jump from chaos to integrability for magnetic geodesic flows,"It is proved that the motion of a charge particle on a hyperbolic oriented
+two-dimensional surface in a magnetic field given by the volume form of the
+hyperbolic metric is completely integrable on the energy levels E < 1/2 in
+terms of real-analytic integrals. However it was known that on the level E=1/2
+every trajectory is transitive and the restrictions of this flow onto the
+levels E>1/2 are Anosov flows",0312430v2
+2000-06-07,Breaking conjugate pairing in thermostatted billiards by magnetic field,"We demonstrate that in the thermostatted three-dimensional Lorentz gas the
+symmetry of the Lyapunov spectrum can be broken by adding to the system an
+external magnetic field not perpendicular to the electric field. For
+perpendicular field vectors, there is a Hamiltonian reformulation of the
+dynamics and the conjugate pairing rule still holds. This indicates that
+symmetric Lyapunov spectra has nothing to do with time reversal symmetry or
+reversibility; instead, it seems to be related to the existence of a
+Hamiltonian connection.",0006010v1
+2001-06-05,Fluctuation formula for nonreversible dynamics in the thermostated Lorentz gas,"We investigate numerically the validity of the Gallavotti-Cohen fluctuation
+formula in the two and three dimensional periodic Lorentz gas subjected to
+constant electric and magnetic fields and thermostated by the Gaussian
+isokinetic thermostat. The magnetic field breaks the time reversal symmetry,
+and by choosing its orientation with respect to the lattice one can have either
+a generalized reversing symmetry or no reversibility at all. Our results
+indicate that the scaling property described by the fluctuation formula may be
+approximately valid for large fluctuations even in the absence of
+reversibility.",0106005v2
+2004-06-24,Semi-classical analysis of real atomic spectra beyond Gutzwiller's approximation,"Real atomic systems, like the hydrogen atom in a magnetic field or the helium
+atom, whose classical dynamics are chaotic, generally present both discrete and
+continuous symmetries. In this letter, we explain how these properties must be
+taken into account in order to obtain the proper (i.e. symmetry projected)
+$\hbar$ expansion of semiclassical expressions like the Gutzwiller trace
+formula. In the case of the hydrogen atom in a magnetic field, we shed light on
+the excellent agreement between present theory and exact quantum results.",0406055v2
+2005-05-26,Spectral Form Factor for Chaotic Dynamics in a Weak Magnetic Field,"Using semiclassical periodic orbit theory for a chaotic system in a weak
+magnetic field, we obtain the form factor predicted by Pandey and Mehta's two
+matrix model up to the third order. The third order contribution has a peculiar
+term which exists only in the intermediate crossover domain between the GOE
+(Gaussian Orthogonal Ensemble) and the GUE (Gaussian Unitary Ensemble)
+universality classes. The exact expression is obtained by taking account of the
+contribution from encounter regions where orbit loops are connected.",0505055v3
+1999-03-13,Neutron Star Vortex Dynamics and Magnetic Field Decay: Implications for High Density Nuclear Matter,"We investigate the effect of the density-dependent proton and neutron gaps on
+vortex dynamics in neutron stars. We argue that the persistence of neutron star
+magnetic fields on timescales of $10^9$ y suggests a superconducting gap curve
+with local maximum at intermediate density. We discuss the implications for
+exotic core phenomena such as pion/kaon condensation or a transition to quark
+matter.",9903039v1
+1999-10-19,Deuteron Magnetic and Quadrupole Moments with a Poincaré Covariant Current Operator in the Front-Form Dynamics,"The deuteron magnetic and quadrupole moments are unambiguosly determined
+within the front-form Hamiltonian dynamics, by using a new current operator
+which fulfills Poincar\'e, parity and time reversal covariance, together with
+hermiticity and the continuity equation. For both quantities the usual
+disagreement between theoretical and experimental results is largely removed.",9910049v1
+2000-03-15,Dynamical Screening and Radiative Parton Energy Loss in a Quark-gluon Plasma,"Dynamical screening in the magnetic part of the one-gluon exchange
+interaction is included in the study of radiative energy loss of a fast parton
+propagating inside a quark-gluon plasma. As a result the final radiative energy
+loss is about twice as large as when only the electric part of one-gluon
+exchange interaction is considered. A non-perturbative magnetic screening mass
+is also used in the estimate of the mean-free-path of parton scattering in a
+hot QCD matter.",0003033v2
+2000-11-29,Finite element approach for simulating quantum electron dynamics in a magnetic field,"A fast and stable numerical method is formulated to compute the time
+evolution of a wave function in a magnetic field by solving the time-dependent
+Schroedinger equation. This computational method is based on the finite element
+method in real space to improved accuracy without any increase of computational
+cost. This method is also based on Suzuki's exponential product theory to
+afford an efficient way to manage the TD-Schroedinger equation with a vector
+potential. Applying this method to some simple electron dynamics, we have
+confirmed its efficiency and accuracy.",0011069v1
+2005-05-06,Microfluidic capturing-dynamics of paramagnetic bead suspensions,"We study theoretically the capturing of paramagnetic beads by a magnetic
+field gradient in a microfluidic channel treating the beads as a continuum.
+Bead motion is affected by both fluidic and magnetic forces. The transfer of
+momentum from beads to the fluid creates an effective bead-bead interaction
+that greatly aids capturing. We demonstrate that for a given inlet flow speed a
+critical density of beads exists above which complete capturing takes place.",0505052v1
+1997-04-10,On the Torus Quantization of Two Anyons with Coulomb Interaction in a Magnetic Field,"We study two anyons with Coulomb interaction in a uniform magnetic field $B$.
+By using the torus quantization we obtain the modified Landau and Zeeman
+formulas for the two anyons. Then we derive a simple algebraic equation for the
+full spectral problem up to the second order in $B$.",9704022v1
+2003-06-16,Quantum Dynamics of the Oscillating Cantilever-Driven Adiabatic Reversals in Magnetic Resonance Force Microscopy,"We simulated the quantum dynamics for magnetic resonance force microscopy
+(MRFM) in the oscillating cantilever-driven adiabatic reversals (OSCAR)
+technique.
+  We estimated the frequency shift of the cantilever vibrations and
+demonstrated that this shift causes the formation of a Schrodinger cat state
+which has some similarities and differences from the conventional MRFM
+technique which uses cyclic adiabatic reversals of spins. The interaction of
+the cantilever with the environment is shown to quickly destroy the coherence
+between the two possible cantilever trajectories. We have shown that using
+partial adiabatic reversals, one can produce a significant increase in the
+OSCAR signal.",0306107v1
+2003-12-17,Quantum dynamics in single spin measurement,"We study the quantum dynamics of a model for the single-spin measurement in
+magnetic-resonance force microscopy. We consider an oscillating driven
+cantilever coupled with the magnetic moment of the sample. Then, the cantilever
+is damped through an external bath and its readout is provided by a radiation
+field. Conditions for reliable measurements will be discussed.",0312147v2
+2006-02-13,Entanglement and dynamics of spin-chains in periodically-pulsed magnetic fields: accelerator modes,"We study the dynamics of a single excitation in a Heisenberg spin-chain
+subjected to a sequence of periodic pulses from an external, parabolic,
+magnetic field. We show that, for experimentally reasonable parameters, a pair
+of counter-propagating coherent states are ejected from the centre of the
+chain. We find an illuminating correspondence with the quantum time evolution
+of the well-known paradigm of quantum chaos, the Quantum Kicked Rotor (QKR).
+  From this we can analyse the entanglement production and interpret the
+ejected coherent states as a manifestation of so-called `accelerator modes' of
+a classically chaotic system.",0602106v2
+2006-11-28,Efficient Dynamic Nuclear Polarization at High Magnetic Fields,"By applying a new technique for dynamic nuclear polarization involving
+simultaneous excitation of electronic and nuclear transitions, we have enhanced
+the nuclear polarization of the nitrogen nuclei in 15N@C60 by a factor of 1000
+at a fixed temperature of 3 K and a magnetic field of 8.6 T, more than twice
+the maximum enhancement reported to date. This methodology will allow the
+initialization of the nuclear qubit in schemes exploiting N@C60 molecules as
+components of a quantum information processing device.",0611276v1
+2007-04-03,Exactly solvable spin dynamics of an electron coupled to large number of nuclei and the electron-nuclear spin echo in a quantum dot,"The model considered in the paper is used nowadays to describe spin dynamics
+of quantum dots after optical excitation. Based on the exact diagonalization of
+a model Hamiltonian, we solve the problems of the electron spin polarization
+decay and magnetic field dependence of the steady state polarization. The
+important role of the nuclear state is shown and methods of its calculation for
+different regimes of optical excitation are proposed. The effect of spin echo
+observed after application of the magnetic field $\pi$-pulse is predicted.",0704.0391v3
+2007-07-27,Excitation of spin dynamics by spin-polarized current in vortex state disks,"A spin-polarized current with the polarization perpendicular to the plane of
+a vortex-state disk results in renormalization of the effective damping for a
+given magnetization mode, and the effective damping becomes zero if the current
+exceeds a threshold value. The lowest threshold current corresponds to the
+lowest frequency vortex gyroscopic mode. For larger values of the current the
+dynamic magnetization state is characterized by precession of the vortex around
+the dot center with non-small amplitude and higher frequency.",0707.4128v1
+2007-10-04,Activation of additional energy dissipation processes in the magnetization dynamics of epitaxial chromium dioxide films,"The precessional magnetization dynamics of a chromium dioxide$(100)$ film is
+examined in an all-optical pump-probe setup. The frequency dependence on the
+external field is used to extract the uniaxial in-plane anisotropy constant.
+The damping shows a strong dependence on the frequency, but also on the laser
+pump fluency, which is revealed as an important experiment parameter in this
+work: above a certain threshold further channels of energy dissipation open and
+the damping increases discontinuously. This behavior might stem from spin-wave
+instabilities.",0710.0986v2
+2007-10-29,Cyclotron motion and magnetic focusing in semiconductor quantum wells with spin-orbit coupling,"We investigate the ballistic motion of electrons in III-V semiconductor
+quantum wells with Rashba spin-orbit coupling in a perpendicular magnetic
+field. Taking into account the full quantum dynamics of the problem, we explore
+the modifications of classical cyclotron orbits due to spin-orbit interaction.
+As a result, for electron energies comparable with the cyclotron energy the
+dynamics are particularly rich and not adequately described by semiclassical
+approximations. Our study is complementary to previous semiclassical approaches
+concentrating on the regime of weaker fields.",0710.5395v2
+2007-12-01,Solitons in isotropic antiferromagnets: beyond a sigma model,"Isotropic antiferromagnets shows a reach variety of magnetic solitons with
+non-trivial static and dynamic properties. One-dimensional soliton elementary
+excitations have a periodic dispersion law. For two-dimensional case, planar
+antiferromagnetic vortices having non-singular macroscopic core with the
+saturated magnetic moment are present. The dynamic properties of these planar
+antiferromagnetic vortex are characterized by presence of a gyroforce",0712.0073v1
+2008-01-11,Giant dynamical Zeeman split in inverse spin valves,"The inversion of a spin valve device is proposed. Opposite to a conventional
+spin valve of a non-magnetic spacer sandwiched between two ferromagnetic
+metals, an inverse spin valve is a ferromagnet sandwiched between two
+non-magnetic metals. It is predicted that, under a bias, the chemical
+potentials of spin-up and spin-down electrons in the metals split at
+metal-ferromagnet interfaces, a dynamical Zeeman effect. This split is of the
+order of an applied bias. Thus, there should be no problem of generating an
+$eV$ split that is not possible to be realized on the earth by the usual Zeeman
+effect.",0801.1775v1
+2008-03-07,Orbital magnetism in transition-metal systems: The role of local correlation effects,"The influence of correlation effects on the orbital moments for transition
+metals and their alloys is studied by first-principle relativistic Density
+Functional Theory in combination with the Dynamical Mean-Field Theory. In
+contrast to the previous studies based on the orbital polarization corrections
+we obtain an improved description of the orbital moments for wide range of
+studied systems as bulk Fe, Co and Ni, Fe-Co disordered alloys and 3$d$
+impurities in Au. The proposed scheme can give simultaneously a correct
+dynamical description of the spectral function as well as static magnetic
+properties of correlated disordered metals.",0803.1000v1
+2008-06-29,The Magnetic Eden Model,"In the magnetic Eden model (MEM), particles have a spin and grow in contact
+with a thermal bath. Although Ising-like interactions affect the growth
+dynamics, deposited spins are frozen and not allowed to flip. This review
+article focuses on recent developments and future prospects, such as
+spontaneous switching phenomena, critical behavior associated with fractal,
+wetting, and order-disorder phase transitions, the equilibrium/nonequilibrium
+correspondence conjecture, as well as dynamical and critical features of the
+MEM defined on complex network substrates.",0806.4767v1
+2008-07-11,Probing the spin polarization of current by soft X-ray imaging of current-induced magnetic vortex dynamics,"Time-resolved soft X-ray transmission microscopy is applied to image the
+current-induced resonant dynamics of the magnetic vortex core realized in a
+micronsized Permalloy disk. The high spatial resolution better than 25 nm
+enables us to observe the resonant motion of the vortex core. The result also
+provides the spin polarization of the current to be 0.67 +/-0.16 for Permalloy
+by fitting the experimental results with an analytical model in the framework
+of the spin-transfer torque.",0807.1782v1
+2008-09-02,Dynamical Correlations of the Spin-1/2 Heisenberg XXZ Chain in a Staggered Field,"We consider the easy-plane anisotropic spin-1/2 Heisenberg chain in combined
+uniform longitudinal and transverse staggered magnetic fields. The low-energy
+limit of his model is described by the sine-Gordon quantum field theory. Using
+methods of integrable quantum field theory we determine the various components
+of the dynamical structure factor. To do so, we derive explicit expressions for
+all matrix elements of the low-energy projections of the spin operators
+involving at most two particles. We discuss applications of our results to
+experiments on one-dimensional quantum magnets.",0809.0398v2
+2008-11-18,Dynamics of Einstein - de Haas Effect: Application to Magnetic Cantilever,"Local time-dependent theory of Einstein - de Haas effect is developed. We
+begin with microscopicinteractions and derive dynamical equations that couple
+elastic deformations with internal twists due to spins. The theory is applied
+to the description of the motion of a magnetic cantilever caused by the
+oscillation of the domain wall. Theoretical results are compared with a recent
+experiment on Einstein - de Haas effect in a microcantilever.",0811.3013v1
+2008-11-25,Dynamics of OH(2Pi)-He collisions in combined electric and magnetic fields,"We use accurate quantum mechanical calculations to analyze the effects of
+parallel electric and magnetic fields on collision dynamics of OH(2Pi)
+molecules. It is demonstrated that spin relaxation in 3He-OH collisions at
+temperatures below 0.01 K can be effectively suppressed by moderate electric
+fields of order 10 kV/cm. We show that electric fields can be used to
+manipulate Feshbach resonances in collisions of cold molecules. Our results can
+be verified in experiments with OH molecules in Stark decelerated molecular
+beams and electromagnetic traps.",0811.4018v1
+2008-12-15,Dynamically dominant excitations of string solutions in the spin-1/2 antiferromagnetic Heisenberg chain in magnetic fields,"Using Bethe-ansatz solutions, we uncover a well-defined continuum in
+dynamical structure factor $S^{+-}(k,\omega)$ of the spin-1/2 antiferromagnetic
+Heisenberg chain in magnetic fields. It comes from string solutions which
+continuously connect the mode of the lowest-energy excitations in the
+zero-field limit and that of bound states of overturned spins from the
+ferromagnetic state near the saturation field. We confirm the relevance to real
+materials through comparisons with experimental results.",0812.2707v1
+2009-01-22,Geometrically frustrated antiferromagnets: statistical mechanics and dynamics,"These lecture notes are intended to provide a simple overview of the physics
+of geometrically frustrated magnets. The emphasis is on classical and
+semiclassical treatments of the statistical mechanics and dynamics of
+frustrated Heisenberg models, and on the ways in which the results provide an
+understanding of some of the main observed properties of these systems.",0901.3492v1
+2009-04-22,Magnetic field-induced soft mode in spin-gapped high-Tc superconductors,"We present an explanation of the dynamical in-gap spin mode in LSCO induced
+by an applied magnetic field H as recently observed by J. Chang et al. Our
+model consists of a phenomenological spin-only Hamiltonian, and the softening
+of the spin mode is caused by vortex pinning of dynamical stripe fluctuations
+which we model by a local ordering of the exchange interactions. The spin gap
+vanishes experimentally around H=7T which in our scenario corresponds to the
+field required for overlapping vortex regions.",0904.3404v1
+2009-07-16,Influence of magnetic viscosity on domain wall dynamics under spin-polarized currents,"We present a theoretical study of the influence of magnetic viscosity on
+current-driven domain wall dynamics. In particular we examine how domain wall
+depinning transitions, driven by thermal activation, are influenced by the
+adiabatic and nonadiabatic spin-torques. We find the Arrhenius law that
+describes the transition rate for activation over a single energy barrier
+remains applicable under currents but with a current-dependent barrier height.
+We show that the effective energy barrier is dominated by a linear current
+dependence under usual experimental conditions, with a variation that depends
+only on the nonadiabatic spin torque coefficient beta.",0907.2867v1
+2009-08-11,Dynamical Axion Field in Topological Magnetic Insulators,"Axions are very light, very weakly interacting particles postulated more than
+30 years ago in the context of the Standard Model of particle physics. Their
+existence could explain the missing dark matter of the universe. However,
+despite intensive searches, they have yet to be detected. In this work, we show
+that magnetic fluctuations of topological insulators couple to the
+electromagnetic fields exactly like the axions, and propose several experiments
+to detect this dynamical axion field. In particular, we show that the axion
+coupling enables a nonlinear modulation of the electromagnetic field, leading
+to attenuated total reflection. We propose a novel optical modulators device
+based on this principle.",0908.1537v1
+2009-11-16,Anomalous Spin Dynamics of Hubbard Model on Honeycomb Lattices,"In this paper, the honeycomb Hubbard model in optical lattices is
+investigated using O(3) non-linear sigma model. A possible quantum non-magnetic
+insulator in a narrow parameter region is found near the metal-insulator
+transition. We study the corresponding dynamics of magnetic properties, and
+find that the narrow region could be widened by hole doping.",0911.3002v1
+2010-01-11,Physics of Solar Prominences: II - Magnetic Structure and Dynamics,"Observations and models of solar prominences are reviewed. We focus on
+non-eruptive prominences, and describe recent progress in four areas of
+prominence research: (1) magnetic structure deduced from observations and
+models, (2) the dynamics of prominence plasmas (formation and flows), (3)
+Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and
+large-scale patterns of the filament channels in which prominences are located.
+Finally, several outstanding issues in prominence research are discussed, along
+with observations and models required to resolve them.",1001.1635v1
+2010-03-10,Dichotomy between large local and small ordered magnetic moment in Iron-based superconductors,"We study a four band model for iron-based superconductors within local
+density approximation + dynamical mean field theory (LDA+DMFT). This
+successfully reproduces the results of models which take As p degrees of
+freedom explicitly into account and has several physical advantages over the
+standard five d-band model. Our findings reveal that the new superconductors
+are more strongly correlated than their single-particle properties suggest.
+Two-particle correlation functions unveil the dichotomy between local and
+ordered magnetic moments in these systems, calling for further experiments to
+better resolve the short time scale spin dynamics.",1003.2162v1
+2010-03-19,Dynamics of magnetization on the topological surface,"We investigate theoretically the dynamics of magnetization coupled to the
+surface Dirac fermions of a three dimensional topological insulator, by
+deriving the Landau-Lifshitz-Gilbert (LLG) equation in the presence of charge
+current. Both the inverse spin-Galvanic effect and the Gilbert damping
+coefficient $\alpha$ are related to the two-dimensional diagonal conductivity
+$\sigma_{xx}$ of the Dirac fermion, while the Berry phase of the ferromagnetic
+moment to the Hall conductivity $\sigma_{xy}$. The spin transfer torque and the
+so-called $\beta$-terms are shown to be negligibly small. Anomalous behaviors
+in various phenomena including the ferromagnetic resonance are predicted in
+terms of this LLG equation.",1003.3769v1
+2010-05-25,Riemann-Lagrange Geometric Dynamics for the Multi-Time Magnetized Non-Viscous Plasma,"In this paper, using Riemann-Lagrange geometrical methods, we construct a
+geometrical model on 1-jet spaces for the study of multi-time relativistic
+magnetized non-viscous plasma, characterized by a given energy-stress-momentum
+distinguished (d-) tensor. In that arena, we give the conservation laws and the
+continuity equations for multi-time plasma. The partial differential equations
+of the stream sheets (the equivalent of stream lines in the classical
+semi-Riemannian geometrical approach of plasma) for multi-time plasma are also
+written.",1005.4567v1
+2010-06-09,Analytical expression of the magneto-optical Kerr effect and Brillouin light scattering intensity arising from dynamic magnetization,"Time-resolved magneto-optical Kerr effect (MOKE) and Brillouin light
+scattering (BLS) spectroscopy are important techniques for the investigation of
+magnetization dynamics. Within this article, we calculate analytically the MOKE
+and BLS signals from prototypical spin-wave modes in the ferromagnetic layer.
+The reliability of the analytical expressions is confirmed by optically exact
+numerical calculations. Finally, we discuss the dependence of the MOKE and BLS
+signals on the ferromagnetic layer thickness.",1006.1906v1
+2010-07-08,Dysprosium magneto-optical traps,"Magneto-optical traps (MOTs) of highly magnetic lanthanides open the door to
+explorations of novel phases of strongly correlated matter such as lattice
+supersolids and quantum liquid crystals. We recently reported the first MOTs of
+the five high abundance isotopes of the most magnetic atom, dysprosium.
+Described here are details of the experimental technique employed for
+repumper-free Dy MOTs containing up to half a billion atoms. Extensive
+characterization of the MOTs' properties---population, temperature, loading,
+metastable decay dynamics, trap dynamics---is provided.",1007.1480v1
+2010-09-11,Nonlinear optical response of hole-trion systems in quantum dots in tilted magnetic fields,"We discuss, from a theoretical point of view, the four wave mixing
+spectroscopy on an ensemble of p-doped quantum dots in a magnetic field
+slightly tilted from the in-plane configuration. We describe the system
+evolution in the density matrix formalism. In the limit of coherent ultrafast
+optical driving, we obtain analytical formulas for the single system dynamics
+and for the response of an inhomogeneously broadened ensemble. The results are
+compared to the previously studied time-resolved Kerr rotation spectroscopy on
+the same system. We show that the Kerr rotation and four wave mixing spectra
+yield complementary information on the spin dynamics (precession and damping).",1009.2202v1
+2010-10-11,Intrinsic coherence dynamics and phase localization in Aharonov-Bohm Interferometers,"The nonequilibrium real-time dynamics of electron coherence is explored in
+the quantum transport through the double-dot Aharonov-Bohm interferometers. We
+solve the exact master equation to find the exact quantum state of the device,
+from which the changes of the electron coherence through the magnetic flux in
+the nonequilibrium transport processes is obtained explicitly. We find that the
+relative phase between the two charge states of the double dot localizes to
+$\frac{\pi}{2}$ or $-\frac{\pi}{2}$ for all different magnetic flux. This
+nontrivial phase localization process can be manifested in the measurable
+occupation numbers.",1010.1977v1
+2010-11-16,Dynamic susceptibility of a spin ice near the critical point,"We consider spin ice magnets (primarily, $\mathrm{Dy_2Ti_2O_7}$) in the
+vicinity of their critical point on the $(H,T)$ plane. We find that the
+longitudinal susceptibility diverges at the critical point, leading to the
+behaviour qualitatively similar to the one which would result from non-zero
+conductance of magnetic charges. We show that dynamics of critical fluctuations
+belongs to the universality class of easy-axis ferroelectric and calculate
+logarithmic corrections (within two-loop approximation) to the mean-field
+critical behavior.",1011.3659v2
+2010-11-25,Dissipative dynamics of a two-qubit system: Four-level lasing,"The dissipative dynamics of a two-qubit system is studied theoretically. We
+make use of the Bloch-Redfield formalism which explicitly includes the
+parameter-dependent relaxation rates. We consider the case of two flux qubits,
+when the controlling parameters are the partial magnetic fluxes through the
+qubits' loops. The strong dependence of the inter-level relaxation rates on the
+controlling magnetic fluxes is demonstrated for the realistic system. This
+allows us to propose several mechanisms for lasing in this four-level system.",1011.5598v2
+2011-07-28,Random Hysteresis Loops,"Dynamical hysteresis is a phenomenon which arises in ferromagnetic systems
+below the critical temperature as a response to adiabatic variations of the
+external magnetic field. We study the problem in the context of the mean-field
+Ising model with Glauber dynamics, proving that for frequencies of the magnetic
+field oscillations of order $N^{2/3}$, with $N$ the size of the system, the
+""critical"" hysteresis loop becomes random.",1107.5662v2
+2011-11-17,Comment on 'Spin Ice: Magnetic Excitations without Monopole Signature Using $μ$SR' (arXiv:1110.0877),"Dunsiger and co-workers have criticised our paper on magnetic monopole
+dynamics spin ice [S. T. Bramwell et al., Nature, 461 956 (2009)]. We consider
+their criticisms and results but show that these do not warrant any revision of
+our earlier conclusions. In contrast, we point out that their conclusion of a
+`new' type of spin dynamics in spin ice is inconsistent with established facts.",1111.4168v1
+2011-11-21,Magnetic Compton profiles of Fe and Ni corrected by dynamical electron correlations,"Magnetic Compton profiles (MCPs) of Ni and Fe along [111] direction have been
+calculated using a combined Density Functional and many-body theory approach.
+At the level of the local spin density approximation the theoretical MCPs does
+not describe correctly the experimental results around the zero momentum
+transfer. In this work we demonstrate that inclusion of electronic correlations
+as captured by Dynamical Mean Field Theory (DMFT) improves significantly the
+agreement between the theoretical and the experimental MCPs. In particular, an
+energy decomposition of Ni MCPs gives indication of spin polarization and
+intrinsic nature of Ni 6 eV satellite, a genuine many-body feature.",1111.4848v1
+2011-11-22,Molecular nanomagnets as quantum simulators,"Quantum simulators are controllable systems that can be used to simulate
+other quantum systems. Here we focus on the dynamics of a chain of molecular
+qubits with interposed antiferromagnetic dimers. We theoretically show that its
+dynamics can be controlled by means of uniform magnetic pulses and used to
+mimic the evolution of other quantum systems, including fermionic ones. We
+propose two proof-of-principle experiments, based on the simulation of the
+Ising model in transverse field and of the quantum tunneling of the
+magnetization in a spin-1 system.",1111.5201v1
+2011-12-14,Dynamics of Thermal Effects in the Spin-Wave Theory of Quantum Antiferromagnets,"We derive a master equation that allows us to study non-equilibrium dynamics
+of a quantum antiferromagnet. By resorting to spin-wave theory, we obtain a
+closed analytic form for the magnon decay rates. These turn out to be closely
+related to form factors, which are experimentally accessible by means of
+neutron and Raman scattering. Furthermore, we compute the time evolution of the
+staggered magnetization showing that, for moderate temperatures, the magnetic
+order is not spoiled even if the coupling is fully isotropic.",1112.3158v3
+2011-12-14,Quenched Slonczewski-Windmill in Spin-Torque Vortex-Oscillators,"We present a combined analytical and numerical study on double-vortex
+spin-torque nano-oscillators and describe a mechanism that suppresses the
+windmill modes. The magnetization dynamics is dominated by the gyrotropic
+precession of the vortex in one of the ferromagnetic layers. In the other layer
+the vortex gyration is strongly damped. The dominating layer for the
+magnetization dynamics is determined by the current polarity. Measurements on
+Fe/Ag/Fe nano-pillars support these findings. The results open up a new
+perspective for building high quality-factor spin-torque oscillators operating
+at selectable, well-separated frequency bands.",1112.3163v1
+2012-03-09,"Relaxation, pre-thermalization and diffusion in a noisy Quantum Ising Chain","We study the dynamics of thermalization resulting from a time-dependent noise
+in a Quantum Ising Chain subject to a sudden quench of the transverse magnetic
+field. For weak noise the dynamics shows a pre-thermalized state at
+intermediate time scales, eventually drifting towards an asymptotic infinite
+temperature steady state characterized by diffusive behavior. By computing
+analytically the density of kinks, as well as the transverse and longitudinal
+magnetic field correlators, we characterize these two regimes, their
+observability and their signatures in the various physical quantities.",1203.2108v3
+2012-05-04,Cyclotron-Bloch dynamics of a quantum particle in a two-dimensional lattice II,"We study the quantum dynamics of a charged particle in a two-dimensional
+lattice, subject to constant and homogeneous electric and magnetic fields. We
+find that different regimes characterize these motions, depending on a
+combination of conditions, corresponding to weak and strong electric field
+intensities, rational or irrational directions of the electric field with
+respect to the lattice, and small or large values of the magnetic (Peierls)
+phase.",1205.0862v1
+2012-09-04,Hamiltonian equation of motion and depinning phase transition in two-dimensional magnets,"Based on the Hamiltonian equation of motion of the $\phi^4$ theory with
+quenched disorder, we investigate the depinning phase transition of the
+domain-wall motion in two-dimensional magnets. With the short-time dynamic
+approach, we numerically determine the transition field, and the static and
+dynamic critical exponents. The results show that the fundamental Hamiltonian
+equation of motion belongs to a universality class very different from those
+effective equations of motion.",1209.0513v1
+2012-10-30,NMR relaxation in spin ice due to diffusing emergent monopoles,"At low temperatures, spin dynamics in ideal spin ice is due mainly to dilute,
+thermally excited magnetic monopole excitations. I consider how these will
+affect the dynamics of a nuclear spin (the same theory applies to muon spin
+resonance if implanted muons do not diffuse). Up to the time scale for nearby
+monopoles to be rearranged, a stretched-exponential form of the relaxation
+functions is expected. I work out the expected exponent in that exponential and
+the formulas for the $T_1$ (longitudinal) and $T_2$ (dephasing) relaxations, as
+a function of the monopole density. Experimental NMR is incompatible with the
+predictions and I suggest is due to magnetic impurities.",1210.8137v1
+2013-01-18,Field-Free Synthetic-Ferromagnet Spin Torque Oscillator,"We study the magnetization dynamics of spin valve structures with a free
+composite synthetic ferromagnet (SyF) that consists of two ferromagnetic layers
+coupled through a normal metal spacer. A ferromagnetically coupled SyF can be
+excited into dynamical precessional states by an applied current without
+external magnetic fields. We analytically determine the stability of these
+states in the space spanned by the current density and SyF interlayer exchange
+coupling. Numerical simulations confirm our analytical results.",1301.4294v1
+2013-10-11,Magnetocapillary Swimmers,"We present an experiment where three mesoscopic soft ferromagnetic beads are
+placed onto a liquid surface and submitted to the influence of magnetic fields.
+A vertical magnetic field creates a repulsion which counterbalances the
+capillary attraction. We show that the competition with a second, oscillating
+field, deforms the structure in a non reciprocal way. As a consequence, the
+structure is able to swim. This experiment is fully described in a fluid
+dynamics video attached to this submission.",1310.3094v1
+2013-10-11,Degenerate Rayleigh-Plateau instability in a magnetically annealed colloidal dispersion,"This fluid dynamics video depicts the evolution of a suspension of
+paramagnetic colloids under the influence of a uniform, pulsed magnetic field.
+At low pulse frequencies, the suspension condenses into columns which decompose
+via a Rayleigh-Plateau instability. At high pulse frequencies, the suspension
+forms a kinetically arrested, system spanning network. We demonstrate the
+degeneration of the Rayleigh-Plateau instability with increasing pulse
+frequency.",1310.3226v2
+2014-02-11,Sliding window and compressive sensing for low-field dynamic magnetic resonance imaging,"We describe an acquisition/processing procedure for image reconstruction in
+dynamic Magnetic Resonance Imaging (MRI). The approach requires sliding window
+to record a set of trajectories in the k-space, standard regularization to
+reconstruct an estimate of the object and compressed sensing to recover image
+residuals. We validated this approach in the case of specific simulated
+experiments and, in the case of real measurements, we showed that the procedure
+is reliable even in the case of data acquired by means of a low-field scanner.",1402.2453v1
+2014-07-25,Escape of Charged Particles Moving around a Weakly Magnetized Kerr Black Hole,"We study the dynamics and escape of charged particles initially orbiting a
+weakly magnetized Kerr black hole after they get kicked in the direction normal
+to the orbit. The case of neutral particles is analysed first and the escape
+conditions are given analytically. A general analysis of charged particles
+innermost stable circular orbits (ISCO)s is performed numerically. We then
+study the charged particles three-dimensional motion and give an effective
+condition for their escape. We also discuss how the black hole rotation affects
+the escape of charged particles and the chaoticness in their dynamics.",1407.7069v1
+2014-10-03,Dynamics of a vortex dipole across a magnetic phase boundary in a spinor Bose-Einstein condensate,"Dynamics of a vortex dipole in a spin-1 Bose-Einstein condensate in which
+magnetic phases are spatially distributed is investigated. When a vortex dipole
+travels from the ferromagnetic phase to the polar phase, or vice versa, it
+penetrates the phase boundary and transforms into one of the various spin
+vortex dipoles, such as a leapfrogging ferromagnetic-core vortex dipole and a
+half-quantum vortex dipole. Topological connections of spin wave functions
+across the phase boundary are discussed.",1410.0743v1
+2014-11-03,Decay rates of magnetic modes below the threshold of a turbulent dynamo,"We measure the decay rates of magnetic field modes in a turbulent flow of
+liquid sodium below the dynamo threshold.We observe that turbulent fluctuations
+induce energy transfers between modes with different symmetries (dipolar and
+quadrupolar). Using symmetry properties, we show how to measure the decay rate
+of each mode without being restricted to the one with the smallest damping
+rate.We observe that the respective values of the decay rates of these modes
+depend on the shape of the propellers driving the flow. Dynamical regimes,
+including field reversals, are observed onlywhen the modes are both nearly
+marginal. This is in linewith a recently proposed model.",1411.0517v1
+2014-11-21,Ballistic dynamics of Dirac particles in electro-magnetic fields,"Investigating properties of two-dimensional Dirac operators coupled to an
+electric and a magnetic field (perpendicular to the plane) requires in general
+unbounded (vector-) potentials. If the system has a certain symmetry, the
+fields can be described by one-dimensional potentials $V$ and $A$. Assuming
+that $|A|<|V|$ outside some arbitrary large ball, we show that absolutely
+continuous states of the effective Dirac operators spread ballistically. These
+results are based on well-known methods in spectral dynamics together with
+certain new Hilbert-Schmidt bounds. We use Lorentz boosts to derive these new
+estimates.",1411.5998v1
+2014-11-30,Spin dynamics of the anisotropic spin-1 antiferromagnetic chain at finite magnetic fields,"We present results of a study of the antiferromagnetic spin-1 chain, subject
+to the simultaneous presence of single-ion anisotropy and external magnetic
+fields. Using quantum Monte-Carlo based on the stochastic series expansion
+method we first uncover a rich quantum phase diagram comprising N\'eel,
+Haldane, Luttinger liquid, and large anisotropy phases. Second, we scan across
+this phase diagram over a wide range of parameters, evaluating the transverse
+dynamic structure factor, which we show to exhibit sharp massive modes, as well
+as multi particle continua. For vanishing anisotropy and fields, comparison
+with existing results from other analytic and numerical approaches shows
+convincing consistency.",1412.0208v2
+2015-03-06,Localizing spin dynamics in a spin-1 Bose-Einstein condensate via magnetic pulses,"Spin exchange interaction between atoms in a spin-1 Bose-Einstein condensate
+causes atomic spin evolving periodically under the single spatial mode
+approximation in the mean field theory. By applying fast magnetic pulses
+according to a two-step or a four-step control protocol, we find analytically
+that the spin dynamics is significantly suppressed for an arbitrary initial
+state. Numerical calculations under single mode approximation are carried out
+to confirm the validity and robustness of these protocols. This localization
+method can be readily utilized to improve the sensitivity of a magnetometer
+based on spin-1 Bose-Einstein condensates.",1503.01828v1
+2015-06-18,Dispersive read-out of ferromagnetic resonance for strongly coupled magnons and microwave photons,"We demonstrate the dispersive measurement of ferromagnetic resonance in a
+yttrium iron garnet sphere embedded within a microwave cavity. The reduction in
+the longitudinal magnetization at resonance is measured as a frequency shift in
+the cavity mode coupled to the sphere. This measurement is a result of the
+intrinsic non-linearity in magnetization dynamics, indicating a promising route
+towards experiments in magnon cavity quantum electro-dynamics.",1506.05631v1
+2015-06-20,Spin and orbital exchange interactions from Dynamical Mean Field Theory,"We derive a set of equations expressing the parameters of the magnetic
+interactions characterizing a strongly correlated electronic system in terms of
+single-electron Green's functions and self-energies. This allows to establish a
+mapping between the initial electronic system and a spin model including up to
+quadratic interactions between the effective spins, with a general interaction
+(exchange) tensor that accounts for anisotropic exchange, Dzyaloshinskii-Moriya
+interaction and other symmetric terms such as dipole-dipole interaction. We
+present the formulas in a format that can be used for computations via
+Dynamical Mean Field Theory algorithms.",1506.06209v1
+2015-06-23,Effects of magnetic anisotropy on spin dynamics of ferromagnetic frustrated chain,"By exploiting density-matrix renormalization group techniques, we investigate
+the spin dynamics of a spin-1/2 one-dimensional J1-J2 XXZ model with competing
+ferromagnetic J1 and antiferromagnetic J2 exchange couplings under applied
+magnetic fields. Numerical results of spin excitation spectra show that in the
+field-induced spin quadrupole regime, the longitudinal component has a gapless
+mode and the transverse component has a gapped mode irrespective of the
+exchange anisotropy. The excitation gap of the transverse spin excitation
+increases as the exchange anisotropy increases over the XY-like and Ising-like
+regions, demonstrating that two-magnon bound states are stabilized due to the
+easy-axis anisotropy.",1506.06883v1
+2015-09-11,"Formation of star-forming clouds from the magnetised, diffuse interstellar medium","Molecular clouds, the birthplaces of stars in galaxies, form dynamically from
+the diffuse atomic gas of the interstellar medium (ISM). The ISM is also
+threaded by magnetic fields which have a large impact on its dynamics. In
+particular, star forming regions must be magnetically supercrit- ical in order
+to accomodate gas clumps which can collapse under their own weight. Based on a
+parameter study of three dimensional magneto-hydrodyamical (MHD) simulations,
+we show that the long-standing problem of how such supercritical regions are
+generated is still an open issue.",1509.03436v1
+2015-09-11,Non-Markovian Effects in the Spin Transfer Dynamics in Diluted Magnetic Semiconductors due to Excitation in Proximity to the Band Edge,"The non-Markovian effects in the spin dynamics in diluted magnetic
+semiconductors found in quantum kinetic calculations can be reproduced very
+well by a much simpler effective single electron theory, if a finite memory is
+accounted for. The resulting integro-differential equation can be solved by a
+differential transform method, yielding the Taylor series of the solution. From
+the comparison of both theories it can be concluded that the non-Markovian
+effects are due to the spectral proximity of the excited electrons to the band
+edge.",1509.03487v1
+2015-12-03,Dynamics of vortices with magnetic impurities,"We investigate the dynamics of BPS vortices in the presence of magnetic
+impurities taking the form of axially-symmetric localised lumps and
+delta-functions. We present numerical results for vortices on flat space, as
+well as exact results for vortices on hyperbolic space in the presence of
+delta-function impurities. In fact, delta-function impurities of appropriate
+strength can be captured within the moduli space approximation by keeping one
+or more of the vortices fixed. We also show that previous work on vortices on
+the 2-sphere extends naturally to the inclusion of delta-function impurities.",1512.01054v1
+2015-12-20,Shapiro like steps reveals molecular nanomagnets' spin dynamics,"We present an accurate way to detect spin dynamics of a nutating molecular
+nanomagnet by inserting it in a tunnel Josephson junction and studying the
+current voltage (I-V) characteristic. The spin nutation of the molecular
+nanomagnet is generated by applying two circularly polarized magnetic fields.
+We demonstrate that modulation of the Josephson current by the nutation of the
+molecular nanomagnet's spin appears as a stepwise structure like Shapiro steps
+in the I-V characteristic of the junction. Width and heights of these
+Shapiro-like steps are determined by two parameters of the spin nutation,
+frequency and amplitude of the nutation, which are simply tuned by the applied
+magnetic fields.",1512.06406v1
+2015-12-30,Distributed chaos and isotropic turbulence,"Power spectrum of the distributed chaos can be represented by a weighted
+superposition of the exponential functions which is converged to a stretched
+exponential $\propto \exp-(k/k_{\beta})^{\beta }$. An asymptotic theory has
+been developed in order to estimate the value of $\beta$ for the isotropic
+turbulence. This value has been found to be $\beta =3/4$. Excellent agreement
+has been established between this theory and the data of direct numerical
+simulations not only for the velocity field but also for the passive scalar,
+energy dissipation rate, and magnetic fields. One can conclude that the
+isotropic turbulence emerges from the distributed chaos.",1512.08837v3
+2016-06-30,Skyrmion dynamics in a chiral magnet driven by periodically varying spin currents,"In this work, we investigated the spin dynamics in a slab of chiral magnets
+induced by an alternating (ac) spin current. Periodic trajectories of the
+skyrmion in real space are discovered under the ac current as a result of the
+Magnus and viscous forces, which originate from the Gilbert damping, the spin
+transfer torque, and the $ \beta $-nonadiabatic torque effects. The results are
+obtained by numerically solving the Landau-Lifshitz-Gilbert equation and can be
+explained by the Thiele equation characterizing the skyrmion core motion.",1606.09326v2
+2016-08-23,Dynamic dependence to domain wall propagation through artificial spin ice,"Domain wall propagation dynamics have been studied in nanostructured
+artificial kagome spin ice structures. A stripline circuit has been used to
+provide localised pulsed magnetic fields within the artificial spin ice
+structure. This provides control of the system through electrically assisted
+domain wall nucleation events. Synchronisation of the pulsed fields with
+additional global magnetic fields and the use of a focussed magneto-optical
+Kerr effect magnetometer allows our experiments to probe the domain wall
+transit through an extended ASI structure. We find that the propagation
+distance depends on the driving field revealing field driven properties of
+domain walls below their intrinsic nucleation field.",1608.06436v1
+2016-11-14,Dynamic Polarization and Relaxation of 75As Nuclei in Silicon at High Magnetic Field and Low Temperature,"We present the results of experiments on dynamic nuclear polarization and
+relaxation of 75As in silicon crystals. Experiments are performed in strong
+magnetic fields of 4.6 T and temperatures below 1 K. At these conditions donor
+electron spins are fully polarized, and the allowed and forbidden ESR
+transitions are well resolved. We demonstrate effective nuclear polarization of
+75As nuclei via the Overhauser effect on the time scale of several hundred
+seconds. Excitation of the forbidden transitions leads to a polarization
+through the solid effect. The relaxation rate of donor nuclei has strong
+temperature dependence characteristic of Orbach process.",1611.04384v1
+2016-12-23,"Defect Dynamics in Artificial Colloidal Ice: Real-Time Observation, Manipulation and Logic Gate","We study the defect dynamics in a colloidal spin ice system realized by
+filling a square lattice of topographic double well islands with repulsively
+interacting magnetic colloids. We focus on the contraction of defects in the
+ground state, and contraction/expansion in a metastable biased state. Combining
+real-time experiments with simulations, we prove that these defects behave like
+emergent topological monopoles obeying a Coulomb law with an additional line
+tension. We further show how to realize a completely resettable ""NOR"" gate,
+which provides guidelines for fabrication of nanoscale logic devices based on
+the motion of topological magnetic monopoles.",1612.08003v1
+2017-05-09,Comparison of CPMG and Uhrig Dynamic Decoupling (UDD) for tissue refocusing in MRI,"Two different dynamic decoupling strategies, the classic CPMG and the more
+recently proposed UDD protocol are compared in the context of magnetic
+resonance imaging (MRI). Both sequences were implemented on a 3T human MRI
+system and relaxometry was performed for a variety of tissue-mimicking agar and
+agarose gels. We find that CPMG provides moderately better decoupling than
+\UDD. The results are consistent with experimental noise spectra obtained from
+\textit{in vivo} spectroscopy results, which suggest that the type of noise
+spectra obtained would favor \CPMG. Theoretical coherence pathway analysis
+further suggests that \UDD\ is more susceptible to systematic errors due to
+static magnetic and radio-frequency field inhomogeneity or imperfect excitation
+and refocusing pulse profiles.",1705.03292v1
+2017-05-16,On free Lie algebras and particles in electro-magnetic fields,"The Poincar\'e algebra can be extended (non-centrally) to the Maxwell algebra
+and beyond. These extensions are relevant for describing particle dynamics in
+electro-magnetic backgrounds and possibly including the backreaction due the
+presence of multipoles. We point out a relation of this construction to free
+Lie algebras that gives a unified description of all possible kinematic
+extensions, leading to a symmetry algebra that we call Maxwell${}_\infty$. A
+specific dynamical system with this infinite symmetry is constructed and
+analysed.",1705.05854v2
+2017-08-10,Control of the gyration dynamics of magnetic vortices by the magnetoelastic effect,"The influence of a strain-induced uniaxial magnetoelastic anisotropy on the
+magnetic vortex core dynamics in microstructured magnetostrictive
+Co$_{40}$Fe$_{40}$B$_{20}$ elements was investigated with time-resolved
+scanning transmission x-ray microscopy. The measurements revealed a
+monotonically decreasing eigenfrequency of the vortex core gyration with the
+increasing magnetoelastic anisotropy, which follows closely the predictions
+from micromagnetic modeling.",1708.03123v1
+2017-08-22,A dynamical mean-field theory study of stripe order and d-wave superconductivity in the two-dimensional Hubbard model,"We use cellular dynamical mean-field theory with extended unit cells to study
+the ground state of the two-dimensional repulsive Hubbard model at finite
+doping. We calculate the energy of states with d-wave superconductivity
+coexisting with spatially uniform magnetic order and find that they are
+energetically favoured in a large doping region as compared to the uniform
+solution. We study the spatial form of the superconducting and magnetic order
+parameters at different doping values.",1708.06749v2
+2017-09-13,Ultrafast spin-lattice relaxation in ferromagnets including effective spin-orbit fields,"We investigate ultrafast demagnetization due to electron-phonon interaction
+in a model band-ferromagnet. We show that the microscopic mechanism behind the
+spin dynamics due to electron-phonon interaction is the interplay of scattering
+and the precession around momentum-dependent effective internal spin-orbit
+magnetic fields. The resulting magnetization dynamics can only be mimicked by
+spin-flip transitions if the spin precession around the internal fields is
+sufficiently fast (compared to the scattering time) so that it averages out the
+transverse spin components.",1709.04253v1
+2017-11-23,Effective Resistivity in Collisionless Magnetic Reconnection,"Magnetic reconnection (MR) in collisionless plasma is often attributed to the
+off-diagonal electron Reynolds stress, which can give rise to a large induction
+electric field in the reconnection region. However, in magneto-hydro-dynamics
+(MHD) simulations of MR, it is difficult to implement the full Reynolds stress,
+which is kinetic in nature. In this paper, we propose a theoretical model of
+effective resistivity from the first principle of particle dynamics. The
+derived theoretical formulation of the effective resistivity is verified by
+full particle-in-cell (PIC) simulations, and the corresponding physics is
+discussed.",1711.08702v1
+2018-01-15,Uncertainty Quantification For A Permanent Magnet Synchronous Machine With Dynamic Rotor Eccentricity,"The influence of dynamic eccentricity on the harmonic spectrum of the torque
+of a permanent magnet synchronous machine is studied. The spectrum is
+calculated by an energy balance method. Uncertainty quantification is applied
+by using generalized Polynomial Chaos and Monte Carlo. It is found that the
+displacement of the rotor impacts the spectrum of the torque the most.",1801.04828v1
+2018-02-26,Dynamics and Instabilities of the Shastry-Sutherland Model,"We study the excitation spectrum in the dimer phase of the Shastry-Sutherland
+model by using an unbiased variational method that works in the thermodynamic
+limit. The method outputs dynamical correlation functions in all possible
+channels. This output is exploited to identify the order parameters with the
+highest susceptibility (single or multitriplon condensation in a specific
+channel) upon approaching a quantum phase transition in the magnetic field
+versus the $J'/J$ phase diagram. We find four different instabilities:
+antiferro spin nematic, plaquette spin nematic, stripe magnetic order, and
+plaquette order, two of which have been reported in previous studies.",1802.09428v2
+2018-03-22,Transient dynamics of strongly coupled spin vortex pairs: effects of anharmonicity and resonant excitation on inertial switching,"Spin vortices in magnetic nanopillars are used as GHz oscillators, with
+frequency however essentially fixed in fabrication. We demonstrate a model
+system of a two-vortex nanopillar, in which the resonance frequency can be
+changed by an order of magnitude, without using high dc magnetic fields. The
+effect is due to switching between the two stable states of the vortex pair,
+which we show can be done with low-amplitude fields of sub-ns duration. We
+detail the relevant vortex-core dynamics and explain how field anharmonicity
+and phase control can be used to enhance the performance.",1803.08413v1
+2018-06-04,Dynamical quadrupole structure factor of frustrated ferromagnetic chain,"We investigate the dynamical quadrupole structure factor of a spin-1/2
+$J_{1}$-$J_{2}$ Heisenberg chain with competing ferromagnetic $J_{1}$ and
+antiferromagnetic $J_{2}$ in a magnetic field by exploiting density-matrix
+renormalization group techniques. In a field-induced spin nematic regime, we
+observe gapless excitations at $q=\pi$ according to quasi-long-range
+antiferro-quadrupole correlations. The gapless excitation mode has a quadratic
+form at the saturation, while it changes into a linear dispersion as the
+magnetization decreases.",1806.01434v1
+2018-08-30,Axion instability and non-linear electromagnetic effect,"We investigate the instability due to dynamical axion field near the
+topological phase transition of insulators. We first point out that the
+amplitude of dynamical axion field is bounded for magnetic insulators in
+general, which suppresses the axion instability. Near the topological phase
+transition, however, the axion field may have a large fluctuation, which
+decreases the critical electric field for the instability and increases the
+axion induced magnetic flux density. Using two different model Hamiltonians, we
+report the electromagnetic response of the axion field in details.",1808.10466v1
+2018-10-14,Explicit symplectic adapted exponential integrators for charged-particle dynamics in a strong and constant magnetic field,"This paper studies explicit symplectic adapted exponential integrators for
+solving charged-particle dynamics in a strong and constant magnetic field. We
+first formulate the scheme of adapted exponential integrators and then derive
+its symplecticity conditions. Based on the symplecticity conditions, we propose
+five practical explicit symplectic adapted exponential integrators. Two
+numerical experiments are carried out and the numerical results demonstrate the
+remarkable numerical behavior of the new methods.",1810.06038v2
+2018-11-06,Nonlinear dynamic interpretation of quantum spin,"In an effort to provide an alternative method to represent a quantum spin, a
+precise nonlinear dynamics semi-classical model is used to show that standard
+quantum spin analysis can be obtained. The model includes a multi-body,
+anti-ferromagnetic ordering, highly coupled quantum spin and a semi-classical
+interpretation of the torque on a spin magnetic moment in the presence of a
+magnetic field. The deterministic nonlinear differential coupling equation is
+used to introduce chaos, which is necessary to reproduce the correct
+statistical quantum results.",1811.02624v1
+2018-11-06,Nonlinear Dynamics Semi-classical Model of Quantum Spin,"A nonlinear dynamics semi-classical model is used to show that standard
+quantum spin analysis can be obtained. The model includes a classically driven
+nonlinear differential equation with dissipation and a semi-classical
+interpretation of the torque on a spin magnetic moment in the presence of a
+realistic magnetic field, which will represent two equilibrium positions. The
+highly complicated driven nonlinear dissipative semi-classical model is used to
+introduce chaos, which is necessary to produce the correct statistical quantum
+results. The resemblance between this semi-classical spin model and the
+thoroughly studied classical driven-damped nonlinear pendulum are shown and
+discussed.",1811.02645v1
+2018-11-14,Fractional calculus approach for the phase dynamics of Josephson junction under the influence of magnetic field,"This article presents the phase dynamics of an inline long Josephson junction
+in voltage state under the influence of constant external magnetic field.
+Fractional calculus approach is used to model the evolution of the phase
+difference between the macroscopic wave functions of the two superconductors
+across the junction. The governing non-linear partial differential equation is
+then solved using finite difference-finite element schemes. Other quantities of
+interest like Josephson current density and voltage across the junction are
+also computed. The effects of various parameters in the model on phase
+difference, Josephson current density and voltage are analyzed graphically with
+the help of numerical simulations.",1811.05691v1
+2019-01-24,Dynamic axion field in the magnetoelectric antiferromagnet chromia,"Chromia is a magnetoelectric insulator whose bulk magnetoelectric
+susceptibility contains a non-zero pseudoscalar component, like that present in
+magnetized topological insulators. We reveal the dynamic axion field of chromia
+by measuring the temperature dependence of its non-linear magnetoelectric
+response using a lock-in technique with an AC electric field stimulus. The
+electric field dependence, magnetic field dependence, and temperature behavior
+of the second harmonic lock-in signal are all in agreement with theoretical
+expectations. Our results demonstrate that chromia magnetoelectric response
+couples strongly to its low-energy quantum and thermal spin fluctuations.",1901.08536v1
+2019-03-08,Dynamical phase transition in the 1D-transverse field Ising chain characterized by the transverse magnetization spectral function,"We study a 1D-Quantum Ising Model in transverse field driven out of
+equilibrium by performing a composite quantum quench to deduce the asymptotic
+properties of the transverse magnetization stationary state via the analysis of
+the spectral function. What emerges is that, in correspondence of the dynamical
+phase transition transition predicted for this model, the spectral function
+vanishes giving a hint of the criticality. This result suggests also that
+linear response experiment can be used to detect this kind of phase transition.",1903.03439v1
+2019-04-01,Synchrony breakdown and noise-induced oscillation death in ensembles of serially connected spin-torque oscillators,"We consider collective dynamics in the ensemble of serially connected
+spin-torque oscillators governed by the Landau-Lifshitz-Gilbert-Slonczewski
+magnetization equation. Proximity to homoclinicity hampers synchronization of
+spin-torque oscillators: when the synchronous ensemble experiences the
+homoclinic bifurcation, the Floquet multiplier, responsible for the temporal
+evolution of small deviations from the ensemble mean, diverges. Depending on
+the configuration of the contour, sufficiently strong common noise, exemplified
+by stochastic oscillations of the current through the circuit, may suppress
+precession of the magnetic field for all oscillators. We derive the explicit
+expression for the threshold amplitude of noise, enabling this suppression.",1904.00897v1
+2019-05-21,Collective spin dynamics of Z2 vortex crystals in triangular Kitaev-Heisenberg antiferromagnets,"We show that the mesoscopic incommensurate $\mathbb{Z}_2$ vortex crystals
+proposed for layered triangular anisotropic magnets can be most saliently
+identified by two distinctive signatures in dynamical spin response
+experiments: The presence of pseudo-Goldstone `phonon' modes at low frequencies
+$\omega$, associated with the collective vibrations of the vortex cores, and a
+characteristic multi-scattered intensity profile at higher $\omega$, arising
+from a large number of Bragg reflections and magnon bandgaps. These are direct
+fingerprints of the large vortex sizes and magnetic unit cells and the
+solitonic spin profile around the vortex cores.",1905.08694v2
+2019-10-18,Kardar-Parisi-Zhang universality from soft gauge modes,"The emergence of superdiffusive spin dynamics in integrable classical and
+quantum magnets is well established by now, but there is no generally valid
+theoretical explanation for this phenomenon. A fundamental difficulty is that
+the hydrodynamic fluctuations of conserved quasiparticle modes are purely
+diffusive. We argue that in isotropic integrable magnets, a complete
+hydrodynamic description must include soft ""gauge"" degrees of freedom, that
+arise from spontaneous breaking of the Bethe pseudovacuum symmetry. We show
+that the coarse-grained time evolution of these modes lies in the
+Kardar-Parisi-Zhang universality class of dynamics.",1910.08266v3
+2019-11-25,Spin liquids in geometrically perfect triangular antiferromagnets,"The cradle of quantum spin liquids, triangular antiferromagnets show strong
+proclivity to magnetic order and require deliberate tuning to stabilize a
+spin-liquid state. In this brief review, we juxtapose recent theoretical
+developments that trace the parameter regime of the spin-liquid phase, with
+experimental results for Co-based and Yb-based triangular antiferromagnets.
+Unconventional spin dynamics arising from both ordered and disordered ground
+states is discussed, and the notion of a geometrically perfect triangular
+system is scrutinized to demonstrate non-trivial imperfections that may assist
+magnetic frustration in stabilizing dynamic spin states with peculiar
+excitations.",1911.11157v2
+2020-01-25,Field-induced freezing in the unfrustrated Ising antiferromagnet,"We study instantaneous quenches from infinite temperature to well below $T_c$
+in the two-dimensional square lattice Ising antiferromagnet in the presence of
+a longitudinal external magnetic field. Under single-spin-flip Metropolis
+algorithm Monte Carlo dynamics, this protocol produces a pair of magnetization
+plateaus that prevent the system from reaching the equilibrium ground state
+except for some special values of the field. We explain the plateaus in terms
+of local spin configurations that are stable under the dynamics.",2001.09268v2
+2019-11-04,THz graphene W-shaped three-port circulator with dynamical control,"We propose a new graphene-based THz circulator. It consists of a circular
+graphene resonator and three graphene nanoribbon waveguides of W-geometry
+placed on a dilectric substrate. Surface plasmon-polariton waves propagate in
+the waveguides. The nanoribbon excites in the resonator dipole resonance.
+Nonreciprocity of the device is defined by nonsymmetry of the conductivity
+tensor of the magnetized graphene. The circulator with the central frequency
+7.5 THz has the bandwidth 4.25\% for isolation -15 dB, insertion loss -2.5 dB.
+Applied DC magnetic field is 0.56T and Fermi energy of graphene
+$\epsilon_F=0.15$eV. The Fermi energy allows one to control dynamically the
+circulator responses.",2001.10078v1
+2020-05-29,On the asymptotic dynamics of 2-D magnetic quantum systems,"In this work we provide results on the long time localisation in space
+(dynamical localisation) of certain two-dimensional magnetic quantum systems.
+The underlying Hamiltonian may have the form $H=H_0+W$, where $H_0$ is
+rotationally symmetric, has dense point spectrum, and $W$ is a perturbation
+that breaks the rotational symmetry.
+  In the latter case, we also give estimates for the growth of the angular
+momentum operator in time.",2006.00134v1
+2020-07-15,"Comment on: ""Relativistic quantum dynamics of a charged particle in cosmic string spacetime in the presence of magnetic field and scalar potential''. Eur. Phys. J. C (2012) 72:2051","We analyze the results of a paper on ``Relativistic quantum dynamics of a
+charged particle in cosmic string spacetime in the presence of magnetic field
+and scalar potential''. We show that the authors did not obtain the spectrum of
+the eigenvalue equation but only one eigenvalue for a specific relationship
+between model parameters. In particular, the existence of allowed cyclotron
+frequencies conjectured by the authors is a mere artifact of the truncation
+condition used to obtain exact solutions to the radial eigenvalue equation.",2008.03376v1
+2020-11-09,Topological charge analysis of dynamic process of transition to Néel-type skyrmion: role of domain wall skyrmions,"Magnetic skyrmions are intriguing topological spin textures that promise
+future high-density spintronic devices. The creation of magnetic skyrmions has
+been understood based on the energetics of skyrmions, but the detailed dynamic
+process of the skyrmion creation remains unclear. Here topological evolution in
+conversion from uneven domains to N\'eel-skyrmions is investigated using
+micromagnetic simulations. We find that, rather than the overall topological
+charge, annihilation of novel topological defects, i.e., recently suggested
+domain wall skyrmions, dominantly govern the skyrmion creation process. Also,
+the topological charge evolution is interpreted in terms of the number and the
+combination of such topological defects.",2011.05299v1
+2021-11-05,A First-Order Approach to Model Simultaneous Control of Multiple Microrobots,"The control of swarm systems is relatively well understood for simple robotic
+platforms at the macro scale. However, there are still several unanswered
+questions about how similar results can be achieved for microrobots. In this
+paper, we propose a modeling framework based on a dynamic model of magnetized
+self-propelling Janus microrobots under a global magnetic field. We verify our
+model experimentally and provide methods that can aim at accurately describing
+the behavior of microrobots while modeling their simultaneous control. The
+model can be generalized to other microrobotic platforms in low Reynolds number
+environments.",2111.03232v1
+2021-12-06,Analysis of finite-size effect of infinite-range Ising model under Glauber dynamics,"We consider an infinite-range Ising model under the Glauber dynamics and
+determine the finite-size effect on the distribution of two spin variables as a
+perturbation of $O \left( 1/N \right)$. Based on several considerations,
+ordinary differential equations are derived for describing the time development
+of both a two-body correlation and the autocorrelation function of
+magnetization. The results of the calculation fit the simulation results,
+unless the perturbation theory breaks down because of critical phenomena or
+magnetization reversal.",2112.02730v1
+2021-12-18,Stability analysis of the Hindmarsh-Rose neuron under electromagnetic induction,"We consider the Hindmarsh-Rose neuron model modified by taking into account
+the effect of electromagnetic induction on membrane potential. We study the
+impact of the magnetic flux on the neuron dynamics, through the analysis of the
+stability of fixed points. Increasing magnetic flux reduces the number of
+equilibrium points and favors their stability. Therefore, electromagnetic
+induction tends to regularize chaotic regimes and to affect regular and
+quasi-regular ones by reducing the number of spikes or even destroying the
+oscillations.",2112.09987v1
+2022-02-25,Regions without invariant tori of given class for the planar circular restricted three-body problem,"A method to establish regions of phase space through which pass no invariant
+tori transverse to a given direction field is applied to the planar circular
+restricted three-body problem. Implications for the location of stable orbits
+for planets around a binary star are deduced. It is expected that lessons
+learnt from this problem will be useful for applications of the method to other
+contexts such as flux surfaces for magnetic fields, guiding centre motion in
+magnetic fields, and classical models of chemical reaction dynamics.",2202.12691v1
+2022-04-29,Long term analysis of splitting methods for charged-particle dynamics,"In this paper, we rigorously analyze the energy, momentum and magnetic moment
+behaviours of two splitting methods for solving charged-particle dynamics. The
+near-conservations of these invariants are given for the system under constant
+magnetic field or quadratic electric potential. By the approach named as
+backward error analysis, we derive the modified equations and modified
+invariants of the splitting methods and based on which, the near-conservations
+over long times are proved. Some numerical experiments are presented to
+demonstrate these long time behaviours.",2205.06659v1
+2022-09-13,Small-scale chaotic dynamo and spontaneous breaking of local reflectional symmetry in magnetohydrodynamics,"It is shown, using results of direct numerical simulations, that the
+spontaneous breaking of local reflectional symmetry (and corresponding
+localized kinetic and magnetic helicities) can dominate chaotic dynamics of the
+small-scale MHD dynamo in the Rayleigh-B{\'e}nard convection, in kinetically
+forced flows under strong stratification, in the near-surface solar convection,
+and in kinetically forced flows at large magnetic Reynolds numbers. The notions
+of deterministic and helical distributed chaos have been used for this purpose.
+The coexistence of large- and small-scale dynamo mechanisms and applications of
+the obtained results to quiet and active regions of the solar photosphere have
+been briefly discussed.",2209.06089v1
+2022-11-28,Dynamical susceptibility of Skyrmion crystal,"Using stereographic projection approach we develop a theory for calculation
+of dynamical susceptibility tensor of Skyrmion crystals (SkX), formed in thin
+ferromagnetic films with Dzyaloshinskii-Moriya interaction and in the external
+magnetic field. Staying whenever possible within analytical framework, we
+employ the model anzats for static SkX configuration and discuss small
+fluctuations around it. The obtained formulas are numerically analyzed in the
+important case of uniform susceptibility, accessible in magnetic resonance (MR)
+experiments. We show that, in addition to three characteristic MR frequencies
+discussed earlier both theoretically and experimentally, one should also expect
+several resonances of smaller amplitude at somewhat higher frequencies.",2211.15740v1
+2023-01-17,Dynamics of self-gravitating systems in non-linearly magnetized chameleonic Brans-Dicke gravity,"We study the effects of magnetic fields of non-linear electrodynamics in
+chameleonic Brans-Dicke theory under the existence of anisotropic spherical
+fluid. In particular, we explore dissipative and non-dissipative
+self-gravitating systems in the quasi-homologous regime with the minimal
+complexity constraint. As a result, under the aforementioned circumstances,
+several analytic solutions are found. Furthermore, by analyzing the dynamics of
+a dissipative fluid, it is demonstrated that a void covering the center can
+satisfy the Darmois criteria. The temperature of the self gravitating systems
+is also investigated.",2301.07105v1
+2023-09-25,Dunkl-Pauli Equation in the Presence of a Magnetic Field,"The Pauli equation, an important equation of quantum mechanics, allows us to
+study the dynamics of spin-$1/2$ particles. The Dunkl derivative, when used
+instead of the ordinary derivative, leads to obtaining parity-dependent
+solutions. Motivated by these facts, in this work, we consider a
+two-dimensional nonrelativistic spin-$1/2$ particle system in the presence of
+an external magnetic field, and we investigate its parity-dependent dynamics by
+solving the Pauli equation analytically. Next, we assume the system to be in
+thermal equilibrium, and we examine various thermal quantities of the system.",2309.14081v2
+2023-12-07,Thermomagnetic Anomalies by Magnonic Criticality in Ultracold Atomic Transport,"We investigate thermomagnetic transport in an ultracold atomic system with
+two ferromagnets linked via a magnetic quantum point contact. Using
+nonequilibrium Green's function approach, we show a divergence in spin
+conductance and a slowing down of spin relaxation that manifest in the weak
+effective-Zeeman-field limit. These anomalous spin dynamics result from the
+magnonic critical point at which magnons become gapless due to spontaneous
+magnetization. Our findings unveil untapped dynamics in ultracold atomic
+systems, opening new avenues in thermomagnetism.",2312.04280v1
+2024-01-31,Magnetic Bloch oscillations in a non-Hermitian quantum Ising chain,"We investigate the impacts of an imaginary transverse field on the dynamics
+of magnetic domain walls in a quantum Ising chain. We show that an imaginary
+field plays a similar role as a real transverse field in forming a low-lying
+Wannier-Stark ladder. However, analytical and numerical calculations of the
+time evolutions in both systems show that the corresponding Bloch oscillations
+exhibit totally different patterns for the same initial states. These findings
+reveal the nontrivial effect of non-Hermiticity on quantum spin dynamics.",2401.17586v2
+2024-03-27,Specificity of $τ$ -- approximation for chaotic electron trajectories on complex Fermi surfaces,"The work examines a special behavior of the magnetic conductivity of metals
+that arises when chaotic electron trajectories appear on the Fermi surface.
+This behavior is due to the scattering of electrons at singular points of the
+dynamic system describing the dynamics of electrons in $\, {\bf p}$-space, and
+caused by small-angle scattering of electrons on phonons. In this situation,
+the electronic system is described by a ""non-standard"" relaxation time, which
+plays the main role in a certain range of temperature and magnetic field
+values.",2403.18457v1
+1999-01-27,Femtosecond electron and spin dynamics probed by nonlinear optics,"A theoretical calculation is performed for the ultrafast spin dynamics in
+nickel using an exact diagonalization method. The present theory mainly focuses
+on a situation where the intrinsic charge and spin dynamics is probed by the
+nonlinear (magneto-)optical responses on the femtosecond time scale, i.e.
+optical second harmonic generation (SHG) and the nonlinear magneto-optical Kerr
+effect (NOLIMOKE). It is found that the ultrafast charge and spin dynamics are
+observable on the time scale of 10 fs. The charge dynamics proceeds ahead of
+the spin dynamics, which indicates the existence of a spin memory time. The
+fast decay results from the loss of coherence in the initial excited state.
+Both the material specific and experimental parameters affect the dynamics. We
+find that the increase of exchange interaction mainly accelerates the spin
+dynamics rather than the charge dynamics. A reduction of the hopping integrals,
+such as present at interfaces, slows down the spin dynamics significantly.
+Besides, it is found that a spectrally broad excitation yields the intrinsic
+speed limit of the charge (SHG) and spin dynamics (NOLIMOKE) while a narrower
+width prolongs the dynamics. This magnetic interface dynamics then should
+become accessible to state of art time resolved nonlinear-optical experiments.",9901303v1
+2003-10-29,Dynamical obstruction in a constrained system and its realization in lattices of superconducting devices,"Hard constraints imposed in statistical mechanics models can lead to
+interesting thermodynamical behaviors, but may at the same time raise
+obstructions in the thoroughfare to thermal equilibration. Here we study a
+variant of Baxter's 3-color model in which local interactions and defects are
+included, and discuss its connection to triangular arrays of Josephson
+junctions of superconductors and \textit{kagom\'e} networks of superconducting
+wires. The model is equivalent to an Ising model in a hexagonal lattice with
+the constraint that the magnetization of each hexagon is $\pm 6$ or 0. For
+ferromagnetic interactions, we find that the system is critical for a range of
+temperatures (critical line) that terminates when it undergoes an exotic first
+order phase transition with a jump from a zero magnetization state into the
+fully magnetized state at finite temperature. Dynamically, however, we find
+that the system becomes frozen into domains. The domain walls are made of
+perfectly straight segments, and domain growth appears frozen within the time
+scales studied with Monte Carlo simulations. This dynamical obstruction has its
+origin in the topology of the allowed reconfigurations in phase space, which
+consist of updates of closed loops of spins. As a consequence of the dynamical
+obstruction, there exists a dynamical temperature, lower than the (avoided)
+static critical temperature, at which the system is seen to jump from a
+``supercooled liquid'' to a ``polycrystalline'' phase. In contrast, for
+antiferromagnetic interactions, we argue that the system orders for
+infinitesimal coupling because of the constraint, and we observe no interesting
+dynamical effects.",0310710v1
+2018-03-08,Probing the collective dynamics of nuclear spin bath in a rare-earth ion doped crystal,"Probing collective spin dynamics is a current challenge in the field of
+magnetic resonance spectroscopy and has important applications in material
+analysis and quantum information protocols. Recently, the rare-earth ion doped
+crystals are an attractive candidate for making long-lived quantum memory.
+Further enhancement of its performance would benefit from the direct knowledge
+on the dynamics of nuclear-spin bath in the crystal. Here we detect the
+collective dynamics of nuclear-spin bath located around the rare-earth ions in
+a crystal using dynamical decoupling spectroscopy method. From the measured
+spectrum, we analyze the configuration of the spin bath and characterize the
+flip-flop time between two correlated nuclear spins in a long time scale ($\sim
+$1s). Furthermore, we experimentally demonstrate that the rare-earth ions can
+serve as a magnetic quantum sensor for external magnetic field. These results
+suggest that the rare-earth ion is a useful probe for complex spin dynamics in
+solids and enable quantum sensing in the low-frequency regime, revealing
+promising possibilities for applications in diverse fields.",1803.03075v2
+2020-03-20,Probing the Possibilities of Ergodicity in the 1D Spin-1/2 XY Chain with Quench Dynamics,"Ergodicity sits at the heart of the connection between statistical mechanics
+and dynamics of a physical system. By fixing the initial state of the system
+into the ground state of the Hamiltonian at zero temperature and tuning a
+control parameter, we consider the occurrence of the ergodicity with quench
+dynamics in the one-dimensional (1D) spin-1/2 XY model in a transverse magnetic
+field. The ground-state phase diagram consists of two ferromagnetic and
+paramagnetic phases. It is known the magnetization in this spin system is
+non-ergodic. We set up two different experiments as we call them single and
+double quenches and test the dynamics of the magnetization along the $Z$-axis
+and the spin-spin correlation function along the $X$-axis which are the order
+parameters of the zero-temperature phases . Our exact results reveal that for
+single quenches at zero-temperature, the ergodicity depends on the initial
+state and the order parameter. Interestingly on the other setup, a double
+quench on a cyclic path, ergodicity is completely broken for starting from the
+phase corresponding to the order parameter. Otherwise, it depends on the first
+quenched point, and the quench time $T$ when the model spent before a second
+quench in the way back which gives an ability to controlling the ergodicity in
+the system. Therefore, and contrary to expectations, in the mentioned model the
+ergodicity can be observed with probing quench dynamics at zero-temperature.
+Our results provide further insight into the zero-temperature dynamical
+behavior of quantum systems and their connections to the ergodicity phenomenon.",2003.09462v2
+2021-01-15,Bethe strings in the spin dynamical structure factor of the Mott-Hubbard phase in one-dimensional fermionic Hubbard model,"The spectra and role in the spin dynamical properties of bound states of
+elementary magnetic excitations named Bethe strings that occur in some
+integrable spin and electronic one-dimensional models have recently been
+identified and realized in several materials by experiments. Corresponding
+theoretical studies have usually relied on the one-dimensional spin-1/2
+Heisenberg antiferromagnet in a magnetic field. At the isotropic point, it
+describes the large onsite repulsion U limit of the spin degrees of freedom of
+the one-dimensional fermionic Hubbard model with one electron per site in a
+magnetic field h. In this paper we consider the thermodynamic limit and study
+the effects of lowering the latter quantum problem ratio u=U/4t, where t is the
+first-neighbor transfer integral, on the line-shape singularities in regions at
+and just above the lower thresholds of the transverse and longitudinal spin
+dynamical structure factors. The most significant spectral weight contribution
+from Bethe strings leads to a gapped continuum in the spectrum of the spin
+dynamical structure factor +-. Our study focuses on the line shape
+singularities at and just above the gapped lower threshold of that continuum,
+which have been identified in experiments. Our results are consistent with the
+contribution of Bethe strings to the spin dynamical structure factor zz being
+small at low spin densities and becoming negligible upon increasing that
+density. Our results provide physically important information about how
+electron itinerancy affects the spin dynamics.",2101.06198v1
+2022-12-19,Nonequilibrium dynamics of the Ising model on heterogeneous networks with an arbitrary distribution of threshold noise,"The Ising model on networks plays a fundamental role as a testing ground for
+understanding cooperative phenomena in complex systems. Here we solve the
+synchronous dynamics of the Ising model on random graphs with an arbitrary
+degree distribution in the high-connectivity limit. Depending on the
+distribution of the threshold noise that governs the microscopic dynamics, the
+model evolves to nonequilibrium stationary states. We obtain an exact dynamical
+equation for the distribution of local magnetizations, from which we find the
+critical line that separates the paramagnetic from the ferromagnetic phase. For
+random graphs with a negative binomial degree distribution, we demonstrate that
+the stationary critical behavior as well as the long-time critical dynamics of
+the first two moments of the local magnetizations depend on the distribution of
+the threshold noise. In particular, for an algebraic threshold noise, these
+critical properties are determined by the power-law tails of the distribution
+of thresholds. We further show that the relaxation time of the average
+magnetization inside each phase exhibits the standard mean-field critical
+scaling. The values of all critical exponents considered here are independent
+of the variance of the negative binomial degree distribution. Our work
+highlights the importance of certain details of the microscopic dynamics for
+the critical behavior of nonequilibrium spin systems.",2212.09424v2
+2023-08-17,Heat-conserving three-temperature model for ultrafast demagnetization of 3d ferromagnets,"We study the ultrafast magnetization dynamics of bcc Fe and fcc Co using the
+recently suggested heat-conserving three-temperature model (HC3TM), together
+with atomistic spin- and lattice dynamics simulations. It is shown that this
+type of Langevin-based simulation is able to reproduce observed trends of the
+ultrafast magnetization dynamics of fcc Co and bcc Fe, in agreement with
+previous findings for fcc Ni. The simulations are performed by using parameters
+that to as large extent as possible are obtained from electronic structure
+theory. The one parameter that was not calculated in this way, was the damping
+term used for the lattice dynamics simulations, and here a range of parameters
+were investigated. It is found that this term has a large influence on the
+details of the magnetization dynamics. The dynamics of iron and cobalt is
+compared with previous results for nickel and similarities and differences in
+the materials' behavior are analysed following the absorption of a femtosecond
+laser pulse. Importantly, for all elements investigated so far with this model,
+we obtain a linear relationship between the value of the maximally demagnetized
+state and the fluence of the laser pulse, which is in agreement with
+experiments.",2308.08996v1
+1995-08-28,Evolution of a Magnetic Flux Tube in a Sunspot Penumbra,"The motion of an individual magnetic flux tube inside the penumbra of a
+sunspot is studied numerically. Here, we present preliminary results. The thin
+flux tube approximation together with a simplified radiative heat exchange with
+the surroundings is used to study the evolution of a flux tube embedded into a
+background given by a global magneto-static sunspot model. The investigation is
+undertaken in order to verify the conjecture that convection in sunspot
+penumbrae occurs by an interchange of magnetic flux tubes. The code being
+developed can be used to study dynamic aspects of filamentary structure in the
+penumbra: the temporal and spatial fluctuations of the temperature and the
+magnetic field, the motion of bright penumbral grains, or the Evershed effect.
+Here we present the evolution of a wave formed by the tube whose fragment
+emerges in the penumbral photosphere and migrates towards the umbra. The
+properties of this wave show qualitative features of the observed bright
+penumbral grains with corresponding upward velocity and its correlation with
+brightness and the inclination of the magnetic field, and also of the Evershed
+effect.",9508128v1
+1996-10-24,Primordial Magnetic Fields from Cosmological First Order Phase Transitions,"We give an improved estimate of primordial magnetic fields generated during
+cosmological first order phase transitions. We examine the charge distribution
+at the nucleated bubble wall and its dynamics. We consider instabilities on the
+bubble walls developing during the phase transition. It is found that damping
+of these instabilities due to viscosity and heat conductivity caused by
+particle diffusion can be important in the QCD phase transition, but is
+probably negligible in the electroweak transition. We show how such
+instabilities together with the surface charge densities on bubble walls excite
+magnetic fields within a certain range of wavelengths. We discuss how these
+magnetic seed fields may be amplified by MHD effects in the turbulent fluid.
+The strength and spectrum of the primordial magnetic field at the present time
+for the cases where this mechanism was operative during the electroweak or the
+QCD phase transition are estimated. On a 10 Mpc comoving scale, field strengths
+of the order 10**(-29) G for electroweak and 10**(-20) G for QCD, could be
+attained for reasonable phase transition parameters.",9610201v1
+1997-07-28,A Possible Dynamical Effect of a Primordial Magnetic Field,"The possible existence of a primordial magnetic field in the universe has
+been previously investigated in many articles. Studies involving the influence
+of a magnetic field in the nucleosyntesis era, studies considering the effects
+in the formation of structures during the radiation era and the matter era have
+been considered. We here assume the existence of a primordial magnetic field
+and study its effect, in particular, in the formation of voids. The study is
+twofold: to put constraints on the strength of the magnetic field during the
+recombination era and to preview its effects on the formation of voids.",9707303v1
+1997-08-27,The Magnetic Field Spectrum in a Plasma in Thermal Equilibrium in the Epoch of Primordial Nucleosynthesis,"The low frequency magnetic field spectrum in the primordial plasma is of
+particular interest as a possible origin of magnetic fields in the universe
+(e.g., Tajima et al. 1992 and Cable and Tajima 1992). We derive the magnetic
+field spectrum in the primordial plasma, in particular, at the epoch of
+primordial nucleosynthesis. The pioneering study of Cable and Tajima (1992) of
+the electromagnetic fluctuations, based on the Fluctuation-Dissipation Theorem,
+is extended. Our model describes both the thermal and collisional effects in a
+plasma. It is based on a kinetic description with the BGK collision term. It is
+shown that the zero-frequency peak found by Cable and Tajima (1992) decreases.
+At high frequencies, the blackbody spectrum is obtained naturally without the
+necessity of the link procedure used by them. At low frequencies ($\omega \leq
+4\omega_{pe}$, where $\omega_{pe}$ is the electron plasma frequency) it is
+shown that the magnetic field spectrum has more energy than the blackbody
+spectrum in vacuum.",9708251v1
+1999-06-18,Solar Nebula Magnetohydrodynamics,"The dynamical state of the solar nebula depends critically upon whether or
+not the gas is magnetically coupled. The presence of a subthermal field will
+cause laminar flow to break down into turbulence. Magnetic coupling, in turn,
+depends upon the ionization fraction of the gas. The inner most region of the
+nebula ($\lesssim 0.1$ AU) is magnetically well-coupled, as is the outermost
+region ($\gtrsim 10$ AU). The magnetic status of intermediate scales ($\sim 1$
+AU) is less certain. It is plausible that there is a zone adjacent to the inner
+disk in which turbulent heating self-consistently maintains the requisite
+ionization levels. But the region adjacent to the active outer disk is likely
+to be magnetically ``dead.'' Hall currents play a significant role in nebular
+magnetohydrodynamics.
+  Though still occasionally argued in the literature, there is simply no
+evidence to support the once standard claim that differential rotation in a
+Keplerian disk is prone to break down into shear turbulence by nonlinear
+instabilities. There is abundant evidence---numerical, experimental, and
+analytic---in support of the stabilizing role of Coriolis forces.
+Hydrodynamical turbulence is almost certainly not a source of enhanced
+turbulence in the solar nebula, or in any other astrophysical accretion disk.",9906317v1
+2000-06-17,3-D MHD Numerical Simulations of Cloud-Wind Interactions,"We present results from three-dimensional (3-D) numerical simulations
+investigating the magnetohydrodynamics of cloud-wind interactions. The initial
+cloud is spherical while the magnetic field is uniform and transverse to the
+cloud motion. A simplified analytical model that describes the magnetic energy
+evolution in front of the cloud is developed and compared with simulation
+results. In addition, it is found the interaction of the cloud with a
+magnetized interstellar medium (ISM) results in the formation of a highly
+structured magnetotail. The magnetic flux in the wake of the cloud organizes
+into flux ropes and a reconnection, current sheet is developed, as field lines
+of opposite polarity are brought close together near the symmetry axis. At the
+same time, magnetic pressure is strongly enhanced at the leading edge of the
+cloud from the stretching of the field lines that occurs there. This has an
+important dynamical effect on the subsequent evolution of the cloud, since some
+unstable modes tend to be strongly enhanced.",0006240v1
+2000-08-08,Disk Formation by AGB Winds in Dipole Magnetic Fields,"We present a simple, robust mechanism by which an isolated star can produce
+an equatorial disk. The mechanism requires that the star have a simple dipole
+magnetic field on the surface and an isotropic wind acceleration mechanism. The
+wind couples to the field, stretching it until the field lines become mostly
+radial and oppositely directed above and below the magnetic equator, as occurs
+in the solar wind. The interaction between the wind plasma and magnetic field
+near the star produces a steady outflow in which magnetic forces direct plasma
+toward the equator, constructing a disk. In the context of a slow (10 km/s)
+outflow (10^{-5} M_sun/yr) from an AGB star, MHD simulations demonstrate that a
+dense equatorial disk will be produced for dipole field strengths of only a few
+Gauss on the surface of the star. A disk formed by this model can be
+dynamically important for the shaping of Planetary Nebulae.",0008129v1
+2000-11-29,Conservation of Magnetic Helicity and Its Constraint on $α$-Effect of Dynamo Theory,"Dynamical studies of MHD turbulence on the one hand, and arguments based upon
+magnetic helicity on the other, have yielded seemingly contradictory estimates
+for the $\alpha$ parameter in turbulent dynamo theory. Here we show, with
+direct numerical simulation of three-dimensional magnetohydrodynamic turbulence
+with a mean magnetic field, $\OB$, that the constraint on the dynamo
+$\alpha$-effect set by the magnetic helicity is time-dependent. A time-scale
+$t_c$ is introduced such that for $t<t_c$, the $\alpha$-coefficient calculated
+from the simulation is close to the result of Pouquet et al and Field et al,
+$-\frac{\tau_{cor}}{3}(< \v \cdot \nabla \times \v > - < \b \cdot \nabla \times
+\b >)$; for $t>t_c$, the classical result of the $\alpha$-coefficient given by
+the Mean-Field Electrodynamics is reduced by a factor of $1/({R_m
+|\OB|^2/v_{rms}^2})$, as argued by Gruzinov & Diamond, Seehafer and Cattaneo &
+Hughes. Here, $R_m$ is the magnetic Reynolds number, $v_{rms}$ the rms velocity
+of the turbulence, $\tau_{cor}$ the correlation time of the turbulence, and
+$\overline B$ is in velocity unit. The applicability of and connection between
+different models of dynamo theory are also discussed.",0011548v2
+2001-01-10,On Turbulent Reconnection,"We examine the dynamics of turbulent reconnection in 2D and 3D reduced MHD by
+calculating the effective dissipation due to coupling between small-scale
+fluctuations and large-scale magnetic fields. Sweet-Parker type balance
+relations are then used to calculate the global reconnection rate. Two
+approaches are employed -- quasi-linear closure and an eddy-damped fluid model.
+Results indicate that despite the presence of turbulence, the reconnection rate
+remains inversely proportional to $\sqrt{R_m}$, as in the Sweet-Parker
+analysis. In 2D, the global reconnection rate is shown to be enhanced over the
+Sweet-Parker result by a factor of magnetic Mach number. These results are the
+consequences of the constraint imposed on the global reconnection rate by the
+requirement of mean square magnetic potential balance. The incompatibility of
+turbulent fluid-magnetic energy equipartition and stationarity of mean square
+magnetic potential is demonstrated.",0101161v1
+2001-05-02,Ring Formation in Magnetically Subcritical Clouds and Multiple Star Formation,"We study numerically the ambipolar diffusion-driven evolution of
+non-rotating, magnetically subcritical, disk-like molecular clouds, assuming
+axisymmetry. Previous similar studies have concentrated on the formation of
+single magnetically supercritical cores at the cloud center, which collapse to
+form isolated stars. We show that, for a cloud with many Jeans masses and a
+relatively flat mass distribution near the center, a magnetically supercritical
+ring is produced instead. The supercritical ring contains a mass well above the
+Jeans limit. It is expected to break up, through both gravitational and
+possibly magnetic interchange instabilities, into a number of supercritical
+dense cores, whose dynamic collapse may give rise to a burst of star formation.
+Non-axisymmetric calculations are needed to follow in detail the expected ring
+fragmentation into multiple cores and the subsequent core evolution.
+Implications of our results on multiple star formation in general and the
+northwestern cluster of protostars in the Serpens molecular cloud core in
+particular are discussed.",0105028v1
+2002-01-30,The Magnetic Field Structure in W51A,"We present 850 micron imaging polarimetry of the W51A massive star forming
+region performed with SCUBA on the JCMT. From the polarimetry we infer the
+column-averaged magnetic field direction, projected onto the plane of the sky.
+We find that the magnetic field geometry in the region is complicated. We
+compare the field geometry with 6 cm and CS J=7-6 emission and determine that
+the magnetic field must be relatively weak and plays a passive role, allowing
+itself to be shaped by pressure forces and dynamics in the ionised and neutral
+gases. Comparisons are drawn between our data and 1.3 mm BIMA interferometric
+polarimetry data, from which we conclude that the magnetic field must increase
+in importance as we move to smaller scales and closer to sites of active star
+formation.",0201499v1
+2004-12-14,Dynamics of the Flows Accreting onto a Magnetized Neutron Star,"Non-stationary column accretion onto a surface of a magnetized neutron star
+is studied with a numerical code based on modified first-order Godunov method
+with splitting. Formation and evolution of shocks in the column is modeled for
+accretion rates ranging from 10^{15} g/s to 10^{16} g/s and surface magnetic
+fields ranging from 5*10^{11} G to 10^{13} G. Non-stationary solutions with
+plasma deceleration at collisionless oscillating shocks are found. The kinetic
+energy of the accreting flow efficiently transforms into a cyclotron radiation
+field. Collisionless stopping of the flow allows a substantial part of
+accreting CNO nuclei to avoid spallation and reach the surface. The nuclei
+survival fraction depends on the surface magnetic field, being higher at lower
+magnetic fields.",0412319v1
+2005-01-13,Quasilinear Drift Of Cosmic Rays In Weak Turbulent Electromagnetic Fields,"A general quasilinear transport parameter for particle drift in arbitrary
+turbulence geometry is presented. The new drift coefficient is solely
+characterized by a nonresonant term and is evaluated for slab and
+two-dimensional turbulence geometry. The calculations presented here
+demonstrate that fluctuating electric fields are a key quantity for
+understanding quasilinear particle drift in slab geometry. It is shown that
+particle drift does not exist in unpolarized and purely magnetic slab
+fluctuations. This is in stark contrast to previous models, which are
+restricted to slab geometry and the field line random walk limit. The
+evaluation of the general transport parameter for two-dimensional turbulence
+geometry, presented here for the first time for dynamical magnetic turbulence,
+results in a drift coefficient valid for a magnetic power spectrum and
+turbulence decay rate varying arbitrarily in wavenumber. For a two-component,
+slab/two-dimensional turbulence model, numerical calculations are presented.
+The new quasilinear drift, induced by the magnetic perturbations, is compared
+with a standard drift expression related to the curvature and gradient of an
+unperturbed heliospheric background magnetic field. The considerations
+presented here offer a solid ground and natural explanation for the hitherto
+puzzling observation that drift models often describe observations much better
+when drift effects are reduced.",0501243v1
+2006-09-06,Dynamo Action in the Solar Convection Zone and Tachocline: Pumping and Organization of Toroidal Fields,"We present the first results from three-dimensional spherical shell
+simulations of magnetic dynamo action realized by turbulent convection
+penetrating downward into a tachocline of rotational shear. This permits us to
+assess several dynamical elements believed to be crucial to the operation of
+the solar global dynamo, variously involving differential rotation resulting
+from convection, magnetic pumping, and amplification of fields by stretching
+within the tachocline. The simulations reveal that strong axisymmetric toroidal
+magnetic fields (about 3000 G in strength) are realized within the lower stable
+layer, unlike in the convection zone where fluctuating fields are predominant.
+The toroidal fields in the stable layer possess a striking persistent
+antisymmetric parity, with fields in the northern hemisphere largely of
+opposite polarity to those in the southern hemisphere. The associated mean
+poloidal magnetic fields there have a clear dipolar geometry, but we have not
+yet observed any distinctive reversals or latitudinal propagation. The presence
+of these deep magnetic fields appears to stabilize the sense of mean fields
+produced by vigorous dynamo action in the bulk of the convection zone.",0609153v1
+2007-02-02,Magnetized Hypermassive Neutron Star Collapse: a candidate central engine for short-hard GRBs,"Hypermassive neutron stars (HMNSs) are equilibrium configurations supported
+against collapse by rapid differential rotation and likely form as transient
+remnants of binary neutron star mergers. Though HMNSs are dynamically stable,
+secular effects such as viscosity or magnetic fields tend to bring HMNSs into
+uniform rotation and thus lead to collapse. We simulate the evolution of
+magnetized HMNSs in axisymmetry using codes which solve the
+Einstein-Maxwell-MHD system of equations. We find that magnetic braking and the
+magnetorotational instability (MRI) both contribute to the eventual collapse of
+HMNSs to rotating black holes surrounded by massive, hot accretion tori and
+collimated magnetic fields. Such hot tori radiate strongly in neutrinos, and
+the resulting neutrino-antineutrino annihilation could power short-hard GRBs.",0702080v1
+1996-04-16,Composite Fermions with Orbital Magnetization,"For quantum Hall systems, in the limit of large magnetic field (or
+equivalently small electron band mass $m_b$), the static response of electrons
+to a spatially varying magnetic field is largely determined by kinetic energy
+considerations. This response is not correctly given in existing approximations
+based on the Fermion Chern-Simons theory of the partially filled Landau level.
+We remedy this problem by attaching an orbital magnetization to each fermion to
+separate the current into magnetization and transport contributions, associated
+with the cyclotron and guiding center motions respectively. This leads to a
+Chern-Simons Fermi liquid description of the $\nu=\frac{1}{2m}$ state which
+correctly predicts the $m_b$ dependence of the static and dynamic response in
+the limit $m_b \rightarrow 0$.",9604103v1
+1996-10-28,Stability and Instability of Relativistic Electrons in Classical Electro magnetic Fields,"The stability of matter composed of electrons and static nuclei is
+investigated for a relativistic dynamics for the electrons given by a suitably
+projected Dirac operator and with Coulomb interactions. In addition there is an
+arbitrary classical magnetic field of finite energy. Despite the previously
+known facts that ordinary nonrelativistic matter with magnetic fields, or
+relativistic matter without magnetic fields is already unstable when the fine
+structure constant, is too large it is noteworthy that the combination of the
+two is still stable provided the projection onto the positive energy states of
+the Dirac operator, which defines the electron, is chosen properly. A good
+choice is to include the magnetic field in the definition. A bad choice, which
+always leads to instability, is the usual one in which the positive energy
+states are defined by the free Dirac operator. Both assertions are proved here.",9610195v4
+1998-03-25,A Mesoscopic Approach to the ``Negative'' Viscosity Effect in Ferrofluids,"We present a mesoscopic approach to analyze the dynamics of a single magnetic
+dipole under the influence of an oscillating magnetic field, based on the
+formulation of a Fokker-Planck equation. The dissipated power and the viscosity
+of a suspension of such magnetic dipoles are calculated from non-equilibrium
+thermodynamics of magnetized systems. By means of this method we have found a
+non-monotonous behaviour of the viscosity as a function of the frequency of the
+field which has been referred to as the ``negative'' viscosity effect.
+Moreover, we have shown that the viscosity depends on the vorticity field thus
+exhibiting non-Newtonian behaviour. Our analysis is complemented with numerical
+simulations which reproduce the behaviour of the viscosity we have found and
+extend the scope of our analytical approach to higher values of the magnetic
+field.",9803305v2
+2000-02-09,Structure and Magnetism of well-defined cobalt nanoparticles embedded in a niobium matrix,"Our recent studies on Co-clusters embedded in various matrices reveal that
+the co-deposition technique (simultaneous deposition of two beams : one for the
+pre-formed clusters and one for the matrix atoms) is a powerful tool to prepare
+magnetic nanostructures with any couple of materials even though they are
+miscible. We study, both sharply related, structure and magnetism of the Co/Nb
+system. Because such a heterogeneous system needs to be described at different
+scales, we used microscopic and macroscopic techniques but also local selective
+absorption ones. We conclude that our clusters are 3 nm diameter f.c.c
+truncated octahedrons with a pure cobalt core and a solid solution between Co
+and Nb located at the interface which could be responsible for the magnetically
+inactive monolayers we found. The use of a very diluted Co/Nb film, further
+lithographed, would allow us to achieve a pattern of microsquid devices in view
+to study the magnetic dynamics of a single-Co cluster.",0002126v2
+2000-03-24,Magnetic Behavior of a Mixed Ising Ferrimagnetic Model in an Oscillating Magnetic Field,"The magnetic behavior of a mixed Ising ferrimagnetic system on a square
+lattice, in which the two interpenetrating square sublattices have spins +- 1/2
+and spins +-1,0, in the presence of an oscillating magnetic field has been
+studied with Monte Carlo techniques. The model includes nearest and
+next-nearest neighbor interactions, a crystal field and the oscillating
+external field. By studying the hysteretic response of this model to an
+oscillating field we found that it qualitatively reproduces the increasing of
+the coercive field at the compensation temperature observed in real
+ferrimagnets, a crucial feature for magneto-optical applications. This behavior
+is basically independent of the frequency of the field and the size of the
+system. The magnetic response of the system is related to a dynamical
+transition from a paramagnetic to a ferromagnetic phase and to the different
+temperature dependence of the relaxation times of both sublattices.",0003403v1
+2000-10-25,"Susceptibility, Magnetization Process and ESR Studies on the Helical Spin System RbCuCl$_{3}$","The static and dynamic magnetic properties of an $S=1/2$ stacked triangular
+antiferromagnet RbCuCl$_{3}$ with a helical spin structure due to lattice
+distortion were investigated by susceptibility, high-field magnetization
+process and ESR measurements. The susceptibilities were analyzed by
+high-temperature expansion approximation in terms of ferromagnetic intrachain
+coupling and the antiferromagnetic interchain coupling. The magnetization
+saturates at $H_{\rm s}\approx 66.8$ T at 1.5 K, the value of which is twice
+that of CsCuCl$_3$. A small magnetization jump indicative of a phase transition
+was observed at $H_{\rm c}=21.2$ T $\approx (1/3)H_{\rm s}$ for $H{\perp}c$.
+ESR modes observed for $H\parallel c$ are well described by the calculation
+based on the helical spin structure. From the present measurements, the
+ferromagnetic intrachain and two kinds of antiferromagnetic interchain exchange
+interactions, and the planar anisotropy energy were determined as $J_0/k_{\rm
+B}=25.7$ K, $J_1/k_{\rm B}=-10.6$ K, $J_1'/k_{\rm B}=-17.4$ K, and
+${\Delta}J_0/k_{\rm B}=-0.45$ K, respectively.",0010388v2
+2001-03-07,Tunneling from a correlated 2D electron system transverse to a magnetic field,"We show that, in a magnetic field parallel to the 2D electron layer, strong
+electron correlations change the rate of tunneling from the layer
+exponentially. It results in a specific density dependence of the escape rate.
+The mechanism is a dynamical Mossbauer-type recoil, in which the Hall momentum
+of the tunneling electron is partly transferred to the whole electron system,
+depending on the interrelation between the rate of interelectron momentum
+exchange and the tunneling duration. We also show that, in a certain
+temperature range, magnetic field can enhance rather than suppress the
+tunneling rate. The effect is due to the magnetic field induced energy exchange
+between the in-plane and out-of-plane motion. Magnetic field can also induce
+switching between intra-well states from which the system tunnels, and a
+transition from tunneling to thermal activation. Explicit results are obtained
+for a Wigner crystal. They are in qualitative and quantitative agreement with
+the relevant experimental data, with no adjustable parameters.",0103151v1
+2001-05-04,Magnetic properties of nanoparticles in the Bethe-Peierls approximation,"In this work we present a new method to calculate the classical properties of
+magnetic nanoparticles. Based on the Bethe-Peierls (pair) approximation, we
+developed a simple system of equations for the classical magnetization of spins
+at any position within the nanoparticle. The nearest neightbor pair
+correlations are treated exactly for Ising spins, and the method can be
+generalized for various lattice symmetries. The master equation is solved for
+the Glauber dynamics (single-spin-flip) in order to obtain the time evolution
+of the magnetization. The capabilities of the model are demonstrated through
+the calculation of hysteresis loops as well as field cooling (FC) and zero
+field cooling (ZFC) magnetization curves of heterogeneous nanoparticles. The
+present method can be an alternative to the usually complex and time consuming
+methods employed in micromagnetism.",0105106v2
+2001-06-04,Haldane-Gapped Spin Chains as Luttinger Liquids: Correlation Functions at Finite Field,"We study the behavior of Heisenberg, antiferromagnetic, integer-spin chains
+in the presence of a magnetic field exceeding the attendant spin gap. For
+temperatures much smaller than the gap, the spin chains exhibit Luttinger
+liquid behavior. We compute exactly both the corresponding Luttinger parameter
+and the Fermi velocity as a function of magnetic field. This enables the
+computation of a number of correlators from which we derive the spin
+conductance, the expected form of the dynamic structure factor relevant to
+inelastic neutron scattering experiments, and NMR relaxation rates. We also
+comment upon the robustness of the magnetically induced gapless phase both to
+finite temperature and finite couplings between neighbouring chains.",0106037v2
+2002-01-14,Magnetic Field Scaling in Spin Glasses and the Mean-Field Theory,"The scaling of the magnetic field dependence of the remanent magnetization
+for different temperatures and different spin-glass samples is studied.
+Particular attention is paid to the effect of the de Almeida-Thouless (AT)
+critical line on spin-glass dynamics. It is shown that results of the
+mean-field theory of aging phenomena, with two additional experimentally
+justified assumptions, predict $H/H_{AT}(T)$ scaling for remanent magnetization
+curves. Experiments on a single crystal Cu:Mn 1.5 at % sample in the
+temperature interval from $0.7T_{g}$ to $0.85T_{g}$ give results consistent
+with this scaling. Magnetization vs. field curves for different Cu:Mn and
+thiospinel samples also scale together. These experimental results support the
+predictions of the mean-field theory of aging phenomena.",0201226v1
+2002-11-19,NMR and Mossbauer study of spin dynamics and electronic structure of Fe{2+x}V{1-x}Al and Fe2VGa,"In order to assess the magnetic ordering process in Fe2VAl and the related
+material Fe2VGa, we have carried out nuclear magnetic resonance (NMR) and
+Mossbauer studies. 27Al NMR relaxation measurements covered the temperature
+range 4 -- 500 K in Fe(2+x)V(1-x)Al samples. We found a peak in the NMR
+spin-lattice relaxation rate, 27T1^-1, corresponding to the magnetic
+transitions in each of these samples. These peaks appear at 125 K, 17 K, and
+165 K for x = 0.10, 0, and - 0.05 respectively, and we connect these features
+with critical slowing down of the localized antisite defects. Mossbauer
+measurements for Fe2VAl and Fe2VGa showed lines with no hyperfine splitting,
+and isomer shifts nearly identical to those of the corresponding sites in Fe3Al
+and Fe3Ga, respectively. We show that a model in which local band filling leads
+to magnetic regions in the samples, in addition to the localized antisite
+defects, can account for the observed magnetic ordering behavior.",0211416v2
+2003-01-20,Magnetic-Field-Induced Localization of Quasiparticles in Underdoped La$_{2-x}$Sr$_x$CuO$_4$ Single Crystals,"Magnetic-field-induced ordering of electrons around vortices is a striking
+phenomenon recently found in high-$T_c$ cuprates. To identify its consequence
+in the quasiparticle dynamics, the magnetic-field ($H$) dependence of the
+low-temperature thermal conductivity $\kappa$ of La$_{2-x}$Sr$_x$CuO$_4$
+crystals is studied for a wide doping range. It is found that the behavior of
+$\kappa(H)$ in the sub-Kelvin region changes drastically across optimum doping,
+and the data for underdoped samples are indicative of unusual
+magnetic-field-induced localization of quasiparticles; this localization
+phenomenon is probably responsible for the unusual ""insulating normal state""
+under high magnetic fields.",0301339v2
+2003-02-17,Thermally assisted magnetization reversal in the presence of a spin-transfer torque,"We propose a generalized stochastic Landau-Lifshitz equation and its
+corresponding Fokker-Planck equation for the magnetization dynamics in the
+presence of spin transfer torques. Since the spin transfer torque can pump a
+magnetic energy into the magnetic system, the equilibrium temperature of the
+magnetic system is ill-defined. We introduce an effective temperature based on
+a stationary solution of the Fokker-Planck equation. In the limit of high
+energy barriers, the law of thermal agitation is derived. We find that the
+N\'{e}el-Brown relaxation formula remains valid as long as we replace the
+temperature by an effective one that is linearly dependent of the spin torque.
+We carry out the numerical integration of the stochastic Landau-Lifshitz
+equation to support our theory. Our results agree with existing experimental
+data.",0302339v2
+2003-02-26,Persistence of Manifolds in Nonequilibrium Critical Dynamics,"We study the persistence P(t) of the magnetization of a d' dimensional
+manifold (i.e., the probability that the manifold magnetization does not flip
+up to time t, starting from a random initial condition) in a d-dimensional spin
+system at its critical point. We show analytically that there are three
+distinct late time decay forms for P(t) : exponential, stretched exponential
+and power law, depending on a single parameter \zeta=(D-2+\eta)/z where D=d-d'
+and \eta, z are standard critical exponents. In particular, our theory predicts
+that the persistence of a line magnetization decays as a power law in the d=2
+Ising model at its critical point. For the d=3 critical Ising model, the
+persistence of the plane magnetization decays as a power law, while that of a
+line magnetization decays as a stretched exponential. Numerical results are
+consistent with these analytical predictions.",0302537v1
+2003-03-08,Current-Driven Magnetic Excitations in Permalloy-Based Multilayer Nanopillars,"We study current-driven magnetization switching in nanofabricated
+Ni84Fe16/Cu/Ni84Fe16 trilayers at 295 K and 4.2 K. The shape of the hysteretic
+switching diagram at low magnetic field changes from 295 K to 4.2 K. The
+reversible behavior at higher field involves two phenomena, a threshold current
+for magnetic excitations closely correlated with the switching current, and a
+peak in differential resistance characterized by telegraph noise, with average
+period that decreases exponentially with current and shifts with temperature.
+We interpret both static and dynamic results at 295 K and 4.2 K in terms of
+thermal activation over a potential barrier, with a current dependent effective
+magnetic temperature.",0303149v2
+2003-06-05,Quasiparticle vanishing driven by geometrical frustration,"We investigate the single hole dynamics in the triangular t-J model. We study
+the structure of the hole spectral function, assuming the existence of a 120
+magnetic Neel order. Within the self-consistent Born approximation (SCBA) there
+is a strong momentum and t sign dependence of the spectra, related to the
+underlying magnetic structure and the particle-hole asymmetry of the model. For
+positive t, and in the strong coupling regime, we find that the low energy
+quasiparticle excitations vanish outside the neighbourhood of the magnetic
+Goldstone modes; while for negative t the quasiparticle excitations are always
+well defined. In the latter, we also find resonances of magnetic origin whose
+energies scale as (J/t)^2/3 and can be identified with string excitations. We
+argue that this complex structure of the spectra is due to the subtle interplay
+between magnon-assisted and free hopping mechanisms. Our predictions are
+supported by an excellent agreement between the SCBA and the exact results on
+finite size clusters. We conclude that the conventional quasiparticle picture
+can be broken by the effect of geometrical magnetic frustration.",0306147v3
+2003-09-08,Absence of magnetic order in Yb3Ga5O12: relation between phase transition and entropy in geometrically frustrated materials,"From muon spin relaxation spectroscopy experiments, we show that the sharp
+peak (lambda type anomaly) detected by specific heat measurements at 54 mK for
+the ytterbium gallium garnet compound, Yb3Ga5O12, does not correspond to the
+onset of a magnetic phase transition, but to a pronounced building up of
+dynamical magnetic pair-correlations. Beside the lambda anomaly, a broad hump
+is observed at higher temperature in the specific heat of this garnet and other
+geometrically frustrated compounds. Comparing with other frustrated magnetic
+systems we infer that a ground state with long-range order is reached only when
+at least 1/4-1/3 of the magnetic entropy is released at the lambda transition.",0309185v1
+2003-12-13,Pathways of structural and magnetic transitions in ferromagnetic shape memory alloys,"A fundamental question in the study of ferromagnetic shap ememory alloys is
+the nature of magnetoelastic coupling and the extent it drives the structural
+transformation. This question also holds the key to developing new and
+optimized alloys that combine high strains at low switching field. In the
+present study it is shown that the reconfiguration of the micromagnetic
+structure is enslaved to and follows the martensitic transformation in these
+alloys using the NiMnGa and FePd alloy systems. This is determined by
+developing a new, high speed electronic method to study the temperature
+dependence of domain dynamics, called magnetic transition spectra. The sequence
+of magnetic and structural transition was found to be as follows. For cooling,
+structural transition followed by magnetic transition and for heating, magnetic
+transition followed by structural transition.",0312343v1
+2004-09-22,Hofstadter spectrum in electric and magnetic fields,"The problem of Bloch electrons in two dimensions subject to magnetic and
+intense electric fields is investigated. Magnetic translations, electric
+evolution and energy translation operators are used to specify the solutions of
+the Schr\""odinger equation. For rational values of the magnetic flux quanta per
+unit cell and commensurate orientations of the electric field relative to the
+original lattice, an extended superlattice can be defined and a complete set of
+mutually commuting space-time symmetry operators is obtained. Dynamics of the
+system is governed by a finite difference equation that exactly includes the
+effects of: an arbitrary periodic potential, an electric field orientated in a
+commensurable direction of the lattice, and coupling between Landau levels. A
+weak periodic potential broadens each Landau level in a series of minibands,
+separated by the corresponding minigaps. The addition of the electric field
+induces a series of avoided and exact crossing of the quasienergies, for
+sufficiently strong electric field the spectrum evolves into equally spaced
+discreet levels, in this ""magnetic Stark ladder"" the energy separation is an
+integer multiple of $ h E / a B $, with $a$ the lattice parameter.",0409579v1
+2004-10-05,The Non--Ergodicity Threshold: Time Scale for Magnetic Reversal,"We prove the existence of a non-ergodicity threshold for an anisotropic
+classical Heisenberg model with all-to-all couplings. Below the threshold, the
+energy surface is disconnected in two components with positive and negative
+magnetizations respectively. Above, in a fully chaotic regime, magnetization
+changes sign in a stochastic way and its behavior can be fully characterized by
+an average magnetization reversal time. We show that statistical mechanics
+predicts a phase--transition at an energy higher than the non-ergodicity
+threshold. We assess the dynamical relevance of the latter for finite systems
+through numerical simulations and analytical calculations. In particular, the
+time scale for magnetic reversal diverges as a power law at the ergodicity
+threshold with a size-dependent exponent, which could be a signature of the
+phenomenon.",0410119v3
+2005-01-13,Fast Switching of Bistable Magnetic Nanowires Through Collective Spin Reversal,"The use of magnetic nanowires as memory units is made possible by the
+exponential divergence of the characteristic time for magnetization reversal at
+low temperature, but the slow relaxation makes the manipulation of the frozen
+magnetic states difficult. We suggest that finite-size segments can show a fast
+switching if collective reversal of the spins is taken into account. This
+mechanism gives rise at low temperatures to a scaling law for the dynamic
+susceptibility that has been experimentally observed for the dilute molecular
+chain Co(hfac)2NitPhOMe. These results suggest a possible way of engineering
+nanowires for fast switching of the magnetization.",0501316v1
+2005-03-02,A two dimensional model for ferromagnetic martensites,"We consider a recently introduced 2-D square-to-rectangle martensite model
+that explains several unusual features of martensites to study ferromagnetic
+martensites. The strain order parameter is coupled to the magnetic order
+parameter through a 4-state clock model. Studies are carried out for several
+combinations of the ordering of the Curie temperatures of the austenite and
+martensite phases and, the martensite transformation temperature. We find that
+the orientation of the magnetic order which generally points along the short
+axis of the rectangular variant, changes as one crosses the twin or the
+martensite-austenite interface. The model shows the possibility of a subtle
+interplay between the growth of strain and magnetic order parameters as the
+temperature is decreased. In some cases, this leads to qualitatively different
+magnetization curves from those predicted by earlier mean field models.
+Further, we find that strain morphology can be substantially altered by the
+magnetic order. We have also studied the dynamic hysteresis behavior.
+  The corresponding dissipation during the forward and reverse cycles has
+features similar to the Barkhausen's noise.",0503054v1
+2005-03-07,Neutron scattering studies of the spin ices Ho2Ti2O7 and Dy2Ti2O7 in applied magnetic field,"Neutron diffraction has been used to investigate the magnetic correlations in
+single crystals of the spin ice materials Ho2Ti2O7 and Dy2Ti2O7 in an external
+magnetic field applied along either the [001] or [1-10] crystallographic
+directions. With the field applied along [001] a long range ordered groundstate
+is selected from the spin ice manifold. With the field applied along [1-10] the
+experiments show that the spin system is separated into parallel (alpha) and
+perpendicular (beta) chains with respect to the field. This leads to partial
+ordering and the appearance of quasi-one-dimensional magnetic structures. In
+both field orientations this frustrated spin system is defined by the
+appearance of metastable states, magnetization plateaux and unusually slow,
+field regulated dynamics.",0503160v1
+2005-05-02,Absence of spin superradiance in resonatorless magnets,"A spin system is considered with a Hamiltonian typical of molecular magnets,
+having dipole-dipole interactions and a single-site magnetic anisotropy. In
+addition, spin interactions through the common radiation field are included. A
+fully quantum-mechanical derivation of the collective radiation rate is
+presented. An effective narrowing of the dipole-dipole attenuation, due to high
+spin polarization is taken into account. The influence of the radiation rate on
+spin dynamics is carefully analysed. It is shown that this influence is
+completely negligible. No noticeable collective effects, such as superradiance,
+can appear in molecular magnets, being caused by electromagnetic spin
+radiation. Spin superradiance can arise in molecular magnets only when these
+are coupled to a resonant electric circuit, as has been suggested earlier by
+one of the authors in Laser Phys. {\bf 12}, 1089 (2002).",0505024v1
+2005-08-10,Stripes and superconductivity in cuprate superconductors,"One type of order that has been observed to compete with superconductivity in
+cuprates involves alternating charge and antiferromagnetic stripes. Recent
+neutron scattering studies indicate that the magnetic excitation spectrum of a
+stripe-ordered sample is very similar to that observed in superconducting
+samples. In fact, it now appears that there may be a universal magnetic
+spectrum for the cuprates. One likely implication of this universal spectrum is
+that stripes of a dynamic form are present in the superconducting samples. On
+cooling through the superconducting transition temperature, a gap opens in the
+magnetic spectrum, and the weight lost at low energy piles up above the gap;
+the transition temperature is correlated with the size of the spin gap.
+Depending on the magnitude of the spin gap with respect to the magnetic
+spectrum, the enhanced magnetic scattering at low temperature can be either
+commensurate or incommensurate. Connections between stripe correlations and
+superconductivity are discussed.",0508272v1
+2005-12-22,Semiclassical degeneracies and ordering for highly frustrated magnets in a field,"We discuss ground state selection by quantum fluctuations in frustrated
+magnets in a strong magnetic field. We show that there exist dynamical
+symmetries -- one a generalisation of Henley's gauge-like symmetry for
+collinear spins, the other the quantum relict of non-collinear weathervane
+modes -- which ensure a partial survival of the classical degeneracies. We
+illustrate these for the case of the kagome magnet, where we find zero-point
+energy differences to be rather small everywhere except near the collinear
+`up-up-down` configurations, where there is rotational but not translational
+symmetry breaking. In the effective Hamiltonian, we demonstrate the presence of
+a term sensitive to a topological `flux'. We discuss the connection of such
+problems to gauge theories by casting the frustrated lattices as medial
+lattices of appropriately chosen simplex lattices, and in particular we show
+how the magnetic field can be used to tune the physical sector of the resulting
+gauge theories.",0512594v1
+2006-01-10,Magneto-mechanical interplay in spin-polarized point contacts,"We investigate the interplay between magnetic and structural dynamics in
+ferromagnetic atomic point contacts. In particular, we look at the effect of
+the atomic relaxation on the energy barrier for magnetic domain wall migration
+and, reversely, at the effect of the magnetic state on the mechanical forces
+and structural relaxation. We observe changes of the barrier height due to the
+atomic relaxation up to 200%, suggesting a very strong coupling between the
+structural and the magnetic degrees of freedom. The reverse interplay is weak,
+i.e. the magnetic state has little effect on the structural relaxation at
+equilibrium or under non-equilibrium, current-carrying conditions.",0601200v1
+2006-01-26,Spin dynamics characterization in magnetic dots,"The spin structure in a magnetic dot, which is an example of a quantum
+few-body system, is studied as a function of exchange coupling strength and dot
+size with in the semiclassical approximation on a discrete lattice. As the
+exchange coupli ng is decreased or the size is increased, the ground state
+undergoes a phase cha nge from a single domain ferromagnet to a spin vortex.
+The line separating these two phases has been calculated numerically for small
+system sizes. %, and analytically for larger dots. The dipolar interaction has
+been fully included in our calculations. Magnon frequencies in such a dot have
+also been calculated in both phases by the linearized equation of motion
+method. These results have also been reproduced f rom the Fourier transform of
+the spin autocorrelation function. From the magnon Density Of States (DOS), it
+is possible to identify the magnetic phase of the dot. Furthermore, the magnon
+modes have been characterized for both the ferromagnetic and the vortex phase,
+and the magnon instability mechanism leading to the vortex-ferro transition has
+also been identified. The results can also be used to compute finite
+temperature magnetization or vort icity of magnetic dots.",0601624v1
+2006-05-10,Magnetic excitations in a new anisotropic Kagomé antiferromagnet,"The Nd-langasite compound contains planes of magnetic Nd3+ ions on a lattice
+topologically equivalent to a kagom\'{e} net. The magnetic susceptibility does
+not reveal any signature of long-range ordering down to 2 K but rather a
+correlated paramagnetism with significant antiferromagnetic interactions
+between the Nd and a single-ion anisotropy due to crystal field effect.
+Inelastic neutron scattering on Nd-langasite powder and single-crystal allowed
+to probe its very peculiar low temperature dynamical magnetic correlations.
+They present unusual dispersive features and are broadly localized in
+wave-vector Q revealing a structure factor associated to characteristics short
+range-correlations between the magnetic atoms. From comparison with theoretical
+calculations, these results are interpreted as a possible experimental
+observation of a spin liquid state in an anisotropic kagom\'{e}
+antiferromagnet.",0605282v1
+2006-10-20,Probing Anomalous Longitudinal Fluctuations of the Interacting Bose Gas via Bose-Einstein Condensation of Magnons,"The emergence of a finite staggered magnetization in quantum Heisenberg
+antiferromagnets subject to a uniform magnetic field can be viewed as
+Bose-Einstein condensation of magnons. Using non-perturbative results for the
+infrared behavior of the interacting Bose gas, we present exact results for the
+staggered spin-spin correlation functions of quantum antiferromagnets in a
+magnetic field at zero temperature. In particular, we show that in dimensions 1
+< D <= 3 the longitudinal dynamic structure factor S_parallel(q,omega)
+describing staggered spin fluctuations in the direction of the staggered
+magnetization exhibits a critical continuum whose weight can be controlled
+experimentally by varying the magnetic field.",0610575v3
+2007-03-23,Transition-metal dimers and physical limits on magnetic anisotropy,"Recent advances in nanoscience have raised interest in the minimum bit size
+required for classical information storage, i.e. for bistability with
+suppressed quantum tunnelling and energy barriers that exceed ambient
+temperatures. In the case of magnetic information storage much attention has
+centred on molecular magnets[1] with bits consisting of ~ 100 atoms, magnetic
+uniaxial anisotropy energy barriers ~ 50 K, and very slow relaxation at low
+temperatures. In this article we draw attention to the remarkable magnetic
+properties of some transition metal dimers which have energy barriers
+approaching ~ 500 K with only two atoms. The spin dynamics of these ultra small
+nanomagnets is strongly affected by a Berry phase which arises from
+quasi-degeneracies at the electronic Highest Occupied Molecular Orbital (HOMO)
+energy. In a giant spin-approximation, this Berry phase makes the effective
+reversal barrier thicker. [1] Gatteschi, D., Sessoli, R. & Villain, J.
+Molecular Nanomagnets. (Oxford, New York 2006).",0703607v2
+2004-10-08,Rotation Effects and The Gravito-Magnetic Approach,"Gravito-electromagnetism is somewhat ubiquitous in relativity. In fact, there
+are many situations where the effects of gravitation can be described by
+formally introducing ""gravito-electric"" and ""gravito-magnetic"" fields, starting
+from the corresponding potentials, in analogy with the electromagnetic theory
+(see also A. Tartaglia's contribution to these proceedings). The ""many faces of
+gravito-electromagnetism"" are related to rotation effects in both approximated
+and full theory approaches. Here we show that, by using a 1+3 splitting,
+relativistic dynamics can be described in terms of gravito-electromagnetic
+(GEM) fields in full theory. On the basis of this formalism, we introduce a
+""gravito-magnetic Aharonov-Bohm effect"", which allows to interpret some
+rotation effects as gravito-magnetic effects. Finally, we suggest a way for
+measuring the angular momentum of celestial bodies by studying the
+gravito-magnetic effects on the propagation of electromagnetic signals.",0410039v2
+1996-09-05,Electric-Magnetic Duality and the Heavy Quark Potential,"We use the assumption of electric-magnetic duality to express the heavy quark
+potential in QCD in terms of a Wilson Loop $W_{eff}(\Gamma)$ determined by the
+dynamics of a dual theory which is weakly coupled at long distances. The
+classical approximation gives the leading contribution to $W_{eff}(\Gamma)$ and
+yields a velocity dependent heavy quark potential which for large $R$ becomes
+linear in $R$, and which for small $R$ approaches lowest order perturbative
+QCD. The corresponding long distance interaction between color magnetic
+monopoles is governed by a Yukawa potential. As a consequence the magnetic
+interaction between the color magnetic moments of the quarks is exponentially
+damped. The semi-classical corrections to $W_{eff}(\Gamma)$ due to fluctuations
+of the classical flux tube should lead to an effective string theory free from
+the conformal anomaly.",9609269v1
+1999-03-02,The Sphaleron in a Magnetic Field and Electroweak Baryogenesis,"The presence of a primordial magnetic field in the early universe affects the
+dynamic of the electroweak phase transition enhancing its strength. This effect
+may enlarge the window for electroweak baryogenesis in the minimal
+supersymmetric extension of the standard model or even resurrect the
+electroweak baryogenesis scenario in the standard model. We compute the
+sphaleron energy in the background of the magnetic field and show that, due to
+the sphaleron dipole moment, the barrier between topologically inequivalent
+vacua is lowered. Therefore, the preservation of the baryon asymmetry calls for
+a much stronger phase transition than required in the absence of a magnetic
+field. We show that this effect overwhelms the gain in the phase transition
+strength, and conclude that magnetic fields do not help electroweak
+baryogenesis.",9903227v1
+1999-05-05,Magnetic Oscillations in Dense Cold Quark Matter with Four-Fermion Interactions,"The phase structures of Nambu-Jona-Lasinio models with one or two flavours
+have been investigated at non-zero values of $\mu$ and $H$, where $H$ is an
+external magnetic field and $\mu$ is the chemical potential. In the phase
+portraits of both models there arise infinitely many massless chirally
+symmetric phases, as well as massive ones with spontaneously broken chiral
+invariance, reflecting the existence of infinitely many Landau levels. Phase
+transitions of first and second orders and a lot of tricritical points have
+been shown to exist in phase diagrams. In the massless case, such a phase
+structure leads unavoidably to the standard van Alphen-de Haas magnetic
+oscillations of some thermodynamical quantities, including magnetization,
+pressure and particle density. In the massive case we have found an oscillating
+behaviour not only for thermodynamical quantities, but also for a dynamical
+quantity as the quark mass. Besides, in this case we have non-standard, i.e.
+non-periodic, magnetic oscillations, since the frequency of oscillations is an
+$H$-dependent quantity.",9905253v1
+2003-06-13,Magnetised Neutron Stars : An Overview,"In the presence of strong magnetic field reported to have been observed on
+the surface of some neutron stars and on what are called Magnetars, a host of
+physical phenomenon from the birth of a neutron star to free streaming neutrino
+cooling phase will be modified. In this review I will discuss the effect of
+magnetic field on the equation of state of high density nuclear matter by
+including the anomalous magnetic moment of the nucleons into consideration. I
+would then go over to discuss the neutrino interaction processes in strong as
+well as in weak magnetic fields. The neutrino processes are important in
+studying the propagation of neutrinos and in studying the energy loss, Their
+study is a prerequisite for the understanding of actual dynamics of supernova
+explosion and on the stabilization of radial pulsation modes through the effect
+on bulk viscosity. The anisotropy introduced in the neutrino emission and
+through the modification of the shape of the neutrino sphere may explain the
+observed pulsar kicks.",0306116v1
+2004-05-18,Magnetic moments of the exotic pentaquark baryons within the chiral quark-soliton model,"We present in this talk recent results of the magnetic moments of the baryon
+antidecuplet within the framework of the chiral quark-soliton model in the
+chiral limit. The dynamic parameters of the model are fixed by using the
+experimental data for those of the baryon octet. Sum rules for the magnetic
+moments are derived. We found that the magnetic moments of the baryon
+antidecuplet have opposite signs to their charges. The magnetic moments of the
+neutral baryon antidecuplet turn out to be compatible with zero.",0405171v1
+2004-05-24,Condensation of Tubular D2-branes in Magnetic Field Background,"It is known that in the Minkowski vacuum a bunch of IIA superstrings with
+D0-branes can be blown-up to a supersymmetric tubular D2-brane, which is
+supported against collapse by the angular momentum generated by crossed
+electric and magnetic Born-Infeld (BI) fields. In this paper we show how the
+multiple, smaller tubes with relative angular momentum could condense to a
+single, larger tube to stabilize the system. Such a phenomena could also be
+shown in the systems under the Melvin magnetic tube or uniform magnetic field
+background. However, depending on the magnitude of field strength, a tube in
+the uniform magnetic field background may split into multiple, smaller tubes
+with relative angular momentum to stabilize the system.",0405192v4
+2005-03-02,Spectral and Propagation Results for Magnetic Schroedinger Operators; a C*-Algebraic Framework,"We study generalised magnetic Schroedinger operators of the form
+H(A,V)=h(P^A)+V, where h is an elliptic symbol, P^A is the generator of the
+magnetic translations, with A a vector potential defining a variable magnetic
+field B, and V is a scalar potential. We are mainly interested in anisotropic
+functions B and V. The first step is to show that these operators are
+affiliated to suitable C*-algebras of (magnetic) pseudodifferential operators.
+A study of the quotient of these C*-algebras by the ideal of compact operators
+leads to formulae for the essential spectrum of H(A,V), expressed as a union of
+spectra of some asymptotic operators, supported by the quasi-orbits of a
+suitable dynamical system. The quotient of the same C*-algebras by other ideals
+give localization results on the functional calculus of the operators H(A,V),
+which can be interpreted as non-propagation properties of their unitary groups.",0503046v1
+2002-01-09,Magnetic edge states,"Magnetic edge states are responsible for various phenomena of
+magneto-transport. Their importance is due to the fact that, unlike the bulk of
+the eigenstates in a magnetic system, they carry electric current along the
+boundary of a confined domain. Edge states can exist both as interior (quantum
+dot) and exterior (anti-dot) states. In the present report we develop a
+consistent and practical spectral theory for the edge states encountered in
+magnetic billiards. It provides an objective definition for the notion of edge
+states, is applicable for interior and exterior problems, facilitates efficient
+quantization schemes, and forms a convenient starting point for both the
+semiclassical description and the statistical analysis. After elaborating these
+topics we use the semiclassical spectral theory to uncover nontrivial spectral
+correlations between the interior and the exterior edge states. We show that
+they are the quantum manifestation of a classical duality between the
+trajectories in an interior and an exterior magnetic billiard.",0201012v1
+2005-04-14,Control of stochasticity in magnetic field lines,"We present a method of control which is able to create barriers to magnetic
+field line diffusion by a small modification of the magnetic perturbation. This
+method of control is based on a localized control of chaos in Hamiltonian
+systems. The aim is to modify the perturbation locally by a small control term
+which creates invariant tori acting as barriers to diffusion for Hamiltonian
+systems with two degrees of freedom. The location of the invariant torus is
+enforced in the vicinity of the chosen target. Given the importance of
+confinement in magnetic fusion devices, the method is applied to two examples
+with a loss of magnetic confinement. In the case of locked tearing modes, an
+invariant torus can be restored that aims at showing the current quench and
+therefore the generation of runaway electrons. In the second case, the method
+is applied to the control of stochastic boundaries allowing one to define a
+transport barrier within the stochastic boundary and therefore to monitor the
+volume of closed field lines.",0504033v2
+1997-03-07,Nonlinear Dynamics of a Single Ferrofluid-Peak in an Oscillating Magnetic Field,"If a magnetic field normal to the surface of a magnetic fluid is increased
+beyond a critical value a spontaneous deformation of the surface arises (normal
+field instability). The instability is subcritical and leads to peaks of a
+characteristic shape. We investigate the neighborhood of this instability
+experimentally under the influence of a temporal modulation of the magnetic
+field. We use a small vessel, where only one peak arises. The modulation can
+either be stabilizing or destabilizing, depending on the frequency and
+amplitude. We observe a cascade of odd-numbered response-periods up to period
+11, and also a domain of even-numbered periods. We propose a minimal model
+involving a cutoff-condition which captures the essence of the experimental
+observations.
+  PACS: 47.20.-k, 47.20.Ky, 75.50.Mm
+  Keywords: magnetic fluid; nonlinear oscillator; subharmonic response; surface
+instability;",9703003v1
+1999-05-22,Excitation of nonlinear one-dimensional wake waves in underdense and overdense magnetized plasma by a relativistic electron bunch,"The excitation of wake waves by a relativistic homogeneous electron bunch
+passing through cold magnetized plasma at equilibrium is studied for arbitrary
+values of the ratio of bunch density to plasma density. The analysis is based
+on the assumption that the magnetic field is sufficiently strong ($\omega_B\gg
+\omega_p$, where $\omega_p$ and $\omega_B$ are the electron plasma and
+cyclotron frequences respectively). The periodic and nonperiodic solutions for
+the momentum of plasma electrons inside and outside the bunch are analyzed. It
+was shown that the presence of strong external magnetic field may increase the
+amplitude of wake waves and the maximum transformer ratio, the latter being
+reached at densities of bunch lower than that in the absence of magnetic field.
+The optimum conditions for obtaining the maximum values of the wake field
+amplitude and of the transformer ratio are found.",9905046v1
+2004-09-07,Contactless inductive flow tomography,"The three-dimensional velocity field of a propeller driven liquid metal flow
+is reconstructed by a contactless inductive flow tomography (CIFT). The
+underlying theory is presented within the framework of an integral equation
+system that governs the magnetic field distribution in a moving electrically
+conducting fluid. For small magnetic Reynolds numbers this integral equation
+system can be cast into a linear inverse problem for the determination of the
+velocity field from externally measured magnetic fields. A robust
+reconstruction of the large scale velocity field is already achieved by
+applying the external magnetic field alternately in two orthogonal directions
+and measuring the corresponding sets of induced magnetic fields. Kelvin's
+theorem is exploited to regularize the resulting velocity field by using the
+kinetic energy of the flow as a regularizing functional. The results of the new
+technique are shown to be in satisfactory agreement with ultrasonic
+measurements.",0409036v1
+2004-11-02,Temperature dependent magnetic properties of FePt: effective spin Hamiltonian model,"A model of magnetic interactions in the ordered ferromagnetic FePt is
+proposed on the basis of first-principles calculations of non-collinear
+magnetic configurations and shown to be capable of explaining recent
+measurements of magnetic anisotropy energy (MAE). The site (Fe,Pt) resolved
+contributions to the MAE have been distinguished with small Fe easy-plane and
+large Pt easy-axis terms. This model has been tested against available
+experimental data on the temperature dependence of MAE showing scaling of
+uniaxial MAE (K$_{1}$(T)) with magnetization (M(T)) $K_{1}(T) \sim
+M(T)^{\gamma}$ characterized by the unusual exponent of $\gamma= 2.1$. It is
+shown that this unusual behavior of the FePt can be quantitatively explained
+within the proposed model and originates from an effective anisotropic exchange
+mediated by the induced Pt moment. The latter is expected to be a common
+feature of 3d-5d(4d) alloys having 5d/4d elements with large spin-orbit
+coupling and exchange enhanced Stoner susceptibility.",0411020v1
+2004-11-05,Scaling and singularity characteristics of solar wind and magnetospheric fluctuations,"Preliminary results are presented which suggest that scaling and singularity
+characteristics of solar wind and ground based magnetic fluctuations appear to
+be a significant component in the solar wind - magnetosphere interaction
+processes. Of key importance is the intermittence of the ""magnetic turbulence""
+as seen in ground based and solar wind magnetic data. The methods used in this
+paper (estimation of flatness and multifractal spectra) are commonly used in
+the studies of fluid or MHD turbulence. The results show that single
+observatory characteristics of magnetic fluctuations are different from those
+of the multi-observatory AE-index. In both data sets, however, the influence of
+the solar wind fluctuations is recognizable. The correlation between the
+scaling/singularity features of solar wind magnetic fluctuations and the
+corresponding geomagnetic response is demonstrated in a number of cases. The
+results are also discussed in terms of patchy reconnection processes in
+magnetopause and forced or/and self-organized criticality (F/SOC) of internal
+magnetosphere dynamics.",0411055v1
+2005-05-26,"Shell to shell energy transfer in MHD, Part I: steady state turbulence","We investigate the transfer of energy from large scales to small scales in
+fully developed forced three-dimensional MHD-turbulence by analyzing the
+results of direct numerical simulations in the absence of an externally imposed
+uniform magnetic field. Our results show that the transfer of kinetic energy
+from the large scales to kinetic energy at smaller scales, and the transfer of
+magnetic energy from the large scales to magnetic energy at smaller scales, are
+local, as is also found in the case of neutral fluids, and in a way that is
+compatible with Kolmogorov (1941) theory of turbulence. However, the transfer
+of energy from the velocity field to the magnetic field is a highly non-local
+process in Fourier space. Energy from the velocity field at large scales can be
+transfered directly into small scale magnetic fields without the participation
+of intermediate scales. Some implications of our results to MHD turbulence
+modeling are also discussed.",0505183v1
+2005-11-03,Observation of a Turbulence-Induced Large Scale Magnetic Field,"An axisymmetric magnetic field is applied to a spherical, turbulent flow of
+liquid sodium. An induced magnetic dipole moment is measured which cannot be
+generated by the interaction of the axisymmetric mean flow with the applied
+field, indicating the presence of a turbulent electromotive force. It is shown
+that the induced dipole moment should vanish for any axisymmetric laminar flow.
+Also observed is the production of toroidal magnetic field from applied
+poloidal magnetic field (the omega-effect). Its potential role in the
+production of the induced dipole is discussed.",0511029v2
+2006-06-28,Intermittent magnetic field excitation by a turbulent flow of liquid sodium,"The magnetic field measured in the Madison Dynamo Experiment shows
+intermittent periods of growth when an axial magnetic field is applied. The
+geometry of the intermittent field is consistent with the fastest growing
+magnetic eigenmode predicted by kinematic dynamo theory using a laminar model
+of the mean flow. Though the eigenmodes of the mean flow are decaying, it is
+postulated that turbulent fluctuations of the velocity field change the flow
+geometry such that the eigenmode growth rate is temporarily positive.
+Therefore, it is expected that a characteristic of the onset of a turbulent
+dynamo is magnetic intermittency.",0606239v2
+2006-12-12,Structure of the Wake of a Magnetic Obstacle,"We use a combination of numerical simulations and experiments to elucidate
+the structure of the flow of an electrically conducting fluid past a localized
+magnetic field, called magnetic obstacle. We demonstrate that the stationary
+flow pattern is considerably more complex than in the wake behind an ordinary
+body. The steady flow is shown to undergo two bifurcations (rather than one)
+and to involve up to six (rather than just two) vortices. We find that the
+first bifurcation leads to the formation of a pair of vortices within the
+region of magnetic field that we call inner magnetic vortices, whereas a second
+bifurcation gives rise to a pair of attached vortices that are linked to the
+inner vortices by connecting vortices.",0612103v3
+2007-01-06,Generation of magnetic field by dynamo action in a turbulent flow of liquid sodium,"We report the observation of dynamo action in the VKS experiment, i.e., the
+generation of magnetic field by a strongly turbulent swirling flow of liquid
+sodium. Both mean and fluctuating parts of the field are studied. The dynamo
+threshold corresponds to a magnetic Reynolds number Rm \sim 30. A mean magnetic
+field of order 40 G is observed 30% above threshold at the flow lateral
+boundary. The rms fluctuations are larger than the corresponding mean value for
+two of the components. The scaling of the mean square magnetic field is
+compared to a prediction previously made for high Reynolds number flows.",0701075v1
+1997-02-08,Non--locality of particle spin: a consequence of interaction energy?,"Neutron interference measurements with macroscopic beam separation allow to
+study the influence of magnetic fields on spin properties. By calculating the
+interaction energy with a dynamic and deterministic model, we are able to
+establish that the phase shift on one component of the neutron beam is linear
+with magnetic intensity, and equally, that interaction energy as well as phase
+shifts do not depend on the orientation of the magnetic field. The theoretical
+treatment allows the conclusion that the non-local properties of particle spin
+derive from the classical equation for interaction energy and the fact, that
+interaction energy does not depend on magnetic field orientation. Additionally,
+it can be established that the 4 pi symmetry of spinors in this case depends on
+the scaling of magnetic fields.",9702023v1
+2007-04-27,Flow instabilities of magnetic flux tubes II. Longitudinal flow,"Flow-induced instabilities are relevant for the storage and dynamics of
+magnetic fields in stellar convection zones and possibly also in other
+astrophysical contexts. We continue the study started in the first paper of
+this series by considering the stability properties of longitudinal flows along
+magnetic flux tubes. A linear stability analysis was carried out to determine
+criteria for the onset of instability in the framework of the approximation of
+thin magnetic flux tubes. In the non-dissipative case, we find Kelvin-Helmholtz
+instability for flow velocities exceeding a critical speed that depends on the
+Alfv{\'e}n speed and on the ratio of the internal and external densities.
+Inclusion of a friction term proportional to the relative transverse velocity
+leads to a friction-driven instability connected with backward (or negative
+energy) waves. We discuss the physical nature of this instability. In the case
+of a stratified external medium, the Kelvin-Helmholtz instability and the
+friction-driven instability can set in for flow speeds significantly lower than
+the Alfv{\'e}n speed. Dissipative effects can excite flow-driven instability
+below the thresholds for the Kelvin-Helmholtz and the undulatory (Parker-type)
+instabilities. This may be important for magnetic flux storage in stellar
+convection zones and for the stability of astrophysical jets.",0704.3685v1
+2007-05-04,Discovery of inward moving magnetic enhancements in sunspot penumbrae,"Sunspot penumbrae show a fine structure in continuum intensity that displays
+considerable dynamics. The magnetic field, in contrast, although also highly
+structured, has appeared to be relatively static. Here we report the discovery
+of inward moving magnetic enhancements in the penumbrae of two regular sunspots
+based on time series of SOHO/MDI magnetograms. Local enhancements of the LOS
+component of the magnetic field in the inner part of the penumbral region move
+inward to the umbra-penumbra boundary with a radial speed of about 0.3 km
+s$^{-1}$. These local inward-moving enhancements of the LOS component of the
+magnetic fields appear to be relatively common. They are associated with dark
+structures and tend to display downflows relatively to the penumbral
+background. Possible explanations are discussed.",0705.0604v1
+2007-06-07,Influence of an external magnetic field on the decoherence of a central spin coupled to an antiferromagnetic environment,"Using the spin wave approximation, we study the decoherence dynamics of a
+central spin coupled to an antiferromagnetic environment under the application
+of an external global magnetic field. The external magnetic field affects the
+decoherence process through its effect on the antiferromagnetic environment. It
+is shown explicitly that the decoherence factor which displays a Gaussian decay
+with time depends on the strength of the external magnetic field and the
+crystal anisotropy field in the antiferromagnetic environment. When the values
+of the external magnetic field is increased to the critical field point at
+which the spin-flop transition (a first-order quantum phase transition) happens
+in the antiferromagnetic environment, the decoherence of the central spin
+reaches its highest point. This result is consistent with several recent
+quantum phase transition witness studies. The influences of the environmental
+temperature on the decoherence behavior of the central spin are also
+investigated.",0706.0934v1
+2007-08-26,Geodesic plasma flows instabilities of Riemann twisted solar loops,"Riemann and sectional curvatures of magnetic twisted flux tubes in Riemannian
+manifold are computed to investigate the stability of the plasma astrophysical
+tubes. The geodesic equations are used to show that in the case of thick
+magnetic tubes, the curvature of planar (Frenet torsion-free) tubes have the
+effect ct of damping the flow speed along the tube. Stability of geodesic flows
+in the Riemannian twisted thin tubes (almost filaments), against constant
+radial perturbations is investigated by using the method of negative sectional
+curvature for unstable flows. No special form of the flow like Beltrami flows
+is admitted, and the proof is general for the case of thin magnetic flux tubes.
+In the magnetic equilibrium state, the twist of the tube is shown to display
+also a damping effect on the toroidal velocity of the plasma flow. It is found
+that for positive perturbations and angular speed of the flow, instability is
+achieved, since the sectional Ricci curvature of the magnetic twisted tube
+metric is negative. Solar flare production may appear from these geometrical
+instabilities of the twisted solar loops.",0708.3473v1
+2007-09-13,"Electric-Magnetic Struggle in QGP, Deconfinement and Baryons","We argue that quite unusual properties of Quark-Gluon Plasma in the RHIC
+temperature domain $T=(1-2)T_c$ are consequences of the approximate equilibrium
+between electric and magnetic sectors reached above the deconfinement
+temperature. Already classical study of few body motion in a electric-magnetic
+plasma shows abnormally large scattering rate due to the so called ``magnetic
+bottle'' effect. Molecular dynamics simulation have found that equal mixture of
+electric and magnetic quasiparticles do produce plasmas of small viscosity and
+even smaller diffusion rate, comparable to what is needed to explain RHIC data
+and also to what follows from AdS/CFT.
+  As a separate issue, we point out that right above $T_c$ there should be
+surviving s-wave baryons made of quarks ($N,\Delta$), as well as adjoint
+objects, 3-gluon and 3-monopole chains (the latter being nothing else but
+``calorons'' or finite-T instantons).",0709.2175v1
+2007-10-24,Time-dependent magnetohydrodynamic self-similar extragalactic jets,"Extragalactic jets are visualized as dynamic erruptive events modelled by
+time-dependent magnetohydrodynamic (MHD) equations. The jet structure comes
+through the temporally self-similar solutions in two-dimensional axisymmetric
+spherical geometry. The two-dimensional magnetic field is solved in the finite
+plasma pressure regime, or finite $\beta$ regime, and it is described by an
+equation where plasma pressure plays the role of an eigenvalue. This allows a
+structure of magnetic lobes in space, among which the polar axis lobe is
+strongly peaked in intensity and collimated in angular spread comparing to the
+others. For this reason, the polar lobe overwhelmes the other lobes, and a jet
+structure arises in the polar direction naturally. Furthermore, within each
+magnetic lobe in space, there are small secondary regions with closed
+two-dimensional field lines embedded along this primary lobe. In these embedded
+magnetic toroids, plasma pressure and mass density are much higher accordingly.
+These are termed as secondary plasmoids. The magnetic field lines in these
+secondary plasmoids circle in alternating sequence such that adjacent plasmoids
+have opposite field lines. In particular, along the polar primary lobe, such
+periodic plasmoid structure happens to be compatible with radio observations
+where islands of high radio intensities are mapped.",0710.4513v1
+2007-11-06,Magnetic dynamo action in helical turbulence,"We investigate magnetic field amplification in a turbulent velocity field
+with nonzero helicity, in the framework of the kinematic Kazantsev-Kraichnan
+model. We present the numerical solution of the model for the practically
+important case of Kolmogorov distribution of velocity fluctuations, with a
+large magnetic Reynolds number. We find that in contrast to the nonhelical case
+where growing magnetic fields are described by a few bound eigenmodes
+concentrated inside the inertial interval of the velocity field, in the helical
+case the number of bound eigenmodes considerably increases; moreover, new
+unbound eigenmodes appear. Both bound and unbound eigenmodes contribute to the
+large-scale magnetic field. This indicates a limited applicability of the
+conventional alpha model of a large-scale dynamo action, which captures only
+unbound modes.",0711.0973v2
+2007-12-20,The role of the disk magnetization on the hysteresis behavior of X-ray binaries,"We present a framework for understanding the dynamical and spectral
+properties of X-ray Binaries, where the presence of an organized large scale
+magnetic field plays a major role. Such a field is threading the whole
+accretion disk with an amplitude measured by the disk magnetization $\mu(r,t)
+=B_z^2/(\mu_o P_{tot})$, where $P_{tot}$ is the total, gas and radiation,
+pressure.
+  Below a transition radius $r_J$, a jet emitting disk (the JED) is settled and
+drives self-collimated non relativistic jets. Beyond $r_J$, no jet is produced
+despite the presence of the magnetic field and a standard accretion disc (the
+SAD) is established. The radial distribution of the disk magnetization $\mu$
+adjusts itself to any change of the disk accretion rate $\dot m$, thereby
+modifying the transition radius $r_J$.
+  We propose that a SAD-to-JED transition occurs locally, at a given radius, in
+a SAD when $\mu=\mu_{max} \simeq 1$ while the reverse transition occurs in a
+JED only when $\mu=\mu_{min}\simeq 0.1$. This bimodal behavior of the accretion
+disk provides a promising way to explain the hysteresis cycles followed by
+X-ray binaries during outbursts.",0712.3388v1
+2008-01-07,Magnetization reversal driven by spin-injection : a mesoscopic spin-transfer effect,"A mesoscopic description of spin-transfer effect is proposed, based on the
+spin-injection mechanism occurring at the junction with a ferromagnet. The
+effect of spin-injection is to modify locally, in the ferromagnetic
+configuration space, the density of magnetic moments. The corresponding
+gradient leads to a current-dependent diffusion process of the magnetization.
+In order to describe this effect, the dynamics of the magnetization of a
+ferromagnetic single domain is reconsidered in the framework of the
+thermokinetic theory of mesoscopic systems. Assuming an Onsager
+cross-coefficient that couples the currents, it is shown that spin-dependent
+electric transport leads to a correction of the Landau-Lifshitz-Gilbert
+equation of the ferromagnetic order parameter with supplementary diffusion
+terms. The consequence of spin-injection in terms of activation process of the
+ferromagnet is deduced, and the expressions of the effective energy barrier and
+of the critical current are derived. Magnetic fluctuations are calculated: the
+correction to the fluctuations is similar to that predicted for the activation.
+These predictions are consistent with the measurements of spin-transfer
+obtained in the activation regime and for ferromagnetic resonance under
+spin-injection.",0801.1019v1
+2008-01-11,Charge pumping in magnetic tunnel junctions: Scattering theory,"We study theoretically the charge transport pumped by magnetization dynamics
+through epitaxial FIF and FNIF magnetic tunnel junctions (F: Ferromagnet, I:
+Insulator, N: Normal metal). We predict a small but measurable DC pumping
+voltage under ferromagnetic resonance conditions for collinear magnetization
+configurations, which may change sign as function of barrier parameters. A much
+larger AC pumping voltage is expected when the magnetizations are at right
+angles. Quantum size effects are predicted for an FNIF structure as a function
+of the normal layer thickness.",0801.1779v3
+2008-02-18,Diamagnetic pumping near the base of a stellar convection zone,"The property of inhomogeneous turbulence in conducting fluids to expel
+large-scale magnetic fields in the direction of decreasing turbulence intensity
+is shown as important for the magnetic field dynamics near the base of a
+stellar convection zone. The downward diamagnetic pumping confines a fossil
+internal magnetic field in the radiative core so that the field geometry is
+appropriate for formation of the solar tachocline. For the stars of solar age,
+the diamagnetic confinement is efficient only if the ratio of turbulent
+magnetic diffusivity of the convection zone to the (microscopic or turbulent)
+diffusivity of the radiative interiour is larger than 10^5. Confinement in
+younger stars require still larger diffusivity ratio. The observation of
+persistent magnetic structures on young solar-type stars can thus provide
+evidences for the nonexistence of tachoclines in stellar interiors and on the
+level of turbulence in radiative cores.",0802.2415v1
+2008-02-19,Temperature memory and resistive glassy behaviors of a perovskite manganite,"This paper reports the observations of long-time relaxation, aging, and
+temperature memory behaviors of resistance and magnetization in the
+ferromagnetic state of a polycrystalline La0.7Ca0.3Mn0.925Ti0.075O3 compound.
+The observed glassy dynamics of the electrical transport appears to be
+magnetically originated and has a very close association with the magnetic
+glassiness of the sample. Phase separation and strong correlation between
+magnetic interactions and electronic conduction play the essential roles in
+producing such a resistive glassiness. We explain the observed effects in terms
+of a coexistence of two competing thermomagnetic processes, domain growth and
+magnetic freezing, and propose that hole-doped perovskite manganites can be
+considered as ""resistive glasses"".",0802.2729v1
+2008-02-24,Dynamics of the Solar Magnetic Network. II. Heating the Magnetized Chromosphere,"We consider recent observations of the chromospheric network, and argue that
+the bright network grains observed in the Ca II H & K lines are heated by an as
+yet unidentified quasi-steady process. We propose that the heating is caused by
+dissipation of short-period magnetoacoustic waves in magnetic flux tubes
+(periods less than 100 s). Magnetohydrodynamic (MHD) models of such waves are
+presented. We consider wave generation in the network due to two separate
+processes: (a) by transverse motions at the base of the flux tube; and (b) by
+the absorption of acoustic waves generated in the ambient medium. We find that
+the former mechanism leads to an efficient heating of the chromosphere by slow
+magnetoacoustic waves propagating along magnetic field lines. This heating is
+produced by shock waves with a horizontal size of a few hundred kilometers. In
+contrast, acoustic waves excited in the ambient medium are converted into
+transverse fast modes that travel rapidly through the flux tube and do not form
+shocks, unless the acoustic sources are located within 100 km from the tube
+axis. We conclude that the magnetic network may be heated by magnetoacoustic
+waves that are generated in or near the flux tubes.",0802.3509v1
+2008-03-19,Transport magnetic currents driven by moving kink crystal in chiral helimagnets,"We show that the bulk transport magnetic current is generated by the moving
+magnetic kink crystal (chiral soliton lattice) formed in the chiral helimagnet
+under the static magnetic field applied perpendicular to the helical axis. The
+current is caused by the non-equilibrium transport momentum with the kink mass
+being determined by the spin fluctuations around the kink crystal state. An
+emergence of the transport magnetic currents is then a consequence of the
+dynamical off-diagonal long range order along the helical axis. We derive an
+explicit formula for the inertial mass of the kink crystal and the current in
+the weak field limit.",0803.2750v1
+2008-03-19,Strong linewidth variation for spin-torque nano-oscillators as a function of in-plane magnetic field angle,"We measure the microwave signals produced by spin-torque-driven magnetization
+dynamics in patterned magnetic multilayer devices at room temperature, as a
+function of the angle of a magnetic field applied in the sample plane. We find
+strong variations in the frequency linewidth of the signals, with a decrease by
+more than a factor of 20 as the field is rotated from the magnetic easy axis to
+the in-plane hard axis. Based on micromagnetic simulations, we identify these
+variations as due to a transition from spatially incoherent to coherent
+precession.",0803.2871v1
+2008-04-16,Quantum Zeno Effect Underpinning the Radical-Ion-Pair Mechanism of Avian Magnetoreception,"The intricate biochemical processes underlying avian magnetoreception, the
+sensory ability of migratory birds to navigate using earths magnetic field,
+have been narrowed down to spin-dependent recombination of radical-ion pairs to
+be found in avian species retinal proteins. The avian magnetic field detection
+is governed by the interplay between magnetic interactions of the radicals
+unpaired electrons and the radicals recombination dynamics. Critical to this
+mechanism is the long lifetime of the radical-pair spin coherence, so that the
+weak geomagnetic field will have a chance to signal its presence. It is here
+shown that a fundamental quantum phenomenon, the quantum Zeno effect, is at the
+basis of the radical-ion-pair magnetoreception mechanism. The quantum Zeno
+effect naturally leads to long spin coherence lifetimes, without any
+constraints on the systems physical parameters, ensuring the robustness of this
+sensory mechanism. Basic experimental observations regarding avian magnetic
+sensitivity are seamlessly derived. These include the magnetic sensitivity
+functional window and the heading error of oriented bird ensembles, which so
+far evaded theoretical justification. The findings presented here could be
+highly relevant to similar mechanisms at work in photosynthetic reactions. They
+also trigger fundamental questions about the evolutionary mechanisms that
+enabled avian species to make optimal use of quantum measurement laws.",0804.2646v1
+2008-05-19,Impact of impellers on the axisymmetric magnetic mode in the VKS2 dynamo experiment,"In the VKS2 (von K\'arm\'an Sodium 2) successful dynamo experiment of
+September 2006, the magnetic field that was observed showed a strong
+axisymmetric component, implying that non axisymmetric components of the flow
+field were acting. By modeling the induction effect of the spiraling flow
+between the blades of the impellers in a kinematic dynamo code, we find that
+the axisymmetric magnetic mode is excited and becomes dominant in the vicinity
+of the dynamo threshold. % The control parameters are the magnetic Reynolds
+number of the mean flow, the coefficient measuring the induction effect,
+$\alpha$, and the type of boundary conditions (vacuum for steel impellers and
+normal field for soft iron impellers). We show that using realistic values of
+$\alpha$, the observed critical magnetic Reynolds number, $Rm^c \approx 32$,
+can be reached easily with ferromagnetic boundary conditions. We conjecture
+that the dynamo action achieved in this experiment may not be related to the
+turbulence in the bulk of the flow, but rather to the alpha effect induced by
+the impellers.",0805.2805v2
+2008-05-24,Solar convection and oscillations in magnetic regions,"The goal of this research is to investigate how magnetic field affects the
+dynamics of granular convection and excitation of solar oscillations by means
+of realistic numerical simulations. We have used a 3D, compressible, non-linear
+radiative magnetohydrodynamics code developed at the NASA Ames Research Center.
+This code takes into account several physical phenomena: compressible fluid
+flow in a highly stratified medium, sub-grid scale turbulence models, radiative
+energy transfer between the fluid elements, and a real-gas equation of state.
+We have studied the influence of the magnetic field of various strength on the
+convective cells and on the excitation mechanisms of the acoustic oscillations
+by calculating spectral properties of the convective motions and oscillations.
+The results reveal substantial changes of the granulation structure with
+increased magnetic field, and a frequency-dependent reduction in the
+oscillation power in a good agreement with solar observations. These
+simulations suggest that the enhanced high-frequency acoustic emission at the
+boundaries of active region (""acoustic halo"" phenomenon) is caused by the
+changes of the spatial-temporal spectrum of the turbulent convection in
+magnetic field, resulting in turbulent motions of smaller scales and higher
+frequencies than in quiet Sun regions.",0805.3741v1
+2008-05-28,Photonic Dipole Contours of Ferrofluid Hele-Shaw Cell,"This investigation describes and demonstrates a novel technique for the
+visualization of magnetic fields. Two ferrofluid Hele-Shaw cells have been
+constructed to facilitate the imaging of magnetic field lines. We deduce that
+magnetically induced photonic band gap arrays similar to electrostatic liquid
+crystal operation are responsible for the photographed images and seek to
+mathematically prove the images are of dipole nature.
+  A simple way of explaining this work is to think of the old magnetic iron
+filling experiments; but now each iron filling is a molecule floating in a
+liquid. Each molecule has the freedom to act as an independent lens that can be
+aligned by an external magnetic field. Because each lens directs light, the
+external field can be analyzed by following the light paths captured in the
+photographs.",0805.4364v2
+2008-06-05,Theory of spin current in chiral helimagnet,"We give detailed description of the transport spin current in the chiral
+helimagnet. Under the static magnetic field applied perpendicular to the
+helical axis, the magnetic kink crystal (chiral soliton lattice) is formed.
+Once the kink crystal begins to move under the Galilean boost, the spin-density
+accumulation occurs inside each kink and there emerges periodic arrays of the
+induced magnetic dipoles carrying the transport spin current. The coherent
+motion of the kink crystal dynamically generates the spontaneous
+demagnetization field. This mechanism is analogous to the
+D\""{o}ring-Becker-Kittel mechanism of the domain wall motion in ferromagnets.
+To describe the kink crystal motion, we took account of not only the tangential
+$\phi$-fluctuations but the longitudinal $\theta$-fluctuations around the
+helimagnetic configuration. Based on the collective coordinate method and the
+Dirac's canonical formulation for the singular Lagrangian system, we derived
+the closed formulae for the mass, spin current and induced magnetic dipole
+moment accompanied with the kink crystal motion. To materialize the theoretical
+model presented here, symmetry-adapted material synthesis would be required,
+where the interplay of crystallographic and magnetic chirality plays a key role
+there.",0806.0968v2
+2008-07-02,Magnetohydrodynamic experiments on cosmic magnetic fields,"It is widely known that cosmic magnetic fields, i.e. the fields of planets,
+stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving
+electrically conducting fluids. It is less well known that cosmic magnetic
+fields play also an active role in cosmic structure formation by enabling
+outward transport of angular momentum in accretion disks via the
+magnetorotational instability (MRI). Considerable theoretical and computational
+progress has been made in understanding both processes. In addition to this,
+the last ten years have seen tremendous efforts in studying both effects in
+liquid metal experiments. In 1999, magnetic field self-excitation was observed
+in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently,
+self-excitation was also obtained in the French ""von Karman sodium"" (VKS)
+experiment. An MRI-like mode was found on the background of a turbulent
+spherical Couette flow at the University of Maryland. Evidence for MRI as the
+first instability of an hydrodynamically stable flow was obtained in the
+""Potsdam Rossendorf Magnetic Instability Experiment"" (PROMISE). In this review,
+the history of dynamo and MRI related experiments is delineated, and some
+directions of future work are discussed.",0807.0299v2
+2008-07-22,Exponential equilibration by slow cooling in the planar random-anisotropy magnet: experiments and simulations,"Neutron measurements of the equilibration of the staggered magnetization in
+DyAs(0.35)V(0.65)O4 are compared with Monte Carlo simulations of spin dynamics
+in a planar random-anisotropy magnet. The simulation results are in agreement
+with striking observed relaxation phenomena: when cooled rapidly to a low
+temperature no magnetic ordering is observed, but when cooled in small steps an
+ordered magnetic moment appears which is found to equilibrate exponentially
+with time at temperatures through and below the transition temperature. In
+contrast to the freezing of spins in other random systems, the time scale of
+the relaxation in this system does not increase significantly even at the
+lowest temperatures.",0807.3536v1
+2008-09-04,Properties of anisotropic magnetic impurities on surfaces,"Using numerical renormalization group techniques, we study static and dynamic
+properties of a family of single-channel Kondo impurity models with axial
+magnetic anisotropy $DS_z^2$ terms; such models are appropriate to describe
+magnetic impurity atoms adsorbed on non-magnetic surfaces, which may exhibit
+surface Kondo effect. We show that for positive anisotropy $D$ and for any spin
+$S$, the systems behave at low temperatures as regular Fermi liquids with fully
+compensated impurity spin. The approach to the stable fixed point depends on
+the value of the spin $S$ and on the ratio $D/T_K^{(0)}$, where $T_K^{(0)}$ is
+the Kondo temperature in the absence of the anisotropy. For S=1, the screening
+occurs in two stages if $D<T_K^{(0)}$; the second Kondo temperature is
+exponentially reduced in this case. More generally, there is an effective
+spin-1/2 Kondo effect for any integer $S$ if $D<T_K^{(0)}$ and for any
+half-integer $S$ if $D>T_K^{(0)}$. For negative anisotropy $D$, the system is a
+non-Fermi liquid with residual anisotropic exchange interaction. However, the
+presence of transverse magnetic anisotropy $E(S_x^2-S_y^2)$ restores
+Fermi-liquid behavior in real systems.",0809.0759v1
+2008-10-31,"Anisotropy, Itineracy, and Magnetic Frustration in High-Tc Iron Pnictides","Using first-principle density functional theory calculations combined with
+insight from a tight-binding representation, dynamical mean field theory, and
+linear response theory, we have extensively investigated the electronic
+structures and magnetic interactions of nine ferropnictides representing three
+different structural classes. The calculated magnetic interactions are found to
+be short-range, and the nearest ($J_{1a}$) and next-nearest ($J_{2}$) exchange
+constants follow the universal trend of J_{1a}/2J_{2}\sim 1, despite their
+itinerant origin and extreme sensitivity to the z-position of As. These results
+bear on the discussion of itineracy versus magnetic frustration as the key
+factor in stabilizing the superconducting ground state. The calculated spin
+wave dispersions show strong magnetic anisotropy in the Fe plane, in contrast
+to cuprates.",0811.0034v3
+2008-12-19,Spin-bias driven magnetization reversal and nondestructive detection in a single molecular magnet,"The magnetization reversal in a single molecular magnet (SMM) weakly coupled
+to an electrode with spin-dependent splitting of chemical potentials (spin
+bias) is theoretically investigated by means of the rate equation. A
+microscopic mechanism for the reversal is demonstrated by the avalanche
+dynamics at the reversal point. The magnetization as a function of the spin
+bias shows hysteresis loops tunable by the gate voltage and varying with
+temperature. The nondestructive measurement to the orientation of giant spin in
+SMM is presented by measuring the fully polarized electric current in the
+response to a small spin bias. For Mn$_{12}$ac molecule, its small transverse
+anisotropy only slightly violates the results above. The situation when there
+is an angle between the easy axis of the SMM and the spin quantization
+direction of the electrode is also studied.",0812.3713v2
+2009-01-12,3D MHD simulations of magnetic fields and radio polarization of barred galaxies,"We present results of three-dimensional, fully nonlinear MHD simulations of a
+large-scale magnetic field evolution in a barred galaxy. The model does not
+take into consideration the dynamo process. We find that the obtained magnetic
+field configurations are highly similar to the observed maps of the polarized
+intensity of barred galaxies, because the modeled vectors form coherent
+structures along the bar and spiral arms. Due to the dynamical influence of the
+bar the gas forms spiral waves which go radially outward. Each spiral arm forms
+the magnetic arm which stays much longer in the disk, than the gaseous spiral
+structure. Additionally the modeled total energy of magnetic field grows due to
+strong compression and shear of non-axisymmetrical bar flows and differential
+rotation, respectively.",0901.1564v1
+2009-03-13,Dirac-Neutrino Magnetic Moment and the Dynamics of a Supernova Explosion,"The double conversion of the neutrino helicity $\nu_L \to \nu_R \to \nu_L$
+has been analyzed for supernova conditions, where the first stage is due to the
+interaction of the neutrino magnetic moment with plasma electrons and protons
+in the supernova core, and the second stage, due to the resonance spin flip of
+the neutrino in the magnetic field of the supernova envelope. It is shown that,
+in the presence of the neutrino magnetic moment in the range $10^{-13} \mu_{\rm
+B} < \mu_\nu < 10^{-12} \mu_{\rm B}$ and a magnetic field of $\sim 10^{13}$ G
+between the neutrinosphere and the shock-stagnation region, an additional
+energy of about $10^{51}$ erg, which is sufficient for a supernova explosion,
+can be injected into this region during a typical shock-stagnation time.",0903.2321v1
+2009-05-26,Scattering Theory of Charge-Current Induced Magnetization Dynamics,"In ferromagnets, charge currents can excite magnons via the spin-orbit
+coupling. We develop a novel and general scattering theory of charge current
+induced macrospin magnetization torques in normal metal$|$ferromagnet$|$normal
+metal layers. We apply the formalism to a dirty GaAs$|$(Ga,Mn)As$|$GaAs system.
+By computing the charge current induced magnetization torques and solving the
+Landau-Lifshitz-Gilbert equation, we find magnetization switching for current
+densities as low as $ 5\times 10^{6}$~A/cm$^2$. Our results are in agreement
+with a recent experimental observation of charge-current induced magnetization
+switching in (Ga,Mn)As.",0905.4170v2
+2009-07-14,Las ondas viajeras son los ojos nuevos de la resonancia en medicina,"Magnetic Resonance Imaging is one of the most versatile experimental
+techniques in chemistry, physics and biology, providing insight into the
+structure and dynamics of matter at the molecular scale. A group led by Klaas
+Pruessmann at ETH Zurich (Brunner, D.O. et al. Travelling-wave nuclear magnetic
+resonance. Nature 457;994:2009) has now demonstrated an alternative approach
+that radically departs from the conventional view of MRI as a near-field,
+inductive technique. This approach also required that radiofre-quency wave is
+propagated from an antenna positioned at one end of the cylindrical magnet;
+this wave travels through the specimen within the bore of the magnet, producing
+signals that are received either by the same antenna or by another one
+positioned at the opposite end. The resulting instrument considerably extends
+the scale of imaging possible with Magnetic Resonance Imaging, and initial
+tests demonstrated uniform high-field imaging of a variety of samples, both
+inorganic and inorganic.",0907.2446v1
+2009-10-06,Cold and Ultracold Rydberg Atoms in Strong Magnetic Fields,"Cold Rydberg atoms exposed to strong magnetic fields possess unique
+properties which open the pathway for an intriguing many-body dynamics taking
+place in Rydberg gases consisting of either matter or anti-matter systems. We
+review both the foundations and recent developments of the field in the cold
+and ultracold regime where trapping and cooling of Rydberg atoms have become
+possible. Exotic states of moving Rydberg atoms such as giant dipole states are
+discussed in detail, including their formation mechanisms in a strongly
+magnetized cold plasma. Inhomogeneous field configurations influence the
+electronic structure of Rydberg atoms, and we describe the utility of
+corresponding effects for achieving tightly trapped ultracold Rydberg atoms. We
+review recent work on large, extended cold Rydberg gases in magnetic fields and
+their formation in strongly magnetized ultracold plasmas through collisional
+recombination. Implications of these results for current antihydrogen
+production experiments are pointed out, and techniques for trapping and cooling
+of such atoms are investigated.",0910.1037v1
+2009-10-06,First Detection of the Zeeman Effect in the 36 GHz Class I methanol maser line with the EVLA,"We report the first detection of the Zeeman effect in the 36 GHz Class I
+methanol maser line. The observations were carried out with 13 antennas of the
+EVLA toward the high mass star forming region M8E. Based on our adopted Zeeman
+splitting factor of $z = 1.7 Hz/mG, we detect a line of sight magnetic field of
+-31.3 +/- 3.5 mG and 20.2 +/- 3.5 mG to the northwest and southeast of the
+maser line peak respectively. This change in sign over a 1300 AU size scale may
+indicate that the masers are tracing two regions with different fields, or that
+the same field curves across the regions where the masers are being excited.
+The detected fields are not significantly different from the magnetic fields
+detected in the 6.7 GHz Class II methanol maser line, indicating that methanol
+masers may trace the large scale magnetic field, or that the magnetic field
+remains unchanged during the early evolution of star forming regions. Given
+what is known about the densities at which 36 GHz methanol masers are excited,
+we find that the magnetic field is dynamically significant in the star forming
+region.",0910.1081v1
+2009-11-02,Response of spin polarized neutron matter under the presence of a strong magnetic field with Skyrme interactions,"The effects of a strong magnetic field in the dynamical response of a pure
+neutron system to a weak neutrino probe are studied within the framework of the
+Landau Fermi Liquid Theory in the non-relativistic Hartree-Fock approximation.
+We use Skyrme forces to parametrize the partially magnetized nuclear
+interacting plasma and describe its collective modes. We study the vector and
+vector-axial matter response functions and the neutrino mean free path in this
+two-component fermion system with net spin polarization and density dependent
+in-medium correlations. We find a decrease in the neutrino opacity of
+magnetized matter with respect to the non-magnetized case for fields $log_{10}
+B(G) \gtrsim 17$.",0911.0378v1
+2009-11-09,Role of dipole-dipole interactions in multiple quantum transitions in magnetic nanoparticles,"In order to better understand the origin of multiple quantum transitions
+observed in superparamagnetic nanoparticles, electron magnetic resonance (EMR)
+studies have been performed on iron oxide nanoparticles assembled inside the
+anodic alumina membrane. The positions of both the main resonance and
+""forbidden"" (double-quantum, 2Q) transitions observed at the half-field
+demonstrate the characteristic angular dependence with the line shifts
+proportional to 3cos2q-1, where q is the angle between the channel axis and
+external magnetic field B. This result can be attributed to the interparticle
+dipole-dipole interactions within elongated aggregates inside the channels. The
+angular dependence of the 2Q intensity is found to be proportional to
+sin2qcos2q, that is consistent with the predictions of quantum-mechanical
+calculations with the account for the mixing of states by non-secular
+inter-particle dipole-dipole interactions. Good agreement is demonstrated
+between different kinds of measurements (magnetization curves, line shifts and
+2Q intensity), evidencing applicability of the quantum approach to the
+magnetization dynamics of superparamagnetic objects.",0911.1752v1
+2009-11-16,On the magnetic field of off-limb spicules,"Determining the magnetic field related to solar spicules is vital for
+developing adequate models of these plasma jets, which are thought to play a
+key role in the thermal, dynamic and magnetic structure of the Chromosphere.
+Here we report on the magnetic properties of off-limb spicules in a very quiet
+region of the solar atmosphere, as inferred from new spectropolarimetric
+observations in the He I 10830 A triplet obtained with the Tenerife Infrared
+Polarimeter. We have used a novel inversion code for Stokes profiles caused by
+the joint action of atomic level polarization and the Hanle and Zeeman effects
+(HAZEL) to interpret the observations. Magnetic fields as strong as ~40G were
+detected in a very localized area of the slit, which could represent a possible
+lower value of the field strength of organized network spicules.",0911.3149v1
+2009-11-23,Ligand exchange in gold-coated FePt nanoparticles,"In this work we present the magnetic properties of gold coated FePt
+nanoparticles and the study of stable aqueous dispersions of FePt@Au and FePt
+synthesized after ligand exchange with mercaptoundecanoic acid. The particle
+size determined from TEM micrographs goes from 4 nm for the uncoated
+nanoparticles to a maximum of 10 nm for the gold coated ones indicating that
+the thickness of the shell ranges from 1 to 3 nm. The magnetic characterization
+consists in hysteresis cycles at 10 and 300 K. The results show that, at low
+field and room temperature, the magnetic behavior of uncoated and coated
+nanoparticles are surprisingly quite similar. Since the gold coated
+nanoparticles keep the magnetic properties of FePt and the presence of gold
+improves the functionalization of nanoparticles, the system is suitable for
+biological application. Mercaptoundecanoic ligand transfer was used to render
+water stable nanoparticles in a wide pH range. Transmission electron microscopy
+and dynamic light scattering results show the nanoparticles slightly
+agglomerate after ligand exchange. Fourier transform infrared spectroscopy
+results suggest that thiol bind to the gold atoms of the surface.",0911.4374v1
+2010-01-07,Extracting Nucleon Magnetic Moments and Electric Polarizabilities from Lattice QCD in Background Electric Fields,"Nucleon properties are investigated in background electric fields. As the
+magnetic moments of baryons affect their relativistic propagation in constant
+electric fields, electric polarizabilities cannot be determined without
+knowledge of magnetic moments. This is analogous to the experimental situation,
+for which determination of polarizabilities from the Compton amplitude requires
+subtraction of Born terms. With the background field method, we devise
+combinations of nucleon correlation functions in constant electric fields that
+isolate magnetic moments and electric polarizabilities. Using an ensemble of
+anisotropic gauge configurations with dynamical clover fermions, we demonstrate
+how both observables can be determined from lattice QCD simulations in
+background electric fields. We obtain results for the neutron and proton,
+however, our study is currently limited to electrically neutral sea quarks. The
+value we extract for the nucleon isovector magnetic moment is comparable to
+those obtained from measuring lattice three-point functions at similar pion
+masses.",1001.1131v2
+2010-01-11,Dynamics of braided coronal loops - I. Onset of magnetic reconnection,"The response of the solar coronal magnetic field to small-scale photospheric
+boundary motions including the possible formation of current sheets via the
+Parker scenario is one of open questions of solar physics. Here we address the
+problem via a numerical simulation. The three-dimensional evolution of a
+braided magnetic field which is initially close to a force-free state is
+followed using a resistive MHD code. A long-wavelength instability takes place
+and leads to the formation of two thin current layers. Magnetic reconnection
+occurs across the current sheets with three-dimensional features shown,
+including an elliptic magnetic field structure about the reconnection site, and
+results in an untwisting of the global field structure.",1001.1717v3
+2010-01-13,Numerical code SELFAS-3 and electrodynamic aggregation of magnetized nanodust,"The principles of the parallel numerical code SELFAS-3 are presented. The
+code modifies previous version of the code to enable parallel computations of
+electrodynamic aggregation in a many-body system of basic blocks which are
+taken as strongly magnetized thin rods (i.e., one-dimensional static magnetic
+dipoles), with electric conductivity and static electric charge, screened with
+its own static plasma sheath. The aggregation modelling includes the electric
+current dynamics in a complicated evolving network to describe the processes of
+external and internal electric short-circuiting. The code enables the
+continuous modelling of a transition between the following states: randomly
+situated ensemble of solitary basic blocks; electric current-carrying
+filamentary system; restructured filamentary network with a trend towards a
+fractal skeletal structuring. The latter trend is illustrated with generation
+of a bigger magnetic dipole in (i) homogeneous random ensemble between the
+biased electrodes in the presence of a plasma electric current filament and
+(ii) random ensemble around a straight linear nanodust filament with
+inhomogeneous distribution of the trapped magnetic flux along the filament.",1001.2328v1
+2010-01-28,Static and Dynamical Susceptibility of LaO1-xFxFeAs,"The mechanism of superconductivity and magnetism and their possible interplay
+have recently been under debate in pnictides. A likely pairing mechanism
+includes an important role of spin fluctuations and can be expressed in terms
+of the magnetic susceptibility chi. The latter is therefore a key quantity in
+the determination of both the magnetic properties of the system in the normal
+state, and of the contribution of spin fluctuations to the pairing potential. A
+basic ingredient to obtain chi is the independent-electron susceptibility chi0.
+Using LaO1-xFxFeAs as a prototype material, in this report we present a
+detailed ab-initio study of chi0(q,omega), as a function of doping and of the
+internal atomic positions. The resulting static chi0(q,0) is consistent with
+both the observed M-point related magnetic stripe phase in the parent compound,
+and with the existence of incommensurate magnetic structures predicted by
+ab-initio calculations upon doping.",1001.5154v1
+2010-02-02,Model for Dynamic Self-Assembled Magnetic Surface Structures,"We propose a first-principles model for self-assembled magnetic surface
+structures on the water-air interface reported in earlier experiments
+\cite{snezhko2,snezhko4}. The model is based on the Navier-Stokes equation for
+liquids in shallow water approximation coupled to Newton equations for
+interacting magnetic particles suspended on the water-air interface. The model
+reproduces most of the observed phenomenology, including spontaneous formation
+of magnetic snake-like structures, generation of large-scale vortex flows,
+complex ferromagnetic-antiferromagnetic ordering of the snake, and
+self-propulsion of bead-snake hybrids. The model provides valuable insights
+into self-organization phenomena in a broad range of non-equilibrium magnetic
+and electrostatic systems with competing interactions.",1002.0328v1
+2010-02-18,Hamilton--Jacobi theory for continuation of magnetic field across a toroidal surface supporting a plasma pressure discontinuity,"The vanishing of the divergence of the total stress tensor (magnetic plus
+kinetic) in a neighborhood of an equilibrium plasma containing a toroidal
+surface of discontinuity gives boundary and jump conditions that strongly
+constrain allowable continuations of the magnetic field across the surface. The
+boundary conditions allow the magnetic fields on either side of the
+discontinuity surface to be described by surface magnetic potentials, reducing
+the continuation problem to that of solving a Hamilton--Jacobi equation. The
+characteristics of this equation obey Hamiltonian equations of motion, and a
+necessary condition for the existence of a continued field across a general
+toroidal surface is that there exist invariant tori in the phase space of this
+Hamiltonian system. It is argued from the Birkhoff theorem that existence of
+such an invariant torus is also, in general, sufficient for continuation to be
+possible. An important corollary is that the rotational transform of the
+continued field on a surface of discontinuity must, generically, be irrational.",1002.3499v1
+2010-04-05,Abrikosov Gluon Vortices in Color Superconductors,"In this talk I will discuss how the in-medium magnetic field can influence
+the gluon dynamics in a three-flavor color superconductor. It will be shown how
+at field strengths comparable to the charged gluon Meissner mass a new phase
+can be realized, giving rise to Abrikosov's vortices of charged gluons. In that
+phase, the inhomogeneous gluon condensate anti-screens the magnetic field due
+to the anomalous magnetic moment of these spin-1 particles. This paramagnetic
+effect can be of interest for astrophysics, since due to the gluon vortex
+antiscreening mechanism, compact stars with color superconducting cores could
+have larger magnetic fields than neutron stars made up entirely of nuclear
+matter. I will also discuss a second gluon condensation phenomenon connected to
+the Meissner instability attained at moderate densities by two-flavor color
+superconductors. In this situation, an inhomogeneous condensate of charged
+gluons emerges to remove the chromomagnetic instability created by the pairing
+mismatch, and as a consequence, the charged gluonic currents induce a magnetic
+field. Finally, I will point out a possible relation between glitches in
+neutron stars and the existence of the gluon vortices.",1004.0733v1
+2010-05-07,Importance of Itinerancy and Quantum Fluctuations for the Magnetism in Iron Pnictides,"By applying density functional theory, we find strong evidence for an
+itinerant nature of magnetism in two families of iron pnictides. Furthermore,
+by employing dynamical mean field theory with continuous time quantum Monte
+Carlo as an impurity solver, we observe that the antiferromagnetic metal with
+small magnetic moment naturally arises out of coupling between unfrustrated and
+frustrated bands. Our results point to a possible scenario for magnetism in
+iron pnictides where magnetism originates from a strong instability at the
+momentum vector ($\pi$, $\pi$, $\pi$) while it is reduced by quantum
+fluctuations due to the coupling between weakly and strongly frustrated bands.",1005.1170v2
+2010-06-04,The effect of spin-orbit interaction and attractive Coulomb potential on the magnetic properties of Ga$_{1-x}$Mn$_{x}$As,"We employ the dynamical mean-field approximation to study the magnetic
+properties of a model relevant for the dilute magnetic semiconductors. Our
+model includes the spin-orbit coupling on the hole bands, the exchange
+interaction, and the attractive Coulomb potential between the negatively
+charged magnetic ions and the itinerant holes. The inclusion of the Coulomb
+potential significantly renormalizes the exchange coupling and enhances the
+ferromagnetic transition temperature for a wide range of couplings. We also
+explore the effect of the spin-orbit interaction by using two different values
+of the ratio of the effective masses of the heavy and light holes. We show that
+in the regime of small $J_{c}$-$V$ the spin-orbit interaction enhances $T_{c}$,
+while for large enough values of $J_{c}$-$V$ magnetic frustration reduces $T_c$
+to values comparable to the previously calculated strong coupling limit.",1006.0998v2
+2010-06-07,Roles of adiabatic and nonadiabatic spin transfer torques on magnetic domain wall motion,"Electric current exerts torques-so-called spin transfer torques (STTs)-on
+magnetic domain walls (DWs), resulting in DW motion. At low current densities,
+the STTs should compete against disorders in ferromagnetic nanowires but the
+nature of the competition remains poorly understood. By achieving
+two-dimensional contour maps of DW speed with respect to current density and
+magnetic field, here we visualize unambiguously distinct roles of the two
+STTs-adiabatic and nonadiabatic-in scaling behaviour of DW dynamics arising
+from the competition. The contour maps are in excellent agreement with
+predictions of a generalized scaling theory, and all experimental data collapse
+onto a single curve. This result indicates that the adiabatic STT becomes
+dominant for large current densities, whereas the nonadiabatic STT-playing the
+same role as a magnetic field-subsists at low current densities required to
+make emerging magnetic nanodevices practical.",1006.1216v1
+2010-07-22,Strong reduction of V4+ amount in vanadium oxide/hexadecylamine nanotubes by doping with Co2+ and Ni2+ ions: EPR and magnetic studies,"In this work we present a complete characterization and magnetic study of
+vanadium oxide/hexadecylamine nanotubes (VOx/Hexa NT's) doped with Co2+ and
+Ni2+ ions. The morphology of the NT's has been characterized by Transmission
+Electron Microscopy (TEM) while the metallic elements have been quantified by
+Instrumental Neutron Activation Analysis (INAA) technique. The static and
+dynamic magnetic properties were studied collecting data of magnetization as a
+function of magnetic field and temperature and by Electron Paramagnetic
+Resonance (EPR). We observed that the incorporation of metallic ions (Co2+,
+S=3/2 and Ni2+, S=1) decrease notably the amount of V4+ ions in the system,
+from 14-16% (non-doped case) to 2-4%, with respect to the total vanadium atoms
+into the tubular nanostructure, improving considerably their potential
+technological applications as Li-ion batteries cathodes.",1007.3968v1
+2010-08-02,Instabilities of Shercliff and Stewartson layers in spherical Couette flow,"We explore numerically the flow induced in a spherical shell by
+differentially rotating the inner and outer spheres. The fluid is also taken to
+be electrically conducting (in the low magnetic Reynolds number limit), and a
+magnetic field is imposed parallel to the axis of rotation. If the outer sphere
+is stationary, the magnetic field induces a Shercliffe layer on the tangent
+cylinder, the cylinder just touching the inner sphere and parallel to the
+field. If the magnetic field is absent, but a strong overall rotation is
+present, Coriolis effects induce a Stewartson layer on the tangent cylinder.
+The non-axisymmetric instabilities of both types of layer separately have been
+studied before; here we consider the two cases side by side, as well as the
+mixed case, and investigate how magnetic and rotational effects interact. We
+find that if the differential rotation and the overall rotation are in the same
+direction, the overall rotation may have a destabilizing influence, whereas if
+the differential rotation and the overall rotation are in the opposite
+direction, the overall rotation always has a stabilizing influence.",1008.0328v1
+2010-08-04,Magnetic aspects of QCD and compact stars,"Magnetic properties of quark matter are discussed. The possibility of
+ferromagnetic transition is studied by using the one-gluon-exchange
+interaction. Magnetic susceptibility is evaluated within Landau Fermi liquid
+theory, and the important roles of the screening for the gluon propagation are
+elucidated. Static screening for the longitudinal gluons improves the infrared
+singularities, while the transverse gluons receive only dynamic screening. The
+latter property gives rise to a novel non-Fermi-liquid behaviour in the
+magnetic susceptibility. The critical density is estimated to be around the
+nuclear density and the Curie temperature several tens MeV. The spin density
+wave is also discussed at moderate densities, where chiral transition becomes
+important. Pseudoscalar condensate as well as scalar one takes a spatially
+non-uniform form in a chirally invariant way. Accordingly magnetization
+oscillates like spin density wave. These results should have some implications
+on compact star phenomena.",1008.0709v1
+2010-08-04,Spin relaxation due to electron-electron magnetic interaction in high Lande g-factor semiconductors,"We investigate spin transport in InSb/InAlSb heterostructure using the Monte
+Carlo approach, generalized by including density matrix description of spin for
+taking spin dynamics into account. In addition to the dominant Dyakonov-Perel
+(DP) mechanism for spin control and relaxation, we consider magnetic
+interaction between electrons which assumes importance due to high electronic
+Lande g-factor in the material. It is found that while the effect of magnetic
+interaction is not important at low densities, it reduces the spin relaxation
+length by as much as 50% at higher densities. We also present a calculation
+which elucidates the suppression of decoherence attributed to wave vector
+dependent magnetic field in the DP relaxation mechanism. We note that magnetic
+interaction is a general relaxation mechanism which may assume importance in
+materials with high electronic Lande g-factor.",1008.0739v1
+2010-08-23,Magnetic aspects of QCD at finite density and temperature,"Some magnetic aspects of QCD are discussed at finite density and temperature.
+Possibility of spontaneous magnetization is studied within Landau Fermi-liquid
+theory, and the important roles of the screening effects for gluon propagation
+are elucidated. Static screening for the longitudinal gluons improves the
+infrared singularities, while the transverse gluons receive only dynamic
+screening. The latter property gives rise to a novel non-Fermi-liquid behaviour
+for the magnetic susceptibility. Appearance of a density-wave state is also
+discussed in relation to chiral transition, where pseudoscalar condensate as
+well as scalar one takes a spatially non-uniform form in a chirally invariant
+way. Accordingly magnetization of quark matter oscillates like spin density
+wave. A hadron-quark continuity is suggested in this aspect, remembering pion
+condensation in hadronic phase.",1008.3753v1
+2010-08-29,Stochastic Flux-Freezing and Magnetic Dynamo,"We argue that magnetic flux-conservation in turbulent plasmas at high
+magnetic Reynolds numbers neither holds in the conventional sense nor is
+entirely broken, but instead is valid in a novel statistical sense associated
+to the ""spontaneous stochasticity"" of Lagrangian particle tra jectories. The
+latter phenomenon is due to the explosive separation of particles undergoing
+turbulent Richardson diffusion, which leads to a breakdown of Laplacian
+determinism for classical dynamics. We discuss empirical evidence for
+spontaneous stochasticity, including our own new numerical results. We then use
+a Lagrangian path-integral approach to establish stochastic flux-freezing for
+resistive hydromagnetic equations and to argue, based on the properties of
+Richardson diffusion, that flux-conservation must remain stochastic at infinite
+magnetic Reynolds number. As an important application of these results we
+consider the kinematic, fluctuation dynamo in non-helical, incompressible
+turbulence at unit magnetic Prandtl number. We present results on the
+Lagrangian dynamo mechanisms by a stochastic particle method which demonstrate
+a strong similarity between the Pr = 1 and Pr = 0 dynamos. Stochasticity of
+field-line motion is an essential ingredient of both. We finally consider
+briefly some consequences for nonlinear MHD turbulence, dynamo and reconnection",1008.4959v1
+2010-09-14,Anisotropy-axis orientation effect on the magnetization of γ-Fe2O3 frozen ferrofluid,"The effect of magnetic anisotropy-axis alignment on the superparamagnetic
+(SPM) and superspin glass (SSG) states in a frozen ferrofluid has been
+investigated. The ferrofluid studied here consists of maghemite nanoparticles
+(\gamma-Fe2O3, mean diameter = 8.6 nm) dispersed in glycerine at a volume
+fraction of ~15%. In the high temperature SPM state, the magnetization of
+aligned ferrofluid increased by a factor varying between 2 and 4 with respect
+to that in the randomly oriented state. The negative interaction energy
+obtained from the Curie-Weiss fit to the high temperature susceptibility in the
+SPM states as well as the SSG phase onset temperature determined from the
+linear magnetization curves were found to be rather insensitive to the
+anisotropy axis alignment. The low temperature aging behaviour, explored via
+""zero-field cooled magnetization"" (ZFCM) relaxation measurements, however, show
+distinct difference in the aging dynamics in the anisotropy-axis aligned and
+randomly oriented SSG states.",1009.2610v1
+2010-09-18,Cascades and dissipation ratio in rotating MHD turbulence at low magnetic Prandtl number,"A phenomenology of isotropic magnetohydrodynamic turbulence subject to both
+rotation and applied magnetic field is presented. It is assumed that the triple
+correlations decay-time is the shortest between the eddy turn-over time and the
+ones associated to the rotating frequency and Alfv\'en wave period. For $Pm=1$
+it leads to four kinds of piecewise spectra, depending on the four parameters,
+injection rate of energy, magnetic diffusivity, rotation rate and applied
+field. With a shell model of MHD turbulence (including rotation and applied
+magnetic field), spectra for $Pm \le 1$ are presented, together with the ratio
+between magnetic and viscous dissipation.",1009.3549v2
+2010-10-08,Time-resolved detection of spin-transfer-driven ferromagnetic resonance and spin torque measurement in magnetic tunnel junctions,"Several experimental techniques have been introduced in recent years in
+attempts to measure spin transfer torque in magnetic tunnel junctions (MTJs).
+The dependence of spin torque on bias is important for understanding
+fundamental spin physics in magnetic devices and for applications. However,
+previous techniques have provided only indirect measures of the torque and
+their results to date for the bias dependence are qualitatively and
+quantitatively inconsistent. Here we demonstrate that spin torque in MTJs can
+be measured directly by using time-domain techniques to detect resonant
+magnetic precession in response to an oscillating spin torque. The technique is
+accurate in the high-bias regime relevant for applications, and because it
+detects directly small-angle linear-response magnetic dynamics caused by spin
+torque it is relatively immune to artifacts affecting competing techniques. At
+high bias we find that the spin torque vector differs markedly from the simple
+lowest-order Taylor series approximations commonly assumed.",1010.1777v1
+2010-10-24,Formation of Accretion Disks in Close-Binary Systems with Magnetic Fields,"We have developed a three-dimensional numerical model and applied it to
+simulate plasma flows in semi-detached binary systems whose accretor possesses
+a strong intrinsic magnetic field. The model is based on the assumption that
+the plasma dynamics are determined by the slow mean flow, which forms a
+backdrop for the rapid propagation of MHD waves. The equations describing the
+slow motion of matter were obtained by averaging over rapidly propagating
+pulsations. The numerical model includes the diffusion of magnetic field by
+current dissipation in turbulent vortices, magnetic buoyancy, and wave MHD
+turbulence. A modified three-dimensional, parallel, numerical code was used to
+simulate the flow structure in close binary systems with various accretor
+magnetic fields, from $10^5$ to $10^8$ G. The conditions for the formation of
+the accretion disk and the criteria distinguishing the two types of flow
+corresponding to intermediate polars and polars are discussed.",1010.4949v1
+2010-11-04,Spin polarization phenomena in dense neutron matter at a strong magnetic field,"Spin polarized states in neutron matter at strong magnetic fields up to
+$10^{18}$ G are considered in the model with the Skyrme effective interaction.
+Analyzing the self-consistent equations at zero temperature, it is shown that a
+thermodynamically stable branch of solutions for the spin polarization
+parameter as a function of density corresponds to the negative spin
+polarization when the majority of neutron spins are oriented oppositely to the
+direction of the magnetic field. Besides, it is found that in a strong magnetic
+field the state with the positive spin polarization can be realized as a
+metastable state at the high density region in neutron matter. At finite
+temperature, the entropy of the thermodynamically stable branch demonstrates
+the unusual behavior being larger than that for the nonpolarized state (at
+vanishing magnetic field) above certain critical density which is caused by the
+dependence of the entropy on the effective masses of neutrons in a spin
+polarized state.",1011.1244v1
+2010-11-25,Energy and system-size dependence of the Chiral Magnetic Effect,"The energy dependence of the local ${\cal P}$ and ${\cal CP}$ violation in
+Au+Au and Cu+Cu collisions in a large energy range is estimated within a simple
+phenomenological model. It is expected that at LHC the chiral magnetic effect
+will be about 20 times weaker than at RHIC. At lower energy range, covered by
+the low-energy scan at RHIC and future NICA/FAIR facilities, the created
+magnetic field strength and energy density of deconfined matter are rather high
+providing necessary conditions for the chiral magnetic effect. However, the
+particular model for the chiral magnetic effect predicts that this effect
+should vanish sharply at energy somewhere above the top SPS one. To elucidate
+CME background effects the Hadron-String-Dynamics (HSD) transport model
+including electromagnetic fields is put forward. Importance of new planning
+experiments at LHC and for the low-energy RHIC scan program is emphasized.",1011.5589v1
+2010-12-14,"Modeling the Galactic Magnetic Field using Rotation Measure Observations in the Galactic Disk from the CGPS, SGPS, and the VLA","Interstellar magnetic fields play critical roles in many astrophysical
+processes. Yet despite their importance, our knowledge about magnetic fields in
+our Galaxy remains limited. For the field within the Milky Way, much of what we
+do know comes from observations of polarisation and Faraday rotation measures
+(RMs) of extragalactic sources and pulsars. A high angular density of RM
+measurements in several critical areas of the Galaxy is needed to clarify the
+Galactic magnetic field structure. Using observations made with the VLA, we
+have determined RMs for sources in regions of the Galactic plane not covered by
+the Canadian Galactic Plane Survey (CGPS) and Southern Galactic Plane Survey
+(SGPS). We have combined these new RMs with those determined from the CGPS and
+SGPS and have produced a new model for the magnetic field of the Galactic disk.",1012.2936v1
+2011-01-17,Research into Orbital Motion Stability in System of Two Magnetically Interacting Bodies,"The stability of the orbital motion of two long cylindrical magnets
+interacting exclusively with magnetic forces is described. To carry out
+analytical studies a model of magnetically interacting symmetric tops [1] is
+used. The model was previously developed within the quasi-stationary approach
+for an electromagnetic field based on the general expression of the energy of
+interacting magnetic bodies [2]. A special role in the investigation of the
+stability of orbital motions is played by the so-called relative equilibria
+[3], i.e. the trajectories of the system dynamics which are at the same time
+one-parameter subgroups of the system invariance group. Nowadays their
+stability is normally investigated using two similar approaches --
+energy-momentum and energy-Casimir methods. The most suitable criterion for the
+system stability investigation was formulated in the theorem of [4]; this
+stability criterion successfully generalizes both the methods mentioned above
+and covers the Hamiltonian formalism based on Poisson structures [1]. The
+necessary and sufficient conditions for the circular orbit stability are
+derived from this theorem.",1101.3237v1
+2011-01-24,Detailed Analysis of Fan-Shaped jets in Three Dimensional Numerical Simulation,"We performed three dimensional resistive magnetohydrodynamic simulations to
+study the magnetic reconnection using an initially shearing magnetic field
+configuration (force free field with a current sheet in the middle of the
+computational box). It is shown that there are two types of reconnection jets:
+the ordinary reconnection jets and fan-shaped jets, which are formed along the
+guide magnetic field. The fan-shaped jets are much different from the ordinary
+reconnection jets which are ejected by magnetic tension force. There are two
+driving forces for accelerating the fan-shaped jets. The one is the Lorentz
+force which dominates the motion of fluid elements at first and then the gas
+pressure gradient force accelerates the fluid elements in the later stage. The
+dependence on magnetic reconnection angle and resistivity value has also been
+studied. The formation and evolution of these jets provide a new understanding
+of dynamic magnetohydrodynamic jets.",1101.4598v1
+2011-02-12,Electrical control of ferromagnetism in Mn-doped semiconductor heterostructures,"The interplay of tunneling transport and carrier-mediated ferromagnetism in
+narrow semiconductor multi-quantum well structures containing layers of GaMnAs
+is investigated within a self-consistent Green's function approach, accounting
+for disorder in the Mn--doped regions and unwanted spin-flips at
+heterointerfaces on phenomenological ground. We find that the magnetization in
+GaMnAs layers can be controlled by an external electric bias. The underlying
+mechanism is identified as spin-selective hole tunneling in and out of the
+Mn-doped quantum wells, whereby the applied bias determines both hole
+population and spin polarization in these layers. In particular we predict
+that, near resonance, ferromagnetic order in the Mn doped quantum wells is
+destroyed. The interplay of both magnetic and transport properties combined
+with structural design potentially leads to several interrelated physical
+phenomena, such as dynamic spin filtering, electrical control of magnetization
+in individual magnetic layers, and, under specific bias conditions, to
+self-sustained current and magnetization oscillations
+(magneticmulti-stability). Relevance to recent experimental results is
+discussed.",1102.2507v2
+2011-02-15,Non-equilibrium two-fluid plasmas can generate magnetic fields and flows simultaneously,"A new analytical solution of the set of highly nonlinear two-fluid equations
+is presented to explain the mechanism for the generation of ""seed"" magnetic
+field and plasma flow by assuming the density n to have a profile like an
+exponential in xy-plane and temperature profiles of electrons (ions) to be
+linear in yz-plane. {It is shown that the baroclinic vectors -
+$\nabla\Psi\times\nabla T_{j}$ (where $\Psi = ln\bar{n}, \bar{n}$ is normalized
+density, and $T_{j}$ denote the temperatures of electrons and ions for j = e,
+i) can generate not only the magnetic field but the plasma flow as well.} It is
+also pointed out that the electron magnetohydrodynamics (EMHD) model has
+inconsistencies because it does not take into account the ion dynamics while
+the magnetic field is produced on slow time scale. The estimate of the
+magnitude of the magnetic field in a classical laser plasma using this model is
+in agreement with the experimental observations.",1102.2968v1
+2011-02-25,Mechanism of magnetic field effect in cryptochrome,"Creatures as varied as mammals, fish, insects, reptiles, and migratory birds
+have an intriguing `sixth' sense that allows them to distinguish north from
+south by using the Earth's intrinsic magnetic field. Yet despite decades of
+study, the physical basis of this magnetic sense remains elusive. A likely
+mechanism is furnished by magnetically sensitive radical pair reactions
+occurring in the retina, the light-sensitive part of the eyes. A photoreceptor,
+cryptochrome, has been suggested to endow birds with magnetoreceptive abilities
+as the protein has been shown to exhibit the biophysical properties required
+for an animal magnetoreceptor to operate properly. Here, we propose a concrete
+light-driven reaction cycle in cryptochrome that lets a magnetic field
+influence the signaling state of the photoreceptor. The reaction cycle ties
+together transient absorption and electron-spin-resonance observations with
+known facts on avian magnetoreception. Our analysis establishes the feasibility
+of cryptochrome to act as a geomagnetic compass in birds, gives insight into
+structural and dynamic design features required for optimal detection of the
+geomagnetic field direction, and suggests further theoretical and experimental
+studies.",1102.5359v2
+2011-03-05,Injection and extraction magnets: septa,"An accelerator has limited dynamic range: a chain of accelerators is required
+to reach high energy. A combination of septa and kicker magnets is frequently
+used to inject and extract beam from each stage. The kicker magnets typically
+produce rectangular field pulses with fast rise- and/or fall-times, however the
+field strength is relatively low. To compensate for their relatively low field
+strength, the kicker magnets are generally combined with electromagnetic septa.
+The septa provide relatively strong field strength but are either DC or slow
+pulsed. This paper discusses injection and extraction systems with particular
+emphasis on the hardware required for the septa.",1103.1062v1
+2011-03-19,SDO Observations of Magnetic Reconnection at Coronal Hole Boundaries,"With the observations from the Atmospheric Imaging Assembly (AIA) and the
+Helioseismic and Magnetic Imager (HMI) aboard the \emph{Solar Dynamics
+Observatory}, we investigate the coronal hole boundaries (CHBs) of an
+equatorial extension of polar coronal hole. At the CHBs, lots of
+extreme-ultraviolet (EUV) jets, which appear to be the signatures of magnetic
+reconnection, are observed in the 193 {\AA} images, and some jets occur
+repetitively at the same sites. The evolution of the jets is associated with
+the emergence and cancelation of magnetic fields. We notice that both the east
+and the west CHBs shift westward, and the shift velocities are close to the
+velocities of rigid rotation compared with those of the photospheric
+differential rotation. This indicates that magnetic reconnection at CHBs
+results in the evolution of CHBs and maintains the rigid rotation of coronal
+holes.",1103.3751v1
+2011-03-26,Paraelectricity in Magnetized Massless QED,"We show that the chiral-symmetry-broken phase of massless QED in the presence
+of a magnetic field exhibits strong paraelectricity. A large anisotropic
+electric susceptibility develops in the infrared region, where most of the
+fermions are confined to their lowest Landau level, and dynamical mass and
+anomalous magnetic moment are generated via the magnetic catalysis mechanism.
+The nonperturbative nature of this effect is reflected in the dependence of the
+electric susceptibility on the fine-structure constant. The strong
+paraelectricity is linked to the electric dipole moments of the
+particle/anti-particle pairs that form the chiral condensate. The significant
+electric susceptibility can be used as a probe to detect the realization of the
+magnetic catalysis of chiral symmetry breaking in physical systems.",1103.5152v2
+2011-04-27,Coupled spin models for magnetic variation of planets and stars,"Geomagnetism is characterized by intermittent polarity reversals and rapid
+fluctuations. We have recently proposed a coupled macro-spin model to describe
+these dynamics based on the idea that the whole dynamo mechanism is described
+by the coherent interactions of many small dynamo elements. In this paper, we
+further develop this idea and construct a minimal model for magnetic
+variations. This simple model naturally yields many of the observed features of
+geomagnetism: its time evolution, the power spectrum, the frequency
+distribution of stable polarity periods, etc. This model has coexistent two
+phases; i.e. the cluster phase which determines the global dipole magnetic
+moment and the expanded phase which gives random perpetual perturbations that
+yield intermittent polarity flip of the dipole moment. This model can also
+describe the synchronization of the spin oscillation. This corresponds to the
+case of sun and the model well describes the quasi-regular cycles of the solar
+magnetism. Furthermore, by analyzing the relevant terms of MHD equation based
+on our model, we have obtained a scaling relation for the magnetism for
+planets, satellites, sun, and stars. Comparing it with various observations, we
+can estimate the scale of the macro-spins.",1104.5093v1
+2011-05-02,Chiral magnetic effect in lattice QCD with a chiral chemical potential,"We perform a first lattice QCD simulation including two-flavor dynamical
+fermion with a chiral chemical potential. Because the chiral chemical potential
+gives rise to no sign problem, we can exactly analyze a chirally imbalanced QCD
+matter by the Monte Carlo simulation. By applying an external magnetic field to
+this system, we obtain a finite induced current along the magnetic field, which
+corresponds to the chiral magnetic effect. The obtained induced current is
+proportional to the magnetic field and to the chiral chemical potential, which
+is consistent with an analytical prediction.",1105.0385v3
+2011-05-17,Magnetic Resonance Force Microscopy of paramagnetic electron spins at millikelvin temperatures,"Magnetic Resonance Force Microscopy (MRFM) is a powerful technique to detect
+a small number of spins that relies on force-detection by an ultrasoft
+magnetically tipped cantilever and selective magnetic resonance manipulation of
+the spins. MRFM would greatly benefit from ultralow temperature operation,
+because of lower thermomechanical noise and increased thermal spin
+polarization. Here, we demonstrate MRFM operation at temperatures as low as 30
+mK, thanks to a recently developed SQUID-based cantilever detection technique
+which avoids cantilever overheating. In our experiment, we detect dangling bond
+paramagnetic centers on a silicon surface down to millikelvin temperatures.
+Fluctuations of such kind of defects are supposedly linked to 1/f magnetic
+noise and decoherence in SQUIDs as well as in several superconducting and
+single spin qubits. We find evidence that spin diffusion plays a key role in
+the low temperature spin dynamics.",1105.3395v3
+2011-05-30,Dynamics of rising magnetized cavities and UHECR acceleration in clusters of galaxies,"We study the expansion of low density cavities produced by Active Galactic
+Nuclei jets in clusters of galaxies. The long term stability of these cavities
+requires the presence of linked magnetic fields. We find solutions describing
+the self-similar expansion of structures containing large-scale electromagnetic
+fields. Unlike the force-free spheromak-like configurations, these solutions
+have no surface currents and, thus, are less susceptible to resistive decay.
+The cavities are internally confined by external pressure, with zero gradient
+at the surface. If the adiabatic index of the plasma within the cavity is
+$\Gamma>4/3$, the expansion ultimately leads to the formation of large-scale
+current sheets. The resulting dissipation of the magnetic field can only
+partially offset the adiabatic and radiative losses of radio emitting
+electrons. We demonstrate that if the formation of large-scale current sheets
+is accompanied by explosive reconnection of the magnetic field, the resulting
+reconnection layer can accelerate cosmic rays to ultra high energies. We
+speculate that the enhanced flux of UHECRs towards Centaurus A originates at
+the cavities due to magnetic reconnection.",1105.6092v1
+2011-07-01,"High frequency magnetic behavior through the magnetoimpedance effect in CoFeB/(Ta, Ag, Cu) multilayered ferromagnetic thin films","We studied the dynamics of magnetization through an investigation of the
+magnetoimpedance effect in CoFeB/(Ta, Ag, Cu) multilayered thin films grown by
+magnetron sputtering. Impedance measurements were analyzed in terms of the
+mechanisms responsible for their variations at different frequency intervals
+and the magnetic and structural properties of the multilayers. Analysis of the
+mechanisms responsible for magnetoimpedance according to frequency and external
+magnetic field showed that for the CoFeB/Cu multilayer, ferromagnetic resonance
+(FMR) contributes significantly to the magnetoimpedance effect at frequencies
+close to 470 MHz. This frequency is low when compared to the results obtained
+for CoFeB/Ta and CoFeB/Ag multilayers and is a result of the anisotropy
+distribution and non-formation of regular bilayers in this sample. The MImax
+values occurred at different frequencies according to the used non-magnetic
+metal. Variations between 25% and 30% were seen for a localized frequency band,
+as in the case of CoFeB/Ta and CoFeB/Ag, as well as for a wide frequency range,
+in the case of CoFeB/Cu.",1107.0204v1
+2011-07-06,Cross-helicity effects and turbulent transport in magnetohydrodynamic flow,"In the presence of large-scale vortical motions and/or magnetic-field
+strains, the turbulent cross helicity (velocity--magnetic-field correlation in
+fluctuations) may contribute to the turbulent electromotive force and the
+Reynolds stress. These effects of cross helicity are considered to balance the
+primary effects of turbulence such as the turbulent magnetic diffusivity in
+magnetic-field evolution and the eddy viscosity in the momentum transport. The
+cross-helicity effects may suppress the enhanced transports due to turbulence.
+Physical interpretation of the effects is presented with special emphasis on
+the difference between the cross-helicity effect and the usual $\alpha$ or
+helicity effect in the dynamo action. The relative importance of the
+cross-helicity effect in dynamo action is validated with the aid of a direct
+numerical simulation (DNS) of the Kolmogorov flow with an imposed magnetic
+field. Several mechanisms that provide turbulence with the cross helicity are
+also discussed.",1107.1154v1
+2011-08-01,"Softening the ""crystal-scaffold"" for life's emergence","Del Giudice's group study how water can organize on hydrophilic surfaces
+forming coherent domains (loaning energy from the quantum vacuum), plus
+quasi-free electrons, whose excitations produce cold vortices, aligning to
+ambient fields. Their electric and magnetic dipolar modes can couple to
+oscillatory (electric-organic-dipoles), and/or rotary
+(magnetic-mineral-dipoles), besides responding to magnetic potentials. Thus,
+imprinted electromagnetic patterns of catalytic colloids - c.f. Cairns-Smith's
+""crystal-scaffold""- on their structured water partners could have equipped the
+latter with a selection-basis for 'choosing' their context-based ""soft-matter""
+(de Gennes) replacements. We consider the potential of the scenario of an
+external control on magnetic colloids forming in the Hadean hydrothermal
+setting (of Russell and coworkers) - via a magnetic-rock-field - conceptually
+enabling self-assembly, induction of asymmetries, response effects towards
+close-to-equilibrium dynamics, associative-networks, besides providing a
+coherent environment for stabilizing associated symmetry-broken quanta, and
+their feedback-interactions with those of coherent water-domains, to address
+the emergence of metabolism and replication.",1108.0309v2
+2011-08-04,Energy and Angular Momentum Storage in a Rotating Magnet,"We consider a cylindrical metallic magnet that is set into rotation about a
+horizontal axis by a falling mass. In such a system the magnetic field will
+cause a radial current which is non-solenoidal. This leads to charge
+accumulation and a partial attenuation of radial current. The magnetic field
+acting on the radially flowing current slows down the acceleration. Using
+newtonian dynamics we evaluate the angular velocity and displacement. We
+explicitly show that the electromagnetic angular momentum must be taken into
+consideration in order to account for the change in angular momentum due to the
+external torque on the system. Further the loss in potential energy of the
+falling mass can be accounted for only after taking into consideration the
+electrostatic energy and the Joule loss. We suggest that this example will be
+of pedagogical value to intermediate physics students. A version of this is
+scheduled to appear in American Journal of Physics 2011.
+  Keywords: Rotating magnet, Charge accumulation",1108.1231v1
+2011-08-31,Quantum impurity coupled to Majorana edge fermions,"We study a quantum impurity coupled to the edge states of a two-dimensional
+helical topological superconductor, i.e., to a pair of counterpropagating
+Majorana fermion edge channels with opposite spin polarizations. For an
+impurity described by the Anderson impurity model, we show that the problem
+maps onto a variant of the interacting resonant two-level model which, in turn,
+maps onto the ferromagnetic Kondo model. Both magnetic and non-magnetic
+impurities are considered. For magnetic impurities, the bosonization and
+numerical renormalization group analyses show that the system flows to a fixed
+point with residual ln 2 entropy and we find characteristically anisotropic
+static and dynamic impurity magnetic susceptibilities. For non-magnetic
+impurities, the system flows to a fixed point with no residual entropy and we
+find diamagnetic response at low temperatures. We comment on the
+Schrieffer-Wolff transformation for problems with non-standard conduction band
+continua and on the issues related to the differences in describing the
+impurities by either Anderson or Kondo impurity models.",1108.6142v2
+2011-09-06,Detection of negative effective magnetic pressure instability in turbulence simulations,"We present the first demonstration of the negative effective magnetic
+pressure instability in direct numerical simulations of stably stratified,
+externally forced, isothermal hydromagnetic turbulence in the regime of large
+plasma beta. By the action of this instability, an initially uniform horizontal
+magnetic field forms flux concentrations whose scale is large compared to the
+turbulent scale. We further show that the magnetic energy of these large-scale
+structures is only weakly dependent on the magnetic Reynolds number, provided
+its value is large enough for the instability to be excited. Our results
+support earlier mean-field calculations and analytic work which identified this
+instability. Applications to the formation of active regions in the Sun are
+discussed.",1109.1270v3
+2011-09-13,Interplay between non equilibrium and equilibrium spin torque using synthetic ferrimagnets,"We discuss the current induced magnetization dynamics of spin valves F0|N|SyF
+where the free layer is a synthetic ferrimagnet SyF made of two ferromagnetic
+layers F1 and F2 coupled by RKKY exchange coupling. In the interesting
+situation where the magnetic moment of the outer layer F2 dominates the
+magnetization of the ferrimagnet, we find that the sign of the effective spin
+torque exerted on the free middle layer F1 is controlled by the strength of the
+RKKY coupling: for weak coupling one recovers the usual situation where spin
+torque tends to, say, anti-align the magnetization of F1 with respect to the
+pinned layer F0. However for large coupling the situation is reversed and the
+spin torque tends to align F1 with respect to F0. Careful numerical simulations
+in the intermediate coupling regime reveal that the competition between these
+two incompatible limits leads generically to spin torque oscillator (STO)
+behavior. The STO is found in the absence of magnetic field, with very
+significant amplitude of oscillations and frequencies up to 50 GHz or higher.",1109.2705v2
+2011-09-19,Axial dipolar dynamo action in the Taylor-Green vortex,"We present a numerical study of the magnetic field generated by the
+Taylor-Green vortex. We show that periodic boundary conditions can be used to
+mimic realistic boundary conditions by prescribing the symmetries of the
+velocity and magnetic fields. This gives insight in some problems of central
+interest for dynamos: the possible effect of velocity fluctuations on the
+dynamo threshold, the role of boundary conditions on the threshold and on the
+geometry of the magnetic field generated by dynamo action. In particular, we
+show that an axial dipolar dynamo similar to the one observed in a recent
+experiment can be obtained with an appropriate choice of the symmetries of the
+magnetic field. The nonlinear saturation is studied and a simple model
+explaining the magnetic Prandtl number dependence of the super/sub critical
+nature of the dynamo transition is given.",1109.4063v2
+2011-09-22,Universal characteristics of ion-acoustic wave dynamics in magnetized plasmas with emphasis on Tsallis distribution,"Using the extended Poincar\'{e}-Lighthill-Kuo (PLK) reductive perturbation
+method, which incorporates the phase-shift variations, it is shown that common
+features on propagation and head-on collisions of ion-acoustic waves exist for
+a magnetized plasmas of different inertial-less particle distributions. For
+instance it is remarked that, the soliton amplitude is always independent of
+magnetic field strength while strictly depends on its angle regarding the
+propagation direction. Both types of solitons (compressive or rarefactive) are
+shown to exist which are defined through the critical angle $\gamma=\pi/2$ or
+other critical values depending on plasma fractional parameters. These critical
+plasma parameter values also define the sign of head-on collision phase shift.
+Furthermore, it is proved that for a given set of plasma parameters there is
+always a relative angle of propagation regarding to that of the magnetic-field
+for which the soliton width is maximum. Current findings applies to a wide
+range of magnetized plasmas including those containing background dust
+ingredients or two-temperature inertial-less particles and may be used to study
+laboratory or astrophysical magnetoplasmas.",1109.4746v1
+2011-09-24,Interaction of a highly magnetized impulsive relativistic flow with an external medium,"Important astrophysical sources, such as gamma-ray bursts (GRBs) or tidal
+disruption events, are impulsive -- strongly varying with time. These outflows
+are likely highly magnetized near the central source, but their interaction
+with the external medium is not yet fully understood. Here I consider the
+combined impulsive magnetic acceleration of an initially highly magnetized
+shell of plasma and its deceleration by the external medium. I find four main
+dynamical regimes, that (for a given outflow) depend on the external density.
+(I) For small enough external densities the shell becomes kinetically dominated
+before it is significantly decelerated, thus reverting to the familiar
+unmagnetized ""thin shell"" case, which produces bright reverse shock emission
+that peaks well after the prompt GRB. (II) For larger external densities the
+shell remains highly magnetized and the reverse shock is strongly suppressed.
+It eventually transfers most of its energy through pdV work to the shocked
+external medium, whose afterglow emission peaks on a timescale similar to the
+prompt GRB duration. (III) For even larger external densities there is no
+initial impulsive acceleration phase. (IV) For the highest external densities
+the flow remains Newtonian.",1109.5314v2
+2011-10-16,Spin Torque in Anisotropic Tunneling Junctions,"Spin transport in magnetic tunnel junctions comprising a single magnetic
+layer in the presence of interfacial spin-orbit interaction (SOI) is
+investigated theoretically. Due to the presence of interfacial SOI, a
+current-driven spin torque can be generated at the second order in SOI, even in
+the absence of an external spin polarizer. This torque possesses two
+components, in-plane and perpendicular to the plane of rotation, that can
+induce either current-driven {\em magnetization switching} from in-plane to
+out-of-plane configuration or {\em magnetization precessions}, similarly to
+Spin Transfer Torque in spin-valves. Consequently, it appears that it is
+possible to control the magnetization steady state and dynamics by either
+varying the bias voltage or electrically modifying the SOI at the interface.",1110.3488v1
+2011-11-04,Magnetospheres of massive stars across the EM spectrum,"Magnetic massive stars -- which are being discovered with increasing
+frequency -- represent a new category of wind-shaping mechanism for O and B
+stars. Magnetic channeling of these stars' radiation-driven winds, the
+Magnetically Confined Wind Shock paradigm, leads to the formation of a
+shock-heated magnetosphere, which can radiate X-rays, modify UV resonance
+lines, and create disks of Halpha emitting material. The dynamical properties
+of these magnetospheres are well understood from a theoretical point of view as
+an interplay between the magnetic wind confinement and rotation. However, the
+manifestations of magnetospheres across the spectrum may be more complex and
+various than first anticipated. On the other hand, recent advances in modeling
+these magnetospheres provide a key to better understand massive star winds in
+general. We will summarize the coordinated observational, theoretical, and
+modeling efforts from the Magnetism in Massive Star Project, addressing key
+outstanding questions regarding magnetosphere manifestations across the
+spectral domain.",1111.1238v1
+2011-12-01,Dangling bonds and magnetism of grain boundaries in graphene,"Grain boundaries with dangling bonds (DBGB) in graphene are studied by
+atomistic Monte Carlo and molecular dynamics simulations in combination with
+density functional (SIESTA) calculations. The most stable configurations are
+selected and their structure is analyzed in terms of grain boundary
+dislocations. It is shown that the grain boundary dislocation with the core
+consisting of pentagon, octagon and heptagon (5-8-7 defect) is a typical
+structural element of DBGB with relatively low energies. Electron energy
+spectrum and magnetic properties of the obtained DBGB are studied by density
+functional calculations. It is shown that the 5-8-7 defect is magnetic and that
+its magnetic moment survives after hydrogenation. The effects of hydrogenation
+and of out of plane deformations on the magnetic properties of DBGB are
+studied.",1112.0160v2
+2011-12-05,Magnetic anisotropy of elongated thin ferromagnetic nano-islands for artifical spin ice arrays,"The energetics of thin elongated ferromagnetic nano-islands is considered for
+some different shapes, aspect ratios, and applied magnetic field directions.
+These nano-island particles are important for artificial spin-ice materials.
+For low temperature, the magnetic internal energy of an individual particle is
+evaluated numerically as a function of the direction of a particle's net
+magnetization. This leads to estimations of effective anisotropy constants for
+(1) the easy axis along the particle's long direction, and (2) the hard axis
+along the particle's thin direction. A spin relaxation algorithm together with
+fast Fourier transform for the demagnetization field is used to solve the
+micromagnetics problem for a thin system. The magnetic hysteresis is also
+found. The results indicate some possibilities for controlling the equilibrium
+and dynamics in spin-ice materials by using different island geometries.",1112.0913v2
+2011-12-08,Magnetic fields and gas flows around circumnuclear starbursts,"Radio continuum observations of barred galaxies revealed strong magnetic
+fields of >= 50-100 muG in the circumnuclear starbursts. Such fields are
+dynamically important and give rise to magnetic stress that causes inflow of
+gas towards the center at a rate of several solar masses per year, possibly
+along the spiral field seen in radio polarization and as optical dust lanes.
+This may solve the long-standing question of how to feed active nuclei, and
+explain the relation between the bolometric luminosity of AGN nuclei and the
+star-formation rate of their hosts. The strong magnetic fields generated in
+young galaxies may serve as the link between star formation and accretion onto
+supermassive black holes. -- Magnetic fields of >= 160 muG strength were
+measured in the central region of the almost edge-on starburst galaxy NGC 253.
+Four filaments emerging from the inner disk delineate the boundaries of the
+central outflow cone of hot gas. Strong Faraday rotation of the polarized
+emission from the background disk indicates a large-scale helical field in the
+outflow walls.",1112.1823v1
+2011-12-12,Magnetic and Kinetic Power Spectra as a Tool to Probe the Turbulent Dynamo,"Generation and diffusion of the magnetic field on the Sun is a key mechanism
+responsible for solar activity on all spatial and temporal scales - from the
+solar cycle down to the evolution of small-scale magnetic elements in the quiet
+Sun. The solar dynamo operates as a non-linear dynamical process and is thought
+to be manifest in two types: as a global dynamo responsible for the solar cycle
+periodicity, and as a small-scale turbulent dynamo responsible for the
+formation of magnetic carpet in the quiet Sun. Numerous MHD simulations of the
+solar turbulence did not yet reach a consensus as to the existence of a
+turbulent dynamo on the Sun. At the same time, high-resolution observations of
+the quiet Sun from Hinode instruments suggest possibilities for the turbulent
+dynamo. Analysis of characteristics of turbulence derived from observations
+would be beneficial in tackling the problem. We analyse magnetic and velocity
+energy spectra as derived from Hinode/SOT, SOHO/MDI, SDO/HMI and the New Solar
+Telescope (NST) of Big Bear Solar Observatory (BBSO) to explore the
+possibilities for the small-scale turbulent dynamo in the quiet Sun.",1112.2750v1
+2011-12-20,In-plane magnetic anisotropy of Fe atoms on Bi$_2$Se$_3$(111),"The robustness of the gapless topological surface state hosted by a 3D
+topological insulator against perturbations of magnetic origin has been the
+focus of recent investigations. We present a comprehensive study of the
+magnetic properties of Fe impurities on a prototypical 3D topological insulator
+Bi$_2$Se$_3$ using local low temperature scanning tunneling microscopy and
+integral x-ray magnetic circular dichroism techniques. Single Fe adatoms on the
+Bi$_2$Se$_3$ surface, in the coverage range $\approx 1%$ are heavily relaxed
+into the surface and exhibit a magnetic easy axis within the surface-plane,
+contrary to what was assumed in recent investigations on the opening of a gap.
+Using \textit{ab initio} approaches, we demonstrate that an in-plane easy axis
+arises from the combination of the crystal field and dynamic hybridization
+effects.",1112.4621v2
+2011-12-23,Temperature gradient assisted magnetodynamics in a ferromagnetic nanowire,"The dynamics of the low energy excitations in a ferromagnet is studied in
+case a temperature gradient is coupled to the local magnetization. Due to the
+different time scales of changing temperature and magnetization it is argued
+that only the coupling between the spatially varying part of the temperature
+field and the magnetization is relevant. Using variational principles the
+evolution equation for the magnetic system is found which is strongly
+influenced by the local temperature profile. The system offers damped spin wave
+excitations where the strength of damping is determined by the magneto-thermal
+coupling. Applying the model to nanowires it is demonstrated that the energy
+spectrum is significantly affected by the boundary conditions as well as the
+initial temperature distribution. In particular, the coupling between
+temperature and magnetization is expected to be several orders stronger for the
+open as for the isolated wire.",1112.5562v1
+2012-01-02,Localized domain-wall excitations in patterned magnetic dots probed by broadband ferromagnetic resonance,"We investigate the magnetization dynamics in circular Permalloy dots with
+spatially separated magnetic vortices interconnected by domain walls (double
+vortex state). We identify a novel type of quasi one-dimensional (1D) localised
+spin wave modes confined along domain walls, connecting each of two vortex
+cores with two edge half-antivortices. Variation of the mode eigenfrequencies
+with the dot size is in quantitative agreement with the developed model, which
+considers a dipolar origin of the localized 1D spin waves or so-called
+Winter\'s magnons [J.M. Winter, Phys.Rev. 124, 452 (1961)]. These spin waves
+are analogous to the displacement waves of strings, and could be excited in a
+wide class of patterned magnetic nanostructures possessing domain walls, namely
+in triangular, square, circular or elliptic magnetic dots.",1201.0482v1
+2012-01-09,"""Skew"" scattering of cold unpolarized neutrons in ferromagnetic crystal","The problem of neutron scattering by the single magnetic atom is
+theoretically considered in the second order perturbation theory. It is
+demonstrated that elastic scattering of unpolarized neutron by magnetic atom is
+skewed, i.e. contains the term with the symmetry of mixed product of the atom
+magnetic moment and wave vectors of incident and scattered neutrons. The
+problem of dynamical diffraction of unpolarized neutrons by the perfect
+ferromagnetic crystal is investigated. The case is considered when the Bragg
+condition is satisfied for two reciprocal lattice vectors. In this case neutron
+skew scattering manifests itself as the dependence of the diffracted beam
+intensity on the sign of the crystal magnetization. The calculations have been
+done for the diffraction of unpolarized neutrons by Dy crystal. In case of the
+diffraction by Dy the change of the intensity under the magnetization reversal
+achieves 50%.",1201.1758v2
+2012-01-27,Fermi Surface Reconstruction by Dynamic Magnetic Fluctuations,"We demonstrate that nearly critical quantum magnetic fluctuations in strongly
+correlated electron systems can change the Fermi surface topology and also lead
+to spin charge separation (SCS) in two dimensions. To demonstrate these effects
+we consider a small number of holes injected into the bilayer antiferromagnet.
+The system has a quantum critical point (QCP) which separates magnetically
+ordered and disordered phases. We demonstrate that in the physically
+interesting regime there is a magnetically driven Lifshitz point (LP) inside
+the magnetically disordered phase. At the LP the topology of the hole Fermi
+surface is changed. We also demonstrate that in this regime the hole spin and
+charge necessarily separate when approaching the QCP. The considered model
+sheds light on generic problems concerning the physics of the cuprates.",1201.5700v2
+2012-02-10,A model of magnetic order in hexagonal HoMnO3,"Symmetry arguments are used to develop a spin Hamiltonian for the description
+of the complex magnetic ordering in HoMnO$_3$. Using a novel application of the
+Landau Lifshitz Gilbert dynamic torque equations to this model of the
+frustrated Mn ions on an $AB$ stacked triangular antiferromagnetic, it is shown
+that the four principal spin configurations observed in this compound are
+stabilized. Ho-Mn coupling is found to be a consequence of an unusual trigonal
+anisotropy term which is responsible for simultaneous Mn spin reorientation and
+onset of Ho magnetic order. Based on these microscopic considerations, a
+mean-field Landau-type free energy is derived which reproduces the succession
+of observed temperature driven magnetic phase transitions at zero field,
+including re-entrant behavior. In addition, our analysis suggests that the
+basal-plane magnetic order should be slightly incommensurate with the lattice.",1202.2321v1
+2012-02-10,Conceptual designs of dipole magnet for muon collider ring,"Conceptual designs of a superconducting dipole magnet for a Storage Ring of a
+Muon Collider with a 1.5 TeV center of mass (c.o.m.) energy and an average
+luminosity of 10 34 cm-2s-1 are presented. In contrast to proton machines, the
+dipoles for the Muon Collider should be able to handle ~0.5 kW/m of dynamic
+heat load from the muon beam decays. The magnets are based on Nb3Sn
+superconductor and designed to provide an operating field of 10 T in the 20-mm
+aperture with the critical current margin required for reliable machine
+operation. The magnet cross-sections were optimized to achieve the best
+possible field quality in the aperture occupied by beams. The developed
+mechanical structures provide adequate coil prestress and support at the
+maximum level of Lorentz forces in the coil. Magnet parameters are reported and
+compared with the requirements.",1202.2380v1
+2012-03-02,Investigation of Optical Spin Transfer Torque in Ferromagnetic Semiconductor GaMnAs by Magneto-Optical Pump-and-Probe Method,"We report on magnetization precession induced in (Ga,Mn)As by an optical spin
+transfer torque (OSTT). This phenomenon, which corresponds to a transfer of
+angular momentum from optically-injected spin-polarized electrons to
+magnetization, was predicted theoretically in 2004 and observed experimentally
+by our group in 2012. In this paper we provide experimental details about the
+observation of OSTT by a time-resolved pump-and-probe magneto-optical
+technique. In particular, we show that the precession of magnetization due to
+OSTT can be experimentally separated from that induced by the well known
+magnetic-anisotropy-related mechanism in a hybrid structure
+piezo-stressor/(Ga,Mn)As with an in situ electrical control of the magnetic
+anisotropy. We also illustrate that OSTT is clearly apparent in the measured
+dynamical magneto-optical signal in a large variety of (Ga,Mn)As samples with a
+Mn concentration from 3% to 9%.",1203.0483v1
+2012-03-07,Photon Self-Energy and Electric Susceptibility in a Magnetized Three-flavor Color Superconductor,"We study the photon self-energy for the in-medium photon in a three-flavor
+color superconductor in the presence of a magnetic field. At strong magnetic
+field, the quark dynamics becomes $(1+1)$-dimensional and the self-energy
+tensor only has longitudinal components. In this approximation there is no
+Debye or Meissner screenings at zero temperature, but the electric
+susceptibility is nonzero and highly anisotropic. In the direction transverse
+to the applied field, the electric susceptibility is the same as in vacuum,
+while in the longitudinal direction it depends on the magnitude of the magnetic
+field. Such a behavior is a realization in cold-dense QCD of the
+magnetoelectric effect, which was first discovered in condensed matter physics.
+The magnetic permeability remains equal to that in vacuum for both transverse
+and longitudinal components. We discuss the importance of the Pauli-Villars
+regularization to get meaningful physical results in the infrared limit of the
+polarization operator. We also find the covariant form of the polarization
+operator in the reduced (1+1)-D space of the lowest Landau level and proves its
+transversality.",1203.1630v1
+2012-03-20,Magnetic catalysis in hot and dense quark matter and quantum fluctuations,"We analyze chiral symmetry breaking in quark matter in an external magnetic
+field at zero and finite temperature and quark chemical potential. We first
+give a brief overview of analytic results within the mean-field approximation.
+There the critical temperature for chiral restoration is increased by the
+magnetic field effect. Then we investigate the effects of matter and quantum
+fluctuations on the Magnetic Catalysis. More specifically, we compute the
+critical coupling as a function of the magnetic field and the temperature for
+zero and finite quark chemical potential in the presence of quantum
+fluctuations. As soon as a non-zero temperature and/or density is turned on,
+long-range correlations are screened and the critical coupling is no longer
+vanishing. We extend our dynamical results beyond the leading-order bubble
+resummation which results in a non-local four-Fermi coupling. This includes
+in-medium meson effects on the more quantitative level.",1203.4330v1
+2012-04-12,Evidence for an exotic magnetic transition in the triangular spin system FeGa2S4,"We report positive muon spin relaxation measurements on the triangular
+lattice magnetic system FeGa2S4. A magnetic transition not previously detected
+by specific heat and magnetic susceptibility measurements is found in zero
+field at T^* \simeq 30 K. It is observed through the temperature dependencies
+of the signal amplitude and the spin-lattice relaxation rate. This transition
+is therefore not a conventional magnetic phase transition. Since persistent
+spin dynamics is observed down to 0.1 K, the ground state cannot be of the
+canonical spin-glass type, which could be suggested from hysteresis effects in
+the bulk susceptibility below T_f \simeq 16 K. These results are compared to
+those found for the isomorph NiGa2S4. It is argued that the fate of the
+transition, which has been interpreted in terms of the Z_2 topological
+transition in this latter system, is probably different in FeGa2S4.",1204.2739v1
+2012-05-02,Heavy-Fermion Instability in Double-Degenerate Plasmas,"In this work we study the propagations of normal frequency modes for quantum
+hydrodynamic (QHD) waves in the linear limit and introduce a new kind of
+instability in a double-degenerate plasma. Three different regimes, namely,
+low, intermediate and high magnetic field strengths are considered which span
+the applicability of the work to a wide variety of environments. Distinct
+behavior is observed for different regimes, for instance, in the
+laboratory-scale field regime no frequency-mode instability occurs unlike those
+of intermediate and high magnetic-field strength regimes. It is also found that
+the instability of this kind is due to the heavy-fermions which appear below a
+critical effective-mass parameter ($\mu_{cr}=\sqrt{3}$) and that the responses
+of the two (lower and upper frequency) modes to fractional effective-mass
+change in different effective-mass parameter ranges (below and above the
+critical value) are quite opposite to each other. It is shown that, the
+heavy-fermion instability due to extremely high magnetic field such as that
+encountered for a neutron-star crust can lead to confinement of stable
+propagations in both lower and upper frequency modes to the magnetic poles.
+Current study can have important implications for linear wave dynamics in both
+laboratory and astrophysical environments possessing high magnetic fields.",1205.0566v1
+2012-05-16,Exact Nonlinear Excitations in Double-Degenerate Plasmas,"In this work we use the conventional hydrodynamics (HD) formalism and
+incorporate the Chew-Goldberger-Low (CGL) double-adiabatic theory to evaluate
+the nonlinear electrostatic ion excitations in double-degenerate (electron
+spin-orbit degenerate) magnetized quantum plasmas. Based on the Sagdeev
+pseudopotential method an exact general pseudopotential is calculated which
+leads to the allowed Mach-number range criteria for such localized density
+structures in an anisotropic magnetized plasma. We employ the criteria on the
+Mach-number range for diverse magnetized quantums plasma with different
+equations of state (EoS). It is remarked that various plasma fractional
+parameters such as the system dimensionality, ion-temperature,
+relativistic-degeneracy, Zeeman-energy, and plasma composition are involved in
+the stability of an obliquely propagating nonlinear ion-acoustic wave in a
+double-degenerate quantum plasma. Current study is most appropriate for
+nonlinear wave analysis in the dense astrophysical magnetized plasma
+environments such as white-dwarfs and neutron-star crusts where the strong
+magnetic fields can be present.",1205.3818v1
+2012-06-09,Spin-Electromagnetic Hydrodynamics and Magnetization Induced by Spin-Magnetic Interaction,"The hydrodynamic model including the spin degree of freedom and the
+electromagnetic field was discussed. In this derivation, we applied
+electromagnetism for macroscopic medium proposed by Minkowski. For the equation
+of motion of spin, we assumed that the hydrodynamic representation of the Pauli
+equation is reproduced when the many-body effect is neglected. Then the
+spin-magnetic interaction in the Pauli equation was converted to a part of the
+magnetization. The fluid and spin stress tensors induced by the many-body
+effect were obtained by employing the algebraic positivity of the entropy
+production in the framework of the linear irreversible thermodynamics,
+including the mixing effect of the irreversible currents. We further
+constructed the constitutive equation of the polarization and the
+magnetization. Our polarization equation is more reasonable compared to another
+result obtained using electromagnetism for macroscopic medium proposed by de
+Groot-Mazur.",1206.1976v3
+2012-06-11,Enhanced Dissipation Rate of Magnetic Field in Striped Pulsar Winds by the Effect of Turbulence,"In this letter we report on turbulent acceleration of the dissipation of
+magnetic field in the postshock re- gion of a Poynting flux-dominated flow,
+such as the Crab pulsar wind nebula. We have performed two- dimensional
+resistive relativistic magnetohydrodynamics simulations of subsonic turbulence
+driven by the Richtmyer-Meshkov instability at the shock fronts of the Poynting
+flux-dominated flows in pulsar winds. We find that turbulence stretches current
+sheets which substantially enhances the dissipation of magnetic field, and that
+most of the initial magnetic field energy is dissipated within a few
+eddy-turnover times. We also develop a simple analytical model for turbulent
+dissipation of magnetic field that agrees well with our simulations. The
+analytical model indicates that the dissipation rate does not depend on
+resistivity even in the small resistivity limit. Our findings can possibly
+alleviate the {\sigma}-problem in the Crab pulsar wind nebulae.",1206.2087v1
+2012-06-25,A mechanism to pin skyrmions in chiral magnets,"We propose a mechanism to pin skyrmions in chiral magnets by introducing
+local maximum of magnetic exchange strength, which can be realized in chiral
+magnetic thin films by engineering the local density of itinerate electrons.
+Thus we find a way to artificially control the position of a single skyrmion in
+chiral magnetic thin films. The stationary properties and the dynamical pinning
+and depinning processes of an isolated skyrmion around a pinning center are
+studied. We do a series of simulations to show that the critical current to
+depin a skyrmion has linearly dependence on the pinning strength. We also
+estimate the critical current to have order of magnitude
+10^{7}\sim10^{8}A/m^{2} .",1206.5661v1
+2012-08-31,"Influence of Mg, Ag and Al substitutions on the magnetic excitations in the triangular-lattice antiferromagnet CuCrO2","Magnetic excitations in CuCrO$_{2}$, CuCr$_{0.97}$Mg$_{0.03}$O$_{2}$,
+Cu$_{0.85}$Ag$_{0.15}$CrO$_{2}$, and CuCr$_{0.85}$Al$_{0.15}$O$_{2}$ have been
+studied by powder inelastic neutron scattering to elucidate the element
+substitution effects on the spin dynamics in the Heisenberg triangular-lattice
+antiferromagnet CuCrO$_{2}$. The magnetic excitations in
+CuCr$_{0.97}$Mg$_{0.03}$O$_{2}$ consist of a dispersive component and a flat
+component. Though this feature is apparently similar to CuCrO$_{2}$, the energy
+structure of the excitation spectrum shows some difference from that in
+CuCrO$_{2}$. On the other hand, in Cu$_{0.85}$Ag$_{0.15}$CrO$_{2}$ and
+CuCr$_{0.85}$Al$_{0.15}$O$_{2}$ the flat components are much reduced, the
+low-energy parts of the excitation spectra become intense, and additional
+low-energy diffusive spin fluctuations are induced. We argued the origins of
+these changes in the magnetic excitations are ascribed to effects of the doped
+holes or change of the dimensionality in the magnetic correlations.",1208.6353v1
+2012-09-24,Transport blocking and topological phases using ac magnetic fields,"We analyze electron dynamics and topological properties of open double
+quantum dots (DQDs) driven by circularly polarized ac-magnetic fields. In
+particular we focus on the system symmetries which can be tuned by the
+ac-magnetic field. Remarkably, we show that in the electron spin resonance
+(ESR) configuration, where the magnetic fields in each dot oscillate with a
+phase difference of $\pi$, charge localization occurs giving rise to transport
+blocking at arbitrary intensities of the ac field. The conditions for charge
+localization are obtained by means of Floquet theory and related with
+quasienergies degeneracy. We also demonstrate that a topological phase
+transition can be induced in the adiabatic regime for a phase difference of
+$\pi$, either by tuning the coupling between dots or by modifying the intensity
+of the driving magnetic field.",1209.5301v1
+2012-10-08,Inelastic magnetic scattering effect on LDOS of topological insulators,"Magnetic ions such as Fe, Mn and Co with localized spins may be adsorbed on
+the surface of topological insulators like \Bi. They form scattering centers
+for the helical surface states which have a Dirac cone dispersion as long as
+the local spins are disordered. However, the local density of states (LDOS) may
+be severely modified by the formation of bound states. Commonly only elastic
+scattering due to normal and exchange potentials of the adatom is assumed.
+Magnetization measurements show, however, that considerable magnetic single ion
+anisotropies exist which lead to a splitting of the local impurity spin states
+resulting in a singlet ground state. Therefore inelastic scattering processes
+of helical Dirac electrons become possible as described by a dynamical local
+self energy of second order in the exchange interaction. The self energy
+influences bound state formation and leads to significant new anomalies in the
+LDOS at low energies and low temperatures which we calculate within T-matrix
+approach. We propose that they may be used for spectroscopy of local impurity
+spin states by appropriate tuning of chemical potential and magnetic field.",1210.2222v2
+2012-10-10,On the magnetic quenching of mean-field effects in supersonic interstellar turbulence,"The emergence of large-scale magnetic fields observed in the diffuse
+interstellar medium is explained by a turbulent dynamo. The underlying
+transport coefficients have previously been extracted from numerical
+simulations. So far, this was restricted to the kinematic regime, but we aim to
+extend our analysis into the realm of dynamically important fields. This marks
+an important step on which derived mean-field models rely to explain observed
+equipartition strength fields. As in previous work, we diagnose turbulent
+transport coefficients by means of the test-field method. We derive quenching
+functions for the dynamo {\alpha} effect, diamagnetic pumping, and turbulent
+diffusivity, which are compared with theoretical expectations. At late times,
+we observe the suppression of the vertical wind. Because this potentially
+affects the removal of small-scale magnetic helicity, new concerns arise about
+circumventing constraints imposed by the conservation of magnetic helicity at
+high magnetic Reynolds numbers. While present results cannot safely rule out
+this possibility, the issue only becomes important at late stages and is absent
+when the dynamo is quenched by the wind itself.",1210.2928v1
+2012-10-24,Coherent structures and the saturation of a nonlinear dynamo,"Eulerian and Lagrangian tools are used to detect coherent structures in the
+velocity and magnetic fields of a mean--field dynamo, produced by direct
+numerical simulations of the three--dimensional compressible
+magnetohydrodynamic equations with an isotropic helical forcing and moderate
+Reynolds number. Two distinct stages of the dynamo are studied, the kinematic
+stage, where a seed magnetic field undergoes exponential growth, and the
+saturated regime. It is shown that the Lagrangian analysis detects structures
+with greater detail, besides providing information on the chaotic mixing
+properties of the flow and the magnetic fields. The traditional way of
+detecting Lagrangian coherent structures using finite--time Lyapunov exponents
+is compared with a recently developed method called function M. The latter is
+shown to produce clearer pictures which readily permit the identification of
+hyperbolic regions in the magnetic field, where chaotic transport/dispersion of
+magnetic field lines is highly enhanced.",1210.6637v1
+2012-11-19,Symmetry breaking for ratchet transport in presence of interactions and magnetic field,"We study the microwave induced ratchet transport of two-dimensional electrons
+on an oriented semidisk Galton board. The magnetic field symmetries of ratchet
+transport are analyzed in presence of electron-electron interactions. Our
+results show that a magnetic field asymmetric ratchet current can appear due to
+two contributions, a Hall drift of the rectified current that depends only
+weakly on electron-electron interactions and a breaking of the time reversal
+symmetry due to the combined effects of interactions and magnetic field. In the
+latter case, the asymmetry between positive and negative magnetic fields
+vanishes in the weak interaction limit. We also discuss the recent experimental
+results on ratchet transport in asymmetric nanostructures.",1211.4411v1
+2012-11-22,Gravity induced evolution of a magnetized fermion gas with finite temperature,"We examine the near collapse dynamics of a self-gravitating magnetized
+electron gas at finite temperature, taken as the source of a Bianchi-I
+spacetime described by the Kasner metric. The set of Einstein-Maxwell field
+equations reduces to a complete and self-consistent system of non-linear
+autonomous ODE's. By considering a representative set of initial conditions,
+the numerical solutions of this system show the gas collapsing into both,
+isotropic (""point--like"") and anisotropic (""cigar-like"") singularities,
+depending on the intensity of the magnetic field. We also examined the behavior
+during the collapse stage of all relevant state and kinematic variables: the
+temperature, the expansion scalar, the magnetic field, the magnetization and
+energy density. We notice a significant qualitative difference in the behavior
+of the gas for a range of temperatures between the values
+$\hbox{T}\sim10^{3}\hbox{K}$ and $\hbox{T}\sim 10^{7}\hbox{K}$.",1211.5980v1
+2012-11-28,Cosmic-ray-induced filamentation instability in collisionless shocks,"We used unprecedentedly large 2D and 3D hybrid (kinetic ions - fluid
+electrons) simulations of non-relativistic collisionless strong shocks in order
+to investigate the effects of self-consistently accelerated ions on the overall
+shock dynamics. The current driven by suprathermal particles streaming ahead of
+the shock excites modes transverse to the background magnetic field. The
+Lorentz force induced by these self-amplified fields tends to excavate tubular,
+underdense, magnetic-field-depleted cavities that are advected with the fluid
+and perturb the shock surface, triggering downstream turbulent motions. These
+motions further amplify the magnetic field, up to factors of 50-100 in
+knot-like structures. Once downstream, the cavities tend to be filled by hot
+plasma plumes that compress and stretch the magnetic fields in elongated
+filaments; this effect is particularly evident if the shock propagates parallel
+to the background field. Highly-magnetized knots and filaments may provide
+explanations for the rapid X-ray variability observed in RX J1713.7-3946 and
+for the regular pattern of X-ray bright stripes detected in Tycho's supernova
+remnant.",1211.6765v2
+2012-11-30,Sensitive Magnetic Control of Ensemble Nuclear Spin Hyperpolarisation in Diamond,"Dynamic nuclear polarisation, which transfers the spin polarisation of
+electrons to nuclei, is routinely applied to enhance the sensitivity of nuclear
+magnetic resonance; it is also critical in spintronics, particularly when spin
+hyperpolarisation can be produced and controlled optically or electrically.
+Here we show the complete polarisation of nuclei located near the
+optically-polarised nitrogen-vacancy (NV) centre in diamond. When approaching
+the ground-state level anti-crossing condition of the NV electron spins, 13C
+nuclei in the first-shell are polarised in a pattern that depends sensitively
+and sharply upon the magnetic field. Based on the anisotropy of the hyperfine
+coupling and of the optical polarisation mechanism, we predict and observe a
+complete reversal of the nuclear spin polarisation with a few-mT change in the
+magnetic field. The demonstrated sensitive magnetic control of nuclear
+polarisation at room temperature will be useful for sensitivity-enhanced NMR,
+nuclear-based spintronics, and quantum computation in diamond.",1212.0035v1
+2012-12-26,Epitaxial strain induced magnetic transitions and phonon instabilities of the tetragonal SrRuO3,"Using density-functional theory calculations, we investigate the magnetic as
+well as the dynamical properties of tetragonal SrRuO3 (SRO) under the influence
+of epitaxial strain. It is found that both the tensile and compressive strain
+in the xy-plane could induce the abrupt change in the magnetic moment of Ru
+atom. In particular, under the in-plane ~4% compressive strain, a ferromagnetic
+to nonmagnetic transition is induced. Whereas for the tensile strain larger
+than 3%, the Ru magnetic moment drops gradually with the increase of the
+strain, exhibiting a weak ferromagnetic state. We find that such magnetic
+transitions could be qualitatively explained by the Stoner model. In addition,
+frozen phonon calculations at {\Gamma} point reveal structural instabilities
+could occur under both compressive and tensile strains. Such instabilities are
+very similar to those of the ferroelectric perovskite oxides, even though SRO
+remains to be metallic in the range we studied. These might have influence on
+the physical properties of oxide supercells taking SRO as constituent.",1212.6132v1
+2013-02-17,Effect of Self-Magnetic Fields on the Nonlinear Dynamics of Relativistic Electron Beam with Virtual Cathode,"The report is devoted to the results of the numerical study of the virtual
+cathode formation conditions in the relativistic electron beam under the
+influence of the self-magnetic and external axial magnetic fields. The
+azimuthal instability of the relativistic electron beam leading to the
+formation of the vortex electron structure in the system was found out. This
+instability is determined by the influence of the self-magnetic fields of the
+relativistic electron beam and it leads to the decrease of the critical value
+of the electron beam current (current when the non-stationary virtual cathode
+is formed in the drift space). The typical dependencies of the critical current
+on the external uniform magnetic field value were discovered. The effect of the
+beam thickness on the virtual cathode formation conditions was also analyzed.",1302.4044v1
+2013-02-27,Weak magnetic transitions in pyrochlore Bi2Ir2O7,"Muon spin relaxation measurements on Bi2Ir2O7 show that it undergoes a bulk
+magnetic transition at 1.84(3) K. This is accompanied by increases in the muon
+spin relaxation rate and the amplitude of the non-relaxing part of the signal.
+The magnetic field experienced by muons is estimated to be 0.7 mT at
+low-temperature, around two orders of magnitude smaller than that in other
+pyrochlore iridates. These results suggest that the low-temperature state
+represents ordering of exceptionally small magnetic moments with persistent
+weak dynamics. The relaxation rate increases further below 0.23(4) K,
+coincident with a growth in the specific heat, suggesting the existence of a
+second low-temperature magnetic transition.",1302.6905v2
+2013-03-04,Numerical Relativity Simulations of Magnetized Black Hole-Neutron Star Mergers,"We present new numerical techniques we developed for launching the first
+parameter study of {\it magnetized} black hole--neutron star (BHNS) mergers,
+varying the magnetic fields seeded in the initial neutron star. We found that
+magnetic fields have a negligible impact on the gravitational waveforms and
+bulk dynamics of the system during merger, regardless of magnetic field
+strength or BH spin. In a recent simulation, we seeded the remnant disk from an
+unmagnetized BHNS merger simulation with large-scale, purely poloidal magnetic
+fields, which are otherwise absent in the full simulation. The outcome appears
+to be a viable sGRB central engine.",1303.0837v1
+2013-03-05,The Induced Electric Field Distribution in Solar Atmosphere,"A method of calculating induced electric field is presented in this paper.
+Induced electric field in solar atmosphere is derived by the time variation of
+magnetic field when the charged particle accumulation is neglected. In order to
+get the spatial distribution of magnetic field, several extrapolation methods
+are introduced. With observational data from Helioseismic and Magnetic Imager
+(HMI) aboard the NASA's Solar Dynamics Observatory (SDO) on May 20th, 2010, we
+extrapolate the magnetic field to the upper atmosphere from the photosphere. By
+calculating the time variation of magnetic field, we can get the induced
+electric field. The derived induced electric field can reach a value of 100
+V/cm and the average electric field has a maximum point at the layer of 360 km
+above the photosphere. The Monte Carlo statistics method is used to compute the
+triple integration of induced electric field.",1303.0987v1
+2013-03-07,Theory of atomistic simulation of spin-transfer torque in nanomagnets,"In spin-transfer torque (STT) for technological applications, the
+miniaturization of the magnet may reach the stage of requiring a fully
+quantum-mechanical treatment. We present an STT theory which uses the quantum
+macrospin ground and excited (magnon) states of the nanomagnet. This allows for
+energy and angular momentum exchanges between the current electron and the
+nano-magnet. We develop a method of magnetization dynamics simulation which
+captures the heating effect on the magnet by the spin-polarized current and the
+temperature-dependence in STT. We also discuss the magnetostatics effect on
+magnon scattering for ferromagnetic relaxation in a thin film. Our work
+demonstrates a realistic step towards simulation of quantum spin-transfer
+torque physics in nano-scale magnets.",1303.1775v1
+2013-03-12,Global Simulations of Magnetorotational Instability in The Collapsed Core of A Massive Star,"We performed the first numerical simulations of magnetorotational instability
+from a sub-magnetar-class seed magnetic field in core collapse supernovae. As a
+result of axisymmetric ideal MHD simulations, we found that the magnetic field
+is greatly amplified to magnetar-class strength. In saturation phase, a
+substantial part of the core is dominated by turbulence, and the magnetic field
+possesses dominant large scale components, comparable to the size of the
+proto-neutron star. A pattern of coherent chanel flows, which generally appears
+during exponential growth phase in previous local simulations, is not observed
+in our global simulations. While the approximate convergence in the exponential
+growth rate is attained by increasing spatial resolution, that of the
+saturation magnetic field is not achieved due to still large numerical
+diffusion. Although the effect of magnetic field on the dynamics is found to be
+mild, a simulation with a high-enough resolution might result in a larger
+impact.",1303.2856v1
+2013-03-26,Enhanced pinning in high-temperature superconducting cuprate single crystals at low DC magnetic field,"Low density flux dynamics in Nd based cuprate (NdBa2Cu3O7-x) HTSC single
+crystals trapped in 1 Oe range DC magnetic fields were investigated for the
+first time. Complex measurements of time, temperature and field dependence of
+magnetization were performed. Using the results obtained and the Anderson-Kim
+model the normalized magnetization relaxation rate S and the averaged effective
+pinning potential U were calculated. We show a significant (one or even two
+orders) increase in the effective pinning potential in these samples in
+comparison with measurements performed in high magnetic fields for similar
+cuprate single crystals formerly. In a wide enough range of temperatures close
+to Tc (0.72 < T/Tc < 0.93) it has been shown that the doping of NdBa2Cu3O7-x
+single crystals with calcium atoms leads to the increase of the averaged
+effective pinning potential with an insignificant decreasing of the critical
+temperature.",1303.6501v1
+2013-04-29,Polarimetric Properties of Flux-Ropes and Sheared Arcades in Coronal Prominence Cavities,"The coronal magnetic field is the primary driver of solar dynamic events.
+Linear and circular polarization signals of certain infrared coronal emission
+lines contain information about the magnetic field, and to access this
+information, either a forward or an inversion method must be used. We study
+three coronal magnetic configurations that are applicable to polar-crown
+filament cavities by doing forward calculations to produce synthetic
+polarization data. We analyze these forward data to determine the
+distinguishing characteristics of each model. We conclude that it is possible
+to distinguish between cylindrical flux ropes, spheromak flux ropes, and
+sheared arcades using coronal polarization measurements. If one of these models
+is found to be consistent with observational measurements, it will mean
+positive identification of the magnetic morphology that surrounds certain
+quiescent filaments, which will lead to a greater understanding of how they
+form and why they erupt.",1304.7594v1
+2013-06-10,Attosecond Magnetic Field Pulse Generation by Intense Few Cycle Circularly Polarized UV Pulses,"Intense attosecond magnetic field pulses are predicted to be produced by
+intense few cycle circularly polarized UV pulses. Numerical solutions of the
+time dependent Schr\""{o}dinger equation for H$_2^+$ are used to study the
+dynamical process. Spiralling attosecond circular electron wave packets are
+created with nanometer molecular dimensions, thus generating magnetic fields of
+several tens of Teslas ($10^5$ Gauss). Simulations show that the induced
+magnetic field is critically dependent on the pulse wavelength $\lambda$ and
+pulse duration $n\tau$ ($n$ number of cycle) as predicted by a classical model.
+For ultrashort few cycle circularly polarized attosecond pulses, molecular
+orientation influences the generation of the induced magnetic fields as a
+result of preferential ionization perpendicular to the molecular axis.",1306.2209v2
+2013-06-12,Atomic spin-orbit coupling synthesized with magnetic-field-gradient pulses,"We discuss a general scheme for creating atomic spin-orbit coupling (SOC)
+such as the Rashba or Dresselhaus types using magnetic-field-gradient pulses.
+In contrast to conventional schemes based on adiabatic center-of-mass motion
+with atomic internal states restricted to a dressed-state subspace, our scheme
+works for the complete subspace of a hyperfine-spin manifold by utilizing the
+coupling between the atomic magnetic moment and external magnetic fields. A
+spatially dependent pulsed magnetic field acts as an internal-state-dependent
+impulse, thereby coupling the atomic internal spin with its orbital
+center-of-mass motion, as in the Einstein-de Haas effect. This effective
+coupling can be dynamically manipulated to synthesize SOC of any type (Rashba,
+Dresselhaus, or any linear combination thereof). Our scheme can be realized
+with most experimental setups of ultracold atoms and is especially suited for
+atoms with zero nuclear spins.",1306.2829v1
+2013-06-20,Ultracold molecular collisions in combined electric and magnetic fields,"We consider collisions of electric and magnetic polar molecules, taking the
+OH radical as an example, subject to combined electric and magnetic static
+fields. We show that the relative orientation of the fields has an important
+effect on the collision processes for different fields magnitude at different
+collision energies. This is due to the way the molecules polarize in the
+combined electric and magnetic fields and hence the way the electric
+dipole-dipole interaction rises. If OH molecules are confined in magnetic
+quadrupole traps and if an electric field is applied, molecular collisions will
+strongly depend on the position as well as the velocity of the molecules, and
+consequences on the molecular dynamics are discussed.",1306.4846v1
+2013-06-21,Magnetic properties of a family of quinternary oxalates,"We report on the magnetic properties of four isomorphous compounds of a
+family of quinternary oxalates down to 60 mK. In all these materials, the
+magnetic FeII ions with a strong magneto-crystalline anisotropy form a
+distorted kagome lattice, topologically equivalent to a perfect kagome one if
+nearest-neighbor interactions only are considered. All the compounds order at
+low temperature in an antiferromagnetic arrangement with magnetic moments at
+120{\deg}. A remarkable magnetic behavior emerges below the N\'eel temperature
+in three compounds (with inter-kagome-layer Zr, Sn, Fe but not with Al): the
+spin anisotropy combined with a low exchange path network connectivity lead to
+domain walls intersecting the kagome planes through strings of free spins.
+These produce an unfamiliar slow spin dynamics in the ordered phase observed by
+AC susceptibility, evolving from exchange-released spin-flips towards a
+cooperative behavior on decreasing the temperature.",1306.5188v1
+2013-07-10,RF amplification property of the MgO-based magnetic tunnel junction using field-induced ferromagnetic resonance,"The radio-frequency (RF) voltage amplification property of a tunnel
+magnetoresistance device driven by an RF external-magnetic-field-induced
+ferromagnetic resonance was studied. The proposed device consists of a magnetic
+tunnel junction (MTJ) and an electrically isolated coplanar waveguide. The
+input RF voltage applied to the waveguide can excite the resonant dynamics in
+the free layer magnetization, leading to the generation of an output RF voltage
+under a DC bias current. The dependences of the RF voltage gain on the static
+external magnetic field strength and angle were systematically investigated.
+The design principles for the enhancement of the gain factor are also
+discussed.",1307.2745v1
+2013-07-15,Extracting scaling laws from numerical dynamo models,"Earth's magnetic field is generated by processes in the electrically
+conducting, liquid outer core, subsumed under the term `geodynamo'. In the last
+decades, great effort has been put into the numerical simulation of core
+dynamics following from the magnetohydrodynamic (MHD) equations. However, the
+numerical simulations are far from Earth's core in terms of several control
+parameters. Different scaling analyses found simple scaling laws for quantities
+like heat transport, flow velocity, magnetic field strength and magnetic
+dissipation time.
+  We use an extensive dataset of 116 numerical dynamo models compiled by
+Christensen and co-workers to analyse these scalings from a rigorous model
+selection point of view. Our method of choice is leave-one-out cross-validation
+which rates models according to their predictive abilities. In contrast to
+earlier results, we find that diffusive processes are not negligible for the
+flow velocity and magnetic field strength in the numerical dynamos. Also the
+scaling of the magnetic dissipation time turns out to be more complex than
+previously suggested. Assuming that the processes relevant in the numerical
+models are the same as in Earth's core, we use this scaling to estimate an
+Ohmic dissipation of 3-8 TW for the core. This appears to be consistent with
+recent high CMB heat flux scenarios.",1307.3938v1
+2013-07-19,Damping and non-linearity of a levitating magnet in rotation above a superconductor,"We study the dissipation of moving magnets in levitation above a
+superconductor. The rotation motion is analyzed using optical tracking
+techniques. It displays a remarkable regularity together with long damping time
+up to several hours. The magnetic contribution to the damping is investigated
+in detail by comparing 14 distinct magnetic configurations, and points towards
+amplitude-dependent dissipation mechanisms. The non-linear dynamics of the
+mechanical rotation motion is also revealed and described with an effective
+Duffing model. The obtained picture of the coupling of levitating magnets to
+their environment sheds light on their potential as ultra-low dissipation
+mechanical oscillators for high precision physics.",1307.5155v1
+2013-08-02,Skyrmion ground state and gyration of skyrmions in magnetic nanodisks without the Dzyaloshinsky-Moriya interaction,"We show by micromagnetic simulations that spontaneous skyrmion ground state
+can exist in Co/Ru/Co nanodisks without the Dzyaloshinsky-Moriya interaction
+(DMI), which can remain stable in the applied magnetic field along +z direction
+even up to 0.44 T. The guiding center ($R_x$,$R_y$) of skyrmion defined by the
+moments of the topological density presents a novel gyration with a star-like
+trajectory in a pulsed magnetic field and a hexagonal trajectory after the
+field is switched off, which is different from that of vortex or bubble. One of
+the coupled skyrmions could move without an external magnetic field, but only
+induced by the motion of the other one due to strong inter-layer magnetostatic
+interactions. This work sheds light on how novel skyrmions can be discovered in
+various (not limited to magnetic) systems with competing energies and
+contributes to the understanding of the dynamical properties of skyrmion.",1308.0412v2
+2013-08-02,Bimodal Distribution of Magnetic Fields and Areas of Sunspots,"We applied automatic identification of sunspot umbrae and penumbrae to daily
+observations from the Helioseismic Magnetic Imager (HMI) on board the Solar
+Dynamics Observatory (SDO) to study their magnetic flux (B) and area (A). The
+results confirm a previously known logarithmic relationship between the area of
+sunspots and their maximum flux density. In addition, we find that the relation
+between average magnetic flux (Bavg) and sunspot area shows a bimodal
+distribution: for small sunspots and pores (A < 20 millionth of solar
+hemisphere, MSH), Bavg = 800 G (gauss), and for large sunspots (A > 100 MSH),
+Bavg is about 600 G. For intermediate sunspots, average flux density linearly
+decreases from about 800 G to 600 G. A similar bimodal distribution was found
+in several other integral parameters of sunspots. We show that this bimodality
+can be related to different stages of sunspot penumbra formation and can be
+explained by the difference in average inclination of magnetic fields at the
+periphery of small and large sunspots.",1308.0535v1
+2013-08-09,"The Hour-Glass Magnetic Spectrum Arising from a Striped, Cluster Spin Glass Ground State in La1.75Sr0.25CoO4","We report inelastic neutron scattering results that reveal an hour-glass
+magnetic excitation spectrum in La1.75Sr0.25CoO4. The magnetic spectrum is
+similar to that observed previously in La1.67Sr0.33CoO4, but the spectral
+features are broader. We show that the spectrum of La1.75Sr0.25CoO4 can be
+modeled by the spin dynamics of a system with a disordered cluster spin glass
+ground state. Bulk magnetization measurements are presented which support the
+proposed glassy ground state. The observations reiterate the importance of
+quasi-one-dimensional magnetic correlations and disorder for the hour-glass
+spectrum, and suggest that disordered spin and charge stripes exist at lower
+doping in La2-xSrxCoO4 than previously thought.",1308.2141v1
+2013-09-09,Quantitative stray field imaging of a magnetic vortex core,"Thin-film ferromagnetic disks present a vortex spin structure whose dynamics,
+added to the small size (~10 nm) of their core, earned them intensive study.
+Here we use a scanning nitrogen-vacancy (NV) center microscope to
+quantitatively map the stray magnetic field above a 1 micron-diameter disk of
+permalloy, unambiguously revealing the vortex core. Analysis of both
+probe-to-sample distance and tip motion effects through stroboscopic
+measurements, allows us to compare directly our quantitative images to
+micromagnetic simulations of an ideal structure. Slight perturbations with
+respect to the perfect vortex structure are clearly detected either due to an
+applied in-plane magnetic field or imperfections of the magnetic structures.
+This work demonstrates the potential of scanning NV microscopy to map tiny
+stray field variations from nanostructures, providing a nanoscale,
+non-perturbative detection of their magnetic texture.",1309.2171v2
+2013-09-17,Quantum Nature of Edge Magnetism in Graphene,"It is argued that the subtle crossover from decoherence-dominated classical
+magnetism to fluctuation-dominated quantum magnetism is experimentally
+accessible in graphene nanoribbons. We show that the width of a nanoribbon
+determines whether the edge magnetism is on the classical side, on the quantum
+side, or in between. In the classical regime, decoherence is dominant and leads
+to static spin polarizations at the ribbon edges, which are well described by
+mean-field theories. The quantum Zeno effect is identified as the basic
+mechanism which is responsible for the spin polarization and thereby enables
+the application of graphene in spintronics. On the quantum side, however, the
+spin polarization is destroyed by dynamical processes. The great tunability of
+graphene magnetism thus offers a viable route for the study of the
+quantum-classical crossover.",1309.4446v2
+2013-09-18,Numerical study of broadband spectra caused by internal shocks in magnetized relativistic jets of blazars,"The internal-shocks scenario in relativistic jets has been used to explain
+the variability of blazars' outflow emission. Recent simulations have shown
+that the magnetic field alters the dynamics of these shocks producing a whole
+zoo of spectral energy density patterns. However, the role played by
+magnetization in such high-energy emission is still not entirely understood.
+With the aid of \emph{Fermi}'s second LAT AGN catalog, a comparison with
+observations in the $\gamma$-ray band was performed, in order to identify the
+effects of the magnetic field.",1309.4612v1
+2013-09-21,Comparison of physical properties of quiet and active regions through the analysis of MHD simulations of the solar photosphere,"Recent observations have shown that the photometric and dynamic properties of
+granulation and of small-scale magnetic features depend on the amount of
+magnetic flux of the region they are embedded in. We analyze results from
+numerical Hydro and Magneto Hydrodynamic simulations characterized by different
+amount of average magnetic flux and find qualitatively the same differences as
+those reported from observations. We show that these different physical
+properties result from the inhibition of convection induced by the presence of
+the magnetic field, which changes the temperature stratification of both quiet
+and magnetic regions. Our results are relevant for solar irradiance variations
+studies, as such differences are still not properly taken into account in
+irradiance reconstruction models.",1309.5494v1
+2013-10-18,Quantitative characterization of the spin orbit torque using harmonic Hall voltage measurements,"Solid understanding of current induced torques is key to the development of
+current and voltage controlled magnetization dynamics in ultrathin magnetic
+heterostructures. To evaluate the size and direction of such torques, or
+effective fields, a number of methods have been employed. Here we examine the
+adiabatic (low frequency) harmonic Hall voltage measurement that has been used
+to study the effective field. We derive an analytical formula for the harmonic
+Hall voltages to evaluate the effective field for both out of plane and
+in-plane magnetized systems. The formula agrees with numerical calculations
+based on a macrospin model. Two different in-plane magnetized films,
+Pt|CoFeB|MgO and CuIr|CoFeB|MgO are studied using the formula developed. The
+effective field obtained for the latter system shows relatively good agreement
+with that estimated using a spin torque switching phase diagram measurements
+reported previously. Our results illustrate the versatile applicability of
+harmonic Hall voltage measurement for studying current induced torques in
+magnetic heterostructures.",1310.4879v1
+2013-11-01,Coherent Magnetism and Spin-Orbit Interaction in Garnet Films Probed with Femtosecond Magneto-Optical Four Wave Mixing,"We report about the dephasing of the spins states in a Garnet film excited by
+femtosecond laser pulses. It is shown that magneto-optical four-wave-mixing
+signals are efficiently generated and controlled with an external static
+magnetic field. The self-diffraction of either two or three femtosecond pulses
+allows us determining independently the coherent response time ($T_2$ < 50 fs)
+and the population relaxation, which occurs in several steps. After the laser
+induced demagnetization, the spin-lattice relaxation is the dominant mechanism
+($T_{1,spin-lat}$ < 1.35 ps) and the precession of the magnetization takes
+place at later times ($T_{1,prec}$ < 150 ps). The coherent response of the
+spins states is modeled with a multi-level hydrogen-like system, taking into
+account the fundamental relativistic quantum dynamics of the spins. Our
+experimental approach is general and opens the way to investigating quantum
+magnetism in ordered magnetic systems useful for applications in information
+and communications technologies.",1311.0080v1
+2013-11-06,Magnetization dynamics of cobalt grown on graphene,"Ferromagnetic resonance (FMR) spin pumping is a rapidly growing field which
+has demonstrated promising results in a variety of material systems. This
+technique utilizes the resonant precession of magnetization in a ferromagnet to
+inject spin into an adjacent non-magnetic material. Spin pumping into graphene
+is attractive on account of its exceptional spin transport properties. This
+article reports on FMR characterization of cobalt grown on CVD graphene and
+examines the validity of linewidth broadening as an indicator of spin pumping.
+In comparison to cobalt samples without graphene, direct contact
+cobalt-on-graphene exhibits increased FMR linewidth--an often used signature of
+spin pumping. Similar results are obtained in Co/MgO/graphene structures, where
+a 1nm MgO layer acts as a tunnel barrier. However, SQUID, MFM, and Kerr
+microscopy measurements demonstrate increased magnetic disorder in cobalt grown
+on graphene, perhaps due to changes in the growth process and an increase in
+defects. This magnetic disorder may account for the observed linewidth
+enhancement due to effects such as two-magnon scattering or mosaicity. As such,
+it is not possible to conclude successful spin injection into graphene from FMR
+linewidth measurements alone.",1311.1441v1
+2013-11-17,On magnetic reconnection and flux rope topology in solar flux emergence,"We present an analysis of the formation of atmospheric flux ropes in a
+magnetohydrodynamic (MHD) solar flux emergence simulation. The simulation
+domain ranges from the top of the solar interior to the low corona. A twisted
+magnetic flux tube emerges from the solar interior and into the atmosphere
+where it interacts with the ambient magnetic field. By studying the
+connectivity of the evolving magnetic field, we are able to better understand
+the process of flux rope formation in the solar atmosphere. In the simulation,
+two flux ropes are produced as a result of flux emergence. Each has a different
+evolution resulting in different topological structures. These are determined
+by plasma flows and magnetic reconnection. As the flux rope is the basic
+structure of the coronal mass ejection (CME), we discuss the implications of
+our findings for solar eruptions.",1311.4225v1
+2013-11-18,Prediction of superconductivity of $3d$ transition-metal based antiperovskites via magnetic phase diagram,"We theoretically studied the electronic structure, magnetic properties, and
+lattice dynamics of a series of $3d$ transition-metal antiperovskite compounds
+AXM$_{3}$ by density function theory. Based on the Stoner criterion, we drew
+the magnetic phase diagram of carbon-based antiperovskites ACM$_{3}$. In the
+phase diagram, compounds with non-magnetic ground state but locating near the
+ferromagnetic boundary are suggested to yield sizeable electron-phonon coupling
+and behave superconductivity. To approve this deduction, we systematically
+calculated the phonon spectra and electron-phonon coupling of a series of
+Cr-based antiperovskites ACCr$_{3}$ and ANCr$_{3}$. The results show that
+AlCCr$_{3}$, GaCCr$_{3}$, and ZnNCr$_{3}$ could be moderate coupling BCS
+superconductors. The influence of spin fluctuation on superconductivity are
+discussed. Furthermore, other potential superconducting AXM$_{3}$ including
+some new Co-base and Fe-based antiperovskite superconductors are predicted from
+the magnetic phase diagram.",1311.4240v3
+2013-12-11,Two-dimensional nonlinear travelling waves in magnetohydrodynamic channel flow,"The present study is concerned with the stability of a flow of viscous
+conducting liquid driven by pressure gradient in the channel between two
+parallel walls subject to a transverse magnetic field. Although the magnetic
+field has a strong stabilizing effect, this flow, similarly to its hydrodynamic
+counterpart -- plane Poiseuille flow, is known to become turbulent
+significantly below the threshold predicted by linear stability theory. We
+investigate the effect of the magnetic field on 2D nonlinear travelling-wave
+states which are found at substantially subcritical Reynolds numbers starting
+from $Re_n=2939$ without the magnetic field and from $Re_n\sim6.50\times10^3Ha$
+in a sufficiently strong magnetic field defined by the Hartmann number $Ha.$
+Although the latter value is by a factor of seven lower than the linear
+stability threshold $Re_l\sim4.83\times10^4Ha$,it is still more by an order of
+magnitude higher than the experimentally observed value for the onset of
+turbulence in the MHD channel flow.",1312.3264v3
+2013-12-17,Non-Hermitian quantum rings,"We investigate the spectral and dynamical properties of a quantum particle
+constrained on a ring threaded by a magnetic flux in presence of a complex
+(non-Hermitian) potential. For a static magnetic flux, the quantum states of
+the particle on the ring can be mapped into the Bloch states of a complex
+crystal, and magnetic flux tuning enables to probe the spectral features of the
+complex crystal, including the appearance of exceptional points. For a
+time-varying (linearly-ramped) magnetic flux, Zener tunneling among energy
+states is realized owing to the induced electromotive force. As compared to the
+Hermitian case, striking effects are observed in the non-Hermitian case, such
+as a highly asymmetric behavior of particle motion when reversing the direction
+of the magnetic flux and field-induced delayed transparency.",1312.4693v1
+2013-12-30,Impurity entanglement through electron scattering in a magnetic field,"We study the entanglement of magnetic impurities in an environment of
+electrons through successive scattering while an external magnetic field is
+applied. We show that the dynamics of the problem can be approximately
+described by a reduced model of three interacting spins, which reveals an
+intuitive view on how spins can be entangled by controlled electron scattering.
+The role of the magnetic field is rather crucial. Depending on the initial
+state configuration, the magnetic field can either increase or decrease the
+resulting entanglement but more importantly it can allow the impurities to be
+maximally entangled.",1401.0005v1
+2014-01-05,Analytic form of head-to-head domain walls in thin ferromagnetic cylinders,"The one-dimensional problem of a static head-to-head domain wall structure in
+a thin soft-magnetic nanowire with circular cross-section is treated within the
+framework of micromagnetic theory. A radius-dependent analytic form of the
+domain wall profile is derived by decomposing the magnetostatic energy into a
+monopolar and a dipolar term. We present a model in which the dipolar term of
+the magnetostatic energy resulting from the transverse magnetization in the
+center of the domain wall is calculated with Osborn's formulas for
+homogeneously magnetized ellipsoids [Phys. Rev. 67, 351 (1945)]. The analytic
+results agree almost perfectly with simulation data as long as the wire
+diameter is sufficiently small to prevent inhomogeneities of the magnetization
+along the cross-section. Owing to the recently demonstrated negligible D\""oring
+mass of these walls, our results should also apply to the dynamic case, where
+domain walls are driven by spin-transfer toque effects and/or an axial magnetic
+field.",1401.0909v1
+2014-02-10,Determination of Intrinsic Magnetic Response from Local Measurements of Fringing Fields,"Micron-sized Hall bars and micro-SQUIDs are now used routinely to measure the
+local static and dynamic magnetic response with micron-scale spatial
+resolution. While this provides a powerful new tool, determining the intrinsic
+magnetization presents new challenges, as it requires correcting for
+demagnetization fields that vary widely with position on a sample. In this
+paper we develop a method to correct for the demagnetization effect at local
+points of a rectangular prism shaped sample using a finite element analysis of
+Maxwell's equation applied to local Hall sensor measurements calibrated by bulk
+measurements of the magnetization. This method can be generalized to other
+geometric shapes to analyze data obtained with local magnetic probes.",1402.2247v1
+2014-03-02,Effect of magnetic field on the velocity autocorrelation and the caging of particles in two-dimensional Yukawa liquids,"We investigate the effect of an external magnetic field on the velocity
+autocorrelation function and the ""caging"" of the particles in a two-dimensional
+strongly coupled Yukawa liquid, via numerical simulations. The influence of the
+coupling strength on the position of the dominant peak in the frequency
+spectrum of the velocity autocorrelation function confirms the onset of a joint
+effect of the magnetic field and strong correlations at high coupling. Our
+molecular dynamics simulations quantify the decorrelation of the particles'
+surroundings - the magnetic field is found to increase significantly the caging
+time, which reaches values well beyond the timescale of plasma oscillations.
+The observation of the increased caging time is in accordance with findings
+that the magnetic field decreases diffusion in similar systems.",1403.0232v1
+2014-04-08,The Link between Magnetic Fields and Cloud/Star Formation,"The question whether magnetic fields play an important role in the processes
+of molecular cloud and star formation has been debated for decades. Recent
+observations have revealed a simple picture that may help illuminate these
+questions: magnetic fields have a tendency to preserve their orientation at all
+scales that have been probed - from 100-pc scale inter-cloud media down to
+sub-pc scale cloud cores. This ordered morphology has implications for the way
+in which self-gravity and turbulence interact with magnetic fields: both
+gravitational contraction and turbulent velocities should be anisotropic, due
+to the influence of dynamically important magnetic fields. Such anisotropy is
+now observed. Here we review these recent observations and discuss how they can
+improve our understanding of cloud/star formation.",1404.2024v1
+2014-04-08,Resonant Spin Wave Excitation by Terahertz Magnetic Near-field Enhanced with Split Ring Resonator,"Excitation of antiferromagnetic spin waves in HoFeO$_{3}$ crystal combined
+with a split ring resonator (SRR) is studied using terahertz (THz)
+electromagnetic pulses. The magnetic field in the vicinity of the SRR induced
+by the incident THz electric field component excites and the Faraday rotation
+of the polarization of a near-infrared probe pulse directly measures
+oscillations that correspond to the antiferromagnetic spin resonance mode. The
+good agreement of the temperature-dependent magnetization dynamics with the
+calculation using the two-lattice Landau-Lifshitz-Gilbert equation confirms
+that the spin wave is resonantly excited by the THz magnetic near-field
+enhanced at the LC resonance frequency of the SRR, which is 20 times stronger
+than the incident magnetic field.",1404.2179v1
+2014-04-23,Anisotropic Magnetic Response in Kondo Lattice with Antiferromagnetic Order,"Magnetic properties are investigated for the Kondo lattice by using the
+continuous time quantum Monte Colro (CT-QMC) and the dynamical mean field
+theory (DMFT). The DMFT+CT-QMC approach is extended so as to derive the
+anisotropic magnetic response in the antiferromagnetic phase. The longitudinal
+and transverse magnetic susceptibilities are numerically derived in the
+antiferromagnetic phase. For the RKKY regime with a small Kondo coupling, the
+transverse susceptibility does not decrease below the transition temperature
+while the longitudinal susceptibility decreases as expected from the mean field
+picture. In the competing region between the RKKY interaction and the Kondo
+effect, however, both longitudinal and transverse susceptibilities decrease
+below the transition temperature. The results obtained naturally explain the
+temperature dependence of the magnetic susceptibility observed in
+CeT$_2$Al$_{10}$ ($T$=Ru,Os,Fe) family.",1404.5718v1
+2014-05-05,Mimetic Methods for Lagrangian Relaxation of Magnetic Fields,"We present a new code that performs a relaxation of a magnetic field towards
+a force-free state (Beltrami field) using a Lagrangian numerical scheme.
+Beltrami fields are of interest for the dynamics of many technical and
+astrophysical plasmas as they are the lowest energy states that the magnetic
+field can reach. The numerical method strictly preserves the magnetic flux and
+the topology of magnetic field lines. In contrast to other implementations we
+use mimetic operators for the spatial derivatives in order to improve accuracy
+for high distortions of the grid. Compared with schemes using direct
+derivatives we find that the final state of the simulation approximates a
+force-free state with a significantly higher accuracy. We implement the scheme
+in a code which runs on graphical processing units (GPU), which leads to an
+enhanced computing speed compared to previous relaxation codes.",1405.0942v2
+2014-05-25,Clusters of small eruptive flares produced by magnetic reconnection in the sun,"We report on the formation of small solar flares produced by patchy magnetic
+reconnection between interacting magnetic loops. A three-dimensional (3D)
+magnetohydrodynamic (MHD) numerical experiment was performed, where a uniform
+magnetic flux sheet was injected into a fully developed convective layer. The
+gradual emergence of the field into the solar atmosphere results in a network
+of magnetic loops, which interact dynamically forming current layers at their
+interfaces. The formation and ejection of plasmoids out of the current layers
+leads to patchy reconnection and the spontaneous formation of several small
+(size ? 1-2Mm) flares. We find that these flares are short-lived (30 s - 3 min)
+bursts of energy in the range O(10^25 - 10^27) ergs, which is basically the
+nanoflare-microflare range. Their persistent formation and co-operative action
+and evolution leads to recurrent emission of fast EUV/X-ray jets and
+considerable plasma heating in the active corona.",1405.6420v1
+2014-06-15,Direct and inverse spin-orbit torques,"In collinear magnets lacking inversion symmetry application of electric
+currents induces torques on the magnetization and conversely magnetization
+dynamics induces electric currents. The two effects, which both rely on
+spin-orbit interaction (SOI), are reciprocal to each other and denoted direct
+spin-orbit torque (SOT) and inverse spin-orbit torque (ISOT), respectively. We
+derive expressions for SOT and ISOT within the Kubo linear response formalism.
+We show that expressions suitable for density-functional theory calculations
+can be derived either starting from a Kohn-Sham Hamiltonian with time-dependent
+exchange field or by expressing general susceptibilities in terms of the
+Kohn-Sham susceptibilities. For the case of magnetic bilayer systems we derive
+the general form of the ISOT current induced under ferromagnetic resonance.
+Using \textit{ab initio} calculations within density-functional theory we
+investigate SOT and ISOT in Co/Pt(111) magnetic bilayers. We determine the
+spatial distribution of spin and charge currents as well as torques in order to
+expose the mechanisms underlying SOT and ISOT and to highlight their
+reciprocity on the microscopic level. We find that the spin Hall effect is
+position-dependent close to interfaces.",1406.3866v2
+2014-08-27,The thickness of a weakly-magnetized accretion flow inside the last stable orbit of a Kerr black hole,"If accretion disc contains weak frozen-in entangled magnetic fields, their
+dynamical effect may be important inside the last stable orbit because of the
+decompression near the sonic point. Here, I consider the radial and vertical
+structure of a nearly free-falling flow inside the last stable orbit of a thin
+disc around a Kerr black hole. The thickness of such a flow is determined
+primarily by the vertical stress created by radial and azimuthal magnetic
+fields. The thickness is predicted to oscillate vertically around its
+equilibrium value determined by the magnetic field balance with gravity. For
+thin discs, this thickness is much larger than that of the accretion disc
+itself. Numerical simulations with HARM2d show the vertical structure is more
+complicated. In particular, magnetically supported disc seems to be unstable to
+segregation of matter into thinner streams with the vertical scale determined
+by thermal pressure or other processes.",1408.6449v1
+2014-09-03,Pair separation of magnetic elements in the quiet Sun,"The dynamic properties of the quiet Sun photosphere can be investigated by
+analyzing the pair dispersion of small-scale magnetic fields (i.e., magnetic
+elements).
+  By using $25$ hr-long Hinode magnetograms at high spatial resolution
+($0"".3$), we tracked $68,490$ magnetic element pairs within a supergranular
+cell near the disk center.
+  The computed pair separation spectrum, calculated on the whole set of
+particle pairs independently of their initial separation, points out what is
+known as a super-diffusive regime with spectral index $\gamma=1.55\pm0.05$, in
+agreement with the most recent literature, but extended to unprecedented
+spatial and temporal scales (from granular to supergranular). Furthermore, for
+the first time, we investigated here the spectrum of the mean square
+displacement of pairs of magnetic elements, depending on their initial
+separation $r_0$. We found that there is a typical initial distance above
+(below) which the pair separation is faster (slower) than the average. A
+possible physical interpretation of such a typical spatial scale is also
+provided.",1409.1010v2
+2014-09-05,Magneto-ionic Control of Interfacial Magnetism,"In metal/oxide heterostructures, rich chemical, electronic, magnetic and
+mechanical properties can emerge from interfacial chemistry and structure. The
+possibility to dynamically control interface characteristics with an electric
+field paves the way towards voltage control of these properties in solid-state
+devices. Here we show that electrical switching of the interfacial oxidation
+state allows for voltage control of magnetic properties to an extent never
+before achieved through conventional magnetoelectric coupling mechanisms. We
+directly observe, for the first time, in situ voltage driven O$^{2-}$ migration
+in a Co/metal-oxide bilayer, which we use to toggle the interfacial magnetic
+anisotropy energy by >0.6 erg/cm$^2$. We exploit the thermally-activated nature
+of ion migration to dramatically increase the switching efficiency and to
+demonstrate reversible patterning of magnetic properties through local
+activation of ionic migration. These results suggest a path towards
+voltage-programmable materials based on solid-state switching of interface
+oxygen chemistry.",1409.1843v1
+2014-09-17,Coupled magnetic and electric hysteresis in the multiferroic double perovskite Lu2MnCoO6,"We investigate a magnetic hysteresis loop with a remanent moment that couples
+to electric polarization to create coupled hysteretic multiferroic behavior in
+Lu2MnCoO6. Measurements of elastic neutron diffraction, muon spin relaxation,
+and micro-Hall magnetometry demonstrate an unusual mechanism for the magnetic
+hysteresis, namely the hysteretic evolution of a microscopic magnetic order,
+and not classic ferromagnetic domain effects. We show how the frustrated spin
+system evolves from antiferromagnetism with an incommensurate long-wavelength
+modulation and strong fluctuations towards a net magnetism. We also clarify the
+different temperature scales for the onset of ordering, dynamics, and
+hysteresis.",1409.5072v2
+2014-11-07,Magnetic exchange in $α$-iron from the ab initio calculations in the paramagnetic phase,"Applying the local density approximation (LDA) and dynamical mean field
+theory (DMFT) to paramagnetic $\alpha $-iron, we revisit a problem of
+theoretical description of its magnetic properties. The analysis of local
+magnetic susceptibility shows that at sufficiently low temperatures $T<1500K$,
+both, $e_{g}$ and $t_{2g}$ states equally contribute to the formation of the
+effective magnetic moment with spin S=1. The self-energy of t_{2g} states shows
+sizable deviations from Fermi-liquid form, which accompanies earlier found
+non-quasiparticle form of e_{g} states. By considering the non-uniform magnetic
+susceptibility we find that the non-quasiparticle form of $e_{g}$ states is
+crucial for obtaining ferromagnetic instability in $\alpha $-iron. The main
+contribution to the exchange interaction, renormalized by the effects of
+electron interaction, comes from the hybridization between $t_{2g}$ and $e_{g}$
+states. We furthermore suggest the effective spin-fermion model for $\alpha
+$-iron, which allows us to estimate the exchange interaction from paramagnetic
+phase, which is in agreement with previous calculations in the ordered state
+within the LDA approaches.",1411.1888v2
+2014-12-04,(Inverse) Magnetic Catalysis in Bose-Einstein Condensation of Neutral Bound Pairs,"The Bose-Einstein condensation of bound pairs made of oppositely charged
+fermions in a magnetic field is investigated. We find that the condensation
+temperature shows the magnetic catalysis effect in weak coupling and the
+inverse magnetic catalysis effect in strong coupling. The different responses
+to the magnetic field can be attributed to the competition between the
+dimensional reduction by Landau orbitals in pairing dynamics and the anisotropy
+of the kinetic spectrum of fluctuations (bound pairs in the normal phase)",1412.1647v3
+2014-12-11,Non-collinear Magnetic Configurations at Finite Temperature in Thin Films,"The finite-temperature magnetism of a monolayer on a bcc (110) surface was
+examined using a model Hamiltonian containing ferromagnetic or
+antiferromagnetic exchange interactions, Dzyaloshinsky-Moriya interactions and
+easy-axis on-site anisotropy. We examined the competition between the collinear
+ground state parallel to the easy axis and the spin spiral state in the plane
+perpendicular to this axis preferred by the Dzyaloshinsky-Moriya interaction.
+Using approximative methods to calculate the magnon spectrum at finite
+temperatures, it was found that even if the ground state is collinear,
+increasing the Dzyaloshinsky-Moriya interaction strongly decreases the critical
+temperature where this collinear order disappears. Using atomistic spin
+dynamics simulations it was found that at this critical temperature the system
+transforms into the non-collinear state. Including external magnetic field
+helps stabilising the ferromagnetic state. An effect due to the finite size of
+the magnetic monolayer was included in the model by considering a different
+value for the anisotropy at the edges of the monolayer. This effect was shown
+to stabilize the spin spiral state by fixing the phase at the ends of the
+stripe.",1412.3591v1
+2014-12-31,Dissipation of magnetic fields in star-forming clouds with different metallicities,"We study dissipation process of magnetic fields in the metallicity range $0-1
+Z_{\odot}$ for contracting prestellar cloud cores. By solving non-equilibrium
+chemistry for important charged species including charged grains, we evaluate
+the drift velocity of the magnetic-field lines with respect to the gas. We find
+that the magnetic flux dissipates in the density range $10^{12}{\rm cm^{-3}}
+\lesssim n_{\rm H} \lesssim 10^{17}{\rm cm^{-3}}$ for the solar-metallicity
+case at the scale of the core, which is assumed to be the Jeans scale. The
+dissipation density range becomes narrower for lower metallicity. The magnetic
+field is always frozen to the gas below metallicity $\lesssim
+10^{-7}-10^{-6}Z_\odot$, depending on the ionization rate by cosmic rays and/or
+radioactivity. With the same metallicity, the dissipation density range becomes
+wider for lower ionization rate. The presence of such a dissipative regime is
+expected to cause various dynamical phenomena in protostellar evolution such as
+the suppression of jet/outflow launching and fragmentation of the circumstellar
+disks depending on the metallicity.",1501.00087v1
+2015-01-08,What flows in the chiral magnetic effect? -- Simulating the particle production with CP-breaking backgrounds,"To address a question of whether the chiral magnetic current is a static
+polarization or a genuine flow of charged particles, we elucidate the numerical
+formulation to simulate the net production of right-handed particles and
+anomalous currents with CP-breaking background fields which cause an imbalance
+between particles and anti-particles. For a concrete demonstration we
+numerically impose pulsed electric and magnetic fields to confirm our answer to
+the question that the produced net particles flow in the dynamical chiral
+magnetic effect. The rate for the particle production and the chiral magnetic
+current generation is quantitatively consistent with the axial anomaly, while
+they appear with a finite response time. We emphasize the importance to
+quantify the response time that would suppress observable effects of the
+anomalous current.",1501.01940v4
+2015-01-26,Vortex Polarity Switching in Magnets with Surface Anisotropy,"Vortex core reversal in magnetic particle is essentially influenced by a
+surface anisotropy. Under the action of a perpendicular static magnetic field
+the vortex core undergoes a shape deformationof pillow- or barrel-shaped type,
+depending on the type of the surface anisotropy. This deformation plays a key
+point in the switching mechanism: We predict that the vortex polarity switching
+is accompanied (i) by a linear singularity in case of Heisenberg magnet with
+bulk anisotropy only and (ii) by a point singularities in case of surface
+anisotropy or exchange anisotropy. We study in details the switching process
+using spin-lattice simulations and propose a simple analytical description
+using a wired core model, which provides an adequate description of the Bloch
+point statics, its dynamics and the Bloch point mediated switching process. Our
+analytical predictions are confirmed by spin-lattice simulations for Heisenberg
+magnet and micromagnetic simulations for nanomagnet with account of a dipolar
+interaction.",1501.06548v1
+2015-01-29,Energy Deposition Studies for the Hi-Lumi LHC Inner Triplet Magnets,"A detailed model of the High Luminosity LHC inner triplet region with new
+large-aperture Nb3Sn magnets, field maps, corrector packages, and segmented
+tungsten inner absorbers was built and implemented into the FLUKA and MARS15
+codes. In the optimized configuration, the peak power density averaged over the
+magnet inner cable width is safely below the quench limit. For the integrated
+luminosity of 3000 fb -1, the peak dose in the innermost magnet insulator
+ranges from 20 to 35 MGy. Dynamic heat loads to the triplet magnet cold mass
+are calculated to evaluate the cryogenic capability. In general, FLUKA and MARS
+results are in a very good agreement.",1501.07623v1
+2015-02-25,Observation of room temperature magnetic skyrmions and their current-driven dynamics in ultrathin Co films,"Magnetic skyrmions are topologically-protected spin textures that exhibit
+fascinating physical behaviors and large potential in highly energy efficient
+spintronic device applications. The main obstacles so far are that skyrmions
+have been observed in only a few exotic materials and at low temperatures, and
+manipulation of individual skyrmions has not yet been achieved. Here, we report
+the observation of stable magnetic skyrmions at room temperature in ultrathin
+transition metal ferromagnets with magnetic transmission soft x-ray microscopy.
+We demonstrate the ability to generate stable skyrmion lattices and drive
+trains of individual skyrmions by short current pulses along a magnetic
+racetrack. Our findings provide experimental evidence of recent predictions and
+open the door to room-temperature skyrmion spintronics in robust thin-film
+heterostructures.",1502.07376v1
+2015-02-27,Numerical simulations of the internal shock model in magnetized relativistic jets of blazars,"The internal shocks scenario in relativistic jets is used to explain the
+variability of the blazar emission. Recent studies have shown that the magnetic
+field significantly alters the shell collision dynamics, producing a variety of
+spectral energy distributions and light-curves patterns. However, the role
+played by magnetization in such emission processes is still not entirely
+understood. In this work we numerically solve the magnetohydodynamic evolution
+of the magnetized shells collision, and determine the influence of the
+magnetization on the observed radiation. Our procedure consists in
+systematically varying the shell Lorentz factor, relative velocity, and viewing
+angle. The calculations needed to produce the whole broadband spectral energy
+distributions and light-curves are computationally expensive, and are achieved
+using a high-performance parallel code.",1502.07882v1
+2015-04-02,Energy deposition studies for the High-Luminosity Large Hadron Collider inner triplet magnets,"A detailed model of the High Luminosity LHC inner triplet region with new
+large-aperture Nb3Sn magnets, field maps, corrector packages, and segmented
+tungsten inner absorbers was built and implemented into the FLUKA and MARS15
+codes. In the optimized configuration, the peak power density averaged over the
+magnet inner cable width is safely below the quench limit. For the integrated
+luminosity of 3000 fb-1, the peak dose in the innermost magnet insulator ranges
+from 20 to 35 MGy. Dynamic heat loads to the triplet magnet cold mass are
+calculated to evaluate the cryogenic capability. In general, FLUKA and MARS
+results are in a very good agreement.",1504.00594v1
+2015-04-14,Magnetic charges and magnetoelectricity in hexagonal rare-earth manganites and ferrites,"Magnetoelectric (ME) materials are of fundamental interest and show broad
+potential for technological applications. Commonly the dominant contribution to
+the ME response is the lattice-mediated one, which is proportional to both the
+Born electric charge $Z^{\rm e}$ and its analogue, the dynamical magnetic
+charge $Z^{\rm m}$. Our previous study has shown that exchange striction acting
+on noncollinear spins induces much larger magnetic charges than those that
+depend on spin-orbit coupling. The hexagonal manganites $R$MnO$_3$ and ferrites
+$R$FeO$_3$ ($R$ = Sc, Y, In, Ho-Lu) exhibit strong couplings between electric,
+magnetic and structural degrees of freedom, with the transition-metal ions in
+the basal plane antiferromagnetically coupled through super-exchange so as to
+form a 120$^\circ$ noncollinear spin arrangement. Here we present a theoretical
+study of the magnetic charges, and of the spin-lattice and spin-electronic ME
+constants, in these hexagonal manganites and ferrites, clarifying the
+conditions under which exchange striction leads to an enhanced $Z^{\rm m}$
+values and anomalously large in-plane spin-lattice ME effects.",1504.03405v1
+2015-05-04,Phase Diagrams of Forced Magnetic Reconnection in Taylor's Model,"Recent progress in the understanding of how externally driven magnetic
+reconnection evolves is organized in terms of parameter space diagrams. These
+diagrams are constructed using four pivotal dimensionless parameters: the
+Lundquist number $S$, the magnetic Prandtl number $P_m$, the amplitude of the
+boundary perturbation $\hat \Psi_0$, and the perturbation wave number $\hat k$.
+This new representation highlights the parameters regions of a given system in
+which the magnetic reconnection process is expected to be distinguished by a
+specific evolution. Contrary to previously proposed phase diagrams, the
+diagrams introduced here take into account the dynamical evolution of the
+reconnection process and are able to predict slow or fast reconnection regimes
+for the same values of $S$ and $P_m$, depending on the parameters that
+characterize the external drive, never considered so far. These features are
+important to understand the onset and evolution of magnetic reconnection in
+diverse physical systems",1505.00726v1
+2015-05-06,Hydromagnetics of advective accretion flows around black holes: Removal of angular momentum by large scale magnetic stresses,"We show that the removal of angular momentum is possible in the presence of
+large scale magnetic stresses in geometrically thick, advective, sub-Keplerian
+accretion flows around black holes in steady-state, in the complete absence of
+alpha-viscosity. The efficiency of such an angular momentum transfer could be
+equivalent to that of alpha-viscosity with alpha=0.01-0.08. Nevertheless,
+required field is well below its equipartition value, leading to a magnetically
+stable disk flow. This is essentially important in order to describe the hard
+spectral state of the sources, when the flow is non/sub-Keplerian. We show in
+our simpler 1.5-dimensional, vertically averaged disk model that larger the
+vertical-gradient of azimuthal component of magnetic field, stronger the rate
+of angular momentum transfer is, which in turn may lead to a faster rate of
+outflowing matter. Finding efficient angular momentum transfer, in black hole
+disks, via magnetic stresses alone is very interesting, when the generic origin
+of alpha-viscosity is still being explored.",1505.01281v1
+2015-05-12,Getting through to a qubit by magnetic solitons,"We propose a method for acting on the spin state of a spin-1/2 localized
+particle, or `qubit', by means of a magnetic signal effectively generated by
+the nearby transit of a magnetic soliton, there conveyed through a transmission
+line. We first introduce the specific magnetic soliton of which we will make
+use, and briefly review the properties that make it apt to represent a signal.
+We then show that a Heisenberg spin chain can serve as transmission line, and
+propose a method for injecting a soliton into the chain by acting just on one
+of its ends. We finally demonstrate that the resulting magnetic pulse can
+indeed cause, just passing by the spin-1/2 localized particle embodying the
+qubit, a permanent change in its spin state, thus realizing the possibility of
+getting through to a single, localized qubit, and manipulate its state. A
+thorough analysis of how the overall dynamical system operates depending on the
+setting of its parameters demonstrates that fine tuning is not necessary as it
+exists an extended region in the parameters space that corresponds to an
+effective functioning. Moreover, we show that possible noise on the
+transmission line does not invalidate the scheme.",1505.02954v1
+2015-05-15,Electric-field guiding of magnetic skyrmions,"We theoretically study equilibrium and dynamic properties of nanosized
+magnetic skyrmions in thin magnetic films with broken inversion symmetry, where
+electric field couples to magnetization via spin-orbit coupling. Based on a
+symmetry-based phenomenology and micromagnetic simulations we show that this
+electric-field coupling, via renormalizing the micromagnetic energy, modifies
+the equilibrium properties of the skyrmion. This change, in turn, results in a
+significant alteration of the current-induced skyrmion motion. Particularly,
+speed and direction of the skyrmion can be manipulated by designing a desired
+energy landscape electrically, which we describe within Thiele's analytical
+model and demonstrate in micromagnetic simulations including
+electric-field-controlled magnetic anisotropy. We additionally use this
+electric-field control to construct gates for controlling skyrmion motion
+exhibiting a transistor-like and multiplexer-like function. The proposed
+electric-field effect can thus provide a low energy electrical knob to extend
+the reach of information processing with skyrmions.",1505.03972v1
+2015-06-02,Nonlocal Magnetoresistance Mediated by Spin Superfluidity,"The electrical response of two diffusive metals is studied when they are
+linked by a magnetic insulator hosting a topologically stable (superfluid) spin
+current. We discuss how charge currents in the metals induce a spin
+supercurrent state, which in turn generates a magnetoresistance that depends on
+the topology of the electrical circuit. This magnetoresistance relies on phase
+coherence over the entire magnet and gives direct evidence for spin
+superfluidity. We show that driving the magnet with an ac current allows
+coherent spin transport even in the presence of U(1)-breaking magnetic
+anisotropy that can preclude dc superfluid transport. Spin transmission in the
+ac regime shows a series of resonance peaks as a function of frequency. The
+peak locations, heights, and widths can be used to extract static interfacial
+properties, e.g., the spin-mixing conductance and effective spin Hall angle,
+and to probe dynamic properties such as the spin-wave dispersion. Thus, ac
+transport may provide a simpler route to realizing nonequilbrium coherent spin
+transport and a useful way to characterize the magnetic system, serving as a
+precursor to the realization of dc superfluid spin transport.",1506.01059v2
+2015-06-11,Regular Reduction of Controlled Magnetic Hamiltonian System with Symmetry of the Heisenberg Group,"A controlled magnetic Hamiltonian (CMH) system is a regular controlled
+Hamiltonian (RCH) system with magnetic symplectic form, it is an important
+special case of RCH system. Note that there is a magnetic term on the cotangent
+bundle of the Heisenberg group, such that we can define a CMH system with
+symmetry of the Heisenberg group. Since the set of the CMH systems with
+symmetries is a subset of the RCH systems with symmetries, and it is not
+complete under the regular point reduction of RCH system, in this paper, then
+we give the regular point reduction of a CMH system with symmetry of the
+Heisenberg group, and discuss the M-CH-equivalence and MR-CH-equivalence, and
+prove the regular point reduction theorem for such CMH system. In particular,
+we deduce the regular point reduced CMH system on the generalization of
+coadjoint orbit of the Heisenberg group by calculation in detail. As an
+application, we consider the motion of the Heisenberg particle in a magnetic
+field.",1506.03640v4
+2015-07-13,Magnetic reconnection in plasma under inertial confinement fusion conditions driven by heat flux effects in Ohm's law,"In the interaction of high-power laser beams with solid density plasma there
+are a number of mechanisms that generate strong magnetic fields. Such fields
+subsequently inhibit or redirect electron flows, but can themselves be advected
+by heat fluxes, resulting in complex interplay between thermal transport and
+magnetic fields.We show that for heating by multiple laser spots reconnection
+of magnetic field lines can occur, mediated by these heat fluxes, using a fully
+implicit 2D Vlasov-Fokker-Planck code. Under such conditions, the reconnection
+rate is dictated by heat flows rather than Alfv\`enic flows. We find that this
+mechanism is only relevant in a high $\beta$ plasma. However, the Hall
+parameter $\omega_c \tau_{ei}$ can be large so that thermal transport is
+strongly modified by these magnetic fields, which can impact longer time scale
+temperature homogeneity and ion dynamics in the system.",1507.03629v1
+2015-07-23,Nanomagnet coupled to quantum spin Hall edge: An adiabatic quantum motor,"The precessing magnetization of a magnetic islands coupled to a quantum spin
+Hall edge pumps charge along the edge. Conversely, a bias voltage applied to
+the edge makes the magnetization precess. We point out that this device
+realizes an adiabatic quantum motor and discuss the efficiency of its operation
+based on a scattering matrix approach akin to Landauer-B""uttiker theory.
+Scattering theory provides a microscopic derivation of the
+Landau-Lifshitz-Gilbert equation for the magnetization dynamics of the device,
+including spin-transfer torque, Gilbert damping, and Langevin torque. We find
+that the device can be viewed as a Thouless motor, attaining unit efficiency
+when the chemical potential of the edge states falls into the
+magnetization-induced gap. For more general parameters, we characterize the
+device by means of a figure of merit analogous to the ZT value in
+thermoelectrics.",1507.06505v2
+2015-10-24,"On the ""force-free surface "" of the magnetized celestial bodies","The field of a uniformly magnetized rotating sphere is studied with special
+attention to the surface where the electric and magnetic fields are orthogonal
+to each other. The equation of this surface, valid at arbitrary distances from
+the rotating magnetized sphere, is obtained. Inside the light cylinder this
+surface can be considered as a force-free surface, i.e. as a place where the
+particles with strong radiation damping can be trapped due to their energy
+loss. Outside the light cylinder this surface makes just a geometric locus
+which moves with a superlight velocity around the axis of rotation. The 2- and
+3-dimensional plots of the force-free surface are constructed. Estimation of
+influence of the centrifugal force on the particle dynamics is made. It is
+shown, that in case of strong magnetic field the centrifugal force is
+negligible small everywhere except a narrow neighbourhood of the light
+cylinder.",1510.07122v1
+2015-10-29,Self-Organization and Heating by Inward Diffusion in Magnetospheric Plasmas,"Through the process of inward diffusion, a strongly localized clump of plasma
+is created in a magnetosphere. The creation of the density gradient, instead of
+the usual flattening by a diffusion process, can be explained by the
+topological constraints given by the adiabatic invariants of magnetized
+particles. After developing a canonical formalism for the standard guiding
+center dynamics in a dipole magnetic field, we complete our attempt to build a
+statistical mechanics on a constrained phase space by discussing the
+construction principles of the associated diffusion operator. We then
+investigate the heating mechanism associated with inward diffusion: as
+particles move toward regions of higher magnetic field, they experience
+preferential heating of the perpendicular (with respect to the magnetic field)
+temperature in order to preserve the magnetic moment. A relationship between
+conservation of bounce action and temperature isotropy emerged. We further show
+that this behavior is scaled by the diffusion parameter of the Fokker-Planck
+equation. These results are confirmed by numerical simulations.",1510.08571v2
+2015-10-29,Indirect switching of vortex polarity through magnetic dynamic coupling,"Magnetic vortex cores exhibit a gyrotropic motion, and may reach a critical
+velocity, at which point they invert their z-component of the magnetization. We
+performed micromagnetic simulations to describe this vortex core polarity
+reversal in magnetic nanodisks presenting a perpendicular anisotropy. We found
+that the critical velocity decreases with increasing perpendicular anisotropy,
+therefore departing from a universal criterion, that relates this velocity only
+to the exchange stiffness of the material. This leads to a critical velocity
+inversely proportional to the vortex core radius. We have also shown that in a
+pair of interacting disks, it is possible to switch the core vortex polarity
+through a non-local excitation; exciting one disk by applying a rotating
+magnetic field, one is able to switch the polarity of a neighbor disk, with a
+larger perpendicular anisotropy.",1510.08783v1
+2015-11-12,Magnetic Rigid Rotor in the Quantum Regime: Theoretical Toolbox,"We describe the quantum dynamics of a magnetic rigid rotor in the mesoscopic
+scale where the Einstein-De Haas effect is predominant. In particular, we
+consider a single-domain magnetic nanoparticle with uniaxial anisotropy in a
+magnetic trap. Starting from the basic Hamiltonian of the system under the
+macrospin approximation, we derive a bosonized Hamiltonian describing the
+center-of-mass motion, the total angular momentum, and the macrospin degrees of
+freedom of the particle treated as a rigid body. This bosonized Hamiltonian can
+be approximated by a simple quadratic Hamiltonian that captures the rich
+physics of a nanomagnet tightly confined in position, nearly not spinning, and
+with its macrospin anti-aligned to the magnetic field. The theoretical tools
+derived and used here can be applied to other quantum mechanical rigid rotors.",1511.04022v4
+2015-11-12,Thermally-driven spin torques in layered magnetic insulators,"Thermally-driven spin-transfer torques have recently been reported in
+electrically insulating ferromagnet$|$normal-metal heterostructures. In this
+paper, we propose two physically distinct mechanisms for such torques. The
+first is a local effect: out-of-equilibrium, thermally-activated magnons in the
+ferromagnet, driven by a spin Seebeck effect, exert a torque on the
+magnetization via magnon-magnon scattering with coherent dynamics. The second
+is a nonlocal effect which requires an additional magnetic layer to provide the
+symmetry breaking necessary to realize a thermal torque. The simplest structure
+in which to induce a nonlocal thermal torque is a spin valve composed of two
+insulating magnets separated by a normal metal spacer; there, a thermal flux
+generates a pure spin current through the spin valve, which results in a torque
+when the magnetizations of the layers are misaligned.",1511.04104v1
+2015-11-24,Ferromagnetic Resonance of a YIG film in the Low Frequency Regime,"An improved method for characterizing the magnetic anisotropy of films with
+cubic symmetry is described and is applied to an yttrium iron garnet (111)
+film. Analysis of the FMR spectra performed both in-plane and out-of-plane from
+0.7 to 8 GHz yielded the magnetic anisotropy constants as well as the
+saturation magnetization. The field at which FMR is observed turns out to be
+quite sensitive to anisotropy constants (by more than a factor ten) in the low
+frequency (< 2 GHz) regime and when the orientation of the magnetic field is
+nearly normal to the sample plane; the restoring force on the magnetization
+arising from the magnetocrystalline anisotropy fields is then comparable to
+that from the external field, thereby allowing the anisotropy constants to be
+determined with greater accuracy. In this region, unusual dynamical behaviors
+are observed such as multiple resonances and a switching of FMR resonance with
+only a 1 degree change in field orientation at 0.7 GHz.",1511.07892v1
+2015-11-27,RD-NMR spectra of the crystal states of the two-dimensional electron gas in a quantizing magnetic field,"Transport experiments on the two-dimensional electron gas (2DEG) confined
+into a semiconductor quantum well and subjected to a quantizing magnetic field
+have uncovered a rich variety of uniform and nonuniform phases such as the
+Laughlin liquids, the Wigner, bubble and Skyrme crystals and the quantum Hall
+stripe state. Optically pumped nuclear magnetic resonance (OP-NMR) has also
+been extremely useful in studying the magnetization and dynamics of electron
+solids with exotic spin textures such as the Skyrme crystal. Recently, it has
+been demonstrated that a related technique, resistively-detected nuclear
+magnetic resonance (RD-NMR), could be a good tool to study the topography of
+the electron solids in the fractional and integer quantum Hall regimes. In this
+work, we compute theoretically the RD-NMR line shapes of various crystal phases
+of the 2DEG and study the relation between their spin density and texture and
+their NMR spectra. This allows us to evaluate the ability of the RD-NMR to
+discriminate between the various types of crystal states.",1511.08702v1
+2015-12-10,Magnetic ordering and non-Fermi-liquid behavior in the multichannel Kondo-lattice model,"Scaling equations for the Kondo lattice in the paramagnetic and magnetically
+ordered phases are derived to two-loop order with account of spin dynamics. The
+results are applied to describe various mechanisms of the non-Fermi-liquid
+(NFL) behavior in the multichannel Kondo-lattice model where a fixed point
+occurs in the weak-coupling region. The corresponding temperature dependences
+of electronic and magnetic properties are discussed. The model describes
+naturally formation of a magnetic state with soft boson mode and small moment
+value. An important role of Van Hove singularities in the magnon spectral
+function is demonstrated. The results are rather sensitive to the type of
+magnetic ordering and space dimensionality, the conditions for NFL behavior
+being more favorable in the antiferromagnetic and 2D cases.",1512.03161v3
+2015-12-22,Observation of Unusual Magnetoelastic Effects in a Quasi-1D Spiral Magnet,"We present a systematic study of spin and lattice dynamics in the
+quasi-one-dimensional spiral magnet CuBr2, using Raman scattering in
+conjunction with infrared and neutron spectroscopy. Along with the development
+of spin correlations upon cooling, we observe a rich set of broad Raman bands
+at energies that correspond to phonon-dispersion energies near the
+one-dimensional magnetic wave vector. The low-energy bands further exhibit a
+distinct intensity maximum at the spiral magnetic ordering temperature. We
+attribute these unusual observations to two possible underlying mechanisms: (1)
+formation of hybrid spin-lattice excitations, and/or (2) ""quadrumerization"" of
+the lattice caused by spin-singlet entanglement in competition with the spiral
+magnetism.",1512.07120v2
+2016-01-04,Influence of magnetic quantum confined Stark effect on the spin lifetime of indirect excitons,"We report on the unusual and counter-intuitive behaviour of spin lifetime of
+excitons in coupled semiconductor quantum wells (CQWs) in the presence of
+in-plane magnetic field. Instead of conventional acceleration of spin
+relaxation due to the Larmor precession of electron and hole spins we observe a
+strong increase of the spin relaxation time at low magnetic fields followed by
+saturation and decrease at higher fields. We argue that this non-monotonic spin
+relaxation dynamics is a fingerprint of the magnetic quantum confined Stark
+effect. In the presence of electric field along the CQW growth axis, an applied
+magnetic field efficiently suppresses the exciton spin coherence, due to
+inhomogeneous broadening of the $g$-factor distribution.",1601.00427v1
+2016-02-25,Nonequilibrium current-carrying steady states in the anisotropic $XY$ spin chain,"Out-of-equilibrium behavior is explored in the one-dimensional anisotropic
+$XY$ model. Initially preparing the system in the isotropic $XX$ model with a
+linearly varying magnetic field to create a domain-wall magnetization profile,
+dynamics is generated by rapidly changing the exchange interaction anisotropy
+and external magnetic field. Relaxation to a nonequilibrium steady state is
+studied analytically at the critical transverse Ising point, where correlation
+functions may be computed in closed form. For arbitrary values of anisotropy
+and external field, an effective generalized Gibbs' ensemble is shown to
+accurately describe observables in the long-time limit. Additionally, we find
+spatial oscillations in the exponentially decaying, transverse spin-spin
+correlation functions with wavelength set by the magnetization jump across the
+initial domain wall. This wavelength depends only weakly on anisotropy and
+magnetic field in contrast to the current, which is highly dependent on these
+parameters.",1602.08027v2
+2016-03-03,"Two dimensional, electronic particle tracking in liquids with a graphene-based magnetic sensor array","The investigation of liquid flow at the nanoscale is a key area of applied
+research with high relevance to Physics, Chemistry and Biology. We introduce a
+method and a device that allows to spatially resolve liquid flow by integrating
+an array of graphene-based magnetic sensors used for tracking the movement of
+magnetic nanoparticles in the liquid under investigation. With a novel device
+conception based on standard integration processes and experimentally verified
+material parameters, we simulate the performance of a single sensor pixel, as
+well as the whole array, for tracking magnetic nanoparticles. The results
+demonstrate the ability (a) to detect individual nanoparticles in the liquid
+and (b) to reconstruct particle trajectories across the sensor array as a
+function of time, in what we call ""Magnetic Nanoparticle Velocimetry""
+technique. Being a non-optical detection method, potential applications include
+particle tracking and flow analysis in opaque media at sub-micron scales.",1603.01298v1
+2016-03-18,A Comparison between Abraham and Minkowski Momenta,"In this paper I compare the Abraham and the Minkowski forms for the momentum
+pertaining to an electromagnetic wave inside a dielectric or a magnetic
+material. The discussion is based on a careful treatment of the surface charges
+and currents and of the forces acting on them. While in the dielectric case the
+Abraham momentum is certainly more appealing from the physical point of view,
+for a magnetic material it suggests an interpretation in terms of magnetic
+charges and re- lated magnetic currents. The Minkowski momentum for magnetic
+non conducting materials, on the contrary, has a natural interpretation in
+terms of an amperian model, in which the dynamics is determined by the Lorentz
+force acting on bulk and surface electric currents.",1603.05812v1
+2016-04-02,3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum,"Measurement of the coronal magnetic field is a crucial ingredient in
+understanding the nature of solar coronal dynamic phenomena at all scales. We
+employ STEREO/COR1 data obtained near maximum of solar activity in December
+2012 (Carrington rotation, CR 2131) to retrieve and analyze the
+three-dimensional (3D) coronal electron density in the range of heights from
+$1.5$ to $4\ \mathrm{R}_\odot$ using a tomography method and qualitatively
+deduce structures of the coronal magnetic field. The 3D electron density
+analysis is complemented by the 3D STEREO/EUVI emissivity in 195 \AA \ band
+obtained by tomography for the same CR period. We find that the magnetic field
+configuration during CR 2131 has a tendency to become radially open at
+heliocentric distances below $\sim 2.5 \ \mathrm{R}_\odot$. We compared the
+reconstructed 3D coronal structures over the CR near the solar maximum to the
+one at deep solar minimum. Results of our 3D density reconstruction will help
+to constrain solar coronal field models and test the accuracy of the magnetic
+field approximations for coronal modeling.",1604.00535v1
+2016-04-18,Slipping magnetic reconnections with multiple flare ribbons during an X-class solar flare,"With the observations of the Solar Dynamics Observatory, we present the
+slipping magnetic reconnections with multiple flare ribbons (FRs) during an
+X1.2 eruptive flare on 2014 January 7. A center negative polarity was
+surrounded by several positive ones, and there appeared three FRs. The three
+FRs showed apparent slipping motions, and hook structures formed at their ends.
+Due to the moving footpoints of the erupting structures, one tight
+semi-circular hook disappeared after the slippage along its inner and outer
+edge, and coronal dimmings formed within the hook. The east hook also faded as
+a result of the magnetic reconnection between the arcades of a remote filament
+and a hot loop that was impulsively heated by the under flare loops. Our
+results are accordant with the slipping magnetic reconnection regime in 3D
+standard model for eruptive flares. We suggest that complex structures of the
+flare is likely a consequence of the more complex flux distribution in the
+photosphere, and the eruption involves at least two magnetic reconnections.",1604.04982v1
+2016-04-21,Inverse Magnetic Catalysis in Bottom-Up Holographic QCD,"We explore the effect of magnetic field on chiral condensation in QCD via a
+simple bottom up holographic model which inputs QCD dynamics through the
+running of the anomalous dimension of the quark bilinear. Bottom up holography
+is a form of effective field theory and we use it to explore the dependence on
+the coefficients of the two lowest order terms linking the magnetic field and
+the quark condensate. In the massless theory, we identify a region of parameter
+space where magnetic catalysis occurs at zero temperature but inverse magnetic
+catalysis at temperatures of order the thermal phase transition. The model
+shows similar non-monotonic behaviour in the condensate with B at intermediate
+T as the lattice data. This behaviour is due to the separation of the meson
+melting and chiral transitions in the holographic framework. The introduction
+of quark mass raises the scale of B where inverse catalysis takes over from
+catalysis until the inverse catalysis lies outside the regime of validity of
+the effective description leaving just catalysis.",1604.06307v1
+2016-04-26,Tuning the resonant frequencies of a drop by a magnetic field,"We report an experimental study of a magnetic liquid drop deposited on a
+superhydrophobic substrate and subjected to vertical vibrations in presence of
+a static magnetic field. It is well-known that a flattened drop of usual liquid
+displays oscillating lobes at its periphery when vibrated. By adding
+ferromagnetic nanoparticles to a water drop and varying the strength of the
+magnetic field, we are experimentally able to efficiently tune the resonant
+frequencies of the drop. By using conservation energy arguments, we show that
+the magnetic field contribution is equivalent to adding an effective negative
+surface tension to the drop. Our model is found in good agreement with the
+experiments with no fitting parameter.",1604.07686v1
+2016-04-27,History dependence of the magnetic properties of single-crystal Fe$_{1-x}$Co$_{x}$Si,"We report the magnetization, ac susceptibility, and specific heat of
+optically float-zoned single crystals of Fe$_{1-x}$Co$_{x}$Si, $0.20 \leq x
+\leq 0.50$. We determine the magnetic phase diagrams for all major
+crystallographic directions and cooling histories. After zero-field cooling,
+the phase diagrams resemble that of the archetypal stoichiometric cubic chiral
+magnet MnSi. Besides the helical and conical state, we observe a pocket of
+skyrmion lattice phase just below the helimagnetic ordering temperature. At the
+phase boundaries between these states evidence for slow dynamics is observed.
+When the sample is cooled in small magnetic fields, the phase pocket of
+skyrmion lattice may persist metastably down to lowest temperatures. Taken
+together with the large variation of the transition temperatures, transition
+fields, and the helix wavelength as a function of composition, this hysteresis
+identifies Fe$_{1-x}$Co$_{x}$Si as an ideal material for future experiments
+exploring, for instance, the topological unwinding of the skyrmion lattice.",1604.08025v1
+2016-05-06,Observations of an X-shaped Ribbon Flare in the Sun and Its Three-dimensional Magnetic Reconnection,"We report evolution of an atypical X-shaped flare ribbon which provides novel
+observational evidence of three-dimensional (3D) magnetic reconnection at a
+separator. The flare occurred on 2014 November 9. High-resolution slit-jaw 1330
+A images from the Interface Region Imaging Spectrograph reveal four
+chromospheric flare ribbons that converge and form an X-shape. Flare
+brightening in the upper chromosphere spreads along the ribbons toward the
+center of the ""X"" (the X-point), and then spreads outward in a direction more
+perpendicular to the ribbons. These four ribbons are located in a quadrupolar
+magnetic field. Reconstruction of magnetic topology in the active region
+suggests the presence of a separator connecting to the X-point outlined by the
+ribbons. The inward motion of flare ribbons in the early stage therefore
+indicates 3D magnetic reconnection between two sets of non-coplanar loops that
+approach laterally, and reconnection proceeds downward along a section of
+vertical current sheet. Coronal loops are also observed by the Atmospheric
+Imaging Assembly on board the Solar Dynamics Observatory confirming the
+reconnection morphology illustrated by ribbon evolution.",1605.01833v1
+2016-06-01,Magnetic field strength in an intermediate-velocity ionized filament in the First Galactic Quadrant,"We investigate the magnetic field in an intermediate-velocity filament for
+which the H$\alpha$ intensity in the WHAM survey correlates with excess Faraday
+rotation of extragalactic radio sources over the length of the filament from b
+~ 20 degr. to b ~ 55 degr. The density-weighted mean magnetic field is 2.8 +/-
+0.8 microgauss, derived from rotation measures and an empirical relation
+between H-alpha emission measure and dispersion measure from Berkhuijsen et al.
+(2006). In view of the uncertainties in the derived magnetic field strength, we
+propose an alternative use of the available data, rotation measure and emission
+measure, to derive a lower limit to the Alfven speed, weighted by electron
+density n_e^1.5. We find lower limits to the Alfven speed that are comparable
+to, or larger than the sound speed in a 10^4 K plasma, and conclude that the
+magnetic field is dynamically important. We discuss the role of
+intermediate-velocity gas as a locus of Faraday rotation in the interstellar
+medium, and propose this lower limit to the Alfven speed may also be applicable
+to Faraday rotation by galaxy clusters.",1606.00415v1
+2016-06-12,Using SDO/HMI magnetograms as a source of the solar mean magnetic field data,"The solar mean magnetic field (SMMF) provided by the Wilcox Solar Observatory
+(WSO) is compared with the SMMF acquired by the \textit{Helioseismic and
+Magnetic Imager} (HMI) onboard the \textit{Solar Dynamic Observatory} (SDO). We
+found that despite the different spectral lines and measurement techniques used
+in both instruments the Pearson correlation coefficient between these two
+datasets equals 0.86 while the conversion factor is very close to unity: B(HMI)
+= 0.99(2)B(WSO). We also discuss artifacts of the SDO/HMI magnetic field
+measurements, namely the 12 and 24-hour oscillations in SMMF and in sunspots
+magnetic fields that might be caused by orbital motions of the spacecraft. The
+artificial harmonics of SMMF reveal significant changes in amplitude and the
+nearly stable phase. The connection between the 24-hour harmonic amplitude of
+SMMF and the presence of sunspots is examined. We also found that opposite
+phase artificial 12 and/or 24-hour oscillations exist in sunspots of opposite
+polarities.",1606.03710v1
+2016-06-20,Fundamental Implications of Intergalactic Magnetic Field Observations,"Helical intergalactic magnetic fields at the $\sim 10^{-14}~{\rm G}$ level on
+$\sim 10~{\rm Mpc}$ length scales are indicated by current gamma ray
+observations. The existence of magnetic fields in cosmic voids and their
+non-trivial helicity suggest that they must have originated in the early
+universe and thus have implications for the fundamental interactions. I combine
+present knowledge of the observational constraints and the dynamics of
+cosmological magnetic fields to derive characteristics that would need to be
+explained by the magnetic field generation mechanism. The importance of CP
+violation and a possible crucial role for chiral effects in the early universe
+are pointed out.",1606.06186v2
+2016-06-23,QCD Phase-transition and chemical freezeout in nonzero magnetic field at NICA,"Because of relativistic off-center motion of the charged spectators and the
+local momentum-imbalance experienced by the participants, a huge magnetic field
+is likely generated in high-energy collisions. The influence of such
+short-lived magnetic field on the QCD phase-transition(s) shall be analysed.
+From Polyakov linear-sigma model, we study the chiral phase-transition and the
+magnetic response and susceptibility in dependence on temperature, density and
+magnetic field strength. The systematic measurements of the phase-transition
+characterizing signals, such as the fluctuations, the dynamical correlations
+and the in-medium modifications of rho-meson, for instance, in different
+interacting systems and collision centralities are conjectured to reveal an
+almost complete description for the QCD phase-structure and the chemical
+freezeout. We limit the discussion to NICA energies.",1606.09153v1
+2016-06-30,Landau levels of cold dense quark matter in a strong magnetic field,"The occupied Landau levels of strange quark matter are investigated in the
+framework of the SU(3) NJL model with a conventional coupling and a
+magnetic-field dependent coupling respectively. At lower density, the Landau
+levels are mainly dominated by u and d quarks. Threshold values of the chemical
+potential for the s quark onset are shown in the $\mu$-$B$ plane. The
+magnetic-field-dependent running coupling can broaden the region of
+three-flavor matter by decreasing the dynamical masses of $s$ quarks. Before
+the onset of $s$ quarks, the Landau level number of light quarks is directly
+dependent on the magnetic field strength $B$ by a simple inverse proportional
+relation $k_{i,\mathrm{max}}\approx B_i^0/B$ with $B_d^0=5\times 10^{19}$ G,
+which is approximately 2 times $B_u^0$ of $u$ quarks at a common chemical
+potential. When the magnetic field increases up to $B^0_d$, almost all three
+flavors are lying in the lowest Landau level.",1606.09336v2
+2016-07-18,A low upper limit on the subsurface rise speed of solar active regions,"Magnetic field emerges at the surface of the Sun as sunspots and active
+regions. This process generates a poloidal magnetic field from a rising
+toroidal flux tube, it is a crucial but poorly understood aspect of the solar
+dynamo. The emergence of magnetic field is also important because it is a key
+driver of solar activity. We show that measurements of horizontal flows at the
+solar surface around emerging active regions, in combination with numerical
+simulations of solar magnetoconvection, can constrain the subsurface rise speed
+of emerging magnetic flux. The observed flows imply that the rise speed of the
+magnetic field is no larger than 150 m/s at a depth of 20 Mm, that is, well
+below the prediction of the (standard) thin flux tube model but in the range
+expected for convective velocities at this depth. We conclude that convective
+flows control the dynamics of rising flux tubes in the upper layers of the Sun
+and cannot be neglected in models of flux emergence.",1607.05250v1
+2016-08-08,Low-energy magnetoelectric control of domain states in exchange-coupled heterostructures,"The electric manipulation of antiferromagnets has become an area of great
+interest recently for zero-stray-field spintronic devices, and for their rich
+spin dynamics. Generally, the application of antiferromagnetic media for
+information memories and storage requires a heterostructure with a
+ferromagnetic layer for readout through the exchange-bias field. In
+magnetoelectric and multiferroic antiferromagnets, the exchange coupling exerts
+an additional impediment (energy barrier) to magnetization reversal by the
+applied magnetoelectric energy. We proposed and verified a method to overcome
+this barrier. We controlled the energy required for switching the magnetic
+domains in magnetoelectric \cro films by compensating the exchange-coupling
+energy from the ferromagnetic layer with the Zeeman energy of a small
+volumetric spontaneous magnetization found for the sputtered \cro films. Based
+on a simplified phenomenological model of the field-cooling process, the
+magnetic and electric fields required for switching could be tuned. As an
+example, the switching of antiferromagnetic domains around a zero-threshold
+electric field was demonstrated at a magnetic field of 2.6 kOe.",1608.02390v2
+2016-08-24,Maximizing Influence in an Ising Network: A Mean-Field Optimal Solution,"Influence maximization in social networks has typically been studied in the
+context of contagion models and irreversible processes. In this paper, we
+consider an alternate model that treats individual opinions as spins in an
+Ising system at dynamic equilibrium. We formalize the \textit{Ising influence
+maximization} problem, which has a natural physical interpretation as
+maximizing the magnetization given a budget of external magnetic field. Under
+the mean-field (MF) approximation, we present a gradient ascent algorithm that
+uses the susceptibility to efficiently calculate local maxima of the
+magnetization, and we develop a number of sufficient conditions for when the MF
+magnetization is concave and our algorithm converges to a global optimum. We
+apply our algorithm on random and real-world networks, demonstrating,
+remarkably, that the MF optimal external fields (i.e., the external fields
+which maximize the MF magnetization) shift from focusing on high-degree
+individuals at high temperatures to focusing on low-degree individuals at low
+temperatures. We also establish a number of novel results about the structure
+of steady-states in the ferromagnetic MF Ising model on general graph
+topologies, which are of independent interest.",1608.06850v2
+2016-09-09,The effect of magnetic field on mean flow generation by rotating two-dimensional convection,"Motivated by the significant interaction of convection, rotation and magnetic
+field in many astrophysical objects, we investigate the interplay between
+large-scale flows driven by rotating convection and an imposed magnetic field.
+We utilise a simple model in two dimensions comprised of a plane layer that is
+rotating about an axis inclined to gravity. It is known that this setup can
+result in strong mean flows; we numerically examine the effect of an imposed
+horizontal magnetic field on such flows. We show that increasing the field
+strength in general suppresses the time-dependent mean flows, but in some cases
+it organises them leading to stronger time-averaged flows. Further, we discuss
+the effect of the field on the correlations responsible for driving the flows
+and the competition between Reynolds and Maxwell stresses. A change in
+behaviour is observed when the (fluid and magnetic) Prandtl numbers are
+decreased. In the smaller Prandtl number regime, it is shown that significant
+mean flows can persist even when the quenching of the overall flow velocity by
+the field is relatively strong.",1609.02693v1
+2016-09-12,Spin decoherence of magnetic atoms on surfaces,"We review the problem of spin decoherence of magnetic atoms deposited on a
+surface. Recent breakthroughs in scanning tunnelling microscopy (STM) make it
+possible to probe the spin dynamics of individual atoms, either isolated or
+integrated in nanoengineered spin structures. Transport pump and probe
+techniques with spin polarized tips permit measuring the spin relaxation time
+$T_1$, while novel demonstration of electrically driven STM single spin
+resonance has provided a direct measurement of the spin decoherence time $T_2$
+of an individual magnetic adatom. Here we address the problem of spin
+decoherence from the theoretical point of view. First we provide a short
+general overview of decoherence in open quantum systems and we discuss with
+some detail ambiguities that arise in the case of degenerate spectra, relevant
+for magnetic atoms. Second, we address the physical mechanisms that allows
+probing the spin coherence of magnetic atoms on surfaces. Third, we discuss the
+main spin decoherence mechanisms at work on a surface, most notably, Kondo
+interaction, but also spin-phonon coupling and dephasing by Johnson noise.
+Finally, we propose some schemes to engineer spin decoherence.",1609.03389v2
+2016-09-16,Heat and momentum transfer for magnetoconvection in a vertical external magnetic field,"The scaling theory of Grossmann and Lohse (J. Fluid Mech. 407, 27 (2000)) for
+the turbulent heat and momentum transfer is extended to the magnetoconvection
+case in the presence of a (strong) vertical magnetic field. The comparison with
+existing laboratory experiments and direct numerical simulations in the
+quasistatic limit allows to restrict the parameter space to very low Prandtl
+and magnetic Prandtl numbers and thus to reduce the number of unknown
+parameters in the model. Also included is the Chandrasekhar limit for which the
+outer magnetic induction field B is large enough such that convective motion is
+suppressed and heat is transported by diffusion. Our theory identifies four
+distinct regimes of magnetoconvection which are distinguished by the strength
+of the outer magnetic field and the level of turbulence in the flow,
+respectively.",1609.05031v1
+2016-09-20,Static and Dynamic Magnetic Response of Fragmented Haldane-like Spin Chains in Layered Li3Cu2SbO6,"The structure and the magnetic properties of layered Li3Cu2SbO6 are
+investigated by powder X-ray diffraction, static susceptibility, and electron
+spin resonance studies up to 330 GHz. The XRD data experimentally verify the
+space group C2/m with halved unit cell volume in contrast to previously
+reported C2/c. In addition, the data show significant Li/Cu-intersite exchange.
+Static magnetic susceptibility and ESR measurements show two magnetic
+contributions, i.e. quasi-free spins at low-temperature and a spin-gapped
+magnetic subsystem, with about half of the spins being associated to each
+subsystem. The data suggest ferromagnetic-antiferromagnetic alternating chains
+with JFM = -285 K and JAFM = 160 K with a significant amount of Li-defects in
+the chains. The results are discussed in the scenario of fragmented 1D S = 1
+AFM chains with a rather high defect concentration of about 17% and associated
+S = 1/2 edge states of the resulting finite Haldane chains.",1609.06091v1
+2016-10-04,Magnetomechanical coupling and ferromagnetic resonance in magnetic nanoparticles,"We address the theory of the coupled lattice and magnetization dynamics of
+freely suspended single-domain nanoparticles. Magnetic anisotropy generates
+low-frequency satellite peaks in the microwave absorption spectrum and a
+blueshift of the ferromagnetic resonance (FMR) frequency. The low-frequency
+resonances are very sharp with maxima exceeding that of the FMR, because their
+magnetic and mechanical precessions are locked, thereby suppressing Gilbert
+damping. Magnetic nanoparticles can operate as nearly ideal motors that convert
+electromagnetic into mechanical energy. The Barnett/Einstein-de Haas effect is
+significant even in the absence of a net rotation.",1610.01072v2
+2016-10-10,"Spin-Wave Spectrum in Magnetic Nanodot with Continuous Transition between Vortex, Bloch-type Skyrmion and Néel-type Skyrmion States","We study spin-wave excitations in a circular ferromagnetic nanodot in
+different inhomogeneous, topologically non-trivial magnetization states,
+specifically, vortex and skyrmion states. Gradual change in the strength of the
+out-of-plane magnetic anisotropy and the Dzyaloshinskii-Moriya exchange
+interaction leads to continuous phase transitions between different stable
+magnetic configurations and allows for mapping of dynamic spin modes in and
+between the vortex, Bloch-type skyrmion and N\'eel-type skyrmion states. Our
+study elucidates the connections between gyrotropic modes, azimuthal spin waves
+and breathing modes in various stable magnetization states and helps to
+understand the rich spin excitation spectrum on the skyrmion background.",1610.02859v1
+2016-10-28,On the ions acceleration via collisionless magnetic reconnection in laboratory plasmas,"This work presents an analysis of the ion outflow from magnetic reconnection
+throughout fully kinetic simulations with typical laboratory plasmas values. A
+symmetric initial configuration for the density and magnetic field is
+considered across the current sheet. After analyzing the behavior of a set of
+nine simulations with a reduced mass ratio and with a permuted value of three
+initial electron temperature and magnetic field intensity, the best ion
+acceleration scenario is further studied with a realistic mass ratio in terms
+of the ion dynamics and energy budget. Interestingly, a series of shock waves
+structures are observed in the outflow, resembling the shock discontinuities
+found in recent magnetohydrodynamic (MHD) simulations. An analysis of the ion
+outflow at several distances from the reconnection point is presented, in light
+of possible laboratory applications. The analysis suggests that magnetic
+reconnection could be used as a tool for plasma acceleration, with applications
+ranging from electric propulsion to production of ion thermal beams.",1610.09104v1
+2016-12-17,$Ξ_c γ\rightarrowΞ^\prime_c$ transition in lattice QCD,"We evaluate the electromagnetic $\Xi_c \gamma \rightarrow\Xi_c^\prime$
+transition on 2+1 flavor lattices corresponding to a pion mass of $\sim 156$
+MeV. We extract the magnetic Sachs and Pauli form factors which give the
+$\Xi_c$-$\Xi_c^\prime$ transition magnetic moment and the decay rates of
+$\Xi_c^\prime$ baryons. We did not find a signal for the magnetic form factor
+of the neutral transition $\Xi_c^0 \gamma \rightarrow\Xi_c^{\prime 0}$, which
+is suppressed by the U-spin flavor symmetry. As a byproduct, we extract the
+magnetic form factors and the magnetic moments of $\Xi_c$ and $\Xi_c^\prime$
+baryons, which give an insight to the dynamics of $u/d$, $s$ and $c$ quarks
+having masses at different scales.",1612.05722v2
+2016-12-19,On the fragmentation boundary in magnetised self-gravitating discs,"We investigate the role of magnetic fields in the fragmentation of
+self-gravitating discs using 3D global ideal magnetohydrodynamic simulations
+performed with the ""phantom"" smoothed particle hydrodynamics code.
+  For initially toroidal fields, we find two regimes. In the first, where the
+cooling time is greater than five times the dynamical time, magnetic fields
+reduce spiral density wave amplitudes, which in turn suppresses fragmentation.
+This is the case even if the magnetic pressure is only a tenth of the thermal
+pressure. The second regime occurs when the cooling time is sufficiently short
+that magnetic fields cannot halt fragmentation.
+  We find that magnetised discs produce more massive fragments, due to both the
+additional pressure exerted by the magnetic field, and the additional angular
+momentum transport induced by Maxwell stresses. The fragments are confined to a
+narrower range of initial semimajor axes than those in unmagnetised discs. The
+orbital eccentricity and inclination distributions of unmagnetised and
+magnetised disc fragments are similar. Our results suggest the fragmentation
+boundary could be at cooling times a factor of two lower than predicted by
+purely hydrodynamical models.",1612.06145v1
+2017-01-10,"Dynamos and Differential Rotation: Advances at the Crossroads of Analytics, Numerics, and Observations","The recent observational, theoretical, and numerical progress made in
+understanding stellar magnetism is discussed. Particularly, this review will
+cover the physical processes thought to be at the origin of these magnetic
+fields and their variability, namely dynamo action arising from the interaction
+between convection, rotation, radiation and magnetic fields. Some care will be
+taken to cover recent analytical advances regarding the dynamics and magnetism
+of radiative interiors, including some thoughts on the role of a tachocline.
+Moreover, recent and rapidly advancing numerical modeling of convective dynamos
+will be discussed, looking at rapidly rotating convective systems, grand minima
+and scaling laws for magnetic field strength. These topics are linked to
+observations or their observational implications.",1701.02591v1
+2017-01-17,Corotating Magnetic Reconnection Site in Saturn's Magnetosphere,"Using measurements from the Cassini spacecraft in Saturn's magnetosphere, we
+propose a 3D physical picture of a corotating reconnection site, which can only
+be driven by an internally generated source. Our results demonstrate that the
+corotating magnetic reconnection can drive an expansion of the current sheet in
+Saturn's magnetosphere and, consequently, can produce Fermi acceleration of
+electrons. This reconnection site lasted for longer than one of Saturn's
+rotation period. The long-lasting and corotating natures of the magnetic
+reconnection site at Saturn suggest fundamentally different roles of magnetic
+reconnection in driving magnetospheric dynamics (e.g., the auroral
+precipitation) from the Earth. Our corotating reconnection picture could also
+potentially shed light on the fast rotating magnetized plasma environments in
+the solar system and beyond.",1701.04559v2
+2017-02-02,In-vivo biomagnetic characterisation of the American cockroach,"We present a quantitative method, utilising a highly sensitive quantum
+sensor, that extends applicability of magnetorelaxometry to biological samples
+at physiological temperature. The observed magnetic fields allow for
+non-invasive determination of physical properties of magnetic materials and
+their surrounding environment inside the specimen. The method is applied to
+American cockroaches and reveals magnetic deposits with strikingly different
+behaviour in alive and dead insects. We discuss consequences of this finding to
+cockroach magneto-reception. To our knowledge, this work represents the first
+characterisation of the magnetisation dynamics in live insects and helps to
+connect results from behavioural experiments on insects in magnetic fields with
+characterisation of magnetic materials in their corpses.",1702.00538v2
+2017-02-02,A majority gate with chiral magnetic solitons,"In magnetic materials nontrivial spin textures may emerge owing to the
+competition among different types of magnetic interactions. Among such spin
+textures, chiral magnetic solitons represent topologically protected spin
+configurations with particle-like properties. Based on atomistic spin dynamics
+simulations, we demonstrate that these chiral magnetic solitons are ideal to
+use for logical operations, and we demonstrate the functionality of a
+three-input majority gate, in which the input states can be controlled by
+applying an external electromagnetic field or spin-polarized currents. One of
+the main advantages of the proposed device is that the input and output signals
+are encoded in the chirality of solitons, that may be moved, allowing to
+perform logical operations using only minute electric currents. As an example
+we illustrate how the three input majority gate can be used to perform logical
+relations, such as Boolean AND and OR.",1702.00579v1
+2017-02-07,Propulsion and controlled steering of magnetic nanohelices,"Externally controlled motion of micro and nanomotors in a fluid environment
+constitutes a promising tool in biosensing, targeted delivery and environmental
+remediation. In particular, recent experiments have demonstrated that fuel-free
+propulsion can be achieved through the application of external magnetic fields
+on magnetic helically shaped structures. The magnetic interaction between
+helices and the rotating field induces a torque that rotates and propels them
+via the coupled rotational-translational motion. Recent works have shown that
+there exist certain optimal geometries of helical shapes for propulsion.
+However, experiments show that controlled motion remains a challenge at the
+nanoscale due to Brownian motion that interferes with the deterministic motion
+and makes it difficult to achieve controlled steering. In the present work we
+employ quantitatively accurate simulation methodology to design a setup for
+which magnetic nanohelices of 30 nm in radius, with and without cargo, can be
+accurately propelled and steered in the presence of thermal fluctuations. In
+particular, we demonstrate fast transport of such nanomotors and devise
+protocols in manipulating external fields to achieve directionally controlled
+steering at biologically relevant temperatures.",1702.01989v1
+2017-02-16,Microscopic theory of electrically induced spin torques in magnetic Weyl semimetals,"We theoretically study electrical responses of magnetization in Weyl
+semimetals. The Weyl semimetal is a new class of topological semimetals,
+possessing hedgehog type spin textures in momentum space. Because of this
+peculiar spin texture, an interplay of electron transport and spin dynamics
+might provide new method to electrical control of magnetization. In this paper,
+we consider the magnetically doped Weyl semimetals, and systematically study
+current- and charge-induced spin torque exerted on the local magnetization in
+three-dimensional Dirac-Weyl metals. We determine all current-induced spin
+torques including spin-orbit torque, spin-transfer torque, and the so-called
+$\beta$-term, up to first order with respect to spatial and temporal derivation
+and electrical currents. We find that spin-transfer torque and $\beta$-term are
+absent while spin-orbit torque is proportional to the axial current density. We
+also calculate the charge-induced spin torque microscopically. We find the
+charge-induced spin torque originates from the chiral anomaly due to the
+correspondence between spin operators and axial current operators in our model.",1702.04918v1
+2017-03-08,Spin dynamics of antiferromagnets in the presence of a homogeneous magnetization,"We use general hydrodynamic equations to determine the long-wavelength spin
+excitations in isotropic antiferromagnets in the presence of a homogeneous
+magnetization. The latter may be induced, such as in antiferromagnets in an
+external magnetic field, or spontaneous, such as in ferrimagnetic or canted
+phases that are characterized by the coexistence of antiferromagnetic and
+ferromagnetic order. Depending on the physical situation, we find propagating
+spin waves that are gapped in some cases and gapless in others, diffusive
+modes, or relaxational modes. The excitation spectra turn out to be
+qualitatively different depending on whether or not the homogeneous
+magnetization is a conserved quantity. The results lay the foundation for a
+description of a variety of quantum phase transitions, including the transition
+from a ferromagnetic metal to an antiferromagnetic one, and the spin-flop
+transitions that are observed in some antiferromagnets. They also are crucial
+for incorporating weak-localization and Altshuler-Aronov effects into the
+descriptions of quantum phases in both clean and disordered magnetic metals.",1703.03009v1
+2017-03-15,Model-Free Based Digital Control for Magnetic Measurements,"This paper presents a novel digital control strategy successfully implemented
+for a soft magnetic material characterization bench (Epstein frame type). The
+main objective is to control the magnetic induction waveform whatever the
+applied excitation and the material under study. Given the nonlinear nature of
+the magnetization curves of magnetic materials, an original model-free based
+control technique is considered. Special mention should be made of the
+interesting dynamic properties in closed-loop against the changes of the
+operating point related basically to the hysteresis form. The operation and the
+performances of the digital control method are illustrated in different working
+conditions through both simulation and experimental measurements.",1703.05395v1
+2017-03-20,Vortices in two-dimensional nanorings studied by means of the dynamical matrix method,"This paper concerns an investigation of the spin wave excitations in magnetic
+nanoparticles. We provide a detailed derivation of the theoretical method for
+the determination of the normal modes of confined magnetic systems based on a
+discrete lattice of magnetic moments. The method is based on the damping-free
+Landau-Lifshitz equation and general enough to be utilized for the magnetic
+system of any dimensionality, magnetic structure, shape, and size. As an
+example we explore the influence of the competition between exchange and
+dipolar interactions on the spectrum of normal modes as well as on the
+stability of the vortex state in two-dimensional nanorings. We show the
+lowest-frequency mode to be indicative of the dipolar-to-exchange iterations
+ratio. We also study behavior of the fundamental mode and present the influence
+of both, the discreteness of the lattice and the dipolar-to-exchange iterations
+ratio, on its hybridization with azimuthal modes. We complete the paper with a
+selective review of the spin wave excitations in circular dots to compare with
+the results obtained for the rings.",1703.06678v1
+2017-03-24,Evolution of magnetic and dielectric properties in Sr-substituted high temperature multiferroic YBaCuFeO5,"We report the evolution of structural, magnetic and dielectric properties due
+to partial substitution of Ba by Sr in the high temperature multiferroic
+YBaCuFeO5. This compound exhibits ferroelectric and antiferromagnetic
+transitions around 200 K and these two phenomena are presumed to be coupled
+with each other. Our studies on magnetic and dielectric properties of the
+YBa1-xSrxCuFeO5 (x = 0.0, 0.25 and 0.5) show that substitution of Sr shifts
+magnetic transition towards higher temperature whereas dielectric transition to
+lower temperature. These results points to the fact that magnetic and
+dielectric transitions get decoupled as a result of chemical pressure in form
+of Sr substitution. The nature of magnetodielectric coupling changes across the
+series with the presence of higher order coupling terms. Additionally in these
+compounds glassy dynamics of electric dipoles is observed at low temperatures.",1703.08319v1
+2017-04-07,Terahertz spectroscopy of crystal-field transitions in magnetoelectric TmAl3(BO3)4,"Dynamic magnetic properties of magnetoelectric TmAl3(BO3)4 borate have been
+investigated by terahertz spectroscopy. Crystal field (CF) transitions within
+the ground multiplet 3H6 of Tm3+ ions are observed and they are identified as
+magnetic-dipole transitions from the ground singlet A1 to the next excited
+doublet E of Tm3+ ions. Unexpected fine structure of the transitions is
+detected at low temperatures. The new modes are assigned to local distortions
+of the sites with D3 symmetry by Bi3+ impurities, which resulted in the
+splitting of A1 -> E transition. Two types of locally distorted sites are
+identified and investigated. The main contribution to the static magnetic
+susceptibility is shown to be determined by the matrix elements of the observed
+magnetic transitions. We demonstrate that even in case of local distortions the
+symmetry of the undistorted crystal is recovered for magnetic and for quadratic
+magnetoelectric susceptibilities.",1704.02198v1
+2017-04-11,Flux noise in a superconducting transmission line,"We study a superconducting transmission line (TL) formed by distributed LC
+oscillators and excited by external magnetic fluxes which are aroused from
+random magnetization (A) placed in substrate or (B) distributed at interfaces
+of a two-wire TL. Low-frequency dynamics of a random magnetic field is
+described based on the diffusion Langevin equation with a short-range source
+caused by (a) random amplitude or (b) gradient of magnetization. For a TL
+modeled as a two-port network with open and shorted ends, the effective
+magnetic flux at the open end has non-local dependency on noise distribution
+along the TL. The flux-flux correlation function is evaluated and analyzed for
+the regimes (Aa), (Ab). (Ba), and (Bb). Essential frequency dispersion takes
+place around the inverse diffusion time of random flux along the TL. Typically,
+noise effect increases with size faster than the area of TL. The flux-flux
+correlator can be verified both via the population relaxation rate of the
+qubit, which is formed by the Josephson junction shunted by the TL with flux
+noises, and via random voltage at the open end of the TL.",1704.03408v2
+2017-04-13,Majorana flipping of quarkonium spin states in transient magnetic field,"We demonstrate that spin flipping transitions occur between various
+quarkonium spin states due to transient magnetic field produced in non central
+heavy ion collisions (HICs). The inhomogeneous nature of the magnetic field
+results in \textit{non adiabatic evolution} of (spin)states of quarkonia moving
+inside the transient magnetic environment. Our calculations explicitly show
+that the consideration of azimuthal inhomogeneity gives rise to dynamical
+mixing between different spin states owing to Majorana spin flipping. Notably,
+this effect of non-adiabaticity is novel and distinct from previously predicted
+mixing of the singlet and one of the triplet states of quarkonia in the
+presence of a static and homogeneous magnetic field.",1704.04094v2
+2017-04-14,"Structures, phase transitions, and magnetic properties of Co3Si from first-principles calculations","Co3Si was recently reported to exhibit remarkable magnetic properties in the
+nanoparticle form [Appl. Phys. Lett. 108, 152406 (2016)], yet better
+understanding of this material is to be promoted. Here we report a study on the
+crystal structures of Co3Si using adaptive genetic algorithm, and discuss its
+electronic and magnetic properties from first-principles calculations. Several
+competing phases of Co3Si have been revealed from our calculations. We show
+that the hexagonal Co3Si structure reported in experiments has lower energy in
+non-magnetic state than ferromagnetic state at zero temperature. The
+ferromagnetic state of the hexagonal structure is dynamically unstable with
+imaginary phonon modes and transforms to a new orthorhombic structure, which is
+confirmed by our structure searches to have the lowest energy for both Co3Si
+and Co3Ge. Magnetic properties of the experimental hexagonal structure and the
+lowest-energy structures obtained from our structure searches are investigated
+in detail.",1704.04514v2
+2017-04-26,Experimental investigation of surface instability of a thin layer of a magnetic fluid,"In the present work the instability of a flat horizontal thin layer of a
+magnetic fluid (the depth of no more than 50 \mum) under the action of a
+uniform magnetic field is studied experimentally. It was revealed that the
+development of instability under the action of tilted magnetic field can lead
+to the formation of parallel ridges on a fluid surface; the ridges undergo a
+transformation into hexagonal system of conical peaks with the magnetic field
+increasing. The necessary conditions for the formation of these surface
+patterns are studied. It was found that the development of instability of quite
+thin layers may result in layers breakup. The dependencies of instability wave
+number on the system physical parameters are obtained. The time for the
+development of instability is measured. The experimental results are compared
+with the existing theory and discussed.",1704.08304v1
+2017-05-23,Magnetic field dynamos and magnetically triggered flow instabilities,"The project A2 of the LIMTECH Alliance aimed at a better understanding of
+those magnetohydrodynamic instabilities that are relevant for the generation
+and the action of cosmic magnetic fields. These comprise the hydromagnetic
+dynamo effect and various magnetically triggered flow instabilities, such as
+the magnetorotational instability and the Tayler instability. The project was
+intended to support the experimental capabilities to become available in the
+framework of the DREsden Sodium facility for DYNamo and thermohydraulic studies
+(DRESDYN). An associated starting grant was focused on the dimensioning of a
+liquid metal experiment on the newly found magnetic destabilization of rotating
+flows with positive shear. In this paper, the main results of these two
+projects are summarized.",1705.08189v1
+2017-05-29,Double Hall instability: A catalyzer of magnetic energy release,"A pictorial explanation for shear-Hall instability is suggested and shows
+that the shear flow is not necessary for the instability because its role can
+be played by the Hall effect of an inhomogeneous background magnetic field.
+Linear stability analysis for a simple model of magnetic field varying
+periodically in space confirms such a 'double Hall' instability. Numerical
+computations show a considerable increase in Ohmic dissipation rate at the
+nonlinear stage of instability development. Field dissipation has a spiky
+character associated with magnetic reconnection in current sheets and X-points.
+Double Hall instability can be significant for magnetic field dissipation in
+neutron star crusts and, possibly, in the solar corona.",1705.10077v3
+2017-06-11,Magnetization spin dynamics in a (LuBi)3Fe5O12 (BLIG) epitaxial film,"Bismuth substituted lutetium iron garnet (BLIG) films exhibit larger Faraday
+rotation, and have a higher Curie temperature than yttrium iron garnet. We have
+observed magnetic stripe domains and measured domain widths of 1.4 {\mu}{\mu}m
+using Fourier domain polarization microscopy, Faraday rotation experiments
+yield a coercive field of 5 Oe. These characterizations form the basis of
+micromagnetic simulations that allow us to estimate and compare spin wave
+excitations in BLIG films. We observed that these films support thermal magnons
+with a precessional frequency of 7 GHz with a line width of 400 MHz. Further,
+we studied the dependence of precessional frequency on the externally applied
+magnetic field. Brillouin light scattering experiments and precession
+frequencies predicted by simulations show similar trend with increasing field.",1706.03340v1
+2017-08-02,Realistic finite temperature simulations of magnetic systems using quantum statistics,"We have performed realistic atomistic simulations at finite temperatures
+using Monte Carlo and atomistic spin dynamics simulations incorporating quantum
+(Bose-Einstein) statistics. The description is much improved at low
+temperatures compared to classical (Boltzmann) statistics normally used in
+these kind of simulations, while at higher temperatures the classical
+statistics are recovered. This corrected low-temperature description is
+reflected in both magnetization and the magnetic specific heat, the latter
+allowing for improved modeling of the magnetic contribution to free energies. A
+central property in the method is the magnon density of states at finite
+temperatures and we have compared several different implementations for
+obtaining it. The method has no restrictions regarding chemical and magnetic
+order of the considered materials. This is demonstrated by applying the method
+to elemental ferromagnetic systems, including Fe and Ni, as well as Fe-Co
+random alloys and the ferrimagnetic system GdFe$_3$ .",1708.00709v1
+2017-08-16,Magnetoconductance signatures of chiral domain-wall bound states in magnetic topological insulators,"Recent magnetoconductance measurements performed on magnetic topological
+insulator candidates have revealed butterfly-shaped hysteresis. This hysteresis
+has been attributed to the formation of gapless chiral domain-wall bound states
+during a magnetic field sweep. We treat this phenomenon theoretically,
+providing a link between microscopic magnetization dynamics and butterfly
+hysteresis in magnetoconductance. Further, we illustrate how a spatially
+resolved conductance measurement can probe the most striking feature of the
+domain-wall bound states: their chirality. This work establishes a regime where
+a definitive link between butterfly hysteresis in longitudinal
+magneto-conductance and domain-wall bound states can be made. This analysis
+provides an important tool for the identification of magnetic topological
+insulators.",1708.05032v2
+2017-08-18,Antiferromagnetic nano-oscillator in external magnetic fields,"We describe the dynamics of an antiferromagnetic nano-oscillator in an
+external magnetic field of any given time distribution. The oscillator is
+powered by a spin current originating from spin-orbit effects in a neighboring
+heavy metal layer, and is capable of emitting a THz signal in the presence of
+an additional easy-plane anisotropy. We derive an analytical formula describing
+the interaction between such a system and an external field, which can affect
+the output signal character. Interactions with magnetic pulses of different
+shapes, with a sinusoidal magnetic field and with a sequence of rapidly
+changing magnetic fields are discussed. We also perform numerical simulations
+based on the Landau-Lifshitz-Gilbert equation with spin-transfer torque effects
+to verify the obtained results and find a very good quantitative agreement
+between analytical and numerical predictions.",1708.05590v2
+2017-09-08,Dynamics of trapped magnetic flux in superconducting FeTe0.65Se0.35,"The magnetic moment in the superconducting and normal state of a crystalline
+FeTe0.65Se0.35 superconductor, grown by the Bridgman's method with relatively
+high growth rate, was measured. The temperature and magnetic field dependences
+of magnetization and its relaxation time were determined. Studied crystal,
+being non-uniform due to high growth rate of 5 mm/h, exhibits smaller width of
+superconducting transition in comparison with an ideal crystal grown with
+velocity of 1 mm/h, and the difference in magnetic properties of crystals grown
+with various growth rate, related to their microstructure, is discussed.",1709.02627v1
+2017-09-28,Monolayer phosphorene under time-dependent magnetic field,"We obtain the exact wave function of a monolayer phosphorene under a low-
+intensity time-dependent magnetic field using the dynamical invariant method.
+We calculate the quantum-mechanical energy expectation value and the transition
+probability for a constant and an oscillatory magnetic field. For the former we
+observe that the Landau level energy varies linearly with the quantum numbers n
+and m and the magnetic field intensity B_0. No transition takes place. For the
+latter, we observe that the energy oscillates in time, increasing linearly with
+the Landau level n and m and nonlinearly with the magnetic field. The (k,l) to
+(n,m) transitions take place only for l=m. We investigate the (0,0) to (n,0)
+and (1,l) and (2,l) probability transitions.",1709.10188v1
+2017-10-03,Nonlinear Phononic Control and Emergent Magnetism in Mott Insulating Titanates,"Optical control of structure-driven magnetic order offers a platform for
+magneto-optical terahertz devices. We control the magnetic phases of $d^1$ Mott
+insulating titanates using nonlinear phononics to transiently perturb the
+atomic structure based on density functional theory (DFT) simulations and
+solutions to a lattice Hamiltonian including nonlinear multi-mode interactions.
+We show that magnetism is tuned by indirect excitation of a Raman-active phonon
+mode, which affects the amplitude of the TiO$_6$ octahedral rotations that
+couple to static Ti--O Jahn-Teller distortions, through infrared-active phonon
+modes of LaTiO$_3$ and YTiO$_3$. The mode excitation reduces the rotational
+angle, driving a magnetic phase transition from ferromagnetic (FM) to $A$-type
+antiferromagnetic (AFM), and finally a $G$-type AFM state. This novel $A$-AFM
+state arises from a change in the exchange interactions and is absent in the
+bulk equilibrium phase diagram, but it emerges as a dynamically accessible
+optically induced state under multi-mode excitations. Our work shows nonlinear
+phononic coupling is able to stabilize phases inaccessible to static chemical
+pressure or epitaxial strain.",1710.00993v2
+2017-10-09,Weak magnetic anisotropy in GdRh$_2$Si$_2$ studied by magnetic resonance,"The antiferromagnetically (AFM) ordered state of GdRh$_{2}$Si$_{2}$ which
+consists of AFM-stacked ferromagnetic layers is investigated by magnetic
+resonance spectroscopy. The almost isotropic Gd$^{3+}$ paramagnetic resonance
+becomes anisotropic in the AFM ordered region below 107 K. The emerging
+internal anisotropic exchange-fields are still small enough to allow an
+investigation of their magnetization dynamics by using a standard
+microwave-frequency magnetic resonance technique. We could characterize this
+anisotropy in detail in the ferromagnetic layers of the excitation at 9 and 34
+GHz. We derived a resonance condition for the AFM ordered phase to describe the
+weak in-plane anisotropic behaviour in combination with a mean-field analysis.",1710.03079v1
+2017-11-01,Far-field theory for trajectories of magnetic ellipsoids in rectangular and circular channels,"We report a method to control the positions of ellipsoidal magnets in flowing
+channels of rectangular or circular cross section at low Reynolds number.A
+static uniform magnetic field is used to pin the particle orientation, and the
+particles move with translational drift velocities resulting from hydrodynamic
+interactions with the channel walls which can be described using Blake's image
+tensor.Building on his insights, we are able to present a far-field theory
+predicting the particle motion in rectangular channels, and validate the
+accuracy of the theory by comparing to numerical solutions using the boundary
+element method.We find that, by changing the direction of the applied magnetic
+field, the motion can be controlled so that particles move either to a curved
+focusing region or to the channel walls.We also use simulations to show that
+the particles are focused to a single line in a circular channel.Our results
+suggest ways to focus and segregate magnetic particles in lab-on-a-chip
+devices.",1711.00376v1
+2017-11-03,Heteronuclear magnetisms with ultracold spinor bosonic gases in optical lattices,"Motivated by recent realizations of spin-1 NaRb mixtures in the experiments,
+here we investigate heteronuclear magnetism in the Mott-insulating regime.
+Different from the identical mixtures where the boson (fermion) statistics only
+admits even (odd) parity states from angular momentum composition, for
+heteronuclear atoms in principle all angular momentum states are allowed, which
+can give rise to new magnetic phases. Various magnetic phases can be developed
+over these degenerate spaces, however, the concrete symmetry breaking phases
+depend not only on the degree of degeneracy, but also the competitions from
+many-body interactions. We unveil these rich phases using the bosonic dynamical
+mean-field theory approach. These phases are characterized by various orders,
+including spontaneous magnetization order, spin magnitude order, singlet
+pairing order and nematic order, which may coexist, especially in the regime
+with odd parity. Finally we address the possible parameter regimes for
+observing these spin-ordered Mott phases.",1711.01203v1
+2017-11-19,Oblique propagation of electrostatic waves in a magnetized EPI plasma,"A theoretical investigation is carried out to understand the basic features
+of nonlinear propagation of heavy ion-acoustic (HIA) waves subjected to an
+external magnetic field in an electron-positron-ion (EPI) plasma which consists
+of cold magnetized positively charged heavy ion fluids, and superthermal
+distributed electrons and positrons. In the nonlinear regime, the Korteweg-de
+Vries (K-dV) and modified K-dV(MK-dV) equations describing the propagation of
+HIA waves are derived. The latter admits a solitary wave solution with both
+positive and negative potentials (for K-dV equation) and only positive
+potential (for mK-dV equation) in the weak amplitude limit. It is observed that
+the effects of external magnetic field (obliqueness), superthermal electrons
+and positrons, different plasma species concentration, heavy ion dynamics and
+temperature ratio significantly modify the basic features of solitary waves
+(SWs). The application of the results in a magnetized EPI plasma, which occurs
+in many astrophysical objects (e.g., pulsars, cluster explosions, and active
+galactic nuclei) is briefly discussed.",1711.06975v1
+2017-11-20,"Azimuthal Spin Wave Excitations in Magnetic Nanodots over the Soliton Background: Vortex, Bloch and Néel-like skyrmions","We study azimuthal spin-wave (SW) excitations in a circular ferromagnetic
+nanodot in different inhomogeneous, topologically non-trivial magnetization
+states, specifically, vortex, Bloch-type skyrmion and N\'eel-type skyrmion
+states. Continuous mapping of the SW spectrum between these states is realized
+with gradual change of the out-of-plane magnetic anisotropy and
+Dzyaloshinskii-Moriya exchange interaction (DMI). Our study shows lifting of
+the SW frequencies degeneracy and change in systematics of the frequency
+levels. The change is induced by a geometrical Berry phase, that is present for
+the dot-edge localized SWs in a vortex state and vanishes in skyrmion states.
+Furthermore, channeling of the azimuthal SWs localized at the skyrmion edge is
+present and induces large frequency splitting. This is attributed to DMI
+induced nonreciprocity, while coupling of the breathing and gyrotropic modes is
+related to soliton motion. Finally, an efficient coupling of the dynamic
+magnetization in the skyrmion state to uniform magnetic field in nanodots with
+non-circular symmetry is shown.",1711.07186v1
+2017-12-02,Coherent transport structures in magnetized plasmas II: Numerical results,"In a pair of linked articles (called Article I and II respectively) we apply
+the concept of Lagrangian Coherent Structures borrowed from the study of
+Dynamical Systems to magnetic field configurations in order to separate regions
+where field lines have different kind of behavior. In the present article,
+article II, by means of a numerical procedure we investigate the Lagrangian
+Coherent Structures in the case of a two-dimensional magnetic configuration
+with two island chains that are generated by magnetic reconnection and evolve
+nonlinearly in time. The comparison with previous results, obtained by assuming
+a fixed magnetic field configuration, allows us to explore the dependence of
+transport barriers on the particle velocity.",1712.00591v1
+2017-12-07,Enhancement of Pressure Perturbations in Ablation due to Kinetic Magnetised Transport Effects under Direct-Drive ICF relevant conditions,"We present for the first time kinetic 2D Vlasov-Fokker-Planck simulations,
+including both self-consistent magnetic fields and ablating ion outflow, of a
+planar ablating foil subject to nonuniform laser irradiation. Even for small
+hall parameters ($\omega \tau_{ei} \lesssim 0.05$) self-generated magnetic
+fields are sufficient to invert and enhance pressure perturbations. The mode
+inversion is caused by a combination of the Nernst advection of the magnetic
+field and the Righi-Leduc heat-flux. Non-local effects modify these processes.
+The mechanism is robust under plasma conditions tested; it is amplitude
+independent and occurs for a broad spectrum of perturbation wavelengths,
+$\lambda_p = 10-100\,$\mu m$. The ablating plasma response to a dynamically
+evolving speckle pattern perturbation, analogous to an optically smoothed beam,
+is also simulated. Similar to the single mode case, self-generated magnetic
+fields increase the degree of nonuniformity at the ablation surface by up to an
+order of magnitude and are found to preferentially enhance lower modes due to
+the resistive damping of high mode number magnetic fields.",1712.02663v3
+2017-12-18,Origin and dynamics of the Primordial Magnetic field in a parity violating plasma,"In this thesis, we have studied the generation and evolution of the magnetic
+field in the early Universe. We investigated the generation of magnetic fields
+in the presence of chiral symmetry and gravitational anomaly. We have used
+modified kinetic theory by Berry curvature and derived expressions for magnetic
+and vortical conductivities. We have also shown that there are two length
+scales: kinetic and viscous, which is one of the important results. In the
+latter part of the thesis, we have shown the effect of second-order viscous
+effects on the modes of the magnetic fields.",1712.06291v2
+2018-01-08,Low frequency spin dynamics in XY quantum spin ice Yb$_2$Pt$_2$O$_7$,"The XY pyrochlore Yb$_2$Ti$_2$O$_7$, with pseudo spin 1/2 at the Yb$^{3+}$
+site, has been celebrated as potential host for the quantum spin ice state. The
+substitution of non-magnetic Ti with Pt gives Yb$_2$Pt$_2$O$_7$, a system with
+remarkably similar magnetic properties. The large nuclear gyromagnetic ratio
+($\gamma_{n}/2 \pi = 9.15$~MHz/T) of $^{195}$Pt makes Yb$_2$Pt$_2$O$_7$ an
+ideal material for NMR investigation of its unconventional magnetic properties.
+Based on the $^{195}$Pt nuclear spin-lattice relaxation rate $1/T_1$ and the
+magnetic specific heat $C_{p}$ measured in a broad range of magnetic field
+$B_{ext}$, we demonstrate that the field-induced magnon gap linearly decreases
+with $B_{ext}$ but additional low energy mode of spin excitations emerge below
+$\sim 0.5$~T.",1801.02724v2
+2018-01-15,Incompressible inviscid resistive MHD surface waves in 2D,"We consider the dynamics of a layer of an incompressible electrically
+conducting fluid interacting with the magnetic field in a two-dimensional
+horizontally periodic setting. The upper boundary is in contact with the
+atmosphere, and the lower boundary is a rigid flat bottom. We prove the global
+well-posedness of the inviscid and resistive problem with surface tension
+around a non-horizontal uniform magnetic field; moreover, the solution decays
+to the equilibrium almost exponentially. One of the key observations here is an
+induced damping structure for the fluid vorticity due to the resistivity and
+transversal magnetic field.",1801.04694v2
+2018-01-18,The Of?p stars of the Magellanic Clouds: Are they strongly magnetic?,"All known Galactic Of?p stars have been shown to host strong, organized,
+magnetic fields. Recently, five Of?p stars have been discovered in the
+Magellanic Clouds. They posses photometric \citep{Naze} and spectroscopic
+\citep{Walborn} variability compatible with the Oblique Rotator Model (ORM).
+However, their magnetic fields have yet to be directly detected. We have
+developed an algorithm allowing for the synthesis of photometric observables
+based on the Analytic Dynamical Magnetosphere (ADM) model of \citet{Owocki}. We
+apply our model to OGLE photometry in order to constrain their magnetic
+geometries and surface dipole strengths. We predict that the field strengths
+for some of these candidate extra-Galactic magnetic stars may be within the
+detection limits of the FORS2 instrument.",1801.06152v1
+2018-01-25,Magnetic orders in a Fermi gas induced by cavity-field fluctuations,"We study magnetic orders of fermions under cavity-assisted Raman couplings in
+a one-dimensional lattice at half filling. The cavity-enhanced atom-photon
+coupling introduces a dynamic long-range interaction between the fermions,
+which competes with the short-range on-site interaction and leads to a variety
+of magnetic orders. Adopting a numerical density-matrix-renormalization-group
+method, we investigate the various magnetic orders and map out the steady-state
+phase diagram. Interestingly, as all the phase transitions take place outside
+the superradiant regime, the magnetic orders are associated with cavity-field
+fluctuations with a vanishing number of photons on the mean-field level.",1801.08254v1
+2018-01-29,Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems,"Spin-orbit coupling in inversion-asymmetric magnetic crystals and structures
+has emerged as a powerful tool to generate complex magnetic textures,
+interconvert charge and spin under applied current, and control magnetization
+dynamics. Current-induced spin-orbit torques mediate the transfer of angular
+momentum from the lattice to the spin system, leading to sustained magnetic
+oscillations or switching of ferromagnetic as well as antiferromagnetic
+structures. The manipulation of magnetic order, domain walls and skyrmions by
+spin-orbit torques provides evidence of the microscopic interactions between
+charge and spin in a variety of materials and opens novel strategies to design
+spintronic devices with potentially high impact in data storage, nonvolatile
+logic, and magnonic applications. This paper reviews recent progress in the
+field of spin-orbitronics, focusing on theoretical models, material properties,
+and experimental results obtained on bulk noncentrosymmetric conductors and
+multilayer heterostructures, including metals, semiconductors, and topological
+insulator systems. Relevant aspects for improving the understanding and
+optimizing the efficiency of nonequilibrium spin-orbit phenomena in future
+nanoscale devices are also discussed.",1801.09636v2
+2018-03-02,Laser induced phase transition in epitaxial FeRh layers studied by pump-probe valence band photoemission,"We use time-resolved X-ray photoelectron spectroscopy to probe the electronic
+and magnetization dynamics in FeRh films after ultrafast laser excitations. We
+present experimental and theoretical results which investigate the electronic
+structure of the FeRh during the first-order phase transition identifying a
+clear signature of the magnetic phase. We find that a spin polarized feature at
+the Fermi edge is a fingerprint of the magnetic status of the system that is
+independent of the long-range ferromagnetic alignment of the magnetic domains.
+We use this feature to follow the phase transition induced by a laser pulse in
+a pump-probe experiment and find that the magnetic transition occurs in less
+than 50 ps, and reaches its maximum in 100 ps.",1803.00780v1
+2018-03-04,Latitude dependence of convection and magnetic field generation in the cube,"The 3D thermal convection in the Boussinesq approximation with heating from
+below and dynamo in the cube are considered. We study dependence of the
+convection intensity and magnetic field generation on the latitude in
+$\beta$-plane approximation. It is shown that kinetic energy gradually
+increases from the poles to the equator more than order of magnitude. The model
+predicts the strong azimuthal thermal wind, which direction depends on the sign
+of the thermal convective fluctuations. The spatial scale of the arising flow
+is comparable to the scale of the physical domain. The magnetic energy
+increases as well, however dynamo efficiency, i.e., the ratio of the magnetic
+energy to the kinetic one decreases to the equator. This effect can explain
+predominance of the dipole configuration of the magnetic field observed in the
+planets and stars. The approach is useful for modeling of the
+magnetohydrodynamic turbulence in planetary cores and stellar convective zones.",1803.01344v1
+2018-03-07,Magnetic-field-induced crossover from the inverse Faraday effect to the optical orientation in EuTe,"A time-resolved optical pump-probe technique has been applied for studying
+the ultrafast dynamics in the magnetic semiconductor EuTe near the absorption
+band gap. We show that application of external magnetic field up to 6 T results
+in crossover from the inverse Faraday effect taking place on the femtosecond
+time scale to the optical orientation phenomenon with an evolution in the
+picosecond time domain. We propose a model which includes both these processes
+possessing different spectral and temporal properties. The circularly polarized
+optical pumping induces the optical electronic transition $4f^75d^0 \rightarrow
+4f^65d^1$ forming the absorption band gap in EuTe. The observed crossover is
+related to a strong magnetic-field shift of the band gap in EuTe at low
+temperatures. It was found that manipulation of spin states on intrinsic defect
+levels takes place on a time scale of 19 ps in the applied magnetic field of 6
+T.",1803.02633v1
+2018-03-12,Properties of Confined Ammonium Nitrate Ionic Liquids,"Ethylammonium nitrate (EAN) and propylammonium nitrate ionic liquids confined
+between polar glass plates and exposed to a strong magnetic field demonstrate
+gradually slowing diffusivity, a process that can be reversed by removing the
+sample from the magnetic field. The process can be described well by the Avrami
+equation, which is typical for autocatalytic (particularly, nucleation
+controlled) processes. The transition can be stopped by freezing the sample.
+Cooling and heating investigations showed differences in the freezing and
+melting behavior of the sample depending on whether it had been exposed to the
+magnetic field. After exposure to the magnetic field, the sample demonstrated a
+change in the state of residual water. Generally, our findings confirm our
+previous suggestion that alteration of the dynamic properties of confined
+ammonium nitrate ionic liquids exposed to a magnetic field is related to the
+alteration of real physical-chemical phases.",1803.04372v1
+2018-03-29,Giant resonant nonlinear damping in nanoscale ferromagnets,"Magnetic damping is a key metric for emerging technologies based on magnetic
+nanoparticles, such as spin torque memory and high-resolution biomagnetic
+imaging. Despite its importance, understanding of magnetic dissipation in
+nanoscale ferromagnets remains elusive, and the damping is often treated as a
+phenomenological constant. Here we report the discovery of a giant
+frequency-dependent nonlinear damping that strongly alters the response of a
+nanoscale ferromagnet to spin torque and microwave magnetic field. This novel
+damping mechanism originates from three-magnon scattering that is strongly
+enhanced by geometric confinement of magnons in the nanomagnet. We show that
+the giant nonlinear damping can invert the effect of spin torque on a
+nanomagnet leading to a surprising current-induced enhancement of damping by an
+antidamping torque. Our work advances understanding of magnetic dynamics in
+nanoscale ferromagnets and spin torque devices.",1803.10925v1
+2018-06-02,Ultra-low damping insulating magnetic thin films get perpendicular,"A magnetic material combining low losses and large Perpendicular Magnetic
+Anisotropy (PMA) is still a missing brick in the magnonic and spintronic
+fields. We report here on the growth of ultrathin Bismuth doped
+Y$_{3}$Fe$_{5}$O$_{12}$ (BiYIG) films on Gd$_{3}$Ga$_{5}$O$_{12}$ (GGG) and
+substituted GGG (sGGG) (111) oriented substrates. A fine tuning of the PMA is
+obtained using both epitaxial strain and growth induced anisotropies. Both
+spontaneously in-plane and out-of-plane magnetized thin films can be
+elaborated. Ferromagnetic Resonance (FMR) measurements demonstrate the high
+dynamic quality of these BiYIG ultrathin films, PMA films with Gilbert damping
+values as low as 3 10$^{-4}$ and FMR linewidth of 0.3 mT at 8 GHz are achieved
+even for films that do not exceed 30 nm in thickness. Moreover, we measure
+Inverse Spin Hall Effect (ISHE) on Pt/BiYIG stacks showing that the magnetic
+insulator$'$s surface is transparent to spin current making it appealing for
+spintronic applications.",1806.00658v1
+2018-06-04,Two-sided-loop jets associated with magnetic reconnection between emerging loops and twisted filament threads,"Coronal jets are always produced by magnetic reconnection between emerging
+flux and pre-existing overlying magnetic fields. When the overlying field is
+vertical/obilique or horizontal, the coronal jet will appear as anemone type or
+two-sided-loop type. Most of observational jets are of the anemone type, and
+only a few of two-sided-loop jets have been reported. Using the high-quality
+data from New Vacuum Solar Telescope, Interface Region Imaging Spectrograph,
+and Solar Dynamics Observatory, we present an example of two-sided-loop jets
+simultaneously observed in the chromosphere, transition region, and corona. The
+continuous emergence of magnetic flux brought in successively emerging of
+coronal loops and the slowly rising of an overlying horizontal filament
+threads. Sequentially, there appeared the deformation of the loops, the
+plasmoids ejection from the loop top, and pairs of loop brightenings and jet
+moving along the untwisting filament threads. All the observational results
+indicate there exist magnetic reconnection between the emerging loops and
+overlying horizontal filament threads, and it is the first example of
+two-sided-loop jets associated with ejected plasmoids and twisted overlying
+fields.",1806.00957v1
+2018-06-29,Magnetic impurities in Kondo insulators: An application to samarium hexaboride,"Impurities and defects in Kondo insulators can have an unusual impact on
+dynamics that blends with effects of intrinsic electron correlations. Such
+crystal imperfections are difficult to avoid, and their consequences are
+incompletely understood. Here we study magnetic impurities in Kondo insulators
+via perturbation theory of the s-d Kondo impurity model adapted to small
+bandgap insulators. The calculated magnetization and specific heat agree with
+recent thermodynamic measurements in samarium hexaboride (SmB$_6$). This
+qualitative agreement supports the physical picture of multi-channel Kondo
+screening of local moments by electrons and holes involving both intrinsic and
+impurity bands. Specific heat is thermally activated in zero field by Kondo
+screening through sub-gap impurity bands and exhibits a characteristic upturn
+as the temperature is decreased. In contrast, magnetization obtains a dominant
+quantum correction from partial screening by virtual particle-hole pairs in
+intrinsic bands. We point out that magnetic impurities could impact de Haas-van
+Alphen quantum oscillations in SmB$_6$, through the effects of Landau
+quantization in intrinsic bands on the Kondo screening of impurity moments.",1807.00005v2
+2018-08-21,Recent advances in spin-orbit torques: Moving towards device applications,"The ability of spintronic devices to utilize an electric current for
+manipulating the magnetization has resulted in large-scale developments, such
+as, magnetic random access memories and boosted the spintronic research area.
+In this regard, over the last decade, magnetization manipulation using
+spin-orbit torque has been devoted a lot of research attention as it shows a
+great promise for future ultrafast and power efficient magnetic memories. In
+this review, we summarize the latest advancements in spin-orbit torque research
+and highlight some of the technical challenges for practical spin-orbit torque
+devices. We will first introduce the basic concepts and highlight the latest
+material choices for spin-orbit torque devices. Then, we will summarize the
+important advancements in the study of magnetization switching dynamics using
+spin-orbit torque, which are important from scientific as well as technological
+aspect. The final major section focuses on the concept of external assist field
+free spin-orbit torque switching which is a requirement for practical
+spin-orbit torque devices.",1808.06829v1
+2018-08-25,Twisted magnetization states and inhomogeneous resonance modes in a Fe/Gd ferrimagnetic multilayer,"Static and dynamic magnetic properties of a ferrimagnetic
+[Fe(35A)/Gd(50A)]x12 superlattice were investigated in a wide 4-300 K
+temperature range using magneto-optical Kerr effect (MOKE) and ferromagnetic
+resonance (FMR) techniques. The multilayer structure was sputtered on a
+transparent glass substrate which made it possible to perform MOKE measurements
+on both Fe and Gd terminated sides of the superlattice. These experiments
+allowed us to detect a transition between field-aligned and canted magnetic
+states on both sides of the film and to distinguish between the bulk and
+surface twisted phases of the superlattice. As a result, the experimental H-T
+magnetic phase diagram of the system was obtained. FMR studies at frequencies
+7-36 GHz demonstrated a complex evolution of absorption spectra as temperature
+decreased from room down to 4 K. Two spectral branches were detected in the
+sample. Theoretical simulations show that the observed spectral branches
+correspond to different types of inhomogeneous resonance modes in the
+multilayer with non-uniform magnetization precession inside Gd layers.",1808.08466v1
+2018-09-19,A hypercritical accretion scenario in Central Compact Objects accompanied with an expected neutrino burst,"The measurement of the period and period derivative, and the canonical model
+of dipole radiation have provided a method to estimate the low superficial
+magnetic fields in the so-called Central Compact Objects (CCOs). In the present
+work, a scenario is introduced in order to explain the magnetic behavior of
+such CCOs. Based on magnetohydrodynamic simulations of the post core-collapse
+supernova phase during the hypercritical accretion episode, we argue that the
+magnetic field of a newborn neutron star could have been early buried. During
+this phase, thermal neutrinos are created mainly by the pair annihilation,
+plasmon decay, photo-neutrino emission and other processes. We study the
+dynamics of these neutrinos in this environment and also estimate the number
+expected of the neutrino events with their flavor ratios on Earth. The neutrino
+burst is the only viable observable that could provide compelling evidence of
+the hypercritical phase and therefore, the hidden magnetic field mechanism as
+the most favorable scenario to explain the anomalous low magnetic fields
+estimated for CCOs.",1809.07057v2
+2018-09-27,Decay of turbulence in a liquid metal duct flow with transverse magnetic field,"Decay of honeycomb-generated turbulence in a duct with a static transverse
+magnetic field is studied via direct numerical simulations. The simulations
+follow the revealing experimental study of Sukoriansky et al. (1986), in
+particular the paradoxical observation of high-amplitude velocity fluctuations,
+which exist in the downstream portion of the flow when the strong transverse
+magnetic field is imposed in the entire duct including the honeycomb exit, but
+not in other configurations. It is shown that the fluctuations are caused by
+the large-scale quasi-two-dimensional structures forming in the flow at the
+initial stages of the decay and surviving the magnetic suppression. Statistical
+turbulence properties, such as the energy decay curves, two-point correlations
+and typical length scales are computed. The study demonstrates that turbulence
+decay in the presence of a magnetic field is a complex phenomenon critically
+depending on the state of the flow at the moment the field is introduced.",1809.10777v2
+2018-09-28,Observation of magnetic-field-sweep-direction-dependent dynamic nuclear polarization under periodic optical electron spin pumping,"Optical pump-probe techniques are used to generate and measure electron spin
+polarization in a gallium arsenide epilayer in which the electron spin
+coherence time exceeds the mode-locked laser repetition period. Resonant spin
+amplification occurs at magnetic fields at which the electron spin polarization
+excited by successive laser pulses add constructively. Measurements of Kerr
+rotation as a function of applied magnetic field reveal nuclear spin
+polarization that aligns either with or against the external magnetic field
+depending on whether the applied magnetic field is being decreased or
+increased. Furthermore, the nuclear spin polarization magnitude varies in
+proportion to the perpendicular net electron spin polarization as the latter
+changes due to resonant spin amplification and other causes. We also report an
+experimental technique that reveals a minutes-long memory of precise field
+history in the electron-nuclear spin system.",1810.00055v2
+2018-10-31,Theory of chiral effects in magnetic textures with spin-orbit coupling,"We present a theoretical study of two-dimensional spatially and temporally
+varying magnetic textures in the presence of spin-orbit coupling (SOC) of both
+the Rashba and Dresselhaus types. We show that the effective gauge field due to
+these SOCs, contributes to the dissipative and reactive spin torques in exactly
+the same way as in electromagnetism. Our calculations reveal that Rashba
+(Dresselhaus) SOC induces a chiral dissipation in interfacial (bulk) inversion
+asymmetric magnetic materials. Furthermore, we show that in addition to chiral
+dissipation $\alpha_c$, these SOCs also produce a chiral renormalization of the
+gyromagnetic ratio $\tilde{\gamma}_c$, and show that the latter is
+intrinsically linked to the former via a simple relation $\alpha_c =
+(\tau/\tau_{\rm ex}) \tilde{\gamma}_c$, where $\tau_{\rm ex}$ and $\tau$ are
+the exchange time and the electron relaxation time, respectively. Finally, we
+propose a theoretical scheme based on the Scattering theory to calculate and
+investigate the properties of damping in chiral magnets. Our findings should in
+principle provide a guide for material engineering of effects related to chiral
+dynamics in magnetic textures with SOC.",1810.13065v1
+2018-12-20,Unidirectional spin-wave channeling along magnetic domain walls of Bloch type,"From the pioneering work of Winter [Phys. Rev. 124, 452 (1961)], a magnetic
+domain wall of Bloch type is known to host a special wall-bound spin-wave mode,
+which corresponds to spin-waves being channeled along the magnetic texture.
+Using micromagnetic simulations, we investigate spin-waves travelling inside
+Bloch walls formed in thin magnetic media with perpendicular-to-plane magnetic
+anisotropy and we show that their propagation is actually strongly
+nonreciprocal, as a result of dynamic dipolar interactions. We investigate
+spin-wave non-reciprocity effects in single Bloch walls, which allows us to
+clearly pinpoint their origin, as well as in arrays of parallel walls in stripe
+domain configurations. For such arrays, a complex domain-wall-bound spin-wave
+band structure develops, some aspects of which can be understood qualitatively
+from the single-wall picture by considering that a wall array consists of a
+sequence of up/down and down/up walls with opposite non-reciprocities.
+Circumstances are identified in which the non-reciprocity is so extreme that
+spin-wave propagation inside individual walls becomes unidirectional.",1812.08741v1
+2018-12-21,"Local magnetism, magnetic order and spin freezing in the 'nonmetallic metal' FeCrAs","We present the results of x-ray scattering and muon-spin relaxation
+($\mu^{+}$SR) measurements on the iron-pnictide compound FeCrAs. Polarized
+non-resonant magnetic x-ray scattering results reveal the 120$^\circ$
+periodicity expected from the suggested three-fold symmetric, non-collinear
+antiferromagnetic structure. $\mu^+$SR measurements indicate a magnetically
+ordered phase throughout the bulk of the material below $T_\mathrm{N}$=105(5)
+K. There are signs of fluctuating magnetism in a narrow range of temperatures
+above $T_\mathrm{N}$ involving low-energy excitations, while at temperatures
+well below $T_\mathrm{N}$ behaviour characteristic of freezing of dynamics is
+observed, likely reflecting the effect of disorder in our polycrystalline
+sample. Using density functional theory we propose a distinct muon stopping
+site in this compound and assess the degree of distortion induced by the
+implanted muon.",1812.09252v3
+2018-12-22,Diamagnetic field states in cosmological plasmas,"Using a generally covariant Electro-Vortic (magnetofluid) formalism for
+relativistic plasmas, the dynamical evolution of a generalized vorticity (a
+combination of the magnetic and kinematic parts) is studied in a cosmological
+context. We derive macroscopic vorticity and magnetic field structures that can
+emerge in spatial equilibrium configurations of the relativistic plasma. These
+fields, however, evolve in time. These magnetic and velocity fields fields are
+self-consistently sustained in a diamagnetic state in the expanding Universe,
+and do not require an external seed for their existence. In particular, we
+explore a special class of magnetic/velocity field structures supported by a
+plasma in which the generalized vorticity vanishes. We derive a highly
+interesting characteristic of such ""superconductor--like"" fields in a
+cosmological plasmas in the radiation--era in early Universe. In that case, the
+fields grow proportional to the scale factor, establishing a deep connection
+between the expanding universe and the primordial magnetic fields.",1812.09425v1
+2018-12-26,Self-diffusion in two-dimensional quasi-magnetized rotating dusty plasmas,"The self-diffusion phenomenon in a two-dimensional dusty plasma at extremely
+strong (effective) magnetic fields is studied experimentally and by means of
+molecular dynamics simulations. In the experiment the high magnetic field is
+introduced by rotating the particle cloud and observing the particle
+trajectories in a co-rotating frame, which allows reaching effective magnetic
+fields up to 3000 Tesla. The experimental results confirm the predictions of
+the simulations: (i) super-diffusive behavior is found at intermediate
+time-scales and (ii) the dependence of the self-diffusion coefficient on the
+magnetic field is well reproduced.",1812.10253v1
+2018-12-31,Electric field switching of the uniaxial magnetic anisotropy of an antiferromagnet,"Electric field control of magnetic anisotropy in ferromagnets has been
+intensively pursued in spintronics to achieve efficient memory and computing
+devices with low energy consumption. Compared with ferromagnets,
+antiferromagnets hold huge potential in high-density information storage for
+their ultrafast spin dynamics and vanishingly small stray field. However, the
+switching of magnetic anisotropy of antiferromagnets via electric field remains
+elusive. Here we use ferroelastic strain from piezoelectric materials to switch
+the uniaxial magnetic anisotropy and the N\'eel order reversibly in
+antiferromagnetic Mn2Au films with an electric field of only a few kV/cm at
+room temperature. Owing to the uniaxial magnetic anisotropy, a ratchet-like
+switching behavior driven by the N\'eel spin-orbit torque is observed in the
+Mn2Au, which can be reversed by electric fields.",1812.11868v1
+2019-01-02,Exploring the thermodynamics of spin-1 $^{87}$Rb Bose Gases with synthetic magnetization,"In this work, we study the thermodynamic properties of a spin-1 Bose gas
+across the Bose-Einstein condensation transition. We present the theoretical
+description of the thermodynamics of a trapped ideal spin-1 Bose gas and we
+describe the phases that can be obtained in this system as a function of the
+temperature and of the populations in the different spin components. We propose
+a simple way to realize a ""synthetic magnetization"" that can be used to probe
+the entire phase diagram while keeping the real magnetization of the system
+fixed. We experimentally demonstrate the use of such method to explore
+different phases in a sample with zero total magnetization. Our work opens up
+new perspectives to study isothermal quenching dynamics through different
+magnetic phases in spinor condensates.",1901.00427v2
+2019-02-04,Solitary wave excitations of skyrmion strings in chiral magnets,"Chiral magnets possess topological line excitations where the magnetization
+within each cross section forms a skyrmion texture. We study analytically and
+numerically the low-energy, non-linear dynamics of such a skyrmion string in a
+field-polarized cubic chiral magnet, and we demonstrate that it supports
+solitary waves. Theses waves are in general non-reciprocal, i.e., their
+properties depend on the sign of their velocity $v$, but this non-reciprocity
+diminishes with decreasing $|v|$. An effective field-theoretical description of
+the solitary waves is derived that is valid in the limit $v \to 0$ and gives
+access to their profiles and their existence regime. Our analytical results are
+quantitatively confirmed with micromagnetic simulations for parameters
+appropriate for the chiral magnet FeGe. Similarities with solitary waves found
+in vortex filaments of fluids are pointed out.",1902.01420v1
+2019-02-08,Magnetization beyond the Ising limit of Ho$_2$Ti$_2$O$_7$,"We report that the local Ising anisotropy in pyrochlore oxides - the crucial
+requirement for realizing the spin-ice state - can be broken by means of high
+magnetic fields. For the case of the well-established classical spin-ice
+compound Ho$_2$Ti$_2$O$_7$ the magnetization exceeds the angle-dependent
+saturation value of the Ising limit using ultra-high fields up to 120 T.
+However, even under such extreme magnetic fields full saturation cannot be
+achieved. Crystal-electric-field calculations reveal that a level crossing for
+two of the four ion positions leads to magnetization steps at 55 and 100 T. In
+addition, we show that by using a field sweep rate in the range of the
+spin-relaxation time the dynamics of the spin system can be probed. Exclusively
+at 25 ns/T a new peak of the susceptibility appears around 2 T. We argue, this
+signals the cross-over between spin-ice and polarized correlations.",1902.02990v1
+2019-02-12,Constraining Jupiter's internal flows using Juno magnetic and gravity measurements,"Deciphering the flow below the cloud-level of Jupiter remains a critical
+milestone in understanding Jupiter's internal structure and dynamics. The
+expected high-precision Juno measurements of both the gravity field and the
+magnetic field might help to reach this goal. Here we propose a method that
+combines both fields to constrain the depth dependent flow field inside
+Jupiter. This method is based on a mean-field electrodynamic balance that
+relates the flow field to the anomalous magnetic field, and geostrophic balance
+that relates the flow field to the anomalous gravity field. We find that the
+flow field has two distinct regions of influence - an upper region in which the
+flow affects mostly the gravity field, and a lower region in which the flow
+affects mostly the magnetic field. An optimization procedure allows to reach a
+unified flow structure that is consistent with both the gravity and the
+magnetic fields.",1902.04329v1
+2019-02-12,Hydrodynamic and Magnetohydrodynamic Simulations of Wire Turbulence,"We report on simulations of laboratory experiments in which magnetized
+supersonic flows are driven through a wire mesh. The goal of the study was to
+investigate the ability of such a configuration to generate supersonic, MHD
+turbulence. We first report on the morphological structures that develop in
+both magnetized and non-magnetized cases. We then analyze the flow using a
+variety of statistical measures, including power spectra and probability
+distribution functions of the density. Using these results we estimate the
+sonic mach number in the flows downstream of the wire mesh. We find the
+initially hypersonic (M=20) planar shock through the wire mesh does lead to
+downstream turbulent conditions. However, in both magnetized and non-magnetized
+cases, the resultant turbulence was marginally supersonic to transonic (M~1),
+and highly anisotropic in structure.",1902.05063v2
+2019-02-19,Electric quadrupole moment and the tensor magnetic polarizability of twisted electrons and a potential for their measurements,"For a twisted (vortex) Dirac particle in nonuniform electric and magnetic
+fields, the relativistic Foldy-Wouthuysen Hamiltonian is derived including high
+order terms describing new effects. The result obtained shows for the first
+time that a twisted spin-1/2 particle possesses a tensor magnetic
+polarizability and a measurable (spectroscopic) electric quadrupole moment. We
+have calculated the former parameter and have evaluated the latter one for a
+twisted electron. The tensor magnetic polarizability of the twisted electron
+can be measured in a magnetic storage ring because a beam with an initial
+orbital tensor polarization acquires a horizontal orbital vector polarization.
+The electric quadrupole moment is rather large and strongly influences the
+dynamics of the intrinsic orbital angular momentum. Three different methods of
+its measurements, freezing the intrinsic orbital angular momentum and two
+resonance methods, are proposed. The existence of the quadrupole moment of
+twisted electrons can lead to practical applications.",1902.06882v1
+2019-03-04,Thermoelectric microscopy of magnetic skyrmions,"The magnetic skyrmion is a nanoscale topological object characterized by the
+winding of the magnetic moments, appearing in magnetic materials with broken
+inversion symmetry. Because of its low current threshold for driving, the
+skyrmions have been intensely studied toward novel storage applications by
+using electron-beam, X-ray, and visible light microscopies. Here, we show that
+the skyrmions can be imaged via thermoelectric signals of spin-caloritronic
+phenomena in combination with focused heating. We applied a local temperature
+gradient to a CoFeB/Ta/W multilayer film with scanning a heating position and,
+by exploiting a Hall bar structure, mapped the magnitude as well as the
+direction of the resultant thermoelectric current distributions, which link to
+skyrmions' inner magnetic textures. This method also enables the observation of
+skyrmion dynamics under driving current pulses, being a useful imaging
+technique for the development of skyrmion devices.",1903.01037v2
+2019-03-06,Magneto-Rayleigh-Taylor instability in an elastic finite-width medium overlying an ideal fluid,"We present the linear theory of two-dimensional incompressible
+magneto-Rayleigh-Taylor instability in a system composed of a linear elastic
+(Hookean) layer above a lighter semi-infinite ideal fluid with magnetic fields
+present, above and below the layer. As expected, magnetic field effects and
+elasticity effects together enhance the stability of thick layers. However, the
+situation becomes more complicated for relatively thin slabs, and a number of
+new and unexpected phenomena are observed. In particular, when the magnetic
+field beneath the layer dominates, its effects compete with effects due to
+elasticity, and counteract the elasticity stabilising effects. As a
+consequence, the layer can become more unstable than when only one of these
+stabilising mechanism is acting. This somewhat unexpected result is explained
+by the different physical mechanisms for which elasticity and magnetic fields
+stabilise the system. Implications for experiments on magnetically driven
+accelerated plates and implosions are discussed. Moreover, the relevance for
+triggering of crust-quakes in strongly magnetised neutron stars is also pointed
+out.",1903.02257v1
+2019-03-06,Anomalous Magnetic Behavior in Ba2CoO4 with Isolated CoO4 Tetrahedra,"The dimensionality of the electronic and magnetic structure of a given
+material is generally predetermined by its crystal structure. Here, using
+elastic and inelastic neutron scattering combined with magnetization
+measurements, we find unusual magnetic behavior in three-dimensional (3D)
+Ba2CoO4. In spite of isolated CoO4 tetrahedra, the system exhibits a 3D
+noncollinear antiferromagnetic order in the ground state with an anomalously
+large Curie-Weiss temperature of 110 K compared to TN = 26 K. More
+unexpectedly, spin dynamics displays quasi-2D spin wave dispersion with an
+unusually large spin gap, and 1D magnetoelastic coupling. Our results indicate
+that Ba2CoO4 is a unique system for exploring the interplay between isolated
+polyhedra, low-dimensional magnetism, and novel spin states in oxides.",1903.02490v1
+2019-03-22,On possible types of magnetospheres of hot Jupiters,"We show that the orbits of exoplanets of the ""hot Jupiter"" type, as a rule,
+are located close to the Alf\'{v}en point of the stellar wind of the parent
+star. At this, many hot Jupiters can be located in the sub-Alf\'{v}en zone in
+which the magnetic pressure of the stellar wind exceeds its dynamic pressure.
+Therefore, magnetic field of the wind must play an extremely important role for
+the flow of the stellar wind around the atmospheres of the hot Jupiters. This
+factor must be considered both in theoretical models and in the interpretation
+of observational data. The analysis shows that many typical hot Jupiters should
+have shock-less intrinsic magnetospheres, which, apparently, do not have
+counterparts in the Solar System. Such magnetospheres are characterized,
+primarily, by the absence of the bow shock, while the magnetic barrier
+(ionopause) is formed by the induced currents in the upper layers of the
+ionosphere. We confirmed this inference by the three-dimensional numerical
+simulation of the flow of the parent star stellar wind around the hot Jupiter
+HD 209458b in which we took into account both proper magnetic field of the
+planet and magnetic field of the wind.",1903.09459v1
+2019-03-25,The supernova-regulated ISM -- VI. Magnetic effects on the structure of the interstellar medium,"We explore the effect of magnetic fields on the vertical distribution and
+multiphase structure of the supernova-driven interstellar medium (ISM) in
+simulations that admit dynamo action. As the magnetic field is amplified to
+become dynamically significant, gas becomes cooler and its distribution in the
+disc becomes more homogeneous. We attribute this to magnetic quenching of
+vertical velocity, which leads to a decrease in the cooling length of hot gas.
+A non-monotonic vertical distribution of the large-scale magnetic field
+strength, with the maximum at |z| $\approx$ 300 pc causes a downward pressure
+gradient below the maximum which acts against outflow driven by SN explosions,
+while it provides pressure support above the maximum.",1903.10263v2
+2019-04-09,Permanent mean spin source of the chiral magnetic effect in neutron stars,"We suggest the generalization of the Anomalous Magneto-Hydro-Dynamics (AMHD)
+in the chiral plasma of a neutron star (NS) accounting for the mean spin in the
+ultrarelativistic degenerate electron gas within the magnetized NS core as a
+continuing source of the chiral magnetic effect. Using the mean field dynamo
+model generalized in AMHD, one can obtain the growth of a seed magnetic field
+up to $10^{18}\,\text{G}$ for an old non-superfluid NS at its neutrino cooling
+era $t < 10^6\,\text{yr}$, while neglecting any matter turbulence within its
+core and assuming the rigid NS rotation. The application of the suggested
+approach to the evolution of magnetic fields observed in magnetars, $B\sim
+10^{15}\,\text{G}$, should be self-consistent with all approximations used in
+the suggested laminar dynamo, at least, up to the jumps of growing fields.",1904.05768v2
+2019-04-25,Low damping magnetic properties and perpendicular magnetic anisotropy with strong volume contribution in the Heusler alloy Fe1.5CoGe,"We present a study of the dynamic magnetic properties of TiN-buffered
+epitaxial thin films of the Heusler alloy Fe$_{1.5}$CoGe. Thickness series
+annealed at different temperatures are prepared and the magnetic damping is
+measured, a lowest value of $\alpha=2.18\times 10^{-3}$ is obtained. The
+perpendicular magnetic anisotropy properties in Fe$_{1.5}$CoGe/MgO are also
+characterized. The evolution of the interfacial perpendicular anisotropy
+constant $K^{\perp}_{\rm S}$ with the annealing temperature is shown and
+compared with the widely used CoFeB/MgO interface. A large volume contribution
+to the perpendicular anisotropy of $(4.3\pm0.5)\times 10^{5}$ $\rm J/m^3$ is
+also found, in contrast with vanishing bulk contribution in common Co- and
+Fe-based Heusler alloys.",1904.11247v1
+2019-06-04,Magnetoresistance in Metallic Ferroelectrics,"Polar metals with ferroelectric-like displacements in metals have been
+achieved recently, half century later than Anderson and Blount's prediction.
+However, the genuine ferroelectricity with electrical dipolar switching has not
+yet been attained experimentally in the conducting materials, especially the
+ones possessing magnetic responses. Here we report the coexistence of
+ferroelectricity and magnetoresistance (MR) in the metallic PbNb0.12Ti0.88O3
+(PNTO) thin films. We found that the conducting and magnetic responses of PNTO
+films are highly asymmetric. Negative MR up to 50% is observed under an
+in-plane magnetic field; the MR switches to positive with the magnetic field
+applied parallel to the surface normal. Such unique behavior is attributed to
+the moving electron caused effective magnetic field which couples with the
+spins of electrons, which form a dynamic multiferroic state in the metallic
+PNTO. These findings break a path to multiferroic metal and offer a great
+potential to the multi-functional devices.",1906.01257v1
+2019-06-18,Interplay between disorder driven Non-Fermi-liquid behavior and magnetism in Ce0.24La0.76Ge compound,"In this work, we investigate the magnetic, heat capacity and electrical
+transport properties of Ce0.6La0.4Ge and Ce0.24La0.76Ge compounds. Our results
+show that two antiferromagnetic transitions (~ at 4.7 and 2.7 K) exhibited by
+Ce0.6La0.4Ge are suppressed below 1.8 K for Ce0.24La0.76Ge. Interestingly, for
+Ce0.24La0.76Ge, susceptibility, heat capacity and electrical resistivity vary
+with temperature as: T0.75, T0.5 and T1.6 respectively. The observation of such
+anomalous temperature variation suggests to the Non-Fermi-liquid (NFL) behavior
+due to the presence of disordered 4f spins due to Ce-site dilution. Under the
+application of magnetic field, it is noted that a crossover from the NFL to a
+magnetic state occurs around 2 Tesla, where, short-range correlations among the
+spins is prevalent due to the dominance of coupling between the magnetic
+moments via conduction electrons. Magnetoresistance scaling indicates that
+behavior of disorder driven NFL state is described by the dynamical mean field
+theory of the spin glass quantum critical point.",1906.07482v1
+2019-07-01,"Structural, magnetostatic and magnetodynamic studies of Co/Mo-based uncompensated synthetic antiferromagnets","In this work, we comprehensively investigate and discuss the structural,
+magnetostatic, dynamic, and magnetoresistive properties of epitaxial Co/Mo
+superlattices. The magnetization of the Co sublayers is coupled
+antiferromagnetically with a strength that depends on the thickness of the
+nonmagnetic Mo spacer. The magnetization and magnetoresistance hysteresis loops
+clearly reflect interlayer exchange coupling and the occurrence of uniaxial
+magnetic anisotropy induced by the strained Co sublayers. Upon accounting for a
+deviation of the sublayer thicknesses from the nominal value, theoretical
+modeling, including both micromagnetic and macrospin approaches, precisely
+reproduces experimental magnetic hysteresis loops, magnetoresistance curves,
+and ferromagnetic resonance dispersion relations. The Mo spacer thickness as a
+function of the interlayer magnetic coupling is determined as a fitting
+parameter by modeling the experimental results.",1907.00592v2
+2019-07-17,Low Barrier Nanomagnet Design for Binary Stochastic Neurons: Design Challenges for Real Nanomagnets with Fabrication Defects,"Much attention has been focused on the design of low barrier nanomagnets
+(LBM), whose magnetizations vary randomly in time owing to thermal noise, for
+use in binary stochastic neurons (BSN) which are hardware accelerators for
+machine learning. The performance of BSNs depend on two important parameters:
+the correlation time associated with the random magnetization dynamics in a
+LBM, and the spin-polarized pinning current which stabilizes the magnetization
+of a LBM in a chosen direction within a chosen time. Here, we show that common
+fabrication defects in LBMs make these two parameters unpredictable since they
+are strongly sensitive to the defects. That makes the design of BSNs with real
+LBMs very challenging. Unless the LBMs are fabricated with extremely tight
+control, the BSNs which use them could be unreliable or suffer from poor yield.",1907.07525v1
+2019-08-02,Dense Quark-Gluon Plasma in strong magnetic fields,"A non-perturbative (np) method of Field Correlators (FCM) was applied to
+study QCD at temperatures above the deconfinement transition
+($1<T/T_c<3,~T_c\sim0.16~GeV$) and nonzero baryon densities (baryon chemical
+potential $\mu_B<0.5~GeV$) in an external uniform magnetic field
+($eB<0.5~GeV^2$). Within FCM, the np high-temperature dynamics is embodied in
+the Polyakov loop and in the Debye mass due to the Color-Magnetic Confinement.
+Analytic expressions for quark pressure and magnetic susceptibility were
+obtained. The expressions were represented as series and in integral form.
+Magnetic susceptibility was found to increase rapidly with temperature and
+slowly with density. The results at the zero density limit are in agreement
+with lattice data.",1908.00800v2
+2019-08-20,Comparing all-optical switching in synthetic-ferrimagnetic multilayers and alloys,"We present an experimental and theoretical investigation of all-optical
+switching by single femtosecond laser pulses. Our experimental results
+demonstrate that, unlike rare earth-transition metal ferrimagnetic alloys,
+Pt/Co/[Ni/Co]$_N$/Gd can be switched in the absence of a magnetization
+compensation temperature, indicative for strikingly different switching
+conditions. In order to understand the underlying mechanism, we model the
+laser-induced magnetization dynamics in Co/Gd bilayers and GdCo alloys on an
+equal footing, using an extension of the microscopic three-temperature model to
+multiple magnetic sublattices and including exchange scattering. In agreement
+with our experimental observations, the model shows that Co/Gd bilayers can be
+switched for an arbitrary thickness of the Co layer, i.e, even far away from
+compensating the total Co and Gd magnetic moment. We identify the switching
+mechanism in Co/Gd bilayers as a front of reversed Co magnetization that
+nucleates at the Co/Gd interface and propagates through the Co layer driven by
+exchange scattering.",1908.07292v2
+2019-09-01,Magnetic field-dependent low-energy magnon dynamics in $α$-RuCl3,"Revealing the spin excitations of complex quantum magnets is key to
+developing a minimal model that explains the underlying magnetic correlations
+in the ground state. We investigate the low-energy magnons in $\alpha$-RuCl$_3$
+by combining time-domain terahertz spectroscopy under an external magnetic
+field and model Hamiltonian calculations. We observe two absorption peaks
+around 2.0 and 2.4 meV, which we attribute to zone-center spin waves. Using
+linear spin-wave theory with only nearest-neighbor terms of the exchange
+couplings, we calculate the antiferromagnetic resonance frequencies and reveal
+their dependence on an external field applied parallel to the nearest-neighbor
+Ru-Ru bonds. We find that the magnon behavior in an applied magnetic field can
+be understood only by including an off-diagonal $\Gamma$ exchange term to the
+minimal Heisenberg-Kitaev model. Such an anisotropic exchange interaction that
+manifests itself as a result of strong spin-orbit coupling can naturally
+account for the observed mixing of the modes at higher fields strengths.",1909.00462v1
+2019-09-12,Single pulse all-optical toggle switching of magnetization without Gd: The example of Mn2RuxGa,"Energy-efficient control of magnetization without the help of a magnetic
+field is a key goal of spintronics. Purely heat-induced single-pulse
+all-optical toggle switching has been demonstrated, but so far only in Gd based
+amorphous ferrimagnet films. In this work, we demonstrate toggle switching in
+the half-metallic compensated ferrimagnetic Heusler alloys Mn2RuxGa, which have
+two crystallographically-inequivalent Mn sublattices. Moreover, we observe the
+switching at room temperature in samples that are immune to external magnetic
+fields in excess of 1 T, provided they exhibit compensation above room
+temperature. Observations of the effect in compensated ferrimagnets without Gd
+challenges our understanding of all-optical switching. The dynamic behavior
+indicates that Mn2RuxGa switches in 2 ps or less. Our findings widen the basis
+for fast optical switching of magnetization and break new ground for engineered
+materials that can be used for nonvolatile ultrafast switches using ultrashort
+pulses of light.",1909.05809v2
+2019-09-27,Effective description of non-equilibrium currents in cold magnetized plasma,"The dynamics of cold strongly magnetized plasma -- traditionally the domain
+of force-free electrodynamics -- has recently been reformulated in terms of
+symmetries and effective field theory, where the degrees of freedom are the
+momentum and magnetic flux carried by a fluid of cold strings. In physical
+applications where the electron mass can be neglected one might expect the
+presence of extra light charged modes -- electrons in the lowest Landau level
+-- propagating parallel to the magnetic field lines. We construct an effective
+description of such electric charges, describing their interaction with plasma
+degrees of freedom in terms of a new collective mode that can be thought of as
+a bosonization of the electric charge density along each field line. In this
+framework QED phenomena such as charged pair production and the axial anomaly
+are described at the classical level. Formally, our construction corresponds to
+gauging a particular part of the higher form symmetry associated with magnetic
+flux conservation. We study some simple applications of our effective theory,
+showing that the scattering of magnetosonic modes generically creates particles
+and that the rotating Michel monopole is now surrounded by a cloud of electric
+charge.",1909.12609v1
+2019-10-14,Magnetic helicity dissipation and production in an ideal MHD code,"We study a turbulent helical dynamo in a periodic domain by solving the ideal
+magnetohydrodynamic (MHD) equations with the FLASH code using the
+divergence-cleaning eight-wave method and compare our results with direct
+numerical simulations (DNS) using the Pencil Code. At low resolution, FLASH
+reproduces the DNS results qualitatively by developing the large-scale magnetic
+field expected from DNS, but at higher resolution, no large-scale magnetic
+field is obtained. In all those cases in which a large-scale magnetic field is
+generated, the ideal MHD results yield too little power at small scales. As a
+consequence, the small-scale current helicity is too small compared with that
+of the DNS. The resulting net current helicity has then always the wrong sign,
+and its statistical average also does not approach zero at late times, as
+expected from the DNS. Our results have implications for astrophysical dynamo
+simulations of stellar and galactic magnetism using ideal MHD codes.",1910.06074v3
+2019-11-12,Large-scale dynamo action of magnetized Taylor-Couette flows,"A conducting Taylor-Couette flow with quasi-Keplerian rotation law containing
+a toroidal magnetic field serves as a mean-field dynamo model of the
+Tayler-Spruit-type. The flows are unstable against nonaxisymmetric
+perturbations which form electromotive forces defining $\alpha$ effect and eddy
+diffusivity. If both degenerated modes with $m=\pm 1$ are excited with the same
+power then the global $\alpha$ effect vanishes and a dynamo cannot work. It is
+shown, however, that the Tayler instability produces finite $\alpha$ effects if
+only an isolated mode is considered but this intrinsic helicity of the
+single-mode is too low for an $\alpha^2$ dynamo. Moreover, an $\alpha\Om$
+dynamo model with quasi-Keplerian rotation requires a minimum magnetic Reynolds
+number of rotation of ${\rm Rm}\simeq 2.000$ to work. Whether it really works
+depends on assumptions about the turbulence energy. For a
+steeper-than-quadratic dependence of the turbulence intensity on the magnetic
+field, however, dynamos are only excited if the resulting magnetic eddy
+diffusivity approximates its microscopic value, $\eta_{\rm T}\simeq \eta$. By
+basically lower or larger eddy diffusivities the dynamo instability is
+suppressed.",1911.05105v2
+2019-12-16,Generic properties of Mañé's set of exact magnetic Lagrangians,"Let $M$ be a closed manifold and $L$ an exact magnetic Lagrangian. In this
+paper we proved that there exists a residual $\mathcal{G}$ of $H^{1}\left(
+M;\mathbb{R}\right)$ such that the property: \begin{equation*}
+{\widetilde{\mathcal{M}}}\left( c\right) ={\widetilde{\mathcal{A}}}\left(
+c\right) ={\widetilde{\mathcal{N}}}\left( c\right), \forall c\in \mathcal{G}
+\end{equation*} with ${\widetilde{\mathcal{M}}}\left( c\right)$ supports on a
+uniquely ergodic measure, is generic in the family of exact magnetic
+Lagrangians. We also prove that, fixed the cohomology class $c$, there exists a
+residual set of exact magnetic Lagrangians such that when this unique measure
+is supported on a periodic orbit, this orbit is hyperbolic and its stable and
+unstable manifolds intersect transversally. This result is a version of Theorem
+D of \cite{gon5} for the exact magnetic Lagrangian case.",1912.07535v1
+2019-12-18,Quantitative Modeling of the UV Line Profiles of Magnetic Massive Stars,"Recent spectropolarimetric surveys (MiMeS, BOB) have revealed that
+approximately 7% of massive stars host stable, surface dipolar magnetic fields
+with strengths on the order of kG. These fields channel the dense radiatively
+driven stellar wind into a circumstellar magnetosphere. Wind-sensitive UV
+spectral lines can probe the density and velocity structure of massive star
+magnetospheres, providing insight into wind-field interactions. To date,
+large-scale magnetohydrodynamic modeling of this phenomenon has been limited by
+the associated computational cost. Our analysis, using the Analytic Dynamical
+Magnetosphere model, solves this problem by applying a simple analytic
+prescription to efficiently calculate synthetic UV spectral lines. It can
+therefore be applied in the context of a larger parameter study to derive the
+wind properties for the population of known magnetic O stars. We also present
+the latest UV spectra of the magnetic O star NGC 1624-2 obtained with HST/COS,
+which test the limits of our models and suggest a particularly complex
+magnetospheric structure for this archetypal object.",1912.08748v1
+2020-01-08,Simultaneous Wide-field Imaging of Phase and Magnitude of AC Magnetic Signal Using Diamond Quantum Magnetometry,"Spectroscopic analysis of AC magnetic signal using diamond quantum
+magnetometry is a promising technique for inductive imaging. Conventional
+dynamic decoupling like XY8 provides a high sensitivity of an oscillating
+magnetic signal with intricate dependence on magnitude and phase, complicating
+high throughput detection of each parameter. In this study, a simple
+measurement scheme for independent and simultaneous detection of magnitude and
+phase is demonstrated by a sequential measurement protocol. Wide-field imaging
+experiment was performed for an oscillating magnetic field with approximately
+100$\mu$m-squared observation area. Single pixel phase precision was
+$2.1^\circ$ for 0.76$\mu$T AC magnetic signal. Our method enables potential
+applications including inductive inspection and impedance imaging.",2001.02374v1
+2020-01-10,Switching time of spin-torque-driven magnetization in biaxial ferromagnets,"We analytically model the magnetization switching time of a biaxial
+ferromagnet driven by an antidamping-like spin torque. The macrospin
+magnetization dynamics is mapped to an energy-flow equation, wherein a
+rational-function approximation of the elliptic integrals for moderate spin
+current and small damping results in a closed-form expression of the switching
+time. Randomness in the initial angle of magnetization gives the distribution
+function of the switching time. The analytic model conforms to the results
+obtained from Monte Carlo simulation for a broad range of material parameters.
+Our results can ameliorate design and benchmarking of in-plane spin torque
+magnetic memory by obviating expensive numerical computation.",2001.03300v2
+2020-01-13,High Frequency Microwave Emission of a Tri-layer Magnetic Tunnel Junction in the Absence of External Bias-Magnetic Field,"We perform an experimental study of DC current induced microwave emission in
+a magnetic tunnel junction (MTJ) consisting of three active magnetic layers.
+For this tri-layer structure, in addition to a conventional bilayer orthogonal
+MTJ containing a perpendicular free layer and an in-plane fixed layer, a second
+perpendicular layer has been introduced. We found that the microwave emission
+frequency induced by spin-transfer torque (STT) can reach as high as 6 GHz in
+the absence of any applied magnetic field. Moreover, microwave emission is
+observed for both current polarizations where a redshift is seen with increase
+in magnitude of current. We discuss spin-dynamics of the observed
+bi-directional high-frequency emission and the physical origin of the
+red-shift. The distinct microwave emission properties exhibited in this
+tri-layer MTJ structure could potentially be useful for future applications in
+nanoscale spintronics devices such as microwave communication and neuromorphic
+computing.",2001.04539v1
+2020-02-07,Probability Distribution of Magnetic Field Strengths through the Cyclotron Lines in High-Mass X-ray Binaries,"The study of variation of measured cyclotron lines is of fundamental
+importance to understand the physics of the accretion process in magnetized
+neutron star systems. We investigate the magnetic field formation, evolution
+and distribution for several High- Mass X-ray Binaries (HMXBs). We focus our
+attention on the cyclotron lines that have been detected in HMXB classes in
+their X-ray spectra. As has been correctly pointed out, several sources show
+variation in cyclotron lines, this can result due to the effect of accretion
+dynamics, and hence that would reflect the magnetic field characteristics.
+Besides, the difference in time scales of variation of accretion rate and
+different type of companion can be used to distinguish between magnetized
+neutron stars.",2002.03011v3
+2020-02-19,Photon Self-energy in Magnetized Chiral Plasma from Kinetic Theory,"We study the photon self-energy in magnetized chiral plasma by solving the
+response of electromagnetic field perturbations in chiral kinetic theory with
+Landau level states. With lowest Landau level approximation and in
+collisionless limit, we find solutions for three particular perturbations:
+parallel electric field, static perpendicular electric and magnetic field,
+corresponding to chiral magnetic wave, drift state and tilted state, from which
+we extract components of photon self-energy in different kinematics. We show no
+solution is possible for more general field perturbations. We argue this is an
+artifact of the collisionless limit: while static solution corresponding to
+drift state and tilted state can be found, they cannot be realized dynamically
+without interaction between Landau levels. We also discuss possible
+manifestation of side-jump effect due to both boost and rotation, with the
+latter due to the presence of background magnetic field.",2002.07959v1
+2020-03-13,Efficient acceleration of cylindrical jets: effects of radiative cooling and tangled magnetic field,"Diverging supersonic flows are accelerating, as in the case of a de Laval
+nozzle, and the same concept has been applied for acceleration of
+magnetohydrodynamic flows in the universe. Here, we study the dynamics of
+""non-diverging"" cylindrical supersonic flows and show that they can be
+accelerated by effects of radiative cooling and the tangled magnetic field. In
+addition to radiative cooling of the jet materials (cooling effect), conversion
+of the ordered magnetic field into the turbulent one (conversion effect) and
+dissipation of the turbulent magnetic field (dissipation effect) are formulated
+according to our study on pulsar wind nebulae. Although each of the cooling and
+conversion effects is an ineffective acceleration process, the terminal
+velocity of magnetized cylindrical jets attains about half of the maximum
+possible value when the cooling, conversion and dissipation effects work
+simultaneously. The radiation efficiency is also about half of the total
+luminosity of the jet in the case of maximal acceleration. The concept for flow
+acceleration by the non-ideal MHD effects may be useful for studying
+relativistic jets in active galactic nuclei, in which the region near the jet
+axis is expected to be cylindrical and kink unstable.",2003.06140v1
+2020-03-18,Directed transport of suspended ferromagnetic nanoparticles under both gradient and uniform magnetic fields,"The suspended ferromagnetic particles subjected to the gradient and uniform
+magnetic fields experience both the translational force generated by the field
+gradient and the rotational torque generated by the fields strengths. Although
+the uniform field does not contribute to the force, it nevertheless influences
+the translational motion of these particles. This occurs because the
+translational force depends on the direction of the particle magnetization,
+which in turn depends on the fields strengths. To study this influence, a
+minimal set of equations describing the coupled translational and rotational
+motions of nanosized ferromagnetic particles is introduced and solved in the
+low Reynolds number approximation. Trajectory analysis reveals that, depending
+on the initial positions of nanoparticles, there exist four regimes of their
+directed transport. The intervals of initial positions that correspond to
+different dynamical regimes are determined, their dependence on the uniform
+magnetic field is established, and strong impact of this field on the directed
+transport is demonstrated. The ability and efficiency of the uniform magnetic
+field to control the separation of suspended ferromagnetic nanoparticles is
+also discussed.",2003.08498v2
+2020-03-27,Modulation instability in the nonlinear Schrödinger equation with a synthetic magnetic field: gauge matters,"We theoretically investigate the phenomenon of modulation instability for
+systems obeying nonlinear Schr\""odinger equation, which are under the influence
+of an external homogeneous synthetic magnetic field. For an initial condition,
+the instability is detected numerically by comparing dynamics with and without
+a small initial perturbation; the perturbations are characterized in a standard
+fashion by wavevectors in momentum space. We demonstrate that the region of
+(in)stability in momentum space, as well as time-evolution in real space, for
+identical initial conditions, depend on the choice of the gauge (i.e., vector
+potential) used to describe the homogeneous synthetic magnetic field. This
+superficially appears as if the gauge invariance is broken, but this is not
+true. When the system is evolved from an identical initial condition in two
+different gauges, it is equivalent to suddenly turning on the synthetic
+magnetic field at $t=0$. This gives rise, via Faraday's law, to an initial
+instantaneous kick of a synthetic electric field to the wavepacket, which can
+differ for gauges yielding an identical uniform magnetic field at $t>0$.",2003.12620v1
+2020-04-08,Deconfinement in the presence of a strong magnetic field,"We study the impact of a finite magnetic field on the deconfinement phase
+transition for heavy quarks by computing the fluctuations of the Polyakov
+loops. It is demonstrated that the explicit Z(3) breaking field increases with
+the magnetic field, leading to a decrease in the (pseudo) critical temperatures
+and a shrinking first-order region in the phase diagram. Phenomenological
+equations that capture the behaviors of the Z(3) breaking field at strong and
+weak magnetic fields for massive and massless quarks are given. Lastly, we
+explore the case of dynamical light quarks and demonstrate how an improved
+constituent quark mass function can enforce the correct magnetic field
+dependence of the deconfinement temperature in an effective model, as observed
+in Lattice QCD calculations.",2004.04138v2
+2020-04-17,Magnetic-field evolution with large-scale velocity circulation in a neutron-star crust,"We examine the effects of plastic flow that appear in a neutron-star crust
+when a magnetic stress exceeds the threshold. The dynamics involved are
+described using the Navier--Stokes equation comprising the viscous-flow term,
+and the velocity fields for the global circulation are determined using
+quasi-stationary approximation.
+  We simulate the magnetic-field evolution by taking into consideration the
+Hall drift, Ohmic dissipation, and fluid motion induced by the Lorentz force.
+The decrease in the magnetic energy is enhanced, as the energy converts to the
+bulk motion energy and heat. It is found that the bulk velocity induced by the
+Lorentz force has a significant influence in the low-viscosity and
+strong-magnetic-field regimes. This effect is crucial near magnetar surfaces.",2004.08006v1
+2020-05-07,Thermal Activation Barriers for Creation and Annihilation of Magnetic Droplet Solitons in the Presence of Spin Transfer Torque,"We study noise-induced creation and annihilation of magnetic droplet solitons
+in experimental parameter regions in which they are linearly stable against
+drift. Exploiting the rotational symmetry of the problem, we transform to the
+reference frame rotating with the droplet soliton and introduce an effective
+potential energy that accounts for the work done against spin-transfer torque
+to rotate the magnetization between two different orientations. We use this
+function to compute the activation barrier in both directions between the
+uniform magnetization state and the droplet soliton state for a variety of
+nanocontact radii and currents. We investigate droplet soliton structures with
+both zero and nonzero spin-torque asymmetry parameter. Our approach can be
+applied to estimate activation barriers for dynamical systems where
+non-gradient terms can be absorbed by changes of reference frames, and suggests
+a technique applicable to extended systems that may not be uniformly
+magnetized.",2005.03416v1
+2020-05-11,Manipulating 1-dimensinal skyrmion motion by external magnetic field gradient,"We have investigated an analytic formula of the 1-dimensional magnetic
+skyrmion dynamics under external magnetic field gradient. We find excellent
+agreement between the analytical model and micromagnetic simulation results for
+various magnetic parameters such as the magnetic field gradient, Gilbert
+damping constant. We also observe much faster velocity of the chiral domain
+wall (DW) motion. The chiral DW is exist with smaller interfacial
+Dzyaloshinskii-Moriya interaction energy density cases. These results provide
+to develop efficient control of skyrmion for spintronic devices.",2005.05011v1
+2020-05-16,All-optical switching of magnetic domains in Co/Gd heterostructures with Dzyaloshinskii-Moriya Interaction,"Given the development of hybrid spintronic-photonic devices and chiral
+magnetic structures, a combined interest in all-optical switching (AOS) of
+magnetization and current-induced domain wall motion in synthetic ferrimagnetic
+structures with strong Dzyaloshinskii-Moriya Interaction (DMI) is emerging. In
+this study, we report a study on single-pulse all-optical toggle switching and
+asymmetric bubble expansion in specially engineered Co/Gd-based multilayer
+structures. In the absence of any external magnetic fields, we look into the
+AOS properties and the potential role of the DMI on the AOS process as well as
+the stability of optically written micro-magnetic domains. Particularly,
+interesting dynamics are observed in moon-shaped structures written by two
+successive laser pulses. The stability of domains resulting from an interplay
+of the dipolar interaction and domain-wall energy are compared to simple
+analytical models and micromagnetic simulations.",2005.07969v2
+2020-06-07,Anomalous magnetic suppression of spin relaxation in a two-dimensional electron gas in a GaAs/AlGaAs quantum well,"We study the spin dynamics in a high-mobility two-dimensional electron gas
+confined in a GaAs/AlGaAs quantum well. An unusual magnetic field dependence of
+the spin relaxation is found: as the magnetic field becomes stronger, the spin
+relaxation time first increases quadratically but then changes to a linear
+dependence, before it eventually becomes oscillatory, whereby the longitudinal
+and transverse times reach maximal values at even and odd filling Landau level
+factors, respectively. We show that the suppression of spin relaxation is due
+to the effect of electron gyration on the spin-orbit field, while the
+oscillations correspond to oscillations of the density of states appearing at
+low temperatures and high magnetic fields. The transition from quadratic to
+linear dependence can be related to a transition from classical to Bohm
+diffusion and reflects an anomalous behavior of the two-dimensional electron
+gas analogous to that observed in magnetized plasmas.",2006.04110v1
+2020-06-09,Estimating a fluctuating magnetic field with a continuously monitored atomic ensemble,"We study the problem of estimating a time dependent magnetic field by
+continuous optical probing of an atomic ensemble. The magnetic field is assumed
+to follow a stochastic Ornstein-Uhlenbeck process and it induces Larmor
+precession of the atomic ground state spin, which is read out by the Faraday
+polarization rotation of a laser field probe. The interactions and the
+measurement scheme are compatible with a hybrid quantum-classical Gaussian
+description of the unknown magnetic field, and the atomic and field variables.
+This casts the joint conditional quantum dynamics and classical parameter
+estimation problem in the form of update formulas for the first and second
+moments of the classical and quantum degrees of freedom. Our hybrid
+quantum-classical theory is equivalent with the classical theory of Kalman
+filtering and with the quantum theory of Gaussian states. By reference to the
+classical theory of smoothing and with the quantum theory of past quantum
+states, we show how optical probing after time $t$ improves our estimate of the
+value of the magnetic field at time $t$, and we present numerical simulations
+that analyze and explain the improvement over the conventional filtering
+approach.",2006.05516v2
+2020-07-02,Magnetic-field-induced reorientation in the SDW and the spin-stripe phases of the frustrated spin-1/2 chain compound $β$-TeVO$_4$,"$\beta$-TeVO$_4$ is a frustrated spin 1/2 zig-zag chain system,where
+spin-density-wave (SDW), vector chiral (VC)and an exotic dynamic spin-stripe
+phase compete at low temperatures. Here we use torque magnetometry to study the
+anisotropy of these phases in magnetic fields of up to 5 T. Our results show
+that the magnetic-field-induced spin reorientation occurs in the SDW and in the
+spin stripe phases for $\mu_0 H \geq 2$~T. The observed spin reorientation is a
+new element of the anisotropic phase diagram for the field directions in the
+$ac$ and $a^*b$ crystallographic planes. The presented results should help
+establishing the model of anisotropic magnetic interactions, which are
+responsible for the formation of complex magnetic phases in $\beta$-TeVO$_4$
+and similar quantum systems.",2007.00932v1
+2020-07-07,Nonequilibrium Multiple Transitions in the Core-shell Ising Nanoparticles Driven by Randomly Varying Magnetic Fields,"The nonequilibrium behaviour of a core-shell nanoparticle has been studied by
+Monte- Carlo simulation. The core consists of Ising spins of $\sigma=1/2$ and
+the shell contains Ising spins of $S=1$. The interactions within the core and
+in the shell are considered ferromagnetic but the interfacial interaction
+between core and shell is antiferromagnetic. The nanoparticle system is kept in
+open boundary conditions and is driven by randomly varying (in time but uniform
+over the space) magnetic field. Depending on the width of the randomly varying
+field and the temperature of the system, the core, shell and total
+magnetization varies in such a manner that the time averages vanish for higher
+magnitude of the width of random field, exhibiting a dynamical symmetry
+breaking transitions. The susceptibilities get peaked at two different
+temperatures indicating nonequilibrium multiple transitions. The phase
+boundaries of the nonequilibrium multiple transitions are drawn in the plane
+formed by the axes of temperature and the width of the randomly varying field.
+Furthermore, the effects of the core and shell thicknesses on the multiple
+transitions have been discussed.",2007.03280v2
+2020-07-10,Magnetic effects of QCD parameters from finite energy sum rules,"One of the advantages of the finite energy sum rules is the fact that every
+operator in the operator product expansion series can be selected individually
+by the use of an appropriate kernel function which removes other operator
+poles. This characteristic is maintained by QCD systems in the presence of
+external homogeneous magnetic field, providing interesting information about
+the magnetic evolution of QCD and hadronic parameters. In this work finite
+energy sum rules are applied on QCD in the light quark sector, combining axial
+and pseudoscalar channels in the presence of an external homogeneous magnetic
+field, obtaining the magnetic evolution of the light quark masses, pion mass,
+the pion decay constant, the gluon condensate and the continuum hadronic
+threshold.",2007.05642v1
+2020-07-18,Adsorption transition of a grafted ferromagnetic filament controlled by external magnetic fields,"Extensive Langevin dynamics simulations are used to characterize the
+adsorption transition of a flexible magnetic filament grafted onto an
+attractive planar surface. Our results identify different structural
+transitions at different ratios of the thermal energy to the surface attraction
+strength: filament straightening, adsorption and the magnetic flux closure. The
+adsorption temperature of a magnetic filament is found to be higher in
+comparison to an equivalent nonmagnetic chain. The adsorption has been also
+investigated under the application of a static homogeneous external magnetic
+field. We found that the strength and the orientation of the field can be used
+to control the adsorption process, providing a precise switching mechanism.
+Interestingly, we have observed that the characteristic field strength and tilt
+angle at the adsorption point are related by a simple power law.",2007.09489v1
+2020-07-21,Giant effective magnetic fields from optically driven chiral phonons in 4$f$ paramagnets,"We present a mechanism by which optically driven chiral phonon modes in
+rare-earth trihalides generate giant effective magnetic fields acting on the
+paramagnetic $4f$ spins. With cerium trichloride (CeCl$_3$) as our example
+system, we calculate the coherent phonon dynamics in response to the excitation
+by an ultrashort terahertz pulse using a combination of phenomenological
+modeling and first-principles calculations. We find that effective magnetic
+fields of over 100 tesla can possibly be generated that polarize the spins for
+experimentally accessible pulse energies. The direction of induced
+magnetization can be reversed by changing the handedness of circular
+polarization of the laser pulse. The underlying process is a phonon analog of
+the inverse Faraday effect in optics that has been described recently, and
+which enables novel ways of achieving control over and switching of magnetic
+order at terahertz frequencies.",2007.10556v3
+2020-08-13,Comparison of measured and simulated spin-wave mode spectra of magnetic nanostructures,"Motivated by the importance of magnetization dynamics in nanomagnets for the
+development and optimization of magnetic devices and sensors, we measured and
+modeled spin wave spectra in patterned elliptical nanomagnets. Ferromagnetic
+resonance spectra for multiple nanomagnets of Ni80Fe20 , fabricated by
+electron-beam lithography to have nominal short-axes of 200 nm or 100 nm, were
+measured by use of heterodyne magneto-optical microwave microscopy. Scanning
+electron microscope images taken of the same nanomagnets were used to define
+element shapes for micromagnetic simulations. Measured spectra show significant
+differences between nominally identical nanomagnets, which could be only
+partially attributed to uncontrolled shape variations in the patterning
+process, as evidence by the limited agreement between the measured and
+simulated spectra. Agreement between measurements and simulations was improved
+by including a zone of reduced magnetization and exchange at the edges of the
+nanomagnets in the simulations. Our results show that the reduction of shape
+variations between individual magnetic random-access memory elements can
+potentially improve their performance. However, unambiguous determination of
+materials parameters in nanomagnets based on analysis and modeling of spin wave
+spectra remains problematic.",2008.05662v1
+2020-09-22,Magnetic mixed valent semimetal EuZnSb$_2$ with Dirac states in the band structure,"We report discovery of new antiferromagnetic semimetal EuZnSb$_2$, obtained
+and studied in the form of single crystals. Electric resistivity, magnetic
+susceptibility and heat capacity indicate antiferromagnetic order of Eu with
+$T_N$ = 20 K. The effective moment of Eu$^{2+}$ inferred from the magnetization
+and specific heat measurement is 3.5 $\mu_B$, smaller than the theoretical
+value of Eu$^{2+}$ due to presence of both Eu$^{3+}$ and Eu$^{2+}$. Magnetic
+field-dependent resistivity measurements suggest dominant quasi two dimensional
+Fermi surfaces whereas the first-principle calculations point to the presence
+of Dirac fermions. Therefore, EuZnSb$_2$ could represent the first platform to
+study the interplay of dynamical charge fluctuations, localized magnetic 4$f$
+moments and Dirac states with Sb orbital character.",2009.10720v1
+2020-10-06,"Trigonal layered rosiaite-related antiferromagnet MnSnTeO6: ion-exchange preparation, structure and magnetic properties","Ion-exchange treatment of Na2SnTeO6 in molten salt mixtures resulted in
+rosiaite (PbSb2O6)-related MnSnTeO6. Its crystal structure was refined by the
+Rietveld method. Of the three possible models of Sn/Te distribution, the
+disordered model ((P3 Im, a = 5.23093(11) A, c = 4.62430(16) A was preferred
+based on bond distances. However, it is supposed that each individual
+(SnTeO6)2- layer retains complete ordering of the precursor and the apparent
+disorder is only due to stacking faults. The magnetic studies have shown that
+MnSnTeO6 orders antiferromagnetically at Neel temperature TN = 9.8 K. The
+effective magnetic moment reasonably agrees with theoretical estimations
+assuming high-spin configuration of Mn2+ (S = 5/2). Electron spin resonance
+reveals spin dynamics in accordance with aniferromagnetic ordering with
+critical broadening of ESR linewidth indicating the low-dimentional type of
+exchange interactions. Based on the temperature and field-dependent
+magnetization studies, the magnetic phase diagram of the new compound was
+constructed.",2010.03003v1
+2020-10-12,Line-drag damping of Alfvén waves in radiatively driven winds of magnetic massive stars,"Line-driven stellar winds from massive (OB) stars are subject to a strong
+line-deshadowing instability. Recently, spectropolarimetric surveys have
+collected ample evidence that a subset of Galactic massive stars hosts strong
+surface magnetic fields. We investigate here the propagation and stability of
+magneto-radiative waves in such a magnetised, line-driven wind. Our analytic,
+linear stability analysis includes line-scattering from the stellar radiation,
+and accounts for both radial and non-radial perturbations. We establish a
+bridging law for arbitrary perturbation wavelength after which we analyse
+separately the long- and short-wavelength limits. While long-wavelength
+radiative and magnetic waves are found to be completely decoupled, a key result
+is that short-wavelength, radially propagating Alfv\'en waves couple to the
+scattered radiation field and are strongly damped due to the line-drag effect.
+This damping of magnetic waves in a scattering-line-driven flow could have
+important effects on regulating the non-linear wind dynamics, and so might also
+have strong influence on observational diagnostics of the wind structure and
+clumping of magnetic line-driven winds.",2010.05650v1
+2020-10-23,Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere,"Coronal plasma in the cores of solar active regions is impulsively heated to
+more than 5 MK. The nature and location of the magnetic energy source
+responsible for such impulsive heating is poorly understood. Using observations
+of seven active regions from the Solar Dynamics Observatory, we found that a
+majority of coronal loops hosting hot plasma have at least one footpoint rooted
+in regions of interacting mixed magnetic polarity at the solar surface. In
+cases when co-temporal observations from the Interface Region Imaging
+Spectrograph space mission are available, we found spectroscopic evidence for
+magnetic reconnection at the base of the hot coronal loops. Our analysis
+suggests that interactions of magnetic patches of opposite polarity at the
+solar surface and the associated energy release during reconnection are key to
+impulsive coronal heating.",2010.12560v3
+2020-11-04,Turbulent transport of fast ions in tokamak plasmas in the presence of resonant magnetic perturbations,"The effects of resonant magnetic perturbations on the turbulent transport of
+fast ions in tokamak devices are investigated using a theoretical transport
+model of test-particle type. The direct numerical simulation method is used to
+compute, via the transport model, the diffusion coefficients. The numerical
+results are in good agreement with other, analytically derived, estimations. It
+is found that finite Larmor radius effects decrease algebraically the
+transport, while the amplitude of magnetic perturbations has an opposite
+effect. In the presence of stochastic dynamics, the asymmetric toroidal
+magnetic field induces a small, radial, outward pinch. A synergistic mechanism
+of non-linear coupling between turbulence and magnetic perturbations enhances
+the radial diffusion. General scaling laws are proposed for the transport
+coefficients.",2011.02302v1
+2020-11-11,Role of impurity clusters for the current-driven motion of magnetic Skyrmions,"We study how impurities influence the current-induced dynamics of magnetic
+Skyrmions moving in a racetrack geometry. For this, we solve numerically the
+generalized Landau-Lifshitz-Gilbert equation extended by the current-induced
+spin transfer torque. In particular, we investigate two classes of impurities,
+non-conducting and magnetic impurities. The former are magnetically rigid
+objects and yield to an inhomogeneous current density over the racetrack which
+we determine separately by solving the fundamental electrostatic equations. In
+contrast, magnetic impurities leave the applied current density homogeneous
+throughout the stripe. Depending on parameters, we observe four different
+scenarios of Skyrmion motions in the presence of disorder, the Skyrmion decay,
+the pinning, the creation of additional Skyrmions, and ordinary Skyrmion
+passage. We calculate and discuss phase diagrams in dependence of the impurity
+concentration and radii of the impurities.",2011.06027v1
+2020-11-16,Spin Entanglement and Magnetic Competition via Long-range Interactions in Spinor Quantum Optical Lattices,"Quantum matter at ultra-low temperatures offers a testbed for analyzing and
+controlling desired properties in strongly correlated systems. Under typical
+conditions the nature of the atoms fixes the magnetic character of the system.
+Beyond classical light potentials leading to optical lattices and short range
+interactions, high-Q cavities introduce novel dynamics into the system via the
+quantumness of light. Here we propose a theoretical model and we analyze it
+using exact diagonalization and density matrix renormalization group
+simulations. We explore the effects of cavity mediated long range magnetic
+interactions and optical lattices in ultracold matter. We find that global
+interactions modify the underlying magnetic character of the system while
+introducing competition scenarios. Antiferromagnetic correlated bosonic matter
+emerges in conditions beyond to what nature typically provides. These allow new
+alternatives toward the design of robust mechanisms for quantum information
+purposes, exploiting the properties of magnetic phases of strongly correlated
+quantum matter.",2011.07765v3
+2020-11-25,Evolution of axions in the presence of primordial magnetic fields,"We study the evolution of axions interacting with primordial magnetic fields
+(PMFs) starting just from the QCD phase transition in the expanding universe.
+This interaction is owing to the Primakoff effect. Adopting the zero mode
+approximation for axions, we derive the system of equations for axions and
+magnetic fields, where the expansion of the universe and the spectra of
+magnetic fields are accounted for exactly. We find that the contribution of the
+Primakoff effect to the dynamics of axions and magnetic fields is rather weak.
+It confirms some previous estimates leading to analogous conclusions, when
+accounting here for the Hubble expansion both for an uniform axion field and
+non-uniform PMFs using Fourier spectra for their energy and helicity densities.
+We solve the corresponding system of the evolution equations and find that the
+axion zero mode, when evolving during radiation era, has its amplitude at the
+level sufficient for that axion to be a good candidate for the cold dark
+matter.",2011.12712v1
+2020-11-26,Chaotic exits from a weakly magnetized Schwarzschild black hole,"A charged particle kicked from an initial circular orbit around a weakly
+magnetized Schwarzschild black hole undergoes transient chaotic motion before
+either getting captured by the black hole or escaping upstream or downstream
+with respect to the direction of the magnetic field. These final states form
+basins of attraction in the space of initial states. We provide a detailed
+numerical study of the basin structure of this initial state space. We find it
+to possess the peculiar Wada property: each of its basin boundaries is shared
+by all three basins. Using basin entropy as a measure, we show that uncertainty
+in predicting the final exit state increases with stronger magnetic
+interaction. We also present an approximate analytic expression of the critical
+escape energy for a vertically-kicked charged particle, and discuss how this
+depends on the strength of the magnetic interaction.",2011.13402v2
+2020-12-07,Free-fall velocities and heat transport enhancement in liquid metal magneto-convection,"In geo- and astrophysics, low Prandtl number convective flows often interact
+with magnetic fields. Although a static magnetic field acts as a stabilizing
+force on such flow fields, we find that self-organized convective flow
+structures reach an optimal state where the heat transport significantly
+increases and convective velocities reach the theoretical free-fall limit, i.e.
+the maximum possible velocity a fluid parcel can achieve when its potential
+buoyant energy is fully converted into kinetic energy. Our measurements show
+that the application of a static magnetic field leads to an anisotropic, highly
+ordered flow structure and a decrease of the turbulent fluctuations. When the
+magnetic field strength is increased beyond the optimum, Hartmann braking
+becomes dominant and leads to a reduction of the heat and momentum transport.
+The results are relevant for the understanding of magneto-hydrodynamic
+convective flows in planetary cores and stellar interiors in regions with
+strong toroidal magnetic fields oriented perpendicular to temperature
+gradients.",2012.03905v2
+2020-12-10,Magnetic properties of poly(trimethylene terephthalate-block-poly(tetramethylene oxide) copolymer nanocomposites reinforced by graphene oxide-Fe3O4 hybrid nanoparticles,"Thermoplastic elastomeric nanocomposites based on poly(trimethylene
+terephthalate-block-poly(tetramethylene oxide) copolymer (PTT-PTMO) and
+graphene oxide-Fe3O4 nanoparticle hybrid were prepared by in situ
+polymerization. Superparamagnetic GO-Fe3O4 hybrid nanoparticles before
+introducing to elastomeric matrix were characterized by X-ray photoelectron
+spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA)
+and scanning electron microscopy (SEM). The effect of loading (0.3 and 0.5 wt%)
+of GO-Fe3O4 nanoparticle hybrid on the phase structure, tensile and magnetic
+properties of synthesized nanocomposites was investigated. The phase structure
+of nanocomposites was evaluated by differential scanning calorimetry (DSC) and
+dynamic mechanical thermal analysis (DMTA). Dispersion of GO-Fe3O4
+nanoparticles in elastomeric matrix was evaluated by transmission electron
+microscopy (TEM). Magnetic properties of GO-Fe3O4 nanoparticle hybrid and
+nanocomposites with their content were characterized by using two different
+techniques: dc SQUID magnetization measurements as a function of temperature
+(from 2 to 300 K) and external magnetic field and ferromagnetic resonance (FMR)
+at microwave frequency.",2012.05819v1
+2020-12-20,Inverse transfer of magnetic helicity in direct numerical simulations of compressible isothermal turbulence: helical transfers,"The role of the different helical components of the magnetic and velocity
+fields in the inverse spectral transfer of magnetic helicity is investigated
+through Fourier shell-to-shell transfer analysis. Both magnetic helicity and
+energetic transfer analysis are performed on chosen data from direct numerical
+simulations of homogeneous isothermal compressible magnetohydrodynamic
+turbulence, subject to both a large-scale mechanical forcing and a small-scale
+helical electromotive driving. The root mean square Mach number of the
+hydrodynamic turbulent steady-state taken as initial condition varies from 0.1
+to about 11. Three physical phenomena can be distinguished in the general
+picture of the spectral transfer of magnetic helicity towards larger spatial
+scales: local inverse transfer, non-local inverse transfer and local direct
+transfer. A shell decomposition allows to associate these three phenomena with
+clearly distinct velocity scales while the helical decomposition allows to
+establish the role of the different helical components and the compressive part
+of the velocity field on the different transfer processes. The locality and
+relative strength of the different helical contributions are mainly determined
+by the triad helical geometric factor.",2012.10855v1
+2021-01-05,Fast Quasi-Geostrophic Magneto-Coriolis Modes in the Earth's core,"Fast changes of Earth's magnetic field could be explained by inviscid and
+diffusion-less quasi-geostrophic (QG) Magneto-Coriolis modes. We present a
+hybrid QG model with columnar flows and three-dimensional magnetic fields and
+find modes with periods of a few years at parameters relevant to Earth's core.
+For the simple poloidal magnetic field that we consider here they show a
+localization of kinetic and magnetic energy in the equatorial region. This
+concentration of energy near the equator and the high frequency make them a
+plausible mechanism to explain similar features observed in recent geomagnetic
+field observations. Our model potentially opens a way to probe the otherwise
+inaccessible magnetic field structure in the Earth's outer core.",2101.01493v2
+2021-01-20,Efficient highly-subsonic turbulent dynamo and growth of primordial magnetic fields,"We present the first study on the amplification of magnetic fields by the
+turbulent dynamo in the highly subsonic regime, with Mach numbers ranging from
+$10^{-3}$ to $0.4$. We find that for the lower Mach numbers the saturation
+efficiency of the dynamo, $(E_{\mathrm{mag}}/E_{\mathrm{kin}})_{\mathrm{sat}}$,
+increases as the Mach number decreases. Even in the case when injection of
+energy is purely through longitudinal forcing modes,
+$(E_{\mathrm{mag}}/E_{\mathrm{kin}})_{\mathrm{sat}}$ $\gtrsim 10^{-2}$ at a
+Mach number of $10^{-3}$. We apply our results to magnetic field amplification
+in the early Universe and predict that a turbulent dynamo can amplify
+primordial magnetic fields to $\gtrsim$ $10^{-16}$ Gauss on scales up to 0.1 pc
+and $\gtrsim$ $10^{-13}$ Gauss on scales up to 100 pc. This produces fields
+compatible with lower limits of the intergalactic magnetic field inferred from
+blazar $\gamma$-ray observations.",2101.08256v1
+2021-02-03,"Formation of magnetized spatial structures in the Beta Lyrae system III. Reflection of magnetically controlled matter in circumbinary structures in helium lines, in particular arising from metastable levels","Spatial gaseous structures in the Beta Lyrae system have been studied with
+the fact of change in the longitudinal component of the donor's magnetic field
+during the orbital period in mind. The investigation was based primarily on the
+study of the dynamics of the circumstellar structures surrounding the binary
+system as a whole. The special emphasis was placed on the study of complex
+helium lines, in particular those arising from metastable levels. A number of
+different observable facts from the ultraviolet to the red spectral region were
+analyzed. The configuration of the donor magnetic field is a factor that not
+only enhances mass transfer and influences the formation of spatial gas
+structures between stellar components but, to some extent, also affects the
+outflow of matter and the formation of external gas structures around this
+interacting binary system. Together with previous articles
+\citep{Skulskyy2020a, Skulskyy2020b}, the pieces of evidence of this work,
+confirming the reflection of magnetically controlled matter in circumbinary
+structures, define the basis for a coherent picture of the mass exchange
+between components and outflows of matter outwards",2102.01964v1
+2021-02-03,"Magnetic dipole moments of the hidden-charm pentaquark states: $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$","In this work, we employ the light-cone QCD sum rule to calculate the magnetic
+dipole moments of the $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$ pentaquark
+states by considering them as the diquark-diquark-antiquark and molecular
+pictures with quantum numbers $J^P = \frac{3}{2}^-$, $J^P = \frac{1}{2}^-$ and
+$J^P = \frac{1}{2}^-$, respectively. In the analyses, we use the
+diquark-diquark-antiquark and molecular form of interpolating currents, and
+photon distribution amplitudes to obtain the magnetic dipole moment of
+pentaquark states. Theoretical examinations on magnetic dipole moments of the
+hidden-charm pentaquark states, are essential as their results can help us
+better figure out their substructure and the dynamics of the QCD as the theory
+of the strong interaction. As a by product, we extract the electric quadrupole
+and magnetic octupole moments of the $P_c(4440)$ pentaquark. These values show
+a non-spherical charge distribution.",2102.01996v2
+2021-02-15,"Angular-Dependent Dynamic Response and Magnetization Reversal in Fibonacci-Distorted, Kagome Artificial Spin Ice","We have measured the angular dependence of ferromagnetic resonance (FMR)
+spectra for Fibonacci-distorted, Kagome artificial spin ice (ASI). The number
+of strong modes in the FMR spectra depend on the orientation of the applied DC
+magnetic field. In addition, discontinuities observed in the FMR
+field-frequency dispersion curves also depend on DC field orientation, and
+signal a multi-step DC magnetization reversal, which is caused by the reduced
+energy degeneracy of Fibonacci-distorted vertices. The results suggest the
+orientation of applied magnetic field and severity of Fibonacci distortion
+constitute control variables for FMR modes and multi-step reversal in future
+magnonic devices and magnetic switching systems.",2102.07532v1
+2021-03-15,Nonlinear magnetoelectric effect in atomic vapor,"Magnetoelectric (ME) effect refers to the coupling between electric and
+magnetic fields in a medium resulting in electric polarization induced by
+magnetic fields and magnetization induced by electric fields. The linear ME
+effect in certain magnetoelectric materials such as multiferroics has been of
+great interest due to its application in the fabrication of spintronics
+devices, memories, and magnetic sensors. However, the exclusive studies on the
+nonlinear ME effect are mostly centered on the investigation of second-harmonic
+generation in chiral materials. Here, we report the demonstration of nonlinear
+wave mixing of optical electric fields and radio-frequency (rf) magnetic fields
+in thermal atomic vapor, which is the consequence of the higher-order nonlinear
+ME effect in the medium. The experimental results are explained by comparing
+with density matrix calculations of the system. We also experimentally verify
+the expected dependence of the generated field amplitudes on the rf field
+magnitude as evidence of the magnetoelectric effect. This study can open up the
+possibility for precision rf-magnetometry due to its advantage in terms of
+larger dynamic range and arbitrary frequency resolution.",2103.08168v1
+2021-03-24,Evolution of localized magnetic field perturbations and the nature of turbulent dynamo,"Kinematic dynamo in incompressible isotropic turbulent flows with high
+magnetic Prandtl number is considered. The approach interpreting an arbitrary
+magnetic field distribution as a superposition of localized perturbations
+(blobs) is proposed. We derive a relation between stochastic properties of a
+blob and a stochastically homogenous distribution of magnetic field advected by
+the same stochastic flow. This relation allows to investigate the evolution of
+a localized blob at late stage when its size exceeds the viscous scale. It is
+shown that in 3-dimansional flows, the average magnetic field of the blob
+increases exponentially in the inertial range of turbulence, as opposed to the
+late-Batchelor stage when it decreases. Our approach reveals the mechanism of
+dynamo generation in the inertial range both for blobs and homogenous
+contributions. It explains the absence of dynamo in the two-dimensional case
+and its efficiency in three dimensions. We propose the way to observe the
+mechanism in numerical simulations.",2103.13091v1
+2021-03-25,Transport efficiency of biofunctionalized magnetic particles tailored by surfactant concentration,"Controlled transport of surface functionalized magnetic beads in a liquid
+medium is a central requirement for the handling of captured biomolecular
+targets in microfluidic lab-on-chip biosensors. Here, the influence of the
+physiological liquid medium on the transport characteristics of functionalized
+magnetic particles and on the functionality of the coupled protein is studied.
+These aspects are theoretically modeled and experimentally investigated for
+prototype superparamagnetic beads, surface functionalized with green
+fluorescent protein immersed in buffer solution with different concentrations
+of a surfactant. The model reports on the tunability of the steady-state
+particle substrate separation distance to prevent their surface sticking via
+the choice of surfactant concentration. Experimental and theoretical average
+velocities are discussed for a ratchet like particle motion induced by a
+dynamic external field superposed on a static locally varying magnetic field
+landscape. The developed model and experiment may serve as a basis for
+quantitative forecasts on the functionality of magnetic particle transport
+based lab-on-chip devices.",2103.13934v1
+2021-04-06,Diffusion of a magnetic skyrmion in 2-dimensional space,"Two-dimensional magnetic skyrmions are particle-like magnetic domains in
+magnetic thin films. The kinetic property of the magnetic skyrmions at finite
+temperature is well described by the Thiele equation, including a stochastic
+field and a finite mass. In this paper, the validity of the constant-mass
+approximation is examined by comparing the Fourier spectrum of Brownian motions
+described by the Thiele equation and the Landau-Lifshitz-Gilbert equation.
+Then, the 4-dimensional Fokker-Planck equation is derived from the Thiele
+equation with a mass-term. Consequently, an expression of the diffusion flow
+and diffusion constant in a tensor form is derived, extending Chandrasekhar's
+method for Thiele dynamics.",2104.02345v2
+2021-04-21,Generation of magnetic fields by thermomagnetic effects in a nonuniformly rotating layer of an electrically conductive fluid,"In this paper, the generation of magnetic fields in a nonuniformly rotating
+layer of finite thickness of an electrically conducting fluid by thermomagnetic
+(TM) instability. This instability arises due to the temperature gradient
+$\nabla T_0$ and thermoelectromotive coefficient gradient $\nabla\alpha $. The
+influence of the generation of a toroidal magnetic field by TM instability on
+convective instability in a nonuniformly rotating layer of an electrically
+conductive fluid in the presence of a vertical constant magnetic field
+${\bf{B}}_0 \| {\rm OZ}$ is established. As a result of applying the method of
+perturbation theory for the small parameter $ \epsilon = \sqrt {(\textrm
+{Ra}-\textrm {Ra}_c) / \textrm {Ra}_c} $ of supercriticality of the stationary
+Rayleigh number $\textrm {Ra}_c$ a nonlinear equation of the Ginzburg-Landau
+type was obtained. This equation describes the evolution of the finite
+amplitude of perturbations. Numerical solutions of this equation made it
+possible to determine the heat transfer in the fluid layer with and without TM
+effects. It is shown that the amplitude of the stationary toroidal magnetic
+field noticeably increases with allowance for TM effects.",2104.11068v1
+2021-06-03,Resonant Nonlinear Hall Effect in Two-Dimensional Electron Systems,"We study the Hall conductivity of a two-dimensional electron gas under an
+inhomogeneous magnetic field $B(x)$. First, we prove using the quantum kinetic
+theory that an odd magnetic field can lead to a purely nonlinear Hall response.
+Second, considering a real-space magnetic dipole consisting of a sign-changing
+magnetic field and based on numerical semiclassical dynamics, we unveil a
+parametric resonance involving the cyclotron ratio and a characteristic width
+of $B(x)$, which can greatly enhance the Hall response. Different from previous
+mechanisms that rely on the bulk Berry curvature dipole, here, the effect
+largely stems from boundary states associated with the real-space magnetic
+dipole. Our findings pave a new way to engineer current rectification and
+higher harmonic generation in two-dimensional materials having or not crystal
+inversion symmetry.",2106.02001v2
+2021-06-13,Floquet Engineering of Magnetism in Topological Insulator Thin Films,"Dynamic manipulation of magnetism in topological materials is demonstrated
+here via a Floquet engineering approach using circularly polarized light.
+Increasing the strength of the laser field, besides the expected topological
+phase transition, the magnetically doped topological insulator thin film also
+undergoes a magnetic phase transition from ferromagnetism to paramagnetism,
+whose critical behavior strongly depends on the quantum quenching. In sharp
+contrast to the equilibrium case, the non-equilibrium Curie temperatures vary
+for different time scale and experimental setup, not all relying on change of
+topology. Our discoveries deepen the understanding of the relationship between
+topology and magnetism in the non-equilibrium regime and extend optoelectronic
+device applications to topological materials.",2106.06977v1
+2021-07-05,Kapitsa pendulum effects in Josephson junction + nanomagnet under external periodic drive,"We investigate reorientation effects under external periodic drive in the
+nanomagnet dynamics coupled to a Josephson junction. The Kapitsa pendulum is
+introduced as a mechanical analog to this system and we demonstrate the
+reorientation of the easy axis of the nanomagnet. The magnetic field generated
+by the Josephson junction and external drive plays the role of the oscillating
+force of the suspension point in the Kapitsa pendulum. The high frequency
+oscillations change the orientation of the magnetic moment. The magnetic field
+of the quasiparticle current determines the frequency dependence of the
+magnetic moment's orientation. We obtain simple analytical formulas for the
+stable position of the magnetic moment, both under the external periodic drive
+and without it. The influence of external periodic drive on the voltage of
+complete reorientation have been demonstrated.",2107.01882v2
+2021-07-09,Magnetic moments of spin--1/2 triply-heavy baryons: A study of Light-cone QCD and Quark-diquark model,"In this study, the magnetic moments of the spin-1/2 triply-heavy baryons have
+been calculated using both light-cone QCD sum rules and Quark-diquark model.
+Theoretical investigations on magnetic moments of the triply-heavy baryons, are
+crucial as their results can help us better understand their internal structure
+and the dynamics of the QCD as the theory of the strong interaction. We compare
+the results extracted for the magnetic moment with the existing theoretical
+predictions. It is seen that the obtained magnetic moment values are quite
+compatible with the results in the literature.",2107.04361v2
+2021-07-27,Measuring magnetic flux suppression in high-power laser-plasma interactions,"Biermann battery magnetic field generation driven by high power laser-solid
+interactions is explored in experiments performed with the OMEGA EP laser
+system. Proton deflectometry captures changes to the strength, spatial profile,
+and temporal dynamics of the self-generated magnetic fields as the target
+material or laser intensity is varied. Measurements of the magnetic flux during
+the interaction are used to help validate extended magnetohydrodynamic (MHD)
+simulations. Results suggest that kinetic effects cause suppression of the
+Biermann battery mechanism in laser-plasma interactions relevant to both direct
+and indirect-drive inertial confinement fusion. Experiments also find that more
+magnetic flux is generated as the target atomic number is increased, which is
+counter to a standard MHD understanding.",2107.12864v1
+2021-08-07,Normal Forms and Near-Axis Expansions for Beltrami Magnetic Fields,"A formal series transformation to Birkhoff-Gustavson normal form is obtained
+for toroidal magnetic field configurations in the neighborhood of a magnetic
+axis. Bishop's rotation-minimizing coordinates are used to obtain a local
+orthogonal frame near the axis in which the metric is diagonal, even if the
+curvature has zeros. We treat the cases of vacuum and force-free (Beltrami)
+fields in a unified way, noting that the vector potential is essentially the
+Poincar\'e-Liouville one-form of Hamiltonian dynamics, and the resulting
+magnetic field corresponds to the canonical two-form of a nonautonomous
+one-degree-of-freedom system. Canonical coordinates are obtained and Floquet
+theory is used to transform to a frame in which the lowest-order Hamiltonian is
+autonomous. The resulting magnetic axis can be elliptic or hyperbolic, and
+resonant elliptic cases are treated. The resulting expansion for the field is
+shown to be well-defined to all orders, and is explicitly computed to degree
+four. An example is given for an axis with constant torsion near a 1:3
+resonance.",2108.03337v1
+2021-08-26,Quantized electrical conductivity in binary neutron star mergers,"We examine nature of longitudinal electrical conductivity in magnetized
+electron-ion plasma in the context of binary neutron star mergers. In presence
+of strong magnetic field, high density and temperature, quantum oscillatory
+behaviour for electrons emerge due to breakdown of the classical description.
+For pronounced thermodynamic effects, we consider zeroth Landau level
+population of electrons for electrical conductivity. We solve Boltzmann
+equation in presence of magnetic field to obtain the dissipative component of
+the conductivity. The conductivity is formulated considering dynamically
+scattering centres in the medium with magnetically modified screening.
+Numerical estimations show that the effect of magnetically modified screening
+mass on electrical conductivity is less. On the other hand, we observe that
+frequency dependent screening reduces electrical conductivity leading to a
+reduction in the Ohmic decay time scale to become of the order of the
+characteristic timescale of the merger process in the low density regime. This
+indicates the relevance of dissipative process for the merger simulation in the
+above mentioned domain.",2108.11878v1
+2021-08-26,Coupling of magnetic and optomechanical structuring in cold atoms,"Self-organized phases in cold atoms as a result of light-mediated
+interactions can be induced by coupling to internal or external degrees of the
+atoms. There has been growing interest in the interaction of internal spin
+degrees of freedom with the optomechanical dynamics of the external
+centre-of-mass motion. We present a model for the coupling between magnetic and
+optomechanical structuring in a $J=1/2 \to J'=3/2$ system in a single-mirror
+feedback scheme, being representative for a larger class of diffractively
+coupled systems such as longitudinally pumped cavities and counter-propagating
+beam schemes. For negative detunings, a linear stability analysis demonstrates
+that optical pumping and optomechanical driving cooperate to create magnetic
+ordering. However, for long-period transmission gratings the magnetic driving
+will strongly dominate the optomechanical driving, unless one operates very
+close to the existence range of the magnetic instability. At small lattice
+periods, in particular at wavelength-scale periods, the optomechanical driving
+will dominate.",2108.12064v3
+2021-09-05,Ion Temperature Effects on Plasma Flow in the Magnetic Mirror Configuration,"Effects of finite ion temperature on plasma flow in the converging-diverging
+magnetic field, the magnetic mirror, or equivalently, magnetic nozzle
+configuration, are studied using a quasineutral paraxial two-fluid MHD model
+with isothermal electrons and warm magnetized ions. The ion acceleration was
+studied with an emphasis on the role of the singularity at the sonic point
+transition. It is shown that the regularity of the sonic point defines a global
+solution describing plasma acceleration from subsonic to supersonic velocity.
+Stationary accelerating solutions were obtained and compared with the time
+dependent dynamics, confirming that the solutions of the time-dependent
+equations converge to the stationary solutions and therefore are stable. The
+effects of the ion pressure anisotropy were analyzed using Chew-Goldberger-Low
+model and its generalization. It is shown that the mirror force (manifested by
+the perpendicular ion pressure) enhances plasma acceleration. The role of
+ionization and charge exchange on plasma flow acceleration have been
+investigated.",2109.02006v3
+2021-09-12,Evolution of neutron star magnetic fields,"Neutron stars are natural physical laboratories allowing us to study a
+plethora of phenomena in extreme conditions. In particular, these compact
+objects can have very strong magnetic fields with non-trivial origin and
+evolution. In many respects its magnetic field determines the appearance of a
+neutron star. Thus, understanding the field properties is important for
+interpretation of observational data. Complementing this, observations of
+diverse kinds of neutron stars enable us to probe parameters of
+electro-dynamical processes at scales unavailable in terrestrial laboratories.
+In this review we first briefly describe theoretical models of formation and
+evolution of magnetic field of neutron stars, paying special attention to field
+decay processes. Then we present important observational results related to
+field properties of different types of compact objects: magnetars, cooling
+neutron stars, radio pulsars, sources in binary systems. After that, we discuss
+which observations can shed light on obscure characteristics of neutron star
+magnetic fields and their behaviour. We end the review with a subjective list
+of open problems.",2109.05584v1
+2021-09-13,Andreev Reflections in NbN/graphene Junctions under Large Magnetic Fields,"Hybrid superconductor/graphene (SC/g) junctions are excellent candidates for
+investigating correlations between Cooper pairs and quantum Hall (QH) edge
+modes. Experimental studies are challenging as Andreev reflections are
+extremely sensitive to junction disorder and high magnetic fields are required
+to form QH edge states. We fabricated low-resistance SC/g interfaces, composed
+of graphene edge contacted with NbN with a barrier strength of $Z\approx 0.4$,
+that remain superconducting under magnetic fields larger than $18$ T. We
+establish the role of graphene's Dirac band structure on zero-field Andreev
+reflections and demonstrate dynamic tunability of the Andreev reflection
+spectrum by moving the boundary between specular and retro Andreev reflections
+with parallel magnetic fields. Through the application of perpendicular
+magnetic fields, we observe an oscillatory suppression of the 2-probe
+conductance in the $\nu = 4$ Landau level attributed to the reduced efficiency
+of Andreev processes at the NbN/g interface, consistent with theoretical
+predictions.",2109.06285v1
+2021-10-25,A resolution criterion based on characteristic timescales for MHD simulations of molecular clouds,"We investigate the effect of numerical magnetic diffusion in
+magnetohydrodynamic simulations of magnetically supported molecular clouds. To
+this end, we have performed numerical studies on adaptive mesh isothermal
+simulations of marginally sub-critical molecular clouds. We find that
+simulations with low and intermediate resolutions collapse, contrary to what is
+theoretically expected. However, the simulation with the highest numerical
+resolution oscillates around an equilibrium state without collapsing. In order
+to quantify the numerical diffusion of the magnetic field, we ran a second suit
+of current-sheet simulations in which the numerical magnetic diffusion
+coefficient can be directly measured, and computed the corresponding diffusion
+times at various numerical resolutions. On this basis, we propose a criterion
+for the resolution of magnetic fields in MHD simulations based on requiring
+that the diffusion time to be larger than the characteristic timescale of the
+physical process responsible for the dynamic evolution of the structure.",2110.13281v2
+2021-11-03,Primordial Helical Magnetic Fields from Inflation?,"We revisit the mechanism of helical magnetogenesis during inflation with a
+parity violating interaction using the formalism of stochastic inflation. One
+of the polarization of the gauge field undergoes tachyonic growth leading to
+the generation of helical magnetic fields. We obtain the Langevin equations
+associated with the electromagnetic fields which are in the form of
+Ornstein-Uhlenbeck stochastic differential equations. Consequently, the
+tachyonic growth of the helical magnetic fields is balanced by a mean-reverting
+process of stochastic dynamics such that the magnetic fields settle down to an
+equilibrium state with the amplitude smaller than what is obtained in the
+absence of the stochastic noises. Working in the parameter space of the model
+where both the backreaction and the strong coupling problems are under control
+the model does not provide large enough seed to be amplified by the galactic
+dynamo as the source of the magnetic fields observed on cosmological scales.",2111.02147v2
+2021-11-29,Density perturbation and cosmological evolution in the presence of magnetic field in $f(R)$ gravity models,"In this paper, we have investigated the density perturbations and
+cosmological evolution in the FLRW universe in presence of a cosmic magnetic
+field, which may be assumed to mimic primordial magnetic fields. Such magnetic
+fields have sufficient strength to influence galaxy formation and cluster
+dynamics, thereby leaving an imprint on the CMB anisotropies. We have
+considered the FLRW universe as a representative of the isotropic cosmological
+model in the 1+3 covariant formalism for $f(R)$ gravity. The propagation
+equations have been determined and analyzed, where we have assumed that the
+magnetic field is aligned uniformly along the $x$-direction, resulting in a
+diagonal shear tensor. Subsequently,the density perturbation evolution
+equations have been studied and the results have been interpreted. We have also
+indicated how these results change in the general relativistic case and briefly
+mentioned the expected change in higher-order gravity theories.",2111.14898v2
+2021-12-07,Interaction effects of pseudospin-based magnetic monopoles and kinks in a doped dipolar superlattice gas,"Magnetic monopoles and kinks are topological excitations extensively
+investigated in quantum spin systems, but usually they are studied in different
+setups. We explore the conditions for the coexistence and the interaction
+effects of these quasiparticles in the pseudospin chain of the atomic dipolar
+superlattice gas. In this chain, the magnetic kink is the intrinsic
+quasiparticle, and the particle/hole defect takes over the role of the
+north/south magnetic monopole, exerting monopolar magnetic fields to
+neighboring spins. A confinement effect between the monopole and kink is
+revealed, which renormalizes the dispersion of the kink. The corresponding
+dynamical deconfinement process is observed and arises due to the kink-antikink
+annihilation. The rich interaction effects of the two quasiparticles could
+stimulate corresponding investigations in bulk spin systems.",2112.03496v2
+2021-12-13,Causal Interaction between the subsurface rotation rate residuals and radial magnetic field in different timescales,"We studied the presence and spatiotemporal characteristics and evolution of
+the variations in the differential rotation rates and radial magnetic fields in
+the Schwabe and Quasi-biennial-oscillation (QBO) timescales. To achieve these
+objectives, we used rotation rate residuals and radial magnetic field data from
+the Michelson Doppler Imager on the Solar and Heliospheric Observatory and the
+Helioseismic and Magnetic Imager on the Solar Dynamics Observatory, extending
+from May 1996 to August 2020, covering solar cycles 23 and 24, respectively.
+Under the assumption that the radial surface magnetic field is non-local and
+the differential rotation is symmetric around the equator, our results suggest
+that the source region of the Schwabe cycle is confined between
+$\sim$30$^{\circ}$ N and S throughout the convection zone. As for the source
+region of the QBO, our results suggest that it is below 0.78R$_{\odot}$.",2112.06499v1
+2021-12-13,Long-Term Variation of Helioseismic Far-Side Images and What Causes It,"A new time--distance far-side imaging technique was recently developed by
+utilizing multiple multi-skip acoustic waves. The measurement procedure is
+applied to 11 years of Doppler observations from the Solar Dynamics Observatory
+/ Helioseismic and Magnetic Imager, and over 8000 far-side images of the Sun
+have been obtained with a 12-hour temporal cadence. The mean travel-time shifts
+in these images unsurprisingly vary with the solar cycle. However, the temporal
+variation does not show good correlations with the magnetic activity in their
+respective northern or southern hemisphere, but show very good anti-correlation
+with the global-scale magnetic activity. We investigate four possible causes of
+this travel-time variation. Our analysis demonstrates that the acoustic waves
+that are used for mapping the Sun's far side experience surface reflections
+around the globe, where they may interact with surface or near-surface magnetic
+field, and carry travel-time deficits with them. The mean far-side travel-time
+shifts from these acoustic waves therefore vary in phase with the Sun's
+magnetic activity.",2112.06985v1
+2021-12-20,Failure of the mean-field description of magnetic fluctuations in the superconducting quantum dot,"The zero-temperature physics of interacting quantum dots attached to
+superconducting leads is now well understood. The overall qualitative picture
+is obtained from the static mean-field approximation. The situation drastically
+changes at non-zero temperatures. No reliable solutions apart from numerical
+simulations exist there. We show that any static mean-field approximation fails
+at non-zero temperatures since magnetic fluctuations induce dynamical
+corrections that lead to broadening of the in-gap state energies to energy
+bands. Spin-symmetric equilibrium state at non-zero temperatures is unstable
+with respect to magnetic fluctuations and the zero magnetic field can be
+reached only as a weak limit of the spin-polarized solution like in a
+magnetically ordered phase.",2112.10397v1
+2021-12-26,Field-controlling patterns of sheared ferrofluid droplets,"We investigate how ferrofluid droplets suspended in a wall-bounded shear flow
+can organise when subjected to an external magnetic field. By tuning the
+magnitude of the external magnetic field, we find that the ferrofluid droplets
+form chain-like structures in the flow direction when the magnetic field is
+weak, while forming a crystal-like pattern in a strong magnetic field. We
+provide the phase diagram and the critical conditions for this chain-to-crystal
+transition, by applying both numerical simulations and analytic calculations.
+We also examine how the organised patterns of the ferrofluid droplets can be
+controlled by simply changing the direction of the magnetic field. This work
+demonstrates new aspects of field-controllable ferrofluid droplets as a
+configurable and reprocessable metamaterial.",2112.13362v2
+2022-01-14,The Magnetic Field versus Density relation in Star-Forming Molecular Clouds,"We study the magnetic field to density ($B-\rho$) relation in turbulent
+molecular clouds with dynamically important magnetic fields using nonideal
+three-dimensional magnetohydrodynamic simulations. Our simulations show that
+there is a distinguishable break density $\rho_{\rm T}$ between the relatively
+flat low density regime and a power-law regime at higher densities. We present
+an analytic theory for $\rho_{\rm T}$ based on the interplay of the magnetic
+field, turbulence, and gravity. The break density $\rho_{\rm T}$ scales with
+the strength of the initial Alfv\'en Mach number $\mathcal{M}_{\rm A0}$ for
+sub-Alfv\'enic ( $\mathcal{M}_{\rm A0}<1$) and trans-Alfv\'enic
+($\mathcal{M}_{\rm A0} \sim 1$) clouds. We fit the variation of $\rho_{\rm T}$
+for model clouds as a function of $\mathcal{M}_{\rm A0}$, set by different
+values of initial sonic Mach number $\mathcal{M_{\rm 0}}$ and the initial ratio
+of gas pressure to magnetic pressure $\beta_{\rm 0}$. This implies that
+$\rho_{\rm T}$, which denotes the transition in mass-to-flux ratio from the
+subcritical to supercritical regime, is set by the initial turbulent
+compression of the molecular cloud.",2201.05620v2
+2022-01-19,On the limitations of magneto-frictional relaxation,"The magneto-frictional method is used in solar physics to compute both static
+and quasi-static models of the Sun's coronal magnetic field. Here, we examine
+how accurately magneto-friction (without fluid pressure) is able to predict the
+relaxed state in a one-dimensional test case containing two magnetic null
+points. Firstly, we show that relaxation under the full ideal
+magnetohydrodynamic equations in the presence of nulls leads necessarily to a
+non-force-free state, which could not be reached exactly by magneto-friction.
+Secondly, the magneto-frictional solutions are shown to lead to breakdown of
+magnetic flux conservation, whether or not the friction coefficient is scaled
+with magnetic field strength. When this coefficient is constant, flux is
+initially conserved, but only until discontinuous current sheets form at the
+null points. In the ensuing weak solution, we show that magnetic flux is
+dissipated at these current sheets. The breakdown of flux conservation does not
+occur for an alternative viscous relaxation scheme.",2201.07485v1
+2022-01-25,Hydrodynamics of interacting spinons in the magnetized spin-$1/2$ chain with the uniform Dzyaloshinskii-Moriya interaction,"We use a hydrodynamic approach to investigate dynamic spin susceptibility of
+the antiferromagnetic spin-$1/2$ Heisenberg chain with a uniform
+Dzyaloshinskii-Moriya (DM) interaction in the presence of an external magnetic
+field. We find that transverse (with respect to the magnetic field) spin
+susceptibility harbors two (respectively, three) spin excitation modes when the
+magnetic field is parallel (respectively, orthogonal) to the DM axis. In all
+cases, the marginally irrelevant backscattering interaction between the spinons
+creates a finite energy splitting between optical branches of excitations at $k
+= 0$. Additionally, for the orthogonal geometry, the two lower spin branches
+exhibit avoided crossing at finite momentum which is determined by the total
+magnetic field (the sum of the external and internal molecular fields) acting
+on spinons. Our approximate analytical calculations compare well with numerical
+results obtained using matrix-product-state (MPS) techniques. Physical
+consequences of our findings for the electron spin resonance experiments are
+discussed in detail.",2201.10570v2
+2022-02-01,Control of sensitivity in vortex-type magnetic tunnel junction magnetometer sensors by the pinned layer geometry,"The tuning of sensitivity and dynamic range in linear magnetic sensors is
+required in various applications. We demonstrate the control and design of the
+sensitivity in magnetic tunnel junction (MTJ) sensors with a vortex-type
+sensing layer. In this work, we develop sensor MTJs with NiFe sensing layers
+having a vortex magnetic configuration. We demonstrate that by varying the
+pinned layer size, the sensitivity to magnetic field is tuned linearly. We
+obtain a high magnetoresistance ratio of 140 %, and we demonstrate a
+controllable sensitivity from 0.85 to 4.43 %/Oe, while keeping the vortex layer
+fixed in size. We compare our experimental results with micromagnetic
+simulations. We find that the linear displacement of vortex core by an applied
+field makes the design of vortex sensors simple. The control of the pinned
+layer geometry is an effective method to increase the sensitivity, without
+affecting the vortex state of the sensing layer. Furthermore, we propose that
+the location of the pinned layer can be used to realize more sensing
+functionalities from a single sensor.",2202.00207v1
+2022-02-09,First-principles calculations for transient absorption of laser-excited magnetic materials,"We investigate the modification in the optical properties of laser-excited
+bulk cobalt and nickel using the time-dependent density functional theory at a
+finite electron temperature. As a result of the first-principles simulation, a
+complex change in the photoabsorption of the magnetic materials is observed
+around the $M_{2,3}$ absorption edge. Based on the microscopic analysis, we
+clarify that this complex absorption change consists of the two following
+components: (i) the decrease in the photoabsorption in a narrow energy range
+around the $M_{2,3}$ edge, which reflects the blue shift of the absorption edge
+due to the light-induced demagnetization, and (ii) the increase in the
+photoabsorption in a wider range around the $M_{2,3}$ edge, which reflects the
+modification in the local-field effect due to the light-induced electron
+localization. The relation between the transient optical and magnetic
+properties may open a way to monitor ultrafast (de)magnetization and spin
+dynamics in magnetic materials via transient absorption spectroscopy.",2202.04226v1
+2022-02-18,Chiral plasma instability and inverse cascade from nonequilibrium left-handed neutrinos in core-collapse supernovae,"We show that the backreaction of left-handed neutrinos out of equilibrium on
+the matter sector induces an electric current proportional to a magnetic field
+even without a chiral imbalance for electrons in core-collapse supernovae. We
+derive the transport coefficient of this effect based on the recently
+formulated chiral radiation transport theory for neutrinos. This chiral
+electric current generates a strong magnetic field via the so-called chiral
+plasma instability, which could provide a new mechanism for the strong and
+stable magnetic field of magnetars. We also numerically study the physical
+origin of the inverse cascade of the magnetic energy in the
+magnetohydrodynamics including this current. Our results indicate that
+incorporating the chiral effects of neutrinos would drastically modify the
+hydrodynamic evolutions of supernovae, which may also be relevant to the
+explosion dynamics.",2202.09205v2
+2022-02-19,Configuration of magnetotail current sheet prior to magnetic reconnection onset,"The magnetotail current sheet configuration determines magnetic reconnection
+properties that control the substorm onset, one of the most energetic phenomena
+in the Earth's magnetosphere. The quiet-time current sheet is often
+approximated as a two-dimensional (2D) magnetic field configuration balanced by
+isotropic plasma pressure gradients. However, reconnection onset is preceded by
+the current sheet thinning and the formation of a nearly one-dimensional (1D)
+magnetic field configuration. In this study, using particle-in-cell
+simulations, we investigate the force balance of such thin current sheets when
+they are driven by plasma inflow. We demonstrate that the magnetic field
+configuration transitions from 2D to 1D thanks to the formation of plasma
+pressure nongyrotropy and reveal its origin in the nongyrotropic terms of the
+ion distributions. We show that substorm onset may be controlled by the
+instability and dynamics of such nongyrotropic current sheets, having
+properties much different from the most commonly investigated 2D isotropic
+configuration.",2202.09539v2
+2022-03-01,Excitations in the ordered and paramagnetic states of honeycomb magnet Na2Co2TeO6,"Na2Co2TeO6 is a proposed approximate Kitaev magnet, yet its actual magnetic
+interactions are elusive due to a lack of knowledge on the full excitation
+spectrum. Here, using inelastic neutron scattering and single crystals, we
+determine the system's temperature-dependent magnetic excitations over the
+entire Brillouin zone. Without committing to specific models, we unveil a
+distinct signature of the third-nearest-neighbor coupling in the spin waves,
+which signifies the associated distance as an emerging ""soft link"" in the
+ordered state. The presence of at least six non-overlapping spin-wave branches
+is at odds with all models proposed to date. Above the ordering temperature,
+persisting dynamic correlations can be described by equal-time magnetic
+structure factors of a hexagonal cluster, which reveal the leading
+instabilities. Our result sets definitive constraint on theoretical models for
+Na2Co2TeO6 and provides new insight for the materialization of the Kitaev
+model.",2203.00282v1
+2022-03-28,Role of a magnetic field in the context of inhomogeneous gravitational collapse,"Magnetic fields have been found to have an inherent capability of acting
+against gravity. An important question posed in the literature is whether
+presence of a magnetic field can alter the dynamics of a gravitational collapse
+and prevent the final formation of a singularity. Inhomogeneous models of
+collapse have not been explored significantly in this context. In the present
+work we investigate the role of magnetic fields in the evolution of
+inhomogeneous cylindrically symmetric models. We use an approach based on the
+Raychaudhuri equation for such an analysis. We show that it is quite possible
+for the magnetic field to avert the gravitational collapse in these models.",2203.14877v2
+2022-05-03,"Carrier Doping Modulates 2D Intrinsic Ferromagnetic Mn2Ge2Te6 Monolayer High Curie Temperature, Large Magnetic Crystal Anisotropy","The Mn2Ge2Te6 shows intrinsic ferromagnetic (FM) order, with Curie
+temperature (Tc) of 316 K. The FM order origins from superexchange interaction
+between Mn and Te atoms. Mn2Ge2Te6 is half-metal (HM), and spin-\b{eta}
+electron is a semiconductor with gap of 1.462 eV. Mn2Ge2Te6 tends in-plane
+anisotropy (IPA), with magnetic anisotropy energy (MAE) of -13.2 meV/f.u.. The
+Mn2Ge2Te6 shows good dynamical and thermal stability. Moreover, Mn2Ge2Te6
+presents good ferromagnetic and half-metallic stability under charge doping.
+The carriers doping could effectively tune magnetic and electronic properties.
+Specifically, the magnetic moment, exchange parameter, and MAE could be
+efficiently tuned. The total magnetic moment changes linearly with charges
+doping. The exchange parameters could be controlled by the doping carriers. The
+carriers doping could modulate MAE to -18.4 (+0.4 e), -0.85 (-1.6 e), 1.31
+(-2.4 e) meV/f.u., by changing hybridization between Te atoms' py and pz
+orbitals. Mn2Ge2Te6 with intrinsic ferromagnetism, high tunable MAE, good
+stability of ferromagnetism and half-metallicity could help researchers to
+investigate its wide application in the electronics and spintronics.",2205.01498v1
+2022-06-15,Giant Rashba electrical control of magnetism in band models,"It is of considerable technological importance to achieve an electrical
+control of magnetism of sufficient magnitude. To overcome the in-plane shape
+anisotropy, needed is the electrical control of a perpendicular magnetic
+anisotropy (PMA). It is known, within a free electron model, the Rashba
+spin-orbit coupling provides such a control. Surprisingly, this same Rashba PMA
+is enhanced by two to three orders of magnitude when a periodic potential is
+added. Usually spin Berry phase physics reflects time dependent magnetic
+fields. Here it is shown, within a time independent model, such physics arises
+because the Rashba effective magnetic field has texture within the unit cell.
+Predicted are electrical controllable band-structure gaps, linear in the
+applied electric field $E$, that can result in a truly giant linear PMA. Also
+possible is a Peierls mechanism, in which the magnetisation tilts from the
+vertical, shifting these gaps to the Fermi level. As a consequence there are
+low dissipation electric field driven dynamics, an alternative to the more
+dissipative spin torque transfer (STT) effect. The theory requires the
+introduction of an intrinsic spin Berry connection $\vec A_s$, an effective
+vector potential, and is incompatible with current density functional theories
+(DFT).",2206.07399v1
+2022-06-30,Ce and Dy substitutions in Nd$_{2}$Fe$_{14}$B: site-specific magnetic anisotropy from first-principles,"A first-principles approach combining density functional and dynamical
+mean-field theories in conjunction with a quasi-atomic approximation for the
+strongly localized 4$f$ shell is applied to Nd$_{2}$Fe$_{14}$B-based hard
+magnets in order to evaluate crystal-field and exchange-field parameters at
+rare-earth sites and their corresponding single-ion contribution to the
+magnetic anisotropy. In pure Nd$_2$Fe$_{14}$B, our calculations reproduce the
+easy-cone to easy axis transition; theoretical magnetization curves agree
+quantitatively with experiment. Our study reveals that the rare-earth
+single-ion anisotropy in the ""2-14-1"" structure is strongly site-dependent,
+with the $g$ rare-earth site exhibiting a larger value. In particular, we
+predict that increased $f$ and $g$-site occupancy of $R=$ Ce and Dy,
+respectively, leads to an increase of the magnetic anisotropy of the
+corresponding (Nd,$R$)$_{2}$Fe$_{14}$B substituted compounds.",2206.15093v1
+2022-07-07,Exciton-assisted low-energy magnetic excitations in a photoexcited Mott insulator on a square lattice,"The photoexcitation of a Mott insulator on a square lattice weakens the
+intensity of both single- and two-magnon excitations as observed in
+time-resolved resonant-inelastic X-ray scattering and time-resolved Raman
+scattering, respectively. However, the spectral changes in the low-energy
+regions below the magnons have not yet been clearly understood. To uncover the
+nature of the photoinduced low-energy magnetic excitations of the Mott
+insulator, we numerically investigate the transient magnetic dynamics in a
+photoexcited half-filled Hubbard model on a square lattice. After turning off a
+pump pulse tuned for an absorption edge, new magnetic signals clearly emerge
+well below the magnon energy in both single- and two-magnon excitations. We
+find that the low-energy excitations are predominantly created via excitonic
+states at the absorption edge. These exciton-assisted magnetic excitations may
+provide a possible explanation for the low-energy spectral weight in a recent
+time-resolved two-magnon Raman scattering experiment for insulating
+YBa$_2$Cu$_3$O$_{6.1}$.",2207.03141v2
+2022-07-14,Spin relaxation dynamics of radical-pair processes at low magnetic fields,"We report measurements of room-temperature spin-relaxation times $T_1$ and
+$T_2$ of charge-carrier spins in a $\pi$-conjugated polymer thin film under
+bipolar injection and low ($1\mbox{ mT}\lesssim B_0\lesssim 10\mbox{ mT}$)
+static magnetic fields, using electrically detected magnetic resonant Hahn-echo
+and inversion-recovery pulse sequences. The experiments confirm the correlation
+between the magnetic-field sensitive observables of radical-pair processes,
+which include both the spin-dependent recombination currents in organic
+semiconductors and the associated spin-relaxation times when random local
+hyperfine fields and external magnetic fields compete in magnitude. Whereas a
+striking field dependence of spin-lattice relaxation exists in the low-field
+regime, the apparent spin decoherence time remains field independent as the
+distinction between the two is lifted at low fields.",2207.07086v1
+2022-08-10,Spin and valley effects on the quantum phase transition in two dimensions,"Using several independent methods, we find that the metal-insulator
+transition occurs in the strongly-interacting two-valley two-dimensional
+electron system in ultra-high mobility SiGe/Si/SiGe quantum wells in zero
+magnetic field. The transition survives in this system in parallel magnetic
+fields strong enough to completely polarize the electrons' spins, thus making
+the electron system ""spinless"". In both cases, the resistivity on the metallic
+side near the transition increases with decreasing temperature, reaches a
+maximum at a temperature $T_{\text{max}}$, and then decreases. The decrease
+reaches more than an order of magnitude in zero magnetic field. The value of
+$T_{\text{max}}$ in zero magnetic field is found to be close to the
+renormalized Fermi temperature. However, rather than increasing along with the
+Fermi temperature, the value $T_{\text{max}}$ decreases appreciably for
+spinless electrons in spin-polarizing magnetic fields. The observed behavior of
+$T_{\text{max}}$ cannot be described by existing theories. The results indicate
+the spin-related origin of the effect. At the same time, the low-temperature
+resistivity drop in both spin-unpolarized and spinless electron systems is
+described quantitatively by the dynamical mean-field theory.",2208.05356v1
+2022-10-17,Ultrafast laser-driven topological spin textures on a 2D magnet,"Ultrafast laser excitations provide an efficient and low-power consumption
+alternative since different magnetic properties and topological spin states can
+be triggered and manipulated at the femtosecond (fs) regime. However, it is
+largely unknown whether laser excitations already used in data information
+platforms can manipulate the magnetic properties of recently discovered
+two-dimensional (2D) van der Waals (vdW) materials. Here we show that
+ultrashort laser pulses (30$-$85 fs) can not only manipulate magnetic domains
+of 2D-XY CrCl$_3$ ferromagnets, but also induce the formation and control of
+topological nontrivial meron and antimeron spin textures. We observed that
+these spin quasiparticles are created within $\sim$100 ps after the excitation
+displaying rich dynamics through motion, collision and annihilation with
+emission of spin waves throughout the surface. Our findings highlight
+substantial opportunities of using photonic driving forces for the exploration
+of spin textures on 2D magnetic materials towards magneto-optical topological
+applications.",2210.09210v1
+2022-10-19,Generalised form of the magnetic anisotropy field in micromagnetic and atomistic spin models,"We present a general approach to the derivation of the effective anisotropy
+field which determines the dynamical behaviour of magnetic spins according to
+the Landau-Lifshitz-Gilbert equation. The approach is based on the gradient in
+spherical polar coordinates with the final results being expressed in Cartesian
+coordinates as usually applied in atomistic and micromagnetic model
+calculations. The approach is generally valid for all orders of anisotropies
+including higher order combinations of azimuthal and rotational anisotropies
+often found in functional magnetic materials such as permanent magnets and an
+emerging class of antiferromagnetic materials with applications in spintronics.
+Anisotropies are represented in terms of spherical harmonics which have the
+important property of rational temperature scaling. Effective field vectors are
+given for anisotropies up to sixth order, presenting a unified framework for
+implementing higher order magnetic anisotropies in numerical simulations.",2210.10916v4
+2022-10-28,Stripe order and spin dynamics in triangular-lattice antiferromagnet KErSe$_{2}$: A single-crystal study with a theoretical description,"The rare-earth triangular-lattice chalcogenide is a great platform for
+exploring both spin liquids and novel magnetic orders with anisotropic spin
+interactions and magnetic frustrations. Here, we report the thermodynamic and
+neutron scattering measurements of rare-earth triangular-lattice chalcogenide
+KErSe$_{2}$, using single-crystal samples. Our experiments revealed a
+long-range stripe order below 0.2 K. Although the magnetic order was
+three-dimensional, magnetic excitations exhibited negligible modulation along
+the z direction, indicating very weak interlayer coupling. Furthermore,
+magnetic excitation developed a well-defined spin-wave dispersion with a gap of
+$\sim$0.03 meV at M points. Both the stripe order and spin-wave excitations
+could be quantitatively understood from the anisotropic spin interactions of
+the Er$^{3+}$ Kramers doublets.",2210.15867v1
+2022-10-28,Self-similar collapse in a circular magnetic field and electron beam jets by hybrid transverse plasmon,"Based on the set of nonlinear coupling equations describing the interaction
+of the high-frequency field, the self-generated magnetic field and the
+ion-acoustic field, the dispersion relation for the circular magnetic field is
+obtained. The numerical results indicate that the strength of the magnetic
+field have influence on the growth rate of modulation instability. The
+self-generated magnetic field has the tendency to self-similar collapse which
+makes the electron escapes along the axial region and form collimated jets. The
+velocity of jets is calculated and the results are consistent with experimental
+observations. The research may be applied to understand the dynamic process of
+electron beam jets in laboratory and space plasma.",2210.15899v1
+2022-11-04,Picosecond x-ray magnetic circular dichroism spectroscopy at the Fe L-edges with a laser-driven plasma source,"Time-resolved x-ray magnetic circular dichroism (XMCD) enables a unique
+spectroscopic view on complex spin and charge dynamics in multi-elemental
+magnetic materials. So far, its application in the soft-x-ray range has been
+limited to synchrotron-radiation sources and free-electron lasers. By combining
+a laser-driven plasma source with a magnetic thin-film polarizer, we generate
+circularly polarized photons in the soft x-ray regime, enabling the first XMCD
+spectroscopy at the Fe L edges in a laser laboratory. Our approach can be
+readily adapted to other transition metal L and rare earth M absorption edges
+and with a temporal resolution of < 10 ps, a wide range of ultrafast
+magnetization studies can be realized.",2211.02777v1
+2022-11-15,Intrinsic and tunable quantum anomalous Hall effect and magnetic topological phases in XYBi2Te5,"By first-principles calculations, we study the magnetic and topological
+properties of XYBi2Te5-family (X, Y = Mn, Ni, V, Eu) compounds. The strongly
+coupled double magnetic atom-layers can significantly enhance the magnetic
+ordering temperature while keeping the topologically nontrivial properties.
+Particularly, NiVBi2Te5 is found to be a magnetic Weyl semimetal in bulk and a
+Chern insulator in thin film with both the Curie temperature (~150 K) and full
+gap well above 77 K. Ni2Bi2Te5, MnNiBi2Te5, NiVBi2Te5 and NiEuBi2Te5 exhibits
+intrinsic dynamic axion state. Among them, MnNiBi2Te5 has a Neel temperature
+over 200 K and Ni2Bi2Te5 even demonstrates antiferromagnetic order above room
+temperature. These results indicate an approach to realize high temperature
+quantum anomalous Hall effect and other topological quantum effects for
+practical applications.",2211.08163v2
+2022-11-15,Far-from-equilibrium universality in two-dimensional Heisenberg antiferromagnets,"We study the far-from-equilibrium dynamics of isolated two-dimensional
+Heisenberg antiferromagnets. We consider spin spiral initial conditions which
+imprint a position-dependent staggered-magnetization (or Neel order) in the
+two-dimensional lattice. Remarkably, we find a long-lived prethermal regime
+characterized by self-similar behavior of staggered magnetization fluctuations,
+although the system has no long-range order at finite energy and the staggered
+magnetization does not couple with conserved charges. Exploiting the separation
+of length scales introduced by the initial condition, we derive a simplified
+analytical model that allow us to compute the spatial-temporal scaling
+exponents and power-law distribution of the staggered magnetization
+fluctuations analytically, and find excellent agreement with numerical
+simulations using phase space methods. The scaling exponents are insensitive to
+details of the initial condition, in particular, no fine-tuning of energy is
+required to trigger the self-similar scaling regime. Compared with recent
+results on far-from-equilibrium universality on the Heisenberg ferromagnet, we
+find quantitatively distinct spatial-temporal scaling exponents, therefore
+suggesting that the same model with ferromagnetic and antiferromagnetic initial
+conditions can host different universal regimes. Our predictions are relevant
+to ultra-cold atoms simulators of Heisenberg magnets and driven
+antiferromagnetic insulators.",2211.08392v1
+2022-11-23,Pressure-Strain Interaction: III. Particle-in-Cell Simulations of Magnetic Reconnection,"How energy is converted into thermal energy in weakly collisional and
+collisionless plasma processes such as magnetic reconnection and plasma
+turbulence has recently been the subject of intense scrutiny. The
+pressure-strain interaction has emerged as an important piece, as it describes
+the rate of conversion between bulk flow and thermal energy density. In two
+companion studies, we presented an alternate decomposition of the
+pressure-strain interaction to isolate the effects of converging/diverging flow
+and flow shear instead of compressible and incompressible flow, and we derived
+the pressure-strain interaction in magnetic field-aligned coordinates. Here, we
+use these results to study pressure-strain interaction during two-dimensional
+anti-parallel magnetic reconnection. We perform particle-in-cell simulations
+and plot the decompositions in both Cartesian and magnetic field-aligned
+coordinates. We identify the mechanisms contributing to positive and negative
+pressure-strain interaction during reconnection. This study provides a roadmap
+for interpreting numerical and observational data of the pressure-strain
+interaction, which should be important for studies of reconnection, turbulence,
+and collisionless shocks.",2211.13159v1
+2022-11-26,Spontaneous superconducting diode effect in non-magnetic Nb/Ru/Sr$_2$RuO$_4$ topological junctions,"Non-reciprocal electronic transport in a material occurs if both time
+reversal and inversion symmetries are broken. The superconducting diode effect
+(SDE) is an exotic manifestation of this type of behavior where the critical
+current for positive and negative currents are mismatched, as recently observed
+in some non-centrosymmetric superconductors with a magnetic field. Here, we
+demonstrate a SDE in non-magnetic Nb/Ru/Sr$_2$RuO$_4$ Josephson junctions
+without applying an external magnetic field. The cooling history dependence of
+the SDE suggests that time-reversal symmetry is intrinsically broken by the
+superconducting phase of Sr$_2$RuO$_4$. Applied magnetic fields modify the SDE
+dynamically by randomly changing the sign of the non-reciprocity. We propose a
+model for such a topological junction with a conventional superconductor
+surrounded by a chiral superconductor with broken time reversal symmetry.",2211.14626v2
+2023-01-18,Exploring the magnetic dipole moments of $T_{QQ \bar q \bar s}$ and $T_{QQ \bar s \bar s}$ states in the framework of QCD light-cone sum rules,"Motivated by the recent observation of the tetraquark $ T_{cc}^{+}$, we
+investigate the magnetic dipole moments of the possible single and double
+strange partners, $T_{QQ \bar q \bar s}$ and $T_{QQ \bar s \bar s}$, with the
+spin-parity $ J^{P} = 1^{+}$ by means of the QCD light-cone sum rules. To this
+end, we model these states as diquark-antidiquark states with different
+organizations and interpolating currents. The results of magnetic dipole
+moments obtained using different diquark-antidiquark structures differ from
+each other, considerably. The magnetic dipole moment is the leading-order
+response of a bound system to a soft external magnetic field. Therefore, it
+provides an excellent platform for investigation of the inner structures of
+hadrons governed by the quark-gluon dynamics of QCD.",2301.07713v2
+2023-02-05,On semiconductor--metal transition in FeSi induced by ultrahigh magnetic field,"At low temperatures, iron monosilicide is a strongly correlated narrow-gap
+semiconductor. A first order transition to metal state induced by magnetic
+field was observed for the first time at 355 T in Ref. [Yu. B. Kudasov et al.,
+JETP Lett. 68 (1998) 350]. However, recently a smooth transition from 230 T to
+270 T was found under similar conditions in Ref. [D. Nakamura et al., Phys.
+Rev. Lett. 127 (2021) 156601]. This discrepancy goes far beyond experimental
+errors and deserves a careful study. A methodological analysis of inductive and
+RF techniques of conductivity measurements shows that the difference of these
+critical magnetic field estimations stems from a divergence in dynamic ranges
+of the techniques. In fact, the above mentioned methods supplement each other.
+The semiconductor-metal transition under magnetic field in FeSi is a complex
+phenomenon which occurs at the wide range of magnetic fields.",2302.02448v1
+2022-12-24,Particle-level Simulation of Magnetorheological Fluids: A Fully-Resolved Solver,"Magnetorheological fluids (MRFs) are smart materials consisting of
+micro-scale magnetizable particles suspended in a carrier fluid. The
+rheological properties of a MRF can be changed from a fluid-state to a
+solid-state upon the application of an external magnetic field. This study
+reports the development of a particle-level simulation code for magnetic solid
+spheres moving through an incompressible Newtonian carrier fluid. The numerical
+algorithm is implemented within an open-source finite-volume solver coupled
+with an immersed boundary method (FVM-IBM) to perform fully-resolved
+simulations. The particulate phase of the MRF is modeled using the discrete
+element method (DEM). The resultant force acting on the particles due to the
+external magnetic field is computed based on the Clausius-Mossotti
+relationship. The fixed and mutual dipole magnetic models are then used to
+account for the magnetic (MAG) interactions between particles. Several
+benchmark flows were simulated using the newly-developed FVM-IBM-DEM-MAG
+algorithm to assess the accuracy and robustness of the calculations.",2302.03755v1
+2023-02-15,The effect of weak magnetic photon emission from quark-gluon plasma,"We propose a novel effect that accounts for the photon emission from a
+quark-gluon plasma in the presence of a weak external magnetic field. Although
+the weak magnetic photon emission from quark-gluon plasma only leads to a small
+correction to the photon production rate, the induced photon spectrum can be
+highly azimuthally anisotropic, as a consequence of the coupled effect of the
+magnetic field and the longitudinal dynamics in the background medium. With
+respect to a realistic medium evolution containing a tilted fireball
+configuration, the direct photon elliptic flow from experiments is reproduced.
+In comparison to the experimental data of direct photon elliptic flow, in
+heavy-ion collisions the magnitude of the magnetic field before 1 fm/c can be
+extracted. For the top energy of RHIC collisions, right after the
+pre-equilibrium evolution, $|eB|$ is found no larger than a few percent of the
+pion mass square.",2302.07696v3
+2023-04-17,The impact of local pinning sites in magnetic tunnel junctions with non-homogeneous free layers,"Pinning at local defects is a significant road block for the successful
+implementation of technological paradigms which rely on the dynamic properties
+of non-trivial magnetic textures. In this report a comprehensive study of the
+influence of local pinning sites for non-homogeneous magnetic layers integrated
+as the free layer of a magnetic tunnel junction is presented, both
+experimentally and with corresponding micromagnetic simulations. The pinning
+sites are found to be extremely detrimental to the frequency controllability of
+the devices, a key requirement for their use as synapses in a frequency
+multiplexed artificial neural networks. In addition to describing the impact of
+the local pinning sites in the more conventional NiFe, a vortex-based magnetic
+tunnel junction with an amorphous free layer is presented which shows
+significantly improved frequency selectivity, marking a clear direction for the
+design of future low power devices.",2304.08228v1
+2023-04-18,Efficient characteristics of exchange coupling and spin-flop transition in Py/Gd bilayer using anisotropic magnetoresistance,"The interlayer antiferromagnetic coupling rare-earth/transition-metal bilayer
+ferrimagnet systems have attracted much attention because they present
+variously unusual temperature-and field-dependent nontrivial magnetic states
+and dynamics. These properties and the implementation of their applications in
+spintronics highly depend on the significant temperature dependence of the
+magnetic exchange stiffness constant A. Here, we quantitatively determine the
+temperature dependence of magnetic exchange stiffness A_{Py-Gd} and A_{Gd} in
+the artificially layered ferrimagnet consisting of a Py/Gd bilayer, using a
+measurement of anisotropic magnetoresistance (AMR) of the bilayer thin film at
+different temperatures and magnetic fields. The obtained temperature dependence
+of A_{Py-Gd} and A_{Gd} exhibit a scaling power law with the magnetization of
+Gd. The critical field of spin-flop transition and its temperature dependence
+can also be directly obtained by this method. Additionally, the experimental
+results are well reproduced by micromagnetic simulations with the obtained
+parameters A_{Py-Gd} and A_{Gd}, which further confirms the reliability of this
+easily accessible technique.",2304.08858v1
+2023-04-18,Electron correlation effects in paramagnetic cobalt,"We study the influence of Coulomb correlations on spectral and magnetic
+properties of fcc cobalt using a combination of density functional theory and
+dynamical mean-field theory. The computed uniform and local magnetic
+susceptibilities obey the Curie-Weiss law, which, as we demonstrate, occurs due
+to the partial formation of local magnetic moments. We find that the lifetime
+of these moments in cobalt is significantly less than in bcc iron, suggesting a
+more itinerant magnetism in cobalt. In contrast to the bcc iron, the obtained
+electronic self-energies exhibit a quasiparticle shape with the quasiparticle
+mass enhancement factor ${m^*/m}\sim$1.8, corresponding to moderately
+correlated metal. Finally, our calculations reveal that the static magnetic
+susceptibility of cobalt is dominated by ferromagnetic correlations, as
+evidenced by its momentum dependence.",2304.08980v1
+2023-05-03,Statistics of Pressure Fluctuations in Turbulent Kinetic Plasmas,"In this study we explore the statistics of pressure fluctuations in kinetic
+collisionless turbulence. A 2.5D kinetic particle-in-cell (PIC) simulation of
+decaying turbulence is used to investigate pressure balance via the evolution
+of thermal and magnetic pressure in a plasma with beta of order unity. We also
+discuss the behavior of thermal, magnetic and total pressure structure
+functions and their corresponding wavenumber spectra. The total pressure
+spectrum exhibits a slope of -7/3 extending for about a decade in the
+ion-inertial range. In contrast, shallower -5/3 spectra are characteristic of
+the magnetic pressure and thermal pressure. The steeper total pressure spectrum
+is a consequence of cancellation caused by density-magnetic field magnitude
+anticorrelation. Further, we evaluate higher order total pressure structure
+functions in an effort to discuss intermittency and compare the power exponents
+with higher order structure functions of velocity and magnetic fluctuations.
+Finally, applications to astrophysical systems are also discussed.",2305.02068v1
+2023-05-08,Pickup Ion-Mediated Magnetic Reconnection in the Outer Heliosphere,"Pickup ions (PUIs) play a crucial role in the heliosphere, contributing to
+the mediation of large-scale structures such as the distant solar wind, the
+heliospheric termination shock (HTS), and the heliopause. While magnetic
+reconnection is thought to be a common process in the heliosphere due to the
+presence of heliospheric current sheets, it is poorly understood how PUIs might
+affect the evolution of magnetic reconnection. Although it is reasonable to
+suppose that PUIs decrease the reconnection rate since the plasma beta becomes
+much larger than $1$ when PUIs are included, we show for the first time that
+such a supposition is invalid and that PUI-induced turbulence, heat conduction,
+and viscosity can preferentially boost magnetic reconnection in heliospheric
+current sheets in the distant solar wind. This suggests that it is critical to
+include the effect of the turbulence, heat conduction, and viscosity caused by
+PUIs to understand the dynamics of magnetic reconnection in the outer
+heliosphere.",2305.04910v1
+2023-05-23,"Combined funnel, concentrator, and particle valve functional element for magnetophoretic bead transport based on engineered magnetic domain patterns","Controlled actuation of superparamagnetic beads (SPBs) within a microfluidic
+environment using tailored dynamic magnetic field landscapes (MFLs) is a potent
+approach for the realization of point-of-care diagnostics within Lab-on-a-chip
+(LOC) systems. Making use of an engineered magnetic domain pattern as the MFL
+source, a functional LOC-element with combined magnetophoretic funnel,
+concentrator, and valve functions for micron-sized SPBs is presented. A
+parallel-stripe domain pattern design with periodically increasing/decreasing
+stripe lengths has been fabricated in a topographically flat continuous
+exchange biased (EB) thin film system by ion bombardment induced magnetic
+patterning (IBMP). It is demonstrated that, upon application of external
+magnetic field pulses, a fully reversible concentration of SPBs at the domain
+pattern focal point occurs. In addition, it is shown that this functionality
+may be used as an SPB funnel, allowing only a maximum number of particles to
+pass through the focal point. Adjusting the pulse time length, the focal point
+can be clogged up for incoming SPBs, resembling an on-and-off switchable
+particle valve. The observations are supported by quantitative theoretical
+force considerations.",2305.14278v1
+2023-06-05,Dynamic Calculations of Magnetic Field and Implications on Spin Polarization and Spin Alignment in Heavy Ion Collisions,"Magnetic field plays a crucial role in various novel phenomena in heavy-ion
+collisions. We solve the Maxwell equations numerically in a medium with
+time-dependent electric conductivity by using the Finite-Difference Time-Domain
+(FDTD) algorithm. We investigate the time evolution of magnetic fields in two
+scenarios with different electric conductivities at collision energies ranging
+from $\sqrt{s_\text{NN}}=$ 7.7 to 200 GeV. Our results suggest that the
+magnetic field may not persist long enough to induce a significant splitting
+between the global spin polarizations of $\Lambda$ and $\bar{\Lambda}$ at
+freeze-out stage. However, our results do not rule out the possibility of the
+magnetic field influencing the spin (anti-)alignment of vector mesons.",2306.02829v1
+2023-06-06,Magnetic reconnection-driven turbulence and turbulent reconnection acceleration,"This paper employs an MHD-PIC method to perform numerical simulations of
+magnetic reconnection-driven turbulence and turbulent reconnection acceleration
+of particles. Focusing on the dynamics of the magnetic reconnection, the
+properties of self-driven turbulence, and the behavior of particle
+acceleration, we find that: (1) when reaching a statistically steady state of
+the self-driven turbulence, the magnetic energy is almost released by 50\%,
+while the kinetic energy of the fluid increases by no more than 15\%. (2) the
+properties of reconnection-driven turbulence are more complex than the
+traditional turbulence driven by an external force. (3) the strong magnetic
+field tends to enhance the turbulent reconnection efficiency to accelerate
+particles more efficiently, resulting in a hard spectral energy distribution.
+Our study provides a particular perspective on understanding turbulence
+properties and turbulent reconnection-accelerated particles.",2306.03418v1
+2023-06-09,Generation of sub-ion scale magnetic holes from electron shear flow instabilities in plasma turbulence,"Magnetic holes (MHs) are coherent structures associated with strong magnetic
+field depressions in magnetized plasmas. They are observed in many
+astrophysical environments at a wide range of scales but their origin is still
+under debate. In this work we investigate the formation of sub-ion scale MHs
+using a fully kinetic 2D simulation of plasma turbulence initialized with
+parameters typical of the Earth's magnetosheath. Our analysis shows that the
+turbulence is capable of generating sub-ion scale MHs from large scale
+fluctuations via the following mechanism: first, the nonlinear large scale
+dynamics spontaneously leads to the development of thin and elongated electron
+velocity shears; these structures then become unstable to the electron
+Kelvin-Helmholtz instability and break up into small scale electron vortices;
+the electric current carried by these vortices locally reduces the magnetic
+field, inducing the formation of sub-ion scale MHs. The MHs thus produced
+exhibit features consistent with satellite observations and with previous
+numerical studies. We finally discuss the kinetic properties of the observed
+sub-ion scale MHs, showing that they are characterized by complex
+non-Maxwellian electron velocity distributions exhibiting anisotropic and
+agyrotropic features.",2306.05874v1
+2023-07-02,Ferromagnetic filament shapes in a rotating field reveal their magnetoelastic properties,"Flexible ferromagnetic filaments can be used to control the flow on the
+micro-scale with external magnetic field. To accurately model them, it is
+crucial to know their parameters such as their magnetization and bending
+modulus, the latter of which is hard to determine precisely. We present a
+method how the ferromagnetic filament's shape in a rotating field can be used
+to determine the magnetoelastic number $Cm$ - the ratio of magnetic to elastic
+forces. Then once the magnetization of the filament is known, it is possible to
+determine its bending modulus. The main idea of the method is that $Cm$ is the
+only parameter that determines whether the filament is straight or whether its
+tips are bent towards the magnetic field direction. Comparing with numerical
+solutions, we show that the method results in an error of $15...20\%$ for the
+determined $Cm$, what is more precise than estimations from other methods. This
+method will allow to improve the comparability between theoretical filament
+models and experimental measurements.",2307.00685v1
+2023-07-07,Weak-Coupling Theory of Neutron Scattering as a Probe of Altermagnetism,"Inelastic neutron scattering provides a powerful probe of the magnetic
+excitations of quantum magnets. Altermagnets have recently emerged as a new
+class of magnets with vanishing net magnetization characteristic of
+antiferromagnets and with a spin-split electronic structure typical of
+ferromagnets. Here we introduce a minimal Hubbard model with two-sublattice
+orthorhombic anisotropy as a framework to study altermagnetism. Using
+unrestricted Hartree-Fock calculations, we find an altermagnetic state for this
+model that evolves from a metallic state to an insulating state with increasing
+Hubbard-$U$ Coulomb repulsion. We then examine the inelastic neutron scattering
+response in these states using random-phase approximation calculations of the
+dynamic spin susceptibility $\chi''({\bf q}, \omega)$. We find that the
+magnetic excitation spectrum depends on its chirality for ${\bf q}$ along
+certain directions in reciprocal space, an observation that may be used in
+inelastic neutron scattering experiments as a probe of altermagnetism.",2307.03793v2
+2023-07-10,Graph Representation of the Magnetic Field Topology in High-Fidelity Plasma Simulations for Machine Learning Applications,"Topological analysis of the magnetic field in simulated plasmas allows the
+study of various physical phenomena in a wide range of settings. One such
+application is magnetic reconnection, a phenomenon related to the dynamics of
+the magnetic field topology, which is difficult to detect and characterize in
+three dimensions. We propose a scalable pipeline for topological data analysis
+and spatiotemporal graph representation of three-dimensional magnetic vector
+fields. We demonstrate our methods on simulations of the Earth's magnetosphere
+produced by Vlasiator, a supercomputer-scale Vlasov theory-based simulation for
+near-Earth space. The purpose of this work is to challenge the machine learning
+community to explore graph-based machine learning approaches to address a
+largely open scientific problem with wide-ranging potential impact.",2307.09469v2
+2023-07-23,Simulations of Weakly Magnetized Turbulent Mixing Layers,"Radiative turbulent mixing layers are expected to form pervasively at the
+phase boundaries in multiphase astrophysical systems. This inherently small
+scale structure is dynamically crucial because it directly regulates the mass,
+momentum and energy exchanges between adjacent phases. Previous studies on
+hydrodynamic turbulent mixing layers have revealed the interactions between
+cold and hot phases in the context of the circumgalactic medium, offering
+important insight into the fate of cold clouds traveling through hot galactic
+winds. However, the role of magnetic field has only been sparsely investigated.
+We perform a series of 3D magnetohydrodynamics (MHD) simulations of such mixing
+layers in the presence of weak to modest background magnetic field. We find
+that due to field amplification, even relatively weak background magnetic
+fields can significantly reduce the surface brightness and inflow velocity of
+the hot gas in the mixing layer. This reduction is attributed to a combination
+of magnetic pressure support and direct suppression of turbulent mixing, both
+of which alter the phase structures. Our results are largely independent of
+thermal conduction and converged with resolution, offering insights on the
+survival of cold gas in multiphase systems.",2307.12355v2
+2023-08-21,Shape deformation of magnetically levitated fluid droplets,"Diamagnetic levitation can provide a completely passive method to support
+materials against the pull of gravity, and researchers have levitated both
+solids and fluids. Such levitation can be assisted by increasing the magnetic
+susceptibility contrast by using a surrounding paramagnetic medium and through
+buoyancy forces, known as magneto-Archimedean levitation. The
+magneto-Archimedean levitation of solids has proved useful in chemistry and
+biology. However, the levitation of fluid droplets has an additional interest
+because the fluid droplet's shape can deform. We perform experiments and
+simulations to gauge the squashing or eccentricity of the static magnetically
+levitated fluid droplet. By carefully characterizing all the parameters
+affecting the droplet's levitation, using image analysis to estimate the
+droplet's eccentricity, and using finite element adaptive simulations to find
+the lowest energy droplet shape, we find good agreement between the simulations
+and experimental results. As a potential application, we show that the
+droplet's eccentricity can be used to perform magnetic gradiometry with a
+potential resolution of $S\sim 8\,{\rm nT/cm}$, over a volume of 10 mm$^3$,
+which is competitive with other room-temperature magnetic gradiometer
+techniques.",2308.10503v1
+2023-08-27,Magnetostatic modes and criticality in uniaxial magnetic materials,"We analyze modes in a dipole-dipole coupled quantum magnetic material, taking
+into consideration domain structure and other shape effects present in any real
+magnet. We find that the soft mode governing quantum criticality in a
+non-ellipsoidal sample is an inhomogeneous magnetostatic mode which negates
+dynamic, demagnetization-field effects. The demagnetization field is analyzed
+from a microscopic perspective. Furthermore, we find a magnetostatic mode
+originating from variations in the magnetization of the sample, caused by
+domain structure and quantum or thermal fluctuations, will be lower in energy
+than the soft mode governing quantum criticality in the bulk of the magnet.
+Experimental evidence for these theoretical results is provided by analysis of
+electronuclear modes in LiHoF$_4$, an archetypal dipolar quantum Ising
+material, in a microwave resonator.",2308.14169v1
+2023-09-06,Scissors Modes of a Bose-Einstein Condensate in a Synthetic Magnetic Field,"We study the scissors modes of a harmonically trapped Bose-Einstein
+condensate under the influence of a synthetic magnetic field, which induces
+rigid rotational components in the velocity field. Our investigation reveals
+that the scissors mode, excited in the plane perpendicular to the synthetic
+magnetic field, becomes coupled to the quadrupole modes of the condensate,
+giving rise to typical beating effects. Moreover, the two scissors modes
+excited in the vertical planes are also coupled together by the synthetic
+magnetic field, resulting in intriguing gyroscope dynamics. Our analytical
+results, derived from a spinor hydrodynamic theory, are further validated
+through numerical simulations of the three-dimensional Gross-Pitaevskii
+equation. These predictions for the condensates subject to a synthetic magnetic
+field are experimentally accessible with current cold-atom setups and hold
+promise for potential applications in quantum sensing.",2309.02627v1
+2023-09-12,Reconstruction Formulae for 3D Field-Free Line Magnetic Particle Imaging,"Magnetic Particle Imaging (MPI) is a promising noninvasive in vivo imaging
+modality that makes it possible to map the spatial distribution of
+superparamagnetic nanoparticles by exposing them to dynamic magnetic fields. In
+the Field-Free Line (FFL) scanner topology, the spatial encoding of the
+particle distribution is performed by applying magnetic fields vanishing on
+straight lines. The voltage induced in the receiving coils by the particles
+when exposed to the magnetic fields constitute the signal from which the
+particle distribution is to be reconstructed. To avoid lengthy calibration,
+model-based reconstruction formulae have been developed for the 2D FFL scanning
+topology. In this work we develop reconstruction formulae for 3D FFL. Moreover,
+we provide a model-based reconstruction algorithm for 3D FFL and we validate it
+with a numerical experiment.",2309.06254v1
+2023-09-13,Looking at the magnetic properties of half metal from the paramagnetic phase: DFT+DMFT study of exchange interactions in CrO$_2$,"We study magnetic properties of CrO$_2$ within the density functional theory
+plus dynamical mean-field theory (DFT+DMFT) approach in the paramagnetic phase.
+We consider the 3-orbital (per Cr site) model, containing only $t_{2g}$ states,
+the $5$-orbital model, including all $d$-states, as well as the model including
+also the oxygen $p$-states. Using the recently proposed approach of calculation
+of exchange interactions in paramagnetic phase, we extract exchange interaction
+parameters and magnon dispersions for these models. While the magnon dispersion
+in the 3-orbital model possesses negative branches in accordance with previous
+studies in ferromagnetic phase, this drawback is removed in the $5$-orbital
+model. The model containing oxygen states overestimates the exchange
+interactions and spin stiffness. Therefore, the $5$-orbital model appears as
+most adequate for describing magnetic properties of CrO$_2$, in accordance with
+the recent experimental data of fixed valence of chromium in this compound. The
+possibility of describing magnetic properties of this material starting from
+paramagnetic phase points to the correspondence of magnetic properties in this
+phase and ferromagnetic phase and possible important contributions of RKKY
+exchange interactions in paramagnetic phase of CrO$_2$.",2309.06892v1
+2023-09-14,Magnetic flutter effect on validated edge turbulence simulations,"Small magnetic fluctuations ($B_1/B_0 \sim 10^{-4}$) are intrinsically
+present in a magnetic confinement plasma due to turbulent currents. While the
+perpendicular transport of particles and heat is typically dominated by
+fluctuations of the electric field, the parallel stream of plasma is affected
+by fluttering magnetic field lines. In particular through electrons, this
+indirectly impacts the turbulence dynamics. Even in low beta conditions, we
+find that $E\times B$ turbulent transport can be reduced by more than a factor
+2 when magnetic flutter is included in our validated edge turbulence
+simulations of L-mode ASDEX Upgrade. The primary reason for this is the
+stabilization of drift-Alfv\'en-waves, which reduces the phase shifts of
+density and temperature fluctuations with respect to potential fluctuations.
+This stabilization can be qualitatively explained by linear analytical theory,
+and appreciably reinforced by the flutter nonlinearity. As a secondary effect,
+the steeper temperature gradients and thus higher $\eta_i$ increase the impact
+of the ion-temperature-gradient mode on overall turbulent transport. With
+increasing beta, the stabilizing effect on $E\times B$ turbulence increases,
+balancing the destabilization by induction, until direct electromagnetic
+perpendicular transport is triggered. We conclude that including flutter is
+crucial for predictive edge turbulence simulations.",2309.07763v1
+2023-10-16,Magnetic response of a two-dimensional viscous electron fluid,"It has been established that the Coulomb interactions can transform the
+electron gas into a viscous fluid. This fluid is realized in a number of
+platforms, including graphene and two-dimensional semiconductor
+heterostructures. The defining characteristic of the electron fluid is the
+formation of layers of charge carriers that are in local thermodynamic
+equilibrium, as in classical fluids. In the presence of nonuniformities,
+whirlpools and nontrivial flow profiles are formed, which have been directly
+imaged in recent experiments. In this paper, we theoretically study the
+response of the electron fluid to localized magnetic fields. We find that the
+electric current is suppressed by viscous vortices in regions where magnetic
+field is sharply varying, causing strong transport signatures. Experimentally,
+our considerations are relevant since local magnetic fields can be applied to
+the system through implanting adatoms or embedding micromagnets in the
+top-gate. Our theory is essential for the characterization and future
+applications of electron fluids in hydrodynamic spin transport.",2310.10032v1
+2023-11-13,Chiral Symmetry Restoration and the Ultraquantum limit of Axionic Charge Density Waves in Weyl Semimetals,"A new mechanism for chiral symmetry restoration at extreme high magnetic
+fields is proposed in the context of the Magnetic Catalysis scenario in Weyl
+Semimetals. Contrary to previous proposals, here we show that, at very large
+magnetic fields, the transverse velocity of the axion field, the phase mode of
+the chiral condensate $\langle \bar{\Psi}\Psi\rangle$, becomes effectively
+one-dimensional and its fluctuations destroy a possible nonzero value of this
+fermionic condensate. We also show that, despite of the $U(1)$ chiral symmetry
+not being broken at extremely large magnetic fields, the spectrum of the system
+is comprised by a well defined gapless bosonic excitation, connected to the
+axion mode, and a correlated insulating fermionic liquid that is neutral to
+$U(1)$ chiral transformations. When the theory is supplemented with the
+inclusion of dynamical electromagnetic fields, the chiral symmetry is broken
+again, and the conventional scenario of magnetic catalysis can be recovered.",2311.07644v3
+2023-11-17,Phononic dynamical axion in magnetic Dirac insulators,"In cosmology, the axion is a hypothetical particle that is currently
+considered as candidate for dark matter. In condensed matter, a counterpart of
+the axion (the ""axion quasiparticle"") has been predicted to emerge in
+magnetoelectric insulators with fluctuating magnetic order and in
+charge-ordered Weyl semimetals. To date, both the cosmological and
+condensed-matter axions remain experimentally elusive or unconfirmed. Here, we
+show theoretically that ordinary lattice vibrations can form an axion
+quasiparticle in Dirac insulators with broken time- and space-inversion
+symmetries, even in the absence of magnetic fluctuations. The physical
+manifestation of the phononic axion is a magnetic-field-induced phonon
+effective charge, which can be probed in optical spectroscopy. By replacing
+magnetic fluctuations with lattice vibrations, our theory widens the scope for
+the observability of the axion quasiparticle in condensed matter.",2311.10674v1
+2023-11-27,Case study of the validity of truncation schemes of kinetic equations of motion: few magnetic impurities in a semiconductor quantum ring,"We carry out a study on the validity and limitations of truncation schemes
+customarily employed to treat the quantum kinetic equations of motion of
+complex interacting systems. Our system of choice is a semiconductor quantum
+ring with one electron interacting with few magnetic impurities via a
+Kondo-like Hamiltonian. This system is an interesting prototype which displays
+the necessary complexity when suitably scaled (large number of magnetic
+impurities) but can also be solved exactly when few impurities are present. The
+complexity in this system comes from the indirect electron-mediated
+impurity-impurity interaction and is reflected in the Heisenberg equations of
+motion, which form an infinite hierarchy. For the cases of two and three
+magnetic impurities, we solve for the quantum dynamics of our system both
+exactly and following a truncation scheme developed for diluted magnetic
+semiconductors in the bulk. We find an excellent agreement between the two
+approaches when physical observables like the impurities' spin angular momentum
+are computed for times that well exceed the time window of validity of
+perturbation theory. On the other hand, we find that within time ranges of
+physical interest, the truncation scheme introduces negative populations which
+represents a serious methodological drawback.",2311.15872v1
+2023-12-14,"Self-Diffusion and Structure of a Quasi Two-Dimensional, Classical Coulomb Gas Under Increasing Magnetic Field and Temperature","The influence of a magnetic field applied perpendicularly to the plane of a
+quasi two dimensional, low density classical Coulomb gas, with interparticle
+potential U of r as 1 over r, is studied using momentum conserving dissipative
+particle dynamics simulations. The self diffusion and structure of the gas are
+studied as functions of temperature and strength of the magnetic field. It is
+found that the gas undergoes a topological phase transition when the
+temperature is varied, in accord with the Bohr van Leeuwen BvL theorem, the
+structural properties being unaffected, resembling those of the strictly two
+dimensional Kosterlitz Thouless transition, with U of r as varying as ln r.
+Consistent with the BvL theorem, the transition temperature and the melting
+process of the condensed phase are unchanged by the field. Conversely, the self
+diffusion coefficient of the gas is strongly reduced by the magnetic field. At
+the largest values of the cyclotron frequency, the self diffusion coefficient
+is inversely proportional to the applied magnetic field. The implications of
+these results are discussed.",2312.09318v1
+2024-01-03,"Quasi-two-dimensionality of three-dimensional, magnetically dominated, decaying turbulence","Decaying magnetohydrodynamic (MHD) turbulence is important in various
+astrophysical contexts, including early universe magnetic fields, star
+formation, turbulence in galaxy clusters, magnetospheres and solar corona.
+Previously known in the nonhelical case of magnetically dominated decaying
+turbulence, we show that magnetic reconnection is important also in the fully
+helical case and is likely the agent responsible for the inverse transfer of
+energy. Again, in the fully helical case, we find that there is a similarity in
+power law decay exponents in both 2.5D and 3D simulations. To understand this
+intriguing similarity, we investigate the possible quasi-two-dimensionalization
+of the 3D system. We perform Minkowski functional analysis and find that the
+characteristic length scales of a typical magnetic structure in the system are
+widely different, suggesting the existence of local anisotropies. Finally, we
+provide a quasi-two-dimensional hierarchical merger model which recovers the
+relevant power law scalings. In the nonhelical case, we show that a
+helicity-based invariant cannot constrain the system, and the best candidate is
+still anastrophy or vector potential squared, which is consistent with the
+quasi-two-dimensionalization of the system.",2401.01965v1
+2024-01-08,So You Want to Image Myelin Using MRI: Magnetic Susceptibility Source Separation for Myelin Imaging,"In MRI, researchers have long endeavored to effectively visualize myelin
+distribution in the brain, a pursuit with significant implications for both
+scientific research and clinical applications. Over time, various methods such
+as myelin water imaging, magnetization transfer imaging, and relaxometric
+imaging have been developed, each carrying distinct advantages and limitations.
+Recently, an innovative technique named as magnetic susceptibility source
+separation has emerged, introducing a novel surrogate biomarker for myelin in
+the form of a diamagnetic susceptibility map. This paper comprehensively
+reviews this cutting-edge method, providing the fundamental concepts of
+magnetic susceptibility, susceptibility imaging, and the validation of the
+diamagnetic susceptibility map as a myelin biomarker that indirectly measure
+myelin content. Additionally, the paper explores essential aspects of data
+acquisition and processing, offering practical insights for readers. A
+comparison with established myelin imaging methods is also presented, and both
+current and prospective clinical and scientific applications are discussed to
+provide a holistic understanding of the technique. This work aims to serve as a
+foundational resource for newcomers entering this dynamic and rapidly expanding
+field.",2401.03690v2
+2024-01-10,Self-generated spin-orbit torque driven by anomalous Hall current,"Spin-orbit torques enable energy-efficient manipulation of magnetization by
+electric current and hold promise for applications ranging from nonvolatile
+memory to neuromorphic computing. Here we report the discovery of a giant
+spin-orbit torque induced by anomalous Hall current in ferromagnetic
+conductors. This anomalous Hall torque is self-generated as it acts on
+magnetization of the ferromagnet that engenders the torque. The magnitude of
+the anomalous Hall torque is sufficiently large to fully negate magnetic
+damping of the ferromagnet, which allows us to implement a microwave spin
+torque nano-oscillator driven by this torque. The peculiar angular symmetry of
+the anomalous Hall torque favors its use over the conventional spin Hall torque
+in coupled nano-oscillator arrays. The universal character of the anomalous
+Hall torque makes it an integral part of the description of coupled spin
+transport and magnetization dynamics in magnetic nanostructures.",2401.05006v1
+2024-01-14,Robust Parahydrogen-Induced Polarization at High Concentrations,"Parahydrogen-Induced Polarization (PHIP) is a potent technique for generating
+target molecules with high nuclear spin polarization. The PHIP process involves
+a chemical reaction between parahydrogen and a target molecule, followed by the
+transformation of nuclear singlet spin order into magnetization of a designated
+nucleus through magnetic field manipulations. Although the
+singlet-to-magnetization polarization transfer process works effectively at
+moderate concentrations, it is observed to become much less efficient at high
+molar polarization, defined as the product of polarization and concentration.
+This strong dependence on the molar polarization is attributed to interference
+from the field produced by the sample's magnetization during polarization
+transfer, which leads to complex dynamics and can severely impact the
+scalability of the technique. We address this challenge with a pulse sequence
+that negates the influence of the distant dipolar field, while simultaneously
+achieving singlet-to-magnetization polarization transfer to the desired target
+spins, free from restrictions on the molar polarization.",2401.07243v1
+2024-01-23,Vanishing vortex creep at the transition from ordered to disordered vortex phases in Ba$_{0.64}$K$_{0.36}$Fe$_2$As$_2$,"By measuring the dynamical and conventional magnetization relaxation of the
+Ba$_{0.64}$K$_{0.36}$Fe$_2$As$_2$ single crystals, we found strong second peak
+effect on the magnetization hysteresis loops. It is found that there is a kink
+of magnetization at a field between the valley and maximum magnetization.
+Interestingly, the magnetization relaxation rate has a deep minimum at the
+field with the kink, indicating a diminished vortex creep. The relaxation rate
+at this field is clearly smaller than the so-called universal lower limit of
+the relaxation rate characterized by ($S_0\approx \ Gi^{1/2}(T/T_\mathrm{c}$).
+This diminished vortex creep is associated with the origin of the SMP effect
+and attributed to the strongly hindered flux motion when experiencing the
+transition from the quasi-ordered to disordered vortex phases.",2401.12551v1
+2024-01-31,Heavy flavor production under a strong magnetic field,"The magnetic field created in high energy nuclear collisions will affect the
+dynamical processes in the QCD medium, especially the heavy quark production
+that happens in the initial stage of the collisions. We calculate in a strong
+magnetic field the heavy quark production cross section for the elementary
+process gg {\rightarrow} Q{\bar Q} at leading order and the corresponding
+transverse momentum distribution in nucleus-nucleus collisions. In comparison
+to the QED process, the heavy quark production is dominated by the unique QCD
+channel with gluon self-interaction. Due to the dimension reduction of quark
+phase space in a strong magnetic field, the production is concentrated in a
+very narrow energy region above the threshold. Since the translation invariance
+is broken, the production becomes anisotropic in magnetic field.",2401.17559v1
+2024-01-31,Magnetically tunable electrokinetic instability and structuring of non-equilibrium nanoparticle gradients,"Inspired by emergent behaviors of living matter, there is increasing interest
+in developing approaches to create dynamic patterns and structures in synthetic
+materials with controllable complexity to enable functionalities that are not
+possible in thermodynamic equilibrium. Here we show that electrophoretically
+driven and maintained non-equilibrium gradients of magnetic nanoparticles in
+non-polar solvent can undergo electrokinetic instabilities (EKI), leading to
+various electrically controllable spatiotemporally patterned states. These
+electrokinetic instabilities and patterns can be tuned with a magnetic field
+via magnetostatic energy reduction mechanism to both increase and decrease the
+pattern complexity. We reflect the experimental observations on the theoretical
+electrokinetic and magnetostatic arguments. We further show that small amounts
+of polar water in the otherwise non-polar system are critical enablers for the
+electrophoretic mobility of the nanoparticles. Since functionalities of
+magnetic nanoparticles are widely tunable, we foresee that the combination of
+dissipative electrokinetic driving and magnetic energy reduction can lead to
+novel functional dissipative materials.",2401.17956v1
+2024-04-01,Effect of magnetic field on the Bose-Einstein condensation of quantum well exciton-polaritons,"We theoretically examine the effect of the magnetic field on the relaxation
+process of the exciton-polariton toward the Bose-Einstein condensation in GaAs
+quantum wells. As a result of the modification of the exciton's effective mass,
+Rabi splitting, and dispersion, the relaxation rate of polaritons toward
+condensation has been significantly modified. Using a continuous pumping, the
+dynamics of total and condensated polariton versus magnetic field has been
+clarified. It has been shown that for low-energy pumping, the condensation is
+significantly reduced with a magnetic field, and this arises from the reduction
+of the scattering rate between energy levels when the steepness of the
+dispersion at higher energy is reduced. Increasing of pump energy together with
+the magnetic field could lead to a more effective relaxation and a much higher
+number of condensated polariton is obtained.",2404.00970v1
+1996-02-23,Rotation And Magnetic Evolution Of Superconducting Strange Stars,"Is pulsar make up of strange matter? The magnetic field decay of a pulsar may
+be able to give us an answer. Since Cooper pairing of quarks occurs inside a
+sufficiently cold strange star, the strange stellar core is superconducting. In
+order to compensate the effect of rotation, different superconducting species
+inside a rotating strange star try to set up different values of London fields.
+Thus, we have a frustrated system. Using Ginzburg-Landau formalism, I solved
+the problem of rotating a superconducting strange star: Instead of setting up a
+global London field, vortex bundles carrying localized magnetic fields are
+formed. Moreover, the number density of vortex bundles is directly proportional
+to the angular speed of the star. Since it is energetically favorable for the
+vortex bundles to pin to magnetic flux tubes, the rotational dynamics and
+magnetic evolution of a strange star are coupled together, leading to the
+magnetic flux expulsion as the star slows down. I investigate this effect
+numerically and find that the characteristic field decay time is much less than
+20~Myr in all reasonable parameter region. On the other hand, the
+characteristic magnetic field decay time for pulsars is $\geq 20$~Myr. Thus, my
+finding cast doubt on the hypothesis that pulsars are strange stars.",9602130v1
+1997-09-10,Magnetic Field Effects on the Head Structure of Protostellar Jets,"We present the results of 3-D SPMHD numerical simulations of
+supermagnetosonic, overdense, radiatively cooling jets. Two initial magnetic
+configurations are considered: (i) a helical and (ii) a longitudinal field. We
+find that magnetic fields have important effects on the dynamics and structure
+of radiative cooling jets, especially at the head. The presence of a helical
+field suppresses the formation of the clumpy structure which is found to
+develop at the head of purely hydrodynamical jets. On the other hand, a cooling
+jet embedded in a longitudinal magnetic field retains clumpy morphology at its
+head. This fragmented structure resembles the knotty pattern commonly observed
+in HH objects behind the bow shocks of HH jets. This suggests that a strong
+(equipartition) helical magnetic field configuration is ruled out at the jet
+head. Therefore, if strong magnetic fields are present, they are probably
+predominantly longitudinal in those regions. In both magnetic configurations,
+we find that the confining pressure of the cocoon is able to excite
+short-wavelength MHD K-H pinch modes that drive low-amplitude internal shocks
+along the beam. These shocks are not strong however, and it likely that they
+could only play a secondary role in the formation of the bright knots observed
+in HH jets.",9709092v1
+1997-11-21,Effects of Cooling on the Propagation of Magnetized Jets,"We present multi-dimensional simulations of magnetized radiative jets
+appropriate to Young Stellar Objects. Magnetized jets subject to collisionally
+excited radiative losses have not, as yet, received extensive scrutiny. The
+purpose of this letter is to articulate the propagation dynamics of radiative
+MHD jets in the context of the extensive jet literature. Most importantly, we
+look for morphological and kinematic diagnostics that may distinguish
+hydrodynamic protostellar jets from their magnetically dominated cousins. Our
+simulations are axisymmetric (2.5-D). A toroidal B_phi field geometry is used.
+Our models have high sonic Mach numbers (Ms approx 10), but lower fast mode
+Mach number (Mf approx 5). This is approximately the case for jets formed via
+disk-wind or X-wind models - currently the consensus choice for launching and
+collimating YSO jets. Time-dependent radiative losses are included via a
+coronal cooling curve. Our results demonstrate that the morphology and
+propagation characteristics of strongly magnetized radiative jets can differ
+significantly from jets with weak fields. In particular the formation of
+nose-cones via post-shock hoop stresses leads to narrow bow shocks and enhanced
+bow shock speeds. In addition, the hoop stresses produce strong shocks in the
+jet beam which constrasts with the relatively unperturbed beam in radiative
+hydrodynamic jets. Our simulations show that pinch modes produced by magnetic
+tension can strongly effect magnetized protostellar jets.",9711250v1
+1997-12-11,On the difficulty of launching an outflow from an accretion disk,"We solve for the local vertical structure of a thin accretion disk threaded
+by a poloidal magnetic field. The angular velocity deviates from the Keplerian
+value as a result of the radial Lorentz force, but is constant on magnetic
+surfaces. Angular momentum transport and energy dissipation in the disk are
+parametrized by an alpha-prescription, and a Kramers opacity law is assumed to
+hold. We also determine the stability of the equilibria with respect to the
+magnetorotational (or Balbus-Hawley) instability. If the magnetic field is
+sufficiently strong, stable equilibria can be found in which the angle of
+inclination, i, of the magnetic field to the vertical at the surface of the
+disk has any value in the range [0,90 degrees). By analyzing the dynamics of a
+transonic outflow in the corona of the disk, we show that a certain potential
+difference must be overcome even when i > 30 degrees. We determine this
+potential difference as a function of i for increasing values of the vertical
+magnetic field strength. For magnetorotationally stable equilibria, the
+potential difference increases faster than the fourth power of the magnetic
+field strength, quickly exceeding a value corresponding to the central
+temperature of the disk, and is minimized with respect to i at i approximately
+equal to 38 degrees. We show that this property is relatively insensitive to
+the form of the opacity law. Our results suggest that an additional source of
+energy, such as coronal heating, may be required for the launching of an
+outflow from a magnetized disk.",9712150v1
+2000-01-12,Regular magnetic fields in the dwarf irregular galaxy NGC 4449,"We present a high-resolution VLA study of the total power and polarized radio
+continuum emission at 8.46 and 4.86 GHz of the irregular galaxy NGC 4449, known
+for its weak rotation and non-systematic gas motions. We found strong
+galaxy-scale regular magnetic fields, which is surprising because of a lack of
+ordered rotation required for the dynamo action. The strength of the regular
+field reaches 8 $\mu$G and that of the total field 14 $\mu$G, comparable to
+that of the total magnetic field strength in radio-bright spirals. The magnetic
+vectors in NGC 4449 form radial ``fans'' in the central region and fragments of
+a spiral pattern in the galaxy's outskirts. These structures are associated
+with large regions of systematic Faraday rotation, implying genuine
+galaxy-scale magnetic fields rather than random ones compressed and stretched
+by gas flows. The observed pattern of polarization B-vectors is similar to
+dynamo-type fields in normal spirals. Nonstandard, fast dynamo concepts are
+required to explain the observed field strengths, though it is unknown what
+kind of magnetic field geometry can be produced in slowly and chaotically
+rotating objects. The so far neglected role of magnetic fields for the dynamics
+and star formation in dwarf irregulars also needs to be revised.",0001205v1
+2001-05-24,"Transport of Magnetic Fields in Convective, Accreting Supernova Cores","We consider the amplification and transport of a magnetic field in the
+collapsed core of a massive star, including both the region between the
+neutrinosphere and the shock, and the central, opaque core. An analytical
+argument explains why rapid convective overturns persist within a newly formed
+neutron star for roughly 10 seconds ($> 10^3$ overturns), consistent with
+recent numerical models. A dynamical balance between turbulent and magnetic
+stresses within this convective layer corresponds to flux densities in excess
+of $10^{15}$G. Material accreting onto the core is heated by neutrinos and also
+becomes strongly convective. We compare the expected magnetic stresses in this
+convective `gain layer' with those deep inside the neutron core.
+  Buoyant motions of magnetized fluid are greatly aided by the intense neutrino
+flux. We calculate the transport rate through a medium containing free neutrons
+protons, and electrons, in the limiting cases of degenerate or non-degenerate
+nucleons. Fields stronger than $\sim 10^{13}$ G are able to rise through the
+outer degenerate layers of the neutron core during the last stages of
+Kelvin-Helmholtz cooling (up to 10 seconds post-collapse), even though these
+layers have become stable to convection. We also find the equilibrium shape of
+a thin magnetic flux rope in the dense hydrostatic atmosphere of the neutron
+star, along with the critical separation of the footpoints above which the rope
+undergoes unlimited expansion against gravity. The implications of these
+results for pulsar magnetism are summarized, and applied to the case of late
+fallback over the first 1,000-10,000 s of the life of a neutron star",0105425v1
+2002-01-25,"Nonaxisymmetric Evolution of Magnetically Subcritical Clouds: Bar Growth, Core Elongation, and Binary Formation","We have begun a systematic numerical study of the nonlinear growth of
+nonaxisymmetric perturbations during the ambipolar diffusion-driven evolution
+of initially magnetically subcritical molecular clouds, with an eye on the
+formation of binaries, multiple stellar systems and small clusters. In this
+initial study, we focus on the $m=2$ (or bar) mode, which is shown to be
+unstable during the dynamic collapse phase of cloud evolution after the central
+region has become magnetically supercritical. We find that, despite the
+presence of a strong magnetic field, the bar can grow fast enough that for a
+modest initial perturbation (at 5% level) a large aspect ratio is obtained
+during the isothermal phase of cloud collapse. The highly elongated bar is
+expected to fragment into small pieces during the subsequent adiabatic phase.
+Our calculations suggest that the strong magnetic fields observed in some
+star-forming clouds and envisioned in the standard picture of single star
+formation do not necessarily suppress bar growth and fragmentation; on the
+contrary, they may actually promote these processes, by allowing the clouds to
+have more than one (thermal) Jeans mass to begin with without collapsing
+promptly. Nonlinear growth of the bar mode in a direction perpendicular to the
+magnetic field, coupled with flattening along field lines, leads to the
+formation of supercritical cores that are triaxial in general. It removes a
+longstanding objection to the standard scenario of isolated star formation
+involving subcritical magnetic field and ambipolar diffusion based on the
+likely prolate shape inferred for dense cores. Continuted growth of the bar
+mode in already elongated starless cores, such as L1544, may lead to future
+binary and multiple star formation.",0201419v1
+2002-08-26,Magnetized Accretion-Ejection Structures: 2.5D MHD simulations of continuous Ideal Jet launching from resistive accretion disks,"We present numerical magnetohydrodynamic (MHD) simulations of a magnetized
+accretion disk launching trans-Alfvenic jets. These simulations, performed in a
+2.5 dimensional time-dependent polytropic resistive MHD framework, model a
+resistive accretion disk threaded by an initial vertical magnetic field. The
+resistivity is only important inside the disk, and is prescribed as eta =
+alpha_m V_AH exp(-2Z^2/H^2), where V_A stands for Alfven speed, H is the disk
+scale height and the coefficient alpha_m is smaller than unity. By performing
+the simulations over several tens of dynamical disk timescales, we show that
+the launching of a collimated outflow occurs self-consistently and the ejection
+of matter is continuous and quasi-stationary. These are the first ever
+simulations of resistive accretion disks launching non-transient ideal MHD
+jets. Roughly 15% of accreted mass is persistently ejected. This outflow is
+safely characterized as a jet since the flow becomes super-fastmagnetosonic,
+well-collimated and reaches a quasi-stationary state. We present a complete
+illustration and explanation of the `accretion-ejection' mechanism that leads
+to jet formation from a magnetized accretion disk. In particular, the magnetic
+torque inside the disk brakes the matter azimuthally and allows for accretion,
+while it is responsible for an effective magneto-centrifugal acceleration in
+the jet. As such, the magnetic field channels the disk angular momentum and
+powers the jet acceleration and collimation. The jet originates from the inner
+disk region where equipartition between thermal and magnetic forces is
+achieved. A hollow, super-fastmagnetosonic shell of dense material is the
+natural outcome of the inwards advection of a primordial field.",0208459v1
+2005-02-07,"Quiescent Cores and the Efficiency of Turbulence-Accelerated, Magnetically Regulated Star Formation","The efficiency of star formation, defined as the ratio of the stellar to
+total (gas and stellar) mass, is observed to vary from a few percent in regions
+of dispersed star formation to about a third in cluster-forming cores. This
+difference may reflect the relative importance of magnetic fields and
+turbulence in controlling star formation. We investigate the interplay between
+supersonic turbulence and magnetic fields using numerical simulations, in a
+sheet-like geometry. We demonstrate that star formation with an efficiency of a
+few percent can occur over several gravitational collapse times in moderately
+magnetically subcritical clouds that are supersonically turbulent. The
+turbulence accelerates star formation by reducing the time for dense core
+formation. The dense cores produced are predominantly quiescent, with subsonic
+internal motions. These cores tend to be moderately supercritical. They have
+lifetimes long compared with their local gravitational collapse time. Some of
+the cores collapse to form stars, while others disperse away without star
+formation. In turbulent clouds that are marginally magnetically supercritical,
+the star formation efficiency is higher, but can still be consistent with the
+values inferred for nearby embedded clusters. If not regulated by magnetic
+fields at all, star formation in a multi-Jeans mass cloud endowed with a strong
+initial turbulence proceeds rapidly, with the majority of cloud mass converted
+into stars in a gravitational collapse time. The efficiency is formally higher
+than the values inferred for nearby cluster-forming cores, indicating that
+magnetic fields are dynamically important even for cluster formation.",0502130v1
+2005-07-07,Simulating field-aligned diffusion of a cosmic ray gas,"The macroscopic behaviour of cosmic rays in turbulent magnetic fields is
+discussed. An implementation of anisotropic diffusion of cosmic rays with
+respect to the magnetic field in a non-conservative, high-order,
+finite-difference magnetohydrodynamic code is discussed. It is shown that the
+standard implementation fails near singular X-points of the magnetic field,
+which are common if the field is random. A modification to the diffusion model
+for cosmic rays is described and the resulting telegraph equation (implemented
+by solving a dynamic equation for the diffusive flux of cosmic rays) is used;
+it is argued that this modification may better describe the physics of cosmic
+ray diffusion. The present model reproduces several processes important for the
+propagation and local confinement of cosmic rays, including spreading
+perpendicular to the local large-scale magnetic field, controlled by the
+random-to-total magnetic field ratio, and the balance between cosmic ray
+pressure and magnetic tension. Cosmic ray diffusion is discussed in the context
+of a random magnetic field produced by turbulent dynamo action. It is argued
+that energy equipartition between cosmic rays and other constituents of the
+interstellar medium do not necessarily imply that cosmic rays play a
+significant role in the balance of forces.",0507176v2
+2005-11-01,Magnetic Reynolds number dependence of reconnection rate and flow structure of the self-similar evolution model of fast magnetic reconnection,"This paper investigates Magnetic Reynolds number dependence of the
+``self-similar evolution model'' (Nitta et al. 2001) of fast magnetic
+reconnection. I focused my attention on the flow structure inside and around
+the reconnection outflow, which is essential to determine the entire
+reconnection system (Nitta et al. 2002). The outflow is consist of several
+regions divided by discontinuities, e.g., shocks, and it can be treated by a
+shock-tube approximation (Nitta 2004). By solving the junction conditions
+(e.g., Rankine-Hugoniot condition), the structure of the reconnection outflow
+is obtained. Magnetic reconnection in most astrophysical problems is
+characterized by a huge dynamic range of its expansion ($sim 10^7$ for typical
+solar flares) in a free space which is free from any influence of external
+circumstances. Such evolution results in a spontaneous self-similar expansion
+which is controlled by two intrinsic parameters: the plasma-$beta$ and the
+magnetic Reynolds number. The plasma-$beta$ dependence had been investigated in
+our previous paper. This paper newly clarifies the relation between the
+reconnection rate and the inflow structure just outside the Petschek-like slow
+shock: As the magnetic Reynolds number increases, strongly converging inflow
+toward the Petschek-like slow shock forms, and it significantly reduces the
+reconnection rate.",0511013v1
+2006-12-29,Dynamic confinement of jets by magneto-torsional oscillations,"Many quasars and active galactic nuclei (AGN) appear in radio, optical, and
+X-ray maps, as a bright nuclear sources from which emerge single or double
+long, thin jets (Thomson et al., 1993). When observed with high angular
+resolution these jets show structure with bright knots separated by relatively
+dark regions. High percentages of polarization, sometimes more then 50% in some
+objects, indicates the nonthermal nature of the radiation which is well
+explained as the synchrotron radiation of the relativistic electrons in an
+ordered magnetic field.
+  A strong collimation of jets is most probably connected with ordered magnetic
+fields. The mechanism of magnetic collimation, first suggested by
+Bisnovatyi-Kogan et al. (1969), was based on the initial charge separation,
+leading to creation of oscillating electrical current, which produces azimuthal
+magnetic field, preventing jet expansion and disappearance. Here we consider
+magnetic collimation, connected with torsional oscillations of a cylinder with
+elongated magnetic field. Instead of initial blobs with charge separation, we
+consider a cylinder with a periodically distributed initial rotation around the
+cylinder axis. The stabilizing azimuthal magnetic field is created here by
+torsional oscillations, where charge separation is not necessary. Approximate
+simplified model is developed. Ordinary differential equation is derived, and
+solved numerically, what gives a possibility to estimate quantitatively the
+range of parameters where jets may be stabilized by torsional oscillations.",0612781v1
+2007-02-05,Magnetic Helicity and the Relaxation of Fossil Fields,"In the absence of an active dynamo, purely poloidal magnetic field
+configurations are unstable to large-scale dynamical perturbations, and decay
+via reconnection on an Alfvenic timescale. Nevertheless, a number of classes of
+dynamo-free stars do exhibit significant, long-lived, surface magnetic fields.
+Numerical simulations suggest that the large-scale poloidal field in these
+systems is stabilized by a toroidal component of the field in the stellar
+interior. Using the principle of conservation of total helicity, we develop a
+variational principle for computing the structure of the magnetic field inside
+a conducting sphere surrounded by an insulating vacuum. We show that, for a
+fixed total helicity, the minimum energy state corresponds to a force-free
+configuration. We find a simple class of axisymmetric solutions, parametrized
+by angular and radial quantum numbers. However, these solutions have a
+discontinuity in the toroidal magnetic field at the stellar surface which will
+exert a toroidal stress on the surface of the star. We then describe two other
+classes of solutions, the standard spheromak solutions and ones with fixed
+surface magnetic fields, the latter being relevant for neutron stars with rigid
+crusts. We discuss the implications of our results for the structure of neutron
+star magnetic fields, the decay of fields, and the origin of variability and
+outbursts in magnetars.",0702128v2
+2007-03-09,Burial of the polar magnetic field of an accreting neutron star. II. Hydromagnetic stability of axisymmetric equilibria,"The theory of polar magnetic burial in accreting neutron stars predicts that
+a mountain of accreted material accumulates at the magnetic poles of the star,
+and that, as the mountain spreads equatorward, it is confined by, and
+compresses, the equatorial magnetic field. Here, we extend previous,
+axisymmetric, Grad-Shafranov calculations of the hydromagnetic structure of a
+magnetic mountain up to accreted masses as high as $\Ma = 6\times
+10^{-4}\Msun$, by importing the output from previous calculations (which were
+limited by numerical problems and the formation of closed bubbles to $\Ma <
+10^{-4}\Msun$) into the time-dependent, ideal-magnetohydrodynamic code ZEUS-3D
+and loading additional mass onto the star dynamically. The rise of buoyant
+magnetic bubbles through the accreted layer is observed in these experiments.
+We also investigate the stability of the resulting hydromagnetic equilibria by
+perturbing them in ZEUS-3D. Surprisingly, it is observed that the equilibria
+are marginally stable for all $\Ma\leq 6\times 10^{-4}\Msun$; the mountain
+oscillates persistently when perturbed, in a combination of Alfv\'en and
+acoustic modes, without appreciable damping or growth, and is therefore not
+disrupted (apart from a transient Parker instability initially, which expels $<
+1 %$ of the mass and magnetic flux).",0703203v1
+2001-03-21,Asymptotic properties of turbulent magnetohydrodynamics,"The dynamic renormalization group (RG) is used to study the large-distance
+and long-time limits of viscous and resistive incompressible
+magnetohydrodynamics subject to random forces and currents. The scale-dependent
+viscosity and magnetic resistivity are derived and used for carrying out
+RG-improved perturbation theory. This is applied to derive both the asymptotic
+scaling and the overall proportionality coefficients for both the velocity and
+magnetic field correlation functions as well as the kinetic and magnetic energy
+density spectral functions. The Kolmogorov, Iroshnikov-Kraichnan, as well as
+other energy spectra, formally can be obtained by suitable choice of injected
+noise, although the method limits the validity of these energy spectra only to
+the asymptotic regime . Injection of a random magnetic helicity is considered,
+its RG-improved spectral density derived, and its contribution to the velocity
+and magnetic field correlation functions determined. The RG scaling solutions
+are used to determine information at asymptotic scales about energy and
+helicity cascade directions and mixing between magnetic and kinetic energy.
+Some of the results found here also are shown to be valid for the Navier-Stokes
+hydrodynamic equation. The results have applicability to geomagnetism as well
+as cosmic magnetic fields at astrophysical and cosmological scales.",0103447v3
+2003-11-18,"Field-induced magnetic order in La$sub {2-x}$Sr$sub x$CuO$sub 4$ (x = 0.10, 0.115, 0.13) studied by in-plane thermal conductivity measurements","We have measured the thermal conductivity in the $ab$-plane of
+La$_{2-x}$Sr$_x$CuO$_4$ ($x =$ 0.10, 0.115, 0.13) in magnetic fields up to 14 T
+parallel to the c-axis and also parallel to the $ab$-plane. By the application
+of magnetic fields parallel to the c-axis, the thermal conductivity has been
+found to be suppressed at low temperatures below the temperature $T_\kappa$
+which is located above the superconducting transition temperature and is almost
+independent of the magnitude of the magnetic field. The suppression is marked
+in $x =$ 0.10 and 0.13, while it is small in $x =$ 0.115. Furthermore, no
+suppression is observed in the 1 % Zn-substituted
+La$_{2-x}$Sr$_x$Cu$_{0.99}$Zn$_{0.01}$O$_4$ with $x =$ 0.115. Taking into
+account the experimental results that the temperature dependence of the
+relative reduction of the thermal conductivity is quite similar to the
+temperature dependence of the intensity of the incommensurate magnetic Bragg
+peak corresponding to the static stripe order and that the Zn substitution
+tends to stabilize the static order, it is concluded that the suppression of
+the thermal conductivity in magnetic fields is attributed to the development of
+the static stripe order. The present results suggest that the field-induced
+magnetic order in La$_{2-x}$Sr$_x$CuO$_4$ originates from the pinning of the
+dynamical stripes of spins and holes by vortex cores.",0311402v3
+2005-02-23,Phonon Bottleneck Effect Leads to Observation of Quantum Tunneling of the Magnetization and Butterfly Hysteresis Loops in (Et4N)3Fe2F9,"A detailed investigation of the unusual dynamics of the magnetization of
+(Et4N)3Fe2F9 (Fe2), containing isolated [Fe2F9]3- dimers, is presented and
+discussed. Fe2 possesses an S=5 ground state with an energy barrier of 2.40 K
+due to an axial anisotropy. Poor thermal contact between sample and bath leads
+to a phonon bottleneck situation, giving rise to butterfly-shaped hysteresis
+loops below 5 K concomitant with slow decay of the magnetization for magnetic
+fields Hz applied along the Fe--Fe axis. The butterfly curves are reproduced
+using a microscopic model based on the interaction of the spins with resonant
+phonons. The phonon bottleneck allows for the observation of resonant quantum
+tunneling of the magnetization at 1.8 K, far above the blocking temperature for
+spin-phonon relaxation. The latter relaxation is probed by AC magnetic
+susceptibility experiments at various temperatures and bias fields. At H=0, no
+out-of-phase signal is detected, indicating that at T smaller than 1.8 K Fe2
+does not behave as a single-molecule magnet. At 1 kG, relaxation is observed,
+occurring over the barrier of the thermally accessible S=4 first excited state
+that forms a combined system with the S=5 state.",0502548v1
+2006-02-09,Magnetization damping in polycrystalline Co ultra-thin films: Evidence for non-local effects,"The magnetic properties and magnetization dynamics of polycrystalline
+ultra-thin Co layers were investigated using a broadband ferromagnetic
+resonance (FMR) technique at room temperature. A variable thickness (1 nm $\leq
+t \leq$ 10 nm) Co layer is sandwiched between 10 nm thick Cu layers (10 nm Cu|
+t Co|10 nm Cu), while materials in contact with the Cu outer interfaces are
+varied to determine their influence on the magnetization damping. The resonance
+field and the linewidth were studied for in-plane magnetic fields in field
+swept experiments at a fixed frequency, from 4 to 25 GHz. The Co layers have a
+lower magnetization density than the bulk, and an interface contribution to the
+magnetic anisotropy normal to the film plane. The Gilbert damping, as
+determined from the frequency dependence of the linewidth, increases with
+decreasing Co layer thickness for films with outer Pt layers. This enhancement
+is not observed in structures without Pt layers. The result can be understood
+in terms of a non-local contribution to the damping due to spin pumping from Co
+through the Cu layer and spin relaxation in Pt layers. Pt layers just 1.5 nm
+thick are found to be sufficient to enhance the damping and thus act as
+efficient ""spin-sinks"". In structures with Pt outer layers, this non-local
+contribution to the damping becomes predominant when the Co layer is thinner
+than 4 nm.",0602243v2
+2006-05-06,Three-dimensionality of field-induced magnetism in a high-temperature superconductor,"Many physical properties of high-temperature (high-Tc) superconductors are
+two-dimensional phenomena derived from their square planar CuO2 building
+blocks. This is especially true of the magnetism from the copper ions. As
+mobile charge carriers enter the CuO2 layers, the antiferromagnetism of the
+parent insulators, where each copper spin is antiparallel to its nearest
+neighbours1, evolves into a fluctuating state where the spins show tendencies
+towards magnetic order of a longer periodicity. For certain charge carrier
+densities, quantum fluctuations are sufficiently suppressed to yield static
+long-period order2,3,4,5,6, and external magnetic fields also induce such
+order7,8,9,10,11,12. Here we show that in contrast to the chemically-controlled
+order in superconducting samples, the field-induced order in these same samples
+is actually three-dimensional, implying significant magnetic linkage between
+the CuO2 planes. The results are important because they show that there are
+three-dimensional magnetic couplings which survive into the superconducting
+state, and coexist with the crucial inter-layer couplings responsible for
+three-dimensional superconductivity. Both types of coupling will straighten the
+vortex lines, implying that we have finally established a direct link between
+technical superconductivity, which requires zero electrical resistance in an
+applied magnetic field and depends on vortex dynamics, and the underlying
+antiferromagnetism of the cuprates.",0605164v1
+2006-08-10,The origin of the spin glass transition in a model geometrically frustrated magnet,"Highly frustrated systems have macroscopically degenerate ground states that
+lead to novel properties. In magnetism its consequences underpin exotic and
+technologically important effects, such as, high temperature superconductivity,
+colossal magnetoresistence, and the anomalous Hall effect. One of the enduring
+mysteries of frustrated magnetism is why certain experimental systems have a
+spin glass transition and its exact nature, given that it is not determined by
+the strength of the dominant magnetic interactions. There have been some
+suggestions that real systems possess disorder of the magnetic sites or bonds
+that are responsible. We show that the spin glass transition in the model
+kagome antiferromagnet hydronium jarosite arises from a spin anisotropy. This
+weaker energy scale is much smaller than that of the magnetic exchange, yet it
+is responsible for the energy barriers that are necessary to stabilise a glassy
+magnetic phase at finite temperature. The resultant glassy phase is quite
+unlike those found in conventional disordered spin glasses as it is based on
+complex collective rearrangements of spins called ""spin folds"". This simplifies
+hugely theoretical treatment of both the complex dynamics characteristic of a
+spin glass and the microscopic nature of the spin glass transition itself.",0608234v1
+2003-03-17,Constituent-Quark Model and New Particles,"An elementary constituent-quark (CQ) model by Mac Gregor is reviewed with
+currently published data from light meson spectroscopy. It was previously shown
+in the CQ model that there existed several mass quanta m = 70 MeV, B = 140 MeV
+and X = 420 MeV, which were responsible for the quantization of meson yrast
+levels. The existence of a 70-MeV quantum was postulated by Mac Gregor and was
+shown to fit the Nambu empirical mass formula mn = (n/2)137me, n a positive
+integer. The 70-MeV quantum can be derived in three different ways: 1) pure
+electric coupling, 2) pure magnetic coupling, and 3) mixed electric and
+magnetic charges (dyons). Schwinger first introduced dyons in a magnetic model
+of matter. It is shown in this paper that recent data of new light mesons fit
+into the CQ model (a pure electric model) without the introduction of magnetic
+charges. However, by introducing electric and magnetic quarks (dyons) into the
+CQ model, new dynamical forces can be generated by the presence of magnetic
+fields internal to the quarks (dyons). The laws of angular momentum and of
+energy conservation are valid in the presence of magnetic charge. With the
+introduction of the Russell-Saunders coupling scheme into the CQ model, several
+new meson particles are predicted to exist. The existence of the f0(560) meson
+is predicted and is shown to fit current experimental data from the Particle
+Data Group listing. The existence of meson partners or groupings is shown.",0303139v3
+2002-02-06,From U(1) Maxwell Chern-Simons to Azbel-Hofstadter: Testing Magnetic Monopoles and Gravity to $\sim 10^{-15}$\textit{m}?,"It is built a map between an Abelian Topological Quantum Field Theory, $2+1D$
+compact U(1) gauge Maxwell Chern-Simons Theory and the nonrelativistic quantum
+mechanics Azbel-Hofstadter model of Bloch electrons. The $U_q(sl_2)$ quantum
+group and the magnetic translations group of the Azbel-Hofstadter model
+correspond to discretized subgroups of U(1) with linear gauge parameters. The
+magnetic monopole confining and condensate phases in the Topological Quantum
+Field Theory are identified with the extended (energy bands) and localized
+(gaps) phases of the Bloch electron. The magnetic monopole condensate is
+associated, at the nonrelativistic level, with gravitational white holes due to
+deformed classical gauge fields. These gravitational solutions render the
+existence of finite energy pure magnetic monopoles possible. This mechanism
+constitutes a dynamical symmetry breaking which regularizes the solutions on
+those localized phases allowing physical solutions of the Shr\""odinger equation
+which are chains of electron filaments connecting several monopole-white
+holes.To test these results would be necessary a strong external magnetic field
+$B\sim 5 T$ at low temperature $T<1 K$. To be accomplished, it would test the
+existence of magnetic monopoles and classical gravity to a scale of $\sim
+10^{-15}$ \textit{meters}, the dimension of the monopole-white hole. A proper
+discussion of such experiment is out of the scope of this theoretical work.",0202033v3
+2004-11-11,The magnetized dusty plasma discharge : negative and positive space charge modes,"The structure of a discharge across a magnetic field in a dusty plasma is
+analysed. The dust macroparticles are negatively charged, but are unmagnetized
+because of their high mass. The electrons are highly magnetized, and the ions
+have intermediate magnetization. This results in different transport rates of
+the different species across the magnetic field. Depending on the size of the
+magnetic field, and the relative charge on the different species, the dust
+grains can be the dominant current carrier. The space charge clouds near the
+electrodes will then be determined by the relative mobility of the different
+species. The discharge can operate in one of two modes, a positive space charge
+(PSC) mode, characterized by a strong cathode fall, and a negative space charge
+(NSC) mode, characterized by a broad anode fall. Features unique to the dust
+particles can also play a role in the structure of the discharge, such as the
+variable equilibrium charge on the grains, dependent on the local potential and
+species temperatures, the effect of gravity on the grain dynamics, and the rate
+of charging of the grains. The dust grains can also form an ordered structure,
+the dust-plasma crystal. A fluid model of the different species is used to
+calculate the structure of the resulting discharge, incorporating the above
+effects. The transition from the PSC mode to the NSC mode as the magnetic
+field, pressure and dust properties are varied is demonstrated.",0411116v1
+2006-06-14,Paradox of inductionless magnetorotational instability in a Taylor-Couette flow with a helical magnetic field,"We consider the magnetorotational instability (MRI) of a hydrodynamically
+stable Taylor-Couette flow with a helical external magnetic field in the
+inductionless approximation defined by a zero magnetic Prandtl number
+($\Pm=0)$. This leads to a considerable simplification of the problem
+eventually containing only hydrodynamic variables. First, we point out that the
+energy of any perturbation growing in the presence of magnetic field has to
+grow faster without the field. This is a paradox because the base flow is
+stable without the magnetic while it is unstable in the presence of a helical
+magnetic field without being modified by the latter as it has been found
+recently by Hollerbach and Rudiger [Phys. Rev. Lett. 95, 124501 (2005)]. We
+revisit this problem by using a Chebyshev collocation method to calculate the
+eigenvalue spectrum of the linearized problem. In this way, we confirm that MRI
+with helical magnetic field indeed works in the inductionless limit where the
+destabilization effect appears as an effective shift of the Rayleigh line.
+Second, we integrate the linearized equations in time to study the transient
+behavior of small amplitude perturbations, thus showing that the energy
+arguments are correct as well. However, there is no real contradiction between
+both facts. The linear stability theory predicts the asymptotic development of
+an arbitrary small-amplitude perturbation, while the energy stability theory
+yields the instant growth rate of any particular perturbation, but it does not
+account for the evolution of this perturbation.",0606122v1
+2007-08-21,Magnetogenesis from Cosmic String Loops,"Large-scale coherent magnetic fields are observed in galaxies and clusters,
+but their ultimate origin remains a mystery. We reconsider the prospects for
+primordial magnetogenesis by a cosmic string network. We show that the magnetic
+flux produced by long strings has been overestimated in the past, and give
+improved estimates. We also compute the fields created by the loop population,
+and find that it gives the dominant contribution to the total magnetic field
+strength on present-day galactic scales. We present numerical results obtained
+by evolving semi-analytic models of string networks (including both one-scale
+and velocity-dependent one-scale models) in a Lambda-CDM cosmology, including
+the forces and torques on loops from Hubble redshifting, dynamical friction,
+and gravitational wave emission. Our predictions include the magnetic field
+strength as a function of correlation length, as well as the volume covered by
+magnetic fields. We conclude that string networks could account for magnetic
+fields on galactic scales, but only if coupled with an efficient dynamo
+amplification mechanism.",0708.2901v3
+2007-12-20,Magnetized CMB observables: a dedicated numerical approach,"Large-scale magnetic fields affect the scalar modes of the geometry whose
+ultimate effect is to determine the anisotropies of the Cosmic Microwave
+Background (CMB in what follows). For the first time, a consistent numerical
+approach to the magnetized CMB anisotropies is pursued with the aim of
+assessing the angular power spectra of temperature and polarization when the
+scalar modes of the geometry and a stochastic background of inhomogeneous
+magnetic fields are simultaneously present in the plasma. The effects related
+to the magnetized nature of the plasma are taken into account both at the level
+of the dynamical equations and at the level of the initial conditions of the
+Einstein-Boltzmann hierarchy. The temperature and polarization observables are
+exploited to infer the peculiar signatures of a pre-equality magnetic field.
+Using the extrapolated best fit to the three year WMAP data the increase and
+distortions of the first seven peaks in the TT autocorrelations are monitored
+for different values of the regularized magnetic field intensity and for the
+physical range of spectral indices. Similar analyses are also conducted for the
+first few anticorrelation (and corrrelation) peaks of the TE power spectra.
+Possible interesting degeneracies and stimulating perspectives are pointed out
+and explored.",0712.3483v1
+2008-04-01,Magnetic Component of Quark-Gluon Plasma is also a Liquid!,"The so called magnetic scenario recently suggested in \cite{Liao_ES_mono}
+emphasizes the role of monopoles in strongly coupled quark-gluon plasma (sQGP)
+near/above the deconfinement temperature, and specifically predicts that they
+help reduce its viscosity by the so called ""magnetic bottle"" effect. Arguments
+for ""magnetic liquid"" in 1-2$T_c$ based on lattice measurement of monopole
+density were provided in \cite{Chernodub}. Here we present results for
+monopole-(anti)monopole correlation functions from the same classical molecular
+dynamics simulations, which are found to be in very good agreement with recent
+lattice results \cite{D'Alessandro:2007su}. We show that the magnetic Coulomb
+coupling does run in the direction $opposite$ to the electric one, as expected,
+and it is roughly inverse of the asymptotic freedom formula for the electric
+one. However, as $T$ decreases to $T_c$, the magnetic coupling never gets weak,
+with the plasma parameter always large enough ($\Gamma>1$). This nicely agrees
+with empirical evidences from RHIC experiments, implying that magnetic objects
+cannot have large mean free path and should also form a good liquid with low
+viscosity.",0804.0255v4
+2009-03-02,"Ferromagnetic properties of p-(Cd,Mn)Te quantum wells: Interpretation of magneto-optical measurements by Monte Carlo simulations","In order to single out dominant phenomena that account for carrier-controlled
+magnetism in p-(Cd,Mn)Te quantum wells we have carried out magneto-optical
+measurements and Monte Carlo simulations of time dependent magnetization. The
+experimental results show that magnetization relaxation is faster than 20 ns in
+the paramagnetic state. Decreasing temperature below the Curie temperature Tc
+results in an increase of the relaxation time but to less than 10 micro
+seconds. This fast relaxation may explain why the spontaneous spin splitting of
+electronic states is not accompanied by the presence of non-zero macroscopic
+magnetization below Tc. Our Monte Carlo results reproduce the relative change
+of the relaxation time on decreasing temperature. At the same time, the
+numerical calculations demonstrate that antiferromagnetic spin-spin
+interactions, which compete with the hole-mediated long-range ferromagnetic
+coupling, play an important role in magnetization relaxation of the system. We
+find, in particular, that magnetization dynamics is largely accelerated by the
+presence of antiferromagnetic couplings to the Mn spins located outside the
+region, where the holes reside. This suggests that macroscopic spontaneous
+magnetization should be observable if the thickness of the layer containing
+localized spins will be smaller than the extension of the hole wave function.
+Furthermore, we study how a spin-independent part of the Mn potential affects
+Tc. Our findings show that the alloy disorder potential tends to reduce Tc, the
+effect being particularly strong for the attractive potential that leads to
+hole localization.",0903.0406v1
+2009-05-04,Magnetic field structure due to the global velocity field in spiral galaxies,"We present a set of global, self-consistent N-body/SPH simulations of the
+dynamic evolution of galactic discs with gas and including magnetic fields. We
+have implemented a description to follow the evolution of magnetic fields with
+the ideal induction equation in the SPH part of the Vine code. Results from a
+direct implementation of the field equations are compared to a representation
+by Euler potentials, which pose a div(B)-free description, an constraint not
+fulfilled for the direct implementation. All simulations are compared to an
+implementation of magnetic fields in the Gadget code which includes also
+cleaning methods for div(B).
+  Starting with a homogeneous seed field we find that by differential rotation
+and spiral structure formation of the disc the field is amplified by one order
+of magnitude within five rotation periods of the disc. The amplification is
+stronger for higher numerical resolution. Moreover, we find a tight connection
+of the magnetic field structure to the density pattern of the galaxy in our
+simulations, with the magnetic field lines being aligned with the developing
+spiral pattern of the gas. Our simulations clearly show the importance of
+non-axisymmetry for the evolution of the magnetic field.",0905.0351v1
+2009-07-12,Magnetic field evolution in simulations with Euler potentials,"Using two- and three-dimensional hydromagnetic simulations for a range of
+different flows, including laminar and turbulent ones, it is shown that
+solutions expressing the field in terms of Euler potentials (EP) are in general
+incorrect if the EP are evolved with an artificial diffusion term. In three
+dimensions, standard methods using the magnetic vector potential are found to
+permit dynamo action when the EP give decaying solutions. With an imposed
+field, the EP method yields excessive power at small scales. This effect is
+more exaggerated in the dynamic case, suggesting an unrealistically reduced
+feedback from the Lorentz force. The EP approach agrees with standard methods
+only at early times when magnetic diffusivity did not have time to act. It is
+demonstrated that the usage of EP with even a small artificial magnetic
+diffusivity does not converge to a proper solution of hydromagnetic turbulence.
+The source of this disagreement is not connected with magnetic helicity or the
+three-dimensionality of the magnetic field, but is simply due to the fact that
+the nonlinear representation of the magnetic field in terms of EP that depend
+on the same coordinates is incompatible with the linear diffusion operator in
+the induction equation.",0907.1906v2
+2009-07-22,Quantized spin wave modes in magnetic tunnel junction nanopillars,"We present an experimental and theoretical study of the magnetic field
+dependence of the mode frequency of thermally excited spin waves in rectangular
+shaped nanopillars of lateral sizes 60x100, 75x150, and 105x190 nm2, patterned
+from MgO-based magnetic tunnel junctions. The spin wave frequencies were
+measured using spectrally resolved electrical noise measurements. In all
+spectra, several independent quantized spin wave modes have been observed and
+could be identified as eigenexcitations of the free layer and of the synthetic
+antiferromagnet of the junction. Using a theoretical approach based on the
+diagonalization of the dynamical matrix of a system of three coupled, spatially
+confined magnetic layers, we have modeled the spectra for the smallest pillar
+and have extracted its material parameters. The magnetization and exchange
+stiffness constant of the CoFeB free layer are thereby found to be
+substantially reduced compared to the corresponding thin film values. Moreover,
+we could infer that the pinning of the magnetization at the lateral boundaries
+must be weak. Finally, the interlayer dipolar coupling between the free layer
+and the synthetic antiferromagnet causes mode anticrossings with gap openings
+up to 2 GHz. At low fields and in the larger pillars, there is clear evidence
+for strong non-uniformities of the layer magnetizations. In particular, at zero
+field the lowest mode is not the fundamental mode, but a mode most likely
+localized near the layer edges.",0907.3792v2
+2009-07-27,Observations of The Magnetic Reconnection Signature of An M2 Flare on 2000 March 23,"Multi-wavelength observations of an M 2.0 flare event on 2000 March 23 in
+NOAA active region 8910 provide us a good chance to study the detailed
+structure and dynamics of the magnetic reconnection region. In the process of
+the flare, extreme ultraviolet (EUV) loops displayed two times of sideward
+motions upon a loop-top hard X-ray source with average velocities of 75 and
+25.6 km/s, respectively. We consider these two motions to be the observational
+evidence of reconnection inflow, and find an X-shaped structure upon the
+post-flare loops during the period of the second motion. Two separations of the
+flare ribbons are associated with these two sideward motions, with average
+velocities of 3.3 and 1.3 km/s, separately. Using the observation of
+photospheric magnetic field, the velocities of the sideward motions and the
+separations, we deduce the corresponding coronal magnetic field strength to be
+about 13.2-15.2 G, and estimate the reconnection rates to be 0.05 and 0.02 for
+these two magnetic reconnection processes, respectively. We also observe
+motions of bright points upward and downward along the EUV loops with
+velocities ranging from 45.4 to 556.7 km/s. A cloud of bright material flowing
+outward from the loop-top hard X-ray source with an average velocity of 51 km/s
+in the process of the flare may be accelerated by the tension force of the
+newly reconnected magnetic field lines. All the observations can be explained
+by schematic diagrams of magnetic reconnection.",0907.4541v1
+2009-08-17,Parameters of the Magnetic Flux inside Coronal Holes,"Parameters of magnetic flux distribution inside low-latitude coronal holes
+(CHs) were analyzed. A statistical study of 44 CHs based on Solar and
+Heliospheric Observatory (SOHO)/MDI full disk magnetograms and SOHO/EIT 284\AA
+images showed that the density of the net magnetic flux, $B_{{\rm net}}$, does
+not correlate with the associated solar wind speeds, $V_x$. Both the area and
+net flux of CHs correlate with the solar wind speed and the corresponding
+spatial Pearson correlation coefficients are 0.75 and 0.71, respectively. A
+possible explanation for the low correlation between $B_{{\rm net}}$ and $V_x$
+is proposed. The observed non-correlation might be rooted in the structural
+complexity of the magnetic field. As a measure of complexity of the magnetic
+field, the filling factor, $ f(r)$, was calculated as a function of spatial
+scales. In CHs, $f(r)$ was found to be nearly constant at scales above 2 Mm,
+which indicates a monofractal structural organization and smooth temporal
+evolution. The magnitude of the filling factor is 0.04 from the Hinode SOT/SP
+data and 0.07 from the MDI/HR data. The Hinode data show that at scales smaller
+than 2 Mm, the filling factor decreases rapidly, which means a mutlifractal
+structure and highly intermittent, burst-like energy release regime. The
+absence of necessary complexity in CH magnetic fields at scales above 2 Mm
+seems to be the most plausible reason why the net magnetic flux density does
+not seem to be related to the solar wind speed: the energy release dynamics,
+needed for solar wind acceleration, appears to occur at small scales below 1
+Mm.",0908.2460v1
+2009-12-28,Universality between current- and field-driven domain wall dynamics in ferromagnetic nanowires,"Spin-polarized electric current exerts torque on local magnetic spins,
+resulting in magnetic domain-wall (DW) motion in ferromagnetic nanowires. Such
+current-driven DW motion opens great opportunities toward next-generation
+magnetic devices controlled by current instead of magnetic field. However, the
+nature of the current-driven DW motion--considered qualitatively different from
+magnetic-field-driven DW motion--remains yet unclear mainly due to the
+painfully high operation current densities J_OP, which introduce uncontrollable
+experimental artefacts with serious Joule heating. It is also crucial to reduce
+J_OP for practical device operation. By use of metallic Pt/Co/Pt nanowires with
+perpendicular magnetic anisotropy, here we demonstrate DW motion at current
+densities down to the range of 10^9 A/m^2--two orders smaller than existing
+reports. Surprisingly the current-driven motion exhibits a scaling behaviour
+identical to the field-driven motion and thus, belongs to the same universality
+class despite their qualitative differences. Moreover all DW motions driven by
+either current or field (or by both) collapse onto a single curve, signalling
+the unification of the two driving mechanisms. The unified law manifests
+non-vanishing current efficiency at low current densities down to the practical
+level, applicable to emerging magnetic nanodevices.",0912.5127v2
+2010-03-12,Turbulent magnetic reconnection in 2D and 3D,"Magnetic field embedded in a perfectly conducting fluid preserves its
+topology for all time. Although ionized astrophysical objects, like stars and
+galactic disks, are almost perfectly conducting, they show indications of
+changes in topology, `magnetic reconnection', on dynamical time scales.
+Reconnection can be observed directly in the solar corona, but can also be
+inferred from the existence of large scale dynamo activity inside stellar
+interiors. Solar flares and gamma ray busts are usually associated with
+magnetic reconnection. Previous work has concentrated on showing how
+reconnection can be rapid in plasmas with very small collision rates. Here we
+present numerical evidence, based on three dimensional simulations, that
+reconnection in a turbulent fluid occurs at a speed comparable to the rms
+velocity of the turbulence, regardless of the value of the resistivity. In
+particular, this is true for turbulent pressures much weaker than the magnetic
+field pressure so that the magnetic field lines are only slightly bent by the
+turbulence. These results are consistent with the proposal by Lazarian and
+Vishniac (1999) that reconnection is controlled by the stochastic diffusion of
+magnetic field lines, which produces a broad outflow of plasma from the
+reconnection zone. This work implies that reconnection in a turbulent fluid
+typically takes place in approximately a single eddy turnover time, with broad
+implications for dynamo activity and particle acceleration throughout the
+universe. In contrast, the reconnection in 2D configurations in the presence of
+turbulence depends on resistivity, i.e. is slow.",1003.2656v1
+2010-04-16,Gravitational Wave Signatures of Magnetohydrodynamically-Driven Core-Collapse Supernova Explosions,"By performing a series of two-dimensional, special relativistic
+magnetohydrodynamic (MHD) simulations, we study signatures of gravitational
+waves (GWs) in the magnetohydrodynamically-driven core-collapse supernovae. In
+order to extract the gravitational waveforms, we present a stress formula
+including contributions both from magnetic fields and special relativistic
+corrections. By changing the precollapse magnetic fields and initial angular
+momentum distributions parametrically, we compute twelve models. As for the
+microphysics, a realistic equation of state is employed and the neutrino
+cooling is taken into account via a multiflavor neutrino leakage scheme.
+  With these computations, we find that the total GW amplitudes show a
+monotonic increase after bounce for models with a strong precollapse magnetic
+field ($10^{12}$G) also with a rapid rotation imposed.
+  We show that this trend stems both from the kinetic contribution of MHD
+outflows with large radial velocities and also from the magnetic contribution
+dominated by the toroidal magnetic fields that predominantly trigger MHD
+explosions. For models with weaker initial magnetic fields, the total GW
+amplitudes after bounce stay almost zero, because the contribution from the
+magnetic fields cancels with the one from the hydrodynamic counterpart.
+  These features can be clearly understood with a careful analysis on the
+explosion dynamics. We point out that the GW signals with the increasing trend,
+possibly visible to the next-generation detectors for a Galactic supernova,
+would be associated with MHD explosions with the explosion energies exceeding
+$10^{51}$ erg.",1004.2896v2
+2010-08-24,Protostellar collapse of magneto-turbulent cloud cores: shape during collapse and outflow formation,"We investigate protostellar collapse of molecular cloud cores by numerical
+simulations, taking into account turbulence and magnetic fields. By using the
+adaptive mesh refinement technique, the collapse is followed over a wide
+dynamic range from the scale of a turbulent cloud core to that of the first
+core. The cloud core is lumpy in the low density region owing to the
+turbulence, while it has a smooth density distribution in the dense region
+produced by the collapse. The shape of the dense region depends mainly on the
+mass of the cloud core; a massive cloud core tends to be prolate while a less
+massive cloud core tends to be oblate. In both cases, anisotropy of the dense
+region increases during the isothermal collapse. The minor axis of the dense
+region is always oriented parallel to the local magnetic field. All the models
+eventually yield spherical first cores supported mainly by the thermal
+pressure. Most of turbulent cloud cores exhibit protostellar outflows around
+the first cores. These outflows are classified into two types, bipolar and
+spiral flows, according to the morphology of the associated magnetic field.
+Bipolar flow often appears in the less massive cloud core. The rotation axis of
+the first core is oriented parallel to the local magnetic field for bipolar
+flow, while the orientation of the rotation axis from the global magnetic field
+depends on the magnetic field strength. In spiral flow, the rotation axis is
+not aligned with the local magnetic field.",1008.3984v2
+2010-09-23,Magnetic loops in the quiet Sun,"We investigate the fine structure of magnetic fields in the atmosphere of the
+quiet Sun. We use photospheric magnetic field measurements from {\sc
+Sunrise}/IMaX with unprecedented spatial resolution to extrapolate the
+photospheric magnetic field into higher layers of the solar atmosphere with the
+help of potential and force-free extrapolation techniques. We find that most
+magnetic loops which reach into the chromosphere or higher have one foot point
+in relatively strong magnetic field regions in the photosphere. $91%$ of the
+magnetic energy in the mid chromosphere (at a height of 1 Mm) is in field
+lines, whose stronger foot point has a strength of more than 300 G, i.e. above
+the equipartition field strength with convection. The loops reaching into the
+chromosphere and corona are also found to be asymmetric in the sense that the
+weaker foot point has a strength $B < 300$ G and is located in the
+internetwork. Such loops are expected to be strongly dynamic and have short
+lifetimes, as dictated by the properties of the internetwork fields.",1009.4715v1
+2011-01-01,Signature effects of spin clustering and distribution of spin couplings on magnetization behaviour in Ni-Fe-Mo and Ni-Fe-W alloys,"The spontaneous magnetization as a function of temperature is investigated
+for a number of disordered Ni-Fe-Mo and Ni-Fe-W alloys using superconducting
+quantum interference device magnetometry, with a focus on the low-T behavior as
+well as the critical exponents associated with the magnetic phase transition.
+While the low-T magnetization is found to be well described by Bloch's T^{3/2}
+law, an extraordinary enhancement of the spin-wave parameter B and the reduced
+coefficient B_{3/2}=BT_C ^{3/2} are observed with increasing Fe dilution as
+compared to conventional 3d ferromagnets, whereas the critical amplitudes are
+found to decrease systematically. Recent locally self-consistent calculations
+of finite-temperature spin dynamics in a generic diluted magnet provide an
+understanding in terms of two distinct energy scales associated with weakly
+coupled bulk spins in the FM matrix and strongly coupled cluster spins. In view
+of similar behaviour observed in diluted magnetic semiconductors and other
+ferromagnetic alloys, it is proposed that these distinctive features
+corresponding to the three important temperature regimes provide macroscopic
+indicators of signature effects of spin clustering on magnetization behaviour
+in disordered ferromagnets.",1101.0343v2
+2011-08-23,Buoyant Magnetic Loops in a Global Dynamo Simulation of a Young Sun,"The current dynamo paradigm for the Sun and sun-like stars places the
+generation site for strong toroidal magnetic structures deep in the solar
+interior. Sunspots and star-spots on sun-like stars are believed to arise when
+sections of these magnetic structures become buoyantly unstable and rise from
+the deep interior to the photosphere. Here we present the first 3-D global
+magnetohydrodynamic (MHD) simulation in which turbulent convection,
+stratification, and rotation combine to yield a dynamo that self-consistently
+generates buoyant magnetic loops. We simulate stellar convection and dynamo
+action in a spherical shell with solar stratification, but rotating three times
+faster than the current solar rate. Strong wreaths of toroidal magnetic field
+are realized by dynamo action in the convection zone. By turning to a dynamic
+Smagorinsky model for subgrid-scale turbulence, we here attain considerably
+reduced diffusion in our simulation. This permits the regions of strongest
+magnetic field in these wreaths to rise toward the top of the convection zone
+via a combination of magnetic buoyancy instabilities and advection by
+convective giant cells. Such a global simulation yielding buoyant loops
+represents a significant step forward in combining numerical models of dynamo
+action and flux emergence.",1108.4697v1
+2012-07-31,Circular Ribbon Flares and Homologous Jets,"Solar flare emissions in the chromosphere often appear as elongated ribbons
+on both sides of the magnetic polarity inversion line (PIL), which has been
+regarded as evidence of a typical configuration of magnetic reconnection.
+However, flares having a circular ribbon have rarely been reported, although it
+is expected in the fan--spine magnetic topology involving reconnection at a
+three-dimensional (3D) coronal null point. We present five circular ribbon
+flares with associated surges, using high-resolution and high-cadence halpha
+blue wing observations obtained from the recently digitized films of Big Bear
+Solar Observatory. In all the events, a central parasitic magnetic field is
+encompassed by the opposite polarity, forming a circular PIL traced by filament
+material. Consequently, a flare kernel at the center is surrounded by a
+circular flare ribbon. The four homologous jet-related flares on 1991 March 17
+and 18 are of particular interest, as (1) the circular ribbons brighten
+sequentially, with co-spatial surges, rather than simultaneously, (2) the
+central flare kernels show an intriguing ""round-trip"" motion and become
+elongated, and (3) remote brightenings occur at a region with the same magnetic
+polarity as the central parasitic field and are co-temporal with a separate
+phase of flare emissions. In another flare on 1991 February 25, the circular
+flare emission and surge activity occur successively, and the event could be
+associated with magnetic flux cancellation across the circular PIL. We discuss
+the implications of these observations combining circular flare ribbons,
+homologous jets, and remote brightenings for understanding the dynamics of 3D
+magnetic restructuring.",1207.7345v2
+2012-08-10,Ion energy distribution functions behind the sheaths of magnetized and non magnetized radio frequency discharges,"The effect of a magnetic field on the characteristics of capacitively coupled
+radio frequency discharges is investigated and found to be substantial. A
+one-dimensional particle-in-cell simulation shows that geometrically symmetric
+discharges can be asymmetrized by applying a spatially inhomogeneous magnetic
+field. This effect is similar to the recently discovered electrical asymmetry
+effect. Both effects act independently, they can work in the same direction or
+compensate each other. Also the ion energy distribution functions at the
+electrodes are strongly affected by the magnetic field, although only
+indirectly. The field influences not the dynamics of the sheath itself but
+rather its operating conditions, i.e., the ion flux through it and voltage drop
+across it. To support this interpretation, the particle-in-cell results are
+compared with the outcome of the recently proposed ensemble-in-spacetime
+algorithm. Although that scheme resolves only the sheath and neglects
+magnetization, it is able to reproduce the ion energy distribution functions
+with very good accuracy, regardless of whether the discharge is magnetized or
+not.",1208.2248v2
+2012-08-16,Multiple views of magnetism in cool stars,"Magnetic fields are regarded as a crucial element for our understanding of
+stellar physics. They can be studied with a variety of methods which provide
+complementary - and sometimes contradictory - information about the structure,
+strength and dynamics of the magnetic field and its role in the evolution of
+stars. Stellar magnetic fields can be investigated either with direct methods
+based on the Zeeman effect or through the observation of activity phenomena
+resulting from the interaction of the field with the stellar atmosphere. In
+this Cool Stars XVII Splinter Session we discussed the results obtained by the
+many ongoing studies of stellar activity and direct studies of surface magnetic
+fields, as well as the state- of-the-art techniques on which they are based. We
+show the strengths and limitations of the various approaches currently used and
+to point out their evolution as well as the interest of coupling various
+magnetism and activity proxies.",1208.3338v1
+2012-10-29,Small-Scale Dynamo Action in Primordial Halos,"The first galaxies form due to gravitational collapse of primordial halos.
+During this collapse, weak magnetic seed fields get amplified exponentially by
+the small-scale dynamo - a process converting kinetic energy from turbulence
+into magnetic energy. We use the Kazantsev theory, which describes the
+small-scale dynamo analytically, to study magnetic field amplification for
+different turbulent velocity correlation functions. For incompressible
+turbulence (Kolmogorov turbulence), we find that the growth rate is
+proportional to the square root of the hydrodynamic Reynolds number, Re^(1/2).
+In the case of highly compressible turbulence (Burgers turbulence) the growth
+rate increases proportional to Re^(1/3). With a detailed chemical network we
+are able to follow the chemical evolution and determine the kinetic and
+magnetic viscosities (due to Ohmic and ambipolar diffusion) during the collapse
+of the halo. This way, we can calculate the growth rate of the small-scale
+dynamo quantitatively and predict the evolution of the small-scale magnetic
+field. As the magnetic energy is transported to larger scales on the local
+eddy-timescale, we obtain an estimate for the magnetic field on the Jeans
+scale. Even there, we find that equipartition with the kinetic energy is
+reached on small timescales. Dynamically relevant field structures can thus be
+expected already during the formation of the first objects in the Universe.",1210.7751v1
+2012-11-30,Global Dynamics of Subsurface Solar Active Regions,"We present three-dimensional numerical simulations of a magnetic loop
+evolving in either a convectively stable or unstable rotating shell. The
+magnetic loop is introduced in the shell in such a way that it is buoyant only
+in a certain portion in longitude, thus creating an \Omega-loop. Due to the
+action of magnetic buoyancy, the loop rises and develops asymmetries between
+its leading and following legs, creating emerging bipolar regions whose
+characteristics are similar to the ones of observed spots at the solar surface.
+In particular, we self-consistently reproduce the creation of tongues around
+the spot polarities, which can be strongly affected by convection. We moreover
+emphasize the presence of ring-shaped magnetic structures around our simulated
+emerging regions, which we call ""magnetic necklace"" and which were seen in a
+number of observations without being reported as of today. We show that those
+necklaces are markers of vorticity generation at the periphery and below the
+rising magnetic loop. We also find that the asymmetry between the two legs of
+the loop is crucially dependent on the initial magnetic field strength. The
+tilt angle of the emerging regions is also studied in the stable and unstable
+cases and seems to be affected both by the convective motions and the presence
+of a differential rotation in the convective cases.",1211.7251v1
+2013-01-26,Role of uniform horizontal magnetic field on convective flow,"The effect of uniform magnetic field applied along a fixed horizontal
+direction in Rayleigh-B\'enard convection in low-Prandtl-number fluids has been
+studied using a low dimensional model. The model shows the onset of convection
+(primary instability) in the form of two dimensional stationary rolls in the
+absence of magnetic field, when the Rayleigh number $R$ is raised above a
+critical value $R_c$. The flow becomes three dimensional at slightly higher
+values of Rayleigh number via wavy instability. These wavy rolls become chaotic
+for slightly higher values of $R$ in low-Prandtl-number ($P_r$) fluids. A
+uniform magnetic field along horizontal plane strongly affects all kinds of
+convective flows observed at higher values of $R$ in its absence. As the
+magnetic field is raised above certain value, it orients the convective rolls
+in its own direction. Although the horizontal magnetic field does not change
+the threshold for the primary instability, it affects the threshold for
+secondary (wavy) instability. It inhibits the onset of wavy instability. The
+critical Rayleigh number $R_o (Q,P_r)$ at the onset of wavy instability, which
+depends on Chandrasekhar's number $Q$ and $P_r$, increases monotonically with
+$Q$ for a fixed value of $P_r$. The dimensionless number $R_o (Q, P_r)/(R_c Q
+P_r)$ scales with $Q$ as $Q^{-1}$. A stronger magnetic field suppresses chaos
+and makes the flow two dimensional with roll pattern aligned along its
+direction.",1301.6220v1
+2013-02-26,Resonant state selection in synthetic ferrimagnets,"Resonant activation of a synthetic antiferromagnet (SAF) is known to result
+in a dynamic running state, where the SAF's symmetric spin-flop pair
+continuously rotates between the two antiparallel ground states of the system,
+with the two magnetic moments in-phase in the so-called acoustical
+spin-resonance mode. The symmetry of an ideal SAF does not allow, however, to
+deterministically select a particular ground state using a resonant excitation.
+In this work, we study asymmetric SAF's, or synthetic ferrimagnets (SFi), in
+which the two magnetic particles are different in thickness or are biased
+asymmetrically with an external field. We show how the magnetic phase space of
+the system can be reversibly tuned, post-fabrication, between the antiferro-
+and ferri-magnetic behavior by exploiting these two asymmetry parameters and
+applying a uniform external field. We observe a splitting of the optical
+spin-resonance for the two ground states of the SFi system, with a frequency
+spacing that can be controlled by a quasistatic uniform external field. We
+demonstrate how the tunable magnetic asymmetry in SFi allows to
+deterministically select a particular ground state using the splitting of the
+optical spin-resonance. These results offer a new way of controlling the
+magnetic state of a spin-flop bilayer, currently used in such large scale
+applications as magnetic memory.",1302.6483v2
+2013-04-29,Magnetic Structure Producing X- and M-Class Solar Flares in Solar Active Region 11158,"We study the three-dimensional magnetic structure of solar active region
+11158, which produced one X-class and several M-class flares on 2011 February
+13$-$16. We focus on the magnetic twist in four flare events, M6.6, X2.2, M1.0,
+and M1.1. The magnetic twist is estimated from the nonlinear force-free field
+extrapolated from the vector fields obtained from the Helioseismic and Magnetic
+Imager on board the Solar Dynamic Observatory using magnetohydrodynamic
+relaxation method developed by \cite{2011ApJ...738..161I}. We found that
+strongly twisted lines ranging from half-turn to one-turn twist were built up
+just before the M6.6- and X2.2 flares and disappeared after that. Because most
+of the twist remaining after these flares was less than half-turn twist, this
+result suggests that the buildup of magnetic twist over the half-turn twist is
+a key process in the production of large flares. On the other hand, even though
+these strong twists were also built up just before the M1.0 and M1.1 flares,
+most of them remained afterwords. Careful topological analysis before the M1.0
+and M1.1 flares shows that the strongly twisted lines were surrounded mostly by
+the weakly twisted lines formed in accordance with the clockwise motion of the
+positive sunspot, whose footpoints are rooted in strong magnetic flux regions.
+These results imply that these weakly twisted lines might suppress the activity
+of the strongly twisted lines in the last two M-class flares.",1304.8073v1
+2013-05-22,"Measuring the Magnetic Field Strength of the Quiet Solar Corona Using ""EIT Waves""","Variations in the propagation of globally-propagating disturbances (commonly
+called ""EIT waves"") through the low solar corona offer a unique opportunity to
+probe the plasma parameters of the solar atmosphere. Here, high-cadence
+observations of two ""EIT wave"" events taken using the Atmospheric Imaging
+Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO) are
+combined with spectroscopic measurements from the Extreme ultraviolet Imaging
+Spectrometer (EIS) onboard the Hinode spacecraft and used to examine the
+variability of the quiet coronal magnetic-field strength. The combination of
+pulse kinematics from SDO/AIA and plasma density from Hinode/EIS is used to
+show that the magnetic-field strength is in the range ~2-6 G in the quiet
+corona. The magnetic-field estimates are then used to determine the height of
+the pulse, allowing a direct comparison with theoretical values obtained from
+magnetic-field measurements from the Helioseismic and Magnetic Imager (HMI)
+onboard SDO using PFSS and local-domain extrapolations. While local-scale
+extrapolations predict heights inconsistent with prior measurements, the
+agreement between observations and the PFSS model indicates that ""EIT waves""
+are a global phenomenon influenced by global-scale magnetic field.",1305.5169v1
+2013-05-28,"DR 21(OH): a highly fragmented, magnetized, turbulent dense core","We present high-angular-resolution observations of the massive star forming
+core DR21(OH) at 880 mum using the Submillimeter Array (SMA). The dense core
+exhibits an overall velocity gradient in a Keplerian-like pattern, which breaks
+at the center of the core where SMA 6 and SMA 7 are located. The dust
+polarization shows a complex magnetic field, compatible with a toroidal
+configuration. This is in contrast with the large, parsec-scale filament that
+surrounds the core, where there is a smooth magnetic field. The total magnetic
+field strengths in the filament and in the core are 0.9 and 2.1 mG,
+respectively. We found evidence of magnetic field diffusion at the core scales,
+far beyond the expected value for ambipolar diffusion. It is possible that the
+diffusion arises from fast magnetic reconnection in the presence of turbulence.
+The dynamics of the DR 21(OH) core appear to be controlled energetically in
+equal parts by the magnetic field, magneto-hydrodynamic (MHD) turbulence and
+the angular momentum. The effect of the angular momentum (this is a fast
+rotating core) is probably causing the observed toroidal field configuration.
+Yet, gravitation overwhelms all the forces, making this a clear supercritical
+core with a mass-to-flux ratio of ~6 times the critical value. However,
+simulations show that this is not enough for the high level of fragmentation
+observed at 1000 AU scales. Thus, rotation and outflow feedback is probably the
+main cause of the observed fragmentation.",1305.6509v2
+2013-08-05,Axisymmetry vs. nonaxisymmetry of a Taylor-Couette flow with azimuthal magnetic fields,"The instability of a supercritical Taylor-Couette flow of a conducting fluid
+with resting outer cylinder under the influence of a uniform axial electric
+current is investigated for magnetic Prandtl number Pm=1. In the linear theory
+the critical Reynolds number for axisymmetric perturbations is not influenced
+by the current-induced axisymmetric magnetic field but all axisymmetric
+magnetic perturbations decay. The nonaxisymmetric perturbations with m=1 are
+excited even without rotation for large enough Hartmann numbers (""Tayler
+instability""). For slow rotation their growth rates scale with the Alfv\'en
+frequency of the magnetic field but for fast rotation they scale with the
+rotation rate of the inner cylinder. In the nonlinear regime the ratio of the
+energy of the magnetic m=1 modes and the toroidal background field is very low
+for the non-rotating Tayler instability but it strongly grows if differential
+rotation is present. For super-Alfv\'enic rotation the energies in the m=1
+modes of flow and field do not depend on the molecular viscosity, they are
+almost in equipartition and contain only 1.5% of the centrifugal energy of the
+inner cylinder. The geometry of the excited magnetic field pattern is strictly
+nonaxisymmetric for slow rotation but it is of the mixed-mode type for fast
+rotation -- contrary to the situation which has been observed at the surface of
+Ap stars.",1308.1026v2
+2014-02-11,Chaotic motion of charged particles in toroidal magnetic configurations,"We study the motion of a charged particle in a tokamak magnetic field and
+discuss its chaotic nature. Contrary to most of recent studies, we do not make
+any assumption on any constant of the motion and solve numerically the
+cyclotron gyration using Hamiltonian formalism. We take advantage of a
+symplectic integrator allowing us to make long-time simulations. First
+considering an idealized magnetic configuration, we add a non generic
+perturbation corresponding to a magnetic ripple, breaking one of the invariant
+of the motion. Chaotic motion is then observed and opens questions about the
+link between chaos of magnetic field lines and chaos of particle trajectories.
+Second, we return to a axi-symmetric configuration and tune the safety factor
+(magnetic configuration) in order to recover chaotic motion. In this last
+setting with two constants of the motion, the presence of chaos implies that no
+third global constant exists, we highlight this fact by looking at variations
+of the first order of the magnetic moment in this chaotic setting. We are
+facing a mixed phase space with both regular and chaotic regions and point out
+the difficulties in performing a global reduction such as gyrokinetics.",1402.2625v2
+2014-03-13,Orbital Magnetism of Graphene Nanostructures: Bulk and Confinement Effects,"We consider the orbital magnetic properties of non-interacting charge
+carriers in graphene-based nanostructures in the low-energy regime. The
+magnetic response of such systems results both, frombulk contributions and from
+confinement effects that can be particularly strong in ballistic quantum dots.
+First we provide a comprehensive study of the magnetic susceptibility $\chi$ of
+bulk graphene in a magnetic field for the different regimes arising from the
+relative magnitudes of the energy scales involved, i.e. temperature, Landau
+level spacing and chemical potential. We show that for finite temperature or
+chemical potential, $\chi$ is not divergent although the diamagnetic
+contribution $\chi_{0}$ from the filled valance band exhibits the well-known
+$-B^{-1/2}$ dependence. We further derive oscillatory modulations of $\chi$,
+corresponding to de Haas-van Alphen oscillations of conventional
+two-dimensional electron gases. These oscillations can be large in graphene,
+thereby compensating the diamagnetic contribution $\chi_{0}$ and yielding a net
+paramagnetic susceptibility for certain energy and magnetic field regimes.
+Second, we predict and analyze corresponding strong, confinement-induced
+susceptibility oscillations in graphene-based quantum dots with amplitudes
+distincly exceeding the corresponding bulk susceptibility. Within a
+semiclassical approach we derive generic expressions for orbital magnetism of
+graphene quantum dots with regular classical dynamics. Graphene-specific
+features can be traced back to pseudospin interference along the underlying
+periodic orbits. We demonstrate the quality of the semiclassical approximation
+by comparison with quantum mechanical results for two exemplary mesoscopic
+systems, a graphene disk with infinite mass-type edges and a rectangular
+graphene structure with armchair and zigzag edges, using numerical
+tight-binding calculations in the latter case.",1403.3688v3
+2014-04-07,Lattice strain accompanying the colossal magnetoresistance effect in EuB$_6$,"The coupling of magnetic and electronic degrees of freedom to the crystal
+lattice in the ferromagnetic semimetal EuB$_6$, which exhibits a complex
+ferromagnetic order and a colossal magnetoresistance (CMR) effect, %, very
+likely involving magnetic polarons, is studied by high-resolution thermal
+expansion and magnetostriction experiments. EuB$_6$ may be viewed as a model
+system, where pure magnetism-tuned transport and the response of the crystal
+lattice can be studied in a comparatively simple environment,i.e., not
+influenced by strong crystal-electric field effects and Jahn-Teller
+distortions. We find a very large lattice response, quantified by (i) the
+magnetic Gr\""uneisen parameter, (ii) the spontaneous strain when entering the
+ferromagnetic region and (iii) the magnetostriction in the paramagnetic
+temperature regime. Our analysis reveals that a significant part of the lattice
+effects originates in the magnetically-driven delocalization of charge
+carriers, consistent with the scenario of percolating magnetic polarons. A
+strong effect of the formation and dynamics of local magnetic clusters on the
+lattice parameters is suggested to be a general feature of CMR materials.",1404.1693v1
+2014-04-16,Manipulation of edge magnetism in hexagonal graphene nanoflake,"We explore possible ways to manipulate the intrinsic edge magnetism in
+hexagonal graphene nanoflake with zigzag edges, using density functional theory
+supplemented with on-site Coulomb interaction. The effect of carrier doping,
+chemical modification at the edge, and finite temperature on the edge magnetism
+has been studied. The magnetic phase diagram with varied carrier doping, and
+on-site Coulomb interaction is found to be complex. In addition to the
+intrinsic antiferromag- netic solution, as predicted for charge neutral
+hexagonal nanoflake, fully polarized ferromagnetic, and mixed phase solutions
+are obtained depending on the doped carrier concentration, and on-site Coulomb
+interaction. The complexity arises due to the competing nature of local Coulomb
+in- teraction and carrier doping, favoring antiferromagnetic and ferromagnetic
+coupling, respectively. Chemical modification of the edge atoms by hydrogen
+leads to partial quenching of local moments, giving rise to a richer phase
+diagram consisting of antiferromagnetic, ferromagnetic, mixed, and nonmagnetic
+phases. We further report the influence of temperature on the long-range
+magnetic ordering at the edge using ab initio molecular dynamics. In agreement
+with the recent experimental observations, we find that temperature can also
+alter the magnetic state of neutral nanoflake, which is otherwise
+antiferromagnetic at zero temperature. These findings will have important
+implications in controlling magnetism in graphene based low dimensional
+structures for technological purpose, and in understanding varied experimental
+reports.",1404.4143v2
+2014-07-28,Microscopic electronic configurations after ultrafast magnetization dynamics,"We provide a model for the prediction of the electronic and magnetic
+configurations of ferromagnetic Fe after an ultrafast decrease or increase of
+magnetization. The model is based on the well-grounded assumption that, after
+the ultrafast magnetization change, the system achieves a partial thermal
+equilibrium. With statistical arguments it is possible to show that the
+magnetic configurations are qualitatively different in the case of reduced or
+increased magnetization. The predicted magnetic configurations are then used to
+compute the dielectric response at the 3p (M) absorption edge, which can be
+related to the changes observed in the experimental T-MOKE data. The good
+qualitative agreement between theory and experiment offers a substantial
+support to the existence of an ultrafast increase of magnetisation, which has
+been fiercely debated in the last years.",1407.7411v2
+2014-08-06,Non-Axisymmetric Flows on Hot Jupiters with Oblique Magnetic Fields,"Giant planets that reside in close proximity to their host stars are subject
+to extreme irradiation, which gives rise to thermal ionization of trace Alkali
+metals in their atmospheres. On objects where the atmospheric electrical
+conductivity is substantial, the global circulation couples to the background
+magnetic field, inducing supplementary fields and altering the nature of the
+flow. To date, a number of authors have considered the influence of a spin-pole
+aligned dipole magnetic field on the dynamical state of a weakly-ionized
+atmosphere and found that magnetic breaking may lead to significantly slower
+winds than predicted within a purely hydrodynamical framework. Here, we
+consider the effect of a tilted dipole magnetic field on the circulation and
+demonstrate that in addition to regulating wind velocities, an oblique field
+generates stationary non-axisymmetric structures that adhere to the geometry of
+the magnetic pole. Using a kinematic perturbative approach, we derive a
+closed-form solution for the perturbed circulation and show that the fractional
+distortion of zonal jets scales as the product of the field obliquity and the
+Elsasser number. The results obtained herein suggest that on planets with
+oblique magnetic fields, advective shifts of dayside hotspots may have
+substantial latitudinal components. This prediction may be tested
+observationally using the eclipse mapping technique.",1408.1386v1
+2014-10-01,Evidence for magnetic clusters in Ni$_{1-x}$V$_{x}$ close to the quantum critical concentration,"The d-metal alloy Ni$_{1-x}$V$_{x}$ undergoes a quantum phase transition from
+a ferromagnetic ground state to a paramagnetic ground state as the vanadium
+concentration $x$ is increased. We present magnetization, ac-susceptibility and
+muon-spin relaxation data at several vanadium concentrations near the critical
+concentration $x_c \approx11.6%$ at which the onset of ferromagnetic order is
+suppressed to zero temperature. Below $x_c$, the muon data reveal a broad
+magnetic field distribution indicative of long-range ordered ferromagnetic
+state with spatial disorder. We show evidence of magnetic clusters in the
+ferromagnetic phase and close to the phase boundary in this disordered
+itinerant system as an important generic ingredient of a disordered quantum
+phase transition. In contrast, the temperature dependence of the magnetic
+susceptibility above $x_c$ is best described in terms of a magnetic quantum
+Griffiths phase with a power-law distribution of fluctuation rates of dynamic
+magnetic clusters. At the lowest temperatures, the onset of a short-range
+ordered cluster-glass phase is recognized by an increase in the muon
+depolarization in transverse fields and maxima in ac-susceptibility.",1410.0094v1
+2014-12-26,"A Laboratory Experiment of Magnetic Reconnection: Outflows, Heating and Waves in Chromospheric Jets","Hinode observations have revealed intermittent recurrent plasma
+ejections/jets in the chromosphere. These are interpreted as a result of
+non-perfectly anti-parallel magnetic reconnection, i.e. component reconnection,
+between a twisted magnetic flux tube and the pre-existing coronal/chromospheric
+magnetic field, though the fundamental physics of component reconnection is
+unrevealed. In this paper, we experimentally reproduced the magnetic
+configuration and investigated the dynamics of plasma ejections, heating and
+wave generation triggered by component reconnection in the chromosphere. We set
+plasma parameters as in the chromosphere (density 10^14 cm^-3, temperature 5-10
+eV, i.e. (5-10)x10^4 K, and reconnection magnetic field 200 G) using argon
+plasma. Our experiment shows bi-directional outflows with the speed of 5 km/s
+at maximum, ion heating in the downstream area over 30 eV and magnetic
+fluctuations mainly at 5-10 us period. We succeeded in qualitatively
+reproducing chromospheric jets, but quantitatively we still have some
+differences between observations and experiments such as jet velocity, total
+energy and wave frequency. Some of them can be explained by the scale gap
+between solar and laboratory plasma, while the others probably by the
+difference of microscopy and macroscopy, collisionality and the degree of
+ionization, which have not been achieved in our experiment.",1412.7903v1
+2015-03-09,Magnetic field measurements at milliarcsecond resolution around massive young stellar objects,"Magnetic fields have only recently been included in theoretical simulations
+of high-mass star formation. The simulations show that magnetic fields can play
+a crucial role not only in the formation and dynamics of molecular outflows,
+but also in the evolution of circumstellar disks. Therefore, new measurements
+of magnetic fields at milliarcsecond resolution close to massive young stellar
+objects (YSOs) are fundamental for providing new input for numerical
+simulations and for understanding the formation process of massive stars. The
+polarized emission of 6.7 GHz CH3OH masers allows us to investigate the
+magnetic field close to the massive YSO where the outflows and disks are
+formed. Recently, we have detected with the EVN CH3OH maser polarized emission
+towards 10 massive YSOs. From a first statistical analysis we have found
+evidence that magnetic fields are primarily oriented along the molecular
+outflows. To improve our statistics we are carrying on a large observational
+EVN campaign for a total of 19 sources, the preliminary results of the first
+seven sources are presented in this contribution. Furthermore, we also describe
+our efforts to estimate the Lande' g-factors of the CH3OH maser transition to
+determine the magnetic field strength from our Zeeman-splitting measurements.",1503.02403v1
+2015-03-12,Parallelization of the SIR code for the investigation of small-scale features in the solar photosphere,"Magnetic fields are one of the most important drivers of the highly dynamic
+processes that occur in the lower solar atmosphere. They span a broad range of
+sizes, from large- and intermediate-scale structures such as sunspots, pores
+and magnetic knots, down to the smallest magnetic elements observable with
+current telescopes. On small scales, magnetic flux tubes are often visible as
+Magnetic Bright Points (MBPs). Apart from simple $V/I$ magnetograms, the most
+common method to deduce their magnetic properties is the inversion of
+spectropolarimetric data. Here we employ the SIR code for that purpose. SIR is
+a well-established tool that can derive not only the magnetic field vector and
+other atmospheric parameters (e.g., temperature, line-of-sight velocity), but
+also their stratifications with height, effectively producing 3-dimensional
+models of the lower solar atmosphere. In order to enhance the runtime
+performance and the usability of SIR we parallelized the existing code and
+standardized the input and output formats. This and other improvements make it
+feasible to invert extensive high-resolution data sets within a reasonable
+amount of computing time. An evaluation of the speedup of the parallel SIR code
+shows a substantial improvement in runtime.",1503.03710v1
+2015-03-16,Observation of the zero Hall plateau in a quantum anomalous Hall insulator,"Quantum anomalous Hall (QAH) effect in magnetic topological insulator (TI) is
+a novel transport phenomenon in which the Hall resistance reaches the quantum
+plateau in the absence of external magnetic field. Recently, this exotic effect
+has been discovered experimentally in an ultrathin film of the Bi2Te3 family TI
+with spontaneous ferromagnetic (FM) order. An important question concerning the
+QAH state is whether it is simply a zero-magnetic-field version of the quantum
+Hall (QH) effect, or if there is new physics beyond the conventional paradigm.
+Here we report experimental investigations on the quantum phase transition
+between the two opposite Hall plateaus of a QAH insulator caused by
+magnetization reversal. We observe a well-defined plateau with zero Hall
+conductivity over a range of magnetic field around coercivity, consistent with
+a recent theoretical prediction. The features of the zero Hall plateau are
+shown to be closely related to that of the QAH effect, but its temperature
+evolution exhibits quantitative differences from the network model for
+conventional QH plateau transition. We propose that the chiral edge states
+residing at the magnetic domain boundaries, which are unique to a QAH
+insulator, are responsible for the zero Hall plateau. The rich magnetic domain
+dynamics makes the QAH effect a distinctive class of quantum phenomenon that
+may find novel applications in spintronics.",1503.04569v1
+2015-06-21,Fast magnetic field amplification in the early Universe: growth of collisionless plasma instabilities in turbulent media,"In this work we report a numerical study of the cosmic magnetic field
+amplification due to collisionless plasma instabilities. The collisionless
+magnetohydrodynamic equations derived account for the pressure anisotropy that
+leads, in specific conditions, to the firehose and mirror instabilities. We
+study the time evolution of seed fields in turbulence under the influence of
+such instabilities. An approximate analytical time evolution of magnetic field
+is provided. The numerical simulations and the analytical predictions are
+compared. We found that i) amplification of magnetic field was efficient in
+firehose unstable turbulent regimes, but not in the mirror unstable models, ii)
+the growth rate of the magnetic energy density is much faster than the
+turbulent dynamo, iii) the efficient amplification occurs at small scales. The
+analytical prediction for the correlation between the growth timescales with
+pressure anisotropy ratio is confirmed by the numerical simulations. These
+results reinforce the idea that pressure anisotropies - driven naturally in a
+turbulent collisionless medium, e.g. the intergalactic medium -, could
+efficiently amplify the magnetic field in the early Universe
+(post-recombination era), previous to the collapse of the first large-scale
+gravitational structures. This mechanism, though fast for the small scale
+fields ($\sim$kpc scales), is however unable to provide relatively strong
+magnetic fields at large scales. Other mechanisms that were not accounted here
+(e.g., collisional turbulence once instabilities are quenched, velocity shear,
+or gravitationally induced inflows of gas into galaxies and clusters) could
+operate afterwards to build up large scale coherent field structures in the
+long time evolution.",1506.06398v1
+2015-08-28,Control of magnetic relaxation by electric-field-induced ferroelectric phase transition and inhomogeneous domain switching,"Electric-field modulation of magnetism in strain-mediated multiferroic
+heterostructures is considered a promising scheme for enabling memory and
+magnetic microwave devices with ultralow power consumption. However, it is not
+well understood how electric-field-induced strain influences magnetic
+relaxation, an important physical process for device applications. Here we
+investigate resonant magnetization dynamics in ferromagnet/ferrolectric
+multiferroic heterostructures, FeGaB/PMN-PT and NiFe/PMN-PT, in two distinct
+strain states provided by electric-field-induced ferroelectric phase
+transition. The strain not only modifies magnetic anisotropy but also magnetic
+relaxation. In FeGaB/PMN-PT, we observe a nearly two-fold change in intrinsic
+Gilbert damping by electric field, which is attributed to strain-induced tuning
+of spin-orbit coupling. By contrast, a small but measurable change in extrinsic
+linewidth broadening is attributed to inhomogeneous ferroelastic domain
+switching during the phase transition of the PMN-PT substrate.",1508.07290v2
+2015-10-13,Critical decay index at the onset of solar eruptions,"Magnetic flux ropes are topological structures consisting of twisted magnetic
+field lines that globally wrap around an axis. The torus instability model
+predicts that a magnetic flux rope of major radius $R$ undergoes an eruption
+when its axis reaches a location where the decay index $-d(\ln B_{ex})/d(\ln
+R)$ of the ambient magnetic field $B_{ex}$ is larger than a critical value. In
+the current-wire model, the critical value depends on the thickness and
+time-evolution of the current channel. We use magneto-hydrodynamic (MHD)
+simulations to investigate if the critical value of the decay index at the
+onset of the eruption is affected by the magnetic flux rope's internal current
+profile and/or by the particular pre-eruptive photospheric dynamics. The
+evolution of an asymmetric, bipolar active region is driven by applying
+different classes of photospheric motions. We find that the critical value of
+the decay index at the onset of the eruption is not significantly affected by
+either the pre-eruptive photospheric evolution of the active region or by the
+resulting different magnetic flux ropes. As in the case of the current-wire
+model, we find that there is a `critical range' $ [1.3-1.5]$, rather than a
+`critical value' for the onset of the torus instability. This range is in good
+agreement with the predictions of the current-wire model, despite the inclusion
+of line-tying effects and the occurrence of tether-cutting magnetic
+reconnection.",1510.03713v1
+2015-10-19,Filament formation in wind-cloud interactions. I. Spherical clouds in uniform magnetic fields,"Filamentary structures are ubiquitous in the interstellar medium, yet their
+formation, internal structure, and longevity have not been studied in detail.
+We report the results from a comprehensive numerical study that investigates
+the characteristics, formation, and evolution of filaments arising from
+magnetohydrodynamic interactions between supersonic winds and dense clouds.
+Here we improve on previous simulations by utilising sharper density contrasts
+and higher numerical resolutions. By following multiple density tracers, we
+find that material in the envelopes of the clouds is removed and deposited
+downstream to form filamentary tails, while the cores of the clouds serve as
+footpoints and late-stage outer layers of these tails. Aspect ratios >12,
+subsonic velocity dispersions ~0.1-0.3 of the wind sound speed, and magnetic
+field amplifications ~100 are found to be characteristic of these filaments. We
+also report the effects of different magnetic field strengths and orientations.
+The magnetic field strength regulates vorticity production: sinuous filamentary
+towers arise in non-magnetic environments, while strong magnetic fields inhibit
+small-scale perturbations at boundary layers making tails less turbulent.
+Magnetic field components aligned with the direction of the flow favour the
+formation of pressure-confined flux ropes inside the tails, whilst transverse
+components tend to form current sheets. Softening the equation of state to
+nearly isothermal leads to suppression of dynamical instabilities and further
+collimation of the tail. Towards the final stages of the evolution, we find
+that small cloudlets and distorted filaments survive the break-up of the clouds
+and become entrained in the winds, reaching velocities ~0.1 of the wind speed.",1510.05356v1
+2015-10-23,Soft spin-amplitude fluctuations in a Mott-insulating ruthenate,"Magnetism in transition-metal compounds (TMCs) has traditionally been
+associated with spin degrees of freedom, because the orbital magnetic moments
+are typically largely quenched. On the other hand, magnetic order in 4f- and
+5d-electron systems arises from spin and orbital moments that are rigidly tied
+together by the large intra-atomic spin-orbit coupling (SOC). Using inelastic
+neutron scattering on the archetypal 4d-electron Mott insulator Ca$_2$RuO$_4$,
+we report a novel form of excitonic magnetism in the intermediate-strength
+regime of the SOC. The magnetic order is characterized by ``soft'' magnetic
+moments with large amplitude fluctuations manifested by an intense, low-energy
+excitonic mode analogous to the Higgs mode in particle physics. This mode
+heralds a proximate quantum critical point separating the soft magnetic order
+driven by the superexchange interaction from a quantum-paramagnetic state
+driven by the SOC. We further show that this quantum critical point can be
+tuned by lattice distortions, and hence may be accessible in epitaxial
+thin-film structures. The unconventional spin-orbital-lattice dynamics in
+Ca$_2$RuO$_4$ identifies the SOC as a novel source of quantum criticality in
+TMCs.",1510.07011v1
+2015-11-07,Do magnetic fields enhance turbulence at low magnetic Reynolds number ?,"Imposing a magnetic field on a turbulent flow of electrically conducting
+fluid incurs the Joule effect. A current paradigm is that the corresponding
+dissipation increases with the intensity of the magnetic field, and as a result
+turbulent fluctuations are all the more damped as the magnetic field is strong.
+While this idea finds apparent support in the phenomenology of decaying
+turbulence, measurements of turbulence in duct flows and other, more complex
+configurations have produced seemingly contradicting results. The root of the
+controversy is that magnetic fields promote sufficient scale-dependent
+anisotropy to profoundly reorganise the structure of turbulence, so their net
+effect cannot be understood in terms of the additional dissipation only. Here
+we show that when turbulence is forced in a magnetic field that acts on
+turbulence itself rather than on the mechanisms that generate it, the field
+promotes large, nearly 2D structures capturing sufficient energy to offset the
+loss due to Joule dissipation, with the net effect of increasing the intensity
+of turbulent fluctuations. This change of paradigm potentially carries
+important consequences for systems as diverse as the liquid cores of planets,
+accretion disks and a wide range of metallurgical and nuclear engineering
+applications.",1511.02364v4
+2015-12-04,Observations of a Series of Flares and Associated Jet-like Eruptions Driven by the Emergence of Twisted Magnetic Fields,"We studied temporal changes of morphological and magnetic properties of a
+succession of four confined flares followed by an eruptive flare using the
+high-resolution New Solar Telescope (NST) operating at the Big Bear Solar
+Observatory (BBSO), Helioseismic and Magnetic Imager (HMI) magnetograms and
+Atmospheric Image Assembly (AIA) EUV images provided by Solar Dynamics
+Observatory (SDO). From the NST/Halpha and the SDO/AIA~304 A observations we
+found that each flare developed a jet structure that evolved in a manner
+similar to evolution of the blowout jet : 1) an inverted-Y shape jet appeared
+and drifted away from its initial position; 2) jets formed a curtain-like
+structure that consisted of many fine threads accompanied with subsequent
+brightenings near the footpoints of the fine threads; and finally 3) the jet
+showed a twisted structure visible near the flare maximum. Analysis of the HMI
+data showed that both the negative magnetic flux and the magnetic helicity have
+been gradually increasing in the positive polarity region indicating the
+continuous injection of magnetic twist before and during the series of flares.
+Based on these results, we suggest that the continuous emergence of twisted
+magnetic flux played an important role in producing a successive flares and
+developing a series of blowout jets.",1512.01330v1
+2015-12-05,Kinetic theory of spin-polarized systems in electric and magnetic fields with spin-orbit coupling: II. RPA response functions and collective modes,"The spin and density response functions in the random phase approximation
+(RPA) are derived by linearizing the kinetic equation including a magnetic
+field, the spin-orbit coupling, and mean fields with respect to an external
+electric field. Different polarization functions appear describing various
+precession motions showing Rabi satellites due to an effective Zeeman field.
+The latter turns out to consist of the mean-field magnetization, the magnetic
+field, and the spin-orbit vector. The collective modes for charged and neutral
+systems are derived and a threefold splitting of the spin waves dependent on
+the polarization and spin-orbit coupling is shown. The dielectric function
+including spin-orbit coupling, polarization and magnetic fields is presented
+analytically for long wave lengths and in the static limit. The dynamical
+screening length as well as the long-wavelength dielectric function shows an
+instability in charge modes, which are interpreted as spin segregation and
+domain formation. The spin response describes a crossover from damped
+oscillatory behavior to exponentially damped behavior dependent on the
+polarization and collision frequency. The magnetic field causes ellipsoidal
+trajectories of the spin response to an external electric field and the
+spin-orbit coupling causes a rotation of the spin axes. The spin-dephasing
+times are extracted and discussed in dependence on the polarization, magnetic
+field, spin-orbit coupling and single-particle relaxation times.",1512.01661v1
+2015-11-25,Magneto-optical extinction trend inversion in ferrofluids,"Effects of pulse magnetic field on the optical transmission properties of
+thin ferrofluid (FF) layers were experimentally investigated. It was observed
+that, under an influence of an external uniform magnetic field, pulses applied
+to the samples surfaces in normal direction decrease the optical transmission
+with further returning it to its original state, even before the end of the
+field pulse. The dependencies of the observed effects on the magnetic pulse
+magnitude and the samples thickness were investigated. The experimental results
+are explained using FF columnar aggregates growth and lateral coalescence under
+influence of a magnetic field, leading to a light scattering type
+Rayleigh-to-Mie transition. Further evolution of this process comes to a
+geometrical optics scale and respective macroscopic observable opaque FF
+columnar aggregates emergence. These changes of optical transmission are
+non-monotonic during the magnetic field pulse duration with minimal value in
+the case of Mie scattering, which is known as a magneto-optical extinction
+trend inversion. The residual inversion was detected after the external
+magnetic field pulse falling edge. Using molecular dynamics simulation, we
+showed that a homogeneous external magnetic field is enough for the formation
+of columnar aggregates and their fusion. The results clarify the known Li
+theory (Li et al., J. Phys. D: Appl. Phys. 37 (2004) 3357, and Sci. Technol.
+Adv. Mate. 8 (2007) 448), implying an inhomogeneous field as a required
+prerequisite for the magneto-optical extinction trend inversion phenomenon.",1512.04572v3
+2015-12-15,Local Magnetism and Spin Dynamics of the Frustrated Honeycomb Rhodate Li2RhO3,"We report magnetization, heat capacity, 7Li - nuclear magnetic resonance
+(NMR), and muSR (muon spin roration) measurements on the honeycomb 4d5 spin
+liquid candidate Li2RhO3. The magnetization in small magnetic fields provides
+evidence of the partial spin-freezing of a small fraction of Rh4+ -moments at 6
+K, whereas the Curie-Weiss behavior above 100 K suggests a pseudo-spin-1/2
+paramagnet with a moment of about 2.2 muB. The magnetic specific heat (Cm)
+exhibits no field dependence and demonstrates the absence of long range
+magnetic order down to 0.35 K. Cm/T passes through a broad maximum at about 10
+K and Cm=T^2 at low temperatures. Measurements of the spin-lattice relaxation
+rate (1/T1) reveal a gapless slowing down of spin fluctuations upon cooling
+with 1/T1=T^2.2. The results from NMR and muSR are consistent with a scenario
+in which a minority of Rh4+ moments are in a ahort-range correlated frozen
+state and coexist with a majority of moments in a liquid-like state that
+continue to fluctuate at low temperatures.",1512.04904v4
+2016-02-09,Measuring nanoscale magnetic write head fields using a hybrid quantum register,"The generation and control of nanoscale magnetic fields are of fundamental
+interest in material science and a wide range of applications. Nanoscale
+magnetic resonance imaging quantum spintronics for example require single spin
+control with high precision and nanoscale spatial resolution using fast
+switchable magnetic fields with large gradients. Yet, characterizing those
+fields on nanometer length scales at high band width with arbitrary orientation
+has not been possible so far. Here we demonstrate single electron and nuclear
+spin coherent control using the magnetic field of a hard disc drive write head.
+We use single electron spins for measuring fields with high spatial resolution
+and single nuclear spins for large band width measurements. We are able to
+derive field profiles from coherent spin Rabi oscillations close to GHz in
+fields with gradients of up to 10 mT/nm and measure all components of a static
+and dynamic magnetic field independent of its orientation. Our method paves the
+way for precision measurement of the magnetic fields of nanoscale write heads
+important for future miniaturization of the devices.",1602.02948v1
+2016-02-26,"Spin dynamics, electronic and thermal transport properties of two-dimensional CrPS4 single crystal","2-Dimensional (2D) CrPS4 single crystals have been grown by the chemical
+vapor transport method. The crystallographic, magnetic, electronic and thermal
+transport properties of the single crystals were investigated by the
+room-temperature X-ray diffraction, electrical resistivity \r{ho}(T), specific
+heat CP(T) and the electronic spin response (ESR) measurements. CrPS4 crystals
+crystallize into a monoclinic structure. The electrical resistivity \r{ho}(T)
+shows a semiconducting behavior with an energy gap Ea=0.166 eV. The
+antiferromagntic (AFM) transition temperature is about TN=36 K. The spin
+flipping induced by the applied magnetic field is observed along the c axis.
+The magnetic phase diagram of CrPS4 single crystal has been discussed. The
+extracted magnetic entropy at TN is about 10.8 J/mol K, which is consistent
+with the theoretical value R ln(2S + 1) for S = 3/2 of the Cr3+ ion. Based on
+the mean-field theory, the magnetic exchange constants J1 and Jc corresponding
+to the interactions of the intralayer and between layers are about 0.143 meV
+and -0.955 meV are obtained based on the fitting of the susceptibility above
+TN, which agree with the results obtained from the ESR measurements. With the
+help of the strain for tuning the magnetic properties, monolayer CrPS4 may be a
+promising candidate to explore 2D magnetic semiconductors.",1602.08174v1
+2016-03-15,Kinetic simulations of the lowest-order unstable mode of relativistic magnetostatic equilibria,"We present the results of particle-in-cell numerical pair plasma simulations
+of relativistic 2D magnetostatic equilibria known as the 'ABC' fields. In
+particular, we focus on the lowest-order unstable configuration consisting of
+two minima and two maxima of the magnetic vector potential. Breaking of the
+initial symmetry leads to exponential growth of the electric energy and to the
+formation of two current layers, which is consistent with the picture of
+'X-point collapse' first described by Syrovatskii. Magnetic reconnection within
+the layers heats a fraction of particles to very high energies. After the
+saturation of the linear instability, the current layers are disrupted and the
+system evolves chaotically, diffusing the particle energies in a stochastic
+second-order Fermi process leading to the formation of power-law energy
+distributions. The power-law slopes harden with the increasing mean
+magnetization, but they are significantly softer than those produced in
+simulations initiated from Harris-type layers. The maximum particle energy is
+proportional to the mean magnetization, which is attributed partly to the
+increase of the effective electric field and partly to the increase of the
+acceleration time scale. We describe in detail the evolving structure of the
+dynamical current layers, and report on the conservation of magnetic helicity.
+These results can be applied to highly magnetized astrophysical environments,
+where ideal plasma instabilities trigger rapid magnetic dissipation with
+efficient particle acceleration and flares of high-energy radiation.",1603.04850v1
+2016-04-08,Binary neutron star mergers: a jet engine for short gamma-ray bursts,"We perform magnetohydrodynamic simulations in full general relativity (GRMHD)
+of quasi-circular, equal-mass, binary neutron stars that undergo merger. The
+initial stars are irrotational, $n=1$ polytropes and are magnetized. We explore
+two types of magnetic-field geometries: one where each star is endowed with a
+dipole magnetic field extending from the interior into the exterior, as in a
+pulsar, and the other where the dipole field is initially confined to the
+interior. In both cases the adopted magnetic fields are initially dynamically
+unimportant. The merger outcome is a hypermassive neutron star that undergoes
+delayed collapse to a black hole (spin parameter $a/M_{\rm BH} \sim 0.74$)
+immersed in a magnetized accretion disk. About $4000M \sim 60(M_{\rm
+NS}/1.625M_\odot)$ ms following merger, the region above the black hole poles
+becomes strongly magnetized, and a collimated, mildly relativistic outflow ---
+an incipient jet --- is launched. The lifetime of the accretion disk, which
+likely equals the lifetime of the jet, is $\Delta t \sim 0.1 (M_{\rm
+NS}/1.625M_\odot)$ s. In contrast to black hole--neutron star mergers, we find
+that incipient jets are launched even when the initial magnetic field is
+confined to the interior of the stars.",1604.02455v2
+2016-07-13,Sunspot Rotation as a Driver of Major Solar Eruptions in NOAA Active Region 12158,"We studied the developing conditions of sigmoid structure under the influence
+of magnetic non-potential characteristics of a rotating sunspot in the active
+region (AR) 12158. Vector magnetic field measurements from Helioseismic
+Magnetic Imager and coronal EUV observations from Atmospheric Imaging Assembly
+reveal that the erupting inverse-S sigmoid had roots in the location of the
+rotating sunspot. Sunspot rotates at a rate of 0-5deg/h with increasing trend
+in the first half followed by a decrease. Time evolution of many non-potential
+parameters had a well correspondence with the sunspot rotation. The evolution
+of the AR magnetic structure is approximated by a time series of force free
+equilibria. The NLFFF magnetic structure around the sunspot manifests the
+observed sigmoid structure. Field lines from the sunspot periphery constitute
+the body of the sigmoid and those from interior overly the sigmoid similar to a
+fluxrope structure. While the sunspot is being rotating, two major CME
+eruptions occurred in the AR. During the first (second) event, the coronal
+current concentrations enhanced (degraded) consistent with the photospheric net
+vertical current, however the magnetic energy is released during both the
+cases. The analysis results suggest that the magnetic connections of the
+sigmoid are driven by slow motion of sunspot rotation, which transforms to a
+highly twisted flux rope structure in a dynamical scenario. An exceeding
+critical twist in the flux rope probably leads to the loss of equilibrium and
+thus triggering the onset of two eruptions.",1607.03806v1
+2016-08-13,Detection and optical imaging of induced convection under the action of static gradient magnetic field in a non-conducting diamagnetic fluid,"The report elaborates for the first time visual observations of induced
+convections in a non-conducting diamagnetic fluid under the action of static
+gradient magnetic field in the absence of thermal gradients and the techniques
+employed to observe and record them. Suspension of Deionized (DI) and double
+distilled water and Lycopodium pollen grains was used as the fluid in a test
+tube. Permanent magnets having field strength of 0.12T each were used to
+provide the static gradient magnetic field. The suspension filled test tube was
+kept in a room temperature water bath. The convections were visually observed
+and recorded using travelling microscope attached with a web camera. Various
+geometrical configurations of magnets in the vicinity of test tube provided
+different types of magnetic gradient shapes. These gradients were responsible
+for the occurrence of different types of orientations in the convective flows
+in the test tube. Convections were observed over a range of fluid volumes from
+0.2ml-10ml. The experimentally observed results provide proof of concept that
+irrespective of the weak interactions of diamagnetic fluids with magnetic
+fields, these effects can be easily observed and recorded with the use of low
+tech laboratory equipments.",1608.03973v2
+2016-08-18,Turbulent dynamo in a conducting fluid and partially ionized gas,"By following the Kazantsev theory and taking into account both microscopic
+and turbulent diffusion of magnetic fields, we develop a unified treatment of
+the kinematic and nonlinear stages of turbulent dynamo, and study the dynamo
+process for a full range of magnetic Prandtl number Pm and ionization
+fractions. We find a striking similarity between the dependence of dynamo
+behavior on Pm in a conducting fluid and R (a function of ionization fraction)
+in partially ionized gas. In a weakly ionized medium, the kinematic stage is
+largely extended, including not only exponential growth but a new regime of
+dynamo characterized by linear-in-time growth of magnetic field strength, and
+the resulting magnetic energy is much higher than the kinetic energy carried by
+viscous-scale eddies. Unlike the kinematic stage, the subsequent nonlinear
+stage is unaffected by microscopic diffusion processes and has a universal
+linear-in-time growth of magnetic energy with the growth rate as a constant
+fraction $3/38$ of the turbulent energy transfer rate, showing good agreement
+with earlier numerical results. Applying the analysis to the first stars and
+galaxies, we find that the kinematic stage is able to generate a field strength
+only an order of magnitude smaller than the final saturation value. But the
+generation of large-scale magnetic fields can only be accounted for by the
+relatively inefficient nonlinear stage and requires longer time than the
+free-fall time. It suggests that magnetic fields may not have played a
+dynamically important role during the formation of the first stars.",1608.05161v2
+2016-09-15,Crossover from magnetostatic to exchange coupling in La0.67Ca0.33MnO3/YBa2Cu3O7/La0.67Ca0.33MnO3 heterostructures,"The influence of YBa2Cu3O4 (YBCO) superconductor layer (S-layer) with varying
+thickness d-YBCO = 20 to 50 nm on the magnetic coupling between two
+La0.67Ca0.33MnO3 (LCMO) ferromagnet layers (F-layer, thickness d-LCMO = 50 nm)
+in F/S/F heterostructures (HSs) was investigated by measuring global
+magnetization (M) in a temperature (T) range = 2 - 300 K and magnetic field (H)
+range = 0 - 10 kOe. All the HSs were superconducting with critical temperature
+(Tc) decreasing from = 78 to 36 K with decrease in d-YBCO, whereas the
+ferromagnetic ordering temperature Tm = 250 K did not change much.
+Systematically measured M-H loops of all HSs at both T > Tc and T < Tc show
+three main results- (a) the two step magnetic reversal above Tc converts into a
+four step reversal below Tc in HSs with d-YBCO >= 30 nm, (b) the magnetic field
+corresponding to the additional two switching steps and their magnitude show
+characteristic evolution with T and d-YBCO and (c) the HS with d-YBCO = 20 nm
+shows radically different behaviour, where the two step magnetic reversal above
+Tc continues to persist below Tc and converts into a single step reversal at T
+<< Tc. The first two results indicate magnetostatic coupling between the
+magnetic domains and the vortices across the two F/S interfaces resulting in
+reversal dynamics different from that deep within the LCMO layers. Whereas, the
+result c reveals indirect exchange coupling between LCMO layers through the
+superconducting YBCO layer, which is a clear experimental evidence of
+coexistence of ferromagnetism and superconductivity in nm scale F/S/F HSs
+expected theoretically by C.A.R. Sa de Melo (Physica C 387, 17-25 (2003)).",1609.04519v1
+2016-10-17,Vector magnetic field measurements along a cooled stereo-imaged coronal loop,"The variation of the vector magnetic field along structures in the solar
+corona remains unmeasured. Using a unique combination of spectropolarimetry and
+stereoscopy, we infer and compare the vector magnetic field structure and
+three-dimensional morphology of an individuated coronal loop structure
+undergoing a thermal instability. We analyze spectropolarimetric data of the He
+I 10830 {\AA} triplet ($1s2s{\ }^{3}S_{1} - 1s2p{\ }^{3}P_{2,1,0}$) obtained at
+the Dunn Solar Telescope with the Facility Infrared Spectropolarimeter on 19
+September 2011. Cool coronal loops are identified by their prominent drainage
+signatures in the He I data (redshifts up to 185 km sec$^{-1}$). Extinction of
+EUV background radiation along these loops is observed by both the Atmospheric
+Imaging Assembly onboard the Solar Dynamics Observatory and the Extreme
+Ultraviolet Imager onboard spacecraft A of the Solar Terrestrial Relations
+Observatory, and is used to stereoscopically triangulate the loop geometry up
+to heights of 70 Mm ($0.1$ $R_{sun}$) above the solar surface. The He I
+polarized spectra along this loop exhibit signatures indicative of atomic-level
+polarization as well as magnetic signatures through the Hanle and Zeeman
+effects. Spectropolarimetric inversions indicate that the magnetic field is
+generally oriented along the coronal loop axis, and provide the height
+dependence of the magnetic field intensity. The technique we demonstrate is a
+powerful one that may help better understand the thermodynamics of coronal fine
+structure magnetism.",1610.05332v1
+2017-03-22,Magnetization induced dynamics of a Josephson junction coupled to a nanomagnet,"We study the superconducting current of a Josephson junction (JJ) coupled to
+an external nanomagnet driven by a time dependent magnetic field both without
+and in the presence of an external AC drive. We provide an analytic, albeit
+perturbative, solution for the Landau-Lifshitz (LL) equations governing the
+coupled JJ-nanomagnet system in the presence of a magnetic field with arbitrary
+time-dependence oriented along the easy axis of the nanomagnet's magnetization
+and in the limit of weak dimensionless coupling $\epsilon_0$ between the JJ and
+the nanomagnet. We show the existence of Shapiro-like steps in the I-V
+characteristics of the JJ subjected to a voltage bias for a constant or
+periodically varying magnetic field and explore the effect of rotation of the
+magnetic field and the presence of an external AC drive on these steps. We
+support our analytic results with exact numerical solution of the LL equations.
+We also extend our results to dissipative nanomagnets by providing a
+perturbative solution to the Landau-Lifshitz-Gilbert (LLG) equations for weak
+dissipation. We study the fate of magnetization-induced Shapiro steps in the
+presence of dissipation both from our analytical results and via numerical
+solution of the coupled LLG equations. We discuss experiments which can test
+our theory.",1703.07717v3
+2017-03-26,Sausage Instabilities on Top of Kinking Lengthening Current-Carrying Magnetic Flux Tubes,"We theoretically explore the possibility of sausage instabilities developing
+on top of a kink instability in lengthening current-carrying magnetic flux
+tubes. Observations indicate that the dynamics of magnetic flux tubes in our
+cosmos and terrestrial experiments can involve topological changes faster than
+time scales predicted by resistive magnetohydrodynamics. Recent laboratory
+experiments suggest that hierarchies of instabilities, such as kink and
+Rayleigh-Taylor, could be responsible for initiating fast topological changes
+by locally accessing two fluid and kinetic regimes. Sausage instabilities can
+also provide this coupling mechanism between disparate scales. Flux tube
+experiments can be classified by the flux tube's evolution in a configuration
+space described by a normalized inverse aspect-ratio $\bar{k}$ and
+current-to-magnetic flux ratio $\bar{\lambda}$. A lengthening current-carrying
+magnetic flux tube traverses this $\bar{k}$ - $\bar{\lambda}$ space and crosses
+stability boundaries. We derive a single general criterion for the onset of the
+sausage and kink instabilities in idealized magnetic flux tubes with core and
+skin currents. The criterion indicates a dependence of the stability boundaries
+on current profiles and shows overlapping kink and sausage unstable regions in
+the $\bar{k}$ - $\bar{\lambda}$ space with two free parameters. Numerical
+investigation of the stability criterion reduces the number of free parameters
+to a single one that describes the current profile, and confirms the
+overlapping sausage and kink unstable regions in $\bar{k}$ - $\bar{\lambda}$
+space. A lengthening, ideal current-carrying magnetic flux tube can therefore
+become sausage unstable after it becomes kink unstable.",1703.08771v2
+2017-04-24,Magnetic nulls and super-radial expansion in the solar corona,"Magnetic fields in the sun's outer atmosphere -- the corona -- control both
+solar-wind acceleration and the dynamics of solar eruptions. We present the
+first clear observational evidence of coronal magnetic nulls in off-limb
+linearly polarized observations of pseudostreamers, taken by the Coronal
+Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where
+magnetic reconnection is likely to act as a catalyst for solar activity. CoMP
+linear-polarization observations also provide an independent, coronal proxy for
+magnetic expansion into the solar wind, a quantity often used to parameterize
+and predict the solar wind speed at Earth. We introduce a new method for
+explicitly calculating expansion factors from CoMP coronal linear-polarization
+observations, which does not require photospheric extrapolations. We conclude
+that linearly-polarized light is a powerful new diagnostic of critical coronal
+magnetic topologies and the expanding magnetic flux tubes that channel the
+solar wind.",1704.07470v2
+2017-05-17,The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows,"Non-ideal MHD effects may play a significant role in determining the
+dynamics, thermal properties, and observational signatures of radiatively
+inefficient accretion flows onto black holes. In particular, particle
+acceleration during magnetic reconnection events may influence black hole
+spectra and flaring properties. We use representative GRMHD simulations of
+black hole accretion flows to identify and explore the structures and
+properties of current sheets as potential sites of magnetic reconnection. In
+the case of standard and normal (SANE) disks, we find that, in the reconnection
+sites, the plasma beta ranges from $0.1$ to $1000$, the magnetization ranges
+from $10^{-4}$ to $1$, and the guide fields are weak compared to the
+reconnecting fields. In magnetically arrested (MAD) disks, we find typical
+values for plasma beta from $10^{-2}$ to $10^3$, magnetizations from $10^{-3}$
+to $10$, and typically stronger guide fields, with strengths comparable to or
+greater than the reconnecting fields. These are critical parameters that govern
+the electron energy distribution resulting from magnetic reconnection and can
+be used in the context of plasma simulations to provide microphysics inputs to
+global simulations. We also find that ample magnetic energy is available in the
+reconnection regions to power the fluence of bright X-ray flares observed from
+the black hole in the center of the Milky Way.",1705.06293v1
+2017-05-17,Magnetic tension and instabilities in the Orion A integral shaped filament,"The Orion nebula is a prime example of a massive star-forming region in our
+galaxy. Observations have shown that gravitational and magnetic energy are
+comparable in its integral shaped filament (ISF) on a scale of ~1 pc, and that
+the population of pre-main sequence stars appears dynamically heated compared
+to the protostars. These results have been attributed to a slingshot mechanism
+resulting from the oscillation of the filament (Stutz & Gould 2016). In this
+paper, we show that radially contracting filaments naturally evolve toward a
+state where gravitational, magnetic, and rotational energy are comparable.
+While the contraction of the filament will preferentially amplify the axial
+component of the magnetic field, the presence of rotation leads to a helical
+field structure. We show how magnetic tension can give rise to a filament
+oscillation, and estimate a typical timescale of 0.7 million years for the
+motion of the filament to the position of maximum displacement, consistent with
+the characteristic timescale of the ejected stars. Furthermore, the presence of
+helical magnetic fields is expected to give rise to magneto-hydrodynamical
+instabilities. We show here that the presence of a magnetic field significantly
+enhances the overall instability, which operates on a characteristic scale of
+about 1 pc. We expect the physics discussed here to be generally relevant in
+massive star forming regions, and encourage further investigations in the
+future.",1705.06302v2
+2017-06-19,Spin order and dynamics in the diamond-lattice Heisenberg antiferromagnets CuRh2O4 and CoRh2O4,"Antiferromagnetic insulators on the diamond lattice are candidate materials
+to host exotic magnetic phenomena ranging from spin-orbital entanglement to
+degenerate spiral ground-states and topological paramagnetism. Compared to
+other three-dimensional networks of magnetic ions, such as the geometrically
+frustrated pyrochlore lattice, the investigation of diamond-lattice magnetism
+in real materials is less mature. In this work, we characterize the magnetic
+properties of model A-site spinels CoRh2O4 (cobalt rhodite) and CuRh2O4 (copper
+rhodite) by means of thermo-magnetic and neutron scattering measurements and
+perform group theory analysis, Rietveld refinement, mean-field theory, and spin
+wave theory calculations to analyze the experimental results. Our investigation
+reveals that cubic CoRh2O4 is a canonical S=3/2 diamond-lattice Heisenberg
+antiferromagnet with a nearest neighbor exchange J = 0.63 meV and a Neel
+ordered ground-state below a temperature of 25 K. In tetragonally distorted
+CuRh2O4, competiting exchange interactions between up to third nearest-neighbor
+spins lead to the development of an incommensurate spin helix at 24 K with a
+magnetic propagation vector k = (0,0,0.79). Strong reduction of the ordered
+moment is observed for the S=1/2 spins in CuRh2O4 and captured by our 1/S
+corrections to the staggered magnetization. Our work identifies CoRh2O4 and
+CuRh2O4 as reference materials to guide future work searching for exotic
+quantum behavior in diamond-lattice antiferromagnets.",1706.05881v1
+2017-08-14,Solar Eruption and Local Magnetic Parameters,"It is now a common practice to use local magnetic parameters such as magnetic
+decay index for explaining solar eruptions from active regions, but there can
+be an alternative view that the global properties of the source region should
+be counted as a more important factor. We discuss this issue based on {\it
+Solar Dynamics Observatory} (SDO) observations of the three successive
+eruptions within 1.5 hours from the NOAA active region 11444 and the magnetic
+parameters calculated using the nonlinear force-free field (NLFFF) model. Two
+violent eruptions occurred in the regions with relatively high magnetic twist
+number (0.5--1.5) and high decay index (0.9--1.1) at the nominal height of the
+filament (12$''$) and otherwise a mild eruption occurred, which supports the
+local parameter paradigm. Our main point is that the time sequence of the
+eruptions did not go with these parameters. It is argued that an additional
+factor, in the form of stabilizing force, should operate to determine the onset
+of the first eruption and temporal behaviors of subsequent eruptions. As
+supporting evidence, we report that the heating and fast plasma flow continuing
+for a timescale of an hour was the direct cause for the first eruption, and
+that the unidirectional propagation of the disturbance determined the timing of
+subsequent eruptions. Both of these factors are associated with the overall
+magnetic structure rather than local magnetic properties of the active region.",1708.04055v1
+2017-09-18,Cobalt substitution induced magnetodielectric enhancement in multiferroic Bi2Fe4O9,"Antiferromagnetic Bi_{2}Fe_{4}O_{9} (BFO), lightly substituted by cobalt is
+studied for magnetodielectricity. The substitution causes a substantial
+decrease in the Neel temperature (T_N) from 250 K (in parent sample, BFO) to
+152 K (in 2% Co substituted sample). At the same time, the substituted samples
+display a pronounced irreversibility in the ZFC-FC magnetization data for T $<$
+370 K and opening of hysteresis in the M-H plot, thus signifying the onset of
+weak ferromagnetism (FM) and magnetic glassiness. The induced magnetic
+glassiness is found to slow down the dynamics such that the magnetization decay
+follows. The dielectric measurement in the same temperature window shows
+unusual oppression in, for T$\sim$T_N and contrasting nature of tan loss for
+temperatures above and below T_N, thus hinting a plausible coupling between the
+magnetic and electric order parameters. A confirmation to this coupling is seen
+in the magnetodielectric (MD) results, in which it is found that the
+substitution induces an additional component in the MD, apart from the usual
+components in BFO. This additional component of MD is found to obey behaviour,
+with the n values being comparable to 1-p of magnetization. The temperature
+variation of MD also shows a contrasting behaviour for the parent and 2% Co
+substituted sample with an enhancement of two times in MD value. In summary,
+our study shows ME coupling introduced by the magnetic glassiness and its
+behaviour is very much different from the intrinsic one.",1709.05854v1
+2017-11-24,Magneto-Rayleigh-Taylor instability driven by a rotating magnetic field: Cylindrical liner configuration,"We propose using a directional time-varying (rotating) driving magnetic field
+to suppress magneto-Rayleigh-Taylor (MRT) instability in dynamic Z-pinches. A
+rotational drive magnetic field is equivalent to two magnetic-field components,
+{\Theta} and Z, that alternate in time, referred to as an alternate
+Theta-Z-pinch configuration. We consider the finitely thick cylindrical liner
+configuration in this paper. We numerically integrate the perturbation equation
+to stagnation time based on the optimal background unperturbed trajectories. We
+assess the cumulative growth of the dominant mode selected by some mechanism at
+the beginning of an implosion. The maximum e-folding number at stagnation of
+the dominant mode of an optimized alternate Theta-Z-pinch is significantly
+lower than that of the standard Theta- or Z-pinch. The directional rotation of
+the magnetic field contributes to suppress the instabilities, independent of
+the finite thickness. The finite thickness effect plays a role only when the
+orientation of the magnetic field varies in time whereas it does not appear in
+the standard Theta- or Z-pinch. The rotating frequency of the magnetic field
+and the thickness of liner are both having a monotonic effect on suppression.
+Their synergistic effect can enhance the suppression on MRT instability.
+Because the MRT instability can be well suppressed in this way, the alternate
+Theta-Z-pinch configuration has potential applications in liner inertial
+fusion. This work is supported by the NSFC (Grant Nos. 11405167, 51407171,
+11571293, 11605188, and 11605189) and the Foundation of the China Academy of
+Engineering Physics (No. 2015B0201023).",1711.08891v2
+2018-01-22,Role of quantum fluctuations on spin liquids and ordered phases in the Heisenberg model on the honeycomb lattice,"Motivated by the rich physics of honeycomb magnetic materials, we obtain the
+phase diagram and analyze magnetic properties of the spin-1/2 and spin-1
+J1-J2-J3 Heisenberg model on the honeycomb lattice. Based on the SU(2) and
+SU(3) symmetry representations of the Schwinger boson approach, which treats
+disordered spin liquids and magnetically ordered phases on an equal footing, we
+obtain the complete phase diagrams in the (J2,J3)plane. This is achieved using
+a fully unrestricted approach which does not assume any pre-defined Ansatze.
+For S=1/2, we find a quantum spin liquid (QSL) stabilized between the N\'eel,
+spiral and collinear antiferromagnetic phases in agreement with previous
+theoretical work. However, by increasing S from 1/2 to 1, the QSL is quickly
+destroyed due to the weakening of quantum fluctuations indicating that the
+model already behaves as a quasi-classical system. The dynamical structure
+factors and temperature dependence of the magnetic susceptibility are obtained
+in order to characterize all phases in the phase diagrams. Moreover, motivated
+by the relevance of the single-ion anisotropy, D, to various S=1 honeycomb
+compounds, we have analyzed the destruction of magnetic order based on a SU(3)
+representation of the Schwinger bosons. Our analysis provides a unified
+understanding of the magnetic properties of honeycomb materials realizing the
+J1-J2-J3 Heisenberg model from the strong quantum spin regime at S=1/2 to the
+S=1 case. Neutron scattering and magnetic susceptibility experiments can be
+used to test the destruction of the QSL phase when replacing S=1/2 by S=1
+localized moments in certain honeycomb compounds.",1801.07042v1
+2018-01-23,A Statistical Comparison between Photospheric Vector Magnetograms Obtained by SDO/HMI and Hinode/SP,"Since May 1, 2010, we have been able to study (almost) continuously the
+vector magnetic field in the Sun, thanks to two space-based observatories: the
+Solar Dynamics Observatory (SDO) and Hinode. Both are equipped with instruments
+able to measure the Stokes parameters of Zeeman-induced polarization of
+photospheric line radiation. But the observation modes, the spectral lines, the
+spatial, spectral and temporal sampling, and even the inversion codes used to
+recover magnetic and thermodynamic information from the Stokes profiles are
+different. We compare the vector magnetic fields derived from observations with
+the HMI instrument on board SDO, with those observed by the SP instrument on
+Hinode. We have obtained relationships between components of magnetic vectors
+in the umbra, penumbra and plage observed in 14 maps of NOAA AR 11084.
+Importantly, we have transformed SP data into observables comparable to those
+of HMI, to explore possible influences of the different modes of operation of
+the two instruments, and the inversion schemes used to infer the magnetic
+fields. The assumed filling factor (fraction of each pixel containing a Zeeman
+signature) produces the most significant differences in derived magnetic
+properties, especially in the plage. The spectral and angular samplings have
+the next largest effects. We suggest to treat the disambiguation in the same
+way in the data provided by HMI and SP. That would make the relationship
+between the vector magnetic field recovered from these data stronger, what
+would favor the simultaneous or complementary use of both instruments.",1801.07374v1
+2018-01-23,"Similarity solution for the flow behind a magnetogasdynamic exponential shock wave in a perfect gas with varying density, heat conduction and radiation heat flux","Similarity solutions are obtained for one dimensional, unsteady, adiabatic
+propagation of an exponential shock wave in a perfect gas with heat conduction
+and radiation heat flux, in the presence of azimuthal magnetic field. The shock
+wave is driven out by a piston moving with time according to an exponential
+law. The equilibrium flow conditions are maintained. The heat conduction is
+expressed in terms of Fourier's law and the radiation is considered to be of
+the diffusion type for an optically thick grey gas model. The thermal
+conductivity and the absorption coefficient are assumed to vary with
+temperature and density according to power law. The density and magnetic field
+ahead of the shock front, are assumed to vary as an exponential law. The
+effects of the variation of the strength of ambient magnetic field, heat
+transfer parameters, adiabatic exponent, ambient density variation index on the
+shock strength, the distance between the piston and the shock front, and on the
+flow variables are studied out in detail. The similarity solution exists only
+when the sum of shock radius and ambient magnetic field exponent is equal to
+the half of the ambient density exponent. It is manifested that the shock
+strength decreases by increasing the strength of ambient magnetic field but it
+is independent from the heat transfer parameters. The total energy of the flow
+field behind the shock front is not constant but varies as power of shock
+radius. The compressibility of the medium is increased in the non-magnetic
+field. Also, the presence of the magnetic field have significant effects on the
+shock wave.",1801.07697v1
+2018-02-09,"Relations between variability of the photospheric and interplanetary magnetic fields, solar wind and geomagnetic characteristics","Large scale solar magnetic field topology has a great influence on the
+structure of the corona, heliosphera and geomagnetic perturbations.
+  Data obtained over the last three solar cycles have been analysed to reveal
+the relationships between the photospheric field measured along the line of
+sight by the WSO group at 30 levels of heliolatitudes from -75 to 75 degrees
+and the interplanetary magnetic field The main aim of this first paper is to
+make a direct comparison between the basic structure and dynamics of the
+photospheric magnetic field and components and intensity of the interplanetary
+magnetic field % solar wind and geomagnetic parameters without using
+theoretical assumptions, models, physical expectations, etc.
+  The second paper by Gavryuseva, 2018d presents the raports between different
+characteristics of the solar wind at the Earth orbit, and geomagnetic
+parameters provided by the OMNI team. % Data obtained over the last three solar
+cycles have been analysed % to reveal the relationships % between the
+photospheric field measured along the line of sight % by the WSO group % at
+heliolatitudes from -75 to 75 degrees averaged over one year % and the
+interplanetary magnetic field, different characteristics % of the solar wind at
+the Earth orbit, and geomagnetic parameters. % provided by the OMNI team.
+  The heliospheric and geomagnetic data are found to be divided into two groups
+characterized by their response to variability of the solar magnetic field
+latitudinal structures on short and on long time scales.",1802.03135v1
+2018-02-13,Inverted hysteresis and negative remanence in a homogeneous antiferromagnet,"Magnetic remanence - found in bar magnets or magnetic storage devices - is
+probably the oldest and most ubiquitous phenomenon underpinning technological
+applications of magnetism. It is a macroscopic non-equilibrium phenomenon: a
+remanent magnetisation appears when a magnetic field is applied to an initially
+unmagnetised ferromagnet, and then taken away. Here, we present an inverted
+magnetic hysteresis loop in the pyrochlore compound Nd$_2$Hf$_2$O$_7$: the
+remanent magnetisation points in a direction opposite to the applied field.
+This phenomenon is exquisitely tunable as a function of the protocol in field
+and temperature, and it is reproducible as in a quasi-equilibrium setting. We
+account for this phenomenon in considerable detail in terms of the properties
+of non-equilibrium population of domain walls which exhibit a magnetic moment
+between domains of an ordered antiferromagnetic state which itself has zero net
+magnetisation. Properties and (non-equilibrium) dynamics of topological defects
+play an important role in modern spintronics, and our study adds an instance
+where a uniform field couples selectively to domain walls rather than the bulk.",1802.04610v1
+2018-03-22,Rotation and magnetism in intermediate mass stars,"Rotation and magnetism are increasingly recognized as important phenomena in
+stellar evolution. Surface magnetic fields from a few to $20{,}000\,$G have
+been observed and models have suggested that magnetohydrodynamic transport of
+angular momentum and chemical composition could explain the peculiar
+composition of some stars. Stellar remnants such as white dwarfs have been
+observed with fields from a few to more than $10^{9}\,$G. We investigate the
+origin of and the evolution, on thermal and nuclear rather than dynamical
+time-scales, of an averaged large-scale magnetic field throughout a star's life
+and its coupling to stellar rotation. Large-scale magnetic fields sustained
+until late stages of stellar evolution with conservation of magnetic flux could
+explain the very high fields observed in white dwarfs. We include these effects
+in the Cambridge stellar evolution code using three time-dependant
+advection-diffusion equations coupled to the structural and composition
+equations of stars to model the evolution of angular momentum and the two
+components of the magnetic field. We present the evolution in various cases for
+a $3\rm\,M_{\odot}$ star from the beginning to the late stages of its life. Our
+particular model assumes that turbulent motions, including convection, favour
+small-scale field at the expense of large-scale field. As a result the
+large-scale field concentrates in radiative zones of the star and so is
+exchanged between the core and the envelope of the star as it evolves. The
+field is sustained until the end of the asymptotic giant branch, when it
+concentrates in the degenerate core.",1803.08270v1
+2018-04-30,Field-Free Switching of Perpendicular Magnetic Tunnel Junction via Voltage-Gated Spin Hall Effect for Low-Power Spintronic Memory,"Spin Hall effect (SHE) and voltage-controlled magnetic anisotropy (VCMA) are
+two promising methods for low-power electrical manipulation of magnetization.
+Recently, magnetic field-free switching of perpendicular magnetization through
+SHE has been reported with the aid of an exchange bias from an
+antiferromagnetic IrMn layer. In this letter, we experimentally demonstrate
+that the IrMn/CoFeB/MgO structure exhibits a VCMA effect of 39 fJ/Vm, which is
+comparable to that of the Ta/CoFeB/MgO structure. Magnetization dynamics under
+a combination of the SHE and VCMA are modeled and simulated. It is found that,
+by applying a voltage of 1.5 V, the critical SHE switching current can be
+decreased by 10 times owing to the VCMA effect, leading to low-power
+operations. Furthermore, a high-density spintronic memory structure can be
+built with multiple magnetic tunnel junctions (MTJs) located on a single IrMn
+strip. Through hybrid CMOS/MTJ simulations, we demonstrate that fast-speed
+write operations can be achieved with power consumption of only 8.5 fJ/bit.
+These findings reveal the possibility to realize high-density and low-power
+spintronic memory manipulated by voltage-gated SHE.",1804.11025v1
+2018-06-11,Intermediate gapless phase and topological phase transition of Kitaev model in a uniform magnetic field,"We study the Kitaev spin liquid (KSL) in a [001] magnetic field employing the
+mean field theory (MFT/MF) in the Majorana fermion representation. The MF
+Hamiltonian of the system has the Bogoliubov de-Gennes (BdG) form of a 2D Weyl
+superconductor. We discover a robust gapless regime in intermediate magnetic
+field for both gapless and gapped AFM KSL with Jx = Jy before the system is
+polarized in high magnetic field. A topological phase transition (PT)
+connecting two gapless phases with nodal lines takes place at a critical
+magnetic field hc1 in this regime. While the nodal lines at hc1 is protected by
+the mirror symmetry with Jx = Jy and disappear at Jx 6= Jy with a gap opening
+near the critical field, the nodal points at E = 0 can exist at intermediate
+fields even without mirror symmetry. We reveal that the phase evolution of the
+KSL in the magnetic field is driven by the competition between the magnetic
+field and the particle-hole (p-h) asymmetry of the normal state of the BdG
+Hamiltonian, which results in the robust intermediate gapless phase for AFM
+KSL. For FM KSL, there is no intermediate PT before polarization. The above
+phase diagrams are confirmed by dynamical MFT (DMFT) results.",1806.04184v2
+2018-08-14,A Survey of Changes in Magnetic Helicity Flux on the Photosphere During Relatively Low Class Flares,"Using the 135-second cadence of the photospheric vector data provided by the
+Helioseismic and Magnetic Imager telescope on board the Solar Dynamic
+Observatory, we examined the time-evolution of magnetic helicity fluxes across
+the photosphere during 16 flares with the energy class lower than M5.0. During
+the flare in 4 out of 16 events, we found impulsive changes in the helicity
+fluxes. This indicates that even the flare with less energy could be associated
+with anomalistic transportation of the magnetic helicity across the
+photosphere. Accompanying the impulsive helicity fluxes, the poynting fluxes
+across the photosphere evolved from positive to negative. As such, the
+transportations of magnetic energy across the photosphere were toward solar
+interior during these flares. In each of the 4 events, the impulsive change in
+the helicity flux was always mainly contributed by abrupt change in horizontal
+velocity field on a sunspot located near the flaring polarity inversion line.
+The velocity field on each sunspot shows either an obvious vortex patten or an
+shearing patten relative to the another magnetic polarity, which tended to
+relax the magnetic twist or shear in the corona. During these flares, abrupt
+change in the Lorentz force acting on these sunspots were found. The rotational
+motions and shearing motions of these sunspots always had the same directions
+with the resultant Lorentz forces. These results support the view that the
+impulsive helicity transportation during the flare could be driven by the
+change in the Lorentz force applied on the photosphere.",1808.04591v1
+2018-08-30,Accelerating the calculation of dipolar interactions in particle based simulations with open boundary conditions by means of the P2NFFT method,"Magnetic gels are soft elastic materials consisting of magnetic particles
+embedded in a polymer network. Their shape and elasticity can be controlled by
+an external magnetic field, which gives rise to both, engineering and
+biomedical applications. Computer simulations are a commonly used tool to study
+these materials. A well-known bottleneck of these simulations is the demanding
+calculation of dipolar interactions. Under periodic boundary conditions
+established algorithms are available for doing this, however, at the expense of
+restricting the way in which the gels can deform in an external magnetic field.
+Moreover, the magnetic properties depend on the sample shape, ruling out
+periodic boundary conditions entirely for some research questions. In this
+article we will employ the recently developed dipolar variant of the P$^2$NFFT
+method that is able to calculate dipolar interactions under open boundary
+conditions with an $N \log N$ scaling in the number of particles, rather than
+the expensive $N^2$ scaling of a direct summation of pair forces. The dipolar
+P$^2$NFFT method has been implemented within the ScaFaCoS library. The
+molecular dynamics software ESPResSo has been extended to make use of the
+library.
+  After a short summary of the method, we will discuss its value for studying
+magnetic soft matter systems. A particular focus is put on developing a tuning
+strategy to reach the best performance of the method at a predefined accuracy,
+and lastly applying the method to a magnetic gel model. Here, adapting to the
+gel's change in shape during the course of a simulation is of particular
+interest.",1808.10341v1
+2018-09-09,High-speed shear driven dynamos. Part 1. Asymptotic analysis,"Rational large Reynolds number matched asymptotic expansions of
+three-dimensional nonlinear magneto-hydrodynamic (MHD) states are concerned.
+The nonlinear MHD states, assumed to be predominantly driven by a
+unidirectional shear, can be sustained without any linear instability of the
+base flow and hence are responsible for subcritical transition to turbulence.
+Two classes of nonlinear MHD states are found. The first class of nonlinear
+states emerged out of a nice combination of the purely hydrodynamic vortex/wave
+interaction theory by Hall \& Smith (1991) and the resonant absorption theories
+on Alfv\'en waves, developed in the solar physics community (e.g. Sakurai et
+al. 1991; Goossens et al. 1995). Similar to the hydrodynamic theory, the
+mechanism of the MHD states can be explained by the successive interaction of
+the roll, streak, and wave fields, which are now defined both for the
+hydrodynamic and magnetic fields. The derivation of this `vortex/Alfv\'en wave
+interaction' state is rather straightforward as the scalings for both of the
+hydrodynamic and magnetic fields are identical. It turns out that the leading
+order magnetic field of the asymptotic states appears only when a small
+external magnetic field is present. However, it does not mean that purely
+shear-driven dynamos are not possible. In fact, the second class of
+`self-sustained shear driven dynamo theory' shows the magnetic generation that
+is slightly smaller size in the absence of any external field. Despite small
+size, the magnetic field causes the novel feedback mechanism in the velocity
+field through resonant absorption, wherein the magnetic wave becomes more
+strongly amplified than the hydrodynamic counterpart.",1809.03853v2
+2018-11-26,The overdamped chiral magnetic wave,"About eight years ago it was predicted theoretically that a charged chiral
+plasma could support the propagation of the so-called chiral magnetic waves,
+which are driven by the anomalous chiral magnetic and chiral separation
+effects. This prompted intensive experimental efforts in search of signatures
+of such waves in relativistic heavy-ion collisions. In fact, several
+experiments have already reported a tentative detection of the predicted
+signal, albeit with a significant background contribution. Here, we critically
+reanalyze the theoretical foundations for the existence of the chiral magnetic
+waves. We find that the commonly used background-field approximation is not
+sufficient for treating the waves in hot chiral plasmas in the long-wavelength
+limit. Indeed, the back-reaction from dynamically induced electromagnetic
+fields turns the chiral magnetic wave into a diffusive mode. While the
+situation is slightly better in the strongly-coupled near-critical regime of
+quark-gluon plasma created in heavy-ion collisions, the chiral magnetic wave is
+still strongly overdamped due to the effects of electrical conductivity and
+charge diffusion.",1811.10635v2
+2019-01-14,Magnetized interstellar molecular clouds: II. The Large-Scale Structure and Dynamics of Filamentary Molecular Clouds,"We perform ideal MHD high resolution AMR simulations with driven turbulence
+and self-gravity and find that long filamentary molecular clouds are formed at
+the converging locations of large-scale turbulence flows and the filaments are
+bounded by gravity. The magnetic field helps shape and reinforce the long
+filamentary structures. The main filamentary cloud has a length of ~4.4 pc.
+Instead of a monolithic cylindrical structure, the main cloud is shown to be a
+collection of fiber/web-like sub-structures similar to filamentary clouds such
+as L1495. Unless the line-of-sight is close to the mean field direction, the
+large-scale magnetic field and striations in the simulation are found roughly
+perpendicular to the long axis of the main cloud, similar to 1495. This
+provides strong support for a large-scale moderately strong magnetic field
+surrounding L1495. We find that the projection effect from observations can
+lead to incorrect interpretations of the true three-dimensional physical shape,
+size, and velocity structure of the clouds. Helical magnetic field structures
+found around filamentary clouds that are interpreted from Zeeman observations
+can be explained by a simple bending of the magnetic field that pierces through
+the cloud. We demonstrate that two dark clouds form a T-shape configuration
+which are strikingly similar to the Infrared dark cloud SDC13 leading to the
+interpretation that SDC13 results from a collision of two long filamentary
+clouds. We show that a moderately strong magnetic field (M_A ~ 1) is crucial
+for maintaining a long and slender filamentary cloud for a long period of time
+~0.5 million years.",1901.04593v2
+2019-02-28,To Heat or not to Heat: a Study of the Performances of Iron Carbide Nanoparticles in Magnetic Heating,"Heating magnetic nanoparticles with high frequency magnetic fields is a topic
+of interest for biological applications (magnetic hyperthermia) as well as for
+heterogeneous catalysis. This study shows why FeC NPs of similar structures and
+static magnetic properties display radically different heating power (SAR from
+0 to 2 kW.g-1). By combining results from Transmission Electron Microscopy
+(TEM), Dynamic Light Scattering (DLS) and static and time-dependent
+high-frequency magnetic measurements, we propose a model describing the heating
+mechanism in FeC nanoparticles. Using, for the first time, time-dependent
+high-frequency hysteresis loop measurements, it is shown that in the samples
+displaying the larger heating powers, the hysteresis is strongly time
+dependent. More precisely, the hysteresis area increases by a factor 10 on a
+timescale of a few tens of seconds. This effect is directly related to the
+ability of the nanoparticles to form chains under magnetic excitation, which
+depends on the presence or not of strong dipolar couplings. These differences
+are due to different ligand concentrations on the surface of the particles. As
+a result, this study allows the design of a scalable synthesis of nanomaterials
+displaying a controllable and reproducible SAR.",1902.10965v1
+2019-03-11,Vacancy mediated magnetization and healing of a graphene monolayer,"Vacancy-induced magnetization of a graphene layer is investigated by means of
+a first principle DFT method. Calculations of the formation energy and the
+magnetization by creating the different number of vacancies in a supercell show
+that a clustering with big number of vacancies in the cluster is rather
+favorable than that of isolated vacancies, homogeneously distributed in the
+layer. The magnetic moment of a cluster with big number of vacancies is shown
+to be not proportional with the vacancy concentration, which is in good
+agreement with the recent experimental results. Our studies support the idea
+that although the vacancies in a graphene create a magnetic moment, they do not
+produce a magnetic ordering. It is shown that although the Lieb's rule for the
+magnetization in a hexagonal structure violates, two-vacancies, including a
+di-vacancy, in the supercell generate quasi-localized state when they belong to
+the different sublattices, and instead two-vacancies generate an extended state
+when they belong to the same sublattices. Analytical investigation of the
+dynamics of carbon atom- and vacancy-concentrations according to the non-linear
+continuity equations shows that the vacancies, produced by irradiation at the
+middle of a graphene layer, migrate to the edge of the sample resulting in a
+specific {\it 'segregation'} of the vacancy concentration and self-healing of
+the graphene.",1903.04180v1
+2019-03-13,Wide-field Magnetic Field and Temperature Imaging using Nanoscale Quantum Sensors,"The simultaneous imaging of magnetic fields and temperature (MT) is important
+in a range of applications, including studies of carrier transport, solid-state
+material dynamics, and semiconductor device characterization. Techniques exist
+for separately measuring temperature (e.g., infrared (IR) microscopy,
+micro-Raman spectroscopy, and thermo-reflectance microscopy) and magnetic
+fields (e.g., scanning probe magnetic force microscopy and superconducting
+quantum interference devices). However, these techniques cannot measure
+magnetic fields and temperature simultaneously. Here, we use the exceptional
+temperature and magnetic field sensitivity of nitrogen vacancy (NV) spins in
+conformally-coated nanodiamonds to realize simultaneous wide-field MT imaging.
+Our ""quantum conformally-attached thermo-magnetic"" (Q-CAT) imaging enables (i)
+wide-field, high-frame-rate imaging (100 - 1000 Hz); (ii) high sensitivity; and
+(iii) compatibility with standard microscopes. We apply this technique to study
+the industrially important problem of characterizing multifinger gallium
+nitride high-electron-mobility transistors (GaN HEMTs). We spatially and
+temporally resolve the electric current distribution and resulting temperature
+rise, elucidating functional device behavior at the microscopic level. The
+general applicability of Q-CAT imaging serves as an important tool for
+understanding complex MT phenomena in material science, device physics, and
+related fields.",1903.05717v1
+2019-03-25,Self-gravitating magnetised tori around black holes in general relativity,"We investigate stationary, self-gravitating, magnetised disks (or tori)
+around black holes. The models are obtained by numerically solving the coupled
+system of the Einstein equations and the equations of ideal
+general-relativistic magnetohydrodynamics. The mathematical formulation and
+numerical aspects of our approach are similar to those reported in previous
+works modeling stationary self-gravitating perfect-fluid tori, but the
+inclusion of magnetic fields represents a new ingredient. Following previous
+studies of purely hydrodynamical configurations, we construct our models
+assuming Keplerian rotation in the disks and both spinning and spinless black
+holes. We focus on the case of a toroidal distribution of the magnetic field
+and build a large set of models corresponding to a wide range of values of the
+magnetisation parameter, starting with weakly magnetised disks and ending at
+configurations in which the magnetic pressure dominates over the thermal one.
+In all our models, the magnetic field affects the equilibrium structure of the
+torus mainly due to the magnetic pressure. In particular, an increasing
+contribution of the magnetic field shifts the location of the maximum of the
+rest-mass density towards inner regions of the disk. The total mass of the
+system and the angular momentum are affected by the magnetic field in a complex
+way, that depends on the black hole spin and the location of the inner radius
+of the disk. The non-linear dynamical stability of the solutions presented in
+this paper will be reported elsewhere.",1903.10408v1
+2019-03-29,Modulated rotating waves in the magnetized spherical Couette system,"We present a study devoted to a detailed description of modulated rotating
+waves (MRW) in the magnetized spherical Couette system. The set-up consists of
+a liquid metal confined between two differentially rotating spheres and
+subjected to an axially applied magnetic field. When the magnetic field
+strength is varied, several branches of MRW are obtained by means of three
+dimensional direct numerical simulations (DNS). The MRW originate from parent
+branches of rotating waves (RW) and are classified according to Rand's (Arch.
+Ration. Mech. Anal 79:1-37, 182) and Coughling & Marcus (J. Fluid Mech.
+234:1-18,1992) theoretical description. We have found relatively large
+intervals of multistability of MRW at low magnetic field, corresponding to the
+radial jet instability known from previous studies. However, at larger magnetic
+field, corresponding to the return flow regime, the stability intervals of MRW
+are very narrow and thus they are unlikely to be found without detailed
+knowledge of their bifurcation point. A careful analysis of the spatio-temporal
+symmetries of the most energetic modes involved in the different classes of MRW
+will allow in the future a comparison with the HEDGEHOG experiment, a
+magnetized spherical Couette device hosted at the Helmholtz-Zentrum
+Dresden-Rossendorf.",1904.00056v2
+2019-04-03,The impact of magnetic fields on cold streams feeding galaxies,"High redshift, massive halos are observed to have sustained, high star
+formation rates, which require that the amount of cold gas in the halo is
+continuously replenished. The cooling time scale for the hot virialized halo
+gas is too long to provide the source of cold gas. Supersonic, cold streams
+have been invoked as a mechanism for feeding massive halos at high redshift and
+deliver the cold gas required for continued star formation at the rates
+observed. This mechanism for replenishing the cold gas reservoir is motivated
+by some cosmological simulations. However, the cold streams are likely to be
+subject to the supersonic version of the Kelvin-Helmholtz instability (KHI),
+which eventually leads to stream disruption. Cosmological simulations have yet
+to obtain the spatial resolution required for understanding the detailed
+stability properties of cold streams. In this paper, we consider instead an
+idealized model of magnetized cold streams that we spatially resolve. Using
+linear theory we show how magnetic fields with dynamically important field
+strengths do not inhibit the KHI but rather enhance its growth rate. We perform
+nonlinear simulations of magnetized stream disruption and find that magnetic
+fields can nevertheless increase stream survival times by suppressing the
+mixing rate of cold gas with the circumgalactic medium. We find that magnetic
+fields can allow streams to survive $\sim 2-8$ times longer and, consequently,
+that streams $\sim 2-8$ times thinner can reach the central galaxy if the
+magnetic field strength is $\sim 0.3-0.8 \mu$G.",1904.02167v2
+2019-05-22,Ultra-low magnetic damping in Co 2 Mn-based Heusler compounds: promising materials for spintronic,"The prediction of ultra-low magnetic damping in Co 2 MnZ Heusler half-metal
+thin-film magnets is explored in this study and the damping response is shown
+to be linked to the underlying electronic properties. By substituting the Z
+elements in high crystalline quality films (Co 2 MnZ with Z=Si, Ge, Sn, Al, Ga,
+Sb), electronic properties such as the minority spin band gap, Fermi energy
+position in the gap and spin polarization can be tuned and the consequence on
+magnetization dynamics analyzed. The experimental results allow us to directly
+explore the interplay of spin polarization, spin gap, Fermi energy position and
+the magnetic damping obtained in these films, together with ab initio
+calculation predictions. The ultra-low magnetic damping coefficients measured
+in the range 4.1 10-4-9 10-4 for Co 2 MnSi, Ge, Sn, Sb are the lowest values
+obtained on a conductive layer and offers a clear experimental demonstration of
+theoretical predictions on Half-Metal Magnetic Heusler compounds and a pathway
+for future materials design.",1905.08987v1
+2019-05-29,The effect of internal magnetic field on collective flow in heavy ion collisions at intermediate energies,"The properties of nuclear matter under extreme conditions of high
+temperature, density and isospin-asymmetry have attracted wide attentions in
+recent years. At present, heavy ion reactions in combination with corresponding
+model simulations are one of the most important ways to investigate this
+subject. It is known that a strong magnetic field can be created in heavy ion
+collisions. However, its effect on the motion of charged particles is usually
+neglected in previous transport model simulations. In this work, within the
+Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, the temporal
+evolution and spatial distribution of the internal magnetic field are
+calculated. The magnetic field strength is found to reach about $eB\approx470$
+MeV$^{2}$ ($B\approx8\times10^{16}$ G) for Au+Au collisions at
+$E_{\text{lab}}$=1 GeV/nucleon with impact parameter of 7 fm. The magnetic
+field in Cu+Au collisions exhibits somewhat different spatial distribution from
+that in Au+Au collisions. The magnetic field is found to affect the directed
+flow of pions at forward and backward rapidities to some extent, dependent of
+the impact parameter and beam energy while the effect on the elliptic flow is
+small. This suggests that, because $\pi$ mesons produced in heavy ion
+collisions at intermediate energies are considered as a sensitive probe for the
+nuclear symmetry energy, it is necessary to consider the effect of the internal
+magnetic field.",1905.12492v1
+2019-06-18,Nuclear magnetic resonance spectroscopy with a superconducting flux qubit,"We theoretically analyze the performance of the nuclear magnetic resonance
+(NMR) spectroscopy with a superconducting flux qubit (FQ). Such NMR with the FQ
+is attractive because of the possibility to detect the relatively small number
+of nuclear spins in a local region ($\sim\mu$m) with low temperatures ($\sim$
+mK) and low magnetic fields ($\sim$ mT), in which other types of quantum
+sensing schemes cannot easily access. A sample containing nuclear spins is
+directly attached on the FQ, and the FQ is used as a magnetometer to detect
+magnetic fields from the nuclear spins. Especially, we consider two types of
+approaches to NMR with the FQ. One of them is to use spatially inhomogeneous
+excitations of the nuclear spins, which are induced by a spatially asymmetric
+driving with radio frequency~(RF) pulses. Such an inhomogeneity causes a change
+in the DC magnetic flux penetrating a loop of the FQ, which can be detected by
+a standard Ramsey measurement on the FQ. The other approach is to use a
+dynamical decoupling on the FQ to measure AC magnetic fields induced by Larmor
+precession of the nuclear spins. In this case, neither a spin excitation nor a
+spin polarization is required since the signal comes from fluctuating magnetic
+fields of the nuclear spins. We calculate the minimum detectable density
+(number) of the nuclear spins for the FQ with experimentally feasible
+parameters. We show that the minimum detectable density (number) of the nuclear
+spins with these approaches is around $10^{21}$ /cm$^3$ ($10^8$) with an
+accumulation time of a second.",1906.07386v1
+2019-07-11,Analysis of azimuthal magnetorotational instability of rotating MHD flows and Tayler instability via an extended Hain-Lust equation,"We consider a differentially rotating flow of an incompressible electrically
+conducting and viscous fluid subject to an external axial magnetic field and to
+an azimuthal magnetic field that is allowed to be generated by a combination of
+an axial electric current external to the fluid and electrical currents in the
+fluid itself. In this setting we derive an extended version of the celebrated
+Hain-Lust differential equation for the radial Lagrangian displacement that
+incorporates the effects of the axial and azimuthal magnetic fields,
+differential rotation, viscosity, and electrical resistivity. We apply the
+Wentzel-Kramers-Brillouin method to the extended Hain-Lust equation and derive
+a new comprehensive dispersion relation for the local stability analysis of the
+flow to three-dimensional disturbances. We confirm that in the limit of low
+magnetic Prandtl numbers, in which the ratio of the viscosity to the magnetic
+diffusivity is vanishing, the rotating flows with radial distributions of the
+angular velocity beyond the Liu limit, become unstable subject to a wide
+variety of the azimuthal magnetic fields, and so is the Keplerian flow. In the
+analysis of the dispersion relation we find an evidence of a new
+long-wavelength instability which is caught also by the numerical solution of
+the boundary value problem for a magnetized Taylor-Couette flow.",1907.05488v3
+2019-07-17,Negative-vector-chirality 120$^\circ$ spin structure in the defect- and distortion-free quantum kagome antiferromagnet YCu$_3$(OH)$_6$Cl$_3$,"The magnetic ground state of the ideal quantum kagome antiferromagnet (QKA)
+has been a long-standing puzzle, mainly because perturbations to the
+nearest-neighbor isotropic Heisenberg Hamiltonian can lead to various
+fundamentally different ground states. Here we investigate a recently
+synthesized QKA representative YCu$_3$(OH)$_6$Cl$_3$, where perturbations
+commonly present in real materials, like lattice distortion and intersite ion
+mixing, are absent. Nevertheless, this compound enters a long-range
+magnetically ordered state below $T_N=15$ K. Our powder neutron diffraction
+experiment reveals that its magnetic structure corresponds to a coplanar
+$120^\circ$ state with negative vector spin chirality. The ordered magnetic
+moments are suppressed to $0.42(2)\mu_B$, which is consistent with the
+previously detected spin dynamics persisting to the lowest experimentally
+accessible temperatures. This indicates either a coexistence of magnetic order
+and disorder or the presence of strong quantum fluctuations in the ground state
+of YCu$_3$(OH)$_6$Cl$_3$. The origin of the magnetic order is sought in terms
+of Dzyaloshinskii-Moriya magnetic anisotropy and further-neighbor isotropic
+exchange interactions.",1907.07489v2
+2019-09-10,Magnetic phase diagram of a spin S=1/2 antiferromagnetic two-leg ladder in the presence of modulated along legs Dzyaloshinskii-Moriya interaction,"We study the ground-state magnetic phase diagram of a spin S=1/2
+antiferromagnetic two-leg ladder in the presence of period two lattice units
+modulated, Dzyaloshinskii-Moriya (DM) interaction along the legs. We consider
+the case of collinear DM vectors and strong rung exchange and magnetic field.
+In this limit we map the initial ladder model onto the effective spin
+$\sigma=1/2$ XXZ chain and study the latter using the continuum-limit
+bosonization approach. We identified four quantum phase transitions and
+corresponding critical magnetic fields, which mark transitions from the spin
+gapped regimes into the gapless quantum spin-liquid regimes. In the gapped
+phases the magnetization curve of the system shows plateaus at magnetisation
+M=0 and to its saturation value per rung M=1. We have shown that the very
+presence of alternating DM interaction leads to opening of a gap in the
+excitation spectrum at magnetization M=0.5. The width of the magnetization
+plateau at M=0.5, is determined by the associated with the dynamical generation
+of a gap in the spectrum is calculated and is shown that its length scales as
+$(D_{0}D_{1}/J^{2})^{\alpha}$ where $D_{0},D_{1}$ are uniform and staggered
+components of the DM term, $J$ is the intraleg exchange and $\alpha \leq 3/4$
+and weakly depends on the DM couplings.",1909.04618v1
+2019-10-08,Holographic Vector Field Electron Tomography of Three-Dimensional Nanomagnets,"Complex 3D magnetic textures in nanomagnets exhibit rich physical properties,
+for example in their dynamic interaction with external fields and currents, and
+play an increasing role for current technological challenges such as
+energy-efficient memory devices. To study these magnetic nanostructures
+including their dependency on geometry, composition and crystallinity, a 3D
+characterization of the magnetic field with nanometer spatial resolution is
+indispensable. Here we show how holographic vector field electron tomography
+can reconstruct all three components of magnetic induction as well as the
+electrostatic potential of a Co/Cu nanowire with sub 10\,nm spatial resolution.
+We address the workflow from acquisition, via image alignment to holographic
+and tomographic reconstruction. Combining the obtained tomographic data with
+micromagnetic considerations we derive local key magnetic characteristics, such
+as magnetization current or exchange stiffness, and demonstrate how
+magnetization configurations, such as vortex states in the Co-disks, depend on
+small structural variations of the as-grown nanowire.",1910.03430v1
+2019-10-29,Imaging and control of critical spin fluctuations in two-dimensional magnets,"Strong spin fluctuations are expected near the thermodynamic critical point
+of a continuous magnetic phase transition. Such critical spin fluctuations are
+highly correlated and in principle can occur at any time- and length-scales;
+they govern critical phenomena and potentially can drive new phases. Although
+theoretical studies have been made for decades, direct observation of critical
+spin fluctuations remains elusive. The recent discovery of two-dimensional (2D)
+layered magnets, in which spin fluctuations significantly modify magnetic
+properties as compared to their bulk counterparts and integration into
+heterostructures and devices can be easily achieved, provides an ideal platform
+to investigate and harness critical spin phenomena. Here we develop a fast and
+sensitive magneto-optical imaging microscope to achieve wide-field, real-time
+monitoring of critical spin fluctuations in single-layer CrBr3, which is a 2D
+ferromagnetic insulator. We track the critical phenomena directly from the
+fluctuation correlations and observe both slowing-down dynamics and enhanced
+correlation length. Through real-time feedback control of critical spin
+fluctuations, we further achieve switching of magnetic states solely by
+electrostatic gating without applying a magnetic field or a Joule current. The
+ability to directly image and control critical spin fluctuations in 2D magnets
+opens up exciting opportunities to explore critical phenomena and develop
+applications in nanoscale engines and information science.",1910.13023v1
+2019-12-11,Magnetic field effects on electron transport in nanoring with orbital Rashba coupling,"We study the effects of a Zeeman magnetic field on the electron transport of
+one-dimensional quantum rings which are marked by electronic states with
+$d-$orbital symmetry in the presence of spin-orbit and orbital Rashba
+couplings. By considering phase-coherent propagation, we analyse the geometric
+Aharonov-Anandan (AA) phase of the channels which is acquired in a closed path,
+by demonstrating that the orbital polarization can influence the electronic
+transport when amplitude and magnetic field directions are varied. We explore
+all the possible cases for the injection of electrons at various energies in
+the regime of low electron filling. The magnetic field can allow the selection
+of only one channel where the transmission is uniquely affected by the AA
+phase. Conversely, when more orbital channels are involved there is also a
+dynamical contribution that lead to oscillations in the transmission as the
+magnetic field is varied. In particular, the transmission is chiral when the
+energy states are close to the absolute minimum of the energy bands. Instead,
+when an interference between the channels occurs the orbital and spin
+contributions tend to balance each other with the increasing of the magnetic
+field amplitude resulting in a trivial AA phase. This saturation effect does
+not occur in the high magnetic field regime when orbital and spin properties of
+the channels exhibit sharp variations with direct consequences on the
+transport.",1912.05602v1
+2020-01-15,Generation of Solenoidal Modes and Magnetic Fields in Turbulence Driven by Compressive Driving,"We perform numerical simulations of hydrodynamic (HD) and magnetohydrodynamic
+(MHD) turbulence driven by compressive driving to study generation of
+solenoidal velocity component and small-scale magnetic field. We mainly focus
+on the effects of mean magnetic field ($B_0$) and the sonic Mach number
+($M_s$). We also consider two different driving schemes in terms of correlation
+timescale of forcing vectors: a finite-correlated driving and a
+delta-correlated driving. The former has a longer correlation timescale of
+forcing vectors, which is comparable to large-eddy turnover time, than the
+latter. Our findings are as follows. First, when we fix the value of $B_0$, the
+level of solenoidal velocity component after saturation increases as $M_s$
+increases. A similar trend is observed for generation of magnetic field when
+$B_0$ is small. Second, when we fix the value of $M_s$, HD and MHD simulations
+result in similar level of the solenoidal component when $B_0$ $\lesssim$ 0.2
+(or Alfven Mach number of $\sim$ 5). However, the level increases when $B_0$
+$\gtrsim$ 0.2. Roughly speaking, the magnetic energy density after saturation
+is a linearly increasing function of $B_0$ irrespective of $M_s$. Third,
+generation of solenoidal velocity component is not sensitive to numerical
+resolution, but that of magnetic energy density is mildly sensitive. Lastly,
+when initial conditions are same, the finite-correlated driving always produces
+more solenoidal velocity and small-scale magnetic field components than the
+delta-correlated driving. We additionally analyze the vorticity equation to
+understand why higher $M_s$ and $B_0$ yield larger quantity of the solenoidal
+velocity component.",2001.05154v1
+2020-02-20,Ultrafast ratchet dynamics of skyrmion by defect engineering under gigahertz magnetic fields,"The novel ratchet motion of magnetic skyrmions driven by microwave magnetic
+fields, with the motion direction and speed tunable by field parameters,
+provides a promising route to drive magnetic skyrmions in materials with poor
+conductivity. However, as an indirect motion, skyrmion ratchet motion speed is
+generally low in comparison with the direct motions driven by current. Toward
+practical applications, it is important to ask if there are mechanisms to
+realize ultrafast ratchet motion of magnetic skyrmions and how such novel
+motion can be integrated into racetrack-type skyrmion devices. In this work, we
+explore the effects of defects and edges on the ratchet motion of magnetic
+skyrmions under time-varying magnetic fields in GHz. We demonstrate that the
+ratchet motion of skyrmion is not only guided along the defect tracks or edges,
+but also with a remarkable speed-up (with a factor over ten) compared with that
+in the bulk region. The skyrmion ratchet motion speed reaches 100 m/s along a
+straight defect track/edge and 10^9 rad/s along a circular edge under a field
+of ~50 mT, comparable to those direct motions driven by currents. Moreover, the
+skyrmion ratchet motion along the defect track/edge can be facilely controlled
+by the field and defect parameters. Analysis based on time-averaged Thiele
+equation of skyrmion verifies that such a speed-up effect is due to the
+increased time-averaged driving force perpendicular to the skyrmion motion when
+it approaches the defect track or edge, analogous to that discovered in direct
+motions driven by currents.",2002.08865v2
+2020-03-02,Spin-caloritronic transport in hexagonal graphene nanoflakes,"We investigate the spin-dependent thermoelectric effect of graphene flakes
+with magnetic edges in the ballistic regime. Employing static, respectively,
+dynamic mean-field theory we first show that magnetism appears at the zigzag
+edges for a window of Coulomb interactions that increases significantly with
+increasing flake size. We then use the Landauer formalism in the framework of
+the non-equilibrium Green's function method to calculate the spin and charge
+currents in magnetic hexagonal graphene flakes by varying the temperature of
+the junction for different flake sizes. While in non-magnetic gated graphene
+the temperature gradient drives a charge current, we observe a significant spin
+current for hexagonal graphene flakes with magnetic zigzag edges. Specifically,
+we show that in the ""meta"" configuration of a hexagonal flake subject to weak
+Coulomb interactions, a pure spin current can be driven just by a temperature
+gradient in a temperature range that is promising for device applications.
+Bigger flakes are found to yield a bigger window of Coulomb interactions where
+such spin currents are induced by the magnetic zigzag edges, and larger values
+of the current.",2003.01139v2
+2020-03-06,Mixed topology ring states for Hall effect and orbital magnetism in skyrmions of Weyl semimetals,"Skyrmion lattices as a novel type of chiral spin states are attracting
+increasing attention, owing to their peculiar properties stemming from
+real-space topological properties. At the same time, the properties of magnetic
+Weyl semimetals with complex $k$-space topology are moving into the focus of
+research in spintronics. We consider the Hall transport properties and orbital
+magnetism of skyrmion lattices imprinted in topological semimetals, by
+employing a minimal model of a 2D mixed Weyl semimetal which, as a function of
+the magnetization direction, exhibits two Chern insulator phases separated by a
+Weyl state for an an in-plane magnetization direction. We find that while the
+orbital magnetization is topologically robust and Hall transport properties are
+very sensitive to the details of the spin distribution in accordance to the
+behavior expected from the recently discovered chiral Hall effect[1], their
+behavior in the region of the Chern insulator gap is largely determined by the
+properties of the so-called mixed topology ring states, emerging in domain
+walls that separate the skyrmion core from the ferromagnetic background. In
+particular, we show that these localized ring states possess a given orbital
+chirality which reverses sign as a function of the skyrmion radius, thereby
+mediating a smooth switching dynamics of the orbital magnetization of the
+skyrmion lattice. We speculate that while the emergent ring states can possibly
+play a role in the physics of Majorana states, probing their properties
+experimentally can provide insights into the details of skyrmionic spin
+structures.",2003.03243v2
+2020-04-06,Spin Hall magnetoresistance in antiferromagnetic insulators,"Antiferromagnetic materials promise improved performance for spintronic
+applications, as they are robust against external magnetic field perturbations
+and allow for faster magnetization dynamics compared to ferromagnets. The
+direct observation of the antiferromagnetic state, however, is challenging due
+to the absence of a macroscopic magnetization. Here, we show that the spin Hall
+magnetoresistance (SMR) is a versatile tool to probe the antiferromagnetic spin
+structure via simple electrical transport experiments by investigating the
+easy-plane antiferromagnetic insulators $\alpha$-Fe2O3 (hematite) and NiO in
+bilayer heterostructures with a Pt heavy metal top electrode. While rotating an
+external magnetic field in three orthogonal planes, we record the longitudinal
+and the transverse resistivities of Pt and observe characteristic resistivity
+modulations consistent with the SMR effect. We analyze both their amplitude and
+phase and compare the data to the results from a prototypical collinear
+ferrimagnetic Y3Fe5O12/Pt bilayer. The observed magnetic field dependence is
+explained in a comprehensive model, based on two magnetic sublattices and
+taking into account magnetic field-induced modifications of the domain
+structure. Our results show that the SMR allows us to understand the spin
+configuration and to investigate magnetoelastic effects in antiferromagnetic
+multi-domain materials. Furthermore, in $\alpha$-Fe2O3/Pt bilayers, we find an
+unexpectedly large SMR amplitude of $2.5 \times 10^{-3}$, twice as high as for
+prototype Y3Fe5O12/Pt bilayers, making the system particularly interesting for
+room-temperature antiferromagnetic spintronic applications.",2004.02639v2
+2020-05-11,Skyrmion confinement and dynamics in tracks patterned with magnetic anisotropy: theory and simulations,"Skyrmion is a topologically protected spin texture excited in magnetic thin
+films. The radii of skyrmions are typically 10-100 nm. Because of the size, the
+skyrmion is expected to be a candidate for memory and novel-device usages. To
+realize the futuristic devices that will be using the skyrmion circuit, the
+tracks which guide the motion of skyrmions are needed. The tracks patterned
+with differences in the magnetic-anisotropy energy are well-paved without a
+potential pocket, whereas the tracks carved out of magnetic films have the
+potential pockets at corners due to the demagnetizing field. Therefore, the
+tracks patterned with the magnetic anisotropy plays a key role in making the
+skyrmion circuits. The experiment along this idea has been conducted for the
+hub and bent tracks. However, we have little known the motion of skyrmions in
+these tracks. This work aims to identify the forces acting between skyrmions
+and walls of the tracks. The static force on a skyrmion can be expressed as
+minus the gradient of the potential energy caused by the magnetic-anisotropy
+undulation. The potential can be estimated numerically, modeling the shape of
+skyrmions with their radii and domain wall widths. We find that the forces
+depend not only on the distance from the wall but also on the shape of
+skyrmions. We have also performed micromagnetic simulations where the Magnus
+force and the acceleration by the magnetic-anisotropy gradient are taken into
+account as well as the force by the walls. The simulation results show good
+agreement with those calculated from the modeled skyrmions.",2005.04860v1
+2020-07-27,Estimating Satellite Orbital Drag During Historical Magnetic Superstorms,"Understanding extreme space weather events is of paramount importance in
+efforts to protect technological systems in space and on the ground.
+Particularly in the thermosphere, the subsequent extreme magnetic storms can
+pose serious threats to low-Earth orbit (LEO) spacecraft by intensifying errors
+in orbit predictions. Extreme magnetic storms (minimum Dst $\leq$ --250 nT) are
+extremely rare: only 7 events occurred during the era of spacecraft with
+high-level accelerometers such as CHAMP (CHAllenge Mini-satellite Payload) and
+GRACE (Gravity Recovery And Climate experiment), and none with minimum Dst
+$\leq$ --500 nT, here termed magnetic superstorms. Therefore, current knowledge
+of thermospheric mass density response to superstorms is very limited. Thus, in
+order to advance this knowledge, four known magnetic superstorms in history,
+i.e., events occurring before CHAMP's and GRACE's commission times, with
+complete datasets, are used to empirically estimate density enhancements and
+subsequent orbital drag. The November 2003 magnetic storm (minimum Dst = --422
+nT), the most extreme event observed by both satellites, is used as the
+benchmark event. Results show that, as expected, orbital degradation is more
+severe for the most intense storms. Additionally, results clearly point out
+that the time duration of the storm is strongly associated with storm-time
+orbital drag effects, being as important as or even more important than storm
+intensity itself. The most extreme storm-time decays during CHAMP/GRACE-like
+sample satellite orbits estimated for the March 1989 magnetic superstorm show
+that long-lasting superstorms can have highly detrimental consequences for the
+orbital dynamics of satellites in LEO.",2007.13892v1
+2020-08-17,Magnetorotational core collapse of possible GRB progenitors. III. Three-dimensional models,"We explore the influence of non-axisymmetric modes on the dynamics of the
+collapsed core of rotating, magnetized high-mass stars in three-dimensional
+simulations of a rapidly rotating star with an initial mass of $M_{ZAMS}$ = 35
+solar masses endowed with four different pre-collapse configurations of the
+magnetic field, ranging from moderate to very strong field strength and
+including the field predicted by the stellar evolution model. The model with
+the weakest magnetic field achieves shock revival due to neutrino heating in a
+gain layer characterized by a large-scale, hydrodynamic m = 1 spiral mode.
+Later on, the growing magnetic field of the proto-neutron star launches weak
+outflows into the early ejecta. Their orientation follows the evolution of the
+rotational axis of the proto-neutron star, which starts to tilt from the
+original orientation due to the asymmetric accretion flows impinging on its
+surface. The models with stronger magnetization generate mildly relativistic,
+magnetically driven polar outflows propagating over a distance of $10^4$ km
+within a few 100 ms. These jets are stabilized against disruptive
+non-axisymmetric instabilities by their fast propagation and by the shear of
+their toroidal magnetic field. Within the simulation times of around 1 s, the
+explosions reach moderate energies and the growth of the proto-neutron star
+masses ceases at values substantially below the threshold for black hole
+formation, which, in combination with the high rotational energies, might
+suggest a possible later proto-magnetar activity.",2008.07205v2
+2020-09-04,NV-Diamond Magnetic Microscopy using a Double Quantum 4-Ramsey Protocol,"We introduce a double quantum (DQ) 4-Ramsey measurement protocol that enables
+wide-field magnetic imaging using nitrogen vacancy (NV) centers in diamond,
+with enhanced homogeneity of the magnetic sensitivity relative to conventional
+single quantum (SQ) techniques. The DQ 4-Ramsey protocol employs
+microwave-phase alternation across four consecutive Ramsey (4-Ramsey)
+measurements to isolate the desired DQ magnetic signal from any residual SQ
+signal induced by microwave pulse errors. In a demonstration experiment
+employing a 1-$\mu$m-thick NV layer in a macroscopic diamond chip, the DQ
+4-Ramsey protocol provides volume-normalized DC magnetic sensitivity of
+$\eta^\text{V}=34\,$nTHz$^{-1/2} \mu$m$^{3/2}$ across a $125\,\mu$m$
+\,\times\,125\,\mu $m field of view, with about 5$\times$ less spatial
+variation in sensitivity across the field of view compared to a SQ measurement.
+The improved robustness and magnetic sensitivity homogeneity of the DQ 4-Ramsey
+protocol enable imaging of dynamic, broadband magnetic sources such as
+integrated circuits and electrically-active cells.",2009.02371v2
+2020-09-16,Impact of magnetic field on neutrino-matter interactions in core-collapse supernova,"We explore the impact of magnetic field on neutrino-matter interactions in
+core-collapse supernova. We first derive the modified source terms for
+neutrino-nucleon scattering and neutrino absorption and emission processes in
+the moment formalism. Then we perform full relativistic three-dimensional,
+magnetorotational core-collapse supernova simulations of a 20 $M_\odot$ star
+with spectral neutrino transport. Our simulations treat self-consistently the
+parity violation effects of weak interaction in the presence of external
+magnetic field. The result shows a significant global asymmetry, mostly
+confined in the proto-neutron star, with clearly reflecting the magnetic field
+structure. The asymmetric property arises from two factors: the angle between
+the neutrino flux and magnetic field, and the term, which is parallel to the
+magnetic field and is also proportional to the deviation of distribution
+function of neutrinos from thermal equilibrium. The typical correction value
+amounts to $\sim1$ % relative to the total neutrino-matter interaction rate for
+the magnetic field strength of $\sim 10^{15-16}$~G. Although these asymmetric
+properties do not immediately affect the explosion dynamics, our results imply
+that they would be significant once the neutrinos diffuse out the proto-neutron
+star core carrying those asymmetries away. We also show that, during our
+simulation time of $\sim370$ ms after bounce, our results indicate that the
+correction value due to the modified inelastic scattering process dominates
+over that of the modified neutrino absorption and emission process.",2009.07733v2
+2020-09-20,Inverse transfer of magnetic helicity in direct numerical simulations of compressible isothermal turbulence: scaling laws,"The inverse transfer of magnetic helicity is investigated through direct
+numerical simulations of large-scale-mechanically-driven turbulent flows in the
+isothermal ideal magnetohydrodynamics (MHD) framework. The mechanical forcing
+is either purely solenoidal or purely compressive and the turbulent
+steady-states considered exhibit root mean square (RMS) Mach numbers 0.1
+$\lesssim$ M $\lesssim$ 11. A continuous small-scale electromotive forcing
+injects magnetic helical fluctuations, which lead to the build-up of ever
+larger magnetic structures. Spectral scaling exponents are observed which, for
+low Mach numbers, are consistent with previous research done in the
+incompressible case. Higher compressibility leads to flatter magnetic helicity
+scaling exponents. The deviations from the incompressible case are
+comparatively small for solenoidally-driven turbulence, even at high Mach
+numbers, as compared to those for compressively-driven turbulence, where strong
+deviations are already visible at relatively mild RMS Mach numbers M $\gtrsim$
+3. Compressible effects can thus play an important role in the inverse transfer
+of magnetic helicity, especially when the turbulence drivers are rather
+compressive. Theoretical results observed in the incompressible case can,
+however, be transferred to supersonic turbulence by an appropriate change of
+variables, using the Alfv\'en velocity in place of the magnetic field.",2009.09374v1
+2020-09-14,Magnetohydrodynamic Simulation of Magnetic Null-point Reconnections and Coronal dimmings during the X2.1 flare in NOAA AR 11283,"The magnetohydrodynamics of active region NOAA 11283 is simulated using an
+initial non-force-free magnetic field extrapolated from its photospheric vector
+magnetogram. We focus on the magnetic reconnections at a magnetic null point
+that participated in the X2.1 flare on 2011 September 6 around 22:21 UT
+(SOL2011-09-06T22:21X2.1) followed by the appearance of circular flare ribbons
+and coronal dimmings. The initial magnetic field from extrapolation displays a
+three-dimensional (3D) null topology overlying a sheared arcade. Prior to the
+flare, magnetic loops rise due to the initial Lorentz force, and reconnect at
+the 3D null, leading to expansion and loss of confined plasma that produce the
+observed pre-flare coronal dimmings. Further, the simulated dynamics documents
+the transfer of twist from the arcade to the overlying loops through
+reconnections, developing a flux rope. The non-parallel field lines comprising
+the rope and lower-lying arcades form an X-type geometry. Importantly, the
+simultaneous reconnections at the 3D null and the X-type geometry can explain
+the observed circular and parallel flare ribbons. Reconnections at the 3D null
+transform closed inner spine field lines into open field lines of the outer
+spine. The footpoints of these open field lines correspond to a ring-shaped
+coronal dimming region, tracing the dome. Further, the flux rope bifurcates
+because of these reconnections which also results in the generation of open
+magnetic field lines. The plasma loss along the open field lines can
+potentially explain the observed coronal dimming.",2009.11109v1
+2020-10-13,Magnetic Helicity Flux across Solar Active Region Photospheres: I. Hemispheric Sign Preference in Solar Cycle 24,"A hemispheric preference in the dominant sign of magnetic helicity has been
+observed in numerous features in the solar atmosphere: i.e.,
+left-handed/right-handed helicity in the northern/southern hemisphere. The
+relative importance of different physical processes which may contribute to the
+observed hemispheric sign preference (HSP) of magnetic helicity is still under
+debate. Here, we estimate magnetic helicity flux ($dH/dt$) across the
+photospheric surface for 4,802 samples of 1,105 unique active regions (ARs)
+that appeared over an 8-year period from 2010 to 2017 during solar cycle 24,
+using photospheric vector magnetic field observations by the Helioseismic and
+Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The
+estimates of $dH/dt$ show that 63% and 65% of the investigated AR samples in
+the northern and southern hemispheres, respectively, follow the HSP. We also
+find a trend that the HSP of $dH/dt$ increases from ~50-60% up to ~70-80% as
+ARs (1) appear at the earlier inclining phase of the solar cycle or higher
+latitudes; (2) have larger values of $|dH/dt|$, the total unsigned magnetic
+flux, and the average plasma flow speed. These observational findings support
+the enhancement of the HSP mainly by the Coriolis force acting on a buoyantly
+rising and expanding flux tube through the turbulent convection zone. In
+addition, the differential rotation on the solar surface as well as the
+tachocline $\alpha$-effect of flux-transport dynamo may reinforce the HSP for
+ARs at higher latitudes.",2010.06134v1
+2020-10-26,Structure and magnetism of the skyrmion hosting family GaV$_4$S$_{8-y}$Se$_y$ with low levels of substitutions between $0 \leq y \leq 0.5$ and $7.5 \leq y\leq 8$,"Polycrystalline members of the GaV$_4$S$_{8-y}$Se$_y$ family of materials
+with small levels of substitution between $0 \leq y \leq 0.5$ and $7.5 \leq
+y\leq 8$ have been synthesized in order to investigate their magnetic and
+structural properties. Substitutions to the skyrmion hosting parent compounds
+GaV$_4$S$_8$ and GaV$_4$Se$_8$, are found to suppress the temperature of the
+cubic to rhombohedral structural phase transition that occurs in both end
+compounds and to create a temperature region around the transition where there
+is a coexistence of these two phases. Similarly, the magnitude of the
+magnetization and temperature of the magnetic transition are both suppressed in
+all substituted compounds until a glassy-like magnetic state is realized. There
+is evidence from the $ac$ susceptibility data that skyrmion lattices with
+similar dynamics to those in GaV$_4$S$_8$ and GaV$_4$Se$_8$ are present in
+compounds with very low levels of substitution, $0 < y< 0.2$ and $7.8 < y < 8$,
+however, these states vanish at higher levels of substitution. The magnetic
+properties of these substituted materials are affected by the substitution
+altering exchange pathways and resulting in the creation of increasingly
+disordered magnetic states.",2010.13450v1
+2020-11-02,Signatures of magnetostriction and spin-phonon coupling in magnetoelectric hexagonal 15R-BaMnO3,"Spin-phonon coupling, the interaction of spins with surrounding lattice is a
+key parameter to understand the underlying physics of multiferroics and
+engineer their magnetization dynamics. Elementary excitations in multiferroic
+materials are strongly influenced by spin-phonon interaction, making Raman
+spectroscopy a unique tool to probe these coupling(s). Recently, it has been
+suggested that the dielectric and magnetic properties of 15R-type hexagonal
+BaMnO3 are correlated through the spin-lattice coupling. Here, we report the
+observation of an extensive renormalization of the Raman spectrum of 15R-BaMnO3
+at 230 K, 280 K, and 330 K. Magnetic measurements reveal the presence of a
+long-range and a short-range magnetic ordering in 15R-BaMnO3 at 230 K and 330
+K, respectively. The Raman spectrum shows the appearance of new Raman modes in
+the magnetically ordered phases. Furthermore, an additional Raman phonon
+appears below ~ 280 K, possibly arising from a local lattice-distortion due to
+the displacement of Mn-ions, that exhibits anomalous shift with temperature.
+The origin of the observed renormalization and phonon anomalies in Raman
+spectra are discussed based on the evidences from temperature- and
+magnetic-field-dependent Raman spectra, temperature-dependent x-ray
+diffraction, magnetization, and specific heat measurements. Our results
+indicate the presence of magnetostriction and spin-phonon coupling in
+15R-BaMnO3 thus suggesting that the optical phonons are strongly correlated to
+its magnetoelectric properties.",2011.00757v1
+2020-11-05,Large-Scale Vortex Motion and Multiple Plasmoid Ejection Due to Twisting Prominence Threads and Associated Reconnection,"We analyze the characteristics of a quiescent polar prominence using the
+Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory
+(SDO). Initially, small-scale barb-like structures are evident on the solar
+disk, which firstly grow vertically and thereafter move towards the south-west
+limb. Later, a spine connects these barbs and we observe apparent rotating
+motions in the upper part of the prominence. These apparent rotating motions
+might play an important role for the evolution and growth of the filament by
+transferring cool plasma and magnetic twist. The large-scale vortex motion is
+evident in the upper part of the prominence, and consists of a swirl-like
+structure within it. The slow motion of the footpoint twists the legs of the
+prominence due to magnetic shear, causing two different kinds of magnetic
+reconnection. The internal reconnection is initiated by a resistive
+tearing-mode instability, which leads to the formation of multiple plasmoids in
+the elongated current sheet. The estimated growth rate was found to be
+0.02--0.05. The magnetic reconnection heats the current sheet for a small
+duration. However, most of the energy release due to magnetic reconnection is
+absorbed by the surrounding cool and dense plasma and used to accelerate the
+plasmoid ejection. The multiple plasmoid ejections destroy the current sheet.
+Therefore, the magnetic arcades collapse near the X-point. Oppositely directed
+magnetic arcades may reconnect with the southern segment of the prominence and
+an elongated thin current sheet is formed. This external reconnection drives
+prominence eruption.",2011.02950v1
+2020-11-19,Coronal heating and solar wind formation in quiet Sun and coronal holes: a unified scenario,"Coronal holes (CHs) are darker than quiet Sun (QS) when observed in coronal
+channels. This study aims to understand the similarities and differences
+between CHs and QS in the transition region using the \ion{Si}{4}~1394~{\AA}
+line recorded by the Interface Region Imaging Spectrograph (IRIS) by
+considering the distribution of magnetic field measured by the Helioseismic and
+Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We find
+that \ion{Si}{4} intensities obtained in CHs are lower than those obtained in
+QS for regions with identical magnetic flux densities. Moreover, the difference
+in intensities between CHs and QS increases with increasing magnetic flux. For
+the regions with equal magnetic flux density, QS line profiles are more
+redshifted than those measured in CHs. Moreover, the blue shifts measured in
+CHs show an increase with increasing magnetic flux density unlike in the QS.
+The non-thermal velocities in QS, as well as in CHs, show an increase with
+increasing magnetic flux. However, no significant difference was observed in QS
+and CHs, albeit a small deviation at small flux densities. Using these results,
+we propose a unified model for the heating of the corona in the QS and in CHs
+and the formation of the solar wind.",2011.09803v1
+2020-11-23,Asymmetric depinning of chiral domain walls in ferromagnetic trilayers,"We show that the coupling between two ferromagnetic layers separated by a
+nonmagnetic spacer can be used to control the depinning of domain walls and
+induce unidirectional domain wall propagation. We investigated CoFeB/Ti/CoFeB
+trilayers where the easy axis of the magnetization of the top CoFeB layer is
+out-of-plane and that of the bottom layer is in-plane. Using Magneto-optic Kerr
+effect microscopy, we find that the depinning of a domain wall in the
+perpendicularly magnetized CoFeB layer is influenced by the orientation of the
+magnetization of the in-plane layer, which gives rise to a field-driven
+asymmetric domain expansion. This effect occurs due to the magnetic coupling
+between the internal magnetization of the domain wall and the magnetization of
+the in-plane CoFeB layer, which breaks the symmetry of up-down and down-up
+homochiral N\'eel domain walls in the perpendicular CoFeB layer. Micromagnetic
+simulations support these findings by showing that the interlayer coupling
+either opposes or favors the Dzyaloshinskii-Moriya interaction in the domain
+wall, thereby generating an imbalance in the depinning fields. This effect also
+allows for artificially controlling the chirality and dynamics of domain walls
+in magnetic layers lacking a strong Dzyaloshinskii-Moriya interaction.",2011.11290v1
+2021-01-01,Superparamagnetic dynamics and blocking transition in Fe$_3$O$_4$ nanoparticles probed by vibrating sample magnetometry and muon spin relaxation,"The magnetic properties of Fe$_3$O$_4$ nanoparticle assemblies have been
+investigated in detail through a combination of vibrating sample magnetometry
+and muon spin relaxation ($\mu$SR) techniques. Two samples with average
+particle sizes of 5 nm and 20 nm, respectively, were studied. For both samples,
+the magnetometry and $\mu$SR results exhibit clear signatures of the
+superparmagnetic state at high temperature and the magnetically blocked state
+at low temperature. The $\mu$SR data demonstrate that the transition from the
+superparamagnetic to the blocked state occurs gradually throughout the sample
+volume over a broad temperature range due to the finite particle size
+distribution of each sample. The transition occurs between approximately 3 K
+and 45 K for the 5 nm sample and 150 K and 300 K for the 20 nm sample. The
+magnetometry and $\mu$SR data are further analyzed to yield estimates of
+microscopic magnetic parameters including the nanoparticle spin-flip activation
+energy $E_A$, magnetic anisotropy $K$, and intrinsic nanoparticle spin reversal
+attempt time $\tau_0$. These results highlight the complementary information
+about magnetic nanoparticles that can be obtained by bulk magnetic probes such
+as magnetometry and local magnetic probes such as $\mu$SR.",2101.00258v1
+2021-01-11,Current-driven domain wall dynamics in ferrimagnetic Ni-doped Mn4N films : very large domain wall velocities and reversal of motion direction across the magnetic compensation point,"Spin-transfer torque (STT) and spin-orbit torque (SOT) are spintronic
+phenomena allowing magnetization manipulation using electrical currents. Beyond
+their fundamental interest, they allow developing new classes of magnetic
+memories and logic devices, in particular based on domain wall (DW) motion. In
+this work, we report the study of STT driven DW motion in ferrimagnetic
+manganese nickel nitride (Mn4-xNixN) films, in which a fine adjustment of the
+Ni content allows setting the magnetic compensation at room temperature. The
+reduced magnetization, combined with the large spin polarization of conduction
+electrons, strongly enhances the STT so that domain wall velocities approaching
+3000 m/s can be obtained for Ni compositions close to the compensation point.
+In addition, a reversal of the domain wall motion direction is observed when
+the magnetic compensation composition is crossed. This striking feature,
+related to the change of direction of the spin polarization with respect to
+that of the net magnetization, is clarified by ab initio band structure
+calculations.",2101.04220v2
+2021-02-10,Direct visualization of three-dimensional shape of skyrmion strings in a noncentrosymmetric magnet,"Magnetic skyrmion, i.e. a topologically stable swirling spin texture, appears
+as a particle-like object in the two-dimensional (2D) systems, and has recently
+attracted attention as a candidate of novel information carrier. In the real
+three-dimensional (3D) systems, a skyrmion is expected to form a string
+structure along an extra dimension, while its experimental identification has
+rarely been achieved. Here, we report the direct visualization of 3D shape of
+individual skyrmion strings, for the recently discovered room-temperature
+skyrmion-hosting noncentrosymmetric compound Mn1.4Pt0.9Pd0.1Sn. For this
+purpose, we have newly developed the magnetic X-ray tomography measurement
+system that can apply magnetic field, which plays a key role on the present
+achievement. Through the tomographic reconstruction of the 3D magnetization
+distribution based on the transmission images taken from various angles, a
+genuine skyrmion string running through the entire thickness of the sample, as
+well as various defect structures such as the interrupted and Y-shaped strings,
+are successfully identified. The observed point defect may represent the
+emergent magnetic monopole, as recently proposed theoretically. The present
+tomographic approach with tunable magnetic field paves the way for the direct
+visualization of the structural dynamics of individual skyrmion strings in the
+3D space, which will contribute to the better understanding of the creation,
+annihilation and transfer process of these topological objects toward the
+potential device applications.",2102.05556v1
+2021-03-05,Could switchbacks originate in the lower solar atmosphere? I. Formation mechanisms of switchbacks,"The recent rediscovery of magnetic field switchbacks or deflections embedded
+in the solar wind flow by the Parker Solar Probe mission lead to a huge
+interest in the modelling of the formation mechanisms and origin of these
+switchbacks. Several scenarios for their generation were put forth, ranging
+from lower solar atmospheric origins by reconnection, to being a manifestation
+of turbulence in the solar wind, and so on. Here we study some potential
+formation mechanisms of magnetic switchbacks in the lower solar atmosphere,
+using three-dimensional magneto-hydrodynamic (MHD) numerical simulations. The
+model is that of an intense flux tube in an open magnetic field region, aiming
+to represent a magnetic bright point opening up to an open coronal magnetic
+field structure, e.g. a coronal hole. The model is driven with different plasma
+flows in the photosphere, such as a fast up-shooting jet, as well as shearing
+flows generated by vortex motions or torsional oscillations. In all scenarios
+considered, we witness the formation of magnetic switchbacks in regions
+corresponding to chromospheric heights. Therefore, photospheric plasma flows
+around the foot-points of intense flux tubes appear to be suitable drivers for
+the formation of magnetic switchbacks in the lower solar atmosphere.
+Nevertheless, these switchbacks do not appear to be able to enter the coronal
+heights of the simulation in the present model. In conclusion, based on the
+presented simulations, switchbacks measured in the solar wind are unlikely to
+originate from photospheric or chromospheric dynamics.",2103.03726v1
+2021-03-15,Nature of the ferromagnetic-antiferromagnetic transition in Y$_{1-x}$La$_{x}$TiO$_{3}$,"We explore the magnetically-ordered ground state of the
+isovalently-substituted Mott-insulator Y$_{1-x}$La$_{x}$TiO$_{3}$ for $x$
+$\leq$ 0.3 via single crystal growth, magnetometry, neutron diffraction, x-ray
+magnetic circular dichroism (XMCD), muon spin rotation ($\mu$SR) and
+small-angle neutron scattering (SANS). We find that the decrease in the
+magnetic transition temperature on approaching the ferromagnetic (FM) -
+antiferromagnetic (AFM) phase boundary at the La concentration $x_c$ $\approx$
+0.3 is accompanied by a strong suppression of both bulk and local ordered
+magnetic moments, along with a volume-wise separation into magnetically-ordered
+and paramagnetic regions. The thermal phase transition does not show
+conventional second-order behavior, since neither a clear signature of dynamic
+critical behavior nor a power-law divergence of the magnetic correlation length
+is found for the studied substitution range; this finding becomes increasingly
+obvious with substitution. Finally, from SANS and magnetometry measurements, we
+discern a crossover from easy-axis to easy-plane magneto-crystalline anisotropy
+with increasing La substitution. These results indicate complex changes in
+magnetic structure upon approaching the phase boundary.",2103.08565v1
+2021-03-24,Magnetic ordering of the distorted kagome antiferromagnet Y$_3$Cu$_9$(OH)$_{18}$[Cl$_8$(OH)] prepared via optimal synthesis,"Experimental studies of high-purity kagome-lattice antiferromagnets (KAFM)
+are of great importance in attempting to better understand the predicted
+enigmatic quantum spin-liquid ground state of the KAFM model. However,
+realizations of this model can rarely evade magnetic ordering at low
+temperatures due to various perturbations to its dominant isotropic exchange
+interactions. Such a situation is for example encountered due to sizable
+Dzyaloshinskii-Moriya magnetic anisotropy in YCu$_3$(OH)$_6$Cl$_3$, which
+stands out from other KAFM materials by its perfect crystal structure. We find
+evidence of magnetic ordering also in the distorted sibling compound
+Y$_3$Cu$_9$(OH)$_{18}$[Cl$_8$(OH)], which has recently been proposed to feature
+a spin-liquid ground state arising from a spatially anisotropic kagome lattice.
+Our findings are based on a combination of bulk susceptibility, specific heat,
+and magnetic torque measurements that disclose a N\'eel transition temperature
+of $T_N=11$~K in this material, which might feature a coexistence of magnetic
+order and persistent spin dynamics as previously found in
+YCu$_3$(OH)$_6$Cl$_3$. Contrary to previous studies of single crystals and
+powders containing impurity inclusions, we use high-purity single crystals of
+Y$_3$Cu$_9$(OH)$_{18}$[Cl$_8$(OH)] grown via an optimized hydrothermal
+synthesis route that minimizes such inclusions. This study thus demonstrates
+that the lack of magnetic ordering in less pure samples of the investigated
+compound does not originate from the reduced symmetry of spin lattice but is
+instead of extrinsic origin.",2103.13254v2
+2021-03-29,Nonequilibrium Dynamics of the Chiral Quark Condensate under a Strong Magnetic Field,"Strong magnetic fields impact quantum-chromodynamics (QCD) properties in
+several situations; examples include the early universe, magnetars, and
+heavy-ion collisions. These examples share a common trait: time evolution. A
+prominent QCD property impacted by a strong magnetic field is the quark
+condensate, an approximate order parameter of the QCD transition between a
+high-temperature quark-gluon phase and a low-temperature hadronic phase. We use
+the linear sigma model with quarks to address the quark condensate time
+evolution under a strong magnetic field. We use the closed time path formalism
+of nonequilibrium quantum field theory to integrate out the quarks and obtain a
+mean-field Langevin equation for the condensate. The Langevin equation features
+dissipation and noise kernels controlled by a damping coefficient. We compute
+the damping coefficient for magnetic field and temperature values achieved in
+peripheral relativistic heavy-ion collisions and solve the Langevin equation
+for a temperature quench scenario. The magnetic field changes the dissipation
+and noise pattern by increasing the damping coefficient compared to the
+zero-field case. An increased damping coefficient increases fluctuations and
+time scales controlling condensate's short-time evolution, a feature that can
+impact hadron formation at the QCD transition. The formalism developed here can
+be extended to include other order parameters, hydrodynamic modes, and system's
+expansion to address magnetic field effects in complex settings as heavy-ion
+collisions, the early universe, and magnetars.",2103.15665v1
+2021-04-01,Crystallographic and magnetic structures of the VI$_3$ and LiVI$_3$ van der Waals compounds,"Two-dimensional (2D) layered magnetic materials are generating a great amount
+of interest for the next generation of electronic devices thanks to their
+remarkable properties associated to spin dynamics. The recently discovered
+layered VI$_3$ ferromagnetic phase belongs to this family, although a full
+understanding of its properties is limited by an ill-defined crystallographic
+structure. This is not any longer true. Here, we investigate the VI$_3$ crystal
+structure upon cooling using both synchrotron X-ray and neutron powder
+diffraction and provide structural models for the two structural transitions
+occurring at 76 K and 32 K. Moreover, we confirm by magnetic measurements that
+VI$_3$ becomes ferromagnetic at 50 K and discuss the difficulty of solving its
+full magnetic structure by neutrons. We equally determined the magnetic
+properties of our recently reported LiVI$_3$ phase, which is alike the
+well-known CrI$_3$ ferromagnetic phase in terms of electronic and
+crystallographic structures and found to our surprise an antiferromagnetic
+behavior with a N\'eel temperature of 12 K. Such a finding provides extra clues
+for a better understanding of magnetism in these low dimension compounds.
+Finally, the easiness of preparing novel Li-based 2D magnetic materials by
+chemical/electrochemical means opens wide the opportunity to design materials
+with exotic properties.",2104.00457v1
+2021-05-03,Relaxation of a single defect spin by the low-frequency gyrotropic mode of a magnetic vortex,"We excite the gyrotropic mode of a magnetic vortex and observe the resulting
+effect on the spin state of a nearby nitrogen-vacancy (NV) defect in diamond.
+Thin permalloy disks fabricated on a diamond sample are magnetized in a vortex
+state in which the magnetization curls around a central core. The magnetization
+dynamics of this configuration are described by a discrete spectrum of confined
+magnon modes, as well as a low-frequency gyrotropic mode in which the vortex
+core precesses about its equilibrium position. Despite the spin transition
+frequencies being far-detuned from the modes of the ferromagnet, we observe
+enhanced relaxation of the NV spin when driving the gyrotropic mode. Moreover,
+we map the spatial dependence of the interaction between the vortex and the
+spin by translating the vortex core within the disk with an applied magnetic
+field, resulting in steplike motion as the vortex is pinned and de-pinned. The
+strong spin relaxation is observed when the vortex core is within approximately
+250 nm of the NV center defect. We attribute this effect to the higher
+frequencies in the spectrum of the magnetic fringe field arising from the
+soliton-like nature of the gyrotropic mode when driven with sufficiently large
+amplitude.",2105.00927v1
+2021-05-17,AC susceptometry of 2D van der Waals magnets enabled by the coherent control of quantum sensors,"Precision magnetometry is fundamental to the development of novel magnetic
+materials and devices. Recently, the nitrogen-vacancy (NV) center in diamond
+has emerged as a promising probe for static magnetism in 2D van der Waals
+materials, capable of quantitative imaging with nanoscale spatial resolution.
+However, the dynamic character of magnetism, crucial for understanding the
+magnetic phase transition and achieving technological applications, has rarely
+been experimentally accessible in single 2D crystals. Here, we coherently
+control the NV center's spin precession to achieve ultra-sensitive,
+quantitative ac susceptometry of a 2D ferromagnet. Combining dc hysteresis with
+ac susceptibility measurements varying temperature, field, and frequency, we
+illuminate the formation, mobility, and consolidation of magnetic domain walls
+in few-layer CrBr3. We show that domain wall mobility is enhanced in ultrathin
+CrBr3, with minimal decrease for excitation frequencies exceeding hundreds of
+kilohertz, and is influenced by the domain morphology and local pinning of the
+flake. Our technique extends NV magnetometry to the multi-functional ac and dc
+magnetic characterization of wide-ranging spintronic materials at the
+nanoscale.",2105.08030v1
+2021-05-25,Low-temperature high-frequency dynamic magnetic susceptibility of classical spin-ice Dy$_2$Ti$_2$O$_7$,"Radio-frequency (14.6 MHz) AC magnetic susceptibility, $\chi^{\prime}_{AC}$,
+of \dytio\ was measured using a self-oscillating tunnel-diode resonator.
+Measurements were made with the excitation AC field parallel to the
+superimposed DC magnetic field up 5 T in a wide temperature range from 50 mK to
+100 K. At 14.6 MHz a known broad peak of $\chi^{\prime}_{AC}(T)$ from kHz -
+range audio-frequency measurements around 15~K for both [111] and [110]
+directions shifts to 45~K, continuing the Arrhenius activated behavior with the
+same activation energy barrier of $E_a \approx 230$~K. Magnetic field
+dependence of $\chi^{\prime}_{AC}$ along [111] reproduces previously reported
+low-temperature two-in-two-out to three-in-one-out spin configuration
+transition at about 1~T, and an intermediate phase between 1 and 1.5~T. The
+boundaries of the intermediate phase show reasonable overlap with the
+literature data and connect at a critical endpoint of the first-order
+transition line, suggesting that these low-temperature features are frequency
+independent. An unusual upturn of magnetic susceptibility at $T \to 0$ was
+observed in magnetic fields between 1.5~T and 2~T for both magnetic field
+directions, before fully polarized configuration sets in above 2~T.",2105.12218v1
+2021-05-29,Directional field-dependence of tunable magnetic domains in noncentrosymmetric ferromagnetic Weyl semimetal CeAlSi,"Dynamics and textures of magnetic domain walls (DWs) may largely alter the
+electronic behaviors in a Weyl semimetal system via emergent gauge fields.
+However, very little is known about even the basic properties of these domain
+walls in Weyl materials. In this work, we imaged the spontaneous magnetization
+and magnetic susceptibility of a ferromagnetic (FM) Weyl semimetal CeAlSi using
+scanning SQUID microscopy. We observed the ferromagnetic DWs lined-up with the
+[100] direction (or other degenerate directions). We also discovered the
+coexistence of stable and metastable domain phases, which arise likely due to
+magnetoelastic and magnetostriction effects and are expected to be highly
+tunable with small strains. We applied an in-plane external field as the CeAlSi
+sample was cooled down to below the magnetic phase transition of 8.3K, showing
+that the pattern of FM domains is strongly correlated with both the amplitude
+and the orientation of the external field even for weak fields of a few Gauss.
+The area of stable domains increases with field and reaches maximum when the
+field is parallel to the main crystallographic axes of the CeAlSi crystal. Our
+results suggest that the manipulation of these heterogeneous phases can provide
+a practical way to study the interplay between magnetism and electronic
+properties in Weyl systems, and that these systems can even serve as a new
+platform for magnetic sensors.",2105.14384v1
+2021-07-02,Scaling of Turbulent Viscosity and Resistivity: Extracting a Scale-dependent Turbulent Magnetic Prandtl Number,"Turbulent viscosity $\nu_t$ and resistivity $\eta_t$ are perhaps the simplest
+models for turbulent transport of angular momentum and magnetic fields,
+respectively. The associated turbulent magnetic Prandtl number $Pr_t\equiv
+\nu_t/\eta_t$ has been well recognized to determine the final magnetic
+configuration of accretion disks. Here, we present an approach to determining
+these ''effective transport'' coefficients acting at different length-scales
+using coarse-graining and recent results on decoupled kinetic and magnetic
+energy cascades [Bian & Aluie 2019]. By analyzing the kinetic and magnetic
+energy cascades from a suite of high-resolution simulations, we show that our
+definitions of $\nu_t$, $\eta_t$, and $Pr_t$ have power-law scalings in the
+''decoupled range.'' We observe that $Pr_t\approx1 \text{~to~}2$ at the
+smallest inertial-inductive scales, increasing to $\approx 5$ at the largest
+scales. However, based on physical considerations, our analysis suggests that
+$Pr_t$ has to become scale-independent and of order unity in the decoupled
+range at sufficiently high Reynolds numbers (or grid-resolution), and that the
+power-law scaling exponents of velocity and magnetic spectra become equal. In
+addition to implications to astrophysical systems, the scale-dependent
+turbulent transport coefficients offer a guide for large eddy simulation
+modeling.",2107.00861v1
+2021-08-30,Bright and dark states of two distant macrospins strongly coupled by phonons,"We study the collective dynamics of two distant magnets coherently coupled by
+acoustic phonons that are transmitted through an intercalated crystal. By
+tuning the ferromagnetic resonances of the two magnets to an acoustic resonance
+of the crystal, we control a coherent three levels system. We show that the
+parity of the phonon mode governs the nature of the indirect coupling between
+the magnets: the resonances with odd / even phonon modes correspond to
+out-of-phase / in-phase lattice displacements at the magnets, leading to bright
+/ dark states in response to uniform microwave magnetic fields, respectively.
+The sample is a tri-layer garnet consisting of two thin magnetic layers
+epitaxially grown on both sides of a half-millimeter thick non-magnetic single
+crystal. In spite of the relatively weak magneto-elastic interaction, the long
+lifetimes of the magnon and phonon modes in the sample are the key to unveil
+this long range strong coupling. This demonstrates that garnets are a great
+platform to study multi-partite hybridization process between magnon and
+phonons at microwave frequencies.",2108.13272v2
+2021-09-09,Magnetic field induced quantum spin liquid in the two coupled trillium lattices of K$_2$Ni$_2$(SO$_4$)$_3$,"Quantum spin liquids are exotic states of matter which form when strongly
+frustrated magnetic interactions induce a highly entangled quantum paramagnet
+far below the energy scale of the magnetic interactions. Three-dimensional
+cases are especially challenging due to the significant reduction of the
+influence of quantum fluctuations. Here, we report the magnetic
+characterization of {\kni} forming a three dimensional network of Ni$^{2+}$
+spins. Using density functional theory calculations we show that this network
+consists of two interconnected spin-1 trillium lattices. In the absence of a
+magnetic field, magnetization, specific heat, neutron scattering and muon spin
+relaxation experiments demonstrate a highly correlated and dynamic state,
+coexisting with a peculiar, very small static component exhibiting a strongly
+renormalized moment. A magnetic field $B \gtrsim 4$ T diminishes the ordered
+component and drives the system in a pure quantum spin liquid state. This shows
+that a system of interconnected $S=1$ trillium lattices exhibit a significantly
+elevated level of geometrical frustration.",2109.04102v1
+2021-09-10,Predicting the Magnetic Fields of a Stealth CME Detected by Parker Solar Probe at 0.5 AU,"Stealth coronal mass ejection (CMEs) are eruptions from the Sun that are not
+associated with appreciable low-coronal signatures. Because they often cannot
+be linked to a well-defined source region on the Sun, analysis of their initial
+magnetic configuration and eruption dynamics is particularly problematic. In
+this manuscript, we address this issue by undertaking the first attempt at
+predicting the magnetic fields of a stealth CME that erupted in 2020 June from
+the Earth-facing Sun. We estimate its source region with the aid of off-limb
+observations from a secondary viewpoint and photospheric magnetic field
+extrapolations. We then employ the Open Solar Physics Rapid Ensemble
+Information (OSPREI) modelling suite to evaluate its early evolution and
+forward-model its magnetic fields up to Parker Solar Probe, which detected the
+CME in situ at a heliocentric distance of 0.5 AU. We compare our hindcast
+prediction with in-situ measurements and a set of flux rope reconstructions,
+obtaining encouraging agreement on arrival time, spacecraft crossing location,
+and magnetic field profiles. This work represents a first step towards reliable
+understanding and forecasting of the magnetic configuration of stealth CMEs and
+slow, streamer-blowout events.",2109.04933v1
+2021-09-12,Zero-field magnetometry using hyperfine-biased nitrogen-vacancy centers near diamond surfaces,"Shallow nitrogen-vacancy (NV) centers in diamond are promising for
+nano-magnetometry for they can be placed proximate to targets. To study the
+intrinsic magnetic properties, zero-field magnetometry is desirable. However,
+for shallow NV centers under zero field, the strain near diamond surfaces would
+cause level anti-crossing between the spin states, leading to clock transitions
+whose frequencies are insensitive to magnetic signals. Furthermore, the charge
+noises from the surfaces would induce extra spin decoherence and hence reduce
+the magnetic sensitivity. Here we demonstrate that the relatively strong
+hyperfine coupling (130 MHz) from a first-shell 13C nuclear spin can provide an
+effective bias field to an NV center spin so that the clock-transition
+condition is broken and the charge noises are suppressed. The hyperfine bias
+enhances the dc magnetic sensitivity by a factor of 22 in our setup. With the
+charge noises suppressed by the strong hyperfine field, the ac magnetometry
+under zero field also reaches the limit set by decoherence due to the nuclear
+spin bath. In addition, the 130 MHz splitting of the NV center spin transitions
+allows relaxometry of magnetic noises simultaneously at two well-separated
+frequencies (~2.870 +/- 0.065 GHz), providing (low-resolution) spectral
+information of high-frequency noises under zero field. The hyperfine-bias
+enhanced zero-field magnetometry can be combined with dynamical decoupling to
+enhance single-molecule magnetic resonance spectroscopy and to improve the
+frequency resolution in nanoscale magnetic resonance imaging.",2109.05445v1
+2021-09-20,Sympathetic Filament Eruptions within a Fan-spine Magnetic System,"It is unclear whether successive filament eruptions at different sites within
+a short time interval are physically connected or not. Here, we present the
+observations of the successive eruptions of a small and a large filament in a
+tripolar magnetic field region whose coronal magnetic field showed as a
+fan-spine magnetic system. By analyzing the multi-wavelength observations taken
+by the Solar Dynamic Observatory (SDO) and the extrapolated three-dimensional
+coronal magnetic field, we find that the two filaments resided respectively in
+the two lobes that make up the inner fan structure of the fan-spine magnetic
+system. In addition, a small fan-spine system was also revealed by the
+squashing factor Q map, which located in the east lobe of the fan structure of
+the large fan-spine system. The eruption of the small filament was a failed
+filament eruption, which did not cause any coronal mass ejection (CME) except
+for three flare ribbons and two post-flare-loop systems connecting the three
+magnetic polarities. The eruption of the large filament not only caused similar
+post-flare-loop systems and flare ribbons as observed in the small filament
+eruption, but also a large-scale CME. Based on our analysis results, we
+conclude that the two successive filament eruptions were physically connected,
+in which the topology change caused by the small filament eruption is thought
+to be the physical linkage. In addition, the eruption of the small fan-spine
+structure further accelerated the instability and violent eruption of the large
+filament.",2109.09285v1
+2021-11-19,Streaming instabilities in accreting and magnetized laminar protoplanetary disks,"The streaming instability is one of the most promising pathways to the
+formation of planetesimals from pebbles. Understanding how this instability
+operates under realistic conditions expected in protoplanetary disks is
+therefore crucial to assess the efficiency of planet formation. Contemporary
+models of protoplanetary disks show that magnetic fields are key to driving gas
+accretion through large-scale, laminar magnetic stresses. However, the effect
+of such magnetic fields on the streaming instability has not been examined in
+detail. To this end, we study the stability of dusty, magnetized gas in a
+protoplanetary disk. We find the streaming instability can be enhanced by
+passive magnetic torques and even persist in the absence of a global radial
+pressure gradient. In this case, instability is attributed to the azimuthal
+drift between dust and gas, unlike the classical streaming instability, which
+is driven by radial drift. This suggests that the streaming instability can
+remain effective inside dust-trapping pressure bumps in accreting disks. When a
+live vertical field is considered, we find the magneto-rotational instability
+can be damped by dust feedback, while the classic streaming instability can be
+stabilized by magnetic perturbations. We also find that Alfv\'en waves can be
+destabilized by dust-gas drift, but this instability requires nearly ideal
+conditions. We discuss the possible implications of these results for dust
+dynamics and planetesimal formation in protoplanetary disks.",2111.10381v1
+2021-12-08,Magnetic Fields in Primordial Galaxies,"Magnetic fields play a vital role in numerous astrophysical processes such as
+star formation and the interstellar medium. In particular, their role in the
+formation and evolution of galaxies is not well understood. This paper presents
+high-resolution magnetohydrodynamic (MHD) simulations performed with GIZMO to
+investigate the effect of magnetic fields on primordial galaxy formation.
+Physical processes such as relevant gas physics (e.g., gas cooling and gas
+chemistry), star formation, stellar and supernova feedback, and chemical
+enrichment were considered in the simulations. The simulation results suggest
+that cosmic magnetic fields can be amplified from 1e-13 G to a few microgauss
+during cosmic structure evolution and galaxy formation. In the ideal MHD
+setting, in primordial galaxies at z>8, the magnetic energy is less than the
+thermal and kinetic energy, and therefore, magnetic fields hardly affect the
+gas dynamics and star formation in these galaxies. Specifically, the
+consideration of micro-physics properties such as metal diffusion, heat
+conduction, and viscosity in the MHD simulations, could increase the magnetic
+field strength. Notably, metal diffusion reduced gas cooling by decreasing the
+metallicity and thereby suppresses star formation in the primordial galaxies.
+As a result, the cosmic re-ionization driven by these primordial galaxies may
+be delayed.",2112.04512v1
+2021-12-13,Fluctuating magnetic droplets immersed in a sea of quantum spin liquid,"The search of quantum spin liquid (QSL), an exotic magnetic state with
+strongly-fluctuating and highly-entangled spins down to zero temperature, is a
+main theme in current condensed matter physics. However, there is no
+smoking-gun evidence for deconfined spinons in any QSL candidate so far. The
+disorders and competing exchange interactions may prevent the formation of an
+ideal QSL state on frustrated spin lattices. Here we report comprehensive and
+systematic measurements of the magnetic susceptibility, ultra-low temperature
+specific heat, muon spin relaxation (muSR), nuclear magnetic resonance (NMR),
+and thermal conductivity for NaYbSe2 single crystals, in which Yb3+ ions with
+effective spin-1/2 form a perfect triangular lattice. All these complementary
+techniques find no evidence of long-range magnetic order down to their
+respective base temperatures. Instead, specific heat, muSR and NMR measurements
+suggest the coexistence of quasi-static and dynamic spins in NaYbSe2. The
+scattering from these quasi-static spins may cause the absence of magnetic
+thermal conductivity. Thus, we propose a scenario of fluctuating ferrimagnetic
+droplets immersed in a sea of QSL. This may be quite common on the way pursuing
+an ideal QSL, and provides a brand-new platform to study how a QSL state
+survives impurities and coexists with other magnetically ordered states.",2112.06523v1
+2021-12-20,Stable and unstable supersonic stagnation of an axisymmetric rotating magnetized plasma,"The Naval Research Laboratory ""Mag Noh problem"", described in this paper, is
+a self-similar magnetized implosion flow, which contains a fast MHD outward
+propagating shock of constant velocity. We generalize the classic Noh (1983)
+problem to include azimuthal and axial magnetic fields as well as rotation. Our
+family of ideal MHD solutions is five-parametric, each solution having its own
+self-similarity index, gas gamma, magnetization, the ratio of axial to the
+azimuthal field, and rotation. While the classic Noh problem must have a
+supersonic implosion velocity to create a shock, our solutions have an
+interesting three-parametric special case with zero initial velocity in which
+magnetic tension, instead of implosion flow, creates the shock at $t=0+$. Our
+self-similar solutions are indeed realized when we solve the initial value MHD
+problem with finite volume MHD code Athena. We numerically investigated the
+stability of these solutions and found both stable and unstable regions in
+parameter space. Stable solutions can be used to test the accuracy of numerical
+codes. Unstable solutions have also been widely used to test how codes
+reproduce linear growth, transition to turbulence, and the practically
+important effects of mixing. Now we offer a family of unstable solutions
+featuring all three elements relevant to magnetically driven implosions:
+convergent flow, magnetic field, and a shock wave.",2112.10828v1
+2022-01-06,On-demand augmentation in heat transfer of Taylor bubble flows using ferrofluids,"The thermo-fluidic transport characteristics of ferrofluids can be influenced
+by the application of a magnetic field. The magnetic manipulations of
+ferrofluids have been useful in augmenting heat transfer, as evident from
+recent investigations. In the present study, we examine a novel strategy for
+augmenting two-phase heat transfer and show that the magnetic manipulation of
+non-boiling Taylor bubble flow (TBF) of ferrofluids can provide on-demand
+augmentation. In an earlier investigation (DOI:10.1016/j.colsurfa.2020.124589),
+we had shown that the characteristics of the TBF of ferrofluids could be
+altered through external magnetic manipulations. As transport characteristics
+of TBFs primarily depend on their flow morphology, it was anticipated that such
+alteration would affect their thermal transport characteristics, which are
+examined in the present work. The generation of smaller bubbles and unit-cells
+through magnetic manipulations decreases the void fraction of the resulting
+TBF. In addition, a greater number of units participated in the heat exchange
+process compared to larger bubble-slug systems at any time instance. Such flow
+modifications cause considerable augmentation (which can go up to 100%) in
+two-phase heat transfer. The extent of augmentation depends on the applied
+magnetic field and induced magnetic force, homogeneous gas fraction, liquid
+film thickness/void fraction and flow morphology of the resulting TBF, which
+are examined in the present study. The application of ferrofluids in TBFs
+provides multiple benefits, such as suspension of nanoparticles with better
+thermal properties and additional functionality of the flow manipulations
+through external means. The proposed application with the suggested
+manipulation technique provides an effective alternative for an on-demand
+augmentation in two-phase heat transfer in low Reynolds number flows.",2201.02145v1
+2022-04-10,Effect of iron vacancies on the magnetic order and spin dynamics of the spin ladder BaFe$_{2-δ}$S$_{1.5}$Se$_{1.5}$,"Quasi-one-dimensional iron chalcogenides possess various magnetic states
+depending on the lattice distortion, electronic correlations, and presence of
+defects. We present neutron diffraction and inelastic neutron scattering
+experiments on the spin ladder compound BaFe$_{2-\delta}$S$_{1.5}$Se$_{1.5}$
+with $\sim$6% iron vacancies. The data reveal that long-range magnetic order is
+absent, while the characteristic magnetic excitations that correspond to both
+the stripe- and block-type antiferromagnetic correlations are observed.
+First-principles calculations support the existence of both stripe and
+block-type antiferromagnetic short-range order in the experimental sample. The
+disappearance of long-range magnetic order may be due to the competition
+between these two magnetic orders, which is greatly enhanced for a certain
+concentration of iron vacancies, which we calculate to be about 6%, consistent
+with the measured iron vacancy concentration. Our results highlight how iron
+vacancies in the iron-based spin ladder system strongly influence the magnetic
+ground state.",2204.04697v1
+2022-04-19,Electric field-induced domain wall motion in spin spiral multiferroics,"Switching in magnetic materials gives rise to rich physical phenomena and
+lies at the heart of their technological applications. Although domain wall
+motion in ferro- and antiferromagnets has been studied, in spiral magnets it is
+still poorly understood despite 20 years of active research since the discovery
+of spiral multiferroics. The problem of the domain wall motion in a spiral
+magnet is a compelling one, the more so the magnetic domain walls in cycloidal
+spiral phase are also ferroelectric, thus enabling electric control of
+magnetism, i.e. domain wall motion under the action of an external electric
+field. Phase transition to a spiral phase leads to a formation of chiral
+domains with opposite spin rotation senses, that are separated by chiral domain
+walls. Spiral order breaks inversion symmetry and induces a ferroelectric
+polarization, whose sign is determined by the chirality of the domain. Thus the
+spiral order allows for the manipulation of spins via an external electric
+field. Here we study domain wall motion in magnets with spiral ground state,
+that are the most basic non-collinear magnets. We formulate a simplified
+variational model and derive the equation of motion for the domain wall driven
+by an external electric field. The results are corroborated with atomistic spin
+dynamics simulations. The results suggest a linear dependence of the wall speed
+on the external electric field, and a peculiar dependence on the system
+geometry and domain structure.",2204.09027v3
+2022-05-05,Incommensurate magnetic order in Sm$_3$BWO$_9$ with the distorted kagome lattice,"We investigate the magnetic ground state of Sm$_3$BWO$_9$ with the distorted
+kagome lattice. A magnetic phase transition is identified at $T_N=0.75$ K from
+the temperature dependence of specific heat. From $^{11}$B nuclear magnetic
+resonance (NMR) measurements, an incommensurate magnetic order is shown by the
+double-horn type spectra under a $c$-axis magnetic field. While, absence of
+line splitting is observed for field oriented within the $ab$-plane, indicating
+the incommensurate modulation of the internal field strictly along $c$-axis.
+From the spin dynamics, the critical slowing down behavior is observed in the
+temperature dependence of $1/T_1$ with $\mu_0H\perp c$-axis, which is
+completely absent in that with $\mu_0H||c$-axis. Based on the local symmetry of
+$^{11}$B sites, we analyze the hyperfine coupling tensors and propose two
+constraints on the possible magnetic structure. The single ion anisotropy
+should play an important role in the determination of the contrasting ground
+states of Sm$_3$BWO$_9$ and Pr$_3$BWO$_9$.",2205.02448v2
+2022-07-25,Spin-orbit torque switching of magnetic tunnel junctions for memory application,"Spin-orbit torques (SOT) provide a versatile tool to manipulate the
+magnetization of diverse classes of materials and devices using electric
+currents, leading to novel spintronic memory and computing approaches. In
+parallel to spin transfer torques (STT), which have emerged as a leading
+non-volatile memory technologie, SOT broaden the scope of current-induced
+magnetic switching to applications that run close to the clock speed of the
+central processing unit and unconventional computing architectures. In this
+paper, we review the fundamental characteristics of SOT and their use to switch
+magnetic tunnel junction (MTJ) devices, the elementary unit of the
+magnetoresistive random access memory (MRAM). In the first part, we illustrate
+the physical mechanisms that drive the SOT and magnetization reversal in
+nanoscale structures. In the second part, we focus on the SOT-MTJ cell. We
+discuss the anatomy of the MTJ in terms of materials and stack development,
+summarize the figures of merit for SOT switching, review the field-free
+operation of perpendicularly magnetized MTJs, and present options to combine
+SOT, STT and voltage-gate assisted switching. In the third part, we consider
+SOT-MRAMs in the perspective of circuit integration processes, introducing
+considerations on scaling and performance, as well as macro-design
+architectures. We thus bridge the fundamental description of SOT-driven
+magnetization dynamics with an application-oriented perspective, including
+device and system-level considerations, goals, and challenges.",2207.11974v1
+2022-08-10,Magnetic field effects on nucleosynthesis and kilonovae from neutron star merger remnants,"We investigate the influence of parametric magnetic field configurations of a
+hypermassive neutron star (HMNS) on electromagnetic (EM) observables,
+specifically the kilonova lightcurves and nucleosynthesis yields. We perform
+three-dimensional (3D) dynamical-spacetime general-relativistic
+magnetohydrodynamic (GRMHD) simulations, including a neutrino leakage scheme,
+microphysical finite-temperature equation of state (EOS), and an initial
+poloidal magnetic field. We find that varying the magnetic field strength and
+falloff impacts the formation of magnetized winds or mildy-relativistic jets,
+which in turn has profound effects on the outflow properties. All of the
+evolved configurations collapse to a black hole (BH) $\sim 21-23$ ms after the
+onset of the simulations, however, the ones forming jets may be considerably
+more effective at transporting angular momentum out of the system, resulting in
+earlier collapse times. Larger mass ejecta rates and radial velocities of
+unbound material characterise the systems that form jets. The bolometric light
+curves of the kilonovae and $r$-process yields change considerably with
+different magnetic field parameters. We conclude that the magnetic field
+strength and falloff have robust effects on the outflow properties and
+electromagnetic observables. This can be particularly important as the total
+ejecta mass from our simulations ($\simeq 10^{-3}\;M_{\odot}$) makes the ejecta
+from HMNS a compelling source to power kilonova through radioactive decay of
+$r$-process elements.",2208.05330v1
+2022-08-24,Complex magnetoelectric effect in PFN-PT/CoFe$_{2-x}$Zn$_x$O$_4$ bulk particulate composites,"The structural, dielectric, magnetic, and magnetoelectric (ME) properties of
+particulate composites containing lead-iron niobate and lead titanate
+piezoelectric 0.94[PbFe$_{0.5}$Nb$_{0.5}$O$_3$]-0.06[PbTi$_{0.5}$O$_3$]
+(PFN-PT) and Zn-substituted cobalt ferrite magnetostrictive
+CoFe$_{2-x}$Zn$_{x}$O$_4$ (CF$_{2-x}$Z$_{x}$O);
+0.6(PFN-PT)/0.4(CF$_{2-x}$Z$_{x}$O), x=0, 0.025, 0.1, 0.2, 0.3 (with ratio of
+60 Wt\% ferroelectric and 40 Wt\% ferrite); have been investigated. We
+investigated the ME voltage coefficient as a complex quantity for all composite
+samples using the dynamic piezomagnetic coefficient, $q^{ac}$=$\partial
+\lambda^{ac}/{\partial H}$. The results reveal that tuning the magnetostrictive
+phase has a strong effect on the real part of the ME voltage coefficient.
+Doping zinc into cobalt ferrite modified the magnetic properties of the
+magnetic phase, such as magnetic anisotropy and coercive field, and hence the
+ME properties. The highest ME coefficient value of 12.33 $\frac{mV}{cm. Oe}$
+was obtained for x=0.1 at the magnetic field of 755 Oe. In addition, the
+magnetic field at which the maximum value of the ME coefficient was observed
+($H_{peak}$) strongly depends on the value of Zn substitution. The results were
+interpreted using the magnetic field dependence of the CF$_{2-x}$Z$_{x}$O
+magnetostriction.",2208.11317v1
+2022-09-17,MHD Simulations on Magnetic Compression of Field Reversed Configurations,"The magnetic compression has long been proposed a promising method for the
+plasma heating in a field reversed configuration (FRC), however, it remains a
+challenge to fully understand the physical mechanisms underlying the
+compression process, due to its highly dynamic nature beyond the
+one-dimensional (1D) adiabatic theory model [R. L. Spencer et al., Phys. Fluids
+26, 1564 (1983)]. In this work, magnetohydrodynamics (MHD) simulations on the
+magnetic compression of FRCs using the NIMROD code [C. R. Sovinec et al., J.
+Comput. Phys. 195, 355 (2004)] and their comparisons with the 1D theory have
+been performed. The effects of the assumptions of the theory on the compression
+process have been explored, and the detailed profiles of the FRC during
+compression have been investigated. The pressure evolution agrees with the
+theoretical prediction under various initial conditions. The axial contraction
+of the FRC can be affected by the initial density profile and the ramping rate
+of the compression magnetic field, but the theoretical predictions on the FRC's
+length in general and the relation $r_s=\sqrt{2}r_o$ in particular hold
+approximately well during the whole compression process, where $r_s$ is the
+major radius of FRC separatrix and $r_o$ is that of the magnetic axis. The
+evolutions of the density and temperature can be affected significantly by the
+initial equilibrium profile and the ramping rate of the compression magnetic
+field. During the compression, the major radius of the FRC is another parameter
+that is susceptible to the ramping rate of the compression field. Basically,
+for the same magnetic compression ratio, the peak density is higher and the
+FRC's radius $r_s$ is smaller than the theoretical predictions.",2209.08280v1
+2022-09-29,Magnetic helicity fluxes from triple correlators,"Fluxes of the magnetic helicity density play an important role in large-scale
+turbulent dynamos, allowing the growth of large-scale magnetic fields while
+overcoming catastrophic quenching. We show here, analytically, how several
+important types of magnetic helicity fluxes can arise from terms involving
+triple correlators of fluctuating fields in the helicity density evolution
+equation. For this, we assume incompressibility and weak inhomogeneity, and use
+a quasinormal closure approximation: fourth-order correlators are replaced by
+products of second-order ones, and the effect of the fourth-order cumulants on
+the evolution of the third moments is modelled by a strong damping term. First,
+we show how a diffusive helicity flux, till now only measured in simulations,
+arises from the triple correlation term. This is accompanied by what we refer
+to as a `random advective flux', which predominantly transports magnetic
+helicity along the gradients of the random fields. We also find that a new
+helicity flux contribution, in some aspects similar to that first proposed by
+Vishniac, can arise from the triple correlator. This contribution depends on
+the gradients of the random magnetic and kinetic energies along the large-scale
+vorticity, and thus arises in any rotating, stratified system, even if the
+turbulence is predominantly nonhelical. It can source a large-scale dynamo by
+itself while spatially transporting magnetic helicity within the system.",2209.14810v2
+2022-10-14,An Evolution and Eruption of the Coronal Magnetic Field through a Data-Driven MHD Simulation,"We present a newly developed data-driven magnetohydrodynamics (MHD)
+simulation code under a zero-beta approximation based on a method proposed by
+Hayashi et al. 2018 and 2019. Although many data-driven MHD simulations have
+been developed and conducted, there are not many studies on how accurately
+those simulations can reproduce the phenomena observed in the solar corona. In
+this study, we investigated the performance of our data-driven simulation
+quantitatively using ground-truth data. The ground-truth data was produced by
+an MHD simulation in which the magnetic field is twisted by the sunspot
+motions. A magnetic flux rope (MFR) is created by the cancellation of the
+magnetic flux at the polarity inversion line due to the converging flow on the
+sunspot, which eventually leads the eruption of the MFR. We attempted to
+reproduce these dynamics using the data-driven MHD simulation. The coronal
+magnetic fields are driven by the electric fields, which are obtained from a
+time-series of the photospheric magnetic field that is extracted from the
+ground-truth data, on the surface. As a result, the data-driven simulation
+could capture the subsequent MHD processes, the twisted coronal magnetic field
+and formation of the MFR, and also its eruption. We report these results and
+compare with the ground-truth data, and discuss how to improve the accuracy and
+optimize numerical method.",2210.07492v1
+2022-11-02,Unravelling the origin of the peculiar transition in the magnetically ordered phase of the Weyl semimetal Co3Sn2S2,"Recent discovery of topologically non-trivial behavior in Co3Sn2S2 stimulated
+a notable interest in this itinerant ferromagnet (Tc = 174 K). The exact
+magnetic state remains ambiguous, with several reports indicating the existence
+of a second transition in the range 125 -- 130 K, with antiferromagnetic and
+glassy phases proposed to coexist with the ferromagnetic phase. Using detailed
+angle-dependent DC and AC magnetization measurements on large, high-quality
+single crystals we reveal a highly anisotropic behavior of both static and
+dynamic response of Co3Sn2S2. It is established that many observations related
+to sharp magnetization changes when B || c are influenced by the
+demagnetization factor of a sample. On the other hand, a genuine transition has
+been found at Tp = 128 K, with the magnetic response being strictly
+perpendicular to the c-axis and several orders of magnitude smaller than for B
+|| c. Calculations using density-functional theory indicate that the ground
+state magnetic structure consist of magnetic moments canted away from the
+c-axis by a small angle (~ 1.5deg). We argue that the second transition
+originates from a small additional canting of moments within the kagome plane,
+with two equivalent orientations for each spin.",2211.01483v1
+2022-11-15,Modification of three-magnon splitting in a flexed magnetic vortex,"We present an experimental and numerical study of three-magnon splitting in a
+micrometer-sized magnetic disk with the vortex state strongly deformed by
+static in-plane magnetic fields. Excited with a large enough power at frequency
+$f_\mathrm{RF}$, the primary radial magnon modes of a cylindrical magnetic
+vortex can decay into secondary azimuthal modes via spontaneous three-magnon
+splitting. This nonlinear process exhibits selection rules leading to
+well-defined and distinct frequencies $f_\mathrm{RF}/2\pm \Delta f$ of the
+secondary modes. Here, we demonstrate that three-magnon splitting in vortices
+can be significantly modified by deforming the magnetic vortex with in-plane
+magnetic fields, leading to a much richer three-magnon response. We find that,
+with increasing field, an additional class of secondary modes is excited which
+are localized to the highly-flexed regions adjacent to the displaced vortex
+core. While these modes satisfy the same selection rules of three-magnon
+splitting, they exhibit a much lower three-magnon threshold power compared to
+regular secondary modes of a centered vortex. The applied static magnetic
+fields are small ($\simeq$ 10 mT), providing an effective parameter to control
+the nonlinear spectral response of confined vortices. Our work expands the
+understanding of nonlinear magnon dynamics in vortices and advertises these for
+potential neuromorphic applications based on magnons.",2211.08226v2
+2022-11-21,General time-reversal equivariant neural network potential for magnetic materials,"This study introduces time-reversal E(3)-equivariant neural network and
+SpinGNN++ framework for constructing a comprehensive interatomic potential for
+magnetic systems, encompassing spin-orbit coupling and noncollinear magnetic
+moments. SpinGNN++ integrates multitask spin equivariant neural network with
+explicit spin-lattice terms, including Heisenberg, Dzyaloshinskii-Moriya,
+Kitaev, single-ion anisotropy, and biquadratic interactions, and employs
+time-reversal equivariant neural network to learn high-order spin-lattice
+interactions using time-reversal E(3)-equivariant convolutions. To validate
+SpinGNN++, a complex magnetic model dataset is introduced as a benchmark and
+employed to demonstrate its capabilities. SpinGNN++ provides accurate
+descriptions of the complex spin-lattice coupling in monolayer CrI$_3$ and
+CrTe$_2$, achieving sub-meV errors. Importantly, it facilitates large-scale
+parallel spin-lattice dynamics, thereby enabling the exploration of associated
+properties, including the magnetic ground state and phase transition.
+Remarkably, SpinGNN++ identifies a new ferrimagnetic state as the ground
+magnetic state for monolayer CrTe2, thereby enriching its phase diagram and
+providing deeper insights into the distinct magnetic signals observed in
+various experiments.",2211.11403v3
+2022-12-15,Exploration of all-3d Heusler alloys for permanent magnets: an ab initio based high-throughput study,"Heusler alloys have attracted interest in various fields of functional
+materials since their properties can quite easily be tuned by composition.
+Here, we have investigated the relatively new class of all-3d Heusler alloys in
+view of its potential as permanent magnets. To identify suitable candidates, we
+performed a high-throughput study using an electronic structure database to
+search for X$_2$YZ-type Heusler systems with tetragonal symmetry and high
+magnetization. For the alloys which passed our selection filters, we have used
+a combination of density functional theory calculations and spin dynamics
+modelling to investigate their magnetic properties including the
+magnetocrystalline anisotropy energy and exchange interactions. The candidates
+which fulfilled all the search criteria served as input for the investigation
+of the temperature dependence of the magnetization and determination of Curie
+temperature. Based on our results, we suggest that Fe$_2$NiZn, Fe$_2$NiTi and
+Ni$_2$CoFe are potential candidates for permanent magnets with large
+out-of-plane magnetic anisotropy (1.23, 0.97 and 0.82 MJ/m$^3$ respectively)
+and high Curie temperatures lying more than 200 K above the room temperature.
+We further show that the magnitude and direction of anisotropy is very
+sensitive to the strain by calculating the values of anisotropy energy for
+several tetragonal phases. Thus, application of strain can be used to tune the
+anisotropy in these compounds.",2212.07845v3
+2023-01-20,A Unified Model for Bipolar Outflows from Young Stars: Apparent Magnetic Jet Acceleration,"We explore a new, efficient mechanism that can power toroidally magnetized
+jets up to two to three times their original terminal velocity after they enter
+a self-similar phase of magnetic acceleration. Underneath the elongated outflow
+lobe formed by a magnetized bubble, a wide-angle free wind, through the
+interplay with its ambient toroid, is compressed and accelerated around its
+axial jet. The extremely magnetic bubble can inflate over its original size,
+depending on the initial Alfv\'en Mach number $M_A$ of the launched flow. The
+shape-independent slope $\partial{}v_r/\partial{}r=2/3t$ is a salient feature
+of the self-similarity in the acceleration phase. Peculiar kinematic signatures
+are observable in the position--velocity (PV) diagrams and can combine with
+other morphological signatures as probes for the density-collimated jets
+arising in toroidally dominated magnetized winds. The apparent second
+acceleration is powered by the decrease of the toroidal magnetic field but
+operates far beyond the scales of the primary magnetocentrifugal launch region
+and the free asymptotic terminal state. Rich implications may connect the jets
+arising from the youngest protostellar outflows such as HH 211 and HH 212 and
+similar systems with parsec-scale jets across the mass and evolutionary
+spectra.",2301.08512v1
+2023-03-02,Statistical analysis of the total magnetic flux decay rate in solar active regions,"We used line-of-sight magnetograms acquired by the Helioseismic and Magnetic
+Imager on board the Solar Dynamics Observatory to derive the decay rate of
+total unsigned magnetic flux for 910 ephemeral and active regions (ARs)
+observed between 2010 and 2017. We found that: i) most of the ARs obey the
+power law dependence between the peak magnetic flux and the magnetic flux decay
+rate, $DR$, so that $DR\sim \Phi^{0.70}$; ii) larger ARs lose smaller fraction
+of their magnetic flux per unit of time than the smaller ARs; iii) there exists
+a cluster of ARs exhibiting significantly lower decay rate than it would follow
+from the power law and all of them are unipolar sunspots with total fluxes in
+the narrow range of $(2 - 8) \times 10^{21}$ Mx; iv) a comparison with our
+previous results shows that the emergence rate is always higher than the decay
+rate. The emergence rate follows a power law with a shallower slope than the
+slope of the decay-rate power law. The results allowed us to suggest that not
+only the maximum total magnetic flux determines the character of the decaying
+regime of the AR, some of the ARs end up as a slowly decaying unipolar sunspot;
+there should be certain physical mechanisms to stabilize such a sunspot.",2303.01321v2
+2023-03-07,Effects of Magnetic Fields on Gas Dynamics and Star Formation in Nuclear Rings,"Nuclear rings at the centers of barred galaxies are known to be strongly
+magnetized. To explore the effects of magnetic fields on star formation in
+these rings and nuclear gas flows, we run magnetohydrodynamic simulations in
+which there is a temporally-constant magnetized inflow to the ring,
+representing a bar-driven inflow. The mass inflow rate is
+$1\,M_\odot\,\mathrm{yr}^{-1}$, and we explore models with a range of field
+strength in the inflow. We adopt the TIGRESS framework developed by Kim &
+Ostriker to handle radiative heating and cooling, star formation, and resulting
+supernova (SN) feedback. We find that magnetic fields are efficiently amplified
+in the ring due to rotational shear and SN feedback. Within a few
+$100\,\mathrm{Myr}$, the turbulent component $B_\mathrm{trb}$ in the ring
+saturates at $\sim 35\,\mu\mathrm{G}$ (in rough equipartition with the
+turbulent kinetic energy density), while the regular component $B_\mathrm{reg}$
+exceeds $50\,\mu\mathrm{G}$. Expanding superbubbles created by clustered SN
+explosions vertically drag predominantly-toroidal fields from near the midplane
+to produce poloidal fields in high-altitude regions. The growth of magnetic
+fields greatly suppresses star formation at late times. Simultaneously, strong
+magnetic tension in the ring drives radially inward accretion flows from the
+ring to form a circumnuclear disk in the central region; this feature is absent
+in the unmagnetized model.",2303.04206v1
+2023-03-15,Ultrafast Opto-magnetic Effects in the Extreme Ultraviolet Spectral Range,"Coherent light-matter interactions mediated by opto-magnetic phenomena like
+the inverse Faraday effect (IFE) are expected to provide a non-thermal pathway
+for ultrafast manipulation of magnetism on timescales as short as the
+excitation pulse itself. As the IFE scales with the spin-orbit coupling
+strength of the involved electronic states, photo-exciting the strongly
+spin-orbit coupled core-level electrons in magnetic materials appears as an
+appealing method to transiently generate large opto-magnetic moments. Here, we
+investigate this scenario in a ferrimagnetic GdFeCo alloy by using intense and
+circularly polarized pulses of extreme ultraviolet radiation. Our results
+reveal ultrafast and strong helicity-dependent magnetic effects which are in
+line with the characteristic fingerprints of an IFE, corroborated by ab initio
+opto-magnetic IFE theory and atomistic spin dynamics simulations.",2303.08564v1
+2023-03-15,Particle acceleration by magnetic reconnection in relativistic jets: the transition from small to large scales,"Several MHD works and, in particular, the recent one by Medina-Torrejon et
+al. (2021) based on three-dimensional MHD simulations of relativistic jets,
+have evidenced that particle acceleration by magnetic reconnection driven by
+the turbulence in the flow occurs from the resistive up to the large injection
+scale of the turbulence. Particles experience Fermi-type acceleration up to
+ultra-high-energies, predominantly of the parallel velocity component to the
+local magnetic field, in the reconnection layers in all scales due to the ideal
+electric fields of the background fluctuations ($V\times B$, where $V$ and $B$
+are the velocity and magnetic field of the fluctuations, respectively). In this
+work, we show MHD-particle-in-cell (MHD-PIC) simulations following the early
+stages of the particle acceleration in the relativistic jet which confirm these
+previous results, demonstrating the strong potential of magnetic reconnection
+driven by turbulence to accelerate relativistic particles to extreme energies
+in magnetically dominated flows. Our results also show that the dynamical time
+variations of the background magnetic fields do not influence the acceleration
+of the particles in this process.",2303.08780v3
+2023-03-28,Understanding the deflection of the `Cartwheel CME': data analysis and modeling,"We study the low corona evolution of the `Cartwheel' coronal mass ejection
+(CME; 2008-04-09) by reconstructing its 3D path and modeling it with
+magneto-hydrodynamic simulations. This event exhibits a double-deflection that
+has been reported and analyzed in previous works but whose underlying cause
+remained unclear. The `Cartwheel CME' travels toward a coronal hole (CH) and
+against the magnetic gradients. Using a high-cadence, full trajectory
+reconstruction, we accurately determine the location of the magnetic flux rope
+(MFR) and, consequently, the magnetic environment in which it is immersed. We
+find a pseudostreamer (PS) structure whose null point may be responsible for
+the complex evolution of the MFR at the initial phase. From the pre-eruptive
+magnetic field reconstruction, we estimate the dynamic forces acting on the MFR
+and provide a new physical insight on the motion exhibited by the 2008-04-09
+event. By setting up a similar magnetic configuration in a 2.5D numerical
+simulation we are able to reproduce the observed behavior, confirming the
+importance of the PS null point. We find that the magnetic forces directed
+toward the null point cause the first deflection, directing the MFR towards the
+CH. Later, the magnetic pressure gradient of the CH produces the reversal
+motion of the MFR.",2303.15998v2
+2023-04-18,A True Random Number Generator for Probabilistic Computing using Stochastic Magnetic Actuated Random Transducer Devices,"Magnetic tunnel junctions (MTJs), which are the fundamental building blocks
+of spintronic devices, have been used to build true random number generators
+(TRNGs) with different trade-offs between throughput, power, and area
+requirements. MTJs with high-barrier magnets (HBMs) have been used to generate
+random bitstreams with $\lesssim$ 200~Mb/s throughput and pJ/bit energy
+consumption. A high temperature sensitivity, however, adversely affects their
+performance as a TRNG. Superparamagnetic MTJs employing low-barrier magnets
+(LBMs) have also been used for TRNG operation. Although LBM-based MTJs can
+operate at low energy, they suffer from slow dynamics, sensitivity to process
+variations, and low fabrication yield. In this paper, we model a TRNG based on
+medium-barrier magnets (MBMs) with perpendicular magnetic anisotropy. The
+proposed MBM-based TRNG is driven with short voltage pulses to induce
+ballistic, yet stochastic, magnetization switching. We show that the proposed
+TRNG can operate at frequencies of about 500~MHz while consuming less than
+100~fJ/bit of energy. In the short-pulse ballistic limit, the switching
+probability of our device shows robustness to variations in temperature and
+material parameters relative to LBMs and HBMs. Our results suggest that
+MBM-based MTJs are suitable candidates for building fast and energy-efficient
+TRNG hardware units for probabilistic computing.",2304.08808v1
+2023-05-02,Low-temperature Magnetic Fluctuations Investigated by $^{125}$Te-NMR on the Uranium-based Superconductor UTe$_{2}$,"To investigate the static and dynamic magnetic properties on the
+uranium-based superconductor UTe$_{2}$, we measured the NMR Knight shift $K$
+and the nuclear spin-lattice relaxation rate $1/T_{1}$ in $H \parallel a$ by
+$^{125}$Te-NMR on a $^{125}$Te-enriched single-crystal sample. $1/T_1T$ in $H
+\parallel a$ is much smaller than $1/T_1T$ in $H \parallel b$ and $c$, and
+magnetic fluctuations along each axis are derived from the $1/T_1T$ measured in
+$H$ parallel to all three crystalline axes. The magnetic fluctuations are
+almost identical at two Te sites and isotropic at high temperatures, but become
+anisotropic below 40 K, where heavy-fermion state is formed. The character of
+magnetic fluctuations in UTe$_2$ is discussed with the comparison to its static
+susceptibility and the results on other U-based superconductors. It is
+considered that the magnetic fluctuations probed with the NMR measurements are
+determined by the magnetic properties inside the two-leg ladder formed by U
+atoms, which are dominated by the $q_a$ = 0 ferromagnetic fluctuations.",2305.01218v1
+2023-05-05,Are Non-thermal Velocities in Active Region Coronal Loops Anisotropic?,"We have measured line widths in active region coronal loops in order to
+determine whether the non-thermal broadening is anisotropic with respect to the
+magnetic field direction. These non-thermal velocities are caused by unresolved
+fluid motions. Our analysis method combines spectroscopic data and a magnetic
+field extrapolation. We analyzed spectra from the Extreme Ultraviolet Imaging
+Spectrometer on Hinode. A differential emission measure analysis showed that
+many spectral lines that are commonly considered to be formed in the active
+region have a substantial contribution from the background quiet Sun. From
+these spectra we identified lines whose emission was dominated by the active
+region loops rather than background sources. Using these lines, we constructed
+maps of the non-thermal velocity. With data from the Helioseismic Magnetic
+Imager on the Solar Dynamics Observatory and the Coronal Modeling System
+nonlinear force-free magnetic field reconstruction code, we traced several of
+the magnetic field lines through the active region. Comparing the spectroscopic
+and magnetic data, we looked for correlations of non-thermal velocity with the
+viewing angle between the line of sight and the magnetic field. We found that
+non-thermal velocities show a weak anti-correlation with the viewing angle.
+That is, the tendency is for the non-thermal velocity to be slightly larger in
+the parallel direction. This parallel broadening may be due to acoustic waves
+or unresolved parallel flows.",2305.03808v1
+2023-06-20,Asymmetries of frequency splittings of dipolar mixed modes: a window on the topology of deep magnetic fields,"Space asteroseismology is revolutionizing our knowledge of the internal
+structure and dynamics of stars. A breakthrough is ongoing with the recent
+discoveries of signatures of strong magnetic fields in the core of red giant
+stars. The key signature for such a detection is the asymmetry these fields
+induce in the frequency splittings of observed dipolar mixed gravito-acoustic
+modes. We investigate the ability of the observed asymmetries of the frequency
+splittings of dipolar mixed modes to constrain the geometrical properties of
+deep magnetic fields. We use the powerful analytical Racah-Wigner algebra used
+in Quantum Mechanics to characterize the geometrical couplings of dipolar mixed
+oscillation modes with various possible realistic fossil magnetic fields'
+topologies and compute the induced perturbation of their frequencies. First, in
+the case of an oblique magnetic dipole, we provide the exact analytical
+expression of the asymmetry as a function of the angle between the rotation and
+magnetic axes. Its value provides a direct measure of this angle. Second,
+considering a combination of axisymmetric dipolar and quadrupolar fields, we
+show how the asymmetry is blind to unravel the relative strength and sign of
+each component. Finally, in the case of a given multipole, we show that a
+negative asymmetry is a signature of non-axisymmetric topologies. Therefore,
+asymmetries of dipolar mixed modes provide key but only partial information on
+the geometrical topology of deep fossil magnetic fields. Asteroseismic
+constraints should therefore be combined with spectropolarimetric observations
+and numerical simulations, which aim to predict the more probable stable
+large-scale geometries.",2306.11587v1
+2023-07-11,"Dzyaloshinskii-Moriya interactions, Néel skyrmions and V$_4$ magnetic clusters in multiferroic lacunar spinel GaV$_4$S$_8$","Using ab initio density functional theory with static mean-field
+correlations, we calculate the Heisenberg and Dzyaloshinskii-Moriya
+interactions (DMI) for an atomistic spin Hamiltonian for the lacunar spinel,
+GaV$_4$S$_8$. The parameters describing these interactions are used in
+atomistic spin dynamics and micromagnetic simulations. The magnetic properties
+of the lacunar spinel GaV$_4$S$_8$, a material well-known from experiment to
+host magnetic skyrmions of N\'eel character, are simulated with these ab initio
+calculated parameters. The Dzyaloshinskii-Moriya contribution to the
+micromagnetic energy is a sum of two Lifshitz invariants, supporting the
+formation of N\'eel skyrmions and its symmetry agrees with what is usually
+expected for $C_{3\nu}$-symmetric systems. The are several conclusions one may
+draw from this work. One concerns the quantum nature of the magnetism, where we
+show that the precise magnetic state of the V$_4$ cluster is crucial for
+understanding quantitatively the magnetic phase diagram. In particular we
+demonstrate that a distributed-moment state of each V$_4$ cluster explains well
+a variety of properties of GaV$_4$S$_8$, such as the band gap, observed Curie
+temperature and especially the stability of N\'eel skyrmions in the
+experimentally relevant temperature and magnetic-field range. In addition, we
+find that electronic correlations change visibly the calculated value of the
+DMI.",2307.05733v1
+2023-07-17,Confinement of spinons in the XXZ spin-1/2 chain in presence of the transverse magnetic field,"We study the tuning effect of a transverse magnetic field on the confinement
+of spinons in the infinite XXZ spin-1/2 chain. The spinon confinement in this
+model takes place in the gapped antiferromagnetic phase upon application of a
+staggered longitudinal magnetic field. The tuning transverse magnetic field has
+mutually orthogonal uniform and staggered components. The energy spectra of the
+two-spinon bound states (the `mesons') in the confinement regime are
+analytically calculated in this model using two different perturbative schemes.
+The first one applies in the extreme anisotropic (Ising) limit and employs the
+inverse anisotropy constant as a small parameter. The second perturbative
+scheme, which applies at any anisotropy in the gapped antiferromagnetic domain,
+exploits the integrability of the XXZ spin chain at zero magnetic field. The
+small parameters in the second technique are the components of the transverse,
+and staggered longitudinal magnetic fields. It is shown, that the weak
+transverse magnetic field mixes the transverse and longitudinal meson modes,
+and leads to an avoided crossing of their energies upon increase of its
+strength. The explicit formulas for the two-spinon contribution to the
+dynamical structure factors of local spin operators are obtained as well in
+this model in the weak confinement regime for wave-vectors close to the points
+k = 0 and k = \pi.",2307.08328v3
+2023-07-28,Magnetic Antiskyrmions in Two-Dimensional van der Waals Magnets Engineered by Layer Stacking,"Magnetic skyrmions and antiskyrmions are topologically protected
+quasiparticles exhibiting a whirling spin texture in real space. Antiskyrmions
+offer some advantages over skyrmions as they are expected to have higher
+stability and can be electrically driven with no transverse motion. However,
+unlike the widely investigated skyrmions, antiskyrmions are rarely observed due
+to the required anisotropic Dzyaloshinskii-Moriya interaction (DMI). Here we
+propose to exploit the recently demonstrated van der Waals (vdW) assembly of
+two-dimensional (2D) materials that breaks inversion symmetry and creates
+conditions for anisotropic DMI. Using a 2D vdW magnet CrI${}_3$ as an example,
+we demonstrate, based on density functional theory (DFT) calculations, that
+this strategy is a promising platform to realize antiskyrmions. Polar layer
+stacking of two centrosymmetric magnetic monolayers of CrI${}_3$ efficiently
+lowers the symmetry, resulting in anisotropic DMI that supports antiskyrmions.
+The DMI is reversible by switching the ferroelectric polarization inherited
+from the polar layer stacking, offering the control of antiskyrmions by an
+electric field. Furthermore, we find that the magnetocrystalline anisotropy and
+DMI of CrI${}_3$ can be efficiently modulated by Mn doping, creating a
+possibility to control the size of antiskyrmions. Using atomistic spin dynamics
+simulations with the parameters obtained from our DFT calculations, we predict
+the formation of antiskyrmions in a Cr${}_{0.88}$Mn${}_{0.12}$I${}_3$ bilayer
+and switching their spin texture with polarization reversal. Our results open a
+new direction to generate and control magnetic antiskyrmions in 2D vdW magnetic
+systems.",2307.15769v1
+2023-08-07,"Buzdin, Shapiro and Chimera Steps in $\varphi_0$ Josephson Junctions","The unique resonance and locking phenomena in the
+superconductor-ferromagnet-superconductor $\varphi_0$ Josephson junction under
+external electromagnetic radiation are demonstrated when not just the electric
+but also the magnetic component of external radiation is taken into account.
+Due to the coupling of superconductivity and magnetism in this system, the
+magnetic moment precession of the ferromagnetic layer caused by the magnetic
+component of external radiation can lock the Josephson oscillations, which
+results in the appearance of a particular type of steps in the current-voltage
+characteristics, completely different from the well-known Shapiro steps. We
+call these steps the Buzdin steps in the case when the system is driven only by
+the magnetic component and the Chimera steps in the case when both magnetic and
+electric components are present. Unlike the Shapiro steps where the
+magnetization remains constant along the step, here it changes though the
+system is locked. The spin-orbit coupling substantially contributes to the
+amplitude, i.e., the size of these steps. Dramatic changes in their amplitudes
+are also observed at frequencies near the ferromagnetic resonance. Combinations
+of the Josephson and Kittel ferromagnetic resonances together with different
+types of locking pronounced in dynamics and current-voltage characteristics
+make the physics of this system very interesting and open up a series of new
+applications.",2308.03701v2
+2023-08-10,Budget equations and astrophysical nonlinear mean-field dynamos,"Solar, stellar and galactic large-scale magnetic fields are originated due to
+a combined action of non-uniform (differential) rotation and helical motions of
+plasma via mean-field dynamos. Usually, nonlinear mean-field dynamo theories
+take into account algebraic and dynamic quenching of alpha effect and algebraic
+quenching of turbulent magnetic diffusivity. However, the theories of the
+algebraic quenching do not take into account the effect of modification of the
+source of turbulence by the growing large-scale magnetic field. This phenomenon
+is due to the dissipation of the strong large-scale magnetic field resulting in
+an increase of the total turbulent energy. This effect has been studied using
+the budget equation for the total turbulent energy (which takes into account
+the feedback of the generated large-scale magnetic field on the background
+turbulence) for (i) a forced turbulence, (ii) a shear-produced turbulence and
+(iii) a convective turbulence. As the result of this effect, a nonlinear dynamo
+number decreases with increase of the large-scale magnetic field, so that that
+the mean-field $\alpha\Omega$, $\alpha^2$ and $\alpha^2\Omega$ dynamo
+instabilities are always saturated by the strong large-scale magnetic field.",2308.05590v3
+2023-09-11,Dynamics of photospheric magnetic flux distribution and variations in solar RVs -- a study using HARPS-N solar and SDO observations,"The distribution and evolution of photospheric magnetic field in sunspots,
+plages and network, and variations in their relative flux content, play key
+roles in radial velocity (RV) fluctuations observed in Sun-as-a-star spectra.
+Differentiating and disentangling such magnetic contributions to RVs help in
+building models to account for stellar activity signals in high precision RV
+exoplanet searches. In this work, as earlier authors, we employ high-resolution
+images of the solar magnetic field and continuum intensities from SDO/HMI to
+understand the activity contributions to RVs from HARPS-N solar observations.
+Using well observed physical relationships between strengths and fluxes of
+photospheric magnetic fields, we show that the strong fields (spots, plages and
+network) and the weak internetwork fields leave distinguishing features in
+their contributions to the RV variability. We also find that the fill-factors
+and average unsigned magnetic fluxes of different features correlate
+differently with the RVs and hence warrant care in employing either of them as
+a proxy for RV variations. In addition, we examine disk averaged UV intensities
+at 1600 \r{A} and 1700 \r{A} wavelength bands imaged by SDO/AIA and their
+performances as proxies for variations in different magnetic features. We find
+that the UV intensities provide a better measure of contributions of plage
+fields to RVs than the Ca II H-K emission indices, especially during high
+activity levels when the latter tend to saturate.",2309.05428v1
+2023-09-19,Engineering skyrmion from spin spiral in transition metal multilayers,"Skyrmions having topologically protected field configurations with
+particle-like properties play an important role in various field of science.
+Our present study focus on the generation of skyrmion from spin spiral in the
+magnetic multilayers of 4d-Fe/Ir(111) with 4d = Y, Zr, Nb, Mo, Ru, Rh. Here we
+investigate the impact of 4d transition metals on the isotropic Heisenberg
+exchanges and anti-symmetric Dzyaloshinskii-Moriya interactions originating
+from the broken inversion symmetry at the interface of 4d-Fe/Ir(111)
+multilayers. We find a strong exchange frustration due to the hybridization of
+the Fe-3d layer with both 4d and Ir-5d layers which modifies due to band
+filling effects of the 4d transition metals. We strengthen the analysis of
+exchange frustration by shedding light on the orbital decomposition of
+isotropic exchange interactions of Fe-3d orbitals. Our spin dynamics and Monte
+Carlo simulations indicate that the magnetic ground state of 4d-Fe/Ir(111)
+transition multilayers is a spin spiral in the $ab$-plane with a period of 1 to
+2.5 nm generated by magnetic moments of Fe atoms and propagating along the
+$a$-direction. The spiral wavelengths in Y-Fe/Ir(111) are much larger compared
+to Rh-Fe/Ir(111). In order to manipulate the skyrmion phase in 4d-Fe/Ir(111),
+we investigate the magnetic ground state of 4d-Fe/Ir(111) transition
+multilayers with different external magnetic field. An increasing external
+magnetic field of $\sim$ 12 T is responsible for deforming the spin spiral into
+a isolated skyrmion which flips into skyrmion lattice phase around $\sim$ 18 T
+in Rh-Fe/Ir(111). Our study predict that the stability of magnetic skyrmion
+phase in Rh-Fe/Ir(111) against thermal fluctuations is upto temperature T $\leq
+90$ K.",2309.10752v1
+2023-09-29,Muon Spin Relaxation Study of frustrated Tm$_3$Sb$_3$Mg$_2$O$_{14}$ with kagomé lattice,"The structure and magnetic properties of rare-earth ions Tm$^{3+}$ kagom\'{e}
+lattice Tm$_3$Sb$_3$Mg$_2$O$_{14}$ are studied by X-ray diffraction, magnetic
+susceptibility and muon spin relaxation ($\mu$SR) experiments. The existence of
+a small amount of Tm/Mg site-mixing disorder is revealed. DC magnetic
+susceptibility measurement shows that Tm$^{3+}$ magnetic moments are
+antiferromagnetically correlated with a negative Curie-Weiss temperature of
+-26.3 K. Neither long-range magnetic order nor spin-glass transition is
+observed by DC and AC magnetic susceptibility, and confirmed by $\mu$SR
+experiment down to 0.1 K. However, the emergence of short-range magnetic order
+is indicated by the zero-field $\mu$SR experiments, and the absence of spin
+dynamics at low temperatures is evidenced by the longitudinal-field $\mu$SR
+technique. Compared with the results of Tm$_3$Sb$_3$Zn$_2$O$_{14}$, another
+Tm-based kagom\'{e} lattice with much more site-mixing disorder, the gapless
+spin liquid like behaviors in Tm$_3$Sb$_3$Zn$_2$O$_{14}$ can be induced by
+disorder effect. Samples with perfect geometrical frustration are in urgent
+demand to establish whether QSL exits in this kind of materials with rare-earth
+kagom\'{e} lattice.",2309.16947v1
+2023-11-03,Magnetic properties and spin dynamics in a spin-orbit driven Jeff= 1/2 triangular lattice antiferromagnet,"Frustration-induced strong quantum fluctuations accompanied by spin-orbit
+coupling and crystal electric field can give rise to rich and diverse magnetic
+phenomena associated with unconventional low-energy excitations in rare-earth
+based quantum magnets. Herein, we present crystal structure, magnetic
+susceptibility, specific heat, muon spin relaxation(muSR), and electron spin
+resonance (ESR) studies on the polycrystalline samples of Ba6Yb2Ti4O17 in which
+Yb3+ ions constitute a perfect triangular lattice in ab-plane without
+detectable anti-site disorder between atomic sites. The Curie-Weiss fit of
+low-temperature magnetic susceptibility data suggest the spin-orbit entangled
+Jeff = 1/2 degrees of freedom of Yb3+ spin with weak antiferromagnetic exchange
+interactions in the Kramers doublet ground state. The zero-field specific heat
+data reveal the presence of long-range magnetic order at TN = 77 mK which is
+suppressed in a magnetic field 1 T. The broad maximum in specific heat is
+attributed to the Schottky anomaly implying the Zeeman splitting of the Kramers
+doublet ground state. The ESR measurements suggest the presence of anisotropic
+exchange interaction between the moments of Yb3+ spins and the well separated
+Kramers doublet state. muSR experiments reveal a fluctuating state of Yb3+
+spins in the temperature range 0.1 K-100 K owing to depopulation of crystal
+electric field levels, which suggests that the Kramers doublets are well
+separated consistent with thermodynamic and ESR results. In addition to the
+intraplane nearest-neighbor superexchange interaction, the interplane exchange
+interaction and anisotropy are expected to stabilize the long-range ordered
+state in this triangular lattice antiferromagnet.",2311.01858v1
+2024-01-08,Computational approaches to modeling dynamos in galaxies,"Galaxies are observed to host magnetic fields with a typical total strength
+of around 15microgauss. A coherent large-scale field constitutes up to a few
+microgauss of the total, while the rest is built from strong magnetic
+fluctuations over a wide range of spatial scales. This represents sufficient
+magnetic energy for it to be dynamically significant. Several questions
+immediately arise: What is the physical mechanism that gives rise to such
+magnetic fields? How do these magnetic fields affect the formation and
+evolution of galaxies? In which physical processes do magnetic fields play a
+role, and how can that role be characterized? Numerical modelling of magnetized
+flows in galaxies is playing an ever-increasing role in finding those answers.
+We review major techniques used for these models. Current results strongly
+support the conclusion that field growth occurs during the formation of the
+first galaxies on timescales shorter than their accretion timescales due to
+small-scale turbulent dynamos. The saturated small-scale dynamo maintains field
+strengths at a few percent of equipartition with turbulence. The subsequent
+action of large-scale dynamos in differentially rotating discs produces
+observed modern field strengths in equipartition with the turbulence and having
+power at large scales. The field structure resulting appears consistent with
+observations including Faraday rotation and polarisation from synchrotron and
+dust thermal emission. Major remaining challenges include scaling numerical
+models toward realistic scale separations and Prandtl and Reynolds numbers.",2401.04015v1
+2024-01-08,Outflows Driven from a Magnetic Pseudodisk,"Outflows play a pivotal role in star formation as one of its most visible
+markers and a means of transporting mass, momentum, and angular momentum from
+the infalling gas into the surrounding molecular cloud. Their wide reach (at
+least thousands of au) is a contrast to typical disk sizes ($\sim 10-100$ au).
+We employ high-resolution three-dimensional nested-grid nonideal
+magnetohydrodynamic (MHD) simulations to study outflow properties in the Class
+0 phase. We find that no disk wind is driven from the extended centrifugal disk
+that has weak magnetic coupling. The low-velocity winds emerge instead from the
+infalling magnetic pseudodisk. Much of the disk actually experiences an infall
+of matter rather than outflowing gas. Some of the pseudodisk wind (PD-wind)
+moves inward to regions above the disk and either falls onto the disk or
+proceeds upward. The upward flow gives the impression of a disk wind above a
+certain height even if the gas is originally emerging from the pseudodisk. The
+PD-wind has the strongest flow coming from a disk interaction zone that lies
+just outside the disk and is an interface between the inwardly advected
+magnetic field of the pseudodisk and the outwardly diffusing magnetic field of
+the disk. The low-velocity wind exhibits the features of a flow driven by the
+magnetic pressure gradient force in some regions and those of a
+magnetocentrifugal wind in other regions. We interpret the structure and
+dynamics of the outflow zone in terms of the basic physics of gravity, angular
+momentum, magnetic fields, and nonideal MHD.",2401.04260v3
+2024-02-01,Comparing growth of titania and carbonaceous dusty nanoparticles in weakly magnetised capacitively coupled plasmas,"This study investigates the growth cycles of titania and carbonaceous dusty
+nanoparticles in capacitively coupled radiofrequency plasmas, focusing on the
+impact of weak magnetic field of approximately 480 Gauss. The growth of dusty
+nanoparticles in these plasmas is cyclic, with particles reaching their maximum
+size and subsequently moving out of the plasma, followed by the initiation of a
+new particle growth cycle. We compare the growth of titania and carbonaceous
+dusty particles in the presence and absence of a magnetic field. The presence
+of the magnetic field fastens the growth cycle in both types of dusty plasmas.
+Langmuir probe measurement of the background plasma parameters such as electron
+temperature and floating potential reveal radial variations in floating
+potential but not electron temperature. Furthermore, the magnetic field changes
+the radial variation of floating potential. The magnetic field also influences
+the spatial distribution of the two dust cloud differently. It is possible that
+these differences arises due to the material's different response to the
+magnetic field. These findings shed light on the intricate dynamics of titania
+and carbonaceous dusty plasma particle growth, offering insights into the
+impact of weak magnetization on dust behavior, which have implications for
+various applications, from space science to semiconductor processing.",2402.00951v3
+2024-02-06,Ultrafast terahertz field control of the emergent magnetic and electronic interactions at oxide interfaces,"Ultrafast electric-field control of emergent electronic and magnetic states
+at oxide interfaces offers exciting prospects for the development of new
+generations of energy-efficient devices. Here, we demonstrate that the
+electronic structure and emergent ferromagnetic interfacial state in epitaxial
+LaNiO3/CaMnO3 superlattices can be effectively controlled using intense
+single-cycle THz electric-field pulses. We employ a combination of
+polarization-dependent X-ray absorption spectroscopy with magnetic circular
+dichroism and X-ray resonant magnetic reflectivity to measure a detailed
+magneto-optical profile and thickness of the ferromagnetic interfacial layer.
+Then, we use time-resolved and temperature-dependent magneto-optical Kerr
+effect, along with transient optical reflectivity and transmissivity
+measurements, to disentangle multiple correlated electronic and magnetic
+processes driven by ultrafast high-field (~1 MV/cm) THz pulses. These processes
+include an initial sub-picosecond electronic response, consistent with
+non-equilibrium Joule heating; a rapid (~270 fs) demagnetization of the
+ferromagnetic interfacial layer, driven by THz-field-induced nonequilibrium
+spin-polarized currents; and subsequent multi-picosecond dynamics, possibly
+indicative of a change in the magnetic state of the superlattice due to the
+transfer of spin angular momentum to the lattice. Our findings shed light on
+the intricate interplay of electronic and magnetic phenomena in this strongly
+correlated material system, suggesting a promising avenue for efficient control
+of two-dimensional ferromagnetic states at oxide interfaces using ultrafast
+electric-field pulses.",2402.04302v1
+2024-02-12,Magnetic field of gas giant exoplanets and its influence on the retention of their exomoons,"We study the magnetic and tidal interactions of a gas-giant exoplanet with
+its host star and with its exomoons, and focus on their retention. We briefly
+revisit the scaling law for planetary dynamo in terms of its mass, radius and
+luminosity. Based on the virial theorem, we construct an evolution law for
+planetary magnetic field and find that its initial entropy is important for the
+field evolution of a high-mass planet. We estimate the magnetic torques on
+orbit arising from the star-planet and planet-moon magnetic interactions, and
+find that it can compensate tidal torques and bypass frequency valleys where
+dynamical-tide response is ineffective. For exomoon's retention we consider two
+situations. In the presence of a circumplanetary disk (CPD), by comparison
+between CPD's inner and outer radii, we find that planets with too strong
+magnetic fields or too small distance from its host star tend not to host
+exomoons. During the subsequent CPD-free evolution, we find, by comparison
+between planet's spindown and moon's migration timescales, that hot Jupiters
+with periods of several days are unlikely to retain large exomoons, albeit they
+could be surrounded by rings from the debris of tidally disrupted moons. In
+contrast, moons, if formed around warm or cold Jupiters, can be preserved.
+Finally, we estimate the radio power and flux density due to the star-planet
+and planet-moon magnetic interactions and give the upper limit of detection
+distance by FAST.",2402.07387v5
+2024-03-12,Noncentrosymmetric Triangular Magnet CaMnTeO$_6$: Strong Quantum Fluctuations and Role of s0 vs. s2 Electronic States in Competing Exchange Interactions,"Noncentrosymmetric triangular magnets offer a unique platform for realizing
+strong quantum fluctuations. However, designing these quantum materials remains
+an open challenge attributable to a knowledge gap in the tunability of
+competing exchange interactions at the atomic level. Here, we create a new
+noncentrosymmetric triangular S = 3/2 magnet CaMnTeO$_6$ based on careful
+chemical and physical considerations. The model material displays competing
+magnetic interactions and features nonlinear optical responses with the
+capability of generating coherent photons. The incommensurate magnetic ground
+state of CaMnTeO$_6$ with an unusually large spin rotation angle of 127 deg.(1)
+indicates that the anisotropic interlayer exchange is strong and competing with
+the isotropic interlayer Heisenberg interaction. The moment of 1.39(1) $\mu$B,
+extracted from low-temperature heat capacity and neutron diffraction
+measurements, is only 46% of the expected value of the static moment 3 $\mu$B.
+This reduction indicates the presence of strong quantum fluctuations in the
+half-integer spin S = 3/2 CaMnTeO$_6$ magnet, which is rare. By comparing the
+spin-polarized band structure, chemical bonding, and physical properties of
+AMnTeO$_6$ (A = Ca, Sr, Pb), we demonstrate how quantum-chemical interpretation
+can illuminate insights into the fundamentals of magnetic exchange
+interactions, providing a powerful tool for modulating spin dynamics with
+atomically precise control.",2403.08069v1
+2001-05-16,A dynamical mean field theory for the magnetic transition temperature of ferromagnetic semiconductors,"This paper has been withdrawn by the authors due to a numerical error. A
+revised version will be posted shortly.",0105331v2
+2007-01-25,The anisotropic XY model on the inhomogeneous periodic chain,"The static and dynamic properties of the anisotropic XY-model $(s=1/2)$ on
+the inhomogeneous periodic chain, composed of $N$ cells with $n$ different
+exchange interactions and magnetic moments, in a transverse field $h,$ are
+determined exactly at arbitrary temperatures. The properties are obtained by
+introducing the Jordan-Wigner fermionization and by reducing the problem to a
+diagonalization of a finite matrix of $nth$ order. The quantum transitions are
+determined exactly by analyzing, as a function of the field, the induced
+magnetization $1/n\sum_{m=1}^{n}\mu_{m}\left< S_{j,m}^{z}\right>$ ($j$ denotes
+the cell, $m$ the site within the cell, $\mu_{m}$ the magnetic moment at site
+$m$ within the cell) and the spontaneous magnetization $1/n\sum_{m=1}^{n}\left<
+S_{j,m}^{x},\right>$ which is obtained from the correlations $\left<
+S_{j,m}^{x}S_{j+r,m}^{x}\right>$ for large spin separations. These results,
+which are obtained for infinite chains, correspond to an extension of the ones
+obtained by Tong and Zhong(\textit{Physica B} \textbf{304,}91 (2001)). The
+dynamic correlations, $\left<
+S_{j,m}^{z}(t)S_{j^{\prime},m^{\prime}}^{z}(0)\right>$, and the dynamic
+susceptibility, $\chi_{q}^{zz}(\omega),$ are also obtained at arbitrary
+temperatures. Explicit results are presented in the limit T=0, where the
+critical behaviour occurs, for the static susceptibility $\chi_{q}^{zz}(0)$ as
+a function of the transverse field $h$, and for the frequency dependency of
+dynamic susceptibility $\chi_{q}^{zz}(\omega)$.",0701630v2
+2005-09-22,"Ericson fluctuations in an open, deterministic quantum system: theory meets experiment","We provide numerically exact photoexcitation cross sections of rubidium
+Rydberg states in crossed, static electric and magnetic fields, in quantitative
+agreement with recent experimental results. Their spectral backbone underpins a
+clear transition towards the Ericson regime.",0509189v1
+2006-02-24,Gyroelectric cubic-quintic dissipative solitons,"The influence of an externally applied magnetic field upon classic cubic
+quintic dissipative solitons is investigated using both exact simulations and a
+Lagrangian technique. The basic approach is to use a spatially inhomogeneous
+magnetic field and to consider two important geometries, namely the Voigt and
+the Faraday effects. A layered structure is selected for the Voigt case with
+the principal aim being to demonstrate non-reciprocal behaviour for various
+classes of spatial solitons that are known to exist as solutions of the complex
+Ginzburg-Landau cubic-quintic envelope equation under dissipative conditions.
+The system is viewed as dynamical and an opportunity is taken to display the
+behaviour patterns of the spatial solitons in terms of two-dimensional
+dynamical plots involving the total energy and the peak amplitude of the
+spatial solitons. This action this leads to limit cycle plots that beautifully
+reveal the behaviour of the solitons solutions at all points along the
+propagation axis. The closed contour that exists in the absence of a magnetic
+field is opened up and a limit point is exposed. The onset of chaos is revealed
+in a dramatic way and it is clear that detailed control by the external
+magnetic field can be exercised. The Lagrangian approach is adjusted to deal
+with dissipative systems and through the choice of particular trial functions,
+aspects of the dynamic behaviour of the spatial are predicted by this approach.
+Finally, some vortex dynamics in the Faraday configuration are investigated.",0602166v1
+2007-07-13,Effect of antiferromagnetic exchange interactions on the Glauber dynamics of one-dimensional Ising models,"We study the effect of antiferromagnetic interactions on the single spin-flip
+Glauber dynamics of two different one-dimensional (1D) Ising models with spin
+$\pm 1$. The first model is an Ising chain with antiferromagnetic exchange
+interaction limited to nearest neighbors and subject to an oscillating magnetic
+field. The system of master equations describing the time evolution of
+sublattice magnetizations can easily be solved within a linear field
+approximation and a long time limit. Resonant behavior of the magnetization as
+a function of temperature (stochastic resonance) is found, at low frequency,
+only when spins on opposite sublattices are uncompensated owing to different
+gyromagnetic factors (i.e., in the presence of a ferrimagnetic short range
+order). The second model is the axial next-nearest neighbor Ising (ANNNI)
+chain, where an antiferromagnetic exchange between next-nearest neighbors (nnn)
+is assumed to compete with a nearest-neighbor (nn) exchange interaction of
+either sign. The long time response of the model to a weak, oscillating
+magnetic field is investigated in the framework of a decoupling approximation
+for three-spin correlation functions, which is required to close the system of
+master equations. The calculation, within such an approximate theoretical
+scheme, of the dynamic critical exponent z, defined as ${1/\tau} \approx ({1/
+{\xi}})^z$ (where \tau is the longest relaxation time and \xi is the
+correlation length of the chain), suggests that the T=0 single spin-flip
+Glauber dynamics of the ANNNI chain is in a different universality class than
+that of the unfrustrated Ising chain.",0707.1953v1
+2008-07-20,Nonlinear Solar Dynamo Model with Magnetic Helicity,"Variations of the sunspot number are important indicators of the solar
+activity cycles. The sunspot formation is a result of a dynamo process inside
+the Sun, which is far from being understood. We use simple dynamical models of
+the dynamo process to simulate the magnetic field evolution and investigate
+general properties of the sunspot number variations during the solar cycles. We
+have found that the classical Parker's model with a standard kinetic helicity
+quenching cannot represent the typical profiles of the solar-cycle variations
+of the sunspot number, and also does not give chaotic solutions. For modeling
+of the solar cycle properties we use a nonlinear dynamo model of Kleeorin and
+Ruzmaikin (1982), which takes into account dynamics of the turbulent magnetic
+helicity. We have obtained a series of periodic and chaotic solutions for
+different layers of the convective zone. The solutions qualitatively reproduce
+some basic observational features of the solar cycle properties, in particular,
+the relationship between the growth time and the cycle amplitude. Also, on the
+longer time scale the dynamo model with the magnetic helicity has intermittent
+solutions, which may be important for modeling long-term variations of the
+solar cycles.",0807.3192v2
+2008-09-15,Kinetics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model,"We present a study, within a mean-field approach, of the kinetics of a mixed
+ferrimagnetic model on a square lattice in which two interpenetrating square
+sublattices have spins that can take two values, $\sigma=\pm1/2$, alternated
+with spins that can take the four values, $S=\pm3/2, \pm1/2$. We use the
+Glauber-type stochastic dynamics to describe the time evolution of the system
+with a crystal-field interaction in the presence of a time-dependent
+oscillating external magnetic field. The nature (continuous and discontinuous)
+of transition is characterized by studying the thermal behaviors of average
+order parameters in a period. The dynamic phase transition points are obtained
+and the phase diagrams are presented in the reduced magnetic field amplitude
+$(h)$ and reduced temperature $(T)$ plane, and in the reduced temperature and
+interaction parameter planes, namely in the $(h, T)$ and $(d, T)$ planes, $d$
+is the reduced crystal-field interaction. The phase diagrams always exhibit a
+tricritical point in $(h, T)$ plane, but do not exhibit in the $(d, T)$ plane
+for low values of $h$. The dynamic multicritical point or dynamic critical end
+point exist in the $(d, T)$ plane for low values of $h$. Moreover, phase
+diagrams contain paramagnetic $(p)$, ferromagnetic $(f)$, ferrimagnetic $(i)$
+phases, two coexistence or mixed phase regions, $(f+p)$ and $(i+p)$, that
+strongly depend on interaction parameters.",0809.2450v1
+2009-02-17,Helicity and the Mañé critical value,"We establish a relationship between the helicity of a magnetic flow on a
+closed surface of genus $\geq 2$ and the Ma\~n\'e critical value.",0902.2903v2
+2011-04-24,"Reduced fluid-kinetic equations for low-frequency dynamics, magnetic reconnection and electron heating in low-beta plasmas","A minimal model for magnetic reconnection and, generally, low-frequency
+dynamics in low-beta plasmas is proposed. The model combines analytical and
+computational simplicity with physical realizability: it is a rigorous limit of
+gyrokinetics for plasma beta of order the electron-ion mass ratio. The model
+contains collisions and can be used both in the collisional and collisionless
+reconnection regimes. It includes gyrokinetic ions (not assumed cold) and
+allows for the topological rearrangement of the magnetic field lines by either
+resistivity or electron inertia, whichever predominates. The two-fluid dynamics
+are coupled to electron kinetics --- electrons are not assumed isothermal and
+are described by a reduced drift-kinetic equation. The model therefore allows
+for irreversibility and conversion of magnetic energy into electron heat via
+parallel phase mixing in velocity space. An analysis of the exchanges between
+various forms of free energy and its conversion into electron heat is provided.
+It is shown how all relevant linear waves and regimes of the tearing
+instability (collisionless, semicollisional and fully resistive) are recovered
+in various limits of our model. An efficient way to simulate our equations
+numerically is proposed, via the Hermite representation of the velocity space.
+It is shown that small scales in velocity space will form, giving rise to a
+shallow Hermite-space spectrum, whence it is inferred that, for steady-state or
+sufficiently slow dynamics, the electron heating rate will remain finite in the
+limit of vanishing collisionality.",1104.4622v2
+2012-08-04,Dynamical and stationary critical behavior of the Ising ferromagnet in a thermal gradient,"In this paper we present and discuss results of Monte Carlo numerical
+simulations of the two-dimensional Ising ferromagnet in contact with a heat
+bath that intrinsically has a thermal gradient. The extremes of the magnet are
+at temperatures $T_1<T_c<T_2$, where $T_c$ is the Onsager critical temperature.
+In this way one can observe a phase transition between an ordered phase
+($T<T_c$) and a disordered one ($T>T_c$) by means of a single simulation. By
+starting the simulations with fully disordered initial configurations with
+magnetization $m\equiv 0$ corresponding to $T=\infty$, which are then suddenly
+annealed to a preset thermal gradient, we study the short-time critical dynamic
+behavior of the system. Also, by setting a small initial magnetization $m=m_0$,
+we study the critical initial increase of the order parameter. Furthermore, by
+starting the simulations from fully ordered configurations, which correspond to
+the ground state at T=0 and are subsequently quenched to a preset gradient, we
+study the critical relaxation dynamics of the system. Additionally, we perform
+stationary measurements ($t\rightarrow\infty$) that are discussed in terms of
+the standard finite-size scaling theory. We conclude that our numerical
+simulation results of the Ising magnet in a thermal gradient, which are
+rationalized in terms of both dynamic and standard scaling arguments, are fully
+consistent with well established results obtained under equilibrium conditions.",1208.0965v1
+2012-10-01,"Seismology of the Sun : Inference of Thermal, Dynamic and Magnetic Field Structures of the Interior","Recent overwhelming evidences show that the sun strongly influences the
+Earth's climate and environment. Moreover existence of life on this Earth
+mainly depends upon the sun's energy. Hence, understanding of physics of the
+sun, especially the thermal, dynamic and magnetic field structures of its
+interior, is very important. Recently, from the ground and space based
+observations, it is discovered that sun oscillates near 5 min periodicity in
+millions of modes. This discovery heralded a new era in solar physics and a
+separate branch called helioseismology or seismology of the sun has started.
+Before the advent of helioseismology, sun's thermal structure of the interior
+was understood from the evolutionary solution of stellar structure equations
+that mimicked the present age, mass and radius of the sun. Whereas solution of
+MHD equations yielded internal dynamics and magnetic field structure of the
+sun's interior. In this presentation, I review the thermal, dynamic and
+magnetic field structures of the sun's interior as inferred by the
+helioseismology.",1210.0467v1
+2014-12-17,Chromospheric diagnosis with Ca II lines: forward modeling in forward scattering (I),"This paper shows the first synthetic tomography of the quiet solar
+chromosphere formed by spatial maps of scattering polarization. It has been
+calculated for the CaII 8498, 8542 and 3934 A lines by solving the NLTE
+(non-local thermodynamical equilibrium) RT (radiative transfer) problem of the
+second kind in a 3D atmosphere model obtained from realistic MHD
+(magneto-hydrodynamical) simulations. Maps of circular polarization were
+calculated neglecting atomic polarization. Our investigation focuses on the
+linear polarization signals induced by kinematics, radiation field anisotropy
+and Hanle effect in forward-scattering geometry. Thus, instead of considering
+slit profiles at the limb as normally done in the study of the second solar
+spectrum, we synthetize and analyze spatial maps of polarization at disk
+center. It allows us to understand the spatial signatures of dynamics and
+magnetic field in the linear polarization for discriminating them
+observationally. Our results suggest new ideas for chromospheric diagnosis that
+will be developed throughout a serie of papers. In particular, Hanle Polarity
+Inversion Lines and dynamic Hanle diagrams are two concepts introduced in the
+present work. We find that chromospheric dynamics and magnetic field topology
+create spatial fingerprints in the polarization maps that trace the dynamic
+situation of the plasma and the magnetic field. Based on such spatial features
+we reconstruct the magnetic field intensity in the middle chromosphere along
+grooves of null linear polarization. We finally address the problems of
+diagnosing Hanle saturation and kinematic amplification of scattering signals
+using Hanle diagrams.",1412.5386v1
+2015-03-03,A simple and universal setup of quasi-monocolor gamma-ray source,"Strict classic 3-D dynamics theory reveals that arbitrarily high center
+frequency light source can be achieved by flexible application of
+not-too-strong static electric field and static magnetic field. The magnitudes
+of the fields are not required to be high.",1503.00815v1
+2015-05-25,Quantum Dynamical Phase Transition in a Spin-Orbit Coupled Bose Condensate,"Spin-orbit coupled bosons can exhibit rich equilibrium phases at low
+temperature and in the presence of particle-particle interactions. In the case
+with a 1D synthetic spin-orbit interaction, it has been observed that the
+ground state of a Bose gas can be a normal phase, stripe phase, or magnetized
+phase in different experimentally controllable parameter regimes. The
+magnetized states are doubly degenerate and consist of a many-particle
+two-state system. In this work, we investigate the nonequilibrium quantum
+dynamics by switching on an external perturbation to induce resonant couplings
+between the magnetized phases, and predict the novel quantum spin dynamics
+which cannot be obtained in the single-particle systems. In particular, due to
+particle-particle interactions, the transition of the Bose condensate from one
+magnetized phase to the other is forbidden when the strength of external
+perturbation is less than a critical value, and a full transition can occur
+only when the perturbation exceeds such critical strength. This phenomenon
+manifests itself a quantum dynamical phase transition, with the critical point
+behavior being exactly solvable. From the numerical simulations and exact
+analytic studies we show that the predicted many-body effects can be well
+observed with the current experiments.",1505.06687v1
+2015-07-13,Macrospin Dynamics in Antiferromagnets Triggered by Sub-20 femtosecond Injection of Nanomagnons,"The understanding of how the sub-nanoscale exchange interaction evolves in
+macroscale correlations and ordered phases of matter, such as magnetism and
+superconductivity, requires to bridge the quantum and classical worlds. This
+monumental challenge has so far only been achieved for systems close to their
+thermodynamical equilibrium. Here we follow in real time the ultrafast dynamics
+of the macroscale magnetic order parameter triggered by the impulsive optical
+generation of spin excitations with the shortest possible nanometer-wavelength
+and femtosecond-period. Our experiments also disclose a possibility for the
+coherent control of these femtosecond nanomagnons, which are defined by the
+exchange energy. These findings open up novel opportunities for fundamental
+research on the role of short-wavelength spin excitations in magnetism and
+high-temperature superconductivity, since they provide a macroscopic probe of
+the femtosecond dynamics of sub-nanometer spin-spin correlations and,
+ultimately, of the exchange energy. With this approach it becomes possible to
+trace the dynamics of such short-range magnetic correlations for instance
+during phase transitions. Moreover, our work suggests that nanospintronics and
+nanomagnonics can employ phase-controllable spin waves with frequencies in the
+20 THz domain.",1507.03377v1
+2015-09-01,Lattice dynamics and a magnetic-structural phase transition in the nickel orthoborate $Ni_{3}(BO_{3})_{2}$,"Nickel orthoborate $Ni_{3}(BO_{3})_{2}$ having a complex orthorhombic
+structure $P_{nnm}$ (#58, Z=2) of the kotoite type is known for quite a long
+time as an antiferromagnetic material below $T_{N}$ = 46 K, but up to now its
+physical properties including the lattice dynamics have not been explored. Six
+magnetic nickel $Ni^{2+}$ ions (S=1) in the unit cell are distributed over the
+2a and 4f positions in the centers of distorted $[O_{6}]$ octahedra. The
+$[NiO_{6}]$ units are linked via rigid $[BO_{3}]$ groups and these structural
+particularities impose restrictions on the lattice dynamics and spin-phonon
+interactions. We performed the symmetry analysis of the phonon modes at the
+center of the Brillouin zone. The structural parameters and phonon modes were
+calculated using Dmol3 program. We report and analyze results of infrared and
+Raman studies of phonon spectra measured in all required polarizations. Most of
+the even and odd phonons predicted on the basis of the symmetry analysis and
+theoretical calculations were reliably identified in the measured spectra.
+Absorption measurements in the infrared region showed emergence of several very
+narrow and weak phonons at the magnetic ordering temperature $T_{N}$. This
+observation proves the existence of a structural phase transition not reported
+before which is evidently coupled intrinsically with the magnetic dynamics of
+$Ni_{3}(BO_{3})_{2}$. A clear evidence of spin-phonon interaction was observed
+for some particular phonons below $T_{N}$.",1509.00344v2
+2015-12-14,The dynamics of Wolf numbers based on nonlinear dynamo with magnetic helicity: comparisons with observations,"We investigate the dynamics of solar activity using a nonlinear
+one-dimensional dynamo model and a phenomenological equation for the evolution
+of Wolf numbers. This system of equations is solved numerically. We take into
+account the algebraic and dynamic nonlinearities of the alpha effect. The
+dynamic nonlinearity is related to the evolution of a small-scale magnetic
+helicity, and it leads to a complicated behavior of solar activity. The
+evolution equation for the Wolf number is based on a mechanism of formation of
+magnetic spots as a result of the negative effective magnetic pressure
+instability (NEMPI). This phenomenon was predicted 25 years ago and has been
+investigated intensively in recent years through direct numerical simulations
+and mean-field simulations. The evolution equation for the Wolf number includes
+the production and decay of sunspots. Comparison between the results of
+numerical simulations and observational data of Wolf numbers shows a 70 %
+correlation over all intervals of observation (about 270 years). We determine
+the dependence of the maximum value of the Wolf number versus the period of the
+cycle and the asymmetry of the solar cycles versus the amplitude of the cycle.
+These dependencies are in good agreement with observations.",1512.04363v4
+2016-01-08,Spin-glass like dynamics of ferromagnetic clusters in La$_{0.75}$Ba$_{0.25}$CoO$_3$,"We report the magnetization study of the compound
+La$_{0.75}$Ba$_{0.25}$CoO$_3$ where Ba$^{2+}$ doping is just above the critical
+limit for percolation of ferromagnetic clusters. The field cooled (FC) and zero
+field cooled (ZFC) magnetization exhibit a thermomagnetic irreversibility and
+the ac susceptibility show a frequency dependent peak at the ferromagnetic
+ordering temperature (T$_C$$\approx$203~K) of the clusters. These features
+indicate about the presence of a non-equilibrium state below T$_C$. In the
+non-equilibrium state, the dynamic scaling of the imaginary part of ac
+susceptibility and the static scaling of the nonlinear susceptibility clearly
+establish a spin-glass like cooperative freezing of ferromagnetic clusters at
+200.9(2)~K. The existence of spin-glass like freezing of ferromagnetic clusters
+is further substantiated by the ZFC aging and memory experiments. We also
+observe certain dynamical features which are not present in a typical
+spin-glass, such as, initial magnetization after ZFC aging first increases and
+then decreases with the wait time and an imperfect recovery of relaxation in
+negative temperature cycling experiments. This imperfect recovery transforms to
+perfect recovery on concurrent field cycling. Our analysis suggests that these
+additional dynamical features have their origin in inter-cluster exchange
+interaction and cluster size distribution. The inter-cluster exchange
+interaction above the magnetic percolation gives a superferromagnetic state in
+some granular thin films but our results show the absence of typical
+superferromagnetic like state in La$_{0.75}$Ba$_{0.25}$CoO$_3$.",1601.02009v1
+2017-02-24,Magnetic order and spin dynamics across a ferromagnetic quantum critical point: $μ$SR investigations of YbNi$_4$(P$_{1-x}$As$_x$)$_2$,"In the quasi-1D heavy-fermion system YbNi$_4$(P$_{1-x}$As$_x$)$_2$ the
+presence of a ferromagnetic (FM) quantum critical point (QCP) at $x_c$ $\approx
+0.1$ with unconventional quantum critical exponents in the thermodynamic
+properties has been recently reported. Here, we present muon-spin relaxation
+($\mu$SR) experiments on polycrystals of this series to study the magnetic
+order and the low energy 4$f$-electronic spin dynamics across the FM QCP. The
+zero field $\mu$SR measurements on pure YbNi$_4$(P$_{2}$ proved static long
+range magnetic order and suggested a strongly reduced ordered Yb moment of
+about 0.04$\mu_B$. With increasing As substitution the ordered moment is
+reduced by half at $x = 0.04$ and to less than 0.005 $\mu_B$ at $x=0.08$. The
+dynamic behavior in the $\mu$SR response show that magnetism remains
+homogeneous upon As substitution, without evidence for disorder effect. In the
+paramagnetic state across the FM QCP the dynamic muon-spin relaxation rate
+follows 1/$T_{1}T\propto T^{-n}$ with $1.01 \pm 0.04 \leq n \leq 1.13 \pm
+0.06$. The critical fluctuations are very slow and are even becoming slower
+when approaching the QCP.",1702.07504v2
+2017-03-22,Time evolution of a pair of distinguishable interacting spins subjected to controllable and noisy magnetic fields,"The quantum dynamics of a
+$\hat{\mathbf{J}}^2=(\hat{\mathbf{j}}_1+\hat{\mathbf{j}}_2)^2$-conserving
+Hamiltonian model describing two coupled spins $\hat{\mathbf{j}}_1$ and
+$\hat{\mathbf{j}}_2$ under controllable and fluctuating time-dependent magnetic
+fields is investigated. Each eigenspace of $\hat{\mathbf{J}}^2$ is dynamically
+invariant and the Hamiltonian of the total system restricted to any one of such
+$(j_1+j_2)-|j_1-j_2|+1$ eigenspaces, possesses the SU(2) structure of the
+Hamiltonian of a single fictitious spin acted upon by the total magnetic field.
+We show that such a reducibility holds regardless of the time dependence of the
+externally applied field as well as of the statistical properties of the noise,
+here represented as a classical fluctuating magnetic field. The time evolution
+of the joint transition probabilities of the two spins $\hat{\mathbf{j}}_1$ and
+$\hat{\mathbf{j}}_2$ between two prefixed factorized states is examined,
+bringing to light peculiar dynamical properties of the system under scrutiny.
+When the noise-induced non-unitary dynamics of the two coupled spins is
+properly taken into account, analytical expressions for the joint Landau-Zener
+transition probabilities are reported. The possibility of extending the
+applicability of our results to other time-dependent spin models is pointed
+out.",1703.07673v3
+2017-05-02,Slow spin tunneling in the paramagnetic phase of the pyrochlore Nd2Sn2O7,"The insulating pyrochlore compound Nd2Sn2O7 has been shown to undergo a
+second order magnetic phase transition at Tc ~ 0.91 K to a noncoplanar
+all-in--all-out magnetic structure of the Nd3+ magnetic moments. An anomalously
+slow paramagnetic spin dynamics has been evidenced from neutron backscattering
+and muon spin relaxation (muSR). In the case of muSR this has been revealed
+through the strong effect of a 50 mT longitudinal field on the spin-lattice
+relaxation rate. Here, motivated by a recent successful work performed for
+Yb2Ti2O7 and Yb2Sn2O7, analyzing the shape of the muSR longitudinal
+polarization function, we substantiate the existence of extremely slow
+paramagnetic spin dynamics in the microsecond time range for Nd2Sn2O7. Between
+1.7 and 7 K, this time scale is temperature independent. This suggests a double
+spin-flip tunneling relaxation mechanism to be at play, probably involving spin
+substructures such as tetrahedra. Unexpectedly, the standard deviation of the
+field distribution at the muon site increases as the system is cooled. This
+exotic spin dynamics is in sharp contrast with the dynamics above 100 K which
+is driven by the Orbach relaxation mechanism involving single Nd3+ magnetic
+moments.",1705.01004v1
+2017-05-18,Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy,"Studies of magnetization dynamics have incessantly facilitated the discovery
+of fundamentally novel physical phenomena, making steady headway in the
+development of magnetic and spintronics devices. The dynamics can be induced
+and detected electrically, offering new functionalities in advanced electronics
+at the nanoscale. However, its scattering mechanism is still disputed.
+Understanding the mechanism in thin films is especially important, because most
+spintronics devices are made from stacks of multilayers with nanometer
+thickness. The stacks are known to possess interfacial magnetic anisotropy, a
+central property for applications, whose influence on the dynamics remains
+unknown. Here, we investigate the impact of interfacial anisotropy by adopting
+CoFeB/MgO as a model system. Through systematic and complementary measurements
+of ferromagnetic resonance (FMR), on a series of thin films, we identify
+narrower FMR linewidths at higher temperatures. We explicitly rule out the
+temperature dependence of intrinsic damping as a possible cause, and it is also
+not expected from existing extrinsic scattering mechanisms for ferromagnets. We
+ascribe this observation to motional narrowing, an old concept so far neglected
+in the analyses of FMR spectra. The effect is confirmed to originate from
+interfacial anisotropy, impacting the practical technology of spin-based
+nanodevices up to room temperature.",1705.06624v1
+2018-02-20,Ultrafast magnetization dynamics in pure and doped Heusler and inverse Heusler alloys,"By using a multiscale approach based on first-principles density functional
+theory combined with atomistic spin dynamics, we investigate the electronic
+structure and magnetization dynamics of an inverse Heusler and a Heusler
+compound and their alloys, i. e. Mn$_{2-x}Z_x$CoAl and Mn$_{2-x}Z_x$VAl, where
+$Z$ = Mo, W, Os and Ru, respectively. A signature of the ferrimagnetic ordering
+of Mn$_{2}$CoAl and Mn$_{2}$VAl Heusler alloys is reflected in the calculated
+Heisenberg exchange constants. They decay very rapidly with the interatomic
+distance and have short range, which is a consequence of the existence of the
+finite gap in the minority spin band. The calculated Gilbert damping parameter
+of both Mn$_2$CoAl and Mn$_2$VAl is high compared to other half-metals, but
+interestingly in the particular case of the inverse Mn$_{2}$CoAl alloys and due
+to the spin-gapless semiconducting property, the damping parameters decrease
+with the doping concentration in clear contradiction to the general trend.
+Atomistic spin dynamics simulations predict ultrafast magnetisation switching
+in Mn$_{2}$CoAl and Mn$_{2}$VAl under the influence of an external magnetic
+field, starting from a threshold field of $2\text{T}$. Our overall finding
+extends with Heusler and inverse Heusler alloys, the class of materials that
+exhibits laser induced magnetic switching.",1802.07195v1
+2018-06-24,Nanoscopic time crystal obtained by nonergodic spin dynamics,"We study the far-from-equilibrium properties of quenched magnetic nanoscopic
+classical spin systems. In particular, we focus on the interplay between
+lattice vibrations and magnetic frustrations induced by surface effects typical
+of an antiferromagnet. We use a combination of Monte Carlo simulations and
+explore the dynamical behaviours by solving the stochastic
+Landau-Lifshitz-Gilbert equation at finite temperature. The Monte Carlo
+approach treats both the ionic degrees of freedom and spin variables on the
+same footing, via an extended Lennard-Jones Hamiltonian with a spin-lattice
+coupling. The zero temperature phase diagram of the finite size nanoscopic
+systems with respect to the range of the Heisenberg interaction and the
+Lennard-Jones coupling constant shows two main structures with non-trivial
+magnetisation triggered by antiferromagnetism: a simple cubic and a
+body-centred cubic. At non zero temperature, the competition between spins and
+the ionic vibrations considerably affects the magnetization of the system.
+Exploring the dynamics reveals a non-trivial structural induced behaviour in
+the spin relaxation with a concomitant memory of the initially applied
+ferromagnetic quench. We report the observation of a non-trivial dynamical
+scenario, obtained after a ferromagnetic magnetic quench at low temperature.
+Furthermore, we observe long-lived non-thermal states which could open new
+avenues for nano-technology.",1806.09130v4
+2018-08-01,Spin fluctuations in the light-induced high spin state of Cobalt valence tautomers,"We present a study of the static magnetic properties and spin dynamics in
+Cobalt valence tautomers (VT), molecules where a low-spin (LS) to high-spin
+(HS) crossover driven by an intramolecular electron transfer can be controlled
+by the temperature, by the external pressure or by light irradiation. In the
+investigated complex, a LS-Co(III) ion bound to a dinegative organic ligand can
+be reversibly converted into the HS-Co(II) bound to a mononegative one. By
+combining magnetization measurements with Nuclear Magnetic Resonance (NMR) and
+Muon Spin Relaxation ({\mu}SR), we have investigated the static magnetic
+properties and the spin dynamics as a function of the temperature. Moreover,
+the effect of the external pressure as well as of the infrared light
+irradiation have been explored through magnetometry and NMR measurements to
+determine the spin dynamics of the HS state. The photoinduced HS state, which
+can have a lifetime of several hours below 30 K, is characterized by spin
+dynamics in the MHz range, which persist at least down to 10 K. The application
+of an external pressure causes a progressive increase of the LS-HS crossover,
+which reaches room temperature for pressures around 10 kbar.",1808.04229v1
+2019-04-17,Peculiarities of the Dynamics of Solar NOAA Active Region 12673,"The dynamics of active region (AR) 12673 is qualitatively studied using
+observational data obtained with the Helioseismic and Magnetic Imager of the
+Solar Dynamics Observatory on August 31--September 8, 2017. This AR was
+remarkable for its complex structure and extraodinary flare productivity. The
+sunspot group in this AR consisted of (1) an old, well-developed and highly
+stable, coherent sunspot, which had also been observed two solar rotations
+earlier, and (2) a rapidly developing cluster of umbral and penumbral
+fragments. Cluster (2) formed two elongated, arc-shaped chains of spot
+elements, skirting around the major sunspot (1), with two chains of magnetic
+elements spatially coinciding with the arcs. AR components (1) and (2) were in
+relative motion, cluster (2) overtaking spot (1), and their relative velocity
+agrees in order of magnitude with the velocity jump over the near-surface shear
+layer, or leptocline. The pattern of motion of the features about the main spot
+bears amazing resemblance to the pattern of a fluid flow about a roundish body.
+This suggests that spot (1) was dynamically coupled with the surface layers,
+while cluster (2) developed in deeper layers of the convection zone. The
+magnetic-flux emergence in cluster (2) appeared to be associated with fluid
+motions similar to roll convection. The mutual approach of components (1) and
+(2) gave rise to lights bridges in the umbrae of sunspots with the magnetic
+field having the same sign on both sides of the bridge.",1904.08367v3
+2019-08-12,"Spin beats in the photoluminescence polarization dynamics of charged excitons in InP/(In,Ga)P quantum dots in presence of nuclear quadrupole interaction","The spin dynamics of positively (X$^{+}$) and negatively (X$^{-}$) charged
+excitons in InP/In$_{0.48}$Ga$_{0.52}$P quantum dots subject to a magnetic
+field is studied. We find that a characteristic feature of the system under
+study is the presence of nuclear quadrupole interaction, which leads to
+stabilization of the nuclear and electron spins in a quantum dot in zero
+external magnetic field. In detail, the nuclear quadrupole interaction leads to
+pinning of the Overhauser field along the quadrupole axis, which is close to
+the growth axis of the heterostructure. The nuclear effects are observed only
+when resident electrons are confined in the quantum dots, i.e. for X$^{-}$
+trion photoexcitation. The presence of X$^{-}$ and X$^{+}$ trion contributions
+to the photoluminescence together with the quadrupole interaction significantly
+affects the dynamics of optical orientation in Voigt magnetic field. In absence
+of dynamic nuclear spin polarization the time evolution of the
+photoluminescence polarization was fitted by a form which describes the
+electron spin relaxation in ""frozen"" nuclear field fluctuations. In relatively
+large external magnetic fields exceeding 60 mT good agreement between theory
+and experiment is achieved.",1908.04167v1
+2020-10-17,Ferromagnetic Gyroscopes for Tests of Fundamental Physics,"A ferromagnetic gyroscope (FG) is a ferromagnet whose angular momentum is
+dominated by electron spin polarization and that will precess under the action
+of an external torque, such as that due to a magnetic field. Here we model and
+analyze FG dynamics and sensitivity, focusing on practical schemes for
+experimental realization. In the case of a freely floating FG, we model the
+transition from dynamics dominated by libration in relatively high externally
+applied magnetic fields, to those dominated by precession at relatively low
+applied fields. Measurement of the libration frequency enables in situ
+measurement of the magnetic field and a technique to reduce the field below the
+threshold for which precession dominates the FG dynamics. We note that evidence
+of gyroscopic behavior is present even at magnetic fields much larger than the
+threshold field below which precession dominates. We also model the dynamics of
+an FG levitated above a type-I superconductor via the Meissner effect, and find
+that for FGs with dimensions larger than about 100 nm the observed precession
+frequency is reduced compared to that of a freely floating FG. This is akin to
+negative feedback that arises from the distortion of the field from the FG by
+the superconductor. Finally we assess the sensitivity of an FG levitated above
+a type-I superconductor to exotic spin-dependent interactions under practical
+experimental conditions, demonstrating the potential of FGs for tests of
+fundamental physics.",2010.08731v1
+2021-01-10,On the origin of the solar hemispherical helicity rules: Simulations of the rise of magnetic flux concentrations in a background field,"Solar active regions and sunspots are believed to be formed by the emergence
+of strong toroidal magnetic flux from the solar interior. Modeling of such
+events has focused on the dynamics of compact magnetic entities, colloquially
+known as ""flux tubes"", often considered to be isolated magnetic structures
+embedded in an otherwise field-free environment. In this paper, we show that
+relaxing such idealized assumptions can lead to surprisingly different
+dynamics. We consider the rise of tube-like flux concentrations embedded in a
+large-scale volume-filling horizontal field in an initially quiescent
+adiabatically-stratified compressible fluid. In a previous letter, we revealed
+the unexpected major result that concentrations that have their twist aligned
+with the background field at the bottom of the tube are more likely to rise
+than the opposite orientation (for certain values of the parameters). This bias
+leads to a selection rule which, when applied to solar dynamics, is in
+agreement with the observations known as the solar hemispheric helicity rule(s)
+(SHHR). Here, we examine this selection mechanism in more detail than was
+possible in the earlier letter. We explore the dependence on the parameters via
+simulations, delineating the Selective Rise Regime (SRR), where the bias
+operates. We provide a theoretical model to predict and explain the simulation
+dynamics. Furthermore, we create synthetic helicity maps from Monte Carlo
+simulations to mimic the SHHR observations and demonstrate that our mechanism
+explains the observed scatter in the rule and its variation over the solar
+cycle.",2101.03472v1
+2021-06-11,Fast collective oscillations and clustering phenomena in an antiferromagnetic mean-field model,"We study the out-of-equilibrium properties of the antiferromagnetic
+Hamiltonian Mean-Field model at low energy. In this regime, the Hamiltonian
+dynamics exhibits the presence of a stationary state where the rotators are
+gathered in a bicluster. This state is not predicted by equilibrium statistical
+mechanics in the microcanonical ensemble. Performing a low kinetic energy
+approximation, we derive the explicit expression of the magnetization vector as
+a function of time. We find that the latter displays coherent oscillations, and
+we show numerically that the probability distribution for its phase is bimodal
+or quadrimodal. We then look at the individual rotator dynamics as a motion in
+an external time-dependent potential, given by the magnetization. This dynamics
+exhibits two distinct time scales, with the fast one associated to the
+oscillations of the global magnetization vector. Performing an average over the
+fast oscillations, we derive an expression for the effective force acting on
+the individual rotator. This force is always bimodal, and determines a low
+frequency oscillation of the rotators. Our approach leads to a self-consistent
+theory linking the time-dependence of the magnetization to the motion of the
+rotators, providing a heuristic explanation for the formation of the bicluster.",2106.07392v1
+2022-06-20,First-principles calculation of the parameters used by atomistic magnetic simulations,"While the ground state of magnetic materials is in general well described on
+the basis of spin density functional theory (SDFT), the theoretical description
+of finite-temperature and non-equilibrium properties require an extension
+beyond the standard SDFT. Time-dependent SDFT (TD-SDFT), which give for example
+access to dynamical properties are computationally very demanding and can
+currently be hardly applied to complex solids. Here we focus on the alternative
+approach based on the combination of a parameterized phenomenological spin
+Hamiltonian and SDFT-based electronic structure calculations, giving access to
+the dynamical and finite-temperature properties for example via spin-dynamics
+simulations using the Landau-Lifshitz-Gilbert (LLG) equation or Monte Carlo
+simulations. We present an overview on the various methods to calculate the
+parameters of the various phenomenological Hamiltonians with an emphasis on the
+KKR Green function method as one of the most flexible band structure methods
+giving access to practically all relevant parameters. Concerning these, it is
+crucial to account for the spin-orbit coupling (SOC) by performing relativistic
+SDFT-based calculations as it plays a key role for magnetic anisotropy and
+chiral exchange interactions represented by the DMI parameters in the spin
+Hamiltonian. This concerns also the Gilbert damping parameters characterizing
+magnetization dissipation in the LLG equation, chiral multispin interaction
+parameters of the extended Heisenberg Hamiltonian, as well as spin-lattice
+interaction parameters describing the interplay of spin and lattice dynamics
+processes, for which an efficient computational scheme has been developed
+recently by the present authors.",2206.09969v1
+2022-08-17,The quantum dynamic range of room temperature spin imaging,"Magnetic resonance imaging of spin systems combines scientific applications
+in medicine, chemistry and physics. Here, we investigate the pixel-wise
+coherent quantum dynamics of spins consisting of a 40 by 40 micron sized region
+of interest implanted with nitrogen vacancy centers (NV) coupled to a
+nano-magnetic flake of $\mathrm{CrTe_2}$. $\mathrm{CrTe_2}$ is an in-plane van
+der Waals ferromagnet, which we can probe quantitatively by the NV electron's
+spin signal even at room temperature. First, we combine the nano-scale sample
+shapes measured by atomic force microscope with the magnetic resonance imaging
+data. We then map out the coherent dynamics of the colour centers coupled to
+the van der Waals ferromagnet using pixel-wise coherent Rabi and Ramsey imaging
+of the NV sensor layer. Next, we fit the pixel-wise solution of the Hamiltonian
+to the quantum sensor data. Combining data and model, we can explore the
+detuning range of the spin oscillation with a quantum dynamic range of over
+$\left|\Delta_{max}\right|= 60 { }\mathrm{MHz} $ in the Ramsey interferometry
+mode. Finally, we show the effect of the $\mathrm{CrTe_2}$ van der Waals magnet
+on the coherence of the NV sensor layer and measure a 70 times increase in the
+maximum frequency of the quantum oscillation going from the Rabi to the Ramsey
+imaging mode.",2208.08146v1
+2022-11-07,Multilayer spintronic neural networks with radio-frequency connections,"Spintronic nano-synapses and nano-neurons perform complex cognitive
+computations with high accuracy thanks to their rich, reproducible and
+controllable magnetization dynamics. These dynamical nanodevices could
+transform artificial intelligence hardware, provided that they implement
+state-of-the art deep neural networks. However, there is today no scalable way
+to connect them in multilayers. Here we show that the flagship nano-components
+of spintronics, magnetic tunnel junctions, can be connected into multilayer
+neural networks where they implement both synapses and neurons thanks to their
+magnetization dynamics, and communicate by processing, transmitting and
+receiving radio frequency (RF) signals. We build a hardware spintronic neural
+network composed of nine magnetic tunnel junctions connected in two layers, and
+show that it natively classifies nonlinearly-separable RF inputs with an
+accuracy of 97.7%. Using physical simulations, we demonstrate that a large
+network of nanoscale junctions can achieve state-of the-art identification of
+drones from their RF transmissions, without digitization, and consuming only a
+few milliwatts, which is a gain of more than four orders of magnitude in power
+consumption compared to currently used techniques. This study lays the
+foundation for deep, dynamical, spintronic neural networks.",2211.03659v1
+2022-11-09,Time-resolved measurement of spin excitations in Cu$_2$OSeO$_3$,"Magnetic diffraction in combination with x-ray detected ferromagnetic
+resonance (DFMR) is a powerful technique for performing time-resolved
+measurements on individual spin textures. Here, we study the ferromagnetic
+resonance (FMR) modes of both the conical and field-polarized phases in the
+chiral magnet Cu$_2$OSeO$_3$. Following the identification of the FMR modes at
+different temperatures using broadband vector network analyzer FMR, we use DFMR
+on the crystalline (001) Bragg peak to reveal the time-dependent spin
+configurations of the selected FMR modes. By being able to measure both the
+amplitude and phase response of the spin system across the resonance, a
+continuous phase advance (of 180$^\circ$) in the conical mode, and a phase lag
+(of 180$^\circ$) in the field-polarized mode is found. By performing dynamic
+measurements in the conical phase as a function of the linear polarization
+angle of the x-rays, i.e., successively probing the dynamics of the moments, we
+find an inversion of the dynamics along the conical axis upon inverting the
+applied field direction. By allowing for time-resolved measurements of the
+phase and amplitude of individual magnetic phases, DFMR opens up new
+opportunities for obtaining a deeper understanding of the complex dynamics of
+chiral magnets.",2211.05195v1
+2023-04-26,Charged particle dynamics in parabolic magnetosphere around Schwarzschild black hole,"The study of charged particle dynamics in the combined gravitational and
+magnetic field can provide important theoretical insight into astrophysical
+processes around black holes. In this paper, we explore the charged particle
+dynamics in parabolic magnetic field configuration around Schwarzschild black
+hole, since the paraboloidal shapes of magnetic field lines around black holes
+are well motivated by the numerical simulations and supported by observations
+of relativistic jets. Analysing the stability of bounded orbits and using the
+effective potential approach, we show the possibility of existence of stable
+circular off-equatorial orbits around the symmetry axis. We also show the
+influence of radiation reaction force on the dynamics of charged particles, in
+particular on the chaoticity of the motion and Poincar\'{e} sections,
+oscillatory frequencies, and emitted electromagnetic spectrum. Applied to
+Keplerian accretion disks, we show that in parabolic magnetic field
+configuration, the thin accretion configurations can be either destroyed or
+transformed into a thick toroidal structure given the radiation reaction and
+electromagnetic-disk interactions included. Calculating the Fourier spectra for
+radiating charged particle trajectories, we find that the radiation reaction
+force does not affect the main frequency peaks, however, it lowers the higher
+harmonics making the spectrum more flat and diluted in high frequency range.",2304.13603v1
+2023-07-22,Magnetization dynamics due to field interplay in field free spin Hall nano-oscillators,"Spin Hall nano oscillators (SHNOs) have shown applications in unconventional
+computing schemes and broadband frequency generation in the presence of applied
+external magnetic field. However, under field-free conditions, the oscillation
+characteristics of SHNOs display a significant dependence on the effective
+field, which can be tuned by adjusting the constriction width, thereby
+presenting an intriguing area of study. Here we study the effect of nano
+constriction width on the magnetization dynamics in anisotropy assisted field
+free SHNOs. In uniaxial anisotropy-based field-free SHNOs, either the
+anisotropy field or the demagnetization field can dominate the magnetization
+dynamics depending on the constriction width. Our findings reveal distinct
+auto-oscillation characteristics in narrower constrictions with 20 nm and 30 nm
+constriction width compared to their wider counterpart with 100 nm width. The
+observed frequency shift variations with input current and constriction widths
+stem from the inherent nonlinearity of the system. The interplay between the
+B_demag and B_anis, coupled with changes in constriction width, yields rich
+dynamics and offers control over frequency tunability, auto oscillation
+amplitude, and threshold current. Notably, the spatial configuration of spin
+wave wells within the constriction undergoes transformations in response to
+changes in both constriction width and anisotropy. The findings highlight the
+significant influence of competing fields at the constriction on the field-free
+auto oscillations of SHNOs, with this impact intensifying as the constriction
+width is varied.",2307.12068v1
+2023-12-12,Sliding Dynamics of Current-Driven Skyrmion Crystal and Helix in Chiral Magnets,"The skyrmion crystal (SkX) and helix (HL) phases, present in typical chiral
+magnets, can each be considered as forms of density waves but with distinct
+topologies. The SkX exhibits gyrodynamics analogous to electrons under a
+magnetic field, while the HL state resembles topological trivial spin density
+waves. However, unlike the charge density waves, the theoretical analysis of
+the sliding motion of SkX and HL remains unclear, especially regarding the
+similarities and differences in sliding dynamics between these two spin density
+waves. In this work, we systematically explore the sliding dynamics of SkX and
+HL in chiral magnets in the limit of large current density. We demonstrate that
+the sliding dynamics of both SkX and HL can be unified within the same
+theoretical framework as density waves, despite their distinct microscopic
+orders. Furthermore, we highlight the significant role of gyrotropic sliding
+induced by impurity effects in the SkX state, underscoring the impact of
+nontrivial topology on the sliding motion of density waves. Our theoretical
+analysis shows that the effect of impurity pinning is much stronger in HL
+compared with SkX, i.e., $\chi^{SkX}/\chi^{HL}\sim \alpha^2$ ($\chi^{SkX}$,
+$\chi^{HL}$: susceptibility to the impurity potential, $\alpha$ ($\ll 1$) is
+the Gilbert damping). Moreover, the velocity correction is mostly in the
+transverse direction to the current in SkX. These results are further
+substantiated by realistic Landau-Lifshitz-Gilbert simulations.",2312.07116v2
+2023-12-14,Dust Dynamics in Hall-effected Protoplanetary Disks. I. Background Drift Hall Instability,"Recent studies have shown that the large-scale gas dynamics of protoplanetary
+disks (PPDs) are controlled by non-ideal magneto-hydrodynamics (MHD), but how
+this influences dust dynamics is not fully understood. To this end, we
+investigate the stability of dusty, magnetized disks subject to the Hall
+effect, which applies to planet-forming regions of PPDs. We find a novel
+Background Drift Hall Instability (BDHI) that may facilitate planetesimal
+formation in Hall-effected disk regions. Through a combination of linear
+analysis and nonlinear simulations, we demonstrate the viability and
+characteristics of BDHI. We find it can potentially dominate over the classical
+streaming instability (SI) and standard MHD instabilities at low dust-to-gas
+ratios and weak magnetic fields. We also identify magnetized versions of the
+classic SI, but these are usually subdominant. We highlight the complex
+interplay between magnetic fields and dust-gas dynamics in PPDs, underscoring
+the need to consider non-ideal MHD like the Hall effect in the broader
+narrative of planet formation.",2312.09180v1
+2024-03-11,Ultrafast switching of sliding ferroelectricity and dynamical magnetic field in van der Waals bilayer induced by light,"Sliding ferroelectricity is a unique type of polarity recently observed in a
+properly stacked van der Waals bilayer. However, electric-field control of
+sliding ferroelectricity is hard and could induce large coercive electric
+fields and serious leakage currents which corrode the ferroelectricity and
+electronic properties, which are essential for modern two-dimensional
+electronics and optoelectronics. Here, we proposed laser-pulse deterministic
+control of sliding ferroelectricity in bilayer h-BN by first principles and
+molecular dynamics simulation with machine-learned force fields. The laser
+pulses excite shear modes which exhibit certain directional movements of
+lateral sliding between bilayers. The vibration of excited modes under laser
+pulses is predicted to overcome the energy barrier and achieve the switching of
+sliding ferroelectricity. Furthermore, it is found that three possible sliding
+transitions - between AB (BA) and BA (AB) stacking - can lead to the occurrence
+of dynamical magnetic fields along three different directions. Remarkably, the
+magnetic fields are generated by the simple linear motion of nonmagnetic
+species, without any need for more exotic (circular, spiral) pathways. Such
+predictions of deterministic control of sliding ferroelectricity and
+multi-states of dynamical magnetic field thus expand the potential applications
+of sliding ferroelectricity in memory and electronic devices.",2403.06531v2
+1996-08-07,Dynamics of the 1D Heisenberg model and optical absorption of spinons in cuprate antiferromagnetic chains,"We use numerical and analytical results to construct a simple ansatz for the
+energy dynamical correlation function of the 1D antiferromagnetic Heisenberg
+model. This is applied to compute the phonon assisted absorption spectra of
+magnetic excitations (spinons) in quasi-one dimensional spin 1/2 insulators and
+show to reproduce very well recent infrared measurements in Sr$_2$CuO$_3$.",9608035v1
+1998-07-08,Integrability and Quantum Chaos in Spin Glass Shards,"We study spin glass clusters (""shards"") in a random transverse magnetic
+field, and determine the regime where quantum chaos and random matrix level
+statistics emerge from the integrable limits of weak and strong field.
+Relations with quantum phase transition are also discussed.",9807123v1
+1998-12-09,Critical Relaxation and Critical Exponents,"Dynamic relaxation of the XY model and fully frustrated XY model quenched
+from an initial ordered state to the critical temperature or below is
+investigated with Monte Carlo methods. Universal power law scaling behaviour is
+observed. The dynamic critical exponent $z$ and the static exponent $\eta$ are
+extracted from the time-dependent Binder cumulant and magnetization. The
+results are competitive to those measured with traditional methods.",9812147v1
+2000-09-25,Spin dynamics in Cuprates and its relation to superconductivity,"The relevance of magnetism for the mechanism responsible for high-temperature
+superconductivity remains an open and still interesting issue. The observation
+by inelastic neutron scattering of strong antiferromagnetic dynamical
+correlations in superconducting cuprates is discussed in relation to the
+unusual physical properties of the cuprates as well as in relation to the
+superconducting pairing.",0009373v1
+2000-11-21,Time resolved nanosecond vortex dynamics in high Tc superconducting films,"We report on the observation of the rearrangement of vortices in the ns time
+scale following a fast magnetic field variation due to selective local heating
+of a high Tc superconducting film. Detailed simulations describing the measured
+photoinduced voltage signals along the film lead to a better understanding of
+vortex dynamics in fast regimes, where mean vortex velocities reach 10000 m/s",0011347v1
+2001-04-27,Magnetic order in the Ising model with parallel dynamics,"It is discussed how the equilibrium properties of the Ising model are
+described by an Hamiltonian with an antiferromagnetic low temperature behavior
+if only an heat bath dynamics, with the characteristics of a Probabilistic
+Cellular Automaton, is assumed to determine the temporal evolution of the
+system.",0104529v1
+2001-10-19,Very low-frequency excitations in frustrated two-dimensional $S=1/2$ Heisenberg antiferromagnets,"muSR and 7Li NMR relaxation measurements in frustrated two-dimensional S=1/2
+Heisenberg antiferromagnets on a square lattice are presented. It is found that
+both in Li2VOSiO4 and Li2VOGeO4, spin dynamics at frequencies well below the
+Heisenberg exchange frequency are present. These dynamics are associated with
+the motions of walls separating coexisting collinear domains with a magnetic
+wave vector rotated by 90 degrees.",0110398v1
+2002-08-20,"Comment on ""Critical Dynamics of a Vortex-Loop Model for the Superconducting Transition""","Recently, Aji and Goldenfeldt [Phys. Rev. Lett. 87, 197003 (2001),
+cond-mat/0105622] put forward an explanation for the value of the dynamic
+critical exponent z observed in certain Monte Carlo simulations of the
+superconducting phase transition in zero magnetic field. In this Comment, we
+point out that their analysis is based on incorrect assumptions regarding the
+scaling dimension of the vortex density.",0208380v1
+2003-10-30,Time and length scales in spin glasses,"We discuss the slow, nonequilibrium, dynamics of spin glasses in their glassy
+phase. We briefly review the present theoretical understanding of the
+spectacular phenomena observed in experiments and describe new numerical
+results obtained in the first large-scale simulation of the nonequilibrium
+dynamics of the three dimensional Heisenberg spin glass.",0310721v1
+2004-02-03,Simulations of Dynamical Ordering in Pinned Vortex Systems,"We model a vortex system in a sample with bulk pinning and superficial
+pinning generated by a magnetic decoration. We perform a sequence of finite
+temperature numerical experiments in which external forces are applied to
+obtain a dynamically ordered vortex lattice. We analyze the final structures
+and the behavior of the total energy of the system.",0402098v1
+2005-02-10,Mott--Hubbard and Anderson Transitions in Dynamical Mean--Field Theory,"The Anderson--Hubbard Hamiltonian at half--filling is investigated within
+dynamical mean--field theory at zero temperature. The local density of states
+is calculated by taking the geometric and arithmetic mean, respectively. The
+non--magnetic ground state phase diagrams obtained within the different
+averaging schemes are compared.",0502257v1
+2005-03-03,Quantum dynamics of a nanomagnet in a rotating field,"Quantum dynamics of a two-state spin system in a rotating magnetic field has
+been studied. Analytical and numerical results for the transition probability
+have been obtained along the lines of the Landau-Zener-Stueckelberg theory. The
+effect of various kinds of noise on the evolution of the system has been
+analyzed.",0503085v1
+2005-08-29,Effect of nuclear spins on the electron spin dynamics in negatively charged InP quantum dots,"Kinetics of polarized photoluminescence of the negatively charged InP quantum
+dots in weak magnetic field is studied experimentally. Effect of both the
+nuclear spin fluctuations and the dynamical nuclear polarization on the
+electron spin orientation is observed.",0508698v1
+1993-11-19,Exploring the Dynamics of Three-Dimensional Lattice Gauge Theories by External Fields,"We investigate the dynamics of three-dimensional lattice gauge theories by
+means of an external Abelian magnetic field. For the SU(2) lattice gauge theory
+we find evidence of the unstable modes.",9311024v1
+2004-07-13,Dynamical correlation functions of the XXZ spin-1/2 chain,"We derive a master equation for the dynamical spin-spin correlation functions
+of the XXZ spin-1/2 Heisenberg finite chain in an external magnetic field. In
+the thermodynamic limit, we obtain their multiple integral representation.",0407108v1
+2001-10-18,Topological entropy of a magnetic flow and the growth of the number of trajectories,Final version. To appear in Discrete and Continuous Dynamical Systems - A.,0110194v3
+1998-02-02,Muon Dynamics in a Toroidal Sector Magnet,"We present a Hamiltonian formulation of muon dynamics in toroidal sector
+solenoids (bent solenoids)",9802002v1
+2004-05-11,Dynamic effects in nonlinear magneto-optics of atoms and molecules,"A brief review is given of topics relating to dynamical processes arising in
+nonlinear interactions between light and resonant systems (atoms or molecules)
+in the presence of a magnetic field.",0405049v1
+2006-08-03,Periodically forced ferrofluid pendulum: effect of polydispersity,"We investigate a torsional pendulum containing a ferrofluid that is forced
+periodically to undergo small-amplitude oscillations. A homogeneous magnetic
+field is applied perpendicular to the pendulum axis. We give an analytical
+formula for the ferrofluid-induced ``selfenergy'' in the pendulum's dynamic
+response function for monodisperse as well as for polydisperse ferrofluids.",0608037v1
+2007-10-17,On the dynamics created by a time--dependent Aharonov-Bohm flux,"We study the dynamics of classical and quantum particles moving in a
+punctured plane under the influence of a homogeneous magnetic field and driven
+by a time-dependent singular flux tube through the hole.",0710.3270v1
+2009-06-22,A tool to estimate the critical dynamics and thickness of superconducting films and interfaces,"We demonstrate that the magnetic field dependence of the conductivity
+measured at the transition temperature allows the dynamical critical exponent,
+the thickness of thin superconducting films and interfaces, and the limiting
+lateral length to be determined. The resulting tool is applied to the
+conductivity data of an amorphous Nb0.15 Si0.85 film and a LaAlO3/SrTiO3
+interface.",0906.3990v1
+2009-10-07,Gauge invariance and classical dynamics of noncommutative particle theory,"We consider a model of classical noncommutative particle in an external
+electromagnetic field. For this model, we prove the existence of generalized
+gauge transformations. Classical dynamics in Hamiltonian and Lagrangian form is
+discussed, in particular, the motion in the constant magnetic field is studied
+in detail.",0910.1341v1
+2012-07-24,Dynamic aperture and space charge effect studies for the Recycler ring for Project-X,"A simplified Recycler lattice was created to fine tune injection straight,
+ring tune, and phase trombone. In this paper, we will present detailed
+modifications for further optimization of Recycler lattice which requires the
+investigation of tune footprint and dynamic aperture based on higher order
+momentum components of the magnetic fields, together with the space charge
+effects.",1207.5733v1
+2013-02-14,"Bounded analytic maps, Wall fractions and ABC flow","In this work we study the qualitative properties of real analytic bounded
+maps defined in the infinite complex strip. The main tool is approximation by
+continued g-fractions of Wall. As an application, the ABC flow system is
+considered which is essential to the origin of the solar magnetic field.",1302.3279v3
+2013-08-25,Open problems and questions about geodesics,"The paper surveys open problems and questions related to geodesics defined by
+Riemannian, Finsler, semi Riemannian and magnetic structures on manifolds.",1308.5417v3
+2014-06-16,Macroscopic limit of a bipartite Curie-Weiss model: a dynamical approach,"We analyze the Glauber dynamics for a bi-populated Curie-Weiss model. We
+obtain the limiting behavior of the empirical averages in the limit of
+infinitely many particles. We then characterize the phase space of the model in
+absence of magnetic field and we show that several phase transitions in the
+inter-groups interaction strength occur.",1406.4044v2
+2016-07-07,MHD turbulence and distributed chaos,"It is shown, using results of recent direct numerical simulations, that
+spectral properties of distributed chaos in MHD turbulence with zero mean
+magnetic field are similar to those of hydrodynamic turbulence. An exception is
+MHD spontaneous breaking of space translational symmetry, when the stretched
+exponential spectrum $\exp(-k/k_{\beta})^{\beta}$ has $\beta=4/7$.",1607.02073v2
+2017-02-12,Vortex Dynamics in Type II Superconductors,"Time dependent Ginzburg-Landau equation is solved for type II superconductors
+numerically, and the dynamics of entering vortices, geometric defects and
+pinning effects have been investigated. A superconducting wire with ratchet
+defects is designed to pump the vortices move in a specific direction and
+enhance the supercurrent when applying the periodical magnetic field. Some
+properties of this wire have been investigated numerically and analytically.",1702.08842v2
+2022-11-02,Light-induced ultrafast dynamics of spin crossovers in LaCoO3,"Ultrafast quantum dynamics relaxation of a photoexcited state in a strongly
+correlated spin crossover system LaCoO3 under a sudden perturbation is
+considered with the density matrix generalized master equation. The
+magnetization and cobalt-oxygen bond length oscillations were found. The
+evolution of the electronic band structure during relaxation is calculated in
+the framework of the LDA+GTB method.",2211.01300v1
+2022-11-02,Drift approximation by the modified Boris algorithm of charged-particle dynamics in toroidal geometry,"In this paper, we study the charged-particle dynamics under strong magnetic
+field in a toroidal axi-symmetric geometry. Using modulated Fourier expansions
+of the exact and numerical solutions, the long-term drift motion of the exact
+solution in toroidal geometry is derived and the error analysis of the
+large-stepsize modified Boris algorithm over long time scales is provided.
+Numerical experiments illustrate the theoretical results.",2211.01462v1
+2023-06-29,Approximate Entropy Analysis for Nonlinear Beam Dynamics,"In this paper, we apply approximate entropy (ApEn) analysis to the nonlinear
+beam dynamics in circular accelerators. Due to the presence of strong nonlinear
+magnets, chaos of beam motion gradually increases with amplitude. Such chaos
+can be quantitatively characterized with ApEn of beam turn-by-turn readings.
+Then ApEn, as a chaos indicator, can be used for nonlinear lattice optimization
+and analysis.",2306.17297v1
+2023-11-07,Dynamics of Carrollian Scalar Fields,"Adopting an intrinsic Carrollian viewpoint, we show that the generic
+Carrollian scalar field action is a combination of electric and magnetic
+actions, found in the literature by taking the Carrollian limit of the
+relativistic scalar field. This leads to non-trivial dynamics: even a single
+particle with non-vanishing energy can move in Carrollian physics.",2311.04113v2
+1997-11-12,Transonic Magnetic Slim Accretion Disks and kilo-Hertz Quasi-Periodic Oscillations in Low-Mass X-Ray Binaries,"The inner regions of accretion disks of weakly magnetized neutron stars are
+affected by general relativity and stellar magnetic fields. Even for field
+strengths sufficiently small so that there is no well-defined magnetosphere
+surrounding the neutron star, there is still a region in the disk where
+magnetic field stress plays an important dynamical role. We construct magnetic
+slim disk models appropriate for neutron stars in low-mass X-ray binaries
+(LMXBs) which incorporate both effects (GR and magnetic fields). The
+B-field--disk interaction is treated in a phenomenological manner, allowing for
+both closed and open field configurations. We show that even for surface
+magnetic fields as weak as $10^7-10^8$ G, the sonic point of the accretion flow
+can be significantly modified from the pure GR value (near $6M$). We derive an
+approximate analytical expression for the sonic radius and show that it mainly
+depends on the surface field strength $B_0$ and mass accretion rate $\dot M$
+through the ratio $b^2\propto B_0^2/\dot M$. The sonic radius thus obtained
+approaches the usual Alfven radius for high $b^2$, and asymptotes to $6M$ as
+$b^2\to 0$. We therefore suggest that for neutron stars in LMXBs, the
+distinction between the disk sonic radius and the magnetospheric radius may not
+exist. We apply our theoretical results to the kHz QPOs observed in the X-ray
+fluxes of LMXBs. If these QPOs are associated with the orbital frequency at the
+inner radius of the disk, then the QPO frequencies and their correlation with
+mass accretion rate can provide useful constraints on the nature of the
+magnetic field -- disk interactions as well as on the structure of magnetic
+fields in LMXBs. Current observational data may suggest that the magnetic
+fields in LMXBs have complex topology.",9711142v2
+2007-04-07,Magnetic fields in protoplanetary disks,"Magnetic fields likely play a key role in the dynamics and evolution of
+protoplanetary discs. They have the potential to efficiently transport angular
+momentum by MHD turbulence or via the magnetocentrifugal acceleration of
+outflows from the disk surface, and magnetically-driven mixing has implications
+for disk chemistry and evolution of the grain population. However, the weak
+ionisation of protoplanetary discs means that magnetic fields may not be able
+to effectively couple to the matter. I present calculations of the ionisation
+equilibrium and magnetic diffusivity as a function of height from the disk
+midplane at radii of 1 and 5 AU. Dust grains tend to suppress magnetic coupling
+by soaking up electrons and ions from the gas phase and reducing the
+conductivity of the gas by many orders of magnitude. However, once grains have
+grown to a few microns in size their effect starts to wane and magnetic fields
+can begin to couple to the gas even at the disk midplane. Because ions are
+generally decoupled from the magnetic field by neutral collisions while
+electrons are not, the Hall effect tends to dominate the diffusion of the
+magnetic field when it is able to partially couple to the gas.
+  For a standard population of 0.1 micron grains the active surface layers have
+a combined column of about 2 g/cm^2 at 1 AU; by the time grains have aggregated
+to 3 microns the active surface density is 80 g/cm^2. In the absence of grains,
+x-rays maintain magnetic coupling to 10% of the disk material at 1 AU (150
+g/cm^2). At 5 AU the entire disk thickness becomes active once grains have
+aggregated to 1 micron in size.",0704.0970v3
+2009-07-05,Magnetic survey of emission line B-type stars with FORS1 at the VLT,"We report the results of our search for magnetic fields in a sample of 16
+field Be stars, the binary emission-line B-type star upsilon Sgr, and in a
+sample of fourteen members of the open young cluster NGC3766 in the Carina
+spiral arm. The sample of cluster members includes Be stars, normal B-type
+stars and He-strong/He-weak stars. Nine Be stars have been studied with
+magnetic field time series obtained over ~1 hour to get an insight into the
+temporal behaviour and the correlation of magnetic field properties with
+dynamical phenomena taking place in Be star atmospheres. The
+spectropolarimetric data were obtained at the European Southern Observatory
+with the multi-mode instrument FORS1 installed at the 8m Kueyen telescope. We
+detect weak photospheric magnetic fields in four field Be stars, HD62367, mu
+Cen, o Aqr, and epsilon Tuc. The strongest longitudinal magnetic field,
+<B_z>=117+-38G, was detected in the Be star HD62367. Among the Be stars studied
+with time series, one Be star, lambda Eri, displays cyclic variability of the
+magnetic field with a period of 21.12min. The binary star upsilon Sgr, in the
+initial rapid phase of mass exchange between the two components with strong
+emission lines in the visible spectrum, is a magnetic variable star, probably
+on a timescale of a few months. The maximum longitudinal magnetic field
+<B_z>=-102+-10G at MJD54333.018 was measured using hydrogen lines. The cluster
+NGC3766 seems to be extremely interesting, where we find evidence for the
+presence of a magnetic field in seven early B-type stars out of the observed
+fourteen cluster members.",0907.0882v1
+2010-02-03,"Magnetic transitions induced by tunnelling electrons in individual adsorbed M-Phthalocyanine molecules (M $\equiv$ Fe, Co)","We report on a theoretical study of magnetic transitions induced by
+tunnelling electrons in individual adsorbed M-Phthalocyanine (M-Pc) molecules
+where M is a metal atom: Fe-Pc on a Cu(110)(2$\times$1)-O surface and Co-Pc
+layers on Pb(111) islands. The magnetic transitions correspond to the change of
+orientation of the spin angular momentum of the metal ion with respect to the
+surroundings and possibly an applied magnetic field. The adsorbed Fe-Pc system
+is studied with a Density Functional Theory (DFT) transport approach showing
+that i) the magnetic structure of the Fe atom in the adsorbed Fe-Pc is quite
+different from that of the free Fe atom or of other adsorbed Fe systems and ii)
+that injection of electrons (holes) into the Fe atom in the adsorbed Fe-Pc
+molecule dominantly involves the Fe $3d_{z^2}$ orbital. These results fully
+specify the magnetic structure of the system and the process responsible for
+magnetic transitions. The dynamics of the magnetic transitions induced by
+tunnelling electrons is treated in a strong-coupling approach. The Fe-Pc
+treatment is extended to the Co-Pc case. The present calculations accurately
+reproduce the strength of the magnetic transitions as observed by magnetic IETS
+(Inelastic Electron Tunnelling Spectroscopy) experiments; in particular, the
+dominance of the inelastic current in the conduction of the adsorbed M-Pc
+molecule is accounted for.",1002.0728v1
+2010-05-26,Shear-driven and diffusive helicity fluxes in alpha-Omega dynamos,"We present nonlinear mean-field alpha-Omega dynamo simulations in spherical
+geometry with simplified profiles of kinematic alpha effect and shear. We take
+magnetic helicity evolution into account by solving a dynamical equation for
+the magnetic alpha effect. This gives a consistent description of the quenching
+mechanism in mean-field dynamo models. The main goal of this work is to explore
+the effects of this quenching mechanism in solar-like geometry, and in
+particular to investigate the role of magnetic helicity fluxes, specifically
+diffusive and Vishniac-Cho (VC) fluxes, at large magnetic Reynolds numbers
+(Rm). For models with negative radial shear or positive latitudinal shear, the
+magnetic alpha effect has predominantly negative (positive) sign in the
+northern (southern) hemisphere. In the absence of fluxes, we find that the
+magnetic energy follows an Rm^-1 dependence, as found in previous works. This
+catastrophic quenching is alleviated in models with diffusive magnetic helicity
+fluxes resulting in magnetic fields comparable to the equipartition value even
+for Rm=10^7. On the other hand, models with a shear-driven Vishniac-Cho flux
+show an increase of the amplitude of the magnetic field with respect to models
+without fluxes, but only for Rm<10^4. This is mainly a consequence of assuming
+a vacuum outside the Sun which cannot support a significant VC flux across the
+boundary. However, in contrast with the diffusive flux, the VC flux modifies
+the distribution of the magnetic field. In addition, if an ill-determined
+scaling factor in the expression for the VC flux is large enough, subcritical
+dynamo action is possible that is driven by the action of shear and the
+divergence of current helicity flux.",1005.4818v1
+2010-06-30,Characteristics and Evolution of the Magnetic field and Chromospheric Emission in an Active Region Core Observed by Hinode,"We describe the characteristics and evolution of the magnetic field and
+chromospheric emission in an active region core observed by the Solar Optical
+Telescope on Hinode. Consistent with previous studies, we find that the moss is
+unipolar, the spatial distribution of magnetic flux evolves slowly, and the
+magnetic field is only moderately inclined. We show that the field line
+inclination and horizontal component are coherent, and that the magnetic field
+is mostly sheared in the inter-moss regions where the highest magnetic flux
+variability is seen. Using extrapolations from SP magnetograms we show that the
+magnetic connectivity in the moss is different than in the quiet Sun because
+most of the magnetic field extends to significant coronal heights. The magnetic
+flux, field vector, and chromospheric emission in the moss also appear highly
+dynamic, but actually show only small scale variations in magnitude on
+time-scales longer than the cooling times for hydrodynamic loops computed from
+our extrapolations, suggesting high-frequency (continuous) heating events. Some
+evidence is found for flux (Ca 2 intensity) changes on the order of 100--200 G
+(DN) on time-scales of 20--30 mins that could be taken as indicative of
+low-frequency heating. We find, however, that only a small fraction (10%) of
+our simulated loops would be expected to cool on these time-scales, and we find
+no clear evidence that the flux changes consistently produce intensity changes
+in the chromosphere. The magnetic flux and chromospheric intensity in most
+individual SOT pixels in the moss vary by less than ~ 20% and ~ 10%,
+respectively, on loop cooling time-scales. In view of the high energy
+requirements of the chromosphere, we suggest that these variations could be
+sufficient for the heating of `warm' EUV loops, but that the high basal levels
+may be more important for powering the hot core loops rooted in the moss.",1006.5776v1
+2010-07-16,Magnetism and Charge Dynamics in Iron Pnictides,"In a wide variety of materials, such as copper oxides, heavy fermions,
+organic salts, and the recently discovered iron pnictides, superconductivity is
+found in close proximity to a magnetically ordered state. The character of the
+proximate magnetic phase is thus believed to be crucial for understanding the
+differences between the various families of unconventional superconductors and
+the mechanism of superconductivity. Unlike the AFM order in cuprates, the
+nature of the magnetism and of the underlying electronic state in the iron
+pnictide superconductors is not well understood. Neither density functional
+theory nor models based on atomic physics and superexchange, account for the
+small size of the magnetic moment. Many low energy probes such as transport,
+STM and ARPES measured strong anisotropy of the electronic states akin to the
+nematic order in a liquid crystal, but there is no consensus on its physical
+origin, and a three dimensional picture of electronic states and its relations
+to the optical conductivity in the magnetic state is lacking. Using a first
+principles approach, we obtained the experimentally observed magnetic moment,
+optical conductivity, and the anisotropy of the electronic states. The theory
+connects ARPES, which measures one particle electronic states, optical
+spectroscopy, probing the particle hole excitations of the solid and neutron
+scattering which measures the magnetic moment. We predict a manifestation of
+the anisotropy in the optical conductivity, and we show that the magnetic phase
+arises from the paramagnetic phase by a large gain of the Hund's rule coupling
+energy and a smaller loss of kinetic energy, indicating that iron pnictides
+represent a new class of compounds where the nature of magnetism is
+intermediate between the spin density wave of almost independent particles, and
+the antiferromagnetic state of local moments.",1007.2867v1
+2011-10-20,Relativistic MHD in dynamical spacetimes: Improved EM gauge condition for AMR grids,"We recently developed a new general relativistic magnetohydrodynamic code
+with adaptive mesh refinement that evolves the electromagnetic (EM) vector
+potential (A) instead of the magnetic fields directly. Evolving A enables one
+to use any interpolation scheme on refinement level boundaries and still
+guarantee that the magnetic field remains divergenceless. As in classical EM, a
+gauge choice must be made when evolving A, and we chose a straightforward
+""algebraic"" gauge condition to simplify the A evolution equation. However,
+magnetized black hole-neutron star (BHNS) simulations in this gauge exhibit
+unphysical behavior, including the spurious appearance of strong magnetic
+fields on refinement level boundaries. This spurious behavior is exacerbated
+when matter crosses refinement boundaries during tidal disruption of the NS.
+Applying Kreiss-Oliger dissipation to the evolution of the magnetic vector
+potential A slightly weakens this spurious magnetic effect, but with undesired
+consequences. We demonstrate via an eigenvalue analysis and a numerical study
+that zero-speed modes in the algebraic gauge, coupled with the frequency
+filtering that occurs on refinement level boundaries, are responsible for the
+creation of spurious magnetic fields. We show that the EM Lorenz gauge exhibits
+no zero-speed modes, and as a consequence, spurious magnetic effects are
+quickly propagated away, allowing for long-term, stable magnetized BHNS
+evolutions. Our study demonstrates how the EM gauge degree of freedom can be
+chosen to one's advantage, and that for magnetized BHNS simulations the Lorenz
+gauge constitutes a major improvement over the algebraic gauge.",1110.4633v3
+2012-10-08,Orbital and Mass Ratio Evolution of Protobinaries Driven by Magnetic Braking,"The majority of stars reside in multiple systems, especially binaries. The
+formation and early evolution of binaries is a longstanding problem in star
+formation that is not fully understood. In particular, how the magnetic field
+observed in star-forming cores shapes the binary characteristics remains
+relatively unexplored. We demonstrate numerically, using the ENZO-MHD code,
+that a magnetic field of the observed strength can drastically change two of
+the basic quantities of a binary system: the orbital separation and mass ratio
+of the two components. Our calculations focus on the protostellar mass
+accretion phase, after a pair of stellar 'seeds' have already formed. We find
+that, in dense cores magnetized to a realistic level, the angular momentum of
+the gas accreted by the protobinary is greatly reduced by magnetic braking.
+Accretion of strongly braked material shrinks the protobinary separation by a
+large factor compared to the non-magnetic case. The magnetic braking also
+changes the evolution of the mass ratio of unequal-mass protobinaries by
+producing gas of low specific angular momentum that accretes preferentially
+onto the primary rather than the secondary. This is in contrast with the
+preferential mass accretion onto the secondary previously found for
+protobinaries accreting from an unmagnetized envelope, which tends to drive the
+mass ratio towards unity. In addition, the magnetic field greatly modifies the
+morphology and dynamics of the protobinary accretion flow. It suppresses the
+circumstellar and circumbinary disks that feed the protobinary in the
+non-magnetic case; the binary is fed instead by a fast collapsing pseudodisk
+whose rotation is strongly braked. The magnetic braking-driven inward migration
+of binaries from their birth locations may be constrained by high-resolution
+observations of the orbital distribution of deeply embedded protobinaries,
+especially with ALMA.",1210.2308v2
+2012-10-29,Exploring Magnetic Field Structure in Star-Forming Cores with Polarization of Thermal Dust Emission,"The configuration and evolution of the magnetic field in star-forming cores
+are investigated in order to directly compare simulations and observations. We
+prepare four different initial clouds having different magnetic field strengths
+and rotation rates, in which magnetic field lines are aligned/misaligned with
+the rotation axis. First, we calculate the evolution of such clouds from the
+prestellar stage until long after protostar formation. Then, we calculate the
+polarization of thermal dust emission expected from the simulation data. We
+create polarization maps with arbitrary viewing angles and compare them with
+observations. Using this procedure, we confirmed that the polarization
+distribution projected on the celestial plane strongly depends on the viewing
+angle of the cloud. Thus, by comparing the observations with the polarization
+map predicted by the simulations, we can roughly determine the angle between
+the direction of the global magnetic field and the line of sight. The
+configuration of the polarization vectors also depends on the viewing angle. We
+find that an hourglass configuration of magnetic field lines is not always
+realized in a collapsing cloud when the global magnetic field is misaligned
+with the cloud rotation axis. Depending on the viewing angle, an S-shaped
+configuration of the magnetic field (or the polarization vectors) appears early
+in the protostellar accretion phase. This indicates that not only the magnetic
+field but also the cloud rotation affects the dynamical evolution of such a
+cloud. In addition, by comparing the simulated polarization with actual
+observations, we can estimate properties of the host cloud such as the
+evolutionary stage, magnetic field strength, and rotation rate.",1210.7637v1
+2013-08-02,Magnetic arms generated by multiple interfering galactic spiral patterns,"Interfering two- and three-arm spiral patterns have previously been inferred
+to exist in many galaxies and also in numerical simulations, and invoked to
+explain important dynamical properties, such as lack of symmetry, kinks in
+spiral arms, and star formation in armlets. The non-axisymmetric galactic
+mean-field dynamo model of Chamandy et al. is generalized to allow for such
+multiple co-existing spiral patterns in the kinetic alpha_k effect, leading to
+the existence of magnetic spiral arms in the large-scale magnetic field with
+several new properties. The large-scale magnetic field produced by an evolving
+superposition of two- and three-arm (or two- and four-arm) patterns evolves
+with time along with the superposition. Magnetic arms can be stronger and more
+extended in radius and in azimuth when produced by two interfering patterns
+rather than by one pattern acting alone. Transient morphological features arise
+in the magnetic arms, including bifurcations, disconnected armlets, and
+temporal and spatial variation in arm strength and pitch angles. Pitch angles
+of the large-scale magnetic field and magnetic arm structures (ridges) are
+smaller than those typically inferred from observations of spiral galaxies for
+model parameters of Chamandy et al., but can become comparable to typically
+inferred values for certain (still realistic) parameters. The magnetic field is
+sometimes strongest in between the alpha_k-arms, unlike in standard models with
+a single pattern, where it is strongest within the alpha_k-arms. Moreover, for
+models with a two- and three-arm pattern, some amount of m=1 azimuthal symmetry
+is found to be present in the magnetic field, which is generally not the case
+for forcing by single two- or three-arm patterns. (abridged)",1308.0432v2
+2013-09-19,Radiative accretion shocks along nonuniform stellar magnetic fields in classical T Tauri stars,"(abridged) AIMS. We investigate the dynamics and stability of post-shock
+plasma streaming along nonuniform stellar magnetic fields at the impact region
+of accretion columns. We study how the magnetic field configuration and
+strength determine the structure, geometry, and location of the shock-heated
+plasma. METHODS. We model the impact of an accretion stream onto the
+chromosphere of a CTTS by 2D axisymmetric magnetohydrodynamic simulations. Our
+model takes into account the gravity, the radiative cooling, and the
+magnetic-field-oriented thermal conduction. RESULTS. The structure, stability,
+and location of the shocked plasma strongly depend on the configuration and
+strength of the magnetic field. For weak magnetic fields, a large component of
+B may develop perpendicular to the stream at the base of the accretion column,
+limiting the sinking of the shocked plasma into the chromosphere. An envelope
+of dense and cold chromospheric material may also develop around the shocked
+column. For strong magnetic fields, the field configuration determines the
+position of the shock and its stand-off height. If the field is strongly
+tapered close to the chromosphere, an oblique shock may form well above the
+stellar surface. In general, a nonuniform magnetic field makes the distribution
+of emission measure vs. temperature of the shocked plasma lower than in the
+case of uniform magnetic field. CONCLUSIONS. The initial strength and
+configuration of the magnetic field in the impact region of the stream are
+expected to influence the chromospheric absorption and, therefore, the
+observability of the shock-heated plasma in the X-ray band. The field strength
+and configuration influence also the energy balance of the shocked plasma, its
+emission measure at T > 1 MK being lower than expected for a uniform field. The
+above effects contribute in underestimating the mass accretion rates derived in
+the X-ray band.",1309.5038v1
+2014-06-12,Coronal magnetic reconnection driven by CME expansion -- the 2011 June 7 event,"Coronal mass ejections (CMEs) erupt and expand in a magnetically structured
+solar corona. Various indirect observational pieces of evidence have shown that
+the magnetic field of CMEs reconnects with surrounding magnetic fields,
+forming, e.g., dimming regions distant from the CME source regions. Analyzing
+Solar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on
+2011 June 7, we present the first direct evidence of coronal magnetic
+reconnection between the fields of two adjacent ARs during a CME. The
+observations are presented jointly with a data-constrained numerical
+simulation, demonstrating the formation/intensification of current sheets along
+a hyperbolic flux tube (HFT) at the interface between the CME and the
+neighbouring AR 11227. Reconnection resulted in the formation of new magnetic
+connections between the erupting magnetic structure from AR 11226 and the
+neighboring active region AR 11227 about 200 Mm from the eruption site. The
+onset of reconnection first becomes apparent in the SDO/AIA images when
+filament plasma, originally contained within the erupting flux rope, is
+re-directed towards remote areas in AR 11227, tracing the change of large-scale
+magnetic connectivity. The location of the coronal reconnection region becomes
+bright and directly observable at SDO/AIA wavelengths, owing to the presence of
+down-flowing cool, dense (10^{10} cm^{-3}) filament plasma in its vicinity. The
+high-density plasma around the reconnection region is heated to coronal
+temperatures, presumably by slow-mode shocks and Coulomb collisions. These
+results provide the first direct observational evidence that CMEs reconnect
+with surrounding magnetic structures, leading to a large-scale re-configuration
+of the coronal magnetic field.",1406.3153v1
+2014-07-30,Impulsive energy release and non-thermal emission in a confined M4.0 flare triggered by rapidly evolving magnetic structures,"We present observations of a confined M4.0 flare from NOAA 11302 on 2011
+September 26. Observations at high temporal, spatial, and spectral resolution
+from Solar Dynamics Observatory, Reuven Ramaty High Energy Solar Spectroscopic
+Imager, and Nobeyama Radioheliograph enabled us to explore the possible
+triggering and energy release processes of this flare despite its very
+impulsive behavior and compact morphology. The flare light curves exhibit an
+abrupt rise of non-thermal emission with co-temporal hard X-ray (HXR) and
+microwave (MW) bursts that peaked instantly without any precursor emission.
+This stage was associated with HXR emission up to 200 keV that followed a power
+law with photon spectral index ($\delta$) $\sim$3. Another non-thermal peak,
+observed 32 s later, was more pronounced in the MW flux than the HXR profiles.
+Dual peaked structure in the MW and HXR light curves suggest a two-step
+magnetic reconnection process. Extreme ultraviolet (EUV) images exhibit a
+sequential evolution of the inner and outer core regions of magnetic loop
+system while the overlying loop configuration remained unaltered. Combined
+observations in HXR, (E)UV, and H$\alpha$ provide support for flare models
+involving interaction of coronal loops. The magnetograms obtained from
+Helioseismic and Magnetic Imager (HMI) reveal the emergence of magnetic flux
+which started $\sim$5 hr before the flare. However, the more crucial changes in
+the photospheric magnetic flux occurred about 1 minute prior to the flare onset
+with opposite polarity magnetic transients appearing at the early flare
+location within the inner core region. The spectral, temporal, and spatial
+properties of magnetic transients suggest that the sudden changes in the
+small-scale magnetic field have likely triggered the flare by destabilizing the
+highly sheared pre-flare magnetic configuration.",1407.8115v3
+2014-10-17,Ferromagnetic resonance in $ε$-Co magnetic composites,"We investigate the electromagnetic properties of assemblies of nanoscale
+$\epsilon$-cobalt crystals with size range between 5 nm to 35 nm, embedded in a
+polystyrene (PS) matrix, at microwave (1-12 GHz) frequencies. We investigate
+the samples by transmission electron microscopy (TEM) imaging, demonstrating
+that the particles aggregate and form chains and clusters. By using a broadband
+coaxial-line method, we extract the magnetic permeability in the frequency
+range from 1 to 12 GHz, and we study the shift of the ferromagnetic resonance
+with respect to an externally applied magnetic field. We find that the
+zero-magnetic field ferromagnetic resonant peak shifts towards higher
+frequencies at finite magnetic fields, and the magnitude of complex
+permeability is reduced. At fields larger than 2.5 kOe the resonant frequency
+changes linearly with the applied magnetic field, demonstrating the transition
+to a state in which the nanoparticles become dynamically decoupled. In this
+regime, the particles inside clusters can be treated as non-interacting, and
+the peak position can be predicted from Kittel's ferromagnetic resonance theory
+for non-interacting uniaxial spherical particles combined with the
+Landau-Lifshitz-Gilbert (LLG) equation. In contrast, at low magnetic fields
+this magnetic order breaks down and the resonant frequency in zero magnetic
+field reaches a saturation value reflecting the interparticle interactions as
+resulting from aggregation. Our results show that the electromagnetic
+properties of these composite materials can be tuned by external magnetic
+fields and by changes in the aggregation structure.",1410.4789v2
+2015-05-13,A Supercooled Spin Liquid State in the Frustrated Pyrochlore Dy2Ti2O7,"A ""supercooled"" liquid develops when a fluid does not crystallize upon
+cooling below its ordering temperature. Instead, the microscopic relaxation
+times diverge so rapidly that, upon further cooling, equilibration eventually
+becomes impossible and glass formation occurs. Classic supercooled liquids
+exhibit specific identifiers including microscopic relaxation times diverging
+on a Vogel-Tammann-Fulcher (VTF) trajectory, a Havriliak-Negami (HN) form for
+the dielectric function, and a general Kohlrausch-Williams-Watts (KWW) form for
+time-domain relaxation. Recently, the pyrochlore Dy2Ti2O7 has become of
+interest because its frustrated magnetic interactions may, in theory, lead to
+highly exotic magnetic fluids. However, its true magnetic state at low
+temperatures has proven very difficult to identify unambiguously. Here we
+introduce high-precision, boundary-free magnetization transport techniques
+based upon toroidal geometries and gain a fundamentally new understanding of
+the time- and frequency-dependent magnetization dynamics of Dy2Ti2O7. We
+demonstrate a virtually universal HN form for the magnetic susceptibility, a
+general KWW form for the real-time magnetic relaxation, and a divergence of the
+microscopic magnetic relaxation rates with precisely the VTF trajectory. Low
+temperature Dy2Ti2O7 therefore exhibits the characteristics of a supercooled
+magnetic liquid; the consequent implication is that this translationally
+invariant lattice of strongly correlated spins is evolving towards an
+unprecedented magnetic glass state, perhaps due to many-body localization of
+spin.",1505.03484v2
+2016-02-05,Irreversible Rapid Changes of Magnetic Field Associated with the 2012 October 23 Circular Near-limb X1.8 Flare,"It has been found that photospheric magnetic fields can change in accordance
+with the three-dimensional magnetic field restructuring following solar
+eruptions. Previous studies mainly use vector magnetic field data taken for
+events near the disk center. In this paper, we analyze the magnetic field
+evolution associated with the 2012 October 23 X1.8 flare in NOAA AR 11598 that
+is close to the solar limb, using both the 45 s cadence line-of-sight and 12
+minute cadence vector magnetograms from the Helioseismic and Magnetic Imager on
+board Solar Dynamic Observatory. This flare is classified as a circular-ribbon
+flare with spine-fan type magnetic topology containing a null point. In the
+line-of-sight magnetograms, there are two apparent polarity inversion lines
+(PIL). The PIL closer to the limb is affected more by the projection effect.
+Between these two PILs there lie positive polarity magnetic fields, which are
+surrounded by negative polarity fields outside the PILs. We find that after the
+flare, both the apparent limb-ward and disk-ward negative fluxes decrease,
+while the positive flux in-between increases. We also find that the horizontal
+magnetic fields have a significant increase along the disk-ward PIL, while in
+surrounding area, they decrease. Synthesizing the observed field changes, we
+conclude that the magnetic fields collapse toward the surface above the
+disk-ward PIL as depicted in the coronal implosion scenario, while the
+peripheral field turns to a more vertical configuration after the flare. We
+also suggest that this event is an asymmetric circular-ribbon flare: a flux
+rope is likely present above the disk-ward PIL. Its eruption causes the
+instability of the entire fan-spine structure and the implosion near that PIL.",1602.02080v1
+2016-07-04,Large-scale-vortex dynamos in planar rotating convection,"Several recent studies have demonstrated how large-scale vortices may arise
+spontaneously in rotating planar convection. Here we examine the dynamo
+properties of such flows in rotating Boussinesq convection. For moderate values
+of the magnetic Reynolds number ($100 \lesssim Rm \lesssim 550$, with $Rm$
+based on the box depth and the convective velocity), a large-scale (i.e.
+system-size) magnetic field is generated. The amplitude of the magnetic energy
+oscillates in time, nearly out of phase with the oscillating amplitude of the
+large-scale vortex. The large-scale vortex is disrupted once the magnetic field
+reaches a critical strength, showing that these oscillations are of magnetic
+origin. The dynamo mechanism relies on those components of the flow that have
+length scales lying between that of the large-scale vortex and the typical
+convective cell size; smaller-scale flows are not required. The large-scale
+vortex plays a crucial role in the magnetic induction despite being essentially
+two-dimensional; we thus refer to this dynamo as a large-scale-vortex dynamo.
+For larger magnetic Reynolds numbers, the dynamo is small scale, with a
+magnetic energy spectrum that peaks at the scale of the convective cells. In
+this case, the small-scale magnetic field continuously suppresses the
+large-scale vortex by disrupting the correlations between the convective
+velocities that allow it to form. The suppression of the large-scale vortex at
+high $Rm$ therefore probably limits the relevance of the large-scale-vortex
+dynamo to astrophysical objects with moderate values of $Rm$, such as planets.
+In this context, the ability of the large-scale-vortex dynamo to operate at low
+magnetic Prandtl numbers is of great interest.",1607.00824v2
+2017-01-24,Magnetic field formation in the Milky Way-like disk galaxies of the Auriga project,"The magnetic fields observed in the Milky~Way and nearby galaxies appear to
+be in equipartition with the turbulent, thermal, and cosmic ray energy
+densities, and hence are expected to be dynamically important. However, the
+origin of these strong magnetic fields is still unclear, and most previous
+attempts to simulate galaxy formation from cosmological initial conditions have
+ignored them altogether. Here, we analyse the magnetic fields predicted by the
+simulations of the Auriga Project, a set of 30 high-resolution cosmological
+zoom simulations of Milky~Way-like galaxies, carried out with a moving-mesh
+magneto-hydrodynamics code and a detailed galaxy formation physics model. We
+find that the magnetic fields grow exponentially at early times owing to a
+small-scale dynamo with an e-folding time of roughly $100\,\rm{Myr}$ in the
+center of halos until saturation occurs around $z=2-3$, when the magnetic
+energy density reaches about $10\%$ of the turbulent energy density with a
+typical strength of $10-50\,\rm{\mu G}$. In the galactic centers the ratio
+between magnetic and turbulent energy remains nearly constant until $z=0$. At
+larger radii, differential rotation in the disks leads to linear amplification
+that typically saturates around $z=0.5$ to $z=0$. The final radial and vertical
+variations of the magnetic field strength can be well described by two joint
+exponential profiles, and are in good agreement with observational constraints.
+Overall, the magnetic fields have only little effect on the global evolution of
+the galaxies as it takes too long to reach equipartition. We also demonstrate
+that our results are well converged with numerical resolution.",1701.07028v2
+2017-06-28,Pr-magnetism in the quasi-skutterudite compound PrFe$_2$Al$_8$,"The intermetallic compound \PFA\ that possesses a three-dimensional network
+structure of Al polyhedra centered at the transition metal element Fe and the
+rare earth Pr is investigated through neutron powder diffraction and inelastic
+neutron scattering in order to elucidate the magnetic ground state of Pr and Fe
+and the crystal field effects of Pr. Our neutron diffraction study confirms
+long-range magnetic order of Pr below $T_N $ = 4.5~K in this compound.
+Subsequent magnetic structure estimation reveals a magnetic propagation vector
+$k$ = ($\frac{1}{2}$~0~$\frac{1}{2}$) with a magnetic moment value of
+2.5~$\mu_\mathrm{B}$/Pr along the orthorhombic $c$-axis and evidence the lack
+of ordering in the Fe sublattice. The inelastic neutron scattering study
+reveals one crystalline electric field excitation near 19~meV at 5~K in \PFA.
+The energy-integrated intensity of the 19~meV excitation as a function of |$Q$|
+$(A^{-1})$ follows the square of the magnetic form factor of Pr$^{3+}$ thereby
+confirming that the inelastic excitation belongs to the Pr sublattice. The
+second sum rule applied to the dynamic structure factor indicates only
+1.6(2)~$\mu_\mathrm{B}$ evolving at the 19~meV peak compared to the
+3.58~$\mu_\mathrm{B}$ for free Pr$^{3+}$, indicating that the crystal field
+ground state is magnetic and the missing moment is associated with the
+resolution limited quasi-elastic line. The magnetic order occurring in Pr in
+\PFA\ is counter-intuitive to the symmetry-allowed crystal field level scheme,
+hence, is suggestive of exchange-mediated mechanisms of ordering stemming from
+the magnetic ground state of the crystal field levels.",1706.09081v1
+2017-08-14,Modeling Coronal Response in Decaying Active Regions with Magnetic Flux Transport and Steady Heating,"We present new measurements of the dependence of the Extreme Ultraviolet
+radiance on the total magnetic flux in active regions as obtained from the
+Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager on
+board the Solar Dynamics Observatory (SDO). Using observations of nine active
+regions tracked along different stages of evolution, we extend the known
+radiance - magnetic flux power-law relationship ($I\propto\Phi^{\alpha}$) to
+the AIA 335 \AA\ passband, and the Fe XVIII 93.93 \AA\ spectral line in the 94
+\AA\ passband. We find that the total unsigned magnetic flux divided by the
+polarity separation ($\Phi/D$) is a better indicator of radiance for the Fe
+XVIII line with a slope of $\alpha=3.22\pm0.03$. We then use these results to
+test our current understanding of magnetic flux evolution and coronal heating.
+We use magnetograms from the simulated decay of these active regions produced
+by the Advective Flux Transport (AFT) model as boundary conditions for
+potential extrapolations of the magnetic field in the corona. We then model the
+hydrodynamics of each individual field line with the Enthalpy-based Thermal
+Evolution of Loops (EBTEL) model with steady heating scaled as the ratio of the
+average field strength and the length ($\bar{B}/L$) and render the Fe XVIII and
+335 \AA\ emission. We find that steady heating is able to partially reproduce
+the magnitudes and slopes of the EUV radiance - magnetic flux relationships and
+discuss how impulsive heating can help reconcile the discrepancies. This study
+demonstrates that combined models of magnetic flux transport, magnetic topology
+and heating can yield realistic estimates for the decay of active region
+radiances with time.",1708.04324v1
+2017-11-15,Laminar and turbulent dynamos in chiral magnetohydrodynamics. II. Simulations,"Using direct numerical simulations (DNS), we study laminar and turbulent
+dynamos in chiral magnetohydrodynamics (MHD) with an extended set of equations
+that accounts for an additional contribution to the electric current due to the
+chiral magnetic effect (CME). This quantum phenomenon originates from an
+asymmetry between left- and right-handed relativistic fermions in the presence
+of a magnetic field and gives rise to a chiral dynamo. We show that the
+magnetic field evolution proceeds in three stages: (1) a small-scale chiral
+dynamo instability; (2) production of chiral magnetically driven turbulence and
+excitation of a large-scale dynamo instability due to a new chiral effect
+(alpha_mu effect); and (3) saturation of magnetic helicity and magnetic field
+growth controlled by a conservation law for the total chirality. The
+$\alpha_\mu$ effect becomes dominant at large fluid and magnetic Reynolds
+numbers and is not related to kinetic helicity. The growth rate of the
+large-scale magnetic field and its characteristic scale measured in the
+numerical simulations agree well with theoretical predictions based on
+mean-field theory. The previously discussed two-stage chiral magnetic scenario
+did not include stage (2) during which the characteristic scale of magnetic
+field variations can increase by many orders of magnitude. Based on the
+findings from numerical simulations, the relevance of the CME and the chiral
+effects revealed in the relativistic plasma of the early universe and of
+proto-neutron stars are discussed.",1711.09733v3
+2017-11-29,Solar Jet on 2014 April 16 Modeled by Kelvin--Helmholtz Instability,"We study here the arising of Kelvin--Helmholtz Instability (KHI) in one fast
+jet of 2014 April 16 observed by the Atmospheric Imaging Assembly (AIA) on
+board Solar Dynamics Observatory (SDO) in different UV and EUV wavelengths. The
+evolution of jet indicates the blob like structure at its boundary which could
+be the observational evidence of the KHI. We model the jet as a moving
+cylindrical magnetic flux tube of radius $a$ embedded in a magnetic field B_i
+and surrounded by rest magnetized plasma with magnetic field B_e. We explore
+the propagation of the kink MHD mode along the jet that can become unstable
+against the KHI if its speed exceeds a critical value. Concerning magnetic
+fields topology we consider three different configurations, notably of (i)
+spatially homogeneous magnetic fields (untwisted magnetic flux tube), (ii)
+internal (label `i') twisted magnetic field and external homogeneous one (label
+`e') (single-twisted flux tube), and (iii) both internal and external twisted
+magnetic fields (double-twisted magnetic flux tube). Plasma densities in the
+two media rho_i and rho_e are assumed to be homogeneous. The density contrast
+is defined in two ways: first as rho_e/rho_i and second as rho_e/(rho_i +
+rho_e). Computations show that the KHI can occur at accessible flow velocities
+in all the cases of untwisted and single-twisted flux tubes. It turns out,
+however, that in the case of a double-twisted flux tube the KHI can merge at an
+accessible jet speed only when the density contrast is calculated from the
+ratio rho_e/(rho_i} + rho_e). Evaluated KHI developing times and kink mode wave
+phase velocities at wavelength of 4 Mm lie in the ranges of 1--6.2 min and
+202--271 km/s, respectively---all being reasonable for the modeled jet.",1711.10734v1
+2018-01-21,Magnetic reconnection at the earliest stage of solar flux emergence,"On 2016 September 20, the Interface Region Imaging Spectrograph observed an
+active region during its earliest emerging phase for almost 7 hours. The
+Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory
+observed continuous emergence of small-scale magnetic bipoles with a rate of
+$\sim$10$^{16}$ Mx~s$^{-1}$. The emergence of magnetic fluxes and interactions
+between different polarities lead to frequent occurrence of ultraviolet (UV)
+bursts, which exhibit as intense transient brightenings in the 1400 \AA{}
+images. In the meantime, discrete small patches with the same magnetic polarity
+tend to move together and merge, leading to enhancement of the magnetic fields
+and thus formation of pores (small sunspots) at some locations. The spectra of
+these UV bursts are characterized by the superposition of several chromospheric
+absorption lines on the greatly broadened profiles of some emission lines
+formed at typical transition region temperatures, suggesting heating of the
+local materials to a few tens of thousands of kelvin in the lower atmosphere by
+magnetic reconnection. Some bursts reveal blue and red shifts of
+$\sim$100~km~s$^{-1}$ at neighboring pixels, indicating the spatially resolved
+bidirectional reconnection outflows. Many such bursts appear to be associated
+with the cancellation of magnetic fluxes with a rate of the order of
+$\sim$10$^{15}$ Mx~s$^{-1}$. We also investigate the three-dimensional magnetic
+field topology through a magneto-hydrostatic model and find that a small
+fraction of the bursts are associated with bald patches (magnetic dips).
+Finally, we find that almost all bursts are located in regions of large
+squashing factor at the height of $\sim$1 Mm, reinforcing our conclusion that
+these bursts are produced through reconnection in the lower atmosphere.",1801.06785v1
+2019-03-07,Interferometric observations of magnetic fields in forming stars,"The magnetic field is a key ingredient in the recipe of star formation. Over
+the past two decades, millimeter and submillimeter interferometers have made
+major strides in unveiling the role of the magnetic field in star formation at
+progressively smaller spatial scales. From the kiloparsec scale of molecular
+clouds down to the inner few hundred au immediately surrounding forming stars,
+the polarization at millimeter and submillimeter wavelengths is dominated by
+polarized thermal dust emission, where the dust grains are aligned relative to
+the magnetic field. Interferometric studies have focused on this dust
+polarization and occasionally on the polarization of spectral-line emission. We
+review the current state of the field of magnetized star formation in the
+context of several questions that continue to motivate the studies of high- and
+low-mass star formation. By aggregating and analyzing the results from
+individual studies, we come to several conclusions: (1) Magnetic fields and
+outflows from low-mass protostellar cores are randomly aligned, suggesting that
+the magnetic field at ~1000 au scales is not the dominant factor in setting the
+angular momentum of embedded disks and outflows. (2) Recent measurements of the
+thermal and dynamic properties in high-mass star-forming regions reveal small
+virial parameters, challenging the assumption of equilibrium star formation.
+However, we estimate that a magnetic field strength of a fraction of a mG to
+several mG in these objects could bring the dense gas close to a state of
+equilibrium. Finally, (3) We find that the small number of sources with
+hourglass-shaped magnetic field morphologies at 0.01 -- 0.1 pc scales cannot be
+explained purely by projection effects, suggesting that while it does occur
+occasionally, magnetically dominated core collapse is not the predominant mode
+of low- or high-mass star formation. [Abridged]",1903.03177v1
+2020-05-27,High-resolution tunneling spin transport characteristics of topologically distinct magnetic skyrmionic textures from theoretical calculations,"High-resolution tunneling electron spin transport properties (longitudinal
+spin current (LSC) and spin transfer torque (STT) maps) of topologically
+distinct real-space magnetic skyrmionic textures are reported by employing a
+3D-WKB combined scalar charge and vector spin transport theory in the framework
+of spin-polarized scanning tunneling microscopy (SP-STM). For our theoretical
+investigation metastable skyrmionic spin structures with various topological
+charges ($Q=-3,-2,-1,0,1,2$) in the (Pt$_{0.95}$Ir$_{0.05}$)/Fe/Pd(111)
+ultrathin magnetic film are considered. Using an out-of-plane magnetized SP-STM
+tip it is found that the maps of the LSC vectors acting on the spins of the
+magnetic textures and all STT vector components exhibit the same topology as
+the skyrmionic objects. In contrast, an in-plane magnetized tip generally does
+not result in spin transport vector maps that are topologically equivalent to
+the underlying spin structure, except for the LSC vectors acting on the spins
+of the skyrmionic textures at a specific relation between the spin
+polarizations of the sample and the tip. The magnitudes of the spin transport
+vector quantities exhibit close relations to charge current SP-STM images
+irrespectively of the skyrmionic topologies. Moreover, we find that the STT
+efficiency (torque/current ratio) acting on the spins of the skyrmions can
+reach large values up to $\sim$25 meV/$\mu$A ($\sim$0.97 $h/e$) above the rim
+of the magnetic objects, but it considerably varies between large and small
+values depending on the lateral position of the SP-STM tip above the
+topological spin textures. A simple expression for the STT efficiency is
+introduced to explain its variation. Our calculated spin transport vectors can
+be used for the investigation of spin-polarized tunneling-current-induced spin
+dynamics of topologically distinct surface magnetic skyrmionic textures.",2005.13266v2
+2020-08-20,Formation of magnetized spatial structures in the Beta Lyrae system II. Reflection of magnetically controlled structures in the visible spectrum,"This article proposes a picture of magnetized accretion structures formed
+during the mass transfer in the Beta Lyrae system. It is shown that the
+structure of the gaseous flows between the donor and the gainer is due to the
+spatial configuration of the donor magnetic field. Its dipole axis is deviated
+substantially from the line joining the centers of the components and is
+inclined to the orbital plane of the binary system; the center of the magnetic
+dipole is displaced from the donor center toward the gainer. The surface around
+the donor magnetic pole, which is close to the gainer, is a region of an
+additional matter loss from the donor surface. The effective collision of the
+magnetized plasma with the accretion disk is enhanced by the fast
+counter-rotation of this disk, especially in the secondary quadrature phases,
+in which the high-temperature medium and the system of formed accretion flows
+are observed. This concept is demonstrated, primarily, in the obvious
+correlations between the phase variability of the donor magnetic field and the
+corresponding variability of the dynamic and energy characteristics of the
+various complex lines. This refers to the behavior of the radial velocity
+curves of the emission-absorption lines formed in the gaseous structures of
+type H$\alpha$, HeI $\lambda$ 7065, or the variability of their equivalent
+width and intensity, and the variability of conventional absorption lines of
+the donor atmosphere. This is true for the phase variability of the absolute
+flux in the H$\alpha$ emission line and the fast varying of the continuum in
+the H$\alpha$ region as certain parameters, which reflect the phase variability
+of the donor magnetic field. This approach made it possible to determine the
+phase boundaries of the location of the magnetic polar region on the donor
+surface above which the matter outflows are formed.",2008.08787v1
+2020-11-20,A three-dimensional thermal model of the human cochlea for magnetic cochlear implant surgery,"In traditional cochlear implant surgery, physical trauma may occur during
+electrode array insertion. Magnetic guidance of the electrode array has been
+proposed to mitigate this medical complication. After insertion, the guiding
+magnet attached to the tip of the electrode array must be detached via a
+heating process and removed. This heating process may, however, cause thermal
+trauma within the cochlea. In this study, a validated three-dimensional finite
+element heat transfer model of the human cochlea is applied to perform an
+intracochlear thermal analysis necessary to ensure the safety of the magnet
+removal phase. Specifically, the maximum safe input power density to detach the
+magnet is determined as a function of the boundary conditions, heating
+duration, cochlea size, implant electrode array radius and insertion depth,
+magnet size, and cochlear fluid. A dimensional analysis and numerical
+simulations reveal that the maximum safe input power density increases with
+increasing cochlea size and the radius of the electrode array, whereas it
+decreases with increasing electrode array insertion depth and magnet size. The
+best cochlear fluids from the thermal perspective are perilymph and a soap
+solution. Even for the worst case scenario in which the cochlear walls are
+assumed to be adiabatic except at the round window, the maximum safe input
+power density is larger than that required to melt 1 $\rm{mm^3}$ of paraffin
+bonding the magnet to the implant electrode array. By combining the outcome of
+this work with other aspects of the design of the magnetic insertion process,
+namely the magnetic guidance procedure and medical requirements, it will be
+possible to implement a thermally safe patient-specific surgical procedure.",2011.10183v1
+2021-01-08,Shear rheology of a dilute emulsion of ferrofluid droplets dispersed in a non-magnetizable carrier fluid under the influence of a uniform magnetic field,"The effect of a spatially uniform magnetic field on the shear rheology of a
+dilute emulsion of monodispersed ferrofluid droplets, immersed in a
+non-magnetizable immiscible fluid, is investigated using direct numerical
+simulations. The direction of the applied magnetic field is normal to the shear
+flow direction. The droplets extra stress tensor arising from the presence of
+interfacial forces of magnetic nature is modeled on the basis of the seminal
+work of G. K. Batchelor, J. Fluid Mech., 41.3 (1970) under the assumptions of a
+linearly magnetizable ferrofluid phase and negligible inertia. The results show
+that even relatively small magnetic fields can have significant consequences on
+the rheological properties of the emulsion due to the magnetic forces that
+contribute to deform and orient the droplets towards the direction of the
+applied magnetic vector. In particular, we have observed an increase of the
+effective (bulk) viscosity and a reversal of the sign of the two normal stress
+differences with respect to the case without magnetic field for those
+conditions where the magnetic force prevails over the shearing force.
+Comparisons between the results of our model with a direct integration of the
+viscous stress have provided an indication of its reliability to predict the
+effective viscosity of the suspension. Moreover, this latter quantity has been
+found to behave as a monotonic increasing function of the applied magnetic
+field for constant shearing flows (""magneto-thickening"" behaviour), which
+allowed us to infer a simple constitutive equation describing the emulsion
+viscosity.",2101.03166v2
+2021-02-25,Fully General Relativistic Magnetohydrodynamic Simulations of Accretion Flows onto Spinning Massive Black Hole Binary Mergers,"We perform the first suite of fully general relativistic magnetohydrodynamic
+simulations of spinning massive black hole binary mergers. We consider binary
+black holes with spins of different magnitudes aligned to the orbital angular
+momentum, which are immersed in a hot, magnetized gas cloud. We investigate the
+effect of the spin and degree of magnetization (defined through the fluid
+parameter $\beta^{-1}\equiv p_{\mathrm{mag}}/p_{\mathrm{fluid}}$) on the
+properties of the accretion flow. We find that magnetized accretion flows are
+characterized by more turbulent dynamics, as the magnetic field lines are
+twisted and compressed during the late inspiral. Post-merger, the polar regions
+around the spin axis of the remnant Kerr black hole are magnetically dominated,
+and the magnetic field strength is increased by a factor $\sim$10$^2$
+(independently from the initial value of $\beta^{-1}$). The magnetized gas in
+the equatorial plane acquires higher angular momentum, and settles in a thin
+circular structure around the black hole. We find that mass accretion rates of
+magnetized configurations are generally smaller than in the unmagnetized cases
+by up to a factor $\sim$3. Black hole spins have also a suppressing effect on
+the accretion rate, as large as $\sim$48\%. As a potential driver for
+electromagnetic emission we follow the evolution of the Poynting luminosity,
+which increases after merger up to a factor $\sim2$ with increasing spin,
+regardless of the initial level of magnetization of the fluid. Our results
+stress the importance of taking into account both spins and magnetic fields
+when studying accretion processes onto merging massive black holes.",2102.13166v2
+2022-02-21,Detecting deep axisymmetric toroidal magnetic fields in stars. The traditional approximation of rotation for differentially rotating deep spherical shells with a general azimuthal magnetic field,"Asteroseismology has revealed small core-to-surface rotation contrasts in
+stars in the whole HR diagram. This is the signature of strong transport of
+angular momentum (AM) in stellar interiors. One of the plausible candidates to
+efficiently carry AM is magnetic fields with various topologies that could be
+present in stellar radiative zones. Among them, strong axisymmetric azimuthal
+magnetic fields have received a lot of interest. Indeed, if they are subject to
+the so-called Tayler instability, the accompanying triggered Maxwell stresses
+can transport AM efficiently. In addition, the electromotive force induced by
+the fluctuations of magnetic and velocity fields could potentially sustain a
+dynamo action that leads to the regeneration of the initial strong axisymmetric
+azimuthal magnetic field. The key question we aim to answer is: can we detect
+signatures of these deep strong azimuthal magnetic fields? The only way to
+answer this question is asteroseismology and the best laboratories of study are
+intermediate-mass and massive stars. Most of these are rapid rotators during
+their main-sequence. Therefore, we have to study stellar pulsations propagating
+in stably stratified, rotating, and potentially strongly magnetised radiative
+zones. We generalise the traditional approximation of rotation by
+simultaneously taking general axisymmetric differential rotation and azimuthal
+magnetic fields into account in a non-perturbative way. Using this new
+formalism, we derive the asymptotic properties of magneto-gravito-inertial
+(MGI) waves and their period spacings. We find that toroidal magnetic fields
+induce a shift in the period spacings of MGI modes. An equatorial azimuthal
+magnetic field with an amplitude of the order of $10^5\,\rm G$ leads to
+signatures that can be detectable thanks to modern space photometry. More
+complex hemispheric configurations are more difficult to observe.",2202.10026v2
+2022-06-03,Turbulent magnetic field in the HII region Sh 2-27,"Magnetic fields in the turbulent interstellar medium (ISM) are a key element
+in understanding Galactic dynamics, but there are many observational
+challenges. One useful probe for studying the magnetic field component parallel
+to the line of sight (LoS) is Faraday rotation of linearly polarized radio
+synchrotron emission, combined with H$\alpha$ observations. HII regions are the
+perfect laboratories to probe such magnetic fields as they are localized in
+space, and are well-defined sources often with known distances and measurable
+electron densities. We chose the HII region Sharpless 2-27 (Sh 2-27). By using
+a map of the magnetic field strength along the LoS ($B_{\parallel}$) for the
+first time, we investigate the basic statistical properties of the turbulent
+magnetic field inside Sh 2-27. We study the scaling of the magnetic field
+fluctuations, compare it to the Kolmogorov scaling, and attempt to find an
+outer scale of the turbulent magnetic field fluctuations. We estimate the
+median value of $n_e$ as $7.3\pm0.1$ cm$^{-3}$, and the median value of
+$B_{\parallel}$ as $-4.5\pm0.1$ $\mu$G, which is comparable to the magnetic
+field strength in diffuse ISM. The slope of the structure function of the
+estimated $B_{\parallel}$-map is found to be slightly steeper than Kolmogorov,
+consistent with our Gaussian-random-field $B_{\parallel}$ simulations revealing
+that an input Kolmogorov slope in the magnetic field results in a somewhat
+steeper slope in $B_{\parallel}$. These results suggest that the lower limit to
+the outer scale of turbulence is 10 pc in the HII region, which is comparable
+to the size of the computation domain. This may indicate that the turbulence
+probed here could actually be cascading from the larger scales in the ambient
+medium, associated with the interstellar turbulence in the general ISM, which
+is illuminated by the presence of Sh 2-27.",2206.01787v1
+2022-10-05,Tracking magnetic flux and helicity from Sun to Earth -- Multi-spacecraft analysis of a magnetic cloud and its solar source,"We analyze the complete chain of effects caused by a solar eruptive event in
+order to better understand the dynamic evolution of magnetic-field related
+quantities in interplanetary space, in particular that of magnetic flux and
+helicity. We study a series of connected events (a confined C4.5 flare, a
+flare-less filament eruption and a double-peak M-class flare) that originated
+in NOAA active region (AR) 12891 on 2021 November 1 and November 2. We deduce
+the magnetic structure of AR 12891 using stereoscopy and nonlinear force-free
+(NLFF) magnetic field modeling, allowing us to identify a coronal flux rope and
+to estimate its axial flux and helicity. Additionally, we compute reconnection
+fluxes based on flare ribbon and coronal dimming signatures from remote sensing
+imagery. Comparison to corresponding quantities of the associated magnetic
+cloud (MC), deduced from in-situ measurements from Solar Orbiter and near-Earth
+spacecraft, allows us to draw conclusions on the evolution of the associated
+interplanetary coronal mass ejection (ICME). The latter are aided through the
+application of geometric fitting techniques (graduated cylindrical shell
+modeling; GCS) and interplanetary propagation models (drag based ensemble
+modeling; DBEM) to the ICME. NLFF modeling suggests the host AR's magnetic
+structure in the form of a left-handed (negative-helicity) sheared arcade/flux
+rope reaching to altitudes of 8-10 Mm above photospheric levels, in close
+agreement with the corresponding stereoscopic estimate. Revealed from GCS and
+DBEM modeling, the ejected flux rope propagated in a self-similar expanding
+manner through interplanetary space. Comparison of magnetic fluxes and
+helicities processed by magnetic reconnection in the solar source region and
+the respective budgets of the MC indicate a considerable contribution from the
+eruptive process, though the pre-eruptive budgets appear of relevance too.",2210.02228v1
+2022-10-18,Mean opacities of a strongly magnetized high temperature plasma,"Geometry and dynamical structure of emission regions in accreting pulsars are
+shaped by the interplay between gravity, radiation, and strong magnetic field,
+which significantly affects the opacities of a plasma and radiative pressure
+under such extreme conditions. Quantitative consideration of magnetic plasma
+opacities is, therefore, an essential ingredient of any self-consistent
+modeling of emission region structure of X-ray pulsars. We present results of
+computations of the Rosseland and Planck mean opacities of a strongly
+magnetized plasma with a simple chemical composition,namely the solar
+hydrogen/helium mix. We consider all relevant specific opacities of the
+magnetized plasma including vacuum polarization effect and contribution of
+electron-positron pairs where the pair number density is computed in the
+thermodynamic equilibrium approximation. The magnetic Planck mean opacity
+determines the radiative cooling of an optically thin strongly magnetized
+plasma. It is by factor of three smaller than non-magnetic Planck opacity at
+$k_{\rm B}T < 0.1\,E_{\rm cyc}$ and increases by a factor of $10^2 - 10^4$ at
+$k_{\rm B}T > 0.3\,E_{\rm cyc}$ due to cyclotron thermal processes. We propose
+a simple approximate expression which has sufficient accuracy for the magnetic
+Planck opacity description. We provide the Rosseland opacity in a tabular form
+computed in the temperature range 1 - 300 keV, magnetic field range $3 \times
+10^{10} - 10^{15}$ G, and a broad range of plasma densities. We demonstrate
+that the scattering on the electron-positron pairs increases the Rosseland
+opacity drastically at temperatures >50 keV in the case of mass densities
+typical for accretion channel in X-ray pulsars.",2210.09995v1
+2022-12-06,Application of a magnetic-field-induced transition in Fe X to solar and stellar coronal magnetic field measurements,"Magnetic fields play a key role in driving a broad range of dynamic phenomena
+in the atmospheres of the Sun and other stars. Routine and accurate
+measurements of the magnetic fields at all the atmospheric layers are of
+critical importance to understand these magnetic activities, but in the solar
+and stellar coronae such a measurement is still a challenge due to the weak
+field strength and the high temperature. Recently, a magnetic-field-induced
+transition (MIT) of Fe X at 257.26 {\AA} has been proposed for the magnetic
+field measurements in the solar and stellar coronae. In this review, we present
+an overview of recent progresses in the application of this method in
+astrophysics. We start by introducing the theory underlying the MIT method and
+reviewing the existing atomic data critical for the spectral modeling of Fe X
+lines. We also discuss the laboratory measurements that verify the potential
+capability of the MIT technique as a probe for diagnosing the plasma magnetic
+fields. We then continue by investigating the suitability and accuracy of solar
+and stellar coronal magnetic field measurements based on the MIT method through
+forward modeling. Furthermore, we discuss the application of the MIT method to
+the existing spectroscopic observations obtained by the Extreme-ultraviolet
+Imaging Spectrometer onboard Hinode. This novel technique provides a possible
+way for routine measurements of the magnetic fields in the solar and stellar
+coronae, but still requires further efforts to improve its accuracy. Finally,
+the challenges and prospects for future research on this topic are discussed.",2212.02873v2
+2022-12-14,Competing magnetic fluctuations and orders in a multiorbital model of doped SrCo$_2$As$_2$,"We revisit the intriguing magnetic behavior of the paradigmatic itinerant
+frustrated magnet $\rm{Sr}\rm{Co}_2\rm{As}_2$, which shows strong and competing
+magnetic fluctuations yet does not develop long-range magnetic order. By
+calculating the static spin susceptibility $\chi(\mathbf{q})$ within a
+realistic sixteen orbital Hubbard-Hund model, we determine the leading
+instability to be ferromagnetic (FM). We then explore the effect of doping and
+calculate the critical Hubbard interaction strength $U_c$ that is required for
+the development of magnetic order. We find that $U_c$ decreases under electron
+doping and with increasing Hund's coupling $J$, but increases rapidly under
+hole doping. This suggests that magnetic order could possibly emerge under
+electron doping but not under hole doping, which agrees with experimental
+findings. We map out the leading magnetic instability as a function of doping
+and Hund's coupling and find several antiferromagnetic phases in addition to
+FM. We also quantify the degree of itinerant frustration in the model and
+resolve the contributions of different orbitals to the magnetic susceptibility.
+Finally, we discuss the dynamic spin susceptibility, $\chi(\mathbf{q},
+\omega)$, at finite frequencies, where we recover the anisotropy of the peaks
+at $\mathbf{Q}_\pi = (\pi, 0)$ and $(0, \pi)$ observed by inelastic neutron
+scattering that is associated with the phenomenon of itinerant magnetic
+frustration. By comparing results between theory and experiment, we conclude
+that the essential experimental features of doped SrCo$_2$As$_2$ are well
+captured by a Hubbard-Hund multiorbital model if one considers a small shift of
+the chemical potential towards hole doping.",2212.07511v2
+2023-03-09,Zonostrophic instabilities in magnetohydrodynamic Kolmogorov flow,"This paper concerns the stability of Kolmogorov flow u = (0, sin x) in the
+infinite (x,y)-plane. A mean magnetic field of strength B0 is introduced and
+the MHD linear stability problem studied for modes with wave-number k in the
+y-direction, and Bloch wavenumber l in the x-direction. The parameters
+governing the problem are Reynolds number 1/nu, magnetic Prandtl number P, and
+dimensionless magnetic field strength B0. The mean magnetic field can be taken
+to have an arbitrary direction in the (x,y)-plane and a mean x-directed flow U0
+can be incorporated.
+  First the paper considers Kolmogorov flow with y-directed mean magnetic
+field, referred to as vertical. Taking l=0, the suppression of the pure
+hydrodynamic instability is observed with increasing field strength B0. A
+branch of strong-field instabilities occurs for magnetic Prandtl number P less
+than unity, as found by A.E. Fraser, I.G. Cresser and P. Garaud (J. Fluid Mech.
+949, A43, 2022). Analytical results using eigenvalue perturbation theory in the
+limit k->0 support the numerics for both weak- and strong-field instabilities,
+and originate in the coupling of large-scale modes with x-wavenumber n=0, to
+smaller-scale modes.
+  The paper considers the case of horizontal or x-directed mean magnetic field.
+The unperturbed state consists of steady, wavey magnetic field lines. As the
+magnetic field is increased, the purely hydrodynamic instability is suppressed
+again, but for stronger fields a new branch of instabilities appears. Allowing
+a non-zero Bloch wavenumber l allows further instability, and in some
+circumstances when the system is hydrodynamically stable, arbitrarily weak
+magnetic fields can give growing modes. Numerical results are presented
+together with eigenvalue perturbation theory in the limits k,l->0. The theory
+gives analytical approximations for growth rates and thresholds in good
+agreement with those computed.",2303.05212v1
+2023-06-19,Onion-like Fe3O4/MgO/CoFe2O4 magnetic nanoparticles: new ways to control magnetic coupling between soft/hard phases,"The control of the magnetization inversion dynamics is one of the main
+challenges driving the design of new nanostructured magnetic materials for
+magnetoelectronic applications. Nanoparticles with onion-like architecture
+offer a unique opportunity to expand the possibilities allowing to combine
+different phases at the nanoscale and also modulate the coupling between
+magnetic phases by introducing spacers in the same structure. Here we report
+the fabrication, by a three-step high temperature decomposition method, of
+Fe3O4/MgO/CoFe2O4 onio-like nanoparticles and their detailed structural
+analysis, elemental compositional maps and magnetic response. The
+core/shell/shell nanoparticles present epitaxial growth and cubic shape with
+overall size of (29+-6) nm. These nanoparticles are formed by cubic iron oxide
+core of (22+-4) nm covered by two shells, the inner of magnesium oxide and the
+outer of cobalt ferrite of ~1 and ~2.5 nm of thickness, respectively. The
+magnetization measurements show a single reversion magnetization curve and the
+enhancement of the coercivity field, from HC~608 Oe for the Fe3O4/MgO to
+HC~5890 Oe to the Fe3O4/MgO/CoFe2O4 nanoparticles at T=5 K, ascribed to the
+coupling between both ferrimagnetic phases with a coupling constant of =2
+erg/cm2. The system also exhibits exchange bias effect, where the exchange bias
+field increases up to HEB~2850 Oe at 5 K accompanied with the broadening of the
+magnetization loop of HC~6650 Oe. This exchange bias effect originates from the
+freezing of the surface spins below the freezing temperature TF=32 K that
+pinned the magnetic moment of the cobalt ferrite shell.",2306.13108v1
+2023-07-04,Electrical operation of planar Ge hole spin qubits in an in-plane magnetic field,"In this work we present a comprehensive theory of spin physics in planar Ge
+hole quantum dots in an in-plane magnetic field, where the orbital terms play a
+dominant role in qubit physics, and provide a brief comparison with
+experimental measurements of the angular dependence of electrically driven spin
+resonance. We focus the theoretical analysis on electrical spin operation,
+phonon-induced relaxation, and the existence of coherence sweet spots. We find
+that the choice of magnetic field orientation makes a substantial difference
+for the properties of hole spin qubits. Furthermore, although the
+Schrieffer-Wolff approximation can describe electron dipole spin resonance
+(EDSR), it does not capture the fundamental spin dynamics underlying qubit
+coherence. Specifically, we find that: (i) EDSR for in-plane magnetic fields
+varies non-linearly with the field strength and weaker than for perpendicular
+magnetic fields; (ii) The EDSR Rabi frequency is maximized when the a.c.
+electric field is aligned parallel to the magnetic field, and vanishes when the
+two are perpendicular; (iii) The Rabi ratio $T_1/T_\pi$, i.e. the number of
+EDSR gate operation per unit relaxation time, is expected to be as large as
+$5{\times}10^5$ at the magnetic fields used experimentally; (iv) The orbital
+magnetic field terms make the in-plane $g$-factor strongly anisotropic in a
+squeezed dot, in excellent agreement with experimental measurements; (v) The
+coherence sweet spots do not exist in an in-plane magnetic field, as the
+orbital magnetic field terms expose the qubit to all components of the defect
+electric field. These findings will provide a guideline for experiments to
+design ultrafast, highly coherent hole spin qubits in Ge.",2307.01451v1
+2023-09-22,Probing the strongly correlated magnetic state of Co$_2$C nanoparticles at low temperatures using $μ$SR,"Co$_2$C nanoparticles (NPs) are amongst transition metal carbides whose
+magnetic properties have not been well explored. A recent study by Nirmal Roy
+et al. [1] showed that a collection of Co$_2$C NPs exhibit an exchange bias
+(EB) effect below T$_{EB}$ = 50 K and also a spin glass (SG) state below
+T$_{SG}$ = 5 K. We use magnetic, electrical transport, specific heat, and muon
+spin rotation ($\mu$SR) measurements to explore further the magnetic properties
+of these NPs. We uncover the onset of Kondo localization at Kondo temperature
+T$_K$ (= 40.1 K), near the onset of EB effect. A crossover from the
+Kondo-screened scenario to an RKKY interaction-dominated regime is also
+observed for T < T$_K$. Specific heat measurements confirm Kondo localization
+and heavy fermionic nature in Co$_2$C at low T. At low T, zero field $\mu$SR
+spectra reveal a dominant magnetically disordered fraction with slow relaxation
+and a smaller fraction with short-range order exhibiting fast relaxation, with
+no evidence of long-range magnetic order. We observe an increase in this fast
+relaxation rate between T$_{EB}$ and T$_{SG}$, suggesting a slowing down of the
+fluctuating local magnetic environment around muons. Transverse field $\mu$SR
+spectra show the emergence of a stable, multi-peaked local magnetic field
+distribution below T$_{EB}$. Longitudinal field $\mu$SR spectra shows distinct
+changes in the dynamics of fluctuations suggesting the presence of a frozen
+glassy like state below 6 K. Our results suggest that below T$_{EB}$, Co$_2$C
+NPs pellet develops a magnetic interface, separating disordered and short-range
+order fractions. The Exchange interaction that sets in below T$_{EB}$ at the
+interface couples them and suppresses the fluctuations. With the suppression of
+magnetic fluctuations below T$_{EB}$, strong correlation effects in the
+electronic state of Co$_2$C lead to Kondo localization.",2309.12797v1
+2023-12-01,Exploring kinetically induced bound states in triangular lattices with ultracold atoms: spectroscopic approach,"Quantum simulations with ultracold fermions in triangular optical lattices
+have recently emerged as a new platform for studying magnetism in frustrated
+systems. Experimental realizations of the Fermi Hubbard model revealed striking
+contrast between magnetism in bipartite and triangular lattices. In bipartite
+lattices magnetism peaks at half filling, and doped charge carriers tend to
+suppress magnetic correlations. In triangular lattices for large $U/t$,
+magnetism is enhanced by doping away from $n=1$ because kinetic energy of
+dopants can be lowered through developing magnetic correlations. This
+corresponds to formation of magnetic polarons, with hole and doublon doping
+resulting in antiferro- and ferromagnetic polarons respectively. Snapshots
+obtained with quantum gas microscopes revealed formation of magnetic polarons
+around dopants at temperatures exceeding the superexchange energy scale. In
+this work we discuss theoretically that additional insight into properties of
+magnetic polarons can be achieved using spectroscopic experiments with
+ultracold atoms. We consider starting from a spin polarized state with small
+hole doping and applying a two-photon Raman photoexcitation, which transfers
+atoms into a different spin state. We show that such magnon injection spectra
+exhibit a separate peak corresponding to formation of a bound state between a
+hole and a magnon. This polaron peak is separated from the simple magnon
+spectrum by energy proportional to single particle tunneling and can be easily
+resolved with currently available experimental techniques. For some momentum
+transfer there is an additional peak corresponding to photoexciting a bound
+state between two holes and a magnon. We point out that in two component Bose
+mixtures in triangular lattices one can also create dynamical magnetic
+polarons, with one hole and one magnon forming a repulsive bound state.",2312.00768v1
+2023-12-07,On the role of numerical diffusivity in MHD simulations of global accretion disc dynamos,"Observations, mainly of outbursts in dwarf novae, imply that the anomalous
+viscosity in highly ionized accretion discs is magnetic in origin, and requires
+that the plasma $\beta \sim 1$. Until now most simulations of the magnetic
+dynamo in accretion discs have used a local approximation (known as the
+shearing box). While these simulations demonstrate the possibility of a
+self-sustaining dynamo, the magnetic activity generated in these models
+saturates at $\beta \gg 1$. This long-standing discrepancy has previously been
+attributed to the local approximation itself. There have been recent attempts
+at simulating magnetic activity in global accretion discs with parameters
+relevant to the dwarf novae. These too find values of $\beta \gg 1$. We
+speculate that the tension between these models and the observations may be
+caused by numerical magnetic diffusivity. As a pedagogical example, we present
+exact time-dependent solutions for the evolution of weak magnetic fields in an
+incompressible fluid subject to linear shear and magnetic diffusivity. We find
+that the maximum factor by which the initial magnetic energy can be increased
+depends on the magnetic Reynolds number as ${\mathcal R}_{\rm m}^{2/3}$. We
+estimate that current global numerical simulations of dwarf nova discs have
+numerical magnetic Reynolds numbers around 6 orders of magnitude less than the
+physical value found in dwarf nova discs of ${\mathcal R}_{\rm m} \sim
+10^{10}$. We suggest that, given the current limitations on computing power,
+expecting to be able to compute realistic dynamo action in observable accretion
+discs using numerical MHD is, for the time being, a step too far.",2312.04400v1
+2023-12-30,"Onset mechanism of an inverted U-shaped solar filament eruption revealed by NVST, SDO, and STEREO-A observations","Utilizing observations from the New Vacuum Solar Telescope (NVST), Solar
+Dynamics Observatory (SDO), and Solar Terrestrial Relations Observatory-Ahead
+(STEREO-A), we investigate the event from two distinct observational
+perspectives: on the solar disk using NVST and SDO, and on the solar limb using
+STEREO-A. We employ both a non-linear force-free field model and a potential
+field model to reconstruct the coronal magnetic field, aiming to understand its
+magnetic properties. Two precursor jet-like activities were observed before the
+eruption, displaying an untwisted rotation. The second activity released an
+estimated twist of over two turns. During these two jet-like activities,
+Y-shaped brightenings, newly emerging magnetic flux accompanied by magnetic
+cancellation, and the formation of newly moving fibrils were identified.
+Combining these observational features, it can be inferred that these two
+precursor jet-like activities released the magnetic field constraining the
+filament and were triggered by newly emerging magnetic flux. Before the
+filament eruption, it was observed that some moving flows had been ejected from
+the site as the onset of two jet-like activities, indicating the same physical
+process as two jet-like activities. Extrapolations revealed that the filament
+laid under the height of the decay index of 1.0 and had strong magnetic field
+(540 Gauss) and a high twisted number (2.4 turns) before the eruption. An
+apparent rotational motion was observed during the filament eruption. We deduce
+that the solar filament, exhibiting an inverted U-shape, is a significantly
+twisted flux rope. The eruption of the filament was initiated by the release of
+constraining magnetic fields through continuous magnetic reconnection. This
+reconnection process was triggered by the emergence of newly magnetic flux.",2401.00185v1
+2020-03-24,Anomalous out-of-equilibrium dynamics in the spin-ice material Dy$_2$Ti$_2$O$_7$ under moderate magnetic fields,"We study experimentally and numerically the dynamics of the spin ice material
+Dy$_2$Ti$_2$O$_7$ in the low temperature ($T$) and moderate magnetic field
+($\mathbf{B}$) regime ($T\in[0.1,1.7]K$, $B\in[0,0.3]T$). Our objective is to
+understand the main physics shaping the out-of-equilibrium magnetisation vs.
+temperature curves in two different regimes. Very far from equilibrium, turning
+on the magnetic field after having cooled the system in zero field (ZFC) can
+increase the concentration of magnetic monopoles; this accelerates the
+dynamics. Similarly to electrolytes, this occurs through dissociation of bound
+monopole pairs. However, for spin ices the polarisation of the vacuum out of
+which the monopole pairs are created is a key factor shaping the magnetisation
+curves, with no analog. We observe a threshold field near $0.2T$ for this fast
+dynamics to take place, linked to the maximum magnetic force between the
+attracting pairs. Surprisingly, within a regime of low temperatures and
+moderate fields, an extended Ohm's law can be used to describe the ZFC
+magnetisation curve obtained with the dipolar spin-ice model. However, in real
+samples the acceleration of the dynamics appears even sharper than in
+simulations, possibly due to the presence of avalanches. On the other hand, the
+effect of the field nearer equilibrium can be just the opposite to that at very
+low temperatures. Single crystals, as noted before for powders, abandon
+equilibrium at a blocking temperature $T_B$ which increases with field.
+Curiously, this behaviour is present in numerical simulations even within the
+nearest-neighbours interactions model. Simulations and experiments show that
+the increasing trend in $T_B$ is stronger for $\mathbf{B}\parallel[100]$. This
+suggests that the field plays a part in the dynamical arrest through monopole
+suppression, which is quite manifest for this field orientation.",2003.11088v2
+2006-02-17,Dynamic Alignment in Driven Magnetohydrodynamic Turbulence,"Motivated by recent analytic predictions, we report numerical evidence
+showing that in driven incompressible magnetohydrodynamic turbulence the
+magnetic- and velocity-field fluctuations locally tend to align the directions
+of their polarizations. This dynamic alignment is stronger at smaller scales
+with the angular mismatch between the polarizations decreasing with the scale
+\lambda approximately as \theta_\lambda ~ \lambda^{1/4}. This can naturally
+lead to a weakening of the nonlinear interactions and provide an explanation
+for the energy spectrum E(k) ~ k^{-3/2} that is observed in numerical
+experiments of strongly magnetized turbulence.",0602382v2
+1997-11-14,Comparison of meanfield and Monte Carlo approaches to dynamic hysteresis in Ising ferromagnets,"The dynamical hysteresis is studied in the kinetic Ising model in the
+presence of a sinusoidal magnetic field both by Monte Carlo simulation and by
+solving the dynamical meanfield equation for the averaged magnetisation. The
+frequency variations of the dynamic coercive field are studied below the
+critical temperature. In both the cases, it shows a power law frequency
+variation however it becomes frequency independent in the low frequency regime
+for the meanfield case.",9711132v1
+1998-01-26,Dynamic Approach to the Fully Frustrated XY Model,"Using Monte Carlo simulations, we systematically investigate the
+non-equilibrium dynamics of the chiral degree of freedom in the two-dimensional
+fully frustrated XY model. The critical initial increase of the staggered
+chiral magnetization is observed. By means of the short-time dynamics approach,
+we estimate the second order phase transition temperature $T_{c}$ and all the
+dynamic and static critical exponents $\theta$, z, $\beta$ and $\nu$.",9801253v1
+1999-08-31,Dynamic scaling of I-V data for the neutral 2D Coulomb gas,"The value of the dynamic critical exponent z has been studied for
+experimental two-dimensional superconducting and Josephson Junction array
+systems in zero magnetic field via the Fisher-Fisher-Huse dynamic scaling
+analysis. We found z~5.6, a relatively large value indicative of non-diffusive
+dynamics. We extend this work here to simulational I-V curves that are also
+found to be characterized by the same large value of z.",9908473v1
+2000-04-04,Static and dynamic coupling transitions of vortex lattices in disordered anisotropic superconductors,"We use three-dimensional molecular dynamics simulations of magnetically
+interacting pancake vortices to study vortex matter in disordered, highly
+anisotropic materials such as BSCCO. We observe a sharp 2D-3D transition from
+vortex lines to decoupled pancakes as a function of relative interlayer
+coupling strength, with an accompanying large increase in the critical current
+remniscent of a second peak effect. We find that decoupled pancakes, when
+driven, simultaneously recouple and order into a crystalline-like state at high
+drives. We construct a dynamic phase diagram and show that the dynamic
+recoupling transition is associated with a double peak in dV/dI.",0004054v1
+2002-03-14,Spin dynamics in a hole-doped S=1/2 Heisenberg antiferromagnet with a disordered ground state,"Only 3% hole doping by Li is sufficient to suppress the long-range
+antiferromagnetic order in La2CuO4. Spin dynamics in such a disordered state
+was investigated with measurements of the dynamic magnetic structure factor
+S(omega,q), using cold neutron spectroscopy, for La2(Cu0.94Li0.06)O4. The
+S(omega,q) is found to sharply peak at (pi,pi), and its dynamics to be
+relaxational. Confirming theoretical expectation for the quantum disordered 2D
+S=1/2 Heisenberg antiferromagnet, the energy scale saturates at a finite value
+at low temperatures. Possible connection to the ``pseudo spin gap'' phenomenon
+observed in the NMR/NQR studies on underdoped cuprates is discussed.",0203318v1
+2002-04-16,Universality and scaling study of the critical behavior of the two-dimensional Blume-Capel model in short-time dynamics,"In this paper we study the short-time behavior of the Blume-Capel model at
+the tricritical point as well as along the second order critical line. Dynamic
+and static exponents are estimated by exploring scaling relations for the
+magnetization and its moments at early stage of the dynamic evolution. Our
+estimates for the dynamic exponents, at the tricritical point, are $z=
+2.215(2)$ and $\theta= -0.53(2)$.",0204346v1
+2002-11-15,Relationship between dynamical heterogeneities and stretched exponential relaxation,"We identify the dynamical heterogeneities as an essential prerequisite for
+stretched exponential relaxation in dynamically frustrated systems. This
+heterogeneity takes the form of ordered domains of finite but diverging
+lifetime for particles in atomic or molecular systems, or spin states in
+magnetic materials. At the onset of the dynamical heterogeneity, the
+distribution of time intervals spent in such domains or traps becomes stretched
+exponential at long time. We rigorously show that once this is the case, the
+autocorrelation function of the renewal process formed by these time intervals
+is also stretched exponential at long time.",0211322v3
+2003-09-01,Direct-Current Induced Dynamics in Co90Fe10/Ni80Fe20 Point Contacts,"We have directly measured coherent high-frequency magnetization dynamics in
+ferromagnet films induced by a spin-polarized DC current. The precession
+frequency can be tuned over a range of several gigahertz, by varying the
+applied current. The frequencies of excitation also vary with applied field,
+resulting in a microwave oscillator that can be tuned from below 5 GHz to above
+40 GHz. This novel method of inducing high-frequency dynamics yields
+oscillations having quality factors from 200 to 800. We compare our results
+with those from single-domain simulations of current-induced dynamics.",0309042v1
+2006-02-10,Low-frequency vortex dynamic susceptibility and relaxation in mesoscopic ferromagnetic dots,"Vortex dynamics in a restricted geometry is considered for a magnetic system
+consisting of ferromagnetic cylindrical dots. To describe the vortex dynamic
+susceptibility and relaxation the equation of motion for the vortex center
+position is applied. The dependencies of the vortex dynamic susceptibility and
+resonance linewidth on geometrical parameters are calculated. A new method of
+extracting damping parameter from the vortex low-frequency resonance peaks is
+proposed and applied for interpretation of resonance data on FeNi circular
+dots.",0602279v1
+2006-05-17,Dynamic Critical Behavior of Percolation Observables in the 2d Ising Model,"We present preliminary results of our numerical study of the critical
+dynamics of percolation observables for the two-dimensional Ising model. We
+consider the (Monte-Carlo) short-time evolution of the system obtained with a
+local heat-bath method and with the global Swendsen-Wang algorithm. In both
+cases, we find qualitatively different dynamic behaviors for the magnetization
+and Omega, the order parameter of the percolation transition. This may have
+implications for the recent attempts to describe the dynamics of the QCD phase
+transition using cluster observables.",0605015v1
+2002-04-25,N=2-Supersymmetric Dynamics of a Spin-1/2 Particle in an Extended External Field,"One considers the quantum dynamics of a charged spin-1/2 particle in an
+extended external eletromagnetic field that arises from the reduction of a
+5-dimensional Abelian gauge theory. The non-relativistic regime of the reduced
+4D-dynamics is worked out and one identifies the system as a sector of an
+N=2-supersymmetric quantum-mechanical dynamics. The full supersymmetric model
+is studied and one checks the algebra of the fermionic charges; the conclusion
+is that no central charge drops out. The possible r\^ole of the extra external
+fields, a scalar and a magnetic-like field, is discussed.",0204220v2
+2004-12-20,Dynamical delocalization in random Landau Hamiltonians,"We prove the existence of dynamical delocalization for random Landau
+Hamiltonians near each Landau level. Since typically there is dynamical
+localization at the edges of each disordered-broadened Landau band, this
+implies the existence of at least one dynamical mobility edge at each Landau
+band, namely a boundary point between the localization and delocalization
+regimes, which we prove to converge to the corresponding Landau level as either
+the magnetic field or the disorder goes to zero.",0412070v1
+2005-06-29,Singularity dynamics: Action and Reaction,"The interaction between singular and regular fields is considered for
+Lorentz-invariant scalar and vector wave equations. The singular field is
+generated by a Dirac source term. Its dynamics are deduced from the total field
+Lagrangian. At non-relativistic speeds, the resulting equations of motion are
+those of a mass in a scalar potential. Using this method we deduce the
+relationship between source amplitude (scalar gravitational mass) and dynamic
+mass (inertial mass). Generalising this method implies Lorentz forces for
+charge singularities in the electromagnetic field and describes the dynamics
+and interaction of hypothetical magnetic monopoles.",0506209v1
+2007-10-18,Dynamics in One-Dimensional Spin Systems - Density-Matrix Renormalization Group Study,"We study the one-dimensional $S=1/2$ Heisenberg model with a uniform and a
+staggered magnetic fields, using the dynamical density-matrix renormalization
+group (DDMRG) technique. The DDMRG enables us to investigate the dynamical
+properties of chain with lengths up to a few hundreds, and the results are
+numerically exact in the same sense as 'exact diagonalization' results are.
+Thus, we can analyze the low-energy spectrum almost in the thermodynamic limit.
+In this work, we calculate the dynamical spin structure factor and demonstrate
+the performance of the DDMRG method applying the open-end boundary condition as
+well as the periodic boundary condition.",0710.3506v1
+2007-12-05,"Glauber dynamics for the mean-field Ising model: cut-off, critical power law, and metastability","We study the Glauber dynamics for the Ising model on the complete graph, also
+known as the Curie-Weiss Model. For beta < 1, we prove that the dynamics
+exhibits a cut-off: the distance to stationarity drops from near 1 to near 0 in
+a window of order n centered at [2(1-beta)]^{-1} n log n. For beta = 1, we
+prove that the mixing time is of order n^{3/2}. For beta > 1, we study
+metastability. In particular, we show that the Glauber dynamics restricted to
+states of non-negative magnetization has mixing time O(n log n).",0712.0790v2
+2007-12-15,Dynamic structure factors of the spin-1/2 XX chain with Dzyaloshinskii-Moriya interaction,"We consider the spin-1/2 isotropic XY chain in a (z) transverse magnetic
+field with the Dzyaloshinskii-Moriya interaction directed along the z-axis in
+spin space and examine the effects of the latter interaction on the zz, xx (yy)
+and xy (yx) dynamic structure factors. The Dzyaloshinskii-Moriya interaction
+does not manifest itself in the zz dynamic quantities. In contrast, the xx (yy)
+and xy (yx) dynamic structure factors show dramatical changes owing to the
+Dzyaloshinskii-Moriya interaction. Implications of our results for electron
+spin resonance experiments are briefly discussed.",0712.2507v1
+2008-06-06,Quantum-Fluctuation-Driven Coherent Spin Dynamics in Small Condensates,"We have studied quantum spin dynamics of small condensates of cold sodium
+atoms. For a condensate initially prepared in a mean field ground state, we
+show that coherent spin dynamics are {\em purely} driven by quantum
+fluctuations of collective spin coordinates and can be tuned by quadratic
+Zeeman coupling and magnetization. These dynamics in small condensates can be
+probed in a high-finesse optical cavity where temporal behaviors of excitation
+spectra of a coupled condensate-photon system reveal the time evolution of
+populations of atoms at different hyperfine spin states.",0806.1220v1
+2009-05-11,Non-Markovian dynamics of clusters during nucleation,"Most theories of homogeneous nucleation are based on a Fokker-Planck-like
+description of the behavior of the mass of clusters. Here we will show that
+these approaches are incomplete for a large class of nucleating systems, as
+they assume the effective dynamics of the clusters to be Markovian, i.e.,
+memoryless. We characterize these non-Markovian dynamics and show how this
+influences the dynamics of clusters during nucleation. Our results are
+validated by simulations of a three-dimensional Ising model with locally
+conserved magnetization.",0905.1588v1
+2010-01-07,Localization of spin mixing dynamics in a spin-1 Bose-Einstein condensate,"We propose to localize spin mixing dynamics in a spin-1 Bose-Einstein
+condensate by a temporal modulation of spin exchange interaction, which is
+tunable with optical Feshbach resonance. Adopting techniques from coherent
+control, we demonstrate the localization/freezing of spin mixing dynamics, and
+the suppression of the intrinsic dynamic instability and spontaneous spin
+domain formation in a ferromagnetically interacting condensate of $^{87}$Rb
+atoms. This work points to a promising scheme for investigating the weak
+magnetic spin dipole interaction, which is usually masked by the more dominant
+spin exchange interaction.",1001.1035v2
+2010-03-30,Disentangling phonons from spins in ion-trap-based quantum spin simulators,"We compute how phonon creation affects the fidelity of the quantum spin
+dynamics in trapped ion simulators. A rigorous treatment of the quantum
+dynamics is made by employing an exact operator factorization of the evolution
+operator. Although it is often assumed that phonon creation modifies the
+dynamics of the spin evolution, for an Ising spin-spin interaction in an
+external magnetic field, phonons have \textit{no effect} on the probabilities
+of spin product states measured in the direction of the Ising model axis.
+Phonons play a much more important role in influencing the effective spin
+dynamics for Heisenberg or XY model spin simulators or for other observables,
+like witness operators in the Ising model.",1003.5901v1
+2010-06-01,Coherent control of interacting particles using dynamical and Aharonov-Bohm phases,"A powerful method of manipulating the dynamics of quantum coherent particles
+is to control the phase of their tunneling. We consider a system of two
+electrons hopping on a quasi one-dimensional lattice in the presence of a
+uniform magnetic field, and study the effect of adding a time-periodic driving
+potential. We show that the dynamical phases produced by the driving can
+combine with the Aharonov-Bohm phases to give precise control of the
+localization and dynamics of the particles, even in the presence of strong
+particle interactions.",1006.0188v1
+2011-03-29,Efficient control of accelerator maps,"Recently, the Hamiltonian Control Theory was used in [Boreux et al.] to
+increase the dynamic aperture of a ring particle accelerator having a localized
+thin sextupole magnet. In this letter, these results are extended by proving
+that a simplified version of the obtained general control term leads to
+significant improvements of the dynamic aperture of the uncontrolled model. In
+addition, the dynamics of flat beams based on the same accelerator model can be
+significantly improved by a reduced controlled term applied in only 1 degree of
+freedom.",1103.5631v2
+2011-09-29,A new deterministic model for chaotic reversals,"We present a new chaotic system of three coupled ordinary differential
+equations, limited to quadratic nonlinear terms. A wide variety of dynamical
+regimes are reported. For some parameters, chaotic reversals of the amplitudes
+are produced by crisis-induced intermittency, following a mechanism different
+from what is generally observed in similar deterministic models. Despite its
+simplicity, this system therefore generates a rich dynamics, able to model more
+complex physical systems. In particular, a comparison with reversals of the
+magnetic field of the Earth shows a surprisingly good agreement, and highlights
+the relevance of deterministic chaos to describe geomagnetic field dynamics.",1109.6569v2
+2012-02-07,Dynamic effect of overhangs and islands at the depinning transition in two-dimensional magnets,"With the Monte Carlo methods, we systematically investigate the short-time
+dynamics of domain-wall motion in the two-dimensional random-field Ising model
+with a driving field ?DRFIM?. We accurately determine the depinning transition
+field and critical exponents. Through two different definitions of the domain
+interface, we examine the dynamics of overhangs and islands. At the depinning
+transition, the dynamic effect of overhangs and islands reaches maximum. We
+argue that this should be an important mechanism leading the DRFIM model to a
+different universality class from the Edwards-Wilkinson equation with quenched
+disorder",1202.1349v1
+2012-03-03,On perturbations of generalized Landau-Lifshitz dynamics,"We consider deterministic and stochastic perturbations of dynamical systems
+with conservation laws in $\R^3$. The Landau-Lifshitz equation for the
+magnetization dynamics in ferromagnetics is a special case of our system. The
+averaging principle is a natural tool in such problems. But bifurcations in the
+set of invariant measures lead to essential modification in classical
+averaging. The limiting slow motion in this case, in general, is a stochastic
+process even if pure deterministic perturbations of a deterministic system are
+considered. The stochasticity is a result of instabilities in the non-perturbed
+system as well as of existence of ergodic sets of a positive measure. We
+effectively describe the limiting slow motion.",1203.0602v1
+2012-03-20,Vortex dynamics in the presence of excess energy for the Landau-Lifschitz-Gilbert equation,"We study the Landau-Lifshitz-Gilbert equation for the dynamics of a magnetic
+vortex system. We present a PDE-based method for proving vortex dynamics that
+does not rely on strong well-preparedness of the initial data and allows for
+instantaneous changes in the strength of the gyrovector force due to bubbling
+events. The main tools are estimates of the Hodge decomposition of the
+supercurrent and an analysis of the defect measure of weak convergence of the
+stress energy tensor. Ginzburg-Landau equations with mixed dynamics in the
+presence of excess energy are also discussed.",1203.4426v1
+2012-07-27,"Dynamic Phases, Pinning, and Pattern Formation for Driven Dislocation Assemblies","We show that driven dislocation assemblies exhibit a set of dynamical phases
+remarkably similar to those of driven systems with quenched disorder such as
+vortices in superconductors, magnetic domain walls, and charge density wave
+materials. These phases include jammed, fluctuating, and dynamically ordered
+states, and each produces distinct dislocation patterns as well as specific
+features in the noise fluctuations and transport properties. Our work suggests
+that many of the results established for systems with quenched disorder
+undergoing depinning transitions can be applied to dislocation systems,
+providing a new approach for understanding dislocation pattern formation and
+dynamics.",1207.6657v1
+2012-08-09,Voter models with conserved dynamics,"We propose a modified voter model with locally conserved magnetization and
+investigate its phase ordering dynamics in two dimensions in numerical
+simulations. Imposing a local constraint on the dynamics has the surprising
+effect of speeding up the phase ordering process. The system is shown to
+exhibit a scaling regime characterized by algebraic domain growth, at odds with
+the logarithmic coarsening of the standard voter model. A phenomenological
+approach based on cluster diffusion and similar to Smoluchowski ripening
+correctly predicts the observed scaling regime. Our analysis exposes unexpected
+complexity in the phase ordering dynamics without thermodynamic potential.",1208.2050v1
+2013-03-26,Dynamics of strain bifurcations in magnetostrictive ribbon,"We develop a coupled nonlinear oscillator model involving magnetization and
+strain to explain several experimentally observed dynamical features exhibited
+by forced magnetostrictive ribbon. Here we show that the model recovers the
+observed period doubling route to chaos as function of the dc field for a fixed
+ac field and quasiperiodic route to chaos as a function of the ac field,
+keeping the dc field constant. The model also predicts induced and suppressed
+chaos under the influence of an additional small-amplitude near resonant ac
+field. Our analysis suggests rich dynamics in coupled order parameter systems
+like magnetomartensitic and magnetoelectric materials.",1303.6602v1
+2013-09-24,Dynamics of the modified Kibble-Żurek mechanism in antiferromagnetic spin-1 condensates,"We investigate the dynamics and outcome of a quantum phase transition from an
+antiferromagnetic to phase separated ground state in a spin-1 Bose-Einstein
+condensate of ultracold atoms. We explicitly demonstrate double universality in
+dynamics within experiments with various quench time. Furthermore, we show that
+spin domains created in the nonequilibrium transition constitute a set of
+mutually incoherent quasicondensates. The quasicondensates appear to be
+positioned in a semi-regular fashion, which is a result of the conservation of
+local magnetization during the post-selection dynamics.",1309.6107v1
+2013-11-18,Thermoconvective structure dynamics in horizontal Homeotropic Nematics films heated from above,"Homeotropic Nematic Liquid Crystal heated from above present convective
+Rayleigh-Benard instability for applied thermal gradients greater than
+$\Delta$Tc. This threshold increase with the intensity of applied external
+magnetic field parallel to the initial molecular orientation (vertical). We
+studied the different patterns which exist near to and away from the threshold,
+such as hexagons and squares, and the transitions between them. The study of
+patterns evolution away the threshold shows coexistence between patterns and a
+global system dynamics. Also we studied how this general dynamics change with
+the inclination of the cell, where for very small angles (1 degree) the
+hexagons and squares are transformed into rolls.",1311.4271v1
+2014-10-14,Wave packet dynamics in various two-dimensional systems: a unified description,"In this article we present an exact and unified description of wave-packet
+dynamics in various 2D systems in presence of a transverse magnetic field. We
+consider an initial minimum-uncertainty Gaussian wave-packet, and find that its
+long term dynamics displays the universal phenomena of spontaneous collapse and
+quantum revival. We estimate the timescales associated with these phenomena
+based on very general arguments for various materials, whose carrier dynamics
+is described either by the Schr\""odinger equation or by the Dirac equation.",1410.3548v1
+2015-04-24,Universal coarsening dynamics of a quenched ferromagnetic spin-1 condensate,"We demonstrate that a quasi-two-dimensional spin-1 condensate quenched to a
+ferromagnetic phase undergoes universal coarsening in its late time dynamics.
+The quench can be implemented by a sudden change in the applied magnetic field
+and, depending on the final value, the ferromagnetic phase has easy-axis
+(Ising) or easy-plane (XY) symmetry, with different dynamical critical
+exponents. Our results for the easy-plane phase reveal a fractal domain
+structure and the crucial role of polar-core spin vortices in the coarsening
+dynamics.",1504.06404v2
+2016-08-19,Nonequilibrium phase transitions in isotropic Ashkin-Teller Model,"Dynamic behaviour of an isotropic Ashkin-Teller model in the presence of a
+periodically oscillating magnetic field has been analysed by means of the mean
+field approximation. The dynamic equation of motion has been constructed with
+the help of a Glauber type stochastic process and solved for a square lattice.
+  After defining the possible dynamical phases of the system, phase diagrams
+have been given and the behaviour of the hysteresis loops has been investigated
+in detail. The hysteresis loop for specific order parameter of isotropic
+Ashkin-Teller model has been defined and characteristics of this loop in
+different dynamical phases have been given.",1608.05492v1
+2016-11-05,Dynamic multiscaling in magnetohydrodynamic turbulence,"We present the first study of the multiscaling of time-dependent velocity and
+magnetic-field structure functions in homogeneous, isotropic
+magnetohydrodynamic (MHD) turbulence in three dimensions. We generalize the
+formalism that has been developed for analogous studies of time-dependent
+structure functions in fluid turbulence to MHD. By carrying out detailed
+numerical studies of such time-dependent structure functions in a shell model
+for three-dimensional MHD turbulence, we obtain both equal-time and dynamic
+scaling exponents.",1611.01660v1
+2019-04-10,Estimating Lyapunov exponents in billiards,"Dynamical billiards are paradigmatic examples of chaotic Hamiltonian
+dynamical systems with widespread applications in physics. We study how well
+their Lyapunov exponent, characterizing the chaotic dynamics, and its
+dependence on external parameters can be estimated from phase space volume
+arguments, with emphasis on billiards with mixed regular and chaotic phase
+spaces. We show that in the very diverse billiards considered here the leading
+contribution to the Lyapunov exponent is inversely proportional to the chaotic
+phase space volume, and subsequently discuss the generality of this
+relationship. We also extend the well established formalism by Dellago, Posch,
+and Hoover to calculate the Lyapunov exponents of billiards to include external
+magnetic fields and provide a software implementation of it.",1904.05108v2
+2019-11-12,Coding closed and open quantum systems in MATLAB: applications in quantum optics and condensed matter,"We develop a package of numerical simulations implemented in MATLAB to solve
+complex many-body quantum systems. We focus on widely used examples that
+include the calculation of the magnetization dynamics for the closed and open
+Ising model, dynamical quantum phase transition in cavity QED arrays, Markovian
+dynamics for interacting two-level systems, and the non-Markovian dynamics of
+the pure-dephasing spin-boson model. These examples will be useful for
+undergraduate and graduate students with a medium or high background in MATLAB,
+and also for researches interested in numerical studies applied to quantum
+optics and condensed matter systems.",1911.04906v2
+2023-12-04,Dynamical description of the phase transition into the superconducting state,"Dynamical equations that are valid in the vicinity of the phase transition
+into the superconducting state are given. Probable effects of the field of
+charge carriers' magnetic interactions and the field of temperature
+fluctuations were taken into account. The order of the phase transition is
+discussed. Considerations in favor of the applicability of the stochastic
+dynamical model A to describe the dynamics of this phase transition are given.",2312.01927v1
+1997-12-29,Nonequilibrium phase transition in the kinetic Ising model: Is transition point the maximum lossy point ?,"The nonequilibrium dynamic phase transition, in the kinetic Ising model in
+presence of an oscillating magnetic field, has been studied both by Monte Carlo
+simulation (in two dimension) and by solving the meanfield dynamical equation
+of motion for the average magnetization. The temperature variations of
+hysteretic loss (loop area) and the dynamic correlation have been studied near
+the transition point. The transition point has been identified as the
+minimum-correlation point. The hysteretic loss becomes maximum above the
+transition point. An analytical formulation has been developed to analyse the
+simulation results. A general relationship among hysteresis loop area, dynamic
+order parameter and dynamic correlation has also been developed.",9712309v2
+1998-11-06,Dynamic transitions and hysteresis,"When an interacting many-body system, such as a magnet, is driven in time by
+an external perturbation, such as a magnetic field,the system cannot respond
+instantaneously due to relaxational delay. The response of such a system under
+a time-dependent field leads to many novel physical phenomena with intriguing
+physics and important technological applications. For oscillating fields, one
+obtains hysteresis that would not occur under quasistatic conditions in the
+presence of thermal fluctuations. Under some extreme conditions of the driving
+field, one can also obtain a non-zero average value of the variable undergoing
+such dynamic hysteresis. This non-zero value indicates a breaking of symmetry
+of the hysteresis loop, around the origin. Such a transition to the
+spontaneously broken symmetric phase occurs dynamically when the driving
+frequency of the field increases beyond its threshold value which depends on
+the field amplitude and the temperature. Similar dynamic transitions also occur
+for pulsed and stochastically varying fields. We present an overview of the
+ongoing researches in this not-so-old field of dynamic hysteresis and
+transitions.",9811086v1
+2000-09-06,Dynamical Properties of the 1/r^2-Type Supersymmetric t-J Model in a Magnetic Field: Manifestation of Spin-Charge Separation,"Quasi-particle picture in a magnetic field is pursued for dynamical spin and
+charge correlation functions of the one-dimensional supersymmetric t-J model
+with inverse-square interaction. With use of exact diagonalization and the
+asymptotic Bethe-ansatz equations for finite systems, excitation contents of
+relevant excited states are identified which are valid in the thermodynamic
+limit. The excitation contents are composed of spinons, antispinons, holons and
+antiholons obeying fractional statistics. Both longitudinal and transverse
+components of the dynamical spin structure factor are independent of the
+electron density in the region where only quasi-particles with spin degrees of
+freedom (spinons and antispinons) contribute. The dynamical charge structure
+factor does not depend on the spin-polarization density in the region where
+only quasi-particles with charge (holons and antiholons) are excited. These
+features indicate the strong spin-charge separation in dynamics, reflecting the
+high symmetry of the model.",0009075v1
+2003-02-22,On the dynamical anomalies in the Hamiltonian Mean Field model,"We study the N-dependence of the thermodynamical variables and the dynamical
+behavior of the well-known Hamiltonian Mean Field model. Microcanonical
+analysis revealed a thermodynamic limit which defers from the a priory
+traditional assumption of the N-dependence of the coupling constant g as 1/N:
+to tend N?infinity keeping constant E/N^3 and g/N, prescription which
+guarantees the extensivity of the Boltzmann entropy. The analysis of dynamics
+leads to approximate the time evolution of the magnetization density m by means
+of a Langevin equation with multiplicative noise. This equation leads to a
+Fokker-Planck's equation which is N-independent when the time variable is
+scaled by the N-dependent time constant T_{mac}=sqrt(IN/g), which represents
+the characteristic time scale for the dynamical evolution of the macroscopic
+observables derived from the magnetization density. This results explains the
+origin of the slow relaxation regimen observed in microcanonical numerical
+computations of dynamics of this model system. Connection with the system
+self-similarity is suggested.",0302456v2
+2004-09-07,Spin Dynamics of Layered Triangular Antiferromagnets with Uniaxial Anisotropy,"The spin dynamics of the semiclassical Heisenberg model with uniaxial
+anisotropy, on the layered triangular lattice with antiferromagnetic coupling
+for both intralayer nearest neighbor interaction and interlayer interaction is
+studied both in the ordered phase and in the paramagnetic phase, using the
+Monte Carlo-molecular dynamics technique. The important quantities calculated
+are the full dynamic structure function $S(\bf q, \omega)$, the chiral dynamic
+structure function $S_{chi}(\omega)$, the static order parameter and some
+thermodynamic quantities. Our results show the existence of propagating modes
+corresponding to both $S(\bf q, \omega)$ and $S_{chi}(\omega)$ in the ordered
+phase, supporting the recent conjectures. Our results for the static properties
+show the magnetic ordering in each layer to be of coplanar 3-sublattice type
+deviating from 120 degree structure. In the presence of magnetic trimerization
+however, we find the 3-sublattice structure to be weakened alongwith the
+tendency towards non-coplanarity of the spins.",0409151v1
+2004-09-27,Dynamics at a smeared phase transition,"We investigate the effects of rare regions on the dynamics of Ising magnets
+with planar defects, i.e., disorder perfectly correlated in two dimensions. In
+these systems, the magnetic phase transition is smeared because static
+long-range order can develop on isolated rare regions. We first study an
+infinite-range model by numerically solving local dynamic mean-field equations.
+Then we use extremal statistics and scaling arguments to discuss the dynamics
+beyond mean-field theory. In the tail region of the smeared transition the
+dynamics is even slower than in a conventional Griffiths phase: the spin
+autocorrelation function decays like a stretched exponential at intermediate
+times before approaching the exponentially small equilibrium value following a
+power law at late times.",0409688v2
+2005-09-12,Spin and Charge Dynamics in a Renormalised Perturbation Theory,"We calculate the spin and charge dynamical susceptibilities of a strongly
+correlated impurity model in a renormalised perturbation theory.
+  The irreducible for vertices for the quasiparticle scattering are deduced
+from the renormalised parameters, which have been calculated by fitting of the
+low-lying levels of a numerical renormalisation group (NRG) calculation to
+those of an effective Anderson model. The susceptibilities are asymptotically
+exact in the low frequency limit and satisfy the Korringa-Shiba relation. By
+comparing the results with those calculated from a direct NRG calculation, we
+show that the renormalised perturbation theory (RPT) description gives a very
+good description of spin dynamics for all values of the local interaction U,
+not only at low frequencies but over the whole relevant frequency range.
+  In the presence of a magnetic field the approach can be generalised using
+field dependent renormalised parameters to calculate the transverse and
+parallel spin dynamic susceptibilities. The RPT results give accurate results
+for the spin dynamics over the whole frequency range and for all values of the
+magnetic field.",0509296v1
+2005-11-15,Dynamic response of HTS composite tapes to pulsed currents,"Dynamic voltage-current characteristics of an HTS Ag/BiSCCO composite tape
+are studied both experimentally and theoretically. The tape is subjected by
+pulsed currents with different shapes and magnitude and voltage traces are
+measured using the four-point method with different location of potential taps
+on the sample surface. Clockwise and anticlockwise hysteresis loops are
+obtained for the same sample depending on location of the potential taps. The
+dynamic characteristics deviate substantially from the DC characteristic,
+especially in the range of low voltages where a criterion for the critical
+current value is usually chosen (1-10 mkV/cm). The critical current determined
+from dynamic characteristics and its change with the pulse magnitude depend on
+location of the potential taps and on the curve branch chosen for the critical
+current determination (ascending or descending). The theoretical analysis is
+based on a model of the magnetic flux diffusion into a composite tape for a
+superconductor described by the flux creep characteristic. Numerical simulation
+based on this model gives the results in good agreement with the experimental
+ones and explains the observed peculiarities of the dynamic characteristics of
+HTS composite tapes. The difference between the magnetic diffusion into a tape
+and a slab is discussed.",0511365v1
+2006-03-15,Field momentum and gyroscopic dynamics of classical systems with topological defects,"The standard relation between the field momentum and the force is generalized
+for the system with a field singularity: in addition to the regular force,
+there appear the singular one. This approach is applied to the description of
+the gyroscopic dynamics of the classical field with topological defects. The
+collective variable Lagrangian description is considered for gyroscopical
+systems with account of singularities. Using this method we describe the
+dynamics of two-dimensional magnetic solitons. We establish a relation between
+the gyroscopic force and the singular one. An effective Lagrangian description
+is discussed for the magnetic soliton dynamics.",0603035v3
+2009-05-11,Flux dynamics in NdO1-xFxFeAs bulk sample,"We present data of multi harmonic magneto-dynamic experiments. In particular,
+we performed ac magnetic susceptibility experiments on layered pnictide-oxide
+quaternary compound NdOFeAs doped with fluorine. The experiments allow measure
+the critical temperature and probe the flux dynamic behavior using the third
+harmonic component of the ac susceptibility of a NdF0.16FeAsO0.84 bulk sample
+as a function of temperature and frequency of the applied ac magnetic fields.
+Measured signals are connected with the non-linear superconducting flux dynamic
+behavior and are characterized by a flux critical states sustaining a
+superconducting critical current. In this framework the irreversibility line
+that describes the stable superconducting state has been extracted from the
+onset of the third harmonic signal vs. frequency. Finally we present also the
+analysis of the flux dynamic dimensionality in the investigated sample.",0905.1633v1
+2010-05-30,From Phase Space Representation to Amplitude Equations in a Pattern Forming Experiment,"We describe and demonstrate a method to reconstruct an amplitude equation
+from the nonlinear relaxation dynamics in the succession of the Rosensweig
+instability. A flat layer of a ferrofluid is cooled such that the liquid has a
+relatively high viscosity. Consequently, the dynamics of the formation of the
+Rosensweig pattern becomes very slow. By sudden switching of the magnetic
+induction, the system is pushed to an arbitrary point in the phase space
+spanned by the pattern amplitude and the magnetic induction. Afterwards, it is
+allowed to relax to its equilibrium point. From the dynamics of this
+relaxation, we reconstruct the underlying fully nonlinear equation of motion of
+the pattern amplitude. The measured nonlinear dynamics serves to select the
+best weakly nonlinear expansion which describes this hysteretic transition.",1005.5544v1
+2011-04-05,Emergent gauge dynamics of highly frustrated magnets,"Condensed matter exhibits a wide variety of exotic emergent phenomena such as
+the fractional quantum Hall effect and the low temperature cooperative behavior
+of highly frustrated magnets. I consider the classical Hamiltonian dynamics of
+spins of the latter phenomena using a method introduced by Dirac in the 1950s
+by assuming they are constrained to their lowest energy configurations as a
+simplifying measure. Focusing on the kagome antiferromagnet as an example, I
+find it is a gauge system with topological dynamics and non-locally connected
+edge states for certain open boundary conditions similar to doubled
+Chern-Simons electrodynamics expected of a $Z_2$ spin liquid. These dynamics
+are also similar to electrons in the fractional quantum Hall effect. The
+classical theory presented here is a first step towards a controlled
+semi-classical description of the spin liquid phases of many pyrochlore and
+kagome antiferromagnets and towards a description of the low energy classical
+dynamics of the corresponding unconstrained Heisenberg models.",1104.0721v3
+2012-03-03,Effective field investigation of dynamic phase transitions for site diluted Ising ferromagnets driven by a periodically oscillating magnetic field,"Dynamic behavior of a site diluted Ising ferromagnet in the presence of
+periodically oscillating magnetic field has been analyzed by means of the
+effective field theory (EFT). Dynamic equation of motion have been solved for a
+honeycomb lattice ($z=3$) with the help of a Glauber type stochastic process.
+The global phase diagrams and the variation of the corresponding dynamic order
+parameter as a function of the Hamiltonian parameters and temperature has been
+investigated in detail and it has been shown that the system exhibits reentrant
+phenomena, as well as a dynamic tricritical point which disappears for
+sufficiently weak dilution.",1203.0639v1
+2012-08-11,Dynamical Configurations and Bistability of Helical Nanostructures under External Torque,"We study the motion of a ferromagnetic helical nanostructure under the action
+of a rotating magnetic field. A variety of dynamical configurations were
+observed that depended strongly on the direction of magnetization and the
+geometrical parameters, which were also confirmed by a theoretical model, based
+on the dynamics of a rigid body under Stokes flow. Although motion at low
+Reynolds numbers is typically deterministic, under certain experimental
+conditions, the nanostructures showed a surprising bistable behavior, such that
+the dynamics switched randomly between two configurations, possibly induced by
+thermal fluctuations. The experimental observations and the theoretical results
+presented in this letter are general enough to be applicable to any system of
+ellipsoidal symmetry under external force or torque.",1208.2381v1
+2013-08-20,Dynamic-Symmetry-Breaking Breathing and Spreading Transitions in Ferromagnetic Film Irradiated by Spherical Electromagnetic Wave,"The dynamical responses of a ferromagnetic film to a propagating spherical
+electromagnetic wave passing through it are studied by Monte Carlo simulation
+of two dimensional Ising ferromagnet. For a fixed set of values of the
+frequency and wavelength of the spherical EM wave, and depending on the values
+of amplitude of the EM wave and temperature of the system, three different
+modes are identified. The static pinned mode, the localised dynamical breathing
+mode and extended dynamical spreading mode are observed. The nonequilibrium
+dynamical-symmetry-breaking breathing and spreading phase transitions are also
+observed and the transition temperatures are obtained as functions of the
+amplitude of the magnetic field of EM wave. A comprehensive phase diagram is
+drawn. The boundaries of breathing and spreading transitions merge eventually
+at the equilibrium transition temperature for two dimensional Ising ferromagnet
+as the value of the amplitude of the magnetic field becomes vanishingly small.",1308.4277v1
+2013-10-24,Dynamics in spinor condensates controlled by a microwave dressing field,"We experimentally study spin dynamics in a sodium antiferromagnetic spinor
+condensate with off-resonant microwave pulses. In contrast to a magnetic field,
+a microwave dressing field enables us to explore rich spin dynamics under the
+influence of a negative net quadratic Zeeman shift $q_{\rm net}$. We find an
+experimental signature to determine the sign of $q_{\rm net}$, and observe
+harmonic spin population oscillations at every $q_{\rm net}$ except near each
+separatrix in phase space where spin oscillation period diverges. In the
+negative and positive $q_{\rm net}$ regions, we also observe a remarkably
+different relationship between each separatrix and the magnetization. Our data
+confirms an important prediction derived from the mean-field theory:
+spin-mixing dynamics in spin-1 condensates substantially depends on the sign of
+the ratio of $q_{\rm net}$ and the spin-dependent interaction energy. This work
+may thus be the first to use only one atomic species to reveal mean-field spin
+dynamics, especially the separatrix, which are predicted to appear differently
+in spin-1 antiferromagnetic and ferromagnetic spinor condensates.",1310.6785v1
+2016-02-17,Fractional Spin Fluctuation as a Precursor of Quantum Spin Liquids: Majorana Dynamical Mean-Field Study for the Kitaev Model,"Experimental identification of quantum spin liquids remains a challenge, as
+the pristine nature is to be seen in asymptotically low temperatures. We here
+theoretically show that the precursor of quantum spin liquids appears in the
+spin dynamics in the paramagnetic state over a wide temperature range. Using
+the cluster dynamical mean-field theory and the continuous-time quantum Monte
+Carlo method, which are newly developed in the Majorana fermion representation,
+we calculate the dynamical spin structure factor, relaxation rate in nuclear
+magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model
+whose ground state is a canonical example of the quantum spin liquid. We find
+that dynamical spin correlations show peculiar temperature and frequency
+dependence even below the temperature where static correlations saturate. The
+results provide the experimentally-accessible symptoms of the fluctuating
+fractionalized spins evincing the quantum spin liquids.",1602.05253v2
+2016-06-10,Nanoscale confinement of ultrafast spin transfer torque exciting non-uniform spin dynamics by femtosecond spin current pulses,"Spintronics had a widespread impact over the past decades due to transferring
+information by spin rather than electric currents. Its further development
+requires miniaturization and reduction of characteristic timescales of spin
+dynamics combining the sub-nanometer spatial and femtosecond temporal ranges.
+These demands shift the focus of interest towards the fundamental open question
+of the interaction of femtosecond spin current (SC) pulses with a ferromagnet
+(FM). The spatio-temporal properties of the impulsive spin transfer torque
+exerted by ultrashort SC pulses on the FM open the time domain for probing
+non-uniform magnetization dynamics. Here we employ laser-generated ultrashort
+SC pulses for driving ultrafast spin dynamics in FM and analyzing its transient
+local source. Transverse spins injected into FM excite inhomogeneous
+high-frequency spin dynamics up to 0.6 THz, indicating that the perturbation of
+the FM magnetization is confined to 2 nm.",1606.03403v1
+2017-03-09,Dynamics and inertia of a skyrmion in chiral magnets and interfaces: A linear response approach based on magnon excitations,"Taking all the magnon modes into account, we derive the skyrmion dynamics in
+response to a weak external drive. A skyrmion has rotational symmetry and the
+magnon modes can be characterized by an angular momentum. For a weak distortion
+of a skyrmion, only the magnon modes with an angular momentum $|m|=1$ govern
+the dynamics of skyrmion topological center. The skyrmion inertia is determined
+by the magnon modes in the continuum spectrum. For a skyrmion driven by a
+magnetic field gradient or by a spin transfer torque generated by a current,
+the dynamical response is practically instantaneous. This justifies the rigid
+skyrmion approximation used in Thiele's collective coordinate approach. For a
+skyrmion driven by a spin Hall torque, the torque couples to the skyrmion
+motion through the magnons in the continuum and damping, therefore the skyrmion
+dynamics shows sizable inertia in this case. The trajectory of a skyrmion is an
+ellipse for an ac drive of spin Hall torque.",1703.03099v2
+2017-03-30,Protected ultrastrong coupling regime of the two-photon quantum Rabi model with trapped ions,"We propose a robust realization of the two-photon quantum Rabi model in a
+trapped-ion setting based on a continuous dynamical decoupling scheme. In this
+manner the magnetic dephasing noise, which is identified as the main obstacle
+to achieve long time coherent dynamics in ion-trap simulators, can be safely
+eliminated. More specifically, we investigate the ultrastrong coupling regime
+of the two-photon quantum Rabi model whose realization in trapped ions involves
+second-order sideband processes. Hence, the resulting dynamics becomes
+unavoidably slow and more exposed to magnetic noise requiring an appropriate
+scheme for its elimination. Furthermore, we discuss how dynamical decoupling
+methods take a dual role in our protocol, namely they remove the main source of
+decoherence from the dynamics while actively define the parameter regime of the
+simulated model.",1703.10539v1
+2017-07-13,Simulation of left ventricle fluid dynamics with mitral regurgitation from magnetic resonance images with fictitious elastic structure regularization,"Computer modeling can provide quantitative insight into cardiac fluid
+dynamics phenomena that are not evident from standard imaging tools. We propose
+a new approach to modeling left ventricle fluid dynamics based on an
+image-driven model-based description of ventricular motion. In this approach,
+the end-diastolic geometry and time-dependent deformation of the left ventricle
+cavity are obtained from cardiac magnetic resonance images and a fictitious
+elastic structure is used to impose the contractile behavior of the left
+ventricle. This allows seamless treatment of the isovolumic phases. Besides the
+ventricular motion, the intracavitary fluid dynamics is controlled by the
+mitral valve. Three different mitral valve models are included in the
+simulation: an idealized diode (with or without regurgitation) and a lumped
+parameter model accounting for the opening dynamics of the valve and including
+regurgitation.",1707.03998v1
+2018-01-30,Massively parallel symplectic algorithm for coupled magnetic spin dynamics and molecular dynamics,"A parallel implementation of coupled spin-lattice dynamics in the LAMMPS
+molecular dynamics package is presented. The equations of motion for both spin
+only and coupled spin-lattice dynamics are first reviewed, including a detailed
+account of how magneto-mechanical potentials can be used to perform a proper
+coupling between spin and lattice degrees of freedom. A symplectic numerical
+integration algorithm is then presented which combines the Suzuki-Trotter
+decomposition for non-commuting variables and conserves the geometric
+properties of the equations of motion. The numerical accuracy of the serial
+implementation was assessed by verifying that it conserves the total energy and
+the norm of the total magnetization up to second order in the timestep size.
+Finally, a very general parallel algorithm is proposed that allows large
+spin-lattice systems to be efficiently simulated on large numbers of processors
+without degrading its mathematical accuracy. Its correctness as well as scaling
+efficiency were tested for realistic coupled spin-lattice systems, confirming
+that the new parallel algorithm is both accurate and efficient.",1801.10233v1
+2018-01-31,Constructing effective free energies for dynamical quantum phase transitions in the transverse-field Ising chain,"The theory of dynamical quantum phase transitions represents an attempt to
+extend the concept of phase transitions to the far from equilibrium regime.
+While there are many formal analogies to conventional transitions, it is a
+major question to which extent it is possible to formulate a nonequilibrium
+counterpart to a Landau-Ginzburg theory. In this work we take a first step in
+this direction by constructing an effective free energy for continuous
+dynamical quantum phase transitions appearing after quantum quenches in the
+transverse-field Ising chain. Due to unitarity of quantum time evolution this
+effective free energy becomes a complex quantity transforming the conventional
+minimization principle of the free energy into a saddle-point equation in the
+complex plane of the order parameter, which as in equilibrium is the
+magnetization. We study this effective free energy in the vicinity of the
+dynamical quantum phase transition by performing an expansion in terms of the
+complex magnetization and discuss the connections to the equilibrium case.
+Furthermore, we study the influence of perturbations and signatures of these
+dynamical quantum phase transitions in spin correlation functions.",1802.00020v3
+2018-09-21,Anomalous transport of magnetic colloids in a liquid crystal-magnetic colloid mixture,"We report an extensive molecular dynamics study on the translational dynamics
+of a hybrid system composed of dipolar soft spheres (DSS), representing
+ferromagnetic particles, suspended in a liquid crystal (LC) matrix. We observe
+that the LC matrix strongly modifies the dynamics of the DSS. In the isotropic
+regime, the DSS show a crossover from subdiffusive to normal diffusive behavior
+at long times, with an increase of the subdiffusive regime as the dipolar
+coupling strength is increased. In the nematic regime, the LC matrix, due to
+collective reorientation of LC particles, imposes a cylindrical confinement on
+the DSS chains. This leads to a diffusive dynamics of DSS along the nematic
+director and a subdiffusive dynamics (with an exponent $\sim 0.5$) in the
+perpendicular direction. The confinement provided by the LC matrix is also
+reflected by oscillatory behavior of the components of the velocity
+autocorrelation function of the DSS in the nematic phase.",1809.08288v2
+2018-11-07,"Magnetization and energy dynamics in spin ladders: Evidence of diffusion in time, frequency, position, and momentum","The dynamics of magnetization and energy densities are studied in the two-leg
+spin-1/2 ladder. Using an efficient pure-state approach based on the concept of
+typicality, we calculate spatio-temporal correlation functions for large
+systems with up to 40 lattice sites. In addition, two subsequent Fourier
+transforms from real to momentum space as well as from time to frequency domain
+yield the respective dynamic structure factors. Summarizing our main results,
+we unveil the existence of genuine diffusion both for spin and energy. In
+particular, this finding is based on four distinct signatures which can all be
+equally well detected: (i) Gaussian density profiles, (ii) time-independent
+diffusion coefficients, (iii) exponentially decaying density modes, and (iv)
+Lorentzian line shapes of the dynamic structure factor. The combination of (i)
+- (iv) provides a comprehensive picture of high-temperature dynamics in
+thisarchetypal nonintegrable quantum model.",1811.02806v2
+2019-01-04,Collisional N-Body Dynamics Coupled to Self-Gravitating Magnetohydrodynamics Reveals Dynamical Binary Formation,"We describe a star cluster formation model that includes individual star
+formation from self-gravitating, magnetized gas, coupled to collisional stellar
+dynamics. The model uses the Astrophysical Multi-purpose Software Environment
+(AMUSE) to integrate an adaptive-mesh magnetohydrodynamics code (FLASH) with a
+fourth order Hermite N-body code (ph4), a stellar evolution code (SeBa), and a
+method for resolving binary evolution (multiples). This combination yields
+unique star formation simulations that allow us to study binaries formed
+dynamically from interactions with both other stars and dense, magnetized gas
+subject to stellar feedback during the birth and early evolution of stellar
+clusters. We find that for massive stars, our simulations are consistent with
+the observed dynamical binary fractions and mass ratios. However, our binary
+fraction drops well below observed values for lower mass stars, presumably due
+to unincluded binary formation during initial star formation. Further, we
+observe a build up of binaries near the hard-soft boundary that may be an
+important mechanism driving early cluster contraction.",1901.01132v1
+2019-02-14,Coupled dynamics of long-range and internal spin cluster order in Cu$_{2}$OSeO$_{3}$,"Cu$_4$ triplet clusters form the relevant spin entity for the formation of
+long-range magnetic order in the cluster magnet Cu$_2$OSeO$_3$. Using
+time-resolved Raman spectroscopy, we probed photoinduced spin and lattice
+dynamics in this Mott insulator. Multiple ps-decade spin-lattice relaxation
+dynamics is observed, evidencing a separation of the order parameter dynamics
+into disordering of long-range and internal spin cluster order. Our study
+exemplifies the double order parameter dynamics of generalized molecular
+crystals of charge, spin, and orbital nature.",1902.05329v1
+2019-03-22,Exceptional points in classical spin dynamics,"Non-conservative physical systems admit a special kind of spectral
+degeneracy, known as exceptional point (EP), at which eigenvalues and
+eigenvectors of the corresponding non-Hermitian Hamiltonian coalesce. Dynamical
+parametric encircling of the EP can lead to non-adiabatic evolution associated
+with a state flip, a sharp transition between the resonant modes. Physical
+consequences of the dynamical encircling of EPs in open dissipative systems
+have been explored in optics and photonics. Building on the recent progress in
+understanding the parity-time (PT)-symmetric dynamics in spin systems, we use
+topological properties of EPs to implement chiral non-reciprocal transmission
+of a spin through the material with non-uniform magnetization, like helical
+magnet. We consider an exemplary system, spin-torque-driven single spin
+described by the time-dependent non-Hermitian Hamiltonian. We show that
+encircling individual EPs in parameter space results in non-reciprocal spin
+dynamics and find the range of optimal protocol parameters for high-efficiency
+asymmetric spin filter based on this effect. Our findings offer a platform for
+non-reciprocal spin devices for spintronics and magnonics.",1903.09729v2
+2019-04-10,Dynamics of Phase Separated States in the Double Exchange Model,"We present extensive large-scale dynamical simulations of phase-separated
+states in the double exchange model. These inhomogeneous electronic states that
+play a crucial role in the colossal magnetoresistance phenomenon are composed
+of ferromagnetic metallic clusters embedded in an antiferromagnetic insulating
+matrix. We compute the dynamical structure factor of these nanoscale textures
+using an efficient real-space formulation of coupled spin and electron
+dynamics. Dynamical signatures of the various underlying magnetic structures
+are identified. At small hole doping, the structure factor exhibits a
+dominating signal of magnons from the background N\'eel order and localized
+modes from magnetic polarons. A low-energy continuum due to large-size
+ferromagnetic clusters emerges at higher doping levels. Implications for
+experiments on magnetoresistive manganites are discussed.",1904.05252v2
+2019-08-06,Electron Induced Massive Dynamics of Magnetic Domain Walls,"We study the dynamics of domain walls (DWs) in a metallic, ferromagnetic
+nanowire. We develop a Keldysh collective coordinate technique to describe the
+effect of conduction electrons on rigid magnetic structures. The effective
+Lagrangian and Langevin equations of motion for a DW are derived. The DW
+dynamics is described by two collective degrees of freedom: position and
+tilt-angle. The coupled Langevin equations therefore involve two correlated
+noise sources, leading to a generalized fluctuation-dissipation theorem (FDT).
+The DW response kernel due to electrons contains two parts: one related to
+dissipation via FDT, and another `inertial' part. We prove that the latter term
+leads to a mass for both degrees of freedom, even though the intrinsic bare
+mass is zero. The electron-induced mass is present even in a clean system
+without pinning or specifically engineered potentials. The resulting equations
+of motion contain rich dynamical solutions and point toward a new way to
+control domain wall motion in metals via the electronic system properties. We
+discuss two observable consequences of the mass, hysteresis in the DW dynamics
+and resonant response to ac current.",1908.02299v1
+2020-10-19,Ultrafast dynamics in relativistic Mott insulators,"We study the photoinduced ultrafast dynamics in relativistic Mott insulators,
+i.e., Mott insulators with strong spin-orbit coupling. For this purpose, we
+consider a minimal one-band Hubbard model on lattices with square and
+triangular symmetries, as relevant for layered transition metal compounds such
+as Sr$_2$IrO$_4$. Depending on the lattice and the spin-orbit coupling, the
+systems have canted antiferromagnetic or $120^\circ$ order. They are excited by
+simulating a short laser pulse, and the dynamics is solved using nonequilibrium
+dynamical mean-field theory. The pulse generates hot carriers, which
+subsequently perturb the magnetic order due to the coupling between the
+collective order and photocarriers. We find that this dynamics, which is known
+form regular antiferromagnets, depends sensitively on the spatial structure of
+the spin-orbit coupling. On the triangular lattice, in particular, relaxation
+times are influenced by the spin-orbit coupling for the chiral $120^\circ$
+order, while on the square lattice with canted antiferromagnetic order the
+spin-orbit induced canting angle remains unchanged after the excitation. Our
+study opens up new possibilities of controlling magnetism and exotic spin
+states on the ultrafast timescales.",2010.09253v1
+2021-06-30,Influence of Roughening Transition on Magnetic Ordering,"In the literature of magnetic phase transitions, in addition to a critical
+point, existence of another special point has been discussed. This is related
+to the broadening of interface between two different ordering phases and is
+referred to as the point of roughening transition. While there exists good
+understanding on equilibrium properties associated with this transition,
+influence of this on nonequilibrium dynamics has not been investigated. In this
+paper we present comprehensive results, from Monte Carlo simulations, on
+coarsening dynamics in a system, over a wide range of temperature, in space
+dimension d = 3, for which there exists roughening transition at a nonzero
+temperature. State-of-the-art analysis of the simulation data, on structure,
+growth and aging, shows that the onset of unexpected glass-like slow dynamics
+in this system, that has received much attention in recent times, for quenches
+to zero temperature, actually occurs at this transition point. This
+demonstrates an important structure-dynamics connection in phase-ordering
+dynamics. We compare the key results with those from d = 2, for which there
+exists no non-zero roughening transition temperature. Absence of the above
+mentioned anomalous features in the latter dimension places our conjecture on
+the role of roughening transition on a firmer footing.",2106.16232v1
+2021-12-27,Skyrmion based energy efficient straintronic physical reservoir computing,"Physical Reservoir Computing (PRC) is an unconventional computing paradigm,
+which exploits nonlinear dynamics of reservoir blocks to perform recognition
+and classification tasks. Here we show with simulations that patterned thin
+films hosting several skyrmions, particularly one, two, four and nine
+skyrmions, can implement energy efficient reservoir computing. This reservoir
+computing (RC) block is based on nonlinear breathing dynamics of skyrmions,
+which are coupled to each other through dipole interaction and spin waves, in
+response to a voltage generated strain. This nonlinear and coupled
+magnetization dynamics is exploited to perform temporal pattern recognition.
+Two performance metrics, namely Short-Term Memory (STM) and Parity Check (PC)
+capacity are studied to demonstrate the potential of such skyrmion based PRC in
+addition to showing it can classify sine and square waves with 100% accuracy.
+Furthermore, our study demonstrates that nonlinear magnetization dynamics and
+interaction through spin waves and dipole coupling have a strong influence on
+STM and PC capacity, thus explaining the role of physical interactions in a
+dynamical system on its ability to perform Reservoir Computing (RC).",2112.13527v2
+2022-12-19,Discrete Laplacian Thermostat for Spin Systems with Conserved Dynamics,"A well-established numerical technique to study the dynamics of spin systems
+in which symmetries and conservation laws play an important role is to
+microcanonically integrate their reversible equations of motion, obtaining
+thermalization through initial conditions drawn with the canonical
+distribution. In order to achieve a more realistic relaxation of the magnetic
+energy, numerically expensive methods that explicitly couple the spins to the
+underlying lattice are normally employed. Here we introduce a stochastic
+conservative thermostat that relaxes the magnetic energy while preserving the
+constant of motions, thus turning microcanonical spin dynamics into a
+conservative canonical dynamics, without actually simulating the lattice. We
+test the thermostat on the Heisenberg antiferromagnet in d=3 and show that the
+method reproduces the exact values of the static and dynamic critical
+exponents, while in the low-temperature phase it yields the correct spin wave
+phenomenology. Finally, we demonstrate that the relaxation coefficient of the
+new thermostat is quantitatively connected to the microscopic parameters of the
+spin-lattice coupling.",2212.09647v2
+2023-01-18,Topology in the space-time scaling limit of quantum dynamics,"We investigate the role of topology in the space-time scaling limit of
+quantum quench dynamics, where both time and system size tend to infinity at a
+constant ratio. There, while the standard topological characterization relying
+on local unitary transformations becomes ill defined, we show how a different
+dynamical notion of topology naturally arises through a dynamical winding
+number encoding the linear response of the Berry phase to a magnetic flux.
+Specifically, we find that the presence of a locally invisible constant
+magnetic flux is revealed by a dynamical staircase behavior of the Berry phase,
+whose topologically quantized plateaus characterize the space-time scaling
+limit of a quenched Rice-Mele model. These jumps in the Berry phase are also
+shown to be related to the interband elements of the DC current operator. We
+outline possible experimental platforms for observing the predicted phenomena
+in finite systems.",2301.07752v2
+2023-04-19,Interacting quantum walk on a two-leg flux ladder: Emergence of re-entrant dynamics,"We study the quench dynamics of interacting bosons on a two-leg flux ladder
+by implementing the continuous-time quantum walk and explore the combined
+effect of the magnetic field and onsite interaction in the presence of uniform
+flux. We show that in the regime of weak interaction, the magnetic field
+substantially slows down the spreading of the particles' wavefunction during
+the dynamics. However, in the presence of strong interaction, we obtain an
+interesting re-entrant behaviour in the dynamics where the radial velocity
+associated to the spreading first increases, then decreases, and increases
+again as a function of the flux strength. We also find a re-entrant dynamics in
+the chiral motion of the particles as a function of interaction for fixed flux
+strengths.",2304.09796v1
+2023-06-17,Bloch dynamics in inversion symmetry broken monolayer phosphorene,"We investigate Bloch oscillations of wave packets in monolayer phosphorene
+with broken inversion symmetry. We find that the real space trajectories, Berry
+and group velocities of Bloch electron undergo Bloch oscillations in the
+system. The strong dependence of Bloch dynamics on the crystal momentum is
+illustrated. It is shown that the spin-orbit interaction crucially affects the
+dynamics of the Bloch electron. We also demonstrate the dynamics in external
+electric and magnetic field within the framework of Newton's equations of
+motion, leading to the geometric visualization of such an oscillatory motion.
+In the presence of both applied in-plane electric and transverse magnetic
+fields, the system undergoes a dynamical transition from confined to
+de-confined state and vice versa, tuned by the relative strength of the fields.",2306.10314v1
+2024-03-19,Kinetically constrained models constructed from dissipative quantum dynamics,"We propose a construction of kinetically constrained models using the
+Markovian quantum dynamics under strong dissipation. Using the
+Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) formalism, we show that strong
+dissipation leads to the emergent decoherence-free subspaces, within which
+constrained quantum many-body unitary dynamics can take place. We argue that
+the unitary dynamics constructed by the GKSL dynamics is more tightly
+constrained than that constructed by the strongly interacting Hamiltonian,
+where the interactions have the same form with the GKSL jump operators. As an
+example, we demonstrate that a one-dimensional spin system with two-site
+dissipation leads to the kinetically constrained ``PXQ"" model, which exhibits
+the free domain-wall motion with an additional frozen-block structure. Under
+the uniform magnetic field, the PXQ model shows the domain-wall localization,
+similar to the Wannier-Stark localization. We then couple two PXQ chains with
+the magnetic field and inter-chain interaction. We discover that, while
+localization of the domain walls persists despite the interactions for typical
+parameter regimes, a non-trivial partial delocalization appears for a certain
+parameter line.",2403.12548v1
+2001-11-25,Dynamical Quenching of the $α^2$ Dynamo,"We present a two-scale approximation for the dynamics of a nonlinear
+$\alpha^2$ dynamo. Solutions of the resulting nonlinear equations agree with
+the numerical simulations of Brandenburg (2001), and show that $\alpha$ is
+quenched by the buildup of magnetic helicity at the forcing scale $1/k_2$ as
+the $\alpha$ effect transfers it from the large scale $1/k_1$. For times $t >
+(k_1/k_2)R_{M,2}$ in eddy turnover units (where $R_{M,2}$ is the magnetic
+Reynolds number of the forcing scale), $\alpha$ is resistively limited in the
+form predicted for the steady-state case. However, for $t << R_{M,2}$, $\alpha$
+takes on its kinematic value, independent of $R_{M,2}$, allowing the production
+of large-scale magnetic energy equal to $k_1/k_2$ times equipartition. Thus the
+dynamic theory of $\alpha$ predicts substantial ""fast"" growth of large-scale
+field despite being ""slow"" at large times.",0111470v2
+1998-03-16,Probing Physics of Magnetohydrodynamic Turbulence Using Direct Numerical Simulation,"The energy spectrum and the nolinear cascade rates of MHD turbulence is not
+clearly understood. We have addressed this problem using direct numerical
+simulation and analytical calculations. Our numerical simulations indicate that
+Kolmogorov-like phenomenology with $k^{-5/3}$ energy spectrum, rather than
+Kraichnan's $k^{-3/2}$, appears to be applicable in MHD turbulence. Here, we
+also construct a self-consistent renomalization group procedure in which the
+mean magnetic field gets renormalized, which in turns yields $k^{-5/3}$ energy
+spectrum. The numerical simulations also show that the fluid energy is
+transferred to magnetic energy. This result could shed light on the generation
+magnetic field as in dynamo mechanism.",9803022v2
+1994-09-07,Diamagnetic Response due to Localization in Chains of Connected Mesoscopic Rings,"A dynamic response to a magnetic field of a chain of connected mesoscopic
+rings is considered. We show that the low frequency behavior corresponds to
+localization of the elctrons along the chain and to diamagnetic dynamic
+currents inside rings. The magnetization density due to these currents does not
+vanish even in the limit of the infinitely long chain of strongly connected
+rings. showing that this is a macroscopic effect. Being of a dynamic origin the
+currents can be destroyed by inelastic scattering, but we argue that the
+corresponding decay time can at low enough temperatures be large compared to
+all other time scales of the system. We suggest to check our results by
+measuring the magnetization of an ensemble of chains of connected rings in the
+diffusive regime or alternatively of linear antidot lattices where the mean
+free path due to elastic scattering is smaller than the superlattice spacing.
+This yields a new contactless method of studying the localization.",9409026v1
+1997-02-12,Suppression of chaotic dynamics and localization of two-dimensional electrons by a weak magnetic field,"We study a two-dimensional motion of a charged particle in a weak random
+potential and a perpendicular magnetic field. The correlation length of the
+potential is assumed to be much larger than the de Broglie wavelength. Under
+such conditions, the motion on not too large length scales is described by
+classical equations of motion. We show that the phase-space averaged diffusion
+coefficient is given by Drude-Lorentz formula only at magnetic fields $B$
+smaller than certain value $B_c$. At larger fields, the chaotic motion is
+suppressed and the diffusion coefficient becomes exponentially small. In
+addition, we calculate the quantum-mechanical localization length as a function
+of $B$ in the minima of $\sigma_{xx}$. At $B < B_c$ it is exponentially large
+but decreases with increasing $B$. At $B > B_c$, the localization length drops
+precipitously, and ceases to be exponentially large at a field $B_\ast$, which
+is only slightly above $B_c$. Implications for the crossover from the
+Shubnikov-de Haas oscillations to the quantum Hall effect are discussed.",9702121v1
+1998-02-05,Coarsening on percolation clusters: out-of-equilibrium dynamics versus non linear response,"We analyze the violations of linear fluctuation-dissipation theorem (FDT) in
+the coarsening dynamics of the antiferromagnetic Ising model on percolation
+clusters in two dimensions. The equilibrium magnetic response is shown to be
+non linear for magnetic fields of the order of the inverse square root of the
+number of sites. Two extreme regimes can be identified in the thermoremanent
+magnetization: (i) linear response and out-of-equilibrium relaxation for small
+waiting times (ii) non linear response and equilibrium relaxation for large
+waiting times. The function $X(C)$ characterizing the deviations from linear
+FDT cross-overs from unity at short times to a finite positive value for longer
+times, with the same qualitative behavior whatever the waiting time. We show
+that the coarsening dynamics on percolation clusters exhibits stronger
+long-term memory than usual euclidian coarsening.",9802062v1
+1999-11-16,Dynamic Radio-Frequency Transverse Susceptibility in Magnetic Nanoparticle Systems,"A novel resonant method based on a tunnel-diode oscillator (TDO) is used to
+study the dynamic transverse susceptibility in a Fe nanoparticle system. The
+magnetic system consists of an aggregate of nanometer-size core (Au)-shell (Fe)
+structure, synthesized by reverse micelle methods. Static and dynamic
+magnetization measurements carried out in order to characterize the system
+reveal a superparamagnetic behavior at high temperature. The field-dependent
+transverse susceptibility at radio-frequencies (RF), for different temperatures
+reveals distinct peak structure at characteristics fields (H_k, H_c) which
+changes with temperature. It is proposed that relaxation processes could
+explain the influence of the temperature on the field dependence of the
+transverse susceptibility on the MI.",9911242v1
+2000-03-17,Mean field and Monte Carlo studies of the magnetization-reversal transition in the Ising model,"Detailed mean field and Monte Carlo studies of the dynamic
+magnetization-reversal transition in the Ising model in its ordered phase under
+a competing external magnetic field of finite duration have been presented
+here. Approximate analytical treatment of the mean field equations of motion
+shows the existence of diverging length and time scales across this dynamic
+transition phase boundary. These are also supported by numerical solutions of
+the complete mean field equations of motion and the Monte Carlo study of the
+system evolving under Glauber dynamics in both two and three dimensions.
+Classical nucleation theory predicts different mechanisms of domain growth in
+two regimes marked by the strength of the external field, and the nature of the
+Monte Carlo phase boundary can be comprehended satisfactorily using the theory.
+The order of the transition changes from a continuous to a discontinuous one as
+one crosses over from coalescence regime (stronger field) to nucleation regime
+(weaker field). Finite size scaling theory can be applied in the coalescence
+regime, where the best fit estimates of the critical exponents are obtained for
+two and three dimensions.",0003294v2
+2001-09-11,Spin dynamics and coherent tunnelling in the molecular magnetic rings Fe_6 and Fe_8,"We present detailed calculations of low-energy spin dynamics in the ``ferric
+wheel'' systems Na:Fe_6 and Cs:Fe_8 in a magnetic field. We compute by exact
+diagonalisation the low-energy spectra and matrix elements for total-spin and
+N'eel-vector components, and thus the time-dependent correlation functions of
+these operators. Comparison of our results with the semiclassical theory of
+coherent quantum tunnelling of the N'eel vector demonstrates the validity of a
+two-state description for the low-energy dynamics of ferric wheels. We discuss
+the implications of our results for mesoscopic quantum coherent phenomena, and
+for the experimental techniques to observe them, in molecular magnetic rings.",0109201v2
+2002-04-29,Dynamic transitions and resonances in Josephson-junction arrays under oscillating magnetic fields,"We investigate dynamic transitions and stochastic resonance phenomena in
+two-dimensional fully frustrated Josephson-junction arrays driven by staggered
+oscillating magnetic fields. As the temperature is lowered, the dynamic order
+parameter, defined to be the average staggered magnetization, is observed to
+acquire nonzero values. The resulting transition is found to belong to the same
+universality as the equilibrium Z_2 transition for small driving amplitudes
+while large driving fields appear to induce deviation from the universality
+class. The transition is also manifested by the stochastic resonance peak of
+the signal-to-noise ratio, which develops above the transition temperature.",0204598v1
+2002-07-24,Vortex dynamics and pinning properties analysis of MgB2 bulk samples by ac susceptibility measurements,"The flux lines dynamics have been investigated on MgB2 bulk superconductors
+obtained by reactive liquid infiltration by measuring the ac magnetic
+susceptibility. The fundamental and third harmonics have been studied as a
+function of temperature, dc magnetic field, ac field amplitude and frequency.
+In order to determine the dynamical regimes governing the vortex motion, the
+experimental results have been compared with susceptibility curves obtained by
+numerical calculations of the non-linear diffusion equation for the magnetic
+field. The frequency behaviour of the third harmonic response, that cannot be
+explained by frequency dependent critical state models, has been related to the
+current dependence of the flux creep activation energy U(J) in the diffusion
+coefficient. In this way we have shown that the measured curves are correctly
+interpreted within the framework of a vortex glass description.",0207580v1
+2003-03-20,"Towards a Fully Ab-Initio Description of the Diluted Magnetic Semiconductor $Ga_{1-x}Mn_{x}As$. Ferromagnetism, Electronic Structure, and Optical Response","There are two competing views of itinerant ferromagnetism, the first viewing
+ferromagnetism as resulting from the indirect coupling between local moments
+via the itinerant carrier dynamics, the so-called RKKY mechanism, while in the
+alternative picture, ferromagnetism results from the spin polarization of
+itinerant carriers by the strong atomic Hund interaction - the so-called double
+exchange (DE) scenario. Which view describes the ferromagnetism in diluted
+magnetic semiconductors, materials with promise for spintronic applications, is
+still unclear. Here, we describe the detailed physical response of the
+prototype material $Ga_{1-x}Mn_{x}As$ using a combination of first-principles
+bandstructure with methods based on dynamical mean field theory to incorporate
+strong, dynamical correlations {\it and} intrinsic as well as extrinsic
+disorder in one single theoretical picture. We show how ferromagnetism is
+driven by DE, in agreement with very recent observations, along with a good
+quantitative description of the details of the electronic structure, as probed
+by scanning tunnelling microscopy (STM) and optical conductivity. Our results
+show how ferromagnetism can be driven by DE even in diluted magnetic
+semiconductors with small carrier concentration.",0303427v1
+2005-03-09,Magnetic properties of a Kondo insulator with RKKY interaction: Extended dynamical mean field study,"We study the Kondo lattice model with the Heisenberg-type RKKY-exchange
+coupling among localized f-spins in the presence of a magnetic field. By means
+of an extended dynamical mean field theory combined with the non-crossing
+approximation, we investigate the one-particle spectral function and the
+dynamical spin correlation function in the Kondo insulating phase. It is shown
+that the magnetic field and the RKKY exchange interaction both cause the
+instability to the antiferromagnetic order with enhanced transverse spin
+fluctuations, which give rise to a strong renormalization of quasi-particles as
+the system approaches the quantum critical point. This leads to a tendency to
+retain the Kondo insulating gap up to rather large fields.",0503228v1
+2005-12-29,Current-induced magnetization dynamics in disordered itinerant ferromagnets,"Current-driven magnetization dynamics in ferromagnetic metals are studied in
+a self-consistent adiabatic local-density approximation in the presence of
+spin-conserving and spin-dephasing impurity scattering. Based on a quantum
+kinetic equation, we derive Gilbert damping and spin-transfer torques entering
+the Landau-Lifshitz equation to linear order in frequency and wave vector.
+Gilbert damping and a current-driven dissipative torque scale identically and
+compete, with the result that a steady current-driven domain-wall motion is
+insensitive to spin dephasing in the limit of weak ferromagnetism. A uniform
+magnetization is found to be much more stable against spin torques in the
+itinerant than in the \textit{s}-\textit{d} model for ferromagnetism. A dynamic
+spin-transfer torque reminiscent of the spin pumping in multilayers is
+identified and shown to govern the current-induced domain-wall distortion.",0512715v4
+2006-02-23,Dynamical magneto-electric coupling in helical magnets,"Collective mode dynamics of the helical magnets coupled to electric
+polarization via spin-orbit interaction is studied theoretically. The soft
+modes associated with the ferroelectricity are not the transverse optical
+phonons, as expected from the Lyddane-Sachs-Teller relation, but are the spin
+waves hybridized with the electric polarization. This leads to the Drude-like
+dielectric function $\epsilon(\omega)$ in the limit of zero magnetic
+anisotropy. There are two more low-lying modes; phason of the spiral and
+rotation of helical plane along the polarization axis. The roles of these soft
+modes in the neutron scattering and antiferromagnetic resonance are revealed,
+and a novel experiment to detect the dynamical magneto-electric coupling is
+proposed.",0602547v1
+2006-05-17,Short-time Dynamics of Percolation Observables,"We consider the critical short-time evolution of magnetic and
+droplet-percolation order parameters for the Ising model in two and three
+dimensions, through Monte-Carlo simulations with the (local) heat-bath method.
+We find qualitatively different dynamic behaviors for the two types of order
+parameters. More precisely, we find that the percolation order parameter does
+not have a power-law behavior as encountered for the magnetization, but
+develops a scale (related to the relaxation time to equilibrium) in the
+Monte-Carlo time. We argue that this difference is due to the difficulty in
+forming large clusters at the early stages of the evolution. Our results show
+that, although the descriptions in terms of magnetic and percolation order
+parameters may be equivalent in the equilibrium regime, greater care must be
+taken to interprete percolation observables at short times. In particular, this
+concerns the attempts to describe the dynamics of the deconfinement phase
+transition in QCD using cluster observables.",0605438v1
+2006-09-26,Spin Dynamics in a Tunnel Junction between Ferromagnets,"The dynamics of a single spin embedded in the tunnel junction (quantum point
+contact) between ferromagnets is addressed. Using the Keldysh technique, we
+derive a quantum Langevin equation. As a consequence of the spin-polarization
+in the leads, the spin displays a rich and unusual dynamics. Parallel
+configured and equally strong magnetic moments in the leads yield an ordinary
+spin precession with a Larmor frequency given by the effective magnetic field.
+Unequal and/or non-parallel configured magnetization, however, causes nutation
+of the spin in addition to the precession. Our predictions may be directly
+tested for macroscopic spin clusters.",0609673v3
+2000-07-07,Dynamical Systems Approach to Magnetised Cosmological Perturbations,"Assuming a large-scale homogeneous magnetic field, we follow the covariant
+and gauge-invariant approach used by Tsagas and Barrow to describe the
+evolution of density and magnetic field inhomogeneities and curvature
+perturbations in a matter-radiation universe. We use a two parameter
+approximation scheme to linearize their exact non-linear general-relativistic
+equations for magneto-hydrodynamic evolution. Using a two-fluid approach we set
+up the governing equations as a fourth order autonomous dynamical system.
+Analysis of the equilibrium points for the radiation dominated era lead to
+solutions similar to the super-horizon modes found analytically by Tsagas and
+Maartens. We find that a study of the dynamical system in the dust-dominated
+era leads naturally to a magnetic critical length scale closely related to the
+Jeans Length. Depending on the size of wavelengths relative to this scale,
+these solutions show three distinct behaviours: large-scale stable growing
+modes, intermediate decaying modes, and small-scale damped oscillatory
+solutions.",0007010v2
+1994-05-10,Catalysis of Dynamical Flavor Symmetry Breaking by a Magnetic Field in $2+1$ Dimensions,"It is shown that in $2+1$ dimensions, a constant magnetic field is a strong
+catalyst of dynamical flavor symmetry breaking, leading to generating a fermion
+dynamical mass even at the weakest attractive interaction between fermions. The
+effect is illustrated in the Nambu-Jona-Lasinio model in a magnetic field. The
+low-energy effective action in this model is derived and the thermodynamic
+properties of the model are established. The relevance of this effect for
+planar condensed matter systems is pointed out.",9405262v2
+2005-10-06,Gauge independent approach to chiral symmetry breaking in a strong magnetic field,"The gauge independence of the dynamical fermion mass generated through chiral
+symmetry breaking in QED in a strong, constant external magnetic field is
+critically examined. We show that the bare vertex approximation, in which the
+vertex corrections are ignored, is a consistent truncation of the
+Schwinger-Dyson equations in the lowest Landau level approximation. The
+dynamical fermion mass, obtained as the solution of the truncated
+Schwinger-Dyson equations evaluated on the fermion mass shell, is shown to be
+manifestly gauge independent. By establishing a direct correspondence between
+the truncated Schwinger-Dyson equations and the 2PI (two-particle-irreducible)
+effective action truncated at the lowest nontrivial order in the loop expansion
+as well as in the 1/N_f expansion (N_f is the number of fermion flavors), we
+argue that in a strong magnetic field the dynamical fermion mass can be
+reliably calculated in the bare vertex approximation.",0510066v3
+2006-04-11,Effect of Electric and Magnetic Fields on Spin Dynamics in the Resonant Electric Dipole Moment Experiment,"A buildup of the vertical polarization in the resonant electric dipole moment
+(EDM) experiment [Y. F. Orlov, W. M. Morse, and Y. K. Semertzidis, Phys. Rev.
+Lett. 96, 214802 (2006)] is affected by a horizontal electric field in the
+particle rest frame oscillating at a resonant frequency. This field is defined
+by the Lorentz transformation of an oscillating longitudinal electric field and
+a uniform vertical magnetic one. The effect of a longitudinal electric field is
+significant, while the contribution from a magnetic field caused by forced
+coherent longitudinal oscillations of particles is dominant. The effect of
+electric field on the spin dynamics was not taken into account in previous
+calculations. This effect is considerable and leads to decreasing the EDM
+effect for the deuteron and increasing it for the proton. The formula for
+resonance strengths in the EDM experiment has been derived. The spin dynamics
+has been calculated.",0604095v2
+2001-10-27,Quantum Field Dynamics in a Uniform Magnetic Field: Description using Fields in Oblique Phase Space,"We present a simple field transformation which changes the field arguments
+from the ordinary position-space coordinates to the oblique phase-space
+coordinates that are linear in position and momentum variables. This is useful
+in studying quantum field dynamics in the presence of external uniform magnetic
+field: here, the field transformation serves to separate the dynamics within
+the given Landau level from that between different Landau levels. We apply this
+formalism to both nonrelativistic and relativistic field theories. In the large
+external magnetic field our formalism provides an efficient method for
+constructing the relevant lower-dimensional effective field theories with the
+field degrees defined only on the lowest Landau level.",0110249v1
+2003-08-07,Non-integrability of the problem of a rigid satellite in gravitational and magnetic fields,"In this paper we analyse the integrability of a dynamical system describing
+the rotational motion of a rigid satellite under the influence of gravitational
+and magnetic fields. In our investigations we apply an extension of the Ziglin
+theory developed by Morales-Ruiz and Ramis. We prove that for a symmetric
+satellite the system does not admit an additional real meromorphic first
+integral except for one case when the value of the induced magnetic moment
+along the symmetry axis is related to the principal moments of inertia in a
+special way.",0308010v2
+1997-06-01,How to Probe for Dynamical Structure in the Collapse of Entangled States Using Nuclear Magnetic Resonance,"The spin state of two magnetically inequivalent protons in contiguous atoms
+of a molecule becomes entangeled by the indirect spin-spin interaction
+(j-coupling). The degree of entanglement oscillates at the beat frequency
+resulting from the splitting of a degeneracy. This beating is manifest in NMR
+spectroscopy as an envelope of the transverse magnetization and should be
+visible in the free induction decay signal. The period (approximately 1 sec) is
+long enough for interference between the linear dynamics and collapse of the
+wave-function induced by a Stern-Gerlach inhomogeneity to significantly alter
+the shape of that envelope. Various dynamical collapse theories can be
+distinguished by their observably different predictions with respect to this
+alteration. Adverse effects of detuning due to the Stern-Gerlach inhomogeneity
+can be reduced to an acceptable level by having a sufficiently thin sample or a
+strong rf field.",9706002v2
+2005-03-15,Direct versus measurement assisted bipartite entanglement in multi-qubit systems and their dynamical generation in spin systems,"We consider multi-qubit systems and relate quantitatively the problems of
+generating cluster states with high value of concurrence of assistance, and
+that of generating states with maximal bipartite entanglement. We prove an
+upper bound for the concurrence of assistance. We consider dynamics of spin-1/2
+systems that model qubits, with different couplings and possible presence of
+magnetic field to investigate the appearance of the discussed entanglement
+properties. We find that states with maximal bipartite entanglement can be
+generated by an XY Hamiltonian, and their generation can be controlled by the
+initial state of one of the spins. The same Hamiltonian is capable of creating
+states with high concurrence of assistance with suitably chosen initial state.
+We show that the production of graph states using the Ising Hamiltonian is
+controllable via a single-qubit rotation of one spin-1/2 subsystem in the
+initial multi-qubit state. We shown that the property of Ising dynamics to
+convert a product state basis into a special maximally entangled basis is
+temporally enhanced by the application of a suitable magnetic field. Similar
+basis transformations are found to be feasible in the case of isotropic XY
+couplings with magnetic field.",0503133v1
+2007-04-19,Magnetic induction in a turbulent flow of liquid sodium: mean behaviour and slow fluctuations,"We study the flow response to an externally imposed homogeneous magnetic
+field in a turbulent swirling flow of liquid sodium -- the VKS2 experiment in
+which magnetic Reynolds numbers Rm up to 50 are reached. Induction effects are
+larger than in the former VKS1 experiment. At Rm larger than about 25, the
+local amplitude of induced field components supersedes that of the applied
+field, and exhibits non-Gaussian fluctuations. Slow dynamical instationarities
+and low-frequency bimodal dynamics are observed in the induction, presumably
+tracing back to large scale fluctuations in the hydrodynamic flow.",0704.2565v1
+2007-11-02,Dynamical feedback of the curvature drift instability on its saturation process,"We investigate the reconstruction of pulsar magnetospheres close to the light
+cylinder surface to study the curvature drift instability (CDI) responsible for
+the twisting of magnetic field lines in the mentioned zone. The influence of
+plasma dynamics on the saturation process of the CDI is studied. On the basis
+of the Euler, continuity, and induction equations, we derive the increment of
+the CDI and analyze parametrically excited drift modes. The dynamics of the
+reconstruction of the pulsar magnetosphere is studied analytically. We show
+that there is a possibility of a parametrically excited rotational-energy
+pumping-process in the drift modes. It is indicated by the generation of a
+toroidal component of the magnetic field that transforms the field lines into
+such a configuration, in which plasma particles do not experience any forces.
+At this stage, the instability process saturates and the further amplification
+of the toroidal component to the magnetic field lines is suspended.",0711.0295v8
+2008-03-20,Hidden magnetic frustration by quantum relaxation in anisotropic Nd-langasite,"The static and dynamic magnetic properties of the Nd$_3$Ga$_5$SiO$_{14}$
+compound, which appears as the first materialization of a rare-earth
+kagome-type lattice, were re-examined, owing to contradictory results in the
+previous studies. Neutron scattering, magnetization and specific heat
+measurements were performed and analyzed, in particular by fully taking account
+of the crystal electric field effects on the Nd$^{3+}$ ions. One of the novel
+findings is that the peculiar temperature independent spin dynamics observed
+below 10 K expresses single-ion quantum processes. This would short-circuit the
+frustration induced cooperative dynamics, which would emerge only at very low
+temperature.",0803.3056v2
+2008-11-03,Collective spin dynamics in magnetic nanomaterials,"Magnetic nanomaterials are considered, formed by magnetic nanomolecules with
+high spins. The problem of spin reversal in these materials is analyzed, which
+is of interest for the possible use of such materials for quantum information
+processing and quantum computing. The fastest spin reversal can be achieved by
+coupling the spin sample to a resonant electric circuit and by an appropriate
+choice of the system parameters. A principal point is to choose these
+parameters so that to organize coherent spin motion. Dynamics of collective
+motion is modelled by computer simulations, which confirm the high level of
+dynamical coherence of molecular spins in the process of spin reversal.",0811.0267v1
+2009-04-23,Spin dynamics in rare earth single molecule magnets from muSR and NMR in [TbPc$_{2}$]$^{0}$ and [DyPc$_{2}$]$^{0}$,"The spin dynamics in [TbPc$_{2}$]$^{0}$ and [DyPc$_{2}$]$^{0}$ single
+molecule magnets have been investigated by means of muon and nuclear
+spin-lattice relaxation rate measurements. The correlation time for the spin
+fluctuations was found to be close to 0.1 ms already at 50 K, about two orders
+of magnitude larger than the one previously found in other lanthanide based
+single molecule magnets. In [TbPc$_{2}$]$^{0}$ two different regimes for the
+spin fluctuations have been evidenced: a high temperature activated one
+involving spin fluctuations across a barrier $\Delta\simeq 880 K$ separating
+the ground and first excited states and a low temperature regime involving
+quantum fluctuations within the twofold degenerate ground-state. In
+[DyPc$_{2}$]$^{0}$ a high temperature activated spin dynamics is also evidenced
+which, however, cannot be explained in terms of a single spin-phonon coupling
+constant.",0904.3619v1
+2009-06-19,Lattice dynamics in magnetic superelastic Ni-Mn-In alloys. Neutron scattering and ultrasonic experiments,"Neutron scattering and ultrasonic methods have been used to study the lattice
+dynamics of two single crystals of Ni-Mn-In Heusler alloys close to
+Ni$_{50}$Mn$_{34}$In$_{16}$ magnetic superelastic composition. The paper
+reports the experimental determination of the low-lying phonon dispersion
+curves and the elastic constants for this alloy system. We found that the
+frequencies of the TA$_{2}$ branch are relatively low and it exhibits a small
+dip anomaly at a wave number $\xi_{0} \approx 1/3$, which softens with
+decreasing temperature. Associated with the softening of this phonon, we also
+observed the softening of the shear elastic constant $C'=(C_{11}-C_{12})/2$.
+Both temperature softenings are typical for bcc based solids which undergo
+martensitic transformations and reflect the dynamical instability of the cubic
+lattice against shearing of $\{110\}$ planes along $<1\bar{1}0>$ directions.
+Additionally, we measured low-lying phonon dispersion branches and elastic
+constants in applied magnetic fields aimed to characterize the magnetoelastic
+coupling.",0906.3622v1
+2009-12-24,Current driven magnetization dynamics in ferromagnetic nanowires with Dzyaloshinskii-Moriya interaction,"We study current induced magnetization dynamics in a long thin ferromagnetic
+wire with Dzyaloshinskii-Moriya interaction (DMI). We find a spiral domain wall
+configuration of the magnetization and obtain an analytical expression for the
+width of the domain wall as a function of the interaction strengths. Our
+findings show that above a certain value of DMI a domain wall configuration
+cannot exist in the wire. Below this value we determine the domain wall
+dynamics for small currents, and calculate the drift velocity of the domain
+wall along the wire. We show that the DMI suppresses the minimum value of
+current required to move the domain wall. Depending on its sign, the DMI
+increases or decreases the domain wall drift velocity.",0912.4732v1
+2010-01-22,Dynamics of domain growth driven by dipolar interactions in a perpendicularly magnetized ultrathin film,"Measurements of the ac magnetic susceptibility of perpendicularly magnetized
+Fe/2ML Ni/W(110) ultrathin films show a clear signature of the dynamics of
+domain growth and domain density changes in the striped domain pattern that
+this system supports. The susceptibility peak measured at different constant
+heating rates in the range 0.20 K/s < R < 0.70 K/s shifts to higher temperature
+as the heating rate is increased. Analysis using a relaxation model
+demonstrates quantitatively that the dynamics is driven by a non-equilibrium
+domain density at (nearly) zero field (i.e. by dipole interactions), and that
+the temperature shift is due to a response time determined by the pinning of
+local domain wall segments by structural defects. The fundamental time scale
+for relaxation of the domain density driven by dipole interactions is of order
+10^5 times slower than the fundamental time scale for an individual Barkhausen
+step driven by an applied field. The increase in the fundamental time scale
+reflects the relative size of dipole and Zeeman energies, and the need for the
+correlated motion of many local domain wall segments to affect domain growth.",1001.4069v1
+2010-02-27,Fast magnetic reconnection in three dimensional MHD simulations,"We present a constructive numerical example of fast magnetic reconnection in
+a three dimensional periodic box. Reconnection is initiated by a strong,
+localized perturbation to the field lines. The solution is intrinsically three
+dimensional, and its gross properties do not depend on the details of the
+simulations. $\sim 50%$ of the magnetic energy is released in an event which
+lasts about one Alfven time, but only after a delay during which the field
+lines evolve into a critical configuration. We present a physical picture of
+the process. The reconnection regions are dynamical and mutually interacting.
+In the comoving frame of these regions, reconnection occurs through an X-like
+point, analogous to Petschek reconnection. The dynamics appear to be driven by
+global flows, not local processes.",1003.0105v1
+2010-03-23,Low frequency spin dynamics in the quantum magnet copper pyrazine dinitrate,"The S=1/2 antiferromagnetic Heisenberg chain exhibits a magnetic field driven
+quantum critical point. We study the low frequency spin dynamics in copper
+pyrazine dinitrate (CuPzN), a realization of this model system of quantum
+magnetism, by means of $^{13}$C-NMR spectroscopy. Measurements of the nuclear
+spin-lattice relaxation rate $T_1^{-1}$ in the vicinity of the saturation field
+are compared with quantum Monte Carlo calculations of the dynamic structure
+factor. Both show a strong divergence of low energy excitations at temperatures
+in the quantum regime. The analysis of the anisotropic $T_1^{-1}$-rates and
+frequency shifts allows one to disentangle the contributions from transverse
+and longitudinal spin fluctuations for a selective study and to determine the
+transfer of delocalized spin moments from copper to the neighboring nitrogen
+atoms.",1003.4535v1
+2010-04-28,Dynamics of atoms in a time-orbiting-potential trap: consequences of the classical description,"The classical model that describes the motion of an atom in a magnetic trap
+is solved in order to investigate the relationship between the failure of the
+usual adiabatic approximation assumption and the physical parameters of the
+trap. This allows to evaluate the effect that reversing of the bias field
+rotation produces on the vertical position of the atomic orbit, a displacement
+that is closely related to the adiabatic character of the trap motion. The
+present investigation has been motivated by a similar experimental test
+previously carried out in the actual magnetic time orbiting potential trap. We
+find that the non-adiabatic effects provided by the classical model are
+extremely small. Thus, we conclude that the theoretical explanation of the
+experimental measures, requires a quantum description of the dynamics in
+magnetic traps.",1004.4978v1
+2010-05-31,Can catastrophic quenching be alleviated by separating shear and alpha effect?,"The small-scale magnetic helicity produced as a by-product of the large-scale
+dynamo is believed to play a major role in dynamo saturation. In a mean-field
+model the generation of small-scale magnetic helicity can be modelled by using
+the dynamical quenching formalism. Catastrophic quenching refers to a decrease
+of the saturation field strength with increasing Reynolds number. It has been
+suggested that catastrophic quenching only affects the region of non-zero
+helical turbulence (i.e. where the kinematic alpha operates) and that it is
+possible to alleviate catastrophic quenching by separating the region of strong
+shear from the alpha layer. We perform a systematic study of a simple
+axisymmetric two-layer alpha-omega dynamo in a spherical shell for Reynolds
+numbers in the range 1 < Rm < 10^5. In the framework of dynamical quenching we
+show that this may not be the case, suggesting that magnetic helicity fluxes
+would be necessary.",1005.5708v1
+2010-09-30,Magnetic Cycles and Meridional Circulation in Global Models of Solar Convection,"We review recent insights into the dynamics of the solar convection zone
+obtained from global numerical simulations, focusing on two recent developments
+in particular. The first is quasi-cyclic magnetic activity in a long-duration
+dynamo simulation. Although mean fields comprise only a few percent of the
+total magnetic energy they exhibit remarkable order, with multiple polarity
+reversals and systematic variability on time scales of 6-15 years. The second
+development concerns the maintenance of the meridional circulation. Recent
+high-resolution simulations have captured the subtle nonlinear dynamical
+balances with more fidelity than previous, more laminar models, yielding more
+coherent circulation patterns. These patterns are dominated by a single cell in
+each hemisphere, with poleward and equatorward flow in the upper and lower
+convection zone respectively. We briefly address the implications of and future
+of these modeling efforts.",1009.6184v2
+2010-10-18,Chemical spots and their dynamical evolution on HgMn stars,"Our recent studies of late B-type stars with HgMn peculiarity revealed for
+the first time the presence of fast dynamical evolution of chemical spots on
+their surfaces. These observations suggest a hitherto unknown physical process
+operating in the stars with radiative outer envelopes. Furthermore, we have
+also discovered existence of magnetic fields on these stars that have up to now
+been thought to be non-magnetic. Here we will discuss the dynamical spot
+evolution on HD 11753 and our new results on magnetic fields on AR Aur.",1010.3509v1
+2011-05-24,Model of bound interface dynamics for coupled magnetic domain walls,"A domain wall in a ferromagnetic system will move under the action of an
+external magnetic field. Ultrathin Co layers sandwiched between Pt have been
+shown to be a suitable experimental realization of a weakly disordered 2D
+medium in which to study the dynamics of 1D interfaces (magnetic domain walls).
+The behavior of these systems is encapsulated in the velocity-field response
+v(H) of the domain walls. In a recent paper [P.J. Metaxas et al., Phys. Rev.
+Lett. 104, 237206 (2010)] we studied the effect of ferromagnetic coupling
+between two such ultrathin layers, each exhibiting different v(H)
+characteristics. The main result was the existence of bound states over
+finite-width field ranges, wherein walls in the two layers moved together at
+the same speed. Here, we discuss in detail the theory of domain wall dynamics
+in coupled systems. In particular, we show that a bound creep state is expected
+for vanishing H and we give the analytical, parameter free expression for its
+velocity which agrees well with experimental results.",1105.4728v1
+2011-06-19,Anomalous slow dynamics in the metallic helimagnet Gd_{1-x}Y_{x},"Ac-suseptibility measurements were performed in the metallic helimagnet
+Gd_{1-x}Y_{x} alloy. A remarkable increase of the imaginary part of the
+ac-suseptibility was observed in the temperature range of the helimagnetic
+phase. Moreover, a strong nonlinearity of the magnetization was observed at
+paramagnetic-helimagnetic transition temperature T_{N}. On the other hand,
+These anomalous behavior were not observed in similar rare-earth helimagnets Ho
+and Ho_{1-x}Y_{x}. It strongly suggests that the weak magnetic anisotropy of
+the Gd-moments is responsible for the anomalous slow dynamics in the
+helimagnetic phase and for the strong nonlinearity of the magnetization at
+T_{N}. The slow dynamics may result from a chiral-domain motion, or a long-time
+variation of the period of the helimagnetic structure.",1106.3730v1
+2011-08-24,Microwave state transfer and adiabatic dynamics of magnetically trapped polar molecules,"Cold and ultracold polar molecules with nonzero electronic angular momentum
+are of great interest for studies in quantum chemistry and control,
+investigations of novel quantum systems, and precision measurement. However, in
+mixed electric and magnetic fields, these molecules are generically subject to
+a large set of avoided crossings among their Zeeman sublevels; in magnetic
+traps, these crossings lead to distorted potentials and trap loss from electric
+bias fields. We have characterized these crossings in OH by
+microwave-transferring trapped OH molecules from the upper |f; M = +3/2> parity
+state to the lower |e; +3/2> state and observing their trap dynamics under an
+applied electric bias field. Our observations are very well described by a
+simple Landau-Zener model, yielding insight to the rich spectra and dynamics of
+polar radicals in mixed external fields.",1108.4871v1
+2011-10-06,Equation of state of paramagnetic CrN from ab initio molecular dynamics,"Equation of state for chromium nitride has been debated in the literature in
+connection with a proposed collapse of its bulk modulus following the pressure
+induced transition from the paramagnetic cubic phase to the antiferromagnetic
+orthorhombic phase [F. Rivadulla et al., Nat Mater 8, 974 (2009); B. Alling et
+al., Nat Mater 9, 283 (2010)]. Experimentally the measurements are complicated
+due to the low transition pressure, while theoretically the simulation of
+magnetic disorder represent a major challenge. Here a first-principles method
+is suggested for the calculation of thermodynamic properties of magnetic
+materials in their high temperature paramagnetic phase. It is based on
+ab-initio molecular dynamics and simultaneous redistributions of the disordered
+but finite local magnetic moments. We apply this disordered local moments
+molecular dynamics method to the case of CrN and simulate its equation of
+state. In particular the debated bulk modulus is calculated in the paramagnetic
+cubic phase and is shown to be very similar to that of the antiferromagnetic
+orthorhombic CrN phase for all considered temperatures.",1110.1331v1
+2011-11-09,A dynamical phase transition in ferromagnetic granular materials,"We study, using simulations the dynamical properties of complex ferromagnetic
+granular materials. The system of grains is modeled by a disordered
+two-dimensional lattice in which the grains are embedded, while the magnitude
+and direction of the easy axis are random. Using the monte-carlo method we
+track the dynamics of the magnetic moments of the grains. We observe a
+transition of the system from a macroscopic blocked (ferromagnetic) phase at
+low temperature in which the grain's magnetic moment do not flip to the other
+direction to an unblocked (superparamagnetic) phase at high temperature in
+which the magnetic moment is free to rotate. Our results suggest that this
+transition exhibits the characteristics of a second order phase transition such
+as the appearance of a giant cluster of unblocked grains which is fractal at
+the critical temperature, a peak in the size of the second largest cluster at
+the same temperature and a power law distribution of cluster sizes near the
+criticality.",1111.2130v1
+2011-11-20,Detection of picosecond magnetization dynamics of 50 nm magnetic dots down to the single dot regime,"We report an all-optical time-domain detection of picosecond magnetization
+dynamics of arrays of 50 nm Ni80Fe20 (permalloy) dots down to the single
+nanodot regime. In the single nanodot regime the dynamics reveals one dominant
+resonant mode corresponding to the edge mode of the 50 nm dot with slightly
+higher damping than that of the unpatterned thin film. With the increase in
+areal density of the array both the precession frequency and damping increases
+significantly due to the increase in magnetostatic interactions between the
+nanodots and a mode splitting and sudden jump in apparent damping are observed
+at an edge-to-edge separation of 50 nm.",1111.4625v1
+2011-11-25,On the dynamics of vortex modes within magnetic islands,"Recent work investigating the interaction of magnetic islands with
+micro-turbulence has uncovered the striking observation of large scale vortex
+modes forming within the island structure [W.A. Hornsby {\it et al.}, Phys.
+Plasmas {\bf 17} 092301 (2010)]. These electrostatic vortices are found to be
+the size of the island and are oscillatory. It is this oscillatory behaviour
+and the presence of turbulence that leads us to believe that the dynamics are
+related to the Geodesic Acoustic Mode (GAM), and it is this link that is
+investigated in this paper.
+  Here we derive an equation for the GAM in the MHD limit, in the presence of a
+magnetic island modified three-dimensional axisymmetric geometry. The
+eigenvalues and eigenfunctions are calculated numerically and then utilised to
+analyse the dynamics of oscillatory large-scale electrostatic potential
+structures seen in both linear and non-linear gyro-kinetic simulations.",1111.5981v2
+2011-12-05,Vortex core magnetization dynamics induced by thermal excitation,"We investigate the effect of temperature on the dynamic properties of
+magnetic vortices in small disks. Our calculations use a stochastic version of
+the Landau-Lifshitz-Gilbert (LLG) equation, valid for finite temperatures well
+below the Curie critical temperature. We show that a finite temperature induces
+a vortex precession around the center of the disk, even in the absence of other
+excitation sources. We discuss the origin and implications of the appearance of
+this new dynamics. We also show that a temperature gradient plays a role
+similar to that of a small constant magnetic field.",1112.0911v2
+2012-03-23,"Scaling, Finite Size Effects, and Crossovers of the Resistivity and Current-Voltage Characteristics in Two-Dimensional Superconductors","We revisit the scaling properties of the resistivity and the current-voltage
+characteristics at and below the Berezinskii-Kosterlitz-Thouless transition,
+both in zero and nonzero magnetic field. The scaling properties are derived by
+integrating the renormalization group flow equations up to a scale where they
+can be reliably matched to simple analytic expressions. The vortex fugacity
+turns out to be dangerously irrelevant for these quantities below Tc, thereby
+altering the scaling behavior. We derive the possible crossover effects as the
+current, magnetic field, or system size is varied, and find a strong
+multiplicative logarithmic correction near Tc, all of which is necessary to
+account for when interpreting experiments and simulation data. Our analysis
+clarifies a longstanding discrepancy between the finite size dependence found
+in many simulations and the current-voltage characteristics of experiments. We
+further show that the logarithmic correction can be avoided by approaching the
+transition in a magnetic field, thereby simplifying the scaling analysis. We
+confirm our results by large-scale numerical simulations, and calculate the
+dynamic critical exponent z, for relaxational Langevin dynamics and for
+resistively and capacitively shunted Josephson junction dynamics.",1203.5317v2
+2012-05-09,"Spinor Bose gases: Explorations of symmetries, magnetism and quantum dynamics","Spinor Bose gases form a family of quantum fluids manifesting both magnetic
+order and superfluidity. This article reviews experimental and theoretical
+progress in understanding the static and dynamic properties of these fluids.
+The connection between system properties and the rotational symmetry properties
+of the atomic states and their interactions are investigated. Following a
+review of the experimental techniques used for characterizing spinor gases,
+their mean-field and many-body ground states, both in isolation and under the
+application of symmetry-breaking external fields, are discussed. These states
+serve as the starting point for understanding low-energy dynamics, spin
+textures and topological defects, effects of magnetic dipole interactions, and
+various non-equilibrium collective spin-mixing phenomena. The paper aims to
+form connections and establish coherence among the vast range of works on
+spinor Bose gases, so as to point to open questions and future research
+opportunities.",1205.1888v2
+2012-08-28,A Lagrangian kinetic model for collisionless magnetic reconnection,"A new fully kinetic system is proposed for modeling collisionless magnetic
+reconnection. The formulation relies on fundamental principles in Lagrangian
+dynamics, in which the inertia of the electron mean flow is neglected in the
+expression of the Lagrangian, rather then enforcing a zero electron mass in the
+equations of motion. This is done upon splitting the electron velocity into its
+mean and fluctuating parts, so that the latter naturally produce the
+corresponding pressure tensor. The model exhibits a new Coriolis force term,
+which emerges from a change of frame in the electron dynamics. Then, if the
+electron heat flux is neglected, the strong electron magnetization limit yields
+a hybrid model, in which the electron pressure tensor is frozen into the
+electron mean velocity.",1208.5674v2
+2012-09-24,The effect of disorder on transverse domain wall dynamics in magnetic nanostrips,"We study the effect of disorder on the dynamics of a transverse domain wall
+in ferromagnetic nanostrips, driven either by magnetic fields or spin-polarized
+currents, by performing a large ensemble of GPU-accelerated micromagnetic
+simulations. Disorder is modeled by including small, randomly distributed
+non-magnetic voids in the system. Studying the domain wall velocity as a
+function of the applied field and current density reveals fundamental
+differences in the domain wall dynamics induced by these two modes of driving:
+For the field-driven case, we identify two different domain wall pinning
+mechanisms, operating below and above the Walker breakdown, respectively,
+whereas for the current-driven case pinning is absent above the Walker
+breakdown. Increasing the disorder strength induces a larger Walker breakdown
+field and current, and leads to decreased and increased domain wall velocities
+at the breakdown field and current, respectively. Furthermore, for adiabatic
+spin transfer torque, the intrinsic pinning mechanism is found to be suppressed
+by disorder. We explain these findings within the one-dimensional model in
+terms of an effective damping parameter $\alpha^*$ increasing with the disorder
+strength.",1209.5274v1
+2012-10-09,Dynamic Correlation Length Growth in Superspin Glass: Bridging Experiments and Simulations,"Interacting magnetic nanoparticles display a wide variety of magnetic
+behaviors that are now being gathered in the emerging field of
+'supermagnetism.' We have investigated how the out-of-equilibrium dynamics in
+the disordered superspin glass (SSG) state of a frozen ferrofluid sample is
+affected by texturation. Via magnetization relaxation experiments at low
+temperatures, we were able to estimate superspin correlation lengths for both
+textured and non-textured samples. The comparison with simulations and
+experiments on atomic spin glasses shows that the dynamic correlations in SSG's
+appear to develop in a way reminiscent to those in atomic spin glasses at
+intermediate time/length scales.",1210.2524v1
+2012-12-15,Non-equilibrium magnetic interactions in strongly correlated systems,"We formulate a low-energy theory for the magnetic interactions between
+electrons in the multi-band Hubbard model under non-equilibrium conditions
+determined by an external time-dependent electric field which simulates
+laser-induced spin dynamics. We derive expressions for dynamical exchange
+parameters in terms of non-equilibrium electronic Green functions and
+self-energies, which can be computed, e.g., with the methods of time-dependent
+dynamical mean-field theory. Moreover, we find that a correct description of
+the system requires, in addition to exchange, a new kind of magnetic
+interaction, that we name ""twist exchange"", which formally resembles
+Dzyaloshinskii-Moriya coupling, but is not due to spin-orbit, and is actually
+due to an effective three-spin interaction. Our theory allows the evaluation of
+the related time-dependent parameters as well.",1212.3671v1
+2013-01-20,Lattice QCD Methods for Hadronic Polarizabilities,"Chiral dynamics makes definitive predictions for the electromagnetic
+polarizabilities of hadrons near the chiral limit; but, agreement with
+experiment is tenuous in some cases. We provide an overview of lattice QCD
+methods to compute the electric and magnetic polarizabilities of hadrons.
+Central to these methods is the lattice simulation of quarks in uniform,
+classical electromagnetic fields. A long-term goal is the determination of
+polarizabilities directly from lattice computations, however, in the near term,
+one may need to rely on partially quenched chiral perturbation theory.
+Nonetheless the same striking predictions for the pion mass dependence of
+electric and magnetic polarizabilities can be made from chiral dynamics, and
+tested with lattice QCD. A particular focus is a novel new method to handle
+charged particle correlation functions in magnetic fields.",1301.4622v1
+2013-03-19,Vortex Wall Dynamics and Pinning in Helical Magnets,"Domain walls formed by one dimensional array of vortex lines have been
+recently predicted to exist in disordered helical magnets and multiferroics.
+These systems are on one hand analogues to the vortex line lattices in type-II
+superconductors while on the other hand they propagate in the magnetic medium
+as a domain boundary. Using a long wavelength approach supported by numerical
+optimization we lay out detailed theory for dynamics and structure of such
+topological fluctuations at zero temperature in presence of weak disorder. We
+show the interaction between vortex lines is weak. This is the direct
+consequence of the screening of the vorticity by helical background in the
+system. We explain how one can use this result to understand the elasticity of
+the wall with a vicinal surface approach. Also we show the internal degree of
+freedom of this array leads to the enhancement of its mobility. We present
+estimates for the interaction and mobility enhancements using the microscopic
+parameters of the system. Finally we determine the range of velocities/force
+densities in which the internal movement of the vortex wall can be effective in
+its dynamics.",1303.4780v4
+2013-03-21,Spin dynamics of two bosons in an optical lattice site: a role of anharmonicity and anisotropy of the trapping potential,"We study a spin dynamics of two magnetic Chromium atoms trapped in a single
+site of a deep optical lattice in a resonant magnetic field. Dipole-dipole
+interactions couple spin degrees of freedom of the two particles to their
+motion in the site. The motion is quantized, therefore a trap geometry combined
+with two-body contact s-wave interactions influence a spin dynamics through the
+energy spectrum of the two atom system. Anharmonicity and anisotropy of the
+site results in a `fine' structure of two body eigenenergies. The structure can
+be easily resolved by a weak magnetic dipole-dipole interactions. As an example
+we examine the effect of anharmonicity and anisotropy of the binding potential
+on the Einstein-de Haas effect. We show that the weak dipolar interactions
+provide a perfect tool for a precision spectroscopy of the energy spectrum of
+the interacting few particle system.",1303.5232v2
+2013-04-30,Correlation effects in insulating surface nanostructures,"We study the role of static and dynamical Coulomb correlation effects on the
+electronic and magnetic properties of individual Mn, Fe and Co adatoms
+deposited on the CuN surface. For these purposes, we construct a realistic
+Anderson model, solve it by using finite-temperature exact diagonalization
+method and compare the calculated one-particle spectral functions with the
+LDA+$U$ densities of states. In contrast to Mn/CuN and Fe/CuN, the cobalt
+system tends to form the electronic excitations at the Fermi level. Based on
+the calculated magnetic response functions, the relative relaxation times for
+the magnetic moments of impurity orbitals are estimated. To study the effect of
+the dynamical correlations on the exchange interaction in nanoclusters, we
+solve the two-impurity Anderson model for the Mn dimer on the CuN surface. It
+is found that the experimental exchange interaction can be well reproduced by
+employing $U$=3 eV, which is two times smaller than the value used in static
+mean-field LDA+$U$ calculations. This suggests on important role of dynamical
+correlations in the interaction between adatoms on a surface.",1304.8044v1
+2013-06-13,Speed limit of FePt spin dynamics on femtosecond timescales,"Magnetization manipulation is becoming an indispensable tool for both basic
+and applied research. Theory predicts two types of ultrafast demagnetization
+dynamics classified as type I and type II. In type II materials, a second
+slower process takes place after the initial fast drop of magnetization. In
+this letter we investigate this behavior for FePt recording materials with
+perpendicular anisotropy. The magnetization dynamics have been simulated using
+a thermal micromagnetic model based on the Landau-Lifshitz-Bloch equation. We
+identify a transition to type II behavior and relate it to the electron
+temperatures reached by the laser heating. This slowing down is a fundamental
+limit to reconding speeds in heat assisted reversal.",1306.3112v1
+2013-07-03,Universal properties of magnetization dynamics in polycrystalline ferromagnetic films,"We investigate the scaling behavior in the statistical properties of
+Barkhausen noise in ferromagnetic films. We apply the statistical treatment
+usually employed for bulk materials in experimental Barkhausen noise time
+series measured with the traditional inductive technique in polycrystalline
+ferromagnetic films having different thickness from 100 up to 1000 nm, and
+investigate the scaling exponents. Based on this procedure, we can group the
+samples in a single universality class, characterized by exponents \tau \sim
+1.5, \alpha \sim 2.0, and 1/\sigma \nu z \sim \vartheta \sim 2.0. We interpret
+these results in terms of theoretical models and provide experimental evidence
+that a well-known mean-field model for the dynamics of a ferromagnetic domain
+wall in three-dimensional ferromagnets can be extended for films. We identify
+that the films present an universal three-dimensional magnetization dynamics,
+governed by long-range dipolar interactions, even at the smallest thicknesses,
+indicating that the two-dimensional magnetic behavior commonly verified for
+films cannot be generalized for all thickness ranges.",1307.1154v1
+2013-08-15,Detection of the microwave spin pumping using the inverse spin Hall effect,"We report electrical detection of the dynamical part of the spin pumping
+current emitted during ferromagnetic resonance (FMR) using the inverse Spin
+Hall Effect (ISHE). The experiment is performed on a YIG$|$Pt bilayer. The
+choice of YIG, a magnetic insulator, ensures that no charge current flows
+between the two layers and only pure spin current produced by the magnetization
+dynamics are transferred into the adjacent strong spin-orbit Pt layer via spin
+pumping. To avoid measuring the parasitic eddy currents induced at the
+frequency of the microwave source, a resonance at half the frequency is induced
+using parametric excitation in the parallel geometry. Triggering this nonlinear
+effect allows to directly detect on a spectrum analyzer the microwave component
+of the ISHE voltage. Signals as large as 30 $\mu$V are measured for precession
+angles of a couple of degrees. This direct detection provides a novel efficient
+means to study magnetization dynamics on a very wide frequency range with great
+sensitivity.",1308.3433v2
+2013-10-16,Terahertz out-of-plane resonances due to spin-orbit coupling,"A microscopic kinetic theory is developed which allows to investigate
+non-Abelian SU(2) systems interacting with meanfields and spin-orbit coupling
+under magnetic fields in one, two, and three dimensions. The coupled kinetic
+equations for the scalar and spin components are presented and linearized with
+respect to an external electric field. The dynamical classical and quantum Hall
+effect are described in this way as well as the anomalous Hall effect where a
+new symmetric dynamical contribution to the conductivity is presented. The
+coupled density and spin response functions to an electric field are derived
+including arbitrary magnetic fields. The magnetic field induces a staircase
+structure at frequencies of the Landau levels. It is found that for linear
+Dresselhaus and Rashba spin-orbit coupling a dynamical out-of-plane spin
+response appears at these Landau level frequencies establishing terahertz
+resonances.",1310.4405v1
+2013-11-18,The structure and dynamics of self-assembling colloidal monolayers in oscillating magnetic fields,"Many fascinating phenomena such as large-scale collective flows, enhanced
+fluid mixing and pattern formation have been observed in so-called active
+fluids, which are composed of particles that can absorb energy and dissipate it
+into the fluid medium. For active particles immersed in liquids, fluid-mediated
+viscous stresses can play an important role on the emergence of collective
+behavior. Here, we experimentally investigate their role in the dynamics of
+self-assembling magnetically-driven colloidal particles which can rapidly form
+organized hexagonal structures. We find that viscous stresses reduce hexagonal
+ordering, generate smaller clusters, and significantly decrease the rate of
+cluster formation, all while holding the system at constant number density.
+Furthermore, we show that time and length scales of cluster formation depend on
+the Mason number (Mn), or ratio of viscous to magnetic forces, scaling as t /
+Mn and L / Mn^(1/2). Our results suggest that viscous stresses hinder
+collective behavior in a self-assembling colloidal system.",1311.4497v1
+2014-01-07,Dynamical magnetic charges and linear magnetoelectricity,"Magnetoelectric (ME) materials are of fundamental interest and have been
+investigated for their broad potential for technological applications. The
+search for, and eventually the theoretical design of, materials with large ME
+couplings present challenging issues. First-principles methods have only
+recently been developed to calculate the full ME response tensor $\alpha$
+including both electronic and ionic (i.e., lattice-mediated) contributions. The
+latter is proportional to both the Born dynamical electric charge $Z^{\rm e}$
+and its analogue, the dynamical magnetic charge $Z^{\rm m}$. Here we present a
+theoretical study of the magnetic charge $Z^{\rm m}$ and the mechanisms that
+could enhance it. Using first-principles density-functional methods, we
+calculate the atomic $Z^{\rm m}$ tensors in $\rm{Cr_2O_3}$, a prototypical
+magnetoelectric, and in KITPite, a fictitious material that has previously been
+reported to show a strong ME response arising from exchange striction effects.
+Our results confirm that in $\rm{Cr_2O_3}$, the $Z^{\rm m}$ values and
+resulting ME responses arise only from spin-orbit coupling (SOC) and are
+therefore rather weak. In KITPite, by contrast, the exchange striction acting
+on the non-collinear spin structure induces much $Z^{\rm m}$ values that
+persist even when SOC is completely absent.",1401.1538v1
+2014-03-24,Dynamics and polarization of superparamagnetic chiral nanomotors in a rotating magnetic field,"Externally powered magnetic nanomotors are of particular interest due to the
+potential use for \emph{in vivo} biomedical applications. Here we develop a
+theory for dynamics and polarization of recently fabricated superparamagnetic
+chiral nanomotors powered by a rotating magnetic field. We study in detail
+various experimentally observed regimes of the nanomotor dynamic orientation
+and propulsion and establish the dependence of these properties on polarization
+and geometry of the propellers. Based on the proposed theory we introduce a
+novel ""steerability"" parameter $\gamma$ that can be used to rank polarizable
+nanomotors by their propulsive capability. The theoretical predictions of the
+nanomotor orientation and propulsion speed are in excellent agreement with
+available experimental results. Lastly, we apply slender-body approximation to
+estimate polarization anisotropy and orientation of the easy-axis of
+superparamagnetic helical propellers.",1403.6007v1
+2014-05-04,Spin Torque Oscillators with Thermal Noise: A Constant Energy Orbit Approach,"We consider a biaxial macrospin with an easy and hard axis, and study its
+dynamical evolution under the combined effects of thermal noise and spin
+transfer torque. The spin-torque is associated with both a perpendicularly
+magnetized polarizer and an in-plane magnetized reference layer, leading to an
+effective tilt between the easy and spin polarization axes. Using techniques
+based on energy averaging over the relevant dynamical trajectories, we analyze
+the effects of tilt on the dynamics and derive the conditions for the
+occurrence of stable out-of-plane precessionary states. The presence of these
+states and their predicted stability boundaries can be tested in experiments on
+orthogonal spin-transfer devices, and may also serve as a test of the
+applicability of the macrospin model to real devices, which have internal
+magnetic degrees of freedom.",1405.0731v3
+2014-06-04,"Spin-Phonon Coupling, High Pressure Phase Transitions and Thermal Expansion of Multiferroic GaFeO3: A Combined First Principles and Inelastic Neutron Scattering Study","We have carried out an extensive phonon study on multiferroic GaFeO3 to
+elucidate its dynamical behavior. Inelastic neutron scattering measurements are
+performed over a wide temperature range, 150 to 1198 K. First principles
+lattice dynamical calculations are done for the sake of the analysis and
+interpretation of the observations. The comparison of the phonon spectra from
+magnetic and non-magnetic calculations highlights pronounced differences. The
+energy range of the vibrational atomistic contributions of the Fe and O ions
+are found to differ significantly in the two calculation types. Therefore,
+magnetism induced by the active spin degrees of freedom of Fe cations plays a
+key role in stabilizing the structure and dynamics of GaFeO3. Moreover, the
+computed enthalpy in various phases of GaFeO3 is used to gain deeper insights
+into the high pressure phase stability of this material. Further, the volume
+dependence of the phonon spectra is used to determine its thermal expansion
+behavior.",1406.1027v1
+2014-10-22,Resonating Valence-Bond State in an Orbitally Degenerate Quantum Magnet with Dynamical Jahn-Teller Effect,"Short-range resonating-valence bond states in an orbitally degenerate magnet
+on a honeycomb lattice is studied. A quantum-dimer model is derived from the
+Hamiltonian which represents the superexchange interaction and the dynamical
+Jahn-Teller (JT) effect. We introduce two local units termed ""spin-orbital
+singlet dimer"", where two spins in a nearest-neighbor bond form a singlet state
+associated with an orbital polarization along the bond, and ""local JT singlet"",
+where an orbital polarization is quenched due to the dynamical JT effect. A
+derived quantum-dimer model consists of the hopping of the spin-orbital singlet
+dimers and the JT singlets, and the chemical potential of the JT singlets. We
+analyze the model by the mean-field approximation, and find that a
+characteristic phase, termed ""JT liquid phase"", where both the spin-orbital
+singlet dimers and the JT singlets move quantum mechanically, is realized.
+Possible scenarios for the recently observed non magnetic-ordered state in
+Ba$_3$CuSb$_2$O$_9$ are discussed.",1410.6009v1
+2015-01-02,"Inertia, diffusion and dynamics of a driven skyrmion","Skyrmions recently discovered in chiral magnets are a promising candidate for
+magnetic storage devices because of their topological stability, small size
+($\sim 3-100$nm), and ultra-low threshold current density ($\sim
+10^{6}$A/m$^2$) to drive their motion. However, the time-dependent dynamics has
+hitherto been largely unexplored. Here we show, by combining the numerical
+solution of the Landau-Lifshitz-Gilbert equation and the analysis of a
+generalized Thiele's equation, that inertial effects are almost completely
+absent in skyrmion dynamics driven by a time-dependent current. In contrast,
+the response to time-dependent magnetic forces and thermal fluctuations depends
+strongly on frequency and is described by a large effective mass and a (anti-)
+damping depending on the acceleration of the skyrmion. Thermal diffusion is
+strongly suppressed by the cyclotron motion and is proportional to the Gilbert
+damping coefficient $\alpha$. This indicates that the skyrmion position is
+stable, and its motion responds to the time-dependent current without delay or
+retardation even if it is fast. These findings demonstrate the advantages of
+skyrmions as information carriers.",1501.00444v1
+2015-02-27,Collective dynamical skyrmions excitations in magnonic crystal,"We investigate theoretically skyrmion magnonic crystal, i.e., the dynamics of
+the magnetization in a chain of the ferromagnetic nanodots being in skyrmion
+magnetic configuration. We show that collective excitations are possible to be
+observed in the structure. We present the dispersion relation of the coupled
+skyrmions. It exhibit a periodical property in dependence on wave vector,
+characteristic feature of the band structure in magnonic crystals. Spatial
+analysis of the magnetization amplitude associated with the magnonic bands
+confirms type of the excited modes, as breathing and clockwise gyrotropic
+dynamical skyrmions. These high and low frequency excitations, propagate with
+negative and positive group velocity, respectively, and can be explored for
+study fundamental properties and technological applications in spintronics and
+magnonics.",1502.08024v1
+2015-05-20,Simulating coronal condensation dynamics in 3D,"We present numerical simulations in 3D settings where coronal rain phenomena
+take place in a magnetic configuration of a quadrupolar arcade system. Our
+simulation is a magnetohydrodynamic simulation including anisotropic thermal
+conduction, optically thin radiative losses, and parametrised heating as main
+thermodynamical features to construct a realistic arcade configuration from
+chromospheric to coronal heights. The plasma evaporation from chromospheric and
+transition region heights eventually causes localised runaway condensation
+events and we witness the formation of plasma blobs due to thermal instability,
+that evolve dynamically in the heated arcade part and move gradually downwards
+due to interchange type dynamics. Unlike earlier 2.5D simulations, in this case
+there is no large scale prominence formation observed, but a continuous coronal
+rain develops which shows clear indications of Rayleigh-Taylor or interchange
+instability, that causes the denser plasma located above the transition region
+to fall down, as the system moves towards a more stable state. Linear stability
+analysis is used in the non-linear regime for gaining insight and giving a
+prediction of the system's evolution. After the plasma blobs descend through
+interchange, they follow the magnetic field topology more closely in the lower
+coronal regions, where they are guided by the magnetic dips.",1505.05333v1
+2015-05-28,Dynamic and rate-dependent yielding behavior of Co0.9Ni0.1 nanocluster based magnetorheological fluids,"In this paper we performed steady shear and oscillatory magnetorheological
+(MR) studies in magnetic fluids containing CoNi nanoclusters of 450 nm in
+diameter. Co-rich nanoclusters were synthesized by conventional homogeneous
+nucleation without any external surfactant or reducing agent in liquid polyol
+at elevated temperature. The x-ray diffraction, energy dispersive X-Ray
+analysis, scanning and transmission electron microscopy studies were done for
+analyzing the sample composition and morphology. Two variants of fluid samples
+were prepared by dispersing 15 vol% and 20 Vol% of CoNi powders in castor oil.
+Room temperature steady magnetoshear studies indicate viscoplastic behavior
+with stronger dependence of static yield stress on magnetization than a dipolar
+coupling that was operational in the dynamic yield stress. Magnetosweep
+measurements at constant shear rate showed interesting relaxation at high
+magnetic fields. We also explored dynamical elastic behavior through
+oscillatory magnetorheological studies under both strain sweep and frequency
+sweep modes, and showed glass transition like phenomenon occurring in them
+above critical shear amplitudes.",1505.07591v2
+2015-09-10,Ultrafast cooling and heating scenarios for the laser induced phase transition in CuO,"The multiferroic compound CuO exhibits low temperature magnetic properties
+similar to antiferromagnetic iron oxides, while the electronic properties have
+much more in common with the high $T_c$ cuprate superconductors. This suggests
+novel possibilities for the ultrafast optical excitation of magnetism. On the
+basis on atomistic spin dynamics simulations, we study the effect of
+phonon-assisted multimagnon absorption and photodoping on the spin dynamics in
+the vicinity of the first-order phase transition from collinear to spin-spiral
+magnetic order. Similar as in recent experiments, we find that for both
+excitations the phase transition can proceed on the picosecond timescale.
+Interestingly, however, these excitation mechanisms display very distinct
+dynamics. Following photodoping, the spin system first cools down on sub-ps
+timescales, which we explain as an ultrafast magnetocaloric effect. Opposed to
+this, following phonon-assisted multimagnon excitation the spin systems rapidly
+heats up and subsequently evolves to the noncollinear phase even under the
+influence of isotropic exchange interactions alone.",1509.03202v2
+2015-12-16,The Hamiltonian Dynamics of Planar Magnetic Confinement,"Inspired by a question of Colin de Verdi\`{e}re and Truc we study the
+dynamics of a classical charged particle moving in a bounded planar domain
+$\Omega$ under the influence of a magnetic field $\mathbf{B}$ which blows up at
+the boundary of the domain. We prove that under appropriate blow-up conditions
+the particle will never reach the boundary. As a corollary we obtain
+completeness of the magnetic flow. Our blow-up condition is that $\mathbf{B}$
+should not be integrable along normal rays to the boundary, while its
+tangential derivative should be integrable along those same rays.",1512.05308v3
+2016-01-19,Minimal Radius of Magnetic Skyrmions: Statics and Dynamics,"In a broad range of applied magnetic fields and material parameters isolated
+magnetic skyrmions condense into skyrmion lattices. While the geometry of
+isolated skyrmions and their lattice counterparts strongly depend on field and
+Dzyaloshinski-Moriya interaction, this issue has not been adequately addressed
+in previous studies. Meanwhile, this information is extremely important for
+applications, because the skyrmion size and the interskyrmion distance have to
+be tuned for skyrmion based memory and logic devices. In this investigation we
+elucidate the size and density-dependent phase diagram showing traditional
+phases in field vs. material parameters space by means of Monte-Carlo
+simulations on a discrete lattice. The obtained diagram permits us to establish
+that, in contrast to the continuum limit, skyrmions on a discrete lattice
+cannot be smaller than some critical size and have a very specific shape. These
+minimal skyrmions correspond to the micromagnetic configuration at the energy
+barrier between the ferromagnetic and the skyrmionic states. Furthermore, we
+use atomistic Landau-Lifshitz-Gilbert simulations to study dynamics of the
+skyrmion annihilation. It is shown that this procees consists of two stages:
+the continuous skyrmion contraction and its discontinuous annihilation. The
+detailed analysis of this dynamical process is given.",1601.04898v1
+2016-03-25,Microscopic theory of spin-orbit torques and skyrmion dynamics,"We formulate a general microscopic approach to spin-orbit torques in thin
+ferromagnet/heavy-metal bilayers in linear response to electric current or
+electric field. The microscopic theory we develop avoids the notion of spin
+currents and spin-Hall effect. Instead, the torques are directly related to a
+local spin polarization of conduction electrons, which is computed from
+generalized Kubo-St\v{r}eda formulas. A symmetry analysis provides a one-to-one
+correspondence between polarization susceptibility tensor components and
+different torque terms in the Landau-Lifshitz-Gilbert equation for
+magnetization dynamics. The spin-orbit torques arising from Rashba or
+Dresselhaus type of spin-orbit interaction are shown to have different
+symmetries. We analyze these spin-orbit torques microscopically for a generic
+electron model in the presence of an arbitrary smooth magnetic texture. For a
+model with spin-independent disorder we find a major cancelation of the
+torques. In this case the only remaining torque corresponds to the
+magnetization-independent Edelstein effect. Furthermore, our results are
+applied to analyze the dynamics of a Skyrmion under the action of electric
+current.",1603.07994v2
+2016-05-10,Dynamical supersymmetry breaking on magnetized tori and orbifolds,"We construct several dynamical supersymmetry breaking (DSB) models within a
+single ten-dimensional supersymmetric Yang-Mills (SYM) theory, compactified on
+magnetized tori with or without orbifolding. We study the case that the
+supersymmetry breaking is triggered by a strong dynamics of $SU(N_C)$ SYM
+theory with $N_F$ flavors contained in the four-dimensional effective theory.
+We show several configurations of magnetic fluxes and orbifolds, those
+potentially yield, below the compactification scale, the field contents and
+couplings required for triggering DSB. We especially find a class of
+self-complete DSB models on orbifolds, where all the extra fields are
+eliminated by the orbifold projection and DSB successfully occurs within the
+given framework. Comments on some perspectives for associating the obtained DSB
+models with the other sectors, such as the visible sector and another hidden
+sector for, e.g., stabilizing moduli, are also given.",1605.02922v1
+2016-10-13,Spin-wave spectra in periodically surface-modulated ferromagnetic thin films,"This article presents theoretical results for the dynamic response of
+periodically surface-modulated ferromagnetic thin films. For such system, the
+role of the periodic dipolar field induced by the modulation is addressed by
+using the plane-wave method. By controlling the geometry of the modulated
+volumes within the film, the frequency modes and spatial profiles of spin waves
+can be manipulated. The angular dependence of the frequency band-gaps unveils
+the influence of both dynamic and static magnetic charges, which reside in the
+edges of the etching periodic zones, and it is stablished that band-gap widths
+created by static magnetic charges are broader than the one created by dynamic
+magnetic charges. To corroborate the validity of the model, the theoretical
+results are compared with ferromagnetic resonance simulations, where a very
+good agreement is achieved between both methods. The theoretical model allows
+for a detailed understanding of the physics underlying these kind of systems,
+thereby providing an outlook to potential applications associated with magnonic
+crystals-based devices.",1610.04176v1
+2016-11-23,"Electron interactions, spin-orbit coupling, intersite correlations in pyrochlore iridates","We perform combined density functional and dynamical mean-field calculations
+to study the pyrochlore iridates Lu$_2$Ir$_2$O$_7$, Y$_2$Ir$_2$O$_7$ and
+Eu$_2$Ir$_2$O$_7$. Both single-site and cluster dynamical mean-field
+calculations are performed and spin-orbit coupling is included. Paramagnetic
+metallic phases, antiferromagnetic metallic phases with tilted Weyl cones and
+antiferromagnetic insulating phases are found. The magnetic phases display
+all-in/all-out magnetic ordering, consistent with previous studies. Unusually
+for electronically three dimensional materials, the single-site dynamical
+mean-field approximation fails to reproduce qualitative material trends,
+predicting in particular that the paramagnetic phase properties of
+Y$_2$Ir$_2$O$_7$ and Eu$_2$Ir$_2$O$_7$ are almost identical, although in
+experiments the Y compound has a much higher resistance than the Eu compound.
+This qualitative failure is attributed to the importance of intersite magnetic
+correlations in the physics of these materials.",1611.07997v2
+2016-11-29,Dynamical Shiba states by precessing magnetic moments in an s-wave superconductor,"We study theoretically the dynamics of a Shiba state forming around
+precessing classical spin in an s-wave superconductor. Utilizing a rotating
+wave description for the precessing magnetic impurity, we find the resulting
+Shiba bound state quasi-energy and the spatial extension of the Shiba
+wavefunction. We show that such a precession pertains to dc charge and spin
+currents flowing through a normal STM tip tunnel coupled to the superconductor
+in the vicinity of the impurity. We calculate these currents and find that they
+strongly depend on the magnetic impurity precession frequency, precession
+angle, and on the position of the Shiba energy level in the superconducting
+gap. The resulting charge current is found to be proportional to the difference
+between the electron and hole wavefunctions of the Shiba state, being a direct
+measure for such an asymmetry. By dynamically driving the impurity one can
+infer the spin dependence of the Shiba states in the absence of a
+spin-polarized STM tip",1611.09722v1
+2016-12-04,Dynamic Magnetometer Calibration and Alignment to Inertial Sensors by Kalman Filtering,"Magnetometer and inertial sensors are widely used for orientation estimation.
+Magnetometer usage is often troublesome, as it is prone to be interfered by
+onboard or ambient magnetic disturbance. The onboard soft-iron material
+distorts not only the magnetic field, but the magnetometer sensor frame
+coordinate and the cross-sensor misalignment relative to inertial sensors. It
+is desirable to conveniently put magnetic and inertial sensors information in a
+common frame. Existing methods either split the problem into successive
+intrinsic and cross-sensor calibrations, or rely on stationary accelerometer
+measurements which is infeasible in dynamic conditions. This paper formulates
+the magnetometer calibration and alignment to inertial sensors as a state
+estimation problem, and collectively solves the magnetometer intrinsic and
+cross-sensor calibrations, as well as the gyroscope bias estimation. Sufficient
+conditions are derived for the problem to be globally observable, even when no
+accelerometer information is used at all. An extended Kalman filter is designed
+to implement the state estimation and comprehensive test data results show the
+superior performance of the proposed approach. It is immune to acceleration
+disturbance and applicable potentially in any dynamic conditions.",1612.01044v1
+2016-12-18,Non-equilibrium critical dynamics of the two-dimensional Ashkin-Teller model at the Baxter line,"We investigate the short-time universal behavior of the two dimensional
+Ashkin-Teller model at the Baxter line by performing time-dependent Monte Carlo
+Simulations. First, as preparatory results, we obtain the critical parameters
+by searching the optimal power law decay of the magnetization. Thus, the
+dynamic critical exponents $\theta _{m}$ and $\theta _{p}$, related to the
+magnetic and electric order parameters, as well as the persistence exponent
+$\theta _{g}$, are estimated using heat-bath Monte Carlo simulations. In
+addition, we estimate the dynamic exponent $z$ and the static critical
+exponents $\beta $ and $\nu $ for both order parameters. We propose a refined
+method to estimate the static exponents that considers two different averages:
+one that combines an internal average using several seeds with another which is
+taken over geographic variations in the power laws. Moreover, we also performed
+the bootstrapping method for a complementary analysis. Our results show that
+the ratio $\beta /\nu $ exhibits universal behavior along the critical line
+corroborating the conjecture for both magnetization and polarization.",1612.05842v1
+2017-02-13,Spin Pumping and Inverse Spin Hall Voltages from Dynamical Antiferromagnets,"Dynamical antiferromagnets pump spins efficiently into adjacent conductors as
+ferromagnets. The high antiferromagnetic resonance frequencies represent a
+challenge for experimental detection, but magnetic fields can reduce these
+resonance frequencies. We compute the inverse spin Hall voltages resulting from
+dynamical spin excitations as a function of a magnetic field along the easy
+axis and the polarization of the driving AC magnetic field perpendicular to the
+easy axis. We consider the insulating antiferromagnets MnF$_2$, FeF$_2$, and
+NiO. Near the spin-flop transition, there is a significant enhancement of the
+DC spin pumping and inverse spin Hall voltage for the uniaxial antiferromagnets
+MnF$_2$ and FeF$_2$. In the biaxial NiO, the voltages are much weaker, and
+there is no spin-flop enhancement of the DC component.",1702.03779v1
+2017-03-16,Generation of droplet arrays with rational number spacing patterns driven by a periodic energy landscape,"The generation of droplets at low Reynolds numbers is driven by non-linear
+dynamics that give rise to complex patterns concerning both the
+droplet-to-droplet spacing and the individual droplet sizes. Here we
+demonstrate an experimental system in which a time-varying energy landscape
+provides a periodic magnetic force that generates an array of droplets from an
+immiscible mixture of ferrofluid and silicone oil. The resulting droplet
+patterns are periodic, owing to the nature of the magnetic force, yet the
+droplet spacing and size can vary greatly by tuning a single bias pressure
+applied on the ferrofluid phase; for a given cycle period of the magnetic
+force, droplets can be generated either at integer multiples (1, 2, etc.), or
+at rational fractions (3/2, 5/3, 5/2, etc.) of this period with mono- or
+multidisperse droplet sizes. We develop a discrete-time dynamical systems model
+not only to reproduce the phenotypes of the observed patterns but also provide
+a framework for understanding systems driven by such periodic energy
+landscapes.",1703.05489v2
+2017-04-13,Fluctuations and Noise Signatures of Driven Magnetic Skyrmions,"Magnetic skyrmions are particle-like objects with topologically-protected
+stability which can be set into motion with an applied current. Using a
+particle-based model we simulate current-driven magnetic skyrmions interacting
+with random quenched disorder and examine the skyrmion velocity fluctuations
+parallel and perpendicular to the direction of motion as a function of
+increasing drive. We show that the Magnus force contribution to skyrmion
+dynamics combined with the random pinning produces an isotropic effective
+shaking temperature. As a result, the skyrmions form a moving crystal at large
+drives instead of the moving smectic state observed in systems with a
+negligible Magnus force where the effective shaking temperature is anisotropic.
+We demonstrate that spectral analysis of the velocity noise fluctuations can be
+used to identify dynamical phase transitions and to extract information about
+the different dynamic phases, and show how the velocity noise fluctuations are
+correlated with changes in the skyrmion Hall angle, transport features, and
+skyrmion lattice structure.",1704.04272v1
+2017-04-25,Chirality-mediated bistability and strong frequency downshifting of the gyrotropic resonance of a dynamically de-stiffened magnetic vortex,"We demonstrate an enhanced, bidirectional, in-plane magnetic field tuning of
+the gyrotropic resonance frequency of a magnetic vortex within a disk by
+introducing a flat edge. When the core is in its vicinity, the flat edge
+locally reduces the core's directional dynamic stiffness for movement parallel
+to the edge. This strongly reduces the net dynamic core stiffness, leading to
+the gyrotropic frequency being significantly less than when the core is
+centered (or located near the round edge). This leads to the measurable range
+of gyrotropic frequencies being more than doubled and also results in a clear
+chirality-mediated bistability of the gyrotropic resonance frequency due to
+what is effectively a chirality-dependence of the core's confining potential.",1704.07748v1
+2017-05-09,Nonlinear parametric excitation effect induces stability transitions in swimming direction of flexible superparamagnetic microswimmers,"Microscopic artificial swimmers have recently become highly attractive due to
+their promising potential for biomedical applications. The pioneering work of
+Dreyfus et al (2005) has demonstrated the motion of a microswimmer with an
+undulating chain of superparamagnetic beads, which is actuated by an
+oscillating external magnetic field. Interestingly, it has also been
+theoretically predicted that the swimming direction of this swimmer will
+undergo a $90^\circ$-transition when the magnetic field's oscillations
+amplitude is increased above a critical value of $\sqrt{2}$. In this work, we
+further investigate this transition both theoretically and experimentally by
+using numerical simulations and presenting a novel flexible microswimmer with a
+superparamagnetic head. We realize the $90^\circ$-transition in swimming
+direction, prove that this effect depends on both frequency and amplitude of
+the oscillating magnetic field, and demonstrate the existence of an optimal
+amplitude, under which, maximal swimming speed can be achieved. By
+asymptotically analyzing the dynamic motion of microswimmer with a minimal
+two-link model, we reveal that the stability transitions representing the
+changes in the swimming direction are induced by the effect of nonlinear
+parametric excitation.",1705.03486v1
+2017-05-16,Bloch line dynamics within moving domain walls in 3D ferromagnets,"We study field-driven magnetic domain wall dynamics in garnet strips by
+large-scale three-dimensional micromagnetic simulations. The domain wall
+propagation velocity as a function of the applied field exhibits a low-field
+linear part terminated by a sudden velocity drop at a threshold field
+magnitude, related to the onset of excitations of internal degrees of freedom
+of the domain wall magnetization. By considering a wide range of strip
+thicknesses from 30 nm to 1.89 $\mu$m, we find a non-monotonic thickness
+dependence of the threshold field for the onset of this instability, proceeding
+via nucleation and propagation of Bloch lines within the domain wall. We
+identify a critical strip thickness above which the velocity drop is due to
+nucleation of horizontal Bloch lines, while for thinner strips and depending on
+the boundary conditions employed, either generation of vertical Bloch lines, or
+close-to-uniform precession of the domain wall internal magnetization takes
+place. For strips of intermediate thicknesses, the vertical Bloch lines assume
+a deformed structure due to demagnetizing fields at the strip surfaces,
+breaking the symmetry between the top and bottom faces of the strip, and
+resulting in circulating Bloch line dynamics along the perimeter of the domain
+wall.",1705.05642v1
+2017-05-23,Coherent many-body spin dynamics in a long-range interacting Ising chain,"Coherent many-body quantum dynamics lies at the heart of quantum simulation
+and quantum computation. Both require coherent evolution in the exponentially
+large Hilbert space of an interacting many-body system. To date, trapped ions
+have defined the state of the art in terms of achievable coherence times in
+interacting spin chains. Here, we establish an alternative platform by
+reporting on the observation of coherent, fully interaction-driven quantum
+revivals of the magnetization in Rydberg-dressed Ising spin chains of atoms
+trapped in an optical lattice. We identify partial many-body revivals at up to
+about ten times the characteristic time scale set by the interactions. At the
+same time, single-site-resolved correlation measurements link the magnetization
+dynamics with inter-spin correlations appearing at different distances during
+the evolution. These results mark an enabling step towards the implementation
+of Rydberg atom based quantum annealers, quantum simulations of higher
+dimensional complex magnetic Hamiltonians, and itinerant long-range interacting
+quantum matter.",1705.08372v1
+2017-12-12,Dynamical Negative Differential Resistance in Antiferromagnetically Coupled Few-Atom Spin-Chains,"We present the appearance of negative differential resistance (NDR) in
+spin-dependent electron transport through a few-atom spin-chain. A chain of
+three antiferromagnetically coupled Fe atoms(Fe trimer) was positioned on a
+Cu2N/Cu(100) surface and contacted with the spin-polarized tip of a scanning
+tunneling microscope, thus coupling the Fe trimer to one non-magnetic and one
+magnetic lead. Pronounced NDR appears at the low bias of 7 mV where inelastic
+electron tunneling dynamically locks the atomic spin in a long-lived excited
+state. This causes a rapid increase of the magnetoresistance between
+spin-polarized tip and Fe trimer and quenches elastic tunneling. By varying the
+coupling strength between tip and Fe trimer we find that in this transport
+regime the dynamic locking of the Fe trimer competes with magnetic exchange
+interaction, which statically forces the Fe trimer into the
+high-magnetoresistance state and removes the NDR.",1712.04213v1
+2017-12-20,Nonlinear mean-field dynamo and prediction of solar activity,"We apply a nonlinear mean-field dynamo model which includes a budget equation
+for the dynamics of Wolf numbers to predict solar activity. This dynamo model
+takes into account the algebraic and dynamic nonlinearities of the alpha
+effect, where the equation for the dynamic nonlinearity is derived from the
+conservation law for the magnetic helicity. The budget equation for the
+evolution of the Wolf number is based on a formation mechanism of sunspots
+related to the negative effective magnetic pressure instability. This
+instability redistributes the magnetic flux produced by the mean-field dynamo.
+To predict solar activity on the time scale of one month we use a method based
+on a combination of the numerical solution of the nonlinear mean-field dynamo
+equations and the artificial neural network. A comparison of the results of the
+prediction of the solar activity with the observed Wolf numbers demonstrates a
+good agreement between the forecast and observations.",1712.07501v4
+2018-01-18,Magpy: A C++ accelerated Python package for simulating magnetic nanoparticle stochastic dynamics,"Magpy is a C++ accelerated Python package for modelling and simulating the
+magnetic dynamics of nano-sized particles. Nanoparticles are modelled as a
+system of three-dimensional macrospins and simulated with a set of coupled
+stochastic differential equations (the Landau-Lifshitz-Gilbert equation), which
+are solved numerically using explicit or implicit methods. The results of the
+simulations may be used to compute equilibrium states, the dynamic response to
+external magnetic fields, and heat dissipation. Magpy is built on a C++
+library, which is optimised for serial execution, and exposed through a Python
+interface utilising an embarrassingly parallel strategy. Magpy is free,
+open-source, and available on github under the 3-Clause BSD License.",1801.06073v2
+2018-02-02,Stochastic model for quantum spin dynamics in magnetic nanostructures,"We develop a numerical model that reproduces the thermal equilibrium and the
+spin transfer mechanisms in magnetic nanomaterials. We analyze the coherent
+two-particle spin exchange interaction and the electron-electron collisions.
+Our study is based on a quantum atomistic approach and the particle dynamics is
+performed by using a Monte Carlo technique. The coherent quantum evolution of
+the atoms is interrupted by instantaneous collisions with itinerant electrons.
+The collision processes are associated to the quantum collapse of the local
+atomic wave function. We show that particle-particle interactions beyond the
+molecular field approximation can be included in this framework. Our model is
+able to reproduce the thermal equilibrium and strongly out-of-equilibrium
+phenomena such as the ultrafast dynamics of the magnetization in nanomatrials.",1802.00663v1
+2018-02-12,Gyrotropic resonance of individual Néel skyrmions in Ir/Fe/Co/Pt multilayers,"Magnetic skyrmions are nanoscale spin structures recently discovered at room
+temperature (RT) in multilayer films. Employing their novel topological
+properties towards exciting technological prospects requires a mechanistic
+understanding of the excitation and relaxation mechanisms governing their
+stability and dynamics. Here we report on the magnetization dynamics of RT
+N\'eel skyrmions in Ir/Fe/Co/Pt multilayer films. We observe a ubiquitous
+excitation mode in the microwave absorption spectrum, arising from the
+gyrotropic resonance of topological skyrmions, and robust over a wide range of
+temperatures and sample compositions. A combination of simulations and
+analytical calculations establish that the spectrum is shaped by the interplay
+of interlayer and interfacial magnetic interactions unique to multilayers,
+yielding skyrmion resonances strongly renormalized to lower frequencies. Our
+work provides fundamental spectroscopic insights on the spatiotemporal dynamics
+of topological spin structures, and crucial directions towards their
+functionalization in nanoscale devices.",1802.03979v1
+2018-03-05,Attenuation of the NMR signal due to hydrodynamic Brownian motion,"Nuclear magnetic resonance (NMR) is a widely used nondestructive method to
+study random motion of spin-bearing particles in different systems. In the
+long-time limit the theoretical description of the NMR experiments is well
+developed and allows proper interpretation of measurements of normal and
+anomalous diffusion. The traditional description becomes, however, insufficient
+for the shorter-time dynamics of the particles. In the present paper, the
+all-time attenuation function of the NMR signal in a magnetic-field gradient
+due to the Brownian motion (BM) of particles in incompressible liquids is
+calculated by using the method of accumulation of phases by a precessing
+magnetic moment, without reference to a concrete model of the stochastic
+dynamics. The obtained expressions are then used to evaluate the attenuation
+within the hydrodynamic theory of the BM. It is shown that the well-known time
+behavior of the formulas corresponding to the Einstein theory of diffusion in
+the case of steady gradient and Hahn's echo experiments is reached at times
+much larger than the characteristic time of the loss of memory in the particle
+dynamics. At shorter times the attenuation function significantly differs from
+the classical formulas used to interpret these experiments.",1803.01554v1
+2018-04-06,Assessing the Capabilities of Dynamic Coronal Seismology of Alfvénic Waves through Forward Modeling,"Coronal seismology is a diagnostic tool used in solar physics for measuring
+parameters that are otherwise hard to measure; of these parameters, magnetic
+field values are arguably the most important. The parameters are inferred by
+combining observations of waves with magnetohydrodynamic (MHD) wave theory. To
+date, coronal seismology has successfully been applied to various
+single-oscillation events. Such events are relatively rare, resulting in rare
+occasions to use diagnostics. Ubiquitous waves in the solar atmosphere might,
+however, allow for the possibility of dynamic coronal seismology, which
+involves the continuous inversions of coronal parameters and would constitute a
+huge leap forward in many areas of solar physics. In this paper, we investigate
+the robustness and accuracy of magnetic field diagnostics applied to
+forward-modeled 3D MHD simulations of propagating Alfv\'enic waves. We find
+that the seismologically measured magnetic field values are reassuringly close
+to the input value (within 20%) for a range of setups studied, providing
+encouragement and confidence for the further development of dynamic coronal
+seismology.",1804.02175v2
+2018-06-29,Intra-cell dynamics and cyclotron motion without magnetic field,"Intra-cell motion endows rich non-trivial phenomena to a wide variety of
+quantum materials. The most prominent example is a transverse current in the
+absence of a magnetic field (i.e. the anomalous Hall effect). Here we show
+that, in addition to a dc Hall effect, anomalous Hall materials possess
+circulating currents and cyclotron motion without magnetic field. These are
+generated from the intricate wavefunction dynamics within the unit cell, and
+correspond to interband transitions (coherences) in much the same way that
+cyclotron resonances arise from inter-Landau level transitions in
+magneto-optics. Curiously, anomalous cyclotron motion exhibits an intrinsic
+decay in time (even in pristine materials) displaying a characteristic power
+law decay. This reveals an intrinsic dephasing similar to that of inhomogeneous
+broadening of spinors. Circulating currents can manifest as the emission of
+circularly polarized light pulses in response to incident linearly polarized
+(pulsed) electric field, and provide a direct means of interrogating the
+intra-unit-cell dynamics of quantum materials.",1807.00014v1
+2018-07-29,Magnetic Polymer Models for Epigenomic Organisation and Phase Separation,"The genetic instructions stored in the genome require an additional layer of
+information to robustly determine cell fate. This additional regulation is
+provided by the interplay between chromosome-patterning biochemical
+(""epigenetic"") marks and three-dimensional genome folding. Yet, the physical
+principles underlying the dynamical coupling between three-dimensional genomic
+organisation and one-dimensional epigenetic patterns remain elusive. To shed
+light on this issue, here we study by mean field theory and Brownian dynamics
+simulations a magnetic polymer model for chromosomes, where each monomer
+carries a dynamic epigenetic mark. At the single chromosome level, we show that
+a first order transition describes the unlimited spreading of epigenetic marks,
+a phenomenon that is often observed in vivo. At the level of the whole nucleus,
+experiments suggest chromosomes form micro-phase separated compartments with
+distinct epigenetic marks. We here discover that for a melt of magnetic
+polymers such a morphology is thermodynamically unstable, but can be stabilised
+by a non- equilibrium and ATP-mediated epigenetic switch between different
+monomer states.",1807.11101v1
+2018-09-27,Non-equilibrium Quantum Langevin dynamics of orbital diamagnetic moment,"We investigate the time dependent orbital diamagnetic moment of a charged
+particle in a magnetic field in a viscous medium via the Quantum Langevin
+Equation. We study how the interplay between the cyclotron frequency and the
+viscous damping rate governs the dynamics of the orbital magnetic moment in the
+high temperature classical domain and the low temperature quantum domain for an
+Ohmic bath. These predictions can be tested via state of the art cold atom
+experiments with hybrid traps for ions and neutral atoms. We also study the
+effect of a confining potential on the dynamics of the magnetic moment. We
+obtain the expected Bohr Van Leeuwen limit in the high temperature, asymptotic
+time ($ \gamma t\longrightarrow \infty$, where $ \gamma $ is the viscous
+damping coefficient) limit.",1809.10370v1
+2018-10-01,Determination of spin Hall angle in heavy metal/CoFeB-based heterostructures with interfacial spin-orbit fields,"Magnetization dynamics in W/CoFeB, CoFeB/Pt and W/CoFeB/Pt multilayers was
+investigated using spin-orbit-torque ferromagnetic resonance (SOT-FMR)
+technique. An analytical model based on magnetization dynamics due to SOT was
+used to fit heavy metal (HM) thickness dependence of symmetric and
+antisymmetric components of the SOT-FMR signal. The analysis resulted in a
+determination of the properties of HM layers, such as spin Hall angle and spin
+diffusion length. The spin Hall angle of -0.36 and 0.09 has been found in the
+W/CoFeB and CoFeB/Pt bilayers, respectively, which add up in the case of
+W/CoFeB/Pt trilayer. More importantly, we have determined effective interfacial
+spin-orbit fields at both W/CoFeB and CoFeB/Pt interfaces, which are shown to
+cancel Oersted field for particular thicknesses of the heavy metal layers,
+leading to pure spin-current-induced dynamics and indicating the possibility
+for a more efficient magnetization switching.",1810.00641v1
+2018-11-05,Nonadiabatic dynamics and geometric phase of an ultrafast rotating electron spin,"The spin in a rotating frame has attracted a lot of attentions recently, as
+it deeply relates to both fundamental physics such as pseudo-magnetic field and
+geometric phase, and applications such as gyroscopic sensors. However, previous
+studies only focused on adiabatic limit, where the rotating frequency is much
+smaller than the spin frequency. Here we propose to use a levitated
+nano-diamond with a built-in nitrogen-vacancy (NV) center to study the dynamics
+and the geometric phase of a rotating electron spin without adiabatic
+approximation. We find that the transition between the spin levels appears when
+the rotating frequency is comparable to the spin frequency at zero magnetic
+field. Then we use Floquet theory to numerically solve the spin energy
+spectrum, study the spin dynamics and calculate the geometric phase under a
+finite magnetic field, where the rotating frequency to fulfill the resonant
+transition condition could be greatly reduced.",1811.01641v1
+2018-12-05,Single spin sensing of domain wall structure and dynamics in a thin film skyrmion host,"Skyrmions are nanoscale magnetic structures with features promising for
+future low-power memory or logic devices. In this work, we demonstrate novel
+scanning techniques based on nitrogen vacancy center magnetometry that
+simultaneously probe both the magnetic dynamics and structure of room
+temperature skyrmion bubbles in a thin film system Ta/CoFeB/MgO. We confirm the
+handedness of the Dzyaloshinskii-Moriya interaction in this material and
+extract the helicity angle of the skyrmion bubbles. Our measurements also show
+that the skyrmion bubbles in this material change size in discrete steps,
+dependent on the local pinning environment, with their average size determined
+dynamically as their domain walls hop between pinning sites. In addition, an
+increase in magnetic field noise is observed near all skyrmion bubble domain
+walls. These measurements highlight the importance of interactions between
+internal degrees of freedom of skyrmion bubble domain walls and pinning sites
+in thin film systems. Our observations have relevance for future devices based
+on skyrmion bubbles where pinning interactions will determine important aspects
+of current-driven motion.",1812.01764v1
+2019-02-01,Collective magnetization dynamics in nano-arrays of thin FePd discs,"We report on the magnetization dynamics of a square array of mesoscopic
+discs, fabricated from an iron palladium alloy film. The dynamics properties
+were explored using ferromagnetic resonance measurements and micromagnetic
+simulations. The obtained spectra exhibit features resulting from the
+interactions between the discs, with a clear dependence on both temperature and
+the direction of the externally applied field. We demonstrate a qualitative
+agreement between the measured and calculated spectra. Furthermore, we
+calculated the mode profiles of the standing spin waves excited during a
+time-dependent magnetic field excitations. The resulting maps confirm that the
+features appearing in the ferromagnetic resonance absorption spectra originate
+from the temperature and directional dependent inter-disc interactions.",1902.00403v1
+2019-04-02,Scale-invariant spin dynamics and the quantum limits of field sensing,"We describe quantum limits to field sensing that relate noise, geometry and
+measurement duration to fundamental constants, with no reference to particle
+number. We cast the Tesche and Clarke (TC) bound on dc-SQUID sensitivity as
+such a limit, and find analogous limits for volumetric spin-precession
+magnetometers. We describe how randomly-arrayed spins, coupled to an external
+magnetic field of interest and to each other by the magnetic dipole-dipole
+interaction, execute a spin dynamics that depolarizes the spin ensemble even in
+the absence of coupling to an external reservoir. We show the resulting spin
+dynamics are scale invariant, with a depolarization rate proportional to spin
+number density and thus a number-independent quantum limit on the energy
+resolution per bandwidth $E_R$. Numerically, we find $E_R \ge \alpha \hbar$,
+$\alpha \sim 1$, in agreement with the TC limit, for paradigmatic spin-based
+measurements of static and oscillating magnetic fields.",1904.01528v2
+2019-04-17,Controlling Dipolar Exchange Interactions in a Dense 3D Array of Large Spin Fermions,"Dipolar interactions are ubiquitous in nature and rule the behavior of a
+broad range of systems spanning from energy transfer in biological systems to
+quantum magnetism. Here, we study magnetization-conserving dipolar induced
+spin-exchange dynamics in dense arrays of fermionic erbium atoms confined in a
+deep three-dimensional lattice. Harnessing the special atomic properties of
+erbium, we demonstrate control over the spin dynamics by tuning the dipole
+orientation and changing the initial spin state within the large 20 spin
+hyperfine manifold. Furthermore, we demonstrate the capability to quickly turn
+on and off the dipolar exchange dynamics via optical control. The experimental
+observations are in excellent quantitative agreement with numerical
+calculations based on discrete phase-space methods, which capture entanglement
+and beyond-mean field effects. Our experiment sets the stage for future
+explorations of rich magnetic behaviors in long-range interacting dipoles,
+including exotic phases of matter and applications for quantum information
+processing.",1904.08262v1
+2019-05-20,Spin dynamics of hot excitons in diluted magnetic semiconductors with spin-orbit interaction,"We explore the impact of a Rashba-type spin-orbit interaction in the
+conduction band on the spin dynamics of hot excitons in diluted magnetic
+semiconductor quantum wells. In materials with strong spin-orbit coupling, we
+identify parameter regimes where spin-orbit effects greatly accelerate the spin
+decay and even change the dynamics qualitatively in the form of damped
+oscillations. Furthermore, we show that the application of a small external
+magnetic field can be used to either mitigate the influence of spin-orbit
+coupling or entirely remove its effects for fields above a material-dependent
+threshold.",1905.07947v3
+2019-05-27,Phase Diagram and Quench Dynamics in a Spinful Interacting Kitaev Chain,"We consider an exact solvable interacting spinful Kitaev chain which is a
+generalization of the Mattis-Nam model. A nearest-neighbor dimerized
+interaction favoring the production of disjoint molecules drives the quantum
+phase into an insulating one. The phases are characterized statically and
+dynamically in terms of magnetization and spin-singlet correlations by using
+the exact solution. The model is shown to be exactly solvable also in the
+presence of boundary interactions which are originated from a spin-singlet
+superconducting pairing and a magnetic field. We exploit the exact solution to
+investigate the out-of-equilibrium dynamics as due to a quench at the boundary.
+The propagation of the disturbance in nearest-neighbor magnetic and
+spin-singlet pairing displays a ballistic behavior for long times with
+different velocities.",1905.11090v3
+2019-06-24,Weak focusing low emittance storage ring with large 6d dynamic aperture based on canted cosine theta magnet technology,"We developed a low emittance electron storage ring with large 6D dynamic
+aperture. Contrary to the traditional approach using strong focusing magnetic
+cells with optimized (and large) horizontal phase advance, which yields huge
+natural chromaticity, we employed a relatively weak focusing lattice with low
+chromaticity per cell and, consequently, wide on- and off-momentum dynamic
+aperture. Inevitable for weak focusing emittance growth, we compensated by
+slicing the lattice into many short, with small bending angle, elementary
+periodic cells. To reduce the size, we superimposed focusing gradient and
+chromaticity compensating sextupole components over the dipole field utilizing
+superconducting magnets based on the Canted Cosine Theta (CCT) winding
+technology. The result is a model lattice with 50 pm horizontal emittance at 3
+GeV beam energy, with 400-500 m circumference and large 6D aperture.",1906.09692v1
+2019-06-27,Magnetic Bloch Oscillations and domain wall dynamics in a near-Ising ferromagnetic chain,"When charged particles in periodic lattices are subjected to a constant
+electric field, they respond by oscillating. Here we demonstrate that the
+magnetic analogue of these Bloch oscillations are realised in a one-dimensional
+ferromagnetic easy axis chain. In this case, the ""particle"" undergoing
+oscillatory motion in the presence of a magnetic field is a domain wall.
+Inelastic neutron scattering reveals three distinct components of the low
+energy spin-dynamics including a signature Bloch oscillation mode. Using
+parameter-free theoretical calculations, we are able to account for all
+features in the excitation spectrum, thus providing detailed insights into the
+complex dynamics in spin-anisotropic chains.",1906.11554v1
+2019-07-01,The importance of thermal gradients on the vortex dynamics and magnetic behavior of mesoscopic superconducting samples,"Usually, the measurements of electronic and magnetic properties of
+superconducting samples are carried out under a constant temperature bath. On
+the other hand, thermal gradients induce local variation of the superconducting
+order parameter, and the vortex dynamics can present interesting behaviors. In
+this work, we solved the time-dependent Ginzburg-Landau equations simulating
+samples under two different thermal gradients, and considering two values of
+the Ginzburg-Landau parameter, \k{appa}. We find out that both parameters,
+i.e., \k{appa} and thermal gradients, play an important role on the vortex
+dynamics and on the magnetization behavior of the samples.",1907.01088v1
+2019-07-25,Order out of a Coulomb phase and Higgs transtion: frustrated transverse interactions of Nd2Zr2O7,"The pyrochlore material Nd$_2$Zr$_2$O$_7$ with an ""all-in-all-out"" (AIAO)
+magnetic order shows novel quantum moment fragmentation with gapped flat
+dynamical spin ice modes. The parameterized spin Hamiltonian with a dominant
+frustrated ferromagnetic transverse term reveals a proximity to a U(1) spin
+liquid. Here we study magnetic excitations of Nd$_2$Zr$_2$O$_7$ above the
+ordering temperature ($T_\text{N}$) using high-energy-resolution inelastic
+neutron scattering. We find strong spin ice correlations at zero energy with
+the disappearance of gapped magnon excitations of the AIAO order. It seems that
+the gap to the dynamical spin ice closes above $T_\text{N}$ and the system
+enters a quantum spin ice state competing with and suppressing the AIAO order.
+Classical Monte Carlo, molecular dynamics and quantum boson calculations
+support the existence of a Coulombic phase above $T_\text{N}$. Our findings
+relate the magnetic ordering of Nd$_2$Zr$_2$O$_7$ with the Higgs mechanism and
+provide explanations for several previously reported experimental features.",1907.11056v1
+2019-09-04,Vortex phases and glassy dynamics in the highly anisotropic superconductor HgBa$_2$CuO$_{4+δ}$,"We present an extensive study of vortex dynamics in a high-quality single
+crystal of HgBa$_2$CuO$_{4+\delta}$ (Hg1201), a highly anisotropic
+superconductor that is a model system for studying the effects of anisotropy.
+From magnetization $M$ measurements over a wide range of temperatures $T$ and
+fields $H$, we construct a detailed vortex phase diagram. We find that the
+temperature-dependent vortex penetration field $H_p(T)$, second magnetization
+peak $H_{smp}(T)$, and irreversibility field $H_{irr}(T)$ all decay
+exponentially at low temperatures and exhibit an abrupt change in behavior at
+high temperatures $T/T_c \gtrsim 0.5$. By measuring the rates of thermally
+activated vortex motion (creep) $S(T,H)=|d \ln M(T,H) / d \ln t|$, we reveal
+glassy behavior involving collective creep of bundles of 2D pancake vortices as
+well as temperature- and time-tuned crossovers from elastic (collective)
+dynamics to plastic flow. Based on the creep results, we show that the second
+magnetization peak coincides with the elastic-to-plastic crossover at low $T$,
+yet the mechanism changes at higher temperatures.",1909.01618v1
+2019-10-25,Nutation Wave as a Platform for Ultrafast Spin Dynamics in Ferromagnets,"At short time scales the inertia term becomes relevant for the magnetization
+dynamics of ferromagnets and leads to nutation for the magnetization vector.
+For the case of spatially extended magnetic systems, for instance Heisenberg
+spin chains with isotropic spin-exchange interaction, this leads to the
+appearance of a novel collective excitation, the ""nutation wave"", whose
+properties are elucidated by analytic arguments and numerical studies. The
+one--particle excitations can be identified as relativistic massive particles.
+These particles, the ""nutatons"", acquire their mass via the Brout-Englert-Higgs
+mechanism, through the interaction of the wave with an emergent topological
+gauge field. This spin excitation would appear as a peak in the spectrum of the
+scattering structure factor in inelastic neutron scattering experiments. The
+high frequency and speed of the nutation wave can open new paths for realizing
+ultrafast spin dynamics.",1910.11897v3
+2019-11-05,Engineering the dynamics of topological spin textures by anisotropic spin-orbit torques,"Integrating topologically stabilized magnetic textures such as skyrmions as
+nanoscale information carriers into future technologies requires the reliable
+control by electric currents. Here, we uncover that the relevant skyrmion Hall
+effect, which describes the deflection of moving skyrmions from the current
+flow direction, acquires important corrections owing to anisotropic spin-orbit
+torques that alter the dynamics of topological spin structures. Thereby, we
+propose a viable means for manipulating the current-induced motion of skyrmions
+and antiskyrmions. Based on these insights, we demonstrate by first-principles
+calculations and symmetry arguments that the motion of spin textures can be
+tailored by materials design in magnetic multilayers of Ir/Co/Pt and Au/Co/Pt.
+Our work advances the understanding of the current-induced dynamics of these
+magnetic textures, which underlies a plethora of memory and logic applications.",1911.01987v1
+2019-11-30,Microwave dynamics of pure and doped anisotropic S=1 chain antiferromagnet NiCl2-4SC(NH2)2,"We studied electron spin resonance in a quantum magnet NiCl2-4SC(NH2)2,
+demonstrating a field-induced quantum phase transition from a
+quantum-disordered phase to an antiferromagnet. We observe two branches of the
+antiferromagnetic resonance of the ordered phase, one of them has a gap and the
+other is a Goldstone mode with zero frequency at a magnetic field along the
+four-fold axis. This zero frequency mode acquires a gap at a small tilting of
+the magnetic field with respect to this direction. The upper gap was found to
+be reduced in the doped compound Ni(Cl(1-x)Br(x))2-4SC(NH2)2 with $x=0.21$.
+This reduction is unexpected because of the previously reported rise of the
+main exchange constant in a doped compound. Further, a nonresonant diamagnetic
+susceptibility $\chi^{\prime}$ was found for the ordered phase in a wide
+frequency range above the quasi-Goldstone mode. This dynamic diamagnetism is as
+large as the dynamic susceptibility of the paramagnetic resonance. We speculate
+that it originates from a two-magnon absorption band of low-frequency
+dispersive magnon branch.",1912.00172v1
+2020-03-10,Global Evolution of Solar Magnetic Fields and Prediction of Activity Cycles,"Prediction of solar activity cycles is challenging because physical processes
+inside the Sun involve a broad range of multiscale dynamics that no model can
+reproduce and because the available observations are highly limited and cover
+mostly surface layers. Helioseismology makes it possible to probe solar
+dynamics in the convective zone, but variations in differential rotation and
+meridional circulation are currently available for only two solar activity
+cycles. It has been demonstrated that sunspot observations, which cover over
+400 years, can be used to calibrate the Parker-Kleeorin-Ruzmaikin dynamo model,
+and that the Ensemble Kalman Filter (EnKF) method can be used to link the
+modeled magnetic fields to sunspot observations and make reliable predictions
+of a following activity cycle. However, for more accurate predictions, it is
+necessary to use actual observations of the solar magnetic fields, which are
+available only for the last four solar cycles. In this paper I briefly discuss
+the influence of the limited number of available observations on the accuracy
+of EnKF estimates of solar cycle parameters, the criteria to evaluate the
+predictions, and application of synoptic magnetograms to the prediction of
+solar activity.",2003.04563v1
+2020-07-15,Effect of pseudospin polarization on wave packet dynamics in graphene antidot lattices (GALs) in the presence of a normal magnetic field,"We have investigated the role of pseudospin polarization in electron wave
+packet dynamics in pristine graphene and in a graphene antidot lattice subject
+to an external magnetic field. Employing a Green's function formalism, we show
+that the electron dynamics can be controlled by tuning pseudospin polarization.
+We find that in Landau quantized pristine graphene both the propagation of an
+electron wave packet and Zitterbewegung oscillations strongly depend on
+pseudospin polarization. The electron wave packet is found to propagate in the
+direction of initial pseudospin polarization. We also show that, in this
+system, the propagation of an electron can be enhanced in any desired direction
+by carving a one dimensional antidot lattice in that direction. The study
+suggests that a graphene antidot lattice can serve as a channel for electron
+transport with the possibility of tunability by means of pseudospin
+polarization, antidot potential and applied normal magnetic field strength.",2007.07836v2
+2020-08-28,Optical Magnetic Lens: towards actively tunable terahertz optics,"As we read this text, our eyes dynamically adjust the focal length to keep
+the line image in focus on the retina. Similarly, in many optics applications
+the focal length must be dynamically tunable. In the quest for compactness and
+tunability, flat lenses based on metasurfaces were introduced. However, their
+dynamic tunability is still limited because their functionality mostly relies
+upon fixed geometry. In contrast, we put forward an original concept of a
+tunable Optical Magnetic Lens (OML) that focuses photon beams using a
+subwavelength-thin layer of a magneto-optical material in a non-uniform
+magnetic field. We applied the OML concept to a wide range of materials and
+found out that the effect of OML is present in a broad frequency range from
+microwaves to visible light. For terahertz light, OML can allow 50% relative
+tunability of the focal length on the picosecond time scale, which is of
+practical interest for ultrafast shaping of electron beams in microscopy. The
+OML based on magneto-optical natural bulk and 2D materials may find broad use
+in technologies such as 3D optical microscopy and acceleration of charged
+particle beams by THz beams.",2008.12640v1
+2020-10-11,Beyond the gyrotropic motion: dynamic C-state in vortex spin torque oscillators,"In the present study, we investigate a dynamical mode beyond the gyrotropic
+(G) motion of a magnetic vortex core in a confined magnetic disk of a
+nano-pillar spin torque nano oscillator. It is characterized by the in-plane
+circular precession associated to a C-shaped magnetization distribution. We
+show a transition between G and C-state mode which is found to be purely
+stochastic in a current-controllable range. Supporting our experimental
+findings with micromagnetic simulations, we believe that the results provide
+novel opportunities for the dynamic and stochastic control of STOs, which could
+be interesting to be implemented for example in neuromorphic networks.",2010.06437v1
+2021-01-17,Dynamics of self-accelerating electron beams in a homogeneous magnetic field,"We examine the dynamics of electron beams that, in free space, are
+self-accelerating, in the presence of an additional magnetic field. We focus
+our attention in the case of Airy beams that follow parabolic trajectories and
+in generalized classes of beams associated with power-law trajectories. We
+study the interplay between beam self-acceleration and the circular motion
+caused by the magnetic field. In the case of Airy beams, using an integral
+representation, we find closed-form solutions for the electron wavefunction. We
+also derive asymptotic formulas for the beam trajectories both for Airy beams
+and for self-accelerating power-law beams. A ray optics description is rather
+useful for the interpretation of the beam dynamics. Our results are in
+excellent comparison with direct numerical simulations.",2101.06754v1
+2021-02-28,Motion of classical charged particles with magnetic moment in external plane-wave electromagnetic fields,"We study the motion of a charged particle with magnetic moment in external
+electromagnetic fields utilizing covariant unification of Gilbertian and
+Amperian descriptions of particle magnetic dipole moment. Considering the case
+of a current loop, our approach is verified by comparing classical dynamics
+with the classical limit of relativistic quantum dynamics. We obtain motion of
+a charged particle in the presence of an external linearly polarized EM (laser)
+plane wave field incorporating the effect of spin dynamics. For specific
+laser-particle initial configurations, we determine that the Stern-Gerlach
+force can have a cumulative effect on the trajectory of charged particles.",2103.02594v2
+2021-03-27,Zeeman term for the Néel vector in a two sublattice antiferromagnet using Dzyaloshinsky-Moriya interaction and magnetic field,"We theoretically investigate the dynamics of solitons in two sublattice
+antiferromagnets under external perturbations, focusing on the effect of
+Dzyaloshinsky-Moriya (DM) interactions. To this end, we construct a
+micromagnetic field theory for the antiferromagnet in the presence of the
+external magnetic field, DM interaction, and spin-transfer torque. In
+particular, we show external magnetic field and spin current couple to N\'eel
+vector in a Zeeman-like manner when DM interactions present, which can be used
+to efficiently drive antiferromagnetic solitons of different dimensions.
+Besides, we study the effect of straining the local lattice. It can serve as an
+external handle on the N\'eel field inertia and thus dynamical properties. Our
+findings may find applications in antiferromagnetic spintronics.",2103.14982v2
+2021-05-05,Spin dynamical decoupling for generating macroscopic superpositions of a free-falling nanodiamond,"Levitated nanodiamonds containing negatively charged nitrogen-vacancy centers
+(${\text{NV}}^{-}$) have been proposed as a platform to generate macroscopic
+spatial superpositions. Requirements for this include having a long
+${\text{NV}}^{-}$ spin coherence time, which necessitates formulating a
+dynamical decoupling strategy in which the regular spin flips do not cancel the
+growth of the superposition through the Stern-Gerlach effect in an
+inhomogeneous magnetic field. Here, we propose a scheme to place a
+$250$-nm-diameter diamond in a superposition with spatial separation of over
+$250$ nm, while incorporating dynamical decoupling. We achieve this by letting
+a diamond fall for $2.4$ m through a magnetic structure, including $1.13$ m in
+an inhomogeneous region generated by magnetic teeth.",2105.02105v3
+2021-05-31,"Dynamic polarization of electron spins in indirect band gap (In,Al)As/AlAs quantum dots in weak magnetic field: experiment and theory","A novel spin orientation mechanism - dynamic electron spin polarization has
+been recently suggested in Phys. Rev. Lett. $\mathbf{125}$, 156801 (2020). It
+takes place for unpolarized optical excitation in weak magnetic fields of the
+order of a few millitesla. In this paper we demonstrate experimentally and
+theoretically that the dynamic electron spin polarization degree changes sign
+as a function of time, strength of the applied magnetic field and its
+direction. The studies are performed on indirect band-gap (In,Al)As/AlAs
+quantum dots and their results are explained in the framework of a theoretical
+model developed for our experimental setting.",2106.00044v1
+2021-07-02,Dynamic impurities in two-dimensional topological insulator-edge states,"Helical edge states of two-dimensional topological insulators show a gap in
+the density of states (DOS) and suppressed conductance in the presence of
+ordered magnetic impurities. Here we will consider the dynamical effects on the
+DOS and transmission when the magnetic impurities are driven periodically.
+Using the Floquet formalism and Green's functions, the system properties are
+studied as a function of the driving frequency and the potential energy
+contribution of the impurities. We see that increasing the potential part
+closes the DOS gap for all driving regimes. The transmission gap is also
+closed, showing a pronounced asymmetry as a function of energy. These features
+indicate that the dynamical transport properties could yield valuable
+information about the magnetic impurities.",2107.00994v2
+2021-10-01,Thermalization of nuclear spins in lanthanide molecular magnets,"Single molecule magnets distinguish themselves in the field of quantum
+magnetism through the ability to combine fundamental research with promising
+applications, the evolution of quantum spintronics in the last decade
+exemplifying the potential held by molecular based quantum devices. Notably,
+the read-out and manipulation of the embedded nuclear spin states was used in
+proof of principle studies of quantum computation at the single molecule level.
+In this paper we study the relaxation dynamics of the $^{159}$Tb nuclear spins
+in a diluted molecular crystal by using recently acquired understanding of the
+nonadiabatic dynamics of TbPc$_2$ molecules. We find that phonon modulated
+hyperfine interaction opens a direct relaxation channel between the nuclear
+spins and the phonon bath. We highlight the potential importance of the
+discovered mechanism for the theory of spin bath and the relaxation dynamics of
+the molecular spins at crossover temperatures.",2110.00161v1
+2021-12-12,Rodlike Heisenberg nanomagnet driven by propagating magnetic field: Nonequilibrium phase transition,"The dynamical responses of a rodlike anisotropic Heisenberg ferromagnet,
+irradiated by the propagating magnetic field wave, have been studied by Monte
+Carlo simulation using Metropolis single spin-flip algorithm. A nonequilibrium
+dynamical phase transition has been observed. The transition temperature has
+been obtained from the peak position of the variance of the dynamic order
+parameter plotted as a function of the temperature. The transition has been
+found to occur at a lower temperature for the higher value of the amplitude of
+the propagating magnetic field wave. A comprehensive phase boundary was drawn.
+The phase boundary has been found to be insensitive to the wavelength of the
+propagating field wave. The boundary encloses more area of the region of the
+ordered phase for stronger anisotropy.",2112.06138v2
+2022-01-22,Microwave-free dynamic nuclear polarization via sudden thermal jumps,"Dynamic Nuclear Polarization (DNP) presently stands as the preferred strategy
+to enhance the sensitivity of nuclear magnetic resonance measurements, but its
+application relies on the use of high-frequency microwave to manipulate
+electron spins, an increasingly demanding task as the applied magnetic field
+grows. Here we investigate the dynamics of a system hosting a polarizing agent
+formed by two distinct paramagnetic centers near a level anti-crossing. We
+theoretically show that nuclear spins polarize efficiently under a cyclic
+protocol that combines alternating thermal jumps and radio-frequency pulses
+connecting hybrid states with opposite nuclear and electronic spin alignment.
+Central to this process is the difference between the spin-lattice relaxation
+times of either electron spin species, transiently driving the electronic spin
+bath out of equilibrium after each thermal jump. Without the need for microwave
+excitation, this route to enhanced nuclear polarization may prove convenient,
+particularly if the polarizing agent is designed to feature electronic level
+anti-crossings at high magnetic fields.",2201.09092v1
+2022-02-06,Magnetic monopole relaxation effects probed by modulation calorimetry in small spin-ice samples,"We use modulation calorimetry to study the heat capacity of small samples (30
+nano gram-10 micro gram) of the classical spin-ice compounds Dy2Ti2O7 and
+Ho2Ti2O7 at low temperature (0.5-3 K). Using modulation frequencies of 0.1-200
+Hz we find a strong frequency dependence in the measured heat capacity and are
+able to study thermal relaxation effects on the corresponding timescales.
+Performing dynamic Monte Carlo simulations we verify that the specific heat
+frequency response has its origin in the slow magnetic monopole dynamics
+indigenous to spin ice. We find a timescale of 20ms per Monte Carlo step at 4K
+in contrast to 2.5ms mentioned in previous studies by other 1 techniques. Our
+study establishes modulation calorimetry as a versatile experimental probe of
+dynamic processes in frustrated magnetic materials.",2202.02801v1
+2022-03-21,Advances and Challenges in Observations and Modeling of the Global-Sun Dynamics and Dynamo,"Computational heliophysics has shed light on the fundamental physical
+processes inside the Sun, such as the differential rotation, meridional
+circulation, and dynamo-generation of magnetic fields. However, despite the
+substantial advances, the current results of 3D MHD simulations are still far
+from reproducing helioseismic inferences and surface observations. The reason
+is the multi-scale nature of the solar dynamics, covering a vast range of
+scales, which cannot be solved with the current computational resources. In
+such a situation, significant progress has been achieved by the mean-field
+approach, based on the separation of small-scale turbulence and large-scale
+dynamics. The mean-field simulations can reproduce solar observations,
+qualitatively and quantitatively, and uncover new phenomena. However, they do
+not reveal the complex physics of large-scale convection, solar magnetic
+cycles, and the magnetic self-organization that causes sunspots and solar
+eruptions. Thus, developing a synergy of these approaches seems to be a
+necessary but very challenging task.",2203.10721v1
+2022-05-15,Phase coexistence and associated non-equilibrium dynamics under simultaneously applied magnetic field and pressure,"A quantitative estimation of the effect of simultaneously applied external
+pressure (P) and magnetic field (H) on the phase coexistence has been presented
+for Pr0.5Ca0.5Mn0.975Al0.025O3 and La0.5Ca0.5MnO3, where the ferromagnetic
+(FM)-metal and antiferromagnetic (AFM)-insulator phases compete in real space.
+We found that the nonequilibrium dynamics across the FM-AFM transition is
+primarily dictated by the effect of P and H on the supercooling, superheating
+temperatures, and the nucleation and growth rate of the equilibrium phase.
+These effects across the transition is also responsible for the relative volume
+fraction of the competing phases at low temperature. Importantly in the entire
+magnetic field-pressure-temperature range of phase coexistence, the interface
+between the two competing phases having different spin and structural order
+plays a very important role in controlling the non-equilibrium dynamics.",2205.07192v2
+2022-05-27,Quantum Simulation of the Two-Dimensional Weyl Equation in a Magnetic Field,"Quantum simulation of 1D relativistic quantum mechanics has been achieved in
+well-controlled systems like trapped ions, but properties like spin dynamics
+and response to external magnetic fields that appear only in higher dimensions
+remain unexplored. Here we simulate the dynamics of a 2D Weyl particle. We show
+the linear dispersion relation of the free particle and the discrete Landau
+levels in a magnetic field, and we explicitly measure the spatial and spin
+dynamics from which the conservation of helicity and properties of
+antiparticles can be verified. Our work extends the application of an ion trap
+quantum simulator in particle physics with the additional spatial and spin
+degrees of freedom.",2205.14038v1
+2022-06-09,Reconfigurable Reservoir Computing in a Magnetic Metamaterial,"In-materia reservoir computing (RC) leverages the intrinsic physical
+responses of functional materials to perform complex computational tasks.
+Magnetic metamaterials are exciting candidates for RC due to their huge state
+space, nonlinear emergent dynamics, and non-volatile memory. However, to be
+suitable for a broad range of tasks, the material system is required to exhibit
+a broad range of properties, and isolating these behaviours experimentally can
+often prove difficult. By using an electrically accessible device consisting of
+an array of interconnected magnetic nanorings -- a system shown to exhibit
+complex emergent dynamics -- here we show how reconfiguring the reservoir
+architecture allows exploitation of different aspects the system's dynamical
+behaviours. This is evidenced through state-of-the-art performance in diverse
+benchmark tasks with very different computational requirements, highlighting
+the additional computational configurability that can be obtained by altering
+the input/output architecture around the material system.",2206.04446v3
+2022-08-02,Entanglement dynamics and phase transitions of the Floquet cluster spin chain,"Cluster states were introduced in the context of measurement based quantum
+computing. In one dimension, the cluster Hamiltonian possesses topologically
+protected states. We investigate the Floquet dynamics of the cluster spin chain
+in an external field, interacting with a particle. We explore the entanglement
+properties of the topological and magnetic phases, first in the integrable spin
+lattice case, and then in the interacting quantum walk case. We find, in
+addition to thermalization, dynamical phase transitions separating low- and
+high-entanglement nonthermal states, reminiscent of the ones present in the
+integrable case, but differing in their magnetic properties. The nonergodic
+phases are characterized by the emergence of magnetic order, persistent at long
+times.",2208.01706v2
+2022-10-01,Nonlinear features of the superconductor--ferromagnet--superconductor $\varphi_0$ Josephson junction in ferromagnetic resonance region,"We demonstrate the manifestations of the nonlinear features in magnetic
+dynamics and IV-characteristics of the $\varphi_0$ Josephson junction in the
+ferromagnetic resonance region. We show that at small values of system
+parameters, namely, damping, spin-orbit interaction, and Josephson to magnetic
+energy ratio, the magnetic dynamics is reduced to the dynamics of the scalar
+Duffing oscillator, driven by the Josephson oscillations. The role of
+increasing superconducting current in the resonance region is clarified.
+Shifting of the ferromagnetic resonant frequency and the reversal of its
+damping dependence due to nonlinearity are demonstrated by the full
+Landau-Lifshitz-Gilbert-Josephson system of equations, and in its different
+approximations. Finally, we demonstrate the negative differential resistance in
+the IV--characteristics, and its correlation with the foldover effect.",2210.00366v1
+2022-10-21,Emergent many-body composite excitations of interacting spin-1/2 trimers,"Understanding exotic forms of magnetism in quantum spin systems is an
+emergent topic of modern condensed matter physics. Quantum dynamics can be
+described by particle-like carriers of information, known-as quasiparticles
+that appear from the collective behaviour of the underlying system. Spinon
+excitations, governing the excitations of quantum spin-systems, have been
+accurately calculated and precisely verified experimentally for the
+antiferromagnetic chain model. However, identification and characterization of
+novel quasiparticles emerging from the topological excitations of the spin
+system having periodic exchange interactions are yet to be obtained. Here, we
+report the identification of emergent composite excitations of the novel
+quasiparticles doublons and quartons in spin-1/2 trimer-chain antiferromagnet
+Na2Cu3Ge4O12 (having periodic intrachain exchange interactions J1-J1-J2) and
+its topologically protected quantum 1/3 magnetization-plateau state. The
+characteristic energies, dispersion relations, and dynamical structure factor
+of neutron scattering as well as macroscopic quantum 1/3 magnetization-plateau
+state are in good agreement with the state-of-the-art dynamical density matrix
+renormalization group calculations.",2210.11765v1
+2022-11-02,Pump--probe x-ray microscopy of photo-induced magnetization dynamics at MHz repetition rates,"We present time-resolved scanning x-ray microscopy measurements with
+picosecond photo-excitation via a tailored infrared pump laser at a scanning
+transmission x-ray microscope. Specifically, we image the laser-induced
+demagnetization and remagnetization of thin ferrimagnetic GdFe films proceeding
+on a few nanoseconds time scale. Controlling the heat load on the sample via
+additional reflector and heat-sink layers allows us to conduct destruction-free
+measurements at a repetition rate of \SI{50}{\mega\hertz}. Near-field
+enhancement of the photo-excitation and controlled annealing effects lead to
+laterally heterogeneous magnetization dynamics which we trace with
+\SI{30}{\nano\meter} spatial resolution. Our work opens new opportunities to
+study photo-induced dynamics on the nanometer scale, with access to picosecond
+to nanosecond timescales, which is of technological relevance, especially in
+the field of magnetism.",2211.01230v2
+2023-01-01,Spin Hall Induced Magnetization Dynamics in Multiferroic Tunnel Junction,"The combination of spin-orbit coupling driven effects and multiferroic
+tunneling properties was explored experimentally in thin Pt/Co/BTO/LSMO
+multilayers. The presence of a Pt heavy metal allows for the spin
+current-induced magnetization precession of Co upon radio-frequency charge
+current injection. The utilization of a BTO ferroelectric tunnel barrier
+separating the Co and LSMO ferromagnetic electrodes gives rise to both
+tunneling-magnetoresistance and electroresistance. Using the spin-orbit torque
+ferromagnetic resonance, the maganetization dynamics of the Co/Pt bilayers was
+studied at room temperature. Unexpectedly the magnetization dynamics study in
+the same geometry performed at low temperature reveals the existence of both Co
+and LSMO resonance peaks indicating efficient spin current generation both
+using the spin Hall effect in Pt and spin pumping in LSMO that tunnel via the
+BTO barrier.",2301.00459v1
+2023-03-10,Dynamic Exchange Coupling between Magnets Mediated by Attenuating Elastic Waves,"Coupling between spatially separated magnets can be mediated by excitations
+such as photons and phonons, which can be characterized as coherent coupling
+and dissipative coupling with real and imaginary coupling rate. We
+theoretically predict the existence of dynamic exchange coupling in a closed
+magneto-elastic system mediated by attenuating elastic waves and whose coupling
+rate is complex in general, leading to alternating repulsive or attractive
+spectrum depending on thickness of the elastic media. The presence of dynamic
+exchange coupling and its competition with coherent coupling are numerically
+verified according to the generalized Hooke's law in magneto-elastic systems.
+The predicted mechanism provides a new strategy to synchronize precessing
+magnets as well as other excitations over long distance and pave the way for
+non-Hermitian engineering of collective modes in hybrid magnonics, phononics
+and photonics.",2303.05778v1
+2023-03-10,Ultrafast magnetization reversal in ferromagnetic spin-valves: an s-d model perspective,"We present an extension to simple s-d models, aiming at simulating ultrafast
+magnetization dynamics and spin transport in metallic heterostructures. In
+particular, we consider an alternative spin dissipation channel due to a finite
+exchange splitting of the s band. From this theory, we show three different
+mechanisms governing the dynamics of spin accumulation. On top of the already
+widely discussed ""-dM/dt"" electron-magnon mechanism, we study the role of a
+dynamic change of exchange splitting (of conduction electrons) as well as the
+rotation of spins reflected at an interface with a ferromagnet. Finally, we use
+the presented theory to explain the recent observation of subpicosecond
+reversal of a ferromagnet in rare-earth free spin-valves. Our conclusion agrees
+with the one of reference [1] favoring magnetization reversal due to the
+rotation of the spin polarization of a reflected spin current.",2303.05907v1
+2023-03-16,Ultrafast dynamics of electrons excited by femtosecond laser pulses: spin polarization and spin-polarized currents,"Laser radiation incident on a ferromagnetic sample produces excited electrons
+and currents whose spin polarization must not be aligned with the magnetization
+-- an effect due to spin-orbit coupling that is ubiquitous in spin- and
+angle-resolved photoemission. In this Paper, we report on a systematic
+investigation of the dynamics of spin polarization and spin-polarized currents
+produced by femtosecond laser pulses, modeled within our theoretical framework
+EVOLVE. The spin polarization depends strongly on the properties of the laser
+pulse and on the sample composition, as is shown by comparing results for
+Cu(100), Co(100), and a Co/Cu heterostructure. We find a transition from
+coherence before the laser pulse's maximum to incoherence thereafter. Moreover,
+the time dependence of the spin-polarization components induced by spin-orbit
+coupling differ significantly in Cu and Co: in Cu, we find long-period
+oscillations with tiny rapid modulations, whereas in Co prominent rapid
+oscillations with long period ones are superimposed. The pronounced spatial
+dependencies of the signals underline the importance of inhomogeneities, in
+particular magnetic/non-magnetic interfaces `act as source' for ultrafast
+spin-polarization effects. Our investigation provides detailed insight into
+electron dynamics during and shortly after a femtosecond laser excitation.",2303.09291v1
+2023-03-25,Muon spin relaxation and emergence of disorder-induced unconventional dynamic magnetic fluctuations in Dy$_{2}$Zr$_{2}$O$_{7}$,"The disordered pyrochlore oxide Dy$_{2}$Zr$_{2}$O$_{7}$ shows the signatures
+of field-induced spin freezing with remnant zero-point spin-ice entropy at 5
+kOe magnetic field. We have performed zero-field and longitudinal field Muon
+spin relaxation ($\mu$SR) studies on Dy$_{2}$Zr$_{2}$O$_{7}$. Our zero field
+studies reveal the absence of both long-range ordering and spin freezing down
+to 62 mK. The $\mu$SR relaxation rate exhibits a temperature-independent
+plateau below 4 K, indicating a dynamic ground state of fluctuating spins
+similar to the well-known spin ice system Dy$_{2}$Ti$_{2}$O$_{7}$. The
+low-temperature spin fluctuations persist in the longitudinal field of 20 kOe
+as well and show unusual field dependence of the relaxation rate, which is
+uncommon for a spin-liquid system. Our results, combined with the previous
+studies do not show any evidence of spin ice or spin glass ground state, rather
+point to a disorder-induced dynamic magnetic ground state in the
+Dy$_{2}$Zr$_{2}$O$_{7}$ material.",2303.14426v1
+2023-03-29,Dynamical criticality of magnetization transfer in integrable spin chains,"Recent studies have found that fluctuations of magnetization transfer in
+integrable spin chains violate the central limit property. Here we revisit the
+problem of anomalous counting statistics in the Landau-Lifshitz field theory by
+specializing to two distinct anomalous regimes featuring a dynamical critical
+point. By performing optimized numerical simulations using an integrable
+space-time discretization we extract the algebraic growth exponents of
+time-dependent cumulants which attain their threshold values. The distinctly
+non-Gaussian statistics of magnetization transfer in the easy-axis regime is
+found to converge towards the universal distribution of charged single-file
+systems. At the isotropic point we infer a weakly non-Gaussian distribution,
+corroborating the view that superdiffusive spin transport in integrable spin
+chains does not belong to any known dynamical universality class.",2303.16691v5
+2023-04-07,A two-color dual-comb system for time-resolved measurements of ultrafast magnetization dynamics using triggerless asynchronous optical sampling,"We report on an Er-doped fiber (EDF)-laser-based dual-comb system that allows
+us to perform triggerless asynchronous optical sampling (ASOPS) pump-probe
+measurements of ultrafast demagnetization and spin precession in magnetic
+materials. Because the oscillation frequencies of the two frequency-comb light
+sources are highly stabilized, the pulse-to-pulse timing jitter is sufficiently
+suppressed and data accumulation without any trigger signals is possible. To
+effectively induce spin precession in ferromagnetic thin films, the spectral
+bandwidth of the output of one of the EDF frequency comb sources is broadened
+by a highly nonlinear fiber and then amplified at a wavelength of about 1030 nm
+by a Yb-doped fiber amplifier. The output of the other frequency comb source is
+converted to about 775 nm by second harmonic generation. We used this system to
+observe the ultrafast demagnetization and spin precession dynamics on the
+picosecond and nanosecond time scales in a permalloy thin film. This
+time-domain spectroscopy system is promising for the rapid characterization of
+spin-wave generation and propagation dynamics in magnetic materials.",2304.03666v1
+2023-05-01,Coherent and incoherent magnons induced by strong ultrafast demagnetization in thin permalloy films,"Understanding spin dynamics on femto- and picosecond timescales offers new
+opportunities for faster and more efficient spintronic devices. Here, we
+experimentally investigate the coherent spin dynamics after ultrashort laser
+excitation by time-resolved magneto optical Kerr effect (TR-MOKE) in thin
+Ni80Fe20 films. We provide a detailed study of the magnetic field and pump
+fluence dependence of the coherent precessional dynamics. We show that the
+coherent precession lifetime increases with the applied external magnetic field
+which cannot be understood by viscous Gilbert damping of the coherent magnons.
+Instead, it can be explained by nonlinear magnon interactions and by the change
+in the fraction of incoherent magnons. This interpretation is in agreement with
+the observed trends of the coherent magnon amplitude and lifetime as a function
+of the exciting laser fluence. Our results provide a new insight into the
+magnetization relaxation processes in ferromagnetic thin films, which is of
+great importance for further spintronic applications.",2305.00814v2
+2023-06-10,Statistical Analysis of Magnetic Domain Wall Dynamics to Quantify Dzyaloshinskii-Moriya Interaction,"We utilize statistical tools to analyze the magnetic domain wall dynamics in
+a nanostrip, which can quantify the magnitude and reveal the effects of
+interfacial Dzyaloshinskii-Mariya interaction. We find that there exist two
+peaks in the velocity frequency spectrum, the magnitude ratio of which can be
+used to determine the DMI strength. Our approach is validated using a
+collective-coordinate model, and is demonstrated to be robust against thermal
+noise and material impurities. Moreover, third-order cumulant and third-order
+time-dependent correlation function of velocity are calculated and yield
+valuable information regarding the asymmetry induced by DMI. Our findings offer
+novel and efficient analysis tools to understand physical process of domain
+wall dynamics under DMI and exotic magnetic phenomena.",2306.06451v1
+2023-06-22,Ultrafast Dynamics of Orbital Angular Momentum of Electrons Induced by Femtosecond Laser Pulses: Generation and Transfer Across Interfaces,"The orbital angular momenta (OAM) of electrons play an increasingly important
+role in ultrafast electron and magnetization dynamics. In this theoretical
+study, we investigate the electron dynamics induced by femtosecond laser pulses
+in a normal metal, a ferromagnet, and a ferromagnet/normal metal
+heterostructure. We analyze the spatio-temporal distributions of the
+laser-induced OAM and their respective currents. Our findings demonstrate that
+a circularly polarized laser pulse can induce a sizable and long-lasting OAM
+component in a normal metal. Furthermore, an interface between a ferromagnet
+and a normal metal facilitates the demagnetization of the magnet by the OAM
+contribution to the total magnetization. Finally, to transfer OAM from a
+ferromagnet into a normal metal, it is advantageous to use a laser setup that
+induces the desired OAM component in the ferromagnet, but not in the normal
+metal.",2306.12810v1
+2023-07-24,Super narrow peaks in excitation spectrum of alkali spin polarization: non-adiabatic case of spin dynamics,"We theoretically describe the phenomenon of non-adiabatic spin dynamics,
+which occurs in a gas cell filled by alkali vapor in presence of a strong
+alternating magnetic field and pump light. Steep increase of the spin
+polarization occurs if frequency of the magnetic field is equal to the certain
+value. Although, the observable effect relies on the periodic field that
+consists of two perpendicular components defined by harmonics with the same
+amplitudes and different frequencies. Considered spin effect cannot be
+explained by a resonance, because the own Larmor frequency of spin precession
+is absent without a constant component of magnetic field. Moreover, there are
+some clearly visible peaks in the excitation spectrum of spin polarization, and
+they are super narrow in comparison to relaxation rate. Detailed analysis
+according to proposed quantum model results in the reasoning of the effect via
+qualitative properties of non-adiabatic dynamics of atomic spin.",2307.12647v2
+2023-07-29,Single-spin spectroscopy of spontaneous and phase-locked spin torque oscillator dynamics,"We employ N-$V$ magnetometry to measure the stray field dynamics of a
+ferromagnetic permalloy nanowire driven by spin-orbit torques. Specifically, we
+observe the optically detected magnetic resonance (ODMR) signatures of both
+spontaneous DC-driven magnetic oscillations and phase-locking to a second
+harmonic drive, developing a simple macrospin model that captures the salient
+features. We also observe signatures of dynamics beyond the macrospin model,
+including an additional ODMR feature (associated with a second SW mode) and one
+mode sapping power from another. Our results provide additional insight into
+N-$V$-spin wave coupling mechanisms, and represent a new modality for
+sub-wavelength N-$V$ scanned probe microscopy of nanoscale magnetic
+oscillators.",2307.16049v1
+2023-08-21,Three-dimensional Turbulent Reconnection within Solar Flare Current Sheet,"Solar flares can release coronal magnetic energy explosively and may impact
+the safety of near-earth space environments. Their structures and properties on
+macroscale have been interpreted successfully by the generally-accepted
+two-dimension standard model invoking magnetic reconnection theory as the key
+energy conversion mechanism. Nevertheless, some momentous dynamical features as
+discovered by recent high-resolution observations remain elusive. Here, we
+report a self-consistent high-resolution three-dimension magnetohydrodynamical
+simulation of turbulent magnetic reconnection within a flare current sheet. It
+is found that fragmented current patches of different scales are spontaneously
+generated with a well-developed turbulence spectrum at the current sheet, as
+well as at the flare loop-top region. The close coupling of tearing-mode and
+Kelvin-Helmholtz instabilities plays a critical role in developing turbulent
+reconnection and in forming dynamical structures with synthetic observables in
+good agreement with realistic observations. The sophisticated modeling makes a
+paradigm shift from the traditional to three-dimension turbulent reconnection
+model unifying flare dynamical structures of different scales.",2308.10494v1
+2023-09-04,Quantum Barkhausen Noise Induced by Domain Wall Co-Tunneling,"Most macroscopic magnetic phenomena (including magnetic hysteresis) are
+typically understood classically. Here, we examine the dynamics of a uniaxial
+rare-earth ferromagnet deep within the quantum regime, so that domain wall
+motion, and the associated hysteresis, is dominated by large-scale quantum
+tunneling of spins, rather than classical thermal activation over a potential
+barrier. The domain wall motion is found to exhibit avalanche dynamics,
+observable as an unusual form of Barkhausen noise. We observe non-critical
+behavior in the avalanche dynamics that only can be explained by going beyond
+traditional renormalization group methods or classical domain wall models. We
+find that this ``quantum Barkhausen noise'' exhibits two distinct mechanisms
+for domain wall movement, each of which is quantum-mechanical, but with very
+different dependences on an external magnetic field applied transverse to the
+spin (Ising) axis. These observations can be understood in terms of the
+correlated motion of pairs of domain walls, nucleated by co-tunneling of
+plaquettes (sections of domain wall), with plaquette pairs correlated by
+dipolar interactions; this correlation is suppressed by the transverse field.
+Similar macroscopic correlations may be expected to appear in the hysteresis of
+other systems with long-range interactions.",2309.01799v1
+2023-09-10,Resonant excitation of vortex gyrotropic mode via surface acoustic waves,"Finding new energy-efficient methods for exciting magnetization dynamics is
+one of the key challenges in magnonics. In this work, we present an approach to
+excite the gyrotropic dynamics of magnetic vortices through the phenomenon of
+inverse magnetostriction, also known as the Villari effect. We develop an
+analytical model based on the Thiele formalism that describes the gyrotropic
+motion of the vortex core including the energy contributions due to inverse
+magnetostriction. Based on this model, we predict excitations of the vortex
+core resonances by surface acoustic waves whose frequency is resonant with the
+frequency of the vortex core. We verify the model's prediction using
+micromagnetic simulations, and show the dependence of the vortex core's
+oscillation radius on the surface acoustic wave amplitude and the static bias
+field. Our study contributes to the advancement of energy-efficient magnetic
+excitations by relying on voltage-induced driven dynamics, which is an
+alternative to conventional current-induced excitations.",2309.04987v1
+2023-09-18,Nonlinear dynamics and magneto-elasticity of nanodrums near the phase transition,"Nanomechanical resonances of two-dimensional (2D) materials are sensitive
+probes for condensed-matter physics, offering new insights into magnetic and
+electronic phase transitions. Despite extensive research, the influence of the
+spin dynamics near a second-order phase transition on the nonlinear dynamics of
+2D membranes has remained largely unexplored. Here, we investigate nonlinear
+magneto-mechanical coupling to antiferromagnetic order in suspended
+FePS$_3$-based heterostructure membranes. By monitoring the motion of these
+membranes as a function of temperature, we observe characteristic features in
+both nonlinear stiffness and damping close to the N\'{e}el temperature
+$T_{\rm{N}}$. We account for these experimental observations with an analytical
+magnetostriction model in which these nonlinearities emerge from a coupling
+between mechanical and magnetic oscillations, demonstrating that
+magneto-elasticity can lead to nonlinear damping. Our findings thus provide
+insights into the thermodynamics and magneto-mechanical energy dissipation
+mechanisms in nanomechanical resonators due to the material's phase change and
+magnetic order relaxation.",2309.09672v1
+2023-09-29,SpinView: General Interactive Visual Analysis Tool for Multiscale Computational Magnetism,"Multiscale magnetic simulations, including micromagnetic and atomistic spin
+dynamics simulations, are widely used in the study of complex magnetic systems
+over a wide range of spatial and temporal scales. The advances in these
+simulation technologies have generated considerable amounts of data. However, a
+versatile and general tool for visualization, filtering, and denoising this
+data is largely lacking. To overcome these limitations, we have developed
+SpinView, a general interactive visual analysis tool for graphical exploration
+and data distillation. Combined with dynamic filters and a built-in database,
+it is possible to generate reproducible publication-quality images, videos, or
+portable interactive webpages within seconds. Since the basic input to SpinView
+is a vector field, it can be directly integrated with any spin dynamics
+simulation tool. With minimal effort on the part of the user, SpinView delivers
+a simplified workflow, speeds up analysis of complex datasets and trajectories,
+and enables new types of analysis and insight. SpinView is available from
+https://mxjk851.github.io/SpinView/",2309.17367v2
+2023-11-14,Magnetic dynamics driven integer and fractional high harmonic generation arising from highly nonlinear instantaneous energy levels,"We demonstrate that the strongly nonlinear regime of the magnetic dynamics
+driven high harmonic generation (HHG) can be captured through an adiabatic
+treatment. Within this approximation, the instantaneous energy levels reveal a
+highly nonlinear term that mirrors the high-frequency excitations present in
+non-equilibrium transport quantities. Therefore, we find that the revelation of
+nonlinear dynamics in the instantaneous energy levels offers a simplified
+understanding of HHG in magnetic systems. Additionally, leveraging the highly
+nonlinear nature of these instantaneous bands, we predict the emergence of
+tunable integer and fractional high harmonics in the presence of a
+time-modulated spin-orbit interaction. Our findings initiate tantalizing
+prospects for harnessing HHG in condensed matter systems.",2311.08368v3
+2024-01-09,Data-driven scale identification in oscillatory dynamos,"Parker's mean-field model includes two processes generating large-scale
+oscillatory dynamo waves: stretching of magnetic field lines by small-scale
+helical flows, and by differential rotation. In this work, we investigate the
+capacity of data-driven modal analysis, Dynamic Mode Decomposition, to identify
+coherent magnetic field structures of this model. In its canonical form, the
+only existing field scale corresponds to the dynamo instability. To take into
+account multi-scale nature of the dynamo, the model was augmented with coherent
+in time flow field, forcing small-scale magnetic field with a faster temporal
+evolution. Two clusters of DMD modes were obtained: the ``slow"" cluster,
+located near the dynamo wave frequency and associated with its nonlinear
+self-interaction, and the ``fast"" cluster, centered around the forcing
+frequency and resulting from the interaction between the wave and the flow.
+Compared to other widely used methods of data analysis, such as Fourier
+transform, DMD provides a natural spatiotemporal basis for the dynamo, related
+to its nonlinear dynamics. We assess how the parameters of the DMD model, rank
+and delay, influence its accuracy, and finally discuss the limitations of this
+approach when applied to randomly forced, more complex dynamo flows.",2401.04505v1
+2024-03-30,Chaotic dynamics under the influence of synthetic magnetic field in optomechanical system,"The optomechanical systems produce chaotic behaviour due to nonlinear
+interaction between photons and phonons, and the same systems are used to
+understand the synthetic fields as well. Here, we report on the study of
+chaotic behaviour in the presence of a phononic synthetic magnetic field in a
+closed loop configuration consisting of a single optical mode and two
+mechanical modes. The modulation phase of the mechanical coupling between the
+two mechanical modes plays a critical role in determining the mechanical and
+optical intensity dynamics in the nonlinear regime. Our study shows the dark
+mode breaking effect in the presence of a synthetic magnetic field, which
+brings about a complex way of mechanical energy exchange that causes the cavity
+field to alternate between chaotic and regular behaviour periodically in
+temporal domain. However in the stronger nonlinear regime the temporal dynamics
+demonstrate predominantly chaotic behaviour. Besides, with the advent of
+advanced fabrication technologies, this study holds promises in developing
+phase tunable integrated low-power chaotic light sources to support efficient
+optical secure communication systems.",2404.00472v2
+2017-03-22,Fast domain wall motion induced by antiferromagnetic spin dynamics at the angular momentum compensation temperature of ferrimagnets,"Antiferromagnetic spintronics is an emerging research field which aims to
+utilize antiferromagnets as core elements in spintronic devices. A central
+motivation toward this direction is that antiferromagnetic spin dynamics is
+expected to be much faster than ferromagnetic counterpart because
+antiferromagnets have higher resonance frequencies than ferromagnets. Recent
+theories indeed predicted faster dynamics of antiferromagnetic domain walls
+(DWs) than ferromagnetic DWs. However, experimental investigations of
+antiferromagnetic spin dynamics have remained unexplored mainly because of the
+immunity of antiferromagnets to magnetic fields. Furthermore, this immunity
+makes field-driven antiferromagnetic DW motion impossible despite rich physics
+of field-driven DW dynamics as proven in ferromagnetic DW studies. Here we show
+that fast field-driven antiferromagnetic spin dynamics is realized in
+ferrimagnets at the angular momentum compensation point TA. Using rare-earth
+3d-transition metal ferrimagnetic compounds where net magnetic moment is
+nonzero at TA, the field-driven DW mobility remarkably enhances up to 20 km/sT.
+The collective coordinate approach generalized for ferrimagnets and atomistic
+spin model simulations show that this remarkable enhancement is a consequence
+of antiferromagnetic spin dynamics at TA. Our finding allows us to investigate
+the physics of antiferromagnetic spin dynamics and highlights the importance of
+tuning of the angular momentum compensation point of ferrimagnets, which could
+be a key towards ferrimagnetic spintronics.",1703.07515v1
+2020-09-14,Non-Hamiltonian dynamics of indirectly coupled classical impurity spins,"We discuss the emergence of an effective low-energy theory for the real-time
+dynamics of two classical impurity spins within the framework of a prototypical
+and purely classical model of indirect magnetic exchange: Two classical
+impurity spins are embedded in a host system which consists of a finite number
+of classical spins localized on the sites of a lattice and interacting via a
+nearest-neighbor Heisenberg exchange. An effective low-energy theory for the
+slow impurity-spin dynamics is derived for the regime, where the local exchange
+coupling between impurity and host spins is weak. To this end we apply the
+recently developed adiabatic spin dynamics (ASD) theory. Besides the
+Hamiltonian-like classical spin torques, the ASD additionally accounts for a
+novel topological spin torque that originates as a holonomy effect in the
+close-to-adiabatic-dynamics regime. It is shown that the effective low-energy
+precession dynamics cannot be derived from an effective Hamilton function and
+is characterized by a non-vanishing precession frequency even if the initial
+state deviates only slightly from a ground state. The effective theory is
+compared to the fully numerical solution of the equations of motion for the
+whole system of impurity and host spins to identify the parameter regime where
+the adiabatic effective theory applies. Effective theories beyond the adiabatic
+approximation must necessarily include dynamic host degrees of freedom and go
+beyond the idea of a simple indirect magnetic exchange. We discuss an example
+of a generalized constrained spin dynamics which does improve the description
+but also fails for certain geometrical setups.",2009.06296v2
+2005-05-31,"The Core-Collapse Supernova with ""Non-Uniform"" Magnetic Fields","We perform two-dimensional numerical simulations on the core-collapse of a
+massive star with strong magnetic fields and differential rotations using a
+numerical code ZEUS-2D. Changing field configurations and laws of differential
+rotation parametrically, we compute 14 models and investigate effects of these
+parameters on the dynamics. In our models, we do not solve the neutrino
+transport and instead employ a phenomenological parametric EOS that takes into
+account the neutrino emissions. As a result of the calculations, we find that
+the field configuration plays a significant role in the dynamics of the core if
+the initial magnetic field is large enough. Models with initially concentrated
+fields produce more energetic explosions and more prolate shock waves than the
+uniform field. Quadrapole-like fields produce remarkably collimated and fast
+jet, which might be important for gamma-ray bursts(GRB). The Lorentz forces
+exerted in the region where the plasma-beta is less than unity are responsible
+for these dynamics. The pure toroidal field, on the other hand, does not lead
+to any explosion or matter ejection. This suggests the presupernova models of
+Heger et al.(2003), in which toroidal fields are predominant, is
+disadvantageous for the magnetorotation-induced supernova considered here.
+Models with initially weak magnetic fields do not lead to explosion or matter
+ejection, either. In these models magnetic fields play no role as they do not
+grow on the timescale considered in this paper so that the magnetic pressure
+could be comparable to the matter pressure. This is because the exponential
+field growth as expected in MRI is not seen in our models. The magnetic field
+is amplified mainly by field-compression and field-wrapping in our simulations.",0505611v3
+2008-05-01,Improved ring potential of QED at finite temperature and in the presence of weak and strong magnetic field,"Using the general structure of the vacuum polarization tensor
+$\Pi_{\mu\nu}(k_{0},\mathbf{k})$ in the infrared (IR) limit, $k_{0}\to 0$, the
+ring contribution to QED effective potential at finite temperature and non-zero
+magnetic field is determined beyond the static limit, $(k_{0}\to
+0,\mathbf{k}\to \mathbf{0})$. The resulting ring potential is then studied in
+weak and strong magnetic field limit. In the limit of weak magnetic field, at
+high temperature and for $\alpha\to 0$, the improved ring potential consists of
+a term proportional to $T^{4}\alpha^{5/2}$, in addition to the expected
+$T^{4}\alpha^{3/2}$ term arising from the static limit. Here, $\alpha$ is the
+fine structure constant. In the limit of strong magnetic field, where QED
+dynamics is dominated by the lowest Landau level (LLL), the ring potential
+includes a novel term consisting of dilogarithmic function
+$(eB){Li}_{2}(-\frac{2\alpha}{\pi}\frac{eB}{m^{2}})$. Using the ring improved
+(one-loop) effective potential including the one-loop effective potential and
+ring potential in the IR limit, the dynamical chiral symmetry breaking of QED
+is studied at finite temperature and in the presence of strong magnetic field.
+The gap equation, the dynamical mass and the critical temperature of QED in the
+regime of LLL dominance are determined in the improved IR as well as in the
+static limit. For a given value of magnetic field, the improved ring potential
+is shown to be more efficient in decreasing the critical temperature arising
+from one-loop effective potential.",0805.0078v2
+2012-06-28,Poloidal-Field Instability in Magnetized Relativistic Stars,"We investigate the instability of purely poloidal magnetic fields in
+nonrotating neutron stars by means of three-dimensional general-relativistic
+magnetohydrodynamics simulations, extending the work presented in Ciolfi et al.
+(2011). Our aim is to draw a clear picture of the dynamics associated with the
+instability and to study the final configuration reached by the system, thus
+obtaining indications on possible equilibria in a magnetized neutron star.
+Furthermore, since the internal rearrangement of magnetic fields is a highly
+dynamical process, which has been suggested to be behind magnetar giant flares,
+our simulations can provide a realistic estimate of the electromagnetic and
+gravitational-wave emission which should accompany the flare event. Our main
+findings are the following: (i) the initial development of the instability
+meets all the expectations of perturbative studies in terms of the location of
+the seed of the instability, the timescale for its growth and the generation of
+a toroidal component; (ii) in the subsequent nonlinear reorganization of the
+system, ~90% of magnetic energy is lost in few Alfven timescales mainly through
+electromagnetic emission, and further decreases on a much longer timescale;
+(iii) all stellar models tend to achieve a significant amount of magnetic
+helicity and the equipartition of energy between poloidal and toroidal magnetic
+fields, and evolve to a new configuration which does not show a subsequent
+instability on dynamical or Alfven timescales; (iv) the electromagnetic
+emission matches the duration of the initial burst in luminosity observed in
+giant flares, giving support to the internal rearrangement scenario; (v) only a
+small fraction of the energy released during the process is converted into
+f-mode oscillations and in the consequent gravitational-wave emission, thus
+resulting in very low chances of detecting this signal with present and..",1206.6604v2
+2019-04-23,Spin injection and pumping generated by a direct current flowing through a magnetic tunnel junction,"A charge flow through a magnetic tunnel junction (MTJ) leads to the
+generation of a spin-polarized current which exerts a spin-transfer torque
+(STT) on the magnetization. When the density of applied direct current exceeds
+some critical value, the STT excites high-frequency magnetization precession in
+the ""free"" electrode of MTJ. Such precession gives rise to microwave output
+voltage and, furthermore, can be employed for spin pumping into adjacent normal
+metal or semiconductor. Here we describe theoretically the spin dynamics and
+charge transport in the CoFeB/MgO/CoFeB/Au tunneling heterostructure connected
+to a constant-current source. The magnetization dynamics in the free CoFeB
+layer with weak perpendicular anisotropy is calculated by numerical integration
+of the Landau-Lifshitz-Gilbert-Slonczewski equation accounting for both STT and
+voltage controlled magnetic anisotropy associated with the CoFeB|MgO interface.
+It is shown that a large-angle magnetization precession, resulting from
+electrically induced dynamic spin reorientation transition, can be generated in
+a certain range of relatively low current densities. An oscillating spin
+current, which is pumped into the Au overlayer owing to such precession, is
+then evaluated together with the injected spin current. Considering both the
+driving spin-polarized charge current and the pumped spin current, we also
+describe the charge transport in the CoFeB/Au bilayer with the account of
+anomalous and inverse spin Hall effects. An electric potential difference
+between the lateral sides of the CoFeB/Au bilayer is calculated as a function
+of distance from the CoFeB|MgO interface. It is found that this transverse
+voltage signal in Au is large enough for experimental detection, which
+indicates significant efficiency of the proposed current-driven spin injector.",1904.10361v1
+2020-10-20,Ultrafast current and field driven domain-wall dynamics in van der Waals antiferromagnet MnPS3,"The discovery of magnetism in two-dimensional (2D) van der Waals (vdW)
+materials has flourished a new endeavour of fundamental problems in magnetism
+as well as potential applications in computing, sensing and storage
+technologies. Of particular interest are antiferromagnets, which due to their
+intrinsic antiferromagnetic exchange coupling show several advantages in
+relation to ferromagnets such as robustness against external magnetic
+perturbations. This property is one of the cornerstones of antiferromagnets and
+implies that information stored in antiferromagnetic domains is invisible to
+applied magnetic fields preventing it from being erased or manipulated. Here we
+show that, despite this fundamental understanding, the magnetic domains of
+recently discovered vdW MnPS3 antiferromagnet can be controlled via external
+magnetic fields and currents. We realize ultrafast domain-wall dynamics with
+velocities up to 1500 m/s and 3000 m/s respectively to a broad range of fields
+and current densities. Both domain wall dynamics are determined by the edge
+terminations which generated uncompensated spins following the underlying
+symmetry of the honeycomb structure. We find that edge atoms belonging to
+different magnetic sublattices function as geometrical constrictions preventing
+the displacement of the wall, whereas having atoms of the same sublattice at
+both edges of the material allows for the field-driven domain wall motion which
+is only limited by the spin-flop transition of the antiferromagnet beyond 25 T.
+Conversely, electric currents can induce motion of domain walls in most of the
+edges except those where the two sublattices are present at the borders (e.g.
+armchair edges). Our results indicate that the implementation of 2D vdW
+antiferromagnets in real applications requires the engineering of the layer
+edges which enables an unprecedented functional feature in ultrathin device
+platforms.",2010.10466v2
+2021-03-28,Magnetic field-induced softening of spin waves and hard-axis order in Kondo-lattice ferromagnet CeAgSb$_{2}$,"A significant number of Kondo-lattice ferromagnets order perpendicular to the
+easy magnetization axis dictated by the crystalline electric field. The nature
+of this phenomenon has attracted considerable attention, but remains poorly
+understood. In the present paper we use inelastic neutron scattering supported
+by magnetization and specific heat measurements to study the spin dynamics in
+the hard-axis ferromagnet CeAgSb2. In the zero field state we observed two
+sharp magnon modes, which are associated with Ce ordering and extended up to
+$\approx 3 meV with a considerable spin gap of 0.6 meV. Application of a
+magnetic field perpendicular to the moment direction reduces the spectral
+intensity and suppresses the gap and significantly enhances the low-temperature
+specific heat at a critical field of Bc ~ 2.8 T via a mean-field-like
+transition. Above the transition, in the field polarized state, the gap
+eventually reopens due to the Zeeman effect. We modeled the observed dispersion
+using linear spin-wave theory (LSWT) taking into account the ground state Gamma
+6 doublet and exchange anisotropy. Our model correctly captures the essential
+features of the spin dynamics including magnetic dispersion, distribution of
+the spectral intensity as well as the field-induced behavior, although several
+minor features remain obscure. The observed spectra do not show significant
+broadening due to the finite lifetime of the quasiparticles. Along with a
+moderate electronic specific heat coefficient gamma = 46 mJ/mol K2 this
+indicates that the Kondo coupling is relatively weak and the Ce moments are
+well localized. Altogether, our results provide profound insight into the spin
+dynamics of the hard-axis ferromagnet CeAgSb2 and can be used as solid ground
+for studying magnetic interactions in isostructural compounds including
+CeAuSb2, which exhibits nematicity and unusual mesoscale magnetic textures.",2103.15137v2
+2021-12-15,Turbulent magnetic field amplification in binary neutron star mergers,"Magnetic fields are expected to play a key role in the dynamics and the
+ejection mechanisms that accompany the merger of two neutron stars. General
+relativistic magnetohydrodynamic (MHD) simulations offer a unique opportunity
+to unravel the details of the ongoing physical processes. Nevertheless, current
+numerical studies are severely limited by the fact that any affordable
+resolution remains insufficient to fully capture the small-scale dynamo,
+initially triggered by the Kelvin-Helmholtz instability, and later sourced by
+several MHD processes involving differential rotation. Here, we alleviate this
+limitation by using explicit large-eddy simulations, a technique where the
+unresolved dynamics occurring at the sub-grid scales (SGS) is modeled by extra
+terms, which are functions of the resolved fields and their derivatives. The
+combination of high-order numerical schemes, high resolutions, and the gradient
+SGS model allow us to capture the small-scale dynamos produced during the
+binary neutron star mergers. Here we follow the first 50 milliseconds after the
+merger and, for the first time, we find numerical convergence on the magnetic
+field amplification, in terms of integrated energy and spectral distribution
+over spatial scales. We also find that the average intensity of the magnetic
+field in the remnant saturates at $\sim 10^{16}$~G around $5$~ms after the
+merger. After $20-30$~ms, both toroidal and poloidal magnetic field components
+grow continuously, fed by the winding mechanism that provides a slow inverse
+cascade. We find no clear hints for magneto-rotational instabilities, and no
+significant impact of the magnetic field on the redistribution of angular
+momentum in the remnant in our simulations, probably due to the very turbulent
+and dynamical topology of the magnetic field at all stages, with small-scale
+components largely dominating over the large-scale ones.",2112.08413v2
+2022-10-27,Fast broadband cluster spin-glass dynamics in PbFe$_{1/2}$Nb$_{1/2}$O$_{3}$,"PbFe$_{1/2}$Nb$_{1/2}$O$_{3}$ (PFN) is a relaxor ferroelectric (T$_{c}$
+$\sim$ 400 K) consisting of disordered magnetic Fe$^{3+}$ (S=${5\over2}$,
+L$\approx$0) ions resulting in a low temperature ``cluster glass"" phase (W.
+Kleemann $\textit{et al.}$ Phys. Rev. Lett. ${\bf{105}}$, 257202 (2010)). We
+apply neutron scattering to investigate the dynamic magnetism of this phase in
+a large single crystal which displays a low temperature spin glass transition
+(T$_{g} \sim$ 15 K), but no observable spatially long-range antiferromagnetic
+order. The static response in the cluster glass phase (sampled on the timescale
+set by our resolution) is found to be characterized by an average magnetic spin
+direction that lacks any preferred direction. The dynamics that drive this
+phase are defined by a magnetic correlation length that gradually increases
+with decreasing temperature. However, below $\sim$ 50 K the spatial
+correlations gradually becoming more short range indicative of increasing
+disorder on cooling, thereby unravelling magnetism, until the low temperature
+glass phase sets in at T$_{g}$ $\sim$ 15 K. Neutron spectroscopy is used to
+characterize the spin fluctuations in the cluster glass phase and are found to
+be defined by a broadband of frequencies on the scale of $\sim$ THz, termed
+here ``fast"" fluctuations. The frequency bandwidth driving the magnetic
+fluctuations mimics the correlation length and decreases until $\sim$ 50 K, and
+then increases again until the glass transition. Through investigating the
+low-energy acoustic phonons we find evidence of multiple distinct structural
+regions which form the basis of the clusters, generating a significant amount
+of local disorder. We suggest that random molecular fields originating from
+conflicting interactions between clusters is important for the destruction of
+magnetic order and the eventual formation of the cluster glass in PFN.",2210.15706v1
+2023-06-12,"Transition from small-scale to large-scale dynamo in a supernova-driven, multiphase medium","Magnetic fields are widely recognised as critical at many scales to galactic
+dynamics and structure, including multiphase pressure balance, dust processing,
+and star formation. Using imposed magnetic fields cannot reliably model the
+interstellar medium's (ISM) dynamical structure nor phase interactions. Dynamos
+must be modelled. ISM models exist of turbulent magnetic fields using
+small-scale dynamo (SSD). Others model the large-scale dynamo (LSD) organising
+magnetic fields at scale of the disc or spiral arms. Separately, neither can
+fully describe the galactic magnetic field dynamics nor topology. We model the
+LSD and SSD together at sufficient resolution to use the low explicit
+Lagrangian resistivity required. The galactic SSD saturates within 20 Myr. We
+show that the SSD is quite insensitive to the presence of an LSD and is even
+stronger in the presence of a large-scale shear flow. The LSD grows more slowly
+in the presence of SSD, saturating after 5 Gyr vs. 1--2 Gyr in studies where
+the SSD is weak or absent. The LSD primarily grows in warm gas in the galactic
+midplane. Saturation of the LSD occurs due to ${\alpha}$-quenching near the
+midplane as the growing mean field produces a magnetic ${\alpha}$ that opposes
+the kinetic ${\alpha}$. The magnetic energy in our models of the LSD shows
+slightly sublinear response to increasing resolution, indicating that we are
+converging towards the physical solution at 1 pc resolution. Clustering
+supernovae in OB associations increases the growth rates for both the SSD and
+the LSD, compared to a horizontally uniform supernova distribution.",2306.07051v3
+2010-03-22,Coherent Control of Quantum Dynamics with Sequences of Unitary Phase-Kick Pulses,"Coherent optical control schemes exploit the coherence of laser pulses to
+change the phases of interfering dynamical pathways in order to manipulate
+dynamical processes. These active control methods are closely related to
+dynamical decoupling techniques, popularized in the field of Quantum
+Information. Inspired by Nuclear Magnetic Resonance (NMR) spectroscopy,
+dynamical decoupling methods apply sequences of unitary operations to modify
+the interference phenomena responsible for the system dynamics thus also
+belonging to the general class of coherent control techniques. Here we review
+related developments in the fields of coherent optical control and dynamical
+decoupling, with emphasis on control of tunneling and decoherence in general
+model systems. Considering recent experimental breakthroughs in the
+demonstration of active control of a variety of systems, we anticipate that the
+reviewed coherent control scenarios and dynamical decoupling methods should
+raise significant experimental interest.",1003.4269v1
+2017-05-09,Dynamic finite-size scaling at first-order transitions,"We investigate the dynamic behavior of finite-size systems close to a
+first-order transition (FOT). We develop a dynamic finite-size scaling (DFSS)
+theory for the dynamic behavior in the coexistence region where different
+phases coexist. It is characterized by an exponentially large time scale
+related to the tunneling between the two phases. We show that, when considering
+time scales of the order of the tunneling time, the dynamic behavior can be
+described by a two-state coarse-grained dynamics. This allows us to obtain
+exact predictions for the dynamical scaling functions. To test the general DFSS
+theory at FOTs, we consider the two-dimensional Ising model in the
+low-temperature phase, where the external magnetic field drives a FOT, and the
+20-state Potts model, which undergoes a thermal FOT. Numerical results for a
+purely relaxational dynamics fully confirm the general theory.",1705.03198v2
+2020-12-19,Unconsciousness reconfigures modular brain network dynamics,"The dynamic core hypothesis posits that consciousness is correlated with
+simultaneously integrated and differentiated assemblies of transiently
+synchronized brain regions. We represented time-dependent functional
+interactions using dynamic brain networks, and assessed the integrityof the
+dynamic core by means of the flexibility and largest multilayer module of these
+networks. As a first step, we constrained parameter selection using a newly
+developed benchmark for module detection in heterogeneous temporal networks.
+Next, we applied a multilayer modularity maximization algorithm to dynamic
+brain networks computed from functional magnetic resonance imaging (fMRI) data
+acquired during deep sleep and under propofol anesthesia. We found that
+unconsciousness reconfigured network flexibility and reduced the size of the
+largest spatiotemporal module, which we identified with the dynamic core. Our
+results present a first characterization of modular brain network dynamics
+during states of unconsciousness measured with fMRI, adding support to the
+dynamic core hypothesis of human consciousness.",2012.10785v1
+2022-08-03,Ultrafast Demagnetization Dynamics Due to Electron-Electron Scattering and Its Relation to Momentum Relaxation in Ferromagnets,"We analyze theoretically the demagnetization dynamics in a ferromagnetic
+model system due to the interplay of spin-orbit coupling and electron-electron
+Coulomb scattering. We compute the $k$-resolved electronic reduced spin-density
+matrix including precessional dynamics around internal spin-orbit and exchange
+fields as well as the electron-electron Coulomb scattering for densities and
+spin coherences. Based on a comparison with numerical solutions of the full
+Boltzmann scattering integrals, we establish that the $k$-resolved reduced
+spin-density matrix dynamics are well described using a simpler generalized
+relaxation-time ansatz for the reduced spin-density matrix. This ansatz allows
+one to relate the complicated scattering dynamics underlying the
+demagnetization dynamics to a physically meaningful momentum relaxation time
+$\tau$. Our approach reproduces the behaviors of the demagnetization time
+$\tau_{m} \propto 1/\tau$ and $\tau_{m} \propto \tau$ for the limits of short
+and long $\tau$, respectively, and is also valid for the intermediate regime.
+The ansatz thus provides a tool to include the correct demagnetization behavior
+in approaches that treat other contributions to the magnetization dynamics such
+as transport or magnon/phonon dynamics.",2208.02356v1
+1999-09-02,The MHD Kelvin-Helmholtz Instability III: The Role of Sheared Magnetic Field in Planar Flows,"We have carried out simulations of the nonlinear evolution of the
+magnetohydrodynamic (MHD) Kelvin-Helmholtz (KH) instability for compressible
+fluids in $2\frac{1}{2}$-dimensions, extending our previous work by Frank et al
+(1996) and Jones \etal (1997). In the present work we have simulated flows in
+the x-y plane in which a ``sheared'' magnetic field of uniform strength
+``smoothly'' rotates across a thin velocity shear layer from the z direction to
+the x direction, aligned with the flow field. We focus on dynamical evolution
+of fluid features, kinetic energy dissipation, and mixing of the fluid between
+the two layers, considering their dependence on magnetic field strength for
+this geometry. The introduction of magnetic shear can allow a Cat's Eye-like
+vortex to form, even when the field is stronger than the nominal linear
+instability limit given above. For strong fields that vortex is asymmetric with
+respect to the preliminary shear layer, however, so the subsequent dissipation
+is enhanced over the uniform field cases of comparable field strength. In fact,
+so long as the magnetic field achieves some level of dynamical importance
+during an eddy turnover time, the asymmetries introduced through the magnetic
+shear will increase flow complexity, and, with that, dissipation and mixing.
+The degree of the fluid mixing between the two layers is strongly influenced by
+the magnetic field strength. Mixing of the fluid is most effective when the
+vortex is disrupted by magnetic tension during transient reconnection, through
+local chaotic behavior that follows.",9909033v1
+2001-03-21,Spectra and Growth Rates of Fluctuating Magnetic Fields in the Kinematic Dynamo Theory with Large Magnetic Prandtl Numbers,"The existence of a weak galactic magnetic field has been repeatedly confirmed
+by observational data. The origin of this field has not as yet been explained
+in a fully satisfactory way and represents one of the main challenges of the
+astrophysical dynamo theory. In both the galactic dynamo theory and the
+primordial-origin theory, a major influence is exerted by the small-scale
+magnetic fluctuations. This article is devoted to constructing a systematic
+second-order statistical theory of such small-scale fields. The statistics of
+these fields are studied in the kinematic approximation and for the case of
+large Prandtl numbers, which is relevant for the galactic and protogalactic
+plasma. The advecting velocity field is assumed to be Gaussian and short-time
+correlated. Theoretical understanding of this kinematic dynamo model is a
+necessary prerequisite for any prospective nonlinear dynamo theory. The theory
+is developed for an arbitrary degree of compressibility and formally in d
+dimensions, which generalizes the previously known results, elicits the
+structure of the solutions, and uncovers a number of new effects. The magnetic
+energy spectra are studied as they grow and spread over scales during the
+initial stage of the field amplification. Exact Green's-function solutions are
+obtained. The spectral theory is supplemented by the study of magnetic-field
+correlation functions in the configuration space, where the dynamo problem can
+be mapped onto a particular one-dimensional quantum-mechanical problem. The
+latter approach is most suitable for the description of the kinematic dynamo in
+the long-time limit, i.e. when the magnetic excitation has spread over all
+scales present in the system. A simple way of calculating the growth rates of
+the magnetic fields in this long-time limit is proposed.",0103333v2
+2005-01-21,Magnetic Flux Tube Reconnection: Tunneling Versus Slingshot,"The discrete nature of the solar magnetic field as it emerges into the corona
+through the photosphere indicates that it exists as isolated flux tubes in the
+convection zone, and will remain as discrete flux tubes in the corona until it
+collides and reconnects with other coronal fields. Collisions of these flux
+tubes will in general be three dimensional, and will often lead to
+reconnection, both rearranging the magnetic field topology in fundamental ways,
+and releasing magnetic energy. With the goal of better understanding these
+dynamics, we carry out a set of numerical experiments exploring fundamental
+characteristics of three dimensional magnetic flux tube reconnection. We first
+show that reconnecting flux tubes at opposite extremes of twist behave very
+differently: in some configurations, low twist tubes slingshot while high twist
+tubes tunnel. We then discuss a theory explaining these differences: by
+assuming helicity conservation during the reconnection one can show that at
+high twist, tunneled tubes reach a lower magnetic energy state than slingshot
+tubes, whereas at low twist the opposite holds. We test three predictions made
+by this theory. 1) We find that the level of twist at which the transition from
+slingshot to tunnel occurs is about two to three times higher than predicted on
+the basis of energetics and helicity conservation alone, probably because the
+dynamics of the reconnection play a large role as well. 2) We find that the
+tunnel occurs at all flux tube collision angles predicted by the theory. 3) We
+find that the amount of magnetic energy a slingshot or a tunnel reconnection
+releases agrees reasonably well with the theory, though at the high
+resistivities we have to use for numerical stability, a significant amount of
+magnetic energy is lost to diffusion, independent of reconnection.",0501473v1
+2007-06-21,Bubble-Wrap for Bullets: The Stability Imparted By A Thin Magnetic Layer,"There has been significant recent work which examines a situation where a
+thin magnetic layer is `draped' over a core merging into a larger cluster; the
+same process also appears to be at work at a bubble rising from the cluster
+centre. Such a thin magnetic layer could thermally isolate the core from the
+cluster medium, but only if the same shear process which generates the layer
+does not later disrupt it. On the other hand, if the magnetized layer can
+stabilize against the shear instabilities, then the magnetic layer can have the
+additional dynamical effect of reducing the shear-driven mixing of the core's
+material during the merger process. These arguments could equally well to
+underdense cluster bubbles, which would be even more prone to disruption. While
+it is well known that magnetic fields can suppress instabilities, it is less
+clear that a thin layer can suppress instabilities on scales significantly
+larger than its thickness. Here we consider the stability imparted by a thin
+magnetized layer. Such a layer can have a significant stabilizing effect even
+on modes with wavelengths much larger than the thickness of the layer l; to
+stabilize modes ten times larger requires only that the Alfv\'en speed in the
+magnetized layer is comparable to the relevant destabilizing velocity -- the
+shear velocity in the case of pure Kelvin-Helmholtz like instability, or a
+typical buoyancy velocity in the case of pure Rayleigh-Taylor. We confirm our
+calculations with two-dimensional numerical experiments using the Athena code.",0706.3216v3
+2008-04-23,Three Dimensional Magnetohydrodynamical Simulations of Core Collapse Supernova,"We show three-dimensional magnetohydrodynamical simulations of core collapse
+supernova in which the progenitor has magnetic fields inclined to the rotation
+axis. The simulations employed a simple empirical equation of state in which
+the pressure of degenerate gas is approximated by piecewise polytropes for
+simplicity. Neither energy loss due to neutrino is taken into account for
+simplicity. The simulations start from the stage of dynamical collapse of an
+iron core. The dynamical collapse halts at $ t $ = 189 ms by the pressure of
+high density gas and a proto-neutron star (PNS) forms. The evolution of PNS was
+followed about 40 milli-seconds in typical models. When the initial rotation is
+mildly fast and the initial magnetic fields are mildly strong, bipolar jets are
+launched from an upper atmosphere ($ r \sim 60 {\rm km} $) of the PNS. The jets
+are accelerated to $ \sim 3 \times 10 ^4 $ km s$^{-1}$, which is comparable to
+the escape velocity at the foot point. The jets are parallel to the initial
+rotation axis. Before the launch of the jets, magnetic fields are twisted by
+rotation of the PNS. The twisted magnetic fields form torus-shape multi-layers
+in which the azimuthal component changes alternately. The formation of magnetic
+multi-layers is due to the initial condition in which the magnetic fields are
+inclined with respect to the rotation axis. The energy of the jet depends only
+weakly on the initial magnetic field assumed. When the initial magnetic fields
+are weaker, the time lag is longer between the PNS formation and jet ejection.
+It is also shown that the time lag is related to the Alfv\'en transit time.
+Although the nearly spherical prompt shock propagates outward in our
+simulations, it is ...",0804.3700v3
+2010-01-12,Nonlinear Processes in Coronal Heating and Slow Solar Wind Acceleration,"This work consists of two parts: the first devoted to the study of the
+heating of the magnetically confined Solar Corona, and the second to the
+acceleration of the Slow Solar Wind.
+  Direct 3D reduced MHD simulations are presented. They model the heating of
+coronal loops in the solar atmosphere via the tangling of coronal field lines
+by photospheric footpoints motions within the framework of the ""Parker
+scenario"". We have derived scalings of physical quantities with loop length,
+and the ratio of photospheric to coronal Alfven velocities. The development of
+a turbulent dynamics makes the dissipation rate independent of the Reynolds
+number. The dynamics in physical space are desribed by weak turbulence, which
+develops when an MHD system is embedded in a strong axial magnetic field.
+  The slow wind originates in and around the coronal streamer belt. The LASCO
+instrument onboard the SOHO spacecraft has observed plasma density enhancements
+forming beyond the cusp of a helmet streamer. Previous theoretical models for
+the formation and initial motion of these density enhancements are improved.
+  The average expansion suffered by a parcel of plasma propagating outward, and
+the diamagnetic force due to the overall magnetic field radial gradients are
+now included. It is found that the magnetized wake configuration is resistively
+unstable, that an outward accelerating magnetic island develops at the center
+of the streamer, and that density enhancements occur within the magnetic
+islands. The values of the acceleration and density contrasts can be in good
+agreement with LASCO observations, provided the spherical divergence of the
+magnetic lines starts beyond a critical distance from the Sun. This result
+provides a constraint on the topology of the magnetic field.",1001.1770v1
+2012-07-25,Bipolar jets launched from magnetically diffusive accretion disks. I. Ejection efficiency vs field strength and diffusivity,"We investigate the launching of jets and outflows from magnetically diffusive
+accretion disks. Using the PLUTO code we solve the time-dependent resistive MHD
+equations taking into account the disk and jet evolution simultaneously. The
+main question we address is which kind of disks do launch jets and which kind
+of disks do not? In particular, we study how the magnitude and distribution of
+the (turbulent) magnetic diffusivity affect mass loading and jet acceleration.
+We have applied a turbulent magnetic diffusivity based on \alpha-prescription,
+but have also investigate examples where the scale height of diffusivity is
+larger than that of the disk gas pressure. We further investigate how the
+ejection efficiency is governed by the magnetic field strength. Our simulations
+last for up to 5000 dynamical time scales corresponding to 900 orbital periods
+of the inner disk. As a general result we observe a continuous and robust
+outflow launched from the inner part of the disk, expanding into a collimated
+jet of super fast magneto-sonic speed. For long time scales the disk internal
+dynamics changes, as due to outflow ejection and disk accretion the disk mass
+decreases. For magneto-centrifugally driven jets we find that for i) less
+diffusive disks, ii) a stronger magnetic field, iii) a low poloidal
+diffusivity, or a iv) lower numerical diffusivity (resolution), the mass
+loading of the outflow is increased - resulting in more powerful jets with high
+mass flux. For weak magnetization the (weak) outflow is driven by the magnetic
+pressure gradient. We further investigate the jet asymptotic velocity and the
+jet rotational velocity in respect of the different launching scenarios. We
+find a lower degree of jet collimation than previous studies, most probably due
+to our revised outflow boundary condition.",1207.6086v1
+2013-05-02,Magnetic monopole field exposed by electrons,"Magnetic monopoles have provided a rich field of study, leading to a wide
+area of research in particle physics, solid state physics, ultra-cold gases,
+superconductors, cosmology, and gauge theory. So far, no true magnetic
+monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the
+central results of quantum physics, shows however, that an effective monopole
+field can be produced. Understanding the effects of such a monopole field on
+its surroundings is crucial to its observation and provides a better grasp of
+fundamental physical theory. We realize the diffraction of fast electrons at a
+magnetic monopole field generated by a nanoscopic magnetized ferromagnetic
+needle. Previous studies have been limited to theoretical semiclassical optical
+calculations of the motion of electrons in such a monopole field. Solid state
+systems like the recently studied 'spin ice' provide a constrained system to
+study similar fields, but make it impossible to separate the monopole from the
+material. Free space diffraction helps to understand the dynamics of the
+electron-monopole system without the complexity of a solid state system. The
+use of a simple object such as a magnetized needle will allow various areas of
+physics to use the general dynamical effects of monopole fields without
+requiring a monopole particle or specific solids which have internal
+monopole-like properties. The experiment performed here shows that even without
+a true magnetic monopole particle, the theoretical background on monopoles
+serves as a basis for experiments and can be applied to efficiently create
+electron vortices. Various predictions about angular momentum and general field
+effects can readily be studied using the available equipment. This realization
+provides insights for the scientific community on how to detect magnetic
+monopoles in high energy collisions, cosmological processes, or novel
+materials.",1305.0570v2
+2013-06-10,Interpreting Eruptive Behavior in NOAA AR 11158 via the Region's Magnetic Energy and Relative Helicity Budgets,"In previous works we introduced a nonlinear force-free method that
+self-consistently calculates the instantaneous budgets of free magnetic energy
+and relative magnetic helicity in solar active regions (ARs). Calculation is
+expedient and practical, using only a single vector magnetogram per
+computation. We apply this method to a timeseries of 600 high-cadence vector
+magnetograms of the eruptive NOAA AR 11158 acquired by the Helioseismic and
+Magnetic Imager onboard the Solar Dynamics Observatory over a five-day
+observing interval. Besides testing our method extensively, we use it to
+interpret the dynamical evolution in the AR, including eruptions. We find that
+the AR builds large budgets of both free magnetic energy and relative magnetic
+helicity, sufficient to power many more eruptions than the ones it gave within
+the interval of interest. For each of these major eruptions, we find
+eruption-related decreases and subsequent free-energy and helicity budgets that
+are consistent with the observed eruption (flare and coronal-mass-ejection
+[CME]) sizes. In addition, we find that (1) evolution in the AR is consistent
+with the recently proposed (free) energy - (relative) helicity diagram of solar
+ARs, (2) eruption-related decreases occur {\it before} the flare and the
+projected CME-launch times, suggesting that CME progenitors precede flares, and
+(3) self-terms of free energy and relative helicity most likely originate from
+respective mutual-terms, following a progressive mutual-to-self conversion
+pattern that most likely stems from magnetic reconnection. This results in the
+non-ideal formation of increasingly helical pre-eruption structures and
+instigates further research on the triggering of solar eruptions with magnetic
+helicity firmly placed in the eruption cadre.",1306.2135v2
+2014-08-24,Thickness dependence of dynamic and static magnetic properties of pulsed laser deposited La$_{0.7}$Sr$_{0.3}$MnO$_3$ films on SrTiO$_3$(001),"We present a comprehensive study of the thickness dependence of static and
+magneto-dynamic magnetic properties of La$_{0.7}$Sr$_{0.3}$MnO$_3$. Epitaxial
+pulsed laser deposited La$_{0.7}$Sr$_{0.3}$MnO$_3$ / SrTiO$_3$(001) thin films
+in the range from 3 unit cells (uc) to 40 uc (1.2 - 16 nm) have been
+investigated through ferromagnetic resonance spectroscopy (FMR) and SQUID
+magnetometry at variable temperature. Magnetodynamically, three different
+thickness, $d$, regimes are identified: 20 uc $\lesssim d$ uc where the system
+is bulk like, a transition region 8 uc $\le d \lesssim 20$ uc where the FMR
+line width and position depend on thickness and $d=6$ uc which displays
+significantly altered magnetodynamic properties, while still displaying bulk
+magnetization. Magnetization and FMR measurements are consistent with a
+nonmagnetic volume corresponding to $\sim$ 4 uc. We observe a reduction of
+Curie temperature ($T_C$) with decreasing thickness, which is coherent with a
+mean field model description. The reduced ordering temperature also accounts
+for the thickness dependence of the magnetic anisotropy constants and resonance
+fields. The damping of the system is strongly thickness dependent, and is for
+thin films dominated by thickness dependent anisotropies, yielding both a
+strong 2-magnon scattering close to $T_c$ and a low temperature broadening. For
+the bulk like samples a large part of the broadening can be linked to spread in
+magnetic anisotropies attributed to crystal imperfections/domain boundaries of
+the bulk like film.",1408.5631v1
+2015-01-22,A Measure of Monopole Inertia in the Quantum Spin Ice Yb$_2$Ti$_2$O$_7$,"An important and continuing theme of modern solid state physics is the
+realization of exotic excitations in materials (e.g. quasiparticles) that have
+no analogy (or have not yet been observed) in the actual physical vacuum of
+free space. Although they are not fundamental particles, such quasiparticles do
+constitute the most basic description of the excited states of the ""vacuum"" in
+which they reside. In this regard the magnetic textures of the excited states
+of spin ices, magnetic pyrochlore oxides with dominant Ising interactions, are
+proposed to be modeled as effective magnetic charge monopoles. Recent inelastic
+neutron scattering experiments have established the pyrochlore material
+Yb$_2$Ti$_2$O$_7$ (YbTO) as a quantum spin ice, where in addition to the Ising
+interactions there are substantial transverse terms that may induce quantum
+dynamics and - in principle - coherent monopole motion. Here we report a
+combined time domain terahertz spectroscopy (TDTS) and microwave cavity study
+of YbTO to probe its complex dynamic magnetic susceptibility. We find that the
+form of the susceptibility is consistent with monopole motion and a magnetic
+monopole conductivity can be defined and measured. Using the unique phase
+sensitive capabilities of these techniques, we observe a sign change in the
+reactive part of the magnetic response. In generic models of monopole motion
+this is only possible through introducing inertial effects, e.g. a mass
+dependent term, to the equations of motion. Analogous to conventional electric
+charge systems, measurement of the conductivity's spectral weight allows us to
+derive a value for the magnetic monopole mass, which we find to be
+approximately 1800 electron masses. Our results establish the magnetic
+monopoles of quantum spin ice as true coherently propagating quasiparticles of
+this system.",1501.05638v1
+2015-02-24,Ultra-high-resolution Observations of MHD Waves in Photospheric Magnetic Structures,"Here we review the recent progress made in the detection, examination,
+characterisation and interpretation of oscillations manifesting in small-scale
+magnetic elements in the solar photosphere. This region of the Sun's atmosphere
+is especially dynamic, and importantly, permeated with an abundance of magnetic
+field concentrations. Such magnetic features can span diameters of hundreds to
+many tens of thousands of km, and are thus commonly referred to as the
+`building blocks' of the magnetic solar atmosphere. However, it is the smallest
+magnetic elements that have risen to the forefront of solar physics research in
+recent years. Structures, which include magnetic bright points, are often at
+the diffraction limit of even the largest of solar telescopes. Importantly, it
+is the improvements in facilities, instrumentation, imaging techniques and
+processing algorithms during recent years that have allowed researchers to
+examine the motions, dynamics and evolution of such features on the smallest
+spatial and temporal scales to date. It is clear that while these structures
+may demonstrate significant magnetic field strengths, their small sizes make
+them prone to the buffeting supplied by the ubiquitous surrounding convective
+plasma motions. Here, it is believed that magnetohydrodynamic waves can be
+induced, which propagate along the field lines, carrying energy upwards to the
+outermost extremities of the solar corona. Such wave phenomena can exist in a
+variety of guises, including fast and slow magneto-acoustic modes, in addition
+to Alfven waves. Coupled with rapid advancements in magnetohydrodynamic wave
+theory, we are now in an ideal position to thoroughly investigate how wave
+motion is generated in the solar photosphere, which oscillatory modes are most
+prevalent, and the role that these waves play in supplying energy to various
+layers of the solar atmosphere.",1502.06960v1
+2016-05-23,Dynamical model for spindown of solar-type stars,"Since their formation, stars slow down their rotation rates by the removal of
+angular momentum from their surfaces, e.g. via stellar winds. Despite the
+complexity of the processes involved, a traditional model, where the removal of
+angular momentum loss by magnetic fields is prescribed, has provided a useful
+framework to understand observational relations between stellar rotation and
+age and magnetic field strength. Here, a spindown model is proposed where loss
+of angular momentum by magnetic fields is evolved dynamically, instead of being
+kinematically prescribed. To this end, we evolve the stellar rotation and
+magnetic field simultaneously over stellar evolution time by extending our
+previous work on a dynamo model which incorporates the nonlinear feedback
+mechanisms on rotation and magnetic fields. Our extended model reproduces key
+observations and explains the presence of the two branches of (fast and slow
+rotating) stars which have different relations between rotation rate $\Omega$
+vs. time (age), magnetic field strength $|B|$ vs. rotation rate, and frequency
+of magnetic field $\omega_{cyc}$ vs. rotation rate. For fast rotating stars we
+find: (i) an exponential spindown $\Omega \propto e^{-1.35t}$, with $t$
+measured in Gyrs, (ii) $|B|$ saturates for higher rotation rate, (iii)
+$\omega_{cyc} \propto \Omega^{0.85}$. For slow rotating stars we obtain: (i) a
+power law spindown $\Omega \propto t^{-0.52}$, (ii) $|B|$ scales almost
+linearly with rotation rate, (iii) $\omega_{cyc} \propto \Omega^{1.16}$. The
+results obtained are in good agreement with observations. The Vaughan-Preston
+gap is consistently explained in our model by the shortest spindown timescale
+in this transition from fast to slow rotators. Our results highlight the
+importance of self-regulation of magnetic fields and rotation by direct and
+indirect interactions involving nonlinear feedback in stellar evolution.",1605.07125v2
+2017-04-30,Laminar and turbulent dynamos in chiral magnetohydrodynamics-I: Theory,"The magnetohydrodynamic (MHD) description of plasmas with relativistic
+particles necessarily includes an additional new field, the chiral chemical
+potential associated with the axial charge (i.e., the number difference between
+right- and left-handed relativistic fermions). This chiral chemical potential
+gives rise to a contribution to the electric current density of the plasma
+(\emph{chiral magnetic effect}). We present a self-consistent treatment of the
+\emph{chiral MHD equations}, which include the back-reaction of the magnetic
+field on a chiral chemical potential and its interaction with the plasma
+velocity field. A number of novel phenomena are exhibited. First, we show that
+the chiral magnetic effect decreases the frequency of the Alfv\'{e}n wave for
+incompressible flows, increases the frequencies of the Alfv\'{e}n wave and of
+the fast magnetosonic wave for compressible flows, and decreases the frequency
+of the slow magnetosonic wave. Second, we show that, in addition to the
+well-known laminar chiral dynamo effect, which is not related to fluid motions,
+there is a dynamo caused by the joint action of velocity shear and chiral
+magnetic effect. In the presence of turbulence with vanishing mean kinetic
+helicity, the derived mean-field chiral MHD equations describe turbulent
+large-scale dynamos caused by the chiral alpha effect, which is dominant for
+large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an
+interaction of the chiral magnetic effect and fluctuations of the small-scale
+current produced by tangling magnetic fluctuations (which are generated by
+tangling of the large-scale magnetic field by sheared velocity fluctuations).
+These dynamo effects may have interesting consequences in the dynamics of the
+early universe, neutron stars, and the quark--gluon plasma.",1705.00378v3
+2017-12-22,"Dynamic, magnetic and electronic properties of the C14 Laves phase Nb0.975Fe2.025 compound: Mössbauer-effect study","C14 Laves phase Nb0.975Fe2.025 compound was investigated by means of the
+M\""ossbauer spectroscopy. Spectra were recorded in the temperature range of
+5-300K. Their analysis in terms of three sub spectra yielded information on
+magnetic and lattice dynamical properties of Fe atoms regularly occupying 2a
+and 6h lattice sites and, excessively, 4f sites. No indication of magnetism was
+observed down to the temperature of T=ca.50K, and spectral parameters viz.
+center shift, CS, and the main component of the electric field gradient, Vzz,
+behave regularly. In particular, analysis of CS(T) in terms of the Debye model
+yielded the following values of the Debye temperature, T_D: 453(5) K for the
+site 6h, 544(10) K for the site 2a, 479(4) K for the weighted average over 6h
+and 2a sites, and 363(35) K for the site 4f. Below ca.50K anomalous behavior
+was observed: a broadening of the spectrum appeared indicating thereby a
+transition into a magnetic phase. Analysis of a temperature dependence of the
+hyperfine field, B, associated with the 6h and 2a sub spectra yielded the
+magnetic ordering temperature T_C1=ca.50K for the former and T_C2=ca.31K for
+the latter. The maximum values of the hyperfine field at 5K, Bo, were 8.2 kGs
+and 3.3 kGs, respectively. The Bo-values were used to estimate values the
+underlying magnetic moments, m_Fe(6h)=0.055-0.065 Bohr magneton and
+m_Fe(2a)=0.02-0.025 Bohr magneton. Noteworthy, they are over one order of
+magnitude lower than those theoretically calculated. The CS and Vzz parameters
+showed anomalies in the magnetic phase, in particular the former exhibited a
+strong departure from the Debye model prediction testifying to a significant
+effect of magnetism on the lattice vibrations.",1712.08514v1
+2018-02-15,Characterization of methanol as a magnetic field tracer in star-forming regions,"Magnetic fields play an important role during star formation. Direct magnetic
+field strength observations have proven specifically challenging in the
+extremely dynamic protostellar phase. Because of their occurrence in the
+densest parts of star forming regions, masers, through polarization
+observations, are the main source of magnetic field strength and morphology
+measurements around protostars. Of all maser species, methanol is one of the
+strongest and most abundant tracers of gas around high-mass protostellar disks
+and in outflows. However, as experimental determination of the magnetic
+characteristics of methanol has remained largely unsuccessful, a robust
+magnetic field strength analysis of these regions could hitherto not be
+performed. Here we report a quantitative theoretical model of the magnetic
+properties of methanol, including the complicated hyperfine structure that
+results from its internal rotation. We show that the large range in values of
+the Land\'{e} g-factors of the hyperfine components of each maser line lead to
+conclusions which differ substantially from the current interpretation based on
+a single effective g-factor. These conclusions are more consistent with other
+observations and confirm the presence of dynamically important magnetic fields
+around protostars. Additionally, our calculations show that (non-linear) Zeeman
+effects must be taken into account to further enhance the accuracy of
+cosmological electron-to-proton mass ratio determinations using methanol.",1802.05764v1
+2018-05-17,Large magneto-optical Kerr effect and imaging of magnetic octupole domains in an antiferromagnetic metal,"When a polarized light beam is incident upon the surface of a magnetic
+material, the reflected light undergoes a polarization rotation. This
+magneto-optical Kerr effect (MOKE) has been intensively studied in a variety of
+ferro- and ferrimagnetic materials because it provides a powerful probe for
+electronic and magnetic properties as well as for various applications
+including magneto-optical recording. Recently, there has been a surge of
+interest in antiferromagnets (AFMs) as prospective spintronic materials for
+high-density and ultrafast memory devices, owing to their vanishingly small
+stray field and orders of magnitude faster spin dynamics compared to their
+ferromagnetic counterparts. In fact, the MOKE has proven useful for the study
+and application of the antiferromagnetic (AF) state. Although limited to
+insulators, certain types of AFMs are known to exhibit a large MOKE, as they
+are weak ferromagnets due to canting of the otherwise collinear spin structure.
+Here we report the first observation of a large MOKE signal in an AF metal at
+room temperature. In particular, we find that despite a vanishingly small
+magnetization of $M \sim$0.002 $\mu_{\rm B}$/Mn, the non-collinear AF metal
+Mn$_3$Sn exhibits a large zero-field MOKE with a polar Kerr rotation angle of
+20 milli-degrees, comparable to ferromagnetic metals. Our first-principles
+calculations have clarified that ferroic ordering of magnetic octupoles in the
+non-collinear Neel state may cause a large MOKE even in its fully compensated
+AF state without spin magnetization. This large MOKE further allows imaging of
+the magnetic octupole domains and their reversal induced by magnetic field. The
+observation of a large MOKE in an AF metal should open new avenues for the
+study of domain dynamics as well as spintronics using AFMs.",1805.06758v1
+2018-08-10,Hot Grain Dynamics by Electric Charging and Magnetic Trapping in Debris Disks,"The recent discovery of hot dust grains in the vicinity of main-sequence
+stars has become a hot issue among the scientific community of debris disks.
+Hot grains must have been enormously accumulated near their sublimation zones,
+but it is a mystery how such a high concentration of hot grains is sustained.
+The most difficult conundrum is that the size of hot dust grains is estimated
+to lie in the submicrometer range, while submicrometer-sized grains are
+instantly swept away from near-stellar environments by stellar radiation
+pressure. One and only mechanism proposed for prolonging the residence time of
+hot grains in the near-stellar environments is trapping of charged
+nanoparticles by stellar magnetic fields. We revisit the model of magnetic
+grain trapping around main-sequence stars of various spectral classes by taking
+into account sublimation and electric charging of the grains. The model of
+magnetic grain trapping predicts that hot dust grains are present in the
+vicinity of main-sequence stars with high rotation velocities and intermediate
+magnetic-field strengths. On the contrary, we find that the detection of hot
+dust grains has no correlation with the rotation velocities of central stars
+nor the magnetic field strengths of the stars. Our numerical evaluation of
+electric grain charging indicates that the surface potential of
+submicrometer-sized grains in the vicinity of main-sequence stars is typically
+4-5 V, which is one order of magnitude smaller than the value assumed by the
+model of magnetic grain trapping. On the basis of our numerical simulation on
+sublimation of dust grains in the vicinity of a star, it turns out that their
+lives end due to sublimation in a timescale much shorter than the period of one
+revolution at the gyroradius. It is, therefore, infeasible to dynamically
+extend the dwell time of hot grains inside the sublimation zone by magnetic
+trapping, ...",1808.03389v1
+2020-01-11,Comparative Study of Data-driven Solar Coronal Field Models Using a Flux Emergence Simulation as a Ground-truth Data Set,"For a better understanding of magnetic field in the solar corona and dynamic
+activities such as flares and coronal mass ejections, it is crucial to measure
+the time-evolving coronal field and accurately estimate the magnetic energy.
+Recently, a new modeling technique called the data-driven coronal field model,
+in which the time evolution of magnetic field is driven by a sequence of
+photospheric magnetic and velocity field maps, has been developed and revealed
+the dynamics of flare-productive active regions. Here we report on the first
+qualitative and quantitative assessment of different data-driven models using a
+magnetic flux emergence simulation as a ground-truth (GT) data set. We compare
+the GT field with those reconstructed from the GT photospheric field by four
+data-driven algorithms. It is found that, at least, the flux rope structure is
+reproduced in all coronal field models. Quantitatively, however, the results
+show a certain degree of model dependence. In most cases, the magnetic energies
+and relative magnetic helicity are comparable to or at most twice of the GT
+values. The reproduced flux ropes have a sigmoidal shape (consistent with GT)
+of various sizes, a vertically-standing magnetic torus, or a packed structure.
+The observed discrepancies can be attributed to the highly non-force-free input
+photospheric field, from which the coronal field is reconstructed, and to the
+modeling constraints such as the treatment of background atmosphere, the bottom
+boundary setting, and the spatial resolution.",2001.03721v1
+2020-07-30,Large-scale magnetic field in the Monoceros OB-1 East molecular cloud,"We study the large-scale magnetic field structure and its interplay with the
+gas dynamics in the Monoceros OB1 East molecular cloud. We combine observations
+of dust polarised emission from the Planck telescope and CO molecular line
+emission observations from the Taeduk Radio Astronomy Observatory 14-metre
+telescope. We calculate the strength of the plane-of-the-sky magnetic field
+using a modified Chandrasekhar-Fermi method and estimate mass over flux ratios
+in different regions of the cloud. We use the comparison of the velocity and
+intensity gradients of the molecular line observations with the polarimetric
+observations to trace dynamically active regions. The molecular complex shows
+an ordered large-scale plane-of-the-sky magnetic field structure. In the
+Northern part, it is mostly orientated along the filamentary structures while
+the Southern part shows at least two regions with distinct magnetic field
+orientations. We find that in the Northern filaments the magnetic field is
+unlikely to provide support against fragmentation at large scales. Our analysis
+reveals a shock region in the Northern part of the complex right in-between two
+filamentary clouds which were previously suggested to be in collision.
+Moreover, the shock seems to extend farther towards the Western part of the
+complex. In the Southern part, we find that either the magnetic field guides
+the accretion of interstellar matter towards the cloud or it was dragged by the
+matter towards the densest regions. The large-scale magnetic field in Monoceros
+OB-1 East molecular clouds is tightly connected to the global structure of the
+complex and, in the Northern part, it seems to be dominated by gravity and
+turbulence, while in the Southern part it influences the structuring of matter.",2007.15344v2
+2020-12-02,Synthesis and Characterization of Sodium Iron Antimonate Na2FeSbO5 One-Dimensional Antiferromagnetic Chain Compound with a Spin Glass Ground State,"A new oxide, sodium iron antimonate, Na2FeSbO5, was synthesized and
+structurally characterized, and its static and dynamic magnetic properties were
+comprehensively studied both experimentally by dc and ac magnetic
+susceptibility, magnetization, specific heat, electron spin resonance (ESR) and
+Moessbauer measurements, and theoretically by density functional calculations.
+The resulting single-crystal structure (a = 15.6991(9) A; b = 5.3323 (4) A; c =
+10.8875(6) A; S.G. Pbna) consists of edge-shared SbO6 octahedral chains, which
+alternate with vertex-linked, magnetically active FeO4 tetrahedral chains. The
+57Fe Moessbauer spectra confirmed the presence of high-spin Fe3+ (3d5) ions in
+a distorted tetrahedral oxygen coordination. The magnetic susceptibility and
+specific heat data show the absence of a long-range magnetic ordering in
+Na2FeSbO5 down to 2 K, but ac magnetic susceptibility unambigously demonstrates
+spin-glass-type behavior with a unique two-step freezing at Tf1 about 80 K and
+Tf2 about 35 K. Magnetic hyperfine splitting of 57Fe Moessbauer spectra was
+observed below T* about 104 K (Tf1 < T*). The spectra just below T* (Tf1 < T <
+T*) exhibit a relaxation behavior caused by critical spin fluctuations,
+indicating the existence of short-range correlations. The stochastic model of
+ionic spin relaxation was used to account for the shape of the Moessbauer
+spectra below the freezing temperature. A complex slow dynamics is further
+supported by ESR data revealing two different absorption modes presumably
+related to ordered and disordered segments of spin chains. The data imply a
+spin-cluster ground state for Na2FeSbO5.",2012.01106v1
+2021-10-22,Jet Launching from Merging Magnetized Binary Neutron Stars with Realistic Equations of State,"We perform general relativistic, magnetohydrodynamic (GRMHD) simulations of
+binary neutron stars in quasi-circular orbit that merge and undergo delayed or
+prompt collapse to a black hole (BH). The stars are irrotational and modeled
+using an SLy or an H4 nuclear equation of state. To assess the impact of the
+initial magnetic field configuration on jet launching, we endow the stars with
+a purely poloidal magnetic field that is initially unimportant dynamically and
+is either confined to the stellar interior or extends from the interior into
+the exterior as in typical pulsars. Consistent with our previous results, we
+find that only the BH + disk remnants originating from binaries that form
+hypermassive neutron stars (HMNSs) and undergo delayed collapse can drive
+magnetically-powered jets. We find that the closer the total mass of the binary
+is to the threshold value for prompt collapse, the shorter is the time delay
+between the gravitational wave peak amplitude and jet launching. This time
+delay also strongly depends on the initial magnetic field configuration. We
+also find that seed magnetic fields confined to the stellar interior can launch
+a jet over $\sim 25\,\rm ms$ later than those with pulsar-like magnetic fields.
+The lifetime of the jet [$\Delta t\lesssim 150\,\rm ms$] and its outgoing
+Poynting luminosity [$L_{\rm EM}\sim 10^{52\pm 1}\rm erg/s$] are consistent
+with typical short gamma-ray burst central engine lifetimes, as well as with
+the Blandford--Znajek mechanism for launching jets and their associated
+Poynting luminosities. Our numerical results also suggest that the dynamical
+ejection of matter can be enhanced by the magnetic field. Therefore, GRMHD
+studies are required to fully understand kilonova signals from GW170818-like
+events.",2110.11968v2
+2022-02-25,Energy balance and Alfvén Mach numbers in compressible magnetohydrodynamic turbulence with a large-scale magnetic field,"Energy equipartition is a powerful theoretical tool for understanding
+astrophysical plasmas. It is invoked, for example, to measure magnetic fields
+in the interstellar medium (ISM), as evidence for small-scale turbulent dynamo
+action, and, in general, to estimate the energy budget of star-forming
+molecular clouds. In this study we motivate and explore the role of the
+volume-averaged root-mean-squared (rms) magnetic coupling term between the
+turbulent, $\delta\mathbf{B}$ and large-scale, $\mathbf{B}_0$ fields, $\left<
+(\delta\mathbf{B}\cdot\mathbf{B}_0)^{2} \right>^{1/2}_{\mathcal{V}}$. By
+considering the second moments of the energy balance equations we show that the
+rms coupling term is in energy equipartition with the volume-averaged turbulent
+kinetic energy for turbulence with a sub-Alfv\'enic large-scale field. Under
+the assumption of exact energy equipartition between these terms, we derive
+relations for the magnetic and coupling term fluctuations, which provide
+excellent, parameter-free agreement with time-averaged data from 280 numerical
+simulations of compressible MHD turbulence. Furthermore, we explore the
+relation between the turbulent, mean-field and total Alfv\'en Mach numbers, and
+demonstrate that sub-Alfv\'enic turbulence can only be developed through a
+strong, large-scale magnetic field, which supports an extremely
+super-Alfv\'enic turbulent magnetic field. This means that the magnetic field
+fluctuations are significantly subdominant to the velocity fluctuations in the
+sub-Alfv\'enic large-scale field regime. Throughout our study, we broadly
+discuss the implications for observations of magnetic fields and understanding
+the dynamics in the magnetised ISM.",2202.13020v2
+2022-05-30,Sustaining Rabi oscillations by using a phase-tunable image drive,"Recent electron spin resonance experiments on CaWO$_4$:Gd$^{3+}$ and on other
+magnetic impurities have demonstrated that sustained Rabi oscillations can be
+created by driving a magnetic moment with a microwave field frequency slightly
+larger than the Larmor frequency and tuned to the Floquet resonance together
+with another microwave field (image drive). These observations are confirmed by
+the new experimental results reported in this paper. We investigate several
+mechanisms of decoherence and dissipation by using a combination of numerical
+and analytical techniques. The first microscopic model describes a magnetic
+moment in external magnetic fields, interacting with a bath of two-level
+systems acting as a source of decoherence and dissipation. The second model
+describes a collection of the identical, interacting magnetics moments, all
+subject to the same magnetic fields. In this case, the many-body interactions
+causes a decay of the Rabi oscillations. In addition, we also study the effect
+of the inhomogeneity of the microwave radiation on the decay of the Rabi
+oscillations. Our simulation results show that the dynamics of a magnetic
+moment subject to the two microwave fields with different frequencies and in
+contact with an environment is highly nontrivial. We show that under
+appropriate conditions, and in particular at the Floquet resonance, the
+magnetization exhibits sustained Rabi oscillations, in some cases with
+additional beatings. Although these two microscopic models separately describe
+the experimental data well, a simulation study that simultaneously accounts for
+both types of interactions is currently prohibitively costly. To gain further
+insight into the microscopic dynamics of these two different models, we study
+the time dependence of the bath and system energy and of the correlations of
+the spins, data that is not readily accessible experimentally.",2205.14863v1
+2023-11-01,"Misaligned magnetized accretion flows onto spinning black holes: magneto-spin alignment, outflow power and intermittent jets","Magnetic fields regulate black hole (BH) accretion, governing both the inflow
+and outflow dynamics. When a BH becomes saturated with large-scale vertical
+magnetic flux, it enters a magnetically-arrested disk (MAD) state. The
+dynamically-important BH magnetic flux powers highly efficient relativistic
+outflows (or jets) and sporadically erupts from the BH into the disk midplane.
+Here we explore the evolution of MADs when the BH and gas angular momentum are
+misaligned, which is expected to be more common. Using numerical simulations,
+we find that jets from rapidly spinning, prograde BHs force the inner accretion
+flow into alignment with the BH spin via the magneto-spin alignment mechanism
+for disks initially misaligned at $\mathcal{T}\lesssim 60^{\circ}$. Extremely
+misaligned MAD disks, on the other hand, exhibit intermittent jets that blow
+out parts of the disk to $\approx 100$ gravitational radii before collapsing,
+leaving behind hot cavities and magnetized filaments. These intermittent jet
+mechanism forms a mini-feedback cycle and could explain some cases of X-ray and
+radio quasi-periodic eruptions observed in dim AGN. Further, we find that (i)
+for BHs with low power jets, the BH spin and initial disk tilt angle changes
+the amount of horizon magnetic flux, and (ii) geometrically-thick, misaligned
+accretion flows do not undergo sustained Lense-Thirring (LT) precession.
+Thereby, we suggest that low-luminosity accreting BHs ($\dot{M}\ll 10^{-3}
+\dot{M}_{\rm Edd}$) are not likely to exhibit quasi-periodic oscillations in
+lightcurves due to LT precession, in agreement with observations of BH X-ray
+binaries and AGN in the low-hard/quiescent state. Instead, we suggest that
+magnetic flux eruptions can mimic precession-like motion, such as observed in
+the M87 jet, by driving large-scale surface waves in the jets.",2311.00432v1
+2023-12-04,Magnetic Fields in the Central Molecular Zone Influenced by Feedback and Weakly Correlated with Star Formation,"Magnetic fields of molecular clouds in the Central Molecular Zone (CMZ) have
+been relatively underobserved at sub-parsec resolution. Here we report
+JCMT/POL2 observations of polarized dust emission in the CMZ, which reveal
+magnetic field structures in dense gas at ~0.5 pc resolution. The eleven
+molecular clouds in our sample including two in the western part of the CMZ
+(Sgr C and a far-side cloud candidate), four around the Galactic longitude 0
+(the 50 km s-1 cloud, CO0.02-0.02, the `Stone' and the `Sticks & Straw' among
+the Three Little Pigs), and five along the Dust Ridge (G0.253+0.016, clouds b,
+c, d, and e/f), for each of which we estimate the magnetic field strength using
+the angular dispersion function method. The morphologies of magnetic fields in
+the clouds suggest potential imprints of feedback from expanding H II regions
+and young massive star clusters. A moderate correlation between the total viral
+parameter versus the star formation rate and the dense gas fraction of the
+clouds is found. A weak correlation between the mass-to-flux ratio and the star
+formation rate, and a weak anti-correlation between the magnetic field and the
+dense gas fraction are also found. Comparisons between magnetic fields and
+other dynamic components in clouds suggest a more dominant role of self-gravity
+and turbulence in determining the dynamical states of the clouds and affecting
+star formation at the studied scales.",2312.01776v2
+2007-05-12,"A case for variational geomagnetic data assimilation: insights from a one-dimensional, nonlinear, and sparsely observed MHD system","Secular variations of the geomagnetic field have been measured with a
+continuously improving accuracy during the last few hundred years, culminating
+nowadays with satellite data. It is however well known that the dynamics of the
+magnetic field is linked to that of the velocity field in the core and any
+attempt to model secular variations will involve a coupled dynamical system for
+magnetic field and core velocity. Unfortunately, there is no direct observation
+of the velocity. Independently of the exact nature of the above-mentioned
+coupled system -- some version being currently under construction -- the
+question is debated in this paper whether good knowledge of the magnetic field
+can be translated into good knowledge of core dynamics. Furthermore, what will
+be the impact of the most recent and precise geomagnetic data on our knowledge
+of the geomagnetic field of the past and future? These questions are cast into
+the language of variational data assimilation, while the dynamical system
+considered in this paper consists in a set of two oversimplified
+one-dimensional equations for magnetic and velocity fields. This toy model
+retains important features inherited from the induction and Navier-Stokes
+equations: non-linear magnetic and momentum terms are present and its linear
+response to small disturbances contains Alfv\'en waves. It is concluded that
+variational data assimilation is indeed appropriate in principle, even though
+the velocity field remains hidden at all times; it allows us to recover the
+entire evolution of both fields from partial and irregularly distributed
+information on the magnetic field. This work constitutes a first step on the
+way toward the reassimilation of historical geomagnetic data and geomagnetic
+forecast.",0705.1777v1
+2008-07-30,The solar chromosphere at high resolution with IBIS. II. Acoustic shocks in the quiet internetwork and the role of magnetic fields,"(Abridged)
+  Aims: We characterize the dynamics of the quiet inter-network chromosphere by
+studying the occurrence of acoustic shocks and their relation with the
+concomitant photospheric structure and dynamics.
+  Methods: We analyze a comprehensive data set that includes high resolution
+chromospheric and photospheric spectra obtained with the IBIS imaging
+spectrometer in two quiet-Sun regions. This is complemented by high-resolution
+sequences of MDI magnetograms of the same targets. From the chromospheric
+spectra we identify the spatio-temporal occurrence of the acoustic shocks. We
+compare it with the photospheric dynamics by means of both Fourier and wavelet
+analysis, and study the influence of magnetic structures.
+  Results: Mid-chromospheric shocks occur as a response to underlying powerful
+photospheric motions at periodicities nearing the acoustic cut-off, consistent
+with 1-D hydrodynamical modeling. However, their spatial distribution within
+the supergranular cells is highly dependent on the local magnetic topology,
+both at the network and internetwork scale. Large portions of the internetwork
+regions undergo very few shocks, as ""shadowed"" by the horizontal component of
+the magnetic field. The latter is betrayed by the presence of chromospheric
+fibrils, observed in the core of the CaII line as slanted structures with
+distinct dynamical properties. The shadow mechanism appears to operate also on
+the very small scales of inter-network magnetic elements, and provides for a
+very pervasive influence of the magnetic field even in the quietest region
+analyzed.",0807.4966v2
+2014-05-15,Dynamic properties of bright points in an active region,"Context. Bright points (BPs) are small-scale, magnetic features ubiquitous
+across the solar surface. Previously, we have observed and noted their
+properties for quiet Sun regions. Here, we determine the dynamic properties of
+BPs using simultaneous quiet Sun and active region data. Methods. High spatial
+and temporal resolution G-band observations of active region AR11372 were
+obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the
+Dunn Solar Telescope. Three subfields of varying polarity and magnetic flux
+density were selected with the aid of magnetograms obtained from the
+Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory.
+Bright points within these subfields were subsequently tracked and analysed.
+Results. It is found that BPs within active regions display attenuated velocity
+distributions with an average horizontal velocity of ~0.6 km/s, compared to the
+quiet region which had an average velocity of 0.9 km/s. Active region BPs are
+also ~21% larger than quiet region BPs and have longer average lifetimes
+(~132s) than their quiet region counterparts (88 s). No preferential flow
+directions are observed within the active region subfields. The diffusion index
+(gamma) is estimated at ~1.2 for the three regions. Conclusions. We confirm
+that the dynamic properties of BPs arise predominately from convective motions.
+The presence of stronger field strengths within active regions is the likely
+reason behind the varying properties observed. We believe that larger amounts
+of magnetic flux will attenuate BP velocities by a combination of restricting
+motion within the intergranular lanes and by increasing the number of
+stagnation points produced by inhibited convection. Larger BPs are found in
+regions of higher magnetic flux density and we believe that lifetimes increase
+in active regions as the magnetic flux stabilises the BPs.",1405.3923v1
+2017-10-09,Magnetization dynamics of weakly interacting sub-100 nm square artificial spin ices,"Artificial Spin Ice (ASI), consisting of a two dimensional array of nanoscale
+magnetic elements, provides a fascinating opportunity to observe the physics of
+out of equilibrium systems. Initial studies concentrated on the static, frozen
+state, whilst more recent studies have accessed the out-of-equilibrium dynamic,
+fluctuating state. This opens up exciting possibilities such as the observation
+of systems exploring their energy landscape through monopole quasiparticle
+creation, potentially leading to ASI magnetricity, and to directly observe
+unconventional phase transitions. In this work we have measured and analysed
+the magnetic relaxation of thermally active ASI systems by means of SQUID
+magnetometry. We have investigated the effect of the interaction strength on
+the magnetization dynamics at different temperatures in the range where the
+nanomagnets are thermally active and have observed that they follow an
+Arrhenius-type N\'eel-Brown behaviour. An unexpected negative correlation of
+the average blocking temperature with the interaction strength is also
+observed, which is supported by Monte Carlo simulations. The magnetization
+relaxation measurements show faster relaxation for more strongly coupled
+nanoelements with similar dimensions. The analysis of the stretching exponents
+obtained from the measurements suggest 1-D chain-like magnetization dynamics.
+This indicates that the nature of the interactions between nanoelements lowers
+the dimensionality of the ASI from 2-D to 1-D. Finally, we present a way to
+quantify the effective interaction energy of a square ASI system, and compare
+it to the interaction energy calculated from a simple dipole model and also to
+the magnetostatic energy computed with micromagnetic simulations.",1710.03018v2
+2018-02-02,"Stellar dynamics: rotation, convection, and magnetic fields","Stars are changing entities in a constant evolution during their lives. At
+non-secular time scales (from seconds to years) the effect of dynamical
+processes such as convection, rotation, and magnetic fields can modify the
+stellar oscillations. Convection excites acoustic modes in solar-like stars,
+while rotation and magnetic fields can perturb the oscillation frequencies
+lifting the degeneracy in the azimuthal component m of the eigenfrequencies.
+Moreover, the interaction between rotation, convection, and magnetic fields can
+produce magnetic dynamos, which sometimes yield to regular magnetic activity
+cycles. In this chapter we review how stellar dynamics can be studied and
+explain what long-term seismic observations can bring to the understanding of
+this field. Thus, we show how we can study some properties of the convective
+time scales operating in a star like the Sun. We also compare the stratified
+information we can obtain on the internal (radial) differential rotation from
+main sequence solar-like stars, to the Sun, and to more evolved sub giants, and
+giants. We complement this information on the internal rotation with the
+determination of the surface (latitudinal differential) rotation obtained
+directly from the light curves. Indeed, when stars are active there can be
+spots on their surfaces dimming the light emitted. When the star rotates, the
+emitted light will be modulated by the presence of these spots with a period
+corresponding to the rotation rate at the active latitudes (where the spots
+develop). We conclude this chapter by discussing the seismology of fast
+rotating stars and, from a theoretical point of view, what are the current
+challenges to infer properties of the internal structure and dynamics of
+intermediate- and high-mass stars.",1802.00666v2
+2019-08-28,Masses and Implications for Ages of Low-Mass Pre-Main Sequence Stars in Taurus and Ophiuchus,"The accuracy of masses of pre-main sequence (PMS) stars derived from their
+locations on the Hertzsprung-Russell Diagram (HRD) can be tested by comparison
+with accurate and precise masses determined independently. We present 29 single
+stars in the Taurus star-forming region (SFR) and 3 in the Ophiuchus SFR with
+masses measured dynamically to a precision of at least $10 \%$. Our results
+include 9 updated mass determinations and 3 that have not had their dynamical
+masses published before. This list of stars with fundamental, dynamical masses,
+M$_{dyn}$, is drawn from a larger list of 39 targets in the Taurus SFR and 6 in
+the Ophiuchus SFR. Placing the stars with accurate and precise dynamical masses
+on HRDs that do not include internal magnetic fields underestimates the mass
+compared to M$_{dyn}$ by about $30 \%$. Placing them on an HRD that does
+include magnetic fields yields mass estimates in much better agreement with
+M$_{dyn}$, with an average difference between M$_{dyn}$ and the estimated track
+mass of $0.01\pm0.02$~\msun. The ages of the stars, 3--10 MY on tracks that
+include magnetic fields, is older than the 1--3 MY indicated by the
+non-magnetic models. The older ages of T Tauri stars predicted by the magnetic
+models increase the time available for evolution of their disks and formation
+of the giant gas exoplanets. The agreement between our M$_{dyn}$ values and the
+masses on the magnetic field tracks provides indirect support for these older
+ages.",1908.10952v1
+2019-10-30,Large-scale dynamics of winds originated from black hole accretion flows: (II) Magnetohydrodynamics,"Winds from black hole accretion disks are essential ingredients in
+understanding the coevolution between the supermassive black hole and its host
+galaxy. The great difference of dynamical ranges from small-scale accretion
+disk simulations to large-scale or cosmological simulations places barriers to
+track wind kinematics. In the first paper of this series, we have studied the
+dynamics of disk winds from the outer edge of the accretion disk toward galaxy
+scales in the hydrodynamical framework. In this paper, we further incorporate
+magnetic fields to understand the wind dynamics by adopting one-dimensional
+magnetohydrodynamical (MHD) model, with boundary conditions set for hot
+accretion flows. The geometry of poloidal magnetic field is prescribed as a
+straight line with an angle $\theta=45^\circ$ from the rotational axis, and the
+strength satisfies the divergence free condition. The wind solution is achieved
+through requesting gas to pass through the slow, Alfv\'{e}n and fast
+magneto-sonic points smoothly. Physical quantities are found to show a
+power-law dependence on cylindrical radius $R$ beyond the fast magneto-sonic
+point, for which $\rho \propto R^{-2}, v_{\rm p}\propto {\rm const.}, v_{\rm
+\phi}\propto R^{-1}, B_{\rm \phi}\propto R^{-1},$ and $ \beta \propto
+\rho^{\gamma-1}$. The magnetization of wind is dominant in determining the wind
+properties. The wind is accelerated to a greater terminal velocity with strong
+magnetization ($v_{\rm Ap0}>1$) compared to the hydrodynamical case, which the
+magnetic pressure gradient dominates and the centrifugal potential converts to
+the kinetic energy. The dependance of wind physical quantities on
+magnetization, temperature, field line angular velocity, and adiabatic index is
+also discussed.",1910.13779v4
+2020-03-21,First-principles perspective on magnetic second sound,"The fluctuations of the magnetic order parameter, or longitudinal spin
+excitations, are investigated theoretically in the ferromagnetic Fe and Ni as
+well as in the antiferromagnetic phase of the pnictide superconductor FeSe. The
+charge and spin dynamics of these systems is described by evaluating the
+generalized charge and spin density response function calculated from
+first-principles linear response time dependent density functional theory
+within adiabatic local spin density approximation. We observe that the formally
+non-interacting Kohn-Sham system features strong coupling between the
+magnetization and charge dynamics in the longitudinal channel and that the
+coupling is effectively removed upon the inclusion of the Coulomb interaction
+in the charge channel and the resulting appearance of plasmons. The
+longitudinal spin fluctuations acquire a collective character without the
+emergence of the Goldstone boson, similar to the case of paramagnon excitations
+in non-magnetic metals like Pd. In ferromagnetic Fe and Ni the longitudinal
+spin dynamics is governed by interactions between low-energy intraband
+electron-hole pairs while in quasi two dimensional antiferromagnet FeSe it is
+dominated by the interband transitions with energies of the order of exchange
+splitting. In the later material, the collective longitudinal magnetization
+fluctuations feature well defined energies and long life times for small
+momenta and appear below the particle-hole continuum. The modes become strongly
+Landau-damped for growing wave-vectors. We relate our theoretical findings to
+existing experimental spin-polarized electron energy loss spectroscopy results.
+In bulk bcc Fe, the longitudinal magnetic modes appear above the typical
+energies of transverse spin-waves, have energies comparable with the Stoner
+spin-flip excitation continuum, and are order of magnitude less energetic than
+the charge dynamics.",2003.09735v3
+2021-04-20,Unusual spin dynamics in the low-temperature magnetically ordered state of Ag$_{3}$LiIr$_{2}$O$_{6}$,"Recently, there have been contrary claims of Kitaev spin-liquid behaviour and
+ordered behavior in the honeycomb compound Ag$_3$LiIr$_2$O$_6$ based on various
+experimental signatures. Our investigations on this system reveal a
+low-temperature ordered state with persistent dynamics down to the lowest
+temperatures. Magnetic order is confirmed by clear oscillations in the muon
+spin relaxation ($\mu$SR) time spectrum below 9 K till 52 mK. Coincidentally in
+$^7$Li nuclear magnetic resonance, a wipe-out of the signal is observed below
+$\sim$ 10 K which again strongly indicates magnetic order in the low
+temperature regime. This is supported by our density functional theory
+calculations which show an appreciable Heisenberg exchange term in the spin
+Hamiltonian that favors magnetic ordering. The $^7$Li shift and spin-lattice
+relaxation rate also show anomalies at $\sim$ 50 K. They are likely related to
+the onset of dynamic magnetic correlations, but their origin is not completely
+clear. Detailed analysis of our $\mu$SR data is consistent with a co-existence
+of incommensurate N\'eel and striped environments. A significant and
+undiminished dynamical relaxation rate ($\sim 5$ MHz) as seen in $\mu$SR deep
+into the ordered phase indicates enhanced quantum fluctuations in the ordered
+state.",2104.10057v2
+2023-05-12,Improving the Understanding of Subsurface Structure and Dynamics of Solar Active Regions (A white paper submitted to the decadal survey for solar and space Physics (Heliophysics) -- SSPH 2024-2033),"The goal of helioseismology is to provide accurate information about the
+Sun's interior from the observations of the wave field at its surface. In the
+last three decades, both global and local helioseismology studies have made
+significant advances and breakthroughs in solar physics. However, 3-d mapping
+of the structure and dynamics of sunspots and active regions below the surface
+has been a challenging task and are among the longest standing and intriguing
+puzzles of solar physics due to the complexity of the turbulent and dynamic
+nature of sunspots. Thus the key problems that need to be addressed during the
+next decade are: (i) Understanding the wave excitation mechanisms in the quiet
+Sun and magnetic regions, (ii) Characterizing the wave propagation and
+transformation in strong and inclined magnetic field regions and understanding
+the magnetic portals in the chromosphere, (iii) Improving helioseismology
+techniques and investigating the whole life cycle of active regions, from
+magnetic flux emergence to dissipation, and (iv) Detecting helioseismic
+signature of the magnetic flux of active regions before it becomes visible on
+the surface so as to provide warnings several days before the emergence. For a
+transformative progress on these problems require full disk, simultaneous
+Doppler and vector magnetic field measurements of the photosphere up to the
+chromosphere with a spatial resolution of about 2 arc-sec as well as
+large-scale radiative MHD simulations of the plasma dynamics from the
+sub-photosphere to the chromosphere.",2305.07585v1
+2017-01-05,Turbulent geodynamo simulations: a leap towards Earth's core,"We present an attempt to reach realistic turbulent regime in direct numerical
+simulations of the geodynamo. We rely on a sequence of three convection-driven
+simulations in a rapidly rotating spherical shell. The most extreme case
+reaches towards the Earth's core regime by lowering viscosity (magnetic Prandtl
+number Pm=0.1) while maintaining vigorous convection (magnetic Reynolds number
+Rm>500) and rapid rotation (Ekman number E=1e-7), at the limit of what is
+feasible on today's supercomputers. A detailed and comprehensive analysis
+highlights several key features matching geomagnetic observations or dynamo
+theory predictions -- all present together in the same simulation -- but it
+also unveils interesting insights relevant for Earth's core dynamics.In this
+strong-field, dipole-dominated dynamo simulation, the magnetic energy is one
+order of magnitude larger than the kinetic energy. The spatial distribution of
+magnetic intensity is highly heterogeneous, and a stark dynamical contrast
+exists between the interior and the exterior of the tangent cylinder (the
+cylinder parallel to the axis of rotation that circumscribes the inner core).In
+the interior, the magnetic field is strongest, and is associated with a
+vigorous twisted polar vortex, whose dynamics may occasionally lead to the
+formation of a reverse polar flux patch at the surface of the shell.
+Furthermore, the strong magnetic field also allows accumulation of light
+material within the tangent cylinder, leading to stable stratification there.
+Torsional Alfv{\'e}n waves are frequently triggered in the vicinity of the
+tangent cylinder and propagate towards the equator.Outside the tangent
+cylinder, the magnetic field inhibits the growth of zonal winds and the kinetic
+energy is mostly non-zonal. Spatio-temporal analysis indicates that the
+low-frequency, non-zonal flow is quite geostrophic (columnar) and predominantly
+large-scale: an m=1 eddy spontaneously emerges in our most extreme simulations,
+without any heterogeneous boundary forcing.Our spatio-temporal analysis further
+reveals that (i) the low-frequency, large-scale flow is governed by a balance
+between Coriolis and buoyancy forces -- magnetic field and flow tend to align,
+minimizing the Lorentz force; (ii) the high-frequency flow obeys a balance
+between magnetic and Coriolis forces; (iii) the convective plumes mostly live
+at an intermediate scale, whose dynamics is driven by a 3-term 1 MAC balance --
+involving Coriolis, Lorentz and buoyancy forces. However, small-scale (E^{1/3})
+quasi-geostrophic convection is still observed in the regions of low magnetic
+intensity.",1701.01299v3
+1995-03-30,Coarsening in the q-State Potts Model and the Ising Model with Globally Conserved Magnetization,"We study the nonequilibrium dynamics of the $q$-state Potts model following a
+quench from the high temperature disordered phase to zero temperature. The time
+dependent two-point correlation functions of the order parameter field satisfy
+dynamic scaling with a length scale $L(t)\sim t^{1/2}$. In particular, the
+autocorrelation function decays as $L(t)^{-\lambda(q)}$. We illustrate these
+properties by solving exactly the kinetic Potts model in $d=1$. We then analyze
+a Langevin equation of an appropriate field theory to compute these correlation
+functions for general $q$ and $d$. We establish a correspondence between the
+two-point correlations of the $q$-state Potts model and those of a kinetic
+Ising model evolving with a fixed magnetization $(2/q-1)$. The dynamics of this
+Ising model is solved exactly in the large q limit, and in the limit of a large
+number of components $n$ for the order parameter. For general $q$ and in any
+dimension, we introduce a Gaussian closure approximation and calculate within
+this approximation the scaling functions and the exponent $\lambda (q)$. These
+are in good agreement with the direct numerical simulations of the Potts model
+as well as the kinetic Ising model with fixed magnetization. We also discuss
+the existing and possible experimental realizations of these models.",9503163v1
+2005-01-21,The isotropic XY model on the inhomogeneous periodic chain,"The static and dynamic properties of the isotropic XY-model $(s=1/2)$ on the
+inhomogeneous periodic chain, composed of \emph{N} segments with \emph{n}
+different exchange interactions and magnetic moments, in a transverse field
+\emph{h} are obtained exactly at arbitrary temperatures. The properties are
+determined by introducing the generalized Jordan-Wigner transformation and by
+reducing the problem to a diagonalization of a finite matrix of \emph{n-th}
+order. The diagonalization procedure is discussed in detail and the critical
+behaviour induced by the transverse field, at T=0, is presented. The quantum
+transitions are determined by analyzing the behaviour of the induced
+magnetization, defined as $(1/n)\sum_{m=1}^{n}\mu_{m}<S_{j,m}^{z}>$ where
+$\mu_{m}$ is the magnetic moment at site \emph{m} within the segment \emph{j},
+as a function of the field, and the critical fields determined exactly. The
+dynamic correlations, $<S_{j,m}^{z}(t)S_{j^{'},m^{'}}^{z}(0)>$, and the dynamic
+susceptibility $\chi_{q}^{zz}(\omega)$ are also obtained at arbitrary
+temperatures. Explicit results are also presented in the limit T=0, where the
+critical behaviour occurs, for the static susceptibility $\chi_{q}^{zz}(0)$ as
+a function of the transverse field \emph{h}, and for the frequency dependency
+of dynamic susceptibility $\chi_{q}^{zz}(\omega)$. Also in this limit, the
+transverse time-correlation $<S_{j,m}^{x}(t)S_{j^{'},m^{'}}^{x}(0)>$, the
+dynamic and isothermal susceptibilities, $\chi_{q}^{xx}(\omega)$ and
+$\chi_{T}^{xx}$, are obtained for the transverse field greater or equal than
+the saturation field.",0501525v1
+2006-03-14,Critical Behavior of an Ising System on the Sierpinski Carpet: A Short-Time Dynamics Study,"The short-time dynamic evolution of an Ising model embedded in an infinitely
+ramified fractal structure with noninteger Hausdorff dimension was studied
+using Monte Carlo simulations. Completely ordered and disordered spin
+configurations were used as initial states for the dynamic simulations. In both
+cases, the evolution of the physical observables follows a power-law behavior.
+Based on this fact, the complete set of critical exponents characteristic of a
+second-order phase transition was evaluated. Also, the dynamic exponent $\theta
+$ of the critical initial increase in magnetization, as well as the critical
+temperature, were computed. The exponent $\theta $ exhibits a weak dependence
+on the initial (small) magnetization. On the other hand, the dynamic exponent
+$z$ shows a systematic decrease when the segmentation step is increased, i.e.,
+when the system size becomes larger. Our results suggest that the effective
+noninteger dimension for the second-order phase transition is noticeably
+smaller than the Hausdorff dimension. Even when the behavior of the
+magnetization (in the case of the ordered initial state) and the
+autocorrelation (in the case of the disordered initial state) with time are
+very well fitted by power laws, the precision of our simulations allows us to
+detect the presence of a soft oscillation of the same type in both magnitudes
+that we attribute to the topological details of the generating cell at any
+scale.",0603387v1
+2006-08-02,Magnetocatalytic Adiabatic Spin Torque Orbital Transformations for Novel Chemical and Catalytic Reaction Dynamics: The Little Effect,"In this manuscript the theory and phenomena associated with the Little Effect
+are introduced as the spin induced orbital dynamics of confined fermions under
+strong magnetic and thermal environments. This Little Effect is considered in
+details for the electron transfer reactions associated with redox processes of
+Cu-Ag alloy within deionized water and for the orbital dynamics during the iron
+catalyzed covalent bond rearrangements associated with amorphous carbon
+conversion to diamond. Furthermore, prolong extreme conditions of 74,000 amps,
+403 V, strong Lorentz compression, and thermal stresses upon this Cu-Ag- H2O
+system on the basis of the Little Effect of high spin, thermally induced
+orbital dynamics are predicted and demonstrated to cause the magnetically
+organized reverse beta, electron capture, proton capture and neutron capture
+processes for various infrequent pycnonuclear transmutations within the Cu-Ag
+coil. The general experimental verification and the broad implications of this
+Little Effect on chemistry are demonstrated within these two ideal systems: an
+ionic case and a molecular case. The Little Effect is contrasted with the
+Hedvall Effect as a dynamical phenomenon causing the kinematics of the Hedvall
+Effect. The compatibility of the Little Effect with the Woodward-Hoffmann Rule
+is demonstrated. The Little Effect provides greater understanding of order in
+systems far from equilibrium. The implications of the Little Effect for other
+interesting phenomena such as ferromagnetism, unconventional magnetism,
+superparamagnetism, superconductivity, and pycnonuclear effects are concluded.",0608071v1
+2000-05-09,Dynamical Symmetry Breaking in Supersymmetric SU(n_c) and USp(2n_c) Gauge Theories,"We find the phase and flavor symmetry breaking pattern of each N=1
+supersymmetric vacuum of SU(n_c) and USp(2 n_c) gauge theories, constructed
+from the exactly solvable N=2 theories by perturbing them with small adjoint
+and generic bare hypermultiplet (quark) masses. In SU(n_c) theories with n_f
+\leq n_c the vacua are labelled by an integer r, in which the flavor U(n_f)
+symmetry is dynamically broken to U(r) \times U(n_f-r) in the limit of
+vanishing bare hyperquark masses. In the r=1 vacua the dynamical symmetry
+breaking is caused by the condensation of magnetic monopoles in the n_f
+representation. For general r, however, the monopoles in the {}_{n_f}C_r
+representation, whose condensation could explain the flavor symmetry breaking
+but would produce too-many Nambu--Goldstone multiplets, actually ""break up""
+into ""magnetic quarks"": the latter with nonabelian interactions condense and
+induce confinement and dynamical symmetry breaking. In USp(2n_c) theories with
+n_f \leq n_c + 1, the flavor SO(2n_f) symmetry is dynamically broken to U(n_f),
+but with no description in terms of a weakly coupled local field theory. In
+both SU(n_c) and USp(2 n_c) theories, with larger numbers of quark flavors,
+besides the vacua with these properties, there exist also vacua in free
+magnetic phase, with unbroken global symmetry.",0005076v2
+2006-09-07,"Magnetic Monopole Dynamics, Supersymmetry, and Duality","We review the properties of BPS, or supersymmetric, magnetic monopoles, with
+an emphasis on their low-energy dynamics and their classical and quantum bound
+states. After an overview of magnetic monopoles, we discuss the BPS limit and
+its relation to supersymmetry. We then discuss the properties and construction
+of multimonopole solutions with a single nontrivial Higgs field. The low-energy
+dynamics of these monopoles is most easily understood in terms of the moduli
+space and its metric. We describe in detail several known examples of these.
+This is then extended to cases where the unbroken gauge symmetry include a
+non-Abelian factor. We next turn to the generic supersymmetric Yang-Mills (SYM)
+case, in which several adjoint Higgs fields are present. Working first at the
+classical level, we describe the effects of these additional scalar fields on
+the monopole dynamics, and then include the contribution of the fermionic zero
+modes to the low-energy dynamics. The resulting low-energy effective theory is
+itself supersymmetric. We discuss the quantization of this theory and its
+quantum BPS states, which are typically composed of several loosely bound
+compact dyonic cores. We close with a discussion of the D-brane realization of
+${\cal N}=4$ SYM monopoles and dyons and explain the ADHMN construction of
+monopoles from the D-brane point of view.",0609055v2
+2010-04-23,Time domain study of frequency-power correlation in spin-torque oscillators,"This paper describes a numerical experiment, based on full micromagnetic
+simulations of current-driven magnetization dynamics in nanoscale spin valves,
+to identify the origins of spectral linewidth broadening in spin torque
+oscillators. Our numerical results show two qualitatively different regimes of
+magnetization dynamics at zero temperature: regular (single-mode precessional
+dynamics) and chaotic. In the regular regime, the dependence of the oscillator
+integrated power on frequency is linear, and consequently the dynamics is well
+described by the analytical theory of current-driven magnetization dynamics for
+moderate amplitudes of oscillations. We observe that for higher oscillator
+amplitudes, the functional dependence of the oscillator integrated power as a
+function of frequency is not a single-valued function and can be described
+numerically via introduction of nonlinear oscillator power. For a range of
+currents in the regular regime, the oscillator spectral linewidth is a linear
+function of temperature. In the chaotic regime found at large current values,
+the linewidth is not described by the analytical theory. In this regime we
+observe the oscillator linewidth broadening, which originates from sudden jumps
+of frequency of the oscillator arising from random domain wall nucleation and
+propagation through the sample. This intermittent behavior is revealed through
+a wavelet analysis that gives superior description of the frequency jumps
+compared to several other techniques.",1004.4184v1
+2010-10-28,"The Interplay of Magnetic Fields, Fragmentation and Ionization Feedback in High-Mass Star Formation","Massive stars disproportionately influence their surroundings. How they form
+has only started to become clear recently through radiation gas dynamical
+simulations. However, until now, no simulation has simultaneously included both
+magnetic fields and ionizing radiation. Here we present the results from the
+first radiation-magnetohydrodynamical (RMHD) simulation including ionization
+feedback, comparing an RMHD model of a 1000 M_sol rotating cloud to earlier
+radiation gas dynamical models with the same initial density and velocity
+distributions. We find that despite starting with a strongly supercritical mass
+to flux ratio, the magnetic field has three effects. First, the field offers
+locally support against gravitational collapse in the accretion flow,
+substantially reducing the amount of secondary fragmentation in comparison to
+the gas dynamical case. Second, the field drains angular momentum from the
+collapsing gas, further increasing the amount of material available for
+accretion by the central, massive, protostar, and thus increasing its final
+mass by about 50% from the purely gas dynamical case. Third, the field is wound
+up by the rotation of the flow, driving a tower flow. However, this flow never
+achieves the strength seen in low-mass star formation simulations for two
+reasons: gravitational fragmentation disrupts the circular flow in the central
+regions where the protostars form, and the expanding H II regions tend to
+further disrupt the field geometry. Therefore, outflows driven by ionization
+heating look likely to be more dynamically important in regions of massive star
+formation.",1010.5905v2
+2011-03-09,"First-Principles Dynamical Coherent-Potential Approximation Approach to the Ferromagnetism of Fe, Co, and Ni","Magnetic properties of Fe, Co, and Ni at finite temperatures have been
+investigated on the basis of the first-principles dynamical CPA (Coherent
+Potential Approximation) combined with the LDA (Local Density Approximation) +
+$U$ Hamiltonian in the Tight-Binding Linear Muffintin Orbital (TB-LMTO)
+representation. The Hamiltonian includes the transverse spin fluctuation terms.
+Numerical calculations have been performed within the harmonic approximation
+with 4th-order dynamical corrections. Calculated single-particle densities of
+states in the ferromagnetic state indicate that the dynamical effects reduce
+the exchange splitting, suppress the band width of the quasi-particle state,
+and causes incoherent excitations corresponding the 6 eV satellites. Results of
+the magnetization vs temperature curves, paramagnetic spin susceptibilities,
+and the amplitudes of local moments are presented. Calculated Curie
+temperatures ($T_{\rm C}$) are reported to be 1930K for Fe, 2550K for Co, and
+620K for Ni; $T_{\rm C}$ for Fe and Co are overestimated by a factor of 1.8,
+while $T_{\rm C}$ in Ni agrees with the experimental result. Effective Bohr
+magneton numbers calculated from the inverse susceptibilities are 3.0 $\mu_{\rm
+B}$ (Fe), 3.0 $\mu_{\rm B}$ (Co), and 1.6 $\mu_{\rm B}$ (Ni), being in
+agreement with the experimental ones. Overestimate of $T_{\rm C}$ in Fe and Co
+is attributed to the neglects of the higher-order dynamical effects as well as
+the magnetic short range order.",1103.1683v1
+2014-06-18,Anisotropic transport and early dynamical impact of Cosmic Rays around Supernova remnants,"We present a novel implementation of cosmic rays (CR) in the
+magneto-hydrodynamic code FLASH. CRs are described as separate fluids with
+different energies. CR advection, energy dependent anisotropic diffusion with
+respect to the magnetic field and adiabatic losses to follow the evolution of
+spectra are taken into account. We present a first study of the transport and
+immediate (~150 kyr) dynamical impact of CRs on the turbulent magnetised
+interstellar medium around supernova remnants on scales up to 80 pc. CR
+diffusion quickly leads to an efficient acceleration of low-density gas (mainly
+perpendicular to the magnetic field) with accelerations up to two orders of
+magnitude above the thermal values. Peaked (at 1 GeV) CR injection spectra have
+a stronger impact on the dynamics than power-law spectra. For realistic
+magnetic field configurations low energy CRs (with smaller diffusion
+coefficients) distribute anisotropically with large spatial variations of a
+factor of ten and more. Adiabatic losses can change the local spectra
+perceptibly but do not have an integral effect on the dynamics at the spatial
+and temporal scales considered here. We discuss the potential global impact of
+CRs and anisotropic transport on the dynamical structure of the ISM and also
+detail the limitations of the model.",1406.4861v1
+2014-10-22,Spin dynamics of Mn impurities and their bound acceptors in GaAs,"We present results of tight-binding spin-dynamics simulations of individual
+and pairs of substitutional Mn impurities in GaAs. Our approach is based on the
+mixed quantum-classical scheme for spin dynamics, with coupled equations of
+motions for the quantum subsystem, representing the host, and the localized
+spins of magnetic dopants, which are treated classically. In the case of a
+single Mn impurity, we calculate explicitly the time evolution of the Mn spin
+and the spins of nearest-neighbors As atoms, where the acceptor (hole) state
+introduced by the Mn dopant resides. We relate the characteristic frequencies
+in the dynamical spectra to the two dominant energy scales of the system,
+namely the spin-orbit interaction strength and the value of the p-d exchange
+coupling between the impurity spin and the host carriers. For a pair of Mn
+impurities, we find signatures of the indirect (carrier-mediated) exchange
+interaction in the time evolution of the impurity spins. Finally, we examine
+temporal correlations between the two Mn spins and their dependence on the
+exchange coupling and spin-orbit interaction strength, as well as on the
+initial spin-configuration and separation between the impurities. Our results
+provide insight into the dynamic interaction between localized magnetic
+impurities in a nano-scaled magnetic-semiconductor sample, in the extremely
+dilute (solotronics) regime.",1410.5978v1
+2017-03-20,Spin-Wave Dynamics in the Presence of Magnetic Vortices,"This chapter describes spin-wave excitations in nanosized dots and rings in
+the presence of the vortex state. The special attention is paid to the
+manifestation of the competition between exchange and dipolar interactions in
+the spin-wave spectrum as well as the correlation between the spectrum and the
+stability of the vortex. The calculation method uses the dynamic matrix for an
+all-discrete system, the numerical diagonalization of which yields the spectrum
+of frequencies and spin-wave profiles of normal modes of the dot. We study
+in-plane vortices of two types: a circular magnetization in circular dots and
+rings and the Landau state in square rings. We examine the influence of the
+dipolar-exchange competition and the geometry of the dot on the stability of
+the vortex and on the spectrum of spin waves. We show that the lowest-frequency
+mode profile proves to be indicative of the dipolar-to-exchange interaction
+ratio and the vortex stability is closely related to the spin-wave profile of
+the soft mode. The negative dispersion relation is also shown. Our results
+obtained for in-plane vortices are in qualitative agreement with results for
+core-vortices obtained from experiments, micromagnetic simulations, and
+analytical calculations.",1703.06668v1
+2021-07-06,Transverse Linear Beam Dynamics,"The subject of this introductory course is transverse dynamics of charged
+particle beams in linear approximation. Starting with a discussion of the most
+important types of magnets and defining their multipole strengths, the
+linearized equations of motion of charged particles in static magnetic fields
+are derived using an orthogonal reference frame following the design orbit.
+Analytical solutions are determined for linear elements of a typical beam
+transfer line (drift, dipole and quadrupole magnets), and stepwise combined by
+introducing the matrix formalism in which each element's contribution is
+represented by a single transfer matrix. Application of this formalism allows
+to calculate single particle's trajectories in linear approximation. After
+introducing the beam emittance as the area occupied by a particle beam in phase
+space, a linear treatment of transverse beam dynamics based on appropriately
+defined optical functions is introduced. The formalism is applied to the
+concepts of both weak and strong focusing, in particular discussing the
+properties of the widely-used FODO cell. Specific characteristics of transverse
+beam dynamics in periodic systems like circular accelerators are studied in
+detail, emphazising the effects of linear field errors on orbit stability and
+introducing the phenomena of optical resonances. Finally, the dynamics of
+off-momentum particles is presented, introducing dispersion functions and
+explaining effects like chromaticity.",2107.02614v2
+2021-09-08,Dynamics of spin relaxation in nonequilibrium magnetic nanojunctions,"We investigate nonequilibrium phenomena in magnetic nano-junctions using a
+numerical approach that combines classical spin dynamics with the hierarchical
+equations of motion technique for quantum dynamics of conduction electrons. Our
+focus lies on the spin dynamics, where we observe non-monotonic behavior in the
+spin relaxation rates as a function of the coupling strength between the
+localized spin and conduction electrons. Notably, we identify a distinct
+maximum at intermediate coupling strength, which we attribute to a competition
+that involves the increasing influence of the coupling between the classical
+spin and electrons, as well as the influence of decreasing local density of
+states at the Fermi level. Furthermore, we demonstrate that the spin dynamics
+of a large open system can be accurately simulated by a short chain coupled to
+semi-infinite metallic leads. In the case of a magnetic junction subjected to
+an external DC voltage, we observe resonant features in the spin relaxation,
+reflecting the electronic spectrum of the system. The precession of classical
+spin gives rise to additional side energies in the electronic spectrum, which
+in turn leads to a broadened range of enhanced damping in the voltage.",2109.03476v3
+2022-09-23,Realization of high-dynamic-range broadband magnetic-field sensing with ensemble nitrogen-vacancy centers in diamond,"We present a new magnetometry method integrating an ensemble of
+nitrogen-vacancy (NV) centers in a single-crystal diamond with an extended
+dynamic range for monitoring the fast changing magnetic-field. The NV-center
+spin resonance frequency is tracked using a closed-loop frequency locked
+technique with fast frequency hopping to achieve a 10 kHz measurement
+bandwidth, thus, allowing for the detection of fast changing magnetic signals
+up to 0.723 T/s.This technique exhibits an extended dynamic range subjected to
+the working bandwidth of the microwave source. This extended dynamic range can
+reach up to 4.3 mT, which is 86 times broader than the intrinsic dynamic range.
+The essential components for NV spin control and signal processing such as
+signal generation, microwave frequency control, data processing and readout are
+integrated in a board-level system. With this platform, we demonstrate
+broadband magnetometry with an optimized sensitivity of 4.2 nT-Hz-1/2. This
+magnetometry method has the potential to be implemented in a multichannel
+frequency locked vector magnetometer suitable for a wide range of practical
+applications such as magnetocardiography and high-precision current sensors.",2209.11360v1
+2023-05-15,Order parameter dynamics in Mn$_3$Sn driven by DC and pulsed spin-orbit torques,"We numerically investigate and develop analytic models for both the DC and
+pulsed spin-orbit-torque (SOT)-driven response of order parameter in
+single-domain Mn$_3$Sn, which is a metallic antiferromagnet with an anti-chiral
+120$^\circ$ spin structure. We show that DC currents above a critical threshold
+can excite oscillatory dynamics of the order parameter in the gigahertz to
+terahertz frequency spectrum. Detailed models of the oscillation frequency
+versus input current are developed and found to be in excellent agreement with
+the numerical simulations of the dynamics. In the case of pulsed excitation,
+the magnetization can be switched from one stable state to any of the other
+five stable states in the Kagome plane by tuning the duration or the amplitude
+of the current pulse. Precise functional forms of the final switched state
+versus the input current are derived, offering crucial insights into the
+switching dynamics of Mn$_3$Sn. The readout of the magnetic state can be
+carried out via either the anomalous Hall effect, or the recently demonstrated
+tunneling magnetoresistance in an all-Mn$_3$Sn junction. We also discuss
+possible disturbance of the magnetic order due to heating that may occur if the
+sample is subject to large currents. Operating the device in pulsed mode or
+using low DC currents reduces the peak temperature rise in the sample due to
+Joule heating. Our predictive modeling and simulation results can be used by
+both theorists and experimentalists to explore the interplay of SOT and the
+order dynamics in Mn$_3$Sn, and to further benchmark the device performance.",2305.08728v2
+2014-01-08,Dynamic exchange via spin currents in acoustic and optical modes of ferromagnetic resonance in spin-valve structures,"Two ferromagnetic layers magnetically decoupled by a thick normal metal
+spacer layer can be, nevertheless, dynamically coupled via spin currents
+emitted by the spin-pump and absorbed through the spin-torque effects at the
+neighboring interfaces. A decrease of damping in both layers due to a partial
+compensation of the angular momentum leakage in each layer was previously
+observed at the coincidence of the two ferromagnetic resonances. In case of
+non-zero magnetic coupling, such a dynamic exchange will depend on the mutual
+precession of the magnetic moments in the layers. A difference in the linewidth
+of the resonance peaks is expected for the acoustic and optical regimes of
+precession. However, the interlayer coupling hybridizes the resonance responses
+of the layers and therefore can also change their linewidths. The interplay
+between the two mechanisms has never been considered before. In the present
+work, the joint influence of the hybridization and non-local damping on the
+linewidth has been studied in weakly coupled NiFe/CoFe/Cu/CoFe/MnIr spin-valve
+multilayers. It has been found that the dynamic exchange by spin currents is
+different in the optical and acoustic modes, and this difference is dependent
+on the interlayer coupling strength. In contrast to the acoustic precession
+mode, the dynamic exchange in the optical mode works as an additional damping
+source. A simulation in the framework of the Landau-Lifshitz-Gilbert formalism
+for two ferromagnetic layers coupled magnetically and by spin currents has been
+done to separate the effects of the non-local damping from the resonance modes
+hybridization. In our samples both mechanisms bring about linewidth changes of
+the same order of magnitude, but lead to a distinctly different angular
+behavior. The obtained results are relevant for a broad class of coupled
+magnetic multilayers with ballistic regime of the spin transport.",1401.1672v1
+2003-10-17,Morphology of Rising Hydrodynamic and Magneto-hydrodynamic Bubbles from Numerical Simulations,"Recent Chandra and XMM-Newton observations of galaxy cluster cooling flows
+have revealed X-ray emission voids of up to 30 kpc in size that have been
+identified with buoyant, magnetized bubbles. Motivated by these observations,
+we have investigated the behavior of rising bubbles in stratified atmospheres
+using the FLASH adaptive-mesh simulation code. We present results from 2-D
+simulations with and without the effects of magnetic fields, and with varying
+bubble sizes and background stratifications. We find purely hydrodynamic
+bubbles to be unstable; a dynamically important magnetic field is required to
+maintain a bubble's integrity. This suggests that, even absent thermal
+conduction, for bubbles to be persistent enough to be regularly observed, they
+must be supported in large part by magnetic fields. Thermal conduction
+unmitigated by magnetic fields can dissipate the bubbles even faster. We also
+observe that the bubbles leave a tail as they rise; the structure of these
+tails can indicate the history of the dynamics of the rising bubble.",0310517v2
+1998-10-28,Energy transfer in two-dimensional magnetohydrodynamic turbulence,"In an earlier paper (physics/0006012) we had developed a method for computing
+the effective energy transfer between any two Fourier modes in fluid or
+magnetohydrodynamic (MHD) flows. This method is applied to a pseudo-spectral,
+direct numerical simulation (DNS) study of energy transfer in the quasi-steady
+state of 2-D MHD turbulence with large scale kinetic forcing. Two aspects of
+energy transfer are studied: the energy fluxes, and the energy transfer between
+different wavenumber regions ({\it shells}). The picture of energy fluxes that
+emerges is quite complex - there is a forward cascade of magnetic energy, an
+inverse cascade of kinetic energy, a flux of energy from the kinetic to the
+magnetic field, and a reverse flux which transfers the energy back to the
+kinetic from the magnetic. The energy transfer between different wave number
+shells is also complex - local and nonlocal transfers often possess opposing
+features, i.e., energy transfer between some wave number shells occurs from
+kinetic to magnetic, and between other wave number shells this transfer is
+reversed. The net transfer of energy is from kinetic to magnetic. The results
+obtained from the flux studies and the shell-to-shell energy transfer studies
+are consistent with each other.",9810032v2
+1999-05-11,The Radiative Kicked Oscillator: A Stochastic Web or Chaotic Attractor ?,"A relativistic charged particle moving in a uniform magnetic field and kicked
+by an electric field is considered. Under the assumption of small magnetic
+field, an iterative map is developed. We consider both the case in which no
+radiation is assumed and the radiative case, using the Lorentz-Dirac equation
+to describe the motion. Comparison between the non-radiative case and the
+radiative case shows that in both cases one can observe a stochastic web
+structure for weak magnetic fields, and, although there are global differences
+in the result of the map, that both cases are qualitatively similar in their
+small scale behavior. We also develop an iterative map for strong magnetic
+fields. In that case the web structure no longer exists; it is replaced by a
+rich chaotic behavior. It is shown that the particle does not diffuse to
+infinite energy; it is limited by the boundaries of an attractor (the
+boundaries are generally much smaller than light velocity). Bifurcation occurs,
+converging rapidly to Feigenbaum's universal constant. The chaotic behavior
+appears to be robust.
+  For intermediate magnetic fields, it is more difficult to observe the web
+structure, and the influence of the unstable fixed point is weaker.",9905013v1
+1998-09-07,Non-Dissipative Logic Device NOT Based on Two Coupled Quantum Dots,"Non-dissipative dynamics of interacting electrons in two tunnel-coupled
+quantum dots is studied theoretically within the framework of the Hubbard
+model. Various values of intra-dot Coulomb repulsion energy $U$ and inter-dot
+tunneling energy $V$ are considered, which correspond to various size of the
+dots and to various distance between them. In the ground state, the average
+value of the spin projection (magnetic moment) at each dot is zero. The input
+signal (the local external magnetic field $H$) applied to one of the dots at a
+time $t=0$ causes the electronic subsystem to evolve in such a way that
+magnetic moments of quantum dots become oriented in the opposite directions at
+any time $t>0$. For any set of $U$ and $V$, there exist optimal values of $H$
+and $t$ which maximize the absolute values of magnetic moments at both dots,
+and magnetic moments become almost saturated. Thus, the antiferromagnetic-like
+spin ordering can be realized at the stage of coherent temporal evolution, well
+before the relaxation to a new ground state at the sacrifice of inelastic
+processes. This effect (""dynamical antiferromagnetism"") may be used for
+implementation of a logic function NOT in an extremely short time. A
+possibility to use the arrays of quantum dots as high-speed single-electron
+devices of new generation is discussed.",9809112v1
+1999-01-07,^{139}La Spectrum and Spin-Lattice Relaxation Measurements of La_{2/3}Ca_{1/3}MnO_3 in the Paramagnetic State,"^{139}La NMR measurements of La_{2/3}Ca_{1/3}MnO_3 performed in the
+paramagnetic state and high magnetic fields are reported. Analysis of the high
+temperature spectrum measured establishes that the spectrum it is a standard
+powder pattern broadened by a variation in lattice distortions. At lower
+temperatures, the spectrum shifts and broadens. Both the shift and broadening
+exhibit Curie-Weiss behavior, indicating that the shift measures the
+polarization of the electron spin system, and the broadening reflects a
+distribution of magnetic susceptibilities. This distribution may result from
+variations of local susceptibility in the bulk of the sample or from
+differences in demagnetizing factors among powder grains. The spectrum also
+indicates that the lattice distortions do not change as the temperature lowers.
+Spectral diffusion measurements suggest that the temperature dependence of the
+spectrum shape does not result from freezing out of motion of magnetic
+polarons. Variation of the nuclear spin-lattice relaxation across the spectrum
+indicate that magnetic fluctuations, not lattice vibrations, dominate nuclear
+relaxation. Nuclear spin-lattice relaxation therefore measures electron spin
+dynamics in this system. The magnetic field dependence of the spin-lattice
+relaxation indicates that the electron spin-spin correlation function adopts
+simple single exponential behavior with a slow field-independent correlation
+time of 10^{-8} seconds near Tc. The spin-spin correlation function changes
+form at higher temperatures, but remains slow. The spin-lattice relaxation
+therefore indicates the presence of extremely slow dynamics above Tc.",9901048v1
+2000-10-12,Thermal Magnetization Reversal in Arrays of Nanoparticles,"The results of large-scale simulations investigating the dynamics of
+magnetization reversal in arrays of single-domain nanomagnets after a rapid
+reversal of the applied field at nonzero temperature are presented. The
+numerical micromagnetic approach uses the Landau-Lifshitz-Gilbert equation
+including contributions from thermal fluctuations and long-range dipole-dipole
+demagnetizing effects implemented using a fast-multipole expansion. The
+individual model nanomagnets are 9 nm x 9 nm x 150 nm iron pillars similar to
+those fabricated on a surface with STM-assisted chemical vapor deposition [S.
+Wirth, et al., J. Appl. Phys {\bf 85}, 5249 (1999)]. Nanomagnets oriented
+perpendicular to the surface and spaced 300 nm apart in linear arrays are
+considered. The applied field is always oriented perpendicular to the surface.
+When the magnitude of the applied field is less than the coercive value, about
+2000 Oe for an individual nanomagnet, magnetization reversal in the nanomagnets
+can only occur by thermally activated processes. Even though the interaction
+from the dipole moment of neighboring magnets in this geometry is only about 1
+Oe, less than 1% of the coercive field, it can have a large impact on the
+switching dynamics. What determines the height of the free-energy barrier is
+the difference between the coercive and applied fields, and 1 Oe can be a
+significant fraction of that. The magnetic orientations of the neighbors are
+seen to change the behavior of the nanomagnets in the array significantly.",0010184v2
+2000-10-25,Spin and charge dynamics of the ferromagnetic and antiferromagnetic two-dimensional half-filled Kondo lattice model,"We present a detailed numerical study of spin and charge dynamics of the
+two-dimensional Kondo lattice model with hopping t and exchange J. At T=0 and J
+> 0, the competition between the RKKY interaction and Kondo effect triggers a
+quantum phase transition between magnetically ordered and disordered
+insulators: J_c/t = 1.45(5). The quasiparticle gap scales as |J|. S(q,\omega),
+evolves smoothly from its strong coupling form with spin gap at q = (\pi,\pi)
+to a spin wave form. At J>0, A(\vec{k},\omega) shows a dispersion relation
+following that of hybridized bands. For J < J_c this feature is supplemented by
+shadows thus pointing to a coexistence of Kondo screening and magnetism. For J
+< 0 A(\vec{k},\omega) is similar to that of non-interacting electrons in a
+staggered magnetic field. Spin, T_S, and charge, T_C, scales are defined. For
+weak to intermediate couplings, T_S marks the onset of antiferromagnetic
+fluctuations and follows a J^2 law. At strong couplings T_S scales as J. T_C
+scales as J both at weak and strong couplings. At and slightly below T_C we
+observe i) a rise in the resistivity as a function of decreasing temperature,
+ii) a dip in the integrated density of states at the Fermi energy and iii) the
+occurrence of hybridized bands in A(k,\omega). It is shown that in the weak
+coupling limit, the charge gap of order J is of magnetic origin. The specific
+heat shows a two peak structure, the low temperature peak being of magnetic
+origin. Our results are compared to various mean-field theories.",0010393v1
+2002-08-09,Persistent magnetoresistive memory in phase separated manganites,"We have studied magnetic and transport properties on different manganese
+oxide based compounds exhibiting phase separation: polycrystalline
+La5/8-yPryCa3/8MnO3 (y=0.3) and La1/2Ca1/2Mn1-zFezO3 (z = 0.05), and single
+crystals of La5/8-yPryCa3/8MnO3 (y=0.35). Time dependent effects indicate that
+the fractions of the coexisting phases are dynamically changing in a definite
+temperature range. We found that in this range the ferromagnetic fraction f can
+be easily tuned by application of low magnetic fields (< 1 T). The effect is
+persistent after the field is turned off, thus the field remains imprinted in
+the actual value of f and can be recovered through transport measurements. This
+effect is due both to the existence of a true phase separated equilibrium state
+with definite equilibrium fraction f0, and to the slow growth dynamics. The
+fact that the same global features were found on different compounds and in
+polycrystalline and single crystalline samples, suggests that the effect is a
+general feature of some phase separated media.",0208199v1
+2006-08-31,FFLO State and Peak Effect Dynamics in CeCoIn_5: Magnetization Studies,"Magnetization measurements were performed on CeCoIn_5 at temperature down to
+30 mK with the magnetic field applied in three different orientations:
+parallel, near parallel ($\sim$ 10$^{0}$ rotated) and perpendicular to the
+ab-plane. For these three orientations we have observed crossover features in
+the torque/magnetization traces at fields just below $H_{c2}$, giving further
+evidence for the formation of a high field Fulde-Ferrel-Larkin-Ovchinnikov
+(FFLO) superconducting state in CeCoIn_5 for $H \parallel ab$-plane and newly
+indicates that the FFLO state persists for out-of-plane field orientations.
+Furthermore, for the (near) parallel to $ab$-plane field configurations and
+$T\leq \mathrm{50 mK}$, we have found an anomalous peak effect(APE) just below
+the crossover field when the magnetic field is sweeping down from normal to
+superconducting state. The dynamics of this peak suggests the existence of a
+metastable phase occurring in the vicinity of the FFLO phase and raises
+questions about the order (first or second) of the transition from FFLO to the
+superconducting state. None of the above features were found in a
+Ce_{0.98}Gd_{0.02}CoIn_{5} crystal.",0608722v1
+2007-06-18,Understanding of complex periodic transformations of moving domain walls in magnetic nanostripes,"The magnetic field (or electric current) driven domain-wall motion in
+magnetic nanostripes is of considerable interest because it is essential to the
+performance of information storage and logic devices. One of the currently key
+problems is to unveil the complex behaviors of oscillatory domain-wall motions
+under applied magnetic fields stronger than the so-called Walker field, beyond
+which the velocity of domain walls markedly drops. Here, we provide not only
+considerably better understandings but also new details of the complex
+domain-wall motions. In a certain range just above the Walker field, the
+motions are not chaotic but rather periodic with different unique periodicities
+of dynamic transformations of a moving domain wall between the different types
+of its internal structure. Three unique periodicities found, which consist of
+different types of domain wall that are transformed from type one to another.
+The transformation periods vary with the field strength and the nanostripe
+width. This novel phenomenon can be described by the dynamic motion of a
+limited number of magnetic topological solitons such as vortex and antivortex
+in nanostripes.",0706.2542v1
+2007-10-16,A Tale Of Two Spicules: The Impact of Spicules on the Magnetic Chromosphere,"We use high-resolution observations of the Sun in Ca II H 3968 A from the
+Solar Optical Telescope on Hinode to show that there are at least two types of
+spicules that dominate the structure of the magnetic solar chromosphere. Both
+types are tied to the relentless magnetoconvective driving in the photosphere,
+but have very different dynamic properties. ``Type-I'' spicules are driven by
+shock waves that form when global oscillations and convective flows leak into
+the upper atmosphere along magnetic field lines on 3-7 minute timescales.
+``Type-II'' spicules are much more dynamic: they form rapidly (in ~10s), are
+very thin (<200km wide), have lifetimes of 10-150s (at any one height) and seem
+to be rapidly heated to (at least) transition region temperatures, sending
+material through the chromosphere at speeds of order 50-150 km/s. The
+properties of Type II spicules suggest a formation process that is a
+consequence of magnetic reconnection, typically in the vicinity of magnetic
+flux concentrations in plage and network. Both types of spicules are observed
+to carry Alfven waves with significant amplitudes of order 20 km/s.",0710.2934v2
+2008-12-27,Bistability of vortex core dynamics in a single perpendicularly magnetized nano-disk,"Microwave spectroscopy of individual vortex-state magnetic nano-disks in a
+perpendicular bias magnetic field, $H$, is performed using a magnetic resonance
+force microscope (MRFM). It reveals the splitting induced by $H$ on the
+gyrotropic frequency of the vortex core rotation related to the existence of
+the two stable polarities of the core. This splitting enables spectroscopic
+detection of the core polarity. The bistability extends up to a large negative
+(antiparallel to the core) value of the bias magnetic field $H_r$, at which the
+core polarity is reversed. The difference between the frequencies of the two
+stable rotational modes corresponding to each core polarity is proportional to
+$H$ and to the ratio of the disk thickness to its radius. Simple analytic
+theory in combination with micromagnetic simulations give quantitative
+description of the observed bistable dynamics.",0812.4733v2
+2009-10-20,Flow instabilities of magnetic flux tubes IV. Flux storage in the solar overshoot region,"We consider the effects of material flows on the dynamics of toroidal
+magnetic flux tubes located close to the base of the solar convection zone,
+initially within the overshoot region. The problem is to find the physical
+conditions in which magnetic flux can be stored for periods comparable to the
+dynamo amplification time, which is of the order of a few years. We carry out
+nonlinear numerical simulations to investigate the stability and dynamics of
+thin flux tubes subject to perpendicular and longitudinal flows. We compare the
+simulations with the results of simplified analytical approximations. We
+determine ranges of the flow parameters for which a linearly Parker-stable
+magnetic flux tube is stored in the middle of the overshoot region for a period
+comparable to the dynamo amplification time. The residence time for magnetic
+flux tubes with fluxes of 2x10^{21} Mx in the convective overshoot layer is
+comparable to the dynamo amplification time, provided that the average speed
+and the duration of the downflow do not exceed about 50 m/s and 100 days,
+respectively, and that the lateral extension of the flow is smaller than about
+10 degrees.",0910.3858v1
+2010-07-16,Relativistic magnetohydrodynamics in dynamical spacetimes: A new AMR implementation,"We have written and tested a new general relativistic magnetohydrodynamics
+(GRMHD) code, capable of evolving MHD fluids in dynamical spacetimes with
+adaptive-mesh refinement (AMR). Our code solves the Einstein-Maxwell-MHD system
+of coupled equations in full 3+1 dimensions, evolving the metric via the
+Baumgarte-Shapiro Shibata-Nakamura (BSSN) formalism and the MHD and magnetic
+induction equations via a conservative, high-resolution shock-capturing scheme.
+The induction equations are recast as an evolution equation for the magnetic
+vector potential, which exists on a grid that is staggered with respect to the
+hydrodynamic and metric variables. The divergenceless constraint div(B)=0 is
+enforced by the curl of the vector potential. Our MHD scheme is fully
+compatible with AMR, so that fluids at AMR refinement boundaries maintain
+div(B)=0. In simulations with uniform grid spacing, our MHD scheme is
+numerically equivalent to a commonly used, staggered-mesh constrained-transport
+scheme. We present code validation test results, both in Minkowski and curved
+spacetimes. They include magnetized shocks, nonlinear Alfv\'en waves,
+cylindrical explosions, cylindrical rotating disks, magnetized Bondi tests, and
+the collapse of a magnetized rotating star. Some of the more stringent tests
+involve black holes. We find good agreement between analytic and numerical
+solutions in these tests, and achieve convergence at the expected order.",1007.2848v1
+2010-11-26,Generation of electric currents in the chromosphere via neutral-ion drag,"We consider the generation of electric currents in the solar chromosphere
+where the ionization level is typically low. We show that ambient electrons
+become magnetized even for weak magnetic fields (30 G); that is, their
+gyrofrequency becomes larger than the collision frequency while ion motions
+continue to be dominated by ion-neutral collisions. Under such conditions, ions
+are dragged by neutrals, and the magnetic field acts as if it is frozen-in to
+the dynamics of the neutral gas. However, magnetized electrons drift under the
+action of the electric and magnetic fields induced in the reference frame of
+ions moving with the neutral gas. We find that this relative motion of
+electrons and ions results in the generation of quite intense electric
+currents. The dissipation of these currents leads to resistive electron heating
+and efficient gas ionization. Ionization by electron-neutral impact does not
+alter the dynamics of the heavy particles; thus, the gas turbulent motions
+continue even when the plasma becomes fully ionized, and resistive dissipation
+continues to heat electrons and ions. This heating process is so efficient that
+it can result in typical temperature increases with altitude as large as
+0.1-0.3 eV/km. We conclude that this process can play a major role in the
+heating of the chromosphere and corona",1011.5834v1
+2011-02-01,Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations,"A kinetic treatment is developed for collisionless magnetized plasmas
+occurring in high-temperature, low-density astrophysical accretion disks, such
+as are thought to be present in some radiatively-inefficient accretion flows
+onto black holes. Quasi-stationary configurations are investigated, within the
+framework of a Vlasov-Maxwell description. The plasma is taken to be
+axisymmetric and subject to the action of slowly time-varying gravitational and
+electromagnetic fields. The magnetic field is assumed to be characterized by a
+family of locally nested but open magnetic surfaces. The slow collisionless
+dynamics of these plasmas is investigated, yielding a reduced gyrokinetic
+Vlasov equation for the kinetic distribution function. For doing this, an
+asymptotic quasi-stationary solution is first determined, represented by a
+generalized bi-Maxwellian distribution expressed in terms of the relevant
+adiabatic invariants. The existence of the solution is shown to depend on
+having suitable kinetic constraints and conditions leading to particle trapping
+phenomena. With this solution one can treat temperature anisotropy, toroidal
+and poloidal flow velocities and finite Larmor-radius effects. An asymptotic
+expansion for the distribution function permits analytic evaluation of all of
+the relevant fluid fields. Basic theoretical features of the solution and their
+astrophysical implications are discussed. As an application, the possibility of
+describing the dynamics of slowly time-varying accretion flows and the
+self-generation of magnetic field by means of a \textquotedblleft kinetic
+dynamo effect\textquotedblright\ is discussed. Both effects are shown to be
+related to intrinsically-kinetic physical mechanisms.",1102.0179v2
+2011-04-04,Computer simulations of colloidal transport on a patterned magnetic substrate,"We study the transport of paramagnetic colloidal particles on a patterned
+magnetic substrate with kinetic Monte Carlo and Brownian dynamics computer
+simulations. The planar substrate is decorated with point dipoles in either
+parallel or zigzag stripe arrangements and exposed to an additional external
+magnetic field that oscillates in time. For the case of parallel stripes we
+find that the magnitude and direction of the particle current is controlled by
+the tilt angle of the external magnetic field. The effect is reliably obtained
+in a wide range of ratios between temperature and magnetic permeability.
+Particle transport is achieved only when the period of oscillation of the
+external field is greater than a critical value. For the case of zigzag stripes
+a current is obtained using an oscillating external field normal to the
+substrate. In this case, transport is only possible in the vertex of the
+zigzag, giving rise to a narrow stream of particles. The magnitude and
+direction of the particle current are found to be controlled by a combination
+of the zigzag angle and the distance of the colloids from the substrate.
+Metropolis Monte Carlo and Brownian dynamics simulations predict results that
+are in good agreement with each other. Using kinetic Monte Carlo we find that
+at high density the particle transport is hindered by jamming.",1104.0544v1
+2011-07-18,Quasi-static magnetohydrodynamic turbulence at high Reynolds number,"We analyse the anisotropy of homogeneous turbulence in an electrically
+conducting fluid submitted to a uniform magnetic field, for low magnetic
+Reynolds number, in the quasi- static approximation. We interpret disagreeing
+previous predictions between linearized theory and simulations: in the linear
+limit, the kinetic energy of transverse velocity components, normal to the
+magnetic field, decays faster than the kinetic energy of the axial component,
+along the magnetic field (Moffatt (1967)); whereas many numerical studies
+predict a final state characterised by dominant energy of transverse velocity
+components. We investigate the corresponding nonlinear phenomenon using Direct
+Numerical Simulations of freely-decaying turbulence, and a two-point
+statistical spectral closure based on the Eddy Damped Quasi-Normal Markovian
+model. The transition from the three-dimensional turbulent flow to a
+""two-and-a-half-dimensional"" flow (Montgomery & Turner (1982)) is a result of
+the combined effects of short-time linear Joule dissipation and longer time
+nonlinear creation of polarisation anisotropy. It is this combination of linear
+and nonlinear effects which explains the disagreement between predictions from
+linearized theory and results from numerical simulations. The transition is
+characterized by the elongation of turbulent structures along the applied
+magnetic field, and by the strong anisotropy of directional two-point
+correlation spectra, in agreement with experimental evidence. Inertial
+equatorial transfers in both DNS and the model are presented to describe in
+detail the most important equilibrium dynamics. Spectral scalings are
+maintained in high Reynolds number turbulence attainable only with the EDQNM
+model, which also provides simplified modelling of the asymptotic state of
+quasi-static MHD turbulence.",1107.3435v1
+2011-09-17,Magnetic clouds in the solar wind: A numerical assessment study of analytical models,"Magnetic clouds (MCs) are ""magnetized plasma clouds"" moving in the solar
+wind. MCs transport magnetic flux and helicity away from the Sun. These
+structures are not stationary but feature temporal evolution as they propagate
+in the solar wind. Simplified analytical models are frequently used for the
+description of MCs, and fit certain observational data well. The goal of the
+present study is to investigate numerically the validity of an analytical model
+which is widely used for the description of MCs, and to determine under which
+conditions this model's implied assumptions cease to be valid. A numerical
+approach is applied. Analytical solutions that have been derived in previous
+studies are implemented in a \textbf{3-D magnetohydrodynamic} simulation code
+as initial conditions. Initially, the analytical model represents the main
+observational features of the MCs. However, these characteristics prevail only
+if the structure moves with a velocity close to the velocity of the background
+flow. In this case an MC's evolution can quite accurately be described using an
+analytic, self-similar approach. The dynamics of the magnetic structures which
+move with a velocity significantly above or below that of the velocity of the
+solar wind is investigated in detail. Besides the standard case in which MCs
+only expand and propagate in the solar wind, the case of an MC rotating around
+its axis of symmetry is also considered, and the resulting influence on the
+MC's dynamics is studied.",1109.3790v1
+2012-03-27,High frequency permeability of magnonic metamaterials with magnetic inclusions of complex shape,"We present a method of calculation of the effective magnetic permeability of
+magnonic metamaterials containing periodically arranged magnetic inclusions of
+arbitrary shapes. The spectrum of spin wave modes confined in the inclusions is
+fully taken into account. Within the scope of the proposed method, we compare
+two approaches. The first approach is based on a simple semi-analytical theory
+that uses the numerically calculated susceptibility tensor of an isolated
+inclusion as input data. Within the second approach, micromagnetic packages
+with periodic boundary conditions (PBC) are used to calculate the
+susceptibility of a single 2D periodic array of such inclusions, with the whole
+3D metamaterial consisting of a stack of such arrays. To calculate the
+susceptibility tensor of an isolated inclusion, we have implemented and
+compared two different methods: (a) a micromagnetic method, in which we have
+employed three different micromagnetic packages: the finite element package
+NMAG and the two finite differences packages OOMMF and MicroMagus; and (b) the
+modified dynamical matrix method. To illustrate the methodology, we have
+calculated the effective permeability of a metamaterial consisting of a stack
+of hexagonal arrays of magnetic nanodisks in a non-magnetic matrix. The range
+of geometrical parameters for which such a metamaterial is characterized by the
+negative permeability has been identified. The critical comparison of the
+different micromagnetic packages and the dynamical matrix method (based on the
+calculation of the susceptibility tensor of an isolated inclusion) has
+demonstrated that their results agree to within 3 %.",1203.6116v1
+2012-05-11,Simulated Tempering and Magnetizing: An Application of Two-Dimensional Simulated Tempering to Two-Dimensional Ising Model and Its Crossover,"We performed two-dimensional simulated tempering (ST) simulations of the
+two-dimensional Ising model with different lattice sizes in order to
+investigate the two-dimensional ST's applicability to dealing with phase
+transitions and to study the crossover of critical scaling behavior. The
+external field, as well as the temperature, was treated as a dynamical variable
+updated during the simulations. Thus, this simulation can be referred to as
+""Simulated Tempering and Magnetizing (STM)."" We also performed the ""Simulated
+Magnetizing"" (SM) simulations, in which the external field was considered as a
+dynamical variable and temperature was not. As has been discussed by previous
+studies, the ST method is not always compatible with first-order phase
+transitions. This is also true in the magnetizing process. Flipping of the
+entire magnetization did not occur in the SM simulations under $T_\mathrm{c}$
+in large lattice-size simulations. However, the phase changed through the high
+temperature region in the STM simulations. Thus, the dimensional extension let
+us eliminate the difficulty of the first-order phase transitions and study wide
+area of the phase space. We then discuss how frequently parameter-updating
+attempts should be made for optimal convergence. The results favor frequent
+attempts. We finally study the crossover behavior of the phase transitions with
+respect to the temperature and external field. The crossover behavior was
+clearly observed in the simulations in agreement with the theoretical
+implications.",1205.2523v1
+2012-06-08,Electron cyclotron resonance near the axis of the gas-dynamic trap,"Propagation of an extraordinary electromagnetic wave in the vicinity of
+electron cyclotron resonance surface in an open linear trap is studied
+analytically, taking into account inhomogeneity of the magnetic field in
+paraxial approximation. Ray trajectories are derived from a reduced dispersion
+equation that makes it possible to avoid the difficulty associated with a
+transition from large propagation angles to the case of strictly longitudinal
+propagation. Our approach is based on the theory, originally developed by the
+Zvonkov and Timofeev [1], who used the paraxial approximation for the magnetic
+field strength, but did not consider the slope of the magnetic field lines,
+which led to considerable error, as has been recently noted by Gospodchikov and
+Smolyakova [2]. We have found ray trajectories in analytic form and
+demonstrated that the inhomogeneity of both the magnetic field strength and the
+field direction can qualitatively change the picture of wave propagation and
+significantly affect the efficiency of electron cyclotron heating of a plasma
+in a linear magnetic trap. Analysis of the ray trajectories has revealed a
+criterion for the resonance point on the axis of the trap to be an attractor
+for the ray trajectories. It is also shown that a family of ray trajectories
+can still reach the resonance point on the axis if the latter generally repels
+the ray trajectories.
+  As an example, results of general theory are applied to the electron
+cyclotron resonance heating experiment which is under preparation on the Gas
+Dynamic Trap in the Budker Institute of Nuclear Physics [3].",1206.1670v1
+2012-07-31,Surface Acoustic Wave-Driven Ferromagnetic Resonance in Nickel Thin Films: Theory and Experiment,"We present an extensive experimental and theoretical study of surface
+acoustic wave-driven ferromagnetic resonance. In a first modeling approach
+based on the Landau-Lifshitz-Gilbert equation, we derive expressions for the
+magnetization dynamics upon magnetoelastic driving that are used to calculate
+the absorbed microwave power upon magnetic resonance as well as the spin
+current density generated by the precessing magnetization in the vicinity of a
+ferromagnet/normal metal interface. In a second modeling approach, we deal with
+the backaction of the magnetization dynamics on the elastic wave by solving the
+elastic wave equation and the Landau-Lifshitz-Gilbert equation
+selfconsistently, obtaining analytical solutions for the acoustic wave phase
+shift and attenuation. We compare both modeling approaches with the complex
+forward transmission of a LiNbO$_3$/Ni surface acoustic wave hybrid device
+recorded experimentally as a function of the external magnetic field
+orientation and magnitude, rotating the field within three different planes and
+employing three different surface acoustic wave frequencies. We find
+quantitative agreement of the experimentally observed power absorption and
+surface acoustic wave phase shift with our modeling predictions using one set
+of parameters for all field configurations and frequencies.",1208.0001v1
+2012-10-01,51V-NMR study of antiferromagnetic state and spin dynamics in the quasi-one-dimensional BaCo2V2O8,"We report on our 51V-NMR study of static and dynamical magnetic properties in
+the quasi-one-dimensional antiferromagnet BaCo2V2O8. Although the NMR spectrum
+shows well-defined antiferromagnetic (AF) order in the N\'eel ground state, the
+AF characteristic from the NMR spectrum is incomplete between 3.5 K and TN= 5.4
+K, which could be affected by quantum spin fluctuations. The AF NMR spectrum
+indicates two V sites experiencing different magnetic field magnitudes, HA1=2.1
+kOe and HA2=3.8 kOe. These internal fields could be explained by accounting for
+the classical and the pseudo-dipolar fields from Co2+ spins with a proposed
+magnetic structure based on the neutron diffraction measurements. In the
+paramagnetic state, the nuclear spin relaxation is dominated by AF spin
+fluctuations through the dipolar-type coupling between V and surrounding Co2+
+ions. The linear relation between the nuclear spin-lattice relaxation rate
+1/T1T and the magnetic susceptibility chi indicates that the Q component of
+magnetic susceptibility chi(Q) is roughly proportional to chi, where Q is the
+AF wave number. A change in slope of 1/T1T with respect to \chi around 150 K
+suggests a change in the AF spin fluctuation spectrum.",1210.0272v1
+2013-01-21,Frustration effect on magnetic excitations in a two-leg spin-ladder system,"We theoretically study the magnetic excitations in a frustrated two-leg
+spin-ladder system, in which antiferromagnetic exchange interactions act on the
+nearest-neighbor and next-nearestneighbor bonds in the leg direction, and on
+the nearest-neighbor bonds in the rung direction. A dynamical spin correlation
+function at zero temperature is calculated by using the dynamical
+density-matrix renormalization-group method for possible magnetic phases, i.e.,
+columnar-dimer and rung-singlet phases. The columnar-dimer phase is
+characterized by multi-spinon excitations with spin gap, while the rung-singlet
+phase is dominated by the triplet excitation in the rung direction. It is found
+that a major difference between these two phases appears in the spectral weight
+of magnetic excitations, in particular, of the bonding and anti-bonding modes
+in the rung direction. Therefore, we can distinguish one phase from the other
+by the difference of the spectral weight. Furthermore, we examine frustration
+effect on both modes in the rung-singlet phase with a perturbation theory from
+the strong coupling limit. It is shown that the anti-bonding mode is stable
+against the frustration, and a wavenumber with minimum excitation energy is
+shifted from the commensurate to incommensurate ones. On the other hand, the
+bonding mode is merged into the continuum excitation of multiple triplet
+excitations by increasing the frustration. By comparing our results with
+inelastic neutron scattering experiments for BiCu$_2$PO$_6$, the magnitude of
+the magnetic exchange interactions and the ground state will be determined.",1301.4740v3
+2013-02-14,Influence of electromagnetic fields on the evolution of initially homogeneous and isotropic universe,"Simple exact solutions presented here describe the universes which spatial
+geometries are asymptotically homogeneous and isotropic near the initial
+singularity, but which evolution goes under the influence of primordial
+magnetic fields. In all these ""deformed"" Friedmann models (spatially flat, open
+or closed), the initial magnetic fields are concentrated near some axis of
+symmetry and their lines are the circles -- the lines of the azimuthal
+coordinate $\varphi$. Caused by the expansion of the universe, the
+time-dependence of a magnetic field induces (in accordance with the Faraday
+law) the emergence of source-free electric fields. In comparison with the
+Friedmann models, the cosmological expansion goes with acceleration in spatial
+directions across the magnetic field, and with deceleration along the magnetic
+lines, so that in flat and open models, in fluid comoving coordinates, the
+lengths of $\varphi$-circles of large enough radius or for late enough times
+decrease and vanish for $t\to\infty$. This means that in flat and open models,
+we have a partial dynamical closure of space-time at large distances from the
+axis, i.e. from the regions where the electromagnetic fields in our solutions
+are concentrated. To get simple exact solutions of the Einstein-Maxwell and
+perfect fluid equations, we assume for the perfect fluid (which supports the
+isotropic and homogeneous ""background"" Friedmann geometries) rather exotic,
+stiff matter equation of state $\varepsilon=p$. However, it seems reasonable to
+expect that similar effects might take place in the mutual dynamics of geometry
+and strong electromagnetic fields in the universes with more realistic matter
+equations of state.",1302.3338v1
+2013-02-18,Local support against gravity in magneto-turbulent fluids,"Comparisons of the integrated thermal pressure support of gas against its
+gravitational potential energy lead to critical mass scales for gravitational
+instability such as the Jeans and the Bonnor-Ebert masses, which play an
+important role in analysis of many physical systems, including the heuristics
+of numerical simulations. In a strict theoretical sense, however, neither the
+Jeans nor the Bonnor-Ebert mass are meaningful when applied locally to
+substructure in a self-gravitating turbulent medium. For this reason, we
+investigate the local support by thermal pressure, turbulence, and magnetic
+fields against gravitational compression through an approach that is
+independent of these concepts. At the centre of our approach is the dynamical
+equation for the divergence of the velocity field. We carry out a statistical
+analysis of the source terms of the local compression rate (the negative time
+derivative of the divergence) for simulations of forced self-gravitating
+turbulence in periodic boxes with zero, weak, and moderately strong mean
+magnetic fields (measured by the averages of the magnetic and thermal
+pressures). We also consider the amplification of the magnetic field energy by
+shear and by compression. Thereby, we are able to demonstrate that the support
+against gravity is dominated by thermal pressure fluctuations, although
+magnetic pressure also yields a significant contribution. The net effect of
+turbulence in the highly supersonic regime, however, is to enhance compression
+rather than supporting overdense gas even if the vorticity is very high. This
+is incommensurate with the support of the highly dynamical substructures in
+magneto-turbulent fluids being determined by local virial equilibria of volume
+energies without surface stresses.",1302.4292v2
+2013-04-10,Magnetization and spin dynamics of the spin S=1/2 hourglass nanomagnet Cu5(OH)2(NIPA)4*10H2O,"We report a combined experimental and theoretical study of the spin S=1/2
+nanomagnet Cu5(OH)2(NIPA)4*10H2O (Cu5-NIPA). Using thermodynamic, electron spin
+resonance and 1H nuclear magnetic resonance measurements on one hand, and ab
+initio density-functional band-structure calculations, exact diagonalizations
+and a strong coupling theory on the other, we derive a microscopic magnetic
+model of Cu5-NIPA and characterize the spin dynamics of this system. The
+elementary five-fold Cu2+ unit features an hourglass structure of two
+corner-sharing scalene triangles related by inversion symmetry. Our microscopic
+Heisenberg model comprises one ferromagnetic and two antiferromagnetic exchange
+couplings in each triangle, stabilizing a single spin S=1/2 doublet ground
+state (GS), with an exactly vanishing zero-field splitting (by Kramer's
+theorem), and a very large excitation gap of \Delta~68 K. Thus, Cu5-NIPA is a
+good candidate for achieving long electronic spin relaxation (T1) and coherence
+(T2) times at low temperatures, in analogy to other nanomagnets with low-spin
+GS's. Of particular interest is the strongly inhomogeneous distribution of the
+GS magnetic moment over the five Cu2+ spins. This is a purely
+quantum-mechanical effect since, despite the non-frustrated nature of the
+magnetic couplings, the GS is far from the classical collinear ferrimagnetic
+configuration. Finally, Cu5-NIPA is a rare example of a S=1/2 nanomagnet
+showing an enhancement in the nuclear spin-lattice relaxation rate 1/T1 at
+intermediate temperatures.",1304.2826v1
+2013-04-27,Quantum motion and level quantization of a skyrmion in a pinning potential in chiral magnets,"A new topological excitation called skyrmion has been observed experimentally
+in chiral magnets without spatial inversion symmetry. The dynamics of a
+skyrmion is equivalent to an electron moving in a strong magnetic field. As a
+skyrmion involves large number of spins, it is not clear whether there exist
+observable quantum effects. In this work, we study the quantum dynamics of a
+skyrmion in a pinning potential. Without a pinning potential, the skyrmion
+performs cyclotron motion due to the strong emergent magnetic field originating
+from the Berry phase of spins, and all skyrmions occupy the lowest Landau
+level. Their wave functions are strongly localized in a region with radius less
+than $1\ \AA$ when no driving force is applied. Thus in most circumstances, the
+quantum effects of a skyrmion are weak. In the presence of a pinning potential,
+the lowest Landau level for skyrmions is split into quantized levels,
+characterized by the orbital moments. The transition between quantized levels
+can be observed experimentally by microwave absorption measurements in low
+temperature region. The quantum effects are more prominent for a skyrmion with
+a small size, which can be realized in magnets with a large
+Dzyaloshinskii-Moriya interaction.",1304.7322v2
+2013-08-14,A strong magnetic field around the supermassive black hole at the centre of the Galaxy,"The centre of our Milky Way harbours the closest candidate for a supermassive
+black hole. The source is thought to be powered by radiatively inefficient
+accretion of gas from its environment. This form of accretion is a standard
+mode of energy supply for most galactic nuclei. X-ray measurements have already
+resolved a tenuous hot gas component from which it can be fed. However, the
+magnetization of the gas, a crucial parameter determining the structure of the
+accretion flow, remains unknown. Strong magnetic fields can influence the
+dynamics of the accretion, remove angular momentum from the infalling gas,
+expel matter through relativistic jets and lead to the observed synchrotron
+emission. Here we report multi-frequency measurements with several radio
+telescopes of a newly discovered pulsar close to the Galactic Centre and show
+that its unusually large Faraday rotation indicates a dynamically relevant
+magnetic field near the black hole. If this field is accreted down to the event
+horizon it provides enough magnetic flux to explain the observed emission from
+the black hole, from radio to X-rays.",1308.3147v1
+2013-12-11,Electric and magnetic response of hot QCD matter,"We study the electric conductivity as well as the magnetic response of hot
+QCD matter at various temperatures $T$ and chemical potentials $\mu_q$ within
+the off-shell Parton-Hadron-String Dynamics (PHSD) transport approach for
+interacting partonic systems in a finite box with periodic boundary conditions.
+The response of the strongly-interacting system in equilibrium to an external
+electric field defines the electric conductivity $\sigma_0$ whereas the
+response to a moderate external magnetic field defines the induced diamagnetic
+moment $\mu_L$ ($T, \mu_q$) as well as the spin susceptibility $\chi_S(T,
+\mu_q)$. We find a sizeable temperature dependence of the dimensionless ratio
+$\sigma_0/T$ well in line with calculations in a relaxation time approach for
+$T_c \! < \! T < \! 2.5 \!\, T_c$ as well as an increase of $\sigma_0$ with
+$\mu_q^2/T^2$. Furthermore, the frequency dependence of the electric
+conductivity $\sigma(\Omega)$ shows a simple functional form well in line with
+results from the Dynamical QuasiParticle Model (DQPM). The spin susceptibility
+$\chi_S(T,\mu_q)$ is found to increase with temperature $T$ and to rise $\sim
+\mu_q ^2/T^2$, too. The actual values for the magnetic response of the QGP in
+the temperature range below 250 MeV show that the QGP should respond
+diamagnetically in actual ultra-relativistic heavy-ion collisions since the
+maximal magnetic fields created in these collisions are smaller than $B_c(T)$
+which defines a boundary between diamagnetism and paramagnetism.",1312.3189v2
+2014-06-25,"Surface acoustic wave driven ferromagnetic resonance in (Ga,Mn)(As,P) epilayers","Interdigitated transducers were used to generate and detect surface acoustic
+waves on a thin layer of (Ga,Mn)(As,P). The out-of-plane uniaxial magnetic
+anisotropy of this dilute magnetic semiconductor is very sensitive to the
+strain of the layer, making it an ideal test material for the dynamic control
+of magnetization via magneto-striction. The time-domain measurement of the
+amplitude and phase of the transmitted SAW during magnetic field sweeps
+indicated a clear resonant behavior at a field close to the one calculated to
+give a precession frequency equal to the SAW frequency. A resonance was
+observed from 5K to 85K, just below the Curie temperature of the layer. A full
+analytical treatment of the coupled magnetization/acoustic dynamics showed that
+the magneto-strictive coupling modifies the elastic constants of the material
+and accordingly the wave-vector solution to the elastic wave equation. The
+shape and position of the resonance were well reproduced by the calculations,
+in particular the fact that velocity (phase) variations resonated at lower
+fields than the acoustic attenuation variations.",1406.6483v1
+2014-10-04,Reconnection Properties of Large-Scale Current Sheets During Coronal Mass Ejection Eruptions,"We present a detailed analysis of the properties of magnetic reconnection at
+large-scale current sheets in a high cadence version of the Lynch & Edmondson
+(2013) 2.5D MHD simulation of sympathetic magnetic breakout eruptions from a
+pseudostreamer source region. We examine the resistive tearing and breakup of
+the three main current sheets into chains of X- and O-type null points and
+follow the dynamics of magnetic island growth, their merging, transit, and
+ejection with the reconnection exhaust. For each current sheet, we quantify the
+evolution of the length-to-width aspect ratio (up to $\sim$100:1), Lundquist
+number ($\sim$10$^3$), and reconnection rate (inflow-to-outflow ratios reaching
+$\sim$0.40). We examine the statistical and spectral properties of the
+fluctuations in the current sheets resulting from the plasmoid instability,
+including the distribution of magnetic island area, mass, and flux content. We
+show that the temporal evolution of the spectral index of the
+reconnection-generated magnetic energy density fluctuations appear to reflect
+global properties of the current sheet evolution. Our results are in excellent
+agreement with recent, high resolution reconnection-in-a-box simulations even
+though our current sheets' formation, growth, and dynamics are intrinsically
+coupled to the global evolution of sequential sympathetic CME eruptions.",1410.1089v2
+2015-01-19,Negative magnetic eddy diffusivities from test-field method and multiscale stability theory,"The generation of large-scale magnetic field in the kinematic regime in the
+absence of an alpha-effect is investigated by following two different
+approaches, namely the test-field method and multiscale stability theory
+relying on the homogenisation technique. We show analytically that the former,
+applied for the evaluation of magnetic eddy diffusivities, yields results that
+fully agree with the latter. Our computations of the magnetic eddy diffusivity
+tensor for the specific instances of the parity-invariant flow-IV of G.O.
+Roberts and the modified Taylor-Green flow in a suitable range of parameter
+values confirm the findings of previous studies, and also explain some of their
+apparent contradictions. The two flows have large symmetry groups; this is used
+to considerably simplify the eddy diffusivity tensor. Finally, a new analytic
+result is presented: upon expressing the eddy diffusivity tensor in terms of
+solutions to auxiliary problems for the adjoint operator, we derive relations
+between magnetic eddy diffusivity tensors that arise for opposite small-scale
+flows v(x) and -v(x).",1501.04465v3
+2015-01-29,Mitigating Radiation Impact on Superconducting Magnets of the Higgs Factory Muon Collider,"Recent discovery of a Higgs boson boosted interest in a low-energy
+medium-luminosity Muon Collider as a Higgs Factory (HF). A preliminary design
+of the HF storage ring (SR) is based on cos-theta Nb3Sn superconducting (SC)
+magnets with the coil inner diameter ranging from 50 cm in the interaction
+region to 16 cm in the arc. The coil cross-sections were chosen based on the
+operation margin, field quality and quench protection considerations to provide
+an adequate space for the beam pipe, helium channel and inner absorber (liner).
+With the 62.5-GeV muon energy and 2 x 10^12 muons per bunch, the electrons from
+muon decays deposit about 300 kW in the SC magnets, or unprecedented 1 kW/m
+dynamic heat load, which corresponds to a multi-MW room temperature equivalent.
+Based on the detailed MARS15 model built and intense simulations, a
+sophisticated protection system was designed for the entire SR to bring the
+peak power density in the SC coils safely below the quench limit and reduce the
+dynamic heat load to the cold mass by a factor of 100. The system consists of
+tight tungsten masks in the magnet interconnect regions and elliptical tungsten
+liners optimized for each magnet.",1501.07624v1
+2015-03-12,"Classification of magnetized star--planet interactions: bow shocks, tails, and inspiraling flows","Close-in exoplanets interact with their host stars gravitationally as well as
+via their magnetized plasma outflows. The rich dynamics that arises may result
+in distinct observable features. Our objective is to study and classify the
+morphology of the different types of interaction that can take place between a
+giant close-in planet (a Hot Jupiter) and its host star, based on the physical
+parameters that characterize the system. We perform 3D magnetohydrodynamic
+numerical simulations to model the star--planet interaction, incorporating a
+star, a Hot Jupiter, and realistic stellar and planetary outflows. We explore a
+wide range of parameters and analyze the flow structures and magnetic
+topologies that develop. Our study suggests the classification of star--planet
+interactions into four general types, based on the relative magnitudes of three
+characteristic length scales that quantify the effects of the planetary
+magnetic field, the planetary outflow, and the stellar gravitational field in
+the interaction region. We describe the dynamics of these interactions and the
+flow structures that they give rise to, which include bow shocks, cometary-type
+tails, and inspiraling accretion streams. We point out the distinguishing
+features of each of the classified cases and discuss some of their
+observationally relevant properties. The magnetized interactions of
+star--planet systems can be categorized, and their general morphologies
+predicted, based on a set of basic stellar, planetary, and orbital parameters.",1503.03551v1
+2015-03-16,Spontaneous decay of periodic magnetostatic equilibria,"In order to understand the conditions which lead a highly magnetized,
+relativistic plasma to become unstable, and in such cases how the plasma
+evolves, we study a prototypical class of magnetostatic equilibria where the
+magnetic field satisfies $\nabla \times\mathbf B = \alpha \mathbf B$, where
+$\alpha$ is spatially uniform, on a periodic domain. Using numerical solutions
+we show that generic examples of such equilibria are unstable to ideal modes
+(including incompressible ones) which are marked by exponential growth in the
+linear phase. We characterize the unstable mode, showing how it can be
+understood in terms of merging magnetic and current structures, and explicitly
+demonstrate its instability using the energy principle. Following the nonlinear
+evolution of these solutions, we find that they rapidly develop regions with
+relativistic velocities and electric fields of comparable magnitude to the
+magnetic field, liberating magnetic energy on dynamical timescales and
+eventually settling into a configuration with the largest allowable wavelength.
+These properties make such solutions a promising setting for exploring the
+mechanisms behind extreme cosmic sources of gamma rays.",1503.04793v3
+2015-05-04,Spatially resolved ultrafast magnetic dynamics launched at a complex-oxide hetero-interface,"Static strain in complex oxide heterostructures has been extensively used to
+engineer electronic and magnetic properties at equilibrium. In the same spirit,
+deformations of the crystal lattice with light may be used to achieve
+functional control across hetero-interfaces dynamically. Here, by exciting
+large amplitude infrared-active vibrations in a LaAlO3 substrate we induce
+magnetic order melting in a NdNiO3 film across a hetero-interface. Femtosecond
+Resonant Soft X-ray Diffraction is used to determine the spatial and temporal
+evolution of the magnetic disordering. We observe a magnetic melt front that
+grows from the substrate interface into the film, at a speed that suggests
+electronically driven propagation. Light control and ultrafast phase front
+propagation at hetero-interfaces may lead to new opportunities in
+optomagnetism, for example by driving domain wall motion to transport
+information across suitably designed devices.",1505.00601v1
+2015-05-20,Three dimensional MHD Modeling of Vertical Kink Oscillations in an Active Region Plasma Curtain,"Observations on 2011 August 9 of an X6.9-class flare in active region (AR)
+11263 by the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics
+Observatory (SDO), were followed by a rare detection of vertical kink
+oscillations in a large-scale coronal active region plasma curtain in EUV
+coronal lines. The damped oscillations with periods in the range 8.8-14.9 min
+were detected and analyzed recently. Our aim is to study the generation and
+propagation of the MHD oscillations in the plasma curtain taking into account
+realistic 3D magnetic and density structure of the curtain. We also aim at
+testing and improving coronal seismology for more accurate determination of the
+magnetic field than with standard method. We use the observed morphological and
+dynamical conditions, as well as plasma properties of the coronal curtain based
+on Differential Emission Measure (DEM) analysis to initialize a 3D MHD model of
+its vertical and transverse oscillations by implementing the impulsively
+excited velocity pulse mimicking the flare generated nonlinear fast
+magnetosonic propagating disturbance interacting with the curtain obliquely.
+The model is simplified by utilizing initial dipole magnetic field, isothermal
+energy equation, and gravitationally stratified density guided by observational
+parameters. Using the 3D MHD model, we are able to reproduce the details of the
+vertical oscillations and study the process of their excitation by nonlinear
+fast magnetosonic pulse, propagation, and damping, finding agreement with the
+observations. We estimate the accuracy of simplified slab-based coronal
+seismology by comparing the determined magnetic field strength to actual values
+from the 3D MHD modeling results and demonstrate the importance of taking into
+account more realistic magnetic geometry and density for improving coronal
+seismology.",1505.05427v1
+2015-06-23,Layer-resolved magnetic exchange interactions of surfaces of late 3d elements: effects of electronic correlations,"We present the results of an ab initio study of magnetic properties of Fe, Co
+and Ni surfaces. In particular, we discuss their electronic structure and
+magnetic exchange interactions (Jij), as obtained by means of a combination of
+density functional theory and dynamical mean-field theory. All studied systems
+have a pronounced tendency to ferromagnetism both for bulk and surface atoms.
+The presence of narrow-band surface states is shown to enhance the magnetic
+moment as well as the exchange couplings. The most interesting results were
+obtained for the Fe surface where the atoms have a tendency to couple
+antiferromagnetically with each other. This interaction is relatively small,
+when compared to interlayer ferromagnetic interaction, and strongly depends on
+the lattice parameter. Local correlation effects are shown to lead to strong
+changes of the overall shape of the spectral functions. However, they seem to
+not play a decisive role on the overall picture of the magnetic couplings
+studied here. We have also investigated the influence of correlations on the
+spin and orbital moments of the bulk-like and surface atoms. We found that
+dynamical correlations in general lead to enhanced values of the orbital
+moment.",1506.07126v2
+2015-07-09,Validity of the Néel-Arrhenius model for highly anisotropic Co_xFe_{3-x}O_4 nanoparticles,"We report a systematic study on the structural and magnetic properties of
+Co_{x}Fe_{3-x}O_{4} magnetic nanoparticles with sizes between $5$ to $25$ nm,
+prepared by thermal decomposition of Fe(acac)_{3} and Co(acac)_{2}. The large
+magneto-crystalline anisotropy of the synthesized particles resulted in high
+blocking temperatures ($42$ K \leqq $T_B$ $\leqq 345$ K for $5 \leqq$ d $\leqq
+13$ nm ) and large coercive fields ($H_C \approxeq 1600$ kA/m for $T = 5$ K).
+The smallest particles ($<d>=5$ nm) revealed the existence of a magnetically
+hard, spin-disordered surface. The thermal dependence of static and dynamic
+magnetic properties of the whole series of samples could be explained within
+the N\'{e}el-Arrhenius relaxation framework without the need of ad-hoc
+corrections, by including the thermal dependence of the magnetocrystalline
+anisotropy constant $K_1(T)$ through the empirical Br\""{u}khatov-Kirensky
+relation. This approach provided $K_1(0)$ values very similar to the bulk
+material from either static or dynamic magnetic measurements, as well as
+realistic values for the response times ($\tau_0 \simeq 10^{-10}$ s).
+Deviations from the bulk anisotropy values found for the smallest particles
+could be qualitatively explained based on Zener\'{}s relation between $K_1(T)$
+and M(T).",1507.02711v1
+2016-01-27,On the use of financial analysis tools for the study of Dst time series in the frame of complex systems,"Technical analysis is considered the oldest, currently omnipresent, method
+for financial markets analysis, which uses past prices aiming at the possible
+short-term forecast of future prices. In the frame of complex systems, methods
+used to quantitatively analyze specific dynamic phenomena are often used to
+analyze phenomena from other disciplines on the grounds that are governed by
+similar dynamics. An interesting task is the forecast of a magnetic storm. The
+hourly Dst is used as a global index for the monitoring of Earth's
+magnetosphere, which could be either in quiet (normal) or in magnetic storm
+(pathological) state. This work is the first attempt to apply technical
+analysis tools on Dst time series, aiming at the identification of indications
+which could be used for the study of the temporal evolution of Earth's
+magnetosphere state. We focus on the analysis of Dst time series around the
+occurrence of magnetic storms, discussing the possible use of the resulting
+information in the frame of multidisciplinary efforts towards extreme events
+forecasting. We employ the following financial analysis tools: simple moving
+average (SMA), Bollinger bands, and relative strength index (RSI). Using these
+tools, we formulate a methodology based on all indications that could be
+revealed in order to infer the onset, duration and recovery phase of a magnetic
+storm, focusing on the temporal sequence they occur. The applicability of the
+proposed methodology is examined on characteristic cases of magnetic storms
+with encouraging results for space weather forecasting.",1601.07334v1
+2016-03-03,"Cantilever detected ferromagnetic resonance in thin Fe$_{50}$Ni$_{50}$, Co$_2$FeAl$_{0.5}$Si$_{0.5}$ and Sr$_2$FeMoO$_6$ films using a double modulation technique","In this work we introduce a new method of a ferromagnetic resonance (FMR)
+detection from thin, nm-size, films. Our setup is based on the commercial
+piezo-cantilever, used for atomic force microscopy. It has an option to rotate
+the sample in the magnetic field and it operates up to the high microwave
+frequencies of 160 GHz. Using our cantilever based FMR spectrometer we have
+investigated a set of samples, namely quasi-bulk and 84 nm film
+Co$_2$FeAl$_{0.5}$Si$_{0.5}$ samples, 16 nm Fe$_{50}$Ni$_{50}$ film and 150 nm
+Sr$_2$FeMoO$_6$ film. The high frequency ferromagnetic resonance (FMR) response
+from an extremely thin Fe$_{50}$Ni$_{50}$ film we have fitted with the
+conventional model for the magnetization dynamics. The cantilever detected FMR
+experiments on Sr$_2$FeMoO$_6$ film reveal an inability of the conventional
+model to fit frequency and angular dependences with the same set of parameters,
+which suggests that one has to take into account much more complicated nature
+of the magnetization precession in the Sr$_2$FeMoO$_6$ at low temperatures and
+high frequencies. Moreover, the complicated dynamics of the magnetization
+apparent in all investigated samples is suggested by a drastic increase of the
+linewidths with increasing microwave frequency, and by an emergence of the
+second line with an opposite angular dependence.",1603.01142v1
+2016-03-09,Subarcsecond Bright Points and Quasi-periodic Upflows Below a Quiescent Filament Observed by the IRIS,"Using UV spectra and SJIs from the IRIS, and coronal images and magnetograms
+from the Solar Dynamics Observatory (SDO), we present the new features in a
+quiescent filament channel: subarcsecond bright points (BPs) and quasi-periodic
+upflows. The BPs in the TR have a spatial scale of about 350$-$580 km and
+lifetime of more than several tens of minutes. They are located at stronger
+magnetic structures in the filament channel, with magnetic flux of about
+10$^{17}$$-$10$^{18}$ Mx. Quasi-periodic brightenings and upflows are observed
+in the BPs and the period is about 4$-$5 min. The BP and the associated
+jet-like upflow comprise a ""tadpole-shaped"" structure. The upflows move along
+bright filament threads and their directions are almost parallel to the spine
+of the filament. The upflows initiated from the BPs with opposite polarity
+magnetic fields have opposite directions. The velocity of the upflows in plane
+of sky is about 5$-$50 km s$^{-1}$. The emission line of Si IV 1402.77 {\AA} at
+the locations of upflows exhibits obvious blueshifts of about 5$-$30 km
+s$^{-1}$, and the line profile is broadened with the width of more than 20 km
+s$^{-1}$. The BPs seem to be the bases of filament threads and the upflows are
+able to convey mass for the dynamic balance of the filament. The
+""counter-streaming"" flows in previous observations may be caused by the
+propagation of bi-directional upflows initiated from opposite polarity magnetic
+fields. We suggest that quasi-periodic brightenings of BPs and quasi-periodic
+upflows result from small-scale oscillatory magnetic reconnections, which are
+modulated by solar p-mode waves.",1603.02809v1
+2016-03-31,Numerical optimization of writer and media for bit patterned magnetic recording,"In this work we present a micromagnetic study of the performance potential of
+bit-patterned (BP) magnetic recording media via joint optimization of the
+design of the media and of the magnetic write heads. Because the design space
+is large and complex, we developed a novel computational framework suitable for
+parallel implementation on compute clusters. Our technique combines advanced
+global optimization algorithms and finite-element micromagnetic solvers.
+Targeting data bit densities of $4\mathrm{Tb}/\mathrm{in}^2$, we optimize
+designs for centered, staggered, and shingled BP writing. The magnetization
+dynamics of the switching of the exchange-coupled composite BP islands of the
+media is treated micromagnetically. Our simulation framework takes into account
+not only the dynamics of on-track errors but also of the thermally induced
+adjacent-track erasure. With co-optimized write heads, the results show
+superior performance of shingled BP magnetic recording where we identify two
+particular designs achieving write bit-error rates of $1.5\mathrm{x}10^{-8}$
+and $8.4\mathrm{x}10^{-8}$, respectively. A detailed description of the key
+design features of these designs is provided and contrasted with centered and
+staggered BP designs which yielded write bit error rates of only
+$2.8\mathrm{x}10^{-3}$ (centered design) and $1.7\mathrm{x}10^{-2}$ (staggered
+design) even under optimized conditions.",1603.09493v4
+2016-04-18,Relationship between chromospheric evaporation and magnetic field topology in M-class solar flare,"Chromospheric evaporation is observed as Doppler blueshift during solar
+flares. It plays one of key roles in dynamics and energetics of solar flares,
+however, its mechanism is still unknown. In this paper we present a detailed
+analysis of spatially-resolved multi-wavelength observations of chromospheric
+evaporation during an M 1.0 class solar flare (SOL2014-06-12T21:12) using data
+from the NASA's IRIS (Interface Region Imaging Spectrograph) and HMI/SDO
+(Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory)
+telescopes, and VIS/NST (Visible Imaging Spectrometer at New Solar Telescope)
+high-resolution observations, covering the temperature range from 10^4 K to
+10^7 K. The results show that the averaged over the region Fe XXI blueshift of
+the hot evaporating plasma is delayed relative to the C II redshift of the
+relatively cold chromospheric plasma by about 1 min. The spatial distribution
+of the delays is not uniform across the region and can be as long as 2 min in
+several zones. Using vector magnetograms from HMI we reconstruct the magnetic
+field topology and the quasi-separatrix layer (QSL) and find that the blueshift
+delay regions as well as the H-alpha flare ribbons are connected to the region
+of magnetic polarity inversion line (PIL) and an expanding flux rope via a
+system of low-lying loop arcades with height < ~4.5 Mm. This allows us to
+propose an interpretation of the chromospheric evaporation based on the
+geometry of local magnetic fields, and the primary energy source associated
+with the PIL.",1604.05346v1
+2016-05-29,Heisenberg Necklace Model in Magnetic Field,"Motivated by the experimental realizations of nearly one-dimensional spin-1/2
+Heisenberg model found in chain cuprates SrCuO$_2$ and Sr$_2$CuO$_3$, which
+remain in a quantum-critical Luttinger liquid state down to temperatures that
+are much lower than in-chain exchange coupling, we consider the perturbation to
+this state caused by interactions with nuclear spins on the same sites. We
+study the low-energy sector of the Heisenberg Necklace model and estimate the
+effect of the coupling between the nuclear and the electronic spins on the
+overall spins dynamics and its dependence on the magnetic field. We find that
+the Necklace model has a characteristic energy scale, $\Lambda \sim
+J^{1/3}(\gamma I)^{2/3}$, at which the coupling between spins of the necklace
+and the spins of the Heisenberg chain becomes strong. In the strong magnetic
+field $\mu_B B > \Lambda$ the low energy spectrum is gapless, but two gapless
+bosonic modes have different velocities whose ratio at strong fields approaches
+a universal number, $\sqrt 2 +1$. In the case of Sr$_2$CuO$_3$ the energy scale
+$\Lambda $ is sizable and comparable to the Neel ordering temperature induced
+by the inter-chain coupling, and thus could noticeably modify the low
+temperature magnon dynamics. We further find that the above energy scale is
+insensitive to strong magnetic field, $\mu_B B \gg \Lambda \sim J^{1/3}(\gamma
+I)^{2/3}$, and therefore the interaction with nuclear spins cannot lead to
+unusually strong magnetic field dependence of the magnon spectrum observed by
+ESR in Sr$_2$CuO$_3$, which has been attributed to the magnon interaction with
+the Higgs mode.",1605.09014v2
+2016-06-02,Dynamical structure of magnetized dissipative accretion flow around black holes,"We study the global structure of optically thin, advection dominated,
+magnetized accretion flow around black holes. We consider the magnetic field to
+be turbulent in nature and dominated by the toroidal component. With this, we
+obtain the complete set of accretion solutions for dissipative flows where
+bremsstrahlung process is regarded as the dominant cooling mechanism. We show
+that rotating magnetized accretion flow experiences virtual barrier around
+black hole due to centrifugal repulsion that can trigger the discontinuous
+transition of the flow variables in the form of shock waves. We examine the
+properties of the shock waves and find that the dynamics of the post-shock
+corona (PSC) is controlled by the flow parameters, namely viscosity, cooling
+rate and strength of the magnetic field, respectively. We separate the
+effective region of the parameter space for standing shock and observe that
+shock can form for wide range of flow parameters. We obtain the critical
+viscosity parameter that allows global accretion solutions including shocks. We
+estimate the energy dissipation at the PSC from where a part of the accreting
+matter can deflect as outflows and jets. We compare the maximum energy that
+could be extracted from the PSC and the observed radio luminosity values for
+several super-massive black hole sources and the observational implications of
+our present analysis are discussed.",1606.00526v1
+2016-08-29,A proposed paradigm for solar cycle dynamics mediated via turbulent pumping of magnetic flux in Babcock-Leighton type solar dynamos,"At present, Babcock-Leighton flux transport solar dynamo models appear as the
+most promising model for explaining diverse observational aspects of the
+sunspot cycle. The success of these flux transport dynamo models is largely
+dependent upon a single-cell meridional circulation with a deep equatorward
+component at the base of the Sun's convection zone. However, recent
+observations suggest that the meridional flow may in fact be very shallow
+(confined to the top 10 % of the Sun) and more complex than previously thought.
+Taken together these observations raise serious concerns on the validity of the
+flux transport paradigm. By accounting for the turbulent pumping of magnetic
+flux as evidenced in magnetohydrodynamic simulations of solar convection, we
+demonstrate that flux transport dynamo models can generate solar-like magnetic
+cycles even if the meridional flow is shallow. Solar-like periodic reversals is
+recovered even when meridional circulation is altogether absent, however, in
+this case the solar surface magnetic field dynamics does not extend all the way
+to the polar regions. Very importantly, our results demonstrate that the
+Parker-Yoshimura sign rule for dynamo wave propagation can be circumvented in
+Babcock-Leighton dynamo models by the latitudinal component of turbulent
+pumping -- which can generate equatorward propagating sunspot belts in the
+absence of a deep, equatorward meridional flow. We also show that variations in
+turbulent pumping coefficients can modulate the solar cycle amplitude and
+periodicity. Our results suggest the viability of an alternate magnetic flux
+transport paradigm -- mediated via turbulent pumping -- for sustaining
+solar-stellar dynamo action.",1608.08167v1
+2016-11-29,Critical quench dynamics of random quantum spin chains: Ultra-slow relaxation from initial order and delayed ordering from initial disorder,"By means of free fermionic techniques combined with multiple precision
+arithmetic we study the time evolution of the average magnetization,
+$\overline{m}(t)$, of the random transverse-field Ising chain after global
+quenches. We observe different relaxation behaviors for quenches starting from
+different initial states to the critical point. Starting from a fully ordered
+initial state, the relaxation is logarithmically slow described by
+$\overline{m}(t) \sim \ln^a t$, and in a finite sample of length $L$ the
+average magnetization saturates at a size-dependent plateau $\overline{m}_p(L)
+\sim L^{-b}$; here the two exponents satisfy the relation $b/a=\psi=1/2$.
+Starting from a fully disordered initial state, the magnetization stays at zero
+for a period of time until $t=t_d$ with $\ln t_d \sim L^{\psi}$ and then starts
+to increase until it saturates to an asymptotic value $\overline{m}_p(L) \sim
+L^{-b'}$, with $b'\approx 1.5$. For both quenching protocols, finite-size
+scaling is satisfied in terms of the scaled variable $\ln t/L^{\psi}$.
+Furthermore, the distribution of long-time limiting values of the magnetization
+shows that the typical and the average values scale differently and the average
+is governed by rare events. The non-equilibrium dynamical behavior of the
+magnetization is explained through semi-classical theory.",1611.09495v2
+2017-01-27,Application of Spin-Exchange Relaxation-Free Magnetometry to the Cosmic Axion Spin Precession Experiment,"The Cosmic Axion Spin Precession Experiment (CASPEr) seeks to measure
+oscillating torques on nuclear spins caused by axion or axion-like-particle
+(ALP) dark matter via nuclear magnetic resonance (NMR) techniques. A sample
+spin-polarized along a leading magnetic field experiences a resonance when the
+Larmor frequency matches the axion/ALP Compton frequency, generating precessing
+transverse nuclear magnetization. Here we demonstrate a Spin-Exchange
+Relaxation-Free (SERF) magnetometer with sensitivity $\approx 1~{\rm
+fT/\sqrt{Hz}}$ and an effective sensing volume of 0.1 $\rm{cm^3}$ that may be
+useful for NMR detection in CASPEr. A potential drawback of
+SERF-magnetometer-based NMR detection is the SERF's limited dynamic range. Use
+of a magnetic flux transformer to suppress the leading magnetic field is
+considered as a potential method to expand the SERF's dynamic range in order to
+probe higher axion/ALP Compton frequencies.",1701.08082v5
+2017-03-11,Spin-wave dynamics in Permalloy/Cobalt magnonic crystals in the presence of a non-magnetic spacer,"In this paper, we theoretically study the influence of a non-magnetic spacer
+between ferromagnetic dots and ferromagnetic matrix on the frequency dispersion
+of the spin wave excitations in two-dimensional bi-component magnonic crystals.
+By means of the dynamical matrix method we investigate structures inhomogeneous
+across the thickness represented by square arrays of Cobalt or Permalloy dots
+in a Permalloy matrix. We show that the introduction of a non-magnetic spacer
+significantly modifies the total internal magnetic field especially at the
+edges of the grooves and dots. This permits the manipulation of the magnonic
+band structure of spin waves localized either at the edges of the dots or in
+matrix material at the edges of grooves. According to the micromagnetic
+simulations two types of end modes were found. The corresponding frequencies
+are significantly influenced by the end modes localization region. We also show
+that, with the use of a single ferromagnetic material, it is possible to design
+a magnonic crystal preserving properties of bi-component magnonic crystals and
+magnonic antidot lattices. Finally, the influence of the non-magnetic spacers
+on the technologically relevant parameters like group velocity and magnonic
+band width are discussed.",1703.03978v1
+2017-03-23,Mott Transition and Magnetism in Rare Earth Nickelates and its Fingerprint on the X-ray Scattering,"The metal-insulator transition (MIT) remains among the most thoroughly
+studied phenomena in solid state physics, but the complexity of the phenomena,
+which usually involves cooperation of many degrees of freedom including
+orbitals, fluctuating local moments, magnetism, and the crystal structure, have
+resisted predictive ab-initio treatment. Here we develop ab-initio theoretical
+method for correlated electron materials, based on Dynamical Mean Field Theory,
+which can predict the change of the crystal structure across the MIT at finite
+temperature. This allows us to study the coupling between electronic, magnetic
+and orbital degrees of freedom with the crystal structure across the MIT in
+rare-earth nickelates. We predict the free energy profile of the competing
+states, and the theoretical magnetic ground state configuration, which is in
+agreement with neutron scattering data, but is different from the magnetic
+models proposed before. The resonant elastic X-ray response at the K-edge,
+which was argued to be a direct probe of the charge order, is theoretically
+modelled within the Dynamical Mean Field Theory, including the core-hole
+interaction. We show that the line-shape of the measured resonant elastic X-ray
+response can be explained with the ""site-selective"" Mott scenario without real
+charge order on Ni sites.",1703.08196v2
+2017-06-05,Quantum Kinetic Theory of the Chiral Anomaly,"We present a general quantum kinetic theory of low-field magnetotransport in
+weakly disordered crystals that accounts fully for the interplay between
+electric-field induced interband coherence, Bloch-state scattering, and an
+external magnetic field. The quantum kinetic equation we derive for the
+Bloch-state density matrix naturally incorporates the momentum-space Berry
+phase effects whose influence on Bloch-state wavepacket dynamics is normally
+incorporated into transport theory in an ad hoc manner. The Berry phase
+correction to the momentum-space density of states in the presence of an
+external magnetic field implied by semiclassical wavepacket dynamics is
+captured by our theory as an intrinsic density-matrix response to a magnetic
+field. We propose a simple and general procedure for expanding the linear
+response of the Bloch-state density matrix to an electric field in powers of
+magnetic field. As an illustration, we apply our theory to magnetotransport in
+Weyl semimetals. We show that the chiral anomaly (positive magnetoconductivity
+quadratic in magnetic field) that appears when separate Fermi surface pockets
+surround distinct Weyl points survives only when intervalley scattering is very
+weak compared to intravalley scattering.",1706.01200v3
+2017-06-06,Coronal rain in magnetic bipolar weak fields,"We intend to investigate the underlying physics for the coronal rain
+phenomenon in a representative bipolar magnetic field, including the formation
+and the dynamics of coronal rain blobs. With the MPI-AMRVAC code, we performed
+three dimensional radiative magnetohydrodynamic (MHD) simulation with strong
+heating localized on footpoints of magnetic loops after a relaxation to quiet
+solar atmosphere. Progressive cooling and in-situ condensation starts at the
+loop top due to radiative thermal instability. The first large-scale
+condensation on the loop top suffers Rayleigh-Taylor instability and becomes
+fragmented into smaller blobs. The blobs fall vertically dragging magnetic
+loops until they reach low beta regions and start to fall along the loops from
+loop top to loop footpoints. A statistic study of the coronal rain blobs finds
+that small blobs with masses of less than 10^10 g dominate the population. When
+blobs fall to lower regions along the magnetic loops, they are stretched and
+develop a non-uniform velocity pattern with an anti-parallel shearing pattern
+seen to develop along the central axis of the blobs. Synthetic images of
+simulated coronal rain with Solar Dynamics Observatory Atmospheric Imaging
+Assembly well resemble real observations presenting dark falling clumps in hot
+channels and bright rain blobs in a cool channel. We also find density
+inhomogeneities during a coronal rain ""shower"", which reflects the observed
+multi-stranded nature of coronal rain.",1706.01804v1
+2017-09-15,I. Jet Formation and Evolution due to 3D Magnetic Reconnection,"Using simulated data-driven three-dimensional resistive MHD simulations of
+the solar atmosphere, we show that magnetic reconnection can be responsible of
+the formation of jets with characteristic of Type II spicules. For this, we
+numerically model the photosphere-corona region using the C7 equilibrium
+atmosphere model. The initial magnetic configuration is a 3D potential magnetic
+field, extrapolated up to the solar corona region from a dynamic realistic
+simulation of solar photospheric magnetoconvection model which is mimicking
+quiet-Sun. In this case we consider a uniform and constant value of the
+magnetic resistivity of $12.56 ~\Omega~{\rm m}$. We have found that formation
+of the jets depends on the Lorentz force, which helps to accelerate the plasma
+upwards. Analyzing various properties of the jet dynamics, we found that the
+jet structure shows Doppler shift near to regions with high vorticity. The
+morphology, upward velocity, covering a range up to 100 $\rm km$ $\rm s^{-1}$,
+and life-time of the estructure, bigger than 100 ${\rm s}$, are similar to
+those expected for Type II spicules.",1709.05066v2
+2017-11-07,Negative magnetic eddy diffusivity due to oscillogenic $α$-effect,"We study large-scale kinematic dynamo action of steady mirror-antisymmetric
+flows of incompressible fluid, that involve small spatial scales only, by
+asymptotic methods of the multiscale stability theory. It turns out that, due
+to the magnetic $\alpha$-effect in such flows, the large-scale mean field
+experiences harmonic oscillations in time on the scale O($\varepsilon t$)
+without growth or decay. Here $\varepsilon$ is the spatial scale ratio and $t$
+is the fast time of the order of the flow turnover time. The interaction of the
+accompanying fluctuating magnetic field with the flow gives rise to an
+anisotropic magnetic eddy diffusivity, whose dependence on the direction of the
+large-scale wave vector generically exhibits a singular behaviour, and thus to
+negative eddy diffusivity for whichever molecular magnetic diffusivity.
+Consequently, such flows always act as kinematic dynamos on the time scale
+O($\varepsilon^2t$); for the directions at which eddy diffusivity is infinite,
+the large-scale mean-field growth rate is finite on the scale
+O($\varepsilon^{3/2}t$). We investigate numerically this dynamo mechanism for
+two sample flows.",1711.02390v4
+2018-01-08,Dynamic magnetic-transformation-induced exchange bias in (Fe2O3)0.1-(FeTiO3)0.9,"Up to now, for the conventional exchange bias (EB) systems there has been one
+pinning phase and one pinned phase, and the pinning and pinned phases are
+inherent to the material and do not mutually transform into each other.
+Interestingly, we show here that EB is observed in a special system
+(Fe2O3)0.1(FeTiO3)0.9 (HI9) different from the conventional EB system. Neutron
+powder diffraction and magnetic measurement confirm that for HI9: i) two types
+of short range antiferromagnetic ordering coexist, ii) there are two pinning
+phases and one pinned phase, iii) the pinned phase is not intrinsic to the
+structure but can be dynamically produced from the pinning phase with the help
+of an external magnetic field. Consequently, two anomalous EB behaviors are
+observed: i) both the coercivity (HC) and the exchange bias field (HE)
+simultaneously decrease to zero at 30 K, ii) for a high cooling field (Hcool)
+HE decreases logarithmically with increasing Hcool. Using Arrott plots it is
+confirmed that the first order magnetic phase transformation (FOMPT) from the
+AFM Fe2+ to ferromagnetic (FM) Fe2+ and the second order magnetic phase
+transformation (SOMPT) for the process whereby the FM Fe2+ aligns with the
+external field direction coexist in HI-9. The Morin transition and FOMPT cause
+the anomalous EB behaviors. This work may provide fresh ideas for research into
+EB behavior.",1801.02420v1
+2018-01-29,Spin dynamics and exchange interactions in CuO measured by neutron scattering,"The magnetic properties of CuO encompass several contemporary themes in
+condensed matter physics, including quantum magnetism, magnetic frustration,
+magnetically-induced ferroelectricity and orbital currents. Here we report
+polarized and unpolarized neutron inelastic scattering measurements which
+provide a comprehensive map of the cooperative spin dynamics in the low
+temperature antiferromagnetic (AFM) phase of CuO throughout much of the
+Brillouin zone. At high energies ($E \gtrsim 100$\,meV) the spectrum displays
+continuum features consistent with the des Cloizeax--Pearson dispersion for an
+ideal $S=\frac{1}{2}$ Heisenberg AFM chain. At lower energies the spectrum
+becomes more three-dimensional, and we find that a linear spin-wave model for a
+Heisenberg AFM provides a very good description of the data, allowing for an
+accurate determination of the relevant exchange constants in an effective spin
+Hamiltonian for CuO. In the high temperature helicoidal phase, there are
+features in the measured low-energy spectrum that we could not reproduce with a
+spin-only model. We discuss how these might be associated with the
+magnetically-induced multiferroic behavior observed in this phase.",1801.09473v2
+2018-04-30,Spin-fluctuation and spin-relaxation effects of single adatoms from first principles,"Single adatoms offer an exceptional playground for studying magnetism and its
+associated dynamics at the atomic scale. Here we review recent results on
+single adatoms deposited on metallic substrates, based on time-dependent
+density functional theory. First we analyze quantum zero-point
+spin-fluctuations (ZPSF) as calculated from the fluctuation-dissipation
+theorem, and show how they affect the magnetic stability by modifying the
+magnetic anisotropy energy. We also assess the impact of ZPSF in the limit of
+small hybridization to the substrate characteristic of semi-insulating
+substrates, connecting to recent experimental investigations where magnetic
+stability of a single adatom was achieved for the first time. Secondly, we
+inspect further the dynamics of single adatoms by considering the longitudinal
+and transverse spin-relaxation processes, whose time-scales are analyzed and
+related to the underlying electronic structure of both the adatom and the
+substrate. Thirdly, we analyze spin-fluctuation modes of paramagnetic adatoms,
+i.e., adatoms where the Stoner criterion for magnetism is almost fulfilled.
+Interestingly, such modes can develop well-defined peaks in the meV range,
+their main characteristics being determined by two fundamental electronic
+properties, namely the Stoner parameter and the density of states at the Fermi
+level. Furthermore, simulated inelastic scanning tunneling spectroscopy curves
+reveal that these spin-fluctuation modes can be triggered by tunneling
+electrons, opening up potential applications also for paramagnetic adatoms.
+Lastly, an overview of the outstanding issues and future directions is given.",1805.00347v1
+2018-06-26,Terahertz magnetic field enhancement in an asymmetric spiral metamaterial,"We use finite element simulations in both the frequency and the time-domain
+to study the terahertz resonance characteristics of a metamaterial (MM)
+comprising a spiral connected to a straight arm. The MM acts as a RLC circuit
+whose resonance frequency can be precisely tuned by varying the characteristic
+geometrical parameters of the spiral: inner and outer radius, width and number
+of turns. We provide a simple analytical model that uses these geometrical
+parameters as input to give accurate estimates of the resonance frequency.
+Finite element simulations show that linearly polarized terahertz radiation
+efficiently couples to the MM thanks to the straight arm, inducing a current in
+the spiral, which in turn induces a resonant magnetic field enhancement at the
+center of the spiral. We observe a large (approximately 20 times) and uniform
+(over an area of $\sim 10~\mu m^{2}$) enhancement of the magnetic field for
+narrowband terahertz radiation with frequency matching the resonance frequency
+of the MM. When a broadband, single-cycle terahertz pulse propagates towards
+the metamaterial, the peak magnetic field of the resulting band-passed waveform
+still maintains a 6-fold enhancement compared to the peak impinging field.
+Using existing laser-based terahertz sources, our metamaterial design allows to
+generate magnetic fields of the order of 2 T over a time scale of several
+picoseconds, enabling the investigation of non-linear ultrafast spin dynamics
+in table-top experiments. Furthermore, our MM can be implemented to generate
+intense near-field narrowband, multi-cycle electromagnetic fields to study
+generic ultrafast resonant terahertz dynamics in condensed matter.",1806.10100v1
+2018-06-29,Sequential eruptions triggered by flux emergence - observations and modeling,"We describe and analyze observations by the Solar Dynamics Observatory of the
+emergence of a small, bipolar active region within an area of unipolar magnetic
+flux that was surrounded by a circular, quiescent filament. Within only eight
+hours of the start of the emergence, a partial splitting of the filament and
+two consecutive coronal mass ejections took place. We argue that all three
+dynamic events occurred as a result of particular magnetic-reconnection
+episodes between the emerging bipole and the pre-existing coronal magnetic
+field. In order to substantiate our interpretation, we consider
+three-dimensional magnetohydrodynamic simulations that model the emergence of
+magnetic flux in the vicinity of a large-scale coronal flux rope. The
+simulations qualitatively reproduce most of the reconnection episodes suggested
+by the observations; as well as the filament-splitting, the first eruption, and
+the formation of sheared/twisted fields that may have played a role in the
+second eruption. Our results suggest that the position of emerging flux with
+respect to the background magnetic configuration is a crucial factor for the
+resulting evolution, while previous results suggest that parameters such as the
+orientation or the amount of emerging flux are important as well. This poses a
+challenge for predicting the onset of eruptions that are triggered by flux
+emergence, and it calls for a detailed survey of the relevant parameter space
+by means of numerical simulations.",1807.00020v1
+2018-07-06,Spin wave modes in a cylindrical nanowire in crossover dipolar-exchange regime,"Nanoscale magnetic systems have been studied extensively in various
+geometries, such as wires of different cross-sections, arrays of wires, dots,
+rings, etc. Such systems have interesting physical properties and promising
+applications in advanced magnetic devices. Uniform magnetic nanowires are the
+basic structures which were broadly investigated. However, some of their
+dynamical properties, like: (anti)crossing between the spin wave modes and
+impact of the magnetic field on spin wave spectrum, still need to be exploited.
+We continue this research by investigation of the spin wave dynamics in solid
+Ni nanowire of the circular cross-section. We use two approaches:
+semi-analytical calculations and numerical computations based on finite element
+method. We solve coupled Landau-Lifshitz and Maxwell equations and consider
+both magnetostatic and exchange interactions. We identify the dispersion
+brunches and its (anti)crossing by plotting the spatial profiles of spin wave
+amplitudes and magnetostatic potential. We also check how we can tune the
+spectrum of the modes by application of the external magnetic field and how it
+affects the modes and their dominating type of interaction.",1807.02580v3
+2018-08-15,The SILCC project - V. The impact of magnetic fields on the chemistry and the formation of molecular clouds,"Magnetic fields are ubiquitously observed in the interstellar medium (ISM) of
+present-day star-forming galaxies with dynamically relevant energy densities.
+Using three-dimensional magneto-hydrodynamic (MHD) simulations of the supernova
+(SN) driven ISM in the flux-freezing approximation (ideal MHD) we investigate
+the impact of the magnetic field on the chemical and dynamical evolution of the
+gas, fragmentation and the formation of molecular clouds. We follow the
+chemistry with a network of six species (H$^{+}$, H, H$_2$, C$^+$, CO, free
+electrons) including local shielding effects. We find that magnetic fields
+thicken the disc by a factor of a few to a scale height of
+$\sim100\,\mathrm{pc}$, delay the formation of dense (and molecular) gas by
+$\sim25\,\mathrm{Myr}$ and result in differently shaped gas structures. The
+magnetised gas fragments into fewer clumps, which are initially at subcritical
+mass-to-flux ratios, $M/\Phi\approx0.3(M/\Phi)_\mathrm{crit}$, and accrete gas
+preferentially parallel to the magnetic field lines until supercritial
+mass-to-flux ratios of up to order 10 are reached. The accretion rates onto
+molecular clouds scale with $\dot{M}\propto M^{1.5}$. The median of the
+inter-cloud velocity dispersion is $\sim2-5\,\mathrm{km\,s}^{-1}$ and lower
+than the internal velocity dispersion in the clouds
+($\sim3-7\,\mathrm{km\,s}^{-1}$). However, individual cloud-cloud collisions
+occur at speeds of a few $10\,\mathrm{km\,s}^{-1}$.",1808.05222v1
+2018-11-01,Competition between static and dynamic magnetism in the Kitaev spin liquid material Cu2IrO3,"Anyonic excitations emerging from a Kitaev spin liquid can form a basis for
+quantum computers. Searching for such excitations motivated intense research on
+the honeycomb iridate materials. However, access to a spin liquid ground state
+has been hindered by magnetic ordering. Cu2IrO3 is a new honeycomb iridate
+without thermodynamic signatures of a long-range order. Here, we use muon spin
+relaxation to uncover the magnetic ground state of Cu2IrO3. We find a
+two-component depolarization with slow and fast relaxation rates corresponding
+to distinct regions with dynamic and static magnetism, respectively. X-ray
+absorption spectroscopy and first principles calculations identify a mixed
+copper valence as the origin of this behavior. Our results suggest that a
+minority of Cu2+ ions nucleate regions of static magnetism whereas the majority
+of Cu+/Ir4+ on the honeycomb lattice give rise to a Kitaev spin liquid.",1811.00565v1
+2018-11-13,Ferromagnetic resonance and magnetic precessions in $\varphi_0$ junction,"The Josephson $\varphi_0$ junctions with the current-phase relation $I = I_c
+\sin (\varphi-\varphi_0)$, where the phase shift $\varphi_0$ is proportional to
+the magnetic moment perpendicular to the gradient of the asymmetric spin-orbit
+potential, demonstrate a number of unique features important for
+superconducting spintronics and modern informational technologies. Here we show
+that a current sweep along IV-characteristic of the $\varphi_0$ junction may
+lead to regular magnetization dynamics with a series of specific phase
+trajectories. The origin of these trajectories is related to a direct coupling
+between the magnetic moment and the Josephson oscillations in these junctions,
+and ferromagnetic resonance when Josephson frequency coincides with the
+ferromagnetic one. We demonstrate that an external electromagnetic field can
+control the dynamics of magnetic moment within a current interval corresponding
+to a Shapiro step and produce topological transformation of specific precession
+trajectories. We demonstrate the appearance of the DC component of
+superconducting current and clarify its role in the transformation of
+IV-characteristics in the resonance region. Good agreement between numerical
+and analytical results has been found in the ferromagnetic resonance region.
+The presented results might be used for developing novel resonance methods of
+determination of the spin-orbit coupling parameter in the non-centrosymmetric
+materials. We discuss experiments which can test our results.",1811.05282v2
+2019-02-08,Subnanosecond Fluctuations in Low-Barrier Nanomagnets,"Fast magnetic fluctuations due to thermal torques have useful technological
+functionality ranging from cryptography to probabilistic computing. The
+characteristic time of fluctuations in typical uniaxial anisotropy magnets
+studied so far is bounded from below by the well-known energy relaxation
+mechanism. This time scales as $\alpha^{-1}$, where $\alpha$ parameterizes the
+strength of dissipative processes. Here, we theoretically analyze the
+fluctuating dynamics in easy-plane and antiferromagnetically coupled
+nanomagnets. We find in such magnets, the dynamics are strongly influenced by
+fluctuating intrinsic fields, which give rise to an additional dephasing-type
+mechanism for washing out correlations. In particular, we establish two time
+scales for characterizing fluctuations (i) the average time for a nanomagnet to
+reverse|which for the experimentally relevant regime of low damping is governed
+primarily by dephasing and becomes independent of $\alpha$, (ii) the time scale
+for memory loss of a single nanomagnet|which scales as $\alpha^{-1/3}$ and is
+governed by a combination of energy dissipation and dephasing mechanism. For
+typical experimentally accessible values of intrinsic fields, the resultant
+thermal-fluctuation rate is increased by multiple orders of magnitude when
+compared with the bound set solely by the energy relaxation mechanism in
+uniaxial magnets. This could lead to higher operating speeds of emerging
+devices exploiting magnetic fluctuations.",1902.03312v3
+2019-04-30,Magnetism trends in doped Ce-Cu intermetallics in the vicinity of quantum criticality: realistic Kondo lattice models based on dynamical mean-field theory,"The quantum critical point (QCP) in the archetypical heavy-fermion compound
+CeCu$_6$ doped by Au is described, accounting for the localized $4f$-electron
+of Ce, using realistic electronic structure calculations combined with
+dynamical mean-field theory (DMFT). Magnetism trends in
+Ce(Cu$_{1-\epsilon}$Au$_\epsilon$)$_6$ are compared with those in Co-doped
+CeCu$_{5}$, which resides on the non-ferromagnetic side of the composition
+space of one of the earliest rare-earth permanent magnet compounds,
+Ce(Co,Cu)$_5$. The construction of a realistic Doniach phase diagram shows that
+the system crosses over a magnetic quantum critical point in the Kondo lattice
+in $0.2<x<0.4$ of Ce(Cu$_{1-x}$Co$_x$)$_5$. Comparison between Au-doped
+CeCu$_6$ and Co-doped CeCu$_5$ reveals that the swept region in the vicinity of
+QCP for the latter thoroughly covers that of the former. The implications of
+these trends on the coercivity of the bulk rare-earth permanent magnets are
+discussed.",1904.13160v5
+2019-05-16,Element-specific visualization of dynamic magnetic coupling in a Co/Py bilayer microstructure,"We present the element-specific and time resolved visualization of uniform
+ferromagnetic resonance excitations of a Permalloy (Py) disk - Cobalt (Co)
+stripe bilayer microstructure. The transverse high frequency component of the
+resonantly excited magnetization is sampled in the ps regime by a combination
+of ferromagnetic resonance (FMR) and scanning transmission X-ray microscopy
+(STXM- FMR) recording snapshots of the local magnetization precession of Py and
+Co with nanometer spatial resolution. The approach allows us to individually
+image the resonant dynamic response of each element, and we find that angular
+momentum is transferred from the Py disk to the Co stripe and vice versa at
+their respective resonances. The integral (cavity) FMR spectrum of our sample
+shows an unexpected additional third resonance. This resonance is observed in
+the STXM-FMR experiments as well and our microscopic findings suggest that it
+is governed by magnetic exchange between Py and Co, showing for the Co stripe a
+difference in relative phase of the magnetization due to stray field influence.",1905.06772v6
+2019-05-18,Characterising Jupiter's dynamo radius using its magnetic energy spectrum,"Jupiter's magnetic field is generated by the convection of liquid metallic
+hydrogen in its interior. The transition from molecular hydrogen to metallic
+hydrogen as temperature and pressure increase is believed to be a smooth one.
+As a result, the electrical conductivity in Jupiter varies continuously from
+being negligible at the surface to a large value in the deeper region. Thus,
+unlike the Earth where the upper boundary of the dynamo---the dynamo
+radius---is definitively located at the core-mantle boundary, it is not clear
+at what depth dynamo action becomes significant in Jupiter. In this paper,
+using a numerical model of the Jovian dynamo, we examine the magnetic energy
+spectrum at different depth and identify a dynamo radius below which (and away
+from the deep inner core) the shape of the magnetic energy spectrum becomes
+invariant. We find that this shift in the behaviour of the magnetic energy
+spectrum signifies a change in the dynamics of the system as electric current
+becomes important. Traditionally, a characteristic radius derived from the
+Lowes--Mauersberger spectrum---the Lowes radius---gives a good estimate to the
+Earth's core-mantle boundary. We argue that in our model, the Lowes radius
+provides a lower bound to the dynamo radius. We also compare the
+Lowes--Mauersberger spectrum in our model to that obtained from recent Juno
+observations. The Lowes radius derived from the Juno data is significantly
+lower than that obtained from our models. The existence of a stably stratified
+region in the neighbourhood of the transition zone might provide an explanation
+of this result.",1905.07661v2
+2019-06-18,Noninertial and spin effects on the 2D Dirac oscillator in the magnetic cosmic string background,"In this work, we analyze the influence of noninertial and spin effects on the
+dynamics of the 2D Dirac oscillator in the magnetic cosmic string background.
+To model this background, we consider a uniform magnetic field, the
+Aharonov-Bohm effect, and a parameter $\eta$ generated by a cosmic string.
+Posteriorly, we determine the bound-state solutions of the system: the Dirac
+spinor and the relativistic energy spectrum. We verified that this spinor is
+written in terms of the generalized Laguerre polynomials and this spectrum
+depends on the effective quantum number $N_r$, angular velocity $\Omega$ and
+parameter $s$ associated to the noninertial and spin effects, magnetic flux
+$\Phi$, cyclotron frequency $\omega_c$, zero-point energy $E_0$, and on the
+deficit angle $\eta$. In particular, we note that besides this spectrum to be a
+periodic function and asymmetric, its values infinitely increase when $\eta\to
+0$ or $N_r=\omega_c=\Omega\to\infty$. We also note that the energies of the
+antiparticle with spin down are larger than of the particle with spin up or
+down. In the nonrelativistic limit, we get the Schr\""{o}dinger-Pauli oscillator
+with two types of couplings: the spin-orbit coupling and the spin-rotation
+coupling, and two Hamiltonians: one quantum harmonic oscillator-type and other
+Zeeman-type. Finally, we compare our results with other works, where we
+verified that our problem generalizes some particular cases of the literature
+when $\Omega$, $\omega_c$, $\Phi$, $s$ or $\eta$ are excluded from the system.",1906.07369v2
+2019-09-04,Global dynamics of the interstellar medium in magnetised disc galaxies,"Magnetic fields are an elemental part of the interstellar medium in galaxies.
+However, their impact on gas dynamics and star formation in galaxies remains
+controversial. We use a suite of global magnetohydrodynamical simulations of
+isolated disc galaxies to study the influence of magnetic fields on the diffuse
+and dense gas in the discs. We find that the magnetic field acts in multiple
+ways. Stronger magnetised discs fragment earlier due to the shorter growth time
+of the Parker instability. Due to the Parker instability in the magnetised
+discs we also find cold ($T<50\,\mathrm{K}$) and dense
+($n\sim10^3-10^4\,\mathrm{cm}^{-3}$) gas several hundred pc above/below the
+midplane without any form of stellar feedback. In addition, magnetic fields
+change the fragmentation pattern. While in the hydrodynamical case, the disc
+breaks up into ring-like structures, magnetised discs show the formation of
+filamentary entities that extent both in the azimuthal and radial direction.
+These kpc scale filaments become magnetically (super-)critical very quickly and
+allow for the rapid formation of massive giant molecular clouds. Our
+simulations suggest that major differences in the behaviour of star formation -
+due to a varying magnetisation - in galaxies could arise.",1909.01623v1
+2019-10-18,Comparison of the Scaling Properties of EUV Intensity Fluctuations in Coronal Hole and Quiet-Sun Regions,"Using detrended fluctuation analysis (DFA) and rescaled range (R/S) analysis,
+we investigate the scaling properties of EUV intensity fluctuations of
+low-latitude coronal holes (CHs) and neighboring quiet-Sun (QS) regions in
+signals obtained with the Solar Dynamics Observatory/Atmospheric Imaging
+Assembly (SDO/AIA) instrument. Contemporaneous line-of-sight SDO/Helioseismic
+and Magnetic Imager (HMI) magnetic fields provide a context for the physical
+environment. We find that the intensity fluctuations in the time series of EUV
+images present at each spatial point a scaling symmetry over the range $\sim
+20$ min to $\sim$ 1 hour. Thus we are able to calculate a generalized Hurst
+exponent and produce image maps, not of physical quantities like intensity or
+temperature, but of a single dynamical parameter that sums up the statistical
+nature of the intensity fluctuations at each pixel. In quiet-Sun (QS) regions
+and in coronal holes (CHs) with magnetic bipoles, the scaling exponent ($1.0 <
+\alpha \leq 1.5$) corresponds to anti-correlated turbulent-like processes. In
+coronal holes, and in quiet-Sun regions primarily associated with (open)
+magnetic field of dominant polarity, the generalized exponent (0.5 $< \alpha <$
+1) corresponds to positively-correlated (persistent) processes. We identify a
+tendency for $\alpha$ $\sim$ $1$ near coronal hole boundaries and in other
+regions in which open and closed magnetic fields are in proximity. This is a
+signature of an underlying $1/f$ type process that is characteristic for
+self-organized criticality and shot-noise models.",1910.09541v1
+2019-11-17,Expansion of Solar Coronal Hot Electrons in an Inhomogeneous Magnetic Field: 1-D PIC Simulation,"The expansion of hot electrons in flaring magnetic loops is crucial to
+understanding the dynamics of solar flares. In this paper we investigate, for
+the first time, the transport of hot electrons in a magnetic mirror field based
+on a 1-D particle-in-cell (PIC) simulation. The hot electrons with small pitch
+angle transport into the cold plasma, which leads to the generation of Langmuir
+waves in the cold plasma and ion acoustic waves in the hot plasma. The large
+pitch angle electrons can be confined by the magnetic mirror, resulting in the
+different evolution time scale between electron parallel and perpendicular
+temperature. This will cause the formation of electron temperature anisotropy,
+which can generate the whistler waves near the interface between hot electrons
+and cold electrons. The whistler waves can scatter the large pitch angle
+electrons to smaller value through the cyclotron resonance, leading to
+electrons escaping from the hot region. These results indicate that the
+whistler waves may play an important role in the transport of electrons in
+flaring magnetic loops. The findings from this study provide some new insights
+to understand the electron dynamics of solar flares.",1911.07207v1
+2019-11-18,The Formation and Evolution of Wide-Orbit Stellar Multiples In Magnetized Clouds,"Stars rarely form in isolation. Nearly half of the stars in the Milky Way
+have a companion, and this fraction increases in star-forming regions. However,
+why some dense cores and filaments form bound pairs while others form single
+stars remains unclear. We present a set of three-dimensional,
+gravo-magnetohydrodynamic simulations of turbulent star-forming clouds, aimed
+at understanding the formation and evolution of multiple-star systems formed
+through large scale (>~$10^3$ AU) turbulent fragmentation. We investigate three
+global magnetic field strengths, with global mass-to-flux ratios of
+$\mu_\phi$=2, 8, and 32. The initial separations of protostars in multiples
+depends on the global magnetic field strength, with stronger magnetic fields
+(e.g., $\mu_\phi$=2) suppressing fragmentation on smaller scales. The overall
+multiplicity fraction (MF) is between 0.4-0.6 for our strong and intermediate
+magnetic field strengths, which is in agreement with observations. The weak
+field case has a lower fraction. The MF is relatively constant throughout the
+simulations, even though stellar densities increase as collapse continues.
+While the MF rarely exceeds 60% in all three simulations, over 80% of all
+protostars are part of a binary system at some point. We additionally find that
+the distribution of binary spin mis-alignment angles is consistent with a
+randomized distribution. In all three simulations, several binaries originate
+with wide separations and dynamically evolve to <~ $10^2$ AU separations. We
+show that a simple model of mass accretion and dynamical friction with the gas
+can explain this orbital evolution.",1911.07863v1
+2020-01-13,Hydrodynamics of magnetic fluid droplets on superhydrophobic surfaces,"The study reports the aspects of postimpact hydrodynamics of ferrofluid
+droplets on superhydrophobic SH surfaces in the presence of a horizontal
+magnetic field. A wide gamut of dynamics was observed by varying the impact
+Weber number We, the Hartmann number Ha and the magnetic field strength
+manifested through the magnetic Bond number Bom. For a fixed We 60, we observed
+that at moderately low Bom 300, droplet rebound off the SH surface is
+suppressed. The noted We is chosen to observe various impact outcomes and to
+reveal the consequent ferrohydrodynamic mechanisms. We also show that
+ferrohydrodynamic interactions leads to asymmetric spreading, and the droplet
+spreads preferentially in a direction orthogonal to the magnetic field lines.
+We show analytically that during the retraction regime, the kinetic energy of
+the droplet is distributed unequally in the transverse and longitudinal
+directions due to the Lorentz force. This ultimately leads to suppression of
+droplet rebound. We study the role of Bom at fixed We 60, and observed that the
+liquid lamella becomes unstable at the onset of retraction phase, through
+nucleation of holes, their proliferation and rupture after reaching a critical
+thickness only on SH surfaces, but is absent on hydrophilic surfaces. We
+propose an analytical model to predict the onset of instability at a critical
+Bom. The analytical model shows that the critical Bom is a function of the
+impact We, and the critical Bom decreases with increasing We. We illustrate a
+phase map encompassing all the post impact ferrohydrodynamic phenomena on SH
+surfaces for a wide range of We and Bom.",2001.04273v1
+2020-01-23,Global simulations of self-gravitating magnetized protoplanetary disks,"In the early stages of a protoplanetary disk, when its mass is a significant
+fraction of its star's, turbulence generated by gravitational instability (GI)
+should feature significantly in the disk's evolution. At the same time, the
+disk may be sufficiently ionised for magnetic fields to play some role in the
+dynamics. Though usually neglected, the impact of magnetism on the GI may be
+critical, with consequences for several processes: the efficiency of accretion,
+spiral structure formation, fragmentation, and the dynamics of solids. In this
+paper, we report on global three-dimensional magnetohydrodynamical simulations
+of a self-gravitating protoplanetary disk using the meshless finite mass (MFM)
+Lagrangian technique. We confirm that GI spiral waves trigger a dynamo that
+amplifies an initial magnetic field to nearly thermal amplitudes (plasma beta <
+10), an order of magnitude greater than that generated by the
+magneto-rotational instability alone. We also determine the dynamo's nonlinear
+back reaction on the gravitoturbulent flow: the saturated state is
+substantially hotter, with an associated larger Toomre parameter and weaker,
+more 'flocculent' spirals. But perhaps of greater import is the dynamo's
+boosting of accretion via a significant Maxwell stress; mass accretion is
+enhanced by factors of several relative to either pure GI or pure MRI. Our
+simulations use ideal MHD, an admittedly poor approximation in protoplanetary
+disks, and thus future studies should explore the full gamut of non-ideal MHD.
+In preparation for that, we exhibit a small number of Ohmic runs that reveal
+that the dynamo, if anything, is stronger in a non-ideal environment. This work
+confirms that magnetic fields are a potentially critical ingredient in
+gravitoturbulent young disks, possibly controlling their evolution, especially
+via their enhancement of (potentially episodic) accretion.",2001.08693v1
+2020-02-14,"Comparative ab initio study of the structural, electronic, magnetic, and dynamical properties of LiOsO$_3$ and NaOsO$_3$","Despite similar chemical compositions, LiOsO$_3$ and NaOsO$_3$ exhibit
+remarkably distinct structural, electronic, magnetic, and spectroscopic
+properties. At low temperature, LiOsO$_3$ is a polar bad metal with a
+rhombohedral $R3c$ structure without the presence of long-range magnetic order,
+whereas NaOsO$_3$ is a $G$-type antiferromagnetic insulator with an
+orthorhombic $Pnma$ structure. By means of comparative first-principles DFT+$U$
+calculations with the inclusion of the spin-orbit coupling, we ($i$) identify
+the origin of the different structural ($R3c$ vs. $Pnma$) properties using a
+symmetry-adapted soft mode analysis, ($ii$) provide evidence that all
+considered exchange-correlation functionals (LDA, PBE, PBEsol, SCAN, and HSE06)
+and the spin disordered polymorphous descriptions are unsatisfactory to
+accurately describe the electronic and magnetic properties of both systems
+simultaneously, and ($iii$) clarify that the distinct electronic (metallic vs.
+insulating) properties originates mainly from a cooperative steric and magnetic
+effect. Finally, we find that although at ambient pressure LiOsO$_3$ with a
+$Pnma$ symmetry and NaOsO$_3$ with a $R\bar{3}c$ symmetry are energetically
+unfavorable, they do not show soft phonons and therefore are dynamically
+stable. A pressure-induced structural phase transition from $R3c$ to $Pnma$ for
+LiOsO$_3$ is predicted, whereas for NaOsO$_3$ no symmetry change is discerned
+in the considered pressure range.",2002.06081v1
+2020-05-07,Effect of interfacial oxidation layer in spin pumping experiments on Ni$_{80}$Fe$_{20}$/SrIrO$_3$ heterostructures,"SrIrO$_3$ with its large spin-orbit coupling and low charge conductivity has
+emerged as a potential candidate for efficient spin-orbit torque magnetization
+control in spintronic devices. We here report on the influence of an
+interfacial oxide layer on spin pumping experiments in Ni$_{80}$Fe$_{20}$
+(NiFe)/SrIrO$_3$ bilayer heterostructures. To investigate this scenario we have
+carried out broadband ferromagnetic resonance (BBFMR) measurements, which
+indicate the presence of an interfacial antiferromagnetic oxide layer. We
+performed in-plane BBFMR experiments at cryogenic temperatures, which allowed
+us to simultaneously study dynamic spin pumping properties (Gilbert damping)
+and static magnetic properties (such as the effective magnetization and
+magnetic anisotropy). The results for NiFe/SrIrO$_3$ bilayer thin films were
+analyzed and compared to those from a NiFe/NbN/SrIrO$_3$ trilayer reference
+sample, where a spin-transparent, ultra-thin NbN layer was inserted to prevent
+oxidation of NiFe. At low temperatures, we observe substantial differences in
+the magnetization dynamics parameters of these samples, which can be explained
+by an antiferromagnetic interfacial layer in the NiFe/SrIrO$_3$ bilayers.",2005.03727v1
+2020-05-30,Magnetization dynamics in proximity-coupled superconductor/ferromagnet/superconductor multilayers,"In this work, magnetization dynamics is studied in
+superconductor/ferromagnet/superconductor three-layered films in a wide
+frequency, field, and temperature ranges using the broad-band ferromagnetic
+resonance measurement technique. It is shown that in presence of both
+superconducting layers and of superconducting proximity at both
+superconductor/ferromagnet interfaces a massive shift of the ferromagnetic
+resonance to higher frequencies emerges. The phenomenon is robust and
+essentially long-range: it has been observed for a set of samples with the
+thickness of ferromagnetic layer in the range from tens up to hundreds of
+nanometers. The resonance frequency shift is characterized by proximity-induced
+magnetic anisotropies: by the positive in-plane uniaxial anisotropy and by the
+drop of magnetization. The shift and the corresponding uniaxial anisotropy grow
+with the thickness of the ferromagnetic layer. For instance, the anisotropy
+reaches 0.27~T in experiment for a sample with 350~nm thick ferromagnetic
+layer, and about 0.4~T in predictions, which makes it a ferromagnetic film
+structure with the highest anisotropy and the highest natural resonance
+frequency ever reported. Various scenarios for the superconductivity-induced
+magnetic anisotropy are discussed. As a result, the origin of the phenomenon
+remains unclear. Application of the proximity-induced anisotropies in
+superconducting magnonics is proposed as a way for manipulations with a
+spin-wave spectrum.",2006.00348v1
+2020-06-20,Momentum-dependent magnon lifetime in the metallic non-collinear triangular antiferromagnet CrB2,"Non-collinear magnetic order arises for various reasons in several magnetic
+systems and exhibits interesting spin dynamics. Despite its ubiquitous
+presence, little is known of how magnons, otherwise stable quasiparticles,
+decay in these systems, particularly in metallic magnets. Using inelastic
+neutron scattering, we examine the magnetic excitation spectra in a metallic
+non-collinear antiferromagnet CrB$_{2}$, in which Cr atoms form a triangular
+lattice and display incommensurate magnetic order. Our data show intrinsic
+magnon damping and continuum-like excitations that cannot be explained by
+linear spin wave theory. The intrinsic magnon linewidth $\Gamma(q,E_{q})$ shows
+very unusual momentum dependence, which our analysis shows to originate from
+the combination of two-magnon decay and the Stoner continuum. By comparing the
+theoretical predictions with the experiments, we identify where in the momentum
+and energy space one of the two factors becomes more dominant. Our work
+constitutes a rare comprehensive study of the spin dynamics in metallic
+non-collinear antiferromagnets. It reveals, for the first time, definite
+experimental evidence of the higher-order effects in metallic antiferromagnets.",2006.11530v2
+2020-09-22,"Dynamics evolution of a solar active-region filament from quasi-static state to eruption: rolling motion, untwisting motion, material transfer, and chirality","To better understand magnetic structure and eruptive process of solar
+filaments, a solar active-region filament (labeled F2) eruption associated with
+a B-class flare was investigated by using high-resolution H$\alpha$ data from
+the 1 m New Vacuum Solar Telescope (NVST), combined with EUV observations of
+the Solar Dynamical Observatory (SDO). The filament F2 was disturbed by another
+filament (labeled F1) eruption that experienced a whip-like motion. Before the
+filament F2 eruption, the Dopplergrams show that the southern and the northern
+parts of the filament F2 body exhibit blueshift and redshift along the filament
+spine, simultaneously. It implies that the filament F2 was rolling from one
+side to the other. During the filament F2 eruption, the Doppler velocity shifts
+of the filament body are opposite to that before its eruption. It demonstrates
+that the filament body exhibits an untwisting motion, which can be also
+identified by tracing the movement of the eruptive filament threads. Moreover,
+it is found that the material of the filament F2 was transferred to the
+surrounding magnetic field loops, which is caused by magnetic reconnection
+between the filament F2 and the surrounding magnetic loops. According to the
+right-bearing threads of the filament F2 before its eruption, it can be deduced
+that the filament F2 is initially supported by a sheared arcade. The following
+observations reveal that the twisted magnetic structure of the filament F2
+formed in the eruption phase.",2009.10345v1
+2020-10-14,Dynamic detection of current-induced spin-orbit magnetic fields: a phase independent approach,"Current induced spin-orbit torques (SOTs) in ferromagnet/non-magnetic metal
+heterostructures open vast possibilities to design spintronic devices to store,
+process and transmit information in a simple architecture. It is a central task
+to search for efficient SOT-devices, and to quantify the magnitude as well as
+the symmetry of current-induced spin-orbit magnetic fields (SOFs). Here, we
+report a novel approach to determine the SOFs based on magnetization dynamics
+by means of time-resolved magneto-optic Kerr microscopy. A microwave current in
+a narrow Fe/GaAs (001) stripe generates an Oersted field as well as SOFs due to
+the reduced symmetry at the Fe/GaAs interface, and excites standing spin wave
+(SSW) modes because of the lateral confinement. Due to their different
+symmetries, the SOFs and the Oersted field generate distinctly different mode
+patterns. Thus it is possible to determine the magnitude of the SOFs from an
+analysis of the shape of the SSW patterns. Specifically, this method, which is
+conceptually different from previous approaches based on lineshape analysis, is
+phase independent and self-calibrated. It can be used to measure the current
+induced SOFs in other material systems, e.g., ferromagnetic metal/non-magnetic
+metal heterostructures.",2010.06960v1
+2021-03-04,Canted antiferromagnetic order and spin dynamics in the honeycomb-lattice Tb2Ir3Ga9,"Single crystal neutron diffraction, inelastic neutron scattering, bulk
+magnetization measurements, and first-principles calculations are used to
+investigate the magnetic properties of the honeycomb lattice $\rm
+Tb_2Ir_3Ga_9$. While the $R\ln2$ magnetic contribution to the low-temperature
+entropy indicates a $\rm J_{eff}=1/2$ moment for the lowest-energy
+crystal-field doublet, the Tb$^{3+}$ ions form a canted antiferromagnetic
+structure below 12.5 K. Due to the Dzyalloshinskii-Moriya interactions, the Tb
+moments in the $ab$ plane are slightly canted towards $b$ by $6^\circ$ with a
+canted moment of 1.22 $\mu_{\rm B} $ per formula unit. A minimal $xxz$ spin
+Hamiltonian is used to simultaneously fit the spin-wave frequencies along the
+high symmetry directions and the field dependence of the magnetization along
+the three crystallographic axes. Long-range magnetic interactions for both
+in-plane and out-of-plane couplings up to the second nearest neighbors are
+needed to account for the observed static and dynamic properties. The $z$
+component of the exchange interactions between Tb moments are larger than the
+$x$ and $y$ components. This compound also exhibits bond-dependent exchange
+with negligible nearest exchange coupling between moments parallel and
+perpendicular to the 4$f$ orbitals. Despite the $J_{{\rm eff}}=1/2$ moments,
+the spin Hamiltonian is denominated by a large in-plane anisotropy $K_z \sim
+-1$ meV. DFT calculations confirm the antiferromagnetic ground state and the
+substantial inter-plane coupling at larger Tb-Tb distances.",2103.03157v1
+2021-03-10,"Spin texture induced by non-magnetic doping and spin dynamics in 2D triangular lattice antiferromagnet h-Y(Mn,Al)O3","Novel effects induced by nonmagnetic impurities in frustrated magnets and
+quantum spin liquid represent a highly nontrivial and interesting problem. A
+theoretical proposal of extended modulated spin structures induced by doping of
+such magnets, distinct from the well-known skyrmions has attracted significant
+interest. Here, we demonstrate that nonmagnetic impurities can produce such
+extended spin structures in h-YMnO3, a triangular antiferromagnet with
+noncollinear magnetic order. Using inelastic neutron scattering (INS), we
+measured the full dynamical structure factor in Al-doped h-YMnO3 and confirmed
+the presence of magnon damping with a clear momentum dependence. Our
+theoretical calculations can reproduce the key features of the INS data,
+supporting the formation of the proposed spin textures. As such, our study
+provides the first experimental confirmation of the impurity-induced spin
+textures. It offers new insights and understanding of the impurity effects in a
+broad class of noncollinear magnetic systems.",2103.05936v2
+2021-05-10,The global structure of magnetic fields and gas in simulated Milky Way-analogue galaxies,"We simulate an isolated, magnetised Milky Way-like disc galaxy using a
+self-consistent model of unresolved star formation and feedback, evolving the
+system until it reaches statistical steady state. We show that the
+quasi-steady-state structure is distinctly layered in galactocentric height
+$z$, with an innermost region having comparable gas and magnetic pressures
+(plasma beta $\beta \sim 1$), an outermost region having dominant gas pressures
+($\beta \gg 1$), and an intermediate region between $300$ pc $\lesssim |z|
+\lesssim 3$ kpc that is dynamically dominated by magnetic fields ($\beta \ll
+1$). We find field strengths, gas surface densities, and star formation rates
+that agree well with those observed both in the Galactic centre and in the
+Solar neighbourhood. The most significant dynamical effect of magnetic fields
+on the global properties of the disc is a reduction of the star formation rate
+by a factor of 1.5-2 with respect to an unmagnetised control simulation. At
+fixed star formation rate, there is no significant difference in the mass
+outflow rates or profiles between the magnetised and non-magnetised
+simulations. Our results for the global structure of the magnetic field have
+significant implications for models of cosmic ray-driven winds and cosmic-ray
+propagation in the Galaxy, and can be tested against observations with the
+forthcoming Square Kilometre Array and other facilities. Finally, we report the
+discovery of a physical error in the implementation of neutral gas heating and
+cooling in the popular GIZMO code, which may lead to qualitatively incorrect
+phase structures if not corrected.",2105.04136v1
+2021-06-21,Crystallization of Bosonic Quantum Hall States,"The dominance of interactions over kinetic energy lies at the heart of
+strongly correlated quantum matter, from fractional quantum Hall liquids, to
+atoms in optical lattices and twisted bilayer graphene. Crystalline phases
+often compete with correlated quantum liquids, and transitions between them
+occur when the energy cost of forming a density wave approaches zero. A prime
+example occurs for electrons in high magnetic fields, where the instability of
+quantum Hall liquids towards a Wigner crystal is heralded by a roton-like
+softening of density modulations at the magnetic length. Remarkably,
+interacting bosons in a gauge field are also expected to form analogous liquid
+and crystalline states. However, combining interactions with strong synthetic
+magnetic fields has been a challenge for experiments on bosonic quantum gases.
+Here, we study the purely interaction-driven dynamics of a Landau gauge
+Bose-Einstein condensate in and near the lowest Landau level (LLL). We observe
+a spontaneous crystallization driven by condensation of magneto-rotons,
+excitations visible as density modulations at the magnetic length. Increasing
+the cloud density smoothly connects this behaviour to a quantum version of the
+Kelvin-Helmholtz hydrodynamic instability, driven by the sheared internal flow
+profile of the rapidly rotating condensate. At long times the condensate
+self-organizes into a persistent array of droplets, separated by vortex
+streets, which are stabilized by a balance of interactions and effective
+magnetic forces.",2106.11300v1
+2021-06-29,The sub-millimetre non-uniformity measurement of residual and coil-generated field in the magnetic shield using atomic vapor cell,"Magnetic field source localization and imaging happen at different scales.
+The sensing baseline ranges from meter scale such as magnetic anomaly
+detection, centimeter scale such as brain field imaging to nanometer scale such
+as the imaging of magnetic skyrmion and single cell. Here we show how atomic
+vapor cell can be used to realize a baseline of 109.6 {\mu}m with a magnetic
+sensitivity of 10pT/sqrt(Hz)@0.6-100Hz and a dynamic range of 2062-4124nT.We
+use free induction decay (FID) scheme to suppress low-frequency noise and avoid
+scale factor variation for different domains due to light non-uniformity. The
+measurement domains are scanned by digital micro-mirror device (DMD). The
+currents of 22mA, 30mA, 38mA and 44mA are applied in the coils to generate
+different fields along the pumping axis which are measured respectively by
+fitting the FID signals of the probe light. The residual fields of every domain
+are obtained from the intercept of linearly-fitting of the measurement data
+corresponding to these four currents. The coil-generated fields are calculated
+by deducting the residual fields from the total fields. The results demonstrate
+that the hole of shield affects both the residual and the coil-generated field
+distribution. The potential impact of field distribution measurement with an
+outstanding comprehensive properties of spatial resolution, sensitivity and
+dynamic range is far-reaching. It could lead to capability of 3D magnetography
+for small stuffs and/or organs in millimeter or even smaller scale.",2106.15310v2
+2021-07-05,Two Classes of Eruptive Events During Solar Minimum,"During solar minimum, the Sun is relatively inactive with few sunspots
+observed on the solar surface. Consequently, we observe a smaller number of
+highly energetic events such as solar flares or coronal mass ejections (CMEs),
+which are often associated with active regions on the photosphere. Nonetheless,
+our magnetofrictional simulations during the minimum period suggest that the
+solar corona is still dynamically evolving in response to the large-scale
+shearing velocities on the solar surface. The non-potential evolution of the
+corona leads to the accumulation of magnetic free energy and helicity, which is
+periodically shed in eruptive events. We find that these events fall into two
+distinct classes: One set of events are caused by eruption and ejection of
+low-lying coronal flux ropes, and they could explain the origin of occasional
+CMEs during solar minimum. The other set of events are not driven by
+destabilisation of low-lying structures but rather by eruption of overlying
+sheared arcades. These could be associated with streamer blowouts or stealth
+CMEs. The two classes differ significantly in the amount of magnetic flux and
+helicity shed through the outer coronal boundary. We additionally explore how
+other measurables such as current, open magnetic flux, free energy, coronal
+holes, and the horizontal component of the magnetic field on the outer model
+boundary vary during the two classes of event. This study emphasises the
+importance and necessity of understanding the dynamics of the coronal magnetic
+field during solar minimum.",2107.01941v1
+2021-09-10,Thermally-induced magnetic order from glassiness in elemental neodymium,"Temperature in thermodynamics is synonymous with disorder, and responsible
+for ultimately destroying ordered phases. Here, we show an unusual magnetic
+transition where, with increasing the temperature of elemental neodymium,
+long-range multi-Q magnetic order emerges from a self-induced spin glass. Using
+temperature-dependent spin-polarized scanning tunneling microscopy, we
+characterize the local Q order in the spin-Q glass phase and quantify the
+emergence of long-range multi-Q order with increasing temperature. We develop
+two distinct analysis tools, which enable the quantification of the glass
+transition temperature, based on measured spatially-dependent magnetization. We
+compare these observations with atomic spin dynamics simulations, which
+reproduce the qualitative observation of a phase transition from a
+low-temperature spin glass phase to an intermediate ordered multi-Q phase.
+These simulations trace the origin of the unexpected high temperature order in
+weakened frustration driven by temperature-dependent sublattice correlations.
+These findings constitute an example of order from disorder and provide a rich
+platform to study magnetization dynamics in a self-induced spin glass.",2109.04815v1
+2021-11-17,Small-scale magnetic flux ropes and their properties based on in-situ measurements from Parker Solar Probe,"We report small-scale magnetic flux ropes via the Parker Solar Probe in situ
+measurements during the first six encounters and present additional analyses to
+supplement our prior work in Chen et al. 2021. These flux ropes are detected by
+the Grad-Shafranov-based algorithm with the duration and scale size ranging
+from 10 seconds to $\lesssim$1 hour and from a few hundred kilometers to
+10$^{-3}$ au, respectively. They include both static structures and those with
+significant field-aligned plasma flows. Most structures tend to possess large
+cross helicity, while the residual energy distributes in wide ranges. We find
+that these dynamic flux ropes mostly propagate anti-sunward, with no
+preferential sign of magnetic helicity. The magnetic flux function follows a
+power law and is proportional to scale size. We also present case studies
+showing reconstructed two-dimensional (2D) configurations, which confirm that
+the static and dynamic flux ropes have the common configuration of spiral
+magnetic field lines (also streamlines). Moreover, the existence of such events
+hints at the interchange reconnection as a possible mechanism to generate flux
+rope-like structures near the Sun. Lastly, we summarize the major findings and
+discuss the possible correlation between these flux rope-like structures and
+turbulence due to the process of local Alfvenic alignment.",2111.09261v1
+2021-12-22,Untangling magnetic massive star properties with linear polarization variability and the Analytic Dynamical Magnetosphere model,"Light scattered off particles can become linearly polarized. Stars surrounded
+by oblique, co-rotating envelopes are therefore expected to manifest periodic
+linear polarimetric variations. The electron scattering magnetospheres of
+magnetic massive stars are expected to be suitable candidates to observe this
+effect. In this paper, we present the first semi-analytical model capable of
+synthesizing the continuum polarimetric signatures of magnetic O-type stars in
+an optically thin, single electron scattering limit. The purpose of this
+investigation is to improve our general understanding of magnetic hot stars by
+characterizing their polarimetric behaviour. Our linear polarization model is
+constructed by combining the analytical expressions for the polarimetric
+variations of an obliquely rotating envelope with the Analytic Dynamical
+Magnetosphere model to represent a physical model for the envelope density
+structure. We compute grids of model Stokes $Q$ and $U$ curves and show that
+their shapes are unique to the choice of inclination and obliquity angles. We
+apply our model to HD 191612, a prototypical Of?p-type star, having both
+polarimetric and photometric observations. We find that the polarimetric
+modulations are best reproduced with $i=19^{+12}_{-3}$$^\circ$,
+$\beta=71^{+3}_{-9}$$^\circ$, and $\log \dot{M}_{B=0}=-6.11^{+0.12}_{-0.06}$
+[M$_{\odot}$ yr$^{-1}$]. These results agree with previous investigations of
+this star. By combining both polarimetric and photometric synthesis tools, we
+simultaneously model the observations thus adding further refinement of the
+wind and magnetic properties of HD 191612.",2112.11942v1
+2022-04-28,"Low-energy spin excitations of the frustrated ferromagnetic $J_1$-$J_2$ chain material linarite, PbCuSO$_4$(OH)$_2$, in applied magnetic fields $\mathbf{H} \parallel b$ axis","We report a study of the spin dynamics of the frustrated ferromagnetic
+$J_1$-$J_2$ chain compound linarite, PbCuSO$_4$(OH)$_2$, in applied magnetic
+fields up to field polarization. By means of an extreme-environment inelastic
+neutron scattering experiment, we have measured the low-energy spin excitations
+of linarite in fields up to 8.8 T for $\mathbf{H} \parallel b$ axis. We have
+recorded the spin excitation spectra along $h$, $k$ and $l$ for the
+field-induced magnetic phases IV, V and the field polarized state close to
+saturation. By employing first-principles calculations, we estimate the leading
+magnetic exchanges out of the $bc$ plane and model the dispersion relations
+using linear spin-wave theory. In this way, we find evidence for a (very weak)
+residual magnetic exchange coupling out of the $bc$ plane. Together with the
+previously established dominant intrachain couplings $J_1$ and $J_2$ and the
+interchain coupling $J_3$, we derive an effective set of exchange couplings for
+a microscopic description of linarite. Further, we find that the peculiar
+character of phase V manifests itself in the measured spin dynamics.",2204.13482v2
+2022-05-12,"Investigation of lattice dynamics, magnetism and electronic transport in $β$-Na$_{0.33}$V$_2$O$_{5}$","We investigate the electronic and magnetic properties as well as lattice
+dynamics and spin-phonon coupling of $\beta$-Na$_{0.33}$V$_2$O$_5$ using
+temperature-dependent Raman scattering, dc-magnetization and dc-resistivity,
+x-ray photoemission, and absorption spectroscopy. The Rietveld refinement of
+XRD pattern with space group C2/m confirms the monoclinic structure. The
+analysis of temperature-dependent Raman spectra in a temperature range of
+13--673~K reveals an anharmonic dependence of the phonon frequency and full
+width at half maximum, which is accredited to the symmetric phonon decay.
+However, below about 40 K, the hardening of the phonon frequency beyond
+anharmonicity is attributed to the spin-phonon coupling. Interestingly, the
+estimated effective magnetic moment $\mu_{\rm eff}=$ 0.63~$\mu_B$ from the
+magnetization data manifests a mixed-valence state of V ions in 4+ (18$\pm$1\%)
+and 5+ (82$\pm$1\%). A similar ratio of V$^{4+}$ to V$^{5+}$ is also observed
+in the x-ray photoemission and x-ray absorption near-edge spectra and that is
+found to be consistent with the sample stoichiometry. In addition, the V$^{4+}$
+ions are distributed between different vanadium (V1 and V3) sites. The analysis
+of extended x-ray absorption fine structure at different V-sites gives the
+corresponding V--O bond lengths, which are utilized in the assignment of Raman
+modes. Moreover, the temperature-dependent resistivity resembles a
+semiconducting behavior where the charge carrier transport is facilitated by
+the band conduction at higher temperatures and via hopping $\le$260~K.",2205.06019v2
+2022-05-31,Dualities of Adjoint QCD$_3$ from Branes,"We consider an 'electric' $U(N)$ level $k$ QCD$_3$ theory with one adjoint
+Majorana fermion. Inspired by brane dynamics, we suggest that for $k \ge N/2$
+the massive $m<0$ theory, in the vicinity of the supersymmetric point, admits a
+$U(k-\frac{N}{2})_{-(\frac{1}{2}k+\frac{3}{4}N),-(k+\frac{N}{2})}$ 'magnetic'
+dual with one adjoint Majorana fermion. The magnetic theory flows in the IR to
+a topological $U(k-\frac{N}{2})_{-N,-(k+\frac{N}{2})}$ pure Chern-Simons theory
+in agreement with the dynamics of the electric theory. When $k<N/2$ the
+magnetic dual is $U(\frac{N}{2}-k)_{\frac{1}{2}k+\frac{3}{4}N,N}$ with one
+adjoint Majorana fermion. Depending on the sign of the fermion mass, the
+magnetic theory flows to either $U(\frac{N}{2}-k)_{N,N}$ or
+$U(\frac{N}{2}-k)_{\frac{1}{2}N+k,N}$ TQFT. A second magnetic theory,
+$U(N/2+k)_{\frac{1}{2}k-\frac{3}{4}N,-N}$, flows to either
+$U(\frac{N}{2}+k)_{-N,-N}$ or $U(\frac{N}{2}+k)_{-(\frac{1}{2}N-k),-N}$ TQFT.
+Dualities for $SO$ and $USp$ theories with one adjoint fermion are also
+discussed.",2205.15706v4
+2022-06-06,Quantitative theory of magnetic interactions in solids,"In this report we review the method of explicit calculations of interatomic
+exchange interactions of magnetic materials. This involves exchange mechanisms
+normally referred to as Heisenberg exchange, Dzyaloshinskii-Moriya interaction
+and anisotropic symmetric exchange. The connection between microscopic theories
+of the electronic structure, such as density functional theory or dynamical
+mean field theory, and interatomic exchange, is given in detail. The different
+aspects of extracting information for an effective spin Hamiltonian that
+involves thousands of atoms, from electronic structure calculations considering
+significantly fewer atoms (1-50) is highlighted. Examples of exchange
+interactions of a large group of materials is presented, which involves heavy
+elements of the 3d period, alloys between transition metals, Heusler compounds,
+multilayer systems as well as overlayers and adatoms on a substrate, transition
+metal oxides, 4f elements, magnetic materials in two dimensions and molecular
+magnets. Where possible, a comparison to experimental data is made, that
+naturally becomes focused on the magnon dispersion. The influence of relativity
+is reviewed for a few cases, as is the importance of dynamical correlations.
+Development to theories that handle out of equilibrium conditions is also
+described here. The review ends with a short description of extensions of the
+theories behind explicit calculations of interatomic exchange, to non-magnetic
+situations, e.g. that describe chemical (charge) order and superconductivity.",2206.02415v2
+2022-11-07,A Census of Outflow to Magnetic Field Orientations in Nearby Molecular Clouds,"We define a sample of 200 protostellar outflows showing blue and redshifted
+CO emission in the nearby molecular clouds Ophiuchus, Taurus, Perseus and Orion
+to investigate the correlation between outflow orientations and local, but
+relatively large-scale, magnetic field directions traced by Planck 353 GHz dust
+polarization. At high significance (p~1e-4), we exclude a random distribution
+of relative orientations and find that there is a preference for alignment of
+projected plane of sky outflow axes with magnetic field directions. The
+distribution of relative position angles peaks at ~30deg and exhibits a broad
+dispersion of ~50deg. These results indicate that magnetic fields have
+dynamical influence in regulating the launching and/or propagation directions
+of outflows. However, the significant dispersion around perfect alignment
+orientation implies that there are large measurement uncertainties and/or a
+high degree of intrinsic variation caused by other physical processes, such as
+turbulence or strong stellar dynamical interactions. Outflow to magnetic field
+alignment is expected to lead to a correlation in the directions of nearby
+outflow pairs, depending on the degree of order of the field. Analyzing this
+effect we find limited correlation, except on relatively small scales < 0.5 pc.
+Furthermore, we train a convolutional neural network to infer the inclination
+angle of outflows with respect to the line of sight and apply it to our outflow
+sample to estimate their full 3D orientations. We find that the angles between
+outflow pairs in 3D space also show evidence of small-scale alignment.",2211.03781v1
+2022-11-13,Non-perturbative diffusion of Heavy Quark moving in a hot and magnetised Quark Gluon Plasma,"Heavy Quarks (HQs) serve as excellent probes to understand various
+characteristics of deconfined hot QCD medium, comprising light quarks and
+gluons, created in the Heavy Ion Collisions (HICs). Strong magnetic fields in
+non-central HICs may significantly affect HQ dynamics in this medium. Exploring
+the impact of the magnetic field on the perturbative and non-perturbative
+transport coefficients of HQ is an intriguing endeavor. This necessitates the
+development of a comprehensive theoretical framework accommodating the
+non-perturbative Quantum Chromo Dynamics(npQCD) description alongside
+perturbative QCD(pQCD). The present work provides such a formulation in which
+Quarkonium potential in the hot and magnetic QCD medium is implemented as the
+effective gluon propagator to calculate the rate of elastic scattering between
+HQ and the light partons inside a medium of hot Quark Gluon Plasma(QGP) in the
+presence of a strong but uniform magnetic field. Diffusion coefficients of a
+charm quark have been computed for a short-range Yukawa potential ( pQCD) as
+well as a long-range confining/non-perturbative potential (npQCD) for two cases
+in which the velocity of the charm quark is parallel and perpendicular to the
+magnetic field respectively. Non-perturbative contribution is seen to dominate
+over the perturbative one in the regime of low temperatures and low to
+intermediate momenta of charm quark. As the momentum of charm quark as well as
+the temperature of the medium increase pQCD starts to gain on the npQCD
+contribution, ultimately prevailing at higher temperatures and charm momenta.",2211.06985v3
+2022-12-14,Magnetic fluxes of solar active regions of different magneto-morphological classes: I. Cyclic variations,"Data for 3046 solar active regions (ARs) observed since May 12, 1996 to
+December 27, 2021 were utilized to explore how the magnetic fluxes from ARs of
+different complexity follow the solar cycle. Magnetograms from the Michelson
+Doppler Imager instrument on the Solar and Heliospheric Observatory and from
+the Helioseismic and Magnetic Imager instrument on the Solar Dynamics
+Observatory were utilized. Each AR was classified as a regular bipolar AR
+(classes A1 or A2), or as an irregular bipolar AR (class B1), or as a
+multipolar AR (classes B2 or B3). Unipolar ARs were segregated into a specific
+class U. We found the following results. Unsigned magnetic fluxes from ARs of
+different classes evolve synchronously following the cycle, the correlation
+coefficient between the flux curves varies in a range of (0.70 - 0.99). The
+deepest solar minimum is observed simultaneously for all classes. Only the most
+simple ARs were observed during a deepest minimum: A1- and B1-class ARs. The
+overall shape of a cycle is governed by the regular ARs, whereas the fine
+structure of a solar maximum is determined by the most complex irregular ARs.
+Approximately equal amount of flux (45$-$50% of the total flux) is contributed
+by the A-class and B-class ARs during a solar maximum. Thus, observations allow
+us to conclude that the appearance of ARs with the magnetic flux above
+10$^{21}$ Mx is caused by the solar dynamo that operates as a unique process
+displaying the properties of a non-linear dynamical dissipative system with a
+cyclic behaviour and unavoidable fluctuations.",2212.07115v1
+2023-01-02,Tailoring the escape rate of a Brownian particle by combining a vortex flow with a magnetic field,"The probability per unit time for a thermally activated Brownian particle to
+escape over a potential well is in general well-described by Kramers theory.
+Kramers showed that the escape time decreases exponentially with increasing
+barrier height. The dynamics slow down when the particle is charged and
+subjected to a Lorentz force due to an external magnetic field. This is evident
+via a rescaling of the diffusion coefficient entering as a prefactor in the
+Kramers escape rate without any impact on the barrier-height-dependent
+exponent. Here we show that the barrier height can be effectively changed when
+the charged particle is subjected to an external vortex flow. While the
+external vortex alone does not affect the mean escape time of the particle,
+when combined with a magnetic field it effectively pushes the fluctuating
+particle either radially outside or inside depending on its sign relative to
+that of the magnetic field. In particular, the effective potential over which
+the particle escapes can be changed to a flat, a stable, and an unstable
+potential by tuning the signs and magnitudes of the external vortex and the
+applied magnetic field. Notably, the last case corresponds to enhanced escape
+dynamics.",2301.00589v1
+2023-02-01,A Brillouin light scattering study of the spin-wave magnetic field dependence in a magnetic hybrid system made of an artificial spin-ice structure and a film underlayer,"We present a combined Brillouin light scattering and micromagnetic simulation
+investigation of the magnetic-field dependent spin-wave spectra in a hybrid
+structure made of permalloy (NiFe) artificial spin-ice (ASI) systems, composed
+of stadium-shaped nanoislands, deposited on the top of an unpatterned permalloy
+film with a nonmagnetic spacer layer. The thermal spin-wave spectra were
+recorded by Brillouin light scattering (BLS) as a function of the magnetic
+field applied along the symmetry direction of the ASI sample. Magneto-optic
+Kerr effect magnetometry was used to measure the hysteresis loops in the same
+orientation as the BLS measurements. The frequency and intensity of several
+spin-wave modes detected by BLS were measured as a function of the applied
+magnetic field. Micromagnetic simulations enabled us to identify the modes in
+terms of their frequency and spatial symmetry and to extract information about
+the existence and strength of the dynamic coupling, relevant only to a few
+modes of a given hybrid system. Using this approach, we suggest a way to
+understand if dynamic coupling between ASI and film modes is present or not,
+with interesting implications for the development of future three-dimensional
+magnonic applications and devices.",2302.00483v1
+2023-04-07,A Numerical Study of the Impact of Jet Magnetic Topology on Radio Galaxy Evolution,"The propagation of active galactic nucleus jets depends both on the
+environment into which they propagate and on their internal structure. To test
+the impact that different magnetic topologies have on the observable properties
+of radio galaxies on kpc scales, we conducted a series of magneto-hydrodynamic
+simulations of jets injected with different magnetic field configurations
+propagating into a gaseous atmosphere modeled on the Perseus cluster. The
+simulations show that the structure of the field affects the collimation and
+propagation of the jets on cluster scales and thus the morphology of the radio
+lobes inflated by the jets, due both to magnetic collimation and the
+development of dynamical instabilities in jets with different magnetic
+topologies. In all cases, the simulations show a distinct reversal of the
+sychrotron spectral age gradient in the radio lobes about a dynamical time
+after the jets turn off due to large scale circulation inside the radio lobe,
+driven primarily by buoyancy, which could provide a way to constrain the age of
+radio sources in cluster environments without the need for detailed spectral
+modeling and thus constrain the radio mode feedback efficiency. We suggest a
+robust diagnostic to search for such age gradients in multi-frequency radio
+data.",2304.03863v1
+2023-06-27,"Three-dimensional spin-wave dynamics, localization and interference in a synthetic antiferromagnet","Spin waves are collective perturbations in the orientation of the magnetic
+moments in magnetically ordered materials. Their rich phenomenology is
+intrinsically three dimensional, from the trajectory of the spin precession
+during their propagation, to the profiles of the spin-wave mode throughout the
+volume of the magnetic system. This gives rise to novel complex phenomena with
+high potential for applications in the field of magnonics. However, the
+three-dimensional imaging of spin waves, key to understanding and harnessing
+these phenomena, has so far not been possible. Here, we image the
+three-dimensional dynamics of spin waves excited in a synthetic
+antiferromagnet, with nanoscale spatial resolution and sub-ns temporal
+resolution, using time-resolved magnetic laminography. In this way, we map the
+distribution of the spin-wave modes throughout the volume of the structure,
+revealing unexpected depth-dependent profiles originating from the interlayer
+dipolar interaction. We experimentally demonstrate the existence of complex
+three-dimensional interference patterns, and analyze them via micromagnetic
+modelling. We find that these patterns are generated by the superposition of
+spin waves with non-uniform amplitude profiles, and that their features can be
+controlled by tuning the composition and structure of the magnetic system. Our
+results open unforeseen possibilities for the study of complex spin-wave modes
+and their interaction within nanostructures, and for the generation and
+manipulation of three-dimensional spin-wave landscapes for the design of novel
+functions in magnonic devices.",2306.15404v1
+2023-06-28,Dipolar Ultrastrong Magnon-Magnon Coupling in a 3D Multilayered Artificial Spin-Vortex Ice,"Strongly-interacting nanomagnetic arrays are ideal systems for exploring
+reconfigurable magnonics. They provide huge microstate spaces and integrated
+solutions for storage and neuromorphic computing alongside GHz functionality.
+These systems may be broadly assessed by their range of reliably accessible
+states and the strength of magnon coupling phenomena and nonlinearities.
+  Increasingly, nanomagnetic systems are expanding into three-dimensional
+architectures. This has enhanced the range of available magnetic microstates
+and functional behaviours, but engineering control over 3D states and dynamics
+remains challenging.
+  Here, we introduce a 3D magnonic metamaterial composed from multilayered
+artificial spin ice nanoarrays. Comprising two magnetic layers separated by a
+non-magnetic spacer, each nanoisland may assume four macrospin or vortex states
+per magnetic layer. This creates a system with a rich $16^N$ microstate space
+and intense static and dynamic dipolar magnetic coupling.
+  The system exhibits a broad range of emergent phenomena driven by the strong
+inter-layer dipolar interaction, including ultrastrong magnon-magnon coupling
+with normalised coupling rates of $\frac{\Delta \omega}{\gamma} = 0.57$, GHz
+mode shifts in zero applied field and chirality-selective magneto-toroidal
+microstate programming and corresponding magnonic spectral control.",2306.16159v2
+2023-10-03,Controlled Quasi-Latitudinal Solutions for ultra-fast Spin-Torque Precessional Magnetization Switching,"The aim of the paper is to present a novel class of time-dependent controls
+to realize ultra-fast magnetization switching in nanomagnets driven by
+spin-torques produced by spin-polarized electric currents. Magnetization
+dynamics in such systems is governed by the Landau-Lifshitz-Slonczewski
+equation which describes the precessional motion of (dimensionless)
+magnetization vector on the unit-sphere. The relevant case of nanoparticles
+with uniaxial anisotropy having in-plane easy and intermediate axes and
+out-of-plane hard axis is considered. By exploiting the characteristic
+smallness of damping and spin-torque intensity, the aforementioned controls are
+constructed via suitable perturbative tools in a way to realise approximate
+\emph{latitudinal solutions} (i.e. motions on a sphere in which the
+out-of-plane magnetization component stays constant) with the effect to fast
+``switch'' the system from one stationary state to another. The possibility to
+keep a (``small'') bounded value of the out-of-plane coordinate throughout this
+process of ``transfer'', turns out to be advantageous in the applications as it
+sensibly reduces the post-switching relaxation oscillations that may cause the
+failure of switching in real samples. Further relevant quantitative results on
+the behaviour of the solutions during the pre- and post-switching stages
+(termed ``expulsion'' and ``attraction'', respectively), are given as a
+byproduct. A selection of validating numerical experiments is presented
+alongside the corresponding theoretical results.",2310.02070v1
+2023-10-17,Winds and Disk Turbulence Exert Equal Torques on Thick Magnetically Arrested Disks,"The conventional accretion disk lore is that magnetized turbulence is the
+principal angular momentum transport process that drives accretion. However,
+when dynamically important magnetic fields thread an accretion disk, they can
+produce mass and angular momentum outflows that also drive accretion. Yet, the
+relative importance of turbulent and wind-driven angular momentum transport is
+still poorly understood. To probe this question, we analyze a long-duration
+($1.2 \times 10^5 r_{\rm g}/c$) simulation of a rapidly rotating ($a=0.9$)
+black hole (BH) feeding from a thick ($H/r\sim0.3$), adiabatic, magnetically
+arrested disk (MAD), whose dynamically-important magnetic field regulates mass
+inflow and drives both uncollimated and collimated outflows (e.g., ""winds"" and
+""jets"", respectively). By carefully disentangling the various angular momentum
+transport processes occurring within the system, we demonstrate the novel
+result that both disk winds and disk turbulence extract roughly equal amounts
+of angular momentum from the disk. We find cumulative angular momentum and mass
+accretion outflow rates of $\dot{L}\propto r^{0.9}$ and $\dot{M}\propto
+r^{0.4}$, respectively. This result suggests that understanding both turbulent
+and laminar stresses is key to understanding the evolution of systems where
+geometrically thick MADs can occur, such as the hard state of X-ray binaries,
+low-luminosity active galactic nuclei, some tidal disruption events, and
+possibly gamma ray bursts.",2310.11490v1
+2023-10-29,"Double-loop hysteresis of multisite dilute Sr(Y$_{1-x}$Dy$_x$)$_2$O$_4$ single crystal Kramers paramagnets: electron-phonon interaction, quantum tunneling and cross-relaxation","Experimental and theoretical studies of the dynamic magnetization in swept
+magnetic fields of the orthorhombic SrY$_2$O$_4$ single-crystals doped with the
+Dy$^{3+}$ Kramers ions (0.01 and 0.5 at.%) with natural abundances of even and
+odd Dy isotopes are presented. Impurity ions substitute for Y$^{3+}$ ions at
+two nonequivalent crystallographic sites with the same local $C_s$ symmetry but
+strongly different crystal fields. Well pronounced double-loop hysteresis is
+observed at temperatures 2, 4, 5 and 6 K for sweeping rates of 5 and 1 mT/s.
+The microscopic model of spectral, magnetic and kinetic properties of Dy$^{3+}$
+ions is developed based on the results of EPR, site selective optical spectra
+and magnetic relaxation measurements. The derived approach to the dynamic
+magnetization in the sweeping field based on the numerical solution of
+generalized master equations with time-dependent transition probabilities
+induced by the electron-phonon interaction, quantum tunneling and
+cross-relaxation allowed us to reproduce successfully the evolution of the
+hysteresis loop shape with temperature, sweeping rate and concentration of
+paramagnetic ions.",2310.18947v1
+2023-12-14,In situ Remnants of Solar Surface Structures from Jensen-Shannon Scalogram,"The heliosphere is permeated with highly structured solar wind originating
+from the sun. One of the primary science objectives of Parker Solar Probe (PSP)
+is to determine the structures and dynamics of the plasma and magnetic fields
+at the sources of the solar wind. However, establishing the connection between
+in situ measurements and structures and dynamics in the solar atmosphere is
+challenging: most of the magnetic footpoint mapping techniques have significant
+uncertainties in the source localization of a plasma parcel observed in situ,
+and the PSP plasma measurements suffer from a limited field of view. Therefore
+it lacks a universal tool to self-contextualize the in situ measurements. Here
+we develop a novel time series visualization method named Jensen-Shannon
+Scalogram. Utilizing this method, by analyzing the magnetic magnitude data from
+both PSP and Ulysses, we successfully identify in situ remnants of solar
+atmospheric and magnetic structures spanning more than seven orders of
+magnitude, from years to seconds, including polar and mid-latitude coronal
+holes, as well as structures compatible with super-granulation, ``jetlets'' and
+very small scale flaring activity. Furthermore, computer simulations of
+Alfv\'enic turbulence support key features of the observed magnetic magnitude
+distribution. Building upon these discoveries, the Jensen-Shannon Scalogram
+therefore not only enables us to reveal the fractal fine structures in the
+solar wind time series from both PSP and decades-old data archive, but will
+also serve as a general-purpose data visualization method applicable to all
+time series.",2312.08669v1
+2002-12-20,Disk Accretion Flow Driven by Large-Scale Magnetic Fields: Solutions with Constant Specific Energy,"(Abridged) We study the dynamical evolution of a stationary, axisymmetric,
+and perfectly conducting cold accretion disk containing a large-scale magnetic
+field around a Kerr black hole, trying to understand the relation between
+accretion and the transportation of angular momentum and energy. We solve the
+radial momentum equation for solutions corresponding to an accretion flow that
+starts from a subsonic state at infinity, smoothly passes the fast critical
+point, then supersonically falls into the horizon of the black hole. The
+solutions always have the following features: 1) The specific energy of fluid
+particles remains constant but the specific angular momentum is effectively
+removed by the magnetic field. 2) At large radii, where the disk motion is
+dominantly rotational, the energy density of the magnetic field is
+equipartitioned with the rotational energy density of the disk. 3) Inside the
+fast critical point, where radial motion becomes important, the ratio of the
+electromagnetic energy density to the kinetic energy density drops quickly. The
+results indicate that: 1) Disk accretion does not necessarily imply energy
+dissipation since magnetic fields do not have to transport or dissipate a lot
+of energy as they effectively transport angular momentum. 2) When resistivity
+is small, the large-scale magnetic field is amplified by the shearing rotation
+of the disk until the magnetic energy density is equipartitioned with the
+rotational energy density, ending up with a geometrically thick disk. This is
+in contrast with the evolution of small-scale magnetic fields where if the
+resistivity is nonzero the magnetic energy density is likely to be
+equipartitioned with the kinetic energy density associated with local random
+motions (e.g., turbulence), making a thin Keplerian disk possible.",0212503v2
+2003-08-10,Meissner Effect and Vortex Dynamics in Quark Stars -- A Model for Soft Gamma-Ray Repeaters,"We present a new model for soft gamma-ray repeaters based on a quark star
+born with temperatures above the critical value (T_c) for the onset of the
+colour-flavor locked superconductivity. The quark star then quickly cools below
+T_c, expelling a fraction of the surface magnetic field via the Meissner
+effect. We show that if a small fraction (\leq 10%) of the surface magnetic
+field (10^{14} - 10^{15} {\rm G}) is expelled, it quickly decays via magnetic
+reconnection and heats up the quark star surface to temperatures > 10^9 {\rm
+K}. Created (e^{+},e^{-}) pairs annihilate into gamma rays emitted in a giant
+burst (the first burst in our model), with a luminosity of \sim 10^{45} {\rm
+ergs} {\rm s}^{-1}. Subsequent bursts result from the restructuring of the
+surface magnetic field following the formation and relaxation of a vortex
+lattice which confines the internal magnetic field. During this phase, energy
+is sporadically released as a consequence of magnetic reconnection events in
+the entangled surface magnetic field as it evolves into a smooth, more stable,
+configuration. The star eventually enters a quiescent phase in which energy is
+continuously supplied by vortex annihilation at the surface. As the star spins
+down, the outermost vortex lines will be pushed to the surface where they
+annihilate and release their confined magnetic field. We show that the
+corresponding luminosity is L_v \sim 10^{36} {\rm ergs} {\rm s}^{-1} for a
+typical soft gamma-ray repeater spinning with a period of 8 {\rm s} and a
+surface magnetic field not exceeding 10^{15} {\rm G}. Our model can be applied
+to any situation where a T>T_{\rm c} quark star is generated. We discuss the
+connection between anomalous X-ray pulsars and soft gamma-ray repeaters in the
+context of our model.",0308166v2
+2004-09-15,Observations of magnetic fields in the Milky Way and in nearby galaxies with a Square Kilometre Array,"The role of magnetic fields in the dynamical evolution of galaxies and of the
+interstellar medium (ISM) is not well understood, mainly because such fields
+are difficult to directly observe. Radio astronomy provides the best tools to
+measure magnetic fields: synchrotron radiation traces fields illuminated by
+cosmic-ray electrons, while Faraday rotation and Zeeman splitting allow us to
+detect fields in all kinds of astronomical plasmas, from lowest to highest
+densities. Here we describe how fundamental new advances in studying magnetic
+fields, both in our own Milky Way and in other nearby galaxies, can be made
+through observations with the proposed Square Kilometre Array. Underpinning
+much of what we propose is an all-sky survey of Faraday rotation, in which we
+will accumulate tens of millions of rotation measure measurements toward
+background radio sources. This will provide a unique database for studying
+magnetic fields in individual Galactic supernova remnants and HII regions, for
+characterizing the overall magnetic geometry of our Galaxy's disk and halo, and
+for understanding the structure and evolution of magnetic fields in galaxies.
+Also of considerable interest will be the mapping of diffuse polarized emission
+from the Milky Way in many narrow bands over a wide frequency range. This will
+allow us to carry out Faraday tomography of the Galaxy, yielding a
+high-resolution three-dimensional picture of the magnetic field within a few
+kpc of the Sun, and allowing us to understand its coupling to the other
+components of the ISM. Finally, direct synchrotron imaging of a large number of
+nearby galaxies, combined with Faraday rotation data, will allow us to
+determine the magnetic field structure in these sources, and to test both the
+dynamo and primordial field theories for field origin and amplification.",0409368v2
+2010-03-05,Small magnetic loops connecting the quiet surface and the hot outer atmosphere of the Sun,"Sunspots are the most spectacular manifestation of solar magnetism, yet, 99%
+of the solar surface remains 'quiet' at any time of the solar cycle. The quiet
+sun is not void of magnetic fields, though; they are organized at smaller
+spatial scales and evolve relatively fast, which makes them difficult to
+detect. Thus, although extensive quiet Sun magnetism would be a natural driver
+to a uniform, steady heating of the outer solar atmosphere, it is not clear
+what the physical processes involved would be due to lack of observational
+evidence. We report the topology and dynamics of the magnetic field in very
+quiet regions of the Sun from spectropolarimetric observations of the Hinode
+satellite, showing a continuous injection of magnetic flux with a well
+organized topology of Omega-loop from below the solar surface into the upper
+layers. At first stages, when the loop travels across the photosphere, it has a
+flattened (staple-like) geometry and a mean velocity ascent of $\sim3$ km/s.
+When the loop crosses the minimum temperature region, the magnetic fields at
+the footpoints become almost vertical and the loop topology ressembles a
+potential field. The mean ascent velocity at chromospheric height is $\sim12$
+km/s. The energy input rate of these small-scale loops in the lower boundary of
+the chromosphere is (at least) of 1.4x10^6-2.2x10^7 erg cm-2 s-1. Our findings
+provide empirical evidence for solar magnetism as a multi-scale system, in
+which small-scale low-flux magnetism plays a crucial role, at least as
+important as active regions, coupling different layers of the solar atmosphere
+and being an important ingredient for chromospheric and coronal heating models.",1003.1255v1
+2010-07-12,Simple models for dynamic hysteresis loops calculation: Application to hyperthermia optimization,"To optimize the heating properties of magnetic nanoparticles (MNPs) in
+magnetic hyperthermia applications, it is necessary to calculate the area of
+their hysteresis loops in an alternating magnetic field. The three types of
+theories suitable for describing the hysteresis loops of MNPs are presented and
+compared to numerical simulations: equilibrium functions, Stoner-Wohlfarth
+model based theories (SWMBTs) and linear response theory (LRT). Suitable
+formulas to calculate the hysteresis area of major cycles are deduced from
+SWMBTs and from numerical simulations; the domain of validity of the analytical
+formula is explicitly studied. In the case of minor cycles, the hysteresis area
+calculations are based on the LRT. A perfect agreement between LRT and
+numerical simulations of hysteresis loops is obtained. The domain of validity
+of the LRT is explicitly studied. Formulas to calculate the hysteresis area at
+low field valid for any anisotropy of the MNP are proposed. Numerical
+simulations of the magnetic field dependence of the area show it follows
+power-laws with a large range of exponents. Then, analytical expressions
+derived from LRT and SWMBTs are used for a theoretical study of magnetic
+hyperthermia. It is shown that LRT is only pertinent for MNPs with strong
+anisotropy and that SWMBTs should be used for weak anisotropy MNPs. The optimum
+volume of MNPs for magnetic hyperthermia as function of material and
+experimental parameters is derived. The maximum specific absorption rate (SAR)
+achievable is calculated versus the MNP anisotropy. It is shown that an optimum
+anisotropy increases the SAR and reduces the detrimental effects of size
+distribution. The optimum anisotropy is simple to calculate and depends on the
+magnetic field used in the hyperthermia experiments and on the MNP
+magnetization only. The theoretical optimum parameters are compared to the one
+of several magnetic materials.",1007.2009v2
+2011-08-03,Dynamical evolution of a magnetic cloud from the Sun to 5.4 AU,"Magnetic Clouds (MCs) are a particular subset of Interplanetary Coronal Mass
+Ejections (ICMEs), forming large scale magnetic flux ropes. In this work we
+analyze the evolution of a particular MC (observed on March 1998) using {\it in
+situ} observations made by two spacecraft approximately aligned with the Sun,
+the first one at 1 AU from the Sun and the second one at 5.4 AU. We study the
+MC expansion, its consequent decrease of magnetic field intensity and mass
+density, and the possible evolution of the so-called global ideal-MHD
+nvariants. We describe the magnetic configuration of the MC at both spacecraft
+using different models and compute relevant global quantities (magnetic fluxes,
+helicity and energy) at both helio-distances. We also track back this structure
+to the Sun, in order to find out its solar source. We find that the flux rope
+is significantly distorted at 5.4 AU. However, we are able to analyze the data
+before the flux rope center is over-passed and compare it with observations at
+1 AU. From the observed decay of magnetic field and mass density, we quantify
+how anisotropic is the expansion, and the consequent deformation of the flux
+rope in favor of a cross section with an aspect ratio at 5.4 AU of $\approx
+1.6$ (larger in the direction perpendicular to the radial direction from the
+Sun). We quantify the ideal-MHD invariants and magnetic energy at both
+locations, and find that invariants are almost conserved, while the magnetic
+energy decays as expected with the expansion rate found. The use of MHD
+invariants to link structures at the Sun and the interplanetary medium is
+supported by the results of this multispacecraft study. We also conclude that
+the local dimensionless expansion rate, that is computed from the velocity
+profile observed by a single spacecraft, is very accurate for predicting the
+evolution of flux ropes in the solar wind.",1108.0951v1
+2011-08-30,Morphology and magnetism of multifunctional nanostructured $γ$-Fe$_2$O$_3$ films: Simulation and experiments,"This paper introduces a new approach for simulating magnetic properties of
+nanocomposites comprising magnetic particles embedded in a non-magnetic matrix,
+taking into account the 3D structure of the system in which particles'
+positions correctly mimic real samples. The proposed approach develops a
+multistage simulation procedure in which the size and distribution of particles
+within the hosting matrix is firstly attained by means of the Cell Dynamic
+System (CDS) model. The 3D structure provided by the CDS step is further
+employed in a Monte Carlo (MC) simulation of zero-field-cooled/field-cooled
+(ZFC/FC) and magnetic hysteresis loops ($M \times H$ curves) for the system.
+Simulations are aimed to draw a realistic picture of the as-produced ultra-thin
+films comprising maghemite nanoparticles dispersed in polyaniline. Comparison
+(ZFC/FC and $M \times H$ curves) between experiments and simulations regarding
+the maximum of the ZFC curve ($T_{\scriptsize MAX}$), remanence ($M_R/M_s$) and
+coercivity ($H_C$) revealed the great accuracy of the multistage approach
+proposed here while providing information about the system's morphology and
+magnetic properties. For a typical sample the value we found experimentally for
+$T_{\scriptsize MAX}$ (54 K) was very close to the value provided by the
+simulation (53 K). For the parameters depending on the nanoparticle clustering
+the experimental values were consistently lower ($M_R/M_s$ = 0.32 and $H_C$ =
+210 Oe) than the values we found in the simulation ($M_R/M_s$ = 0.53 and $H_C$
+= 274 Oe). Indeed, the approach introduced here is very promising for the
+design of real magnetic nanocomposite samples with optimized features.",1108.6099v2
+2012-01-12,A Magnetic Calibration of Photospheric Doppler Velocities,"The zero point of measured photospheric Doppler shifts is uncertain for at
+least two reasons: instrumental variations (from, e.g., thermal drifts), and
+the convective blueshift, a known correlation between intensity and upflows.
+Calibrated Doppler velocities would be useful for (i) improving estimates of
+the Poynting flux of magnetic energy across the photosphere, and (ii)
+constraining processes underlying flux cancellation, the mutual apparent loss
+of magnetic flux in closely spaced, opposite-polarity magnetogram features. We
+present a method to absolutely calibrate line-of-sight (LOS) velocities in
+solar active regions (ARs) near disk center using three successive vector
+magnetograms and one Dopplergram coincident with the central magnetogram. It
+exploits the fact that Doppler shifts measured along polarity inversion lines
+(PILs) of the LOS magnetic field determine one component of the velocity
+perpendicular to the magnetic field, and optimizes consistency between changes
+in LOS flux near PILs and the transport of transverse magnetic flux by LOS
+velocities, assuming ideal electric fields govern the magnetic evolution. We
+apply our method to vector magnetograms of AR 11158, observed by the
+Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory,
+and find clear evidence of offsets in the Doppler zero point, in the range of
+50 -- 550 m s$^{-1}$. In addition, we note that a simpler calibration can be
+determined from an LOS magnetogram and Dopplergram pair from the median Doppler
+velocity among all near-disk-center PIL pixels. We briefly discuss shortcomings
+in our initial implementation, and suggest ways to address these. In addition,
+as a step in our data reduction, we discuss use of temporal continuity in the
+transverse magnetic field direction to correct apparently spurious fluctuations
+in resolution of the 180$^\circ$ ambiguity.",1201.2451v4
+2014-07-15,Magnetic Fields and Massive Star Formation,"Massive stars ($M > 8$ \msun) typically form in parsec-scale molecular clumps
+that collapse and fragment, leading to the birth of a cluster of stellar
+objects. We investigate the role of magnetic fields in this process through
+dust polarization at 870 $\mu$m obtained with the Submillimeter Array (SMA).
+The SMA observations reveal polarization at scales of $\lsim$ 0.1 pc. The
+polarization pattern in these objects ranges from ordered hour-glass
+configurations to more chaotic distributions. By comparing the SMA data with
+the single dish data at parsec scales, we found that magnetic fields at dense
+core scales are either aligned within $40^\circ$ of or perpendicular to the
+parsec-scale magnetic fields. This finding indicates that magnetic fields play
+an important role during the collapse and fragmentation of massive molecular
+clumps and the formation of dense cores. We further compare magnetic fields in
+dense cores with the major axis of molecular outflows. Despite a limited number
+of outflows, we found that the outflow axis appears to be randomly oriented
+with respect to the magnetic field in the core. This result suggests that at
+the scale of accretion disks ($\lsim 10^3$ AU), angular momentum and dynamic
+interactions possibly due to close binary or multiple systems dominate over
+magnetic fields. With this unprecedentedly large sample massive clumps, we
+argue on a statistical basis that magnetic fields play an important role during
+the formation of dense cores at spatial scale of 0.01 - 0.1 pc in the context
+of massive star and cluster star formation.",1407.3984v1
+2015-01-28,Spin and Magnetism of White Dwarfs,"The magnetism and rotation of white dwarf (WD) stars are investigated in
+relation to a hydromagnetic dynamo operating in the progenitor during shell
+burning phases. The downward pumping of angular momentum in the convective
+envelope, in combination with the absorption of a planet or tidal spin-up from
+a binary companion, can trigger strong dynamo action near the core-envelope
+boundary. Several arguments point to the outer core as the source for a
+magnetic field in the WD remnant: the outer third of a $\sim 0.55\,M_\odot$ WD
+is processed during the shell burning phase(s) of the progenitor; the escape of
+magnetic helicity through the envelope mediates the growth of (compensating)
+helicity in the core, as is needed to maintain a stable magnetic field in the
+remnant; and the intense radiation flux at the core boundary facilitates
+magnetic buoyancy within a relatively thick tachocline layer. The helicity flux
+into the growing core is driven by a dynamical imbalance with a
+latitude-dependent rotational stress. The magnetic field deposited in an
+isolated massive WD is concentrated in an outer shell of mass $\lesssim
+0.1\,M_\odot$ and can reach $\sim 10\,$MG. A buried toroidal field experiences
+moderate ohmic decay above an age $\sim 0.3$ Gyr, which may lead to growth or
+decay of the external magnetic field. The final WD spin period is related to a
+critical spin rate below which magnetic activity shuts off, and core and
+envelope decouple; it generally sits in the range of hours to days. WD periods
+ranging up to a year are possible if the envelope re-expands following a late
+thermal pulse.",1501.07197v3
+2015-02-20,Magnetic properties of (Fe$_{1-x}$Co$_x$)$_2$B alloys and the effect of doping by 5$d$ elements,"We have explored, computationally and experimentally, the magnetic properties
+of \fecob{} alloys. Calculations provide a good agreement with experiment in
+terms of the saturation magnetization and the magnetocrystalline anisotropy
+energy with some difficulty in describing Co$_2$B, for which it is found that
+both full potential effects and electron correlations treated within dynamical
+mean field theory are of importance for a correct description. The material
+exhibits a uniaxial magnetic anisotropy for a range of cobalt concentrations
+between $x=0.1$ and $x=0.5$. A simple model for the temperature dependence of
+magnetic anisotropy suggests that the complicated non-monotonous temperature
+behaviour is mainly due to variations in the band structure as the exchange
+splitting is reduced by temperature. Using density functional theory based
+calculations we have explored the effect of substitutional doping the
+transition metal sublattice by the whole range of 5$d$ transition metals and
+found that doping by Re or W elements should significantly enhance the
+magnetocrystalline anisotropy energy. Experimentally, W doping did not succeed
+in enhancing the magnetic anisotropy due to formation of other phases. On the
+other hand, doping by Ir and Re was successful and resulted in magnetic
+anisotropies that are in agreement with theoretical predictions. In particular,
+doping by 2.5~at.\% of Re on the Fe/Co site shows a magnetocrystalline
+anisotropy energy which is increased by 50\% compared to its parent
+(Fe$_{0.7}$Co$_{0.3}$)$_2$B compound, making this system interesting, for
+example, in the context of permanent magnet replacement materials or in other
+areas where a large magnetic anisotropy is of importance.",1502.05916v3
+2015-04-20,The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona,"Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation
+modules are implemented at the Joint Science Operation Center (JSOC) of Solar
+Dynamics Observatory (SDO). The modules regularly produce three-dimensional
+data of the time-relaxed minimum-energy state of the solar corona using global
+solar-surface magnetic-field maps created from Helioseismic Magnetic Imager
+(HMI) full-disk magnetogram data. With the assumption of polytropic gas with
+specific heat ratio of 1.05, three types of simulation products are currently
+generated: i) simulation data with medium spatial resolution using the
+definitive calibrated synoptic map of the magnetic field with a cadence of one
+Carrington rotation, ii) data with low spatial resolution using the definitive
+version of the synchronic frame format of the magnetic field, with a cadence of
+one day, and iii) low-resolution data using near-real-time (NRT) synchronic
+format of the magnetic field on daily basis. The MHD data available in the JSOC
+database are three-dimensional, covering heliocentric distances from 1.025 to
+4.975 solar radii, and contain all eight MHD variables: the plasma density,
+temperature and three components of motion velocity, and three components of
+the magnetic field. This article describes details of the MHD simulations as
+well as the production of the input magnetic-field maps, and details of the
+products available at the JSOC database interface. In order to assess the
+merits and limits of the model, we show the simulated data in early 2011 and
+compare with the actual coronal features observed by the Atmospheric Imaging
+Assembly (AIA) and the near-Earth in-situ data.",1504.05217v1
+2015-08-05,North-South asymmetry in the magnetic deflection of polar coronal hole jets,"Measurements of the magnetic field in the interplanetary medium, of the
+sunspots area, and of the heliospheric current sheet position, reveal a
+possible North-South asymmetry in the magnetic field of the Sun. We study the
+North-South asymmetry as inferred from measurements of the deflection of polar
+coronal hole jets when they propagate throughout the corona. Since the corona
+is an environment where the magnetic pressure is greater than the kinetic
+pressure, we can assume that magnetic field controls the dynamics of plasma. On
+average, jets during their propagation follow the magnetic field lines,
+highlighting its local direction. The average jet deflection is studied both in
+the plane perpendicular to the line of sight, and, for a reduced number of
+jets, in three dimensional space. The observed jet deflection is studied in
+terms of an axisymmetric magnetic field model comprising dipole We measured the
+position angles at 1 rs and at 2 rs of the 79 jets from the catalogue of
+Nistico et al 2009., based on the STEREO ultraviolet and white-light
+coronagraph observations during the solar minimum period March 2007-April 2008.
+We found that the propagation is not radial, in agreement with the deflection
+due to magnetic field lines. Moreover, the amount of the deflection is
+different between jets over the north and those from the south pole. Comparison
+of jet deflections and field line tracing shows that a ratio g2/g1 ~ -0.5 for
+the quadrupole and a ratio g3/g1 ~ 1.6-2.0 for the esapole can describe the
+field. The presence of a non-negligible quadrupole moment. We find that the
+magnetic deflection of jets is larger in the North than in the South of the
+order of 25-40%, with an asymmetry which is consistent with a southward
+deflection of the heliospheric current sheet of the order of 10 deg, consistent
+with that inferred from other, independent, datasets and instruments.",1508.01072v1
+2016-08-05,Upper Chromospheric Magnetic Field of a Sunspot Penumbra: Observations of Fine Structure,"The fine-structure of magnetic field of a sunspot penumbra in the upper
+chromosphere is to be explored and compared to that in the photosphere. High
+spatial resolution spectropolarimetric observations were recorded with the
+1.5-meter GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The
+observed spectral domain includes the upper chromospheric He I triplet at
+1083.0 nm and the photospheric Si I 1082.7 nm and Ca I 1083.3 nm spectral
+lines. The upper chromospheric magnetic field is obtained by inverting the He I
+triplet assuming a Milne-Eddington type model atmosphere. A height dependent
+inversion was applied to the Si I 1082.7 nm and Ca I 1083.3 nm lines to obtain
+the photospheric magnetic field. We find that the inclination of the magnetic
+field shows variations in the azimuthal direction both in the photosphere, but
+also in the upper chromosphere. The chromospheric variations remarkably well
+coincide with the variations in the inclination of the photospheric field and
+resemble the well-known spine and inter-spine structure in the photospheric
+layers of penumbrae. The typical peak-to-peak variations in the inclination of
+the magnetic field in the upper chromosphere is found to be 10-15 degree, i.e.,
+roughly half the variation in the photosphere. In contrast, the magnetic field
+strength of the observed penumbra does not show variations on small spatial
+scales in the upper chromosphere. Thanks to the high spatial resolution
+observations possible with the GREGOR telescope at 1.08 microns, we find that
+the prominent small-scale fluctuations in the magnetic field inclination, which
+are a salient part of the property of sunspot penumbral photospheres, also
+persist in the chromosphere, although at somewhat reduced amplitudes. Such a
+complex magnetic configuration may facilitate penumbral chromospheric dynamic
+phenomena, such as penumbral micro-jets or transient bright dots.",1608.01988v1
+2016-09-27,Report on imaging of individual skyrmions of MML systems made by different techniques,"Deliverable 1.1 is a report on imaging of individual skyrmions of MML systems
+made by different techniques. This deliverable falls within work package 1
+(WP1:Static equilibrium properties of interface induced skyrmions in magnetic
+films and multilayers) of the MAGicSky research proposal whose objectives are:
+the growth of magnetic multilayer systems with large interfacial chiral
+interaction, the determination of the amplitude of the Dzyaloshinskii--Moriya
+interactions (DMi), the detailed structural and magnetic characterization of
+interfaces, the magnetic imaging of individual skyrmions and the thermal
+stability and interaction of skyrmions with intrinsic and/or artificial
+defects. It should be emphasized that imaging magnetic skyrmionic structures
+forms the basis for all the planned subsequent material optimization,
+electrical transport experiments and devices preparation in the MAGicSky
+research program. In particular, imaging is paramount as a technique since it
+enables us to unequivocally demonstrate chiral magnetic skyrmions by directly
+imaging i) the effects of engineering multilayer samples with large DMis and
+ii) the skyrmionic structure and properties. In order to get complementary
+physical insight on the properties of magnetic skyrmions and to corroborate our
+research results, we utilise a plethora of key state-of-the-art advanced
+magnetic imaging techniques, namely: i) Spin-polarised Scanning Tunnelling
+Microscopy (SP-STM), Scanning Transmission X-ray Microscopy (STXM) Lorentz
+Transmission Electron Microscopy (Lorentz TEM) as well as, Magnetic Force
+Microscopy (MFM). These imaging experiments can therefore stand as the base for
+all the other objectives in WP1 as well as WP2 that will study Dynamic
+properties: nucleation, propagation and detection of skyrmions. Imaging has
+been aimed to test and get feedback from the theoretical and numerical
+investigations of skyrmion systems of WP3. Finally, for WP4: Towards skyrmion
+based devices for information storage and processing, some of the techniques
+detailed here in D1.1 will enable us to image and test the first devices and
+their functionality. In short, the MAGicSky consortium research results in D1.1
+constitute a major milestone that acts as a stepping-stone to every other
+experimental effort and we have achieved it. The results relevant to the D1.1
+deliverable were presented in 5 publications and several invited talks at
+international workshop and conferences:",1609.08415v1
+2016-11-15,Three-dimensional structure of a sunspot light bridge,"Active regions are the most prominent manifestations of solar magnetic
+fields; their generation and dissipation are fundamental problems in solar
+physics. Light bridges are commonly present during sunspot decay, but a
+comprehensive picture of their role in the removal of photospheric magnetic
+field is still missing. We study the three dimensional configuration of a
+sunspot and in particular its light bridge during one of the last stages of its
+decay. We present the magnetic and thermodynamical stratification inferred from
+full Stokes inversions of the photospheric Si I 10827 \AA\ and Ca I 10839 \AA\
+lines obtained with the GREGOR Infrared Spectrograph of the GREGOR telescope at
+Observatorio del Teide, Tenerife, Spain. The analysis is complemented by a
+study of continuum images covering the disk passage of the active region, which
+are provided by the Helioseismic and Magnetic Imager on board the Solar
+Dynamics Observatory. The sunspot shows a light bridge with penumbral continuum
+intensity that separates the central umbra from a smaller umbra. We find that
+in this region the magnetic field lines form a canopy with lower magnetic field
+strength in the inner part. The photospheric light bridge is dominated by gas
+pressure (high-$\beta$), as opposed to the surrounding umbra where the magnetic
+pressure is higher. A convective flow is observed in the light bridge. This
+flow is able to bend the magnetic field lines and to produce field reversals.
+The field lines close above the light bridge and become as vertical and strong
+as in the surrounding umbra. We conclude that it develops because of two highly
+magnetized regions which come closer during the sunspot evolution.",1611.04803v1
+2017-03-02,On flare-CME characteristics from Sun to Earth combining remote-sensing image data with in-situ measurements supported by modeling,"We analyze the well observed flare-CME event from October 1, 2011
+(SOL2011-10-01T09:18) covering the complete chain of action - from Sun to Earth
+- for a better understanding of the dynamic evolution of the CME and its
+embedded magnetic field. We study the solar surface and atmosphere associated
+with the flare-CME from SDO and ground-based instruments, and also track the
+CME signature off-limb from combined EUV and white-light data with STEREO. By
+applying 3D reconstruction techniques (GCS, total mass) to stereoscopic
+STEREO-SoHO coronagraph data, we track the temporal and spatial evolution of
+the CME in interplanetary space and derive its geometry and 3D-mass. We combine
+the GCS and Lundquist model results to derive the axial flux and helicity of
+the MC from in-situ measurements (Wind). This is compared to nonlinear
+force-free (NLFF) model results as well as to the reconnected magnetic flux
+derived from the flare ribbons (flare reconnection flux) and the magnetic flux
+encompassed by the associated dimming (dimming flux). We find that magnetic
+reconnection processes were already ongoing before the start of the impulsive
+flare phase, adding magnetic flux to the flux rope before its final eruption.
+The dimming flux increases by more than 25% after the end of the flare,
+indicating that magnetic flux is still added to the flux rope after eruption.
+Hence, the derived flare reconnection flux is most probably a lower limit for
+estimating the magnetic flux within the flux rope. We find that the magnetic
+helicity and axial magnetic flux are reduced in interplanetary space by ~50%
+and 75%, respectively, possibly indicating to an erosion process. A mass
+increase of 10% for the CME is observed over the distance range from ~4-20 Rs.
+The temporal evolution of the CME associated core dimming regions supports the
+scenario that fast outflows might supply additional mass to the rear part of
+the CME.",1703.00694v1
+2017-07-25,The Non-Linear Growth of the Magnetic Rayleigh-Taylor Instability,"This work examines the effect of the embedded magnetic field strength on the
+non-linear development of the magnetic Rayleigh-Taylor Instability (RTI) (with
+a field-aligned interface) in an ideal gas close to the incompressible limit in
+three dimensions. Numerical experiments are conducted in a domain sufficiently
+large so as to allow the predicted critical modes to develop in a physically
+realistic manner. The ratio between gravity, which drives the instability in
+this case (as well as in several of the corresponding observations), and
+magnetic field strength is taken up to a ratio which accurately reflects that
+of observed astrophysical plasma, in order to allow comparison between the
+results of the simulations and the observational data which served as
+inspiration for this work. This study finds reduced non-linear growth of the
+rising bubbles of the RTI for stronger magnetic fields, and that this is
+directly due to the change in magnetic field strength, rather than the indirect
+effect of altering characteristic length scales with respect to domain size. By
+examining the growth of the falling spikes, the growth rate appears to be
+enhanced for the strongest magnetic field strengths, suggesting that rather
+than affecting the development of the system as a whole, increased magnetic
+field strengths in fact introduce an asymmetry to the system. Further
+investigation of this effect also revealed that the greater this asymmetry, the
+less efficiently the gravitational energy is released. By better understanding
+the under-studied regime of such a major phenomenon in astrophysics, deeper
+explanations for observations may be sought, and this work illustrates that the
+strength of magnetic fields in astrophysical plasmas influences observed RTI in
+subtle and complex ways.",1707.07987v1
+2017-08-15,Comparing UV/EUV line parameters and magnetic field in a quiescent prominence with tornadoes,"Context. Understanding the close relationship between the plasma and the
+magnetic field is important to describe and explain the observed complex
+dynamics of solar prominences. Aims. We determine if a close relationship
+between plasma and magnetic field parameters measured in a well-observed solar
+prominence with high spatial resolution can be found. Methods. We select a
+prominence observed on 15 July 2014 from space (IRIS, Hinode, SDO) and from the
+ground (THEMIS). We perform a robust co-alignment of the data sets using a 2D
+cross-correlation technique. We derive the magnetic field parameters from
+spectropolarimetric measurements of the He I D3 line taken by THEMIS. Line
+ratios and line-of-sight velocities from the Mg II h and k lines observed by
+IRIS are compared with magnetic field strength, inclination and azimuth.
+Electron densities are calculated using Hinode/EIS Fe XII line ratios and also
+compared with THEMIS and IRIS data. Results. We find Mg II k/h ratios of around
+1.4 everywhere, similar to values found previously in prominences. We also find
+that the magnetic field is strongest (around 30 G) and predominantly horizontal
+in the tornado-like legs of the prominence. The k3 Doppler shift is found to be
+between +/- 10 km/s everywhere. Electron densities at a temperature of 1.5e6 K
+are found to be around 1e9 /cm3. No significant correlations are found between
+the magnetic field parameters, and any of the other plasma parameters inferred
+from EUV spectroscopy, which may be explained by the large differences in the
+temperatures of the lines used in this study. Conclusions. This is the first
+time that a detailed statistical study of plasma and magnetic field parameters
+has been carried out at high spatial resolution in a prominence. Our results
+provide important constraints on future models of the plasma and magnetic field
+in these structures.",1708.04606v1
+2018-05-29,Emergence of Weyl metals driven by doped magnetic impurities in spin-orbit coupled semiconductors,"Constructing an effective field theory in terms of doped magnetic impurities
+(described by an O(3) vector model with a random mass term), itinerant
+electrons of spin-orbit coupled semiconductors (given by a Dirac theory with a
+relatively large mass term), and effective interactions between doped magnetic
+ions and itinerant electrons (assumed by an effective Zeeman coupling term), we
+perform the perturbative renormalization group analysis in the one-loop level
+based on the dimensional regularization technique. As a result, we find that
+the mass renormalization in dynamics of itinerant electrons acquires negative
+feedback effects due to quantum fluctuations involved with the Zeeman coupling
+term, in contrast with that of the conventional problem of quantum
+electrodynamics, where such interaction effects enhance the fermion mass more
+rapidly. Recalling that the applied magnetic field decreases the band gap in
+the presence of spin-orbit coupling, this renormalization group analysis shows
+that the external magnetic field overcomes the renormalized band gap, allowed
+by doped magnetic impurities even without ferromagnetic ordering. In other
+words, the Weyl metal physics can be controlled by doping magnetic impurities
+into spin-orbit coupled semiconductors, even if the external magnetic field
+alone cannot realize the Weyl metal phase due to relatively large band gaps of
+semiconductors. Furthermore, we emphasize that quasiparticles do not exist in
+this emergent disordered Weyl metal phase due to correlations with strong
+magnetic fluctuations. This non-Fermi liquid type Weyl metal state may be
+regarded to be a novel metallic phase in the respect that a topologically
+nontrivial band structure appears in the vicinity of quantum criticality.",1805.11209v3
+2018-09-27,Electrodynamics of double neutron star mergers,"We consider electromagnetic interaction and precursor emission of merging
+neutron stars. Orbital motion of the magnetized neutron stars may revive pair
+production within the common magnetosphere years before the merger, igniting
+pulsar-like magnetospheric dynamics. We identify two basic scenarios: (i) only
+one star is magnetized (1M-DNS scenario) and (ii) both stars are magnetized
+(2M-DNS scenario). Inductively created electric fields can have component along
+the total magnetic field (gaps) and/or the electric field may exceed the value
+of the local magnetic field. The key to the detection is orbital modulation of
+the emission. If only one star is magnetized (1M-DNS scenario) the emission is
+likely to be produced along the direction of the magnetic field at the location
+of the secondary; then, if the magnetic axis is misaligned with the orbital
+spin, this direction is modulated on the orbital period. For the 2M-DNS
+scenario, the structure of the common magnetosphere of the non-rotating neutron
+stars is complicated, with gaps, but no $E>B$ regions; there is strong orbital
+variations for the case of misaligned magnetic moments. For the same parameters
+of neutron stars the 2M-DNS scenario has intrinsically higher potential than
+the 1M-DNS one. The overall powers are not very high, $\leq 10^{45} $ erg
+s$^{-1}$; the best chance to detect electromagnetic precursors to the merging
+neutron stars is if the interaction of their magnetospheres leads to the
+production of pulsar-like coherent radio emission modulated at the orbital
+period, with luminosity of up to $\sim 1$ Jankys at the time the merger.",1809.10478v4
+2018-10-31,Magnetohydrodynamic Simulation of the X9.3 Flare on 2017 September 6: Evolving Magnetic Topology,"Three-dimensional magnetic topology is crucial to understanding the explosive
+release of magnetic energy in the corona during solar flares. Much attention
+has been given to the pre-flare magnetic topology to identify candidate sites
+of magnetic reconnection, yet it is unclear how the magnetic reconnection and
+its attendant topological changes shape the eruptive structure and how the
+topology evolves during the eruption. Here we employed a realistic,
+data-constrained magnetohydrodynamic simulation to study the evolving magnetic
+topology for an X9.3 eruptive flare that occurred on 2017 September 6. The
+simulation successfully reproduces the eruptive features and processes in
+unprecedented detail. The numerical results reveal that the pre-flare corona
+contains multiple twisted flux systems with different connections, and during
+the eruption, these twisted fluxes form a coherent flux rope through
+tether-cutting-like magnetic reconnection below the rope. Topological analysis
+shows that the rising flux rope is wrapped by a quasi-separatrix layer, which
+intersects itself below the rope, forming a topological structure known as
+hyperbolic flux tube, where a current sheet develops, triggering the
+reconnection. By mapping footpoints of the newly-reconnected field lines, we
+are able to reproduce both the spatial location and, for the first time, the
+temporal separation of the observed flare ribbons, as well as the dynamic
+boundary of the flux rope's feet. Futhermore, the temporal profile of the total
+reconnection flux is comparable to the soft X-ray light curve. Such a
+sophisticated characterization of the evolving magnetic topology provides
+important insight into the eventual understanding and forecast of solar
+eruptions.",1810.13095v1
+2018-11-08,Solar Sources of Interplanetary Magnetic Clouds Leading to Helicity Prediction,"This study identifies the solar origins of magnetic clouds that are observed
+at 1 AU and predicts the helical handedness of these clouds from the solar
+surface magnetic fields. We started with the magnetic clouds listed by the
+Magnetic Field Investigation (MFI) team supporting NASA's WIND spacecraft in
+what is known as the MFI table and worked backwards in time to identify solar
+events that produced these clouds. Our methods utilize magnetograms from the
+Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics
+Observatory (SDO) spacecraft so that we could only analyze MFI entries after
+the beginning of 2011. This start date and the end date of the MFI table gave
+us 37 cases to study. Of these we were able to associate only eight surface
+events with clouds detected by WIND at 1 AU. We developed a simple algorithm
+for predicting the cloud helicity which gave the correct handedness in all
+eight cases. The algorithm is based on the conceptual model that an ejected
+flux tube has two magnetic origination points at the positions of the strongest
+radial magnetic field regions of opposite polarity near the places where the
+ejected arches end at the solar surface. We were unable to find events for the
+remaining 29 cases: lack of a halo or partial halo CME in an appropriate time
+window, lack of magnetic and/or filament activity in the proper part of the
+solar disk, or the event was too far from disk center. The occurrence of a
+flare was not a requirement for making the identification but in fact flares,
+often weak, did occur for seven of the eight cases.",1811.03560v1
+2019-01-03,Turbulent viscosity and effective magnetic Prandtl number from simulations of isotropically forced turbulence,"(abridged) Context: Turbulent diffusion of large-scale flows and magnetic
+fields play major roles in many astrophysical systems. Aims: Our goal is to
+compute turbulent viscosity and magnetic diffusivity, relevant for diffusing
+large-scale flows and magnetic fields, respectively, and their ratio, the
+turbulent magnetic Prandtl number, ${\rm Pm}_{\rm t}$, for isotropically forced
+homogeneous turbulence. Methods: We use simulations of forced turbulence in
+fully periodic cubes composed of isothermal gas with an imposed large-scale
+sinusoidal shear flow. Turbulent viscosity is computed either from the
+resulting Reynolds stress or from the decay rate of the large-scale flow.
+Turbulent magnetic diffusivity is computed using the test-field method. The
+scale dependence of the coefficients is studied by varying the wavenumber of
+the imposed sinusoidal shear and test fields. Results: We find that turbulent
+viscosity and magnetic diffusivity are in general of the same order of
+magnitude. Furthermore, the turbulent viscosity depends on the fluid Reynolds
+number (${\rm Re}$) and scale separation ratio of turbulence. The scale
+dependence of the turbulent viscosity is found to be well approximated by a
+Lorentzian. The results for the turbulent transport coefficients appear to
+converge at sufficiently high values of ${\rm Re}$ and the scale separation
+ratio. However, a weak decreasing trend is found even at the largest values of
+${\rm Re}$. The turbulent magnetic Prandtl number converges to a value that is
+slightly below unity for large ${\rm Re}$ whereas for small ${\rm Re}$, we find
+values between 0.5 and 0.6. Conclusions: The turbulent magnetic diffusivity is
+in general consistently higher than the turbulent viscosity. The actual value
+of ${\rm Pm}_{\rm t}$ found from the simulations ($\approx0.9\ldots0.95$) at
+large ${\rm Re}$ and scale separation ratio is higher than any of the analytic
+predictions.",1901.00787v2
+2019-09-12,Spectral decimation of the magnetic Laplacian on the Sierpinski gasket: Solving the Hofstadter-Sierpinski butterfly,"The magnetic Laplacian (also called the line bundle Laplacian) on a connected
+weighted graph is a self-adjoint operator wherein the real-valued adjacency
+weights are replaced by unit complex-valued weights $\{\omega_{xy}\}_{xy\in
+E}$, satisfying the condition that $\omega_{xy}=\overline{\omega_{yx}}$ for
+every directed edge $xy$. When properly interpreted, these complex weights give
+rise to magnetic fluxes through cycles in the graph.
+  In this paper we establish the spectrum of the magnetic Laplacian, as a set
+of real numbers with multiplicities, on the Sierpinski gasket graph ($SG$)
+where the magnetic fluxes equal $\alpha$ through the upright triangles, and
+$\beta$ through the downright triangles. This is achieved upon showing the
+spectral self-similarity of the magnetic Laplacian via a 3-parameter map
+$\mathcal{U}$ involving non-rational functions, which takes into account
+$\alpha$, $\beta$, and the spectral parameter $\lambda$. In doing so we provide
+a quantitative answer to a question of Bellissard [Renormalization Group
+Analysis and Quasicrystals (1992)] on the relationship between the dynamical
+spectrum and the actual magnetic spectrum.
+  Our main theorems lead to two applications. In the case $\alpha=\beta$, we
+demonstrate the approximation of the magnetic spectrum by the filled Julia set
+of $\mathcal{U}$, the Sierpinski gasket counterpart to Hofstadter's butterfly.
+Meanwhile, in the case $\alpha,\beta\in \{0,\frac{1}{2}\}$, we can compute the
+determinant of the magnetic Laplacian determinant and the corresponding
+asymptotic complexity.",1909.05662v4
+2020-01-15,"Emergence of weak pyrochlore phase and signature of field induced spin ice ground state in Dy$_{2-x}$La$_{x}$Zr$_{2}$O$_{7}$; x = 0, 0.15, 0.3","The pyrochlore oxides Dy$_{2}$Ti$_{2}$O$_{7}$ and Ho$_{2}$Ti$_{2}$O$_{7}$ are
+well studied spin ice systems and have shown the evidences of magnetic monopole
+excitations. Unlike these, Dy$_{2}$Zr$_{2}$O$_{7}$ is reported to crystallize
+in a distorted fluorite structure. We present here the magnetic and heat
+capacity studies of La substituted Dy$_{2}$Zr$_{2}$O$_{7}$. Our findings
+suggest the absence of spin ice state in Dy$_{2}$Zr$_{2}$O$_{7}$ but the
+emergence of the magnetic field induced spin freezing near T $\approx$ 10 K in
+ac susceptibility measurements which is similar to Dy$_{2}$Ti$_{2}$O$_{7}$. The
+magnetic heat capacity of Dy$_{2}$Zr$_{2}$O$_{7}$ shows a shift in the peak
+position from 1.2 K in zero field to higher temperatures in the magnetic field,
+with the corresponding decrease in the magnetic entropy. The low temperature
+magnetic entropy at 5 kOe field is Rln2 - (1/2)Rln(3/2) which is same as for
+the spin ice state. Substitution of non-magnetic, isovalent La$^{3+}$ for
+Dy$^{3+}$ gradually induces the structural change from highly disordered
+fluorite to weakly ordered pyrochlore phase. The La$^{3+}$ substituted
+compounds with less distorted pyrochlore phase show the spin freezing at lower
+field which strengthens further on the application of magnetic field. Our
+results suggest that the spin ice state can be stabilized in
+Dy$_{2}$Zr$_{2}$O$_{7}$ either by slowing down of the spin dynamics or by
+strengthening the pyrochlore phase by suitable substitution in the system.",2001.05244v2
+2020-04-08,"Magnetic, thermal, and electronic-transport properties of EuMg2Bi2 single crystals","The trigonal compound EuMg2Bi2 has recently been discussed in terms of its
+topological band properties. These are intertwined with its magnetic
+properties. Here detailed studies of the magnetic, thermal, and electronic
+transport properties of EuMg2Bi2 single crystals are presented. The Eu{+2}
+spins-7/2 in EuMg2Bi2 exhibit an antiferromagnetic (AFM) transition at a
+temperature TN = 6.7 K, as previously reported. By analyzing the anisotropic
+magnetic susceptibility chi data below TN in terms of molecular-field theory
+(MFT), the AFM structure is inferred to be a c-axis helix, where the ordered
+moments in the hexagonal ab-plane layers are aligned ferromagnetically in the
+ab plane with a turn angle between the moments in adjacent moment planes along
+the c axis of about 120 deg. The magnetic heat capacity exhibits a lambda
+anomaly at TN with evidence of dynamic short-range magnetic fluctuations both
+above and below TN. The high-T limit of the magnetic entropy is close to the
+theoretical value for spins-7/2. The in-plane electrical resistivity rho(T)
+data indicate metallic character with a mild and disorder-sensitive upturn
+below Tmin = 23 K. An anomalous rapid drop in rho(T) on cooling below TN as
+found in zero field is replaced by a two-step decrease in magnetic fields. The
+rho(T) measurements also reveal an additional transition below TN in applied
+fields of unknown origin that is not observed in the other measurements and may
+be associated with an incommensurate to commensurate AFM transition. The
+dependence of TN on the c-axis magnetic field Hperp was derived from the
+field-dependent chi(T), Cp(T), and rho(T) measurements. This TN(Hperp) was
+found to be consistent with the prediction of MFT for a c-axis helix with S =
+7/2 and was used to generate a phase diagram in the Hperp-T plane.",2004.03753v2
+2020-05-21,ALMA reveals the coherence of the magnetic field geometry in OH 231.8+4.2,"In a continuing effort to investigate the role of magnetic fields in evolved
+low and intermediate mass stars (principally regarding the shaping of their
+envelopes), we present new ALMA high resolution polarization data obtained for
+the nebula OH 231.8+4.2. We found that the polarized emission likely arises
+from aligned grains in the presence of magnetic fields rather than radiative
+alignment and self scattering. The ALMA data show well organized electric field
+orientations in most of the nebula and the inferred magnetic field vectors
+(rotated by 90 degrees) trace an hourglass morphology centred on the central
+system of the nebula. One region in the southern part of OH 231.8+4.2 shows a
+less organized distribution probably due to the shocked environment. These
+findings, in conjunction with earlier investigations (maser studies and dust
+emission analysis at other scales and wavelengths) suggest an overall magnetic
+hourglass located inside a toroidal field. We propose the idea that the
+magnetic field structure is closely related to the architecture of a magnetic
+tower and that the outflows were therefore magnetically launched. While the
+current dynamical effect of the fields might be weak in the equatorial plane
+principally due to the evolution of the envelope, it would still be affecting
+the outflows. In that regard, the measurement of the magnetic field at the
+stellar surface, which is still missing, combined with a full MHD treatment are
+required to better understand and constrain the events occurring in OH
+231.8+4.2.",2005.10398v1
+2020-07-09,Magnetic resonance of collective paramagnets with gapped excitations spectrum,"Some magnets due to particular geometry of the exchange bonds do not undergo
+transition to the conventional magnetically ordered state despite of the
+presence of significant exchange couplings. Instead, a collective paramagnetic
+state is formed. The later state can remain stable down to $T=0$ if the ground
+state of this magnet turns out to be nonmagnetic singlet separated from the
+excited triplet states by an energy gap. Low-temperature spin dynamics of the
+collective paramagnets with gapped excitations spectrum (or spin-gap magnets)
+can be described in terms of a dilute gas of the triplet excitations. Applied
+magnetic field can suppress the energy gap, resulting in the formation of the
+gapless spin-liquid state or even leading to the unusual phenomenon of
+field-induced antiferromagnetic order. Introduction of defects in the
+crystallographic structure of the spin-gap magnet can result either in the
+formation of multi-spin paramagnetic center or in the formation of randomly
+distributed modified exchange bonds in the crystal. This review includes
+results of electron spin resonance (ESR) spectroscopy study of several
+representative quantum paramagnets with gapped excitations spectrum:
+quasy-two-dimensional magnet \phcc{}, quasy-one-dimensional magnets of
+""spin-tube"" type \sul{} and ""spin-ladder"" type \dimpy{}. We will demonstrate
+that ESR absorption spectra reveal common features of these systems: ESR
+spectroscopy allows to observe and characterize fine structure if the triplet
+energy levels, to identify many-particles relaxation processes in the gas of
+triplet excitations and to observe collective spin-wave oscillations in the
+field induced antiferromagnetically ordered state, as well as to observe some
+individual features of the studied systems.",2007.04885v1
+2020-08-21,Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets--I. A Systematic Study,"Blazars are relativistic magnetized plasma outflows from supermassive black
+holes that point very close to our line of sight. Their emission is nonthermal
+dominated and highly variable across the entire electromagnetic spectrum.
+Relativistic magnetic reconnection has been proposed as the driver of particle
+acceleration during blazar flares. While recent particle-in-cell simulations
+have self-consistently studied the evolution of magnetic reconnection and
+particle acceleration therein, the resulting radiation signatures have not been
+systematically explored. In particular, the polarization signatures, which
+directly reflect the characteristic strongly dynamical magnetic field evolution
+during reconnection, have not been carefully investigated. In this paper, we
+present a systematic study of radiation and polarization signatures arising
+from magnetic reconnection in blazars, based on combined PIC and polarized
+radiation transfer simulations with various physical parameters. We identify a
+harder-when-brighter trend in the spectral evolution. Moreover,
+higher-frequency bands tend to flare earlier than lower-frequency bands in the
+synchrotron spectral component. Most importantly, polarization signatures
+appear more variable with higher frequencies. We find that the temporal
+polarization variations strongly depends on the guide field strength.
+Specifically, reconnection with significant guide field component leads to very
+high polarization degree that contradict to typical blazar observations, while
+large polarization angle rotations are unique signatures of magnetic
+reconnection between nearly anti-parallel magnetic field lines. These rotations
+are at least $90^o$ and can extend to $>180^o$, and they may rotate in both
+directions. These results imply that blazars that have shown large polarization
+angle rotations intrinsically have more nearly anti-parallel magnetic field
+morphology.",2008.09444v1
+2020-08-30,Time Series Analysis of Photospheric Magnetic Parameters of Flare-quiet versus Flaring Active Regions: Scaling Properties of Fluctuations,"Time series of photospheric magnetic parameters of solar active regions (ARs)
+are used to answer whether scaling properties of fluctuations embedded in such
+time series help to distinguish between flare-quiet and flaring ARs. We examine
+a total of 118 flare-quiet and 118 flaring AR patches (called HARPs), which
+were observed from 2010 to 2016 by the Helioseismic and Magnetic Imager (HMI)
+on board the Solar Dynamics Observatory (SDO). Specifically, the scaling
+exponent of fluctuations is derived applying the Detrended Fluctuation Analysis
+(DFA) method to a dataset of 8-day time series of 18 photospheric magnetic
+parameters at 12-min cadence for all HARPs under investigation. We first find a
+statistically significant difference in the distribution of the scaling
+exponent between the flare-quiet and flaring HARPs, in particular for some
+space-averaged, signed parameters associated with magnetic field line twist,
+electric current density, and current helicity. The flaring HARPs tend to show
+higher values of the scaling exponent compared to those of the flare-quiet
+ones, even though there is considerable overlap between their distributions. In
+addition, for both the flare-quiet and flaring HARPs the DFA analysis indicates
+that (1) time series of most of various magnetic parameters under consideration
+are non-stationary, and (2) time series of the total unsigned magnetic flux and
+the mean photospheric magnetic free energy density in general present a
+non-stationary, persistent property, while the total unsigned flux near
+magnetic polarity inversion lines and parameters related to current density
+show a non-stationary, anti-persistent trend in their time series.",2008.13085v1
+2020-09-15,Experimental validation of a three-dimensional heat transfer model within the scala tympani with application to magnetic cochlear implant surgery,"Magnetic guidance of cochlear implants is a promising technique to reduce the
+risk of physical trauma during surgery. In this approach, a magnet attached to
+the tip of the implant electrode array is guided within the scala tympani using
+a magnetic field. After surgery, the magnet must be detached from the implant
+electrode array via localized heating and removed from the scala tympani which
+may cause thermal trauma. Objectives: The objective of this work is to
+experimentally validate a three-dimensional (3D) heat transfer model of the
+scala tympani which will enable accurate predictions of the maximum safe input
+power to avoid localized hyperthermia when detaching the magnet from the
+implant electrode array. Methods: Experiments are designed using a rigorous
+scale analysis and performed by measuring transient temperatures in a
+3D-printed scala tympani phantom subjected to a sudden change in its thermal
+environment and localized heating via a small heat source. Results: The
+measured and predicted temperatures are in good agreement with an error less
+than 6$\%$. Conclusions: The validated 3D heat transfer model of the scala
+tympani is finally applied to evaluate the maximum safe input power to avoid
+localized hyperthermia when detaching the magnet. For the most conservative
+case where all boundaries except the insertion opening are adiabatic, the power
+required to release the magnet attached to the implant electrode array by 1
+mm$^3$ of paraffin is approximately half of the predicted maximum safe input
+power. Significance: This work will enable the design of a thermally safe
+magnetic cochlear implant surgery procedure.",2009.07199v1
+2021-03-03,Long-Timescale Magnetization Ordering Induced by an Adsorbed Chiral Monolayer on Ferromagnets,"When an electron passes through a chiral molecule there is a high probability
+for a correlation between the momentum and spin of the charge, thus leading to
+spin polarized current. This phenomenon is known as the chiral induced spin
+selectivity (CISS) effect. One of the most surprising experimental results
+recently demonstrated is that magnetization reversal in a ferromagnet (FM) with
+perpendicular anisotropy can be realized solely by chemisorbing a chiral
+molecular monolayer without applying any current or external magnetic field.
+This result raises the currently open question of whether this effect is due to
+the bonding event, held by the ferromagnet, or a long timescale effect
+stabilized by exchange interactions. In this work we have performed vectorial
+magnetic field measurements of the magnetization reorientation of a
+ferromagnetic layer exhibiting perpendicular anisotropy due to CISS using
+nitrogen-vacancy centers in diamond, and followed the time dynamics of this
+effect. In parallel, we have measured the molecular monolayer tilt angle in
+order to find a correlation between the time dependence of the magnetization
+re-orientation and the change of the tilt angle of the molecular monolayer. We
+have identified that changes in the magnetization direction correspond to
+changes of the molecular monolayer tilt angle, providing evidence for a
+long-timescale characteristic of the induced magnetization reorientation. This
+suggests that the CISS effect has an effect over long-timescales which we
+attribute to exchange interactions. These results offer significant insights
+into the fundamental processes underlying the CISS effect, contributing to the
+implementation of CISS in state-of-the-art applications such as spintronic and
+magnetic memory devices.",2103.04772v1
+2021-03-12,The Alfvénic nature of chromospheric swirls,"We investigate the evolution and origin of small-scale chromospheric swirls
+by analyzing numerical simulations of the quiet solar atmosphere, using the
+radiative magnetohydrodynamic code CO$5$BOLD. We are interested in finding
+their relation with magnetic field perturbations and in the processes driving
+their evolution. For the analysis, the swirling strength criterion and its
+evolution equation are applied in order to identify vortical motions and to
+study their dynamics. We introduce a new criterion, the magnetic swirling
+strength, which allows us to recognize torsional perturbations in the magnetic
+field. We find a strong correlation between swirling strength and magnetic
+swirling strength, in particular in intense magnetic flux concentrations, which
+suggests a tight relation between vortical motions and torsional magnetic field
+perturbations. Furthermore, we find that swirls propagate upward with the local
+Alfv\'en speed as unidirectional swirls, in the form of pulses, driven by
+magnetic tension forces alone. In the photosphere and low chromosphere, the
+rotation of the plasma co-occurs with a twist in the upwardly directed magnetic
+field that is in the opposite direction of the plasma flow. All together, these
+are characteristics of torsional Alfv\'en waves. We also find indications of an
+imbalance between the hydrodynamic and magnetohydrodynamic baroclinic effects
+being at the origin of the swirls. At the base of the chromosphere, we find a
+net upwardly directed Poynting flux, which is mostly associated with large and
+complex swirling structures that we interpret as the superposition of various
+small-scale vortices. We conclude that the ubiquitous swirling events observed
+in simulations are tightly correlated with perturbations of the magnetic field.
+At photospheric and chromospheric levels, they form Alfv\'en pulses that
+propagate upward and may contribute to chromospheric heating.",2103.07366v1
+2021-04-15,MHD Modeling of Solar Coronal Magnetic Evolution Driven by Photospheric Flow,"It is well known that magnetic fields dominate the dynamics in the solar
+corona, and new generation of numerical modelling of the evolution of coronal
+magnetic fields, as featured with boundary conditions driven directly by
+observation data, are being developed. This paper describes a new approach of
+data-driven magnetohydrodynamic (MHD) simulation of solar active region (AR)
+magnetic field evolution, which is for the first time that a data-driven
+full-MHD model utilizes directly the photospheric velocity field from DAVE4VM.
+We constructed a well-established MHD equilibrium based on a single vector
+magnetogram by employing an MHD-relaxation approach with sufficiently small
+kinetic viscosity, and used this MHD equilibrium as the initial conditions for
+subsequent data-driven evolution. Then we derived the photospheric surface
+flows from a time series of observed magentograms based on the DAVE4VM method.
+The surface flows are finally inputted in time sequence to the bottom boundary
+of the MHD model to self-consistently update the magnetic field at every time
+step by solving directly the magnetic induction equation at the bottom
+boundary. We applied this data-driven model to study the magnetic field
+evolution of AR 12158 with SDO/HMI vector magnetograms. Our model reproduced a
+quasi-static stress of the field lines through mainly the rotational flow of
+the AR's leading sunspot, which makes the core field lines to form a coherent S
+shape consistent with the sigmoid structure as seen in the SDO/AIA images. The
+total magnetic energy obtained in the simulation matches closely the
+accumulated magnetic energy as calculated directly from the original vector
+magnetogram with the DAVE4VM derived flow field. Such a data-driven model will
+be used to study how the coronal field, as driven by the slow photospheric
+motions, reaches a unstable state and runs into eruptions.",2104.07229v1
+2021-06-05,Naked emergence of an anti-Hale active region I. Overall evolution and magnetic properties,"{In order to understand the emergence of the active region, we investigate
+the emerging process and magnetic properties of a naked anti-Hale active region
+during the period between August 24 to 25, 2018.}
+  {Using the data from Helioseismic and Magnetic Imager on board the Soar
+Dynamic Observatory and the New Vacuum Solar Telescope, we calculated different
+evolving parameters (such as pole separation, tilt angle) and magnetic
+parameters (such as vertical electric current, force-free parameter, relative
+magnetic helicity) during the emergence of the active region. With these
+calculated parameters and some reasonable assumptions, we use two different
+methods to estimate the twist of the active region.}
+  {The magnetic flux and pole separation continue increasing while the tilt
+angle exhibits a decreasing pattern during the emergence of the active region.
+The increase of the pole separation is mainly contributed as a result of the
+enhancement in the longitude direction. A power-law relationship between pole
+separation and total flux is found during the emergence of the active region.
+On the other hand, it is found that both the positive and negative electric
+currents increased equivalently and the average flux-weighted force-free
+parameter $\tilde \alpha$ remains almost consistently positive, on the order of
+$\sim$ 10$^{-8}$ m$^{-1}$. The relative magnetic helicity is mainly contributed
+by the shear term, while the relative magnetic helicity injection flux of the
+shear term changes its sign at the latter stage of the emergence. The twist
+number of the whole active region remains on the order of 10$^{-1}$ turns
+during the emergence of the active region.}
+  {We find that the magnetic flux tube with low twist also could emerge into
+the solar atmosphere.}",2106.02786v1
+2022-01-18,Using small-angle scattering to guide functional magnetic nanoparticle design,"Magnetic nanoparticles offer unique potential for various technological,
+biomedical, or environmental applications thanks to the size-, shape- and
+material-dependent tunability of their magnetic properties. To optimize
+particles for a specific application, it is crucial to interrelate their
+performance with their structural and magnetic properties. This review presents
+the advantages of small-angle X-ray and neutron scattering techniques for
+achieving a detailed multiscale characterization of magnetic nanoparticles and
+their ensembles in a mesoscopic size range from 1 to a few hundred nanometers
+with nanometer resolution. Both X-rays and neutrons allow the ensemble-averaged
+determination of structural properties, such as particle morphology or particle
+arrangement in multilayers and 3D assemblies. Additionally, the magnetic
+scattering contributions enable retrieving the internal magnetization profile
+of the nanoparticles as well as the inter-particle moment correlations caused
+by interactions within dense assemblies. Most measurements are used to
+determine the time-averaged ensemble properties, in addition advanced
+small-angle scattering techniques exist that allow accessing particle and spin
+dynamics on various timescales. In this review, we focus on conventional
+small-angle X-ray and neutron scattering (SAXS and SANS), X-ray and neutron
+reflectometry, gracing-incidence SAXS and SANS, X-ray resonant magnetic
+scattering, and neutron spin-echo spectroscopy techniques. For each technique,
+we provide a general overview, present the latest scientific results, and
+discuss its strengths as well as sample requirements. Finally, we give our
+perspectives on how future small-angle scattering experiments, especially in
+combination with micromagnetic simulations, could help to optimize the
+performance of magnetic nanoparticles for specific applications.",2201.06905v1
+2022-04-26,Evidence of Ferromagnetic Clusters and Griffiths Singularity in Magnetic Weyl Semimetal Co$ _{3} $Sn$ _{2} $S$ _{2} $,"Cobalt based sulphides of compositional formula Co$ _{3} $A$ _{2} $S$ _{2} $
+(A = Sn and In) are endowed with frustrated kagome lattice structure and a
+plethora of novel phenomena determined from the topological band structure.
+Here-in, we report on the detailed exploration of anisotropic magnetic
+properties of single crystals of ferromagnetic compound Co$ _{3} $Sn$ _{2} $S$
+_{2} $ under magnetic field $H$ applied along the c-axis $(H\parallel c)$ and
+the ab-plane $(H\parallel ab)$. A low temperature clustered-glassy magnetic
+behaviour is revealed in field-cooled and zero field-cooled magnetization and
+memory effect measurement protocols. The sharp downturn and non-linearity
+observed in the inverse susceptibility above the critical temperature $T
+_{\text{C}} $ in the paramagnetic region corroborates to the presence of
+short-range ferromagnetic clusters above $ T _{\text{C}} $ in Co$ _{3} $Sn$
+_{2} $S$ _{2} $. The deviation from linear Curie-Weiss behaviour in the
+paramagnetic state signifies the strong Griffiths singularity in the material.
+The slow spin dynamics behaviour and zero spontaneous magnetization above $ T
+_{\text{C}} $ give an evidence of Griffiths phase owing to the ferromagnetic
+clusters. The Arrott plots derived from magnetization reveal convex type
+curvature at low fields and linear positive behavior in the high field region,
+confirming the second order magnetic phase transition in Co$ _{3} $Sn$ _{2} $S$
+_{2} $. The Takahashi spin fluctuation theory analysis provides sufficient
+evidence for itinerant ferromagnetism in Co$ _{3} $Sn$ _{2} $S$ _{2} $. A large
+magneto-crystalline anisotropy concomitant with a high anisotropy field
+suggests the dominance of strong spin orbit coupling phenomenon. Our
+experimental results emphasize an intuitive understanding of the complex nature
+of magnetism present in Co-based shandite systems.",2204.12252v1
+2022-07-08,The Role of Magnetic Fields in the Formation of the Filamentary Infrared Dark Cloud G11.11-0.12,"We report on the near-infrared polarimetric observations of G11.11-0.12
+(hereafter G11) obtained with SIRPOL on the 1.4 m IRSF telescope. The starlight
+polarisation of the background stars reveals the on-sky component of magnetic
+fields in G11, and these are consistent with the field orientation observed
+from polarised dust emission at $850\,\mu$m. The magnetic fields in G11 are
+perpendicular to the filament, and are independent of the filament's
+orientation relative to the Galactic plane. The field strength in the envelope
+of G11 is in the range $50-100\,\mu$G, derived from two methods. The analyses
+of the magnetic fields and gas velocity dispersion indicate that the envelope
+of G11 is supersonic but sub-Alfv{\'e}nic. The critical mass-to-flux ratio in
+the envelope of G11 is close to 1 and increases to $\gtrsim 1$ on the spine of
+G11. The relative weights on the importance of magnetic fields, turbulence and
+gravity indicate that gravity dominates the dynamical state of G11, but with
+significant contribution from magnetic fields. The field strength,
+$|\mathbf{B}|$, increases slower than the gas density, $n$, from the envelope
+to the spine of G11, characterized by $|\mathbf{B}|\propto n^{0.3}$. The
+observed strength and orientation of magnetic fields in G11 imply that
+supersonic and sub-Alfv{\'e}nic gas flow is channelled by the strong magnetic
+fields and is assembled into filaments perpendicular to the magnetic fields.
+The formation of low-mass stars is enhanced in the filaments with high column
+density, in agreement with the excess of low-mass protostars detected in the
+densest regions of G11.",2207.03695v3
+2022-10-26,Magnetic field extrapolation in active region well comparable with observations in multiple layers,"Magnetic field extrapolation is a fundamental tool to reconstruct the
+three-dimensional magnetic field above the solar photosphere. However, the
+prevalently used force-free field model might not be applicable in the lower
+atmosphere with non-negligible plasma \b{eta}, where the crucial process of
+flux rope formation and evolution could happen. In this work, we perform
+extrapolation in active region (AR) 12158, based on an recently developed
+magnetohydrostatic (MHS) method which takes plasma forces into account. By
+comparing the results with those from the force-free field extrapolation
+methods, we find that the overall properties, which are characterized by the
+magnetic free energy and helicity, are roughly the same. The major differences
+lie in the magnetic configuration and the twist number of magnetic flux rope
+(MFR). Unlike previous works either obtained sheared arcades or one coherent
+flux rope, the MHS method derives two sets of MFR, which are highly twisted and
+slightly coupled. Specifically, the result in the present work is more
+comparable with the high-resolution observations from the chromosphere, through
+the transition region to the corona, such as the filament fibrils, pre-eruptive
+braiding characteristics and the eruptive double-J shaped hot channel. Overall,
+our work shows that the newly developed MHS method is more promising to
+reproduce the magnetic fine structures that can well match the observations at
+multiple layers, and future data-driven simulation based on such extrapolation
+will benefit in understanding the critical and precise dynamics of flux rope
+before eruption.",2210.15074v3
+2022-11-19,Nonlinear evolution of magnetorotational instability in a magnetized Taylor-Couette flow: scaling properties and relation to upcoming DRESDYN-MRI experiment,"Magnetorotational instability (MRI) is the most likely mechanism driving
+angular momentum transport in astrophysical disks. However, despite many
+efforts, a conclusive experimental evidence of MRI is still missing. Recently,
+performing 1D linear analysis of the standard MRI (SMRI) in a cylindrical
+Taylor-Couette (TC) flow with an axial magnetic field, we showed that SMRI can
+be detected in the upcoming DRESDYN-MRI experiment based on a magnetized TC
+flow of liquid sodium. In this study, also related to DRESDYN-MRI experiments,
+we focused on the nonlinear evolution and saturation properties of SMRI and
+analyzed its scaling behavior with respect to the main parameters of the TC
+flow. We did a detailed analysis over the extensive ranges of magnetic Reynolds
+number $Rm\in [8.5, 37.1]$, Lundquist number $Lu\in[1.5, 15.5]$ and Reynolds
+number, $Re\in[10^3, 10^5]$. We considered small magnetic Prandtl numbers, $Pm
+\ll 1$, down to $Pm\sim 10^{-4}$, aiming at values typical of liquid sodium in
+the experiments. In the saturated state, the magnetic energy of SMRI and torque
+due to perturbations on the cylinders, which characterizes angular momentum
+transport, both increase with $Rm$ for fixed $(Lu, Re)$, while for fixed $(Lu,
+Rm)$, the magnetic energy decreases and torque increases with increasing $Re$.
+We studied the scaling of the magnetic energy and torque in the saturated state
+as a function of $Re$ and find a power law dependence $Re^{-0.6...-0.5}$ for
+the magnetic energy and $Re^{0.4...0.5}$ for the torque at all $(Lu, Rm)$ and
+high $Re\geq 4000$. We also explored the dependence on Lundquist number and
+angular velocity of the cylinders. These scaling laws will be instrumental in
+the subsequent analysis of more realistic finite-length TC flows and comparison
+of numerical results with those obtained from the DRESDYN-MRI experiments to
+unambiguously identify SMRI in laboratory.",2211.10811v3
+2022-11-21,Comparison of magnetic energy and helicity in coronal jet simulations,"While free/non-potential magnetic energy is a necessary element of any active
+phenomenon in the solar corona, its role as a marker of the trigger of eruptive
+process remains elusive. Based on the unique decomposition of the magnetic
+field into potential and non-potential components, magnetic energy and helicity
+can also both be uniquely decomposed into two quantities. Using two 3D MHD
+parametric simulations of a configuration that can produce coronal jets, we
+compare the dynamics of the magnetic energies and of the relative magnetic
+helicities. Both simulations share the same initial set-up and line-tied
+bottom-boundary driving profile. However, they differ by the duration of the
+forcing. In one simulation the system is driven sufficiently so that an helical
+jet is induced. The generation of the jet is however markedly delayed: a
+relatively long phase of lower-intensity reconnection takes place before the
+jet is eventually induced. In the other reference simulation, the system is
+driven during a shorter time, and no jet is produced. As expected, we observe
+that the Jet producing simulation contains a higher value of non-potential
+energy and non-potential helicity. Focusing on the phase between the end of the
+driving-phase and the jet generation, we note that magnetic energies remain
+relatively constant, while magnetic helicities have a noticeable evolution.
+During this post-driving phase, the ratio of the non-potential to total
+magnetic energy very slightly decreases while the helicity eruptivity index
+significantly increases. The jet is generated when the system is at the highest
+value of this helicity eruptivity index. This proxy critically decreases during
+the jet generation phase. The free energy also decreases but does not present
+any peak when the jet is being generated.",2211.11265v1
+2022-11-21,Room Temperature Optically and Magnetically Active Edges in Phosphorene Nanoribbons,"Nanoribbons - nanometer wide strips of a two-dimensional material - are a
+unique system in condensed matter physics. They combine the exotic electronic
+structures of low-dimensional materials with an enhanced number of exposed
+edges, where phenomena including ultralong spin coherence times, quantum
+confinement and topologically protected states can emerge. An exciting prospect
+for this new material concept is the potential for both a tunable
+semiconducting electronic structure and magnetism along the nanoribbon edge.
+This combination of magnetism and semiconducting properties is the first step
+in unlocking spin-based electronics such as non-volatile transistors, a route
+to low-energy computing, and has thus far typically only been observed in doped
+semiconductor systems and/or at low temperatures. Here, we report the magnetic
+and semiconducting properties of phosphorene nanoribbons (PNRs). Static (SQUID)
+and dynamic (EPR) magnetization probes demonstrate that at room temperature,
+films of PNRs exhibit macroscopic magnetic properties, arising from their edge,
+with internal fields of ~ 250 to 800 mT. In solution, a giant magnetic
+anisotropy enables the alignment of PNRs at modest sub-1T fields. By leveraging
+this alignment effect, we discover that upon photoexcitation, energy is rapidly
+funneled to a dark-exciton state that is localized to the magnetic edge and
+coupled to a symmetry-forbidden edge phonon mode. Our results establish PNRs as
+a unique candidate system for studying the interplay of magnetism and
+semiconducting ground states at room temperature and provide a stepping-stone
+towards using low-dimensional nanomaterials in quantum electronics.",2211.11374v1
+2023-05-03,Reconnection generated plasma flows in the quasi-separatrix layer in localised solar corona,"Multiwavelength observations of the propagating disturbances (PDs),
+discovered by Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics
+Observatory (SDO), are analyzed to determine its driving mechanism and physical
+nature. Two magnetic strands in the localised corona are observed to approach
+and merge with each other followed by the generation of brightening, which
+further propagates in a cusp-shaped magnetic channel. Differential emission
+measure analysis shows an occurrence of heating in this region-of-interest
+(ROI). We extrapolate potential magnetic field lines at coronal heights from
+observed Helioseismic and Magnetic Imager (HMI) vector magnetogram via Green's
+function method using MPI-AMRVAC. We analyze the field to locate magnetic nulls
+and quasi-separatrix layers (QSLs) which are preferential locations for
+magnetic reconnection. Dominant QSLs including a magnetic null are found to
+exist and match the geometry followed by PDs, therefore, it provides conclusive
+evidence of magnetic reconnection. In addition, spectroscopic analysis of
+Interface Region Imaging Spectrograph (IRIS) Si IV 1393.77 {\AA} line profiles
+show a rise of line-width in the same time range depicting presence of mass
+motion in the observed cusp-shaped region. PDs are observed to exhibit
+periodicities of around four minutes. The speeds of PDs measured by Surfing
+Transform Technique are almost close to each other in four different SDO/AIA
+bandpasses, i.e., 304, 171, 193 and 131 {\AA} excluding the interpretation of
+PDs in terms of slow magnetoacoustic waves. We describe comprehensively the
+observed PDs as quasi-periodic plasma flows generated due to periodic
+reconnection in vicinity of a coronal magnetic null.",2305.02277v1
+2023-08-30,Energy distribution and substructure formation in astrophysical MHD simulations,"During substructure formation in magnetized astrophysical plasma, dissipation
+of magnetic energy facilitated by magnetic reconnection affects the system
+dynamics by heating and accelerating the ejected plasmoids. Numerical
+simulations are a crucial tool for investigating such systems. In astrophysical
+simulations, the energy dissipation, reconnection rate and substructure
+formation critically depend on the onset of reconnection of numerical or
+physical origin. In this paper, we hope to assess the reliability of the
+state-of-the-art numerical codes, PLUTO and KORAL by quantifying and discussing
+the impact of dimensionality, resolution, and code accuracy on magnetic energy
+dissipation, reconnection rate, and substructure formation. We quantitatively
+compare results obtained with relativistic and non-relativistic, resistive and
+non-resistive, as well as two- and three-dimensional setups performing the
+Orszag-Tang test problem. We find the sufficient resolution in each model, for
+which numerical error is negligible and the resolution does not significantly
+affect the magnetic energy dissipation and reconnection rate. The
+non-relativistic simulations show that at sufficient resolution, magnetic and
+kinetic energies convert to internal energy and heat up the plasma. The results
+show that in the relativistic system, energy components undergo mutual
+conversion during the simulation time, which leads to a substantial increase in
+magnetic energy at 20\% and 90\% of the total simulation time of $10$
+light-crossing times -- the magnetic field is amplified by a factor of five due
+to relativistic shocks. We also show that the reconnection rate in all our
+simulations is higher than $0.1$, indicating plasmoid-mediated regime. It is
+shown that in KORAL simulations magnetic energy is slightly larger and more
+substructures are captured than in PLUTO simulations.",2308.16062v2
+2023-10-25,Fundamental MHD scales -- II: the kinematic phase of the supersonic small-scale dynamo,"The small-scale dynamo (SSD) amplifies weak magnetic fields exponentially
+fast via kinetic motions. While there exist well-established theories for SSDs
+in incompressible flows, many astrophysical SSDs operate in supersonic
+turbulence. To understand the impact of compressibility on amplified magnetic
+fields, we perform an extensive set of visco-resistive SSD simulations,
+covering a wide range of sonic Mach number $\mathcal{M}$, hydrodynamic Reynolds
+number Re, and magnetic Prandtl number Pm. We develop robust methods for
+measuring kinetic and magnetic energy dissipation scales $\ell_\nu$ and
+$\ell_\eta$, as well as the scale at which magnetic fields are strongest
+$\ell_p$ during the kinematic phase of these simulations. We show that
+$\ell_\nu/\ell_\eta \sim$ Pm$^{1/2}$ is a universal feature in the kinematic
+phase of Pm $\geq 1$ SSDs, regardless of $\mathcal{M}$ or Re, and we confirm
+earlier predictions that SSDs operating in incompressible plasmas (either
+$\mathcal{M} \leq 1$ or Re $<$ Re$_{\rm crit} \approx 100$) concentrate
+magnetic energy at the smallest scales allowed by magnetic dissipation, $\ell_p
+\sim \ell_\eta$, and produce fields organised with field strength and
+field-line curvature inversely correlated. However, we show that these
+predictions fail for compressible SSDs ($\mathcal{M} > 1$ and Re $>$ Re$_{\rm
+crit}$), where shocks concentrate magnetic energy in large-scale, over-dense,
+coherent structures, with size $\ell_p \sim (\ell_{\rm turb} / \ell_{\rm
+shock})^{1/3} \ell_\eta \gg \ell_\eta$, where $\ell_{\rm shock} \sim
+\mathcal{M}^2 / [$Re $ (\mathcal{M} - 1)^2]$ is shock width, and $\ell_{\rm
+turb}$ is the turbulent outer scale; magnetic field-line curvature becomes
+almost independent of the field strength. We discuss the implications for
+galaxy mergers and for cosmic-ray transport models in the interstellar medium
+that are sensitive to field-line curvature statistics.",2310.17036v1
+2024-01-02,A study of the magnetocaloric behavior of Dy-substituted YMn$_2$O$_5$ compounds,"In this paper, we report on the magnetic and magnetocaloric features of
+Dy-substituted YMn$_2$O$_5$ (Y$_{1-x}$Dy$_x$Mn$_2$O$_5$) with $x=$ 0.6, 0.8,
+and 1 series elaborated by sol-gel method. X-ray diffraction and Raman
+measurements attest well the high quality of our polycrystalline samples that
+crystallize in an orthorhombic structure with the Pbam space group. The Raman
+phonon frequencies were carried out and compared with the lattice dynamics
+calculations to identify the vibrational properties of all detected modes at
+room temperature. As expected, our magnetic study reveals that the
+magnetization was enhanced by the substitution of Y$^{3+}$ by Dy$^{3+}$. The
+Dy-substituted YMn$_2$O$_5$ sets the N\'eel transition [TN (Mn)] in the
+temperature range going from 40 to 45 K favoring the emergence of a transition
+at a very low temperature due to the long-range ordering of the Dy3+ magnetic
+moments below 13K [TN (Dy)]. Dual peaks in the magnetic entropy change curve
+are also observed being in good agreement with magnetization data, which
+enlarges the range of application of these materials. On the other hand, a
+large magnetocaloric effect is observed close to 13 K which is mainly due the
+ordering of Dy$^{3+}$ magnetic moments. Also, the incommensurate
+antiferromagnetic transition of Mn magnetic moment taking place around 40 K
+affects slightly the entropy change. Our refrigerant capacity (RC) findings are
+higher compared to the average of RC for a, b, c axis of single crystal samples
+as HoMn$_2$O$_5$ and TbMn$_2$O$_5$, which confirms that our polycrystalline
+materials stand for promising magnetic refrigerant candidates that can be
+invested in space technology, hydrogen and helium liquefaction at cryogenic
+temperature.",2401.01431v1
+2024-01-31,"Formation Mechanism of Laser-Driven Magnetized ""Pillars of Creation""","Pillars of Creation, one of the most recognized objects in the sky, are
+believed to be associated with the formation of young stars. However, so far,
+the formation and maintenance mechanism for the pillars are still not fully
+understood due to the complexity of the nonlinear radiation
+magneto-hydrodynamics (RMHD). Here, assuming laboratory laser-driven
+conditions, we studied the self-consistent dynamics of pillar structures in
+magnetic fields by means of two-dimensional (2D) and three-dimensional (3D)
+RMHD simulations, and these results also support our proposed experimental
+scheme. We find only when the magnetic pressure and ablation pressure are
+comparable, the magnetic field can significantly alter the plasma
+hydrodynamics. For medium magnetized cases ($\beta_{initial} \approx 3.5$),
+{the initial magnetic fields undergo compression and amplification. This
+amplification results in the magnetic pressure inside the pillar becoming large
+enough to support the sides of the pillar against radial collapse due to
+pressure from the surrounding hot plasma. This effect is particularly
+pronounced for the parallel component ($B_y$), which is consistent with
+observational results.} In contrast, a strong perpendicular ($B_x, B_z$)
+magnetic field ($\beta_{initial} < 1$) almost remains its initial distribution
+and significantly suppresses the expansion of blow-off gas plasma, leading to
+the inability to form pillar-like structures. The 3D simulations suggest that
+the bending at the head of `Column \uppercase\expandafter{\romannumeral1}' in
+pillars of creation may be due to the non-parallel magnetic fields. After
+similarity scaling transformation, our results can be applied to explain the
+formation and maintenance mechanism of the pillars, and can also provide useful
+information for future experimental designs.",2401.17561v1
+2024-02-09,Characterization of the Clinically Approved MRI Tracer Resotran for Magnetic Particle Imaging in a Comparison Study,"Objective. The availability of magnetic nanoparticles with medical approval
+for human intervention is fundamental to the clinical translation of magnetic
+particle imaging (MPI). In this work, we thoroughly evaluate and compare the
+magnetic properties of an magnetic resonance imaging (MRI) approved tracer to
+validate its performance for MPI in future human trials. Approach. We analyze
+whether the recently approved MRI tracer Resotran is suitable for MPI. In
+addition, we compare Resotran with the previously approved and extensively
+studied tracer Resovist, with Ferrotran, which is currently in a clinical phase
+III study, and with the tailored MPI tracer Perimag. Main results. Initial
+magnetic particle spectroscopy measurements indicate that Resotran exhibits
+performance characteristics akin to Resovist, but below Perimag. We provide
+data on four different tracers using dynamic light scattering, transmission
+electron microscopy, vibrating sample magnetometry measurements, magnetic
+particle spectroscopy to derive hysteresis, point spread functions, and a
+serial dilution, as well as system matrix based MPI measurements on a
+preclinical scanner (Bruker 25/20 FF), including reconstructed images.
+Significance. Numerous approved magnetic nanoparticles used as tracers in MRI
+lack the necessary magnetic properties essential for robust signal generation
+in MPI. The process of obtaining medical approval for dedicated MPI tracers
+optimized for signal performance is an arduous and costly endeavor, often only
+justifiable for companies with a well-defined clinical business case. Resotran
+is an approved tracer that has become available in Europe for MRI. In this
+work, we study the eligibility of Resotran for MPI in an effort to pave the way
+for human MPI trials.",2402.06350v1
+2024-03-21,The dependence of the magnetism of a near-limb sunspot on height,"The physical parameters of the sunspot are not fully understood, especially
+the height dependence of the magnetic field. So far, it is also an open
+question as to which heights the He I 1083 nm spectral line is formed at. Our
+aim is to investigate the magnetic and dynamical properties in the atmosphere
+above a sunspot, from the photosphere to the chromosphere. We analyzed the
+photospheric and chromospheric magnetic field properties of a stable sunspot in
+AR 12553 on June 20, 2016 using spectropolarimetric observations obtained with
+GRIS at GREGOR. A spectral-line inversion technique was used to infer the
+magnetic field vector and Doppler velocities from the full Stokes profiles. In
+total, three spectral lines were inverted and the variation of the magnetic
+properties was qualified using the average values of the radial circles. The
+sunspot is located close to the solar limb, and thus this allows us to make a
+geometrical determination of the height of the spectral line He I 1083 nm. We
+find the height of helium spectral line to be 970 km above the photospheric
+spectral lines directly from observation at a stable sunspot. The total
+magnetic field strength decreases with height over the sunspot; the rates are
+-0.34 G/km for the umbra and -0.28 G/km for the penumbra. The inclination
+increases with increasing height in the umbra, but decreases in the penumbra.
+In the umbra, the vertical component ($B_z$) decreases with height, while the
+horizontal component ($B_{hor}$) remains almost constant. In the penumbra this
+is reversed, as $B_z$ remains nearly constant over height, while $B_{hor}$
+decreases. We also observe fast velocities with 30 km/s in small chromospheric
+patches on the central side of the spot. The key parameters depending on height
+in the sunspot are the $B_{z}$ component of the magnetic field for the umbra
+and the $B_{hor}$ component of the magnetic field for the penumbra.",2403.14532v1
+2000-01-07,Theory of the spin bath,"The quantum dynamics of mesoscopic or macroscopic systems is always
+complicated by their coupling to many ""environmental"" modes.At low T these
+environmental effects are dominated by localised modes, such as nuclear and
+paramagnetic spins, and defects (which also dominate the entropy and specific
+heat). This environment, at low energies, maps onto a ""spin bath"" model. This
+contrasts with ""oscillator bath"" models (originated by Feynman and Vernon)
+which describe {\it delocalised} environmental modes such as electrons,
+phonons, photons, magnons, etc. One cannot in general map a spin bath to an
+oscillator bath (or vice-versa); they constitute distinct ""universality
+classes"" of quantum environment. We show how the mapping to spin bath models is
+made, and then discuss several examples in detail, including moving particles,
+magnetic solitons, nanomagnets, and SQUIDs, coupled to nuclear and paramagnetic
+spin environments. We show how to average over spin bath modes, using an
+operator instanton technique, to find the system dynamics, and give analytic
+results for the correlation functions, under various conditions. We then
+describe the application of this theory to magnetic and superconducting
+systems.Particular attention is given to recent work on tunneling magnetic
+macromolecules, where the role of the nuclear spin bath in controlling the
+tunneling is very clear; we also discuss other magnetic systems in the quantum
+regime, and the influence of nuclear and paramagnetic spins on flux dynamics in
+SQUIDs.",0001080v2
+2001-07-24,Diluted quantum antiferromagnets: spin excitations and long-range order,"We have studied the static and dynamic magnetic properties of two-dimensional
+(2D) and quasi-two-dimensional, spin-S, quantum Heisenberg antiferromagnets
+(QHAF) diluted with spinless vacancies. Using spin-wave theory and T-matrix
+approximation we have calculated the staggered magnetization, M(x,T), the
+neutron scattering dynamical structure factor, S(k,omega), the 2D magnetic
+correlation length, \xi(x,T), and the Neel temperature, T_N(x), for the
+quasi-2D case. We find that in 2D the hydrodynamic description of excitations
+in terms of spin-waves breaks down at the wavelength larger than \ell/a ~
+exp(\pi/4x), x being impurity concentration and ""a"" the lattice spacing. The
+density of states acquires a constant term and exhibits an anomalous peak at
+omega omega_0 associated with the low-energy localized excitations. These
+anomalies lead to a substantial enhancement of the magnetic specific heat, C_M,
+at low temperatures. Although the dynamical properties are significantly
+modified we show that 2D is not the lower critical dimension for this problem.
+Our results are in quantitative agreement with the recent Monte Carlo
+simulations and experimental data for S=1/2, S=1, and S=5/2.",0107488v1
+2007-03-21,Dynamics of the Magnetic Flux Trapped in Fractal Clusters of a Normal Phase in Percolative Superconductors,"The effect of the fractal clusters of a normal phase, which act as pinning
+centers, on the dynamics of magnetic flux in percolative type-II superconductor
+is considered. The main features of these clusters are studied in detail: the
+cluster statistics is analyzed; the fractal dimension of their boundary is
+estimated; the distribution of critical currents is obtained, and its
+peculiarities are explored. It is found that there is the range of fractal
+dimension where this distribution has anomalous statistical properties,
+specifically, its dispersion becomes infinite. It is examined how the finite
+resolution capacity of the cluster geometric size measurement affects the
+estimated value of fractal dimension. The effect of fractal properties of the
+normal phase clusters on the electric field arisen from magnetic flux motion is
+investigated for the cluster area distribution of different kinds. The
+voltage-current characteristics of fractal superconducting structures in the
+resistive state are obtained for an arbitrary fractal dimension. It is revealed
+that the fractality of the boundaries of the normal phase clusters intensifies
+the magnetic flux trapping and thereby raises the critical current of a
+superconductor.",0703541v1
+2007-05-24,Optical investigations of quantum-dot spin dynamics,"We have performed all-optical measurements of spin relaxation in single
+self-assembled InAs/GaAs quantum dots (QD) as a function of static external
+electric and magnetic fields. To study QD spin dynamics we measure the degree
+of resonant absorption which results from a competition between optical spin
+pumping induced by the resonant laser field and spin relaxation induced by
+reservoirs. Fundamental interactions that determine spin dynamics in QDs are
+hyperfine coupling to QD nuclear spin ensembles, spin-phonon coupling and
+exchange-type interactions with a nearby Fermi sea of electrons. We show that
+the strength of spin relaxation generated by the three fundamental interactions
+can be changed by up to five orders of magnitude upon varying the applied
+electric and magnetic fields. We find that the strength of optical spin pumping
+that we use to study the spin relaxation is determined predominantly by
+hyperfine-induced mixing of single-electron spin states at low magnetic fields
+and heavy-light hole mixing at high magnetic fields. Our measurements allow us
+to determine the rms value of the hyperfine (Overhauser) field to be ~15 mTesla
+with an electron g-factor of g_e=0.6 and a hole mixing strength of |epsilon|^2
+= 0.0005.",0705.3557v1
+2007-07-24,Dynamics of wave packets in two-dimensional crystals under external magnetic and electric fields: Vortices formation,"In the present work we deal with the dynamics of wave packets in a
+two-dimensional crystal under the action of magnetic and electric fields. The
+magnetic field is perpendicular to the plane and the electric field is on the
+plane. In the simulations we considered a symmetric gauge for the vector
+potential while the initial wave packet was assumed to have a gaussian
+structure with given velocities. The parameters that control the kind of time
+evolution of the packets are: the width of the gaussian, its velocity, and, the
+intensity and direction of the electric field as well as the magnitude of the
+magnetic field. In order to characterize the kind of propagation we evaluated
+the mean-square displacement (MSD), the participation function and which is
+more important we were able to follow the wave at different times, which
+allowed us to see the time evolution of the centroid of the wave packets. A
+novel effect was observed, namely, the dynamics is such that the wave function
+\emph{splits} into two or more components and \emph{reconstructs} successively
+as time goes, vortices are forming. To our understanding this is the first time
+such an effect is reported. As for the inclusion of the electric field, we
+observe a complex behavior of the wave packet as well as note that the vortices
+propagate in direction perpendicular to the applied electric field. A similar
+behavior presented by the classical treatment, In our case we give a quantum
+mechanics explanation for that",0707.3554v1
+2008-04-17,Dynamical effects of self-generated magnetic fields in cosmic ray modified shocks,"Recent observations of greatly amplified magnetic fields ($\delta B/B\sim
+100$) around supernova shocks are consistent with the predictions of the
+non-linear theory of particle acceleration (NLT), if the field is generated
+upstream of the shock by cosmic ray induced streaming instability. The high
+acceleration efficiencies and large shock modifications predicted by NLT need
+however to be mitigated to confront observations, and this is usually assumed
+to be accomplished by some form of turbulent heating. We show here that
+magnetic fields with the strength inferred from observations have an important
+dynamical role on the shock, and imply a shock modification substantially
+reduced with respect to the naive unmagnetized case. The effect appears as soon
+as the pressure in the turbulent magnetic field becomes comparable with the
+pressure of the thermal gas. The relative importance of this unavoidable effect
+and of the poorly known turbulent heating is assessed. More specifically we
+conclude that even in the cases in which turbulent heating may be of some
+importance, the dynamical reaction of the field cannot be neglected, as instead
+is usually done in most current calculations.",0804.2884v2
+2008-06-26,Ferromagnetic resonance force spectroscopy of individual sub-micron size samples,"We review how a magnetic resonance force microscope (MRFM) can be applied to
+perform ferromagnetic resonance (FMR) spectroscopy of \emph{individual}
+sub-micron size samples. We restrict our attention to a thorough study of the
+spin-wave eigen-modes excited in permalloy (Py) disks patterned out of the same
+43.3 nm thin film. The disks have a diameter of either 1.0 or $0.5 \mu$m and
+are quasi-saturated by a perpendicularly applied magnetic field. It is shown
+that \emph{quantitative} spectroscopic information can be extracted from the
+MRFM measurements. In particular, the data are extensively compared with
+complementary approximate models of the dynamical susceptibility: i) a 2D
+analytical model, which assumes an homogeneous magnetization dynamics along the
+thickness and ii) a full 3D micromagnetic simulation, which assumes an
+homogeneous magnetization dynamics below a characteristic length scale $c$ and
+which approximates the cylindrical sample volume by a discretized
+representation with regular cubic mesh of lateral size $c=3.9$ nm. In our
+analysis, the distortions due to a breaking of the axial symmetry are taken
+into account, both models incorporating the possibility of a small misalignment
+between the applied field and the normal of the disks.",0806.4244v1
+2008-08-22,Development of Anisotropy in Incompressible Magnetohydrodynamic Turbulence,"We present a set of three-dimensional (3D) direct numerical simulations of
+incompressible decaying magnetohydrodynamic turbulence in which we investigate
+the influence of an external uniform magnetic field B_0. A parametric study in
+terms of B_0 intensity is made where, in particular, we distinguish the shear-
+from the pseudo-Alfven waves dynamics. The initial kinetic and magnetic
+energies are equal with a negligible cross-correlation. Both the temporal and
+spectral effects of B_0 are discussed. A sub-critical balance is found between
+the Alfven and nonlinear times with both a global and a spectral definition.
+The nonlinear dynamics of strongly magnetized flows is characterized by a
+different k_perp-spectrum (where B_0 defines the parallel direction) if it is
+plotted at a fixed k_// (2D spectrum) or if it is integrated (averaged) over
+all k_// (1D spectrum). In the former case a much wider inertial range is found
+with a steep power law, closer to the wave turbulence prediction than the
+Kolmogorov one like in the latter case. It is believed that the averaging
+effect may be a source of difficulty to detect the transition towards wave
+turbulence in natural plasmas. For the first time, the formation of filaments
+is reported within current and vorticity sheets in strongly magnetized flows
+which modifies our classical picture of dissipative sheets in conductive flows.",0808.3061v1
+2010-02-11,Forward and adjoint quasi-geostrophic models of the geomagnetic secular variation,"We introduce a quasi-geostrophic model of core dynamics, which aims at
+describing core processes on geomagnetic secular variation timescales. It
+extends the formalism of Alfv\'en torsional oscillations by incorporating
+non-zonal motions. Within this framework, the magnetohydrodynamics takes place
+in the equatorial plane; it involves quadratic magnetic quantities, which are
+averaged along the direction of rotation of the Earth. In addition, the
+equatorial flow is projected on the core-mantle boundary. It interacts with the
+magnetic field at the core surface, through the radial component of the
+magnetic induction equation. That part of the model connects the dynamics and
+the observed secular variation, with the radial component of the magnetic field
+acting as a passive tracer. We resort to variational data assimilation to
+construct formally the relationship between model predictions and observations.
+Variational data assimilation seeks to minimize an objective function, by
+computing its sensitivity to its control variables. The sensitivity is
+efficiently calculated after integration of the adjoint model. We illustrate
+that framework with twin experiments, performed first in the case of the
+kinematic core flow inverse problem, and then in the case of Alfv\'en torsional
+oscillations. In both cases, using the adjoint model allows us to retrieve core
+state variables which, while taking part in the dynamics, are not directly
+sampled at the core surface. We study the effect of several factors on the
+solution (width of the assimilation time window, amount and quality of data),
+and we discuss the potential of the model to deal with real geomagnetic
+observations.",1002.2323v1
+2010-04-22,Critical current and vortex dynamics in single crystals of Ca(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$,"We investigate the critical current density and vortex dynamics in single
+crystals of Ca(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$ ($x$ = 0.051, 0.056, 0.065, and
+0.073). The samples exhibit different critical temperatures and superconducting
+phase fractions. We show that in contrast to their Ba-based counterpart, the
+crystals do not exhibit a second peak in the field dependence of magnetization.
+The calculated composition-dependent critical current density ($j_{\rm c}$)
+increases initially with Co doping, maximizing at $x$ = 0.065, and then
+decreases. This variation in $j_{\rm c}$ follows the superconducting phase
+fractions in this series. The calculated $j_{\rm c}$ shows strong temperature
+dependence, decreasing rapidly upon heating. Magnetic relaxation measurements
+imply a nonlogarithmic dependence on time. We find that the relaxation rate is
+large, reflecting weak characteristic pinning energy. The analysis of
+temperature- and field-dependent magnetic relaxation data suggests that vortex
+dynamics in these compounds is consistent with plastic creeping rather than the
+collective creep model, unlike other 122 pnictide superconductors. This
+difference may cause the absence of the second peak in the field dependent
+magnetization of Ca(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$.",1004.3910v1
+2010-05-29,"Confinement of the Sun's interior magnetic field, with implications for lithium burning","The simplest interior magnetic field B_i that can explain the observed
+uniform rotation of the Sun's radiative envelope is an axial dipole stabilized
+by a deep toroidal field. It can explain the uniform rotation only if confined
+in the polar caps. The field must be prevented from diffusing up into the
+high-latitude convection zone, whose slower rotation must remain decoupled from
+the radiative interior. This paper describes new analytical and numerical
+solutions of the relevant magnetohydrodynamic equations showing that such
+confinement and decoupling is dynamically possible by means of a laminar
+""magnetic confinement layer"" at the bottom of the tachocline. With realistic
+values of the microscopic diffusivities, a weak laminar downwelling flow
+U~10^{-5}cm/s over the poles is enough to enforce exponential decay of B_i with
+altitude, in a confinement layer only a fraction of a megameter thick.
+Downwelling in the polar tachocline is implied both by helioseismic
+observations, combined with elementary dynamics, and by theoretical arguments
+about the ""gyroscopic pumping"" that would spread differential rotation downward
+in the absence of B_i. Our confinement-layer solutions are the first to take
+account of all the relevant physical effects in a self-consistent mathematical
+model. The effects include magnetic diffusion, baroclinicity and stable
+stratification (thermal and compositional), Coriolis effects, and thermal
+relaxation. We discuss how the confinement layers at each pole might fit into a
+global dynamical picture of the solar tachocline. That picture, in turn,
+suggests a new insight into the early Sun and solar lithium depletion.",1005.5481v2
+2012-06-26,Transport and semiclassical dynamics of coupled quantum dots interacting with a local magnetic moment,"We present a theory of magnetotransport through a system of two coupled
+electronic orbitals, where the electron spin interacts with a (large) local
+magnetic moment via an exchange interaction. For the physical realization of
+such a set-up we have in mind, for example, semiconductor quantum dots coupled
+to an ensemble of nuclear spins in the host material or molecular orbitals
+coupled to a local magnetic moment. Using a semiclassical approximation, we
+derive a set of Ehrenfest equations of motion for the electron density matrix
+and the mean value of the external spin (Landau equations): Due to the spin
+coupling they turn out to be nonlinear and, importantly, also coherences
+between electron states with different spin directions need to be considered.
+The electronic spin-polarized leads are implemented in form of a Lindblad-type
+dissipator in the infinite bias limit. We have solved this involved dynamical
+system numerically for various isotropic and anisotropic coupling schemes. For
+isotropic spin coupling and spin-polarized leads we study the effect of
+current-induced magnetization of the attached spin and compare this with a
+single quantum dot set-up. We further demonstrate that an anisotropic coupling
+can lead to a rich variety of parametric oscillations in the average current
+reflecting the complicated interplay between the Larmor precession of the
+external spin and the dissipative coherent dynamics of the electron spin.",1206.5994v2
+2012-07-04,The chromosphere and prominence magnetometer,"The Chromosphere and Prominence Magnetometer (ChroMag) is conceived with the
+goal of quantifying the intertwined dynamics and magnetism of the solar
+chromosphere and in prominences through imaging spectro-polarimetry of the full
+solar disk. The picture of chromospheric magnetism and dynamics is rapidly
+developing, and a pressing need exists for breakthrough observations of
+chromospheric vector magnetic field measurements at the true lower boundary of
+the heliospheric system. ChroMag will provide measurements that will enable
+scientists to study and better understand the energetics of the solar
+atmosphere, how prominences are formed, how energy is stored in the magnetic
+field structure of the atmosphere and how it is released during space weather
+events like flares and coronal mass ejections. An integral part of the ChroMag
+program is a commitment to develop and provide community access to the
+""inversion"" tools necessary for the difficult interpretation of the
+measurements and derive the magneto-hydrodynamic parameters of the plasma.
+Measurements of an instrument like ChroMag provide critical physical context
+for the Solar Dynamics Observatory (SDO) and Interface Region Imaging
+Spectrograph (IRIS) as well as ground-based observatories such as the future
+Advanced Technology Solar Telescope (ATST).",1207.0969v1
+2013-02-25,Monte Carlo investigation of a spherical ferrimagnetic core-shell nanoparticle under a time dependent magnetic field,"Monte Carlo simulation based on Metropolis algorithm has been used with a
+great success to analyze the dynamic phase transition properties of a single
+spherical core-shell nanoparticle system with a spin-3/2 core surrounded by a
+spin-1 shell layer with antiferromagnetic interface coupling under the
+influence of a time dependent oscillating magnetic filed. It has been found
+that the dynamic phase boundaries strongly depend on the Hamiltonian parameters
+such as for the high amplitude and period values of the external field, the
+phase transition temperature sharply changes whereas it tends to slowly alter
+as the reduced magnitude of interlayer parameter $\mathrm{J_{int}/J_{sh}}$
+increases. Moreover, it is observed that the magnetization curves of the
+particle have been found to obey P-type, N-type and Q-type classification
+schemes under certain conditions. Much effort has also been paid to the
+influence of the particle size on the thermal and magnetic properties of the
+particle. Finally, a comparison of our observations with those of recently
+published study including dynamic treatments of a nanocubic core-shell system
+is represented and the findings indicate that there exists a qualitatively good
+agreement with some relatively distinct differences.",1302.6227v2
+2015-02-26,The decay of wall-bounded MHD turbulence at low Rm,"We present Direct Numerical Simulations of decaying Magnetohydrodynamic (MHD)
+turbulence at low magnetic Reynolds number. The domain considered is bounded by
+periodic boundary conditions in the two directions perpendicular to the
+magnetic field and by two plane Hartmann walls in the third direction. High
+magnetic fields (Hartmann number of up to 896) are considered thanks to a
+numerical method based on a spectral code using the eigenvectors of the
+dissipation operator. It is found that the decay proceeds through two phases:
+first, energy and integral lengthscales vary rapidly during a
+two-dimensionalisation phase extending over about one Hartmann friction time.
+During this phase, the evolution of the former appears significantly more
+impeded by the presence of walls than that of the latter. Once the large scales
+are close to quasi-two dimensional, the decay results from the competition of a
+two-dimensional dynamics driven by dissipation in the Hartmann boundary layers
+and the three-dimensional dynamics of smaller scales. In the later stages of
+the decay, three-dimensionality subsists under the form of barrel-shaped
+structures. A purely quasi-two dimensional decay dominated by friction in the
+Hartmann layers is not reached, because of residual dissipation in the bulk.
+However, this dissipation is not generated by the three-dimensionality that
+subsists, but by residual viscous friction due to horizontal velocity
+gradients. Also, the energy in the velocity component aligned with the magnetic
+field is found to be strongly suppressed, as is transport in this direction.
+This results reproduces the experimental findings of Kolesnikov & Tsinober
+(1974).",1502.07631v2
+2015-03-11,Current-Driven Dynamics of Skyrmions Stabilized in MnSi Nanowires Revealed by Topological Hall Effect,"Skyrmions, novel topologically stable spin vortices, hold promise for
+next-generation magnetic storage due to their nanoscale domains to enable high
+information storage density and their low threshold for current-driven motion
+to enable ultralow energy consumption. One-dimensional (1D) nanowires are ideal
+hosts for skyrmions since they not only serve as a natural platform for
+magnetic racetrack memory devices but also can potentially stabilize skyrmions.
+Here we use the topological Hall effect (THE) to study the phase stability and
+current-driven dynamics of the skyrmions in MnSi nanowires. The THE was
+observed in an extended magnetic field-temperature window (15 to 30 K),
+suggesting stabilization of skyrmion phase in nanowires compared with the bulk
+(27 to 29.5 K). Furthermore, for the first time, we study skyrmion dynamics in
+this extended skyrmion phase region and found that under the high
+current-density of $10^{8}-10^{9} Am^{-2}$ enabled by nanowire geometry, the
+THE decreases with increasing current densities, which demonstrates the
+current-driven motion of skyrmions generating the emergent electric field.
+These results open up the exploration of nanowires as an attractive platform
+for investigating skyrmion physics in 1D systems and exploiting skyrmions in
+magnetic storage concepts.",1503.03523v2
+2015-04-28,Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5-10 GHz frequency range,"We present a scanning transmission x-ray microscopy setup combined with a
+novel microwave synchronization scheme in order to study high frequency
+magnetization dynamics at synchrotron light sources. The sensitivity necessary
+to detect small changes of the magnetization on short time scales and nanometer
+spatial dimensions is achieved by combination of the developed excitation
+mechanism with a single photon counting electronics that is locked to the
+synchrotron operation frequency. The required mechanical stability is achieved
+by a compact design of the microscope. Our instrument is capable of creating
+direct images of dynamical phenomena in the 5-10 GHz range, with 35 nm
+resolution. When used together with circularly polarized x-rays, the above
+capabilities can be combined to study magnetic phenomena at microwave
+frequencies, such as ferromagnetic resonance (FMR) and spin waves. We
+demonstrate the capabilities of our technique by presenting phase resolved
+images of a 6 GHz nanoscale spin wave generated by a spin torque oscillator, as
+well as the uniform ferromagnetic precession with ~0.1 deg amplitude at 9 GHz
+in a micrometer-sized cobalt strip.",1504.07561v1
+2015-08-02,Soliton-like magnetic domain wall motion induced by the interfacial Dzyaloshinskii-Moriya interaction,"Topological defects such as magnetic solitons, vortices, Bloch lines, and
+skyrmions have started to play an important role in modern magnetism because of
+their extraordinary stability, which can be exploited in the production of
+memory devices. Recently, a novel type of antisymmetric exchange interaction,
+namely the Dzyaloshinskii-Moriya interaction (DMI), has been uncovered and
+found to influence the formation of topological defects. Exploring how the DMI
+affects the dynamics of topological defects is therefore an important task.
+Here we investigate the dynamic domain wall (DW) under a strong DMI and find
+that the DMI induces an annihilation of topological vertical Bloch lines (VBLs)
+by lifting the four-fold degeneracy of the VBL. As a result, velocity reduction
+originating from the Walker breakdown is completely suppressed, leading to a
+soliton-like constant velocity of the DW. Furthermore, the strength of the DMI,
+which is the key factor for soliton-like DW motion, can be quantified without
+any side effects possibly arising from current-induced torques or extrinsic
+pinnings in magnetic films. Our results therefore shed light on the physics of
+dynamic topological defects, which paves the way for future work in
+topology-based memory applications.",1508.00197v1
+2015-08-22,Helical mode interactions and spectral transfer processes in magnetohydrodynamic turbulence,"Spectral transfer processes in magnetohydrodynamic (MHD) turbulence are
+investigated analytically by decomposition of the velocity and magnetic fields
+in Fourier space into helical modes. Steady solutions of the dynamical system
+which governs the evolution of the helical modes are determined, and a
+stability analysis of these solutions is carried out. The interpretation of the
+analysis is that unstable solutions lead to energy transfer between the
+interacting modes while stable solutions do not. From this, a dependence of
+possible interscale energy and helicity transfers on the helicities of the
+interacting modes is derived. As expected from the inverse cascade of magnetic
+helicity in 3D MHD turbulence, mode interactions with like helicities lead to
+transfer of energy and magnetic helicity to smaller wavenumbers. However, some
+interactions of modes with unlike helicities also contribute to an inverse
+energy transfer. As such, an inverse energy cascade for nonhelical magnetic
+fields is shown to be possible. Furthermore, it is found that high values of
+the cross-helicity may have an asymmetric effect on forward and reverse
+transfer of energy, where forward transfer is more quenched in regions of high
+cross-helicity than reverse transfer. This conforms with recent observations of
+solar wind turbulence. For specific helical interactions the relation to dynamo
+action is established.",1508.05528v2
+2015-11-05,Spinor Bose-Einstein gases,"In a spinor Bose-Einstein gas, the non-zero hyperfine spin of the gas becomes
+an accessible degree of freedom. At low temperature, such a gas shows both
+magnetic and superfluid order, and undergoes both density and spin dynamics.
+These lecture notes present a general overview of the properties of spinor
+Bose-Einstein gases. The notes are divided in five sections. In the first, we
+summarize basic properties of multi-component quantum fluids, focusing on the
+specific case of spinor Bose-Einstein gases and the role of rotational symmetry
+in defining their properties. Second, we consider the magnetic state of a
+spinor Bose-Einstein gas, highlighting effects of thermodynamics and
+Bose-Einstein statistics and also of spin-dependent interactions between atoms.
+In the third section, we discuss methods for measuring the properties of
+magnetically ordered quantum gases and present newly developed schemes for
+spin-dependent imaging. We then discuss the dynamics of spin mixing in which
+the spin composition of the gas evolves through the spin-dependent interactions
+within the gas. We discuss spin mixing first from a microscopic perspective,
+and then advance to discussing collective and beyond-mean-field dynamics. The
+fifth section reviews recent studies of the magnetic excitations of
+quantum-degenerate spinor Bose gases. We conclude with some perspectives on
+future directions for research.",1511.01575v1
+2016-09-02,Abnormal oscillation modes in a waning light bridge,"A sunspot acts as a waveguide in response to the dynamics of the solar
+interior; the trapped waves and oscillations could reveal its thermal and
+magnetic structures.
+  We study the oscillations in a sunspot intruded by a light bridge, the
+details of the oscillations could reveal the fine structure of the magnetic
+topology.
+  We use the Solar Dynamics Observatory/Atmospheric Imaging Assembly data to
+analyse the oscillations in the emission intensity of light bridge plasma at
+different temperatures and investigate their spatial distributions.
+  The extreme ultraviolet emission intensity exhibits two persistent
+oscillations at five-minute and sub-minute ranges. The spatial distribution of
+the five-minute oscillation follows the spine of the bridge; whereas the
+sub-minute oscillations overlap with two flanks of the bridge. Moreover, the
+sub-minute oscillations are highly correlated in spatial domain, however, the
+oscillations at the eastern and western flanks are asymmetric with regard to
+the lag time. In the meanwhile, jet-like activities are only found at the
+eastern flank.
+  Asymmetries in forms of oscillatory pattern and jet-like activities
+\textbf{are} found between two flanks of a granular light bridge. Based on our
+study and recent findings, we propose a new model of twisted magnetic field for
+a light bridge and its dynamic interactions with the magnetic field of a
+sunspot.",1609.00596v1
+2016-10-28,Insulating nanomagnets driven by spin torque,"Magnetic insulators, such as yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$), are
+ideal materials for ultra-low power spintronics applications due to their low
+energy dissipation and efficient spin current generation and transmission.
+Recently, it has been realized that spin dynamics can be driven very
+effectively in micrometer-sized Y$_3$Fe$_5$O$_{12}$/Pt heterostructures by
+spin-Hall effects. We demonstrate here the excitation and detection of spin
+dynamics in Y$_3$Fe$_5$O$_{12}$/Pt nanowires by spin-torque ferromagnetic
+resonance. The nanowires defined via electron-beam lithography are fabricated
+by conventional room temperature sputtering deposition on Gd$_3$Ga$_5$O$_{12 }$
+substrates and lift-off. We observe field-like and anti-damping-like torques
+acting on the magnetization precession, which are due to simultaneous
+excitation by Oersted fields and spin-Hall torques. The Y$_3$Fe$_5$O$_{12}$/Pt
+nanowires are thoroughly examined over a wide frequency and power range. We
+observe a large change in the resonance field at high microwave powers, which
+is attributed to a decreasing effective magnetization due to microwave
+absorption. These heating effects are much more pronounced in the investigated
+nanostructures than in comparable micron-sized samples. By comparing different
+nanowire widths, the importance of geometrical confinements for magnetization
+dynamics becomes evident: quantized spin-wave modes across the width of the
+wires are observed in the spectra. Our results are the first stepping stones
+toward the realization of integrated magnonic logic devices based on
+insulators, where nanomagnets play an essential role.",1610.09360v1
+2017-03-13,Quantum kinetic equations for the ultrafast spin dynamics of excitons in diluted magnetic semiconductor quantum wells after optical excitation,"Quantum kinetic equations of motion for the description of the exciton spin
+dynamics in II-VI diluted magnetic semiconductor quantum wells with laser
+driving are derived. The model includes the magnetic as well as the nonmagnetic
+carrier-impurity interaction, the Coulomb interaction, Zeeman terms, and the
+light-matter coupling, allowing for an explicit treatment of arbitrary
+excitation pulses. Based on a dynamics-controlled truncation scheme,
+contributions to the equations of motion up to second order in the generating
+laser field are taken into account. The correlations between the carrier and
+the impurity subsystems are treated within the framework of a correlation
+expansion. For vanishing magnetic field, the Markov limit of the quantum
+kinetic equations formulated in the exciton basis agrees with existing theories
+based on Fermi's golden rule. For narrow quantum wells excited at the $1s$
+exciton resonance, numerical quantum kinetic simulations reveal pronounced
+deviations from the Markovian behavior. In particular, the spin decays
+initially with approximately half the Markovian rate and a non-monotonic decay
+in the form of an overshoot of up to $10\,\%$ of the initial spin polarization
+is predicted.",1703.04435v3
+2017-03-03,Correlations and dynamics of spins in an XY-like spin-glass (Ni0.4Mn0.6)TiO3 single crystal system,"Elastic and inelastic neutron scattering (ENS and INS) experiments were
+performed on a single crystal of (Ni0.4Mn0.6)TiO3 (NMTO) to study the spatial
+correlations and dynamics of spins in the XY-like spin-glass (SG) state.
+Magnetization measurements reveal signatures of SG behavior in NMTO with a
+freezing temperature of TSG ~ 9.1 K. The ENS experiments indicated that the
+intensity of magnetic diffuse scattering starts to increase around 12 K, which
+is close to TSG. Also, spin-spin correlation lengths (zeta) at 1.5 K are
+approximately (21) and (73) angstrom in the interlayer and the in-plane
+directions, respectively, demonstrating that magnetic correlations in NMTO
+exhibit quasi two-dimensional antiferromagnetic order. In addition, critical
+exponent (beta) is determined to be 0.37 from the intensity of magnetic diffuse
+scattering confirms the XY-like SG state of NMTO. INS results show
+quasi-elastic neutron scattering (QENS) profiles below TSG. The life-time of
+dynamic correlations obtained from the half width at half maximum of the
+Lorentzian QENS profiles, are approximately 16 and 16 ps at 10 K for two
+positions (0.00, 0.00, 1.52) and (0.01, 0.01, 1.50), respectively. Therefore,
+our experimental findings demonstrate that short-range-ordered
+antiferromagnetic clusters with short-lived spin correlations are present in
+the XY-like SG state of NMTO.",1703.09773v1
+2017-04-02,Electron-magnetohydrodynamic simulations of electron scale current sheet dynamics in the Vineta.II guide field reconnection experiment,"Three dimensional electron-magnetohydrodynamic (EMHD) simulations of electron
+current sheet dynamics in a background of stationary and unmagnetized ions and
+the subsequent generation of electromagnetic fluctuations are carried out. The
+physical parameters and initial magnetic configuration in the simulations are
+chosen to be similar to those in the \textsc{Vineta}.II magnetic reconnection
+experiment. Consistent with the experimental results, our 3D EMHD simulations
+show the formation of an elongated electron scale current sheet together with
+the excitation of electromagnetic fluctuations within this sheet. The
+fluctuations in the simulations are generated by an electron shear flow
+instability growing on the in-plane (perpendicular to the direction of the main
+current in the sheet) electron shear flow (or current) developed during the
+current sheet evolution. Similar to the experiments, the magnetic field
+fluctuations perpendicular to the guide magnetic field exhibit a broadband
+frequency spectrum following a power law and a positive correlation with the
+axial current density. Although the experimental results show that ions
+influence the spectral properties of the fluctuations, the simulations suggest
+that the electron dynamics, even in the absence of ion motion, primarily
+determines the formation of the current sheet and the generation of
+electromagnetic fluctuations observed in the experiments.",1704.00287v2
+2018-04-10,"Effects of a strong magnetic field on internal gravity waves: trapping, phase mixing, reflection and dynamical chaos","The spectrum of oscillation modes of a star provides information not only
+about its material properties (e.g. mean density), but also its symmetries.
+Spherical symmetry can be broken by rotation and/or magnetic fields. It has
+been postulated that strong magnetic fields in the cores of some red giants are
+responsible for their anomalously weak dipole mode amplitudes (the ""dipole
+dichotomy"" problem), but a detailed understanding of how gravity waves interact
+with strong fields is thus far lacking. In this work, we attack the problem
+through a variety of analytical and numerical techniques, applied to a
+localised region centred on a null line of a confined axisymmetric magnetic
+field which is approximated as being cylindrically symmetric. We uncover a rich
+variety of phenomena that manifest when the field strength exceeds a critical
+value, beyond which the symmetry is drastically broken by the Lorentz force.
+When this threshold is reached, the spatial structure of the g-modes becomes
+heavily altered. The dynamics of wave packet propagation transitions from
+regular to chaotic, which is expected to fundamentally change the organisation
+of the mode spectrum. In addition, depending on their frequency and the
+orientation of field lines with respect to the stratification, waves impinging
+on different parts of the magnetised region are found to undergo either
+reflection or trapping. Trapping regions provide an avenue for energy loss
+through Alfven wave phase mixing. Our results may find application in various
+astrophysical contexts, including the dipole dichotomy problem, the solar
+interior, and compact star oscillations.",1804.03664v1
+2018-04-26,Large voltage tuning of Dzyaloshinskii-Moriya Interaction: a route towards dynamic control of skyrmion chirality,"Electric control of magnetism is a prerequisite for efficient and low power
+spintronic devices. More specifically, in heavy metal/ ferromagnet/ insulator
+heterostructures, voltage gating has been shown to locally and dynamically tune
+magnetic properties like interface anisotropy and saturation magnetization.
+However, its effect on interfacial Dzyaloshinskii-Moriya Interaction (DMI),
+which is crucial for the stability of magnetic skyrmions, has been challenging
+to achieve and has not been reported yet for ultrathin films. Here, we
+demonstrate 130% variation of DMI with electric field in Ta/FeCoB/TaOx
+trilayers through Brillouin Light Spectroscopy (BLS). Using polar-
+Magneto-Optical-Kerr-Effect microscopy, we further show a monotonic variation
+of DMI and skyrmionic bubble size with electric field, with an unprecedented
+efficiency. We anticipate through our observations that a sign reversal of DMI
+with electric field is possible, leading to a chirality switch. This dynamic
+manipulation of DMI establishes an additional degree of control to engineer
+programmable skyrmion based memory or logic devices.",1804.09955v2
+2018-08-23,Relativity and Synchrotron Radiation: Critical Reexamination of Existing Theory,"Maxwell's equations are valid only in Lorentz frame i.e. in inertial frame
+where the Einstein synchronization procedure is used to assign values of the
+time coordinate. Einstein time order must be applied and kept in consistent way
+in both dynamics and electrodynamics. However, the usual for accelerator
+engineering non-covariant treatment of relativistic particle dynamics in a
+constant magnetic field looks precisely the same as in non-relativistic
+Newtonian dynamics. According to both treatments, the magnetic field is only
+capable of altering the direction of motion, but not the speed of an electron.
+However, the non-covariant trajectory does not include relativistic kinematics
+effects. The covariant electron trajectory is viewed from the Lorentz lab frame
+as a result of successive infinitesimal Lorentz transformations. One of the
+consequences of non-commutativity of non-collinear Lorentz boosts is a
+difference between covariant and non-covariant single particle trajectories in
+a constant magnetic field. One can see that this essential point has never
+received attention in the physical community. As a result a correction of the
+conventional radiation theory is required. In this paper we present a critical
+reexamination of existing synchrotron radiation theory. The main emphasis of
+this paper is on spontaneous synchrotron radiation from bending magnets and
+undulators.",1808.07808v1
+2019-02-21,Effects of the removal of Ta capping layer on the magnetization dynamics of Permalloy thin films,"We have investigated the spin wave dynamics of Permalloy (Py) thin films with
+and without a Ta capping layer for varying Py thickness (15 nm, 20 nm and 30
+nm) using all optical time-resolved magneto-optical Kerr effect measurements.
+XPS measurements confirm the oxidation of the originally-prepared samples and
+also that the removal of the Ta capping layer is achievable by a few sputtering
+cycles. The magnetic field strength dependencies of the spin wave modes with
+the variation of the Py film thickness for the samples are studied. We observe
+that the presence of the Ta capping layer reduces the precessional frequencies
+of the samples while the samples without a Ta capping layer enhance the role of
+Py thickness. We also observe that the decay time of spin waves is highly
+dependent on the top layer of the samples. The decay time increases with
+increasing Py thicknesses for Ta/Py/Ta samples implying that the enhancement of
+decay time is caused by the Ta/Py/Ta interfaces. Whereas, for Ta/Py samples the
+decay time decreases with increasing Py thickness. The results of this work
+extend the knowledge on the magnetization dynamics of Py thin films giving
+information on how to resume and even enhance the spin mobility after a
+deleterious oxidation process. This can open new scenarios on the building
+process and on the maintenance of fast magnetic switching devices.",1902.07832v1
+2019-03-15,The dynamics of AR 12700 in its early emerging phase I: interchange reconnection,"The emergence of active regions (ARs) leads to various dynamic activities.
+Using high-resolution and long-lasting H$\alpha$ observations from the New
+Vacuum Solar Telescope, we report the dynamics of NOAA AR 12700 in its emerging
+phase on 26 February 2018 in detail. In this AR, constant interchange
+reconnections between emerging fibrils and preexisting ones were detected.
+Driven by the flux emergence, small-scale fibrils observed in H$\alpha$
+wavelength continuously emerged at the center of the AR and reconnected with
+the ambient preexisting fibrils, forming new longer fibrils. We investigate
+three scenarios of such interchange reconnection in two hours. Specially, the
+third scenario of reconnection resulted in the formation of longer fibrils that
+show pronounced rotation motion. To derive the evolution of the magnetic
+structure during the reconnections, we perform nonlinear force-free field
+extrapolations. The extrapolated three-dimensional magnetic fields clearly
+depict a set of almost potential emerging loops, two preexisting flux ropes at
+03:00 UT before the second reconnection scenario, and a set of newly formed
+loops with less twist at 03:48 UT after the third reconnection scenario. All of
+these extrapolated structures are consistent with the fibrils detected in
+H$\alpha$ wavelength. The aforementioned observations and extrapolation results
+suggest that the constant interchange reconnections resulted in that the
+magnetic twist was redistributed from preexisting flux ropes towards the
+newly-formed system with longer magnetic structure and weaker twist.",1903.06352v1
+2019-10-02,Stability and dynamics of in-plane skyrmions in collinear ferromagnets,"We study the emergence and dynamics of in-plane skyrmions in collinear
+ferromagnetic heterostructures. We present a minimal energy model for this
+class of magnetic textures, determine the crystal symmetries compatible with it
+and propose material candidates, based on symmetries only, for the observation
+of these topological solitons. We calculate exact solutions of the energy model
+for in-plane skyrmions in the absence of dipolar interactions at critical
+coupling, the latter defined by the relations $H = K$ and $D = \sqrt{AK}$ for
+the strength of the external magnetic field and the Dzyaloshinskii coupling
+constant, respectively, with $K$ and $A$ being the anisotropy constant and the
+exchange stiffness of the material. Through micromagnetic simulations, we
+demonstrate the possibility of in-plane skyrmion production via i) the motion
+of domain walls through a geometrical constriction and ii) shedding from a
+magnetic impurity driven both by spin-transfer torques. In-plane skyrmion
+dynamics triggered by spin-orbit torques are also investigated analytically and
+numerically. Our findings point towards the possibility of designing racetracks
+for in-plane skyrmions, whose speed could be tuned by adjusting the angle
+between the charge current and the uniform background magnetization; in
+particular, the speed is maximum for currents parallel to the easy axis and
+becomes zero for currents transverse to it.",1910.00987v2
+2019-11-23,Dynamics of interacting particle systems: Modeling implications of the repulsive interactions and experiments on magnetic prototypes,"In this work, we investigate the dynamics of interacting particle systems
+subjected to repulsive forces, such as lattices of magnetized particles. To
+this end, we first develop a general model capable of capturing the complete
+dynamical behavior of interacting particle systems governed by arbitrary
+potentials. The model elucidates the important role played by the static
+repulsive forces exchanged between particles in the initial equilibrium
+configuration, which is distilled and mathematically captured by a dedicated
+component of the stiffness matrix. The implications of the model are then
+examined through the simple illustrative example of a magnetic particle
+oscillator, by which we show that the effect associated with the initial static
+forces is germane to two- or higher-dimensional particle systems and vanishes
+for 1D chains. In the context of wave propagation, we show that this type of
+effect manifests as modal-selective corrections of the dispersion relation of
+2D repulsive lattices. To corroborate these findings, we perform laser
+vibrometry experiments on a lattice prototype consisting of a triangular grid
+of magnets supported by an elastic foundation of thin pillars. The tests
+unequivocally confirm the emergence of distinctive dispersive regimes in
+quantitative accordance to the model.",1911.10410v3
+2020-04-08,Spin dynamics and a nearly continuous magnetic phase transition in an entropy-stabilized oxide antiferromagnet,"The magnetic order and the spin dynamics in the antiferromagnetic
+entropy-stabilized oxide (Mg$_{0.2}$Co$_{0.2}$Ni$_{0.2}$Cu$_{0.2}$Zn$_{0.2}$)O
+(MgO-ESO) have been studied using muon spin relaxation ($\mu$SR) and inelastic
+neutron scattering. We find that antiferromagnetic order develops gradually in
+the sample volume as it is cooled below 140 K, becoming fully ordered around
+100 K. The spin dynamics show a critical slowing down in the vicinity of the
+transition, and the magnetic order parameter grows continuously in the ordered
+state. These results indicate that the antiferromagnetic transition is
+continuous but proceeds with a Gaussian distribution of ordering temperatures.
+The magnetic contribution to the specific heat determined from inelastic
+neutron scattering likewise shows a broad feature centered around 120 K.
+High-resolution inelastic neutron scattering further reveals an initially
+gapped spectrum at low temperature which sees an increase in a quasielastic
+contribution upon heating until the ordering temperature.",2004.04218v2
+2020-08-31,Dynamic State Analysis of a Driven Magnetic Pendulum using Ordinal Partition Networks and Topological Data Analysis,"The use of complex networks for time series analysis has recently shown to be
+useful as a tool for detecting dynamic state changes for a wide variety of
+applications. In this work, we implement the commonly used ordinal partition
+network to transform a time series into a network for detecting these state
+changes for the simple magnetic pendulum. The time series that we used are
+obtained experimentally from a base-excited magnetic pendulum apparatus, and
+numerically from the corresponding governing equations.The magnetic pendulum
+provides a relatively simple, non-linear example demonstrating transitions from
+periodic to chaotic motion with the variation of system parameters. For our
+method, we implement persistent homology, a shape measuring tool from
+Topological Data Analysis (TDA), to summarize the shape of the resulting
+ordinal partition networks as a tool for detecting state changes. We show that
+this network analysis tool provides a clear distinction between periodic and
+chaotic time series. Another contribution of this work is the successful
+application of the networks-TDA pipeline, for the first time, to signals from
+non-autonomous nonlinear systems. This opens the door for our approach to be
+used as an automatic design tool for studying the effect of design parameters
+on the resulting system response. Other uses of this approach include fault
+detection from sensor signals in a wide variety of engineering operations.",2009.02149v1
+2020-09-18,Floquet dynamical quantum phase transition in the extended XY model: nonadiabatic to adiabatic topological transition,"We investigate both pure and mixed states Floquet dynamical quantum phase
+transition (DQPT) in the periodically time-dependent extended XY model. We
+exactly show that the proposed Floquet Hamiltonian of interacting spins can be
+expressed as a sum of noninteracting quasi-spins imposed by an effective time
+dependent magnetic field (Schwinger-Rabi model). The calculated Chern number
+indicates that there is a topological transition from nonadiabatic to adiabatic
+regime. In the adiabatic regime, the quasi-spins trace the time dependent
+effective magnetic field and then oscillate between spin up and down states.
+While in the nonadiabatic regime, the quasi-spins cannot follow the time
+dependent effective magnetic field and feel an average magnetic field. We find
+the range of driving frequency over which the quasi-spins experience adiabatic
+cyclic processes. Moreover, we obtain the exact expression of the Loschmidt
+amplitude and generalized Loschmidt amplitude of the proposed Floquet system.
+The results represent that both pure and mixed states dynamical phase
+transition occurs when the system evolves adiabatically. In other words, the
+minimum required driving frequency for the appearance of Floquet DQPT is equal
+to the threshold frequency needed for transition from nonadiabatic to adiabatic
+regime.",2009.09008v1
+2020-10-15,Spin injection characteristics of Py/graphene/Pt by gigahertz and terahertz magnetization dynamics driven by femtosecond laser pulse,"Spin transport characteristics of graphene has been extensively studied so
+far. The spin transport along c-axis is however reported by rather limited
+number of papers. We have studied spin transport characteristics through
+graphene along c-axis with permalloy(Py)/graphene(Gr)/Pt by gigahertz (GHz) and
+terahertz (THz) magnetization dynamics driven by femtosecond laser pulses. The
+relatively simple sample structure does not require electrodes on the sample.
+The graphene layer was prepared by chemical vapor deposition and transferred on
+Pt film. The quality of graphene layer was characterized by Raman microscopy.
+Time resolved magneto-optical Kerr effect is used to characterize gigahertz
+magnetization dynamics. Magnetization precession is clearly observed both for
+Pt/Py and Pt/Gr/Py. The Gilbert damping constant of Pt/Py was 0.015, indicates
+spin pumping effect from Py to Pt. The Gilbert damping constant of Pt/Gr/Py is
+found to be 0.011, indicates spin injection is blocked by graphene layer. We
+have also performed the measurement of THz emission for Pt/Py and Pt/Gr/Py.
+While the THz emission is clearly observed for Pt/Py, a strong reduction of THz
+emission is observed for Pt/Gr/Py. With these two different experiments, and
+highly anisotropic resistivity of graphite, we conclude that the vertical spin
+transport is strongly suppressed by the graphene layer.",2010.07694v1
+2020-11-18,Domain Wall Motion in Magnetic Nanostrips,"Domain walls are the transition regions between two magnetic domains. These
+objects have been very relevant during the last decade, not only due to their
+intrinsic interest in the development of novel spintronics devices but also
+because of their fundamental interest. The study of domain wall has been linked
+to the research on novel spin-orbit coupling phenomena such as the
+Dzyaloshinskii-Moriya interaction and the spin Hall effect amount others.
+Domain walls can be nucleated in ferromagnetic nanostrips and can be driven by
+conventional magnetic fields and spin currents due to the injection of
+electrical pulses, which make them very promising for technological
+applications of recording and logic devices. In this review, based on full
+micromagnetic simulations supported by extended one-dimensional models, we
+describe the static and dynamic properties of domain walls in thin
+ferromagnetic and ferrimagnetic wires with perpendicular magnetic anisotropy.
+The present chapter aims to provide a fundamental theoretical description of
+the fundaments of domain walls, and the numerical tools and models which allow
+describing the DW dynamics in previous and future experimental setups.",2011.09423v2
+2020-12-08,Stable and unstable trajectories in a dipolar chain,"In classical mechanics, solutions can be classified according to their
+stability. Each of them is part of the possible trajectories of the system.
+However, the signatures of unstable solutions are hard to observe in an
+experiment, and most of the times if the experimental realization is adiabatic,
+they are considered just a nuisance. Here we use a small number of XY magnetic
+dipoles subject to an external magnetic field for studying the origin of their
+collective magnetic response. Using bifurcation theory we have found all the
+possible solutions being stable or unstable, and explored how those solutions
+are naturally connected by points where the symmetries of the system are lost
+or restored. Unstable solutions that reveal the symmetries of the system are
+found to be the culprit that shape hysteresis loops in this system. The
+complexity of the solutions for the nonlinear dynamics is analyzed using the
+concept of boundary basin entropy, finding that the damping time scale is
+critical for the emergence of fractal structures in the basins of attraction.
+Furthermore, we numerically found domain wall solutions that are the smallest
+possible realizations of transverse walls and vortex walls in magnetism. We
+experimentally confirmed their existence and stability showing that our system
+is a suitable platform to study domain wall dynamics at the macroscale.",2012.04173v1
+2020-12-14,Homologous flaring activity over a sunspot light bridge in an emerging active region,"Sunspot light bridges are known to exhibit a variety of dynamic and
+persistent phenomena such as surges, small-scale jets etc. in the chromosphere
+and transition region. While it has generally been proposed that magnetic
+reconnection is responsible for this small-scale dynamism, persistent flaring
+activity lasting several hours from the same spatial location on a sunspot
+light bridge, has rarely been reported. We combine observations from the
+Atmospheric Imaging Assembly and the Helioseismic Magnetic Imager on board the
+Solar Dynamics Observatory to investigate homologous flaring activity over a
+small sunspot light bridge in an emerging flux region. The homologous flares
+all produced broad, collimated jets, including a B6.4 class flare. The jets
+rise at a speed of about 200 km/s, reach projected heights of about 98 Mm, and
+emerge from the same spatial location for nearly 14 hrs, after which they cease
+completely. A non-linear force free extrapolation of the photospheric magnetic
+field shows a low-lying flux rope connecting the light bridge to a remote
+opposite-polarity network. The persistent flares occur as a result of the rapid
+horizontal motion of the leading sunspot that causes the relatively vertical
+magnetic fields in the adjacent umbra to reconnect with the low-lying flux rope
+in the light bridge. Our results indicate that the flaring ceases once the flux
+rope has lost sufficient twist through repeated reconnections.",2012.07454v1
+2021-03-30,Photoinduced Transient States of Antiferromagnetic Orderings in La${}_{1/3}$Sr${}_{2/3}$FeO${}_{3}$ and SrFeO${}_{3}$ Thin Films Observed through Time-resolved Resonant Soft X-ray Scattering,"The relationship between the magnetic interaction and photoinduced dynamics
+in antiferromagnetic perovskites is investigated in this study. In
+La${}_{1/3}$Sr${}_{2/3}$FeO${}_{3}$ thin films, commensurate spin ordering is
+accompanied by charge disproportionation, whereas SrFeO${}_{3}$ thin films show
+incommensurate helical antiferromagnetic spin ordering due to increased
+ferromagnetic coupling compared to La${}_{1/3}$Sr${}_{2/3}$FeO${}_{3}$. To
+understand the photoinduced spin dynamics in these materials, we investigate
+the spin ordering through time-resolved resonant soft X-ray scattering. In
+La${}_{1/3}$Sr${}_{2/3}$FeO${}_{3}$, ultrafast quenching of the magnetic
+ordering within 130 fs through a nonthermal process is observed, triggered by
+charge transfer between the Fe atoms. We compare this to the photoinduced
+dynamics of the helical magnetic ordering of SrFeO${}_{3}$. We find that the
+change in the magnetic coupling through optically induced charge transfer can
+offer an even more efficient channel for spin-order manipulation.",2103.16038v1
+2021-03-30,Magnetic Fluctuations in Gyrokinetic Simulations of Tokamak Scrape-Off Layer Turbulence,"Understanding turbulent transport physics in the tokamak edge and scrape-off
+layer (SOL) is critical to developing a successful fusion reactor. The dynamics
+in these regions plays a key role in achieving high fusion performance by
+determining the edge pedestal that suppresses turbulence in H-mode.
+Additionally, the survivability of a reactor is set by the heat load to the
+vessel walls, making it important to understand turbulent spreading of heat as
+it flows along open magnetic field lines in the SOL. Large-amplitude
+fluctuations, magnetic X-point geometry, and plasma interactions with material
+walls make simulating turbulence in the edge/SOL more challenging than in the
+core region, necessitating specialized gyrokinetic codes. Further, the
+inclusion of electromagnetic effects in gyrokinetic simulations that can handle
+the unique challenges of the boundary plasma is critical to the understanding
+of phenomena such as the pedestal and ELMs, for which electromagnetic dynamics
+are expected to be important.
+  In this thesis, we develop the first capability to simulate electromagnetic
+gyrokinetic turbulence on open magnetic field lines. This is an important step
+towards comprehensive electromagnetic gyrokinetic simulations of the coupled
+edge/SOL system. By using a continuum full-f approach via an energy-conserving
+discontinuous Galerkin (DG) discretization scheme that avoids the Ampere
+cancellation problem, we show that electromagnetic fluctuations can be handled
+in a robust, stable, and efficient manner in the gyrokinetic module of the
+Gkeyll code. We then present results which roughly model the scrape-off layer
+of the National Spherical Torus Experiment (NSTX), and show that
+electromagnetic effects can affect blob dynamics and transport. We also
+formulate the gyrokinetic system in field-aligned coordinates for modeling
+realistic edge and scrape-off layer geometries in experiments.",2103.16062v1
+2021-06-09,Spin dynamics slowdown near the antiferromagnetic critical point in atomically thin FePS3,"Two-dimensional (2D) magnetic materials have attracted much recent interest
+with unique properties emerging at the few-layer limit. Beyond the reported
+impacts on the static magnetic properties, the effects of reducing the
+dimensionality on the magnetization dynamics are also of fundamental interest
+and importance for 2D device development. In this report, we investigate the
+spin dynamics in atomically-thin antiferromagnetic FePS3 of varying layer
+numbers using ultrafast pump-probe spectroscopy. Following the absorption of an
+optical pump pulse, the time evolution of the antiferromagnetic order parameter
+is probed by magnetic linear birefringence. We observe a strong divergence in
+the demagnetization time near the N\'eel temperature. The divergence can be
+characterized by a power-law dependence on the reduced temperature, with an
+exponent decreasing with sample thickness. We compare our results to
+expectations from critical slowing down and a two-temperature model involving
+spins and phonons, and discuss the possible relevance of spin-substrate phonon
+interactions.",2106.05159v1
+2021-06-23,Alignment of the magnetic field in star forming regions and why it might be difficult to observe,"Magnetic fields are an important component of the interstellar medium (ISM)
+and exhibit strongly varying field strengths and a non-trivial correlation with
+the gas density. Its dynamical impact varies between individual regions of the
+ISM and correlates with the orientation of the field with respect to the gas
+structures. Using high-resolution magneto-hydrodynamical simulations of the ISM
+we explore the connection between the orientation of the field and the
+dynamical state of the gas. We find that the onset of gravitational instability
+in molecular gas above a density of $\rho\sim10^{-21}\,\mathrm{g\,cm^{-3}}$
+$(n\sim400\,\mathrm{cm^{-3}})$ coincides with an alignment of the magnetic
+field lines and the gas flow. At this transition the gradient of the density
+changes from mainly perpendicular to preferentially parallel to the field
+lines. A connection between the three-dimensional alignment and projected
+two-dimensional observables is non-trivial, because of a large dispersion of
+the magnetic field orientation along the line of sight. The turbulent
+correlation lengths can be small compared to the typical integration lengths.
+As a consequence the small scale signal of the orientation can sensitively
+depend on the line of sight or the dynamical state of the cloud, can fluctuate
+stochastically or be completely averaged out. With higher spatial resolution
+more small scale structures are resolved, which aggravates the link between
+magneto-hydrodynamical quantities and projected observables.",2106.12596v3
+2021-06-25,"Ultraviolet Line Profiles of Slowly Rotating Massive Star Winds Using the ""Analytic Dynamical Magnetosphere"" Formalism","Recent large-scale spectropolarimetric surveys have established that a small
+but significant percentage of massive stars host stable, surface dipolar
+magnetic fields with strengths on the order of kG. These fields channel the
+dense, radiatively driven stellar wind into circumstellar magnetospheres, whose
+density and velocity structure can be probed using ultraviolet (UV)
+spectroscopy of wind-sensitive resonance lines. Coupled with appropriate
+magnetosphere models, UV spectroscopy provides a valuable way to investigate
+the wind-field interaction, and can yield quantitative estimates of the wind
+parameters of magnetic massive stars. We report a systematic investigation of
+the formation of UV resonance lines in slowly rotating magnetic massive stars
+with dynamical magnetospheres. We pair the Analytic Dynamical Magnetosphere
+(ADM) formalism with a simplified radiative transfer technique to produce
+synthetic UV line profiles. Using a grid of models, we examine the effect of
+magnetosphere size, the line strength parameter, and the cooling parameter on
+the structure and modulation of the line profile. We find that magnetic massive
+stars uniquely exhibit redshifted absorption at most viewing angles and
+magnetosphere sizes, and that significant changes to the shape and variation of
+the line profile with varying line strengths can be explained by examining the
+individual wind components described in the ADM formalism. Finally, we show
+that the cooling parameter has a negligible effect on the line profiles.",2106.13676v1
+2021-07-23,Generalized Bloch model: a theory for pulsed magnetization transfer,"Purpose: The paper introduces a classical model to describe the dynamics of
+large spin-1/2 ensembles associated with nuclei bound in large molecule
+structures, commonly referred to as the semi-solid spin pool, and their
+magnetization transfer (MT) to spins of nuclei in
+  Theory and Methods: Like quantum-mechanical descriptions of spin dynamics and
+like the original Bloch equations, but unlike existing MT models, the proposed
+model is based on the algebra of angular momentum in the sense that it
+explicitly models the rotations induced by radio-frequency (RF) pulses. It
+generalizes the original Bloch model to non-exponential decays, which are,
+e.g., observed for semi-solid spin pools. The combination of rotations with
+non-exponential decays is facilitated by describing the latter as Green's
+functions, comprised in an integro-differential equation.
+  Results: Our model describes the data of an inversion-recovery
+magnetization-transfer experiment with varying durations of the inversion pulse
+substantially better than established models. We made this observation for all
+measured data, but in particular for pulse durations small than 300$\mu$s.
+Furthermore, we provide a linear approximation of the generalized Bloch model
+that reduces the simulation time by approximately a factor 15,000, enabling
+simulation of the spin dynamics caused by a rectangular RF-pulse in roughly
+2$\mu$s.
+  Conclusion: The proposed theory unifies the original Bloch model, Henkelman's
+steady-state theory for magnetization transfer, and the commonly assumed
+rotation induced by hard pulses (i.e., strong and infinitesimally short
+applications of RF fields) and describes experimental data better than previous
+models.",2107.11000v3
+2022-10-04,Terahertz electric-field driven dynamical multiferroicity in SrTiO$_3$,"The emergence of collective order in matter is among the most fundamental and
+intriguing phenomena in physics. In recent years, the ultrafast dynamical
+control and creation of novel ordered states of matter not accessible in
+thermodynamic equilibrium is receiving much attention. Among those, the
+theoretical concept of dynamical multiferroicity has been introduced to
+describe the emergence of magnetization by means of a time-dependent electric
+polarization in non-ferromagnetic materials. In simple terms, a large amplitude
+coherent rotating motion of the ions in a crystal induces a magnetic moment
+along the axis of rotation. However, the experimental verification of this
+effect is still lacking. Here, we provide evidence of room temperature
+magnetization in the archetypal paraelectric perovskite SrTiO$_3$ due to this
+mechanism. To achieve it, we resonantly drive the infrared-active soft phonon
+mode with intense circularly polarized terahertz electric field, and detect a
+large magneto-optical Kerr effect. A simple model, which includes two coupled
+nonlinear oscillators whose forces and couplings are derived with ab-initio
+calculations using self-consistent phonon theory at a finite temperature,
+reproduces qualitatively our experimental observations on the temporal and
+frequency domains. A quantitatively correct magnitude of the effect is obtained
+when one also considers the phonon analogue of the reciprocal of the Einsten -
+de Haas effect, also called the Barnett effect, where the total angular
+momentum from the phonon order is transferred to the electronic one. Our
+findings show a new path for designing ultrafast magnetic switches by means of
+coherent control of lattice vibrations with light.",2210.01690v1
+2022-11-17,Delayed Hopf bifurcation and control of a ferrofluid interface via a time-dependent magnetic field,"A ferrofluid droplet confined in a Hele-Shaw cell can be deformed into a
+stably spinning ``gear,'' using crossed magnetic fields. Previously, fully
+nonlinear simulation revealed that the spinning gear emerges as a stable
+traveling wave along the droplet's interface bifurcates from the trivial
+(equilibrium) shape. In this work, a center manifold reduction is applied to
+show the geometrical equivalence between a two-harmonic-mode coupled system of
+ordinary differential equations arising from a weakly nonlinear analysis of the
+interface shape and a Hopf bifurcation. The rotating complex amplitude of the
+fundamental mode saturates to a limit circle as the periodic traveling wave
+solution is obtained. An amplitude equation is derived from a
+multiple-time-scale expansion as a reduced model of the dynamics. Then,
+inspired by the well-known delay behavior of time-dependent Hopf bifurcations,
+we design a slowly time-varying magnetic field such that the timing and
+emergence of the interfacial traveling wave can be controlled. The proposed
+theory allows us to determine the time-dependent saturated state resulting from
+the dynamic bifurcation and delayed onset of instability. The amplitude
+equation also reveals hysteresis-like behavior upon time reversal of the
+magnetic field. The state obtained upon time reversal differs from the state
+obtained during the initial (forward-time) period, yet it can still be
+predicted by the proposed reduced-order theory.",2211.09758v3
+2023-09-20,Magic Angle Spinning Effects on Longitudinal NMR Relaxation: 15N in L-Histidine,"Solid-state magnetic resonance is a unique technique that can reveal the
+dynamics of complex biological systems with atomic resolution. Longitudinal
+relaxation is a mechanism that returns longitudinal nuclear magnetization to
+its thermal equilibrium by incoherent processes. The measured longitudinal
+relaxation rate constant however represents the combination of both incoherent
+and coherent contributions to the change of nuclear magnetization. This work
+demonstrates the effect of magic angle spinning rate on the longitudinal
+relaxation rate constant in two model compounds: L-histidine hydrochloride
+monohydrate and glycine serving as proxies for isotopically-enriched biological
+materials. Most notably, it is demonstrated that the longitudinal 15N
+relaxation of the two nitrogen nuclei in the imidazole ring in histidine is
+reduced by almost three orders of magnitude at the condition of rotational
+resonance with the amine, while the amine relaxation rate constant is increased
+at these conditions. The observed phenomenon may have radical implications for
+the solid-state magnetic resonance in biophysics and materials, especially in
+the proper measurement of dynamics and as a selective serial transfer step in
+dynamic nuclear polarization.",2310.03029v3
+2023-12-01,Volkov solutions for relativistic magnetized plasma in strong field quantum electrodynamics regime,"This study shows the dynamics of relativistic electrons in terms of Dirac
+equation solutions when an ultra-intense short laser pulse of intensity $\ge
+10^{23} {W.cm^{-2}}$ propagates through magnetized dense plasma ($B_0\approx
+{1MG})$. The interaction dynamics is analyzed near the strong-field quantum
+electrodynamics (SF-QED) regime. Our study finds new solutions in plasma media
+considering the effects of the re-normalized mass of relativistic electrons and
+the nonzero effective mass of accelerated photons. We have provided a general
+method for constructing exact solutions of the Dirac relativistic equation that
+correctly explains the dynamics of electrons in the strongly magnetized plasma
+medium. The modified solutions of the Dirac equation for one electron are
+derived and compared to the Volkov solutions. The new solutions are a basis for
+a feasible explanation of quantum attributes of relativistic electrons in a
+strong electromagnetic field of very short ultra-intense laser pulses with
+intensity near Schwinger field intensity. The solutions are called new Volkov
+solutions in a plasma medium. These solutions can be used to understand better
+the theory of quantum radiation reaction for the next-generation laser-plasma
+accelerator. Our results show that the Volkov solutions are not applicable in a
+magnetized plasma medium",2312.00493v1
+2024-02-01,"Element-specific and high-bandwidth ferromagnetic resonance spectroscopy with a coherent, extreme ultraviolet (EUV) source","We developed and applied a tabletop, ultrafast, high-harmonic generation
+(HHG) source to measure the element-specific ferromagnetic resonance (FMR) in
+ultra-thin magnetic alloys and multilayers on an opaque Si substrate. We
+demonstrate a continuous wave bandwidth of 62 GHz, with promise to extend to
+100 GHz or higher. This laboratory-scale instrument detects the FMR using
+ultrafast, extreme ultraviolet (EUV) light, with photon energies spanning the
+M-edges of most relevant magnetic elements. An RF frequency comb generator is
+used to produce a microwave excitation that is intrinsically synchronized to
+the EUV pulses with a timing jitter of 1.4 ps or better. We apply this system
+to measure the dynamics in a multilayer system as well as Ni-Fe and Co-Fe
+alloys. Since this instrument operates in reflection-mode, it is a milestone
+toward measuring and imaging the dynamics of the magnetic state and spin
+transport of active devices on arbitrary and opaque substrates. The higher
+bandwidth also enables measurements of materials with high magnetic anisotropy,
+as well as ferrimagnets, antiferromagnets, and short-wavelength (high
+wavevector) spinwaves in nanostructures or nanodevices. Furthermore, the
+coherence and short wavelength of the EUV will enable extending these studies
+using dynamic nanoscale lensless imaging techniques such as coherent
+diffractive imaging, ptychography, and holography.",2402.00783v1
+2024-03-16,Nonequilibrium tricritical behaviour in anisotropic XY ferromagnet driven by elliptically polarised propagating magnetic field wave,"Three dimensional anisotropic XY ferromagnet driven by elliptically polarized
+propagating magnetic field wave has been extensively investigated by Monte
+Carlo simulation with Metropolis single spin flip algorithm. Both the effects
+of the bilinear exchange type and the single site anisotropies are thoroughly
+investigated. The time average magnetisation (over the complete cycle of the
+elliptically polarized propagating magnetic field wave) components play the
+role of dynamic order parameter. For fixed set of values of the strength of
+anisotropy and the field amplitudes, the system has been found to get
+dynamically ordered at a pseudocritical temperature. The pseudocritical
+temperature of such dynamic nonequilibrium phase transition has been found to
+depend on both the strength of anisotropy and the amplitudes of the
+elliptically polarized propagating magnetic field wave. A comprehensive phase
+diagram is represented here in the form of image plot of the pseudocritical
+temperature in the plane formed by the strength of anisotropy and field
+amplitudes. Interestingly, this nonequilibrium phase transition has been found
+discontinuous (first order) for higher values of the field amplitude and lower
+values of the anisotropy. On the other hand, the continuous (second order)
+transition has been noticed for lower values of the field amplitude and higher
+values of the anisotropy.",2403.10975v2
+1999-03-02,Dynamics of Vortices in Two-Dimensional Magnets,"Theories, simulations and experiments on vortex dynamics in
+quasi-two-dimensional magnetic materials are reviewed. These materials can be
+modelled by the classical two-dimensional anisotropic Heisenberg model with XY
+(easy-plane) symmetry. There are two types of vortices, characterized by their
+polarization (a second topological charge in addition to the vorticity): Planar
+vortices have Newtonian dynamics (even-order equations of motion) and exhibit
+strong discreteness effects, while non-planar vortices have non-Newtonian
+dynamics (odd-order equations of motion) and smooth trajectories. The influence
+of thermal fluctuations on single vortices is investigated. Different types of
+noise and damping are discussed and implemented into the microscopic equations
+which yields stochastic equations of motion for the vortices. The solutions of
+the these equations are compared with Langevin dynamics simulations. Moreover,
+noise-induced transitions between opposite polarizations of a vortex are
+investigated. For temperatures above the Kosterlitz-Thouless vortex-antivortex
+unbinding transition, a phenomenological theory, namely the vortex gas
+approach, yields central peaks in the dynamic form factors for the spin
+correlations. Such peaks are observed both in combined Monte Carlo- and Spin
+Dynamics-Simulations and in inelastic neutron scattering experiments. However,
+the assumption of ballistic vortex motion appears questionable.",9903037v1
+2014-06-26,Blume-Capel model on cylindrical Ising nanowire with core/shell structure: Existence of a dynamic compensation temperatures,"We present a study, within a mean-field approach, of the kinetics of the
+spin-1 Blume-Capel model on cylindrical Ising nanowire in the presence of a
+time-dependent oscillating external magnetic field. We employ the Glauber
+transition rates to construct the mean-field dynamical equations. We
+investigate the thermal behavior of the dynamic order parameters. From these
+studies, we obtain the dynamic phase transition (DPT) points. Then, we study
+the temperature dependence of the dynamic total magnetization to find the
+dynamic compensation points as well as to determine the type of behavior. We
+also investigate the effect of a crystal-field interaction and the exchange
+couplings between the nearest-neighbor pairs of spins on the compensation
+phenomenon and construct the phase diagrams in four different planes. The
+dynamic phase diagrams contain paramagnetic (P), ferromagnetic (F), the
+antiferromagnetic (AF), and two coexistence or mixed phase regions, namely, the
+F + P and AF + P that strongly depend on interaction parameters. The system
+also exhibits the compensation temperatures, or the N-, P-, Q-, S- type
+behaviors. Furthermore, we also observed two compensation temperatures, namely
+W-type behaviors, which this result is compared with some experimental works
+and a good overall agreement is found.",1406.6926v1
+2017-04-10,Majorana dynamical mean-field study of spin dynamics at finite temperatures in the honeycomb Kitaev model,"A prominent feature of quantum spin liquids is fractionalization of the spin
+degree of freedom. Fractionalized excitations have their own dynamics in
+different energy scales, and hence, affect finite-temperature ($T$) properties
+in a peculiar manner even in the paramagnetic state harboring the quantum spin
+liquid state. We here present a comprehensive theoretical study of the spin
+dynamics in a wide $T$ range for the Kitaev model on a honeycomb lattice, whose
+ground state is such a quantum spin liquid. In this model, the
+fractionalization occurs to break up quantum spins into itinerant matter
+fermions and localized gauge fluxes, which results in two crossovers at very
+different $T$ scales. Extending the previous study for the isotropic coupling
+case [J. Yoshitake, J. Nasu, and Y. Motome, Phys. Rev. Lett. ${\textbf 117}$,
+157203 (2016)], we calculate the dynamical spin structure factor, the NMR
+relaxation rate, and the magnetic susceptibility while changing the anisotropy
+in the exchange coupling constants, by using the dynamical mean-field theory
+and the continuous-time quantum Monte Carlo method based on a Majorana fermion
+representation. We find that the system exhibits peculiar behaviors below the
+high-$T$ crossover whose temperature is comparable to the average of the
+exchange constants, reflecting the spin fractionalization in the paramagnetic
+region. Among them, the dichotomy between the static and dynamical spin
+correlations is unusual behavior hardly seen in conventional magnets. We
+discuss the relation between the dichotomy and the spatial configuration of
+gauge fluxes. Our results could stimulate further experimental and theoretical
+analyses of candidate materials for the Kitaev quantum spin liquids.",1704.02707v1
+2019-01-03,High Performance Direct-Current Generator Based on Dynamic PN Junctions,"After the electromagnetic generator, searching for novel electric generators
+without strong magnetic field is highly demanded. The generator without strong
+magnetic field calls for a physical picture distinct from the traditional
+generators. As the counterpart of the static PN junction has been widely used
+in the integrated circuits, we develop an electric generator named dynamic PN
+generator with a high current density and voltage output, which converts
+mechanical energy into electricity by sliding two semiconductors with different
+Fermi level. A dynamic N-GaAs/SiO2/P-Si generator with the open-circuit voltage
+of 3.1 V and short-circuit density of 1.0 A/m2 have been achieved. The physical
+mechanism of the dynamic PN generator is proposed based on the built-in
+electric field bounding back diffusing carriers in dynamic PN junctions, which
+breaks the equilibrium between drift and diffusion current in the PN junction.
+Moreover, the dynamic MoS2/AlN/Si generator with the open-circuit voltage of
+5.1 V and short-circuit density of 112 A/m2 (11.2 mA/cm2) have also been
+achieved, which can effectively output a direct-current and light up a blue
+light-emitting diode directly. This dynamic MoS2/AlN/Si generator can
+continuously work for hours without obvious degradation, demonstrating its
+unique mechanism and potential applications in many fields where the mechanical
+energy is available.",1901.00701v1
+2019-06-19,Large dynamical axion field in topological antiferromagnetic insulator Mn$_2$Bi$_2$Te$_5$,"The dynamical axion field is a new state of quantum matter where the
+magnetoelectric response couples strongly to its low-energy magnetic
+fluctuations. It is fundamentally different from an axion insulator with a
+static quantized magnetoelectric response. The dynamical axion field exhibits
+many exotic phenomena such as axionic polariton and axion instability. However,
+these effects have not been experimentally confirmed due to the lack of proper
+topological magnetic materials. Here by combining analytic models and
+first-principles calculations, we predict a series of van der Waal layered
+Mn$_2$Bi$_2$Te$_5$-related topological antiferromagnetic materials could host
+the long-sought dynamical axion field with a topological origin. We also show a
+large dynamical axion field can be achieved in antiferromagnetic insulating
+states close to the topological phase transition. We further propose the
+optical and transport experiments to detect such a dynamical axion field. Our
+results could directly aid and facilitate the search for topological-origin
+large dynamical axion field in realistic materials.",1906.07891v3
+2021-09-23,Dynamics in an exact solvable quantum magnet: benchmark for quantum computer,"Quantum magnets are never short of novel and fascinating dynamics, yet its
+simulation by classical computers requires exponentially-scaled computation
+resources, which renders the research on large-scale many-body dynamics
+fiendishly difficult. In this letter, we explore the dynamic behavior of 2D
+large-scale ferromagnetic J1-J2 Heisenberg model both theoretically and
+experimentally. First, the analytical solution of magnon dynamics is obtained
+to show an obvious ballistic propagation of magnon, which is typical for
+quantum walk. Then, we verify the dynamic behavior of the system through
+numerical approach of exact diagonalization and tensor network method. We also
+calculate out-of-time ordered correlators and butterfly velocities among
+different lattice points, finding that they can well depict the competition
+between different couplings. Finally, a quantum walk experiment is designed and
+conducted on the basis of IBM programmable quantum processors, and the
+experimental results are in consistence with our theoretical predictions. Since
+the analytical results can be used, in principle, to predict the behavior of
+large-scale quantum many-body systems and even those infinitely large, this
+work will help facilitate further research on quantum walk and quantum
+many-body dynamics in large-scale lattice systems, guide future design of
+quantum computers, as well as popularize quantum computers until they are known
+and available to every household in the world.",2109.11371v5
+2023-08-23,State-transition dynamics of resting-state functional magnetic resonance imaging data: Model comparison and test-to-retest analysis,"Electroencephalogram (EEG) microstate analysis entails finding dynamics of
+quasi-stable and generally recurrent discrete states in multichannel EEG time
+series data and relating properties of the estimated state-transition dynamics
+to observables such as cognition and behavior. While microstate analysis has
+been widely employed to analyze EEG data, its use remains less prevalent in
+functional magnetic resonance imaging (fMRI) data, largely due to the slower
+timescale of such data. In the present study, we extend various data clustering
+methods used in EEG microstate analysis to resting-state fMRI data from healthy
+humans to extract their state-transition dynamics. We show that the quality of
+clustering is on par with that for various microstate analyses of EEG data. We
+then develop a method for examining test-retest reliability of the
+discrete-state transition dynamics between fMRI sessions and show that the
+within-participant test-retest reliability is higher than between-participant
+test-retest reliability for different indices of state-transition dynamics,
+different networks, and different data sets. This result suggests that
+state-transition dynamics analysis of fMRI data could discriminate between
+different individuals and is a promising tool for performing fingerprinting
+analysis of individuals.",2308.11910v2
+2023-08-24,Dynamics of quantum spin-nematics: Comparisons with canted antiferromagnets,"The identification of spin-nematic states is challenging due to the absence
+of Bragg peaks. However, the study of dynamical physical quantities provides a
+promising avenue for characterizing these states. In this study, we investigate
+the dynamical properties of spin-nematic states in three-dimensional quantum
+spin systems in a magnetic field, using a two-component boson theory that
+incorporates magnons and bi-magnons. Our particular focus lies on the dynamical
+spin structure factor at zero temperature and the nuclear magnetic resonance
+(NMR) relaxation rate at finite temperatures. Our findings reveal that the
+dynamical structure factor does not exhibit any diverging singularity across
+momentum and frequency while providing valuable information about the form
+factor of bi-magnon states and the underlying structure of spin-nematic order.
+Furthermore, we find a temperature dependence in the NMR relaxation rate
+proportional to $T^3$ at low temperatures, similar to canted antiferromagnets.
+A clear distinction arises as there is no critical divergence of the NMR
+relaxation rate at the spin-nematic transition temperature. Our theoretical
+framework provides a comprehensive understanding of the excitation spectrum and
+the dynamical properties of spin-nematic states, covering arbitrary spin values
+$S$ and encompassing site and bond nematic orders. Additionally, we apply the
+same methodology to analyze these dynamical quantities in a canted
+antiferromagnetic state and compare the results with those in the spin-nematic
+states.",2308.12569v2
+1994-07-21,The Dynamics of Flux Tubes in a High Beta Plasma,"We suggest a new model for the structure of a magnetic field embedded high
+$\beta$ turbulent plasma, based on the popular notion that the magnetic field
+will tend to separate into individual flux tubes. We point out that
+interactions between the flux tubes will be dominated by coherent effects
+stemming from the turbulent wakes created as the fluid streams by the flux
+tubes. Balancing the attraction caused by shielding effects with turbulent
+diffusion we find that flux tubes have typical radii comparable to the local
+Mach number squared times the large scale eddy length, are arranged in a one
+dimensional fractal pattern, have a radius of curvature comparable to the
+largest scale eddies in the turbulence, and have an internal magnetic pressure
+comparable to the ambient pressure. When the average magnetic energy density is
+much less than the turbulent energy density the radius, internal magnetic field
+and curvature scale of the flux tubes will be smaller than these estimates.
+Realistic resistivity does not alter the macroscopic properties of the fluid or
+the large scale magnetic field. In either case we show that the Sweet-Parker
+reconnection rate is much faster than an eddy turnover time. Realistic stellar
+plasmas are expected to either be in the ideal limit (e.g. the solar
+photosphere) or the resistive limit (most of the solar convection zone). All
+current numerical simulations of three dimensional MHD turbulence are in the
+viscous regime and are inapplicable to stars or accretion disks.",9407063v1
+1997-08-15,Instability of toroidal magnetic field in jets and plerions,"Jets and pulsar-fed supernova remnants (plerions) tend to develop highly
+organized toroidal magnetic field. Such a field structure could explain the
+polarization properties of some jets, and contribute to their lateral
+confinement. A toroidal field geometry is also central to models for the Crab
+Nebula - the archetypal plerion - and leads to the deduction that the Crab
+pulsar's wind must have a weak magnetic field. Yet this `Z-pinch' field
+configuration is well known to be locally unstable, even when the magnetic
+field is weak and/or boundary conditions slow or suppress global modes. Thus,
+the magnetic field structures imputed to the interiors of jets and plerions are
+unlikely to persist.
+  To demonstrate this, I present a local analysis of Z-pinch instabilities for
+relativistic fluids in the ideal MHD limit. Kink instabilities dominate,
+destroying the concentric field structure and probably driving the system
+toward a more chaotic state in which the mean field strength is independent of
+radius (and in which resistive dissipation of the field may be enhanced). I
+estimate the timescales over which the field structure is likely to be
+rearranged and relate these to distances along relativistic jets and radii from
+the central pulsar in a plerion.
+  I conclude that a concentric toroidal field is unlikely to exist well outside
+the Crab pulsar's wind termination shock. There is thus no dynamical reason to
+conclude that the magnetic energy flux carried by the pulsar wind is much
+weaker than the kinetic energy flux. Abandoning this inference would resolve a
+long-standing puzzle in pulsar wind theory.",9708142v1
+2003-01-22,Understanding Helical Magnetic Dynamo Spectra with a Nonlinear Four-Scale Theory,"Recent MHD dynamo simulations for magnetic Prandtl number $>1$ demonstrate
+that when MHD turbulence is forced with sufficient kinetic helicity, the
+saturated magnetic energy spectrum evolves from having a single peak below the
+forcing scale to become doubly peaked with one peak at the system (=largest)
+scale and one at the forcing scale. The system scale field growth is well
+modeled by a recent nonlinear two-scale nonlinear helical dynamo theory in
+which the system and forcing scales carry magnetic helicity of opposite sign.
+But a two-scale theory cannot model the shift of the small-scale peak toward
+the forcing scale. Here I develop a four-scale helical dynamo theory which
+shows that the small-scale helical magnetic energy first saturates at very
+small scales, but then successively saturates at larger values at larger
+scales, eventually becoming dominated by the forcing scale. The transfer of the
+small scale peak to the forcing scale is completed by the end of the kinematic
+growth regime of the large scale field, and does not depend on magnetic
+Reynolds number $R_M$ for large $R_M$. The four-scale and two-scale theories
+subsequently evolve almost identically, and both show significant field growth
+on the system and forcing scales that is independent of $R_M$. In the present
+approach, the helical and nonhelical parts of the spectrum are largely
+decoupled. Implications for fractionally helical turbulence are discussed.",0301432v2
+2003-05-22,Polarization of prompt GRB emission: evidence for electromagnetically-dominated outflow,"Observations by the {\RHESSI} satellite of large polarization of the prompt
+$\gamma$-ray emission from the Gamma Ray Burst GRB021206 \citep{coburn03} imply
+that the magnetic field coherence scale is larger than the size of the visible
+emitting region, $\sim R/\Gamma$, where $R$ is the radius of the flow, $\Gamma$
+is the associated Lorentz factor.
+  Such fields cannot be generated in a causally disconnected, hydrodynamically
+dominated outflow. Electromagnetic models of GRBs \citep{lyutikov02}, in which
+large scale, dynamically dominant, magnetic fields are present in the outflow
+from the very beginning, provide a natural explanation of this large reported
+linear polarization. We derive Stokes parameters of synchrotron emission of a
+relativistically moving plasma with a given magnetic field configuration and
+calculate the pulse averaged polarization fraction of the emission from a
+relativistically expanding shell carrying global toroidal magnetic field. For
+viewing angles larger than $1/\Gamma$ the observed patch of the emitting shell
+has almost homogeneous magnetic field, producing a large fractional
+polarization ($56% $ for a power-law energy distribution of relativistic
+particles $dn/d\epsilon \propto \epsilon^{-3}$). The maximum polarization is
+smaller than the theoretical upper limit for a stationary plasma in uniform
+magnetic field due to relativistic kinematic effects.",0305410v2
+2003-07-16,Magnetohydrodynamical Accretion Flows: Formation of Magnetic Tower Jet and Subsequent Quasi-Steady State,"We present three-dimensional (3-D) magnetohydrodynamical (MHD) simulations of
+radiatively inefficient accretion flow around black holes. General relativistic
+effects are simulated by using the pseudo-Newtonian potential. We start
+calculations with a rotating torus threaded by localized poloidal magnetic
+fields with plasma beta, a ratio of the gas pressure to the magnetic pressure,
+$\beta =10$ and 100. When the bulk of torus material reaches the innermost
+region close to a central black hole, a magnetically driven jet emerges. This
+magnetic jet is derived by vertically inflating toroidal fields (`magnetic
+tower') and has a two-component structure: low-$\beta$ ($\lsim 1$) plasmas
+threaded with poloidal (vertical) fields are surrounded by that with toroidal
+fields. The collimation width of the jet depends on external pressure, pressure
+of ambient medium; the weaker the external pressure is, the wider and the
+longer-lasting becomes the jet. Unless the external pressure is negligible, the
+bipolar jet phase ceases after several dynamical timescales at the original
+torus position and a subsequent quasi-steady state starts. The black hole is
+surrounded by quasi-spherical zone with highly inhomogeneous structure in which
+toroidal fields are dominant except near the rotation axis. Mass accretion
+takes place mainly along the equatorial plane. Comparisons with other MHD
+simulation results and observational implications are discussed.",0307306v2
+2003-10-24,Synthetic Observations of Simulated Radio Galaxies I: Radio and X-ray Analysis,"We present an extensive synthetic observational analysis of numerically-
+simulated radio galaxies designed to explore the effectiveness of conventional
+observational analyses at recovering physical source properties. These are the
+first numerical simulations with sufficient physical detail to allow such a
+study. The present paper focuses on extraction of magnetic field properties
+from nonthermal intensity information. Synchrotron and inverse-Compton
+intensities provided meaningful information about distributions and strengths
+of magnetic fields, although considerable care was called for. Correlations
+between radio and X-ray surface brightness correctly revealed useful dynamical
+relationships between particles and fields. Magnetic field strength estimates
+derived from the ratio of X-ray to radio intensity were mostly within about a
+factor of two of the RMS field strength along a given line of sight. When
+emissions along a given line of sight were dominated by regions close to the
+minimum energy/equipartition condition, the field strengths derived from the
+standard power-law-spectrum minimum energy calculation were also reasonably
+close to actual field strengths, except when spectral aging was evident.
+Otherwise, biases in the minimum- energy magnetic field estimation mirrored
+actual differences from equipartition. The ratio of the inverse-Compton
+magnetic field to the minimum-energy magnetic field provided a rough measure of
+the actual total energy in particles and fields in most instances, within an
+order of magnitude. This may provide a practical limit to the accuracy with
+which one may be able to establish the internal energy density or pressure of
+optically thin synchrotron sources.",0310719v1
+2003-12-01,"Magnetic Braking in Differentially Rotating, Relativistic Stars","We study the magnetic braking and viscous damping of differential rotation in
+incompressible, uniform density stars in general relativity. Differentially
+rotating stars can support significantly more mass in equilibrium than
+nonrotating or uniformly rotating stars. The remnant of a binary neutron star
+merger or supernova core collapse may produce such a ""hypermassive"" neutron
+star. Although a hypermassive neutron star may be stable on a dynamical
+timescale, magnetic braking and viscous damping of differential rotation will
+ultimately alter the equilibrium structure, possibly leading to delayed
+catastrophic collapse. Here we consider the slow-rotation, weak-magnetic field
+limit in which E_rot << E_mag << W, where E_rot is the rotational kinetic
+energy, E_mag is the magnetic energy, and W is the gravitational binding energy
+of the star. We assume the system to be axisymmetric and solve the MHD
+equations in both Newtonian gravitation and general relativity. Toroidal
+magnetic fields are generated whenever the angular velocity varies along the
+initial poloidal field lines. We find that the toroidal fields and angular
+velocities oscillate independently along each poloidal field line, which
+enables us to transform the original 2+1 equations into 1+1 form and solve them
+along each field line independently. The incoherent oscillations on different
+field lines stir up turbulent-like motion in tens of Alfven timescales (""phase
+mixing""). In the presence of viscosity, the stars eventually are driven to
+uniform rotation, with the energy contained in the initial differential
+rotation going into heat. Our evolution calculations serve as qualitative
+guides and benchmarks for future, more realistic MHD simulations in full 3+1
+general relativity.",0312038v1
+2004-04-06,Estimating galaxy cluster magnetic fields by the classical and hadronic minimum energy criterion,"We wish to estimate magnetic field strengths of radio emitting galaxy
+clusters by minimising the non-thermal energy density contained in cosmic ray
+electrons (CRe), protons (CRp), and magnetic fields. The classical minimum
+energy estimate can be constructed independently of the origin of the radio
+synchrotron emitting CRe yielding thus an absolute minimum of the non-thermal
+energy density. Provided the observed synchrotron emission is generated by a
+CRe population originating from hadronic interactions of CRp with the ambient
+thermal gas of the intra-cluster medium, the parameter space of the classical
+scenario can be tightened by means of the hadronic minimum energy criterion.
+For both approaches, we derive the theoretically expected tolerance regions for
+the inferred minimum energy densities. Application to the radio halo of the
+Coma cluster and the radio mini-halo of the Perseus cluster yields
+equipartition between cosmic rays and magnetic fields within the expected
+tolerance regions. In the hadronic scenario, the inferred central magnetic
+field strength ranges from 2.4 muG (Coma) to 8.8 muG (Perseus), while the
+optimal CRp energy density is constrained to 2% +/- 1% of the thermal energy
+density (Perseus). We discuss the possibility of a hadronic origin of the Coma
+radio halo while current observations favour such a scenario for the Perseus
+radio mini-halo. Combining future expected detections of radio synchrotron,
+hard X-ray inverse Compton, and hadronically induced gamma-ray emission should
+allow an estimate of volume averaged cluster magnetic fields and provide
+information about their dynamical state.",0404119v2
+2005-04-04,Amplification of Interstellar Magnetic Fields and Turbulent Mixing by Supernova-Driven Turbulence Part II - The Role of Dynamical Chaos,"In this paper we further advance the study of magnetic field amplification in
+the interstellar medium that was started in Balsara et al (2004, Paper I). We
+show that the flux growth rate is comparable to the rate of magnetic energy
+growth found in Paper I. We also demonstrate the role of intermittency in field
+amplification. The density shows a double-peaked PDF, consistent with the
+cooling curve that was used. The PDF of the magnetic field shows a high-end
+tail, providing a tell-tale signature of the operation of the small scale
+dynamo. The magnetic field strength correlates positively with the density. As
+a result, the field amplification takes place more vigorously in the lower
+temperature, denser gas. The Lagrangian chaos in the simulated turbulent flows
+is studied in substantial detail. It is shown that the stretching rate of
+material lines as well as the Lyapunov exponents can be used to gain important
+insights into the growth of magnetic field. The cancellation exponent for the
+small scale supernova-driven dynamo is derived and it is shown that
+constructive folding of field lines in the dynamo is very inefficient. We also
+show that our Lagrangian approach can yield actual measures of the turbulent
+diffusivity in the simulated ISM. The turbulent diffusivity provides insights
+into the mixing of elements from supernova ejecta on macroscopic scales. The
+high rates of line stretching in interstellar turbulence suggests that the
+eventual diffusion of elements at the molecular level is very efficient. Many
+of the diagnostics of turbulence that are presented here can be used to make
+direct connections between simulations and observations.",0504065v1
+2005-12-16,The Double Helix Nebula: a magnetic torsional wave propagating out of the Galactic centre,"Radioastronomical studies have indicated that the magnetic field in the
+central few hundred parsecs of our Milky Way Galaxy has a dipolar geometry and
+a strength substantially larger than elsewhere in the Galaxy, with estimates
+ranging up to a milligauss. A strong, large-scale magnetic field can affect the
+Galactic orbits of molecular clouds by exerting a drag on them, it can inhibit
+star formation, and it can guide a wind of cosmic rays away from the central
+region, so a characterization of the magnetic field at the Galactic center is
+important for understanding much of the activity there. Here, we report Spitzer
+Space Telescope observations of an unprecedented infrared nebula having the
+morphology of an intertwined double helix. This feature is located about 100 pc
+from the Galaxy's dynamical centre toward positive Galactic latitude, and its
+axis is oriented perpendicular to the Galactic plane. The observed segment is
+about 25 pc in length, and contains about 1.25 full turns of each of the two
+continuous, helically wound strands. We interpret this feature as a torsional
+Alfven wave propagating vertically away from the Galactic disk, driven by
+rotation of the magnetized circumnuclear gas disk. As such, it offers a new
+morphological probe of the Galactic center magnetic field. The direct
+connection between the circumnuclear disk and the double helix is ambiguous,
+but the MSX images show a possible meandering channel that warrants further
+investigation.",0512452v1
+2006-01-11,"Turbulence, magnetic fields and plasma physics in clusters of galaxies","Observations of galaxy clusters show that the intracluster medium (ICM) is
+likely to be turbulent and is certainly magnetized. The properties of this
+magnetized turbulence are determined both by fundamental nonlinear
+magnetohydrodynamic interactions and by the plasma physics of the ICM, which
+has very low collisionality. Cluster plasma threaded by weak magnetic fields is
+subject to firehose and mirror instabilities. These saturate and produce
+fluctuations at the ion gyroscale, which can scatter particles, increasing the
+effective collision rate and, therefore, the effective Reynolds number of the
+ICM. A simple way to model this effect is proposed. The model yields a
+self-accelerating fluctuation dynamo whereby the field grows explosively fast,
+reaching the observed, dynamically important, field strength in a fraction of
+the cluster lifetime independent of the exact strength of the seed field. It is
+suggested that the saturated state of the cluster turbulence is a combination
+of the conventional isotropic magnetohydrodynamic turbulence, characterized by
+folded, direction-reversing magnetic fields and an Alfv\'en-wave cascade at
+collisionless scales. An argument is proposed to constrain the reversal scale
+of the folded field. The picture that emerges appears to be in qualitative
+agreement with observations of magnetic fields in clusters.",0601246v2
+2006-04-03,A Revised Prescription for the Tayler-Spruit Dynamo: Magnetic Angular Momentum Transport in Stars,"Angular momentum transport by internal magnetic fields is an important
+ingredient for stellar interior models. In this paper we critically examine the
+basic heuristic assumptions in the model of the Tayler-Spruit dynamo, which
+describes how a pinch-type instability of a toroidal magnetic field in
+differentially rotating stellar radiative zones may result in large-scale fluid
+motion. We agree with prior published work both on the existence of the
+instability and its nearly horizontal geometry for perturbations. However, the
+approximations in the original Acheson dispersion relation are valid only for
+small length scales, and we disagree that the dispersion relation can be
+extrapolated to horizontal length scales of order the radius of the star. We
+contend that dynamical effects, in particular angular momentum conservation,
+limit the maximum horizontal length scale. We therefore present transport
+coefficients for chemical mixing and angular momentum redistribution by
+magnetic torques that are significantly different from previous published
+values. The new magnetic viscosity is reduced by 2 to 3 orders of magnitude
+compared to the old one, and we find that magnetic angular momentum transport
+by this mechanism is very sensitive to gradients in the mean molecular weight.
+The revised coefficients are more compatible with empirical constraints on the
+timescale of core-envelope coupling in young stars than the previous ones.
+However, solar models including only this mechanism possess a rapidly rotating
+core, in contradiction with helioseismic data. (abridged)",0604045v2
+2006-04-04,Which jet launching mechanism(s) in TTauri stars?,"AIMS: We examine whether ejection phenomena from accreting T Tauri stars can
+be described by only one type of self-collimated jet model. METHODS: We present
+analytical kinematic predictions valid soon after the Alfv\'en surface for all
+types of steady magnetically self-confined jets. RESULTS: We show that extended
+disc winds, X-winds, and stellar winds occupy distinct regions in the poloidal
+speed vs. specific angular momentum plane. Comparisons with current
+observations of T Tauri jets yield quantitative constraints on the range of
+launching radii, magnetic lever arms, and specific energy input in disc and
+stellar winds. Implications on the origin of jet asymmetries and disc magnetic
+fields are outlined. CONCLUSIONS: We argue that ejection phenomena from
+accreting T Tauri stars most likely include three dynamical components: (1) an
+outer self-collimated steady disc wind carrying most of the mass-flux in the
+optical jet (when present), confining (2) a pressure-driven coronal stellar
+wind and (3) a hot inner flow made of blobs sporadically ejected from the
+magnetopause. If the stellar magnetic moment is parallel to the disc magnetic
+field, then the highly variable inner flow resembles a ""Reconnection X-wind"",
+that has been proven to efficiently brake down an accreting and contracting
+young star. If the magnetic moment is anti-parallel, then larger versions of
+the solar coronal mass ejections are likely to occur. The relative importance
+of these three components in the observed outflows and the range of radii
+involved in the disc wind are expected to vary with time, from the stage of
+embedded source to the optically revealed T Tauri star phase.",0604053v1
+2006-05-24,Synchrotron emission in small scale magnetic field as possible explanation for prompt emission spectra of gamma-ray bursts,"Synchrotron emission is believed to be a major radiation mechanism during
+gamma-ray bursts' (GRBs) prompt emission phase. A significant drawback of this
+assumption is that the theoretical predicted spectrum, calculated within the
+framework of the ``internal shocks'' scenario using the standard assumption
+that the magnetic field maintains a steady value throughout the shocked region,
+leads to a slope F_\nu \propto \nu^{-1/2} below 100 keV, which is in
+contradiction to the much harder spectra observed. This is due to the electrons
+cooling time being much shorter than the dynamical time. In order to overcome
+this problem, we propose here that the magnetic field created by the internal
+shocks decays on a length scale much shorter than the comoving width of the
+plasma. We show that under this assumption synchrotron radiation can reproduce
+the observed prompt emission spectra of the majority of the bursts. We
+calculate the required decay length of the magnetic field, and find it to be
+\~10^4 - 10^5 cm (equivalent to 10^5 - 10^6 skin depths), much shorter than the
+characteristic comoving width of the plasma, ~3*10^{9} cm. We implement our
+model to the case of GRB050820A, where a break at <~ 4 keV was observed, and
+show that this break can be explained by synchrotron self absorption. We
+discuss the consequences of the small scale magnetic field scenario on current
+models of magnetic field generation in shock waves.",0605641v2
+2006-11-09,Grain Alignment and Polarized Emission from Magnetized T Tauri Disks,"The structure of magnetic fields within protostellar disks may be studied via
+polarimetry provided that grains are aligned in respect to magnetic field
+within the disks. We explore alignment of dust grains by radiative torque in T
+Tauri disks and provide predictions for polarized emission for disks viewed at
+different wavelengths and viewing angles. We show that the alignment is
+especially efficient in outer part of the disks. In the presence of magnetic
+field, these aligned grains produce polarized emission in infrared wavelengths.
+We consider a simple model of an accretion disk and provide predictions for
+polarization that should be available to both instruments that do not resolve
+the disks and future instruments that will resolve the disks. As the surface
+magnetic field and the bulk magnetic field play different roles for the disk
+dynamics, we consider separately the contributions that arises from the surface
+areas of the disk and its interior. We find that the polarized emission drops
+for wavelengths shorter than $\sim 10 \mu m$. Between $\sim 10 \mu m$ and $\sim
+100 \mu m$, the polarized emission is dominated by the emission from the
+surface layer of the disks and the degree of polarization can be as large as
+$\sim 10%$ for unresolved disks. The degree of polarization is around 2-3 %
+level at wavelengths larger than $\sim100\mu m$.",0611280v2
+2006-11-14,Paramagnetism in color superconductivity and compact stars,"It is quite plausible that color superconductivity occurs in the inner
+regions of neutron stars. At the same time, it is known that strong magnetic
+fields exist in the interior of these compact objects. In this paper we discuss
+some important effects that can occur in the color superconducting core of
+compact stars due to the presence of the stars' magnetic field. In particular,
+we consider the modification of the gluon dynamics for a color superconductor
+with three massless quark flavors in the presence of an external magnetic
+field. We show that the long-range component of the external magnetic field
+that penetrates the color-flavor locked phase produces an instability for field
+values larger than the charged gluons' Meissner mass. As a consequence, the
+ground state is restructured forming a vortex state characterized by the
+condensation of charged gluons and the creation of magnetic flux tubes. In the
+vortex state the magnetic field outside the flux tubes is equal to the applied
+one, while inside the tubes its strength increases by an amount that depends on
+the amplitude of the gluon condensate. This paramagnetic behavior of the color
+superconductor can be relevant for the physics of compact stars.",0611460v2
+2007-01-21,Cosmological magnetic fields from nonlinear effects,"In the standard cosmological model, magnetic fields and vorticity are
+generated during the radiation era via second-order density perturbations. In
+order to clarify the complicated physics of this second-order magnetogenesis,
+we use a covariant approach and present the electromagneto-dynamical equations
+in the nonlinear regime. We use the tight-coupling approximation to analyze
+Thomson and Coulomb scattering. At the zero-order limit of exact
+tight-coupling, we show that the vorticity is zero and no magnetogenesis takes
+place at any nonlinear order. We show that magnetogenesis also fails at all
+orders if either protons or electrons have the same velocity as the radiation,
+and momentum transfer is neglected. Then we prove a key no-go result: at
+first-order in the tight-coupling approximation, magnetic fields and vorticity
+still cannot be generated even via nonlinear effects. The tight-coupling
+approximation must be broken at first order, for the generation of vorticity
+and magnetic fields, and we derive a closed set of nonlinear evolution
+equations that governs this generation. We estimate that the amplitude of the
+magnetic field at recombination on the horizon scale is $\sim 10^{-27} $G.",0701596v2
+2007-02-20,Polarization of the Crab Nebula with disordered magnetic components,"In this paper, we present an expanding disc model to derive polarization
+properties of the Crab nebula. The distribution function of the plasma and the
+energy density of the magnetic field are prescribed as function of the distance
+from the pulsar by using the model by Kennel and Coroniti (1984) with $\sigma =
+0.003$, where $\sigma$ is the ratio of Poynting flux to the kinetic energy flux
+in the bulk motion just before the termination shock. Unlike previous models,
+we introduce disordered magnetic field, which is parameterized by the
+fractional energy density of the disordered component. Flow dynamics is not
+solved. The mean field is toroidal. Averaged polarization degree over the disc
+is obtained as a function of inclination angle and fractional energy density of
+the disordered magnetic field. It is found for the Crab that the disordered
+component has about 60 percent of the magnetic field energy. This value is also
+supported by the facts that the disc appears not `lip-shape' but as `rings' in
+the intensity map as was observed, and that the highest polarization degree of
+$\sim 40$ percent is reproduced for rings, being consistent with the
+observation. We suggest that because the disordered field contributes rather
+pressure than tension, the pinch force may be over-estimated in previous
+relativistic magnetohydrodynamic simulations. Disruption of the toroidal
+magnetic field with alternating direction, which is proposed by Lyubarski
+(2003), may actually takes place. The relativistic flow speed, which is
+indicated by the front-back contrast, can be detected in asymmetry in
+distributions of the position angle and depolarization.",0702512v2
+1994-12-02,Statistical Mechanics of Nonuniform Magnetization Reversal,"The magnetization reversal rate via thermal creation of soliton pairs in
+quasi-1D ferromagnetic systems is calculated. Such a model describes e.g. the
+time dependent coercivity of elongated particles as used in magnetic recording
+media. The energy barrier that has to be overcome by thermal fluctuations
+corresponds to a soliton-antisoliton pair whose size depends on the external
+field. In contrast to other models of first order phase transitions such as the
+phi^4 model, an analytical expression for this energy barrier is found for all
+values of the external field. The magnetization reversal rate is calculated
+using a functional Fokker-Planck description of the stochastic magnetization
+dynamics. Analytical results are obtained in the limits of small fields and
+fields close to the anisotropy field. In the former case the hard-axis
+anisotropy becomes effectively strong and the magnetization reversal rate is
+shown to reduce to the nucleation rate of soliton-antisoliton pairs in the
+overdamped double sine-Gordon model. The present theory therefore includes the
+nucleation rate of soliton-antisoliton pairs in the double sine-Gordon chain as
+a special case. These results demonstrate that for elongated particles, the
+experimentally observed coercivity is significantly lower than the value
+predicted by the standard theories of N\'eel and Brown.",9412010v2
+1996-08-29,Towards a Fermi Liquid Theory of the $ν$=1/2 State : Magnetized Composite Fermions,"The Fermionic Chern-Simons approach has had remarkable success in the
+description of quantum Hall states at even denominator filling fractions
+$\nu=\frac{1}{2m}$. In this paper we review a number of recent works concerned
+with modeling this state as a Landau-Silin Fermi liquid. We will then focus on
+one particular problem with constructing such a Landau theory that becomes
+apparent in the limit of high magnetic field, or equivalently the limit of
+small electron band mass $m_b$. In this limit, the static response of electrons
+to a spatially varying magnetic field is largely determined by kinetic energy
+considerations. We then remedy this problem by attaching an orbital
+magnetization to each fermion to separate the current into magnetization and
+transport contributions, associated with the cyclotron and guiding center
+motions respectively. This leads us to a description of the $\nu=\frac{1}{2m}$
+state as a Fermi liquid of magnetized composite fermions which correctly
+predicts the $m_b$ dependence of the static and dynamic response in the limit
+$m_b \rightarrow 0$. As an aside, we derive a sum rule for the Fermi liquid
+coefficients for the Chern-Simons Fermi liquid. This paper is intended to be
+readable by people who may not be completely familiar with this field.",9608147v1
+1999-11-22,Spectral and transport properties of doped Mott-Hubbard systems with incommensurate magnetic order,"We present spectral and optical properties of the Hubbard model on a
+two-dimensional square lattice using a generalization of dynamical mean-field
+theory to magnetic states in finite dimension. The self-energy includes the
+effect of spin fluctuations and screening of the Coulomb interaction due to
+particle-particle scattering. At half-filling the quasiparticles reduce the
+width of the Mott-Hubbard `gap' and have dispersions and spectral weights that
+agree remarkably well with quantum Monte Carlo and exact diagonalization
+calculations. Away from half-filling we consider incommensurate magnetic order
+with a varying local spin direction, and derive the photoemission and optical
+spectra. The incommensurate magnetic order leads to a pseudogap which opens at
+the Fermi energy and coexists with a large Mott-Hubbard gap. The quasiparticle
+states survive in the doped systems, but their dispersion is modified with the
+doping and a rigid band picture does not apply. Spectral weight in the optical
+conductivity is transferred to lower energies and the Drude weight increases
+linearly with increasing doping. We show that incommensurate magnetic order
+leads also to mid-gap states in the optical spectra and to decreased scattering
+rates in the transport processes, in qualitative agreement with the
+experimental observations in doped systems. The gradual disappearence of the
+spiral magnetic order and the vanishing pseudogap with increasing temperature
+is found to be responsible for the linear resistivity. We discuss the possible
+reasons why these results may only partially explain the features observed in
+the optical spectra of high temperature superconductors.",9911355v1
+2000-02-06,Local magnetic structures induced by inhomogeneities of the lattice in S=1/2 bond-alternating chains and response to time-dependent magnetic field with a random noise,"We study effect of inhomogeneities of the lattice in the S=1/2
+bond-alternating chain by using a quantum Monte Carlo method and an exact
+diagonalization method. We adopt a defect in the alternating order as the
+inhomogeneity and we call it `bond impurity'. Local magnetic structures induced
+by the bond impurities are investigated both in the ground state and at very
+low temperatures. The local magnetic structure can be looked on as an effective
+S=1/2 spin and the weakness of the interaction between the local structures
+causes the quasi-degenerate states in the low energy. We also investigate the
+force acting between bond impurities and find that the force is generally
+attractive. We also study the dynamical property of the local magnetic
+structure. While the local magnetic structure behaves as an isolated S=1/2 spin
+in the response to a time-dependent uniform field, it is found to be robust
+against the effect of a random noise applied at each site individually in the
+sweeping filed.",0002082v2
+2004-08-05,Spectroscopy of spontaneous spin noise as a probe of spin dynamics and magnetic resonance,"Not all noise in experimental measurements is unwelcome. Certain fundamental
+noise sources contain valuable information about the system itself -- a notable
+example being the inherent voltage fluctuations that exist across any resistor
+(Johnson noise), from which temperature may be determined[1,2]. In magnetic
+systems, fundamental noise can exist in the form of random spin
+fluctuations[3,4]. Felix Bloch noted in 1946 that statistical fluctuations of N
+paramagnetic spins should generate measurable noise of order \sqrt{N} spins,
+even in zero magnetic field[5,6]. Here we address precisely these same spin
+fluctuations, using off-resonant Faraday rotation to passively[7,8] ""listen"" to
+the magnetization noise in an equilibrium ensemble of paramagnetic alkali
+atoms. These random fluctuations generate spontaneous spin coherences which
+precess and decay with the same characteristic energy and time scales as the
+macroscopic magnetization of an intentionally polarized or driven ensemble.
+Correlation spectra of the measured spin noise reveals g-factors, nuclear spin,
+isotope abundance ratios, hyperfine splittings, nuclear moments, and spin
+coherence lifetimes -- without having to excite, optically pump, or otherwise
+drive the system away from thermal equilibrium. These noise signatures scale
+inversely with interaction volume, suggesting routes towards non-perturbative,
+sourceless magnetic resonance of small systems.",0408107v1
+2005-12-20,Theory of Spin Torque in a nanomagnet,"We present a complete theory of the spin torque phenomena in a ultrasmall
+nanomagnet coupled to non-collinear ferromagnetic electrodes through tunnelling
+junctions. This model system can be described by a simple microscopic model
+which captures many physical effects characteristic of spintronics: tunneling
+magneto resistance, intrinsic and transport induced magnetic relaxation,
+current induced magnetization reversal and spin accumulation. Treating on the
+same footing the magnetic and transport degrees of freedom, we arrive at a
+closed equation for the time evolution of the magnetization. This equation is
+very close to the Landau-Lifshitz-Gilbert equation used in spin valves
+structures. We discuss how the presence of the Coulomb blockade phenomena and
+the discretization of the one-body spectrum gives some additional features to
+the current induced spin torque. Depending on the regime, the dynamic induced
+by the coupling to electrode can be viewed either as a spin torque or as a
+relaxation process. In addition to the possibility of stabilizing uniform spin
+precession states, we find that the system is highly hysteretic: up to three
+different magnetic states can be simultaneously stable in one region of the
+parameter space (magnetic field and bias voltage).We also discuss how the
+magneto-resistance can be used to provide additional information on the
+non-equilibrium peaks present in the nanomagnet spectroscopy experiments.",0512508v1
+2006-08-29,Collective modes for an array of magnetic dots in the vortex state,"The dispersion relations for collective magnon modes for square-planar arrays
+of vortex-state magnetic dots, having closure magnetic flux are calculated. The
+array dots have no direct contact between each other, and the sole source of
+their interaction is the magnetic dipolar interaction. The magnon formalism
+using Bose operators along with translational symmetry of the lattice, with the
+knowledge of mode structure for the isolated dot, allows the diagonalization of
+the system Hamiltonian giving the dispersion relation. Arrays of vortex-state
+dots show a large variety of collective mode properties, such as positive or
+negative dispersion for different modes. For their description, not only
+dipolar interaction of effective magnetic dipoles, but non-dipolar terms common
+to higher multipole interaction in classical electrodynamics can be important.
+The dispersion relation is shown to be non-analytic as the value of the
+wavevector approaches zero for all dipolar active modes of the single dot. For
+vortex-state dots the interdot interaction is not weak, because, the dynamical
+part (in contrast to the static magnetization of the vortex state) dot does not
+contain the small parameter, the ratio of vortex core size to the dot radius.
+This interaction can lead to qualitative effects like the formation of modes of
+angular standing waves instead of modes with definite azimuthal number known
+for the insolated vortex state dot.",0608638v1
+2004-07-27,Domain wall dynamics driven by adiabatic spin transfer torques,"In a first approximation, known as the adiabatic process, the direction of
+the spin polarization of currents is parallel to the local magnetization vector
+in a domain wall. Thus the spatial variation of the direction of the spin
+current inside the domain wall results in an adiabatical spin transfer torque
+on the magnetization. We show that domain wall motion driven by this spin
+torque has many unique features that do not exist in the conventional wall
+motion driven by a magnetic field. By analytically and numerically solving the
+Landau-Lifshitz-Gilbert equation along with the adiabatic spin torque in
+magnetic nanowires, we find the domain wall has its maximum velocity at the
+initial application of the current but the velocity decreases to zero as the
+domain wall begins to deform during its motion. We have computed domain wall
+displacement and domain wall deformation of nanowires, and concluded that the
+spin torque based on the adiabatic propagation of the spin current in the
+domain wall is unable to maintain wall movement. We also introduce a novel
+concept of domain wall inductance to characterize the capacity of the
+spin-torque induced magnetic energy stored in a domain wall. In the presence of
+domain wall pinning centers, we construct a phase diagram for the domain wall
+depinning by the combined action of the magnetic field and the spin current.",0407064v1
+2006-11-26,A new class of quantum bound states: diprotons in extreme magnetic fields,"This paper considers the possibility that two charged particles with an
+attractive short-ranged potential between them which is not strong enough to
+form bound states in free space, may bind in uniform magnetic fields. It is
+shown that in the formal limit where Coulomb repulsion is negligible (q -> 0
+and B_0 -> \infty with q B_0 fixed where q is the charge and B_0 the field
+strength) there always exists a bound state for a system of two identical
+charged particles in a constant magnetic field, provided that there is a
+short-range uniformly attractive potential between them. Moreover, it is shown
+that in this limit {\it any} potential with an attractive s-wave scattering
+length will posses bound states provided that the range of the potential is
+much smaller than the characteristic magnetic length, r_0 = (\frac{q
+B_0}{4})^{-1/2}. For this case, the binding is computed numerically. We
+estimate the size of the magnetic field needed to approximately reach a regime
+where the formal limit considered becomes a good approximation to the dynamics.
+These numerical estimates indicate that two protons in an extremely strong
+magnetic field such as might be found in a magnetar will bind to form a
+diproton.",0611092v1
+2001-04-23,Axisymmetric equilibria of a gravitating plasma with incompressible flows,"It is found that the ideal magnetohydrodynamic equilibrium of an axisymmetric
+gravitating magnetically confined plasma with incompressible flows is governed
+by a second-order elliptic differential equation for the poloidal magnetic flux
+function containing five flux functions coupled with a Poisson equation for the
+gravitation potential, and an algebraic relation for the pressure. This set of
+equations is amenable to analytic solutions. As an application, the
+magnetic-dipole static axisymmetric equilibria with vanishing poloidal plasma
+currents derived recently by Krasheninnikov, Catto, and Hazeltine [Phys. Rev.
+Lett. {\bf 82}, 2689 (1999)] are extended to plasmas with finite poloidal
+currents, subject to gravitating forces from a massive body (a star or black
+hole) and inertial forces due to incompressible sheared flows. Explicit
+solutions are obtained in two regimes: (a) in the low-energy regime
+$\beta_0\approx \gamma_0\approx \delta_0 \approx\epsilon_0\ll 1$, where
+$\beta_0$, $\gamma_0$, $\delta_0$, and $\epsilon_0$ are related to the thermal,
+poloidal-current, flow and gravitating energies normalized to the
+poloidal-magnetic-field energy, respectively, and (b) in the high-energy regime
+$\beta_0\approx \gamma_0\approx \delta_0 \approx\epsilon_0\gg 1$. It turns out
+that in the high-energy regime all four forces, pressure-gradient,
+toroidal-magnetic-field, inertial, and gravitating contribute equally to the
+formation of magnetic surfaces very extended and localized about the symmetry
+plane such that the resulting equilibria resemble the accretion disks in
+astrophysics.",0104072v1
+2002-05-03,Molecular gyroscopes and biological effects of weak ELF magnetic fields,"Extremely-low-frequency magnetic fields are known to affect biological
+systems. In many cases, biological effects display `windows' in biologically
+effective parameters of the magnetic fields: most dramatic is the fact that
+relatively intense magnetic fields sometimes do not cause appreciable effect,
+while smaller fields of the order of 10--100 $\mu$T do. Linear resonant
+physical processes do not explain frequency windows in this case. Amplitude
+window phenomena suggest a nonlinear physical mechanism. Such a nonlinear
+mechanism has been proposed recently to explain those `windows'. It considers
+quantum-interference effects on protein-bound substrate ions. Magnetic fields
+cause an interference of ion quantum states and change the probability of
+ion-protein dissociation. This ion-interference mechanism predicts specific
+magnetic-field frequency and amplitude windows within which biological effects
+occur. It agrees with a lot of experiments. However, according to the
+mechanism, the lifetime $\Gamma^{-1}$ of ion quantum states within a protein
+cavity should be of unrealistic value, more than 0.01 s for frequency band
+10--100 Hz. In this paper, a biophysical mechanism has been proposed that (i)
+retains the attractive features of the ion interference mechanism and (ii) uses
+the principles of gyroscopic motion and removes the necessity to postulate
+large lifetimes. The mechanism considers dynamics of the density matrix of the
+molecular groups, which are attached to the walls of protein cavities by two
+covalent bonds, i.e., molecular gyroscopes. Numerical computations have shown
+almost free rotations of the molecular gyros. The relaxation time due to van
+der Waals forces was about 0.01 s for the cavity size of 28 angstr\""{o}ms.",0205008v2
+2003-12-11,Magnetically induced anions,"The main focus of this review is on magnetically induced anions. Before
+discussing these new anionic states which exclusively exist in the presence of
+magnetic fields, we review in some detail the anionic physics without external
+field. For completeness, we also outline the properties of field-free existing
+anions when exposed to magnetic fields. The magnetically induced states
+constitute an infinite manifold assuming that the nucleus of the anion is
+infinitely heavy. At laboratory field strengths the corresponding binding
+energies show two different scaling properties belonging to the ground
+($\propto B^2$) and the excited ($\propto B^3$) magnetically induced states. We
+provide a detailed discussion of the physics of the moving anion taking into
+account the coupling between the anionic centre of mass and its electronic
+degrees of freedom. A number of field-adapted techniques exploiting exact
+constants of motion and the adiabatic separation of motions are applied to
+simplify the Hamiltonian that describes the effective interaction between the
+centre of mass and the electronic degrees of freedom. Employing classical
+simulations the autodetachment process of the anions in the field is observed
+and a rich variety of spectral properties of moving anions is predicted:
+depending on the parameters, such as the mass and polarizability of the neutral
+system as well as the field strength, induced bound states, resonances and
+detaching states of the corresponding anions are to be expected. An outline of
+an {\it{ab initio}} quantum approach is provided that allows quantum dynamical
+investigations of the moving anion.",0312076v1
+2006-06-01,In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth's magnetotail,"Magnetic reconnection is one of the most important processes in
+astrophysical, space and laboratory plasmas. Identifying the structure around
+the point at which the magnetic field lines break and subsequently reform,
+known as the magnetic null point, is crucial to improving our understanding
+reconnection. But owing to the inherently three-dimensional nature of this
+process, magnetic nulls are only detectable through measurements obtained
+simultaneously from at least four points in space. Using data collected by the
+four spacecraft of the Cluster constellation as they traversed a diffusion
+region in the Earth's magnetotail on 15 September, 2001, we report here the
+first in situ evidence for the structure of an isolated magnetic null. The
+results indicate that it has a positive-spiral structure whose spatial extent
+is of the same order as the local ion inertial length scale, suggesting that
+the Hall effect could play an important role in 3D reconnection dynamics.",0606014v2
+2008-02-01,Collapse of magnetized hypermassive neutron stars in general relativity: Disk evolution and outflows,"We study the evolution in axisymmetry of accretion disks formed
+self-consistently through collapse of magnetized hypermassive neutron stars to
+black holes. Such stars can arise following the merger of binary neutron stars.
+They are differentially rotating, dynamically stable, and have rest masses
+exceeding the mass limit for uniform rotation. However, hypermassive neutron
+stars are secularly unstable to collapse due to MHD-driven angular momentum
+transport. The rotating black hole which forms in this process is surrounded by
+a hot, massive, magnetized torus and a magnetic field collimated along the spin
+axis. This system is a candidate for the central engine of a short-hard
+gamma-ray burst (GRB). Our code integrates the coupled Einstein-Maxwell-MHD
+equations and is used to follow the collapse of magnetized hypermassive neutron
+star models in full general relativity until the spacetime settles down to a
+quasi-stationary state. We then employ the Cowling approximation, in which the
+spacetime is frozen, to track the subsequent evolution of the disk. This
+approximation allows us to greatly extend the disk evolutions and study the
+resulting outflows, which may be relevant to the generation of a GRB. We find
+that outflows are suppressed when a stiff equation of state is assumed for low
+density disk material and are sensitive to the initial magnetic field
+configuration.",0802.0200v1
+2008-04-08,Frequent Occurrence of High-speed Local Mass Downflows on the Solar Surface,"We report on new spectro-polarimetric measurements with simultaneous filter
+imaging observation, revealing the frequent appearance of polarization signals
+indicating high-speed, probably supersonic, downflows that are associated with
+at least three different configurations of magnetic fields in the solar
+photosphere. The observations were carried out with the Solar Optical Telescope
+onboard the {\em Hinode} satellite. High speed downflows are excited when a
+moving magnetic feature is newly formed near the penumbral boundary of
+sunspots. Also, a new type of downflows is identified at the edge of sunspot
+umbra that lack accompanying penumbral structures. These may be triggered by
+the interaction of magnetic fields sweeped by convection with well-concentrated
+magnetic flux. Another class of high speed downflows are observed in quiet sun
+and sunspot moat regions. These are closely related to the formation of small
+concentrated magnetic flux patches. High speed downflows of all types are
+transient time-dependent mass motions. These findings suggest that the
+excitation of supersonic mass flows are one of the key observational features
+of the dynamical evolution occurring in magnetic-field fine structures on the
+solar surface.",0804.1167v1
+2008-05-05,Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics,"Most numerical investigations on the role of magnetic fields in turbulent
+molecular clouds (MCs) are based on ideal magneto-hydrodynamics (MHD). However,
+MCs are weakly ionized, so that the time scale required for the magnetic field
+to diffuse through the neutral component of the plasma by ambipolar diffusion
+(AD) can be comparable to the dynamical time scale. We have performed a series
+of 256^3 and 512^3 simulations on supersonic but sub-Alfvenic turbulent systems
+with AD using the Heavy-Ion Approximation developed in Li, McKee, & Klein
+(2006). Our calculations are based on the assumption that the number of ions is
+conserved, but we show that these results approximately apply to the case of
+time-dependent ionization in molecular clouds as well. Convergence studies
+allow us to determine the optimal value of the ionization mass fraction when
+using the heavy-ion approximation for low Mach number, sub-Alfvenic turbulent
+systems. We find that ambipolar diffusion steepens the velocity and magnetic
+power spectra compared to the ideal MHD case. Changes in the density PDF, total
+magnetic energy, and ionization fraction are determined as a function of the AD
+Reynolds number. The power spectra for the neutral gas properties of a strongly
+magnetized medium with a low AD Reynolds number are similar to those for a
+weakly magnetized medium; in particular, the power spectrum of the neutral
+velocity is close to that for Burgers turbulence.",0805.0597v1
+2008-05-10,Modelling of magnetic field structure of the Ergodic Divertor of Tore Supra and comparison to the Dynamic Ergodic Divertor of TEXTOR,"An analytical model previously developed to study the structure of the
+magnetic field for the TEXTOR-DED [S.S. Abdullaev et al. Phys. Plasmas, 6, 153
+(1999)] is applied to the similar study of the Ergodic Divertor of Tore Supra
+tokamak [Ph. Ghendrih, Plasma Phys. Control. Fusion, 38, 1653 (1996)]. The coil
+configuration of ED Tore Supra consists of six modules equidistantly located
+along the toroidal direction on the low-field-side of the torus with given
+toroidal and poloidal extensions. The Hamiltonian formulation of field line
+equations in straight-field-line coordinates (Boozer coordinates) and the
+computationally efficient mapping method for integration of the Hamiltonian
+field line equations are used to study the magnetic field structure in the ED.
+Asymptotical formulas for the perturbation magnetic field created by the ED
+coils are obtained and the spectrum of magnetic perturbations is analyzed and
+compared with the one of the TEXTOR-DED. The structure of ergodic and laminar
+zones are studied by plotting Poincare sections, so-called laminar plots
+(contour plots of wall to wall connection lengths) and magnetic footprints. The
+radial profiles of field line diffusion coefficients are calculated for
+different perturbation currents and it is found that for the Tore Supra case in
+the ergodic zone the numerical field line diffusion coefficients perfectly
+follow the quasilinear formula for smaller perturbation currents although the
+situation is different for the maximum perturbation current.",0805.1477v1
+2008-06-26,The magnetic field of the proto-planetary nebula candidate IRAS 19296+2227,"Context: Magnetic fields are thought to be one of the possible mechanisms
+responsible for shaping the generally spherical outflow of evolved stars into
+often aspherical planetary nebulae. However, direct measurements of magnetic
+fields during the transition to the planetary nebula phase are rare.
+  Aims: The aim of this project is to expand the number of magnetic field
+measurements of stars in the (proto-)planetary nebula phase and find if the
+magnetic field strength is sufficient to affect the stellar outflow.
+  Methods: We used Very Long Baseline Array observations to measure the
+circular polarization due to the Zeeman splitting of 22 GHz water masers in the
+envelope of the proto-planetary nebula candidate star IRAS 19296+2227 and the
+planetary nebula K3-35.
+  Results: A strong magnetic field of B||=-135+-28 is detected in the water
+maser region of the proto-planetary nebula candidate IRAS 19296+2227. The water
+masers of K3-35 are too weak to detect circular polarization although we do
+present the measurements of weak linear polarization in those masers.
+  Conclusions: The field measured in the masers of IRAS 19296+2227 is
+dynamically important and, if it is representative of the large scale field, is
+an important factor in driving the stellar mass loss and shaping the stellar
+outflow.",0806.4261v1
+2008-12-19,Magnetic control of large room-temperature polarization,"Numerous authors have referred to room-temperature magnetic switching of
+large electric polarizations as The Holy Grail of magnetoelectricity.We report
+this long-sought effect using a new physical process of coupling between
+magnetic and ferroelectric relaxor nano-regions. Here we report magnetic
+switching between the normal ferroelectric state and the ferroelectric relaxor
+state. This gives both a new room-temperature, single-phase, multiferroic
+magnetoelectric, PbZr0.46Ti0.34Fe0.13W0.07O3, with polarization, loss (<4%),
+and resistivity (typically 108 -109 ohm.cm) equal to or superior to BiFeO3, and
+also a new and very large magnetoelectric effect: switching not from +Pr to
+negative Pr with applied H, but from Pr to zero with applied H of less than a
+Tesla. This switching of the polarization occurs not because of a conventional
+magnetically induced phase transition, but because of dynamic effects:
+Increasing H lengthens the relaxation time by x500 from <200 ns to >100 ?s, and
+it couples strongly the polarization relaxation and spin relaxations. The
+diverging polarization relaxation time accurately fits a modified Vogel-Fulcher
+Equation in which the freezing temperature Tf is replaced by a critical
+freezing field Hf that is 0.92 positive/negative 0.07 Tesla. This field
+dependence and the critical field Hc are derived analytically from the
+spherical random bond random field (SRBRF) model with no adjustable parameters
+and an E2H2 coupling. This device permits 3-state logic (+Pr,0,negative Pr) and
+a condenser with >5000% magnetic field change in its capacitance.",0812.3875v2
+2008-12-29,Measuring interstellar magnetic fields by radio synchrotron emission,"Radio synchrotron emission, its polarization and its Faraday rotation are
+powerful tools to study the strength and structure of interstellar magnetic
+fields. The total intensity traces the strength and distribution of total
+magnetic fields. Total fields in gas-rich spiral arms and bars of nearby
+galaxies have strengths of 20-30 $\mu$Gauss, due to the amplification of
+turbulent fields, and are dynamically important. In the Milky Way, the total
+field strength is about 6 $\mu$G near the Sun and several 100 $\mu$G in
+filaments near the Galactic Center. -- The polarized intensity measures ordered
+fields with a preferred orientation, which can be regular or anisotropic
+fields. Ordered fields with spiral structure exist in grand-design, barred,
+flocculent and even in irregular galaxies. The strongest ordered fields are
+found in interarm regions, sometimes forming ""magnetic spiral arms"" between the
+optical arms. Halo fields are X-shaped, probably due to outflows. -- The
+Faraday rotation of the polarization vectors traces coherent regular fields
+which have a preferred direction. In some galaxies Faraday rotation reveals
+large-scale patterns which are signatures of dynamo fields. However, in most
+galaxies the field has a complicated structure and interacts with local gas
+flows. In the Milky Way, diffuse polarized radio emission and Faraday rotation
+of the polarized emission from pulsars and background sources show many
+small-scale and large-scale magnetic features, but the overall field structure
+in our Galaxy is still under debate.",0812.4925v1
+2009-03-03,Detecting and Switching Magnetization of Stoner Nanograin in Non-local Spin Valve,"The magnetization detection and switching of an ultrasmall Stoner nanograin
+in a non-local spin valve (NLSV) device is studied theoretically. With the help
+of the rate equations, a unified description can be presented on the same
+footing for the NLSV signal that reads out the magnetization, and for the
+switching process. The setup can be viewed as that the grain is connected to
+two non-magnetic leads via sequential tunneling. In one lead, the chemical
+potentials for spin-up and -down electrons are split due to the spin injection
+in the NLSV. This splitting (or the spin bias) is crucial to the NLSV signal
+and the critical condition to the magnetization switching. By using the
+standard spin diffusion equation and parameters from recent NLSV device, the
+magnitude of the spin bias is estimated, and found large enough to drive the
+magnetization switching of the cobalt nanograin reported in earlier
+experiments. A microscopic interpretation of NLSV signal in the sequential
+tunneling regime is thereby raised, which show properties due to the ultrasmall
+size of the grain. The dynamics at the reversal point shows that there may be a
+spin-polarized current instead of the anticipated pure spin current flowing
+during the reversal due to the electron accumulation in the floating lead used
+for the readout of NLSV signal.",0903.0456v2
+2009-03-12,Field-induced suppression of the pi-band superconductivity and magnetic hysteresis in the microwave surface resistance of MgB_2 at temperatures near T_c,"We report on the magnetic-field-induced variations of the microwave surface
+resistance, R_s, in a polycrystalline MgB_2 sample, at different values of
+temperature. We have detected a magnetic hysteresis in R_s, which exhibits an
+unexpected plateau on decreasing the DC magnetic field below a certain value.
+In particular, at temperatures near T_c the hysteresis manifests itself only
+through the presence of the plateau. Although we do not quantitatively justify
+the anomalous shape of the magnetic hysteresis, we show that the results
+obtained in the reversible region of the R_s(H) curve can be quite well
+accounted for by supposing that, in this range of magnetic field, the pi-gap is
+almost suppressed by the applied field and, consequently, all the pi-band
+charge carriers are quasiparticles. On this hypothesis, we have calculated
+R_s(H) supposing that fluxons assume a conventional (single core) structure and
+the flux dynamics can be described in the framework of conventional models.
+  From the fitting of the experimental results, we determine the values of
+H_{c2}^pi(T) at temperatures near T_c. In our opinion, the most important
+result of our investigation is that, at least at temperatures near T_c, the
+value of the applied field that separates the reversible and irreversible
+regions of the R_s(H) curves is just H_{c2}^pi(T); a qualitative discussion of
+the possible reason of this finding is given.",0903.2162v1
+2009-05-13,Chiral MHD description of a perfect magnetized QGP using the effective NJL model in a strong magnetic field,"To study the effect of a strong magnetic field $B$ on the sound velocity
+$v_{s}$ of plane waves propagating in a strongly magnetized quark-gluon plasma
+(QGP), a chiral magnetohydrodynamical (MHD) description of a perfect
+(non-dissipative) QGP exhibiting dynamical chiral symmetry breaking (D$\chi$SB)
+is developed using the effective action of the Nambu-Jona-Lasinio (NJL) model
+of QCD at finite temperature, finite baryon chemical potential and in the
+presence of a strong magnetic field. Here, the D$\chi$SB arises due to the
+phenomenon of magnetic catalysis. Apart from an interesting frequency
+dependence, for plane waves propagating in the transverse or longitudinal
+direction with respect to the $B$ field, the sound velocity is anisotropic and
+depends on the angle between the corresponding wave vectors and the direction
+of the $B$ field. Moreover, for plane waves propagating in the transverse
+(longitudinal) direction to the external $B$ field, the sound velocity has a
+maximum (minimum) at $T<T_{c}$, reaches a local minimum (maximum) at $T\sim
+T_{c}$ and remains constant at $T\gtrsim T_{c}$. Here, $T_{c}$ is the critical
+temperature of the chiral phase transition. Thus, the constant value $v_{s}\sim
+1.5 c_{s}$ at $T \gtrsim T_{c}$ turns out to be a lower (upper) bound for waves
+propagating in the transverse (longitudinal) direction with respect to the
+external $B$ field. Here, $c_{s}=1/\sqrt{3}$ is the sound velocity in an ideal
+gas.",0905.2097v1
+2009-08-31,Cobalt nano-clusters on metal supported Xe monolayers: influence of the substrate on cluster formation kinetics and magnetism,"The growth dynamics of submonolayer coverages of Cobalt during buffer layer
+assisted growth on Ag(111) and Pt(111) substrates is investigated by variable
+temperature scanning tunneling microscopy in the temperature range between 80
+and 150 Kelvin. It is found that attractive cluster-substrate interactions can
+govern the cluster formation on the Xe buffer layer, if the Xe layer is
+sufficiently thin. The interpretation of the microscopy results are supported
+by x-ray magnetic circular dichroism which monitors the effect of
+cluster-substrate interactions on the formation of magnetic moments and
+magnetic anisotropy of Co nanocluster during the different stages of growth.
+{\it Ab-initio} calculations show that the cluster magnetism is controlled by
+the interface anisotropy, leading to perpendicular magnetization for Co on
+Pt(111). Limits of and new potential for nanocluster fabrication by buffer
+layer assisted growth are discussed.",0908.4365v2
+2009-11-18,Kelvin-Helmholtz Instability of the Magnetopause of Disc-Accreting Stars,"This work investigates the short wavelength stability of the magnetopause
+between a rapidly-rotating, supersonic, dense accretion disc and a
+slowly-rotating low-density magnetosphere of a magnetized star. The
+magnetopause is a strong shear layer with rapid changes in the azimuthal
+velocity, the density, and the magnetic field over a short radial distance and
+thus the Kelvin-Helmholtz (KH) instability may be important. The plasma
+dynamics is treated using non-relativistic, compressible (isentropic)
+magnetohydrodynamics. It is necessary to include the displacement current in
+order that plasma wave velocities remain less than the speed of light. We focus
+mainly on the case of a star with an aligned dipole magnetic field so that the
+magnetic field is axial in the disc midplane and perpendicular to the disc flow
+velocity. However, we also give results for cases where the magnetic field is
+at an arbitrary angle to the flow velocity. For the aligned dipole case the
+magnetopause is most unstable for KH waves propagating in the azimuthal
+direction perpendicular to the magnetic field which tends to stabilize waves
+propagating parallel to it. The wave phase velocity is that of the disc matter.
+A quasi-linear theory of the saturation of the instability leads to a
+wavenumber ($k$) power spectrum $\propto k^{-1}$ of the density and temperature
+fluctuations of the magnetopause, and it gives the mass accretion and angular
+momentum inflow rates across the magnetopause. For self-consistent conditions
+this mass accretion rate will be equal to the disc accretion rate at large
+distances from the magnetopause.",0911.3590v1
+2010-01-20,Theory of Magnetic Seed-Field Theory of Magnetic Seed-Field Generation during the Cosmological First-Order Electroweak Phase Transition,"We present a theory of the generation of magnetic seed fields in bubble
+collisions during a first-order electroweak phase transition (EWPT) possible
+for some choices of parameters in the minimal supersymmetric Standard Model.
+The theory extends earlier work and is formulated to assess the importance of
+surface dynamics in such collisions. We are led to linearized equations of
+motion with O(3) symmetry appropriate for examining collisions in which the
+Higgs field is relatively unperturbed from its mean value in the collision
+volume. Coherent evolution of the charged $W$ fields within the bubbles is the
+main source of the electromagnetic current for generating the seed fields, with
+fermions also contributing through the conductivity terms. We present numerical
+simulations within this formulation to quantify the role of the surface of the
+colliding bubbles, particularly the thickness of the surface, and to show how
+conclusions drawn from earlier work are modified. The main sensitivity arises
+such that the steeper the bubble surface the more enhanced the seed fields
+become. Consequently, the magnetic seed fields may be several times larger and
+smoother over the collision volume than found in earlier studies. Our work thus
+provides additional support to the supposition that magnetic fields produced
+during the EWPT in the early universe seed the galactic and extra-galactic
+magnetic fields observed today.",1001.3694v1
+2010-02-03,Magnetic fields and radiative feedback in the star formation process,"Star formation is a complex process involving the interplay of many physical
+effects, including gravity, turbulent gas dynamics, magnetic fields and
+radiation. Our understanding of the process has improved substantially in
+recent years, primarily as a result of our increased ability to incorporate the
+relevant physics in numerical calculations of the star formation process. In
+this contribution we present an overview of our recent studies of star cluster
+formation in turbulent, magnetised clouds using self-gravitating
+radiation-magnetohydrodynamics calculations (Price and Bate 2008, 2009). Our
+incorporation of magnetic fields and radiative transfer into the Smoothed
+Particle Hydrodynamics method are discussed. We highlight how magnetic fields
+and radiative heating of the gas around newborn stars can solve several of the
+key puzzles in star formation, including an explanation for why star formation
+is such a slow and inefficient process. However, the presence of magnetic
+fields at observed strengths in collapsing protostellar cores also leads to
+problems on smaller scales, including a difficulty in forming protostellar
+discs and binary stars (Price and Bate 2007, Hennebelle and Teyssier 2008),
+which suggests that our understanding of the role of magnetic fields in star
+formation is not yet complete.",1002.0650v2
+2010-04-20,Edge pinch instability of oblate liquid metal drops in a transverse AC magnetic field,"This paper considers the stability of liquid metal drops subject to a
+high-frequency AC magnetic field. An energy variation principle is derived in
+terms of the surface integral of the scalar magnetic potential. This principle
+is applied to a thin perfectly conducting liquid disk, which is used to model
+the drops constrained in a horizontal gap between two parallel insulating
+plates. Firstly, the stability of a circular disk is analysed with respect to
+small-amplitude harmonic edge perturbations. Analytical solution shows that the
+edge deformations with the azimuthal wavenumbers m=2,3,4... start to develop as
+the magnetic Bond number exceeds the critical threshold Bm_c=3pi(m+1)/2. The
+most unstable is m=2 mode, which corresponds to an elliptical deformation.
+Secondly, strongly deformed equilibrium shapes are modelled numerically by
+minimising the associated energy in combination with the solution of a surface
+integral equation for the scalar magnetic potential on an unstructured
+triangular mesh. The edge instability is found to result in the equilibrium
+shapes of either two- or threefold rotational symmetry depending on the
+magnetic field strength and the initial perturbation. The shapes of higher
+rotational symmetries are unstable and fall back to one of these two basic
+states. The developed method is both efficient and accurate enough for
+modelling of strongly deformed drop shapes.",1004.3467v3
+2010-06-02,Interaction of a magnetized shell with an ambient medium: limits on impulsive magnetic acceleration,"The interaction of relativistic magnetized ejecta with an ambient medium is
+studied for a range of structures and magnetization of the unshocked ejecta. We
+particularly focus on the effect of the ambient medium on the dynamics of an
+impulsive, high-sigma shell. It is found that for sufficiently high values of
+the initial magnetization $\sigma_0$ the evolution of the system is
+significantly altered by the ambient medium well before the shell reaches its
+coasting phase. The maximum Lorentz factor of the shell is limited to values
+well below $\sigma_0$; for a shell of initial energy $E=10^{52}E_{52}$ ergs and
+size $r_0=10^{12}T_{30}$ cm expelled into a medium having a uniform density
+$n_i$ we obtain $\Gamma_{\rm max}\simeq180(E_{52}/T_{30}^3 n_i)^{1/8}$ in the
+high sigma limit. The reverse shock and any internal shocks that might form if
+the source is fluctuating are shown to be very weak. The restriction on the
+Lorentz factor is more severe for shells propagating in a stellar wind.
+Intermittent ejection of small sub-shells doesn't seem to help, as the shells
+merge while still highly magnetized. Lower sigma shells start decelerating
+after reaching the coasting phase and spreading away. The properties of the
+reverse shock then depend on the density profiles of the coasting shell and the
+ambient medium. For a self-similar cold shell the reverse shock becomes strong
+as it propagates inwards, and the system eventually approaches the self-similar
+solution derived recently by Nakamura \& Shigeyama.",1006.0336v3
+2010-11-04,"Magnetic order, metamagnetic transitions, and low-temperature spin freezing in Ca3Co2O6: an NMR study","We report on a 59Co NMR investigation of the trigonal cobaltate Ca3Co2O6
+carried out on a single crystal, providing precise determinations of the
+electric field gradient and chemical shift tensors, and of the internal
+magnetic fields at the non-magnetic Co I sites, unavailable from former studies
+on powders. The magnetic field-induced ferri- and ferromagnetic phases at
+intermediate temperature (e.g. 10 K) are identified by distinct internal
+fields, well accounted for by purely dipolar interactions. The vanishing
+transferred hyperfine field at the Co I site indicates that the Co3+(I)
+orbitals do not participate in the intra-chain superexchange, in disagreement
+with a previous theoretical model. The strong Ising character of the system is
+confirmed experimentally by the field dependence of the resonance lines,
+indicating that local moments are saturated even at the phase boundaries. In
+the vicinity of the critical fields, nuclear spin-spin relaxations detect the
+spin reversal dynamics of large magnetic assemblies, either Ising chain
+fragments or finite size domains, which drive the metamagnetic transitions.
+Such collective excitations exhibit a glassy behavior, slowing down to
+subacoustic frequencies and freezing at low temperature. The relevance of such
+slow fluctuation modes for the low-temperature multi-step behavior reported in
+the magnetization is discussed.",1011.1142v2
+2010-11-25,Calculation of the Expected Zero Field Muon Relaxation Rate in the Geometrically Frustrated Rare Earth Pyrochlore Gd2Sn2O7 Antiferromagnet,"The magnetic insulator Gd2Sn2O7 is one of many geometrically frustrated
+magnetic materials known to exhibit a nonzero muon spin polarization relaxation
+rate, $\lambda(T)$, down to the lowest temperature (T) studied. Such behaviour
+is typically interpreted as a significant level of persisting spin dynamics
+(PSD) of the host material. In the case of Gd2Sn2O7, such PSD comes as a
+surprise since magnetic specific heat measurements suggest conventional gapped
+magnons, which would naively lead to an exponentially vanishing $\lambda(T)$ as
+$T \rightarrow 0$. In contrast to most materials that display PSD, the ordered
+phase of Gd2Sn2O7 is well characterized and both the nature and the magnitude
+of the interactions have been inferred from the magnetic structure and the
+temperature dependence of the magnetic specific heat. Based on this
+understanding, the temperature dependence of the muon spin polarization
+relaxation through the scattering of spin waves (magnons) is calculated. The
+result explicitly shows that, despite the unusual extensive number of weakly
+dispersive (gapped)excitations characterizing Gd2Sn2O7, a remnant of the zero
+modes of the parent frustrated pyrochlore Heisenberg antiferromagnet, the
+temperature dependence of the calculated $\lambda(T)$ differs dramatically from
+the experimental one. Indeed, the calculation conforms to the naive expectation
+of an exponential collapse of $\lambda(T)$ at temperatures below ~ 0.7K. This
+result, for the first time, illustrates crisply and quantitatively the paradox
+that presents itself with the pervasive occurrence of PSD in highly frustrated
+magnetic systems as evinced by muon spin relaxation measurements.",1011.5689v1
+2010-12-01,Effect of Randomness on Quantum Data Buses of Heisenberg Spin Chains,"A strongly coupled spin chain can mediate long-distance effective couplings
+or entanglement between remote qubits, and can be used as a quantum data bus.
+We study how the fidelity of a spin-1/2 Heisenberg chain as a spin bus is
+affected by static random exchange couplings and magnetic fields. We find that,
+while non-uniform exchange couplings preserve the isotropy of the qubit
+effective couplings, they cause the energy levels, the eigenstates, and the
+magnitude of the couplings to vary locally. On the other hand, random local
+magnetic fields lead to an avoided level crossing for the bus ground state
+manifold, and cause the effective qubit couplings to be anisotropic.
+Interestingly, the total magnetic moment of the ground state of an odd-size bus
+may not be parallel to the average magnetic field. Its alignment depends on
+both the direction of the average field and the field distribution, in contrast
+with the ground state of a single spin which always aligns with the applied
+magnetic field to minimize the Zeeman energy. Lastly, we calculate
+sensitivities of the spin bus to such local variations, which are potentially
+useful for evaluating decoherence when dynamical fluctuations in the exchange
+coupling or magnetic field are considered.",1012.0288v2
+2011-01-18,Simulation of dark lanes in post--flare supra--arcades,"Using two simulations of 1.5D, for the first time, in Costa et al. (2009) and
+Shulz et al. (2010) we numerically reproduce the observational dark inflows
+described in Verwichte et al. (2005). We show that the dark tracks can be
+explained as hot plasma vacuums generated upstream of a slow magnetoacoustic
+shock wave produced by a localized deposition of energy. In this work, we show
+that the overall 2D results are in agreement with the observational behaviour.
+However they show a slight shift in the characteristic parameter with respect
+to those found previously. Also, we confirm qualitatively the behaviour found
+in the previous papers, i.e. for a given numerical domain the period of the
+kink--like structure is a function of the magnetic field intensity: larger
+periods are associated with lower magnetic field intensities. Contrary to the
+1D result -where the sunward dynamic is independent of the magnetic field
+intensity due to its exclusively waveguide role- in the 2D simulation the
+sunward speed is larger for larger values of the magnetic field. This can be
+interpreted as the capability of the low coronal plasma to collimate the
+deposition of energy into the magnetic field direction. The moving features
+consistent of low--density and high--temperature plasma cavities have larger
+inside values of the structuring parameter beta than the neighboring media.
+Thus, the voids seem to be the emergence structures of a whole nonlinear
+interacting plasma context of shocks and waves more than voided plasma loops
+magnetically structured.",1101.3530v1
+2011-01-30,Dynamics of entanglement in a two-dimensional spin system,"We consider the time evolution of entanglement in a finite two dimensional
+transverse Ising model. The model consists of a set of 7 localized spin-1/2
+particles in a two dimensional triangular lattice coupled through nearest
+neighbor exchange interaction in presence of an external time dependent
+magnetic field. The magnetic field is applied in different function forms:
+step, exponential, hyperbolic and periodic. We found that the time evolution of
+the entanglement shows an ergodic behavior under the effect of the time
+dependent magnetic fields. Also we found that while the step magnetic field
+causes great disturbance to the system creating rabid oscillations, the system
+shows great controllability under the effect of the other magnetic fields where
+the entanglement profile follows closely the shape of the applied field even
+with the same frequency for periodic fields. This follow up trend breaks down
+as the strength of the field, the transition constant for exponential and
+hyperbolic, or frequency for periodic field increase leading to rapid
+oscillations. We observed that the entanglement is very sensitive to the
+initial value of the applied periodic field, the smaller the initial value the
+less distorted is the entanglement profile. Furthermore, the effect of thermal
+fluctuations is very devastating to the entanglement which decays very rapidly
+as the temperature increases. Interestingly, although large value of the
+magnetic field strength may yield small entanglement, it was found to be more
+persistent against thermal fluctuations than the small field strengths.",1101.5784v1
+2011-02-06,LES of turbulent convection in solar-type stars and formation of large-scale magnetic structures,"In this study we investigate the effects of turbulent convection on formation
+of large-scale inhomogeneous magnetic structures by means of Large-Eddy
+Simulation (LES) for convection in solar-type stars. The main idea of this
+study is the implementation of a new subgrid-scale model for the effective
+Lorentz force in a three-dimensional nonlinear radiative magnetohydrodynamics
+(MHD) code developed for simulating the upper solar convection zone and lower
+atmosphere. To this end we derived the energy budget equations, which include
+the effects of the subgrid-scale turbulence on the Lorentz-force, and
+implemented the new subgrid-scale turbulence model (TELF-Model) in a
+three-dimensional nonlinear MHD LES code. Using imposed initial vertical and
+horizontal uniform magnetic fields in LES with the TELF-Model, we have shown
+that the magnetic flux tubes formation is started when the initial mean
+magnetic field is larger than a threshold value (about 100 G). This is in
+agreement with the theoretical studies by Rogachevskii and Kleeorin (2007). We
+have determined the vertical profiles of the velocity and magnetic
+fluctuations, total MHD energy and anisotropy of turbulent magneto-convection,
+kinetic and current and cross helicities.",1102.1206v1
+2011-04-07,The magnetic phase diagram of an extended J1-J2 model on a modulated square lattice and its implications for the antiferromagnetic phase of KyFexSe2,"Motivated by the experimentally observed $\sqrt{5} \times \sqrt{5}$ iron
+vacancy order and a block spin antiferromagnetic phase with large magnetic
+moment in $\mathrm{K}_{0.8}\mathrm{Fe}_{1.6}\mathrm{Se}_2$, we study the
+magnetic phase diagram of an extended $J_1-J_2$ model on a 1/5-depleted square
+lattice with $\sqrt{5} \times \sqrt{5}$ vacancy order, using a classical Monte
+Carlo analysis. The magnetic phase diagram involves various
+antiferromagnetically ordered phases, and most of them have higher order
+commensuration. We find that the experimentally relevant block-spin state
+occupies a significant portion of the phase diagram, and we discuss the spin
+dynamics of this phase using a linear spin-wave analysis. Based on our spin
+wave calculations in different parameter regimes corresponding to the block
+spin antiferromagnetic phase, we show how spin-wave degeneracy along the high
+symmetry directions of the magnetic Brillouin zone can provide information
+regarding the underlying exchange couplings. We have also analyzed the magnetic
+phase diagram of a $J_1-J_2$ model on two different modulated square lattices
+relevant for $\mathrm{K}_y\mathrm{Fe}_{1.5}\mathrm{Se}_2$, which respectively
+exhibit 1/4-depleted $2\times2$ and $4\times2$ vacancy ordering.",1104.1445v2
+2011-05-10,Numerical Experiments on the Two-step Emergence of Twisted Magnetic Flux Tubes in the Sun,"We present the new results of the two-dimensional numerical experiments on
+the cross-sectional evolution of a twisted magnetic flux tube rising from the
+deeper solar convection zone (-20,000 km) to the corona through the surface.
+The initial depth is ten times deeper than most of previous calculations
+focusing on the flux emergence from the uppermost convection zone. We find that
+the evolution is illustrated by the two-step process described below: the
+initial tube rises due to its buoyancy, subject to aerodynamic drag due to the
+external flow. Because of the azimuthal component of the magnetic field, the
+tube maintains its coherency and does not deform to become a vortex roll pair.
+When the flux tube approaches the photosphere and expands sufficiently, the
+plasma on the rising tube accumulates to suppress the tube's emergence.
+Therefore, the flux decelerates and extends horizontally beneath the surface.
+This new finding owes to our large scale simulation calculating simultaneously
+the dynamics within the interior as well as above the surface. As the magnetic
+pressure gradient increases around the surface, magnetic buoyancy instability
+is triggered locally and, as a result, the flux rises further into the solar
+corona. We also find that the deceleration occurs at a higher altitude than in
+our previous experiment using magnetic flux sheets (Toriumi and Yokoyama). By
+conducting parametric studies, we investigate the conditions for the two-step
+emergence of the rising flux tube: field strength > 1.5x10^4 G and the twist >
+5.0x10^-4 km^-1 at -20,000 km depth.",1105.1904v1
+2011-05-19,Driving magnetic order in a manganite by ultrafast lattice excitation,"Optical control of magnetism, of interest for high-speed data processing and
+storage, has only been demonstrated with near-infrared excitation to date.
+However, in absorbing materials, such high photon energies can lead to
+significant dissipation, making switch back times long and miniaturization
+challenging. In manganites, magnetism is directly coupled to the lattice, as
+evidenced by the response to external and chemical pressure, or to
+ferroelectric polarization. Here, femtosecond mid-infrared pulses are used to
+excite the lattice in La0.5Sr1.5MnO4 and the dynamics of electronic order are
+measured by femtosecond resonant soft x-ray scattering with an x-ray free
+electron laser. We observe that magnetic and orbital orders are reduced by
+excitation of the lattice. This process, which occurs within few picoseconds,
+is interpreted as relaxation of the complex charge-orbital-spin structure
+following a displacive exchange quench - a prompt shift in the equilibrium
+value of the magnetic and orbital order parameters after the lattice has been
+distorted. A microscopic picture of the underlying unidirectional lattice
+displacement is proposed, based on nonlinear rectification of the
+directly-excited vibrational field, as analyzed in the specific lattice
+symmetry of La0.5Sr1.5MnO4. Control of magnetism through ultrafast lattice
+excitation has important analogies to the multiferroic effect and may serve as
+a new paradigm for high-speed optomagnetism.",1105.3866v1
+2011-05-31,Jet rotation driven by MHD shocks in helical magnetic fields,"In this paper we present a detailed numerical investigation of the hypothesis
+that a rotation of astrophysical jets can be caused by magnetohydrodynamic
+shocks in a helical magnetic field. Shock compression of the helical magnetic
+field results in a toroidal Lorentz force component which will accelerate the
+jet material in toroidal direction. This process transforms magnetic angular
+momentum (magnetic stress) carried along the jet into kinetic angular momentum
+(rotation). The mechanism proposed here only works in a helical magnetic field
+configuration. We demonstrate the feasibility of this mechanism by axisymmetric
+MHD simulations in 1.5D and 2.5D using the PLUTO code. In our setup the jet is
+injected into the ambient gas with zero kinetic angular momentum (no rotation).
+Different dynamical parameters for jet propagation are applied such as the jet
+internal Alfven Mach number and fast magnetosonic Mach number, the density
+contrast of jet to ambient medium, or the external sonic Mach number of the
+jet. The mechanism we suggest should work for a variety of jet applications,
+e.g. protostellar or extragalactic jets, and internal jet shocks (jet knots) or
+external shocks between the jet and ambient gas (entrainment). For typical
+parameter values for protostellar jets, the numerically derived rotation
+feature looks consistent with the observations, i.e. rotational velocities of
+0.1-1 percent of the jet bulk velocity.",1105.6232v1
+2011-06-07,Towards Unquenched Holographic Magnetic Catalysis,"We propose a string dual to the SU(Nc) N=4 SYM coupled to Nf massless
+fundamental flavors in an external magnetic field. The flavors are introduced
+by homogeneously smeared Nf D7-branes and the external magnetic field via a
+non-trivial Kalb-Ramond B-field. Our solution is perturbative in a parameter
+that counts the number of internal flavor loops. In the limit of vanishing
+B-field the background reduces to the supersymmetric one obtained in
+hep-th/0612118. We introduce an additional probe D7--brane and in the
+supersymmetric limit of vanishing B-field perform a holographic renormalization
+of its ""on-shell"" action. We consider also non-supersymmetric probes with fixed
+worldvolume gauge field corresponding to a magnetic field coupled only to the
+fundamental fields of the probe brane. We study the influence of the
+backreacted flavors on the effect of dynamical mass generation. Qualitatively
+the physical picture remains unchanged. In the next step we consider the case
+when the magnetic field couples to both the backreacted and the probe
+fundamental degrees of freedom. At sufficiently strong magnetic field the meson
+spectrum signals an instability of the probe D7-brane, which we interpret as
+reflecting an instability of the supergravity background.",1106.1330v2
+2011-06-08,Kinematics and Fine Structure of An Unwinding Polar Jet Observed by SDO/AIA,"We present an observational study of the kinematics and fine structure of an
+unwinding polar jet, with high temporal and spatial observations taken by the
+Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO)
+and the Solar Magnetic Activity Research Telescope (SMART). During the rising
+period, the shape of the jet resembled a cylinder with helical structures on
+the surface, while the mass of the jet was mainly distributed on the cylinder's
+shell. In the radial direction, the jet expanded successively at its western
+side. The radial expansion presented three distinct phases: the gradually
+expanding phase, the fast expanding phase, and the steady phase. Each phase
+lasted for about 12 minutes. The angular speed of the unwinding jet and the
+twist transferred into the outer corona during the eruption are estimated to be
+11.1 \times 10{-3} rad/s (period = 564 s) and 1.17 to 2.55 turns (or 2.34 to
+5.1{\pi}) respectively. On the other hand, by calculating the azimuthal
+component of the magnetic field in the jet and comparing the free energy stored
+in the non-potential magnetic field with the jet's total energy, we find that
+the non-potential magnetic field in the jet is enough to supply the energy for
+the ejection. These new observational results strongly support the scenario
+that the jets are driven by the magnetic twist, which is stored in the twisted
+closed field of a bipole, and released through magnetic reconnection between
+the bipole and its ambient open field.",1106.1489v2
+2011-06-22,Spin correlations in the extended kagome system YBaCo3FeO7,"The transition metal based oxide YBaCo3FeO7 is structurally related to the
+mineral Swedenborgite SbNaBe4O7, a polar non-centrosymmetric crystal system.
+The magnetic Co3Fe sublattice consists of a tetrahedral network containing
+kagome-like layers with trigonal interlayer sites. This geometry causes
+frustration effects for magnetic ordering, which were investigated by
+magnetization measurements, M\""ossbauer spectroscopy, polarized neutron
+diffraction, and neutron spectroscopy. Magnetization measurement and neutron
+diffraction do not show long range ordering even at low temperature (1 K)
+although a strong antiferromagnetic coupling (~2000 K) is deduced from the
+magnetic susceptibility. Below 590 K, we observe two features, a spontaneous
+weak anisotropic magnetization hysteresis along the polar crystallographic axis
+and a hyperfine field on the Fe kagome sites, whereas the Fe spins on the
+interlayer sites remain idle. Below ~50 K, the onset of a hyperfine field shows
+the development of moments static on the M\""ossbauer time scale also for the Fe
+interlayer sites. Simultaneously, an increase of spin correlations is found by
+polarized neutron diffraction. The relaxation part of the dynamic response has
+been further investigated by high-resolution neutron spectroscopy, which
+reveals that the spin correlations start to freeze in below ~50 K. Monte Carlo
+simulations show that the neutron scattering results at lower temperatures are
+compatible with a recent proposal that the particular geometric frustration in
+the Swedenborgite structure promotes quasi one dimensional partial order.",1106.4465v1
+2011-07-28,Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar,"We report on a spectroscopic study of the spin-wave eigen-modes inside an
+individual normally magnetized two layers circular nano-pillar
+(Permalloy$|$Copper$|$Permalloy) by means of a Magnetic Resonance Force
+Microscope (MRFM). We demonstrate that the observed spin-wave spectrum
+critically depends on the method of excitation. While the spatially uniform
+radio-frequency (RF) magnetic field excites only the axially symmetric modes
+having azimuthal index $\ell=0$, the RF current flowing through the
+nano-pillar, creating a circular RF Oersted field, excites only the modes
+having azimuthal index $\ell=+1$. Breaking the axial symmetry of the
+nano-pillar, either by tilting the bias magnetic field or by making the pillar
+shape elliptical, mixes different $\ell$-index symmetries, which can be excited
+simultaneously by the RF current. Experimental spectra are compared to
+theoretical prediction using both analytical and numerical calculations. An
+analysis of the influence of the static and dynamic dipolar coupling between
+the nano-pillar magnetic layers on the mode spectrum is performed.",1107.5699v2
+2011-07-29,Large-scale magnetic field generation via the kinetic Kelvin-Helmholtz instability in unmagnetized scenarios,"Collisionless plasma instabilities are fundamental in magnetic field
+generation in astrophysical scenarios, but their role has been addressed in
+scenarios where velocity shear is absent. In this work we show that velocity
+shears must be considered when studying realistic astrophysical scenarios,
+since these trigger the collisionless Kelvin-Helmholtz instability (KHI). We
+present the first self-consistent three-dimensional (3D) particle-in-cell (PIC)
+simulations of the KHI in conditions relevant for unmagnetized relativistic
+outflows with velocity shear, such as active galactic nuclei (AGN) and
+gamma-ray bursts (GRBs). We show the generation of a strong large-scale DC
+magnetic field, which extends over the entire shear-surface, reaching
+thicknesses of a few tens of electron skin depths, and persisting on
+time-scales much longer than the electron time scale. This DC magnetic field is
+not captured by MHD models since it arises from intrinsically kinetic effects.
+Our results indicate that the KHI can generate intense magnetic fields yielding
+equipartition values up to \epsilon_B/\epsilon_p ~ 10^-3 in the electron
+time-scale. The KHI-induced magnetic fields have a characteristic structure
+that will lead to a distinct radiation signature, and can seed the turbulent
+dynamo amplification process. The dynamics of the KHI are relevant for
+non-thermal radiation modeling and can also have a strong impact on the
+formation of relativistic shocks in presence of velocity shears.",1107.6037v2
+2011-09-02,Thermally Activated Magnetization and Resistance Decay during Near Ambient Temperature Aging of Co Nanoflakes in a Confining Semi-metallic Environment,"We report the observation of magnetic and resistive aging in a self assembled
+nanoparticle system produced in a multilayer Co/Sb sandwich. The aging decays
+are characterized by an initial slow decay followed by a more rapid decay in
+both the magnetization and resistance. The decays are large accounting for
+almost 70% of the magnetization and almost 40% of the resistance for samples
+deposited at 35 $^oC$. For samples deposited at 50 $^oC$ the magnetization
+decay accounts for $\sim 50%$ of the magnetization and 50% of the resistance.
+During the more rapid part of the decay, the concavity of the slope of the
+decay changes sign and this inflection point can be used to provide a
+characteristic time. The characteristic time is strongly and systematically
+temperature dependent, ranging from $\sim1$x$10^2 s$ at 400K to $\sim3$x$10^5
+s$ at 320K in samples deposited at $35 ^oC$. Samples deposited at 50 $^oC$
+displayed a 7-8 fold increase in the characteristic time (compared to the $35
+^oC$ samples) for a given aging temperature, indicating that this timescale may
+be tunable. Both the temperature scale and time scales are in potentially
+useful regimes. Pre-Aging, Scanning Tunneling Microscopy (STM) reveals that the
+Co forms in nanoscale flakes. During aging the nanoflakes melt and migrate into
+each other in an anisotropic fashion forming elongated Co nanowires. This aging
+behavior occurs within a confined environment of the enveloping Sb layers. The
+relationship between the characteristic time and aging temperature fits an
+Arrhenius law indicating activated dynamics.",1109.0506v2
+2011-10-03,Small-scale dynamo action in rotating compressible convection,"We study dynamo action in a convective layer of electrically-conducting,
+compressible fluid, rotating about the vertical axis. At the upper and lower
+bounding surfaces, perfectly-conducting boundary conditions are adopted for the
+magnetic field. Two different levels of thermal stratification are considered.
+If the magnetic diffusivity is sufficiently small, the convection acts as a
+small-scale dynamo. Using a definition for the magnetic Reynolds number $R_M$
+that is based upon the horizontal integral scale and the horizontally-averaged
+velocity at the mid-layer of the domain, we find that rotation tends to reduce
+the critical value of $R_M$ above which dynamo action is observed. Increasing
+the level of thermal stratification within the layer does not significantly
+alter the critical value of $R_M$ in the rotating calculations, but it does
+lead to a reduction in this critical value in the non-rotating cases. At the
+highest computationally-accessible values of the magnetic Reynolds number, the
+saturation levels of the dynamo are similar in all cases, with the mean
+magnetic energy density somewhere between 4 and 9% of the mean kinetic energy
+density. To gain further insights into the differences between rotating and
+non-rotating convection, we quantify the stretching properties of each flow by
+measuring Lyapunov exponents. Away from the boundaries, the rate of stretching
+due to the flow is much less dependent upon depth in the rotating cases than it
+is in the corresponding non-rotating calculations. It is also shown that the
+effects of rotation significantly reduce the magnetic energy dissipation in the
+lower part of the layer. We also investigate certain aspects of the saturation
+mechanism of the dynamo.",1110.0374v1
+2012-01-03,Reversible room-temperature ferromagnetism in Nb-doped SrTiO3 single crystals,"The search for oxide-based room-temperature ferromagnetism has been one of
+the holy grails in condensed matter physics. Room-temperature ferromagnetism
+observed in Nb-doped SrTiO3 single crystals is reported in this Rapid
+Communication. The ferromagnetism can be eliminated by air annealing (making
+the samples predominantly diamagnetic) and can be recovered by subsequent
+vacuum annealing. The temperature dependence of magnetic moment resembles the
+temperature dependence of carrier density, indicating that the magnetism is
+closely related to the free carriers. Our results suggest that the
+ferromagnetism is induced by oxygen vacancies. In addition, hysteretic
+magnetoresistance was observed for magnetic field parallel to current,
+indicating that the magnetic moments are in the plane of the samples. The x-ray
+photoemission spectroscopy, the static time-of-flight and the dynamic secondary
+ion mass spectroscopy and proton induced x-ray emission measurements were
+performed to examine magnetic impurities, showing that the observed
+ferromagnetism is unlikely due to any magnetic contaminant.",1201.0579v4
+2012-01-03,The alpha-effect in a turbulent liquid-metal plane Couette flow,"We calculate the mean electromotive force in plane Couette flows of a
+nonrotating conducting fluid under the influence of a large-scale magnetic
+field for driven turbulence. A vertical stratification of the turbulence
+intensity results in an alpha effect owing to the presence of horizontal shear.
+Here we discuss the possibility of an experimental determination of the
+components of the alpha tensor using both quasilinear theory and nonlinear
+numerical simulations. For magnetic Prandtl numbers of the order of unity, we
+find that in the high-conductivity limit the alpha effect in the direction of
+the flow clearly exceeds the component in spanwise direction. In this limit,
+alpha runs linearly with the magnetic Reynolds number Rm while in the
+low-conductivity limit it runs with the product Rm*Re, where Re is the kinetic
+Reynolds number so that for given Rm the alpha effect grows with decreasing
+magnetic Prandtl number.
+  For the small magnetic Prandtl numbers of liquid metals, a common value for
+the horizontal elements of the alpha tensor appears, which makes it unimportant
+whether the alpha effect is measured in the spanwise or streamwise directions.
+The resulting effect should lead to an observable voltage in both directions of
+about 0.5 mV for magnetic fields of 1 kgauss and velocity fluctuations of about
+1 m/s in a channel of 50 cm height (independent of its width).",1201.0652v2
+2012-02-04,Directional dependence of color superconducting gap in two-flavor QCD in a magnetic field,"We study the effect of a magnetic field on the pairing dynamics in two-flavor
+color superconducting dense quark matter. The study is performed in the weakly
+coupled regime of QCD at asymptotically high density, using the framework of
+the Schwinger-Dyson equation in the improved rainbow approximation. We show
+that the superconducting gap function develops a directional dependence in
+momentum space. Quasiparticles with momenta perpendicular to the direction of
+the magnetic field have the largest gaps, while quasiparticles with momenta
+parallel to the field have the smallest gaps. We argue that the directional
+dependence is a consequence of a long-range interaction in QCD. The
+quantitative measure of the ellipticity of the gap function is determined by a
+dimensionless ratio, proportional to the square of the magnetic field and
+inversely proportional to the fourth power of the quark chemical potential. For
+magnetic fields in stars, $B\lesssim 10^{18} G$, the corresponding ratio is
+estimated to be less than about $10^{-2}$, justifying the use of the weak
+magnetic field limit in all stellar applications.",1202.0872v2
+2012-02-13,Collisionless magnetic reconnection in a plasmoid chain,"The kinetic features of plasmoid chain formation and evolution are
+investigated by two dimensional Particle-in-Cell simulations. Magnetic
+reconnection is initiated in multiple X points by the tearing instability.
+Plasmoids form and grow in size by continuously coalescing. Each chain plasmoid
+exhibits a strong out-of plane core magnetic field and an out-of-plane electron
+current that drives the coalescing process. The disappearance of the X points
+in the coalescence process are due to anti-reconnection, a magnetic
+reconnection where the plasma inflow and outflow are reversed with respect to
+the original reconnection flow pattern. Anti-reconnection is characterized by
+the Hall magnetic field quadrupole signature. Two new kinetic features, not
+reported by previous studies of plasmoid chain evolution, are here revealed.
+First, intense electric fields develop in-plane normally to the separatrices
+and drive the ion dynamics in the plasmoids. Second, several bipolar electric
+field structures are localized in proximity of the plasmoid chain. The analysis
+of the electron distribution function and phase space reveals the presence of
+counter-streaming electron beams, unstable to the two stream instability, and
+phase space electron holes along the reconnection separatrices.",1202.2663v1
+2012-03-15,Two-color QCD with staggered fermions at finite temperature under the influence of a magnetic field,"In this paper we investigate the influence of a constant external magnetic
+field on the finite-temperature phase structure and the chiral properties of a
+simplified lattice model for QCD. We assume an SU(2) gauge symmetry and employ
+dynamical staggered fermions of identical mass without rooting, corresponding
+to Nf=4 flavors of identical electric charge. For fixed mass (given in lattice
+units) the critical temperature is seen to rise with the magnetic field
+strength. For three fixed beta-values, selected such that we stay (i) within
+the chirally broken phase, (ii) within the transition region or (iii) within
+the chirally restored phase, we study the approach to the chiral limit for
+various values of the magnetic field. Within the chirally broken (confinement)
+phase the chiral condensate is found to increase monotonically with a growing
+magnetic field strength. In the chiral limit the increase starts linear in
+agreement with a chiral model studied by Shushpanov and Smilga. Within the
+chirally restored (deconfinement) phase the chiral condensate tends to zero in
+the chiral limit, irrespective of the strength of the magnetic field.",1203.3360v2
+2012-05-16,Self-cancellation of ephemeral regions in the quiet Sun,"With the observations from the Helioseismic and Magnetic Imager aboard the
+Solar Dynamics Observatory, we statistically investigate the ephemeral regions
+(ERs) in the quiet Sun. We find that there are two types of ERs: normal ERs
+(NERs) and self-cancelled ERs (SERs). Each NER emerges and grows with
+separation of its opposite polarity patches which will cancel or coalesce with
+other surrounding magnetic flux. Each SER also emerges and grows and its
+dipolar patches separate at first, but a part of magnetic flux of the SER will
+move together and cancel gradually, which is described with the term
+""self-cancellation"" by us. We identify 2988 ERs among which there are 190 SERs,
+about 6.4% of the ERs. The mean value of self-cancellation fraction of SERs is
+62.5%, and the total self-cancelled flux of SERs is 9.8% of the total ER flux.
+Our results also reveal that the higher the ER magnetic flux is, (i) the easier
+the performance of ER self-cancellation is, (ii) the smaller the
+self-cancellation fraction is, and (iii) the more the self-cancelled flux is.
+We think that the self-cancellation of SERs is caused by the submergence of
+magnetic loops connecting the dipolar patches, without magnetic energy release.",1205.3716v1
+2012-07-17,Thermal Shielding of an Emerging Active Region,"The interaction between emerging active regions and the pre-existing coronal
+magnetic field is important to understand better the mechanisms of storage and
+release of magnetic energy from the convection zone to the high corona. We are
+aiming at describing the first steps of the emergence of an active region
+within a pre-existing quiet-Sun corona in terms of the thermal and magnetic
+structure. We use unprecedented spatial, temporal and spectral coverage from
+the Atmospheric Imager Assembly (AIA) and from the Helioseismic and Magnetic
+Imager (HMI) on board the Solar Dynamics Observatory (SDO). Starting on 30 May
+2010 at 17:00 UT and for 8 hours, we follow the emergence of the active region
+AR11076 within a quiet-Sun region. Using several SDO/AIA filters covering
+temperatures from 50000K to 10 MK, we show that the emerging process is
+characterised by a thermal shield at the interface between the emerging flux
+and pre-existing quiet-Sun corona. The active region 11076 can be considered as
+a peculiar example of emerging active region as (i) the polarities emerge in a
+photospheric quiet-Sun region near a supergranular-like distribution, (ii) the
+polarities forming the bipolar emerging structure do not rotate with respect to
+each other indicating a small amount of twist in the emerging flux bundle.
+There is a thermal shield formed at the interface between the emerging active
+region and the pre-existing quiet-Sun region. The thermal shielding structure
+deduced from all SDO/AIA channels exhibits a strong asymmetry between the two
+polarities of the active region suggesting that the heating mechanism for one
+polarity is more likely to be magnetic reconnection, whilst it is due to
+increasing magnetic pressure for the opposite polarity.",1207.3992v1
+2012-08-06,A Non-radial Eruption in a Quadrupolar Magnetic Configuration with a Coronal Null,"We report one of several homologous non-radial eruptions from NOAA active
+region (AR) 11158 that are strongly modulated by the local magnetic field as
+observed with the Solar Dynamic Observatory (SDO). A small bipole emerged in
+the sunspot complex and subsequently created a quadrupolar flux system.
+Non-linear force-free field (NLFFF) extrapolation from vector magnetograms
+reveals its energetic nature: the fast-shearing bipole accumulated ~2e31 erg
+free energy (10% of AR total) over just one day despite its relatively small
+magnetic flux (5% of AR total). During the eruption, the ejected plasma
+followed a highly inclined trajectory, over 60 degrees with respect to the
+radial direction, forming a jet-like, inverted-Y shaped structure in its wake.
+Field extrapolation suggests complicated magnetic connectivity with a coronal
+null point, which is favorable of reconnection between different flux
+components in the quadrupolar system. Indeed, multiple pairs of flare ribbons
+brightened simultaneously, and coronal reconnection signatures appeared near
+the inferred null. Part of the magnetic setting resembles that of a
+blowout-type jet; the observed inverted-Y structure likely outlines the open
+field lines along the separatrix surface. Owing to the asymmetrical
+photospheric flux distribution, the confining magnetic pressure decreases much
+faster horizontally than upward. This special field geometry likely guided the
+non-radial eruption during its initial stage.",1208.1097v1
+2012-08-28,Instrumentation status of the low-b magnet systems at the Large Hadron Collider (LHC),"The low-beta magnet systems are located in the Large Hadron Collider (LHC)
+insertion regions around the four interaction points. They are the key elements
+in the beams focusing/defocusing process allowing proton collisions at
+luminosity up to 10**34/cm**2s. Those systems are a contribution of the US-LHC
+Accelerator project. The systems are mainly composed of the quadrupole magnets
+(triplets), the separation dipoles and their respective electrical feed-boxes
+(DFBX). The low-beta magnet systems operate in an environment of extreme
+radiation, high gradient magnetic field and high heat load to the cryogenic
+system due to the beam dynamic effect. Due to the severe environment, the
+robustness of the diagnostics is primordial for the operation of the triplets.
+The hardware commissioning phase of the LHC was completed in February 2010. In
+the sake of a safer and more user-friendly operation, several consolidations
+and instrumentation modifications were implemented during this commissioning
+phase. This paper presents the instrumentation used to optimize the engineering
+process and operation of the final focusing/defocusing quadrupole magnets for
+the first years of operation.",1208.5779v1
+2012-09-07,General relativistic simulations of black hole-neutron star mergers: Effects of tilted magnetic fields,"Black hole--neutron star (BHNS) binary mergers can form disks in which
+magnetorotational instability (MRI)-induced turbulence may drive accretion onto
+the remnant BH, supporting relativistic jets and providing the engine for a
+short-hard gamma-ray burst (SGRB). Our earlier study of magnetized BHNSs showed
+that NS tidal disruption winds the magnetic field into a toroidal
+configuration, with poloidal fields so weak that capturing MRI with full-disk
+simulations would require $\sim 10^8$ CPU-hours. In that study we imposed
+equatorial symmetry, suppressing poloidal magnetic fields that might be
+generated from plasma crossing the orbital plane. Here we show that initial
+conditions that break this symmetry (i.e., {\it tilted} poloidal magnetic
+fields in the NS) generate much stronger poloidal fields in the disk,
+indicating that asymmetric initial conditions may be necessary for establishing
+BHNS mergers as SGRB progenitors via fully general relativistic MHD
+simulations. We demonstrate that BHNS mergers may form an SGRB engine under the
+right conditions by seeding the remnant disk from an unmagnetized BHNS
+simulation with purely poloidal fields dynamically unimportant initially, but
+strong enough to resolve MRI. Magnetic turbulence occurs in the disk, driving
+accretion and supporting Poynting-dominated jet outflows sufficient to power an
+SGRB.",1209.1632v2
+2012-11-26,Nonlinear Evolution of the Radiation-Driven Magneto-Acoustic Instability (RMI),"We examine the nonlinear development of unstable magnetosonic waves driven by
+a background radiative flux -- the Radiation-Driven Magneto-Acoustic
+Instability (RMI, a.k.a. the ""photon bubble"" instability). The RMI may serve as
+a persistent source of density, radiative flux, and magnetic field fluctuations
+in stably-stratified, optically-thick media. The conditions for instability are
+present in a variety of astrophysical environments, and do not require the
+radiation pressure to dominate or the magnetic field to be strong. Here we
+numerically study the saturation properties of the RMI, covering three orders
+of magnitude in the relative strength of radiation, magnetic field, and gas
+energies. Two-dimensional, time-dependent radiation-MHD simulations of local,
+stably-stratified domains are conducted with Zeus-MP in the optically-thick,
+highly-conducting limit. Our results confirm the theoretical expectations of
+Blaes and Socrates (2003) in that the RMI operates even in gas
+pressure-dominated environments that are weakly magnetized. The saturation
+amplitude is a monotonically increasing function of the ratio of radiation to
+gas pressure. Keeping this ratio constant, we find that the saturation
+amplitude peaks when the magnetic pressure is comparable to the radiation
+pressure. We discuss the implications of our results for the dynamics of
+magnetized stellar envelopes, where the RMI should act as a source of
+sub-photospheric perturbations.",1211.6107v2
+2012-12-21,Buoyant Magnetic Loops Generated by Global Convective Dynamo Action,"Our global 3D simulations of convection and dynamo action in a Sun-like star
+reveal that persistent wreaths of strong magnetism can be built within the bulk
+of the convention zone. Here we examine the characteristics of buoyant magnetic
+structures that are self-consistently created by dynamo action and turbulent
+convective motions in a simulation with solar stratification but rotating at
+three times the current solar rate. These buoyant loops originate within
+sections of the magnetic wreaths in which turbulent flows amplify the fields to
+much larger values than is possible through laminar processes. These amplified
+portions can rise through the convective layer by a combination of magnetic
+buoyancy and advection by convective giant cells, forming buoyant loops. We
+measure statistical trends in the polarity, twist, and tilt of these loops.
+Loops are shown to preferentially arise in longitudinal patches somewhat
+reminiscent of active longitudes in the Sun, although broader in extent. We
+show that the strength of the axisymmetric toroidal field is not a good
+predictor of the production rate for buoyant loops or the amount of magnetic
+flux in the loops that are produced.",1212.5612v1
+2013-04-15,"Collisions, magnetization, and transport coefficients in the lower solar atmosphere","The lower solar atmosphere is an intrinsically multi-component and
+collisional environment with electron and proton collision frequencies in the
+range $10^{8}-10^{10}$ Hz, which may be considerably higher than the
+gyro-frequencies for both species. We aim to provide a reliable quantitative
+set of data for collision frequencies, magnetization, viscosity, and thermal
+conductivity for the most important species in the lower solar atmosphere.
+Having such data at hand is essential for any modeling that is aimed at
+describing realistic properties of the considered environment.
+  We describe the altitude dependence of the parameters and the different
+physics of collisions between charged species, and between charged and neutrals
+species. Regions of dominance of each type of collisions are clearly
+identified. We determine the layers within which either electrons or ions or
+both are unmagnetized. Protons are shown to be un-magnetized in the lower
+atmosphere in a layer that is at least 1000 km thick even for a kilo-Gauss
+magnetic field that decreases exponentially with altitude. In these layers the
+dynamics of charged species cannot be affected by the magnetic field, and this
+fact is used in our modeling. Viscosity and thermal conductivity coefficients
+are calculated for layers where ions are unmagnetized. We compare viscosity and
+friction and determine the regions of dominance of each of the phenomena.
+  We provide the most reliable quantitative values for most important
+parameters in the lower solar atmosphere to be used in analytical modeling and
+numerical simulations of various phenomena such as waves, transport and
+magnetization of particles, and the triggering mechanism of coronal mass
+ejections.",1304.4010v1
+2013-04-29,Spatially periodic domain wall pinning potentials: Asymmetric pinning and dipolar biasing,"Domain wall propagation has been measured in continuous, weakly disordered,
+quasi-two-dimensional, Ising-like magnetic layers that are subject to spatially
+periodic domain wall pinning potentials. The potentials are generated
+non-destructively using the stray magnetic field of ordered arrays of
+magnetically hard [Co/Pt]$_m$ nanoplatelets which are patterned above and are
+physically separated from the continuous magnetic layer. The effect of the
+periodic pinning potentials on thermally activated domain wall creep dynamics
+is shown to be equivalent, at first approximation, to that of a uniform,
+effective retardation field, $H_{ret}$, which acts against the applied field,
+$H$. We show that $H_{ret}$ depends not only on the array geometry but also on
+the relative orientation of $H$ and the magnetization of the nanoplatelets. A
+result of the latter dependence is that wall-mediated hysteresis loops obtained
+for a set nanoplatelet magnetization exhibit many properties that are normally
+associated with ferromagnet/antiferromagnet exchange bias systems. These
+include a switchable bias, coercivity enhancement and domain wall roughness
+that is dependent on the applied field polarity.",1304.7560v1
+2013-05-16,Out-of-Equilibrium Chiral Magnetic Effect at Strong Coupling,"We study the charge transports originating from triangle anomaly in
+out-of-equilibrium conditions in the framework of AdS/CFT correspondence at
+strong coupling, to gain useful insights on possible charge separation effects
+that may happen in the very early stages of heavy-ion collisions. We first
+construct a gravity background of a homogeneous mass shell with a finite
+(axial) charge density gravitationally collapsing to a charged blackhole, which
+serves as a dual model for out-of-equilibrium charged plasma undergoing
+thermalization. We find that a finite charge density in the plasma slows down
+the thermalization. We then study the out-of-equilibrium properties of Chiral
+Magnetic Effect and Chiral Magnetic Wave in this background. As the medium
+thermalizes, the magnitude of chiral magnetic conductivity and the response
+time delay grow. We find a dynamical peak in the spectral function of retarded
+current correlator, which we identify as an out-of-equilibrium chiral magnetic
+wave. The group velocity of the out-of-equilibrium chiral magnetic wave is
+shown to receive a dominant contribution from a non-equilibrium effect, making
+the wave moving much faster than in the equilibrium, which may enhance the
+charge transports via triangle anomaly in the early stage of heavy-ion
+collisions.",1305.3949v2
+2013-06-20,"Magnetic orders, excitations, and phase transitions in Fe_1+yTe","We study the magnetic properties of Fe_1+y Te, a parent compound of the
+iron-based high-temperature superconductors. Motivated by recent neutron
+scattering experiments, we show that a spin-1 exchange model, supplemented by a
+single-ion spin anisotropy, accounts well for the experimentally observed low
+temperature magnetic phase diagram, that exhibits a commensurate bicollinear
+order at low Fe dopings (y < 0.12) and an incommensurate spin-spiral order at
+high Fe dopings (y > 0.12). We suggest that the commensurate-incommensurate
+transition at y = 0.12 is due to the competition between the exchange
+interaction and the local spin anisotropy. At low Fe dopings, the single-ion
+spin anisotropy is strong and pins the spins along the easy axis, which,
+together with the spatially anisotropic exchanges, induces a unusual
+bicollinear commensurate magnetic order. The low-energy spin-wave excitation is
+gapped due to the explict breaking of spin-rotational symmetry by the local
+spin anisotropy. At high Fe dopings, the single-ion anisotropy is weak, and the
+exchange favors an incommensurate coplanar state. The incommensurate magnetic
+wavevector averages out the spin anisotropy so that a gapless low-energy
+spin-wave excitation is obtained. We also analyze the low-energy hydrodynamic
+model and use it to describe the magneto-structural transition and the static
+and dynamical spin structure factors across the magnetic ordering transitions.",1306.4730v2
+2013-08-01,Quark confinement via magnetic color-flavor locking,"The color-flavor locking phenomenon in the magnetic picture can be the
+microscopic description of the quark confinement in QCD. We demonstrate it in
+an N=2 supersymmetric SU(Nc)xSU(Nc) quiver gauge theory coupled to Nf flavors
+of quarks (Nf<Nc). This model reduces to SU(Nc) gauge theory with Nf flavors
+when the vacuum expectations value of the link field is much larger than the
+dynamical scales, and thus provides a continuous deformation of the N=2
+supersymmetric QCD. We study a vacuum which survives upon adding a
+superpotential term to reduce to N=1 while preserving the vectorial SU(Nf)
+flavor symmetry. We find a region of the parameter space where the confinement
+is described by the Higgsing of a weakly coupled magnetic SU(Nf)xU(1) gauge
+theory. The Higgsing locks the quantum numbers of SU(Nf) magnetic color to
+those of SU(Nf) flavor symmetry, and thus the massive magnetic gauge bosons
+become the singlet and adjoint representations of the flavor group, i.e, the
+vector mesons. If the qualitative picture remains valid in non-supersymmetric
+QCD, one can understand the Hidden Local Symmetry as the magnetic dual
+description of QCD, and the confining string is identified as the vortex of
+vector meson fields.",1308.0093v2
+2013-09-10,Artificial magnetic field induced by an evanescent wave,"Cold atomic gases are perfect laboratories for realization of quantum
+simulators. In order to simulate solid state systems in the presence of
+magnetic fields special effort has to be made because atoms are charge neutral.
+There are different methods for realization of artificial magnetic fields, that
+is the creation of specific conditions so that the motion of neutral particles
+mimics the dynamics of charged particles in an effective magnetic field. Here,
+we consider adiabatic motion of atoms in the presence of an evanescent wave.
+Theoretical description of the adiabatic motion involves artificial vector and
+scalar potentials related to the Berry phases. Due to the large gradient of the
+evanescent field amplitude, the potentials can be strong enough to induce
+measurable effects in cold atomic gases. We show that the resulting artificial
+magnetic field is able to induce vortices in a Bose-Einstein condensate trapped
+close to a surface of a prism where the evanescent wave is created. We also
+analyze motion of an atomic cloud released from a magneto-optical trap that
+falls down on the surface of the prism. The artificial magnetic field is able
+to reflect falling atoms that can be observed experimentally.",1309.2674v4
+2013-09-13,Laminar and transitional liquid metal duct flow near a magnetic point dipole,"The flow transformation and the generation of vortex structures by a strong
+magnetic dipole field in a liquid metal duct flow is studied by means of
+three-dimensional direct numerical simulations. The dipole is considered as the
+paradigm for a magnetic obstacle which will deviate the streamlines due to
+Lorentz forces acting on the fluid elements. The duct is of square
+cross-section. The dipole is located above the top wall and is centered in
+spanwise direction. Our model uses the quasi-static approximation which is
+applicable in the limit of small magnetic Reynolds numbers. The analysis covers
+the stationary flow regime at small hydrodynamic Reynolds numbers Re as well as
+the transitional time-dependent regime at higher values which may generate a
+turbulent flow in the wake of the magnetic obstacle. We present a systematic
+study of these two basic flow regimes and their dependence on Re and on the
+Hartmann number Ha, a measure of the strength of the magnetic dipole field.
+Furthermore, three orientations of the dipole are compared: streamwise,
+spanwise and wall-normal oriented dipole axes. The most efficient generation of
+turbulence at a fixed distance above the duct follows for the spanwise
+orientation, which is caused by a certain configuration of Hartmann layers and
+reversed flow at the top plate. The enstrophy in the turbulent wake grows
+linearly with Ha which is connected with a dominance of the wall-normal
+z-derivative of the streamwise velocity.",1309.3506v2
+2013-11-25,A study of crossover from 3D ferrimagnetic Bulk $NiCr_{2}O_{4}$ compound into 2D spin-glass like nanophase,"In this report, the magnetic behaviour of $NiCr_{2}O_{4}$ bulk and
+nanoparticle samples under different applied magnetic field has been
+investigated extensively. Nanoparticles of $NiCr_{2}O_{4}$ were obtained by
+mechanical milling of polycrystalline powder prepared by polyol method. FC-ZFC
+measurement of bulk at different applied magnetic field has revealed the
+existence of a ferrimagnetic transition around 66K followed by an
+antiferromagnetic transition close to 30K. However, its nano counterpart has
+shown remarkable change in magnetic properties - a suppression of ferrimagnetic
+transition accompanied by strengthening low temperature magnetic phase and
+observation of a new transition at 90K ($T_P$), which is weakly magnetic in
+nature. The frequency dependent ac susceptibility data of nanoparticle have
+been fitted to the well known de Almedia-Thouless equation and a $H^{2/3}$
+dependence of the low temperature peak is observed with a resulting zero field
+freezing temperature ($T_f^0$) equal to 10.1K. Further, the dynamical behaviour
+near freezing temperature has been analysed in terms of critical behaviour and
+the obtained fitted parameters values being as $\tau_0$(relaxation time
+constant) = $3.6 X 10^{-6}s$, $T_f^0=8.7$K and $z\nu = 11.1$. Moreover,
+Vogel-Fulcher law has been used to understand the nature of freezing transition
+and the parameter after fitting are obtained as $E_a/k_B = 58.9$K, $\tau_0 =
+5.22 \times 10^{-8}$ and $T_0 = 8.03$K. Finally, the spin-glass phase is
+concluded. Moreover, in contrast to bulk, the $H^{2/3}$ dependence of freezing
+temperature of nanoparticle sample (75h) does support the 2D surface like spin
+glass nature.",1311.6269v1
+2014-01-23,Spin-correlations and magnetic structure in an Fe monolayer on 5d transition metal surfaces,"We present a detailed first principles study on the magnetic structure of an
+Fe monolayer on different surfaces of 5d transition metals. We use the
+spin-cluster expansion technique to obtain parameters of a spin model, and
+predict the possible magnetic ground state of the studied systems by employing
+the mean field approach and in certain cases by spin dynamics calculations. We
+point out that the number of shells considered for the isotropic exchange
+interactions plays a crucial role in the determination of the magnetic ground
+state. In the case of Ta substrate we demonstrate that the out-of-plane
+relaxation of the Fe monolayer causes a transition from ferromagnetic to
+antiferromagnetic ground state. We examine the relative magnitude of nearest
+neighbour Dzyaloshinskii-Moriya (D) and isotropic (J) exchange interactions in
+order to get insight into the nature of magnetic pattern formations. For the
+Fe/Os(0001) system we calculate a very large D/J ratio, correspondingly, a spin
+spiral ground state. We find that, mainly through the leading isotropic
+exchange and Dzyaloshinskii-Moriya interactions, the inward layer relaxation
+substantially influences the magnetic ordering of the Fe monolayer. For the
+Fe/Re(0001) system characterized by large antiferromagnetic interactions we
+also determine the chirality of the $120^{\circ}$ N\'eel-type ground state.",1401.6073v2
+2014-01-24,A search for magnetic fields on central stars in planetary nebulae,"One of the possible mechanisms responsible for the panoply of shapes in
+planetary nebulae is the presence of magnetic fields that drive the ejection of
+ionized material during the proto-planetary nebula phase. Therefore, detecting
+magnetic fields in such objects is of key importance for understanding their
+dynamics. Still, magnetic fields have not been detected using polarimetry in
+the central stars of planetary nebulae. Circularly polarized light spectra have
+been obtained with the Focal Reducer and Low Dispersion Spectrograph at the
+Very Large Telescope of the European Southern Observatory and the Intermediate
+dispersion Spectrograph and Imaging System at the William Herschel Telescope.
+Nineteen planetary nebulae spanning very different morphology and evolutionary
+stages have been selected. Most of central stars have been observed at
+different rotation phases to point out evidence of magnetic variability. In
+this paper, we present the result of two observational campaigns aimed to
+detect and measure the magnetic field in the central stars of planetary nebulae
+on the basis of low resolution spectropolarimetry. In the limit of the adopted
+method, we can state that large scale fields of kG order are not hosted on the
+central star of planetary nebulae.",1401.6282v1
+2014-02-12,Properties of sunspot umbrae observed in Cycle 24,"We analyzed the size, intensity, and magnetic field strength of sunspot
+umbrae to compare the present cycle 24 with the previous one. We used data of
+the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory and
+selected all sunspots between May 2010 and October 2012, using one image per
+day. We created two subsets of this data with a manual tracking algorithm, both
+without duplication. One is containing each sunspot (910 umbrae within 488
+spots) and was used to analyze the distribution of umbral areas, selected with
+an automated thresholding method. The other one contains 205 fully evolved
+sunspots. We find nonlinear relations between umbral minimum intensity and size
+and between maximum magnetic field strength and size. The field strength scales
+linear with the intensity and the umbral size scales roughly linear with the
+total magnetic flux, while the size and field strength level off with stronger
+flux. When separated in hemisphere and averaged temporally, the southern umbrae
+show a temporal increase in size and the northern umbrae stay constant. There
+is no temporal variation in the umbral mean intensity detectable. The
+probability density function of the umbral area in the ascending phase of the
+current solar cycle is similar to that of the last solar cycle. From our
+investigation of umbral area, magnetic field, magnetic flux and umbral
+intensity of the sunspots of the rising phase of cycle 24, we do not find a
+significant difference to the previous cycle, and hence no indication for a
+long-term decline of solar activity.",1402.2881v1
+2014-03-12,Deciphering Solar Magnetic Activity I: On The Relationship Between The Sunspot Cycle And The Evolution Of Small Magnetic Features,"Sunspots are a canonical marker of the Sun's internal magnetic field which
+flips polarity every ~22-years. The principal variation of sunspots, an
+~11-year variation in number, modulates the amount of magnetic field that
+pierces the solar surface and drives significant variations in our Star's
+radiative, particulate and eruptive output over that period. This paper
+presents observations from the Solar and Heliospheric Observatory and Solar
+Dynamics Observatory indicating that the 11-year sunspot variation is
+intrinsically tied it to the spatio-temporal overlap of the activity bands
+belonging to the 22-year magnetic activity cycle. Using a systematic analysis
+of ubiquitous coronal brightpoints, and the magnetic scale on which they appear
+to form, we show that the landmarks of sunspot cycle 23 can be explained by
+considering the evolution and interaction of the overlapping activity bands of
+the longer scale variability.",1403.3071v3
+2014-03-18,Two-Fluid Description of Wave-Particle Interactions in Strong Buneman Turbulence,"To understand the nature of anomalous resistivity in magnetic reconnection,
+we investigate turbulence-induced momentum transport and energy dissipation
+while a plasma is unstable to the Buneman instability in force-free current
+sheets. Using 3D particle-in-cell simulations, we find that the macroscopic
+effects generated by wave-particle interactions in Buneman instability can be
+approximately described by a set of electron fluid equations. We show that both
+energy dissipation and momentum transport along electric current in the current
+layer are locally quasi-static, but globally dynamic and irreversible.
+Turbulent drag dissipates both the streaming energy of the current sheet and
+the associated magnetic energy. The net loss of streaming energy is converted
+into the electron component heat conduction parallel to the magnetic field and
+increases the electron Boltzmann entropy. The growth of self-sustained Buneman
+waves satisfies a Bernoulli-like equation that relates the turbulence-induced
+convective momentum transport and thermal momentum transport. Electron trapping
+and de-trapping drive local momentum transports, while phase mixing converts
+convective momentum into thermal momentum. The drag acts like a micro-macro
+link in the anomalous heating processes. The decrease of magnetic field
+maintains an inductive electric field that re-accelerates electrons, but most
+of the magnetic energy is dissipated and converted into the component heat of
+electrons perpendicular to the magnetic field. This heating process is
+decoupled from the heating of Buneman instability in the current sheets. Ion
+heating is weak but ions plays an important role in assisting energy exchanges
+between waves and electrons. Cold ion fluid equations together with our
+electron fluid equations form a complete set of equations that describes the
+occurrence, growth, saturation and decay of the Buneman instability.",1403.4552v2
+2014-03-31,The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He I 10830 A triplet,"Context: The determination of the magnetic field vector in quiescent solar
+prominences is possible by interpreting the Hanle and Zeeman effects in
+spectral lines. However, observational measurements are scarce and lack high
+spatial resolution. Aims: To determine the magnetic field vector configuration
+along a quiescent solar prominence by interpreting spectropolarimetric
+measurements in the He I 1083.0 nm triplet obtained with the Tenerife Infrared
+Polarimeter installed at the German Vacuum Tower Telescope of the Observatorio
+del Teide. Methods. The He I 1083.0 nm triplet Stokes profiles are analyzed
+with an inversion code that takes into account the physics responsible of the
+polarization signals in this triplet. The results are put into a solar context
+with the help of extreme ultraviolet observations taken with the Solar Dynamic
+Observatory and the Solar Terrestrial Relations Observatory satellites.
+Results: For the most probable magnetic field vector configuration, the
+analysis depicts a mean field strength of 7 gauss. We do not find local
+variations in the field strength except that the field is, in average, lower in
+the prominence body than in the prominence feet, where the field strength
+reaches 25 gauss. The averaged magnetic field inclination with respect to the
+local vertical is 77 degrees. The acute angle of the magnetic field vector with
+the prominence main axis is 24 degrees for the sinistral chirality case and 58
+degrees for the dextral chirality. These inferences are in rough agreement with
+previous results obtained from the analysis of data acquired with lower spatial
+resolutions.",1403.7976v1
+2014-05-07,Dynamic Evolution of an X-shaped Structure above a Trans-equatorial Quadrupole Solar Active Region Group,"In the solar corona, magnetic reconnection usually takes place at the
+singular configuration of magnetic field, in particular near a magnetic null
+owing to its high susceptibility to perturbations. In this Letter, we report a
+rare X-shaped structure, encompassing a magnetic null, above a trans-equatorial
+quadrupole active region group that is well observed by the Atmospheric Imaging
+Assembly (AIA). The observations show that this X-shaped structure is visible
+in all AIA EUV passbands and stably exists for days. However, possibly induced
+by flare activities at the northern part of the quadrupole active region group,
+the X-shaped structure starts to destabilize and meanwhile a jet erupted near
+its center at 15:05 UT on 2013 October 7. Through the non-linear force-free
+field modeling, we identify a magnetic null, which is above the quadrupole
+polarities and well corresponds to the X-shaped structure. After the jet
+eruption, the temperature and emission measure of the plasma near the X-shaped
+structure rise from 2.3 MK and 1.2x10^27 cm-5 at 15:01 UT to 5.4 MK and
+3.7x10^27 cm-5 at 15:36 UT, respectively, revealed by the differential emission
+measure analysis, indicating that magnetic reconnection most likely takes place
+there to heat the plasma. Moreover, the height of the null has an increase of
+10 Mm, which is most likely due to the partial opening of the field lines near
+the fan surface that makes the null underneath rise to seek for a new
+equilibrium.",1405.1563v1
+2014-06-06,High speed photospheric material flow observed at the polarity inversion line of a delta-type sunspot producing an X5.4 flare on 7 March 2012,"Solar flares abruptly release the free energy stored as a non-potential
+magnetic field in the corona and may be accompanied by eruptions of the coronal
+plasma. Formation of a non-potential magnetic field and the mechanisms for
+triggering the onset of flares are still poorly understood. In particular,
+photospheric dynamics observed near those polarity inversion lines that are
+sites of major flare production have not been well observed with high spatial
+resolution spectro-polarimetry. This paper reports on a remarkable high-speed
+material flow observed along the polarity inversion line located between flare
+ribbons at the main energy release side of an X5.4 flare on 7 March 2012.
+Observations were carried out by the spectro-polarimeter of the Solar Optical
+Telescope onboard Hinode. The high-speed material flow was observed in the
+horizontally-oriented magnetic field formed nearly parallel to the polarity
+inversion line. This flow persisted from at least 6 hours before the onset of
+the flare, and continued for at least several hours after the onset of the
+flare. Observations suggest that the observed material flow represents neither
+the emergence nor convergence of the magnetic flux. Rather, it may be
+considered to be material flow working both to increase the magnetic shear
+along the polarity inversion line and to develop magnetic structures favorable
+for the onset of the eruptive flare.",1406.1617v1
+2014-09-24,Modelling MHD accretion-ejection - episodic ejections of jets triggered by a mean-field disk dynamo,"We present MHD simulations exploring the launching, acceleration and
+collimation of jets and disk winds. The evolution of the disk structure is
+consistently taken into account. Extending our earlier studies, we now consider
+the self-generation of the magnetic field by an $\alpha^2\Omega$ mean-field
+dynamo. The disk magnetization remains on a rather low level, that helps to
+evolve the simulations for $T > 10,000$ dynamical time steps on a domain
+extending 1500 inner disk radii. We find a magnetic field of the inner disk
+similar to the commonly found open field structure, favoring
+magneto-centrifugal launching. The outer disk field is highly inclined and
+predominantly radial. Here, differential rotation induces a strong toroidal
+component that plays a key role in outflow launching. These outflows from the
+outer disk are slower, denser, and less collimated. If the dynamo action is not
+quenched, magnetic flux is continuously generated, diffuses outward the disk,
+and fills the entire disk. We have invented a toy model triggering a
+time-dependent mean-field dynamo. The duty cycles of this dynamo lead to
+episodic ejections on similar timescales. When the dynamo is suppressed as the
+magnetization falls below a critical value, the generation of the outflows and
+also accretion is inhibited. The general result is that we can steer episodic
+ejection and {\em large-scale jet knots} by a {\em disk-intrinsic dynamo} that
+is time-dependent and regenerates the jet-launching magnetic field.",1409.7003v1
+2014-11-07,Coronal magnetic field and the plasma beta determined from radio and multiple satellite observations,"We derived the coronal magnetic field, plasma density, and temperature from
+the observation of polarization and intensity of radio thermal free-free
+emission using the Nobeyama Radioheliograph (NoRH) and extreme ultraviolet
+(EUV) observations. We observed a post-flare loop on the west limb 11 April
+2013. The line-of-sight magnetic field was derived from the circularly
+polarized free-free emission observed by NoRH. The emission measure and
+temperature were derived from the Atmospheric Imaging Assembly (AIA) onboard
+Solar Dynamics Observatory (SDO). The derived temperature was used to estimate
+the emission measure from the NoRH radio free-free emission observations. The
+derived density from NoRH was larger than that determined using AIA, which can
+be explained by the fact that the low temperature plasma is not within the
+temperature coverage of the AIA filters used in this study. We also discuss the
+other observation of the post-flare loops by the EUV Imager onboard the Solar
+Terrestrial Relations Observatory (STEREO), which can be used in future studies
+to reconstruct the coronal magnetic field strength. The derived plasma
+parameters and magnetic field were used to derive the plasma beta, which is a
+ratio between the magnetic pressure and the plasma pressure. The derived plasma
+beta is about 5.7*10^(-4) to 7.6*10^(-4) at the loop top region.",1411.1913v1
+2014-11-18,The Turbulent Dynamo in Highly Compressible Supersonic Plasmas,"The turbulent dynamo may explain the origin of cosmic magnetism. While the
+exponential amplification of magnetic fields has been studied for
+incompressible gases, little is known about dynamo action in
+highly-compressible, supersonic plasmas, such as the interstellar medium of
+galaxies and the early Universe. Here we perform the first quantitative
+comparison of theoretical models of the dynamo growth rate and saturation level
+with three-dimensional magnetohydrodynamical simulations of supersonic
+turbulence with grid resolutions of up to 1024^3 cells. We obtain numerical
+convergence and find that dynamo action occurs for both low and high magnetic
+Prandtl numbers Pm = nu/eta = 0.1-10 (the ratio of viscous to magnetic
+dissipation), which had so far only been seen for Pm >= 1 in supersonic
+turbulence. We measure the critical magnetic Reynolds number, Rm_crit = 129
+(+43, -31), showing that the compressible dynamo is almost as efficient as in
+incompressible gas. Considering the physical conditions of the present and
+early Universe, we conclude that magnetic fields need to be taken into account
+during structure formation from the early to the present cosmic ages, because
+they suppress gas fragmentation and drive powerful jets and outflows, both
+greatly affecting the initial mass function of stars.",1411.4707v2
+2015-01-26,Primordial magnetic fields from self-ordering scalar fields,"A symmetry-breaking phase transition in the early universe could have led to
+the formation of cosmic defects. Because these defects dynamically excite not
+only scalar and tensor type cosmological perturbations but also vector type
+ones, they may serve as a source of primordial magnetic fields. In this study,
+we calculate the time evolution and the spectrum of magnetic fields that are
+generated by a type of cosmic defects, called global textures, using the
+non-linear sigma (NLSM) model. Based on the standard cosmological perturbation
+theory, we show, both analytically and numerically, that a vector-mode relative
+velocity between photon and baryon fluids is induced by textures, which
+inevitably leads to the generation of magnetic fields over a wide range of
+scales. We find that the amplitude of the magnetic fields is given by
+$B\sim{10^{-9}}{((1+z)/10^3)^{-2.5}}({v}/{m_{\rm pl}})^2({k}/{\rm
+Mpc^{-1}})^{3.5}/{\sqrt{N}}$ Gauss in the radiation dominated era for
+$k\lesssim 1$ Mpc$^{-1}$, with $v$ being the vacuum expectation value of the
+O(N) symmetric scalar fields. By extrapolating our numerical result toward
+smaller scales, we expect that $B\sim {10^{-17}}((1+z)/1000)^{-1/2}({v}/{m_{\rm
+pl}})^2({k}/{\rm Mpc^{-1}})^{1/2}/{\sqrt{N}}$ Gauss on scales of $k\gtrsim 1$
+Mpc$^{-1}$ at redshift $z\gtrsim 1100$. This might be a seed of the magnetic
+fields observed on large scales today.",1501.06304v1
+2015-02-26,Laws of volume elasticity of the physical processes and the parameter effect,"We consider the mechanism of elastic strains and stresses as the main
+controlling factor of structure change under the influence of temperature,
+magnetic field, hydrostatic pressure. We should take into account that the
+energy of elastic deformation is commensurate to the energy of electric
+interactions and that is much higher than the rest of the bonds of lower energy
+value. Besides, the energy elastic stresses are of long range, so it forms the
+linearity in magnetization and bulk change. These regularities requires a
+fundamental understanding of the laws of interaction with respect to accepted
+interpretation of quantum mechanical forces of short range that are attributes
+of magnetism formation. Due to the high sensitivity of electronic and resonance
+properties with respect to small changes of the structure, we were able to
+define the direct relation between elastic stresses and field-frequency
+dependencies, as well as to analyze the evolution of the dynamics of phase
+transitions and phase states. A cycle of studies of the influence of
+hydrostatic pressure on the resonance properties are presented also. The
+analysis of the effect of magnetic, magneto-elastic and elastic energy allowed
+us to define the combinations of magneto-elastic interactions. The role of
+elastic stresses in the linear changes of the magnetostriction, magnetization,
+magnetoelasticity of single-crystal magnetic semiconductors is described in
+details.",1502.07473v1
+2015-03-15,Stability of toroidal magnetic fields in stellar interiors,"We present 3D MHD simulations of purely toroidal and mixed poloidal-toroidal
+magnetic field configurations to study the behavior of the Tayler instability.
+For the first time the simultaneous action of rotation and magnetic diffusion
+are taken into account and the effects of a poloidal field on the dynamic
+evolution of unstable toroidal magnetic fields is included. In the absence of
+diffusion, fast rotation (rotation rate compared to Alfv\'en frequency) is able
+to suppress the instability when the rotation and magnetic axes are aligned and
+when the radial field strength gradient p < 1.5. When diffusion is included,
+this system turns unstable for diffusion dominated and marginally diffusive
+dominated regions. If the magnetic and rotation axes are perpendicular to each
+other the stabilizing effect induced by the Coriolis force is scale dependent
+and decreases with increasing wavenumber. In toroidal fields with radial field
+gradients bigger than p > 1.5, rapid rotation does not suppress the instability
+but instead introduces a damping factor to the growth rate in agreement with
+the analytic predictions. For the mixed poloidal-toroidal fields we find an
+unstable axisymmetric mode, not predicted analytically, right at the stability
+threshold for the non-axisymmetric modes; it has been argued that an
+axisymmetric mode is necessary for the closure of the Tayler-Spruit dynamo
+loop.",1503.04450v1
+2015-03-19,Consistent generation of magnetic fields in axion inflation models,"There has been a growing evidence for the existence of magnetic fields in the
+extra-galactic regions, while the attempt to associate their origin with the
+inflationary epoch alone has been found extremely challenging. We therefore
+take into account the consistent post-inflationary evolution of the magnetic
+fields that are originated from vacuum fluctuations during inflation. In the
+model of our interest, the electromagnetic (EM) field is coupled to a
+pseudo-scalar inflaton $\phi$ through the characteristic term $\phi F\tilde F$,
+breaking the conformal invariance. This interaction dynamically breaks the
+parity and enables a continuous production of only one of the polarization
+states of the EM field through tachyonic instability. The produced magnetic
+fields are thus helical. We find that the dominant contribution to the observed
+magnetic fields in this model comes from the modes that leave the horizon near
+the end of inflation, further enhanced by the tachyonic instability right after
+the end of inflation. The EM field is subsequently amplified by parametric
+resonance during the period of inflaton oscillation. Once the thermal plasma is
+formed (reheating), the produced helical magnetic fields undergo a turbulent
+process called inverse cascade, which shifts their peak correlation scales from
+smaller to larger scales. We consistently take all these effects into account
+within the regime where the perturbation of $\phi$ is negligible and obtain
+$B_{\rm eff} \sim 10^{-19}$G, indicating the necessity of additional mechanisms
+to accommodate the observations.",1503.05802v2
+2015-03-27,Magnetic Correlations in the Quasi-2D Semiconducting Ferromagnet CrSiTe$_3$,"Intrinsic, two-dimensional ferromagnetic semiconductors are an important
+class of materials for overcoming the limitations of dilute magnetic
+semiconductors for spintronics applications. CrSiTe$_3$ is a particularly
+interesting member of this class, since it can likely be exfoliated down to
+single layers, where T$_C$ is predicted to increase dramatically. Establishing
+the nature of the magnetism in the bulk is a necessary precursor to
+understanding the magnetic behavior in thin film samples and the possible
+applications of this material. In this work, we use elastic and inelastic
+neutron scattering to measure the magnetic properties of single crystalline
+CrSiTe$_3$. We find that there is a very small single ion anisotropy favoring
+magnetic ordering along the $c$-axis and that the measured spin waves fit well
+to a model where the moments are only weakly coupled along that direction.
+Finally, we find that both static and dynamic correlations persist within the
+$ab$-plane up to at least 300 K, strong evidence of this material's
+two-dimensional characteristics that are relevant for future studies on thin
+film and monolayer samples.",1503.08199v2
+2015-04-01,Evidence of the Dynamics of Relativistic Jet Launching in Quasars,"Hubble Space Telescope (HST) spectra of the extreme ultraviolet (EUV), the
+optically thick emission from the innermost accretion flow onto the central
+supermassive black hole, indicate that RLQs tend to be EUV weak compared to the
+radio quiet quasars (RQQs); yet the remainder of the optically thick thermal
+continuum is indistinguishable. The deficit of EUV emission in RLQs has a
+straightforward interpretation as a missing or a suppressed innermost region of
+local energy dissipation in the accretion flow. This article is an examination
+of the evidence for a distribution of magnetic flux tubes in the innermost
+accretion flow that results in magnetically arrested accretion (MAA) and
+creates the EUV deficit. These same flux tubes and possibly the interior
+magnetic flux that they encircle are the source of the jet power as well. In
+the MAA scenario, islands of large scale magnetic vertical flux perforate the
+innermost accretion flow of RLQs. The first prediction of the theory that is
+supported by the HST data is that the strength of the (large scale poloidal
+magnetic fields) jets in the MAA region is regulated by the ram pressure of the
+accretion flow in the quasar environment. The second prediction that is
+supported by the HST data is that the rotating magnetic islands remove energy
+from the accretion flow as a Poynting flux dominated jet in proportion to the
+square of the fraction of the EUV emitting gas that is displaced by these
+islands.",1504.00228v1
+2015-04-17,Chiral damping of magnetic domain walls,"Structural symmetry breaking in magnetic materials is responsible for a
+variety of outstanding physical phenomena. Examples range from the existence of
+multiferroics, to current induced spin orbit torques (SOT) and the formation of
+topological magnetic structures. In this letter we bring into light a novel
+effect of the structural inversion asymmetry (SIA): a chiral damping mechanism.
+This phenomenon is evidenced by measuring the field driven domain wall (DW)
+motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The
+difficulty in evidencing the chiral damping is that the ensuing DW dynamics
+exhibit identical spatial symmetry to those expected from the
+Dzyaloshinskii-Moriya interaction (DMI). Despite this fundamental resemblance,
+the two scenarios are differentiated by their time reversal properties: while
+DMI is a conservative effect that can be modeled by an effective field, the
+chiral damping is purely dissipative and has no influence on the equilibrium
+magnetic texture. When the DW motion is modulated by an in-plane magnetic
+field, it reveals the structure of the internal fields experienced by the DWs,
+allowing to distinguish the physical mechanism. The observation of the chiral
+damping, not only enriches the spectrum of physical phenomena engendered by the
+SIA, but since it can coexists with DMI it is essential for conceiving DW and
+skyrmion devices.",1504.04411v1
+2015-06-24,Ultrafast quantum spin-state switching in the Co-octaethylporphyrin molecular magnet with a terahertz pulsed magnetic field,"Molecular spin crossover switches are the objects of intense theoretical and
+experimental studies in recent years. This interest is due to the fact that
+these systems allow one to control their spin state by applying an external
+photo-, thermo-, piezo-, or magnetic stimuli. The greatest amount of research
+is currently devoted to the study the effect of the photoexcitation on the
+bi-stable states of spin crossover single molecular magnets (SMMs). The main
+limitation of photo-induced bi-stable states is their short lifetime. In this
+paper we present the results of a study of the spin dynamics of the CoOEP
+molecule in the Low Spin (LS) state and the High Spin (HS) state induced by
+applying the magnetic pulse of 36.8 T. We show that the spin switching in case
+of the HS state of the CoOEP molecule is characterized by a long lifetime and
+is dependent on the magnitude and duration of the applied field. Thus, after
+applying an external stimuli the system in the LS state after the spin
+switching reverts to its ground state, whereas the system in the HS state
+remains in the excited state for a long time. We found that the temperature
+dependency of magnetic susceptibility shows an abrupt thermal spin transition
+between two spin states at 40K. The proposed here theoretical approach opens
+the way to create modern devices for spintronics with the controllable spin
+switching process.",1506.07315v1
+2015-06-30,Realistic modeling of local dynamo processes on the Sun,"Magnetic fields are usually observed in the quiet Sun as small-scale elements
+that cover the entire solar surface (the `salt and pepper' patterns in
+line-of-sight magnetograms). By using 3D radiative MHD numerical simulations we
+find that these fields result from a local dynamo action in the top layers of
+the convection zone, where extremely weak 'seed' magnetic fields (e.g., from a
+$10^{-6}$ G) can locally grow above the mean equipartition field, to a stronger
+than 2000~G field localized in magnetic structures. Our results reveal that the
+magnetic flux is predominantly generated in regions of small-scale helical
+downflows. We find that the local dynamo action takes place mostly in a
+shallow, about 500~km deep, subsurface layer, from which the generated field is
+transported into the deeper layers by convective downdrafts. We demonstrate
+that the observed dominance of vertical magnetic fields at the photosphere and
+horizontal fields above the photosphere can be explained by small-scale
+magnetic loops produced by the dynamo. Such small-scale loops play an important
+role in the structure and dynamics of the solar atmosphere and that their
+detection in observations is critical for understanding the local dynamo action
+on the Sun.",1506.08924v1
+2015-07-02,Confined Flares in Solar Active Region 12192 from 2014 October 18 to 29,"Using the observations from the Atmospheric Imaging Assembly (AIA) and
+Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory
+(SDO), we investigate six X-class and twenty-nine M-class flares occurring in
+solar active region (AR) 12192 from October 18 to 29. Among them, thirty
+(including six X- and twenty-four M-class) flares originated from the AR core
+and the other five M-flares appeared at the AR periphery. Four of the X-flares
+exhibited similar flaring structures, indicating they were homologous flares
+with analogous triggering mechanism. The possible scenario is: photospheric
+motions of emerged magnetic fluxes lead to shearing of the associated coronal
+magnetic field, which then yields a tether-cutting favorable configuration.
+Among the five periphery M-flares, four were associated with jet activities.
+The HMI vertical magnetic field data show that the photospheric fluxes of
+opposite magnetic polarities emerged, converged and canceled with each other at
+the footpoints of the jets before the flares. Only one M-flare from the AR
+periphery was followed by a coronal mass ejection (CME). From October 20 to 26,
+the mean decay index of the horizontal background field within the height range
+of 40-105 Mm is below the typical threshold for torus instability onset. This
+suggests that a strong confinement from the overlying magnetic field might be
+responsible for the poor CME production of AR 12192.",1507.00651v1
+2015-07-13,Enhanced Acoustic Emission in Relation to the Acoustic Halo Surrounding Active Region 11429,"The use of acoustic holography in the high-frequency $p$-mode spectrum can
+resolve the source distributions of enhanced acoustic emissions within halo
+structures surrounding active regions. In doing so, statistical methods can
+then be applied to ascertain relationships with the magnetic field. This is the
+focus of this study. The mechanism responsible for the detected enhancement of
+acoustic sources around solar active regions has not yet been explained.
+Furthermore the relationship between the magnetic field and enhanced acoustic
+emission has not yet been comprehensively examined. We have used vector
+magnetograms from the \Helioseismic and Magnetic Imager (HMI) on-board the
+Solar Dynamics Observatory (SDO) to image the magnetic-field properties in the
+halo. We have studied the acoustic morphology of an active region, with a
+complex halo and ""glories,"" and we have linked some acoustic properties to the
+magnetic-field configuration. In particular, we find that acoustic sources are
+significantly enhanced in regions of intermediate field strength with
+inclinations no different from the distributions found in the quiet Sun.
+Additionally we have identified a transition region between the active region
+and the halo, in which the acoustic source power is hindered by inclined fields
+of intermediate field strength. Finally, we have compared the results of
+acoustic emission maps, calculated from holography, and the commonly used local
+acoustic maps, finding that the two types of maps have similar properties with
+respect to the magnetic field but lack spatial correlation when examining the
+highest-powered regions.",1507.03447v1
+2015-08-19,Termination of the magnetorotational instability via parasitic instabilities in core-collapse supernovae,"The magnetorotational instability (MRI) can be a powerful mechanism
+amplifying the magnetic field in core-collapse supernovae. Whether initially
+weak magnetic fields can be amplified by this instability to dynamically
+relevant strengths is still a matter of debate. One of the main uncertainties
+concerns the process that terminates the growth of the instability. Parasitic
+instabilities of both Kelvin-Helmholtz and tearing-mode type have been
+suggested to play a crucial role in this process, disrupting MRI channel flows
+and quenching magnetic field amplification. We perform two-dimensional and
+three-dimensional sheering-disc simulations of a differentially rotating
+protoneutron star layer in non-ideal magnetohydrodynamics with unprecedented
+high numerical accuracy, finding that Kelvin-Helmholtz parasitic modes dominate
+tearing modes in the regime of large hydrodynamic and magnetic Reynolds
+numbers, as encountered close to the surface of protoneutron stars. They also
+determine the maximum magnetic field stress achievable during the exponential
+growth of the MRI. Our results are consistent with the theory of parasitic
+instabilities based on a local stability analysis. To simulate the
+Kelvin-Helmholtz instabilities properly, a very high numerical resolution is
+necessary. Using ninth-order spatial reconstruction schemes, we find that at
+least eight grid zones per MRI channel are necessary to simulate the growth
+phase of the MRI and reach an accuracy of ~10 per cent in the growth rate,
+while more than ~60 zones per channel are required to achieve convergent
+results for the value of the magnetic stress at MRI termination.",1508.04799v2
+2015-09-01,Light Bridge in a Developing Active Region. II. Numerical Simulation of Flux Emergence and Light Bridge Formation,"Light bridges, the bright structure dividing umbrae in sunspot regions, show
+various activity events. In Paper I, we reported on analysis of
+multi-wavelength observations of a light bridge in a developing active region
+(AR) and concluded that the activity events are caused by magnetic reconnection
+driven by magnetconvective evolution. The aim of this second paper is to
+investigate the detailed magnetic and velocity structures and the formation
+mechanism of light bridges. For this purpose, we analyze numerical simulation
+data from a radiative magnetohydrodynamics model of an emerging AR. We find
+that a weakly-magnetized plasma upflow in the near-surface layers of the
+convection zone is entrained between the emerging magnetic bundles that appear
+as pores at the solar surface. This convective upflow continuously transports
+horizontal fields to the surface layer and creates a light bridge structure.
+Due to the magnetic shear between the horizontal fields of the bridge and the
+vertical fields of the ambient pores, an elongated cusp-shaped current layer is
+formed above the bridge, which may be favorable for magnetic reconnection. The
+striking correspondence between the observational results of Paper I and the
+numerical results of this paper provides a consistent physical picture of light
+bridges. The dynamic activity phenomena occur as a natural result of the bridge
+formation and its convective nature, which has much in common with those of
+umbral dots and penumbral filaments.",1509.00205v1
+2015-09-01,Investigation of Umbral Dots with the New Vacuum Solar Telescope,"Umbral dots (UDs) are small isolated brightenings observed in sunspot umbrae.
+They are convective phenomena existing inside umbrae. UDs are usually divided
+into central UDs (CUDs) and peripheral UDs (PUDs) according to their positions
+inside an umbra. Our purpose is to investigate UD properties and analyze their
+relationships, and further to find whether or not the properties depend on
+umbral magnetic field strengths. Thus, we selected high-resolution TiO images
+of four active regions (ARs) taken under the best seeing conditions with the
+\textit{New Vacuum Solar Telescope} in the Fuxian Solar Observatory of the
+Yunnan Astronomical Observatory, China. The four ARs (NOAA 11598, 11801, 12158,
+and 12178) include six sunspots. A total of 1220 CUDs and 603 PUDs were
+identified. Meanwhile, the radial component of the vector magnetic field of the
+sunspots taken with the \textit{Helioseismic and Magnetic Imager} on-board the
+\textit{Solar Dynamics Observatory} was used to analyze relationships between
+UD properties and umbral magnetic field strengths. We find that diameters and
+lifetimes of UDs exhibit an increasing trend with the brightness, but
+velocities do not. Moreover, diameters, intensities, lifetimes and velocities
+depend on the surrounding magnetic field. A CUD diameter was found larger, the
+CUD brighter, its lifetime longer, and its motion slower in a weak umbral
+magnetic field environment than in a strong one.",1509.00312v4
+2015-09-21,On the current solar magnetic activity in the light of its behaviour during the Holocene,"Solar modulation potential (SMP) reconstructions based on cosmogenic nuclide
+records reflect changes in the open solar magnetic field and can therefore help
+us obtain information on the behaviour of the open solar magnetic field over
+the Holocene period. We aim at comparing the Sun's large-scale magnetic field
+behaviour over the last three solar cycles with variations in the SMP
+reconstruction through the Holocene epoch. To achieve these objectives, we use
+the IntCal13 $^{14}$C data to investigate distinct patterns in the occurrences
+of grand minima and maxima during the Holocene period. We then check whether
+these patterns might mimic the recent solar magnetic activity by investigating
+the evolution of the energy in the Sun's large-scale dipolar magnetic field
+using the Wilcox Solar Observatory data. The cosmogenic radionuclide data
+analysis shows that $\sim$71\% of grand maxima during the period from 6600 BC
+to 1650 AD were followed by a grand minimum. The occurrence characteristics of
+grand maxima and minima are consistent with the scenario in which the dynamical
+non-linearity induced by the Lorentz force leads the Sun to act as a relaxation
+oscillator. This finding implies that the probability for these events to occur
+is non-uniformly distributed in time, as there is a memory in their driving
+mechanism, which can be identified via the back reaction of the Lorentz force.",1509.06182v1
+2015-10-06,"Role of boundary conditions, topology and disorder in the chiral magnetic effect in Weyl semimetals","Quantum field theory predicts Weyl semimetals to possess a peculiar response
+of the longitudinal current density to the application of a DC magnetic field.
+Such a response function has been shown to be at odds with a general result
+showing the vanishing of the bulk current in an equilibrium system on any real
+material with a lattice in an external magnetic field. Here we resolve this
+apparent contradiction by introducing a model where a current flows in response
+to a magnetic field even without Weyl nodes. We point out that the previous
+derivation of a vanishing CME in the limit of vanishing real frequency is a
+consequence of the assumption of periodic boundary conditions of the system. A
+more realistic system with open boundary conditions is not subject to these
+constraints and can have a non-vanishing CME. Consistent with recent work, we
+found the finite frequency CME to be non-vanishing in general when there was a
+non-vanishing Berry curvature on the Fermi surface. This does not necessitate
+having a topological Berry flux as in the case of a Weyl node. Finally, we
+study how the perturbation theory in magnetic field might be more stable in the
+presence of disorder. Using the standard diagrammatic treatment of disorder
+within the Born approximation, we have found that in a realistic disordered
+system, the chiral magnetic response is really a dynamical phenomena and
+vanishes in the DC limit.",1510.01767v2
+2015-10-21,Automatic Detection of Magnetic delta in Sunspot Groups,"Large and magnetically complex sunspot groups are known to be associated with
+flares. To date, the Mount Wilson scheme has been used to classify sunspot
+groups based on their morphological and magnetic properties. The most flare
+prolific class, the delta sunspot-group, is characterised by opposite polarity
+umbrae within a common penumbra, separated by less than 2 degrees. In this
+article, we present a new system, called the Solar Monitor Active Region
+Tracker - Delta Finder (SMART-DF), that can be used to automatically detect and
+classify magnetic deltas in near-realtime. Using continuum images and
+magnetograms from the Helioseismic and Magnetic Imager (HMI) onboard NASA's
+Solar Dynamics Observatory (SDO), we first estimate distances between opposite
+polarity umbrae. Opposite polarity pairs having distances of less that 2
+degrees are then identified, and if these pairs are found to share a common
+penumbra, they are identified as a magnetic delta configuration. The algorithm
+was compared to manual delta detections reported by the Space Weather
+Prediction Center (SWPC), operated by the National Oceanic and Atmospheric
+Administration (NOAA). SMART-DF detected 21 out of 23 active regions (ARs) that
+were marked as delta spots by NOAA during 2011 - 2012 (within +/- 60 degrees
+longitude). SMART-DF in addition detected five ARs which were not announced as
+delta spots by NOAA. The near-relatime operation of SMART-DF resulted in many
+deltas being identified in advance of NOAA's daily notification. SMART-DF will
+be integrated with SolarMonitor (www.solarmonitor.org) and the near-realtime
+information will be available to the public.",1510.06413v1
+2015-11-04,Magnetic fields in primordial accretion disks,"Magnetic fields are considered as a vital ingredient of contemporary star
+formation, and may have been important during the formation of the first stars
+in the presence of an efficient amplification mechanism. Initial seed fields
+are provided via plasma fluctuations, and are subsequently amplified by the
+small-scale dynamo, leading to a strong tangled magnetic field. Here we explore
+how the magnetic field provided by the small-scale dynamo is further amplified
+via the $\alpha-\Omega$ dynamo in a protostellar disk and assess its
+implications. For this purpose, we consider two characteristic cases, a typical
+Pop.~III star with $10$~M$_\odot$ and an accretion rate of
+$10^{-3}$~M$_\odot$~yr$^{-1}$, and a supermassive star with $10^5$~M$_\odot$
+and an accretion rate of $10^{-1}$~M$_\odot$~yr$^{-1}$. For the $10$~M$_\odot$
+Pop.~III star, we find that coherent magnetic fields can be produced on scales
+of at least $100$~AU, which are sufficient to drive a jet with a luminosity of
+$100$~L$_\odot$ and a mass outflow rate of $10^{-3.7}$~M$_\odot$~yr$^{-1}$. For
+the supermassive star, the dynamical timescales in its environment are even
+shorter, implying smaller orbital timescales and an efficient magnetization out
+to at least $1000$~AU. The jet luminosity corresponds to
+$\sim10^{6.0}$~L$_\odot$, and a mass outflow rate of
+$10^{-2.1}$~M$_\odot$~yr$^{-1}$. We expect that the feedback from the
+supermassive star can have a relevant impact on its host galaxy.",1511.01317v1
+2015-11-05,Polarization Evolution of Early Optical Afterglows of Gamma-Ray Bursts,"The central engine and jet composition of gamma-ray bursts (GRBs) remain
+mysterious. Here we suggest that observations on polarization evolution of
+early optical afterglows may shed light on these questions. We first study the
+dynamics of a reverse shock and a forward shock that are generated during the
+interaction of a relativistic jet and its ambient medium. The jet is likely
+magnetized with a globally large-scale magnetic field from the central engine.
+The existence of the reverse shock requires that the magnetization degree of
+the jet should not be high ($\sigma\leq 1$), so that the jet is mainly composed
+of baryons and leptons. We then calculate the light curve and polarization
+evolution of an early optical afterglow, and find that when the polarization
+position angle changes by $90^\circ$ during the early afterglow, the
+polarization degree is zero for a toroidal magnetic field but is very likely to
+be non-zero for an aligned magnetic field. This result would be expected to
+provide a probe for the central engine of GRBs, because an aligned field
+configuration could originate from a magnetar central engine and a toroidal
+field configuration could be produced from a black hole via the
+Blandford-Znajek mechanism. Finally, for such two kinds of magnetic field
+configurations, we fit the observed data of the early optical afterglow of GRB
+120308A equally well.",1511.01582v2
+2015-11-26,Theoretical formalism for collective spin-wave edge excitations in arrays of dipolarly interacting magnetic nanodots,"A general theory of edge spin wave excitations in semi-infinite and finite
+periodic arrays of magnetic nanodots existing in a spatially uniform
+magnetization ground state is developed. The theory is formulated using a
+formalism of multi-vectors of magnetization dynamics, which allows one to study
+edge excitations in arrays having arbitrary complex primitive cells and lattice
+geometry. The developed formalism can describe edge excitations localized both
+at the physical edges of the array and at the internal ""domain walls""
+separating array regions existing in different static magnetization states.
+Using a perturbation theory in the framework of the developed formalism it is
+possible to calculate damping of edge modes and their excitation by external
+variable magnetic fields. The theory is illustrated on the following
+practically important examples: (i) calculation of the FMR absorption in a
+finite nanodot array having the shape of a right triangle, (ii) calculation of
+nonreciprocal spin wave spectra of edge modes, including modes at the physical
+edges of an array and modes at the domain walls inside an array, (iii) study of
+the influence of the domain wall modes on the FMR spectrum of an array existing
+in a non-ideal chessboard antiferromagnetic ground state.",1511.08483v3
+2015-11-30,Near field magnetostatics and Neel Brownian interactions mediated magnetorheological characteristics of highly stable nano ferrocolloids,"Magnetic nanocolloids with synthesized super paramagnetic Fe3O4 nanoparticles
+(SPION) (5 to 15 nm) dispersed in insitu developed Polyethylene Glycol (PEG
+400) and nano silica complex have been synthesized. The PEG nano Silica complex
+physically encapsulates the SPIONs, ensuring no phase separation under high
+magnetic fields (1.2 T). Exhaustive magnetorheological investigations have been
+performed to comprehend the structural behavior and response of the
+ferrocolloids. Remarkable stability and reversibility have been observed under
+magnetic field for concentrated systems. The results exhibit the impact of
+particle concentration, size and encapsulation efficiency on parameters such as
+shear viscosity, yield stress, viscoelastic moduli, magnetoviscous hysteresis
+etc. Analytical models to reveal the system mechanism and mathematically
+predict the magnetoviscosity and magneto yield stress has been theorized. The
+mechanistic approach based on near field magnetostatics and Neel Brownian
+interactivities can predict the colloidal properties under the effect of field
+accurately. The colloid exhibits amplified storage and loss moduli alongside
+highly augmented linear viscoelastic region under magnetic stimuli. The
+transition of the colloidal state from fluidic phase to soft condensed phase
+and its viscoelastic stimuli under the influence of magnetic field has been
+explained based on the mathematical analysis. The remarkable stability,
+magnetic properties and accurate physical models reveal good promise for the
+colloids in transient situations viz. magneto MEMS/ NEMS devices, antiseismic
+damping, biomedical invasive treatments etc.",1512.00081v1
+2015-12-01,Magnetization reversal of an individual exchange biased permalloy nanotube,"We investigate the magnetization reversal mechanism in an individual
+permalloy (Py) nanotube (NT) using a hybrid magnetometer consisting of a
+nanometer-scale SQUID (nanoSQUID) and a cantilever torque sensor. The Py NT is
+affixed to the tip of a Si cantilever and positioned in order to optimally
+couple its stray flux into a Nb nanoSQUID. We are thus able to measure both the
+NT's volume magnetization by dynamic cantilever magnetometry and its stray flux
+using the nanoSQUID. We observe a training effect and temperature dependence in
+the magnetic hysteresis, suggesting an exchange bias. We find a low blocking
+temperature $T_B = 18 \pm 2$ K, indicating the presence of a thin
+antiferromagnetic native oxide, as confirmed by X-ray absorption spectroscopy
+on similar samples. Furthermore, we measure changes in the shape of the
+magnetic hysteresis as a function of temperature and increased training. These
+observations show that the presence of a thin exchange-coupled native oxide
+modifies the magnetization reversal process at low temperatures. Complementary
+information obtained via cantilever and nanoSQUID magnetometry allows us to
+conclude that, in the absence of exchange coupling, this reversal process is
+nucleated at the NT's ends and propagates along its length as predicted by
+theory.",1512.00199v1
+2015-12-03,Orbitally induced hierarchy of exchange interactions in zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6,"We report the revised crystal structure, static and dynamic magnetic
+properties of quasi-two dimensional honeycomb-lattice silver delafossite
+Ag3Co2SbO6. The magnetic susceptibility and specific heat data are consistent
+with the onset of antiferromagnetic long range order at low temperatures with
+N\'eel temperature TN ~ 21.2 K. In addition, the magnetization curves revealed
+a field-induced (spin-flop type) transition below TN in moderate magnetic
+fields. The GGA+U calculations show the importance of the orbital degrees of
+freedom, which maintain a hierarchy of exchange interaction in the system. The
+strongest antiferromagnetic exchange coupling was found in the shortest Co-Co
+pairs and is due to direct and superexchange interactions between the
+half-filled xz+yz orbitals pointing directly to each other. The other four out
+of six nearest neighbor exchanges within the cobalt hexagon are suppressed,
+since for these bonds active half-filled orbitals turned out to be parallel and
+do not overlap. The electron spin resonance (ESR) spectra reveal a Gaussian
+shape line attributed to Co2+ ion in octahedral coordination with average
+effective g-factor g=2.3+/-0.1 at room temperature and shows strong divergence
+of ESR parameters below 120 K, which imply an extended region of short-range
+correlations. Based on the results of magnetic and thermodynamic studies in
+applied fields, we propose the magnetic phase diagram for the new
+honeycomb-lattice delafossite.",1512.01016v1
+2015-12-15,Ginzburg-Landau theory for skyrmions in inversion-symmetric magnets with competing interactions,"Magnetic skyrmions have attracted considerable attention recently for their
+huge potential in spintronic applications. Generally skyrmions are big compared
+to the atomic lattice constant, which allows for the Ginzburg-Landau type
+description in the continuum limit. Such a description successfully captures
+the main experimental observations on skyrmions in B20 compound without
+inversion symmetry. Skyrmions can also exist in inversion-symmetric magnets
+with competing interactions. Here we derive a general Ginzburg-Landau theory
+for skyrmions in these magnets valid in the long wavelength limit. We study the
+unusual static and dynamical properties of skyrmions based on the derived
+Ginzburg-Landau theory. We show that an easy axis spin anisotropy is sufficient
+to stabilize a skyrmion lattice. Interestingly, the skyrmion in
+inversion-symmetric magnets has a new internal degree of freedom associated
+with the rotation of helicity, i.e. the ""spin"" of the skyrmion as a particle,
+in addition to the usual translational motion of skyrmions (orbital motion).
+The orbital and spin degree of freedoms of an individual skyrmion can couple to
+each other, and give rise to unusual behavior that is absent for the skyrmions
+stabilized by the Dzyaloshinskii-Moriya interaction. The derived
+Ginzburg-Landau theory provides a convenient and general framework to discuss
+skyrmion physics and will facilitate the search for skyrmions in
+inversion-symmetric magnets.",1512.05012v1
+2016-01-05,Quantum revivals and magnetization tunneling in effective spin systems,"Quantum mechanical objects or nanoobjects have been proposed as bits for
+information storage. While time-averaged properties of magnetic,
+quantum-mechanical particles have been extensively studied experimentally and
+theoretically, experimental investigations of the real time evolution of
+magnetization in the quantum regime were not possible until recent developments
+in pump-probe techniques. Here we investigate the quantum dynamics of effective
+spin systems by means of analytical and numerical treatments. Particular
+attention is paid to the quantum revival time and its relation to the
+magnetization tunneling. The quantum revival time has been initially defined as
+the recurrence time of a total wave-function. Here we show that the quantum
+revivals of wave-functions and expectation values in spin systems may be quite
+different which gives rise to a more sophisticated definition of the quantum
+revival within the realm of experimental research. Particularly, the revival
+times for integer spins coincide which is not the case for half-integer spins.
+Furthermore, the quantum revival is found to be shortest for integer ratios
+between the on-site anisotropy and an external magnetic field paving the way to
+novel methods of anisotropy measurements. We show that the quantum tunneling of
+magnetization at avoided level crossing is coherent to the quantum revival time
+of expectation values, leading to a connection between these two fundamental
+properties of quantum mechanical spins.",1601.00803v1
+2016-02-07,Interaction of microwave photons with nanostructured magnetic metasurfaces,"A theoretical formalism for the description of the interaction of microwave
+photons with a thin (compared to the photon wavelength) magnetic metasurface
+comprised of dipolarly interacting nano-scale magnetic elements is developed. A
+scattering matrix describing the processes of photon transmission and
+reflection at the metasurface boundary is derived. As an example of the use of
+the developed formalism, it is demonstrated, that the introduction of a
+magnetic metasurface inside a microstrip electromagnetic waveguide
+quantitatively changes the dispersion relation of the fundamental waveguide
+mode, opening a non-propagation frequency band gap in the waveguide spectrum.
+The frequency position and the width of the band gap are dependent on the
+waveguide thickness, and can be controlled dynamically by switching the
+magnetic ground state of the metasurface. For sufficiently thin waveguides the
+position of the band gap is shifted from the resonance absorption frequency of
+the metasurface. In such a case, the magnetic metasurface inside a waveguide
+works as an efficient reflector, as the energy absorption in the metasurface is
+small, and most of the electromagnetic energy inside the non-propagation band
+gap is reflected.",1602.02340v2
+2016-02-18,Spin Liquid State in the 3D Frustrated Antiferromagnet PbCuTe2O6: NMR and muSR Studies,"PbCuTe2O6 is a rare example of a spin liquid candidate featuring a three
+dimensional magnetic lattice. Strong geometric frustration arises from the
+dominant antiferromagnetic interaction which generates a hyperkagome network of
+Cu2+ ions although additional interactions enhance the magnetic lattice
+connectivity. Through a combination of magnetization measurements and local
+probe investigation by NMR and muSR down to 20 mK, we provide a robust evidence
+for the absence of magnetic freezing in the ground state. The local spin
+susceptibility probed by the NMR shift hardly deviates from the macroscopic one
+down to 1 K pointing to a homogeneous magnetic system with a low defect
+concentration. The saturation of the NMR shift and the sublinear power law
+temperature (T) evolution of the 1/T1 NMR relaxation rate at low T point to a
+non-singlet ground state favoring a gapless fermionic description of the
+magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics
+is witnessed, which may signal a reconstruction of spinon Fermi surface.
+Nonetheless, the compound remains in a fluctuating spin liquid state down to
+the lowest temperature of the present investigation.",1602.05818v1
+2016-02-22,Electromagnetic spectral properties and Debye screening of a strongly magnetized hot medium,"We have evaluated the electromagnetic spectral function and its spectral
+properties by computing the one-loop photon polarization tensor in presence of
+magnetic field, particularly in a strong field approximation compared to the
+thermal scale. When the magnetic scale is higher than the thermal scale the
+lowest Landau level (LLL) becomes effectively (1+1) dimensional strongly
+correlated system that provides a kinematical threshold based on the mass
+scale. Beyond this threshold the photon strikes the LLL and the spectral
+strength starts with a high value due to the dimensional reduction and then
+falls off with increase of the photon energy due to LLL dynamics in a strong
+field approximation. This strongly enhances the dilepton rate over the thermal
+perturbative leading order (Born) rate at very low invariant mass. We have also
+investigated the electromagnetic screening by computing the Debye screening
+mass and it depends distinctively on three different scales (mass of the
+quasiquark, temperature and the magnetic field strength) of a hot magnetized
+system. The mass dependence of the Debye screening supports the occurrence of a
+magnetic catalysis effect in the strong field approximation.",1602.06769v3
+2016-04-19,Formation of the penumbra and start of the Evershed flow,"We studied the variations of line-of-sight photospheric plasma flows during
+the formation phase of the penumbra around a pore in Active Region NOAA 11490.
+We used a high spatial, spectral, and temporal resolution data set acquired by
+the Interferometric BIdimensional Spectrometer (IBIS) operating at the NSO/Dunn
+Solar Telescope as well as data taken by the Helioseismic and Magnetic Imager
+onboard the Solar Dynamics Observatory satellite (SDO/HMI). Before the penumbra
+formed we observed a redshift of the spectral line in the inner part of the
+annular zone surrounding the pore as well as a blueshift of material associated
+with opposite magnetic polarity further away from the pore. We found that the
+onset of the classical Evershed flow occurs in a very short time scale -- 1-3
+hours -- while the penumbra is forming. During the same time interval we found
+changes in the magnetic field inclination in the penumbra, with the vertical
+field actually changing sign near the penumbral edge, while the total magnetic
+field showed a significant increase, about 400 G. To explain these and other
+observations related to the formation of the penumbra and the onset of the
+Evershed flow we propose a scenario in which the penumbra is formed by magnetic
+flux dragged down from the canopy surrounding the initial pore. The Evershed
+flow starts when the sinking magnetic field dips below the solar surface and
+magnetoconvection sets in.",1604.05610v1
+2016-04-20,Resonance-based Detection of Magnetic Nanoparticles and Microbeads Using Nanopatterned Ferromagnets,"Biosensing with ferromagnet-based magnetoresistive devices has been dominated
+by electrical detection of particle-induced changes to the devices' static
+magnetic configuration. There are however potential advantages to be gained
+from using field dependent, high frequency magnetization dynamics for magnetic
+particle detection. Here we demonstrate the use of nano-confined ferromagnetic
+resonances in periodically patterned magnetic films for the detection of
+adsorbed magnetic particles with diameters ranging from 6 nm to 4 $\mu$m. The
+nanopatterned films contain arrays of holes which can act as preferential
+adsorption sites for small particles. Hole-localized particles act in unison to
+shift the resonant frequencies of the various modes of the patterned layer with
+shift polarities determined by the localization of each mode within the
+nanopattern's repeating unit cell. The same polarity shifts are observed for a
+large range of coverages, even when hole-localized particles are covered by
+quasi-continuous particle sheets. For large particles however, preferential
+adsorption no longer occurs, leading to resonance shifts with polarities which
+are independent of the mode localization. Analogous shifts are seen in
+continuous layers where, for small particles, the shift of the layer's
+fundamental mode is typically about 10 times less than in patterned systems and
+induced by relatively weak fields emanating beyond the particle in the
+direction of the static applied field. This highlights the importance of having
+confined modes consistently positioned with respect to nearby particles.",1604.05835v1
+2016-07-28,On the Rotation of Sunspots and Their Magnetic Polarity,"The rotation of sunspots of 2 yr in two different solar cycles is studied
+with the data from the Helioseismic and Magnetic Imager on board the \it Solar
+Dynamics Observatory \rm and the Michelson Doppler Imager instrument on board
+the \it Solar and Heliospheric Observataory.\rm We choose the $\alpha$ sunspot
+groups and the relatively large and stable sunspots of complex active regions
+in our sample. In the year of 2003, the $\alpha$ sunspot groups and the
+preceding sunspots tend to rotate counterclockwise and have positive magnetic
+polarity in the northern hemisphere. In the southern hemisphere, the magnetic
+polarity and rotational tendency of the $\alpha$ sunspot groups and the
+preceding sunspots are opposite to the northern hemisphere. The average
+rotational speed of these sunspots in 2003 is about $0^{\circ}.65 \rm \
+hr^{-1}$. From 2014 January to 2015 February, the $\alpha$ sunspot groups and
+the preceding sunspots tend to rotate clockwise and have negative magnetic
+polarity in the northern hemisphere. The patterns of rotation and magnetic
+polarity of the southern hemisphere are also opposite to those of the northern
+hemisphere. The average rotational speed of these sunspots in 2014/2015 is
+about $1^{\circ}.49 \rm \ hr^{-1}$. The rotation of the relatively large and
+stable preceding sunspots and that of the $\alpha$ sunspot groups located in
+the same hemisphere have opposite rotational direction in 2003 and 2014/2015.",1607.08343v1
+2016-07-29,The relevance of ambipolar diffusion for neutron star evolution,"We study ambipolar diffusion in strongly magnetised neutron stars, with
+special focus on the effects of neutrino reaction rates and the impact of a
+superfluid/superconducting transition in the neutron star core. For
+axisymmetric magnetic field configurations, we determine the deviation from
+$\beta-$equilibrium induced by the magnetic force and calculate the velocity of
+the slow, quasi-stationary, ambipolar drift. We study the temperature
+dependence of the velocity pattern and clearly identify the transition to a
+predominantly solenoidal flow. For stars without superconducting/superfluid
+constituents and with a mixed poloidal-toroidal magnetic field of typical
+magnetar strength, we find that ambipolar diffusion proceeds fast enough to
+have a significant impact on the magnetic field evolution only at low core
+temperatures, $T \lesssim 1-2\times10^8$ K. The ambipolar diffusion timescale
+becomes appreciably shorter when fast neutrino reactions are present, because
+the possibility to balance part of the magnetic force with pressure gradients
+is reduced. We also find short ambipolar diffusion timescales in the case of
+superconducting cores for $T \lesssim 10^9$ K, due to the reduced interaction
+between protons and neutrons. In the most favourable scenario, with fast
+neutrino reactions and superconducting cores, ambipolar diffusion results in
+advection velocities of several km/kyr. This velocity can substantially
+reorganize magnetic fields in magnetar cores, in a way that can only be
+confirmed by dynamical simulations.",1608.00001v2
+2016-08-08,Magnetically self-regulated formation of early protoplanetary discs,"The formation of protoplanetary discs during the collapse of molecular dense
+cores is significantly influenced by angular momentum transport, notably by the
+magnetic torque. In turn, the evolution of the magnetic field is determined by
+dynamical processes and non-ideal MHD effects such as ambipolar diffusion.
+Considering simple relations between various timescales characteristic of the
+magnetized collapse, we derive an expression for the early disc radius, $ r
+\simeq 18 \, {\rm AU} \, \left({\eta_{\rm AD} / 0.1 \, {\rm s}} \right)^{2/9}
+\left({B_z / 0.1\, {\rm G}} \right) ^{-4/9} \left({M / 0.1 \msol} \right)
+^{1/3},$ where $M$ is the total disc plus protostar mass, $\eta_\mathrm{AD}$ is
+the ambipolar diffusion coefficient and $B_z$ is the magnetic field in the
+inner part of the core. This is about significantly smaller than the discs that
+would form if angular momentum was conserved.
+  The analytical predictions are confronted against a large sample of 3D,
+non-ideal MHD collapse calculations covering variations of a factor 100 in core
+mass, a factor 10 in the level of turbulence, a factor 5 in rotation, and
+magnetic mass-to-flux over critical mass-to-flux ratios 2 and 5. The disc
+radius estimates are found to agree with the numerical simulations within less
+than a factor 2.
+  A striking prediction of our analysis is the weak dependence of circumstellar
+disc radii upon the various relevant quantities, suggesting weak variations
+among class-0 disc sizes. In some cases, we note the onset of large spiral arms
+beyond this radius.",1608.02525v1
+2016-08-21,Manipulating antiferromagnets with magnetic fields: ratchet motion of multiple domain walls induced by asymmetric field pulses,"Future applications of antiferromagnets (AFs) in many spintronics devices
+rely on the precise manipulation of domain walls. The conventional approach
+using static magnetic fields is inefficient due to the low susceptibility of
+AFs. Recently proposed electrical manipulation with spin-orbit torques is
+restricted to metals with a specific crystal structure.
+  Here we propose an alternative, broadly applicable approach: using asymmetric
+magnetic field pulses to induce controlled ratchet motion of AF domain walls.
+  The efficiency of this approach is based on three peculiarities of AF
+dynamics. First, a time-dependent magnetic field couples with an AF order
+parameter stronger than a static magnetic field, which leads to higher mobility
+of the domain walls. Second, the rate of change of the magnetic field couples
+with the spatial variation of the AF order parameter inside the domain and this
+enables synchronous motion of multiple domain walls with the same structure.
+Third, tailored asymmetric field pulses in combination with static friction can
+prevent backward motion of domain walls and thus lead to the desired controlled
+ratchet effect.
+  The proposed use of an external field, rather than internal spin-orbit
+torques, avoids any restrictions on size, conductivity, and crystal structure
+of the AF material.
+  We believe that our approach paves a way for the development of new AF-based
+devices based on controlled motion of AF domain walls.",1608.05967v1
+2016-09-26,Mechanical force involved multiple fields switching of both local ferroelectric and magnetic domain in a Bi5Ti3FeO15 thin film,"Multiferroics have received intense attention due to their great application
+potential in multi-state information storage devices and new types of sensors.
+Coupling among ferroic orders such as ferroelectricity, (anti-)ferromagnetism,
+ferroelasticity, etc. will enable dynamic interaction between these ordering
+parameters. Direct visualization of such coupling behaviour in single phase
+multiferroic materials is highly desirable for both applications and
+fundamental study. Manipulation of both ferroelectric and magnetic domains of
+Bi5Ti3FeO15 thin film using electric field and external mechanical force is
+reported, which confirms the magnetoelectric coupling in Bi5Ti3FeO15, indicates
+the electric and magnetic orders are coupled through ferroelasticity. Due to
+the anisotropic relaxation of ferroelastic strain, the back-switching of
+out-of-plane electric domains is not as obvious as in-plane. An inevitable
+destabilization of the coupling between elastic and magnetic ordering happens
+because of the elastic strain relaxation, which result in a subsequent decay of
+magnetic domain switching. Mechanical force applied on the surface of
+Bi5Ti3FeO15 film generates by an AFM tip will effectively drive a transition of
+the local ferroelastic strain state, reverse both the polarization and
+magnetization in a way similar to an electric field. Current work provides a
+framework for exploring cross-coupling among multiple orders and potential for
+developing novel nanoscale functional devices.",1609.07831v1
+2016-10-27,Spin Currents and Magnon Dynamics in Insulating Magnets,"Nambu-Goldstone theorem provides gapless modes to both relativistic and
+nonrelativistic systems. The Nambu-Goldstone bosons in insulating magnets are
+called magnons or spin-waves and play a key role in magnetization transport. We
+review here our past works on magnetization transport in insulating magnets and
+also add new insights, with a particular focus on magnon transport. We
+summarize in detail the magnon counterparts of electron transport, such as the
+Wiedemann-Franz law, the Onsager reciprocal relation between the Seebeck and
+Peltier coefficients, the Hall effects, the superconducting state, the
+Josephson effects, and the persistent quantized current in a ring to list a
+few. Focusing on the electromagnetism of moving magnons, i.e., magnetic
+dipoles, we theoretically propose a way to directly measure magnon currents. As
+a consequence of the Mermin-Wagner-Hohenberg theorem, spin transport is
+drastically altered in one-dimensional antiferromagnetic (AF) spin-1/2 chains;
+where the N\'eel order is destroyed by quantum fluctuations and a quasiparticle
+magnon-like picture breaks down. Instead, the low-energy collective excitations
+of the AF spin chain are described by a Tomonaga-Luttinger liquid (TLL) which
+provides the spin transport properties in such antiferromagnets some universal
+features at low enough temperature. Finally, we enumerate open issues and
+provide a platform to discuss the future directions of magnonics.",1610.08901v2
+2016-10-31,Validation of a Scaling Law for the Coronal Magnetic Field Strengths and Loop Lengths of Solar and Stellar Flares,"Shibata & Yokoyama (1999, 2002) proposed a method of estimating the coronal
+magnetic field strengths ($B$) and magnetic loop lengths ($L$) of solar and
+stellar flares, on the basis of magnetohydrodynamic simulations of the magnetic
+reconnection model. Using the scaling law provided by Shibata & Yokoyama (1999,
+2002), $B$ and $L$ are obtained as functions of the emission measure
+($EM=n^2L^3$) and temperature ($T$) at the flare peak. Here, $n$ is the coronal
+electron density of the flares. This scaling law enables the estimation of $B$
+and $L$ for unresolved stellar flares from the observable physical quantities
+$EM$ and $T$, which is helpful for studying stellar surface activities. To
+apply this scaling law to stellar flares, we discuss its validity for spatially
+resolved solar flares. $EM$ and $T$ were calculated from GOES soft X-ray flux
+data, and $B$ and $L$ are theoretically estimated using the scaling law. For
+the same flare events, $B$ and $L$ were also observationally estimated with
+images taken by Solar Dynamics Observatory (SDO)/ Helioseismic and Magnetic
+Imager (HMI) Magnetogram and Atmospheric Imaging Assembly (AIA) 94{\AA} pass
+band. As expected, a positive correlation was found between the theoretically
+and observationally estimated values. We interpret this result as indirect
+evidence that flares are caused by magnetic reconnection. Moreover, this
+analysis makes us confident in the validity of applying this scaling law to
+stellar flares as well as solar flares.",1610.09811v1
+2016-10-31,"Kinetic analysis of spin current contribution to spectrum of electromagnetic waves in spin-1/2 plasma, Part II: Dispersion dependencies","The dielectric permeability tensor for spin polarized plasmas derived in
+terms of the spin-1/2 quantum kinetic model in six-dimensional phase space in
+Part I of this work is applied for study of spectra of high-frequency
+transverse and transverse-longitudinal waves propagating perpendicular to the
+external magnetic field. Cyclotron waves are studied at consideration of waves
+with electric field directed parallel to the external magnetic field. It is
+found that the separate spin evolution modifies the spectrum of cyclotron
+waves. These modifications increase with the increase of the spin polarization
+and the number of the cyclotron resonance. Spin dynamics with no account of the
+anomalous magnetic moment gives a considerable modification of spectra either.
+The account of anomalous magnetic moment leads to a fine structure of each
+cyclotron resonance. So, each cyclotron resonance splits on three waves.
+Details of this spectrum and its changes with the change of spin polarization
+are studied for the first and second cyclotron waves. A cyclotron resonance
+existing at $\omega\approx0.001\mid\Omega_{e}\mid$ due to the anomalous
+magnetic moment is also described, where $\mid\Omega_{e}\mid$ is the cyclotron
+frequency. The ordinary waves does not have any considerable modification. The
+electrostatic and electromagnetic Berstein modes are studied during the
+analysis of waves propagating perpendicular to the external magnetic field with
+the electric field perturbation directed perpendicular to the external field. A
+modification of the oscillatory structure caused by the equilibrium spin
+polarization is found in both regimes. Similar modification is found for the
+extraordinary wave spectrum.",1611.00046v1
+2016-12-02,Unveiling Magnetic Interactions of Ruthenium Trichloride via Constraining Direction of Orbital moments: Potential Routes to Realize Quantum Spin Liquid,"Recent experiments reveal that the honeycomb ruthenium trichloride
+{\alpha}-RuCl3 is a prime candidate of the Kitaev quantum spin liquid (QSL).
+However, there is no theoretical model which can properly describe its
+experimental dynamical response, due to the lack of a full understanding of its
+magnetic interactions. Here, we propose a general scheme to calculate the
+magnetic interactions in systems (e.g., {\alpha}-RuCl3) with non-negligible
+orbital moments by constraining the directions of orbital moments. With this
+scheme, we put forward a minimal J1-K1-{\Gamma}1-J3-K3 model for {\alpha}-RuCl3
+and find that: (I) The third nearest neighbor (NN) antiferromagnetic Heisenberg
+interaction J3 stabilizes the zigzag antiferromagnetic order; (II) The NN
+symmetric off-diagonal exchange {\Gamma}1 plays a pivotal role in determining
+the preferred direction of magnetic moments and generating the spin wave gap.
+Exact diagonalization study on this model shows that the Kitaev QSL can be
+realized by suppressing the NN symmetric off-diagonal exchange {\Gamma}1 and
+the third NN Heisenberg interaction J3. Thus, we not only propose a powerful
+general scheme for investigating the intriguing magnetism of Jeff=1/2 magnets,
+but also point out future directions for realizing the Kitaev QSL in the
+honeycomb ruthenium trichloride {\alpha}-RuCl3.",1612.00761v1
+2017-02-03,Physical properties of a candidate quantum spin-ice system Pr2Hf2O7,"Physical properties of a pyrohafnate compound Pr2Hf2O7 have been investigated
+by ac magnetic susceptibility \chi_ ac(T), dc magnetic susceptibility \chi(T),
+isothermal magnetization M(H) and heat capacity C_p(T) measurements on
+polycrystalline as well as single crystal samples combined with high-resolution
+synchrotron x-ray diffraction (XRD) for structural characterization and
+inelastic neutron scattering (INS) to determine the crystal field energy level
+scheme and wave functions. Synchrotron XRD data confirm the ordered cubic
+pyrochlore (Fd-3m) structure without any noticeable site mixing or oxygen
+deficiency. No clear evidence of long range magnetic ordering is observed down
+to 90 mK, however the \chi_ac(T) evinces slow spin dynamics revealed by a
+frequency dependent broad peak associated with spin freezing. The INS data
+reveal the expected five well defined magnetic excitations due to crystal field
+splitting of the J = 4 ground state multiplet of the Pr^3+. The crystal field
+parameters and ground state wavefunction of Pr^3+ have been determined. The
+Ising anisotropic nature of magnetic ground state is inferred from the INS as
+well as \chi(T) and M(H) data. Together these properties make Pr2Hf2O7 a
+candidate compound for quantum spin-ice behavior.",1702.01098v1
+2017-02-09,Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma,"Magnetic fields are ubiquitous in the Universe. Extragalactic disks, halos
+and clusters have consistently been shown, via diffuse radio-synchrotron
+emission and Faraday rotation measurements, to exhibit magnetic field strengths
+ranging from a few nG to tens of $\mu$G. The energy density of these fields is
+typically comparable to the energy density of the fluid motions of the plasma
+in which they are embedded, making magnetic fields essential players in the
+dynamics of the luminous matter. The standard theoretical model for the origin
+of these strong magnetic fields is through the amplification of tiny seed
+fields via turbulent dynamo to the level consistent with current observations.
+Here we demonstrate, using laser-produced colliding plasma flows, that
+turbulence is indeed capable of rapidly amplifying seed fields to near
+equipartition with the turbulent fluid motions. These results support the
+notion that turbulent dynamo is a viable mechanism responsible for the observed
+present-day magnetization of the Universe.",1702.03016v1
+2017-02-16,Spectral Analysis of Non-Ideal MRI Modes: The effect of Hall diffusion,"The effect of magnetic field diffusion on the stability of accretion disks is
+a problem that has attracted considerable interest of late. In particular, the
+Hall effect has the potential to bring about remarkable changes in the
+dynamical behavior of disks that are without parallel. In this paper, we
+conduct a systematic examination of the linear eigenmodes in a weakly
+magnetized differentially rotating gas with special focus on Hall diffusion. We
+first develop a geometrical representation of the eigenmodes and provide a
+detailed quantitative description of the polarization properties of the
+oscillatory modes under the combined influence of the Coriolis and Hall
+effects. We also analyze the effects of magnetic diffusion on the structure of
+the unstable modes and derive analytical expressions for the kinetic and
+magnetic stresses and energy densities associated with the non-ideal MRI. Our
+analysis explicitly demonstrates that, if the dissipative effects are
+relatively weak, the kinetic stresses and energies make up the dominant
+contribution to the total stress and energy density when the equilibrium
+angular momentum and magnetic field vectors are anti-parallel. This is in sharp
+contrast to what is observed in the case of the ideal or dissipative MRI. We
+conduct shearing box simulations and find very good agreement with the results
+derived from linear analysis. As the modes in consideration are also exact
+solutions of the non-linear equations, the unconventional nature of the kinetic
+and magnetic stresses may have significant implications for the non-linear
+evolution in some regions of protoplanetary disks.",1702.04979v1
+2017-02-22,Testing the Accuracy of Data Driven MHD Simulations of Active Region Evolution,"Models for the evolution of the solar coronal magnetic field are vital for
+understanding solar activity, yet the best measurements of magnetic field lie
+at the photosphere, necessitating the development of coronal models which are
+\textit{""data-driven""} at the photosphere. We present an investigation to
+determine the feasibility and accuracy of such methods. Our validation
+framework uses a simulation of active region (AR) formation, modeling the
+emergence of magnetic flux from the convection zone to the corona, as a
+ground-truth dataset, to supply both the photospheric information, and to
+perform the validation of the data-driven method. We focus our investigation on
+how the data-driven model accuracy depends on the temporal frequency of the
+driving data. The Helioseismic and Magnetic Imager on NASA's Solar {\jl
+Dynamics} Observatory produces full-disk vector magnetic field measurements at
+a 12 minute cadence. Using our framework we show that ARs that emerge over 25
+hours can be modeled by the data-driving method with only $\sim$1\% error in
+the free magnetic energy, assuming the photospheric information is specified
+every 12 minutes. However, for rapidly evolving features, under-sampling of the
+dynamics at this cadence leads to a strobe effect, generating large electric
+currents and incorrect coronal morphology and energies. We derive a sampling
+condition for the driving cadence based on the evolution of these small-scale
+features, and show that higher-cadence driving can lead to acceptable errors.
+Future work will investigate the source of errors associated with deriving
+plasma variables from the photospheric magnetograms as well as other sources of
+errors such as reduced resolution and instrument bias and noise.",1702.06808v1
+2017-02-27,Single shot ultrafast all optical magnetization switching of ferromagnetic Co/Pt multilayers,"In a number of recent experiments, it has been shown that femtosecond laser
+pulses can control magnetization on picosecond timescales, which is at least an
+order of magnitude faster compared to conventional magnetization dynamics.
+Among these demonstrations, one material system (GdFeCo ferromagnetic films) is
+particularly interesting, as deterministic toggle-switching of the magnetic
+order has been achieved without the need of any symmetry breaking magnetic
+field. This phenomenon is often referred to as all optical switching (AOS).
+However, so far, GdFeCo remains the only material system where such
+deterministic switching has been observed. When extended to ferromagnetic
+systems, which are of greater interest in many technological applications, only
+a partial effect can be achieved, which in turn requires repeated laser pulses
+for full switching. However, such repeated pulsing is not only energy hungry,
+it also negates the speed advantage of AOS. Motivated by this problem, we have
+developed a general method for single-shot, picosecond timescale, complete all
+optical switching of ferromagnetic materials. We demonstrate that in
+exchange-coupled layers of Co/Pt and GdFeCo, single shot, switching of the
+ferromagnetic Co/Pt layer is achieved within 7 picoseconds after irradiation by
+a femtosecond laser pulse. We believe that this approach will greatly expand
+the range of materials and applications for ultrafast magnetic switching.",1702.08491v3
+2017-03-23,Confinement of rotating convection by a laterally varying magnetic field,"Spherical shell dynamo models based on rotating convection show that the flow
+within the tangent cylinder is dominated by an off-axis plume that extends from
+the inner core boundary to high latitudes and drifts westward. Earlier studies
+explained the formation of such a plume in terms of the effect of a uniform
+axial magnetic field that significantly increases the lengthscale of convection
+in a rotating plane layer. However, rapidly rotating dynamo simulations show
+that the magnetic field within the tangent cylinder has severe lateral
+inhomogeneities that may influence the onset of an isolated plume. Increasing
+the rotation rate in our dynamo simulations (by decreasing the Ekman number
+$E$) produces progressively thinner plumes that appear to seek out the location
+where the field is strongest. Motivated by this result, we examine the linear
+onset of convection in a rapidly rotating fluid layer subject to a laterally
+varying axial magnetic field. A cartesian geometry is chosen where the finite
+dimensions $(x,z)$ mimic $(\phi,z)$ in cylindrical coordinates. The lateral
+inhomogeneity of the field gives rise to a unique mode of instability where
+convection is entirely confined to the peak-field region. The localization of
+the flow by the magnetic field occurs even when the field strength (measured by
+the Elsasser number $\varLambda$) is small and viscosity controls the smallest
+lengthscale of convection. The lowest Rayleigh number at which an isolated
+plume appears within the tangent cylinder in spherical shell dynamo simulations
+agrees closely with the viscous-mode Rayleigh number in the plane layer linear
+magnetoconvection model. The localized excitation of viscous-mode convection by
+a laterally varying magnetic field provides a mechanism for the formation of
+isolated plumes within Earth's tangent cylinder.",1703.08051v2
+2017-03-29,Measuring the magnetic field of a trans-equatorial loop system using coronal seismology,"""EIT waves"" are freely-propagating global pulses in the low corona which are
+strongly associated with the initial evolution of coronal mass ejections
+(CMEs). They are thought to be large-amplitude, fast-mode magnetohydrodynamic
+waves initially driven by the rapid expansion of a CME in the low corona. An
+""EIT wave"" was observed on 6 July 2012 to impact an adjacent trans-equatorial
+loop system which then exhibited a decaying oscillation as it returned to rest.
+Observations of the loop oscillations were used to estimate the magnetic field
+strength of the loop system by studying the decaying oscillation of the loop,
+measuring the propagation of ubiquitous transverse waves in the loop and
+extrapolating the magnetic field from observed magnetograms. Observations from
+the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory
+(SDO/AIA) and the Coronal Multi-channel Polarimeter (CoMP) were used to study
+the event. An Empirical Mode Decomposition analysis was used to characterise
+the oscillation of the loop system in CoMP Doppler velocity and line width and
+in AIA intensity. The loop system was shown to oscillate in the 2nd harmonic
+mode rather than at the fundamental frequency, with the seismological analysis
+returning an estimated magnetic field strength of ~5.5+/-1.5 G. This compares
+to the magnetic field strength estimates of ~1-9 G and ~3-9 G found using the
+measurements of transverse wave propagation and magnetic field extrapolation
+respectively.",1703.10020v1
+2017-04-18,"Study on Precursor Activity of the X1.6 Flare in the Great AR 12192 with SDO, IRIS, and Hinode","The physical properties and its contribution to the onset of solar flare are
+still unclear although chromospheric brightening is considered a precursor
+phenomenon of flare. Many studies suggested that photospheric magnetic field
+changes cause destabilization of large-scale coronal structure. We aim to
+understand how a small photospheric change contributes to a flare and to reveal
+how the intermediary chromosphere behaves in the precursor phase. We analyzed
+the precursor brightening of the X1.6 flare on 2014 October 22 in the AR 12192
+using the Interface Region Imaging Spectrograph (IRIS) and Hinode/EUV Imaging
+Spectrometer (EIS) data. We investigated a localized jet with the strong
+precursor brightening, and compared the intensity, Doppler velocity, and line
+width in C II, Mg II k, Si IV lines by IRIS and He II, Fe XII, Fe XV lines by
+Hinode/EIS. We also analyzed photospheric magnetic field and
+chromospheric/coronal structures using Solar Dynamics Observatory
+(SDO)/Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly
+(AIA). We found a significant blueshift (~ 100 km/s), which is related to the
+strong precursor brightening over a characteristic magnetic field structure,
+and the blueshift was observed at all the temperature. This might indicate that
+the flow is accelerated by Lorentz force. Moreover, the large-scale coronal
+loop that connects the foot-points of the flare ribbons was destabilized just
+after the precursor brightening with the blueshift. It suggests that magnetic
+reconnection locally occurred in the lower chromosphere and it triggered
+magnetic reconnection of the X1.6 flare in the corona.",1704.05158v1
+2017-04-27,Novel self-similar rotating solutions of non-ideal transverse magnetohydrodynamics,"The evolution of electromagnetic and thermodynamic fields in a non-ideal
+fluid are studied in the framework of ultrarelativistic transverse
+magnetohydrodynamics (MHD), which is essentially characterized by electric and
+magnetic fields being transverse to the fluid velocity. Extending the method of
+self-similar solutions of relativistic hydrodynamics to the case of
+non-conserved charges, the differential equations of non-ideal transverse MHD
+are solved, and two novel sets of self-similar solutions are derived. The first
+set turns out to be a boost-invariant and exact solution, which is
+characterized by non-rotating electric and magnetic fields. The second set is a
+non-boost-invariant solution, which is characterized by rotating electric and
+magnetic fields. The rotation occurs with increasing rapidity $\eta$, as the
+angular velocity is defined by
+$\omega_{0}\equiv\frac{\partial\zeta}{\partial\eta}=\frac{\partial\phi}{\partial\eta}$,
+with $\zeta$ and $\phi$ being the angles of electric and magnetic vectors with
+respect to a certain axis in the local rest frame of the fluid. For both sets
+of solutions, the electric and magnetic fields are either parallel or
+anti-parallel to each other. Performing a complete numerical analysis, the
+effects of finite electric conductivity as well as electric and magnetic
+susceptibilities of the medium on the evolution of rotating and non-rotating
+MHD solutions are explored, and the interplay between the angular velocity
+$\omega_{0}$ and these quantities is scrutinized. The lifetime of
+electromagnetic fields and the evolution of the temperature of the
+electromagnetized fluid are shown to be affected by $\omega_{0}$.",1705.00536v1
+2017-05-07,Non-potential field formation in the X-shaped quadrupole magnetic field configuration,"Some types of solar flares are observed in X-shaped quadrupolar field
+configuration. To understand the magnetic energy storage in such a region, we
+studied non-potential field formation in an X-shaped quadrupolar field region
+formed in the active region NOAA 11967, which produced three X-shaped M-class
+flares on February 2, 2014. Nonlinear force-free field modeling was applied to
+a time series of vector magnetic field maps from the Solar Optical Telescope on
+board Hinode and Helioseismic and Magnetic Imager on board Solar Dynamics
+Observatory. Our analysis of the temporal three-dimensional magnetic field
+evolution shows that the sufficient free energy had already been stored more
+than 10 hours before the occurrence of the first M-class flare and that the
+storage was observed in a localized region. In this localized region,
+quasi-separatrix layers (QSLs) started to develop gradually from 9 hours before
+the first M-class flare. One of the flare ribbons that appeared in the first
+M-class flare was co-spatial with the location of the QSLs, suggesting that the
+formation of the QSLs is important in the process of energy release. These QSLs
+do not appear in the potential field calculation, indicating that they were
+created by the non-potential field. The formation of the QSLs was associated
+with the transverse photospheric motion of the pre-emerged flux and the
+emergence of a new flux. This observation indicates that the occurrence of the
+flares requires the formation of QSLs in the non-potential field in which free
+magnetic energy is stored in advance.",1705.02560v2
+2017-07-14,Successive Two-sided loop Jets Caused by Magnetic Reconnection between Two adjacent Filamentary Threads,"We present observational analysis of two successive two-sided loop jets
+observed by the ground-based New Vacuum Solar Telescope (NVST) and the
+space-borne Solar Dynamics Observatory ( SDO). The two successive two-sided
+loop jets manifested similar evolution process and both were associated with
+the interaction of two small-scale adjacent filamentary threads, magnetic
+emerging and cancellation processes at the jet's source region. High temporal
+and high spatial resolution observations reveal that the two adjacent ends of
+the two filamentary threads are rooted in opposite magnetic polarities within
+the source region. The two threads approached to each other, and then an
+obvious brightening patch is observed at the interaction position.
+Subsequently, a pair of hot plasma ejections are observed heading to opposite
+directions along the paths of the two filamentary threads, and with a typical
+speed of two-sided loop jets of the order 150 km/s. Close to the end of the
+second jet, we report the formation of a bright hot loop structure at the
+source region, which suggests the formation of new loops during the
+interaction. Based on the observational results, we propose that the observed
+two-sided loop jets are caused by the magnetic reconnection between the two
+adjacent filamentary threads, largely different from the previous scenario that
+a two-sided loop jet is generated by magnetic reconnection between an emerging
+bipole and the overlying horizontal magnetic fields.",1707.04421v1
+2017-07-17,Coupling of structure to magnetic and superconducting orders in quasi-one-dimensional $\text{K}_2\text{Cr}_3\text{As}_3$,"Quasi-one-dimensional $A_2\text{Cr}_3\text{As}_3$ (with $A = \text{K, Cs,
+Rb}$) is an intriguing new family of superconductors which exhibit many similar
+features to the cuprate and iron-based unconventional superconductor families.
+Yet in contrast to these systems, no charge or magnetic ordering has been
+observed which could provide the electronic correlations presumed necessary for
+an unconventional superconducting pairing mechanism - an absence which defies
+predictions of first principles models. We report the results of neutron
+scattering experiments on polycrystalline $\text{K}_2\text{Cr}_3\text{As}_3$
+$(T_c \sim 7\text{K})$ which probed the low temperature dynamics near $T_c$ .
+Neutron diffraction data evidence a strong response of the nuclear lattice to
+the onset of superconductivity while inelastic scattering reveals a highly
+dispersive column of intensity at the commensurate wavevector $q =
+(00\frac{1}{2})$ which loses intensity beneath $T_c$ - indicative of
+short-range magnetic fluctuations. Using linear spin-wave theory we model the
+observed scattering and suggest a possible structure to the short-range
+magnetic order. These observations suggest that
+$\text{K}_2\text{Cr}_3\text{As}_3$ is in close proximity to a magnetic
+instability and that the incipient magnetic order both couples strongly to the
+lattice and competes with superconductivity - in direct analogy with the
+iron-based superconductors.",1707.05286v1
+2017-07-19,Engineering elliptical spin-excitations by complex anisotropy fields in Fe adatoms and dimers on Cu(111),"We investigate the dynamics of Fe adatoms and dimers deposited on the Cu(111)
+metallic surface in the presence of spin-orbit coupling, within time-dependent
+density functional theory. The \textit{ab initio} results provide
+material-dependent parameters that can be used in semiclassical approaches,
+which are used for insightful interpretations of the excitation modes. By
+manipulating the surroundings of the magnetic elements, we show that elliptical
+precessional motion may be induced through the modification of the magnetic
+anisotropy energy. We also demonstrate how different kinds of spin precession
+are realized, considering the symmetry of the magnetic anisotropy energy, the
+ferro- or antiferromagnetic nature of the exchange coupling between the
+impurities, and the strength of the magnetic damping. In particular, the normal
+modes of a dimer depend on the initial magnetic configuration, changing
+drastically by going from a ferromagnetic metastable state to the
+antiferromagnetic ground state. By taking into account the effect of the
+damping into their resonant frequencies, we reveal that an important
+contribution arises for strongly biaxial systems and specially for the
+antiferromagnetic dimers with large exchange couplings. Counter intuitively,
+our results indicate that the magnetic damping influences the quantum
+fluctuations by decreasing the zero-point energy of the system.",1707.06087v2
+2017-07-31,Lattice Quantum Monte Carlo Study of Chiral Magnetic Effect in Dirac Semimetals,"In this paper Chiral Magnetic Effect (CME) in Dirac semimetals is studied by
+means of lattice Monte Carlo simulation. We measure conductivity of Dirac
+semimetals as a function of external magnetic field in parallel
+$\sigma_{\parallel}$ and perpendicular $\sigma_{\perp}$ to the external field
+directions. The simulations are carried out in three regimes: semimetal phase,
+onset of the insulator phase and deep in the insulator phase. In the semimetal
+phase $\sigma_{\parallel}$ grows whereas $\sigma_{\perp}$ drops with magnetic
+field. Similar behaviour was observed in the onset of the insulator phase but
+conductivity is smaller and its dependence on magnetic field is weaker. Finally
+in the insulator phase conductivities $\sigma_{\parallel, \perp}$ are close to
+zero and do not depend on magnetic field. In other words, we observe
+manifestation of the CME current in the semimetal phase, weaker manifestation
+of the CME in the onset of the insulator phase. We do not observe signatures of
+CME in the insulator phase. We believe that the suppression of the CME current
+in the insulator phase is connected to chiral symmetry breaking and generation
+of dynamical fermion mass which take place in this phase.",1707.09810v2
+2017-08-07,Field dependence of non-reciprocal magnons in chiral MnSi,"Spin waves in chiral magnetic materials are strongly influenced by the
+Dzyaloshinskii-Moriya interaction resulting in intriguing phenomena like
+non-reciprocal magnon propagation and magnetochiral dichroism. Here, we study
+the non-reciprocal magnon spectrum of the archetypical chiral magnet MnSi and
+its evolution as a function of magnetic field covering the field-polarized and
+conical helix phase. Using inelastic neutron scattering, the magnon energies
+and their spectral weights are determined quantitatively after deconvolution
+with the instrumental resolution. In the field-polarized phase the imaginary
+part of the dynamical susceptibility $\chi''(\varepsilon, {\bf q})$ is shown to
+be asymmetric with respect to wavevectors ${\bf q}$ longitudinal to the applied
+magnetic field ${\bf H}$, which is a hallmark of chiral magnetism. In the
+helimagnetic phase, $\chi''(\varepsilon, {\bf q})$ becomes increasingly
+symmetric with decreasing ${\bf H}$ due to the formation of helimagnon bands
+and the activation of additional spinflip and non-spinflip scattering channels.
+The neutron spectra are in excellent quantitative agreement with the low-energy
+theory of cubic chiral magnets with a single fitting parameter being the
+damping rate of spin waves.",1708.02098v2
+2017-10-09,Global solar magnetic field organization in the outer corona: influence on the solar wind speed and mass flux over the cycle,"The dynamics of the solar wind depends intrinsically on the structure of the
+global solar magnetic field, which undergoes fundamental changes over the 11-yr
+solar cycle. For instance, the wind terminal velocity is thought to be
+anti-correlated with the expansion factor, a measure of how the magnetic field
+varies with height in the solar corona, usually computed at a fixed height
+($\approx 2.5 R_{\odot}$, the source surface radius which approximates the
+distance at which all magnetic field lines become open). However, the magnetic
+field expansion affects the solar wind in a more detailed way, its influence on
+the solar wind properties remaining significant well beyond the source surface.
+We demonstrate this using 3D global MHD simulations of the solar corona,
+constrained by surface magnetograms over half a solar cycle (1989-2001). A
+self-consistent expansion beyond the solar wind critical point (even up to
+$10R_{\odot}$) makes our model comply with observed characteristics of the
+solar wind, namely, that the radial magnetic field intensity becomes latitude
+independent at some distance from the Sun, and that the mass flux is mostly
+independent of the terminal wind speed. We also show that near activity
+minimum, the expansion in the higher corona has more influence on the wind
+speed than the expansion below $2.5 R_{\odot}$.",1710.02908v1
+2017-10-12,Magnetic monolayer Li$_{2}$N: Density Functional Theory Calculations,"Density functional theory (DFT) calculations are used to investigate the
+electronic and magnetic structures of a two-dimensional (2D) monolayer
+Li$_{2}$N. It is shown that bulk Li$_{3}$N is a non-magnetic semiconductor. The
+non-spinpolarized DFT calculations show that $p$ electrons of N in 2D Li$_{2}$N
+form a narrow band at the Fermi energy $E_{\rm{F}}$ due to a low coordination
+number, and the density of states at the Fermi energy ($g(E_{\rm{F}}$)) is
+increased as compared with bulk Li$_{3}$N. The large $g(E_{\rm{F}}$) shows
+instability towards magnetism in Stoner's mean field model. The spin-polarized
+calculations reveal that 2D Li$_{2}$N is magnetic without intrinsic or impurity
+defects. The magnetic moment of 1.0\,$\mu_{\rm{B}}$ in 2D Li$_{2}$N is mainly
+contributed by the $p_{z}$ electrons of N, and the band structure shows
+half-metallic behavior. {Dynamic instability in planar Li$_{2}$N monolayer is
+observed, but a buckled Li$_{2}$N monolayer is found to be dynamically stable.}
+The ferromagnetic (FM) and antiferromagnetic (AFM) coupling between the N atoms
+is also investigated to access the exchange field strength. {We found that
+planar (buckled) 2D Li$_{2}$N is a ferromagnetic material with Curie
+temperature $T_{c}$ of 161 (572) K.}",1710.04440v1
+2017-10-18,Valence Bonds in Random Quantum Magnets: Theory and Application to YbMgGaO4,"We analyze the effect of quenched disorder on spin-1/2 quantum magnets in
+which magnetic frustration promotes the formation of local singlets. Our
+results include a theory for 2d valence-bond solids subject to weak bond
+randomness, as well as extensions to stronger disorder regimes where we make
+connections with quantum spin liquids. We find, on various lattices, that the
+destruction of a valence-bond solid phase by weak quenched disorder leads
+inevitably to the nucleation of topological defects carrying spin-1/2 moments.
+This renormalizes the lattice into a strongly random spin network with
+interesting low-energy excitations. Similarly when short-ranged valence bonds
+would be pinned by stronger disorder, we find that this putative glass is
+unstable to defects that carry spin-1/2 magnetic moments, and whose residual
+interactions decide the ultimate low energy fate. Motivated by these results we
+conjecture Lieb-Schultz-Mattis-like restrictions on ground states for
+disordered magnets with spin-1/2 per statistical unit cell. These conjectures
+are supported by an argument for 1d spin chains. We apply insights from this
+study to the phenomenology of YbMgGaO$_4$, a recently discovered triangular
+lattice spin-1/2 insulator which was proposed to be a quantum spin liquid. We
+instead explore a description based on the present theory. Experimental
+signatures, including unusual specific heat, thermal conductivity, and
+dynamical structure factor, and their behavior in a magnetic field, are
+predicted from the theory, and compare favorably with existing measurements on
+YbMgGaO$_4$ and related materials.",1710.06860v2
+2017-10-26,Time-reversed magnetically controlled perturbation (TRMCP) optical focusing inside scattering media,"Manipulating and focusing light deep inside biological tissue and tissue-like
+complex media has been desired for long yet considered challenging. One
+feasible strategy is through optical wavefront engineering, where the optical
+scattering-induced phase distortions are time reversed or pre-compensated so
+that photons travel along different optical paths interfere constructively at
+the targeted position within a scattering medium. To define the targeted
+position, an internal guidestar is needed to guide or provide a feedback for
+wavefront engineering. It could be injected or embedded probes such as
+fluorescence or nonlinear microspheres, ultrasonic modulation, as well as
+absorption perturbation. Here we propose to use a magnetically controlled
+optical absorbing microsphere as the internal guidestar. Using a digital
+optical phase conjugation system, we obtained sharp optical focusing within
+scattering media through time-reversing the scattered light perturbed by the
+magnetic microshpere. Since the object is magnetically controlled, dynamic
+optical focusing is allowed with a relatively large field-of-view by scanning
+the magnetic field externally. Moreover, the magnetic microsphere can be
+packaged with an organic membrane, using biological or chemical means to serve
+as a carrier. Therefore the technique may find particular applications for
+enhanced targeted drug delivery, and imaging and photoablation of angiogenic
+vessels in tumours.",1710.09603v3
+2017-10-30,Enhancement of intrinsic magnetic damping in defect-free epitaxial Fe3O4 thin films,"We have investigated the magnetic damping of precessional spin dynamics in
+defect-controlled epitaxial grown Fe$_3$O$_4$(111)/Yttria-stabilized Zirconia
+(YSZ) nanoscale films by all-optical pump-probe measurements. The intrinsic
+damping constant of the defect-free Fe$_3$O$_4$ film is found to be strikingly
+larger than that of the as-grown Fe$_3$O$_4$ film with structural defects. We
+demonstrate that the population of the first-order perpendicular standing spin
+wave (PSSW) mode, which is exclusively observed in the defect-free film under
+sufficiently high external magnetic fields, leads to the enhancement of the
+magnetic damping of the uniform precession (Kittel) mode. We propose a physical
+picture in which the PSSW mode acts as an additional channel for the extra
+energy dissipation of the Kittel mode. The energy transfer from Kittel mode to
+PSSW mode increases as in-plane magnetization precession becomes more uniform,
+resulting in the unique intrinsic magnetic damping enhancement in the
+defect-free Fe$_3$O$_4$ film.",1710.10938v2
+2017-11-03,"Relativistic MHD modeling of magnetized neutron stars, pulsar winds, and their nebulae","Neutron stars are among the most fascinating astrophysical sources, being
+characterized by strong gravity, densities about the nuclear one or even above,
+and huge magnetic fields. Their observational signatures can be extremely
+diverse across the electromagnetic spectrum, ranging from the periodic and
+low-frequency signals of radio pulsars, up to the abrupt high-energy gamma-ray
+flares of magnetars, where energies of ~10^46 erg are released in a few
+seconds. Fast-rotating and highly magnetized neutron stars are expected to
+launch powerful relativistic winds, whose interaction with the supernova
+remnants gives rise to the non-thermal emission of pulsar wind nebulae, which
+are known cosmic accelerators of electrons and positrons up to PeV energies. In
+the extreme cases of proto-magnetars (magnetic fields of ~10^15 G and
+millisecond periods), a similar mechanism is likely to provide a viable engine
+for the still mysterious gamma-ray bursts. The key ingredient in all these
+spectacular manifestations of neutron stars is the presence of strong magnetic
+fields in their constituent plasma. Here we will present recent updates of a
+couple of state-of-the-art numerical investigations by the high-energy
+astrophysics group in Arcetri: a comprehensive modeling of the steady-state
+axisymmetric structure of rotating magnetized neutron stars in general
+relativity, and dynamical 3-D MHD simulations of relativistic pulsar winds and
+their associated nebulae.",1711.01120v1
+2017-11-29,Plasma Beta Stratification in the Solar Atmosphere: A Possible Explanation for the Penumbra Formation,"Plasma beta is an important and fundamental physical quantity in order to
+understand plasma dynamics, particularly in the context of magnetically active
+stars, because it tells about the domination of magnetic versus thermodynamic
+processes on the plasma motion. We estimate the value ranges of plasma beta in
+different regions within the solar atmosphere and we describe a possible
+mechanism that helps forming a penumbra. For that we evaluate data from a 3D
+magnetohydrodynamic model of the solar corona above a magnetically active
+region. We compare our results with previously established data that is based
+on magnetic field extrapolations and that was matched for some observations.
+Our model data suggest that plasma beta in the photosphere should be considered
+to be larger than unity outside of sunspots. However, in the corona we also
+find that the beta value range reaches lower than previously thought, which
+coincides with a recent observation. We present an idea based on a
+gravity-driven process in a high-beta regime that might be responsible for the
+formation of the penumbra around sunspot umbra, where the vertical field
+strength reaches a given threshold. This process would also explain
+counter-Evershed flows. Regarding the thermal and magnetic pressure within the
+mixed-polarity solar atmosphere, including non-vertical magnetic field and
+quiet regions, plasma beta may reach unity at practically any height from the
+photosphere to the outer corona.",1711.10965v1
+2017-12-07,Signatures of Star-planet interactions,"Planets interact with their host stars through gravity, radiation and
+magnetic fields, and for those giant planets that orbit their stars within
+$\sim$10 stellar radii ($\sim$0.1 AU for a sun-like star), star-planet
+interactions (SPI) are observable with a wide variety of photometric,
+spectroscopic and spectropolarimetric studies. At such close distances, the
+planet orbits within the sub-alfv\'enic radius of the star in which the
+transfer of energy and angular momentum between the two bodies is particularly
+efficient. The magnetic interactions appear as enhanced stellar activity
+modulated by the planet as it orbits the star rather than only by stellar
+rotation. These SPI effects are informative for the study of the internal
+dynamics and atmospheric evolution of exoplanets. The nature of magnetic SPI is
+modeled to be strongly affected by both the stellar and planetary magnetic
+fields, possibly influencing the magnetic activity of both, as well as
+affecting the irradiation and even the migration of the planet and rotational
+evolution of the star. As phase-resolved observational techniques are applied
+to a large statistical sample of hot Jupiter systems, extensions to other
+tightly orbiting stellar systems, such as smaller planets close to M dwarfs
+become possible. In these systems, star-planet separations of tens of stellar
+radii begin to coincide with the radiative habitable zone where planetary
+magnetic fields are likely a necessary condition for surface habitability.",1712.02814v1
+2017-12-12,Critical phenomena in the general spherically symmetric Einstein-Yang-Mills system,"We study critical behavior in gravitational collapse of a general spherically
+symmetric Yang-Mills field coupled to the Einstein equations. Unlike the
+magnetic ansatz used in previous numerical work, the general Yang-Mills
+connection has two degrees of freedom in spherical symmetry. This fact changes
+the phenomenology of critical collapse dramatically. The magnetic sector
+features both type I and type II critical collapse, with universal critical
+solutions. In contrast, in the general system type I disappears and the
+critical behavior at the threshold between dispersal and black hole formation
+is always type II. We obtain values of the mass scaling and echoing exponents
+close to those observed in the magnetic sector, however we find some
+indications that the critical solution differs from the purely magnetic
+discretely self-similar attractor and exact self-similarity and universality
+might be lost. The additional ""type III"" critical phenomenon in the magnetic
+sector, where black holes form on both sides of the threshold but the
+Yang-Mills potential is in different vacuum states and there is a mass gap,
+also disappears in the general system. We support our dynamical numerical
+simulations with calculations in linear perturbation theory; for instance, we
+compute quasi-normal modes of the unstable attractor (the Bartnik-McKinnon
+soliton) in type I collapse in the magnetic sector.",1712.04458v2
+2017-12-19,Active Region Photospheric Magnetic Properties Derived from Line-of-sight and Radial Fields,"The effect of using two representations of the normal-to-surface magnetic
+field to calculate photospheric measures that are related to active region (AR)
+potential for flaring is presented. Several AR properties were computed using
+line-of-sight ($B_{\rm los}$) and spherical-radial ($B_{r}$) magnetograms from
+the Space-weather HMI Active Region Patch (SHARP) products of the \emph{Solar
+Dynamics Observatory}, characterizing the presence and features of magnetic
+polarity inversion lines, fractality, and magnetic connectivity of the AR
+photospheric field. The data analyzed corresponds to $\approx$ 4,000 AR
+observations, achieved by randomly selecting 25 % of days between September
+2012 and May 2016 for analysis at 6-hr cadence. Results from this statistical
+study include: i) the $B_{r}$ component results in a slight upwards shift of
+property values in a manner consistent with a field-strength underestimation by
+the $B_{\rm los}$ component; ii) using the $B_{r}$ component results in
+significantly lower inter-property correlation in one-third of the cases,
+implying more independent information about the state of the AR photospheric
+magnetic field; iii) flaring rates for each property vary between the field
+components in a manner consistent with the differences in property-value ranges
+resulting from the components; iv) flaring rates generally increase for higher
+values of properties, except Fourier spectral power index that has flare rates
+peaking around a value of $5/3$. These findings indicate that there may be
+advantages in using $B_{r}$ rather than $B_{\rm los}$ in calculating
+flare-related AR magnetic properties, especially for regions located far from
+central meridian.",1712.06902v1
+2018-01-04,Synchronized Observations of Bright Points from the Solar Photosphere to Corona,"One of the most important features in the solar atmosphere is magnetic
+network and its rela- tionship with the transition region (TR), and coronal
+brightness. It is important to understand how energy is transported into the
+corona and how it travels along the magnetic-field lines be- tween deep
+photosphere and chromosphere through the TR and corona. An excellent proxy for
+transportation is the Interface Region Imaging Spectrograph (IRIS) raster scans
+and imaging observations in near-ultraviolet (NUV) and far-ultraviolet (FUV)
+emission channels with high time-spatial resolutions. In this study, we focus
+on the quiet Sun as observed with IRIS. The data with high signal to noise
+ratio in Si IV, C II and Mg II k lines and with strong emission intensities
+show a high correlation in TR bright network points. The results of the IRIS
+intensity maps and dopplergrams are compared with those of Atmo- spheric
+Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) instruments
+onboard the Solar Dynamical Observatory (SDO). The average network intensity
+profiles show a strong correlation with AIA coronal channels. Furthermore, we
+applied simultaneous observations of magnetic network from HMI and found a
+strong relationship between the network bright points in all levels of the
+solar atmosphere. These features in network elements exhibited high doppler
+velocity regions and large mag- netic signatures. A dominative fraction of
+corona bright points emission, accompanied by the magnetic origins in
+photosphere, suggest that magnetic-field concentrations in the network rosettes
+could help couple between inner and outer solar atmosphere.",1801.01307v1
+2018-01-29,Magnetism of a Co monolayer on Pt(111) capped by overlayers of $5d$ elements: a spin-model study,"Using first-principles calculations, we study the magnetic properties of a Co
+monolayer on a Pt(111) surface with a capping monolayer of selected $5d$
+elements (Re, Os, Ir, Pt and Au). First we determine the tensorial exchange
+interactions and magnetic anisotropies characterizing the Co monolayer for all
+considered systems. We find a close relationship between the magnetic moment of
+the Co atoms and the nearest-neighbor isotropic exchange interaction, which is
+attributed to the electronic hybridization between the Co and the capping
+layers, in spirit of the Stoner picture of ferromagnetism. The
+Dzyaloshinskii-Moriya interaction is decreased for all overlayers compared to
+the uncapped Co/Pt(111) system, while even the sign of the
+Dzyaloshinskii-Moriya interaction changes in case of the Ir overlayer. We
+conclude that the variation of the Dzyaloshinskii-Moriya interaction is well
+correlated with the change of the magnetic anisotropy energy and of the orbital
+moment anisotropy. The unique influence of the Ir overlayer on the
+Dzyaloshinskii-Moriya interaction is traced by scaling the strength of the
+spin--orbit coupling of the Ir atoms in Ir/Co/Pt(111) and by changing the Ir
+concentration in the Au$_{1-x}$Ir$_{x}$/Co/Pt(111) system. Our spin dynamics
+simulations indicate that the magnetic ground state of Re/Co/Pt(111) thin film
+is a spin spiral with a tilted normal vector, while the other systems are
+ferromagnetic.",1801.09426v1
+2018-02-20,Implosive collapse about magnetic null points: A quantitative comparison between 2D and 3D nulls,"Null collapse is an implosive process whereby MHD waves focus their energy in
+the vicinity of a null point, forming a current sheet and initiating magnetic
+reconnection. We consider, for the first time, the case of collapsing 3D
+magnetic null points in nonlinear, resistive MHD using numerical simulation,
+exploring key physical aspects of the system as well as performing a detailed
+parameter study. We find that within a particular plane containing the 3D null,
+the plasma and current density enhancements resulting from the collapse are
+quantitatively and qualitatively as per the 2D case in both the linear and
+nonlinear collapse regimes. However, the scaling with resistivity of the 3D
+reconnection rate - which is a global quantity - is found to be less favourable
+when the magnetic null point is more rotationally symmetric, due to the action
+of increased magnetic back-pressure. Furthermore, we find that with increasing
+ambient plasma pressure the collapse can be throttled, as is the case for 2D
+nulls. We discuss this pressure-limiting in the context of fast reconnection in
+the solar atmosphere and suggest mechanisms by which it may be overcome. We
+also discuss the implications of the results in the context of null collapse as
+a trigger mechanism of Oscillatory Reconnection, a time-dependent reconnection
+mechanism, and also within the wider subject of wave-null point interactions.
+We conclude that, in general, increasingly rotationally-asymmetric nulls will
+be more favourable in terms of magnetic energy release via null collapse than
+their more symmetric counterparts.",1802.07076v1
+2018-03-07,Spheroidal and conical shapes of ferrofluid-filled capsules in magnetic fields,"We investigate the deformation of soft spherical elastic capsules filled with
+a ferrofluid in external uniform magnetic fields at fixed volume by a
+combination of numerical and analytical approaches. We develop a numerical
+iterative solution strategy based on nonlinear elastic shape equations to
+calculate the stretched capsule shape numerically and a coupled finite element
+and boundary element method to solve the corresponding magnetostatic problem,
+and employ analytical linear response theory, approximative energy
+minimization, and slender-body theory. The observed deformation behavior is
+qualitatively similar to the deformation of ferrofluid droplets in uniform
+magnetic fields. Homogeneous magnetic fields elongate the capsule, and a
+discontinuous shape transition from a spheroidal shape to a conical shape takes
+place at a critical field strength. We investigate how capsule elasticity
+modifies this hysteretic shape transition. We show that conical capsule shapes
+are possible but involve diverging stretch factors at the tips, which gives
+rise to rupture for real capsule materials. In a slender-body approximation we
+find that the critical susceptibility above which conical shapes occur for
+ferrofluid capsules is the same as for droplets. At small fields capsules
+remain spheroidal, and we characterize the deformation of spheroidal capsules
+both analytically and numerically. Finally, we determine whether wrinkling of a
+spheroidal capsule occurs during elongation in a magnetic field and how it
+modifies the stretching behavior. We find the nontrivial dependence between the
+extent of the wrinkled region and capsule elongation. Our results can be
+helpful in order to quantitatively determine capsule or ferrofluid material
+properties from magnetic deformation experiments. All results also apply to
+elastic capsules filled with a dielectric liquid in an external uniform
+electric field.",1803.02607v2
+2018-03-22,A Statistical Study of the Magnetic Imprints of X-Class Solar Flares,"Magnetic imprints, the rapid and irreversible evolution of photospheric
+magnetic fields as a feedback from flares in the corona, have been confirmed by
+many previous studies. These studies showed that the horizontal field will
+permanently increase at the polarity inversion line (PIL) after eruptions,
+indicating that a more horizontal geometry of photospheric magnetic field is
+produced. In this study, we analyze 20 X-class flares since the launch of the
+Solar Dynamics Observatory (SDO) in 15 active regions (ARs) with heliographic
+angle no greater than 45 degrees. We observe clear magnetic imprints in 16
+flares, whereas 4 flares are exceptional. The imprint regions of the horizontal
+field are located not only at the PIL but also at sunspot penumbra with strong
+vertical fields. Making use of the observed mass and speed of the corresponding
+coronal mass ejections (CMEs) , we find that the CMEs with larger momenta are
+associated with stronger magnetic imprints. Furthermore, a linear relationship,
+with a Kendall's Tau-b coefficient 0.54, between the CME momentum and the
+change of Lorentz force is revealed. Based on that, we quantify the back
+reaction time to be around 70 s, with a 90% confidence interval from about 50 s
+to 90 s.",1803.08310v2
+2018-04-30,The effect of cosmic-ray acceleration on supernova blast wave dynamics,"Non-relativistic shocks accelerate ions to highly relativistic energies
+provided that the orientation of the magnetic field is closely aligned with the
+shock normal (quasi-parallel shock configuration). In contrast,
+quasi-perpendicular shocks do not efficiently accelerate ions. We model this
+obliquity-dependent acceleration process in a spherically expanding blast wave
+setup with the moving-mesh code {\sc arepo} for different magnetic field
+morphologies, ranging from homogeneous to turbulent configurations. A
+Sedov-Taylor explosion in a homogeneous magnetic field generates an oblate
+ellipsoidal shock surface due to the slower propagating blast wave in the
+direction of the magnetic field. This is because of the efficient cosmic ray
+(CR) production in the quasi-parallel polar cap regions, which softens the
+equation of state and increases the compressibility of the post-shock gas. We
+find that the solution remains self-similar because the ellipticity of the
+propagating blast wave stays constant in time. This enables us to derive an
+effective ratio of specific heats for a composite of thermal gas and CRs as a
+function of the maximum acceleration efficiency. We finally discuss the
+behavior of supernova remnants expanding into a turbulent magnetic field with
+varying coherence lengths. For a maximum CR acceleration efficiency of about 15
+per cent at quasi-parallel shocks (as suggested by kinetic plasma simulations),
+we find an average efficiency of about 5 per cent, independent of the assumed
+magnetic coherence length.",1805.00128v1
+2018-05-02,Magnetohydrodynamic simulation of magnetic null-point reconnections in NOAA AR12192 initiated with an extrapolated non-force-free-field,"Magnetohydrodynamics of the solar corona is simulated numerically. The
+simulation is initialized with an extrapolated non-force-free magnetic field
+using the vector magnetogram of the active region (AR) NOAA 12192 obtained on
+the solar photosphere. Particularly, we focus on the magnetic reconnections
+occurring close to a magnetic null-point that resulted in appearance of
+circular chromospheric flare ribbons on October 24, 2014 around 21:21 UT, after
+peak of an X3.1 flare. The extrapolated field lines show the presence of the
+three-dimensional (3D) null near one of the polarity inversion lines---where
+the flare was observed. In the subsequent numerical simulation, we find
+magnetic reconnections occurring near the null point, where the magnetic field
+lines from the fan-plane of the 3D null form a X-type configuration with
+underlying arcade field lines. The footpoints of the dome-shaped field lines,
+inherent to the 3D null, show high gradients of the squashing factor. We find
+slipping reconnections at these quasi-separatrix layers, which are co-located
+with the post-flare circular brightening observed at the chromospheric heights.
+This demonstrates the viability of the initial non-force-free field along with
+the dynamics it initiates. Moreover, the initial field and its simulated
+evolution is found to be devoid of any flux rope, which is in congruence with
+the confined nature of the flare.",1805.00635v1
+2018-05-30,Low-frequency Alfven Waves Produced by Magnetic Reconnection in the Sun's Magnetic Carpet,"The solar corona is a hot, dynamic, and highly magnetized plasma environment
+whose source of energy is not yet well understood. One leading contender for
+that energy source is the dissipation of magnetohydrodynamic (MHD) waves or
+turbulent fluctuations. Many wave-heating models for the corona and the solar
+wind presume that these fluctuations originate at or below the Sun's
+photosphere. However, this paper investigates the idea that magnetic
+reconnection may generate an additional source of MHD waves over a gradual
+range of heights in the low corona. A time-dependent Monte Carlo simulation of
+the mixed-polarity magnetic field is used to predict the properties of
+reconnection-driven coronal MHD waves. The total power in these waves is
+typically small in comparison to that of photosphere-driven waves, but their
+frequencies are much lower. Reconnection-driven waves begin to dominate the
+total power spectrum at periods longer than about 30 minutes. Thus, they may
+need to be taken into account in order to understand the low-frequency
+power-law spectra observed by both coronal spectropolarimetry and in-situ
+particle/field instruments. These low-frequency Alfven waves should carry more
+magnetic energy than kinetic energy, and thus they may produce less nonthermal
+Doppler broadening (in comparison to photosphere-driven high-frequency waves)
+in emission lines observed above the solar limb.",1805.12184v1
+2018-06-20,Evaluation of noise limits of a precision ADC for direct digital signal integration of magnetic measurements,"The characterization of laboratory plasma instabilities, magnetic
+reconnection and turbulence associated phenomena, require the simultaneous
+signal sampling from arrays of magnetic sensors (hundreds or even thousands) to
+obtain spatial resolution, with several hundred kHz for time resolution.
+Magnetic measurements based on pick-up (Mirnov) coil are quite common in
+experimental pulsed devices for plasma research, thanks to their simplicity and
+reliability. Being the signal from this type of sensor proportional to the time
+variation of the magnetic field ($dB/dt$), it has to be time-integrated to
+recover the instant value of magnetic field. Depending on the required
+integration time usually either analog integrators or chopped integrators are
+used. However these solutions tend to limit the frequency bandwidth in the kHz
+range, they are not easy to design and build, and require additional fast
+channels to directly acquire the $dB/dt$ signal to recover the plasma dynamic
+features at higher frequencies. In this paper we evaluate the feasibility of
+using a direct single channel precision ADC to allow the simultaneous
+acquisition of $dB/dt$ measurements and to provide the integrated B measurement
+by means of digital integration on the new RFX-mod2 device. On this purpose we
+interfaced an existing ADC-module to a Xilinx Zynq FPGA, in order to evaluate
+the intrinsic noise and to investigate the feasible integration window of this
+configuration. The result opens the door to a compact, cost-effective and
+reliable acquisition system, usable for simultaneous real-time control and
+transient signal recording, scalable from tenths to thousands channels,
+applicable to a broad class of pulsed plasma experimental devices.",1806.07886v1
+2018-07-30,Standing shocks in magnetized advection accretion flows onto a rotating black hole,"We present the global structure of magnetized advective accretion flow around
+the rotating black holes in presence of dissipation. By considering accretion
+flow to be threaded by toroidal magnetic fields and by assuming synchrotron
+radiative mechanism to be the dominant cooling process, we obtain global
+transonic accretion solutions in terms of dissipation parameters, such as
+viscosity ($\alpha_B$), accretion rate (${\dot m}$) and plasma-$\beta$,
+respectively. In the rotating magnetized accretion flow, centrifugal barrier is
+developed in the nearby region of the black hole that triggers the
+discontinuous shock transition in the flow variables. Evidently, the shock
+properties and the dynamics of the post-shock flow (hereafter post-shock corona
+(PSC)) are being governed by the flow parameters. We study the role of
+dissipation parameters in the formation of standing shock wave and find that
+global shocked accretion solutions exist both in gas pressure dominated flows
+and in magnetic pressure dominated flows. In addition, we observe that standing
+shock continues to form around the rapidly rotating black holes as well. We
+identify the range of dissipation parameters that permits shocked accretion
+solutions and find that standing shocks continue to form even in presence of
+high dissipation limit, although the likelihood of shock formation diminishes
+with the increase of dissipation. Further, we compute the critical accretion
+rate (${\dot m}^{\rm cri}$) that admits shock and observe that standing shock
+exists in a magnetically dominated accretion flow when the accretion rate lies
+in general in the sub-Eddington domain. At the end, we calculate the maximum
+dissipated energy that may be escaped from the PSC and indicate its possible
+implication in the astrophysical context.",1807.11417v1
+2018-08-10,Diamond magnetic microscopy of malarial hemozoin nanocrystals,"Magnetic microscopy of malarial hemozoin nanocrystals was performed using
+optically detected magnetic resonance imaging of near-surface diamond
+nitrogen-vacancy centers. Hemozoin crystals were extracted from
+$Plasmodium$-$falciparum$-infected human blood cells and studied alongside
+synthetic hemozoin crystals. The stray magnetic fields produced by individual
+crystals were imaged at room temperature as a function of applied field up to
+350 mT. More than 100 nanocrystals were analyzed, revealing the distribution of
+their magnetic properties. Most crystals ($96\%$) exhibit a linear dependence
+of stray field magnitude on applied field, confirming hemozoin's paramagnetic
+nature. A volume magnetic susceptibility $\chi=3.4\times10^{-4}$ is inferred
+using a magnetostatic model informed by correlated scanning electron microscopy
+measurements of crystal dimensions. A small fraction of nanoparticles (4/82 for
+$Plasmodium$-produced and 1/41 for synthetic) exhibit a saturation behavior
+consistent with superparamagnetism. Translation of this platform to the study
+of living malaria-infected cells may shed new light on hemozoin formation
+dynamics and their interaction with antimalarial drugs.",1808.03636v2
+2018-09-09,High-speed shear driven dynamos. Part 2. Numerical analysis,"This paper aims to numerically verify the large Reynolds number asymptotic
+theory of magneto-hydrodynamic (MHD) flows proposed in the companion paper
+Deguchi (2019). To avoid any complexity associated with the chaotic nature of
+turbulence and flow geometry, nonlinear steady solutions of the
+viscous-resistive magneto-hydrodynamic equations in plane Couette flow have
+been utilised. Two classes of nonlinear MHD states, which convert kinematic
+energy to magnetic energy effectively, have been determined. The first class of
+nonlinear states can be obtained when a small spanwise uniform magnetic field
+is applied to the known hydrodynamic solution branch of the plane Couette flow.
+The nonlinear states are characterised by the hydrodynamic/magnetic roll-streak
+and the resonant layer at which strong vorticity and current sheets are
+observed. These flow features, and the induced strong streamwise magnetic
+field, are fully consistent with the vortex/Alfv\'en wave interaction theory
+proposed in Deguchi (2019). When the spanwise uniform magnetic field is
+switched off, the solutions become purely hydrodynamic. However, the second
+class of `self-sustained shear driven dynamos' at the zero-external magnetic
+field limit can be found by homotopy via the forced states subject to a
+spanwise uniform current field. The discovery of the dynamo states has
+motivated the corresponding large Reynolds number matched asymptotic analysis
+in Deguchi (2019). Here, the reduced equations derived by the asymptotic theory
+have been solved numerically. The asymptotic solution provides remarkably good
+predictions for the finite Reynolds number dynamo solutions.",1809.03855v2
+2018-09-11,Magnetic field resilient superconducting coplanar waveguide resonators for hybrid cQED experiments,"Superconducting coplanar waveguide resonators that can operate in strong
+magnetic fields are important tools for a variety of high frequency
+superconducting devices. Magnetic fields degrade resonator performance by
+creating Abrikosov vortices that cause resistive losses and frequency
+fluctuations, or suppressing superconductivity entirely. To mitigate these
+effects we investigate lithographically defined artificial defects in
+resonators fabricated from NbTiN superconducting films. We show that by
+controlling the vortex dynamics the quality factor of resonators in
+perpendicular magnetic fields can be greatly enhanced. Coupled with the
+restriction of the device geometry to enhance the superconductors critical
+field, we demonstrate stable resonances that retain quality factors $\simeq
+10^5$ at the single photon power level in perpendicular magnetic fields up to
+$B_\perp \simeq$ 20 mT and parallel magnetic fields up to $B_\parallel \simeq$
+6 T. We demonstrate the effectiveness of this technique for hybrid systems by
+integrating an InSb nanowire into a field resilient superconducting resonator,
+and use it to perform fast charge readout of a gate defined double quantum dot
+at $B_\parallel =$ 1 T.",1809.03932v1
+2018-10-05,Magnetic field direction dependent antiskyrmion motion with microwave electric fields,"Magnetic skyrmions are regarded as promising information candidates in future
+spintronic devices, which have been investigated theoretically and
+experimentally in isotropic system. Recently, the sta- bilization of
+antiskyrmions in the presence of anisotropic Dzyaloshinskii-Moriya interaction
+and its dynamics driven by current have been investigated. Here, we report the
+antiskyrmion motion with the combined action of the in-plane magnetic field and
+microwave electric fields. The in-plane mag- netic field breaks the rotation
+symmetry of the antiskyrmion, and perpendicular microwave electric field
+induces the pumping of magnetic anisotropy, leading to antiskyrmion breathing
+mode. With above two effects, the antiskyrmion propagates with a desired
+trajectory. Antiskyrmion propagation velocity depends on the frequency,
+amplitude of anisotropy pumping, and damping constant as well as strength of
+in-plane field, which reaches the maximum value when the frequency of microwave
+electric field is in consist with the resonance frequency of antiskyrmion.
+Moreover, we show that the antiskyrmion propagation depends on the direction of
+magnetic field, where the antiskyrmion Hall angle can be suppressed or
+enhanced. At a critical direction of magnetic field, the Hall angle is zero.
+Our results introduce a possible application of antiskyrmion in
+antiskyrmion-based spintronic devices with lower energy consumption.",1810.02464v1
+2018-10-15,Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo$_2$F$_7$,"We report high-frequency/high-field electron spin resonance (ESR) and
+high-field magnetization studies on single crystals of the bond-disordered
+pyrochlore NaCaCo$_2$F$_7$. Frequency- and temperature-dependent ESR
+investigations above the freezing temperature $T_f \sim 2.4$ K reveal the
+coexistence of two distinct magnetic phases. A cooperative paramagnetic phase,
+evidenced by a gapless excitation mode, is found as well as a spin-glass phase
+developing below 20 K which is associated with a gapped low-energy excitation.
+Effective $g$-factors close to 2 are obtained for both modes in line with
+pulsed high-field magnetization measurements which show an unsaturated
+isotropic behavior up to 58 T at 2 K. In order to describe the field-dependent
+magnetization in high magnetic fields, we propose an empirical model accounting
+for highly anisotropic ionic $g$-tensors expected for this material and taking
+into account the strongly competing interactions between the spins which lead
+to a frustrated ground state. As a detailed quantitative relation between
+effective $g$-factors as determined from ESR and the local $g$-tensors obtained
+by neutron scattering [Ross et al., Phys. Rev. B 93, 014433 (2016)] is still
+sought after, our work motivates further theoretical investigations of the
+low-energy excitations in bond-disordered pyrochlores.",1810.06399v2
+2018-10-22,Nonlinear Evolution of the Resonant Drag Instability in Magnetized Gas,"We investigate, for the first time, the nonlinear evolution of the magnetized
+""resonant drag instabilities"" (RDIs). We explore magnetohydrodynamic (MHD)
+simulations of gas mixed with (uniform) dust grains subject to Lorentz and drag
+forces, using the GIZMO code. The magnetized RDIs exhibit fundamentally
+different behaviour than the purely acoustic RDIs. The dust organizes into
+coherent structures and the system exhibits strong dust-gas separation. In the
+linear and early nonlinear regime, the growth rates agree with linear theory
+and the dust self-organizes into two-dimensional planes or ""sheets."" Eventually
+the gas develops fully nonlinear, saturated Alfv\'enic and compressible
+fast-mode turbulence, which fills the under-dense regions with a small amount
+of dust, and drives a dynamo which saturates at equipartition of kinetic and
+magnetic energy. The dust density fluctuations exhibit significant
+non-Gaussianity, and the power spectrum is strongly weighted towards the
+largest (box-scale) modes. The saturation level can be understood via
+quasi-linear theory, as the forcing and energy input via the instabilities
+becomes comparable to saturated tension forces and dissipation in turbulence.
+The magnetized simulation presented here is just one case; it is likely that
+the magnetic RDIs can take many forms in different parts of parameter space.",1810.09491v1
+2018-11-08,Magnetoelastics of High Field Phenomena in Antiferromagnets UO2 and CeRhIn5,"We use a recently developed optical fiber Bragg grating technique, in
+continuous and pulsed magnetic fields in excess of 90T, to study magnetoelastic
+correlations in magnetic materials at cryogenic temperatures. Both insulating
+UO2 and metallic CeRhIn5 present antiferromagnetic ground states, at T_N =
+30.3K and T_N = 3.85K respectively. A strong coupling of the magnetism to the
+crystal lattice degrees of freedom in UO2 is found, revealing piezomagnetism as
+well as the dynamics of antiferromagnetic domain switching between spin
+arrangements connected by time reversal. The AFM domains become harder to
+switch as the temperature is reduced, reaching a record value H_PZ(T = 4K) =
+18T. The effect of strong magnetic fields is also studied in CeRhIn5, where an
+anomaly in the sample crystallographic c-axis of magnitude Delta_c/c = 2 ppm is
+found associated to a recently proposed electronic nematic state at H_en = 30T
+applied 11o off the c-axis. Here we show that while this anomaly is absent when
+the magnetic field is applied 18o off the a-axis, strong magnetoelastic quantum
+oscillations attest to the high quality of the single crystal samples.",1811.03701v3
+2018-11-28,Effect of magnetic anisotropy on Skyrmions with a high topological number in itinerant magnets,"We report our numerical results for the effect of magnetic anisotropy on a
+Skyrmion crystal with a high topological number of two, which was recently
+discovered in an itinerant electron model [R. Ozawa, S. Hayami, and Y. Motome,
+Phys. Rev. Lett. 118, 147205 (2017)]. By performing numerical simulations based
+on the kernel polynomial method and the Langevin dynamics for the Kondo lattice
+model on a triangular lattice, we find that the topological property remains
+robust against the single-ion anisotropy, while the magnetic texture is
+deformed continuously. The resultant spin structure is characterized by three
+wave numbers (triple-$Q$ state), in which the $xy$ component of spins forms a
+magnetic vortex crystal and the $z$ component of spins behaves a sinusoidal
+wave. For larger anisotropy, we show that the system exhibits a phase
+transition from the Skyrmion crystal to topologically trivial phases with
+vanishing scalar chirality: a single-$Q$ collinear and double-$Q$ noncoplanar
+states for the easy-axis and easy-plane anisotropy, respectively. We also
+examine the effect of the single-ion anisotropy in an external magnetic field,
+and find that the field range of the Skyrmion crystal is rather insensitive to
+the anisotropy, in contrast to another Skyrmion crystal with the topological
+number of one whose field range is considerably extended (reduced) by the
+easy-axis (easy-plane) anisotropy.",1811.11336v1
+2018-12-21,Dynamo saturation down to vanishing viscosity: strong-field and inertial scaling regimes,"We present analytical examples of fluid dynamos that saturate through the
+action of the Coriolis and inertial terms of the Navier-Stokes equation. The
+flow is driven by a body force and is subject to global rotation and uniform
+sweeping velocity. The model can be studied down to arbitrarily low viscosity
+and naturally leads to the strong-field scaling regime for the magnetic energy
+produced above threshold: the magnetic energy is proportional to the global
+rotation rate and independent of the viscosity. Depending on the relative
+orientations of global rotation and large-scale sweeping, the dynamo
+bifurcation is either supercritical or subcritical. In the supercritical case,
+the magnetic energy follows the scaling-law for supercritical strong-field
+dynamos predicted on dimensional grounds by Petrelis & Fauve (2001). In the
+subcritical case, the system jumps to a finite-amplitude dynamo branch. The
+magnetic energy obeys a magneto-geostrophic scaling-law (Roberts & Soward
+1972), with a turbulent Elsasser number of the order of unity, where the
+magnetic diffusivity of the standard Elsasser number appears to be replaced by
+an eddy diffusivity. In the absence of global rotation, the dynamo bifurcation
+is subcritical and the saturated magnetic energy obeys the equipartition
+scaling regime. We consider both the vicinity of the dynamo threshold and the
+limit of large distance from threshold to put these various scaling behaviors
+on firm analytical ground.",1812.09166v1
+2018-12-24,Non-Reciprocal Spin Pumping in Asymmetric Magnetic Trilayers,"In magnetic trilayer systems, spin pumping is generally addressed as a
+reciprocal mechanism characterized by one unique spin mixing conductance common
+to both interfaces. However, this assumption is questionable in cases where
+different types of interfaces are present in the material. Here, we present a
+general theory for analyzing spin pumping in cases with more than one unique
+interface. The theory is applied to analyze layer-resolved ferromagnetic
+resonance experiments on the trilayer system
+Ni$_{20}$Fe$_{80}$/Ru/Fe$_{49}$Co$_{49}$V$_2$ where the Ru spacer thickness is
+varied to tune the indirect exchange coupling. The results show that the spin
+pumping in trilayer systems with dissimilar magnetic layers is non-reciprocal,
+with a surprisingly large difference between spin-pumping induced damping of
+different interfaces. Our findings have importance on dynamics of spintronic
+devices based on magnetic multilayer materials.",1812.09978v1
+2019-01-16,Quantum oscillations in strongly correlated topological Kondo insulators,"The observation of quantum oscillations in topological Kondo insulators SmB6
+and YbB12 is a recent puzzling experimental discovery. Quantum oscillations
+observed in the resistivity and the magnetization are usually explained by the
+existence of the Fermi surface. However, Kondo insulators do not have a Fermi
+surface and thus should not show quantum oscillations. By performing dynamical
+mean-field calculations for topologically nontrivial Kondo insulators in a
+magnetic field, we analyze the effect of correlations on the emergence of
+quantum oscillations in narrow-gap topological Kondo insulators and demonstrate
+that the interplay between correlations and nonlocal hybridization,
+ubiquitously occurring in topological Kondo insulators, can lead to observable
+quantum oscillations without the necessity of a Fermi surface. Particularly, we
+show that correlations make it easier to observe quantum oscillations in the
+magnetization and the resistivity of the bulk material. The fundamental
+mechanism for these quantum oscillations is a combination of correlation
+effects and Landau levels coming very close to the Fermi energy. We furthermore
+demonstrate that quantum oscillations in a three-dimensional system can be
+understood by analyzing the physics on the two-dimensional planes in the
+momentum space for which the hybridization in direction of the magnetic field
+vanishes. We believe that this scenario is relevant to understanding the
+observation of quantum oscillations in the magnetic torque for SmB6 as well as
+oscillations in the resistivity and the magnetic torque of YbB12.",1901.05099v2
+2019-02-13,The Role of a Tiny Brightening in a Huge Geo-effective Solar Eruption Leading to the St Patrick's Day Storm,"The largest magnetic storm in solar cycle 24 was caused by a fast coronal
+mass ejection (CME) that was related to a small C9.1 flare that occurred on 15
+March 2015 in solar active region (AR) NOAA 12297. The purpose of this study is
+to understand the onset mechanism of the geo-effective huge solar eruption. We
+focused on the C2.4 flare that occurred prior to the C9.1 flare of the filament
+eruption. The magnetic field structure in the AR was complicated: there were
+several filaments including the one that erupted and caused the CME. We hence
+carefully investigated the photospheric magnetic field, brightenings observed
+in the solar atmosphere, and the three-dimensional coronal magnetic field
+extrapolated from nonlinear force-free field modeling, using data from Hinode
+and Solar Dynamics Observatory. We found three intriguing points : (1) There
+was a compact but noticeably highly twisted magnetic field structure that is
+represented by a small filament in the C2.4 flaring region, where a tiny
+precursor brightening was observed before the C2.4 flare. (2) The C2.4 flaring
+region is located in the vicinity of a foot point of the closed field that
+prohibits the filament from erupting. (3) The filament shows a sudden eruption
+after the C2.4 flare and accompanying small filament eruption. From our
+analysis, we suggest that a small magnetic disturbance that was represented by
+the tiny precursor brightening at the time of the C2.4 flare is related to the
+trigger of the huge filament eruption.",1902.04871v1
+2019-03-07,Transient magnetic domain wall AC dynamics by means of MOKE microscopy,"The domain wall response under constant external magnetic fields reveals a
+complex behavior where sample disorder plays a key role. Furthermore, the
+response to alternating magnetic fields has only been explored in limited cases
+and analyzed in terms of the constant field solution. Here we unveil phenomena
+in the evolution of magnetic domain walls under the application of alternating
+magnetic fields within the creep regime, well beyond a small fuctuation limit
+of the domain wall position. Magnetic field pulses were applied in ultra-thin
+ferromagnetic films with perpendicular anisotropy, and the resulting domain
+wall evolution was characterized by polar magneto-optical Kerr effect
+microscopy. Whereas the DC characterization is well predicted by the elastic
+interface model, striking unexpected features are observed under the
+application of alternating square pulses: magneto-optical images show that
+after a transient number of cycles, domain walls evolve toward strongly
+distorted shapes concomitantly with a modification of domain area. The
+morphology of domain walls is characterized with a roughness exponent when
+possible and contrasted with alternative observables which result to be more
+suitable for the characterization of this transient evolution. The final
+stationary convergence as well as the underlying physics is discussed.",1903.03006v1
+2019-03-10,The decisive role of magnetic anisotropy in honeycomb layered Li$_3$Ni$_2$SbO$_6$ and Na$_3$Ni$_2$SbO$_6$,"The decisive role of magnetic anisotropy even in systems with small
+anisotropy is illustrated for the honeycomb-layered antiferromagnets The
+decisive role of magnetic anisotropy in honeycomb layered Li$_3$Ni$_2$SbO$_6$
+and Na$_3$Ni$_2$SbO$_6$ with $A$ = Li and Na. Both systems evolve long range
+magnetic order below $T_{\rm N}$ = 14 and 16.5~K, respectively. The magnetic
+phase diagrams obtained from static magnetisation studies up to 15~T imply
+competing antiferromagnetic phases and a tricritical point at $T_{\rm N}$. The
+phase boundaries are visible in the dynamic response of the antiferromagnetic
+resonance modes, too, which investigation by means of high frequency/high field
+electron spin resonance enables precise determination of magnetic anisotropy.
+The anisotropy gap amounts to $\Delta = 360 \pm 2$~GHz in Na$_3$Ni$_2$SbO$_6$
+while in Li$_3$Ni$_2$SbO$_6$ orthorhombicity is associated with $\Delta = 198
+\pm 4$ and $218 \pm 4$~GHz. Above $T_{\rm N}$, the data imply short-range
+antiferromagnetic order up to at least 80~K. The data suggest a crucial role of
+anisotropy for selecting the actual spin structure at $B=0$~T.",1903.04041v1
+2019-03-26,"Partial invariants, large-scale dynamo action, and the inverse transfer of magnetic helicity","The existence of partially conserved enstrophy-like quantities is conjectured
+to cause inverse energy transfers to develop embedded in magnetohydrodynamical
+(MHD) turbulence, in analogy to the influence of enstrophy in two-dimensional
+nonconducting turbulence. By decomposing the velocity and magnetic fields in
+spectral space onto helical modes, we identify subsets of three-wave (triad)
+interactions conserving two new enstrophy-like quantities which can be mapped
+to triad interactions recently identified with facilitating large-scale
+$\alpha$-type dynamo action and the inverse transfer of magnetic helicity. Due
+to their dependence on interaction scale locality, the invariants suggest that
+the inverse transfer of magnetic helicity might be facilitated by both local-
+and nonlocal-scale interactions, and is a process more local than the
+$\alpha$-dynamo. We test the predicted embedded (partial) energy fluxes by
+constructing a shell model (reduced wave-space model) of the minimal set of
+triad interactions (MTI) required to conserve the ideal MHD invariants.
+Numerically simulated MTIs demonstrate that, for a range of forcing
+configurations, the partial invariants are, with some exceptions, indeed useful
+for understanding the embedded contributions to the total spectral energy flux.
+Furthermore, we demonstrate that strictly inverse energy transfers may develop
+if enstrophy-like conserving interactions are favoured, a mechanism recently
+attributed to the energy cascade reversals found in nonconducting
+three-dimensional turbulence subject to strong rotation or confinement. The
+presented results have implications for the understanding of the physical
+mechanisms behind large-scale dynamo action and the inverse transfer of
+magnetic helicity, processes thought to be central to large-scale magnetic
+structure formation.",1903.10725v2
+2019-05-17,Mapping Dynamical Magnetic Responses of Ultra-thin Micron-size Superconducting Films using Nitrogen-vacancy Centers in Diamond,"Two-dimensional superconductors have attracted growing interest because of
+their scientific novelty, structural tunability, and useful properties. Studies
+of their magnetic responses, however, are often hampered by difficulties to
+grow large-size samples of high quality and uniformity. We report here an
+imaging method that employed NV- centers in diamond as sensor capable of
+mapping out the microwave magnetic field distribution on an ultrathin
+superconducting film of micron size. Measurements on a 33nm-thick film and a
+125nm-thick bulk-like film of $Bi_2Sr_2CaCu_2O_{8+\delta}$ revealed that the ac
+Meissner effect (or repulsion of ac magnetic field) set in at 78K and 91K,
+respectively; the latter was the superconducting transition temperature (Tc) of
+both films. The unusual ac magnetic response of the thin film presumably was
+due to thermally excited vortex-antivortex diffusive motion in the film.
+Spatial resolution of our ac magnetometer was limited by optical diffraction
+and the noise level was at 14 ${\mu}T/Hz^{1/2}$. The technique could be
+extended with better detection sensitivity to extract local ac
+conductivity/susceptibility of ultrathin or monolayer superconducting samples
+as well as ac magnetic responses of other two-dimensional exotic thin films of
+limited lateral size.",1905.07083v1
+2019-05-20,Orbitally Dominated Rashba-Edelstein Effect in Noncentrosymmetric Antiferromagnets,"Efficient manipulation of magnetic order with electric current pulses is
+desirable for achieving fast spintronic devices. The Rashba-Edelstein effect,
+wherein a spin polarization is electrically induced in noncentrosymmetric
+systems, provides a mean to achieve current-induced staggered spin-orbit
+torques. Initially predicted for spin, the orbital counterpart of this effect
+has been disregarded up to now. Here, we present a generalized Rashba-Edelstein
+effect, which generates not only spin polarization but also orbital
+polarization, which we find to be far from being negligible and could play a
+crucial role in the magnetization dynamics. We show that the orbital
+Rashba-Edelstein effect does not require spin-orbit coupling to exist. We
+present first-principles calculations of the frequency-dependent spin and
+orbital Rashba-Edelstein susceptibility tensors for the noncentrosymmetric
+antiferromagnets CuMnAs and Mn2Au. We show that the electrically induced local
+magnetization has both staggered in-plane components and non-staggered
+out-of-plane components, and can exhibit Rashba-like or Dresselhaus-like
+symmetries, depending on the magnetic configuration. Furthermore, there is an
+induced local magnetization on the nonmagnetic atoms as well, that is smaller
+in Mn2Au than in CuMnAs. We compute sizable induced magnetizations at optical
+frequencies, which suggest that electric-field driven switching could be
+achieved at much higher frequencies.",1905.08279v1
+2019-05-22,Ultradense Tailored Vortex Pinning Arrays in Superconducting YBa$_2$Cu$_3$O$_{7-δ}$ Thin Films Created by Focused He Ion Beam Irradiation for Fluxonics Applications,"Magnetic fields penetrate a type-II superconductor as magnetic flux quanta,
+called vortices. In a clean superconductor they arrange in a hexagonal lattice,
+while by adding periodic artificial pinning centers many other arrangements can
+be realized. Using the focused beam of a helium ion microscope we have
+fabricated periodic patterns of dense pinning centers with spacings as small as
+70 nm in thin films of the cuprate superconductor
+YBa$_{2}$Cu$_{3}$O$_{7-\delta}$. In these ultradense kagom\'e-like patterns,
+the voids lead to magnetic caging of vortices, resulting in unconventional
+commensurability effects that manifest themselves as peaks in the critical
+current and minima in the resistance versus applied magnetic field up to $\sim
+0.4\,$T. The various vortex patterns at different magnetic fields are analyzed
+by molecular dynamics simulations of vortex motion, and the magnetic field
+dependence of the critical current is confirmed. These findings open the way
+for a controlled manipulation of vortices in cuprate superconductors by
+artificial sub-100 nm pinning landscapes.",1905.09070v2
+2019-08-06,"Tunable magnetization in nanoscale LuFeO3: Role of morphology, ortho-hexa phase ratio and local structure","We have observed enhancement and shift in the spin reorientation transition
+temperature as a consequence of coexistence of orthorhombic and hexagonal
+phases and higher aspect ratio in nanoscale LuFeO3. Nanoparticles and
+nanofibers of LuFeO3 are considered for this work. Nanoparticles have 75 %
+orthorhombic phase and 25 % hexagonal phase, while nanofibers have 23%
+orthorhombic phase and 77%-hexagonal phase. Larger aspect ratio in case of
+nanofibers is seen to help strain-stabilize the hexagonal phase in the
+material. Magnetic measurements show significant difference in the magnetic
+behavior and spin reorientation temperature; 183K for the nanoparticle case and
+150K for the case of nanofibers. Moreover, the ferromagnetic moment is two
+order of magnitude higher for nanofibers than that of nanoparticles, In
+hexagonal phase, frustration of triangular lattice, works against the long
+range ordering while magnetic anisotropy works in favor of the long range
+ordering, which contributes towards the enhanced and anomalous magnetic
+behavior in case of fibers. X -ray absorption near edge spectroscopy (XANES) at
+the Fe K-edge has been used to probe the symmetry driven dynamics of Fe 3d- 4p
+orbitals. It established that due to noncentrocymmetry of the Fe atom, the
+nanofibers have decreased 3d-4p orbital mixing and reduced crystal field
+splitting energy, which are also contributing factor for the enhanced magnetic
+behaviour.",1908.02073v1
+2019-10-21,Energy origination and triggering mechanism of a series of homologous confined flares,"Using the H$\alpha$ data from the New Vacuum Solar Telescope (NVST) at the
+Fuxian Solar Observatory together with multi-wavelength images and magnetograms
+obtained by Solar Dynamics Observatory (SDO), we study the detailed process of
+three homologous confined flares in active-region (AR) NOAA 11861 on 2013
+October 12. All of the three flares occurred at same location, with similar
+morphologies and comparable class. Through analyzing the evolution of magnetic
+field and flow field, we found an emergence of magnetic flux and a strong
+shearing motion between two opposite polarities near the following sunspot. The
+magnetic flux and the average transverse field strength exhibited a decrease
+before each eruption and reached the lowest point at the onset of each
+eruption. By calculating the shearing and the emergence energy in the
+photosphere, we found that the integral of energy injected from the
+photosphere, for a few hours, could provide enough energy for the flares. The
+reconnection between different loops was observed in H$\alpha$ images during
+the occurrence of each flare. These results suggest that the emerging magnetic
+flux and the shearing motion in the photosphere can inject the energy to the
+sheared magnetic loops and the energy finally was released via magnetic
+reconnection to power the solar flares.",1910.09147v1
+2019-10-23,Giant room temperature anomalous Hall effect and magnetically tuned topology in the ferromagnetic Weyl semimetal Co2MnAl,"Weyl semimetals (WSM) have been extensively studied due to their exotic
+properties such as topological surface states and anomalous transport
+phenomena. Their band structure topology is usually predetermined by material
+parameters and can hardly be manipulated once the material is formed. Their
+unique transport properties appear usually at very low temperature, which sets
+challenges for practical device applications. In this work, we demonstrate a
+way to modify the band topology via a weak magnetic field in a ferromagnetic
+topological semimetal, Co2MnAl, at room temperature. We observe a tunable,
+giant anomalous Hall effect, which is induced by the transition between Weyl
+points and nodal rings as rotating the magnetization axis. The anomalous Hall
+conductivity is as large as that of a 3D quantum anomalous Hall effect (QAHE),
+with the Hall angle reaching a record value (21%) at the room temperature among
+magnetic conductors. Furthermore, we propose a material recipe to generate the
+giant anomalous Hall effect by gaping nodal rings without requiring the
+existence of Weyl points. Our work reveals an ideal intrinsically magnetic
+platform to explore the interplay between magnetic dynamics and topological
+physics for the development of a new generation of spintronic devices.",1910.10378v1
+2019-10-25,Numerical simulations of the emerging plasma blob into a solar coronal hole,"We numerically simulate emergence of a magnetic plasma blob into a solar
+coronal hole. This blob may be associated with granulation and therefore it has
+a weak magnetic field. Two-dimensional simulations are performed using the
+MAGNUS code which solves magnetohydrodynamic equations, taking into account
+magnetic resistivity and thermal conduction. As a result of the interaction of
+the emerging blob with the ambient plasma, the magnetic lines experience
+reconnection with the blob getting flattened and deformed with time.
+Additionally, this process launches a vertical outflow of hot plasma and the
+chromosphere in its response increases its temperature. We perform parametric
+studies by varying the magnitude of the magnetic field of the blob and
+observing the net heating of the chromosphere. These studies are inspired by
+realistic simulations of granulation made with the use of two-fluid JOANNA
+code. In these simulations a number of magnetic blobs are detected in the
+convection zone and in the photosphere. From the numerical results, we conclude
+that as a result of granulation operating in a solar quiet region the emerging
+blob may trigger very complex dynamics in the upper regions of the solar
+atmosphere, and the associated outflows may be a source of heating of the
+chromosphere and possibly the solar corona.",1910.11814v1
+2019-11-07,Properties of two-temperature magnetized advective accretion flow around rotating black hole,"We study the two-temperature magnetized advective accretion flow around the
+Kerr black holes. During accretion, ions are heated up due to viscous
+dissipation, and when Coulomb coupling becomes effective, they transfer a part
+of their energy to the electrons. On the contrary, electrons lose energy due to
+various radiative cooling processes, namely bremsstrahlung, synchrotron, and
+Comtonization processes, respectively. To account for the magnetic contribution
+inside the disc, we consider the toroidal magnetic fields which are assumed to
+be dominant over other components. Moreover, we adopt the relativistic equation
+of state to describe the thermal characteristics of the flow. With this, we
+calculate the global transonic accretion solutions around the rotating black
+holes. We find that accretion solution containing multiple critical points may
+harbor shock wave provided the standing shock conditions are satisfied.
+Further, we investigate the shock properties, such as shock location ($x_s$)
+and compression ratio ($R$) that delineate the post-shock corona (hereafter
+PSC) and find that the dynamics of PSC is controlled by the flow parameters,
+such as accretion rate (${\dot m}$) and magnetic fields ($\beta$, defined as
+the ratio of gas pressure to the magnetic pressure), etc. Finally, we calculate
+the emission spectra of the accretion flows containing PSC and indicate that
+both ${\dot m}$ and $\beta$ play the pivotal roles in explaining the spectral
+state transitions commonly observed for black hole X-ray binaries.",1911.02757v2
+2019-11-08,Spatio-temporal behavior of magnetohydrodynamic fluctuations with cross-helicity and background magnetic field,"We study the spatio-temporal behavior of the Els\""asser variables describing
+magnetic and velocity field fluctuations, using direct numerical simulations of
+three-dimensional magnetohydrodynamic turbulence. We consider cases with
+relatively small, intermediate, and large values of a mean background magnetic
+field, and with null, small, and high cross-helicity (correlations between the
+velocity and the magnetic field). Wavenumber-dependent time correlation
+functions are computed for the different simulations. From these correlation
+functions, the decorrelation time is computed and compared with different
+theoretical characteristic times: the local non-linear time, the
+random-sweeping time, and the Alfv\'enic time. It is found that decorrelation
+times are dominated by sweeping effects for low values of the mean magnetic
+field and for low values of the cross-helicity, while for large values of the
+background field or of the cross-helicity and for wave vectors sufficiently
+aligned with the guide field, decorrelation times are controlled by Alfv\'enic
+effects. Finally, we observe counter-propagation of Alfv\'enic fluctuations due
+to reflections produced by inhomogeneities in the total magnetic field. This
+effect becomes more prominent in flows with large cross-helicity, strongly
+modifying the propagation of waves in turbulent magnetohydrodynamic flows.",1911.03400v1
+2019-11-11,Global axisymmetric simulations of photoevaporation and magnetically driven protoplanetary disk winds,"Photoevaporation and magnetically driven winds are two independent mechanisms
+to remove mass from protoplanetary disks. In addition to accretion, the effect
+of these two principles acting concurrently could be significant and the
+transition between those two has not been extensively studied and quantified in
+the literature yet. In order to contribute to the understanding of disk winds,
+we present the phenomena emerging in the framework of two-dimensional
+axisymmetric, non-ideal magnetohydrodynamic simulations including EUV-/ X-ray
+driven photoevaporation. Of particular interest are the examination of the
+transition region between photoevaporation and magnetically driven wind, the
+possibility of emerging magneto-centrifugal wind effects, as well as the
+morphology of the wind itself depending on the strength of the magnetic field.
+We use the PLUTO code in a 2.5D axisymmetric configuration with additional
+treatment of EUV-/ X-ray heating and dynamic ohmic diffusion based on a
+semi-analytical chemical model. We identify the transition between both outflow
+types to occur for values of the initial plasma beta $\beta \geq 10^7$, while
+magnetically driven winds generally outperform photoevaporation for stronger
+fields. In our simulations we observe irregular and asymmetric outflows for
+stronger magnetic fields. In the weak field regime the photoevaporation rates
+are slightly lowered by perturbations of the gas density in the inner regions
+of the disk. Overall, our results predict a wind with a lever arm smaller than
+1.5, consistent with a hot magneto-thermal wind. Stronger accretion flows are
+present for values of $\beta < 10^7$.",1911.04510v2
+2019-11-25,Magnetic response of FeRh to static and dynamic disorder,"Changes of the magnetic and crystal structure on the microscopic scale in 40
+nm FeRh thin films have been applied to investigate the phenomena of a disorder
+induced ferromagnetism at room temperature initiated through light
+ion-irradiation with fluences up to 0.125 Ne$^+$/nm$^{-2}$. Magnetometry shows
+an increase of magnetic ordering at low temperatures and a decrease of the
+transition temperature combined with a broadening of the hysteresis with rising
+ion fluence. $^{57}$Fe M\""ossbauer spectroscopy reveals the occurrence of an
+additional magnetic contributions with an hyperfine splitting of 27.2 T -
+identical to that of ferromagnetic B2-FeRh. The appearance of an anti-site
+Fe-contribution can be assumed to be lower than 0.6 Fe-at%, indicating that no
+change of the chemical composition is evident. The investigation of the local
+structure shows an increase of the static mean square relative displacement
+determined by X-ray absorption fine structure spectroscopy, while an increase
+of the defect-concentration has been determined by positron annihilation
+spectroscopy. From the changes of the microscopic magnetic structure a
+similarity between the temperature induced and the structural disorder induced
+ferromagnetic phase can be observed. These findings emphasize the relationship
+between magnetic ordering and the microscopic defect structure in FeRh.",1911.11256v1
+2019-12-03,The dynamo-wind feedback loop: Assessing their non-linear interplay,"Though generated deep inside the convection zone, the solar magnetic field
+has a direct impact on the Earth space environment via the Parker spiral. It
+strongly modulates the solar wind in the whole heliosphere, especially its
+latitudinal and longitudinal speed distribution over the years. However the
+wind also influences the topology of the coronal magnetic field by opening the
+magnetic field lines in the coronal holes, which can affect the inner magnetic
+field of the star by altering the dynamo boundary conditions. This coupling is
+especially difficult to model because it covers a large variety of
+spatio-temporal scales. Quasi-static studies have begun to help us unveil how
+the dynamo-generated magnetic field shapes the wind, but the full interplay
+between the solar dynamo and the solar wind still eludes our understanding.
+  We use the compressible magnetohydrodynamical (MHD) code PLUTO to compute
+simultaneously in 2.5D the generation and evolution of magnetic field inside
+the star via an alpha-Omega dynamo process and the corresponding evolution of a
+polytropic coronal wind over several activity cycles for a young Sun. A
+multi-layered boundary condition at the surface of the star connects the inner
+and outer stellar layers, allowing both to adapt dynamically. Our continuously
+coupled dynamo-wind model allows us to characterize how the solar wind
+conditions change as a function of the cycle phase, and also to quantify the
+evolution of integrated quantities such as the Alfv\'en radius. We further
+assess the impact of the solar wind on the dynamo itself by comparing our
+results with and without wind feedback.",1912.01271v1
+2019-12-04,MnSnTeO6: a Chiral Antiferromagnet Prepared by a Two-Step Topotactic Transformation,"MnSnTeO6, a new chiral antiferromagnet, was prepared both by topotactic
+transformation of the metastable rosiaite-type polymorph and by direct
+synthesis from coprecipitated hydroxides. Its structure, static and dynamic
+magnetic properties were studied comprehensively both experimentally (through
+X-ray and neutron powder diffraction, magnetization, specific heat, dielectric
+permittivity and ESR techniques) and theoretically (by means of ab initio
+density functional theory (DFT) calculations within the spin-polarized
+generalized gradient approximation). MnSnTeO6 is isostructural with MnSb2O6
+(space group P321) and does not show any structural transition between 3 and
+300 K. The magnetic susceptibility and specific heat exhibit an
+antiferromagnetic ordering at TN=9.8 K, which is confirmed by low-temperature
+neutron data. At the same time, the thermodynamic parameters demonstrate an
+additional anomaly on the temperature dependences of magnetic susceptibility
+chi(T), specific heat Cp(T) and dielectric permittivity epsilon(T) at T*=4.9 K,
+which is characterized by significant temperature hysteresis. Clear enhancement
+of the dielectric permittivity at T* is most likely to reflect the coupling of
+dielectric and magnetic subsystems leading to development of electric
+polarization. It was established that the ground state of MnSnTeO6 is
+stabilized by seven exchange parameters, and neutron diffraction revealed
+incommensurate magnetic structure with propagation vector k= (0, 0, 0.183)
+analogous to that of MnSb2O6. Ab initio DFT calculations demonstrate that the
+strongest exchange coupling occurs between planes along diagonals. All exchange
+parameters are antiferromagnetic and reveal moderate frustration.",1912.02623v1
+2019-12-12,A Curious Case of Circular Polarization in the 25 GHz Methanol Maser Line toward OMC-1,"We report the detection of a circular polarization signature in the Stokes
+$V$ profile of a 25 GHz Class I CH$_3$OH maser toward the high mass star
+forming region OMC-1. Such a feature usually constitutes a detection of the
+Zeeman effect. If due to a magnetic field in OMC-1, this would represent the
+first detection and discovery of the Zeeman effect in the 25 GHz Class I
+CH$_3$OH maser. The feature in Stokes $V$ is detected in two observations with
+different angular resolutions taken eight years apart with the Very Large Array
+(VLA); for our 2009 D-configuration observations, the fitted value for $z
+B_\text{los}$ is $152 \pm 12$ Hz, where $z$ is the Zeeman splitting factor and
+$B_\text{los}$ is the line-of-sight magnetic field. For our 2017
+C-configuration observations, the fitted value for $zB_\text{los} = 149 \pm
+19~$Hz, likely for the same maser spot. These correspond to $B_\text{los}$ in
+the range 171-214 mG, depending on which hyperfine transition is responsible
+for the maser line. While these $B_\text{los}$ values are high, they are not
+implausible. If the magnetic field increases in proportion to the molecular
+hydrogen density in shocked regions, then our detected fields predict values
+for the pre-shock magnetic field that are in agreement with observations. With
+$B_\text{los}$ =171-214 mG, the magnetic energy in the post-shocked regions
+where these 25 GHz Class I CH$_3$OH masers occur would dominate over the
+kinetic energy density and be at least of the order of the pressure in the
+shock, implying that the magnetic field would exert significant influence over
+the dynamics of these regions.",1912.06235v1
+2020-02-18,Quantum dynamics in strongly driven random dipolar magnets,"The random dipolar magnet LiHo$_x$Y$_{1-x}$F$_4$ enters a strongly frustrated
+regime for small Ho$^{3+}$ concentrations with $x<0.05$. In this regime, the
+magnetic moments of the Ho$^{3+}$ ions experience small quantum corrections to
+the common Ising approximation of LiHo$_x$Y$_{1-x}$F$_4$, which lead to a
+$Z_2$-symmetry breaking and small, degeneracy breaking energy shifts between
+different eigenstates. Here we show that destructive interference between two
+almost degenerate excitation pathways burns spectral holes in the magnetic
+susceptibility of strongly driven magnetic moments in LiHo$_x$Y$_{1-x}$F$_4$.
+Such spectral holes in the susceptibility, microscopically described in terms
+of Fano resonances, can already occur in setups of only two or three frustrated
+moments, for which the driven level scheme has the paradigmatic
+$\Lambda$-shape. For larger clusters of magnetic moments, the corresponding
+level schemes separate into almost isolated many-body $\Lambda$-schemes, in the
+sense that either the transition matrix elements between them are negligibly
+small or the energy difference of the transitions is strongly off-resonant to
+the drive. This enables the observation of Fano resonances, caused by many-body
+quantum corrections to the common Ising approximation also in the thermodynamic
+limit. We discuss its dependence on the driving strength and frequency as well
+as the crucial role that is played by lattice dissipation.",2002.07834v1
+2020-02-20,Numerical simulation of the wave turbulence on the surface of a ferrofluid in a horizontal magnetic field,"The turbulence of capillary waves on the surface of a ferrofluid with a high
+permeability in a horizontal magnetic field is considered in the framework of a
+one-dimensional weakly nonlinear model. In the limit of a strong magnetic
+field, the surface waves under study can propagate without distortions along or
+against the direction of external field, i.e., similar to Alfv\'en waves in a
+perfectly conducting fluid. The interaction of counter-propagating nonlinear
+waves leads to the development of wave turbulence on the surface of the liquid.
+The computational data show that the spectrum of turbulence is divided into two
+parts: a low-frequency dispersionless region, where the magnetic forces
+dominate and a high-frequency dispersive one, in which the influence of
+capillary forces becomes significant. In the first region, the spectrum of the
+surface elevation has the same exponent in $k$ and $\omega$ domains and its
+value is close to $-3.5$, what is in a good agreement with the estimation
+obtained from the dimensional analysis of the weak turbulence spectra. At the
+high frequencies, the computed spatial spectrum of the surface waves is close
+to $k^{-5/2}$ which corresponds to $\omega^{-5/3}$ in terms of the frequency.
+This spectrum does not coincide with the Zakharov-Filonenko spectrum obtained
+for pure capillary waves. A possible explanation of this fact is in the
+influence of coherent structures (like shock waves) usually arising in media
+with weak dispersion.",2002.08698v1
+2020-02-29,Magnetoelectric polarizability: A microscopic perspective,"We extend a field theoretic approach for the investigation of the electronic
+charge-current density response of crystalline systems to arbitrary applied
+electromagnetic fields. The approach leads to the introduction of microscopic
+polarization and magnetization fields, as well as free charge and current
+densities, the dynamics of which are described by a lattice gauge theory. The
+spatial averages of such quantities constitute the fields of macroscopic
+electrodynamics. We implement this formalism to study the orbital electronic
+response of a class of insulators to applied uniform dc electric and magnetic
+fields at zero temperature. To first-order in the applied fields, the free
+charge and current densities vanish; thus the response of the system is
+characterized by the first-order modifications to the microscopic polarization
+and magnetization fields. Associated with the dipole moment of the microscopic
+polarization (magnetization) field is a macroscopic polarization
+(magnetization), for which we extract various response tensors. We focus on the
+orbital magnetoelectric polarizability (OMP) tensor, and find the accepted
+expression as derived from the ""modern theory of polarization and
+magnetization."" Since our results are based on the spatial averages of
+microscopic fields, we can identify the distinct contributions to the OMP
+tensor from the perspective of this microscopic theory, and we establish the
+general framework in which extensions to finite frequency can be made.",2003.00313v2
+2020-04-12,Hybridized quadrupolar excitations in the spin-anisotropic frustrated magnet FeI2,"Magnetic order is usually associated with well-defined magnon excitations.
+Exotic magnetic fluctuations with fractional, topological or multipolar
+character, have been proposed for radically different forms of magnetic matter
+such as spin-liquids. As a result, considerable efforts have searched for, and
+uncovered, low-spin materials with suppressed dipolar order at low
+temperatures. Here, we report neutron-scattering experiments and quantitative
+theoretical modeling of an exceptional spin-1 system -- the uniaxial triangular
+magnet FeI2 -- where a bright and dispersive band of mixed dipolar-quadrupolar
+fluctuations emerges just above a dipolar ordered ground-state. This excitation
+arises from anisotropic exchange interactions that hybridize overlapping modes
+carrying fundamentally different quantum numbers. Remarkably, a generalization
+of spin-wave theory to local SU(3) degrees of freedom accounts for all details
+of the low-energy dynamical response of FeI2 without going beyond quadratic
+order. Our work highlights that quantum excitations without classical
+counterparts can be realized even in presence of fully developed magnetic
+order.",2004.05623v1
+2020-05-01,Magnetic catalysis and the chiral condensate in holographic QCD,"We investigate the effect of a non-zero magnetic field on the chiral
+condensate using a holographic QCD approach. We extend the model proposed by
+Iatrakis, Kiritsis and Paredes in arXiv:1010.1364 that realises chiral symmetry
+breaking dynamically from 5d tachyon condensation. We calculate the chiral
+condensate, magnetisation and susceptibilities for the confined and deconfined
+phases. The model leads, in the probe approximation, to magnetic catalysis of
+chiral symmetry breaking in both confined and deconfined phases. In the chiral
+limit, $m_q=0$, we find that in the deconfined phase a sufficiently strong
+magnetic field leads to a second order phase transition from the chirally
+restored phase to a chirally broken phase. The transition becomes a crossover
+as the quark mass increases. Due to a scaling in the temperature, the chiral
+transition will also be interpreted as a transition in the temperature for
+fixed magnetic field. We elaborate on the relationship between the chiral
+condensate, magnetisation and the (magnetic) free energy density. We compare
+our results at low and moderate temperatures temperatures with lattice QCD
+results.",2005.00500v3
+2020-05-04,Current-driven skyrmionium in a frustrated magnetic system,"Magnetic skyrmionium can be used as a nanometer-scale non-volatile
+information carrier, which shows no skyrmion Hall effect due to its special
+structure carrying zero topological charge. Here, we report the static and
+dynamic properties of an isolated nanoscale skyrmionium in a frustrated
+magnetic monolayer, where the skyrmionium is stabilized by competing
+interactions. The frustrated skyrmionium has a size of about $10$ nm, which can
+be further reduced by tuning perpendicular magnetic anisotropy or magnetic
+field. It is found that the nanoscale skyrmionium driven by the damping-like
+spin-orbit torque shows directional motion with a favored Bloch-type helicity.
+A small driving current or magnetic field can lead to the transformation of an
+unstable N\'eel-type skyrmionium to a metastable Bloch-type skyrmionium. A
+large driving current may result in the distortion and collapse of the
+Bloch-type skyrmionium. Our results are useful for the understanding of
+frustrated skyrmionium physics, which also provide guidelines for the design of
+spintronic devices based on topological spin textures.",2005.01403v2
+2020-05-14,Field Cooled Annular Josephson Tunnel Junctions,"We investigate the physics of planar annular Josephson tunnel junctions
+quenched through their transition temperature in the presence of an external
+magnetic field. Experiments carried out with long Nb/Al-AlOx/Nb annular
+junctions showed that the magnetic flux trapped in the high-quality
+doubly-connected superconducting electrodes forming the junction generates a
+persistent current whose associated magnetic field affects the both the static
+and dynamics properties of the junctions. More specifically, the field trapped
+in the hole of one electrode combined with a d.c. bias current induces a
+viscous flow of dense trains of Josephson vortices which manifests itself
+through the sequential appearance of displaced linear slopes, Fiske step
+staircases and Eck steps in the junction's current-voltage characteristic.
+Furthermore, a field shift is observed in the first lobe of the magnetic
+diffraction pattern. The effects of the persistent current can be mitigated or
+even canceled by an external magnetic field perpendicular to the junction
+plane. The radial field associated with the persistent current can be
+accurately modeled with the classical phenomenological sine-Gordon model for
+extended one-dimensional Josephson junctions. Extensive numerical simulations
+were carried out to disclose the basic flux-flow mechanism responsible for the
+appearance of the magnetically induced steps and to elucidate the role of
+geometrical parameters. It was found that the imprint of the field cooling is
+enhanced in confocal annular junctions which are the natural generalization of
+the well studied circular annular junctions.",2005.06816v1
+2020-05-18,The Einstein - de Haas effect at radio frequencies in and near magnetic equilibrium,"The Einstein-de Haas (EdH) effect and its reciprocal the Barnett effect are
+fundamental to magnetism and uniquely yield measures of the ratio of magnetic
+moment to total angular momentum. These effects, small and generally difficult
+to observe, are enjoying a resurgence of interest as contemporary techniques
+enable new approaches to their study. The high mechanical resonance frequencies
+in nanomechanical systems offer a tremendous advantage for the observation of
+EdH torques in particular. At radio frequencies, the EdH effect can become
+comparable to or even exceed in magnitude conventional cross-product magnetic
+torques. In addition, the RF-EdH torque is expected to be phase-shifted by 90
+degrees relative to cross-product torques, provided the magnetic system remains
+in quasi-static equilibrium, enabling separation in quadratures when both
+sources of torque are operative. Radio frequency EdH measurements are
+demonstrated through the full hysteresis range of micrometer scale,
+monocrystalline yttrium iron garnet (YIG) disks. Equilibrium behavior is
+observed in the vortex state at low bias field. Barkhausen-like features emerge
+in the in-plane EdH torque at higher fields in the vortex state, revealing
+magnetic disorder too weak to be visible through the in-plane cross-product
+torque. Beyond vortex annihilation, peaks arise in the EdH torque versus bias
+field, and these together with their phase signatures indicate additional
+utility of the Einstein-de Haas effect for the study of RF-driven spin
+dynamics.",2005.08406v1
+2020-04-14,An experimental design for the control and assembly of magnetic microwheels,"Superparamagnetic colloidal particles can be reversibly assembled into
+wheel-like structures called microwheels ($\mu$wheels) which roll on surfaces
+due to friction and can be driven at user-controlled speeds and directions
+using rotating magnetic fields. Here, we describe the hardware and software to
+create and control the magnetic fields that assemble and direct wheel motion
+and the optics to visualize them. Motivated by portability, adaptability and
+low-cost, an extruded aluminum heat dissipating frame incorporating open optics
+and audio speaker coils outfitted with high magnetic permeability cores was
+constructed. Open-source software was developed to define the magnitude,
+frequency, and orientation of the magnetic field, allowing for real time
+joystick control of $\mu$wheels through two-dimensional (2D) and
+three-dimensional (3D) fluidic environments. With this combination of hardware
+and software, $\mu$wheels translate at speeds up to 50 $\mu$m/s through sample
+sizes up to 5 cm x 5 cm x 5 cm using 0.75-2.5 mT magnetic fields with rotation
+frequencies of 5-40 Hz. Heat dissipation by aluminum coil clamps maintained
+sample temperatures within 3 C of ambient temperature, a range conducive for
+biological applications. With this design, $\mu$wheels can be manipulated and
+imaged in 2D and 3D networks at length scales of micrometers to centimeters",2006.02524v1
+2020-06-08,Transverse Chiral Magnetic Photocurrent Induced by Linearly Polarized Light in Mirror-Symmetric Weyl Semimetals,"A new class of photocurrents is predicted to occur in both type-I and type-II
+Weyl semimetals. Unlike the previously studied photocurrents in chiral
+materials, the proposed current requires neither circularly polarized light,
+nor an absence of symmetry with respect to a plane of reflection. We show that
+if a Weyl semimetal has a broken inversion symmetry then linearly polarized
+light can induce a photocurrent transverse to the direction of an applied
+magnetic field, in spite of the symmetry with respect to a reflection plane and
+the time reversal symmetry. The class of materials in which we expect this to
+occur is sufficiently broad and includes the transition metal monopnictides
+such as TaAs. The effect stems from the dynamics of Weyl chiral quasi-particles
+in a magnetic field, restricted by the symmetries described above; because the
+resulting current is transverse to the direction of magnetic field, we call it
+the transverse chiral magnetic photocurrent. The magnitude of the resulting
+photocurrent is predicted to be significant in the THz frequency range, about
+$0.75\; \mathrm{\mu A}$ for type-I and $2.5\; \mathrm{\mu A}$ for type-II Weyl
+semimetals. This opens the possibility to utilize the predicted transverse
+chiral magnetic photocurrent for sensing unpolarized THz radiation.",2006.04857v2
+2020-06-26,Elasticity of tangled magnetic fields,"The fundamental difference between incompressible ideal magnetohydrodynamics
+and the dynamics of a non-conducting fluid is that magnetic fields exert a
+tension force that opposes their bending; magnetic fields behave like elastic
+strings threading the fluid. It is natural, therefore, to expect that a
+magnetic field tangled at small length scales should resist a large-scale shear
+in an elastic way, much as a ball of tangled elastic strings responds
+elastically to an impulse. Furthermore, a tangled field should support the
+propagation of `magnetoelastic waves', the isotropic analogue of Alfv\'en waves
+on a straight magnetic field. Here, we study magnetoelasticity in the idealised
+context of an equilibrium tangled field configuration. In contrast to previous
+treatments, we explicitly account for intermittency of the Maxwell stress, and
+show that this intermittency necessarily decreases the frequency of
+magnetoelastic waves in a stable field configuration. We develop a mean-field
+formalism to describe magnetoelastic behaviour, retaining leading-order
+corrections due to the coupling of large- and small-scale motions, and solve
+the initial-value problem for viscous fluids subjected to a large-scale shear,
+showing that the development of small-scale motions results in anomalous
+viscous damping of large-scale waves. Finally, we test these analytic
+predictions using numerical simulations of standing waves on tangled, linear
+force-free magnetic-field equilibria.",2006.15141v1
+2020-07-03,Inconsistencies Between Local and Global Measures of CME Radial Expansion as Revealed by Spacecraft Conjunctions,"The radial expansion of coronal mass ejections (CMEs) is known to occur from
+remote observations; from the variation of their properties with radial
+distance; and from local in situ plasma measurements showing a decreasing speed
+profile throughout the magnetic ejecta (ME). However, little is known on how
+local measurements compare to global measurements of expansion. Here, we
+present results from the analysis of 42 CMEs measured in the inner heliosphere
+by two spacecraft in radial conjunction. The magnetic field decrease with
+distance provides a measure of their global expansion. Near 1 au, the decrease
+in their bulk speed provides a measure of their local expansion. We find that
+these two measures have little relation with each other. We also investigate
+the relation between characteristics of CME expansion and CME properties. We
+find that the expansion depends on the initial magnetic field strength inside
+the ME, but not significantly on the magnetic field inside the ME measured near
+1 au. This is an indirect evidence that CME expansion in the innermost
+heliosphere is driven by the high magnetic pressure inside the ME, while by the
+time the MEs reach 1 au, they are expanding due to the decrease in the solar
+wind dynamic pressure with distance. We also determine the evolution of the ME
+tangential and normal magnetic field components with distance, revealing
+significant deviations as compared to the expectations from force-free field
+configurations as well as some evidence that the front half of MEs expand at a
+faster rate than the back half.",2007.01699v1
+2020-07-09,Intertwined Magnetic Sub-Lattices in the Double Perovskite Compound LaSrNiReO6,"We report a muon spin rotation ($\mu^{+}$SR) study of the magnetic properties
+of the double perovskite compound LaSrNiReO$_{6}$. Using the unique length and
+time scales of the $\mu^{+}$SR technique, we successfully clarify the magnetic
+ground state of LaSrNiReO$_{6}$, which was previously deemed as a spin glass
+state. Instead, our $\mu^{+}$SR results point towards a long-range dynamically
+ordered ground state below $T_{\rm C}= 23$ K, for which a static limit is
+foreseen at $T=0$. Furthermore, between 23 K$<T\leq$300 K, three different
+magnetic phases are identified: a dense ($23$ K$<T\leq75$ K), a dilute ($75$
+K$<T\leq250$ K), and a paramagnetic ($T>250$ K) state. Our results reveal how
+two separate, yet intertwined magnetic lattices interact within the unique
+double perovskite structure and the importance of using complementary
+experimental techniques to obtain a complete understanding of the microscopic
+magnetic properties of complex materials.",2007.04616v3
+2020-08-14,Analysis of quiet-sun turbulence on the basis of SDO/HMI and Goode Solar Telescope data,"We analysed line-of-sight magnetic fields and magnetic power spectra of an
+undisturbed photosphere using magnetograms acquired by the Helioseismic and
+Magnetic Imager (HMI) on-board the Solar Dynamic Observatory (SDO) and the Near
+InfraRed Imaging Spectrapolarimeter (NIRIS) operating at the Goode Solar
+Telescope (GST) of the Big Bear Solar Observatory. In the NIRIS data revealed
+the presence of thin flux tubes of 200-400~km in diameter and of field strength
+of 1000-2000~G. The HMI power spectra determined for a coronal hole, a quiet
+sun and a plage areas exhibit the same spectral index of -1 on a broad range of
+spatial scales from 10-20~Mm down to 2.4~Mm. This implies that the same
+mechanism(s) of magnetic field generation operate everywhere in the undisturbed
+photosphere. The most plausible one is the local turbulent dynamo. When
+compared to the HMI spectra, the -1.2 slope of the NIRIS spectrum appears to be
+more extended into the short spatial range until the cutoff at 0.8-0.9~Mm,
+after which it continues with a steeper slope of -2.2. Comparison of the
+observed and Kolmogorov-type spectra allowed us to infer that the Kolmogorov
+turbulent cascade cannot account for more than 35\% of the total magnetic
+energy observed in the scale range of 3.5-0.3~Mm. The energy excess can be
+attributed to other mechanisms of field generation such as the local turbulent
+dynamo and magnetic super-diffusivity observed in an undisturbed photosphere
+that can slow down the rate of the Kolmogorov cascade leading to a shallower
+resulting spectrum.",2008.06264v1
+2020-08-16,Magnetic Excitations of the Hybrid Multiferroic (ND4)2FeCl5D2O,"We report a comprehensive inelastic neutron scattering study of the hybrid
+molecule-based multiferroic compound (ND4)2FeCl5D2O in the zero-field
+incommensurate cycloidal phase and the high-field quasi-collinear phase. The
+spontaneous electric polarization changes its direction concurrently with the
+field-induced magnetic transition, from mostly aligned with the
+crystallographic a-axis to the c-axis. To account for such change of
+polarization direction, the underlying multiferroic mechanism was proposed to
+switch from the spin-current model induced via the inverse
+Dzyalloshinskii-Moriya interaction to the p-d hybridization model. We perform a
+detailed analysis of the inelastic neutron data of (ND4)2FeCl5D2O using linear
+spin-wave theory to quantify magnetic interaction strengths and investigate
+possible impact of different multiferroic mechanisms on the magnetic couplings.
+Our result reveals that the spin dynamics of both multiferroic phases can be
+well-described by a Heisenberg Hamiltonian with an easy-plane anisotropy. We do
+not find notable differences between the optimal model parameters of the two
+phases. The hierarchy of exchange couplings and the balance among frustrated
+interactions remain the same between two phases, suggesting that magnetic
+interactions in (ND4)2FeCl5D2O are much more robust than the electric
+polarization in response to delicate reorganizations of the electronic degrees
+of freedom in an applied magnetic field.",2008.06827v2
+2020-08-26,Nature of the magnetic stripes in fully oxygenated La$_{2}$CuO$_{4+y}$,"We present triple-axis neutron scattering studies of static and dynamic
+magnetic stripes in an optimally oxygen-doped cuprate superconductor,
+La$_{2}$CuO$_{4+y}$, which exhibits a clean superconducting transition at
+$T_{\rm c}=42$ K. Polarization analysis reveals that the magnetic stripe
+structure is equally represented along both of the tetragonal crystal axes and
+that the fluctuating stripes display significant weight for in-plane as well as
+out-of-plane spin components. Both static magnetic order as well as low-energy
+fluctuations are fully developed in zero applied magnetic field and the
+low-energy spin fluctuations at $\hbar \omega = 0.3-10$ meV intensify upon
+cooling. We interpret this as an indication that superconductivity and
+low-energy spin fluctuations co-exist microscopically in spatial regions which
+are separated from domains with static magnetic order.",2008.11527v1
+2020-09-06,Adiabatic and Nonadiabatic Spin-transfer Torques in Antiferromagnets,"Electron transport in magnetic orders and the magnetic orders dynamics have a
+mutual dependence, which provides the key mechanisms in spin-dependent
+phenomena. Recently, antiferromagnetic orders are focused on as the magnetic
+order, where current-induced spin-transfer torques, a typical effect of
+electron transport on the magnetic order, have been debatable mainly because of
+the lack of an analytic derivation based on quantum field theory. Here, we
+construct the microscopic theory of spin-transfer torques on the slowly-varying
+staggered magnetization in antiferromagnets with weak canting. In our theory,
+the electron is captured by bonding/antibonding states, each of which is the
+eigenstate of the system, doubly degenerates, and spatially spreads to
+sublattices because of electron hopping. The spin of the eigenstates depends on
+the momentum in general, and a nontrivial spin-momentum locking arises for the
+case with no site inversion symmetry, without considering any spin-orbit
+couplings. The spin current of the eigenstates includes an anomalous component
+proportional to a kind of gauge field defined by derivatives in momentum space
+and induces the adiabatic spin-transfer torques on the magnetization.
+Unexpectedly, we find that one of the nonadiabatic torques has the same form as
+the adiabatic spin-transfer torque, while the obtained forms for the adiabatic
+and nonadiabatic spin-transfer torques agree with the phenomenological
+derivation based on the symmetry consideration. This finding suggests that the
+conventional explanation for the spin-transfer torques in antiferromagnets
+should be changed. Our microscopic theory provides a fundamental understanding
+of spin-related physics in antiferromagnets.",2009.02686v1
+2020-09-21,Influence of ambipolar and Hall effects on vorticity in 3D simulations of magneto-convection,"This paper presents the results of the analysis of 3D simulations of solar
+magneto-convection that include the joint action of the ambipolar diffusion and
+the Hall effect. Three simulation-runs are compared: one including both
+ambipolar diffusion and Hall effect; one including only ambipolar diffusion;
+and one without any of these two effects. The magnetic field is amplified from
+initial field to saturation level by the action of turbulent local dynamo. In
+each of these cases, we study 2 hours of simulated solar time after the local
+dynamo reaches the saturation regime. We analyze the power spectra of
+vorticity, of magnetic field fluctuations and of the different components of
+the magnetic Poynting flux responsible for the transport of vertical or
+horizontal perturbations. Our preliminary results show that the ambipolar
+diffusion produces a strong reduction of vorticity in the upper chromospheric
+layers and that it dissipates the vortical perturbations converting them into
+thermal energy. The Hall effect acts in the opposite way, strongly enhancing
+the vorticity. When the Hall effect is included, the magnetic field in the
+simulations becomes, on average, more vertical and long-lived flux tube-like
+structures are produced. We trace a single magnetic structure to study its
+evolution pattern and the magnetic field intensification, and their possible
+relation to the Hall effect.",2009.09753v1
+2020-09-28,Nanoscale transient magnetization gratings excited and probed by femtosecond extreme ultraviolet pulses,"We utilize coherent femtosecond extreme ultraviolet (EUV) pulses derived from
+a free electron laser (FEL) to generate transient periodic magnetization
+patterns with periods as short as 44 nm. Combining spatially periodic
+excitation with resonant probing at the dichroic M-edge of cobalt allows us to
+create and probe transient gratings of electronic and magnetic excitations in a
+CoGd alloy. In a demagnetized sample, we observe an electronic excitation with
+50 fs rise time close to the FEL pulse duration and ~0.5 ps decay time within
+the range for the electron-phonon relaxation in metals. When the experiment is
+performed on a sample magnetized to saturation in an external field, we observe
+a magnetization grating, which appears on a sub-picosecond time scale as the
+sample is demagnetized at the maxima of the EUV intensity and then decays on
+the time scale of tens of picoseconds via thermal diffusion. The described
+approach opens prospects for studying dynamics of ultrafast magnetic phenomena
+on nanometer length scales.",2009.13330v1
+2020-09-29,"Ferrofluidic aqueous two-phase system with ultralow interfacial tension, instabilities and pattern formation","Ferrofluids are strongly magnetic fluids consisting of magnetic nanoparticles
+dispersed in a carrier fluid. Besides their technological applications, they
+have a tendency to form beautiful and intriguing patterns when subjected to
+external static and dynamic magnetic fields. Most of the patterns occur in
+systems consisting of two fluids: one ferrofluidic and one non-magnetic (oil,
+air, etc.), wherein the fluid-fluid interface deforms as a response to magnetic
+fields. Usually, the fluids are completely immiscible and so the interfacial
+energy in this systems is very large. Here we show that it is possible to
+design a fully aqueous ferrofluid system by using phase separation of
+incompatible polymers. This continuous aqueous system allows an ultralow
+interfacial tension (down to 1 $\mu$N/m) and nearly vanishing pinning at three
+phase contact lines. We demonstrate the normal-field instability with the
+system and focus on the miniaturization of the pattern length from the typical
+$\sim$10 mm size down to $\sim$200 $\mu$m. The normal-field instability is
+characterized in glass capillaries of thickness comparable to the pattern
+length. This system paves way towards interesting physics such as the
+interaction between magnetic instabilities and thermal capillary waves and
+offers a way to evaluate extremely small interfacial tensions.",2009.13945v1
+2020-10-01,On the rate of crustal failures in young magnetars,"The activity of magnetars is powered by their intense and dynamic magnetic
+fields and has been proposed as the trigger to extragalactic Fast Radio Bursts.
+Here we estimate the frequency of crustal failures in young magnetars, by
+computing the magnetic stresses in detailed magneto-thermal simulations
+including Hall drift and Ohmic dissipation. The initial internal topology at
+birth is poorly known but is likely to be much more complex than a dipole.
+Thus, we explore a wide range of initial configurations, finding that the
+expected rate of crustal failures varies by orders of magnitude depending on
+the initial magnetic configuration. Our results show that this rate scales with
+the crustal magnetic energy, rather than with the often used surface value of
+the dipolar component related to the spin-down torque. The estimated frequency
+of crustal failures for a given dipolar component can vary by orders of
+magnitude for different initial conditions, depending on how much magnetic
+energy is distributed in the crustal non-dipolar components, likely dominant in
+newborn magnetars. The quantitative reliability of the expected event rate
+could be improved by a better treatment of the magnetic evolution in the core
+and the elastic/plastic crustal response, here not included. Regardless of
+that, our results are useful inputs in modelling the outburst rate of young
+Galactic magnetars, and their relation with the Fast Radio Bursts in our and
+other galaxies.",2010.00617v1
+2020-10-07,Orbital isotropy of magnetic fluctuations in correlated electron materials induced by Hund's exchange coupling,"Characterizing non-local magnetic fluctuations in materials with strong
+electronic Coulomb interactions remains one of the major outstanding challenges
+of modern condensed matter theory. In this work we address the spatial symmetry
+and orbital structure of magnetic fluctuations in perovskite materials. To this
+aim, we develop a consistent multi-orbital diagrammatic extension of dynamical
+mean field theory, which we apply to an anisotropic three-orbital model of
+cubic $t_{2g}$ symmetry. We find that the form of spatial spin fluctuations is
+governed by the local Hund's coupling. For small values of the coupling,
+magnetic fluctuations are anisotropic in orbital space, which reflects the
+symmetry of the considered $t_{2g}$ model. Large Hund's coupling enhances
+collective spin excitations, which mixes orbital and spatial degrees of
+freedom, and magnetic fluctuations become orbitally isotropic. Remarkably, this
+effect can be seen only in two-particle quantities; single-particle observables
+remain anisotropic for any value of the Hund's coupling. Importantly, we find
+that the orbital isotropy can be induced both, at half-filling and for the case
+of $4$ electrons per lattice site, where the magnetic instability is associated
+with different, antiferromagnetic and ferromagnetic modes, respectively.",2010.03433v4
+2020-10-14,Exact hybrid-kinetic equilibria for magnetized plasmas with shearing flows,"Context. Magnetized plasmas characterized by shearing flows are present in
+many natural contexts, such as the Earth's magnetopause and the solar wind. The
+collisionless nature of involved plasmas requires a kinetic description. When
+the width of the shear layer is of the order of ion scales, the Hybrid
+Vlasov-Maxwell approach can be adopted. Aims. The aim of the paper is to derive
+explicit forms for stationary configurations of magnetized plasmas with planar
+shearing flows,within the Hybrid Vlasov-Maxwell description. Two configurations
+are considered: the first with a uniform magnetic field obliquely directed with
+respect to the bulk velocity; and the second with a uniform-magnitude
+variable-direction magnetic field. Methods. Stationary ion distribution
+functions are obtained by combining single-particle constant of motions, which
+are derived studying particle dynamics. Preliminary information about the form
+of the distribution functions are analytically derived considering a local
+approximation for the background electromagnetic field. Then, a numerical
+method is set up to obtain a solution for general profiles. Results. The
+explicit distribution functions that are found allow to obtain profiles of
+density, bulk velocity, temperature and heat flux. Anisotropy and agyrotropy in
+the distribution function are also evaluated. Stationarity of the solution
+during numerical simulations is checked in the uniform oblique magnetic field
+case. Conclusions. The considered configurations can be used as models for the
+Earth's magnetopause in simulations of the Kelvin-Helmholtz instability.",2010.06929v1
+2020-10-20,On the deceleration of Fanaroff-Riley Class I jets: mass loading of magnetized jets by stellar winds,"In this paper we present steady-state RMHD simulations that include a
+mass-load term to study the process of jet deceleration. The mass-load mimics
+the injection of a proton-electron plasma from stellar winds within the host
+galaxy into initially pair plasma jets, with mean stellar mass-losses ranging
+from $10^{-14}$ to $10^{-9}\,{M_\odot\,yr^{-1}}$. The spatial jet evolution
+covers $\sim 500\,{\rm pc}$ from jet injection in the grid at 10~pc from the
+jet nozzle. Our simulations use a relativistic gas equation of state and a
+pressure profile for the ambient medium. We compare these simulations with
+previous dynamical simulations of relativistic, non-magnetised jets. Our
+results show that toroidal magnetic fields can prevent fast jet expansion and
+the subsequent embedding of further stars via magnetic tension. In this sense,
+magnetic fields avoid a runaway deceleration process. Furthermore, when the
+mass-load is large enough to increase the jet density and produce fast,
+differential jet expansion, the conversion of magnetic energy flux into kinetic
+energy flux (i.e., magnetic acceleration), helps to delay the deceleration
+process with respect to non-magnetised jets. We conclude that the typical
+stellar population in elliptical galaxies cannot explain jet deceleration in
+classical FRI radio galaxies. However, we observe a significant change in the
+jet composition, thermodynamical parameters and energy dissipation along its
+evolution, even for moderate values of the mass-load.",2010.10234v1
+2020-11-02,Subcritical dynamos in rapidly-rotating planar convection,"We study dynamo action using numerical simulations of planar Boussinesq
+convection at rapid rotation (low Ekman numbers, Ek), focusing on subcritical
+dynamo action in which the dynamo is sustained for Rayleigh numbers, Ra, below
+the critical Rayleigh number for the onset of nonmagnetic convection, Ra$_c$.
+These solutions are found by first investigating the supercritical regime, in
+which the dynamo is able to generate a large-scale magnetic field that
+significantly influences the convective motions, with an associated Elsasser
+number of order Ek$^{1/3}$. Subcritical solutions are then found by tracking
+this solution branch into the subcritical regime, taking a supercritical
+solution and then gradually lowering the corresponding Rayleigh number. We show
+that decreasing the Ekman number leads to an extension of the subcritical range
+of Ra/Ra$_c$, down to an optimal value of Ek$=10^{-5}$. For magnetic Prandtl
+numbers of order unity, subcriticality is then hampered by the emergence of a
+large-scale mode at lower Ekman numbers when the dynamo driven by the smaller
+scale convection generates relatively stronger large-scale magnetic field. The
+inability of the large-scale mode to sustain dynamo action leads to an
+intermittent behaviour that appears to inhibit subcriticality. The subcritical
+solutions are also sensitive to the value of the magnetic Reynolds number (or
+equivalently, the magnetic Prandtl number, Pm), as values of the magnetic
+Reynolds number greater than 70 are required to produce dynamo action, but
+large values lead to fluctuations that are able to push the system too far from
+the subcritical branch and towards the trivial conducting state.",2011.00852v2
+2020-11-24,The rotation rate of solar active and ephemeral regions -- I. Dependence on morphology and peak magnetic flux,"Using magnetic field maps acquired by the Helioseismic and Magnetic Imager on
+board the Solar Dynamics Observatory we measured rotation rates of 864 active
+and 322 ephemeral regions observed between 2010 and 2016. We found smaller
+magnetic tracers to show a tendency to rotate faster as compared to larger
+ones. Thus, ephemeral regions exhibit on average the fastest rotation rate. We
+further divided active regions into three classes. Class A comprised magnetic
+bipoles obeying Hale's polarity law, Joy's law, and exhibiting more coherent
+leading polarity in comparison with the following one. The second class B
+included active regions violating at least one of the aforementioned empirical
+laws. The third class U comprised unipolar active regions. We found no
+significant difference between the rotation rates of active regions of classes
+A and B. In contrast, unipolar active regions exhibited on average lower
+rotation rate and narrower distribution of the rotation rate differences.
+Assuming the rotation rate to indicate the anchoring depth of the magnetic
+structure within the convection zone, we supposed that active regions of
+classes A and B might be anchored throughout the entire convective envelope
+while unipolar active regions a rooted within a thin layer located either near
+the base of the convection zone or at a shallow near-surface depth.",2011.12060v1
+2021-01-04,Influence of the martensitic transformation kinetics on the magnetocaloric effect in Ni-Mn-In,"The inverse magnetocaloric effect (MCE) in Ni-Mn-based Heusler compounds
+occurs during the magnetostructural transition between low-temperature,
+low-magnetization martensite and high-temperature, high-magnetization
+austenite. In this study, we analyze the metamagnetic transformation of a
+$Ni_{49.8}Mn_{35}In_{15.2}$ compound by simultaneous adiabatic temperature
+change and strain measurements in pulsed magnetic fields up to 10 T. We observe
+an adiabatic temperature change of -10 K and a strain of -0.22 % when the
+reverse martensitic transition is fully induced at a starting temperature of
+285 K. By a variation of the magnetic field-sweep rates between 316 Ts$^{-1}$,
+865 Ts$^{-1}$ and 1850 Ts$^{-1}$, the transitional dynamics of the reverse
+martensitic transformation have been investigated. Our experiments reveal an
+apparent delay upon the end of the reverse martensitic transformation at field
+rates exceeding 865 Ts$^{-1}$ which is related to the annihilation of retained
+martensite. As a consequence, the field hysteresis increases and higher fields
+are required to saturate the transition. In contrast, no time-dependent effects
+on the onset of the reverse martensitic transformation were observed in the
+studied field-sweep range. Our results demonstrate that kinetic effects in
+Heusler compounds strongly affect the magnetic cooling cycle, especially when
+utilising a multicaloric ""exploiting-hysteresis cycle"" where high magnetic
+field-sweep rates are employed.",2101.00840v1
+2021-01-14,Laser-induced THz magnetism of antiferromagnetic CoF$_2$,"Excitation, detection and control of coherent THz magnetic excitation in
+antiferromagnets are challenging problems that can be addressed using ever
+shorter laser pulses. We study experimentally excitation of magnetic dynamics
+at THz frequencies in an antiferromagnetic insulator CoF$_2$ by sub-10 fs laser
+pulses. Time-resolved pump-probe polarimetric measurements at different
+temperatures and probe polarizations reveal laser-induced transient circular
+birefringence oscillating at the frequency of 7.45 THz and present below the
+N\'eel temperature. The THz oscillations of circular birefringence are ascribed
+to oscillations of the magnetic moments of Co$^{2+}$ ions induced by the
+laser-driven coherent E$_g$ phonon mode via the THz analogue of the transverse
+piezomagnetic effect. It is also shown that the same pulse launches coherent
+oscillations of the magnetic linear birefringence at the frequency of 3.4 THz
+corresponding to the two-magnon mode. Analysis of the probe polarization
+dependence of the transient magnetic linear birefringence at the frequency of
+the two-magnon mode enables identifying its symmetry.",2101.05622v5
+2021-02-02,Distinct magnetic ground states of $R_2$ZnIrO$_6$ ($R$ = La and Nd) determined by neutron powder diffraction,"Double perovskite iridates $A_2$ZnIrO$_6$ ($A$ = alkaline or lanthanide) show
+complex magnetic behaviors ranging from weak ferromagnetism to successive
+antiferromagnetic transitions. Here we report the static ($dc$) and dynamic
+($ac$) magnetic susceptibility, and neutron powder diffraction measurements for
+$A$ = La and Nd compounds to elucidate the magnetic ground state. Below 10~K,
+the $A$ = La compound is best described as canted iridium moments in an
+antiferromagnet arrangement with a propagation vector \textbf{k} = 0 and a net
+ferromagnetic component along the $c$-axis. On the other hand, Nd$_2$ZnIrO$_6$
+is described well as an antiferromagnet with a propagation vector \textbf{k} =
+(1/2~1/2~0) below $T_\mathrm{N} \sim$ 17 K. Scattering from both the Nd and Ir
+magnetic sublattices were required to describe the data and both were found to
+lie almost completely within the $ab$-plane. $Dc$ susceptibility revealed a
+bifurcation between the zero-field-cooled and field-cooled curves below
+$\sim$13 K in Nd$_2$ZnIrO$_6$. A glassy state was ruled out by $ac$
+susceptibility but detailed magnetic isotherms revealed the opening of the loop
+below 13~K. These results suggest a delicate balance exists between the
+Dzyaloshinskii-Moriya, crystal field schemes, and $d$-$f$ interaction in this
+series of compounds.",2102.01276v1
+2021-02-04,Evaluating the reliability of a simple method to map the magnetic field azimuth in the solar chromosphere,"The Zeeman effect is of limited utility for probing the magnetism of the
+quiet solar chromosphere. The Hanle effect in some spectral lines is sensitive
+to such magnetism, but the interpretation of the scattering polarization
+signals requires taking into account that the chromospheric plasma is highly
+inhomogeneous and dynamic (i.e., that the magnetic field is not the only cause
+of symmetry breaking). Here we investigate the reliability of a well-known
+formula for mapping the azimuth of chromospheric magnetic fields directly from
+the scattering polarization observed in the \ion{Ca}{2}~8542~\AA\, line, which
+is typically in the saturation regime of the Hanle effect. To this end, we use
+the Stokes profiles of the \ion{Ca}{2}~8542~\AA\, line computed with the PORTA
+radiative transfer code in a three-dimensional (3D) model of the solar
+chromosphere, degrading them to mimic spectropolarimetric observations for a
+range of telescope apertures and noise levels. The simulated observations are
+used to obtain the magnetic field azimuth at each point of the field of view,
+which we compare with the actual values within the 3D model. We show that,
+apart from intrinsic ambiguities, the method provides solid results. Their
+accuracy depends more on the noise level than on the telescope diameter.
+Large-aperture solar telescopes, like DKIST and EST, are needed to achieve the
+required noise-to-signal ratios using reasonable exposure times.",2102.02880v1
+2021-02-09,Chiral Magnetic Effect and Three-point Function from AdS/CFT Correspondence,"The chiral magnetic effect with a fluctuating chiral imbalance is more
+realistic in the evolution of quark-gluon plasma, which reflects the random
+gluonic topological transition. Incorporating this dynamics, we calculate the
+chiral magnetic current in response to space-time dependent axial gauge
+potential and magnetic field in AdS/CFT correspondence. In contrast to
+conventional treatment of constant axial chemical potential, the response
+function here is the AVV three-point function of the $\mathcal{N}=4$ super
+Yang-Mills at strong coupling. Through an iterative solution of the nonlinear
+equations of motion in Schwarzschild-AdS$_5$ background, we are able to express
+the AVV function in terms of two Heun functions and prove its UV/IR finiteness,
+as expected for $\mathcal{N}=4$ super Yang-Mills theory. We found that the
+dependence of the chiral magnetic current on a non-constant chiral imbalance is
+non-local, different from hydrodynamic approximation, and demonstrates the
+subtlety of the infrared limit discovered in field theoretic approach. We
+expect our results enrich the understanding of the phenomenology of the chiral
+magnetic effect in the context of relativistic heavy ion collisions.",2102.04851v2
+2021-02-28,Topological excitations in quasi two-dimensional quantum magnets with weak interlayer interactions,"The study of topological magnetic excitations has attracted widespread
+attention in the past few years. In this thesis, I have studied some examples
+of novel topological magnonic phases/phenomena in low-dimensional quantum
+magnets. The first chapter motivates the research based on the research gap in
+this field of study. The second chapter is written to make the thesis
+self-sufficient and the concepts are explained through examples. In the second
+chapter, the following formalisms and physical observables are described:
+Holstein-Primakoff, bond operator, Schwinger boson, Bogoliubov-Valatin, Group
+theory, Berry-phase, Berry-curvature, Chern number, thermal Hall conductance,
+Nernst conductivity, dynamical spin structure factor, edge-current. The main
+results of the thesis are shown in the third, fourth, and fifth chapters. In
+the third chapter, I have shown that anti-chiral edge states (co-propagating
+edge states) arise in the ferromagnetic Heisenberg model on the honeycomb
+lattice with Dzyaloshinskii-Moriya (DM) interactions. My results suggest that
+such anti-chiral edge states may be induced in certain realistic models of
+quantum magnets. In the fourth chapter, I have found the emergence of many
+magnon band-topological phases in the flux state of the Shastry-Sutherland
+model. I have derived a simple analytical form of the temperature dependence of
+derivative of thermal Hall conductivity near the band topological transition
+point which I propose to be experimentally useful. In the fifth chapter, I have
+investigated the emergence of Weyl triplons due to inter-layer DM-interaction
+in a microscopic model of SrCu2(BO3)2, a widely studied frustrated quantum
+magnet. I have shown that the thermal magnon Hall conductivity has a
+quasi-linear dependence as a function of the magnetic field in a Weyl-triplon
+region.",2103.00401v1
+2021-03-13,What Causes Faint Solar Coronal Jets from Emerging Flux Regions in Coronal Holes?,"Using EUV images and line-of-sight magnetograms from Solar Dynamics
+Observatory, we examine eight emerging bipolar magnetic regions (BMRs) in
+central-disk coronal holes for whether the emerging magnetic arch made any
+noticeable coronal jets directly, via reconnection with ambient open field as
+modeled by Yokoyama and Shibata (1995). During emergence, each BMR produced no
+obvious EUV coronal jet of normal brightness, but each produced one or more
+faint EUV coronal jets that are discernible in AIA 193 {\AA} images. The spires
+of these jets are much fainter and usually narrower than for typical EUV jets
+that have been observed to be produced by minifilament eruptions in quiet
+regions and coronal holes. For each of 26 faint jets from the eight emerging
+BMRs, we examine whether the faint spire was evidently made a la Yokoyama and
+Shibata (1995). We find: (1) 16 of these faint spires evidently originate from
+sites of converging opposite-polarity magnetic flux and show base brightenings
+like those in minifilament-eruption-driven coronal jets, (2) the 10 other faint
+spires maybe were made by a burst of the external-magnetic-arcade-building
+reconnection of the emerging magnetic arch with the ambient open field,
+reconnection directly driven by the arch's emergence, but (3) none were
+unambiguously made by such emergence-driven reconnection. Thus, for these eight
+emerging BMRs the observations indicate that emergence-driven external
+reconnection of the emerging magnetic arch with ambient open field at most
+produces a jet spire that is much fainter than in previously-reported, much
+more obvious coronal jets driven by minifilament eruptions.",2103.07813v1
+2021-05-04,Energy-gap driven low-temperature magnetic and transport properties in Cr$_{1/3}M$S$_2$ ($M$ = Nb or Ta),"The helimagnets Cr$_{1/3}M$S$_2$ ($M$ = Nb or Ta) have attracted renewed
+attention due to the discovery of a chiral soliton lattice (CSL) stabilized in
+an applied magnetic field, but reports of unusual low-temperature transport and
+magnetic properties in this system lack a unifying explanation. Here we present
+electronic structure calculations that demonstrate the materials are
+half-metals. There is also a gap-like feature (width in range 40-100 meV) in
+the density of states of one spin channel. This electronic structure explains
+the low-temperature electronic and magnetic properties of Cr$_{1/3}M$S$_2$ ($M$
+= Nb or Ta), with the gap-like feature particularly important for explaining
+the magnetic behavior. Our magnetometry measurements confirm the existence of
+this gap. Dynamic spin fluctuations driven by excitations across this gap are
+seen over a wide range of frequencies (0.1 Hz to MHz) with AC susceptibility
+and muon-spin relaxation ($\mu^+$SR) measurements. We show further how effects
+due to the CSL in Cr$_{1/3}$NbS$_2$, as detected with $\mu^+$SR, dominate over
+the gap-driven magnetism when the CSL is stabilized as the majority phase.",2105.01393v3
+2021-05-14,Magnetic field and thermal radiation induced entropy generation in a multiphase non-isothermal plane Poiseuille flow,"The effect of radiative heat transfer on the entropy generation in a
+two-phase non-isothermal fluid flow between two infinite horizontal parallel
+plates under the influence of a constant pressure gradient and transverse
+non-invasive magnetic field have been explored. Both the fluids are considered
+to be viscous, incompressible, immiscible, Newtonian, and electrically
+conducting. The governing equations in Cartesian coordinate are solved
+analytically with the help of appropriate boundary conditions to obtain the
+velocity and temperature profile inside the channel. Application of transverse
+magnetic field is found to reduce the throughput and the temperature
+distribution of the fluids in a pressure-driven flow. The temperature and fluid
+flow inside the channel can also be non-invasively altered by tuning the
+magnetic field intensity, the temperature difference between the channel walls
+and the fluids, and several intrinsic fluid properties. The entropy generation
+due to the heat transfer, magnetic field, and fluid flow irreversibilities can
+be controlled by altering the Hartmann number, radiation parameter, Brinkmann
+number, filling ratio, and the ratios of fluid viscosities, thermal and
+electrical conductivities. The surfaces of the channel wall are found to act as
+a strong source of entropy generation and heat transfer irreversibility. The
+rate of heat transfer at the channel walls can also be tweaked by the magnetic
+field intensity, temperature differences, and fluid properties. The proposed
+strategies in the present study can be of significance in the design and
+development of gen-next microscale reactors, micro heat exchangers, and energy
+harvesting devices.",2105.06682v2
+2021-05-20,Spin dynamics of the quantum dipolar magnet Yb$_3$Ga$_5$O$_{12}$ in an external field,"We investigate ytterbium gallium garnet Yb$_{3}$Ga$_{5}$O$_{12}$ in the
+paramagnetic phase above the supposed magnetic transition at $T_{\lambda}
+\approx 54$ mK. Our study combines susceptibility and specific heat
+measurements with neutron scattering experiments and theoretical calculations.
+Below 500 mK, the elastic neutron response is strongly peaked in the momentum
+space. Along with that the inelastic spectrum develops flat excitation modes.
+In magnetic field, the lowest energy branch follows a Zeeman shift in
+accordance with the field-dependent specific heat data. An intermediate state
+with spin canting away from the field direction is evidenced in small magnetic
+fields. In the field of 2 T, the total magnetization almost saturates and the
+measured excitation spectrum is well reproduced by the spin-wave calculations
+taking into account solely the dipole-dipole interactions. The small positive
+Curie-Weiss temperature derived from the susceptibility measurements is also
+accounted for by the dipole spin model. Altogether, our results suggest that
+Yb$_{3}$Ga$_{5}$O$_{12}$ is a quantum dipolar magnet.",2105.09817v1
+2021-06-05,Optimization of Magnetic Flux Ropes Modeled with the RBSL method,"The so-called regularized Biot-Savart laws (RBSLs) provide an efficient and
+flexible method for modeling pre-eruptive magnetic configurations of coronal
+mass ejections (CMEs) whose characteristics are constrained by observational
+images and magnetic-field data. This method allows one to calculate the field
+of magnetic flux ropes (MFRs) with small circular cross-sections and an
+arbitrary axis shape. The field of the whole configuration is constructed as a
+superposition of (1) such a flux-rope field and (2) an ambient potential field
+derived, for example, from an observed magnetogram. The RBSL kernels are
+determined from the requirement that the MFR field for a straight cylinder must
+be exactly force-free. For a curved MFR, however, the magnetic forces are
+generally unbalanced over the whole path of the MFR. To minimize these forces,
+we apply a modified Gauss-Newton method to find optimal MFR parameters. This is
+done by iteratively adjusting the MFR axis path and axial current. We then try
+to relax the resulting optimized configuration in a subsequent line-tied
+zero-beta magnetohydrodynamic simulation toward a force-free equilibrium. By
+considering two models of the sigmoidal pre-eruption configuration for the 2009
+February 13 CME, we demonstrate how this approach works and what it is capable
+of. We show, in particular, that the building blocks of the core magnetic
+structure described by these models match to morphological features typically
+observed in such type of configurations. Our method will be useful for both the
+modeling of particular eruptive events and theoretical studies of idealized
+pre-eruptive MFR configurations.",2106.02789v1
+2021-06-28,Laminar flow characterization using low-field magnetic resonance techniques,"Laminar flow velocity profiles depend heavily on fluid rheology. Developing
+methods of laminar flow characterization, based on low-field magnetic resonance
+(MR), contributes to the widespread industrial application of the MR technique
+in rheology. In this paper, we designed a low-cost, palm-sized permanent magnet
+with a 1H resonance frequency of 20.48 MHz to measure laminar flow. The magnet
+consists of two disk magnets, which were each tilted at an angle of 1{\deg}
+from a starting separation of 1.4 cm to generate a constant gradient, 65
+gauss/cm, in the direction of flow. Subsequently, a series of process methods,
+for MR measurements, were proposed to characterize Newtonian and non-Newtonian
+fluid flows in a pipe, including phase-based method, magnitude-based method,
+and velocity spectrum method. The accuracies of the proposed methods were
+validated by simulations, and experiments of Poiseuille flow and shear-thinning
+flow on the designed magnet. The new velocity profile methods proposed are
+advantageous because the MR instrumentation and measurement methods are simple
+and portable. The sophistication is found in the analysis although the physical
+principles are straight forward.",2106.14967v2
+2021-08-03,Comparative study of magnetic properties of Mn$^{3+}$ magnetic clusters in GaN using classical and quantum mechanical approach,"Currently, simulations of many-body quantum systems are known to be
+computationally too demanding to be solved on classical computers. The main
+problem is that the computation time and memory necessary for performing the
+calculations usually grow exponentially with the number of particles $N$. An
+efficient approach to simulate many-body quantum systems is the use of
+classical approximation. However, it is known that at least at low
+temperatures, the allowed spin fluctuations in this approach are overestimated
+what results in enhanced thermal fluctuations. It is therefore timely and
+important to assess the validity of the classical approximation. To this end,
+in this work, we compare the results of numerical calculations of small
+Mn$^{3+}$ magnetic clusters in GaN, where the Mn spins are treated classically
+with those where they are treated quantum-mechanically (crystal field model).
+In the first case, we solve the Landau-Lifshitz-Gilbert (LLG) equation that
+describes the precessional dynamics of spins represented by classical vectors.
+On the other hand, in the crystal field model, the state of Mn$^{3+}$ ion
+($d^4$ configuration with $S=2$, $L=2$) is characterized by the set of orbital
+and spin quantum numbers $|m_s,m_L>$. Particular attention is paid to use
+numerical parameters that ensure the same single ion magnetic anisotropy in
+both classical and quantum approximation. Finally, a detailed comparative study
+of magnetization $\mathbf{M}(\mathbf{H}, T)$ as a function of the magnetic
+field $\mathbf{H}$, temperature $T$, number of ions in a given cluster $N$ and
+the strength of super-exchange interaction $J$, obtained from both approaches
+will be presented.",2108.01474v1
+2021-09-28,Evolution of primordial magnetic fields during large-scale structure formation,"Primordial magnetic fields could explain the large-scale magnetic fields
+present in the Universe. Inflation and phase transitions in the early Universe
+could give rise to such fields with unique characteristics. We investigate the
+magneto-hydrodynamic evolution of these magnetogenesis scenarios with
+cosmological simulations. We evolve inflation-generated magnetic fields either
+as (i) uniform (homogeneous) or as (ii) scale-invariant stochastic fields, and
+phase transition-generated ones either as (iii) helical or as (iv) non-helical
+fields from the radiation-dominated epoch. We find that the final distribution
+of magnetic fields in the simulated cosmic web shows a dependence on the
+initial strength and the topology of the seed field. Thus, the observed field
+configuration retains information on the initial conditions at the moment of
+the field generation. If detected, primordial magnetic field observations would
+open a new window for indirect probes of the early universe. The differences
+between the competing models are revealed on the scale of galaxy clusters,
+bridges, as well as filaments and voids. The distinctive spectral evolution of
+different seed fields produces imprints on the correlation length today. We
+discuss how the differences between rotation measures from highly ionized
+regions can potentially be probed with forthcoming surveys.",2109.13520v2
+2021-09-29,Convectively coupled equatorial trapped waves in stars and planets,"In this paper, we have studied the convectively coupled equatorially trapped
+waves in rotating stars, with and without magnetic field. The equatorial
+trapped HD and MHD Poincar\'e, Rossby, mixed Rossby-Poincar\'e, and Kelvin
+waves were identified. The effects of stratification and non-traditional
+Coriolis force terms have been investigated. When the flow is strongly
+stratified, the wave frequencies of the convectively coupled model are almost
+the same as those of shallow water model. However, when the flow is weakly
+stratified, the wave frequencies are constrained by the buoyancy frequency. The
+non-traditional Coriolis terms affect the widths and phases of the equatorial
+waves. The width increases with the increasing non-traditional Coriolis
+parameter. Phase shift occurs when the non-traditional Coriolis parameter is
+included. Magnetic effect is significant when the magnetic field is strong. We
+have applied the model in the solar atmosphere and solar tachocline to explain
+the Rieger type periodicities. For the solar atmosphere, when magnetic effect
+is taken into account, we find that the magnetic field should be smaller than
+$5G$ in the solar photosphere. Otherwise, the Rieger type periodicities can be
+only attributed to long Rossby waves. For the solar tachocline, we find that
+magnetic field of the solar tachocline should be smaller than $50kG$ to observe
+the 160 days Rieger period. In addition, we find that the effect of the
+non-traditional Coriolis terms is not obvious in the solar photosphere, but its
+effect on the tachocline is significant.",2109.14283v1
+2021-10-12,Vortex dynamics and second magnetization peak in the iron-pnictide superconductor Ca$_{0.82}$La$_{0.18}$Fe$_{0.96}$Ni$_{0.04}$As$_2$,"We report the studies of detailed magnetic relaxation and isothermal
+magnetization measurements in the vortex state of the 112-type iron-pnictide
+Ca$_{0.82}$La$_{0.18}$Fe$_{0.96}$Ni$_{0.04}$As$_2$ superconductor with $T_c$
+$\sim$ 22 K. In the isothermal $M(H)$, a well defined second magnetization peak
+(SMP) feature is observed in the entire temperature range below $T_c$ for
+measurements with $H$ $\parallel$ $c$-axis. However, for $H$ $\parallel$
+$ab$-planes, the SMP feature is suppressed at low temperatures, which might be
+due to 2D Josephson vortices forming at low temperatures and high magnetic
+fields in such an anisotropic system. A rigorous analysis considering the
+magnetic relaxation data for $H$ $\parallel$ $c$-axis suggests an elastic to
+plastic pinning crossover across $H_p$, which also seems accompanied with a
+possible phase transition in vortex lattice near $H_p$. Moreover, point
+disorder and surface defects are likely to be the dominant sources of pinning,
+which contribute to the $\delta l$-type of pinning in the sample. A high $J_c$,
+in access of 10$^5$ A/cm$^2$ observed could potentially make this material
+technologically important.",2110.05677v1
+2021-11-17,Dynamics of relativistic electrons in non-uniform magnetic fields and its applications in quantum computing and astrophysics,"We explore the two-dimensional motion of relativistic electrons when they are
+trapped in magnetic fields having spatial power-law variation. Its impacts
+include lifting of degeneracy that emerged in the case of the constant magnetic
+field, special alignment of Landau levels of spin-up and spin-down electrons
+depending on whether the magnetic field is increasing or decreasing from the
+centre, splitting of Landau levels of electrons with zero angular momentum from
+that of positive one and the change in the equation of state of matter. Landau
+quantization (LQ) in variable magnetic fields has interdisciplinary
+applications in a variety of disciplines ranging from condensed matter to
+quantum information. As examples, we discuss the increase in quantum speed of
+the electron in presence of spatially increasing magnetic field; and the
+attainment of super Chandrasekhar mass of white dwarfs by taking into account
+LQ and Lorentz force simultaneously.",2111.09334v1
+2021-12-01,Low power continuous-wave all-optical magnetic switching in ferromagnetic nanoarrays,"All-optical magnetic switching promises ultrafast, high-resolution
+magnetisation control with the technological attraction of requiring no
+magnetic field. Existing all-optical switching schemes are driven by ultrafast
+transient effects, typically requiring power-hungry femtosecond-pulsed lasers
+and complex magnetic materials. Here, we demonstrate deterministic, all-optical
+magnetic switching in simple ferromagnetic nanomagnets (Ni$_{81}$Fe$_{19}$,
+Ni$_{50}$Fe$_{50}$) with sub-diffraction limit dimensions using a focused
+low-power, linearly-polarised continuous-wave laser. Isolated nanomagnets are
+switched across a range of dimensions, laser wavelengths and powers. All
+square-geometry artificial spin ice vertex configurations are written,
+including ground-state and energetically-unfavourable `monopole-like' states at
+powers as low as 2.74 mW. Usually, magnetic switching with linearly polarised
+light is symmetry-forbidden; however, here the laser spot has a similar size to
+the nanomagnets, producing an absorption distribution dependent on the relative
+nanoisland-spot displacement. We attribute the observed deterministic switching
+to the transient dynamics of this asymmetric absorption. No switching is
+observed in Co samples, suggesting the multi-species nature of NiFe alloys
+plays a role in reversal. The results presented here usher in cheap, low-power
+optically-controlled devices with impact across data storage, neuromorphic
+computation and reconfigurable magnonics.",2112.00697v2
+2022-01-11,Resonant Precession of Magnetization and Precession -- Induced DC voltages in FeGaB Thin Films,"Measurements of frequency dependent ferromagnetic resonance (FMR) and spin
+pumping driven dc voltage (V_{dc}) are reported for amorphous films of
+Fe_{78}Ga_{13}B_{9} (FeGaB) alloy to address the phenomenon of self-induced
+inverse spin Hall effect (ISHE) in plain films of metallic ferromagnets. The
+V_{dc} signal, which is antisymmetric on field reversal, comprises of symmetric
+and asymmetric Lorentzians centered around the resonance field. Dominant role
+of thin film size effects is seen in setting the magnitude of static
+magnetization, V_{dc} and dynamics of magnetization precession in thinner films
+(\leq 8 nm). The film thickness dependence of magnetization parameters
+indicates the presence of a magnetically disordered region at the
+film-substrate interface, which may promote preferential flow of spins
+generated by the precessing magnetization towards the substrate. However, the
+V_{dc} signal also draws contributions from rectification effects of a \approx
+0.4 \% anisotropic magnetoresistance and a large (\approx 54 n\Omega.m)
+anomalous Hall resistivity (AHR) of these films which ride over the effect of
+spin-orbit coupling driven spin-to-charge conversion near the film-substrate
+interface. We have addressed these data in the framework of the existing
+theories of electrodynamics of a ferromagnetic film subjected to
+radio-frequency field in a coplanar waveguide geometry. Our estimation of the
+self-induced ISHE for the sample with 54 n\Omega.m AHR shows that it may
+contribute significantly (\approx 90\%) to the measured symmetric voltage. This
+study is expected to be very useful for fully understanding the spin pumping
+induced dc voltages in metallic ferromagnets with disordered interfaces and
+large anomalous Hall effect.",2201.03739v1
+2022-01-17,Magnetic imprints of eruptive and non-eruptive Solar flares as observed by Solar Dynamics Observatory,"The abrupt and permanent changes of photospheric magnetic field in the
+localized regions of active regions during solar flares called magnetic
+imprints (MIs), have been observed for the past nearly three decades. The well
+known ""coronal implosion"" model is assumed to explain such flare associated
+changes but the complete physical understanding is still missing and debatable.
+In this study, we made a systematic analysis of flare-related changes of
+photospheric magnetic field during 21 flares (14 eruptive and 7 non-eruptive)
+using the high-cadence (\texttt{135s}) vector-magnetogram data obtained from
+Helioseismic and Magnetic Imager. The MI regions for eruptive flares are found
+to be strongly localised, whereas the majority of non-eruptive events
+($>70~\%$) have scattered imprint regions. To quantify the strength of the MIs,
+we derived the integrated change of horizontal field and total change of
+Lorentz force over an area. These quantities correlate well with the flare
+strength, irrespective of whether flares being eruptive or not, short or long
+duration. Further, the free-energy (FE), determined from virial-theorem
+estimates, exhibits statistically significant downward trend which starts
+around the flare time is observed in majority of flares. The change of FE
+during flares do not depend on eruptivity but have a strong positive
+correlation ($\approx 0.8$) with the Lorentz force change, indicating that the
+part of FE released would penetrate into the photosphere. While these results
+strongly favor the idea of significant feedback from corona on the photospheric
+magnetic field, the characteristics of MIs are quite indistinguishable for
+flares being eruptive or not.",2201.06550v1
+2022-01-27,Slow spin dynamics in the hyper-honeycomb Lattice [(C2H5)3NH]2Cu2(C2O4)3 revealed by 1H NMR studies,"We report the results of magnetic susceptibility $\chi$ and $^1$H nuclear
+magnetic resonance (NMR) measurements on a three-dimensional hyper-honeycomb
+lattice compound [(C$_2$H$_5$)$_3$NH]$_2$Cu$_2$(C$_2$O$_4$)$_3$ (CCCO). The
+average value of the antiferromagnetic (AFM) exchange coupling between the
+Cu$^{2+}$ ($S$ = 1/2) spins was determined to be $J$~$\sim$~50 K from the
+$\chi$ measurements. No long-range magnetic ordering has been observed down to
+$T$ = 50 mK, although NMR lines become slightly broader at low temperatures
+below 1 K. The broadening of the NMR spectrum observed below 1 K reveals that
+the Cu spin moments remain at this temperature, suggesting a non-spin-singlet
+ground state. The temperature and magnetic field dependence of 1/$T_1$ at
+temperatures above 20 K is well explained by paramagnetic thermal spin
+fluctuations where the fluctuation frequency of Cu$^{2+}$ spins is higher than
+the NMR frequency of the order of MHz. However, a clear signature of the
+slowing down of the Cu$^{2+}$ spin fluctuations was observed at low
+temperatures where 1/$T_1$ shows a thermally-activated behavior. The magnetic
+field dependence of the magnitude of the spin excitation gap suggests that the
+magnetic behaviors of CCCO are characterized as an AFM chain at low
+temperatures.",2201.11243v2
+2022-02-07,Sr$_2$IrO$_4$/Sr$_3$Ir$_2$O$_7$ superlattice for a model 2D quantum Heisenberg antiferromagnet,"Spin-orbit entangled pseudospins hold promise for a wide array of exotic
+magnetism ranging from a Heisenberg antiferromagnet to a Kitaev spin liquid
+depending on the lattice and bonding geometry, but many of the host materials
+suffer from lattice distortions and deviate from idealized models in part due
+to inherent strong pseudospin-lattice coupling. Here, we report on the
+synthesis of a magnetic superlattice comprising the single ($n$=1) and the
+double ($n$=2) layer members of the Ruddlesden-Popper series iridates
+Sr$_{n+1}$Ir$_{n}$O$_{3n+1}$ alternating along the $c$-axis, and provide a
+comprehensive study of its lattice and magnetic structures using scanning
+transmission electron microscopy, resonant elastic and inelastic x-ray
+scattering, third harmonic generation measurements and Raman spectroscopy. The
+superlattice is free of the structural distortions reported for the parent
+phases and has a higher point group symmetry, while preserving the magnetic
+orders and pseudospin dynamics inherited from the parent phases, featuring two
+magnetic transitions with two symmetry-distinct orders. We infer weaker
+pseudospin-lattice coupling from the analysis of Raman spectra and attribute it
+to frustrated magnetic-elastic couplings. Thus, the superlattice expresses a
+near ideal network of effective spin-one-half moments on a square lattice.",2202.02982v2
+2022-02-11,Disorder-induced broadening of the spin waves in a triangular-lattice quantum-spin-liquid candidate YbZnGaO$_4$,"Disorder is important in the study of quantum spin liquids, but its role on
+the spin dynamics remains elusive. Here, we explore the disorder effect by
+investigating the magnetic-field dependence of the low-energy magnetic
+excitations in a triangular-lattice frustrated magnet YbZnGaO$_4$ with
+inelastic neutron scattering. With an intermediate field of 2.5 T applied along
+the $c$-axis, the broad continuum at zero field becomes more smeared both in
+energy and momentum. With a field up to 10 T, which fully polarizes the
+magnetic moments, we observe clear spin-wave excitations with a gap of
+$\sim$1.4 meV comparable to the bandwidth. However, the spectra are
+significantly broadened. The excitation spectra both at zero and high fields
+can be reproduced by performing classical Monte Carlo simulations which take
+into account the disorder effect arising from the random site mixing of
+nonmagnetic Zn$^{2+}$ and Ga$^{3+}$ ions. These results elucidate the critical
+role of disorder in broadening the magnetic excitation spectra and mimicking
+the spin-liquid features in frustrated quantum magnets.",2202.05462v1
+2022-02-15,Assessing the Influence of Input Magnetic Maps on Global Modeling of the Solar Wind and CME-driven Shock in the 2013 April 11 Event,"In the past decade, significant efforts have been made in developing
+physics-based solar wind and coronal mass ejection (CME) models, which have
+been or are being transferred to national centers (e.g., SWPC, CCMC) to enable
+space weather predictive capability. However, the input data coverage for space
+weather forecasting is extremely limited. One major limitation is the solar
+magnetic field measurements, which are used to specify the inner boundary
+conditions of the global magnetohydrodynamic (MHD) models. In this study, using
+the Alfven wave solar model (AWSoM), we quantitatively assess the influence of
+the magnetic field map input (synoptic/diachronic vs. synchronic magnetic maps)
+on the global modeling of the solar wind and the CME-driven shock in the 2013
+April 11 solar energetic particle (SEP) event. Our study shows that due to the
+inhomogeneous background solar wind and dynamical evolution of the CME, the
+CME-driven shock parameters change significantly both spatially and temporally
+as the CME propagates through the heliosphere. The input magnetic map has a
+great impact on the shock connectivity and shock properties in the global MHD
+simulation. Therefore this study illustrates the importance of taking into
+account the model uncertainty due to the imperfect magnetic field measurements
+when using the model to provide space weather predictions.",2202.07214v1
+2022-03-17,Anticollinear order and degeneracy lifting in square lattice antiferromagnet LaSrCrO4,"We report the static and dynamic magnetic properties of LaSrCrO$_4$, a
+seemingly canonical spin-3/2 square-lattice antiferromagnet that exhibits
+frustration between magnetic layers -- owing to their AB stacking -- and offers
+a rare testbed to investigate accidental-degeneracy lifting in magnetism.
+Neutron diffraction experiments on single-crystal samples uncover a remarkable
+anticollinear magnetic order below $T_N$ = 170 K characterized by a N\'eel
+arrangement of the spins within each layer and an orthogonal arrangement
+between adjacent layers. To understand the origin of this unusual magnetic
+structure, we analyze the spin-wave excitation spectrum by means of inelastic
+neutron scattering and bulk measurements. A spectral gap of 0.5 meV, along with
+a spin-flop transition at 3.2\, T, reflect the energy scale associated with the
+degeneracy-lifting. A minimal model to explain these observations requires both
+a positive biquadratic interlayer exchange and dipolar interactions, both of
+which are on the order of 10$^{-4}$ meV, only a few parts per million of the
+dominant exchange interaction $J_1 \approx 11$ meV. These results provide
+direct evidence for the selection of a non-collinear magnetic structure by the
+combined effect of two distinct degeneracy lifting interactions.",2203.09049v1
+2022-04-14,Piezoelectric ferromagnetism in Janus monolayer YBrI: a first-principle prediction,"Coexistence of intrinsic ferromagnetism and piezoelectricity, namely
+piezoelectric ferromagnetism (PFM), is crucial to advance multifunctional
+spintronic technologies. In this work, we demonstrate that Janus monolayer YBrI
+is a PFM, which is dynamically, mechanically and thermally stable. Electronic
+correlation effects on physical properties of YBrI are investigated by using
+generalized gradient approximation plus $U$ (GGA+$U$) approach. For
+out-of-plane magnetic anisotropy, YBrI is a ferrovalley (FV) material, and the
+valley splitting is larger than 82 meV in considered $U$ range. The anomalous
+valley Hall effect (AVHE) can be achieved under an in-plane electric field.
+However, for in-plane magnetic anisotropy, YBrI is a common ferromagnetic (FM)
+semiconductor. When considering intrinsic magnetic anisotropy, the easy axis of
+YBrI is always in-plane with magnetic anisotropy energy (MAE) from 0.309 meV to
+0.237 meV ($U$=0.0 eV to 3.0 eV). However, the magnetization can be adjusted
+from the in-plane to off-plane direction by external magnetic field, and then
+lead to the occurrence of valley polarization. Moreover, missing centrosymmetry
+along with mirror symmetry breaking results in both in-plane and out-of-plane
+piezoelectricity in YBrI monolayer. At a typical $U$=2.0 eV, the $d_{11}$ is
+predicted to be -5.61 pm/V, which is higher than or compared with ones of other
+two-dimensional (2D) known materials. The electronic and piezoelectric
+properties of YBrI can be effectively tuned by applying a biaxial strain. For
+example, tensile strain can enhance valley splitting and $d_{11}$ (absolute
+value). The predicted Curie temperature of YBrI is higher than those of
+experimentally synthesized 2D ferromagnetic materials $\mathrm{CrI_3}$ and
+$\mathrm{Cr_2Ge_2Te_6}$.",2204.06713v1
+2022-05-14,Strain effects on topological and valley properties of Janus monolayer $\mathrm{VSiGeN_4}$,"Strain is an effective method to tune the electronic properties of
+two-dimension (2D) materials, and can induce novel phase transition. Recently,
+2D $\mathrm{MA_2Z_4}$ family materials are of interest because of their
+emerging topological, magnetic and superconducting properties. Here, we
+investigate the impact of strain effects ($a/a_0$:0.96$\sim$1.04) on the
+physical properties of Janus monolayer $\mathrm{VSiGeN_4}$ as a derivative of
+$\mathrm{VSi_2N_4}$ or $\mathrm{VGe_2N_4}$, which possesses dynamical,
+mechanical and thermal stabilities. For out-of-plane magnetic anisotropy, with
+increasing strain, $\mathrm{VSiGeN_4}$ undergoes transition between ferrovalley
+semiconductor (FVS), half-valley-metal (HVM), valley-polarized quantum
+anomalous Hall insulator (VQAHI), HVM and FVS. These imply twice topological
+phase transitions, which are related with sign-reversible Berry curvature and
+band inversion between $d_{xy}$+$d_{x^2-y^2}$ and $d_{z^2}$ orbitals for K or
+-K valley. The band inversion also leads to transformation of valley splitting
+strength between valence and conduction bands. However, for in-plane magnetic
+anisotropy, no special quantum anomalous Hall (QAH) states and valley
+polarization exist within the considered strain range. The actual magnetic
+anisotropy energy (MAE) shows no special QAH and HVM states in monolayer
+$\mathrm{VSiGeN_4}$. Fortunately, these can be easily achieved by external
+magnetic field, which adjusts the easy magnetization axis of
+$\mathrm{VSiGeN_4}$ from in-plane one to out-of-plane one. Our findings shed
+light on how strain can be employed to engineer the electronic states of
+$\mathrm{VSiGeN_4}$, which may open new perspectives for multifunctional
+quantum devices in valleytronics and spintronics.",2205.07012v2
+2022-05-26,The competition between the hydrodynamic instability from noise and magnetorotational instability in the Keplerian disks,"We venture for the comparison between growth rates for magnetorotational
+instability (MRI) and hydrodynamics instability in the presence of an extra
+force in the local Keplerian accretion flow. The underlying model is described
+by the Orr-Sommerfeld and Squire equations in the presence of rotation,
+magnetic field and an extra force, plausibly noise with a nonzero mean. We
+obtain MRI using Wentzel-Kramers-Brillouin (WKB) approximation without extra
+force for purely vertical magnetic field and vertical wavevector of the
+perturbations. Expectedly, MRI is active within a range of magnetic field,
+which changes depending on the perturbation wavevector magnitude. Next, to
+check the effect of noise on the growth rates, a quartic dispersion relation
+has been obtained. Among those four solutions for growth rate, the one that
+reduces to MRI growth rate at the limit of vanishing mean of noise in the MRI
+active region of the magnetic field, is mostly dominated by MRI. However, in
+MRI inactive region, in the presence of noise the solution turns out to be
+unstable, which are almost independent of the magnetic field. Another growth
+rate, which is almost complementary to the previous one, leads to stability at
+the limit of vanishing noise. The remaining two growth rates, which correspond
+to the hydrodynamical growth rates at the limit of the vanishing magnetic
+field, are completely different from the MRI growth rate. More interestingly,
+the latter growth rates are larger than that of the MRI. If we consider
+viscosity, the growth rates decrease depending on the Reynolds number.",2205.13230v1
+2022-06-12,Kagome lattice promotes chiral spin fluctuations,"Magnetic materials with tilted electron spins often exhibit conducting
+behavior that cannot be explained from semiclassical theories without invoking
+fictitious (emergent) electromagnetic fields. Quantum-mechanical models
+explaining such phenomena are rooted in the concept of a moving quasiparticle's
+Berry phase, driven by a chiral (left- or right-handed) spin-habit. Dynamical
+and nearly random spin fluctuations, with a slight bent towards left- or
+right-handed chirality, represent a promising route to realizing Berry-phase
+phenomena at elevated temperatures, but little is known about the effect of
+crystal lattice geometry on the resulting macroscopic observables. Here, we
+report thermoelectric and electric transport experiments on two metals with
+large magnetic moments on a triangular and on a slightly distorted kagom\'e
+lattice, respectively. We show that the impact of chiral spin fluctuations is
+strongly enhanced for the kagom\'e lattice. Both these spiral magnets have
+similar magnetic phase diagrams including a periodic array of magnetic
+skyrmions. However, our modelling shows that the geometry of the kagom\'e
+lattice, with corner-sharing spin-trimers, helps to avoid cancellation of
+Berry-phase contributions; spin fluctuations are endowed with a net chiral
+habit already in the thermally disordered (paramagnetic) state. Hence, our
+observations for the kagom\,e material contrast with theoretical models
+treating magnetization as a continuous field, and emphasize the role of lattice
+geometry on emergent electrodynamic phenomena.",2206.05756v2
+2022-06-22,Tracing the magnetic field topology of the quiet corona using propagating disturbances,"The motion of faint propagating disturbances (PD) in the solar corona reveals
+an intricate structure which must be defined by the magnetic field. Applied to
+quiet Sun observations by the Atmospheric Imaging Assembly (AIA)/Solar Dynamics
+Observatory (SDO), a novel method reveals a cellular network, with cells of
+typical diameters 50\arcsec\ in the cool 304\AA\ channel, and 100\arcsec\ in
+the coronal 193\AA\ channel. The 193\AA\ cells can overlie several 304\AA\
+cells, although both channels share common source and sink regions. The sources
+are points, or narrow corridors, of divergence that occupy the centres of
+cells. They are significantly aligned with photospheric network features and
+enhanced magnetic elements. This shows that the bright network is important to
+the production of PDs, and confirms that the network is host to the source
+footpoint of quiet coronal loops. The other footpoint, or the sinks of the PDs,
+form the boundaries of the coronal cells. These are not significantly aligned
+with the photospheric network - they are generally situated above the dark
+internetwork photosphere. They form compact points or corridors, often without
+an obvious signature in the underlying photosphere. We argue that these sink
+points can either be concentrations of closed field footpoints associated with
+minor magnetic elements in the internetwork, or concentrations of
+upward-aligned open field. The link between the coronal velocity and magnetic
+fields is strengthened by a comparison with a magnetic extrapolation, which
+shows several general and specific similarities, thus the velocity maps offer a
+valuable additional constraint on models.",2206.11077v1
+2022-06-24,Transition from Pauli paramagnetism to Curie-Weiss behaviour in vanadium,"We study electron correlations and their impact on magnetic properties of bcc
+vanadium by a combination of density functional and dynamical mean-field
+theory. The calculated uniform magnetic susceptibility {in bcc structure} is of
+Pauli type at low temperatures, while it obeys the Curie-Weiss law at higher
+temperatures. Thus, we qualitatively reproduce the experimental temperature
+dependence of magnetic susceptibility without introducing the martensitic phase
+transition. Our results for local spin-spin correlation function and local
+susceptibility reveal that the Curie-Weiss behavior appears due to partial
+formation of local magnetic moments, which originate from $t_{2g}$ states and
+occur due to local spin correlations caused by Hund's rule coupling. At the
+same time, the fermionic quasiparticles remain well-defined, while the
+formation of local moments is accompanied by a deviation from the Fermi-liquid
+behavior. In particular, the self-energy of the $t_{2g}$ states shows the
+non-analytic frequency dependence, which is a characteristic of the
+spin-freezing behavior, while the quasiparticle damping changes approximately
+linearly with temperature in the intermediate temperature range $200$--$700$~K.
+By analyzing the momentum dependence of static magnetic susceptibility, we find
+incommensurate magnetic correlations, which may provide a mechanism for
+unconventional superconductivity at low temperatures.",2206.12383v3
+2022-07-20,Numerical modelling of imposed magnetohydrodynamic effects in hypersonic flows,"Weakly ionised plasmas, formed in high enthalpy hypersonic flows, can be
+actively manipulated via imposed magnetic fields - a concept termed
+magnetohydrodynamic (MHD) flow control. Imposed MHD effects, within flows which
+exhibit multiple shock interactions, are consequential for emerging aerospace
+technologies: including aerodynamic control via magnetic actuation. However,
+numerical modelling of this flow type remains challenging due to the
+sensitivity of feature formation and the real gas modelling of weakly ionised,
+electrically conductive, air plasma. In this work, numerical simulation
+capabilities have been developed for the study of MHD affected, hypersonic
+flows, around 2D axisymmetric non-simple geometries. The validated numerical
+methodology, combined with an advanced 19 species equation of state for air
+plasma, achieves quantitative agreement between simulation and experiment for a
+Mach 5.6 double cone geometry with applied magnetic field. Numerical studies
+are conducted for varied conical surface angle and magnetic field
+configuration. This paper demonstrates how, for hypersonic flows with complex
+shock interactions, the MHD affected flow is not only augmented in terms of
+shock position, but may exhibit topological adaptations in the fundamental flow
+structure. A classification system is introduced for the emergent flow
+topologies. The applied numerical studies examine the mechanisms by which the
+magnetic field configuration influences the MHD augmented shock structure,
+leading to: (1) differences in magnitude of MHD enhancement effect, and (2)
+structural adaptations of the flow topology. Most critically, classes of
+conditions are identified which produce topological equivalence between the
+magnetic interaction effects and a generalised mechanical control surface.",2207.09857v1
+2022-08-05,Nature of helicity injection in non-erupting solar active regions,"Using time-sequence vector magnetic field and coronal observations from
+\textit{Solar Dynamics Observatory}, we report the observations of the magnetic
+field evolution and coronal activity in four emerging active regions (ARs). The
+ARs emerge with leading polarity being the same as for the majority of ARs in a
+hemisphere of solar cycle 24. After emergence, the magnetic polarities separate
+each other without building a sheared polarity inversion line. In all four ARs,
+the magnetic fields are driven by foot point motions such that the sign of the
+helicity injection ($dH/dt$) in the first half of the evolution is changed to
+the opposite sign in the later part of the observation time. This successive
+injection of opposite helicity is also consistent with the sign of mean
+force-free twist parameter ($\alpha_{av}$). Further, the EUV light curves of
+the ARs in 94\AA~and GOES X-ray flux reveal flaring activity below C-class
+magnitude. Importantly, the white-light coronagraph images in conjunction with
+the AR images in AIA 94 \AA~delineate the absence of associated CMEs with the
+studied ARs. These observations imply that the ARs with successive injection of
+opposite sign magnetic helicity are not favorable to twisted flux rope
+formation with excess coronal helicity, and therefore are unable to launch
+CMEs, according to recent reports. This study provides the characteristics of
+helicity flux evolution in the ARs referring to the conservative property of
+magnetic helicity and more such studies would help to quantify the eruptive
+capability of a given AR.",2208.03228v1
+2022-08-19,Revealing nanoscale disorder in W/CoFeB/MgO ultra-thin films using domain wall motion,"Disorder in ultra-thin magnetic films can significantly hinder domain wall
+motion. One of the main issues on the path towards efficient domain wall based
+devices remains the characterization of the pinning landscape at the nanoscale.
+In this paper, we study domain wall motion in W/CoFeB/MgO thin films with
+perpendicular magnetic anisotropy crystallized by annealing at 400$^{\circ}$C
+and a process based on He$^{+}$ irradiation combined with elevated
+temperatures. Magnetic properties are similar for the whole series of samples,
+while the magnetic domain wall mobility is critically improved in the
+irradiated samples. By using an analytical model to extract nanoscale pinning
+parameters, we reveal important variations in the disorder of the crystallized
+samples. This work offers a unique opportunity to selectively analyze the
+effects of disorder on the domain wall dynamics, without the contribution of
+changes in the magnetic properties. Our results highlight the importance of
+evaluating the nanoscale pinning parameters of the material when designing
+devices based on domain wall motion, which in return can be a powerful tool to
+probe the disorder in ultra-thin magnetic films.",2208.09280v1
+2022-10-08,Magnetohydrodynamics evolution of three-dimensional magnetic null in NOAA active region 11515 initiated using non-force-free field extrapolation,"Magnetohydrodynamics simulation of active region NOAA 11515 is performed to
+examine the initiation of the M5.6 flaring event that starts around 10:43 UT on
+2012 July 2. The simulation is conducted using an extrapolated non-force-free
+magnetic field generated from the photospheric vector magnetogram of the active
+region as the initial magnetic field. The magnetic field shows the presence of
+a three-dimensional (3D) magnetic null with the corresponding dome overlying a
+filament and a low-lying magnetic flux rope, observed in 304~\AA~ and 131~\AA~
+respectively.
+  The simulated dynamics, triggered by the initial Lorentz force, lead to the
+bifurcations of the flux rope, which is similar to the observed bifurcation in
+the 131 \AA~ brightenings. Additionally, the rope exhibits a rise and
+reconnects at the 3D null. These reconnections convert field lines of the rope
+into the anchored outer spine of the 3D null -- explaining the occurrence of a
+nearby confined C-class flare. Further, the results show that the field lines
+of the flux rope reach the vicinity of the filament and become non-parallel to
+the field lines of the filament. This initiates the reconnections between the
+rope and the field lines of the filament -- activating the filament for the
+eruption. This interesting interaction of the flux rope and filament seems to
+contribute to the onset of the M-class flare.",2210.03957v1
+2022-10-29,On the specific energy and pressure in near-Earth magnetic clouds,"The pressure and energy density of the gas and magnetic field inside solar
+coronal mass ejections (in relation to that in the ambient solar wind) is
+thought to play an important role in determining their dynamics as they
+propagate through the heliosphere. We compare the specific energy (${\rm
+erg\,g^{-1}}$) [comprising kinetic ($H_{\rm k}$), thermal ($H_{\rm th }$) and
+magnetic field ($H_{\rm mag}$) contributions] inside MCs and the solar wind
+background. We examine if the excess thermal + magnetic pressure and specific
+energy inside MCs (relative to the background) is correlated with their
+propagation and internal expansion speeds. We ask if the excess thermal +
+magnetic specific energy inside MCs might make them resemble rigid bodies in
+the context of aerodynamic drag. We use near-Earth in-situ data from the WIND
+spacecraft to identify a sample of 152 well observed interplanetary coronal
+mass ejections and their MC counterparts. We compute various metrics using
+these data to address our questions. We find that the total specific energy
+($H$) inside MCs is approximately equal to that in the background solar wind.
+We find that the the excess (thermal + magnetic) pressure and specific energy
+are not well correlated with the near-Earth propagation and expansion speeds.
+We find that the excess thermal+magnetic specific energy $\gtrsim$ the specific
+kinetic energy of the solar wind incident on 81--89 \% of the MCs we study.
+This might explain how MCs retain their structural integrity and resist
+deformation by the solar wind bulk flow.",2210.16571v1
+2022-11-09,Modelling the magnetic structure of a large-scale horse-shoe-like filament in a decaying and diffuse active region,"A large-scale, horse-shoe-like filament was investigated and the magnetic
+field around it was reconstructed. This is an intermediate filament (IF) that
+appeared on the solar disk for the first time at 02:00 UT on 2015 November 7,
+and took 8 days to move to the central median on the solar disk. The active
+region AR 12452 around which the filament occurred was diffuse so that the
+magnetic field nearby was weak, the average field strength is 106 G. Therefore,
+the existing approaches to extrapolating the coronal magnetic field and to
+constructing the filament configuration in the region with strong background
+field do not work well here. On the basis of the regularized Biot-Savart laws
+method, we successfully constructed a data-constrained, non-linear force-free
+field configuration for this IF observed on 2015 November 14. The overall IF
+configuration obtained in this way matches well the morphology suggested by a
+304~\AA \ image taken by the Atmospheric Imaging Assembly on board Solar
+Dynamics Observatory. Magnetic dips in the configuration were coincident in
+space with the H$\alpha$ features of the filament, which is lower in altitude
+than the features seen in 304~\AA. This suggests that the cold plasma fills the
+lower part of the filament, and hot plasma is situated in the higher region. A
+quasi-separatrix layer wraps the filament, and both the magnetic field and the
+electric current are stronger near the inner edge of the filament.",2211.04842v1
+2022-11-11,Frequency and Amplitude Optimizations for Magnetic Particle Spectroscopy Applications,"Nowadays, there is a growing interest in the field of magnetic particle
+spectroscopy (MPS)-based bioassays. MPS monitors the dynamic magnetic response
+of surface-functionalized magnetic nanoparticles (MNPs) upon excitation by an
+alternating magnetic field (AMF) to detect various target analytes. This
+technology has flourished in the past decade due to its low cost, low
+background magnetic noise interference from biomatrix, and fast response time.
+A large number of MPS variants have been reported by different groups around
+the world, with applications ranging from disease diagnosis to foodborne
+pathogen detection, and virus detection. However, there is an urgent need for
+guidance on how to optimize the sensitivity of MPS detection by choosing
+different types of MNPs, AMF modalities, and MPS assay strategies (i.e.,
+volume- and surface-based assays). In this work, we systematically study the
+effect of AMF frequencies and amplitudes on the responses of single- and
+multi-core MNPs under two extreme conditions, namely, the bound and unbound
+states. Our results show that some modalities such as dual-frequency MPS
+utilizing multicore MNPs are more suitable for surface-based bioassay
+applications, whereas, single-frequency MPS systems using single- or multi-core
+MNPs are better suited for volumetric bioassay applications. Furthermore, the
+bioassay sensitivities for these modalities can be further improved by careful
+selection of AMF frequencies and amplitudes.",2211.05936v1
+2022-11-17,A simplified lattice Boltzmann implementation of the quasi-static approximation in pipe flows under the presence of non-uniform magnetic fields,"We propose a single-step simplified lattice Boltzmann algorithm capable of
+performing magnetohydrodynamic (MHD) flow simulations in pipes for very small
+values of magnetic Reynolds numbers $R_m$. In some previous works, most lattice
+Boltzmann simulations are performed with values of $R_m$ close to the Reynolds
+numbers for flows in simplified rectangular geometries. One of the reasons is
+the limitation of some traditional lattice Boltzmann algorithms in dealing with
+situations involving very small magnetic diffusion time scales associated with
+most industrial applications in MHD, which require the use of the so-called
+quasi-static (QS) approximation. Another reason is related to the significant
+dependence that many boundary conditions methods for lattice Boltzmann have on
+the relaxation time parameter. In this work, to overcome the mentioned
+limitations, we introduce an improved simplified algorithm for velocity and
+magnetic fields which is able to directly solve the equations of the QS
+approximation, among other systems, without preconditioning procedures. In
+these algorithms, the effects of solid insulating boundaries are included by
+using an improved explicit immersed boundary algorithm, whose accuracy is not
+affected by the values of $R_m$. Some validations with classic benchmarks and
+the analysis of the energy balance in examples including uniform and
+non-uniform magnetic fields are shown in this work. Furthermore, a progressive
+transition between the scenario described by the QS approximation and the MHD
+canonical equations in pipe flows is visualized by studying the evolution of
+the magnetic energy balance in examples with unsteady flows.",2211.09370v3
+2022-11-29,Magnetic interactions of 4$f$ electrons in the topological insulator chalcogenide Bi$_{2}$Se$_{3}$,"The gap opening mechanism of a topological insulator, the quantum anomalous
+Hall effect and the axion physics are still pressing open questions and a
+microscopic viewpoint to further understand the role of magnetism in topology
+is highly desirable. In this work we have performed a microscopic
+investigation, by means of electron spin resonance (ESR) along with
+complementary bulk measurements, on the chalcogenide
+(Bi$_{1-x}$Gd$_{x}$)$_{2}$Se$_{3}$ ($x$ = 0, 0.001, 0.002 and 0.006). Our
+analysis of the Gd$^{3+}$ spin dynamics reveal no significant change of the
+Fermi surface as a function of Gd$^{3+}$ concentration, which indicates that
+the 4$f$ magnetism is different from the non-local effects induced by
+transition metals ($d$ electrons) substitutions. Additionally, we observe an
+unusual evolution of the Gd$^{3+}$ ESR spectra as a function of the applied
+magnetic field, which we discuss considering the magnetic interaction between
+Gd$^{3+}$ 4$f$ electrons and impurity centers such as Se vacancies. This
+interaction would give rise to a local weak antilocalization effect surrounding
+the Gd$^{3+}$ ions. Such mechanism is observable due to particular details of
+the Gd$^{3+}$ 4$f$ electrons magnetism in this system compared to $d$
+electrons. Our work points out that rare earth substitutions in this model
+topological insulator is a promising path to explore the axion insulating
+systems.",2211.16048v1
+2023-01-10,Magnetic anisotropy and low-energy spin dynamics in the van der Waals compounds Mn$_{2}$P$_{2}$S$_{6}$ and MnNiP$_{2}$S$_{6}$,"We report the detailed high-field and high-frequency electron spin resonance
+(HF-ESR) spectroscopic study of the single-crystalline van der Waals compounds
+Mn$_{2}$P$_{2}$S$_{6}$ and MnNiP$_{2}$S$_{6}$. Analysis of magnetic excitations
+shows that in comparison to Mn$_{2}$P$_{2}$S$_{6}$ increasing the Ni content
+yields a larger magnon gap in the ordered state and a larger g-factor value and
+its anisotropy in the paramagnetic state. The studied compounds are found to be
+strongly anisotropic having each the unique ground state and type of magnetic
+order. Stronger deviation of the g-factor from the free electron value in the
+samples containing Ni suggests that the anisotropy of the exchange is an
+important contributor to the stabilization of a certain type of magnetic order
+with particular anisotropy. At temperatures above the magnetic order, we have
+analyzed the spin-spin correlations resulting in a development of slowly
+fluctuating short-range order. They are much stronger pronounced in
+MnNiP$_{2}$S$_{6}$ compared to Mn$_{2}$P$_{2}$S$_{6}$. The enhanced spin
+fluctuations in MnNiP$_{2}$S$_{6}$ are attributed to the competition of
+different types of magnetic order. Finally, the analysis of the temperature
+dependent critical behavior of the magnon gaps below the ordering temperature
+in Mn$_{2}$P$_{2}$S$_{6}$ suggests that the character of the spin wave
+excitations in this compound undergoes a field induced crossover from a 3D-like
+towards 2D XY regime.",2301.04239v2
+2023-01-22,Responses of quark-antiquark interaction and heavy quark dynamics to magnetic field,"We study how a magnetic field induced by colliding nuclei influences both
+heavy quark (HQ) potential and HQ momentum diffusion coefficients beyond the
+lowest Landau level approximation. By means of real-time hard thermal loop
+resummed technique combined with dimension two gluon condensate, the effective
+gluon propagator describing both perturbative and nonperturbative QCD nature at
+finite temperature and magnetic field are obtained. We find that HQ momentum
+diffusion coefficients in magnetized QCD medium become anisotropic, and with
+increasing temperature, the higher Landau levels become significant, which
+leads to the reduction of the anisotropic ratio ($>$ 1) and even overturn the
+behavior ($<$ 1) at high temperature. The nonperturbative (perturbative)
+contribution of HQ momentum diffusion coefficient in the low (high) temperature
+is dominant. And the anisotropy feature of the real part of the potential is
+essentially encoded in angular dependent Coulomb coupling and string tension.
+Whereas, the imaginary part of the potential from quark-loop in this work
+displays a significant anisotropy even though using the angular-independent
+Coulomb coupling and string tension. Furthermore, we study the magnetic
+response of viscous quark matter, which is manifested in the non-equilibrium
+distribution function of (anti-)quark by solving Boltzmann equation within the
+relaxation time approximation. We find the anisotropy ratio is almost
+insensitive to the magnetized bulk viscosity, although HQ momentum diffusion
+coefficient and HQ potential itself have visible changes.",2301.09110v1
+2023-02-22,Magnetized fingering convection in stars,"Fingering convection (also known as thermohaline convection) is a process
+that drives the vertical transport of chemical elements in regions of stellar
+radiative zones where the mean molecular weight increases with radius.
+Recently, Harrington & Garaud (2019) used three-dimensional direct numerical
+simulations to show that a vertical magnetic field can dramatically enhance the
+rate of chemical mixing by fingering convection. Furthermore, they proposed a
+so-called ""parasitic saturation"" theory to model this process. Here, we test
+their model over a broad range of parameter space, using a suite of direct
+numerical simulations of magnetized fingering convection varying the magnetic
+Prandtl number, magnetic field strength, and composition gradient. We find that
+the rate of chemical mixing measured in the simulations is not always predicted
+accurately by their existing model, in particular when the magnetic diffusivity
+is large. We then present an extension of the Harrington & Garaud (2019) model
+which resolves this issue. When applied to stellar parameters, it recovers the
+results of Harrington & Garaud (2019) except in the limit where fingering
+convection becomes marginally stable, where the new model is preferred. We
+discuss the implications of our findings for stellar structure and evolution.",2302.11610v3
+2023-03-07,Tetrahedral triple-Q magnetic ordering and large spontaneous Hall conductivity in the metallic triangular antiferromagnet Co1/3TaS2,"The triangular lattice antiferromagnet (TLAF) has been the standard paradigm
+of frustrated magnetism for several decades. The most common magnetic ordering
+in insulating TLAFs is the 120 structure. However, a new triple-Q chiral
+ordering can emerge in metallic TLAFs, representing the short wavelength limit
+of magnetic skyrmion crystals. We report the metallic TLAF Co1/3TaS2 as the
+first example of tetrahedral triple-Q magnetic ordering with the associated
+topological Hall effect (non-zero {\sigma}_{xy}(H=0)). We also present a
+theoretical framework that describes the emergence of this magnetic ground
+state, which is further supported by the electronic structure measured by
+angle-resolved photoemission spectroscopy. Additionally, our measurements of
+the inelastic neutron scattering cross section are consistent with the
+calculated dynamical structure factor of the tetrahedral triple-Q state.",2303.03760v5
+2023-03-09,Eruption of a Magnetic Flux Rope in a Comprehensive Radiative Magnetohydrodynamic Simulation of flare-productive active regions,"Radiative magnetohydrodynamic simulation includes sufficiently realistic
+physics to allow for the synthesis of remote sensing observables that can be
+quantitatively compared with observations. We analyze the largest flare in a
+simulation of the emergence of large flare-productive active regions described
+by Chen et al. The flare releases $4.5\times10^{31}$ erg of magnetic energy and
+is accompanied by a spectacular coronal mass ejection. Synthetic soft X-ray
+flux of this flare reaches M2 class. The eruption reproduces many key features
+of observed solar eruptions. A pre-existing magnetic flux rope is formed along
+the highly sheared polarity inversion line between a sunspot pair and is
+covered by an overlying multi-pole magnetic field. During the eruption, the
+progenitor flux rope actively reconnects with the canopy field and evolves to
+the large-scale multi-thermal flux rope that is observed in the corona.
+Meanwhile, the magnetic energy released via reconnection is channeled down to
+the lower atmosphere and gives rise to bright soft X-ray post-flare loops and
+flare ribbons that reproduce the morphology and dynamic evolution of observed
+flares. The model helps to shed light on questions of where and when the a flux
+rope may form and how the magnetic structures in an eruption are related to
+observable emission properties.",2303.05405v2
+2023-03-22,Physical Models for Solar Cycle Predictions,"The dynamic activity of stars such as the Sun influences (exo)planetary space
+environments through modulation of stellar radiation, plasma wind, particle and
+magnetic fluxes. Energetic stellar phenomena such as flares and coronal mass
+ejections act as transient perturbations giving rise to hazardous space
+weather. Magnetic fields -- the primary driver of stellar activity -- are
+created via a magnetohydrodynamic dynamo mechanism within stellar convection
+zones. The dynamo mechanism in our host star -- the Sun -- is manifest in the
+cyclic appearance of magnetized sunspots on the solar surface. While sunspots
+have been directly observed for over four centuries, and theories of the origin
+of solar-stellar magnetism have been explored for over half a century, the
+inability to converge on the exact mechanism(s) governing cycle to cycle
+fluctuations and inconsistent predictions for the strength of future sunspot
+cycles have been challenges for models of solar cycle forecasts. This review
+discusses observational constraints on the solar magnetic cycle with a focus on
+those relevant for cycle forecasting, elucidates recent physical insights which
+aid in understanding solar cycle variability, and presents advances in solar
+cycle predictions achieved via data-driven, physics-based models. The most
+successful prediction approaches support the Babcock-Leighton solar dynamo
+mechanism as the primary driver of solar cycle variability and reinforces the
+flux transport paradigm as a useful tool for modelling solar-stellar magnetism.",2303.12648v1
+2023-03-25,The gap-size influence on the excitation of magnetorotational instability in cylindrical Couette flows,"The excitation conditions of the magnetorotational instability are studied
+for axially unbounded Taylor-Couette flows of various gap widths between the
+cylinders. The cylinders are considered as made from both perfect-conducting or
+insulating material and the conducting fluid with a finite but small magnetic
+Prandtl number rotates with a quasi-Keplerian velocity profile. The solutions
+are optimized with respect to the wave number and the Reynolds number of the
+rotation of the inner cylinder. For the axisymmetric modes we find the critical
+Lundquist number of the applied axial magnetic field the lower the wider the
+gap between the cylinders. A similar result is obtained for the induced cell
+structure: the wider the gap the more spherical the cells are. The marginal
+rotation rate of the inner cylinder -- for fixed size of the outer cylinder --
+always possesses a minimum for not too wide and not too narrow gap widths. For
+perfect-conducting walls the minimum lies at $r_{\rm in}\simeq 0.4$ while it is
+at $r_{\rm in}\simeq 0.5$ for insulating walls where $r_{\rm in}$ is the
+normalized radius of the inner cylinder. The lowest magnetic field amplitudes
+to excite the instability are required for Taylor-Couette flows between
+perfect-conducting cylinders with gaps corresponding to $r_{\rm in}\simeq 0.2$.
+For even wider and also for very thin gaps the needed magnetic fields and
+rotation frequencies are shown to become rather huge.
+  Also the nonaxisymmetric modes with $|m|=1$ have been considered. Their
+excitation generally requires stronger magnetic fields and higher magnetic
+Reynolds numbers in comparison to those for the axisymmetric modes which is
+true for wide-gap containers with $r_{\rm in} \lesssim 0.3$.",2303.14547v1
+2023-06-07,The magnetic dual chiral density wave phase in a rotating cold quark matter,"The effect of rotation on the formation of the magnetic dual chiral density
+wave (\MD) in a dense and magnetized cold quark matter is studied. This phase
+is supposed to exist in the extreme conditions prevailing, e.g., in a neutron
+star. These conditions are, apart from high densities and strong magnetic
+fields, a relatively large angular velocity. To answer the question of whether
+the rotation enhances or suppresses the formation of this phase, we first
+determine the effect of rotation on the energy dispersion relation of a
+fermionic system in the presence of a constant magnetic field and then focus on
+the thermodynamic potential of the model at low temperature $T$ and finite
+chemical potential $\mu$. The thermodynamic potential consists, in particular,
+of an anomalous part leading to certain topological effects. We show that in
+comparison with the nonrotating case, a term proportional to the angular
+velocity appears in this anomalous potential. We then solve the corresponding
+gap equations to the chiral and spatial modulation condensates, and study the
+dependence of these dynamical variables on the chemical potential ($\mu$),
+magnetic field ($eB$), and angular velocity ($\Omega$). It turns out that the
+interplay between these parameters suppresses the formation of the \MD~phase in
+relevant regimes for cold neutron stars. This is interpreted as the
+manifestation of the inverse magnetorotational catalysis, which is also
+reflected in the phase portraits $eB$-$\mu$, $eB$-$\Omega R$, and $\mu$-$\Omega
+R$, explored in this work.",2306.04472v2
+2023-06-16,Probing the Anomalous Hall Transport and Magnetic Reversal of Chiral-Lattice Antiferromagnet Co$_{1/3}$NbS$_2$,"Antiferromagnets exhibiting giant anomalous Hall effect (AHE) and anomalous
+Nernst effect (ANE) have recently aroused broad interest, not only for their
+potential applications in future electronic devices, but also because of the
+rich physics arising from the Berry curvature near the Fermi level.
+$\rm{Co_{1/3}NbS_2}$, by intercalating $\rm{Co^{2+}}$ ions between $\rm{NbS_2}$
+layers, is a quasi-two-dimensional layered antiferromagnet with a chiral
+lattice. A large AHE has been observed in $\rm{Co_{1/3}NbS_2}$, but its origin
+is under debate. In this letter, we report the large AHE and ANE in exfoliated
+$\rm{Co_{1/3}NbS_2}$ flakes. By analyzing the thermoelectric data via the Mott
+relation, we determined that the observed large AHE and ANE primarily result
+from the intrinsic Berry curvature. We also observed the magnetic domains in
+$\rm{Co_{1/3}NbS_2}$ by reflective magnetic circular dichroism measurements.
+Combined with electrical transport measurements, we confirmed that the magnetic
+reversal in $\rm{Co_{1/3}NbS_2}$ is determined by domain wall motion, and the
+critical field ($H_c$) exhibits a memory effect of consecutive magnetic sweeps.
+Our work provides insight into the topological properties of
+$\rm{Co_{1/3}NbS_2}$ and paves the way to studying the spin configuration and
+magnetic domain dynamics in this fascinating antiferromagnet.",2306.09616v1
+2023-07-10,Periodicity staircase in a Fe/Gd magnetic thin film,"Presence of multiple competing periodicities may result in a system to go
+through states with modulated periodicities, an example of which is the
+self-similar staircase-like structure called the Devil's staircase. Herein we
+report on a novel staircase structure of domain periodicity in an amorphous and
+achiral Fe/Gd magnetic thin film wherein the reciprocal space wavevector
+\textbf{Q} due to the ordered stripe domains does not evolve continuously,
+rather exhibits a staircase structure. Resonant X-ray scattering experiments
+show jumps in the periodicity of the stripe domains as a function of an
+external magnetic field. When resolved in components, the step change along
+Q$_x$ was found to be an integral multiple of a minimum step height of 7 nm,
+which resembles closely to the exchange length of the system. Modeling the
+magnetic texture in the Fe/Gd thin film as an achiral spin arrangement, we have
+been able to reproduce the steps in the magnetization using a Landau-Lifshitz
+spin dynamics calculation. Our results indicate that anisotropy and not the
+dipolar interaction is the dominant cause for the staircase pattern, thereby
+revealing the effect of achiral magnetism.",2307.04938v3
+2023-08-12,Avalanches and the Distribution of Reconnection Events in Magnetized Circumstellar Disks,"Cosmic rays produced by young stellar objects can potentially alter the
+ionization structure, heating budget, chemical composition, and accretion
+activity in circumstellar disks. The inner edges of these disks are truncated
+by strong magnetic fields, which can reconnect and produce flaring activity
+that accelerates cosmic radiation. The resulting cosmic rays can provide a
+source of ionization and produce spallation reactions that alter the
+composition of planetesimals. This reconnection and particle acceleration are
+analogous to the physical processes that produce flaring in and heating of
+stellar coronae. Flaring events on the surface of the Sun exhibit a power-law
+distribution of energy, reminiscent of those measured for Earthquakes and
+avalanches. Numerical lattice-reconnection models are capable of reproducing
+the observed power-law behavior of solar flares under the paradigm of
+self-organized criticality. One interpretation of these experiments is that the
+solar corona maintains a nonlinear attractor -- or ``critical'' -- state by
+balancing energy input via braided magnetic fields and output via reconnection
+events. Motivated by these results, we generalize the lattice-reconnection
+formalism for applications in the truncation region of magnetized disks. Our
+numerical experiments demonstrate that these nonlinear dynamical systems are
+capable of both attaining and maintaining criticality in the presence of
+Keplerian shear and other complications. The resulting power-law spectrum of
+flare energies in the equilibrium attractor state is found to be nearly
+universal in magnetized disks. This finding indicates that magnetic
+reconnection and flaring in the inner regions of circumstellar disks occur in a
+manner similar to activity on stellar surfaces.",2308.06650v1
+2023-09-08,Magnetic Fields and Velocity Gradients in L1551: The Role of Stellar Feedback,"Magnetic fields play a crucial role in star formation, yet tracing them
+becomes particularly challenging, especially in the presence of outflow
+feedback in protostellar systems. We targeted the star-forming region L1551,
+notable for its apparent outflows, to investigate the magnetic fields. These
+fields were probed using polarimetry observations from the Planck satellite at
+353 GHZ/849 $\mu$m, the SOFIA/HAWC+ measurement at 214 $\mu$m, and the
+JCMT/SCUPOL 850 $\mu$m survey. Consistently, all three measurements show that
+the magnetic fields twist towards the protostar IRS 5. Additionally, we
+utilized the Velocity Gradients Technique (VGT) on the $^{12}$CO (J = 1-0)
+emission data to distinguish the magnetic fields directly associated with the
+protostellar outflows. These were then compared with the polarization results.
+Notably, in the outskirts of the region, these measurements generally align.
+However, as one approaches the center of IRS 5, the measurements tend to yield
+mostly perpendicular relative orientations. This suggests that the outflows
+might be dynamically significant from a scale of approximately $\sim0.2$~pc,
+causing the velocity gradient to change direction by 90 degrees. Furthermore,
+we discovered that the polarization fraction $p$ and the total intensity $I$
+correlate as $p \propto I^{-\alpha}$. Specifically, $\alpha$ is approximately
+$1.044\pm0.06$ for SCUPOL and around $0.858\pm0.15$ for HAWC+. This indicates
+that the outflows could significantly impact the alignment of dust grains and
+magnetic fields in the L1551 region.",2309.04173v2
+2023-09-20,Evaluating Gilbert Damping in Magnetic Insulators from First Principles,"Magnetic damping has a significant impact on the performance of various
+magnetic and spintronic devices, making it a long-standing focus of research.
+The strength of magnetic damping is usually quantified by the Gilbert damping
+constant in the Landau-Lifshitz-Gilbert equation. Here we propose a
+first-principles based approach to evaluate the Gilbert damping constant
+contributed by spin-lattice coupling in magnetic insulators. The approach
+involves effective Hamiltonian models and spin-lattice dynamics simulations. As
+a case study, we applied our method to Y$_3$Fe$_5$O$_{12}$, MnFe$_2$O$_4$ and
+Cr$_2$O$_3$. Their damping constants were calculated to be $0.8\times10^{-4}$,
+$0.2\times10^{-4}$, $2.2\times 10^{-4}$, respectively at a low temperature. The
+results for Y$_3$Fe$_5$O$_{12}$ and Cr$_2$O$_3$ are in good agreement with
+experimental measurements, while the discrepancy in MnFe$_2$O$_4$ can be
+attributed to the inhomogeneity and small band gap in real samples. The
+stronger damping observed in Cr$_2$O$_3$, compared to Y$_3$Fe$_5$O$_{12}$,
+essentially results from its stronger spin-lattice coupling. In addition, we
+confirmed a proportional relationship between damping constants and the
+temperature difference of subsystems, which had been reported in previous
+studies. These successful applications suggest that our approach serves as a
+promising candidate for estimating the Gilbert damping constant in magnetic
+insulators.",2309.11152v1
+2023-10-04,A Database of Magnetic and Thermodynamic Properties of Confined And Eruptive Solar Flares,"Solar flares sometimes lead to coronal mass ejections that directly affect
+the Earth's environment. However, a large fraction of flares, including on
+solar-type stars, are confined flares. What are the differences in physical
+properties between confined and eruptive flares? For the first time, we
+quantify thermodynamic and magnetic properties of hundreds of confined and
+eruptive flares of GOES class C5.0 and above, 480 flares total. We first
+analyze large flares of GOES class M1.0 and above observed by the Solar
+Dynamics Observatory (SDO): 216 flares total, including 103 eruptive and 113
+confined flares, from 2010 until 2016 April, we then look at the entire dataset
+above C5.0 of 480 flares. We compare GOES X-ray thermodynamic flare properties,
+including peak temperature and emission measure, and active-region and
+flare-ribbon magnetic field properties, including reconnected magnetic flux and
+peak reconnection rate. We find that for fixed peak X-ray flux, confined and
+eruptive flares have similar reconnection fluxes; however, for fixed peak X-ray
+flux confined flares have on average larger peak magnetic reconnection rates,
+are more compact, and occur in larger active regions than eruptive flares.
+These findings suggest that confined flares are caused by reconnection between
+more compact, stronger, lower lying magnetic-fields in larger active regions
+that reorganizes smaller fraction of these regions' fields. This reconnection
+proceeds at faster rates and ends earlier, potentially leading to more
+efficient flare particle acceleration in confined flares.",2310.02878v3
+2023-10-06,An Analytic Model For Magnetically-Dominated Accretion Disks,"Recent numerical cosmological
+radiation-magnetohydrodynamic-thermochemical-star formation simulations have
+resolved the formation of quasar accretion disks with Eddington or
+super-Eddington accretion rates onto supermassive black holes (SMBHs) down to a
+few hundred gravitational radii. These 'flux-frozen' and hyper-magnetized disks
+appear to be qualitatively distinct from classical $\alpha$ disks and
+magnetically-arrested disks: the midplane pressure is dominated by toroidal
+magnetic fields with plasma $\beta \ll 1$ powered by advection of magnetic flux
+from the interstellar medium (ISM), and they are super-sonically and
+trans-Alfvenically turbulent with cooling times short compared to dynamical
+times yet remain gravitationally stable owing to magnetic support. In this
+paper, we present a simple analytic similarity model for such disks. For
+reasonable assumptions, the model is entirely specified by the boundary
+conditions (inflow rate at the BH radius of influence [BHROI]). We show that
+the scalings from this model are robust to various detailed assumptions, agree
+remarkably well with the simulations (given their simplicity), and demonstrate
+the self-consistency and gravitational stability of such disks even in the
+outer accretion disk (approaching the BHROI) at hyper-Eddington accretion
+rates.",2310.04507v2
+2023-10-09,Mapping of Spin-Wave Transport in Thulium Iron Garnet Thin Films Using Diamond Quantum Microscopy,"Spin waves, collective dynamic magnetic excitations, offer crucial insights
+into magnetic material properties. Rare-earth iron garnets offer an ideal
+spin-wave (SW) platform with long propagation length, short wavelength,
+gigahertz frequency, and applicability to magnon spintronic platforms. Of
+particular interest, thulium iron garnet (TmIG) has attracted a huge interest
+recently due to its successful growth down to a few nanometers, observed
+topological Hall effect and spin orbit torque-induced switching effects.
+However, there is no direct spatial measurement of its SW properties. This work
+uses diamond nitrogen vacancy (NV) magnetometry in combination with SW
+electrical transmission spectroscopy to study SW transport properties in TmIG
+thin films. NV magnetometry allows probing spin waves at the sub-micrometer
+scale, seen by the amplification of the local microwave magnetic field due to
+the coupling of NV spin qubits with the stray magnetic field produced by the
+microwave-excited spin waves. By monitoring the NV spin resonances, the SW
+properties in TmIG thin films are measured as function of the applied magnetic
+field, including their amplitude, decay length (~ 50 um), and wavelength (0.8 -
+2 um). These results pave the way for studying spin qubit-magnon interactions
+in rare-earth magnetic insulators, relevant to quantum magnonics applications.",2310.06188v4
+2023-10-29,Bridging Scales in Black Hole Accretion and Feedback: Magnetized Bondi Accretion in 3D GRMHD,"Fueling and feedback couple supermassive black holes (SMBHs) to their host
+galaxies across many orders of magnitude in spatial and temporal scales, making
+this problem notoriously challenging to simulate. We use a multi-zone
+computational method based on the general relativistic magneto-hydrodynamic
+(GRMHD) code KHARMA that allows us to span $7$ orders of magnitude in spatial
+scale, to simulate accretion onto a non-spinning SMBH from an external medium
+with Bondi radius $R_B\approx 2\times 10^5 \,GM_\bullet/c^2$, where $M_\bullet$
+is the SMBH mass. For the classic idealized Bondi problem, spherical gas
+accretion without magnetic fields, our simulation results agree very well with
+the general relativistic analytic solution. Meanwhile, when the accreting gas
+is magnetized, the SMBH magnetosphere becomes saturated with a strong magnetic
+field. The density profile varies as $\sim r^{-1}$ rather than $r^{-3/2}$ and
+the accretion rate $\dot{M}$ is consequently suppressed by over 2 orders of
+magnitude below the Bondi rate $\dot{M}_B$. We find continuous energy feedback
+from the accretion flow to the external medium at a level of
+$\sim10^{-2}\dot{M}c^2 \sim 5\times 10^{-5} \dot{M}_B c^2$. Energy transport
+across these widely disparate scales occurs via turbulent convection triggered
+by magnetic field reconnection near the SMBH. Thus, strong magnetic fields that
+accumulate on horizon scales transform the flow dynamics far from the SMBH and
+naturally explain observed extremely low accretion rates compared to the Bondi
+rate, as well as at least part of the energy feedback.",2310.19135v2
+2023-11-30,Induced quantum magnetism in CEF singlet ground state models: Thermodynamics and excitations,"We present a comparative investigation of singlet ground state induced
+magnetism for singlet, doublet and triplet excited CEF states of non-Kramers
+f-electrons relevant primarily for Pr- and U- based compounds. This type of
+magnetic order is of intrinsic quantum nature because it requires the
+superposition of singlet ground state with excited states due to non-diagonal
+matrix elements of the effective intersite exchange to generate local moments.
+In contrast to conventional magnets the local moments and their ordering appear
+simultaneously at the transition temperature. It is finite only if the control
+parameter proportional to the ratio of exchange strength to level splitting
+exceeds a critical value marking the quantum critical point of the models. We
+determine the dependence of transition temperature, saturation moment,
+renormalised level splitting, specific heat jumps and low-temperature
+susceptibility as function of control parameter. Furthermore the temperature
+dependence of these quantities is calculated for control parameters above and
+below the quantum critical point and the distinction to conventional magnetism
+is discussed. In addition we investigate the dynamical properties of the three
+models, deriving the magnetic exciton dispersion and their critical behaviour.
+In particular the conditions for true and arrested soft-mode behaviour at the
+ordering wave vector are identified.",2311.18416v2
+2024-01-09,Microwave magnetic excitations in U-type hexaferrite Sr$_4$CoZnFe$_{36}$O$_{60}$ ceramics,"Microwave (MW) spectra of ferrimagnetic U-hexaferrite
+Sr$_4$CoZnFe$_{36}$O$_{60}$ ceramics were studied using several experimental
+techniques from 100 MHz to 50 GHz at temperatures between 10 and 390 K. They
+revealed 9 excitations, which exhibit remarkable temperature dependences near
+the magnetic phase transitions at 145 K and 305 K. Some of them also change
+under the application of a weak bias magnetic field at room temperature. Three
+lowest-frequency modes seen between 200 MHz and 3 GHz were assigned to the
+dynamics of the magnetic domains. The mode attributed to the natural
+ferromagnetic resonance exhibits a dramatic critical slowing-down from 25 GHz
+at 390 K to 5 GHz near the 305 K phase transition, and again a hardening to ~11
+GHz on further cooling. The higher-frequency excitations are most likely spin
+wave (magnon) modes arising from the complex ferrimagnetic structure of
+Sr$_4$CoZnFe$_{36}$O$_{60}$. The high sensitivity of the MW spectra to the weak
+magnetic bias field $H$ < 700 Oe at room temperature is shown to be caused by
+the transformation of the polydomain magnetic structure in randomly oriented
+ceramic grains to a monodomain one. The MW response measured above 2 GHz using
+coplanar and microstrip lines with different electromagnetic field distribution
+and sample coupling revealed the same excitations with similar temperature and
+bias field dependences. It confirms the reliability of the results and proves
+the effectiveness of the used MW techniques.",2401.04678v1
+2024-01-25,Nucleosynthesis in magnetorotational supernovae: impact of the magnetic field configuration,"The production of heavy elements is one of the main by-products of the
+explosive end of massive stars. A long sought goal is finding differentiated
+patterns in the nucleosynthesis yields, which could permit identifying a number
+of properties of the explosive core. Among them, the traces of the magnetic
+field topology are particularly important for \emph{extreme} supernova
+explosions, most likely hosted by magnetorotational effects. We investigate the
+nucleosynthesis of five state-of-the-art magnetohydrodynamic models with fast
+rotation that have been previously calculated in full 3D and that involve an
+accurate neutrino transport (M1). One of the models does not contain any
+magnetic field and synthesizes elements around the iron group, in agreement
+with other CC-SNe models in literature. All other models host a strong magnetic
+field of the same intensity, but with different topology. For the first time,
+we investigate the nucleosynthesis of MR-SNe models with a quadrupolar magnetic
+field and a 90 degree tilted dipole. We obtain a large variety of ejecta
+compositions reaching from iron nuclei to nuclei up to the third r-process
+peak. We assess the robustness of our results by considering the impact of
+different nuclear physics uncertainties such as different nuclear masses,
+$\beta^{-}$-decays and $\beta^{-}$-delayed neutron emission probabilities,
+neutrino reactions, fission, and a feedback of nuclear energy on the
+temperature. We find that the qualitative results do not change with different
+nuclear physics input. The properties of the explosion dynamics and the
+magnetic field configuration are the dominant factors determining the ejecta
+composition.",2401.14402v1
+2024-02-02,Skyrmions: A review on materials perspective for future electronic devices,"Recent years have witnessed an enormous rise in research interest in magnetic
+skyrmions owing to their capability to improve over contemporary spintronic
+devices. An overview of the various magnetic interactions responsible for the
+formation of skyrmion together with distinct noncentrosymmetric and
+centrosymmetric skyrmion candidates is given in this review article. The
+magnetic interactions known as Dzyaloshinskii-Moriya interactions (DMI) have
+been extensively studied over the years to better understand the mechanism of
+skyrmions in chiral magnets that have larger skyrmion sizes. Because of their
+low skyrmion size, the centrosymmetric frustrated magnets are dwelling to
+skyrmions controlled by long-range interactions such as the
+Ruderman-Kittel-Kasuya-Yosida interaction (RKKY), which may be useful in the
+development of high-density memory devices. To lay a solid foundation for the
+magnetic interactions involved in skyrmion formations and many other special
+physical properties, more research in the field of centrosymmetric skyrmions is
+required. Apart from studying candidates with low skyrmion sizes, one of the
+main goals for the future is to better understand the dynamics of skyrmion
+using polarized magnons, which has the potential to be extremely beneficial for
+spintronic applications.",2402.01503v3
+2024-03-12,Fragmentation of Dense Rotation-Dominated Structures Fed by Collapsing Gravomagneto-Sheetlets and Origin of Misaligned 100 au-Scale Binaries and Multiple Systems,"The majority of stars are in binary/multiple systems. How such systems form
+in turbulent, magnetized cores of molecular clouds in the presence of non-ideal
+MHD effects remains relatively under-explored. Through ATHENA++-based non-ideal
+MHD AMR simulations with ambipolar diffusion, we show that the collapsing
+protostellar envelope is dominated by dense gravomagneto-sheetlets, a
+turbulence-warped version of the classic pseuodisk produced by anisotropic
+magnetic resistance to the gravitational collapse, in agreement with previous
+simulations of turbulent, magnetized single-star formation. The sheetlets feed
+mass, magnetic fields, and angular momentum to a Dense ROtation-Dominated
+(DROD) structure, which fragments into binary/multiple systems. This DROD
+fragmentation scenario is a more dynamic variant of the traditional disk
+fragmentation scenario for binary/multiple formation, with dense spiral
+filaments created by inhomogeneous feeding from the highly structured
+larger-scale sheetlets rather than the need for angular momentum transport,
+which is dominated by magnetic braking. Collisions between the dense spiraling
+filaments play a key role in pushing the local magnetic Toomre parameter
+$Q_\mathrm{m}$ below unity, leading to gravitational collapse and stellar
+companion formation provided that the local material is sufficiently
+demagnetized, with a plasma-$\beta$ of order unity or more. This mechanism can
+naturally produce {\it in situ} misaligned systems on the 100-au scale, often
+detected with high-resolution ALMA observations. Our simulations also highlight
+the importance of non-ideal MHD effects, which affect whether fragmentation
+occurs and, if so, the masses and orbital parameters of the stellar companions
+formed.",2403.07777v1
+2024-04-04,Dynamics and Emission Properties of Flux Ropes from Two-Temperature GRMHD Simulations with Multiple Magnetic Loops,"Flux ropes erupting from the vicinity of the black hole are thought to be a
+potential model for the flares observed in Sgr\,A$^*$. In this study, we
+examine the radiative properties of flux ropes that emerged from the vicinity
+of the black hole. We have performed three-dimensional two-temperature General
+Relativistic Magnetohydrodynamic (GRMHD) simulations of magnetized accretion
+flows with alternating multiple magnetic loops, and General Relativistic
+Radiation Transfer (GRRT) calculations. In GRMHD simulations, two different
+sizes of initial magnetic loops are implemented. In the small loop case,
+magnetic dissipation leads to a weaker excitement of magneto-rotational
+instability inside the torus which generates a lower accretion rate compared to
+the large loop case. However, it makes more generation of flux ropes due to
+frequent reconnection by magnetic loops with different polarities. By
+calculating the thermal synchrotron emission, we found that the variability of
+light curves and emitting region are tightly related. At $230\,\rm GHz$ and
+higher frequency, the emission from the flux ropes is relatively stronger
+compared with the background, which is responsible for the filamentary
+structure in the images. At lower frequencies, e.g. $43\,\rm GHz$, emission
+comes from more extended regions, which have a less filamentary structure in
+the image. Our study shows self-consistent electron temperature models are
+essential for the calculation of thermal synchrotron radiation and the
+morphology of the GRRT images. Flux ropes contribute considerable emission at
+frequencies $\gtrsim 230\,\rm GHz$.",2404.03237v1
+1998-02-13,Dynamics on the Edge: Star-Disk Interaction,"Our understanding of the dynamical processes which control the structure and
+evolution of the interaction region between an accretion disk and the central
+star is reviewed. If the central star is unmagnetized, this interaction is in
+the form of a classical boundary layer. However, if the central star is
+strongly magnetized, it is expected that the inner disk is truncated by the
+stellar field, and the accretion flow follows the stellar field lines to the
+magnetic poles. Several outstanding questions remain regarding this picture. It
+is likely that numerical MHD simulations will prove essential to answering
+these questions. However, in order to model the MHD turbulence, angular
+momentum transport, and possible dynamo action associated with the dynamics of
+star-disk interaction, fully three-dimensional simulations spanning long
+dynamical times are required.",9802190v1
+1997-09-29,"Spin conductance, dynamic spin stiffness and spin diffusion in itinerant magnets","We discuss analogies between the charge- and spin response functions of
+itinerant magnets. We show that the spin-analog of the charge stiffness is not
+given by the usual spin stiffness rho_s, but by the dynamic spin stiffness D_s,
+which is obtained from the dynamic spin conductance G_s (omega) in the limit of
+vanishing frequency omega. The low-frequency behavior of G_s (omega) is used to
+define ideal spin conductors, normal spin conductors, and spin insulators.
+Assuming diffusive spin dynamics, we show that the spin diffusion coefficient
+is proportional to lim_{omega rightarrow 0} {Re} {G}_s (omega). We exploit this
+fact to develop a new extrapolation scheme for the spin diffusion coefficient
+in the paramagnetic phase of the Hubbard model.",9709316v2
+1997-11-23,Dynamical universality classes of the superconducting phase transition,"We present a finite temperature Monte Carlo study of the XY-model in the
+vortex representation, and study its dynamical critical behavior in two limits.
+The first neglects magnetic field fluctuations, corresponding to the absence of
+screening, which should be a good approximation in high $T_c$ superconductors
+($\kappa\to \infty$) except extremely close to the critical point. Here, from
+finite size scaling of the linear resistivity we find the dynamical critical
+exponent of the vortex motion to be $z\approx 1.5$. The second limit includes
+magnetic field fluctuations in the strong screening limit ($\kappa\to 0$)
+corresponding to the true asymptotic inverted XY critical regime, where we find
+the unexpectedly large value $z\approx 2.7$. We compare these results, obtained
+from dissipative dynamics in the vortex representation, with the universality
+class of the corresponding model in the phase representation with propagating
+(spin wave) modes. We also discuss the effect of disorder and the relevance of
+our results for experiments.",9711236v1
+1998-04-07,Peierls Dimerization with Non-Adiabatic Spin-Phonon Coupling,"We study the magnetic properties of a frustrated Heisenberg spin chain with a
+dynamic spin-phonon interaction. By Lanczos diagonalization, preserving the
+full lattice dynamics, we explore the non-adiabatic regime with phonon
+frequencies comparable to the exchange coupling energy which is e.g. the
+relevant limit for the spin-Peierls compound $CuGeO_3$. When compared to the
+static limit of an alternating spin chain the magnetic properties are strongly
+renormalized due to the coupled dynamics of spin and lattice degrees of
+freedom. The magnitude of the spin triplet excitation gap changes from a strong
+to a weak dimerization dependence with increasing phonon frequencies implying
+the necessity to include dynamic effects in an attempt for a quantitative
+description of the spin-Peierls state.",9804085v2
+1999-12-20,Spin dynamics simulations - a powerful method for the study of critical dynamics,"Spin-dynamics techniques can now be used to study the deterministic
+time-dependent behavior of magnetic systems containing over 10^5 spins with
+quite good accuracy. This approach will be introduced, including the
+theoretical foundations of the methods of analysis. Then newly developed,
+improved techniques based upon Suzuki-Trotter decomposition methods will be
+described. The current ``state-of-the-art'' will be evaluated with specific
+examples drawn from data on simple magnetic models. The examination of dynamic
+critical behavior will be highlighted but the extraction of information about
+excitations at low temperatures will be included.",9912375v1
+2000-04-05,Low-frequency spin dynamics in the orthorombic phase of La_2CuO_4,"An effective field theory is derived that describes the low-frequency spin
+dynamics in the low-temperature orthorombic phase of La_2CuO_4. Restricted to a
+single CuO_2 layer the effective theory is a simple generalization of the
+relativistic nonlinear sigma model to include all spin interactions allowed by
+symmetry. Incorporating a weak interlayer interaction leads to two coupled
+nonlinear sigma models which provide an efficient description of the complete
+bilayer dynamics. Particular attention is paid to the weak-ferromagnetic and
+spin-flop transitions induced by external magnetic fields. The main features of
+the observed (covert) weak ferromagnetism are thus accounted for in a
+straightforward manner but some of the finer theoretical predictions would
+require further experimental investigation. The derived framework is also
+suitable for the study of the structure and dynamics of magnetic domains in
+undoped La_2CuO_4.",0004071v1
+2002-02-15,Novel dynamical effects and persistent memory in phase separated manganites,"The time dependent response of the magnetic and transport properties of
+Fe-doped phase separated (PS) manganite La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ is
+reported. The nontrivial coexistence of ferromagnetic (FM) and non FM regions
+induces a slow dynamics which leads to time relaxation and cooling rate
+dependence within the PS regime. This dynamics influences drastically on
+physical properties. On one hand, metallic like behavior, assumed to be a
+fingerprint of percolation, can be also observed before the FM phase percolates
+as a result of dynamical contributions. On the other one, two novel effects for
+the manganites are reported, namely the rejuvenation of the resistivity after
+ageing, and a persistent memory of low magnetic fields ($<$ 1 T), imprinted in
+the amount of the FM phase. As a distinctive fact, this memory can be recovered
+through transport measurements.",0202263v1
+2003-02-13,Optimization and self-organized criticality in a magnetic system,"We propose a kind of Bak-Sneppen dynamics as a general optimization technique
+to treat magnetic systems. The resulting dynamics shows self-organized
+criticality with power law scaling of the spatial and temporal correlations. An
+alternative method of the extremal optimization is also analyzed here. We
+provided a numerical confirmation that, for any possible value of its free
+parameter $\tau$, the extremal optimization dynamics exhibits a non-critical
+behavior with an infinite spatial range and exponential decay of the
+avalanches. Using the chiral clock model as our test system, we compare the
+efficiency of the two dynamics with regard to their abilities to find the
+system's ground state.",0302260v1
+2003-02-22,The dynamics of quantum phases in a spinor condensate,"We discuss the quantum phases and their diffusion dynamics in a spinor-1
+atomic Bose-Einstein condensate. For ferromagnetic interactions, we obtain the
+exact ground state distribution of the phases associated with the total atom
+number ($N$), the total magnetization (${\cal M}$), and the alignment (or
+hypercharge) ($Y$) of the system. The mean field ground state is stable against
+fluctuations of atom numbers in each of the spin components, and the phases
+associated with the order parameter for each spin components diffuse while
+dynamically recover the two broken continuous symmetries [U(1) and SO(2)] when
+$N$ and ${\cal M}$ are conserved as in current experiments. We discuss the
+implications to the quantum dynamics due to an external (homogeneous) magnetic
+field. We also comment on the case of a spinor-1 condensate with
+anti-ferromagnetic interactions.",0302464v1
+2003-10-15,Quasiparticle Relaxation Dynamics in Two Distinct Gap Structures: La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ and LaMnO$_{3}$,"The spin and quasiparticle relaxation dynamics in
+La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ and LaMnO$_{3}$ single crystals and thin films
+is investigated as a function of temperature and magnetic field by pump-probe
+spectroscopy. The unusually slow spin-lattice relaxation dynamics is governed
+by the temperature- and magnetic field- dependent pseudogap in
+La$_{0.67}$Ca$_{0.33}$MnO$_{3}$, and by the temperature-independent Jahn-Teller
+gap in LaMnO$_{3}$. Our results show that the coupled dynamics of charge, spin
+and lattice is strongly correlated with the distinct gap structures in these
+manganites.",0310359v1
+2005-01-06,Electron Spin Dynamics and Hyperfine Interactions in Fe/Al_0.1Ga_0.9As/GaAs Spin Injection Heterostructures,"We have studied hyperfine interactions between spin-polarized electrons and
+lattice nuclei in Al_0.1Ga_0.9As/GaAs quantum well (QW) heterostructures. The
+spin-polarized electrons are electrically injected into the semiconductor
+heterostructure from a metallic ferromagnet across a Schottky tunnel barrier.
+The spin-polarized electron current dynamically polarizes the nuclei in the QW,
+and the polarized nuclei in turn alter the electron spin dynamics. The
+steady-state electron spin is detected via the circular polarization of the
+emitted electroluminescence. The nuclear polarization and electron spin
+dynamics are accurately modeled using the formalism of optical orientation in
+GaAs. The nuclear spin polarization in the QW is found to depend strongly on
+the electron spin polarization in the QW, but only weakly on the electron
+density in the QW. We are able to observe nuclear magnetic resonance (NMR) at
+low applied magnetic fields on the order of a few hundred Oe by electrically
+modulating the spin injected into the QW. The electrically driven NMR
+demonstrates explicitly the existence of a Knight field felt by the nuclei due
+to the electron spin.",0501096v1
+2005-06-24,Critical dynamics and effective exponents of magnets with extended impurities,"We investigate the asymptotic and effective static and dynamic critical
+behavior of (d=3)-dimensional magnets with quenched extended defects,
+correlated in $\epsilon_d$ dimensions (which can be considered as the
+dimensionality of the defects) and randomly distributed in the remaining
+$d-\epsilon_d$ dimensions. The field-theoretical renormalization group
+perturbative expansions being evaluated naively do not allow for the reliable
+numerical data. We apply the Chisholm-Borel resummation technique to restore
+convergence of the two-loop expansions and report the numerical values of the
+asymptotic critical exponents for the model A dynamics. We discuss different
+scenarios for static and dynamic effective critical behavior and give values
+for corresponding non-universal exponents.",0506644v1
+2006-10-17,Inhomogeneous phase separation and domain wall dynamics in the orthorhombically distorted La_{0.87}MnO_x,"We observe the interesting magnetization and resistivity results in the
+orthorhombically distorted self doped manganite, La_{0.87}MnO_x. A significant
+irreversibility between zero-field-cooled and field-cooled resistivities as
+well as magnetization data is clearly observed up to a temperature which is
+well above the both paramagnetic to ferromagnetic (T_c) and metal to insulator
+transition (T_{MI}) temperatures. In the ferromagnetically ordered and metallic
+states the magnetotransport results suggest the influence of domain wall
+dynamics. Interesting scenario of memory effects through the domain wall
+dynamics is strikingly observed in the relaxation of resistivity in a limited
+temperature region. The characteristic features of magnetotransport behaviour
+are suggested duo to the co-existence of structurally driven inhomogeneous
+phase separation and domain wall dynamics.",0610464v1
+2007-03-21,Ultrafast Vortex-Core Reversal Dynamics in Ferromagnetic Nanodots,"To verify the exact underlying mechanism of ultrafast vortex-core reversal as
+well as the vortex state stability we conducted numerical calculations of the
+dynamic evolution of magnetic vortices in Permalloy cylindrical nanodots under
+an oscillating in-plane magnetic field over a wide range of the frequency and
+amplitude. The calculated results reveal different kinds of the non-trivial
+dynamic responses of vortices to the driving external field. In particular, the
+results offer insight into the 10 ps scale underlying physics of the ulrafast
+vortex-core reversals driven by small amplitude (~10 Oe) in-plane fields. This
+work also provides fundamentals of how to manipulate effectively the dynamical
+switching of the vortex-core orientation.",0703538v1
+2000-06-07,Dynamical Symmetry Breaking and Magnetic Confinement in QCD,"We present a gauge independent method to construct the effective action of
+QCD, and calculate the one loop effective action of $SU(2)$ QCD in an arbitrary
+constant background field. Our result establishes the existence of a dynamical
+symmetry breaking by demonstrating that the effective potential develops a
+unique and stable vacuum made of the monopole condensation in one loop
+approximation. This provides a strong evidence for the magnetic confinement of
+color through the dual Meissner effect in the non-Abelian gauge theory. The
+result is obtained by separating the topological degrees which describe the
+non-Abelian monopoles from the dynamical degrees of the gauge potential, and
+integrating out all the dynamical degrees of QCD. We present three independent
+arguments to support our result.",0006051v3
+2005-01-01,Equatorial and related non-equilibrium states in magnetization dynamics of ferromagnets: Generalization of Suhl's spin-wave instabilities,"We investigate the nonlinear dynamics underlying the evolution of a 2-D
+nanoscale ferromagnetic film with uniaxial anisotropy in the presence of
+perpendicular pumping. Considering the associated Landau-Lifshitz spin
+evolution equation with Gilbert damping together with Maxwell equation for the
+demagnetization field, we study the dynamics in terms of the stereographic
+variable. We identify several new fixed points for suitable choice of external
+field in a rotating frame of reference. In particular, we identify explicit
+equatorial and related fixed points of the spin vector in the plane transverse
+to the anisotropy axis when the pumping frequency coincides with the amplitude
+of the static parallel field. We then study the linear stability of these novel
+fixed points under homogeneous and spin wave perturbations and obtain a
+generalized Suhl's instability criterion, giving the condition for exponential
+growth of P-modes under spin wave perturbations. Two parameter phase diagrams
+(in terms of amplitudes of static parallel and oscillatory perpendicular
+magnetic fields) for stability are obtained, which differ qualitatively from
+those for the conventional ferromagnetic resonance near thermal equilibrium and
+are amenable to experimental tests.",0501002v2
+2007-08-15,Density-Profile Processes Describing Biological Signaling Networks: Almost Sure Convergence to Deterministic Trajectories,"We introduce jump processes in R^k, called density-profile process, to model
+biological signaling networks. They describe the macroscopic evolution of
+finite-size spin-flip models with k types of spins interacting through a
+non-reversible Glauber dynamics. We focus on the the k-dimensional
+empirical-magnetization vector in the thermodynamic limit, and prove that,
+within arbitrary finite time-intervals, its path converges almost surely to a
+deterministic trajectory determined by a first-order (non-linear) differential
+equation. As parameters of the spin-flip dynamics change, the associated
+dynamical system may go through bifurcations, associated to phase transitions
+in the statistical mechanical setting. We present a simple example of spin-flip
+stochastic model leading to a dynamical system with Hopf and pitchfork
+bifurcations; depending on the parameter values, the magnetization random path
+can either converge to a unique stable fixed point, converge to one of a pair
+of stable fixed points, or asymptotically evolve close to a deterministic orbit
+in R^k.",0708.2044v1
+2007-11-27,Non-linear dynamics and two-dimensional solitons for spin $ S=1$ ferromagnets with biquadratic exchange,"We develop a consistent semiclassical theory of spin dynamics for an
+isotropic ferromagnet with a spin $ S=1$ taking into consideration both
+bilinear and biquadratic over spin operators exchange interaction. For such
+non-Heisenberg magnets, a peculiar class of spin oscillations and waves, for
+which the quantum spin expectation value $ {\rm {\bf m}}=<{\rm {\bf S}}>$ does
+not change it direction, but changes in length, is presented. Such
+``longitudinal'' excitations do not exist in regular magnets, dynamics of which
+are described in terms of the Landau-Lifshitz equation or by means of the spin
+Heisenberg Hamiltonian. We demonstrate the presence of non-linear uniform
+oscillations and waves, as well as self-localized dynamical excitations
+(solitons) with finite energy. A possibility of excitation of such oscillations
+by ultrafast laser pulse is discussed.",0711.4285v1
+2008-12-08,A Diffusive Strategic Dynamics for Social Systems,"We propose a model for the dynamics of a social system, which includes
+diffusive effects and a biased rule for spin-flips, reproducing the effect of
+strategic choices. This model is able to mimic some phenomena taking place
+during marketing or political campaigns. Using a cost function based on the
+Ising model defined on the typical quenched interaction environments for social
+systems (Erdos-Renyi graph, small-world and scale-free networks), we find, by
+numerical simulations, that a stable stationary state is reached, and we
+compare the final state to the one obtained with standard dynamics, by means of
+total magnetization and magnetic susceptibility. Our results show that the
+diffusive strategic dynamics features a critical interaction parameter strictly
+lower than the standard one. We discuss the relevance of our findings in social
+systems.",0812.1435v3
+2008-12-29,Vortex dynamics in confined stratified conditions,"We report on linear spin dynamics in the vortex state of the Permalloy dots
+subjected to stratified (magnetic) field. We demonstrate experimentally and by
+simulations the existence of two distinct dynamic regimes corresponding to the
+vortex stable and metastable states. Breaking cylindrical symmetry leads to
+unexpected eigenmodes frequency splitting in the stable state and appearance of
+new eigenmodes in the metastable state above the vortex nucleation field.
+Dynamic response in the metastable state strongly depends on relative
+orientation of the external rf pumping and the bias magnetic fields. These
+findings may be relevant for different vortex states in confined and stratified
+conditions.",0812.4954v1
+2009-01-30,Theory of magnetism with temporal disorder applied to magnetically doped ZnO,"A dynamic model of the asymmetric Ising glass is presented: an Ising model
+with antiferromagnet bonds with probabilities q arranged at random in a
+ferromagnetic matrix. The dynamics is introduced by changing the arrangement of
+the antiferromagnetic bonds after n Monte Carlo steps but keeping the same
+value of q and spin configuration. In the region where there is a second order
+transition between the ferromagnetic and paramagnetic states the dynamic
+behaviour follows that expected for motional narrowing and reverts to the
+static behaviour only for large n. There is a different dynamic behaviour where
+there is a first order transition between the ferromagnetic and spin glass
+states where it shows no effects of motional narrowing. The implications of
+this are discussed. This model is devised to explain the properties of doped
+ZnO where the magnetisation is reduced when the exchange interactions change
+with time.",0901.4947v1
+2009-03-06,Kondo effect and conductance of nanocontacts with magnetic impurities,"We study the impact of dynamical correlations on the electronic structure and
+coherent transport properties of Cu nanocontacts hosting a single magnetic
+impurity (Ni,Co,Fe) in the contact region. The strong dynamical correlations of
+the impurity 3d-electrons are fully taken into account by combining density
+functional calculations with a dynamical treatment of the impurity 3d-shell in
+the one-crossing approximation. We find that dynamical correlations give rise
+to the Kondo effect and lead to Fano features in the coherent transport
+characteristics similar to those observed in related experiments.",0903.1274v2
+2009-05-14,Dynamical signature of a domain phase transition in a perpendicularly-magnetized ultrathin film,"Domain phases in ultrathin Fe/Ni/W(110) films with perpendicular anisotropy
+have been studied using the ac magnetic susceptibility. Dynamics on time scales
+of minutes to hours were probed by quenching the system from high temperature
+to the stripe phase region, and varying the constant rate of temperature
+increase as the susceptibility traces were measured. The entire susceptibility
+peak is observed to relax slowly along the temperature axis, with the peak
+temperature increasing as the rate of heating is decreased. This is precisely
+opposite to what would happen if this slow relaxation was driven by changes in
+the domain density within the stripe phase. The data are instead consistent
+with a simple model for the removal of a significant density of pattern defects
+and curvature trapped in the quench from high temperature. A quantitative
+analysis confirms that the relaxation dynamics are consistent with the
+mesoscopic rearrangement of domains required to remove pattern defects, and
+that the experiment constitutes a ""dynamical"" observation of the phase
+transition from a high temperature, positionally disordered phase to the low
+temperature, ordered stripe phase.",0905.2339v2
+2009-10-27,Contribution of a time-dependent metric on the dynamics of an interface between two immiscible electro-magnetically controllable Fluids,"We consider the case of a deformable material interface between two
+immiscible moving media, both of them being magnetiable. The time dependence of
+the metric at the interface introduces a non linear term, proportional to the
+mean curvature, in the surface dynamical equations of mass momentum and angular
+momentum. We take into account the effects of that term also in the singular
+magnetic and electric fields inside the interface which lead to the existence
+of currents and charges densities through the interface, from the derivation of
+the Maxwell equations inside both bulks and the interface. Also, we give the
+expression for the entropy production and of the different thermo-dynamical
+fluxes. Our results enlarge previous results from other theories where the
+specific role of the time dependent surface metric was insufficiently stressed.",0910.5020v1
+2010-07-13,Asymmetric optical nuclear spin pumping in a single uncharged quantum dot,"A highly asymmetric dynamic nuclear spin pumping is observed in a single self
+assembled InGaAs quantum dot subject to resonant optical pumping of the neutral
+exciton transition leading to a large maximum polarization of 54%. This dynamic
+nuclear polarization is found to be much stronger following pumping of the
+higher energy Zeeman state. Time-resolved measurements allow us to directly
+monitor the buildup of the nuclear spin polarization in real time and to
+quantitatively study the dynamics of the process. A strong dependence of the
+observed dynamic nuclear polarization on the applied magnetic field is found,
+with resonances in the pumping efficiency being observed for particular
+magnetic fields. We develop a model that fully accounts for the observed
+behaviour, where the pumping of the nuclear spin system is due to
+hyperfine-mediated spin flip transitions between the states of the neutral
+exciton manifold.",1007.2145v2
+2010-09-01,Single- and few-electron dynamic quantum dots in a perpendicular magnetic field,"We present experimental studies of the current pumped through a dynamic
+quantum dot over a wide range of magnetic fields. At low fields we observe
+repeatable structure indicating increased confinement of the electrons in the
+dynamic dot. At higher fields (B>3T), we observe structure which changes
+markedly from device to device suggesting that in this regime the transport is
+sensitive to local disorder. The results are significant for the development of
+dynamic quantum dot pumps as quantum standards of electrical current.",1009.0203v1
+2010-09-24,Photoinduced dynamics in quantum rings,"We investigate the spin-dependent dynamical response of a semiconductor
+quantum ring with a spin orbit interaction (SOI) upon the application of a
+single and two linearly polarized, picosecond, asymmetric electromagnetic
+pulses in the presence of a static magnetic flux. We find that the
+pulse-generated electric dipole moment is spin dependent. It is also shown that
+the SOI induces an extra SU(2) effective flux in addition to the static
+external magnetic flux which is reflected in an additional periodicity of the
+spin-dependent dipole moment. Furthermore, the pulses may induce a net
+dynamical charge currents (CC) and dynamical spin currents (SC) when the
+clockwise and anti-clockwise symmetry of the carrier is broken upon the pulse
+application.",1009.4809v1
+2010-11-12,Irradiated bilayer graphene,"We describe the gated bilayer graphene system when it is subjected to intense
+terahertz frequency electromagnetic radiation. We examine the electron band
+structure and density of states via exact diagonalization methods within
+Floquet theory. We find that dynamical states are induced which lead to
+modification of the band structure. We first examine the situation where there
+is no external magnetic field. In the unbiased case, dynamical gaps appear in
+the spectrum which manifest as dips in the density of states. For finite
+interlayer bias (where a static gap is present in the band structure of
+unirradiated bilayer graphene), dynamical states may be induced in the static
+gap. These states can show a high degree of valley polarization. When the
+system is placed in a strong magnetic field, the radiation induces coupling
+between the Landau levels which allows dynamical levels to exist. For strong
+fields, this means the Landau levels are smeared to form a near-continuum of
+states.",1011.3043v1
+2011-03-16,Collective beating of artificial microcilia,"We combine technical, experimental and theoretical efforts to investigate the
+collective dynamics of artificial microcilia in a viscous fluid. We take
+advantage of soft-lithography and colloidal self-assembly to devise microcapets
+made of hundreds of slender magnetic rods. This novel experimental setup is
+used to investigate the dynamics of extended cilia arrays driven by a
+precessing magnetic field. Whereas the dynamics of an isolated cilium is a
+rigid body rotation, collective beating results in a symmetry breaking of the
+precession patterns. The trajectories of the cilia are anisotropic and
+experience a significant structural evolution as the actuation frequency
+increases. We present a minimal model to account for our experimental findings
+and demonstrate how the global geometry of the array imposes the shape of the
+trajectories via long range hydrodynamic interactions.",1103.3122v1
+2011-06-06,Simulating cyclotron-Bloch dynamics of a charged particle in a 2D lattice by means of cold atoms in driven quasi 1D optical lattices,"Quantum dynamics of a charged particle in a 2D lattice subject to magnetic
+and electric fields is a rather complicated interplay between cyclotron
+oscillations (the case of vanishing electric field) and Bloch oscillations
+(zero magnetic field), details of which has not yet been completely understood.
+In the present work we suggest to study this problem by using cold atoms in
+optical lattices. We introduce a 1D model which can be easily realized in
+laboratory experiments with quasi 1D optical lattices and show that this model
+captures many features of the cyclotron-Bloch dynamics of the quantum particle
+in 2D square lattices.",1106.0945v1
+2011-06-16,Non-Arrhenius relaxation of the Heisenberg model with dipolar and anisotropic interactions,"The dynamical properties of a 2D Heisenberg model with dipolar interactions
+and perpendicular anisotropy are studied using Monte Carlo simulations in two
+different ordered regions of the equilibrium phase diagram. We find a
+temperature defining a dynamical transition below which the relaxation suddenly
+slows down and the system aparts from the typical Arrhenius relaxation to a
+Vogel-Fulcher-Tamann law. This anomalous behavior is observed in the scaling of
+the magnetic relaxation and may eventually lead to a freezing of the system.
+Through the analysis of the domain structures we explain this behavior in terms
+of the domains dynamics. Moreover, we calculate the energy barriers
+distribution obtained from the data of the magnetic viscosity. Its shape
+supports our comprehension of both, the Vogel-Fulcher-Tamann dynamical slowing
+down and the freezing mechanism.",1106.3301v1
+2011-07-21,A nonstationary nonparametric Bayesian approach to dynamically modeling effective connectivity in functional magnetic resonance imaging experiments,"Effective connectivity analysis provides an understanding of the functional
+organization of the brain by studying how activated regions influence one
+other. We propose a nonparametric Bayesian approach to model effective
+connectivity assuming a dynamic nonstationary neuronal system. Our approach
+uses the Dirichlet process to specify an appropriate (most plausible according
+to our prior beliefs) dynamic model as the ""expectation"" of a set of plausible
+models upon which we assign a probability distribution. This addresses model
+uncertainty associated with dynamic effective connectivity. We derive a Gibbs
+sampling approach to sample from the joint (and marginal) posterior
+distributions of the unknowns. Results on simulation experiments demonstrate
+our model to be flexible and a better candidate in many situations. We also
+used our approach to analyzing functional Magnetic Resonance Imaging (fMRI)
+data on a Stroop task: our analysis provided new insight into the mechanism by
+which an individual brain distinguishes and learns about shapes of objects.",1107.4181v1
+2012-02-06,Spin Dynamics at Very Low Temperature in Spin Ice Dy$_2$Ti$_2$O$_7$,"We have performed AC susceptibility and DC magnetic relaxation measurements
+on the spin ice system Dy$_2$Ti$_2$O$_7$ down to 0.08 K. The relaxation time of
+the magnetization has been estimated below 2 K down to 0.08 K. The spin
+dynamics of Dy$_2$Ti$_2$O$_7$ is well described by using two relaxation times
+($\tau_{\rm S}$ (short time) and $\tau_{\rm L}$ (long time)). Both $\tau_{\rm
+S}$ and $\tau_{\rm L}$ increase on cooling. Assuming the Arrhenius law in the
+temperature range 0.5-1 K, we obtained an energy barrier of 9 K. Below 0.5 K,
+both $\tau_{\rm S}$ and $\tau_{\rm L}$ show a clear deviation from the thermal
+activated dynamics toward temperature independent relaxation, suggesting a
+quantum dynamics.",1202.1107v1
+2012-03-29,Theory of spin dynamics of magnetic adatoms traced by time-resolved scanning tunneling spectroscopy,"The inelastic scanning tunneling microscopy (STM) has been shown recently
+(Loth et al. Science 329, 1628 (2010)) to be extendable as to access the
+nanosecond, spin-resolved dynamics of magnetic adatoms and molecules. Here we
+analyze theoretically this novel tool by considering the time-resolved spin
+dynamics of a single adsorbed Fe atom excited by a tunneling current pulse from
+a spin-polarized STM tip. The adatom spin-configuration can be controlled and
+probed by applying voltage pulses between the substrate and the spin-polarized
+STM tip. We demonstrate how, in a pump-probe manner, the relaxation dynamics of
+the sample spin is manifested in the spin-dependent tunneling current. Our
+model calculations are based on the scattering theory in a wave-packet
+formulation. The scheme is nonpertubative and hence, is valid for all voltages.
+The numerical results for the tunneling probability and the conductance are
+contrasted with the prediction of simple analytical models and compared with
+experiments.",1203.6476v1
+2012-06-22,Internal and external dynamics of antihydrogen in electric and magnetic fields of arbitrary orientation,"We have studied the motion of antihydrogen atoms in electric and magnetic
+fields of arbitrary orientation. Our aim was to find an exact model of external
+(centre-of-charge) and internal dynamics which would allow us to describe
+antihydrogen motion in a realistic way. After analysing the kinematics of the
+charge exchange reaction producing antihydrogen and of antihydrogen
+deexcitation, we discuss the dynamics in cases of special fields
+configurations. Finally, we propose an expression for the force acting on an
+antihydrogen atom when the field configuration is arbitrary. The general
+formula -- when reduced in the special field configurations -- matches the
+results which we obtained independently before. The focus is both on the centre
+of charge dynamics and on the accurate internal quantum characteristics.",1206.5171v1
+2012-08-16,"The effect of the size of the system, aspect ratio and impurities concentration on the dynamic of emergent magnetic monopoles in artificial spin ice systems","In this work we study the dynamical properties of a finite array of
+nanomagnets in artificial kagome spin ice at room temperature. The dynamic
+response of the array of nanomagnets is studied by implementing a ""frustrated
+celular aut\'omata"" (FCA), based in the charge model and dipolar model. The FCA
+simulations, allow us to study in real-time and deterministic way, the dynamic
+of the system, with minimal computational resource. The update function is
+defined according to the coordination number of vertices in the system. Our
+results show that for a set geometric parameters of the array of nanomagnets,
+the system exhibits high density of Dirac strings and high density emergent
+magnetic monopoles. A study of the effect of disorder in the arrangement of
+nanomagnets is incorporated in this work.",1208.3482v1
+2012-08-22,Transport through single-level systems: Spin dynamics in the nonadiabatic regime,"We investigate the Fano-Anderson model coupled to a large ensemble of spins
+under the influence of an external magnetic field. The interaction between the
+two spin systems is treated within a meanfield-approach and we assume an
+anisotropic coupling between these two systems. By using a nonadiabatic
+approach, we make no further approximations in the theoretical description of
+our system, apart from the semiclassical treatment. Therewith, we can include
+the short-time dynamics as well as the broadening of the energy levels arising
+due to the coupling to the external electronic reservoirs. We study the spin
+dynamics in the regime of low and high bias. For the infinite bias case, we
+compare our results to those obtained from a simpler rate equation approach,
+where higher-order transitions are neglected. We show, that these higher-order
+terms are important in the range of low magnetic field. Additionally, we
+analyze extensively the finite bias regime with methods from nonlinear
+dynamics, and we discuss the possibility of switching of the large spin.",1208.4574v2
+2012-08-31,Dynamics and hysteresis in square lattice artificial spin-ice,"Dynamical effects under geometrical frustration are considered in a model for
+artificial spin ice on a square lattice in two dimensions. Each island of the
+spin ice has a three-component Heisenberg-like dipole moment subject to shape
+anisotropies that influence its direction. The model has real dynamics,
+including rotation of the magnetic degrees of freedom, going beyond the
+Ising-type models of spin ice. The dynamics is studied using a Langevin
+equation solved via a second order Heun algorithm. Thermodynamic properties
+such as the specific heat are presented for different couplings. A peak in
+specific heat is related to a type of melting-like phase transition present in
+the model. Hysteresis in an applied magnetic field is calculated for model
+parameters where the system is able to reach thermodynamic equilibrium.",1208.6557v2
+2012-10-01,Staggered Dynamics in Antiferromagnets by Collective Coordinates,"Antiferromagnets can be used to store and manipulate spin information, but
+the coupled dynamics of the staggered field and the magnetization are very
+complex. We present a theory which is conceptually much simpler and which uses
+collective coordinates to describe staggered field dynamics in
+antiferromagnetic textures. The theory includes effects from dissipation,
+external magnetic fields, as well as reactive and dissipative current-induced
+torques. We conclude that, at low frequencies and amplitudes, currents induce
+collective motion by means of dissipative rather than reactive torques. The
+dynamics of a one-dimensional domain wall, pinned at 90$^{\circ}$ at its ends,
+are described as a driven harmonic oscillator with a natural frequency
+inversely proportional to the length of the texture.",1210.0429v2
+2012-10-23,Out-of-equilibrium dynamics in systems with long-range interactions: characterizing quasi-stationary states,"Systems with long-range interactions (LRI) display unusual thermodynamical
+and dynamical properties that stem from the non-additive character of the
+interaction potential. We focus in this work on the lack of relaxation to
+thermal equilibrium when a LRI system is started out-of-equilibrium. Several
+attempts have been made at predicting the so-called quasi-stationary state
+(QSS) reached by the dynamics and at characterizing the resulting transition
+between magnetized and non-magnetized states. We review in this work recent
+theories and interpretations about the QSS. Several theories exist but none of
+them has provided yet a full account of the dynamics found in numerical
+simulations.",1210.6316v1
+2013-04-17,Viscosity control of the dynamic self-assembly in ferromagnetic suspensions,"Recent studies of dynamic self-assembly in ferromagnetic colloids suspended
+in liquid-air or liquid-liquid interfaces revealed a rich variety of dynamic
+structures ranging from linear snakes to axisymmetric asters, which exhibit
+novel morphology of the magnetic ordering accompanied by large-scale
+hydrodynamic flows. Based on controlled experiments and first principle theory,
+we argue that the transition from snakes to asters is governed by the viscosity
+of the suspending liquid where less viscous liquids favor snakes and more
+viscous, asters. By obtaining analytic solutions of the time-averaged
+Navier-Stokes equations, we gain insights into the role of mean hydrodynamic
+flows and an overall balance of forces governing the self-assembly. Our results
+illustrate that the viscosity can be used to control the outcome of the dynamic
+self-assembly in magnetic colloidal suspensions.",1304.4968v1
+2013-04-30,A Dynamical Systems Approach to a Bianchi Type I Viscous Magnetohydrodynamic Model,"We use the expansion-normalized variables approach to study the dynamics of a
+non-tilted Bianchi Type I cosmological model with both a homogeneous magnetic
+field and a viscous fluid. In our model the perfect magnetohydrodynamic
+approximation is made, and both bulk and shear viscous effects are retained.
+The dynamical system is studied in detail through a fixed-point analysis which
+determines the local sink and source behavior of the system. We show that the
+fixed points may be associated with Kasner-type solutions, a flat universe FLRW
+solution, and interestingly, a new solution to the Einstein Field equations
+involving non-zero magnetic fields, and non-zero viscous coefficients. It is
+further shown that for certain values of the bulk and shear viscosity and
+equation of state parameters, the model isotropizes at late times.",1304.8042v5
+2013-09-03,Detection and measurement of spin-dependent dynamics in random telegraph signals,"A quantum point contact was used to observe single-electron fluctuations of a
+quantum dot in a GaAs heterostructure. The resulting random telegraph signals
+(RTS) contain statistical information about the electron spin state if the
+tunneling dynamics are spin-dependent. We develop a statistical method to
+extract information about spin-dependent dynamics from RTS and use it to
+demonstrate that these dynamics can be studied in the thermal energy regime.
+The tunneling rates of each spin state are independently measured in a finite
+external magnetic field. We confirm previous findings of a decrease in overall
+tunneling rates for the spin excited state compared to the ground state as an
+external magnetic field is increased.",1309.0567v2
+2013-12-19,On Dynamics of G-Band Bright Points,"Various parameters describing the dynamics of G-band bright points (GBPs)
+were derived from G-band images, acquired by the Dutch Open Telescope (DOT), of
+a quiet region close to the disk center. Our study is based on four commonly
+used diagnostics (effective velocity, change in the effective velocity, change
+in the direction angle, and centrifugal acceleration) and two new ones (rate of
+motion and time lag between recurrence of GBPs). The results concerning the
+commonly used parameters are in agreement with previous studies for a
+comparable spatial and temporal resolution of the used data.To broaden our
+understanding of the dynamics of GBPs, two new parameters were defined: the
+real displacement between their appearance and disappearance (rate of motion)
+and the frequency of their recurrence at the same locations (time lag). Results
+for both new parameters indicate that the locations of different dynamical
+types of GBPs (stable/farther traveling or with short/long lifetimes) are bound
+to the locations of more stable and long-living magnetic field concentrations.
+Thus, the disappearance/reappearance of the tracked GBPs cannot be perceived as
+the disappearance/reappearance of their corresponding magnetic field
+concentrations.",1312.5464v1
+2014-01-11,Dynamics of mobile interacting ferromagnetic films: theory and numerical implementation,"Coating two nearby bodies with thin ferromagnetic films one obtains, below
+the Curie temperature, two interacting sets of magnetic domains. The dynamical
+properties of the bodies in presence of this domain interaction have never been
+investigated so far. In this work I derive a set of equations to simultaneously
+describe both the domain evolution within the two films and the dynamics of the
+coated bodies. The shape, size and mobility of the domains can be easily
+controlled with an external magnetic field or properly choosing the material
+properties, thus unravelling how the domain characteristics influence the
+system dynamics. This can be thus of great technological relevance, providing
+new means to control and actuate mechanical motion at the micro- and
+nano-scale.",1401.2513v1
+2014-07-16,Spin dynamics and magneto-optical response in charge-neutral tunnel-coupled quantum dots,"We model the electron and hole spin dynamics in an undoped double quantum dot
+structure, considering the carrier tunneling between quantum dots. Taking into
+account also the presence of an in-plane or tilted magnetic field, we provide
+the simulation of magneto-optical experiments, like the time resolved Kerr
+rotation measurement, which are performed currently on such structures to probe
+the temporal spin dynamics. With our model, we reproduce the experimentally
+observed effect of the extension of the spin polarization life time caused by
+the spatial charge separation, which may occur in structures of this type.
+Moreover, we provide a number of qualitative predictions concerning the
+necessary conditions for observation of this effect as well as about possible
+channels of its suppression, including the spin-orbit coupling, which leads to
+tunneling of carriers accompanied by a spin-flip. We consider also the impact
+of the magnetic field tilting, which results in an interesting spin
+polarization dynamics.",1407.4529v4
+2014-10-02,Stability and dynamics of magnetocapillary interactions,"Recent experiments have shown that floating ferromagnetic beads, under the
+influence of an oscillating background magnetic field, can move along a
+liquid-air interface in a sustained periodic locomotion [Lumay et al., Soft
+Matter, 2013, 9, 2420]. Dynamic activity arises from a periodically induced
+dipole-dipole repulsion between the beads acting in concert with capillary
+attraction. We investigate analytically and numerically the stability and
+dynamics of this magnetocapillary swimming, and explore other related topics
+including the steady and periodic equilibrium configurations of two and three
+beads, and bead collisions. The swimming speed and system stability depend on a
+dimensionless measure of the relative repulsive and attractive forces which we
+term the magnetocapillary number. An oscillatory magnetic field may stabilize
+an otherwise unstable collinear configuration, and striking behaviors are
+observed in fast transitions to and from locomotory states, offering insight
+into the behavior and self-assembly of interface-bound micro-particles.",1410.0429v2
+2014-11-21,"The Sun's interior structure and dynamics, and the solar cycle","The Sun's internal structure and dynamics can be studied with
+helioseismology, which uses the Sun's natural acoustic oscillations to build up
+a profile of the solar interior. We discuss how solar acoustic oscillations are
+affected by the Sun's magnetic field. Careful observations of these effects can
+be inverted to determine the variations in the structure and dynamics of the
+Sun's interior as the solar cycle progresses. Observed variations in the
+structure and dynamics can then be used to inform models of the solar dynamo,
+which are crucial to our understanding of how the Sun's magnetic field is
+generated and maintained.",1411.5941v2
+2015-01-19,Numerical study of the depinning transition of a ferromagnetic magnetic domain wall in films,"We report first principle numerical study of domain wall (DW) depinning in
+two-dimensional magnetic film, which is modeled by 2D random-field Ising system
+with the dipole-dipole interaction. We observe nonconventional activation-type
+motion of DW and reveal its fractal structure of DW near the depinning
+transition. We determine scaling functions describing critical dynamics near
+the transition and obtain universal exponents establishing connection between
+thermal softening of pinning potential and critical dynamics. We observe that
+tuning the strength of the dipole-dipole interaction switches DW dynamics
+between two different universality classes corresponding to two distinct
+dynamic regimes, motion in the random potential and that in the random force.",1501.04436v1
+2015-02-10,Numerical code for multi-component galaxies: from N-body to chemistry and magnetic fields,"We present a numerical code for multi-component simulation of the galactic
+evolution. Our code includes the following parts: $N$-body is used to evolve
+dark matter, stellar dynamics and dust grains, gas dynamics is based on
+TVD-MUSCL scheme with the extra modules for thermal processes, star formation,
+magnetic fields, chemical kinetics and multi-species advection. We describe our
+code in brief, but we give more details for the magneto-gas dynamics. We
+present several tests for our code and show that our code have passed the tests
+with a reasonable accuracy. Our code is parallelized using the MPI library. We
+apply our code to study the large scale dynamics of galactic discs.",1502.02935v1
+2015-03-14,Dynamic nuclear polarization as kinetically constrained diffusion,"Dynamic nuclear polarization (DNP) is a promising strategy for generating a
+significantly increased non-thermal spin polarization in nuclear magnetic
+resonance (NMR) applications thereby circumventing the need for strong magnetic
+fields. Although much explored in recent experiments, a detailed theoretical
+understanding of the precise mechanism behind DNP is so far lacking. We address
+this issue by theoretically investigating solid effect DNP in a system where a
+single electron is coupled to an ensemble of interacting nuclei and which can
+be microscopically modelled by a quantum master equation. By deriving effective
+equations of motion that govern the polarization dynamics we show analytically
+that DNP can be understood as kinetically constrained spin diffusion. On the
+one hand this approach provides analytical insights into the mechanism and
+timescales underlying DNP. On the other hand it permits the numerical study of
+large ensembles which are typically intractable from the perspective of a
+quantum master equation. This paves the way for a detailed exploration of DNP
+dynamics which might form the basis for future NMR applications.",1503.04357v1
+2015-04-21,Tailoring the magnetodynamic properties of nanomagnets using magnetocrystalline and shape anisotropies,"Magnetodynamical properties of nanomagnets are affected by the demagnetizing
+fields created by the same nanoelements. In addition, magnetocrystalline
+anisotropy produces an effective field that also contributes to the spin
+dynamics. In this article we show how the dimensions of magnetic elements can
+be used to balance crystalline and shape anisotropies, and that this can be
+used to tailor the magnetodynamic properties. We study ferromagnetic ellipses
+patterned from a 10 nm thick epitaxial Fe film with dimensions ranging from 50
+x 150 nm to 150 x 450 nm. The study combines ferromagnetic resonance (FMR)
+spectroscopy with analytical calculations and micromagnetic simulations, and
+proves that the dynamical properties can be effectively controlled by changing
+the size of the nanomagnets. We also show how edge defects in the samples
+influence the magnetization dynamics. Dynamical edge modes localized along the
+sample edges are strongly influenced by edge defects, and this needs to be
+taken into account in understanding the full FMR spectrum",1504.05404v2
+2015-04-26,Amplitude modes and dynamic coexistence of competing orders in multicomponent superconductors,"We study the nonequilibrium dynamics of an electronic model with competing
+spin-density-wave and unconventional superconductivity in the context of iron
+pnictides. Focusing on the collisionless regime, we find that magnetic and
+superconducting order parameters may coexist dynamically after a sudden quench,
+even though the equilibrium thermodynamic state supports only one order
+parameter. We consider various initial conditions concomitant with the phase
+diagram and in a certain regime identify different oscillatory amplitude modes
+with incommensurate frequencies for magnetic and superconducting responses. At
+the technical level we solve the equations of motion for the electronic Green's
+functions and self-consistency conditions by reducing the problem to a closed
+set of Bloch equations in a pseudospin representation. For certain quench
+scenarios the nonadiabatic dynamics of the pairing amplitude is completely
+integrable and in principle can be found exactly.",1504.06874v2
+2015-06-09,Strain induced coherent dynamics of coupled carriers and Mn spins in a quantum dot,"We report on the coherent dynamics of the spin of an individual magnetic atom
+coupled to carriers in a semiconductor quantum dot which has been investigated
+by resonant photoluminescence of the positively charged exciton (X+). We
+demonstrate that a positively charged CdTe/ZnTe quantum dot doped with a single
+Mn atom forms an ensemble of optical Lambda systems which can be addressed
+independently. We show that the spin dynamics of the X+Mn complex is dominated
+by the electron-Mn exchange interaction and report on the coherent dynamics of
+the electron-Mn spin system that is directly observed in the time domain.
+Quantum beats reflecting the coherent transfer of population between
+electron-Mn spin states, which are mixed by an anisotropic strain in the plane
+of the quantum dot, are clearly observed. We finally highlight that this strain
+induced coherent coupling is tunable with an external magnetic field.",1506.02821v1
+2015-12-01,Electric voltage generation by antiferromagnetic dynamics,"We theoretically demonstrate dc and ac electric voltage generation due to
+spinmotive forces originating from domain wall motion and magnetic resonance,
+respectively, in two-sublattice antiferromagnets. Our theory accounts for the
+canting between the sublattice magnetizations, the nonadiabatic electron spin
+dynamics, and the Rashba spin-orbit coupling, with the inter-sublattice
+electron dynamics treated as a perturbation. This work suggests a new way to
+observe and explore the dynamics of antiferromagnetic textures by electrical
+means, an important aspect in the emerging field of antiferromagnetic
+spintronics, where both manipulation and detection of antiferromagnets are
+needed.",1512.00509v6
+2016-03-17,Formation and plasma circulation of solar prominences,"Solar prominences are long-lived cool and dense plasma curtains in the hot
+and rarefied outer solar atmosphere or corona. The physical mechanism
+responsible for their formation and especially for their internal plasma
+circulation has been uncertain for decades. The observed ubiquitous down flows
+in quiescent prominences are difficult to interpret as plasma with high
+conductivity seems to move across horizontal magnetic field lines. Here we
+present three-dimensional numerical simulations of prominence formation and
+evolution in an elongated magnetic flux rope as a result of in-situ plasma
+condensations fueled by continuous plasma evaporation from the solar
+chromosphere. The prominence is born and maintained in a fragmented, highly
+dynamic state with continuous reappearance of multiple blobs and thread
+structures that move mainly downward dragging along mass-loaded field lines.
+The prominence plasma circulation is characterized by the dynamic balance
+between the drainage of prominence plasma back to the chromosphere and the
+formation of prominence plasma via continuous condensation. Plasma evaporates
+from the chromosphere, condenses into the prominence in the corona, and drains
+back to the chromosphere, establishing a stable chromosphere-corona plasma
+cycle. Synthetic images of the modeled prominence with the Solar Dynamics
+Observatory Atmospheric Imaging Assembly closely resemble actual observations,
+with many dynamical threads underlying an elliptical coronal cavity.",1603.05397v1
+2016-04-06,Post Markovian Dynamics of Quantum Correlations: Entanglement vs. Discord,"Dynamics of an open two-qubit system is investigated in the post-Markovian
+regime, where the environments have a short-term memory. Each qubit is coupled
+to separate environment which is held in its own temperature. The inter-qubit
+interaction is modeled by XY-Heisenberg model in the presence of spin-orbit
+interaction and inhomogeneous magnetic field. The dynamical behavior of
+entanglement and discord has been considered. The results show that, quantum
+discord is more robust than quantum entanglement, during the evolution. Also
+the asymmetric feature of quantum discord can be monitored by introducing the
+asymmetries due to inhomogeneity of magnetic field and temperature difference
+between the reservoirs. By employing proper parameters of the model, it is
+possible to maintain non-vanishing quantum correlation at high degree of
+temperature. The results can provide a useful recipe for studying of dynamical
+behavior of two-qubit systems such as trapped spin-electrons in coupled quantum
+dots.",1604.01786v2
+2016-06-16,Spin dynamics of counterrotating Kitaev spirals via duality,"Incommensurate spiral order is a common occurrence in frustrated magnetic
+insulators. Typically, all magnetic moments rotate uniformly, through the same
+wavevector. However the honeycomb iridates family Li2IrO3 shows an
+incommensurate order where spirals on neighboring sublattices are
+counter-rotating, giving each moment a different local environment.
+Theoretically describing its spin dynamics has remained a challenge: the Kitaev
+interactions proposed to stabilize this state, which arise from strong
+spin-orbit effects, induce magnon umklapp scattering processes in spin-wave
+theory. Here we propose an approach via a (Klein) duality transformation into a
+conventional spiral of a frustrated Heisenberg model, allowing a direct
+derivation of the dynamical structure factor. We analyze both Kitaev and
+Dzyaloshinskii-Moriya based models, both of which can stabilize counterrotating
+spirals, but with different spin dynamics, and we propose experimental tests to
+identify the origin of counterrotation.",1606.05356v2
+2016-09-05,Coarsening dynamics of topological defects in thin Permalloy films,"We study the dynamics of topological defects in the magnetic texture of
+rectangular Permalloy thin film elements during relaxation from random
+magnetization initial states. Our full micromagnetic simulations reveal complex
+defect dynamics during relaxation towards the stable Landau closure domain
+pattern, manifested as temporal power-law decay, with a system-size dependent
+cut-off time, of various quantities. These include the energy density of the
+system, and the number densities of the different kinds of topological defects
+present in the system. The related power-law exponents assume non-trivial
+values, and are found to be different for the different defect types. The
+exponents are robust against a moderate increase in the Gilbert damping
+constant and introduction of quenched structural disorder. We discuss details
+of the processes allowed by conservation of the winding number of the defects,
+underlying their complex coarsening dynamics.",1609.01094v1
+2016-10-03,Quench dynamics of spin-imbalanced Fermi-Hubbard model in one dimension,"We study a nonequilibrium dynamics of a one-dimensional spin-imbalanced
+Fermi-Hubbard model following a quantum quench of on-site interaction,
+realizable, for example, in Feshbach-resonant atomic Fermi gases. We focus on
+the post-quench evolution starting from the initial BCS and
+FuldeFerrell-Larkin-Ovchinnikov (FFLO) ground states and analyze the
+corresponding spin-singlet, spin-triplet, density-density, and
+magnetization-magnetization correlation functions. We find that beyond a
+light-cone crossover time, rich post-quench dynamics leads to thermalized and
+pre-thermalized stationary states that display strong dependence on the initial
+ground state. For initially gapped BCS state, the long-time stationary state
+resembles thermalization with the effective temperature set by the initial
+value of the Hubbard interaction. In contrast, while the initial gapless FFLO
+state reaches a stationary pre-thermalized form, it remains far from
+equilibrium. We suggest that such post-quench dynamics can be used as a
+fingerprint for identification and study of the FFLO phase.",1610.00670v2
+2016-12-19,Dynamical Multiferroicity,"An appealing mechanism for inducing multiferroicity in materials is the
+generation of electric polarization by a spatially varying magnetization that
+is coupled to the lattice through the spin-orbit interaction. Here we describe
+the reciprocal effect, in which a time-dependent electric polarization induces
+magnetization even in materials with no existing spin structure. We develop a
+formalism for this dynamical multiferroic effect in the case for which the
+polarization derives from optical phonons, and compute the strength of the
+phonon Zeeman effect, which is the solid-state equivalent of the
+well-established vibrational Zeeman effect in molecules, using density
+functional theory. We further show that a recently observed behavior -- the
+resonant excitation of a magnon by optically driven phonons -- is described by
+the formalism. Finally, we discuss examples of scenarios that are not driven by
+lattice dynamics and interpret the excitation of Dzyaloshinskii-Moriya-type
+electromagnons and the inverse Faraday effect from the viewpoint of dynamical
+multiferroicity.",1612.06331v2
+2017-01-20,Fast vortex wall motion in wide Permalloy strips from double switching of the vortex core,"We study vortex domain wall dynamics in wide Permalloy strips driven by
+applied magnetic fields and spin-polarized electric currents. As recently
+reported [V. Est\'evez and L. Laurson, Phys. Rev. B, 93, 064403 (2016)], for
+sufficiently wide strips and above a threshold field, periodic dynamics of the
+vortex core are localized in the vicinity of one of the strip edges, and the
+velocity drop typically observed for narrow strips is replaced by a
+high-velocity plateau. Here, we analyze this behavior in more detail by means
+of micromagnetic simulations. We show that the high-velocity plateau originates
+from a repeated double switching of the magnetic vortex core, underlying the
+periodic vortex core dynamics in the vicinity of the strip edge, i.e., the
+""attraction-repulsion"" effect. We also discuss the corresponding dynamics
+driven by spin-polarized currents, as well as the effect of including quenched
+random structural disorder to the system.",1701.05732v2
+2017-02-20,Spin-resolved dynamical conductance of correlated large-spin magnetic molecules,"The finite-frequency transport properties of a large-spin molecule attached
+to ferromagnetic contacts are studied theoretically in the Kondo regime. The
+focus is on the behavior of the dynamical conductance in the linear response
+regime, which is determined by using the numerical renormalization group
+method. It is shown that the dynamical conductance depends greatly on the
+magnetic configuration of the device and intrinsic parameters of the molecule.
+In particular, conductance exhibits characteristic features for frequencies
+corresponding to the dipolar and quadrupolar exchange fields resulting from the
+presence of spin-dependent tunneling. Moreover, a dynamical spin accumulation
+in the molecule, associated with the off-diagonal-in-spin component of the
+conductance, is predicted. This spin accumulation becomes enhanced with
+increasing the spin polarization of the leads, and it results in a nonmonotonic
+dependence of the conductance on frequency, with local maxima occurring for
+characteristic energy scales.",1702.05935v1
+2017-03-13,Dynamical amplification of magnetoresistances and Hall currents up to the THz regime,"Spin-orbit-related effects offer a highly promising route for reading and
+writing information in magnetic units of future devices. These phenomena rely
+not only on the static magnetization orientation but also on its dynamics to
+achieve fast switchings that can reach the THz range. In this work, we consider
+Co/Pt and Fe/W bilayers to show that accounting for the phase difference
+between different processes is crucial to the correct description of the
+dynamical currents. By tuning each system towards its ferromagnetic resonance,
+we reveal that dynamical spin Hall angles can non-trivially change sign and be
+boosted by over 500%, reaching giant values. We demonstrate that charge and
+spin pumping mechanisms can greatly magnify or dwindle the currents flowing
+through the system, influencing all kinds of magnetoresistive and Hall effects,
+thus impacting also dc and second harmonic experimental measurements.",1703.04493v2
+2017-04-09,Test particle energization and the anisotropic effects of dynamical MHD turbulence,"In this paper we analyze the effect of dynamical three-dimensional MHD
+turbulence on test particle acceleration, and compare how this evolving system
+affects particle energization by current sheets interaction, against
+frozen-in-time fields. To do this we analize the ensamble particle acceleration
+for static electromagnetic fields extracted from direct numerical simulations
+of the MHD equations, and compare with the dynamical fields. We show that a
+reduction in particle acceleration in the dynamical model results from the
+particle trapping in the field lines, which forces the particles to remain in a
+moving current sheet that suppress the longer exposure at the strong electric
+field gradients located between structures, which is an efficient particle
+acceleration mechanism. In addition, we analize the effect of anisotropy caused
+by the mean magnetic field. It is well known that for sufficiently strong
+external fields, the system suffers a transition towards a two-dimensional
+flow. This causes an increment in the size of the coherent structures,
+resulting in a magnetized state of the particles and the reduction of the
+particle energization.",1704.02642v1
+2018-03-16,Dynamically enhanced magnetic incommensurability: Effects of local dynamics on non-local spin-correlations in a strongly correlated metal,"We compute the spin susceptibility of the two-dimensional Hubbard model away
+from half-filling, and analyze the impact of frequency dependent vertex
+corrections as obtained from the dynamical mean field theory (DMFT). We find
+that the local dynamics captured by the DMFT vertex strongly affects non-local
+spin correlations, and thus the momentum dependence of the spin susceptibility.
+While the widely used random phase approximation yields commensurate
+N\'eel-type antiferromagnetism as the dominant instability over a wide doping
+range, the vertex corrections favor incommensurate ordering wave vectors away
+from $(\pi,\pi)$. Our results indicate that the connection between the magnetic
+ordering wave vector and the Fermi surface geometry, familiar for weakly
+interacting systems, can hold in a strongly correlated metal, too.",1803.06175v1
+2018-06-13,Dynamical response and dimensional crossover for spatially anisotropic antiferromagnets,"Theoretically challenging, the understanding of the dynamical response in
+quantum antiferromagnets is of great interest, in particular for both inelastic
+neutron scattering (INS) and nuclear magnetic resonance (NMR) experiments. In
+such a context, we theoretically address this question for
+quasi-one-dimensional quantum magnets, e.g. weakly coupled spin chains for
+which many compounds are available in Nature. In this class of systems, the
+dimensional crossover between a three-dimensional ordered regime at low
+temperature towards one-dimensional physics at higher temperature is a
+non-trivial issue, notably difficult concerning dynamical properties. Here we
+present a comprehensive theoretical study based on both analytical calculations
+(bosonization + random phase and self-consistent harmonic approximations) and
+numerical simulations (quantum Monte Carlo + stochastic analytic continuation)
+which allows us to describe the full temperature crossover for the NMR
+relaxation rate $1/T_1$, from one-dimensional Tomonaga-Luttinger liquid physics
+to the three-dimensional ordered regime, as a function of inter-chain
+couplings. The dynamical structure factor, directly probing the INS intensity,
+is also computed in the different regimes.",1806.04913v2
+2018-07-18,Observation of Transient Overcritical Currents in YBCO Thin Films using High-Speed Magneto-Optical Imaging and Dynamic Current Mapping,"The dynamics of transient current distributions in superconducting YBCO thin
+films were investigated during and immediately following an external field
+ramp, using high-speed (real-time) Magneto-Optical Imaging and calculation of
+dynamic current profiles. A number of qualitatively unique and previously
+unobserved features are seen in this novel analysis of the evolution of
+supercurrent during penetration. As magnetic field ramps up from zero, the
+dynamic current profile is characterized by strong peaks, the magnitude of
+which exceed the conventional critical current density (as determined from
+static current profiles). These peaks develop close to the sample edges,
+initially resembling screening currents but quickly growing in intensity as the
+external field increases. A discontinuity in field and current behaviour is
+newly observed, indicating a novel transition from increasing peak current
+toward relaxation behaviour. After this transition, the current peaks move
+toward the centre of the sample while reducing in intensity as magnetic
+vortices penetrate inward. This motion slows exponentially with time, with the
+current distribution in the long-time limit reducing to the expected Kim-model
+profile.",1807.06745v1
+2018-11-14,Microscopic Theory of Ultrafast Out-of-Equilibrium Dynamics in Magnetic Insulators. Unraveling the Magnon-Phonon Coupling,"The interaction between lattice and spins is at the heart of an extremely
+intriguing ultrafast dynamics in magnetic materials. In this work we formulate
+a general non-equilibrium theory that disentangles the complex interplay
+between them in a THz laser-excited antiferromagnetic insulator. The theory
+provides a quantitative description of the transient energy flow between the
+spin and lattice sub-systems, subject to magnon-phonon and phonon-phonon
+scatterings, giving rise to finite life-times of the quasiparticles and to the
+equilibration time of the system. We predict a novel kind of scattering process
+where two magnons of opposite polarizations decay into a phonon, previously
+omitted in the literature. The theory is combined with first-principle
+calculations and then applied to simulate a realistic dynamics of NiO. The main
+relaxation channels and hot spots in the reciprocal space, giving the strongest
+contribution to the energy transfer between phonons and magnons are identified.
+The diverse interaction strengths lead to distinct coupled dynamics of the
+lattice and spin systems and subsequently to different equilibration
+timescales.",1811.05841v1
+2018-11-21,The high-frequency dynamics of domain walls with strong Dzyaloshinskii-Moriya interaction,"Domain walls (DWs) in perpendicularly magnetized nanotracks (PMNTs) with
+interfacial Dzyaloshinskii-Moriya interaction (DMI) have become the primary
+objects of theoretical and experimental interest due to their technological
+suitability in spintronic nanodevices. Chiral DWs in PMNTs can be driven
+efficiently by the spin-orbit torque. However, the high-frequency dynamic
+behavior of the chiral DW has not been explored. In this work, using
+micromagnetic calculation, we have discovered a novel dynamic mode, the sway
+mode, of DWs under an out-of-plane high-frequency alternating current (AC)
+magnetic field in a PMNT with strong DMI. This dynamic phenomenon is strictly
+related with DMI-related boundary effect and can be understood in terms of the
+propagation of an amplitude-tuned spin wave in the DW plane. The spin wave
+exhibits some characteristic frequencies due to the space-confinement of DW.
+This work offers the possibility of a visual route for characterizing DMI.",1811.08590v1
+2019-03-16,Can the dynamical Lamb effect be observed in a superconducting circuit?,"The dynamical Lamb effect is predicted to arise in superconducting circuits
+when the coupling of a superconducting qubit with a resonator is periodically
+switched ""on"" and ""off"" nonadiabatically. We show that by using a
+superconducting circuit which allows to switch between longitudinal and
+transverse coupling of a qubit to a resonator, it is possible of to observe the
+dynamical Lamb effect. {The switching between longitudinal and transverse
+coupling can be achieved by modulating the magnetic flux through the circuit
+loops.} By solving the Schr\""{o}dinger equation for a qubit coupled to a
+resonator, we calculate the time evolution of the probability of excitation of
+the qubit and the creation of $n$ photons in the resonator due to the dynamical
+Lamb effect. The probability is maximum when the coupling is periodically
+switched between longitudinal and transverse using a square-wave or sinusoidal
+modulation of the magnetic flux with frequency equal to the sum of the average
+qubit and photon transition frequencies.",1903.06880v2
+2019-03-25,Quench dynamics of spin in quantum dots coupled to spin-polarized leads,"We investigate the quench dynamics of a quantum dot strongly coupled to
+spin-polarized ferromagnetic leads. The real-time evolution is calculated by
+means of the time-dependent density-matrix numerical renormalization group
+method implemented within the matrix product states framework. We examine the
+system's response to a quench in the spin-dependent coupling strength to
+ferromagnetic leads as well as in the position of the dot's orbital level. The
+spin dynamics is analyzed by calculating the time-dependent expectation values
+of the quantum dot's magnetization and occupation. Based on these, we determine
+the time-dependence of a ferromagnetic-contact-induced exchange field and
+predict its nonmonotonic build-up. In particular, two time scales are
+identified, describing the development of the exchange field and the dot's
+magnetization sign change. Finally, we study the effects of finite temperature
+on the dynamical behavior of the system.",1903.10381v1
+2019-08-05,The dynamic critical exponent $z$ of the three-dimensional Ising universality class: Monte Carlo simulations of the improved Blume-Capel model,"We study purely dissipative relaxational dynamics in the three-dimensional
+Ising universality class. To this end, we simulate the improved Blume-Capel
+model on the simple cubic lattice by using local algorithms. We perform a
+finite size scaling analysis of the integrated autocorrelation time of the
+magnetic susceptibility in equilibrium at the critical point. We obtain
+$z=2.0245(15)$ for the dynamic critical exponent. As a complement, fully
+magnetized configurations are suddenly quenched to the critical temperature,
+giving consistent results for the dynamic critical exponent. Furthermore, our
+estimate of $z$ is fully consistent with recent field theoretic results.",1908.01702v2
+2020-04-17,Scaling properties of the dynamics at first-order quantum transitions when boundary conditions favor one of the two phases,"We address the out-of-equilibrium dynamics of a many-body system when one of
+its Hamiltonian parameters is driven across a first-order quantum transition
+(FOQT). In particular, we consider systems subject to fixed boundary
+conditions, favoring one of the two phases separated by the FOQT: more
+precisely, boundary conditions that favor the same magnetized phase (EFBC) or
+opposite phases (OFBC) at the two ends of the chain. These issues are
+investigated within the paradigmatic one-dimensional quantum Ising model, in
+which FOQTs are driven by the longitudinal magnetic field h. We study the
+dynamic behavior for an instantaneous quench and for a protocol in which h is
+slowly varied across the FOQT. We develop a dynamic finite-size scaling theory
+for both EFBC and OFBC, which displays some remarkable differences with respect
+to the case of neutral boundary conditions. The corresponding relevant time
+scale shows a qualitative different size dependence in the two cases: it
+increases exponentially with the size in the case of EFBC, and as a power of
+the size in the case of OFBC.",2004.08360v1
+2020-07-03,Dynamic spin-triplet order induced by alternating electric fields in superconductor-ferromagnet-superconductor Josephson junctions,"Dynamic states offer extended possibilities to control the properties of
+quantum matter. Recent efforts are focused on studying the ordered states which
+appear exclusively under the time-dependent drives. Here we demonstrate a class
+of systems which feature dynamic spin-triplet superconducting order stimulated
+by the alternating electric field. The effect is based on the interplay of
+ferromagnetism, interfacial spin-orbital coupling (SOC) and the condensate
+motion driven by the field, which converts hidden static p-wave order, produced
+by the joint action of the ferromagnetism and the SOC, into dynamical s-wave
+equal-spin triplet correlations. We demonstrate that the critical current of
+Josephson junctions hosting these states is proportional to the electromagnetic
+power, supplied either by the external irradiation or by the ac current source.
+Based on these unusual properties we propose the scheme of a Josephson
+transistor which can be switched by the ac voltage and demonstrates an
+even-numbered sequence of Shapiro steps. Combining the photo-active Josephson
+junctions with recently discovered Josephson phase batteries we find
+photo-magnetic SQUID devices which can generate spontaneous magnetic fields
+while being exposed to irradiation.",2007.01805v2
+2021-02-24,Finite-momentum energy dynamics in a Kitaev magnet,"We study the energy-density dynamics at finite momentum of the
+two-dimensional Kitaev spin-model on the honeycomb lattice. Due to
+fractionalization of magnetic moments, the energy relaxation occurs through
+mobile Majorana matter, coupled to a static $\mathbb{Z}_2$ gauge field. At
+finite temperatures, the $\mathbb{Z}_2$ flux excitations act as an emergent
+disorder, which strongly affects the energy dynamics. We show that sufficiently
+far above the flux proliferation temperature, but not yet in the classical
+regime, gauge disorder modifies the coherent low-temperature energy-density
+dynamics into a form which is almost diffusive, with hydrodynamic momentum
+scaling of a diffusion-kernel, which however remains retarded, primarily due to
+the presence of two distinct relaxation channels of particle-hole and
+particle-particle nature. Relations to thermal conductivity are clarified. Our
+analysis is based on complementary calculations in the low-temperature
+homogeneous gauge and a mean-field treatment of thermal gauge fluctuations,
+valid at intermediate and high temperatures.",2102.12492v1
+2021-03-03,THz Field-induced Spin Dynamics in Ferrimagnetic Iron Garnets,"THz magnetization dynamics is excited in ferrimagnetic thulium iron garnet
+with a picosecond, single-cycle magnetic field pulse and seen as a
+high-frequency modulation of the magneto-optical Faraday effect. Data analysis
+combined with numerical modelling and evaluation of the effective Lagrangian
+allow us to conclude that the dynamics corresponds to the exchange mode excited
+by Zeeman interaction of the THz field with the antiferromagnetically coupled
+spins. We argue that THz-pump IR-probe experiments on ferrimagnets offer a
+unique tool for quantitative studies of dynamics and mechanisms to control
+antiferromagnetically coupled spins.",2103.02449v1
+2021-05-24,Response Dynamics of Alkali Metal-Noble Gas Hybrid Trispin System,"With numerical calculation of coupled Bloch equations, we have simulated the
+spin dynamics of nuclear magnetic resonance gyroscope based on alkali
+metal-noble gas hybrid trispin system. From the perspective of damping harmonic
+oscillator, a thorough analysis of the response dynamics is demonstrated. The
+simulation results shows a linear increasing response of gyroscope signal while
+the noblge gas nuclear spin magnetization and alkali atomic spin lifetime
+parameters are at the over damping condition. An upper limit of response is
+imposed on the NMR gyroscope signal due to the inherent dynamics of the hybrid
+trispin system. The results agrees with present available experimental results
+and provide useful guidings for future experiments.",2105.11124v2
+2021-06-15,Ultrafast Optical Control of Magnetic Order and Fermi Surface Topology at a Quantum Critical Point,"Designing material properties on demand has important implications to
+potential future technological applications. While theoretically it is always
+possible to tune various intrinsic energy scales, there are fundamental
+limitations to this approach in experiment. In recent years, ultrafast
+spectroscopy has evolved as a promising tool to use light to dynamically induce
+non-trivial electronic states of matter. Here we theoretically investigate
+light pulse driven dynamics in a Kondo system close to quantum criticality. We
+show, that light can dehybridize the local Kondo screening and induce magnetic
+order out of a previously paramagnetic state. We demonstrate that, depending on
+the laser pulse field parameters, it is possible to deconfine the Kondo singlet
+and thereby induce second order phase transition to a dynamically ordered
+state, as well as a dynamic Lifshitz transition that changes the Fermi surface
+topology from hole- to electron-like.",2106.08220v1
+2021-07-05,Dynamical signatures of point-gap Weyl semimetal,"We demonstrate a few unique dynamical properties of point-gap Weyl semimetal,
+an intrinsic non-Hermitian topological phase in three dimensions. We consider a
+concrete model where a pair of Weyl points reside on the imaginary axis of the
+complex energy plane, opening up a point gap characterized by a topological
+invariant, the three-winding number $W_3$. This gives rise to surface spectra
+and dynamical responses that differ fundamentally from those in Hermitian Weyl
+semimetals. First, we predict a time-dependent current flow along the magnetic
+field in the absence of an electric field, in sharp contrast to the current
+driven by the chiral anomaly, which requires both electric and magnetic fields.
+Second, we reveal a novel type of boundary-skin mode in the wire geometry which
+becomes localized at two corners of the wire cross section. We explain its
+origin and show its experimental signatures in wave-packet dynamics.",2107.02135v3
+2021-11-18,Floquet dynamical quantum phase transitions under synchronized periodic driving,"We study a generic class of fermionic two-band models under synchronized
+periodic driving, i.e., with the different terms in a Hamiltonian subject to
+periodic drives with the same frequency and phase. With all modes initially in
+a maximally mixed state, the synchronized drive is found to produce nonperiodic
+patterns of dynamical quantum phase transitions, with their appearance
+determined by an interplay of the band structure and the frequency of the
+drive. A case study of the anisotropic XY chain in a transverse magnetic field,
+transcribed to an effective two-band model, shows that the modes come with
+quantized geometric phases, allowing for the construction of an effective
+dynamical order parameter. Numerical studies in the limit of a strong magnetic
+field reveal distinct signals of precursors of dynamical quantum phase
+transitions also when the initial state of the XY chain is perturbed slightly
+away from maximal mixing, suggesting that the transitions may be accessible
+experimentally. A blueprint for an experiment built around laser-trapped
+circular Rydberg atoms is proposed.",2111.09926v3
+2021-12-22,Machine learning nonequilibrium electron forces for adiabatic spin dynamics,"We present a generalized potential theory of nonequilibrium torques for the
+Landau-Lifshitz equation. The general formulation of exchange forces in terms
+of two potential energies allows for the implementation of accurate machine
+learning models for adiabatic spin dynamics of out-of-equilibrium itinerant
+magnetic systems. To demonstrate our approach, we develop a deep-learning
+neural network that successfully learns the forces in a driven s-d model
+computed from the nonequilibrium Green's function method. We show that the
+Landau-Lifshitz dynamics simulations with forces predicted from the neural-net
+model accurately reproduce the voltage-driven domain-wall propagation. Our work
+opens a new avenue for multi-scale modeling of nonequilibrium dynamical
+phenomena in itinerant magnets and spintronics based on machine-learning
+models.",2112.12124v1
+2022-02-09,A Nonlinear Proportional Integral Disturbance Observer and Motion Control Technique for Permanent Magnet Synchronous Motors,"In this paper, we present a Nonlinear-Proportional Integrator (N-PI)
+disturbance observer (DOB) to enhance the motion tracking of the performance of
+a surface-mounted Permanent Magnet Synchronous Motor (SPMSM) in rapidly speed
+varying regions. By presenting an N-PI-DOB for load torque estimation with
+torque modulation technique, we show that the tracking error dynamics of
+angular position/velocity are coupled with tracking errors of currents loop and
+estimation errors. After analyzing disturbances of currents tracking error
+dynamics, we design the N-PI-DOB and Lyapunov-based nonlinear currents
+controller to enhance the motion tracking performances. With these N-PI-DOBs
+and motion controllers, we analyze the stability of motion tracking error
+dynamics and estimation error dynamics. We experimentally perform a comparative
+study with/without the N-PI-DOB to verify the effectiveness of the proposed
+method in the condition of the unknown load torque and rapidly speed-varying.",2202.04594v1
+2022-02-10,Dynamical quantum phase transition in diamond: applications in quantum metrology,"Nonequilibrium dynamics is a paramount scenario for studying quantum systems.
+The emergence of new features with no equilibrium counterpart, such as
+dynamical quantum phase transition (DQPT), has attracted wide attention. In
+this work, we depart from the well known Ising model and showcase an
+experimentally accessible configuration of a negatively charged
+Nitrogen-Vacancy center that interacts with nearby Carbon-13 nuclear spins. We
+provide new insights into this system in the context of DQPT. We show that
+nuclear spins undergo DQPT by appropriately choosing the relation between the
+transverse and longitudinal components of an external magnetic field.
+Furthermore, we can steer the DQPT via a time-dependent longitudinal magnetic
+field and apply this control to enhance the estimation of the coupling strength
+between the nuclear spins. Moreover, we propose a novel quenched dynamics that
+originates from the rotation of the central electron spin, which controls the
+DQPT relying on the anisotropy of the hyperfine coupling.",2202.05216v1
+2022-02-22,Dynamical scaling as a signature of multiple phase competition in Yb$_2$Ti$_2$O$_7$,"$\rm Yb_2Ti_2O_7$ is a celebrated example of a pyrochlore magnet with
+highly-frustrated, anisotropic exchange interactions. To date, attention has
+largely focused on its unusual, static properties, many of which can be
+understood as coming from the competition between different types of magnetic
+order. Here we use inelastic neutron scattering with exceptionally high energy
+resolution to explore the dynamical properties of $\rm Yb_2Ti_2O_7$. We find
+that spin correlations exhibit dynamical scaling, analogous to behavior found
+near to a quantum critical point. We show that the observed scaling collapse
+can be explained within a phenomenological theory of multiple--phase
+competition, and confirm that a scaling collapse is also seen in
+semi--classical simulations of a microscopic model of $\rm Yb_2Ti_2O_7$. These
+results suggest a general picture for dynamics in systems with competing ground
+states.",2202.11085v1
+2022-06-17,Dynamics of a pair of magnetic dipoles with nonreciprocal interactions due to a moving conductor,"Recently it was demonstrated theoretically and experimentally that the
+presence of a moving conductor can break the reciprocity in the interactions
+between magnetic dipoles. In this article we investigate the influence of
+nonreciprocity on the dynamics of a pair of rigid XY dipoles, which have been
+realized in experiments. In particular, we focus on the energy nonconservation,
+which is a consequence of the nonreciprocity. We find that the dynamics indeed
+has regimes, wherein the kinetic energy grows quadratically. However, whether
+energy absorption occurs depends strongly on the initial conditions on the
+dipoles. Simulations for various initial conditions reveal an intricate
+dependence, resulting in a rich structure of the energy absorbing regime in the
+initial condition space. Nevertheless, we provide a qualitative explanation of
+these observations, interpreting the absence of energy absorption as a
+confinement of the dynamics in phase space.",2206.08765v2
+2022-07-06,Field-driven side-by-side magnetic domain wall dynamics in ferromagnetic nanostrips,"There has been a plethora of studies on domain wall dynamics in magnetic
+nanostrips, mainly because of its versatile non-linear physics and potential
+applications in data storage devices. However, most of the studies focus on
+out-of-plane domain walls or in-plane head-to-head (tail-to-tail) domain walls.
+Here, we numerically study the field-driven dynamics of in-plane side-by-side
+domain walls in ferromagnetic strips, which can be stable in the presence of an
+in-plane easy-axis anisotropy transverse to the strip. The domain walls move in
+a rigid-body manner at low field, and show complex Walker breakdown behavior at
+high field. We observe a multi-step Walker breakdown through vortex nucleation
+in wide strips. In the presence of Dzyaloshinskii-Moriya interaction (DMI), the
+first Walker breakdown field first decreases then increases with interfacial
+DMI, while keeps increasing with bulk DMI. These findings complement the
+current understanding on domain wall dynamics.",2207.02494v1
+2022-11-10,Waves in planetary dynamos,"This Special Topic focuses on magnetohydrodynamic (MHD) processes in deep
+interiors of planets, in which their fluid dynamos are in operation. The
+dynamo-generated, global, magnetic fields provide a background for our
+solar-terrestrial environment. Probing the processes within the dynamos is a
+significant theoretical and computational challenge and any window into
+interior dynamics greatly increases our understanding. Such a window is
+provided by exploring rapid dynamics, particularly MHD waves about the
+dynamo-defined basic state. This field is the subject of current attention as
+geophysical observations and numerical modellings advance. We give here
+particular attention to torsional Alfv\'{e}n waves/oscillations and magnetic
+Rossby waves, which may be regarded as typical axisymmetric and nonaxisymmetric
+modes, respectively, amongst a wide variety of wave classes of the
+rapidly-rotating MHD fluids. The excitation of those waves is being evidenced
+for the geodynamo, whilst also being suggested for Jupiter. We shall overview
+their dynamics, summarise our current understanding, and give open questions
+for future perspectives.",2211.05270v1
+2022-12-16,Relaxation dynamics of an unlike spin pair system,"Redfield master equation was applied to study the dynamics of an ensemble of
+interacting pair of unlike spins at room temperature. This spin quantum system
+is a workbench quantum model to analyze the relaxation dynamics of a
+heteronuclear two-level spin system interacting by a pure dipole-dipole
+coupling. Expressions for the density matrix elements and their relaxation rate
+constants of each coherence order were computed. In addition, the solutions
+were evaluated considering three initial quantum states, and the theoretical
+predictions, such as multi-exponential evolutions and enhancement, are
+behaviors that the solutions preserve and agree with previous studies performed
+for magnetization time evolutions. Moreover, the solutions computed to predict
+the dynamics of the longitudinal magnetization avoid the disagreement reported
+by I. Solomon.",2212.08747v2
+2023-02-06,Accelerated Dynamic Magnetic Resonance Imaging from Spatial-Subspace Reconstructions (SPARS),"Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) ideally
+requires a high spatial and high temporal resolution, but hardware limitations
+prevent acquisitions from simultaneously achieving both. Existing image
+reconstruction techniques can artificially create spatial resolution at a given
+temporal resolution by estimating data that is not acquired, but, ultimately,
+spatial details are sacrificed at very high acceleration rates. The purpose of
+this paper is to introduce the concept of spatial subspace reconstructions
+(SPARS) and demonstrate its ability to reconstruct high spatial resolution
+dynamic images from as few as one acquired radial spoke per dynamic frame.
+Briefly, a low-temporal-high-spatial resolution organization of the acquired
+raw data is used to estimate a spatial subspace in which the
+high-temporal-high-spatial ground truth data resides. This subspace is then
+used to estimate entire images from single k-space spokes. In both simulated
+and human in-vivo data, the proposed SPARS reconstruction method outperformed
+standard GRASP and GRASP-Pro reconstruction, providing a shorter reconstruction
+time and yielding higher accuracy from both a spatial and temporal perspective.",2302.02564v3
+2023-03-23,Dualities of 3D $\mathcal{N}=1$ SQCD from Branes and non-SUSY deformations,"We study the dynamics of an 'electric' $\mathcal{N}=1$ 3D
+$U(N_c)_{k,k+\frac{N_c}{2}}$ SQCD theory. By embedding the theory in string
+theory, we propose that the theory admits a 'magnetic' dual and analyse the low
+energy dynamics of the theory using its dual. When $\frac{N_f}{2}
+\ge\frac{N_c}{2}-k$ the IR dynamics is described by either a TQFT for large
+quark masses, or a Grassmanian and a Wess-Zumino (WZ) term for small masses. We
+also consider non-supersymmetric mass deformations and RG flows in the vicinity
+of the SUSY point and find agreement between the IR of the electric and its
+magnetic dual. When $\frac{N_f}{2} < \frac{N_c}{2}-k$ supersymmetry is broken
+and the IR dynamics is a described by a TQFT accompanied by a Goldstino. We
+also discuss SQCD theories based on $SO$/$USp$ gauge groups.",2303.13597v2
+2023-03-31,Characterization and Coherent Control of Spin Qubits with Modulated Electron Beam and Resonator,"The coherent dynamics and control of spin qubits are essential requirements
+for quantum technology. A prominent challenge for coherent control of a spin
+qubit in a set of qubits is the destructive effect of the applied magnetic
+field on the coherent dynamics of neighbouring qubits due to its spatial
+extension. We propose a novel scheme to characterize the coherent dynamics of
+these quantum systems and to coherently control them using a magnetic field.
+Our scheme consists of a resonator that encompasses the desired quantum system
+and a modulated electron beam that passes through the resonator in close
+proximity to the quantum system of interest. The dynamics of the system is
+obtained by solving the Lindblad master equation. To verify the reliability of
+our model, we tested the model on a Potassium atom, $^{41}$K and NV$^-$ centre
+in Diamond. The results show that by properly controlling the parameters of the
+resonator and the electron beam, the coherence and decoherence rates of these
+quantum systems can be improved. Our model has the potential to be used for
+characterizing different types of spin-based quantum systems, and implementing
+quantum logic gates for quantum computation.",2303.17952v1
+2023-05-03,An overview of the spin dynamics of antiferromagnetic Mn$_5$Si$_3$,"The metallic compound Mn$_5$Si$_3$ hosts a series of antiferromagnetic phases
+which can be controlled by external stimuli such as temperature and magnetic
+field. In this work, we investigate the spin-excitation spectrum of bulk
+Mn$_5$Si$_3$ by combining inelastic neutron scattering measurements and density
+functional theory calculations. We study the evolution of the dynamical
+response under external parameters and demonstrate that the spin dynamics of
+each phase is robust against any combination of temperature and magnetic field.
+In particular, the high-energy spin dynamics is very characteristic of the
+different phases consisting of either spin waves or broad fluctuations
+patterns.",2305.02409v2
+2023-05-04,Dynamics of magnetoelastic robots in water-saturated granular beds,"We investigate the dynamics of a magnetoelastic robot with a dipolar magnetic
+head and a slender elastic body as it performs undulatory strokes and burrows
+through water-saturated granular beds. The robot is actuated by an oscillating
+magnetic field and moves forward when the stroke amplitude increases above a
+critical threshold. By visualizing the medium, we show that the undulating body
+fluidizes the bed, resulting in the appearance of a dynamic burrow, which
+rapidly closes in behind the moving robot as the medium loses energy. We
+investigate the applicability of Lighthill's elongated body theory of fish
+locomotion, and estimate the contribution of thrust generated by the undulating
+body and the drag incorporating the granular volume fraction-dependent
+effective viscosity of the medium. The projected speeds are found to be
+consistent with the measured speeds over a range of frequencies and amplitudes
+above the onset of forward motion. However, systematic deviations are found to
+grow with increasing driving, pointing to a need for further sophisticated
+modelling of the medium-structure interactions.",2305.02903v2
+2023-05-17,Substantial reduction of write-error rate for voltage-controlled magnetoresistive random access memory by in-plane demagnetizing field and voltage-induced negative out-of-plane anisotropy field,"Voltage-controlled magnetoresistive random access memory (VC-MRAM) based on
+voltage-induced dynamic switching in magnetic tunnel junctions (MTJs) is a
+promising ultimate non-volatile memory with ultralow power consumption.
+However, the dynamic switching in a conventional MTJ is accompanied by a
+relatively high write error rate (WER), hindering the reliable operation of
+VC-MRAM. Here, we propose a reliable writing scheme using the in-plane
+demagnetizing field (IDF) and voltage-induced negative out-of-plane anisotropy
+field (NOAF). Numerical simulations based on macrospin model demonstrate that
+the voltage-induced NOAF modifies the switching dynamics and increases the
+torque due to the IDF, thereby reducing the switching time. The IDF and
+voltage-induced NOAF also reduce the mean energy difference between the
+magnetization direction at the end of the pulse and the equilibrium direction.
+As a result, an appropriate combination of the IDF and voltage-induced NOAF
+reduces the WER by one order of magnitude compared with that of the dynamic
+switching in a conventional MTJ.",2305.09883v1
+2023-06-20,"Magnetoelectric fractals, Magnetoelectric parametric resonance and Hopf bifurcation","In the present work, we study the dynamics of a magnetic nanoparticle coupled
+through the magnetoelectric coupling to the ferroelectric crystal. The model of
+our interest is nonlinear, and we explore the problem under different limits of
+weak and strong linearity. By applying two electric fields with different
+frequencies, we control the form of the confinement potential of the
+ferroelectric subsystem and realize different types of dynamics. We proved that
+the system is more sensitive to magnetoelectric coupling in the case of
+double-well potential. In particular, in the case of strong nonlinearity,
+arbitrary small values of magnetoelectric coupling lead to chaotic dynamics. In
+essence, magnetoelectric coupling plays a role akin to the small perturbations
+destroying invariant tors according to the KAM theorem. We showed that
+bifurcations in the system are of Hopf's type. We observed the formation of
+magnetoelectric fractals in the system. In the limit of weak nonlinearity, we
+studied a problem of parametric nonlinear resonance and enhancement of magnetic
+oscillations through magnetoelectric coupling.",2306.13110v1
+2023-08-23,Magnetic-order-mediated carrier and phonon dynamics in MnBi2Te4,"We investigate the quasiparticle dynamics in MnBi2Te4 single crystal using
+the ultrafast optical spectroscopy. Our results show that there exist anomalous
+dynamical optical responses below the antiferromagnetic (AFM) ordering
+temperature TN. In specific, we reveal that both the initial carrier decay and
+recombination processes can be modulated via introducing the AFM order in
+sub-picosecond and picosecond timescales, respectively. We also discover a long
+relaxation process emerging below TN with a timescale approaching to the
+nanosecond regime, and can be attributed to the T-dependent spin-lattice
+interaction. There also emerges an unusual phonon energy renormalization below
+TN , which is found to arise from its coupling the spin degree via the exchange
+interaction and magnetic anisotropy. Our findings provide key information for
+understanding the dynamical properties of non-equilibrium carrier, spin and
+lattice in MnBi2Te4.",2308.11935v1
+2023-08-28,Spacetime dynamics of chiral magnetic currents in a hot non-Abelian plasma,"The correlations of electric currents in hot non-Abelian plasma are
+responsible for the experimental manifestations of the chiral magnetic effect
+(CME) in heavy-ion collisions. We evaluate these correlations using holography,
+and show that they are driven by large-scale topological fluctuations. In a
+non-Abelian plasma with chiral fermions, local axial charge can be generated
+either by topological fluctuations (creating domains with nonzero Chern-Simons
+number) or by thermal fluctuations. Within holography, we investigate the
+dynamical creation of the axial charge and isolate the imprint of the
+topological dynamics on the spatial correlations of electric current. In
+particular, we show that the spatial extent of the current correlation is quite
+large ($\sim 1\ {\rm fm}$) and grows with time, which is consistent with
+sphaleronlike dynamics. We provide numerical estimates for this spatial size
+that can be used as an input in phenomenological analyses.",2308.14825v2
+2023-09-22,Dynamical defects in a two-dimensional Wigner crystal: self-doping and kinetic magnetism,"We study the quantum dynamics of interstitials and vacancies in a
+two-dimensional Wigner crystal (WC) using a semi-classical instanton method
+that is asymptotically exact at low density, i.e., in the $r_s\to \infty$
+limit. The dynamics of these point defects mediates magnetism with much higher
+energy scales than the exchange energies of the pure WC. Via exact
+diagonalization of the derived effective Hamiltonians in the single-defect
+sectors, we find the dynamical corrections to the defect energies. The
+resulting expression for the interstitial (vacancy) energy extrapolates to 0 at
+$r_s = r_{\rm mit} \approx 70$ ($r_s \approx 30$), suggestive of a self-doping
+instability to a partially melted WC for some range of $r_s$ below $r_{\rm
+mit}$. We thus propose a ""metallic electron crystal'' phase of the
+two-dimensional electron gas at intermediate densities between a low density
+insulating WC and a high density Fermi fluid.",2309.13121v2
+2023-11-01,Coupled spin-lattice dynamics from the tight-binding electronic structure,"We developed a method which performs the coupled adiabatic spin and lattice
+dynamics based on the tight-binding electronic structure model, where the
+intrinsic magnetic field and ionic forces are calculated from the converged
+self-consistent electronic structure at every time step. By doing so, this
+method allows us to explore limits where the physics described by a
+parameterized spin-lattice Hamiltonian is no longer accurate. We demonstrate
+how the lattice dynamics is strongly influenced by the underlying magnetic
+configuration, where disorder is able to induce significant lattice
+distortions. The presented method requires significantly less computational
+resources than ab initio methods, such as time-dependent density functional
+theory (TD-DFT). Compared to parameterized Hamiltonian-based methods, it also
+describes more accurately the dynamics of the coupled spin and lattice degrees
+of freedom, which becomes important outside of the regime of small lattice and
+spin fluctuations.",2311.00765v1
+2024-01-19,Diversity of Ultrafast Spin Dynamics Near the Tricritical Point in a Ferrimagnetic Gd/FeCo Multilayer,"It is found that subtle changes in the external magnetic field and
+temperature result in dramatic changes in the ultrafast response of spins to a
+femtosecond laser excitation in a ferrimagnetic Gd/FeCo multilayer. A total of
+six distinct types of spin dynamics were observed and explained by considering
+the spin-flop transition to the noncollinear phase and the concept of a
+tricritical point in the $H$-$T$ phase diagram. A particularly interesting type
+of dynamics is the exchange-driven reversal. These exchange-driven dynamics
+provide new insights into the tricritical point, which is shown to separate two
+thermodynamically distinct noncollinear phases with the transition-metal
+magnetization pointing on adjacent sides of the anisotropy plane.",2401.10671v1
+2024-01-25,Dynamic image reconstruction in MPI with RESESOP-Kaczmarz,"In Magnetic Particle Imaging (MPI), it is typically assumed that the studied
+specimen is stationary during the data acquisition. In practical applications
+however, the searched-for 3D distribution of the magnetic nanoparticles might
+show a dynamic behavior, caused by e.g. breathing or movement of the blood.
+Neglecting those dynamics during the reconstruction step results in motion
+artifacts and a reduced image quality.
+  This article addresses the challenge of capturing high quality images in the
+presence of motion. A promising technique provides the Regularized Sequential
+Subspace Optimization (RESESOP) algorithm, which takes dynamics as model
+inexactness into account, significantly improving reconstruction compared to
+standard static algorithms like regularized Kaczmarz. Notably, this algorithm
+operates with minimal prior information and the method allows for subframe
+reconstruction, making it suitable for scenarios with rapid particle movement.
+The performance of the proposed method is demonstrated on both simulated and
+real data sets.",2401.14202v1
+2024-02-01,Longtime dynamics for the Landau Hamiltonian with a time dependent magnetic field,"We consider a modulated magnetic field, $B(t) = B_0 +\varepsilon f(\omega
+t)$, perpendicular to a fixed plane, where $B_0$ is constant, $\varepsilon>0$
+and $f$ a periodic function on the torus ${\mathbb T}^n$. Our aim is to study
+classical and quantum dynamics for the corresponding Landau Hamiltonian. It
+turns out that the results depend strongly on the chosen gauge. For the Landau
+gauge the position observable is unbounded for ""almost all"" non resonant
+frequencies $\omega$. On the contrary, for the symmetric gauge we obtain that,
+for ""almost all"" non resonant frequencies $\omega$, the Landau Hamiltonian is
+reducible to a two dimensional harmonic oscillator and thus gives rise to
+bounded dynamics. The proofs use KAM algorithms for the classical dynamics.
+Quantum applications are given. In particular, the Floquet spectrum is
+absolutely continuous in the Landau gauge while it is discrete, of finite
+multiplicity, in symmetric gauge.",2402.00428v1
+1996-09-23,Gravitational Dynamics of Cold Matter using the Deformation Tensor,"In this paper we present a new local Lagrangian approximation to the
+gravitational dynamics of cold matter. We describe the dynamics of a Lagrangian
+fluid element through only one quantity, the deformation tensor. We show that
+this tensor is clearly suited to the study of gravitational dynamics and,
+moreover, that knowing its evolution is enough to completely describe a fluid
+element. Our approximate dynamics treat exactly the conservation of mass, of
+the velocity divergence and of the shear and is exact in the case of planar,
+cylindrical and spherical collapses. It also reproduces very accurately the
+evolution of all dynamical quantities for a very wide class of initial
+conditions as illustrated by a detailed comparison with the homogeneous
+ellipsoid model. Beside, we highlight, for the first time, the important
+dynamical role played by the Newtonian counterpart of the magnetic part of the
+Weyl tensor.",9609156v1
+1996-11-23,Nonequilibrium Phase Transition in the Kinetic Ising model: Critical Slowing Down and Specific-heat Singularity,"The nonequilibrium dynamic phase transition, in the kinetic Ising model in
+presence of an oscillating magnetic field, has been studied both by Monte Carlo
+simulation and by solving numerically the mean field dynamic equation of motion
+for the average magnetisation. In both the cases, the Debye 'relaxation'
+behaviour of the dynamic order parameter has been observed and the 'relaxation
+time' is found to diverge near the dynamic transition point. The Debye
+relaxation of the dynamic order parameter and the power law divergence of the
+relaxation time have been obtained from a very approximate solution of the mean
+field dynamic equation. The temperature variation of appropiately defined
+'specific-heat' is studied by Monte Carlo simulation near the transition point.
+The specific-heat has been observed to diverge near the dynamic transition
+point.",9611181v1
+1997-01-24,Nonequilibrium phase transition in the kinetic Ising model: Divergences of fluctuations and responses near the transition point,"The nonequilibrium dynamic phase transition, in the kinetic Ising model in
+presence of an oscillating magnetic field, has been studied by Monte Carlo
+simulation. The fluctuation of dynamic order parameter has been studied as a
+function of temperature near the dynamic transition point. The temperature
+variation of appropriately defined `susceptibility' has also been studied near
+the dynamic transition point. Similarly, fluctuation of energy and
+appropriately defined `specific-heat' have been studied as a function of
+temperature near the dynamic transition point. In both the cases, the
+fluctuations (of dynamic order parameter and energy) and the corresponding
+responses diverge (as power law fashion) near the dynamic transition point with
+similar critical behavior (with identical exponent values).",9701180v2
+1997-05-20,Current-induced vortex dynamics in Josephson-junction arrays: Imaging experiments and model simulations,"We study the dynamics of current-biased Josephson-junction arrays with a
+magnetic penetration depth smaller than the lattice spacing. We compare the
+dynamics imaged by low-temperature scanning electron microscopy to the vortex
+dynamics obtained from model calculations based on the resistively-shunted
+junction model, in combination with Maxwell's equations. We find three bias
+current regions with fundamentally different array dynamics. The first region
+is the subcritical region, i.e. below the array critical current I_c. The
+second, for currents I above I_c, is a ""vortex region"", in which the response
+is determined by the vortex degrees of freedom. In this region, the dynamics is
+characterized by spatial domains where vortices and antivortices move across
+the array in opposite directions in adjacent rows and by transverse voltage
+fluctuations. In the third, for still higher currents, the dynamics is
+dominated by coherent-phase motion, and the current-voltage characteristics are
+linear.",9705194v1
+1999-02-10,Low Temperature Static and Dynamic Behavior of the Two-Dimensional Easy-Axis Heisenberg Model,"We apply the self-consistent harmonic approximation (SCHA) to study static
+and dynamic properties of the two-dimensional classical Heisenberg model with
+easy-axis anisotropy. The static properties obtained are magnetization and spin
+wave energy as functions of temperature, and the critical temperature as a
+function of the easy-axis anisotropy. We also calculate the dynamic correlation
+functions using the SCHA renormalized spin wave energy. Our analytical results,
+for both static properties and dynamic correlation functions, are compared to
+numerical simulation data combining cluster-Monte Carlo algorithms and Spin
+Dynamics. The comparison allows us to conclude that far below the transition
+temperature, where the SCHA is valid, spin waves are responsible for all
+relevant features observed in the numerical simulation data; topological
+excitations do not seem to contribute appreciably. For temperatures closer to
+the transition temperature, there are differences between the dynamic
+correlation functions from SCHA theory and Spin Dynamics; these may be due to
+the presence of domain walls and solitons.",9902149v1
+2006-03-20,Local and cluster critical dynamics of the 3d random-site Ising model,"We present the results of Monte Carlo simulations for the critical dynamics
+of the three-dimensional site-diluted quenched Ising model. Three different
+dynamics are considered, these correspond to the local update Metropolis scheme
+as well as to the Swendsen-Wang and Wolff cluster algorithms. The lattice sizes
+of L=10-96 are analysed by a finite-size-scaling technique. The site dilution
+concentration p=0.85 was chosen to minimize the correction-to-scaling effects.
+We calculate numerical values of the dynamical critical exponents for the
+integrated and exponential autocorrelation times for energy and magnetization.
+As expected, cluster algorithms are characterized by lower values of dynamical
+critical exponent than the local one: also in the case of dilution critical
+slowing down is more pronounced for the Metropolis algorithm. However, the
+striking feature of our estimates is that they suggest that dilution leads to
+decrease of the dynamical critical exponent for the cluster algorithms. This
+phenomenon is quite opposite to the local dynamics, where dilution enhances
+critical slowing down.",0603521v1
+2008-12-26,Thermalization dynamics close to a quantum phase transition,"We investigate the dissipative dynamics of a quantum critical system in
+contact with a thermal bath. In analogy with the standard protocol employed to
+analyze aging, we study the response of a system to a sudden change of the bath
+temperature. The specific example of the XY model in a transverse magnetic
+field whose spins are locally coupled to a set of bosonic baths is considered.
+The peculiar nature of the dynamics is encoded in the correlations developing
+out of equilibrium. By means of a kinetic equation we analyze the spin-spin
+correlations and block correlations. We identify some universal features in the
+out-of-equilibrium dynamics. Two distinct regimes, characterized by different
+time and length scales, emerge. During the initial transient the dynamics is
+characterized by the same critical exponents as those of the equilibrium
+quantum phase transition and resembles the dynamics of thermal phase
+transitions. At long times equilibrium is reached through the propagation along
+the chain of a thermal front in a manner similar to the classical Glauber
+dynamics.",0812.4717v2
+2010-12-15,A message-passing scheme for non-equilibrium stationary states,"We study stationary states in a diluted asymmetric (kinetic) Ising model. We
+apply the recently introduced dynamic cavity method to compute magnetizations
+of these stationary states. Depending on the update rule, different versions of
+the dynamic cavity method apply. We here study synchronous updates and random
+sequential updates, and compare local properties computed by the dynamic cavity
+method to numerical simulations. Using both types of updates, the dynamic
+cavity method is highly accurate at high enough temperatures. At low enough
+temperatures, for sequential updates the dynamic cavity method tends to a fixed
+point, but which does not agree with numerical simulations, while for parallel
+updates, the dynamic cavity method may display cyclic behavior. When it
+converges and is accurate, the dynamic cavity method offers a huge speed-up
+compared to Monte Carlo, particularly for large systems.",1012.3388v2
+2012-12-01,Time evolution of autocorrelation function in dynamical replica theory,"Asynchronous dynamics given by the master equation in the
+Sherrington--Kirkpatrick (SK) spin-glass model is studied based on dynamical
+replica theory (DRT) with an extension to take into account the autocorrelation
+function. The dynamical behaviour of the system is approximately described by
+dynamical equations of the macroscopic quantities: magnetization, energy
+contributed by randomness, and the autocorrelation function. The dynamical
+equations under the replica symmetry assumption are derived by introducing the
+subshell equipartitioning assumption and exploiting the replica method. The
+obtained dynamical equations are compared with Monte Carlo (MC) simulations,
+and it is demonstrated that the proposed formula describes well the time
+evolution of the autocorrelation function in some parameter regions. The study
+offers a reasonable description of the autocorrelation function in the SK
+spin-glass system.",1212.0058v1
+2017-08-27,Symmetry Protected Dynamical Symmetry in the Generalized Hubbard Models,"In this letter we present a theorem on the dynamics of the generalized
+Hubbard models. This theorem shows that the symmetry of the single particle
+Hamiltonian can protect a kind of dynamical symmetry driven by the
+interactions. Here the dynamical symmetry refers to that the time evolution of
+certain observables are symmetric between the repulsive and attractive Hubbard
+models. We demonstrate our theorem with three different examples in which the
+symmetry involves bipartite lattice symmetry, reflection symmetry and
+translation symmetry, respectively. Each of these examples relates to one
+recent cold atom experiment on the dynamics in the optical lattices where such
+a dynamical symmetry is manifested. These experiments include expansion
+dynamics of cold atoms, chirality of atomic motion within a synthetic magnetic
+field and melting of charge-density-wave order. Therefore, our theorem provides
+a unified view of these seemingly disparate phenomena.",1708.08070v2
+2018-01-30,Chaos in Homeostatically Regulated Neural Systems,"Low-dimensional yet rich dynamics often emerge in the brain. Examples include
+oscillations and chaotic dynamics during sleep, epilepsy, and voluntary
+movement. However, a general mechanism for the emergence of low dimensional
+dynamics remains elusive. Here, we consider Wilson-Cowan networks and
+demonstrate through numerical and analytical work that a type of homeostatic
+regulation of the network firing rates can paradoxically lead to a rich
+dynamical repertoire. The dynamics include mixed-mode oscillations, mixed-mode
+chaos, and chaotic synchronization. This is true for single recurrently coupled
+node, pairs of reciprocally coupled nodes without self-coupling, and networks
+coupled through experimentally determined weights derived from functional
+magnetic resonance imaging data. In all cases, the stability of the homeostatic
+set point is analytically determined or approximated. The dynamics at the
+network level are directly determined by the behavior of a single node system
+through synchronization in both oscillatory and non-oscillatory states. Our
+results demonstrate that rich dynamics can be preserved under homeostatic
+regulation or even be caused by homeostatic regulation.",1801.09997v1
+2019-01-18,CRDN: Cascaded Residual Dense Networks for Dynamic MR Imaging with Edge-enhanced Loss Constraint,"Dynamic magnetic resonance (MR) imaging has generated great research
+interest, as it can provide both spatial and temporal information for clinical
+diagnosis. However, slow imaging speed or long scanning time is still one of
+the challenges for dynamic MR imaging. Most existing methods reconstruct
+Dynamic MR images from incomplete k-space data under the guidance of compressed
+sensing (CS) or low rank theory, which suffer from long iterative
+reconstruction time. Recently, deep learning has shown great potential in
+accelerating dynamic MR. Our previous work proposed a dynamic MR imaging method
+with both k-space and spatial prior knowledge integrated via multi-supervised
+network training. Nevertheless, there was still a certain degree of smooth in
+the reconstructed images at high acceleration factors. In this work, we propose
+cascaded residual dense networks for dynamic MR imaging with edge-enhance loss
+constraint, dubbed as CRDN. Specifically, the cascaded residual dense networks
+fully exploit the hierarchical features from all the convolutional layers with
+both local and global feature fusion. We further utilize the total variation
+(TV) loss function, which has the edge enhancement properties, for training the
+networks.",1901.06111v1
+2019-05-08,Diffusive transport in a quasiperiodic Fibonacci chain: absence of many-body localization at small interactions,"We study high-temperature magnetization transport in a many-body spin-1/2
+chain with on-site quasiperiodic potential governed by the Fibonacci rule. In
+the absence of interactions it is known that the system is critical with the
+transport described by a continuously varying dynamical exponent (from
+ballistic to localized) as a function of the on-site potential strength. Upon
+introducing weak interactions, we find that an anomalous noninteracting
+dynamical exponent becomes diffusive for any potential strength. This is borne
+out by a boundary-driven Lindblad dynamics as well as unitary dynamics, with
+agreeing diffusion constants. This must be contrasted to random potential where
+transport is subdiffusive at such small interactions. Mean-field treatment of
+the dynamics for small U always slows down the non-interacting dynamics to
+subdiffusion, and is therefore unable to describe diffusion in an interacting
+quasiperiodic system. Finally, briefly exploring larger interactions we find a
+regime of interaction-induced subdiffusive dynamics, despite the on-site
+potential itself having no ""rare-regions"".",1905.03128v2
+2019-05-21,Quantum quench and non-equilibrium dynamics in lattice-confined spinor condensates,"We present an experimental study on non-equilibrium dynamics of a spinor
+condensate after it is quenched across a superfluid to Mott insulator (MI)
+phase transition in cubic lattices. Intricate dynamics consisting of
+spin-mixing oscillations at multiple frequencies are observed in time
+evolutions of the spinor condensate localized in deep lattices after the
+quantum quench. Similar spin dynamics also appear after spinor gases in the MI
+phase are suddenly moved away from their ground states via quenching magnetic
+fields. We confirm these observed spectra of spin-mixing dynamics can be
+utilized to reveal atom number distributions of an inhomogeneous system, and to
+study transitions from two-body to many-body dynamics. Our data also imply the
+non-equilibrium dynamics depend weakly on the quench speed but strongly on the
+lattice potential. This enables precise measurements of the spin-dependent
+interaction, a key parameter determining the spinor physics.",1905.08738v1
+2020-06-22,The dynamics of a driven harmonic oscillator coupled to independent Ising spins in random fields,"We aim at an understanding of the dynamical properties of a periodically
+driven damped harmonic oscillator coupled to a Random Field Ising Model (RFIM)
+at zero temperature, which is capable to show complex hysteresis. The system is
+a combination of a continuous (harmonic oscillator) and a discrete (RFIM)
+subsystem, which classifies it as a hybrid system. In this paper we focus on
+the hybrid nature of the system and consider only independent spins in quenched
+random local fields, which can already lead to complex dynamics such as chaos
+and multistability. We study the dynamic behavior of this system by using the
+theory of piecewise-smooth dynamical systems and discontinuity mappings.
+Specifically, we present bifurcation diagrams, Lyapunov exponents as well as
+results for the shape and the dimensions of the attractors and the
+self-averaging behavior of the attractor dimensions and the magnetization.
+Furthermore we investigate the dynamical behavior of the system for an
+increasing number of spins and the transition to the thermodynamic limit, where
+the system behaves like a driven harmonic oscillator with an additional
+nonlinear smooth external force.",2006.12588v2
+2022-06-21,Markov property of the Super-MAG Auroral Electrojet Indices,"The dynamics of the Earth's magnetosphere exhibits strongly fluctuating
+patterns as well as non-stationary and non-linear interactions, more pronounced
+during magnetospheric substorms and magnetic storms. This complex dynamics
+comprises both stochastic and deterministic features occurring at different
+time scales. Here we investigate the stochastic nature of the magnetospheric
+substorm dynamics by analysing the Markovian character of SuperMAG SME and SML
+geomagnetic indices. By performing the Chapman-Kolmogorov test, the SME/SML
+dynamics appears to satisfy the Markov condition at scales below 60 minutes.
+The Kramers-Moyal analysis instead highlights that a purely diffusive process
+is not representative of the magnetospheric dynamics, thus a model that
+includes both diffusion and Poisson-jump processes is used to reproduce the SME
+dynamical features at small scales. A discussion of the similarities and
+differences between this model and the SME properties is provided with a
+special emphasis on the metastability of the Earth's magnetospheric dynamics.
+Finally, the relevance of our results in the framework of Space Weather is also
+addressed.",2206.10378v3
+2022-06-30,Experimental quantum simulation of non-Hermitian dynamical topological states using stochastic Schrödinger equation,"Noise is ubiquitous in real quantum systems, leading to non-Hermitian quantum
+dynamics, and may affect the fundamental states of matter. Here we report in
+experiment a quantum simulation of the two-dimensional non-Hermitian quantum
+anomalous Hall (QAH) model using the nuclear magnetic resonance processor.
+Unlike the usual experiments using auxiliary qubits, we develop a stochastic
+average approach based on the stochastic Schr\""odinger equation to realize the
+non-Hermitian dissipative quantum dynamics, which has advantages in saving the
+quantum simulation sources and simplifies implementation of quantum gates. We
+demonstrate the stability of dynamical topology against weak noise, and observe
+two types of dynamical topological transitions driven by strong noise.
+Moreover, a region that the emergent topology is always robust regardless of
+the noise strength is observed. Our work shows a feasible quantum simulation
+approach for dissipative quantum dynamics with stochastic Schr\""odinger
+equation and opens a route to investigate non-Hermitian dynamical topological
+physics.",2206.15127v1
+2023-11-30,Dynamic Phase Transition in 2D Ising Systems: Effect of Anisotropy and Defects,"We investigate the dynamic phase transition in two-dimensional Ising models
+whose equilibrium characteristics are influenced by either anisotropic
+interactions or quenched defects. The presence of anisotropy reduces the
+dynamical critical temperature, leading to the expected result that the
+critical temperature approaches zero in the full-anisotropy limit. We show that
+a comprehensive understanding of the dynamic behavior of systems with quenched
+defects requires a generalized definition of the dynamic order parameter. By
+doing so, we demonstrate that the inclusion of quenched defects lowers the
+dynamic critical temperature as well, with a linear trend across the range of
+defect fractions considered. We also explore if and how it is possible to
+predict the dynamic behavior of specific magnetic systems with quenched
+randomness. Various geometric quantities, such as a defect potential index, the
+defect dipole moment, and the properties of the defect Delaunay triangulation,
+prove useful for this purpose.",2312.00153v2
+2024-03-14,Quantum analog of Landau-Lifshitz-Gilbert dynamics,"The Landau-Lifshitz-Gilbert (LLG) and Landau-Lifshitz (LL) equations play an
+essential role for describing the dynamics of magnetization in solids. While a
+quantum analog of the LL dynamics has been proposed in [Phys. Rev. Lett. 110,
+147201 (2013)], the corresponding quantum version of LLG remains unknown. Here,
+we propose such a quantum LLG equation that inherently conserves purity of the
+quantum state. We examine the quantum LLG dynamics of a dimer consisting of two
+interacting spin-1/2 particles. Our analysis reveals that, in the case of
+ferromagnetic coupling, the evolution of initially uncorrelated spins mirrors
+the classical LLG dynamics. However, in the antiferromagnetic scenario, we
+observe pronounced deviations from classical behavior, underscoring the unique
+dynamics of becoming a spinless state, which is non-locally correlated.
+Moreover, when considering spins that are initially correlated, our study
+uncovers an unusual form of transient quantum correlation dynamics, which
+differ significantly from what is typically seen in open quantum systems.",2403.09255v1
+2007-09-24,The Spin Density Matrix II: Application to a system of two quantum dots,"This work is a sequel to our work ""The Spin Density Matrix I: General Theory
+and Exact Master Equations"" (eprint arXiv:0708.0644 [cond-mat]). Here we
+compare pure- and pseudo-spin dynamics using as an example a system of two
+quantum dots, a pair of localized conduction-band electrons in an n-doped GaAs
+semiconductor. Pure-spin dynamics is obtained by tracing out the orbital
+degrees of freedom, whereas pseudo-spin dynamics retains (as is conventional)
+an implicit coordinate dependence. We show that magnetic field inhomogeneity
+and spin-orbit interaction result in a non-unitary evolution in pure-spin
+dynamics, whereas these interactions contribute to the effective pseudo-spin
+Hamiltonian via terms that are asymmetric in spin permutations, in particular,
+the Dzyaloshinskii-Moriya (DM) spin-orbit interaction. We numerically
+investigate the non-unitary effects in the dynamics of the triplet states
+population, purity, and Lamb energy shift, as a function of interdot distance
+and magnetic field difference. The spin-orbit interaction is found to produce
+effects of roughly four orders of magnitude smaller than those due to magnetic
+field difference in the pure-spin model. We estimate the spin-orbit interaction
+magnitude in the DM-interaction term. Our estimate gives a smaller value than
+that recently obtained by Kavokin [Phys. Rev. B 64, 075305 (2001)], who did not
+include double occupancy effects. We show that a necessary and sufficient
+condition for obtaining a universal set of quantum logic gates, involving only
+two spins, in both pure- and pseudo-spin models is that the magnetic field
+inhomogeneity and the Heisenberg interaction are both non-vanishing. We also
+briefly analyze pure-spin dynamics in the electron on liquid helium system
+recently proposed by Lyon [Phys. Rev. A 74, 052338 (2006)].",0709.3685v1
+2016-12-22,Disruption of sheetlike structures in Alfvénic turbulence by magnetic reconnection,"We propose a mechanism whereby the intense, sheet-like structures naturally
+formed by dynamically aligning Alfv\'enic turbulence are destroyed by magnetic
+reconnection at a scale $\hat{\lambda}_{\rm D}$, larger than the dissipation
+scale predicted by models of intermittent, dynamically aligning turbulence. The
+reconnection process proceeds in several stages: first, a linear tearing mode
+with $N$ magnetic islands grows and saturates, and then the $X$-points between
+these islands collapse into secondary current sheets, which then reconnect
+until the original structure is destroyed. This effectively imposes an upper
+limit on the anisotropy of the structures within the perpendicular plane, which
+means that at scale $\hat{\lambda}_{\rm D}$ the turbulent dynamics change: at
+scales larger than $\hat{\lambda}_{\rm D}$, the turbulence exhibits
+scale-dependent dynamic alignment and a spectral index approximately equal to
+$-3/2$, while at scales smaller than $\hat{\lambda}_{\rm D}$, the turbulent
+structures undergo a succession of disruptions due to reconnection, limiting
+dynamic alignment, steepening the effective spectral index and changing the
+final dissipation scale. The scaling of $\hat{\lambda}_{\rm D}$ with the
+Lundquist (magnetic Reynolds) number $S_{L_\perp}$ depends on the order of the
+statistics being considered, and on the specific model of intermittency; the
+transition between the two regimes in the energy spectrum is predicted at
+approximately $\hat{\lambda}_{\rm D} \sim S_{L_\perp}^{-0.6}$. The spectral
+index below $\hat{\lambda}_{\rm D}$ is bounded between $-5/3$ and $-2.3$. The
+final dissipation scale is at $\hat{\lambda}_{\eta,\infty}\sim
+S_{L_\perp}^{-3/4}$, the same as the Kolmogorov scale arising in theories of
+turbulence that do not involve scale-dependent dynamic alignment.",1612.07604v3
+2005-02-16,Global Dynamical Evolution of the ISM in Star Forming Galaxies - I. High Resolution 3D HD and MHD Simulations: Effect of the Magnetic Field,"In star forming disk galaxies, matter circulation between stars and the
+interstellar gas, and, in particular the energy input by random and clustered
+supernova explosions, determine the dynamical and chemical evolution of the
+ISM, and hence of the galaxy as a whole. Using a 3D MHD code with adaptive mesh
+refinement developed for this purpose, we have investigated the r\^ole of
+magnetized matter circulation between the gaseous disk and the surrounding
+galactic halo. Special emphasis has been put on the effect of the magnetic
+field with respect to the volume and mass fractions of the different ISM
+``phases'', the relative importance of ram, thermal and magnetic pressures, and
+whether the field can prevent matter transport from the disk into the halo. The
+simulations were performed on a grid with an area of 1 kpc$^{2}$, centered on
+the solar circle, extending $\pm 10$ kpc perpendicular to the galactic disk
+with a resolution as high as 1.25 pc. The simulations were run for a time scale
+of 400 Myr, sufficiently long to avoid memory effects of the initial setup, and
+to allow for a global dynamical equilibrium to be reached in case of a constant
+energy input rate. (...) We find that in general gas transport into the halo in
+3D is not prevented by an initial disk parallel magnetic field, but only
+delayed initially, for as long as it is needed to punch holes into the thick
+magnetized gas disk. The mean volume filling factor of the hot phase in the
+disk is similar in HD and MHD (the latter with a total field strength of 4.4
+$\mu$G) runs, amounting to $\sim 17-21%$ for the Galactic supernova rate.",0502327v2
+2007-01-10,Magnetic fields in barred galaxies. V. Modelling NGC 1365,"We present a model of the global magnetic field in the barred galaxy NGC 1365
+based jointly on the large-scale velocity field of interstellar gas fitted to
+HI and CO observations of this galaxy and on mean-field dynamo theory. The aim
+of the paper is to present a detailed quantitative comparison of a galactic
+dynamo model with independent radio observations. We consider several gas
+dynamical and nonlinear dynamo models that include plausible variations of
+parameters that are poorly known. Models of cosmic ray distribution in the
+galaxy are introduced to produce synthetic radio polarization maps allowing
+direct comparison with those observed at 3.5cm and 6.2cm. We show that the
+dynamo model is robust in that the most important magnetic features are
+controlled by the relatively well established properties of the density
+distribution and gas velocity field. The optimal agreement between the
+synthetic polarization maps and observations is obtained when a uniform cosmic
+ray distribution is adopted. We find some indirect evidence for enhanced
+turbulence in the regions of strong velocity shear and within 1-2kpc of the
+galactic centre. We confirm that magnetic stresses can drive an inflow of gas
+into the inner 1kpc of the galaxy at a rate of a few solar masses per year. The
+dynamo models are successful to some extent in modelling the large scale
+regular magnetic field in this galaxy. Our results demonstrate that dynamo
+models and synthetic polarization maps can provide information about both the
+gas dynamical models and conditions in the interstellar medium. We demonstrate
+that the dynamical effects of magnetic fields cannot be everywhere ignored in
+galaxy modelling.",0701277v1
+2007-12-17,Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation,"Building upon our previous MHD simulation study of magnetic channeling in
+radiatively driven stellar winds, we examine here the additional dynamical
+effects of stellar {\em rotation} in the (still) 2-D axisymmetric case of an
+aligned dipole surface field. In addition to the magnetic confinement parameter
+$\eta_{\ast}$ introduced in Paper I, we characterize the stellar rotation in
+terms of a parameter $W \equiv V_{\rm{rot}}/V_{\rm{orb}}$ (the ratio of the
+equatorial surface rotation speed to orbital speed), examining specifically
+models with moderately strong rotation $W =$ 0.25 and 0.5, and comparing these
+to analogous non-rotating cases. Defining the associated Alfv\'{e}n radius
+$R_{\rm{A}} \approx \eta_{\ast}^{1/4} \Rstar$ and Kepler corotation radius
+$R_{\rm{K}} \approx W^{-2/3} \Rstar$, we find rotation effects are weak for
+models with $R_{\rm{A}} < R_{\rm{K}}$, but can be substantial and even dominant
+for models with $R_{\rm{A}} \gtwig R_{\rm{K}}$. In particular, by extending our
+simulations to magnetic confinement parameters (up to $\eta_{\ast} = 1000$)
+that are well above those ($\eta_{\ast} = 10$) considered in Paper I, we are
+able to study cases with $R_{\rm{A}} \gg R_{\rm{K}}$; we find that these do
+indeed show clear formation of the {\em rigid-body} disk predicted in previous
+analytic models, with however a rather complex, dynamic behavior characterized
+by both episodes of downward infall and outward breakout that limit the buildup
+of disk mass. Overall, the results provide an intriguing glimpse into the
+complex interplay between rotation and magnetic confinement, and form the basis
+for a full MHD description of the rigid-body disks expected in strongly
+magnetic Bp stars like $\sigma$ Ori E.",0712.2780v1
+2011-02-10,A Constraint on the Organization of the Galactic Center Magnetic Field Using Faraday Rotation,"We present new 6 and 20 cm Very Large Array (VLA) observations of polarized
+continuum emission of roughly 0.5 square degrees of the Galactic center (GC)
+region. The 6 cm observations detect diffuse linearly-polarized emission
+throughout the region with a brightness of roughly 1 mJy per 15""x10"" beam. The
+Faraday rotation measure (RM) toward this polarized emission has structure on
+degree size scales and ranges from roughly +330 rad/m2 east of the dynamical
+center (Sgr A) to -880 rad/m2 west of the dynamical center. This RM structure
+is also seen toward several nonthermal radio filaments, which implies that they
+have a similar magnetic field orientation and constrains models for their
+origin. Modeling shows that the RM and its change with Galactic longitude are
+best explained by the high electron density and strong magnetic field of the GC
+region. Considering the emissivity of the GC plasma shows that while the
+absolute RM values are indirect measures of the GC magnetic field, the RM
+longitude structure directly traces the magnetic field in the central
+kiloparsec of the Galaxy. Combining this result with previous work reveals a
+larger RM structure covering the central ~2 degrees of the Galaxy. This RM
+structure is similar to that proposed by Novak and coworkers, but is shifted
+roughly 50 pc west of the dynamical center of the Galaxy. If this RM structure
+originates in the GC region, it shows that the GC magnetic field is organized
+on ~300 pc size scales. The pattern is consistent with a predominantly poloidal
+field geometry, pointing from south to north, that is perturbed by the motion
+of gas in the Galactic disk.",1102.2204v1
+2014-11-11,Magnonic Charge Pumping via Spin-Orbit Coupling,"The interplay between spin, charge, and orbital degrees of freedom has led to
+the development of spintronic devices like spin-torque oscillators, spin-logic
+devices, and spin-transfer torque magnetic random-access memories. In this
+development spin pumping, the process where pure spin-currents are generated
+from magnetisation precession, has proved to be a powerful method for probing
+spin physics and magnetisation dynamics. The effect originates from direct
+conversion of low energy quantised spin-waves in the magnet, known as magnons,
+into a flow of spins from the precessing magnet to adjacent normal metal leads.
+The spin-pumping phenomenon represents a convenient way to electrically detect
+magnetisation dynamics, however, precessing magnets have been limited so far to
+pump pure spin currents, which require a secondary spin-charge conversion
+element such as heavy metals with large spin Hall angle or multi-layer layouts
+to be detectable. Here, we report the experimental observation of charge
+pumping in which a precessing ferromagnet pumps a charge current, demonstrating
+direct conversion of magnons into high-frequency currents via the relativistic
+spin-orbit interaction. The generated electric current, differently from spin
+currents generated by spin-pumping, can be directly detected without the need
+of any additional spin to charge conversion mechanism and amplitude and phase
+information about the relativistic current-driven magnetisation dynamics. The
+charge-pumping phenomenon is generic and gives a deeper understanding of the
+recently observed spin-orbit torques, of which it is the reciprocal effect and
+which currently attract interest for their potential in manipulating magnetic
+information. Furthermore, charge pumping provides a novel link between
+magnetism and electricity and may find application in sourcing alternating
+electric currents.",1411.2779v1
+2017-04-05,"Interplay of transitions between oscillations with emergence of fireballs and quantification of phase coherence, scaling index in a magnetized glow discharge plasma of toroidal assembly","Interplay of transition of floating potential fluctuations in a glow
+discharge plasma in the toroidal vacuum vessel of SINP tokamak has been
+observed. With variation in the strength of the vertical and toroidal magnetic
+fields, regular and inverted relaxation oscillations as well as sinusoidal
+oscillations are observed with the slow and fast time scale of the relaxation
+oscillations reversing their nature at a high value of vertical magnetic field
+strength. However for small value of toroidal magnetic field the transitions
+follow relaxation $\rightarrow$ chaotic oscillations with the chaotic nature
+prevailing at higher values of toroidal magnetic field. Evolution of associated
+anode fireball dynamics under the action of increasing vertical, toroidal as
+well as increasing vertical field at a fixed toroidal field (mixed field) of
+different strength has been studied. Estimation of phase coherence index for
+each case has been carried out to examine the evidence of finite nonlinear
+interaction. A comprehensive study of the dynamics of the fireball is found to
+be associated with the values of phase coherence index. The index is found to
+take maximum values for the case of toroidal, mixed field when there is an
+existence of power/energy concentration in a large region of frequency band. A
+detailed study of the scaling region using detrended fluctuation analysis (DFA)
+by estimating the scaling exponent has been carried out for increasing values
+of discharge voltage, vertical, toroidal as well as the mixed field (toroidal
+plus vertical). A persistence long range behaviour associated with the nature
+of the anode glow has been investigated in case of higher values of toroidal,
+mixed field whereas increasing DV, vertical magnetic field leads to a perfectly
+correlated dynamics with values of scaling exponent greater than unity",1704.01325v1
+2019-01-14,A 3D kinematic Babcock Leighton solar dynamo model sustained by dynamic magnetic buoyancy and flux transport processes,"Magnetohydrodynamic interactions between plasma flows and magnetic fields is
+fundamental to the origin and sustenance of the 11-year sunspot cycle. These
+processes are intrinsically three-dimensional (3D) in nature. Our goal is to
+construct a 3D solar dynamo model that on the one hand captures the buoyant
+emergence of tilted bipolar sunspot pairs, and on the other hand produces
+cyclic large-scale field reversals mediated via surface flux-transport
+processes -- that is, the Babcock-Leighton mechanism. We perform kinematic
+dynamo simulations where the prescribed velocity field is a combination of
+solar-like differential rotation and meridional circulation, along with a
+parametrized turbulent diffusivity. We use a novel methodology for modeling
+magnetic buoyancy through field-strength-dependent 3D helical up-flows that
+results in the formation of tilted bipolar sunspots. The bipolar spots produced
+in our simulations participate in the process of poloidal-field generation
+through the Babcock-Leighton mechanism, resulting in self-sustained and
+periodic large-scale magnetic field reversal. Our parameter space study varying
+the amplitude of the meridional flow, the convection zone diffusivity, and
+parameters governing the efficiency of the magnetic buoyancy mechanism reveal
+their relative roles in determining properties of the sunspot cycle such as
+amplitude, period, and dynamical memory relevant to solar cycle prediction. We
+also derive a new dynamo number for the Babcock-Leighton solar dynamo mechanism
+which reasonably captures our model dynamics. This study elucidates the
+relative roles of different flux-transport processes in the Sun's convection
+zone in determining the properties and physics of the sunspot cycle and could
+potentially lead to realistic, data-driven 3D dynamo models for solar-activity
+predictions and exploration of stellar magnetism and starspot formation in
+other stars.",1901.04251v1
+2020-07-06,Spin-canting effects in GMR sensors with wide dynamic field range,"Magnetoresistive (xMR) sensors find extensive application in science and
+industry, replacing Hall sensors in various low field environments. While there
+have been some efforts in increasing the dynamic field range of xMR sensors,
+Hall sensors remain to dominate high field applications due to their wide
+linear range. Using a perpendicular magnetized reference system and an in-plane
+free layer allows us to overcome this disadvantage of xMR sensors, and,
+furthermore, investigate spin-canting effects in interlayer exchange coupled
+perpendicular synthetic antiferromagnets (p-SAF). We created p-SAFs with
+exchange coupling fields of up to 10 kOe, based on magnetic Co/Pt multilayer
+systems. The p-SAFs are either designed as ""single"" p-SAFs, where two Co/Pt
+multilayers are interlayer exchange coupled via a 4 {\AA} thick Ru spacer, or
+as ""double"" p-SAFs, where an additional Co layer is interlayer exchange coupled
+to the top multilayer. These p-SAFs are used for giant magnetoresistance (GMR)
+sensors with wide dynamic field range. By using a p-SAF as the reference system
+and employing an in-plane magnetic layer as the GMR's free layer, the linear
+range can be effectively increased limited only by the p-SAF's switching
+fields. Additionally, the magnetic anisotropy of the in-plane free layer is
+fully controlled, which allows saturation fields by design. Different
+configurations were investigated, ranging from free layer magnetic saturation
+at lower to far higher fields than the p-SAF's switching fields. We can show
+through micromagnetic simulations that certain GMR transfer curves are
+dominated by spin-canting effects in the interlayer exchange coupled reference
+system. Finally, our simulation results lay out the correlation of the p-SAF's
+design parameters and its magnetization reversal behavior.",2007.02640v1
+2020-08-17,A global model of particle acceleration at pulsar wind termination shocks,"Pulsar wind nebulae are efficient particle accelerators, and yet the
+processes at work remain elusive. Self-generated, microturbulence is too weak
+in relativistic magnetized shocks to accelerate particles over a wide energy
+range, suggesting that the global dynamics of the nebula may be involved in the
+acceleration process instead. In this work, we study the role played by the
+large-scale anisotropy of the transverse magnetic field profile on the shock
+dynamics. We performed large two-dimensional particle-in-cell simulations for a
+wide range of upstream plasma magnetizations. A large-scale velocity shear and
+current sheets form in the equatorial regions and at the poles, where they
+drive strong plasma turbulence via Kelvin-Helmholtz vortices and kinks. The
+mixing of current sheets in the downstream flow leads to efficient nonthermal
+particle acceleration. The power-law spectrum hardens with increasing
+magnetization, akin to those found in relativistic reconnection and kinetic
+turbulence studies. The high end of the spectrum is composed of particles
+surfing on the wake produced by elongated spearhead-shaped cavities forming at
+the shock front and piercing through the upstream flow. These particles are
+efficiently accelerated via the shear-flow acceleration mechanism near the Bohm
+limit. Magnetized relativistic shocks are very efficient particle accelerators.
+Capturing the global dynamics of the downstream flow is crucial to
+understanding them, and therefore local plane parallel studies may not be
+appropriate for pulsar wind nebulae and possibly other astrophysical
+relativistic magnetized shocks. A natural outcome of such shocks is a variable
+and Doppler-boosted synchrotron emission at the high end of the spectrum
+originating from the shock-front cavities, reminiscent of the mysterious Crab
+Nebula gamma-ray flares.",2008.07253v1
+2020-10-26,Dynamics of test particles around renormalization group improved Schwarzschild black holes,"In this paper we have investigated the dynamics of neutral, electrically
+charged and magnetized particles around renormalized group improved (RGI)
+Schwarzschild black hole in the presence of external asymptotically uniform
+magnetic field. We have analyzed the spacetime structure around RGI black hole
+by investigating Ricci, the square of Ricci tensor and Kretschmann curvature
+scalars and shown that only in the case when the parameter $\gamma=0$ the
+curvature becomes infinite at the center of the black hole, while for non-zero
+values of $\gamma$ parameter the black hole curvature reflects the properties
+of regular black hole. Analyzing the innermost stable circular orbits of test
+neutral particles around RGI black hole and comparing with the results for
+rotating Kerr black hole we have shown that RGI black hole parameters can mimic
+the rotation parameter of Kerr black hole upto $a/M \lesssim 0.31$ providing
+the same ISCO radius. Since according to the astronomical observations of the
+accretion disks confirm that the astrophysical black holes are rapidly rotating
+with the spin parameter upto $a/M \sim 0.99$ one may conclude that the effects
+of parameters of RGI Schwarzschild black hole on the circular orbits of the
+neutral particles can not mimic the Kerr black hole. Then the Hamilton-Jacobi
+equation has been used to analyze the charged and magnetized particles motion
+near the RGI black hole in the presence of the strong interaction between
+external asymptotically uniform magnetic (electromagnetic) field and magnetized
+(electrically charged) particle. We have shown that RGI black hole parameters
+quantitatively change the dynamics of the charged and magnetized particles, in
+particular ISCO radius of the particles decreases with increasing the parameter
+$\lambda$, while the increase of the parameter $\gamma$ causes to increase of
+it.",2010.15079v1
+2021-08-10,Gravity Versus Magnetic Fields in Forming Molecular Clouds,"Magnetic fields are dynamically important in the diffuse interstellar medium.
+Understanding how gravitationally bound, star-forming clouds form requires
+modeling of the fields in a self-consistent, supernova-driven, turbulent,
+magnetized, stratified disk. We employ the FLASH magnetohydrodynamics code to
+follow the formation and early evolution of clouds with final masses of 3-8
+$\times 10^3 M_{\odot}$ within such a simulation. We use the code's adaptive
+mesh refinement capabilities to concentrate numerical resolution in zoom-in
+regions covering single clouds, allowing us to investigate the detailed
+dynamics and field structure of individual self-gravitating clouds in a
+consistent background medium. Our goal is to test the hypothesis that dense
+clouds are dynamically evolving objects far from magnetohydrostatic
+equilibrium. We find that the cloud envelopes are magnetically supported with
+field lines parallel to density gradients and flow velocity, as indicated by
+the histogram of relative orientations and other statistical measures. In
+contrast, the dense cores of the clouds are gravitationally dominated, with
+gravitational energy exceeding internal, kinetic, or magnetic energy and
+accelerations due to gravity exceeding those due to magnetic or thermal
+pressure gradients. In these regions field directions vary strongly, with a
+slight preference towards being perpendicular to density gradients, as shown by
+three-dimensional histograms of relative orientation.",2108.04967v2
+2003-07-27,Magnetohydrodynamic Density Waves in a Composite Disk System of Interstellar Medium and Cosmic-Ray Gas,"Multi-wavelength observations from radio to soft X-ray bands of large-scale
+galactic spiral structures offer synthesized and comprehensive views of nearby
+disk galaxies. In the presence of a massive dark-matter halo, the density-wave
+dynamics on galactic scales involves the stellar disk, the gas disk of
+interstellar medium (ISM), the magnetic field, and the cosmic-ray gas (CRG). In
+this paper, we explore the dynamic and electromagnetic interplay between the
+magnetized ISM disk and CRG disk so that structural and diagnostic features of
+optical, infrared, and synchrotron radio-continuum emissions from a spiral
+galaxy can be physically understood. On timescales of galactic density waves,
+cosmic rays collectively may be treated as a relativistically hot tenuous gas
+fluid that is tied to the large-scale mean magnetic field in transverse bulk
+motions but moves otherwise differently along the magnetic field relative to
+the ISM. For both fast and slow magnetohydrodynamic (MHD) density waves in a
+composite disk system of magnetized ISM and CRG, the minute CRG mass density
+enhancement is phase shifted relative to the enhancement of parallel magnetic
+field. Owing to an extremely small number of cosmic rays, the large-scale
+magnetic field enhancement dominates in synchrotron radio-continuum emissions
+(as if the CRG is almost unperturbed) for spiral structural manifestations. In
+addition to the fast and slow MHD density waves, there also exists a
+suprathermal MHD wave mode by which CRG adjusts itself with an effective
+suprathermal sound speed close to the speed of light c.",0307466v1
+2004-10-22,Development of supersonic plasma flows by use of a magnetic nozzle and an ICRF heating,"A high-beta, supersonic plasma flow plays a crucial role in MHD phenomena in
+space and fusion plasmas. There are a few experimental researches on production
+and control of a fast flowing plasma in spite of a growing significance in the
+magnetized-plasma flow dynamics. A magneto-plasma-dynamic arcjet (MPDA) is one
+of promising devices to produce a supersonic plasma flow and has been utilized
+as an electric propulsion device with a higher specific impulse and a
+relatively larger thrust. We have improved the performance of an MPDA to
+produce a quasi-steady plasma flow with a transonic and supersonic Mach number
+in a highly-ionized state. There are two methods in order to control an
+ion-acoustic Mach number of the plasma flow exhausted from an MPDA: one is to
+use a magnetic Laval nozzle to convert a thermal energy to a flow energy and
+the other is a combined system of an ion heating and a divergent magnetic
+nozzle. The former is an analogous method to a compressible air flow and the
+latter is the method proposed in an advanced thruster for a manned
+interplanetary space mission. We have clarified the plasma flow characteristics
+in various shapes of a magnetic field configuration. It was demonstrated that
+the Mach number of the plasma flow could increase up to almost 3 in a divergent
+magnetic nozzle field. This paper reports recent results on the flow field
+improvements: one is on a magnetic-Laval-nozzle effects observed at the muzzle
+region of the MPDA, and the other is on ICRF (ion-cyclotron-range of frequency)
+heating of a supersonic plasma by use of a helical antenna.",0410205v1
+2008-06-03,Euler-Lagrange models with complex currents of three-phase electrical machines and observability issues,"A new Lagrangian formulation with complex currents is developed and yields a
+direct and simple method for modeling three-phase permanent-magnet and
+induction machines. The Lagrangian is the sum a mechanical one and of a
+magnetic one. This magnetic Lagrangian is expressed in terms of rotor angle,
+complex stator and rotor currents. A complexification procedure widely used in
+quantum electrodynamic is applied here in order to derive the Euler-Lagrange
+equations with complex stator and rotor currents. Such complexification process
+avoids the usual separation into real and imaginary parts and simplifies
+notably the calculations. Via simple modifications of such magnetic Lagrangians
+we derive new dynamical models describing permanent-magnet machines with both
+saturation and saliency, and induction machines with both magnetic saturation
+and space harmonics. For each model we also provide its Hamiltonian thus its
+magnetic energy. This energy is also expressed with complex currents and can be
+directly used in Lyapunov and/or passivity based control. Further, we briefly
+investigate the observability of this class of Euler-Lagrange models, in the
+so-called sensorless case when the measured output is the stator current and
+the load torque is constant but unknown. For all the dynamical models obtained
+via such variational principles, we prove that their linear tangent systems are
+unobservable around a one-dimensional family of steady-states attached to the
+same constant stator voltage and current. This negative result explains why
+sensorless control of three-phase electrical machines around zero stator
+frequency remains yet a difficult control problem.",0806.0387v4
+2008-09-19,"Magnetism, FeS colloids, and Origins of Life","A number of features of living systems: reversible interactions and weak
+bonds underlying motor-dynamics; gel-sol transitions; cellular connected
+fractal organization; asymmetry in interactions and organization; quantum
+coherent phenomena; to name some, can have a natural accounting via $physical$
+interactions, which we therefore seek to incorporate by expanding the horizons
+of `chemistry-only' approaches to the origins of life. It is suggested that the
+magnetic 'face' of the minerals from the inorganic world, recognized to have
+played a pivotal role in initiating Life, may throw light on some of these
+issues. A magnetic environment in the form of rocks in the Hadean Ocean could
+have enabled the accretion and therefore an ordered confinement of
+super-paramagnetic colloids within a structured phase. A moderate H-field can
+help magnetic nano-particles to not only overcome thermal fluctuations but also
+harness them. Such controlled dynamics brings in the possibility of accessing
+quantum effects, which together with frustrations in magnetic ordering and
+hysteresis (a natural mechanism for a primitive memory) could throw light on
+the birth of biological information which, as Abel argues, requires a
+combination of order and complexity. This scenario gains strength from
+observations of scale-free framboidal forms of the greigite mineral, with a
+magnetic basis of assembly. And greigite's metabolic potential plays a key role
+in the mound scenario of Russell and coworkers-an expansion of which is
+suggested for including magnetism.",0809.3316v5
+2011-02-01,A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence,"Cosmic structure formation is characterized by the complex interplay between
+gravity, turbulence, and magnetic fields. The processes by which gravitational
+energy is converted into turbulent and magnetic energies, however, remain
+poorly understood. Here, we show with high-resolution, adaptive-mesh
+simulations that MHD turbulence is efficiently driven by extracting energy from
+the gravitational potential during the collapse of a dense gas cloud.
+Compressible motions generated during the contraction are converted into
+solenoidal, turbulent motions, leading to a natural energy ratio of E_sol/E_tot
+of approximately 2/3. We find that the energy injection scale of gravity-driven
+turbulence is close to the local Jeans scale. If small seeds of the magnetic
+field are present, they are amplified exponentially fast via the small-scale
+dynamo process. The magnetic field grows most efficiently on the smallest
+scales, for which the stretching, twisting, and folding of field lines, and the
+turbulent vortices are sufficiently resolved. We find that this scale
+corresponds to about 30 grid cells in the simulations. We thus suggest a new
+minimum resolution criterion of 30 cells per Jeans length in
+(magneto)hydrodynamical simulations of self-gravitating gas, in order to
+resolve turbulence on the Jeans scale, and to capture minimum dynamo
+amplification of the magnetic field. Due to numerical diffusion, however, any
+existing simulation today can at best provide lower limits on the physical
+growth rates. We conclude that a small, initial magnetic field can grow to
+dynamically important strength on time scales significantly shorter than the
+free-fall time of the cloud.",1102.0266v2
+2014-04-07,The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Overview and Performance,"The Helioseismic and Magnetic Imager (HMI) began near-continuous full-disk
+solar measurements on 1 May 2010 from the Solar Dynamics Observatory (SDO). An
+automated processing pipeline keeps pace with observations to produce
+observable quantities, including the photospheric vector magnetic field, from
+sequences of filtergrams. The primary 720s observables were released in mid
+2010, including Stokes polarization parameters measured at six wavelengths as
+well as intensity, Doppler velocity, and the line-of-sight magnetic field. More
+advanced products, including the full vector magnetic field, are now available.
+Automatically identified HMI Active Region Patches (HARPs) track the location
+and shape of magnetic regions throughout their lifetime.
+  The vector field is computed using the Very Fast Inversion of the Stokes
+Vector (VFISV) code optimized for the HMI pipeline; the remaining 180 degree
+azimuth ambiguity is resolved with the Minimum Energy (ME0) code. The
+Milne-Eddington inversion is performed on all full-disk HMI observations. The
+disambiguation, until recently run only on HARP regions, is now implemented for
+the full disk. Vector and scalar quantities in the patches are used to derive
+active region indices potentially useful for forecasting; the data maps and
+indices are collected in the SHARP data series, hmi.sharp_720s. Patches are
+provided in both CCD and heliographic coordinates.
+  HMI provides continuous coverage of the vector field, but has modest spatial,
+spectral, and temporal resolution. Coupled with limitations of the analysis and
+interpretation techniques, effects of the orbital velocity, and instrument
+performance, the resulting measurements have a certain dynamic range and
+sensitivity and are subject to systematic errors and uncertainties that are
+characterized in this report.",1404.1881v1
+2015-02-27,Blowing Magnetic Skyrmion Bubbles,"Soap bubbles form when blowing air through a suspended thin film of soapy
+water and this phenomenon entertains children and adults alike. The formation
+of soap bubbles from thin films is accompanied by topological transitions, and
+thus the natural question arises whether this concept is applicable to the
+generation of other topological states. Here we show how a magnetic topological
+structure, namely a skyrmion bubble, can be generated in a solid state system
+in a similar manner. Beyond enabling the investigation of complex
+surface-tension driven dynamics in a novel physical system, this observation
+has also practical implications, since the topological charge of magnetic
+skyrmions has been envisioned as an information carrier for new data processing
+technologies. A main goal towards this end is the experimental creation and
+manipulation of individual mobile skyrmions at room temperature. By utilizing
+an inhomogeneous in-plane current in a system with broken inversion asymmetry,
+we experimentally blow magnetic skyrmion bubbles through a geometrical
+constriction. The presence of a spatially divergent spin-orbit torque gives
+rise to instabilities of the magnetic domain structures that are reminiscent of
+Rayleigh-Plateau instabilities in fluid flows. Experimentally we can determine
+the electric current versus magnetic field phase diagram for skyrmion formation
+and we reveal the efficient manipulation of these dynamically created
+skyrmions, including depinning and motion. The demonstrated current-driven
+transformation from stripe domains to magnetic skyrmion bubbles could provide
+additional avenues for implementing skyrmion-based spintronics.",1502.08028v1
+2015-12-20,Turbulent dynamo in a collisionless plasma,"Magnetic fields pervade the entire Universe and affect the formation and
+evolution of astrophysical systems from cosmological to planetary scales. The
+generation and dynamical amplification of extragalactic magnetic fields through
+cosmic times, up to $\mu$Gauss levels reported in nearby galaxy clusters, near
+equipartition with kinetic energy of plasma motions and on scales of at least
+tens of kiloparsecs, is a major puzzle largely unconstrained by observations. A
+dynamo effect converting kinetic flow energy into magnetic energy is often
+invoked in that context, however extragalactic plasmas are weakly collisional
+(as opposed to magnetohydrodynamic fluids), and whether magnetic-field growth
+and sustainment through an efficient turbulent dynamo instability is possible
+in such plasmas is not established. Fully kinetic numerical simulations of the
+Vlasov equation in a six-dimensional phase space necessary to answer this
+question have until recently remained beyond computational capabilities. Here,
+we show by means of such simulations that magnetic-field amplification via a
+dynamo instability does occur in a stochastically-driven, non-relativistic
+subsonic flow of initially unmagnetized collisionless plasma. We also find that
+the dynamo self-accelerates and becomes entangled with kinetic instabilities as
+magnetization increases. The results suggest that such a plasma dynamo may be
+realizable in laboratory experiments, support the idea that intracluster medium
+(ICM) turbulence may have significantly contributed to the amplification of
+cluster magnetic fields up to near-equipartition levels on a timescale shorter
+than the Hubble time, and emphasize the crucial role of multiscale kinetic
+physics in high-energy astrophysical plasmas.",1512.06455v2
+2017-11-10,Artificial Magnetic Field Quenches in Synthetic Dimensions,"Recent cold atom experiments have realized models where each hyperfine state
+at an optical lattice site can be regarded as a separate site in a synthetic
+dimension. In such synthetic ribbon configurations, manipulation of the
+transitions between the hyperfine levels provide direct control of the hopping
+in the synthetic dimension. This effect was used to simulate a magnetic field
+through the ribbon. Precise control over the hopping matrix elements in the
+synthetic dimension makes it possible to change this artificial magnetic field
+much faster than the time scales associated with atomic motion in the lattice.
+In this paper, we consider such a magnetic flux quench scenario in synthetic
+dimensions. Sudden changes have not been considered for real magnetic fields as
+such changes in a conducting system would result in large induced currents.
+Hence, we first study the difference between a time varying real magnetic field
+and an artificial magnetic field using a minimal six site model. This minimal
+model clearly shows the connection between gauge dependence and the lack of on
+site induced scalar potential terms. We then investigate the dynamics of a
+wavepacket in an infinite two or three leg ladder following a flux quench and
+find that the gauge choice has a dramatic effect on the packet dynamics.
+Specifically, a wavepacket splits into a number of smaller packets. Both the
+weights and the number of packets depend on the implemented gauge. If an
+initial packet, prepared under zero flux in a n--leg ladder, is quenched to
+Hamiltonian with a vector potential parallel to the ladder; it splits into at
+most $n$ smaller wavepackets. The same initial packet splits up to $n^2$
+packets if the vector potential is implemented to be along the rungs. Finally,
+we show that edge states in a thick ribbon are robust under the quench only
+when the same gap supports an edge state for the final Hamiltonian.",1711.03777v2
+2017-12-15,Optimization of Photospheric Electric Field Estimates for Accurate Retrieval of Total Magnetic Energy Injection,"Estimates of the photospheric magnetic, electric and plasma velocity fields
+are essential for studying the dynamics of the solar atmosphere, for example
+through the derivative quantities of Poynting and relative helicity flux and by
+using of the fields to obtain the lower boundary condition for data-driven
+coronal simulations. In this paper we study the performance of a data
+processing and electric field inversion approach that requires only
+high-resolution and high-cadence line-of-sight or vector magnetograms -- which
+we obtain from Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics
+Observatory (SDO). The approach does not require any photospheric velocity
+estimates, and the lacking velocity information is compensated using ad hoc
+assumptions. We show that the free parameters of these assumptions can be
+optimized to reproduce the time evolution of the total magnetic energy
+injection through the photosphere in NOAA AR 11158, when compared to the recent
+estimates for this active region. However, we find that the relative magnetic
+helicity injection is reproduced poorly reaching at best a modest
+underestimation. We discuss also the effect of some of the data processing
+details on the results, including the masking of the noise-dominated pixels and
+the tracking method of the active region, both of which have not received much
+attention in the literature so far. In most cases the effect of these details
+is small, but when the optimization of the free parameters of the ad hoc
+assumptions is considered a consistent use of the noise mask is required. The
+results found in this paper imply that the data processing and electric field
+inversion approach that uses only the photospheric magnetic field information
+offers a flexible and straightforward way to obtain photospheric magnetic and
+electric field estimates suitable for practical applications such as coronal
+modeling studies.",1712.05757v1
+2018-07-15,LiZn$_{2}$V$_{3}$O$_{8}$: A new geometrically frustrated cluster spin-glass,"We have investigated the structural and magnetic properties of a new cubic
+spinel LiZn$_{2}$V$_{3}$O$_{8}$ (LZVO) through x-ray diffraction, dc and ac
+susceptibility, magnetic relaxation, aging, memory effect, heat capacity and
+$^{7}$Li nuclear magnetic resonance (NMR) measurements. A Curie-Weiss fit of
+the dc susceptibility $\chi_{\mathrm{dc}}$($\mathit{T}$) yields a Curie-Weiss
+temperature $\mathrm{\theta}_{\mathrm{CW}}$ = -185 K. This suggests strong
+antiferromagnetic (AFM) interactions among the magnetic vanadium ions. The dc
+and ac susceptibility data indicate the spin-glass behavior below a freezing
+temperature $T_{f}$ $\simeq$ 3 K. The frequency dependence of the $T_{f}$ is
+characterized by the Vogel-Fulcher law and critical dynamic scaling behavior or
+power law. From both fitting, we obtained the value of the characteristic
+angular frequency $\omega_{0}$ $\approx$ 3.56$\times$10$^{6}$ Hz, the dynamic
+exponent $\mathit{zv}$ $\approx$ 2.65, and the critical time constant
+$\tau_{0}$ $\approx$ 1.82$\times$10$^{-6}$ s, which falls in the conventional
+range for typical cluster spin-glass (CSG) systems. The value of relative shift
+in freezing temperature $\delta T_{f}$ $\simeq$ 0.039 supports a CSG ground
+states. We also found aging phenomena and memory effects in LZVO. The
+asymmetric response of the magnetic relaxation below $T_{f}$ supports the
+hierarchical model. Heat capacity data show no long-range or short-range
+ordering down to 2 K. Only about 25% magnetic entropy change $(\Delta
+S_{\mathrm{m}})$ signifies the presence of strong frustration in the system.
+The $^{7}$Li NMR spectra show a shift and broadening with decreasing
+temperature. The spin-lattice and spin-spin relaxation rates show anomalies due
+to spin freezing around 3 K as the bulk magnetization.",1807.05612v3
+2019-09-23,Does magnetic field impact tidal dynamics inside the convective zone of low-mass stars along their evolution?,"The dissipation of the kinetic energy of wave-like tidal flows within the
+convective envelope of low-mass stars is one of the key physical mechanisms
+that shapes the orbital and rotational dynamics of short-period exoplanetary
+systems. Although low-mass stars are magnetically active objects, the question
+of how the star's magnetic field impacts large-scale tidal flows and the
+excitation, propagation and dissipation of tidal waves still remains open. Our
+goal is to investigate the impact of stellar magnetism on the forcing of tidal
+waves, and their propagation and dissipation in the convective envelope of
+low-mass stars as they evolve. We have estimated the amplitude of the magnetic
+contribution to the forcing and dissipation of tidally induced magneto-inertial
+waves throughout the structural and rotational evolution of low-mass stars
+(from M to F-type). For this purpose, we have used detailed grids of rotating
+stellar models computed with the stellar evolution code STAREVOL. The amplitude
+of dynamo-generated magnetic fields is estimated via physical scaling laws at
+the base and the top of the convective envelope. We find that the large-scale
+magnetic field of the star has little influence on the excitation of tidal
+waves in the case of nearly-circular orbits and coplanar hot-Jupiter planetary
+systems, but that it has a major impact on the way waves are dissipated. Our
+results therefore indicate that a full magneto-hydrodynamical treatment of the
+propagation and dissipation of tidal waves is needed to properly assess the
+impact of star-planet tidal interactions throughout the evolutionary history of
+low-mass stars hosting short-period massive planets.",1909.10490v1
+2019-09-30,First-principles theory of proximity spin-orbit torque on a two-dimensional magnet: Current-driven antiferromagnet-to-ferromagnet reversible transition in bilayer CrI$_3$,"The recently discovered two-dimensional (2D) magnetic insulator CrI$_3$ is an
+intriguing case for basic research and spintronic applications since it is a
+ferromagnet in the bulk, but an antiferromagnet in bilayer form, with its
+magnetic ordering amenable to external manipulations. Using first-principles
+quantum transport approach, we predict that injecting unpolarized charge
+current parallel to the interface of bilayer-CrI$_3$/monolayer-TaSe$_2$ van der
+Waals heterostructure will induce spin-orbit torque (SOT) and thereby driven
+dynamics of magnetization on the first monolayer of CrI$_3$ in direct contact
+with TaSe$_2$. By combining calculated complex angular dependence of SOT with
+the Landau-Lifshitz-Gilbert equation for classical dynamics of magnetization,
+we demonstrate that current pulses can switch the direction of magnetization on
+the first monolayer to become parallel to that of the second monolayer, thereby
+converting CrI$_3$ from antiferromagnet to ferromagnet while not requiring any
+external magnetic field. We explain the mechanism of this reversible
+current-driven nonequilibrium phase transition by showing that first monolayer
+of CrI$_3$ carries current due to evanescent wavefunctions injected by metallic
+transition metal dichalcogenide TaSe$_2$, while concurrently acquiring strong
+spin-orbit coupling (SOC) via such proximity effect, whereas the second
+monolayer of CrI$_3$ remains insulating. The transition can be detected by
+passing vertical read current through the vdW heterostructure, encapsulated by
+bilayer of hexagonal boron nitride and sandwiched between graphite electrodes,
+where we find tunneling magnetoresistance of $\simeq 240$%.",1909.13876v2
+2020-10-23,"An observational correlation between magnetic field, angular momentum and fragmentation in the envelopes of Class 0 protostars?","To assess the potential role of magnetic fields in regulating the envelope
+rotation and the fragmentation of Class 0 protostars, we carried out
+observations of the dust polarized emission at 0.87 mm with the SMA, in the
+envelopes of a large sample of 20 Class 0 protostars. We estimate the mean
+magnetic field orientation over the central 1000 au envelope scales and
+compared it to that of the protostellar outflow in order to study the relation
+between their misalignment and the kinematics of the circumstellar gas. We
+discover a strong relationship between the misalignment of the magnetic field
+orientation with the outflow and the amount of angular momentum observed at
+similar scales in the protostellar envelope, revealing a potential link between
+the kinetic and the magnetic energy at envelope scales. The relation could be
+driven by favored B misalignments in more dynamical envelopes or a dependence
+of the envelope dynamics with the large-scale B initial configuration.
+Comparing the trend with the presence of fragmentation, we observe that single
+sources are mostly associated with conditions of low angular momentum in the
+inner envelope and good alignment of the magnetic field with protostellar
+outflows, at intermediate scales. Our results suggest that the properties of
+the magnetic field in protostellar envelopes bear a tight relationship with the
+rotating-infalling gas directly involved in the star and disk formation: we
+find that it may not only influence the fragmentation of protostellar cores
+into multiple stellar systems, but also set the conditions establishing the
+pristine properties of planet-forming disks.",2010.12466v2
+2020-12-27,Exploring scalar-photon interactions in energetic astrophysical events,"Scalar fields like dilaton appear in quantum field theory (QFT) due to scale
+symmetry breaking. Their appeal also extends to modified theories of gravity,
+like $F(R)$ gravity, Horva Lifshitz gravity etc. In unified theories they make
+their appearance through compactification of the extra dimension. Apart from
+resolving the issues of compactification scale and size, the particles of their
+fields can also turn out to be excellent candidate to solve the dark energy
+(DE) and dark matter (DM) problem of the universe. In this work we study their
+mixing dynamics with photons in a magnetized media, by incorporating the effect
+of parity violating part of the photon polarization tensor, evaluated in a
+finite density magnetized media. This piece, though in general is odd in the
+external magnetic field strength $eB$; in this work we however have retained
+terms to $O$($eB$). We are able to demonstrate in this work that, in magnetized
+medium a dilatonic scalar field $(\phi)$ can excite the two transverse degrees
+of freedom (DOF) of the photons. One due to direct coupling and the other
+indirectly through the parity violating term originating due to magnetized
+medium effects. This results in the mixing dynamics being governed by, $3\times
+3$ mixing matrices. This mixing results in making the underlying media
+optically active. In this work we focus on the spectro-polarimetric imprints of
+these particles, on the spectra of the electromagnetic (EM) fields of Gamma Ray
+Bursters (GRB). Focusing on a range of parameters (i.e., magnetic field
+strength, plasma frequency $(\omega_{p})$, size of the magnetized volume,
+coupling strength to photons and their mass) we make an attempt to point out
+how space-borne detectors should be designed to optimise their detection
+possibility.",2012.13903v1
+2021-04-16,Evolution of large-amplitude Alfvén waves and generation of switchbacks in the expanding solar wind,"Motivated by recent Parker Solar Probe (PSP) observations of ""switchbacks""
+(abrupt, large-amplitude reversals in the radial magnetic field, which exhibit
+Alfv\'enic correlations) we examine the dynamics of large-amplitude Alfv\'en
+waves in the expanding solar wind. We develop an analytic model which makes
+several predictions: switchbacks should preferentially occur in regions where
+the solar wind plasma has undergone a greater expansion, the switchback
+fraction at radii comparable to PSP should be an increasing function of radius,
+and switchbacks should have their gradients preferentially perpendicular to the
+mean magnetic field direction. The expansion of the plasma generates small
+compressive components as part of the wave's nonlinear evolution: these are
+maximized when the normalized fluctuation amplitude is comparable to
+$\sin\theta$, where $\theta$ is the angle between the propagation direction and
+the mean magnetic field. These compressive components steepen the primary
+Alfv\'enic waveform, keeping the solution in a state of nearly constant
+magnetic field strength as its normalized amplitude $\delta B/B$ grows due to
+expansion. The small fluctuations in the magnetic-field-strength are minimized
+at a particular $\theta$-dependent value of $\beta$, usually of order unity,
+and the density and magnetic-field-strength fluctuations can be correlated or
+anticorrelated depending on $\beta$ and $\theta$. Example solutions of our
+dynamical equation are presented; some do indeed form magnetic-field reversals.
+Our predictions appear to match some previously unexplained phenomena in
+observations and numerical simulations, providing evidence that the observed
+switchbacks result from the nonlinear evolution of the initially
+small-amplitude Alfv\'en waves already known to be present at the coronal base.",2104.08321v1
+2022-09-30,A tabletop Optically Pumped Magnetometer setup for the monitoring of magnetic nanoparticle clustering and immobilization using Thermal Noise Magnetometry,"Many characterization techniques for magnetic nanoparticles depend on the
+usage of external fields. This is not the case in Thermal Noise Magnetometry
+(TNM), where thermal fluctuations in the magnetic signal of magnetic
+nanoparticle ensembles are measured without any external excitation. This can
+provide valuable information about the fundamental dynamical properties of the
+particles, due to the purely observative experiments of this relatively new
+technique. Until now, TNM signals have been detected only by a superconducting
+quantum interference device (SQUID) sensor. We present a tabletop setup using
+Optically Pumped Magnetometers (OPMs) in a small magnetic shield, offering a
+flexible and accessible alternative and show the agreement between both
+measurement systems for two different commercially available nanoparticle
+samples. We argue that the OPM setup with high accessibility complements the
+SQUID setup with high sensitivity and bandwidth. Furthermore, because of its
+excellent sensitivity in the lower frequencies, the OPM tabletop setup is well
+suited to monitor aggregation processes where the magnetization dynamics of the
+particles tend to slow down, e.g. in biological processes. As a proof of
+concept, we show for three different immobilization and clustering processes
+the changes in the noise spectrum measured in the tabletop setup: 1) the
+aggregation of particles due to the addition of ethanol, 2) the formation of
+polymer structures in the sample due to UV exposure, and 3) the cellular uptake
+of the particles by THP-1 cells. From our results we conclude that the tabletop
+setup offers a flexible and widely adoptable sensor measurement unit to monitor
+the immobilization and clustering of magnetic nanoparticles over time for
+different applications.",2209.15360v1
+2024-03-18,Tuning of the ultrafast demagnetization by ultrashort spin polarized currents in multi-sublattice ferrimagnets,"Femtosecond laser pulses can be used to induce ultrafast changes of the
+magnetization in magnetic materials. Several microscopic mechanisms have been
+proposed to explain the observations, including the transport of ultrashort
+spin-polarized hot-electrons (SPHE). Such ultrafast spin currents find growing
+interest because of the recent challenges in ultrafast spintronics however they
+are only poorly characterized. One of the key challenges is to characterize the
+spin-polarized ultrafast currents and the microscopic mechanisms behind SPHE
+induced manipulation of the magnetization, especially in the case of
+technologically relevant ferrimagnetic alloys. Here, we have used a combined
+approach using time- and element-resolved X-ray magnetic circular dichroism and
+theoretical calculations based on atomistic spin-dynamics simulations to
+address the ultrafast transfer of the angular momentum from spin-polarized
+currents into ferrimagnetic Fe74Gd26 films and the concomitant reduction of
+sub-lattice magnetization. Our study shows that using a Co/Pt multilayer as a
+polarizer in a spin-valve structure, the SPHE drives the demagnetization of the
+two sub-lattices of the Fe74Gd26 film. This behaviour is explained based on two
+physical mechanisms, i.e., spin transfer torque and thermal fluctuations
+induced by the SPHE. We provide a quantitative description of the heat transfer
+of the ultrashort SPHE pulse to the Fe74Gd26 films, as well as the degree of
+spin-polarization of the SPHE current density responsible for the observed
+magnetization dynamics. Our work finally characterizes the spin-polarization of
+the SPHEs revealing unexpected opposite spin polarization to the Co
+magnetization, explaining our experimental results.",2403.11739v2
+2013-02-22,Magnetic Fields in the Milky Way and in Galaxies (revised version of September 2023),"Most of the visible matter in the Universe is ionized, so that cosmic
+magnetic fields are quite easy to generate and due to the lack of magnetic
+monopoles hard to destroy. Magnetic fields have been measured in or around
+practically all celestial objects, either by in-situ measurements of
+spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas,
+or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way,
+nearby galaxies, distant radio galaxies, quasars, and even intergalactic space
+in clusters of galaxies have significant magnetic fields. Even larger volumes
+of the Universe may be permeated by so-far invisble magnetic fields.
+Information on cosmic magnetic fields has increased enormously as the result of
+the rapid development of observational methods, especially in radio astronomy.
+In the Milky Way, a wealth of magnetic phenomena was discovered that are only
+partly related to objects visible in other spectral ranges. The large-scale
+structure of the Milky Way's magnetic field is still under debate. The
+available data for external spiral galaxies can well be explained by field
+amplification and ordering via the dynamo mechanism. The measured field
+strengths and the similarity of field patterns and flow patterns of the diffuse
+ionized gas give strong indication that galactic magnetic fields are
+dynamically important. They may affect the formation of spiral arms, outflows,
+and the general evolution of galaxies. In spite of our increasing knowledge on
+magnetic fields, many important questions on the origin and evolution of
+magnetic fields, like their first occurrence in young galaxies or the existence
+of large-scale intergalactic fields, remain unanswered. Progress can be
+expected from new-generation radio telescopes like LOFAR and the SKA, for which
+""cosmic magnetism"" is a key science project.",1302.5663v11
+2017-06-12,Unveiling the Role of the Magnetic Field at the Smallest Scales of Star Formation,"We report ALMA observations of polarized dust emission from the protostellar
+source Ser-emb 8 at a linear resolution of 140 au. Assuming models of
+dust-grain alignment hold, the observed polarization pattern gives a projected
+view of the magnetic field structure in this source. Contrary to expectations
+based on models of strongly magnetized star formation, the magnetic field in
+Ser-emb 8 does not exhibit an hourglass morphology. Combining the new ALMA data
+with previous observational studies, we can connect magnetic field structure
+from protostellar core (~80,000 au) to disk (~100 au) scales. We compare our
+observations with four magnetohydrodynamic gravo-turbulence simulations made
+with the AREPO code that have initial conditions ranging from super-Alfv\'enic
+(weakly magnetized) to sub-Alfv\'enic (strongly magnetized). These simulations
+achieve the spatial dynamic range necessary to resolve the collapse of
+protostars from the parsec scale of star-forming clouds down to the ~100 au
+scale probed by ALMA. Only in the very strongly magnetized simulation do we see
+both the preservation of the field direction from cloud to disk scales and an
+hourglass-shaped field at < 1000 au scales. We conduct an analysis of the
+relative orientation of the magnetic field and the density structure in both
+the Ser-emb 8 ALMA observations and the synthetic observations of the four
+AREPO simulations. We conclude that the Ser-emb 8 data are most similar to the
+weakly magnetized simulations, which exhibit random alignment, in contrast to
+the strongly magnetized simulation, where the magnetic field plays a role in
+shaping the density structure in the source. In the weak-field case, it is
+turbulence -- not the magnetic field -- that shapes the material that forms the
+protostar, highlighting the dominant role that turbulence can play across many
+orders of magnitude in spatial scale.",1706.03806v1
+1995-08-19,Extragalactic Magnetic Field and the Highest Energy Cosmic Rays,"The strength and spectrum of the extragalactic magnetic field are still
+unknown. Its measurement would help answer the question of whether galactic
+fields are purely a primordial relic or were dynamically enhanced from a much
+smaller cosmological seed field. In this letter, we show that the composition,
+spectrum, and directional distribution of extragalactic ultrahigh energy cosmic
+rays with energies above $\simeq 10^{18}\ev$ can probe the large scale
+component of the extragalactic magnetic field below the present observational
+upper limit of $10^{-9}$ Gauss. Cosmic ray detectors under construction or
+currently in the proposal stage should be able to test the existence of the
+extragalactic magnetic fields on scales of a few to tens of Mpc and strengths
+in the range $\simeq 10^{-10} - 10^{-9}$ Gauss.",9508088v2
+1997-02-03,Magnetohydrodynamics in Superconducting-Superfluid Neutron Stars,"MHD equations are presented for the mixture of superfluid neutrons,
+superconducting protons, and normal electrons believed to exist in the outer
+cores of neutron stars. The dissipative effects of electron viscosity and
+mutual friction due to electron-vortex scattering are also included. It is
+shown that Alfven waves are replaced by cyclotron- vortex waves that have not
+been previously derived from MHD theory. The cyclotron- vortex waves are
+analogous to Alfven waves with the tension due to the magnetic energy density
+replaced by the vortex energy density. The equations are then put into a
+simplified form useful for studying the effects of the interior magnetic field
+on the dynamics. Of particular interest is the crust-core coupling time which
+can be inferred from pulsar glitch observations. The hypothesis that
+cyclotron-vortex waves play a significant role in the core spin-up during a
+glitch is used to place limits on the interior magnetic field. The results are
+compared with those of other studies.",9702032v3
+1997-08-01,Magnetic Fields from Phase Transitions,"The generation of primordial magnetic fields from cosmological phase
+transitions is discussed, paying particular attention to the electroweak
+transition and to the various definitions of the `average' field that have been
+put forward. It is emphasised that only the volume average has dynamical
+significance as a seed for galactic dynamos. On rather general grounds of
+causality and energy conservation, it is shown that, in the absence of MHD
+effects that transfer power in the magnetic field from small to large scales,
+processes occurring at the electroweak transition cannot generate fields
+stronger than $10^{-20}$ Gauss on a scale of 0.5 Mpc. However, it is
+implausible that this upper bound could ever be reached, as it would require
+all the energy in the Universe to be turned into a magnetic field coherent at
+the horizon scale. Non-linear MHD effects seem therefore to be necessary if the
+electroweak transition is to create a primordial seed field.",9708004v2
+1998-02-27,Dynamics of Magnetic Flux Elements in the Solar Photosphere,"The interaction of magnetic fields and convection is investigated in the
+context of the coronal heating problem. We study the motions of photospheric
+magnetic elements using filtergrams obtained at the Swedish Vacuum Solar
+Telescope at La Palma. We use potential-field modeling to extrapolate the
+magnetic and velocity fields to larger height. We find that the velocity in the
+chromosphere can be locally enhanced at the separatrix surfaces between
+neighboring flux tubes. The predicted velocities are several km/s,
+significantly larger than those of the photospheric flux tubes, which may have
+important implications for coronal heating. s",9802359v1
+1999-01-26,Magnetic CVs in Globular Clusters,"Cataclysmic variables (CVs) are tracers of dynamical evolution in globular
+clusters. A significant sample has been found by the relatively shallow \Halpha
+surveys conducted with HST thus far in just three globulars: NGC 6397 (3), NGC
+6752 (2), and $\omega$-Cen (2). These are identified with the low luminosity
+x-ray sources discovered in these globulars with similarly moderate-depth ROSAT
+surveys. Follow-up spectroscopy of the initial 3 CV candidates in NGC 6397 with
+the FOS on HST suggests they may be magnetic CVs of the intermediate polar (IP)
+type, and follow-up deep imaging with both HST and ROSAT yield a 4th confirmed
+and 5th strong candidate CV near the center of this collapsed core cluster. The
+optical vs. x-ray properties of the 4 confirmed IP candidates in NGC 6397 are
+compared with disk IPs, and arguments for and against this interpretation are
+presented. The possible strong excess of magnetic CVs in globulars will be
+tested with much deeper HST/AXAF surveys.",9901356v1
+1999-04-02,Scale-free Equilibria of Magnetized Polytropic Clouds,"We investigate the equilibrium properties of self-gravitating magnetized
+clouds with polytropic equations of state with negative index n. In particular,
+we consider scale-free isopedic configurations that have constant dimensionless
+spherical mass-to-flux ratio lambda_r and that may constitute ``pivotal''
+states for subsequent dynamical collapse to form groups or clusters of stars.
+For given Gamma = 1 + 1/n, equilibria with smaller values of lambda_r are more
+flattened, ranging from spherical configurations with lambda_r = infinity to
+completely flattened states for lambda_r=1. For a given amount of support
+provided by the magnetic field as measured by the dimensionless parameter H_0,
+equilibria with smaller values of Gamma are more flattened. However, logatropic
+(defined by Gamma = 0) disks do not exist. The only possible scale-free
+isopedic equilibria with logatropic equation of state are spherical uniformly
+magnetized clouds.",9904028v1
+1999-04-26,Magnetic fields in the early universe in the string approach to MHD,"There is a reformulation of magnetohydrodynamics in which the fundamental
+dynamical quantities are the positions and velocities of the lines of magnetic
+flux in the plasma, which turn out to obey equations of motion very much like
+ideal strings. We use this approach to study the evolution of a primordial
+magnetic field generated during the radiation-dominated era in the early
+Universe. Causality dictates that the field lines form a tangled random
+network, and the string-like equations of motion, plus the assumption of
+perfect reconnection, inevitably lead to a self-similar solution for the
+magnetic field power spectrum. We present the predicted form of the power
+spectrum, and discuss insights gained from the string approximation, in
+particular the implications for the existence or not of an inverse cascade.",9904358v1
+1999-10-20,Enhanced Cloud Disruption by Magnetic Field Interaction,"We present results from the first three-dimensional numerical simulations of
+moderately supersonic cloud motion through a tenuous, magnetized medium. We
+show that the interaction of the cloud with a magnetic field perpendicular to
+its motion has a great dynamical impact on the development of instabilities at
+the cloud surface. Even for initially spherical clouds, magnetic field lines
+become trapped in surface deformations and undergo stretching. The consequent
+field amplification that occurs there and particularly its variation across the
+cloud face then dramatically enhance the growth rate of Rayleigh-Taylor
+unstable modes, hastening the cloud disruption.",9910357v1
+2000-03-13,"Cosmic magnetism, curvature and the expansion dynamics","We discuss how a cosmological magnetic field could affect the expansion of
+the universe, through its interaction with the spacetime geometry. The tension
+of the field lines means that the magneto-curvature coupling tends to
+accelerate positively curved regions and decelerate those with negative
+curvature. Depending on the equation of state of the matter, the effect varies
+from mimicking that of a cosmological constant to resembling a time-decaying
+quintessence. Most interestingly, the coupling between magnetism and geometry
+implies that even weak fields have a significant impact if the curvature
+contribution is strong. This leads to kinematical complications that can
+inhibit the onset of the accelerated phase in spatially open inflationary
+models. We employ a simple cosmological model to illustrate these effects and
+examine the conditions necessary for them to have a appreciable impact.",0003181v3
+2000-12-02,How astrophysical mean field dynamos can circumvent existing quenching constraints,"Mean field dynamo theory is a leading candidate to explain the observed large
+scale magnetic fields of galaxies and stars. However, controversy arises over
+the extent of premature quenching by the backreaction of the growing field. We
+distinguish between rapid mean field dynamo action, which is required by
+astrophysical systems, and resistively limited action. We show how the flow of
+magnetic helicity is important for rapid action. Existing numerical and
+analytic work suggesting that mean field dynamos are prematurely quenched and
+resistively limited include approximations or boundary conditions which
+suppress the magnetic helicity flow from the outset. Thus they do not
+unambiguously reveal whether real astrophysical mean field dynamos are
+dynamically suppressed when the helicity flow is allowed. An outflow of
+helicity also implies an outflow of magnetic energy and so active coronae or
+winds should accompany mean field dynamos. Open boundaries alone may not be
+sufficient for rapid dynamo action and the additional physics of buoyancy and
+outflows may be required. Possible simulation approaches to test some of the
+principles are briefly discussed. Some limitations of the ``Zeldovich
+relation'' are also addressed.",0012048v1
+2001-01-19,Rapid-Process Nucleosynthesis in Neutrino-Magneto-Centrifugally Driven Winds,"We have studied whether the rotation and magnetic fields in neutrino-driven
+winds can be key processes for the rapid-process (r-process) nucleosynthesis.
+We have examined the features of a steady and subsonic wind solutions which
+extend the model of Weber and Davis (1967), which is a representative solar
+wind model. As a result, we found that the entropy per baryon becomes lower and
+the dynamical timescale becomes longer as the angular velocity becomes higher.
+These results are inappropriate for the production of the r-process nuclei. As
+for the effects of magnetic fields, we found that a solution as a steady wind
+from the surface of the proto-neutron star can not be obtained when the
+strength of the magnetic field becomes $\ge$ $10^{11}$ G. Since the magnetic
+field in normal pulsars is of order $10^{12}$ G, a steady wind solution might
+not be realized there, which means that the models in this study may not be
+adopted for normal proto-neutron stars. In this situation, we have little
+choice but to conclude that it is difficult to realize a successful r-process
+nucleosynthesis in the wind models in this framework.",0101347v1
+2001-02-02,Magnetohydrodynamic simulations of black hole accretion,"We discuss the results of three-dimensional magnetohydrodynamic simulations,
+using a pseudo-Newtonian potential, of thin disk (h/r ~ 0.1) accretion onto
+black holes. We find (i) that magnetic stresses persist within the marginally
+stable orbit, and (ii) that the importance of those stresses for the dynamics
+of the flow depends upon the strength of magnetic fields in the disk outside
+the last stable orbit. Strong disk magnetic fields (alpha > 0.1) lead to a
+gross violation of the zero-torque boundary condition at the last stable orbit,
+while weaker fields (alpha ~ 0.01) produce results more akin to traditional
+models for thin disk accretion onto black holes. Fluctuations in the magnetic
+field strength in the disk could lead to changes in the radiative efficiency of
+the flow on short timescales.",0102045v1
+2001-03-30,A Magnetohydrodynamic Nonradiative Accretion Flow in Three Dimensions,"We present a global magnetohydrodynamic (MHD) three dimensional simulation of
+a nonradiative accretion flow originating in a pressure supported torus. The
+evolution is controlled by the magnetorotational instability which produces
+turbulence. The flow forms a nearly Keplerian disk. The total pressure scale
+height in this disk is comparable to the vertical size of the initial torus.
+Gas pressure dominates only near the equator; magnetic pressure is more
+important in the surrounding atmosphere. A magnetically dominated bound outflow
+is driven from the disk. The accretion rate through the disk exceeds the final
+rate into the hole, and a hot torus forms inside 10 r_g. Hot gas, pushed up
+against the centrifugal barrier and confined by magnetic pressure, is ejected
+in a narrow, unbound, conical outflow. The dynamics are controlled by magnetic
+turbulence, not thermal convection, and a hydrodynamic alpha model is
+inadequate to describe the flow. The limitations of two dimensional MHD
+simulations are also discussed.",0103522v1
+2001-06-06,New circumstellar magnetic field diagnostics,"In this paper I will discuss new magnetic field diagnostics and
+instrumentation for an area of astrophysics where magnetic field observations
+have been difficult - circumstellar material. Such diagnostics would be
+particularly relevant to star formation and evolution. Stellar photosphere
+diagnostics include the Zeeman effect and atomic scattering diagnostics like
+the Hanle Effect and atomic alignment. The Zeeman Effect is in general not
+sensitive enough for the field strengths expected for circumstellar material,
+and it is easily defeated by Doppler broadening in a dynamic envelope. Atomic
+scattering diagnostics, pioneered recently for the Sun, are promising, but have
+never been applied outside the Sun. For the study of unresolved envelopes, the
+Hanle Effect may be applicable particularly in the ultraviolet. A medium
+resolution UV spectropolarimeter, for instance, would serve for such studies.
+Atomic alignment effects could utilize a ground-based, high signal-to-noise
+spectropolarimeter, with profile information from high spectral resolution. I
+will briefly mention several instrumentation development efforts in these
+directions.",0106114v1
+2002-04-17,Finite size scaling in the solar wind magnetic field energy density as seen by WIND,"Statistical properties of the interplanetary magnetic field fluctuations can
+provide an important insight into the solar wind turbulent cascade. Recently,
+analysis of the Probability Density Functions (PDF) of the velocity and
+magnetic field fluctuations has shown that these exhibit non-Gaussian
+properties on small time scales while large scale features appear to be
+uncorrelated. Here we apply the finite size scaling technique to explore the
+scaling of the magnetic field energy density fluctuations as seen by WIND. We
+find a single scaling sufficient to collapse the curves over the entire
+investigated range. The rescaled PDF follow a non Gaussian distribution with
+asymptotic behavior well described by the Gamma distribution arising from a
+finite range Levy walk. Such mono scaling suggests that a Fokker-Planck
+approach can be applied to study the PDF dynamics. These results strongly
+suggest the existence of a common, nonlinear process onthe time scale up to ~26
+hours.",0204287v1
+2003-03-26,Radial evolution of solar wind intermittency in the inner heliosphere,"We analyzed intermittency in the solar wind, as observed on the ecliptic
+plane, looking at magnetic field and velocity fluctuations between 0.3 and 1
+AU, for both fast and slow wind and for compressive and directional
+fluctuations. Our analysis focused on the property that probability
+distribution functions of a fluctuating field affected by intermittency become
+more and more peaked at smaller and smaller scales. Since the peakedness of a
+distribution is measured by its flatness factor we studied the behavior of this
+parameter for different scales to estimate the degree of intermittency of our
+time series. We confirmed that both magnetic field and velocity fluctuations
+are rather intermittent and that compressive magnetic fluctuations are
+generally more intermittent than the corresponding velocity fluctuations. In
+addition, we observed that compressive fluctuations are always more
+intermittent than directional fluctuations and that while slow wind
+intermittency does not depend on the radial distance from the sun, fast wind
+intermittency of both magnetic field and velocity fluctuations clearly
+increases with the heliocentric distance....",0303578v1
+2003-03-31,Interaction of a magnetized pulsar wind with its surroundings. MHD simulations of Pulsar Wind Nebulae,"Magnetohydrodynamical simulations are presented of a magnetized pulsar wind
+interacting directly with the interstellar medium, or, in the case of a
+surrounding supernova remnant, with the associated freely expanding ejecta of
+the progenitor star. In both cases the simulations show that the pulsar wind
+nebula will be elongated due to the dynamical influence of the toroidal
+magnetic fields, which confirm predictions from a semi-analytical model
+presented by Begelman & Li. The simulations follow the expansion of the pulsar
+wind nebula when the latter is bounded by a strong shock and show that the
+expansion can be modeled with a standard power-law expansion rate. By
+performing different simulations with different magnetization parameters, I
+show that the latter weakly correlates with the elongation of the pulsar wind
+nebula. The results from the simulations are applied to determine the nature of
+the expansion rate of the pulsar wind nebula 3C58. It is shown that there is
+both observational and theoretical evidence which supports the scenario in
+which the pulsar wind nebula 3C58 has caught up with the reverse shock of the
+associated (but undetected) supernova remnant.",0303661v1
+2003-08-14,Saturated State of the Nonlinear Small-Scale Dynamo,"We consider the problem of incompressible, forced, nonhelical, homogeneous
+and isotropic MHD turbulence with no mean magnetic field and large magnetic
+Prandtl number. This type of MHD turbulence is the end state of the turbulent
+dynamo, which generates folded fields with small-scale direction reversals. We
+propose a model in which saturation is achieved as a result of the velocity
+statistics becoming anisotropic with respect to the local direction of the
+magnetic folds. The model combines the effects of weakened stretching and
+quasi-two-dimensional mixing and produces magnetic-energy spectra in remarkable
+agreement with numerical results at least in the case of a one-scale flow. We
+conjecture that the statistics seen in numerical simulations could be explained
+as a superposition of these folded fields and Alfv\'en-like waves that
+propagate along the folds.",0308252v2
+2003-08-29,The Last Hurrah: PPN Formation by a Magnetic Explosion,"We discuss a mechanism by which a giant star can expel its envelope in an
+outburst, leaving its core exposed. The outburst is powered by rotational
+kinetic energy of the core, transferred to the envelope via the twisting of
+magnetic fields. We show that, if the core is magnetized, and if it has
+sufficient angular momentum, this mechanism may be triggered at the end of the
+asymptotic giant branch phase, and drive a proto-planetary nebula (pPN)
+outflow. This explosion of magnetic energy self-consistently explains some of
+the asymmetries and dynamics of pPNe.",0308548v2
+2003-11-10,Semi-analytical homologous solutions of the gravo-magnetic contraction,"We propose an extension of the semi-analytical solutions derived by Lin et
+al. (1965) describing the two-dimensional homologous collapse of a
+self-gravitating rotating cloud having uniform density and spheroidal shape,
+which includes magnetic field (with important restrictions) and thermal
+pressure. The evolution of the cloud is reduced to three time dependent
+ordinary equations allowing to conduct a quick and preliminary investigation of
+the cloud dynamics during the precollapse phase, for a wide range of
+parameters. We apply our model to the collapse of a rotating and magnetized
+oblate and prolate isothermal core. Hydrodynamical numerical simulations are
+performed and comparison with the semi-analytical solutions is discussed. Under
+the assumption that all cores are similar, an apparent cloud axis ratio
+distribution is calculated from the sequence of successive evolutionary states
+for each of a large set of initial conditions. The comparison with the
+observational distribution of the starless dense cores belonging to the catalog
+of Jijina et al. (1999) shows a good agreement for the rotating and initially
+prolate cores (aspect ratio $\simeq 0.5$) permeated by an helical magnetic
+field ($\simeq 17-20 \mu$G for a density of $\simeq 10^4$ cm$^{-3}$).",0311221v1
+2003-12-24,High-Energy Emission from Presupernovae,"The non-thermal emission in the magnetospheres of presupernova collapsing
+stars with initial dipole magnetic fields and a certain initial energy
+distribution of the charged particles in a magnetosphere is considered. The
+analysis of particle dynamics and its emission in the stellar magnetosphere
+under collapse show that the collapsing stars can be the powerful sources of a
+non-thermal radiation produced by the interaction of charged particles with the
+magnetic field. The radiation flux grows with decreasing stellar radius. This
+flux can be observed in the form of radiation burst with duration equal to the
+stellar collapse time. The radiation flux depends on the distance to the stars,
+the particle spectrum and magnetic field in the magnetosphere. The radiation
+flux is calculated for various collapsing stars with initial dipole magnetic
+fields and an initial power series, relativistic Maxwell, and Boltzmann
+particle energy distribution in the magnetosphere. This radiation can be
+observed by means of modern astronomical instruments.",0312615v1
+2004-09-08,Applying Magnetized Accretion-Ejection Models to Microquasars: a preliminary step,"We present in this proceeding some aspects of a model that should explain the
+spectral state changes observed in microquasars. In this model, ejection is
+assumed to take place only in the innermost disc region where a large scale
+magnetic field is anchored. Then, in opposite to conventional ADAF models, the
+accretion energy can be efficiently converted in ejection and not advected
+inside the horizon. We propose that changes of the disc physical state (e.g.
+transition from optically thick to optically thin states) can strongly modify
+the magnetic accretion-ejection structure resulting in the spectral
+variability. After a short description of our scenario, we give some details
+concerning the dynamically self-consistent magnetized accretion-ejection model
+used in our computation. We also present some preliminary results of spectral
+energy distribution.",0409194v1
+2004-09-21,Coronal heating through braiding of magnetic field lines,"Cool stars like our Sun are surrounded by a million degree hot outer
+atmosphere, the corona. Since more than 60 years the physical nature of the
+processes heating the corona to temperatures well in excess of those on the
+stellar surface remain puzzling. Recent progress in observational techniques
+and numerical modeling now opens a new window to approach this problem. We
+present the first coronal emission line spectra synthesized from
+three-dimensional numerical models describing the evolution of the dynamics and
+energetics as well as of the magnetic field in the corona. In these models the
+corona is heated through motions on the stellar surface that lead to a braiding
+of magnetic field lines inducing currents which are finally dissipated. These
+forward models enable us to synthesize observed properties like (average)
+emission line Doppler shifts or emission measures in the outer atmosphere,
+which until now have not been understood theoretically, even though many
+suggestions have been made in the past. As our model passes these observational
+tests, we conclude that the flux braiding mechanism is a prime candidate for
+being the dominant heating process of the magnetically closed corona of the Sun
+and solar-like stars.",0409504v1
+2004-10-11,Magnetohydrodynamic Simulations of Shock Interactions with Radiative Clouds,"We present results from two-dimensional numerical simulations of the
+interactions between magnetized shocks and radiative clouds. Our primary goal
+is to characterize the dynamical evolution of the shocked clouds. We perform
+runs in both the strong and weak magnetic field limits and consider three
+different field orientations. For the geometries considered, we generally find
+that magnetic fields external to, but concentrated near, the surface of the
+cloud suppress the growth of destructive hydrodynamic instabilities. External
+fields also increase the compression of the cloud by effectively acting as a
+confinement mechanism driven by the interstellar flow and local field
+stretching. This can have a dramatic effect on both the efficiency of radiative
+cooling, which tends to increase with increasing magnetic field strength, and
+on the size and distribution of condensed cooled fragments. In contrast, fields
+acting predominately internally to the cloud tend to resist compression,
+thereby inhibiting cooling. We observe that, even at modest strengths, internal
+fields can completely suppress low-temperature cooling.",0410285v1
+2005-10-24,Collapse of magnetized hypermassive neutron stars in general relativity,"Hypermassive neutron stars (HMNSs) -- equilibrium configurations supported
+against collapse by rapid differential rotation -- are possible transient
+remnants of binary neutron star mergers. Using newly developed codes for
+magnetohydrodynamic simulations in dynamical spacetimes, we are able to track
+the evolution of a magnetized HMNS in full general relativity for the first
+time. We find that secular angular momentum transport due to magnetic braking
+and the magnetorotational instability results in the collapse of an HMNS to a
+rotating black hole, accompanied by a gravitational wave burst. The nascent
+black hole is surrounded by a hot, massive torus undergoing quasistationary
+accretion and a collimated magnetic field. This scenario suggests that HMNS
+collapse is a possible candidate for the central engine of short gamma-ray
+bursts.",0510653v2
+2005-11-10,Spectrum of magnetohydrodynamic turbulence,"We propose a phenomenological theory of strong incompressible
+magnetohydrodynamic turbulence in the presence of a strong large-scale external
+magnetic field. We argue that in the inertial range of scales, magnetic-field
+and velocity-field fluctuations tend to align the directions of their
+polarizations. However, the perfect alignment cannot be reached, it is
+precluded by the presence of a constant energy flux over scales. As a
+consequence, the directions of fluid and magnetic-field fluctuations at each
+scale $\lambda$ become effectively aligned within the angle
+$\phi_{\lambda}\propto \lambda^{1/4}$, which leads to scale-dependent depletion
+of nonlinear interaction and to the field-perpendicular energy spectrum
+$E(k_{\perp})\propto k_{\perp}^{-3/2}$. Our results may be universal, i.e.,
+independent of the external magnetic field, since small-scale fluctuations
+locally experience a strong field produced by large-scale eddies.",0511290v2
+2006-05-12,Physical Origin of the Quadrupole Out-of-Plane Magnetic Field in Hall-MHD Reconnection,"A quadrupole pattern of the out-of-plane component of the magnetic field
+inside a reconnection region is seen as an important signature of the
+Hall-magnetohydrodynamic (Hall-MHD) regime of reconnection. It has been first
+observed in numerical simulations and just recently confirmed in the MRX
+(Magnetic Reconnection Experiment) [M. Yamada, H. Ji, S. Hsu, T. Carter, R.
+Kulsrud, N. Bertz, F. Jobes, Y. Ono, and F. Perkins, Phys. Plasmas 4, 1936
+(1997)] and also seen in spacecraft observations of Earth's magnetosphere. In
+this study, the physical origin of the quadrupole field is analyzed and traced
+to a current of electrons that flows along the lines in and out of the inner
+reconnection region to maintain charge neutrality. The role of the quadrupole
+magnetic field in the overall dynamics of the reconnection process is
+discussed. In addition, the bipolar poloidal electric field is estimated and
+its effect on ion motions is emphasized.",0605309v1
+2006-06-06,Helical Magnetorotational Instability in Magnetized Taylor-Couette Flow,"Hollerbach and Rudiger have reported a new type of magnetorotational
+instability (MRI) in magnetized Taylor-Couette flow in the presence of combined
+axial and azimuthal magnetic fields. The salient advantage of this ""helical''
+MRI (HMRI) is that marginal instability occurs at arbitrarily low magnetic
+Reynolds and Lundquist numbers, suggesting that HMRI might be easier to realize
+than standard MRI (axial field only). We confirm their results, calculate HMRI
+growth rates, and show that in the resistive limit, HMRI is a weakly
+destabilized inertial oscillation propagating in a unique direction along the
+axis. But we report other features of HMRI that make it less attractive for
+experiments and for resistive astrophysical disks. Growth rates are small and
+require large axial currents. More fundamentally, instability of highly
+resistive flow is peculiar to infinitely long or periodic cylinders: finite
+cylinders with insulating endcaps are shown to be stable in this limit. Also,
+keplerian rotation profiles are stable in the resistive limit regardless of
+axial boundary conditions. Nevertheless, the addition of toroidal field lowers
+thresholds for instability even in finite cylinders.",0606125v1
+2006-06-12,"The mean electro-motive force, current- and cross-helicity under the influence of rotation, magnetic field and shear","The mean electromotive force (MEMF) in a rotating stratified
+magnetohydrodynamical turbulence is studied.Our study rests on the mean-field
+magnetohydrodynamics framework and $\tau$ approximation. We compute the effects
+of the large-scale magnetic fields (LSMF), global rotation and large-scale
+shear flow on the different parts of the MEMF (such as $\alpha$ - effect,
+turbulent diffusion, turbulent transport, etc.) in an explicit form. The
+influence of the helical magnetic fluctuations which stem from the small-scale
+dynamo is taken into account, as well. In the paper, we derive the equation
+governing the current helicity evolution. It is shown that the joint effect of
+the differential rotation and magnetic fluctuations in the stratified media can
+be responsible for the generation, maintenance and redistribution of the
+current helicity. The implication of the obtained results to astrophysical
+dynamos is considered as well.",0606265v6
+2006-11-21,Exact scaling laws and the local structure of isotropic magnetohydrodynamic turbulence,"This paper examines the consistency of the exact scaling laws for isotropic
+MHD turbulence in numerical simulations with large magnetic Prandtl numbers Pm
+and with Pm=1. The exact laws are used to elucidate the structure of the
+magnetic and velocity fields. Despite the linear scaling of certain third-order
+correlation functions, the situation is not analogous to the case of Kolmogorov
+turbulence. The magnetic field is adequately described by a model of stripy
+(folded) field with direction reversals at the resistive scale. At currently
+available resolutions, the cascade of kinetic energy is short-circuited by the
+direct exchange of energy between the forcing-scale motions and the stripy
+magnetic fields. This nonlocal interaction is the defining feature of isotropic
+MHD turbulence.",0611692v1
+2007-02-05,On the intermittent character of interplanetary magnetic field fluctuations,"Interplanetary magnetic field magnitude fluctuations are notoriously more
+intermittent than velocity fluctuations in both fast and slow wind. This
+behaviour has been interpreted in terms of the anomalous scaling observed in
+passive scalars in fully developed hydrodynamic turbulence. In this paper, the
+strong intermittent nature of the interplanetary magnetic field is briefly
+discussed comparing results performed during different phases of the solar
+cycle. The scaling properties of the interplanetary magnetic field magnitude
+show solar cycle variation that can be distinguished in the scaling exponents
+revealed by structure functions. The scaling exponents observed around solar
+maximum coincide, within the errors, to those measured for passive scalars in
+hydrodynamic turbulence. However, it is also found that the values are not
+universal in the sense that the solar cycle variation may be reflected in
+dependence on the structure of the velocity field.",0702114v1
+2007-02-14,Quantum Electrodynamical Photon Splitting in Magnetized Nonlinear Pair Plasmas,"We present for the first time the nonlinear dynamics of quantum
+electrodynamic (QED) photon splitting in a strongly magnetized
+electron-positron (pair) plasma. By using a QED corrected Maxwell equation, we
+derive a set of equations that exhibit nonlinear couplings between
+electromagnetic (EM) waves due to nonlinear plasma currents and QED
+polarization and magnetization effects. Numerical analyses of our coupled
+nonlinear EM wave equations reveal the possibility of a more efficient decay
+channel, as well as new features of energy exchange among the three EM modes
+that are nonlinearly interacting in magnetized pair plasmas. Possible
+applications of our investigation to astrophysical settings, such as magnetars,
+are pointed out.",0702364v1
+2007-02-15,Seething Horizontal Magnetic Fields in the Quiet Solar Photosphere,"The photospheric magnetic field outside of active regions and the network has
+a ubiquitous and dynamic line-of-sight component that strengthens from disk
+center to limb as expected for a nearly horizontal orientation. This component
+shows a striking time variation with an average temporal rms near the limb of
+1.7 G at ~3"" resolution. In our moderate resolution observations the nearly
+horizontal component has a frequency variation power law exponent of -1.4 below
+1.5 mHz and is spatially patchy on scales up to ~15 arcsec. The field may be a
+manifestation of changing magnetic connections between eruptions and evolution
+of small magnetic flux elements in response to convective motions. It shows no
+detectable latitude or longitude variations.",0702415v1
+1995-05-04,What happens to the quantum Hall effect when magnetic-field-induced spin-density wave moves,"The influence of the motion of a magnetic-field-induced spin-density wave
+(FISDW) on the quantum Hall effect in a quasi-one-dimensional conductor is
+studied theoretically. In the ideal case of a free FISDW, it is found that the
+counterflow of the FISDW precisely cancels the quantum Hall current, so the
+resultant Hall conductivity is zero. In real systems, the Hall conductivity
+should vanish at the high frequencies, where the pinning and the damping can be
+neglected, and the dynamics of the FISDW is dominated by inertia.",9505016v1
+1996-10-09,Superconducting transition induced by columnar disorder in strong magnetic field,"The superconducting transition in presence of strong columnar disorder
+parallel to the magnetic field is considered. A solvable model appropriate for
+description of the broad crossover regime towards the true ""glassy"" critical
+behavior is constructed, and the behavior of the thermodynamic quantities and
+of the Edwards-Anderson order-parameter is obtained. The critical exponents for
+the correlation lengths orthogonal and parallel to the magnetic field are equal
+and in agreement with the experimental values. The dynamical critical exponent
+is $z=2$, also in agreement with the measured value. Several perturbations to
+the solvable model are considered and shown to be irrelevant for the critical
+behavior. It is argued that there exists an optimal density of defects at which
+the transition temperature at given magnetic field reaches its maximum.",9610083v1
+1996-11-27,Micromagnetic Simulation of Nanoscale Films with Perpendicular Anisotropy,"A model is studied for the theoretical description of nanoscale magnetic
+films with high perpendicular anisotropy. In the model the magnetic film is
+described in terms of single domain magnetic grains with Ising-like behavior,
+interacting via exchange as well as via dipolar forces. Additionally, the model
+contains an energy barrier and a coupling to an external magnetic field.
+Disorder is taken into account in order to describe realistic domain and domain
+wall structures. The influence of a finite temperature as well as the dynamics
+can be modeled by a Monte Carlo simulation.
+  Many of the experimental findings can be investigated and at least partly
+understood by the model introduced above. For thin films the magnetisation
+reversal is driven by domain wall motion. The results for the field and
+temperature dependence of the domain wall velocity suggest that for thin films
+hysteresis can be described as a depinning transition of the domain walls
+rounded by thermal activation for finite temperatures.",9611218v1
+1997-09-17,Theory of Hysteresis Loop in Ferromagnet,"A theory of the hysteresis loop in ferromagnets controlled by the domain wall
+motion is presented. Domain walls are considered as plane or linear interfaces
+moving in a random medium under the action of the external ac magnetic field
+$H=H_0\sin\omega t$. We introduce important characteristics of the hysteresis
+loop, such as dynamic threshold fields, reversal field etc. together with well
+known characteristics as coercive field and hysteresis loop area (HLA) $\cal
+A$. We show that all these characteristics are regulated by two dimensionless
+combinations of the $H_0$ and $\omega$and intrinsic characteristics of the
+ferromagnet. The moving domain wall can create magnetic bubbles playing the
+role of pre-existing nuclei of the reversed magnetization. We discuss a simple
+model of this process. For magnetization reversal determined by domain
+inflation we predict that HLA scales as ${\cal A}\propto
+\omega^{\beta}H_0^{\alpha}$ with $\alpha =1/2$ and $\beta =1/2$. Numerical
+simulations confirmthis result.",9709194v2
+1998-08-03,Coupled quantum dots as quantum gates,"We consider a new quantum gate mechanism based on electron spins in coupled
+semiconductor quantum dots. Such gates provide a general source of spin
+entanglement and can be used for quantum computers. We determine the exchange
+coupling J in the effective Heisenberg model as a function of magnetic (B) and
+electric fields, and of the inter-dot distance (a) within the Heitler-London
+approximation of molecular physics. This result is refined by using
+sp-hybridization, and by the Hund-Mulliken molecular-orbit approach which leads
+to an extended Hubbard description for the two-dot system that shows a
+remarkable dependence on B and a due to the long-range Coulomb interaction. We
+find that the exchange J changes sign at a finite field (leading to a
+pronounced jump in the magnetization) and then decays exponentially. The
+magnetization and the spin susceptibilities of the coupled dots are calculated.
+We show that the dephasing due to nuclear spins in GaAs can be strongly
+suppressed by dynamical nuclear spin polarization and/or by magnetic fields.",9808026v2
+1998-12-31,Anisotropic spin freezing in the S=1/2 zigzag ladder compound SrCuO2,"Using magnetic neutron scattering we characterize an unusual low temperature
+phase in orthorhombic SrCuO2. The material contains zigzag spin ladders formed
+by pairs of S=1/2 chains (J=180 meV) coupled through a weak frustrated
+interaction |J'|<0.1J. At T<Tc1=5.0(4)K an elastic peak develops in a gapless
+magnetic excitation spectrum indicating spin freezing on a time scale larger
+than 200 picoseconds. While the frozen state has long range commensurate
+antiferromagnetic order along the chains with the correlation length exceeding
+200 lattice periods along the c-axis and a substantial correlation length of
+60(25) spacings along the a-axis perpendicular to the zigzag plane, only 2
+lattice units are correlated along the b-axis which is the direction of the
+frustrated interactions. The frozen magnetic moment of each Cu ion is very
+small, 0.033(7) Bohr magneton even at T=0.35K, and has unusual temperature
+dependence with a cusp at Tc2=1.5K reminiscent of a phase transition. We argue
+that slow dynamics of stripe-like cooperative magnetic defects in tetragonal
+a-c planes yield this anisotropic frozen state.",9812440v3
+1999-05-18,From ferromagnetism to spin-density wave: Magnetism in the two channel periodic Anderson model,"The magnetic properties of the two-channel periodic Anderson model for
+uranium ions, comprised of a quadrupolar and a magnetic doublet are
+investigated through the crossover from the mixed-valent to the stable moment
+regime using dynamical mean field theory. In the mixed-valent regime
+ferromagnetism is found for low carrier concentration on a hyper-cubic lattice.
+The Kondo regime is governed by band magnetism with small effective moments and
+an ordering vector $\q$ close to the perfect nesting vector. In the stable
+moment regime nearest neighbour anti-ferromagnetism dominates for less than
+half band filling and a spin density wave transition for larger than half
+filling. $T_m$ is governed by the renormalized RKKY energy scale $\mu_{eff}^2
+<X_\sigma>^2 J^2\rho_0(\mu)$.",9905260v1
+1999-08-10,Magnetic relaxation in a classical spin chain as model for nanowires,"With decreasing particle size, different mechanisms dominate the thermally
+activated magnetization reversal in ferromagnetic particles. We investigate
+some of these mechanisms for the case of elongated, single-domain nanoparticles
+which we describe by a classical Heisenberg spin chain driven by an external
+magnetic field. For sufficiently small system size the magnetic moments rotate
+coherently. With increasing size a crossover to a reversal due to
+soliton-antisoliton nucleation sets in. For even larger systems many of these
+soliton-antisoliton pairs nucleate at the same time. These effects give rise to
+a complex size dependence of the energy barriers and characteristic time scales
+of the relaxation. We study these quantities using Monte Carlo simulations as
+well as a direct integration of the Landau-Lifshitz-Gilbert equation of motion
+with Langevin dynamics and we compare our results with asymptotic solutions for
+the escape rate following from the Fokker-Planck equation. Also, we investigate
+the crossover from coherent rotation to soliton-antisoliton nucleation and
+multi-droplet nucleation, especially its dependence on the system size, the
+external field and the anisotropy of the system.",9908150v1
+1999-08-26,Parallel flow in Hele-Shaw cells with ferrofluids,"Parallel flow in a Hele-Shaw cell occurs when two immiscible liquids flow
+with relative velocity parallel to the interface between them. The interface is
+unstable due to a Kelvin-Helmholtz type of instability in which fluid flow
+couples with inertial effects to cause an initial small perturbation to grow.
+Large amplitude disturbances form stable solitons. We consider the effects of
+applied magnetic fields when one of the two fluids is a ferrofluid. The
+dispersion relation governing mode growth is modified so that the magnetic
+field can destabilize the interface even in the absence of inertial effects.
+However, the magnetic field does not affect the speed of wave propagation for a
+given wavenumber. We note that the magnetic field creates an effective
+interaction between the solitons.",9908377v2
+2000-06-22,Quantum and classical dynamics in complex one-dimensional antiferromagnets,"Of great recent interest in condensed matter physics are phenomena of
+coexistence of quantum and classical properties in the same material. Such
+duality occurs in certain mixed-spin antiferromagnets composed of quantum spin
+chains interacting through ``auxiliary'' magnetic ions. In this category are
+linear-chain rare earth nickelates that exhibit a seemingly paradoxical
+co-existence of long-range magnetic order and one-dimensional gapped quantum
+spin excitations at low temperatures. In the present paper we propose a unified
+physical description of these compounds, supported by recent neutron
+diffraction and inelastic scattering studies. Our basic concept is the
+effective separation between low-frequency classical and high-frequency quantum
+spin correlations. This interpretation enables experimental measurements of
+some previously inaccessible fundamental properties of quantum spin chains, and
+predicts new exotic magnetic excitations and mechanisms of long-range ordering
+in complex quantum magnets.",0006350v1
+2000-07-17,Fine-grid Simulations of Thermally Activated Switching in Nanoscale Magets,"Numerical integration of the Landau-Lifshitz-Gilbert equation with thermal
+fluctuations is used to study the dynamic response of single-domain nanomagnets
+to rapid changes in the applied magnetic field. The simulation can resolve
+magnetization patterns within nanomagnets and uses the Fast Multipole method to
+calculate dipole-dipole interactions efficiently. The thermal fluctuations play
+an essential part in the reversal process whenever the applied field is less
+than the zero-temperature coercive field. In this situation pillar-shaped
+nanomagnets are found to reverse through a local curling mode that involves the
+formation and propagation of a domain wall. Tapering the ends of the pillars to
+reduce pole-avoidance effects changes the energies involved but not the
+fundamental process. The statistical distribution of switching times is well
+described by the independent nucleation and subsequent growth of regions of
+reversed magnetization at both ends of the pillar.",0007279v1
+2000-09-06,Mixing of magnetic and phononic excitations in incommensurate Spin-Peierls systems,"We analyze the excitation spectra of a spin-phonon coupled chain in the
+presence of a soliton. This is taken as a microscopic model of a Spin-Peierls
+material placed in a high magnetic field. We show, by using a semiclassical
+approximation in the bosonized representation of the spins that a trapped
+magnetic state obtained in the adiabatic approximation is destroyed by
+dynamical phonons. Low energy states are phonons trapped by the soliton. When
+the magnetic gap is smaller than the phonon frequencies the only low energy
+state is a mixed magneto-phonon state with the energy of the gap. We emphasize
+that our results are relevant for the Raman spectra of the inorganic
+Spin-Peierls material CuGeO$_3$.",0009091v1
+2000-10-06,Magnetic relaxation phenomena and cluster glass properties of La{0.7-x}Y{x}Ca{0.3}MnO{3} manganites,"The dynamic magnetic properties of the distorted perovskite system
+La{0.7-x}Y{x}Ca{0.3}MnO{3} (0 <= x <= 0.15) have been investigated by
+ac-susceptibility and dc magnetization measurements, with emphasis on
+relaxation and aging studies. They evidence for x >= 0.10 the appearance of a
+metallic cluster glass phase, that develops just below the ferromagnetic
+transition temperature. The clusters grow with decreasing temperature down to a
+temperature T(f0) at which they freeze due to severe intercluster frustration.
+The formation of these clusters is explained by the presence of yttrium induced
+local structural distortions that create localized spin disorder in a magnetic
+lattice where double-exchange ferromagnetism is dominant.",0010110v2
+2000-10-24,Rotating Hele-Shaw cells with ferrofluids,"We investigate the flow of two immiscible, viscous fluids in a rotating
+Hele-Shaw cell, when one of the fluids is a ferrofluid and an external magnetic
+field is applied. The interplay between centrifugal and magnetic forces in
+determining the instability of the fluid-fluid interface is analyzed. The
+linear stability analysis of the problem shows that a non-uniform, azimuthal
+magnetic field, applied tangential to the cell, tends to stabilize the
+interface. We verify that maximum growth rate selection of initial patterns is
+influenced by the applied field, which tends to decrease the number of
+interface ripples. We contrast these results with the situation in which a
+uniform magnetic field is applied normally to the plane defined by the rotating
+Hele-Shaw cell.",0010374v1
+2000-11-20,Spin correlations in the two-leg antiferromagnetic ladder in a magnetic field,"We study the ground-state spin correlations in the gapless incommensurate
+regime of a S=1/2 XXZ chain and a two-leg antiferromagnetic ladder under a
+magnetic field, in which the gapless excitations form a Tomonaga-Luttinger (TL)
+liquid. We calculate numerically the two-spin correlation functions and the
+local magnetization in the two models using the density-matrix
+renormalization-group method. By fitting the numerical results for an open XXZ
+chain of 100 spins to correlation functions of a Gaussian model, we determine
+the TL-liquid parameter K and the amplitudes of the correlation functions. The
+value of K estimated from the fits is in excellent agreement with the exact
+value obtained from the Bethe ansatz. We apply the same method to the open
+ladder consisting of 200 spins and determine the dependence of K on the
+magnetization M. The K-M relation changes drastically depending on the ratio of
+the coupling constants in the leg and rung directions. We also discuss
+implications of these results to experiments on the nuclear spin relaxation
+rate 1/T_1 and dynamical spin structure factors.",0011320v1
+2000-11-23,Quantum Computing in Molecular Magnets,"Shor and Grover demonstrated that a quantum computer can outperform any
+classical computer in factoring numbers and in searching a database by
+exploiting the parallelism of quantum mechanics. Whereas Shor's algorithm
+requires both superposition and entanglement of a many-particle system, the
+superposition of single-particle quantum states is sufficient for Grover's
+algorithm. Recently, the latter has been successfully implemented using Rydberg
+atoms. Here we propose an implementation of Grover's algorithm that uses
+molecular magnets, which are solid-state systems with a large spin; their spin
+eigenstates make them natural candidates for single-particle systems. We show
+theoretically that molecular magnets can be used to build dense and efficient
+memory devices based on the Grover algorithm. In particular, one single crystal
+can serve as a storage unit of a dynamic random access memory device. Fast
+electron spin resonance pulses can be used to decode and read out stored
+numbers of up to 10^5, with access times as short as 10^{-10} seconds. We show
+that our proposal should be feasible using the molecular magnets Fe8 and Mn12.",0011415v2
+2001-03-19,Time decay of the remanent magnetization in the $\pm J$ spin glass model at T=0,"Using the zero-temperature Metropolis dynamics, the time decay of the
+remanent magnetization in the $\pm J$ Edward-Anderson spin glass model with a
+uniform random distribution of ferromagnetic and antiferromagnetic interactions
+has been investigated. Starting from the saturation, the magnetization per spin
+$m$ reveals a slow decrease with time, which can be approximated by a power
+law:$m(t)=m_{\infty}+ ({t\over a_{0}})^{a_{1}}$, $a_{1} < 0$. Moreover, its
+relaxation does not lead it into one of the ground states, and therefore the
+system is trapped in metastable isoenergetic microstates remaining magnetized.
+Such behaviour is discussed in terms of a random walk the system performs on
+its available configuration space.",0103382v4
+2001-06-12,Theory of combined exciton-cyclotron resonance in a two-dimensional electron gas: The strong magnetic field regime,"I develop a theory of combined exciton-cyclotron resonance (ExCR) in a
+low-density two-dimensional electron gas in high magnetic fields. In the
+presence of excess electrons an incident photon creates an exciton and
+simultaneously excites one electron to higher-lying Landau levels. I derive
+exact ExCR selection rules that follow from the existing dynamical symmetries,
+magnetic translations and rotations about the magnetic field axis. The nature
+of the final states in the ExCR is elucidated. The relation between ExCR and
+shake-up processes is discussed. The double-peak ExCR structure for transitions
+to the first electron Landau level is predicted.",0106229v2
+2001-11-20,Semiclassical analysis of a two-electron quantum dot in a magnetic field: dimensional phenomena,"While the dynamics for three-dimensional axially symmetric two-electron
+quantum dots with parabolic confinement potentials is in general non-separable
+we have found an exact separability with three quantum numbers for specific
+values of the magnetic field. Furthermore, it is shown that the magnetic
+properties such as the magnetic moment and the susceptibility are sensitive to
+the presence and strength of a vertical confinement. Using a semiclassical
+approach the calculation of the eigenvalues reduces to simple quadratures
+providing a transparent and almost analytical quantization of the quantum dot
+energy levels which differ from the exact energies only by a few percent.",0111381v2
+2001-12-10,Unusual magneto-elastic forces stabilize the insulating ferromagnetic state of manganites: the La(0.8)Ca(0.2)$MnO(3) case,"The ferromagnetic and insulating state observed in La$_{1-x}$Ca$_{x}$MnO$_3$,
+0.125$<$x$<$0.2, is characterized by structural and magnetic anomalies below
+T$_C$, similar to those observed in the x$_{Sr}$$\approx$1/8. A neutron
+scattering study of the superlattice {\bf Q$_0$}= (0,0,1+/4)$_{cub}$ peak, and
+of the magnetic excitations are reported in the x$_{Ca}$=0.2 sample. The
+occurrence of this superstructure is associated with the observation of a gap
+in the spin dynamics, at a {\bf q$_0$} wave-vector ({\bf q$_0$}={\bf
+Q$_0$}-$\tau$) with the same modulus $|${\bf q$_0$}$|$ in all directions, which
+divides the dispersion into two regimes. For $|${\bf q}$|$$<$$|${\bf q$_0$}$|$
+the dispersion is splitted into two or three curves. For $|${\bf
+q}$|$$>$$|${\bf q$_0$}$|$, magnetic excitations lock on acoustic and optic
+phonon energies, revealing a new kind of magneto-vibrational coupling.
+  We suggest an analysis in terms of two distinct magnetic couplings,
+associated with two ferromagnetic media involved into a collective state.",0112159v1
+2002-01-09,Monte-Carlo simulation of nucleation in the two-dimensional Potts model,"Nucleation in the two-dimensional q-state Potts model has been studied by
+means of Monte-Carlo simulations using the heat-bath dynamics. The initial
+metastable state has been prepared by magnetic quench of the ordered
+low-temperature phase. The magnetic field dependence of the nucleation time has
+been measured as the function of the magnetic field for different q and lattice
+sizes at T=0.5 Tc. A size-dependent crossover from the coalescence to
+nucleation region is observed at all q. The magnetic field dependence of the
+nucleation time is roughly described by the classical nucleation theory. Our
+data show increase of the anisotropy in the shape of the critical droplets with
+increase of q.",0201128v1
+2002-03-10,Thermal Conductivity in 3D NJL Model Under External Magnetic Field,"The thermal conductivity of the (2+1)-dimensional NJL model in the presence
+of a constant magnetic field is calculated in the mean-field approximation and
+its different asymptotic regimes are analyzed. Taking into account the
+dynamical generation of a fermion mass due to the magnetic catalysis
+phenomenon, it is shown that for certain relations among the theory's
+parameters (particle width, temperature and magnetic field), the profile of the
+thermal conductivity versus the applied field exhibits kink- and plateau-like
+behaviors. We point out possible applications to planar condensed matter.",0203217v2
+2002-06-10,"Prediction of huge X-ray Faraday rotation at the Gd N_4,5 threshold","X-ray absorption spectra in a wide energy range around the 4d-4f excitation
+threshold of Gd were recorded by total electron yield from in-plane magnetized
+Gd metal films. Matching the experimental spectra to tabulated absorption data
+reveals unprecedented short light absorption lengths down to 3 nm. The
+associated real parts of the refractive index for circularly polarized light
+propagating parallel or antiparallel to the Gd magnetization, determined
+through the Kramers-Kronig transformation, correspond to a magneto-optical
+Faraday rotation of 0.7 degrees per atomic layer. This finding shall allow the
+study of magnetic structure and magnetization dynamics of lanthanide elements
+in nanosize systems and dilute alloys.",0206154v2
+2002-09-23,Magnetic flux penetration and motion in antiferromagnetic superconductors,"The paper reviews a concept of induced spin-flop domain inside vortices in an
+antiferromagnetic superconductor. Such phenomenon may occur when an external
+magnetic field is strong enough to flip over magnetic moments in the core of
+the vortex from their ground state configuration. The formation of the domain
+structure inside vortices modifies the surface energy barrier of the
+superconductor. During this process the entrance of the flux is stopped and a
+newly created state exhibits perfect shielding. Such behavior should be visible
+as a plateau on the dependence of flux density as a function of the external
+magnetic field. The end of the plateau determines the critical field, which has
+been called the second critical field for flux penetration. Moreover, it is
+predicted and described how this phenomenon modifies flux creep in layered
+superconductors. The various scenarios of changing the creep regime from
+thermal to quantum and vice versa at constant temperature are discussed.",0209526v2
+2002-11-05,Spectral density functional approach to electronic correlations and magnetism in crystals,"A novel approach to electronic correlations and magnetism of crystals based
+on realistic electronic structure calculations is reviewed. In its simplest
+form it is a combination of the ``local density approximation'' (LDA) and the
+dynamical mean field theory (DMFT) approaches. Using numerically exact QMC
+solution to the effective DMFT multi-orbital quantum-impurity problem, a
+successful description of electronic structure and finite temperature magnetism
+of transition metals has been achieved. We discuss a simplified perturbation
+LDA+DMFT scheme which combines the T-matrix and fluctuation-exchange
+approximation (TM-FLEX). We end with a discussion of cluster generalization of
+the non-local DMFT scheme and its applications to the magnetism and
+superconductivity of high-Tc superconductors.",0211076v1
+2002-11-25,Spin-polarized current oscillations in diluted magnetic semiconductor multiple quantum wells,"We study the spin and charge dynamics of electrons in n-doped II--VI
+semiconductor multiple quantum wells when one or more quantum wells are doped
+with Mn. The interplay between strongly nonlinear inter-well charge transport
+and the large tunable spin-splitting induced by exchange interactions with
+spin-polarized Mn ions produces interesting new spin dependent features. The
+tunneling current between quantum wells can be strongly spin polarized and,
+under certain conditions, can develop self sustained oscillations under a
+finite dc voltage. The spin polarization oscillates in both magnetic and
+nonmagnetic quantum wells and the time average in magnetic wells can differ
+from its zero-voltage value. Our numerical simulations demonstrate that the
+amplitude of the spin polarization oscillations depends on the distribution of
+magnetic wells within the sample. We discuss how the spin polarized current and
+the spin polarization of the quantum wells can be tailored experimentally.",0211557v1
+2003-03-18,Extended quantum critical phase in a magnetized spin-1/2 antiferromagnetic chain,"Measurements are reported of the magnetic field dependence of excitations in
+the quantum critical state of the spin S=1/2 linear chain Heisenberg
+antiferromagnet copper pyrazine dinitrate (CuPzN). The complete spectrum was
+measured at k_B T/J <= 0.025 for H=0 and H=8.7 Tesla where the system is ~30%
+magnetized. At H=0, the results are in quantitative agreement with exact
+calculations of the dynamic spin correlation function for a two-spinon
+continuum. At high magnetic field, there are multiple overlapping continua with
+incommensurate soft modes. The boundaries of these continua confirm
+long-standing predictions, and the intensities are consistent with exact
+diagonalization and Bethe Ansatz calculations.",0303364v1
+2003-04-07,Separation Between Antiferromagnetic and Ferromagnetic Transitions in Ru_1-xCu_xSr_2EuCu_2O_8+d,"The macroscopic magnetizations of Ru_1-xCu_xSr_2EuCu_2O_8+d with x between 0
+and 0.15 were investigated. A ferromagnet-like transition as well as an
+antiferromagnet-like transition appear around T_M in the low-field
+magnetization and around T_AM in the high-field differential susceptibility,
+respectively. The separation between them, which is accompanied by a flat
+plateau in the magnetic C_p, increases with x. Superparamagnetic M(H) and slow
+spin dynamics, i.e. characteristics of nanomagnetic clusters, were observed far
+above T_M. A comparison with RuSr_2(Eu_1-yCe_y)Cu_2O_10+d and some manganites
+further suggests that a phase separation occurs, which can describe well the
+conflicting magnetic-superconductivity data previously reported.",0304163v1
+2003-04-24,Ferromagnetism in a dilute magnetic semiconductor -- Generalized RKKY interaction and spin-wave excitations,"Carrier-mediated ferromagnetism in a dilute magnetic semiconductor has been
+studied using i) a single-impurity based generalized RKKY approach which goes
+beyond linear response theory, and ii) a mean-field-plus-spin-fluctuation
+(MF+SF) approach within a (purely fermionic) Hubbard-model representation of
+the magnetic impurities, which incorporates dynamical effects associated with
+finite frequency spin correlations in the ordered state. Due to a competition
+between the magnitude of the carrier spin polarization and its oscillation
+length scale, the ferromagnetic spin coupling is found to be optimized with
+respect to both hole doping concentration and impurity-carrier spin coupling
+energy $J$ (or equivalently $U$). The ferromagnetic transition temperature
+$T_c$, deteremined within the spin-fluctuation theory, corresponds closely with
+the observed $T_c$ values. Positional disorder of magnetic impurities causes
+significant stiffening of the high-energy magnon modes. We also explicitly
+study the stability/instability of the mean-field ferromagnetic state, which
+highlights the role of competing AF interactions causing spin twisting and
+noncollinear ferromagnetic ordering.",0304557v2
+2003-04-27,Nanomechanical Analog of a Laser: Amplification of Mechanical Oscillations by Stimulated Zeeman Transitions,"We propose a magnetomechanical device that exhibits many properties of a
+laser. The device is formed by a nanocantilever and dynamically polarized
+paramagnetic nuclei of a solid sample in a strong external magnetic field. The
+corresponding quantum oscillator and effective two-level systems are coupled by
+the magnetostatic dipole-dipole interaction between a permanent magnet on the
+cantilever tip and the magnetic moments of the spins, so that the entire system
+is effectively described by the Jaynes-Cummings model. We consider the
+possibility of observing transient and cw lasing in this system, and show how
+these processes can be used to improve the sensitivity of magnetic resonance
+force microscopy.",0304605v2
+2003-06-06,The kinetic spherical model in a magnetic field,"The long-time kinetics of the spherical model in an external magnetic field
+and below the equilibrium critical temperature is studied. The solution of the
+associated stochastic Langevin equation is reduced exactly to a single
+non-linear Volterra equation. For a sufficiently small external field, the
+kinetics of the magnetization-reversal transition from the metastable to the
+ground state is compared to the ageing behaviour of coarsening systems quenched
+into the low-temperature phase. For an oscillating magnetic field and below the
+critical temperature, we find evidence for the absence of the
+frequency-dependent dynamic phase transition, which was observed previously to
+occur in Ising-like systems.",0306171v2
+2003-06-24,Optical bandedge of diluted magnetic semiconductors: difference between II-VI and III-V-based DMSs,"Applying the dynamical coherent potential approximation to a simple model, we
+have theoretically studied the behavior of the optical bandedge in diluted
+magnetic semiconductors (DMSs). For $A^{\rm II}_{1-x}$Mn$_{x}B^{\rm VI}$-type
+DMS, the present study reveals that the linear relationship between
+exchange-spitting $\mit\Delta E_{ex} $ and the averaged magnetization $|x < S_z
+>|$ widely holds for different values of $x$. The ratio, $\mit\Delta E_{ex}/x <
+S_z>$, however, depends not only the exchange strength but also the band
+offset. Furthermore, the present study reveals that in the low dilution of
+Ga$_{1-x}$Mn$_x$As the optical bandedge exists not at the bandedge of the
+impurity band but near the bottom of host band. The optical bandedge behaves as
+if the exchange interaction is ferromagnetic although the antiferromagnetic
+exchange interaction actually operates at Mn site. We conclude that the
+spin-dependent shift of the carrier states between the impurity band and host
+band accompanying with the change of magnetization causes the apparently
+ferromagnetic behavior of the optical bandedge which was reported in the
+magnetoreflection measurement of Ga$_{1-x}$Mn$_x$As.",0306588v1
+2003-06-25,Ultrafast Auger spectroscopy of quantum well excitons in a strong magnetic field,"We study theoretically the ultrafast nonlinear optical response of quantum
+well excitons in a perpendicular magnetic field. We address the role of
+many-body correlations originating from the electron scattering between Landau
+levels (LL). In the linear optical response, the processes involving inter-LL
+transitions are suppressed provided that the magnetic field is sufficiently
+strong. However, in the nonlinear response, the Auger processes involving
+inter-LL scattering of two photoexcited electrons remain unsuppressed. We show
+that Auger scattering plays the dominant role in the coherent exciton dynamics
+in strong magnetic field. We perform numerical calculations for the third-order
+four-wave-mixing (FWM) polarization which incorporate the Auger processes
+nonperturbatively. We find that inter-LL scattering leads to a strong
+enhancement and to oscillations of the FWM signal at negative time delays.
+These oscillations represent quantum beats between optically-inactive
+two-exciton states related to each other via Auger processes.",0306630v2
+2003-10-18,Experiment and Dynamic Simulations of Radiation Damping of Laser-polarized liquid 129Xe at low magnetic field in a flow system,"Radiation damping is generally observed when the sample with high spin
+concentration and high gyro-magnetic ratio is placed in a high magnetic field.
+However, we firstly observed liquid state 129Xe radiation damping using
+laser-enhanced nuclear polarization at low magnetic field in a flow system in
+which the polarization enhancement factor for the liquid state 129Xe was
+estimated to be 5000, and furthermore theoretically simulated the envelopes of
+the 129Xe FID and spectral lineshape in the presence of both relaxation and
+radiation damping with different pulse flip angles and ratios of T2*/Trd. The
+radiation damping time constant Trd of 5 ms was derived based on the
+simulations. The reasons of depolarization and the further possible
+improvements were also discussed.",0310435v1
+2004-03-18,"Electrons in 2D periodic magnetic and electric fields: Avoided band crossings, metal-insulator transitions, and changes in the spreading direction","We study the energy spectrum and wave packet dynamics of electrons in a
+two-dimensional periodic potential subject to a perpendicular spatially
+modulated magnetic field. We observe avoided band crossings, metal-insulator
+transitions, and changes in the spreading direction of wave packets in two new
+situations: (i) for a purely magnetic modulation and (ii) in the limit of weak
+electric and magnetic modulations, where the Landau band coupling can be
+neglected. In the second case the corresponding classical system is no longer
+chaotic but integrable, whereby these phenomena are not expected. We argue that
+they are due to tunneling.",0403462v2
+2004-03-19,Charge dynamics and Kondo effect in single electron traps in field effect transistors,"We study magneto-electric properties of single electron traps in
+metal-oxide-semiconductor field effect transistors. Using a microscopic
+description of the system based on the single-site Anderson-Holstein model, we
+derive an effective low energy action for the system. The behavior of the
+system is characterized by simultaneous polaron tunneling (corresponding to the
+charging and discharging of the trap) and Kondo screening of the trap spin in
+the singly occupied state. Hence, the obtained state of the system is a hybrid
+between the Kondo regime, typically associated with single electron occupancy,
+and the mixed valence regime, associated with large charge fluctuations. In the
+presence of a strong magnetic field, we demonstrate that the system is
+equivalent to a two level-level system coupled to an Ohmic bath, with a bias
+controlled by the applied magnetic field. Due to the Kondo screening, the
+effect of the magnetic field is significantly suppressed in the singly occupied
+state. We claim that this suppression can be responsible for the experimentally
+observed anomalous magnetic field dependence of the average trap occupancy in
+${\rm Si-Si0_2}$ field effect transistors.",0403491v1
+2004-07-29,Kondo Effect on Mesoscopic Scale (Review),"Following the discovery of the Kondo effect the bulk transport and magnetic
+behavior of the dilute magnetic alloys have been successfully described. In the
+last fifteen years new directions have been developed as the study of the
+systems of reduced dimensions and the artificial atoms so called quantum dots.
+In this review the first subject is reviewed starting with the scanning
+tunneling microscope (STM) study of a single magnetic impurity. The next
+subject is the reduction of the amplitude of the Kondo effect in samples of
+reduced dimension which was explained by the surface magnetic anisotropy which
+blocks the motion of the integer spin nearby the surface. The electron
+dephasing and energy relaxation experiments are discussed with the possible
+explanation including the surface anisotropy, where the situation in cases of
+integer and half-integer spins is very different. Finally, the present
+situation of the theory of dynamical structural defects is briefly presented
+which may lead to two-channel Kondo behavior.",0407766v1
+2004-08-26,Exchange constants and spin dynamics in Mn12-acetate,"We have obtained new inelastic neutron scattering (INS) data for the
+molecular magnet Mn12-acetate which exhibit at least six magnetic peaks in the
+energy range 5-35 meV. These are compared with a microscopic Heisenberg model
+for the 12 quantum spins localised on the Mn ions, coupled by four inequivalent
+magnetic exchange constants. A fit to the magnetic susceptibility under the
+constraint that the spin of the ground state be S=10 yields two dominant
+exchange constants of very similar value, J1 ~ J2 ~ 65 K (~ 5.5 meV), and two
+smaller exchange constants J3 and J4. We compute the low-lying excitations by
+exact numerical diagonalisation and demonstrate that the parameters determined
+from the ground state and susceptibility fit provide qualitative agreement with
+the excitations observed by INS.",0408576v1
+2004-08-27,Long-range dynamics of magnetic impurities coupled to a two-dimensional Heisenberg antiferromagnet,"We consider a two-dimensional Heisenberg antiferromagnet on a square lattice
+with weakly coupled impurities, i.e. additional spins interacting with the host
+magnet by a small dimensionless coupling constant g<<1. Using linear spin-wave
+theory, we find that the magnetization disturbance at distance r from a single
+impurity behaves as g/r for 1<<r<<1/g and as 1/(gr^3) for r>>1/g. Surprisingly
+the disturbance is inversely proportional to the coupling constant! The
+interaction between two impurities separated by a distance r is proportional to
+g^2/r for 1<<r<<1/g and to 1/r^3 for r>>1/g. Hence at large distances, the
+interaction is universal and independent of the coupling constant. We also find
+that the frequency of Rabi oscillations between two impurities is proportional
+to g^2 ln(gr) at 1<<r<<1/g, logarithmically enhanced compared to the spin-wave
+width. This leads to a new mechanism for NMR, NQR and EPR line broadening. All
+these astonishing results are due to the gapless spectrum of the magnetic
+excitations in the quantum antiferromagnet.",0408598v2
+2004-11-01,Optical Orientation of Excitons in CdSe Self-Assembled Quantum Dots,"We study spin dynamics of excitons confined in self-assembled CdSe quantum
+dots by means of optical orientation in magnetic field. At zero field the
+exciton emission from QDs populated via LO phonon-assisted absorption shows a
+circular polarization of 14%. The polarization degree of the excitonic emission
+increases dramatically when a magnetic field is applied. Using a simple model,
+we extract the exciton spin relaxation times of 100 ps and 2.2 ns in the
+absence and presence of magnetic field, respectively. With increasing
+temperature the polarization of the QD emission gradually decreases.
+Remarkably, the activation energy which describes this decay is independent of
+the external magnetic field, and, therefore, of the degeneracy of the exciton
+levels in QDs. This observation implies that the temperature-induced
+enhancement of the exciton spin relaxation is insensitive to the energy level
+degeneracy and can be attributed to the same excited state distribution.",0411036v1
+2005-02-18,Non-equilibrium Magnetization Dynamics in the Fe_8 Single-Molecule Magnet Induced by High-Intensity Microwave Radiation,"Resonant microwave radiation applied to a single crystal of the molecular
+magnet Fe_8 induces dramatic changes in the sample's magnetization. Transitions
+between excited states are found even though at the nominal system temperature
+these levels have negligible population. We find evidence that the sample heats
+significantly when the resonance condition is met. In addition, heating is
+observed after a short pulse of intense radiation has been turned off,
+indicating that the spin system is out of equilibrium with the lattice.",0502424v2
+2005-02-24,Non-exponential spin relaxation in magnetic field in quantum wells with random spin-orbit coupling,"We investigate the spin dynamics of electrons in quantum wells where the
+Rashba type of spin-orbit coupling is present in the form of random nanosize
+domains. We study the effect of magnetic field on the spin relaxation in these
+systems and show that the spatial randomness of spin-orbit coupling limits the
+minimum relaxation rate and leads to a Gaussian time-decay of spin polarization
+due to memory effects. In this case the relaxation becomes faster with increase
+of the magnetic field in contrast to the well known magnetic field suppression
+of spin relaxation.",0502593v3
+2005-03-25,Bose-Einstein Condensation on a Permanent-Magnet Atom Chip,"We have produced a Bose-Einstein condensate on a permanent-magnet atom chip
+based on periodically magnetized videotape. We observe the expansion and
+dynamics of the condensate in one of the microscopic waveguides close to the
+surface. The lifetime for atoms to remain trapped near this dielectric material
+is significantly longer than above a metal surface of the same thickness. These
+results illustrate the suitability of microscopic permanent-magnet structures
+for quantum-coherent preparation and manipulation of cold atoms.",0503619v2
+2005-05-30,Mechanisms limiting the coherence time of spontaneous magnetic oscillations driven by DC spin-polarized currents,"The spin-transfer torque from a DC spin-polarized current can generate
+highly-coherent magnetic precession in nanoscale magnetic-multilayer devices.
+By measuring linewidths of spectra from the resulting resistance oscillations,
+we argue that the coherence time can be limited at low temperature by thermal
+deflections about the equilibrium magnetic trajectory, and at high temperature
+by thermally-activated transitions between dynamical modes. Surprisingly, the
+coherence time can be longer than predicted by simple macrospin simulations.",0505733v2
+2005-06-17,Magnetic density of states at low energy in geometrically frustrated systems,"Using muon-spin-relaxation measurements we show that the pyrochlore compound
+Gd2Ti2O7, in its magnetically orderered phase below ~ 1 K, displays persistent
+spin dynamics down to temperatures as low as 20 mK. The characteristics of the
+induced muon relaxation can be accounted for by a scattering process involving
+two magnetic excitations, with a density of states characterized by an upturn
+at low energy and a small gap depending linearly on the temperature. We propose
+that such a density of states is a generic feature of geometrically frustrated
+magnetic materials.",0506451v1
+2005-09-27,Memory and aging effect in hierarchical spin orderings of stage-2 CoCl_{2} graphite intercalation compound,"Stage-2 CoCl$_{2}$ graphite intercalation compound undergoes two magnetic
+phase transitions at $T_{cl}$ (= 7.0 K) and $T_{cu}$ (= 8.9 K). The aging
+dynamics of this compound is studied near $T_{cl}$ and $T_{cu}$. The
+intermediate state between $T_{cl}$ and $T_{cu}$ is characterized by a spin
+glass phase extending over ferromagnetic islands. A genuine thermoremnant
+magnetization (TRM) measurement indicates that the memory of the specific spin
+configurations imprinted at temperatures between $T_{cl}$ and $T_{cu}$ during
+the field-cooled (FC) aging protocol can be recalled when the system is
+re-heated at a constant heating rate. The zero-field cooled (ZFC) and TRM
+magnetization is examined in a series of heating and reheating process. The
+magnetization shows both characteristic memory and rejuvenation effects. The
+time $(t)$ dependence of the relaxation rate
+$S_{ZFC}(t)=(1/H)$d$M_{ZFC}(t)$/d$\ln t$ after the ZFC aging protocol with a
+wait time $t_{w}$, exhibits two peaks at characteristic times $t_{cr1}$ and
+$t_{cr2}$ between $T_{cl}$ and $T_{cu}$. An aging process is revealed as the
+strong $t_{w}$ dependence of $t_{cr2}$. The observed aging and memory effect is
+discussed in terms of the droplet model.",0509696v1
+2005-11-11,"Spin amplification, reading, and writing in transport through anisotropic magnetic molecules","Inelastic transport through a single magnetic molecule weakly coupled to
+metallic leads is studied theoretically. We consider dynamical processes that
+are relevant for writing, storing, and reading spin information in molecular
+memory devices. Magnetic anisotropy is found to be crucial for slow spin
+relaxation. In the presence of anisotropy we find giant spin amplification: The
+spin accumulated in the leads if a bias voltage is applied to a molecule
+prepared in a spin-polarized state can be made exponentially large in a
+characteristic energy divided by temperature. For one ferromagnetic and one
+paramagnetic lead the molecular spin can be reversed by applying a bias voltage
+even in the absence of a magnetic field. We propose schemes for reading and
+writing spin information based on our findings.",0511291v2
+2006-03-14,Topological Effects caused by the Fractal Substrate on the Nonequilibrium Critical Behavior of the Ising Magnet,"The nonequilibrium critical dynamics of the Ising magnet on a fractal
+substrate, namely the Sierpinski carpet with Hausdorff dimension $d_H$ =1.7925,
+has been studied within the short-time regime by means of Monte Carlo
+simulations. The evolution of the physical observables was followed at
+criticality, after both annealing ordered spin configurations (ground state)
+and quenching disordered initial configurations (high temperature state), for
+three segmentation steps of the fractal. The topological effects become evident
+from the emergence of a logarithmic periodic oscillation superimposed to a
+power law in the decay of the magnetization and its logarithmic derivative and
+also from the dependence of the critical exponents on the segmentation step.
+These oscillations are discussed in the framework of the discrete scale
+invariance of the substrate and carefully characterized in order to determine
+the critical temperature of the second-order phase transition and the critical
+exponents corresponding to the short-time regime. The exponent $\theta $ of the
+initial increase in the magnetization was also obtained and the results suggest
+that it would be almost independent of the fractal dimension of the susbstrate,
+provided that $d_H$ is close enough to d=2.",0603386v1
+2006-05-05,Bose-Einstein condensation and entanglement in magnetic systems,"We present a study of magnetic field induced quantum phase transitions in
+insulating systems. A generalized scaling theory is used to obtain the
+temperature dependence of several physical quantities along the quantum
+critical trajectory ($H=H_{C}$, $T\to0$) where $H$ is a longitudinal external
+magnetic field and $H_{C}$ the critical value at which the transition occurs.
+We consider transitions from a spin liquid at a critical field $H_{C1}$ and
+from a fully polarized paramagnet, at $H_{C2}$, into phases with long range
+order in the transverse components. The transitions at $H_{C1}$ and $H_{C2}$
+can be viewed as Bose-Einstein condensations of magnons which however belong to
+different universality classes since they have different values of the dynamic
+critical exponent $z$. Finally, we use that the magnetic susceptibility is an
+entanglement witness to discuss how this type of correlation sets in as the
+system approaches the quantum critical point along the critical trajectory,
+$H=H_{C2}$, $T\to0$.",0605148v2
+2006-05-15,Vortex fluctuations and freezing of dipolar-coupled granular moments in thin ferromagnetic films,"Below the Curie temperature T_c of a Heusler-alloy film, consisting of
+densely packed, but exchange-decoupled nanograins, the spontaneous
+magnetization M_s(T) and static in-plane susceptibility \chi_{||}(T) increase
+very slowly signalizing a suppression of magnetization fluctuations. The
+unpredicted variation \chi_{||}(T) ~ G_d^2(T), where G_d ~ M_s^2 is the
+intergranular dipolar coupling, and also the magnetic freezing observed in the
+dynamic susceptibility at lower temperatures is quantitatively reproduced by
+Monte Carlo (MC) simulations with 10^4 dipolar-coupled moments on a disordered
+triangular lattice. At high temperatures, the MC spin configurations clearly
+reveal a dense gas of local vortex structures, which at low temperatures
+condense in regions with stronger disorder. This vortex depletion upon
+decreasing temperature seems to be responsible for the observed
+\textit{increase} of the magnetic relaxation time. For weak disorder, the
+temperature dependence of the MC vorticity and a singularity of the specific
+heat at T_v=1/2 G_d(T_v)/k_B indicate a thermal transition from a vortex gas to
+a state with a single vortex center plus linear vortex structures.",0605377v1
+2006-05-23,Dynamics of a trapped domain wall in a current perpendicular to the plane spin valve nano-structure,"A study of transverse tail-to-tail magnetic domain walls (DW) in novel
+current perpendicular to the plane (CPP) spin valves (SV) of various dimensions
+is presented. For films with dimensions larger than the DW width, we find that
+DW motion can give rise to a substantial low frequency noise. For dimensions
+comparable to the DW width, we show that the DW can be controlled by an
+external field or by a spin momentum torque as opposed to the case of CPP-SV
+with uniform magnetization. It is shown that in a single domain biased CPP-SV,
+the spin torque can give rise to 1/f-type noise. The dipolar field, the spin
+torque and the Oersted field are all accounted for in this work. Our proposed
+SV requires low current densities to move DW and can simulate devices for
+logical operation or magnetic sensing without having to switch the
+magnetization in the free layer.",0605586v1
+2006-05-30,Electric Dipole Induced Spin Resonance in Disordered Semiconductors,"One of the hallmarks of spintronics is the control of magnetic moments by
+electric fields enabled by strong spin-orbit interaction (SOI) in
+semiconductors. A powerful way of manipulating spins in such structures is
+electric dipole induced spin resonance (EDSR), where the radio-frequency fields
+driving the spins are electric, and not magnetic like in standard paramagnetic
+resonance. Here, we present a theoretical study of EDSR for a two-dimensional
+electron gas in the presence of disorder where random impurities not only
+determine the electric resistance but also the spin dynamics via SOI.
+Considering a specific geometry with the electric and magnetic fields parallel
+and in-plane, we show that the magnetization develops an out-of-plane component
+at resonance which survives the presence of disorder. We also discuss the spin
+Hall current generated by EDSR. These results are derived in a diagrammatic
+approach with the dominant effects coming from the spin vertex correction, and
+the optimal parameter regime for observation is identified.",0605735v1
+2006-08-04,Multiferroicity and colossal magneto-capacitance in Cr-thiospinels,"The sulfur based Cr-spinels RCr2S4 with R = Cd and Hg exhibit the coexistence
+of ferromagnetic and ferroelectric properties together with a pronounced
+magnetocapacitive coupling. While in CdCr2S4 purely ferromagnetic order is
+established, in HgCr2S4 a bond-frustrated magnetic ground state is realized,
+which, however, easily can be driven towards a ferromagnetic configuration in
+weak magnetic fields. This paper shall review our recent investigation for both
+compounds. Besides the characterization of the magnetic properties, the complex
+dielectric permittivity was studied by means of broadband dielectric
+spectroscopy as well as measurements of polarization hysteresis and
+pyro-currents. The observed colossal magneto-capacitive effect at the magnetic
+transition seems to be driven by an enormous variation of the relaxation
+dynamics.",0608113v1
+2006-08-13,Observation of superspin-glass behavior in Fe$_{3}$O$_{4}$ nanoparticles,"The aging and memory effects of Fe$_{3}$O$_{4}$ nanoparticles have been
+studied using a series of zero-field cooled (ZFC) and field-cooled (FC)
+magnetization measurements at various aging protocols. The genuine ZFC
+magnetization after the ZFC procedure with a single stop and wait process shows
+an aging dip at the stop temperature on reheating. The depth of the aging dip
+is dependent on the wait time. The frequency dependence of the AC magnetic
+susceptibility is indicative of critical slowing down at a freezing temperature
+$T_{f}$ ($= 30.6 \pm 1.6$ K). The relaxation time $\tau$ is described by a
+power law form with a dynamic critical exponent $x$ ($= 8.2 \pm 1.0$) and a
+microscopic relaxation time $\tau_{0}$ [$=(1.33 \pm 0.05) \times 10^{-9}$ sec].
+The ZFC-peak temperature decreases with increasing magnetic field ($H$),
+forming a critical line with an exponent $p = 1.78 \pm 0.26$, close to the de
+Almeida-Thouless exponent ($p = 3/2$). These results indicate that the
+superspin glass phase occurs below $T_{f}$.",0608297v4
+2006-11-22,Magnetization damping in a local-density approximation,"The linear response of itinerant transition metal ferromagnets to transverse
+magnetic fields is studied in a self-consistent adiabatic local-density
+approximation. The susceptibility is calculated from a microscopic Hamiltonian,
+including spin-conserving impurities, impurity induced spin-orbit interaction
+and magnetic impurities using the Keldysh formalism. The Gilbert damping
+constant in the Landau-Lifshitz-Gilbert equation is identified, parametrized by
+an effective transverse spin dephasing rate, and is found to be inversely
+proportional to the exchange splitting. Our result justify the phenomenological
+treatment of transverse spin dephasing in the study of current-induced
+magnetization dynamics in weak, itinerant ferromagnets by Tserkovnyak
+\textit{et al.}. We show that neglect of gradient corrections in the
+quasiclassical transport equations leads to incorrect results when the exchange
+potential becomes of the order of the Fermi energy.",0611588v1
+2006-12-11,Size Distribution of Superparamagnetic Particles Determined by Magnetic Sedimentation,"We report on the use of magnetic sedimentation as a means to determine the
+size distribution of dispersed magnetic particles. The particles investigated
+here are i) single anionic and cationic nanoparticles of diameter D = 7 nm and
+ii) nanoparticle clusters resulting from electrostatic complexation with
+polyelectrolytes and polyelectrolyte-neutral copolymers. A theoretical
+expression of the sedimentation concentration profiles at the steady state is
+proposed and it is found to describe accurately the experimental data. When
+compared to dynamic light scattering, vibrating sample magnetometry and
+cryogenic transmission electron microscopy, magnetic sedimentation exhibits a
+unique property : it provides the core size and core size distribution of
+nanoparticle aggregates.",0612255v1
+2007-02-01,Quantum Magnetism and Superconductivity,"The spin of the neutron allows neutron scattering to reveal the magnetic
+structure and dynamics of materials over nanometre length scales and picosecond
+timescales. Neutron scattering is particularly in demand in order to understand
+high-temperature superconductors, which lie close to magnetically ordered
+phases, and highly correlated metals with giant effective fermion masses, which
+lie close to magnetic order or pass through a mysterious phase of hidden order
+before becoming superconducting. Neutron scattering also is the probe of choice
+for revealing new phases of matter and new particles, as seen in the surprising
+behaviour of quantum spin chains and ladders where mass gaps and excited
+triplons replace conventional spin waves. Examples are given of quantum
+phenomena where neutron scattering has played a defining role that challenges
+current understanding of condensed matter.",0702024v1
+2007-03-22,Spin-Torque Ferromagnetic Resonance Measurements of Damping in Nanomagnets,"We measure the magnetic damping parameter a in thin film CoFeB and permalloy
+(Py) nanomagnets at room temperature using ferromagnetic resonance driven by
+microwave frequency spin-transfer torque. We obtain $\alpha_{CoFeB} = 0.014 \pm
+0.003$ and $\alpha_{Py}=0.010 \pm 0.002$, values comparable to measurements for
+extended thin films, but significantly less than the effective damping
+determined previously for similar nanomagnets by fits to time-domain studies of
+large-angle magnetic excitations and magnetic reversal. The greater damping
+found for the large amplitude nanomagnet dynamics is attributed to the
+nonlinear excitation of non-uniform magnetic modes.",0703577v1
+1999-05-07,On magnetic catalysis in even-flavor QED3,"In this paper, we discuss the role of an external magnetic field on the
+dynamically generated fermion mass in even-flavor QED in three space-time
+dimensions. Based on some reasonable approximations, we present analytic
+arguments on the fact that, for weak fields, the magnetically-induced mass
+increases quadratically with increasing field, while at strong fields one
+crosses over to a mass scaling logarithmically with the external field. We also
+confirm this type of scaling behavior through quenched lattice calculations
+using the non-compact version for the gauge field. Both the zero and finite
+temperature cases are examined. A preliminary study of the fermion condensate
+in the presence of magnetic flux tubes on the lattice is also included.",9905272v3
+2000-04-17,QED in a Strong External Magnetic Field: Beyond the Constant Mass Approximation,"We solve the Schwinger-Dyson equations for QED in 2+1 or 3+1 dimensions in
+the presence of a strong homogeneous external magnetic field. The magnetic
+field is assumed strong enough, so that the lowest Landau level approximation
+holds, but the usual assumption of a momentum-independent self-energy is not
+made. In 2+1 dimensions, the scaling with logarithm changes to a square root
+dependence on the magnetic field, but the most spectacular result takes place
+in 3+1 dimensions, where the constant mass approximation turns out to be
+unreliable and the (momentum-dependent) dynamical mass is larger by several
+orders of magnitude compared to what has been found till now using the constant
+mass approximation.",0004165v2
+2000-12-06,Charged spin 1/2 particle in an arbitrary magnetic field in two spatial dimensions: a supersymmetric quantum mechanical system,"It is shown that the 2 X 2 matrix Hamiltonian describing the dynamics of a
+charged spin 1/2 particle with g-factor 2 moving in an arbitrary, spatially
+dependent, magnetic field in two spatial dimensions can be written as the
+anticommuator of a nilpotent operator and its hermitian conjugate.
+Consequently, the Hamiltonians for the two different spin projections form
+partners of a supersymmetric quantum mechanical system. The resulting
+supersymmetry algebra can then be exploited to explicitly construct the exact
+zero energy ground state wavefunction for the system. Modulo this ground state,
+the remainder of the eigenstates and eigenvalues of the two partner
+Hamiltonians form positive energy degenerate pairs. We also construct the
+spatially asymptotic form of the magnetic field which produces a finite
+magnetic flux and associated zero energy normalizable ground state
+wavefunction.",0012074v1
+2005-03-23,Exotic and nonexotic magnetic transitions in the context of the SELEX and GRAAL experiments,"We calculate magnetic transition moments in the chiral quark-soliton model,
+with explicit SU(3)-symmetry breaking taken into account. The dynamical model
+parameters are fixed by experimental data for the magnetic moments of the
+baryon octet and from the recent measurements of $\Theta^{+}$ mass. Known
+magnetic transition moments $\mu_{\Lambda\Sigma}$, $\mu_{N\Delta}$ are
+reproduced and predictions for other octet-decuplet and octet-antidecuplet
+transitions are given. In particular $\mu_{\Sigma\Sigma^{\ast}}$ recently
+constrained by SELEX is shown to be below $0.82 \mu_N$. The recent GRAAL data
+on $\eta$ photoproduction off the nucleon are explained in terms of a new
+narrow antidecuplet neutron-like resonance.",0503237v2
+2006-11-09,Strongly coupled plasma with electric and magnetic charges,"A number of theoretical and lattice results lead us to believe that
+Quark-Gluon Plasma not too far from $T_c$ contains not only electrically
+charged quasiparticles -- quarks and gluons -- but magnetically charged ones --
+monopoles and dyons -- as well. Although binary systems like charge-monopole
+and charge-dyon were considered in details before in both classical and quantum
+settings, it is the first study of coexisting electric and magnetic particles
+in many-body context. We perform Molecular Dynamics study of strongly coupled
+plasmas with $\sim 1000$ particles and different fraction of magnetic charges.
+Correlation functions and Kubo formulae lead to such transport properties as
+diffusion constant, shear viscosity and electric conductivity: we compare the
+first two with empirical data from RHIC experiments as well as results from
+AdS/CFT correspondence. We also study a number of collective excitations in
+these systems.",0611131v2
+1995-08-29,Adiabatic Motion of a Quantum Particle in a Two-Dimensional Magnetic Field,"The adiabatic motion of a charged, spinning, quantum particle in a two -
+dimensional magnetic field is studied. A suitable set of operators generalizing
+the cinematical momenta and the guiding center operators of a particle moving
+in a homogeneous magnetic field is constructed. This allows us to separate the
+two degrees of freedom of the system into a {\sl fast} and a {\sl slow} one, in
+the classical limit, the rapid rotation of the particle around the guiding
+center and the slow guiding center drift. In terms of these operators the
+Hamiltonian of the system rewrites as a power series in the magnetic length
+$\lb=\sqrt{\hbar c\over eB}$ and the fast and slow dynamics separates. The
+effective guiding center Hamiltonian is obtained to the second order in the
+adiabatic parameter $\lb$ and reproduces correctly the classical limit.",9508160v1
+1998-11-25,Dynamical Generation of the Primordial Magnetic Field by Ferromagnetic Domain Walls,"The spontaneous generation of uniform magnetic condensate in $QED_3$ gives
+rise to ferromagnetic domain walls at the electroweak phase transition. These
+ferromagnetic domain walls are caracterized by vanishing effective surface
+energy density avoiding, thus, the domain wall problem. Moreover we find that
+the domain walls generate a magnetic field $B \simeq 10^{24} Gauss$ at the
+electroweak scale which account for the seed field in the so called dynamo
+mechanism for the cosmological primordial magnetic field. We find that the
+annihilation processes of walls with size $R \simeq 10^5 Km$ could release an
+energy of order $10^{52} erg$ indicating the invisible ferromagnetic walls as
+possible compact sources of Gamma Ray Bursts.",9811221v1
+1999-10-05,On Magnetic Catalysis and Gauge Symmetry Breaking,"Non-perturbative effects of constant magnetic fields in a Higgs-Yukawa gauge
+model are studied using the extremum equations of the effective action for
+composite operators. It is found that the magnetic field induces a Higgs
+condensate, a fermion-antifermion condensate, and a fermion dynamical mass,
+hence breaking the discrete chiral symmetry of the theory. The results imply
+that for a non-simple group extension of the present model, the external
+magnetic field would either induce or reinforce gauge symmetry breaking.
+Possible cosmological applications of these results in the electroweak phase
+transition are suggested.",9910035v2
+2004-12-08,Non-Abelian Meissner Effect in Yang--Mills Theories at Weak Coupling,"We present a weak-coupling Yang--Mills model supporting non-Abelian magnetic
+flux tubes and non-Abelian confined magnetic monopoles. In the dual description
+the magnetic flux tubes are prototypes of the QCD strings. Dualizing the
+confined magnetic monopoles we get gluelumps which convert a ""QCD string"" in
+the excited state to that in the ground state. Introducing a mass parameter m
+we discover a phase transition between the Abelian and non-Abelian confinement
+at a critical value m=m_* of order of Lambda. Underlying dynamics are governed
+by a Z_N symmetry inherent to the model under consideration. At m>m_* the Z_N
+symmetry is spontaneously broken, resulting in N degenerate Z_N (Abelian)
+strings. At m<m_* the Z_N symmetry is restored, the degeneracy is lifted, and
+the strings become non-Abelian. We calculate tensions of the non-Abelian
+strings, as well as the decay rates of the metastable strings, at N >> 1.",0412082v3
+2006-02-02,Dynamics of O(N) Model in a Strong Magnetic Background Field as a Modified Noncommutative Field Theory,"In the presence of a strong magnetic field, the effective action of a
+composite scalar field in an scalar O(N) model is derived using two different
+methods. First, in the framework of worldline formalism, the 1PI n-point vertex
+function for the composites is determined in the limit of strong magnetic
+field. Then, the n-point effective action of the composites is calculated in
+the regime of lowest Landau level dominance. It is shown that in the limit of
+strong magnetic field, the results coincide and an effective field theory
+arises which is comparable with the conventional noncommutative field theory.
+In contrast to the ordinary case, however, the UV/IR mixing is absent in this
+modified noncommutative field theory.",0602023v1
+2004-04-26,The Gauss-Landau-Hall problem on Riemannian surfaces,"We introduce the notion of Gauss-Landau-Hall magnetic field on a Riemannian
+surface. The corresponding Landau-Hall problem is shown to be equivalent to the
+dynamics of a massive boson. This allows one to view that problem as a globally
+stated, variational one. In this framework, flowlines appear as critical points
+of an action with density depending on the proper acceleration. Moreover, we
+can study global stability of flowlines. In this equivalence, the massless
+particle model correspond with a limit case obtained when the force of the
+Gauss-Landau-Hall increases arbitrarily. We also obtain new properties related
+with the completeness of flowlines for a general magnetic fields. The paper
+also contains new results relative to the Landau-Hall problem associated with a
+uniform magnetic field. For example, we characterize those revolution surfaces
+whose parallels are all normal flowlines of a uniform magnetic field.",0404060v1
+2001-03-22,Field theoretic calculation of energy cascade rates in nonhelical magnetohydrodynamic turbulence,"Energy cascade rates and Kolmogorov's constant for nonhelical steady
+magnetohydrodynamic turbulence have been calculated by solving the flux
+equations to the first order in perturbation. For zero cross helicity and space
+dimension $d=3$, magnetic energy cascades from large length-scales to small
+length-scales (forward cascade). In addition, there are energy fluxes from
+large-scale magnetic field to small-scale velocity field, large-scale velocity
+field to small-scale magnetic field, and large-scale velocity field to
+large-scale magnetic field. Kolmogorov's constant for magnetohydrodynamics is
+approximately equal to that for fluid turbulence ($\approx 1.6$) for Alfv\'{e}n
+ratio $0.5 \le r_A \le \infty$. For higher space-dimensions, the energy fluxes
+are qualitatively similar, and Kolmogorov's constant varies as $d^{1/3}$. For
+the normalized cross helicity $\sigma_c \to 1$, the cascade rates are
+proportional to $(1-\sigma_c)/ (1+\sigma_c)$, and the Kolmogorov's constants
+vary significantly with $\sigma_c$.",0103033v4
+2002-08-07,Dynamo effect beyond the kinematic approximation: suppression of linear instabilities by non-linear feedback,"The turbulent dynamo effect, which describes the generation of magnetic
+fields in astrophysical objects, is described by the dynamo equation. This, in
+the kinematic (linear) approximation gives an unbounded exponential growth of
+the long wavelength part of the magnetic fields. Here we, in a systematic
+diagrammatic, perturbation theory, show how non-linear effects suppress the
+linear instability and bring down the growth rate to zero in the large time
+limit. We work with diffferent background velicity spectrum and initial
+magnetic field correlations. Our results indicate the robustness and very
+general nature of dynamo growth: It is qualitatively independent of the
+background velicty and intial magnetic field spectra. We also argue that our
+results can be justified within the framework of the first order smoothing
+approximation, as applicable for the full non-linear problem. We discuss our
+results from the view points of renormalisation group analysis.",0208010v1
+2002-09-20,The Onset of Dissipation in the Kinematic Dynamo,"The kinematic regime of the magnetic dynamo neglects the backreaction of the
+magnetic field on the flow. For small magnetic diffusivity, in the early stage
+of evolution, there is an ideal phase where dissipative effects can also be
+neglected. We estimate the magnitude of the energy dissipation term (Ohmic
+heating), taking into account differential constraints on chaotic flows. We
+find that the period of ideal evolution is roughly doubled over an estimate
+without constraints. The helicity generation terms are exponentially smaller
+than the energy dissipation, so that large quantities of energy are dissipated
+before any helicity can be created. Helicity flow is exponentially larger than
+net helicity generation. The constraints also lead to the existence of a
+singular initial condition for the magnetic field for which sizable amounts of
+helicity can potentially be created.",0209042v1
+2006-11-16,Magnetic field gradients in solar wind plasma and geophysics periods,"Using recent data obtained by Advanced Composition Explorer (ACE) the pumping
+scale of the magnetic field gradients of the solar wind plasma has been
+calculated. This pumping scale is found to be equal to 24h $\pm$ 2h. The ACE
+spacecraft orbits at the L1 libration point which is a point of Earth-Sun
+gravitational equilibrium about 1.5 million km from Earth. Since the Earth's
+magnetosphere extends into the vacuum of space from approximately 80 to 60,000
+kilometers on the side toward the Sun the pumping scale cannot be a consequence
+of the 24h-period of the Earth's rotation. Vise versa, a speculation is
+suggested that for the very long time of the coexistence of Earth and of the
+solar wind the weak interaction between the solar wind and Earth could lead to
+stochastic synchronization between the Earth's rotation and the pumping scale
+of the solar wind magnetic field gradients. This synchronization could
+transform an original period of the Earth's rotation to the period close to the
+pumping scale of the solar wind magnetic field gradients.",0611034v1
+2003-05-09,Magnetic moments of the N(1535) resonance in the chiral unitary model,"We calculate the magnetic moments of the N(1535) resonance using the chiral
+unitary model, where the resonance is dynamically generated in the scatterings
+of the lowest-lying mesons and baryons. We obtain the magnetic moments of the
+resonance as +1.1 and -0.25 for p(1535) and n(1535), respectively, in units of
+the nuclear magneton. We discuss the origin of these numbers within the chiral
+unitary model, then we compare the present results with those of the quark
+model and the chiral doublet model. The possibility to observe the magnetic
+moments in experiments is also investigated.",0305023v1
+2001-09-25,Weak magnetohydrodynamic turbulence of magnetized plasma,"Weak turbulence of magnetohydrodynamic (MHD) waves in strongly magnetized
+plasma is studied when the thermal pressure is less than the magnetic field
+pressure. In this situation the main nonlinear mechanism is the resonance
+scattering of fast magneto-acoustic and Alfvenic waves on slow magneto-acoustic
+waves. As a result, the former waves serve as the high-frequency waves with
+respect to the latter ones so that the total number of HF waves - an adiabatic
+invariant - conserves additionally. In the weak turbulence regime this
+invariant is shown to generate the Kolmogorov type spectrum with a constant
+flux of HF waves towards large-scale region. In the short-wave region another
+Kolmogorov spectrum can be realized with a constant energy flux. The explicit
+angle dependences for both types of turbulent spectra are found for the
+propagation angles close to the direction of a mean magnetic field.",0109066v1
+2002-12-20,Orbital magnetism in axially deformed sodium clusters: From scissors mode to dia-para magnetic anisotropy,"Low-energy orbital magnetic dipole excitations, known as scissors mode (SM),
+are studied in alkali metal clusters. Subsequent dynamic and static effects are
+explored. The treatment is based on a self-consistent microscopic approach
+using the jellium approximation for the ionic background and the Kohn-Sham mean
+field for the electrons. The microscopic origin of SM and its main features
+(structure of the mode in light and medium clusters, separation into low- and
+high-energy plasmons, coupling high-energy M1 scissors and E2 quadrupole
+plasmons, contributions of shape isomers, etc) are discussed. The scissors M1
+strength acquires large values with increasing cluster size. The mode is
+responsible for the van Vleck paramagnetism of spin-saturated clusters. Quantum
+shell effects induce a fragile interplay between Langevin diamagnetism and van
+Vleck paramagnetism and lead to a remarkable dia-para anisotropy in magnetic
+susceptibility of particular light clusters. Finally, several routes for
+observing the SM experimentally are discussed.",0212084v1
+2003-01-15,Numerical study of homogeneous dynamo based on experimental von Karman type flows,"A numerical study of the magnetic induction equation has been performed on
+von Karman type flows. These flows are generated by two co-axial
+counter-rotating propellers in cylindrical containers. Such devices are
+currently used in the von Karman sodium (VKS) experiment designed to study
+dynamo action in an unconstrained flow. The mean velocity fields have been
+measured for different configurations and are introduced in a periodic
+cylindrical kinematic dynamo code. Depending on the driving configuration, on
+the poloidal to toroidal flow ratio and on the conductivity of boundaries, some
+flows are observed to sustain growing magnetic fields for magnetic Reynolds
+numbers accessible to a sodium experiment. The response of the flow to an
+external magnetic field has also been studied: The results are in excellent
+agreement with experimental results in the single propeller case but can differ
+in the two propellers case.",0301032v1
+2004-10-07,Numerical study of dynamo action at low magnetic Prandtl numbers,"We present a three--pronged numerical approach to the dynamo problem at low
+magnetic Prandtl numbers $P_M$. The difficulty of resolving a large range of
+scales is circumvented by combining Direct Numerical Simulations, a
+Lagrangian-averaged model, and Large-Eddy Simulations (LES). The flow is
+generated by the Taylor-Green forcing; it combines a well defined structure at
+large scales and turbulent fluctuations at small scales. Our main findings are:
+(i) dynamos are observed from $P_M=1$ down to $P_M=10^{-2}$; (ii) the critical
+magnetic Reynolds number increases sharply with $P_M^{-1}$ as turbulence sets
+in and then saturates; (iii) in the linear growth phase, the most unstable
+magnetic modes move to small scales as $P_M$ is decreased and a Kazantsev
+$k^{3/2}$ spectrum develops; then the dynamo grows at large scales and modifies
+the turbulent velocity fluctuations.",0410046v1
+2005-09-08,On the inverse cascade of magnetic helicity,"We study the inverse cascade of magnetic helicity in conducting fluids by
+investigating the detailed transfer of helicity between different spherical
+shells in Fourier space in direct numerical simulations of three-dimensional
+magnetohydrodynamics (MHD). Two different numerical simulations are used, one
+where the system is forced with an electromotive force in the induction
+equation, and one in which the system is forced mechanically with an ABC flow
+and the magnetic field is solely sustained by a dynamo action. The magnetic
+helicity cascade at the initial stages of both simulations is observed to be
+inverse and local (in scale space) in the large scales, and direct and local in
+the small scales. When saturation is approached most of the helicity is
+concentrated in the large scales and the cascade is non-local. Helicity is
+transfered directly from the forced scales to the largest scales. At the same
+time, a smaller in amplitude direct cascade is observed from the largest scale
+to small scales.",0509069v1
+2005-11-28,Magnetic field induced by elliiptical instability in a rotating tidally distorded sphere,"It is usually believed that the geo-dynamo of the Earth or more generally of
+other planets, is created by the convective fluid motions inside their molten
+cores. An alternative to this thermal or compositional convection can however
+be found in the inertial waves resonances generated by the eventual precession
+of these planets or by the possible tidal distorsions of their liquid cores. We
+will review in this paper some of our experimental works devoted to the
+elliptical instability and present some new results when the experimental fluid
+is a liquid metal. We show in particular that an imposed magnetic field is
+distorted by the spin- over mode generated by the elliptical instability. In
+our experiment, the field is weak (20 Gauss) and the Lorenz force is negligible
+compared to the inertial forces, therefore the magnetic field does not modify
+the fluid flow and the pure hydrodynamics growth rates of the instability are
+recovered through magnetic measurements.",0511226v1
+2002-01-22,Macroscopic and mesoscopic matter waves,"It has been shown earlier that matter waves which are known to lie typically
+in the range of a few Angstrom, can also manifest in the macrodomain with a
+wave length of a few centimeters, for electrons propagating along a magnetic
+field. This followed from the predictions of a probability amplitude theory by
+the author in the classical macrodomain of the dynamics of charged particles in
+a magnetic field. It is shown in this paper that this case constitutes only a
+special case of a generic situation whereby composite systems such as atoms and
+molecules in their highly excited internal states,can exhibit matter wave
+manifestation in macro and mesodomains. The wave length of these waves is
+determined, not by the mass of the particle as in the case of the de Broglie
+wave, but by the frequency, associated with the internal state of excitation,
+and is given by a nonquantal expression, $\lambda =2\pi v/\omega$, $v$ being
+the velocity of the particle. For the electrons in a magnetic field the
+frequency corresponds to the gyrofrequency, $\Omega$ and the nonquantal wave
+length is given by $\lambda = 2\pi v_{\parallel}/\Omega$; $v_{\parallel}$ being
+the velocity of electrons along the magnetic field.",0201101v1
+2003-04-04,Creation of effective magnetic fields in optical lattices: The Hofstadter butterfly for cold neutral atoms,"We investigate the dynamics of neutral atoms in a 2D optical lattice which
+traps two distinct internal states of the atoms in different columns. Two Raman
+lasers are used to coherently transfer atoms from one internal state to the
+other, thereby causing hopping between the different columns. By adjusting the
+laser parameters appropriately we can induce a non vanishing phase of particles
+moving along a closed path on the lattice. This phase is proportional to the
+enclosed area and we thus simulate a magnetic flux through the lattice. This
+setup is described by a Hamiltonian identical to the one for electrons on a
+lattice subject to a magnetic field and thus allows us to study this equivalent
+situation under very well defined controllable conditions. We consider the
+limiting case of huge magnetic fields -- which is not experimentally accessible
+for electrons in metals -- where a fractal band structure, the Hofstadter
+butterfly, characterizes the system.",0304038v1
+2004-09-28,Magnetometry with entangled atomic samples,"We present a theory for the estimation of a scalar or a vector magnetic field
+by its influence on an ensemble of trapped spin polarized atoms. The atoms
+interact off-resonantly with a continuous laser field, and the measurement of
+the polarization rotation of the probe light, induced by the dispersive
+atom-light coupling, leads to spin-squeezing of the atomic sample which enables
+an estimate of the magnetic field which is more precise than that expected from
+standard counting statistics. For polarized light and polarized atoms, a
+description of the non-classical components of the collective spin angular
+momentum for the atoms and the collective Stokes vectors of the light-field in
+terms of effective gaussian position and momentum variables is practically
+exact. The gaussian formalism describes the dynamics of the system very
+effectively and accounts explicitly for the back-action on the atoms due to
+measurement and for the estimate of the magnetic field. Multi-component
+magnetic fields are estimated by the measurement of suitably chosen atomic
+observables and precision and efficiency is gained by dividing the atomic gas
+in two or more samples which are entangled by the dispersive atom-light
+interaction.",0409202v1
+2007-04-04,Ising-like dynamics and frozen states in systems of ultrafine magnetic particles,"We use Monte-Carlo simulations to study aging phenomena and the occurence of
+spinglass phases in systems of single-domain ferromagnetic nanoparticles under
+the combined influence of dipolar interaction and anisotropy energy, for
+different combinations of positional and orientational disorder. We find that
+the magnetic moments oriente themselves preferably parallel to their anisotropy
+axes and changes of the total magnetization are solely achieved by 180 degree
+flips of the magnetic moments, as in Ising systems. Since the dipolar
+interaction favorizes the formation of antiparallel chain-like structures,
+antiparallel chain-like patterns are frozen in at low temperatures, leading to
+aging phenomena characteristic for spin-glasses. Contrary to the intuition,
+these aging effects are more pronounced in ordered than in disordered
+structures.",0704.0580v1
+2007-04-26,On the MHD load and the MHD metage,"In analogy with the load and the metage in hydrodynamics, we define
+magnetohydrodynamic load and magnetohydrodynamic metage in the case of
+magnetofluids. They can be used to write the magnetic field in MHD in Clebsch's
+form. We show how these two concepts can be utilised to derive the magnetic
+analogue of the Ertel's theorem and also, how in the presence of non-trivial
+topology of the magnetic field in the magnetofluid one may associate the
+linking number of the magnetic field lines with the invariant MHD loads. The
+paper illustrates that the symmetry translation of the MHD metage in the
+corresponding label space generates the conservation of cross helicity.",0704.3482v1
+2007-05-04,Applicability of layered sine-Gordon models to layered superconductors: II. The case of magnetic coupling,"In this paper, we propose a quantum field theoretical renormalization group
+approach to the vortex dynamics of magnetically coupled layered
+superconductors, to supplement our earlier investigations on the
+Josephson-coupled case. We construct a two-dimensional multi-layer sine-Gordon
+type model which we map onto a gas of topological excitations. With a special
+choice of the mass matrix for our field theoretical model, vortex dominated
+properties of magnetically coupled layered superconductors can be described.
+The well known interaction potentials of fractional flux vortices are
+consistently obtained from our field-theoretical analysis, and the physical
+parameters (vortex fugacity and temperature parameter) are also identified. We
+analyse the phase structure of the multi-layer sine--Gordon model by a
+differential renormalization group method for the magnetically coupled case
+from first principles. The dependence of the transition temperature on the
+number of layers is found to be in agreement with known results based on other
+methods.",0705.0578v3
+2007-05-09,Low-lying magnetic loops in the solar internetwork,"The aim of this work is to study the structure of the magnetic field vector
+in the internetwork and search for the presence of small-scale loops. We invert
+1.56 micron spectropolarimetric observations of internetwork regions at disc
+centre by applying the SIR code. This allows us to recover the atmospheric
+parameters that play a role in the formation of these spectral lines. We are
+mainly interested in the structure of the magnetic field vector. We find that
+many opposite polarity elements of the internetwork are connected by short
+(2-6''), low-lying (photospheric) loops. These loops connect at least the 10-20
+% of the internetwork flux visible in our data. Also we have some evidence that
+points towards a dynamic scenario which can be produced by the emergence of
+internetwork magnetic flux.",0705.1319v1
+2007-05-15,Nonequilibrium critical relaxation at a first-order phase transition point,"We study numerically the nonequilibrium dynamical behavior of an Ising model
+with mixed two-spin and four-spin interactions after a sudden quench from the
+high-temperature phase to the first-order phase transition point. The
+autocorrelation function is shown to approach its limiting value, given by the
+magnetization in the ordered phase at the transition point, m_c, through a
+stretched exponential decay. On the other hand relaxation of the magnetization
+starting with an uncorrelated initial state with magnetization, m_i, approaches
+either m_c, for m_i>0.5, or zero, for m_i<0.5. For small m_i and for m_i
+slightly larger than 0.5 the relaxation of the magnetization shows an
+asymptotic power-law time dependence, thus from a nonequilibrium point of view
+the transition is continuous.",0705.2142v2
+2007-06-01,Influence of the Magnetic Coupling Process on the Advection Dominated Accretion Flows around Black Holes,"A large-scale closed magnetic field can transfer angular momentum and energy
+between a black hole (BH) and its surrounding accretion flow. We investigate
+the effects of this magnetic coupling (MC) process on the dynamics of a hot
+accretion flow (e.g., an advection dominated accretion flow, hereafter ADAF).
+The energy and angular momentum fluxes transported by the magnetic field are
+derived by an equivalent circuit approach. For a rapidly rotating BH, it is
+found that the radial velocity and the electron temperature of the accretion
+flow decrease, whereas the ion temperature and the surface density increase.
+The significance of the MC effects depends on the value of the viscous
+parameter \alpha. The effects are obvious for \alpha=0.3 but nearly ignorable
+for \alpha=0.1. For a BH with specific angular momentum, a_*=0.9, and
+\alpha=0.3, we find that for reasonable parameters the radiative efficiency of
+a hot accretion flow can be increased by about 30%.",0706.0124v2
+2007-06-18,Propagation of UHE protons through a magnetized large scale structure,"The propagation of UHECRs is affected by the intergalactic magnetic fields
+that were produced during the course of the large scale structure formation of
+the universe. We adopt a novel model where the large scale extragalactic
+magnetic fields (EGMF) are estimated from local dynamic properties of the gas
+flows in hydrodynamic simulations of a concordance LambdaCDM universe. With the
+model magnetic fields, we calculate the deflection angle, time delay and energy
+spectrum of protons with E > 10^{19} eV that are injected at cosmological
+sources and then travel through the large scale structure of the universe,
+losing the energy due to interactions with the cosmic background radiation.
+Implications of this study on the origin of UHECRs are discussed.",0706.2597v2
+2007-06-26,Molecular cloud formation and magnetic fields in spiral galaxies,"We present ongoing hydrodynamic and MHD simulations of molecular cloud
+formation in spiral galaxies. The hydrodynamic results show the formation of
+molecular gas clouds where spiral shocks compress atomic gas to high densities.
+The spiral shocks also produce structure in the spiral arms, provided the gas
+is cold (< 1000 K). When both hot and cold components of the ISM are modeled,
+this structure is enhanced. Properties such as the clump mass spectra and
+spatial distribution will be compared from clouds identified in these
+simulations. In particular the multiphase simulations predict the presence of
+much more interarm molecular gas than when a single phase is assumed. We also
+discuss very recent results from galactic-scale MHD calculations. From
+observational comparisons of the magnetic and thermal pressure, magnetic fields
+are expected to be a major factor in explaining the dynamics of the ISM, from
+kpc scales to those of star formation. We describe the difference in structure
+of the spiral arms, and the evolution of the global magnetic field for a range
+of field strengths.",0706.3862v1
+2007-07-31,Coherent spin rotations in open driven double quantum dots,"We analyze the charge and spin dynamics in a DC biased double quantum dot
+driven by crossed DC and AC magnetic fields. In this configuration, spatial
+delocalization due to inter-dot tunnel competes with intra-dot spin rotations
+induced by the time dependent magnetic field, giving rise to a complicated time
+dependent behavior of the tunnelling current. When the Zeeman splitting has the
+same value in both dots and spin flip is negligible, the electrons remain in
+the triplet subspace (dark subspace) performing coherent spin rotations and the
+current does not flow. This electronic trapping is removed either by finite
+spin relaxation or when the Zeeman splitting is different in each quantum dot.
+In the first case, our results show that measuring the current will allow to
+get information on the spin relaxation time. In the last case, we will show
+that applying a resonant bichromatic magnetic field, the electrons become
+trapped in a coherent superposition of states and electronic transport is
+blocked. Then, manipulating AC magnetic fields, electrons are driven to perform
+coherent spin rotations which can be unambiguously detected by direct
+measurement of the tunneling current.",0707.4636v2
+2007-08-03,Equilibrium Low Temperature Heat Capacity of the Spin Density Wave compound (TMTTF)2 Br: effect of a Magnetic Field,"We have investigated the effect of the magnetic field (B) on the very
+low-temperature equilibrium heat capacity ceq of the quasi-1 D organic compound
+(TMTTF)2Br, characterized by a commensurate Spin Density Wave (SDW) ground
+state. Below 1K, ceq is dominated by a Schottky-like contribution, very
+sensitive to the experimental time scale, a property that we have previously
+measured in numerous DW compounds. Under applied field (in the range 0.2- 7 T),
+the equilibrium dynamics, and hence ceq extracted from the time constant,
+increases enormously. For B = 2-3 T, ceq varies like B2, in agreement with a
+magnetic Zeeman coupling. Another specific property, common to other
+Charge/Spin density wave (DW) compounds, is the occurrence of metastable
+branches in ceq, induced at very low temperature by the field exceeding a
+critical value. These effects are discussed within a generalization to SDWs in
+a magnetic field of the available Larkin-Ovchinnikov local model of strong
+pinning. A limitation of the model when compared to experiments is pointed out.",0708.0540v1
+2007-08-22,Pump-Probe Experiments on the Single-Molecule Magnet Fe8 : Measurement of Excited Level Lifetimes,"We present magnetization measurements on the single molecule magnet Fe8 in
+the presence of pulsed microwave radiation. A pump-probe technique is used with
+two microwave pulses with frequencies of 107 GHz and 118 GHz and pulse lengths
+of several nanoseconds to study the spin dynamics via time-resolved
+magnetization measurements using a Hall probe magnetometer. We find evidence
+for short spin-phonon relaxation times of the order of one microsecond. The
+temperature dependence of the spin-phonon relaxation time in our experiments is
+in good agreement with previously published theoretical results. We also
+established the presence of very short energy diffusion times, that act on a
+timescale of about 70 ns.",0708.3024v1
+2007-08-27,Neutrino spin-flavor oscillations in electromagnetic fields of various configurations,"We study spin-flavor oscillations of Dirac neutrinos with mixing and having
+non-zero matrix of magnetic moments in magnetic fields of various
+configurations. We discuss constant transversal and twisting magnetic fields.
+To describe the dynamics of Dirac neutrinos we use relativistic quantum
+mechanics approach based on the exact solutions to the Dirac-Pauli equation in
+an external electromagnetic field. We derive transition probabilities for
+different neutrino magnetic moments matrices.",0708.3572v1
+2007-09-06,Microscopic Theory for the Markovian Decay of Magnetization Fluctuations in Nanomagnets,"We present a microscopic theory for the phonon-driven decay of the
+magnetization fluctuations in a wide class of nanomagnets where the dominant
+energy is set by isotropic exchange and/or uniaxial anisotropy. Based on the
+Zwanzig-Mori projection formalism, the theory reveals that the magnetization
+fluctuations are governed by a single decay rate $\omega_c$, which we further
+identify with the zero-frequency portion of the associated self-energy. This
+dynamical decoupling from the remaining slow degrees of freedom is attributed
+to a conservation law and the discreteness of the energy spectrum, and explains
+the omnipresent mono-exponential decay of the magnetization over several
+decades in time, as observed experimentally. A physically transparent
+analytical expression for $\omega_c$ is derived which highlights the three
+specific mechanisms of the slowing down effect which are known so far in
+nanomagnets.",0709.0914v2
+2007-09-17,Nature of the spin dynamics and 1/3 magnetization plateau in azurite,"We present a specific heat and inelastic neutron scattering study in magnetic
+fields up into the 1/3 magnetization plateau phase of the diamond chain
+compound azurite Cu$_3$(CO$_3$)$_2$(OH)$_2$. We establish that the
+magnetization plateau is a dimer-monomer state, {\it i.e.}, consisting of a
+chain of $S = 1/2$ monomers, which are separated by $S = 0$ dimers on the
+diamond chain backbone. The effective spin couplings $J_{mono}/k_B = 10.1(2)$ K
+and $J_{dimer}/k_B = 1.8(1)$ K are derived from the monomer and dimer
+dispersions. They are associated to microscopic couplings $J_1/k_B = 1(2)$ K,
+$J_2/k_B = 55(5)$ K and a ferromagnetic $J_3/k_B = -20(5)$ K, possibly as
+result of $d_{z^2}$ orbitals in the Cu-O bonds providing the superexchange
+pathways.",0709.2560v1
+2007-09-23,Quantum dynamics and entanglement of spins on a square lattice,"Bulk magnetism in solids is fundamentally quantum mechanical in nature. Yet
+in many situations, including our everyday encounters with magnetic materials,
+quantum effects are masked, and it often suffices to think of magnetism in
+terms of the interaction between classical dipole moments. Whereas this
+intuition generally holds for ferromagnets, even as the size of the magnetic
+moment is reduced to that of a single electron spin (the quantum limit), it
+breaks down spectacularly for antiferromagnets, particularly in low dimensions.
+Considerable theoretical and experimental progress has been made in
+understanding quantum effects in one-dimensional quantum antiferromagnets, but
+a complete experimental description of even simple two-dimensional
+antiferromagnets is lacking. Here we describe a comprehensive set of neutron
+scattering measurements that reveal a non-spin-wave continuum and strong
+quantum effects, suggesting entanglement of spins at short distances in the
+simplest of all two-dimensional quantum antiferromagnets, the square lattice
+Heisenberg system.",0709.3632v1
+2007-10-01,Manipulation with Andreev states in spin active mesoscopic Josephson junctions,"We investigate manipulation with Andreev bound states in Josephson quantum
+point contacts with magnetic scattering. Rabi oscillations in the two-level
+Andreev subsystems are excited by resonant driving the direction of magnetic
+moment of the scatterer, and by modulating the superconducting phase difference
+across the contact. The Andreev level dynamics is manifested by temporal
+oscillation of the Josephson current, accompanied, in the case of magnetic
+manipulation, also by oscillation of the Andreev states spin polarization. The
+interlevel transitions obey a selection rule that forbids manipulations in a
+certain region of external parameters, and results from specific properties of
+Andreev bound states in magnetic contacts: 4$\pi$-periodicity with respect to
+the superconducting phase, and strong spontaneous spin polarization.",0710.0320v2
+2007-10-18,Nonlinear NMR dynamics in hyperpolarized liquid 3He,"In a highly polarized liquid (laser-polarized 3He-4He mixtures in our
+experiment), dipolar magnetic interactions within the liquid introduce a
+significant nonlinear and nonlocal contribution to the Bloch equation that
+leads to instabilities during NMR evolution. We have launched a study of these
+instabilities using spin echo techniques. At high magnetizations, a simple 180
+degree rf pulse fails to refocus magnetization, so we use a standard
+solid-state NMR pulse sequence: the magic sandwich. We report an experimental
+and numerical investigation of the effect of this sequence on unstable NMR
+evolution. Using a series of repeated magic sandwich sequences, the transverse
+magnetization lifetime can be increased by up to three orders of magnitude.",0710.3567v2
+2007-11-12,Landau Analog Levels for Dipoles in the Noncommutative Space and Phase Space,"In the present contribution we investigate the Landau analog energy
+quantization for neutral particles, that possesses a nonzero permanent magnetic
+and electric dipole moments, in the presence of an homogeneous electric and
+magnetic external fields in the context of the noncommutative quantum
+mechanics. Also, we analyze the Landau--Aharonov--Casher and
+Landau--He--McKellar--Wilkens quantization due to noncommutative quantum
+dynamics of magnetic and electric dipoles in the presence of an external
+electric and magnetic fields and the energy spectrum and the eigenfunctions are
+obtained. Furthermore, we have analyzed Landau quantization analogs in the
+noncommutative phase space, and we obtain also the energy spectrum and the
+eigenfunctions in this context.",0711.1773v2
+2007-11-14,Emergent singular solutions of non-local density-magnetization equations in one dimension,"We investigate the emergence of singular solutions in a non-local model for a
+magnetic system. We study a modified Gilbert-type equation for the
+magnetization vector and find that the evolution depends strongly on the length
+scales of the non-local effects. We pass to a coupled density-magnetization
+model and perform a linear stability analysis, noting the effect of the length
+scales of non-locality on the system's stability properties. We carry out
+numerical simulations of the coupled system and find that singular solutions
+emerge from smooth initial data. The singular solutions represent a collection
+of interacting particles (clumpons). By restricting ourselves to the
+two-clumpon case, we are reduced to a two-dimensional dynamical system that is
+readily analyzed, and thus we classify the different clumpon interactions
+possible.",0711.2177v1
+2007-11-28,Magnetically Arrested Disks and Origin of Poynting Jets: Numerical Study,"The dynamics and structure of accretion disks, which accumulate the vertical
+magnetic field in the centers, are investigated using two- and
+three-dimensional MHD simulations. The central field can be built up to the
+equipartition level and disrupts a nearly axisymmetric outer accretion disk
+inside a magnetospheric radius, forming a magnetically arrested disk (MAD). In
+the MAD, the mass accretes in a form of irregular dense spiral streams and the
+vertical field, split into separate bundles, penetrates through the disk plane
+in low-density magnetic islands. The accreting mass, when spiraling inward,
+drags the field and twists it around the axis of rotation, resulting in
+collimated Poynting jets in the polar directions. These jets are powered by the
+accretion flow with the efficiency up to ~1.5% (in units \dot{M}c^2). The
+spiral flow pattern in the MAD is dominated by modes with low azimuthal
+wavenumbers m~1-5 and can be a source of quasi-periodic oscillations in the
+outgoing radiation. The formation of MAD and Poynting jets can naturally
+explain the observed changes of spectral states in Galactic black hole
+binaries. Our study is focused on black hole accretion flows; however, the
+results can also be applicable to accretion disks around nonrelativistic
+objects, such as young stellar objects and stars in binary systems.",0711.4391v1
+2007-12-13,Electromagnon excitations in modulated multiferroics,"The phenomenological theory of ferroelectricity in spiral magnets presented
+in [M. Mostovoy, Phys. Rev. Lett. 96, 067601 (2006)] is generalized to describe
+consistently states with both uniform and modulated-in-space ferroelectric
+polarizations. A key point in this description is the symmetric part of the
+magnetoelectric coupling since, although being irrelevant for the uniform
+component, it plays an essential role for the non-uniform part of the
+polarization. We illustrate this importance in generic examples of modulated
+magnetic systems: longitudinal and transverse spin-density wave states and
+planar cycloidal phase. We show that even in the cases with no uniform
+ferroelectricity induced, polarization correlation functions follow to the soft
+magnetic behavior of the system due to the magnetoelectric effect. Our results
+can be easily generalized for more complicated types of magnetic ordering, and
+the applications may concern various natural and artificial systems in
+condensed matter physics (e.g., magnon properties could be extracted from
+dynamic dielectric response measurements).",0712.2138v2
+2007-12-17,Easy-Axis Kagomé Antiferromagnet: Local-Probe Study of Nd$_3$Ga$_5$SiO$_{14}$,"We report a local-probe investigation of the magnetically anisotropic
+kagom\'e compound Nd$_3$Ga$_5$SiO$_{14}$. Our zero-field $\mu$SR results
+provide a direct evidence of a fluctuating collective paramagnetic state down
+to 60 mK, supported by a wipe-out of the Ga nuclear magnetic resonance (NMR)
+signal below 25 K. At 60 mK a dynamics crossover to a much more static state is
+observed by $\mu$SR in magnetic fields above 0.5 T. Accordingly, the NMR signal
+is recovered at low $T$ above a threshold field, revealing a rapid temperature
+and field variation of the magnetic fluctuations.",0712.2660v2
+2008-01-06,Voltage control of magnetocrystalline anisotropy in ferromagnetic - semiconductor/piezoelectric hybrid structures,"We demonstrate dynamic voltage control of the magnetic anisotropy of a
+(Ga,Mn)As device bonded to a piezoelectric transducer. The application of a
+uniaxial strain leads to a large reorientation of the magnetic easy axis which
+is detected by measuring longitudinal and transverse anisotropic
+magnetoresistance coefficients. Calculations based on the mean-field
+kinetic-exchange model of (Ga,Mn)As provide microscopic understanding of the
+measured effect. Electrically induced magnetization switching and detection of
+unconventional crystalline components of the anisotropic magnetoresistance are
+presented, illustrating the generic utility of the piezo voltage control to
+provide new device functionalities and in the research of micromagnetic and
+magnetotransport phenomena in diluted magnetic semiconductors.",0801.0886v2
+2008-01-23,Helical Magnetic Fields from Sphaleron Decay and Baryogenesis,"Many models of baryogenesis rely on anomalous particle physics processes to
+give baryon number violation. By numerically evolving the electroweak equations
+on a lattice, we show that baryogenesis in these models creates helical cosmic
+magnetic fields. After a transitory period, electroweak dynamics is found to
+conserve the Chern-Simons number and the total electromagnetic helicity. We
+argue that baryogenesis could lead to magnetic fields of nano-Gauss strength
+today on astrophysical length scales. In addition to being astrophysically
+relevant, such helical magnetic fields can provide an independent probe of
+baryogenesis and CP violation in particle physics.",0801.3653v2
+2008-01-30,Time-Resolved X-ray Microscopy of Spin-Torque-Induced Magnetic Vortex Gyration,"Time-resolved X-ray microscopy is used to image the influence of alternating
+high-density currents on the magnetization dynamics of ferromagnetic vortices.
+Spin-torque induced vortex gyration is observed in micrometer-sized permalloy
+squares. The phases of the gyration in structures with different chirality are
+compared to an analytical model and micromagnetic simulations, considering both
+alternating spinpolarized currents and the current's Oersted field. In our case
+the driving force due to spin-transfer torque is about 70% of the total
+excitation while the remainder originates from the current's Oersted field.
+This finding has implications to magnetic storage devices using spin-torque
+driven magnetization switching and domain-wall motion.",0801.4719v1
+2008-02-14,Light-induced magnetization precession in GaMnAs,"We report dynamics of the transient polar Kerr rotation (KR) and of the
+transient reflectivity induced by femtosecond laser pulses in ferromagnetic
+(Ga,Mn)As with no external magnetic field applied. It is shown that the
+measured KR signal consist of several different contributions, among which only
+the oscillatory signal is directly connected with the ferromagnetic order in
+(Ga,Mn)As. The origin of the light-induced magnetization precession is
+discussed and the magnetization precession damping (Gilbert damping) is found
+to be strongly influenced by annealing of the sample.",0802.2043v2
+2008-02-15,Spontaneous vortex phases in ferromagnet-superconductor nanocomposites,"The interplay between superconductivity and magnetism gives rise to many
+intriguing and exciting phenomena. In this Letter we report about a novel
+manifestation of this interplay: a temperature induced phase transition between
+different spontaneous vortex phases in lead superconducting films with embedded
+magnetic nanoparticles. Unlike common vortices in superconductors the vortex
+phase appears without any applied magnetic field. The vortices nucleate
+exclusively due to the stray field of the magnetic nanoparticles, which serve
+the dual role of providing the internal field and simultaneously acting as
+pinning centers. As in usual superconductors, one can move the spontaneous
+vortices with an applied electric current. Transport measurements reveal
+dynamical phase transitions that depend on temperature (T) and applied field
+(H) and support the obtained (H-T) phase diagram. In particular, we used a
+scaling analysis to characterize a transition from a liquid to a novel
+disordered solid resembling a vortex glass.",0802.2252v2
+2008-03-21,Solar and Stellar Active Regions:Cosmic laboratories for the study of Complexity,"Solar active regions are driven dissipative dynamical systems. The turbulent
+convection zone forces new magnetic flux tubes to rise above the photosphere
+and shuffles the magnetic fields which are already above the photosphere. The
+driven 3D active region responds to the driver with the formation of Thin
+Current Sheets in all scales and releases impulsively energy, when special
+thresholds are met, on the form of nano-, micro-, flares and large scale
+coronal mass ejections. It has been documented that active regions form self
+similar structures with area Probability Distribution Functions (PDF's)
+following power laws and with fractal dimensions ranging from $1.2-1.7$. The
+energy release on the other hand follows a specific energy distribution law
+$f(E_T)\sim E_T^{-a}$, where $a \sim 1.6-1.8$ and $E_T$ is the total energy
+released. A possible explanation for the statistical properties of the
+magnetogrms and the energy release by the active region is that the magnetic
+field formation follows rules analogous to \textbf{percolating models}, and the
+3D magnetic fields above the photosphere reach a \textbf{Self Organized
+Critical (SOC) state}. The implications of these findings on the acceleration
+of energetic particles during impulsive phenomena will briefly be outlined.",0803.3158v1
+2008-04-01,Dipolar spinor Bose-Einstein condensates,"Under many circumstances, the only important two-body interaction between
+atoms in ultracold dilute atomic vapors is the short-ranged isotropic s-wave
+collision. Recent studies have shown, however, that situations may arise where
+the dipolar interaction between atomic magnetic or electric dipole moments can
+play a significant role. The long-range anisotropic nature of the dipolar
+interaction greatly enriches the static and dynamic properties of ultracold
+atoms. In the case of dipolar spinor condensates, the interplay between the
+dipolar interaction and the spin exchange interaction may lead to nontrivial
+spin textures. Here we pay particular attention to the spin vortex state that
+is analogous to the magnetic vortex found in thin magnetic films.",0804.0191v1
+2008-05-07,Simulations of 2D magnetic electron drift vortex mode turbulence in plasmas,"Simulations are performed to investigate turbulent properties of nonlinearly
+interacting two-dimensional (2D) magnetic electron drift vortex (MEDV) modes in
+a nonuniform unmagnetized plasma. The relevant nonlinear equations governing
+the dynamics of the MEDV modes are the wave magnetic field and electron
+temperature perturbations in the presence of the equilibrium density and
+temperature gradients. The important nonlinearities come from the advection of
+the electron fluid velocity perturbation and the electron temperature, as well
+as from the nonlinear electron Lorentz force. Computer simulations of the
+governing equations for the nonlinear MEDV modes reveal the generation of
+streamer-like electron flows, such that the corresponding gradients in the
+direction of the inhomogeneities tend to flatten out. By contrast, the
+gradients in an orthogonal direction vary rapidly. Consequently, the inertial
+range energy spectrum in decaying MEDV mode turbulence exhibits a much steeper
+anisotropic spectral index. The magnetic structures in the MEDV mode turbulence
+produce nonthermal electron transport in our nonuniform plasma.",0805.1047v1
+2008-05-19,Intrinsic magnetic properties of NdFeAsO$_{0.9}$F$_{0.1}$ superconductor from local and global measurements,"Magneto-optical imaging was used to study the local magnetization in
+polycrystalline NdFeAsO$_{0.9}$F$_{0.1}$ (NFAOF). Individual crystallites up to
+$\sim200\times100\times30$ $\mu m^{3}$ in size could be mapped at various
+temperatures. The in-grain, persistent current density is about $j\sim10^{5}$
+A/cm$^{2}$ and the magnetic relaxation rate in a remanent state peaks at about
+$T_{m}\sim38$ K. By comparison with with the total magnetization measured in a
+bar-shaped, dense, polycrystalline sample, we suggest that
+NdFeAsO$_{0.9}$F$_{0.1}$ is similar to a layered high-$T_{c}$, compound such as
+Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ and exhibits a $3D\to2D$ crossover in the
+vortex structure. The 2D Ginzburg parameter is about $Gi^{2D}% \simeq10^{-2}$
+implying electromagnetic anisotropy as large as $\epsilon \sim1/30$. Below
+$T_{m}$, the static and dynamic behaviors are consistent with collective
+pinning and creep.",0805.2783v2
+2008-05-23,Magnetism in Gallium doped CeFe_2: The martensitic scenario,"Ce(Fe_{1-x}Ga_x)_2 compounds with x = 0, 0.01, 0.025 and 0.05 have been
+investigated to unravel the effect of Ga on the magnetic state of CeFe_2. For
+the first time, we find that the dynamic antiferromagnetic phase present in
+CeFe_2 gets stabilized with Ga substitution. The hysteresis loops show that
+while the compounds with x = 0 and 0.01 show normal behavior, the other two
+show multiple magnetization steps across the antiferromagnetic-ferromagnetic
+transition region. The virgin curve is found to lie outside the envelope curve
+in these two compounds, similar to the observations made in Ru and Re
+substituted CeFe_2 compounds. Temperature, sweep rate and time dependences of
+the magnetization show that the compounds with x >=0.025 possess glassy
+behavior at low temperatures. Various results obtained reveal that these two
+compounds belong to the martensite family.",0805.3589v1
+2008-05-30,Langevin dynamics in crossed magnetic and electric fields: Hall and diamagnetic fluctuations,"Based on the classical Langevin equation, we have re-visited the problem of
+orbital motion of a charged particle in two dimensions for a normal magnetic
+field crossed with or without an in-plane electric bias. We are led to two
+interesting fluctuation effects: First, we obtain not only a longitudinal
+""work-fluctuation"" relation as expected for a barotropic type system, but also
+a transverse work-fluctuation relation perpendicular to the electric bias. This
+""Hall fluctuation"" involves the product of the electric and the magnetic
+fields. And second, for the case of harmonic confinement without bias, the
+calculated probability density for the orbital magnetic moment gives non-zero
+even moments, not derivable as field derivatives of the classical free energy.",0806.0022v3
+2008-06-16,Interplay of Local-Moment Ferromagnetism and Superconductivity in ErRh$_4$B$_4$ Single Crystals,"Tunnel-diode resonator technique was used to study crystals of ferromagnetic
+re-entrant superconductor, ErRh$_{4}$B$_{4}$. At the boundary between
+ferromagnetism (FM) and superconductivity (SC), dynamic magnetic
+susceptibility, $\chi(T,H)$, exhibits highly asymmetric behavior upon warming
+and cooling as well as enhanced diamagnetism on the SC side. SC phase nucleates
+upon warming in a cascade of discontinuous jumps in magnetic susceptibility
+$\chi(T,H)$, whereas FM phase develops gradually as reported in detail in
+\cite{prozorov2008}. Here we further investigate enhanced diamagnetism. We find
+that when a magnetic field is applied along the magnetic easy axes, a region of
+enhanced diamagnetic screening is smaller than in the perpendicular
+orientation. A discussion of possible causes of this effect is provided.",0806.2479v1
+2008-07-16,Equilibrium tuned by a magnetic field in phase separated manganite,"We present magnetic and transport measurements on La5/8-yPryCa3/8MnO3 with y
+= 0.3, a manganite compound exhibiting intrinsic multiphase coexistence of
+sub-micrometric ferromagnetic and antiferromagnetic charge ordered regions.
+Time relaxation effects between 60 and 120K, and the obtained magnetic and
+resistive viscosities, unveils the dynamic nature of the phase separated state.
+An experimental procedure based on the derivative of the time relaxation after
+the application and removal of a magnetic field enables the determination of
+the otherwise unreachable equilibrium state of the phase separated system. With
+this procedure the equilibrium phase fraction for zero field as a function of
+temperature is obtained. The presented results allow a correlation between the
+distance of the system to the equilibrium state and its relaxation behavior.",0807.2631v1
+2008-07-25,"Spin, orbital ordering and magnetic dynamics of LaVO3: magnetization, heat capacity and neutron scattering studies","We report the results of magnetization, heat capacity and neutron scattering
+studies of LaVO3 single crystals. From the neutron diffraction studies, it was
+found that the compound is magnetically ordered with a C-type antiferromagnetic
+spin structure at about 136 K. In the vicinity of the ordering temperature, we
+also observed hysteresis in the neutron diffraction data measured on cooling
+and heating which indicates the first order nature of the phase transition. In
+the antiferromagnetically ordered phase, the inelastic neutron scattering
+studies reveal the presence of a temperature independent c axis spin-wave gap
+of about 6 meV which is similar to that previously reported for the sister
+compound YVO3.",0807.4195v1
+2008-08-22,Weak quasistatic magnetism in the frustrated Kondo lattice Pr_2Ir_2O_7,"Muon spin relaxation experiments have been performed in the pyrochlore
+iridate Pr_2Ir_2O_7 for temperatures in the range 0.025-250 K. Kubo-Toyabe
+relaxation functions are observed up to > 200 K, indicating static magnetism
+over this temperature range. The T -> 0 static muon spin relaxation rate
+Delta(0) ~ 8 mus^-1 implies a weak quasistatic moment (~0.1 mu_B). The
+temperature dependence of Delta is highly non-mean-field-like, decreasing
+smoothly by orders of magnitude but remaining nonzero below ~150 K. The data
+rule out ordering of the full Pr^3+ CEF ground-state moment (3.0 mu_B) down to
+0.025 K. The weak static magnetism is most likely due to hyperfine-enhanced
+^141Pr nuclear magnetism. The dynamic relaxation rate lambda increases markedly
+below ~20 K, probably due to slowing down of spin fluctuations in the
+spin-liquid state. At low temperatures lambda is strong and
+temperature-independent, indicative of a high density of low-lying spin
+excitations as is common in frustrated antiferromagnets.",0808.3142v1
+2008-08-27,Entanglement control in one-dimensional $s=1/2$ random XY spin chain,"The entanglement in one-dimensional random XY spin systems where the
+impurities of exchange couplings and the external magnetic fields are
+considered as random variables is investigated by solving the different
+spin-spin correlation functions and the average magnetization per spin. The
+entanglement dynamics near particular locations of the system is also studied
+when the exchange couplings (or the external magnetic fields) satisfy three
+different distributions(the Gaussian distribution, double-Gaussian
+distribution, and bimodal distribution). We find that the entanglement can be
+controlled by varying the strength of external magnetic field and the different
+distributions of impurities. Moreover, the entanglement of some
+nearest-neighboring qubits can be increased for certain parameter values of the
+three different distributions.",0808.3678v1
+2008-09-08,Anisotropic three-dimensional magnetism in CaFe2As2,"Inelastic neutron scattering measurements on the low energy spin waves in
+CaFe2As2 show that the magnetic exchange interactions in the Fe layers are
+exceptionally large and similar to the cuprates. However, the exchange between
+layers is ~10% of the coupling in the layers and the magnetism is more
+appropriately categorized as anisotropic three-dimensional, in contrast to the
+two-dimensional cuprates. Band structure calculations of the spin dynamics and
+magnetic exchange interactions are in good agreement with the experimental
+data.",0809.1410v1
+2008-11-28,Dynamic non-null magnetic reconnection in three dimensions - II. Composite solutions,"In this series of papers we examine magnetic reconnection in a domain where
+the magnetic field does not vanish and the non-ideal region is localised in
+space. In a previous paper we presented a technique for obtaining analytical
+solutions to the stationary resistive MHD equations in such a situation and
+examined specific examples of non-ideal reconnective solutions. Here we further
+develop the model, noting that certain ideal solutions may be superimposed onto
+the fundamental non-ideal solutions and examining the effect of imposing
+various such flows. Significant implications are found for the evolution of
+magnetic flux in the reconnection process. It is shown that, in contrast to the
+two-dimensional case, in three-dimensions there is a very wide variety of
+physically different steady reconnection solutions.",0811.4621v1
+2009-01-06,Non-stationary magnetized axially symmetric equilibrium from the fluid equations of motion,"The equations of motion for a fully ionized hydrogenic plasma in applied
+coaxial electric and magnetic fields are analyzed, where the term for the Hall
+effect in the generalized Ohm's law equation picks up a factor of 1/2 relative
+to its usual expression. Magnetization of the medium is incorporated through
+the decomposition of the Hall term and the inclusion of the magnetization
+force, which is found to equal or exceed the gradient of the scalar pressure. A
+limit on the kinetic pressure obtains which corresponds to the usual limit of
+unity for a certain selection of parameters. Solutions of these equations for
+the free motion of the charges in the case of an infinite column with azimuthal
+symmetry are compared for various prescribed pressure profiles, where one finds
+that the profile near the outer edge plays an important role in the feasibility
+of the equilibrium.",0901.0732v2
+2009-01-23,Itinerant magnetic excitations in antiferromagnetic CaFe2As2,"Neutron scattering measurements of the magnetic excitations in single
+crystals of antiferromagnetic CaFe2As2 reveal steeply dispersive and
+well-defined spin waves up to an energy of 100 meV. Magnetic excitations above
+100 meV and up to the maximum energy of 200 meV are however broader in energy
+and momentum than the experimental resolution. While the low energy modes can
+be fit to a Heisenberg model, the total spectrum cannot be described as arising
+from excitations of a local moment system. Ab-initio calculations of the
+dynamic magnetic susceptibility suggest that the high energy behavior is
+dominated by the damping of spin waves by particle-hole excitations.",0901.3784v2
+2009-01-27,Realistic Numerical Modeling of Solar Magnetoconvection and Oscillations,"We have developed 3D, compressible, non-linear radiative MHD simulations to
+study the influence of the magnetic field of various strength and geometry on
+the turbulent convective cells and on the excitation mechanisms of the acoustic
+oscillations. The results reveal substantial changes of the granulation
+structure with increased magnetic field, and a frequency-dependent reduction in
+the oscillation power. These simulation results reproduce the enhanced
+high-frequency acoustic emission observed at the boundaries of active region
+(""acoustic halo"" phenomenon). In the presence of inclined magnetic field the
+solar convection develops filamentary structure with flows concentrated along
+magnetic filaments, and also exhibits behavior of running magnetoconvective
+waves, resembling recent observations of the sunspot penumbra dynamics from
+Hinode/SOT.",0901.4369v2
+2009-02-20,Understanding of the role of magnetic fields: Galactic perspective,"A combination of observation, theory, modeling, and laboratory plasma
+experiments provides a multifaceted approach to develop a much greater
+understanding of how magnetic fields arise in galactic settings and how these
+magnetic fields mediate important processes that affect the dynamics,
+distribution, and composition of galactic plasmas. An important emphasis below
+is the opportunity to connect laboratory experiments to astrophysics. This
+approach is especially compelling for the galactic neighborhood, where the
+distribution and character of magnetic fields can be observed with greater
+detail than what is possible elsewhere in the universe. The ability to produce
+laboratory plasmas with unparalleled accessibility permits an even greater
+level of detail to be assessed and exposed. Theory and modeling provide
+fundamental ways to understand important processes, and they act as the bridge
+to connect experimental validation to astronomical observations. In many cases
+the studies that utilize this approach can make use of existing laboratory
+facilities, resulting in a cost that is quite small compared to the cost of
+measurements in dedicated space missions.",0902.3618v1
+2009-02-26,Low energy spin dynamics in the antiferromagnetic phase of CaFe2As2,"We present 75As nuclear magnetic resonance data in the paramagnetic and
+magnetic states of single crystal CaFe2As2. The electric field gradient and the
+internal magnetic field at the As sites change discontinuously below the first
+order structural transition at T0 = 169 K. In the magnetic state, we find a
+single value of the internal hyperfine field consistent with commensurate
+antiferromagnetic order of Fe moments pointing in the ab plane. The spin
+lattice relaxation rate shows Korringa behavior for T<T0/3, reflecting the
+metallic nature of the ordered state. Surprisingly, 1/T1 exhibits a small peak
+at 10 K, revealing the presence of slow spin fluctuations that may be
+associated with domain wall motion.",0902.4492v1
+2009-03-06,"Lagrangian relaxation schemes for calculating force-free magnetic fields, and their limitations","Force-free magnetic fields are important in many astrophysical settings.
+Determining the properties of such force-free fields -- especially smoothness
+and stability properties -- is crucial to understanding many key phenomena in
+astrophysical plasmas, for example energy release processes that heat the
+plasma and lead to dynamic or explosive events. Here we report on a serious
+limitation on the computation of force-free fields that has the potential to
+invalidate the results produced by numerical force-free field solvers even for
+cases in which they appear to converge (at fixed grid resolution) to an
+equilibrium magnetic field. In the present work we discuss this problem within
+the context of a Lagrangian relaxation scheme that conserves magnetic flux and
+div(B) identically. Error estimates are introduced to assess the quality of the
+calculated equilibrium. We go on to present an algorithm, based on re-writing
+the curl operation via Stokes' theorem, for calculating the current which holds
+great promise for improving dramatically the accuracy of the Lagrangian
+relaxation procedure.",0903.1226v1
+2009-03-11,Magnetic Properties of the Superconducting State of Iron-Based Superconductors,"We show that features of the dynamical spin susceptibility can unambiguously
+distinguish between different pairing symmetries of the superconducting state
+in iron-based superconductors. A magnetic resonance is a unique feature for the
+extended $s_{x^2y^2}$-wave $\cos k_x\cos k_y$ pairing symmetry. It is present
+in the pure superconducting (SC) state, but weakens in the mixed SC and
+magnetically ordered state. We calculate the the RPA correction to the NMR spin
+relaxation rate $1/T_1$ and the Knight shift in the above states and show a
+good agreement with experimental results. Moreover, we argue that the energy
+dispersion of the magnetic resonance along c axis observed in neutron
+scattering experiments is also an indirect evidence supporting the $s_{x^2y^2}$
+pairing symmetry.",0903.2025v1
+2009-03-12,"Magnetic Seed Field Generation from Electroweak Bubble Collisions, with Bubble Walls of Finite Thickness","Building on earlier work, we develop an equation-of-motion method for
+calculating magnetic seed fields generated from currents arising from charged W
+fields in bubble collisions during a first-order primordial electroweak phase
+transition allowed in some proposed extensions of the standard model. The novel
+feature of our work is that it takes into account, for the first time, the
+dynamics of the bubble walls in such collisions. We conclude that for bubbles
+with sufficiently thin surfaces the magnetic seed fields may be comparable to,
+or larger than, those found in earlier work. Thus, our results strengthen the
+conclusions of previous studies that cosmic magnetic fields observed today may
+originate from seeds created during the electroweak phase transition, and
+consequently that these fields may offer a clue relevant to extensions of the
+standard model.",0903.2227v2
+2009-03-18,Magnetic field resonantly enhanced free spins in underdoped YBa$_{2}$Cu$_{3}$O$_{6+x}$,"Using neutron scattering, we investigate the effect of a magnetic field on
+the static and dynamic spin response in heavily underdoped superconducting
+YBa$_{2}$Cu$_{3}$O$_{6+x}$ (YBCO$_{6+x}$) with x=0.33 (T$_{c}$=8 K) and 0.35
+(T$_{c}$=18 K). In contrast to the heavily doped and superconducting monolayer
+cuprates, the elastic central peak characterizing static spin correlations does
+not respond observably to a magnetic field which suppresses superconductivity.
+Instead, we find a magnetic field induced resonant enhancement of the spin
+fluctuations. The energy scale of the enhanced fluctuations matches the Zeeman
+energy within both the normal and vortex phases while the momentum dependence
+is the same as the zero field bilayer response. The magnitude of the
+enhancement is very similar in both phases with a fractional intensity change
+of $(I/I_{0}-1) \sim 0.1$. We suggest that the enhancement is not directly
+correlated with superconductivity but is the result of almost free spins
+located near hole rich regions.",0903.3172v2
+2009-05-01,Collisionless plasma expansion in the presence of a dipole magnetic field,"The collisionless interaction of an expanding high-energy plasma cloud with a
+magnetized background plasma in the presence of a dipole magnetic field is
+examined in the framework of a 2D3V hybrid (kinetic ions and massless fluid
+electrons) model. The retardation of the plasma cloud and the dynamics of the
+perturbed electromagnetic fields and the background plasma are studied for high
+Alfven-Mach numbers using the particle-in-cell method. It is shown that the
+plasma cloud expands excluding the ambient magnetic field and the background
+plasma to form a diamagnetic cavity which is accompanied by the generation of a
+collisionless shock wave. The energy exchange between the plasma cloud and the
+background plasma is also studied and qualitative agreement with the analytical
+model suggested previously is obtained.",0905.0051v1
+2009-05-01,Huge ac magnetoresistance in La0.7Sr0.3MnO3 in sub- kilo gauss magnetic fields,"We report dynamical magnetotransport in a ferromagnetic metallic oxide,
+La0.7Sr0.3MnO3 using the ac impedance technique. The temperature dependence of
+the ac resistance(R) and the inductive reactance (X) of the complex impedance
+(Z = R+jX) under different dc bias magnetic fields (Hdc = 0-1 kOe) were studied
+for different frequencies f = 0.1 to 5 MHz of alternating current. The zero
+field R, which decreases smoothly around the Curie temperature TC for f = 100
+kHz, transforms into a peak for f = 0.5-5 MHz. The peak decreases in amplitude,
+broadens and shifts downward in temperature as the bias field increases. A huge
+ac magnetoresistance (= 45 % at f = 2 MHz) in a field of Hdc = 1 kOe is found
+and we attribute it to the magnetic field- induced enhancement in the skin
+depth and concomitant suppression of magnetic fluctuations near TC. Our study
+suggests that radio frequency magnetotransport provides an alternative strategy
+to enhance the magnetoresistance and probe the spin-charge coupling in
+manganites.",0905.0090v1
+2009-05-16,Local-moment ferromagnetism and unusual magnetic domains in Fe$_{1/4}$TaS$_{2}$ crystals,"Single crystals of Fe$_{1/4}$TaS$_{2}$ have been studied by using
+magneto-optical (MO) imaging and radio-frequency (rf) magnetic susceptibility,
+$\chi$. Real time MO images reveal unusual, slow dynamics of dendritic domain
+formation, the details of which are strongly dependent upon magnetic and
+thermal history. Measurements of $\chi(T)$ show well-defined, local moment
+ferromagnetic transition at $T\approx 155$ K as well as thermal hysteresis for
+50 K$<T<$60 K. This temperature range corresponds to the domain formation
+temperature as determined by MO. Together these observations provide strong
+evidence for local moment ferromagnetism in Fe$_{1/4}$TaS$_{2}$ crystals with
+large, temperature dependent magnetic anisotropy.",0905.2684v1
+2009-05-22,Metal-insulator transition and magnetism in correlated band insulator: FeSi and Fe$_{1-x}$Co$_{x}$Si,"The LDA+DMFT (local density approximation combined with dynamical mean-field
+theory) computation scheme has been used to study spectral and magnetic
+properties of FeSi and Fe$_{1-x}$Co$_{x}$Si. Having compared different models
+we conclude that a correlated band insulator scenario in contrast to Kondo
+insulator model agrees with FeSi band structure as well as experimental data.
+Coulomb correlation effects lead to band narrowing of the states near the Fermi
+level with mass renormalization parameter $m^*\approx 2$ in agreement with the
+results of angle-resolved photoemission spectroscopy (ARPES). Temperature
+dependence of spectral functions and magnetic susceptibility calculated in DMFT
+reproduces transition from nonmagnetic semiconductor to metal with local
+magnetic moments observed experimentally. Cobalt doping leads to ferromagnetism
+that has itinerant nature and can be successfully described by LDA+DMFT method.",0905.3653v1
+2009-05-28,Emerging nonequilibrium bound state in spin-current-local-spin scattering,"Magnetization reversal is a well-studied problem with obvious applicability
+in computer hard-drives. One can accomplish a magnetization reversal in at
+least one of two ways: application of a magnetic field, or through a spin
+current. The latter is more amenable to a fully quantum mechanical analysis. We
+formulate and solve the problem whereby a spin current interacts with a
+ferromagnetic Heisenberg spin chain, to eventually reverse the magnetization of
+the chain. Spin-flips are accomplished through both elastic and inelastic
+scattering. A consequence of the inelastic scattering channel, when it is no
+longer energetically possible, is the occurrence of a new entity: a
+non-equilibrium bound state (NEBS), which is an emergent property of the
+coupled local plus itinerant spin system. For certain definite parameter values
+the itinerant spin lingers near the local spins for some time, before
+eventually leaking out as an outwardly diffusing state. This phenomenon results
+in novel spin-flip dynamics and filtering properties for this type of system.",0905.4708v2
+2009-07-09,Excitation spectrum and magnetic field effects in a quantum critical spin-orbital system:FeSc$_2$S$_4$,"The orbitally degenerate A-site spinel compound FeSc2S4 has been
+experimentally identified as a ``spin-orbital liquid'', with strong
+fluctuations of both spins and orbitals. Assuming that the second neighbor spin
+exchange J2 is the dominant one, we argued in a recent theoretical study [Chen
+et al., Phys. Rev. Lett. 102, 096406 (2009)] that FeSc2S4 is in a local
+``spin-orbital singlet'' state driven by spin orbit coupling, close to a
+quantum critical point, which separates the ``spin-orbital singlet'' phase from
+a magnetically and orbitally ordered phase. In this paper, we refine further
+and develop this theory of FeSc2S4 . First, we show that inclusion of a small
+first neighbor exchange J1 induces a narrow region of incommensurate phase near
+the quantum critical point. Next, we derive the phase diagram in the presence
+of an external magnetic field B, and show that the latter suppresses the
+ordered phase. Lastly, we compute the field dependent dynamical magnetic
+susceptibility $\chi(k, \omega; B)$, from which we extract a variety of
+physical quantities. Comparison with and suggestions for experiment are
+discussed.",0907.1692v1
+2009-07-20,Computational study of microwave oscillations in absence of external field in nonstandard spin valves in the diffusive transport limit,"An anomalous (inverse) spin accumulation in the nonmagnetic spacer may build
+up when the spin valve consists of magnetic films having different spin
+symmetries. This leads to wavy-like dependence of spin-transfer torque on the
+angle between magnetizations, as predicted by spin-dependent diffusive
+transport model, and also confirmed experimentally. Making use of these
+predictions, we have numerically studied the magnetization dynamics in presence
+of such a wavy-torque in Co(8 nm)/Cu(10 nm)/Py(8 nm) nanopillar, considering
+geometry with extended and etched Co layer. In both cases we specify conditions
+for the out-of-plane precession to appear in absence of external magnetic field
+and neglecting thermal fluctuations. We prove the assumption of wavy-like
+torque angular dependence to be fully consistent with experimental
+observations. We also show that some features reported experimentally, like
+nonlinear slope of frequency vs. current behavior, are beyond the applicability
+range of macrospin approximation and can be explained only by means of full
+micromagnetic analysis.",0907.3384v1
+2009-08-12,Small-Scale Kinematic Dynamo and Non-Dynamo in Inertial-Range Turbulence,"We investigate the Lagrangian mechanism of the kinematic ``fluctuation''
+magnetic dynamo in turbulent plasma flow at small magnetic Prandtl numbers. The
+combined effect of turbulent advection and plasma resistivity is to carry
+infinitely many field lines to each space point, with the resultant magnetic
+field at that point given by the average over all the individual line vectors.
+As a consequence of the roughness of the advecting velocity, this remains true
+even in the limit of zero resistivity. We show that the presence of dynamo
+effect requires sufficient angular correlation of the passive line-vectors that
+arrive simultaneously at the SAME space point. We demonstrate this in detail
+for the Kazantsev-Kraichnan model of kinematic dynamo with a Gaussian advecting
+velocity that is spatially rough and white-noise in time. In the regime where
+dynamo action fails, we also obtain the precise rate of decay of the magnetic
+energy. These exact results for the model are obtained by a generalization of
+the ``slow-mode expansion'' of Bernard, Gawedzki and Kupiainen to non-Hermitian
+evolution. Much of our analysis applies also to magnetohydrodynamic turbulence.",0908.1598v1
+2009-08-27,Reciprocal and real space maps for EMCD experiments,"Electron magnetic chiral dichroism (EMCD) is an emerging tool for
+quantitative measurements of magnetic properties using the transmission
+electron microscope (TEM), with the possibility of nanometer resolution. The
+geometrical conditions, data treatment and electron gun settings are found to
+influence the EMCD signal. In this article, particular care is taken to obtain
+a reliable quantitative measurement of the ratio of orbital to spin magnetic
+moment using energy filtered diffraction patterns. For this purpose, we
+describe a method for data treatment, normalization and selection of mirror
+axis. The experimental results are supported by theoretical simulations based
+on dynamical diffraction and density functional theory. Special settings of the
+electron gun, so called telefocus mode, enable a higher intensity of the
+electron beam, as well as a reduction of the influence from artifacts on the
+signal. Using these settings, we demonstrate the principle of acquiring real
+space maps of the EMCD signal. This enables advanced characterization of
+magnetic materials with superior spatial resolution.",0908.3963v1
+2009-09-03,Simulating and detecting artificial magnetic fields in trapped atoms,"A Bose-Einstein condensate exhibiting a nontrivial phase induces an
+artificial magnetic field in immersed impurity atoms trapped in a stationary,
+ring-shaped optical lattice. We present an effective Hamiltonian for the
+impurities for two condensate setups: the condensate in a rotating ring and in
+an excited rotational state in a stationary ring. We use Bogoliubov theory to
+derive analytical formulas for the induced artificial magnetic field and the
+hopping amplitude in the limit of low condensate temperature where the impurity
+dynamics is coherent. As methods for observing the artificial magnetic field we
+discuss time of flight imaging and mass current measurements. Moreover, we
+compare the analytical results of the effective model to numerical results of a
+corresponding two-species Bose-Hubbard model. We also study numerically the
+clustering properties of the impurities and the quantum chaotic behavior of the
+two-species Bose-Hubbard model.",0909.0728v2
+2009-09-11,Magnetism of one-dimensional strongly repulsive spin-1 bosons with antiferromagnetic spin exchange interaction,"We investigate magnetism and quantum phase transitions in a one-dimensional
+system of integrable spin-1 bosons with strongly repulsive density-density
+interaction and antiferromagnetic spin exchange interaction via the
+thermodynamic Bethe ansatz method. At zero temperature, the system exhibits
+three quantum phases: (i) a singlet phase of boson pairs when the external
+magnetic field $H$ is less than the lower critical field $H_{c1}$; (ii) a
+ferromagnetic phase of atoms in the hyperfine state $|F=1, m_{F}=1>$ when the
+external magnetic field exceeds the upper critical field $H_{c2}$; and (iii) a
+mixed phase of singlet pairs and unpaired atoms in the intermediate region
+$H_{c1}<H<H_{c2}$. At finite temperatures, the spin fluctuations affect the
+thermodynamics of the model through coupling the spin bound states to the
+dressed energy for the unpaired $m_{F}=1$ bosons. However, such spin dynamics
+is suppressed by a sufficiently strong external field at low temperatures. Thus
+the singlet pairs and unpaired bosons may form a two-component Luttinger liquid
+in the strong coupling regime.",0909.2097v1
+2009-09-11,Amplification of whistler waves in a thin Keplerian disc embedded in an axisymmetric magnetic field,"The linear stability of thin Keplerian discs of weakly ionized polytropic
+plasma embedded in a mixed (toroidal-poloidal) axisymmetric magnetic field is
+studied. The effects of the central body on the equilibrium state of the discs
+are modeled by an axial total current and a dipole magnetic field. Studying the
+amplification of high-frequency waves shows that Keplerian discs can be
+destabilized due to combined effects of equilibrium density stratification and
+poloidal magnetic field. By considering a boundary value problem in the limit
+of strong Hall effect, it is shown that whistler waves which are free of direct
+influence of compressibility, rotation and gravity, are amplified along their
+trajectory while other modes of wave propagation do not change their amplitude.",0909.2135v1
+2009-10-14,Pseudospin excitations in coaxial nanotubes,"In a 2DEG confined to two coaxial tubes the `tube degree of freedom' can be
+described in terms of pseudospin-1/2 dynamics. The presence of tunneling
+between the two tubes leads to a collective oscillation known as pseudospin
+resonance. We employ perturbation theory to examine the dependence of the
+frequency of this mode with respect to a coaxial magnetic field for the case of
+small intertube distances. Coulomb interaction leads to a shift of the
+resonance frequency and to a finite lifetime of the pseudospin excitations. The
+presence of the coaxial magnetic field gives rise to pronounced peaks in the
+shift of the resonance frequency. For large magnetic fields this shift vanishes
+due to the effects of Zeeman splitting. Finally, an expression for the
+linewidth of the resonance is derived. Numerical analysis of this expression
+suggests that the linewidth strongly depends on the coaxial magnetic field,
+which leads to several peaks of the linewidth as well as regions where damping
+is almost completely suppressed.",0910.2552v2
+2009-10-23,Prandtl number dependence of convection driven dynamos in rotating spherical fluid shells,"The value of the Prandtl number $P$ exerts a strong influence on
+convection-driven dynamos in rotating spherical shells filled with electrically
+conducting fluids. Low Prandtl numbers promote dynamo action through the shear
+provided by differential rotation, while the generation of magnetic fields is
+more difficult to sustain in high-Prandtl-number fluids where higher values of
+the magnetic Prandtl number $P_m$ are required. The magnetostrophic
+approximation often used in dynamo theory appears to be valid only for
+relatively high values of $P$ and $P_m$. Dynamos with a minimum value of $P_m$
+seem to be most readily realizable in the presence of convection columns at
+moderately low values of $P$. The structure of the magnetic field varies
+strongly with $P$ in that dynamos with a strong axial dipole field are found
+for high values of $P$ while the energy of this component is exceeded by that
+of the axisymmetric toroidal field and by that of the non-axisymmetric
+components at low values of $P$. Some conclusions are discussed in relation to
+the problem of the generation of planetary magnetic fields by motions in their
+electrically conducting liquid cores.",0910.4493v1
+2009-11-06,Chiral magnetic effect in 2+1 flavor QCD+QED,"The exciting possibility of direct observation of QCD instantons in heavy-ion
+collisions has recently been proposed by Kharzeev. The underlying phenomenon,
+known as the chiral magnetic effect, may have been observed recently at RHIC,
+and a first principles calculation is needed to confirm and understand the
+results. The chiral magnetic effect is thought to be visible in the symmetric
+phase, at temperatures above the QCD critical temperature, and in the presence
+of an external magnetic field. We report on first 2+1 flavor, domain wall
+fermion, QCD+QED dynamical simulations above the critical temperature, in a
+fixed topological sector(s), which are used to study the electric charge
+separation produced by the effect.",0911.1348v1
+2009-11-18,Screened perturbation theory for 3d Yang-Mills theory and the magnetic modes of hot QCD,"Perturbation theory for non-abelian gauge theories at finite temperature is
+plagued by infrared divergences which are caused by magnetic soft modes ~g^2T,
+corresponding to gluon fields of a 3d Yang-Mills theory. While the divergences
+can be regulated by a dynamically generated magnetic mass on that scale, the
+gauge coupling drops out of the effective expansion parameter requiring
+summation of all loop orders for the calculation of observables. Some gauge
+invariant possibilities to implement such infrared-safe resummations are
+reviewed. We use a scheme based on the non-linear sigma model to estimate some
+of the contributions ~g^6 of the soft magnetic modes to the QCD pressure
+through two loops. The NLO contribution amounts to ~10% of the LO, suggestive
+of a reasonable convergence of the series.",0911.3595v2
+2009-11-24,Low temperature study of field induced antiferro-ferromagnetic transition in Pd doped FeRh,"The first order antiferromagnetic (AFM) to ferromagnetic (FM) transition in
+the functional material Fe49(Rh0.93Pd0.07)51 has been studied at low
+temperatures and high magnetic fields. We have addressed the non-monotonic
+variation of lower critical field required for FM to AFM transition. It is
+shown that critically slow dynamics of the transition dominates below 50 K. At
+low temperature and high magnetic field, state of the system depends on the
+measurement history resulting in tunable coexistence of AFM and FM phases. By
+following cooling and heating in unequal magnetic field (CHUF) protocol it is
+shown that equilibrium state at 6 Tesla magnetic field is AFM state. Glass like
+FM state at 6 T (obtained after cooling in 8 T) shows reentrant transition with
+increasing temperature; viz. devitrification to AFM state followed by melting
+to FM state.",0911.4552v1
+2009-12-15,"Dynamics of Uniform Quantum Gases, II: Magnetic Susceptibility","A general expression for temperature-dependent magnetic susceptibility of
+quantum gases composed of particles possessing both charge and spin degrees of
+freedom has been obtained within the framework of the generalized random-phase
+approximation. The conditions for the existence of dia-, para-, and
+ferro-magnetism have been analyzed in terms of a parameter involving
+single-particle charge and spin. The zero-temperature limit retrieves the
+expressions for the Landau and the Pauli susceptibilities for an electron gas.
+It is found for a Bose gas that on decreasing the temperature, it passes either
+through a diamagnetic incomplete Meissner-effect regime or through a
+paramagnetic-ferromagnetic large magnetization fluctuation regime before going
+to the Meissner phase at BEC critical temperature.",0912.2841v1
+2010-01-12,Dynamic pinning at a Py/Co interface measured using inductive magnetometry,"Broadband FMR responses for metallic single-layer and bi-layer magnetic films
+with total thicknesses smaller than the microwave magnetic skin depth have been
+studied. Two different types of microwave transducers were used to excite and
+detect magnetization precession: a narrow coplanar waveguide and a wide
+microstrip line. Both transducers show efficient excitation of higher-order
+standing spin wave modes. The ratio of amplitudes of the first standing spin
+wave to the fundamental resonant mode is independent of frequency for single
+films. In contrast, we find a strong variation of the amplitudes with frequency
+for bi-layers and the ratio is strongly dependent on the ordering of layers
+with respect to a stripline transducer. Most importantly, cavity FMR
+measurements on the same samples show considerably weaker amplitudes for the
+standing spin waves. All experimental data are consistent with expected effects
+due to screening by eddy currents in films with thicknesses below the microwave
+magnetic skin depth. Finally, conditions for observing eddy current effects in
+different types of experiments are critically examined.",1001.1837v1
+2010-02-04,Neutron scattering and muSR investigations of the spin liquid state with quenched disorder in LuCuGaO4,"LuCuGaO4 has magnetic Cu2+ and diamagnetic Ga3+ ions distributed on a
+triangular bilayer and is suggested to undergo a spin-glass transition with T_g
+approximately 0.4 K. Using muSR and neutron scattering measurements, we show
+that at low temperature the spins form a short-range correlated state with spin
+fluctuations detectable over a wide range of timescales: at 0.05 K magnetic
+fluctuations can be detected in both the muSR time window and also extending
+beyond 7 meV in the inelastic neutron scattering response, indicating magnetic
+fluctuations spanning timescales between 1E-5 and 1E-10 seconds. The dynamical
+susceptibility scales according to the form \chi''(\omega)T^\alpha, with
+\alpha=1, throughout the measured temperature range (0.05 - 50 K). These
+effects are associated with quantum fluctuations and some degree of structural
+disorder in ostensibly quite different materials, including certain heavy
+fermion alloys, kagome spin liquids, quantum spin glasses, and valence bond
+glasses. We therefore suggest LuCuGaO4 is an interesting model compound for the
+further examination of disorder and quantum magnetism.",1002.0975v2
+2010-02-12,The Parker Scenario for Coronal Heating as an MHD Turbulence Problem,"The Parker or field line tangling model of coronal heating is investigated
+through long-time high-resolution simulations of the dynamics of a coronal loop
+in cartesian geometry within the framework of reduced magnetohydrodynamics
+(RMHD). Slow photospheric motions induce a Poynting flux which saturates by
+driving an anisotropic turbulent cascade dominated by magnetic energy and
+characterized by current sheets elongated along the axial magnetic field.
+Increasing the value of the axial magnetic field different regimes of MHD
+turbulence develop with a bearing on coronal heating rates. In physical space
+magnetic field lines at the scale of convection cells appear only slightly
+bended in agreement with observations of large loops of current (E)UV and X-ray
+imagers.",1002.2631v1
+2010-03-11,On the Chiral Magnetic Effect in Soft-Wall AdS/QCD,"The essence of the chiral magnetic effect is generation of an electric
+current along an external magnetic field. Recently it has been studied by
+Rebhan et al. within the Sakai--Sugimoto model, where it was shown to be zero.
+As an alternative, we calculate the chiral magnetic effect in soft-wall AdS/QCD
+and find a non-zero result with the natural boundary conditions. The mechanism
+of the dynamical neutralization of the chiral chemical potential via the string
+production is discussed in the dual two-form representation.",1003.2293v3
+2010-03-11,Electric Charge Separation in Strong Transient Magnetic Fields,"We discuss various mechanisms for the creation of an asymmetric charge
+fluctuation with respect to the reaction plane among hadrons emitted in
+relativistic heavy-ion collisions. We show that such mechanisms exist in both,
+the hadronic gas and the partonic phases of QCD. The mechanisms considered here
+all require the presence of a strong magnetic field (the ``chiral magnetic
+effect''), but they do not involve parity or charge-parity violations. We
+analyze how a transient local electric current fluctuation generated by the
+chiral magnetic effect can dynamically evolve into an asymmetric charge
+distribution among the final-state hadrons in momentum space. We estimate the
+magnitude of the event-by-event fluctuations of the final-state charge
+asymmetry due to the partonic and hadronic mechanisms.",1003.2436v3
+2010-03-18,Self-organization of dissipative and coherent vortex structures in non-equilibrium magnetized two-dimensional plasmas,"The properties of non-equilibrium magnetized plasmas confined in planar
+geometry are studied on the basis of the first principle microscopic Langevin
+dynamics computer simulations. The non-equilibrium state of plasmas is
+maintained due to the recombination and generation of charges.The intrinsic
+microscopic structure of non-equilibrium steady-state magnetized plasmas, in
+particular, the inter-particle correlations and self-organization of vortex
+structures are examined. The simulations have been performed for a wide range
+of parameters including strong plasma coupling, high charge recombination and
+generation rates, and intense magnetic field. As is shown in simulations, the
+non-equilibrium recombination and generation processes trigger the formation of
+ordered dissipative or coherent drift vortex states in 2D plasmas with
+distinctly spatially separated components, which are far from thermal
+equilibrium. This is evident from the unusual properties of binary
+distributions and behavior of the Coulomb energy of the system, which turn out
+to be quite different from the ones typical for the equilibrium state of
+plasmas under the same conditions.",1003.3666v2
+2010-03-22,Nontrivial in-plane-magnetic-field dependence of THz wave emission from intrinsic Josephson junctions controlled by surface impedance,"In THz wave emission from intrinsic Josephson junctions in in-plane magnetic
+fields, emission intensity strongly depends on the surface impedance $Z$
+similarly to the case without external magnetic fields. Cavity resonance modes
+are stabilized for $Z \ge 3$, and the fundamental mode gives the strongest
+emission. As the in-plane magnetic field increases for a fixed number of
+junctions, dynamical phase transitions seem to occur between the
+$\pi$-phase-kink state, various incommensurate phase-kink states, and in-phase
+state. As $Z$ varies, a crossover of the field profile of maximum intensity
+takes place for $Z \approx 50$ between characteristic peaks for smaller $Z$
+(typically $Z \approx 30$) and monotonic decrease for larger $Z$ (typically $Z
+\approx 70$). The double-peak structure reported in experiments can be
+explained for Z=30 by finite-size analysis with respect to number of junctions.",1003.4045v2
+2010-03-30,Shock-triggered formation of magnetically-dominated clouds. II. Weak shock-cloud interaction in three dimensions,"To understand the formation of a magnetically dominated molecular cloud from
+an atomic cloud, we study the interaction of a weak, radiative shock with a
+magnetised cloud. The thermally stable warm atomic cloud is initially in static
+equilibrium with the surrounding hot ionised gas. A shock propagating through
+the hot medium then interacts with the cloud. We follow the dynamical evolution
+of the shocked cloud with a time-dependent ideal magnetohydrodynamic code. By
+performing the simulations in 3D, we investigate the effect of different
+magnetic field orientations including parallel, perpendicular and oblique to
+the shock normal. We find that the angle between the shock normal and the
+magnetic field must be small to produce clouds with properties similar to
+observed molecular clouds.",1003.5843v1
+2010-04-08,Divergent effects of static disorder and hole doping in geometrically frustrated b-CaCr2O4,"The gallium substituted and calcium deficient variants of geometrically
+frustrated b-CaCr2O4, b-CaCr2-2xGa2xO4 (0.02<= x<= 0.25) and b-Ca1-yCr2O4
+(0.075<= y<= 0.15), have been investigated by x-ray powder diffraction,
+magnetization and specific heat measurements. This allows for a direct
+comparison of the effects, in a geometrically frustrated magnet, of the static
+disorder that arises from non-magnetic substitution and the dynamic disorder
+that arises from hole doping. In both cases, disturbing the Cr3+ lattice
+results in a reduction in the degree of magnetic frustration. On substitution
+of Ga, which introduces disorder without creating holes, a gradual release of
+spins from ordered antiferromagnetic states is observed. In contrast, in the
+calcium deficient compounds the introduction of holes induces static
+ferrimagnetic ordering and much stronger perturbations of the b-CaCr2O4 host.",1004.1390v1
+2010-04-14,Simple waves in relativistic fluids,"We consider the Riemann problem for relativistic flows of polytropic fluids
+and find relations for the flow characteristics. Evolution of physical
+quantities take especially simple form for the case of cold magnetized plasmas.
+We find exact, explicit analytical solutions for one dimensional expansion of
+magnetized plasma into vacuum, valid for arbitrary magnetization. We also
+consider expansion into cold unmagnetized external medium both for stationary
+initial conditions and for initially moving plasma, as well as reflection of
+rarefaction wave from a wall. We also find self-similar structure of
+three-dimensional magnetized outflows into vacuum, valid close to the
+plasma-vacuum interface.
+  The key results of this work, the self-similar solutions, were incorporated
+post-initial submission into appendices of the published version of Granot et
+al. (2010).",1004.2428v4
+2010-05-10,"Exchange constant and domain wall width in (Ga,Mn)(As,P) films with self-organization of magnetic domains","The incorporation of Phosphorus into (Ga,Mn)As epilayers allows for the
+tuning of the magnetic easy axis from in-plane to perpendicular-to-plane
+without the need for a (Ga,In)As template. For perpendicular easy axis, using
+magneto-optical imaging a self-organized pattern of up- and down-magnetized
+domains is observed for the first time in a diluted magnetic semiconductor.
+Combining Kerr microscopy, magnetometry and ferromagnetic resonance
+spectroscopy, the exchange constant and the domain wall width parameter are
+obtained as a function of temperature. The former quantifies the effective
+Mn-Mn ferromagnetic interaction. The latter is a key parameter for domain wall
+dynamics. The comparison with results obtained for (Ga,Mn)As/(Ga,In)As reveals
+the improved quality of the (Ga,Mn)As$_{1-y}$P$_y$ layers regarding domain wall
+pinning, an increase of the domain wall width parameter and of the effective
+Mn-Mn spin coupling. However, at constant Mn doping, no significant increase of
+this coupling is found with increasing P concentration in the investigated
+range.",1005.1494v1
+2010-05-11,Zero-field magnetization reversal of two-body Stoner particles with dipolar interaction,"Nanomagnetism has recently attracted explosive attention, in particular,
+because of the enormous potential applications in information industry, e.g.
+new harddisk technology, race-track memory[1], and logic devices[2]. Recent
+technological advances[3] allow for the fabrication of single-domain magnetic
+nanoparticles (Stoner particles), whose magnetization dynamics have been
+extensively studied, both experimentally and theoretically, involving magnetic
+fields[4-9] and/or by spin-polarized currents[10-20]. From an industrial point
+of view, important issues include lowering the critical switching field $H_c$,
+and achieving short reversal times. Here we predict a new technological
+perspective: $H_c$ can be dramatically lowered (including $H_c=0$) by
+appropriately engineering the dipole-dipole interaction (DDI) in a system of
+two synchronized Stoner particles. Here, in a modified Stoner-Wohlfarth (SW)
+limit, both of the above goals can be achieved. The experimental feasibility of
+realizing our proposal is illustrated on the example of cobalt nanoparticles.",1005.1828v1
+2010-05-26,Dispersive magnetized waves in the solar wind plasma,"We derive a generalized linear dispersion relation of waves in a strongly
+magnetized, compressible, homogeneous and isotropic quasineutral plasma.
+Starting from a two fluid model, describing distinguishable electron and ion
+fluids, we obtain a six order linear dispersion relation of magnetized waves
+that contains effects due to electron and ion inertia, finite plasma beta and
+angular dependence of phase speed. We investigate propagation characteristics
+of these magnetized waves in a regime where scale lengths are comparable with
+electron and ion inertial length scales. This regime corresponds essentially to
+the solar wind plasma where length scales, comparable with ion cyclotron
+frequency, lead to dispersive effects. These scales in conjunction with linear
+waves present a great deal of challenges in understanding the high frequency,
+small scale dynamics of turbulent fluctuations in the solar wind plasma.",1005.4902v1
+2010-05-30,Smooth double critical state theory for type-II superconductors,"Several aspects of the general theory for the critical states of a vortex
+lattice and the magnetic flux dynamics in type-II superconductors are examined
+by a direct variational optimisation method and widespread physical principles.
+Our method allows to unify a number of conventional models describing the
+complex vortex configurations in the critical state regime. Special attention
+is given to the discussion of the relation between the flux-line cutting
+mechanism and the depinning threshold limitation. This is done by using a
+smooth double critical state concept which incorporates the so-called
+isotropic, elliptical, T and CT models as well-defined limits of our general
+treatment. Starting from different initial configurations for a superconducting
+slab in a 3D magnetic field, we show that the predictions of the theory range
+from the collapse to zero of transverse magnetic moments in the isotropic
+model, to nearly force free configurations in which paramagnetic values can
+arbitrarily increase with the applied field for magnetically anisotropic
+current voltage laws. Noteworthily, the differences between the several model
+predictions are minimal for the low applied field regime.",1005.5540v1
+2010-05-31,Driven weak to strong pinning crossover in partially nanopatterned 2H-NbSe2 single crystal,"Investigations into the heterogeneous pinning properties of the vortex state
+created by partially nano-patterning single crystals of 2H-NbSe2 reveal an
+atypical magnetization response which is significantly drive dependent.
+Analysis of the magnetization response shows non-monotonic behavior of the
+magnetization relaxation rate with varying magnetic field sweep rate. With all
+the patterned pinning centers saturated with vortices, we find that the pinning
+force experienced by the vortices continues to increase with increasing drive.
+Our studies reveal an unconventional dynamic weak to strong pinning crossover
+where the flow of the vortex state appears to be hindered or jammed as it is
+driven harder through the interstitial voids in the patterned pinning lattice.",1005.5641v1
+2010-06-03,Peristaltic Transport of a Physiological Fluid in an Asymmetric Porous Channel in the Presence of an External Magnetic Field,"The paper deals with a theoretical investigation of the peristaltic transport
+of a physiological fluid in a porous asymmetric channel under the action of a
+magnetic field. The stream function, pressure gradient and axial velocity are
+studied by using appropriate analytical and numerical techniques. Effects of
+different physical parameters such as permeability, phase difference, wave
+amplitude and magnetic parameter on the velocity, pumping characteristics,
+streamline pattern and trapping are investigated with particular emphasis. The
+computational results are presented in graphical form. The results are found to
+be in perfect agreement with those of a previous study carried out for a
+non-porous channel in the absence of a magnetic field.",1006.0616v1
+2010-06-29,Magnetic properties of exchange biased and of unbiased oxide/permalloy thin layers: a ferromagnetic resonance and Brillouin scattering study,"Microstrip ferromagnetic resonance and Brillouin scattering are used to
+provide a comparative determination of the magnetic parameters of thin
+permalloy layers interfaced with a non-magnetic (Al2O3) or with an
+antiferromagnetic oxide (NiO). It is shown that the perpendicular anisotropy is
+monitored by an interfacial surface energy term which is practically
+independent of the nature of the interface. In the investigated interval of
+thicknesses (5-25 nm) the saturation magnetisation does not significantly
+differ from the reported one in bulk permalloy. In-plane uniaxial anisotropy
+and exchange-bias anisotropy are also derived from this study of the dynamic
+magnetic excitations and compared to our independent evaluations using
+conventional magnetometry",1006.5598v1
+2010-07-01,Magnetic dynamics of simple collective modes in a two-sphere plasma model,"A plasma blob is modeled as consisting of two homogeneous spheres of equal
+radius and equal but opposite charge densities that can move relative to each
+other. Relative translational and rotational motion are considered separately.
+Magnetic effects from the current density caused by the relative motion are
+included. Magnetic interaction is seen to cause an inductive inertia. In the
+relative translation case the Coulomb attraction, approximately a linear force
+for small amplitudes, causes an oscillation. For a large number of particles
+the corresponding oscillation frequency will not be the Langmuir plasma
+frequency, because of the large inductive inertia. For rotation an external
+magnetic field is included and the energy and diamagnetism of the plasma in the
+model is calculated. Finally it is noted how the neglect of resistivity is
+motivated by the results.",1007.0216v1
+2010-07-07,Flow and Heat Transfer of a MHD Viscoelastic Fluid in a Channel with Stretching Walls: Some Applications to Haemodynamics,"Of concern in the paper is a study of steady incompressible viscoelastic and
+electrically conducting fluid flow and heat transfer in a parallel plate
+channel with stretching walls in the presence of a magnetic field applied
+externally. The flow is considered to be governed by Walter's liquid B fluid.
+The problem is solved by developing a suitable numerical method. The results
+are found to be in good agrement with those of earlier investigations reported
+in existing scientific literatures. The study reveals that a back flow occurs
+near the central line of the channel due to the stretching walls and further
+that this flow reversal can be stopped by applying a strong external magnetic
+field. The study also shows that with the increase in the strength of the
+magnetic field, the fluid velocity decreases but the temperature increases.
+Thus the study bears potential applications in the study of the haemodynamic
+flow of blood in the cardiovascular system when subjected to an external
+magnetic field.",1007.1228v1
+2010-08-06,Recovering magnetization distributions from their noisy diffraction data,"We study, using simulated experiments inspired by thin film magnetic domain
+patterns, the feasibility of phase retrieval in X-ray diffractive imaging in
+the presence of intrinsic charge scattering given only photon-shot-noise
+limited diffraction data. We detail a reconstruction algorithm to recover the
+sample's magnetization distribution under such conditions, and compare its
+performance with that of Fourier transform holography. Concerning the design of
+future experiments, we also chart out the reconstruction limits of diffractive
+imaging when photon- shot-noise and the intensity of charge scattering noise
+are independently varied. This work is directly relevant to the time-resolved
+imaging of magnetic dynamics using coherent and ultrafast radiation from X-ray
+free electron lasers and also to broader classes of diffractive imaging
+experiments which suffer noisy data, missing data or both.",1008.1136v1
+2010-08-22,Local analysis of the magnetic instability in rotating magneto-hydrodynamics with the short-wavelength approximation,"We investigate analytically the magnetic instability in a rotating and
+electrically conducting fluid induced by an imposed magnetic field with its
+associated electric current. The short-wavelength approximation is used in the
+linear stability analysis, i.e. the length scale of the imposed field is much
+larger than the wavelength of perturbations. The dispersion relationship is
+derived and then simplified to give the criteria for the onset of the magnetic
+instability in three cases of imposed field, namely the axial dependence, the
+radial dependence and the mixed case. The orientation of rotation, imposed
+field and imposed current is important for this instability.",1008.3706v7
+2010-08-28,Modelling stellar coronal magnetic fields,"Our understanding of the structure and dynamics of stellar coronae has
+changed dramatically with the availability of surface maps of both star spots
+and also magnetic field vectors. Magnetic field extrapolations from these
+surface maps reveal surprising coronal structures for stars whose masses and
+hence internal structures and dynamo modes may be very different from that of
+the Sun. Crucial factors are the fraction of open magnetic flux (which
+determines the spin-down rate for the star as it ages) and the location and
+plasma density of closed-field regions, which determine the X-ray and radio
+emission properties. There has been recent progress in modelling stellar
+coronae, in particular the relative contributions of the field detected in the
+bright surface regions and the field that may be hidden in the dark star spots.
+For the Sun, the relationship between the field in the spots and the large
+scale field is well studied over the solar cycle. It appears, however, that
+other stars can show a very different relationship.",1008.4885v1
+2010-09-06,Energy oscillations and a possible route to chaos in a modified Riga dynamo,"Starting from the present version of the Riga dynamo experiment with its
+rotating magnetic eigenfield dominated by a single frequency we ask for those
+modifications of this set-up that would allow for a non-trivial magnetic field
+behaviour in the saturation regime. Assuming an increased ratio of azimuthal to
+axial flow velocity, we obtain energy oscillations with a frequency below the
+eigenfrequency of the magnetic field. These new oscillations are identified as
+magneto-inertial waves that result from a slight imbalance of Lorentz and
+inertial forces. Increasing the azimuthal velocity further, or increasing the
+total magnetic Reynolds number, we find transitions to a chaotic behaviour of
+the dynamo.",1009.1051v1
+2010-09-09,Simulation of RF Cavity Dark Current in Presence of Helical Magnetic Field,"In order to produce muon beam of high enough quality to be used for a Muon
+Collider, its large phase space must be cooled several orders of magnitude.
+This task can be accomplished by ionization cooling. Ionization cooling
+consists of passing a high-emittance muon beam alternately through regions of
+low Z material, such as liquid hydrogen, and very high accelerating RF cavities
+within a multi-Tesla solenoidal focusing channel. But first high power tests of
+RF cavity with beryllium windows in solenoidal magnetic field showed a dramatic
+drop in accelerating gradient due to RF breakdowns. It has been concluded that
+external magnetic fields parallel to RF electric field significantly modifies
+the performance of RF cavities. However, magnetic field in Helical Cooling
+Channel has a strong dipole component in addition to solenoidal one. The dipole
+component essentially changes electron motion in a cavity compare to pure
+solenoidal case, making dark current less focused at field emission sites. The
+simulation of dark current dynamic in HCC performed with CST Studio Suit is
+presented in this paper.",1009.1857v1
+2010-09-22,Long-term decaying evolution of MHD turbulence,"The free decay of MHD turbulence at large Reynolds numbers is studied
+numerically using a shell model. We study the statistical properties based on
+representative sample of realisations (128 realisations for each type of
+initial conditions) over the period of $10^5$ large-scale turnover times. The
+performed simulations show that the force-free non-helical MHD turbulence can
+demonstrate two different scenarios of evolution in spite of similar initial
+conditions. Within the first scenario, the cross-helicity accumulation is so
+fast that the energy cascade vanishes before significant magnetic energy
+dissipates. Then the system approaches the state of maximal cross-helicity.
+Within the second scenario, the cascade process continues to remain active
+until time $10^4$ in units of large-scale turnover time. Then the magnetic
+field becomes vastly helical due to magnetic helicity conservation. Thus the
+magnetic energy does not dissipate with kinetic energy.",1009.4337v1
+2010-09-27,On the Stability of Non Force-Free Magnetic Equilibria in Stars,"The existence of stable magnetic configurations in white dwarfs, neutron
+stars and various non-convective stellar {regions} is now well recognized. It
+has recently been shown numerically that various families of equilibria,
+including axisymmetric mixed poloidal-toroidal configurations, are stable. Here
+we test the stability of an analytically-derived non force-free magnetic
+equilibrium, using three-dimensional magnetohydrodynamic simulations: the mixed
+configuration is compared with the dynamical evolution of its purely poloidal
+and purely toroidal components, both known to be unstable. The mixed
+equilibrium shows no sign of instability under white noise perturbations. {This
+configuration therefore provides a good description of magnetic equilibrium
+topology inside non-convective stellar objects and will be useful to initialize
+magneto-rotational transport in stellar evolution codes.",1009.5384v1
+2010-09-28,Magneto-acoustic wave propagation and mode conversion in a magnetic solar atmosphere: comparing results from the CO5BOLD code with ray theory,"We present simulations of magneto-acoustic wave propagation in a magnetic,
+plane-parallel stratified solar model atmosphere, employing the CO5BOLD-code.
+The tests are carried out for two models of the solar atmosphere, which are
+similar to the ones used by Cally (2007) and Schunker & Cally (2006). The two
+models differ only in the orientation of the magnetic field. A qualitative
+comparison shows good agreement between the numerical results and the results
+from ray theory. The tests are done in view of the application of the present
+numerical code for the computation of energy fluxes of propagating acoustic
+waves into a dynamically evolving magnetic solar atmosphere. For this, we
+consider waves with frequencies above the acoustic cut-off frequency.",1009.5586v1
+2010-09-28,Role of non-collinear magnetization: from ferromagnetic nano wires to quantum rings,"We consider interaction effects related to a nonuniform magnetization in
+ferromagnetic nanowires and their possible generalization to nanorings. First
+we show that the electric current in a ferromagnetic nanowire with more than
+one domain wall induces an exchange coupling between the walls mediated by the
+spin-dependent interference of scattered carriers. This interaction reveals a
+complex behavior as a function of mutual orientations and separation of the
+domain walls, thus affecting the domain wall dynamics. Then we consider how the
+theory should be modified in the case of a magnetized quantum ring. In this
+case the situation is more complicated because the vortex and onion
+magnetization states in the ring are not truly ferromagnetic.",1009.5688v1
+2010-09-30,Existence of a phase transition under finite magnetic field in the long-range RKKY Ising spin glass Dy$_{x}$Y$_{1-x}$Ru$_{2}$Si$_{2}$,"A phase transition of a model compound of the long-range Ising spin glass
+(SG) Dy$_{x}$Y$_{1-x}$Ru$_{2}$Si$_{2}$, where spins interact via the RKKY
+interaction, has been investigated. The static and the dynamic scaling analyses
+reveal that the SG phase transition in the model magnet belongs to the
+mean-field universality class. Moreover, the characteristic relaxation time in
+finite magnetic fields exhibits a critical divergent behavior as well as in
+zero field, indicating a stability of the SG phase in finite fields. The
+presence of the SG phase transition in field in the model magnet strongly
+syggests that the replica symmetry is broken in the long-range Ising SG.",1009.6115v2
+2010-10-01,Magnetic fields and the outer rotation curve of M31,"Recent observations of the rotation curve of M31 show a rise of the outer
+part that can not be understood in terms of standard dark matter models or
+perturbations of the galactic disc by M31's satellites. Here, we propose an
+explanation of this dynamical feature based on the influence of the magnetic
+field within the thin disc. We have considered standard mass models for the
+luminous mass distribution, a NFW model to describe the dark halo, and we have
+added up the contribution to the rotation curve of a magnetic field in the
+disc, which is described by an axisymmetric pattern. Our conclusion is that a
+significant improvement of the fit in the outer part is obtained when magnetic
+effects are considered. The best-fit solution requires an amplitude of ~4
+microG with a weak radial dependence between 10 and 38 kpc.",1010.0270v1
+2010-10-08,A Lagrangian model for the evolution of turbulent magnetic and passive scalar fields,"In this paper we present an extension of the \emph{Recent Fluid Deformation
+(RFD)} closure introduced by Chevillard and Meneveau (2006) which was developed
+for modeling the time evolution of Lagrangian fluctuations in incompressible
+Navier-Stokes turbulence. We apply the RFD closure to study the evolution of
+magnetic and passive scalar fluctuations. This comparison is especially
+interesting since the stretching term for the magnetic field and for the
+gradient of the passive scalar are similar but differ by a sign such that the
+effect of stretching and compression by the turbulent velocity field is
+reversed. Probability density functions (PDFs) of magnetic fluctuations and
+fluctuations of the gradient of the passive scalar obtained from the RFD
+closure are compared against PDFs obtained from direct numerical simulations.",1010.1598v2
+2010-10-18,An extension of gas-kinetic BGK Navier-Stokes scheme to multidimensional astrophysical magnetohydrodynamics,"The multidimensional gas-kinetic scheme for the Navier-Stokes equations under
+gravitational fields [J. Comput. Phys. 226 (2007) 2003-2027] is extended to
+resistive magnetic flows. The non-magnetic part of the magnetohydrodynamics
+equations is calculated by a BGK solver modified due to magnetic field. The
+magnetic part is treated by the flux splitting method based gas-kinetic theory
+[J. Comput. Phys. 153 (1999) 334-352 ], using a particle distribution function
+constructed in the BGK solver. To include Lorentz force effects into gas
+evolution stage is very important to improve the accuracy of the scheme. For
+some multidimensional problems, the deviations tangential to the cell interface
+from equilibrium distribution are essential to keep the scheme robust and
+accurate. Besides implementation of a TVD time discretization scheme, enhancing
+the dynamic dissipation a little bit is a simply and efficient way to stabilize
+the calculation. One-dimensional and two-dimensional shock waves tests are
+calculated to validate this new scheme. A three-dimensional turbulent
+magneto-convection simulation is used to show the applicability of current
+scheme to complicated astrophysical flows.",1010.3594v1
+2010-11-03,Existence of vertical spin stiffness in Landau-Lifshitz-Gilbert equation in ferromagnetic semiconductors,"We calculate the magnetization torque due to the spin polarization of the
+itinerant electrons by deriving the kinetic spin Bloch equations based on the
+$s$-$d$ model. We find that the first-order gradient of the magnetization
+inhomogeneity gives rise to the current-induced torques, which are consistent
+to the previous works. At the second-order gradient, we find an effective
+magnetic field perpendicular to the spin stiffness filed. This field is
+proportional to the nonadiabatic parameter $\beta$. We show that this vertical
+spin stiffness term can significantly modify the domain-wall structure in
+ferromagnetic semiconductors and hence should be included in the
+Landau-Lifshitz-Gilbert equation in studying the magnetization dynamics.",1011.0871v1
+2010-12-13,Cold and ultracold NH--NH collisions in magnetic fields,"Elastic and spin-changing inelastic collision cross sections are presented
+for cold and ultracold magnetically trapped NH. The cross sections are obtained
+from coupled-channel scattering calculations as a function of energy and
+magnetic field. We specifically investigate the influence of the intramolecular
+spin-spin, spin-rotation, and intermolecular magnetic dipole coupling on the
+collision dynamics. It is shown that $^{15}$NH is a very suitable candidate for
+evaporative cooling experiments. The dominant trap-loss mechanism in the
+ultracold regime originates from the intermolecular dipolar coupling term. At
+higher energies and fields, intramolecular spin-spin coupling becomes
+increasingly important. Our qualitative results and conclusions are fairly
+independent of the exact form of the potential and of the size of the channel
+basis set.",1012.2814v1
+2010-12-16,The magneto-ionic medium in the Milky Way,"One way in which the Canadian Galactic Plane Survey has made an important
+contribution to the understanding of the Galactic interstellar medium is
+through its polarization surveys. Investigation of these data has enabled a big
+step in the study of magnetic fields in the interstellar medium and a range of
+discrete, extended, interstellar objects. In this review, I will discuss the
+role that the magnetic field plays in the interstellar medium, summarizing the
+ways in which magnetic field interacts with the other components in the Milky
+Way. Magnetic fields in the Galactic halo are discussed, and an outlook to a
+number of successor surveys of the polarized CGPS in the near future is given.",1012.3755v1
+2010-12-23,Scaling behavior of current- voltage characteristics of Y(1-x)CaxBa2Cu3O(7-δ) polycrystalline samples,"I-V characteristics of polycrystalline Y(1-x)CaxBa2Cu3O(7-{\delta}) samples
+(x=0.025 and 0.20) have been measured at different temperatures and magnetic
+fields in the range 0.1 T-6.9 T. The scaling behavior has been established for
+both samples at all magnetic fields. The dynamic exponent z displays some
+morphology dependence with higher value for small grain size sample
+Y0.8Ca0.2Ba2Cu3O(7-{\delta}). The static exponent {\nu} has been determined
+from {\rho} vs. T dependence at given magnetic field. The critical exponents
+are field independent with one only exception ({\nu} - for
+Y0.975Ca0.025Ba2Cu3O(7-{\delta}) sample). This is connected with the special
+interrelation between the vortex correlation length, {\xi}, and intervortex
+spacing {\alpha} ({\xi} \leq {\alpha}) at all magnetic fields above Tg for this
+sample and its better pinning.",1012.5267v1
+2011-01-06,Confined Magnetic Monopoles in Dense QCD,"Non-Abelian strings exist in the color-flavor locked phase of dense QCD. We
+show that kinks appearing in the world-sheet theory on these strings, in the
+form of the kink-antikink bound pairs, are the magnetic monopoles ---
+descendants of the 't Hooft-Polyakov monopoles surviving in such a special form
+in dense QCD. Our consideration is heavily based on analogies and inspiration
+coming from certain supersymmetric non-Abelian theories. This is the first ever
+analytic demonstration that objects unambiguously identifiable as the magnetic
+monopoles are ""native"" to non-Abelian Yang-Mills theories (albeit our analysis
+extends only to the phase of the monopole confinement and has nothing to say
+about their condensation). Technically our demonstration becomes possible due
+to the fact that low-energy dynamics of the non-Abelian strings in dense QCD is
+that of the orientational zero modes. It is described by an effective
+two-dimensional CP(2) model on the string world sheet. The kinks in this model
+representing confined magnetic monopoles are in a highly quantum regime.",1101.1120v1
+2011-01-30,Spin transport in magnetically ordered systems: effect of the lattice relaxation time,"Spin resistivity $R$ has been shown to result mainly from the scattering of
+itinerant spins with magnetic impurities and lattice spins. $R$ is proportional
+to the spin-spin correlation so that its behavior is very complicated near and
+at the magnetic phase transition of the lattice spins. For the time being there
+are many new experimental data on the spin resistivity going from
+semiconductors to superconductors. Depending on materials, various behaviors
+have been observed. There is however no theory so far which gives a unified
+mechanism for spin resistivity in magnetic materials. Recently, we have showed
+Monte Carlo results for different systems. We found that the spin resistivity
+is very different from one material to another. In this paper, we show for the
+first time how the dynamic relaxation time of the lattice spins affects the
+resistivity of itinerant spins observed in Monte Carlo simulation.",1101.5789v1
+2011-02-07,Vortex dynamics and irreversibility line in optimally doped SmFeAsO$_{0.8}$F$_{0.2}$ from ac susceptibility and magnetization measurements,"Ac susceptibility and static magnetization measurements were performed in the
+optimally doped SmFeAsO$_{0.8}$F$_{0.2}$ superconductor. The field -
+temperature phase diagram of the superconducting state was drawn and, in
+particular, the features of the flux line lattice derived. The dependence of
+the intra-grain depinning energy on the magnetic field intensity was derived in
+the thermally-activated flux creep framework, enlightening a typical 1/H
+dependence in the high-field regime. The intra-grain critical current density
+was extrapolated in the zero temperature and zero magnetic field limit, showing
+a remarkably high value $J_{c0}(0) \sim 2 \cdot 10^{7}$ A/cm$^{2}$, which
+demonstrates that this material is rather interesting for the potential future
+technological applications.",1102.1404v1
+2011-02-10,"Hour-glass magnetic spectrum in an insulating, hole-doped antiferromagnet","Superconductivity in layered copper-oxide compounds emerges when charge
+carriers are added to antiferromagnetically-ordered CuO2 layers. The carriers
+destroy the antiferromagnetic order, but strong spin fluctuations persist
+throughout the superconducting phase and are intimately linked to
+super-conductivity. Neutron scattering measurements of spin fluctuations in
+hole-doped copper oxides have revealed an unusual `hour-glass' feature in the
+momentum-resolved magnetic spectrum, present in a wide range of superconducting
+and non-superconducting materials. There is no widely-accepted explanation for
+this feature. One possibility is that it derives from a pattern of alternating
+spin and charge stripes, an idea supported by measurements on stripe-ordered
+La1.875Ba0.125CuO4. However, many copper oxides without stripe order also
+exhibit an hour-glass spectrum$. Here we report the observation of an
+hour-glass magnetic spectrum in a hole-doped antiferromagnet from outside the
+family of superconducting copper oxides. Our system has stripe correlations and
+is an insulator, which means its magnetic dynamics can conclusively be ascribed
+to stripes. The results provide compelling evidence that the hour-glass
+spectrum in the copper-oxide superconductors arises from fluctuating stripes.",1102.2205v1
+2011-02-13,Kagome Approximation for 3He on Husimi Lattice with Two- and Three-Site Exchange Interactions,"The Ising approximation of the Heisenberg model in a strong magnetic field,
+with two-, and three-spin exchange interactions are studied on a Husimi
+lattice. This model can be considered as an approximation of the third layer of
+3He absorbed on the surface of graphite (kagome lattice). Using dynamic
+approach we have found exact recursion relation for the partition function. For
+different values of exchange parameters and temperature the diagrams of
+magnetization are plotted and showed that magnetization properties of the model
+vary from ferromagnetic to antiferromagnetic depending from the value of model
+parameters. For antiferromagnetic case magnetization plateau at 1/3 of
+saturation field is obtained. Lyapunov exponent for recursion relation are
+considered and showed absents of bifurcation points in thermodynamic limit. The
+Yang-Lee zeros are analyzed in terms of neutral fixed points and showed that
+Yang-Lee zeros of the model are located on the arcs of the circle with the
+radius R=1.",1102.2607v1
+2011-02-17,Theory of flux cutting and flux transport at the critical current of a type-II superconducting cylindrical wire,"I introduce a critical-state theory incorporating both flux cutting and flux
+transport to calculate the magnetic-field and current-density distributions
+inside a type-II superconducting cylinder at its critical current in a
+longitudinal applied magnetic field. The theory is an extension of the elliptic
+critical-state model introduced by Romero-Salazar and Perez-Rodriguez. The
+vortex dynamics depend in detail upon two nonlinear effective resistivities for
+flux cutting (\rho_\parallel) and flux flow (\rho_\perp), and their ratio r =
+\rho_\parallel/\rho_\perp. When r < 1, the low relative efficiency of flux
+cutting in reducing the magnitude of the internal magnetic-flux density leads
+to a paramagnetic longitudinal magnetic moment. As a model for understanding
+the experimentally observed interrelationship between the critical currents for
+flux cutting and depinning, I calculate the forces on a helical vortex arc
+stretched between two pinning centers when the vortex is subjected to a current
+density of arbitrary angle \phi. Simultaneous initiation of flux cutting and
+flux transport occurs at the critical current density J_c(\phi) that makes the
+vortex arc unstable.",1102.3678v1
+2011-02-25,MHD turbulence-Star Formation Connection: from pc to kpc scales,"The transport of magnetic flux to outside of collapsing molecular clouds is a
+required step to allow the formation of stars. Although ambipolar diffusion is
+often regarded as a key mechanism for that, it has been recently argued that it
+may not be efficient enough. In this review, we discuss the role that MHD
+turbulence plays in the transport of magnetic flux in star forming flows. In
+particular, based on recent advances in the theory of fast magnetic
+reconnection in turbulent flows, we will show results of three-dimensional
+numerical simulations that indicate that the diffusion of magnetic field
+induced by turbulent reconnection can be a very efficient mechanism, especially
+in the early stages of cloud collapse and star formation. To conclude, we will
+also briefly discuss the turbulence-star formation connection and feedback in
+different astrophysical environments: from galactic to cluster of galaxy
+scales.",1102.5140v1
+2011-03-05,Dynamic and thermodynamic properties of the generalised diamond chain model for azurite,"The natural mineral azurite Cu3(CO3)2(OH)2 is an interesting spin-1/2 quantum
+antiferromagnet. Recently, a generalised diamond chain model has been
+established as a good description of the magnetic properties of azurite with
+parameters placing it in a highly frustrated parameter regime. Here we explore
+further properties of this model for azurite. First, we determine the inelastic
+neutron scattering spectrum in the absence of a magnetic field and find good
+agreement with experiments, thus lending further support to the model.
+Furthermore, we present numerical data for the magnetocaloric effect and
+predict that strong cooling should be observed during adiabatic
+(de)magnetisation of azurite in magnetic fields slightly above 30T. Finally,
+the presence of a dominant dimer interaction in azurite suggests the use of
+effective Hamiltonians for an effective low-energy description and we propose
+that such an approach may be useful to fully account for the three-dimensional
+coupling geometry.",1103.1080v1
+2011-03-18,Cotunneling theory of inelastic STM spin spectroscopy,"We propose cotunneling as the microscopic mechanism that makes possible
+inelastic electron spectroscopy of magnetic atoms in surfaces for a wide range
+of systems, including single magnetic adatoms, molecules and molecular stacks.
+We describe electronic transport between the scanning tip and the conducting
+surface through the magnetic system (MS) with a generalized Anderson model,
+without making use of effective spin models. Transport and spin dynamics are
+described with an effective cotunneling Hamiltonian in which the correlations
+in the magnetic system are calculated exactly and the coupling to the
+electrodes is included up to second order in the tip-MS and MS-substrate. In
+the adequate limit our approach is equivalent to the phenomenological Kondo
+exchange model that successfully describe the experiments . We apply our method
+to study in detail inelastic transport in two systems, stacks of Cobalt
+Phthalocyanines and a single Mn atom on Cu$_2$N. Our method accounts both, for
+the large contribution of the inelastic spin exchange events to the conductance
+and the observed conductance asymmetry.",1103.3676v1
+2011-03-22,Inductive determination of the optimum tunnel barrier thickness in magnetic tunnelling junction stacks for spin torque memory applications,"We use pulsed inductive microwave magnetometry to study the precessional
+magnetization dynamics of the free layer in CoFeB/MgO/CoFeB based magnetic
+tunnelling junction stacks with varying MgO barrier thickness. From the field
+dependence of the precession frequency we are able to derive the uniaxial
+anisotropy energy and the exchange coupling between the free and the pinned
+layer. Furthermore the field dependence of the effective damping parameter is
+derived. Below a certain threshold barrier thickness we observe an increased
+effective damping for antiparallel orientation of free and pinned layer which
+would inhibit reversible low current density spin torque magnetization
+reversal. Such inductive measurements, in combination with wafer probe station
+based magneto transport experiments, allow a fast determination of the optimum
+tunnel barrier thickness range for spin torque memory applications in a
+lithography free process.",1103.4248v1
+2011-03-30,Numerical simulations of high Lundquist number relativistic magnetic reconnection,"We present the results of two-dimensional and three-dimensional
+magnetohydrodynamical numerical simulations of relativistic magnetic
+reconnection, with particular emphasis on the dynamics of the plasma in a
+Petschek-type configuration with high Lundquist numbers, S\sim 10^5-10^8. The
+numerical scheme adopted, allowing for unprecedented accuracy for this type of
+calculations, is based on high order finite volume and discontinuous Galerkin
+methods as recently proposed by \citet{Dumbser2009}. The possibility of
+producing high Lorentz factors is discussed, showing that Lorentz factors close
+to \sim 4 can be produced for a plasma parameter \sigma_m=20. Moreover, we find
+that the Sweet-Parker layers are unstable, generating secondary magnetic
+islands, but only for S > S_c = 10^8, much larger than what is reported in the
+Newtonian regime. Finally, the effects of a mildly anisotropic Ohm law are
+considered in a configuration with a guide magnetic field. Such effects produce
+only slightly faster reconnection rates and Lorentz factors of about 1% larger
+with respect to the perfectly isotropic Ohm law.",1103.5924v2
+2011-03-30,Intermittent heating in the solar corona employing a 3D MHD model,"We investigate the spatial and temporal evolution of the heating of the
+corona of a cool star such as our Sun in a three-dimensional
+magneto-hydrodynamic (3D MHD) model. We solve the 3D MHD problem numerically in
+a box representing part of the (solar) corona. The energy balance includes
+Spitzer heat conduction along the magnetic field and optically thin radiative
+losses. The self-consistent heating mechanism is based on the braiding of
+magnetic field lines rooted in the convective photosphere. Magnetic stress
+induced by photospheric motions leads to currents in the atmosphere which heat
+the corona through Ohmic dissipation. While the horizontally averaged
+quantities, such as heating rate, temperature or density, are relatively
+constant in time, the simulated corona is highly variable and dynamic, on
+average reaching temperatures and densities as found in observations. The
+strongest heating per particle is found in the transition region from the
+chromosphere to the corona. The heating is concentrated in current sheets
+roughly aligned with the magnetic field and is transient in time and space.
+This supports the idea that numerous small heating events heat the corona,
+often referred to a nanoflares.",1103.6042v2
+2011-03-31,On the two-dimensionalization of quasistatic magnetohydrodynamic turbulence,"We analyze the anisotropy of turbulence in an electrically conducting fluid
+in the presence of a uniform magnetic field, for low magnetic Reynolds number,
+using the quasi-static approximation. In the linear limit, the kinetic energy
+of velocity components normal to the magnetic field decays faster than the
+kinetic energy of component along the magnetic field [Moffatt, JFM 28, 1967].
+However, numerous numerical studies predict a different behaviour, wherein the
+final state is characterized by dominant horizontal energy. We investigate the
+corresponding nonlinear phenomenon using Direct Numerical Simulations. The
+initial temporal evolution of the decaying flow indicates that the turbulence
+is very similar to the so-called ""two-and-a-half-dimensional"" flow [Montgomery
+& Turner, Phys. Fluids 25(2), 1982] and we offer an explanation for the
+dominance of horizontal kinetic energy.",1103.6207v1
+2011-04-26,A multi megawatt ring cyclotron to search for CP violation in the neutrino sector,"A new approach to search for CP violation in the neutrino sector [1,2] is
+proposed by the experiment called DAE{\delta}ALUS (Decay At rest Experiment for
+{\delta}cp At Laboratory for Underground Science). DAE{\delta}ALUS needs three
+sources of neutrino fluxes, each one located at 1.5, 8 and 20 km from the
+underground detector. Here we present the study for a Superconducting Ring
+Cyclotron able to accelerate the H2+ molecules and to deliver proton beam with
+maximum energy of 800 MeV and the required high power. The magnetic field
+produced by the proposed superconducting magnetic sector, simulated by the code
+TOSCA, the isochronous magnetic field, some preliminary feature on the beam
+dynamic and the magnetic forces acting on the coils are here presented.",1104.4985v1
+2011-05-09,Ground state structures of superparamagnetic 2D dusty plasma crystals,"Ground state structures of finite, cylindrically confined two-dimensional
+Yukawa systems composed of charged superparamagnetic dust grains in an external
+magnetic field are investigated numerically, using molecular dynamic
+simulations and lattice summation methods. The ground state configuration of
+the system is identified using, as an approximation, the experimentally
+obtained shape of the horizontal confinement potential in a classical single
+layer dusty plasma experiment with non-magnetic grains. Results are presented
+for the dependence of the number density and lattice parameters of the dust
+layer on (1) the ratio of the magnetic dipole-dipole force to electrostatic
+force between the grains and (2) the orientation of the grain magnetic moment
+with respect to the layer.",1105.1664v1
+2011-05-18,InMnO3 : a fully frustrated multiferroic,"InMnO$_3$ is a peculiar member of the hexagonal manganites h-RMnO$_3$ (where
+R is a rare earth metal element), showing crystalline, electronic and magnetic
+properties at variance with the other compounds of the family. We have studied
+high quality samples synthesized at high pressure and temperature by powder
+neutron diffraction. The position of the Mn ions is found to be close to the
+threshold $\it{x}=1/3$ where superexchange Mn-Mn interactions along the
+$\it{c}$ axis compensate. Magnetic long range order occurs below $T_{\rm N}$=
+120(2) K with a magnetic unit cell doubled along $\it{c}$, whereas short range
+two dimensional dynamical spin correlations are observed above $T_{\rm N}$. We
+propose that pseudo-dipolar interactions are responsible for the long period
+magnetic structure.",1105.3640v1
+2011-05-19,Charged Magnetic Brane Correlators and Twisted Virasoro Algebras,"Prior work using gauge/gravity duality has established the existence of a
+quantum critical point in the phase diagram of 3+1-dimensional gauge theories
+at finite charge density and background magnetic field. The critical theory,
+obtained by tuning the dimensionless charge density to magnetic field ratio,
+exhibits nontrivial scaling in its thermodynamic properties, and an associated
+nontrivial dynamical critical exponent. In the present work, we analytically
+compute low energy correlation functions in the background of the charged
+magnetic brane solution to 4+1-dimensional Einstein-Maxwell-Chern-Simons
+theory, which represents the bulk description of the critical point. Results
+are obtained for neutral scalar operators, the stress tensor, and the
+U(1)-current. The theory is found to exhibit a twisted Virasoro algebra,
+constructed from a linear combination of the original stress tensor and chiral
+U(1)-current. The effective speed of light in the IR is renormalized downward
+for one chirality, but not the other, by finite density, a behavior that is
+consistent with a Luttinger liquid description of fermions in the lowest Landau
+level. The results obtained here do not directly shed light on the mechanism
+driving the phase transition, and we comment on why this is so.",1105.3998v1
+2011-06-01,Remarkable paramagnetic features of Fermi-Dirac plasmas,"In this paper by using the relativistic magnetic susceptibility of a
+Fermi-Dirac (relativistically degenerate) plasma, quantum magnetohydrodynamics
+(QMHD) model is used to investigate the propagation of spin-induced (SI)
+magnetosonic nonlinear excitations in a normally and relativistically
+degenerate dense electron-ion plasma in the presence of the spin magnetization
+effect. Based on the conventional pseudopotential method the matching criterion
+for the evolution of SI solitary structures is evaluated. It is found that, the
+plasma mass density and strength of the magnetic field have significant effects
+on excitation and evolution of magnetosonic nonlinear structures in Fermi-Dirac
+plasmas. Only rarefactive SI magnetosonic solitary structures are found to
+excite in such plasmas. Furthermore, fundamental differences are shown to exist
+in magnetosonic soliton dynamics in the two distinct plasma degeneracy regimes,
+which is due to interplay between the negative spin paramagnetism pressure-like
+and positive relativistic degeneracy pressure of electrons. Current
+investigation can help better understand the electron spin effects on nonlinear
+wave propagations in strongly magnetized dense astrophysical objects such as
+white dwarfs and pulsar magnetospheres.",1106.0226v1
+2011-06-01,Instabilities in magnetized spherical Couette flow,"We report 3D numerical simulations of the flow of an electrically conducting
+fluid in a spherical shell when a magnetic field is applied. Different
+spherical Couette configurations are investigated, by varying the rotation
+ratio between the inner and the outer sphere, the geometry of the imposed
+field, and the magnetic boundary conditions on the inner sphere. Either a
+Stewartson layer or a Shercliff layer, accompanied by a radial jet, can be
+generated depending on the rotation speeds and the magnetic field strength, and
+various non-axisymmetric destabilizations of the flow are observed. We show
+that instabilities arising from the presence of boundaries present striking
+similarities with the magnetorotational instability (MRI). To this end, we
+compare our numerical results to experimental observations of the Maryland
+experiment, who claimed to observe MRI in a similar setup.",1106.0319v1
+2011-06-08,Relating field-induced shift in transition temperature to the kinetics of coexisting phases in magnetic shape memory alloys,"In a magnetic shape memory alloy system, we vary composition following
+phenomenological arguments to tune macroscopic properties. We achieve
+significantly higher shift in austenite to martensitic phase transition
+temperature with magnetic field. This enhancement is accompanied by significant
+broadening of the transition and by field-induced arrest of kinetics, both of
+which are related to the dynamics of the coexisting phases. This reveals
+hitherto unknown interrelationship between different length-scales. This may
+serve as an effective route for comprehensive understanding of similar
+multicomponent systems which show considerable variation in physical properties
+by minor change in microscopic parameters.",1106.1532v1
+2011-06-14,A time-dependent model for magnetic reconnection in the presence of a separator,"We present a model for separator reconnection due to an isolated reconnection
+process. Separator reconnection is a process which occurs in the neighbourhood
+of a distinguished field line (the separator) connecting two null points of a
+magnetic field. It is, for example, important for the dynamics of magnetic flux
+at the dayside magnetopause and in the solar corona. We find that, above a
+certain threshold, such a reconnection process generates new separators which
+leads to a complex system of magnetic flux tubes connecting regions of
+previously separated flux. Our findings are consistent with the findings of
+large numbers of separators in numerical simulations. We discuss how to measure
+and interpret the reconnection rate in a configuration with multiple
+separators.",1106.2672v3
+2011-06-17,Quantum magneto-optics of graphite with trigonal warping,"The optical conductivity of graphite in quantizing magnetic fields is
+studied. Both the dynamical conductivities, longitudinal as well as Hall's, are
+analytically evaluated. The conductivity peaks are explained in terms of
+electron transitions. We have shown that the trigonal warping in graphite can
+be considered within the perturbation theory at the strong magnetic field
+larger than 1 T approximately. The main optical transitions obey the selection
+rule with $\Delta n=1$ for the Landau number $n$, however the $\Delta n=2$
+transitions due to the trigonal warping with the small probability are also
+essential. The Kerr rotation and reflectivity in graphite in the quantizing
+magnetic fields are calculated. Parameters of the Slonczewski--Weiss--McClure
+model are used in the fit taking into account the previous dHvA measurements
+and correcting some of them for the case of the strong magnetic fields.",1106.3401v2
+2011-06-21,Velocity and Magnetic Transients Driven by the X2.2 White-Light Flare of 2011 February 15 in NOAA 11158,"The first X-class flare of the current solar cycle 24 occurred in Active
+Region NOAA 11158 during its central meridian passage on 2011 February 15. This
+two ribbon white-light flare was well observed by the Helioseismic and Magnetic
+Imager (HMI) on board Solar Dynamics Observatory (SDO). During the peak phase
+of the flare, we detected magnetic and Doppler velocity transients appearing
+near the umbral boundary of the main sunspot. These transients persisted for a
+few minutes and showed spatial and temporal correspondence with the flare
+kernels. The observed magnetic polarity at the transients' locations underwent
+sign reversal, together with large enhancement in Doppler velocities. We
+explain this observational phenomena using the HMI spectral data obtained
+before, during and after the flare. These changes were reflected in the maps of
+the AR in all the Stokes parameters. Association of the transient features with
+various signatures of the flare and the cause and effects of their appearance
+are also presented on the basis of present theoretical models.",1106.4166v3
+2011-06-22,Tunable Magnonic Frequency and Damping in [Co/Pd]8 Multilayers with Variable Co Layer Thickness,"We report the experimental observation of collective picosecond magnetization
+dynamics in [Co/Pd]8 multilayers with perpendicular magnetic anisotropy. The
+precession frequency shows large and systematic variation from about 5 GHz to
+about 90 GHz with the decrease in the Co layer thickness from 1.0 nm to 0.22 nm
+due to the linear increase in the perpendicular magnetic anisotropy. The
+damping coefficient 'alpha' is found to be inversely proportional to the Co
+layer thickness and a linear relation between the perpendicular magnetic
+anisotropy and 'alpha' is established. We discuss the possible reasons behind
+the enhanced damping as the d-d hybridization at the interface and spin
+pumping. These observations are significant for the applications of these
+materials in spintronics and magnonic crystals.",1106.4491v1
+2011-06-23,The scale-free texture of the fast solar wind,"The higher order statistics of magnetic field magnitude fluctuations in the
+fast quiet solar wind are quantified systematically scale-by-scale for the
+first time. We find a single global non-Gaussian scale free behaviour from
+minutes to over 5 hours. This spans the signature of an inertial range of
+magnetohydrodynamic (MHD) turbulence and a ~1/f range in magnetic field
+components. This global scaling in field magnitude fluctuations is an intrinsic
+component of the underlying texture of the solar wind and it suggests a single
+stochastic process for magnetic field magnitude fluctuations operating across
+the full range of MHD time scales supported by the solar wind. Intriguingly,
+the magnetic field and velocity components show scale dependent dynamic
+alignment outside of the inertial range.",1106.4705v2
+2011-07-02,Energy dissipation and switching delay in spin-transfer torque switching of nanomagnets with low-saturation magnetization in the presence of thermal fluctuations,"A common ploy to reduce the switching current and energy dissipation in
+spin-transfer-torque driven magnetization switching of shape-anisotropic
+single-domain nanomagnets is to employ magnets with low saturation
+magnetization $M_s$ and high shape-anisotropy. The high shape-anisotropy
+compensates for low $M_s$ to keep the static switching error rate constant.
+However, this ploy increases the switching delay, its variance in the presence
+of thermal noise, and the dynamic switching error rate. Using the stochastic
+Landau-Lifshitz-Gilbert equation with a random torque emulating thermal noise,
+we show that pumping some excess spin-polarized current into the nanomagnet
+during switching will keep the mean switching delay and its variance constant
+as we reduce $M_s$, while still reducing the energy dissipation significantly.",1107.0387v2
+2011-07-04,Influence of randomness and retardation on the FMR-linewidth,"The theory predicts that the spin-wave lifetime $\tau_L$ and the linewidth of
+ferromagnetic resonance $\Delta B$ can be governed by random fields and spatial
+memory. To that aim the effective field around which the magnetic moments
+perform a precession is superimposed by a stochastic time dependent magnetic
+field with finite correlation time. The magnetization dynamics is altered by
+inclusion of a spatial memory effect monitoring a non-local interaction of size
+$\xi$. The underlying Landau-Lifshitz-Gilbert equation (LLG) is modified
+accordingly. The stochastic LLG is equivalent to a Fokker-Planck equation which
+enables to calculate the mean values of the magnetization vector. Within the
+spin-wave approximation we present an analytical solution for the excitation
+energy and its damping. The lifetime and the linewidth are analyzed depending
+on the strength of the random field $D$ and its correlation time $\tau_c$ as
+well as the retardation strength $\Gamma_0$ and the size $\xi$. Whereas
+$\tau_L$ decreases with increasing $D$, retardation strength $\Gamma_0$ and
+$\tau_c$, the lifetime is enhanced for growing width $\xi$ of the spatial
+retardation kernel. In the same manner we calculate the experimentally
+measurable linewidth $\Delta B$ is increased strongly when the correlation time
+$\tau_c$ ranges in the nanosecond interval.",1107.0638v1
+2011-07-08,Time-resolved study of the magnetic field effects on electroluminescence in tri-(8-hydroxyquinoline)- aluminum based organic light emitting devices,"We investigated the magnetic field effects (MFEs) in organic light-emitting
+diodes (OLEDs) through the transient electroluminescence (EL) method. The
+time-resolved MFEs on the emission were obtained for the first time, which
+would be a useful method to clarify the underlying mechanisms of the MFEs. The
+fluorescent dye doped tri-(8-hydroxyquinoline)-aluminum (Alq3) based OLEDs were
+fabricated. Then, the transient EL was measured both with and without a
+magnetic field. To explore the time-resolved MFEs on the emission of the
+device, the excitons population dynamics in the device have been analyzed by a
+kinetic model. Our results suggest that both the intersystem crossing between
+the singlet and triplet electron-hole pairs and the triplet-triplet
+annihilation perturbed by the external magnetic field cause the time-resolved
+MFEs.",1107.1550v1
+2011-07-17,Spin current induced magnetization oscillations in a paramagnetic disc,"When electron spins are injected uniformly into a paramagnetic disc, they can
+precess along the demagnetizing field induced by the resulting magnetic moment.
+Normally this precession damps out by virtue of the spin relaxation which is
+present in paramagnetic materials. We propose a new mechanism to excite a
+steady-state form of this dynamics by injecting a constant spin current into
+this paramagnetic disc. We show that the rotating magnetic field generated by
+the eddy currents provide a torque which makes this possible. Unlike the
+ferromagnetic equivalent, the spin-torque-oscillator, the oscillation frequency
+is fixed and determined by the dimensions and intrinsic parameters of the
+paramagnet. The system possesses an intrinsic threshold for spin injection
+which needs to be overcome before steady-state precession is possible. The
+additional application of a magnetic field lowers this threshold. We discuss
+the feasibility of this effect in modern materials. Transient analysis using
+pump-probe techniques should give insight in the physical processes which
+accompany this effect.",1107.3288v1
+2011-07-27,Debye-Hückel theory for spin ice at low temperature,"At low temperatures, spin ice is populated by a finite density of magnetic
+monopoles-pointlike topological defects with a mutual magnetic Coulomb
+interaction. We discuss the properties of the resulting magnetic Coulomb liquid
+in the framework of Debye H\""{u}ckel theory, for which we provide a detailed
+context-specific account. We discuss both thermodynamical and dynamical
+signatures, and compare Debye H\""{u}ckel theory to experiment as well as
+numerics, including data for specific heat and AC susceptibility. We also
+evaluate the entropic Coulomb interaction which is present in addition to the
+magnetic one and show that it is quantitatively unimportant in the current
+compounds. Finally, we address the role of bound monopole anti-monopole pairs
+and derive an expression for the monopole mobility.",1107.5482v2
+2011-08-18,Relativistic quantum dynamics of a charged particle in cosmic string spacetime in the presence of magnetic field and scalar potential,"In this paper we analyze the relativistic quantum motion of charged spin-0
+and spin-1/2 particles in the presence of a uniform magnetic field and scalar
+potentials in the cosmic string spacetime. In order to develop this analysis,
+we assume that the magnetic field is parallel to the string and the scalar
+potentials present a cylindrical symmetry with their center on the string. Two
+distinct configurations for the scalar potential, $S(r)$, are considered: $(i)$
+the potential proportional to the inverse of the polar distance, i.e.,
+$S\propto1/r$, and $(ii)$ the potential proportional to this distance, i.e.,
+$S\propto r$. The energy spectra are explicitly computed for different physical
+situations and presented their dependences on the magnetic field strength and
+scalar coupling constants.",1108.3786v2
+2011-09-09,On the 2D behavior of 3D MHD with a strong guiding field,"The Magneto-hydrodynamic (MHD) equations in the presence of a guiding
+magnetic field are investigated by means of direct numerical simulations. The
+basis of the investigation consists of 9 runs forced at the small scales. The
+results demonstrate that for a large enough uniform magnetic field the large
+scale flow behaves as a two dimensional (non-MHD) fluid exhibiting an inverse
+cascade of energy in the direction perpendicular to the magnetic field, while
+the small scales behave like a three dimensional MHD-fluid cascading the energy
+forwards. The amplitude of the inverse cascade is sensitive to the magnetic
+field amplitude, the domain size, the forcing mechanism, and the forcing scale.
+All these dependencies are demonstrated by the varying parameters of
+simulations. Furthermore, in the case that the system is forced anisotropically
+in the small parallel scales an inverse cascade in the parallel direction is
+observed that is feeding the 2D modes.",1109.2039v1
+2011-09-12,Microfluidic propulsion by the metachronal beating of magnetic artificial cilia: a numerical analysis,"In this work we study the effect of metachronal waves on the flow created by
+magnetically-driven plate-like artificial cilia in microchannels using
+numerical simulations. The simulations are performed using a coupled
+magneto-mechanical solid-fluid computational model that captures the physical
+interactions between the fluid flow, ciliary deformation and applied magnetic
+field. When a rotating magnetic field is applied to super-paramagnetic
+artificial cilia, they mimic the asymmetric motion of natural cilia, consisting
+of an effective and recovery stroke. When a phase-difference is prescribed
+between neighbouring cilia, metachronal waves develop. Due to the discrete
+nature of the cilia, the metachronal waves change direction when the phase
+difference becomes sufficiently large, resulting in antiplectic as well as
+symplectic metachrony. We show that the fluid flow created by the artificial
+cilia is significantly enhanced in the presence of metachronal waves and that
+the fluid flow becomes unidirectional. Antiplectic metachrony is observed to
+lead to a considerable enhancement in flow compared to symplectic metachrony,
+when the cilia spacing is small. Obstruction of flow in the direction of the
+effective stroke for the case of symplectic metachrony was found to be the key
+mechanism that governs this effect.",1109.2547v1
+2011-09-13,Thickness-dependent magnetic structure of ultrathin Fe/Ir(001) films: from spin-spiral states towards ferromagnetic order,"We present a detailed study of the ground-state magnetic structure of
+ultrathin Fe films on the surface of fcc Ir(001). We use the spin-cluster
+expansion technique in combination with the relativistic disordered local
+moment scheme to obtain parameters of spin models and then determine the
+favored magnetic structure of the system by means of a mean field approach and
+atomistic spin dynamics simulations. For the case of a single monolayer of Fe
+we find that layer relaxations very strongly influence the ground-state spin
+configurations, whereas Dzyaloshinskii-Moriya (DM) interactions and biquadratic
+couplings also have remarkable effects. To characterize the latter effect we
+introduce and analyze spin collinearity maps of the system. While for two
+monolayers of Fe we find a single-q spin spiral as ground state due to DM
+interactions, for the case of four monolayers the system shows a noncollinear
+spin structure with nonzero net magnetization. These findings are consistent
+with experimental measurements indicating ferromagnetic order in films of four
+monolayers and thicker.",1109.2721v1
+2011-09-14,Antiferromagnetic coupling across silicon regulated by tunneling currents,"We report on the enhancement of antiferromagnetic coupling in epitaxial
+Fe/Si/Fe structures by voltage-driven spin-polarized tunneling currents. Using
+the ballistic electron magnetic microscopy we established that the hot-electron
+collector current reflects magnetization alignment and the magnetocurrent
+exceeds 200% at room temperature. The saturation magnetic field for collector
+current corresponding to parallel alignment of magnetizations rises up with the
+tunneling current, thus demonstrating stabilization of the antiparallel
+alignment and increasing antiferromagnetic coupling. We connect the enhancement
+of antiferromagnetic coupling with local dynamic spin torques mediated by
+tunneling electrons",1109.3106v1
+2011-09-16,An MHD Model of the December 13 2006 Eruptive Flare,"We present a 3D MHD simulation that qualitatively models the coronal mag-
+netic field evolution associated with the eruptive flare that occurred on
+December 13, 2006 in the emerging {\delta}-sunspot region NOAA 10930 observed
+by the Hinode satellite. The simulation is set up where we drive the emergence
+of an east-west oriented magnetic flux rope at the lower boundary into a
+pre-existing coronal field constructed from the SOHO/MDI full-disk magnetogram
+at 20:51:01 UT on December 12, 2006. The resulting coronal flux rope embedded
+in the ambi- ent coronal magnetic field first settles into a stage of
+quasi-static rise, and then undergoes a dynamic eruption, with the leading edge
+of the flux rope cavity accel- erating to a steady speed of about 830 km/s. The
+pre-eruption coronal magnetic field shows morphology that is in qualitative
+agreement with that seen in the Hinode soft X-ray observation in both the
+magnetic connectivity as well as the development of an inverse-S shaped X-ray
+sigmoid. We examine the properties of the erupting flux rope and the morphology
+of the post-reconnection loops, and compare them with the observations.",1109.3734v1
+2011-09-21,Itinerant and local-moment magnetism in strongly correlated electron systems,"Detailed analysis of the magnetic properties of the Hubbard model within
+dynamical mean-field theory (DMFT) is presented. Using a RPA-like decoupling of
+two-particle propagators we derive a universal form for susceptibilities, which
+captures essential aspects of localized and itinerant pictures. This expression
+is shown to be quantitatively valid whenever long-range coherence of
+particle-hole excitations can be neglected, as is the case in large parts of
+the phase diagram where antiferromag- netism is dominant. The applicability of
+an interpretation in terms of the two archetypical pictures of magnetism is
+investigated for the Hubbard model on a body-centered cubic lattice with
+additional next-nearest neighbor hopping t'. For large values of the Coulomb
+interaction, local-moment mag- netism is found to be dominant, while for weakly
+interacting band electrons itinerant quasiparticle magnetism prevails. In the
+intermediate regime and for finite t' an re-entrant behavior is discovered,
+where antiferromagnetism only exists in a finite temperature interval.",1109.4509v2
+2011-09-23,Ubiquitous rotating network magnetic fields and EUV cyclones in the quiet Sun,"We present the {\it Solar Dynamics Observatory} (SDO) Atmospheric Imaging
+Assembly (AIA) observations of EUV cyclones in the quiet Sun. These cyclones
+are rooted in the Rotating Network magnetic Fields (RNFs). Such cyclones can
+last several to more than ten hours, and, at the later phase, they are found to
+be associated with EUV brightenings (microflares) and even EUV waves. SDO
+Helioseismic and Magnetic Imager (HMI) observations show an ubiquitous presence
+of the RNFs. Using HMI line-of-sight magnetograms on 2010 July 8, we find 388
+RNFs in an area of 800$\times$980 square arcseconds near the disk center where
+no active region is present. The sense of rotation shows a weak hemisphere
+preference. The unsigned magnetic flux of the RNFs is about 4.0$\times10^{21}$
+Mx, or 78% of the total network flux. These observational phenomena at small
+scale reported in this letter are consistent with those at large scale in
+active regions. The ubiquitous RNFs and EUV cyclones over the quiet Sun may
+suggest an effective way to heat the corona.",1109.5003v1
+2011-09-23,Chiral Magnetic Effect and evolution of electromagnetic field,"The energy dependence of observable two particle correlator in search for the
+local strong parity violation in Au+Au collisions is estimated within a simple
+phenomenological model. The model reproduces available RHIC data but at LHC
+predicts that the Chiral Magnetic effect (CME) will be about 20 times weaker
+than at RHIC, contrary to the first LHC measurements. In the lower energy range
+this effect should vanish sharply at energy somewhere above the top SPS one
+with agreement with the preliminary results of the Beam Energy Scan program. To
+elucidate CME background effects a transport HSD model including magnetic field
+evolution is put forward and electromagnetic dynamics at the RHIC energy is
+investigated. It is observed that the electromagnetic field included into the
+hadronic model does not influence on observables due to mutual compensation of
+effects of electric and magnetic fields.",1109.5015v3
+2011-10-10,Magnetic order and frustrated dynamics in Li(Ni0.8Co0.1Mn0.1)O2: a study by μ+SR and SQUID magnetometry,"Recently, the mixed transition metal oxides of the form Li(Ni1-y-zCoyMnz)O2,
+have become the center of attention as promising candidates for novel battery
+material. These materials have also revealed very interesting magnetic
+properties due to the alternate stacking of planes of metal oxides on a 2D
+triangular lattice and the Li-layers. The title compound,
+Li(Ni0.8Co0.1Mn0.1)O2, has been investigated by both magnetometry and
+measurements and {\mu}+SR. We find the evolution of localized magnetic moments
+with decreasing temperature below 70 K. The magnetic ground state (T = 2 K) is,
+however, shown to be a frustrated system in 3D, followed by a transition into a
+possible 2D spinglass above 22 K. With further increasing temperature the
+compound show the presence of remaining correlations with increasing effective
+dimensionality all the way up to the ferrimagnetic transition at TC = 70 K.",1110.2071v1
+2011-10-10,Magnetic order and transitions in the spin-web compound Cu3TeO6,"The spin-web compound Cu3TeO6, belongs to an intriguing group of materials
+where magnetism is governed by 3d9 copper Cu2+ ions. This compound has been
+sparsely experimentally studied and we here present the first investigation of
+its local magnetic properties using muon-spin relaxation/rotation ({\mu}+SR).
+Our results show a clear long-range 3D magnetic order below TN as indicated by
+clear zero-field (ZF) muon-precessions. At TN = 61.7 K a very sharp transition
+is observed in the weak transverse-field (wTF) as well as ZF data. Contrary to
+suggestions by susceptibility measurements and inelastic neutron scattering, we
+find no evidence for either static or dynamic (on the time-scale of {\mu}+SR)
+spin-correlations above TN.",1110.2073v1
+2011-10-12,Spin supercurrent in Josephson contacts with noncollinear ferromagnets,"We present a theoretical study of the Josephson coupling of two s-wave
+superconductors which are connected through a diffusive contact consisting of
+noncollinear ferromagnetic domains. First, we consider a contact with two
+domains with magnetization vectors misoriented by an angle $\theta$. Using the
+quantum circuit theory, we find that in addition to the charge supercurrent, a
+spin supercurrent, which is even in $\phi$ and odd in $\theta$, with a spin
+polarization normal to the magnetization vectors flows between the domains.
+Furthermore, with asymmetric insulating barriers at the interfaces of the
+junction, the system may experience an antiferromagnetic-ferromagnetic phase
+transition for $\phi=\pi$. Secondly, we discuss the spin supercurrent in an
+extended magnetic texture with multiple domainwalls. We find the
+position-dependent spin supercurrent. The magnitude of the spin supercurrent
+strongly depends on the phase difference between the superconductors and the
+number of domain walls. Our results demonstrate the possibility to couple the
+superconducting phase to the magnetization dynamics.",1110.2568v1
+2011-10-19,Current-induced switching in transport through anisotropic magnetic molecules,"Anisotropic single-molecule magnets may be thought of as molecular switches,
+with possible applications to molecular spintronics. In this paper, we consider
+current-induced switching in single-molecule junctions containing an
+anisotropic magnetic molecule. We assume that the carriers interact with the
+magnetic molecule through the exchange interaction and focus on the regime of
+high currents in which the molecular spin dynamics is slow compared to the time
+which the electrons spend on the molecule. In this limit, the molecular spin
+obeys a non-equilibrium Langevin equation which takes the form of a generalized
+Landau-Lifshitz-Gilbert equation and which we derive microscopically by means
+of a non-equilibrium Born-Oppenheimer approximation. We exploit this Langevin
+equation to identify the relevant switching mechanisms and to derive the
+current-induced switching rates. As a byproduct, we also derive S-matrix
+expressions for the various torques entering into the Landau-Lifshitz-Gilbert
+equation which generalize previous expressions in the literature to
+non-equilibrium situations.",1110.4270v2
+2011-11-08,Analysis of the Collective Behavior of a 10 by 10 Array of Fe3O4 Dots in a Large Micromagnetic Simulation,"We report a full (3D) micromagnetic simulation of a set of 100 ferrite
+(Fe$_3$O$_4$) cylindrical dots, arranged in a 10 by 10 square (planar) array of
+side 3.27 $\mu$m, excited by an external in-plane magnetic field. The resulting
+power spectrum of magnetic excitations and the dynamical magnetization field at
+the resulting resonance modes were investigated. The absorption spectrum
+deviates considerably from that of a single particle reference simulation,
+presenting a mode-shifting and splitting effect. We found an inversion symmetry
+through the center of the array, in the sense that each particle and its
+inversion counterpart share approximately the same magnetization mode behavior.
+Magnonic designs aiming at synchronous or coherent tunings of spin-wave
+excitations at given spatially separated points within a regular square array
+may benefit from the new effects here described.",1111.1866v1
+2011-11-18,Charge and Spin Transport in Magnetic Tunnel Junctions: Microscopic Theory,"We study the charge and spin currents passing through a magnetic tunnel
+junction (MTJ) on the basis of a tight-binding model. The currents are
+evaluated perturbatively with respect to the tunnel Hamiltonian. The charge
+current has the form $A[\bm M_1(t)\times\dot{\bm M}_1(t)]\cdot\bm M_2+B\dot{\bm
+M}_1(t)\cdot\bm M_2$, where $\bm M_1(t)$ and $\bm M_2$ denote the directions of
+the magnetization in the free layer and fixed layer, respectively. The constant
+$A$ vanishes when one or both layers are insulators, {while the constant $B$
+disappears when both layers are insulators or the same ferromagnets.} The first
+term in the expression for charge current represents dissipation driven by the
+effective electric field induced by the dynamic magnetization. In addition,
+from an investigation of the spin current, we obtain the microscopic expression
+for the enhanced Gilbert damping constant $\varDelta \alpha$. We show that
+$\varDelta\alpha$ is proportional to the tunnel conductance and depends on the
+bias voltage.",1111.4295v2
+2011-12-01,Compressible hydromagnetic nonlinearities in the predecoupling plasma,"The adiabatic inhomogeneities of the scalar curvature lead to a compressible
+flow affecting the dynamics of the hydromagnetic nonlinearities. The influence
+of the plasma on the evolution of a putative magnetic field is explored with
+the aim of obtaining an effective description valid for sufficiently large
+scales. The bulk velocity of the plasma, computed in the framework of the
+LambdaCDM scenario, feeds back into the evolution of the magnetic power spectra
+leading to a (nonlocal) master equation valid in Fourier space and similar to
+the ones discussed in the context of wave turbulence. Conversely, in physical
+space, the magnetic power spectra obey a Schroedinger-like equation whose
+effective potential depends on the large-scale curvature perturbations.
+Explicit solutions are presented both in physical space and in Fourier space.
+It is argued that curvature inhomogeneities, compatible with the WMAP 7yr data,
+shift to lower wavenumbers the magnetic diffusivity scale.",1112.0191v1
+2011-12-01,Cosmological Simulations using GCMHD+,"Radio observations of galaxy clusters show that the intra cluster medium is
+permeated by \mu G magnetic fields. The origin and evolution of these
+cosmological magnetic fields is currently not well understood and so their
+impact on the dynamics of structure formation is not known. Numerical
+simulations are required to gain a greater understanding and produce
+predictions for the next generation of radio telescopes. We present the
+galactic chemodynamics smoothed particle magnetohydrodynamic (SPMHD) code
+(GCMHD+), which is an MHD implementation for the cosmological smoothed particle
+hydrodynamic code GCD+. The results of 1, 2 and 3 dimensional tests are
+presented and the performance of the code is shown relative to the ATHENA grid
+code. GCMHD+ shows good agreement with the reference solutions produced by
+ATHENA. The code is then used to simulate the formation of a galaxy cluster
+with a simple primordial magnetic field embedded in the gas. A homogeneous seed
+field of 10^-11 G is amplified by a factor of 10^3 during the formation of the
+cluster. The results show good agreement with the profiles found in other
+magnetic cluster simulations of similar resolution.",1112.0340v1
+2011-12-30,Ultrafast Magneto-Acoustics in Nickel Films,"We report about the existence of magneto-acoustic pulses propagating in a
+200-nm-thick ferromagnetic nickel film excited with 120 fs laser pulses. They
+result from the coupling between the magnetization of the ferromagnetic film
+and the longitudinal acoustic waves associated to the propagation of the
+lattice deformation induced by the femtosecond laser pulses. The
+magneto-acoustic pulses are detected from both the front and back sides of the
+film, using the time-resolved magneto-optical Kerr technique, measuring both
+the time dependent rotation and ellipticity. We show that the propagating
+acoustic pulse couples efficiently to the magnetization and is strong enough to
+induce a precession of the magnetization. It is due to a transient change of
+the crystalline anisotropy associated to the lattice deformation. It is shown
+that the results can be interpreted by combining the concepts of acoustic pulse
+propagation and ultrafast magnetization dynamics.",1201.0170v1
+2012-01-06,Magnetic field decay with Hall drift in neutron star crusts,"The dynamics of magnetic field decay with Hall drift is investigated.
+Assuming that axisymmetric magnetic fields are located in a spherical crust
+with uniform conductivity and electron number density, long-term evolution is
+calculated up to Ohmic dissipation. The nonlinear coupling between poloidal and
+toroidal components is explored in terms of their energies and helicity.
+Nonlinear oscillation by the drift in strongly magnetized regimes is clear only
+around the equipartition between two components. Significant energy is
+transferred to the poloidal component when the toroidal component initially
+dominates. However, the reverse is not true. Once the toroidal field is less
+dominant, it quickly decouples due to a larger damping rate. The polar field at
+the surface is highly distorted from the initial dipole during the Hall drift
+timescale, but returns to the initial dipole in a longer dissipation timescale,
+since it is the least damped one.",1201.1346v1
+2012-02-03,Magnetic topology of a naked sunspot: Is it really naked?,"The high spatial, temporal and spectral resolution achieved by Hinode
+instruments give much better understanding of the behavior of some elusive
+solar features, such as pores and naked sunspots. Their fast evolution and, in
+some cases, their small sizes have made their study difficult. The moving
+magnetic features, despite being more dynamic structures, have been studied
+during the last 40 years. They have been always associated with sunspots,
+especially with the penumbra. However, a recent observation of a naked sunspot
+(one with no penumbra) has shown MMF activity. The authors of this reported
+observation expressed their reservations about the explanation given to the
+bipolar MMF activity as an extension of the penumbral filaments into the moat.
+How can this type of MMFs exist when a penumbra does not? In this paper, we
+study the full magnetic and (horizontal) velocity topology of the same naked
+sunspot, showing how the existence of a magnetic field topology similar to that
+observed in sunspots can explain these MMFs, even when the intensity map of the
+naked sunspot does not show a penumbra.",1202.0591v1
+2012-02-16,Two-dimensional incommensurate magnetic fluctuations in Sr$_2$(Ru$_{0.99}$Ti$_{0.01}$)O$_4$,"We investigate the imaginary part of the wave vector dependent dynamic spin
+susceptibility in Sr$_2$(Ru$_{0.99}$Ti$_{0.01}$)O$_4$ as a function of
+temperature using neutron scattering. At T=5 K, two-dimensional incommensurate
+(IC) magnetic fluctuations are clearly observed around
+$\mathbf{Q}_\text{c}=(0.3,0.3,L)$ up to approximately 60 meV energy transfer.
+We find that the IC excitations disperse to ridges around the $(\pi,\pi)$
+point. Below 50 K, the energy and temperature dependent excitations are well
+described by the phenomenological response function for a Fermi liquid system
+with a characteristic energy of 4.0(1) meV. Although the wave vector dependence
+of the IC magnetic fluctuations in Sr$_2$(Ru$_{0.99}$Ti$_{0.01}$)O$_4$ is
+similar to that in the Fermi liquid state of the parent compound,
+Sr$_2$RuO$_4$, the magnetic fluctuations are clearly suppressed by the
+Ti-doping.",1202.3654v1
+2012-02-20,Semiclassical Dynamics and Magnetic Weyl Calculus,"Weyl quantization and related semiclassical techniques can be used to study
+conduction properties of crystalline solids subjected to slowly-varying,
+external electromagnetic fields. The case where the external magnetic field is
+constant, is not covered by existing theory as proofs involving usual Weyl
+calculus break down. This is the regime of the so-called quantum Hall effect
+where quantization of transverse conductance is observed. To rigorously derive
+semiclassical equations of motion, one needs to systematically develop a
+magnetic Weyl calculus which contains a semiclassical parameter.
+  Mathematically, the operators involved in the analysis are magnetic
+pseudodifferential operators, a topic which by itself is of interest for the
+mathematics and mathematical physics community alike. Hence, we will devote two
+additional chapters to further understanding of properties of those operators.",1202.4668v2
+2012-02-23,Multiscale methods for Levitron Problems: Theory and Applications,"In this paper, we describe a multiscale model based on magneto-static traps
+of neutral atoms or ion traps. The idea is to levitate a magnetic spinning top
+in the air repelled by a base magnet.
+  For such a problem, we have to deal with different time and spatial scales
+and we propose a novel splitting method for solving the levitron problem.
+  We focus on the multiscale problem, which we obtain by coupling the kinetic T
+and the potential U part of our equation. The kinetic and potential parts, can
+be seen as generators of flows.
+  The main problem is based on the accurate computation of the Hamiltonian
+equation and we propose a novel higher order splitting scheme to obtain stable
+states near the relative equilibrium. To improve the splitting scheme we apply
+a novel method so called MPE (multiproduct expansion method), which include
+higher order extrapolation schemes.
+  In numerical studies, we discuss the stability near this relative equilibrium
+with our improved time-integrators. Best results are obtained by iterative and
+extrapolated Verlet schemes in comparison to higher order explicit Runge-Kutta
+schemes. Experiments are applied to a magnetic top in an axisymmetric magnetic
+field (i.e. the Levitron) and we discuss the future applications to quantum
+computations.",1202.5169v1
+2012-03-16,Turbulence and magnetic field amplification from spiral SASI modes in core-collapse supernovae,"The stationary accretion shock instability (SASI) plays a central role in
+modern simulations of the explosion phase of core-collapse supernovae (CCSNe).
+It may be key to realizing neutrino powered explosions, and possibly links
+birth properties of pulsars (e.g., kick, spin, and magnetic field) to supernova
+dynamics. Using high-resolution magnetohydrodynamic simulations, we study the
+development of turbulence, and subsequent amplification of magnetic fields in a
+simplified model of the post-bounce core-collapse supernova environment.
+Turbulence develops from secondary instabilities induced by the SASI. Our
+simulations suggest that the development of turbulence plays an important role
+for the subsequent evolution of the SASI. The turbulence also acts to amplify
+weak magnetic fields via a small-scale dynamo.",1203.3748v1
+2012-04-05,Dynamical magnetic anisotropy and quantum phase transitions in a vibrating spin-1 molecular junction,"We study the electronic transport through a spin-1 molecule in which
+mechanical stretching produces a magnetic anisotropy. In this type of device, a
+vibron mode along the stretching axis will couple naturally to the molecular
+spin. We consider a single molecular vibrational mode and find that the
+electron-vibron interaction induces an effective correction to the magnetic
+anisotropy that shifts the ground state of the device toward a non-Fermi liquid
+phase. A transition into a Fermi liquid phase could then be achieved, by means
+of mechanical stretching, passing through an underscreened spin-1 Kondo regime.
+We present numerical renormalization group results for the differential
+conductance, the spectral density, and the magnetic susceptibility across the
+transition.",1204.1108v2
+2012-04-10,Observation of spin-glass behavior in nickel adsorbed few layer graphene,"Nickel-adsorbed graphene was prepared by first synthesizing graphite oxide
+(GO) by modified Hummers' method and then reducing a solution containing both
+GO and $Ni^{2+}$. EDX analysis showed 31 atomic percent nickel was present.
+Magnetization measurements under both dc and ac magnetic fields were carried
+out in the temperature range 2 K to 300 K. The zero field cooled and field
+cooled magnetization data showed a pronounced irreversibility at a temperature
+around 20 K. The analysis of the ac susceptibility data were carried out by
+both Vogel-Fulcher as well as power law. From dynamic scaling analysis the
+microscopic flipping time $\tau_{0}\sim 10^{-13} s$ and critical exponent
+$z\nu=5.9\pm0.1$ were found, indicating presence of conventional spin glass in
+the system. The spin glass transition temperature was estimated as 19.5 K.
+  Decay of thermoremanent magnetization (TRM) was explained by stretched
+exponential function with a value of the exponent as 0.6 .
+  From the results it is concluded that nickel adsorbed graphene behaves like a
+spin-glass.",1204.2123v2
+2012-04-18,Electronic properties and magnetism of iron at the Earth's inner core conditions,"We employ state-of-the-art ab initio simulations within the dynamical
+mean-field theory to study three likely phases of iron (hexogonal close-packed,
+hcp, face centered cubic, fcc, and body centered cubic, bcc) at the Earth's
+core conditions. We demonstrate that the correction to the electronic free
+energy due to correlations can be significant for the relative stability of the
+phases. The strongest effect is observed in bcc Fe, which shows a non-Fermi
+liquid behaviour, and where a Curie-Weiss behaviour of the uniform
+susceptbility hints at a local magnetic moment still existing at 5800 K and 300
+GPa. We predict that all three structures have sufficiently high magnetic
+susceptibility to stabilize the geodynamo.",1204.3954v2
+2012-04-19,Plasma Pressure Driven Asymmetric Supernovae and Highly Collimated Gamma-Ray Bursts,"During the process of collapse of a massive star, a cavity is generated
+between the central iron core and an outer stellar envelope. The dynamics of
+this cavity, filled with plasma and magnetic field of the rapidly rotating
+proto-magnetar's magnetosphere, is believed to be very relevant in
+understanding supernovae and gamma-ray bursts. The interactions of the
+pressurized conducting plasma and the magnetic fields are described by a set of
+magnetohydrodynamic (MHD) equations with poloidal and toroidal plasma flows not
+aligned with magnetic fields. A sequence of MHD equilibria in response to the
+increasing plasma pressure in the cavity, by continuous filling from the
+rotating magnetosphere, is solved to account for asymmetric supernovae, highly
+collimated gamma-ray burst jets, and also active galactic nucleus plasma torus.
+It is shown that the magnetosphere of the central compact star is likely the
+central engine of supernova and gamma-ray burst by feeding them plasma,
+magnetic energy, and rotational energy.",1204.4360v2
+2012-04-27,Prediction of polaron-like vortices and dissociation depinning transition in magnetic superconductors: The example of ErNi2B2C,"In borocarbide ErNi$_2$B$_2$C the phase transition to the commensurate spin
+density wave at 2.3 K leaves 1/20 part of Ising-like Er spins practically free.
+Vortices polarize these spins nonuniformly and repolarize them when moving. At
+a low spin relaxation rate and at low bias currents vortices carrying magnetic
+polarization clouds become polaron-like and their velocities are determined by
+the effective drag coefficient which is significantly bigger than the
+Bardeen-Stephen (BS) one. As current increases, at a critical current $J_c$
+vortices release polarization clouds and the velocity as well as the voltage in
+the I-V characteristics jump to values corresponding to the BS drag
+coefficient. The nonuniform components of the magnetic field and magnetization
+drop as velocity increases resulting in weaker polarization and discontinuous
+dynamic dissociation depinning transition. As current decreases, on the way
+back, vortices are retrapped by polarization clouds at the current $J_r<J_c$.",1204.6348v2
+2012-05-13,Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions,"We demonstrate excitation of ferromagnetic resonance in CoFeB/MgO/CoFeB
+magnetic tunnel junctions (MTJs) by the combined action of voltage-controlled
+magnetic anisotropy (VCMA) and spin transfer torque (ST). Our measurements
+reveal that GHz-frequency VCMA torque and ST in low-resistance MTJs have
+similar magnitudes, and thus that both torques are equally important for
+understanding high-frequency voltage-driven magnetization dynamics in MTJs. As
+an example, we show that VCMA can increase the sensitivity of an MTJ-based
+microwave signal detector to the sensitivity level of semiconductor Schottky
+diodes.",1205.2835v2
+2012-05-22,Unraveling Orbital Correlations via Magnetic Resonant Inelastic X-ray Scattering,"Although orbital degrees of freedom are a factor of fundamental importance in
+strongly correlated transition metal compounds, orbital correlations and
+dynamics remain very difficult to access, in particular by neutron scattering.
+Via a direct calculation of scattering amplitudes we show that instead magnetic
+resonant inelastic x-ray scattering (RIXS) does reveal orbital correlations. In
+contrast to neutron scattering, the intensity of the magnetic excitations in
+RIXS depends very sensitively on both the symmetry of the orbitals that spins
+occupy, and on photon polarizations. We show in detail how this effect allows
+magnetic RIXS to distinguish between alternating orbital ordered and
+ferro-orbital (or orbital liquid) states.",1205.4940v3
+2012-05-22,Quantum magneto-optics of graphite family,"The optical conductivity of graphene, bilayer graphene, and graphite in
+quantizing magnetic fields is studied. Both dynamical conductivities,
+longitudinal and Hall's, are analytically evaluated. The conductivity peaks are
+explained in terms of electron transitions. We have shown that trigonal warping
+can be considered within the perturbation theory for strong magnetic fields
+larger than 1 T and in the semiclassical approach for weak fields when the
+Fermi energy is much larger than the cyclotron frequency. The main optical
+transitions obey the selection rule with \Deltan = 1 for the Landau number n,
+however the \Deltan = 2 transitions due to the trigonal warping are also
+possible. The Faraday/Kerr rotation and light transmission/reflection in the
+quantizing magnetic fields are calculated. Parameters of the
+Slonczewski-Weiss-McClure model are used in the fit taking into account the
+previous dHvA measurements and correcting some of them for the case of strong
+magnetic fields.",1205.4952v1
+2012-06-13,Scanning superconducting quantum interference device on a tip for magnetic imaging of nanoscale phenomena,"We describe a new type of scanning probe microscope based on a
+superconducting quantum interference device (SQUID) that resides on the apex of
+a sharp tip. The SQUID-on-tip is glued to a quartz tuning fork which allows
+scanning at a tip-sample separation of a few nm. The magnetic flux sensitivity
+of the SQUID is 1.8 {\mu}_0/Hz^{1/2} and the spatial resolution is about 200
+nm, which can be further improved. This combination of high sensitivity,
+spatial resolution, bandwidth, and the very close proximity to the sample
+provides a powerful tool for study of dynamic magnetic phenomena on the
+nanoscale. The potential of the SQUID-on-tip microscope is demonstrated by
+imaging of the vortex lattice and of the local AC magnetic response in
+superconductors.",1206.2853v1
+2012-07-04,Negative-μ regime in the ac magnetic response of superconductor nanoshells,"The time-dependent Ginzburg-Landau formalism is applied to analyze the vortex
+states and vortex dynamics in superconducting spherical nanoshells, subjected
+to mutually perpendicular strong dc and weak ac magnetic fields. We demonstrate
+that nonuniformity of the shell thickness can dramatically affect the ac
+magnetic response of a 3D array of superconducting nanoshells. Remarkably, this
+response is strongly influenced not only by the relevant geometric and material
+parameters and the ac-field frequency but also by the magnitude of the applied
+dc field: by changing this field the real part of the effective ac magnetic
+permeability can be tuned from positive values significantly larger than one
+down to negative values.",1207.0971v1
+2012-07-05,Out-of-phase oscillation between superfluid and thermal components for a trapped Bose condensate under oscillatory excitation,"The vortex nucleation and the emergence of quantum turbulence induced by
+oscillating magnetic fields, introduced by Henn E A L, et al. 2009 (Phys. Rev.
+A 79, 043619) and Henn E A L, et al. 2009 (Phys. Rev. Lett. 103, 045301), left
+a few open questions concerning the basic mechanisms causing those interesting
+phenomena. Here, we report the experimental observation of the slosh dynamics
+of a magnetically trapped $^{87}$Rb Bose-Einstein condensate (BEC) under the
+influence of a time-varying magnetic field. We observed a clear relative
+displacement in between the condensed and the thermal fraction center-of-mass.
+We have identified this relative counter move as an out-of-phase oscillation
+mode, which is able to produce ripples on the condensed/thermal fractions
+interface. The out-of-phase mode can be included as a possible mechanism
+involved in the vortex nucleation and further evolution when excited by time
+dependent magnetic fields.",1207.1146v2
+2012-07-26,On the structure of MHD shock waves in a viscous gas,"The exact solutions for MHD shock waves in an ideal gas are obtained taking
+into consideration only the viscosity of the gas. In view of an axial magnetic
+field, the analytical expressions for the particle velocity, temperature,
+pressure and change-in-entropy within the shock transition region are obtained.
+The flow variables are numerical analysed to explore the influence of static
+magnetic field, shock strength, specific heat ratio, initial pressure, initial
+density and coefficient of viscosity on the flow variables. The findings
+confirm that thickness of MHD shock front increases with increase in the
+viscosity of the gas and the change in thickness is more noticeable for large
+values of the strength of magnetic field. The results provided a clear picture
+of whether and how the viscosity of gas and the magnetic field affect the
+thickness of shock front.",1207.6166v4
+2012-08-11,Contribution of the magnetic resonance to the third harmonic generation from a fishnet metamaterial,"We investigate experimentally and theoretically the third harmonic generated
+by a double-layer fishnet metamaterial. To unambiguously disclose most notably
+the influence of the magnetic resonance, the generated third harmonic was
+measured as a function of the angle of incidence. It is shown experimentally
+and numerically that when the magnetic resonance is excited by pump beam, the
+angular dependence of the third harmonic signal has a local maximum at an
+incidence angle of {\theta} \simeq 20{\deg}. This maximum is shown to be a
+fingerprint of the antisymmetric distribution of currents in the gold layers.
+An analytical model based on the nonlinear dynamics of the electrons inside the
+gold shows excellent agreement with experimental and numerical results. This
+clearly indicates the difference in the third harmonic angular pattern at
+electric and magnetic resonances of the metamaterial.",1208.2370v2
+2012-09-13,Structural and magnetic properties of the new cobaltate series (BaSr)4-xLa2xCo4O15,"We report the structural and magnetic properties of a new class of cobaltates
+with the chemical formula (BaSr)4-xLa2xCo4O15 (x = 0, 0.5 and 1). These
+compounds crystallize in a hexagonal structure in which cobalt ions are
+distributed among two distinct crystallographic sites with different oxygen
+coordination. Three Co-O tetrahedra and one octahedron are linked by shared
+oxygen atoms to form Co4O15 clusters, which are packed together into a
+honeycomb-like network. Partial substitution of Sr and/or Ba atoms by La allows
+one to adjust the degree of Co valence mixing, but all compositions remain
+subject to a random distribution of charge. Magnetic susceptibility together
+with neutron scattering measurements reveal that all studied specimens are
+characterized by competing ferro- and antiferro-magnetic exchange interactions
+that give rise to a three dimensional Heisenberg spin-glass state. Neutron
+spectroscopy shows a clear trend of slowing down of spin-dynamics upon
+increasing La concentration, suggesting a reduction in charge randomness in the
+doped samples.",1209.2986v1
+2012-09-18,Nonrelativistic parallel shocks in unmagnetized and weakly magnetized plasmas,"We present results of 2D3V particle-in-cell simulations of non-relativistic
+plasma collisions with absent or parallel large-scale magnetic field for
+parameters applicable to the conditions at young supernova remnants. We study
+the collision of plasma slabs of different density, leading to two different
+shocks and a contact discontinuity. Electron dynamics play an important role in
+the development of the system. While non-relativistic shocks in both
+unmagnetized and magnetized plasmas can be mediated by Weibel-type
+instabilities, the efficiency of shock-formation processes is higher when a
+large-scale magnetic field is present. The electron distributions downstream of
+the forward and reverse shocks are generally isotropic, whereas that is not
+always the case for the ions. We do not see any significant evidence of
+pre-acceleration, neither in the electron population nor in the ion
+distribution.",1209.3938v1
+2012-10-04,Multiscale Gyrokinetics for Rotating Tokamak Plasmas II: Reduced Models for Electron Dynamics,"In this paper, we extend the multiscale approach developed in [Abel et. al.,
+Rep. Prog. Phys., submitted] by exploiting the scale separation between ions
+and the electrons. The gyrokinetic equation is expanded in powers of the
+electron to ion mass ratio, which provides a rigorous method for deriving the
+reduced electron model. We prove that ion-scale electromagnetic turbulence
+cannot change the magnetic topology, and argue that to lowest order the
+magnetic field lies on fluctuating flux surfaces. These flux surfaces are used
+to construct magnetic coordinates, and in these coordinates a closed system of
+equations for the electron response to ion-scale turbulence is derived. All
+fast electron timescales have been eliminated from these equations. We also use
+these magnetic surfaces to construct transport equations for electrons and for
+electron heat in terms of the reduced electron model.",1210.1417v3
+2012-10-05,MRI: a possible mechanism for funnel flows?,"The magnetorotational instability (MRI) has been suggested to have an
+important role on the dynamics of accretion disks. We investigate MRI as an
+alternative way for guiding the plasma from the disk to the funnel flow at the
+disk-magnetosphere boundary of classical T Tauri stars (CTTSs) by considering
+the diamagnetic effects. We solve the magnetohydrodynamic equations by
+including the effect of both the magnetic field gradient and the perpendicular
+(to the field) velocity gradient produced by the magnetization current at the
+disk-magnetosphere boundary for the first time. Diamagnetic current modified
+MRI produces a non-propagating mode which may lift the plasma from the disk
+towards the vertical magnetic field lines. Our model also shows that the
+diamagnetic effects play an important role in triggering the MRI. The
+instability becomes more powerful with the inclusion of the gradient in the
+magnetic field and the perpendicular velocity.",1210.1733v1
+2012-10-17,The power-law spectra of energetic particles during multi-island magnetic reconnection,"Power-law distributions are a near universal feature of energetic particle
+spectra in the heliosphere. Anomalous Cosmic Rays (ACRs), super-Alfv\'enic ions
+in the solar wind and the hardest energetic electron spectra in flares all have
+energy fluxes with power-laws that depend on energy $E$ approximately as
+$E^{-1.5}$. We present a new model of particle acceleration in systems with a
+bath of merging magnetic islands that self-consistently describes the
+development of velocity-space anisotropy parallel and perpendicular to the
+local magnetic field and includes the self-consistent feedback of pressure
+anisotropy on the merging dynamics. By including pitch-angle scattering we
+obtain an equation for the omni-directional particle distribution $f(v,t)$ that
+is solved in closed form to reveal $v^{-5}$ (corresponding to an energy flux
+varying as $E^{-1.5}$) as a near-universal solution as long as the
+characteristic acceleration time is short compared with the characteristic loss
+time. In such a state the total energy in the energetic particles reaches
+parity with the remaining magnetic free energy. More generally, the resulting
+transport equation can serve as the basis for calculating the distribution of
+energetic particles resulting from reconnection in large-scale inhomogeneous
+systems.",1210.4830v1
+2012-10-21,Reshaping and Capturing Leidenfrost drops with a magnet,"Liquid oxygen, which is paramagnetic, also undergoes Leidenfrost effect at
+room temperature. In this article, we first study the deformation of oxygen
+drops in a magnetic field and show that it can be described via an effective
+capillary length, which includes the magnetic force. In a second part, we
+describe how these ultra-mobile drops passing above a magnet significantly slow
+down and can even be trapped. The critical velocity below which a drop is
+captured is determined from the deformation induced by the field.",1210.5718v3
+2012-10-29,Thermally-Assisted Spin-Transfer Torque Magnetization Reversal of Uniaxial Nanomagnets in Energy Space,"The asymptotic behavior of switching time as a function of current for a
+uniaxial macrospin under the effects of both spin-torque and thermal noise is
+explored analytically by focusing on its diffusive energy space dynamics. The
+scaling dependence ($I\rightarrow 0$, $<\tau\propto\exp(-\xi(1-I)^2)$) is shown
+to confirm recent literature results. The analysis shows the mean switching
+time to be functionally independent of the angle between the spin current and
+magnet's uniaxial axes. These results have important implications for modeling
+the energetics of thermally assisted magnetization reversal of spin transfer
+magnetic random access memory bit cells.",1210.7682v2
+2012-10-30,Quantum Tunneling in Half-Integer-Spin Kagome-Lattice Langasites,"Employing the muon spin relaxation technique we evidence temperature
+independent magnetic fluctuations persisting down to the lowest temperatures in
+the samarium-based ($J=5/2$) kagome-lattice Langasite. A detailed
+bulk-magnetization characterization and comparison to the neodymium-based
+($J=9/2$) compound allow us to assign the persistent spin dynamics to a quantum
+tunneling process. This is facilitated by pairwise anisotropic magnetic
+interactions, leading to a universal scaling of the muon relaxation. Our study
+reveals a remarkable analogy between weakly interacting half-integer-spin
+rare-earth magnets and molecular nanomagnets.",1210.8187v1
+2012-11-18,Simulation of relativistically colliding laser-generated electron flows,"The plasma dynamics resulting from the simultaneous impact, of two equal,
+ultra-intense laser pulses, in two spatially separated spots, onto a dense
+target is studied via particle-in-cell (PIC) simulations. The simulations show
+that electrons accelerated to relativistic speeds, cross the target and exit at
+its rear surface. Most energetic electrons are bound to the rear surface by the
+ambipolar electric field and expand along it. Their current is closed by a
+return current in the target, and this current configuration generates strong
+surface magnetic fields. The two electron sheaths collide at the midplane
+between the laser impact points. The magnetic repulsion between the
+counter-streaming electron beams separates them along the surface normal
+direction, before they can thermalize through other beam instabilities. This
+magnetic repulsion is also the driving mechanism for the beam-Weibel
+(filamentation) instability, which is thought to be responsible for magnetic
+field growth close to the internal shocks of gamma-ray burst (GRB) jets. The
+relative strength of this repulsion compared to the competing electrostatic
+interactions, which is evidenced by the simulations, suggests that the
+filamentation instability can be examined in an experimental setting.",1211.4195v1
+2012-12-21,Superconductivity and magnetic fluctuations in electron-doped cobaltate superconductors,"We study the interplay between superconductivity and antiferromagnetic spin
+fluctuations in electron-doped cobaltate Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O based
+on the kinetic energy driven superconductivity mechanism. We show that the
+superconducting state is governed by both charge carrier pairing and
+quasiparticle coherent, and displays a common dome-shaped phase diagram in
+agreement with experimental results. By calculating the dynamical spin
+structure factor, we theoretically find that the magnetic excitation shows a
+commensurate resonance peak, which locates at antiferromagnetic wave vector $Q
+(\frac{2\pi}{3},\frac{2\pi}{\sqrt{3}})$ for a broad range of low energies, then
+evolves outward into six incommensurate magnetic scattering peaks with
+increasing energy. Such commensurate-incommensurate spin resonance excitation
+should be measured by the inelastic neutron scattering technique (INS). Our
+present results strongly suggest that magnetic resonance can indeed be one of
+the fundamental features in doped Mott insulators.",1212.5367v1
+2012-12-31,Ubiquitous Solar Eruptions Driven by Magnetized Vortex Tubes,"The solar surface is covered by high-speed jets transporting mass and energy
+into the solar corona and feeding the solar wind. The most prominent of these
+jets have been known as spicules. However, the mechanism initiating these
+eruptions events is still unknown. Using realistic numerical simulations we
+find that small-scale eruptions are produced by ubiquitous magnetized vortex
+tubes generated by the Sun's turbulent convection in subsurface layers. The
+swirling vortex tubes (resembling tornadoes) penetrate into the solar
+atmosphere, capture and stretch background magnetic field, and push surrounding
+material up, generating quasiperiodic shocks. Our simulations reveal a
+complicated high-speed flow patterns, and thermodynamic and magnetic structure
+in the erupting vortex tubes. We found that the eruptions are initiated in the
+subsurface layers and are driven by the high-pressure gradients in the
+subphotosphere and photosphere, and by the Lorentz force in the higher
+atmosphere layers.",1301.0018v1
+2013-01-02,Plasmoid Instability in High-Lundquist-Number Magnetic Reconnection,"Our understanding of magnetic reconnection in resistive magnetohydrodynamics
+has gone through a fundamental change in recent years. The conventional wisdom
+is that magnetic reconnection mediated by resistivity is slow in laminar high
+Lundquist ($S$) plasmas, constrained by the scaling of the reconnection rate
+predicted by Sweet-Parker theory. However, recent studies have shown that when
+$S$ exceeds a critical value $\sim10^{4}$, the Sweet-Parker current sheet is
+unstable to a super-Alfv\'enic plasmoid instability, with a linear growth rate
+that scales as $S^{1/4}$. In the fully developed statistical steady state of
+two-dimensional resistive magnetohydrodynamic simulations, the normalized
+average reconnection rate is approximately 0.01, nearly independent of $S$, and
+the distribution function $f(\psi)$ of plasmoid magnetic flux $\psi$ follows a
+power law $f(\psi)\sim\psi^{-1}$. When Hall effects are included, the plasmoid
+instability may trigger onset of Hall reconnection even when the conventional
+criterion for onset is not satisfied. The rich variety of possible reconnection
+dynamics is organized in the framework of a phase diagram.",1301.0331v2
+2013-01-29,A brief report on statistical study of net electric current in solar active regions with longitudinal fields of opposite polarity,"Dynamic processes occurring in solar active regions are dominated by the
+solar magnetic field. As of now, observations using a solar magnetograph have
+supplied us with the vector components of a solar photospheric magnetic field.
+The two transverse components of a photospheric magnetic field allow us to
+compute the amount of electric current. We found that the electric current in
+areas with positive (negative) polarity due to the longitudinal magnetic field
+have both positive and negative signs in an active region, however, the net
+current is found to be an order-of-magnitude less than the mean absolute
+magnitude and has a preferred sign. In particular, we have statistically found
+that there is a systematic net electric current from areas with negative
+(positive) polarity to areas with positive (negative) polarity in solar active
+regions in the northern (southern) hemisphere, but during the solar minimum
+this tendency is reversed over time at some latitudes. The result indicates
+that there is weak net electric current in areas of solar active regions with
+opposite polarity, thus providing further details about the hemispheric
+helicity rule found in a series of previous studies.",1301.6812v2
+2013-02-07,Identification of intermittent multi-fractal turbulence in fully kinetic simulations of magnetic reconnection,"Recent fully nonlinear, kinetic three-dimensional simulations of magnetic
+reconnection [Daughton et al. 2011] evolve structures and exhibit dynamics on
+multiple scales, in a manner reminiscent of turbulence. These simulations of
+reconnection are among the first to be performed at sufficient spatio-temporal
+resolution to allow formal quantitative analysis of statistical scaling which
+we present here. We find that the magnetic field fluctuations generated by
+reconnection are anisotropic, have non-trivial spatial correlation and exhibit
+the hallmarks of finite range fluid turbulence; they have non-Gaussian
+distributions, exhibit Extended Self-Similarity in their scaling and are
+spatially multifractal. Furthermore, we find that the field J.E is also
+multifractal, so that magnetic energy is converted to plasma kinetic energy in
+a manner that is spatially intermittent. This suggests that dissipation in this
+sense in collisionless reconnection on kinetic scales has an analogue in
+fluid-like turbulent phenomenology, in that it proceeds via multifractal
+structures generated by an intermittent cascade.",1302.1749v1
+2013-02-18,Early stages of magnetization relaxation in superconductors,"Magnetic flux dynamics in type-II superconductors is studied within the model
+of a viscous nonlinear diffusion of vortices for various sample geometries. We
+find that time dependence of magnetic moment relaxation after the field is
+switched off can be accurately approximated by $m(t)\propto
+1-\sqrt{t/\tilde\tau}$ in the narrow initial time interval and by $m(t)\propto
+(1+t/\tau)^{-1}$ at later times before the flux creep sets in. The
+characteristic times $\tilde\tau$ and $\tau$ are proportional to the viscous
+drag coefficient $\eta$. Quantitative agreement with available experimental
+data is obtained for both conventional and high-temperature superconductors
+with $\eta$ exceeding by many orders of magnitude the Bardeen-Stephen
+coefficient for free vortices. Huge enhancement of the drag, as well as its
+exponential temperature dependence, indicates a strong influence of pinning
+centers on the flux diffusion. Notwithstanding complexity of the vortex motion
+in the presence of pinning and thermal agitation, we argue that the initial
+relaxation of magnetization can still be considered as a viscous flux flow with
+an effective drag coefficient.",1302.4312v2
+2013-02-19,Magnetoelectric susceptibility tensor of multiferroic TbMnO3 with cycloidal antiferromagnetic structure in external field,"Magnetoelectric, dielectric and magnetic susceptibility tensors of
+multiferroic TbMnO3 with cycloidal antiferromagnetic structure in external
+electric and magnetic fields have been investigated with taking into account
+dynamics of spin, electro-dipole and acoustic subsystems. All components of
+tensors depend on values of external electric and magnetic fields. The
+possibility of control of electrodynamic properties of multiferroic TbMnO3 with
+cycloidal antiferromagnetic structure by external electric and magnetic fields
+has been shown. The resonant interaction of spin, electro-dipole,
+electromagnetic and acoustic waves in such material is observed.",1302.4515v1
+2013-03-18,Vortex Lattices and Crystalline Geometries,"We consider $AdS_2 \times R^2$ solutions supported by a magnetic field, such
+as those which arise in the near-horizon limit of magnetically charged $AdS_4$
+Reissner-Nordstrom black branes. In the presence of an electrically charged
+scalar field, such magnetic solutions can be unstable to spontaneous formation
+of a vortex lattice. We solve the coupled partial differential equations which
+govern the charged scalar, gauge field, and metric degrees of freedom to lowest
+non-trivial order in an expansion around the critical point, and discuss the
+corrections to the free energy and thermodynamic functions arising from the
+formation of the lattice. We describe how such solutions can also be
+interpreted, via S-duality, as characterizing infrared crystalline phases of
+conformal field theories doped by a chemical potential, but in zero magnetic
+field; the doped conformal field theories are dual to geometries that exhibit
+dynamical scaling and hyperscaling violation.",1303.4390v2
+2013-03-29,Pseudo-magnetic fields in graphene in excess of 300T: theoretical framework,"The experimental demonstration of pseudo-magnetic fields exceeding 300 T in
+graphene [2] nanobubbles represents considerable challenge for the present
+theory connecting the emergence of gauge fields due to strain in the underlying
+lattice. Here we propose a theoretical framework within which the magnitude of
+the pseudo-magnetic fields can be computed more accurately. The basic feature
+of this framework is that the carriers in graphene are considered with their
+three dimensional wave function which is then gradually constrained to the
+graphene surface. In the process, a geometrically induced gauge field emerges
+in the two dimensional equation for the surface dynamics. The computation of
+the magnetic field associated with this gauge potential reproduces the measured
+field strength.",1303.7373v1
+2013-04-21,Superconducting flux-flow type ultra-low-noise magnetic sensors - An alternative to dc-SQUIDs,"A superconducting magnetometers based on the magnetic field dependence of the
+Eck step voltage in long Josephson tunnel junctions (LJTJs) is demonstrated.
+The field to be measured is applied perpendicular to a continuous
+superconducting pickup loop. Wherever the loop has a narrow constriction, the
+density of the flux-restoring circulating currents will become relatively high
+and will locally create a magnetic field large enough to bring a biased LJTJ in
+the flux-flow state, i.e., at a finite voltage proportional to the field
+strength. This method allows the realization of a novel family of robust and
+general-purpose superconducting devices which, despite their simplicity,
+function as ultra-low-noise, wide-band and high-dynamics magnetometers. The
+performances of low-T$_c$ sensor prototypes, among which a highly linear
+voltage responsivity and a magnetic spectral density $S_B^{1/2}<
+3\,fT/Hz^{1/2}$, promise to be competitive with those of the best
+superconducting quantum interference devices.",1304.5761v2
+2013-05-02,Magnetohydrodynamic equilibria in barotropic stars,"Although barotropic matter does not constitute a realistic model for magnetic
+stars, it would be interesting to confirm a recent conjecture that states that
+magnetized stars with a barotropic equation of state would be dynamically
+unstable (Reisenegger 2009). In this work we construct a set of barotropic
+equilibria, which can eventually be tested using a stability criterion. A
+general description of the ideal MHD equations governing these equilibria is
+summarized, allowing for both poloidal and toroidal magnetic field components.
+A new finite-difference numerical code is developed in order to solve the
+so-called Grad-Shafranov equation describing the equilibrium of these
+configurations, and some properties of the equilibria obtained are briefly
+discussed.",1305.0592v1
+2013-05-27,Time-resolved magnetic sensing with electronic spins in diamond,"Quantum probes can measure time-varying fields with high sensitivity and
+spatial resolution, enabling the study of biological, material, and physical
+phenomena at the nanometer scale. In particular, nitrogen-vacancy centers in
+diamond have recently emerged as promising sensors of magnetic and electric
+fields. Although coherent control techniques have measured the amplitude of
+constant or oscillating fields, these techniques are not suitable for measuring
+time-varying fields with unknown dynamics. Here we introduce a coherent
+acquisition method to accurately reconstruct the temporal profile of
+time-varying fields using Walsh sequences. These decoupling sequences act as
+digital filters that efficiently extract spectral coefficients while
+suppressing decoherence, thus providing improved sensitivity over existing
+strategies. We experimentally reconstruct the magnetic field radiated by a
+physical model of a neuron using a single electronic spin in diamond and
+discuss practical applications. These results will be useful to implement
+time-resolved magnetic sensing with quantum probes at the nanometer scale.",1305.6082v2
+2013-06-04,Filament eruption on 2010 October 21 from three viewpoints,"A filament eruption on 2010 October 21 observed from three different
+viewpoints by the Solar Terrestrial Relations Observatory (STEREO) and the
+Solar Dynamic Observatory (SDO) is analyzed with invoking also data from the
+Solar and Heliospheric Observatory (SOHO) and the Kanzelhoehe Solar
+Observatory. The position of the filament just before the eruption at the
+central meridian not far from the center of the solar disk was favorable for
+photospheric magnetic field measurements in the area below the filament.
+Because of this, we were able to calculate with high precision the distribution
+of the coronal potential magnetic field near the filament. We found that the
+filament began to erupt when it approached the height in the corona where the
+magnetic field decay index was greater than one. We determined also that during
+the initial stage of the eruption the filament moved along the magnetic neutral
+surface.",1306.0679v1
+2013-06-10,Using Coronal Cells to Infer the Magnetic Field Structure and Chirality of Filament Channels,"Coronal cells are visible at temperatures of ~ 1.2 MK in Fe XII coronal
+images obtained from the Solar Dynamics Observatory (SDO) and Solar Terrestrial
+Relations Observatory (STEREO) spacecraft. We show that near a filament
+channel, the plumelike tails of these cells bend horizontally in opposite
+directions on the two sides of the channel like fibrils in the chromosphere.
+Because the cells are rooted in magnetic flux concentrations of majority
+polarity, these observations can be used with photospheric magnetograms to
+infer the direction of the horizontal field in filament channels and the
+chirality of the associated magnetic field. This method is similar to the
+procedure for inferring the direction of the magnetic field and the chirality
+of the fibril pattern in filament channels from H-alpha observations. However,
+the coronal cell observations are easier to use and provide clear inferences of
+the horizontal field direction for heights up to ~ 50 Mm into the corona.",1306.2273v3
+2013-06-17,Magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet Cs$_2$CuBr$_4$,"We report on high-field electron spin resonance (ESR) studies of magnetic
+excitations in the spin-1/2 triangular-lattice antiferromagnet Cs$_2$CuBr$_4$.
+Frequency-field diagrams of ESR excitations are measured for different
+orientations of magnetic fields up to 25 T. We show that the substantial
+zero-field energy gap, $\Delta\approx9.5$ K, observed in the low-temperature
+excitation spectrum of Cs$_2$CuBr$_4$ [Zvyagin $et~al.$, Phys. Rev. Lett. 112,
+077206 (2014)], is present well above $T_N$. Noticeably, the transition into
+the long-range magnetically ordered phase does not significantly affect the
+size of the gap, suggesting that even below $T_N$ the high-energy spin dynamics
+in Cs$_2$CuBr$_4$ is determined by short-range-order spin correlations. The
+experimental data are compared with results of model spin-wave-theory
+calculations for spin-1/2 triangle-lattice antiferromagnet.",1306.3887v3
+2013-06-18,Magnetic Dynamics of a Multiferroic with an Antiferromagnetic Layer,"Shape effects in magnetic particles are widely studied, because of the
+ability of the shape and the size to control the parameters of a sample during
+its production. Experiments with nano-sized samples show that the shape can
+affect also the properties of antiferromagnetic (AFM) materials. However, the
+theoretical interpretation of these effects is under discussion. We propose a
+model to study the shape-induced effects in AFM particles at the AFM resonance
+frequency. The Lagrange function method is used to calculate the spectrum of
+resonance oscillations of the AFM vector in a synthetic multiferroic
+(piezoelectric + antiferromagnet). The influence of the specimen shape on the
+AFM resonance frequency in the presence of an external magnetic field is
+studied. Conditions for a resonance under the action of an external force or
+for a parametric resonance to arise in the magnetic subsystem are considered.",1306.4300v1
+2013-06-21,Spinodal decomposition of a binary magnetic fluid confined to a surface,"In our previous work [J. Chem. Phys. \textbf{136}, 024502 (2012)], we
+reported a demixing phase transition of a two-dimensional, binary Heisenberg
+fluid mixture driven by the ferromagnetic interactions of the magnetic species.
+Here, we present a theoretical study for the \textit{time-dependent} coarsening
+occuring within the two-phase region in the density-concentration plane, also
+known as spinodal decomposition. Our investigations are based on Dynamical
+Density Functional Theory (DDFT). The particles in the mixture are modelled as
+Gaussian soft spheres on a two-dimensional surface, where one component carries
+a classical spin of Heisenberg type. To investigate the two-phase region, we
+first present a linear stability analysis with respect to small, harmonic
+density perturbations. Second, to capture non-linear effects, we calculate
+time-dependent structure factors by combining DDFT with Percus' test particle
+method. For the growth of the average domain size $l$ during spinodal
+decomposition with time $t$, we observe a power-law behavior $l\propto
+t^{\delta_\alpha}$ with $\delta_m\simeq 0.333$ for the magnetic species and
+$\delta_n\simeq 0.323$ for the non-magnetic species.",1306.5171v2
+2013-07-03,Asymmetric Magnetic Domain-Wall Motion by the Dzyaloshinskii-Moriya Interaction,"We demonstrate here that ultrathin ferromagnetic Pt/Co/Pt films with
+perpendicular magnetic anisotropy exhibit a sizeable Dzyaloshinskii-Moriya
+interaction (DMI) effect. Such a DMI effect modifies the domain-wall (DW)
+energy density and consequently, results in an asymmetric DW expansion driven
+by an out-of-plane magnetic field under an in-plane magnetic field bias. From
+an analysis of the asymmetry, the DMI effect is estimated to be strong enough
+for the DW to remain in the N\'eel-type configuration in contrast to the
+general expectations of these materials. Our findings emphasize the critical
+role of the DMI effect on the DW dynamics as the underlying physics of the
+asymmetries that are often observed in spin-transfer-related phenomena.",1307.0984v1
+2013-07-12,Intergalactic magnetic fields in Stephan's Quintet,"We present results of the VLA radio continuum total power and polarised
+intensity observations of Stephan's Quintet at 1.43 and 4.86 GHz along with
+complementary 4.85 and 8.35 GHz Effelsberg observations. Our study shows a
+large envelope of radio emission encompassing all the member galaxies and hence
+a large volume of intergalac- tic matter. Infall of the galaxy NGC 7318B
+produces a ridge of intergalactic, polarised emission, for which the magnetic
+field strength was estimated as 11.0 \pm 2.2 {\mu}G, with an ordered component
+of 2.6 \pm 0.8 {\mu}G. The energy density of the field within the ridge area is
+of the same order as estimates of the thermal component, implying a significant
+role of the magnetic field in the dynamics of the intergalactic matter. We also
+report that the tidal dwarf galaxy candidate SQ-B possesses a strong and highly
+anisotropic magnetic field with the total strength being equal to 6.5 \pm 1.9
+{\mu}G and an ordered component reaching 3.5 \pm 1.2 {\mu}G, which is
+comparable to that found in normal-sized galaxies.",1307.3447v1
+2013-07-20,Probing the anharmonicity of the potential well for magnetic vortex core in nanodot,"The anharmonicity of the potential well confining the position of the
+magnetic vortex core is measured dynamically with a Magnetic Resonance Force
+Microscope (MRFM). The stray field of the MRFM tip is used to displace the core
+position away from the well minimum. Anharmonicity is then inferred from the
+relative frequency shift induced on the eigen-frequency of the vortex core
+translational mode. Traces of these shifts are recorded while scanning the tip
+above an isolated nanodot, patterned out of a single crystal FeV film. An
+analytical framework is proposed to analyze the data. It results in a
+quantitative measurement of the anharmonic coefficient found to be positive and
+50% of the parabolic contribution. This calibrates the tunability of the
+gyrotropic mode by external magnetic fields. In our sample, we observe a
+variation of the eigen-frequency as high as +10% for a displacement of the
+vortex core to about one third of the nanodot radius.",1307.5429v2
+2013-07-20,Magnetic properties of Sn/1-x/Cr/x/Te diluted magnetic semiconductors,"We present the studies of Sn/1-x/Cr/x/Te semimagnetic semiconductors with
+chemical composition x ranging from 0.004 to 0.012. The structural
+characterization indicates that even at low average Cr-content x < ?0.012, the
+aggregation into micrometer size clusters appears in our samples. The magnetic
+properties are affected by the presence of clusters. In all our samples we
+observe the transition into the ordered state at temperatures between 130 and
+140 K. The analysis of both static and dynamic magnetic susceptibility data
+indicates that the spin-glass-like state is observed in our samples. The
+addition of Cr to the alloy seems to shift the spin-glass-like transition from
+130 K for x = 0.004 to 140 K for x = 0.012.",1307.5464v1
+2013-08-06,Chirality from interfacial spin-orbit coupling effects in magnetic bilayers,"As nanomagnetic devices scale to smaller sizes, spin-orbit coupling due to
+the broken structural inversion symmetry at interfaces becomes increasingly
+important. Here we study interfacial spin-orbit coupling effects in magnetic
+bilayers using a simple Rashba model. The spin-orbit coupling introduces
+chirality into the behavior of the electrons and through them into the
+energetics of the magnetization. In the derived form of the magnetization
+dynamics, all of the contributions that are linear in the spin-orbit coupling
+follow from this chirality, considerably simplifying the analysis. For these
+systems, an important consequence is a correlation between the
+Dzyaloshinskii-Moriya interaction and the spin-orbit torque. We use this
+correlation to analyze recent experiments.",1308.1198v2
+2013-08-22,Confined dissipative droplet solitons in spin-valve nanowires with perpendicular magnetic anisotropy,"Magnetic dissipative droplets are localized, strongly nonlinear dynamical
+modes excited in nano-contact spin valves with perpendicular magnetic
+anisotropy. These modes find potential application in nanoscale structures for
+magnetic storage and computation, but dissipative droplet studies have so far
+been limited to extended thin films. Here, numerical and asymptotic analyses
+are used to demonstrate the existence and properties of novel solitons in
+confined structures. As a nanowire's width is decreased with a nano-contact of
+fixed size at its center, the observed modes undergo transitions from a fully
+localized two-dimensional droplet into a two-dimensional droplet edge mode and
+then a pulsating one-dimensional droplet. These solitons are interpreted as
+dissipative versions of classical, conservative solitons, allowing for an
+analytical description of the modes and the mechanisms of bifurcation. The
+presented results open up new possibilities for the study of low-dimensional
+solitons and droplet applications in nanostructures.",1308.4812v1
+2013-08-27,Growth rate degeneracies in kinematic dynamos,"We consider the classical problem of kinematic dynamo action in simple steady
+flows. Due to the adjointness of the induction operator, we show that the
+growth rate of the dynamo will be exactly the same for two types of magnetic
+boundary conditions: the magnetic field can be normal (infinite magnetic
+permeability, also called pseudo-vacuum) or tangent (perfect electrical
+conductor) to the boundaries of the domain. These boundary conditions
+correspond to well-defined physical limits often used in numerical models and
+relevant to laboratory experiments. The only constraint is for the velocity
+field u to be reversible, meaning there exists a transformation changing u into
+-u. We illustrate this surprising property using S2T2 type of flows in
+spherical geometry inspired by Dudley and James (1989). Using both types of
+boundary conditions, it is shown that the growth rates of the dynamos are
+identical, although the corresponding magnetic eigenmodes are drastically
+different.",1308.5966v2
+2013-09-05,Asymmetric Energy Transfer Between Coupled Magnetic Vortices by Asymmetric Gyration Amplification,"We present a numerical exploration of the possibility of sustained
+amplification of magnetic vortex gyration by controlling the relative
+polarities of a coupled vortices in short vortex chains. First, we numerically
+establish the asymmetry in gyration of a single vortex based on its polarity by
+use of external magnetic field rotating at the gyrotropic frequency. This
+phenomena can be used to design logical adapters if vortex core switching is
+avoided. The criteria to obtain a good gyration amplitude ratio to easily
+observe true or false output has been examined further. The cases of coupled
+magnetic vortices and short vortex chains have been studied with different
+polarity configurations to reveal other desirable aspects of vortex dynamics
+including, but not limited to, highly efficient signal transfer. These findings
+are important in applications for information signal processing.",1309.1367v2
+2013-09-20,"Ground state and Spin-Wave dynamics in Brownmillerite SrCoO2.5, A combined Hybrid Functional and LSDAU study","We theoretically investigate the ground state magnetic properties of the
+brownmillerite phase of SrCoO2.5. Strong correlations within Co d electrons are
+treated within the local spin density approximations of Density Functional
+theory (DFT) with Hubbard U corrections (LSDAU) and results are compared with
+the Heyd Scuzeria Ernzerhof (HSE) functional. The parameters computed with a U
+value of 7.5 eV are found to match closely to those computed within the HSE
+functional. A G type antiferromagnetic structure is found to be the most stable
+one, consistent with experimental observation. By mapping the total energies of
+different magnetic configurations onto a Heisenberg Hamiltonian we compute the
+magnetic exchange interaction parameters, J, between the nearest neighbor Co
+atoms. The J s obtained are then used to compute the spin wave frequencies and
+inelastic neutron scattering intensities. Among four spin wave branches, the
+lowest energy mode was found to have the largest scattering intensity at the
+magnetic zone center, while the other modes becomes dominant at different
+momenta. These predictions can be tested by experimentally.",1309.5287v1
+2013-09-29,Coupled magnetic and ferroelectric excitations in PbFe_{1/2}Nb_{1/2}O_{3},"A neutron scattering investigation of the magnetoelectric coupling in
+PbFe_{1/2}Nb_{1/2}O_{3} (PFN) has been undertaken. Ferroelectric order occurs
+below 400 K, as evidenced by the softening with temperature and subsequent
+recovery of the zone center transverse optic phonon mode energy (\hbar
+\Omega_{0}). Over the same temperature range, magnetic correlations become
+resolution limited on a terahertz energy scale. In contrast to the behavior of
+nonmagnetic disordered ferroelectrics (namely Pb(Mg,Zn)_{1/3}Nb_{2/3}O_{3}), we
+report the observation of a strong deviation from linearity in the temperature
+dependence of (\hbar \Omega_{0})^{2}. This deviation is compensated by a
+corresponding change in the energy scale of the magnetic excitations, as probed
+through the first moment of the inelastic response. The coupling between the
+short-range ferroelectric and antiferromagnetic correlations is consistent with
+calculations showing that the ferroelectricity is driven by the displacement of
+the body centered iron site, illustrating the multiferroic nature of magnetic
+lead based relaxors in the dynamical regime.",1309.7587v1
+2013-10-09,Interchange reconnection between an active region and a corona hole,"With the data from the Atmospheric Imaging Assembly (AIA) and the
+Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory
+(SDO), we present a magnetic interaction between an isolated coronal hole (CH)
+and an emerging active region (AR). The AR emerged nearby the CH and interacted
+with it. Bright loops constantly formed between them, which led to a continuous
+retreat of the CH boundaries (CHBs). Meanwhile, two coronal dimmings
+respectively appeared at the negative polarity of the AR and the east boundary
+of the bright loops, and the AR was partly disturbed. Loop eruptions followed
+by a flare occurred in the AR. The interaction was also accompanied by many
+jets and an arc-shaped brightening that appeared to be observational signatures
+of magnetic reconnection at the CHBs. By comparing the observations with the
+derived coronal magnetic configuration, it is suggested that the interaction
+between the CH and the AR excellently fitted in with the model of interchange
+reconnection. It appears that our observations provide obvious evidences for
+interchange reconnection.",1310.2395v1
+2013-10-16,Domain wall motion in magnetic nanowires: An asymptotic approach,"We develop a systematic asymptotic description for domain wall motion in
+one-dimensional magnetic nanowires under the influence of small applied
+magnetic fields and currents and small material anisotropy. The magnetization
+dynamics, as governed by the Landau--Lifshitz--Gilbert equation, is
+investigated via a perturbation expansion. We compute leading-order behaviour,
+propagation velocities, and first-order corrections of both travelling waves
+and oscillatory solutions, and find bifurcations between these two types of
+solutions. This treatment provides a sound mathematical foundation for numerous
+results in the literature obtained through more ad hoc arguments.",1310.4442v1
+2013-10-23,Kinematic dynamo action in square and hexagonal patterns,"We consider kinematic dynamo action in rapidly rotating Boussinesq convection
+just above onset. The velocity is constrained to have either a square or a
+hexagonal pattern. For the square pattern, large-scale dynamo action is
+observed at onset, with most of the magnetic energy being contained in the
+horizontally-averaged component. As the magnetic Reynolds number increases,
+small-scale dynamo action becomes possible, reducing the overall growth rate of
+the dynamo. For the hexagonal pattern, the breaking of symmetry between up and
+down flows results in an effective pumping velocity. For intermediate rotation
+rates, this additional effect can prevent the growth of any mean-field dynamo,
+so that only a small-scale dynamo is eventually possible at large enough
+magnetic Reynolds number. For very large rotation rates, this pumping term
+becomes negligible, and the dynamo properties of square and hexagonal patterns
+are qualitatively similar. These results hold for both perfectly conducting and
+infinite magnetic permeability boundary conditions.",1310.6255v1
+2013-11-06,Observation of zero-point quantum fluctuations of a single-molecule magnet through the relaxation of its nuclear spin bath,"A single-molecule magnet placed in a magnetic field perpendicular to its
+anisotropy axis can be truncated to an effective two-level system, with easily
+tunable energy splitting. The quantum coherence of the molecular spin is
+largely determined by the dynamics of the surrounding nuclear spin bath. Here
+we report the measurement of the nuclear spin--lattice relaxation in a single
+crystal of the single-molecule magnet Mn$_{12}$-ac, at $T \approx 30$ mK in
+perpendicular fields $B_{\perp}$ up to 9 T. Although the molecular spin is in
+its ground state, we observe an increase of the nuclear relaxation rates by
+several orders of magnitude up to the highest $B_{\perp}$. This unique finding
+is a consequence of the zero-point quantum fluctuations of the Mn$_{12}$-ac
+spin, which allow it to efficiently transfer energy from the excited nuclear
+spin bath to the lattice. Our experiment highlights the importance of quantum
+fluctuations in the interaction between an `effective two-level system' and its
+surrounding spin bath.",1311.1373v1
+2013-11-25,Notes on analytical study of holographic superconductors with Lifshitz scaling in external magnetic field,"We employ the matching method to analytically investigate the holographic
+superconductors with Lifshitz scaling in an external magnetic field. We discuss
+systematically the restricted conditions for the matching method and find that
+this analytic method is not always powerful to explore the effect of external
+magnetic field on the holographic superconductors unless the matching point is
+chosen in an appropriate range and the dynamical exponent $z$ satisfies the
+relation $z=d-1$ or $z=d-2$. From the analytic treatment, we observe that
+Lifshitz scaling can hinder the condensation to be formed, which can be used to
+back up the numerical results. Moreover, we study the effect of Lifshitz
+scaling on the upper critical magnetic field and reproduce the well-known
+relation obtained from Ginzburg-Landau theory.",1311.6260v3
+2013-11-29,Resonant optical pumping of a Mn spin in a strain free quantum dot,"We report on the spin properties of individual Mn atoms in II-VI
+semiconductor strain free quantum dots. Strain free Mn-doped CdTe quantum dots
+are formed by width fluctuations in thin quantum wells lattice matched on a
+CdTe substrate. These quantum dots permit to optically probe and address any
+spin state of a Mn atom in a controlled strain environment. The absence of
+strain induced magnetic anisotropy prevents an optical pumping of the Mn spin
+at zero magnetic field. Thus, a large photoluminescence is obtained under
+resonant optical excitation of the exciton-Mn complex. An efficient optical
+pumping of the coupled electronic and nuclear spins of the Mn is restored under
+a weak magnetic field. The observed reduction of the resonant photoluminescence
+intensity under magnetic field is well described by a model including the
+hyperfine coupling and a residual crystal field splitting of the Mn atom.
+Finally, we show that the second order correlation function of the resonant
+photoluminescence presents a large photon bunching at short delay which is a
+probe of the dynamics of coupled electronic and nuclear spins of the Mn atom.",1311.7622v1
+2013-12-11,Electric current generation in distorted graphene,"Graphene-like materials can be effectively described by Quantum
+Electrodynamics in (2+1)-dimensions. In a pristine state, these systems exhibit
+a symmetry between the nonequivalent Dirac points in the honeycomb lattice.
+Realistic samples which include distortions and crystalline anisotropies are
+considered through mass gaps of topological and dynamical nature. In this work
+we show that the incorporation of an in-plane uniform external magnetic field
+on this pseudochiral asymmetric configuration generates a non-dissipative
+electric current aligned with the magnetic field: The pseudo chiral magnetic
+effect. This scenario resembles the chiral magnetic effect in Quantum
+Chromodynamics.",1312.3274v3
+2014-01-08,Successive filament eruptions within one solar breakout event,"The magnetic breakout model has been widely used to explain solar eruptive
+activities. Here, we apply it to explain successive filament eruptions occurred
+in a quadrupolar magnetic source region. Based on the high temporal and spatial
+resolution, multi-wavelengths observations taken by the Atmospheric Imaging
+Assembly (AIA) on board the Solar Dynamic Observatory (SDO), we find some
+signatures that support the occurrence of breakout-like external reconnection
+just before the start of the successive filament eruptions. Furthermore, the
+extrapolated three-dimensional coronal field also reveals that the magnetic
+topology above the quadrupolar source region resembles that of the breakout
+model. We propose a possible mechanism within the framework of the breakout
+model to interpret the successive filament eruptions, in which the so-called
+magnetic implosion mechanism is firstly introduced to be the physical linkage
+of successive filament eruptions. We conclude that the structural properties of
+coronal fields are important for producing successive filament eruptions.",1401.1694v1
+2014-01-22,Long-term memory in experiments and numerical simulations of hydrodynamic and magnetohydrodynamic turbulence,"We analyze time series stemming from experiments and direct numerical
+simulations of hydrodynamic and magnetohydrodynamic turbulence. Simulations are
+done in periodic boxes, but with a volumetric forcing chosen to mimic the
+geometry of the flow in the experiments, the von K\'arm\'an swirling flow
+between two counter-rotating impellers. Parameters in the simulations are
+chosen to (within computational limitations) allow comparisons between the
+experiments and the numerical results. Conducting fluids are considered in all
+cases. Two different configurations are considered: a case with a weak
+externally imposed magnetic field, and a case with self-sustained magnetic
+fields. Evidence of long-term memory and $1/f$ noise is observed in experiments
+and simulations, in the case with weak magnetic field associated with the
+hydrodynamic behavior of the shear layer in the von K\'arm\'an flow, and in the
+dynamo case associated with slow magnetohydrodynamic behavior of the large
+scale magnetic field.",1401.5792v1
+2014-03-03,Faraday rotation echo spectroscopy and detection of quantum fluctuations,"Central spin decoherence is useful for detecting many-body physics in
+environments and moreover, the spin echo control can remove the effects of
+static thermal fluctuations so that the quantum fluctuations are revealed. The
+central spin decoherence approach, however, is feasible only in some special
+configurations and often requires uniform coupling between the central spin and
+individual spins in the baths, which are very challenging in experiments. Here,
+by making analogue between central spin decoherence and depolarization of
+photons, we propose a scheme of Faraday rotation echo spectroscopy (FRES) for
+studying quantum fluctuations in interacting spin systems. The echo control of
+the photon polarization is realized by flipping the polarization with a
+birefringence crystal. The FRES, similar to spin echo in magnetic resonance
+spectroscopy, can suppress the effects of the static magnetic fluctuations and
+therefore reveal dynamical magnetic fluctuations. We apply the scheme to a
+rare-earth compound LiHoF4 and calculate the echo signal, which is related to
+the quantum fluctuations of the system. We observe enhanced signals at the
+phase boundary. The FRES should be useful for studying quantum fluctuations in
+a broad range of spin systems, including cold atoms, quantum dots, solid-state
+impurities, and transparent magnetic materials.",1403.0420v1
+2014-03-14,The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Optimization of the Spectral Line Inversion Code,"The Very Fast Inversion of the Stokes Vector (VFISV) is a Milne-Eddington
+spectral line inversion code used to determine the magnetic and thermodynamic
+parameters of the solar photosphere from observations of the Stokes vector in
+the 6173 A Fe I line by the Helioseismic and Magnetic Imager (HMI) onboard the
+Solar Dynamics Observatory (SDO). We report on the modifications made to the
+original VFISV inversion code in order to optimize its operation within the HMI
+data pipeline and provide the smoothest solution in active regions. The changes
+either sped up the computation or reduced the frequency with which the
+algorithm failed to converge to a satisfactory solution. Additionally, coding
+bugs which were detected and fixed in the original VFISV release, are reported
+here.",1403.3677v1
+2014-03-22,Lifshitz Effects on Vector Condensate Induced by a Magnetic Field,"By numerical and analytical methods, we study in detail the effects of the
+Lifshitz dynamical exponent $z$ on the vector condensate induced by an applied
+magnetic field in the probe limit. Concretely, in the presence of the magnetic
+field, we obtain the Landau level independent of $z$, and also find the
+critical value by coupling a Maxwell complex vector field and SU(2) field into
+a (3+1)-dimensional Lifshitz black hole, respectively. The research results
+show that for both two models with the lowest Landau level, the increasing $z$
+improves the response of the critical temperature to the applied magnetic field
+even without the charge density, and the analytical results uphold the
+numerical results. In addition, we find even in the Lifshitz black hole, the
+Maxwell complex vector model is still a generalization of the SU(2) Yang-Mills
+model. Furthermore, we construct the square vortex lattice and discuss the
+implications of these results.",1403.5649v2
+2014-03-25,Long-term Evolution of Large-scale Magnetic Fields in Rotating Stratified Convection,"Convective dynamo simulations are performed in local Cartesian geometry. We
+report the first successful simulation of a large-scale oscillatory dynamo in
+rigidly rotating convection without stably stratified layers. A key requirement
+for exciting the large-scale dynamo is a sufficiently long integration time
+comparable to the ohmic diffusion time. By comparing two models with and
+without stably stratified layers, their effect on the large-scale dynamo is
+also studied. The spatiotemporal evolution of the large-scale magnetic field is
+similar in both models. However, it is intriguing that the magnetic cycle is
+much shorter in the model without the stable layer than with the stable layer.
+This suggests that the stable layer impedes the cyclic variations of the
+large-scale magnetic field.",1403.6221v1
+2014-04-01,"Magnetic order and spin dynamics in La2O2Fe2OSe2 probed by 57Fe-Moessbauer, 139La-NMR, and muon spin relaxation spectroscopy","We present a detailed local probe study of the magnetic order in the
+oxychalcogenide La2O2Fe2OSe2 utilizing 57Fe Moessbauer, 139La NMR, and muon
+spin relaxation spectroscopy. This system can be regarded as an insulating
+reference system of the Fe arsenide and chalcogenide superconductors. From the
+combination of the local probe techniques we identify a non-collinear magnetic
+structure similar to Sr2F2Fe2OS2. The analysis of the magnetic order parameter
+yields an ordering temperature TN = 90.1 K and a critical exponent of beta =
+0.133, which is close to the 2D Ising universality class as reported in the
+related oxychalcogenide family.",1404.0249v2
+2014-04-15,Molding the flow of light with a magnetic field: plasmonic cloaking and directional scattering,"We investigate electromagnetic scattering and plasmonic cloaking in a system
+composed by a dielectric cylinder coated with a magneto-optical shell. In the
+long-wavelength limit we demonstrate that the application of an external
+magnetic field can not only switch on and off the cloaking mechanism but also
+mitigate losses, as the absorption cross-section is shown to be minimal
+precisely at the cloaking operation frequency band. We also show that the
+angular distribution of the scattered radiation can be effectively controlled
+by applying an external magnetic field, allowing for a swift change in the
+scattering pattern. By demonstrating that these results are feasible with
+realistic, existing magneto-optical materials, such as graphene epitaxially
+grown on SiC, we suggest that magnetic fields could be used as an effective,
+versatile external agent to tune plasmonic cloaks and to dynamically control
+electromagnetic scattering in an unprecedented way, we hope that these results
+may find use in disruptive photonic technologies.",1404.3979v1
+2014-05-02,Weyl fermions induced Magnon electrodynamics in Weyl semimetal,"Weyl fermions, which are fermions with definite chiralities, can give rise to
+anomalous breaking of the symmetry of the physical system which they are a part
+of. In their (3+1)-dimensional realizations in condensed matter systems, i.e.,
+the so-called Weyl semimetals, this anomaly gives rise to topological
+electromagnetic response of magnetic fluctuations, which takes the form of
+non-local interaction between magnetic fluctuations and electromagnetic fields.
+We study the physical consequences of this non-local interaction, including
+electric field assisted magnetization dynamics, an extra gapless magnon
+dispersion, and polariton behaviors that feature ""sibling"" bands in small
+magnetic fields.",1405.0491v2
+2014-05-15,Reducing error rates in straintronic multiferroic dipole-coupled nanomagnetic logic by pulse shaping,"Dipole-coupled nanomagnetic logic (NML), where nanomagnets with bistable
+magnetization states act as binary switches and information is transferred
+between them via dipole coupling and Bennett clocking, is a potential
+replacement for conventional transistor logic since magnets dissipate less
+energy than transistors when they switch in response to the clock. However,
+dipole-coupled NML is much more error-prone than transistor logic because
+thermal noise can easily disrupt magnetization dynamics. Here, we study a
+particularly energy-efficient version of dipole-coupled NML known as
+straintronic multiferroic logic (SML) where magnets are clocked/switched with
+electrically generated mechanical strain. By appropriately shaping the voltage
+pulse that generates strain, the error rate in SML can be reduced to tolerable
+limits. In this paper, we describe the error probabilities associated with
+various stress pulse shapes and discuss the trade-off between error rate and
+switching speed in SML.",1405.4000v1
+2014-05-17,Noise-enhanced synchronization of stochastic magnetic oscillators,"We present an experimental study of phase-locking in a stochastic magnetic
+oscillator. The system comprises a magnetic tunnel junction with a
+superparamagnetic free layer, whose magnetization dynamics is driven with spin
+torques through an external periodic driving current. We show that
+synchronization of this stochastic oscillator to the input current is possible
+for current densities below $3 \times 10^6$ A/cm$^2$, and occurs for input
+frequencies lower than the natural mean frequency of the stochastic oscillator.
+We show that such injection-locking is robust and leads to a drastic reduction
+in the phase diffusion of the stochastic oscillator, despite the presence of a
+frequency mismatch between the oscillator and the excitation.",1405.4360v1
+2014-05-17,Attitude dynamics and control of spacecraft using geomagnetic Lorentz force,"The attitude stabilization of a charged rigid spacecraft in Low Earth Orbit
+(LEO) using torques due to Lorentz force in pitch and roll directions is
+considered. A spacecraft that generates an electrostatic charge on its surface
+in the Earth magnetic field will be subject to perturbations from Lorentz
+force. The Lorentz force acting on an electrostatically charged spacecraft may
+provide a useful thrust for controlling a spacecraft's orientation. We assume
+that the spacecraft is moving in the Earth's magnetic field in an elliptical
+orbit under the effects of the gravitational, geomagnetic and Lorentz torques.
+The magnetic field of the Earth is modeled as a non-tilted dipole. A model
+incorporating all Lorentz torques as a function of orbital elements has been
+developed on the basis of electric and magnetic fields. The stability of the
+spacecraft orientation is investigated both analytically and numerically. The
+existence and stability of equilibrium positions is investigated for different
+values of the charge to mass ratio ($\alpha^*$). Stable orbits are identified
+for various values of $\alpha^*$. The main parameters for stabilization of the
+spacecraft are $\alpha^*$ and the difference between the components of the
+moment of inertia of spacecraft.",1405.4411v1
+2014-05-18,Ultracold Spin-Orbit Coupled Bose-Einstein Condensate in a Cavity: Route to Magnetic Phases Through Cavity Transmission,"We study the spin orbit coupled ultra cold Bose-Einstein condensate placed in
+a single mode Fabry-P\'erot cavity. The cavity introduces a quantum optical
+lattice potential which dynamically couples with the atomic degrees of freedom
+and realizes a generalized extended Bose Hubbard model whose zero temperature
+phase diagram can be controlled by tuning the cavity parameters. In the
+non-interacting limit, where the atom-atom interaction is set to zero, the
+resulting atomic dispersion shows interesting features such as bosonic analogue
+of Dirac points, cavity controlled Hofstadter spectrum which bears the hallmark
+of pseudo-spin-1/2 bosons in presence of Abelian and non-Abelian gauge field
+(the later due to spin-orbit coupling) in a cavity induced optical lattice
+potential. In the presence of atom-atom interaction, using a mapping to a
+generalized Bose Hubbard model of spin-orbit coupled bosons in classical
+optical lattice, we show that the system realizes a host of quantum magnetic
+phases whose magnetic order can be be detected from the cavity transmission.
+This provides an alternative approach for detecting quantum magnetism in ultra
+cold atoms. We discuss the effect of cavity induced optical bistability on this
+phases and their experimental consequences.",1405.4500v1
+2014-06-02,Tracking Temperature Dependent Relaxation Times of Individual Ferritin Nanomagnets with a Wide-band Quantum Spectrometer,"We demonstrate the tracking of the spin dynamics of ensemble and individual
+magnetic ferritin proteins from cryogenic up to room temperature using the
+nitrogen-vacancy color center in diamond as magnetic sensor. We employ
+different detection protocols to probe the influence of the ferritin
+nanomagnets on the longitudinal and transverse relaxation of the
+nitrogen-vacancy center, which enables magnetic sensing over a wide frequency
+range from Hz to GHz. The temperature dependence of the observed spectral
+features can be well understood by the thermally induced magnetization
+reversals of the ferritin and enables the determination of the anisotropy
+barrier of single ferritin molecules.",1406.0362v1
+2014-06-25,Ion and electron heating during magnetic reconnection in weakly collisional plasmas,"Magnetic reconnection and associated heating of ions and electrons in
+strongly magnetised, weakly collisional plasmas are studied by means of
+gyrokinetic simulations. It is shown that an appreciable amount of the released
+magnetic energy is dissipated to yield (irreversible) electron and ion heating
+via phase mixing. Electron heating is mostly localized to the magnetic island,
+not the current sheet, and occurs after the dynamical reconnection stage. Ion
+heating is comparable to electron heating only in high-beta plasmas, and
+results from both parallel phase mixing and perpendicular phase mixing due to
+finite Larmor radius effects; in space, ion heating is localized to the
+interior of a secondary island (plasmoid) that arises from the instability of
+the current sheet.",1406.6456v2
+2014-09-16,Phonon-modulated magnetic interactions and spin Tomonaga-Luttinger liquid in the p-orbital antiferromagnet CsO2,"The magnetic response of antiferromagnetic CsO2, coming from the p-orbital
+S=1/2 spins of anionic O2- molecules, is followed by 133Cs nuclear magnetic
+resonance across the structural phase transition occuring at Ts1=61 K on
+cooling. Above Ts1, where spins form a square magnetic lattice, we observe a
+huge, nonmonotonic temperature dependence of the exchange coupling originating
+from thermal librations of O2- molecules. Below Ts1, where antiferromagnetic
+spin chains are formed as a result of p-orbital ordering, we observe a spin
+Tomonaga-Luttinger-liquid behavior of spin dynamics. These two interesting
+phenomena, which provide rare simple manifestations of the coupling between
+spin, lattice and orbital degrees of freedom, establish CsO2 as a model system
+for molecular solids.",1409.4818v2
+2014-09-18,Decoherence imaging of spin ensembles using a scanning single-electron spin in diamond,"The nitrogen-vacancy (NV) defect center in diamond has demonstrated great
+capability for nanoscale magnetic sensing and imaging for both static and
+periodically modulated target fields. However, it remains a challenge to detect
+and image randomly fluctuating magnetic fields. Recent theoretical and
+numerical works have outlined detection schemes that exploit changes in
+decoherence of the detector spin as a sensitive measure for fluctuating fields.
+Here we experimentally monitor the decoherence of a scanning NV center in order
+to image the fluctuating magnetic fields from paramagnetic impurities on an
+underlying diamond surface. We detect a signal corresponding to roughly 800
+${\mu}_B$ in 2 s of integration time, without any control on the target spins,
+and obtain magnetic-field spectral information using dynamical decoupling
+techniques. The extracted spatial and temporal properties of the surface
+paramagnetic impurities provide insight to prolonging the coherence of
+near-surface qubits for quantum information and metrology applications.",1409.5418v1
+2014-09-23,A strategy for the design of skyrmion racetrack memories,"Magnetic storage based on racetrack memory is very promising for the design
+of ultra-dense, low-cost and low-power storage technology. Information can be
+coded in a magnetic region between two domain walls or, as predicted recently,
+in topological magnetic objects known as skyrmions. Here, we show the
+technological advantages and limitations of using Bloch and Neel skyrmions
+manipulated by spin current generated within the ferromagnet or via the
+spin-Hall effect arising from a non-magnetic heavy metal underlayer. We found
+that the Neel skyrmion moved by the spin-Hall effect is a very promising
+strategy for technological implementation of the next generation of skyrmion
+racetrack memories (zero field, high thermal stability, and ultra-dense
+storage). We employed micromagnetics reinforced with an analytical formulation
+of skyrmion dynamics that we developed from the Thiele equation. We identified
+that the excitation, at high currents, of a breathing mode of the skyrmion
+limits the maximal velocity of the memory.",1409.6491v2
+2014-09-30,Towards the stabilization of extra dimensions by brane dynamics,"All the models of elementary particles and their interactions derived from
+String Theory involve a compact six-dimensional internal space. Its volume and
+shape should be fixed or stabilized, since otherwise massless scalar fields
+(moduli) reflecting their deformations appear in our four-dimensional
+space-time, with sizable effects on known particles and fields. We propose a
+strategy towards stabilizing the compact space without fluxes of three-form
+fields from closed strings. Our main motivation and goal is to proceed insofar
+as possible within conventional string world-sheet theory. As we shall see,
+D-branes with magnetic flux (""magnetized D-branes"") and the forces between them
+can be used to this end. We investigate here some necessary ingredients: open
+string one-loop vacuum amplitudes between magnetized D-branes, magnetized
+D-branes fixed at orbifold singularities, and potential energies among such
+D-branes in the compact space that result from tree-level closed string
+exchanges.",1409.8401v3
+2014-10-03,Vortices at the magnetic equator generated by hybrid Alfven resonant waves,"We performed three-dimensional magnetohydrodynamic simulations of shear
+Alfven waves in a full field line system with magnetosphere-ionosphere coupling
+and plasma non-uniformities. Feedback instability of the Alfven resonant modes
+showed various nonlinear features under the field line cavities: i) a secondary
+flow shear instability occurs at the magnetic equator, ii) trapping of the
+ionospheric Alfven resonant modes facilitates deformation of field-aligned
+current structures, and iii) hybrid Alfven resonant modes grow to cause
+vortices and magnetic oscillations around the magnetic equator. Essential
+features in the initial brightening of auroral arc at substorm onsets could be
+explained by the dynamics of Alfven resonant modes, which are the nature of the
+field line system responding to a background rapid change.",1410.0764v1
+2014-10-15,Magneto-optical properties of paramagnetic superrotors,"We study the dynamics of paramagnetic molecular superrotors in an external
+magnetic field. Optical centrifuge is used to create dense ensembles of oxygen
+molecules in ultra-high rotational states. It is shown for the first time, that
+the gas of rotating molecules becomes optically birefringent in the presence of
+magnetic field. The discovered effect of ""magneto-rotational birefringence""
+indicates preferential alignment of molecular axes along the field direction.
+We provide an intuitive qualitative model, in which the influence of the
+applied magnetic field on the molecular orientation is mediated by the
+spin-rotation coupling. This model is supported by the direct imaging of the
+distribution of molecular axes, the demonstration of the magnetic reversal of
+the rotational Raman signal, and by numerical calculations.",1410.4257v4
+2014-10-24,Rectification of radio frequency current in giant magnetoresistance spin valve,"We report on a highly efficient spin diode effect in an exchange-biased
+spin-valve giant magnetoresistance (GMR) strips. In such multilayer structures,
+symmetry of the current distribution along the vertical direction is broken
+and, as a result, a non-compensated Oersted field acting on the magnetic free
+layer appears. This field, in turn, is a driving force of magnetization
+precessions. Due to the GMR effect, resistance of the strip oscillates
+following the magnetization dynamics. This leads to rectification of the
+applied radio frequency current and induces a direct current voltage $V_{DC}$.
+We present a theoretical description of this phenomenon and calculate the spin
+diode signal, $V_{DC}$, as a function of frequency, external magnetic field,
+and angle at which the external field is applied. A satisfactory quantitative
+agreement between theoretical predictions and experimental data has been
+achieved. Finally, we show that the spin diode signal in GMR devices is
+significantly stronger than in the anisotropic magnetoresistance
+permalloy-based devices.",1410.6672v1
+2014-10-24,Non-linear spin-wave excitation at low bias fields,"Non-linear magnetization dynamics is essential for the operation of many
+spintronics devices. For microwave assisted switching of magnetic elements the
+low field regime is of particular interest. In addition a large number of
+experiments uses high amplitude FMR in order to generate d.c. currents via spin
+pumping mechanism. Here we use time resolved X-ray magnetic circular dichroism
+experiments to determine the number density of excited magnons in magnetically
+soft Ni_80Fe_20 thin films at small bias fields and large rf-excitation
+amplitudes. Our data shows that the common model of non-linear ferromagnetic
+resonance is not suitable to describe the low bias field limit. Here we derive
+a new model of parametric spin-wave excitation which correctly predicts
+threshold amplitudes and decay rates also at low bias fields. In fact a new
+series of critical modes with amplitude phase oscillations is found,
+generalizing the theory of parametric spin-wave excitation.",1410.6693v1
+2014-10-26,Short-range correlations in the magnetic ground state of Na4Ir3O8,"The magnetic ground state of the hyper-kagome lattice in Na4Ir3O8 is explored
+via combined bulk magnetization, muon spin relaxation, and neutron scattering
+measurements. A short-range, frozen, state comprised of quasi-static moments
+develops below a characteristic temperature of T_F=6 K, revealing an
+inhomogeneous distribution of spins occupying the entirety of the sample
+volume. Quasi-static, short-range, spin correlations persist until at least 20
+mK and differ substantially from the nominally dynamic response of a quantum
+spin liquid. Our data demonstrate that an inhomogeneous magnetic ground state
+arises in Na4Ir3O8 driven either by disorder inherent to the creation of the
+hyper-kagome lattice itself or stabilized via quantum fluctuations.",1410.7072v1
+2014-11-12,Electric-Field Control over Spin-Wave and Current Induced Domain Wall Motion and Magnonic Torques in Multiferroics,"We discover that the way spin-waves exert magnetic torques in multiferroic
+materials can cause not only domain wall motion, but also magnetization
+dynamics for homogeneous magnetization textures. Interestingly, the domain wall
+motion can be controlled via purely electrical means with the spin-waves being
+generated by an ac electric field $E$ while the direction of the wall motion
+also is sensitive to an applied dc $E$ field. Moreover, we determine the
+interaction between spin-transfer torque from an electric current and a
+magnetic domain wall in multiferroics and show that the Walker breakdown
+threshold scales with the magnitude of a perpendicular electric field, offering
+a way to control the properties of domain wall propagation via electric gating.",1411.3327v2
+2014-11-03,Magnetic Critical Solutions in Holography,"The AdS/CFT correspondence is a realization of the holographic principle in
+the context of string theory. It is a map between a quantum field theory and a
+string theory living in one or more extra dimensions. Holography provides new
+tools to study strongly-coupled quantum field theories. It has important
+applications in quantum chromodynamics (QCD) and condensed matter (CM) systems,
+which are usually complicated and strongly coupled. Quantum critical CM
+theories have scaling symmetries and can be connected to higher-dimensional
+scale invariant space-times. The Effective Holographic Theory paradigm may be
+used to describe the low-energy (IR) holographic dynamics of quantum critical
+systems by the Einstein-Maxwell-Dilaton (EMD) theory. We find the magnetic
+critical scaling solutions of an EMD theory containing an extra parity-odd term
+$F\wedge F$. Previous studies in the absence of magnetic fields have shown the
+existence of quantum critical lines separated by quantum critical points. We
+find this is also true in the presence of a magnetic field. The critical
+solutions are characterized by the triplet of critical exponents
+($\theta,z,\zeta$), the first two describing the geometry, while the latter
+describes the charge density.",1411.3579v3
+2014-11-26,Electrical manipulation of orbital occupancy and magnetic anisotropy in manganites,"Electrical manipulation of lattice, charge, and spin has been realized
+respectively by the piezoelectric effect, field-effect transistor, and electric
+field control of ferromagnetism, bringing about dramatic promotions both in
+fundamental research and industrial production. However, it is generally
+accepted that the orbital of materials are impossible to be altered once they
+have been made. Here we use electric-field to dynamically tune the electronic
+phase transition in (La,Sr)MnO3 films with different Mn^4+/(Mn^3+ + Mn^4+)
+ratios. The orbital occupancy and corresponding magnetic anisotropy of these
+thin films are manipulated by gate voltage in a reversible and quantitative
+manner. Positive gate voltage increases the proportion of occupancy of the
+orbital and magnetic anisotropy that were initially favored by strain
+(irrespective of tensile and compressive), while negative gate voltage reduces
+the concomitant preferential orbital occupancy and magnetic anisotropy. Besides
+its fundamental significance in orbital physics, our findings might advance the
+process towards practical oxide-electronics based on orbital.",1411.7128v1
+2014-11-27,Inverse Magnetic Catalysis in the three-flavor NJL model with axial-vector interaction,"In this paper we explore the chiral phase transition in QCD within the
+three-flavor Nambu-Jona-Lasinio (NJL) model with a negative coupling constant
+in the isoscalar axial-vector channel, which is associated with a polarized
+instanton--anti-instanton molecule background. The QCD phase diagram described
+in this scenario shows a new first order phase transition around the transition
+temperature $T_c$ toward a phase without chiral condensates, but with
+nontrivial dynamic chiral chemical potentials for the light quarks,
+spontaneously giving rise to local $\mathcal {CP}$ violation and local
+chirality imbalance. The corresponding critical temperature $T_{5c}$ for this
+phase transition decreases with the magnetic field and it gives a natural
+explanation to the inverse magnetic catalysis effect for light quarks when
+incorporating a reasonable value of the coupling constant in the isoscalar
+axial-vector channel. Furthermore, when the isoscalar axial-vector interaction
+is dominant in light quark sector and suppressed in strange quark sector, it is
+found that there is no inverse magnetic catalysis for strange quark condensate,
+which agrees with lattice results.",1411.7552v2
+2014-12-23,Super-elastic Collision of Large-scale Magnetized Plasmoids in The Heliosphere,"Super-elastic collision is an abnormal collisional process, in which some
+particular mechanisms cause the kinetic energy of the system increasing. Most
+studies in this aspect focus on solid-like objects, but they rarely consider
+gases or liquids, as the collision of the latter is primarily a mixing process.
+With cross-field diffusion being effectively prohibited, magnetized plasmoids
+are different from ordinary gases. But it remains unclear how they act during a
+collision. Here we present the global picture of a unique collision between two
+coronal mass ejections in the heliosphere, which are the largest magnetized
+plasmoids erupting from the Sun. Our analysis for the first time reveals that
+these two magnetized plasmoids collided like solid-like objects with a 73%
+likelihood of being super-elastic. Their total kinetic energy surprisingly
+increased by about 6.6% through the collision, which significantly influenced
+the dynamics of the plasmoids.",1412.7375v1
+2015-01-06,Design and simulation of a hybrid controller for a multi-input multi-output magnetic suspension system,"In this paper we present a Fuzzy Logic control approach designed to stabilize
+a multi-input multi-output magnetic suspension system. The system has four
+cubic floaters and four actuators that apply magnetic forces on the floaters,
+the suspension is performed by changing the voltages applied on the actuators,
+hence changing their currents, producing vertical magnetic forces that balance
+with the gravitational force. A fuzzy logic controller is used to control each
+actuator; the system is nonlinear and sensitive to initial conditions. Another
+fuzzy logic controller is used as a supervisory controller in order to increase
+the dynamic range of the system, enabling it to stabilize the floaters when the
+initial displacements are relatively big. Another design consideration was to
+keep the four floaters in the same plane as much as possible, to perform that
+task, a PD controller was set to modulate the currents of the four actuators in
+order to minimize an error signal measuring the relative vertical displacement
+of all the four floaters. Simulation results show that the designed control
+scheme stabilized the system for the design constrains.",1501.01294v1
+2015-01-12,Magnetic correlations beyond the Heisenberg model in an Fe monolayer on Rh(001),"Motivated by a recent experimental observation of a complex magnetic
+structure [Takada et al. 2013 J. Magn. Magn. Mater. 329 95] we present a
+theoretical study of the magnetic structure of an Fe monolayer deposited on
+Rh(001). We use a classical spin Hamiltonian with parameters obtained from ab
+initio calculations and go beyond the usual anisotropic Heisenberg model by
+including isotropic biquadratic interactions. Zero-temperature
+Landau--Lifshitz--Gilbert spin dynamics simulations lead to a complex collinear
+spin configuration that, however, contradicts experimental finding. We thus
+conclude that higher order multi-spin interactions are likely needed to account
+for the magnetic ordering of the system.",1501.02657v1
+2015-01-12,Multiply periodic states and isolated skyrmions in an anisotropic frustrated magnet,"Multiply periodic states appear in a wide variety of physical contexts, such
+as the Rayleigh-Benard convection, Faraday waves, liquid crystals, domain
+patterns in ferromagnetic films and skyrmion crystals recently observed in
+chiral magnets. Here we study a simple model of an anisotropic frustrated
+magnet and show that its zero-temperature phase diagram contains numerous
+multi-q states including the skyrmion crystal. We clarify the mechanism for
+stabilization of these states, discuss their multiferroic properties and
+formulate rules for finding new skyrmion materials. In addition to skyrmion
+crystal, we find stable isolated skyrmions with topological charge 1 and 2.
+Physics of isolated skyrmions in frustrated magnets is very rich. Their
+statical and dynamical properties are strongly affected by the new zero mode -
+skyrmion helicity.",1501.02757v1
+2015-01-27,Wave Heating of the Solar Atmosphere,"Magnetic waves are a relevant component in the dynamics of the solar
+atmosphere. Their significance has increased because of their potential as a
+remote diagnostic tool and their presumed contribution to plasma heating
+processes. We discuss our current understanding on coronal heating by magnetic
+waves, based on recent observational evidence and theoretical advances. The
+discussion starts with a selection of observational discoveries that have
+brought magnetic waves to the forefront of the coronal heating discussion.
+Then, our theoretical understanding on the nature and properties of the
+observed waves and the physical processes that have been proposed to explain
+observations are described. Particular attention is given to the sequence of
+processes that link observed wave characteristics with concealed energy
+transport, dissipation, and heat conversion. We conclude with a commentary on
+how the combination of theory and observations should help us understanding and
+quantifying magnetic wave heating of the solar atmosphere.",1501.06708v1
+2015-02-12,Integrated information storage and transfer with a coherent magnetic device,"Quantum systems are inherently dissipation-less, making them excellent
+candidates even for classical information processing. We propose to use an
+array of large-spin quantum magnets for realizing a device which has two modes
+of operation: memory and data-bus. While the weakly interacting low-energy
+levels are used as memory to store classical information (bits), the
+high-energy levels strongly interact with neighboring magnets and mediate the
+spatial movement of information through quantum dynamics. Despite the fact that
+memory and data-bus require different features, which are usually prerogative
+of different physical systems -- well isolation for the memory cells, and
+strong interactions for the transmission -- our proposal avoids the notorious
+complexity of hybrid structures. The proposed mechanism can be realized with
+different setups. We specifically show that molecular magnets, as the most
+promising technology, can implement hundreds of operations within their
+coherence time, while adatoms on surfaces probed by a scanning tunneling
+microscope is a future possibility.",1502.03857v2
+2015-02-19,Exciton-polaron complexes in pulsed electrically-detected magnetic resonance,"Several microscopic pathways have been proposed to explain the large magnetic
+effects observed in organic semiconductors, but identifying and characterising
+which microscopic process actually influences the overall magnetic field
+response is challenging. Pulsed electrically-detected magnetic resonance
+provides an ideal platform for this task as it intrinsically monitors the
+charge carriers of interest and provides dynamical information which is
+inaccessible through conventional magnetoconductance measurements. Here we
+develop a general time domain theory to describe the spin-dependent reaction of
+exciton-charge complexes following the coherent manipulation of paramagnetic
+centers through electron spin resonance. A general Hamiltonian is treated, and
+it is shown that the transition frequencies and resonance positions of the
+exciton-polaron complex can be used to estimate inter-species coupling. This
+work also provides a general formalism for analysing multi-pulse experiments
+which can be used to extract relaxation and transport rates.",1502.05470v1
+2015-02-23,Quantum metrology for the Ising Hamiltonian with transverse magnetic field,"We consider quantum metrology for unitary evolutions generated by
+parameter-dependent Hamiltonians. We focus on the unitary evolutions generated
+by the Ising Hamiltonian that describes the dynamics of a one-dimensional chain
+of spins with nearest-neighbour interactions and in the pres- ence of a global,
+transverse, magnetic field. We analytically solve the problem and show that the
+precision with which one can estimate the magnetic field (interaction strength)
+given one knows the interaction strength (magnetic field) scales at the
+Heisenberg limit, and can be achieved by a linear superposition of the vacuum
+and N free fermion states. In addition, we show that GHZ-type states exhibit
+Heisenberg scaling in precision throughout the entire regime of parameters.
+Moreover, we numerically observe that the optimal precision using a product
+input state scales at the standard quantum limit.",1502.06459v3
+2015-02-26,Coils and the Electromagnet Used in the Joule Balance at the NIM,"In the joule balance developed at National Institute of Metrology (NIM), the
+dynamic phase of a watt balance is replaced by the mutual inductance
+measurement in an attempt to provide an alternative method for the kg
+redefinition. But for this method a rather large current in the exciting coil,
+is needed to offer the necessary magnetic field in the force weighing phase,
+and the coil heating becomes an important uncertainty source. To reduce coil
+heating, a new coil system, in which a ferromagnetic material is used to
+increase the magnetic field was designed recently. But adopting the
+ferromagnetic material brings the difficulty from the nonlinear characteristic
+of material. This problem can be removed by measuring the magnetic flux linkage
+difference of the suspended coil at two vertical positions directly to replace
+the mutual inductance parameter. Some systematic effects of this magnet are
+discussed.",1502.07456v1
+2015-02-28,Distinct magnetic signatures of fractional vortex configurations in multiband superconductors,"Vortices carrying fractions of a flux quantum are predicted to exist in
+multiband superconductors, where vortex core can split between multiple
+band-specific components of the superconducting condensate. Using the
+two-component Ginzburg-Landau model, we examine such vortex configurations in a
+two-band superconducting slab in parallel magnetic field. The fractional
+vortices appear due to the band-selective vortex penetration caused by
+different thresholds for vortex entry within each band-condensate, and
+stabilize near the edges of the sample. We show that the resulting fractional
+vortex configurations leave distinct fingerprints in the static measurements of
+the magnetization, as well as in ac dynamic measurements of the magnetic
+susceptibility, both of which can be readily used for the detection of these
+fascinating vortex states in several existing multiband superconductors.",1503.00047v2
+2015-03-02,Dynamical chiral symmetry breaking in the NJL model with a constant external magnetic field,"In this paper we develop a new method that is different from Schwinger proper
+time method to deduce the fermion propagator with a constant external magnetic
+field. In the NJL model, we use this method to find out the gap equation at
+zero and non-zero temperature, and give the numerical results and phase diagram
+between magnetic field and temperature. Beside these, we also introduce current
+mass to study the susceptibilities, because there is a new parameter (the
+strength of external magnetic field) in this problem, corresponding this new
+parameter, we have defined a new susceptibility $\chi_B$ to compare with the
+other two susceptibilities $\chi_c$ (chiral susceptibility) and $\chi_T$
+(thermal susceptibility), and all of the three susceptibilities show than when
+current mass is not zero, the phase transition is a crossover, while for
+comparison, in the chiral limit, the susceptibilities show a second order phase
+transition. At last, we give out the critical coefficients of different
+susceptibilities in the chiral limit.",1503.00452v1
+2015-03-03,Magnetic Fields of Uranus and Neptune: Metallic Fluid Hydrogen,"The magnetic fields of the Ice Giant Planets Uranus and Neptune (U/N) are
+unique in the solar system. Based on a substantial database measured on Earth
+for representative planetary fluids at representative dynamic pressures up to
+200 GPa (2 Mbar) and a few 1000 K, the complex magnetic fields of U/N are (i)
+probably made primarily by degenerate metallic fluid H (MFH) at or near the
+crossover from the H-He envelopes to Ice cores at ~100 GPa (Mbar) pressures and
+normalized radii of ~90% of the radii of U/N; (ii) because those magnetic
+fields are made relatively close to the surfaces of U/N, non-dipolar fields can
+be expected; (iii) the Ice cores are most probably a heterogeneous fluid
+mixture of H, N, O, C, Fe/Ni and silicate-oxides and their mutual reaction
+products at high pressures and temperatures,as discussed elsewhere. Ironically,
+there is probably little nebular Ice in the Ice Giant Planets.",1503.01042v2
+2015-03-30,Broadband Setup for Magnetic-Field-Induced Domain Wall Motion in Cylindrical Nanowires,"In order to improve the precision of domain wall dynamics measurements, we
+develop a coplanar waveguide-based setup where the domain wall motion should be
+triggered by pulses of magnetic field. The latter are produced by the Oersted
+field of the waveguide as a current pulse travels toward its termination, where
+it is dissipated. Our objective is to eliminate a source of bias in domain wall
+speed estimation while optimizing the field amplitude. Here, we present
+implementations of this concept for magnetic force microscopy (MFM) and
+synchrotron-based investigation.",1503.08557v2
+2015-04-01,Direct observation and imaging of a spin-wave soliton with $p-$like symmetry,"The prediction and realization of magnetic excitations driven by electrical
+currents via the spin transfer torque effect, enables novel magnetic
+nano-devices where spin-waves can be used to process and store information. The
+functional control of such devices relies on understanding the properties of
+non-linear spin-wave excitations. It has been demonstrated that spin waves can
+show both an itinerant character, but also appear as localized solitons. So
+far, it was assumed that localized solitons have essentially cylindrical,
+$s-$like symmetry. Using a newly developed high-sensitivity time-resolved
+magnetic x-ray microscopy, we instead observe the emergence of a novel
+localized soliton excitation with a nodal line, i.e. with $p-$like symmetry.
+Micromagnetic simulations identify the physical mechanism that controls the
+transition from $s-$ to $p-$like solitons. Our results suggest a potential new
+pathway to design artificial atoms with tunable dynamical states using
+nanoscale magnetic devices.",1504.00144v1
+2015-04-01,All-magnetic control of skyrmions in nanowires by a spin wave,"Magnetic skyrmions are topologically protected nanoscale objects, which are
+promising building blocks for novel magnetic and spintronic devices. Here, we
+investigate the dynamics of a skyrmion driven by a spin wave in a magnetic
+nanowire. It is found that (i) the skyrmion is first accelerated and then
+decelerated exponentially; (ii) it can turn L-corners with both right and left
+turns; and (iii) it always turns left (right) when the skyrmion number is
+positive (negative) in the T- and Y-junctions. Our results will be the basis of
+skyrmionic devices driven by a spin wave.",1504.00409v2
+2015-04-09,Low-field microwave absorption and magnetoresistance in iron nanostructures grown by electrodeposition on n-type lightly-doped silicon substrates,"In this study we investigate magnetic properties, surface morphology and
+crystal structure in iron nanoclusters electrodeposited on lightly-doped (100)
+n-type silicon substrates. Our goal is to investigate the spin injection and
+detection in the Fe/Si lateral structures. The samples obtained under electric
+percolation were characterized by magnetoresistive and magnetic resonance
+measurements with cycling the sweeping applied field in order to understand the
+spin dynamics in the as-produced samples. The observed hysteresis in the
+magnetic resonance spectra, plus the presence of a broad peak in the
+non-saturated regime confirming the low field microwave absorption (LFMA), were
+correlated to the peaks and slopes found in the magnetoresistance curves. The
+results suggest long range spin injection and detection in low resistive
+silicon and the magnetic resonance technique is herein introduced as a
+promising tool for analysis of electric contactless magnetoresistive samples.",1504.02508v1
+2015-04-15,Buckling of paramagnetic chains in soft gels,"We study the magneto-elastic coupling behavior of paramagnetic chains in soft
+polymer gels exposed to external magnetic fields. To this end, a laser scanning
+confocal microscope is used to observe the morphology of the paramagnetic
+chains together with the deformation field of the surrounding gel network. The
+paramagnetic chains in soft polymer gels show rich morphological shape changes
+under oblique magnetic fields, in particular a pronounced buckling deformation.
+The details of the resulting morphological shapes depend on the length of the
+chain, the strength of the external magnetic field, and the modulus of the gel.
+Based on the observation that the magnetic chains are strongly coupled to the
+surrounding polymer network, a simplified model is developed to describe their
+buckling behavior. A coarse-grained molecular dynamics simulation model
+featuring an increased matrix stiffness on the surfaces of the particles leads
+to morphologies in agreement with the experimentally observed buckling effects.",1504.03884v1
+2015-04-20,"Electric field-induced magnetization switching in interface-coupled multiferroic heterostructures: A highly-dense, non-volatile, and ultra-low-energy computing paradigm","Electric-field induced magnetization switching in multiferroic
+magnetoelectric devices is promising for beyond Moore's law computing. We show
+here that interface-coupled multiferroic heterostructures, i.e., a
+ferroelectric layer coupled with a ferromagnetic layer, are particularly
+suitable for highly-dense, non-volatile, and ultra-low-energy computing. By
+solving stochastic Landau-Lifshitz-Gilbert equation of magnetization dynamics
+in the presence of room-temperature thermal fluctuations, we demonstrate that
+error-resilient switching of magnetization is possible in sub-nanosecond delay
+while expending a minuscule amount of energy of $\sim$1 attojoule. Such devices
+can be operated by drawing energy from the environment without the need for an
+external battery.",1504.05572v1
+2015-04-22,From pulsar scintillations to coronal heating: discontinuities in magnetohydrodynamics,"From pulsar scintillations we infer the presence of sheet-like structures in
+the ISM; it has been suggested that these are current sheets. Current sheets
+probably play an important role in heating the solar corona, and there is
+evidence for their presence in the solar wind. Such magnetic discontinuities
+have been found in numerical simulations with particular boundary conditions,
+as well as in simulations using an incompressible equation of state. Here, I
+investigate their formation under more general circumstances by means of
+topological considerations as well as numerical simulations of the relaxation
+of an arbitrary smoothly-varying magnetic field. The simulations are performed
+with a variety of parameters and boundary conditions: in low, high and
+of-order-unity plasma-$\beta$ regimes, with periodic and fixed boundaries, with
+and without a friction force, at various resolutions and with various
+diffusivities. Current sheets form, over a dynamical timescale, under {\it all}
+conditions explored. At higher resolution they are thinner, and there is a
+greater number of weaker current sheets. The magnetic field eventually relaxes
+into a smooth minimum energy state, the energy of which depends on the magnetic
+helicity, as well as on the nature of the boundaries.",1504.05952v1
+2015-04-23,The Tayler instability at low magnetic Prandtl numbers: between chiral symmetry breaking and helicity oscillations,"The Tayler instability is a kink-type, current driven instability that plays
+an important role in plasma physics but might also be relevant in liquid metal
+applications with high electrical currents. In the framework of the
+Tayler-Spruit dynamo model of stellar magnetic field generation, the question
+of spontaneous helical (chiral) symmetry breaking during the saturation of the
+Tayler instability has received considerable interest. Focusing on fluids with
+low magnetic Prandtl numbers, for which the quasistatic approximation can be
+applied, we utilize an integro-differential equation approach in order to
+investigate the saturation mechanism of the Tayler instability. Both the
+exponential growth phase and the saturated phase are analyzed in terms of the
+action of the alpha and beta effects of mean-field magnetohydrodynamics. In the
+exponential growth phase we always find a spontaneous chiral symmetry breaking
+which, however, disappears in the saturated phase. For higher degrees of
+supercriticality, we observe helicity oscillations in the saturated regime. For
+Lundquist numbers in the order of one we also obtain chiral symmetry breaking
+of the saturated magnetic field.",1504.06120v1
+2015-05-01,Real-time simulation of non-equilibrium transport of magnetization in large open quantum spin systems driven by dissipation,"Using quantum Monte Carlo, we study the non-equilibrium transport of
+magnetization in large open strongly correlated quantum spin $\frac{1}{2}$
+systems driven by purely dissipative processes that conserve the uniform or
+staggered magnetization. We prepare both a low-temperature Heisenberg
+ferromagnet and an antiferromagnet in two parts of the system that are
+initially isolated from each other. We then bring the two subsystems in contact
+and study their real-time dissipative dynamics for different geometries. The
+flow of the uniform or staggered magnetization from one part of the system to
+the other is described by a diffusion equation that can be derived
+analytically.",1505.00135v2
+2015-06-01,The Antisymmetry of Distortions,"Distortions are ubiquitous in nature. Under perturbations such as stresses,
+fields, or other changes, a physical system reconfigures by following a path
+from one state to another; this path, often a collection of atomic
+trajectories, describes a distortion. Here we introduce an antisymmetry
+operation called distortion reversal, 1*, that reverses a distortion pathway.
+The symmetry of a distortion pathway is then uniquely defined by a distortion
+group involving 1*; it has the same form as a magnetic group that involves time
+reversal, 1'. Given its isomorphism to magnetic groups, distortion groups could
+potentially have commensurate impact in the study of distortions as the
+magnetic groups have had in the study of magnetic structures. Distortion
+symmetry has important implications for a range of phenomena such as structural
+and electronic phase transitions, diffusion, molecular conformational changes,
+vibrations, reaction pathways, and interface dynamics.",1506.00325v1
+2015-06-01,Closing the hierarchy for non-Markovian magnetization dynamics,"We propose a stochastic approach for the description of the time evolution of
+the magnetization of nanomagnets, that interpolates between the
+Landau--Lifshitz--Gilbert and the Landau--Lifshitz--Bloch approximations, by
+varying the strength of the noise. In addition, we take into account the
+autocorrelation time of the noise and explore the consequences, when it is
+finite, on the scale of the response of the magnetization, i.e. when it may be
+described as colored, rather than white, noise and non-Markovian features
+become relevant. We close the hierarchy for the moments of the magnetization,
+by introducing a suitable truncation scheme, whose validity is tested by direct
+numerical solution of the moment equations and compared to the average deduced
+from a numerical solution of the corresponding stochastic Langevin equation. In
+this way we establish a general framework, that allows both coarse-graining
+simulations and faster calculations beyond the truncation approximation used
+here.",1506.00544v1
+2015-06-10,Emergent Coulombic criticality and Kibble-Zurek scaling in a topological magnet,"When a classical system is driven through a continuous phase transition, its
+nonequilibrium response is universal and exhibits Kibble-Zurek scaling. We
+explore this dynamical scaling in the novel context of a three-dimensional
+topological magnet with fractionalized excitations, namely the liquid-gas
+transition of the emergent mobile magnetic monopoles in dipolar spin ice. Using
+field-mixing and finite-size scaling techniques, we place the critical point of
+the liquid-gas line in the three-dimensional Ising universality class. We then
+demonstrate Kibble-Zurek scaling for sweeps of the magnetic field through the
+critical point. Unusually slow microscopic time scales in spin ice offer a
+unique opportunity to detect this universal nonequilibrium physics in current
+experimental setups.",1506.03472v2
+2015-06-25,Critical entropies and magnetic-phase-diagram analysis of ultracold three-component fermionic mixtures in optical lattices,"We study theoretically many-body equilibrium magnetic phases and
+corresponding thermodynamic characteristics of ultracold three-component
+fermionic mixtures in optical lattices described by the SU(3)-symmetric
+single-band Hubbard model. Our analysis is based on the generalization of the
+exact diagonalization solver for multicomponent mixtures that is used in the
+framework of the dynamical mean-field theory. It allows us to obtain a
+finite-temperature phase diagram with the corresponding transition lines to
+magnetically ordered phases at filling one particle per site (1/3 band filling)
+in simple cubic lattice geometry. Based on the developed theoretical approach,
+we also attain the necessary accuracy to study the entropy dependence in the
+vicinity of magnetically ordered phases that allows us to make important
+predictions for ongoing and future experiments aiming to approach and study
+long-range-order phases in ultracold atomic mixtures.",1506.07642v2
+2015-06-18,Separating read and write units in multiferroic devices,"Strain-mediated multiferroic composites, i.e., piezoelectric-magnetostrictive
+heterostructures, hold profound promise for energy-efficient computing in
+beyond Moore's law era. While reading a bit of information stored in the
+magnetostrictive nanomagnets using a magnetic tunnel junction (MTJ), a material
+selection issue crops up since magnetostrictive materials in general cannot be
+utilized as the free layer of the MTJ. This is an important issue since we need
+to achieve a high magnetoresistance for technological applications. We show
+here that magnetically coupling the magnetostrictive nanomagnet and the free
+layer e.g., utilizing the magnetic dipole coupling between them can circumvent
+this issue. By solving stochastic Landau-Lifshitz-Gilbert equation of
+magnetization dynamics in the presence of room-temperature thermal
+fluctuations, we show that such design can eventually lead to a superior
+energy-delay product.",1506.07865v1
+2015-07-11,Coherent nonhelical shear dynamos driven by magnetic fluctuations at low Reynolds numbers,"Nonhelical shear dynamos are studied with a particular focus on the
+possibility of coherent dynamo action. The primary results -- serving as a
+follow up to the results of Squire & Bhattacharjee [arXiv:1506.04109 (2015)] --
+pertain to the ""magnetic shear-current effect"" as a viable mechanism to drive
+large-scale magnetic field generation. This effect raises the interesting
+possibility that the saturated state of the small-scale dynamo could drive
+large-scale dynamo action, and is likely to be important in the unstratified
+regions of accretion disk turbulence. In this paper, the effect is studied at
+low Reynolds numbers, removing the complications of small-scale dynamo
+excitation and aiding analysis by enabling the use of quasi-linear statistical
+simulation methods. In addition to the magnetically driven dynamo, new results
+on the kinematic nonhelical shear dynamo are presented. These illustrate the
+relationship between coherent and incoherent driving in such dynamos,
+demonstrating the importance of rotation in determining the relative dominance
+of each mechanism.",1507.03154v1
+2015-08-04,Magnetic properties of light nuclei from lattice QCD,"After a short review of Lattice QCD methodology and techniques, I summarize
+recent results of Lattice QCD calculations of the interactions of nucleons and
+light nuclei with magnetic fields at pion masses of 805 MeV and 450 MeV.
+Interestingly, the magnetic moments are found to be consistent with the
+experimental values when given in terms of natural nuclear magnetons. The very
+low-energy cross section for $np\rightarrow d\gamma$ is calculated and found to
+agree with the experimental measurement. First calculations of the magnetic
+polarizabilities of light nuclei are presented, with a large isovector
+polarizability observed for the nucleon at these heavier pion masses.",1508.00892v1
+2015-08-04,Acoustic signatures of the phases and phase transitions in Yb$_2$Ti$_2$O$_7$,"We report on measurements of the sound velocity and attenuation in a single
+crystal of the candidate quantum- spin-ice material Yb$_2$Ti$_2$O$_7$ as a
+function of temperature and magnetic field. The acoustic modes couple to the
+spins magneto-elastically and, hence, carry information about the spin
+correlations that sheds light on the intricate magnetic phase diagram of
+Yb$_2$Ti$_2$O$_7$ and the nature of spin dynamics in the material.
+Particularly, we find a pronounced thermal hysteresis in the acoustic data with
+a concomitant peak in the specific heat indicating a possible first-order phase
+transition at about $0.17$ K. At low temperatures, the acoustic response to
+magnetic field saturates hinting at the development of magnetic order.
+Furthermore, mean-field calculations suggest that Yb$_2$Ti$_2$O$_7$ undergoes a
+first-order phase transition from a cooperative paramagnetic phase to a
+ferromagnet below $T\approx 0.17$ K.",1508.00925v1
+2015-08-06,Electromotive force due to magnetohydrodynamic fluctuations in sheared rotating turbulence,"This article presents a calculation of the mean electromotive force arising
+from general small-scale magnetohydrodynamical turbulence, within the framework
+of the second-order correlation approximation. With the goal of improving
+understanding of the accretion disk dynamo, effects arising through small-scale
+magnetic fluctuations, velocity gradients, density and turbulence
+stratification, and rotation, are included. The primary result, which
+supplements numerical findings, is that an off-diagonal turbulent resistivity
+due to magnetic fluctuations can produce large-scale dynamo action -- the
+magnetic analogue of the ""shear-current"" effect. In addition, consideration of
+$\alpha$ effects in the stratified regions of disks gives the puzzling result
+that there is no strong prediction for a sign of $\alpha$, since the effects
+due to kinetic and magnetic fluctuations, as well as those due to shear and
+rotation, are each of opposing signs and tend to cancel each other.",1508.01566v1
+2015-09-03,Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures,"We measure the dissipation and frequency shift of a magnetically coupled
+cantilever in the vicinity of a silicon chip, down to $25$ mK. The dissipation
+and frequency shift originates from the interaction with the unpaired
+electrons, associated with the dangling bonds in the native oxide layer of the
+silicon, which form a two dimensional system of electron spins. We approach the
+sample with a $3.43$ $\mu$m-diameter magnetic particle attached to an ultrasoft
+cantilever, and measure the frequency shift and quality factor as a function of
+temperature and the distance. Using a recent theoretical analysis [J. M. de
+Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting
+of a spin and a magnetic resonator, we are able to fit the data and extract the
+relaxation time $T_1=0.39\pm0.08$ ms and spin density $\sigma=0.14\pm0.01$
+spins per nm$^2$. Our analysis shows that at temperatures $\leq500$ mK magnetic
+dissipation is an important source of non-contact friction.",1509.01251v2
+2015-09-16,Variational principle for magnetisation dynamics in a temperature gradient,"By applying a variational principle on a magnetic system within the framework
+of extended irreversible thermodynamics, we find that the presence of a
+temperature gradient in a ferromagnet leads to a generalisation of the
+Landau-Lifshitz equation with an additional magnetic induction field
+proportional to the temperature gradient. This field modulates the damping of
+the magnetic excitation. It can increase or decrease the damping, depending on
+the orientation of the magnetisation wave-vector with respect to the
+temperature gradient. This variational approach confirms the existence of the
+Magnetic Seebeck effect which was derived from thermodynamics and provides a
+quantitative estimate of the strength of this effect.",1509.04825v2
+2015-09-16,A spin dynamics approach to solitonics,"It is spatial dispersion which is exclusively responsible for the emergence
+of exchange interaction and magnetic ordering. In contrast, magneto-crystalline
+anisotropy present in any realistic material brings in a certain non-linearity
+to the equation of motion. Unlike homogeneous ferromagnetic ordering a variety
+of non-collinear ground state configurations emerge as a result of competition
+among exchange, anisotropy, and dipole-dipole interaction. These particle-like
+states, e.g. magnetic soliton, skyrmion, domain wall, form a spatially
+localised clot of magnetic energy. In this paper we explore topologically
+protected magnetic solitons that might potentially be applied for logical
+operations and/or information storage in the rapidly advancing filed of
+solitonics (and skyrmionics). An ability to easily create, address, and
+manipulate such structures is among the prerequisite forming a basis of -onics
+technology, and is investigated in detail here using numerical and analytical
+tools.",1509.04860v2
+2015-09-23,Dirac Spin-Orbit Torques at the Surface of Topological Insulators,"We address the nature of spin-orbit torques at the magnetic surfaces of
+topological insulators, using both Kubo formula and Keldysh formalism. Through
+the analysis of the derived spin-charge equations, we find that the so-called
+Dirac torques possess a different symmetry compared to their Rashba
+counterpart, as well as a high anisotropy as a function of the magnetization
+direction. In particular, the damping torque vanishes when the magnetization
+lies in the plane of the topological insulator surface. This peculiarity has
+important consequences in terms of magnetization dynamics and switching, as
+demonstrated numerically via a macrospin model.",1509.06929v2
+2015-10-05,Continuous dynamical decoupling of a single diamond nitrogen-vacancy center spin with a mechanical resonator,"Inhomogeneous dephasing from uncontrolled environmental noise can limit the
+coherence of a quantum sensor or qubit. For solid state spin qubits such as the
+nitrogen-vacancy (NV) center in diamond, a dominant source of environmental
+noise is magnetic field fluctuations due to nearby paramagnetic impurities and
+instabilities in a magnetic bias field. In this work, we use ac stress
+generated by a diamond mechanical resonator to engineer a dressed spin basis in
+which a single NV center qubit is less sensitive to its magnetic environment.
+For a qubit in the thermally isolated subspace of this protected basis, we
+prolong the dephasing time $T_2^*$ from $2.7\pm0.1$ $\mu$s to $15\pm1$ $\mu$s
+by dressing with a $\Omega=581\pm2$ kHz mechanical Rabi field. Furthermore, we
+develop a model that quantitatively predicts the relationship between $\Omega$
+and $T_2^*$ in the dressed basis. Our model suggests that a combination of
+magnetic field fluctuations and hyperfine coupling to nearby nuclear spins
+limits the protected coherence time over the range of $\Omega$ accessed here.
+We show that amplitude noise in $\Omega$ will dominate the dephasing for larger
+driving fields.",1510.01194v1
+2015-10-13,Entropy produced by magnetic energy density fluctuations in the quiet Sun,"D.J. Evans, et al., [Phys. Rev. Lett. 71, 2401 (1993)] discovered a relation,
+subsequently known as the Fluctuation Theorem (FT), which quantifies the
+probability of observing fluctuations violating the second law of
+thermodynamics in thermostatted dissipative non-equilibrium systems. The FT has
+been confirmed experimentally for small systems. We analyze fluctuations of the
+total entropy production related to the distribution of the magnetic energy
+density in the quiet Sun lower atmosphere inferred by means of
+spectro-polarimetric observations. We show that the magnetic energy density is
+intermittent, at non-equilibrium and has the Markov property. The applicability
+of the FT is proven for the first time in an astronomical environment in spite
+of the seemingly large scales involved. We also found a non-linear behavior of
+the probability current, indicating that the dynamics of the magnetic field
+depends on the field strength. On average, however, the observed
+non-equilibrium behavior is governed by the second law of thermodynamics for
+open systems. Our results provide novel constraints for testing the
+hypothesizes of the solar local dynamo, which should be consistent with the
+inferred statistics of the fluctuations.",1510.03566v2
+2015-10-21,Strong field dynamo action in rapidly rotating convection with no inertia,"The Earth's magnetic field is generated by dynamo action driven by convection
+in the outer core. For numerical reasons, inertial and viscous forces play an
+important role in geodynamo models; however, the primary dynamical balance in
+the Earth's core is believed to be between buoyancy, Coriolis and magnetic
+forces. The hope has been that by setting the Ekman number to be as small as
+computationally feasible, an asymptotic regime would be reached in which the
+correct force balance is achieved. However, recent analyses of geodynamo models
+suggest that the desired balance has still not yet been attained. Here we adopt
+a complementary approach consisting of a model of rapidly rotating convection
+in which inertial forces are neglected from the outset. Within this framework
+we are able to construct a new branch of solutions in which the dynamo
+generates a strong magnetic field that satisfies the expected force balance.
+The resulting strongly magnetized convection is dramatically different to the
+corresponding solutions in which the field is weak.",1510.06220v2
+2015-10-23,Laser-induced THz magnetization precession for a tetragonal Heusler-like nearly compensated ferrimagnet,"Laser-induced magnetization precessional dynamics was investigated in
+epitaxial films of Mn$_3$Ge, which is a tetragonal Heusler-like nearly
+compensated ferrimagnet. The ferromagnetic resonance (FMR) mode was observed,
+the precession frequency for which exceeded 0.5 THz and originated from the
+large magnetic anisotropy field of approximately 200 kOe for this ferrimagnet.
+The effective damping constant was approximately 0.03. The corresponding
+effective Landau-Lifshitz constant of approximately 60 Mrad/s and is comparable
+to those of the similar Mn-Ga materials. The physical mechanisms for the
+Gilbert damping and for the laser-induced excitation of the FMR mode were also
+discussed in terms of the spin-orbit-induced damping and the laser-induced
+ultrafast modulation of the magnetic anisotropy, respectively.",1510.06793v1
+2015-10-23,"Fast, nanoscale addressability of nitrogen-vacancy spins via coupling to a dynamic ferromagnetic vortex","The core of a ferromagnetic vortex domain creates a strong, localized
+magnetic field which can be manipulated on nanosecond timescales, providing a
+platform for addressing and controlling individual nitrogen-vacancy center
+spins in diamond at room temperature, with nanometer-scale resolution. First,
+we show that the ferromagnetic vortex can be driven into proximity with a
+nitrogen-vacancy defect using small applied magnetic fields, inducing
+significant nitrogen-vacancy spin splitting. Second, we find that the magnetic
+field gradient produced by the vortex is sufficient to address spins separated
+by nanometer length scales. By applying a microwave-frequency magnetic field,
+we drive both the vortex and the nitrogen-vacancy spins, resulting in enhanced
+coherent rotation of the spin state. Finally we demonstrate that by driving the
+vortex on fast timescales, sequential addressing and coherent manipulation of
+spins is possible on $\sim100$ ns timescales.",1510.07073v2
+2015-10-26,A publicly available simulation of an enhanced network region of the Sun,"Context. The solar chromosphere is the interface between the solar surface
+and the solar corona. Modelling of this region is difficult because it
+represents the transition from optically thick to thin radiation escape, from
+gas-pressure domination to magnetic-pressure domination, from a neutral to an
+ionised state, from MHD to plasma physics, and from near-equilibrium (LTE) to
+non-equilibrium conditions.
+  Aims. Our aim is to provide the community with realistic simulations of the
+magnetic solar outer atmosphere. This will enable detailed comparison of
+existing and upcoming observations with synthetic observables from the
+simulations, thereby elucidating the complex interactions of magnetic fields
+and plasma that are crucial for our understanding of the dynamic outer
+atmosphere.
+  Methods. We used the radiation magnetohydrodynamics code Bifrost to perform
+simulations of a computational volume with a magnetic field topology similar to
+an enhanced network area on the Sun.
+  Results. The full simulation cubes are made available online. The general
+properties of the simulation are discussed, and limitations are discussed.",1510.07581v1
+2015-11-03,Luminosity of ultrahigh energy cosmic rays and bounds on magnetic luminosity of radio-loud active galactic nuclei,"We investigate the production of magnetic flux from rotating black holes in
+active galactic nuclei (AGNs) and compare it with the upper limit of ultrahigh
+energy cosmic ray (UHECR) luminosities, calculated from observed integral flux
+of GeV-TeV gamma rays for nine UHECR AGN sources. We find that, for the
+expected range of black hole rotations (0.44<a<0.80), the corresponding bounds
+of theoretical magnetic luminosities from AGNs coincides with the calculated
+UHECR luminosity. We argue that such result possibly can contribute to
+constrain AGN magnetic and dynamic properties as phenomenological tools to
+explain the requisite conditions to proper accelerate the highest energy cosmic
+rays.",1511.01003v1
+2015-11-13,The interface between heavy fermions and normal electrons investigated by spatially-resolved nuclear magnetic resonance,"We have studied the superlattices with alternating block layers (BLs) of
+heavy-fermion superconductor CeCoIn5 and conventional-metal YbCoIn5 by
+site-selective nuclear magnetic resonance(NMR) spectroscopy, which uniquely
+offers spatially-resolved dynamical magnetic information. We find that the
+presence of antiferromagnetic fluctuations is confined to the Ce-BLs,
+indicating that magnetic degrees of freedom of f-electrons are quenched inside
+the Yb-BLs. Contrary to simple expectations that the two-dimensionalization
+enhances fluctuations, we observe that antiferromagnetic fluctuations are
+rapidly suppressed with decreasing Ce-BL thickness. Moreover, the suppression
+is more prominent near the interfaces between the BLs. These results imply
+significant effects of local inversion-symmetry breaking at the interfaces.",1511.04209v1
+2015-11-19,Inverse problem in Parker's dynamo,"The inverse solution of the 1D Parker dynamo equations is considered. The
+method is based on minimization of the cost-function, which characterize
+deviation of the model solution properties from the desired ones. The output is
+the latitude distribution of the magnetic field generation sources: the
+$\alpha$- and $\omega$-effects. Minimization is made using the Monte-Carlo
+method. The details of the method, as well as some applications, which can be
+interesting for the broad dynamo community, are considered: conditions when the
+invisible for the observer at the surface of the planet toroidal part of the
+magnetic field is much larger than the poloidal counterpart. It is shown that
+at some particular distributions of $\alpha$ and $\omega$ the well-known thesis
+that sign of the dynamo-number defines equatorial symmetry of the magnetic
+field to the equator plane, is violated. It is also demonstrated in what
+circumstances magnetic field in the both hemispheres have different properties,
+and simple physical explanation of this phenomenon is proposed.",1511.06243v1
+2015-11-27,Magnetic properties of Fe$_{1-x}$Ni$_x$ alloy from CPA+DMFT perspectives,"We use a combination of the coherent potential approximation and dynamical
+mean field theory to study magnetic properties of the Fe$_{1-x}$Ni$_x$ alloy
+from a first principles. Calculated uniform magnetic susceptibilities have a
+Curie-Weiss-like behavior and extracted effective temperatures are in agreement
+with the experimental results. The individual squared magnetic moments obtained
+as function of nickel concentration follow the same trends as experimental
+data. An analysis of the ionic and spin weights shows a possibility of a
+high-spin to intermediate- and low-spin states transitions at high
+temperatures.",1511.08625v2
+2016-01-15,An electron motion induced by magnetic field pulse in bi-layer quantum wire,"We consider theoretically the possibility of an electron acceleration in
+quantum wire by short magnetic pulses lasted bewteen several to few tens of
+picoseconds. We show that such possibility exists provided that, the electron
+is initially localized in part of nanowire that consists of two vertically
+aligned layers which are tunnel coupled. When a horizontally directed magnetic
+field, changeable in time, is also perpendicular to the main axis of a wire, it
+generates a rotational electric field in it which pushes the upper and the
+lower parts of the electron wavepacket in opposite directions. We have found
+however, that for an asymmetric vertical confinement, the majority part of
+charge density starts to move in the direction of local electric field in its
+layer but it also drags the minority part in the same direction what results in
+coherent motion of an entire wavepacket. We discuss the dynamics of this motion
+in dependence on the time characteristics of the magnetic pulse.",1601.03880v1
+2016-02-04,The Global Solar Dynamo,"A brief summary of the various observations and constraints that underlie
+solar dynamo research are presented. The arguments that indicate that the solar
+dynamo is an alpha-omega dynamo of the Babcock-Leighton type are then shortly
+reviewed. The main open questions that remain are concerned with the subsurface
+dynamics, including why sunspots emerge at preferred latitudes as seen in the
+familiar butterfly wings, why the cycle is about 11 years long, and why the
+sunspot groups emerge tilted with respect to the equator (Joy's law). Next, we
+turn to magnetic helicity, whose conservation property has been identified with
+the decline of large-scale magnetic fields found in direct numerical
+simulations at large magnetic Reynolds numbers. However, magnetic helicity
+fluxes through the solar surface can alleviate this problem and connect theory
+with observations, as will be discussed.",1602.01754v1
+2016-02-12,Spin dynamics in the high-field phases of volborthite,"We report single-crystal 51V NMR studies on volborthite Cu3V2O7(OH)2 2H2O,
+which is regarded as a quasi-two-dimensional frustrated magnet with competing
+ferromagnetic and antiferromagnetic interactions. In the 1/3 magnetization
+plateau above 28 T, the nuclear spin-lattice relaxation rate 1/T1 indicates an
+excitation gap with a large effective g factor in the range of 4.6-5.9,
+pointing to magnon bound states. Below 26 T where the gap has closed, the NMR
+spectra indicate small internal fields with a Gaussian-like distribution,
+whereas 1/T1 shows a power-law-like temperature dependence in the paramagnetic
+state, which resembles a slowing down of spin fluctuations associated with
+magnetic order. We discuss the possibility of an exotic spin state caused by
+the condensation of magnon bound states below the magnetization plateau.",1602.04028v2
+2016-02-14,Ultra-sensitive nanoscale magnetic field sensors based on resonant spin filtering,"Solid state magnetic field sensors based on magneto-resistance modulation
+find direct applications in communication devices, specifically in proximity
+detection, rotational reference detection and current sensing. In this work, we
+propose sensor structures based on the magneto-resistance physics of resonant
+spin-filtering and present device designs catered toward exceptional magnetic
+field sensing capabilities. Using the non-equilibrium Green's function spin
+transport formalism self consistently coupled to the Poisson's equation, we
+present highly-tunable pentalayer magnetic tunnel junction structures that are
+capable of exhibiting an ultra-high peak tunnel magneto resistance $(\approx
+2500 \%$). We show how this translates to device designs featuring an
+ultra-high current sensitivity enhancement of over 300\% in comparison with
+typical trilayer MTJ sensors, and a wider tunable range of field sensitivity.
+We also demonstrate that a dynamic variation in sensor functionalities with the
+structural landscape enables a superior design flexibility over typical
+trilayer sensors. An optimal design exhibiting close to a 700\% sensitivity
+increase as a result of angle dependent spin filtering is then presented.This
+work sets a stage to engineer spintronic building blocks via the design of
+functional structures tailored to exhibit ultra-sensitive spin filtering.",1602.04438v1
+2016-02-17,Fermionic response from fractionalization in an insulating two-dimensional magnet,"Conventionally ordered magnets possess bosonic elementary excitations, called
+magnons. By contrast, no magnetic insulators in more than one dimension are
+known whose excitations are not bosons but fermions. Theoretically, some
+quantum spin liquids (QSLs) -- new topological phases which can occur when
+quantum fluctuations preclude an ordered state -- are known to exhibit Majorana
+fermions as quasiparticles arising from fractionalization of spins. Alas,
+despite much searching, their experimental observation remains elusive. Here,
+we show that fermionic excitations are remarkably directly evident in
+experimental Raman scattering data across a broad energy and temperature range
+in the two-dimensional material $\alpha$-RuCl$_3$. This shows the importance of
+magnetic materials as hosts of Majorana fermions. In turn, this first
+systematic evaluation of the dynamics of a QSL at finite temperature emphasizes
+the role of excited states for detecting such exotic properties associated with
+otherwise hard-to-identify topological QSLs.",1602.05277v1
+2016-02-23,Experimental Investigation of Temperature-Dependent Gilbert Damping in Permalloy Thin Films,"The Gilbert damping of ferromagnetic materials is arguably the most important
+but least understood phenomenological parameter that dictates real-time
+magnetization dynamics. Understanding the physical origin of the Gilbert
+damping is highly relevant to developing future fast switching spintronics
+devices such as magnetic sensors and magnetic random access memory. Here, we
+report an experimental study of temperature-dependent Gilbert damping in
+permalloy (Py) thin films of varying thicknesses by ferromagnetic resonance.
+From the thickness dependence, two independent contributions to the Gilbert
+damping are identified, namely bulk damping and surface damping. Of particular
+interest, bulk damping decreases monotonically as the temperature decreases,
+while surface damping shows an enhancement peak at the temperature of ~50 K.
+These results provide an important insight to the physical origin of the
+Gilbert damping in ultrathin magnetic films.",1602.07325v1
+2016-03-14,Merging droplets in double nano-contact spin torque oscillators,"We demonstrate how magnetic droplet soliton pairs, nucleated by two separated
+nano-contact (NC) spin torque oscillators, can merge into a single droplet
+soliton. A detailed description of the magnetization dynamics of this merger
+process is obtained by micromagnetic simulations: A droplet pair with a
+steady-state in-phase spin precession is generated through the spin-transfer
+torque effect underneath two separate NCs, followed by a gradual expansion of
+the droplets volume and the out phase of magnetization on the inner side of the
+two droplets, resulting in the droplets merging into a larger droplet. This
+merger occurs only when the NC separation is smaller than a critical value. A
+transient breathing mode is observed before the merged droplet stabilizes into
+a steady precession state. The precession frequency of the merged droplet is
+lower than that of the droplet pair, consistent with its larger size. Merged
+droplets can again break up into droplet pairs at high enough magnetic field
+with a strong hysteretic response.",1603.04133v1
+2016-03-16,Is the magnetic field making the inner crust of neutron stars more heterogeneous?,"We study the effect of strong magnetic fields, of the order of
+$10^{15}-10^{17}$ G, on the extension of the crust of magnetized neutron stars.
+The dynamical instability region of neutron-proton-electron ($npe$) matter at
+subsaturation densities and the mode with the largest growth rate are
+determined within a relativistic mean field model. It is shown that a strong
+magnetic field has a large effect on the instability region, defining the
+crust-core transition as a wide density range.",1603.05000v2
+2016-05-04,Magnetic moments of the hidden-charm pentaquark states,"The magnetic moment of a baryon state is an equally important dynamical
+observable as its mass, which encodes crucial information of its underlying
+structure. According to the different color-flavor structure, we have
+calculated the magnetic moments of the hidden-charm pentaquark states with
+$J^P={\frac{1}{2}}^{\pm}$, ${\frac{3}{2}}^{\pm}$, ${\frac{5}{2}}^{\pm}$ and
+${\frac{7}{2}}^{+}$ in the molecular model, the diquark-triquark model and the
+diquark-diquark-antiquark model respectively. Although a good description for
+the pentaquark mass spectrum and decay patterns has been obtained in all the
+three models, different color-flavor structures lead to different magnetic
+moments, which can be used to pin down their inner structures and distinguish
+various models.",1605.01337v3
+2016-05-19,Spatially Assisted Schwinger Mechanism and Magnetic Catalysis,"Using the worldline formalism we compute an effective action for fermions
+under a temporally modulated electric field and a spatially modulated magnetic
+field. It is known that the former leads to an enhanced Schwinger Mechanism,
+while we find that the latter can also result in enhanced particle production
+and even cause a reorganization of the vacuum to acquire a larger dynamical
+mass in equilibrium which spatially assists the Magnetic Catalysis.",1605.05957v3
+2016-06-03,General planar transverse domain walls realized by optimized transverse magnetic field pulses in magnetic biaxial nanowires,"We report the realization of a planar transverse domain wall (TDW) with
+arbitrary tilting angle in a magnetic biaxial nanowire under a transverse
+magnetic field (TMF) pulse with fixed strength and optimized orientation
+profile. We smooth any twisting in azimuthal angle plane of a TDW and thus
+completely decouple the polar and azimuthal degrees of freedom. The analytical
+differential equation that describes the polar angle distribution is then
+derived and the resulting solution is not a Walker-ansatz form. With this
+optimized TMF pulse comoving, the field-driven dynamics of the planar TDW is
+investigated. It turns out the comoving TMF pulse increases the wall velocity
+under the same axial driving field. These results will help to design a series
+of modern logic and memory nanodevices based on general planar TDWs.",1606.01046v2
+2016-06-06,Controlled Capillary Assembly of Magnetic Janus Particles at Fluid-Fluid Interfaces,"Capillary interactions can be used to direct assembly of particles adsorbed
+at fluid-fluid interfaces. Precisely controlling the magnitude and direction of
+capillary interactions to assemble particles into favoured structures for
+materials science purposes is desirable but challenging. In this paper, we
+investigate capillary interactions between magnetic Janus particles adsorbed at
+fluid-fluid interfaces. We develop a pair-interaction model that predicts that
+these particles should arrange into a side--side configuration, and carry out
+simulations that confirm the predictions of our model. Finally, we investigate
+the monolayer structures that form when many magnetic Janus particles adsorb at
+the interface. We find that the particles arrange into long, straight chains
+exhibiting little curvature, in contrast with capillary interactions between
+ellipsoidal particles. We further find a regime in which highly ordered,
+lattice-like monolayer structures form, which can be tuned dynamically using an
+external magnetic field.",1606.01646v2
+2016-06-08,Characterization of switching field distributions in Ising-like magnetic arrays,"The switching field distribution within arrays of single-domain ferromagnetic
+islands incorpo- rates both island-island interactions and quenched disorder in
+island geometry. Separating these two contributions is important for
+disentangling the effects of disorder and interactions in the magnetization
+dynamics of island arrays. Using sub-micron, spatially resolved Kerr imaging in
+an external magnetic field for islands with perpendicular magnetic anisotropy,
+we map out the evolution of island arrays during hysteresis loops. Resolving
+and tracking individual islands across four different lattice types and a range
+of inter-island spacings, we extract the individual switching fields of every
+island and thereby determine the relative contributions of interactions and
+quenched disorder in the arrays. The width of the switching field distribution
+is well explained by a simple model comprising the sum of an array-independent
+contribution (interpreted as disorder-induced), and a term proportional to the
+maximum field the fully polarized array could exert on a single island. We
+conclude that disorder in these arrays is primarily a single-island property.",1606.02770v1
+2016-06-17,Mechanical Actuation of Magnetic Domain-Wall Motion,"We theoretically study the motion of a magnetic domain wall induced by
+transverse elastic waves in a one-dimensional magnetic wire, which respects
+both rotational and translational symmetries. By invoking the conservation of
+the associated total angular and linear momenta, we are able to derive the
+torque and the force on the domain wall exerted by the waves. We then show how
+ferromagnetic and antiferromagnetic domain walls can be driven by circularly-
+and linear-polarized waves, respectively. We envision that elastic waves may
+provide effective means to drive the dynamics of magnetic solitons in
+insulators.",1606.05430v3
+2016-06-19,Viscoelasticity of model surfactant solutions determined by rotational magnetic spectroscopy,"Being able to reduce the size of a rheometer down to the micron scale is a
+unique opportunity to explore the mechanical response of expensive and/or
+confined liquids and gels. To this aim, we synthesize micron size wires with
+magnetic properties and examine the possibility of using them as microrheology
+probes. In this work, we exploit the technique of rotational magnetic
+spectroscopy by placing a wire in a rotating magnetic field and monitor its
+temporal evolution by time-lapse microscopy. The wire-based microrheology
+technique is tested on wormlike micellar surfactant solutions showing very
+different relaxation dynamics and viscosities. A model for the wire rotation is
+also developed and used to predict the wire behavior. It is shown that the
+rheological parameters of the surfactant solutions including the static shear
+viscosity, the entangled micellar network relaxation time and the elastic
+modulus are in good agreement with those of conventional rheometry.",1606.06667v1
+2016-07-06,Symmetries and Couplings of Non-Relativistic Electrodynamics,"We examine three versions of non-relativistic electrodynamics, known as the
+electric and magnetic limit theories of Maxwell's equations and Galilean
+electrodynamics (GED) which is the off-shell non-relativistic limit of Maxwell
+plus a free scalar field. For each of these three cases we study the couplings
+to non-relativistic dynamical charged matter (point particles and charged
+complex scalars). The GED theory contains besides the electric and magnetic
+potentials a so-called mass potential making the mass parameter a local
+function. The electric and magnetic limit theories can be coupled to twistless
+torsional Newton-Cartan geometry while GED can be coupled to an arbitrary
+torsional Newton-Cartan background. The global symmetries of the electric and
+magnetic limit theories on flat space consist in any dimension of the infinite
+dimensional Galilean conformal algebra and a $U(1)$ current algebra. For the
+on-shell GED theory this symmetry is reduced but still infinite dimensional,
+while off-shell only the Galilei algebra plus two dilatations remain. Hence one
+can scale time and space independently, allowing Lifshitz scale symmetries for
+any value of the critical exponent $z$.",1607.01753v2
+2016-07-08,Supercurrent-induced Skyrmion dynamics and Tunable Weyl points in Chiral Magnet with Superconductivity,"Recent studies show superconductivity provides new perspectives on
+spintronics. We study a heterostructure composed of an s-wave superconductor
+and a cubic chiral-magnet that can stabilize a topological spin texture, a
+skyrmion. We propose a supercurrent-induced spin torque that originates from
+the spin-orbit coupling, and we show that the spin torque can drive a skyrmion
+in an efficient way that reduces Joule heating. We also study the band
+structure of Bogoliubov quasiparticles and show the existence of Weyl points,
+whose positions can be controlled by the direction of the magnetization. This
+results in an effective magnetic field acting on the quasiparticles in the
+presence spin textures. Furthermore, the tilt of the Weyl cones can also be
+tuned by the strength of the spin-orbit coupling, and we propose a possible
+realization of type-II Weyl points.",1607.02336v4
+2016-07-10,On the motion of free interface in ideal incompressible MHD,"For the free boundary problem of the plasma-vacuum interface to
+three-dimensional ideal incompressible magnetohydrodynamics (MHD), the a priori
+estimates of smooth solutions are proved in Sobolev norms by adopting a
+geometrical point of view and some quantities such as the second fundamental
+form and the velocity of the free interface are estimated. In the vacuum
+region, the magnetic fields are described by the div-curl system of pre-Maxwell
+dynamics, while at the interface the total pressure is continuous and the
+magnetic fields are tangent to the interface, but we do not need any
+restrictions on the size of the magnetic fields on the free interface. We
+introduce the ""virtual particle"" endowed with a virtual velocity field in
+vacuum to reformulate the problem to a fixed boundary problem under the
+Lagrangian coordinates. The $L^2$-norms of any order covariant derivatives of
+the magnetic fields both in vacuum and on the boundaries are bounded in terms
+of initial data and the second fundamental forms of the free interface and the
+rigid wall. The estimates of the curl of the electric fields in vacuum are also
+obtained, which are also indispensable in elliptic estimates.",1607.02731v2
+2016-07-11,Boosting Magnetic Reconnection by Viscosity and Thermal Conduction,"Nonlinear evolution of magnetic reconnection is investigated by means of
+magnetohydrodynamic simulations including uniform resistivity, uniform
+viscosity, and anisotropic thermal conduction. When viscosity exceeds
+resistivity (the magnetic Prandtl number Prm > 1), the viscous dissipation
+dominates outflow dynamics and leads to the decrease in the plasma density
+inside a current sheet. The low-density current sheet supports the excitation
+of the vortex. The thickness of the vortex is broader than that of the current
+for Prm > 1. The broader vortex flow more efficiently carries the upstream
+magnetic flux toward the reconnection region, and consequently boosts the
+reconnection. The reconnection rate increases with viscosity provided that
+thermal conduction is fast enough to take away the thermal energy increased by
+the viscous dissipation (the fluid Prandtl number Pr < 1). The result suggests
+the need to control the Prandtl numbers for the reconnection against the
+conventional resistive model.",1607.02839v2
+2016-07-11,Magnetic Catalysis in Graphene Effective Field Theory,"We report on the first observation of magnetic catalysis at zero temperature
+in a fully nonperturbative simulation of the graphene effective field theory.
+Using lattice gauge theory, a nonperturbative analysis of the theory of
+strongly-interacting, massless, (2+1)-dimensional Dirac fermions in the
+presence of an external magnetic field is performed. We show that in the
+zero-temperature limit, a nonzero value for the chiral condensate is obtained
+which signals the spontaneous breaking of chiral symmetry. This result implies
+a nonzero value for the dynamical mass of the Dirac quasiparticle. This in turn
+has been posited to account for the quantum-Hall plateaus that are observed at
+large magnetic fields.",1607.03137v3
+2016-07-25,Magnetic-field effects on photon-induced quantum transport in a single dot-cavity system,"In this study, we show how a static magnetic field can control photon-induced
+electron transport through a quantum dot system coupled to a photon cavity. The
+quantum dot system is connected to two electron reservoirs and exposed to an
+external perpendicular static magnetic field. The propagation of electrons
+through the system is thus influenced by the static magnetic and the dynamic
+photon fields. It is observed that the photon cavity forms photon replica
+states controlling electron transport in the system. IF the photon field has
+more energy than the cyclotron energy, then the photon field is dominant in the
+electron transport. Consequently, the electron transport is enhanced due to
+activation of photon replica states. By contrast, the electron transport is
+suppressed in the system when the photon energy is smaller than the cyclotron
+energy.",1607.07201v1
+2016-07-27,Magnetic Collapse and the Behavior of Transition Metal Oxides at High Pressure,"We report a detail theoretical study of the electronic structure and phase
+stability of transition metal oxides MnO, FeO, CoO, and NiO in their
+paramagnetic cubic B1 structure by employing dynamical mean-field theory of
+correlated electrons combined with \emph{ab initio} band structure methods
+(DFT+DMFT). Our calculations reveal that under pressure these materials exhibit
+a Mott insulator-metal transition (IMT) which is accompanied by a simultaneous
+collapse of local magnetic moments and lattice volume, implying a complex
+interplay between chemical bonding and electronic correlations. Moreover, our
+results for the transition pressure show a monotonous decrease from ~ 145 GPa
+to 40 GPa, upon moving from MnO to CoO. In contrast to that, in NiO, magnetic
+collapse is found to occur at remarkably higher pressure of ~ 429 GPa. We
+provide a unified picture of such a behavior and suggest that it is primary a
+localized to itinerant moment behavior transition at the IMT that gives rise to
+magnetic collapse in transition metal oxides.",1607.08261v1
+2016-08-02,Lattice Field Theory Study of Magnetic Catalysis in Graphene,"We discuss the simulation of the low-energy effective field theory (EFT) for
+graphene in the presence of an external magnetic field. Our fully
+nonperturbative calculation uses methods of lattice gauge theory to study the
+theory using a hybrid Monte Carlo approach. We investigate the phenomenon of
+magnetic catalysis in the context of graphene by studying the chiral condensate
+which is the order parameter characterizing the spontaneous breaking of chiral
+symmetry. In the EFT, the symmetry breaking pattern is given by $U(4) \to U(2)
+\times U(2)$. We also comment on the difficulty, in this lattice formalism, of
+studying the time-reversal-odd condensate characterizing the ground state in
+the presence of a magnetic field. Finally, we study the mass spectrum of the
+theory, in particular the Nambu-Goldstone (NG) mode as well as the Dirac
+quasiparticle, which is predicted to obtain a dynamical mass.",1608.00666v1
+2016-08-10,The multiplicity problem for periodic orbits of magnetic flows on the 2-sphere,"We consider magnetic Tonelli Hamiltonian systems on the cotangent bundle of
+the 2-sphere, where the magnetic form is not necessarily exact. It is known
+that, on very low and on high energy levels, these systems may have only
+finitely many periodic orbits. Our main result asserts that almost all energy
+levels in a precisely characterized intermediate range $(e_0,e_1)$ possess
+infinitely many periodic orbits. Such a range of energies is non-empty, for
+instance, in the physically relevant case where the Tonelli Lagrangian is a
+kinetic energy and the magnetic form is oscillating (in which case, $e_0=0$ is
+the minimal energy of the system).",1608.03144v1
+2016-08-11,Effective perihelion advance and potentials in a conformastatic background with magnetic field,"An Exact solution of the Einstein-Maxwell field equations for a
+conformastatic metric with magnetized sources is study. In this context,
+effective potential are studied in order to understand the dynamics of the
+magnetic field in galaxies. We derive the equations of motion for neutral and
+charged particles in a spacetime background characterized by this class of
+solutions. In this particular case, we investigate the main physical properties
+of equatorial circular orbits and related effective potentials. In addition, we
+obtain an effective analytic expression for the perihelion advance of test
+particles. Our theoretical predictions are compared with the observational data
+calibrated with the ephemerides of the planets of the Solar system and the Moon
+(EPM2011). We show that, in general, the magnetic punctual mass predicts values
+that are in better agreement with observations than the values predicted in
+Einstein gravity alone.",1608.03813v1
+2016-08-16,Magnetic field generation by intermittent convection,"Magnetic field generation in three-dimensional Rayleigh-B\'enard convection
+of an electrically conducting fluid is studied numerically by fixing the
+Prandtl number at $P=0.3$ and varying the Rayleigh number (Ra) as a control
+parameter. A recently reported route to hyperchaos involving quasiperiodic
+regimes, crises and chaotic intermittent attractors is followed, and the
+critical magnetic Prandtl number ($P_m^c$) for dynamo action is determined as a
+function of Ra. A mechanism for the onset of intermittency in the magnetic
+energy is described, the most beneficial convective regimes for dynamo action
+in this transition to weak turbulence are identified, and the impact of
+intermittency on the dependence of $P_m^c$ on Ra is discussed.",1608.04716v2
+2016-08-25,The mimetic finite difference method for the Landau-Lifshitz equation,"The Landau-Lifshitz equation describes the dynamics of the magnetization
+inside ferromagnetic materials. This equation is highly nonlinear and has a
+non-convex constraint (the magnitude of the magnetization is constant) which
+pose interesting challenges in developing numerical methods. We develop and
+analyze explicit and implicit mimetic finite difference schemes for this
+equation. These schemes work on general polytopal meshes which provide enormous
+flexibility to model magnetic devices with various shapes. A projection on the
+unit sphere is used to preserve the magnitude of the magnetization. We also
+provide a proof that shows the exchange energy is decreasing in certain
+conditions. The developed schemes are tested on general meshes that include
+distorted and randomized meshes. The numerical experiments include a test
+proposed by the National Institute of Standard and Technology and a test
+showing formation of domain wall structures in a thin film.",1608.07309v1
+2016-08-29,High-Energy Neutrino Emission from White Dwarf Mergers,"The merger of two white dwarfs is expected to result in a central fast
+rotating core surrounded by a debris disk, in which magnetorotational
+instabilities give rise to a hot magnetized corona and a magnetized outflow.
+The dissipation of magnetic energy via reconnection could lead to the
+acceleration of cosmic-rays in the expanding material, which would result in
+high energy neutrinos. We discuss the possibility of using these neutrino
+signals as probes of the outflow dynamics, magnetic energy dissipation rate and
+cosmic-ray acceleration efficiency. Importantly, the accompanying high-energy
+gamma-rays are absorbed within these sources because of the large optical
+depth, so these neutrino sources can be regarded as hidden cosmic-ray
+accelerators that are consistent with the non-detection of gamma-rays with
+Fermi-LAT. While the cosmic-ray generation rate is highly uncertain, if it
+reaches $\sim10^{45}\,\rm erg\,Mpc^{-3}\,yr^{-1}$, the diffuse neutrino flux
+could contribute a substantial fraction of the IceCube observations. We also
+evaluate the prospect of observing individual merger events, which provides a
+means for testing such sources in the future.",1608.08150v2
+2016-09-06,Chiral charge pumping in graphene deposited on a magnetic insulator,"We demonstrate that a sizable chiral charge pumping can be achieved at room
+temperature in graphene/Yttrium Iron Garnet (YIG) bilayer systems. The effect,
+which cannot be attributed to the ordinary spin pumping, reveals itself in the
+creation of a dc electric field/voltage in graphene as a response to the
+dynamic magnetic excitations (spin waves) in an adjacent out-of-plane
+magnetized YIG film. We show that the induced voltage changes its sign when the
+orientation of the static magnetization is reversed, clearly indicating the
+broken spatial inversion symmetry in the studied system. The strength of effect
+shows a non-monotonous dependence on the spin-wave frequency, in agreement with
+the proposed theoretical model.",1609.01613v2
+2016-09-21,Level anti-crossing spectra of nitrogen-vacancy centers in diamond detected by using modulation of the external magnetic field,"We report a study of the magnetic field dependence of the photo-luminescence
+of NV$^-$ centers (negatively charged nitrogen-vacancy centers) in diamond
+single crystals. In such a magnetic field dependence characteristic lines are
+observed, which are coming from Level Anti-Crossings (LACs) in the coupled
+electron-nuclear spin system. For enhancing the sensitivity, we used lock-in
+detection to measure the photo-luminescence intensity and observed a remarkably
+strong dependence of the LAC-derived lines on the modulation frequency. Upon
+decreasing of the modulation frequency from 12 kHz to 17 Hz the amplitude of
+the lines increases by approximately two orders of magnitude. To take a
+quantitative account for such effects, we developed a theoretical model, which
+describes the spin dynamics in the coupled electron-nuclear spin system under
+the action of an oscillating external magnetic field. Good agreement between
+experiments and theory allows us to conclude that the observed effects are
+originating from coherent spin polarization exchange in the NV$^-$ center. Our
+results are of great practical importance allowing one to optimize the
+experimental conditions for probing LAC-derived lines in diamond defect
+centers.",1609.06661v1
+2016-10-06,Spin-torque switching and control using chirped oscillating currents,"We propose to use oscillating spin currents with slowly varying frequency
+(chirp) to manipulate and control the magnetization dynamics in a nanomagnet.
+By recasting the Landau-Lifshitz-Slonczewski equation in a quantum-like
+two-level formalism, we show that a chirped spin current polarized in the
+direction normal to the anisotropy axis can induce a stable precession of the
+magnetic moment at any angle (up to $90^\circ$) with respect to the anisotropy
+axis. The drive current can be modest ($10^6\,\rm A/cm^2$ or lower) provided
+the chirp rate is sufficiently slow. The induced precession is stable against
+thermal noise, even for small nano-objects at room temperature. Complete
+reversal of the magnetization can be achieved by adding a small external
+magnetic field antiparallel to the easy axis. Alternatively, a combination of
+chirped ac and dc currents with different polarization directions can also be
+used to trigger the reversal.",1610.01819v2
+2016-10-08,Transitions in a magnetized quasi-laminar spherical Couette Flow,"First results of a new spherical Couette experiment are presented. The liquid
+metal flow in a spherical shell is exposed to a homogeneous axial magnetic
+field. For a Reynolds number Re=1000, we study the effect of increasing
+Hartmann number Ha. The resulting flow structures are inspected by ultrasound
+Doppler velocimetry. With a weak applied magnetic field, we observe an
+equatorially anti-symmetric jet instability with azimuthal wave number m=3. As
+the magnetic field strength increases, this instability vanishes. When the
+field is increased further, an equatorially symmetric return flow instability
+arises. Our observations are shown to be in good agreement with linear
+stability analysis and non-linear flow simulations.",1610.02571v3
+2016-10-10,Magnetic concentrations in stratified turbulence: the negative effective magnetic pressure instability,"In the presence of strong density stratification, hydromagnetic turbulence
+attains qualitatively new properties: the formation of magnetic flux
+concentrations. We review here the theoretical foundations of this mechanism in
+terms of what is now called the negative effective magnetic pressure
+instability. We also present direct numerical simulations of forced turbulence
+in strongly stratified layers and discuss the qualitative and quantitative
+similarities with corresponding mean-field simulations. Finally, the relevance
+to sunspot formation is discussed.",1610.03459v3
+2016-10-30,Time-Resolved Studies of the Spin-Transfer Reversal Mechanism in Perpendicularly Magnetized Magnetic Tunnel Junctions,"Pulsed spin-torque switching has been studied using single-shot time-resolved
+electrical measurements in perpendicularly magnetized magnetic tunnel junctions
+as a function of pulse amplitude and junction size in 50 to 100 nm diameter
+circular junctions. The mean switching time depends inversely on pulse
+amplitude for all junctions studied. However, the switching dynamics is found
+to be strongly dependent on junction size and pulse amplitude. In 50 nm
+diameter junctions the switching onset is stochastic but the switching once
+started, is fast; after being initiated it takes less than 2 ns to switch. In
+larger diameter junctions the time needed for complete switching is strongly
+dependent on the pulse amplitude, reaching times less than 2 ns at large pulse
+amplitudes. Anomalies in the switching rate versus pulse amplitude are shown to
+be associated with the long lived (> 2 ns) intermediate junction resistance
+states.",1610.09710v1
+2016-11-02,Current-induced skyrmion generation and dynamics in symmetric bilayers,"Magnetic skyrmions are textures behaving as quasiparticles which are
+topologically different from other states. Their discovery in systems with
+broken inversion symmetry sparked the search for materials containing such
+magnetic phase at room temperature. Their topological properties combined with
+the chirality-related spin-orbit torques make them interesting objects to
+control the magnetization at nanoscale. Here we show that a pair of coupled
+skyrmions with the same topological charge and opposite chiralities can be
+stabilized in a symmetric magnetic bilayer system by combining
+Dzyaloshinskii-Moriya interaction (DMI) and dipolar coupling effects. This
+effect opens a new path for skyrmion stabilization with much lower DMI. We then
+demonstrate in a single device with two different electrodes that such
+skyrmions can be efficiently and independently written and shifted by electric
+current at large velocities. The skyrmionic nature of the observed
+quasiparticles is further confirmed by using the gyrotropic force as a
+topological filter. These results set the ground for emerging spintronic
+technologies where issues concerning skyrmion stability, nucleation, and
+propagation are paramount.",1611.00647v2
+2016-11-14,Off-equilibrium scaling driven by a time-dependent magnetic field in O(N) vector models,"We investigate the off-equilibrium dynamics of a spin system with O($N$)
+symmetry in $2 < d < 4$ spatial dimensions arising by the presence of a slowly
+varying time-dependent magnetic field $h(t,t_s) \sim t/t_s$, $t_s$ is a time
+scale, at the critical temperature $T = T_c$ and below it $T < T_c$. After
+showing the general theory, we demonstrate the off-equilibrium scaling and we
+formally compute the correlation functions in the limit of large $N$. We derive
+the off-equilibrium scaling relations for the hysteresis loop area and for the
+magnetic work done by the system when the magnetic field $h(t,t_s)$ is varied
+across the phase transitions cyclically in time. We also investigate the first
+deviations from the equilibrium behavior in the correlation functions checking
+the consistence for an exponential approach.",1611.04367v1
+2016-11-15,On the formation of a stable penumbra in a region of flux emergence in the Sun,"We studied the formation of the first penumbral sector around a pore in the
+following polarity of the Active Region (AR) NOAA 11490. We used a high
+spatial, spectral, and temporal resolution data set acquired by the
+Interferometric BIdimensional Spectrometer operating at the NSO/Dunn Solar
+Telescope as well as data taken by the Helioseismic and Magnetic Imager onboard
+the Solar Dynamics Observatory satellite. On the side towards the leading
+polarity, elongated granules in the photosphere and an arch filament system
+(AFS) in the chromosphere are present, while the magnetic field shows a
+sea-serpent configuration, indicating a region of magnetic flux emergence. We
+found that the formation of a stable penumbra in the following polarity of the
+AR begins in the area facing the opposite polarity located below the AFS in the
+flux emergence region, differently from what found by Schlichenmaier and
+colleaguestbf. Moreover, during the formation of the first penumbral sector,
+the area characterized by magnetic flux density larger than 900 G and the area
+of the umbra increase.",1611.04749v1
+2016-11-22,Azimuthal Magnetorotational Instability at low and high magnetic Prandtl numbers,"The magnetorotational instability (MRI) is considered to be one of the most
+powerful sources of turbulence in hydrodynamically stable quasi-Keplerian
+flows, such as those governing accretion disk flows. Although the linear
+stability of these flows with applied external magnetic field has been studied
+for decades, the influence of the instability on the outward angular momentum
+transport, necessary for the accretion of the disk, is still not well known. In
+this work we model Keplerian rotation with Taylor-Couette flow and imposed
+azimuthal magnetic field using both linear and nonlinear approaches. We present
+scalings of instability with Hartmann and Reynolds numbers via linear analysis
+and direct numerical simulations (DNS) for the two magnetic Prandtl numbers of
+$1.4 \cdot 10^{-6}$ and $1$. Inside of the instability domains modes with
+different axial wavenumbers dominate, resulting in sub-domains of
+instabilities, which appear different for each $Pm$. The DNS show the emergence
+of 1- and 2-frequency spatio-temporally oscillating structures for $Pm=1$ close
+the onset of instability, as well as significant enhancement of angular
+momentum transport for $Pm=1$ as compared to $Pm=1.4 \cdot 10^{-6}$.",1611.07296v1
+2016-11-23,MESL: Proposal for a Non-volatile Cascadable Magneto-Electric Spin Logic,"In the quest for novel, scalable and energy-efficient computing technologies,
+many non-charge based logic devices are being explored. Recent advances in
+multi-ferroic materials have paved the way for electric field induced low
+energy and fast switching of nano-magnets using the magneto-electric (ME)
+effect. In this paper, we propose a voltage driven logic-device based on the ME
+induced switching of nano-magnets. We further demonstrate that the proposed
+logic-device, which exhibits decoupled read and write paths, can be used to
+construct a complete logic family including XNOR, NAND and NOR gates. The
+proposed logic family shows good scalability with a quadratic dependence of
+switching energy with respect to the switching voltage. Further, the proposed
+logic-device has better robustness against the effect of thermal noise as
+compared to the conventional current driven switching of nano-magnets. A
+device-to-circuit level coupled simulation framework, including magnetization
+dynamics and electron transport model, has been developed for analyzing the
+present proposal. Using our simulation framework, we present energy and delay
+results for the proposed Magneto-Electric Spin Logic (MESL) gates.",1611.07738v1
+2016-11-27,Positive Quantum Magnetoresistance in Tilted Magnetic Field,"Transport properties of highly mobile 2D electrons are studied in symmetric
+GaAs quantum wells placed in titled magnetic fields. Quantum positive
+magnetoresistance (QPMR) is observed in magnetic fields perpendicular to the 2D
+layer. Application of in-plane magnetic field produces a dramatic decrease of
+the QPMR. This decrease correlates strongly with the reduction of the amplitude
+of Shubnikov de Haas resistance oscillations due to modification of the
+electron spectrum via enhanced Zeeman splitting. Surprisingly no quantization
+of the spectrum is detected when the Zeeman energy exceeds the half of the
+cyclotron energy suggesting an abrupt transformation of the electron dynamics.
+Observed angular evolution of QPMR implies strong mixing between spin subbands.
+Theoretical estimations indicate that in the presence of spin-orbital
+interaction the elastic impurity scattering provides significant contribution
+to the spin mixing in GaAs quantum wells at high filling factors.",1611.08890v1
+2016-11-30,Energy Conservation and the Chiral Magnetic Effect,"We analyze the chiral magnetic effect in a homogeneous neutral plasma from
+the point of view of energy conservation, and construct an effective potential
+for the growth of maximally helical perturbations of the electromagnetic field.
+We show that a negative curvature at the origin of the potential, indicating
+instability of the plasma, is induced by a chiral asymmetry in electron Fermi
+energy, as opposed to number density, while the potential grows at large field
+value. It follows that the ground state for a plasma has zero magnetic
+helicity; a nonzero electron mass will allow an excited state of a plasma with
+nonzero helicity to relax to that ground state quickly. We conclude that a
+chiral plasma instability triggered by weak interactions is not a viable
+mechanism for explaining magnetic fields in stars except possibly when dynamics
+drives the system far from equilibrium.",1612.00032v2
+2017-01-07,Torsion effects on Condensed Matter: like a magnetic field but not so much,"In this work, we study the effects of torsion due to a uniform distribution
+of topological defects (screw dislocations) on free spin/carrier dynamics in
+elastic solids. When a particle moves in such a medium, the effect of the
+torsion associated to the defect distribution is analogous to that of an
+applied magnetic field but with subtle differences. Analogue Landau levels are
+present in this system but they cannot be confined to two dimensions. In the
+case of spinless carriers, zero modes, which do not appear in the magnetic
+Landau levels, show up for quantized values of the linear momentum projected on
+the defects axis. Particles with spin are subjected to a Zeeman-like coupling
+between spin and torsion, which is insensitive to charge. This suggests the
+possibility of spin resonance experiments without a magnetic field for charged
+carriers or quasiparticles without electrical charge, like triplet excitons,
+for instance.",1701.01829v1
+2017-01-07,A quantitative description of Nernst effect in high-temperature superconductors,"A quantitative vortex-fluid model for flux-flow resistivity $\rho$ and Nernst
+signal $e_N$ in high-temperature superconductors (HTSC) is proposed. Two kinds
+of vortices, magnetic and thermal, are considered, and the damping viscosity
+$\eta$ is modeled by extending the Bardeen-Stephen model to include the
+contributions of flux pinning at low temperature and in weak magnetic fields,
+and vortex-vortex collisions in strong magnetic fields. Remarkably accurate
+descriptions for both Nernst signal of six samples and flux flow resistivity
+are achieved over a wide range of temperature $T$ and magnetic field $B$. A
+discrepancy of three orders of magnitude between data and Anderson's model of
+Nernst signal is pointed out and revised using experimental values of $\eta$
+from magnetoresistance. Furthermore, a two-step procedure is developed to
+reliably extract, from the Nernst signal, a set of physical parameters
+characterizing the vortex dynamics, which yields predictions of local
+superfluid density $n_s$, the Kosterlitz coefficient $b$ of thermal vortices,
+and upper critical field and temperature. Application of the model and
+systematic measurement of relevant physical quantities from Nernst signal in
+other HTSC samples are discussed.",1701.01832v1
+2017-01-26,Precision determination of a fluxoid quantum's magnetic moment in a superconducting micro-ring,"Using dynamic cantilever magnetometry and experimentally determining the
+cantilever's vibrational mode shape, we precisely measured the magnetic moment
+of a lithographically defined micron-sized superconducting Nb ring, a key
+element for the previously proposed subpiconewton force standard. The magnetic
+moments due to individual magnetic fluxoids and a diamagnetic response were
+independently determined at T = 4.3 K, with a subfemtoampere-square-meter
+resolution. The results show good agreement with the theoretical estimation
+yielded by the Brandt and Clem model within the spring constant determination
+accuracy.",1701.07598v1
+2017-02-09,Second-order chiral kinetic theory: Chiral magnetic and pseudomagnetic waves,"The consistent chiral kinetic theory accurate to the second order in
+electromagnetic and pseudoelectromagnetic fields is derived for a relativistic
+matter with two Weyl fermions. By making use of such a framework, the
+properties of longitudinal collective excitations, which include both chiral
+magnetic and chiral pseudomagnetic waves, are studied. It is shown that the
+proper treatment of dynamical electromagnetism transforms these gapless waves
+into chiral (pseudo)magnetic plasmons, whose Langmuir (plasma) gap receives
+corrections quadratic in both magnetic and pseudomagnetic fields.",1702.02950v2
+2017-02-26,Chiral Magnetic Effect in a Lattice Model,"We study analytically the one-loop contribution to the Chiral Magnetic
+Effect(CME) using lattice regularization with a Wilson fermion field. In the
+continuum limit, we find that the chiral magnetic current vanishes at nonzero
+temperature but emerges at zero temperature consistent with that found by
+Pauli-Villas regularization. For finite lattice size, however, the chiral
+magnetic current is nonvanishing at nonzero temperature. But the numerical
+vaule of the coefficient of CME current is very small compared with that
+extracted from the full QCD simulation for the same lattice parameters. The
+possibility of higher order corrections from QCD dynamics is also assessed.",1702.07980v1
+2017-03-03,Magnetic field induced polarization enhancement in monolayers of tungsten dichalcogenides: Effects of temperature,"Optical orientation of localized/bound excitons is shown to be effectively
+enhanced by the application of magnetic fields as low as 20 mT in monolayer
+WS$_2$. At low temperatures, the evolution of the polarization degree of
+different emission lines of monolayer WS$_2$ with increasing magnetic fields is
+analyzed and compared to similar results obtained on a WSe$_2$ monolayer. We
+study the temperature dependence of this effect up to $T=60$ K for both
+materials, focusing on the dynamics of the valley pseudospin relaxation. A rate
+equation model is used to analyze our data and from the analysis of the width
+of the polarization deep in magnetic field we conclude that the competition
+between the dark exciton pseudospin relaxation and the decay of the dark
+exciton population into the localized states are rather different in these two
+materials which are representative of the two extreme cases for the ratio of
+relaxation rate and depolarization rate.",1703.01129v1
+2017-03-18,A thermodynamically consistent model of magneto-elastic materials under diffusion at large strains and its analysis,"The theory of elastic magnets is formulated under possible diffusion and heat
+flow governed by Fick's and Fourier's laws in the deformed (Eulerian)
+configuration, respectively. The concepts of nonlocal nonsimple materials and
+viscous Cahn-Hilliard equations are used. The formulation of the problem uses
+Lagrangian (reference) configuration while the transport processes are pulled
+back. Except the static problem, the demagnetizing energy is ignored and only
+local non-selfpenetration is considered. The analysis as far as existence of
+weak solutions of the (thermo)dynamical problem is performed by a careful
+regularization and approximation by a Galerkin method, suggesting also a
+numerical strategy. Either ignoring or combining particular aspects, the model
+has numerous applications as ferro-to-paramagnetic transformation in elastic
+ferromagnets, diffusion of solvents in polymers possibly accompanied by
+magnetic effects (magnetic gels), or metal-hydride phase transformation in some
+intermetalics under diffusion of hydrogen accompanied possibly by magnetic
+effects (and in particular ferro-to-antiferromagnetic phase transformation),
+all in the full thermodynamical context under large strains.",1703.06267v2
+2017-04-01,Ferrofluids and magnetically guided superparamagnetic particles in flows: A review of simulations and modeling,"Ferrofluids are typically suspensions of magnetite nanoparticles, and behave
+as a homogeneous continuum. The production of nanoparticles with a narrow size
+distribution and the achievement of colloidal stability are important
+technological issues. The ability of the ferrofluid to respond to an external
+magnetic field in a controllable manner has made it emerge as a smart material
+in a variety of applications, such as seals, lubricants, electronics cooling,
+shock absorbers and adaptive optics. Magnetic nanoparticle suspensions have
+also gained attraction recently in a range of biomedical applications, such as
+cell separation, hyperthermia, MRI, drug targeting and cancer diagnosis. In
+this review, we provide an introduction to mathematical modeling of three
+problems: motion of superparamagnetic nanoparticles in magnetic drug targeting,
+the motion of a ferrofluid drop consisting of chemically bound nanoparticles
+without a carrier fluid, and the breakage of a thin film of a ferrofluid.",1704.00104v1
+2017-04-05,The role of boundary conditions on helicoidal flow collimation: consequences for the Von-Kármán-Sodium dynamo experiment,"We present hydrodynamic and magneto-hydrodynamic simulations of liquid sodium
+flow with the PLUTO compressible MHD code to investigate influence of magnetic
+boundary conditions on the collimation of helicoidal motions. We use a
+simplified cartesian geometry to represent the flow dynamics in the vicinity of
+one cavity of a multi-blades impeller inspired by those used in the
+Von-K\'{a}rm\'{a}n-Sodium (VKS) experiment. We show that the impinging of the
+large scale flow upon the impeller generates a coherent helicoidal vortex
+inside the blades, located at a distance from the upstream blade piloted by the
+incident angle of the flow. This vortex collimates any existing magnetic field
+lines leading to an enhancement of the radial magnetic field that is stronger
+for ferromagnetic than for conducting blades. The induced magnetic field
+modifies locally the velocity fluctuations, resulting in an enhanced helicity.
+This process possibly explains why dynamo action is more easily triggered in
+the VKS experiment when using soft iron impellers.",1704.01637v1
+2017-04-11,Gluon Spectrum in Quark-Gluon Plasma under Strong Magnetic Fields,"We obtain the general expression of the gluon propagator at finite
+temperature ($T$) and in a magnetic field ($B$), for the case that the four
+transverse tensor structures appear in the gluon self-energy. By using this
+expression and a specific form of the one-loop gluon self-energy in the lowest
+Landau level approximation, we analyze the gluon spectrum in the strong
+magnetic field limit. As a result, we find that there exist two collective
+excitations of which the energies are of the order of $p\sim gT$ with $g$ being
+the coupling constant. One of the two excitations enjoys properties quite
+different from those of the collective excitations at $B=0$ which have been
+discussed by using the hard thermal loop approximation. We also discuss the
+static and dynamical screening effects, which are expected to be important for
+computation of transport coefficients in strong magnetic fields.",1704.03191v3
+2017-04-23,Photonic orbital angular momentum transfer and magnetic skyrmion rotation,"Magnetic skyrmions are chiral quasiparticles that show promise for future
+spintronic applications such as skyrmion racetrack memories and logic devices
+because of their topological stability, small size (typically $\sim3-500$ nm),
+and ultralow threshold force to drive their motion. On the other hand, the
+ability of light to carry and deliver orbital angular momentum (OAM) in the
+form of optical vortices has attracted a lot of interest. In this work, we
+predict a photonic OAM transfer effect, by studying the dynamics of magnetic
+skyrmions subject to Laguerre-Gaussian optical vortices, which manifests a
+rotational motion of the skyrmionic quasiparticle around the beam axis. The
+topological charge of the optical vortex determines both the magnitude and the
+handedness of the rotation velocity of skyrmions. In our proposal, the twisted
+light beam acts as an optical tweezer to enable us displacing skyrmions over
+large-scale defects in magnetic films to avoid being captured.",1704.06926v3
+2017-05-05,Kinetic orbital moments and nonlocal transport in disordered metals with nontrivial geometry,"We study the effects of spatial dispersion in disordered noncentrosymmetric
+metals. These include the kinetic magnetoelectric effect, natural optical
+activity of metals, as well as the so-called dynamic chiral magnetic effect as
+a particular case of the latter. These effects are determined by the linear in
+the wave vector of an electromagnetic perturbation contribution to the
+conductivity tensor of a material, and stem from the magnetic moments of
+quasiparticles near the Fermi surface. We identify new disorder-induced
+contributions to these magnetic moments that come from the skew scattering and
+side jump processes, familiar from the theory of anomalous Hall effect. We show
+that at low frequencies the spatial dispersion of the conductivity tensor comes
+mainly either from the skew scattering or intrinsic contribution, and there is
+always a region of frequencies in which the intrinsic mechanism dominates. Our
+results imply that in clean three-dimensional metals, current-induced
+magnetization is in general determined by impurity skew scattering, rather than
+intrinsic contributions. Intrinsic effects are expected to dominate in cubic
+enantiomorphic crystals with point groups $T$ and $O$, and in polycrystalline
+samples, regardless of their mobility.",1705.02367v1
+2017-05-09,Low spin wave damping in the insulating chiral magnet Cu$_{2}$OSeO$_{3}$,"Chiral magnets with topologically nontrivial spin order such as Skyrmions
+have generated enormous interest in both fundamental and applied sciences. We
+report broadband microwave spectroscopy performed on the insulating chiral
+ferrimagnet Cu$_{2}$OSeO$_{3}$. For the damping of magnetization dynamics we
+find a remarkably small Gilbert damping parameter of about $1\times10^{-4}$ at
+5 K. This value is only a factor of 4 larger than the one reported for the best
+insulating ferrimagnet yttrium iron garnet. We detect a series of sharp
+resonances and attribute them to confined spin waves in the mm-sized samples.
+Considering the small damping, insulating chiral magnets turn out to be
+promising candidates when exploring non-collinear spin structures for high
+frequency applications.",1705.03416v1
+2017-05-10,Long-time coherence in fourth-order spin correlation functions,"We study the long-time decay of fourth-order electron spin correlation
+functions for an isolated singly charged semi-conductor quantum dot. The
+electron spin dynamics is governed by the applied external magnetic field as
+well as the hyperfine interaction. While the long-time coherent oscillations in
+the correlation functions can be understood within an semi-classical approach
+treating the Overhauser field as frozen, the field dependent decay of its
+amplitude reported in different experiments cannot be explained by the
+central-spin model indicating the insufficiency of such a description. By
+incorporating the nuclear Zeeman splitting and the strain induced
+nuclear-electric quadrupolar interaction, we find the correct crossover from a
+fast decay in small magnetic fields to a slow exponential asymptotic in large
+magnetic fields. It originates from a competition between the quadrupolar
+interaction inducing an enhanced spin decay and the nuclear Zeeman term that
+suppressed the spin-flip processes. We are able to explain the magnetic field
+dependency of the characteristic long-time decay time $T_2$ depending on the
+experimental setups. The calculated asymptotic values of $T_2 = 3 -4\,\mu$s
+agree qualitatively well with the experimental data.",1705.03712v2
+2017-05-15,Momentum-dependent susceptibilities and magnetic exchange in bcc iron from supercell DMFT calculations,"We analyze the momentum- and temperature dependences of the magnetic
+susceptibilities and magnetic exchange interaction in paramagnetic bcc iron by
+a combination of density functional theory and dynamical mean-field theory
+(DFT+DMFT). By considering a general derivation of the orbital-resolved
+effective model for spin degrees of freedom for Hund's metals, we relate
+momentum-dependent susceptibilities in the paramagnetic phase to the magnetic
+exchange. We then calculate non-uniform orbital-resolved susceptibilities at
+high-symmetry wave vectors by constructing appropriate supercells in the DMFT
+approach. Extracting the irreducible parts of susceptibilities with respect to
+Hund's exchange interaction, we determine the corresponding orbital-resolved
+exchange interactions, which are then interpolated to the whole Brillouin zone.
+Using the spherical model we estimate the temperature dependence of the
+resulting exchange between local moments.",1705.05296v2
+2017-06-01,Dynamo enhancement and mode selection triggered by high magnetic permeability,"We present results from consistent dynamo simulations, where the electrically
+conducting and incompressible flow inside a cylinder vessel is forced by moving
+impellers numerically implemented by a penalization method. The numerical
+scheme models jumps of magnetic permeability for the solid impellers,
+resembling various configurations tested experimentally in the von-Karman
+Sodium experiment. The most striking experimental observations are reproduced
+in our set of simulations. In particular, we report on the existence of an
+axisymmetric dynamo mode, self-consistently generated when the magnetic
+permeability of the impellers exceeds a threshold. We describe a possible
+scenario involving both the turbulent flow in the vicinity of the impellers and
+the high magnetic permeability of the impellers.",1706.00260v4
+2017-06-13,Experimental Observation of Bethe Strings,"Almost one century ago, string states - complex bound states (Wellenkomplexe)
+of magnetic excitations - have been predicted to exist in one-dimensional
+quantum magnets and since then become a subject of intensive theoretical study.
+However, experimental realization and identification of string states in
+condensed-matter systems remains an unsolved challenge up to date. Here we use
+high-resolution terahertz spectroscopy to identify string states in the
+antiferromagnetic Heisenberg-Ising chain SrCo2V2O8 in strong longitudinal
+magnetic fields. We observe complex bound states (strings) and fractional
+magnetic excitations (psinons and antipsinons) in the field-induced critical
+regime, which are precisely described by the Bethe ansatz. Our study reveals
+that two-string and three-string states govern the quantum spin dynamics close
+to the quantum criticality, while the fractional excitations are dominant at
+low energies, reflecting the antiferromagnetic quantum fluctuations.",1706.04181v1
+2017-06-09,Chiral edge mode in the coupled dynamics of magnetic solitons in a honeycomb lattice,"Motivated by a recent experimental demonstration of a chiral edge mode in an
+array of spinning gyroscopes, we theoretically study the coupled gyration modes
+of topological magnetic solitons, vortices and magnetic bubbles, arranged as a
+honeycomb lattice. The soliton lattice under suitable conditions is shown to
+support a chiral edge mode like its mechanical analogue, the existence of which
+can be understood by mapping the system to the Haldane model for an electronic
+system. The direction of the chiral edge mode is associated with the
+topological charge of the constituent solitons, which can be manipulated by an
+external field or by an electric-current pulse. The direction can also be
+controlled by distorting the honeycomb lattice. Our results indicate that the
+lattices of magnetic solitons can serve as reprogrammable topological
+metamaterials.",1706.04187v2
+2017-06-14,Characteristics of Bi(Pb)SrCaCuO superconducting ceramics samples properties by method of dynamic magnetic susceptibility measurements,"Literature and experimental data about practical determination of phase
+composition and structure of BiHTSC ceramics from results of measurements of
+temperature dependence of magnetic susceptibility are presented. It is shown
+that Bi2223 to Bi2212 phases ratio, calculated by XRD-analysis results, does
+not correlate precisely with magnetic susceptibility - temperature dependence.
+Phase, which is present in smaller amount, especially Bi2212 phase with lower
+critical temperature, appears less pronouncedly at the magnetic susceptibility
+- temperature dependence. Besides, limiting parts of Meissner effect
+manifestation are peculiarities of contacts of superconducting grains.
+Different kinds of such contacts lead to lowering the critical temperature
+together with conservation of narrow transition interval, to division of
+transition into stages, and to increasing of transition interval. Among
+negative consequences of this influence there are hindrances in realization of
+grain oriented Bi ceramics synthesis scheme which imply powdering of samples
+consisting of chaotically evolved grains of Bi2223 phase, ordered placement of
+obtained plate grains of this phase - for example, through vibration
+compacting, and sintering.",1706.04420v1
+2017-06-15,Exploring the Statistics of Magnetic Reconnection X-points in Kinetic Particle-in-Cell (PIC) Turbulence,"Magnetic reconnection is a ubiquitous phenomenon in turbulent plasmas. It is
+an important part of the turbulent dynamics and heating of space and
+astrophysical plasmas. We examine the statistics of magnetic reconnection using
+a quantitative local analysis of the magnetic vector potential, previously used
+in magnetohydrodynamics simulations, and now generalized to fully kinetic PIC
+simulations. Different ways of reducing the particle noise for analysis
+purposes including multiple smoothing techniques are explored. We find that a
+Fourier filter applied at the Debye scale is an optimal choice for analyzing
+PIC data. Finlay, we find a broader distribution of normalized reconnection
+rates compared to the MHD limit with rates as large as 0.5 but with an average
+of approximately 0.1.",1706.04905v1
+2017-07-03,Anisotropic chiral magnetic effect from tilted Weyl cones,"We determine the antisymmetric current-current response for a pair of (type
+I) tilted Weyl cones with opposite chirality. We find that the dynamical chiral
+magnetic effect depends on the magnitude of the tilt and on the angle between
+the tilting direction and the wave vector of the magnetic field. Additionally,
+the chiral magnetic effect is shown to be closely related to the presence of an
+intrinsic anomalous Hall effect with a current perpendicular to the tilting
+direction and the electric field. We investigate the nonanalytic
+long-wavelength limit of the corresponding transport coefficients.",1707.00598v2
+2017-07-06,Strong angular dependent transmission ratio due to interplay between spin waves and the domain wall in perpendicular magnetic anisotropy materials,"Spin waves (SW) can induce rich domain wall (DW) motion in a
+perpendicular-magnetic anisotropy nanostrip. In-plane magnetization tilt angle
+resulting from the fluctuation of the effective field of the magnetization
+response in the DW region plays an essential role in the dynamics of SW
+interacting with a DW. We performed simulation and found that the transmission
+ratio of the propagating SW across the DW depends strongly on the tilt angle in
+the low-frequency regime. The material parameters and the geometrical
+configuration can be fine-tuned for practical devices.",1707.01617v1
+2017-07-18,Solitary potentials in a three component space plasma,"The heavy ion acoustic solitary waves (HIASWs) in a magnetized,
+collisionless, three component space plasma system in the presence of dynamical
+heavy particles and bi-kappa distributed two distinct temperature of electrons
+has been carried out. The Korteweg-de Vries (K-dV), the modified K-dV (mK-dV),
+and the further mK-dV (fmK-dV) equations are derived by employing the well
+known reductive perturbation method. The basic features of HIASWs (speed,
+amplitude, width etc.) are found to be significantly modified by the effects of
+number density of plasma species, superthermal electrons with two distinct
+temperatures and the magnetic field (obliqueness). The K-dV and fm-KdV solitons
+exhibit both compressive and rarefactive structures, whereas the mK-dV solitons
+support only compressive structures. In order to trace the vicinity of the
+critical heavy ion density, neither the magnetized KdV nor magnetized mKdV
+equation is suitable for describing the HIASWs. Therefore, we have considered a
+higher order nonlinearity to describe the solitary profiles by deriving fmK-dV
+equation. The implication of our results in some space and laboratory plasma
+situations are concisely discussed.",1707.05571v1
+2017-07-23,Investigating different $Λ$ and $\barΛ$ polarizations in relativistic heavy-ion collisions,"Based on the chiral kinetic equations of motion, spin polarizations of
+various quarks, due to the magnetic field induced by spectator protons as well
+as the quark-antiquark vector interaction, are studied within a partonic
+transport approach. Although the magnetic field in QGP enhances the splitting
+of the spin polarizations of partons compared to the results under the magnetic
+field in vacuum, the spin polarizations of $s$ and $\bar s$ quarks are also
+sensitive to the quark-antiquark vector interaction, challenging that the
+different $\Lambda$ and $\bar \Lambda$ spin polarization is a good measure of
+the magnetic field in relativistic heavy-ion collisions. It is also found that
+there is no way to obtain the large splitting of the spin polarization between
+$\Lambda$ and $\bar \Lambda$ at $\sqrt{s_{NN}}=7.7$ GeV with partonic dynamics.",1707.07262v3
+2017-07-30,Multi-second magnetic coherence in a single domain spinor Bose-Einstein condensate,"We describe a compact, robust and versatile system for studying magnetic
+dynamics in a spinor Bose-Einstein condensate. Condensates of 87 Rb are
+produced by all-optical evaporation in a 1560 nm optical dipole trap, using a
+non-standard loading sequence that employs an auxiliary 1529 nm beam for
+partial compensation of the strong differential light shift induced by the
+dipole trap itself. We use near-resonance Faraday rotation probing to
+non-destructively track the condensate magnetization, and demonstrate
+few-Larmor-cycle tracking with no detectable degradation of the spin
+polarization. In the ferromagnetic F = 1 ground state, we observe magnetic T1
+and T2$^*$ coherence times limited only by the several-second residence time of
+the atoms in the trap.",1707.09607v1
+2017-08-02,Non-equilibrium 2D Ising model with stationary uphill diffusion,"Usually, in a non-equilibrium setting, a current brings mass from the highest
+density regions to the lowest density ones. Although rare, the opposite
+phenomenon (known as ""uphill diffusion"") has also been observed in
+multicomponent systems, where it appears as an artificial effect of the
+interaction among components. We show here that uphill diffusion can be a
+substantial effect, i.e. it may occur even in single component systems as a
+consequence of some external work. To this aim we consider the 2D ferromagnetic
+Ising model in contact with two reservoirs that fix, at the left and the right
+boundaries, magnetizations of the same magnitude but of opposite signs. We
+provide numerical evidence that a class of non-equilibrium steady states exists
+in which, by tuning the reservoir magnetizations, the current in the system
+changes from ""downhill"" to ""uphill"". Moreover, we also show that, in such
+non-equilibrium set-up, the current vanishes precisely when the reservoir
+magnetizations equal the magnetization of the corresponding equilibrium
+dynamics, thus establishing a novel relation between equilibrium and
+non-equilibrium properties.",1708.00751v3
+2017-08-12,Effects of equatorial chorus wave normal azimuthal distribution on wave propagation,"The non-ducted propagation characteristics of the VLF waves in the inner
+magnetosphere were studied with respect to their frequency, source
+localization, and initial wave normal angle, between the wave-normal and the
+background magnetic field. The ray tracing software based on multi-components
+cold plasma approach was developed by use of the IGRF magnetic field model and
+the GCPM model of plasma density. We described dynamics of the wave-normals
+direction during its propagation and magnetospheric reflection. We showed that
+whistler waves can be reflected when lower hybrid resonance frequency becomes
+greater than the wave frequency: w_LH>w. It corresponds to the magnetic
+latitude of ~50 degrees. The simulation results confirmed the inapplicability
+of the quasi-longitudinal approximation to describe the propagation of
+magnetospheric whistlers. The simulation results of chorus emissions
+propagation, which used realistic distributions of waves on the initial
+parameters were presented. Particularly, we obtained distributions of chorus
+emission waves in dependence on the wave-normal directions for different
+magnetic latitudes. It is required for studying diffusive processes in the
+radiation belts. The results were found to be in a good agreement with the
+CLUSTER STAFF-SA measurements.",1708.03819v1
+2017-08-22,Direct observation of domain wall surface tension by deflating or inflating a magnetic bubble,"The surface energy of a magnetic Domain Wall (DW) strongly affects its static
+and dynamic behaviours. However, this effect was seldom directly observed and
+many related phenomena have not been well understood. Moreover, a reliable
+method to quantify the DW surface energy is still missing. Here, we report a
+series of experiments in which the DW surface energy becomes a dominant
+parameter. We observed that a semicircular magnetic domain bubble could
+spontaneously collapse under the Laplace pressure induced by DW surface energy.
+We further demonstrated that the surface energy could lead to a geometrically
+induced pinning when the DW propagates in a Hall cross or from a nanowire into
+a nucleation pad. Based on these observations, we developed two methods to
+quantify the DW surface energy, which could be very helpful to estimate
+intrinsic parameters such as Dzyaloshinskii-Moriya Interactions (DMI) or
+exchange stiffness in magnetic ultra-thin films.",1708.06719v1
+2017-08-29,Spin Dynamics in a Stripe-ordered Buckled Honeycomb Lattice Antiferromagnet Ba$_{2}$NiTeO$_{6}$,"We carried out inelastic neutron scattering experiments on a buckled
+honeycomb lattice antiferromagnet Ba$_{2}$NiTeO$_{6}$ exhibiting a stripe
+structure at a low temperature. Magnetic excitations are observed in the energy
+range of $\hbar \omega \lesssim 10$ meV having an anisotropy gap of 2 meV at 2
+K. We perform spin-wave calculations to identify the spin model. The obtained
+microscopic parameters are consistent with the location of the stripe structure
+in the classical phase diagram. Furthermore, the Weiss temperature
+independently estimated from a bulk magnetic susceptibility is consistent with
+the microscopic parameters. The results reveal that a competition between the
+NN and NNN interactions that together with a relatively large single ion
+magnetic anisotropy stabilize the stripe magnetic structure.",1708.08717v1
+2017-08-29,Ultrafast hot-electron induced quenching of Tb4f magnetic order,"We have investigated ultrafast quenching of the Tb4f magnetic order in
+Co74Tb26 alloys, induced by femtosecond hot-electrons pulses. The hot-electron
+pulses were produced in specific non-magnetic capping layers by infrared fs
+laser pulses. Our experimental results show that sub-picosecond dynamics of
+Tb4f magnetic moments can be induced by non-thermal and thermal hot-electrons.
+We further demonstrate that the demagnetization efficiencies of non-thermal and
+thermal hot electrons are similar. However, the characteristic demagnetization
+times show values of 0.35 ps for non-thermal hot-electrons excitations and 1.2
+ps for thermal hot-electrons excitations. We explain this temporal elongation
+by the propagation time of thermal hot-electrons through the 15 nm thick CoTb
+film.",1708.08919v2
+2017-09-07,Tunable spin pumping in exchange coupled magnetic trilayers,"Magnetic thin films at ferromagnetic resonance (FMR) leak angular momentum,
+which may be absorbed by adjacent layers. This phenomenon, known as spin
+pumping, is manifested by an increase in the resonance linewidth ($\Delta H$),
+and the closely related Gilbert damping. Another effect of this transfer of
+spin currents is a dynamical and long-range coupling that can drive two
+magnetic layers into a collective precession when their FMR frequencies
+coincide. A collective behavior is also found in magnetic trilayers with
+interlayer exchange coupling (IEC). In this study we investigate the interplay
+between IEC and spin pumping, using Co/Cu/Py pseudo-spin values. We employ
+broadband FMR spectroscopy to explore both the frequency and coupling-strength
+dependence of $\Delta H$. Our observations show that there exists a cut-off
+frequency, set by the IEC strength, below which the precession is truly
+collective and the spin pumping is suppressed. These results demonstrate that
+it is possible to control the spin pumping efficiency by varying the frequency
+or the interlayer exchange coupling.",1709.02295v1
+2017-09-11,Manipulating magnetism by ultrafast control of the exchange interaction,"In recent years, the optical control of exchange interactions has emerged as
+an exciting new direction in the study of the ultrafast optical control of
+magnetic order. Here we review recent theoretical works on antiferromagnetic
+systems, devoted to i) simulating the ultrafast control of exchange
+interactions, ii) modeling the strongly nonequilibrium response of the magnetic
+order and iii) the relation with relevant experimental works developed in
+parallel. In addition to the excitation of spin precession, we discuss examples
+of rapid cooling and the control of ultrafast coherent longitudinal spin
+dynamics in response to femtosecond optically induced perturbations of exchange
+interactions. These elucidate the potential for exploiting the control of
+exchange interactions to find new scenarios for both faster and more
+energy-efficient manipulation of magnetism.",1709.03343v2
+2017-09-28,Magnetic monopoles and nonassociative deformations of quantum theory,"We examine certain nonassociative deformations of quantum mechanics and
+gravity in three dimensions related to the dynamics of electrons in uniform
+distributions of magnetic charge. We describe a quantitative framework for
+nonassociative quantum mechanics in this setting, which exhibits new effects
+compared to ordinary quantum mechanics with sourceless magnetic fields, and the
+extent to which these theoretical consequences may be experimentally testable.
+We relate this theory to noncommutative Jordanian quantum mechanics, and show
+that its underlying algebra can be obtained as a contraction of the alternative
+algebra of octonions. The uncontracted octonion algebra conjecturally describes
+a nonassociative deformation of three-dimensional quantum gravity induced by
+magnetic monopoles, which we propose is realised by a non-geometric
+Kaluza-Klein monopole background in M-theory.",1709.10080v2
+2017-10-07,Thermodynamics of dyonic black holes with Thurston horizon geometries,"In five dimensions, we consider a model described by the Einstein gravity
+with a source given by a scalar field and various Abelian gauge fields with
+dilatonic-like couplings. For this model, we are able to construct two dyonic
+black holes whose three-dimensional horizons are modeled by two nontrivial
+homogeneous Thurston's geometries. The dyonic solutions are of Lifshitz type
+with an arbitrary value of the dynamical exponent. In fact, the first gauge
+field ensures the anisotropy asymptotic while the remaining Abelian fields
+sustain the electric and magnetic charges. Using the Hamiltonian formalism, the
+mass, the electric and magnetic charges are explicitly computed. Interestingly
+enough, the dyonic solutions behave like Chern-Simons vortices in the sense
+that their electric and magnetic charges turn to be proportional. The extension
+with an hyperscaling violating factor is also scrutinized where we notice that
+for specific values of the violating factor, purely magnetic solutions are
+possible.",1710.02720v2
+2017-10-26,"Coherent transport structures in magnetized plasmas, I : Theory","In a pair of linked articles (called Article I and II respectively) we apply
+the concept of Lagrangian Coherent Structures (LCSs) borrowed from the study of
+Dynamical Systems to magnetic field configurations in order to separate regions
+where field lines have different kind of behaviour. In the present article,
+article I, after recalling the definition and the properties of the LCSs, we
+show how this conceptual framework can be applied to the study of particle
+transport in a magnetized plasma. Futhermore we introduce a simplified model
+that allows us to consider explicitly the case where the magnetic configuration
+evolves in time on timescales comparable to the particle transit time through
+the configuration. In contrast with previous works on this topic, this analysis
+requires that a system that is aperiodic in time be investigated. In this case
+the Poincar\'e map technique cannot be applied and LCSs remain the only viable
+tool.",1710.09815v2
+2017-10-27,Single shot all optical switching of intrinsic micron size magnetic domains of a Pt/Co/Pt ferromagnetic stack,"We demonstrate that the magnetization reversal in a ferromagnetic Pt/Co/Pt
+stack can be induced by a single femtosecond laser pulse. We find that the size
+of the switched spot is comparable to the size of the intrinsic magnetic
+domains. It requires an absorbed energy density of $\sim$4 mJ.cm$^{-2}$, beyond
+which the excited spot fragments into a multidomain structure. The switching
+process occurs back and forth with subsequent laser pulses and it is
+helicity-independent. Furthermore, the dynamics of the magnetization reversal
+occurs in a timescale less than one microsecond. These results suggest that all
+optical switching in ferromagnetic films requires to match the laser spot with
+the specific domain sizes.",1710.10341v1
+2017-11-03,A Study of Acoustic Halos in Active Region NOAA 11330 using Multi-Height SDO Observations,"We analyze data from the Helioseismic Magnetic Imager (HMI) and the
+Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics
+Observatory (SDO) to characterize the spatio-temporal acoustic power
+distribution in active regions as a function of the height in the solar
+atmosphere. For this, we use Doppler velocity and continuum intensity observed
+using the magnetically sensitive line at 6173 \AA\ as well as intensity at 1600
+\AA\ and 1700 \AA. We focus on the power enhancements seen around AR 11330 as a
+function of wave frequency, magnetic field strength, field inclination and
+observation height. We find that acoustic halos occur above the acoustic cutoff
+frequency and extends up to 10 mHz in HMI Doppler and AIA 1700 \AA\
+observations. Halos are also found to be strong functions of magnetic field and
+their inclination angle. We further calculate and examine the spatially
+averaged relative phases and cross-coherence spectra and find different wave
+characteristics at different heights.",1711.01259v1
+2017-11-06,"First-principles study of magnetism, lattice dynamics, and superconductivity in LaFeSiH$_x$","The structural, electronic, magnetic, and vibrational properties of
+LaFeSiH$_x$ for $x$ between 0 and 1 are investigated using density functional
+calculations. We find that the electronic and magnetic properties are strongly
+controlled by the hydrogen concentration $x$ in LaFeSiH$_x$. While fully
+hydrogenated LaFeSiH has a striped antiferromagnetic ground state, the
+underdoped LaFeSiH$_x$ for $x\leq0.75$ is not magnetic within the virtual
+crystal approximation or with explicit doping of supercells. The
+antiferromagnetic configuration breaks the symmetry of Fe $d$ orbitals and
+increases electron-phonon coupling up to $50\%$, especially for modes in the
+20-50 meV range that are associated with Fe atomic movement. We find competing
+nearest and next-nearest neighbor exchange interactions and significant
+spin-phonon coupling, qualitatively similar but smaller in magnitude compared
+those found in LaOFeAs superconductors. The superconducting $T_c$ for
+antiferromagnetic LaFeSiH$_x$, assuming conventional superconductivity via
+McMillan's equation, therefore is computed to be 2-10 K, in contrast to
+$T_c\approx0$ for the nonmagnetic material. We also predict that the
+LaFeSiH$_x$ could be a good proton conductor due to phase stability with a wide
+range of hydrogen concentration $x < 1$.",1711.01764v1
+2017-11-14,Observation of vortex-nucleated magnetization reversal in individual ferromagnetic nanotubes,"The reversal of a uniform axial magnetization in a ferromagnetic nanotube
+(FNT) has been predicted to nucleate and propagate through vortex domains
+forming at the ends. In dynamic cantilever magnetometry measurements of
+individual FNTs, we identify the entry of these vortices as a function of
+applied magnetic field and show that they mark the nucleation of magnetization
+reversal. We find that the entry field depends sensitively on the angle between
+the end surface of the FNT and the applied field. Micromagnetic simulations
+substantiate the experimental results and highlight the importance of the ends
+in determining the reversal process. The control over end vortex formation
+enabled by our findings is promising for the production of FNTs with tailored
+reversal properties.",1711.05164v1
+2017-11-16,Direct URCA Processes in Supernovae and Accretion Disks with Arbitrary Magnetic Field,"An effect of a magnetic field of an arbitrary strength on the beta-decay and
+reactions related with it by the crossing symmetry (the beta-processes) in
+supernovae and accretion disks around black holes is analyzed. Rates of the
+beta-processes and the energy and momentum transfered through them to an
+optically transparent matter are calculated. It is shown that the macroscopic
+momentum transferred to the medium increases linearly with the magnetic field
+strength and can substantially affect the dynamics of supernovae and accretion
+disks especially when a matter inside is degenerate. It is also demonstrated
+that the rates of the beta-processes and the energy deposition in these
+reactions for the magnetic field strength $B \lesssim 10^{15}$ G, which is
+assumed to be typical in supernovae and accretion disks, are lower than in the
+absence of the field. This suppression is more pronounced for reactions with
+neutrinos.",1711.06083v1
+2017-11-16,Ideal GLM-MHD: About the entropy consistent nine-wave magnetic field divergence diminishing ideal magnetohydrodynamics equations,"The paper presents two contributions in the context of the numerical
+simulation of magnetized fluid dynamics. First, we show how to extend the ideal
+magnetohydrodynamics (MHD) equations with an inbuilt magnetic field divergence
+cleaning mechanism in such a way that the resulting model is consistent with
+the second law of thermodynamics. As a byproduct of these derivations, we show
+that not all of the commonly used divergence cleaning extensions of the ideal
+MHD equations are thermodynamically consistent. Secondly, we present a
+numerical scheme obtained by constructing a specific finite volume
+discretization that is consistent with the discrete thermodynamic entropy. It
+includes a mechanism to control the discrete divergence error of the magnetic
+field by construction and is Galilean invariant. We implement the new
+high-order MHD solver in the adaptive mesh refinement code FLASH where we
+compare the divergence cleaning efficiency to the constrained transport solver
+available in FLASH (unsplit staggered mesh scheme).",1711.06269v3
+2017-12-05,Surface plasmon-mediated nanoscale localization of laser-driven sub-THz spin dynamics in magnetic dielectrics,"Ultrafast all-optical control of spins with femtosecond laser pulses is one
+of the hot topics at the crossroads of photonics and magnetism with a direct
+impact on future magnetic recording. Unveiling light-assisted recording
+mechanisms for an increase of the bit density beyond the diffraction limit
+without excessive heating of the recording medium is an open challenge. Here we
+show that surface plasmon-polaritons in hybrid metal-dielectric structures can
+provide spatial confinement of the inverse Faraday effect, mediating the
+excitation of localized coherent spin precession with 0.41 THz frequency. We
+demonstrate a two orders of magnitude enhancement of the excitation efficiency
+at the surface plasmon resonance within the 100 nm layer in dielectric garnet.
+Our findings broaden the horizons of ultrafast spin-plasmonics and open
+pathways towards non-thermal opto-magnetic recording at the nano-scale.",1712.01617v1
+2017-12-13,Co$_{2}$PtGa: A promising magnetic shape memory alloy with high martensite transition temperature,"In the present work, a combined theoretical and experimental study on
+Co$_{2}$PtGa Heusler alloy shows that it exhibits a martensite transition
+around 1320 K with a small thermal hysteresis (10 K). Dynamical stability of
+Co$_2$PtGa in the tetragonal phase has been established by the theoretically
+calculated phonon dispersion curves. Magnetization measurements suggest that
+this alloy is a ferromagnetic material with a saturation magnetic moment of
+2.83 $\mu_B$/f.u. at 2 K, which is in excellent agreement with the value
+obtained from \textit{ab-initio} calculations (2.87 $\mu_B$/f.u.). Our present
+study demonstrates that Co$_{2}$PtGa is a promising material for high
+temperature magnetic shape memory application.",1712.04765v4
+2017-12-19,Evolution of magnetic Dirac bosons in a honeycomb lattice,"We examine the presence and evolution of magnetic Dirac nodes in the
+Heisenberg honeycomb lattice. Using linear spin theory, we evaluate the
+collinear phase diagram as well as the change in the spin dynamics with various
+exchange interactions. We show that the ferromagnetic structure produces
+bosonic Dirac and Weyl points due to the competition between superexchange
+interactions. Furthermore, it is shown that the criteria for magnetic Dirac
+nodes are coupled to the magnetic structure and not the overall crystal
+symmetry, where the breaking of inversion symmetry greatly affects the
+antiferromagnetic configurations. The tunability of the nodal points through
+variation of the exchange parameters leads to the possibility of controlling
+Dirac symmetries through an external manipulation of the orbital interactions.",1712.06775v1
+2017-12-19,Standing Shocks in Magnetized Dissipative Accretion Flow around Black Holes,"We explore the global structure of the accretion flow around a Schwarzschild
+black hole where the accretion disc is threaded by toroidal magnetic fields.
+The accretion flow is optically thin and advection dominated. Synchrotron
+radiation is considered to be the active cooling mechanism in the flow. With
+this, we obtain the global transonic accretion solutions and show that
+centrifugal barrier in the rotating magnetized accretion flow causes a
+discontinuous transition of the flow variables in the form of shock waves. The
+shock properties and the dynamics of the post-shock corona are affected by the
+flow parameters such as viscosity, cooling rate and strength of the magnetic
+fields. The shock properties are investigated against these flow parameters. We
+further show that for given set of boundary parameters at the outer edge of the
+disc, accretion flow around a black hole admits shock when the flow parameters
+are tuned for a considerable range.",1712.07588v1
+2018-01-24,Massive star winds interacting with magnetic fields on various scales,"One of the defining processes which govern massive star evolution is their
+continuous mass loss via dense, supersonic line-driven winds. In the case of
+those OB stars which also host a surface magnetic field, the interaction
+between that field and the ionized outflow leads to complex circumstellar
+structures known as magnetospheres. In this contribution, we review recent
+developments in the field of massive star magnetospheres, including current
+efforts to characterize the largest magnetosphere surrounding an O star: that
+of NGC 1624-2. We also discuss the potential of the `analytic dynamical
+magnetosphere' (ADM) model to interpret multi-wavelength observations. Finally,
+we examine the possible effects of -- heretofore undetected -- small-scale
+magnetic fields on massive star winds and compare their hypothetical
+consequences to existing, unexplained observations.",1801.08123v1
+2018-01-25,Theory of high-resolution tunneling spin transport on a magnetic skyrmion,"Tunneling spin transport characteristics of a magnetic skyrmion are described
+theoretically in magnetic scanning tunneling microscopy (STM). The
+spin-polarized charge current in STM (SP-STM) and tunneling spin transport
+vector quantities, the longitudinal spin current and the spin transfer torque,
+are calculated in high spatial resolution within the same theoretical
+framework. A connection between the conventional charge current SP-STM image
+contrasts and the magnitudes of the spin transport vectors is demonstrated that
+enables the estimation of tunneling spin transport properties based on
+experimentally measured SP-STM images. A considerable tunability of the spin
+transport vectors by the involved spin polarizations is also highlighted. These
+possibilities and the combined theory of tunneling charge and vector spin
+transport pave the way for gaining deep insight into electric-current-induced
+tunneling spin transport properties in SP-STM and to the related dynamics of
+complex magnetic textures at surfaces.",1801.08375v2
+2018-02-05,Quantum many-body dynamics of the Einstein-de Haas effect,"In 1915, Einstein and de Haas and Barnett demonstrated that changing the
+magnetization of a magnetic material results in mechanical rotation, and vice
+versa. At the microscopic level, this effect governs the transfer between
+electron spin and orbital angular momentum, and lattice degrees of freedom,
+understanding which is key for molecular magnets, nano-magneto-mechanics,
+spintronics, and ultrafast magnetism. Until now, the timescales of
+electron-to-lattice angular momentum transfer remain unclear, since modeling
+this process on a microscopic level requires addition of an infinite amount of
+quantum angular momenta. We show that this problem can be solved by
+reformulating it in terms of the recently discovered angulon quasiparticles,
+which results in a rotationally invariant quantum many-body theory. In
+particular, we demonstrate that non-perturbative effects take place even if the
+electron--phonon coupling is weak and give rise to angular momentum transfer on
+femtosecond timescales.",1802.01638v2
+2018-02-26,Fractal Universality in Near-Threshold Magnetic Lanthanide Dimers,"Ergodic quantum systems are often quite alike, whereas nonergodic, fractal
+systems are unique and display characteristic properties. We explore one of
+these fractal systems, weakly bound dysprosium lanthanide molecules, in an
+external magnetic field. As recently shown, colliding ultracold magnetic
+dysprosium atoms display a soft chaotic behavior with a small degree of
+disorder. We broaden this classification by investigating the generalized
+inverse participation ratio and fractal dimensions for large sets of molecular
+wave functions. Our exact close-coupling simulations reveal a dynamic phase
+transition from partially localized states to totally delocalized states and
+universality in its distribution by increasing the magnetic field strength to
+only a hundred Gauss (or 10 mT). Finally, we prove the existence of nonergodic
+delocalized phase in the system and explain the violation of ergodicity by
+strong coupling between near-threshold molecular states and the nearby
+continuum.",1802.09586v1
+2018-03-03,Stable spin domains in a non-degenerate ultra-cold gas,"We study the stability of two-domain spin structures in an ultra-cold gas of
+magnetically trapped $^{87}$Rb atoms above quantum degeneracy. Adding a small
+effective magnetic field gradient stabilizes the domains via coherent
+collective spin rotation effects, despite negligibly perturbing the potential
+energy relative to the thermal energy. We demonstrate that domain stabilization
+is accomplished through decoupling the dynamics of longitudinal magnetization,
+which remains in time-independent domains, from transverse magnetization, which
+undergoes a purely transverse spin wave trapped within the domain wall. We
+explore the effect of temperature and density on the steady-state domains, and
+compare our results to a hydrodynamic solution to a quantum Boltzmann equation.",1803.01096v1
+2018-03-07,Spin excitations and thermodynamics of the t-J model on the honeycomb lattice,"We present a spin-rotation-invariant Green-function theory for the dynamic
+spin susceptibility in the spin-1/2 antiferromagnetic t-J Heisenberg model on
+the honeycomb lattice. Employing a generalized mean-field approximation for
+arbitrary temperatures and hole dopings, the electronic spectrum of
+excitations, the spin-excitation spectrum and thermodynamic quantities
+(two-spin correlation functions, staggered magnetization, magnetic
+susceptibility, correlation length) are calculated by solving a coupled system
+of self-consistency equations for the correlation functions. The temperature
+and doping dependence of the magnetic (uniform static) susceptibility is
+ascribed to antiferromagnetic short-range order. Our results on the doping
+dependencies of the magnetization and susceptibility are analyzed in comparison
+with previous results for the t_J model on the square lattice.",1803.03140v1
+2018-03-11,Skyrmions Driven by Intrinsic Magnons,"We study the dynamics of a skyrmion in a magnetic insulating nanowire in the
+presence of time-dependent oscillating magnetic field gradients. These ac
+fields act as a net driving force on the skyrmion via its own intrinsic
+magnetic excitations. In a microscopic quantum field theory approach we include
+the unavoidable coupling of the external field to the magnons, which gives rise
+to time-dependent dissipation for the skyrmion. We demonstrate that the
+magnetic ac field induces a super-Ohmic to Ohmic crossover behavior for the
+skyrmion dissipation kernels with time-dependent Ohmic terms. The ac driving of
+the magnon bath at resonance results in a unidirectional helical propagation of
+the skyrmion in addition to the otherwise periodic bounded motion.",1803.04001v2
+2018-03-12,Pre-Eruptive Magnetic Reconnection within a Multi-Flux-Rope System in the Solar Corona,"The solar corona is frequently disrupted by coronal mass ejections (CMEs),
+whose core structure is believed to be a flux rope made of helical magnetic
+field. This has become a ""standard"" picture although it remains elusive how the
+flux rope forms and evolves toward eruption. While 1/3 of the ejecta passing
+through spacecrafts demonstrate a flux-rope structure, the rest have complex
+magnetic fields. Are they originating from a coherent flux rope, too? Here we
+investigate the source region of a complex ejecta, focusing on a flare
+precursor with definitive signatures of magnetic reconnection, i.e., nonthermal
+electrons, flaring plasma, and bi-directional outflowing blobs. Aided by
+nonlinear force-free field modeling, we conclude that the reconnection occurs
+within a system of multiple braided flux ropes with different degree of
+coherency. The observation signifies the importance of internal structure and
+dynamics in understanding CMEs and in predicting their impacts on Earth.",1803.04088v1
+2018-03-12,Hydrogenation driven formation of local magnetic moments in FeO$_2$H$_x$,"The electronic and magnetic properties of recently discovered new important
+constituent of the Earth's lower mantle FeO2H were investigated by means of the
+density functional theory combined with the dynamical mean field theory
+(DFT+DMFT). Addition of the hydrogen to the parent FeO2 compound, which is an
+uncorrelated bad metal, destroys the most important ingredient of its
+electronic structure - O-O molecular orbitals. In effect physical properties of
+FeO2 and FeO2H turn to be completely different, FeO2H is a correlated metal
+with a mass renormalization, m*/m ~ 2, and magnetic moments on Fe ions become
+well localized with the Curie-Weiss type of uniform magnetic susceptibility.",1803.04255v2
+2018-03-19,Geometric phase magnetometry using a solid-state spin,"Magnetometry is a powerful technique for the non-invasive study of biological
+and physical systems. A key challenge lies in the simultaneous optimization of
+magnetic field sensitivity and maximum field range. In interferometry-based
+magnetometry, a quantum two-level system acquires a dynamic phase in response
+to an applied magnetic field. However, due to the 2{\pi} periodicity of the
+phase, increasing the coherent interrogation time to improve sensitivity
+results in reduced field range. Here we introduce a route towards both large
+magnetic field range and high sensitivity via measurements of the geometric
+phase acquired by a quantum two-level system. We experimentally demonstrate
+geometric-phase magnetometry using the optically addressable electronic spin
+associated with the nitrogen vacancy (NV) color center in diamond. Our approach
+enables unwrapping of the 2{\pi} phase ambiguity, decoupling of magnetic field
+range from sensitivity, and enhancement of the field range by about 400 times.
+We also find additional improvement in sensitivity in the nonadiabatic regime,
+and study how geometric-phase decoherence depends on adiabaticity. Our results
+show that the geometric phase can be a versatile tool for quantum sensing
+applications.",1803.07176v1
+2018-03-26,Development of a SEMPA system for magnetic imaging with ns time resolution and phase-sensitive detection,"Scanning electron microscopy with polarization analysis is a powerful
+lab-based magnetic imaging technique offering parallel imaging of multiple
+magnetization components and a very high spatial resolution. However, one
+drawback of the technique is the long required acquisition time resulting from
+the low inherent efficiency of spin detection, which has limited the
+applicability of the technique to certain quasi-static measurement schemes and
+materials with strong contrast. Here we demonstrate the ability to improve the
+signal-to-noise ratio for particular classes of measurement involving periodic
+excitation of the magnetic structure via the integration of a time-to-digital
+converter to the system and a digital lock-in detection scheme. The modified
+setup provides dynamic imaging capabilities using selected time windows and
+finally full time-resolved imaging with a demonstrated time resolution of
+better than 2 ns.",1803.09775v1
+2018-04-08,Mixed convection in a downward flow in a vertical duct with strong transverse magnetic field,"The downward flow in a vertical duct with one heated and three thermally
+insulated walls is analyzed numerically using the two-dimensional approximation
+valid in the asymptotic limit of an imposed strong transverse magnetic field.
+The work is motivated by the design of liquid metal blankets with poloidal
+ducts for future nuclear fusion reactors, in which the main component of the
+magnetic field is perpendicular to the flow direction and very strong heating
+is applied at the wall facing the reaction chamber. The flow is found to be
+steady-state or oscillating depending on the strengths of the heating and
+magnetic field. A parametric study of the instability leading to the
+oscillations is performed. It is found among other results that the flow is
+unstable and develops high-amplitude temperature oscillations at the conditions
+typical for a fusion reactor blanket.",1804.02659v1
+2018-04-13,Magnetic field topology from non-force free extrapolation and magnetohydrodynamic simulation of its eventual dynamics,"Magnetic reconnections (MRs) for various magnetic field line (MFL) topologies
+are believed to be the initiators of various solar eruptive events like flares
+and coronal mass ejections (CMEs). Consequently, important is a thorough
+understanding and quantification of the MFL topology and their evolution which
+leads to MRs. Contemporary standard is to extrapolate the coronal MFLs using
+equilibrium models where the Lorentz force on the coronal plasma is zero
+everywhere, because either there is no current or the current is parallel to
+the magnetic field. In tandem, a non-force-free-field (NFFF) extrapolation
+scheme has evolved and allows for a Lorentz force which is non-zero only at the
+photosphere but asymptotically vanishes with height. The paper reports
+magnetohydrodynamic (MHD)- simulations initiated by NFFF extrapolation of the
+coronal MFLs for the active region NOAA 11158. Interestingly, quasi-separatrix
+layers (QSLs) which facilitate MRs are detected in the extrapolated MFLs. The
+AR 11158 is flare producing and, the paper makes an attempt to asses the role
+of QSLs in the flare onsets.",1804.04814v1
+2018-04-22,Atom-by-atom construction of attractors in a tunable finite size spin array,"We demonstrate that a two-dimensional finite and periodic array of Ising
+spins coupled via RKKY-like exchange can exhibit tunable magnetic states
+ranging from three distinct magnetic regimes: (1) a conventional ferromagnetic
+regime, (2) a glass-like regime, and (3) a new multi-well regime. These
+magnetic regimes can be tuned by one gate-like parameter, namely the ratio
+between the lattice constant and the oscillating interaction wavelength. We
+characterize the various magnetic regimes, quantifying the distribution of low
+energy states, aging relaxation dynamics, and scaling behavior. The glassy and
+multi-well behavior results from the competing character of the oscillating
+long-range exchange interactions. The multi-well structure features multiple
+attractors, each with a sizable basin of attraction. This may open the possible
+application of such atomic arrays as associative memories.",1804.08093v2
+2018-04-30,Gravity effects on mixing with magnetic micro-convection in microfluidics,"Mixing remains an important problem for development of successful
+microfluidic and lab-on-a-chip devices, where simple and predictable systems
+are particularly interesting. One is magnetic micro-convection, an instability
+happening on the interface of miscible magnetic and non-magnetic fluids in a
+Hele-Shaw cell under applied field. Previous work proved that Brinkman model
+quantitatively explains the experiments. However, a gravity caused convective
+motion complicated the tests. Here we first improve the experimental system to
+exclude the gravitational convective motion. Afterwards, we observe and
+quantify how gravity and laminar flow play an important role in stabilizing the
+perturbations that create the instability. Accordingly, we improve our
+theoretical model and perform linear analysis. Two dimensionless quantities
+explain the experimental observations of change in critical field needed for
+instability and characteristic size of the emerging pattern. Finally, we
+discuss the conditions at which gravity plays an important role in microfluidic
+systems.",1805.00101v2
+2018-05-03,Sculpting the Spin-Wave Response of Artificial Spin Ice via Microstate Selection,"The spin-wave dynamics of the ferromagnetic nanoarrays termed artificial spin
+ice (ASI) are known to vary depending on their magnetic microstate. However,
+little work has been done to characterise this relationship. Recent advances in
+control over the magnetic configuration of ASI bring designs harnessing the
+interplay between spin-wave eigenmodes and the microstate within reach,
+offering diverse applications including reconfigurable magnonic crystals,
+microwave filters and microstate read-out probes. These designs hinge on a
+strong understanding of the underlying spin wave-microstate correspondence.
+  Here, we analyse the effects of the magnetic microstate on spin-wave spectra
+of honeycomb ASI systems via micromagnetic simulation. We find the spin-wave
+spectrum to be highly-tunable via the microstate to an enhanced degree relative
+to existing magnonic crystals, with mode shifting and (de)activation realised
+by reversing individual nanoislands. Symmetries of ASI systems and the
+chirality of magnetic defects are found to play important roles in determining
+the high-frequency response.",1805.01397v3
+2018-05-23,Turbulence in Magnetized Pair Plasmas,"Alfv\'enic-type turbulence in strongly magnetized, low-beta pair plasmas is
+investigated. A coupled set of equations for the evolution of the magnetic and
+flow potentials are derived, covering both fluid and kinetic scales. In the
+fluid (MHD) range those equations are the same as for electron-ion plasmas, so
+turbulence at those scales is expected to be of the Alfv\'enic nature,
+exhibiting critical balance, dynamic alignment, and transition to a tearing
+mediated regime at small scales. The critical scale at which a transition to a
+tearing-mediated range occurs is derived, and the spectral slope in that range
+is predicted to be $k_\perp^{-8/3}$ (or $k_\perp^{-3}$, depending on details of
+the reconnecting configuration assumed). At scales below the electron (and
+positron) skin depth, it is argued that turbulence is dictated by a cascade of
+the inertial Alfv\'en wave, which we show to result in the magnetic energy
+spectrum $\propto k_\perp^{-11/3}$.",1805.09224v1
+2018-06-05,Backscattering immunity of dipole-exchange magnetostatic surface spin waves,"The existence of backscattering-immune spin-wave modes is demonstrated in
+magnetic thin films of nano-scale thickness. Our results reveal that chiral
+Magneto Static Surface Waves (cMSSWs), which propagate perpendicular to the
+magnetization direction in an in-plane magnetized thin film, are robust against
+backscattering from surface defects. cMSSWs are protected against various types
+of surface inhomogeneities and defects as long as their frequency lies inside
+the gap of the volume modes. Our explanation is independent of the topology of
+the modes and predicts that this robustness is a consequence of symmetry
+breaking of the dynamic magnetic fields of cMSSWs due to the off-diagonal part
+of the dipolar interaction tensor, which is present both for long- (dipole
+dominated) and short-wavelength (exchange dominated) spin waves. Micromagnetic
+simulations confirm the robust character of the cMSSWs. Our results open a new
+direction in designing highly efficient magnonic logic elements and devices
+employing cMSSWs in nano-scale thin films.",1806.01554v3
+2018-06-05,Galvano- and thermo-magnetic effects at low and high temperatures within non-Markovian quantum Langevin approach,"The quantum Langevin formalism is used to study the charge carrier transport
+in a twodimensional sample. The center of mass of charge carriers is visualized
+as a quantum particle, while an environment acts as a heat bath coupled to it
+through the particle-phonon interaction. The dynamics of the charge carriers is
+limited by the average collision time which takes effectively into account the
+two-body effects. The functional dependencies of particle-phonon interaction
+and average collision time on the temperature and magnetic field are
+phenomenologically treated. The galvano-magnetic and thermo-magnetic effects in
+the quantum system appear as the result of the transitional processes at low
+temperatures.",1806.01685v1
+2018-06-11,Breaking Kelvin: Circulation conservation and vortex breakup in MHD at low Magnetic Prandtl Number,"In this paper we examine the role of weak magnetic fields in breaking
+Kelvin's circulation theorem and in vortex breakup in two-dimensional
+magnetohydrodynamics for the physically important case of a low magnetic
+Prandtl number (low $Pm$) fluid. We consider three canonical inviscid solutions
+for the purely hydrodynamical problem, namely a Gaussian vortex, a circular
+vortex patch and an elliptical vortex patch. We examine how magnetic fields
+lead to an initial loss of circulation $\Gamma$ and attempt to derive scaling
+laws for the loss of circulation as a function of field strength and diffusion
+as measured by two non-dimensional parameters. We show that for all cases the
+loss of circulation depends on the integrated effects of the Lorentz force,
+with the patch cases leading to significantly greater circulation loss. For the
+case of the elliptical vortex the loss of circulation depends on the total area
+swept out by the rotating vortex and so this leads to more efficient
+circulation loss than for a circular vortex.",1806.03922v1
+2018-06-11,Quantum Spin Fragmentation in Kagome Ice Ho3Mg2Sb3O14,"A promising route to realize entangled magnetic states combines geometrical
+frustration with quantum-tunneling effects. Spin-ice materials are canonical
+examples of frustration, and Ising spins in a transverse magnetic field are the
+simplest many-body model of quantum tunneling. Here, we show that the tripod
+kagome lattice material Ho3Mg2Sb3O14 unites an ice-like magnetic degeneracy
+with quantum-tunneling terms generated by an intrinsic splitting of the Ho3+
+ground-state doublet, realizing a frustrated transverse Ising model. Using
+neutron scattering and thermodynamic experiments, we observe a
+symmetry-breaking transition at T*~0.32 K to a remarkable quantum state with
+three peculiarities: a continuous magnetic excitation spectrum down to T~0.12K;
+a macroscopic degeneracy of ice-like states; and a fragmentation of the spin
+into periodic and aperiodic components strongly affected by quantum
+fluctuations. Our results establish that Ho3Mg2Sb3O14 realizes a
+spin-fragmented state on the kagome lattice, with intrinsic quantum dynamics
+generated by a homogeneous transverse field.",1806.04081v1
+2018-06-14,Planar Superconductor-Ferromagnet-Superconductor Josephson junctions as scanning probe sensors,"We propose a novel type of magnetic scanning probe sensor, based on a single
+planar Josephson junction with a magnetic barrier. The planar geometry together
+with high magnetic permeability of the barrier helps to focus flux in the
+junction and thus enhance the sensitivity of the sensor. As a result, it may
+outperform equally sized SQUID both in terms of the magnetic field sensitivity
+and the spatial resolution in one scanning direction. We fabricate and analyze
+experimentally sensor prototypes with a superparamagnetic CuNi and a
+ferromagnetic Ni barrier. We demonstrate that the planar geometry allows easy
+miniaturization to nm-scale, facilitates an effective utilization of the
+self-field phenomenon for amplification of sensitivity and a simple
+implementation of a control line for feed-back operation in a broad dynamic
+range.",1806.05582v1
+2018-06-21,"Testing Alfvén wave propagation in a ""realistic"" set-up of the solar atmosphere","We present a radiative magneto-hydrodynamic simulation set-up using the
+PENCIL CODE to study the generation, propagation and dissipation of Alfv\'en
+waves in the solar atmosphere which includes a convective layer, photosphere
+below and chromosphere, transition region and the corona above. We prepare a
+setup of steady-state solar convection where the imposed external magnetic
+field also has reached the final value gradually starting from a very small
+value. From that state, we start several simulations by varying the magnetic
+Prandtl number and the forcing strengths. We find the propagation
+characteristics of waves excited in this simulation run depend strongly on the
+magnetic Prandtl number and the wave number of the forcing. For magnetic
+Prandtl number of unity, we obtain localized heating in the corona due to shock
+dissipation.",1806.08166v2
+2018-06-26,Instabilities of MHD flows driven by traveling magnetic fields,"The flow of an electrically conducting fluid driven by a traveling magnetic
+field imposed at the endcaps of a cylindrical annulus is numerically studied.
+At sufficiently large magnetic Reynolds number, the system undergoes a
+transition from synchronism with the traveling field to a stalled flow, similar
+to the one observed in electromagnetic pumps. A new type of boundary layer is
+identified for such electromagnetically-driven flows, that can be understood as
+a combination of Hartmann and Shercliff layers generated by the spatio-temporal
+variations of the magnetic field imposed at the boundaries. An energy budget
+calculation shows that energy dissipation mostly occurs within these boundary
+layers and we observe that the ohmic dissipation Db always overcomes the
+viscous dissipation Dv, suggesting the existence of an upper bound for the
+efficiency of electromagnetic pumps. Finally, we show that the destabilization
+of the flow occurs when both dissipations are nearly equal.",1806.09970v1
+2018-06-26,Fully resolved array of simulations investigating the influence of the magnetic Prandtl number on magnetohydrodynamic turbulence,"We explore the effect of the magnetic Prandtl number Pm on energy and
+dissipation in fully resolved direct numerical simulations of steady-state,
+mechanically forced homogeneous magnetohydrodynamic turbulence in the range Pm
+= 1/32 to 32. We compare the spectra and show that if the simulations are not
+fully resolved, the steepness of the scaling of the kinetic-to-magnetic
+dissipation ratio with Pm is overestimated. We also present results of decaying
+turbulence with helical and nonhelical magnetic fields, where we find
+nonhelical reverse spectral transfer for Pm < 1. The results of this systematic
+analysis have applications including stars, planetary dynamos, and accretion
+disks.",1806.10202v2
+2018-07-05,Mesonic excited states of magnetic monopoles in quantum spin ice,"Spin ice magnetic monopoles are fractionalized emergent excitations in a
+class of frustrated magnets called spin ices. The classical spin ice model has
+an extensive number of ground state spin configurations, whereas magnetic
+monopoles can be thought of as the endpoints of string operators applied to
+these ground states. Introducing quantum fluctuations into the model induces
+monopoles with dynamics, which would normally lift the degeneracy of the
+two-monopole energy level at the linear order of the perturbation. Contrary to
+this expectation, we find that quantum fluctuations in the form of a locally
+transverse field term partially preserve the extensive degeneracy of the
+monopole pairs up to the much weaker splitting of the background monopole-free
+spin ice configurations. Each of these approximately degenerate excited states,
+termed mesons, can be represented as a bound monopole-antimonopole pair
+delocalized in a classical spin ice background.",1807.02193v1
+2018-07-18,Microfluidic pumping using artificial magnetic cilia,"One of the vital functions of naturally occurring cilia is fluid transport.
+Biological cilia use spatially asymmetric strokes to generate a net fluid flow
+that can be utilized for feeding, swimming, and other functions. Biomimetic
+synthetic cilia with similar asymmetric beating can be useful for fluid
+manipulations in lab-on-chip devices. In this paper, we demonstrate the
+microfluidic pumping by magnetically actuated synthetic cilia arranged in
+multi-row arrays. We use a microchannel loop to visualize flow created by the
+ciliary array and to examine pumping for a range of cilia and microchannel
+parameters. We show that magnetic cilia can achieve flow rates of up to 11
+{\mu}l/min with the pressure drop of~ 1 Pa. Such magnetic ciliary array can be
+useful in microfluidic applications requiring rapid and controlled fluid
+transport.",1807.06765v1
+2018-07-25,Programmable collective behavior in dynamically self-assembled mobile microrobotic swarms,"Collective control of mobile microrobotic swarms is indispensable for their
+potential high-impact applications in targeted drug delivery, medical
+diagnostics, parallel micromanipulation, and environmental sensing and
+remediation. Lack of on-board computational and sensing capabilities in current
+microrobotic systems necessitates use of physical interactions among individual
+microrobots for local physical communication and cooperation. Here, we show
+that mobile microrobotic swarms with well-defined collective behavior can be
+designed by engineering magnetic interactions among individual units.
+Microrobots, consisting of a linear chain of self-assembled magnetic
+microparticles, locomote on surfaces in response to a precessing magnetic
+field. Control over the direction of precessing magnetic field allows
+engineering attractive and repulsive interactions among microrobots and, thus,
+collective order with well-defined spatial organization and parallel operation
+over macroscale distances (~1 cm). These microrobotic swarms can be guided
+through confined spaces, while preserving microrobot morphology and function.
+These swarms can further achieve directional transport of large cargoes on
+surfaces and small cargoes in bulk fluids. Described design approach,
+exploiting physical interactions among individual robots, enables facile and
+rapid formation of self-organized and reconfigurable microrobotic swarms with
+programmable collective order.",1807.09702v1
+2018-07-31,Terahertz Spin Transfer Torque Oscillator Based on a Synthetic Antiferromagnet,"Bloch-Bloembergen-Slonczewski equation is adopted to simulate magnetization
+dynamics in spin-valve based spin-transfer torque oscillator with synthetic
+antiferromagnet acting as a free magnetic layer. High frequency up to the
+terahertz scale is predicted in synthetic antiferromagnet spin-transfer torque
+oscillator with no external magnetic field if the following requirements are
+fulfilled: antiferromagnetic coupling between synthetic antiferromagnetic
+layers is sufficiently strong, and the thickness of top (bottom) layer of
+synthetic antiferromagnet is sufficiently thick (thin) to achieve a wide
+current density window for the high oscillation frequency. Additionally, the
+transverse relaxation time of the free magnetic layer should be sufficiently
+larger compared with the longitudinal relaxation time. Otherwise, stable
+oscillation cannot be sustained or scenarios similar to regular spin
+valve-based spin-transfer torque oscillator with relatively low frequency will
+occur. Our calculations pave a new way for exploring THz spintronics devices.",1807.11633v1
+2018-08-03,"Magnetic structure, dipole reversals, and 1/f noise in resistive MHD spherical dynamos","A parametric study of the magnetic dipole behavior in resistive
+incompressible MHD inside a rotating sphere is performed, using direct
+numerical simulations and considering Reynolds and Ekman numbers as controlling
+parameters. The tendency is to obtain geodynamo-like magnetic dipole reversal
+regimes for sufficiently small Ekman and large Reynolds numbers. The typical
+dipole latitude obtained in the reversal regime is around 40 degrees (with
+respect to the rotation axis of the sphere). A statistical analysis of waiting
+times between dipole reversals is also performed, obtaining a non-Poissonian
+distribution of waiting times, indicating long-term memory effects. We also
+report the presence of a $1/f$ frequency power spectrum in the magnetic dipole
+time-series, which also shows a tendency to grow toward lower frequencies as
+the Ekman number is decreased.",1808.01370v2
+2018-08-30,Influence of spin glass-like magnetic relaxation on the zero-field-cooled exchange bias effect,"The zero-field-cooled exchange bias (ZEB) effect is a remarkable phenomenon
+recently reported for some reentrant spin glass-like compounds. In this work,
+the time-evolution of magnetization is thoroughly investigated for two ZEB
+materials in order to figure out the role played by the spin glass-like phase
+on such effect. La$_{1.5}$Sr$_{0.5}$CoMnO$_{6}$ and
+La$_{1.5}$Ca$_{0.5}$CoMnO$_{6}$ were chosen as representative samples of ZEB
+systems, since the former compound presents the largest ZEB reported so far,
+while the second has a much smaller effect, despite being
+structurally/chemically similar. Comprehensive magnetic measurements were
+carried on both samples, and the results are discussed in terms of the amount
+and time-evolution of the spin glass-like phase under the influence of a
+varying field. We also propose a phenomenological model, based on the pinning
+of spin glass-like moments and on the dynamics of their magnetic relaxation, to
+explain the asymmetry observed in the hysteresis loops. The good agreement
+between the simulated and experimental results confirms our hypothesis that the
+spin glass-like phase is key to the ZEB effect.",1808.10305v1
+2018-09-04,Joint Instability and Abrupt Nonlinear Transitions in a Differentially Rotating Plasma,"Global magnetohydrodynamic (MHD) instabilities are investigated in a
+computationally tractable two-dimensional model of the solar tachocline. The
+model's differential rotation yields stability in the absence of a magnetic
+field, but if a magnetic field is present, a joint instability is observed. We
+analyze the nonlinear development of the instability via fully nonlinear direct
+numerical simulation, the generalized quasilinear approximation (GQL), and
+direct statistical simulation (DSS) based upon low-order expansion in
+equal-time cumulants. As the magnetic diffusivity is decreased, the nonlinear
+development of the instability becomes more complicated until eventually a set
+of parameters are identified that produce a previously unidentified long-term
+cycle in which energy is transformed from kinetic energy to magnetic energy and
+back. We find that the periodic transitions, which mimic some aspects of solar
+variability -- for example, the quasiperiodic seasonal exchange of energy
+between toroidal field and waves or eddies -- are unable to be reproduced when
+eddy-scattering processes are excluded from the model.",1809.00921v2
+2018-09-04,Twisted domain walls and skyrmions in perpendicularly magnetized multilayers,"We present an analytical theory to describe three-dimensional magnetic
+textures in perpendicularly magnetized magnetic multilayers that arise in the
+presence of magnetostatic interactions and the Dzyaloshinskii-Moriya
+interaction (DMI). We demonstrate that domain walls in multilayers develop a
+complex twisted structure, which persists even for films with strong DMI. The
+origin of this twist is surface-volume stray field interactions that manifest
+as a depth-dependent effective field whose form mimics the DMI effective field.
+We find that the wall twist has a minor impact on the equilibrium skyrmion or
+domain size, but can significantly affect current-driven dynamics. Our
+conclusions are based on the derived analytical expressions for the
+magnetostatic energy and confirmed by micromagnetic simulations.",1809.01247v1
+2018-09-06,Growth rate distribution and intermittency in kinematic turbulent dynamos : which moment predicts the dynamo onset?,"We consider the generation of magnetic field by a turbulent flow. For the
+linear induction equation (i.e. the kinematic dynamo problem), we show that the
+statistical moments of the magnetic field display multiscaling and in
+particular moments of different order turn unstable for different values of the
+control parameter. On a canonical example, we map the problem onto the
+calculation of the injected power by a time correlated fluctuating force acting
+on a Brownian particle. We are then able to calculate analytically the growth
+rate of the moments of the magnetic field and explain the origin of this
+intermittency. We finally show that the onset for the nonlinear problem is
+predicted by the linear onset of the moment of order 0 + (i.e. the logarithm of
+the magnetic field)",1809.01877v1
+2018-09-07,Anisotropy-driven collisional separation of impurities in magnetized compressing and expanding cylindrical plasmas,"When a cylindrically-symmetric magnetized plasma compresses or expands,
+velocity-space anisotropy is naturally generated as a result of the different
+adiabatic conservation laws parallel and perpendicular to the magnetic field.
+When the compression timescale is comparable to the collision timescale, and
+both are much longer than the gyroperiod, this pressure anisotropy can become
+significant. We show that this naturally-generated anisotropy can dramatically
+affect the transport of impurities in the compressing plasma, even in the
+absence of scalar temperature or density gradients, by modifying the azimuthal
+frictions that give rise to radial particle transport. Although the impurity
+transport direction depends only on the sign of the pressure anisotropy, the
+anisotropy itself depends on the pitch magnitude of the magnetic field and the
+sign of the radial velocity. Thus, pressure anisotropy effects can drive
+impurities either towards or away from the plasma core. These
+anisotropy-dependent terms represent a qualitatively new effect, influencing
+transport particularly in the sparse edge regions of dynamically-compressing
+screw pinch plasmas. Such plasmas are used for both X-ray generation and
+magneto-inertial fusion, applications which are sensitive to impurity
+concentrations.",1809.02528v1
+2018-09-27,Spin wave radiation from vortices in $^3$He-B,"We consider a vortex line in the B phase of superfluid $^3$He under uniformly
+precessing magnetization. The magnetization exerts torque on the vortex,
+causing its order parameter to oscillate. These oscillations generate spin
+waves, which is analogous to an oscillating charge generating electromagnetic
+radiation. The spin waves carry energy, causing dissipation in the system.
+Solving the equations of spin dynamics, we calculate the energy dissipation
+caused by spin wave radiation for arbitrary tipping angles of the magnetization
+and directions of the magnetic field, and for both vortex types of $^3$He-B.
+For the double-core vortex we also consider the anisotropy of the radiation and
+the dependence of the dissipation on twisting of the half cores. The radiated
+energy is compared with experiments in the mid-temperature range $T \sim 0.5
+T_c$. The dependence of the calculated dissipation on several parameters is in
+good agreement with the experiments. Combined with numerically calculated
+vortex structure, the radiation theory produces the order of magnitude of the
+experimental dissipation. The agreement with the experiments indicates that
+spin wave radiation is the dominant dissipation mechanism for vortices in
+superfluid $^3$He-B in the mid-temperature range.",1809.10484v1
+2018-09-27,Crystalline anisotropy induces a second antiferromagnetic phase in the absence of SDW in the heavily hydrogen-doped LaFeAsO$_{1-x}$H$_x$ $(x\sim0.5 )$,"Electronic and magnetic properties of the heavily H-doped
+LaFeAsO$_{1-x}$H$_x$ $(x\sim0.5 )$ were studied in the framework of the density
+functional theory combined with the dynamical mean field theory (DFT+DMFT). We
+found a stripe-like-ordered structure of hydrogen and oxygen atoms, as a ground
+state, with the same configuration as the antiferromagnetic (AF) order. The new
+configuration could explain the existing experimental results related to the
+heavily H-doped LaFeAsO$_{1-x}$H$_x$, such as an in-plane electronic anisotropy
+and a non-uniform magnetic behavior. A significant anisotropy was observed
+between Fe- 3d$_{xz}$ (xz) and Fe-3d$_{yz}$ (yz) orbitals in the ground state
+in the absence of the pseudogap resulting from the spin density wave phase,
+which was found to originate from the crystalline anisotropy. Magnetic moments
+were not spatially uniform and were sensitive to the crystal configuration. We
+found that a non-uniform magnetic behavior is associated with the As-Fe-As bond
+angle in the structure. Our findings would clarify the importance of crystal
+details and orbital degrees of freedom in iron-based superconductors.",1809.10641v1
+2018-10-12,"Quadrupolar Superexchange Interactions, Multipolar Order and Magnetic Phase Transition in UO$_2$","The origin of non-collinear magnetic order in UO$_{2}$ is studied by an ab
+initio dynamical-mean-field-theory framework in conjunction with a
+linear-response approach for evaluating inter-site superexchange interactions
+between U 5$f^{2}$ shells. The calculated quadrupole-quadruple superexchange
+interactions are found to unambiguously resolve the frustration of
+face-centered-cubic U sublattice toward stabilization of the experimentally
+observed non-collinear 3k-magnetic order. Therefore, the exotic 3k
+antiferromagnetic order in UO$_{2}$ can be accounted for by a purely electronic
+exchange mechanism acting in the undistorted cubic lattice structure. The
+quadrupolar short-range order above magnetic ordering temperature $T_N$ is
+found to qualitatively differ from the long-range order below $T_N$.",1810.05484v2
+2018-12-05,Spin-imbalance-induced transverse magnetization in the Hofstadter-Hubbard model,"The fermionic, time-reversal invariant Hofstadter-Hubbard model with a
+population difference between the two spin states is investigated. In the
+strongly interacting regime, where the system can be described by an effective
+spin model, we find an exotic spin structure by means of classical Monte-Carlo
+calculations. Remarkably, this spin structure exhibits a transverse net
+magnetization perpendicular to the magnetization induced by the population
+imbalance. It is thus inherently different from canted antiferromagnetism. We
+further investigate effects of quantum fluctuations within the dynamical
+mean-field approximation and obtain a rich phase diagram including
+ferromagnetic, anti-ferromagnetic, ferrimagnetic, and transverse magnetization
+phases.",1812.02001v2
+2019-01-11,Open quantum system in external magnetic field within non-Markovian quantum Langevin approach,"The non-Markovian dynamics of a charged particle linearly coupled to a
+neutral bosonic heat bath is investigated in an external uniform magnetic
+field. The analytical expressions for the time-dependent and asymptotic
+friction and diffusion coefficients, cyclotron frequencies, variances of the
+coordinate and momentum, and orbital magnetic moments are derived. The role of
+magnetic field in the dissipation and diffusion processes is illustrated by
+several examples in the low- and high-temperature regimes. The localization
+phenomenon for a charged particle is observed. The orbital diamagnetism of
+quantum system in a dissipative environment is studied. The quantization
+conditions are found for the angular momentum.",1901.03562v1
+2019-01-25,"Low temperature magnetic and dielectric properties of LnBaCuFeO5 (Ln = Nd, Eu, Gd, Ho and Yb)","The layered perovskite compounds are interesting due to their intriguing
+physical properties. In this article we report the structural, magnetic and
+dielectric properties of LnBaCuFeO5 (Ln=Nd, Eu, Gd, Ho and Yb). The structural
+parameters decrease from Nd to Yb due to the decrease in the ionic radii of the
+rare earth ions. An antiferromagnetic transition is observed for EuBaCuFeO5
+near 120 K along with the glassy dynamics of the electric dipoles below 100 K.
+The magnetic transition is absent in other compounds, which may be due to the
+dominance of the magnetic moment of the rare earth ions. The dielectric
+constant does not show any anomaly, except in the case of HoBaCuFeO5 where it
+shows a weak frequency dependence around 54 K. These compounds show a
+significant enhancement of dielectric constant at high temperatures which have
+been attributed to Maxwell-Wagner effect. However, no significant
+magneto-dielectric coupling has been observed in these layered perovskites.",1901.08835v1
+2019-01-28,Topological structures of velocity and electric field in the vicinity of a cusp-type magnetic null point,"Topological characteristics reveal important physical properties of plasma
+structures and astrophysical processes. Physical parameters and constraints are
+linked with topological invariants, which are important for describing magnetic
+reconnection scenarios. We analyze stationary non-ideal Ohm's law concerning
+the Poincare classes of all involved physical fields in 2D by calculating the
+corresponding topological invariants of their Jacobian (here: particularly the
+eigenvalues) or Hessian matrices. The magnetic field is assumed to have a cusp
+structure, and the stagnation point of the plasma flow coincides with the cusp.
+We find that the stagnation point must be hyperbolic. Furthermore, the
+functions describing both the resistivity and the Ohmic heating have a saddle
+point structure, being displaced with respect to the cusp point. These results
+imply that there is no monotonous relation between current density and
+anomalous resistivity in the case of a 2D standard magnetic cusp.",1901.09913v1
+2019-02-07,Triplet excitations in the frustrated spin ladder Li$_2$Cu$_2$O(SO$_4$)$_2$,"Magnetic excitations of the recently discovered frustrated spin-1/2 two-leg
+ladder system Li$_2$Cu$_2$O(SO$_4$)$_2$ are investigated using inelastic
+neutron scattering, magnetic susceptibility and infrared absorption
+measurements. Despite the presence of a magnetic dimerization concomitant with
+the tetragonal-to-triclinic structural distortion occurring below 125 K,
+neutron scattering experiments reveal the presence of dispersive triplet
+excitations above a spin gap of $\Delta = 10.6$ meV at 1.5 K, a value
+consistent with the estimates extracted from magnetic susceptibility. The
+likely detection of these spin excitations in infrared spectroscopy is
+explained by invoking a dynamic Dzyaloshinskii-Moriya mechanism in which light
+is coupled to the dimer singlet-to-triplet transition through an optical
+phonon. These results are qualitatively explained by exact diagonalization and
+higher-order perturbation calculations carried out on the basis of the
+dimerized spin Hamiltonian derived from first-principles.",1902.02798v1
+2019-02-10,Spin dynamics of anisotropic azimuthal modes in heterogeneous magnetic nanodisks,"It is well known that azimuthal spin wave modes of magnetic vortex state in
+permalloy nanodisks have circular symmetry. Intuitively, magnetic materials
+having magnetocrystalline anisotropy is not compatible with the circular
+symmetry of the azimuthal modes. In this article, however, we report cubic
+azimuthal modes in heterogeneous nanodisks consisting of a permalloy core and a
+Fe shell. The fourfold symmetry of azimuthal modes is due to the exchange, and
+magneto-static, interactions between the permalloy core and the Fe shell. In
+comparison to results of circular azimuthal mode, the vortex switching occurs
+considerably faster under the excitation of cubic azimuthal mode. The gyration
+path of vortex core turns into square under the influence of induced cubic
+anisotropy in the Py region. We find out periodic oscillation of the vortex
+core size and the gyration speed as well. Our findings may offer a new route
+for spintronic applications using heterogeneous magnetic nanostructures.",1902.03536v1
+2019-02-13,Controlling injection using a magnetic field to produce sub-femtosecond bunches in the laser wakefield accelerator,"It is shown that electron injection into a laser-driven plasma bubble can be
+manipulated by applying an external magnetic field in the presence of a plasma
+density gradient. The down-ramp of the density-tailored plasma locally reduces
+the plasma wave phase velocity, which triggers injection. The longitudinal
+magnetic field dynamically induces an expanding hole in the electron density
+distribution at the rear of the wake bubble, which reduces the peak electron
+velocity in its vicinity. Electron injection is suppressed when the electron
+velocity drops below the phase velocity, which depends on the size of the
+density hole. This enables the start and end of electron injection to be
+independently controlled, which allows generation of sub-femtosecond electron
+bunches with peak currents of a few kilo-Ampere, for an applied magnetic field
+of $\sim 10$ Tesla.",1902.04771v2
+2019-02-15,Magnetization and entanglement after a geometric quench in the XXZ chain,"We investigate the dynamics of the XXZ spin chain after a geometric quench,
+which is realized by connecting two half-chains prepared in their ground states
+with zero and maximum magnetizations, respectively. The profiles of
+magnetization after the subsequent time evolution are studied numerically by
+density-matrix renormalization group methods, and a comparison to the
+predictions of generalized hydrodynamics yields a very good agreement. We also
+calculate the profiles of entanglement entropy and propose an ansatz for the
+noninteracting XX case, based on arguments from conformal field theory. In the
+general interacting case, the propagation of the entropy front is studied
+numerically both before and after the reflection from the chain boundaries.
+Finally, our results for the magnetization fluctuations indicate a leading
+order proportionality relation to the entanglement entropy.",1902.05834v2
+2019-03-03,Theory for spin torque in Weyl semimetal with magnetic texture,"The spin-transfer torque is a fundamental physical quantity to operate the
+spintronics devices such as racetrack memory. We theoretically study the
+spin-transfer torque and analyze the dynamics of the magnetic domain walls in
+magnetic Weyl semimetals. Owing to the strong spin-orbit coupling in Weyl
+semimetals, the spin-transfer torque can be significantly enhanced, because of
+which they can provide a more efficient means of controlling magnetic textures.
+We derive the analytical expression of the spin-transfer torque and find that
+the velocity of the domain wall is one order of magnitude greater than that of
+conventional ferromagnetic metals. Furthermore, due to the suppression of
+longitudinal conductivity in the thin domain-wall configuration, the
+dissipation due to Joule heating for the spin-transfer torque becomes much
+smaller than that in bulk metallic ferromagnets. Consequently, the fast-control
+of the domain wall can be achieved with smaller dissipation from Joule heating
+in the Weyl semimetals as required for application to low-energy-consumption
+spintronics devices.",1903.00849v1
+2019-03-11,Effects of small-scale dynamo and compressibility on the $Λ$ effect,"The $\Lambda$ effect describes a rotation-induced non-diffusive contribution
+to the Reynolds stress. It is commonly held responsible for maintaining the
+observed differential rotation of the Sun and other late-type stars. Here the
+sensitivity of the $\Lambda$ effect to small-scale magnetic fields and
+compressibility is studied by means of forced turbulence simulations either
+with anisotropic forcing in fully periodic cubes or in density-stratified
+domains with isotropic forcing. Effects of small-scale magnetic fields are
+studied in cases where the magnetic fields are self-consistently generated by a
+small-scale dynamo. The results show that small-scale magnetic fields lead to a
+quenching of the $\Lambda$ effect which is milder than in cases where also a
+large-scale field is present. The effect of compressibility on the $\Lambda$
+effect is negligible in the range of Mach numbers from 0.015 to 0.8. Density
+stratification induces a marked anisotropy in the turbulence and a vertical
+$\Lambda$ effect if the forcing scale is roughly two times larger than the
+density scale height.",1903.04363v2
+2019-03-15,Stellar physics with high-resolution UV spectropolarimetry,"Current burning issues in stellar physics, for both hot and cool stars,
+concern their magnetism. In hot stars, stable magnetic fields of fossil origin
+impact their stellar structure and circumstellar environment, with a likely
+major role in stellar evolution. However, this role is complex and thus poorly
+understood as of today. It needs to be quantified with high-resolution UV
+spectropolarimetric measurements. In cool stars, UV spectropolarimetry would
+provide access to the structure and magnetic field of the very dynamic upper
+stellar atmosphere, providing key data for new progress to be made on the role
+of magnetic fields in heating the upper atmospheres, launching stellar winds,
+and more generally in the interaction of cool stars with their environment
+(circumstellar disk, planets) along their whole evolution.",1903.06509v1
+2019-03-28,Magnetic-Resonance-Induced Pseudo-electric Field and Giant Current Response in Axion Insulators,"A quantized version of the magnetoelectric effect, known as the topological
+magnetoelectric effect, can exist in a time-reversal invariant topological
+insulator with all its surface states gapped out by magnetism. This topological
+phase, called the axion insulator phase, has been theoretically proposed but is
+still lack of conclusive experimental evidence due to the small signal of
+topological magnetoelectric effect. In this work, we propose that the dynamical
+in-plane magnetization in an axion insulator can generate a ""pseudo-electric
+field"", which acts on the surface state of topological insulator films and
+leads to the non-zero response current. Strikingly, we find that the current at
+magnetic resonance (either ferromagnetic or anti-ferromagnetic) is larger than
+that of topological magnetoelectric effect by several orders of magnitude, and
+thereby serves as a feasible smoking gun to confirm the axion insulator phase
+in the candidate materials.",1903.12068v2
+2019-03-29,Electrical Néel-order switching in magnetron-sputtered CuMnAs thin films,"Antiferromagnetic materials as active components in spintronic devices
+promise insensitivity against external magnetic fields, the absence of own
+magnetic stray fields, and ultrafast dynamics at the picosecond time scale.
+Materials with certain crystal-symmetry show an intrinsic N\'eel-order
+spin-orbit torque that can efficiently switch the magnetic order of an
+antiferromagnet. The tetragonal variant of CuMnAs was shown to be electrically
+switchable by this intrinsic spin-orbit effect and its use in memory cells with
+memristive properties has been recently demonstrated for high-quality films
+grown with molecular beam epitaxy. Here, we demonstrate that the magnetic order
+of magnetron-sputtered CuMnAs films can also be manipulated by electrical
+current pulses. The switching efficiency and relaxation as a function of
+temperature, current density, and pulse width can be described by a
+thermal-activation model. Our findings demonstrate that CuMnAs can be
+fabricated with an industry-compatible deposition technique, which will
+accelerate the development cycle of devices based on this remarkable material.",1903.12387v2
+2019-04-01,51V-NMR study on the S=1/2 square lattice antiferromagnet K2V3O8,"Static and dynamic properties of the quasi-two-dimensional antiferromagnet
+K$_2$V$_3$O$_8$ have been investigated by $^{51}$V-NMR experiments on
+nonmagnetic V$^{5+}$ sites. Above the structural transition temperature
+$T_{\rm{S}}$ = 115 K, NMR spectra are fully compatible with the $P4bm$ space
+group symmetry. The formation of superstructure below $T_{\rm{S}}$ causes
+splitting of the NMR lines, which get broadened at lower temperatures so that
+individual peaks are not well resolved. Evolution of NMR spectra with magnetic
+field along $c$-axis below the magnetic transition temperature $T_{\rm{N}} \sim
+4$ K is qualitatively consistent with a simple N\'{e}el order and a spin flop
+transition. However, broad feature of the spectra does not rule out possible
+incommensurate spin structure. The spin-lattice relaxation rate $1/T_1$ below
+$T_{\rm{N}}$ shows huge enhancement for a certain range of magnetic field,
+which is independent of temperature and attributed to cross relaxation due to
+anomalously large nuclear spin-spin coupling between V$^{5+}$ and magnetic
+V$^{4+}$ sites. The results indicate strong gapless spin fluctuations, which
+could arise from incommesurate orders or complex spin textures.",1904.00909v1
+2019-04-03,Simulating chiral anomalies with spin dynamics,"Considering that the chiral kinetic equations of motion (CEOM) can be derived
+from the spin kinetic equations of motion (SEOM) for massless particles with
+approximations, we simulate the chiral anomalies by using the latter in a box
+system with the periodic boundary condition under a uniform external magnetic
+field. We found that the chiral magnetic effect is weaker while the damping of
+the chiral magnetic wave is stronger from the SEOM compared with that from the
+CEOM. In addition, effects induced by chiral anomalies from the SEOM are less
+sensitive to the decay of the magnetic field than from the CEOM due to the spin
+relaxation process.",1904.01834v2
+2019-05-10,Magnetoplasmons for the $α$-T$_3$ model with filled Landau levels,"Using the $\alpha$-T$_3$ model, we carried out analytical and numerical
+calculations for the static and dynamic polarization functions in the presence
+of a perpendicular magnetic field. These results were employed to determine the
+longitudinal dielectric function and the magnetoplasmon dispersion relation.
+The magnetic field splits the continuous valence, conduction and flat energy
+subband into discrete Landau levels which present significant effects on the
+polarization function and magnetoplasmon dispersion. We present results for a
+doped layer in the integer quantum Hall regime for fixed hopping parameter
+$\alpha$ and various magnetic fields as well as chosen magnetic field and
+different $\alpha$ in the random phase approximation.",1905.04387v3
+2019-05-15,Background-subtracted Solar Activity Maps,"We introduce the concept of a Background-subtracted Solar Activity Map
+(BaSAM) as a new quantitative tool to assess and visualize the temporal
+variation of the photospheric magnetic field and the UV 160 nm intensity. The
+method utilizes data of the Solar Dynamics Observatory (SDO) and is applicable
+to both full-disk observations and regions-of-interest. We illustrate and
+discuss the potential of BaSAM resorting to datasets representing solar minimum
+and maximum conditions: (1) Contributions of quiet-Sun magnetic fields, i.e.
+the network and (decaying) plage, to solar activity can be better determined
+when their variation is measured with respect to the background given by ""deep""
+magnetograms. (2) Flaring and intermittent brightenings are easily appraised in
+BaSAMs of the UV intensity. (3) Both magnetic-field and intensity variations
+demonstrated that the flux system of sunspots is well connected to the
+surrounding supergranular cells. In addition, producing daily full-disk BaSAMs
+for the entire mission time of SDO provides a unique tool to analyze solar
+cycle variations, showing how vigorous or frail are the variations of
+magnetic-field and intensity features.",1905.06057v1
+2019-05-16,Magnetogenesis from a rotating scalar: à la scalar chiral magnetic effect,"The chiral magnetic effect (CME) is a phenomenon in which an electric current
+is induced parallel to an external magnetic field in the presence of chiral
+asymmetry in a fermionic system. In this paper, we show that the electric
+current induced by the dynamics of a pseudo-scalar field which anomalously
+couples to electromagnetic fields can be interpreted as closely analogous to
+the CME. In particular, the velocity of the pseudo-scalar field, which is the
+phase of a complex scalar, indicates that the system carries a global U(1)
+number asymmetry as the source of the induced current. We demonstrate that an
+initial kick to the phase-field velocity and an anomalous coupling between the
+phase-field and gauge fields are naturally provided, in a set-up such as the
+Affleck-Dine mechanism. The resulting asymmetry carried by the Affleck-Dine
+field can give rise to instability in the (electro)magnetic field. Cosmological
+consequences of this mechanism are also investigated.",1905.06966v2
+2019-05-22,Current-Driven Dynamics of Magnetic Hopfions,"Topological magnetic textures have attracted considerable interest since they
+exhibit new properties and might be useful in information technology. Magnetic
+hopfions are three-dimensional (3D) spatial variations in the magnetization
+with a non-trivial Hopf index. We find that in ferromagnetic materials, two
+types of hopfions, Bloch-type and N\'{e}el-type hopfions, can be excited as
+metastable states in the presence of bulk and interfacial Dzyaloshinskii-Moriya
+interactions, respectively. We further investigate how hopfions can be driven
+by currents via spin-transfer torques (STTs) and spin-Hall torques (SHTs).
+Distinct from 2D ferromagnetic skyrmions, hopfions have a vanishing gyrovector.
+Consequently, there are no undesirable Hall effects. N\'{e}el-type hopfions
+move along the current direction via both STT and SHT, while Bloch-type
+hopfions can be moved either transverse to the current direction by SHT or
+parallel to the current direction by STT. Our findings open the door to
+utilizing hopfions as information carriers.",1905.09154v5
+2019-06-01,Polarized inelastic neutron scattering of non-reciprocal spin waves in MnSi,"We report spin-polarized inelastic neutron scattering of the dynamical
+structure factor of the conical magnetic helix in the cubic chiral magnet MnSi.
+We find that the spectral weight of spin-flip scattering processes is
+concentrated on single branches for wavevector transfer parallel to the helix
+axis as inferred from well-defined peaks in the neutron spectra. In contrast,
+for wavevector transfers perpendicular to the helix the spectral weight is
+distributed among different branches of the magnon band structure as reflected
+in broader features of the spectra. Taking into account the effects of
+instrumental resolution, our experimental results are in excellent quantitative
+agreement with parameter-free theoretical predictions. Whereas the dispersion
+of the spin waves in MnSi appears to be approximately reciprocal at low
+energies and small applied fields, the associated spin-resolved spectral weight
+displays a pronounced non-reciprocity that implies a distinct non-reciprocal
+response in the limit of vanishing uniform magnetization at zero magnetic
+field.",1906.00221v3
+2019-06-01,Magnetic fluctuations in the itinerant ferromagnet LaCrGe3 studied by 139La NMR,"LaCrGe$_3$ is an itinerant ferromagnet with a Curie temperature of $T_{\rm
+c}$ = 85 K and exhibits an avoided ferromagnetic quantum critical point under
+pressure through a modulated antiferromagnetic phase as well as tri-critical
+wing structure in its temperature-pressure-magnetic field ($T$-$p$-$H$) phase
+diagram. In order to understand the static and dynamical magnetic properties of
+LaCrGe$_3$, we carried out $^{139}$La nuclear magnetic resonance (NMR)
+measurements. Based on the analysis of NMR data, using the
+self-consistent-renomalization (SCR) theory, the spin fluctuations in the
+paramagnetic state are revealed to be isotropic ferromagnetic and three
+dimensional (3D) in nature. Moreover, the system is found to follow the
+generalized Rhodes-Wohfarth relation which is expected in 3D itinerant
+ferromagnetic systems. As compared to other similar itinerant ferromagnets, the
+Cr 3$d$ electrons and their spin fluctuations are characterized to have a
+relatively high degree of localization in real space.",1906.00249v1
+2019-06-12,Orbital Selectivity and Magnetic Ordering in Fe intercalated Dirac Semimetal Bi$_2$Se$_3$,"In this paper we investigate the intercalation effects of Iron (Fe) in the
+van der Waals gap of Bi$_2$Se$_3$ on the magnetic and transport properties
+using first-principles band structure estimations combined using dynamical
+mean-field theory. Inclusion of electronic correlations and spin-orbit coupling
+effects are found to result in the emergence of ferromagnetic properties in an
+intercalated Bi$_2$Se$_3$. Further the Dirac cone in the band structure of
+Bismuth Selenide is modified via Fe intercalation at moderate densities.
+Accompanied by novel structural effects, the onset of an orbital selective
+metal insulator transition in the Fe 3$d$ orbitals brings about a magnetic
+phase transition in the Fe intercalated Bi$_2$Se$_3$. Further we have explored
+the dependency of the inter-orbital electron-electron correlations on the
+magnetic ordering and the effects of intercalation in establishing new physical
+properties.",1906.05249v2
+2019-06-16,Kondo impurity at the edge of a superconducting wire,"Quantum impurity models are prevalent throughout many body physics, providing
+some prime examples of strongly correlated systems. Aside from being of great
+interest in themselves they can provide deep insight into the effects of strong
+correlations in general. The classic example is the Kondo model wherein a
+magnetic impurity is screened at low energies by a non interacting metallic
+bath. Here we consider a magnetic impurity coupled to a quantum wire with
+pairing interaction which dynamically generates a mass gap. Using Bethe Ansatz
+we solve the system exactly finding that it exhibits both screened and
+unscreened phases for an antiferromagnetic impurity. We determine the ground
+state density of states and magnetization in both phases as well as the
+excitations. In contrast to the well studied case of magnetic impurities in
+superconductors we find that there are no intragap bound states in the
+spectrum. The phase transition is not associated to a level crossing but with
+quantum fluctuations.",1906.06728v1
+2019-06-19,Edge localization of spin waves in antidot multilayers with perpendicular magnetic anisotropy,"We study the spin-wave dynamics in nanoscale antidot lattices based on Co/Pd
+multilayers with perpendicular magnetic anisotropy. Using time-resolved
+magneto-optical Kerr effect measurements we demonstrate that the variation of
+the antidot shape introduces significant change in the spin-wave spectra,
+especially in the lower frequency range. By employing micromagnetic simulations
+we show that additional peaks observed in the measured spectra are related to
+narrow shell regions around the antidots, where the magnetic anisotropy is
+reduced due to the Ga+ ion irradiation during the focused ion beam milling
+process of the antidot fabrication. The results point at new possibilities for
+exploitation of localized spin waves in out-of-plane magnetized thin films,
+which are easily tunable and suitable for magnonics applications.",1906.08109v2
+2019-06-21,Entanglement-based 3D magnetic gradiometry with an ultracold atomic scattering halo,"Ultracold collisions of Bose-Einstein condensates can be used to generate a
+large number of counterpropagating pairs of entangled atoms, which collectively
+form a thin spherical shell in momentum space, called a scattering halo. Here
+we generate a scattering halo composed almost entirely of pairs in a symmetric
+entangled state and observe a scattering angle-dependent mixing to the
+anti-symmetric state due to the presence of an inhomogeneous magnetic field. We
+report on a proof-of-principle application of the observed parity dynamics to
+demonstrate magnetic gradiometry, insensitive to common-mode fluctuations of
+the background magnetic field. Furthermore, the highly multimode nature and
+narrow radial width of the scattering halos enable 3D tomography of an
+interrogated field without the need for a scanning probe.",1906.08958v1
+2019-07-01,DC spinmotive force from microwave-active resonant dynamics of skyrmion crystal under a tilted magnetic field,"We theoretically show that a temporally oscillating spin-driven electromotive
+force or voltage with a large DC component can be generated by exciting
+microwave-active spin-wave modes of a skyrmion crystal confined in a quasi
+two-dimensional magnet under a tilted magnetic field. The DC component and the
+AC amplitude of the oscillating electric voltage is significantly enhanced when
+the microwave frequency is tuned to an eigenfrequency of the peculiar spin-wave
+modes of the skyrmion crystal called ``rotation modes"" and ``breathing mode"",
+whereas the sign of the DC component depends on the microwave polarization and
+on the spin-wave mode. These results provide an efficient means to convert
+microwaves to a DC electric voltage by using skyrmion-hosting magnets and to
+switch the sign of the voltage via tuning the microwave frequency, which are
+important capabilities for spintronic devices.",1907.00621v1
+2019-07-01,Nonlinear theory of magnetohydrodynamic flows of stratified rotating plasma in two-layer shallow water approximation. Rossby waves and their three-wave interactions,"This article deals with rotating magnetohydrodynamic flows of a thin
+stratified layer of astrophysical plasma in a gravitational field with a
+free-surface in a vertical external magnetic field. Magnetohydrodynamic
+equations are obtained in the two-layer shallow water approximation in an
+external magnetic field when plasma is divided into two layers of different
+densities. In the beta-plane approximation a system of shallow water equations
+for rotating stratified plasma in an external magnetic field is obtained. For
+stationary initial conditions in the form of vertical or horizontal magnetic
+field a linear theory has been developed and solutions have been found in the
+form of magneto-Rossby waves with modifications to them describing the effects
+of stratification. A qualitative analysis of the dispersion curves shows the
+presence of three-wave nonlinear interactions of magneto-Rossby waves for each
+of the stationary solutions. The appearance of parametric instabilities is
+shown and their increments are found.",1907.00743v1
+2019-07-01,Spinon Confinement and a Sharp Longitudinal Mode in Yb$_2$Pt$_2$Pb in Magnetic Fields,"The fundamental excitations in an antiferromagnetic chain of spins-1/2 are
+spinons, de-confined fractional quasiparticles that when combined in pairs,
+form a triplet excitation continuum. In an Ising-like spin chain the continuum
+is gapped and the ground state is N{\'e}el ordered. Here, we report high
+resolution neutron scattering experiments, which reveal how a magnetic field
+closes this gap and drives the spin chains in \YPP\ to a critical, disordered
+Luttinger-liquid state. In \YPP\ the effective spins-1/2 describe the dynamics
+of large, Ising-like Yb magnetic moments, ensuring that the measured
+excitations are exclusively longitudinal, which we find to be well described by
+time-dependent density matrix renormalization group calculations. The
+inter-chain coupling leads to the confinement of spinons, a condensed matter
+analog of quark confinement in quantum chromodynamics. Insensitive to
+transverse fluctuations, our measurements show how a gapless, dispersive
+longitudinal mode arises from confinement and evolves with magnetic order.",1907.01067v1
+2019-07-04,Self-induced spin glass state in elemental and crystalline neodymium,"Spin glasses are a highly complex magnetic state of matter, intricately
+linked to spin frustration and structural disorder. They exhibit no long-range
+order and exude aging phenomena, distinguishing them from quantum spin liquids.
+We report a new type of spin glass state, the spin-Q glass, observable in
+bulk-like crystalline metallic neodymium thick films. Using spin-polarized
+scanning tunneling microscopy combined with ab initio calculations and
+atomistic spin-dynamics simulations, we visualize the variations in
+atomic-scale non-collinear order and its response to magnetic field and
+temperature. We quantify the aging phenomena relating the glassiness to
+crystalline symmetry and the energy landscape. This result not only resolves
+the long-standing debate of the magnetism of neodymium, but also suggests that
+glassiness may arise in other magnetic solids lacking extrinsic disorder.",1907.02295v2
+2019-07-04,Dynamics of the magnetoelastic phase transition and adiabatic temperature change in Mn1.3Fe0.7P0.5Si0.55,"The adiabatic temperature change DTad of a Mn1.3Fe0.7P0.5Si0.55 Fe2P-type
+alloy was measured under different magnetic field-sweep rates from 0.93 Ts-1 to
+2870 Ts-1. We find a field-sweep-rate independent magnetocaloric effect due to
+a partial alignment of magnetic moments in the paramagnetic region overlapping
+with the magnetocaloric effect of the first-order phase transition.
+Additionally, the first-order phase transition is not completed even in fields
+up to 20 T leading to a non-saturating behavior of DTad. Measurements in
+different pulsed fields reveal that the first-order phase transition cannot
+follow the fast field changes as previously assumed, resulting in a distinct
+field-dependent hysteresis in DTad.",1907.02307v1
+2019-07-09,Synthetic dimensions and topological chiral currents in mesoscopic rings,"The recently-introduced concept of ""synthetic dimensions"" allows for the
+realization of higher-dimensional topological phenomena in lower-dimensional
+systems. In this work we study the complementary aspect that synthetic
+dimensions provide a natural route to topological states in mesoscopic hybrid
+devices. We demonstrate this for the current induced into a closed
+one-dimensional Aharonov-Bohm ring by the interaction with a dynamic mesoscopic
+magnet. The quantization of the magnetic moment provides a synthetic dimension
+that complements the charge motion around the ring. We present a direct mapping
+that places the combined ring-magnet system into the class of quantum Hall
+models, and demonstrate that topological features, combined with the magnet's
+anisotropy, can lead to clear signatures in the persistent current of the
+single-particle ground state.",1907.04231v1
+2019-07-10,Non-diffusive angular momentum transport in rotating $\bf z$-pinches,"The stability of conducting Taylor-Couette flows under the presence of
+toroidal magnetic background fields is considered. For strong enough magnetic
+amplitudes such magnetohydrodynamic flows are unstable against nonaxisymmetric
+perturbations which may also transport angular momentum. In accordance with the
+often used diffusion approximation one expects the angular momentum transport
+vanishing for rigid rotation. In the sense of a nondiffusive $\Lambda$ effect,
+however, even for {\em rigidly} rotating $z$-pinches an axisymmetric angular
+momentum flux appears which is directed outward (inward) for large (small)
+magnetic Mach numbers. The internal rotation in a magnetized rotating tank can
+thus never be uniform. Those particular rotation laws are used to estimate the
+value of the instability-induced eddy viscosity for which the nondiffusive
+$\Lambda$ effect and the diffusive shear-induced transport compensate each
+other. The results provide the Shakura-Sunyaev viscosity ansatz leading to
+numerical values linearly growing with the Reynolds number of rotation.",1907.08291v1
+2019-07-30,Oriented propagation of magnetization due to chiral edge modes in Kitaev-type models,"Detecting chiral edge modes in topological materials has been intensively
+pursued in experiments. However, the phenomena caused by the modes are not yet
+elucidated theoretically. We study the dynamics of chiral spinon wave packets
+at the edge in Kitaev-type magnets. More precisely, by relying on the exact
+solvability of the models, we construct a spinon wave packet, localized edge
+magnetization, which shows oriented propagation along the edge, whose behavior
+is expected from the chiral character of the dispersion relation of the chiral
+edge modes. In general, this approach enables us to study not only spin
+transport in anisotropic magnets but also charge transport in Bogoliubov-de
+Gennes-type superconductors because it does not rely on a conserved quantity.",1907.12863v2
+2019-08-12,On a simple derivation of the very low damping escape rate for classical spins by modifying the method of Kramers,"The original perturbative Kramers' method (starting from the phase space
+coordinates) (Kramers, 1940) of determining the energy-controlled-diffusion
+equation for Newtonian particles with separable and additive Hamiltonians is
+generalized to yield the energy-controlled diffusion equation and thus the very
+low damping (VLD) escape rate including spin-transfer torque for classical
+giant magnetic spins with two degrees of freedom. These have dynamics governed
+by the magnetic Langevin and Fokker-Planck equations and thus are generally
+based on non-separable and non-additive Hamiltonians. The derivation of the VLD
+escape rate directly from the (magnetic) Fokker-Planck equation for the surface
+distribution of magnetization orientations in the configuration space of the
+polar and azimuthal angles $(\vartheta, \varphi)$ is much simpler than those
+previously used.",1908.06747v1
+2019-09-12,"Giant Vesicles with Encapsulated Magnetic Nanowires as Versatile Carriers, Transported via Rotating and Non-Homogeneous Magnetic Fields","In this work, two real-time methods to transport magnetic nanowires confined
+in giant hybrid vesi-cles upon the application of different strategies are
+studied. The microscale carriers are either mag-netically guided through the
+viscous medium by a non-homogenous field or advected by precisely monitored
+hydrodynamic flows. The slender geometry of the magnetic component enables the
+ap-plication of large torques, the in-situ characterization of the rotational
+dynamics, as well as the guided propulsion via the continuous thrust of the
+nanowire tip on the confining bilayer. The flexi-bility of the vesicles,
+required to deform along the steering direction during passage through
+mi-croscale openings, is enhanced via the adsorption of non-ionic surfactants
+on the lipid membrane. The resulting integrated system is an excellent
+candidate to transport colloidal cargos or flu-id amounts of some picoliters in
+microfluidic platforms, even in physiological environments, since it combines
+the maneuverability of propelled microscopic systems and the protection
+conferred by the vesicle.",1909.05502v1
+2019-09-15,The Flyby Anomaly and the Gravitational-Magnetic Field Induced Frame-Dragging Effect around the Earth,"The anomalous energy difference observed during the Earth flybys is modelled
+here as a dynamical effect resulting from the coupling of the gravitational and
+the magnetic fields of the Earth. The theoretical analysis shows that general
+relativistic frame-dragging can become modified under the Earth's magnetic
+field by orders of magnitude. For twelve flyby cases, including the null
+results reported in some recent flybys, the predicted velocities correspond to
+the observed velocities within the observational error. The gravito-magnetic
+effect is also shown to account for the linear distance relation,
+time-variation of the anomalous energy, and the reduction in the anomalous
+velocity for high altitude flybys near the Earth.",1909.08083v1
+2019-09-27,Thermally driven two-magnet nano-oscillator with large spin-charge conversion,"Next-generation spintronic applications require material properties that can
+be hardly met by one material candidate. Here we demonstrate that by combining
+insulating and metallic magnets, enhanced spin-charge conversion and
+energy-efficient thermal spin currents can be realized. We develop a nanowire
+device consisting of an yttrium iron garnet and permalloy bi-layer. An
+interfacial temperature gradient drives the nanowire magnetization into
+auto-oscillations at gigahertz frequencies. Interfacial spin coupling and
+magnetoresistance of the permalloy layer translate spin dynamics into sizable
+microwave signals. The results show prospect for energy-efficient spintronic
+devices and present an experimental realization of magnon condensation in a
+heterogeneous magnetic system.",1909.12445v1
+2019-09-29,Perfect optical absorption-enhanced magneto-optic Kerr effect microscopy,"Magnetic and spintronic media have offered fundamental scientific subjects
+and technological applications. Magneto-optic Kerr effect (MOKE) microscopy
+provides the most accessible platform to study the dynamics of spins, magnetic
+quasi-particles, and domain walls. However, in the research of nanoscale spin
+textures and state-of-the-art spintronic devices, optical techniques are
+generally restricted by the extremely weak magneto-optical activity and
+diffraction limit. Highly sophisticated, expensive electron microscopy and
+scanning probe methods thus have come to the forefront. Here, we show that
+perfect optical absorption (POA) dramatically improves the performance and
+functionality of MOKE microscopy. For 1-nm-thin Co film, we demonstrate a Kerr
+amplitude as large as 20 degree and magnetic domain imaging visibility of 0.47.
+Especially, POA-enhanced MOKE microscopy enables real-time detection and
+statistical analysis of sub-wavelength magnetic domain reversals. Furthermore,
+we exploit enhanced magneto-optic birefringence and demonstrate analyser-free
+MOKE microscopy. The POA technique is promising for optical investigations and
+applications of nanomagnetic systems.",1909.13275v1
+2019-09-29,Magnetic Dissipation of Near-Wall Turbulent Coherent Structures in Magnetohydrodynamic Pipe Flows,"Relaminarization of wall-bounded turbulent flows by means of external static
+magnetic fields is a long-known phenomenon in the physics of electrically
+conducting fluids at low magnetic Reynolds numbers. Despite the large
+literature on the subject, it is not yet completely clear what combination of
+the Hartmann ($M$) and the Reynolds number has to be used to predict the
+laminar-turbulent transition in channel or pipe flows fed by upstream turbulent
+flows free of magnetic perturbations. Relying upon standard phenomenological
+approaches related to mixing length and structural concepts, we put forward
+that $M/R_\tau$, where $R_\tau$ is the friction Reynolds number, is the
+appropriate controlling parameter for relaminarization, a proposal which finds
+good support from available experimental data.",1909.13289v3
+2019-10-18,Lattice study of electromagnetic conductivity of quark-gluon plasma in external magnetic field,"We study the electromagnetic (e.m.) conductivity of QGP in a magnetic
+background by lattice simulations with $N_f = 2+1$ dynamical rooted staggered
+fermions at the physical point. We study the correlation functions of the
+e.m.~currents at $T=200,\,250$\,MeV and use the Tikhonov approach to extract
+the conductivity. This is found to rise with the magnetic field in the
+direction parallel to it and to decrease in the transverse direction, giving
+evidence for both the Chiral Magnetic Effect and the magnetoresistance
+phenomenon in QGP. We also estimate the chiral charge relaxation time in QGP.",1910.08516v1
+2019-10-21,Quantum Depinning of a Magnetic Skyrmion,"We investigate the quantum depinning of a weakly driven skyrmion out of an
+impurity potential in a mesoscopic magnetic insulator. For small barrier
+height, the Magnus force dynamics dominates over the inertial one, and the
+problem is reduced to a massless charged particle in a strong magnetic field.
+The universal form of the WKB exponent, the rate of tunneling, and the
+crossover temperature between thermal and quantum tunneling is provided,
+independently of the detailed form of the pinning potential. The results are
+discussed in terms of macroscopic parameters of the insulator Cu2OSeO3 and
+various skyrmion radii. We demonstrate that small enough magnetic skyrmions,
+with a radius of ~ 10 lattice sites, consisting of some thousands of spins, can
+behave as quantum objects at low temperatures in the mK regime.",1910.09585v2
+2019-10-24,Electron spin resonance in spiral antiferromagnet linarite: theory and experiment,"We present combined experimental and theoretical investigation of the
+low-frequency ESR dynamics in the ordered phases of magnetic mineral linarite.
+This material consists of weakly coupled spin-1/2 chains of copper ions with
+frustrated ferro- and antiferromagnetic interactions. In zero magnetic field,
+linarite orders into a spiral structure and exhibits a peculiar magnetic phase
+diagram sensitive to the field orientation. The resonance frequencies and their
+field dependence are analyzed combining microscopic and macroscopic theoretical
+approaches and precise values of magnetic anisotropy constants are obtained. We
+conclude that possible realization of exotic multipolar quantum states in this
+material is greatly influenced by the biaxial anisotropy.",1910.11056v1
+2019-10-24,Spin waves in ferromagnetic thin films,"A spin wave is the disturbance of intrinsic spin order in magnetic materials.
+In this paper, a spin wave in the Landau-Lifshitz-Gilbert equation is obtained
+based on the assumption that the spin wave maintains its shape while it
+propagates at a constant velocity. Our main findings include: (1) in the
+absence of Gilbert damping, the spin wave propagates at a constant velocity
+with the increment proportional to the strength of the magnetic field; (2) in
+the absence of magnetic field, at a given time the spin wave converges
+exponentially fast to its initial profile as the damping parameter goes to zero
+and in the long time the relaxation dynamics of the spin wave converges
+exponentially fast to the easy-axis direction with the exponent proportional to
+the damping parameter; (3) in the presence of both Gilbert damping and magnetic
+field, the spin wave converges to the easy-axis direction exponentially fast at
+a small timescale while propagates at a constant velocity beyond that. These
+provides a comprehensive understanding of spin waves in ferromagnetic
+materials.",1910.11200v1
+2019-10-30,Moiré pattern of spin liquid and Neel magnet in a Kitaev chain,"A moir\'{e} pattern occurs when two periodic structures in a system have a
+slight mismatch period, resulting the coexistence of distinct phases in
+different large-scale spacial regions of the same system. Two periodic
+structures can arise from periodic electric and magnetic fields, respectively.
+We investigated the moir\'{e} pattern via a dimerized Kitaev spin chain with a
+periodic transverse field, which can be mapped onto the system of dimerized
+spinless fermions with p-wave superconductivity. The exact solution for
+staggered field demonstrated that the ground state has two distinct phases: (i)
+Neel magnetic phase for nonzero field, (ii) Spin liquid phase due to the
+emergence of isolated flat Bogoliubov--de Gennes band for vanishing field. We
+computed the staggered magnetization and local density of states
+(\textrm{LDOS}) for the field with a slight difference period to the chain
+lattice. Numerical simulation demonstrated that such two phases appear
+alternatively along the chain with a long beat period. Additionally, we
+proposed a dynamic scheme to detect the Moir\'{e} fringes based on the
+measurement of Loschmidt echo (\textrm{LE}) in the presence of local
+perturbation.",1910.13682v1
+2019-11-05,Spin-selective transmission through a single-stranded magnetic helix,"Magnetic helix (MH) structure can be a role model for future spintronic
+devices. Utilizing the advantage of constructing possible magnetic
+configurations, in the present work first time we investigate spintronic
+behavior, to the best of our knowledge, in a helical geometry with finite
+magnetic ordering. The interplay between short-range and long-range hopping of
+electrons yields many non-trivial features which are thoroughly studied. Quite
+interestingly we see that the MH exhibits the strong chiral-induced spin
+selectivity effect, like what is observed in chiral molecules. Finally, to make
+the model more realistic we also examine the effect of helical dynamics. All
+the results are valid for a wide range of physical parameters, which prove the
+robustness of our analysis.",1911.01630v1
+2019-11-05,Impurity Moments Conceal Low-Energy Relaxation of Quantum Spin Liquids,"We scrutinize the magnetic properties of $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl
+through its first-order metal-insulator transition at $T_{\rm CO}=30$ K by
+means of $^1$H nuclear magnetic resonance (NMR). While in the metal we find
+Fermi-liquid behavior with temperature-independent $(T_1T)^{-1}$, the
+relaxation rate exhibits a pronounced enhancement when charge order sets in.
+The NMR spectra remain unchanged through the transition and no magnetic order
+stabilizes down to 25 mK. Similar to the isostructural spin-liquid candidates
+$\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ and
+$\kappa$-(BEDT-TTF)$_2$Ag$_2$(CN)$_3$, $T_1^{-1}$ acquires a dominant maximum
+(here around 5 K). Field-dependent experiments identify the low-temperature
+feature as a dynamic inhomogeneity contribution that is typically dominant over
+the intrinsic relaxation but gets suppressed with magnetic field.",1911.02057v1
+2019-11-12,Iridium Enabled Field-free Spin-orbit Torque Switching of Perpendicular Magnetic Tunnel Junction Device,"Writing magnetic bits by spin-orbit torques (SOTs) arising from spin Hall
+effect creates new possibilities for ultrafast and low-power magnetoresistive
+random access memory (MRAM). For perpendicular MRAM, an extra in-plane field is
+required to break the symmetry for the deterministic SOT writing of the
+perpendicular storage layer. Although schemes have been demonstrated in
+external-field-free SOT switching of a perpendicular layer, practically
+integrating them with perpendicular MTJs still appears to be challenging. Here,
+we present experimental demonstration of spin-orbit torques (SOTs) switching a
+perpendicular magnetic tunnel junction (MTJ) device without applying an
+external magnetic field. An Ir layer is used to serve dual-purpose of both
+injecting the pure spin current via spin Hall effect and mediating an in-plane
+exchange field to the perpendicular free layer of the MTJ. Robust field-free
+SOT switching with pulsed write path current is demonstrated for various MTJ
+sizes ranging from 50 nm to 500 nm. The effect of MTJ size and pulse width on
+the critical switching current is studied. Combined micromagnetic simulations
+are carried out to provide in-depth analysis of the switching dynamics as well
+as the thermal effect on the switching.",1911.05007v1
+2019-11-19,Unidirectional Seebeck effect in magnetic topological insulators,"We theoretically investigate the temperature gradient-dependent or
+unidirectional Seebeck effect (USE) in a magnetic/ nonmagnetic topological
+insulator (TI) heterostructure with in-plane magnetization in terms of the
+semiclassical electron dynamics and Fermi golden rule. The USE has a quantum
+origin arising from the magnon asymmetric scattering of surface Dirac electrons
+on TI. We discuss the USE in the heterostructures,
+Cr$_{x}$(Bi$_{1-y}$Sb$_y$)$_{2-x}$Te$_{3}$/ (Bi$_{1-y}$Sb$_{y})_2$Te$_{3}$. The
+USE exhibits $\cos\phi$-dependence (measured from $y$-direction) on the
+orientation of magnetization. It's found that the sign of USE stays unchanged
+when the system is transferred from $p$-doping to $n$-doping. The USE shows on
+inverse-linearly temperature dependent at high temperature.",1911.08122v1
+2019-11-27,Radial flow induced by inhomogeneous magnetic field in heavy ion collisions,"In this paper, we study the effects of an in-homogeneous magnetic field on
+the quark gluon plasma dynamics, within the Magneto-Hydrodynamic framework. We
+have investigated the effect of an inhomogeneous external magnetic field on the
+transverse expansion of in-viscid fluid created in high energy nuclear
+collisions. Transverse velocity and energy density are modified by the presence
+of the magnetic field. This effects can also influence the transverse momentum
+spectrum for particles at the freeze-out surface. In this context we obtained
+an interesting comparison with data extracted from heavy-ion collisions.",1911.13209v1
+2019-12-10,Husimi function for electrons moving in magnetic fields,"Husimi functions allow one to obtain sensible and useful phase space
+probability distributions from quantumechanical wavefunctions or classical wave
+fields, linking them to (semi-)classical methods and intuition. They have been
+used in several fields of physics, including electronic transport. We show that
+applying Husimi functions to ballistic electron dynamics in magnetic fields
+needs special consideration in order for them to obey gauge invariance and
+energy conservation. We therefore extend the Husimi function formalism to allow
+for magnetic fields making use of magnetic translation operators. We
+demonstrate the application in tight-binding magneto-transport calculations in
+graphene nanodevices, highlighting connections with Klein tunneling. In
+continuation of recent work, with this paper we further pave the way for using
+the Husimi function to unravel quantum transport phenomena in nanodevices.",1912.04622v1
+2019-12-10,Electron-Acoustic Solitons in Magnetized Collisional Nonthermal Plasmas,"The properties of obliquely propagating dissipative electron-acoustic
+solitary waves (OPdEASWs) have been investigated in a magnetized collisional
+superthermal plasma consisting of inertial cold electrons, inertialess hot
+electrons featuring kappa-distribution and static ions via the fluid dynamical
+approach. By using the reductive perturbation technique, a nonlinear Schamel
+equation that governs the nonlinear features of OPdEASWS is obtained. The
+solitary wave solution of the Schamel equation is used to examine the basic
+features of small, but finite amplitude OPdEASWs in such a magnetized
+collisional superthermal plasma. The basic features (width, amplitude, speed,
+etc.) of OPdEASWs are found to be modified by the different plasma
+configuration parameters, such as the superthermality index, obliquity angle,
+collisional parameter, trapping parameter, and external magnetic field. The
+nature of electrostatic disturbances, that may propagate in different realistic
+space and laboratory plasma systems (e.g., in Saturn ring), are briefly
+discussed.",1912.04756v5
+2019-12-12,Robust spin and charge excitations throughout high-$T_c$-cuprate phase diagram from incipient Mottness,"The generic phase diagram of lightly hole-doped high-$T_c$-cuprates hosts
+antiferromagnetic insulating phase with well-defined spin-wave excitations.
+Contrary to the weak-coupling prediction, these modes persist up to the
+overdoped metallic regime as intense and dispersive paramagnons. Here we report
+on our study of the low-energy magnetic and charge excitations within the
+extended Hubbard model at strong-coupling, using a modified $1/N$ expansion
+method with a variational state serving as the saddle point solution. Despite
+clear separation of magnetic and Hubbard-$U$ energy scales, we find that
+incipient Mottness affects qualitatively dispersions and widths of magnetic
+modes throughout entire phase diagram. The obtained magnetic and charge
+dynamical structure factors agree semi-quantitatively with recent resonant
+$X$-ray and neutron scattering data for
+$\mathrm{La_{2-\mathit{x}}Sr_\mathit{x}CuO_4}$ and
+$\mathrm{(Bi,Pb)_2(Sr,La)_2CuO_{6+\delta}}$ at all available doping levels. The
+weak-coupling random-phase-approximation fails already for underdoped samples,
+pointing to the non-trivial intertwining of distinct energy scales in cuprate
+superconductors. The existence of a discrete charge mode which splits off the
+electron-hole continuum is also predicted.",1912.06232v2
+2019-12-13,The physics of helical electron beam in a uniform magnetic field as a testing ground of gauge principle,"According to Bliokh et al., allowing free propagation along the direction of
+a uniform magnetic field, the familiar Landau electron state can be regarded as
+a non-diffracting version of the helical electron beam propagating along the
+magnetic field. Based on this observation, they argued that, while propagating
+along the magnetic field, the Landau electrons receive characteristic rotation
+with three different angular velocities, depending on the eigen-value $m$ of
+the canonical OAM operator, which is generally gauge-variant, and this
+splitting was in fact experimentally confirmed. Through complete analyses of
+highly mysterious $m$-dependent rotational dynamics of the quantum Landau
+states, we try to make clear how and why their observation does not contradict
+the widely-believed gauge principle.",1912.06297v2
+2019-12-26,Arbitrary amplitude ion acoustic solitary structures in a collisionless magnetized plasma consisting of nonthermal and isothermal electrons,"We have used the Sagdeev pseudo-potential technique to investigate the
+arbitrary amplitude ion acoustic solitons, double layers and supersolitons in a
+collisionless magnetized plasma consisting of adiabatic warm ions, isothermal
+cold electrons and nonthermal hot electrons immersed in an external uniform
+static magnetic field. We have used the phase portraits of the dynamical system
+describing the nonlinear behaviour of ion acoustic waves to confirm the
+existence of different solitary structures. We have also investigated the
+transition of different solitary structures: soliton (before the formation of
+double layer) $\rightarrow$ double layer $\rightarrow$ supersoliton
+$\rightarrow$ soliton (soliton after the formation of double layer) by
+considering the variation of $\theta$ only, where $\theta$ is the angle between
+the direction of the external uniform static magnetic field and the direction
+of propagation of the wave.",1912.11881v1
+2019-12-04,Relativistic and magnetic effects in photo ionization of hydrogen-like ions,"We investigate the role of relativistic and magnetic corrections in photo
+ionization of hydrogen-like ions. For hydrogen, the wavelengths of the laser
+resides in the weakly ultra violet region. For higher nuclear charges, the
+laser parameters are scaled in a manner which renders the time-dependent
+Schr{\""o}dinger equation in the dipole approximation independent of nuclear
+charge. By comparing with numerical solutions of both the relativistic
+time-dependent Dirac equation and the non-relativistic Schr{\""o}dinger equation
+-- with and without magnetic interactions, the influence of these interactions
+are revealed. Moreover, we investigate to what extent relativistic effects are
+induced by the relativistic shift in the structure of the ions or by the strong
+external field. In agreement with a recent work, Ivanova et al., Phys. Rev. A
+{\bf 98}, 063402 (2018), we find that the dominant relativistic correction is
+the former, i.e., the relativistic shift in the binding energy of the ions.
+However, dynamical relativistic corrections induced by the laser field are also
+seen -- in addition to a significant influence of the magnetic field for the
+longer wavelengths.",2001.00646v1
+2020-01-14,Superintegrable Bertrand magnetic geodesic flows,"The problem of description of superintegrable systems (i.e., systems with
+closed trajectories in a certain domain) in the class of rotationally symmetric
+natural mechanical systems goes back to Bertrand and Darboux. We describe all
+superintegrable (in a domain of slow motions) systems in the class of
+rotationally symmetric magnetic geodesic flows. We show that all sufficiently
+slow motions in a central magnetic field on a two-dimensional manifold of
+revolution are periodic if and only if the metric has a constant scalar
+curvature and the magnetic field is homogeneous, i.e. proportional to the area
+form.",2001.05067v1
+2020-01-20,Magnetic skyrmion interactions in the micromagnetic framework,"Magnetic skyrmions are localized swirls of magnetization with a non-trivial
+topological winding number. This winding increases their robustness to
+superparamagnetism and gives rise to a myriad of novel dynamical properties,
+making them attractive as next-generation information carriers. Recently the
+equation of motion for a skyrmion was derived using the approach pioneered by
+Thiele, allowing for macroscopic skyrmion systems to be modeled efficiently.
+This powerful technique suffers from the prerequisite that one must have a
+priori knowledge of the functional form of the interaction between a skyrmion
+and all other magnetic structures in its environment. Here we attempt to
+alleviate this problem by providing a simple analytic expression which can
+generate arbitrary repulsive interaction potentials from the micromagnetic
+Hamiltonian. We also discuss a toy model of the radial profile of a skyrmion
+which is accurate for a wide range of material parameters.",2001.07193v1
+2020-02-06,Simulation of plasmaspheric plume impact on dayside magnetic reconnection,"During periods of strong magnetic activity, cold dense plasma from the
+plasmasphere typically forms a plume extending towards the dayside
+magnetopause, eventually reaching it. In this work, we present a large-scale
+two-dimensional fully kinetic Particle-In-Cell simulation of a reconnecting
+magnetopause hit by a propagating plasmaspheric plume. The simulation is
+designed so that it undergoes four distinct phases: initial unsteady state,
+steady state prior to plume arrival at the magnetospause, plume interaction and
+steady state once the plume is well engulfed in the reconnection site. We show
+the evolution of the magnetopause's dynamics subjected to the modification of
+the inflowing plasma. Our main result is that the change in the plasma
+temperature (cold protons in the plume) have no effects on the magnetic
+reconnection rate, which on average depends only on the inflowing magnetic
+field and total ion density, before, during and after the impact.",2002.02243v1
+2020-03-17,Domain wall dynamics in stepped magnetic nanowire with perpendicular magnetic anisotropy,"Micromagnetic simulation is carried out to investigate the current-driven
+domain wall (DW) in a nanowire with perpendicular magnetic anisotropy (PMA). A
+stepped nanowire is proposed to pin DW and achieve high information storage
+capacity based on multi-bit per cell scheme. The DW speed is found to increase
+for thicker and narrower nanowires. For depinning DW from the stepped region,
+the current density Jdep is investigated with emphasis on device geometry and
+materials intrinsic properties. The Jdep could be analytically determined as a
+function of the nanocontriction dimension and the thickness of the nanowire.
+Furthermore, Jdep is found to exponential dependent on the anisotropy energy
+and saturation magnetization, offering thus more flexibility in adjusting the
+writing current for memory applications.",2003.07721v1
+2020-04-01,The influence of an applied magnetic field on the self-assembly of magnetic nanogels,"Using Langevin dynamics simulations, we investigate the self-assembly of
+magnetic nanogels in the presence of applied magneticfields of moderate
+strength. We find that even weak fields lead to drastic changes in the
+structure factors of both, the embeddedmagnetic nanoparticles and of whole
+nanogel particles. Nanogels assemble by uniting magnetic particle clusters
+forming inter-gelbridges. At zero field the average amount of such bridges for
+a pair of nanogels is close to one, whereas even for weak fields itfastly
+doubles. Rapid growth of cluster size at low values of the applied field is
+followed by a broad region of slow increase, causedby the mechanical
+constraints imposed the polymer matrix. The influence of the latter manifests
+itself in both, the slow growth ofthe magnetisation curve at intermediate
+fields and the slow decay of the total Zeeman energy.",2004.00725v1
+2020-04-09,Nanoscale electrometry based on a magnetic-field-resistant spin sensor,"The nitrogen-vacancy (NV) center is a potential atomic-scale spin sensor for
+electric field sensing. However, its natural susceptibility to the magnetic
+field hinders effective detection of the electric field. Here we propose a
+robust electrometric method utilizing continuous dynamic decoupling (CDD)
+technique. During the CDD period, the NV center evolves in a dressed-state
+space, where the sensor is resistant to magnetic fields but remains sensitive
+to electric fields. As an example, we use this method to isolate the electric
+noise from a complex electro-magnetical environment near diamond surface via
+measuring the dephasing rate between dressed states. By reducing the surface
+electric noise with different covered liquids, we observe an unambiguous
+relation between the dephasing rate and the dielectric permittivity of the
+liquid, which enables a quantitative investigation of electric noise model near
+diamond surface.",2004.04385v1
+2020-04-14,Probing photo-induced rearrangements in the NdNiO$_{3}$ magnetic spiral with polarization-sensitive ultrafast resonant soft x-ray scattering,"We use resonant soft X-ray diffraction to track the photo-induced dynamics of
+the antiferromagnetic structure in a NdNiO$_{3}$ thin film. Femtosecond laser
+pulses with a photon energy of 0.61 eV, resonant with electron transfer between
+long-bond and short-bond nickel sites, are used to excite the material and
+drive an ultrafast insulator-metal transition. Polarization sensitive soft
+X-ray diffraction, resonant to the nickel L$_{3}$-edge, then probes the
+evolution of the underlying magnetic spiral as a function of time delay with 80
+picosecond time resolution. By modelling the azimuthal dependence of the
+scattered intensity for different linear X-ray polarizations, we benchmark the
+changes of the local magnetic moments and the spin alignment. The measured
+changes are consistent with a reduction of the long-bond site magnetic moments
+and an alignment of the spins towards a more collinear structure at early time
+delays.",2004.06752v2
+2020-04-20,"Optical detection of electron spin dynamics driven by fast variations of a magnetic field: a simple method to measure $T_1$, $T_2$, and $T_2^*$ in semiconductors","We develop a simple method for measuring the electron spin relaxation times
+$T_1$, $T_2$ and $T_2^*$ in semiconductors and demonstrate its exemplary
+application to $n$-type GaAs. Using an abrupt variation of the magnetic field
+acting on electron spins, we detect the spin evolution by measuring the Faraday
+rotation of a short laser pulse. Depending on the magnetic field orientation,
+this allows us to measure either the longitudinal spin relaxation time $T_1$ or
+the inhomogeneous transverse spin dephasing time $T_2^*$. In order to determine
+the homogeneous spin coherence time $T_2$, we apply a pulse of an oscillating
+radiofrequency (rf) field resonant with the Larmor frequency and detect the
+subsequent decay of the spin precession. The amplitude of the rf-driven spin
+precession is significantly enhanced upon additional optical pumping along the
+magnetic field.",2004.09408v1
+2020-05-06,Sub-Nanosecond Spin-Transfer Torque in an Ensemble of Superparamagnetic-Like Nanomagnets,"Spin currents can exert spin-transfer torques on magnetic systems even in the
+limit of vanishingly small net magnetization, as is the case for
+antiferromagnets. Here, we experimentally show that a spin-transfer torque is
+operative in a material with weak, short-range magnetic order -- namely, a
+macroscopic ensemble of superparamagnetic-like Co nanomagnets. We employ
+element- and time-resolved X-ray ferromagnetic resonance (XFMR) spectroscopy to
+directly detect sub-ns dynamics of the Co nanomagnets, excited into precession
+with cone angle $\geq$0.003$^{\circ}$ by an oscillating spin current. XFMR
+measurements reveal that as the net moment of the ensemble decreases, the
+strength of the spin-transfer torque increases relative to those of magnetic
+field torques. Our findings point to spin-transfer torque as an effective way
+to manipulate the state of nanomagnet ensembles at sub-ns timescales.",2005.03081v1
+2020-05-21,Temporal Memory with Magnetic Racetracks,"Race logic is a relative timing code that represents information in a
+wavefront of digital edges on a set of wires in order to accelerate dynamic
+programming and machine learning algorithms. Skyrmions, bubbles, and domain
+walls are mobile magnetic configurations (solitons) with applications for
+Boolean data storage. We propose to use current-induced displacement of these
+solitons on magnetic racetracks as a native temporal memory for race logic
+computing. Locally synchronized racetracks can spatially store relative timings
+of digital edges and provide non-destructive read-out. The linear kinematics of
+skyrmion motion, the tunability and low-voltage asynchronous operation of the
+proposed device, and the elimination of any need for constant skyrmion
+nucleation make these magnetic racetracks a natural memory for low-power,
+high-throughput race logic applications.",2005.10704v1
+2020-06-16,Antiferromagnetic long-range order in $5d^1$ double-perovskite Sr$_2$MgReO$_6$,"The double-perovskite A$_2$BB'O$_6$ with heavy transition metal ions on the
+ordered B' sites is an important family of compounds to study the interplay
+between electron correlation and spin-orbit coupling (SOC). Here we prepared
+high-quality Sr$_2$MgReO$_6$ powder and single-crystal samples and performed
+non-resonant and resonant synchrotron x-ray diffraction experiments to
+investigate its magnetic ground state. By combining the magnetic susceptibility
+and heat capacity measurements, we conclude that Sr$_2$MgReO$_6$ exhibits a
+layered antiferromagnetic (AF) order at temperatures below $\sim$ 55 K with a
+propagation vector q = (001), which contrasts the previously suspected spin
+glass state. Our works clarify the magnetic order in Sr$_2$MgReO$_6$ and
+demonstrate it as a candidate system to look for magnetic octupolar orders and
+exotic spin dynamics.",2006.08865v1
+2020-06-19,Tidal Love numbers of Proca stars,"Proca stars (arXiv:1508.05395) are everywhere regular, asymptotically flat
+self-gravitating solitons composed of complex, massive vector bosons, forming a
+macroscopic, star-sized, Bose-Einstein condensate. They have been suggested as
+a classical, dynamical model of exotic compact objects, black hole mimickers
+and dark matter candidates. In spherical symmetry, they are qualitatively
+similar to their scalar cousins, the standard (scalar) boson stars in all
+respects studied so far. Here we study the tidal deformability and the
+quadrupolar tidal Love numbers, both electric-type and magnetic-type, of
+spherically symmetric Proca stars. The equations for the perturbations are
+derived and the numerical values of the Love numbers for some concrete
+background solutions are computed. We observe that both Love numbers are
+qualitatively similar to the ones of the scalar boson stars; in particular, the
+electric-type (magnetic-type) quadrupolar Love numbers are positive (negative)
+for Proca stars. Quantitatively, for the same compactness, the electric and
+magnetic Love numbers in the Proca case are closer (in magnitude) than in the
+scalar case, with the electric Love numbers having a slightly larger magnitude
+than the magnetic ones.",2006.11083v1
+2020-06-22,Spin-orbit torque induced magnetisation dynamics and switching in CoFeB/Ta/CoFeB system with mixed magnetic anisotropy,"Spin-orbit torque (SOT) induced magnetisation switching in CoFeB/Ta/CoFeB
+trilayer with two CoFeB layers exhibiting in-plane magnetic anisotropy (IPMA)
+and perpendicular magnetic anisotropy (PMA) is investigated. Interlayer
+exchange coupling (IEC), measured using ferromagnetic resonance technique is
+modified by varying thickness of Ta spacer. The evolution of the IEC leads to
+different orientation of the magnetic anisotropy axes of two CoFeB layers: for
+thicker Ta layer where magnetisation prefers antiferromagnetic ordering and for
+thinner Ta layer where ferromagnetic coupling exists. Magnetisation state of
+the CoFeB layer exhibiting PMA is controlled by the spin-polarized current
+originating from SOT in $\mu m$ sized Hall bars. The evolution of the critical
+SOT current density with Ta thickness is presented, showing an increase with
+decreasing $t_\mathrm{Ta}$, which coincides with the coercive field dependence.
+In a narrow range of $t_\mathrm{Ta}$ corresponding to the ferromagnetic IEC,
+the field-free SOT-induced switching is achieved.",2006.12068v1
+2020-06-24,Magnetic order and ballistic spin transport in a sine-Gordon spin chain,"We report the results of muon-spin spectroscopy ($\mu^+$SR) measurements on
+the staggered molecular spin chain [pym-Cu(NO$_3$)$_2$(H$_2$O)$_2$] (pym =
+pyrimidine), a material previously described using sine-Gordon field theory.
+Zero-field $\mu^+$SR reveals a long range magnetically-ordered ground state
+below a transition temperature $T_\mathrm{N}=0.22(1)$ K. Using
+longitudinal-field (LF) $\mu^+$SR we investigate the dynamic response in
+applied magnetic fields $0< B < 500$ mT and find evidence for ballistic spin
+transport. Our LF $\mu^+$SR measurements on the chiral spin chain
+[Cu(pym)(H$_2$O)$_4$]SiF$_6 \cdot $H$_2$O instead demonstrate one-dimensional
+spin diffusion and the distinct spin transport in these two systems likely
+reflects differences in their magnetic excitations.",2006.13743v1
+2020-06-30,Operando Control of Skyrmion Density in a Lorentz Transmission Electron Microscope with Current Pulses,"Magnetic skyrmions hold promise for spintronic devices. To explore the
+dynamical properties of skyrmions in devices, a nanoscale method to image spin
+textures in response to a stimulus is essential. Here, we apply a technique for
+operando electrical current pulsing of chiral magnetic devices in a Lorentz
+transmission electron microscope. In ferromagnetic multilayers with interfacial
+Dzyaloshinskii-Moriya interaction (DMI), we study the creation and annihilation
+of skyrmions localized by point-like pinning sites due to defects. Using a
+combination of experimental and micromagnetic techniques, we establish a
+thermal contribution for the creation and annihilation of skyrmions in our
+study. Our work reveals a mechanism for controlling skyrmion density, which
+enables an examination of skyrmion magnetic field stability as a function of
+density. We find that high-density skyrmion states are more stable than
+low-density states or isolated skyrmions resisting annihilation over a magnetic
+field range that increases monotonically with density.",2006.16780v1
+2020-07-04,High Entropy Alloys as a new metaphor in sociophysics,"Most of the opinion dynamics models in sociophysics have their historic
+origin in studies two-dimensional magnetization phenomena. This metaphor has
+proven quite useful, as it allowed to use well known techniques, relating
+individual behaviours of single spins and their interactions, to large scale
+properties, such as magnetization or magnetic domains creation. These physical
+properties were then ``mapped'' to social concepts: spin orientation to a
+person's views on a specific issue, magnetization to global opinion on the
+issue, etc. During the past 20 years, the models were significantly expanded,
+using more complex individual agent characteristics and even more complex types
+of the interactions, but the power of the metaphor remained unchanged. In the
+current paper we propose to use a new physical system as the basis for new
+ideas in sociophysics. We shall argue that the concepts and tools devoted to
+studies of High Entropy Alloys (HEAs) could significantly broaden the range of
+social concepts ``addressable'' by sociophysics, by focusing on a wider range
+of global phenomena, arising from atomic properties, interactions and
+arrangements. We illustrate the new idea by calculating a few characteristics
+of a simple HEA system and their possible ``mapping'' into social concepts.",2007.02154v1
+2020-07-28,Electron correlation effects on exchange interactions and spin excitations in 2D van der Waals materials,"Despite serious effort, the nature of the magnetic interactions and the role
+of electron-correlation effects in magnetic two-dimensional (2D) van der Waals
+materials remain elusive. Using CrI$_3$ as a model system, we show that the
+calculated electronic structure including nonlocal electron correlations yields
+spin excitations consistent with inelastic neutron scattering measurements.
+Remarkably, this approach identifies an unreported correlation-enhanced
+interlayer super-superexchange, which rotates the magnon Dirac lines off, and
+introduces a gap along, the high-symmetry $\Gamma$-$K$-$M$ path. This discovery
+provides a different perspective on the gap opening mechanism observed in
+CrI$_3$, which was previously associated with spin-orbit coupling through the
+Dzyaloshinskii-Moriya interaction or Kitaev interaction. Our observation
+elucidates the critical role of electron correlations on the spin ordering and
+spin dynamics in magnetic van der Waals materials and demonstrates the
+necessity of explicit treatment of electron correlations in the broad family of
+2D magnetic materials.",2007.14518v2
+2020-08-06,Artificial magnetic field for synthetic quantum matter without dynamical modulation,"We propose an all-static method to realize an artificial magnetic field for
+charge neutral particles without introducing any time modulation. Our proposal
+consists of one-dimensional tubes subject to harmonic trapping potentials with
+shifted centers. We show that this setup realizes an artificial magnetic field
+in a hybrid real-momentum space. We discuss how characteristic features of
+particles in a magnetic field, such as chiral edge states and the quantized
+Hall response, can be observed in this setup. We find that the mean-field
+ground state of bosons in this setup in the presence of long-range interactions
+in physical real space can have quantized vortices in the hybrid real-momentum
+space; such a state with vortices exhibits a supersolid structure in the
+physical real space. Our method can be applied to a variety of synthetic
+quantum matter, including ultracold atomic gases, coupled photonic cavities,
+coupled waveguides, and exciton-polariton lattices.",2008.02412v2
+2020-08-07,Cavity magnon polariton based precision magnetometry,"A photon-magnon hybrid system can be realised by coupling the electron spin
+resonance of a magnetic material to a microwave cavity mode. The quasiparticles
+associated with the system dynamics are the cavity magnon polaritons, which
+arise from the mixing of strongly coupled magnons and photons. We illustrate
+how these particles can be used to probe the magnetisation of a sample with a
+remarkable sensitivity, devising suitable spin-magnetometers which ultimately
+can be used to directly assess oscillating magnetic fields. Specifically, the
+capability of cavity magnon polaritons of converting magnetic excitations to
+electromagnetic ones, allows for translating to magnetism the quantum-limited
+sensitivity reached by state-of-the-art electronics. Here we employ hybrid
+systems composed of microwave cavities and ferrimagnetic spheres, to
+experimentally implement two types of novel spin-magnetometers.",2008.03062v2
+2020-08-13,Dynamics of the Parker-Jeans instability of gaseous disks including the effect of cosmic rays,"The effect of cosmic rays on the Parker-Jeans instability in magnetized
+self-gravitating gaseous disks is studied by three-dimensional
+magnetohydrodynamic (MHD) simulations with cosmic rays taken as a massless
+fluid with notable pressure. Cosmic ray diffusion along the magnetic field is
+taken into account in the simulation. The initial configuration of the disk is
+a magnetized cold gas slab sandwiched between hot corona (on top and bottom).
+We show that cosmic rays play an important role in the formation of filaments
+or clumps in some parameter regimes. In a certain range of the thickness of the
+gas slab, the cosmic ray diffusion coefficient plays a decisive role in
+determining whether the filaments lie along or perpendicular to the magnetic
+field. We also consider the effect of rotation on the system.",2008.06117v1
+2020-08-25,Helical magnetic fields from Riemann coupling,"We study the inflationary generation of helical magnetic fields from the
+Riemann coupling with the electromagnetic field. Most models in the literature
+introduce non-minimal coupling to the electromagnetic fields with a scalar
+field, hence, breaking the conformal invariance. In this work, we show that
+non-minimal coupling to the Riemann tensor generates sufficient primordial
+helical magnetic fields at all observable scales. We explicitly show that one
+of the helical states decay while the other helical mode increases, leading to
+a net non-zero helicity. Our model has three key features:~(i) the helical
+power-spectrum has a slight red-tilt for slow-roll inflation consistent with
+bounds from observations and free from backreaction problem, (ii) the energy
+density of the helical fields generated is at least one order of magnitude
+larger than the scalar-field coupled models, and (iii) unlike the scalar field
+coupled models, the generated helical fields are insensitive to the reheating
+dynamics. We show that our model generates the magnetic field of strength 0.01
+PicoGauss over Mpc scale.",2008.10825v2
+2020-08-29,A $j_\mathrm{eff} = 1/2$ pseudospinon continuum in CaIrO$_3$,"In so-called $j_\mathrm{eff} = 1/2$ systems, including some iridates and
+ruthenates, the coherent superposition of $t_\mathrm{2g}$ orbitals in the
+ground state gives rise to hopping processes that strongly depend on the bond
+geometry. Resonant inelastic x-ray scattering (RIXS) measurements on CaIrO$_3$
+reveal a prototypical $j_\mathrm{eff} = 1/2$ pseudospinon continuum, a hallmark
+of one-dimensional (1D) magnetic systems despite its three-dimensional crystal
+structure. The experimental spectra compare very well to the calculated
+magnetic dynamical structure factor of weakly coupled spin-1/2 chains. We
+attribute the onset of such quasi-1D magnetism to the fundamental difference in
+the magnetic interactions between the $j_\mathrm{eff} = 1/2$ pseudospins along
+the corner- and edge-sharing bonds in CaIrO$_3$.",2008.12921v1
+2020-09-09,Symmetric set of transport coefficients for collisional magnetized plasma,"In Braginskii extended magneto-hydrodynamics (ExMHD), applicable to
+collisional astrophysical and high energy density plasmas, the electric field
+and heat flow are described by the $\alpha$, $\beta$ and $\kappa$ transport
+coefficients. We show that magnetic transport relies primarily on
+$\beta_\parallel-\beta_\perp$ and $\alpha_\perp-\alpha_\parallel$, rather than
+$\alpha_\perp$ and $\beta_\perp$ themselves. However, commonly used coefficient
+fit functions [Epperlein and Haines, Phys. Fluids 29, 1029 (1986)] cannot
+accurately calculate these quantities. This means that many ExMHD simulations
+have significantly over-estimated the cross-gradient Nernst advection,
+resulting in artificial magnetic dissipation and discontinuities. We repeat the
+kinetic analysis to provide fits that rectify this problem. Use of these in the
+Gorgon ExMHD code resolves the known discrepancies with kinetic simulations in
+the literature. Recognizing the fundamental importance of
+$\alpha_\perp-\alpha_\parallel$ and $\beta_\parallel-\beta_\perp$, we re-cast
+the set of coefficients to find that each of them now shares the same
+underlying properties. This makes explicit the symmetry of the magnetic and
+thermal transport equations, as well as the symmetry of the coefficients
+themselves.",2009.04562v1
+2020-09-21,"Controllable Capillary Assembly of Magnetic Ellipsoidal Janus Particles into Tunable Rings, Chains and Hexagonal Lattices","Colloidal assembly at fluid interfaces has a great potential for the
+bottom-up fabrication of novel structured materials. However, challenges remain
+in realizing controllable and tunable assembly of particles into diverse
+structures. Herein, we report the capillary assembly of magnetic ellipsoidal
+Janus particles at a fluid-fluid interface. Depending on their tilt angle, i.e.
+the angle the particle main axis forms with the fluid interface, these
+particles deform the interface and generate capillary dipoles or hexapoles.
+Driven by capillary interactions, multiple particles thus assemble into chain-,
+hexagonal lattice- and ring-like structures, which can be actively controlled
+by applying an external magnetic field. We predict a field-strength phase
+diagram in which various structures are present as stable states. Owing to the
+diversity, controllability, and tunability of assembled structures, magnetic
+ellipsoidal Janus particles at fluid interfaces could therefore serve as
+versatile building blocks for novel materials.",2009.09804v2
+2020-10-01,Interband plasmon polaritons in magnetized charge-neutral graphene,"Studying the collective excitations in charge neutral graphene (CNG) has
+recently attracted a great interest because of unusual mechanisms of the charge
+carrier dynamics. The latter can play a crucial role, for instance, for
+superconducting phases in the periodically strained CNG and the magic angle
+twisted bilayer graphene or for formation of graphene plasmon polaritons (GPPs)
+associated with interband transitions due to the strain-induced pseudomagnetic
+field. Importantly, GPP in CNG can be a tool providing new insights into
+various intriguing quantum phenomena in CNG via optical experiments. However,
+interband GPPs in CNG are barely investigated, even in the simplest
+configurations. Here, we show that magnetically biased single layer CNG
+(particularly, at zero temperature) can support interband GPPs of both
+transverse magnetic and transverse electric polarizations. They exist inside
+the narrow absorption bands originating from the electronic transitions between
+Landau levels and are tunable by the external magnetic field. We put our study
+into the context of potential near-field and far-field optical experiments,
+thus opening the door to the exploration of CNG for optics and nanophotonics.",2010.00306v1
+2020-10-13,Origins of anomalously low Raman exponents in single-molecule magnets,"The Raman exponent of single-molecular magnetic relaxation may take various
+unexpected values because of rich phonon spectrum and spin-phonon coupling of
+molecular crystals. We systematically examine the origins of different
+abnormalities, and clarify misunderstandings in the past, particularly the
+appropriateness of the fitting procedures for the exponents. We find that
+exponential laws raised by optical phonons can yield spurious power laws with
+low exponents. This observation indicates long-standing misunderstandings for
+origins of low Raman exponents in a large bulk of single-molecule magnets.
+Resulting from spin-lattice coupling with optical modes, presence of these
+exponents suggests the importance of the local dynamical environment for the
+magnetic relaxation in this regime.",2010.09486v2
+2020-10-21,Spontaneous Chiral-Spin Ordering in Spin-Orbit Coupled Honeycomb Magnets,"Frustrated magnets with highly degenerate ground states are at the heart of
+hunting exotic states of matter. Recent studies in spin-orbit coupled honeycomb
+magnets have generated immense interest in bond-dependent interactions,
+appreciating a symmetric off-diagonal $\Gamma$ interaction which exhibits a
+macroscopic degeneracy in the classical limit. Here, we study a generic spin
+model and discover a novel chiral-spin ordering with spontaneously broken
+time-reversal symmetry near the dominant $\Gamma$ region. The chiral-spin phase
+is demonstrated to possess a staggered chirality relation in different
+sublattices, and it exhibits gapless excitations as revealed by the vanishing
+energy gap and the finite central charge on cylinders. Although there is a
+vestige of a tiny peak in the corner of the second Brillouin zone, the magnetic
+order is likely to vanish as the system size increases. Finally, we also
+attempt to gain insight into the possible topological signature of the
+chiral-spin phase by calculating the dynamic structure factor and the modular
+$\mathcal{S}$ matrix.",2010.11233v2
+2020-10-28,Thermomagnetic instability of plasma composition gradients,"We show that, under Braginskii magneto-hydrodynamics, anti-parallel gradients
+in average ion charge state and electron temperature can be unstable to the
+growth of self-generated magnetic fields. The instability is analogous to the
+field-generating thermomagnetic instability, although it is driven by the
+collisional thermal force magnetic source term rather than the Biermann battery
+term. The gradient in ion charge state causes a gradient in collisionality,
+which couples with temperature perturbations to create a self-generated
+magnetic field. This magnetic field deflects the electron heat flux in a way
+that reinforces the temperature perturbation. The derived linearized growth
+rate, typically on hydrodynamic timescales, includes the resistive and thermal
+smoothing. It increases with large ion composition gradients and electron heat
+flux, conditions typical of the hohlraum walls or contaminant mix jets in
+inertial confinement fusion implosions. However, extended magneto-hydrodynamic
+simulations indicate that the instability is usually dominated and stabilized
+by the nonlinear Nernst advection, in a similar manner to the standard
+thermomagnetic instability.",2010.15072v1
+2020-11-02,Spin-orbital magnetic response of relativistic fermions with band hybridization,"Spins of relativistic fermions are related to their orbital degrees of
+freedom. In order to quantify the effect of hybridization between relativistic
+and nonrelativistic degrees of freedom on spin-orbit coupling, we focus on the
+spin-orbital (SO) crossed susceptibility arising from spin-orbit coupling. The
+SO crossed susceptibility is defined as the response function of their spin
+polarization to the ""orbital"" magnetic field, namely the effect of magnetic
+field on the orbital motion of particles as the vector potential. Once
+relativistic and nonrelativistic fermions are hybridized, their SO crossed
+susceptibility gets modified at the Fermi energy around the band hybridization
+point, leading to spin polarization of nonrelativistic fermions as well. These
+effects are enhanced under a dynamical magnetic field that violates thermal
+equilibrium, arising from the interband process permitted by the band
+hybridization. Its experimental realization is discussed for Dirac electrons in
+solids with slight breaking of crystalline symmetry or doping, and also for
+quark matter including dilute heavy quarks strongly hybridized with light
+quarks, arising in a relativistic heavy-ion collision process.",2011.00882v2
+2020-11-03,Relativistic non-resistive viscous magnetohydrodynamics from the kinetic theory:a relaxation time approach,"We derive the relativistic non-resistive, viscous second-order
+magnetohydrodynamic equations for the dissipative quantities using the
+relaxation time approximation. The Boltzmann equation is solved for a system of
+particles and antiparticles using Chapman-Enskog like gradient expansion of the
+single-particle distribution function truncated at second order. In the first
+order, the transport coefficients are independent of the magnetic field. In the
+second-order, new transport coefficients that couple magnetic field and the
+dissipative quantities appear which are different from those obtained in the
+14-moment approximation \cite{Denicol:2018rbw} in the presence of a magnetic
+field. However, in the limit of the weak magnetic field, the form of these
+equations are identical to the 14-moment approximation albeit with a different
+values of these coefficients. We also derive the anisotropic transport
+coefficients in the Navier-Stokes limit.",2011.01606v1
+2020-11-13,Classification of Magnetic Vortices by Angular Momentum Conservation,"Superfluid vortices are quantum excitations carrying quantized amount of
+orbital angular momentum in a phase where global symmetry is spontaneously
+broken. We address a question of whether magnetic vortices in superconductors
+with dynamical gauge fields can carry nonzero orbital angular momentum or not.
+We discuss the angular momentum conservation in several distinct classes of
+examples from crossdisciplinary fields of physics across condensed matter,
+dense nuclear systems, and cosmology. The angular momentum carried by gauge
+field configurations around the magnetic vortex plays a crucial role in
+satisfying the principle of the conservation law. Based on various ways how the
+angular momentum conservation is realized, we provide a general scheme of
+classifying magnetic vortices in different phases of matter.",2011.06981v1
+2020-11-18,"On the photo-evaporation, dust polarization, and kinematics of two nebulae in Sh2-236","In the work presented here, the impact of magnetic field on the dynamical
+evolution of cometary globules Sim 129 and Sim 130 in Sh2-236 H\,II region and
+the ionized gas streaming out of their surfaces is investigated. The magnetic
+field morphology in the region associated with these globules is inferred using
+optical polarization measurements with the Sampurnanand Telescope at ARIES. The
+nebular emission is probed through radio continuum mapping at 1.4~GHz with the
+archival National Radio Astronomy Observatory (NRAO) very large array (VLA) Sky
+Survey (NVSS) data. The correlation of these measurements suggest that the
+photoevaporated gas from the surfaces of Sim 129 and Sim 130 is accumulated in
+clouds and starts streaming along the magnetic field lines. The $\rm ^{12}CO$
+(J=1-0) molecular line observations are performed towards NGC\,1893 from 14-m
+single dish radio telescope in Taeduk Radio Astronomy Observatory (TRAO). The
+velocity dispersion in $\rm ^{12}CO$ (J=1-0) molecular line and the dispersion
+in polarization angles are used in Davis-Chandrasekhar-Fermi formulation to
+estimate the magnetic field strength towards two sim nebulae. The average value
+of field strength is found to be $\sim$60$\mu$G with uncertainty of 0.5 times
+the estimated value.",2011.09572v1
+2020-11-20,Neutron scattering by magnetic octupoles of a quantum liquid,"Neutron scattering is a powerful tool to study magnetic structures and
+dynamics, benefiting from a precisely established theoretical framework. The
+neutron dipole moment interacts with electrons in materials via their magnetic
+field, which can have spin and orbital origins. Yet in most experimentally
+studied cases the individual degrees of freedom are well described within the
+dipole approximation, sometimes accompanied by further terms of a multipolar
+expansion that usually act as minor corrections to the dipole form factor. Here
+we report a unique example of neutrons diffracted mainly by magnetic octupoles.
+This unusual situation arises in a quantum spin ice where the electronic
+wavefunction becomes essentially octupolar under the effect of correlations.
+The discovery of such a new type of quantum spin liquid that comes with a
+specific experimental signature in neutron scattering is remarkable, because
+these topical states of matter are notoriously difficult to detect.",2011.10418v1
+2020-11-23,Asymmetric spin wave dispersion due to a saturation magnetization gradient,"We demonstrate using micromagnetic simulations and a theoretical model that a
+gradient in the saturation magnetization ($M_s$) of a perpendicularly
+magnetized ferromagnetic film induces a non-reciprocal spin wave propagation
+and, consequently an asymmetric dispersion relation. The $M_s$ gradient adds a
+linear potential to the spin wave equation of motion consistent with the
+presence of a force. We consider a transformation from an inertial reference
+frame in which the $M_s$ is constant to an accelerated reference frame where
+the resulting inertial force corresponds to the force from the $M_s$ gradient.
+As in the Doppler effect, the frequency shift leads to an asymmetric dispersion
+relation. Additionally, we show that under certain circumstances,
+unidirectional propagation of spin waves can be achieved which is essential for
+the design of magnonic circuits. Our results become more relevant in light of
+recent experimental works in which a suitable thermal landscape is used to
+dynamically modulate the saturation magnetization.",2011.11148v2
+2020-11-23,Electron vortex beams in non-uniform magnetic fields,"We consider the quantum theory of paraxial non-relativistic electron beams in
+non-uniform magnetic fields, such as the Glaser field. We find the wave
+function of an electron from such a beam and show that it is a joint eigenstate
+of two ($z$-dependent) commuting gauge-independent operators. This generalized
+Laguerre-Gaussian vortex beam has a phase that is shown to consist of two
+parts, each being proportional to the eigenvalue of one of the two conserved
+operators and each having different symmetries. We also describe the dynamics
+of the angular momentum and cross-sectional area of any mode and how a varying
+magnetic field can split a mode into a superposition of modes. By a suitable
+change in frame of reference all of our analysis also applies to an electron in
+a quantum Hall system with a time-dependent magnetic field.",2011.11729v2
+2020-11-26,Optically-induced frequency up-conversion of the ferromagnetic resonance in an ultrathin garnet,"We perform ultrafast pump-probe measurements on a nanometer-thick crystalline
+Bi-doped yttrium iron garnet film with perpendicular magnetic anisotropy.
+Tuning the photon energy of the pump laser pulses above and below the
+material's bandgap, we trigger ultrafast optical and spin dynamics via both
+one- and two-photon absorption. Contrary to the common scenario, the
+optically-induced heating of the system induces an increase up to 20% of the
+ferromagnetic resonance frequency. We explain this unexpected result in terms
+of a photo-induced modification of the magnetic anisotropy, i.e. of the
+effective field, identifying the necessary conditions to observe this effect.
+Our results disclose the possibility to optically increase the magnetic
+eigenfrequency in nanometer-thick magnets.",2011.13403v1
+2020-12-02,Magneto-active elastic shells with tunable buckling strength,"Shell buckling is central in many biological structures and advanced
+functional materials, even if, traditionally, this elastic instability has been
+regarded as a catastrophic phenomenon to be avoided for engineering structures.
+Either way, predicting critical buckling conditions remains a long-standing
+challenge. The subcritical nature of shell buckling imparts extreme sensitivity
+to material and geometric imperfections. Consequently, measured critical loads
+are inevitably lower than classic theoretical predictions. Here, we present a
+robust mechanism to dynamically tune the buckling strength of shells,
+exploiting the coupling between mechanics and magnetism. Our experiments on
+pressurized spherical shells made of a magnetorheological elastomer demonstrate
+the tunability of their buckling pressure via magnetic actuation. We develop a
+theoretical model for thin magnetic elastic shells, which rationalizes the
+underlying mechanism, in excellent agreement with experiments. A dimensionless
+magneto-elastic buckling number is recognized as the key governing parameter,
+combining the geometrical, mechanical, and magnetic properties of the system.",2012.01163v2
+2020-12-08,Decoupled Strain Response of Ferroic Properties in Multiferroic VOCl2 Monolayer,"Two-dimensional (2D) magnetoelectric multiferroics are promising
+multifunctional materials for miniaturized logic and memory devices. Herein, we
+explore the effectiveness of strain-engineering for tuning the properties of a
+recently predicted 2D antiferromagnetic-ferroelectric, VOCl2 monolayer.
+Interestingly, we find that magnetic-ordering and electric polarization can be
+tuned independently using uniaxial tensile strain along different in-plane
+lattice vectors. A 4% tensile strain along lattice vector b induces a
+transition from an antiferromagnetic (AFM) ground state with an out-of-plane
+magnetization to a ferromagnetic (FM) ground state with in-plane magnetization.
+On the other hand, tensile strain along lattice vector a enhances spontaneous
+electric polarization, without affecting the magnetic ordering. The monolayers
+remain dynamically stable under tensile strain, which further helps to raise
+the Curie temperature of ferromagnetism, as well as ferroelectricity. Such a
+strain-tunable multiferroic material holds great promises for future generation
+nanoelectronic devices.",2012.04592v2
+2020-12-29,"Spin dynamics in the pyrochlore iridate, Er2Ir2O7, investigated by muSR spectroscopy","Building a full understanding of the complex magnetism in the rare-earth
+pyrochlore iridates, A2Ir2O7, is an ongoing issue in condensed matter physics.
+The possibility of two interpenetrating and interacting frustrated magnetic
+pyrochlore sublattices, connected with the strong spin-orbit coupling of the 5d
+Ir4+ ion, lends itself to a wide array of potential electronic and magnetic
+states. In this paper, we present longitudinal field and zero field muSR
+measurements of Er2Ir2O7. The muSR response of Er2Ir2O7 is dominated by the
+strong fluctuating fields of the Er3+ (J = 15/2) moments, showing a peak in
+fitted relaxation rate, {\lambda}_2, at T = 15 K . The muSR spectra show just
+weak signatures of the Ir transition, that were easily suppressed in applied
+longitudinal field, however full decoupling of the muons from local magnetic
+fields was not achieved even in applied fields up to 3 kG.",2012.14730v1
+2021-01-10,A Thermodynamic Core using Voltage-Controlled Spin-Orbit-Torque Magnetic Tunnel Junctions,"We present a magnetic implementation of a thermodynamic computing fabric.
+Magnetic devices within computing cores harness thermodynamics through its
+voltage-controlled thermal stability; while the evolution of network states is
+guided by the spin-orbit-torque effect. We theoretically derive the dynamics of
+the cores and show that the computing fabric can successfully compute ground
+states of a Boltzmann Machine. Subsequently, we demonstrate the physical
+realization of these devices based on a CoFeB-MgO magnetic tunnel junction
+structure. The results of this work pave the path towards the realization of
+highly efficient, high-performance thermodynamic computing hardware. Finally,
+this paper will also give a perspective of computing beyond thermodynamic
+computing.",2101.03448v3
+2021-01-14,Magnetic field-induced thermal emission tuning of InSb-based metamaterials in the terahertz frequency regime,"This work theoretically and analytically demonstrates the magnetic
+field-induced spectral radiative properties of photonic metamaterials
+incorporating both Indium Antimonide (InSb) and Tungsten (W) in the terahertz
+(THz) frequency regime. We have varied multiple factors of the nanostructures,
+including composite materials, layer thicknesses and surface grating fill
+factors, which impact the light-matter interactions and in turn modify the
+thermal emission of the metamaterials. We have proposed and validated a method
+for determining the spectral properties of InSb under an applied direct current
+(DC) magnetic field, and have employed this method to analyze how these
+properties can be dynamically tuned by modulating the magnitude of the field.
+For the first time, we have designed an InSb-W metamaterial exhibiting unity
+narrowband emission which can serve as an emitter for wavelengths around 55
+$\mu$m (approximately 5.5 THz). Additionally, the narrowband emission of this
+metamaterial can be magnetically tuned in both bandwidth and peak wavelength
+with a normal emissivity close to unity.",2101.05852v2
+2021-01-16,Universal Critical Exponents of the Magnetic Domain Wall Depinning Transition,"Magnetic field driven domain wall dynamics in a ferrimagnetic GdFeCo thin
+film with perpendicular magnetic anisotropy is studied using low temperature
+magneto-optical Kerr microscopy. Measurements performed in a practically
+athermal condition allow for the direct experimental determination of the
+velocity ($ \beta = 0.30 \pm 0.03 $) and correlation length ($ \nu = 1.3 \pm
+0.3 $) exponents of the depinning transition. The whole family of exponents
+characterizing the transition is deduced, providing evidence that the depinning
+of magnetic domain walls is better described by the quenched Edwards-Wilkinson
+universality class.",2101.06555v3
+2021-01-25,Raman Spectroscopy and Aging of the Low-Loss Ferrimagnet Vanadium Tetracyanoethylene,"Vanadium tetracyanoethylene (V[TCNE]$_{x}$, $x\approx 2$) is an organic-based
+ferrimagnet with a high magnetic ordering temperature $\mathrm{T_C>600 ~K}$,
+low magnetic damping, and growth compatibility with a wide variety of
+substrates. However, similar to other organic-based materials, it is sensitive
+to air. Although encapsulation of V[TCNE]$_{x}$ with glass and epoxy extends
+the film lifetime from an hour to a few weeks, what is limiting its lifetime
+remains poorly understood. Here we characterize encapsulated V[TCNE]$_{x}$
+films using confocal microscopy, Raman spectroscopy, ferromagnetic resonance
+and SQUID magnetometry. We identify the relevant features in the Raman spectra
+in agreement with \textit{ab initio} theory, reproducing $\mathrm{C=C,C\equiv
+N}$ vibrational modes. We correlate changes in the effective dynamic
+magnetization with changes in Raman intensity and in photoluminescence. Based
+on changes in Raman spectra, we hypothesize possible structural changes and
+aging mechanisms in V[TCNE]$_x$. These findings enable a local optical probe of
+V[TCNE]$_{x}$ film quality, which is invaluable in experiments where assessing
+film quality with local magnetic characterization is not possible.",2101.10240v1
+2021-02-16,Spin-glass behavior in Shastry-Sutherland lattice of Tm$_\textbf{2}$Cu$_\textbf{2}$In,"The spin-glass behavior in the ferromagnetic phase of $\mathrm{Tm_2Cu_2In}$
+was investigated by dc-, ac-magnetization, and non-equilibrium dynamics
+characterizations. Arc-melted polycrystalline compound of $\mathrm{Tm_2Cu_2In}$
+crystallizes in $\mathrm{Mo_2FeB_2}$-type tetragonal structure (space group
+$P_4/mbm$). The temperature variation dc-magnetization exhibits a ferromagnetic
+behavior with Curie temperature $T_C$ = 32.5 K. The zero-field cooled (ZFC) and
+field cooled (FC) magnetic curves show a thermomagnetic irreversible behavior
+below $T_C$. The field dependence of irreversible temperature follows
+Almeida-Thouless line. The frequency and ac-driven field-dependent anomalies in
+ac-susceptibility results indicate the existence of spin-glass state in
+$\mathrm{Tm_2Cu_2In}$. The time dependence of magnetization further supports
+the spin-glass behavior observed in $\mathrm{Tm_2Cu_2In}$. The frequency
+dependence of the freezing temperature in the real part of ac-susceptibility
+has been analyzed on the basis power-law divergence and Vogel-Fulcher law. The
+obtained results revealed that $\mathrm{Tm_2Cu_2In}$ belongs to a ferromagnetic
+canonical spin-glass class of compounds.",2102.08230v2
+2021-02-19,Critical Energy Dissipation in a Binary Superfluid Gas by a Moving Magnetic Obstacle,"We study the critical energy dissipation in an atomic superfluid gas with two
+symmetric spin components by an oscillating magnetic obstacle. Above a certain
+critical oscillation frequency, spin-wave excitations are generated by the
+magnetic obstacle, demonstrating the spin superfluid behavior of the system.
+When the obstacle is strong enough to cause density perturbations via local
+saturation of spin polarization, half-quantum vortices (HQVs) are created for
+higher oscillation frequencies, which reveals the characteristic evolution of
+critical dissipative dynamics from spin-wave emission to HQV shedding. Critical
+HQV shedding is further investigated using a pulsed linear motion of the
+obstacle, and we identify two critical velocities to create HQVs with different
+core magnetization.",2102.09826v2
+2021-02-24,Spin waves and high-frequency response in layered superconductors with helical magnetic structure,"We evaluate the spin-wave spectrum and dynamic susceptibility in a layered
+superconductors with helical interlayer magnetic structure. We especially focus
+on the structure in which the moments rotate 90$^{\circ}$ from layer to layer
+realized in the iron pnictide RbEuFe$_{4}$As$_{4}$. The spin-wave spectrum in
+superconductors is strongly renormalized due to the long-range electromagnetic
+interactions between the oscillating magnetic moments. This leads to strong
+enhancement of the frequency of the mode coupled with uniform field and this
+enhancement exists only within a narrow range of the c-axis wave vectors of the
+order of the inverse London penetration depth. The key feature of materials
+like RbEuFe$_{4}$As$_{4}$ is that this uniform mode corresponds to the maximum
+frequency of the spin-wave spectrum with respect to c-axis wave vector. As a
+consequence, the high-frequency surface resistance acquires a very distinct
+asymmetric feature spreading between the bare and renormalized frequencies. We
+also consider excitation of spin waves with Josephson effect in a tunneling
+contact between helical-magnetic and conventional superconductors and study the
+interplay between the spin-wave features and geometrical cavity resonances in
+the current-voltage characteristics.",2102.12445v2
+2021-03-01,Electron-induced nuclear magnetic ordering in n-type semiconductors,"Nuclear magnetism in n-doped semiconductors with positive hyperfine constant
+is revisited. Two kinds of nuclear magnetic ordering can be induced by resident
+electrons in a deeply cooled nuclear spin system. At positive nuclear spin
+temperature below a critical value, randomly oriented nuclear spin polarons
+similar to that predicted by I. Merkulov [I. Merkulov, Physics of the Solid
+State 40, 930 (1998)] should emerge. These polarons are oriented randomly and
+within each polaron nuclear and electron spins are aligned
+antiferromagnetically. At negative nuclear spin temperature below a critical
+value we predict another type of magnetic ordering - dynamically induced
+nuclear ferromagnet. This is a long-range ferromagnetically ordered state
+involving both electrons and nuclei. It can form if electron spin relaxation is
+dominated by the hyperfine coupling, rather than by the spin-orbit interaction.
+Application of the theory to the n-doped GaAs suggests that the ferromagnetic
+order may be reached at experimentally achievable nuclear spin temperature
+$\Theta_N \approx 0.5$ $\mu$K and lattice temperature $T_L \approx 5$ K.",2103.01120v1
+2021-03-09,A compact and fast magnetic coil for the interaction manipulation of quantum gases with Feshbach resonances,"Cold atom experiments commonly use broad magnetic Feshbach resonances to
+manipulate the interaction between atoms. In order to induce quantum dynamics
+by a change of the interaction strength, rapid ($\sim\mu s$) magnetic field
+changes over several tens of Gauss are required. Here we present a compact
+design of a coil and its control circuit for a change of the magnetic field up
+to $36G$ in $3\mu s$. The setup comprises two concentric solenoids with minimal
+space requirements, which can be readily added to existing apparatuses. This
+design makes the observation of non-equilibrium physics with broad Feshbach
+resonances accessible.",2103.05273v1
+2021-03-12,Mott transition and magnetism in a fragile topological insulator,"We study the effects of electronic correlations on fragile topology using
+dynamical mean-field theory. Fragile topological insulators (FTIs) offer
+obstruction to the formation of exponentially localized Wannier functions, but
+they can be trivialized by adding certain trivial degrees of freedom. For the
+same reason, FTIs do not host symmetry-protected flow of edge states between
+bulk bands in cylindrical boundary conditions but are expected to have a
+spectral flow between the fragile bands and other bands under certain twisted
+boundary conditions. We here analyze commonly observed effects of strong
+correlations, such as the Mott-insulator transition and magnetism, on a known
+model hosting fragile topology. We show that in the nonmagnetic case, fragile
+topology, along with the twisted boundary states, is stable with interactions
+below a critical interaction strength. Above this interaction strength, a
+transition to the Mott insulating phase occurs, and the twisted boundary states
+disappear. Furthermore, by applying a homogeneous magnetic field, the fragile
+topology is destroyed. However, we show that a magnetic field can induce a
+topological phase transition which converts a fragile topological insulator to
+a Chern insulator. Finally, we study ferromagnetic solutions of the fragile
+topological model.",2103.07203v2
+2021-03-17,Micromagnetic description of twisted spin spirals in the B20 chiral magnet FeGe from first principles,"Using the model of classical Heisenberg exchange and Dzyaloshinskii-Moriya
+(DM) interaction we show that the ground state of B20 FeGe chiral magnet is a
+superposition of twisted helical spin-density waves formed by different
+sublattices of the crystal. Such twisted spin-density waves propagate in the
+same direction but with different phases and different directions of the
+rotation axes. We derive an advanced micromagnetic expression describing the
+exchange and DM interaction for such magnetic structures. By employing
+first-principles calculations based on density functional theory and using our
+micromagnetic model we show that the magnitude of the spin-spiral twist in B20
+FeGe is of the same order as global spiraling. While the energy difference
+between the ground state of twisted spirals and the FM state is in good
+agreement with the experimental results, for the spin spirals without a twist
+it is smaller by factor three. In addition, we verify our results by employing
+spin dynamics simulations. This calls for new experiments exploring the ground
+state properties of B20 chiral magnets.",2103.09800v2
+2021-03-22,Hardware realization of the multiply and accumulate operation on radio-frequency signals with magnetic tunnel junctions,"Artificial neural networks are a valuable tool for radio-frequency (RF)
+signal classification in many applications, but digitization of analog signals
+and the use of general purpose hardware non-optimized for training make the
+process slow and energetically costly. Recent theoretical work has proposed to
+use nano-devices called magnetic tunnel junctions, which exhibit intrinsic RF
+dynamics, to implement in hardware the Multiply and Accumulate (MAC) operation,
+a key building block of neural networks, directly using analogue RF signals. In
+this article, we experimentally demonstrate that a magnetic tunnel junction can
+perform multiplication of RF powers, with tunable positive and negative
+synaptic weights. Using two magnetic tunnel junctions connected in series we
+demonstrate the MAC operation and use it for classification of RF signals.
+These results open the path to embedded systems capable of analyzing RF signals
+with neural networks directly after the antenna, at low power cost and high
+speed.",2103.11993v2
+2021-03-24,Effective strain manipulation of the antiferromagnetic state of polycrystalline NiO,"As a candidate material for applications such as magnetic memory,
+polycrystalline antiferromagnets offer the same robustness to external magnetic
+fields, THz spin dynamics, and lack of stray field as their single crystalline
+counterparts, but without the limitation of epitaxial growth and lattice
+matched substrates. Here, we first report the detection of the average Neel
+vector orientiation in polycrystalline NiO via spin Hall magnetoresistance
+(SMR). Secondly, by applying strain through a piezo-electric substrate, we
+reduce the critical magnetic field required to reach a saturation of the SMR
+signal, indicating a change of the anisotropy. Our results are consistent with
+polycrystalline NiO exhibiting a positive sign of the in-plane
+magnetostriction. This method of anisotropy-tuning offers an energy efficient,
+on-chip alternative to manipulate a polycrystalline antiferromagnets magnetic
+state.",2103.13105v1
+2021-03-29,Surface Acoustic Wave induced modulation of tunneling magnetoresistance in magnetic tunnel junctions,"We show that a surface acoustic wave (SAW) applied across the terminals of a
+magnetic tunnel junction (MTJ) decreases both the (time-averaged) parallel and
+antiparallel resistances of the MTJ, with the latter decreasing much more than
+the former. This results in a decrease of the tunneling magnetoresistance (TMR)
+ratio. The coercivities of the free and fixed layer of the MTJ, however, are
+not affected significantly, suggesting that the SAW does not cause large-angle
+magnetization rotation in the magnetic layers through the inverse
+magnetostriction (Villari) effect at the power levels used. This study sheds
+light on the dynamical behavior of an MTJ under periodic compressive and
+tensile strain.",2103.15303v1
+2021-03-31,Itinerant magnetism of chromium under pressure: a DFT+DMFT study,"We consider electronic and magnetic properties of chromium, a well-known
+itinerant antiferromagnet, by a combination of density functional theory (DFT)
+and dynamical mean-field theory (DMFT). We find that electronic correlation
+effects in chromium, in contrast to its neighbours in the periodic table, are
+weak, leading to the quasiparticle mass enhancement factor ${m^*/m \approx
+1.2}$. Our results for local spin-spin correlation functions and distribution
+of weigths of atomic configurations indicate that the local magnetic moments
+are not formed. Similarly to previous results of DFT at ambient pressure, the
+non-uniform magnetic susceptibility as a function of momentum possesses close
+to the wave vector ${{\mathbf Q}_{\rm H}=(0,0,2\pi/a)}$ ($a$ is the lattice
+constant) sharp maxima, corresponding to Kohn anomalies. We find that these
+maxima are preserved by the interaction and are not destroyed by pressure. Our
+calculations qualitatively capture a decrease of the N\'eel temperature with
+pressure and a breakdown of itinerant antiferomagnetism at pressure of $\sim$9
+GPa in agreement with experimental data, although the N\'eel temperature is
+significantly overestimated because of the mean-field nature of DMFT.",2103.17133v2
+2021-04-08,Out-of-plane magnetization oscillation in spin Hall device assisted by field-like torque,"An excitation of a large-amplitude out-of-plane magnetization oscillation in
+a ferromagnet by the spin Hall effect is of great interest for practical
+applications such as microwave generator and neuromorphic computing. However,
+both experimental and theoretical works have revealed that only small-amplitude
+oscillation around an in-plane easy axis can be excited via the spin Hall
+effect. Here, we propose that an out-of-plane oscillation can be excited due to
+an assistance of field-like torque. We focus on an in-plane magnetized
+ferromagnet with an easy axis parallel to current direction. We notice that the
+field-like torque with an appropriate sign provides an additional field
+modifying the dynamic trajectory of the magnetization and drives the
+auto-oscillation. The condition on the sign of the field-like torque is
+satisfied for typical nonmagnet used in spin Hall devices such as tungsten.",2104.04057v1
+2021-04-19,Infrared phonon spectroscopy on the Cairo pentagonal antiferromagnet Bi2Fe4O9: a study through the pressure induced structural transition,"Magnetic and crystallographic transitions in the Cairo pentagonal magnet
+Bi2Fe4O9 are investigated by means of infrared synchrotron-based spectroscopy
+as a function of temperature (20 - 300 K) and pressure (0 - 15.5 GPa). One of
+the phonon modes is shown to exhibit an anomalous softening as a function of
+temperature in the antiferromagnetic phase below 240 K, highlighting
+spin-lattice coupling. Moreover, under applied pressure at 40 K, an even larger
+softening is observed through the pressure induced structural transition.
+Lattice dynamical calculations reveal that this mode is indeed very peculiar as
+it involves a minimal bending of the strongest superexchange path in the
+pentagonal planes, as well as a decrease of the distances between second
+neighbor irons. The latter confirms the hypothesis made by Friedrich et al.,1
+about an increase in the oxygen coordination of irons being at the origin of
+the pressure-induced structural transition. As a consequence, one expects a new
+magnetic superexchange path that may alter the magnetic structure under
+pressure.",2104.09384v1
+2021-04-21,Magnetism of magic-angle twisted bilayer graphene,"We investigate magnetic instabilities in charge-neutral twisted bilayer
+graphene close to so-called ""magic angles"" using a combination of real-space
+Hartree-Fock and dynamical mean-field theories. In view of the large size of
+the unit cell close to magic angles, we examine a previously proposed rescaling
+that permits to mimic the same underlying flat minibands at larger twist
+angles. We find that localized magnetic states emerge for values of the Coulomb
+interaction $U$ that are significantly smaller than what would be required to
+render an isolated layer antiferromagnetic. However, this effect is
+overestimated in the rescaled system, hinting at a complex interplay of
+flatness of the minibands close to the Fermi level and the spatial extent of
+the corresponding localized states. Our findings shed new light on perspectives
+for experimental realization of magnetic states in charge-neutral twisted
+bilayer graphene.",2104.10694v3
+2021-05-04,A drift kinetic model for the expander region of a magnetic mirror,"We present a drift kinetic model for the free expansion of a thermal plasma
+out of a magnetic nozzle. This problem relates to plasma space propulsion
+systems, natural environments such as the solar wind, and end losses from the
+expander region of mirror magnetically confined fusion concepts such as the Gas
+Dynamic Trap. The model incorporates trapped and passing orbit types
+encountered in the mirror expander geometry and maps to an upstream thermal
+distribution. This boundary condition and quasineutrality require the
+generation of an ambipolar potential drop of $\sim5 T_e/e$, forming a thermal
+barrier for the electrons. The model for the electron and ion velocity
+distributions and fluid moments is confirmed with data from a fully kinetic
+simulation. Finally, the model is extended to account for a population of fast
+sloshing ions arising from neutral beam heating within a magnetic mirror, again
+resulting in good agreement with a corresponding kinetic simulation.",2105.01572v1
+2021-05-05,Heavy quark dynamics in a strongly magnetized quark-gluon plasma,"We present a calculation of the heavy quark momentum diffusion coefficients
+in a quark-gluon plasma under the presence of a strong external magnetic field,
+within the Lowest Landau Level (LLL) approximation. In particular, we apply the
+Hard Thermal Loop (HTL) technique for the resummed effective gluon propagator,
+generalized for a hot and magnetized medium. Using the derived effective HTL
+gluon propagator and the LLL quark propagator we analytically derive the full
+results for the longitudinal and transverse momentum diffusion coefficients as
+well as the energy losses for charm and bottom quarks beyond the static limit.
+We also show numerical results for these coefficients in two special cases
+where the heavy quark is moving either parallel or perpendicular to the
+external magnetic field.",2105.02167v2
+2021-05-07,Magnetic properties of the itinerant ferromagnet LaCrGe3 under pressure studied by 139La NMR,"$^{139}$La nuclear magnetic resonance (NMR) measurements under pressure ($p =
+0-2.64$ GPa) have been carried out to investigate the static and dynamic
+magnetic properties of the itinerant ferromagnet LaCrGe$_3$. $^{139}$La-NMR
+spectra for all measured pressures in the ferromagnetically ordered state show
+a large shift due to the internal field induction $|$$B_{\rm int}$$|$ $\sim$ 4
+T at the La site produced by Cr ordered moments. The change in $B_{\rm int}$ by
+less than 5\% with $p$ up to 2.64~GPa indicates that the Cr 3$d$ moments are
+robust under pressure. The temperature dependence of NMR shift and $B_{\rm
+int}$ suggest that the ferromagnetic order develops below $\sim$ 50~K under
+higher pressures in a magnetic field of $\sim$ 7.2 T. Based on the analysis of
+NMR data using the self-consistent-renormalization (SCR) theory, the spin
+fluctuations in the paramagnetic state well above $T_{\rm C}$ are revealed to
+be three dimensional ferromagnetic throughout the measured $p$ region.",2105.03479v1
+2021-05-16,Measurement of magnetic cavitation driven by heat flow in a plasma,"We describe the direct measurement of the expulsion of a magnetic field from
+a plasma driven by heat flow. Using a laser to heat a column of gas within an
+applied magnetic field, we isolate Nernst advection and show how it changes the
+field over a nanosecond timescale. Reconstruction of the magnetic field map
+from proton radiographs demonstrates that the field is advected by heat flow in
+advance of the plasma expansion. This changes the dynamics of high energy
+density plasmas, in which heat flows and fields are strongly coupled, and may
+disrupt magnetised inertial confinement fusion schemes.",2105.07414v3
+2021-05-20,Rate equations model for multiple magnetic mirrors in various thermodynamic scenarios,"Axial particle loss is one of the main challenges for fusion aimed, linear
+magnetic mirror plasma configurations. One way to mitigate this disadvantage
+and increase the confinement time is to use a multiple mirrors setup. The idea
+is to reduce the outgoing flux by collisions in the outer magnetic cells. Here,
+we develop a semi-kinetic rate equation model for the ions' density dynamics,
+including scattering within the magnetic cell and the transmission between
+neighboring cells. The dominant parameter is the ions' mean free path, which
+depends on the temperature and density in each cell. The steady-state flow is
+studied analytically and numerically for three thermodynamic scenarios:
+isothermal plasma, adiabatic expansion, and constant diffusion. It is found
+that the confinement time varies about five-fold over the different scenarios,
+where the adiabatic cooling is the best confining scenario.",2105.09614v2
+2021-06-04,Topological superconducting domain walls in magnetic Weyl semimetals,"Recent experimental breakthrough in magnetic Weyl semimetals have inspired
+exploration on the novel effects of various magnetic structures in these
+materials. Here we focus on a domain wall structure which connects two uniform
+domains with different magnetization directions. We study the topological
+superconducting state in presence of an s-wave superconducting pairing
+potential. By tuning the chemical potential, we can reach a topological state,
+where a chiral Majorana mode or zero-energy Majorana bound state is localized
+at the edges of the domain walls. This property allows a convenient braiding
+operation of Majorana modes by controlling the dynamics of domain walls.",2106.02215v1
+2021-06-07,Voltage-control of damping constant in magnetic-insulator/topological-insulator bilayers,"The magnetic damping constant is a critical parameter for magnetization
+dynamics and the efficiency of memory devices and magnon transport. Therefore,
+its manipulation by electric fields is crucial in spintronics. Here, we
+theoretically demonstrate the voltage-control of magnetic damping in ferro- and
+ferrimagnetic-insulator (FI)/topological-insulator (TI) bilayers. Assuming a
+capacitor-like setup, we formulate an effective dissipation torque induced by
+spin-charge pumping at the FI/TI interface as a function of an applied voltage.
+By using realistic material parameters, we find that the effective damping for
+a FI with 10nm thickness can be tuned by one order of magnitude under the
+voltage with 0.25V. Also, we provide perspectives on the voltage-induced
+modulation of the magnon spin transport on proximity-coupled FIs.",2106.03332v1
+2021-06-09,A Compact Model for Scalable MTJ Simulation,"This paper presents a physics-based modeling framework for the analysis and
+transient simulation of circuits containing Spin-Transfer Torque (STT) Magnetic
+Tunnel Junction (MTJ) devices. The framework provides the tools to analyze the
+stochastic behavior of MTJs and to generate Verilog-A compact models for their
+simulation in large VLSI designs, addressing the need for an industry-ready
+model accounting for real-world reliability and scalability requirements.
+Device dynamics are described by the Landau-Lifshitz-Gilbert-Slonczewsky
+(s-LLGS ) stochastic magnetization considering Voltage-Controlled Magnetic
+Anisotropy (VCMA) and the non-negligible statistical effects caused by thermal
+noise. Model behavior is validated against the OOMMF magnetic simulator and its
+performance is characterized on a 1-Mb 28 nm Magnetoresistive-RAM (MRAM) memory
+product.",2106.04976v1
+2021-06-30,Quantum magnetism and topological superconductivity in Yu-Shiba-Rusinov chains,"Chains of magnetic adatoms on superconductors have been discussed as
+promising systems for realizing Majorana end states. Here, we show that dilute
+Yu-Shiba-Rusinov (YSR) chains are also a versatile platform for quantum
+magnetism and correlated electron dynamics, with widely adjustable spin values
+and couplings. Focusing on subgap excitations, we derive an extended $t-J$
+model for dilute quantum YSR chains and use it to study the phase diagram as
+well as tunneling spectra. We explore the implications of quantum magnetism for
+the formation of a topological superconducting phase, contrasting it to
+existing models assuming classical spin textures.",2107.00031v1
+2021-07-11,Hysteretic Magnetoresistance in a Non-Magnetic SrSnO3 Film via Thermal Coupling to Dynamic Substrate Behavior,"Hysteretic magnetoresistance (MR) is often used as a signature of
+ferromagnetism in conducting oxide thin films and heterostructures. Here,
+magnetotransport is investigated in a non-magnetic uniformly La-doped SrSnO3
+film grown using hybrid molecular beam epitaxy. A 12 nm La:SrSnO3/2 nm
+SrSnO3/GdScO3 (110) film with insulating behavior exhibited a robust hysteresis
+loop in the MR at T < 5 K accompanied by an anomaly at ~ +/- 3 T at T < 2.5 K.
+Furthermore, MR with the field in-plane yielded a value exceeded 100% at 1.8 K.
+Using detailed temperature-, angle- and magnetic field-dependent resistance
+measurements, we illustrate the origin of hysteresis is not due to magnetism in
+the film but rather is associated with the magnetocaloric effect of the GdScO3
+substrate. Given GdScO3 and similar substrates are commonly used in complex
+oxide research, this work highlights the importance of thermal coupling to
+processes in the substrates which must be carefully accounted for in the data
+interpretation for thin films and heterostructures utilizing these substrates.",2107.04965v1
+2021-08-08,Exchange scaling of ultrafast angular momentum transfer in 4$\it{f}$ antiferromagnets,"Ultrafast manipulation of the magnetic state of matter bears great potential
+for future information technologies. While demagnetisation in ferromagnets is
+governed by dissipation of angular momentum, materials with multiple spin
+sublattices, e.g. antiferromagnets, can allow direct angular momentum transfer
+between opposing spins, promising faster functionality. In lanthanides,
+4$\it{f}$ magnetic exchange is mediated indirectly through the conduction
+electrons (the Ruderman-Kittel-Kasuya-Yosida interaction, RKKY), and the effect
+of such conditions on direct spin transfer processes is largely unexplored.
+Here, we investigate ultrafast magnetization dynamics in 4f antiferromagnets,
+and systematically vary the 4$\it{f}$ occupation, thereby altering the
+magnitude of RKKY. By combining time-resolved soft x-ray diffraction with
+ab-initio calculations, we find that the rate of direct transfer between
+opposing moments is directly determined by the magnitude of RKKY. Given the
+high sensitivity of RKKY to the conduction electrons, our results offer a novel
+approach for fine-tuning the speed of magnetic devices.",2108.03714v1
+2021-08-10,Metallic nature and site-selective magnetic collapse in iron oxide Fe4O5 at the extreme conditions of Earth's deep interior,"Properties of iron oxides at the extreme conditions are of essential
+importance in condensed matter physics and Geophysics. The recent discovery of
+a new type of iron oxide, Fe4O5, at high pressure and high temperature of
+Earth's deep interior attracts great interests. In this paper, we report the
+electronic structure and the magnetic properties of Fe4O5 predicted by the
+density functional theory plus dynamic mean field theory (DFT+DMFT) approach.
+We find that Fe4O5 stays metallic from ambient pressure to high pressure. The
+magnetic moments of iron atoms at the three different crystallographic
+positions of Fe4O5 undergo position-dependent collapse as being compressed.
+Such site-selective magnetic moment collapse originates from the shift of
+energy levels and the consequent charge transfer among the Fe-3d orbits under
+compression.",2108.04477v1
+2021-08-11,Q Dependence of Magnetic Resonance Mode on FeTe$_{0.5}$Se$_{0.5}$ Studied by Inelastic Neutron Scattering,"Inelastic neutron scattering measurements have been performed on a
+superconducting single crystal FeTe$_{0.5}$Se$_{0.5}$ to examine the ${\bf
+Q}$-dependent enhancement of the dynamical structure factor, $S({\bf Q},E)$,
+from ${\bf Q}$ = (0, 0) to ($\pi$, $\pi$), including ($\pi$, 0) in the
+superconducting state. In most of iron-based superconductors, $S({\bf Q},E)$ is
+enhanced at ${\bf Q}$ = ($\pi$, 0), where the ""magnetic resonance mode"" is
+commonly observed in the unfolded Brillouin zone. Constant-$E$ cuts of $S({\bf
+Q},E)$ suggest that the enhancement is not uniform in the magnetic excitation,
+and limited around ${\bf Q}$ = ($\pi$, 0). This result is consistent with the
+theoretical simulation of the magnetic resonance mode due to the
+Bardeen$-$Cooper$-$Schrieffer coherence factor with the sign-reversing order
+parameter of s$_{\pm}$ wave.",2108.05051v1
+2021-08-11,Holographic Schwinger effect in the dynamical AdS/QCD model,"In this paper, we discuss the potential analysis of the holographic Schwinger
+effect in the bottom up AdS/QCD model. We study the effect of the magnetic
+field on the critical field and total potential in finite chemical potential
+case. By evaluating the critical electric field from the DBI action, one can
+observe that magnetic field decreases critical electric field Ec. From the
+results of potential analysis, we find the magnetic field reduces the potential
+barrier and favor the Schwinger effect which agrees with the results of the
+critical electric field. Moreover, the Schwinger effect is more obvious when
+pairs are parallel to the magnetic field than that in perpendicular case in
+this Einstein-Maxwell-dilaton model.",2108.05148v1
+2021-08-12,Flexibility and rigidity of free boundary MHD equilibria,"We study stationary free boundary configurations of an ideal incompressible
+magnetohydrodynamic fluid possessing nested flux surfaces. In 2D simply
+connected domains, we prove that if the magnetic field and velocity field are
+never commensurate, the only possible domain for any such equilibria is a disk,
+and the velocity and magnetic field are circular. We give examples of
+non-symmetric equilibria occupying a domain of any shape by imposing an
+external magnetic field generated by a singular current sheet charge
+distribution (external coils). Some results carry over to 3D axisymmetric
+solutions. These results highlight the importance of external magnetic fields
+for the existence of asymmetric equilibria.",2108.05977v2
+2021-08-16,Frustration-induced diffusive scattering anomaly and dimension change in $\rm FeGe_2$,"Magnetic frustration, arising from the competition of exchange interactions,
+has received great attention because of its relevance to exotic quantum
+phenomena in materials. In the current work, we report an unusual
+checkerboard-shaped scattering anomaly in $\rm FeGe_2$, far from the known
+incommensurate magnetic satellite peaks, for the first time by inelastic
+neutron scattering. More surprisingly, such phenomenon appears as spin dynamics
+at low temperature, but it becomes prominent above N\'eel transition as elastic
+scattering. A new model Hamiltonian that includes an intraplane next-nearest
+neighbor was proposed and attributes such anomaly to the near-perfect magnetic
+frustration and the emergence of unexpected two-dimensional magnetic order in
+the quasi-one-dimensional $\rm FeGe_2$.",2108.06882v2
+2021-08-21,Electron dynamics in noncommutative geometry with magnetic field and Zitterbewegung phenomenon,"Starting from a gauge invariant Dirac Hamiltonian with noncommutativity of
+space sector in the presence of an external uniform magnetic field, the
+resulting Dirac equation has been solved for electrons and its corresponding
+zitterbewegung (ZBW) phenomenon has been studied. The corresponding energy
+spectrum is shown to be different from previous studies wherein the non-gauge
+invariant Dirac Hamiltonian has been used. The effects of noncommutativity
+alter the amplitude as well as the cyclotron and the ZBW frequencies of the
+average velocity of charge carriers. This result is contrary to previous
+studies wherein there was no magnetic field and hence, neither the amplitude
+nor the frequency of the motion was affected. Moreover, all of the ZBW
+frequencies of the Landau energy-levels appear in the results. Also, in weak
+magnetic fields, we have calculated the average velocity of charge carriers for
+two initially localized spin-up and spin-down cases. The plotted trajectories
+reveal difference between these two cases. In addition, the ZBW phenomenon has
+been shown that manifests itself as a circular motion whose direction is spin
+dependent while accompanied by the cyclotron motion.",2108.09557v1
+2021-08-22,Nonlinear and Thermal Effects in the Absorption of Microwaves by Random Magnets,"Abstract We study the temperature dependence of the absorption of microwaves
+by random-anisotropy magnets. It is governed by strong metastability due to the
+broad distribution of energy barriers separating different spin configurations.
+At a low microwave power, when the heating is negligible, the spin dynamics is
+close to linear. It corresponds to the precession of ferromagnetically ordered
+regions that are in resonance with the microwave field. Previously we have
+shown (doi.org/10.1103/PhysRevB.103.214414) that in this regime a dielectric
+substance packed with random magnets would be a strong microwave absorber in a
+broad frequency range. Here we demonstrate that on increasing the power,
+heating and over barrier spin transitions come into play, resulting in the
+nonlinear behavior. At elevated temperatures the absorption of microwave power
+decreases dramatically, making the dielectric substance with random magnets
+transparent for the microwaves.",2108.09804v1
+2021-09-02,Magnetic Field Dependent Piezoelectricity in Atomically Thin Co$_2$Te$_3$,"Two dimensional (2D) materials have received a surge in research interest due
+to their exciting range of properties. Here we show that 2D cobalt telluride
+(Co2Te3), successfully synthesized via liquid-phase exfoliation in an organic
+solvent, exhibits weak ferromagnetism and semiconducting behavior at room
+temperature. The magnetic field-dependent piezoelectric properties of 2D Co2Te3
+sample show magneto-electric response of the material and a linear relationship
+between the output voltage and applied magnetic field. First-principles density
+functional theory (DFT) and ab initio molecular dynamics are used to explain
+these experimental results. Our work could pave the way for the development of
+2D materials with coupled magnetism and piezoelectricity, leading to new
+applications in electromagnetics.",2109.02781v1
+2021-09-14,Infinite critical boson non-Fermi liquid on heterostructure interfaces,"We study the emergence of non-Fermi liquid on heterostructure interfaces
+where there exists an infinite number of critical boson modes accounting for
+the magnetic fluctuations in two spatial dimensions. The interfacial
+Dzyaloshinskii-Moriya interaction naturally arises in magnetic interactions due
+to the absence of inversion symmetry, resulting in a degenerate contour for the
+low-energy bosonic modes in the momentum space which simultaneously becomes
+critical near the magnetic phase transition. The itinerant electrons are
+scattered by the critical boson contour via the Yukawa coupling. When the boson
+contour is much smaller than the Fermi surface, it is shown that, there exists
+a regime with a dynamic critical exponent z=3 while the boson contour still
+controls the low-energy magnetic fluctuations. Using a self-consistent
+renormalization calculation for this regime, we uncover a prominent non-Fermi
+liquid behavior in the resistivity with a characteristic temperature scaling
+power. These findings open up new avenues for understanding boson-fermion
+interactions and the novel fermionic quantum criticality.",2109.06594v2
+2021-09-28,Direct numerical simulations of optimal thermal convection in rotating plane layer dynamos,"The heat transfer behavior of convection-driven dynamos in a rotating plane
+layer between two parallel plates, heated from below and cooled from the top,
+is investigated. At a fixed rotation rate (Ekman Number, $E=10^{-6}$) and fluid
+properties (thermal and magnetic Prandtl numbers, $Pr=Pr_m=1$), both dynamo
+convection (DC) and non-magnetic rotating convection (RC) simulations are
+performed to demarcate the effect of magnetic field on heat transport at
+different thermal forcings (Rayleigh Number,
+$Ra=3.83\times10^{9}-3.83\times10^{10}$). In this range, our turbulence
+resolving simulations demonstrate the existence of an optimum thermal forcing,
+at which heat transfer between the plates in DC exhibits maximum enhancement,
+as compared to the heat transport in the RC simulations. Unlike any global
+force balance reported in the literature, the present simulations reveal an
+increase in the Lorentz force in the \textit{thermal boundary layer}, due to
+stretching of magnetic field line by the vortices near the walls with no-slip
+boundary condition. This increase in Lorentz force mitigates turbulence
+suppression owing to the Coriolis force, resulting in enhanced turbulence and
+heat transfer",2109.13455v2
+2021-10-05,Probing modified gravity with magnetically levitated resonators,"We present an experimental procedure, based on Meissner effect levitation of
+neodymium ferromagnets, as a method of measuring the gravitational interactions
+between mg masses. The scheme consists of two superconducting lead traps, with
+a magnet levitating in each trap. The levitating magnets behave as harmonic
+oscillators, and by carefully driving the motion of one magnet on resonance
+with the other, we find that it should be easily possible to measure the
+gravitational field produced by a 4~mg sphere, with the gravitational
+attraction from masses as small as 30~$\mu$g predicted to be measurable within
+realistic a realistic measurement time frame. We apply this acceleration
+sensitivity to one concrete example and show the ability of testing models of
+modified Newtonian dynamics.",2110.02263v1
+2021-10-21,Micromagnetic simulations of clusters of nanoparticles with internal structure: Application to magnetic hyperthermia,"Micromagnetic simulation results on dynamic hysteresis loops of clusters of
+iron oxide nanoparticles (NPs) with internal structure composed of nanorods are
+compared with the widely used macrospin approximation. Such calculations
+allowing for nanorod-composed NPs is facilitated by a previously developed
+coarse-graining method based on the renormalization group approach. With a
+focus on applications to magnetic hyperthermia, we show that magnetostatic
+interactions improve the heating performance of NPs in chains and triangles,
+and reduce heating performance in fcc arrangements. Hysteresis loops of
+triangular and fcc systems of complex NPs are not recovered within the
+macrospin approximation, especially at smaller interparticle distances. For
+triangular arrangements, the macrospin approximation predicts that
+magnetostatic interactions reduce loop area, in contrast to the complex NP
+case. An investigation of the local hysteresis loops of individual NPs and
+macrospins in clusters reveals the impact of the geometry of their neighbours
+on individual versus collective magnetic response, inhomogenous heating within
+clusters, and further differences between simulating NPs with internal
+structure and the use of the macrospin approximation. Capturing the internal
+physical and magnetic structure of NPs is thus important for some applications.",2110.11178v2
+2021-11-03,Lattice QED in external electromagnetic fields,"We study QED in external electromagnetic fields using methods developed for
+simulating lattice QCD. Our first project is to simulate QED in a constant (in
+space and time) external magnetic field on a euclidean space-time lattice using
+the Rational Hybrid Monte Carlo (RHMC) method. Observables we measure include
+the condensate $\langle\bar{\psi}\psi\rangle$ and the effective electron action
+after integrating out the fermion fields. We look for evidence that the
+combined effect of the magnetic field and the electron-positron attraction from
+QED produces a non-zero condensate in the limit of zero electron mass, a
+non-perturbative effect analogous to spontaneous chiral symmetry breaking. Very
+preliminary evidence is that such a condensate exists, at least for strong
+external magnetic fields and unphysically large electric charge. In addition,
+we are storing field configurations to measure the expected distortions and
+screenings of the coulomb field of a charged particle due to the vacuum
+polarization asymmetries produced by the magnetic field. We hope also to
+measure the dynamical contribution to the electron mass produced by the same
+mechanism that produces a finite condensate in the zero input mass limit.",2111.01990v1
+2021-11-15,Model-free approach to the interpretation of restricted and anisotropic self-diffusion in magnetic resonance of biological tissues,"Magnetic resonance imaging (MRI) is the method of choice for noninvasive
+studies of micrometer-scale structures in biological tissues via their effects
+on the time/frequency-dependent (""restricted"") and anisotropic self-diffusion
+of water. Traditional MRI relies on pulsed magnetic field gradients to encode
+the signal with information about translational motion in the direction of the
+gradient, which convolves fundamentally different aspects-such as bulk
+diffusivity, restriction, anisotropy, and flow-into a single effective
+observable lacking specificity to distinguish between biologically plausible
+microstructural scenarios. To overcome this limitation, we introduce a formal
+analogy between measuring rotational correlation functions and interaction
+tensor anisotropies in nuclear magnetic resonance (NMR) spectroscopy and
+investigating translational motion in MRI, which we utilize to convert data
+acquisition and analysis strategies from NMR of rotational dynamics in
+macromolecules to MRI of diffusion in biological tissues, yielding
+model-independent quantitative metrics reporting on relevant microstructural
+properties with unprecedented specificity. Our model-free approach advances the
+state-of-the-art in microstructural MRI, thereby enabling new applications to
+complex multi-component tissues prevalent in both tumors and healthy brain.",2111.07827v1
+2021-11-16,Helicity transfer in strong laser fields via the electron anomalous magnetic moment,"Electron beam longitudinal polarization during the interaction with
+counterpropagating circularly-polarized ultraintense laser pulses is
+investigated, while accounting for the anomalous magnetic moment of the
+electron. Although it is known that the helicity transfer from the laser
+photons to the electron beam is suppressed in linear and nonlinear Compton
+scattering processes, we show that the helicity transfer nevertheless can
+happen via an intermediate step of the electron radiative transverse
+polarization, phase-matched with the driving field, followed up by spin
+rotation into the longitudinal direction as induced by the anomalous magnetic
+moment of the electron. With spin-resolved QED Monte Carlo simulations, we
+demonstrate the consequent helicity transfer from laser photons to the electron
+beam with a degree up to 10%, along with an electron radial polarization up to
+65% after multiple photon emissions in a femtosecond timescale. This effect is
+detectable with currently achievable laser facilities, evidencing the role of
+the leading QED vertex correction to the electron anomalous magnetic moment in
+the polarization dynamics in ultrastrong laser fields.",2111.08167v2
+2021-11-24,Local magnetic moment formation and Kondo screening in the half filled two dimensional single band Hubbard model,"We study formation of local magnetic moments in strongly correlated Hubbard
+model within dynamical mean field theory and associate peculiarities of
+temperature dependence of local charge $\chi_c$ and spin $\chi_s$
+susceptibilities with different stages of local moment formation. Local maximum
+of temperature dependence of the charge susceptibility $\chi_c$ is associated
+with beginning of local magnetic moments formation, while the minimum of the
+susceptibility $\chi_c$ and double occupation, as well as low temperature
+boundary of the plateau of effective local magnetic moment $\mu_{\rm
+eff}^2=T\chi_s$ temperature dependence are connected with full formation of
+local moments. We also obtain interaction dependence of the Kondo temperature
+$T_K$, which is compared to the fingerprint criterion of Phys. Rev. Lett. 126,
+056403 (2021). Near the Mott transition the two criteria coincide, while
+further away from Mott transition the fingerprint criterion somewhat
+overestimates Kondo temperature. The relation of the observed features to the
+behavior of eigenvectors/eigenvalues of fermionic frequency-resolved charge
+susceptibility and divergences of irreducible vertices is discussed.",2111.12441v2
+2021-11-28,Parametrically driven THz magnon-pairs: predictions towards ultimately fast and minimally dissipative switching,"Findings ways to achieve switching between magnetic states at the fastest
+possible time scale that simultaneously dissipates the least amount of energy
+is one of the main challenges in magnetism. Antiferromagnets exhibit intrinsic
+dynamics in the THz regime, the highest among all magnets and are therefore
+ideal candidates to address this energy-time dilemma. Here we study
+theoretically THz-driven parametric excitation of antiferromagnetic
+magnon-pairs at the edge of the Brillouin zone and explore the potential for
+switching between two stable oscillation states. Using a semi-classical theory,
+we predict that switching can occur at the femtosecond time scale with an
+energy dissipation down to a few zepto Joule. This result touches the
+thermodynamical bound of the Landauer principle, and approaches the quantum
+speed limit up to 5 orders of magnitude closer than demonstrated with magnetic
+systems so far.",2111.14202v1
+2021-11-29,Charging up Boosted Black Holes,"Contrary to a prevailing assumption that black holes would swiftly discharge,
+we argue that black holes can charge preferentially when boosted through an
+ambient magnetic field. Though the details are very different, the preference
+for charge is related to the precipitation of the Wald charge on a spinning
+black hole in an ambient magnetic field. The gravito-electrodynamics upstage
+naive arguments about screening electric fields in determining the value of the
+charge accrued. Charged test particles, which build up the black hole charge,
+exhibit chaotic behavior as evidenced by fractal basin boundaries between
+dynamical regions. Charged, boosted black holes will generate their own
+electromagnetic fields and thereby their own luminous signatures, even if they
+are initially bare. We therefore add boosted black holes to the growing list of
+potentially observable black hole signatures, alongside black hole batteries
+and black hole pulsars. The implications should be relevant for supermassive
+black holes that are boosted relative to a galactic magnetic field as well as
+black holes merging with magnetized neutron stars.",2111.15027v3
+2021-12-02,Equation of State of dense QCD in external magnetic field,"In this proceeding we present our first results of the study of the QCD
+Equation of State at non-zero baryon density and in external magnetic field. We
+focused on the first three non-vanishing expansion coefficients of pressure in
+chemical potential and their dependence on magnetic field. The study is carried
+out within lattice simulations with $N_f=2+1$ dynamical quarks with physical
+quark masses. To overcome the sign problem, the simulations are carried out at
+imaginary baryon chemical potential. Our results suggest that external magnetic
+field considerably enhances the expansion coefficients and modifies their
+dependence on temperature.",2112.01032v3
+2021-12-02,Antiferromagnetic spin pumping via hyperfine interaction,"Spin pumping is an interfacial spin current generation from the ferromagnetic
+layer to the non-magnetic metal at its interface. The polarization of the
+pumped spin current $\textbf{J}_s \propto \textbf{m}\times \dot{\textbf{m}}$
+depends on the dynamics of the magnetic moment $\textbf{m}$. When the materials
+are based on light transition metals, mechanism behind the spin current
+transfer is dominated by the exchange interaction between spin of localized
+d-electrons and itinerant conduction electrons. In heavier transition metals,
+however, the interaction is not limited to the exchange interaction. The spin
+of the conduction electron can interact to its nuclear spin by means of
+hyperfine interaction, as observed in the shift of NMR frequency. By studying
+the spin polarization of conduction electron of the non-magnetic metallic layer
+due to a nuclear magnetic moment $\textbf{I}$ of the ferromagnetic layer, we
+show that the hyperfine interaction can mediate the spin pumping. The
+polarization of the spin current generation is shown to have a similar form
+$J_s\propto \textbf{I}\times\dot{\textbf{I}}$.",2112.01111v1
+2021-12-10,Magnetic energy spectrum produced by turbulent dynamo: effect of time irreversibility,"We consider the kinematic stage of evolution of magnetic field advected by
+turbulent hydrodynamic flow. We use a generalization of the Kazantsev-Kraichnan
+model to investigate time irreversible flows. In the viscous range of scales,
+the infinite-time limit of the spectrum is a power law but its slope is more
+flat than that predicted by Kazantsev model. This result agrees with numerical
+simulations. The rate of magnetic energy growth is slower than that in the
+time-symmetric case. We show that for high magnetic Prandtl turbulent plasma,
+the formation of the power-law spectrum shape takes very long time and may
+never happen because of the nonlinearity. We propose another ansatz to describe
+the spectrum shape at finite time.",2112.05736v2
+2021-12-16,Decoupling of Spin Decoherence Paths near Zero Magnetic Field,"We demonstrate a method to quantify and manipulate nuclear spin decoherence
+mechanisms that are active in zero to ultralow magnetic fields. These include:
+(i) non-adiabatic switching of spin quantization axis, due to residual
+background fields; (ii) scalar pathways due to through-bond couplings between
+$^1$H and heteronuclear spin species, such as $^2$H used partially as an
+isotopic substitute for $^1$H. Under conditions of free evolution, scalar
+relaxation due to $^2$H can significantly limit nuclear spin polarization
+lifetimes and thus the scope of magnetic resonance procedures near zero field.
+It is shown that robust trains of pulsed dc magnetic fields that apply $\pi$
+flip angles to one or multiple spin species may switch effective symmetry of
+the nuclear spin Hamiltonian, imposing decoupled or coupled dynamic regimes on
+demand. The method should broaden the spectrum of hyperpolarized biomedical
+contrast-agent compounds and hyperpolarization procedures that are used near
+zero field.",2112.08536v1
+2021-12-30,Identification of active magnetic reconnection using magnetic flux transport in plasma turbulence,"Magnetic reconnection has been suggested to play an important role in the
+dynamics and energetics of plasma turbulence by spacecraft observations,
+simulations and theory over the past two decades, and recently, by
+magnetosheath observations of MMS. A new method based on magnetic flux
+transport (MFT) has been developed to identify reconnection activity in
+turbulent plasmas. This method is applied to a gyrokinetic simulation of
+two-dimensional (2D) plasma turbulence. Results on the identification of three
+active reconnection X-points are reported. The first two X-points have
+developed bi-directional electron outflow jets. Beyond the category of
+electron-only reconnection, the third X-point does not have bi-directional
+electron outflow jets because the flow is modified by turbulence. In all cases,
+this method successfully identifies active reconnection through clear inward
+and outward flux transport around the X-points. This transport pattern defines
+reconnection and produces a new quadrupolar structure in the divergence of MFT.
+This method is expected to be applicable to spacecraft missions such as MMS,
+Parker Solar Probe, and Solar Orbiter.",2112.14878v1
+2022-01-17,Synthetic Hall ladder with tunable magnetic flux,"We describe a synthetic three-leg Hall ladder system with a tunable magnetic
+flux for neutral $^{173}$Yb atoms in a one-dimensional optical lattice. The
+ladder legs are formed by three hyperfine ground spin states of the atoms, and
+the complex interleg links are generated through Raman couplings between the
+spin states using multiple laser beams. The effective magnetic flux through a
+ladder plaquette, $\phi$, is controlled by the angles of the Raman laser beams
+with the lattice axis. We investigate the quench dynamics of the Hall ladder
+system for $\phi\approx\frac{\pi}{3}, \frac{\pi}{2},$ and $\frac{2\pi}{3}$
+after a sudden application of the Raman coupling in various interleg link
+configurations. The semi-classical trajectory of the atoms in the plane of the
+spin composition and lattice position exhibits the characteristic motion for
+the effective magnetic field. In a tube configuration with the three legs
+cyclically linked, the quench evolution was observed to be substantially
+damped, which is attributed to the random flux threading the Hall tube.",2201.06462v1
+2022-01-27,Ab-initio study of the electronic structure and magnetic properties of Ce$_2$Fe$_{17}$,"The Ce$_2$Fe$_{17}$ intermetallic compound has been studied intensely for
+several decades; its low-temperature state is reported experimentally either as
+ferromagnetic or antiferromagnetic by different authors, with a measured
+ordering temperature ranging within a hundred Kelvin. The existing theoretical
+investigations overestimate the experimental total magnetic moment of
+Ce$_2$Fe$_{17}$ by 20-40 % and predict a ferromagnetic ground state. By means
+of first-principle electronic structure calculations, we show that the total
+magnetic moment of Ce$_2$Fe$_{17}$ can be reproduced within the Local Density
+Approximation while functionals based on the Generalized Gradient Approximation
+fail. Atomistic spin dynamics simulations are shown to capture the change in
+the magnetic state of Ce$_2$Fe$_{17}$ with temperature, and closely replicate
+the reported helical structure that appears in some of the experimental
+investigations.",2201.11573v1
+2022-02-06,Longitudinally Modulated Dynamo Action in Simulated M-Dwarf Stars,"M-dwarf stars are well known for the intense magnetic activity that many of
+them exhibit. In cool stars with near-surface convection zones, this magnetic
+activity is thought to be driven largely by the interplay of convection and the
+large scale differential rotation and circulations it establishes. The highly
+nonlinear nature of these flows yields a fascinatingly sensitive and diverse
+parameter space, with a wide range of possible dynamics. We report here on a
+set of three global MHD simulations of rapidly rotating M2 (0.4 $M_\odot$)
+stars. Each of these three models established nests of vigorous convection that
+were highly modulated in longitude at low latitudes. Slight differences in
+their magnetic parameters led each model to disparate dynamo states, but the
+effect of the convective nest was a unifying feature. In each case, the action
+of longitudinally modulated convection led to localized (and in one case,
+global) reversals of the toroidal magnetic field, as well as the formation of
+an active longitude, with enhanced poloidal field amplitudes and flux
+emergence.",2202.02869v1
+2022-02-23,Ferroelectric control of magnetic skyrmions in two-dimensional van der Waals heterostructures,"Magnetic skyrmions are chiral nanoscale spin textures which are usually
+induced by Dzyaloshinskii-Moriya interaction (DMI). Recently, magnetic
+skyrmions have been observed in two-dimensional (2D) van der Waals (vdW)
+ferromagnetic materials, such as Fe$_{3}$GeTe$_{2}$. The electric control of
+skyrmions is important for their potential application in low-power memory
+technologies. Here, we predict that DMI and magnetic skyrmions in a
+Fe$_{3}$GeTe$_{2}$ monolayer can be controlled by ferroelectric polarization of
+an adjacent 2D vdW ferroelectric In$_{2}$Se$_{3}$. Based on density functional
+theory and atomistic spin-dynamics modeling, we find that the interfacial
+symmetry breaking produces a sizable DMI in a
+Fe$_{3}$GeTe$_{2}$/In$_{2}$Se$_{3}$ vdW heterostructure. We show that the
+magnitude of DMI can be controlled by ferroe-lectric polarization reversal,
+leading to creation and annihilation of skyrmions. Furthermore, we find that
+the sign of DMI in a In$_{2}$Se$_{3}$/Fe$_{3}$GeTe$_{2}$/In$_{2}$Se$_{3}$
+heterostructure changes with ferroelectric switching reversing the skyrmion
+chirality. The predicted electrically controlled skyrmion formation may be
+interesting for spintronic applications.",2202.11348v2
+2022-03-07,A dynamo simulation generating Saturn-like small magnetic dipole tilts,"Among planetary dynamos, the magnetic field of Saturn stands out in its
+exceptional level of axisymmetry. One of its peculiar features is that the
+magnetic dipole mode is tilted with respect to the planetary rotation axis by
+only $\approx 0.007^{\circ}$ or less. Numerical dynamo simulations performed in
+this context have had great difficulty in producing such small dipole tilt
+angles without introducing ad hoc ingredients such as a latitudinally varying
+heat flux pattern in the outer layers or stably stratified layers (SSL). Here
+we present a numerical dynamo simulation that generates a highly axisymmetric
+dynamo with a dipole tilt of about $\approx 0.0008^{\circ}$ on average. The
+model consists of a deep dynamo layer and an overlying low-conductivity layer
+but without any SSL. We highlight a novel mechanism where strong differential
+rotation generated in the atmospheric layer penetrates into the dynamo region,
+helping to maintain a very small magnetic dipole tilt.",2203.03520v1
+2022-03-07,Cosmic-void observations reconciled with primordial magnetogenesis,"It has been suggested that the weak magnetic field hosted by the
+intergalactic medium in cosmic voids could be a relic from the early Universe.
+However, accepted models of turbulent magnetohydrodynamic decay predict that
+the present-day strength of fields originally generated at the electroweak
+phase transition (EWPT) without parity violation would be too low to explain
+the observed scattering of $\gamma$-rays from TeV blazars. Here, we propose
+that the decay is mediated by magnetic reconnection and conserves the mean
+square fluctuation level of magnetic helicity. We find that the relic fields
+would be stronger by several orders of magnitude under this theory than was
+indicated by previous treatments, which restores the consistency of the
+EWPT-relic hypothesis with the observational constraints. Moreover, efficient
+EWPT magnetogenesis would produce relics at the strength required to resolve
+the Hubble tension via magnetic effects at recombination and seed
+galaxy-cluster fields close to their present-day strength.",2203.03573v3
+2022-03-08,Accretion of the magnetized neutrino-cooled torus,"Neutrino-cooled accretion flow around a black hole, produced by a compact
+binary merger, is a promising scenario for jet formation and magnetic-driven
+winds to explain short duration gamma ray bursts (GRBs) central engine and
+kilonovae based on GW170817 gravitational wave observation. Magnetorotational
+instability (MRI) turbulence and Blandford-Znajek (BZ) mechanism are expected
+to play key roles in the thermal equilibrium of the disk (balancing neutrino
+cooling) and in driving accretion and creating jets. Using the open-source
+GRMHD HARM-COOL code, we study the magnetically-driven evolution of an
+accretion disk with realistic equation of state in the fixed curved space-time
+background. We identify the effects of the neutrino cooling and the magnetic
+field, paying particular attention to the dynamical, thermal and composition
+evolution of the disk and outflows.",2203.04344v1
+2022-03-10,Dynamics of the collapse of a ferromagnetic skyrmion in a centrosymmetric lattice,"Time dependence of the size and chirality of a ferromagnetic skyrmion in a
+Heisenberg model with the magnetic field on a square lattice has been studied
+analytically and numerically. The lattice and the magnetic field generate
+strong time dependence of the skyrmion chirality. Due to nonlinearity, the
+lattice alone also generates strong intrinsic damping that leads to the
+skyrmion collapse via the emission of spin waves. In the absence of the
+magnetic field the collapse is slow for a large skyrmion but it becomes
+exponentially fast in the presence of the Landau-Lifshitz damping when the
+field is turned on. Magnons emitted by a collapsing skyrmion must have a
+discrete spectrum due to the quantization of the skyrmion magnetic moment.",2203.05342v1
+2022-03-25,Magnetic domain walls of the van der Waals material Fe$_3$GeTe$_2$,"Among two-dimensional materials, Fe$_3$GeTe$_2$ has come to occupy a very
+important place owing to its ferromagnetic nature with one of the highest Curie
+temperatures among known van der Waals materials and the potential for hosting
+skyrmions. In this combined experimental and theoretical work, we investigate
+the magnetic bubble domains as well as the microscopic domain wall profile
+using spin-polarized scanning tunneling microscopy in combination with
+atomistic spin-dynamics simulations performed with parameters from density
+functional theory calculations. We find a weak magneto-electric effect
+influencing the domain wall width by the electric field in the tunneling
+junction and determine the critical magnetic field for the collapse of the
+bubble domains. Our findings shed light on the origins of complex magnetism
+that Fe$_3$GeTe$_2$ exhibits.",2203.13562v1
+2022-05-18,Two ultracold highly magnetic atoms in a one-dimensional harmonic trap,"We theoretically investigate the properties of two interacting ultracold
+highly magnetic atoms trapped in a one-dimensional harmonic potential. The
+atoms interact via an anisotropic long-range dipole-dipole interaction, which
+in one dimension effectively can be modeled by the contact interaction. We
+investigate the interplay of the external magnetic field, the spin-spin
+interaction, and the trapping potential and how they affect the magnetization
+of the system. We show the role of indistinguishability and symmetries in the
+dynamics by studying the time evolution of the observables that could be
+measured experimentally. The presented model may depict the on-site interaction
+of the extended Hubbard models, therefore giving a better understanding of the
+fundamental building block of the respective many-body quantum simulators.",2205.08965v3
+2022-05-30,Self-biased SAW Magnetic Field Sensors Based on Angle Dependent Magneto-acoustic Coupling,"Surface-acoustic-wave (SAW) based devices have emerged as a promising
+technology in magnetic field sensing by integrating a magnetostrictive layer
+with the giant {\Delta}E/{\Delta}G effect. However, almost all SAW magnetic
+field sensors require a bias field to obtain high sensitivity. In addition, the
+true nature of magneto-acoustic coupling still presents a major challenge in
+understanding and designing of this kind of devices. In current work, a dynamic
+magnetoelastic model for the {\Delta}E/{\Delta}G effect is established in
+consideration of the important role of the dipole-dipole interaction. The model
+is also implemented into a FEM software to calculate the resonance frequency
+responses of multiple fabricated sensors with different {\psi} angles between
+of the acoustic wave vector and the induced uniaxial magnetic anisotropy. The
+measured results are in excellent agreement with the simulated ones. A strong
+resonance frequency sensitivity (RFS) of 630.4 kHz/Oe was achieved at zero bias
+field for the device with optimized {\psi} angle. Furthermore, the RFS
+measurements along different directions verify its vector-sensing capability.",2205.14933v2
+2022-05-31,TIC: A Stokes inversion code for scattering polarization with partial frequency redistribution and arbitrary magnetic fields,"We present the Tenerife Inversion Code (TIC), which has been developed to
+infer the magnetic and plasma properties of the solar chromosphere and
+transition region via full-Stokes inversion of polarized spectral lines. The
+code is based on the HanleRT forward engine, which takes into account many of
+the physical mechanisms that are critical for a proper modeling of the Stokes
+profiles of spectral lines originating in the tenuous and highly dynamic
+plasmas of the chromosphere and transition region: quantum level population
+imbalance and interference (atomic polarization), frequency coherence effects
+in polarized resonance scattering (partial frequency redistribution), and the
+impact of arbitrary magnetic fields on the atomic polarization and the
+radiation field. We present first results of atmospheric and magnetic
+inversions, and discuss future developments for the project.",2205.15666v1
+2022-06-02,Skyrmion formation in Ni-based Janus dihalide monolayers: Interplay between magnetic frustration and Dzyaloshinskii-Moriya interaction,"We present a comprehensive theory of the magnetic phases in monolayer
+nickel-based Janus dihalides (NiIBr, NiICl, NiBrCl) through a combination of
+first-principles calculations and atomistic simulations. Phonon band structure
+calculations and finite temperature molecular dynamics simulations show that
+Ni-dihalide Janus monolayers are stable. The parameters of the interacting spin
+Hamiltonian extracted from ab initio calculations show that nickel-dihalide
+Janus monolayers exhibit varying degrees of magnetic frustration together with
+a large Dzyaloshinskii-Moriya interaction due to their inherent inversion
+symmetry breaking. The atomistic simulations reveal a delicate interplay
+between these two competing magnetic interactions in giving rise to skyrmion
+formation.",2206.01325v1
+2022-06-19,Enhancement of spin mixing conductance by $s$-$d$ orbital hybridization in heavy metals,"In a magnetic multilayer, the spin transfer between localized magnetization
+dynamics and itinerant conduction spin arises from the interaction between a
+normal metal and an adjacent ferromagnetic layer. The spin-mixing conductance
+then governs the spin-transfer torques and spin pumping at the magnetic
+interface. Theoretical description of spin-mixing conductance at the magnetic
+interface often employs a single conduction-band model. However, there is
+orbital hybridization between conduction $s$ electron and localized $d$
+electron of the heavy transition metal, in which the single conduction-band
+model is insufficient to describe the $s$-$d$ orbital hybridization. In this
+work, using the generalized Anderson model, we estimate the spin-mixing
+conductance that arises from the $s$-$d$ orbital hybridization. We find that
+the orbital hybridization increases the magnitude of the spin-mixing
+conductance.",2206.09347v2
+2022-06-27,Quantitative and realistic description of the magnetic potential energy of spin-torque vortex oscillators,"Understanding the dynamics of magnetic vortices has emerged as an important
+challenge regarding the recent development of spin-torque vortex oscillators.
+Either micromagnetic simulations or the analytical Thiele equation approach are
+typically used to study such systems theoretically. This work focuses on the
+precise description of the restoring forces exerted on the vortex when it is
+displaced from equilibrium. In particular, the stiffness parameters related to
+a modification of the magnetic potential energy terms are investigated. A
+method is proposed to extract exchange, magnetostatic and Zeeman stiffness
+expressions from micromagnetic simulations. These expressions are then compared
+to state-of-the-art analytical derivations. Furthermore, it is shown that the
+stiffness parameters depend not only on the vortex core position but also on
+the injected current density. This phenomenon is not predicted by commonly used
+analytical ans\""atze. We show that these findings result from a deformation of
+the theoretical magnetic texture caused by the current induced Amp\`ere-Oersted
+field.",2206.13438v2
+2022-06-28,Spin-down by dynamo action in simulated radiative stellar layers,"The evolution of a star is influenced by its internal rotation dynamics
+through transport and mixing mechanisms, which are poorly understood. Magnetic
+fields can play a role in transporting angular momentum and chemical elements,
+but the origin of magnetism in radiative stellar layers is unclear. Using
+global numerical simulations, we identify a subcritical transition to
+turbulence due to the generation of a magnetic dynamo. Our results have many of
+the properties of the theoretically-proposed Tayler-Spruit dynamo mechanism,
+which strongly enhances transport of angular momentum in radiative zones. It
+generates deep toroidal fields that are screened by the stellar outer layers.
+This mechanism could produce strong magnetic fields inside radiative stars,
+without an observable field on their surface.",2206.13819v2
+2022-06-28,Phase structure of electroweak vacuum in a strong magnetic field: the lattice results,"Using first-principle lattice simulations, we demonstrate that in the
+background of a strong magnetic field (around $10^{20}$ T), the electroweak
+sector of the vacuum experiences two consecutive crossover transitions
+associated with dramatic changes in the zero-temperature dynamics of the vector
+$W$ bosons and the scalar Higgs particles, respectively. Above the first
+crossover, we observe the appearance of large, inhomogeneous structures
+consistent with a classical picture of the formation of $W$ and $Z$ condensates
+pierced by vortices. The presence of the $W$ and $Z$ condensates supports the
+emergence of the exotic superconducting and superfluid properties induced by a
+strong magnetic field in the vacuum. We find evidence that the vortices form a
+disordered solid or a liquid rather than a crystal. The second transition
+restores the electroweak symmetry. Such conditions can be realized in the
+near-horizon region of the magnetized black holes.",2206.14008v2
+2022-07-08,Light-induced magnetization driven by interorbital charge motion in a spin-orbit assisted Mott insulator alpha-RuCl3,"In a honeycomb-lattice spin-orbit assisted Mott insulator {\alpha}-RuCl3, an
+ultrafast magnetization is induced by circularly polarized excitation below the
+Mott gap. Photo-carriers play an important role, which are generated by turning
+down the synergy of the on-site Coulomb interaction and the spin-orbit
+interaction realizing the insulator state. An ultrafast 6- fs measurement of
+photo-carrier dynamics and a quantum mechanical analysis clarify the mechanism,
+according to which the magnetization emerges from a coherent charge motion
+between different t2g orbitals (dyz-dxz-dxy) of Ru3+ ions. This ultrafast
+magnetization is weakened in the antiferromagnetic (AF) phase, which is
+opposite to the general tendency that the inverse Faraday effect is larger in
+AF compounds than in paramagnetic ones. This temperature dependence indicates
+that the interorbital charge motion is affected by pseudo-spin rotational
+symmetry breaking in the AF phase.",2207.03877v2
+2022-07-14,Dzyaloshinskii-Moriya spin density by skew scattering,"Anisotropic exchange couplings, such as the Dzyaloshinskii-Moriya interaction
+(DMI), have played a vital role in the formation and dynamics of spin textures.
+This work predicts an anisotropic conduction electron spin density in metals
+with heavy magnetic impurities. The polarization of this
+$Dzyaloshinskii$-$Moriya$ $spin$ $density$ (DM-SD) is not collinear to the
+localized magnetic moments but rotated by the spin-dependent skew scattering of
+heavy atoms. The DM-SD induces the DMI between magnetic moments in metals and,
+therefore, it is the anisotropic extension of the
+Rutherman-Kittel-Kasuya-Yoshida spin density. Our model consists of two
+localized magnetic moments, one with a large spin-orbit coupling (a lanthanide
+or rare earth), in a free electron gas. The lanthanide spin controls the DM-SD
+strength and polarization, promising a flexible control mechanism for
+anisotropic couplings.",2207.06842v2
+2022-07-21,Energy-scale competition in the Hall resistivity of a strange metal,"Anomalous transport behavior -- both longitudinal and Hall -- is the defining
+characteristic of the strange-metal state of High-Tc cuprates. The temperature,
+frequency, and magnetic field dependence of the resistivity is understood
+within strange metal phenomenology as resulting from energy-scale competition
+to set the inelastic relaxation rate. The anomalously strong temperature
+dependence of the Hall coefficient, however, is at odds with this
+phenomenology. Here we report measurements of the Hall resistivity in the
+strange metal state of cuprates over a broad range of magnetic fields and
+temperatures. The observed field and temperature dependent Hall resistivity at
+very high magnetic fields reveals a distinct high-field regime which is
+controlled by energy-scale competition. This extends the strange metal
+phenomenology in the cuprates to include the Hall resistivity and suggests, in
+particular, that the direct effect of magnetic field on the relaxation dynamics
+of quantum fluctuations may be at least partially responsible for the anomalous
+Hall resistivity of the strange metal state.",2207.10244v1
+2022-07-21,Influence of nonuniform magnetization reorientation on spin-orbit torque measurements,"Measurements of spin-orbit torques in a ferromagnetic/nonmagnetic multilayer
+are typically based on an assumption that the entire ferromagnetic layer
+uniformly responds to the spin-orbit torque. This assumption breaks down when
+the thickness of the ferromagnetic layer is comparable to the dynamic exchange
+coupling length, which can be as short as a few nanometers in certain
+measurement geometries. The nonuniform magnetization reorientation coupled with
+nonuniform contribution of each magnetic sublayer to the magnetoresistance or
+the Kerr effect may impact the accuracy in the extrapolation of spin-orbit
+torque, particularly if a thick ferromagnetic layer is used. In this paper, we
+use numerical models to investigate such an impact in three different
+techniques: the magneto-optic-Kerr-effect method, the second-harmonic method
+and the spin torque ferromagnetic resonance method. We show that the
+second-harmonic and magneto-optic-Kerr-effect methods are prone to be
+influenced by the nonuniform magnetization reorientation, while the spin torque
+ferromagnetic resonance method is much less impacted.",2207.10349v1
+2022-07-26,Measuring Lateral Capillary Forces on Floating Particles using the Moses Effect,"This study presents a novel and user-friendly technique for detecting the
+lateral capillary force on a floating spherical particle. The technique
+leverages the interplay between the capillary attracting forces, hydrostatic
+pressure forces, and magnetic repulsion forces. A magnetic field is applied to
+induce a surface curvature in the liquid, resulting in a non-uniform
+distribution of capillary and hydrostatic pressure forces across the particle's
+surface. This leads to a stable equilibrium position of the particle at a
+specific distance from the magnet. The study analyzes the equilibrium position
+and other relevant parameters in comparison with the developed theory.
+Classical mechanics and intermolecular forces are applied to establish the
+theoretical basis for the method, modeling the behavior of the particle in
+response to the magnetic field, surface curvature, and hydrostatic pressure.
+The equilibrium position of the particle is determined by numerically solving
+the balance of forces equation.",2207.13134v3
+2022-08-11,Tunable electronic and magnetic phases in layered ruthenates: SrRuO3-SrTiO3 heterostructure upon strain,"Layered ruthenates are a unique class of systems which manifests a variety of
+electronic and magnetic features emerged from competing energy scales. At the
+heart of such features lies the multi-orbital physics, especially, the
+orbital-selective behavior. Here, we propose that the SrRuO3-SrTiO3
+heterostructure is a highly tunable platform to obtain the various emergent
+properties. Employing the density functional theory plus dynamical mean-field
+theory, we thoroughly investigate the orbital-dependent physics of the system
+and identify the competing magnetic fluctuations. We show that the epitaxial
+strain drives the system towards multi-orbital or orbital selective Mott phases
+from the Hund metal regime. At the same time, the two different types of static
+magnetism are stabilized, ferromagnetism and checkerboard antiferromagnetism,
+from the competition with the spin-density wave instability.",2208.05702v1
+2022-08-10,Effect of interlayer exchange coupling in spin-torque nano oscillator,"The dynamics of the magnetization of the free layer in a spin-torque nano
+oscillator (STNO) influenced by a noncollinear alignment between the
+magnetizations of the free and pinned layers due to an interlayer exchange
+coupling has been investigated theoretically. The orientations of the
+magnetization of the free layer with that of the pinned layer have been
+computed through the macrospin model and they are found to match well with
+experimental results. The bilinear and biquadratic coupling strengths make the
+current to switch the magnetization between two states or oscillate steadily.
+The expressions for the critical currents between which oscillations are
+possible and the critical bilinear coupling strength below which oscillations
+are not possible are derived. The frequency of the oscillations is shown to be
+tuned and increased to or above 300 GHz by the current which is the largest to
+date among nanopillar-shaped STNOs.",2208.07223v1
+2022-08-25,Ultrashort spin-orbit torque generated by femtosecond laser pulses,"To realize the very objective of spintronics, namely the development of
+ultra-high frequency and energy-efficient electronic devices, an ultrafast and
+scalable approach to switch magnetic bits is required. Magnetization switching
+with spin currents generated by the spin-orbit interaction at
+ferromagnetic/non-magnetic interfaces is one of such scalable approaches, where
+the ultimate switching speed is limited by the Larmor precession frequency.
+Understanding the magnetization precession dynamics induced by spin-orbit
+torques (SOTs) is therefore of great importance. Here we demonstrate generation
+of ultrashort SOT pulses that excite Larmor precession at an epitaxial Fe/GaAs
+interface by converting femtosecond laser pulses into high-amplitude current
+pulses in an electrically biased p-i-n photodiode. We control the polarity,
+amplitude, and duration of the current pulses and, most importantly, also their
+propagation direction with respect to the crystal orientation. The SOT origin
+of the excited Larmor precession was revealed by a detailed analysis of the
+precession phase and amplitude at different experimental conditions.",2208.11974v1
+2022-09-07,Acoustic attenuation in magnetic insulator films: effects of magnon polaron formation,"A magnon and a phonon are the quanta of spin wave and lattice wave,
+respectively, and they can hybridize into a magnon polaron when their
+frequencies and wavenumbers match close enough the values at the exceptional
+point. Guided by an analytically calculated magnon polaron dispersion,
+dynamical phase-field simulations are performed to investigate the effects of
+magnon polaron formation on the attenuation of a bulk acoustic wave in a
+magnetic insulator film. It is shown that a stronger magnon-phonon coupling
+leads to a larger attenuation. The simulations also demonstrate the existence
+of a minimum magnon-phonon interaction time required for the magnon polaron
+formation, which is found to decrease with the magnetoelastic coupling
+coefficient but increase with the magnetic damping coefficient. These results
+deepen the understanding of the mechanisms of acoustic attenuation in magnetic
+crystals and provide insights into the design of new-concept spin interconnects
+that operate based on acoustically driven magnon propagation.",2209.03481v2
+2022-09-08,Inflationary magnetogenesis of primordial magnetic fields with multiple vector fields,"In this paper, we discussed the multiple vector fields during the inflation
+era and the inflationary magnetogenesis with multiple vector fields. Instead of
+a single coupling function in single vector field models, the coupling matrix
+between vector fields and scalar field which drive the inflation is introduced.
+The dynamical equations for multiple vector fields are obtained and applied to
+the inflation era. We discussed three cases for the double-field model. In no
+mutual-coupling case, one can find that both electric and magnetic spectrum can
+be scale-invariant at the end of inflation, meanwhile, the strong coupling
+problem can be avoided. The effect of mutual-coupling between different vector
+fields is also discussed. We found that weak mutual-coupling can lead to the
+slightly blue spectrum of the magnetic field. On the other hand, in the strong
+mutual-coupling case, the scale-invariant magnetic spectrum can also be
+obtained but the energy density of electromagnetic fields either lead to the
+backreaction problem or is diluted by inflation.",2209.03545v3
+2022-09-15,Field-free high-frequency exchange-spring spin-torque nano-oscillators,"Spin-torque nano-oscillators (STNOs) are a type of nanoscale microwave
+auto-oscillators utilizing spin-torque to generate magnetodynamics with great
+promise for applications in microwaves, magnetic memory, and neuromorphic
+computing. Here, we report the first demonstration of exchange-spring STNOs,
+with an exchange-spring ([Co/Pd]-Co) reference layer and a perpendicular
+([Co/Ni]) free layer. This magnetic configuration results in high-frequency
+(>10 GHz) microwave emission at a zero magnetic field and exchange-spring
+dynamics in the reference layer and the observation of magnetic droplet
+solitons in the free layer at different current polarities. Our demonstration
+of bipolar and field-free exchange-spring-based STNOs operating over a 20 GHz
+frequency range greatly extends the design freedom and functionality of the
+current STNO technology for energy-efficient high-frequency spintronic and
+neuromorphic applications.",2209.06996v1
+2022-09-17,Identification of a non-axisymmetric mode in laboratory experiments searching for standard magnetorotational instability,"The standard magnetorotational instability (SMRI) is a promising mechanism
+for turbulence and rapid accretion in astrophysical disks. It is a
+magnetohydrodynamic (MHD) instability that destabilizes otherwise
+hydrodynamically stable disk flow. Due to its microscopic nature at
+astronomical distances and stringent requirements in laboratory experiments,
+SMRI has remained unconfirmed since its proposal, despite its astrophysical
+importance. Here we report a nonaxisymmetric MHD instability in a modified
+Taylor-Couette experiment. To search for SMRI, a uniform magnetic field is
+imposed along the rotation axis of a swirling liquid-metal flow. The
+instability initially grows exponentially, becoming prominent only for
+sufficient flow shear and moderate magnetic field. These conditions for
+instability are qualitatively consistent with SMRI, but at magnetic Reynolds
+numbers below the predictions of linear analyses with periodic axial
+boundaries. Three-dimensional numerical simulations, however, reproduce the
+observed instability, indicating that it grows linearly from the primary
+axisymmetric flow modified by the applied magnetic field.",2209.08410v1
+2022-10-01,Centrifugal barriers in magnetospheric accretion,"We reconsider the dynamics of accretion flows onto magnetized central star.
+For dipolar magnetically aligned case, the centrifugal barrier is at $R_{cb} =
+(2/3)^{1/3} R_c = 0.87 R_c$, where $R_c= ( G M/\Omega^2)^{1/3}$ is the
+corotation radius. For oblique dipole direct accretion from the corotation
+radius $R_c$ is possible only for magnetic obliquity satisfying $\tan
+\theta_\mu \geq 1/( 2 \sqrt{3}) $ ($\theta_\mu \geq 16.1^\circ $). The
+accretion proceeds in a form of funnel flows - along two streams centered on
+the $\mu-\Omega$ plane, with azimuthal opening angle $ \cos (\Delta \phi) = {
+\cot^ 2 {\theta_\mu} }/{12} $. For the magnetosphere distorted by the
+diamagnetic disk, the centrifugal barrier can be at as small radius as $R_{cb}=
+0.719 R_c$ for the fully confined dipole, extending out to $R_{cb} \sim R_c$
+for the magnetically balanced case. Type-II X-ray bursts in accreting neutron
+stars may be mediated by the centrifugal barrier; this requires nearly aligned
+configuration. Centrifugally-barriered material trapped in the magnetosphere
+may lead to periodic obscuration (""dips"") in the light curve of the host star,
+e.g., as observed in accreting young stellar objects and X-ray binaries.",2210.00300v3
+2022-10-05,Controlled Ordering of Room-Temperature Magnetic Skyrmions in a Polar Van der Waals Magnet,"Control and understanding of ensembles of skyrmions is important for
+realization of future technologies. In particular, the order-disorder
+transition associated with the 2D lattice of magnetic skyrmions can have
+significant implications for transport and other dynamic functionalities. To
+date, skyrmion ensembles have been primarily studied in bulk crystals, or as
+isolated skyrmions in thin film devices. Here, we investigate the condensation
+of the skyrmion phase at room temperature and zero field in a polar, Van der
+Waals magnet. We demonstrate that we can engineer an ordered skyrmion crystal
+through structural confinement on the $\mu$m scale, showing control over this
+order-disorder transition on scales relevant for device applications.",2210.02546v1
+2022-10-12,"Spin Diffusion in Spin Glasses Require Two Magnetic Variables, $\vec{M}$ and $\vec{m}$","Experiment has established that spin-glasses can support a steady-state spin
+current $\vec{j}_{i}$. However, the accepted theory of spin glass dynamics
+permits oscillations but no steady-state spin current. Onsager's irreversible
+thermodynamics implies that the spin current is proportional to the gradient of
+a magnetization. We argue, however, that the magnon distribution function
+associated with the local equilibrium magnetization $\vec{M}$ cannot diffuse
+because it represents $10^{23}$ variables. We therefore invoke the
+non-equilibrium magnetization $\vec{m}$, which in spintronics is called the
+{\it spin accumulation}. Applying the theory of irreversible thermodynamics we
+indeed find that it predicts spin diffusion, and we consider other experimental
+consequences of the theory, including a wavelength-dependent coupling between
+the reactive and the diffusive degrees of freedom.",2210.05865v2
+2022-10-14,Magnetic-field-induced cavity protection for intersubband polaritons,"We analyse the effect of a strong perpendicular magnetic field on an
+intersubband transition in a disordered doped quantum well strongly coupled to
+an optical cavity. The magnetic field changes the lineshape of the intersubband
+optical transition due to the interface roughness of the quantum well from a
+Lorentzian to a Gaussian one. In this regime, a novel form of
+magnetic-field-induced cavity protection sets in, which strongly reduces the
+polariton linewidth to the cavity contribution only. Implications of our
+results for fundamental studies of nonlinear polariton dynamics and for
+technological applications to polariton lasers are finally highlighted.",2210.08026v2
+2022-10-27,Gravitational and electromagnetic radiation from binary black holes with electric and magnetic charges: Hyperbolic orbits on a cone,"We derive the hyperbolic orbit of binary black holes with electric and
+magnetic charges. In the low-velocity and weak-field regime, by using the
+Newtonian method, we calculate the total emission rate of energy due to
+gravitational and electromagnetic radiation from binary black holes with
+electric and magnetic charges in hyperbolic orbits. Moreover, we develop a
+formalism to derive the merger rate of binary black holes with electric and
+magnetic charges from the two-body dynamical capture. We apply the formalism to
+investigate the effects of the charges on the merger rate for the near-extremal
+case and find that the effects cannot be ignored.",2210.15564v2
+2022-11-03,Deformative Magnetic Marked Length Spectrum Rigidity,"Let $M$ be a closed surface and let $\{g_s \ | \ s \in (-\epsilon,
+\epsilon)\}$ be a smooth one-parameter family of Riemannian metrics on $M$.
+Also let $\{\kappa_s : M \rightarrow \mathbb{R} \ | \ s \in (-\epsilon,
+\epsilon)\}$ be a smooth one-parameter family of functions on $M$. Then the
+family $\{(g_s, \kappa_s) \ | \ s \in (-\epsilon, \epsilon)\}$ gives rise to a
+family of magnetic flows on $TM$. We show that if the magnetic curvatures are
+negative for $s \in (-\epsilon, \epsilon)$ and the lengths of each periodic
+orbit remains constant as the parameter $s$ varies, then there exists a smooth
+family of diffeomorphisms $\{f_s : M \rightarrow M \ | \ s \in (-\epsilon,
+\epsilon)\}$ such that $f_s^*(g_s) = g_0$ and $f_s^*(\kappa_s) = \kappa_0$.
+This generalizes a result of Guillemin and Kazhdan to the setting of magnetic
+flows.",2211.01865v2
+2022-11-07,"Magnetic excitations, phase diagram and order-by-disorder in the extended triangular-lattice Hubbard model","The dynamical structure factor is an important observable of quantum magnets
+but due to numerical and theoretical limitations, it remains a challenge to
+make predictions for Hubbard-like models beyond one dimension. In this work, we
+study the magnetic excitations of the triangular lattice Hubbard model
+including next-nearest neighbor hopping. Starting from the 120$^{\circ}$ and
+stripe magnetic orders we compute the magnon spectra within a self-consistent
+random phase approximation. In the stripe phase, we generically find accidental
+zero modes related to a classical degeneracy known from the corresponding
+$J_1$-$J_2$ Heisenberg model. We extend the order-by-disorder mechanism to
+Hubbard systems and show how quantum fluctuations stabilize the stripe order.
+In addition, the frustration-induced condensation of magnon modes allows us to
+map out the entire phase diagram which is in remarkable agreement with recent
+numerical works. We discuss connections to experiments on triangular lattice
+compounds and the relation of our results to the proposed chiral spin liquid
+phase.",2211.03654v2
+2022-11-14,Spin wave diffraction model for perpendicularly magnetized films,"We present a near-field diffraction model for spin waves in perpendicularly
+magnetized films applicable in any geometries of excitation fields. This model
+relies on Kalinikos-Slavin formalism to express the dynamic susceptibility
+tensor in k-space, and calculate the diffraction patterns via inverse
+2D-Fourier transform of the response functions. We show an excellent
+quantitative agreement between our model and MuMax3 micro-magnetic simulations
+on two different geometries of antennas. Our method benchmarks spin wave
+diffraction in perpendicularly magnetized films, and is readily applicable for
+future designs of magnon beamforming and interferometric devices.",2211.07231v2
+2022-11-15,Turbulent reconnection acceleration,"The ubiquitous turbulence in astrophysical plasmas is important for both
+magnetic reconnection and reconnection acceleration. We study the particle
+acceleration during fast 3D turbulent reconnection with reconnection-driven
+turbulence. Particles bounce back and forth between the reconnection-driven
+inflows due to the mirror reflection and convergence of strong magnetic fields.
+Via successive head-on collisions, the kinetic energy of the inflows is
+converted into the accelerated particles. Turbulence not only regulates the
+inflow speed but also introduces various inflow obliquities with respect to the
+local turbulent magnetic fields. As both the energy gain and escape probability
+of particles depend on the inflow speed, the spectral index of particle energy
+spectrum is not universal. We find it in the range from $\approx 2.5$ to $4$,
+with the steepest spectrum expected at a strong guide field, i.e. a small angle
+between the total incoming magnetic field and the guide field. Without
+scattering diffusion needed for confining particles, the reconnection
+acceleration can be very efficient at a large inflow speed and a weak guide
+field.",2211.08444v1
+2022-11-21,Radon-based Image Reconstruction for MPI using a continuously rotating FFL,"Magnetic particle imaging is a relatively new tracer-based medical imaging
+technique exploiting the non-linear magnetization response of magnetic
+nanoparticles to changing magnetic fields. If the data are generated by using a
+field-free line, the sampling geometry resembles the one in computerized
+tomography. Indeed, for an ideal field-free line rotating only in between
+measurements it was shown that the signal equation can be written as a
+convolution with the Radon transform of the particle concentration. In this
+work, we regard a continuously rotating field-free line and extend the forward
+operator accordingly. We obtain a similar result for the relation to the Radon
+data but with two additive terms resulting from the additional
+time-dependencies in the forward model. We jointly reconstruct particle
+concentration and corresponding Radon data by means of total variation
+regularization yielding promising results for synthetic data.",2211.11683v2
+2022-12-03,Magnetoplasmonics: current challenges and future opportunities,"Plasmonics represents a unique approach to confine and enhance
+electromagnetic radiation well below the diffraction limit, bringing a huge
+potential for novel applications, for instance in energy harvesting,
+optoelectronics, and nanoscale biochemistry. To achieve novel functionalities,
+the combination of plasmonic properties with other material functions has
+become increasingly attractive. In this Perspective, we review the current
+state of the art, challenges, and future opportunities in nanoscale
+magnetoplasmonics, an emerging area aiming to merge magnetism and plasmonics in
+confined geometries to control either plasmons, electromagnetic-induced
+collective electronic excitations, using magnetic properties, or magnetic
+phenomena with plasmons. We begin by highlighting the cornerstones of the
+history and principles of this research field. We then provide our vision of
+its future development by showcasing raising research directions in
+mid-infrared light-driven spintronics and novel materials for
+magnetoplasmonics, such as transparent conductive oxides and hyperbolic
+metamaterials. As well, we provide an overview of recent developments in
+plasmon-driven magnetization dynamics, nanoscale optomagnetism and
+acousto-magnetoplasmonics. We conclude by giving our personal vision of the
+future of this thriving research field.",2212.01684v1
+2022-12-12,Magnon-Plasmon Hybridization Mediated by Spin-Orbit Interaction in Magnetic Materials,"We propose a mechanism for magnon-plasmon coupling and hybridization in
+ferromagnetic (FM) and antiferromagnetic (AFM) systems. The electric field
+associated with plasmon oscillations creates a non-equilibrium spin density via
+the inverse spin galvanic effect. This plasmon-induced spin density couples to
+magnons by an exchange interaction. The strength of magnon-plasmon coupling
+depends on the magneto-electric susceptibility of the system and the wavevector
+at which the level repulsion is happened. This wavevector may be tuned by an
+applied magnetic field. In AFM systems, the degeneracy of two chiral magnons is
+broken in the presence of a magnetic field, and we find two separate hybrid
+modes for left-handed and right-handed AFM magnons. Furthermore, we show that
+magnon-plasmon coupling in AFM systems is enhanced because of strong
+intra-sublattice spin dynamics. We argue that the recently discovered
+two-dimensional magnetic systems are ideal platforms to investigate proposed
+magnon-plasmon hybrid modes.",2212.06105v1
+2022-12-15,Observation of a new light-induced skyrmion phase in the Mott insulator Cu2OSeO3,"We report the discovery of a novel skyrmion phase in the multiferroic
+insulator Cu2OSeO3 for magnetic fields below the equilibrium skyrmion pocket.
+This phase can be accessed by exciting the sample out of equilibrium with
+near-infrared (NIR) femtosecond laser pulses but can not be reached by any
+conventional field cooling protocol. From the strong wavelength dependence of
+the photocreation process and via spin dynamics simulations, we identify the
+magnetoelastic effect as the most likely photocreation mechanism. This effect
+results in a transient modification of the magnetic interaction extending the
+equilibrium skyrmion pocket to lower magnetic fields. Once created, the
+skyrmions rearrange and remain stable over a long time, reaching minutes. The
+presented results are relevant for designing high-efficiency non-volatile data
+storage based on magnetic skyrmions.",2212.07878v1
+2022-12-21,Chirality-dependent spin current generation in a helimagnet: zero-field probe of chirality,"In a magnetic texture, the spin of a conduction electron is forced to be
+aligned to the localized moment. As a result, the topology of the magnetic
+texture affects the electron dynamics in nontrivial ways. A representative
+example is the topological Hall effect in noncoplanar spin textures with finite
+spin chirality. While propagating in the noncoplanar spin texture, electrons
+acquire Berry phase, and their motion is deflected as if they were in a
+magnetic field. Here, we report a distinct Berry phase effect in a coplanar
+helimagnet: the spin moment of the conduction electron is polarized under
+electric currents depending on the chirality of the helimagnet. The accumulated
+spin polarization works as a source of spin current, and the chirality can be
+detected by the inverse spin Hall mechanism. The functionality allows us to
+read out the chirality without magnetic fields, and therefore paves the way to
+future helimagnet-based spintronics.",2212.10980v1
+2023-01-07,Saturn's Magnetic Field at Unprecedented Detail Achieved by Cassini's Close Encounters,"The last 22.5 orbits of the Cassini mission brought the spacecraft to less
+than 3000 km from Saturn's 1-bar surface. These close encounters offered an
+unprecedented view of Saturn's magnetic field, including contributions from the
+internal dynamo, the ionosphere, and the magnetosphere. In this chapter, we
+highlight the new picture of Saturn's magnetic field from the Cassini mission
+including the persistent yet time-varying low-latitude field-aligned currents,
+Alfv\'en waves planet-ward of the D-ring, extreme axisymmetry, and high-degree
+magnetic moments. We then discuss the implications and new questions raised for
+Saturn's innermost magnetosphere, equatorial ionosphere, and interior. We
+conclude this chapter with an outlook for the future exploration of Saturn and
+other giant planets.",2301.02756v1
+2023-01-17,"Observation of field-induced single-ion magnetic anisotropy in a multiorbital Kondo alloy $\mathrm{(Lu,Yb)}\mathrm{Rh}_{2}\mathrm{Zn}_{20}$","We demonstrate field-induced single-ion magnetic anisotropy resulting from
+the multiorbital Kondo effect on the diluted ytterbium alloy
+$(\mathrm{Lu}_{1-x}\mathrm{Yb}_x)\mathrm{Rh}_2\mathrm{Zn}_{20}$. Single-ion
+anisotropic metamagnetic behavior is revealed in low-temperature regions where
+the local Fermi-liquid state is formed. Specific hea, low-field magnetic
+susceptibility, and resistivity indicate reproduction of the ground-state
+properties by the $\mathrm{SU}(N = 8)$ Kondo model with a relatively large
+$c$-$f$ hybridization of $T_{\mathrm{K}} = 60.9 \ \mathrm{K}$. Dynamical
+susceptibility measurements on $\mathrm{Yb}\mathrm{Rh}_2\mathrm{Zn}_{20}$
+support realizing the multiorbital Kondo ground state in
+$(\mathrm{Lu}_{1-x}\mathrm{Yb}_x)\mathrm{Rh}_2\mathrm{Zn}_{20}$. The single-ion
+magnetic anisotropy becomes evident above $\sim5 \ \mathrm{T}$, which is lower
+than the isotropic Kondo crossover field of 22.7 T, verifying blurred low-lying
+crystal field states through the multiorbital Kondo effect.",2301.07038v3
+2023-02-09,Single-shot laser-induced switching of an exchange biased antiferromagnet,"Ultrafast manipulation of magnetic order has challenged our understanding the
+fundamental and dynamic properties of magnetic materials. So far single shot
+magnetic switching has been limited to ferrimagnetic alloys and multilayers. In
+ferromagnetic (FM)/antiferromagnetic (AFM) bilayers, exchange bias (He) arises
+from the interfacial exchange coupling between the two layers and reflects the
+microscopic orientation of the antiferromagnet. Here we demonstrate the
+possibility of single shot switching of the antiferromagnet (change of the sign
+and amplitude of He) with a single femtosecond laser pulse in IrMn/CoGd
+bilayers. We demonstrate the switching for a wide range of fluences for
+different layer thicknesses and compositions. Atomistic simulations predict
+ultrafast switching and recovery of the AFM magnetization on a timescale of 2
+ps. These results provide the fastest and the most energy-efficient method to
+set the exchange bias and pave the way to potential applications for ultrafast
+spintronic devices.",2302.04510v1
+2023-02-13,Helical dynamo growth at modest versus extreme magnetic Reynolds numbers,"Understanding large-scale magnetic field growth in astrophysical objects is a
+persistent challenge. We tackle the long-standing question of how much helical
+large-scale dynamo growth occurs independent of the magnetic Reynolds number
+(Rm) in a closed volume. From modest-Rm numerical simulations, we identify a
+pre-saturation regime when the large-scale field grows independently of Rm, but
+to an Rm-dependent magnitude. For plausible magnetic spectra however, the
+analysis predicts the magnitude to be Rm-independent and substantial as
+Rm$\to\infty$. This gives renewed optimism for the relevance of closed dynamos
+and pinpoints how modest Rm and hyper-diffusive simulations can cause
+misapprehension of the Rm$\to\infty$ behavior.",2302.06042v2
+2023-02-23,Giant supermagnonic Bloch point velocities by jet propulsion effect in cylindrical ferromagnetic nanowires,"Achieving high velocities of magnetic domain walls is a crucial factor for
+their use as information carriers in modern nanoelectronic applications. In
+nanomagnetism and spintronics, these velocities are often limited either by
+internal domain wall instabilities, known as the Walker breakdown phenomenon,
+or by spin wave emission, known as the magnonic regime. In the rigid domain
+wall model, the maximum magnon velocity acts as an effective ""speed of light"",
+providing a relativistic analogy for the domain wall speed limitation.
+Cylindrical magnetic nanowires are an example of systems with the absence of
+the Walker breakdown phenomenon. Here we demonstrate that in cylindrical
+nanowires with high magnetization such as Iron, also the magnonic limit could
+be outstandingly surpassed. Our numerical modelling shows the Bloch point
+domain wall velocities as high as 14 km/s, well above the magnonic limit
+estimated in the interval 1.7-2.0 km/s. The key ingredient is the conical shape
+of the domain wall which elongates and breaks during the dynamics, leading to
+domain wall acceleration due to the jet propulsion effect. This effect will be
+very important for three-dimensional spintronic networks based on cylindrical
+magnetic nanowires.",2302.12329v1
+2023-02-28,How closely does transient magnetic linear dichroism follow the spin moment?,"In highly out-of-equilibrium states of matter, such as those induced by a
+pump laser, the applicability of well established spectroscopic probes of
+magnetic order are called into question. Here we address the validity of x-ray
+absorption techniques in pump laser conditions, focusing on magnetic linear
+dichroism (MLD), a crucial probe of antiferromagnetic (AFM) order. We directly
+compute the dynamics of the square of the spin moment and compare to those
+obtained via the MLD response. For AFM FePd the agreement between these
+distinct routes to the magnetic moment severely degrades at pulse fluences
+greater than 1 mJ/cm$^2$, indicating a breakdown of the MLD response as an
+accurate probe of the transient moment. This contrasts with the MLD for
+ferromagnetic FePt which reliably tracks the moment for fluences (and absorbed
+energies) up to an order of magnitude greater than the breakdown threshold for
+AFM FePd. The underlying microscopic reason for this we find to be increased
+laser induced excitations out of the $d$-band in AFM FePd, where this increase
+is made possible by the AFM pseudogap.",2302.14856v2
+2023-03-01,On the instability of the magnetohydrodynamic pipe flow subject to a transverse magnetic field,"The linear stability of a fully-developed liquid-metal MHD pipe flow subject
+to a transverse magnetic field is studied numerically. Because of the lack of
+axial symmetry in the mean velocity profile, we need to perform a BiGlobal
+stability analysis. For that purpose, we develop a two-dimensional complex
+eigenvalue solver relying on a Chebyshev-Fourier collocation method in physical
+space. By performing an extensive parametric study, we show that in contrast to
+Hagen-Poiseuille flow known to be linearly stable for all Reynolds numbers, the
+MHD pipe flow with transverse magnetic field is unstable to three-dimensional
+disturbances at sufficiently high values of the Hartmann number and wall
+conductance ratio. The instability observed in this regime is attributed to the
+presence of velocity overspeeds in the so-called Roberts layers and the
+corresponding inflection points in the mean velocity profile. The nature and
+characteristics of the most unstable modes are investigated, and we show that
+they vary significantly depending on the wall conductance ratio. A major result
+of this paper is that the global critical Reynolds number for the MHD pipe flow
+with transverse magnetic field is $Re=45230$, and it occurs for a perfectly
+conducting pipe wall and the Hartmann number $Ha=19.7$.",2303.00395v1
+2023-03-15,Extended magnetic reconnection in kinetic plasma turbulence,"Magnetic reconnection and plasma turbulence are ubiquitous processes
+important for laboratory, space and astrophysical plasmas. Reconnection has
+been suggested to play an important role in the energetics and dynamics of
+turbulence by observations, simulations and theory for two decades. The
+fundamental properties of reconnection at kinetic scales, essential to
+understanding the general problem of reconnection in magnetized turbulence,
+remain largely unknown at present. Here we present an application of the
+magnetic flux transport method that can accurately identify reconnection in
+turbulence to a three-dimensional simulation. Contrary to ideas that
+reconnection in turbulence would be patchy and unpredictable, highly extended
+reconnection X-lines, on the same order of magnitude as the system size, form
+at kinetic scales. Extended X-lines develop through bi-directional reconnection
+spreading. They satisfy critical balance characteristic of turbulence, which
+predicts the X-line extent at a given scale. These results present a picture of
+fundamentally extended reconnection in kinetic-scale turbulence.",2303.08642v2
+2023-03-21,Helitronics for classical and unconventional computing,"Magnetic textures are promising candidates for unconventional computing due
+to their non-linear dynamics. We propose to investigate the rich variety of
+seemingly trivial lamellar magnetic phases, e.g., helical, spiral, stripy
+phase, or other one-dimensional soliton lattices. These are the natural stray
+field-free ground states of almost every magnet. The order parameters of these
+phases may be of potential interest for both classical and unconventional
+computing, which we refer to as helitronics. For the particular case of a
+chiral magnet and its helical phase, we use micromagnetic simulations to
+demonstrate the working principles of all-electrical (i) classical binary
+memory cells and (ii) memristor and neuron cells, based on the orientation of
+the helical stripes.",2303.11688v1
+2023-03-25,On Improved Commutation for Moving-Magnet Planar Actuators,"The demand for high-precision and high-throughput motion control systems has
+increased significantly in recent years. The use of moving-magnet planar
+actuators (MMPAs) is gaining popularity due to their advantageous
+characteristics, such as complete environmental decoupling and reduction of
+stage mass. Nonetheless, model-based commutation techniques for MMPAs are
+compromised by misalignment between the mover and coil array and mismatch
+between the ideal electromagnetic model and the physical system, often leading
+to decreased system performance. To address this issue, a novel improved
+commutation approach is proposed in this paper\YB{, which is applicable for
+general planar motor applications,} by means of dynamic regulation of the
+position dependence of the ideal model-based commutation algorithm, which
+allows for attenuation of magnetic misalignment, manufacturing inaccuracies and
+other unmodelled phenomena. The effectiveness of the proposed approach is
+validated through experiments using a state-of-the-art moving-magnet planar
+actuator prototype.",2303.14392v2
+2023-04-19,Cavity magnomechanical coupling with coupled magnon modes in a synthetic antiferromagnet,"On-chip cavity magnomechanics is an emerging field exploring acoustic and
+magnonic functionalities of various ferromagnetic materials and structures
+using strongly confined phonons. It is expected that such cavity magnomechanics
+can be extended to multilayer ferromagnets, especially synthetic
+antiferromagnets (SAFs) that exhibit zero net magnetization through interlayer
+exchange coupling. However, the conventional theoretical framework for a single
+ferromagnet cannot be used directly because of the antiferromagnetic
+magnetization dynamics associated with the interlayer exchange coupling. In
+this paper, we theoretically investigate phonon-magnon coupling with a
+three-layer SAF. Our formulation of the phonon-magnon coupling constants
+reveals that the acoustic (optical) magnon mode dominantly couples to the
+cavity phonon when the magnetization angles in the two ferromagnetic layers are
+antiparallel (orthogonal). Moreover, numerical calculations including the
+effects of dipole-dipole interactions and in-plane uniaxial magnetic anisotropy
+allow us to predict phonon frequency shifts and linewidth broadening that can
+be detected in experiments. These theoretical insights would greatly help us to
+make a strategy for bringing the system into the strong coupling regime and to
+devise novel control protocols in analogy to cavity quantum electrodynamics and
+cavity optomechanics.",2304.09458v2
+2023-04-20,Heliknoton in a film of cubic chiral magnet,"Cubic chiral magnets exhibit a remarkable diversity of two-dimensional
+topological magnetic textures, including skyrmions. However, the experimental
+confirmation of topological states localized in all three spatial dimensions
+remains challenging. In this paper, we investigate a three-dimensional
+topological state called a heliknoton, which is a hopfion embedded into a helix
+or conic background. We explore the range of parameters at which the heliknoton
+can be stabilized under realistic conditions using micromagnetic modeling,
+harmonic transition state theory, and stochastic spin dynamics simulations. We
+present theoretical Lorentz TEM images of the heliknoton, which can be used for
+experimental comparison. Additionally, we discuss the stability of the
+heliknoton at finite temperatures and the mechanism of its collapse. Our study
+offers a pathway for future experimental investigations of three-dimensional
+topological solitons in magnetic crystals.",2304.10181v1
+2023-04-25,Simulations of Magnetization Reversal in FM/AFM Bilayers With THz Frequency Pulses,"It is widely known that antiferromagnets (AFMs) display a high frequency
+response in the terahertz (THz) range, which opens up the possibility for
+ultrafast control of their magnetization for next generation data storage and
+processing applications. However, because the magnetization of the different
+sublattices cancel, their state is notoriously difficult to read. One way to
+overcome this is to couple AFMs to ferromagnets - whose state is trivially read
+via magneto-resistance sensors. Here we present conditions, using theoretical
+modelling, that it is possible to switch the magnetization of an AFM/FM bilayer
+using THz frequency pulses with moderate field amplitude and short durations,
+achievable in experiments. Consistent switching is observed in the phase
+diagrams for an order of magnitude increase in the interface coupling and a
+tripling in the thickness of the FM layer. We demonstrate a range of reversal
+paths that arise due to the combination of precession in the materials and the
+THz-induced fields. Our analysis demonstrates that the AFM drives the switching
+and results in a much higher frequency dynamics in the FM due to the exchange
+coupling at the interface. The switching is shown to be robust over a broad
+range of temperatures relevant for device applications.",2304.12969v1
+2023-05-13,Surface magnetism in the pulsating RV Tauri star R Scuti,"We present the surface magnetic field conditions of the brightest pulsating
+RV Tauri star, R Sct. Our investigation is based on the longest
+spectropolarimetric survey ever performed on this variable star. The analysis
+of high resolution spectra and circular polarization data give sharp
+information on the dynamics of the atmosphere and the surface magnetism,
+respectively. Our analysis shows that surface magnetic field can be detected at
+different phases along a pulsating cycle, and that it may be related to the
+presence of a radiative shock wave periodically emerging out of the photosphere
+and propagating throughout the stellar atmosphere.",2305.07849v1
+2023-05-16,Solar Active Region Magnetogram Image Dataset for Studies of Space Weather,"In this dataset we provide a comprehensive collection of magnetograms (images
+quantifying the strength of the magnetic field) from the National Aeronautics
+and Space Administration's (NASA's) Solar Dynamics Observatory (SDO). The
+dataset incorporates data from three sources and provides SDO Helioseismic and
+Magnetic Imager (HMI) magnetograms of solar active regions (regions of large
+magnetic flux, generally the source of eruptive events) as well as labels of
+corresponding flaring activity. This dataset will be useful for image analysis
+or solar physics research related to magnetic structure, its evolution over
+time, and its relation to solar flares. The dataset will be of interest to
+those researchers investigating automated solar flare prediction methods,
+including supervised and unsupervised machine learning (classical and deep),
+binary and multi-class classification, and regression. This dataset is a
+minimally processed, user configurable dataset of consistently sized images of
+solar active regions that can serve as a benchmark dataset for solar flare
+prediction research.",2305.09492v3
+2023-05-18,Magnetic catalysis in weakly interacting hyperbolic Dirac materials,"Due to linearly vanishing density of states, emergent massless Dirac
+quasiparticle resulting from the free fermion motion on a family of
+two-dimensional half-filled bipartite hyperbolic lattices feature dynamic mass
+generation through quantum phase transitions only for sufficiently strong
+finite-range Coulomb repulsion. As such, strong nearest-neighbor Coulomb
+repulsion ($V$) is conducive to the nucleation of a charge-density-wave (CDW)
+order with a staggered pattern of average fermionic density between two
+sublattices of bipartite hyperbolic lattices. Considering a collection of
+spinless fermions (for simplicity), here we show that application of strong
+external magnetic fields by virtue of producing a \emph{finite} density of
+states near the zero energy triggers the condensation of the CDW order even for
+\emph{infinitesimal} $V$. The proposed magnetic catalysis mechanism is
+operative for uniform as well as inhomogeneous (bell-shaped) magnetic fields.
+We present scaling of the CDW order with the total flux enclosed by hyperbolic
+Dirac materials for a wide range of (especially subcritical) $V$.",2305.11174v1
+2023-05-29,Light-induced weak ferromagnetism through nonlinear magnonic rectification,"Rectification describes the generation of a quasistatic component from an
+oscillating field, such as an electric polarization in optical rectification,
+or a structural distortion in nonlinear phononic rectification. Here, we
+present a third fundamental process for magnetization, in which spin precession
+is rectified along the coordinates of a nonlinearly driven magnon mode in an
+antiferromagnet. We demonstrate theoretically that a quasistatic magnetization
+can be induced by transient spin canting in response to the coherent excitation
+of a chiral phonon mode that produces an effective magnetic field for the
+spins. This mechanism, which we call nonlinear magnonic rectification, is
+generally applicable to magnetic systems that exhibit infrared-active chiral
+phonon modes. Our results serve as an example of light-induced weak
+ferromagnetism and open a promising avenue towards creating dynamical spin
+configurations that are not accessible in equilibrium.",2305.18656v2
+2023-05-31,Pressure evolution of electronic structure and magnetism in the layered van der Waals ferromagnet CrGeTe$_3$,"Layered van der Waals ferromagnets, which preserve their magnetic properties
+down to exfoliated monolayers, are fueling an abundance of fundamental research
+and nanoscale device demonstration. CrGeTe$_3$ is a prime example for this
+class of materials. Its temperature-pressure phase diagram features an
+insulator-to-metal transition and a significant increase of ferromagnetic
+Curie-Weiss temperatures upon entering the metallic state. We use density
+functional theory to understand the magnetic exchange interactions in
+CrGeTe$_3$ at ambient and elevated pressure. We calculate Heisenberg exchange
+couplings, which provide the correct ferromagnetic ground state and explain the
+experimentally observed pressure dependence of magnetism in CrGeTe$_3$.
+Furthermore, we combine density functional theory with dynamical mean field
+theory to investigate the effects of electronic correlations and the nature of
+the high pressure metallic state in CrGeTe$_3$.",2306.00081v2
+2023-06-12,Magnetically tunable exciton valley coherence in monolayer WS$_2$ mediated by the electron-hole exchange and exciton-phonon interactions,"We develop a model, which incorporates both intra- and intervalley
+scatterings to master equation, to explore exciton valley coherence in
+monolayer WS$_2$ subjected to magnetic field. For linearly polarized (LP)
+excitation accompanied with an initial coherence, our determined valley
+dynamics manifests the coherence decay being faster than the exciton population
+relaxation, and agrees with experimental data by Hao et al.[Nat. Phys. 12, 677
+(2016)]. Further, we reveal that magnetic field may quench the electron-hole
+(e-h) exchange induced pure dephasing -- a crucial decoherence source -- as a
+result of lifting of valley degeneracy, allowing to magnetically regulate
+valley coherence. In particular, at low temperatures for which the
+exciton-phonon (ex-ph) interaction is weak, we find that the coherence time is
+expected to attain ${\tau}_{\mathcal{C}}\sim 1$ ps, facilitating full control
+of qubits based on the valley pseudospin. For dark excitons, we demonstrate an
+emerging coherence even in the absence of initial coherent state, which has a
+long coherence time ($\sim 15$ ps) at low temperature. Our work provides an
+insight into tunable valley coherence and coherent valley control based on dark
+excitons.",2306.06977v1
+2023-06-26,Variational Model-Based Reconstruction Techniques for Multi-Patch Data in Magnetic Particle Imaging,"Magnetic Particle Imaging is an emerging imaging modality through which it is
+possible to detect tracers containing superparamagnetic nanoparticles. The
+exposure of the particles to dynamic magnetic fields generates a non-linear
+response that is used to locate the particles and produce an image of their
+distribution. The bounding box that can be covered by a single scan curve
+depends on the strength of the gradients of the magnetic fields applied, which
+is limited due to the risk of causing peripheral nerve stimulation (PNS) in the
+patients. To address this issue, multiple scans are performed by practitioners.
+The scan data must be merged together to produce reconstructions of larger
+regions of interest. In this paper we propose a mathematical framework which
+generalizes the current multi-patch scanning by utilizing transformations. We
+show the flexibility of this framework in a variety of different scanning
+approaches. Moreover, we describe an iterative reconstruction algorithm, show
+its convergence to a minimizer and perform numerical experiments on simulated
+data.",2306.14454v1
+2023-07-03,Emergence of Elastic Softening Featuring Ultra-Slow Dynamics Around Magnetic Critical Endpoint in UCoAl,"We conducted an investigation on the temperature and magnetic field
+dependence of the elastic properties of UCoAl. The longitudinal elastic
+stiffness, $C_{33}$, exhibits significant softening as the system approaches
+the critical endpoint (CEP). This softening is indicative of an ultrasonic
+dispersion phenomenon, where the anomaly in the elastic constants diminishes
+with increasing measurement frequency. Fine structures were observed near the
+CEP in higher frequencies. The magnetic field dependence of $C_{33}$ can be
+explained by assuming a specific field dependence of the relaxation time.
+Remarkably, we recorded a relaxation time of 3.5$\times$10$^{-8}$ s in the
+vicinity of the CEP, which is the longest observed value among solids. These
+peculiar ultrasonic properties cannot be explained solely by Ising-like
+ferromagnetic fluctuations, suggesting the involvement of the quadrupole
+(orbital) degree of freedom in the formation of the CEP. We discussed the
+origin of these observed phenomena in relation to the magnetic ground state of
+the UCoAl system.",2307.00703v1
+2023-07-27,Chiral anomaly and dynamos from inhomogeneous chemical potential fluctuations,"In the standard model of particle physics, the chiral anomaly can occur in
+relativistic plasmas and plays a role in the early Universe, protoneutron
+stars, heavy-ion collisions, and quantum materials. It gives rise to a magnetic
+instability if the number densities of left- and right-handed electrically
+charged fermions are unequal. Using direct numerical simulations, we show this
+can result just from spatial fluctuations of the chemical potential, causing a
+chiral dynamo instability, magnetically driven turbulence, and ultimately a
+large-scale magnetic field through the magnetic alpha effect.",2307.15118v4
+2023-08-22,Theory of defect-induced crystal field perturbations in rare earth magnets,"We present a theory describing the single-ion anisotropy of rare earth (RE)
+magnets in the presence of point defects. Taking the RE-lean 1:12 magnet class
+as a prototype, we use first-principles calculations to show how the
+introduction of Ti substitutions into SmFe$_{12}$ perturbs the crystal field,
+generating new coefficients due to the lower symmetry of the RE environment. We
+then demonstrate that these perturbations can be described extremely
+efficiently using a screened point charge model. We provide analytical
+expressions for the anisotropy energy which can be straightforwardly
+implemented in atomistic spin dynamics simulations, meaning that such
+simulations can be carried out for an arbitrary arrangement of point defects.
+The significant crystal field perturbations calculated here demonstrate that a
+sample which is single-phase from a structural point of view can nonetheless
+have a dramatically varying anisotropy profile at the atomistic level if there
+is compositional disorder, which may influence localized magnetic objects like
+domain walls or skyrmions.",2308.11303v1
+2023-08-31,DFT+DMFT study of the magnetic susceptibility and the correlated electronic structure in transition-metal intercalated NbS$_2$,"The Co-intercalated NbS$_2$ (Co$_{1/3}$NbS$_2$) compound exhibits large
+anomalous Hall conductance, likely due to the non-coplanar magnetic ordering of
+Co spins. In this work, we study the relation between this novel magnetism and
+the correlated electronic structure of Co$_{1/3}$NbS$_2$ by adopting dynamical
+mean field theory (DMFT) to treat the correlation effect of Co $d$ orbitals. We
+find that the hole doping of Co$_{1/3}$NbS$_2$ can tune the size of the Nb hole
+pocket at the DMFT Fermi surface, producing features consistent with those
+observed in angle resolved photoemission spectra [Phys. Rev. B 105, L121102
+(2022)]. We also compute the momentum-resolved spin susceptibility, and
+correlate it with the Fermi surface shape. We find that the magnetic ordering
+wavevector of Co$_{1/3}$NbS$_2$ obtained from the peak in spin susceptibility
+agrees with the one observed experimentally by neutron scattering; it is
+compatible with commensurate non-coplanar $3q$ spin structure. We also discuss
+how results change if some other than Co transition metal intercalations are
+used.",2309.00112v1
+2023-09-04,Suppression of small-scale dynamo in time irreversible turbulence,"The conventional theory of small-scale magnetic field generation in a
+turbulent flow considers time-reversible random flows. However, real turbulent
+flows are known to be time irreversible: the presence of energy cascade is an
+intrinsic property of turbulence. We generalize the 'standard' model to account
+for the irreversibility. We show that even small time asymmetry leads to
+significant suppression of the dynamo effect at low magnetic Prandtl numbers,
+increases the generation threshold and may even make generation impossible for
+any magnetic Reynolds number. We calculate the magnetic energy growth rate as a
+function of the parameters of the flow.",2309.01693v3
+2023-09-07,Nonreciprocal phonon dichroism induced by Fermi pocket anisotropy in two-dimensional Dirac materials,"Electrons in two-dimensional (2D) Dirac materials carry local band geometric
+quantities, such as the Berry curvature and orbital magnetic moments, which,
+combined with electron-phonon coupling, may affect the phonon dynamics in an
+unusual way. Here, we propose intrinsic nonreciprocal linear and circular
+phonon dichroism in magnetic 2D Dirac materials, which originate from nonlocal
+band geometric quantities of electrons and reduce to pure Fermi-surface
+properties for acoustic phonons. We find that to acquire the nonreciprocity,
+the Fermi pocket anisotropy rather than the chirality of electrons is crucial.
+Two possible mechanisms of Fermi pocket anisotropy are suggested: (i) trigonal
+warping and out-of-plane magnetization or (ii) Rashba spin-orbit interaction
+and in-plane magnetization. As a concrete example, we predict appreciable and
+tunable nonreciprocal phonon dichroism in 2H-MoTe 2 on a EuO substrate. Our
+finding points to a different route towards electrical control of phonon
+nonreciprocity for acoustoelectronics applications based on 2D quantum
+materials.",2309.03540v1
+2023-09-15,Linear and nonlinear eccentric mode evolution in unstratified MHD discs,"In this paper we develop a framework for studying unstratified, magnetised
+eccentric discs and compute uniformly precessing eccentric modes in a
+cylindrical annulus which provide convenient initial conditions for numerical
+simulations. The presence of a magnetic field in an eccentric disc can be
+described by an effective gas with a modified equation of state. At magnetic
+field strengths relevant to the magneto-rotational instability the magnetic
+field has negligible influence on the evolution of the eccentric disc, however
+the eccentric disc can significantly enhance the magnetic field strength over
+that in the a circular disc. We verify the suitability of these eccentric disc
+solutions by carrying out 2D simulations in RAMSES. Our simulated modes (in 2D)
+follow a similar evolution to the purely hydrodynamical modes, matching
+theoretical expectations, provided they are adequately resolved. Such solutions
+will provide equilibrium states for studies of the eccentric magneto-rotational
+instability and magnetised parametric instability in unstratified discs and are
+useful for exploring the response of disc turbulence on top of a fluid flow
+varying on the orbital timescale.",2309.08261v1
+2023-09-15,Charge pumping with strong spin-orbit coupling: Fermi surface breathing and higher harmonic generation,"Spin and charge pumping induced by a precessing magnetization has been
+instrumental to the development of spintronics. Nonetheless, most theoretical
+studies so far treat the spin-orbit coupling as a perturbation, which
+disregards the dynamical competition between exchange and spin-orbit fields. In
+this work, based on Keldysh formalism and Wigner expansion, we develop an
+adiabatic theory of spin and charge pumping adapted to multiorbital systems
+with arbitrary spin-orbit coupling. We apply this theory to the magnetic Rashba
+gas and magnetic graphene cases and discuss the pumped ac and dc current. We
+show that the pumped current possesses both intrinsic and extrinsic
+contributions, akin to the magnetic damping. In addition, we find that higher
+harmonics can be generated under large angle precession and we propose a couple
+of experimental setups where such an effect could be experimentally observed.",2309.08597v1
+2023-10-04,Metadynamics calculations of the effect of thermal spin fluctuations on skyrmion stability,"The stability of magnetic skyrmions has been investigated in the past, but
+mostly in the absence of thermal fluctuations. However, thermal spin
+fluctuations modify the magnetic properties (exchange stiffness,
+Dzyaloshinskii-Moriya interaction (DMI) and anisotropy) that define skyrmion
+stability. Thermal magnons also excite internal skrymion dynamics, deforming
+the skyrmion shape. Entropy has also been shown to modify skyrmion lifetimes in
+experiments, but is absent or approximated in previous studies. Here we use
+metadynamics to calculate the free energy surface of a magnetic thin film in
+terms of the topological charge and magnetization. We identify the free energy
+minima corresponding to different spin textures and the lowest energy paths
+between the ferromagnetic and single skyrmion states. We show that at low
+temperatures the lowest free energy barrier is a skyrmion collapse process.
+However, this energy barrier increases with temperature. An alternative path,
+where a singularity forms on the skrymion edge, has a larger free energy
+barrier at low temperatures but decreases with increasing temperature and
+eventually becomes the lowest energy barrier.",2310.03169v1
+2023-10-09,Toward interpreting the IBEX ribbon with mirror diffusion in interstellar turbulent magnetic fields,"We investigate the role of the magnetohydrodynamic (MHD) turbulence measured
+by Voyager in the very local interstellar medium (VLISM) in modeling the
+Interstellar Boundary Explorer (IBEX) ribbon. We demonstrate that the mirroring
+by compressible modes of MHD turbulence dominates over that by the mean
+magnetic field. Based on the new mirror diffusion mechanism identified by
+Lazarian and Xu for particles with large pitch angles in MHD turbulence, we
+find that the mirror diffusion can both confine pickup ions and preserve their
+initial pitch angles, and thus accounts for the enhanced intensity of energetic
+neutral atoms that return to the heliosphere. The ribbon width is determined by
+both the range of pitch angles for effective turbulent mirroring and the field
+line wandering induced by Alfv\'{e}nic modes. It in turn provides a constraint
+on the amplitude of magnetic fluctuations of fast modes. The field line
+wandering also affects the coherence of the ribbon structure across the sky. By
+extrapolating the magnetic energy spectrum measured by Voyager, we find that
+the injection scale of the turbulence in the VLISM is less than $\sim 500$ au
+for the ribbon structure to be coherent.",2310.06032v1
+2023-10-16,Axionic Instability of Periodic Weyl-Semimetal Superstructures,"Weyl-semimetal superstructures with a spiraling position of a pair of Weyl
+nodes of opposite chirality can host a chiral-symmetry preserving Fermi-arc
+metal state, where the chirality is carried by cylindrical Fermi surfaces,
+electron- and hole-like depending on the chirality. The Fermi surfaces nest at
+vanishing momentum separation (zero nesting vector) at the
+electron-hole-compensation energy because the nesting is topologically
+protected by vanishing spatial overlap of any pair of equal-momentum
+opposite-chirality states. In this work we show that the nesting and Coulomb
+interaction drive a spontaneous chiral symmetry breaking in such a Fermi arc
+metal, which leads to a dynamical axion insulator state but without breaking
+translational symmetry (no charge-density-wave order) as in a conventional Weyl
+semimetal. As for material realization, we discuss magnetically doped
+Bi$_2$Se$_3$, for which the Weyl-node positions depend on the order of the
+magnetic dopands. In this case, the axionic condensation can itself stabilize a
+spiral order of the magnetization, and hence the spiraling node positions, even
+if the magnetic interaction is intrinsically ferromagnetic.",2310.10345v1
+2023-11-01,Towards Ultimate Memory with Single-Molecule Multiferroics,"The demand for high-density storage is urgent in the current era of data
+explosion. Recently, several single-molecule (-atom) magnets/ferroelectrics
+have been reported to be promising candidates for high-density storage. As
+another promising candidate, single-molecule multiferroics are not only small
+but also possess ferroelectric and magnetic orderings, which can sometimes be
+strongly coupled and used as data storages to realize the combination of
+electric writing and magnetic reading. However, they have been rarely proposed,
+and never been experimentally reported. Here, by building Hamiltonian models,
+we propose a new model of single-molecule multiferroic in which electric
+dipoles and magnetic moments are parallel and can rotate with the rotation of
+the single molecule. Furthermore, with performing spin-lattice dynamics
+simulations, we reveal the conditions (e.g., large enough single-ion anisotropy
+and appropriate electric field) under which the new single-molecule
+multiferroic can arise. Based on this model, as well as first-principles
+calculations, a realistic example Co(NH3)4N@SWCNT is constructed and
+numerically confirmed to demonstrate the feasibility of the new single-molecule
+multiferroic model. Our work not only sheds light on the discovery of
+single-molecule multiferroics but also provides a new guideline to design
+multifunctional materials for ultimate memory devices.",2311.00255v1
+2023-11-07,A pseudofermion functional renormalization group study of dipolar-octupolar pyrochlore magnets,"Motivated by recent experiments on Ce$_2$Zr$_2$O$_7$ that reveal a dynamic,
+liquid-like ground state, we study the nearest neighbor XYZ Hamiltonian of
+dipolar-octupolar pyrochlore magnets with the pseudofermion functional
+renormalization group (PFFRG), which is numerically implemented by the
+SpinParser software. Taking the interaction between the octupolar components to
+be dominant and antiferromagnetic, we map out the phase diagram demarcating the
+quantum disordered and magnetically ordered states. We identify four distinct
+phases, namely the $0$-flux and $\pi$-flux quantum spin ices, and the
+all-in-all-out magnetic orders along the local $z$ and $x$ axes. We further use
+the static two-spin correlations output by the PFFRG algorithm to compute the
+polarized neutron scattering cross-sections, which are able to capture several
+qualitative features observed experimentally, in the materially relevant
+parameter regime that stabilizes the $\pi$-flux quantum spin ice. Our results
+provide support for a quantum spin liquid ground state in Ce$_2$Zr$_2$O$_7$.",2311.04269v1
+2023-11-15,Amplitude Higgs mode in superconductors with magnetic impurities,"We study nonlinear response of conventional superconducting alloys with weak
+magnetic impurities to an external alternating electromagnetic field. In
+particular, we calculate a correction to superconducting order parameter up to
+the second order in external vector potential. We show that frequency
+dependence of the order parameter amplitude has characteristic resonant shape
+with a maximum at frequency which is smaller than twice the magnitude of the
+pairing amplitude in equilibrium and at the same time exceeds the
+single-particle threshold energy. Our results suggest that in the presence of
+magnetic impurities the dynamics of the pairing amplitude in the collisionless
+regime will remain robust with respect to dissipative processes. We also
+evaluate the third harmonic contribution to the current as a function of the
+probe frequency and for various concentrations of magnetic impurities.",2311.09310v1
+2023-11-17,Critical ultrasonic propagation in magnetic fields,"Effect of an external magnetic field on the critical sound attenuation and
+velocity of the longitudinal wave is studied in ferromagnets. We derive a
+parametric model that incorporates a crossover from the asymptotic critical
+behavior to the Landau-Ginzburg regular behavior far away from the critical
+point. The dynamics is based on the time dependent Ginzburg-Landau model with
+non conserved order parameter (model A). The variations of the sound
+attenuation coefficient and velocity have been obtained for arbitrary values of
+the magnetic field and reduced temperature. The scaling functions are given
+within the renormalization group formalism at one-loop order. Using MnP as an
+example, we show that such parametric crossover model yields an accurate
+description of ultrasonic data in a large region of temperatures and magnetic
+fields around the critical point.",2311.10654v1
+2023-11-19,Analysis of the $Z_b(10650)$ state based on electromagnetic properties,"In this study, the magnetic and quadrupole moments of the $Z_b(10650)$ state
+are determined using the compact diquark-antidiquark interpolating current
+through the QCD light-cone sum rule. The values that are obtained as a result
+of the analysis are as follows: $\mu_{Z_b} = 2.35^{+0.34}_{-0.33}~\mu_N$ and
+$\mathcal{D}_{Z_b} =(1.82^{+0.35}_{-0.31})\times 10^{-2}~\mbox{fm}^2$.
+Examining the results obtained, it can be seen that the magnetic moments are
+large enough to be measured experimentally, while the quadrupole moment is
+obtained as a small but non-zero value, corresponding to a prolate charge
+distribution. The magnetic moment is the leading-order response of a bound
+system to a weak external magnetic field. It therefore provides an excellent
+platform to probe the internal structures of hadrons governed by the
+quark-gluon dynamics of QCD.",2311.11327v2
+2023-11-22,Quantum Sensing of Magnetic Fields with Molecular Spins,"Spins are prototypical systems with the potential to probe magnetic fields
+down to the atomic scale limit. Exploiting their quantum nature through
+appropriate sensing protocols allows to enlarge their applicability to fields
+not always accessible by classical sensors. Here we first show that quantum
+sensing protocols for AC magnetic fields can be implemented on molecular spin
+ensembles embedded into hybrid quantum circuits. We then show that, using only
+echo detection at microwave frequency and no optical readout, Dynamical
+Decoupling protocols synchronized with the AC magnetic fields can enhance the
+sensitivity up to $S = 10^{-10}-10^{-9}T/\sqrt{Hz}$ with a low (4-5) number of
+applied pulses. These results paves the way for the development of strategies
+to exploit molecular spins as quantum sensors.",2311.13504v1
+2023-11-25,Imaging a Semi-Analytical Jet model Generated by 3D GRMHD Simulation,"Employing 3D GRMHD simulation, we study the images of a geometrically thin
+jet, whose emissions concentrate on its surface, for accretion system
+surrounding a central spinning BH. By introducing a strong magnetic field, we
+observe three phases of BH accretion evolution: (a) initially, both the
+accretion rate and the magnetic flux on the horizon gradually increase; (b) at
+an intermediate stage, the magnetic flux approximately reaches saturation, and
+a jet forms via the Blandford-Znajek (BZ) mechanism; (c) ultimately, the entire
+system achieves a dynamic equilibrium, and a magnetically arrested disk (MAD)
+forms. We carefully study the jet images during the saturation and MAD regimes
+at various frequencies and from different observational angles. We reveal the
+presence of U-shaped brighter lines near the jet surface boundaries, which can
+be attributed to the photons whose trajectories skim over the jet surface. The
+existence of these brighter lines is a unique feature of a geometrically thin
+jet. Moreover, we notice that the jet images are relatively insensitive to the
+observed frequencies of interest. Additionally, we observe that the
+time-averaged images for the highly oscillating MAD regime show only slight
+differences from those of the saturation regime.",2311.14954v1
+2023-11-28,A Coarse-grained Model for Aqueous Two-phase Systems: Application to Ferrofluids,"Aqueous two-phase systems (ATPSs), that is, phase-separating solutions of
+water soluble but mutually immiscible molecular species, offer fascinating
+prospects for selective partitioning, purification, and extraction. Here, we
+formulate a general Brownian dynamics based coarse-grained simulation model for
+a polymeric ATPS comprising two water soluble but mutually immiscible polymer
+species. A third solute species, representing, e.g., nanoparticles (NPs),
+additional macromolecular species, or impurities can readily be incorporated
+into the model. We demonstrate that the model captures satisfactorily the phase
+separation, partitioning, and interfacial properties of a model ATPS composed
+of a polymer mixture of dextran and polyethylene glycol (PEG) in which magnetic
+NPs selectively partition into one of the two polymeric phases. The NP
+partitioning is characterized both via the computational model and
+experimentally under different conditions. The simulation model captures the
+trends observed in the experiments and quantitatively links the partitioning
+behavior to the component species interactions. Finally, the response of the
+simulation model to external magnetic field, with the magnetic NPs as the
+additional partitioned component, shows that the ATPS interface fluctuations
+can be controlled by the magnetic field at length scales much smaller than
+those probed experimentally to date.",2311.16906v1
+2023-11-29,Subcritical transition to turbulence triggered by a magnetic dynamo,"It has recently been shown that a significant slowdown of many stars can be
+attributed to the emergence of a strong magnetic field within the radiative
+region, where heat is transferred through radiation in a stably stratified
+layer. Here, we describe how this transition can be understood as a subcritical
+bifurcation to small-scale turbulence in linearly stable flows. The turbulence
+is sustained by a nonlinear mean-field dynamo and can be observed down to
+relatively small differential rotation, arbitrarily far from the linear onset
+of any hydrodynamic instability. In this regime, turbulent fluctuations provide
+diffusivity-free transfer of angular momentum that increases the transport
+generated by the magnetic field triggering the turbulence. Finally, we present
+a simple nonlinear model that captures this scenario and can be used as a
+general description of the transition to turbulence in astrophysical flows, as
+long as it involves a competition between a large-scale dynamo, and a
+small-scale magnetic instability.",2311.17654v1
+2023-12-01,Incommensurate Spiral Spin Order in CaMn$_2$Bi$_2$ observed via High Pressure Neutron Diffraction,"High pressure neutron diffraction is employed to investigate the magnetic
+behavior of CaMn$_2$Bi$_2$ in extreme conditions. In contrast to
+antiferromagnetic ordering on Mn atoms reported at ambient pressure, our
+results reveal that at high pressure, incommensurate spiral spin order emerges
+due to the interplay between magnetism on the Mn atoms and strong spin-orbit
+coupling on the Bi atoms: sinusoidal spin order is observed at pressures as
+high as 7.4 GPa. Competing antiferromagnetic order is observed at different
+temperatures in the partially frustrated lattice. This research provides a
+unique toolbox for conducting experimental magnetic and spin dynamics studies
+on magnetic quantum materials via high pressure neutron diffraction.",2312.00397v1
+2023-12-07,Energy dissipation in astrophysical simulations: results of the Orszag-Tang test problem,"The magnetic field through the magnetic reconnection process affects the
+dynamics and structure of astrophysical systems. Numerical simulations are the
+tools to study the evolution of these systems. However, the resolution,
+dimensions, resistivity, and turbulence of the system are some important
+parameters to take into account in the simulations. In this paper, we
+investigate the evolution of magnetic energy in astrophysical simulations by
+performing a standard test problem for MHD codes, Orszag-Tang. We estimate the
+numerical dissipation in the simulations using state-of-the-art numerical
+simulation code in astrophysics, PLUTO. The estimated numerical resistivity in
+2D simulations corresponds to the Lundquist number $\approx 10^{4}$ in the
+resolution of $512\times512$ grid cells. It is also shown that the plasmoid
+unstable reconnection layer can be resolved with sufficient resolutions. Our
+analysis demonstrates that in non-relativistic magnetohydrodynamics
+simulations, magnetic and kinetic energies undergo conversion into internal
+energy, resulting in plasma heating.",2312.06675v1
+2023-12-14,Tuning the spontaneous exchange bias effect in La1.5Sr0.5CoMnO6 with sintering temperature,"Here, we present a study of the influence of microstructure on the magnetic
+properties of polycrystalline samples of the La1.5Sr0.5CoMnO6 double
+perovskite, with primary attention to the spontaneous exchange bias effect, a
+fascinating recently discovered phenomena for which some materials exhibit
+unidirectional magnetic anisotropy after being cooled in zero magnetic field.
+By sintering La1.5Sr0.5CoMnO6 at different temperatures, we obtained samples
+with distinct average grain sizes, ranging from 0.76(21) to 4.95(1.73) mu_m. A
+detailed investigation of the material's structural, morphologic, electronic,
+and magnetic properties using X-ray powder diffraction, powder neutron
+diffraction, X-ray absorption near edge structure spectroscopy, scanning
+electron microscopy, and AC and DC magnetometry has revealed a systematic
+enhancement of the exchange bias effect with increasing the grain size and the
+intergrain coalescence. Our results regarding the strengthening of the exchange
+coupling at the grain interfaces and its influence on the dynamics of the spin
+glass-like moments present in the samples are discussed.",2312.09149v1
+2023-12-19,Emergence of a potential charge disproportionated insulating state in SrCrO$_{3}$,"We use a combination of density functional theory (DFT) and dynamical
+mean-field theory (DMFT) to investigate the potential emergence of a
+charge-disproportionated insulating phase in SrCrO$_{3}$, whereby the Cr
+cations disproportionate according to $3\text{Cr}^{4+} \rightarrow
+2\text{Cr}^{3+} + \text{Cr}^{6+}$ and arrange in ordered planes perpendicular
+to the cubic [111] direction. We show that the charge disproportionation
+couples to a structural distortion where the oxygen octahedra around the
+nominal Cr$^{6+}$ sites contract, while the octahedra surrounding the Cr$^{3+}$
+sites expand and distort. Our results indicate that the
+charge-disproportionated phase can be stabilized for realistic values of the
+Hubbard $U$ and Hund's $J$ parameters, but this requires a scaling of the
+DFT+DMFT double counting correction by at least 35%. The disproportionated
+state can also be stabilized in DFT+U calculations for a specific magnetic
+configuration with antiparallel magnetic moments on adjacent Cr$^{3+}$ sites
+and no magnetic moment on the Cr$^{6+}$ sites. While this phase is higher in
+energy than other magnetic states that can arise in SrCrO$_{3}$, the presence
+of an energy minimum suggests that the charge disproportionated state
+represents a metastable state of SrCrO$_{3}$.",2312.12033v2
+2023-12-28,Statistical domain wall roughness analysis through correlations,"The geometry and morphology of magnetic domain walls (DWs) are closely
+related to their dynamics when driven by external forces. Under some reliable
+approximations DWs can be considered self-affine interfaces, so universal laws
+govern their behavior. On the other hand, large-scale DW structure has been
+less explored so far. Recently, it has been shown that bubble-like magnetic
+domains can be strongly deformed on a large scale by applying alternating (ac)
+magnetic field pulses. In the present work, we conduct a comprehensive analysis
+of DW structure at both small and large length scales in bubble-like domains
+present in ferromagnetic thin films with perpendicular anisotropy, focusing on
+its initial evolution under the application of ac magnetic pulses. Results
+obtained from the widely used roughness correlation function B(r) and its
+corresponding structure factor, are consistent with those obtained from the
+spatial autocorrelation function of DW fluctuations. Whereas the roughness
+exponent slightly increases during the ac evolution, a strong deformation is
+observed at a large scale, where a striking periodicity (statistically
+speaking) is observed. This period is probably determined by the boundary
+conditions and a characteristic intrinsic length.",2312.16802v1
+2023-12-13,Relativistic spin-0 Duffin-Kemmer-Petiau equation in Bonnor-Melvin-Lambda solution,"In this paper, we conduct a comprehensive exploration of the relativistic
+quantum dynamics of spin-0 scalar particles, as described by the
+Duffin-Kemmer-Petiau (DKP) equation, within the framework of a magnetic
+space-time. Our focus is on the Bonnor-Melvin-Lambda (BML) solution, a
+four-dimensional magnetic universe characterized by a magnetic field that
+varies with axial distance. To initiate this investigation, we derive the
+radial equation using a suitable wave function ansatz and subsequently employ
+special functions to solve it. Furthermore, we extend our analysis to include
+Duffin-Kemmer-Petiau oscillator fields within the same BML space-time
+background. We derive the corresponding radial equation and solve it using
+special functions. Significantly, our results show that the geometry's topology
+and the cosmological constant (both are related with the magnetic field
+strength) influences the eigenvalue solution of spin-0 DKP fields and
+DKP-oscillator fields, leading to substantial modifications in the overall
+outcomes",2401.01359v2
+2024-01-25,Magnon dispersion and spin transport in CrCl$_3$ bilayers under different strain-induced magnetic states,"Atomically-thin van der Waals magnetic materials offer exceptional
+opportunities to mechanically and electrically manipulate magnetic states and
+spin textures. The possibility of efficient spin transport in these materials
+makes them promising for the development of novel nanospintronics technology.
+Using atomistic spin dynamics simulations, we investigate magnetic ground
+state, magnon dispersion, critical temperature, and magnon spin transport in
+CrCl$_3$ bilayers in the absence and presence of compressive and tensile
+strains. We show that in the presence of mechanical strain, the magnon band gap
+at the $\Gamma$ point and the critical temperature of the bilayer are
+increased. Furthermore, our simulations show that the magnon diffusion length
+is reduced in the presence of strain. Moreover, by exciting magnons through the
+spin Seebeck effect and spin Hall-induced torque, we illustrate distinctions
+between magnon spin transport in the antiferromagnetic state, under compressive
+strains, and ferromagnetic states, under tensile strains or in the unstrained
+case.",2401.13984v1
+2024-02-05,Interconnected Renormalization of Hubbard Bands and Green's Function Zeros in Mott Insulators Induced by Strong Magnetic Fluctuations,"We analyze the role of spatial electronic correlations and, in particular, of
+the magnetic fluctuations in Mott insulators. A half-filled Hubbard model is
+solved at large strength of the repulsion U on a two-dimensional square lattice
+using an advanced diagrammatic non-perturbative approach capable of going
+beyond Hartree-Fock and single-site dynamical mean-field theories. We show that
+at high temperatures the magnetic fluctuations are weak, and the electronic
+self-energy of the system is mainly local and is well reproduced by the atomic
+(Hubbard-I) approximation. Lowering the temperature toward the low-temperature
+magnetically ordered phase, the non-locality of the self-energy becomes crucial
+in determining the momentum-dispersion of the Hubbard bands and the Green's
+function zeros. We therefore establish a precise link between Luttinger
+surface, non-local correlations and spectral properties of the Hubbard bands.",2402.02814v2
+2024-02-05,Amorphous quantum magnets in a two-dimensional Rydberg atom array,"Amorphous solids, i.e., systems which feature well-defined short-range
+properties but lack long-range order, constitute an important research topic in
+condensed matter. While their microscopic structure is known to differ from
+their crystalline counterpart, there are still many open questions concerning
+the emergent collective behavior in amorphous materials. This is particularly
+the case in the quantum regime, where the numerical simulations are extremely
+challenging. In this article, we instead propose to explore amorphous quantum
+magnets with an analog quantum simulator. To this end, we first present an
+algorithm to generate amorphous quantum magnets, suitable for Rydberg
+simulators of the Ising model. Subsequently, we use semiclassical approaches to
+get a preliminary insight of the physics of the model. In particular, we
+calculate mean-field phase diagrams, and use the linear-spin-wave theory to
+study localization properties and dynamical structure factors of the
+excitations. Finally, we outline an experimental proposal based on Rydberg
+atoms in programmable tweezer arrays, thus opening the road towards the study
+of amorphous quantum magnets in regimes difficult to simulate classically.",2402.02852v1
+2024-02-06,Elucidating the nature of hidden-charm pentaquark states with spin-$\frac{3}{2}$ through their electromagnetic form factors,"We perform a systematic study of the electromagnetic properties of exotic
+states to shed light on their nature, which is still controversial and not
+fully understood. The magnetic dipole and higher multipole moments of a
+hadronic state are as fundamental a dynamical quantity as its mass, and they
+contain valuable information about the deep structure underlying it. In the
+present work, we have explored the magnetic dipole and higher multipole moments
+of the hidden-charm pentaquarks with quantum number $J^P = 3/2^-$ using the QCD
+light-cone sum rule method and different interpolating currents. The obtained
+results show that different interpolating currents employed to probe
+pentaquarks with the same quark content produce varying results for their
+magnetic dipole and higher multipole moments at all. This can be interpreted to
+mean that there is more than one hidden-charm pentaquark with identical quark
+content but with different magnetic dipole and higher multipole moments. The
+nature, internal structure, and quark-gluon configurations of these states can
+be better understood by studying their electromagnetic properties.",2402.03802v2
+2024-02-06,Probing magnetism in moiré heterostructures with quantum twisting microscopes,"Spin-ordered states close to metal-insulator transitions are poorly
+understood theoretically and challenging to probe in experiments. Here, we
+propose that the quantum twisting microscope, which provides direct access to
+the energy-momentum resolved spectrum of single-particle and collective
+excitations, can be used as a novel tool to distinguish between different types
+of magnetic order. To this end, we calculate the single-particle spectral
+function and the dynamical spin-structure factor for both a ferromagnetic and
+antiferromagnetic generalized Wigner crystal formed in fractionally filled
+moir\'e superlattices of transition metal dichalcogenide heterostructures. We
+demonstrate that magnetic order can be clearly identified in these response
+functions. Furthermore, we explore signatures of quantum phase transitions in
+the quantum twisting microscope response. We focus on the specific case of
+triangular moir\'e lattices at half filling, which have been proposed to host a
+topological phase transition between a chiral spin liquid and a 120 degree
+ordered state. Our work demonstrates the potential for quantum twisting
+microscopes to characterize quantum magnetism in moir\'e heterostructures.",2402.04311v1
+2024-02-09,Supernova dust destruction in the magnetized turbulent ISM,"Dust in the interstellar medium (ISM) is critical to the absorption and
+intensity of emission profiles used widely in astronomical observations, and
+necessary for star and planet formation. Supernovae (SNe) both produce and
+destroy ISM dust. In particular the destruction rate is difficult to assess.
+Theory and prior simulations of dust processing by SNe in a uniform ISM predict
+quite high rates of dust destruction, potentially higher than the supernova
+dust production rate in some cases. Here we show simulations of
+supernova-induced dust processing with realistic ISM dynamics including
+magnetic field effects and demonstrate how ISM inhomogeneity and magnetic
+fields inhibit dust destruction. Compared to the non-magnetic homogeneous case,
+the dust mass destroyed within 1 Myr per SNe is reduced by more than a factor
+of two, which can have a great impact on the ISM dust budget.",2402.06543v1
+2024-02-25,Effect of Magnetic Anisotropy Constants on Skyrmion Formation in Co/Pt,"Skyrmions, which are topologically stable magnetic structures, have
+manifested promising features to be used as an information carrier in new-age,
+non-volatile data storage devices. In this article, we show how the creation
+and stability of skyrmion can be manipulated by external stimuli (here,
+nano-second current pulse). Co/Pt square nano-structure with Co free layer
+thickness in the range 1 nm to 5 nm and first and second-order anisotropy
+constants are taken to study the controlled creation of skyrmions. The
+magnetization dynamics controlled by the current-induced spin transfer torque
+help to nucleate skyrmions by transformation from perpendicularly magnetized
+ground state to a stable state of isolated skyrmions via complex transformation
+of Neel wall following its image inversion. Compared with the first-order
+anisotropy alone, how the higher-order anisotropy constants (up to second
+order) impact the relaxed state of a system has been discussed.",2402.16060v1
+2024-03-02,Zero-field magnetic skyrmions in exchange-biased ferromagnetic-antiferromagnetic bilayers,"We report on the stabilization of ferromagnetic skyrmions in zero external
+magnetic fields, in exchange-biased systems composed of
+ferromagnetic-antiferromagnetic (FM-AFM) bilayers. By performing atomistic spin
+dynamics simulations, we study cases of compensated, uncompensated, and partly
+uncompensated FM-AFM interfaces, and investigate the impact of important
+parameters such as temperature, inter-plane exchange interaction,
+Dzyaloshinskii-Moria interaction, and magnetic anisotropy on the skyrmions
+appearance and stability. The model with an uncompensated FM-AFM interface
+leads to the stabilization of individual skyrmions and skyrmion lattices in the
+FM layer, caused by the effective field from the AFM instead of an external
+magnetic field. Similarly, in the case of a fully compensated FM-AFM interface,
+we show that FM skyrmions can be stabilized. We also demonstrate that
+accounting for interface roughness leads to stabilization of skyrmions both in
+compensated and uncompensated interfaces. Moreover, in bilayers with a rough
+interface, skyrmions in the FM layer are observed for a wide range of exchange
+interaction values through the FM-AFM interface, and the chirality of the
+skyrmions depends critically on the exchange interaction.",2403.01175v1
+2024-03-04,Realization of a Spin Glass in a two-dimensional van der Waals material,"Recent advances in van der Waals (vdW) materials have sparked renewed
+interest in the impact of dimensionality on magnetic phase transitions. While
+ordered magnetic phases have been demonstrated to survive in the
+two-dimensional (2D) limit, the quest for a spin-glass with quenched magnetic
+disorder in lower dimensions has proven elusive. Here we show evidence of a
+spin-glass emerging from randomly distributed Fe atoms in Fe3GeTe2, the first
+time such a state has been reported in a vdW material. AC magnetic
+susceptibility displays a strong frequency dependence indicative of slow spin
+dynamics. Additional distinctive phenomena, including ageing, chaos, and memory
+effects, further substantiate the existence of a glassy state. Remarkably, we
+find that this state persists even in single-unit-cell thick Fe3GeTe2, thereby
+confirming the existence of a 2D spin-glass. The formation of spin-glass states
+via intercalation in vdW systems allows for highly tunable spin-glass states
+that are otherwise difficult to realize.",2403.02088v1
+2024-03-12,QCD Equation of State at nonzero baryon density in external magnetic field,"This paper is devoted to the study of QCD equation of state in external
+magnetic field and nonzero baryon density. Our study is carried out by means of
+lattice simulation with 2+1 dynamical staggered quarks at the physical masses.
+The simulation is conducted at imaginary baryon chemical potential what allowed
+us to overcome the sign problem. We expand the pressure in the baryon imaginary
+chemical potential and study three leading nonzero coefficients in this
+expansion. These coefficients were calculated for the following values of
+magnetic field: $eB=0.3$, $0.6$, $1.2$ GeV$^2$ with the lattice sizes
+$8\times32^3$, $10\times40^3$, $12\times48^3$. Using these data we take
+continuum limit for the coefficients. Our results indicate considerable
+enhancement of the expansion coefficients by the magnetic field.",2403.07783v1
+2024-03-13,Spin-resolved counting statistics as a sensitive probe of spin correlation in transport through a quantum dot spin valve,"We investigate the noise in spin transport through a single quantum dot (QD)
+tunnel coupled to ferromagnetic electrodes with noncollinear magnetizations.
+Based on a spin-resolved quantum master equation, auto- and cross-correlations
+of spin-resolved currents are analyzed to reveal the underlying spin transport
+dynamics and characteristics for various polarizations. We find the currents of
+majority and minority spins could be strongly autocorrelated despite
+uncorrelated charge transfer. The interplay between tunnel coupling and the
+Coulomb interaction gives rise to an exchange magnetic field, leading to the
+precession of the accumulated spin in the QD. It strongly suppresses the
+bunching of spin tunneling events and results in a unique double-peak structure
+in the noise of the net spin current. The spin autocorrelation is found to be
+susceptible to magnetization alignments, which may serve as a sensitive tool to
+measure the magnetization directions between the ferromagnetic electrodes.",2403.08621v1
+2024-03-30,Investigation of self-focusing of Gaussian laser beams within magnetized plasma via source-dependent expansion method,"Self-focusing emerges as a nonlinear optical phenomenon resulting from an
+intense laser field and plasma interaction. This study investigates the
+self-focusing behavior of Gaussian laser beams within magnetized plasma
+environments utilizing a novel approach, source-dependent expansion. By
+employing source-dependent expansion, we explore the intricate dynamics of
+laser beam propagation, considering the influence of plasma density and
+external magnetic fields. The interplay between the beam's Gaussian profile and
+the self-focusing mechanism through rigorous mathematical analysis and
+numerical simulations, particularly in the presence of plasma-induced
+nonlinearities are elucidated here. Our findings reveal crucial insights into
+the evolution of laser beams under diverse parameters, the ponderomotive force,
+relativistic factors, plasma frequency, polarization states, external magnetic
+field, wavelength, and laser intensity. This research not only contributes to
+advancing our fundamental understanding of laser-plasma interactions but also
+holds promise for optimizing laser-driven applications.",2404.00331v1
+2024-04-01,A novel seamless magnetic-based actuating mechanism for end-effector-based robotic rehabilitation platforms,"In this pioneering study, we unveiled a groundbreaking approach for actuating
+rehabilitation robots through the innovative use of magnetic technology as a
+seamless haptic force generator, offering a leap forward in enhancing user
+interface and experience, particularly in end-effector-based robots for
+upper-limb extremity motor rehabilitation. We employed the Extended Kalman
+Filter to meticulously analyze and formalize the robotic system's nonlinear
+dynamics, showcasing the potential of this sophisticated algorithm in
+accurately tracking and compensating for disturbances, thereby ensuring
+seamless and effective motor training. The proposed planar robotic system
+embedded with magnetic technology was evaluated with the recruitment of human
+subjects. We reached a minimum RMS value of 0.2 and a maximum of 2.06 in our
+estimations, indicating our algorithm's capability for tracking the system
+behavior. Overall, the results showed significant improvement in smoothness,
+comfort, and safety during execution and motor training. The proposed novel
+magnetic actuation and advanced algorithmic control opens new horizons for the
+development of more efficient and user-friendly rehabilitation technologies.",2404.01441v1
+2001-04-11,Dynamic disquantization of Dirac equation,"Classical model S_dc of Dirac particle S_D is constructed. S_D is the dynamic
+system described by the Dirac equation. Its classical analog S_dc is described
+by a system of ordinary differential equations, containing the quantum constant
+h as a parameter. Dynamic equations for S_dc are determined by the Dirac
+equation uniquely. Both dynamic systems S_D and S_dc appear to be
+nonrelativistic. One succeeded in transforming nonrelativistic dynamic system
+S_dc into relativistic one S_dcr. The dynamic system S_dcr appears to be a
+two-particle structure (special case of a relativistic rotator). It explains
+freely such properties of S_D as spin and magnetic moment, which are strange
+for pointlike structure. The rigidity function f_r(a), describing rotational
+part of total mass as a function of the radius $a$ of rotator, has been
+calculated for S_dcr. For investigation of S_D and construction of S_dc one
+uses new dynamic methods: dynamic quantization and dynamic disquantization.
+These relativistic pure dynamic procedures do not use principles of quantum
+mechanics (QM). They generalize and replace conventional quantization and
+transition to classical approximation. Totality of these methods forms the
+model conception of quantum phenomena (MCQP). Technique of MCQP is more subtle
+and effective, than conventional methods of QM. MCQP relates to conventional
+QM, much as the statistical physics relates to thermodynamics.",0104060v3
+2023-07-24,Exploring the equilibrium and dynamic phase transition properties of Ising ferromagnet on a decorated triangular lattice,"We study the equilibrium and dynamic phase transition properties of
+two-dimensional Ising model on a decorated triangular lattice under the
+influence of a time-dependent magnetic field composed of a periodic square wave
+part plus a time independent bias term. Using Monte Carlo simulations with
+standard Metropolis algorithm, we determine the equilibrium critical behavior
+in zero field. At a fixed temperature corresponding to the multidroplet regime,
+we locate the relaxation time and the dynamic critical half-period at which a
+dynamic phase transition takes place between ferromagnetic and paramagnetic
+states. Benefiting from finite-size scaling theory, we estimate the dynamic
+critical exponent ratios for the dynamic order parameter and its scaled
+variance, respectively. The response function of the average energy is found to
+follow a logarithmic scaling as a function of lattice size. At the critical
+half-period and in the vicinity of small bias field regime, average of the
+dynamic order parameter obeys a scaling relation with a dynamic scaling
+exponent which is very close to the equilibrium critical isotherm value.
+Finally, in the slow critical dynamics regime, investigation of metamagnetic
+fluctuations in the presence of bias field revels a symmetric double-peak
+behavior for the scaled variance contours of dynamic order parameter and
+average energy. Our results strongly resemble those previously reported for
+kinetic Ising models.",2307.12684v1
+1997-03-16,Dynamics and Structure of Three-Dimensional Poloidally Magnetized Supermagnetosonic Jets,"A set of 3D MHD simulations of magnetized jets has been performed. The jets
+contain an equipartition primarily poloidal magnetic field and the effect of
+jet density on jet dynamics and structure is evaluated. The jet is precessed at
+the origin to excite Kelvin-Helmholtz unstable helical modes. We extensively
+compare the structure in these simulations with linear stability theory. The
+jet that is dense with respect to the external medium develops a high speed
+core surrounded by a less dense sheath consisting of slower moving jet fluid.
+These simulations suggest that extended extragalactic jets propagate to such
+large distances because they are surrounded by a lobe or cocoon whose density
+is less than the jet density. (Abridged abstract.)",9703098v1
+1997-12-02,A dynamical model for the penumbral fine structure and the Evershed effect in sunspots,"Relying on the assumption that the interchange convection of magnetic flux
+tubes is the physical cause for the existence of sunspot penumbrae, we propose
+a model in which the dynamical evolution of a thin magnetic flux tube
+reproduces the Evershed effect and the penumbral fine structure such as bright
+and dark filaments and penumbral grains.
+  According to our model, penumbral grains are the manifestation of the
+footpoints of magnetic flux tubes, along which hot subphotospheric plasma flows
+upwards with a few km/s. Above the photosphere the hot plasma inside the tube
+is cooled by radiative losses as it flows horizontally outwards. As long as the
+flowing plasma is hotter than the surroundings, it constitutes a bright radial
+filament. The flow confined to a thin elevated channel reaches the temperature
+equilibrium with the surrounding atmosphere and becomes optically thin near the
+outer edge of the penumbra.
+  Here, the tube has a height of approximately 100 km above the continuum and
+the flow velocity reaches up to 14 km/s. Such a flow channel can reproduce the
+observed signatures of the Evershed effect.",9712029v1
+1999-01-27,Non-linear dynamics of Kelvin-Helmholtz unstable magnetized jets: three-dimensional effects,"A numerical study of the Kelvin-Helmholtz instability in compressible
+magnetohydrodynamics is presented. The three-dimensional simulations consider
+shear flow in a cylindrical jet configuration, embedded in a uniform magnetic
+field directed along the jet axis. The growth of linear perturbations at
+specified poloidal and axial mode numbers demonstrate intricate non-linear
+coupling effects. The physical mechanims leading to induced secondary
+Kelvin-Helmholtz instabilities at higher mode numbers are identified. The
+initially weak magnetic field becomes locally dominant in the non-linear
+dynamics before and during saturation. Thereby, it controls the jet deformation
+and eventual breakup. The results are obtained using the Versatile Advection
+Code [G. Toth, Astrophys. Lett. Comm. 34, 245 (1996)], a software package
+designed to solve general systems of conservation laws. An independent
+calculation of the same Kelvin-Helmholtz unstable jet configuration using a
+three-dimensional pseudo-spectral code gives important insights into the
+coupling and excitation events of the various linear mode numbers.",9901383v1
+1999-04-03,The Galactic Center Isolated Nonthermal Filaments as Analogs of Cometary Plasma Tails,"We propose a model for the origin of the isolated nonthermal filaments
+observed at the Galactic center based on an analogy to cometary plasma tails.
+We invoke the interaction between a large scale magnetized galactic wind and
+embedded molecular clouds. As the advected wind magnetic field encounters a
+dense molecular cloud, it is impeded and drapes around the cloud, ultimately
+forming a current sheet in the wake. This draped field is further stretched by
+the wind flow into a long, thin filament whose aspect ratio is determined by
+the balance between the dynamical wind and amplified magnetic field pressures.
+The key feature of this cometary model is that the filaments are dynamic
+configurations, and not static structures. As such, they are local
+amplifications of an otherwise weak field and not directly connected to any
+static global field. The derived field strengths for the wind and wake are
+consistent with observational estimates. Finally, the observed synchrotron
+emission is naturally explained by the acceleration of electrons to high energy
+by plasma and MHD turbulence generated in the cloud wake.",9904048v1
+2000-12-01,Singular Isothermal Disks and the Formation of Multiple Stars,"A crucial missing ingredient in previous theoretical studies of fragmentation
+is the inclusion of dynamically important levels of magnetic fields. As a
+minimal model for a candidate presursor to the formation of binary and multiple
+stars, we therefore consider the equilibrium configuration of isopedically
+magnetized, scale-free, singular isothermal disks, without the assumption of
+axial symmetry. We find that lopsided (M=1) configurations exist at any
+dimensionless rotation rate, including zero. Multiple-lobed (M = 2, 3, 4, ...)
+configurations bifurcate from an underlying axisymmetric sequence at
+progressively higher dimensionless rates of rotation, but such nonaxisymmetric
+sequences always terminate in shockwaves before they have a chance to fission
+into separate bodies. We advance the hypothesis that binary and multiple
+star-formation from smooth (i.e., not highly turbulent) starting states that
+are supercritical but in unstable mechanical balance requires the rapid (i.e.,
+dynamical) loss of magnetic flux at some stage of the ensuing gravitational
+collapse.",0012019v1
+2000-12-11,Sheared helical turbulence and the helicity constraint in large-scale dynamos,"The effect of shear on the growth of large scale magnetic fields in helical
+turbulence is investigated. The resulting large-scale magnetic field is also
+helical and continues to evolve, after saturation of the small scale field, on
+a slow resistive time scale. This is a consequence of magnetic helicity
+conservation. Because of shear, the time scale needed to reach an
+equipartition-strength large scale field is shortened proportionally to the
+ratio of the resulting toroidal to poloidal large scale fields.",0012240v1
+2001-12-17,Modeling the Galactic Center Nonthermal Filaments as Magnetized Wake,"We simulate the Galactic Center nonthermal filaments as magnetized wakes
+formed dynamically from amplification of a weak (tens of $\mu$G) global
+magnetic field through the interaction of molecular clouds with a Galactic
+Center wind. One of the key issues in this cometary model is the stability of
+the filament against dynamical disruption. Here we show 2-dimensional MHD
+simulations for interstellar conditions that are appropriate for the Galactic
+Center. The structures eventually disrupt through a shear driven nonlinear
+instability but maintain coherence for lengths up to 100 times their width as
+observed. The final instability, which destroys the filament through shredding
+and plasmoid formation, grows quickly in space (and time) and leads to an
+abrupt end to the structure, in accord with observations. As a by-product, the
+simulation shows that emission should peak well downstream from the cloud-wind
+interaction site.",0112378v1
+2004-06-28,Dynamics and Heating of the Magnetic Network on the Sun: Efficiency of mode transformation,"We aim to identify the physical processes which occur in the magnetic network
+of the chromosphere and which contribute to its dynamics and heating.
+Specifically, we study the propagation of transverse (kink) MHD waves which are
+impulsively excited in flux tubes through footpoint motions. When these waves
+travel upwards, they get partially converted to longitudinal waves through
+nonlinear effects (mode coupling). By solving the nonlinear, time-dependent MHD
+equations we find that significant longitudinal wave generation occurs in the
+photosphere typically for Mach numbers as low as 0.2 and that the onset of
+shock formation occurs at heights of about 600 km above the photospheric base.
+We also investigate the compressional heating due to longitudinal waves and the
+efficiency of mode coupling for various values of the plasma $\beta$, that
+parameterises the magnetic field strength in the network. We find that this
+efficiency is maximum for field strengths corresponding to $\beta\approx 0.2$,
+when the kink and tube wave speeds are almost identical. This can have
+interesting observational implications. Furthermore, we find that even when the
+two speeds are different, once shock formation occurs, the longitudinal and
+transverse shocks exhibit strong mode coupling.",0406626v1
+2005-09-23,The Effect of Coherent Structures on Stochastic Acceleration in MHD Turbulence,"We investigate the influence of coherent structures on particle acceleration
+in the strongly turbulent solar corona. By randomizing the Fourier phases of a
+pseudo-spectral simulation of isotropic MHD turbulence (Re $\sim 300$), and
+tracing collisionless test protons in both the exact-MHD and phase-randomized
+fields, it is found that the phase correlations enhance the acceleration
+efficiency during the first adiabatic stage of the acceleration process. The
+underlying physical mechanism is identified as the dynamical MHD alignment of
+the magnetic field with the electric current, which favours parallel
+(resistive) electric fields responsible for initial injection. Conversely, the
+alignment of the magnetic field with the bulk velocity weakens the acceleration
+by convective electric fields $- \bfu \times \bfb$ at a non-adiabatic stage of
+the acceleration process. We point out that non-physical parallel electric
+fields in random-phase turbulence proxies lead to artificial acceleration, and
+that the dynamical MHD alignment can be taken into account on the level of the
+joint two-point function of the magnetic and electric fields, and is therefore
+amenable to Fokker-Planck descriptions of stochastic acceleration.",0509717v1
+2005-09-29,Are Neutral Sunspot Winds Important for Penumbral Dynamics and the First Ionization Potential Effect?,"The low ionization state in parts of a sunspot may play an important role in
+its evolution and dynamical state. The cool magnetic interior region of the
+sunspot develops a substantial neutral atomic and molecular hydrogen osmotic
+pressure which can drive a wind outward from the umbra. Ambipolar diffusion
+against the magnetically pinned ionized plasma component can also distort the
+umbral magnetic field into a filamentary penumbral structure. This may be
+important for explaining the development of the sunspot penumbra and the
+Evershed flow. This fractionation process may also be important for the ``First
+Ionization Potential'' (FIP) effect seen in the solar wind. In support of this
+mechanism we find evidence for such ionization fractionization in UV
+observations of molecular hydrogen in a sunspot umbra and penumbra.",0509862v1
+1997-07-23,Experimental Study of Bifurcations in A Parametrically Forced Pendulum,"An experimental study of bifurcations associated with stability of stationary
+points (SP's) in a parametrically forced magnetic pendulum and a comparison of
+its results with numerical results are presented. The critical values for which
+the SP's lose or gain their stability are experimentally measured by varying
+the two parameters $\Omega$ (the normalized natural frequency) and $A$ (the
+normalized driving amplitude). It is observed that, when the amplitude $A$
+exceeds a critical value, the normal SP with $\theta=0$ ($\theta$ is the angle
+between the permanent magnet and the magnetic field) becomes unstable either by
+a period-doubling bifurcation or by a symmetry-breaking pitchfork bifurcation,
+depending on the values of $\Omega$. However, in contrast with the normal SP
+the inverted SP with $\theta=\pi$ is observed to become stable as $A$ is
+increased above a critical value by a pitchfork bifurcation, but it also
+destabilizes for a higher critical value of $A$ by a period-doubling
+bifurcation. All of these experimental results agree well with numerical
+results obtained using the Floquet theory.",9707017v1
+1995-12-12,Magnetic Properties of the t-J Model in the Dynamical Mean-Field Theory,"We present a theory for the spin correlation function of the t-J model in the
+framework of the dynamical mean-field theory. Using this mapping between the
+lattice and a local model we are able to obtain an intuitive expression for the
+non-local spin susceptibility, with the corresponding local correlation
+function as input. The latter is calculated by means of local Goldstone
+diagrams following closely the procedures developed and successfully applied
+for the (single impurity) Anderson model.We present a systematic study of the
+magnetic susceptibility and compare our results with those of a Hubbard model
+at large U. Similarities and differences are pointed out and the magnetic phase
+diagram of the t-J model is discussed.",9512096v1
+1997-06-25,Domain Dynamics of Magnetic Films with Perpendicular Anisotropy,"We study the magnetic properties of nanoscale magnetic films with large
+perpendicular anisotropy comparing polarization microscopy measurements on
+Co_28Pt_72 alloy samples based on the magneto-optical Kerr effect with Monte
+Carlo simulations of a corresponding micromagnetic model. We focus on the
+understanding of the dynamics especially the temperature and field dependence
+of the magnetisation reversal process. The experimental and simulational
+results for hysteresis, the reversal mechanism, domain configurations during
+the reversal, and the time dependence of the magnetisation are in very good
+qualitative agreement. The results for the field and temperature dependence of
+the domain wall velocity suggest that for thin films the hysteresis can be
+described as a depinning transition of the domain walls rounded by thermal
+activation for finite temperatures.",9706253v1
+1997-10-20,Row-switched states in two-dimensional underdamped Josephson junction arrays,"When magnetic flux moves across layered or granular superconductor
+structures, the passage of vortices can take place along channels which develop
+finite voltage, while the rest of the material remains in the zero-voltage
+state. We present analytical studies of an example of such mixed dynamics: the
+row-switched (RS) states in underdamped two-dimensional Josephson arrays,
+driven by a uniform DC current under external magnetic field but neglecting
+self-fields. The governing equations are cast into a compact
+differential-algebraic system which describes the dynamics of an assembly of
+Josephson oscillators coupled through the mesh current. We carry out a formal
+perturbation expansion, and obtain the DC and AC spatial distributions of the
+junction phases and induced circulating currents. We also estimate the interval
+of the driving current in which a given RS state is stable. All these
+analytical predictions compare well with our numerics. We then combine these
+results to deduce the parameter region (in the damping coefficient versus
+magnetic field plane) where RS states can exist.",9710204v1
+1997-11-13,NMR study of the S=1/2 Heisenberg Ladder Cu2(C5H12N2)2Cl4 : Quantum phase transition and critical dynamics,"We present an extensive NMR study of the spin-1/2 antiferromagnetic
+Heisenberg ladder Cu2(C5H12N2)2Cl4 in a magnetic field range 4.5 - 16.7 T. By
+measuring the proton NMR relaxation rate 1/T_1 and varying the magnetic field
+around the critical field H_c1 = Delta / g\mu_B = 7.5 T, we have studied the
+transition from a gapped spin liquid ground state to a gapless magnetic regime
+which can be described as a Luttinger liquid. We identify an intermediate
+regime T > |H-H_c1|, where the spin dynamics is (possibly) only controlled by
+the T=0 critical point H_c1.",9711124v1
+1998-01-21,Nucleation and hysteresis in Ising model: Classical theory versus computer simulation,"We have studied the nucleation in the nearest neighbour ferromagnetic Ising
+model, in different (d) dimensions, by extensive Monte Carlo simulation using
+the heat-bath dynamics. The nucleation time (tau) has been studied as a
+function of the magnetic field (h) for various system sizes in different
+dimensions (d=2,3,4). The logarithm of the nucleation time is found to be
+proportional to the power (-(d-1)) of the magnetic field (h) in d dimensions.
+The size dependent crossover from coalescence to nucleation regime is observed
+in all dimensions. The distribution of metastable lifetimes are studied in both
+regions. The numerical results are compared and found to be consistent with the
+classical theoretical predictions. In two dimensions, we have also studied the
+dynamical response to a sinusoidally oscillating magnetic field. The reversal
+time is studied as a function of the inverse of the coercive field. The
+applicability of the classical nucleation theory to study the hysteresis and
+coercivity has been discussed.",9801213v2
+1998-06-11,Dynamical properties of a two-dimensional electron gas in a magnetic field within the composite fermion model,"We investigate the response of a two-dimensional electron gas, in the
+fractional quantum Hall regime, to the sudden appearance of a localised charged
+probe using the Chern-Simons theory of composite fermions. The dynamic
+structure factor of the electron gas is found to have a major influence on the
+spectral function of the probe. In particular, there is an orthogonality
+catastrophe when the filling factor is an even-denominator filling fraction due
+to the compressibility of the state, but there is no catastrophe at
+odd-denominator filling factors because these states have a gap to excitations.
+The catastrophe is found to be more severe for composite fermions in zero
+effective magnetic field than it is for electrons in zero real magnetic field.
+Oscillations in the spectral function, arising when the composite fermions are
+at integer filling, have a period equal to the composite fermion cyclotron
+energy. We propose a tunneling experiment which directly measures the spectral
+function from which one could determine the composite fermion effective mass.",9806149v1
+1998-11-06,Combining dynamical mean-field theory and realistic bandstructure of V2O3,"Recent neutron scattering experiments on V2O3 show that the magnetic
+fluctuations on the metallic side of the antiferromagnetic metal-insulator
+transition are not related to the spin structure of the insulator, but rather
+to the bandstructure-driven spin-density wave phase of the doped system
+V(2-y)O3. We calculate these magnetic fluctuations starting from a
+Slater-Koster bandstructure and incorporating the correlation effects through
+the dynamical mean-field theory (DMFT). Our results demonstrate that the
+magnetic properties of the paramagnetic metallic phase are dominated by the
+Fermi surface topology. On the other hand, the electron-electron interaction
+drives the paramagnetic metal-insulator transition in V2O3. The transition to
+the antiferromagnetic insulator by virtue of orbital ordering is discussed in
+the framework of the DMFT.",9811095v1
+1999-04-06,Non-Fermi-liquid behavior in the Kondo lattices induced by peculiarities of magnetic ordering and spin dynamics,"A scaling consideration of the Kondo lattices is performed with account of
+singularities in the spin excitation spectral function. It is shown that a
+non-Fermi-liquid (NFL) behavior between two critical values of the bare $s-f$
+coupling constant occurs naturally for complicated magnetic structures with
+several magnon branches. This may explain the fact that a NFL behavior takes
+place often in the heavy-fermion systems with peculiar spin dynamics. Another
+kind of a NFL-like state (with different critical exponents) can occur for
+simple antiferromagnets with account of magnon damping, and for paramagnets,
+especially with two-dimensional character of spin fluctuations. The mechanisms
+proposed lead to some predictions about behavior of specific heat, resistivity,
+magnetic susceptibility, and anisotropy parameter, which can be verified
+experimentally.",9904072v3
+1999-07-19,Renormalization of the Spin-Peierls Transition due to Phonon Dynamics,"We report results from a systematic strong-coupling expansion of a spin-1/2
+Heisenberg chain coupled to Einstein phonons. In the non-adiabatic regime this
+model is used to describe zero temperature properties of CuGeO3. The linked
+cluster expansion allows the determination of observables in the thermodynamic
+limit preserving the full lattice dynamics without a truncation of the phononic
+Hilbert space. In particular, the spin gap and the dispersion of the elementary
+triplet excitation are calculated up to 10th order in a dimer expansion. The
+magnetic structure factor of the ground state is evaluated up to 6th order. We
+show that the spin-phonon coupling leads to a renormalization of the elementary
+triplet dispersion. Surprisingly in the non-adiabatic regime a substantial
+renormalization of the spin gap only sets in at much larger couplings than
+those proposed for CuGeO3. The ground state magnetic correlations are found to
+be hardly effected by the spin-phonon coupling, but dominated by the
+frustrating magnetic interaction in the parameter regime relevant for CuGeO3.",9907266v1
+1999-07-26,Magnetic susceptibility of the double exchange model,"Previously a many-body coherent potential approximation (CPA) was used to
+study the double exchange (DE) model with quantum local spins S, both for S=1/2
+and for general S in the paramagnetic state. This approximation, exact in the
+atomic limit, was considered to be a many-body extension of Kubo's one-electron
+dynamical CPA for the DE model. We now extend our CPA treatment to the case of
+general S and spin polarization. We show that Kubo's one-electron CPA is always
+recovered in the empty-band limit and that our CPA is equivalent to dynamical
+mean field theory in the classical spin limit. We then solve our CPA equations
+self-consistently to obtain the static magnetic susceptibility chi in the
+strong-coupling limit. As in the case of the CPA for the Hubbard model we find
+unphysical behaviour in chi at half-filling and no magnetic transition for any
+finite S. We identify the reason for this failure of our approximation and
+propose a modification which gives the correct Curie-law behaviour of chi at
+half-filling and a transition to ferromagnetism for all S.",9907393v1
+1999-12-06,Coherent spin dynamics in diluted-magnetic quantum wells,"Spins of charge carriers, paramagnetic centers, and nuclei in semiconductor
+structures are known to be oriented if circular-polarized light is shined upon
+the structure. This is due to transfer of angular momentum from photons to
+various excitations in the semiconductor. What would happen if the structure is
+anisotropic, so that the angular momentum is not conserved? Experiments
+performed on diluted-magnetic II-VI quantum wells (such as CdMnTe/CdMgTe) show
+that at some conditions the effect of light upon the spin state of the
+semiconductor structure can be greatly amplified. Exchange field of
+photoexcited heavy holes initiates a coherent evolution of a great number of
+localized spins of Mn-ions. In the simplest case, it is just a precession in an
+effective field, but generally the spin dynamics is more intricate. It shows
+up, for instance, in long sequences of spin-flip peaks in Raman spectra, in
+enhanced magnetic-polaron effect, and in modulation of optical response within
+the picosecond time scale.",9912084v1
+2000-01-19,Precision microwave dielectric and magnetic susceptibility measurements of correlated electronic materials using superconducting cavities,"We analyze microwave cavity perturbation methods, and show that the technique
+is an excellent, precision method to study the dynamic magnetic and dielectric
+response in the $GHz$ frequency range. Using superconducting cavities, we
+obtain exceptionally high precision and sensitivity for measurements of
+relative changes. A dynamic electromagnetic susceptibility
+$\tilde{\zeta}(T)=\zeta ^{\prime}+i\zeta ^{\prime \prime}$ is introduced, which
+is obtained from the measured parameters: the shift of cavity resonant
+frequency $\delta f$ and quality factor $Q$. We focus on the case of a
+spherical sample placed at the center of a cylindrical cavity resonant in the
+$TE_{011}$ mode. Depending on the sample characteristics, the magnetic
+permeability $\tilde{\mu}$, the dielectric permittivity $\tilde{\epsilon}$ and
+the complex conductivity $\tilde{\sigma}$ can be extracted from
+$\tilde{\zeta}_{H}$. A full spherical wave analysis of the cavity perturbation
+is given. This analysis has led to the observation of new phenomena in novel
+low dimensional materials.",0001280v1
+2000-05-10,Lineshape predictions via Bethe ansatz for the one-dimensional spin-1/2 Heisenberg antiferromagnet in a magnetic field,"The spin fluctuations parallel to the external magnetic field in the ground
+state of the one-dimensional (1D) s=1/2 Heisenberg antiferromagnet are
+dominated by a two-parameter set of collective excitations. In a cyclic chain
+of N sites and magnetization 0<M_z<N/2, the ground state, which contains 2M_z
+spinons, is reconfigured as the physical vacuum for a different species of
+quasi-particles, identifiable in the framework of the coordinate Bethe ansatz
+by characteristic configurations of Bethe quantum numbers. The dynamically
+dominant excitations are found to be scattering states of two such
+quasi-particles. For N -> \infty, these collective excitations form a continuum
+in (q,\omega)-space with an incommensurate soft mode. Their matrix elements in
+the dynamic spin structure factor S_{zz}(q,\omega) are calculated directly from
+the Bethe wave functions for finite N. The resulting lineshape predictions for
+N -> \infty complement the exact results previously derived via algebraic
+analysis for the exact 2-spinon part of S_{zz}(q,\omega) in the zero-field
+limit. They are directly relevant for the interpretation of neutron scattering
+data measured in nonzero field on quasi-1D antiferromagnetic compounds.",0005174v1
+2001-03-19,Magnetism of correlated systems: beyond LDA,"A novel approach to electronic correlations in magnetic crystals which takes
+into account a dynamical many-body effects is present. In order to to find a
+frequency dependence of the electron self energy, an effective quantum-impurity
+many-particle problem need to be solved within the dynamical mean-field theory.
+The numerically exact QMC-scheme and the spin-polarized fluctuation exchange
+approximation are used for the self-consistent solution of this single-site
+many-particle problem. The calculations of effective exchange interaction
+parameters based on the realistic electronic structure of correlated magnetic
+crystals have been discussed.",0103389v1
+2001-03-30,Thermal magnetization fluctuations in thin films and a new physical form for magnetization damping,"The effect of thermal fluctuations on a thin film magnetoresistive element
+has been calculated. The technique involves adding to the basic spin dynamics a
+general form of interaction with a thermal bath. For a general anisotropic
+magnetic system the resulting equation can be written as a Langevin equation
+for a harmonic oscillator. Our approach predicts two times smaller noise power
+at low frequencies than the conventional stochastic Landau-Lifshitz-Gilbert
+equation. It is shown that equivalent results can be obtained by introducing a
+tensor phenomenological damping term to the gyromagnetic dynamics driven by a
+thermal fluctuating field.",0103624v3
+2001-08-19,Magnetic relaxation and critical current density of $MgB_2$ thin films,"Magnetic relaxation and critical current density have been measured on a
+$MgB_2$ thin film in a wide region of temperature with the magnetic field up to
+8 T. The irreversibility line has also been determined. It is found that the
+relaxation rate has a very weak temperature dependence below $1/2 T_c$ showing
+a clear residual relaxation rate at zero K, which cannot be easily explained as
+due to thermally activated flux creep. Furthermore the relaxation rate has a
+strong field dependence. The flux dynamics of thin films are very similar to
+that of high pressure synthesized bulks although the relaxation rate in thin
+film is systematically higher than that of a bulk sample. All the results here
+together with those from the bulk samples suggest that the flux dynamics may be
+dominated by the quantum effects, such as quantum fluctuation and tunneling.",0108294v1
+2002-05-22,Quantum Spin Dynamics in Molecular Magnets,"The detailed theoretical understanding of quantum spin dynamics in various
+molecular magnets is an important step on the roadway to technological
+applications of these systems. Quantum effects in both ferromagnetic and
+antiferromagnetic molecular clusters are, by now, theoretically well
+understood. Ferromagnetic molecular clusters allow one to study the interplay
+of incoherent quantum tunneling and thermally activated transitions between
+states with different spin orientation. The Berry phase oscillations found in
+Fe_8 are signatures of the quantum mechanical interference of different
+tunneling paths. Antiferromagnetic molecular clusters are promising candidates
+for the observation of coherent quantum tunneling on the mesoscopic scale.
+Although challenging, applications of molecular magnetic clusters for data
+storage and quantum data processing are within experimental reach already with
+present day technology.",0205457v1
+2002-08-27,Semi-analytical solution of the Kondo model in a magnetic field,"The single impurity Kondo model at zero temperature in a magnetic field is
+solved by a semi-analytical approach based on the flow equation method. The
+resulting problem is shown to be equivalent to a resonant level model with a
+non-constant hybridization function. This nontrivial effective hybridization
+function encodes the quasiparticle interaction in the Kondo limit, while the
+magnetic field enters as the impurity orbital energy. The evaluation of static
+and dynamic quantities of the strong-coupling Kondo model becomes very simple
+in this effective model. We present results for thermodynamic quantities and
+the dynamical spin-structure factor and compare them with NRG calculations.",0208539v2
+2003-04-02,Continuous quantum phase transition in a Kondo lattice model,"We study the magnetic quantum phase transition in an anisotropic Kondo
+lattice model. The dynamical competition between the RKKY and Kondo
+interactions is treated using an extended dynamic mean field theory (EDMFT)
+appropriate for both the antiferromagnetic and paramagnetic phases. A quantum
+Monte Carlo approach is used, which is able to reach very low temperatures, of
+the order of 1% of the bare Kondo scale. We find that the finite-temperature
+magnetic transition, which occurs for sufficiently large RKKY interactions, is
+first order. The extrapolated zero-temperature magnetic transition, on the
+other hand, is continuous and locally critical.",0304033v3
+2003-07-05,Anisotropic splitting of intersubband spin plasmons in quantum wells with bulk and structural inversion asymmetry,"In semiconductor heterostructures, bulk and structural inversion asymmetry
+and spin-orbit coupling induce a k-dependent spin splitting of valence and
+conduction subbands, which can be viewed as being caused by momentum-dependent
+crystal magnetic fields. This paper studies the influence of these effective
+magnetic fields on the intersubband spin dynamics in an asymmetric n-type
+GaAs/AlGaAs quantum well. We calculate the dispersions of intersubband spin
+plasmons using linear response theory. The so-called D'yakonov-Perel'
+decoherence mechanism is inactive for collective intersubband excitations,
+i.e., crystal magnetic fields do not lead to decoherence of spin plasmons.
+Instead, we predict that the main signature of bulk and structural inversion
+asymmetry in intersubband spin dynamics is a three-fold, anisotropic splitting
+of the spin plasmon dispersion. The importance of many-body effects is pointed
+out, and conditions for experimental observation with inelastic light
+scattering are discussed.",0307124v1
+2003-12-30,"Dynamical Systems, Topology and Conductivity in Normal Metals in strong magnetic fields","We represent here the full description of all asymptotic regimes of
+conductivity behavior in the so-called ""Geometric Strong Magnetic Field limit""
+in the 3D single crystal normal metals with topologically complicated Fermi
+surfaces. In particular, new observable integer-valued characteristics of
+conductivity of the topological origin were introduced by the present authors
+few years ago; they are based on the Topological Resonance found by the present
+authors and play the basic role in the total picture. Our investigation is
+based on the study of dynamical systems on Fermi surfaces for the
+semi-classical motion of electron in magnetic field realized by the Moscow
+topological group.",0312708v1
+2004-03-29,Two regimes in the magnetic field response of superconducting MgB$_2$,"Using Scanning Tunneling Microscope at low temperature we explore the
+superconducting phase diagram in the $\pi$-band of the two-band superconductor
+MgB$_2$. In this band the peculiar shape of the local tunneling spectra and
+their dynamics in the magnetic field reveal the complex character of the
+quasiparticle density of states (DOS). The gap in the DOS is first rapidly
+filled with states in raising the magnetic field up to 0.5 T and then slowly
+approaches the normal state value : The gap is observed up to 2 T. Such a
+change in the DOS dynamics suggests the existence of two terms in the DOS of
+the $\pi$-band: a first one, reflecting an intrinsic superconductivity in the
+band and a second one, originating from an inter-band coupling to the
+$\sigma$-band. Our findings allow a deeper understanding of the unique phase
+diagram of MgB$_2$.",0403700v1
+2004-03-30,"Finite-Size effects in ""Single Chain Magnets"": an experimental and theoretical study","The problem of finite size effects in s=1/2 Ising systems showing slow
+dynamics of the magnetization is investigated introducing diamagnetic
+impurities in a Co$^{2+}$-radical chain. The static magnetic properties have
+been measured and analyzed considering the peculiarities induced by the
+ferrimagnetic character of the compound. The dynamic susceptibility shows that
+an Arrhenius law is observed with the same energy barrier for the pure and the
+doped compounds while the prefactor decreases, as theoretically predicted.
+Multiple spins reversal has also been investigated.",0403731v1
+2004-04-04,Critical dynamics of the Potts model: short-time Monte Carlo simulations,"We calculate the new dinamic exponent $\theta $ of the 4-state Potts model,
+using short-time simulations. Our estimates $\theta_{1}=-0.0471(33)$ and $%
+\theta_{2}=$ $-0.0429(11)$ obtained by following the behavior of the
+magnetization or measuring the evolution of the time correlation function of
+the magnetization corroborate the conjecture by Okano et. al. In addition,
+these values agree with previous estimate of the same dynamic exponent for the
+two-dimensional Ising model with three-spin interactions in one direction, that
+is known to belong to the same universality class as the 4-state Potts model.
+The anomalous dimension of initial magnetization $% x_{0}=z\theta +\beta /\nu $
+is calculated by an alternative way that mixes two different initial
+conditions. We have also estimated the values of the static exponents $\beta $
+and $\nu $. They are in complete agreement with the pertinent results of the
+literature.",0404083v1
+2004-10-07,Quantum Fluctuations and Excitations in Antiferromagnetic Quasicrystals,"We study the effects of quantum fluctuations and the excitation spectrum for
+the antiferromagnetic Heisenberg model on a two-dimensional quasicrystal, by
+numerically solving linear spin-wave theory on finite approximants of the
+octagonal tiling. Previous quantum Monte Carlo results for the distribution of
+local staggered magnetic moments and the static spin structure factor are
+reproduced well within this approximate scheme. Furthermore, the magnetic
+excitation spectrum consists of magnon-like low-energy modes, as well as
+dispersionless high-energy states of multifractal nature. The dynamical spin
+structure factor, accessible to inelastic neutron scattering, exhibits
+linear-soft modes at low energies, self-similar structures with bifurcations
+emerging at intermediate energies, and flat bands in high-energy regions. We
+find that the distribution of local staggered moments stemming from the
+inhomogeneity of the quasiperiodic structure leads to a characteristic energy
+spread in the local dynamical spin susceptibility, implying distinct nuclear
+magnetic resonance spectra, specific for different local environments.",0410180v1
+2005-09-14,Reentrance during nonequilibrium relaxation,"We consider nonequilibrium critical dynamics of the two-dimensional Ising
+model for which the initial state is prepared by switching on random fields
+with zero mean and variance $H$. In the initial state there is no magnetic
+order but the clusters of parallel spins have a percolation transition for
+small enough $H$. Using heath-bath dynamics we measure the relaxation of the
+magnetization which shows a reentrance in time. Due to cluster dissolution in
+the early time regime there is a decrease of the magnetization, followed by an
+increase due to nonequilibrium domain growth which itself turns to a decrease
+due to equilibrium relaxation. The power law decay of the nonequilibrium
+autocorrelation function is not influenced by the percolation in the initial
+state.",0509372v1
+2005-11-02,Magneto-optical imaging of magnetic flux patterns in superconducting films with antidots,"Superconducting YBaCuO thin films were equipped with a special arrangement of
+antidots (holes) of 1 micron radius in order to guide the stream of magnetic
+flux moving in (or out of) the sample. The flux distribution and its dynamics
+were visualized using real-time magneto-optical imaging. It is clearly
+demonstrated that one-dimensional antidot arrays strongly facilitate
+propagation of magnetic flux. We also demonstrate a possibility to alter the
+direction of flux motion in a controlled way by special arrangement of
+intercepting antidot arrays. Our resolution was sufficient for observation of
+flux in particular antidots, which allows a more detailed dynamic analysis of
+such systems.",0511060v1
+2005-12-01,Nano-magnetic droplets and implications to orbital ordering in La1-xSrxCoO3,"Inelastic cold neutron scattering on LaCoO3 provided evidence for a distinct
+low energy excitation at 0.6 meV coincident with the thermally induced magnetic
+transition. Coexisting strong ferromagnetic (FM) and weaker antiferromagnetic
+(AFM) correlations that are dynamic follow the activation to the excited state,
+identified as the intermediate S=1 spin triplet. This is indicative of
+dynamical orbital ordering favoring the observed magnetic interactions. With
+hole doping as in La1-xSrxCoO3, the FM correlations between Co spins become
+static and isotropically distributed due to the formation of FM droplets. The
+correlation length and condensation temperature of these droplets increase
+rapidly with metallicity due to the double exchange mechanism.",0512030v1
+2006-07-04,Influence of the driving mechanism on the response of systems with athermal dynamics: the example of the random-field Ising model,"We investigate the influence of the driving mechanism on the hysteretic
+response of systems with athermal dynamics. In the framework of local-mean
+field theory at finite temperature (but neglecting thermallly activated
+processes), we compare the rate-independent hysteresis loops obtained in the
+random field Ising model (RFIM) when controlling either the external magnetic
+field $H$ or the extensive magnetization $M$. Two distinct behaviors are
+observed, depending on disorder strength. At large disorder, the $H$-driven and
+$M$-driven protocols yield identical hysteresis loops in the thermodynamic
+limit. At low disorder, when the $H$-driven magnetization curve is
+discontinuous (due to the presence of a macroscopic avalanche), the $M$-driven
+loop is re-entrant while the induced field exhibits strong intermittent
+fluctuations and is only weakly self-averaging. The relevance of these results
+to the experimental observations in ferromagnetic materials, shape memory
+alloys, and other disordered systems is discussed.",0607069v1
+2006-10-10,Slow dynamics in critical ferromagnetic vector models relaxing from a magnetized initial state,"Within the universality class of ferromagnetic vector models with O(n)
+symmetry and purely dissipative dynamics, we study the non-equilibrium critical
+relaxation from a magnetized initial state. Transverse correlation and response
+functions are exactly computed for Gaussian fluctuations and in the limit of
+infinite number n of components of the order parameter. We find that the
+fluctuation-dissipation ratios (FDRs) for longitudinal and transverse modes
+differ already at the Gaussian level. In these two exactly solvable cases we
+completely describe the crossover from the short-time to the long-time
+behavior, corresponding to a disordered and a magnetized initial condition,
+respectively. The effects of non-Gaussian fluctuations on longitudinal and
+transverse quantities are calculated in the first order in the
+epsilon-expansion and reliable three-dimensional estimates of the two FDRs are
+obtained.",0610266v1
+2006-10-11,Computational Experiment on Glassy Dynamic Nature of the Field-Cooled Magnetization in an Ising Spin-Glass Model,"The field-cooled (FC) process on an Ising spin-glass model is investigated by
+a standard Monte Calro (MC) method on one hand, and the equilibrium
+magnetization of the same system is evaluated by the exchang MC method on the
+other hand. The two types of simulation reveal intriguing glassy
+(nonequilibrium) dynamic properties of the FC magnetization (FCM) of the
+system. Particularly, the FCM decrease is observed when the FC process is
+halted at a low temperater, although its value is smaller than the
+corresponding equilibrium value. We present a comprehensive interpretation of
+such peculiar phenomena based on the scenario for the FCM process recently
+propsed by J\""onsson and one of us (HT).",0610284v1
+2007-02-01,Adiabatic Domain Wall Motion and Landau-Lifshitz Damping,"Recent theory and measurements of the velocity of current-driven domain walls
+in magnetic nanowires have re-opened the unresolved question of whether
+Landau-Lifshitz damping or Gilbert damping provides the more natural
+description of dissipative magnetization dynamics. In this paper, we argue that
+(as in the past) experiment cannot distinguish the two, but that
+Landau-Lifshitz damping nevertheless provides the most physically sensible
+interpretation of the equation of motion. From this perspective, (i) adiabatic
+spin-transfer torque dominates the dynamics with small corrections from
+non-adiabatic effects; (ii) the damping always decreases the magnetic free
+energy, and (iii) microscopic calculations of damping become consistent with
+general statistical and thermodynamic considerations.",0702020v3
+1999-04-04,The Physical Interpretation of the Lanczos Tensor,"The field equations of general relativity can be written as first order
+differential equations in the Weyl tensor, the Weyl tensor in turn can be
+written as a first order differential equation in a three index tensor called
+the Lanczos tensor. The Lanczos tensor plays a similar role in general
+relativity to that of the vector potential in electro-magnetic theory. The
+Aharonov-Bohm effect shows that when quantum mechanics is applied to
+electro-magnetic theory the vector potential is dynamically significant, even
+when the electro-magnetic field tensor $F_{ab}$ vanishes. Here it is assumed
+that in the quantum realm the Lanczos tensor is dynamically significant, and
+this leads to an attempt to quantize the gravitational field by pursuing the
+analogy between the vector field and the Lanczos tensor.",9904006v1
+2001-10-22,On the tidally induced gravitational collapse of a particle cluster,"An important issue in the dynamics of neutron star binaries is whether tidal
+interaction can cause the individual stars to collapse into black holes during
+inspiral. To understand this issue better, we study the dynamics of a cluster
+of collisionless particles orbiting a non-rotating black hole, which is part of
+a widely separated circular binary. The companion body's electric- and
+magnetic-type tidal fields distort the black hole and perturb the cluster,
+eventually causing the cluster to collapse into the hole as the companion
+spirals in under the influence of gravitational radiation reaction. We find
+that magnetic-type tidal forces do not significantly influence the evolution of
+the cluster as a whole. However, individual orbits can be strongly affected by
+these forces. For example, some orbits are destabilized due to the addition of
+magnetic-type tidal forces. We find that the most stable orbits are close to
+the companion's orbital plane and retrograde with respect to the companion's
+orbit.",0110091v1
+1998-02-27,Dynamical Flavour Symmetry Breaking by a Magnetic Field in Lattice QED_3,"We perform a lattice study, in the quenched approximation, of dynamical mass
+generation in a system of relativistic (Dirac) fermions, coupled to an Abelian
+gauge field in (2+1)-dimensions, in the presence of an external (constant)
+magnetic field, perpendicular to the spatial planes. It is shown that a strong
+magnetic field catalyzes chiral symmetry breaking, in agreement with results in
+the continuum. The r\^ole of the higher-Landau poles in inducing a critical
+temperature above which the phenomenon disappears is pointed out. We also
+discuss the implications of this model on the opening of a gap in doped
+antiferromagnetic superconductors.",9802037v2
+1997-08-12,Primordial Magnetic Fields and Their Development,"In this talk I discuss the non-linear development of magnetic fields in the
+early universe. I very briefly mention a number of particle physics mechanisms
+for generating magnetic fields in the early universe, but the emphasis is on a
+review of the field theoretic aspects of the developments of these fields,
+mainly on the occurence of inverse cascades, i.e. generation of order from
+disorder in the sense of transfer of energy from smaller to larger scales. In
+this connection it is also briefly reviewed how the Silk effect (photon
+diffusion) is counteracted by the inverse cascade.",9708320v1
+1997-09-15,Chiral Symmetry Breaking in the weakly coupled QED in a Magnetic Field,"The catalysis of chiral symmetry breaking in the massless weakly coupled QED
+in a magnetic field is studied. It is shown that the effect is due to the
+dimensional reduction $D\to D-2$ in the dynamics of fermion pairing in a
+magnetic field. The dynamical mass of fermions (energy gap in the fermion
+spectrum) is determined. The temperature of the symmetry restoration is
+estimated analytically.",9709340v1
+1998-07-14,Dynamical symmetry restoration for a higher-derivative four-fermion model in an external electromagnetic field,"A four-fermion model with additional higher-derivative terms is investigated
+in an external electromagnetic field. The effective potential in the leading
+order of large-N expansion is calculated in external constant magnetic and
+electric fields.
+  It is shown that, in contrast to the former results concerning the universal
+character of ""magnetic catalysis"" in dynamical symmetry breaking, in the
+present higher-derivative model the magnetic field restores chiral symmetry
+broken initially on the tree level. Numerical results describing a second-order
+phase transition that accompanies the symmetry restoration at the quantum level
+are presented.",9807368v1
+2000-04-12,Magnetic Catalysis in the Presence of Scalar Fields,"The influence of scalar field interactions in the magnetic catalysis
+phenomenom is studied in a gauge theory with scalar and fermion fields. It is
+shown that the external magnetic field catalyzes the appearance of a
+fermion-antifermion condensate along with a non-zero scalar vev, hence
+generating a fermion dynamical mass and breaking the discrete chiral symmetry
+of the theory. The model does not require the introduction of a scalar mass
+term with a wrong sign in the original Lagrangian to generate the scalar vev,
+nor does it exhibit dimensional transmutation ''a la Coleman-Weinberg.'' The
+scalar vev noticeably enhances the dynamically generated fermion mass. Possible
+cosmological applications of these results are suggested.",0004113v1
+2001-06-05,"Testing Non-commutative QED, Constructing Non-commutative MHD","The effect of non-commutativity on electromagnetic waves violates Lorentz
+invariance: in the presence of a background magnetic induction field b, the
+velocity for propagation transverse to b differs from c, while propagation
+along b is unchanged. In principle, this allows a test by the Michelson-Morley
+interference method. We also study non-commutativity in another context, by
+constructing the theory describing a charged fluid in a strong magnetic field,
+which forces the fluid particles into their lowest Landau level and renders the
+fluid dynamics non-commutative, with a Moyal product determined by the
+background magnetic field.",0106044v3
+2003-06-16,Can branes travel beyond CTC horizon in Godel Universe?,"Godel universe in M-theory is a supersymmetric and homogeneous background
+with rotation and four-form magnetic flux. It is known that, as seen in
+inertial frame of co-moving observer, all geodesics with zero orbital angular
+momentum orbit inside `surface of light velocity' (CTC horizon). To learn if
+other probes can travel beyond the CTC horizon, we study dynamics of M-graviton
+and, in particular, M2-brane, whose motion is affected by Lorentz force exerted
+by the four-form magnetic flux and by nonzero orbital angular momentum.
+Classically, we find that both probes gyrate closed orbits, but diameter and
+center of gyration depends on sign and magnitude of probe's energy, charge and
+orbital angular momentum. For M2-brane, orbits in general travel outside the
+CTC horizon. Quantum-mechanically, we find that wave function and excitation
+energy levels are all self-similar. We draw analogy of probe's dynamics with
+Landau problem for charged particle in magnetic field.",0306148v2
+2006-10-19,The Noncommutative Anandan's Quantum Phase,"In this work we study the noncommutative nonrelativistic quantum dynamics of
+a neutral particle, that possesses permanent magnetic and electric dipole
+momenta, in the presence of an electric and magnetic fields. We use the
+Foldy-Wouthuysen transformation of the Dirac spinor with a non-minimal coupling
+to obtain the nonrelativistic limit. In this limit, we will study the
+noncommutative quantum dynamics and obtain the noncommutative Anandan's
+geometric phase. We analyze the situation where magnetic dipole moment of the
+particle is zero and we obtain the noncommutative version of the
+He-McKellar-Wilkens effect. We demonstrate that this phase in the
+noncommutative case is a geometric dispersive phase. We also investigate this
+geometric phase considering the noncommutativity in the phase space and the
+Anandan's phase is obtained.",0610222v2
+2005-07-15,Energetic and dynamic properties of a quantum particle in a spatially random magnetic field with constant correlations along one direction,"We consider an electrically charged particle on the Euclidean plane subjected
+to a perpendicular magnetic field which depends only on one of the two
+Cartesian co-ordinates. For such a ``unidirectionally constant'' magnetic field
+(UMF), which otherwise may be random or not, we prove certain spectral and
+transport properties associated with the corresponding one-particle
+Schroedinger operator (without scalar potential) by analysing its ``energy-band
+structure''. In particular, for an ergodic random UMF we provide conditions
+which ensure that the operator's entire spectrum is almost surely absolutely
+continuous. This implies that, along the direction in which the random UMF is
+constant, the quantum-mechanical motion is almost surely ballistic, while in
+the perpendicular direction in the plane one has dynamical localisation. The
+conditions are verified, for example, for Gaussian and Poissonian random UMF's
+with non-zero mean-values. These results may be viewed as ``random analogues''
+of results first obtained by A. Iwatsuka [Publ. RIMS, Kyoto Univ. 21 (1985)
+385] and (non-rigorously) by J. E. Mueller [Phys. Rev. Lett. 68 (1992) 385].",0507035v1
+2003-06-28,Self-similar turbulent dynamo,"The amplification of magnetic fields in a highly conducting fluid is studied
+numerically. During growth, the magnetic field is spatially intermittent: it
+does not uniformly fill the volume, but is concentrated in long thin folded
+structures. Contrary to a commonly held view, intermittency of the folded field
+does not increase indefinitely throughout the growth stage if diffusion is
+present. Instead, as we show, the probability-density function (PDF) of the
+field strength becomes self-similar. The normalized moments increase with
+magnetic Prandtl number in a powerlike fashion. We argue that the
+self-similarity is to be expected with a finite flow scale and system size. In
+the nonlinear saturated state, intermittency is reduced and the PDF is
+exponential. Parallels are noted with self-similar behavior recently observed
+for passive-scalar mixing and for map dynamos.",0306059v3
+2006-11-06,Numerical simulations on cleaning the neutron trap for measuring the neutron lifetime,"We present the results of numerical simulations of the dynamical behavior of
+trajectories of ultra cold neutrons (UCN) in a magnetic trap. The main goal of
+our simulations was to optimize the trap parameters in order to minimize the
+characteristic times for removing from the trap those untrapped neutrons with
+relatively long escape times (cleaning the trap). Our results demonstrate that,
+by a proper choice of the trap parameters cleaning times can be reduced to 15
+sec, or even less. Many other dynamical characteristics of the neutrons in the
+trap, including the conservation of the adiabatic invariant which characterizes
+the orientation of the magnetic moment along the local magnetic field, are also
+discussed.",0611005v1
+1997-12-04,Nonadiabatic Dynamics of Atoms in Nonuniform Magnetic Fields,"Dynamics of neutral atoms in nonuniform magnetic fields, typical of
+quadrupole magnetic traps, is considered by applying an accurate method for
+solving nonlinear systems of differential equations. This method is more
+general than the adiabatic approximation and, thus, permits to check the limits
+of the latter and also to analyze nonadiabatic regimes of motion. An unusual
+nonadiabatic regime is found when atoms are confined from one side of the
+z-axis but are not confined from another side. The lifetime of atoms in a trap
+in this semi-confining regime can be sufficiently long for accomplishing
+experiments with a cloud of such atoms. At low temperature, the cloud is
+ellipsoidal being stretched in the axial direction and moving along the z-axis.
+The possibility of employing the semi-confining regime for studying the
+relative motion of one component through another, in a binary mixture of gases
+is discussed.",9712009v1
+1998-03-15,On the Dynamical Stability of the Hovering Magnetic Top,"In this paper we analyze the dynamic stability of the hovering magnetic top
+from first principles without using any preliminary assumptions. We write down
+the equations of motion for all six degrees of freedom and solve them
+analytically around the equilibrium solution. Using this solution we then find
+conditions which the height of the hovering top above the base, its total mass,
+and its spinning speed have to satisfy for stable hovering. The calculation
+presented in this paper can be used as a guide to the analysis and synthesis of
+magnetic traps for neutral particles.",9803020v1
+1998-12-10,Evidence for a singularity in ideal magnetohydrodynamics: implications for fast reconnection,"Numerical evidence for a finite-time singularity in ideal 3D
+magnetohydrodynamics (MHD) is presented. The simulations start from two
+interlocking magnetic flux rings with no initial velocity. The magnetic
+curvature force causes the flux rings to shrink until they come into contact.
+This produces a current sheet between them. In the ideal compressible
+calculations, the evidence for a singularity in a finite time $t_c$ is that the
+peak current density behaves like $|J|_\infty \sim 1/(t_c-t)$ for a range of
+sound speeds (or plasma betas). For the incompressible calculations consistency
+with the compressible calculations is noted and evidence is presented that
+there is convergence to a self-similar state. In the resistive reconnection
+calculations the magnetic helicity is nearly conserved and energy is
+dissipated.",9812017v2
+1999-10-27,Atomic dynamics in evaporative cooling of trapped alkali atoms in strong magnetic fields,"We investigate how the nonlinearity of the Zeeman shift for strong magnetic
+fields affects the dynamics of rf field induced evaporative cooling in magnetic
+traps. We demonstrate for the 87-Rb and 23-Na F=2 trapping states with wave
+packet simulations how the cooling stops when the rf field frequency goes below
+a certain limit (for the 85-Rb F=2 trapping state the problem does not appear).
+We examine the applicability of semiclassical models for the strong field case
+as an extension of our previous work [Phys. Rev. A 58, 3983 (1998)]. Our
+results verify many of the aspects observed in a recent $^{87}$Rb experiment
+[Phys. Rev. A 60, R1759 (1999)].",9910043v1
+2001-08-06,Quantum Measurement of a Single Spin using Magnetic Resonance Force Microscopy,"Single-spin detection is one of the important challenges facing the
+development of several new technologies, e.g. single-spin transistors and
+solid-state quantum computation. Magnetic resonance force microscopy with a
+cyclic adiabatic inversion, which utilizes a cantilever oscillations driven by
+a single spin, is a promising technique to solve this problem. We have studied
+the quantum dynamics of a single spin interacting with a quasiclassical
+cantilever. It was found that in a similar fashion to the Stern-Gerlach
+interferometer the quantum dynamics generates a quantum superposition of two
+quasiclassical trajectories of the cantilever which are related to the two spin
+projections on the direction of the effective magnetic field in the rotating
+reference frame. Our results show that quantum jumps will not prevent a
+single-spin measurement if the coupling between the cantilever vibrations and
+the spin is small in comparison with the amplitude of the radio-frequency
+external field.",0108025v1
+2007-04-11,Preparation and detection of magnetic quantum phases in optical superlattices,"We describe a novel approach to prepare, detect and characterize magnetic
+quantum phases in ultra-cold spinor atoms loaded in optical superlattices. Our
+technique makes use of singlet-triplet spin manipulations in an array of
+isolated double well potentials in analogy to recently demonstrated quantum
+control in semiconductor quantum dots. We also discuss the many-body
+singlet-triplet spin dynamics arising from coherent coupling between nearest
+neighbor double wells and derive an effective description for such system. We
+use it to study the generation of complex magnetic states by adiabatic and
+non-equilibrium dynamics.",0704.1413v3
+2007-05-24,Nonequilibrium Dynamics of Anisotropic Large Spins in the Kondo Regime: Time-Dependent Numerical Renormalization Group Analysis,"We investigate the time-dependent Kondo effect in a single-molecule magnet
+(SMM) strongly coupled to metallic electrodes. Describing the SMM by a Kondo
+model with large spin S > 1/2, we analyze the underscreening of the local
+moment and the effect of anisotropy terms on the relaxation dynamics of the
+magnetization. Underscreening by single-channel Kondo processes leads to a
+logarithmically slow relaxation, while finite uniaxial anisotropy causes a
+saturation of the SMM's magnetization. Additional transverse anisotropy terms
+induce quantum spin tunneling and a pseudospin-1/2 Kondo effect sensitive to
+the spin parity.",0705.3654v2
+2007-05-30,Structure and Dynamics of the Sun's Open Magnetic Field,"The solar magnetic field is the primary agent that drives solar activity and
+couples the Sun to the Heliosphere. Although the details of this coupling
+depend on the quantitative properties of the field, many important aspects of
+the corona - solar wind connection can be understood by considering only the
+general topological properties of those regions on the Sun where the field
+extends from the photosphere out to interplanetary space, the so-called open
+field regions that are usually observed as coronal holes. From the simple
+assumptions that underlie the standard quasi-steady corona-wind theoretical
+models, and that are likely to hold for the Sun, as well, we derive two
+conjectures on the possible structure and dynamics of coronal holes: (1)
+Coronal holes are unique in that every unipolar region on the photosphere can
+contain at most one coronal hole. (2) Coronal holes of nested polarity regions
+must themselves be nested. Magnetic reconnection plays the central role in
+enforcing these constraints on the field topology. From these conjectures we
+derive additional properties for the topology of open field regions, and
+propose several observational predictions for both the slowly varying and
+transient corona/solar wind.",0705.4430v1
+2007-09-04,Dynamic nuclear polarisation in biased quantum wires with spin-orbit interaction,"We propose a new method for dynamic nuclear polarisation in a quasi
+one-dimensional quantum wire utilising the spin-orbit interaction, the
+hyperfine interaction, and a finite source-drain potential difference. In
+contrast with current methods, our scheme does not rely on external magnetic or
+optical sources which makes independent control of closely placed devices much
+more feasible. Using this method, a significant polarisation of a few per cent
+is possible in currently available InAs wires which may be detected by
+conductance measurements. This may prove useful for nuclear-magnetic-resonance
+studies in nanoscale systems as well as in spin-based devices where external
+magnetic and optical sources will not be suitable.",0709.0333v2
+2007-09-04,Vortices on a superconducting nanoshell: phase diagram and dynamics,"In superconductors, the search for special vortex states such as giant
+vortices focuses on laterally confined or nanopatterned thin superconducting
+films, disks, rings, or polygons. We examine the possibility to realize giant
+vortex states and states with non-uniform vorticity on a superconducting
+spherical nanoshell, due to the interplay of the topology and the applied
+magnetic field. We derive the phase diagram and identify where, as a function
+of the applied magnetic field, the shell thickness and the shell radius, these
+different vortex phases occur. Moreover, the curved geometry allows these
+states (or a vortex lattice) to coexist with a Meissner state, on the same
+curved film. We have examined the dynamics of the decay of giant vortices or
+states with non-uniform vorticity into a vortex lattice, when the magnetic
+field is adapted so that a phase boundary is crossed.",0709.0463v1
+2007-09-07,Linear response subordination to intermittent energy release in off-equilibrium aging dynamics,"The interpretation of experimental and numerical data describing
+off-equilibrium aging dynamics crucially depends on the connection between
+spontaneous and induced fluctuations. The hypothesis that linear response
+fluctuations are statistically subordinated to irreversible outbursts of
+energy, so-called quakes, leads to predictions for averages and fluctuations
+spectra of physical observables in reasonable agreement with experimental
+results [see e.g. Sibani et al., Phys. Rev. B74:224407, 2006]. Using
+simulational data from a simple but representative Ising model with plaquette
+interactions, direct statistical evidence supporting the hypothesis is
+presented and discussed in this work.
+  A strict temporal correlation between quakes and intermittent magnetization
+fluctuations is demonstrated. The external magnetic field is shown to bias the
+pre-existent intermittent tails of the magnetic fluctuation distribution, with
+little or no effect on the Gaussian part of the latter. Its impact on energy
+fluctuations is shown to be negligible.
+  Linear response is thus controlled by the quakes and inherits their temporal
+statistics. These findings provide a theoretical basis for analyzing
+intermittent linear response data from aging system in the same way as thermal
+energy fluctuations, which are far more difficult to measure.",0709.1085v2
+2007-09-11,Finite Temperature Large N Gauge Theory with Quarks in an External Magnetic Field,"Using a ten dimensional dual string background, we study aspects of the
+physics of finite temperature large N four dimensional SU(N) gauge theory,
+focusing on the dynamics of fundamental quarks in the presence of a background
+magnetic field. At vanishing temperature and magnetic field, the theory has N=2
+supersymmetry, and the quarks are in hypermultiplet representations. In a
+previous study, similar techniques were used to show that the quark dynamics
+exhibit spontaneous chiral symmetry breaking. In the present work we begin by
+establishing the non-trivial phase structure that results from finite
+temperature. We observe, for example, that above the critical value of the
+field that generates a chiral condensate spontaneously, the meson melting
+transition disappears, leaving only a discrete spectrum of mesons at any
+temperature. We also compute several thermodynamic properties of the plasma.",0709.1547v2
+2007-10-17,Generation of Magnetic Field by Combined Action of Turbulence and Shear,"The feasibility of a mean-field dynamo in nonhelical turbulence with
+superimposed linear shear is studied numerically in elongated shearing boxes.
+Exponential growth of magnetic field at scales much larger than the outer scale
+of the turbulence is found. The charateristic scale of the field is l_B ~
+S^{-1/2} and growth rate is gamma ~ S, where S is the shearing rate. This newly
+discovered shear dynamo effect potentially represents a very generic mechanism
+for generating large-scale magnetic fields in a broad class of astrophysical
+systems with spatially coherent mean flows.",0710.3359v2
+2007-10-18,Toward theory of quantum Hall effect in graphene,"We analyze a gap equation for the propagator of Dirac quasiparticles and
+conclude that in graphene in a magnetic field, the order parameters connected
+with the quantum Hall ferromagnetism dynamics and those connected with the
+magnetic catalysis dynamics necessarily coexist (the latter have the form of
+Dirac masses and correspond to excitonic condensates). This feature of graphene
+could lead to important consequences, in particular, for the existence of
+gapless edge states. Solutions of the gap equation corresponding to recently
+experimentally discovered novel plateaus in graphene in strong magnetic fields
+are described.",0710.3527v2
+2007-11-10,SU(2) Symmetry and Conservation of Helicity for a Dirac Particle in a Static Magnetic Field at First Order,"We investigate the spin dynamics and the conservation of helicity in the
+first order $S-$matrix of a Dirac particle in any static magnetic field. We
+express the dynamical quantities using a coordinate system defined by the three
+mutually orthogonal vectors; the total momentum
+$\mathbf{k}=\mathbf{p_f}+\mathbf{p_i}$, the momentum transfer
+$\mathbf{q}=\mathbf{p_f-p_i}$, and $\mathbf{l}=\mathbf{k\times q}$. We show
+that this leads to an alternative symmetric description of the conservation of
+helicity in a static magnetic field at first order. In particular, we show that
+helicity conservation in the transition can be viewed as the invariance of the
+component of the spin along $\mathbf{k}$, and the flipping of its component
+along $\mathbf{q}$, just as what happens to the momentum vector of a ball
+bouncing off a wall. We also derive a ""plug and play"" formula for the
+transition matrix element where the only reference to the specific field
+configuration, and the incident and outgoing momenta is through the kinematical
+factors multiplying a general matrix element that is independent of the
+specific vector potential present.",0711.1583v2
+2007-11-27,Nonequilibrium interacting electrons in a ferromagnet,"Dynamics of the magnetization in ferromagnets is examined in the presence of
+transport electrons allowing the latter to interact. It is found that the
+existence of inhomogeneities such as domain wall (DW) structures, leads to
+changes that affect the dynamical structure of the equations of motion for the
+magnetization. Only in the limit of uniform magnetizations or sufficiently wide
+DW's, the equations of motion maintain the form they have in the noninteracting
+case. In this limit, results like the spin torques, the Gilbert parameter, and
+the DW velocities become renormalized. However the length scale that defines
+such a limit depends on the strength of the interaction. It is shown that if
+large ferromagnetic fluctuations exist in the metallic band then the range for
+which conformity with the noninteracting case holds extends to the limit of
+arbitrarily narrow DW's.",0711.4170v2
+2007-12-10,Chirality tunneling and quantum dynamics for domain walls in mesoscopic ferromagnets,"We studied the quantum dynamics of ferromagnetic domain walls (topological
+kink-type solitons) in one dimensional ferromagnetic spin chains. We show that
+the tunneling probability does not depend on the number of spins in a domain
+wall; thus, this probability can be large even for a domain wall containing a
+large number of spins. We also predict that there is a strong interplay between
+the tunneling of a wall from one lattice site to another (tunneling of the kink
+coordinate) and the tunneling of the kink topological charge (so-called
+chirality). Both of these elementary processes are suppressed for kinks in
+one-dimensional ferromagnets with half-integer spin. The dispersion law (i.e.,
+the domain wall energy versus momentum) is essentially different for chains
+with either integer or half-integer spins. The predicted quantum effects could
+be observed for mesoscopic magnetic structures, e.g., chains of magnetic
+clusters, large-spin molecules, or nanosize magnetic dots.",0712.1392v1
+2008-01-14,Hartmann flow with Braginsky viscosity: a test problem for intercluster plasma,"We consider a Hartmann layer, stationary flow of a viscose and resistive
+fluid between two plates with superimposed transverse magnetic field, in the
+limit of gyrotropic plasma, when viscosity across the field is strongly
+suppressed. For zero cross-field viscosity, the problem is not well posed,
+since viscosity then vanishes on the boundaries and in the middle of the layer,
+where there is no longitudinal field. An additional arbitrarily small isotropic
+viscosity allows one to find magnetic field and velocity profiles which are
+independent of this viscosity floor and different from flows with isotropic
+viscosity. Velocity sharply rises in a thin boundary layer, which thickness
+depends both on the Hartmann number and on the Lundquist number of the flow.
+  The implication of the work is that, in simulating ICM dynamics it is
+imperative to use numerical schemes which take into account anisotropic
+viscosity. Although magnetic fields are dynamically subdominant in the ICM they
+do determine its the dissipative properties, stability of embedded structures
+and the transition to turbulence.",0801.2166v1
+2008-01-28,Dynamical correlations in the spin-half two-channel Kondo model,"Dynamical correlations of various local operators are studied in the
+spin-half two-channel Kondo (2CK) model in the presence of channel anisotropy
+or external magnetic field. A conformal field theory-based scaling approach is
+used to predict the analytic properties of various spectral functions in the
+vicinity of the two-channel Kondo fixed point. These analytical results compare
+well with highly accurate density matrix numerical renormalization group
+results. The universal cross-over functions interpolating between
+channel-anisotropy or magnetic field-induced Fermi liquid regimes and the
+two-channel Kondo, non-Fermi liquid regimes are determined numerically. The
+boundaries of the real 2CK scaling regime are found to be rather restricted,
+and to depend both on the type of the perturbation and on the specific operator
+whose correlation function is studied. In a small magnetic field, a universal
+resonance is observed in the local fermion's spectral function. The dominant
+superconducting instability appears in the composite superconducting channel.",0801.4272v1
+2008-02-16,"Hysteresis, transient oscillations, and nonhysteretic switching in resonantly modulated large-spin systems","We study the classical dynamics of resonantly modulated large-spin systems in
+a strong magnetic field. We show that these systems have special symmetry. It
+leads to characteristic nonlinear effects. They include abrupt switching
+between magnetization branches with varying modulating field without hysteresis
+and a specific pattern of switching in the presence of multistability and
+hysteresis. Along with steady forced vibrations the transverse spin components
+can display transient vibrations at a combination of the Larmor frequency and a
+slower frequency determined by the anisotropy energy. The analysis is based on
+a microscopic theory that takes into account relaxation mechanisms important
+for single-molecule magnets and other large-spin systems. We find how the
+Landau-Lifshitz model should be modified in order to describe the classical
+spin dynamics. The occurrence of transient oscillations depends on the
+interrelation between the relaxation parameters.",0802.2304v1
+2008-04-14,Quantum critical dynamics of a S = 1/2 antiferromagnetic Heisenberg chain studied by 13C-NMR spectroscopy,"We present a 13C-NMR study of the magnetic field driven transition to
+complete polarization of the S=1/2 antiferromagnetic Heisenberg chain system
+copper pyrazine dinitrate Cu(C_4H_4N_2)(NO_3)_2 (CuPzN). The static local
+magnetization as well as the low-frequency spin dynamics, probed via the
+nuclear spin-lattice relaxation rate 1/T_1, were explored from the low to the
+high field limit and at temperatures from the quantum regime (k_B T << J) up to
+the classical regime (k_B T >> J). The experimental data show very good
+agreement with quantum Monte Carlo calculations over the complete range of
+parameters investigated. Close to the critical field, as derived from static
+experiments, a pronounced maximum in 1/T_1 is found which we interpret as the
+finite-temperature manifestation of a diverging density of zero-energy magnetic
+excitations at the field-driven quantum critical point.",0804.2170v2
+2008-06-22,"Electronic structures of ternary iron arsenides AFe$_2$As$_2$ (A=Ba, Ca, or Sr)","We have studied the electronic and magnetic structures of the ternary iron
+arsenides AFe$_2$As$_2$ (A = Ba, Ca, or Sr) using the first-principles density
+functional theory. The ground states of these compounds are in a collinear
+antiferromagnetic order, resulting from the interplay between the nearest and
+the next-nearest neighbor superexchange antiferromagnetic interactions bridged
+by As $4p$ orbitals. The correction from the spin-orbit interaction to the band
+structure is small. The pressure can reduce dramatically the magnetic moment
+and diminish the collinear antiferromagnetic order. Based on the calculations,
+we propose that the low energy dynamics of these materials is described
+effectively by a $t-J_H-J_1-J_2$-type model.",0806.3526v3
+2008-06-24,Spin Glass Order Induced by Dynamic Frustration,"Spin glasses are systems whose magnetic moments freeze at low temperature
+into random orientations without long-range order. It is generally accepted
+that both frustration and disorder are essential ingredients in all spin
+glasses, so it was surprising that PrAu2Si2, a stoichiometric compound with a
+well-ordered crystal structure, was reported to exhibit spin glass freezing. In
+this article, we report on inelastic neutron scattering measurements of the
+crystal field excitations, which show that PrAu2Si2 has a singlet ground state
+and that the exchange coupling is very close to the critical value to induce
+magnetic order. We propose that spin glass freezing results from dynamic
+fluctuations of the crystal field levels that destabilize the induced moments
+and frustrate the development of long-range magnetic correlations. This novel
+mechanism for producing a frustrated ground state could provide a method of
+testing the concept of `avoided criticality' in glassy systems.",0806.3935v1
+2008-06-24,Excitability in the vicinity of a saddle-node bifurcation: a mechanism for reversals,"We present a new mechanism for oscillatory or random reversals of the
+magnetic field that occur from a stationary dynamo state. The basic ingredient
+is the existence of two nearly critical dynamo eigenmodes, a stable and an
+unstable one, that collide during a saddle-node bifurcation. Above this
+bifurcation, a finite amplitude limit cycle is generated. In the neighbourhood
+of the bifurcation, even a small amount of turbulent fluctuations is enough to
+generate random reversals of the magnetic field. When the two competing
+eigenmodes have different symmetries, this scenario requires a broken symmetry
+of the flow that generates the dynamo. This is in good agreement with the
+observations of the VKS experiment. It can also explain the dynamics of
+planetary or stellar magnetic fields and can be used to understand reversals of
+large scale flows that often develop on a turbulent background.",0806.3937v2
+2008-07-31,Optical probing of spin fluctuations of a single magnetic atom,"We analyzed the photoluminescence intermittency generated by a single
+paramagnetic spin localized in an individual semiconductor quantum dot. The
+statistics of the photons emitted by the quantum dot reflect the quantum
+fluctuations of the localized spin interacting with the injected carriers.
+Photon correlation measurements which are reported here reveal unique
+signatures of these fluctuations. A phenomenological model is proposed to
+quantitatively describe these observations, allowing a measurement of the spin
+dynamics of an individual magnetic atom at zero magnetic field. These results
+demonstrate the existence of an efficient spin relaxation channel arising from
+a spin-exchange with individual carriers surrounding the quantum dot. A
+theoretical description of a spin-flip mechanism involving spin exchange with
+surrounding carriers gives relaxation times in good agreement with the measured
+dynamics.",0807.5002v1
+2008-09-17,Fermi condensates for dynamic imaging of electro-magnetic fields,"Ultracold gases provide micrometer size atomic samples whose sensitivity to
+external fields may be exploited in sensor applications. Bose-Einstein
+condensates of atomic gases have been demonstrated to perform excellently as
+magnetic field sensors \cite{Wildermuth2005a} in atom chip
+\cite{Folman2002a,Fortagh2007a} experiments. As such, they offer a combination
+of resolution and sensitivity presently unattainable by other methods
+\cite{Wildermuth2006a}. Here we propose that condensates of Fermionic atoms can
+be used for non-invasive sensing of time-dependent and static magnetic and
+electric fields, by utilizing the tunable energy gap in the excitation spectrum
+as a frequency filter. Perturbations of the gas by the field create both
+collective excitations and quasiparticles. Excitation of quasiparticles
+requires the frequency of the perturbation to exceed the energy gap. Thus, by
+tuning the gap, the frequencies of the field may be selectively monitored from
+the amount of quasiparticles which is measurable for instance by
+RF-spectroscopy. We analyse the proposed method by calculating the
+density-density susceptibility, i.e. the dynamic structure factor, of the gas.
+We discuss the sensitivity and spatial resolution of the method which may, with
+advanced techniques for quasiparticle observation \cite{Schirotzek2008a}, be in
+the half a micron scale.",0809.2959v1
+2008-09-20,Mottness scenario for non-Fermi liquid behavior in the periodic Anderson model within Dynamical Mean Field Theory,"We study the Mott metal-insulator transition in the Periodic Anderson Model
+within Dynamical Mean Field Theory (DMFT). Near the quantum transition, we find
+a non-Fermi liquid metallic state down to a vanishing temperature scale. We
+identify the origin of the non-Fermi liquid behavior as due to magnetic
+scattering of the doped carriers by the localized moments. The non-Fermi liquid
+state can be tuned by either doping or external magnetic field. Our results
+show that the coupling to spatial magnetic fluctuations (absent in DMFT) is not
+a prerequisite to realize a non-Fermi liquid scenario for heavy fermion
+systems.",0809.3520v1
+2008-09-30,Investigation of the magnetic fluctuations in Tb$_2$Sn$_2$O$_7$ ordered spin ice by high resolution energy-resolved neutron scattering,"We have studied magnetically frustrated Tb$_2$Sn$_2$O$_7$ by neutron
+diffraction and high resolution energy-resolved neutron scattering. At 0.1 K,
+we observe short range magnetic correlations with a typical scale of 4 \AA,
+close to the near neighbor distance between Tb$^{3+}$ ions. %(3.686 \AA), This
+short range order coexists with ferromagnetic correlations and long range spin
+ice order at the scales of 18 and 190 \AA, respectively. Spin dynamics was
+investigated at a time scale down to 10$^{-9}$s, by energy-resolved experiments
+on a backscattering spectrometer. We observe a freezing of the spin dynamics
+for all length-scales, with a strong slowing down of the spin fluctuations when
+long range order settles in. We discuss the spin fluctuations remaining in the
+ground state in comparison with previous data obtained by muon spectroscopy.",0809.5241v1
+2008-10-20,Magnetically-induced buckling of a whirling conducting rod with applications to electrodynamic space tethers,"We study the effect of a magnetic field on the behaviour of a slender
+conducting elastic structure, motivated by stability problems of electrodynamic
+space tethers. Both statical (buckling) and dynamical (whirling) instability
+are considered and we also compute post-buckling configurations. The equations
+used are the geometrically exact Kirchhoff equations. Magnetic buckling of a
+welded rod is found to be described by a surprisingly degenerate bifurcation,
+which is unfolded when both transverse anisotropy of the rod and angular
+velocity are considered. By solving the linearised equations about the (quasi-)
+stationary solutions we find various secondary instabilities. Our results are
+relevant for current designs of electrodynamic space tethers and potentially
+for future applications in nano- and molecular wires.",0810.3668v1
+2008-10-29,Three-Layer Magnetoconvection,"It is believed that some stars have two or more convection zones in close
+proximity near to the stellar photosphere. These zones are separated by
+convectively stable regions that are relatively narrow. Due to the close
+proximity of these regions it is important to construct mathematical models to
+understand the transport and mixing of passive and dynamic quantities. One key
+quantity of interest is a magnetic field, a dynamic vector quantity, that can
+drastically alter the convectively driven flows, and have an important role in
+coupling the different layers. In this paper we present the first investigation
+into the effect of an imposed magnetic field in such a geometry. We focus our
+attention on the effect of field strength and show that, while there are some
+similarities with results for magnetic field evolution in a single layer, new
+and interesting phenomena are also present in a three layer system.",0810.5279v2
+2008-12-22,Criterion for transformation of transverse domain wall to vortex or antivortex wall in soft magnetic thin-film nanostripes,"We report on the criterion for the dynamic transformation of the internal
+structure of moving domain walls (DWs) in soft magnetic thin-film nanostripes
+above the Walker threshold field, Hw. In order for the process of
+transformation from transverse wall (TW) to vortex wall (VW) or antivortex wall
+(AVW) occurs, the edge-soliton core of the TW-type DW should grow sufficiently
+to the full width at half maximum of the out-of-plane magnetizations of the
+core area of the stabilized vortex (or antivortex) by moving inward along the
+transverse (width) direction. Upon completion of the nucleation of the vortex
+(antivortex) core, the VW (AVW) is stabilized, and then its core accompanies
+the gyrotropic motion in a potential well (hill) of a given nanostripe. Field
+strengths exceeding the Hw, which is the onset field of DW velocity breakdown,
+are not sufficient but necessary conditions for dynamic DW transformation.",0812.4083v1
+2009-01-13,Vortex-Antivortex annihilation dynamics in a square mesoscopic superconducting cylinder,"The dynamics of the annihilation of a vortex-antivortex pair is investigated.
+The pair is activated magnetically during the run of a simulated hysteresis
+loop on a square mesoscopic superconducting cylinder with an antidot inserted
+at its center. We study the nucleation of vortices and antivortices by first
+increasing the magnetic field, applied parallel to the axis of the sample, from
+zero until the first vortex is created. A further increase of the field pulls
+the vortex in, until it reaches the antidot. As the polarity of the field is
+reversed, an antivortex enters the scene, travels toward the center of the
+sample and eventually the pair is annihilated. Depending on the sample size,
+its temperature, and Ginzburg-Landau parameter, the vortex-antivortex encounter
+takes place at the antidot or at the superconducting sea around it. The
+position and velocity of the vortex and antivortex singularities were evaluated
+as a function of time. The current density, magnetization and order parameter
+topology were also calculated.",0901.1829v1
+2009-01-19,Hysteresis and noise in ferromagnetic materials with parallel domain walls,"We investigate dynamic hysteresis and Barkhausen noise in ferromagnetic
+materials with a huge number of parallel and rigid Bloch domain walls.
+Considering a disordered ferromagnetic system with strong in-plane uniaxial
+anisotropy and in-plane magnetization driven by an external magnetic field, we
+calculate the equations of motion for a set of coupled domain walls,
+considering the effects of the long-range dipolar interactions and disorder. We
+derive analytically an expression for the magnetic susceptivity, related to the
+effective demagnetizing factor, and show that it has a logarithmic dependence
+on the number of domains. Next, we simulate the equations of motion and study
+the effect of the external field frequency and the disorder on the hysteresis
+and noise properties. The dynamic hysteresis is very well explained by means of
+the loss separation theory.",0901.2918v1
+2009-05-19,The Effect of Quantized Magnetic Flux Lines on the Dynamics of Superfluid Neutron Star Cores,"We investigate dynamical coupling timescales of a neutron star's superfluid
+core, taking into account the interactions of quantized neutron vortices with
+quantized flux lines of the proton superconductor in addition to the previously
+considered scattering of the charged components against the spontaneous
+magnetization of the neutron vortex line. We compare the cases where vortex
+motion is constrained in different ways by the array of magnetic flux tubes
+associated with superconducting protons. This includes absolute pinning to and
+creep across a uniform array of flux lines. The effect of a toroidal
+arrangement of flux lines is also considered. The inclusion of a uniform array
+of flux tubes in the neutron star core significantly decreases the timescale of
+coupling between the neutron and proton fluid constituents in all cases. For
+the toroidal component, creep response similar to that of the inner crust
+superfluid is possible.",0905.3097v1
+2009-05-22,Some Unusual Properties of Turbulent Convection and Dynamos in Rotating Spherical Shells,"The dynamics of convecting fluids in rotating spherical shells is governed at
+Prandtl numbers of the order unity by the interaction between differential
+rotation and roll-like convection eddies. While the differential rotation is
+driven by the Reynolds stresses of the eddies, its shearing action inhibits
+convection and causes phenomena such as localized convection and turbulent
+relaxation oscillations. The response of the system is enriched in the case of
+dynamo action. Lorentz forces may brake either entirely or partially the
+geostrophic differential rotation and give rise to two rather different dynamo
+states. Bistability of turbulent dynamos exists for magnetic Prandtl numbers of
+the order unity. While the ratios between mean magnetic and kinetic energies
+differ by a factor of 5 or more for the two dynamo states, the mean convective
+heat transports are nearly the same. They are much larger than in the absence
+of a magnetic field.",0905.3723v1
+2009-06-04,Magnetic trapping of ultracold Rydberg atoms in low angular momentum states,"We theoretically investigate the quantum properties of nS, nP, and nD Rydberg
+atoms in a magnetic Ioffe-Pritchard trap. In particular, it is demonstrated
+that the two-body character of Rydberg atoms significantly alters the trapping
+properties opposed to point-like particles with identical magnetic moment.
+Approximate analytical expressions describing the resulting Rydberg trapping
+potentials are derived and their validity is confirmed for experimentally
+relevant field strengths by comparisons to numerical solutions of the
+underlying Schroedinger equation. In addition to the electronic properties, the
+center of mass dynamics of trapped Rydberg atoms is studied. In particular, we
+analyze the influence of a short-time Rydberg excitation, as required by
+certain quantum-information protocols, on the center of mass dynamics of
+trapped ground state atoms. A corresponding heating rate is derived and the
+implications for the purity of the density matrix of an encoded qubit are
+investigated.",0906.0946v2
+2009-06-16,Phase Diagram and Spin Dynamics in Volborthite with a Distorted Kagome Lattice,"We report 51V-NMR study on a high-quality powder sample of volborthite
+Cu3V2O7(OH)2/2H2O, a spin-1/2 Heisenberg antiferromagnet on a distorted kagome
+lattice formed by isosceles triangles. In the magnetic fields below 4.5 T, a
+sharp peak in the nuclear spin-lattice relaxation rate 1/T1 accompanied with
+line broadening revealed a magnetic transition near 1 K. The low temperature
+phase shows anomalies such as a Lorentzian line shape, a 1/T1 propto T behavior
+indicating dense low energy excitations, and a large spin-echo decay rate 1/T2
+pointing to unusually slow fluctuations. Another magnetic phase appears above
+4.5 T with less anomalous spectral shape and dynamics.",0906.2846v2
+2009-06-30,Low-Prandtl-number Bénard-Marangoni convection in a vertical magnetic field,"The effect of a homogeneous magnetic field on surface-tension-driven
+B\'{e}nard convection is studied by means of direct numerical simulations. The
+flow is computed in a rectangular domain with periodic horizontal boundary
+conditions and the free-slip condition on the bottom wall using a
+pseudospectral Fourier-Chebyshev discretization. Deformations of the free
+surface are neglected. Two- and three-dimensional flows are computed for either
+vanishing or small Prandtl number, which are typical of liquid metals. The main
+focus of the paper is on a qualitative comparison of the flow states with the
+non-magnetic case, and on the effects associated with the possible
+near-cancellation of the nonlinear and pressure terms in the momentum equations
+for two-dimensional rolls. In the three-dimensional case, the transition from a
+stationary hexagonal pattern at the onset of convection to three-dimensional
+time-dependent convection is explored by a series of simulations at zero
+Prandtl number.",0906.5466v1
+2009-07-04,One-dimensional magnetic fluctuations in the spin-2 triangular lattice α-NaMnO2,"The S=2 anisotropic triangular lattice alpha-NaMnO2 is studied by neutron
+inelastic scattering. Antiferromagnetic order occurs at T ~ 45 K with opening
+of a spin gap. The spectral weight of the magnetic dynamics above the gap
+(Delta ~ 7.5 meV) has been analysed by the single-mode approximation. Excellent
+agreement with the experiment is achieved when a dominant exchange interaction
+(|J|/k_B ~ 73 K), along the monoclinic b-axis and a sizeable easy-axis magnetic
+anisotropy (|D|/k_B ~ 3 K) are considered. Despite earlier suggestions for
+two-dimensional spin interactions, the dynamics illustrate strongly coupled
+antiferromagnetic S=2 chains and cancellation of the interchain exchange due to
+the lattice topology. alpha-NaMnO2 therefore represents a model system where
+the geometric frustration is resolved through the lowering of the
+dimensionality of the spin interactions.",0907.0742v1
+2009-10-03,Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+,"Frequency and dc magnetic field dependences of dynamic susceptibility in
+diluted paramagnets LiYF$_4$:Ho$^{3+}$ have been measured at liquid helium
+temperatures in the ac and dc magnetic fields parallel to the symmetry axis of
+a tetragonal crystal lattice. Experimental data are analyzed in the framework
+of microscopic theory of relaxation rates in the manifold of 24
+electron-nuclear sublevels of the lowest non-Kramers doublet and the first
+excited singlet in the Ho$^{3+}$ ground multiplet $^5I_8$ split by the crystal
+field of S$_4$ symmetry. The one-phonon transition probabilities were computed
+using electron-phonon coupling constants calculated in the framework of
+exchange charge model and were checked by optical piezospectroscopic
+measurements. The specific features observed in field dependences of the in-
+and out-of-phase susceptibilities (humps and dips, respectively) at the
+crossings (anti-crossings) of the electron-nuclear sublevels are well
+reproduced by simulations when the phonon bottleneck effect and the cross-spin
+relaxation are taken into account.",0910.0519v1
+2009-10-09,Anomalous Hanle Effect in Quantum Dots : Evidence for Strong Dynamical Nuclear Polarization in Transverse Magnetic Field,"Hanle effect is ubiquitous in the study of spin-related phenomena and has
+been used to determine spin lifetime, precession and transport in
+semiconductors. Here, we report an experimental observation of anomalous Hanle
+effect in individual self-assembled InAs/GaAs quantum dots where we find that a
+sizeable photo-created electron spin polarization can be maintained in
+transverse fields as high as 1T until it abruptly collapses. The striking
+broadening of the Hanle curve by a factor of ~20 and its bistability upon
+reversal of the magnetic sweep direction points to a novel dynamical nuclear
+spin polarization mechanism where the effective nuclear magnetic field
+compensates the transverse applied field. This interpretation is further
+supported by the measurement of actual electron Zeeman splitting which exhibits
+an abrupt increase at the Hanle curve collapse. Strong inhomogeneous
+quadrupolar interactions typical for strained quantum dots are likely to play a
+key role in polarizing nuclear spins perpendicular to the optically injected
+spin orientation.",0910.1744v1
+2009-10-28,Study of the ground state properties of $LiHo_xY_{1-x}F_4$ using $μ$SR,"$LiHo_xY_{1-x}F_4$ is an insulating system where the magnetic Ho$^{3+}$ ions
+have an Ising character, and interact mainly through magnetic dipolar fields.
+We used the muon spin relaxation technique to study the nature of the ground
+state for samples with x=0.25, 0.12, 0.08, 0.045 and 0.018. In contrast with
+some previous works, we have not found any signature of canonical spin glass
+behavior down to $\approx$15mK. Instead, below $\approx$300mK we observed
+dynamic magnetism characterized by a single correlation time with a temperature
+independent fluctuation rate. We observed that this low temperature fluctuation
+rate increases with x up to 0.08, above which it levels off. The 300mK energy
+scale corresponds to the Ho3+ hyperfine interaction strength, suggesting that
+the hyperfine interaction may be intimately involved with the spin dynamics in
+this system.",0910.5486v1
+2009-12-10,Spin dynamics in the geometrically frustrated multiferroic CuCrO2,"The spin dynamics of the geometrically frustrated triangular antiferromagnet
+multiferroic CuCrO2 have been mapped out using inelastic neutron scattering.
+The relevant spin Hamiltonian parameters modelling the incommensurate modulated
+helicoid have been determined, and correspond to antiferromagnetic nearest and
+next-nearest neighbour interactions in the ab plane, with a strong planar
+anisotropy. The weakly dispersive excitation along c reflects the essentially
+two-dimensional character of the magnetic interactions and according to
+classical energy calculations it is weakly ferromagnetic. Our results clearly
+point out the relevance of the balance between a ferromagnetic coupling between
+adjacent planes and a weakly antiferromagnetic next-nearest neighbour
+interaction in stabilising the three-dimensional ferroelectric magnetic order
+in CuCrO2. This novel insight on the interplay between magnetic interactions in
+CuCrO2 should provide a useful basis in the design of new delafossite-based
+multiferroic materials.",0912.1962v1
+2009-12-23,Nonexistence of classical diamagnetism and nonequilibrium fluctuation theorems for charged particles on a curved surface,"We show that the classical Langevin dynamics for a charged particle on a
+closed curved surface in a time-independent magnetic field leads to the
+canonical distribution in the long time limit. Thus the Bohr-van Leeuwen
+theorem holds even for a finite system without any boundary and the average
+magnetic moment is zero. This is contrary to the recent claim by Kumar and
+Kumar (EPL, {\bf 86} (2009) 17001), obtained from numerical analysis of
+Langevin dynamics, that a classical charged particle on the surface of a sphere
+in the presence of a magnetic field has a nonzero average diamagnetic moment.
+We extend our analysis to a many-particle system on a curved surface and show
+that the nonequilibrium fluctuation theorems also hold in this geometry.",0912.4697v2
+2009-12-25,Doping Dependence of Spin Dynamics in Electron-Doped Ba(Fe1-xCox)2As2,"The spin dynamics in single crystal, electron-doped Ba(Fe1-xCox)2As2 has been
+investigated by inelastic neutron scattering over the full range from undoped
+to the overdoped regime. We observe damped magnetic fluctuations in the normal
+state of the optimally doped compound (x=0.06) that share a remarkable
+similarity with those in the paramagnetic state of the parent compound (x=0).
+In the overdoped superconducting compound (x=0.14), magnetic excitations show a
+gap-like behavior, possibly related to a topological change in the hole Fermi
+surface (Lifshitz transition), while the imaginary part of the spin
+susceptibility prominently resembles that of the overdoped cuprates. For the
+heavily overdoped, non-superconducting compound (x=0.24) the magnetic
+scattering disappears, which could be attributed to the absence of a hole
+Fermi-surface pocket observed by photoemission.",0912.4945v2
+2010-01-18,Dynamical nuclear spin polarization induced by electronic current through double quantum dots,"We analyze electron spin relaxation in electronic transport through
+coherently coupled double quantum dots in the spin blockade regime. In
+particular, we focus on hyperfine interaction as the spin relaxation mechanism.
+We pay special attention to the effect of the dynamical nuclear spin
+polarization induced by the electronic current on the nuclear environment. We
+discuss the behaviour of the electronic current and the induced nuclear spin
+polarization versus an external magnetic field for different hyperfine coupling
+intensities and interdot tunnelling strengths. We take into account, for each
+magnetic field, all hyperfine mediated spin relaxation processes coming from
+the different opposite spin levels approaches. We find that the current as a
+function of the external magnetic field shows a peak or a dip, and that the
+transition from a current dip to a current peak behaviour is obtained by
+decreasing the hyperfine coupling or by increasing the interdot tunnelling
+strength. We give a physical picture in terms of the interplay between the
+electrons tunnelling out of the double quantum dot and the spin flip processes
+due to the nuclear environment.",1001.3104v2
+2010-02-16,Dynamic Nuclear Polarization and Nuclear Magnetic Resonance in the Simplest Pseudospin Quantum Hall Ferromagnet,"We present dynamic nuclear polarization (DNP) in the simplest pseudospin
+quantum Hall ferromagnet (QHF) of an InSb two-dimensional electron gas with a
+large g factor using tilted magnetic fields. The DNP-induced amplitude change
+of a resistance spike of the QHF at large current enables observation of the
+resistively detected nuclear magnetic resonance of the high nuclear spin
+isotope 115In with nine quadrupole splittings. Our results demonstrate the
+importance of domain structures in the DNP process. The nuclear spin relaxation
+time T1 in this QHF was relatively short (~ 120 s), and almost temperature
+independent.",1002.3087v3
+2010-06-28,Creating artificial magnetic fields for cold atoms by photon-assisted tunneling,"This paper proposes a simple setup for introducing an artificial magnetic
+field for neutral atoms in 2D optical lattices. This setup is based on the
+phenomenon of photon-assisted tunneling and involves a low-frequency periodic
+driving of the optical lattice. This low-frequency driving does not affect the
+electronic structure of the atom and can be easily realized by the same means
+which employed to create the lattice. We also address the problem of detecting
+this effective magnetic field. In particular, we study the center of mass
+wave-packet dynamics, which is shown to exhibit certain features of cyclotron
+dynamics of a classical charged particle.",1006.5270v2
+2010-08-21,Dynamical Corrections to Spin Wave Excitations in Quantum Wells due to Coulomb Interactions and Magnetic Ions,"We have measured dispersions of spin-flip waves and spin-flip single-particle
+excitations of a spin polarized two-dimensional electron gas in a CdMnTe
+quantum well using resonant Raman scattering. We find the energy of the
+spin-flip wave to be below the spin-flip single particle excitation continuum,
+a contradiction to the theory of spin waves in diluted magnetic semiconductors
+put forth in [Phys. Rev. B 70, 045205 (2004)]. We show that the inclusion of
+terms accounting for the Coulomb interaction between carriers in the spin wave
+propagator leads to an agreement with our experimental results. The dominant
+Coulomb contribution leads to an overall red shift of the mixed electron-Mn
+spin modes while the dynamical coupling between Mn ions results in a small blue
+shift. We provide a simulated model system which shows the reverse situation
+but at an extremely large magnetic field.",1008.3663v1
+2010-09-17,Coronal mass ejections as expanding force-free structures,"We mode Solar coronal mass ejections (CMEs) as expanding force-fee magnetic
+structures and find the self-similar dynamics of configurations with spatially
+constant \alpha, where {\bf J} =\alpha {\bf B}, in spherical and cylindrical
+geometries, expanding spheromaks and expanding Lundquist fields
+correspondingly. The field structures remain force-free, under the conventional
+non-relativistic assumption that the dynamical effects of the inductive
+electric fields can be neglected. While keeping the internal magnetic field
+structure of the stationary solutions, expansion leads to complicated internal
+velocities and rotation, induced by inductive electric field. The structures
+depends only on overall radius R(t) and rate of expansion \dot{R}(t) measured
+at a given moment, and thus are applicable to arbitrary expansion laws. In case
+of cylindrical Lundquist fields, the flux conservation requires that both axial
+and radial expansion proceed with equal rates. In accordance with observations,
+the model predicts that the maximum magnetic field is reached before the
+spacecraft reaches the geometric center of a CME.",1009.3463v2
+2010-09-29,Dynamical polarization of monolayer graphene in a magnetic field,"The one-loop dynamical polarization function of graphene in an external
+magnetic field is calculated as a function of wavevector and frequency at
+finite chemical potential, temperature, band gap, and width of Landau levels.
+The exact analytic result is given in terms of digamma functions and
+generalized Laguerre polynomials, and has the form of double sum over Landau
+levels. Various limits (static, clean, etc) are discussed. The Thomas-Fermi
+inverse length $q_F$ of screening of the Coulomb potential is found to be an
+oscillating function of a magnetic field and a chemical potential. At zero
+temperature and scattering rate, it vanishes when the Fermi level lies between
+the Landau levels.",1009.5980v1
+2011-01-27,A pseudogap term in the magnetic response of the cuprate superconductors,"We combine neutron scattering (INS) and NMR/NQR nuclear spin lattice
+relaxation rate data to deduce the existence of a new contribution to the
+magnetic response (dynamic susceptibility) in cuprate superconductors. This
+contribution, which has yet to be observed with INS, is shown to embody the
+magnetic pseudogap effects. As such, it explains the long-standing puzzle of
+pseudogap effects missing from cuprate INS data, dominated by stripe
+fluctuations, for the dynamic susceptibility at low energies. For
+La_(1.86)Sr_(0.14)CuO_(4) and YBa_(2)Ba_(3)O_(6.5), the new term is the chief
+contributor to nuclear spin lattice relaxation at T >> T_(c).",1101.5360v1
+2011-02-08,Dynamics of the Magnetic Susceptibility Deep in the Coulomb Phase of the Dipolar Spin Ice Material Ho2Ti2O7,"Low temperature measurements of the ac magnetic susceptibility along the
+[110] direction of a single crystal of the dipolar spin ice material Ho2Ti2O7,
+in zero static field, are presented. While behavior that is qualitatively
+consistent with previous work on Ho2Ti2O7 and the related material Dy2Ti2O7 is
+observed, this work extends measurements to appreciably lower temperatures and
+frequencies. In the freezing regime, below 1 K, the dynamics are found to be
+temperature activated, thus well described by an Arrhenius law with an
+activation energy close to 6J_eff, a result that is not easily explained with
+the current model of magnetic monopole excitations in dipolar spin ice. The
+form and temperature dependence of the ac susceptibility spectra are found to
+be nontrivial and distinct from standard glassy relaxation. Particular
+attention has been paid to correcting for the demagnetization effect, which is
+quite significant in these materials and has important, even qualitative,
+effects on the susceptibility spectra.",1102.1703v2
+2011-02-16,Magnetization dynamics and Majorana fermions in ferromagnetic Josephson junctions along the quantum spin Hall edge,"We investigate the interplay between ferromagnetic and superconducting order
+at the edge of a quantum spin Hall insulator. Using complementary analytical
+and self-consistent numerical approaches, we study a ferromagnetic Josephson
+junction and show how the direct coupling between magnetism and the
+superconducting U(1) phase gives rise to several unusual phenomena which
+distinguishes the present system from its non-topological equivalent. In
+particular, we demonstrate how the anomalous current-phase relation triggers
+supercurrent-induced magnetization dynamics and also study the spatial
+localization of the Majorana fermions appearing in the junction.",1102.3403v2
+2011-03-02,Switching dynamics of a magnetostrictive single-domain nanomagnet subjected to stress,"The temporal evolution of the magnetization vector of a single-domain
+magnetostrictive nanomagnet, subjected to in-plane stress, is studied by
+solving the Landau-Lifshitz-Gilbert equation. The stress is ramped up linearly
+in time and the switching delay, which is the time it takes for the
+magnetization to flip, is computed as a function of the ramp rate. For high
+levels of stress, the delay exhibits a non-monotonic dependence on the ramp
+rate, indicating that there is an {\it optimum} ramp rate to achieve the
+shortest delay. For constant ramp rate, the delay initially decreases with
+increasing stress but then saturates showing that the trade-off between the
+delay and the stress (or the energy dissipated in switching) becomes less and
+less favorable with increasing stress. All of these features are due to a
+complex interplay between the in-plane and out-of-plane dynamics of the
+magnetization vector induced by stress.",1103.0352v1
+2011-03-09,Gravitational collapse and entropy of Black Holes with magnetic sources,"This thesis is divided in two parts, each one addressing problems that can be
+relevant in the study of compact objects. The first part deals with the study
+of a magnetized and self-gravitating gas of degenerated fermions (electrons and
+neutrons) as sources of a Bianchi-I space-time. We solve numerically the
+Einstein-Maxwell field equations for a large set of initial conditions of the
+dynamical variables. The collapsing singularity is isotropic for the neutron
+gas and can be anisotropic for the electron gas. This result is consistent with
+the fact that electrons exhibit a stronger coupling with the magnetic field,
+which is the source of anisotropy in the dynamical variables. In the second
+part we calculate the entropy of extremal black holes in 4 and 5 dimensions,
+using the entropy function formalism of Sen and taking into account higher
+order derivative terms that come from the complete set of Riemann invariants.
+The resulting entropies show the deviations from the well know
+Bekenstein-Hawking area law.",1103.1828v1
+2011-04-14,The magnetic excitation spectra in BaFe$_{2}$As$_{2}$: a two-particle approach within DFT+DMFT,"We study the magnetic excitation spectra in the paramagnetic state of
+BaFe$_{2}$As$_{2}$ from the \textit{ab initio} perspective. The one-particle
+excitation spectrum is determined within the combination of the density
+functional theory and the dynamical mean-field theory method. The two-particle
+response function is extracted from the local two-particle vertex function,
+also computed by the dynamical mean field theory, and the polarization
+function. This method reproduces all the experimentally observed features in
+inelastic neutron scattering (INS), and relates them to both the one particle
+excitations and the collective modes. The magnetic excitation dispersion is
+well accounted for by our theoretical calculation in the paramagnetic state
+without any broken symmetry, hence nematic order is not needed to explain the
+INS experimental data.",1104.2942v1
+2011-05-26,Non-equilibrium quantum dynamics after local quenches,"We study the quantum dynamics resulting from preparing a one-dimensional
+quantum system in the ground state of initially two decoupled parts which are
+then joined together (local quench). Specifically we focus on the transverse
+Ising chain and compute the time-dependence of the magnetization profile,
+m_l(t), and correlation functions at the critical point, in the
+ferromagnetically ordered phase and in the paramagnetic phase. At the critical
+point we find finite size scaling forms for the nonequilibrium magnetization
+and compare predictions of conformal field theory with our numerical results.
+In the ferromagnetic phase the magnetization profiles are well matched by our
+predictions from a quasi-classical calculation.",1105.5317v1
+2011-06-15,Routh Reduction by Stages,"This paper deals with the Lagrangian analogue of symplectic or point
+reduction by stages. We develop Routh reduction as a reduction technique that
+preserves the Lagrangian nature of the dynamics. To do so we heavily rely on
+the relation between Routh reduction and cotangent symplectic reduction. The
+main results in this paper are: (i) we develop a class of so called magnetic
+Lagrangian systems and this class has the property that it is closed under
+Routh reduction; (ii) we construct a transformation relating the magnetic
+Lagrangian system obtained after two subsequent Routh reductions and the
+magnetic Lagrangian system obtained after Routh reduction w.r.t. to the full
+symmetry group.",1106.2950v2
+2011-08-05,MHD Turbulence Simulation in a Cosmic Structure Context,"The gaseous media of galaxy clusters and cosmic filaments, which constitute
+most of the baryonic matter in the universe, is highly dynamic. It is also
+probably turbulent, although the turbulence properties are poorly known. The
+gas is highly rarefied, essentially fully ionized plasma. Observational
+evidence suggests intracluster media (ICMs) are magnetized at some level. There
+are several possible origins for ICM seed fields; the observed fields are
+likely the result of turbulence in the ICM. We are engaged in a simulation
+study designed to understand in this context how very weak initial magnetic
+fields evolve in driven turbulence. We find that the magnetic fields eventually
+evolve towards equipartition levels with the vortical, solenoidal kinetic
+energy in the turbulence. As they do so the topology of the field structures
+transition from filamentary forms into ribbon-like structures in which the
+field orientations are laminated with vorticity structures.",1108.1369v1
+2011-08-25,Driving Force of Ultrafast Magnetization Dynamics,"Irradiating a ferromagnetic material with an ultrashort laser pulse leads to
+demagnetization on a femtosecond timescale. We implement Elliott-Yafet type
+spin-flip scattering, mediated by electron-electron and electron-phonon
+collisions, into the framework of a spin-resolved Boltzmann equation.
+Considering three mutually coupled reservoirs, (i) spin-up electrons, (ii)
+spin-down electrons and (iii) phonons, we trace non-equilibrium electron
+distributions during and after laser excitation. We identify the driving force
+for ultrafast magnetization dynamics as the equilibration of temperatures and
+chemical potentials between the electronic subsystems. This principle can be
+used to easily predict the maximum quenching of magnetization upon ultrashort
+laser irradiation in any material, as we show for the example of
+3d-ferromagnetic nickel.",1108.5170v1
+2011-08-29,Domain Wall Spin Dynamics in Kagome Antiferromagnets,"We report magnetization and neutron scattering measurements down to 60 mK on
+a new family of Fe based kagome antiferromagnets, in which a strong local spin
+anisotropy combined with a low exchange path network connectivity lead to
+domain walls intersecting the kagome planes through strings of free spins.
+These produce unfamiliar slow spin dynamics in the ordered phase, evolving from
+exchange-released spin-flips towards a cooperative behavior on decreasing the
+temperature, probably due to the onset of long-range dipolar interaction. A
+domain structure of independent magnetic grains is obtained that could be
+generic to other frustrated magnets.",1108.5540v2
+2011-09-14,Domain-wall dynamics in translationally noninvariant nanowires: theory and applications,"We generalize domain-wall dynamics to the case of translationally
+noninvariant ferromagnetic nanowires. The obtained equations of motion make the
+description of the domain-wall propagation more realistic by accounting for the
+variations along the wire, such as disorder or change in the wire shape. We
+show that the effective equations of motion are very general and do not depend
+on the model details. As an example of their use, we consider an
+hourglass-shaped nanostrip in detail. A transverse domain wall is trapped in
+the middle and has two stable magnetization directions. We study the switching
+between the two directions by short current pulses. We obtain the exact time
+dependence of the current pulses required to switch the magnetization with the
+minimal Ohmic losses per switching. Furthermore, we find how the Ohmic losses
+per switching depend on the switching time for the optimal current pulse. As a
+result, we show that as a magnetic memory this nanodevice can be $10^5$ times
+more energy efficient than the best modern devices.",1109.2996v2
+2011-10-02,Metastable magnetic domain wall dynamics,"The dynamics of metastable magnetic domain walls in straight ferromagnetic
+nanowires under spin waves, external magnetic fields, and current induced spin
+transfer torque are studied by micromagnetic simulations. It is found that in
+contrast to a stable wall, it is possible to displace a metastable domain wall
+in the absence of any external excitation. In addition, independent of the
+domain wall excitation method, the velocity of a metastable wall is much
+smaller than a stable wall and their displacement direction could be different
+from the stable wall depending on the structure of metastable walls. Under the
+current induced spin transfer torque excitation, the direction of domain wall
+displacement is directly related to the intensity of nonadiabatic spin transfer
+torque. In a rough nanowire, it is found that the displacement of a metastable
+wall could happen much below the critical excitation of a stable wall.
+Furthermore, we show that it is possible to have either a forward or backward
+displacement of a metastable domain wall by changing the pulse width of the
+excitation.",1110.0175v1
+2011-10-16,Spin Hall Effect-driven Spin Torque in Magnetic Texture,"Current-induced spin torque and magnetization dynamics in the presence of
+spin Hall effect in magnetic textures is studied theoretically. The local
+deviation of the charge current gives rise to a current-induced spin torque of
+the form (1-\beta{\bf M})x[({\bf u}_0+\alpha_H{\bf u}_0x\bf M})\cdot{\bm
+\nabla}]{\bf M}, where {\bf u}_0 is the direction of the injected current,
+\alpha_H is the Hall angle and \beta is the non-adiabaticity parameter due to
+spin relaxation. Since \alpha_H and \beta can have a comparable order of
+magnitude, we show that this torque can significantly modify the
+current-induced dynamics of both transverse and vortex walls.",1110.3485v1
+2011-10-19,Time Dependence of Advection Dominated Accretion Flow with a Toroidal Magnetic Field,"The present study examines self-similarity evolution of advection dominated
+accretion flow (ADAF) in the presence of a toroidal magnetic field. In this
+research, it was assumed that the angular momentum transport is due to viscous
+turbulence and $\alpha$-prescription was used for kinematics coefficient of
+viscosity. In order to solve the integrated equations which govern the
+dynamical behavior of the accretion flow, self-similar solution was used. The
+solutions show that the behavior of physical quantities in a dynamical ADAF are
+different from steady accretion flow and a disk with polytropic approach. The
+solution indicates a transonic point in the accretion flow for all selected
+amounts of advection parameter. Also, by adding strength of the magnetic field
+and the degree of advection, the radial-thickness of the disk decreased and the
+disk compressed. The model implies that the flow has differential rotation and
+is sub-Keplerian at small radii and is super-Keplerian in large radii.",1110.4191v1
+2011-11-15,Surprises in relativistic matter in a magnetic field,"A short review of recent advances in understanding the dynamics of
+relativistic matter in a magnetic field is presented. The emphasis is on the
+dynamics related to the generation of the chiral shift parameter in the normal
+ground state. We argue that the chiral shift parameter contributes to the axial
+current density, but does not modify the conventional axial anomaly relation.
+The analysis based on gauge invariant regularization schemes in the
+Nambu-Jona-Lasinio model suggests that these findings should be valid also in
+gauge theories. It is pointed out that the chiral shift parameter can affect
+observable properties of compact stars and modify the key features of the
+chiral magnetic effect in heavy ion collisions.",1111.3401v2
+2011-12-01,Dynamic RKKY interaction in graphene,"The growing interest in carbon-based spintronics has stimulated a number of
+recent theoretical studies on the RKKY interaction in graphene, based on which
+the energetically favourable alignment between magnetic moments embedded in
+this material can be calculated. The general consensus is that the strength of
+the RKKY interaction in graphene decays as 1/D3 or faster, where D is the
+separation between magnetic moments. Such an unusually fast decay for a
+2-dimensional system suggests that the RKKY interaction may be too short ranged
+to be experimentally observed in graphene. Here we show in a mathematically
+transparent form that a far more long ranged interaction arises when the
+magnetic moments are taken out of their equilibrium positions and set in
+motion. We not only show that this dynamic version of the RKKY interaction in
+graphene decays far more slowly but also propose how it can be observed with
+currently available experimental methods.",1112.0205v2
+2012-01-20,"Vortex Dynamics in Ferromagnetic Superconductors: Vortex Clusters, Domain Walls and Enhanced Viscosity","We demonstrate that there is a long-range vortex-vortex attraction in
+ferromagnetic superconductors due to polarization of the magnetic moments.
+Vortex clusters are then stabilized in the ground state for low vortex
+densities. The motion of vortex clusters driven by the Lorentz force excites
+magnons. This regime becomes unstable at a threshold velocity above which
+domain walls are generated for slow relaxation of the magnetic moments and the
+vortex configuration becomes modulated. This dynamics of vortices and magnetic
+moments can be probed by transport measurements.",1201.4195v3
+2012-01-23,Influence of the magnetoelectric coupling on the electric field induced magnetization reversal in a composite non-strained multiferroic chain,"We study theoretically the multiferroic dynamics in a composite
+one-dimensional system consisting of BaTiO3 multiferroically coupled to an iron
+chain. The method treats the magnetization and the polarization as
+thermodynamic quantities describable via a combination of the Landau-Lifshits-
+Gilbert and the Ginzburg-Landau dynamics coupled via an additional term in the
+total free energy density. This term stems from the multiferroic interaction at
+the interface. For a wide range of strengths of this coupling we predict the
+possibility of obtaining a well-developed hysteresis in the ferromagnetic part
+of the system induced by an external electric field. The dependence of the
+reversal modes on the electric field frequency is also investigated and we
+predict a considerable stability of the magnetization reversal for frequencies
+in the range of 0.5 - 12 [GHz].",1201.4740v1
+2012-01-30,Helical buckling of a whirling conducting rod in a uniform magnetic field,"We study the effect of a magnetic field on the behaviour of a conducting
+elastic rod subject to a novel set of boundary conditions that, in the case of
+a transversely isotropic rod, give rise to exact helical post-buckling
+solutions. The equations used are the geometrically exact Kirchhoff equations
+and both static (buckling) and dynamic (whirling) instability are considered.
+Critical loads are obtained explicitly and are given by a surprisingly simple
+formula. By solving the linearised equations about the (quasi-)stationary
+solutions we also find secondary instabilities described by (Hamiltonian-)Hopf
+bifurcations, the usual signature of incipient `breathing' modes. The boundary
+conditions can also be used to generate and study helical solutions through
+traditional non-magnetic buckling due to compression, twist or whirl.",1201.6351v1
+2012-01-31,Field-Induced Degeneracy Regimes in Quantum Plasmas,"It is shown that in degenerate magnetized Fermi-Dirac plasma where the
+electron-orbital are quantized distinct quantum hydrodynamic (QHD) limits exist
+in which the nonlinear density waves behave differently. The Coulomb
+interaction among degenerate electrons affect the electrostatic nonlinear wave
+dynamics more significant in the ground-state Landau quantization or the
+so-called quantum-limit ($l=0$) rather than in the classical-limit
+($l=\infty$). It is also remarked that the effective electron quantum potential
+unlike the number-density and degeneracy pressure is independent of the applied
+magnetic field in the classical-limit plasma, while, it depends strongly on the
+field strength in the quantum-limit. Current findings are equally important in
+the study of wave dynamics in arbitrarily-high magnetized astrophysical and
+laboratory dense plasmas.",1201.6571v2
+2012-02-15,Residual Energy in Weak and Strong MHD Turbulence,"Recent numerical and observational studies revealed that spectra of magnetic
+and velocity fluctuations in MHD turbulence have different scaling indexes.
+This intriguing feature has been recently explained in the case of weak MHD
+turbulence, that is, turbulence consisting of weakly interacting Alfven waves.
+However, astrophysical turbulence is strong in majority of cases. In the
+present work, we propose a unifying picture that allows one to address weak and
+strong MHD turbulence on the same footing. We argue that magnetic and kinetic
+energies are different in both weak and strong MHD turbulence. Their
+difference, the so-called residual energy, is spontaneously generated by
+turbulence, it has the Fourier spectrum E_r(k)=E_v(k)-E_b(k) \propto
+-f_w(k_||/k_perp) k_perp^{-2} in weak turbulence, and E_r(k) \propto
+-f_s(k_||/k_perp) k_perp^{-3} in strong turbulence. Here f_w,s(x) are functions
+declining fast for x>C_w,s and not significantly varying for $x<C_w,s$ with
+some constants C_w,s, and k_|| and k_perp the field-parallel and
+field-perpendicular wave vectors with respect to the applied strong uniform
+magnetic field.",1202.3453v1
+2012-02-17,Muon Collider interaction region and machine-detector interface design,"One of the key systems of a Muon Collider (MC) - seen as the most exciting
+option for the energy frontier machine in the post-LHC era - is its interaction
+region (IR). Designs of its optics, magnets and machine-detector interface are
+strongly interlaced and iterative. As a result of recent comprehensive studies,
+consistent solutions for the 1.5-TeV c.o.m. MC IR have been found and are
+described here. To provide the required momentum acceptance, dynamic aperture
+and chromaticity, an innovative approach was used for the IR optics. Conceptual
+designs of large-aperture high-field dipole and high-gradient quadrupole
+magnets based on Nb3Sn superconductor were developed and analyzed in terms of
+the operating margin, field quality, mechanics, coil cooling and quench
+protection. Shadow masks in the interconnect regions and liners inside the
+magnets are used to mitigate the unprecedented dynamic heat deposition due to
+muon decays (~0.5 kW/m). It is shown that an appropriately designed
+machine-detector interface (MDI) with sophisticated shielding in the detector
+has a potential to substantially suppress the background rates in the MC
+detector.",1202.3979v1
+2012-02-28,Collisionless reconnection: The sub-microscale mechanism of magnetic field line interaction,"Magnetic field lines are quantum objects carrying one quantum
+$\Phi_0=2\pi\hbar/e$ of magnetic flux and have finite radius $\lambda_m$. Here
+we argue that they possess a very specific dynamical interaction. Parallel
+field lines reject each other. When confined to a certain area they form
+two-dimensional lattices of hexagonal structure. We estimate the filling factor
+of such an area. Antiparallel field lines, on the other hand, attract each
+other. We identify the physical mechanism as being due to the action of the
+gauge potential field which we determine quantum mechanically for two parallel
+and two antiparallel field lines. The distortion of the quantum electrodynamic
+vacuum causes a cloud of virtual pairs. We calculate the virtual pair
+production rate from quantum electrodynamics and estimate the virtual pair
+cloud density, pair current and Lorentz force density acting on the field lines
+via the pair cloud. These properties of field line dynamics become important in
+collisionless reconnection, consistently explaining why and how reconnection
+can spontaneously set on in the field-free centre of a current sheet below the
+electron-inertial scale.",1202.6209v1
+2012-06-28,The Landau-Lifshitz-Bloch equation for ferrimagnetic materials,"We derive the Landau-Lifshitz-Bloch (LLB) equation for a two-component
+magnetic system valid up to the Curie temperature. As an example, we consider
+disordered GdFeCo ferrimagnet where the ultrafast optically induced
+magnetization switching under the action of heat alone has been recently
+reported. The two-component LLB equation contains the longitudinal relaxation
+terms responding to the exchange fields from the proper and the neighboring
+sublattices. We show that the sign of the longitudinal relaxation rate at high
+temperatures can change depending on the dynamical magnetization value and a
+dynamical polarisation of one material by another can occur. We discuss the
+differences between the LLB and the Baryakhtar equation, recently used to
+explain the ultrafast switching in ferrimagnets. The two-component LLB equation
+forms basis for the largescale micromagnetic modeling of nanostructures at high
+temperatures and ultrashort timescales.",1206.6672v1
+2012-07-12,Cosmic magnetization: from spontaneously emitted aperiodic turbulent to ordered equipartition fields,"It is shown that an unmagnetized nonrelativistic thermal electron-proton
+plasma spontaneously emits aperiodic turbulent magnetic field fluctuations of
+strength $|\delta B|=9\beta_eg^{1/3}W_e^{1/2}$ G, where $\beta_e$ is the
+normalized thermal electron temperature, $W_e$ the thermal plasma energy
+density and $g$ the plasma parameter. Aperiodic modes fluctuate only in space,
+but are not propagating. For the unmagnetized intergalactic medium, immediately
+after the reionization onset, the field strength from this mechanism is about
+$4.7\cdot 10^{-16}$ G, too weak to affect the dynamics of the plasma. The shear
+and/or compression of the intergalactic medium exerted by the first supernova
+explosions amplify these seed fields and make them anisotropic, until the
+magnetic restoring forces affect the gas dynamics at ordered plasma betas near
+unity.",1207.2963v1
+2012-08-17,Detection of domain wall eigenfrequency in infinity-shaped magnetic nanostructures,"The dynamics of a magnetic infinity-shaped nanostructure has been
+experimentally studied by two different techniques such as the sinusoidal
+resonance excitation and the damped short pulse excitation to measure the
+eigenfrequency of domain walls. Direct observation of the magnetic domain wall
+nucleation has been measured in the frequency domain. Electrical measurements
+of the domain wall dynamics in the frequency domain reveal the existence of
+multi-eigenmodes for large excitation amplitudes. The time-resolved
+measurements show that the frequency of the damped gyration is similar to that
+of the frequency domain and coexistence of spin wave excitations.",1208.3527v1
+2012-08-29,Persistent spin dynamics intrinsic to amplitude-modulated long-range magnetic order,"An incommensurate elliptical helical magnetic structure in the frustrated
+coupled-spin-chain system FeTe2O5Br is surprisingly found to persist down to
+53(3) mK (T/T_N ~ 1/200), according to neutron scattering and muon spin
+relaxation. In this state, finite spin fluctuations at T -> 0 are evidenced by
+muon depolarization, which is in agreement with specific-heat data indicating
+the presence of both gapless and gapped excitations. We thus show that the
+amplitude-modulated magnetic order intrinsically accommodates contradictory
+persistent spin dynamics and long-range order and can serve as a model
+structure to investigate their coexistence.",1208.5843v2
+2012-09-29,Brownian Motion and Quantum Dynamics of Magnetic Monopoles in Spin Ice,"Spin ice illustrates many unusual magnetic properties, including zero point
+entropy, emergent monopoles and a quasi liquid-gas transition. To reveal the
+quantum spin dynamics that underpin these phenomena is an experimental
+challenge. Here we show how crucial information is contained in the frequency
+dependence of the magnetic susceptibility and in its high frequency or
+adiabatic limit. These measures indicate that monopole diffusion is strictly
+Brownian but is underpinned by spin tunnelling and is influenced by collective
+monopole interactions. We also find evidence of driven monopole plasma
+oscillations in weak applied field, and unconventional critical behaviour in
+strong applied field. Our results resolve contradictions in the present
+understanding of spin ice, reveal unexpected physics and establish adiabatic
+susceptibility as a revealing characteristic of exotic spin systems.",1210.0106v1
+2012-10-03,Torsional Oscillations in a Global Solar Dynamo,"We characterize and analyze rotational torsional oscillations developing in a
+large-eddy magnetohydrodynamical simulation of solar convection (Ghizaru,
+Charbonneau, and Smolarkiewicz, Astrophys. J. Lett., 715, L133 (2010); Racine
+et al., Astrophys. J., 735, 46 (2011)) producing an axisymmetric large-scale
+magnetic field undergoing periodic polarity reversals. Motivated by the many
+solar-like features exhibited by these oscillations, we carry out an analysis
+of the large-scale zonal dynamics. We demonstrate that simulated torsional
+oscillations are not driven primarily by the periodically-varying large-scale
+magnetic torque, as one might have expected, but rather via the magnetic
+modulation of angular-momentum transport by the large-scale meridional flow.
+This result is confirmed by a straightforward energy analysis. We also detect a
+fairly sharp transition in rotational dynamics taking place as one moves from
+the base of the convecting layers to the base of the thin tachocline-like shear
+layer formed in the stably stratified fluid layers immediately below. We
+conclude by discussing the implications of our analyses with regards to the
+mechanism of amplitude saturation in the global dynamo operating in the
+simulation, and speculate on the possible precursor value of torsional
+oscillations for the forecast of solar cycle characteristics.",1210.1209v1
+2012-10-16,"Dynamics of self-generated, large amplitude magnetic fields following high-intensity laser matter interaction","The dynamics of magnetic fields with amplitude of several tens of Megagauss,
+generated at both sides of a solid target irradiated with a high intensity (?
+1019W/cm2) picosecond laser pulse, has been spatially and temporally resolved
+using a proton imaging technique. The amplitude of the magnetic fields is
+sufficiently large to have a constraining effect on the radial expansion of the
+plasma sheath at the target surfaces. These results, supported by numerical
+simulations and simple analytical modeling, may have implications for ion
+acceleration driven by the plasma sheath at the rear side of the target as well
+as for the laboratory study of self-collimated high-energy plasma jets.",1210.4366v1
+2012-11-13,Atomistic spin dynamics of low-dimensional magnets,"We investigate the magnetic properties of a range of low-dimensional
+ferromagnets using a combination of first-principles calculations and atomistic
+spin dynamics simulations. This approach allows us to evaluate the ground state
+and finite temperature properties of experimentally well characterized systems
+such as Co/Cu(111), Co/Cu(001), Fe/Cu(001) and Fe/W(110), for different
+thicknesses of the magnetic layer. We compare our calculated spin wave spectra
+with experimental data available in the literature, and find a good
+quantitative agreement. We also predict magnon spectra for systems for which no
+experimental data exist at the moment, and estimate the role of temperature
+effects.",1211.2964v2
+2012-12-18,Magnetoelasticity in ACr2O4 spinel oxides,"Dynamical properties of the lattice structure was studied by optical
+spectroscopy in ACr2O4 chromium spinel oxide magnetic semiconductors over a
+broad temperature region of T=10-335K. The systematic change of the A-site ions
+(A=Mn, Fe, Co, Ni and Cu) showed that the occupancy of 3d orbitals on the
+A-site, has strong impact on the lattice dynamics. For compounds with orbital
+degeneracy (FeCr2O4, NiCr2O4 and CuCr2O4), clear splitting of infrared-active
+phonon modes and/or activation of silent vibrational modes have been observed
+upon the Jahn-Teller transition and at the onset of the subsequent long-range
+magnetic order. Although MnCr2O4 and CoCr2O4 show multiferroic and
+magnetoelectric character, no considerable magnetoelasticity was found in
+spinel compounds without orbital degeneracy as they closely preserve the
+high-temperature cubic spinel structure even in their magnetic ground state.
+Besides lattice vibrations, intra-atomic 3d-3d transitions of the A$^{2+}$ ions
+were also investigated to determine the crystal field and Racah parameters and
+the strength of the spin-orbit coupling.",1212.4301v1
+2013-01-09,"Quantum reactive scattering of ultracold NH($X\,^3Σ^-$) radicals in a magnetic trap","We investigate the ultracold reaction dynamics of magnetically trapped NH($X
+^3\Sigma^-$) radicals using rigorous quantum scattering calculations involving
+three coupled potential energy surfaces. We find that the reactive NH + NH
+cross section is driven by a short-ranged collisional mechanism, and its
+magnitude is only weakly dependent on magnetic field strength. Unlike most
+ultracold reactions observed so far, the NH + NH scattering dynamics is
+non-universal. Our results indicate that chemical reactions can cause more trap
+loss than spin-inelastic NH + NH collisions, making molecular evaporative
+cooling more difficult than previously anticipated.",1301.1931v1
+2013-02-04,Robust synchronization of an arbitrary number of spin-torque driven vortex nanooscillators,"Non-linear magnetization dynamics in ferromagnetic nanoelements excited by
+the spin-polarized dc-current is one of the most intensively studied phenomena
+in solid state magnetism. Despite immense efforts, synchronization of
+oscillations induced in several such nanoelements (spin-torque driven
+nanooscillators, or STNO) still represents a major challenge both from the
+fundamental and technological points of view. In this paper we propose a system
+where synchronization of any number of STNOs, represented by magnetization
+vortices inside squared nanoelements, can be easily achieved. Using full-scale
+micromagnetic simulations we show that synchronization of these STNOs is
+extremely dynamically stable due to their very large coupling energy provided
+by the magnetodipolar interaction. Finally, we demonstrate that our concept
+allows robust synchronization of an arbitrary number of STNOs (arranged either
+as a 1D chain or as a 2D array), even when current supplying nanocontacts have
+a broad size distribution.",1302.0659v3
+2013-04-25,Critical behavior and magnetic relaxation dynamics of Nd0.4Sr0.6MnO3 nanoparticles,"Detailed dc and ac magnetic properties of chemically synthesized
+Nd0.4Sr0.6MnO3 with different particle size (down to 27 nm) have been studied
+in details. We have found ferromagnetic state in the nanoparticles, whereas,
+the bulk Nd0.4Sr0.6MnO3 is known to be an A-type antiferromagnet. A
+Griffiths-like phase has also been identified in the nanoparticles. Further,
+critical behavior of the nanoparticles has been studied around the second order
+ferromagnetic-paramagnetic transition region (|(T-TC)/TC|{\pounds} 0.04) in
+terms of modified Arrott plot, Kouvel-Fisher plot and critical isotherm
+analysis. The estimated critical exponents (b,g,d) are quite different from
+those predicted according to three-dimensional mean-field, Heisenberg and Ising
+models. This signifies a quite unusual nature of the size-induced ferromagnetic
+state in Nd0.4Sr0.6MnO3. The nanoparticles are found to be interacting and do
+not behave like ideal superparamagnet. Interestingly, we find spin glass like
+slow relaxation of magnetization, aging and memory effect in the nanometric
+samples. These phenomena have been attributed to very broad distribution of
+relaxation time as well as to inter-particle interaction. Experimentally, we
+have found out that the dynamics of the nanoparticle systems can be best
+described by hierarchical model of spin glasses.",1304.6964v1
+2013-05-16,Size-dependent magnetization switching characteristics and spin wave modes of FePt nanostructures,"We present a comprehensive investigation of the size-dependent switching
+characteristics and spin wave modes of FePt nanoelements. Curved nanomagnets
+(""caps"") are compared to flat disks of identical diameter and volume over a
+size range of 100 to 300nm. Quasi-static magnetization reversal analysis using
+first-order reversal curves (FORC) shows that spherical caps have lower vortex
+nucleation and annihilation fields than the flat disks. As the element diameter
+decreases, the reversal mechanism in the caps crosses over sooner to coherent
+rotation than in the disks. The magnetization dynamics are studied using
+optically induced small angle precession and reveal a strong size dependence
+that differs for the two shapes. Flat disks exhibit well-known center and edge
+modes at all sizes, but as the diameter of the caps increases from 100 to 300
+nm, additional oscillation modes appear in agreement with dynamic micromagnetic
+simulations. In addition, we show that the three-dimensional curvature of the
+cap causes a much greater sensitivity to the applied field angle which provides
+an additional way for controlling the ultrafast response of nanomagnetic
+elements.",1305.3686v1
+2013-05-18,Stress due to Electric and Magnetic fields in Viscoelastic Fluids,"A clear understanding of body force densities due to external electromagnetic
+fields is necessary to study flow and deformation of materials exposed to the
+fields. In this paper, we derive an expression for stress in continua with
+viscous and elastic properties in presence of external, static electric or
+magnetic fluids. Our derivation follows from fundamental thermodynamic
+principles. We demonstrate the soundness of our results by showing that they
+reduce to known expressions for Newtonian fluids and elastic solids. We point
+out the extra care to be taken while applying these techniques to permanently
+polarized or magnetized materials and derive an expression for stress in a
+ferro-fluid. Lastly, we derive expressions for ponderomotive forces in several
+situations of interest to fluid dynamics and rheology.",1305.4233v1
+2013-05-23,Spin pumping and interlayer exchange coupling through palladium,"The magnetic behaviour of ultrathin ferromagnetic films deposited on
+substrates is strongly affected by the properties of the substrate. We
+investigate the spin pumping rate, interlayer exchange coupling and dynamic
+exchange coupling between ultrathin ferromagnetic films through palladium, a
+non-magnetic substrate that displays strong Stoner enhancement. We find that
+the interlayer exchange coupling, both in the static and dynamic versions, is
+qualitatively affected by the substrate's Stoner enhancement. For instance, the
+oscillatory behavior that is a hallmark property of the RKKY exchange coupling
+is strongly suppressed by Stoner enhancement. Although the spin pumping rate of
+ferromagnetic films atop palladium is only mildly changed by Stoner enhancement
+the change is large enough to be detected experimentally. The qualitative
+aspects of our results for palladium are expected to remain valid for any
+non-magnetic substrate where Coulomb repulsion is large.",1305.5459v1
+2013-06-05,Kinetic Simulations of Plasmoid Chain Dynamics,"The dynamics of a plasmoid chain is studied with three dimensional
+Particle-in-Cell simulations. The evolution of the system with and without a
+uniform guide field, whose strength is 1/3 the asymptotic magnetic field, is
+investigated. The plasmoid chain forms by spontaneous magnetic reconnection:
+the tearing instability rapidly disrupts the initial current sheet generating
+several small-scale plasmoids, that rapidly grow in size coalescing and
+kinking. The plasmoid kink is mainly driven by the coalescence process. It is
+found that the presence of guide field strongly influences the evolution of the
+plasmoid chain. Without a guide field, a main reconnection site dominates and
+smaller reconnection regions are included in larger ones, leading to an
+hierarchical structure of the plasmoid-dominated current sheet. On the contrary
+in presence of a guide field, plasmoids have approximately the same size and
+the hierarchical structure does not emerge, a strong core magnetic field
+develops in the center of the plasmoid in the direction of the existing guide
+field, and bump-on-tail instability, leading to the formation of electron
+holes, is detected in proximity of the plasmoids.",1306.1050v1
+2013-06-25,Phase Winding a Two-Component BEC in an Elongated Trap: Experimental Observation of Moving Magnetic Orders and Dark-bright Solitons,"We experimentally investigate the phase winding dynamics of a harmonically
+trapped two-component BEC subject to microwave induced Rabi oscillations
+between two pseudospin components. While the single particle dynamics can be
+explained by mapping the system to a two-component Bose-Hubbard model,
+nonlinearities due to the interatomic repulsion lead to new effects observed in
+the experiments: In the presence of a linear magnetic field gradient, a
+qualitatively stable moving magnetic order that is similar to antiferromagnetic
+order is observed after critical winding is achieved. We also demonstrate how
+the phase winding can be used as a new tool to generate copious dark-bright
+solitons in a two-component BEC, opening the door for new experimental studies
+of these nonlinear features.",1306.6102v2
+2013-06-26,Spin dynamics in p-doped semiconductor nanostructures subject to a magnetic field tilted from the Voigt geometry,"We develop a theoretical description of the spin dynamics of resident holes
+in a p-doped semiconductor quantum well (QW) subject to a magnetic field tilted
+from the Voigt geometry. We find the expressions for the signals measured in
+time-resolved Faraday rotation (TRFR) and resonant spin amplification (RSA)
+experiments and study their behavior for a range of system parameters. We find
+that an inversion of the RSA peaks can occur for long hole spin dephasing times
+and tilted magnetic fields. We verify the validity of our theoretical findings
+by performing a series of TRFR and RSA experiments on a p-modulation doped
+GaAs/Al_{0.3}Ga_{0.7}As single QW and showing that our model can reproduce
+experimentally observed signals.",1306.6363v2
+2013-07-31,Freezing a Quantum Magnet by Repeated Quantum Interference: An Experimental Realization,"We experimentally demonstrate the phenomenon of dynamical many-body freezing
+in a periodically driven Ising chain. Theoretically [Phys. Rev. B 82, 172402
+(2010)], for certain values of the drive parameters all fundamental degrees of
+freedom contributing to the response dynamics freeze for all time and for
+arbitrary initial states. Also, since the condition of freezing involves only
+the drive parameters and not on the quantization of the momentum (i.e., the
+system-size), our simulation with a small (3-spin) chain captures all salient
+features of the freezing phenomenon predicted for the infinite chain. Using
+optimal control techniques, we realize high-fidelity cosine modulated drive,
+and observe non-monotonic freezing of magnetization at specific frequencies of
+modulation. Time-evolution of the excitations in momentum space has been
+tracked directly through magnetization measurements.",1307.8219v3
+2013-09-08,Magnetohydrodynamic simulations of the elliptical instability in triaxial ellipsoids,"The elliptical instability can take place in planetary cores and stars
+elliptically deformed by gravitational effects, where it generates large-scale
+three-dimensional flows assumed to be dynamo capable. In this work, we present
+the first magneto-hydrodynamic numerical simulations of such flows, using a
+finite-element method. We first validate our numerical approach by comparing
+with kinematic and dynamic dynamos benchmarks of the literature. We then
+systematically study the magnetic field induced by various modes of the
+elliptical instability from an imposed external field in a triaxial ellipsoidal
+geometry, relevant in a geo- and astrophysical context. Finally, in tidal
+induction cases, the external magnetic field is suddenly shut down and the
+decay rates of the magnetic field are systematically reported.",1309.1929v1
+2013-09-09,Characterization of the International Linear Collider damping ring optics,"A method is presented for characterizing the emittance dilution and dynamic
+aperture for an arbitrary closed lattice that includes guide field magnet
+errors, multipole errors and misalignments. This method, developed and tested
+at the Cornell Electron Storage Ring Test Accelerator (CesrTA), has been
+applied to the damping ring lattice for the International Linear Collider
+(ILC). The effectiveness of beam based emittance tuning is limited by beam
+position monitor (BPM) measurement errors, number of corrector magnets and
+their placement, and correction algorithm. The specifications for damping ring
+magnet alignment, multipole errors, number of BPMs, and precision in BPM
+measurements are shown to be consistent with the required emittances and
+dynamic aperture. The methodology is then used to determine the minimum number
+of position monitors that is required to achieve the emittance targets, and how
+that minimum depends on the location of the BPMs. Similarly, the maximum
+tolerable multipole errors are evaluated. Finally, the robustness of each BPM
+configuration with respect to random failures is explored.",1309.2248v3
+2013-10-28,Maximal Rabi frequency of an electrically driven spin in a disordered magnetic field,"We present a theoretical study of the spin dynamics of a single electron
+confined in a quantum dot. Spin dynamics is induced by the interplay of
+electrical driving and the presence of a spatially disordered magnetic field,
+the latter being transverse to a homogeneous magnetic field. We focus on the
+case of strong driving, i.e., when the oscillation amplitude $A$ of the
+electron's wave packet is comparable to the quantum dot length $L$. We show
+that electrically driven spin resonance can be induced in this system by
+subharmonic driving, i.e., if the excitation frequency is an integer fraction
+(1/2, 1/3, etc) of the Larmor frequency. At strong driving we find that (i) the
+Rabi frequencies at the subharmonic resonances are comparable to the Rabi
+frequency at the fundamental resonance, and (ii) at each subharmonic resonance,
+the Rabi frequency can be maximized by setting the drive strength to an
+optimal, finite value. Our simple model is applied to describe electrical
+control of a spin-valley qubit in a weakly disordered carbon nanotube.",1310.7350v2
+2013-11-02,"Attraction, Merger, Reflection, and Annihilation in Magnetic Droplet Soliton Scattering","The interaction behavior of solitons are defining characteristics of these
+nonlinear, coherent structures. Due to recent experimental observations, thin
+ferromagnetic films offer a promising medium in which to study the scattering
+properties of two-dimensional magnetic droplet solitons, particle-like,
+precessing dipoles. Here, a rich set of two-droplet interaction behaviors are
+classified through micromagnetic simulations. Repulsive and attractive
+interaction dynamics are generically determined by the relative phase and
+speeds of the two droplets and can be classified into four types: (1) merger
+into a breather bound state, (2) counterpropagation trapped along the axis of
+symmetry, (3) reflection, and (4) violent droplet annihilation into spin wave
+radiation and a breather. Utilizing a nonlinear method of images, it is
+demonstrated that these dynamics describe repulsive/attractive scattering of a
+single droplet off of a magnetic boundary with pinned/free spin boundary
+conditions, respectively. These results explain the mechanism by which
+propagating and stationary droplets can be stabilized in a confined
+ferromagnet.",1311.0349v3
+2013-12-05,Hysteresis behavior of the anisotropic quantum Heisenberg model driven by periodic magnetic field,"Dynamic behavior of a quantum Heisenberg ferromagnet in the presence of a
+periodically oscillating magnetic field has been analyzed by means of the
+effective field theory with two spin cluster. The dynamic equation of motion
+has been constructed with the help of a Glauber type stochastic process and
+solved for a simple cubic lattice. After the phase diagrams given, the behavior
+of the hysteresis loop area, coercive field and remanent magnetization with the
+anisotropy in the exchange interaction has been investigated in detail.
+Especially, by comparing of the magnitudes of the hysteresis loop area in the
+high anisotropy limit (i.e. Ising model) and low anisotropy limit (i.e.
+isotropic Heisenberg model), detailed description of the hysteresis loop area
+with the anisotropy in the exchange interaction given. Some interesting
+features have been obtained about this behavior as well as in phase diagrams
+such as tricritical points.",1312.1647v1
+2014-01-16,Electric field driven magnetic domain wall motion in ferromagnetic-ferroelectric heterostructures,"We investigate magnetic domain wall (MDW) dynamics induced by applied
+electric fields in ferromagnetic-ferroelectric thin-film heterostructures. In
+contrast to conventional driving mechanisms where MDW motion is induced
+directly by magnetic fields or electric currents, MDW motion arises here as a
+result of strong pinning of MDWs onto ferroelectric domain walls (FDWs) via
+local strain coupling. By performing extensive micromagnetic simulations, we
+find several dynamical regimes, including instabilities such as spin wave
+emission and complex transformations of the MDW structure. In all cases, the
+time-averaged MDW velocity equals that of the FDW, indicating the absence of
+Walker breakdown.",1401.3959v1
+2014-01-22,Superconducting Spintronics with Magnetic Domain Walls,"The recent experimental demonstration of spin-polarized supercurrents offer a
+venue for establishment of a superconducting analogue to conventional
+spintronics. Whereas domain wall motion in purely magnetic structures is a
+well-studied topic, it is not clear how domain wall dynamics may influence
+superconductivity and if some functional property can be harnessed from such a
+scenario. Here, we demonstrate that domain wall motion in superconducting
+systems offers a unique way of controlling the quantum state of the
+superconductor. Considering both the diffusive and ballistic limits, we show
+that moving the domain wall to different locations in a Josephson junction will
+change the quantum ground state from being in a 0 state to a $\pi$ state.
+Remarkably, we also show that domain wall motion can be used to turn on and off
+superconductivity: the position of the domain wall determines the critical
+temperature $T_c$ and thus if the system is in a resistive state or not,
+causing even a quantum phase transition between the dissipationless and normal
+state at $T=0$. In this way, one achieves dynamical control over the
+superconducting state within a single sample by utilizing magnetic domain wall
+motion.",1401.5806v1
+2014-01-23,The suppression of electron correlations in the collapsed tetragonal phase of CaFe2As2 under ambient pressure demonstrated by 75As NMR-NQR measurements,"The static and the dynamic spin correlations in the low temperature collapsed
+tetragonal and the high temperature tetragonal phase in CaFe2As2 have been
+investigated by 75As nuclear magnetic resonance (NMR) and nuclear quadrupole
+resonance (NQR) measurements.
+  Through the temperature (T) dependence of the nuclear spin lattice relaxation
+rates (1/T1) and the Knight shifts, although stripe-type antiferromagnetic
+(AFM) spin correlations are realized in the high temperature tetragonal phase,
+no trace of the AFM spin correlations can be found in the non-superconducting,
+low temperature, collapsed tetragonal (cT) phase.
+  Given that there is no magnetic broadening in 75As NMR spectra, together with
+the T-independent behavior of magnetic susceptibility (x) and the T dependence
+of 1/T1Tx, we conclude that Fe spin correlations are completely quenched
+statically and dynamically in the non-superconducting cT phase in CaFe2As2.",1401.6191v1
+2014-01-24,Extended Order Parameter and Conjugate Field for the Dynamic Phase Transition in a Ginzburg-Landau Mean-Field Model in an Oscillating Field,"We present numerical evidence for an extended order parameter and conjugate
+field for the dynamic phase transition in a Ginzburg-Landau mean-field model
+driven by an oscillating field. The order parameter, previously taken to be the
+time-averaged magnetization, comprises the deviations of the Fourier components
+of the magnetization from their values at the critical period. The conjugate
+field, previously taken to be the time-averaged magnetic field, comprises the
+even Fourier components of the field. The scaling exponents beta and delta
+associated with the extended order parameter and conjugate field are shown
+numerically to be consistent with their values in the equilibrium mean-field
+model.",1401.6465v1
+2014-01-30,Langevin spin dynamics based on ab initio calculations: numerical schemes and applications,"A method is proposed to study the finite-temperature behaviour of small
+magnetic clusters based on solving the stochastic Landau-Lifshitz-Gilbert
+equations, where the effective magnetic field is calculated directly during the
+solution of the dynamical equations from first principles instead of relying on
+an effective spin Hamiltonian. Different numerical solvers are discussed in the
+case of a one-dimensional Heisenberg chain with nearest-neighbour interactions.
+We performed detailed investigations for a monatomic chain of ten Co atoms on
+top of Au(001) surface. We found a spiral-like ground state of the spins due to
+Dzyaloshinsky-Moriya interactions, while the finite-temperature magnetic
+behaviour of the system was well described by a nearest-neighbour Heisenberg
+model including easy-axis anisotropy.",1401.7885v2
+2014-01-31,Far from equilibrium monopole dynamics in spin ice,"Condensed matter in the low temperature limit reveals much exotic physics
+associated with unusual orders and excitations, examples ranging from helium
+superfluidity to magnetic monopoles in spin ice. The far-from-equilibrium
+physics of such low temperature states may be even more exotic, yet to access
+it in the laboratory remains a challenge. Here we demonstrate a simple and
+robust technique, the 'magnetothermal avalanche quench', and its use in the
+controlled creation of nonequilibrium populations of magnetic monopoles in spin
+ice at millikelvin temperatures. These populations are found to exhibit
+spontaneous dynamical effects that typify far-from-equilibrium systems, yet are
+captured by simple models. Our method thus opens the door to the study of
+far-from-equilibrium states in spin ice and other exotic magnets.",1401.8194v1
+2014-02-12,Dynamics of a Charged Particle Around a Slowly Rotating Kerr Black Hole Immersed in Magnetic Field,"The dynamics of a charged particle moving around a slowly rotating Kerr black
+hole in the presence of an external magnetic field is investigated. We are
+interested to explore the conditions under which the charged particle can
+escape from the gravitational field of the black hole after colliding with
+another particle. The escape velocity of the charged particle in the innermost
+stable circular orbit is calculated. The effective potential and escape
+velocity of the charged particle with angular momentum in the presence of
+magnetic field is analyzed. This work serves as an extension of a preceding
+paper dealing with the Schwarzschild black hole [Zahrani {\it et al}, Phys.
+Rev. D 87, 084043 (2013)].",1402.2731v2
+2014-05-26,Magnetic helicity and the evolution of decaying magnetohydrodynamic turbulence,"Ensemble averaged high resolution direct numerical simulations of reverse
+spectral transfer are presented, extending on the many single realization
+numerical studies done up to now. This identifies this type of spectral
+transfer as a statistical property of magnetohydrodynamic turbulence and thus
+permits reliable numerical exploration of its dynamics. The magnetic energy
+decay exponent from these ensemble runs has been determined to be $n_E = (0.47
+\pm 0.03) + (13.9 \pm 0.8)/R_{\lambda}$ for initially helical magnetic fields.
+We show for the first time that even after removing the Lorentz force term in
+the momentum equation, thus decoupling it from the induction equation, reverse
+spectral transfer still persists. The induction equation is now linear with an
+externally imposed velocity field, thus amenable to numerous analysis
+techniques. A new door has opened for analyzing reverse spectral transfer, with
+various ideas discussed.",1405.6756v3
+2014-06-14,Negative magnetoresistance dynamics in expanded graphite under hydrostatic pressure up to 1.8 GPa,"Basal plane resistivity of expanded graphite was studied under simultaneous
+influence of hydrostatic pressure up to 1.8 GPa and magnetic field 0.8 T in the
+77-300 K temperature region. Magnetic field induces negative magnetoresistance
+in the sample within all temperature and pressure range studied. A change in
+resistivity of the sample under maximum pressure reaches 80%. Significant
+change in resistivity dependence on temperature under the pressure of 0.6 GPa
+suggests for ordering transition in the sample studied. Negative
+magnetoresistance in the graphite reaches about 15% at 0.6 GPa. Magnetic field
+acts in the same way as pressure and potentiates the transition formation and
+further magnetoresistance dynamics. The effects observed are mostly of elastic
+character according to resistivity of the unloaded sample.",1406.3770v1
+2014-06-30,Effect of laser intensity and dynamics of plasma on laser induced breakdown spectroscopy,"Laser-induced breakdown spectroscopy (LIBS) show enhancement in its signal,
+when the laser-induced plasma is confined/decelerated under the effect of an
+external steady magnetic field or in a small cavity. An enhancement in LIBS
+signal has been observed ~2 times in the case of magnetic confinement.
+Combination of magnetic and spatial confinement provide enhancement by an order
+of magnitude. Theoretical analysis of the decelerated plasma has been found in
+agreement with the experimental observations. The enhancement in LIBS signal is
+found dependent on the efficiency of plasma confinement as well as on the time
+duration of laser. The saturation in LIBS signal at higher laser intensity is
+found correlated with electron-ion collision frequency as well as on the
+dynamics and instability of plasma plume. Possibility of further enhancement in
+emission has also been discussed.",1406.7703v1
+2014-07-29,Motion of domain walls and the dynamics of kinks in the magnetic Peierls potential,"We study the dynamics of magnetic domain walls in the Peierls potential due
+to the discreteness of the crystal lattice. The propagation of a narrow domain
+wall (comparable to the lattice parameter) under the effect of a magnetic field
+proceeds through the formation of kinks in its profile. We predict that,
+despite the discreteness of the system, such kinks can behave like sine-Gordon
+solitons in thin films of materials such as yttrium iron garnets, and we derive
+general conditions for other materials. In our simulations we also observe
+long-lived breathers. We provide analytical expressions for the effective mass
+and limiting velocity of the kink in excellent agreement with our numerical
+results.",1407.7754v1
+2014-10-27,Dynamics of a dipolar Bose-Einstein condensate in the vicinity of a superconductor,"We study the dynamics of a dipolar Bose-Einstein condensate, like for example
+a $^{52}$Cr or $^{164}$Dy condensate, interacting with a superconducting
+surface. The magnetic dipole moments of the atoms in the Bose-Einstein
+condensate induce eddy currents in the superconductor. The magnetic field
+generated by eddy currents modifies the trapping potential such that the
+center-of-mass oscillation frequency is shifted. We numerically solve the
+Gross-Pitaevskii equation for this system and compare the results with
+analytical approximations. We present an approximation that gives excellent
+agreement with the numerical results. The eddy currents give rise to anharmonic
+terms, which leads to the excitation of shape fluctuations of the condensate.
+We discuss how the strength of the excitation of such modes can be increased by
+exploiting resonances, and we examine the strength of the resonances as a
+function of the center-of-mass oscillation amplitude of the condensate.
+Finally, we study different orientations of the magnetic dipoles and discuss
+favorable conditions for the experimental observation of the eddy current
+effect.",1410.7153v1
+2015-01-22,Relativistic dynamical spin excitations of magnetic adatoms,"We present a first-principles theory of dynamical spin excitations in the
+presence of spin-orbit coupling. The broken global spin rotational invariance
+leads to a new sum rule. We explore the competition between the magnetic
+anisotropy energy and the external magnetic field, as well as the role of
+electron-hole excitations, through calculations for 3$d$-metal adatoms on the
+Cu(111) surface. The spin excitation resonance energy and lifetime display
+non-trivial behavior, establishing the strong impact of relativistic effects.
+We legitimate the use of the Landau-Lifshitz-Gilbert equation down to the
+atomic limit, but with parameters that differ from a stationary theory.",1501.05509v1
+2015-01-26,Flows and Waves in Braided Solar Coronal Magnetic Structures,"We study the high frequency dynamics in the braided magnetic structure of an
+active region (AR 11520) moss as observed by High-Resolution Coronal Imager
+(Hi-C). We detect quasi periodic flows and waves in these structures. We search
+for high frequency dynamics while looking at power maps of the observed region.
+We find that shorter periodicites (30 - 60 s) are associated with small spatial
+scales which can be resolved by Hi-C only. We detect quasi periodic flows with
+wide range of velocities from 13 - 185 km/s associated with braided regions.
+This can be interpreted as plasma outflows from reconnection sites. We also
+find presence of short period and large amplitude transverse oscillations
+associated with braided magnetic region. Such oscillations could be triggered
+by reconnection or such oscillation may trigger reconnection.",1501.06507v1
+2015-02-26,Dynamics of magnetic shells and information loss problem,"We investigate dynamics of magnetic thin-shells in three dimensional anti de
+Sitter background. Because of the magnetic field, an oscillatory solution is
+possible. This oscillating shell can tunnel to a collapsing shell or a bouncing
+shell, where both of tunnelings induce an event horizon and a singularity. In
+the entire path integral, via the oscillating solution, there is a non-zero
+probability to maintain a trivial causal structure without a singularity.
+Therefore, due to the path integral, the entire wave function can conserve
+information. Since an oscillating shell can tunnel after a number of
+oscillations, in the end, it will allow an infinite number of different
+branchings to classical histories. This system can be a good model of the
+effective loss of information, where information is conserved by a solution
+that is originated from gauge fields.",1502.07471v2
+2015-03-05,Feshbach molecule formation through an oscillating magnetic field: subharmonic resonances,"The conversion of ultracold atoms to molecules via a magnetic Feshbach
+resonance with a sinusoidal modulation of the field is studied. Different
+practical realizations of this method in Bose atomic gases are analyzed. Our
+model incorporates many-body effects through an effective reduction of the
+complete microscopic dynamics. Moreover, we simulate the experimental
+conditions corresponding to the preparation of the system as a thermal gas and
+as a condensate. Some of the experimental findings are clarified. The origin of
+the observed dependence of the production efficiency on the frequency,
+amplitude, and application time of the magnetic modulation is elucidated. Our
+results uncover also the role of the atomic density in the dynamics,
+specifically, in the observed saturation of the atom-molecule conversion
+process.",1503.01700v1
+2015-03-06,Spin-Motive Forces and Current-Induced Torques in Ferromagnets,"In metallic ferromagnets, the spin-transfer torque and spin-motive force are
+known to exhibit a reciprocal relationship. Recent experiments on ferromagnets
+with strong spin-orbit coupling have revealed a rich complexity in the
+interaction between itinerant charge carriers and magnetization, but a full
+understanding of this coupled dynamics is lacking. Here, we develop a general
+phenomenology of the two reciprocal processes of charge pumping by spin-motive
+forces and current-driven magnetization dynamics. The formalism is valid for
+spin-orbit coupling of any strength and presents a systematic scheme for
+deriving all possible torque and charge-pumping terms that obey the symmetry
+requirements imposed by the point group of the system. We demonstrate how the
+different charge pumping and torque contributions are connected via the Onsager
+reciprocal relations. The formalism is applied to two important classes of
+systems: isotropic ferromagnets with non-uniform magnetization and homogeneous
+ferromagnets described by the point group $C_{2v}$.",1503.01899v2
+2015-03-19,Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate,"We report on the observation of half-quantum vortices (HQVs) in the
+easy-plane polar phase of an antiferromagnetic spinor Bose-Einstein condensate.
+Using in situ magnetization-sensitive imaging, we observe that pairs of HQVs
+with opposite core magnetization are generated when singly charged quantum
+vortices are injected into the condensate. The dynamics of HQV pair formation
+is characterized by measuring the temporal evolutions of the pair separation
+distance and the core magnetization, which reveals the short-range nature of
+the repulsive interactions between the HQVs. We find that spin fluctuations
+arising from thermal population of axial magnon excitations do not
+significantly affect the HQV pair formation dynamics. Our results demonstrate
+the instability of a singly charged vortex in the antiferromagnetic spinor
+condensate.",1503.05648v3
+2015-04-01,Multiscale modeling of ultrafast element-specific magnetization dynamics of ferromagnetic alloys,"A hierarchical multiscale approach to model the magnetization dynamics of
+ferromagnetic ran- dom alloys is presented. First-principles calculations of
+the Heisenberg exchange integrals are linked to atomistic spin models based
+upon the stochastic Landau-Lifshitz-Gilbert (LLG) equation to calculate
+temperature-dependent parameters (e.g., effective exchange interactions,
+damping param- eters). These parameters are subsequently used in the
+Landau-Lifshitz-Bloch (LLB) model for multi-sublattice magnets to calculate
+numerically and analytically the ultrafast demagnetization times. The developed
+multiscale method is applied here to FeNi (permalloy) as well as to copper-
+doped FeNi alloys. We find that after an ultrafast heat pulse the Ni sublattice
+demagnetizes faster than the Fe sublattice for the here-studied FeNi-based
+alloys.",1504.00199v1
+2015-04-27,Transition to magnetorotational turbulence in Taylor--Couette flow with imposed azimuthal magnetic field,"The magnetorotational instability (MRI) is thought to be a powerful source of
+turbulence and momentum transport in astrophysical accretion discs, but
+obtaining observational evidence of its operation is challenging. Recently,
+laboratory experiments of Taylor--Couette flow with externally imposed axial
+and azimuthal magnetic fields have revealed the kinematic and dynamic
+properties of the MRI close to the instability onset. While good agreement was
+found with linear stability analyses, little is known about the transition to
+turbulence and transport properties of the MRI. We here report on a numerical
+investigation of the MRI with an imposed azimuthal magnetic field. We show that
+the laminar Taylor--Couette flow becomes unstable to a wave rotating in the
+azimuthal direction and standing in the axial direction via a supercritical
+Hopf bifurcation. Subsequently, the flow features a catastrophic transition to
+spatio-temporal defects which is mediated by a subcritical subharmonic Hopf
+bifurcation. Our results are in qualitative agreement with the PROMISE
+experiment and dramatically extend their realizable parameter range. We find
+that as the Reynolds number increases defects accumulate and grow into
+turbulence, yet the momentum transport scales weakly.",1504.07208v2
+2015-05-20,Effect of Transverse Magnetic Field on Dynamics of Current Driven Domain Wall Motion in the Presence of Spin-Hall Effect,"Theoretically, we study the dynamics of a current induced domain wall in the
+bi-layer structure consists of a ferromagnetic layer and a non-magnetic metal
+layer with strong spin-orbit coupling in the presence of spin-Hall effect. The
+analytical expressions for the velocity and width of the domain wall interms of
+excitation angle are obtained by solving the Landau-Lifshitz-Gilbert equation
+with adiabatic, nonadiabatic and spin Hall effect-spin transfer torques using
+Schryers and Walker's method. Numerical results show that the occurance of
+polarity switching in the domain wall is observed only above the threshold
+current density. The presence of transverse magnetic field along with spin Hall
+effect-spin transfer torque enchances the value of the threshold current
+density, and the corresponding saturated velocity at the threshold current
+density is also increased.",1505.05249v1
+2015-05-22,Effective Hamiltonian and dynamics of edge states in two-dimensional topological insulators under magnetic fields,"The magnetic field opens a gap in the edge state spectrum of two-dimensional
+topological insulators thereby destroying protection of these states against
+backscattering. To relate properties of this gap to parameters of the system
+and to study dynamics of electrons in edge states in the presence of
+inhomogeneous potentials, the effective Hamiltonian theory is developed. Using
+this analytical theory, quantum-mechanical problems of edge-state electron
+transmission through potential steps and barriers, and of motion in constant
+electric field are considered. The influence of magnetic field on the
+resistance of two-dimensional topological insulators based on HgTe quantum
+wells is discussed together with comparison to experimental data.",1505.06144v1
+2015-06-18,Dynamical structure factor of magnetic Bloch oscillations at finite temperatures,"Domain-walls in one-dimensional Ising ferromagnets can undergo Bloch
+oscillations when subjected to a skew magnetic field. Such oscillations imply
+finite temperature non-dispersive low-frequency peaks in the dynamical
+structure factor which can be probed in neutron scattering. We study in detail
+the spectral weight of these peaks. Using an analytical approach based on an
+approximate treatment of a gas of spin-cluster excitations we give an explicit
+expression for the momentum- and temperature-dependence of the spectral
+weights. Generally the spectral weights increase with temperature and
+approaches the same order of magnitude as the spin-wave spectral weights at
+high temperatures. We compare the analytical expression to numerical exact
+diagonalizations and find that it can, without any adjustable parameters,
+account for the temperature and momentum-transfer dependence of the numerically
+obtained spectral weights in the parameter regime where the ratio of magnetic
+fields $h_x/h_z \ll 1$ and the temperature is $h_x < T <\sim J_z/2$. We also
+carry out numerical calculations pertinent to the material CoNb$_2$O$_6$, and
+find qualitatively similar results.",1506.05614v1
+2015-07-08,Phase-sensitive imaging of ferromagnetic resonance using ultrafast heat pulses,"Measuring local magnetization dynamics and its spatial variation is essential
+for advancements in spintronics and relevant applications. Here we demonstrate
+a phase-sensitive imaging technique for studying patterned magnetic structures
+based on picosecond laser heating. With the time-resolved anomalous Nernst
+effect (TRANE) and extensions, we simultaneously image the dynamic
+magnetization and RF driving current density. The stroboscopic detection
+implemented in TRANE microscopy provides access to both amplitude and phase
+information of ferromagnetic resonance (FMR) and RF current. Using this
+approach, we measure the spatial variation of the Oersted driving field angle
+across a uniform channel. In a spatially nonuniform sample with a cross shape,
+a strong spatial variation for the RF current as well as FMR precession is
+observed. We find that both the amplitude and the phase of local FMR precession
+are closely related to those of the RF current.",1507.02303v1
+2015-08-06,Large spin-wave bullet in a ferrimagnetic insulator driven by spin Hall effect,"Due to its transverse nature, spin Hall effects (SHE) provide the possibility
+to excite and detect spin currents and magnetization dynamics even in magnetic
+insulators. Magnetic insulators are outstanding materials for the investigation
+of nonlinear phenomena and for novel low power spintronics applications because
+of their extremely low Gilbert damping. Here, we report on the direct imaging
+of electrically driven spin-torque ferromagnetic resonance (ST-FMR) in the
+ferrimagnetic insulator Y$_3$Fe$_5$O$_{12}$ based on the excitation and
+detection by SHEs. The driven spin dynamics in Y$_3$Fe$_5$O$_{12}$ is directly
+imaged by spatially-resolved microfocused Brillouin light scattering (BLS)
+spectroscopy. Previously, ST-FMR experiments assumed a uniform precession
+across the sample, which is not valid in our measurements. A strong spin-wave
+localization in the center of the sample is observed indicating the formation
+of a nonlinear, self-localized spin-wave `bullet'.",1508.01427v1
+2015-08-13,On the dynamics of the Meissner effect,"The question of how a metal becoming superconducting expels a magnetic field
+is addressed. It is argued that the conventional theory of superconductivity
+has not answered this question despite its obvious importance. We argue that
+the growth of the superconducting into the normal region and associated
+expulsion of magnetic field from the superconducting region can only be
+understood if it is accompanied by motion of charge from the superconducting
+into the normal region. From a microscopic point of view it is shown that the
+perfect diamagnetism of superconductors requires that superconducting electrons
+reside in orbits of spatial extent $2\lambda_L$, with $\lambda_L$ the London
+penetration depth. Associated with this physics, the spin-orbit interaction of
+the electron magnetic moment and the positively charged ionic background gives
+rise to a ""Spin Meissner"" effect, the generation of a macroscopic spin current
+near the surface of superconductors. We point out that both the Meissner and
+the Spin Meissner effect can be understood dynamically under the assumption
+that the superfluid condensate wavefunction $\Psi(\vec{r})$ does not screen
+itself, just like the $\Psi(\vec{r})$ for an electron in a hydrogen atom. We
+argue that the conventional theory of superconductivity cannot explain the
+Meissner effect because it does not contain the physical elements discussed
+here.",1508.03307v1
+2015-09-06,Study of spin dynamics and damping on the magnetic nanowire arrays with various nanowire widths,"We investigate the spin dynamics including Gilbert damping in the
+ferromagnetic nanowire arrays. We have measured the ferromagnetic resonance of
+ferromagnetic nanowire arrays using vector-network analyzer ferromagnetic
+resonance (VNA-FMR) and analyzed the results with the micromagnetic
+simulations. We find excellent agreement between the experimental VNA-FMR
+spectra and micromagnetic simulations result for various applied magnetic
+fields. We find that the demagnetization factor for longitudinal conditions, Nz
+(Ny) increases (decreases) as decreasing the nanowire width in the
+micromagnetic simulations. For the transverse magnetic field, Nz (Ny) increases
+(decreases) as increasing the nanowire width. We also find that the Gilbert
+damping constant increases from 0.018 to 0.051 as the increasing nanowire width
+for the transverse case, while it is almost constant as 0.021 for the
+longitudinal case.",1509.01807v1
+2015-09-14,Arnold diffusion of charged particles in ABC magnetic fields,"We prove the existence of diffusing solutions in the motion of a charged
+particle in the presence of an ABC magnetic field. The equations of motion are
+modeled by a 3DOF Hamiltonian system depending on two parameters. For small
+values of these parameters, we obtain a normally hyperbolic invariant manifold
+and we apply the so-called geometric methods for a priori unstable systems
+developed by A. Delshams, R. de la Llave, and T.M. Seara. We characterize
+explicitly sufficient conditions for the existence of a transition chain of
+invariant tori having heteroclinic connections, thus obtaining global
+instability (Arnold diffusion). We also check the obtained conditions in a
+computer assisted proof. ABC magnetic fields are the simplest force-free type
+solutions of the magnetohydrodynamics equations with periodic boundary
+conditions, so our results are of potential interest in the study of the motion
+of plasma charged particles in a tokamak.",1509.04141v1
+2015-10-19,Oscillatory instability and routes to chaos in Rayleigh-Bénard convection: effect of external magnetic field,"We investigate oscillatory instability and routes to chaos in
+Rayleigh-B\'enard convection of electrically conducting fluids in presence of
+external horizontal magnetic field. Three dimensional direct numerical
+simulations (DNS) of the governing equations are performed for the
+investigation. DNS shows that oscillatory instability is inhibited by the
+magnetic field. The supercritical Rayleigh number for the onset of oscillation
+is found to scale with the Chandrasekhar number $\mathrm{Q}$ as
+$\mathrm{Q}^{\alpha}$ in DNS with $\alpha = 1.8$ for low Prandtl numbers
+($\mathrm{Pr}$). Most interestingly, DNS shows $\mathrm{Q}$ dependent routes to
+chaos for low Prandtl number fluids like mercury ($\mathrm{Pr} = 0.025$). For
+low $\mathrm{Q}$, period doubling routes are observed, while, quasiperiodic
+routes are observed for high $\mathrm{Q}$. The bifurcation structure associated
+with $\mathrm{Q}$ dependent routes to chaos is then understood by constructing
+a low dimensional model from the DNS data. The model also shows similar scaling
+laws as DNS. Bifurcation analysis of the low dimensional model shows that
+origin of different routes are associated with the bifurcation structure near
+the primary instability. These observations show similarity with the previous
+results of convection experiments performed with mercury.",1510.05339v1
+2015-11-12,"Dynamics of a linear magnetic ""microswimmer molecule""","In analogy to nanoscopic molecules that are composed of individual atoms, we
+consider an active ""microswimmer molecule"". It is built up from three
+individual magnetic colloidal microswimmers that are connected by harmonic
+springs and hydrodynamically interact with each other. In the ground state,
+they form a linear straight molecule. We analyze the relaxation dynamics for
+perturbations of this straight configuration. As a central result, with
+increasing self-propulsion, we observe an oscillatory instability in accord
+with a subcritical Hopf bifurcation scenario. It is accompanied by a
+corkscrew-like swimming trajectory of increasing radius. Our results can be
+tested experimentally, using for instance magnetic self-propelled Janus
+particles, supposably linked by DNA molecules.",1511.03918v1
+2015-12-01,Nonequilibrium low temperature phase in pyrochlore iridate Y$_2$Ir$_2$O$_7$: Possibility of glass-like dynamics,"Geometrical frustration and spin-orbit coupling effect together play vital
+role to influence properties in pyrochlore based iridium oxides. Here we have
+investigated detailed structural, magnetic, thermodynamic and transport
+properties of pyrochlore iridate Y$_2$Ir$_2$O$_7$. Magnetization data show
+onset of magnetic irreversibility around temperature $T_{irr}$ $\sim$ 160 K,
+however, no sign of long-range type ferromagnetic ordering is observed below
+$T_{irr}$. Specific heat data show no visible anomaly across $T_{irr}$, and the
+analysis of data indicate sizable density of states across Fermi level.
+Temperature dependent x-ray diffraction measurements show no change in
+structural symmetry down to low temperature. The material, on the other hand,
+shows significant relaxation and aging behavior similar to glassy dynamics. The
+electronic charge transport in this highly insulating system is found to follow
+power law dependence with temperature. The material shows negative
+magnetoresistance which is explained with quantum interference effect.",1512.00233v1
+2016-02-18,Signatures of Topological Phase Transition in 3d Topological Insulators from Dynamical Axion Response,"Axion electrodynamics, first proposed in the context of particle physics,
+manifests itself in condensed matter physics in the topological field theory
+description of 3d topological insulators and gives rise to magnetoelectric
+effect, where applying magnetic (electric) field $\mathbf{B}(\mathbf{E})$
+induces polarization (magnetization) $\mathbf{p}(\mathbf{m})$. We use linear
+response theory to study the associated topological current using the
+Fu-Kane-Mele model of 3d topological insulators in the presence of
+time-dependent uniform weak magnetic field. By computing the dynamical current
+susceptibility $\chi^{\mathbf{j}_p\mathbf{j}_p}_{ij}(\omega)$, we discover from
+its static limit an `order parameter' of the topological phase transition
+between weak topological (or ordinary) insulator and strong topological
+insulator, found to be continuous. The
+$\chi^{\mathbf{j}_p\mathbf{j}_p}_{ij}(\omega)$ shows a sign-changing
+singularity at a critical frequency with suppressed strength in the topological
+insulating state. Our results can be verified in current noise experiment on 3d
+TI candidate materials for the detection of such topological phase transition.",1602.05878v2
+2016-03-11,Time-dependent spin and transport properties of a single-molecule magnet in a tunnel junction,"In single-molecule magnets, the exchange between a localized spin moment and
+the electronic background provides a suitable laboratory for studies of
+dynamical aspects of both local spin and transport properties. Here we address
+the time evolution of a localized spin moment coupled to an electronic level in
+a molecular quantum dot embedded in a tunnel junction between metallic leads.
+The interactions between the localized spin moment and the electronic level
+generate an effective interaction between the spin moment at different
+instances in time. Therefore, we show that, despite being a single-spin system,
+there are effective contributions of isotropic Heisenberg, and anisotropic
+Ising and Dzyaloshinski-Moriya character acting on the spin moment. The
+interactions can be controlled by gate voltage, voltage bias, the spin
+polarization in the leads, in addition to external magnetic fields. Signatures
+of the spin dynamics are found in the transport properties of the tunneling
+system, and we demonstrate that measurements of the spin current may be used
+for read-out of the local spin moment orientation.",1603.03628v2
+2016-04-04,Hindered magnetic dipole transitions between P-wave bottomonia and coupled-channel effects,"In the hindered magnetic dipole transitions of heavy quarkonia, the
+coupled-channel effects originating from the coupling of quarkonia to a pair of
+heavy and anti-heavy mesons can play a dominant role. Here, we study the
+hindered magnetic dipole transitions between two $P$-wave bottomonia, $\chi_b(n
+P)$ and $h_b(n^\prime P)$, with $n\neq n^\prime$. In these processes the
+coupled-channel effects are expected to lead to partial widths much larger than
+the quark model predictions. We estimate these partial widths which, however,
+are very sensitive to unknown coupling constants related to the vertices
+$\chi_{b0}(nP)B\bar B$. A measurement of the hindered M1 transitions can shed
+light on the coupled-channel dynamics in these transitions and hence on the
+size of the coupling constants. We also suggest to check the coupled-channel
+effects by comparing results from quenched and fully dynamical lattice QCD
+calculations.",1604.00770v2
+2016-04-07,Tunable magneto-granular phononic crystals,"This paper reports on the study of the dynamics of 1D magneto-granular
+phononic crystals composed of a chain of spherical steel beads inside a
+properly designed magnetic field. This field is induced by an array of
+permanent magnets, located in a holder at a given distance from the chain. The
+theoretical and experimental results of the band gap structure are displayed,
+including all six degrees of freedom for the beads, i.e. three translations and
+three rotations. Experimental evidence of transverse-rotational modes of
+propagation is pre- sented; moreover, by changing the strength of the magnetic
+field, the dynamic response of the granular chain is tuned. The combination of
+non-contact tunability with the potentially strong nonlinear behavior of gran-
+ular systems ensures the suitability of magneto-granular phononic crystals as
+nonlinear, tunable mechanical metamaterials for use in controlling elastic wave
+propagation.",1604.01973v1
+2016-06-13,Tridimensional to bidimensional transition in magnetohydrodynamic turbulence with a guide field and kinetic helicity injection,"We study the transition in dimensionality of a three-dimensional
+magnetohydrodynamic flow forced only mechanically, when the strength of a
+magnetic guiding field is gradually increased. We use numerical simulations to
+consider cases in which the mechanical forcing injects (or not) helicity in the
+flow. As the guiding field is increased, the strength of the magnetic field
+fluctuations decrease as a power law of the guiding field intensity. We show
+that for strong enough guiding fields, the helical magnetohydrodynamic flow can
+become almost two-dimensional. In this case, the mechanical energy can undergo
+a process compatible with an inverse cascade, being transferred preferentially
+towards scales larger than the forcing scale. The presence of helicity changes
+the spectral scaling of the small magnetic field fluctuations, and affects the
+statistics of the velocity field and of the velocity gradients. Moreover, at
+small scales the dynamics of the flow becomes dominated by a direct cascade of
+helicity, which can be used to derive scaling laws for the velocity field.",1606.04026v3
+2016-06-27,Supercurrent-Induced Spin-Orbit Torques,"We theoretically investigate the supercurrent-induced magnetization dynamics
+of a two-dimensional lattice of ferromagnetically ordered spins placed on a
+conventional superconductor with broken spatial inversion symmetry and strong
+spin-orbit coupling. We develop a phenomenological description of the coupled
+dynamics of the superconducting condensate and the spin system, and demonstrate
+that supercurrents produce a reactive spin-orbit torque on the magnetization.
+By performing a microscopic self-consistent calculation, we show that the
+spin-orbit torque originates from a spin-polarization of the Cooper pairs due
+to current-induced spin-triplet correlations. Interestingly, we find that there
+exists an intrinsic limitation for the maximum achievable spin-orbit torque,
+which is determined by the coupling strength between the condensate and the
+spin system. In proximitized hole-doped semiconductors, the maximum achievable
+spin-orbit torque field is estimated to be on the order of $0.16$ mT, which is
+comparable to the critical field for current-induced magnetization switching in
+ferromagnetic semiconductors.",1606.08470v1
+2016-06-29,Interaction-Induced Topological and Magnetic Phases in the Hofstadter-Hubbard Model,"Interaction effects have been a subject of contemporary interest in
+topological phases of matter. But in the presence of interactions, the accurate
+determination of topological invariants in their general form is difficult due
+to their dependence on multiple integrals containing Green's functions and
+their derivatives. Here we employ the recently proposed ""effective topological
+Hamiltonian"" approach to explore interaction-induced topological phases in the
+time-reversal-invariant Hofstadter-Hubbard model. Within this approach, the
+zero-frequency part of the self-energy is sufficient to determine the correct
+topological invariant. We combine the topological Hamiltonian approach with the
+local self-energy approximation, both for the static and the full dynamical
+self-energy evaluated using dynamical mean field theory (DMFT), and present the
+resulting phase diagram in the presence of many-body interactions. We
+investigate the emergence of quantum spin Hall (QSH) states for different
+interaction strengths by calculating the $\mathbb{Z}_2$ invariant. The
+interplay of strong correlations and a staggered potential also induces
+magnetic long-range order with an associated first order transition. We present
+results for the staggered magnetization ( $m_s$ ), staggered occupancy ( $n_s$
+), and double occupancy across the transition.",1606.09161v2
+2016-07-15,Electrified magnetic catalysis in three-dimensional topological insulators,"The gap equations for the surface quasiparticle propagators in a slab of
+three-dimensional topological insulator in external electric and magnetic
+fields perpendicular to the slab surfaces are analyzed and solved. A different
+type of magnetic catalysis is revealed with the dynamical generation of both
+Haldane and Dirac gaps. Its characteristic feature manifests itself in the
+crucial role that the electric field plays in dynamical symmetry breaking and
+the generation of a Dirac gap in the slab. It is argued that, for a
+sufficiently large external electric field, the ground state of the system is a
+phase with a homogeneous surface charge density.",1607.04649v2
+2016-09-29,Energy dynamics in a generalized compass chain,"We investigate the energy dynamics in a generalized compass chain under an
+external magnetic field. We show that the energy current operators act on three
+contiguous sites in the absence of the magnetic field, and they are
+incorporated with inhomogenous Dzyaloshinskii-Moriya interactions in the
+presence of the magnetic field. These complex interactions remain the
+Hamiltonian be an exactly solvable spin model. We study the effects of the
+three-site interactions and the Dzyaloshinskii-Moriya interactions on the
+energy spectra and phase diagram. The results have revealed that the energy
+current of the pristine quantum compass model is conserved due to the
+associated intermediate symmetries, and for other general cases such
+characteristic does not exist.",1609.09203v1
+2016-10-04,Effect of temperature on spin-transfer torque induced magnetic solitons,"Spin-transfer torques in a nanocontact to an extended magnetic film can
+create spin waves that condense to form dissipative droplet solitons. Here we
+report an experimental study of the temperature dependence of the current and
+applied field thresholds for droplet soliton formation, as well as the
+nanocontact's electrical characteristics associated with droplet dynamics.
+Nucleation of droplet solitons requires higher current densities at higher
+temperatures, in contrast to typical spin-transfer torque induced switching
+between static magnetic states. Magnetoresistance and electrical noise
+measurements show that soliton instabilities become more pronounced with
+increasing temperature. These results are of fundamental interest in
+understanding the influence of thermal noise on droplet solitons, and in
+controlling their dynamics.",1610.00931v1
+2016-10-11,Self-Consistent Field Theory studies of the thermodynamics and quantum spin dynamics of magnetic Skyrmions,"A self-consistent field theory is introduced and used to investigate the
+thermodynamics and spin dynamics of an $S = 1$ quantum spin system with a
+magnetic Skyrmion. The temperature dependence of the Skyrmion profile as well
+as the phase diagram are calculated. It is shown that the Skyrmion carries a
+phase transition to the ferromagnetic phase of first order with increasing
+temperature, while the magnetization of the surrounding ferromagnet undergoes a
+phase transition of second order when changing to the paramagnetic phase.
+Furthermore, the electric field driven annihilation process of the Skyrmion is
+described quantum mechanical by solving the time dependent Schr\""odinger
+equation. The results are compared with the trajectories of the semi-classical
+description of the spin expectation values using a differential equation
+similar to the classical Landau-Lifshitz-Gilbert equation.",1610.03191v2
+2016-10-12,Signatures of Chaos in Thermal Switching of Nanomagnets,"Thermally-activated magnetization dynamics of small nanoparticles subject to
+microwave (AC) external fields is studied. It is shown that, under sufficiently
+strong microwave excitations, chaotic magnetization dynamics may occur close to
+saddle-type heteroclinic connections, and this heteroclinic chaos is
+responsible for the erosion of the safe basin around stable magnetization
+states. The erosion phenomenon is then connected to the escape problem from the
+energy well surrounding a stable equilibrium. It is shown that escape times
+follow a generalized Arrhenius' law governed by temperature, microwave field
+amplitude, frequency and heteroclinic chaos threshold.",1610.03755v3
+2016-10-21,Spin transport and dynamics in all-oxide perovskite La$_{2/3}$Sr$_{1/3}$MnO$_3$/SrRuO$_3$ bilayers probed by ferromagnetic resonance,"Thin films of perovskite oxides offer the possibility of combining emerging
+concepts of strongly correlated electron phenomena and spin current in magnetic
+devices. However, spin transport and magnetization dynamics in these complex
+oxide materials are not well understood. Here, we experimentally quantify spin
+transport parameters and magnetization damping in epitaxial perovskite
+ferromagnet/paramagnet bilayers of La$_{2/3}$Sr$_{1/3}$MnO$_3$/SrRuO$_3$
+(LSMO/SRO) by broadband ferromagnetic resonance spectroscopy. From the SRO
+thickness dependence of Gilbert damping, we estimate a short spin diffusion
+length of $\lesssim$1 nm in SRO and an interfacial spin-mixing conductance
+comparable to other ferromagnet/paramagnetic-metal bilayers. Moreover, we find
+that anisotropic non-Gilbert damping due to two-magnon scattering also
+increases with the addition of SRO. Our results demonstrate LSMO/SRO as a
+spin-source/spin-sink system that may be a foundation for examining
+spin-current transport in various perovskite heterostructures.",1610.06661v1
+2016-12-20,Eigenmodes of Neel skyrmions in ultrathin magnetic films,"The static and dynamic states of N\'eel skyrmions in ultrathin ferromagnetic
+films with interfacial Dzyaloshinskii-Moriya interaction (DMI) have been
+micromagnetically simulated as functions of the interfacial DMI strength and
+applied static magnetic field. Findings reveal that while the breathing,
+counterclockwise (CCW) and clockwise (CW) rotational eigenmodes exist in the
+skyrmion lattice (SkL) phase, only the first two modes are present in the
+isolated skyrmion (ISk) phase. Additionally, the eigenfrequency of the CCW mode
+is insensitive to the magnetic-field driven SkL-ISk phase transition, and the
+inter-skyrmion interaction is largely responsible for exciting the CW mode in
+the SkL phase. The findings provide physical insight into the dynamics of the
+phase transition and would be of use to potential skyrmion-based microwave
+applications.",1612.06622v3
+2017-03-06,Topological Properties of the Chiral Magnetic Effect in Multi-Weyl Semimetals,"We compute the chiral magnetic effect (CME) in multi-Weyl semimetals
+(multi-WSMs) based on the chiral kinetic theory. Multi-WSMs are WSMs with
+multiple monopole charges that have nonlinear and anisotropic dispersion
+relations near Weyl points, and we need to extend conventional computation of
+CME in WSMs with linear dispersion relations. Topological properties of CME in
+multi-WSMs are investigated in details for not only static magnetic fields but
+also time-dependent (dynamic) ones. We propose an experimental setup to measure
+the multiple monopole charge via the topological nature hidden in the dynamic
+CME.",1703.02040v2
+2017-03-08,Vortex dynamics in lattice Bose gases in a synthesized magnetic field with a random noise and a dissipation: Study by the stochastic Gross-Pitaevskii equation,"In this paper, we investigate vortex dynamics in a two-dimensional
+Bose-Hubbard model coupled with a weak artificial magnetic field, a random
+white noise and a dissipation. Origin of the noise and dissipation is
+considered as thermal fluctuations of atoms that do not participate the
+Bose-Einstein condensation (BEC). Solving a stochastic Gross-Pitaevskii
+equation to this system, we show that the interplay of the magnetic field and
+the white noise generates vortices in the bulk of the BEC and stable steady
+states of vortices form after a transition period. We calculate the
+incompressible part of the kinetic-energy spectrum of the BEC. In the
+transition period, a Kolmogorov $k^{-5/3}$ spectrum appears in the infrared
+regime with the wave number $k$, $k<\zeta^{-1}$, where $\zeta$ is the healing
+length, whereas in the ultraviolet region, $k>\zeta^{-1}$, the spectrum behaves
+as $k^{-3}$. On the other hand in the steady states, another scaling low
+appears. We find a relationship between the above mentioned kinetic-energy
+spectra and the velocity of vortices. By an inverse cascade, the large velocity
+of a few created vortices develops the Kolmogorov $k^{-5/3}$ spectrum.",1703.02750v1
+2017-03-16,Rectification and One-Way Street for the Energy Current in Boundary-Driven Asymmetric Quantum Spin Chains,"Motivated by the demand of efficient quantum devices to engineer the energy
+transport, we analyze some inhomogeneous quantum spin systems, including the
+XXZ chains, with magnetization baths at the ends. Aimed at finding general
+properties, we study the effects of suitable transformations on the
+boundary-driven Lindblad master equation associated to the dynamics of the
+systems. For asymmetric models with target polarization at the edges or twisted
+XY boundary gradients, we show properties of the steady state which establish
+features of the energy current, irrespective of the system size and of the
+regime of transport. We show the ubiquitous occurrence of energy rectification
+and, more interestingly, of an unusual phenomenon: in the absence of external
+magnetic field, there is an one-way street for the energy current, i.e., the
+direction of the energy current does not change as we invert the magnetization
+baths at the boundaries. Given the extensiveness of the procedures, which
+essentially involve properties of the Lindblad master equation, our results
+certainly follow for other interactions and other boundary conditions.
+Moreover, our results indicate graded spin chains as genuine quantum
+rectifiers.",1703.05567v1
+2017-03-26,Relativistic magnetohydrodynamics,"We present the equations of relativistic hydrodynamics coupled to dynamical
+electromagnetic fields, including the effects of polarization, electric fields,
+and the derivative expansion. We enumerate the transport coefficients at
+leading order in derivatives, including electrical conductivities, viscosities,
+and thermodynamic coefficients. We find the constraints on transport
+coefficients due to the positivity of entropy production, and derive the
+corresponding Kubo formulas. For the neutral state in a magnetic field, small
+fluctuations include Alfven waves, magnetosonic waves, and the dissipative
+modes. For the state with a non-zero dynamical charge density in a magnetic
+field, plasma oscillations gap out all propagating modes, except for
+Alfven-like waves with a quadratic dispersion relation. We relate the transport
+coefficients in the ""conventional"" magnetohydrodynamics (formulated using
+Maxwell's equations in matter) to those in the ""dual"" version of
+magnetohydrodynamics (formulated using the conserved magnetic flux).",1703.08757v1
+2017-03-27,Anomalous Hall effect and topological defects in antiferromagnetic Weyl semimetals: Mn$_3$Sn/Ge,"We theoretically study the interplay between bulk Weyl electrons and magnetic
+topological defects, including magnetic domains, domain walls, and
+$\mathbb{Z}_6$ vortex lines, in the antiferromagnetic Weyl semimetals \mnsn\
+and Mn$_3$Ge with negative vector chirality. We argue that these materials
+possess a hierarchy of energies scales which allows a description of the spin
+structure and spin dynamics using a XY model with $\mathbb{Z}_6$ anisotropy. We
+propose a dynamical equation of motion for the XY order parameter, which
+implies the presence of $\mathbb{Z}_6$ vortex lines, the double-domain pattern
+in the presence of magnetic fields, and the ability to control domains with
+current. We also introduce a minimal electronic model which allows efficient
+calculation of the electronic structure in the antiferromagnetic configuration,
+unveiling Fermi arcs at domain walls, and sharp quasi-bound states at
+$\mathbb{Z}_6$ vortices. Moreover, we have shown how these materials may allow
+electronic-based imaging of antiferromagnetic microstructure, and propose a
+possible device based on domain-dependent anomalous Hall effect.",1703.08910v1
+2017-03-30,Multidimensional relativistic MHD simulations of Pulsar Wind Nebulae: dynamics and emission,"Pulsar Wind Nebulae, and the Crab nebula in particular, are the best cosmic
+laboratories to investigate the dynamics of magnetized relativistic outflows
+and particle acceleration up to PeV energies. Multidimensional MHD modeling by
+means of numerical simulations has been very successful at reproducing, to the
+very finest details, the innermost structure of these synchrotron emitting
+nebulae, as observed in the X-rays. Therefore, the comparison between the
+simulated source and observations can be used as a powerful diagnostic tool to
+probe the physical conditions in pulsar winds, like their composition,
+magnetization, and degree of anisotropy. However, in spite of the wealth of
+observations and of the accuracy of current MHD models, the precise mechanisms
+for magnetic field dissipation and for the acceleration of the non-thermal
+emitting particles are mysteries still puzzling theorists to date. Here we
+review the methodologies of the computational approach to the modeling of
+Pulsar Wind Nebulae, discussing the most relevant results and the recent
+progresses achieved in this fascinating field of high-energy astrophysics.",1703.10442v1
+2017-04-30,Angular Dependent Magnetization Dynamics of Kagome Artificial Spin Ice Incorporating Topological Defects,"We report angular-dependent spin-wave spectroscopy on kagome artificial spin
+ice made of large arrays of interconnected Ni80Fe20 nanobars. Spectra taken in
+saturated and disordered states exhibit a series of resonances with
+characteristic in-plane angular dependencies. Micromagnetic simulations allow
+us to interpret characteristic resonances of a two-step magnetization reversal
+of the nanomagnets. The dynamic properties are consistent with topological
+defects that are provoked via a magnetic field applied at specific angles.
+Simulations that we performed on previously investigated kagome artificial spin
+ice consisting of isolated nanobars show characteristic discrepancies in the
+spin wave modes which we explain by the absence of vertices.",1705.00270v1
+2017-06-05,Terahertz-driven magnetism dynamics in the orthoferrite DyFeO3,"Terahertz driven magnetization dynamics are explored in the orthoferrite
+DyFeO3. A high-field, single cycle THz pulse is used to excite magnon modes in
+the crystal together with other resonances. Both quasi-ferromagnetic and
+quasi-antiferromagnetic magnon modes are excited and appear in time-resolved
+measurements of the Faraday rotation. Other modes are also observed in the
+measurements of the time-resolved linear birefringence. Analysis of the
+excitation process reveals that despite larger than expected electro-optical
+susceptibility it is mainly the THz magnetic field that couples to the
+quasi-ferromagnetic and quasi-antiferromagnetic magnon branches.",1706.01545v1
+2017-06-09,Magnetically Activated Rotational Vacuum Friction,"We predict the existence of a torque acting on an isotropic neutral
+nanosphere activated by a static magnetic field when the particle temperature
+differs from the surrounding vacuum. This phenomenon originates in
+time-reversal symmetry breaking of the particle interaction with the vacuum
+electromagnetic field. We present a rigorous quantum treatment of photons and
+particle excitations that leads to a nonzero torque even in a motionless
+particle. We also find that the dynamical evolution of the particle temperature
+and rotation frequency follow an exotic dynamics, including spontaneous changes
+in the rotation direction. Magnetically activated thermal vacuum torques open a
+unique avenue for the investigation of the effect of time-reversal
+symmetry-breaking in thermal and Casimir physics.",1706.02924v3
+2017-06-29,Three-dimensional oscillatory magnetic reconnection,"Here we detail the dynamic evolution of localised reconnection regions about
+three-dimensional (3D) magnetic null points by using numerical simulation. We
+demonstrate for the first time that reconnection triggered by the localised
+collapse of a 3D null point due to an external MHD wave involves a
+self-generated oscillation, whereby the current sheet and outflow jets undergo
+a reconnection reversal process during which back-pressure formation at the jet
+heads acts to prise open the collapsed field before overshooting the
+equilibrium into an opposite-polarity configuration. The discovery that
+reconnection at fully 3D nulls can proceed naturally in a time-dependent and
+periodic fashion is suggestive that oscillatory reconnection mechanisms may
+play a role in explaining periodicity in astrophysical phenomena associated
+with magnetic reconnection, such as the observed quasi-periodicity of solar and
+stellar flare emission. Furthermore, we find a consequence of oscillatory
+reconnection is the generation of a plethora of freely-propagating MHD waves
+which escape the vicinity of the reconnection region",1706.09662v1
+2017-08-14,Magnetization dynamics of weak stripe domains in Fe-N thin films: a multi-technique complementary approach,"The resonant eigenmodes of a nitrogen-implanted iron {\alpha}'-FeN
+characterized by weak stripe domains are investigated by Brillouin light
+scattering and broadband ferromagnetic resonance experiments, assisted by
+micromagnetic simulations. The spectrum of the dynamic eigenmodes in the
+presence of the weak stripes is very rich and two different families of modes
+can be selectively detected using different techniques or different
+experimental configurations. Attention is paid to the evolution of the mode
+frequencies and spatial profiles under the application of an external magnetic
+field, of variable intensity, in the direction parallel or transverse to the
+stripes. The different evolution of the modes with the external magnetic field
+is accompanied by a distinctive spatial localization in specific regions, such
+as the closure domains at the surface of the stripes and the bulk domains
+localized in the inner part of the stripes. The complementarity of BLS and FMR
+techniques, based on different selection rules, is found to be a fruitful tool
+for the study of the wealth of localized mag-netic excitations generally found
+in nanostructures.",1708.04178v1
+2017-08-18,General treatment of quantum and classical spinning particles in external fields,"We develop the general theory of spinning particles with electric and
+magnetic dipole moments moving in arbitrary electromagnetic, inertial and
+gravitational fields. Both the quantum-mechanical and classical dynamics is
+investigated. We start from the covariant Dirac equation extended to a
+spin-${\frac 12}$ fermion with anomalous magnetic and electric dipole moments
+and then perform the relativistic Foldy-Wouthuysen transformation. This
+transformation allows us to obtain the quantum-mechanical equations of motion
+for the physical operators in the Schr\""odinger form and to establish the
+classical limit of relativistic quantum mechanics. The results obtained are
+then compared to the general classical description of the spinning particle
+interacting with electromagnetic, inertial and gravitational fields. The
+complete agreement between the quantum mechanics and the classical theory is
+proven in the general case. As an application of the results obtained, we
+consider the dynamics of a spinning particle in a gravitational wave and
+analyze the prospects of using the magnetic resonance setup to find possible
+manifestations of the gravitational wave on spin.",1708.05601v2
+2017-10-30,Spatial symmetry breaking in single-frequency CCP discharge with transverse magnetic field,"An independent control of the flux and energy of ions impacting on an object
+immersed in a plasma is often desirable for many industrial processes such as
+microelectronics manufacturing. We demonstrate that a simultaneous control of
+these quantities is possible by a suitable choice of a static magnetic field
+applied parallel to the plane electrodes in a standard single frequency
+capacitively coupled plasma device. Our particle-in-cell simulations show a 60%
+reduction in the sheath width (that improves control of ion energy) and a four
+fold increase in the ion flux at the electrode as a consequence of the altered
+ion and electron dynamics due to the ambient magnetic field. A detailed
+analysis of the particle dynamics is presented and the optimized operating
+parameters of the device are discussed. The present technique offers a simple
+and attractive alternative to conventional dual frequency based devices that
+often suffer from undesirable limitations arising from frequency coupling and
+electromagnetic effects.",1710.11254v2
+2017-12-01,Active control of thermomagnetic avalanches in superconducting Nb films with tunable anisotropy,"Active triggering and manipulation of ultrafast flux dynamics in
+superconductors are demonstrated in films of Nb. Controlled amounts of magnetic
+flux were injected from a point along the edge of a square sample, which at 2.5
+K responds by nucleation of a thermomagnetic avalanche. Magneto-optical imaging
+was used to show that when such films are cooled in the presence of in-plane
+magnetic fields they become anisotropic, and the morphology of the avalanches
+change systematically, both with the direction and magnitude of the field. The
+images reveal that the avalanching dendrites consistently bend towards the
+direction perpendicular to that of the in-plane field. The effect increases
+with the field magnitude, and at 1.5 kOe the triggered avalanche becomes
+quenched at the nucleation stage. The experimental results are explained based
+on a theoretical model for thermomagnetic avalanche nucleation in
+superconducting films, and by assuming that the frozen-in flux generates
+in-plane anisotropy in the film thermal conductance. The results demonstrate
+that applying in-plane magnetic fields to film superconductors can be a
+versatile external tool for controlling their ultrafast flux dynamics.",1712.00300v1
+2017-12-11,Convergent tangent plane integrators for the simulation of chiral magnetic skyrmion dynamics,"We consider the numerical approximation of the Landau-Lifshitz-Gilbert
+equation, which describes the dynamics of the magnetization in ferromagnetic
+materials. In addition to the classical micromagnetic contributions, the energy
+comprises the Dzyaloshinskii-Moriya interaction, which is the most important
+ingredient for the enucleation and the stabilization of chiral magnetic
+skyrmions. We propose and analyze three tangent plane integrators, for which we
+prove (unconditional) convergence of the finite element solutions towards a
+weak solution of the problem. The analysis is constructive and also establishes
+existence of weak solutions. Numerical experiments demonstrate the
+applicability of the methods for the simulation of practically relevant problem
+sizes.",1712.03795v3
+2018-02-01,Theory of spin and lattice wave dynamics excited by focused laser pulses,"We develop a theory of the spin wave dynamics excited by ultrafast focused
+laser pulses in a magnetic film. We take into account both volume and surface
+spin wave modes in the presence of applied, dipolar and magnetic anisotropy
+fields and include the dependence on laser spot exposure size and magnetic
+damping. We show that the sound waves generated by local heating by an
+ultrafast focused laser pulse can excite a wide spectrum of spin waves (on top
+of a dominant magnon-phonon contribution). Good agreement with recent
+experiments supports the validity of the model.",1802.00178v2
+2018-04-02,Importance of orbital fluctuations for the magnetic dynamics in heavy-fermion compound SmB$_6$,"The emergent dynamical processes associated with magnetic excitations in
+heavy-fermion SmB$_6$ are investigated. By imposing multiorbital interactions
+on a first-principles model, we find the interplay between spin and orbital
+fluctuations in the $f$ manifold is highly sensitive to local correlations. The
+magnetic phase diagram constructed at zero temperature reveals quantum critical
+features with the existence of several competing phases. Within the random
+phase approximation, we perform a comprehensive study of the spin-spin
+correlation function, and our results agree with neutron scattering
+experiments. Spectral weight analysis shows the low energy spin excitations are
+selectively accompanied by orbital fluctuations, indicating a non-trivial
+entanglement between the spin and orbital degree of freedom driven by
+relativistic couplings.",1804.00674v2
+2018-04-02,Spin torques and magnetic texture dynamics driven by the supercurrent in superconductor/ferromagnet structures,"We introduce the general formalism to describe spin torques induced by the
+supercurrents injected from the adjacent superconducting electrodes into the
+spin-textured ferromagnets. By considering the adiabatic limit for the
+equal-spin superconducting correlations in the ferromagnet we show that the
+supercurrent can generate both the field-like spin transfer torque and the
+spin-orbital torque. These dissipationless spin torques are expressed through
+the current-induced corrections to the effective field derived from the system
+energy. The general formalism is applied to show that the supercurrent can
+either shift or move the magnetic domain walls depending on their structure and
+the type of spin-orbital interaction in the system. These results can be used
+for the prediction and interpretation of the experiments studying magnetic
+texture dynamics in superconductor/ferromagnet/superconductor Josephson
+junctions and other hybrid structures.",1804.00718v2
+2018-04-05,Dynamics of macrospin under periodic field and spin transfer torque,"The dynamics of a macrospin model for a single magnetic domain is
+investigated in two cases: (i) under the action of a periodic magnetic field
+and (ii) under the external field plus a spin transfer torque from
+spin-polarized current or spin current. It has been proved that (i) without
+spin transfer torque, the trajectory of magnetization (hysteresis) is always a
+closed curve oscillating between two stable points and following the same path
+each time; (ii) under the action of a constant field (or with small periodic
+perturbation) and a constant spin transfer torque, the spin would always turn
+to the stable solution finally, which is independent of the parameters or
+initial conditions; (iii) considering a periodic oscillating field plus a spin
+transfer torque, the system can also have a stable solution around a limit
+circle, but on some special points on the attractor, the system may be
+sensitive to the initial conditions and have no limit circle.",1804.01667v1
+2018-04-03,Generalisation of Gilbert damping and magnetic inertia parameter as a series of higher-order relativistic terms,"The phenomenological Landau-Lifshitz-Gilbert (LLG) equation of motion remains
+as the cornerstone of contemporary magnetisation dynamics studies, wherein the
+Gilbert damping parameter has been attributed to first-order relativistic
+effects. To include magnetic inertial effects the LLG equation has previously
+been extended with a supplemental inertia term and the arising inertial
+dynamics has been related to second-order relativistic effects. Here we start
+from the relativistic Dirac equation and, performing a Foldy-Wouthuysen
+transformation, derive a generalised Pauli spin Hamiltonian that contains
+relativistic correction terms to any higher order. Using the Heisenberg
+equation of spin motion we derive general relativistic expressions for the
+tensorial Gilbert damping and magnetic inertia parameters, and show that these
+tensors can be expressed as series of higher-order relativistic correction
+terms. We further show that, in the case of a harmonic external driving field,
+these series can be summed and we provide closed analytical expressions for the
+Gilbert and inertial parameters that are functions of the frequency of the
+driving field.",1804.09242v1
+2018-06-03,Dynamical off-equilibrium scaling across magnetic first-order phase transitions,"We investigate the off-equilibrium dynamics of a classical spin system with
+$O(n)$ symmetry in $2< D <4$ spatial dimensions and in the limit $n\to \infty$.
+The system is set up in an ordered equilibrium state is and subsequently driven
+out of equilibrium by slowly varying the external magnetic field $h$ across the
+transition line $h_c=0$ at fixed temperature $T\leq T_c$. We distinguish the
+cases $T = T_c$ where the magnetic transition is continuous and $T<T_c$ where
+the transition is discontinuous. In the former case, we apply a standard
+Kibble-Zurek approach to describe the non-equilibrium scaling and formally
+compute the correlation functions and scaling relations. For the discontinuous
+transition we develop a scaling theory which builds on the coherence length
+rather than the correlation length since the latter remains finite for all
+times. Finally, we derive the off-equilibrium scaling relations for the
+hysteresis loop area during a round-trip protocol that takes the system across
+its phase transition and back. Remarkably, our results are valid beyond the
+large-$n$ limit.",1806.00866v2
+2018-06-28,Thermal fluctuations in antiferromagnetic nanostructures,"A theoretical model is developed that can accurately analyze the effects of
+thermal fluctuations in antiferromagnetic (AFM) nano-particles. The approach is
+based on Fourier series representation of the random effective field with
+cut-off frequencies of physical origin at low and high limits while satisfying
+the fluctuation-dissipation theorem at the same time. When coupled with the
+formalism of a Langevin dynamical equation, it can describe the stochastic
+N\'eel vector dynamics with the AFM parameters, circumventing the arbitrariness
+of the commonly used treatments in the micro-magnetic simulations. Subsequent
+application of the model to spontaneous N\'eel vector switching provides a
+thermal stability analysis of the AFM states. The numerical simulation shows
+that the AFM states are much less prone to the thermally induced accidental
+flips than the ferromagnetic counterparts, suggesting a longer retention time
+for the former.",1806.11130v2
+2018-07-03,Nonlinear dynamo in obliquely rotating stratified electroconductive fluid in an uniformly magnetic field,"We study a new type of large-scale instability, which arises in obliquely
+rotating stratified electroconductive fluid with an external uniform magnetic
+field and a small-scale external force having zero helicity. This force gives
+rise to small-scale oscillations of the velocity with a small Reynolds number.
+Using the method of multi-scale asymptotic expansions there are obtained
+nonlinear equations for vortex and magnetic perturbations in the third order in
+Reynolds number. Studied is the linear stage of magneto-vortex dynamo caused by
+instabilities of $\alpha$-effect type. Stationary solutions for the equations
+of nonlinear magneto-vortex dynamo are found by numerical methods in the form
+of localized chaotic structures.",1807.01986v1
+2018-07-15,Chiral Magnetic Effect in Isobaric Collisions from Anomalous-Viscous Fluid Dynamics (AVFD),"The isobaric collision experiment at RHIC provides the unique opportunity to
+detect the possible signal of Chiral Magnetic Effect (CME) in heavy ion
+collisions. The idea is to contrast the correlation observables of the two
+colliding systems that supposedly have identical flow-driven background
+contributions while quite different CME signal contributions due to the 10%
+variation in their nuclear charge and thus magnetic field strength. With the
+recently developed quantitative simulation tool for computing CME signal, the
+Anomalous-Viscous Fluid Dynamics (AVFD), we demonstrate that a joint
+(multiplicity + elliptic-flow) event selection is crucial for this purpose. We
+further propose to use the absolute difference between RuRu and ZrZr events
+(after using identical event selection) for detecting CME signal and make
+predictions for the correlation observables.",1807.05604v1
+2018-09-12,Inversion and magnetic quantum oscillations in symmetric periodic Anderson model,"We study the symmetric periodic Anderson model of the conduction electrons
+hybridized with the localized correlated electrons on square lattice. Using the
+canonical representation of electrons by Kumar, we do a self-consistent theory
+of its effective charge and spin dynamics, which produces an insulating ground
+state that undergoes continuous transition from the Kondo singlet to N\'eel
+antiferromagnetic phase with decreasing hybridization, and uncovers two
+inversion transitions for the charge quasiparticles. With suitably inverted
+quasiparticle bands for moderate to weaker effective Kondo couplings, this
+effective charge dynamics in the magnetic field coupled to electronic motion
+produces magnetic quantum oscillations with frequency corresponding to the half
+Brillouin zone.",1809.04654v2
+2018-09-21,Quantum hardware simulating four-dimensional inelastic neutron scattering,"Magnetic molecules, modelled as finite-size spin systems, are test-beds for
+quantum phenomena and could constitute key elements in future spintronics
+devices, long-lasting nanoscale memories or noise-resilient quantum computing
+platforms. Inelastic neutron scattering is the technique of choice to probe
+them, characterizing molecular eigenstates on atomic scales. However, although
+large magnetic molecules can be controllably synthesized, simulating their
+dynamics and interpreting spectroscopic measurements is challenging because of
+the exponential scaling of the required resources on a classical computer.
+Here, we show that quantum computers have the potential to efficiently extract
+dynamical correlations and the associated magnetic neutron cross-section by
+simulating prototypical spin systems on a quantum hardware. We identify the
+main gate errors and show the potential scalability of our approach. The
+synergy between developments in neutron scattering and quantum processors will
+help design spin clusters for future applications.",1809.07974v2
+2018-11-05,Vison-Majorana complex zero-energy resonance in Kitaev's spin liquid,"We study the effect of site dilution in Kitaev's model. We derive an
+analytical solution of the dynamical spin correlation functions for arbitrary
+configurations of $Z_2$ fluxes. By incorporating this solution into classical
+Monte Carlo scheme, we address how a site vacancy affects the experimental
+observables, such as the static spin susceptibility and the spin lattice
+relaxation rate, $1/T_1$. As a result, we found an enhancement of dynamical
+magnetic response in the vicinity of vacancy, which leads to Friedel-like
+oscillation in local $1/T_1$, in contrast to limited influences on the static
+susceptibility. Furthermore, we found a sharp zero-energy peak in the magnetic
+excitation spectrum, which is attributed to the Vison & Majorana zero mode
+trapped near the site vacancy. This zero mode can be interpreted as
+fractionalized spin hole into an Ising triplet with differentiated magnetic
+axes, which leads to the characteristic temperature and field-orientational
+dependence of $1/T_1$.",1811.02092v1
+2018-11-23,Axially magnetized Dark Energy cosmological model,"We investigate the behaviour of the skewness parameters for an anisotropic
+universe in the framework of General Relativity. Non interacting dark energy is
+considered in presence of electromagnetic field. A time varying deceleration
+parameter simulated by a hybrid scale factor is considered. The dynamics of the
+universe is investigated in presence and absence of magnetic field. The
+equation of state parameter of dark energy evolves within the range predicted
+by the observations. Magnetic field is observed to have a substantial effect on
+the cosmic dynamics and the skewness parameters. The models discussed here end
+in a big rip and become isotropic at finite time.",1811.09626v3
+2018-11-29,Supertransient Magnetohydrodynamic Turbulence in Keplerian Shear Flows: The role of the Hall Effect,"Space and astrophysical plasmas are frequently found in the regime of
+differential rotation, where the presence of a magnetic field can result in the
+magnetorotational instability, directly responsible for important phenomena
+such as turbulent angular momentum transport in accretion disks. In the absence
+of an imposed magnetic field, a nonlinear dynamo is necessary for this
+transport mechanism to take place. In protoplanetary disks there are regions
+with high density and very low temperatures, which are two necessary conditions
+for the Hall effect to operate, affecting the development of the dynamo and the
+associated turbulence. In this work we perform local magnetohydrodynamic (MHD)
+simulations to study transition to weak turbulence in Keplerian shear flows
+with Hall effect. The Hall effect is shown to lead the system to long-lived
+turbulent transients whose decay time follows an exponential dependence on the
+magnetic Reynolds number and the Hall parameter.",1811.12318v1
+2018-12-05,Characterization and space embedding of directed graphs and social networks through magnetic Laplacians,"Though commonly found in the real world, directed networks have received
+relatively less attention from the literature in which concerns their
+topological and dynamical characteristics. In this work, we develop a magnetic
+Laplacian-based framework that can be used for studying directed complex
+networks. More specifically, we introduce a specific heat measurement that can
+help to characterize the network topology. It is shown that, by using this
+approach, it is possible to identify the types of several networks, as well as
+to infer parameters underlying specific network configurations. Then, we
+consider the dynamics associated with the magnetic Laplacian as a means of
+embedding networks into a metric space, allowing the identification of
+mesoscopic structures in artificial networks or unravel the polarization on
+political blogosphere. By defining a coarse-graining procedure in this metric
+space, we show how to connect the specific heat measurement and the positions
+of nodes in this space.",1812.02160v2
+2018-12-16,Transitions near the onset of low Prandtl-number rotating magnetoconvection,"We investigate the onset of convective instability and subsequent transitions
+near it in Rayleigh-B\'enard convection (RBC) of electrically conducting low
+Prandtl-number (Pr) fluids in the simultaneous presence of rotation about the
+vertical axis and external uniform horizontal magnetic field with free-slip
+boundary conditions. Both three dimensional direct numerical simulations (DNS)
+and low dimensional modeling of the system have been performed for the
+investigation. DNS results show a plethora of patterns near the onset of
+convection for weak magnetic field. Most interestingly, the Nusselt number (Nu)
+computed from the DNS data for relatively stronger magnetic field shows a sharp
+jump at the onset, indicating substantial enhancement of the convective heat
+transfer. The origin of these flow patterns, as well as the reason for a
+notable increase of heat transfer near the onset of convection, are then
+explained using low dimensional models constructed from DNS data.",1812.06422v1
+2018-12-27,Influence of Ohmic and ambipolar heating on thermal structure of accretion discs,"We investigate dynamics of accretion discs of young stars with fossil
+large-scale magnetic field. Our magneto-gas-dynamic (MHD) model of the
+accretion discs includes equations of Shakura and Sunyaev, induction equation,
+equations of thermal and collisional ionization. Induction equation takes into
+account Ohmic and magnetic ambipolar diffusion, magnetic buoyancy. We also
+consider the influence of Ohmic and ambipolar heating on thermal structure of
+the accretion discs. We analyse the influence of considered dissipative MHD
+effects on the temperature of the accretion discs around classical T Tauri
+star. The simulations show that Ohmic and ambipolar heating operate near the
+borders of the region with low ionization fraction (`dead' zone). Temperature
+grows by $\sim 1000$ K near the inner boundary of the `dead' zone, $r\approx
+(0.5-1)$ au, and by $\sim 100$ K near its outer boundary, $r\approx (30-50)$
+au.",1812.10634v1
+2018-12-28,Skyrmion-generated spinmotive forces in inversion broken ferromagnets,"We present an analytical study on the spinmotive force (SMF) generated by
+translational motion of magnetic skyrmion. A SMF refers to an electrical
+voltage induced by dynamical magnetic textures, which reflects the
+spatiotemporal variation of the magnetization. The dynamics of a skyrmion thus
+can be detected by a SMF measurement, which may play an important role in
+future skyrmion-based technologies. We find the dependence of the SMF on
+skyrmion structure (e.g., skyrmion or anti-skyrmion, N\'{e}el or Bloch type,
+and the polarity of the skyrmion core) and Rashba and Dresselhaus spin-orbit
+couplings (SOCs). To this end, we derive explicit formulae for the
+spin-dependent electric fields originating from the two SOCs. Our findings
+offer a comprehensive understanding of the phenomenon and an estimation of the
+electrical voltage signal associated with a moving skyrmion for a given
+experiment.",1812.11120v2
+2019-03-20,Spin dynamics of antiferromagnetically coupled ferromagnetic bilayers -- the case of Cr$_2$WO$_6$ and Cr$_2$MoO$_6$,"Recent inelastic neutron diffraction measurements on Cr$_2$(Te, W, Mo)O$_6$
+have revealed that these systems consist of bilayers of spin-3/2 Cr$^{3+}$ ions
+with strong antiferromagnetic inter-bilayer coupling and tuneable intra-bilayer
+coupling from ferro (for W and Mo) to antiferro (for Te). These measurements
+have determined the ground state spin structure and the values of sublattice
+magnetization, which shows significant reduction of sublattice magnetization
+from the atomic spin value of 3.0$\mu_B$ for Cr$^{3+}$ atoms. In an earlier
+paper we theoretically investigated the low temperature spin dynamics of
+Cr$_2$TeO$_6$ bilayer system where both the intra and inter-bilayer couplings
+are antiferromagnetic. In this paper we investigate Cr$_2$WO$_6$ and
+Cr$_2$MoO$_6$ systems where intra-bilayer exchange couplings are ferromagnetic
+but the inter-bilayer exchange couplings are antiferromagnetic. We obtain the
+magnon dispersion, sublattice magnetization, two-magnon density of states,
+longitudinal spin-spin correlation function, and its powder average and compare
+the results for these systems with results for Cr$_2$TeO$_6$.",1903.08512v1
+2019-04-18,Transient dynamics of nonlinear magneto-optical rotation in the presence of transverse magnetic field,"Nonlinear magneto-optical rotation is studied under non-equilibrium
+conditions. The polarization rotation of linearly polarized light traversing a
+rubidium vapor cell is observed versus the time-dependent (swept) longitudinal
+magnetic field in the presence of static transverse magnetic fields. Presence
+of the transverse fields modifies the character of the observed signals. In
+particular, for weaker transverse fields, field sweep leads two-harmonic
+oscillation of the polarization rotation while crossing zero. Unlike the
+steady-state, it was found that two-frequency oscillations observed in the
+transient signals, are independent of the transverse-field direction. For
+stronger transverse fields, the oscillations deteriorate eventually reaching a
+situation when no-oscillating dynamic signal, with distinct minimum close to
+zero field, is observed. Experimental results are supported with theoretical
+analysis based on the density-matrix formalism. The analysis confirms all the
+features of experimental results while providing an provide intuitive
+explanation of the observed behavior based on angular-momentum probability
+surfaces used for density-matrix visualization.",1904.08753v1
+2019-04-25,Spin-wave propagation in metallic CoFe films determined by microfocused frequency-resolved magneto-optic Kerr effect,"We investigated the magnetization dynamics of a patterned
+Co$_{25}$Fe$_{75}$-based heterostructure with a novel optical measurement
+technique that we call microfocused frequency-resolved magneto optic Kerr
+effect ($\mu$FR-MOKE). We measured the magnetic field dependence of the
+dynamical spin-wave susceptibility and recorded a spatial map of the spin-waves
+excited by a microwave antenna. We compare these results to those obtained on
+the same sample with the established microfocused Brillouin light scattering
+technique. With both techniques, we find a spin-wave propagation length of
+5.6$\mu$m at 10GHz. Furthermore, we measured the dispersion of the wavevector
+and the spin-wave propagation length as a function of the external magnetic
+field. These results are in good agreement with existing literature and with
+the employed Kalinkos-Slavin model.",1904.11273v1
+2019-04-30,Thermal flux-flow regime in long Josephson tunnel junctions,"We study thermal transport induced by soliton dynamics in a long Josephson
+tunnel junction operating in the flux-flow regime. A thermal bias across the
+junction is established by imposing the superconducting electrodes to reside at
+different temperatures, when solitons flow along the junction. Here, we
+consider the effect of both a bias current and an external magnetic field on
+the thermal evolution of the device. In the flux-flow regime, a chain of
+magnetically-excited solitons rapidly moves along the junction driven by the
+bias current. We explore the range of bias current triggering the flux-flow
+regime at fixed values of magnetic field, and the stationary temperature
+distribution in this operation mode. We evidence a steady multi-peaked
+temperature profile which reflects on the average soliton distribution along
+the junction. Finally, we analyse also how the friction affecting the soliton
+dynamics influences the thermal evolution of the system.",1904.13172v2
+2019-04-30,Dynamics of a magnetic skyrmionium in an anisotropy gradient,"Magnetic skyrmionium is a novel magnetization configuration with zero
+skyrmion number, which is composed by two skyrmions with opposite skyrmion
+number. Here, we study the dynamics of skyrmionium under an anisotropy
+gradient. We find that the skyrmionium can be efficiently driven by an
+anisotropy gradient with moving straightly along the direction of gradient. The
+skyrmion Hall angle for skyrmionium is close to zero which is much smaller than
+that of skyrmion. while the speed is much larger. We also demonstrate that the
+skyrmionium motion depends on the damping cofficient, and the skyrmionium
+stabilization in the motion can be modulated by narrowing the width of the
+nanowire. Our work shows a efficient driven method for skyrmionium, which may
+be promising in the application of skyrmionium based racetrack memory.",1904.13332v1
+2019-05-03,Field-induced incommensurate ordering in the Heisenberg chains coupled by Ising interaction: Model for the ytterbium aluminum perovskite YbAlO$_3$,"We study isotropic antiferromagnetic Heisenberg chains coupled by
+antiferromagnetic Ising interaction as an effective spin model for the
+ytterbium aluminum perovskite YbAlO$_3$. Using the density-matrix
+renormalization group (DMRG) method we calculate the magnetization curve, local
+spin, central charge, and dynamical spin structure factors in the presence of
+magnetic field. From the fitting of the experimental magnetization curve, the
+effective intrachain and interchain couplings are estimated as $J=2.3$K and
+$J_{\rm ic}=0.8$K, respectively. We can quantitatively explain the experimental
+observations: (i) phase transition from antiferromagnetic to incommensurate
+order at field 0.35T, and (ii) quantum critical behaviors at the saturation
+field of 1.21T. Furthermore, the low-energy excitations in the experimental
+inelastic neutron scattering spectra can be well described by our DMRG results
+of the dynamical structure factors.",1905.01204v1
+2019-05-30,Wavelet Analysis of Big Data in the Global Investigation of Magnetic Field Variations in Solar-Terrestrial Physics,"We provide a Wavelet analysis of Big Data in Solar Terrestrial Physics. In
+order to explain and predict the dynamics of the geomagnetic phenomena we
+analyze high frequency time series data from different sources: 1. The
+Interplanetary Magnetic Field (from the ACE satellite). 2. The Ionospheric
+parameters - TEC (from ionospheric sounding stations). 3. The ground
+Geomagnetic data (from ground geomagnetic observatories, located in middle
+geographic latitudes). We seek for correlations in the wavelet coefficients
+which explain the dynamics of different magnetic phenomena in the Solar
+Terrestrial Physics. The large variety of data used in our research from both
+Solar Astronomy and Earth Observations makes it a contribution to the newly
+developing area of AstroGeoInformatics.",1905.12923v1
+2019-08-06,Non-equilibrium magnetic phases in spin lattices with gain and loss,"We study the magnetic phases of a non-equilibrium spin chain, where coherent
+interactions between neighboring lattice sites compete with alternating gain
+and loss processes. This competition between coherent and incoherent dynamics
+induces transitions between magnetically aligned and highly mixed phases,
+across which the system changes from a low- to an effective
+infinite-temperature state. We show that the origin of these transitions can be
+traced back to the dynamical effect of parity-time-reversal symmetry breaking,
+which has no counterpart in the theory of equilibrium phase transitions. This
+mechanism also results in very atypical features and we find first-order
+transitions without phase co-existence and mixed-order transitions which do not
+break the underlying $U(1)$ symmetry, even in the appropriate thermodynamic
+limit. Thus, despite its simplicity, the current model considerably extends the
+phenomenology of non-equilibrium phase transitions beyond that commonly assumed
+for driven-dissipative spins and related systems.",1908.02290v2
+2019-10-17,Optical storage for 0.53 seconds in a solid-state atomic frequency comb memory using dynamical decoupling,"Quantum memories with long storage times are key elements in long-distance
+quantum networks. The atomic frequency comb (AFC) memory in particular has
+shown great promise to fulfill this role, having demonstrated multimode
+capacity and spin-photon quantum correlations. However, the memory storage
+times have so-far been limited to about one millisecond, realized in a
+Eu${}^{3+}$ doped Y${}_2$SiO${}_5$ crystal at zero applied magnetic field.
+Motivated by studies showing increased spin coherence times under applied
+magnetic field, we developed a AFC spin-wave memory utilizing a weak 15 mT
+magnetic field in a specific direction that allows efficient optical and spin
+manipulation for AFC memory operations. With this field configuration the AFC
+spin-wave storage time increased to 40 ms using a simple spin-echo sequence.
+Furthermore, by applying dynamical decoupling techniques the spin-wave
+coherence time reaches 530 ms, a 300-fold increase with respect to previous AFC
+spin-wave storage experiments. This result paves the way towards long duration
+storage of quantum information in solid-state ensemble memories.",1910.08009v2
+2019-10-29,Molecular dynamics investigation of soliton propagation in a two-dimensional Yukawa liquid,"We investigate via Molecular Dynamics simulations the propagation of solitons
+in a two-dimensional many-body system characterized by Yukawa interaction
+potential. The solitons are created in an equilibrated system by the
+application of electric field pulses. Such pulses generate pairs of solitons,
+which are characterized by a positive and negative density peak, respectively,
+and which propagate into opposite directions. At small perturbation, the
+features propagate with the longitudinal sound speed, form which an increasing
+deviation is found at higher density perturbations. An external magnetic field
+is found to block the propagation of the solitons, which can, however, be
+released upon the termination of the magnetic field and can propagate further
+into directions that depend on the time of trapping and the magnetic field
+strength.",1910.13303v1
+2019-11-01,Magnetic Polymer Models for Epigenetics-Driven Chromosome Folding,"Epigenetics is a driving force of important and ubiquitous phenomena in
+nature such as cell differentiation or even metamorphosis. Oppositely to its
+widespread role, understanding the biophysical principles that allow
+epigenetics to control and rewire gene regulatory networks remains an open
+challenge. In this work we study the effects of epigenetic modifications on the
+spatial folding of chromosomes -- and hence on the expression of the underlying
+genes -- by mapping the problem to a class of models known as magnetic
+polymers. In this work we show that a first-order phase transition underlies
+the simultaneous spreading of certain epigenetic marks and the conformational
+collapse of a chromosome. Further, we describe Brownian Dynamics simulations of
+the model in which the topology of the polymer and thermal fluctuations are
+fully taken into account and that confirms our mean-field predictions.
+Extending our models to allow for non-equilibrium terms yields new stable
+phases which qualitatively agrees with observations in vivo. Our results show
+that statistical mechanics techniques applied to models of magnetic polymers
+can be successfully exploited to rationalize the outcomes of experiments
+designed to probe the interplay between a dynamic epigenetic landscape and
+chromatin organization.",1911.00444v1
+2019-11-05,Emergent colloidal edge currents generated via exchange dynamics in a broken dimer state,"Controlling the flow of matter down to micrometer-scale confinement is of
+central importance in materials and environmental sciences, with direct
+applications in nano-microfluidics, drug delivery and biothechnology. Currents
+of microparticles are usually generated with external field gradients of
+different nature [e.g., electric, magnetic, optical, thermal or chemical ones]
+which are difficult to control over spatially extended regions and samples.
+Here we demonstrate a general strategy to assemble and transport polarizable
+microparticles in fluid media through combination of confinement and magnetic
+dipolar interactions. We use a homogeneous magnetic modulation to assemble
+dispersed particles into rotating dimeric state and frustrated binary lattices,
+and generate collective edge currents which arise from a novel,
+field-synchronized particle exchange process. These dynamic states are similar
+to cyclotron and skipping orbits in electronic and molecular systems, thus
+paving the way toward understanding and engineering similar processes at
+different length scales across condensed matter.",1911.01698v2
+2019-11-13,Weakly nonlinear magnetic convection in a nonuniformly rotating electrically conductive medium under the action of modulation of external fields,"In this paper we studied the weakly nonlinear stage of stationary convective
+instability in a nonuniformly rotating layer of an electrically conductive
+fluid in an axial uniform magnetic field under the influence of: a) temperature
+modulation of the layer boundaries; b) gravitational modulation; c) modulation
+of the magnetic field; d) modulation of the angular velocity of rotation. As a
+result of applying the method of perturbation theory for the small parameter of
+supercriticality of the stationary Rayleigh number nonlinear non-autonomous
+Ginzburg-Landau equations for the above types of modulation were obtaned. By
+utilizing the solution of the Ginzburg-Landau equation, we determined the
+dynamics of unsteady heat transfer for various types of modulation of external
+fields and for different profiles of the angular velocity of the rotation of
+electrically conductive fluid.",1911.05368v1
+2020-01-03,Real-time chiral dynamics from a digital quantum simulation,"The chiral magnetic effect in a strong magnetic field can be described using
+the chiral anomaly in the $(1+1)$-dimensional massive Schwinger model with a
+time-dependent $\theta$-term. We perform a digital quantum simulation of the
+model at finite $\theta$-angle and vanishing gauge coupling using an IBM-Q
+digital quantum simulator, and observe the corresponding vector current induced
+in a system of relativistic fermions by a global {\it chiral quench} -- a
+sudden change in the chiral chemical potential or $\theta$-angle. At finite
+fermion mass, there appears an additional contribution to this current that
+stems from the non-anomalous relaxation of chirality. Our results are relevant
+for the real-time dynamics of chiral magnetic effect in heavy ion collisions
+and in chiral materials, as well as for modeling high-energy processes at
+hadron colliders.",2001.00698v4
+2020-01-27,Many-body localization with synthetic gauge fields in disordered Hubbard chains,"We analyze the localization properties of the disordered Hubbard model in the
+presence of a synthetic magnetic field. An analysis of level spacing ratio
+shows a clear transition from ergodic to many-body localized phase. The
+transition shifts to larger disorder strengths with increasing magnetic flux.
+Study of dynamics of local correlations and entanglement entropy indicates that
+charge excitations remain localized whereas spin degree of freedom gets
+delocalized in the presence of the synthetic flux. This residual ergodicity is
+enhanced by the presence of the magnetic field with dynamical observables
+suggesting incomplete localization at large disorder strengths. Furthermore, we
+examine the effect of quantum statistics on the local correlations and show
+that the long-time spin oscillations of a hard-core boson system are destroyed
+as opposed to the fermionic case.",2001.09827v2
+2020-02-04,Dynamic neutron imaging of argon bubble flow in liquid gallium in external magnetic field,"This paper presents detailed results of neutron imaging of argon bubble flows
+in a rectangular liquid gallium vessel with and without the application of
+external horizontal magnetic field. The developed image processing algorithm is
+presented and its capability to extract physical information from images of low
+signal-to-noise ratio is demonstrated. Bubble parameters, velocity components,
+trajectories and relevant statistics were computed and analysed. A simpler
+version of the code was applied to the output of computational fluid dynamics
+simulations that reproduced the experiment. This work serves to further
+validate the neutron radiography as a suitable method for monitoring gas bubble
+flow in liquid metals, as well as to outline procedures that might help others
+to extract data from neutron radiography images with a low signal-to-noise
+ratio resulting from high frame rate acquisitions required to resolve rapid
+bubble motion.",2002.10970v2
+2020-02-26,flatspin: A Large-Scale Artificial Spin Ice Simulator,"We present flatspin, a novel simulator for systems of interacting mesoscopic
+spins on a lattice, also known as artificial spin ice (ASI). Our magnetic
+switching criteria enables ASI dynamics to be captured in a dipole model.
+Through GPU acceleration, flatspin can simulate realistic dynamics of millions
+of magnets within practical time frames. We demonstrate flatspin's versatility
+through the reproduction of a diverse set of established experimental results
+from the literature. In particular, magnetization details of ""pinwheel"" ASI
+during field-driven reversal have been reproduced, for the first time, by a
+dipole model. The simulation framework enables quick exploration and
+investigation of new ASI geometries and properties at unprecedented speeds.",2002.11401v1
+2020-02-26,Magnon dispersion and dynamic spin response in three-dimensional spin models for $α$-RuCl$_3$,"In the search for experimental realizations of bond-anisotropic Kitaev
+interactions and resulting spin-liquid phases, the layered magnet
+$\alpha$-RuCl$_3$ is a prime candidate. Its modelling typically involves
+Heisenberg, Kitaev, and symmetric off-diagonal $\Gamma$ interactions on the
+two-dimensional honeycomb lattice. However, recent neutron-scattering
+experiments point towards a sizeable magnetic interlayer coupling. Here we
+study three-dimensional exchange models for $\alpha$-RuCl$_3$, for both
+possible $R\bar{3}$ and $C2/m$ crystal structures. We discuss the symmetry
+constraints on the interlayer couplings, construct minimal models, and use them
+to compute the magnetic mode dispersion and the dynamical spin structure
+factor, in both the zero-field zigzag phase and the paramagnetic high-field
+phase. Our predictions for the interlayer mode dispersion shall guide future
+experiments; they also call for a reevaluation of the quantitative model
+parameters relevant for $\alpha$-RuCl$_3$.",2002.11727v2
+2020-05-22,Signatures of a liquid-crystal transition in spin-wave excitations of skyrmions,"Understanding the spin-wave excitations of chiral magnetic order, such as the
+skyrmion crystal (SkX), is of fundamental interest to confirm such exotic
+magnetic order. The SkX is realized by competing Dzyaloshinskii-Moriya and
+ferromagnetic-exchange interactions with a magnetic field or anisotropy. Here
+we compute the dynamical spin structure factor, using Monte Carlo and spin
+dynamics simulations, extracting the spin-wave spectrum in the SkX, in the
+vicinity of the paramagnet to SkX transition. Inside the SkX, we find six
+spin-wave modes, which are supplemented by another mode originating from the
+ferromagnetic background. Above the critical temperature $T_s$ for the skyrmion
+crystallization, we find a diffusive regime, reminiscent of the
+liquid-to-crystal transition, revealing that topological spin texture of
+skyrmionic character starts to develop above $T_s$ as the precursor of the SkX.
+We discuss the opportunities for the detection of the spin waves of the SkX
+using inelastic-neutron-scattering experiments in manganite-iridate
+heterostructures.",2005.11399v2
+2020-06-02,Dynamic magnetization in non-Hermitian quantum spin system,"We report a global effect induced by the local complex field, associated with
+the spin-exchange interaction. High-order exceptional point up to ($N+1$)-level
+coalescence is created at the critical local complex field applied to the
+$N$-size quantum spin chain. The ($N+1$)-order coalescent level is a saturated
+ferromagnetic ground state in the isotropic spin system. Remarkably, the final
+state always approaches the ground state for an arbitrary initial state with
+any number of spin flips; even if the initial state is orthogonal to the ground
+state. Furthermore, the switch of macroscopic magnetization is solely driven by
+the time and forms a hysteresis loop in the time domain. The retentivity and
+coercivity of the hysteresis loop mainly rely on the non-Hermiticity. Our
+findings highlight the cooperation of non-Hermiticity and the interaction in
+quantum spin system, suggest a dynamical framework to realize magnetization,
+and thus pave the way for the non-Hermitian quantum spin system.",2006.01324v1
+2020-06-02,Rigid body dynamics of diamagnetically levitating graphite resonators,"Diamagnetic levitation is a promising technique for realizing resonant
+sensors and energy harvesters, since it offers thermal and mechanical isolation
+from the environment at zero power. To advance the application of
+diamagnetically levitating resonators, it is important to characterize their
+dynamics in the presence of both magnetic and gravitational fields. Here we
+experimentally actuate and measure rigid body modes of a diamagnetically
+levitating graphite plate. We numerically calculate the magnetic field and
+determine the influence of magnetic force on the resonance frequencies of the
+levitating plate. By analyzing damping mechanisms, we conclude that eddy
+current damping dominates dissipation in mm-sized plates. We use finite element
+simulations to model eddy current damping and find close agreement with
+experimental results. We also study the size-dependent Q-factors (Qs) of
+diamagnetically levitating plates and show that Qs above 100 million are
+theoretically attainable by reducing the size of the diamagnetic resonator down
+to microscale, making these systems of interest for next generation low-noise
+resonant sensors and oscillators.",2006.01733v3
+2020-06-23,Dynamic polarization of electron spins interacting with nuclei in semiconductor nanostructures,"We suggest a new spin orientation mechanism for localized electrons:
+$dynamic~electron~spin~polarization~provided~by~nuclear~spin~fluctuations$. The
+angular momentum for the electrons is gained from the nuclear spin system via
+the hyperfine interaction in a weak magnetic field. For this the sample is
+illuminated by an unpolarized light, which directly polarizes neither the
+electrons nor the nuclei. We predict, that for the electrons bound in localized
+excitons 100% spin polarization can be reached in longitudinal magnetic fields
+of a few millitesla. The proof of principle experiment is performed on
+momentum-indirect excitons in (In,Al)As/AlAs quantum dots, where in a magnetic
+field of 17 mT the electron spin polarization of 30% is measured.",2006.13263v1
+2020-07-08,Dynamics and Clogging of colloidal monolayers magnetically driven through an heterogeneous landscape,"We combine experiments and numerical simulations to investigate the emergence
+of clogging in a system of interacting paramagnetic colloidal particles driven
+against a disordered landscape of larger obstacles. We consider a single
+aperture in a landscape of immobile silica particles which are irreversibly
+attached to the substrate. We use an external rotating magnetic field to
+generate a traveling wave potential which drives the magnetic particles against
+these obstacles at a constant and frequency tunable speed. Experimentally we
+find that the particles display an intermittent dynamics with power law
+distributions at high frequencies. We reproduce these results by using
+numerical simulations and shows that clogging in our system arises at large
+frequency, when the particles desynchronize with the moving landscape. Further,
+we use the model to explore the hidden role of flexibility in the obstacle
+displacements and the effect of hydrodynamic interactions between the
+particles. We also consider numerically the situation of a straight wall and
+investigate the range of parameters where clogging emerges in such case. Our
+work provides a soft matter test-bed system to investigate the effect of
+clogging in driven microscale matter.",2007.04436v1
+2020-07-09,Dynamic Spin Fluctuations in the Frustrated A-site Spinel CuAl2O4,"We performed nuclear magnetic resonance (NMR) and muon spin relaxation
+({\mu}SR) experiments to identify the magnetic ground state of the frustrated
+quantum A-site spinel, CuAl2O4. Our results verify that the ground state does
+not exhibit a long-range magnetic ordering, but a glass-like transition
+manifests at T*=2.3 K. However, the Gaussian shape and the weak longitudinal
+field dependence of {\mu}SR spectra below T* show that the ground state has
+dynamic spin fluctuations, distinct from those of conventional spin-glasses.",2007.04761v1
+2020-07-21,Revisiting Magnetogenesis during Inflation,"We revisit the mechanism of primordial magnetogenesis during inflation by
+taking into account the dynamics of the stochastic noises of the
+electromagnetic perturbations. We obtain the associated Langevin and
+Fokker-Planck equations for the electromagnetic fields and solve them
+analytically. It is shown that while the backreactions of the electric field
+energy density may spoil inflation too early, but there are regions of
+parameter space where the usual decaying behavior of the magnetic fields are
+replaced by a mean-reverting process of stochastic dynamics. As a result, the
+magnetic fields settle down into an equilibrium state with the amplitude
+significantly larger than what is obtained in the absence of the stochastic
+noises. We show that magnetic fields with present time amplitude $\sim
+10^{-13}$ Gauss and coherent length ${\rm Mpc}$ can be generated while the
+backreactions of the electric field perturbations are under control.",2007.11066v1
+2020-08-04,Hall effect and symmetry breaking in non-magnetic metal with dynamic charge stripes,"A comprehensive study of magnetoresistance and Hall effect has been performed
+for the set of the single crystals of non-magnetic metal LuB12 with the
+Jahn-Teller instability of the boron cage and dynamic charge stripes forming
+along <110> direction. Anomalous positive contribution to Hall effect for
+particular direction of magnetic field H//[001] is found in the single crystals
+of LuB12 of the highest quality. This contribution arising at T~ 150 K is shown
+to increase drastically when approaching the disordered ground state below 60
+K. The Hall effect anomaly is shown to appear in combination with the peak of
+magnetoresistance. The various scenarios allowing for the topology of Fermi
+surface, anisotropy of relaxation time for charge carriers and the filamentary
+structure of fluctuating charge stripes are proposed to explain the features of
+magnetotransport in this metal with inhomogeneous distribution of electron
+density. The origin of SdH oscillations, which are observed in this
+non-equilibrium metal with electron phase separation and strong charge carrier
+scattering, is discussed.",2008.01455v1
+2020-08-18,Non-Canonical Hamiltonian Monte Carlo,"Hamiltonian Monte Carlo is typically based on the assumption of an underlying
+canonical symplectic structure. Numerical integrators designed for the
+canonical structure are incompatible with motion generated by non-canonical
+dynamics. These non-canonical dynamics, motivated by examples in physics and
+symplectic geometry, correspond to techniques such as preconditioning which are
+routinely used to improve algorithmic performance. Indeed, recently, a special
+case of non-canonical structure, magnetic Hamiltonian Monte Carlo, was
+demonstrated to provide advantageous sampling properties. We present a
+framework for Hamiltonian Monte Carlo using non-canonical symplectic
+structures. Our experimental results demonstrate sampling advantages associated
+to Hamiltonian Monte Carlo with non-canonical structure. To summarize our
+contributions: (i) we develop non-canonical HMC from foundations in symplectic
+geomtry; (ii) we construct an HMC procedure using implicit integration that
+satisfies the detailed balance; (iii) we propose to accelerate the sampling
+using an {\em approximate} explicit methodology; (iv) we study two novel,
+randomly-generated non-canonical structures: magnetic momentum and the coupled
+magnet structure, with implicit and explicit integration.",2008.08191v1
+2020-10-06,Magnetic microswimmers exhibit Bose-Einstein-like condensation,"We study an active matter system comprised of magnetic microswimmers confined
+in a microfluidic channel and show that it exhibits a new type of
+self-organized behavior. Combining analytical techniques and Brownian dynamics
+simulations, we demonstrate how the interplay of non-equilibrium activity,
+external driving, and magnetic interactions leads to the condensation of
+swimmers at the center of the channel via a non-equilibrium phase transition
+that is formally akin to Bose-Einstein condensation. We find that the effective
+dynamics of the microswimmers can be mapped onto a diffusivity-edge problem,
+and use the mapping to build a generalized thermodynamic framework, which is
+verified by a parameter-free comparison with our simulations. Our work reveals
+how driven active matter has the potential to generate exotic classical
+non-equilibrium phases of matter with traits that are analogous to those
+observed in quantum systems.",2010.02853v1
+2020-10-21,Electric activity at magnetic moment fragmentation in spin ice,"Spin ice systems display a variety of very nontrivial properties, the most
+striking being the existence in them of magnetic monopoles. Such monopole
+states can also have nontrivial electric properties: there exist electric
+dipoles attached to each monopole. A novel situation is encountered in the
+moment fragmentation (MF) state, in which monopoles and antimonopoles are
+perfectly ordered, whereas spins themselves remain disordered. We show that
+such partial ordering strongly modifies the electric activity of such systems:
+the electric dipoles, which are usually random and dynamic, become paired in
+the MF state in (d,-d) pairs, thus strongly reducing their electric activity.
+The electric currents existing in systems with noncoplanar spins are also
+strongly influenced by MF. We also consider modifications in dipole and current
+patterns in magnetic textures (domain walls, local defects) and at excitations
+with nontrivial dynamics in a MF state, which show very rich behaviour and
+which could in principle allow to control them by electric field.",2010.11149v2
+2021-01-15,Linear and Nonlinear Optical Responses in Kitaev Spin Liquids,"We theoretically study THz-light-driven high-harmonic generation (HHG) in the
+spin-liquid states of the Kitaev honeycomb model with a magnetostriction
+coupling between spin and electric polarization. To compute the HHG spectra, we
+numerically solve the Lindblad equation, taking account of the dissipation
+effect. We find that isotropic Kitaev models possess a dynamical symmetry,
+which is broken by a static electric field, analogous to HHG in electron
+systems. We show that the HHG spectra exhibit characteristic continua of
+Majorana fermion excitations, and their broad peaks can be controlled by
+applying static electric or magnetic fields. In particular, the magnetic-field
+dependence of the HHG spectra drastically differs from those of usual ordered
+magnets. These results indicate that an intense THz laser provides a powerful
+tool to observe dynamic features of quantum spin liquids.",2101.06081v2
+2021-01-18,Two body problem on a sphere in the presence of a uniform magnetic field,"We investigate the motion of one and two charged non-relativistic particles
+on a sphere in the presence of a magnetic field of uniform strength. For one
+particle, the motion is always circular, and determined by a simple relation
+between the velocity and the radius of motion. For two identical particles,
+interacting via a cotangent potential, we show there are two families of
+relative equilibria, called Type I and Type II. The Type I relative equilibria
+exist for all strengths of the magnetic field, while those of Type II exist
+only if the field is sufficiently strong. The same is true if the particles are
+of equal mass but opposite charge. We also determine the stability of the two
+families of relative equilibria.",2101.07170v3
+2021-04-14,Spin waves propagating through a stripe magnetic domain structure and their applications to reservoir computing,"Spin waves propagating through a stripe domain structure and reservoir
+computing with their spin dynamics have been numerically studied with focusing
+on the relation between physical phenomena and computing capabilities. Our
+system utilizes a spin-wave-based device that has a continuous magnetic garnet
+film and 1-input/72-output electrodes on the top. To control
+spatially-distributed spin dynamics, a stripe magnetic domain structure and
+amplitude-modulated triangular input waves were used. The spatially-arranged
+electrodes detected spin vector outputs with various nonlinear characteristics
+that were leveraged for reservoir computing. By moderately suppressing
+nonlinear phenomena, our system achieves 100$\%$ prediction accuracy in
+temporal exclusive-OR (XOR) problems with a delay step up to 5. At the same
+time, it shows perfect inference in delay tasks with a delay step more than 7
+and its memory capacity has a maximum value of 21. This study demonstrated that
+our spin-wave-based reservoir computing has a high potential for edge-computing
+applications and also can offer a rich opportunity for further understanding of
+the underlying nonlinear physics.",2104.06794v1
+2021-04-27,Spatiotemporal Crossover between Low- and High-Temperature Dynamical Regimes in the Quantum Heisenberg Magnet,"The stranglehold of low temperatures on fascinating quantum phenomena in
+one-dimensional quantum magnets has been challenged recently by the discovery
+of anomalous spin transport at high temperatures. Whereas both regimes have
+been investigated separately, no study has attempted to reconcile them. For
+instance, the paradigmatic quantum Heisenberg spin-$1/2$ chain falls at low
+temperature within the Tomonaga-Luttinger liquid framework, while its
+high-temperature dynamics is superdiffusive and relates to the
+Kardar-Parisi-Zhang universality class in $1+1$ dimensions. This Letter aims at
+reconciling the two regimes. Building on large-scale matrix product state
+simulations, we find that they are connected by a temperature-dependent
+spatiotemporal crossover. As the temperature $T$ is reduced, we show that the
+onset of superdiffusion takes place at longer length and timescales $\propto
+1/T$. This prediction has direct consequences for experiments including nuclear
+magnetic resonance: it is consistent with earlier measurements on the nearly
+ideal Heisenberg $S=1/2$ chain compound Sr$_2$CuO$_3$, yet calls for new and
+dedicated experiments.",2104.13393v2
+2021-05-13,"Static and dynamic magnetic properties of honeycomb lattice antiferromagnets Na$_{2}M_{2}$TeO$_{6}$, $M$ = Co and Ni","The magnetic structures and spin dynamics of Na$_{2}$Co$_{2}$TeO$_{6}$ and
+Na$_{2}$Ni$_{2}$TeO$_{6}$ are investigated by means of elastic and inelastic
+neutron scattering measurements and the results are discussed in the context of
+a generalized Kitaev-Heisenberg model on honeycomb lattice with strong
+spin-orbit coupling. The large number of parameters involved in the Hamiltonian
+model are evaluated by using an iterative optimization algorithm capable of
+extracting model solutions and simultaneously estimating their uncertainty. The
+analyses establish that both Co$^{2+}$ ($d^7$) and Ni$^{2+}$ ($d^8$)
+antiferromagnets realize bond-dependent anisotropic nearest-neighbor
+interactions, and support the theoretical predictions for the realization of
+Kitaev physics in 3$d$ electron systems with effective spins $S$=1/2 and $S$=1.
+Furthermore, by studying the Na-doped system Na$_{2.4}$Ni$_{2}$TeO$_{6}$, we
+show that the control of Na content can provide an effective route for fine
+tuning the magnetic lattice dimensionality, as well as to controlling the
+bond-dependent anisotropic interactions.",2105.06549v2
+2021-05-31,Far-from-equilibrium universality in the two-dimensional Heisenberg model,"We characterize the universal far-from-equilibrium dynamics of the
+two-dimensional quantum Heisenberg magnet isolated from its environment. For a
+broad range of initial conditions, we find a long-lived universal prethermal
+regime characterized by self-similar behavior of spin-spin correlations. We
+analytically derive the spatial-temporal scaling exponents and find excellent
+agreement with numerics using phase space methods. The scaling exponents are
+insensitive to the choice of initial conditions, which include coherent and
+incoherent spin states with values of total magnetization and energy in a wide
+range. Compared to previously-studied self-similar dynamics in non-equilibrium
+$O(n)$ field theories and Bose gases, we find qualitatively distinct scaling
+behavior originating from the presence of spin modes which remain gapless at
+long times and which are protected by the global SU(2) symmetry. Our
+predictions, which suggest a new non-equilibrium universality class, are
+readily testable in ultra-cold atoms simulators of Heisenberg magnets.",2106.00023v2
+2021-06-17,Large deviations for the Skew-Detailed-Balance Lifted-Markov processes to sample the equilibrium distribution of the Curie-Weiss model,"Among the Markov chains breaking detailed-balance that have been proposed in
+the field of Monte-Carlo sampling in order to accelerate the convergence
+towards the steady state with respect to the detailed-balance dynamics, the
+idea of 'Lifting' consists in duplicating the configuration space into two
+copies $\sigma=\pm$ and in imposing directed flows in each copy in order to
+explore the configuration space more efficiently. The skew-detailed-balance
+Lifted-Markov-chain introduced by K. S. Turitsyn, M. Chertkov and M. Vucelja
+[Physica D Nonlinear Phenomena 240 , 410 (2011)] is revisited for the
+Curie-Weiss mean-field ferromagnetic model, where the dynamics for the
+magnetization is closed. The large deviations at various levels for empirical
+time-averaged observables are analyzed and compared with their detailed-balance
+counterparts, both for the discrete extensive magnetization $M$ and for the
+continuous intensive magnetization $m=\frac{M}{N}$ for large system-size $N$.",2106.09429v3
+2021-09-05,Electric field effect on electron gas spins in two-dimensional magnets with strong spin-orbit coupling,"The recent rise of material platforms combining magnetism and
+two-dimensionality of mobile carriers reveals a diverse spectrum of spin-orbit
+phenomena and stimulates its ongoing theoretical discussions. In this work we
+use the density matrix approach to provide a unified description of subtle
+microscopic effects governing the electron gas spin behavior in the clean limit
+upon electric perturbations in two-dimensional magnets with strong spin-orbit
+coupling. We discuss that an inhomogeneity of electrostatic potential generally
+leads to the electron gas spin tilting with the subsequent formation of
+equilibrium skyrmion-like spin textures and demonstrate that several
+microscopic mechanisms of 2DEG spin response are equally important for this
+effect. We analyze the dynamics of 2DEG spin upon an oscillating electric field
+with a specific focus on the emergent electric dipole spin resonance. We
+address the resonant enhancement of magneto-optical phenomena from the spin
+precession equation perspective and discuss it in terms of the resonant spin
+generation. We also clarify the connection of both static and dynamic spin
+phenomena arising in response to a scalar perturbation with the electronic band
+Berry curvature.",2109.02151v1
+2010-05-27,Exact reduced dynamics for a qubit in a precessing magnetic field and in the contact with a heat-bath,"The two-level quantum system (qubit) in a precessing magnetic field and in
+contact with a heat bath is investigated. The exact reduced dynamics for the
+qubit in question is obtained. We apply the approach based on the block
+operator matrices theory, in contrast with the standard methods provided by the
+theory of the open quantum systems. We also present the solution of the Riccati
+operator equation associated with the Hamiltonian of the system. Next, we study
+the adiabatic approximation for the system under consideration using quantum
+fidelity as a way to measure validity of the adiabatic theory. We find that in
+the weak coupling domain the standard condition that ensures adiabatic behavior
+of the spin in the magnetic field also guarantees its adiabatic evolution in
+the open system variant of this model. Therefore, we provide the explicit
+example of the open quantum system that satisfies the adiabatic approximation
+firstly formulated for the closed quantum systems.",1005.5182v2
+2010-05-29,{\it Ab initio} calculations of magnetic structure and lattice dynamics of Fe/Pt multilayers,"The magnetization distribution, its energetic characterization by the
+interlayer coupling constants and lattice dynamics of (001)-oriented Fe/Pt
+multilayers are investigated using density functional theory combined with the
+direct method to determine phonon frequencies. It is found that ferromagnetic
+order between consecutive Fe layers is favoured, with the enhanced magnetic
+moments at the interface. The bilinear and biquadratic coupling coefficients
+between Fe layers are shown to saturate fast with increasing thickness of
+nonmagnetic Pt layers which separate them. The phonon calculations demonstrate
+a rather strong dependence of partial iron phonon densities of states on the
+actual position of Fe monolayer in the multilayer structure.",1005.5454v1
+2013-08-20,Quantum Dynamics of a Dissipative and Confined Cyclotron Motion,"We study the dissipative dynamics of a charged oscillator in a magnetic field
+by coupling (a la Caldeira and Leggett) it to a heat bath consisting of
+non-interacting harmonic oscillators. We derive here the auto-correlation
+functions of the position and momentum and study its behavior at various
+limiting situations. The equilibrium (steady state) dispersions of position and
+momentum are obtained from their respective autocorrelation functions. We
+analyse the equilibrium position and momentum dispersions at low and high
+temperatures for both low and high magnetic field strengths. We obtain the
+classical diffusive behavior (at long times) as well as the equilibrium
+momentum dispersion of the free quantum charged particle in a magnetic field,
+in the limit of vanishing oscillator potential {\omega}_0 . We establish the
+relations between the reduced partition function and the equilibrium
+dispersions of the dissipative and confined cyclotron problem.",1308.4389v1
+2016-11-29,Domain wall profiles in Co/Ir$_n$/Pt(111) ultrathin films: influence of the Dzyaloshinskii-Moriya interaction,"We perform a study of domain walls in Co/Ir$_n$/Pt(111) (n = 0,1,...,6) films
+by a combined approach of first-principles calculations and spin dynamics
+simulations. We determine the tensorial exchange interactions and the magnetic
+anisotropies for the Co overlayer in both FCC and HCP geometries, depending on
+the number of Ir buffer layers. We find strong ferromagnetic nearest-neighbor
+isotropic exchange interactions between the Co atoms and an out-of-plane
+magnetic anisotropy for the films in FCC geometry. Our simulations show that
+the magnetic domain walls are of N\'eel type, and their rotational sense
+(chirality) is changed upon the insertion of an Ir buffer layer as compared to
+the pristine Co/Pt(111) system. Our spin dynamics simulations indicate a
+twisting of the spins with respect to the planar domain wall profile on the
+triangular lattice. We discuss this domain wall twisting using symmetry
+arguments and in terms of an appropriate micromagnetic continuum model
+considering extra energy terms compared to the available literature.",1611.09518v1
+2017-01-18,Dissipative random quantum spin chain with boundary-driving and bulk-dephasing: magnetization and current statistics in the Non-Equilibrium-Steady-State,"The Lindblad dynamics with dephasing in the bulk and magnetization-driving at
+the two boundaries is studied for the quantum spin chain with random fields
+$h_j$ and couplings $J_j$ (that can be either uniform or random). In the regime
+of strong disorder in the random fields, or in the regime of strong
+bulk-dephasing, the effective dynamics can be mapped onto a classical Simple
+Symmetric Exclusion Process with quenched disorder in the diffusion coefficient
+associated to each bond. The properties of the corresponding
+Non-Equilibrium-Steady-State in each disordered sample between the two
+reservoirs are studied in detail by extending the methods that have been
+previously developed for the Symmetric Exclusion Process without disorder.
+Explicit results are given for the magnetization profile, for the two-point
+correlations, for the mean current and for the current fluctuations, in terms
+of the random fields and couplings defining the disordered sample.",1701.05090v2
+2017-09-07,Fluxtube Dynamics in Neutron Star Cores,"Although the detailed structure of neutron stars remains unknown, their
+equilibrium temperatures lie well below the Fermi temperature of dense nuclear
+matter, suggesting that the nucleons in the stars' core form Cooper pairs and
+exhibit macroscopic quantum behavior. The presence of such condensates impacts
+on the neutron stars' large scale properties. Specifically, superconducting
+protons in the outer core (expected to show type-II properties) alter the
+stars' magnetism as the magnetic field is no longer locked to the charged
+plasma but instead confined to fluxtubes. The motion of these structures
+governs the dynamics of the core magnetic field. To examine if field evolution
+could be driven on observable timescales, several mechanisms affecting the
+fluxtube distribution are addressed and characteristic timescales for realistic
+equations of state estimated. The results suggest that the corresponding
+timescales are not constant but vary for different densities inside the star,
+generally being shortest close to the crust-core interface.",1709.02303v1
+2017-09-13,Emergent Hydrodynamic Bound States Between Magnetically Powered Micropropellers,"Hydrodynamic interactions (HIs), namely solvent mediated long-range
+interactions between dispersed particles, play a crucial role in the assembly
+and dynamics of many active systems, from swimming bacteria to swarms of
+propelling microrobots. Here we experimentally demonstrate the emergence of
+long-living hydrodynamic bound states between model micro-swimmers at low
+Reynolds number. A rotating magnetic field forces colloidal hematite
+microparticles to translate at a constant and frequency-tunable speed close to
+a bounding plane in a viscous fluid. At high driving frequency, HIs dominate
+over magnetic dipolar ones, and close propelling particles couple into bound
+states by adjusting their translational speed in order to optimize the
+transport of the pair. The physical system is described by considering the HIs
+with the boundary surface and the effect of gravity, providing an excellent
+agreement with the experimental data for all the range of parameters explored.
+Moreover, we show that in dense suspensions, these bound states can be extended
+to onedimensional arrays of particles assembled by the sole HIs. Our results
+manifest the importance of the boundary surface in the interaction and dynamics
+of confined propelling microswimmers.",1709.04229v1
+2017-11-03,Dynamical correlation functions and the related physical effects in three-dimensional Weyl/Dirac semimetals,"We present a unified derivation of the dynamical correlation functions
+including density-density, density-current and current-current, of
+three-dimensional Weyl/Dirac semimetals by use of the Passarino-Veltman
+reduction scheme at zero temperature. The generalized Kramers-Kronig relations
+with arbitrary order of subtraction are established to verify these correlation
+functions. Our results lead to the exact chiral magnetic conductivity and
+directly recover the previous ones in several limits. We also investigate the
+magnetic susceptibilities, the orbital magnetization and briefly discuss the
+impact of electron interactions on these physical quantities within the random
+phase approximation. Our work could provide a starting point for the
+investigation of the nonlocal transport and optical properties due to the
+higher-order spatial dispersion in three-dimensional Weyl/Dirac semimetals.",1711.01031v2
+2017-11-11,The hydrodynamic singular vortex on the sphere and the Dirac monopole,"An exact correspondence is established between mathematical description of
+the single ""elementary vortex"" (EV)velocity on the sphere
+(Zermelo,1902;Bogomolov,1977) and the Dirac magnetic monopole (DMM) vector
+potential (Dirac, 1931). Similar analogy with DMM was noted only for the
+vortices in quantum fluid He-3A (Blaha,1976;Volovik,Mineev,1976). Singular EV
+on a sphere is usually considered using compensating vortex field, uniformly
+distributed over the sphere. It is necessary to meet the Gauss-Kelvin theorem
+with zero integral vorticity over the sphere. However since Bogomolov
+(1977)(see also Dritshel,Boatto,2015)uniform vorticity impact on dynamics is
+neglected when only the velocity field of singular EV is taken into account. It
+is not true because the hydrodynamic equations do not allow existence of a
+solution in the form of an isolated EV but allow solutions in the form of the
+antipodal EV pairs. It is also suggested the possibility of DMM existence only
+in the form of the point magnetic dipoles, consisting of two DMM with different
+signs of the magnetic charge.",1711.04124v1
+2017-11-17,Small influence of magnetic ordering on lattice dynamics in TaFe$_{1.25}$Te$_3$,"Raman scattering spectra of zigzag spin chain TaFe$_{1.25}$Te$_3$ single
+crystal are presented in a temperature range from 80 to 300 K. Nine Raman
+active modes of $A_g$ and $B_g$ symmetry are clearly observed and assigned by
+probing different scattering channels, which is confirmed by lattice dynamics
+calculations. Temperature dependence of the Raman modes linewidth is mainly
+governed by the lattice anharmonicity. The only deviation from the conventional
+behavior is observed for $A_g$ symmetry modes in a vicinity of the magnetic
+phase transition at $T_N \approx 200$ K. This implies that the electron-phonon
+interaction weakly changes with temperature and magnetic ordering, whereas
+small changes in the spectra near the critical temperature can be ascribed to
+spin fluctuations.",1711.06572v1
+2017-11-23,Physics of the saturation of particle acceleration in relativistic magnetic reconnection,"We investigate the saturation of particle acceleration in relativistic
+reconnection using two-dimensional particle-in-cell simulations at various
+magnetizations \sigma. We find that the particle energy spectrum produced in
+reconnection quickly saturates as a hard power law that cuts off at
+\gamma~4\sigma, confirming previous work. Using particle tracing, we find that
+particle acceleration by the reconnection electric field in X-points determines
+the shape of the particle energy spectrum. By analyzing the current sheet
+structure, we show that physical cause of saturation is the spontaneous
+formation of secondary magnetic islands that can disrupt particle acceleration.
+By comparing the size of acceleration regions to the typical distance between
+disruptive islands, we show that the maximum Lorentz factor produced in
+reconnection is \gamma ~ 5 \sigma, which is very close to what we find in our
+particle energy spectra. We also show that the dynamic range in Lorentz factor
+of the power law spectrum in reconnection is < 40. The hardness of the power
+law combined with its narrow dynamic range implies that relativistic
+reconnection is capable of producing the hard narrowband flares observed in the
+Crab Nebula but has difficulty producing the softer broadband prompt GRB
+emission.",1711.08701v1
+2018-01-29,Nonlinear Excitations in Magnetic Lattices with Long-Range Interactions,"We study - experimentally, theoretically, and numerically - nonlinear
+excitations in lattices of magnets with long-range interactions. We examine
+breather solutions, which are spatially localized and periodic in time, in a
+chain with algebraically-decaying interactions. It was established two decades
+ago [S. Flach, Phys. Rev. E 58, R4116 (1998)] that lattices with long-range
+interactions can have breather solutions in which the spatial decay of the
+tails has a crossover from exponential to algebraic decay. In this Letter, we
+revisit this problem in the setting of a chain of repelling magnets with a mass
+defect and verify, both numerically and experimentally, the existence of
+breathers with such a crossover.",1801.09560v1
+2018-03-04,Spin hydrodynamics in amorphous magnets,"Spin superfluidity, i.e., coherent spin transport mediated by topologically
+stable textures, is limited by parasitic anisotropies rooted in relativistic
+interactions and spatial inhomogeneities. Since structural disorder in
+amorphous magnets can average out the effect of these undesired couplings, we
+propose this class of materials as platforms for superfluid spin transport. We
+establish nonlinear equations describing the hydrodynamics of spin in
+insulating amorphous magnets, where the currents are defined in terms of
+coherent rotations of a noncollinear texture. Our theory includes dissipation
+and nonequilibrium torques at the interface with metallic reservoirs. This
+framework allows us to determine different regimes of coherent dynamics and
+their salient features in nonlocal magneto-transport measurements. Our work
+paves the way for future studies on macroscopic spin dynamics in materials with
+frustrated interactions.",1803.01309v2
+2018-03-22,Carrier dynamics in doped bilayer iridates near magnetic quantum criticality,"Motivated by experiments on the carrier-doped bilayer iridate
+$(\text{Sr}_{1-x}\text{La}_x)_3\text{Ir}_2\text{O}_7$, we study the dynamics of
+a single doped electron in a bilayer magnet in the presence of spin-orbit
+coupling, taking into account the spatially staggered rotation of IrO$_6$
+octahedra. We employ an effective single-orbital bilayer $t$-$J$ model,
+concentrating on the quantum paramagnetic phase near the magnetic quantum
+critical point. We determine the carrier dispersion using a combination of
+self-consistent Born and bond-operator techniques. Extrapolating to finite
+small carrier density we find that, for experimentally relevant parameters, the
+combination of octahedral rotation and spin-orbit coupling induces a band
+folding which results in a Fermi surface of small double electron pockets, in
+striking agreement with experimental observations. We also determine the
+influence of spin-orbit coupling on the location of the quantum critical point
+in the undoped case, and discuss aspects of the global phase diagram of doped
+bilayer Mott insulators.",1803.08516v3
+2018-05-03,North-South asymmetric Kelvin-Helmholtz instability and induced reconnection at the Earth's magnetospheric flanks,"We present a three-dimensional study of the plasma dynamics at the flank
+magnetopause of the Earth's magnetosphere during mainly northward
+interplanetary magnetic field (IMF) periods. Two-fluid simulations show that
+the initial magnetic shear at the magnetopause and the field line bending
+caused by the dynamics itself (in a configuration taken as representative of
+the properties of the flank magnetopause) influence both the location where the
+Kelvin-Helmholtz (KH) instability and the induced magnetic reconnection take
+place and their nonlinear development. The KH vortices develop asymmetrically
+with respect to the Earth's equatorial plane where the local KH linear growth
+rate is maximal. Vortex driven reconnection processes take place at different
+latitudes, ranging from the equatorial plane to mid-latitude regions, but only
+in the hemisphere that turns out to be the less KH unstable. These results
+suggest that KH-induced reconnection is not limited to specific regions around
+the vortices (inside, below or above), but may be triggered over a broad and
+continuous range of locations in the vicinity of the vortices.",1805.01466v1
+2018-05-07,Force acting on a cluster of magnetic nanoparticles in a gradient field: a Langevin dynamics study,"Magnetophoretic force acting on a rigid spherical cluster of single-domain
+nanoparticles in a constant-gradient weak magnetic field is investigated
+numerically using the Langevin dynamics simulation method. Nanoparticles are
+randomly and uniformly distributed within the cluster volume. They interact
+with each other via long-range dipole-dipole interactions. Simulations reveal
+that if the total amount of particles in the cluster is kept constant, the
+force decreases with increasing nanoparticle concentration due to the
+demagnetizing field arising inside the cluster. Numerically obtained force
+values with great accuracy can be described by the modified mean-field theory,
+which was previously successfully used for the description of various dipolar
+media. Within this theory, a new expression is derived, which relates the
+magnetophoretic mobility of the cluster with the concentration of nanoparticles
+and their dipolar coupling parameter. The expression shows that if the number
+of particles in the cluster is fixed, the mobility is a nonmonotonic function
+of the concentration. The optimal concentration values that maximize the
+mobility for a given amount of magnetic phase and a given dipolar coupling
+parameter are determined.",1805.02347v2
+2018-08-03,Vortex dynamics and losses due to pinning: Dissipation from trapped magnetic flux in resonant superconducting radio-frequency cavities,"We use a model of vortex dynamics and collective weak pinning theory to study
+the residual dissipation due to trapped magnetic flux in a dirty
+superconductor. Using simple estimates, approximate analytical calculations,
+and numerical simulations, we make predictions and comparisons with experiments
+performed in CERN and Cornell on resonant superconducting radio-frequency NbCu,
+doped-Nb and Nb$_3$Sn cavities. We invoke hysteretic losses originating in a
+rugged pinning potential landscape to explain the linear behavior of the
+sensitivity of the residual resistance to trapped magnetic flux as a function
+of the amplitude of the radio-frequency field. Our calculations also predict
+and describe the crossover from hysteretic-dominated to viscous-dominated
+regimes of dissipation. We propose simple formulas describing power losses and
+crossover behavior, which can be used to guide the tuning of material
+parameters to optimize cavity performance.",1808.01293v2
+2018-08-10,Chaotic behavior of Eulerian MHD turbulence,"We study the chaotic properties of a turbulent conducting fluid using direct
+numerical simulation in the Eulerian frame. The maximal Lyapunov exponent is
+measured for simulations with varying Reynolds number and magnetic Prandtl
+number. We extend the Ruelle theory of hydrodynamic turbulence to
+magnetohydrodynamic turbulence as a working hypothesis and find broad agreement
+with results. In other simulations we introduce magnetic helicity and these
+simulations show a diminution of chaos, which is expected to be eliminated at
+maximum helicity. We also find that the difference between two initially close
+fields grows linearly at late times, which was also recently found in
+hydrodynamics. This linear growth rate is found to be dependent on the
+dissipation rate of the relevant field. We discuss the important consequences
+this linear growth has on predictability. We infer that the chaos in the system
+is totally dominated by the velocity field and connect this work to real
+magnetic systems such as solar weather and confined plasmas.",1808.03632v2
+2018-08-27,Exact equilibrium state for pair plasmas near the horizon of a Schwarzschild black hole,"A pair plasma in hidrostatic equilibrium near the horizon of a Schwarzschild
+black hole is an exact state. In this work, we show that an exact
+non--hidrostatic equilibrium state can be sustained for a pair plasma, in which
+its constituents are moving near the horizon of the black hole. This
+equilibrium state solution is not due to a vortical formalism, but by the
+balance of forces in the plasma. This new equilibrium state has a pressure for
+the hydrostatic equilibrium, although the plasma moves. The equilibrium is
+achieved by the generation of a magnetic field that emerges by the interplay
+between the plasma dynamics and the gravitational field, having no flat
+spacetime analogue. No electric fields are needed to sustain the equilibria.
+The magnetic field shows an exponential decaying behavior, governed by a
+function that depends on the properties of the pair plasma and the black, and
+that plays the role of a characteristc length of the dynamics of the magnetic
+field.",1808.08937v3
+2019-02-01,On the dynamics of a charged particle in magnetic fields with cylindrical symmetry,"We study the motion of a charged particle under the action of a magnetic
+field with cylindrical symmetry. In particular we consider magnetic fields with
+constant direction and with magnitude depending on the distance $r$ from the
+symmetry axis of the form $1 + Ar^{-\gamma}$ as $r\to\infty$, with $A\ne 0$ and
+$\gamma > 1$. With perturbative-variational techniques, we can prove the
+existence of infinitely many trajectories whose projection on a plane
+orthogonal to the direction of the field describe bounded curves given by the
+superposition of two motions: a rotation with constant angular speed at a unit
+distance about a point which moves along a circumference of large radius $\rho$
+with a slow angular speed $\varepsilon$. The values $\rho$ and $\varepsilon$
+are suitably related to each other. This problem has some interest also in the
+context of planar curves with prescribed curvature.",1902.00513v1
+2019-06-10,Simulating single-spin dynamics on an IBM five-qubit chip,"In this paper we show how the IBM superconducting chips can be a powerful
+tool for teaching foundations of quantum mechanics for undergraduate students
+(for graduates as well, in some cases). To this end, we briefly discuss about
+the main elements of the IBM Quantum Experience platform necessary to
+understand this paper, i.e., how to implement operations and single-qubit
+measurements. We experimentally study the dynamics of single spin systems
+interacting with static and time-dependent magnetic fields. First, we study the
+resonant behavior of a single spin coupled to a time-dependent rotating
+magnetic field. To end, we study the Larmor precession phenomenon. In both
+cases we show the theoretical and real experimental implementation. This
+article could be useful in introductory courses on quantum mechanics and
+nuclear magnetic resonance foundations, for example.",1906.03925v2
+2019-06-26,Chromospheric cannonballs on the Sun,"In the highly dynamic chromosphere, there exist many kinds of small-scale
+activities, such as spicules, surges, and Ellerman bombs. Here, we report the
+discovery of a new phenomenon in the chromosphere observed with the New Vacuum
+Solar Telescope at the Fuxian Solar Observatory. In the high tempo-spatial
+resolution H$\alpha$ images, some dark or bright structures are found to fly
+along the curved trajectory, looking like cannonballs. Their average size,
+mass, and velocity are about 1.5 $\times$ 10$^{9}$ km$^{3}$, 1.5 $\times$
+10$^{8}$ kg, and 56 km s$^{-1}$, respectively. In the simultaneous
+(extreme-)ultraviolet images obtained by the Solar Dynamics Observatory, these
+cannonballs appear as brighter features compared to the surrounding area,
+implying that there exists some kind of heating during this process. The
+photospheric magnetograms show the magnetic flux emergence and interaction with
+the pre-existing fields. These observations reveal that the cannonballs are
+chromospheric material blobs launched due to the magnetic reconnection between
+emerging magnetic flux and the pre-existing loops.",1906.10850v1
+2019-06-26,Spin-orbit torques and their associated effective fields from gigahertz to terahertz,"Terahertz spintronics offers the prospect of devices which are both faster
+and more energy-efficient. A promising route to achieve this goal is to exploit
+current-induced spin-orbit torques. However, the high-frequency properties of
+these quantities remain unexplored both experimentally and theoretically,
+within a realistic material-specific approach. Here we investigate the
+dynamical transverse components of the torques and uncover contributions
+longitudinal to the magnetic moment capable of changing its magnitude. We show
+that, while the torques can be drastically altered in the dynamical regime, the
+effective magnetic fields that accompany them present a frequency-independent
+behaviour, ranging from the static limit up to the terahertz domain - including
+the ferromagnetic resonance of the system. The outcomes of this work point to
+new ways to control magnetic units in next-generation spintronic devices.",1906.11314v2
+2019-06-30,Quantitative Study on Current-Induced Effect in an Antiferromagnet Insulator/Pt Bilayer Film,"Quantitative investigation on the current-induced torque in antiferromagnets
+represents a great challenge, due to the lack of an independent method for
+controlling N\'eel vectors. Here by utilizing an antiferromagnetic insulator
+with Dzyaloshinskii-Moriya interaction, {\alpha}-Fe2O3, we show that the N\'eel
+vector can be controlled with a moderate external field, which is further
+utilized to calibrate the current-induced magnetic dynamics. We find that the
+current-induced magnetoresistance change in antiferromagnets can be complicated
+by resistive switching that does not have a magnetic origin. By excluding
+non-magnetic switching and comparing the current-induced dynamics with the
+field-induced one, we determine the nature and magnitude of current-induced
+effects in Pt/{\alpha}-Fe2O3 bilayer films.",1907.00314v3
+2019-07-10,Dynamical mean-field study of Vanadium diselenide monolayer ferromagnetism,"To understand the magnetism of VSe$_2$, whose monolayer form has recently
+been reported to be a room temperature ferromagnet, Here, the combined method
+of conventional density functional theory with dynamical mean-field theory has
+been adopted. This higher-level computation method enables us to resolve many
+of existing controversies and contradictions in between theory and experiment.
+First of all, this new approach is shown to give the correct magnetic
+properties of both bulk and two-dimensional limit of VSe$_2$ which demonstrates
+its superiority to the conventional methods. The results demonstrate that
+monolayer VSe$_2$ without charge density waves is a ferromagnet with ordering
+temperature of 250K. From the direct simulation of temperature-dependent
+magnetic susceptibility and ordered moment, it is shown that its ferromagnetism
+is clearly two-dimensional in nature. Further, it is shown that this
+ferromagnetic order is vulnerable to extra charge dopings which provides the
+important insight to elucidate recent experimental controversies.",1907.04790v3
+2019-08-31,Element specificity of transient extreme ultra-violet magnetic dichroism,"In this work we combine theory and experiment to study transient magnetic
+circular dichroism (tr-MCD) in the extreme ultraviolet spectral range (XUV) in
+bulk Co and CoPt. We use the \emph{ab-initio} method of real-time
+time-dependent density functional theory (RT-TDDFT) to simulate the
+magnetization dynamics in the presence of ultrafast laser pulses. From this we
+demonstrate how tr-MCD may be calculated using an approximation to the
+excited-state linear-response. We apply this approximation to Co and CoPt and
+show computationally that element-specific dynamics of the local spin moments
+can be extracted from the tr-MCD in XUV energy range, as is commonly assumed.
+We then compare our theoretical prediction for the tr-MCD for CoPt with
+experimental measurement and find excellent agreement at many different
+frequencies including the $M_{2 3}$-edge of Co and $N_{6 7}$- and $O_{2 3}$-
+edges of Pt.",1909.00199v1
+2019-12-02,The Effect of Anisotropic Viscosity on the Nonlinear Kink Instability,"The kink instability of magnetohydrodynamics is believed to be fundamental to
+many aspects of the dynamic activity of the solar atmosphere, such as the
+initiation of flares and the heating of the solar corona. In this work, we
+investigate the importance of viscosity on the kink instability. In particular,
+we focus on two forms of viscosity; isotropic viscosity (independent of the
+magnetic field) and anisotropic viscosity (with a preferred direction following
+the magnetic field). Through the detailed analysis of magnetohydrodynamic
+simulations of the kink instability with both types of viscosity, we show that
+the form of viscosity has a significant effect on the nonlinear dynamics of the
+instability. The different viscosities allow for different flow and current
+structures to develop, thus affecting the behaviour of magnetic relaxation, the
+formation of secondary instabilities and the Ohmic and viscous heating
+produced. Our results have important consequences for the interpretation of
+solar observations of the kink instability.",1912.01076v1
+2019-12-16,Slave-Boson analysis of the 2D Hubbard model,"We present a comprehensive study of the 2D one-band Hubbard model applying
+the spin rotation invariant slave-boson method. We utilize a spiral magnetic
+mean field and fluctuations around a paramagnetic mean field to determine the
+magnetic phase diagram and find the two approaches to be in good agreement.
+Apart from the commensurate phases characterized by ordering wave vectors
+$\boldsymbol Q = (\pi, \pi), (0, \pi)$, and $(0, 0)$ we find incommensurate
+phases where the ordering wave vectors $\boldsymbol Q = (Q, Q)$, and $(Q, \pi)$
+vary continuously with filling, interaction strength or temperature. The mean
+field quantities magnetization and effective mass are found to change
+discontinuously at the phase boundaries separating the $(Q, Q)$ and $(Q, \pi)$
+phases, indicating a first order transition. The band structure and Fermi
+surface is shown in selected cases. The dynamic spin and charge
+susceptibilities as well as the structure factors are calculated and discussed,
+including the emergence of collective modes of the zero sound and Mott
+insulator type. The dynamical conductivity is calculated in dependence of
+doping, interaction strength and temperature. Finally, a
+temperature-interaction strength phase diagram is established.",1912.07631v1
+2019-12-20,Efficient Ab-initio Multiplet Calculations for Magnetic Adatoms on MgO,"Scanning probe microscopy and spectroscopy, and more recently in combination
+with electron spin resonance, have allowed the direct observation of electron
+dynamics on the single-atom limit. The interpretation of data is strongly
+depending on model Hamiltonians. However, fitting effective spin Hamiltonians
+to experimental data lacks the ability to explore a vast number of potential
+systems of interest. By using plane-wave density functional theory (DFT) as
+starting point, we build a multiplet Hamiltonian making use of
+maximally-localized Wannier functions. The Hamiltonian contains spin-orbit and
+electron-electron interactions needed to obtain the relevant spin dynamics. The
+resulting reduced Hamiltonian is solved by exact diagonalization. We compare
+three prototypical cases of 3d transition metals Mn (total spin $S=5/2$), Fe
+($S=2$) and Co ($S=3/2$) on MgO with experimental data and find that our
+calculations can accurately predict the spin orientation and anisotropy of the
+magnetic adatom. Our method does not rely on experimental input and permits us
+to explore and predict the fundamental magnetic properties of adatoms on
+surfaces.",1912.09793v1
+2020-02-28,Dynamic Nuclear Polarization by optical Stark effect in periodically-pumped gallium arsenide,"Optical pump-probe time- and magnetic-field-resolved Kerr rotation
+measurements provide a window into the mechanisms that generate dynamic nuclear
+polarization in bulk gallium arsenide. Previously, we have reported an
+unexpected dependence of the direction of the nuclear polarization on the sweep
+direction of the applied external magnetic field. In this paper, we present
+numerical calculations based on a model for this nuclear polarization due to
+the optical orientation and optical Stark effect produced by a train of
+ultrafast optical pulses. We demonstrate the correspondence of the model to our
+experimental measurements for different laser wavelengths and magnetic field
+sweep rates. Finally, we show that the model reproduces the sweep direction
+dependence and provides an explanation for this behavior.",2003.00050v1
+2020-03-19,Magnetism and Néel skyrmion dynamics in GaV$_{4}$S$_{8-y}$Se$_{y}$,"We present an investigation of the influence of low-levels of chemical
+substitution on the magnetic ground state and N{\' e}el skyrmion lattice (SkL)
+state in GaV$_4$S$_{8-y}$Se$_y$, where $y =0, 0.1, 7.9$, and $8$. Muon-spin
+spectroscopy ($\mu$SR) measurements on $y=0$ and 0.1 materials reveal the
+magnetic ground state consists of microscopically coexisting incommensurate
+cycloidal and ferromagnetic environments, while chemical substitution leads to
+the growth of localized regions of increased spin density. $\mu$SR measurements
+of emergent low-frequency skyrmion dynamics show that the SkL exists under
+low-levels of substitution at both ends of the series. Skyrmionic excitations
+persist to temperatures below the equilibrium SkL in substituted samples,
+suggesting the presence of skyrmion precursors over a wide range of
+temperatures.",2003.08682v2
+2020-04-22,Suppression of indirect exchange and symmetry breaking in antiferromagnetic metal with dynamic charge stripes,"Precise angle-resolved magnetoresistance (ARM) measurements are applied to
+reveal the origin for the lowering of symmetry in electron transport and the
+emergence of a huge number of magnetic phases in the ground state of
+antiferromagnetic metal HoB12 with fcc crystal structure. By analyzing of the
+polar H-theta-phi magnetic phase diagrams of this compound reconstructed from
+the experimental ARM data we argue that non-equilibrium electron density
+oscillations (dynamic charge stripes) are responsible for the suppression of
+the indirect RKKY exchange along <110> directions between the nearest
+neighboring magnetic moments of Ho3+ ions in this strongly correlated electron
+system.",2004.10421v1
+2020-09-13,Light-matter interactions in synthetic magnetic fields: Landau-photon polaritons,"We study light-matter interactions in two dimensional photonic systems in the
+presence of a spatially homogeneous synthetic magnetic field for light.
+Specifically, we consider one or more two-level emitters located in the bulk
+region of the lattice, where for increasing magnetic field the photonic modes
+change from extended plane waves to circulating Landau levels. This change has
+a drastic effect on the resulting emitter-field dynamics, which becomes
+intrinsically non-Markovian and chiral, leading to the formation of strongly
+coupled Landau-photon polaritons. The peculiar dynamical and spectral
+properties of these quasi-particles can be probed with state-of-the-art
+photonic lattices in the optical and the microwave domain and may find various
+applications for the quantum simulation of strongly interacting topological
+models.",2009.05952v2
+2020-12-16,Magnetic domain wall dynamics in the precessional regime: influence of the Dzyaloshinskii-Moriya interaction,"The domain wall dynamics driven by an out of plane magnetic field was
+measured for a series of magnetic trilayers with different strengths of the
+interfacial Dzyaloshinskii-Moriya interaction (DMI). The features of the
+field-driven domain wall velocity curves strongly depend on the amplitude of
+the HD field stabilising chiral N\'eel walls. The measured Walker velocity,
+which in systems with large DMI is maintained after the Walker field giving
+rise to a velocity plateau up to the Slonczewski field HS, can be easily
+related to the DMI strength. Yet, when the DMI field HD and the domain wall
+demagnetising field HDW have comparable values, a careful analysis needs to be
+done in order to evaluate the impact of the DMI on the domain wall velocity. By
+means of a one-dimensional model and 2D simulations, we successfully extend
+this method to explain experimental results to cases where HD and HDW are
+comparable.",2012.09277v2
+2020-12-17,Curvature-driven AC-assisted creep dynamics of magnetic domain walls,"The dynamics of micrometer-sized magnetic domains in ultra-thin ferromagnetic
+films is so dramatically slowed down by quenched disorder that the spontaneous
+elastic tension collapse becomes unobservable at ambient temperature. By
+magneto-optical imaging we show that a weak zero-bias AC magnetic field can
+assist such curvature-driven collapse, making the area of a bubble to reduce at
+a measurable rate, in spite of the negligible effect that the same curvature
+has on the average creep motion driven by a comparable DC field. An analytical
+model explains this phenomenon quantitatively.",2012.09377v1
+2020-12-29,Bloch point-mediated skyrmion annihilation in three dimensions,"The creation and annihilation of magnetic skyrmions are mediated by three
+dimensional topological defects known as Bloch points. Investigation of such
+dynamical processes is important both for understanding the emergence of exotic
+topological spin textures, and for future engineering of skyrmions in
+technological applications. However, while the annihilation of skyrmions has
+been extensively investigated in two dimensions, in three dimensions the phase
+transitions are considerably more complex. We report field-dependent
+experimental measurements of metastable skyrmion lifetimes in an archetypal
+chiral magnet, revealing two distinct regimes. Comparison to supporting
+three-dimensional geodesic nudged elastic band simulations demonstrates that
+these correspond to skyrmion annihilation into either the helical or conical
+states, each exhibiting a different transition mechanism. The results highlight
+that the lowest energy magnetic configuration of the system plays a crucial
+role when considering the emergence of topological spin structures via
+defect-mediated dynamics, and their stability in future devices.",2012.14813v1
+2021-02-08,Extended space and time correlations in strongly magnetized plasmas,"Molecular dynamics simulations are used to show that strong magnetization
+significantly increases the space and time scales associated with interparticle
+correlations. The physical mechanism responsible is a channeling effect whereby
+particles are confined to move along narrow cylinders with a width
+characterized by the gyroradius and a length characterized by the collision
+mean free path. The predominant interaction is $180^\circ$ collisions at the
+ends of the collision cylinders, resulting in a long-range correlation parallel
+to the magnetic field. Its influence is demonstrated via the dependence of the
+velocity autocorrelation functions and self-diffusion coefficients on the
+domain size and run time in simulations of the one-component plasma. A very
+large number of particles, and therefore domain size, must be used to resolve
+the long-range correlations, suggesting that the number of charged particles in
+the collection must increase in order to constitute a plasma. Correspondingly,
+this effect significantly delays the time it takes to reach a diffusive regime,
+in which the mean square displacement of particles increases linearly in time.
+This result presents challenges for connecting measurements in non-neutral and
+ultracold neutral plasma experiments, as well as molecular dynamics
+simulations, with fluid transport properties due to their finite size.",2102.04289v1
+2021-02-12,Sb-5s lone pair dynamics and collinear magnetic ordering in Ba2FeSbSe5,"Neutron diffraction and X-ray pair distribution function (XPDF) experiments
+were performed in order to investigate the magnetic and local crystal
+structures of Ba2FeSbSe5 and to compare them to the average (i.e. long-range)
+structural model, previously obtained by single crystal X-ray diffraction.
+Changes in the local crystal structure (i.e. in the second coordination sphere)
+are observed upon cooling from 295 K to 95 K resulting in deviations from the
+average (i.e. long-range) crystal structure. This work demonstrates, that these
+observations cannot be explained by local or long-range magnetoelastic effects
+involving Fe-Fe correlations. Instead, we found, that the observed differences
+between local and average crystal structure can be explained by Sb-5s lone pair
+dynamics. We also find, that below the N\'eel temperature (TN = 58 K), the two
+distinct magnetic Fe3+ sites order collinearly, such that a combination of
+antiparallel and parallel spin arrangements along the b-axis results. The
+nearest-neighbor arrangement (J1 = 6 {\AA}) is fully antiferromagnetic, while
+next-nearest-neighbor interactions are ferromagnetic in nature.",2102.06484v1
+2021-03-11,Partial Meissner effect measurement by a superconducting magnetic flux lens,"Magnetic flux trapping in the Meissner transition of superconducting radio
+frequency cavities can substantially increase dissipation which impacts
+cryogenic costs and necessitates expensive magnetic shielding. Recent findings
+point at the material preparation and the cool down dynamics at the vortex
+state as the main ways to counteract flux trapping. Most of the related
+measurements are performed on the cavity, with risk of results being impacted
+by the cool down specifics of each facility. We demonstrate an alternative
+experiment in which flux expulsion is quantified from sheet material, with
+samples conduction cooled in a stand-alone instrument designed to collimate
+expelled flux at controlled cool down conditions. A series of tests reliably
+and reproducibly relate the amount of expelled flux to the cooling rate, the
+velocity of the superconducting front and the spatial temperature gradient. The
+results are in line with tests performed on bare cavities and show that
+expulsion of trapped flux improves with the spatial temperature gradient,
+independent on the cooling rate. Our concept offers means to control the
+dynamics of the Meissner effect and can be used for material qualification
+prior to cavity fabrication.",2103.06697v1
+2021-03-14,Transverse spin dynamics in the anisotropic Heisenberg model realized with ultracold atoms,"In Heisenberg models with exchange anisotropy, transverse spin components are
+not conserved and can decay not only by transport, but also by dephasing. Here
+we utilize ultracold atoms to simulate the dynamics of 1D Heisenberg spin
+chains, and observe fast, local spin decay controlled by the anisotropy.
+Additionally, we directly observe an effective magnetic field created by
+superexchange which causes an inhomogeneous decay mechanism due to variations
+of lattice depth between chains, as well as dephasing within each chain due to
+the twofold reduction of the effective magnetic field at the edges of the
+chains and due to fluctuations of the effective magnetic field in the presence
+of mobile holes. The latter is a new coupling mechanism between holes and
+magnons. All these dephasing mechanisms, corroborated by extensive numerical
+simulations, have not been observed before with ultracold atoms and illustrate
+basic properties of the underlying Hubbard model.",2103.07866v1
+2021-07-05,Transport through dynamic pseudo-gauge fields and snake states in a Corbino geometry,"We propose a Corbino-disk geometry of a graphene membrane under out-of-plane
+strain deformations as a convenient path to detect pseudo-magnetic and electric
+fields via electronic transport. The three-fold symmetric pseudo-magnetic field
+changes sign six times as function of angle, leading to snake states connecting
+the inner and outer contacts and to nearly quantized transport. For dynamical
+strain obtained upon AC gating, the system supports an AC pseudo-electric field
+which, in the presence of the pseudo-magnetic field, produces a net electronic
+charge current in the absence of an external voltage, via a pseudo-Hall effect.",2107.02209v2
+2021-07-20,Spatio temporal analysis of waves in compressively driven magnetohydrodynamics turbulence,"Using direct numerical simulations (DNSs), the interaction between linear
+waves and turbulence under the compressible magnetohydrodynamic (CMHD) approach
+was studied. A set of DNSs in three dimensions for a spatial resolution of
+$128^3$ and $256^3$ were performed. A parametric study was carried out varying
+the sonic Mach number, the mean magnetic field and the compressibility
+amplitude of the forcing. Spatio-temporal spectra of the magnetic energy were
+built and analyzed, allowing for direct identification of all wave modes in a
+CMHD turbulent system and quantification of the amount of energy in each mode
+as a function of the wave number. Thus, linear waves were detected, that is
+Alfv\'en waves and fast and slow magnetosonic waves. Furthermore, different
+responses of the plasma were found according to whether the Mach number or the
+mean magnetic field was varied. On the other hand, making use of
+spatio-temporal spectra and two different integration methods, we accurately
+quantified the amount of energy present in each of the normal modes. Finally,
+although the presence of linear waves was observed, in all the cases studied
+the system was mainly dominated by the non-linear dynamics of the plasma.",2107.09212v1
+2021-07-25,Critical and geometric properties of magnetic polymers across the globule-coil transition,"We study a lattice model of a single magnetic polymer chain, where Ising
+spins are located on the sites of a lattice self-avoiding walk in $d=2$. We
+consider the regime where both conformations and magnetic degrees of freedom
+are dynamic, thus the Ising model is defined on a dynamic lattice and
+conformations generate an annealed disorder. Using Monte Carlo simulations, we
+characterize the globule-coil and ferromaget-to-paramagnet transitions, which
+occur simultaneously at a critical value of the spin-spin coupling. We argue
+that the transition is continuous - in contrast to $d=3$ where it is
+first-order. Our results suggest that at the transition the metric exponent
+takes the theta-polymer value $\nu=4/7$ but the crossover exponent $\phi
+\approx 0.7$, which differs from the expected value for a $\theta$-polymer.",2107.11830v2
+2021-08-19,On self and mutual winding helicity,"The topological underpinning of magnetic fields connected to a planar
+boundary is naturally described by field line winding. This observation leads
+to the definition of winding helicity, which is closely related to the more
+commonly calculated relative helicity. Winding helicity, however, has several
+advantages, and we explore some of these in this work. In particular, we show,
+by splitting the domain into distinct subregions, that winding helicity can be
+decomposed naturally into ""self"" and ""mutual"" components and that these
+quantities can be calculated, in practice, for magnetic fields with complex
+geometries and topologies. Further, winding provides a unified topological
+description from which known expressions for self and mutual helicity can be
+readily derived and generalized. We illustrate the application of calculating
+self and mutual winding helicities in a simulation of an evolving magnetic
+field with non-trivial field line topology.",2108.08888v1
+2021-10-02,Higgs and Goldstone spin-wave modes in striped magnetic texture,"Spontaneous symmetry breaking is ubiquitous in physics. Its spectroscopic
+signature consists in the softening of a specific mode upon approaching the
+transition from the high symmetry side and its subsequent splitting into a
+zero-frequency ""Goldstone"" mode and a non-zero-frequency ""Higgs"" mode. Although
+they determine the whole system dynamics, these features are difficult to
+address in practice because of their vanishing coupling to most experimental
+probes and/or their strong interaction with other fluctuations. In this work,
+we consider a periodic magnetic modulation occurring in a ferromagnetic film
+with perpendicular-to-plane magnetic anisotropy and directly observe its
+Goldstone and Higgs spin-wave modes at room temperature using microwave and
+optical techniques. This simple system constitutes a particularly convenient
+platform for further exploring the dynamics of symmetry breaking.",2110.00882v2
+2021-10-09,Field induced spin freezing and low temperature heat capacity of disordered pyrochlore oxide Ho$_{2}$Zr$_{2}$O$_{7}$,"Spin ice materials are the model systems that have a zero-point entropy as
+\textit{T} $\rightarrow$ 0 K, owing to the frozen disordered states. Here, we
+chemically alter the well-known spin ice Ho$_{2}$Ti$_{2}$O$_{7}$ by replacing
+Ti sites with isovalent but larger Zr ion. Unlike the Ho$_{2}$Ti$_{2}$O$_{7}$
+which is a pyrochlore material, Ho$_{2}$Zr$_{2}$O$_{7}$ crystallizes in
+disordered pyrochlore structure. We have performed detailed structural, ac
+magnetic susceptibility and heat capacity studies on Ho$_{2}$Zr$_{2}$O$_{7}$ to
+investigate the interplay of structural disorder and frustrated interactions.
+The zero-field ground state exhibits large magnetic susceptibility and remains
+dynamic down to 30 mK without showing Pauling's residual entropy. The dynamic
+state is suppressed continuously with the magnetic field and freezing
+transition evolves ($\sim$ 10 K) at a field of $\sim$ 10 kOe. These results
+suggest that the alteration of chemical order and local strain in
+Ho$_{2}$Ti$_{2}$O$_{7}$ prevents the development of spin ice state and provides
+a new material to study the geometrical frustration based on the structure.",2110.04555v1
+2021-10-28,Optical dynamic nuclear polarization of $^{13}$C spins in diamond at a low field with multi-tone microwave irradiation,"Most of dynamic nuclear polarization (DNP) has been requiring helium
+cryogenics and strong magnetic fields for a high degree of polarization. In
+this work, we instead demonstrate an optical hyperpolarization of naturally
+abundant $^{13}$C nuclei in a diamond crystal at a low magnetic field and an
+ambient temperature. It exploits continuous irradiations of pump laser for
+polarizing electron spins of nitrogen vacancy centers and microwave for
+transferring the induced polarization to $^{13}$C nuclear spins. Triplet
+structures corresponding to $^{14}$N hyperfine splitting were clearly observed
+in the spectrum of $^{13}$C polarization. The powers of microwave irradiation
+and pump laser were optimized. By simultaneously irradiating three microwave
+frequencies matching to the peaks of the triplet, we achieved a $^{13}$C bulk
+polarization of 0.113 %, leading to an enhancement of about a factor of 90,000
+over the thermal polarization at 17.6 mT. We believe that the multi-tone
+irradiation can be universally adopted to further enhance the $^{13}$C
+polarization at a low magnetic field.",2110.14850v1
+2021-11-07,Absence of temperature-dependent phonon anomalies in Sr2IrO4 and Sr3Ir2O7,"Following previous works reporting an anomalous behavior of several
+zone-center optical phonons across the magnetic transition of square lattice
+iridates Sr2IrO4 and Sr3Ir2O7, we have investigated the lattice dynamics as a
+function of momentum in these materials by means of high-resolution inelastic
+x-ray scattering (IXS). The observed phonon energies and scattering intensities
+across the Brillouin zone are in excellent agreement with ab-initio lattice
+dynamical calculations based on non-magnetic density-functional-perturbation
+theory (DFPT). Our results do not evidence any renormalization of the phonons
+at finite momentum across the magnetic transition of Sr2IrO4. The only
+anomalous behavior was detected for the in-plane polarized
+longitudinal-acoustic phonon branch in Sr3Ir2O7, which anomalously softens
+towards low temperatures and might be related to anisotropic negative thermal
+expansion in this compound. No anomalies related to potential charge ordering
+were observed.",2111.04081v1
+2021-11-15,Phase diagram and post-quench dynamics in a double spin-chain system in transverse fields,"We propose and explore the physics of a toy multiferroic model by coupling
+two distinct dipolar XXZ models in transverse fields. We determine first the
+rich ground-state phase diagram of the model using density matrix
+renormalization group techniques. Then, we explore the dynamics of the system
+after global and local quenches, using the time-evolving block decimation
+algorithm. After a global quench, the system displays decaying coupled
+oscillations of the electric and magnetic spins, in agreement with the
+Eigenstate Thermalization Hypothesis (ETH) for many-body interacting quantum
+systems. Notably, the spin-spin interactions lead to a sizeable quadratic shift
+in the oscillation frequency as the inter-chain coupling is increased. Local
+quenches lead to a light-cone-like propagation of excitations. In this case,
+the inter-chain coupling drives a transfer of energy between the chains that
+generates a novel fast spin-wave mode along the 'magnetic' chain at the speed
+of the 'electric' spin-wave. This suggests a limited control mechanism for
+faster information transfer in magnetic spin chains using electric fields that
+harnesses the electric dipoles as intermediaries.",2111.07831v1
+2021-11-26,Thermally populated versus field-induced triplon bound states in the Shastry-Sutherland lattice SrCu$_2$(BO$_3$)$_2$,"The Shastry-Sutherland compound SrCu$_2$(BO$_3$)$_2$ constituting
+orthogonally coupled dimers harbors a $S=0$ singlet ground state. The
+confluence of strong interdimer interaction and frustration engenders a
+spectrum of low-energy excitations including localized triplons as well as
+singlet and triplet bound states. Their dynamics are controlled by an external
+magnetic field and temperature. Here, we employ high-field Raman spectroscopy
+to map the field and temperature evolution of such bosonic composite
+quasiparticles on approaching the 1/8 magnetization plateau. Our study unveils
+that the magnetic field and thermal fluctuations show remarkably similar
+effects in melting the singlet bound states, but are disparate in their effects
+on the fine spectral shapes. This, together with the anti-crossing of two
+singlet bound states in the intermediate field $B=10-16$ T, is discussed in
+terms of the correlated dynamics of frustrated, interacting bosons.",2111.13354v1
+2021-11-30,First and second order magnetic anisotropy and damping of europium iron garnet under high strain,"Understanding and tailoring static and dynamic properties of magnetic
+insulator thin films is important for spintronic device applications. Here, we
+grow atomically flat epitaxial europium iron garnet (EuIG) thin films by pulsed
+laser deposition on (111)-oriented garnet substrates with a range of lattice
+parameters. By controlling the lattice mismatch between EuIG and the
+substrates, we tune the strain in EuIG films from compressive to tensile
+regime, which is characterized by X-ray diffraction. Using ferromagnetic
+resonance, we find that in addition to the first-order perpendicular magnetic
+anisotropy which depends linearly on the strain, there is a significant
+second-order one that has a quadratic strain dependence. Inhomogeneous
+linewidth of the ferromagnetic resonance increases notably with increasing
+strain, while the Gilbert damping parameter remains nearly constant (~
+2x10^-2). These results provide valuable insight into the spin dynamics in
+ferrimagnetic insulators and useful guidance for material synthesis and
+engineering of next-generation spintronics applications.",2111.15142v1
+2021-12-02,Experimental study of submerged liquid metal jet in transverse magnetic field,"A liquid metal flow in the form of a submerged round jet entering a square
+duct in the presence of a transverse magnetic field is studied experimentally.
+A range of high Reynolds and Hartmann numbers is considered. Flow velocity is
+measured using electric potential difference probes. A detailed study of the
+flow in the duct's cross-section about seven jet's diameters downstream of the
+inlet reveals the dynamics, which is unsteady and dominated by high-amplitude
+fluctuations resulting from instability of the jet. The flow structure and
+fluctuation properties are largely determined by the value of the Stuart number
+N. At moderate N, the mean velocity profile retains a central jet with
+three-dimensional perturbations increasingly suppressed by the magnetic field
+as N grows. At higher values of N, the flow becomes quasi-two-dimensional and
+acquires the form of an asymmetric macrovortex, with high-amplitude velocity
+fluctuations reemerging.",2112.01600v1
+2021-12-08,Giant Resonant Self-Blocking in Magnetophononically Driven Quantum Magnets,"Magnetophononics, the modulation of magnetic interactions by driven
+infrared-active lattice excitations, is emerging as a key mechanism for the
+ultrafast dynamical control of both semiclassical and quantum spin systems by
+coherent light. We demonstrate that, in a quantum magnetic material with strong
+spin-phonon coupling, resonances between the driven phonon and the spin
+excitation frequencies exhibit a giant self-blocking effect. Instead of
+absorbing more energy, the spin system acts as a strong brake on the driven
+phonon, causing it to absorb only a tiny fraction of the power available from
+the laser. Using the quantum master equations governing the nonequilibrium
+steady states of the coupled spin-lattice system, we show how self-blocking
+dominates the dynamics, demonstrate the creation of mutually repelling hybrid
+spin-phonon states, and control the nonequilibrium renormalization of the
+lattice-driven spin excitation band.",2112.04508v1
+2021-12-21,Nonreciprocal spin-wave dynamics in Pt/Co/W/Co/Pt multilayers,"We present a detailed study of the spin-wave dynamics in single Pt/Co/W and
+double Pt/Co/W/Co/Pt ferromagnetic layer systems. The dispersion of spin waves
+was measured by wavevector-resolved Brillouin light scattering spectroscopy
+while the in-plane and out-of-plane magnetization curves were measured by
+alternating gradient field magnetometry. The interfacial Dzyaloshinskii-Moriya
+interaction induced nonreciprocal dispersion relation was demonstrated for both
+single and double ferromagnetic layers and explicated by numerical simulations
+and theoretical formulas. The results indicate the crucial role of the order of
+layers deposition on the magnetic parameters. A significant difference between
+the perpendicular magnetic anisotropy constant in double ferromagnetic layer
+systems conduces to the decline of the interlayer interactions and different
+dispersion relations for the spin-wave modes. Our study provides a significant
+contribution to the realization of the multifunctional nonreciprocal magnonic
+devices based on ultrathin ferromagnetic/heavy-metal layer systems.",2112.11206v1
+2022-01-17,Consensus from group interactions: An adaptive voter model on hypergraphs,"We study the effect of group interactions on the emergence of consensus in a
+spin system. Agents with discrete opinions $\{0,1\}$ form groups. They can
+change their opinion based on their group's influence (voter dynamics), but
+groups can also split and merge (adaptation). In a hypergraph, these groups are
+represented by hyperedges of different sizes. The heterogeneity of group sizes
+is controlled by a parameter $\beta$. To study the impact of $\beta$ on
+reaching consensus, we provide extensive computer simulations and compare them
+with an analytic approach for the dynamics of the average magnetization. We
+find that group interactions amplify small initial opinion biases, accelerate
+the formation of consensus and lead to a drift of the average magnetization.
+The conservation of the initial magnetization, known for basic voter models, is
+no longer obtained.",2201.06421v1
+2022-01-18,Magnon Spectrum of the Amorphous Ferromagnet Co$_4$P from Atomistic Spin Dynamics,"An anomaly in the magnon dispersion of the amorphous ferromagnet Co$_{4}$P,
+often referred to as a `roton-like' excitation, attracted much attention half a
+century ago. With the current interest in heat and spin currents in amorphous
+magnets, we apply modern simulation methods, combining reverse Monte Carlo to
+build the atomic structure and the stochastic Landau-Lifshitz equation for spin
+dynamics, to re-investigate the magnetic excitation spectrum. We find two
+magnon valleys, one at the origin and another at a finite wavenumber close to
+the observations, but without a magnon gap. We conclude that the second dip is
+due to Umklapp scattering caused by residual long-range order, which may be an
+alternative explanation of the putative roton excitation. Our study paves the
+way to study magnon transport in amorphous magnets and related spintronic
+applications.",2201.06986v1
+2022-01-22,Universal criteria for single femtosecond pulse ultrafast magnetization switching in ferrimagnets,"Single-pulse switching has been experimentally demonstrated in ferrimagnetic
+GdFeCo and Mn$_2$Ru$_x$Ga alloys. Complete understanding of single-pulse
+switching is missing due to the lack of an established theory accurately
+describing the transition to the non-equilibrium reversal path induced by
+femtosecond laser photo-excitation. In this work we present general macroscopic
+theory for the magnetization dynamics of ferrimagnetic materials upon
+femtosecond laser excitation. Our theory reproduces quantitatively all stages
+of the switching process observed in experiments. We directly compare our
+theory to computer simulations using atomistic spin dynamics methods for both
+GdFeCo and Mn$_2$Ru$_x$Ga alloys. We provide explicit expressions for the
+magnetization relaxation rates in terms of microscopic parameters which allows
+us to propose universal criteria for switching in ferrimagnets.",2201.09067v1
+2022-02-15,Analysis of the robustness and dynamics of spin-locking preparations for the detection of oscillatory magnetic fields,"Extracting quantitative information of neuronal signals by non-invasive
+imaging is an outstanding challenge for understanding brain function and
+pathology. However, state-of-the-art techniques offer low sensitivity to deep
+electrical sources. Stimulus induced rotary saturation (SIRS) is a recently
+proposed magnetic resonance imaging (MRI) sequence that detects oscillatory
+magnetic fields using a spin-lock preparation. Phantom experiments and
+simulations proved its efficiency and sensitivity, but the susceptibility of
+the method to field inhomogeneities is still not well understood. In this
+study, we simulated and analyzed the dynamic of three spin-lock preparations
+and their response to field inhomogeneities in the presence of a resonant
+oscillating field. We show that the composite spin-lock preparation is more
+robust against field variations within the double resonance effect. In
+addition, we tested the capability of the chosen composite spin-lock
+preparation to recover information about the spectral components of a composite
+signal. This study sets the bases to move one step further towards the clinical
+application of MR-based neuronal current imaging.",2202.07705v2
+2022-03-22,"Lattice Dynamics, Mechanical Properties, Electronic Structure and Magnetic Properties of Equiatomic Quaternary Heusler Alloys CrTiCoZ (Z =Al,Si) using first principles calculations","First principles calculations are performed to investigate the
+thermodynamical stability, dynamical, mechanical, electronic and magnetic
+properties of CrTiCoZ (Z= Al/Si) novel quaternary Heusler alloys. Y-type III
+atomic configuration is found to be the most stable structure for both
+compounds. The melting temperatures of both compounds are as high as 2142 K and
+2420 K for CrTiCoAl and CrTiCoSi, respectively. The electronic structure
+calculations using GGA-PBE approach show a half metallic behavior of CrTiCoAl.
+The spin-down channel exhibits a direct band gap of 0.15 eV, whereas the
+spin-up channel is metallic making CrTiCoAl a half metallic ferromagnet with
+100% spin polarization and an appreciable magnetic moment of -2 Bohr Magnetons.
+The Curie temperature of CrTiCoAl is well above the room temperature (385K),
+whereas that of CrTiCoSi is below the room temperature (203K).",2203.11858v1
+2022-04-06,Melting of magnetic order in ${\mathrm{NaOsO}}_{3}$ by fs laser pulses,"NaOsO$_3$ has recently attracted significant attention for the strong
+coupling between its electronic band structure and magnetic ordering. Here, we
+used time-resolved magnetic X-ray diffraction to determine the timescale of the
+photoinduced \afm dynamics in NaOsO$_3$. Our measurements are consistent with a
+sub-100~fs melting of the \afm long-range order, that occurs significantly
+faster than the lattice dynamics as monitored by the transient change in
+intensity of selected Bragg structural reflections, which instead show a
+decrease of intensity on a timescale of several ps.",2204.03009v1
+2022-04-15,Dynamical mean-field theory study of a ferromagnetic CrI3 monolayer,"We have employed one of the well-known many-body techniques, density
+functional theory plus dynamical mean-field theory (DFT + DMFT), to investigate
+the electronic structure of ferromagnetic monolayer CrI3 as a function of
+temperature and hole-doping concentration. The computed magnetic susceptibility
+follows the Curie's law, indicating that the ferromagnetism of monolayer CrI3
+originates from localized magnetic moments of Cr atoms rather than Stoner-type
+itinerant ones. The DFT + DMFT calculations show a different coherent
+temperature for each spin component, demonstrating apparent strong
+spin-dependent electronic correlation effects in monolayer CrI3. Furthermore,
+we have explored the doping-dependent electronic structure of monolayer CrI3
+and found that its electronic and magnetic properties are easily tunable by the
+hole-doping.",2204.07307v1
+2022-04-23,Theory of inertial spin dynamics in anisotropic ferromagnets,"Recent experimental observation of inertial spin dynamics calls upon holistic
+reevaluation of the theoretical framework of magnetic resonance in
+ferromagnets. Here, we derive the secular equation of an inertial spin system
+in analogy to the ubiquitous Smit-Beljers formalism. We find that the frequency
+of precessional ferromagnetic resonances is decreased as compared to
+non-inertial case. We also find that the frequency of nutational resonances is
+generally increased due to the presence of magnetic anisotropy and applied
+magnetic field. We obtain exact solutions of the secular equation and
+approximations that employ the terminology of non-inertial theory and thus
+allow for convenient estimates of the inertial effects.",2204.11057v2
+2022-05-11,Domain wall damped harmonic oscillations induced by curvature gradients in elliptical magnetic nanowires,"Understanding the domain wall (DW) dynamics in magnetic nanowires (NW) is
+crucial for spintronic-based applications demanding the use of DWs as
+information carriers. This work focuses on the dynamics of a DW displacing
+along a bent NW with an elliptical shape under the action of spin-polarized
+electric currents and external magnetic fields. Our results evidence that a
+curvature gradient induces an exchange-driven effective tangential field
+responsible for pinning a DW near the maximum curvature point in a NW. The DW
+equilibrium position depends on the competition between the torques produced by
+the external stimuli and the curvature-induced effective fields. When the
+external stimuli are below a certain threshold, the DW follows a damped
+harmonic oscillation around the equilibrium position. Above this threshold, DW
+displaces along the NW under an oscillatory translational motion.",2205.05716v1
+2022-05-17,Semi-discretization and full-discretization with optimal accuracy for charged-particle dynamics in a strong nonuniform magnetic field,"The aim of this paper is to formulate and analyze numerical discretizations
+of charged-particle dynamics (CPD) in a strong nonuniform magnetic field. A
+strategy is firstly performed for the two dimensional CPD to construct the
+semi-discretization and full-discretization which have optimal accuracy. This
+accuracy is improved in the position and in the velocity when the strength of
+the magnetic field becomes stronger. This is a better feature than the usual so
+called ""uniformly accurate methods"". To obtain this refined accuracy, some
+reformulations of the problem and two-scale exponential integrators are
+incorporated, and the optimal accuracy is derived from this new procedure. Then
+based on the strategy given for the two dimensional case, a new class of
+uniformly accurate methods with simple scheme is formulated for the three
+dimensional CPD in maximal ordering case. All the theoretical results of the
+accuracy are numerically illustrated by some numerical tests.",2205.08191v1
+2022-05-24,Relativistic dynamical inversion in manifestly covariant form,"The Relativistic Dynamical Inversion technique, a novel tool for finding
+analytical solutions to the Dirac equation, is written in explicitly covariant
+form. It is then shown how the technique can be used to make a change from
+Cartesian to spherical coordinates of a given Dirac spinor. Moreover the most
+remarkable feature of the new method, which is the ease of performing
+non-trivial change of reference frames, is demonstrated. Such a feature
+constitutes a potentially powerful tool for finding novel solutions to the
+Dirac equation. Furthermore, a whole family of normalizable analytic solutions
+to the Dirac equation is constructed. More specifically, we find exact
+solutions for the case of a Dirac electron in the presence of a magnetic field
+as well as a novel solution comprising of a combination of a spherically
+symmetric electric field and magnetic fields. These solutions shed light on the
+possibility of separating the positive and negative energy parts of localized
+Dirac spinors in the presence as well as in the absence of magnetic fields. The
+presented solutions provide an illustration of the connection between the
+geometrical properties of the spinor and spin-orbit coupling for normalizable
+spinorial wave functions.",2205.14004v1
+2022-06-18,Magnon straintronics in the 2D van der Waals ferromagnet CrSBr from first-principles,"The recent isolation of two-dimensional (2D) magnets offers tantalizing
+opportunities for spintronics and magnonics at the limit of miniaturization.
+One of the key advantages of atomically-thin materials is their outstanding
+deformation capacity, which provides an exciting avenue to control their
+properties by strain engineering. Herein, we investigate the magnetic
+properties, magnon dispersion and spin dynamics of the air-stable 2D magnetic
+semiconductor CrSBr ($T_C$ = 146 K) under mechanical strain using
+first-principles calculations. Our results provide a deep microscopic analysis
+of the competing interactions that stabilize the long-range ferromagnetic order
+in the monolayer. We showcase that the magnon dynamics of CrSBr can be modified
+selectively along the two main crystallographic directions as a function of
+applied strain, probing the potential of this quasi-1D electronic system for
+magnon straintronics applications. Moreover, we predict a strain-driven
+enhancement of $T_C$ considering environmental screening by ~30%, allowing the
+propagation of spin waves at higher temperatures.",2206.09277v1
+2022-07-12,Multitude of exceptional points in van der Waals magnets,"Several works have recently addressed the emergence of exceptional points
+(EPs), i.e., spectral singularities of non-Hermitian Hamiltonians, in the
+long-wavelength dynamics of coupled magnetic systems. Here, by focusing on the
+driven magnetization dynamics of a van der Waals ferromagnetic bilayer, we show
+that exceptional points can appear over extended portions of the first
+Brillouin zone as well. Furthermore, we demonstrate that the effective
+non-Hermitian magnon Hamiltonian, whose eigenvalues are purely real or come in
+complex-conjugate pairs, respects an unusual wavevector-dependent
+pseudo-Hermiticity. Finally, for both armchair and zigzag nanoribbon
+geometries, we discuss both the complex and purely real spectra of the
+topological edge states and their experimental implications.",2207.05326v3
+2022-07-22,Magnetic-Translational Sum Rule and Approximate Models of the Molecular Berry Curvature,"The Berry connection and curvature are key components of electronic structure
+calculations for atoms and molecules in magnetic fields. They ensure the
+correct translational behavior of the effective nuclear Hamiltonian and the
+correct center-of-mass motion during molecular dynamics in these environments.
+In this work, we demonstrate how these properties of the Berry connection and
+curvature arise from the translational symmetry of the electronic wave function
+and how they are fully captured by a finite basis set of London orbitals but
+not by standard Gaussian basis sets. This is illustrated by a series of
+Hartree-Fock calculations on small molecules in different basis sets. Based on
+the resulting physical interpretation of the Berry curvature as the shielding
+of the nuclei by the electrons, we introduce and test a series of
+approximations using the Mulliken fragmentation scheme of the electron density.
+These approximations will be particularly useful in ab initio molecular
+dynamics calculations in a magnetic field, since they reduce the computational
+cost, while recovering the correct physics and up to 95% of the exact Berry
+curvature.",2207.11004v1
+2022-08-02,Fluctuating Fractionalized Spins in Quasi Two-dimensional Magnetic V0.85PS3,"Quantum spin liquid (QSL), a state characterized by exotic low energy
+fractionalized excitations and statistics is still elusive experimentally and
+may be gauged via indirect experimental signatures. Remnant of QSL phase may
+reflect in the spin dynamics as well as quanta of lattice vibrations, i.e.,
+phonons, via the strong coupling of phonons with the underlying fractionalized
+excitations i.e., Majorana fermions. Inelastic light scattering (Raman) studies
+on V1-xPS3 single crystals evidences the spin fractionalization into Majorana
+fermions deep into the paramagnetic phase reflected in the emergence of a low
+frequency quasielastic response along with a broad magnetic continuum marked by
+a crossover temperature T* ~ 200 K from a pure paramagnetic state to
+fractionalized spins regime qualitatively gauged via dynamic Raman
+susceptibility. We further evidenced anomalies in the phonons self-energy
+parameters in particular phonon line broadening and line asymmetry evolution at
+this crossover temperature, attributed to the decaying of phonons into
+itinerant Majorana fermions. This anomalous scattering response is thus
+indicative of fluctuating fractionalized spins suggesting a phase proximate to
+the quantum spin liquid state in this quasi two-dimensional (2D) magnetic
+system.",2208.01550v1
+2022-08-16,Effective Dynamics of Translationally Invariant Magnetic Schrödinger Equations in the High Field Limit,"We study the large field limit in Schr\""odinger equations with magnetic
+vector potentials describing translationally invariant $B$-fields with respect
+to the $z$-axis. In a first step, using regular perturbation theory, we derive
+an approximate description of the solution, provided the initial data is
+compactly supported in the Fourier-variable dual to $z\in \mathbb R$. The
+effective dynamics is thereby seen to produce high-frequency oscillations and
+large magnetic drifts. In a second step we show, by using the theory of almost
+invariant subspaces, that this asymptotic description is stable under
+polynomially bounded perturbations that vanish in the vicinity of the origin.",2208.07894v2
+2022-08-18,Signatures of Open and Noisy Quantum Systems in Single-Qubit Quantum Annealing,"We propose a quantum annealing protocol that more effectively probes the
+dynamics of a single qubit on D-Wave's quantum annealing hardware. This
+protocol uses D-Wave's h-gain schedule functionality, which allows the rapid
+quenching of the longitudinal magnetic field at arbitrary points during the
+anneal. This features enables us to distinguish between open and closed system
+dynamics as well as the presence or absence of longitudinal magnetic field
+noise. We show that both thermal and magnetic field fluctuations are key
+sources of noise that need to be included in an open quantum system model to
+reproduce the output statistics of the hardware.",2208.09068v1
+2022-09-05,Numerical modeling of the influence of randomly macroscopic inhomogeneities on the magnetic induction and temperature dynamics of a high-T$_c$ superconducting slab,"In this study we perform numerical calculations of the spatial and time
+variation of the magnetic induction, current density and temperature in an
+infinite superconducting slab with macroscopic inhomogeneities. We also modeled
+an homogeneuos superconductor as a referential material, considering
+characteristic magnetothermal properties of a high-T$_c$ single crystal. The
+theoretical formalism is enclosed in the dynamical regime and a continuum
+electrodynamic approach. In particular, we studied the correlation between the
+magnetic jumps and temperature rise occurrence with the presence of
+macroscopical inhomogeneities, modeled through an stochastic current-carrying
+ability spatial profile.",2209.02117v1
+2022-08-30,Phonons and phase symmetries in bulk $CrCl_3$ from scattering measurements and theory,"Phonon-derived behaviors are important indicators of novel phenomena in
+transition metal trihalides, including spin liquid behavior, two-dimensional
+magnetism, and spin-lattice coupling. However, phonons and their dependence on
+spin structure and excitations have not been adequately explored. In this work,
+we probe and critically examine the vibrational properties of bulk $CrCl_3$
+using inelastic neutron scattering and density functional theory. We
+demonstrate that magnetic and van der Waals interactions are essential to
+describing the structure and phonons in $CrCl_3$; however, the specific spin
+configuration is unimportant. This provides context for understanding thermal
+transport measurements as governed by dynamical spin-lattice couplings. More
+importantly, we introduce an efficient dynamic method that exploits
+translational symmetries in large conventional unit cells that generates
+insights into phonon dispersions, interactions, and measured spectra in terms
+of quantum phase interference conditions. This work opens new avenues for
+understanding phonons in layered magnets and more generally in conventional
+cell geometries of a variety of materials.",2209.02394v1
+2022-09-21,Coupling of optical phonons with Kondo effect and magnetic orders in antiferromagnetic Kondo lattice CeAuSb$_2$,"Ultrafast optical spectroscopy was used to investigate the ultrafast
+quasiparticle dynamics of antiferromagnetic Kondo lattice CeAuSb$_2$ as a
+function of temperature and fluence. Our results reveal (i) the opening of a
+narrow hybridization gap ($\Delta$ $\sim$ 4.5 meV) near the Fermi level below
+the coherence temperature $T^*$ $\approx$ 100 K, (ii) the coupling of coherent
+phonon modes with Kondo effect and magnetic orders, leading to the frequencies
+anomaly at the characteristic temperatures, and (iii) a possible photoinduced
+nonthermal phase transition. Our observations thus shed light on the
+hybridization dynamics and magnetic orders in heavy fermion systems.",2209.10169v2
+2022-10-06,Magnetic excitations in the helical Rashba superconductor,"We investigate the magnetic excitation spectrum in the helical state of a
+noncentrosymmetric superconductor with inversion symmetry breaking and strong
+Rashba spin-orbit coupling. For this purpose, we derive the general expressions
+of the dynamical spin response functions under the presence of strong Rashba
+splitting of conduction bands, superconducting gap, and external field which
+lead to stabilization of Cooper pairs with finite overall momentum in a helical
+state. The latter is characterized by momentum space regions of paired and
+unpaired states with different quasiparticle dispersions. The magnetic response
+is determined by i) excitations within and between both paired and unpaired
+regions ii) anomalous coherence factors and iii) additional spin matrix
+elements due to helical Rashba spin texture of bands. We show that as a
+consequence typical correlated real space and spin space anisotropies appear in
+the dynamical susceptibility which would be observable as a characteristic
+fingerprint for a helical superconducting state in inelastic neutron scattering
+investigations.",2210.03059v1
+2022-10-12,Critical role of magnetic moments on lattice dynamics in YBa${}_{2}$Cu${}_{3}$O${}_{6}$,"The role of lattice dynamics in unconventional high-temperature
+superconductivity is still vigorously debated. Theoretical insights into this
+problem have long been prevented by the absence of an accurate first-principles
+description of the combined electronic, magnetic, and lattice degrees of
+freedom. Utilizing the recently constructed r$^2$SCAN density functional that
+stabilizes the antiferromagnetic (AFM) state of the pristine oxide
+YBa$_2$Cu$_3$O$_6$, we faithfully reproduce the experimental dispersion of key
+phonon modes. We further find significant magnetoelastic coupling in numerous
+high energy Cu-O bond stretching optical branches, where the AFM results
+improve over the soft non-magnetic phonon bands.",2210.06569v2
+2022-10-21,An energy stable and maximum bound principle preserving scheme for the dynamic Ginzburg-Landau equations under the temporal gauge,"This paper proposes a decoupled numerical scheme of the time-dependent
+Ginzburg--Landau equations under the temporal gauge. For the magnetic potential
+and the order parameter, the discrete scheme adopts the second type Ned${\rm
+\acute{e}}$lec element and the linear element for spatial discretization,
+respectively; and a linearized backward Euler method and the first order
+exponential time differencing method for time discretization, respectively. The
+maximum bound principle (MBP) of the order parameter and the energy dissipation
+law in the discrete sense are proved. The discrete energy stability and
+MBP-preservation can guarantee the stability and validity of the numerical
+simulations, and further facilitate the adoption of an adaptive time-stepping
+strategy, which often plays an important role in long-time simulations of
+vortex dynamics, especially when the applied magnetic field is strong. An
+optimal error estimate of the proposed scheme is also given. Numerical examples
+verify the theoretical results of the proposed scheme and demonstrate the
+vortex motions of superconductors in an external magnetic field.",2210.11678v2
+2022-10-26,Dimensional reduction and incommensurate dynamic correlations in the $S=\frac{1}{2}$ triangular-lattice antiferromagnet Ca$_3$ReO$_5$Cl$_2$,"The observation of spinon excitations in the $S=\frac{1}{2}$ triangular
+antiferromagnet Ca$_3$ReO$_5$Cl$_2$ reveals a quasi-one-dimensional (1D) nature
+of magnetic correlations, in spite of the nominally 2D magnetic structure. This
+phenomenon is known as frustration-induced dimensional reduction. Here, we
+present high-field electron spin resonance spectroscopy and magnetization
+studies of Ca$_3$ReO$_5$Cl$_2$, allowing us not only to refine spin-Hamiltonian
+parameters, but also to investigate peculiarities of its low-energy spin
+dynamics. We argue that the presence of the uniform Dzyaloshinskii-Moriya
+interaction (DMI) shifts the spinon continuum in momentum space and, as a
+result, opens a zero-field gap at the $\Gamma$ point. We observed this gap
+directly. The shift is found to be consistent with the structural modulation in
+the ordered state, suggesting this material as a perfect model
+triangular-lattice system, where a pure DMI-spiral ground state can be
+realized.",2210.14864v1
+2022-11-14,Symmetric Post-Transition-State Bifurcation Reactions with Berry Pseudo-Magnetic Fields,"We investigate how the Berry force (i.e. the pseudo-magnetic force operating
+on nuclei as induced by electronic degeneracy and spin-orbit coupling (SOC))
+might modify a post-transition state bifurcation (PTSB) reaction path and
+affect product selectivity for situations when multiple products share the same
+transition state. To estimate the magnitude of this effect, Langevin dynamics
+are performed on a model system with a valley-ridge inflection (VRI) point in
+the presence of a magnetic field (that mimics the Berry curvature). We also
+develop an analytic model for such selectivity that depends on key parameters
+such as the surface topology, the magnitude of the Berry force, and the nuclear
+friction. Within this dynamical model, static electronic structure calculations
+(at the level of generalized Hartree-Fock with spin-orbit coupling (GHF+SOC)
+theory) suggest that electronic-spin induced Berry force effects may indeed
+lead to noticeable changes in methoxy radical isomerization.",2211.07731v1
+2022-11-28,Muon-spin relaxation investigation of magnetic bistability in a crystalline organic radical compound,"We present the results of a muon-spin relaxation ($\mu^{+}$SR) investigation
+of the crystalline organic radical compound
+4-(2-benzimidazolyl)-1,2,3,5-dithiadiazolyl (HbimDTDA), in which we demonstrate
+the hysteretic magnetic switching of the system that takes place at $T = 274
+\pm 11\,\mathrm{K}$ caused by a structural phase transition. Muon-site analysis
+using electronic structure calculations suggests a range of candidate muon
+stopping sites. The sites are numerous and similar in energy but,
+significantly, differ between the two structural phases of the material.
+Despite the difference in the sites, the muon remains a faithful probe of the
+transition, revealing a dynamically-fluctuating magnetically disordered state
+in the low-temperature structural phase. In contrast, in the high temperature
+phase the relaxation is caused by static nuclear moments, with rapid electronic
+dynamics being motionally narrowed from the muon spectra.",2211.15560v1
+2022-11-30,Precession of magnetars: dynamical evolutions and modulations on polarized electromagnetic waves,"Magnetars are conjectured to be highly magnetized neutron stars (NSs). Strong
+internal magnetic field and elasticity in the crust may deform the stars and
+lead to free precession. We study the precession dynamics of
+triaxially-deformed NSs incorporating the near-field and the far-field
+electromagnetic torques. We obtain timing residuals for different NS geometries
+and torques. We also investigate the polarized X-ray and radio signals from
+precessing magnetars. The modulations on the Stokes parameters are obtained for
+thermal X-rays emitted from the surface of magnetars. For radio signals, we
+apply the simple rotating vector model (RVM) to give the modulations on the
+position angle (PA) of the polarization. Our results are comprehensive, ready
+to be used to search for magnetar precession with timing data and polarizations
+of X-ray and radio emissions. Future observations of precessing magnetars will
+give us valuable information on the geometry and the strength of the strong
+magnetic fields, the emission geometry, as well as the equation of state (EoS)
+of NSs.",2211.17087v1
+2022-12-01,Manipulating non-reciprocity in a two-dimensional magnetic quantum walk,"Non-reciprocity is an important topic in fundamental physics and
+quantum-device design, as much effort has been devoted to its engineering and
+manipulation. Here we experimentally demonstrate non-reciprocal transport in a
+two-dimensional quantum walk of photons, where the directional propagation is
+highly tunable through dissipation and synthetic magnetic flux. The
+non-reciprocal dynamics hereof is a manifestation of the non-Hermitian skin
+effect, with its direction continuously adjustable through the photon-loss
+parameters. By contrast, the synthetic flux originates from an engineered
+geometric phase, which competes with the non-Hermitian skin effect through
+magnetic confinement. We further demonstrate how the non-reciprocity and
+synthetic flux impact the dynamics of the Floquet topological edge modes along
+an engineered boundary. Our results exemplify an intriguing strategy for
+achieving tunable non-reciprocal transport, highlighting the interplay of
+non-Hermiticity and gauge fields in quantum systems of higher dimensions.",2212.00387v1
+2022-12-18,Resonant contributions to oscillatory phenomena under conditions of magnetic breakdown during reconstructions of electron dynamics on the Fermi surface,"We consider here special closed electron trajectories that arise during
+reconstructions of electron dynamics on the Fermi surface in the presence of
+strong magnetic fields, as well as the phenomenon of intraband magnetic
+breakdown that occurs on such trajectories. We consider cases where the
+electronic spectrum arising in such a situation corresponds to the resonant
+contribution to quantum oscillations. In the paper, all cases where this occurs
+are singled out, and the possible influence of the appearance of the Berry
+phase and other effects on the described phenomena is also considered.",2212.09059v3
+2022-12-29,New description of the scaling evolution of the cosmological magneto-hydrodynamic system,"We present a new description of cosmological evolution of the primordial
+magnetic field under the condition that it is non-helical and its energy
+density is larger than the kinetic energy density. We argue that the evolution
+can be described by four different regimes, according to whether the decay
+dynamics is linear or not, and whether the dominant dissipation term is the
+shear viscosity or the drag force. Using this classification and conservation
+of the Hosking integral, we present analytic models to adequately interpret the
+results of various numerical simulations of field evolution with variety of
+initial conditions. It is found that, contrary to the conventional wisdom, the
+decay of the field is generally slow, exhibiting the inverse transfer, because
+of the conservation of the Hosking integral. Using the description proposed
+here, we may trace the intermediate evolution history of the magnetic field and
+clarify whether each process governing its evolution is frozen or not, which is
+essential to follow the evolution of relatively weak magnetic fields.",2212.14355v1
+2022-12-31,Diffusion within pores fully revealed by magnetic resonance,"Probing the transport of fluids within confined domains is important in many
+areas including material science, catalysis, food science, and cell biology.
+The diffusion propagator fully characterizes the diffusion process, which is
+highly sensitive to the confining boundaries as well as the structure within
+enclosed pores. While magnetic resonance has been used extensively to observe
+various features of the diffusion process, its full characterization has been
+elusive. Here, we address this challenge by employing a special sequence of
+magnetic field gradient pulses for measuring the diffusion propagator, which
+allows for `listening to the drum' and determining not only the pore's shape
+but also diffusive dynamics within it.",2301.00116v1
+2023-02-08,Anisotropic skyrmion mass induced by surrounding conduction electrons: A Schwinger-Keldysh field theory approach,"The current-driven motion of magnetic skyrmions, as topologically protected
+winding vector fields of local magnetization, has attracted considerable
+attention due to both fundamental interest in the dynamics of topological
+solitons, and potential spintronic applications. While widely-used Thiele
+equation with zero skyrmion mass captures its rigid motion under the assumption
+of preserved skyrmion shape, experiments on realistic skyrmions find deviation
+due to inertial mass with numerous attempts to account for it by invoking
+internal skyrmion dynamics, geometry of the nanowire, and interaction with
+magnons or phonons. However, experimentally observed skyrmion mass is often
+much larger than predicted by these theories. In this Letter, we employ
+Schwinger-Keldysh field-theoretical approach to study conduction electrons
+interacting with localized magnetic moments comprising a skyrmion to obtain a
+stochastic differential equation of its motion. By analyzing its time-retarded
+damping kernel, we extract an anisotropic mass governed by conduction electrons
+and demonstrate its substantial effect on the current-driven skyrmion motion,
+even in the absence of any skyrmion deformation.",2302.04220v1
+2023-03-23,Majorana-magnon interactions in topological Shiba chains,"A chain of magnetic impurities deposited on the surface of a superconductor
+can form a topological Shiba band that supports Majorana zero modes and holds a
+promise for topological quantum computing. Yet, most experiments scrutinizing
+these zero modes rely on transport measurements, which only capture local
+properties. Here we propose to leverage the intrinsic dynamics of the magnetic
+impurities to access their non-local character. We use linear response theory
+to determine the dynamics of the uniform magnonic mode in the presence of
+external $ac$ magnetic fields and coupling the Shiba electrons. We demonstrate
+that this mode, which spreads over the entire chain of atoms, becomes imprinted
+with the parity of the ground state and, moreover, can discriminate between
+Majorana and trivial zero modes located at the ends of the chain. Our approach
+offers a non-invasive alternative to the scanning tunneling microscopy
+techniques used to probe Majorana zero modes. Conversely, the magnons could
+facilitate the manipulation of Majorana zero modes in topological Shiba chains.",2303.13513v2
+2023-04-03,Multi-thermal jet formation triggered by flux emergence,"Flux emergence is responsible for various solar eruptions. Combining
+observation and simulations, we investigate the influence of flux emergence at
+one footpoint of an arcade on coronal rain as well as induced eruptions. The
+emergence changes the pressure in the loops, and the internal coronal rain all
+moves to the other side. The emerging flux reconnects with the overlying
+magnetic field, forming a current sheet and magnetic islands. The plasma is
+ejected outwards and heated, forming a cool jet ~ 6000 K and a hot X-ray jet ~
+4 MK simultaneously. The jet dynamical properties agree very well between
+observation and simulation. In the simulation, the jet also displays transverse
+oscillations with a period of 8 minutes, a so-called whip-like motion. The
+movement of the jet and dense plasmoids changes the configuration of the local
+magnetic field, facilitating the occurrence of Kelvin--Helmholtz instability,
+and vortex-like structures form at the boundary of the jet. Our simulation
+clearly demonstrates the effect of emergence on coronal rain, the dynamical
+details of reconnecting plasmoid chains, the formation of multi-thermal jets,
+and the cycling of cool mass between the chromosphere and the corona.",2304.01043v1
+2023-04-06,Essential Tools of Linear Algebra for Calculating Nuclear Spin Dynamics of Chemically Exchanging Systems,"In this work, we describe essential tools of linear algebra necessary for
+calculating the effect of chemical exchange on spin dynamics and polarization
+transfer in various nuclear magnetic resonance (NMR) experiments. We show how
+to construct Hamiltonian, relaxation, and chemical exchange superoperators in
+the Liouville space, as well as demonstrate corresponding code in Python.
+Examples of applying the code are given for problems involving chemical
+exchange between NH3 and NH4+ at zero and high magnetic field and polarization
+transfer from parahydrogen relevant in SABRE (signal amplification by
+reversible exchange) at low magnetic field (0-20 mT). The presented methodology
+finds utility for describing the effect of chemical exchange on NMR spectra and
+can be extended further by taking into account non-linearities in the master
+equation.",2304.03139v2
+2023-04-25,Defect-enhanced diffusion of magnetic skyrmions,"Defects, i.e. inhomogeneities of the underlying lattice, are ubiquitous in
+magnetic materials and can have a crucial impact on their applicability in
+spintronic devices. For magnetic skyrmions, localized and topologically
+non-trivial spin textures, they give rise to a spatially inhomogeneous energy
+landscape and can lead to pinning, resulting in an exponentially increased
+dwell time at certain positions and typically a strongly reduced mobility.
+Using atomistic spin dynamics simulations, we reveal that under certain
+conditions defects can instead enhance thermal diffusion of ferromagnetic
+skyrmions. By comparing with results for the diffusion of antiferromagnetic
+skyrmions and using a quasi-particle description based on the Thiele equation,
+we demonstrate that this surprising finding can be traced back to the partial
+lifting of the impact of the topologigal gyrocoupling, which governs the
+dynamics of ferromagnetic skyrmions in the absence of defects.",2304.12917v1
+2023-05-13,Floquet Dynamical Decoupling at Zero Bias,"Dynamical decoupling (DD) is an efficient method to decouple systems from
+environmental noises and to prolong the coherence time of systems. In contrast
+to discrete and continuous DD protocols in the presence of bias field, we
+propose a Floquet DD at zero bias to perfectly suppress both the zeroth and
+first orders of noises according to the Floquet theory. Specifically, we
+demonstrate the effectiveness of this Floquet DD protocol in two typical
+systems including a spinor atomic Bose-Einstein condensate decohered by
+classical stray magnetic fields and a semiconductor quantum dot electron spin
+coupled to nuclear spins. Furthermore, our protocol can be used to sense
+high-frequency noises. The Floquet DD protocol we propose shines new light on
+low-cost and high-portable DD technics without bias field and with low
+controlling power, which may have wide applications in quantum computing,
+quantum sensing, nuclear magnetic resonance and magnetic resonance imaging.",2305.07847v1
+2023-05-15,A general method to construct mean field counter diabatic driving for a ground state search,"The counter diabatic (CD) driving has attracted much attention for
+suppressing non-adiabatic transition in quantum annealing (QA). However, it can
+be intractable to construct the CD driving in the actual experimental setup due
+to the non-locality of the CD dariving Hamiltonian and necessity of exact
+diagonalization of the QA Hamiltonian in advance. In this paper, using the mean
+field (MF) theory, we propose a general method to construct an approximated CD
+driving term consisting of local operators. We can efficiently construct the MF
+approximated CD (MFCD) term by solving the MF dynamics of magnetization using a
+classical computer. As an example, we numerically perform QA with MFCD driving
+for the spin glass model with transverse magnetic fields. We numerically show
+that the MF dynamics with MFCD driving is equivalent to the solution of the
+self-consistent equation in MF theory. Also, we clarify that a ground state of
+the spin glass model with transverse magnetic field can be obtained with high
+fidelity compared to the conventional QA without the CD driving. Moreover, we
+experimentally demonstrate our method by using a D-wave quantum annealer and
+obtain the experimental result supporting our numerical simulation.",2305.08352v1
+2023-05-18,Reconnection in a Pinch,"A recently published, new analysis of current sheets updated the classic
+Harris 1D static solution by considering multiple classes of charged particle
+trajectories in a generalized dynamic current sheet. It used a 1D PIC
+simulation to describe dynamic pinching and bifurcation of the sheet. These 1D
+results strongly suggest that plasma beta or other properties of the inflowing
+plasma have a strong effect on the equilibrium thickness of the pinched current
+sheet, but cannot describe magnetic reconnection. The time appears right to
+carry such 1D studies over to 3D simulations where current sheet thickness has
+been found exert an enabling or disabling influence on reconnection. The
+Magnetospheric Multiscale Mission (MMS), with its well-resolved multipoint
+measurements, has found that reconnection is enabled in collisionless plasma by
+non-adiabatic motions of electrons that can only occur in narrow magnetic
+structures with a scale comparable to electron inertial lengths (de). The
+recent 1D studies strongly suggest that a pinch to such scales can only occur
+for inflowing magnetized plasmas with relatively low plasma beta. We conclude
+that a parametric exploration of 3D simulated and observed inflow conditions,
+especially plasma beta, should shed light on the enablement of reconnection in
+collisionless plasmas.",2305.11238v1
+2023-06-17,Polytropic representation of the kinetic pressure tensor of non-ideal magnetized fluids in equilibrium toroidal structures,"Non-ideal fluids are generally subject to the occurrence of non-isotropic
+pressure tensors, whose determination is fundamental in order to characterize
+their dynamical and thermodynamical properties. This requires the
+implementation of theoretical frameworks provided by appropriate microscopic
+and statistical kinetic approaches in terms of which continuum fluid fields are
+obtained. In this paper the case of non-relativistic magnetized fluids forming
+equilibrium toroidal structures in external gravitational fields is considered.
+Analytical solutions for the kinetic distribution function are explicitly
+constructed, to be represented by a Chapman-Enskog expansion around a
+Maxwellian equilibrium. In this way, different physical mechanisms responsible
+for the generation of non-isotropic pressures are identified and proved to be
+associated with the kinetic constraints imposed on single and collective
+particle dynamics by phase-space symmetries and magnetic field. As a major
+outcome, the validity of a polytropic representation for the kinetic pressure
+tensors corresponding to each source of anisotropy is established, whereby
+directional pressures exhibit a specific power-law functional dependence on
+fluid density. The astrophysical relevance of the solution for the
+understanding of fluid plasma properties in accretion-disc environments is
+discussed.",2306.11742v1
+2023-07-12,Purely antiferromagnetic frustrated Heisenberg model in spin ladder compound BaFe$_2$Se$_3$,"The spin dynamics in the block magnetic phase of the iron-based ladder
+compound \bfs\ has been studied by means of single crystal inelastic neutron
+scattering. Using linear spin wave theory and Monte-Carlo simulations, our
+analysis points to a magnetic Heisenberg model with effective frustrated
+antiferromagnetic couplings only, able to describe both the exotic block order
+and its dynamics. This new and purely antiferromagnetic picture offers a
+fruitful perspective to describe multiferroic properties but also understand
+the origin of the stripe-like magnetic instability observed under pressure as
+well as in other parent compounds with similar crystalline structure.",2307.06193v1
+2023-07-12,The first law for stationary axisymmetric multi-black hole systems,"In the framework of Einstein-Maxwell theory, we consider collinear arrays of
+rotating electrically charged black holes connected by Misner-Dirac strings
+carrying gravimagnetic and magnetic fluxes. The first law of mechanics for
+these systems is derived. It involves as dynamical variables the areas, angular
+momenta and electric charges of the various Killing horizons -- black holes and
+Misner strings. When the gravimagnetic fluxes all vanish, the first law reduces
+to a form where the dynamical variables associated with the strings are the
+string tensions and magnetic fluxes. This form is not generically invariant
+under electric-magnetic duality.",2307.06282v3
+2023-07-16,On magnetized Rossby wave dynamics in the earth's ionosphere,"In the frame of shallow water model the influence of free surface action on
+nonlinear propagation of planetary ULF magnetized Rossby waves in the weakly
+ionized ionospheric D-, E-, and F-layers is revealed. Relevant nonlinear
+dynamic equations satisfying several conservation laws are obtained and
+investigated. The role of Hall and Pedersen conductivities is investigated
+explicitly. It is shown that while potential vorticity is conserved in the
+ionospheric D-,and E-layer it is broken by Pedersen conductivity in the
+ionospheric F-layer. Similar to KdV nonlinearity two new scalar nonlinearities
+due to Pedersen conductivity are revealed in the F-layer. Obtained results
+extend and complement known theoretical investigations and are especially
+relevant for nonlinear vortical propagation of magnetized Rossby waves in the
+weakly ionized ionospheric plasma.",2307.07986v1
+2023-07-21,Current Tomography -- Localization of void fractions in conducting liquids by measuring the induced magnetic flux density,"A novel concept of a measurement technology for the localization and
+determination of the size of gas bubbles is presented, which is intended to
+contribute to a further understanding of the dynamics of efficiency-reducing
+gas bubbles in electrolyzers. A simplified proof-of-concept (POC) model is used
+to numerically simulate the electric current flow through materials with
+significant differences in electrical conductivity. Through an automated
+approach, an extensive data set of electric current density and conductivity
+distributions is generated, complemented with determined magnetic flux
+densities in the surroundings of the POC cell at virtual sensor positions. The
+generated data set serves as testing data for various reconstruction
+approaches. Based on the measurable magnetic flux density, solving Biot-Savarts
+law inversely is demonstrated and discussed with a model-based solution of an
+optimization problem, of which the gas bubble locations are derived.",2307.11540v1
+2023-07-31,Persistent spin dynamics in magnetically ordered honeycomb cobalt oxides,"In the quest to find quantum spin liquids, layered cobalt oxides Na2Co2TeO6
+and Na3Co2SbO6 have been proposed as promising candidates for approximating the
+Kitaev honeycomb model. Yet, their suitability has been thrown into question
+due to observed long-range magnetic order at low temperatures and indications
+of easy-plane, rather than Kitaev-type, spin anisotropy. Here we use muon spin
+relaxation to reveal an unexpected picture: contrary to the anticipated static
+nature of the long-range order, the systems show prevalent spin dynamics with
+spatially uneven distribution and varied correlation times. This underlines
+that the magnetic ground states cannot be solely described by the long-range
+order, suggesting a significant role of quantum fluctuations. Our findings not
+only shed new light on the complex physics of these systems but also underscore
+the need for a refined approach in the search for realizable quantum spin
+liquids.",2307.16451v1
+2023-08-03,Brownian electric bubble quasiparticles,"Recent works on electric bubbles (including the experimental demonstration of
+electric skyrmions) constitute a breakthrough akin to the discovery of magnetic
+skyrmions some 15 years ago. So far research has focused on obtaining and
+visualizing these objects, which often appear to be immobile (pinned) in
+experiments. Thus, critical aspects of magnetic skyrmions - e.g., their
+quasiparticle nature, Brownian motion - remain unexplored (unproven) for
+electric bubbles. Here we use predictive atomistic simulations to investigate
+the basic dynamical properties of these objects in pinning-free model systems.
+We show that it is possible to find regimes where the electric bubbles can
+present long lifetimes ($\sim$ ns) despite being relatively small ($\varnothing
+<$ 2 nm). Additionally, we find that they can display stochastic dynamics with
+large and highly tunable diffusion constants. We thus establish the
+quasiparticle nature of electric bubbles and put them forward for the physical
+effects and applications (e.g., in token-based Probabilistic Computing)
+considered for magnetic skyrmions.",2308.01716v2
+2023-08-30,Internal activities in a solar filament and heating to its threads,"Filaments are one of the most common features in the solar atmosphere, and
+are of significance in solar, stellar and laboratory plasma physics. Using data
+from the Chinese H$\alpha$ Solar Explorer, the Solar Upper Transition Region
+Imager and the Solar Dynamics Observatory, we report on multiwavelength imaging
+and spectral observations of the activation of a small filament. The filament
+activation produces several localized dynamic brightenings, which are probably
+produced by internal reconnections of the braided magnetic fields in the
+filament. The filament expands during the activation and its threads reconnect
+with the ambient magnetic fields, which leads to the formation of hot arcades
+or loops overlying the filament. The thermal energy of each of these localized
+brightenings is estimated in the order of $10^{25}-10^{27} erg$ and the total
+energy is estimated to be $\sim1.77 \times 10^{28} erg$. Our observations
+demonstrate that the internal magnetic reconnections in the filament can lead
+to localized heating to the filament threads and prompt external reconnections
+with ambient corona structures, and thus could contribute to the energy and
+mass transferring into the corona.",2308.15747v1
+2023-09-11,Electromagnetic energy transfer processes in Effective Electro-Magneto Dynamics of axions,"Oscillating and dissipative energy exchange between the electromagnetic and
+axion fields is investigated in an effective electro-magneto dynamical (EEMD)
+model theory, implying the coexistence of axions with hypothetic magnetic
+charges. An exact formula is presented for the energy transfer between the
+electromagnetic and axionic sectors. In a first example we compute analytically
+the homogeneously oscillating electric and magnetic field configurations
+generated by the combined action of a constant static magnetic field and a
+periodically oscillating axion condensate. In the second example the
+electromagnetic radiative energy loss of a gravitationally bound axion
+configuration is computed in the EEMD model. As a result an asymptotic $\sim
+t^{1/5}$ temporal increase of the clump size is found also in EEMD.",2309.05523v1
+2023-09-22,Earthquake-like dynamics in ultrathin magnetic film,"We study the motion of a domain wall on an ultrathin magnetic film using the
+magneto-optical Kerr effect (MOKE). At tiny magnetic fields, the wall creeps
+only via thermal activation over the pinning centers present in the sample. Our
+results show that this creep dynamics is highly intermittent and correlated. A
+localized instability triggers a cascade, akin to aftershocks following a large
+earthquake, where the pinned wall undergoes large reorganizations in a compact
+active region for a few seconds. Surprisingly, the size and shape of these
+reorganizations display the same scale-free statistics of the depinning
+avalanches in agreement with the quenched Kardar-Parisi-Zhang universality
+class.",2309.12898v1
+2023-09-25,Magnetism on the thermal dynamics of 2D antiferromagnetic membranes,"We developed a theoretical scheme of incorporating the magnetoelastic
+contribution into the thermal elastic dynamics for the thin membranes of 2D
+antiferromagnetic material with restricted geometry. We extended the elastic
+Gr\""uneisen relation into an effective version which includes the magnetic
+counterpart to the volume change of internal energy. Based on the specific heat
+and thermal conductivity from the elastic and magnetic origins we predicted the
+dependency of observables, such as effective Gr\""uneisen parameter, thermal
+expansion coefficient, and the damping factor, with respect to a wide range of
+temperature across the phase transition. Our model of analysis as been
+validated by applying to the case of FePS3 flake resonator and the theoretical
+predictions fits well with the reported experiment data.",2309.13991v2
+2023-10-02,SpinPSO: An agent-based optimization workflow for identifying global noncollinear magnetic ground-states from first-principles,"We propose and implement a novel hybrid meta-heuristic optimization algorithm
+for the identification of non-collinear global ground-states in magnetic
+systems. The inputs to this optimization scheme are directly from non-collinear
+density functional theory (DFT), and the workflow is implemented in the atomate
+code framework, making it suitable to run on high-performance computing
+architectures. The hybrid algorithm provides a seamless theoretical extension
+of particle swarm optimization (PSO) algorithms to continuous $\mathcal S^2$
+spins, giving it the name SpinPSO. The hybrid nature of the algorithm stems
+from setting the dynamics of individual spins to be governed by physically
+motivated atomistic spin dynamics. Using this algorithm, we are able to achieve
+convergence to experimentally resolved magnetic ground-states for a set of
+diverse test case materials that exhibit exotic spin textures.",2310.01383v1
+2023-11-06,Lattice QED in an external magnetic field: Evidence for dynamical chiral symmetry breaking,"We simulate QED in a strong constant homogeneous external magnetic field on a
+euclidean space-time lattice using the Rational Hybrid Monte Carlo method,
+developed for simulating lattice QCD. Our primary goal is to measure the chiral
+condensate in the limit when the input electron mass $m$ is zero. We observe a
+non-zero value, indicating that the external magnetic field catalyzes chiral
+symmetry breaking as predicted by approximate truncated Schwinger-Dyson
+methods. Such behaviour is associated with dominance by the lowest Landau level
+which causes the effective dimensional reduction from $3+1$~dimensions to $1+1$
+dimensions for charged particles (electrons and positrons) where the attractive
+forces of QED can produce chiral symmetry breaking with a dynamical electron
+mass and associated chiral condensate. Since our lattice simulations use bare
+(lattice) parameters, while the Schwinger-Dyson analyses work with renormalized
+quantities, direct numerical comparison will require renormalization of our
+lattice results.",2311.03516v1
+2023-12-11,Charged particle dynamics in an elliptically polarized electromagnetic wave and a uniform axial magnetic field,"An analytical study of the charged particle dynamics in the presence of an
+elliptically polarized electromagnetic wave and a uniform axial magnetic field,
+is presented. It is found that for $g\omega_{0}/ \omega' = \pm 1$, maximum
+energy gain occurs respectively for linear and circular polarization;
+$\omega_{0}$ and $\omega'$ respectively being the cyclotron frequency of the
+charged particle in the external magnetic field and Doppler-shifted frequency
+of the wave seen by the particle, and $g =\pm 1$ respectively correspond to
+left and right-handedness of the polarization. An explicit solution of the
+governing equation is presented in terms of particle position or laboratory
+time, for the specific case of resonant energy gain in a circularly polarized
+electromagnetic wave. These explicit position- or time-dependent expressions
+are useful for better insight into various phenomena, viz., cosmic ray
+generation, microwave generation, plasma heating, and particle acceleration,
+etc.",2312.06175v1
+2023-12-07,Scalar fields in Bonnor-Melvin Universe with potential: A study of dynamics of spin-0 particles-antiparticles,"This research focus on the investigation of relativistic quantum dynamics of
+spin0 scalar particles/fields through the utilization of the Klein-Gordon (KG)
+equation within the framework of an electrovacuum space-time in the presence of
+an external scalar potential. Specifically, we focus on a cylindrical symmetric
+Bonnor-Melvin magnetic universe with a cosmological constant, where the
+magnetic field aligns along the symmetry axis direction. We derive the radial
+wave equation of the KG-equation by considering a Cornell-type scalar potential
+in the background of magnetic universe and successfully obtain an analytical
+eigenvalue solution for spin-0 quantum system. Notably, our findings reveal
+that both the energy spectrum and the corresponding radial wave function are
+significantly influenced by the presence of the cosmological constant, the
+topology parameter of the space-time geometry, which induces a deficit in the
+angular coordinates, and the potential parameters.",2312.06612v1
+2024-01-21,Crystallization and dynamics of defects in a magnetic fluctuating medium,"We consider the dynamics of classical particles or defects moving in a
+fluctuating two-dimensional magnetic medium made of Ising spins. These defects
+occupy empty sites, and each of them can move according to simple rules, by
+exchanging its location with one of the neighboring or distant spin if the
+energy is favorable, conserving the magnetization. We use a fermionic
+representation of the theory in order to map the partition function into an
+integral over Grassmannian variables. This model of annealed disorder can be
+described by a Grassmannian action containing quartic interaction terms. We
+study the critical behavior of this system as well as the entropy, specific
+heat, and residual correlation functions which are evaluated within this
+Grassmannian formalism. We found in particular that the correlations are
+strongly attractive at short distances in the low temperature regime and for a
+broader range of distances near the spin critical regime, and slightly
+repulsive at large distances. These results are compared with Monte-Carlo
+simulations.",2401.11528v1
+2024-01-22,Active Inference Demonstrated with Artificial Spin Ice,"A numerical model of interacting nanomagnetic elements is used to demonstrate
+active inference with a three dimensional Artificial Spin Ice structure. It is
+shown that thermal fluctuations can drive this magnetic spin system to evolve
+under dynamic constraints imposed through interactions with an external
+environment as predicted by the neurological free energy principle and active
+inference. The structure is defined by two layers of magnetic nanoelements
+where one layer is a square Artificial Spin Ice geometry. The other magnetic
+layer functions as a sensory filter that mediates interaction between the
+external environment and the hidden Artificial Spin Ice layer. Spin dynamics
+displayed by the bilayer structure are shown to be well described using a
+continuous form of a neurological free energy principle that has been
+previously proposed as a high level description of certain biological neural
+processes. Numerical simulations demonstrate that this proposed bilayer
+geometry is able to reproduce theoretical results derived previously for
+examples of active inference in neurological contexts.",2401.12211v4
+2024-01-24,Dynamical Chiral Nernst Effect in Twisted Van der Waals Few Layers,"The Nernst effect is a fundamental thermoelectric conversion phenomenon that
+was deemed to be possible only in systems with magnetic field or magnetization.
+In this work, we propose a novel dynamical chiral Nernst effect that can appear
+in two-dimensional van der Waals materials with chiral structural symmetry in
+the absence of any magnetic degree of freedom. This unconventional effect is
+triggered by time variation of an out-of-plane electric field, and has an
+intrinsic quantum geometric origin linked to not only the intralayer
+center-of-mass motion but also the interlayer coherence of electronic states.
+We demonstrate the effect in twisted homobilayer and homotrilayer transition
+metal dichalcogenides, where the strong twisted interlayer coupling leads to
+sizable intrinsic Nernst conductivities well within the experimental capacity.
+This work suggests a new route for electric control of thermoelectric
+conversion.",2401.13278v1
+2024-01-25,Universal collective Larmor-Silin mode emerging in magnetized correlated Dirac fermions,"Employing large-scale quantum Monte Carlo simulations, we find in magnetized
+interacting Dirac fermion model, there emerges a new and universal collective
+Larmor-Silin spin wave mode in the transverse dynamical spin susceptibility.
+Such mode purely originates from the interaction among Dirac fermions and
+distinguishes itself from the usual particle-hole continuum with finite
+lifetime and clear dispersion, both at small and large momenta in a large
+portion of the Brillouin zone. Our unbiased numerical results offer the dynamic
+signature of this new collective excitations in interacting Dirac fermion
+systems, and provide experimental guidance for inelastic neutron scattering,
+electron spin resonance and other spectroscopic approaches in the investigation
+of such universal collective modes in quantum Moire materials, topological
+insulators and quantum spin liquid materials under magnetic field, with
+quintessential interaction nature beyond the commonly assumed noninteracting
+Dirac fermion or spinon approximations.",2401.14358v2
+2024-03-13,Quantum skyrmion dynamics studied by neural network quantum states,"We study the dynamics of quantum skyrmions under a magnetic field gradient
+using neural network quantum states. First, we obtain a quantum skyrmion
+lattice ground state using variational Monte Carlo with a restricted Boltzmann
+machine as the variational ansatz for a quantum Heisenberg model with
+Dzyaloshinskii-Moriya interaction. Then, using the time-dependent variational
+principle, we study the real-time evolution of quantum skyrmions after a
+Hamiltonian quench with an inhomogeneous external magnetic field. We show that
+field gradients are an effective way of manipulating and moving quantum
+skyrmions. Furthermore, we demonstrate that quantum skyrmions can decay when
+interacting with each other. This work shows that neural network quantum states
+offer a promising way of studying the real-time evolution of quantum magnetic
+systems that are outside the realm of exact diagonalization.",2403.08184v1
+2016-07-18,Local Helioseismology of Emerging Active Regions: A Case Study,"Local helioseismology provides a unique opportunity to investigate the
+subsurface structure and dynamics of active regions and their effect on the
+large-scale flows and global circulation of the Sun. We use measurements of
+plasma flows in the upper convection zone, provided by the Time-Distance
+Helioseismology Pipeline developed for analysis of solar oscillation data
+obtained by Helioseismic and Magnetic Imager (HMI) on Solar Dynamics
+Observatory (SDO), to investigate the subsurface dynamics of emerging active
+region NOAA 11726. The active region emergence was detected in deep layers of
+the convection zone about 12 hours before the first bipolar magnetic structure
+appeared on the surface, and 2 days before the emergence of most of the
+magnetic flux. The speed of emergence determined by tracking the flow
+divergence with depth is about 1.4 km/s, very close to the emergence speed in
+the deep layers. As the emerging magnetic flux becomes concentrated in sunspots
+local converging flows are observed beneath the forming sunspots. These flows
+are most prominent in the depth range 1-3 Mm, and remain converging after the
+formation process is completed. On the larger scale converging flows around
+active region appear as a diversion of the zonal shearing flows towards the
+active region, accompanied by formation of a large-scale vortex structure. This
+process occurs when a substantial amount of the magnetic flux emerged on the
+surface, and the converging flow pattern remains stable during the following
+evolution of the active region. The Carrington synoptic flow maps show that the
+large-scale subsurface inflows are typical for active regions. In the deeper
+layers (10-13 Mm) the flows become diverging, and surprisingly strong beneath
+some active regions. In addition, the synoptic maps reveal a complex evolving
+pattern of large-scale flows on the scale much larger than supergranulation.",1607.04987v1
+2019-11-22,"Role of Element-Specific Damping on the Ultrafast, Helicity-Independent All-Optical Switching Dynamics in Amorphous (Gd,Tb)Co Thin Films","Ultrafast control of the magnetization in ps timescales by fs laser pulses
+offers an attractive avenue for applications such as fast magnetic devices for
+logic and memory. However, ultrafast helicity-independent all-optical switching
+(HI-AOS) of the magnetization has thus far only been observed in Gd-based,
+ferrimagnetic amorphous (\textit{a}-) rare earth-transition metal
+(\textit{a}-RE-TM) systems, and a comprehensive understanding of the reversal
+mechanism remains elusive. Here, we report HI-AOS in ferrimagnetic
+\textit{a}-Gd$_{22-x}$Tb$_x$Co$_{78}$ thin films, from x = 0 to x = 18, and
+elucidate the role of Gd in HI-AOS in \textit{a}-RE-TM alloys and multilayers.
+Increasing Tb content results in increasing perpendicular magnetic anisotropy
+and coercivity, without modifying magnetization density, and slower
+remagnetization rates and higher critical fluences for switching but still
+shows picosecond HI-AOS. Simulations of the atomistic spin dynamics based on
+the two-temperature model reproduce these results qualitatively and predict
+that the lower damping on the RE sublattice arising from the small spin-orbit
+coupling of Gd (with $L = 0$) is instrumental for the faster dynamics and lower
+critical fluences of the Gd-rich alloys. Annealing
+\textit{a}-Gd$_{10}$Tb$_{12}$Co$_{78}$ leads to slower dynamics which we argue
+is due to an increase in damping. These simulations strongly indicate that
+acounting for element-specific damping is crucial in understanding HI-AOS
+phenomena. The results suggest that engineering the element specific damping of
+materials can open up new classes of materials that exhibit low-energy,
+ultrafast HI-AOS.",1911.09803v3
+2018-08-03,Decoupled spin dynamics in the rare-earth orthoferrite YbFeO$_3$: Evolution of magnetic excitations through the spin-reorientation transition,"In this paper we present a comprehensive study of magnetic dynamics in the
+rare-earth orthoferrite YbFeO$_3$ at temperatures below and above the
+spin-reorientation (SR) transition $T_{\mathrm{SR}}=7.6$ K, in magnetic fields
+applied along the $a, b$ and $c$ axes. Using single-crystal inelastic neutron
+scattering, we observed that the spectrum of magnetic excitations consists of
+two collective modes well separated in energy: 3D gapped magnons with a
+bandwidth of $\sim$60 meV, associated with the antiferromagnetically (AFM)
+ordered Fe subsystem, and quasi-1D AFM fluctuations of $\sim$1 meV within the
+Yb subsystem, with no hybridization of those modes. The spin dynamics of the Fe
+subsystem changes very little through the SR transition and could be well
+described in the frame of semiclassical linear spin-wave theory. On the other
+hand, the rotation of the net moment of the Fe subsystem at $T_{\mathrm{SR}}$
+drastically changes the excitation spectrum of the Yb subsystem, inducing the
+transition between two regimes with magnon and spinon-like fluctuations. At $T
+< T_{\mathrm{SR}}$, the Yb spin chains have a well defined field-induced
+ferromagnetic (FM) ground state, and the spectrum consists of a sharp
+single-magnon mode, a two-magnon bound state, and a two-magnon continuum,
+whereas at $T > T_{\mathrm{SR}}$ only a gapped broad spinon-like continuum
+dominates the spectrum. In this work we show that a weak quasi-1D coupling
+within the Yb subsystem $J_\text{Yb-Yb}$, mainly neglected in previous studies,
+creates unusual quantum spin dynamics on the low energy scales. The results of
+our work may stimulate further experimental search for similar compounds with
+several magnetic subsystems and energy scales, where low-energy fluctuations
+and underlying physics could be ""hidden"" by a dominating interaction.",1808.01269v2
+2019-06-03,Motional Dynamical Decoupling for Matter-Wave Interferometry,"Matter-wave interferometry provides a remarkably sensitive tool for probing
+minute forces and, potentially, the foundations of quantum physics by making
+use of interference between spatially separated matter waves. Furthering this
+development requires ever-increasing stability of the interferometer, typically
+achieved by improving its physical isolation from the environment. Here we
+introduce as an alternative strategy the concept of dynamical decoupling
+applied to spatial degrees of freedom of massive objects. We show that the
+superposed matter waves can be driven along paths in space that render their
+superposition resilient to many important sources of noise. As a concrete
+implementation, we present the case of matter-wave interferometers in a
+magnetic field gradient based on either levitated or free-falling nanodiamonds
+hosting a color center. We present an in-depth analysis of potential sources of
+decoherence in such a setup and of the ability of our protocol to suppress
+them. These effects include gravitational forces, interactions of the net
+magnetic and dipole moments of the diamond with magnetic and electric fields,
+surface dangling bonds, rotational degrees of freedom, Casimir-Polder forces,
+and diamagnetic forces. Contrary to previous analyses, diamagnetic forces are
+not negligible in this type of interferometers and, if not acted upon lead to
+small separation distances that scale with the inverse of the magnetic field
+gradient. We show that our motional dynamical decoupling strategy renders the
+system immune to such limitations while continuing to protect its coherence
+from environmental influences, achieving a linear-in-time growth of the
+separation distance independent of the magnetic field gradient. Hence, motional
+dynamical decoupling may become an essential tool in driving the sensitivity of
+matter-wave interferometry to the next level.",1906.00835v1
+2022-04-11,Curvilinear spin-wave dynamics beyond the thin-shell approximation: Magnetic nanotubes as a case study,"Surface curvature of magnetic systems can lead to many static and dynamic
+effects which are not present in flat systems of the same material. These
+emergent magnetochiral effects can lead to frequency nonreciprocity of spin
+waves, which has been shown to be a bulk effect of dipolar origin and is
+related to a curvature-induced symmetry breaking in the magnetic volume
+charges. So far, such effects have been investigated theoretically mostly for
+thin shells, where the spatial profiles of the spin waves can be assumed to be
+homogeneous along the thickness. Here, using a finite-element dynamic-matrix
+approach, we investigate the transition of the spin-wave spectrum from thin to
+thick curvilinear shells, at the example of magnetic nanotubes in the vortex
+state. With increasing thickness, we observe the appearance of higher-order
+radial modes which are strongly hybridized and resemble the
+perpendicular-standing-waves (PSSWs) in flat films. Along with an increasing
+dispersion asymmetry, we uncover the curvature-induced non-reciprocity of the
+mode profiles. This is explained in a very simple picture general for thick
+curvilinear shells, considering the inhomogeneity of the emergent geometric
+volume charges along the thickness of the shell. Such curvature-induced
+mode-profile asymmetry also leads to non-reciprocal hybridization which can
+facilitate unidirectional spin-wave propagation. With that, we also show how
+curvature allows for nonlinear three-wave splitting of a higher-order radial
+mode into secondary modes which can also propagate unidirectionally. We believe
+that our study provides a significant contribution to the understanding of the
+spin-wave dynamics in curvilinear magnetic systems, but also advertises these
+for novel magnonic applications.",2204.05065v1
+2022-06-25,Static and dynamic magnetization control of extrinsic multiferroics by the converse magneto-photostrictive effect,"In this work, photostrictive manipulations of static and dynamic magnetic
+properties are demonstrated in an extrinsic multiferroic composite. The
+photostriction is achieved with visible light in the blue region of the
+spectrum. The composites consist of 5 nm or 10 nm magnetostrictive
+Fe$_{81}$Ga$_{19}$ thin films coupled to a piezoelectric
+(011)-Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$-Pb(Zr,Ti)O$_3$ substrate. Angular dependent
+magnetization reversals properties are largely enhanced or reduced under a
+converse magneto-photostrictive effect (CMPE). The CMPE strength is analysed
+with a novel coefficient named the converse magneto-photostrictive coupling
+coefficient. This coefficient is proposed as a general approach to analyse and
+to compare different extrinsic multiferroics under the converse
+magneto-photostrictive effect. Its thickness dependence reveals that the CMPE
+strength decreases with an increase of the Fe$_{81}$Ga$_{19}$ thickness.
+Experimental evidence for a control of dynamic magnetic properties under CMPE
+is then revealed by ferromagnetic resonance measurements. Resonant fields are
+shifted under CMPE, whereas their linewidths remain constant. Furthermore,
+resonant field shifts can be either positive or negative depending on the
+in-plane angle. The largest shift under CMPE of +5.7 % is obtained for the 5 nm
+sample. Our study shows that the CMPE provides an efficient approach for a
+control of not only the static but also the dynamic magnetic properties in
+extrinsic multiferroics.",2206.12703v3
+2023-04-05,Scaling laws of the magnetic dynamics driven high harmonic generation in spin-orbit coupled systems,"The emergence of high order harmonics in carrier pumping from magnetic
+dynamics in the presence of spin-orbit coupling has been only recently
+predicted [{Phys. Rev. B \textbf{105}, L180415 (2022)}]. In this effect, the
+number of the excited high harmonics is found to scale up with the spin-orbit
+coupling parameter, the s-d exchange constant of the magnetic system and the
+frequency of the driving dynamics. Motivated by the reproduction of the
+above-mentioned effect, Nikoli\'{c} and Manjarres [arXiv:2212.06895,
+arXiv:2112.14685] confirmed that there is indeed a generation of harmonics as a
+result of the interplay between magnetic dynamics and spin-orbit interaction if
+the exchange coupling $J$ is taken very small ($J=0.1\gamma$). However, they
+claim that the ultrahigh harmonics obtained in the strong $J$ limit can only be
+a result of numerical bugs. It turns out that in these works, conclusions built
+from numerical simulations performed in the perturbative limit
+($J/\hbar\omega\approx 10$) have been applied to criticize results obtained in
+the extremely high non-linear regime ($J/\hbar\omega>10^3$). Regarding this
+fact, we find it necessary to shed light on many aspects related to the physics
+behind the predicted unconventional carrier pumping, in order to enlighten the
+readers of the proposed effect and at the same time the authors of the
+criticizing works. Here, we present numerical simulations of the scaling laws
+underlying the effect. We study the low s-d exchange coupling limit,
+corresponding to the regime studied in the above mentioned criticizing works.
+And further explore, the high s-d coupling regime where the extremely nonlinear
+emission is expected. Furthermore, we provide more insights on the effect and
+demonstrate its robustness and reproducibility in both 1D and 2D magnetic
+structures.",2304.02619v2
+1998-04-10,Dynamical Collapse of Nonrotating Magnetic Molecular Cloud Cores: Evolution Through Point-Mass Formation,"We present a numerical simulation of the dynamical collapse of a nonrotating
+magnetic molecular cloud core and follow the core's evolution through the
+formation of a central point mass and its subsequent growth to a 1 solar-mass
+protostar. The epoch of point-mass formation (PMF) is investigated by a self-
+consistent extension of previously presented models of core formation and
+contraction in axisymmetric, self-gravitating, isothermal, magnetically
+supported interstellar molecular clouds. Prior to PMF, the core is dynamically
+contracting and is not well approximated by a quasistatic equilibrium model.
+Ambipolar diffusion, which plays a key role in the early evolution of the core,
+is unimportant during the dynamical pre-PMF collapse phase. However, the
+appearance of a central mass, through its effect on the gravitational field in
+the inner core regions, leads to a ""revitalization"" of ambipolar diffusion in
+the weakly ionized gas surrounding the central protostar. This process is so
+efficient that it leads to a decoupling of the field from the matter and
+results in an outward propagating hydromagnetic C-type shock. The existence of
+an ambipolar diffusion-mediated shock was predicted by Li & McKee (1996), and
+we find that the basic shock structure given by their analytical model is well
+reproduced by our more accurate numerical results. Our calculation also
+demonstrates that ambipolar diffusion, rather than Ohmic diffusivity operating
+in the innermost core region, is the main field decoupling mechanism
+responsible for driving the shock after PMF.",9804113v1
+2004-08-10,"Collective Spin Dynamics in the ""Coherence Window"" for Quantum Nanomagnets","The spin coherence phenomena and the possibility of their observation in
+nanomagnetic insulators attract more and more attention in the last several
+years. Recently it has been shown that in these systems in large transverse
+magnetic field there can be a fairly narrow ""coherence window"" for phonon and
+nuclear spin-mediated decoherence. What kind of spin dynamics can then be
+expected in this window in a crystal of magnetic nanomolecules coupled to
+phonons, to nuclear spin bath and it to each other via dipole-dipole
+interactions? Studying multispin correlations, we determine the region of
+parameters where ""coherent clusters"" of collective spin excitations can appear.
+Although two particular systems, namely crystals of $Fe_8$-triazacyclonane and
+$Mn_{12}$-acetate molecules, are used in this work to illustrate the results,
+here we are not trying to predict an existence of collective coherent dynamics
+in some particular system. Instead, we discuss the way how any crystalline
+system of dipole-dipole coupled nanomolecules can be analyzed to decide whether
+this system is suitable for attempts to observe coherent dynamics. The
+presented analysis can be useful in the search for magnetic systems showing the
+spin coherence phenomena.",0408220v3
+2003-07-03,Effect of the superconducting wiggler on the DELSY beam dynamics,"The project DELSY is being under development at JINR, Dubna, Russia. This
+synchrotron radiation source is dedicated to the investigation on condensed
+matter physics, atomic physics, biology, medicine, chemistry, micromechanics,
+lithography and others. The storage ring DELSY is an electron storage ring with
+the beam energy 1.2 GeV and 4 straight sections to accommodate accelerator
+equipment and insertion devices. One of the straight sections is intended for a
+10 T superconducting wiggler (wavelength shifter) and one for the undulator
+with 150 periods and a magnetic field of 0.75 T. The wiggler will influence
+many aspects of beam dynamics: linear motion, dynamic aperture, emittance,
+damping times etc. The problem is rather serious for the DELSY machine because
+the energy of the electron beam is small while the wiggler's magnetic field is
+strong. In this paper we consider two models of the wiggler's magnetic field
+with and without the focusing caused by the sextupolar field of the wiggler as
+we need to develop the requirements to the wiggler design. We study the
+influence of the 10 T wiggler on the beam dynamics in the DELSY storage ring
+and propose a possible scheme to cure it. The combined work of the insertion
+device is presented too.",0307028v1
+2007-04-09,Conjugate field and fluctuation-dissipation relation for the dynamic phase transition in the two-dimensional kinetic Ising model,"The two-dimensional kinetic Ising model, when exposed to an oscillating
+applied magnetic field, has been shown to exhibit a nonequilibrium,
+second-order dynamic phase transition (DPT), whose order parameter Q is the
+period-averaged magnetization. It has been established that this DPT falls in
+the same universality class as the equilibrium phase transition in the
+two-dimensional Ising model in zero applied field. Here we study for the first
+time the scaling of the dynamic order parameter with respect to a nonzero,
+period-averaged, magnetic `bias' field, H_b, for a DPT produced by a
+square-wave applied field. We find evidence that the scaling exponent,
+\delta_d, of H_b at the critical period of the DPT is equal to the exponent for
+the critical isotherm, \delta_e, in the equilibrium Ising model. This implies
+that H_b is a significant component of the field conjugate to Q. A finite-size
+scaling analysis of the dynamic order parameter above the critical period
+provides further support for this result. We also demonstrate numerically that,
+for a range of periods and values of H_b in the critical region, a
+fluctuation-dissipation relation (FDR), with an effective temperature
+T_{eff}(T, P, H_0) depending on the period, and possibly the temperature and
+field amplitude, holds for the variables Q and H_b. This FDR justifies the use
+of the scaled variance of Q as a proxy for the nonequilibrium susceptibility,
+\partial<Q> / \partial H_b, in the critical region.",0704.1123v2
+2008-07-02,Dynamical phase transitions in long-range Hamiltonian systems and Tsallis distributions with a time-dependent index,"We study dynamical phase transitions in systems with long-range interactions,
+using the Hamiltonian Mean Field (HMF) model as a simple example. These systems
+generically undergo a violent relaxation to a quasi-stationary state (QSS)
+before relaxing towards Boltzmann equilibrium. In the collisional regime, the
+out-of-equilibrium one-particle distribution function (DF) is a
+quasi-stationary solution of the Vlasov equation, slowly evolving in time due
+to finite $N$ effects. For subcritical energies $7/12<U<3/4$, we exhibit cases
+where the DF is well-fitted by a Tsallis $q$-distribution with an index $q(t)$
+slowly decreasing in time from $q\simeq 3$ (semi-ellipse) to $q=1$ (Boltzmann).
+When the index $q(t)$ reaches a critical value $q_{crit}(U)$, the
+non-magnetized (homogeneous) phase becomes Vlasov unstable and a dynamical
+phase transition is triggered, leading to a magnetized (inhomogeneous) state.
+While Tsallis distributions play an important role in our study, we explain
+this dynamical phase transition by using only conventional statistical
+mechanics. For supercritical energies, we report for the first time the
+existence of a magnetized QSS with a very long lifetime.",0807.0324v2
+2008-09-17,"Late stage, non-equilibrium dynamics in the dipolar Ising model","Magnetic domain structures are a fascinating area of study with interest
+deriving both from technological applications and fundamental scientific
+questions. The nature of the striped magnetic phases observed in ultra-thin
+films is one such intriguing system. The non-equilibrium dynamics of such
+systems as they evolve toward equilibrium has only recently become an area of
+interest and previous work on model systems showed evidence of complex, slow
+dynamics with glass-like properties as the stripes order mesoscopically. To aid
+in the characterization of the observed phases and the nature of the
+transitions observed in model systems we have developed an efficient method for
+identifying clusters or domains in the spin system, where the clusters are
+based on the stripe orientation. Thus we are able to track the growth and decay
+of such clusters of stripes in a Monte Carlo simulation and observe directly
+the nature of the slow dynamics. We have applied this method to consider the
+growth and decay of ordered domains after a quench from a saturated magnetic
+state to temperatures near and well below the critical temperature in the two
+dimensional dipolar Ising model. We discuss our method of identifying stripe
+domains or clusters of stripes within this model and present the results of our
+investigations.",0809.2808v1
+2008-12-05,Using Magnetic Activity and Galactic Dynamics to Constrain the Ages of M Dwarfs,"We present a study of the dynamics and magnetic activity of M dwarfs using
+the largest spectroscopic sample of low-mass stars ever assembled. The age at
+which strong surface magnetic activity (as traced by H-alpha) ceases in M
+dwarfs has been inferred to have a strong dependence on mass (spectral type,
+surface temperature) and explains previous results showing a large increase in
+the fraction of active stars at later spectral types. Using spectral
+observations of more than 40000 M dwarfs from the Sloan Digital Sky Survey, we
+show that the fraction of active stars decreases as a function of vertical
+distance from the Galactic plane (a statistical proxy for age), and that the
+magnitude of this decrease changes significantly for different M spectral
+types. Adopting a simple dynamical model for thin disk vertical heating, we
+assign an age for the activity decline at each spectral type, and thus
+determine the activity lifetimes for M dwarfs. In addition, we derive a
+statistical age-activity relation for each spectral type using the dynamical
+model, the vertical distance from the Plane and the H-alpha emission line
+luminosity of each star (the latter of which also decreases with vertical
+height above the Galactic plane).",0812.1223v1
+2009-06-18,Electron quantum dynamics in closed and open potentials at high magnetic fields: Quantization and lifetime effects unified by semicoherent states,"We have developed a Green's function formalism based on the use of an
+overcomplete semicoherent basis of vortex states, specially devoted to the
+study of the Hamiltonian quantum dynamics of electrons at high magnetic fields
+and in an arbitrary potential landscape smooth on the scale of the magnetic
+length. This formalism is used here to derive the exact Green's function for an
+arbitrary quadratic potential in the special limit where Landau level mixing
+becomes negligible. This solution remarkably embraces under a unified form the
+cases of confining and unconfining quadratic potentials. This property results
+from the fact that the overcomplete vortex representation provides a more
+general type of spectral decomposition of the Hamiltonian operator than usually
+considered. Whereas confining potentials are naturally characterized by
+quantization effects, lifetime effects emerge instead in the case of
+saddle-point potentials. Our derivation proves that the appearance of lifetimes
+has for origin the instability of the dynamics due to quantum tunneling at
+saddle points of the potential landscape. In fact, the overcompleteness of the
+vortex representation reveals an intrinsic microscopic irreversibility of the
+states synonymous with a spontaneous breaking of the time symmetry exhibited by
+the Hamiltonian dynamics.",0906.3375v2
+2011-06-21,Symmetry and the macroscopic dynamics of antiferromagnetic materials in the presence of spin-polarized current,"Antiferromagnetic (AFM) materials with zero or vanishingly small macroscopic
+magnetization are nowadays the constituent elements of spintronic devices.
+However, possibility to use them as active elements that show nontrivial
+controllable magnetic dynamics is still discussible. In the present paper we
+extend the theory [A.F.Andreev, V.I.Marchenko, Sov. Phys. --- Uspekhi, 23
+(1980), 21] of macroscopic dynamics in AFMs for the cases typical for
+spin-valve devices. In particular, we consider the solid-like magnetic dynamics
+of AFMs with strong exchange coupling in the presence of spin-polarized current
+and give an expression for the current-induced Rayleigh dissipation function in
+terms of the rotation vector for different types %generalized potential of
+AFMs. Basing on the analysis of linearized equations of motion we predict the
+current-induced reorientation and AFM resonance, and found the values of
+critical currents in terms of AFMR frequencies and damping constants. We show
+the possibility of current-induced spin-diode effect and second-harmonic
+generation in AF layer. The proposed approach is generalized for the
+description of current-related phenomena in inhomogeneous AFMs.",1106.4231v3
+2011-06-22,Effect of spin diffusion on current generated by spin motive force,"Spin motive force is a spin-dependent force on conduction electrons induced
+by magnetization dynamics. In order to examine its effects on magnetization
+dynamics, it is indispensable to take into account spin accumulation, spin
+diffusion, and spin-flip scattering since the spin motive force is in general
+nonuniform. We examine the effects of all these on the way the spin motive
+force generates the charge and spin currents in conventional situations, where
+the conduction electron spin relaxation dynamics is much faster than the
+magnetization dynamics. When the spin-dependent electric field is spatially
+localized, which is common in experimental situations, we find that the
+conservative part of the spin motive force is unable to generate the charge
+current due to the cancelation effect by the diffusion current. We also find
+that the spin current is a nonlocal function of the spin motive force and can
+be effectively expressed in terms of nonlocal Gilbert damping tensor. It turns
+out that any spin independent potential such as Coulomb potential does not
+affect our principal results. At the last part of this paper, we apply our
+theory to current-induced domain wall motion.",1106.4389v2
+2011-08-06,A Statistical Study on the Morphology of Rays and Dynamics of Blobs in the Wake of Coronal Mass Ejections,"In this paper, with a survey through the Large Angle and Spectrometric
+Coronagraph (LASCO) data from 1996 to 2009, we present 11 events with plasma
+blobs flowing outwards sequentially along a bright coronal ray in the wake of a
+coronal mass ejection. The ray is believed to be associated with the current
+sheet structure that formed as a result of solar eruption, and the blobs are
+products of magnetic reconnection occurring along the current sheet. The ray
+morphology and blob dynamics are investigated statistically. It is found that
+the apparent angular widths of the rays at a fixed time vary in a range of
+2.1-6.6 (2.0-4.4) degrees with an average of 3.5 (2.9) degrees at 3 (4) Rs,
+respectively, and the observed durations of the events vary from 12 h to a few
+days with an average of 27 h. It is also found, based on the analysis of blob
+motions, that 58% (26) of the blobs were accelerated, 20% (9) were decelerated,
+and 22% (10) moved with a nearly-constant speed. Comparing the dynamics of our
+blobs and those that are observed above the tip of a helmet streamer, we find
+that the speeds and accelerations of the blobs in these two cases differ
+significantly. It is suggested that these differences of the blob dynamics stem
+from the associated magnetic reconnection involving different magnetic field
+configurations and triggering processes.",1108.1481v1
+2012-02-15,Noise studies of magnetization dynamics in dilute magnetic semiconductor heterostructures,"We study theoretically and experimentally the frequency and temperature
+dependence of resistivity noise in semiconductor heterostructures delta-doped
+by Mn. The resistivity noise is observed to be non-monotonous as a function of
+frequency. As a function of temperature, the noise increases by two orders of
+magnitude for a resistivity increase of about 50%. We study two possible
+sources of resistivity noise -- dynamic spin fluctuations and charge
+fluctuations, and find that dynamic spin fluctuations are more relevant for the
+observed noise data. The frequency and temperature dependence of resistivity
+noise provide important information on the nature of the magnetic interactions.
+In particular, we show how noise measurements can help resolve a long standing
+debate on whether the Mn-doped GaAs is an p-d Zener/RKKY or double exchange
+ferromagnet. Our analysis includes the effect of different kinds of disorder
+such as spin-glass type of interactions and a site-dilution type of disorder.
+We find that the resistivity noise in these structures is well described by a
+disordered RKKY ferromagnet model dynamics with a conserved order parameter.",1202.3207v2
+2012-05-11,Nonequilibrium quantum dynamics of the magnetic Anderson model,"We study the non-equilibrium dynamics of a spinful single-orbital quantum dot
+with an incorporated quantum mechanical spin-1/2 magnetic impurity. Due to the
+spin degeneracy, double occupancy is allowed, and Coulomb interaction together
+with the exchange coupling of the magnetic impurity influence the dynamics. By
+extending the iterative summation of real-time path integrals (ISPI) to this
+coupled system, we monitor the time-dependent non-equilibrium current and the
+impurity spin polarization to determine features of the time-dependent
+non-equilibrium dynamics. We particulary focus on the deep quantum regime,
+where all time and energy scales are of the same order of magnitude and no
+small parameter is available. We observe a significant influence of the
+non-equilibrium decay of the impurity spin polarization both in the presence
+and in the absence of Coulomb interaction. The exponential relaxation is faster
+for larger bias voltages, electron-impurity interactions and temperatures. We
+show that the exact relaxation rate deviates from the corresponding
+perturbative result. In addition, we study in detail the impurity's back action
+on the charge current and find a reduction of the stationary current for
+increasing coupling to the impurity. Moreover, our approach allows us to
+systematically distinguish mean-field Coulomb and impurity effects from the
+influence of quantum fluctuations and flip-flop scattering, respectively. In
+fact, we find a local maximum of the current for a finite Coulomb interaction
+due to the presence of the impurity.",1205.2462v2
+2013-07-18,Dynamical transition in the D = 3 Edwards-Anderson spin glass in an external magnetic field,"We study the off-equilibrium dynamics of the three-dimensional Ising spin
+glass in the presence of an external magnetic field. We have performed
+simulations both at fixed temperature and with an annealing protocol. Thanks to
+the Janus special-purpose computer, based on FPGAs, we have been able to reach
+times equivalent to 0.01 seconds in experiments. We have studied the system
+relaxation both for high and for low temperatures, clearly identifying a
+dynamical transition point. This dynamical temperature is strictly positive and
+depends on the external applied magnetic field. We discuss different
+possibilities for the underlying physics, which include a thermodynamical
+spin-glass transition, a mode-coupling crossover or an interpretation
+reminiscent of the random first-order picture of structural glasses.",1307.4998v3
+2014-08-20,Coherent transport and manipulation of spins in indirect exciton nanostructures,"We report on the coherent control and transport of indirect exciton (IX)
+spins in GaAs double quantum well (DQW) nanostructures. The spin dynamics was
+investigated by optically generating spins using a focused, circularly
+polarized light spot and by probing their spatial distribution using spatially
+and polarization resolved photoluminescence spectroscopy. Optically injected
+exciton spins precess while diffusing over distances exceeding 20 {\mu}m from
+the excitation spot with a spatial precession frequency that depends on the
+spin transport direction as well as on the bias applied across the DQW
+structure. This behavior is attributed to the spin precession in the effective
+magnetic field induced by the spin-orbit interaction. From the dependence of
+the spin dynamics on the transport direction, bias and external magnetic fields
+we directly determined the Dresselhaus and Rashba spin splitting coefficients
+for the structure. The precession dynamics is essentially independent on the IX
+density, thus indicating that the long spin lifetimes are not associated with
+IX collective effects. The latter, together with the negligible contribution of
+holes to the spin dynamics, are rather attributed to spatial separation of the
+electron and hole wave functions by the electric field, which reduces the
+electron-hole exchange interaction. Coherent spin precession over long
+transport distances as well as the control of the spin vector using electric
+and magnetic fields open the way for the application of IX spins in the quantum
+information processing.",1408.4547v1
+2014-09-16,Resolving the relative influence of strong field spacetime dynamics and MHD on circumbinary disk physics,"In this paper we evolve magnetized and unmagnetized circumbinary accretion
+disks around supermassive black hole binaries in the relativistic regime. We
+use a post-Newtonian expansion to construct an analytical spacetime and
+determine how the order of the post-Newtonian (PN) expansion affects the
+dynamics of the gas. We find very small differences in the late-time bulk
+dynamics of non-magnetized hydrodynamic evolutions between the two spacetimes
+down to separations of approximately $40GM/c^2$ where $M$ is the total mass of
+the binary. For smaller separations, the differences due to PN-order become
+comparable to differences caused by using initial data further from
+equilibrium. For magnetized gas, MHD stresses, which drives the accretion
+dynamics, tends to mask all higher order PN effects even at separations of
+$20GM/c^2$, leading to essentially the same observed electromagnetic
+luminosity. This implies that our calculations of the EM signal may be robust
+down to small binary separations. Our investigation is the first to demonstrate
+how the level of PN accuracy affects a circumbinary disk's evolution and
+informs us of the range in separation within which to trust the PN
+approximation for this kind of study. We also address the influence the initial
+conditions and binary separation have on simulation predictions.",1409.4787v2
+2014-12-23,Dynamical symmetries of Markov processes with multiplicative white noise,"We analyse various properties of stochastic Markov processes with
+multiplicative white noise. We take a single-variable problem as a simple
+example, and we later extend the analysis to the Landau-Lifshitz-Gilbert
+equation for the stochastic dynamics of a magnetic moment. In particular, we
+focus on the non-equilibrium transfer of angular momentum to the magnetization
+from a spin-polarised current of electrons, a technique which is widely used in
+the context of spintronics to manipulate magnetic moments. We unveil two hidden
+dynamical symmetries of the generating functionals of these Markovian
+multiplicative white-noise processes. One symmetry only holds in equilibrium
+and we use it to prove generic relations such as the fluctuation-dissipation
+theorems. Out of equilibrium, we take profit of the symmetry-breaking terms to
+prove fluctuation theorems. The other symmetry yields strong dynamical
+relations between correlation and response functions which can notably simplify
+the numerical analysis of these problems. Our construction allows us to clarify
+some misconceptions on multiplicative white-noise stochastic processes that can
+be found in the literature. In particular, we show that a first-order
+differential equation with multiplicative white noise can be transformed into
+an additive-noise equation, but that the latter keeps a non-trivial memory of
+the discretisation prescription used to define the former.",1412.7564v2
+2015-09-01,Light Bridge in a Developing Active Region. I. Observation of Light Bridge and its Dynamic Activity Phenomena,"Light bridges, the bright structures that divide the umbra of sunspots and
+pores into smaller pieces, are known to produce wide variety of activity events
+in solar active regions (ARs). It is also known that the light bridges appear
+in the assembling process of nascent sunspots. The ultimate goal of this series
+of papers is to reveal the nature of light bridges in developing ARs and the
+occurrence of activity events associated with the light bridge structures from
+both observational and numerical approaches. In this first paper, exploiting
+the observational data obtained by Hinode, IRIS, and Solar Dynamics Observatory
+(SDO), we investigate the detailed structure of the light bridge in NOAA AR
+11974 and its dynamic activity phenomena. As a result, we find that the light
+bridge has a weak, horizontal magnetic field, which is transported from the
+interior by large-scale convective upflow and is surrounded by strong, vertical
+fields of adjacent pores. In the chromosphere above the bridge, a transient
+brightening occurs repeatedly and intermittently, followed by a recurrent dark
+surge ejection into higher altitudes. Our analysis indicates that the
+brightening is the plasma heating due to magnetic reconnection at lower
+altitudes, while the dark surge is the cool, dense plasma ejected from the
+reconnection region. From the observational results, we conclude that the
+dynamic activity observed in a light bridge structure such as chromospheric
+brightenings and dark surge ejections are driven by magnetoconvective evolution
+within the light bridge and its interaction with surrounding magnetic fields.",1509.00183v1
+2015-10-18,Magnetization dynamics in Fe$_x$Co$_{1-x}$ in presence of chemical disorder,"In this paper, we present a theoretical formulation of magnetization dynamics
+in disordered binary alloys based on Kubo linear response theory interfaced
+with the combination of seamlessly three approaches; density functional based
+tight-binding linear muffin-tin orbitals, generalized recursion and Augmented
+space formalism. We apply this method to study the magnetization dynamics in
+chemically disordered Fe$_x$Co$_{1-x}$ ($x$ = 0.2, 0.5, 0.8) alloys. We
+reported that the magnon energies decrease with an increase in Co
+concentration. Significant magnon softening has been observed in
+Fe$_{20}$Co$_{80}$ at the Brillouin zone boundary. The magnon-electron
+scattering increases with increasing Co content which in turn modifies the
+hybridization between the Fe and Co atoms. This reduces the exchange energy
+between the atoms and soften down the magnon energy. The lowest magnon lifetime
+in found in Fe$_{50}$Co$_{50}$, where disorder is maximum. This clearly
+indicates that the damping of magnon energies in Fe$_x$Co$_{1-x}$ is governed
+by the hybridization between Fe and Co whereas the magnon lifetime is
+controlled by disorder configuration. Our atomistic spin dynamics simulations
+show a reasonable agreement with our theoretical approach in magnon dispersion
+for different alloy compositions.",1510.05200v4
+2016-07-28,An `Analytic Dynamical Magnetosphere' formalism for X-ray and optical emission from slowly rotating magnetic massive stars,"Slowly rotating magnetic massive stars develop ""dynamical magnetospheres""
+(DM's), characterized by trapping of stellar wind outflow in closed magnetic
+loops, shock heating from collision of the upflow from opposite loop
+footpoints, and subsequent gravitational infall of radiatively cooled material.
+In 2D and 3D magnetohydrodynamic (MHD) simulations the interplay among these
+three components is spatially complex and temporally variable, making it
+difficult to derive observational signatures and discern their overall scaling
+trends.Within a simplified, steady-state analysis based on overall conservation
+principles, we present here an ""analytic dynamical magnetosphere"" (ADM) model
+that provides explicit formulae for density, temperature and flow speed in each
+of these three components -- wind outflow, hot post-shock gas, and cooled
+inflow -- as a function of colatitude and radius within the closed (presumed
+dipole) field lines of the magnetosphere. We compare these scalings with
+time-averaged results from MHD simulations, and provide initial examples of
+application of this ADM model for deriving two key observational diagnostics,
+namely hydrogen H-alpha emission line profiles from the cooled infall, and
+X-ray emission from the hot post-shock gas. We conclude with a discussion of
+key issues and advantages in applying this ADM formalism toward derivation of a
+broader set of observational diagnostics and scaling trends for massive stars
+with such dynamical magnetospheres.",1607.08568v1
+2016-12-06,A New Two-Fluid Radiation-Hydrodynamical Model for X-ray Pulsar Accretion Columns,"Previous research centered on the hydrodynamics in X-ray pulsar accretion
+columns has largely focused on the single-fluid model, in which the
+super-Eddington luminosity inside the column decelerates the flow to rest at
+the stellar surface. This type of model has been relatively successful in
+describing the overall properties of the accretion flows, but it does not
+account for the possible dynamical effect of the gas pressure. On the other
+hand, the most successful radiative transport models for pulsars generally do
+not include a rigorous treatment of the dynamical structure of the column,
+instead assuming an ad hoc velocity profile. In this paper, we explore the
+structure of X-ray pulsar accretion columns using a new, self-consistent,
+""two-fluid"" model, which incorporates the dynamical effect of the gas and
+radiation pressure, the dipole variation of the magnetic field, the
+thermodynamic effect of all of the relevant coupling and cooling processes, and
+a rigorous set of physical boundary conditions. The model has six free
+parameters, which we vary in order to approximately fit the phase-averaged
+spectra in Her X-1, Cen X-3, and LMC X-4. In this paper, we focus on the
+dynamical results, which shed new light on the surface magnetic field strength,
+the inclination of the magnetic field axis relative to the rotation axis, the
+relative importance of gas and radiation pressure, and the radial variation of
+the ion, electron, and inverse-Compton temperatures. The results obtained for
+the X-ray spectra are presented in a separate paper.",1612.02411v2
+2018-02-26,Fermion Self-energy and Pseudovector Condensate in NJL Model with External Magnetic Field,"In this paper, we aim to study the complete self-energy in the fermion
+propagator within two-flavor NJL model in the case of finite temperature,
+chemical potential and external magnetic field. Through Fierz transformation we
+prove that the self-energy is not simply proportional to dynamical mass in the
+presence of chemical potential, moreover, it contains four kinds of condensates
+after introducing external magnetic field. We find out the appropriate and
+complete form of self-energy and establish new gap equations. We take two of
+the four condensates (scalar and pseudovector condensates) to make an
+approximation and simplify the gap equations. The numerical results show that
+not only the dynamical mass get quantitative modification, but also the
+properties of Nambu phase and Wigner phase are significantly different with
+classic results. Instead of classic Wigner phase with zero dynamic mass in the
+massless NJL model, we propose a new phase - quasi-Wigner phase in this
+article, it has small but nonzero dynamic mass, with increasing chemical
+potential, eventually Nambu phase will turn into quasi-Wigner phase with
+first-order phase transition, therefore the chiral symmetry can never be fully
+restored but be partially restored. Furthermore, we prove that pseudovector
+condensate in self-energy can generate energy splitting in dispersion relation,
+it will cause minor differences of particle numbers with the split energy
+levels.",1802.09942v2
+2018-10-05,Coupling ultracold matter to dynamical gauge fields in optical lattices: From flux-attachment to Z2 lattice gauge theories,"Artificial magnetic fields and spin-orbit couplings have been recently
+generated in ultracold gases in view of realizing topological states of matter
+and frustrated magnetism in a highly-controllable environment. Despite being
+dynamically tunable, such artificial gauge fields are genuinely classical and
+exhibit no back-action from the neutral particles. Here we go beyond this
+paradigm, and demonstrate how quantized dynamical gauge fields can be created
+in mixtures of ultracold atoms in optical lattices. Specifically, we propose a
+protocol by which atoms of one species carry a magnetic flux felt by another
+species, hence realizing an instance of flux-attachment. This is obtained by
+combining coherent lattice modulation techniques with strong Hubbard
+interactions. We demonstrate how this setting can be arranged so as to
+implement lattice models displaying a local Z2 gauge symmetry, both in one and
+two dimensions. We also provide a detailed analysis of a ladder toy model,
+which features a global Z2 symmetry, and reveal the phase transitions that
+occur both in the matter and gauge sectors. Mastering flux-attachment in
+optical lattices envisages a new route towards the realization of
+strongly-correlated systems with properties dictated by an interplay of
+dynamical matter and gauge fields.",1810.02777v1
+2018-11-25,Characterizing breathing dynamics of magnetic (anti-)skyrmions within the Hamiltonian formalism,"We derive an effective Hamiltonian system describing the low energy dynamics
+of circular magnetic skyrmions and antiskyrmions. Using scaling and symmetry
+arguments we model (anti-)skyrmion dynamics through a finite set of coupled,
+canonically conjugated, collective coordinates. The resulting theoretical
+description is independent of both micromagnetic details as well as any
+specificity in the ansatz of the skyrmion profile. Based on the Hamiltonian
+structure we derive a general description for breathing dynamics of
+(anti-)skyrmions in the limit of radius much larger than the domain wall width.
+The effective energy landscape reveals two qualitatively different types of
+breathing behavior. For small energy perturbations we reproduce the well-known
+small breathing mode excitations, where the magnetic moments of the skyrmion
+oscillate around their equilibrium solution. At higher energies we find a
+breathing behavior where the in-plane angle of the skyrmion continuously
+precesses, transforming N\'eel to Bloch skyrmions and vice versa. For a damped
+system we observe the transition from the continuously rotating and breathing
+skyrmion into the oscillatory one. We analyze the characteristic frequencies of
+both breathing types, as well as their amplitudes and distinct energy
+dissipation rates. For rotational (oscillatory) breathing modes we predict on
+average a linear (exponential) decay in energy. We argue that this stark
+difference in dissipative behavior should be observable in the frequency
+spectrum of excited (anti-)skyrmions.",1811.09949v1
+2018-12-17,Comparative study of vortex dynamics in CaKFe4As4 and Ba0.6K0.4Fe2As2 single crystals,"We investigate the vortex dynamics in two typical hole doped iron based
+superconductors CaKFe$_4$As$_4$ (CaK1144) and Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$
+(BaK122) with similar superconducting transition temperatures. It is found that
+the magnetization hysteresis loop exhibits a clear second peak effect in BaK122
+in wide temperature region while it is absent in CaK1144. However, a second
+peak effect of critical current density versus temperature is observed in
+CaK1144, which is however absent in BaK122. The different behaviors of second
+peak effect in BaK122 and CaK1144 may suggest distinct origins of vortex
+pinning in different systems. Magnetization and its relaxation have also been
+measured by using dynamical and conventional relaxation methods for both
+systems. Analysis and comparison of the two distinct systems show that the
+vortex pinning is stronger and the critical current density is higher in BaK122
+system. It is found that the Maley's method can be used and thus the activation
+energy can be determined in BaK122 by using the time dependent magnetization in
+wide temperature region, but this is not applicable in CaK1144 systems. Finally
+we present the different regimes with distinct vortex dynamics in the
+field-temperature diagram for the two systems.",1812.06823v1
+2019-03-27,Emergence of stationary uphill currents in 2D Ising models: the role of reservoirs and boundary conditions,"We investigate the dynamics of a 2D Ising model on a square lattice with
+conservative Kawasaki dynamics in the bulk, coupled with two external
+reservoirs that pull the dynamics out of equilibrium. Two different mechanisms
+for the action of the reservoirs are considered. In the first, called ISF, the
+condition of local equilibrium between reservoir and the lattice is not
+satisfied. The second mechanism, called DB, implements a detailed balance
+condition, thus satisfying the local equilibrium property. We provide numerical
+evidence that, for a suitable choice of the temperature (i.e. below the
+critical temperature of the equilibrium 2D Ising model) and the reservoir
+magnetizations, in the long time limit the ISF model undergoes a ferromagnetic
+phase transition and gives rise to stationary uphill currents, namely positive
+spins diffuse from the reservoir with lower magnetization to the reservoir with
+higher magnetization. The same phenomenon does not occur for DB dynamics with
+properly chosen boundary conditions. Our analysis extends the results reported
+in Colangeli et al. (Phys. Rev. E, 97:030103(R), 2018), shedding also light on
+the effect of temperature and the role of different boundary conditions for
+this model. These issues may be relevant in a variety of situations (e.g.
+mesoscopic systems) in which the violation of the local equilibrium condition
+produces unexpected phenomena that seem to contradict the standard laws of
+transport.",1903.11300v1
+2019-11-05,Continuous-time quantum walks on planar lattices and the role of the magnetic field,"We address the dynamics of continuous-time quantum walk (CTQW) on planar 2D
+lattice graphs, i.e. those forming a regular tessellation of the Euclidean
+plane (triangular, square, and honeycomb lattice graphs). We first consider the
+free particle: on square and triangular lattice graphs we observe the
+well-known ballistic behavior, whereas on the honeycomb lattice graph we obtain
+a sub-ballistic one, although still faster than the classical diffusive one. We
+impute this difference to the different amount of coherence generated by the
+evolution and, in turn, to the fact that, in 2D, the square and the triangular
+lattices are Bravais lattices, whereas the honeycomb one is non-Bravais. From
+the physical point of view, this means that CTQWs are not universally
+characterized by the ballistic spreading. We then address the dynamics in the
+presence of a perpendicular uniform magnetic field and study the effects of the
+field by two approaches: (i) introducing the Peierls phase-factors, according
+to which the tunneling matrix element of the free particle becomes complex, or
+(ii) spatially discretizing the Hamiltonian of a spinless charged particle in
+the presence of a magnetic field. Either way, the dynamics of an initially
+localized walker is characterized by a lower spread compared to the free
+particle case, the larger is the field the more localized stays the walker.
+Remarkably, upon analyzing the dynamics by spatial discretization of the
+Hamiltonian (vector potential in the symmetric gauge), we obtain that the
+variance of the space coordinate is characterized by pseudo-oscillations, a
+reminiscence of the harmonic oscillator behind the Hamiltonian in the
+continuum, whose energy levels are the well-known Landau levels.",1911.01703v1
+2020-01-09,Role of longitudinal fluctuations in L$1_0$ FePt,"L$1_0$ FePt is a technologically important material for a range of novel data
+storage applications. In the ordered FePt structure the normally non-magnetic
+Pt ion acquires a magnetic moment, which depends on the local field originating
+from the neighboring Fe atoms. In this work a model of FePt is constructed,
+where the induced Pt moment is simulated by using combined longitudinal and
+rotational spin dynamics. The model is parameterized to include a linear
+variation of the moment with the exchange field, so that at the Pt site the
+magnetic moment depends on the Fe ordering. The Curie temperature of FePt is
+calculated and agrees well with similar models that incorporate the Pt dynamics
+through an effective Fe-only Hamiltonian. By computing the dynamic correlation
+function the anisotropy field and the Gilbert damping are extracted over a
+range of temperatures. The anisotropy exhibits a power-law dependence with
+temperature with exponent $n\approx2.1$. This agrees well with what observed
+experimentally and it is obtained without including a two-ion anisotropy term
+as in other approaches. Our work shows that incorporating longitudinal
+fluctuations into spin dynamics calculations is crucial for understanding the
+properties of materials with induced moments.",2001.03074v1
+2020-02-10,Giant electron-phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of La$_{1.67}$Sr$_{0.33}$NiO$_4$,"Doped antiferromagnets host a vast array of physical properties and learning
+how to control them is one of the biggest challenges of condensed matter
+physics. La$_{1.7}$Sr$_{0.3}$NiO$_4$ (LSNO) is a classic example of such a
+material. At low temperatures holes introduced via substitution of La by Sr
+segregate into lines to form boundaries between magnetically ordered domains in
+the form of stripes. The stripes become dynamic at high temperatures, but LSNO
+remains insulating presumably because an interplay between magnetic
+correlations and electron-phonon coupling localizes charge carriers. Magnetic
+degrees of freedom have been extensively investigated in this system, but
+phonons are almost completely unexplored. We searched for electron-phonon
+anomalies in LSNO by inelastic neutron scattering. Giant renormalization of
+plane Ni-O bond-stretching modes that modulate the volume around Ni appears on
+entering the dynamic charge stripe phase. Other phonons are a lot less
+sensitive to stripe melting. Dramatic overdamping of the breathing modes
+indicates that dynamic stripe phase may host small polarons. We argue that this
+feature sets electron-phonon coupling in nickelates apart from that in cuprates
+where breathing phonons are not overdamped and point out remarkable
+similarities with the colossal magnetoresistance (CMR) manganites.",2002.03908v3
+2020-06-11,Coupling a mobile hole to an antiferromagnetic spin background: Transient dynamics of a magnetic polaron,"Understanding the interplay between charge and spin and its effects on
+transport is a ubiquitous challenge in quantum many-body systems. In the
+Fermi-Hubbard model, this interplay is thought to give rise to magnetic
+polarons, whose dynamics may explain emergent properties of quantum materials
+such as high-temperature superconductivity. In this work, we use a cold-atom
+quantum simulator to directly observe the formation dynamics and subsequent
+spreading of individual magnetic polarons. Measuring the density- and
+spin-resolved evolution of a single hole in a 2D Hubbard insulator with
+short-range antiferromagnetic correlations reveals fast initial delocalization
+and a dressing of the spin background, indicating polaron formation. At long
+times, we find that dynamics are slowed down by the spin exchange time, and
+they are compatible with a polaronic model with strong density and spin
+coupling. Our work enables the study of out-of-equilibrium emergent phenomena
+in the Fermi-Hubbard model, one dopant at a time.",2006.06672v2
+2020-07-09,Dynamical modes of sheared confined microscale matter,"Based on (overdamped) Stokesian dynamics simulations and video microscopy
+experiments, we study the non equilibrium dynamics of a sheared colloidal
+cluster, which is confined to a two-dimensional disk. The experimental system
+is composed of a mixture of paramagnetic and non magnetic polystyrene
+particles, which are held in the disk by time shared optical tweezers. The
+paramagnetic particles are located at the center of the disk and are actuated
+by an external, rotating magnetic field that induces a magnetic torque. We
+identify two different steady states by monitoring the mean angular velocities
+per ring. The first one is characterized by rare slip events, where the inner
+rings momentarily depin from the outer ring, which is kept static by the set of
+optical traps. For the second state, we find a bistability of the mean angular
+velocities, which can be understood from the analysis of the slip events in the
+particle trajectories. We calculate the particle waiting- and jumping time
+distributions and estimate a time scale between slips, which is also reflected
+by a plateau in the mean squared azimuthal displacement. The dynamical
+transition is further reflected by the components of the stress tensor,
+revealing a shear-thinning behavior as well as shear stress overshoots.
+Finally, we briefly discuss the observed transition in the context of
+stochastic thermodynamics and how it may open future directions in this field.",2007.04601v1
+2013-08-18,Short dynamic fibrils in sunspot chromospheres,"Sunspot chromospheres display vigorous oscillatory signature when observed in
+chromospheric diagnostics like the strong Ca II lines and H-alpha. New
+high-resolution sunspot observations from the Swedish 1-m Solar Telescope show
+the ubiquitous presence of small-scale periodic jet-like features that move up
+and down. This phenomenon has not been described before. Their typical width is
+about 0.3 arcsec and they display clear parabolic trajectories in space-time
+diagrams. The maximum extension of the top of the jets is lowest in the umbra,
+a few 100 km, and progressively longer further away from the umbra in the
+penumbra, with the longest more than 1000 km. These jets resemble dynamic
+fibrils found in plage regions but at smaller extensions. LTE inversion of
+spectro-polarimetric Ca II 8542 observations enabled for a comparison of the
+magnetic field inclination and the properties of these short jets. We find that
+the most extended of these jets also have longer periods and tend to be located
+in regions with more horizontal magnetic fields. This is a direct observational
+confirmation of the mechanism of long-period waves propagating along inclined
+magnetic fields into the solar chromosphere. This mechanism was identified
+earlier as the driver of dynamic fibrils in plage, part of the mottles in quiet
+Sun, and type I spicules at the limb. The sunspot dynamic fibrils that we
+report here represent a new class of manifestation of this mechanism. They are
+not the same as the transient penumbral and umbral micro-jets reported earlier.",1308.3893v1
+2018-03-07,Exploring out-of-equilibrium quantum magnetism and thermalization in a spin-3 many-body dipolar lattice system,"Understanding quantum thermalization through entanglement build-up in
+isolated quantum systems addresses fundamental questions on how unitary
+dynamics connects to statistical physics. Here, we study the spin dynamics and
+approach towards local thermal equilibrium of a macroscopic ensemble of S = 3
+spins prepared in a pure coherent spin state, tilted compared to the magnetic
+field, under the effect of magnetic dipole-dipole interactions. The experiment
+uses a unit filled array of 104 chromium atoms in a three dimensional optical
+lattice, realizing the spin-3 XXZ Heisenberg model. The buildup of quantum
+correlation during the dynamics, especially as the angle approaches pi/2, is
+supported by comparison with an improved numerical quantum phase-space method
+and further confirmed by the observation that our isolated system thermalizes
+under its own dynamics, reaching a steady state consistent with the one
+extracted from a thermal ensemble with a temperature dictated from the system's
+energy. This indicates a scenario of quantum thermalization which is tied to
+the growth of entanglement entropy. Although direct experimental measurements
+of the Renyi entropy in our macroscopic system are unfeasible, the excellent
+agreement with the theory, which can compute this entropy, does indicate
+entanglement build-up.",1803.02628v2
+2019-07-24,The dynamics of AR 12700 in its early emerging phase II: fan-shaped activities relevant to arch filament systems,"The emergence of active regions (ARs) closely relates to the solar dynamo and
+the dynamical atmospheric phenomena.With high-resolution and long-lasting
+observations from the New Vacuum Solar Telescope, we report a new dynamic
+activity phenomenon named ""fan-shaped activity (FSA)"" in the emerging phase of
+NOAA AR 12700. The FSAs are clearly observed at Ha wavelength and are closely
+related to the dynamics of the adjacent arch filament system (AFS), including
+threads deformation and materials downward motions. On 2018 February 26, the
+two most representative FSAs appeared around 05:21 UT and 06:03 UT,
+respectively, and they firstly ascended and then decayed in around 10 minutes.
+At the ascending phase, accompanied by the uplifting of an adjacent AFS, each
+FSA launches up at one end of the AFS and extends for up to 11 Mm. At the
+decaying phase, the FSA gradually vanishes, and materials downflows towards the
+other end of the AFS are detected. After checking the evolution of the magnetic
+fields of AR 12700, we find that each FSA is located between the end of an AFS
+and an adjacent magnetic patch with the same polarity and launches at the onset
+of the collision and compression between these two magnetic patches. We propose
+that the collision lifts up the AFS, and then the initially compact AFS
+laterally expands, resulting in the formation of FSA. A cartoon model is
+proposed to depict the activities.",1907.10345v1
+2019-12-16,Asymmetric Magnetic Relaxation behavior of Domains and Domain Walls Observed Through the FeRh First-Order Metamagnetic Phase Transition,"The phase coexistence present through a first-order phase transition means
+there will be finite regions between the two phases where the structure of the
+system will vary from one phase to the other, known as a phase boundary wall.
+This region is said to play an important but unknown role in the dynamics of
+the first-order phase transitions. Here, by using both x-ray photon correlation
+spectroscopy and magnetometry techniques to measure the temporal isothermal
+development at various points through the thermally activated first-order
+metamagnetic phase transition present in the near-equiatomic FeRh alloy, we are
+able to isolate the dynamic behavior of the domain walls in this system. These
+investigations reveal that relaxation behavior of the domain walls changes when
+phase coexistence is introduced into the system and that the domain wall
+dynamics is different to the macroscale behavior. We attribute this to the
+effect of the exchange coupling between regions of either magnetic phase
+changing the dynamic properties of domain walls relative to bulk regions of
+either phase. We also believe this behavior comes from the influence of the
+phase boundary wall on other magnetic objects in the system.",1912.07635v3
+2020-03-02,Chaotic Synchronization of memristive neurons: Lyapunov function versus Hamilton function,"We study the dynamical behaviors of this improved memristive neuron model by
+changing external harmonic current and the magnetic gain parameters. The model
+shows rich dynamics including periodic and chaotic spiking and bursting, and
+remarkably, chaotic super-bursting, which has greater information encoding
+potentials than a standard bursting activity. Based on Krasovskii-Lyapunov
+stability theory, the sufficient conditions (on the synaptic strengths and
+magnetic gain parameters) for the chaotic synchronization of the improved model
+are obtained. Based on Helmholtz's theorem, the Hamilton function of the
+corresponding error dynamical system is also obtained. It is shown that the
+time variation of this Hamilton function along trajectories can play the role
+of the time variation of the Lyapunov function - in determining the asymptotic
+stability of the synchronization manifold. Numerical computations indicate that
+as the synaptic strengths and the magnetic gain parameters change, the time
+variation of the Hamilton function is always non-zero (i.e., a relatively large
+positive or negative value) only when the time variation of the Lyapunov
+function is positive, and zero (or vanishingly small) only when the time
+variation of the Lyapunov function is also zero. This clearly therefore paves
+an alternative way to determine the asymptotic stability of synchronization
+manifolds, and can be particularly useful for systems whose Lyapunov function
+is difficult to construct, but whose Hamilton function corresponding to the
+dynamic error system is easier to calculate.",2003.00947v1
+2020-03-29,Observation of nonlinear spin dynamics and squeezing in a BEC using dynamic decoupling,"We study the evolution of a Bose-Einstein Condensate (BEC) in a two-state
+superposition due to inter-state interactions. Using a population imbalanced
+dynamic decoupling scheme, we measure inter-state interactions while canceling
+intra-state density shifts and external noise sources. Our measurements show
+low statistical uncertainties for both magnetic sensitive and insensitive
+superpositions, indicating that we successfully decoupled our system from
+strong magnetic noises. We experimentally show that the Bloch sphere
+representing general superposition states is ""twisted"" by inter-state
+interactions, and that the twist rate depends on the difference between
+inter-state and intra-state scattering lengths $a_{22}+a_{11}-2a_{12}$. We use
+the non-linear spin dynamics in our scheme to demonstrate squeezing of gaussian
+noise, showing $2.79 \pm 0.43$ dB squeezing when starting with a noisy state
+and applying 160 echo pulses. Which can be used to increase sensitivity when
+there are errors in state preparation. Our results allow for a better
+understanding of inter-atomic potentials in \textsuperscript{87}Rb. Our scheme
+can be used for spin squeezing beyond the standard quantum limit and observing
+polaron physics close to a Feshbach resonance, where interactions diverge, and
+strong magnetic noises are ever present.",2003.13101v3
+2022-06-28,Quantum mean-field treatment of the dynamics of a two-level atom in a simple cubic lattice,"The mean field approximation is used to investigate the general features of
+the dynamics of a two-level atom in a ferromagnetic lattice close to the Curie
+temperature. Various analytical and numerical results are obtained. We first
+linearize the lattice Hamiltonian, and we derive the self-consistency equation
+for the order parameter of the phase transition for arbitrary direction of the
+magnetic field. The reduced dynamics is deduced by tracing out the degrees of
+freedom of the lattice, which results in the reduction of the dynamics to that
+of an atom in an effective spin bath whose size is equal to the size of a unit
+cell of the lattice. It is found that the dephasing and the excited state
+occupation probability may be enhanced by applying the magnetic field along
+some specific directions. The dependence on the change of the temperature and
+the magnitude of spin is also investigated. It turns out that the increase of
+thermal fluctuations may reduce the occupation probability of the excited
+state. The entanglement of two such atoms that occupy non-adjacent cells is
+studied and its variation in time is found to be not much sensitive to the
+direction of the magnetic field. Entanglement sudden death and revival is shown
+to occur close to the critical temperature.",2206.14156v3
+2022-09-08,Perspective: non-Hermitian physics in magnetic systems,"Non-Hermitian Hamiltonians provide an alternative perspective on the dynamics
+of quantum and classical systems coupled non-conservatively to an environment.
+Once primarily an interest of mathematical physicists, the theory of
+non-Hermitian Hamiltonians has solidified and expanded to describe various
+physically observable phenomena in optical, photonic, and condensed matter
+systems. Self-consistent descriptions of quantum mechanics based on
+non-Hermitian Hamiltonians have been developed and continue to be refined. In
+particular, non-Hermitian frameworks to describe magnonic and hybrid magnonic
+systems have gained popularity and utility in recent years, with new insights
+into the magnon topology, transport properties, and phase transitions coming
+into view. Magnonic systems are in many ways a natural platform in which to
+realize non-Hermitian physics because they are always coupled to a surrounding
+environment and exhibit lossy dynamics. In this perspective we review recent
+progress in non-Hermitian frameworks to describe magnonic and hybrid magnonic
+systems, such as cavity magnonic systems and magnon-qubit coupling schemes. We
+discuss progress in understanding the dynamics of inherently lossy magnetic
+systems as well as systems with gain induced by externally applied spin
+currents. We enumerate phenomena observed in both purely magnonic and hybrid
+magnonic systems which can be understood through the lens of non-Hermitian
+physics, such as PT and Anti-PT-symmetry breaking, dynamical magnetic phase
+transitions, non-Hermitian skin effect, and the realization of exceptional
+points and surfaces. Finally, we comment on some open problems in the field and
+discuss areas for further exploration.",2209.03946v2
+2023-03-07,Polarization-diverse soliton transitions and deterministic switching dynamics in strongly-coupled and self-stabilized microresonator frequency combs,"Dissipative Kerr soliton microcombs in microresonators has enabled
+fundamental advances in chip scale precision metrology, communication,
+spectroscopy, and parallel signal processing. Here we demonstrate polarization
+diverse soliton transitions and deterministic switching dynamics of a self
+stabilized microcomb in a strongly coupled dispersion-managed microresonator
+driven with a single pump laser. The switching dynamics are induced by the
+differential thermorefractivity between coupled transverse magnetic and
+transverse electric supermodes during the forward backward pump detunings. The
+achieved large soliton existence range and deterministic transitions benefit
+from the switching dynamics, leading to the cross polarized soliton microcomb
+formation when driven in the transverse magnetic supermode of the single
+resonator. Resultantly the pump laser always exists at the effective blue
+detuning of the transverse magnetic resonance, fundamentally mitigating the
+thermal destabilization barrier and improving accessibility of the soliton
+formation regime. Subsequently and secondly, we demonstrate two distinct
+polarization diverse soliton formation routes arising from chaotic or
+periodically modulated waveforms via pump power selection. The generated self
+stabilized supermode microcomb features an extraordinarily large soliton
+existence range, a variety of soliton state transitions with well defined pump
+laser tuning, high pump microcomb conversion efficiency, and low repetition
+rate phase noise.",2303.03687v1
+2023-03-17,Energetics and Dynamics of a stable Bloch point,"Magnetic Bloch points (BPs) are highly confined magnetization configurations,
+that often occur in transient spin dynamics processes. However, opposing
+chiralities of adjacent layers for instance in a FeGe bilayer stack can
+stabilize such magnetic BPs at the layer interface. These BPs configurations
+are metastable and consist of two coupled vortices (one in each layer) with
+same circularity and opposite polarity. Each vortex is stabilized by opposite
+sign Dzyaloshinskii-Moriya interactions. This stabilization mechanism
+potentially opens the door towards BP-based spintronic applications. An open
+question, from a methodological point of view, is whether the Heisenberg (HB)
+model approach (atomistic model) as to be used to study such systems or if the
+-- computationally more efficient -- micromagnetic (MM) models can be used and
+still obtain robust results. We are modelling and comparing the energetics and
+dynamics of a stable BP obtained using both HB and MM approaches. We find that
+an MM description of a stable BP leads qualitatively to the same results as the
+HB description, and that an appropriate mesh discretization plays a more
+important role than the chosen model. Further, we study the dynamics by
+shifting the BP with an applied in-plane field and investigating the relaxation
+after switching the filed off abruptly. The precessional motion of coupled
+vortices in a BP state can be drastically reduced compared to a classical
+vortex, which may be also an interesting feature for fast and efficient
+devices. A recent study has shown that a bilayer stack hosting BPs can be used
+to retain information [1].",2303.10091v1
+2023-03-29,Dynamically screened strongly quantized electron transport in binary neutron-star merger,"We examine electron-transport coefficients in magnetized hot and dense
+electron-ion plasma relevant in binary neutron star merger simulation. We
+calculate electrical and thermal conductivities in low density, high
+temperature, highly magnetized plasma of binary neutron star mergers where
+quantum oscillatory behavior of electrons emerge. For pronounced thermodynamic
+effects, we consider zeroth Landau level population of electrons for the
+calculation of conductivity. We solve Boltzmann equation in presence of
+magnetic field to obtain the dissipative components of electrical and thermal
+conductivities. The dissipative coefficients are formulated considering
+frequency dependent dynamical screening in the quantized electron-ion
+scattering rate. Numerical estimations show that the effect of dynamical
+screening of photon propagator on electrical and thermal conductivities is
+pronounced. We observe that dynamical screening reduces the maxima of both the
+electrical and thermal conductivities by factors of thirty one and twenty
+respectively leading to a reduction in the corresponding time scales of these
+coefficients. The common scaling factor between electrical and thermal
+conductivity is also observed to follow cubic relationship with temperature
+violating Wiedemann-Franz law.",2303.16811v1
+2023-06-29,Nonequilibrium generation of charge defects in kagome spin ice under slow cooling,"Kagome spin ice is one of the canonical examples of highly frustrated
+magnets. The effective magnetic degrees of freedom in kagome spin ice are Ising
+spins residing on a two-dimensional network of corner-sharing triangles. Due to
+strong geometrical frustration, nearest-neighbor antiferromagnetic interactions
+on the kagome lattice give rise to a macroscopic number of degenerate classical
+ground states characterized by ice rules. Elementary excitations at low
+temperatures are defect-triangles that violate the ice rules and carry an
+additional net magnetic charge relative to the background. We perform
+large-scale Glauber dynamics simulations to study the nonequilibrium dynamics
+of kagome ice under slow cooling. We show that the density of residual charge
+defects exhibits a power law dependence on the quench rate for the class of
+algebraic cooling protocols. The numerical results are well captured by the
+rate equation for the charge defects based on the reaction kinetics theory. As
+the relaxation time of the kagome ice phase remains finite, there is no
+dynamical freezing as in the Kibble-Zurek scenario. Instead, we show that the
+power-law behavior originates from a thermal excitation that decay
+algebraically with time at the late stage of the cooling schedule. Similarities
+and differences in quench dynamics of other spin ice systems are also
+discussed.",2306.17036v2
+2023-12-28,Anisotropic skyrmion and multi-$q$ spin dynamics in centrosymmetric Gd$_2$PdSi$_3$,"Skyrmions are particle-like vortices of magnetization with non-trivial
+topology, which are usually stabilized by Dzyaloshinskii-Moriya interactions
+(DMI) in noncentrosymmetric bulk materials. Exceptions are centrosymmetric Gd-
+and Eu-based skyrmion-lattice (SkL) hosts with net-zero DMI, where both the SkL
+stabilization mechanisms and magnetic ground states remain controversial. We
+address these by investigating both static and dynamic spin properties of the
+centrosymmetric SkL host Gd$_2$PdSi$_3$ using muon spectroscopy ($\mu$SR). We
+find that spin fluctuations in its non-coplanar SkL phase are highly
+anisotropic, implying that spin anisotropy plays a prominent role in
+stabilizing this phase. We also observe strongly-anisotropic spin dynamics in
+the ground-state (IC-1) incommensurate magnetic phase of the material,
+indicating that it is a meron-like multi-$q$ structure. In contrast, the
+higher-field, coplanar IC-2 phase is found to be single-$q$ with
+nearly-isotropic spin dynamics.",2312.17323v2
+2024-02-05,Circular motion of non-collinear spin textures in Corbino disks: Dynamics of Néel- versus Bloch-type skyrmions and skyrmioniums,"Magnetic skyrmions are nano-scale magnetic whirls that can be driven by
+currents via spin torques. They are promising candidates for spintronic devices
+such as the racetrack memory, where a motion along the uniform current is
+typically desired. However, in Corbino disks, the goal is to achieve a circular
+motion, perpendicular to the radially applied current. As we show, based on
+analytical calculations and micromagnetic simulations, Bloch skyrmions engage
+in a circular motion with frequencies in the MHz range when driven by
+spin-orbit torques. In contrast, N\'eel skyrmions get stuck at the edges of the
+disk. Our analysis reveals that the antagonistic dynamics between Bloch- and
+N\'eel-type magnetic textures arise from their helicity. Furthermore, we find
+that skyrmioniums, which are topologically trivial variations of skyrmions,
+move even faster and allow an increase in the current density without being
+pushed toward the edges of the disk. When driven by spin-transfer torques
+instead, Bloch and N\'eel skyrmions no longer exhibit different dynamics.
+Instead, they move along a circular trajectory due to the skyrmion Hall effect
+caused by their topological charge. Consequently, the topologically trivial
+skyrmioniums inevitably become trapped at the disk edge in this scenario. To
+provide a comprehensive understanding, our study also examines currents applied
+tangentially, further enriching our insights into skyrmion dynamics and
+appropriate current injection methods for skyrmion-based devices.",2402.03023v1
+2004-12-03,Dusty plasmas on galactic scales,"Interstellar dust is spread in galaxies over large scales, often far beyond
+the stellar disks. Several mechanisms can be responsible for carrying the dust
+both in the vertical and radial directions, producing in general different
+spatial dust distributions. In spite of the small mass fraction dust can be in
+some cases dynamically active, and its role in star formation process and
+dynamics of shock waves is still not completely understood. In this review I
+discuss briefly the issues connected with the large scale distribution of the
+interstellar dust, the impact of the dust on star formation and on dynamics of
+shock waves.",0412078v1
+1995-01-02,Dynamics of homogeneous magnetizations in strong transverse driving fields,"Spatially homogeneous solutions of the Landau--Lifshitz--Gilbert equation are
+analysed. The conservative as well as the dissipative case is considered
+explicitly. For the linearly polarized driven Hamiltonian system we apply
+canonical perturbation theory to uncover the main resonances as well as the
+global phase space structure. In the case of circularly polarized driven
+dissipative motion we present the complete bifurcation diagram including
+bifurcations up to codimension three.",9501002v1
+1996-05-01,Can a local repulsive potential trap an electron?,"We study the classical dynamics of a charged particle in two dimensions,
+under the influence of a perpendicular magnetic and an in-plane electric field.
+We prove the surprising fact that there is a finite region in phase space that
+corresponds to the otherwise drifting particle being trapped by a local
+repulsive potential. Our result is a direct consequence of KAM-theory and, in
+particular, of Moser's theorem. We illustrate it by numerical phase portraits
+and by an analytic approximation to invariant curves.",9604018v1
+1999-02-27,Periodic Orbit Quantization of Mixed Regular Chaotic Systems,"A general technique for the periodic orbit quantization of systems with
+near-integrable to mixed regular-chaotic dynamics is introduced. A small set of
+periodic orbits is sufficient for the construction of the semiclassical
+recurrence function up to, in principle, infinite length. As in our recent work
+the recurrence signal is inverted by means of a high resolution spectral
+analyzer (harmonic inversion) to obtain the semiclassical eigenenergies. The
+method is demonstrated for the hydrogen atom in a magnetic field. To our
+knowledge this is the first successful application of periodic orbit
+quantization in the deep mixed regular-chaotic regime.",9903003v1
+1999-06-21,Controlling a leaky tap,"We apply the Ott, Grebogy and Yorke mechanism for the control of chaos to the
+analytical oscillator model of a leaky tap obtaining good results. We exhibit
+the robustness of the control against both dynamical noise and measurement
+noise.A possible way of controlling experimentally a leaky tap using
+magnetic-field-produced variations in the viscosity of a magnetorheological
+fluid is suggested.",9906033v1
+1999-06-22,Chaotic Oscillations in Finite Quantum Systems: Trapped Bose-Einstein Condensates,"We discuss the recently achieved Bose-Einstein condensation for alkali-metal
+atoms in magnetic traps. The theoretically predicted low-energy collective
+oscillations of the condensate have been experimentally confirmed by laser
+imaging techniques. We show by using Poincar\`e sections that at higher
+energies non-linear effects appear and oscillations become chaotic. PACS
+03.75.Fi, 05.30.Jp, 05.45.+b, 32.80.Pj",9906034v1
+1999-09-01,Semiclassical Theory of h/e Aharonov-Bohm Oscillation in Ballistic Regimes,"We study the magneto-transport in Aharonov-Bohm (AB) billiards forming doubly
+connected structures. In these systems, non-averaged conductance oscillates as
+a function of magnetic flux with period h/e. We derive formulas of the
+correlation function C of the magneto-conductance for chaotic and regular AB
+billiards by use of the semiclassical theory. The different higher harmonics
+behaviors for C are related to the differing distribution of classical dwelling
+times. The AB oscillation in ballistic regimes provides an experimental probe
+of quantum signatures of classical chaotic and regular dynamics.",9909006v1
+1995-07-20,Dynamic Jahn-Teller Effect and Colossal Magnetoresistance in $La_{1-x}A_xMnO_3$,"A model for $La_{1-x}Sr_xMnO_3$ which incorporates the physics of dynamic
+Jahn-Teller and double-exchange effects is presented and solved via a dynamical
+mean field approximation. In an intermediate coupling regime the interplay of
+these two effects is found to reproduce the behavior of the resistivity and
+magnetic transition temperature observed in $La_{1-x} Sr_x MnO_3$.",9507084v2
+1995-08-31,Finite Size Scaling and Critical Exponents in Critical Relaxation,"We simulate the critical relaxation process of the two-dimensional Ising
+model with the initial state both completely disordered or completely ordered.
+Results of a new method to measure both the dynamic and static critical
+exponents are reported, based on the finite size scaling for the dynamics at
+the early time. From the time-dependent Binder cumulant, the dynamical exponent
+$z$ is extracted independently, while the static exponents $\beta/\nu$ and
+$\nu$ are obtained from the time evolution of the magnetization and its higher
+moments.",9508148v1
+1995-10-19,Determination of the Critical Point and Exponents from short-time Dynamics,"The dynamic process for the two dimensional three state Potts model in the
+critical domain is simulated by the Monte Carlo method. It is shown that the
+critical point can rigorously be located from the universal short-time
+behaviour. This makes it possible to investigate critical dynamics
+independently of the equilibrium state. From the power law behaviour of the
+magnetization the exponents $\beta / (\nu z)$ and $1/ (\nu z)$ are determined.",9510109v1
+1996-04-29,Percolation and cluster Monte Carlo dynamics for spin models,"A general scheme for devising efficient cluster dynamics proposed in a
+previous letter [Phys.Rev.Lett. 72, 1541 (1994)] is extensively discussed. In
+particular the strong connection among equilibrium properties of clusters and
+dynamic properties as the correlation time for magnetization is emphasized. The
+general scheme is applied to a number of frustrated spin model and the results
+discussed.",9604169v1
+1997-05-19,Anomalous Shift of Chemical Potential in the Double-Exchange Systems,"Double-exchange system is investigated by the dynamical mean-field theory. We
+show that the chemical potential shifts as a function of temperature and
+magnetization, which is anomalously large. We also discuss the influences of
+dynamic Jahn-Teller effect to the shift of the chemical potential. Measurement
+of the shift of the chemical potential casts a constraint to theoretical
+approaches for the magnetoresistance phenomena in ($R$,$A$)MnO$_3$ such as
+double-exchange effects and dynamic Jahn-Teller effects. We also propose a
+method to measure the shift of $\mu$.",9705176v2
+1997-08-13,Chaos and Interacting Electrons in Ballistic Quantum Dots,"We show that the classical dynamics of independent particles can determine
+the quantum properties of interacting electrons in the ballistic regime. This
+connection is established using diagrammatic perturbation theory and
+semiclassical finite-temperature Green functions. Specifically, the orbital
+magnetism is greatly enhanced over the Landau susceptibility by the combined
+effects of interactions and finite size. The presence of families of periodic
+orbits in regular systems makes their susceptibility parametrically larger than
+that of chaotic systems, a difference which emerges from correlation terms.",9708092v1
+1998-05-11,Dynamical simulation of spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin glasses,"Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin
+glasses are studied with and without randaom magnetic anisotropy by dynamical
+Monte Carlo simulations. In isotropic case, clear evidence of a
+finite-temperature chiral-glass transition is presented. While the spin
+autocorrelation exhibits only an interrupted aging, the chirality
+autocorrelation persists to exhibit a pronounced aging effect reminisecnt of
+the one observed in the mean-field model. In anisotropic case, asymptotic
+mixing of the spin and the chirality is observed in the off-equilibrium
+dynamics.",9805117v1
+1998-05-18,Chaotic enhancement in microwave ionization of Rydberg atoms,"The microwave ionization of internally chaotic Rydberg atoms is studied
+analytically and numerically. The internal chaos is induced by magnetic or
+static electric fields. This leads to a chaotic enhancement of microwave
+excitation. The dynamical localization theory gives a detailed description of
+the excitation process even in a regime where up to few thousands photons are
+required to ionize one atom. Possible laboratory experiments are also
+discussed.",9805216v1
+1998-09-01,Non-equilibrium dynamics in a 3d spin-glass,"Non-equilibrium dynamics in a Ag(11%Mn) spin-glass has been studied by low
+frequency ac-susceptibility and magnetic relaxation experiments. The results
+unequivocally show that spin structures that memorize the cooling process are
+imprinted in the system. These imprinted structures disclose themselves through
+dramatic changes of the dynamics on re-heating the spin-glass through the
+temperatures where intermittent stops or changes of the cooling rate have been
+imposed. We can qualitatively interpret our results in terms of the droplet
+spin-glass model developed by Fisher and Huse [Phys. Rev. B 38 (1988) 373;
+386].",9809021v1
+1998-10-08,Nonuniversality in short-time critical dynamics,"We study behaviour of dynamical critical exponents of the two-dimensional
+Ising model with a line of defects. Simulations done at an early time (first
+100 Monte Carlo steps) reveal that the critical exponent of Janssen et al (Z.
+Phys. B 73 539) depends on the strength of the exchange coupling constant (J')
+of the altered line. On the other hand, our simulations permit us to conclude
+that the dynamical critical exponent z is not sensitive to changes in J'. In
+adition, we investigate the possible invariance of the anomalous dimension of
+the magnetization at the beginning of the process.",9810105v1
+1999-04-19,"Dynamic transverse susceptibility in Au-Fe-Au ""nano-onions""","A precision radio-frequency (RF) transverse modulation technique based on a
+resonant tunnel diode oscillator (TDO) has been used to study the dynamic
+susceptibility in novel ring-shaped single domain Fe nanoparticles synthesized
+using reverse-micelle chemistry. Hysteresis loops measured using a SQUID
+magnetometer indicate a large coercivity (Hc = 400Oe) below the blocking
+temperature (TB ~52K). The dynamic susceptibility shows remarkable consistency
+with the M-H data and exhibits peaks at characteristic anisotropy fields.
+Overall, these RF experiments are well suited to probe the magnetic anisotropy
+in nanophase materials.",9904267v1
+1999-08-10,The influence of the Wolff's cluster structure on the determination of the critical dynamic exponent,"Recently we reported some interesting features of the Wolff's algorithm
+behavior when applied to the site-bond-correlated Ising model.Our main results
+were that a stronger correlation diminishes the autocorrelation time but it
+does not change or affectthe critical dynamic exponent.In this paper, we
+analyse the Wolff's cluster structure and how it varies with the spatial
+correlation. The fractal dimensions are determined for several values of the
+magnetic atoms concentration and spacial correlation, giving an estimative of
+the critical dynamic exponent.",9908151v1
+1999-09-22,The Critical Exponent $θ'$ in Spin Glasses,"Short-time dynamic scaling behavior of the 3D $\pm J$ Ising spin glass is
+studied by Monte Carlo methods. Starting the replicas with independent initial
+configurations with a small pseudo magnetization, the dynamic evolution of the
+overlap q(t) between two replicas is measured. The initial increase of the
+overlap q(t) is observed and the corresponding exponent $\theta'$ is obtained.
+  From the scaling relation $\lambda =d/z-\theta'$, the dynamic exponent z is
+estimated.",9909325v1
+2000-03-27,Effect of memory and dynamical chaos in long Josephson junctions,"A long Josephson junction in a constant external magnetic field and in the
+presence of a dc bias current is investigated. It is shown that the system,
+simulated by the sine-Gorgon equation, ""remembers"" a rapidly damping initial
+perturbation and final asymptotic states are determined exactly with this
+perturbation. Numerical solving of the boundary sine-Gordon problem and
+calculations of Lyapunov indices show that this system has a memory even when
+it is in a state of dynamical chaos, i.e., dynamical chaos does not destroy
+initial information having a character of rapidly damping perturbation.",0003421v1
+2000-09-18,Dynamics of metastable vortex states in weakly pinned superconductors: A phenomenological model,"We present a phenomenological model for the vortex dynamics in the peak
+effect region of weakly pinned superconductors. We explain the history
+dependent dynamic response of the metastable vortex states subjected to a
+transport current and the hysteretic voltage-current characteristics observed
+in the vicinity of peak effect in weakly pinned superconductors. A strong
+variation in voltage current characteristics with the current sweep rate and
+the anomalous dependence of critical current density $J_c$ on the magnetic
+field sweep rate have also been accounted for by this model.",0009254v1
+2001-04-24,Dynamics and transformations of Josephson vortex lattice in layered superconductors,"We consider dynamics of Josephson vortex lattice in layered superconductors
+with magnetic, charge (electrostatic) and charge-imbalance (quasiparticle)
+interactions between interlayer Josephson junctions taken into account. The
+macroscopic dynamical equations for interlayer Josephson phase differences,
+intralayer charge and electron-hole imbalance are obtained and used for
+numerical simulations. Different transformations of the vortex lattice
+structure are observed. It is shown that the additional dissipation due to the
+charge imbalance relaxation leads to the stability of triangular lattice.",0104468v1
+2001-05-31,Critical Dynamics of a Vortex Loop Model for the Superconducting Transition,"We calculate analytically the dynamic critical exponent $z_{MC}$ measured in
+Monte Carlo simulations for a vortex loop model of the superconducting
+transition, and account for the simulation results. In the weak screening
+limit, where magnetic fluctuations are neglected, the dynamic exponent is found
+to be $z_{MC} = 3/2$. In the perfect screening limit, $z_{MC} = 5/2$. We relate
+$z_{MC}$ to the actual value of $z$ observable in experiments and find that $z
+\sim 2$, consistent with some experimental results.",0105622v2
+2001-10-11,Dynamical correlations in half-metallic manganites,"Motivated by the recent optical and photoemission measurements on
+half-metallic ferromagnetic three-dimensional manganites, we combine a
+tight-binding fit of the one-particle bandstructure with the dynamical
+mean-field theory, which treats the dynamical orbital correlations and the
+combination of Jahn-Teller and doping-induced disorder on the same footing. We
+show how all of the above effects are necessary to obtain good semiquantitative
+agreement with experimental features. As applications, we show how modest
+external magnetic fields drive drastic changes in the optical spectrum,
+demonstrating the {\it colossal ac magnetoconductivity}. The photoemission
+lineshape contribution is evaluated, and good agreement with published
+experimental work is found.",0110229v1
+2001-12-17,Glassy dynamics of Josephon arrays on a dice lattice,"In this Letter we study the phase diagram and the approach to the equilibrium
+of Josephson junction arrays on a dice lattice for two different values of the
+magnetic frustration ($f=1/2,1/3$). In both cases the array unedrgoes a
+Berezinskii-Kosterlitz-Thouless like phase transition. For the fully frustrated
+array, $f=1/2$, we find evidence of a {\em glassy behavior} although the system
+has {\em no disorder}. For comparison we study dynamics of the array at a
+different value of frustration ($f=1/3$) and find no trace of glassy dynamics.",0112307v1
+2002-01-18,Coherent quantum oscillations in coupled traps with ultracold atoms,"The dynamics of two traps with ultracold atoms and connected by Josephson
+type coupling, is shown to exhibit a transition from dispersive dynamics to
+localized coherent oscillations. This transition is controlled by coupling
+strength and energy offset between the traps. The dynamics is also shown to be
+exactly that of a Heisenberg chain with a linear magnetic field. Possible
+applications for ``quantum-state engineering'' are discussed.",0201335v1
+2002-09-02,Dynamics and phase evolution of Bose-Einstein condensates in one-dimensional optical lattices,"We report experimental results on the dynamics and phase evolution of
+Bose-Einstein condensates in 1D optical lattices. The dynamical behaviour is
+studied by adiabatically loading the condensate into the lattice and
+subsequently switching off the magnetic trap. In this case, the condensate is
+free to expand inside the periodic structure of the optical lattice. The phase
+evolution of the condensate, on the other hand, can be studied by
+non-adiabatically switching on the periodic potential. We observe decays and
+revivals of the interference pattern after a time-of-flight.",0209024v1
+2002-11-08,Rejection-free Monte Carlo Algorithms for Models with Continuous Degrees of Freedom,"We construct a rejection-free Monte Carlo algorithm for a system with
+continuous degrees of freedom. We illustrate the algorithm by applying it to
+the classical three-dimensional Heisenberg model with canonical Metropolis
+dynamics. We obtain the lifetime of the metastable state following a reversal
+of the external magnetic field. Our rejection-free algorithm obtains results in
+agreement with a direct implementation of the Metropolis dynamic and requires
+orders of magnitude less computational time at low temperatures. The treatment
+is general and can be extended to other dynamics and other systems with
+continuous degrees of freedom.",0211164v1
+2003-07-21,Dynamics of ferromagnetic nanomagnets with vortex or single-domain configuration,"We study the dynamics of flat circular permalloy nanomagnets for 1.) magnetic
+vortex and 2.) single-domain configurations, using micromagnetic simulation.
+Dynamical studies for isolated vortex structures show that both the vorticity
+and the central polarity of the out-of-plane component can be switched fast
+(50-100 ps) and independently. Micromagnetic simulations of the switching
+process in thin cylindrical Permalloy (Py) nanoparticles with an initial stable
+single-domain state show nearly homogeneous single-domain behaviour followed by
+excitation of spin waves.",0307503v1
+2003-11-19,Dynamic Kerr Effect and Spectral Weight Transfer in the Manganites,"We perform pump-probe Kerr spectroscopy in the colossally magnetoresistive
+manganite Pr0.67Ca0.33MnO3. Kerr effects uncover surface magnetic dynamics
+undetected by established methods based on reflectivity and optical spectral
+weight transfer. Our findings indicate the connection between spin and charge
+dynamics in the manganites may be weaker than previously thought. Additionally,
+important differences between this system and conventional ferromagnetic metals
+manifest as long-lived, magneto-optical coupling transients, which may be
+generic to all manganites.",0311452v2
+2003-12-22,Out-of-equilibrium critical dynamics at surfaces: Cluster dissolution and non-algebraic correlations,"We study nonequilibrium dynamical properties at a free surface after the
+system is quenched from the high-temperature phase into the critical point. We
+show that if the spatial surface correlations decay sufficiently rapidly the
+surface magnetization and/or the surface manifold autocorrelations has a
+qualitatively different universal short time behavior than the same quantities
+in the bulk. At a free surface cluster dissolution may take place instead of
+domain growth yielding stationary dynamical correlations that decay in a
+stretched exponential form. This phenomenon takes place in the
+three-dimensional Ising model and should be observable in real ferromagnets.",0312583v1
+2004-05-12,The role of orbital dynamics in spin relaxation and weak antilocalization in quantum dots,"We develop a semiclassical theory for spin-dependent quantum transport to
+describe weak (anti)localization in quantum dots with spin-orbit coupling. This
+allows us to distinguish different types of spin relaxation in systems with
+chaotic, regular, and diffusive orbital classical dynamics. We find, in
+particular, that for typical Rashba spin-orbit coupling strengths, integrable
+ballistic systems can exhibit weak localization, while corresponding chaotic
+systems show weak antilocalization. We further calculate the magnetoconductance
+and analyze how the weak antilocalization is suppressed with decreasing quantum
+dot size and increasing additional in-plane magnetic field.",0405266v2
+2004-06-04,Observation of a New Fluxon Resonant Mechanism in Annular Josephson Tunnel Structures,"A novel dynamical state has been observed in the dynamics of a perdurbed
+sine-Gordon system. This resonant state, has been experimentally observed as a
+singularity in the dc current voltage characteristic of an annular Josephson
+tunnel junction, excited in the presence of a magnetic field. With this
+respect, it can be assimilated to self-resonances known as Fiske steps.
+Differently from these, however, we demonstrate, on the basis of numerical
+simulations, that its detailed dynamics involves rotating fluxon pairs, a
+mechanism associated, so far, to self-resonances known as zero-field steps.",0406104v1
+2004-08-18,Hole dynamics in spin and orbital ordered vanadium perovskites,"Hole dynamics in spin and orbital ordered vanadates with perovskite structure
+is investigated. A mobile hole coupled to the spin excitation (magnon) in the
+spin G-type and orbital C-type (SG/OC) ordered phase, and that to the orbital
+excitation (orbiton) in the spin C-type and orbital G-type (SC/OG) one are
+formulated on an equal footing. The observed fragile character of the (SG/OC)
+order is attributed to the orbiton softening caused by a reduction of the
+taggered magnetic order parameter. It is proposed that the qualitatively
+different hole dynamics in the two spin-orbital ordered phases in vanadates can
+be probed by the optical spectra.",0408395v1
+2004-11-02,Critical scaling of thermal transport in model A dynamics for a superconductor,"We consider the scaling of thermal transport in the presence of electric and
+magnetic fields near the finite temperature transition from the metallic normal
+state to the superconductor. We do so with fully relaxational, model A,
+dynamics for the order parameter and particle-hole symmetry. This enables us to
+determine the exact scaling dimension of the heat current operator and hence
+critical exponents for all transport coefficients in terms of the
+(approximately) known values of the correlation length exponent and the dynamic
+scaling exponent. In particular, we determine the critical behavior for the
+Nernst coefficient.",0411040v1
+2004-12-21,Dynamic behaviour of Josephson-junction qubits: crossover between Rabi oscillations and Landau-Zener transitions,"We study the dynamic behaviour of a quantum two-level system with
+periodically varying parameters by solving the master equation for the density
+matrix. Two limiting cases are considered: multiphoton Rabi oscillations and
+Landau-Zener transitions. The approach is applied to the description of the
+dynamics of superconducting qubits. In particular, the case of the
+interferometer-type charge qubit with periodically varying parameters (gate
+voltage or magnetic flux) is investigated. The time-averaged energy level
+populations are calculated as funtions of the qubit's control parameters.",0412588v1
+2005-03-14,Band-selective Measurement of Electronic Dynamics in VO2 using Femtosecond Near Edge X-ray Absorption,"We report on the first demonstration of femtosecond xray absorption
+spectroscopy. Our experiments are made possible by the use of broadly tunable
+bending-magnet radiation from laser-sliced electron bunches within a
+synchrotron storage ring. We measure ultrafast electronic dynamics associated
+with the photo-induced insulator-metal phase transition in VO2. Symmetry and
+element specific xray absorption from near 500 eV V2p and O1s core levels
+separately measures the filling dynamics of differently hybridized V3d O2p
+electronic bands near the Fermi level.",0503311v1
+2005-05-23,Real-time dynamics in Quantum Impurity Systems: A Time-dependent Numerical Renormalization Group Approach,"We develop a general approach to the nonequilibrium dynamics of quantum
+impurity systems for arbitrary coupling strength. The numerical renormalization
+group is used to generate a complete basis set necessary for the correct
+description of the time evolution. We benchmark our method with the exact
+analytical solution for the resonant-level model. As a first application, we
+investigate the equilibration of a quantum dot subject to a sudden change of
+the gate voltage and external magnetic field. Two distinct relaxation times are
+identified for the spin and charge dynamics.",0505553v1
+2005-07-07,Classical memory effects on spin dynamics in two-dimensional systems,"We discuss classical dynamics of electron spin in two-dimensional
+semiconductors with a spin-split spectrum. We focus on a special case, when
+spin-orbit induced random magnetic field is directed along a fixed axis. This
+case is realized in III-V-based quantum wells grown in [110] direction and also
+in [100]-grown quantum wells with equal strength of Dresselhaus and
+Bychkov-Rashba spin-orbit couplings. We show that in such wells the long-time
+spin dynamics is determined by non-Markovian memory effects. Due to these
+effects the non-exponential tail $1/t^2$ appears in the spin polarization.",0507171v2
+2005-08-10,Dynamics of quantum spin chains and multi-fermion excitation continua,"We use the Jordan-Wigner representation to study dynamic quantities for the
+spin-1/2 XX chain in a transverse magnetic field. We discuss in some detail the
+properties of the four-fermion excitation continuum which is probed by the
+dynamic trimer structure factor.",0508265v1
+2005-09-19,Quasi-Kondo Phenomenon due to Dynamical Jahn-Teller Effect,"A mechanism of non-magnetic Kondo effect is proposed on the basis of a
+multiorbital Anderson model coupled with dynamical Jahn-Teller (JT) phonons. An
+electron system coupled dynamically with JT phonons has a vibronic ground state
+with double degeneracy due to clockwise and anti-clockwise rotational modes
+with entropy of $\log 2$. When a temperature is lower than a characteristic
+energy to turn the rotational direction, the rotational degree of freedom is
+eventually suppressed and the corresponding entropy $\log 2$ is released,
+leading to quasi-Kondo behavior. We discuss possible relevance of this
+quasi-Kondo phenomenon to electronic properties of filled skutterudites.",0509473v2
+2005-09-22,Intrinsic spin dynamics in semiconductor quantum dots,"We investigate the characteristic spin dynamics corresponding to
+semiconductor quantum dots within the multiband envelope function approximation
+(EFA). By numerically solving an $8\times8$ $k\cdot p$ Hamiltonian we treat
+systems based on different III-V semiconductor materials.It is shown that, even
+in the absence of an applied magnetic field, these systems show intrinsic spin
+dynamics governed by intraband and interband transitions leading to
+characteristic spin frequencies ranging from the THz to optical frequencies.",0509587v1
+2006-01-20,Semiclassical Dynamics of Electrons in Magnetic Bloch Bands: a Hamiltonian Approach,"y formally diagonalizing with accuracy $\hbar$ the Hamiltonian of electrons
+in a crystal subject to electromagnetic perturbations, we resolve the debate on
+the Hamiltonian nature of semiclassical equations of motion with Berry-phase
+corrections, and therefore confirm the validity of the Liouville theorem. We
+show that both the position and momentum operators acquire a Berry-phase
+dependence, leading to a non-canonical Hamiltonian dynamics. The equations of
+motion turn out to be identical to the ones previously derived in the context
+of electron wave-packets dynamics.",0601472v2
+2006-05-04,Current-driven vortex domain wall dynamics by micromagnetic simulations,"Current-driven vortex wall dynamics is studied by means of a two-dimensional
+analytical model and micromagnetic simulation. By constructing a trial function
+for the vortex wall in the magnetic wire, we analytically solve for domain wall
+velocity and deformation in the presence of the current-induced spin torque. A
+critical current for the domain wall transformation from the vortex wall to the
+transverse wall is calculated. A comparison between the field- and
+current-driven wall dynamics is carried out. Micromagnetic simulations are
+performed to verify our analytical results.",0605125v2
+1995-06-14,Square Gravity,"We simulate the Ising model on dynamical quadrangulations using a
+generalization of the flip move for triangulations with two aims: firstly, as a
+confirmation of the universality of the KPZ/DDK exponents of the Ising phase
+transition, worthwhile in view of some recent surprises with other sorts of
+dynamical lattices; secondly, to investigate the transition of the Ising
+antiferromagnet on a dynamical loosely packed (bipartite) lattice. In the
+latter case we show that it is still possible to define a staggered
+magnetization and observe the antiferromagnetic analogue of the transition.",9506022v1
+2001-11-22,On the dynamics of color magnetic monopoles in full QCD,"We present first results on the dynamics of monopoles in full QCD with N_f=2
+flavors of dynamical quarks. Among the quantities being studied are the
+monopole density and the monopole screening length, the static potential as
+well as the profile of the color electric flux tube. Furthermore, we derive the
+low-energy effective monopole action.",0111042v1
+2004-07-30,Violation of Lorentz invariance and dynamical effects in high energy gamma rays,"The relation between the violation of Lorentz invariance and the dynamical
+effects in high energy gamma rays production is discussed. By using the
+framework of noncommutative classical electrodynamics, it is shown that full
+dynamical calculations are required to put bounds on the Lorentz violating
+scale by the phenomenological analysis of these processes as, for example, the
+synchrotron radiation from the CRAB nebula. It is observed that an improvement
+of the present bound on the scale of noncommutativity can be obtained only by
+astrophysical observations of gamma ray spectra in strong magnetic fields such
+as pulsars.",0407363v1
+1996-08-16,"Duality, Multi-Monopole Dynamics & Quantum Threshold Bound States","Dynamics of many supersymmetric monopoles are studied in the low energy
+approximation. A conjecture for the exact moduli space metric is given for all
+collections of fundamental monopoles of distinct type, and various partial
+confirmations of the conjecture are discussed. Upon the quantization of the
+resulting multi-monopole dynamics in the context of $N=4$ supersymmetric
+Yang-Mills-Higgs theories, one recovers the missing magnetic states that are
+dual to some of the massive vector mesons. A generalization to monopoles with
+nonabelian charges is also discussed.",9608114v1
+2001-06-25,A pseudointegrable Andreev billiard,"A circular Andreev billiard in a uniform magnetic field is studied. It is
+demonstrated that the classical dynamics is pseudointegrable in the same sense
+as for rational polygonal billiards. The relation to a specific polygon, the
+asymmetric barrier billiard, is discussed. Numerical evidence is presented
+indicating that the Poincare map is typically weak mixing on the invariant
+sets. This link between these different classes of dynamical systems throws
+some light on the proximity effect in chaotic Andreev billiards.",0106037v2
+2005-02-16,Self-pulsing dynamics of ultrasound in a magnetoacoustic resonator,"A theoretical model of parametric magnetostrictive generator of ultrasound is
+considered, taking into account magnetic and magnetoacoustic nonlinearities.
+The stability and temporal dynamics of the system is analized with standard
+techniques revealing that, for a given set of parameters, the model presents a
+homoclinic or saddle--loop bifurcation, which predicts that the ultrasound is
+emitted in the form of pulses or spikes with arbitrarily low frequency.",0502034v1
+2003-03-17,Dynamical analysis of the nonlinear growth of the m=n=1 resistive internal mode,"A dynamical analysis is presented that self-consistently takes into account
+the motion of the critical layer, in which the magnetic field reconnects, to
+describe how the m=n=1 resistive internal kink mode develops in the nonlinear
+regime. The amplitude threshold marking the onset of strong nonlinearities due
+to a balance between convective and mode coupling terms is identified. We
+predict quantitatively the early nonlinear growth rate of the m=n=1 mode below
+this threshold.",0303066v1
+2006-01-16,Dynamo action at low magnetic Prandtl numbers: mean flow vs. fully turbulent motion,"We compute numerically the threshold for dynamo action in Taylor-Green
+swirling flows. Kinematic calculations, for which the flow field is fixed to
+its time averaged profile, are compared to dynamical runs for which both the
+Navier-Stokes and the induction equations are jointly solved. The kinematic
+instability is found to have two branches, for all explored Reynolds numbers.
+The dynamical dynamo threshold follows these branches: at low Reynolds number
+it lies within the low branch while at high kinetic Reynolds number it is close
+to the high branch.",0601105v1
+2005-04-25,Analytical Approach to Wave Packet Dynamics of Laser-Driven Particles beyond the Dipole Approximation,"An analytical approach to quantum mechanical wave packet dynamics of
+laser-driven particles is presented. The time-dependent Schroedinger equation
+is solved for an electron exposed to a linearly polarized plane wave of
+arbitrary shape. The calculation goes beyond the dipole approximation, such
+that magnetic field effects like wave packet shearing are included. Analytical
+expressions for the time-dependent widths of the wave packet and its
+orientation are established. These allow for a simple understanding of the wave
+packet dynamics.",0504181v1
+2005-10-20,Entanglement dynamics for two interacting spins,"We study the dynamical generation of entanglement for a very simple system: a
+pair of interacting spins, s1 and s2, in a constant magnetic field. Two
+different situations are considered:(a) s1 ->\infty, s2 = 1/2 and (b) s1 = s2
+->\infty, corresponding, respectively, to a quantum degree of freedom coupled
+to a semiclassical one (a qubit in contact with an environment) and a fully
+semiclassical system, which in this case displays chaotic behavior. Relations
+between quantum entanglement and classical dynamics are investigated.",0510162v1
+2006-06-24,Effective Hamiltonian approach to adiabatic approximation in open systems,"The adiabatic approximation in open systems is formulated through the
+effective Hamiltonian approach. By introducing an ancilla, we embed the open
+system dynamics into a non-Hermitian quantum dynamics of a composite system,
+the adiabatic evolution of the open system is then defined as the adiabatic
+dynamics of the composite system. Validity and invalidity conditions for this
+approximation are established and discussed. A High-order adiabatic
+approximation for open systems is introduced. As an example, the adiabatic
+condition for an open spin-$\frac 1 2$ particle in time-dependent magnetic
+fields is analyzed.",0606203v1
+1995-07-28,Screening current effects in Josephson junction arrays,"The purpose of this work is to compare the dynamics of arrays of Josephson
+junctions in presence of magnetic field in two different frameworks: the so
+called XY frustrated model with no self inductance and an approach that takes
+into account the screening currents (considering self inductances only). We
+show that while for a range of parameters the simpler model is sufficiently
+accurate, in a region of the parameter space solutions arise that are not
+contained in the XY model equations.",9507006v1
+2007-11-02,"Coherent, adiabatic and dissociation regimes in coupled atomic-molecular Bose-Einstein condensates","We discuss the dynamics of a Bose-Einstein condensate of atoms which is
+suddenly coupled to a condensate of molecules by an optical or magnetic
+Feshbach resonance. Three limiting regimes are found and can be understood from
+the transient dynamics occuring for each pair of atoms. This transient dynamics
+can be summarised into a time-dependent shift and broadening of the molecular
+state. A simple Gross-Pitaevskii picture including this shift and broadening is
+proposed to describe the system in the three regimes. Finally, we suggest how
+to explore these regimes experimentally.",0711.0397v2
+2008-03-03,Crackling dynamics in material failure as the signature of a self-organized dynamic phase transition,"We derive here a linear elastic stochastic description for slow crack growth
+in heterogeneous materials. This approach succeeds in reproducing
+quantitatively the intermittent crackling dynamics observed recently during the
+slow propagation of a crack along a weak heterogeneous plane of a transparent
+Plexiglas block [M{\aa}l{\o}y {\it et al.}, PRL {\bf 96} 045501]. In this
+description, the quasi-static failure of heterogeneous media appears as a
+self-organized critical phase transition. As such, it exhibits universal and to
+some extent predictable scaling laws, analogue to that of other systems like
+for example magnetization noise in ferromagnets.",0803.0190v2
+2008-03-31,Spectral Modeling of Magnetohydrodynamic Turbulent Flows,"We present a dynamical spectral model for Large Eddy Simulation of the
+incompressible magnetohydrodynamic (MHD) equations based on the Eddy Damped
+Quasi Normal Markovian approximation. This model extends classical spectral
+Large Eddy Simulations for the Navier-Stokes equations to incorporate general
+(non Kolmogorovian) spectra as well as eddy noise. We derive the model for MHD
+and show that introducing a new eddy-damping time for the dynamics of spectral
+tensors in the absence of equipartition between the velocity and magnetic
+fields leads to better agreement with direct numerical simulations, an
+important point for dynamo computations.",0803.4499v1
+2008-06-20,Dark dynamic acousto-optic ring lattices for ultracold atoms,"We demonstrate the optical generation of dynamic dark optical ring lattices,
+which do not require Laguerre-Gauss beams, large optical coherence lengths or
+interferometric stability. Simple control signals lead to spatial modulation
+and reproducible rotation, offering manifold possibilities for complex dynamic
+ring lattices. In conjunction with a magnetic trap, these scanned 2D intensity
+distributions from a single laser beam will enable precision trapping and
+manipulation of ultracold species using blue-detuned light. The technique is
+ideal for azimuthal ratchet, Mott insulator and persistent current experiments
+with quantum degenerate gases.",0806.3466v1
+2008-11-21,Nonlinear Magnetohydrodynamics from Gravity,"We apply the recently established connection between nonlinear fluid dynamics
+and AdS gravity to the case of the dyonic black brane in AdS_4. This yields the
+equations of fluid dynamics for a 2+1 dimensional charged fluid in a background
+magnetic field. We construct the gravity solution to second order in the
+derivative expansion. From this we find the fluid dynamical stress tensor and
+charge current to second and third order in derivatives respectively, along
+with values for the associated transport coefficients.",0811.3468v3
+2009-01-26,Assessment of Spatial-variant Noise Level in Real-time Dynamic MR Images - a Random Matrix Approach,"Accurate measurement of spatially variant noise in dynamic magnetic resonance
+(MR) images acquired using parallel imaging methods is problematic. We propose
+a new method based on the random matrix theory to accurately assess the noise
+level. The method is validated using numerical simulation and in-vivo dynamic
+cardiac MR images.",0901.4027v2
+2009-02-20,Perturbation theory of the dynamic inverse spin Hall effect with charge conservation,"We present gauge-invariant theory of the dynamic inverse spin Hall effect
+driven by the spin--orbit interaction in metallic systems. Charge conservation
+is imposed diagrammatically by including vertex corrections. We show the charge
+current is induced by an effective electric field that is proportional to the
+spin current pumped by the magnetization dynamics. The result is consistent
+with recent experiments.",0902.3507v2
+2009-06-17,The dynamical Casimir effect in a superconducting coplanar waveguide,"We investigate the dynamical Casimir effect in a coplanar waveguide (CPW)
+terminated by a superconducting quantum interference device (SQUID). Changing
+the magnetic flux through the SQUID parametrically modulates the boundary
+condition of the CPW, and thereby, its effective length. Effective boundary
+velocities comparable to the speed of light in the CPW result in broadband
+photon generation which is identical to the one calculated in the dynamical
+Casimir effect for a single oscillating mirror. We estimate the power of the
+radiation for realistic parameters and show that it is experimentally feasible
+to directly detect this nonclassical broadband radiation.",0906.3127v1
+2010-01-03,Generalized Gravi-Electromagnetism,"A self consistant and manifestly covariant theory for the dynamics of four
+charges (masses) (namely electric, magnetic, gravitational, Heavisidian) has
+been developed in simple, compact and consistent manner. Starting with an
+invariant Lagrangian density and its quaternionic representation, we have
+obtained the consistent field equation for the dynamics of four charges. It has
+been shown that the present reformulation reproduces the dynamics of individual
+charges (masses) in the absence of other charge (masses) as well as the
+generalized theory of dyons (gravito - dyons) in the absence gravito - dyons
+(dyons). key words: dyons, gravito - dyons, quaternion PACS NO: 14.80Hv",1001.0363v1
+2010-04-09,Equilibriumlike invaded cluster algorithm: critical exponents and dynamical properties,"We present a detailed study of the Equilibriumlike invaded cluster algorithm
+(EIC), recently proposed as an extension of the invaded cluster (IC) algorithm,
+designed to drive the system to criticality while still preserving the
+equilibrium ensemble. We perform extensive simulations on two special cases of
+the Potts model and examine the precision of critical exponents by including
+the leading corrections. We show that both thermal and magnetic critical
+exponents can be obtained with high accuracy compared to the best available
+results. The choice of the auxiliary parameters of the algorithm is discussed
+in context of dynamical properties. We also discuss the relation to the
+Li-Sokal bound for the dynamical exponent $z$.",1004.1509v1
+2010-06-08,Quench Dynamics of Entanglement in an Opened Anisotropic Spin-1/2 Heisenberg Chain,"The quantum entanglement dynamics of a one-dimensional spin-1/2 anisotropic
+XXZ model is studied using the method of the adaptive time-dependent
+density-matrix renormalization-group when two cases of quenches are performed
+in the system. An anisotropic interaction quench and the maximum number of
+domain walls of staggered magnetization quench are considered. The dynamics of
+pairwise entanglement between the nearest two qubits in the spin chain is
+investigated. The entanglement of the two-spin qubits can be created and
+oscillates in both cases of the quench. The anisotropic interaction has a
+strong influence on the oscillation frequency of entanglement.",1006.1417v1
+2010-06-09,Biconical critical dynamics,"A complete two loop renormalization group calculation of the multicritical
+dynamics at a tetracritical or bicritical point in anisotropic antiferromagnets
+in an external magnetic field is performed. Although strong scaling for the two
+order parameters (OPs) perpendicular and parallel to the field is restored as
+found earlier, in the experimentally accessible region the effective dynamical
+exponents for the relaxation of the OPs remain different since their equal
+asymptotic values are not reached.",1006.1766v2
+2010-06-24,Field-induced decay dynamics in square-lattice antiferromagnet,"Dynamical properties of the square-lattice Heisenberg antiferromagnet in
+applied magnetic field are studied for arbitrary value S of the spin. Above the
+threshold field for two-particle decays, the standard spin-wave theory yields
+singular corrections to the excitation spectrum with logarithmic divergences
+for certain momenta. We develop a self-consistent approximation applicable for
+S >= 1, which avoids such singularities and provides regularized magnon decay
+rates. Results for the dynamical structure factor obtained in this approach are
+presented for S = 1 and S = 5/2.",1006.4838v2
+2010-09-07,Entanglement dynamics of two qubits under the influence of external kicks and Gaussian pulses,"We have investigated the dynamics of entanglement between two spin-1/2 qubits
+that are subject to independent kick and Gaussian pulse type external magnetic
+fields analytically as well as numerically. Dyson time ordering effect on the
+dynamics is found to be important for the sequence of kicks. We show that
+""almost-steady"" high entanglement can be created between two initially
+unentangled qubits by using carefully designed kick or pulse sequences.",1009.1350v3
+2010-10-27,Classical zitterbewegung in reduced plasma dynamics,"The process of dynamical reduction of the Vlasov-Maxwell equations leads to
+the introduction of classical {\it zitterbewegung} effects in reduced plasma
+dynamics. These effects manifest themselves in the form of an asymmetric
+canonical energy-momentum tensor involving the decoupling of the reduced
+kinetic momentum ${\bf p}$ from the reduced velocity ${\bf u}$ (i.e., ${\bf
+u}\btimes{\bf p} \neq 0$) as well as reduced polarization and magnetization
+effects. The reduced intrinsic torque generated by the antisymmetric part of
+the canonical energy-momentum tensor, which is calculated from the reduced
+ponderomotive potential, acts as the source for the intrinsic (spin) angular
+momentum.",1010.5710v1
+2011-02-26,Electric signature of magnetic domain-wall dynamics,"We study current-induced domain-wall dynamics in a thin ferromagnetic
+nanowire. The domain-wall dynamics is described by simple equations with four
+parameters. We propose the procedure to determine these parameters by
+all-electric measurements of the time-dependent voltage induced by the
+domain-wall motion. We provide an analytical expression for the time variation
+of this voltage. Furthermore, we show that the measurement of the proposed
+effects is within reach with current experimental techniques.",1102.5459v2
+2011-09-12,Fourier-Hankel/Bessel space absolute equilibria of 2D gyrokinetics,"Two global invariants of two dimensional gyrokinetics are shown to be
+""rugged"" (still conserved by the dynamics) concerning both Fourier and
+Hankel/Bessel Galerkin truncations. The truncations are made to keep only a
+finite range of wavenumber $\textbf{k}$ and the Hankel variable $b$ (or $z$ in
+the Bessel series). The absolute equilibria are used for the discussion of the
+spectral transfers in the configuration-velocity scale space of kinetic
+magnetized plasma turbulence. Some interesting aspects of recent numerical
+results, which were not well understood, are explained with more satisfaction.",1109.2511v1
+2011-11-11,Out of equilibrium dynamics of coherent non-abelian gauge fields,"We study out-of-equilibrium dynamics of intense non-abelian gauge fields.
+Generalizing the well-known Nielsen-Olesen instabilities for constant initial
+color-magnetic fields, we investigate the impact of temporal modulations and
+fluctuations in the initial conditions. This leads to a remarkable coexistence
+of the original Nielsen-Olesen instability and the subdominant phenomenon of
+parametric resonance. Taking into account that the fields may be correlated
+only over a limited transverse size, we model characteristic aspects of the
+dynamics of color flux tubes relevant in the context of heavy-ion collisions.",1111.2751v2
+2011-11-29,Average quantum dynamics of closed systems over stochastic Hamiltonians,"We develop a master equation formalism to describe the evolution of the
+average density matrix of a closed quantum system driven by a stochastic
+Hamiltonian. The average over random processes generally results in decoherence
+effects in closed system dynamics, in addition to the usual unitary evolution.
+We then show that, for an important class of problems in which the Hamiltonian
+is proportional to a Gaussian random process, the 2nd-order master equation
+yields exact dynamics. The general formalism is applied to study the examples
+of a two-level system, two atoms in a stochastic magnetic field and the heating
+of a trapped ion.",1111.6686v1
+2012-01-04,Adjacent Spin Operator Dynamical Structure Factor of the S=1/2 Heisenberg Chain,"Considering the adjacent spin operators $S^z_jS^z_{j+1}$ and $S^-_jS^-_{j+1}$
+in the S=1/2 Heisenberg chain, we give a determinant representation of their
+form factors. The dynamical structure factors of the respective operators are
+computed over the whole Brillouin zone in several magnetic fields and the
+resulting signal is analyzed in terms of excitation types. Among other results,
+we find that the $S^z_jS^z_{j+1}$ dynamical structure factor carries a large
+weight of the 4-spinon excitations which are distinguishable from the 2-spinon
+signal because they are located outside the 2-spinon spectrum.",1201.0867v1
+2012-01-20,Simulations of Buoyant Plumes in Solar Prominences,"Observations of solar prominences reveal a complex, dynamic flow field within
+them. The flow field within quiescent prominences is characterized by long
+``threads'' and dark ``bubbles'' that fall and rise (respectively) in a thin
+sheet. The flow field in active prominences display more helical motions that
+travel along the axis of the prominence. We explore the possible dynamics of
+both of these with the aid of 2.5D MHD simulations. Our model, compressible
+plasma possesses density and temperature gradients and resides in magnetic
+field configurations that mimc those of a solar prominence. We present results
+of various configurations and discuss the nonlinear behavior of the resulting
+dynamics.",1201.4352v1
+2012-02-29,Dynamic Critical Behavior of the Heisenberg Model with Strong Easy Plane Anisotropy,"The dynamic critical behavior of the Heisenberg model with a strong
+anisotropy of the exchange constant in the z direction is investigated. The
+main features of the time evolution of this model are revealed. The static and
+dynamic critical behavior of planar magnetic models is shown to be described
+well by the Heisenberg model with strong easy plane anisotropy.",1202.6509v1
+2012-07-21,Controlling high-frequency collective electron dynamics via single-particle complexity,"We demonstrate, through experiment and theory, enhanced high-frequency
+current oscillations due to magnetically-induced conduction resonances in
+superlattices. Strong increase in the ac power originates from complex
+single-electron dynamics, characterized by abrupt resonant transitions between
+unbound and localized trajectories, which trigger and shape propagating charge
+domains. Our data demonstrate that external fields can tune the collective
+behavior of quantum particles by imprinting configurable patterns in the
+single-particle classical phase space.",1207.5166v1
+2012-08-21,Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime,"We report on dynamics of non-local Abrikosov vortex flow in mesoscopic
+superconducting Nb channels. Magnetic field dependence of the non-local voltage
+induced by the flux flow shows that vortices form ordered vortex chains.
+Voltage asymmetry (rectification) with respect to the direction of vortex flow
+is evidence that vortex jamming strongly moderates vortex dynamics in
+mesoscopic geometries. The findings can be applied to superconducting devices
+exploiting vortex dynamics and vortex manipulation, including superconducting
+wires with engineered pinning centers.",1208.4396v1
+2013-01-08,Dynamical Structure of Baryons,"Compton scattering offers a unique opportunity to study the dynamical
+structure of hadrons over a wide kinematic range, with polarizabilities
+characterizing the hadron active internal degrees of freedom. We present
+calculations and detailed analysis of electric and magnetic and the
+spin-dependent dynamical polarizabilities for the lowest in mass SU(3) octet of
+baryons. These extensive calculations are made possible by the recent
+implementation of semi-automatized calculations in chiral perturbation theory
+which allows evaluating polarizabilities from Compton scattering up to
+next-to-the-leading order. The dependencies for the range of photon energies
+covering the majority of the meson photoproduction channels are analyzed.",1301.1383v1
+2013-06-15,Monte Carlo simulations of dynamic phase transitions in ultrathin Blume-Capel films,"Dynamic phase transition phenomena in ultrathin films described by
+Blume-Capel model have been investigated using Monte Carlo simulations.
+Hysteresis loops, micromagnetic structures, and hysteresis loop area curves, as
+well as dynamic correlation between the magnetization and the external field
+have been studied as functions of the field, as well as the film parameters.
+The variation of critical coupling of the modified film surface at which the
+transition temperature becomes independent of film thickness have been
+clarified for varying system parameters. Frequency dispersion of hysteresis
+loop area have been found to obey a power law for low and moderate frequencies
+for both ordinary and enhanced surfaces.",1306.3562v1
+2013-06-24,Non-equilibrium dynamics in the antiferromagnetic Hubbard model,"We investigate by means of the time-dependent Gutzwiller approximation the
+out-of-equilibrium dynamics of an antiferromagnetic state evolved with the
+Hubbard model Hamiltonian after a sudden change of the repulsion strength $U$.
+We find that magnetic order survives more than what expected on the basis of
+thermalization arguments, in agreement with recent DMFT calculations. In
+addition, we find evidence of a dynamical transition for quenches to large
+values of $U$ between a coherent antiferromagnet characterized by a finite
+quasiparticle residue to an incoherent one with vanishing residue, that finally
+turns into a paramagnet for even larger $U$.",1306.5733v2
+2013-06-25,Dynamical spin-spin coupling of quantum dots,"We carried out a nested Schrieffer-Wolff transformation of an Anderson
+two-impurity Hamiltonian to study the spin-spin coupling between two dynamical
+quantum dots under the influence of rotating transverse magnetic field. As a
+result of the rotating field, we predict a novel Ising type spin-spin coupling
+mechanism between quantum dots, whose strength is tunable via the magnitude of
+the rotating field. The strength of the new coupling could be comparable to the
+strength of the RKKY coupling. The dynamical coupling with the intristic RKKY
+coupling enables to construct a four level system of maximally entangled Bell
+states in a controllable manner.",1306.5889v2
+2013-10-12,Resonant dynamics of chromium condensates,"We numerically study the dynamics of a spinor chromium condensate in low
+magnetic fields. We show that the condensate evolution has a resonant character
+revealing rich structure of resonances similar to that already discussed in the
+case of alkali-atoms condensates. This indicates that dipolar resonances occur
+commonly in the systems of cold atoms. In fact, they have been already observed
+experimentally. We further simulate two recent experiments with chromium
+condensates, in which the threshold in spin relaxation and the spontaneous
+demagnetization phenomena were observed. We demonstrate that both these effects
+originate in resonant dynamics of chromium condensate.",1310.3384v1
+2014-06-24,Ultrafast spectroscopy of quasiparticle dynamics in cuprate superconductors,"Ultrafast pump-probe spectroscopy is a powerful tool to study the
+nonequilibrium dynamics in high-Tc cuprate superconductors. The photo-induced
+quasiparticle (QP) dynamics revealed by pump-probe spectroscopy are sensitive
+to the near-Fermi level electronic structures. Here we review several selected
+examples to illustrate the enduring challenges including pairing glue, phase
+separation, and phase transitions in cuprate superconductors. We also present
+the data obtained on thin films of YBa2Cu3O7-{\delta} in connection to these
+issues.",1406.6207v1
+2014-09-19,Dynamical nonlocal coherent-potential approximation for itinerant electron magnetism,"A dynamical generalisation of the nonlocal coherent-potential approximation
+is derived based upon the functional integral approach to the interacting
+electron problem. The free energy is proven to be variational with respect to
+the self-energy provided a self-consistency condition on a cluster of sites is
+satisfied. In the present work, calculations are performed within the static
+approximation and the effect of the nonlocal physics on the formation of the
+local moment state in a simple model is investigated. The results reveal the
+importance of the dynamical correlations.",1409.5652v1
+2014-10-15,Micromagnetic Study of Spin Transfer driven Vortex Dipole and Vortex Quadrupole Dynamics,"Vortices and antivortices are typical non uniform magnetization
+configurations that can be achieved in spin-torque oscillators with in-plane
+materials. Dynamics of a vortex-antivortex pair, namely vortex dipole, were
+predicted and already observed. In this paper, we present a systematic
+micromagnetic study on that kind of dynamics in different spin-valves where the
+current is injected through a nano-aperture. Rotation and translation of vortex
+dipoles and rotation of vortex quadrupoles are shown depending on the shape and
+the size of the spin-valve. The origin of the different behaviors is explained
+within a micromagnetic framework.",1410.3957v1
+2015-07-08,Beam dynamics of the superconducting wiggler on the SSRF storage ring,"In the SSRF Phase-II beamline project, a Superconducting Wiggler (SW) will be
+installed in the electron storage ring. It may greatly impact on the beam
+dynamics due to the very high magnetic field. The emittance growth becomes a
+main problem, even after a well correction of the beam optics. A local
+achromatic lattice is studied, in order to combat the emittance growth and keep
+the good performance of the SSRF storage ring, as well as possible. Other
+effects of the SW are simulated and optimized as well, including the beta
+beating, the tune shift, the dynamic aperture, and the field error effects.",1507.02217v1
+2015-09-03,Dynamic Entanglement Evolution of Two-qubit XYZ Spin Chain in Markovian Environment,"We propose a new approach called Ket-Bra Entangled State (KBES) Method for
+converting master equation into Schr\""{o}dinger-like equation. With this
+method, we investigate decoherence process and entanglement dynamics induced by
+a $2$-qubit spin chain that each qubit coupled with reservoir. The spin chain
+is an anisotropy $XYZ$ Heisenberg model in the external magnetic field $B$, the
+corresponding master equation is solved concisely by KBES method; Furthermore,
+the effects of anisotropy, temperature, external field and initial state on
+concurrence dynamics is analyzed in detail for the case that initial state is
+Extended Wenger-Like(EWL) state. Finally we research the coherence and
+concurrence of the final state (namely the density operator for time tend to
+infinite)",1509.01001v1
+2015-10-16,Reaction diffusion dynamics and the Schryer-Walker solution for domain walls of the Landau-Lifshitz-Gilbert equation,"We study the dynamics of the equation obtained by Schryer and Walker for the
+motion of domain walls. The reduced equation is a reaction diffusion equation
+for the angle between the applied field and the magnetization vector. If the
+hard axis anisotropy $K_d$ is much larger than the easy axis anisotropy $K_u$,
+there is a range of applied fields where the dynamics does not select the
+Schryer-Walker solution. We give analytic expressions for the speed of the
+domain wall in this regime and the conditions for its existence.",1510.04927v1
+2016-02-04,Landscape-Inversion Phase Transition in Dipolar Colloids: Tuning the Structure and Dynamics of 2D Crystals,"We study the 2D crystalline phases of paramagnetic colloidal particles with
+dipolar interactions and constrained on a periodic substrate. Combining theory,
+simulation, and experiments we demonstrate a new scenario of first-order phase
+transitions that occurs via a complete inversion of the energy landscape,
+featuring non-conventional properties that allow for: (i) tuning of crystal
+symmetry; (ii) control of dynamical properties of different crystalline orders
+via tuning of their relative stability with an external magnetic field; (iii)
+an equivalent but independent control of the same dynamic properties via
+temporal modulations of that field; and (iv) non-standard phase-ordering
+kinetics involving spontaneous formation of transient metastable domains.",1602.01810v1
+2016-02-14,Recursive Recovery of Sparse Signal Sequences from Compressive Measurements: A Review,"In this article, we review the literature on design and analysis of recursive
+algorithms for reconstructing a time sequence of sparse signals from
+compressive measurements. The signals are assumed to be sparse in some
+transform domain or in some dictionary. Their sparsity patterns can change with
+time, although, in many practical applications, the changes are gradual. An
+important class of applications where this problem occurs is dynamic projection
+imaging, e.g., dynamic magnetic resonance imaging (MRI) for real-time medical
+applications such as interventional radiology, or dynamic computed tomography.",1602.04518v1
+2016-04-21,Contributions of plasma physics to chaos and nonlinear dynamics,"This topical review focusses on the contributions of plasma physics to chaos
+and nonlinear dynamics bringing new methods which are or can be used in other
+scientific domains. It starts with the development of the theory of Hamiltonian
+chaos, and then deals with order or quasi order, for instance adiabatic and
+soliton theories. It ends with a shorter account of dissipative and high
+dimensional Hamiltonian dynamics, and of quantum chaos. Most of these
+contributions are a spin-off of the research on thermonuclear fusion by
+magnetic confinement, which started in the fifties. Their presentation is both
+exhaustive and compact. [15 April 2016]",1604.06305v2
+2016-05-31,1/f noise in turbulent flows,"We report the experimental observation of $1/f$ fluctuations in three
+different turbulent flow configurations: the large scale velocity driven by a
+two-dimensional turbulent flow, the magnetic field generated by a turbulent
+swirling flow of liquid sodium and the pressure fluctuations due to vorticity
+filaments in a swirling flow. For these three systems, $1/f$ noise is shown to
+result from the dynamics of coherent structures that display transitions
+between a small number of states. The interevent duration is distributed as a
+power-law. The exponent of this power-law and the nature of the dynamics
+(transition between symmetric states or asymmetric ones) select the exponent of
+the $1/f$ fluctuations.",1605.09666v1
+2016-09-20,Renormalization group calculation of dynamic exponent in the models E and F with hydrodynamic fluctuations,"The renormalization group method is applied in order to analyze models E and
+F of critical dynamics in the presence of velocity fluctuations generated by
+the stochastic Navier-Stokes equation. Results are given to the one-loop
+approximation for the anomalous dimension $\gamma_\lambda$ and fixed-points'
+structure. The dynamic exponent $z$ is calculated in the turbulent regime and
+stability of the fixed points for the standard model E is discussed.",1609.06078v2
+2017-07-04,Dynamical Wormhole Definitions Confronted,"Crude comparison between four alternative proposals for the very definition
+of a wormhole is provided, all of which were intended to apply to the dynamical
+cases. An interesting dynamical solution, based upon large scale magnetic
+fields, is used for the comparisons. Such solution goes beyond the perfect
+fluid approximation due to an anisotropic pressure component, bringing to the
+fore some unsuspected features of those definitions. Certain notions as
+reversible traversability are claimed as a way to select among those
+definitions the best suited one to represent our intuition of what a wormhole
+solution is expected to be.",1707.01078v1
+2018-10-07,Tri-spin dynamics in alkali metal-noble gas NMR gyroscope,"Alkali metal-noble gas NMR gyroscope is widely used for precision rotation
+measurement in fundamental and applied physics. By numerically simulating the
+alkali-nuclear-nuclear tri-spin dynamics, we investigate the dependence of
+gyroscope response on alkali spin relaxation time and nuclear spin
+magnetization. We found additional resonance peaks appear due to a new source
+of instability, namely the inherent multistability of tri-spin dynamics. The
+numerical simulation results agree well with the recent experiment, enabling a
+better understanding and exploitation of the gyroscope signal.",1810.03185v4
+2018-12-03,Quantum plateaus in dynamical Hall conductivity,"Dynamical Hall conductivity {\sigma}_H({\omega}) of a 2D electron gas with
+impurities in the perpendicular magnetic field is analyzed. Plateau-like
+behavior at low frequencies as well as at high frequencies provided the
+complete filling of Landau levels is predicted. The broadening of a Landau
+level separates two frequency regions with different behaviour. Imaginary part
+of dynamical Hall conductivity reveals oscillations in the localized states
+region. Comparison with the experiment is carried out.",1812.00603v1
+2019-03-06,Cluster multipole dynamics in non-collinear antiferromagnets,"A systematic framework to investigate spin dynamics in non-collinear
+antiferromagnet is proposed. Taking Mn$_3$Sn as a representative example, we
+derive an effective low energy model based on the multipole expansion of the
+magnetic structure, and investigate the uniform precession and the domain wall
+dynamics. We show that the solution for the effective model accurately
+reproduces the numerical calculation of the Landau-Lifshitz-Gilbert equations.
+Our results indicate that Mn$_3$Sn has preferable properties for applications
+to a racetrack memory and a spin torque oscillator, and thus, is a promising
+candidate for new devices by using the multipole degrees of freedom.",1903.02259v1
+2020-05-04,A Dynamical Mean-Field Theory for Learning in Restricted Boltzmann Machines,"We define a message-passing algorithm for computing magnetizations in
+Restricted Boltzmann machines, which are Ising models on bipartite graphs
+introduced as neural network models for probability distributions over spin
+configurations. To model nontrivial statistical dependencies between the spins'
+couplings, we assume that the rectangular coupling matrix is drawn from an
+arbitrary bi-rotation invariant random matrix ensemble. Using the dynamical
+functional method of statistical mechanics we exactly analyze the dynamics of
+the algorithm in the large system limit. We prove the global convergence of the
+algorithm under a stability criterion and compute asymptotic convergence rates
+showing excellent agreement with numerical simulations.",2005.01560v1
+2020-06-16,Dynamical response and competing orders in two-band Hubbard model,"We present a dynamical mean-field study of two-particle dynamical response
+functions in two-band Hubbard model across several phase transitions. We
+observe that the transition between theexcitonic condensate and spin-state
+ordered state is continuous with a narrow strip of supersolidphase separating
+the two. Approaching transition from the excitonic condensate is announced
+bysoftening of the excitonic mode at theMpoint of the Brillouin zone. Inside
+the spin-state orderedphase there is a magnetically ordered state with 2x2
+periodicity, which has no precursor in thenormal phase.",2006.09058v1
+2021-04-16,Spin-ice dynamics of pyrochlore Dy2GaSbO7 with enhanced Pauling zero-point entropy,"We report the low-temperature magnetothermal properties and spin dynamics of
+a mixed pyrochlore, Dy2GaSbO7 through the coordination of measurements of dc
+magnetization, ac susceptibility, and heat capacity, and CF computation. In
+Dy2GaSbO7, the spins freeze at temperature Tice = 3.1 K, corresponding to
+dynamical spin-freezing into a disordered state in compliance with the spin-ice
+rules, but with enhanced zero-point entropy, unlike cannonical dipolar spin-ice
+materials, Dy2Ti2O7 and Ho2Ti2O7, due to random disorder and varied chemical
+pressure of B-site (GaSb tetrahedra) ions.",2104.07890v1
+2010-05-19,Charge dynamics in two-electron quantum dots,"We investigate charge dynamics in a two-electron double quantum dot. The
+quantum dot is manipulated by using a time-dependent external voltage that
+induces charge oscillations between the dots. We study the dependence of the
+charge dynamics on the external magnetic field and on the periodicity of the
+external potential. We find that for suitable parameter values, it is possible
+to induce both one-electron and two-electron oscillations between the dots.",1005.3369v1
+2013-08-26,Quantum criticality and dynamical instability in the kicked top,"We investigate precursors of critical behavior in the quasienergy spectrum
+due to the dynamical instability in the kicked top. Using a semiclassical
+approach, we analytically obtain a logarithmic divergence in the density of
+states, which is analogous to a continuous excited state quantum phase
+transition in undriven systems. We propose a protocol to observe the cusp
+behavior of the magnetization close to the critical quasienergy.",1308.5640v2
+2016-11-09,Short-Time Dynamics of the Three-Dimensional Fully Frustrated Ising Model,"The critical relaxation from the low-temperature ordered state of the
+three-dimensional fully frustrated Ising model on a simple cubic lattice has
+been studied using the short time dynamics method. Particles with the periodic
+boundary conditions containing N = 262144 spins have been studied. Calculations
+have been performed by the standard Metropolis Monte Carlo algorithm. The
+static critical exponents of the magnetization and correlation radius have been
+obtained. The dynamic critical exponent of the model under study has been
+calculated.",1611.02898v1
+2017-04-27,Periodic orbits in the restricted three-body problem and Arnold's $J^+$-invariant,"We apply Arnold's theory of generic smooth plane curves to Stark-Zeeman
+systems. This is a class of Hamiltonian dynamical systems that describes the
+dynamics of an electron in an external electric and magnetic field, and
+includes many systems from celestial mechanics. Based on Arnold's
+$J^+$-invariant, we introduce invariants of periodic orbits in planar
+Stark-Zeeman systems and study their behaviour.",1704.08568v1
+2018-05-07,Probing dynamics in quantum materials with femtosecond x-rays,"Optical pulses are routinely used to drive dynamical changes in the
+properties of solids. In quantum materials, many new phenomena have been
+discovered, including ultrafast transitions between electronic phases,
+switching of ferroic orders and nonequilibrium emergent behaviors such as
+photo-induced superconductivity. Understanding the underlying non-equilibrium
+physics requires detailed measurements of multiple microscopic degrees of
+freedom at ultrafast time resolution. Femtosecond x-rays are key to this
+endeavor, as they can access the dynamics of structural, electronic and
+magnetic degrees of freedom. Here, we cover a series of representative
+experimental studies in which ultrashort x-ray pulses from free electron lasers
+have been used, opening up new horizons for materials research.",1805.02376v1
+2018-08-28,Nonlinear Dynamics of Coupled Axion-Josephson Junction Systems,"We study the classical dynamics of an axion field (the signal) that is
+coupling into a Josephson junction (the detector) by means of a capacitive
+coupling of arbitrary size. Depending on the size of the coupling constant and
+the initial conditions, we find a rich phase space structure of this nonlinear
+problem. We present general analytic solutions of the equations of motion in
+the limit of small amplitudes of the angle variables, and discuss both the case
+of no dissipation and the case of dissipation in the system. The effect of a
+magnetic field is investigated as well, leading to topological phase
+transitions in the phase space structure.",1808.09417v1
+2021-08-13,Emulating ultrafast dissipative quantum dynamics with deep neural networks,"The simulation of driven dissipative quantum dynamics is often prohibitively
+computation-intensive, especially when it is calculated for various shapes of
+the driving field. We engineer a new feature space for representing the field
+and demonstrate that a deep neural network can be trained to emulate these
+dynamics by mapping this representation directly to the target observables. We
+demonstrate that with this approach, the system response can be retrieved many
+orders of magnitude faster. We verify the validity of our approach using the
+example of finite transverse Ising model irradiated with few-cycle magnetic
+pulses interacting with a Markovian environment. We show that our approach is
+sufficiently generalizable and robust to reproduce responses to pulses outside
+the training set.",2108.06261v1
+2021-08-25,On the derivation of guiding center dynamics without coordinate dependence,"The fundament of the classical guiding center theory is gyro-phase averaging,
+which cannot be well defined over a non-trivial magnetic field topology. The
+local gyro-phase coordinate frame hides the geometric nature of gyro-symmetry.
+A coordinate-free geometric representation should be a more appropriate
+alternative for a deeper understanding of the guiding center dynamics. In this
+paper, the motion of a charged particle is described by a Lagrangian one-form
+on a seven-dimensional phase space. The Lagrangian one-form is geometrically
+decomposed by constructing a coordinate-free gyro-averaging method. As a
+result, we obtain the coordinate-free expression of the non-relativistic
+guiding-center dynamics in the time-dependent slow-varying electromagnetic
+field.",2108.10996v2
+2021-10-27,Tail contributions to gravitational conservative dynamics,"We compute tail contributions to the conservative dynamics of a generic
+self-gravitating system, for every multipole order, of either electric and
+magnetic parity. Such contributions arise when gravitational radiation is
+backscattered by the static curvature generated by the source itself and
+reabsorbed. Tail processes are relevant for the study of compact binary
+dynamics starting from the fourth post-Newtonian order. Within this context, we
+resolve a discrepancy recently arised at fifth post-Newtonian order between
+Effective Field Theory and self-force results.",2110.14146v2
+2021-11-22,Counting edge modes via dynamics of boundary spin impurities,"We study dynamics of the one-dimensional Ising model in the presence of
+static symmetry-breaking boundary field via the two-time autocorrelation
+function of the boundary spin. We find that the correlations decay as a power
+law. We uncover a dynamical phase diagram where, upon tuning the strength of
+the boundary field, we observe distinct power laws that directly correspond to
+changes in the number of edge modes as the boundary and bulk magnetic field are
+varied. We suggest how the universal physics can be demonstrated in current
+experimental setups, such as Rydberg chains.",2111.11428v2
+2022-04-12,Explicit models of motions to understand protein side-chain dynamics,"Nuclear magnetic relaxation is widely used to probe protein dynamics. For
+decades, most analyses of relaxation in proteins have relied successfully on
+the model-free approach, forgoing mechanistic descriptions of motions.
+Model-free types of correlation functions cannot describe a large carbon-13
+relaxation dataset in protein sidechains. Here, we use molecular dynamics
+simulations to design explicit models of motion and solve Fokker-Planck
+diffusion equations. These models of motion provide better agreement with
+relaxation data, mechanistic insight and a direct link to configuration
+entropy.",2204.05813v2
+2022-08-26,"Geometric Reductions, Dynamics and Controls for Hamiltonian System with Symmetry","This is a survey article, from the viewpoint of the completeness of the
+Marsden- Weinstein reduction, to introduce briefly some recent developments of
+the symmetric reductions and Hamilton-Jacobi theory of the regular controlled
+Hamiltonian systems, the nonholonomic controlled Hamiltonian systems and the
+controlled magnetic Hamiltonian systems. These research reveal the deeply
+internal relationships of the geometrical structures of phase spaces, the
+nonholonomic constraint, the dynamical vector fields and the controls of these
+systems.",2208.12465v1
+2022-11-03,Dynamic phase transitions on the kagome Ising ferromagnet,"We perform extensive Monte Carlo simulations to investigate the dynamic phase
+transition properties of the two-dimensional kinetic Ising model on the kagome
+lattice in the presence of square-wave oscillating magnetic field. Through
+detailed finite-size scaling analysis, we study universality aspects of the
+non-equilibrium phase transition. Obtained critical exponents indicate that the
+two-dimensional kagome-lattice kinetic Ising model belongs to the same
+universality class with the corresponding Ising model in equilibrium. Moreover,
+dynamic critical exponent of the local moves used in simulations is determined
+with high precision. Our numerical results are compatible with the previous
+ones on kinetic Ising models.",2211.01709v1
+2023-03-24,Total Angular Momentum Conservation in Ab Initio Born-Oppenheimer Molecular Dynamics,"We prove both analytically and numerically that the total angular momentum of
+a molecular system undergoing adiabatic Born-Oppenheimer dynamics is conserved
+only when pseudo-magnetic Berry forces are taken into account. This finding
+sheds light on the nature of Berry forces for molecular systems with spin-orbit
+coupling and highlights how ab initio Born-Oppenheimer molecular dynamics
+simulations can successfully capture the entanglement of spin and nuclear
+degrees of freedom as modulated by electronic interactions.",2303.13787v1
+2023-08-08,Blocking particle dynamics in diamond chain with spatially increasing flux,"Spatial non-uniformity in tight-binding models serves as a source of rich
+phenomena. In this paper, we study a diamond-chain tight-binding model with a
+spatially-modulated magnetic flux at each plaquette. In the numerical studies
+with various combinations of the minimum and maximum flux values, we find the
+characteristic dynamics of a particle, namely, a particle slows down when
+approaching the plaquette with $\pi$-flux. This originates from the fact that
+the sharply localized eigenstates exist around the $\pi$-flux plaquette. These
+localized modes can be understood from a squared model of the original one.
+This characteristic blocked dynamics will be observed in photonic waveguides or
+cold atoms.",2308.03971v1
+2023-11-17,Enhancing Electron-Nuclear Resonances by Dynamical Control Switching,"We present a general method to realize resonant coupling between spins even
+though their energies are of different scales. Applying the method to the
+electron and nuclear spin systems such as a nitrogen-vacancy (NV) center with
+its nearby nuclei, we show that a specific dynamical switching of the electron
+spin Rabi frequency achieves efficient electron-nuclear coupling, providing a
+much stronger quantum sensing signal and dynamic nuclear polarization than
+previous methods. This protocol has applications in high-field nanoscale
+nuclear magnetic resonances as well as low-power quantum control of nuclear
+spins.",2311.10650v1
+2024-02-01,Dynamics of a Superconducting Linear Slider,"In this paper, the dynamic behavior of a one degree-of-freedom (DOF)
+contactless linear slider based on superconducting magnetic levitation is
+experimentally analyzed. The device is intended for precision positioning of an
+optic mirror in cryogenic environments. Different prototypes of this device
+have been tested at cryogenic temperatures (77 K), and their mechanical
+behavior characterized in the sliding direction for forced and unforced
+oscillations. Experimental results reveal that the slider is self-stable at the
+initial equilibrium position and the dynamic behavior fits well an underdamped
+harmonic oscillator. Finally, the device showed great potential for horizontal
+vibration isolation, acting as a low-pass filter with a resonance at about 0.9
+Hz",2402.00917v1
+2024-03-01,Chaos-assisted Turbulence in Spinor Bose-Einstein Condensates,"We present a turbulence-sustaining mechanism in a spinor Bose-Einstein
+condensate, which is based on the chaotic nature of internal spin dynamics.
+Magnetic driving induces a complete chaotic evolution of the local spin state,
+thereby continuously randomizing the spin texture of the condensate to maintain
+the turbulent state. We experimentally demonstrate the onset of turbulence in
+the driven condensate as the driving frequency changes and show that it is
+consistent with the regular-to-chaotic transition of the local spin dynamics.
+This chaos-assisted turbulence establishes the spin-driven spinor condensate as
+an intriguing platform for exploring quantum chaos and related superfluid
+turbulence phenomena.",2403.00524v1
+2024-03-15,Critical Fluctuations at Finite-Time Dynamical Phase Transition,"We explore the critical properties of the recently discovered finite-time
+dynamical phase transition in the non-equilibrium relaxation of Ising magnets.
+The transition is characterized by a sudden switch in the relaxation dynamics
+and it occurs at a sharp critical time. While previous works have focused
+either on mean-field interactions or on investigating the properties of the
+critical time, we analyze the critical fluctuations at the phase transition in
+the nearest-neighbor Ising model on a square lattice using Monte Carlo
+simulations. By means of a finite-size scaling analysis, we extract the
+critical exponents for the transition. In two spatial dimensions, the exponents
+are consistent with those of the two-dimensional Ising universality class.",2403.10505v1
+2001-11-20,The longitudinal dynamic correlation and dynamic susceptibility of the isotropic XY-model on the 1d alternating superlattice,"The dynamic susceptibility $\chi_{Q}^{zz}(\omega)$ of the isotropic XY-model
+(s=1/2) on the alternating superlattice (closed chain) in a transverse field
+$h$ is obtained exactly at arbitrary temperatures. It is determined from the
+results obtained for the dynamic correlations $<S_{jn}^{z}(t)S_{lm}^{z}(0)>$,
+which have been calculated by introducing the generalized Jordan-Wigner
+transformation, by using Wick's theorem and by reducing the problem to a
+diagonalization of a finite matrix. The static properties are also reobtained
+within this new formalism and all exact results are determined for arbitrary
+temperatures. Explicit results are obtained numerically in the limit T=0, where
+the critical behaviour occurs. A detailed analysis is presented for the
+behaviour of the static susceptibility $\chi_{Q}^{zz}(0)$, as a function of the
+transverse field h, and for the frequency dependency of the dynamic
+susceptibility $\chi_{Q}^{zz}(\omega)$. It is also shown, in this temperature
+limit, that within the magnetization plateaus which correspond to the different
+phases, even when the induced magnetization is not saturated, the effective
+dynamic correlation, $<\sum\limits_{n;m\in
+cell:\text{}j;l}S_{jn}^{z}(t)S_{lm}^{z}(0)>$, is time independent, which
+constitutes an unexpected result.",0111372v1
+2005-12-19,Dynamal (super)symmetries of monopoles and vortices,"The dynamical (super)symmetries for various monopole systems are reviewed.
+For a Dirac monopole, no smooth Runge-Lenz vector can exist; there is, however,
+a spectrum-generating conformal $o(2,1)$ dynamical symmetry that extends into
+$osp(1/1)$ or $osp(1/2)$ for spin 1/2 particles. Self-dual 't
+Hooft-Polyakov-type monopoles admit an $su(2/2)$ dynamical supersymmetry
+algebra, which allows us to reduce the fluctuation equation to the spin zero
+case. For large $r$ the system reduces to a Dirac monopole plus an suitable
+inverse-square potential considered before by McIntosh and Cisneros, and by
+Zwanziger in the spin 0 case, and to the `dyon' of D'Hoker and Vinet for spin
+1/2. The asymptotic system admits a Kepler-type dynamical symmetry as well as a
+`helicity-supersymmetry' analogous to the one Biedenharn found in the
+relativistic Kepler problem. Similar results hold for the Kaluza-Klein monopole
+of Gross-Perry-Sorkin. For the magnetic vortex, the N=2 supersymmetry of the
+Pauli Hamiltonian in a static magnetic field in the plane combines with the
+$o(2)\times o(2,1)$ bosonic symmetry into an $o(2)\times osp(1/2)$ dynamical
+superalgebra.",0512233v2
+2013-07-19,"Gauge turbulence, topological defect dynamics, and condensation in Higgs models","The real-time dynamics of topological defects and turbulent configurations of
+gauge fields for electric and magnetic confinement are studied numerically
+within a 2+1D Abelian Higgs model. It is shown that confinement is appearing in
+such systems equilibrating after a strong initial quench such as the
+overpopulation of the infrared modes. While the final equilibrium state does
+not support confinement, metastable vortex defect configurations appear in the
+gauge field which are found to be closely related to the appearance of
+physically observable confined electric and magnetic charges. These phenomena
+are seen to be intimately related to the approach of a non-thermal fixed point
+of the far-from-equilibrium dynamical evolution, signalled by universal scaling
+in the gauge-invariant correlation function of the Higgs field. Even when the
+parameters of the Higgs action do not support condensate formation in the
+vacuum, during this approach, transient Higgs condensation is observed. We
+discuss implications of these results for the far-from-equilibrium dynamics of
+Yang-Mills fields and potential mechanisms how confinement and condensation in
+non-abelian gauge fields can be understood in terms of the dynamics of Higgs
+models. These suggest that there is an interesting new class of dynamics of
+strong coherent turbulent gauge fields with condensates.",1307.5301v1
+2014-04-24,Computer Simulation of Quantum Dynamics in a Classical Spin Environment,"In this paper a formalism for studying the dynamics of quantum systems
+coupled to classical spin environments is reviewed. The theory is based on
+generalized antisymmetric brackets and naturally predicts open-path
+off-diagonal geometric phases in the evolution of the density matrix. It is
+shown that such geometric phases must also be considered in the
+quantum-classical Liouville equation for a classical bath with canonical phase
+space coordinates; this occurs whenever the adiabatics basis is complex (as in
+the case of a magnetic field coupled to the quantum subsystem). When the
+quantum subsystem is weakly coupled to the spin environment, non-adiabatic
+transitions can be neglected and one can construct an effective non-Markovian
+computer simulation scheme for open quantum system dynamics in classical spin
+environments. In order to tackle this case, integration algorithms based on the
+symmetric Trotter factorization of the classical-like spin propagator are
+derived. Such algorithms are applied to a model comprising a quantum two-level
+system coupled to a single classical spin in an external magnetic field.
+Starting from an excited state, the population difference and the coherences of
+this two-state model are simulated in time while the dynamics of the classical
+spin is monitored in detail. It is the author's opinion that the numerical
+evidence provided in this paper is a first step toward developing the
+simulation of quantum dynamics in classical spin environments into an effective
+tool. In turn, the ability to simulate such a dynamics can have a positive
+impact on various fields, among which, for example, nano-science.",1404.6143v1
+2015-06-26,Dynamical extension of Hellmann-Feynman theorem and application to nonadiabatic quantum processes in Topological and Correlated Matter,"An extension of the Hellmann-Feynman theorem to one employing dynamical
+parameters that vary with time according to quantum dynamics is rigorously
+derived, avoiding any linear response or other approximations. The resulting
+theorem for the dynamics of observables, valid to all orders in external
+fields, is found to contain generalized Berry curvature type of quantities that
+incorporate the dynamics through explicit and nontrivial time-dependence; these
+Berry quantities resemble the so called anomalous terms (in semiclassical
+equations of motion in solids) but are both of magnetic and electric type, the
+former being associated with Quantum Hall Effect type of behaviors and the
+latter with Polarization type of behaviors. By way of application of the new
+theorem, the quantum equations of motion of a spinless and a spinfull electron
+in a solid are derived without any adiabatic or semiclassical approximation.
+The charge current formula for a many-body and interacting spinfull system is
+also derived and is found to consist of a longitudinal and a transverse part;
+phenomenological interpretations with respect to polarization and magnetization
+currents respectively then emerge in a natural way. In addition, a formula for
+the topological magnetoelectric effect for an interacting spinfull electron
+system is also provided. By carefully defining singlevaluedness in parameter
+space, in a nonstandard fashion and in higher rigor than usual, we are able to
+discuss in clarity the issue of possible obstruction of this singlevaluedness,
+the associated creation of Berry monopoles in parameter space and the
+quantization of the flux of Berry curvature (but with nontrivial dynamics
+included in its definition).",1506.08812v2
+2018-06-21,Dynamically Generated Synthetic Electric Fields for Photons,"Static synthetic magnetic fields give rise to phenomena including the Lorentz
+force and the quantum Hall effect even for neutral particles, and they have by
+now been implemented in a variety of physical systems. Moving towards fully
+dynamical synthetic gauge fields allows, in addition, for backaction of the
+particles' motion onto the field. If this results in a time-dependent vector
+potential, conventional electromagnetism predicts the generation of an electric
+field. Here, we show how synthetic electric fields for photons arise
+self-consistently due to the nonlinear dynamics in a driven system. Our
+analysis is based on optomechanical arrays, where dynamical gauge fields arise
+naturally from phonon-assisted photon tunneling. We study open, one-dimensional
+arrays, where synthetic magnetic fields are absent. However, we show that
+synthetic electric fields can be generated dynamically, which, importantly,
+suppress photon transport in the array. The generation of these fields depends
+on the direction of photon propagation, leading to a novel mechanism for a
+photon diode, inducing nonlinear nonreciprocal transport via dynamical
+synthetic gauge fields.",1806.08191v3
+2020-02-23,Anisotropic dynamics of a self-assembled colloidal chain in an active bath,"Anisotropic macromolecules exposed to non-equilibrium (active) noise are very
+common in biological systems, and an accurate understanding of their
+anisotropic dynamics is therefore crucial. Here, we experimentally investigate
+the dynamics of isolated chains assembled from magnetic microparticles at a
+liquid-air interface and moving in an active bath consisting of motile E. coli
+bacteria. We investigate both the internal chain dynamics and the anisotropic
+center-of-mass dynamics through particle tracking. We find that both the
+internal and center-of-mass dynamics are greatly enhanced compared to the
+passive case, i.e., a system without bacteria, and that the center-of-mass
+diffusion coefficient $D$ features a non-monotonic dependence as a function of
+the chain length. Furthermore, our results show that the relationship between
+the components of $D$ parallel and perpendicular with respect to the direction
+of the applied magnetic field is preserved in the active bath compared to the
+passive case, with a higher diffusion in the parallel direction, in contrast to
+previous findings in the literature. We argue that this qualitative difference
+is due to subtle differences in the experimental geometry and conditions and
+the relative roles played by long-range hydrodynamic interactions and
+short-range collisions.",2002.09961v2
+2020-10-12,Tunable dynamical magnetoelectric effect in antiferromagnetic topological insulator MnBi$_2$Te$_4$ films,"More than forty years ago, axion was postulated as an elementary particle
+with a low mass and weak interaction in particle physics to solve the strong
+$\mathcal{CP}$ (charge conjugation and parity) puzzle. Axions are also
+considered as a possible component of dark matter of the universe. However, the
+existence of axions in nature has not been confirmed. Interestingly, axions
+arise as pseudoscalar fields derived from the Chern-Simons theory in condensed
+matter physics. In antiferromagnetic insulators, the axion field can become
+dynamical induced by spin-wave excitations and exhibits rich exotic phenomena,
+such as, the chiral magnetic effect, axionic polariton and so on. However, the
+study of the dynamical axion field is rare due to the lack of real materials.
+Recently, MnBi$_2$Te$_4$ was discovered to be an antiferromagnetic topological
+insulator with a quantized axion field protected by the inversion symmetry
+$\mathcal{P}$ and the magnetic-crystalline symmetry $\mathcal{S}$. Here, we
+studied MnBi$_2$Te$_4$ films in which both the $\mathcal{P}$ and $\mathcal{S}$
+symmetries are spontaneously broken and found that the dynamical axion field
+and largely tunable dynamical magnetoelectric effects can be realized through
+tuning the thickness of MnBi$_2$Te$_4$ films, the temperature and the element
+substitution. Our results open a broad avenue to study axion dynamics in
+antiferromagnetic topological insulator MnBi$_2$Te$_4$ and related materials,
+and also is hopeful to promote the research of dark matter.",2010.05424v1
+2021-01-14,Quantum dynamics of a single fluxon in Josephson junctions parallel arrays with large kinetic inductances,"We present a theoretical study of coherent quantum dynamics of a single
+magnetic fluxon (MF) trapped in Josephson junction parallel arrays (JJPAs) with
+large kinetic inductances. The MF is the topological excitation carrying one
+quantum of magnetic flux, $\Phi_0$. The MF is quantitatively described as the
+$2\pi$-kink in the distribution of Josephson phases, and for JJPAs with high
+kinetic inductances the characteristic length of such distribution (""the size""
+of MF) is drastically reduced. Characterizing such MFs by the Josephson phases
+of three consecutive Josephson junctions we analyse the various coherent
+macroscopic quantum effects in the MF quantum dynamics. In particular, we
+obtain the MF energy band originating from the coherent quantum tunnelling of a
+single MF between adjacent cells of JJPAs. The dependencies of the band width
+$\Delta$ on the Josephson coupling energy $E_J$, charging energy $E_C$ and the
+inductive energy of a cell $E_L$, are studied in detail. In long linear JJPAs
+the coherent quantum dynamics of MF demonstrates decaying quantum oscillations
+with characteristic frequency $f_{qb}=\Delta/h$. In short annular JJPAs the
+coherent quantum dynamics of MF displays complex oscillations controlled by the
+Aharonov-Casher phase $\chi \propto V_g$, where $V_g$ is an externally applied
+gate voltage. In the presence of externally applied dc bias, $I$, a weakly
+incoherent dynamics of quantum MF is realized in the form of macroscopic Bloch
+oscillations leading to a typical ""nose"" current-voltage characteristics of
+JJPAs. As ac current with frequency $f$ is applied the current-voltage
+characteristics displays a set of equidistant current steps at $I_n=2en f$.",2101.05693v1
+2021-01-27,Coherent dynamics of multi-spin $\rm V_B^-$ centers in hexagonal boron nitride,"Hexagonal boron nitride (hBN) has recently been demonstrated to contain
+optically polarized and detected electron spins that can be utilized for
+implementing qubits and quantum sensors in nanolayered-devices. Understanding
+the coherent dynamics of microwave driven spins in hBN is of crucial importance
+for advancing these emerging new technologies. Here, we demonstrate and study
+the Rabi oscillation and related dynamical phenomena of the negatively charged
+boron vacancy ($\rm V_B^-$) spins in hBN. We report on different dynamics of
+the $\rm V_B^-$ spins at weak and strong magnetic fields. In the former case
+the defect behaves like a single electron spin system, while in the latter case
+it behaves like a multi-spin system exhibiting the multiple-frequency dynamical
+oscillation like clear beat in Ramsey fringes. We also carry out theoretical
+simulations for the spin dynamics of $\rm V_B^-$ and reveal that the nuclear
+spins can be driven via the strong electric-nuclear coupling existing in $\rm
+V_B^-$ center, which can be modulated by the magnetic field and microwave
+field.",2101.11220v3
+2019-02-21,Mathematical analysis and numerical solution of models with dynamic Preisach hysteresis,"Hysteresis is a phenomenon that is observed in a great variety of physical
+systems, which leads to a nonlinear and multivalued behavior, making their
+modeling and control difficult. Even though the analysis and mathematical
+properties of classical or rate-independent hysteresis models are known, this
+is not the case for dynamic models where current approaches lack a proper
+functional analytic framework which is essential to formulate optimization
+problems and develop stable numerics, both being crucial in practice. This
+paper deals with the description and mathematical analysis of the dynamic
+Preisach hysteresis model. Toward that end, we complete a widely accepted
+definition of the dynamic model commonly used to describe the constitutive
+relation between the magnetic field H and the magnetic induction B, in which,
+the values of B not only depends on the present values of H but also on the
+past history and its velocity. We first analyze mathematically some important
+properties of the model and compare them with known results for the static
+Preisach model. Then, we consider a parabolic problem with dynamic hysteresis
+motivated by electromagnetic field equations. Under suitable assumptions, we
+show the well posedness of a weak formulation of the problem and solve it
+numerically.
+  Finally, we report a numerical test in order to assess the order of
+convergence and to illustrate the behavior of the numerical solution for
+different configurations of the dynamic Preisach model",1902.08175v1
+2020-09-03,Dynamics of magnetic collective modes in the square and triangular lattice Mott insulators at finite temperature,"We study the equilibrium dynamics of magnetic moments in the Mott insulating
+phase of the Hubbard model on the square and triangular lattice. We rewrite the
+Hubbard interaction in terms of an auxiliary vector field and use a recently
+developed Langevin scheme to study its dynamics. A thermal `noise', derivable
+approximately from the Keldysh formalism, allows us to study the effect of
+finite temperature. At strong coupling, $U \gg t$, where $U$ is the local
+repulsion and $t$ the nearest neighbour hopping, our results reproduce the well
+known dynamics of the nearest neighbour Heisenberg model with exchange $J \sim
+{\cal O}(t^2/U)$. These include crossover from weakly damped dispersive modes
+at temperature $T \ll J$ to strong damping at $T \sim {\cal O}(J)$, and
+diffusive dynamics at $T \gg J$. The crossover temperatures are naturally
+proportional to $J$. To highlight the progressive deviation from Heisenberg
+physics as $U/t$ reduces we compute an effective exchange scale $J_{eff}(U)$
+from the low temperature spin wave velocity. We discover two features in the
+dynamical behaviour with decreasing $U/t$: (i)~the low temperature dispersion
+deviates from the Heisenberg result, as expected, due to longer range and
+multispin interactions, and (ii)~the crossovers between weak damping, strong
+damping, and diffusion take place at noticeably lower values of $T/J_{eff}$. We
+relate this to enhanced mode coupling, in particular to thermal amplitude
+fluctuations, at weaker $U/t$. A comparison of the square and triangular
+lattice reveals the additional effect of geometric frustration on damping.",2009.01833v2
+2020-09-22,Simulating the dynamics and non-thermal emission of relativistic magnetised jets I. Dynamics,"We have performed magneto-hydrodynamic simulations of relativistic jets from
+supermassive blackholes over a few tens of kpc for a range of jet parameters.
+One of the primary aims were to investigate the effect of different MHD
+instabilities on the jet dynamics and their dependence on the choice of jet
+parameters. We find that two dominant MHD instabilities affect the dynamics of
+the jet, small scale Kelvin- Helmholtz (KH) modes and large scale kink modes,
+whose evolution depend on internal jet parameters like the Lorentz factor, the
+ratio of the density and pressure to the external medium and the magnetisation
+and hence consequently on the jet power. Low power jets are susceptible to both
+instabilities, kink modes for jets with higher central magnetic field and KH
+modes for lower magnetisation. Moderate power jets do not show appreciable
+growth of kink modes, but KH modes develop for lower magnetisation. Higher
+power jets are generally stable to both instabilities. Such instabilities
+decelerate and decollimate the jet while inducing turbulence in the cocoon,
+with consequences on the magnetic field structure. We model the dynamics of the
+jets following a generalised treatment of the Begelman-Cioffi relations which
+we present here. We find that the dynamics of stable jets match well with
+simplified analytic models of expansion of non self-similar FRII jets, whereas
+jets with prominent MHD instabilities show a nearly self-similar evolution of
+the morphology as the energy is more evenly distributed between the jet head
+and the cocoon.",2009.10475v1
+2023-04-28,Interplay of electron-magnon scattering and spin-orbit induced electronic spin-flip fcattering in a two-band Stoner model,"Magnons are one of the carriers of angular momentum that are involved in the
+ultrafast magnetization dynamics in ferromagnets, but their contribution to the
+electronic dynamics and their interplay with other scattering process that
+occur during ultrafast demagnetization has not yet been studied in the
+framework of a microscopic dynamical model. The present paper presents such an
+investigation of electronic scattering dynamics in itinerant ferromagnets at
+the level of Boltzmann scattering integrals for the magnon distributions and
+spin-dependent electron distributions. In addition to electron-magnon
+scattering, we include spin-conserving and effective Elliott-Yafet like
+spin-flip electron-electron scattering processes and the influence of phonons.
+In our model system, the creation or annihilation of magnons leads to
+transitions between two spin-split electronic bands with energy and momentum
+conservation. Due to the presence of spin-orbit coupling, Coulomb scattering
+transitions between these bands are also possible, and we describe them on an
+equal footing in terms of Boltzmann scattering integrals. For an instantaneous
+carrier excitation process we analyze the influence of both interaction
+processes on the magnon and spin-dependent electron dynamics, and show that
+their interplay gives rise to an efficient creation of magnons at higher
+energies and wave vectors accompanied by only a small increase of the
+electronic spin polarization. These results present a microscopic dynamical
+scenario that shows how non-equilibrium magnons may dominate the magnetic
+response of a ferromagnet on ultrafast timescales.",2304.14978v1
+2023-11-09,Skyrmion-Excited Spin Wave Fractal Network,"Magnetic skyrmions exhibit unique, technologically relevant pseudo-particle
+behaviors which arise from their topological protection, including
+well-defined, three-dimensional dynamic modes that occur at microwave
+frequencies. During dynamic excitation, spin waves are ejected into the
+interstitial regions between skyrmions, creating the magnetic equivalent of a
+turbulent sea. However, since the spin waves in these systems have a
+well-defined length scale, and the skyrmions are on an ordered lattice, ordered
+structures from spin wave interference can precipitate from the chaos. This
+work uses small angle neutron scattering (SANS) to capture the dynamics in
+hybrid skyrmions and investigate the spin wave structure. Performing
+simultaneous ferromagnetic resonance and SANS, the diffraction pattern shows a
+large increase in low-angle scattering intensity which is present only in the
+resonance condition. This scattering pattern is best fit using a mass fractal
+model, which suggests the spin waves form a long-range fractal network. The
+fractal structure is constructed of fundamental units with a size that encodes
+the spin wave emissions and are constrained by the skyrmion lattice. These
+results offer critical insights into the nanoscale dynamics of skyrmions,
+identify a new dynamic spin wave fractal structure, and demonstrates SANS as a
+unique tool to probe high-speed dynamics.",2311.05469v1
+2003-09-08,Scale-Free Magnetic Networks: Comparing Observational Data with a Self-Organizing Model of the Coronal Field,"We propose that the coronal magnetic field, linking concentrations on the
+photosphere through an interwoven web of flux, embodies a scale-free network.
+It arises from a self-organized critical dynamics including flux emergence, the
+diffusion and merging of magnetic concentrations, as well as avalanches of
+reconnecting flux tubes. Magnetic concentrations such as fragments, pores and
+sunspots, are `nodes' joined by flux tubes or `links'. The number of links
+emanating from a node is scale-free. We reanalyze the quiet-Sun data of Close
+et al and show that the distribution of magnetic concentration strengths is a
+power law with an index $\gamma= 1.7 \pm 0.3$, over the entire range of the
+measurement, about $(2-500)\times 10^{17}$ Mx. This distribution is compatible
+with that for the sizes of active regions reported by Harvey and Schwaan. Thus
+magnetic concentrations may be scale-free from the smallest measurable
+fragments to the large active regions. Numerical simulations of a
+self-organized critical model give the same index $\gamma$, within statistical
+uncertainty. The exponential distribution of flux tube lengths also agrees
+quantitatively with results from the model. Calibration with the measured
+diffusion constant of magnetic concentrations allows us to calculate a flux
+turnover time in the model to be of order 10 hours and the total solar flux to
+be of order $10^{23}$Mx, agreeing with observations. We introduce two other
+statistical quantities to characterize scale-free networks. The probability
+distribution for the amount of flux connecting a pair of concentrations, and
+the number of distinct concentrations linked to a given one are predicted to be
+scale-free, with different indices. Our approach unifies the observation of
+scale free flare energies with the coronal magnetic field structure.",0309230v1
+2007-07-04,Magnetically-dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions,"It has been suggested that magnetic fields play a dynamically-important role
+in core-collapse explosions of massive stars. In particular, they may be
+important in the collapsar scenario for gamma-ray bursts (GRB), where the
+central engine is a hyper-accreting black hole or a millisecond magnetar. The
+present paper is focussed on the magnetar scenario, with a specific emphasis on
+the interaction of the magnetar magnetosphere with the infalling stellar
+envelope. First, the ``Pulsar-in-a-Cavity'' problem is introduced as a paradigm
+for a magnetar inside a collapsing star. The basic set-up of this fundamental
+plasma-physics problem is described, outlining its main features, and simple
+estimates are derived for the evolution of the magnetic field. In the context
+of a collapsing star, it is proposed that, at first, the ram pressure of the
+infalling plasma acts to confine the magnetosphere, enabling a gradual build-up
+of the magnetic pressure. At some point, the growing magnetic pressure
+overtakes the (decreasing) ram pressure of the gas, resulting in a
+magnetically-driven explosion. The explosion should be highly anisotropic, as
+the hoop-stress of the toroidal field, confined by the surrounding stellar
+matter, collimates the magnetically-dominated outflow into two beamed
+magnetic-tower jets. This creates a clean narrow channel for the escape of
+energy from the central engine through the star, as required for GRBs. In
+addition, the delayed onset of the collimated-explosion phase can explain the
+production of large quantities of Nickel-56, as suggested by the GRB-Supernova
+connection. Finally, the prospects for numerical simulations of this scenario
+are discussed.",0707.0576v1
+2008-06-18,Numerical simulation of excitation and propagation of helioseismic MHD waves: Effects of inclined magnetic field,"Investigation of propagation, conversion, and scattering of MHD waves in the
+Sun is very important for understanding the mechanisms of observed oscillations
+and waves in sunspots and active regions. We have developed 3D linear MHD
+numerical model to investigate influence of the magnetic field on excitation
+and properties of the MHD waves. The results show that the magnetic field can
+substantially change the properties of the surface gravity waves (f-mode), but
+their influence on the acoustic-type waves (p-modes) is rather moderate.
+Comparison our simulations with the time-distance helioseismology results from
+SOHO/MDI shows that the travel time variations caused by the inclined magnetic
+field do not exceed 25% of the observed amplitude even for strong fields of
+1400-1900 G. This can be an indication that other effects (e.g. background
+flows and non-uniform distribution of magnetic field) can contribute to the
+observed travel time variations. The travel time variations caused by the wave
+interaction with magnetic field are in phase with the observations for strong
+fields of 1400-1900 G if Doppler velocities are taken at the height of 300 km
+above the photosphere where plasma parameter beta<<1. The simulations show that
+the travel times only weakly depend on the height of velocity observation. For
+the photospheric level the travel times are systematically smaller on
+approximately 0.12 min then for the hight of 300 km above the photosphere for
+all studied ranges of the magnetic field strength and inclination angles. The
+numerical MHD wave modeling and new data from the HMI instrument of the Solar
+Dynamics Observatory will substantially advance our knowledge of the wave
+interaction with strong magnetic fields on the Sun and improve the local
+helioseismology diagnostics.",0806.2897v1
+2008-10-06,"The structure and dynamics of a bright point as seen with Hinode, SoHO and TRACE","Our aim is to determine the plasma properties of a coronal bright point and
+compare its magnetic topology extrapolated from magnetogram data with its
+appearance in X-ray images. We analyse spectroscopic data obtained with
+EIS/Hinode, Ca II H and G-band images from SOT/Hinode, UV images from TRACE,
+X-ray images from XRT/Hinode and high-resolution/high-cadence magnetogram data
+from MDI/SoHO. The BP comprises several coronal loops as seen in the X-ray
+images, while the chromospheric structure consists of tens of small bright
+points as seen in Ca II H. An excellent correlation exists between the Ca II
+BPs and increases in the magnetic field, implying that the Ca II H passband is
+a good indicator for the concentration of magnetic flux. Doppler velocities
+between 6 and 15 km/s are derived from the Fe XII and Fe XIII lines for the BP
+region, while for Fe XIV and Si VII they are in the range from -15 to +15 km/s.
+The coronal electron density is 3.7x10^9 cm^-3. An excellent correlation is
+found between the positive magnetic flux and the X-ray light-curves. The
+remarkable agreement between the extrapolated magnetic field configuration and
+some of the loops composing the BP as seen in the X-ray images suggests that a
+large fraction of the magnetic field in the bright point is close to potential.
+The close correlation between the positive magnetic flux and the X-ray emission
+suggests that energy released by magnetic reconnection is stimulated by flux
+emergence or cancellation.",0810.1020v1
+2009-02-11,Radio Emission from Supernova Remnants: Implications for Post-Shock Magnetic Field Amplification and the Magnetic Fields of Galaxies,"Using observations from the literature, we show that the non-thermal radio
+luminosity (L) of supernova remnants (SNRs) is a strong function of the average
+gas surface density (Sigma) of the galaxy in which the remnants reside, from
+normal spirals to luminous starbursts. We combine a simple theory for electron
+cooling in SNRs with the observed radio luminosities to estimate the remnant
+magnetic field strength (B_SNR): the correlation between L and Sigma implies
+that B_SNR also increases with Sigma. We explore two interpretations of this
+correlation: (1) B_SNR is generated by post-shock magnetic field amplification,
+with B_SNR^2 proportional to Sigma and (2) B_SNR results from shock-compression
+of the ambient ISM magnetic field (B_ISM), with B_ISM being larger in denser
+galaxies. We find that shock compression is, on average, sufficient to produce
+the observed radio emission from SNRs in the densest starbursts; amplification
+of post-shock magnetic fields is not required. By contrast, in normal spirals
+post-shock field amplification (by a factor of a few - 10) is consistent with
+the data; we find tentative evidence that both the Alfven speed and the ratio
+of B_SNR^2 to the post-shock pressure (""epsilon_B"") are constant in SNRs from
+galaxy to galaxy. We discuss observational tests that can be used to
+distinguish between these two interpretations of the radio luminosities of
+SNRs. Regardless of which is correct, the radio emission from SNRs provides an
+upper limit to B_ISM that is independent of the minimum energy assumption. For
+the densest starbursts, the ISM magnetic energy density is below that required
+for hydrostatic equilibrium; thus magnetic fields are not dynamically important
+on the largest scales in starbursts, in contrast with spiral galaxies like our
+own. This dichotomy may have implications for galactic dynamo theory.",0902.1755v1
+2009-02-13,Linear stability of Hunt's flow,"We analyse numerically the linear stability of the fully developed flow of a
+liquid metal in a rectangular duct subject to a transverse magnetic field. The
+walls of the duct perpendicular to the magnetic field are perfectly conducting
+whereas the parallel ones are insulating. In a sufficiently strong magnetic
+field, the flow consists of two jets at the insulating walls and a
+near-stagnant core. We use a vector stream function formulation and Chebyshev
+collocation method to solve the eigenvalue problem for small-amplitude
+perturbations. Due to the two-fold reflection symmetry of the base flow the
+disturbances with four different parity combinations over the duct
+cross-section decouple from each other. Magnetic field renders the flow in a
+square duct linearly unstable at the Hartmann number Ha 5.7 with respect to a
+disturbance whose vorticity component along the magnetic field is even across
+the field and odd along it. For this mode, the minimum of the critical Reynolds
+number Re_c 2018, based on the maximal velocity, is attained at Ha ~ 10.
+Further increase of the magnetic field stabilises this mode with Re_c growing
+approximately as Ha. For Ha>40, the spanwise parity of the most dangerous
+disturbance reverses across the magnetic field. At Ha ~ 46 a new pair of most
+dangerous disturbances appears with the parity along the magnetic field being
+opposite to that of the previous two modes. The critical Reynolds number, which
+is very close for both of these modes, attains a minimum Re_c ~ 1130 at Ha ~ 70
+and increases as Re_c ~ Ha^1/2 for Ha >> 1. The asymptotics of the critical
+wavenumber is k_c ~ 0.525Ha^1/2 while the critical phase velocity approaches
+0.475 of the maximum jet velocity.",0902.2319v2
+2009-08-27,Very Light Magnetized Jets on Large Scales - I. Evolution and Magnetic Fields,"Magnetic fields, which are undoubtedly present in extragalactic jets and
+responsible for the observed synchrotron radiation, can affect the morphology
+and dynamics of the jets and their interaction with the ambient cluster medium.
+We examine the jet propagation, morphology and magnetic field structure for a
+wide range of density contrasts, using a globally consistent setup for both the
+jet interaction and the magnetic field. The MHD code NIRVANA is used to evolve
+the simulation, using the constrained-transport method. The density contrasts
+are varied between \eta = 10^{-1} and 10^{-4} with constant sonic Mach number
+6. The jets are supermagnetosonic and simulated bipolarly due to the low jet
+densities and their strong backflows. The helical magnetic field is largely
+confined to the jet, leaving the ambient medium nonmagnetic. We find magnetic
+fields with plasma \beta \sim 10 already stabilize and widen the jet head.
+Furthermore they are efficiently amplified by a shearing mechanism in the jet
+head and are strong enough to damp Kelvin-Helmholtz instabilities of the
+contact discontinuity. The cocoon magnetic fields are found to be stronger than
+expected from simple flux conservation and capable to produce smoother lobes,
+as found observationally. The bow shocks and jet lengths evolve self-similarly.
+The radio cocoon aspect ratios are generally higher for heavier jets and grow
+only slowly (roughly self-similar) while overpressured, but much faster when
+they approach pressure balance with the ambient medium. In this regime,
+self-similar models can no longer be applied. Bow shocks are found to be of low
+excentricity for very light jets and have low Mach numbers. Cocoon turbulence
+and a dissolving bow shock create and excite waves and ripples in the ambient
+gas. Thermalization is found to be very efficient for low jet densities.",0908.4055v1
+2009-10-16,Asteroseismic model of paramagnetic neutron star,"We investigate an asteroseismic model of non-rotating paramagnetic neutron
+star with core-crust stratification of interior pervaded by homogeneous
+internal and dipolar external magnetic field, presuming that neutron degenerate
+Fermi-matter of the star core is in the state of Pauli's paramagnetic permanent
+magnetization caused by polarization of spin magnetic moments of neutrons along
+the axis of magnetic field of collapsed massive progenitor. The magnetic
+cohesion between metal-like crust and permanent-magnet-like core is considered
+as playing a main part in the dynamics of starquake. Focus is laid on the
+post-quake relaxation of the star by node-free torsional vibrations of highly
+conducting crustal solid-state plasma, composed of nuclei embedded in the
+degenerate Fermi-gas of relativistic electrons, about axis of magnetic field
+frozen in the immobile paramagnetic core. Two scenarios of these axisymmetric
+seismic vibrations are examined, in first of which these are considered as
+maintained by combined action of Lorentz magnetic and Hooke's elastic forces
+and in second one by solely Lorentz force. Based on the energy variational
+method of magneto-solid-mechanical theory of elastic continuous medium, the
+spectral formulae for the frequency and lifetime of this toroidal mode are
+obtained and discussed in the context of theoretical treatment of recently
+discovered quasi-periodic oscillations of the X-ray outburst flux from SGR
+1806-20 and SGR 1900+14 as being produced by above seismic vibrations.",0910.3048v8
+2011-04-28,Effects of magnetic fields on the cosmic-ray ionization of molecular cloud cores,"Low-energy cosmic rays are the dominant source of ionization for molecular
+cloud cores. The ionization fraction, in turn, controls the coupling of the
+magnetic field to the gas and hence the dynamical evolution of the cores. The
+purpose of this work is to compute the attenuation of the cosmic-ray flux rate
+in a cloud core taking into account magnetic focusing, magnetic mirroring, and
+all relevant energy loss processes. We adopt a standard cloud model
+characterized by a mass-to-flux ratio supercritical by a factor of about 2 to
+describe the density and magnetic field distribution of a low-mass starless
+core, and we follow the propagation of cosmic rays through the core along flux
+tubes enclosing different amount of mass. We then extend our analysis to cores
+with different mass-to-flux ratios. We find that mirroring always dominates
+over focusing, implying a reduction of the cosmic-ray ionization rate by a
+factor of about 2-3 over most of a solar-mass core with respect to the value in
+the intercloud medium outside the core. For flux tubes enclosing larger masses
+the reduction factor is smaller, since the field becomes increasingly uniform
+at larger radii and lower densities. We also find that the cosmic-ray
+ionization rate is further reduced in clouds with stronger magnetic field, e.g.
+by a factor of about 4 for a marginally critical cloud. The magnetic field
+threading molecular cloud cores affects the penetration of low-energy cosmic
+rays and reduces the ionization rate by a factor 3-4 depending on the position
+inside the core and the magnetization of the core.",1104.5445v1
+2012-02-13,The Two States of Star Forming Clouds,"We examine the effects of self-gravity and magnetic fields on supersonic
+turbulence in isothermal molecular clouds with high resolution simulations and
+adaptive mesh refinement. These simulations use large root grids (512^3) to
+capture turbulence and four levels of refinement to capture high density, for
+an effective resolution of 8,196^3. Three Mach 9 simulations are performed, two
+super-Alfv\'enic and one trans-Alfv\'enic. We find that gravity splits the
+clouds into two populations, one low density turbulent state and one high
+density collapsing state. The low density state exhibits properties similar to
+non-self-gravitating in this regime, and we examine the effects of varied
+magnetic field strength on statistical properties: the density probability
+distribution function is approximately lognormal; velocity power spectral
+slopes decrease with field strength; alignment between velocity and magnetic
+field increases with field; the magnetic field probability distribution can be
+fit to a stretched exponential. The high density state is characterized by
+self-similar spheres; the density PDF is a power-law; collapse rate decreases
+with increasing mean field; density power spectra have positive slopes,
+P({\rho},k) \propto k; thermal-to-magnetic pressure ratios are unity for all
+simulations; dynamic-to-magnetic pressure ratios are larger than unity for all
+simulations; magnetic field distribution is a power-law. The high Alfv\'en Mach
+numbers in collapsing regions explain recent observations of magnetic influence
+decreasing with density. We also find that the high density state is found in
+filaments formed by converging flows, consistent with recent Herschel
+observations. Possible modifications to existing star formation theories are
+explored.",1202.2594v1
+2012-06-15,Role of rotational symmetry in the magnetism of a multiorbital model,"Effect of rotationally-invariant Hund's rule coupling on a magnetism of
+multiorbital Hubbard models is studied within a dynamical mean field theory
+framework. Comparison of static magnetic susceptibilities and local densities
+of states of two- and three-orbital models of a complete rotationally invariant
+Coulomb interaction and a ""density-density"" Hartree type interaction shows the
+different role of spin-flip interactions for different band fillings. In the
+particle-hole symmetric case the Mott-Hubbard physics dominates due to the
+strong effective Coulomb interaction, while for the multiple electronic
+configurations away from half-filling (two electrons in the three band model)
+the formation of local magnetic moments due to Hund's exchange interaction
+becomes the most significant effect for itinerant magnetic systems. A shift of
+the temperature of magnetic ordering due to the rotationally-invariant Hund's
+rule coupling is found to be the largest in a three-orbital model with a
+two-electron occupancy where the single particle spectrum is metallic and is
+not sensitive to different forms of the Coulomb vertex. A larger enhancement of
+the effective mass in a model with a rotationally-invariant interaction is
+discussed. In the half-filled case we find a drastic change in the density of
+states close to the Mott transition which is related to the spin-flip Kondo
+fluctuations in a degenerate orbital case, while the corresponding shift of the
+magnetic transition temperature is relatively small. It is shown that a change
+in the ground state degeneracy due to a different symmetry of the Coulomb
+interaction in the density-density model leads to a breakdown of the
+quasiparticle peak at the Fermi level in the proximity of a Mott transition on
+the metallic side. We discuss the relevance of rotationally-invariant Hund's
+interaction in the transition metal magnetism.",1206.3416v2
+2012-08-06,Comparing Simulations of Rising Flux Tubes Through the Solar Convection Zone with Observations of Solar Active Regions: Constraining the Dynamo Field Strength,"We study how active-region-scale flux tubes rise buoyantly from the base of
+the convection zone to near the solar surface by embedding a thin flux tube
+model in a rotating spherical shell of solar-like turbulent convection. These
+toroidal flux tubes that we simulate range in magnetic field strength from 15
+kG to 100 kG at initial latitudes of 1 degree to 40 degrees in both
+hemispheres. This article expands upon Weber, Fan, and Miesch (Astrophys. J.,
+741, 11, 2011) (Article 1) with the inclusion of tubes with magnetic flux of
+10^20 Mx and 10^21 Mx, and more simulations of the previously investigated case
+of 10^22 Mx, sampling more convective flows than the previous article, greatly
+improving statistics. Observed properties of active regions are compared to
+properties of the simulated emerging flux tubes, including: the tilt of active
+regions in accordance with Joy's Law as in Article 1, and in addition the
+scatter of tilt angles about the Joy's Law trend, the most commonly occurring
+tilt angle, the rotation rate of the emerging loops with respect to the
+surrounding plasma, and the nature of the magnetic field at the flux tube apex.
+We discuss how these diagnostic properties constrain the initial field strength
+of the active region flux tubes at the bottom of the solar convection zone, and
+suggest that flux tubes of initial magnetic field strengths of \geq 40 kG are
+good candidates for the progenitors of large (10^21 Mx to 10^22 Mx) solar
+active regions, which agrees with the results from Article 1 for flux tubes of
+10^22 Mx. With the addition of more magnetic flux values and more simulations,
+we find that for all magnetic field strengths, the emerging tubes show a
+positive Joy's Law trend, and that this trend does not show a statistically
+significant dependence on the magnetic flux.",1208.1292v1
+2012-10-08,Magnetic fluctuations and effective magnetic moments in γ-iron due to electronic structure peculiarities,"Applying the local density and dynamical mean field approximations to
+paramagnetic \gamma-iron we revisit the problem of theoretical description of
+magnetic properties in a wide temperature range. We show that contrary to
+\alpha-iron, the frequency dependence of the electronic self-energy has a
+quasiparticle form for both, t_{2g} and e_g states. In the temperature range
+T=1200-1500 K, where \gamma-iron exist in nature, this substance can be
+nevertheless characterized by temperature-dependent effective local moments,
+which yield relatively narrow peaks in the real part of the local magnetic
+susceptibility. At the same time, at low temperatures \gamma-iron (which is
+realized in precipitates) is better described in terms of itinerant picture. In
+particular, the nesting features of the Fermi surfaces yield maximum of the
+static magnetic susceptibility at the incommensurate wave vector q_{max}
+belonging the direction q_X-q_W (q_X=(2\pi/a)(1,0,0),q_W=(2\pi/a)(1,1/2,0), a
+is a lattice parameter) in agreement with the experimental data. This state is
+found however to compete closely with the states characterized by magnetic wave
+vectors along the directions q_X-q_L-q_K, where q_L=(2\pi/a)(1/2,1/2,1/2),
+q_K=(2\pi/a)(3/4,3/4,0). From the analysis of the uniform magnetic
+susceptibility we find that contrary to \alpha-iron, the Curie-Weiss law is not
+fulfilled in a broad temperature range, although the inverse susceptibility is
+nearly linear in the moderate-temperature region (1200-1500 K). The
+non-linearity of the inverse uniform magnetic susceptibility in a broader
+temperature range is due to the density of states peak located close to the
+Fermi level. The effective exchange integrals in the paramagnetic phase are
+estimated on the base of momentum dependent susceptibility.",1210.2188v2
+2012-11-01,A Magnetic Confinement vs. Rotation Classification of Massive-Star Magnetospheres,"Building on results from the Magnetism in Massive Stars (MiMeS) project, this
+paper shows how a two-parameter classification of massive-star magnetospheres
+in terms of the magnetic wind confinement (which sets the Alfv\'en radius RA)
+and stellar rotation (which sets the Kepler co-rotation radius RK) provides a
+useful organisation of both observational signatures and theoretical
+predictions. We compile the first comprehensive study of inferred and observed
+values for relevant stellar and magnetic parameters of 64 confirmed magnetic OB
+stars with Teff > 16 kK. Using these parameters, we locate the stars in the
+magnetic confinement-rotation diagram, a log-log plot of RK vs. RA. This
+diagram can be subdivided into regimes of centrifugal magnetospheres (CM), with
+RA > RK, vs. dynamical magnetospheres (DM), with RK > RA. We show how key
+observational diagnostics, like the presence and characteristics of Halpha
+emission, depend on a star's position within the diagram, as well as other
+parameters, especially the expected wind mass-loss rates. In particular, we
+identify two distinct populations of magnetic stars with Halpha emission:
+namely, slowly rotating O-type stars with narrow emission consistent with a DM,
+and more rapidly rotating B-type stars with broader emission associated with a
+CM. For O-type stars, the high mass-loss rates are sufficient to accumulate
+enough material for line emission even within the relatively short free-fall
+timescale associated with a DM: this high mass-loss rate also leads to a rapid
+magnetic spindown of the stellar rotation. For the B-type stars, the longer
+confinement of a CM is required to accumulate sufficient emitting material from
+their relatively weak winds, which also lead to much longer spindown
+timescales. [abbreviated]",1211.0282v1
+2013-02-25,VLA OH Zeeman Observations of the star forming region S88B,"We present observations of the Zeeman effect in OH thermal absorption main
+lines at 1665 and 1667 MHz taken with the Very Large Array (VLA) toward the
+star forming region S88B. The OH absorption profiles toward this source are
+complicated, and contain several blended components toward a number of
+positions. Almost all of the OH absorbing gas is located in the eastern parts
+of S88B, toward the compact continuum source S88B-2 and the eastern parts of
+the extended continuum source S88B-1. The ratio of 1665/1667 MHz OH line
+intensities indicates the gas is likely highly clumped, in agreement with other
+molecular emission line observations in the literature. S88-B appears to
+present a similar geometry to the well-known star forming region M17, in that
+there is an edge-on eastward progression from ionized to molecular gas. The
+detected magnetic fields appear to mirror this eastward transition; we detected
+line-of-sight magnetic fields ranging from 90-400 \mu G, with the lowest values
+of the field to the southwest of the S88B-1 continuum peak, and the highest
+values to its northeast. We used the detected fields to assess the importance
+of the magnetic field in S88B by a number of methods; we calculated the ratio
+of thermal to magnetic pressures, we calculated the critical field necessary to
+completely support the cloud against self-gravity and compared it to the
+observed field, and we calculated the ratio of mass to magnetic flux in terms
+of the critical value of this parameter. All these methods indicated that the
+magnetic field in S88B is dynamically significant, and should provide an
+important source of support against gravity. Moreover, the magnetic energy
+density is in approximate equipartition with the turbulent energy density,
+again pointing to the importance of the magnetic field in this region.",1302.6098v1
+2013-05-04,Recurrent Coronal Jets Induced by Repetitively Accumulated Electric Currents,"Three extreme-ultraviolet (EUV) jets recurred in about one hour on 2010
+September 17 in the following magnetic polarity of active region 11106. The EUV
+jets were observed by the Atmospheric Imaging Assembly (AIA) on board the Solar
+Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager (HMI) on board
+SDO measured the vector magnetic field, from which we derive the magnetic flux
+evolution, the photospheric velocity field, and the vertical electric current
+evolution. The magnetic configuration before the jets is derived by the
+nonlinear force-free field (NLFFF) extrapolation.
+  We derive that the jets are above a pair of parasitic magnetic bipoles which
+are continuously driven by photospheric diverging flows. The interaction drove
+the build up of electric currents that we indeed observed as elongated patterns
+at the photospheric level. For the first time, the high temporal cadence of HMI
+allows to follow the evolution of such small currents. In the jet region, we
+found that the integrated absolute current peaks repetitively in phase with the
+171 A flux evolution. The current build up and its decay are both fast, about
+10 minutes each, and the current maximum precedes the 171 A by also about 10
+minutes. Then, HMI temporal cadence is marginally fast enough to detect such
+changes.
+  The photospheric current pattern of the jets is found associated to the
+quasi-separatrix layers deduced from the magnetic extrapolation. From previous
+theoretical results, the observed diverging flows are expected to build
+continuously such currents. We conclude that magnetic reconnection occurs
+periodically, in the current layer created between the emerging bipoles and the
+large scale active region field. It induced the observed recurrent coronal jets
+and the decrease of the vertical electric current magnitude.",1305.0902v1
+2014-05-29,"Magnetic field amplification and magnetically supported explosions of collapsing, non-rotating stellar cores","We study the amplification of magnetic fields in the collapse and the
+post-bounce evolution of the core of a non-rotating star of 15 solar masses in
+axisymmetry. To this end, we solve the coupled equations of
+magnetohydrodynamics and neutrino transport in the two-moment approximation.
+The pre-collapse magnetic field is strongly amplified by compression in the
+infall. Initial fields of the order of 1010 G translate into proto-neutron star
+fields similar to the ones observed in pulsars, while stronger initial fields
+yield magnetar-like final field strengths. After core bounce, the field is
+advected through the hydrodynamically unstable neutrino-heating layer, where
+non-radial flows due to convection and the standing accretion shock instability
+amplify the field further. Consequently, the resulting amplification factor of
+order five is the result of the number of small-eddy turnovers taking place
+within the time scale of advection through the post-shock layer. Due to this
+limit, most of our models do not reach equipartition between kinetic and
+magnetic energy and, consequently, evolve similarly to the non-magnetic case,
+exploding after about 800 ms when a single or few high-entropy bubbles persist
+over several dynamical time scales. In the model with the strongest initial
+field we studied, \$10^{12}\$ G, for which equipartition between flow and field
+is achieved, the magnetic tension favours a much earlier development of such
+long-lived high-entropy bubbles and enforces a fairly ordered large-scale flow
+pattern. Consequently, this model, after exhibiting very regular shock
+oscillations, explodes much earlier than non-magnetic ones.",1405.7466v2
+2015-06-06,Magnetic Field Structures in Star Forming Regions: Mid-Infrared Imaging Polarimetry of K3-50,"We report new imaging polarimetry observations of the Galactic compact HII
+region K3-50 using CanariCam at the Gran Telescopio Canarias. We use a standard
+polarimetric analysis technique, first outlined by Aitken, to decompose the
+observed polarisation images centred at 8.7, 10.3, and 12.5 $\mu$m into the
+emissive and absorptive components from silicate grains that are aligned with
+the local magnetic field. These components reveal the spatially-resolved
+magnetic field structures across the mid-infrared emission area of K3-50. We
+examine these structures and show that they are consistent with previously
+observed features and physical models of K3-50, such as the molecular torus and
+the ionised outflow. We propose a 3D geometry for all the structures seen at
+different wavelengths. We also compute relevant physical quantities in order to
+estimate the associated magnetic field strengths that would be implied under
+various physical assumptions. We compare these results with MHD simulations of
+protostar formation that predict the magnetic field strength and configuration.
+We find that the magnetic field may be dynamically important in the innermost
+0.2 pc of the molecular torus, but that the torus is more likely to be
+rotationally-supported against gravity outside this radius. Similarly, magnetic
+fields are unlikely to dominate the {\em global} physics of the ionised
+outflow, but they may be important in helping confine the flow near the cavity
+wall in some locations. Ours is the first application of the Aitken technique
+to spatially-resolved magnetic field structures in multiple layers along the
+line of sight, effectively a method of ""polarisation tomography.""",1506.02173v1
+2015-07-13,Effect of shear and magnetic field on the heat-transfer efficiency of convection in rotating spherical shells,"We study rotating thermal convection in spherical shells. We base our
+analysis on a set of about 450 direct numerical simulations of the
+(magneto)hydrodynamic equations under the Boussinesq approximation. The Ekman
+number ranges from $10^{-3}$ to $10^{-5}$. The supercriticality of the
+convection reaches about 1000 in some models. Four sets of simulations are
+considered: non-magnetic simulations and dynamo simulations with either
+free-slip or no-slip flow boundary conditions. The non-magnetic setup with
+free-slip boundaries generates the strongest zonal flows. Both non-magnetic
+simulations with no-slip flow boundary conditions and self-consistent dynamos
+with free-slip boundaries have drastically reduced zonal-flows. Suppression of
+shear leads to a substantial gain in heat-transfer efficiency, increasing by a
+factor of 3 in some cases. Such efficiency enhancement occurs as long as the
+convection is significantly influenced by rotation. At higher convective
+driving the heat-transfer efficiency tends towards that of the classical
+non-rotating Rayleigh-B\'enard system. Analysis of the latitudinal distribution
+of heat flow at the outer boundary reveals that the shear is most effective at
+suppressing heat-transfer in the equatorial regions. Furthermore, we explore
+the influence of the magnetic field on the {\em non-zonal} flow components of
+the convection. For this we compare the heat-transfer efficiency of no-slip
+non-magnetic cases with that of the no-slip dynamo simulations. We find that at
+$E=10^{-5}$ magnetic field significantly affects the convection and a maximum
+gain of about 30\% (as compared to the non-magnetic case) in heat-transfer
+efficiency is obtained for an Elsasser number of about 3. Our analysis
+motivates us to speculate that convection in the polar regions in dynamos at
+$E=10^{-5}$ is probably in a `magnetostrophic' regime.",1507.03649v2
+2015-07-30,X-ray emission from the giant magnetosphere of the magnetic O-type star NGC 1624-2,"We observed NGC 1624-2, the O-type star with the largest known magnetic field
+Bp~20 kG), in X-rays with the ACIS-S camera onboard the Chandra X-ray
+Observatory. Our two observations were obtained at the minimum and maximum of
+the periodic Halpha emission cycle, corresponding to the rotational phases
+where the magnetic field is the closest to equator-on and pole-on,
+respectively. With these observations, we aim to characterise the star's
+magnetosphere via the X-ray emission produced by magnetically confined wind
+shocks. Our main findings are:
+  (i) The observed spectrum of NGC 1624-2 is hard, similar to the magnetic
+O-type star Theta 1 Ori C, with only a few photons detected below 0.8 keV. The
+emergent X-ray flux is 30% lower at the Halpha minimum phase.
+  (ii) Our modelling indicated that this seemingly hard spectrum is in fact a
+consequence of relatively soft intrinsic emission, similar to other magnetic
+Of?p stars, combined with a large amount of local absorption (~1-3 x 10^22
+cm^-2). This combination is necessary to reproduce both the prominent Mg and Si
+spectral features, and the lack of flux at low energies. NGC 1624-2 is
+intrinsically luminous in X-rays (log LX emission ~ 33.4) but 70-95% of the
+X-ray emission produced by magnetically confined wind shocks is absorbed before
+it escapes the magnetosphere (log LX ISM corrected ~ 32.5).
+  (iii) The high X-ray luminosity, its variation with stellar rotation, and its
+large attenuation are all consistent with a large dynamical magnetosphere with
+magnetically confined wind shocks.",1507.08621v1
+2015-09-17,Velocity and magnetic fields within 1000 AU from a massive YSO,"We want to study the velocity and magnetic field morphology in the vicinity
+(<1000 AU) of a massive young stellar object (YSO), at very high spatial
+resolution (10-100 AU). We performed milli-arcsecond polarimetric observations
+of the strong CH3OH maser emission observed in the vicinity of an O-type YSO,
+in G023.01-00.41. We have combined this information with the velocity field of
+the CH3OH masing gas previously measured at the same angular resolution. We
+analyse the velocity and magnetic fields in the reference system defined by the
+direction of the molecular outflow and the equatorial plane of the hot
+molecular core at its base, as recently observed on sub-arcsecond scales. We
+provide a first detailed picture of the gas dynamics and magnetic field
+configuration within a radius of 2000 AU from a massive YSO. We have been able
+to reproduce the magnetic field lines for the outer regions (>600 AU) of the
+molecular envelope, where the magnetic field orientation shows a smooth change
+with the maser cloudlets position (0.2 degree/AU). Overall, the velocity field
+vectors well accommodate with the local, magnetic field direction, but still
+show an average misalignment of 30 degrees. We interpret this finding as the
+contribution of a turbulent velocity field of about 3.5 km/s, responsible for
+braking up the alignment between the velocity and magnetic field vectors. We do
+resolve different gas flows which develop both along the outflow axis and
+across the disk plane, with an average speed of 7 km/s. In the direction of the
+outflow axis, we establish a collimation of the gas flow, at a distance of
+about 1000 AU from the disk plane. In the disk region, gas appears to stream
+outward along the disk plane for radii greater than 500-600 AU, and inward for
+shorter radii.",1509.05428v1
+2016-10-17,"Unveiling the Magnetic Structure of VHE SNRs/PWNe with XIPE, the X-ray Imaging-Polarimetry Satellite","The dynamics, energetics and evolution of pulsar wind nebulae (PWNe) and
+supernova remnants (SNRs), are strongly affected by their magnetic field
+strength and distribution. They are usually strong, extended, sources of
+non-thermal X-ray radiation, producing intrinsically polarised radiation. The
+energetic wind around pulsars produces a highly-magnetised, structured flow,
+often displaying a jet and a torus and different features (i.e. wisps, knots).
+This magnetic-dominant wind evolves as it moves away from the pulsar
+magnetosphere to the surrounding large-scale nebula, becoming kinetic-dominant.
+Basic aspects such how this conversion is produced, or how the jets and torus
+are formed, as well as the level of turbulence in the nebula are still unknown.
+Likewise, the processes ruling the acceleration of particles in shell-like SNRs
+up to 1e15 eV, including the amplification of the magnetic field, are not clear
+yet. Imaging polarimetry in this regard is crucial to localise the regions of
+shock acceleration and to measure the strength and the orientation of the
+magnetic field at these emission sites. X-ray polarimetry with the X-ray
+Imaging Polarimetry Explorer (XIPE) will allow the understanding of the
+magnetic field structure and intensity on different regions in SNRs and PWNe,
+helping to unveil long-standing questions such as i.e. acceleration of cosmic
+rays in SNRs or magnetic-to-kinetic energy transfer. SNRs and PWNe also
+represent the largest population of Galactic very-high energy gamma-ray
+sources, therefore the study of their magnetic distribution with XIPE will
+provide fundamental ingredients on the investigation of those sources at very
+high energies. We will discuss the physics case related to SNRs and PWNe and
+the expectations of the XIPE observations of some of the most prominent SNRs
+and PWNe.",1610.05217v2
+2016-10-26,Analysis of sudden variations in photospheric magnetic fields during a large flare and their influences in the solar atmosphere,"The solar active region NOAA 11719 produced a large two-ribbon flare on 11
+April 2013. We have investigated the sudden variations in the photospheric
+magnetic fields in this active region during the flare employing the
+magnetograms obtained in the spectral line Fe I 6173 Angstrom by the
+Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory
+(SDO). The analysis of the line-of-sight magnetograms from HMI show sudden and
+persistent magnetic field changes at different locations of the active region
+before the onset of the flare and during the flare. The vector magnetic field
+observations available from HMI also show coincident variations in the total
+magnetic field strength and its inclination angle at these locations. Using the
+simultaneous Dopplergrams obtained from HMI, we observe perturbations in the
+photospheric Doppler signals following the sudden changes in the magnetic
+fields in the aforementioned locations. The power spectrum analysis of these
+velocity signals show enhanced acoustic power in these affected locations
+during the flare as compared to the pre-flare condition. Accompanying these
+observations, we have also used the near-simultaneous chromospheric
+observations obtained in the spectral line H-alpha 6562.8 Angstrom by the
+Global Oscillation Network Group (GONG) to study the evolution of flare ribbons
+and intensity oscillations in the active region. The H-alpha intensity
+oscillations also show enhanced oscillatory power during the flare in the
+aforementioned locations. These results indicate that the transient Lorentz
+force associated with the sudden changes in the magnetic fields could drive the
+localized photospheric and chromospheric oscillations, like the flare-induced
+oscillations in the solar atmosphere.",1610.08294v1
+2017-03-29,High-resolution observations of flare precursors in the low solar atmosphere,"Solar flares are generally believed to be powered by free magnetic energy
+stored in the corona, but the build up of coronal energy alone may be
+insufficient for the imminent flare occurrence. The flare onset mechanism is a
+critical but less understood problem, insights into which could be gained from
+small-scale energy releases known as precursors, which are observed as small
+pre-flare brightenings in various wavelengths, and also from certain
+small-scale magnetic configurations such as the opposite polarity fluxes, where
+magnetic orientation of small bipoles is opposite to that of the ambient main
+polarities. However, high-resolution observations of flare precursors together
+with the associated photospheric magnetic field dynamics are lacking. Here we
+study precursors of a flare using unprecedented spatiotemporal resolution of
+the 1.6 m New Solar Telescope, complemented by novel microwave data. Two
+episodes of precursor brightenings are initiated at a small-scale magnetic
+channel (a form of opposite polarity fluxes) with multiple polarity inversions
+and enhanced magnetic fluxes and currents, lying near the footpoints of sheared
+magnetic loops. The low-atmospheric origin of these precursor emissions is
+corroborated by microwave spectra. We propose that the emerging magnetic
+channel field interacts with the sheared arcades to cause precursor
+brightenings at the main flare core region. These high-resolution results
+provide evidence of low-atmospheric small-scale energy release and possible
+relationship to the onset of the main flare.",1703.09866v1
+2017-07-19,Contribution to the Solar Mean Magnetic Field from Different Solar Regions,"Seven-year long seeing-free observations of solar magnetic fields with the
+Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory
+(SDO) were used to study the sources of the solar mean magnetic field, SMMF,
+defined as the net line-of-sight magnetic flux divided over the solar disk
+area. To evaluate the contribution of different regions to the SMMF, we
+separated all the pixels of each SDO/HMI magnetogram into three subsets: weak
+(B_W), intermediate (B_I), and strong (B_S) fields. The B_W component
+represents areas with magnetic flux densities below the chosen threshold; the
+B_I component is mainly represented by network fields, remains of decayed
+active regions (ARs), and ephemeral regions. The B_S component consists of
+magnetic elements in ARs. To derive the contribution of a subset to the total
+SMMF, the linear regression coefficients between the corresponding component
+and the SMMF were calculated. We found that: i) when the threshold level of 30
+Mx cm^-2 is applied, the B_I and B_S components together contribute from 65% to
+95% of the SMMF, while the fraction of the occupied area varies in a range of
+2-6% of the disk area; ii) as the threshold magnitude is lowered to 6 Mx cm^-2,
+the contribution from B_I+B_S grows to 98%, and the fraction of the occupied
+area reaches the value of about 40% of the solar disk. In summary, we found
+that regardless of the threshold level, only a small part of the solar disk
+area contributes to the SMMF. This means that the photospheric magnetic
+structure is an intermittent, inherently porous medium, resembling a
+percolation cluster. These findings suggest that the long-standing concept that
+continuous vast unipolar areas on the solar surface are the source of the SMMF
+may need to be reconsidered.",1707.05971v1
+2017-10-19,Dissipation of the striped pulsar wind,"Rapidly rotating neutron stars blow a relativistic, magnetized wind mainly
+composed of electron-positron pairs. The free expansion of the wind terminates
+far from the neutron star where a weakly magnetized pulsar wind nebula forms,
+implying efficient magnetic dissipation somewhere upstream. The wind current
+sheet that separates the two magnetic polarities is usually considered as the
+most natural place for magnetic dissipation via relativistic reconnection, but
+its efficiency remains an open question. Here, the goal of this work is to
+revisit this issue in light of the most recent progress in the understanding of
+reconnection and pulsar electrodynamics. We perform large two-dimensional
+particle-in-cell simulations of the oblique rotator to capture the multi-scale
+evolution of the wind. We find that the current sheet breaks up into a
+dynamical chain of magnetic islands separated by secondary thin current sheets.
+The sheet thickness increases linearly with radius while the Poynting flux
+decreases monotonically as reconnection proceeds. The radius of complete
+annihilation of the stripes is given by the plasma multiplicity parameter at
+the light cylinder. Current starvation within the sheets does not occur before
+complete dissipation as long as there is enough charges where the sheets form.
+Particles are efficiently heated up to a characteristic energy set by the
+magnetization parameter at the light cylinder. Energetic pulsed synchrotron
+emission peaks close to the light cylinder, and presents sub-pulse variability
+associated with the formation of plasmoids in the sheet. This study suggests
+that the striped component of the wind dissipates far before reaching the
+termination shock in isolated pulsars, even in very-high-multiplicity systems
+such as the Crab pulsar. Pulsars in binary systems may provide the best
+environments to study magnetic dissipation in the wind.",1710.07320v1
+2018-02-15,Spin and charge pumping by steady or pulse current-driven magnetic domain wall: A self-consistent multiscale time-dependent-quantum/time-dependent-classical approach,"We introduce a multiscale framework which combines time-dependent
+nonequilibrium Green function (TD-NEGF) algorithms, scaling linearly in the
+number of time steps and describing quantum-mechanically conduction electrons
+in the presence of time-dependent fields of arbitrary strength or frequency,
+with classical time evolution of localized magnetic moments described by the
+Landau-Lifshitz-Gilbert (LLG) equation. The TD-NEGF+LLG framework can be
+applied to a variety of problems where current-driven spin torque induces
+dynamics of magnetic moments as the key resource for next generation
+spintronics. Using magnetic domain wall (DW) as an example, we predict that its
+motion will pump time-dependent spin and charge currents (on the top of
+unpolarized DC charge current injected through normal metal leads to drive the
+DW motion). The conversion of AC components of spin current, whose amplitude
+increases (decreases) as the DW approaches (distances from) the normal metal
+lead, into AC voltage via the inverse spin Hall effect offers a tool to
+precisely track the DW position along magnetic nanowire. We also quantify the
+DW transient inertial displacement due to its acceleration and deceleration by
+pulse current and the entailed spin and charge pumping. Finally, TD-NEGF+LLG as
+a nonperturbative (i.e., numerically exact) framework allows us to establish
+the limits of validity of the so-called spin-motive force (SMF) theory for
+pumped charge current by time-dependent magnetic textures---the perturbative
+analytical formula of SMF theory becomes inapplicable for large frequencies
+(but unrealistic in magnetic system) and, more importantly, for increasing
+noncollinearity when the angles between neighboring magnetic moments exceed
+$\simeq 10^\circ$.",1802.05682v3
+2018-07-17,On the low magnetic field effect in radical pair reactions,"Radical pair recombination reactions are known to be sensitive to the
+application of both low and high magnetic fields. The application of a weak
+magnetic field reduces the singlet yield of a singlet-born radical pair,
+whereas the application of a strong magnetic field increases the singlet yield.
+The high field effect arises from energy conservation: when the magnetic field
+is stronger than the sum of the hyperfine fields in the two radicals, ${\rm
+S}\to {\rm T}_{\pm}$ transitions become energetically forbidden, thereby
+reducing the number of pathways for singlet to triplet interconversion. The low
+field effect arises from symmetry breaking: the application of a weak magnetic
+field lifts degeneracies among the zero field eigenstates and increases the
+number of pathways for singlet to triplet interconversion. However, the details
+of this effect are more subtle, and have not previously been properly
+explained. Here we present a complete analysis of the low field effect in a
+radical pair containing a single proton, and in a radical pair in which one of
+the radicals contains a large number of hyperfine-coupled nuclear spins. We
+find that the new transitions that occur when the field is switched on are
+between ${\rm S}$ and ${\rm T}_0$ in both cases, and not between ${\rm S}$ and
+${\rm T}_{\pm}$ as has previously been claimed. We then illustrate this result
+by using it in conjunction with semiclassical spin dynamics simulations to
+account for the observation of a biphasic--triphasic--biphasic transition with
+increasing magnetic field strength in the magnetic field effect on the
+time-dependent survival probability of a photoexcited
+carotenoid-porphyrin-fullerene radical pair.",1807.06541v1
+2018-07-29,Incommensurate atomic and magnetic modulations in the spin-frustrated β-NaMnO2 triangular lattice,"The layered {\beta}-NaMnO2, a promising Na-ion energy-storage material has
+been investigated for its triangular lattice capability to promote complex
+magnetic configurations that may release symmetry restrictions for the
+coexistence of ferroelectric and magnetic orders. The complexity of the neutron
+powder diffraction patterns underlines that the routinely adopted commensurate
+structural models are inadequate. Instead, a single-phase superspace symmetry
+description is necessary, demonstrating that the material crystallizes in a
+compositionally modulated q= (0.077(1), 0, 0) structure. Here, Mn3+ Jahn-Teller
+distorted MnO6 octahedra form corrugated layer stacking sequences of the
+{\beta}-NaMnO2 type, which are interrupted by flat sheets of the {\alpha}-like
+oxygen topology. Spontaneous long-range collinear antiferromagnetic order,
+defined by the propagation vector k= (1/2, 1/2, 1/2), appears below TN1= 200 K.
+Moreover, a second transition into a spatially modulated proper-screw magnetic
+state (k+-q) is established at TN2= 95 K, with an antiferromagnetic order
+parameter resembling that of a two-dimensional (2D) system. The evolution of
+23Na NMR spin-lattice relaxation identifies a magnetically inhomogene-ous state
+in the intermediate T-region (TN2 <T< TN1), while its strong suppression below
+TN2 indicates that a spin-gap opens in the excitation spectrum. High-resolution
+neutron inelastic scattering confirms that the magnetic dynamics are indeed
+gapped ({\Delta}~5 meV) in the low-temperature magnetic phase, while
+simulations on the basis of the single-mode approximation suggest that Mn-spins
+residing on ad-jacent antiferromagnetic chains, establish sizable 2D
+correlations. Our analysis points that novel struc-tural degrees of freedom
+promote, cooperative magnetism and emerging dielectric properties in this
+non-perovskite-type of manganite.",1807.10995v1
+2018-09-30,Local-Ising type magnetic order and metamagnetism in the rare-earth pyrogermanate Er$_2$Ge$_2$O$_7$,"The recent discoveries of proximate quantum spin-liquid compounds and their
+potential application in quantum computing informs the search for new candidate
+materials for quantum spin-ice and spin-liquid physics. While the majority of
+such work has centered on members of the pyrochlore family due to their
+inherently frustrated linked tetrahedral structure, the rare-earth
+pyrogermanates also show promise for possible frustrated magnetic behavior.
+With the familiar stoichiometry $RE_2$Ge$_2$O$_7$, these compounds generally
+have tetragonal symmetry with a rare-earth sublattice built of a spiral of
+alternating edge and corner sharing rare-earth site triangles. Studies on
+Dy$_2$Ge$_2$O$_7$ and Ho$_2$Ge$_2$O$_7$ have shown tunable low temperature
+antiferromagnetic order, a high frustration index and spin-ice like dynamics.
+Here we use neutron diffraction to study magnetic order in Er$_2$Ge$_2$O$_7$
+(space group $P4_{1}2_{1}2$ ) and find the lowest yet Ne\'el temperature in the
+pyrogermanates of 1.15 K. Using neutron powder diffraction we find the magnetic
+structure to order with $k = (0,0,0)$ ordering vector, magnetic space group
+symmetry $P4_{1}^{'}2_{1}2^{'}$ and a refined Er moment of $m = 8.1 \mu_B$ -
+near the expected value for the Er$^{3+}$ free ion. Provocatively, the magnetic
+structure exhibits similar 'local-Ising' behavior to that seen in the
+pyrocholres where the Er moment points up or down along the short Er-Er bond.
+Upon applying a magnetic field we find a first order metamagnetic transition at
+$\sim$ 0.35 T to a lower symmetry $P2_{1}^{'}2_{1}^{'}2$ structure. This
+magnetic transition involves an inversion of Er moments aligned antiparallel to
+the applied field describing a class I spin-flip type transition, indicating a
+strong local anisotropy at the Er site - reminiscent of that seen in the
+spin-ice pyrochlores.",1810.00446v1
+2018-10-07,"Role of Spin, Phonon and Plasmon Dynamics on Ferromagnetism in Cr doped 3C-SiC","The defect induced magnetism has initiated a lot of interest in field of
+spintronics. In this regard, SiC is a promising material because of its unique
+properties under extreme conditions. Hence it will be very much interesting to
+investigate the interaction between defects and itinerant carrier in doped SiC
+for spintronics application. We report the structural stability and magnetic
+interaction in Cr doped 3C-SiC synthesized by Thermal Plasma Technique. The EPR
+spectrum of undoped 3C-SiC shows a sharp resonance line corresponding to
+$g=2.00$ associated with the defects present in the system. Anomalous
+temperature evolution tendency of the relative intensity of EPR spectra can be
+attributed to magnetically correlated defects in the host matrix. For the first
+time we report the detailed quantitative analysis of X-band and Q-band EPR
+study in Cr doped 3C-SiC which reveals that Cr can be in multivalent state. The
+non monotonous variation of Longitudinal Mode (LO) of the Raman spectra has
+been explained based on the interaction between carriers and surface plasmon
+using Longitudinal optical plasmon coupling model (LOPC). The carrier density
+calculated by using LOPC fit with experimental data varies from
+$1.8\times10^{15}$ to $4.2\times10^{17}$ cm$^{-3}$. Room temperature magnetic
+measurements exhibit ferromagnetic behavior with non-zero coercivity for all
+the samples up to 7 T field. We, for the first time, show the Curie temperature
+to be above 760 K. Quantitative analysis of magnetic interaction validates the
+applicability of Bound Magnetic Polaron Model (BMP) which probably arises from
+the exchange interaction of Cr$^{3+}$ ions with related (Si, C) defects. The
+polaron density estimated from the BMP fit agrees well with the carrier density
+obtained from the line shape fitting of Raman spectra.",1810.03146v3
+2018-10-27,Evolution of Photospheric Vector Magnetic Field Associated with Moving Flare Ribbons As Seen By GST,"The photospheric response to solar flares, also known as coronal back
+reaction, is often observed as sudden flare-induced changes in vector magnetic
+field and sunspot motions. However, it remains obscure whether evolving flare
+ribbons, the flare signature closest to the photosphere, are accompanied by
+changes in vector magnetic field therein. Here we explore the relationship
+between the dynamics of flare ribbons in the chromosphere and variations of
+magnetic fields in the underlying photosphere, using high-resolution off-band
+H-alpha images and near-infrared vector magnetograms of the M6.5 flare on 2015
+June 22 observed with the 1.6 m Goode Solar Telescope. We find that changes of
+photospheric fields occur at the arrival of the flare ribbon front, thus
+propagating analogously to flare ribbons. In general, the horizontal field
+increases and the field lines become more inclined to the surface. When ribbons
+sweep through regions that undergo a rotational motion, the fields transiently
+turn more vertical with decreased horizontal field and inclination angle, and
+then restore and/or become more horizontal than before the ribbon arrival. The
+ribbon propagation decelerates near the sunspot rotation center, where the
+vertical field becomes permanently enhanced. Similar magnetic field changes are
+discernible in magnetograms from the Helioseismic and Magnetic Imager (HMI),
+and an inward collapse of coronal magnetic fields is inferred from the time
+sequence of non-linear force-free field models extrapolated from HMI
+magnetograms. We conclude that photospheric fields respond nearly
+instantaneously to magnetic reconnection in the corona.",1810.11733v1
+2018-12-13,Magnetic fields and low-frequency acoustic wave-energy supply to the solar chromosphere,"The problem of solar chromospheric heating remains a challenging one with
+wider implications for stellar physics. Several studies in the recent past have
+shown that small-scale inclined magnetic field elements channel copious amount
+of energetic low-frequency acoustic waves, that are normally trapped below the
+photosphere. These magneto-acoustic waves are expected to shock at
+chromospheric heights contributing to chromospheric heating. In this work,
+exploiting simultaneous photospheric vector magnetic field, Doppler, continuum
+and line-core intensity (of FeI 6173 {\AA}) observations from the Helioseismic
+and Magnetic Imager (HMI) and lower-atmospheric UV emission maps in the 1700
+{\AA} and 1600 {\AA} channels of the Atmospheric Imaging Assembly (AIA), both
+onboard the Solar Dynamics Observatory (SDO) of NASA, we revisit the
+relationships between magnetic field properties (inclination and strength) and
+the acoustic wave propagation (phase travel time). We find that the flux of
+acoustic energy, in the 2 - 5 mHz frequency range, between the upper
+photosphere and lower chromosphere is in the range of 2.25 - 2.6 kW m$^{-2}$,
+which is about twice the previous estimates. We identify that the relatively
+less-inclined magnetic field elements in the quiet-Sun channel a significant
+amount of waves of frequency lower than the theoretical minimum for acoustic
+cut-off frequency due to magnetic inclination. We also derive indications that
+these waves steepen and start to dissipate within the heights ranges probed,
+while those let out due to inclined magnetic fields pass through. We explore
+connections with existing theoretical and numerical results that could explain
+the origin of these waves.",1812.05322v1
+2019-03-16,Magnetically-Sensitive Valley Polarization Reversal and Revival of Defect-Localized Excitons in WSe2-WS2,"Manipulating and reserving the valley pseudospin of excitons is one core aim
+in the two-dimensional transition metal dichalcogenides (TMDs). However, due to
+the strong electron-hole exchange and spin-orbit coupling interactions, the
+exciton recombination lifetime is subject to picosecond timescale
+intrinsically, and the valley polarization is hardly modulated by a moderate
+magnetic field. It is fortunate that interlayer and defect-localized excitons
+promise to overcome these difficulties by suppressing the above interactions.
+Here we clearly reveal that the valley polarization can be reversed and revived
+in the defect-localized excitons with a microsecond lifetime in AB-stacked
+WSe2-WS2 heterobilayer. Specifically, for the interlayer defect-localized
+exciton, the valley polarization is reversed and can be efficiently enhanced by
+a weak out-of-plane magnetic field (<0.4 T). In sharp contrast, the valley
+polarization of the intralayer defect-localized exciton can revive after a fast
+decay process and follows the direction of the moderate out-of-plane magnetic
+field (<3 T). We explain the reversed valley polarization with highly magnetic
+sensitivity by the delocalization of defect-localized holes under a weak
+magnetic field and the revival of valley polarization by the valley Zeeman
+effect under a moderate magnetic field. Our results demonstrate that the valley
+pseudospin of defect-localized excitons can be efficiently modulated by the
+external magnetic field and enrich both the understanding and the technical
+approaches on manipulating the valley dynamics in TMDs and their
+heterostructure.",1903.06899v2
+2019-08-29,Pushing down the lateral dimension of single and coupled magnetic dots to the nanometric scale: characteristics and evolution of the spin-wave eigenmodes,"Planar magnetic nanoelements, either single- or multi-layered, are exploited
+in a variety of current or forthcoming spintronic and/or ICT devices, such as
+read heads, magnetic memory cells, spin-torque nano-oscillators, nanomagnetic
+logic circuits, magnonic crystals and artificial spin-ices. The lateral
+dimensions of the elemental magnetic components have been squeezed down during
+the last decade to a few tens of nanometers, but they are still an order of
+magnitude larger that the exchange correlation length of the constituent
+materials. This means that the spectrum of spin-wave eigenmodes, occurring in
+the GHz range, is relatively complex and cannot be described within a simple
+macrospin approximation. On the other hand, a detailed knowledge of the
+dynamical spectrum is needed to understand or to predict crucial
+characteristics of the devices. With this focused review we aim at the analysis
+and the rationalization of the characteristics of the eigenmodes spectrum of
+magnetic nanodots, paying special attention to the following key points: (i)
+Consider and compare the case of in-plane and out of-plane orientation of the
+magnetization, as well as of single- and multi-layered dots, putting in
+evidence similarities and diversities, and proposing a unifying nomenclature
+and labelling scheme; (ii) Underline the evolution of the spectrum when the
+lateral size of magnetic dots is squeezed down from hundreds to tens of
+nanometers, as in current devices, with emphasis given to the occurrence of
+soft modes and to the change of spatial localization of the fundamental mode
+for in-plane magnetized dots; (iii) Extend the analysis from isolated elements
+to twins of dots, as well as to dense arrays of dipolarly interacting dots,
+showing how the discretized eigenmodes distinctive of the single element
+transform in finite-width frequency bands of spin waves propagating through the
+array.",1908.11098v1
+2020-01-13,Magnetic properties of Mn-doped Bi$_2$Se$_3$ topological insulators: ab initio calculations,"Doping Bi$_2$Se$_3$ by magnetic ions represents an interesting problem since
+it may break the time reversal symmetry needed to maintain the topological
+insulator character. Mn dopants in Bi$_2$Se$_3$ represent one of the most
+studied examples here. However, there is a lot of open questions regarding
+their magnetic ordering. In the experimental literature different Curie
+temperatures or no ferromagnetic order at all are reported for comparable Mn
+concentrations. This suggests that magnetic ordering phenomena are complex and
+highly susceptible to different growth parameters, which are known to affect
+material defect concentrations. So far theory focused on Mn dopants in one
+possible position, and neglected relaxation effects as well as native defects.
+We have used ab initio methods to calculate the Bi$_2$Se$_3$ electronic
+structure influenced by magnetic Mn dopants, and exchange interactions between
+them. We have considered two possible Mn positions, the substitutional and
+interstitial one, and also native defects. We have found a sizable relaxation
+of atoms around Mn, which affects significantly magnetic interactions.
+Surprisingly, very strong interactions correspond to a specific position of Mn
+atoms separated by van der Waals gap. Based on the calculated data we performed
+spin dynamics simulations to examine systematically the resulting magnetic
+order for various defect contents. We have found under which conditions the
+experimentally measured Curie temperatures ${T_{\rm{C}}}$ can be reproduced,
+noticing that interstitial Mn atoms appear to be important here. Our theory
+predicts the change of ${T_{\rm{C}}}$ with a shift of Fermi level, which opens
+the way to tune the system magnetic properties by selective doping.",2001.04366v1
+2020-02-25,Magnetic twist profile inside magnetic clouds derived with a superposed epoch analysis,"Magnetic clouds (MCs) are large-scale interplanetary transient structures in
+the heliosphere that travel from the Sun into the interplanetary medium. The
+internal magnetic field lines inside the MCs are twisted, forming a flux rope
+(FR). This magnetic field structuring is determined by its initial solar
+configuration, by the processes involved during its eruption from the Sun, and
+by the dynamical evolution during its interaction with the ambient solar wind.
+One of the most important properties of the magnetic structure inside MCs is
+the twist of the field lines forming the FR (the number of turns per unit
+length). The detailed internal distribution of twist is under debate mainly
+because the magnetic field (B) in MCs is observed only along the spacecraft
+trajectory, and thus it is necessary to complete observations with theoretical
+assumptions. Estimating the twist from the study of a single event is difficult
+because the field fluctuations significantly increase the noise of the observed
+B time series and thus the bias of the deduced twist. The superposed epoch
+applied to MCs has proven to be a powerful technique, permitting the extraction
+of their common features, and removing the peculiarity of individual cases. We
+apply a superposed epoch technique to analyse the magnetic components in the
+local FR frame of a significant sample of moderately asymmetric MCs observed at
+1 au. From the superposed profile of B components in the FR frame, we determine
+the typical twist distribution in MCs. The twist is nearly uniform in the FR
+core (central half part), and it increases moderately, up to a factor two,
+towards the MC boundaries. This profile is close to the Lundquist field model
+limited to the FR core where the axial field component is above about one-third
+of its central value.",2002.10606v1
+2020-06-05,Magnetism Science with the Square Kilometre Array,"The Square Kilometre Array (SKA) will answer fundamental questions about the
+origin, evolution, properties, and influence of magnetic fields throughout the
+Universe. Magnetic fields can illuminate and influence phenomena as diverse as
+star formation, galactic dynamics, fast radio bursts, active galactic nuclei,
+large-scale structure, and Dark Matter annihilation. Preparations for the SKA
+are swiftly continuing worldwide, and the community is making tremendous
+observational progress in the field of cosmic magnetism using data from a
+powerful international suite of SKA pathfinder and precursor telescopes. In
+this contribution, we revisit community plans for magnetism research using the
+SKA, in the light of these recent rapid developments. We focus in particular on
+the impact that new radio telescope instrumentation is generating, thus
+advancing our understanding of key SKA magnetism science areas, as well as the
+new techniques that are required for processing and interpreting the data. We
+discuss these recent developments in the context of the ultimate scientific
+goals for the SKA era.",2006.03172v1
+2020-06-10,On the existence of shear-current effects in magnetized burgulence,"The possibility of explaining shear flow dynamos by a magnetic shear-current
+(MSC) effect is examined via numerical simulations. Our primary diagnostics is
+the determination of the turbulent magnetic diffusivity tensor
+$\boldsymbol{\eta}$. In our setup, a negative sign of its component $\eta_{yx}$
+is necessary for coherent dynamo action by the SC effect. To be able to measure
+turbulent transport coefficients from systems with magnetic background
+turbulence, we present an extension of the test-field method (TFM), applicable
+to our setup where the pressure gradient is dropped from the momentum equation:
+the nonlinear TFM (NLTFM). Our momentum equation is related to Burgers'
+equation and the resulting flows are referred to as magnetized burgulence. We
+use both stochastic kinetic and magnetic forcings to mimic cases without and
+with simultaneous small-scale dynamo action (SSD). When we force only
+kinetically, negative $\eta_{yx}$ are obtained with exponential growth in both
+the radial and azimuthal mean magnetic field components. Using isotropic
+magnetic forcing, the field growth is no longer exponential, while NLTFM yields
+positive $\eta_{yx}$. By employing an alternative forcing from which
+wavevectors having small components are removed, the exponential growth is
+recovered, but the NLTFM results do not change significantly. Analyzing the
+dynamo excitation conditions for the coherent SC and incoherent $\alpha$ and SC
+effects shows that the incoherent effects are the main drivers of the dynamo in
+the majority of cases. We find no evidence for MSC-effect-driven dynamos in our
+simulations.",2006.05661v3
+2020-08-04,Sunspot penumbral filaments intruding into a light bridge and the resultant reconnection jets,"Penumbral filaments and light bridges are prominent structures inside
+sunspots and are important for understanding the nature of sunspot magnetic
+fields and magneto-convection underneath. We investigate an interesting event
+where several penumbral filaments intruded into a sunspot light bridge for more
+insights into magnetic fields of the sunspot penumbral filament and light
+bridge, as well as their interaction. The emission, kinematic, and magnetic
+topology characteristics of the penumbral filaments intruding into the light
+bridge and the resultant jets are studied. At the west part of the light
+bridge, the intruding penumbral filaments penetrated into the umbrae on both
+sides of the light bridge, and two groups of jets were also detected. The jets
+shared the same projected morphology with the intruding filaments and were
+accompanied by intermittent footpoint brightenings. Simultaneous spectral
+imaging observations provide convincing evidences for the presences of magnetic
+reconnection related heating and bidirectional flows near the jet bases and
+contribute to measuring vector velocities of the jets. Additionally, nonlinear
+force-free field extrapolation results reveal strong and highly inclined
+magnetic fields along the intruding penumbral filaments, consistent well with
+the results deduced from the vector velocities of the jets. Therefore, we
+propose that the jets could be caused by magnetic reconnections between
+emerging fields within the light bridge and the nearly horizontal fields of
+intruding filaments. They were then ejected outward along the stronger
+filaments fields. Our study indicates that magnetic reconnection could occur
+between the penumbral filament fields and emerging fields within light bridge
+and produce jets along the stronger filament fields. These results further
+complement the study of magnetic reconnection and dynamic activities within the
+sunspot.",2008.01284v1
+2020-10-15,Solar Coronal Magnetic Field Extrapolation from Synchronic Data with AI-generated Farside,"Solar magnetic fields play a key role in understanding the nature of the
+coronal phenomena. Global coronal magnetic fields are usually extrapolated from
+photospheric fields, for which farside data is taken when it was at the
+frontside, about two weeks earlier. For the first time we have constructed the
+extrapolations of global magnetic fields using frontside and artificial
+intelligence (AI)-generated farside magnetic fields at a near-real time basis.
+We generate the farside magnetograms from three channel farside observations of
+Solar Terrestrial Relations Observatory (STEREO) Ahead (A) and Behind (B) by
+our deep learning model trained with frontside Solar Dynamics Observatory
+extreme ultraviolet images and magnetograms. For frontside testing data sets,
+we demonstrate that the generated magnetic field distributions are consistent
+with the real ones; not only active regions (ARs), but also quiet regions of
+the Sun. We make global magnetic field synchronic maps in which conventional
+farside data are replaced by farside ones generated by our model. The
+synchronic maps show much better not only the appearance of ARs but also the
+disappearance of others on the solar surface than before. We use these
+synchronized magnetic data to extrapolate the global coronal fields using
+Potential Field Source Surface (PFSS) model. We show that our results are much
+more consistent with coronal observations than those of the conventional method
+in view of solar active regions and coronal holes. We present several positive
+prospects of our new methodology for the study of solar corona, heliosphere,
+and space weather.",2010.07553v3
+2021-05-08,Multi-scale Magnetic Fields in the Central Molecular Zone: Inference from the Gradient Technique,"The central molecular zone (CMZ) plays an essential role in regulating the
+nuclear ecosystem of our Galaxy. To get an insight into the magnetic fields of
+the CMZ, we employ the Gradient Technique (GT), which is rooted in the
+anisotropy of magnetohydrodynamic turbulence. Our analysis is based on the data
+of multiple wavelengths, including molecular emission lines, radio 1.4 GHz
+continuum image, and Herschel 70 $\mu$m image, as well as ionized [Ne II] and
+Paschen-alpha emissions. The results are compared with the observations of
+Planck 353 GHz and High-resolution Airborne Wideband Camera Plus (HWAC+) 53
+$\mu$m polarized dust emissions. We map the orientation of the magnetic field
+at multiple wavelengths across the central molecular zone, including close-ups
+of the Radio Arc and Sagittarius A West regions, on multi scales from $\sim$
+0.1 pc to 10 pc. The magnetic fields towards the central molecular zone traced
+by GT are globally compatible with the polarization measurements, accounting
+for the contribution from the galactic foreground and background. This
+correspondence suggests that the magnetic field and turbulence are dynamically
+crucial in the galactic center. We find that the magnetic fields associated
+with the Arched filaments and the thermal components of the Radio Arc are in
+good agreement with the HAWC+ polarization. Our measurement towards the
+non-thermal Radio Arc reveals the poloidal magnetic field components in the
+galactic center. For Sagittarius A West region, we find a great agreement
+between the GT measurement using [Ne II] emission and HWAC+ 53 $\mu$m
+observation. We use GT to predict the magnetic fields associated with ionized
+Paschen-alpha gas down to scales of 0.1 pc.",2105.03605v3
+2021-05-13,Tracing the large-scale magnetic field morphology in protoplanetary disks using molecular line polarization,"(abridged) Magnetic fields are fundamental to the accretion dynamics of
+protoplanetary disks and they likely affect planet formation. Typical methods
+to study the magnetic field morphology observe the polarization of dust or
+spectral lines. However, it has recently become clear that dust-polarization in
+ALMA's spectral regime does not always faithfully trace the magnetic field
+structure of protoplanetary disks, which leaves spectral line polarization as a
+promising method for mapping the magnetic field morphologies of such sources.
+We aim to model the emergent polarization of different molecular lines in the
+ALMA wavelength regime that are excited in protoplanetary disks. We explore a
+variety of disk models and molecules to identify those properties that are
+conducive to the emergence of polarization in spectral lines and may therefore
+be viably used for magnetic field measurements in protoplanetary disks. We used
+PORTAL in conjunction with LIME. Together, they allowed us to treat the
+polarized line radiative transfer of complex three-dimensional physical and
+magnetic field structures. We present simulations of the emergence of spectral
+line polarization of different molecules and molecular transitions in the ALMA
+wavelength regime. We find that molecules that thermalize at high densities,
+such as HCN, are also the most susceptible to polarization. We find that such
+molecules are expected to be significantly polarized in protoplanetary disks,
+while molecules that thermalize at low densities, such as CO, are only
+significantly polarized in the outer disk regions. We present the simulated
+polarization maps at a range of inclinations and magnetic field morphologies,
+and we comment on the observational feasibility of ALMA linear polarization
+observations of protoplanetary disks.",2105.06482v2
+2021-05-30,"Magnetic structure determination of rare-earth based, high moment, atomic laminates; potential parent materials for 2D magnets","We report muon spin rotation ($\mu$SR) and neutron diffraction on the
+rare-earth based magnets (Mo$_{2/3}$RE$_{1/3}$)$_2$AlC, also predicted as
+parent materials for 2D derivatives, where RE = Nd, Gd (only ($\mu$SR), Tb, Dy,
+Ho and Er. By crossing information between the two techniques, we determine the
+magnetic moment ($m$), structure, and dynamic properties of all compounds. We
+find that only for RE = Nd and Gd the moments are frozen on a microsecond time
+scale. Out of these two, the most promising compound for a potential 2D high
+($m$) magnet is the Gd variant, since the parent crystals are pristine with $m
+= 6.5 \pm 0.5 \mu_B$, N\'eel temperature of $29 \pm 1$ K, and the magnetic
+anisotropy between in and out of plane coupling is smaller than $10^{-8}$. This
+result suggests that magnetic ordering in the Gd variant is dominated by
+in-plane magnetic interactions and should therefore remain stable if exfoliated
+into 2D sheets.",2105.14555v2
+2021-06-19,A-type antiferromagnetic order and magnetic phase diagram of the trigonal Eu spin-7/2 triangular-lattice compound EuSn2As2,"The trigonal compound EuSn2As2 was recently discovered to host Dirac surface
+states within the bulk band gap and orders antiferromagnetically below the Neel
+temperature TN = 24 K. Here the magnetic ground state of single-crystal
+EuSn2As2 and the evolution of its properties versus temperature T and applied
+magnetic field H are reported. Included are zero-field single-crystal
+neutron-diffraction measurements versus T, magnetization M(H,T), magnetic
+susceptibility chi(H,T) = M(T)/H, heat capacity Cp(H,T), and electrical
+resistivity rho(H,T) measurements. The neutron-diffraction and chi(T)
+measurements both indicate a collinear A-type antiferromagnetic (AFM) structure
+below TN =23.5(2) K, where the Eu{2+} spins S = 7/2 in a triangular ab-plane
+layer (hexagonal unit cell) are aligned ferromagnetically in the ab plane
+whereas the spins in adjacent Eu planes along the c axis are aligned
+antiferromagnetically. The chi(H{ab},T) and chi(H{c},T) data together indicate
+a smooth crossover between the collinear AFM alignment and an unknown magnetic
+structure at H ~ 0.15 T. Dynamic spin fluctuations up to 60 K are evident in
+the chi(T), Cp(T) and rho(H,T) measurements, a temperature that is more than
+twice TN. The rho(H,T) of the compound does not reflect a contribution of the
+topological state, but rather is consistent with a low-carrier-density metal
+with strong magnetic scattering. The magnetic phase diagrams for both H||c and
+H||ab in the H-T plane are constructed from the TN(H), chi(H,T), Cp(H,T), and
+rho(H,T) data.",2106.10519v1
+2021-09-06,How to Estimate the Far-Side Open Flux using STEREO Coronal Holes,"Global magnetic field models use as input synoptic data, which usually show
+""aging effects"" as the longitudinal 360{\deg} information is not obtained
+simultaneously. Especially during times of increased solar activity, the
+evolution of the magnetic field may yield large uncertainties. A significant
+source of uncertainty is the Sun's magnetic field on the side of the Sun that
+is not visible to the observer. Various methods have been used to complete the
+picture: synoptic charts, flux-transport models, and far side helioseismology.
+In this study, we present a new method to estimate the far-side open flux
+within coronal holes using STEREO EUV observations. First, we correlate the
+structure of the photospheric magnetic field as observed with the Helioseismic
+and Magnetic Imager on board the Solar Dynamics Observatory (HMI/SDO) with
+features in the transition region. From the 304A intensity distribution, which
+we found to be specific to coronal holes, we derive an empirical estimate for
+the open flux. Then we use a large sample of 313 SDO coronal hole observations
+to verify this relation. Finally, we perform a cross-instrument calibration
+from SDO to STEREO data to enable the estimation of the open flux at solar
+longitudes not visible from Earth. We find that the properties of strong,
+unipolar magnetic elements in the photosphere, which determine the coronal
+hole's open flux, can be approximated by open fields in the transition region.
+We find that structures below a threshold of 78% (STEREO) or 94% (SDO) of the
+solar disk median intensity as seen in 304A filtergrams are reasonably well
+correlated with the mean magnetic flux density of coronal holes (cc = 0.59).
+Using the area covered by these structures (A_of) and the area of the coronal
+hole (A_ch), we model the open magnetic flux of a coronal hole as |Phi_ch| =
+0.25 A_ch exp(0.032 A_of) with an estimated uncertainty of 40 to 60%.",2109.02375v1
+2016-11-18,Tuning the pseudospin polarization of graphene by a pseudo-magnetic field,"One of the intriguing characteristics of honeycomb lattices is the appearance
+of a pseudo-magnetic field as a result of mechanical deformation. In the case
+of graphene, the Landau quantization resulting from this pseudo-magnetic field
+has been measured using scanning tunneling microscopy. Here we show that a
+signature of the pseudo-magnetic field is a local sublattice symmetry breaking
+observable as a redistribution of the local density of states. This can be
+interpreted as a polarization of graphene's pseudospin due to a strain induced
+pseudo-magnetic field, in analogy to the alignment of a real spin in a magnetic
+field. We reveal this sublattice symmetry breaking by tunably straining
+graphene using the tip of a scanning tunneling microscope. The tip locally
+lifts the graphene membrane from a SiO$_2$ support, as visible by an increased
+slope of the $I(z)$ curves. The amount of lifting is consistent with molecular
+dynamics calculations, which reveal a deformed graphene area under the tip in
+the shape of a Gaussian. The pseudo-magnetic field induced by the deformation
+becomes visible as a sublattice symmetry breaking which scales with the lifting
+height of the strained deformation and therefore with the pseudo-magnetic field
+strength. Its magnitude is quantitatively reproduced by analytic and
+tight-binding models, revealing fields of 1000 T. These results might be the
+starting point for an effective THz valley filter, as a basic element of
+valleytronics.",1611.06123v2
+2016-11-21,Probing magnetic fields with Square Kilometre array and its precursors,"Origin of magnetic fields, its structure and effects on dynamical processes
+in stars to galaxies are not well understood. Lack of a direct probe has
+hampered its study. The first phase of Square Kilometre Array (SKA-I), will
+have more than an order of magnitude higher sensitivity than existing radio
+telescopes. In this contribution, we discuss specific science cases that are of
+interest to the Indian community concerned with astrophysical turbulence and
+magnetic fields. The SKA-I will allow observations of a large number of
+background sources with detectable polarisation and measure their Faraday
+depths (FDs) through the Milky Way, other galaxies and their circum-galactic
+medium. This will probe line-of-sight magnetic fields in these objects well and
+provide field configurations. Detailed comparison of observational data with
+models which consider various processes giving rise to field amplification and
+maintenance will then be possible. Such observations will also provide the
+coherence scale of the fields and measure its random component. Measuring the
+random component is important to characterise turbulence in the medium.
+Observations of FDs with redshift will provide important information on
+magnetic field evolution as a function of redshift. The background sources
+could also be used to probe magnetic fields and its coherent scale in galaxy
+clusters and in bridges formed between interacting galaxies. Other than FDs,
+sensitive observations of synchrotron emission from galaxies will provide
+complimentary information on their magnetic field strengths in the sky plane.
+The core shift measurements of AGNs can provide more precise measurements of
+magnetic field very close (<pc) to the black hole and its evolution. The low
+band of SKA-I will also be useful to study circularly polarized emission from
+Sun and comparing various models of field configurations with observations.",1611.06966v1
+2019-02-27,Fossil field decay due to nonlinear tides in massive binaries,"Surface magnetic fields have been detected in 5 to 10% of isolated massive
+stars, hosting outer radiative envelopes. They are often thought to have a
+fossil origin, resulting from the stellar formation phase. Yet, magnetic
+massive stars are scarcer in (close) short-period binaries, as reported by the
+BinaMIcS (Binarity and Magnetic Interaction in various classes of Stars)
+collaboration. Different physical conditions in the molecular clouds giving
+birth to isolated stars and binaries are commonly invoked. In addition, we
+propose that the observed lower magnetic incidence in close binaries may be due
+to nonlinear tides. Indeed, close binaries are probably prone to tidal
+instability, a fluid instability growing upon the equilibrium tidal flow via
+nonlinear effects. Yet, stratified effects have hitherto been largely
+overlooked. We theoretically and numerically investigate tidal instability in
+rapidly rotating, stably stratified fluids permeated by magnetic fields. We use
+the short-wavelength stability method to propose a comprehensive (local) theory
+of tidal instability at the linear onset, discussing damping effects. Then, we
+propose a mixing-length theory for the mixing generated by tidal instability in
+the nonlinear regime. We successfully assess our theoretical predictions
+against proof-of-concept, direct numerical simulations. Finally, we compare our
+predictions with the observations of short-period, double-lined spectroscopic
+binary systems. Using new analytical results, cross-validated by a direct
+integration of the stability equations, we show that tidal instability can be
+generated by nonlinear couplings of inertia-gravity waves with the equilibrium
+tidal flow in short-period massive binaries, even against the Joule diffusion.
+In the nonlinear regime, a fossil magnetic field can be dissipated by the
+turbulent magnetic diffusion induced by the saturated tidal flows. We predict
+that the turbulent Joule diffusion of fossil fields would occur in a few
+million years for several short-period massive binaries. Therefore, turbulent
+tidal flows could explain the observed dearth of some short-period magnetic
+binaries.",1902.10599v2
+2019-12-03,Picosecond Spin Orbit Torque Switching,"Reducing energy dissipation while increasing speed in computation and memory
+is a long-standing challenge for spintronics research. In the last 20 years,
+femtosecond lasers have emerged as a tool to control the magnetization in
+specific magnetic materials at the picosecond timescale. However, the use of
+ultrafast optics in integrated circuits and memories would require a major
+paradigm shift. An ultrafast electrical control of the magnetization is far
+preferable for integrated systems. Here we demonstrate reliable and
+deterministic control of the out-of-plane magnetization of a 1 nm-thick Co
+layer with single 6 ps-wide electrical pulses that induce spin-orbit torques on
+the magnetization. We can monitor the ultrafast magnetization dynamics due to
+the spin-orbit torques on sub-picosecond timescales, thus far accessible only
+by numerical simulations. Due to the short duration of our pulses, we enter a
+counter-intuitive regime of switching where heat dissipation assists the
+reversal. Moreover, we estimate a low energy cost to switch the magnetization,
+projecting to below 1fJ for a (20 nm)^3 cell. These experiments prove that
+spintronic phenomena can be exploited on picosecond time-scales for full
+magnetic control and should launch a new regime of ultrafast spin torque
+studies and applications.",1912.01377v4
+2020-04-08,High-order crystal field and rare-earth magnetism in RECo5 intermetallics,"Crystal-field (CF) effects on the rare-earth (RE) ions in ferrimagnetic
+intermetallics NdCo$_5$ and TbCo$_5$ are evaluated using an ab initio density
+functional + dynamical mean-field theory approach in conjunction with a
+quasi-atomic approximation for on-site electronic correlations on the localized
+4$f$ shell. The study reveals an important role of the high-order sectoral
+harmonic component of the CF in the magnetism of RECo$_5$ intermetallics. An
+unexpectedly large value is computed in the both systems for the corresponding
+crystal-field parameter (CFP) $A_6^6 \langle r^6 \rangle$, far beyond what one
+would expect from only electrostatic contributions. It allows solving the
+enigma of the non-saturation of zero-temperature Nd magnetic moments in
+NdCo$_5$ along its easy axis in the Co exchange field. This unsaturated state
+had been previously found out from magnetization distribution probed by
+polarised neutron elastic scattering but had so far remained theoretically
+unexplained. The easy plane magnetic anisotropy of Nd in NdCo$_5$ is strongly
+enhanced by the large value of $A_6^6\langle r^6 \rangle$. Counter-intuitively,
+the polar dependence of anisotropy energy within the easy plane remains rather
+small. The easy plane magnetic anisotropy of Nd is reinforced up to high
+temperatures, which is explained through $J$-mixing effects. The calculated ab
+initio anisotropy constants of NdCo$_5$ and their temperature dependence are in
+quantitative agreement with experiment. Unlike NdCo$_5$, the $A_6^6 \langle r^6
+\rangle$ CFP has negligible effects on the Tb magnetism in TbCo$_5$ suggesting
+that its impact on the RE magnetism is ion-specific across the RECo$_5$ series.
+The origin of its large value is the hybridization of RE and Co states in a
+hexagonally coordinated local environment of the RE ion in RECo$_5$
+intermetallics.",2004.03945v1
+2020-09-18,"Magnetic Ergostars, Jet Formation and Gamma-Ray Bursts: Ergoregions versus Horizons","We perform the first fully general relativistic, magnetohydrodynamic
+simulations of dynamically stable hypermassive neutron stars with and without
+ergoregions to assess the impact of ergoregions on launching
+magnetically--driven outflows. The hypermassive neutron stars are modeled by a
+compressible and causal equation of state and are initially endowed with a
+dipolar magnetic field extending from the stellar interior into its exterior.
+We find that, after a few Alfv\'en times, magnetic field lines in the ergostar
+(star that contains ergoregions) and the normal star have been tightly wound in
+both cases into a helical funnel within which matter begins to flow outward.
+The maximum Lorentz factor in the outflow is $\Gamma_L \sim 2.5$, while the
+force-free parameter holds at $B^2/8\pi\rho_0\lesssim 10$. These values are
+incompatible with highly relativistic, magnetically-driven outflows (jets) and
+short $\gamma$-ray bursts. We compare these results with those of a spinning
+black hole surrounded by a magnetized, massless accretion disk that launches a
+bona fide jet. Our simulations suggest that the Blandford-Znajek mechanism for
+launching relativistic jets only operates when a black hole is present, though
+the Poynting luminosity in all cases is comparable. Therefore, one cannot
+distinguish a magnetized, accreting black hole from a magnetized hypermassive
+neutron star in the so-called mass-gap based solely on the value of the
+observed Poynting luminosity. These results complement our previous studies of
+supramassive remnants and suggest that it would be challenging for either
+normal neutron stars or ergostars in a hypermassive state to be the progenitors
+of short $\gamma$-ray bursts.",2009.08982v2
+2021-03-08,All-optical spin switching probability in [Tb/Co] multilayers,"Since the first experimental observation of all-optical switching phenomena,
+intensive research has been focused on finding suitable magnetic systems that
+can be integrated as storage elements within spintronic devices and whose
+magnetization can be controlled through ultra-short single laser pulses. We
+report here atomistic spin simulations of all-optical switching in multilayered
+structures alternating n monolayers of Tb and m monolayers of Co. By using a
+two temperature model, we numerically calculate the thermal variation of the
+magnetization of each sublattice as well as the magnetization dynamics of
+[Tbn/Com] multilayers upon incidence of a single laser pulse. In particular,
+the condition to observe thermally-induced magnetization switching is
+investigated upon varying systematically both the composition of the sample
+(n,m) and the laser fluence. The samples with one monolayer of Tb as [Tb1/Co2]
+and [Tb1/Co3] are showing thermally induced magnetization switching above a
+fluence threshold. The reversal mechanism is mediated by the residual
+magnetization of the Tb lattice while the Co is fully demagnetized in agreement
+with the models developed for ferrimagnetic alloys. The switching is however
+not fully deterministic but the error rate can be tuned by the damping
+parameter. Increasing the number of monolayers the switching becomes completely
+stochastic. The intermixing at the Tb/Co interfaces appears to be a promising
+way to reduce the stochasticity. These results predict for the first time the
+possibility of TIMS in [Tb/Co] multilayers and suggest the occurrence of
+sub-picosecond magnetization reversal using single laser pulses.",2103.05066v1
+2021-03-24,Magnetism and Spin Dynamics in Room-Temperature van der Waals Magnet Fe$_5$GeTe$_2$,"Two-dimensional (2D) van der Waals (vdWs) materials have gathered a lot of
+attention recently. However, the majority of these materials have Curie
+temperatures that are well below room temperature, making it challenging to
+incorporate them into device applications. In this work, we synthesized a
+room-temperature vdW magnetic crystal Fe$_5$GeTe$_2$ with a Curie temperature
+T$_c = 332$ K, and studied its magnetic properties by vibrating sample
+magnetometry (VSM) and broadband ferromagnetic resonance (FMR) spectroscopy.
+The experiments were performed with external magnetic fields applied along the
+c-axis (H$\parallel$c) and the ab-plane (H$\parallel$ab), with temperatures
+ranging from 300 K to 10 K. We have found a sizable Land\'e g-factor difference
+between the H$\parallel$c and H$\parallel$ab cases. In both cases, the Land\'e
+g-factor values deviated from g = 2. This indicates contribution of orbital
+angular momentum to the magnetic moment. The FMR measurements reveal that
+Fe$_5$GeTe$_2$ has a damping constant comparable to Permalloy. With reducing
+temperature, the linewidth was broadened. Together with the VSM data, our
+measurements indicate that Fe$_5$GeTe$_2$ transitions from ferromagnetic to
+ferrimagnetic at lower temperatures. Our experiments highlight key information
+regarding the magnetic state and spin scattering processes in Fe$_5$GeTe$_2$,
+which promote the understanding of magnetism in Fe$_5$GeTe$_2$, leading to
+implementations of Fe$_5$GeTe$_2$ based room-temperature spintronic devices.",2103.13433v2
+2021-07-23,Multiple Stokes I inversions to infer magnetic fields in the spectral range around Cr I 5782 Å,"The spectral window, containing Fraunhofer lines formed in the solar
+photosphere, around the magnetically sensitive Cr I lines at 5780.9, 5781.1,
+5781.7, 5783.0, and 5783.8 \r{A}, with Land\'e g-factors between 1.6 and 2.5,
+is explored. The goal is to analyze simultaneously 15 spectral lines, which
+comprise Cr I, Cu I, Fe I, Mn I, and Si I lines, without polarimetry to infer
+the thermodynamic and magnetic properties in strongly magnetized plasmas using
+an inversion code. The study is based on a new setup at the Vacuum Tower
+Telescope (VTT, Tenerife) which includes fast spectroscopic scans in the
+wavelength range around the Cr I 5781.75 \r{A} line. The snapshot 385 of the
+Enhanced Network simulation from the Bifrost code serves to synthesize all the
+lines, which are in turn inverted simultaneously with SIR to establish the best
+inversion strategy. This strategy is then applied to VTT observations of a
+sunspot belonging to NOAA 12723 on 2018 September 30 and the results are
+compared to full-disk vector-field data obtained with the Helioseismic and
+Magnetic Imager (HMI). The 15 simultaneously inverted intensity profiles
+(Stokes I) delivered accurate temperatures and Doppler velocities when compared
+against the simulations. The derived magnetic fields and inclinations are most
+accurate when the fields are oriented along the line-of-sight (LOS) and less
+accurate when the fields are transverse to the LOS. In general, the results
+appear similar to the HMI vector-field data, although some discrepancies exist.
+The analyzed spectral range has the potential to deliver thermal, dynamic, and
+magnetic information in strongly magnetized features on the Sun, such as pores
+and sunspots, even without polarimetry. The highest sensitivity of the lines is
+found in the lower photosphere, on average around $\log \tau = -1$. The
+multiple-line inversions provide smooth results across the whole field-of-view.",2107.11116v1
+2021-12-07,"Spinning black holes magnetically connected to a Keplerian disk -- Magnetosphere, reconnection sheet, particle acceleration and coronal heating","Context: Accreting black holes (BHs) may be surrounded by a highly magnetized
+plasma threaded by a poloidal magnetic field. Non-thermal flares and high
+energy components could originate from a hot, collisionless and nearly
+force-free corona. The jets we often observe from these systems are believed to
+be rotation-powered and magnetically-driven.
+  Aims: We study axisymmetric BH magnetospheres where some magnetic field lines
+anchored in a surrounding disk can connect to the event horizon of a rotating
+BH. We identify the sites of magnetic reconnection within 30 gravitational
+radii depending on the BH spin.
+  Methods: With the fully general relativistic particle-in-cell code GRZeltron,
+we solve the time-dependent dynamics of the electron-positron pair plasma and
+of the electromagnetic fields around the BH. The disk is represented by a
+steady plasma in Keplerian rotation, threaded by a frozen dipolar field.
+  Results: For prograde disks, twisted open magnetic field lines crossing the
+horizon power a Blandford-Znajek jet while beyond a critical distance, open
+field lines on the disk are open. In the innermost regions, coupling field
+lines ensure the transfer of significant amounts of angular momentum and energy
+between the BH and the disk. From the Y-point at the intersection, a current
+sheet forms where particle acceleration via magnetic reconnection takes place.
+We compute the synchrotron images of the current sheet emission.
+  Conclusions: Our estimates for jet power and BH-disk exchanges match those
+derived from purely force-free models. Dissipation at the Y-point heats the
+corona and provides a physically motivated source of hard X-rays above the disk
+for reflection models. Episodic plasmoid ejection might explain millisecond
+flares observed in Cyg X-1. Particles flowing from the Y-point down to the disk
+could produce a hot spot at the footpoint of the outermost closed field line.",2112.03933v1
+2022-01-05,Dust entrainment in magnetically and thermally driven disk winds,"Magnetically and thermally driven disk winds have gained popularity in the
+light of the current paradigm of low viscosities in protoplanetary disks that
+nevertheless present large accretion rates even in the presence of inner
+cavities. The possibility of dust entrainment in these winds may explain recent
+scattered light observations and constitutes a way of dust transport towards
+outer regions of the disk. We aim to study the dust dynamics in these winds and
+explore the differences between photoevaporation and magnetically driven disk
+winds in this regard. We quantify maximum entrainable grain sizes, the flow
+angle, and the general detectability. We used the FARGO3D code to perform
+global, 2.5D axisymmetric, nonideal MHD simulations including ohmic and
+ambipolar diffusion. Dust was treated as a pressureless fluid. Synthetic
+observations were created with the radiative transfer code RADMC-3D. We find a
+significant difference in the dust entrainment efficiency of warm, ionized
+winds such as photoevaporation and magnetic winds including X-ray and extreme
+ultraviolet (XEUV) heating compared to cold magnetic winds. The maximum
+entrainable grain size varies from $3\,\mu\mathrm{m}$ to $6\,\mu\mathrm{m}$ for
+ionized winds to $1\,\mu\mathrm{m}$ for cold magnetic winds. Dust grains in
+cold magnetic winds tend to flow along a shallower angle compared to the warm
+winds. With increasing distance to the central star, the dust entrainment
+efficiency decreases. Larger values of the turbulent viscosity increase the
+maximum grain size radius of possible dust entrainment. Our simulations
+indicate that diminishing dust content in the outer regions of the wind can be
+mainly attributed to the dust settling in the disk. In the synthetic images,
+the dusty wind appears as a faint, conical emission region which is brighter
+for a cold magnetic wind.",2201.01478v1
+2022-01-14,Gravitational wave signal from primordial magnetic fields in the Pulsar Timing Array frequency band,"The NANOGrav, Parkes, European, and International Pulsar Timing Array (PTA)
+Collaborations have reported evidence for a common-spectrum process that can
+potentially correspond to a stochastic gravitational wave background (SGWB) in
+the 1--100 nHz frequency range. We consider the scenario in which this signal
+is produced by magnetohydrodynamic (MHD) turbulence in the early Universe,
+induced by a nonhelical primordial magnetic field at the energy scale
+corresponding to the quark confinement phase transition. We perform MHD
+simulations to study the dynamical evolution of the magnetic field and compute
+the resulting SGWB. We show that the SGWB output from the simulations can be
+very well approximated by assuming that the magnetic anisotropic stress is
+constant in time, over a time interval related to the eddy turnover time. The
+analytical spectrum that we derive under this assumption features a change of
+slope at a frequency corresponding to the GW source duration that we confirm
+with the numerical simulations. We compare the SGWB signal with the PTA data to
+constrain the temperature scale at which the SGWB is sourced, as well as the
+amplitude and characteristic scale of the initial magnetic field. We find that
+the generation temperature is constrained to be in the 1--200 MeV range, the
+magnetic field amplitude must be $>1$\% of the radiation energy density at that
+time, and the magnetic field characteristic scale is constrained to be $>10$\%
+of the horizon scale. We show that the turbulent decay of this magnetic field
+will lead to a field at recombination that can help to alleviate the Hubble
+tension and can be tested by measurements in the voids of the Large Scale
+Structure with gamma-ray telescopes like the Cherenkov Telescope Array.",2201.05630v2
+2022-03-10,A magnetic cloud prediction model for forecasting space weather relevant properties of Earth-directed coronal mass ejections,"Coronal Mass Ejections (CMEs) are energetic storms in the Sun that result in
+the ejection of large-scale magnetic clouds (MCs) in interplanetary space that
+contain enhanced magnetic fields with coherently changing field direction. The
+severity of geomagnetic perturbations depends on the direction and strength of
+the interplanetary magnetic field (IMF), as well as the speed and duration of
+passage of the storm. The coupling between the heliospheric environment and
+Earth's magnetosphere is the strongest when the IMF direction is persistently
+southward for a prolonged period. Predicting the magnetic profile of such
+Earth-directed CMEs is crucial for estimating their geomagnetic impact. We aim
+to build upon and integrate diverse techniques towards development of a
+comprehensive magnetic cloud prediction (MCP) model that can forecast the
+magnetic field vectors, Earth-impact time, speed and duration of passage of
+solar storms. A novelty of our scheme is the ability to predict the passage
+duration of the storm without recourse to computationally intensive,
+time-dependent dynamical equations. Our methodology is validated by comparing
+the MCP model output with observations of ten MCs at 1 AU. In our sample, we
+find that eight MCs show a root mean square deviation of less than 0.1 between
+predicted and observed magnetic profiles and the passage duration of seven MCs
+fall within the predicted range. Based on the success of this approach, we
+conclude that predicting the near-Earth properties of MCs based on analysis and
+modelling of near-Sun CME observations is a viable endeavor with potential
+benefits for space weather assessment.",2203.05231v3
+2022-03-26,Ion Alfvén velocity fluctuations and implications for the diffusion of streaming cosmic rays,"The interstellar medium (ISM) of star-forming galaxies is magnetized and
+turbulent. Cosmic rays (CRs) propagate through it, and those with energies from
+$\sim\,\rm{GeV} - \rm{TeV}$ are likely subject to the streaming instability,
+whereby the wave damping processes balances excitation of resonant ionic
+Alfv\'en waves by the CRs, reaching an equilibrium in which the propagation
+speed of the CRs is very close to the local ion Alfv\'en velocity. The
+transport of streaming CRs is therefore sensitive to ionic Alfv\'en velocity
+fluctuations. In this paper we systematically study these fluctuations using a
+large ensemble of compressible MHD turbulence simulations. We show that for
+sub-Alfv\'enic turbulence, as applies for a strongly magnetized ISM, the ionic
+Alfv\'en velocity probability density function (PDF) is determined solely by
+the density fluctuations from shocked gas forming parallel to the magnetic
+field, and we develop analytical models for the ionic Alfv\'en velocity PDF up
+to second moments. For super-Alfv\'enic turbulence, magnetic and density
+fluctuations are correlated in complex ways, and these correlations as well as
+contributions from the magnetic fluctuations sets the ionic Alfv\'en velocity
+PDF. We discuss the implications of these findings for underlying ""macroscopic""
+diffusion mechanisms in CRs undergoing the streaming instability, including
+modeling the macroscopic diffusion coefficient for the parallel transport in
+sub-Alfv\'enic plasmas. We also describe how, for highly-magnetized turbulent
+gas, the gas density PDF, and hence column density PDF, can be used to access
+information about ionic Alfv\'en velocity structure from observations of the
+magnetized ISM.",2203.13952v3
+2022-04-02,Fundamental scales in the kinematic phase of the turbulent dynamo,"The turbulent dynamo is a powerful mechanism that converts turbulent kinetic
+energy to magnetic energy. A key question regarding the magnetic field
+amplification by turbulence, is, on what scale, $k_{\rm p}$, do magnetic fields
+become most concentrated? There has been some disagreement about whether
+$k_{\rm p}$ is controlled by the viscous scale, $k_\nu$ (where turbulent
+kinetic energy dissipates), or the resistive scale, $k_\eta$ (where magnetic
+fields dissipate). Here we use direct numerical simulations of
+magnetohydrodynamic turbulence to measure characteristic scales in the
+kinematic phase of the turbulent dynamo. We run $104$-simulations with
+hydrodynamic Reynolds numbers of $10 \leq {\rm Re} \leq 3600$, and magnetic
+Reynolds numbers of $270 \leq {\rm Rm} \leq 4000$, to explore the dependence of
+$k_{\rm p}$ on $k_\nu$ and $k_\eta$. Using physically motivated models for the
+kinetic and magnetic energy spectra, we measure $k_\nu$, $k_\eta$ and $k_{\rm
+p}$, making sure that the obtained scales are numerically converged. We
+determine the overall dissipation scale relations $k_\nu =
+(0.025^{+0.005}_{-0.006})\, k_{\rm turb}\, {\rm Re}^{3/4}$ and $k_\eta =
+(0.88^{+0.21}_{-0.23})\, k_\nu\, {\rm Pm}^{1/2}$, where $k_{\rm turb}$ is the
+turbulence driving wavenumber and ${\rm Pm}={\rm Rm}/{\rm Re}$ is the magnetic
+Prandtl number. We demonstrate that the principle dependence of $k_{\rm p}$ is
+on $k_\eta$. For plasmas where ${\rm Re} \gtrsim 100$, we find that $k_{\rm p}
+= (1.2_{-0.2}^{+0.2})\, k_\eta$, with the proportionality constant related to
+the power-law `Kazantsev' exponent of the magnetic power spectrum. Throughout
+this study, we find a dichotomy in the fundamental properties of the dynamo
+where ${\rm Re} > 100$, compared to ${\rm Re} < 100$. We report a minimum
+critical hydrodynamic Reynolds number, ${\rm Re}_{\rm crit} = 100$ for bonafide
+turbulent dynamo action.",2204.00828v3
+2022-06-17,Strain and electric field control of magnetic and electrical transport properties in a magneto-elastically coupled Fe3O4/BaTiO3(001) heterostructure,"We present a study of the control of electric field induced strain on the
+magnetic and electrical transport properties in a magneto-elastically coupled
+artificial multiferroic Fe3O4/BaTiO3 heterostructure. In this Fe3O4/BaTiO3
+heterostructure, the Fe3O4 thin film is epitaxially grown in the form of
+bilateral domains, analogous to a-c stripe domains of the underlying
+BaTiO3(001) substrate. By in-situ electric field dependent magnetization
+measurements, we demonstrate the extrinsic control of the magnetic anisotropy
+and the characteristic Verwey metal-insulator transition of the epitaxial Fe3O4
+thin film in a wide temperature range between 20-300 K, via strain mediated
+converse magnetoelectric coupling. In addition, we observe strain induced
+modulations in the magnetic and electrical transport properties of the Fe3O4
+thin film across the thermally driven intrinsic ferroelectric and structural
+phase transitions of the BaTiO3 substrate. In-situ electric field dependent
+Raman measurements reveal that the electric field does not significantly modify
+the anti-phase boundary defects in the Fe3O4 thin film once it is
+thermodynamically stable after deposition and that the modification of the
+magnetic properties is mainly caused by strain induced lattice distortions and
+magnetic anisotropy. These results provide a framework to realize electrical
+control of the magnetization in a classical highly correlated transition metal
+oxide.",2206.08664v1
+2022-10-17,Effects of Emerging Bipolar Magnetic Regions in Mean-field Dynamo Model of Solar Cycles 23 and 24,"We model the physical parameters of Solar Cycles 23 and 24 using a nonlinear
+dynamical mean-field dynamo model that includes the formation and evolution of
+bipolar magnetic regions (BMR). The Parker-type dynamo model consists of a
+complete MHD system in the mean-field formulation: the 3D magnetic induction
+equation, and 2D momentum and energy equations in the anelastic approximation.
+The initialization of BMR is modeled in the framework of Parker's magnetic
+buoyancy instability. It defines the depths of BMR injections, which are
+typically located at the edge of the global dynamo waves. The distribution with
+longitude and latitude and the size of the initial BMR perturbations are taken
+from the NOAA database of active regions. The tilt of the perturbations is
+modeled by random function, and the mean tilt is modeled as a near-surface
+helicity (alpha-effect) term. The data-driven models are compared with the
+models calculated for random longitudinal and latitudinal distributions of the
+initial perturbation. The modeling results are compared with various observed
+characteristics of the solar cycles, including the magnetic butterfly diagram,
+the polar magnetic and basal magnetic fluxes, and the probability distributions
+of the BMR flux on the surface. Our results show that BMR can play a
+substantial role in the dynamo processes, and affect the strength of the solar
+cycle. However, the data-driven model shows that the BMR effect alone cannot
+explain the weak Cycle 24. This weak cycle and the prolonged preceding minimum
+of magnetic activity were probably caused by a decrease of the turbulent
+helicity in the bulk of the convection zone during the decaying phase of Cycle
+23.",2210.08764v2
+2022-11-18,Global simulations of Tayler instability in stellar interiors: a long-time multi-stage evolution of the magnetic field,"Magnetic fields have been observed in massive Ap/Bp stars and presumably are
+also present in the radiative zone of solar-like stars. Yet, to date there is
+no clear understanding of the dynamics of the magnetic field in stably
+stratified layers. A purely toroidal magnetic field configuration is known to
+be unstable, developing mainly non-axisymmetric modes. Rotation and a small
+poloidal field component may lead to a stable configuration. Here we perform
+global MHD simulations with the EULAG-MHD code to explore the evolution of a
+toroidal magnetic field located in a layer whose stratification resembles the
+solar tachocline. Our numerical experiments allow us to explore the initial
+unstable phase as well as the long-term evolution of the magnetic field. During
+the first Alfven cycles, we observe the development of the Tayler instability
+with the prominent longitudinal wavenumber, $m=1$. Rotation decreases the
+growth rate of the instability, and eventually suppresses it. However, after a
+stable phase, sudden energy surges lead to the development of higher order
+modes even for fast rotation. These modes extract energy from the initial
+toroidal field. Nevertheless, our results show that sufficiently fast rotation
+leads to a lower saturation energy of the unstable modes, resulting in a
+magnetic topology with only a small fraction of poloidal field which remains
+steady for several hundreds of Alfven travel times. At this stage, the system
+becomes turbulent and the field is prone to turbulent diffusion. The final
+toroidal-poloidal configuration of the magnetic field may represent an
+important aspect of the field generation and evolution in stably-stratified
+layers.",2211.10536v2
+2022-12-23,Tailing Magnetoelectric properties of Cr2Ge2Te6 by Engineering Covalently bonded Cr Self-intercalation: Ferromagnetic Half-metal,"Two-dimensional intrinsic ferromagnetic half-metal (HM) are important for the
+spintronics. Manipulating the interlayer magnetic coupling of van der Waals
+magnetic materials is an important method to control magnetoelectric
+properties, which is especially useful for the spintronics. Here, based on
+systematical research of CrGeTe3 (CGT) bilayer and multilayers with s of
+self-intercalated (SI) Cr atom, we find that self-intercalation can enhance the
+interlayer magnetic coupling. The super-exchange interaction still dominates
+interlayer magnetic exchange interaction, which results in ferromagnetic
+coupling between neighboring vdW layers. CGT bilayer keeps HM with FM order
+after Cr self-intercalation, independent of self-intercalated Cr (CrSI) atoms'
+concentration. Most importantly, self-intercalated CrGeTe3 (SI-CGT) bilayers
+show ferromagnetic HM, independent of stacking orders. Moreover, SI-CGT
+multilayers keep FM order, independent of films' thickness. However, SI-CGT
+multilayers transform from HM into normal spin-polarized metal, as the states
+at the Fermi-level increases. Moreover, magnetic anisotropy energy (MAE) of
+SI-CGT-AA and SI-CGT-AB are -0.160 and -0.42 meV/.f.u., which are modulated by
+CrSI atoms. The MAE of SI-CGT-AA and SI-CGT-AB are different, as the
+hybridization interaction between Cr's d orbitals is different. SI-CGT
+multilayers' magnetic easy axis (EA) switches from [001] of CGT to [100]
+direction, independent of stacking orders. It origins that MAE mainly
+contributed by hybridization between Te atoms' px and py, py and pz orbitals is
+obvious weakened as CrSI is introduced. SI-CGT multilayers show good dynamical,
+thermal, and magnetic stability at 300 and 500 K. These findings find a
+promising way to manipulate interlayer exchange interaction and magnetoelectric
+properties of CGT multilayers and other vdW magnets.",2212.12111v1
+2023-05-24,Gravitational wave signatures from the phase-transition-induced collapse of a magnetized neutron star,"Strong magnetic fields make neutron stars potential sources of detectable
+electromagnetic and gravitational-wave signals. Hence, inferring these magnetic
+fields is critical to understand the emissions of neutron stars. However, due
+to the lack of direct observational evidence, the interior magnetic field
+configuration remains ambiguous. Here, for the first time, we show that the
+internal magnetic field strength along with the composition of a neutron star
+can be directly constrained by detecting the gravitational waves from the
+phase-transition-induced collapse of a magnetized neutron star. By dynamically
+simulating this collapsing event, we first find that the dominant peaks in the
+gravitational waveform are the fundamental $l=0$ quasi-radial $F$ mode and the
+fundamental $l=2$ quadrupolar $^2f$ mode. We next show that the maximum
+gravitational wave amplitude $|h|_\mathrm{max}$ increases with the maximum
+magnetic field strength of the interior toroidal field
+$\mathcal{B}_\mathrm{max}$ until the maximum rest-mass density at bounce
+$\rho_\mathrm{max,b}$ decreases due to the increasing
+$\mathcal{B}_\mathrm{max}$. We then demonstrated that the magnetic suppression
+of fundamental modes found in our previous work remains valid for the hybrid
+stars formed after the phase-transition-induced collapses. We finally show that
+measuring the frequency ratio between the two fundamental modes $f_{^2f}/f_{F}$
+allows one to infer $\mathcal{B}_\mathrm{max}$ and the baryonic mass fraction
+of matter in the mixed phase $M_\mathrm{mp} / M_{0}$ of the resulting hybrid
+star. Consequently, taking $\mathcal{B}_\mathrm{max}$ and $M_\mathrm{mp} /
+M_{0}$ as examples, this work has demonstrated that much information inside
+neutron stars could be extracted similarly through measuring the oscillation
+modes of the stars.",2305.15181v1
+2023-12-13,Enhanced Magnetization by Defect-Assisted Exciton Recombination in Atomically Thin CrCl$_3$,"Two dimensional (2D) semiconductors present unique opportunities to
+intertwine optical and magnetic functionalities and to tune these performances
+through defects and dopants. In 2D semiconductors, the properties of excitons
+often vary due to the underlying magnetic order, but the modification of their
+magnetic properties by excitonic processes remains difficult to achieve. Here,
+we integrate exciton pumping into a quantum sensing protocol on
+nitrogen-vacancy centers in diamond to image the optically-induced transient
+stray fields in few-layer, antiferromagnetic CrCl$_3$. We discover that exciton
+recombination enhances the in-plane magnetization of the CrCl$_3$ layers, with
+an outsized effect in the surface monolayers and when the surface is
+unencapsulated. Concomitantly, time-resolved photoluminescence measurements
+reveal that a defect-assisted Auger recombination dominates for atomically thin
+CrCl$_3$ with tightly localized, nearly forbidden excitons and amplified
+surface-to-volume ratio. These experimental signatures establish the
+magnetically enhanced state to result from an exciton-activated electron
+transfer between surface impurities and the spin-polarized conduction band.
+Density functional theory calculations identify that the mediating impurity
+state could originate from oxygen adsorbates with spins antiparallel to the
+magnetization of their host layer. Our work unambiguously demonstrates the
+tunability of single intrinsic magnetic layers via defect engineering and opens
+a pathway to dynamically reconfigure these effects in devices through optical
+control.",2312.08476v1
+2024-03-04,Molecular intercalation in the van der Waals antiferromagnets FePS3 and NiPS3,"We have performed electrochemical treatment of the van der Waals
+antiferromagnetic materials FePS$_3$ and NiPS$_3$ with the ionic liquid
+EMIM-BF$_4$, achieving significant molecular intercalation. Mass analysis of
+the intercalated compounds, EMIM$_x$-FePS$_3$ and EMIM$_x$-NiPS$_3$, indicated
+respective intercalation levels, $x$, of approximately 27\% and 37\%, and X-ray
+diffraction measurements demonstrated a massive (over 50\%) enhancement of the
+$c$-axis lattice parameters. To investigate the consequences of these changes
+for the magnetic properties, we performed magnetic susceptibility and $^{31}$P
+nuclear magnetic resonance (NMR) studies of both systems. For
+EMIM$_x$-FePS$_3$, intercalation reduces the magnetic ordering temperature from
+$T_N = 120$~K to 78~K, and we find a spin gap in the antiferromagnetic phase
+that drops from 45~K to 30~K. For EMIM$_x$-NiPS$_3$, the ordering temperature
+is almost unaffected (changing from 148~K to 145~K), but a change towards
+nearly isotropic spin fluctuations suggests an alteration of the magnetic
+Hamiltonian. Such relatively modest changes, given that the huge extension of
+the $c$ axes is expected to cause a very strong suppression any interlayer
+interactions, point unequivocally to the conclusion that the magnetic
+properties of both parent compounds are determined solely by two-dimensional
+(2D), intralayer physics. The changes in transition temperatures and
+low-temperature spin dynamics in both compounds therefore indicate that
+intercalation also results in a significant modulation of the intralayer
+magnetic interactions, which we propose is due to charge doping and
+localization on the P sites. Our study offers chemical intercalation with ionic
+liquids as an effective method to control not only the interlayer but also the
+intralayer interactions in quasi-2D magnetic materials.",2403.01714v1
+2024-03-18,Thermal Tensor Network Approach for Spin-Lattice Relaxation in Quantum Magnets,"Low-dimensional quantum magnets, particularly those with strong spin
+frustration, are characterized by their notable spin fluctuations. Nuclear
+magnetic resonance (NMR) serves as a sensitive probe of low-energy fluctuations
+that offers valuable insight into rich magnetic phases and emergent phenomena
+in quantum magnets. Although experimentally accessible, the numerical
+simulation of NMR relaxation rates, specifically the spin-lattice relaxation
+rate $1/T_1$, remains a significant challenge. Analytical continuation based on
+Monte Carlo calculations are hampered by the notorious negative sign for
+frustrated systems, and the real-time simulations incur significant costs to
+capture low-energy fluctuations. Here we propose computing the relaxation rate
+using thermal tensor networks (TTNs), which provides a streamlined approach by
+calculating its imaginary-time proxy. We showcase the accuracy and versatility
+of our methodology by applying it to one-dimensional spin chains and
+two-dimensional lattices, where we find that the critical exponents $\eta$ and
+$z\nu$ can be extracted from the low-temperature scalings of the simulated
+$1/T_1$ near quantum critical points. Our results also provide insights into
+the low-dimensional and frustrated magnetic materials, elucidating universal
+scaling behaviors in the Ising chain compound CoNb$_2$O$_6$ and revealing the
+renormalized classical behaviors in the triangular-lattice antiferromagnet
+Ba$_8$CoNb$_6$O$_{24}$. We apply the approach to effective model of the family
+of frustrated magnets AYbCh$_2$ (A = Na, K, Cs, and Ch = O, S, Se), and find
+dramatic changes from spin ordered to the proposed quantum spin liquid phase.
+Overall, with high reliability and accuracy, the TTN methodology offers a
+systematic strategy for studying the intricate dynamics observed across a broad
+spectrum of quantum magnets and related fields.",2403.11895v2
+2024-04-01,Transport of the magnetic flux away from a decaying sunspot via convective motions,"Aims. The aim of this paper is to consider relationship between the decay of
+sunspots and convection via the motion of the family of granules and how the
+diffusion mechanism of magnetic field operates in a decaying sunspot. Methods.
+We report the decay of a sunspot observed by the 1.6m Goode Solar Telescope
+(GST) with the TiO Broadband Filter Imager (BFI) and the Near-InfraRed Imaging
+Spectropolarimeter (NIRIS). The analysis was aided by the Helioseismic and
+Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO). In the
+first step, we followed the decay of the sunspot with HMI data over three days
+by constructing its evolving area and total magnetic flux. In the second step,
+the high spatial and temporal resolution of the GST instruments allowed us to
+analyze the causes of the decay of the sunspot. Afterward, we followed the
+emergence of granules in the moat region around the sunspot over six hours. The
+evolution of the trees of fragmenting granules (TFGs) was derived based on
+their relationship with the horizontal surface flows. Results. We find that the
+area and total magnetic flux display an exponential decrease over the course of
+the sunspot decay. We identified 22 moving magnetic features (MMFs) in the
+moats of pores, which is a signature of sunspot decay through diffusion. We
+note that the MMFs were constrained to follow the borders of TFGs during their
+journey away from the sunspot. Conclusions. The TFGs and their development
+contribute to the diffusion of the magnetic field outside the sunspot. The
+conclusion of our analysis shows the important role of the TFGs in sunspot
+decay. Finally, the the family of granules evacuates the magnetic field.",2404.00889v1
+2008-08-28,"Effects of Zn and Ni substitution on the Cu-spin dynamics and superconductivity in La_2-x_Sr_x_Cu_1-y_(Zn,Ni)_y_O_4_ with x=0.15-0.20 studied by the muon spin relaxation and magnetic susceptibility","We have investigated effects of Zn and Ni on the Cu-spin dynamics and
+superconductivity from the zero-field muon-spin-relaxation (ZF-muSR) and
+magnetic-susceptibility, chi, measurements for
+La_2-x_Sr_x_Cu_1-y_(Zn,Ni)_y_O_4_ with x=0.15-0.20, changing y up to 0.10 in
+fine step. In the optimally doped x=0.15, it has been concluded that the
+formation of a magnetic order requires a larger amount of Ni than that of Zn,
+which is similar to our previous results of x=0.13. From the estimation of
+volume fractions of superconducting (SC) and magnetic regions, it has been
+found for x=0.15 that the SC region is in rough correspondence to the region
+where Cu spins fluctuate fast beyond the muSR frequency window for both Zn- and
+Ni-substituted samples. According to the stripe model, it follows that, even
+for x=0.15, the dynamical stripe correlations of spins and holes are pinned and
+localized around Zn and Ni, leading to the formation of the static stripe order
+and the suppression of superconductivity. These may indicate an importance of
+the dynamical stripe in the appearance of the high-T_c_ superconductivity in
+the hole-doped cuprates. In the overdoped regime of x=0.18 and 0.20, on the
+other hand, the SC region seems to be in rough correspondence to the region
+where Cu spins fluctuate fast beyond the muSR frequency window, though it
+appears that the Cu-spin dynamics and superconductivity are affected by the
+phase separation into SC and normal-state regions.",0808.3871v2
+2011-07-11,Understanding quantum measurement from the solution of dynamical models,"The quantum measurement problem, understanding why a unique outcome is
+obtained in each individual experiment, is tackled by solving models. After an
+introduction we review the many dynamical models proposed over the years. A
+flexible and rather realistic model is introduced, describing the measurement
+of the $z$-component of a spin through interaction with a magnetic memory
+simulated by a Curie--Weiss magnet, including $N \gg1$ spins weakly coupled to
+a phonon bath. Initially prepared in a metastable paramagnetic state, it may
+transit to its up or down ferromagnetic state, triggered by its coupling with
+the tested spin, so that its magnetization acts as a pointer.
+  A detailed solution of the dynamical equations is worked out. Conditions are
+found, which ensure that the process satisfies the features of ideal
+measurements. Various imperfections are discussed, as well as attempts of
+incompatible measurements. The first steps consist in the solution of the
+Hamiltonian dynamics for the spin-apparatus density matrix $D(t)$. On a longer
+time scale, the trend towards equilibrium of the magnet produces a final state
+$D(t_{\rm f})$ that involves correlations between the system and the
+indications of the pointer, thus ensuring registration. A difficulty lies in a
+quantum ambiguity: There exist many incompatible decompositions of the density
+matrix $\scriptD(t_{\rm f})$. This difficulty is overcome by dynamics due to
+suitable interactions within the apparatus.
+  Any subset of runs thus reaches over a brief delay a stable state which
+satisfies the same hierarchic property as in classical probability theory.
+Standard quantum statistical mechanics alone appears sufficient to explain the
+occurrence of a unique answer in each run. Finally, pedagogical exercises are
+proposed while the statistical interpretation is promoted for teaching.
+[Abridged]",1107.2138v4
+2015-12-07,Dynamic magnetic susceptibility and electrical detection of ferromagnetic resonance,"The dynamic magnetic susceptibility of magnetic materials near ferromagnetic
+resonance (FMR) is very important in interpreting dc-voltage in electrical
+detection of FMR. Based on the causality principle and the assumption that the
+usual microwave absorption lineshape around FMR is Lorentzian, general forms of
+dynamic susceptibility of an arbitrary sample and the corresponding dc-voltage
+lineshape are obtained. Our main findings are: 1) The dynamic susceptibility is
+not a Polder tensor for material with arbitrary anisotropy. Two off-diagonal
+elements are not in general opposite to each other. However, the linear
+response coefficient of magnetization to total rf field is a Polder tensor.
+This may explain why two off-diagonal elements are always assumed to be
+opposite to each other in analyses. 2) The frequency dependence of dynamic
+susceptibility near FMR is fully characterized by six numbers while its field
+dependence is fully characterized by seven numbers. 3) A recipe of how to
+determine these numbers by standard microwave absorption measurements for an
+arbitrary sample is proposed. Our results allow one to unambiguously separate
+the contribution of the anisotropic magnetoresistance to dc-voltage from that
+of the anomalous Hall effect. With these results, one can reliably extract the
+information of spin pumping and the inverse spin Hall effect, and determine the
+spin-Hall angle. 4) The field-dependence of susceptibility matrix at a fixed
+frequency may have several peaks when the effective field is not monotonic of
+the applied field. In contrast, the frequency-dependence of susceptibility
+matrix at a fixed field has only one peak. Furthermore, in the case that
+resonance frequency is not sensitive to the applied field, the field dependence
+of susceptibility matrix, as well as dc-voltage, may have another non-resonance
+broad peak. Thus, one should be careful in interpreting observed peaks.",1512.01913v1
+2016-12-15,The Dynamics of Charged Dust in Magnetized Molecular Clouds,"We study the dynamics of large, charged dust grains in turbulent giant
+molecular clouds (GMCs). Massive dust grains behave as aerodynamic particles in
+primarily neutral dense gas, and thus are able to produce dramatic small-scale
+fluctuations in the dust-to-gas ratio. Hopkins & Lee (2016) directly simulated
+the dynamics of neutral dust grains in super-sonic MHD turbulence, typical of
+GMCs, and showed that the dust-to-gas fluctuations can exceed factor ~1000 on
+small scales, with important implications for star formation, stellar
+abundances, and dust behavior and growth. However, even in primarily neutral
+gas in GMCs, dust grains are negatively charged and Lorentz forces are
+non-negligible. Therefore, we extend our previous study by including the
+effects of Lorentz forces on charged grains (in addition to drag). For small
+charged grains (sizes <0.1 micron), Lorentz forces suppress dust-to-gas ratio
+fluctuations, while for large grains (sizes >1 micron), Lorentz forces have
+essentially no effect, trends that are well explained with a simple theory of
+dust magnetization. In some special intermediate cases, Lorentz forces can
+enhance dust-gas segregation. Regardless, for the physically expected scaling
+of dust charge with grain size, we find the most important effects depend on
+grain size (via the drag equation) with Lorentz forces/charge as a second-order
+correction. We show that the dynamics we consider are determined by three
+dimensionless numbers in the limit of weak background magnetic fields: the
+turbulent Mach number, a dust drag parameter (proportional to grain size) and a
+dust Lorentz parameter (proportional to grain charge); these allow us to
+generalize our simulations to a wide range of conditions.",1612.05264v2
+2018-12-22,Spin dynamics of $3d$ and $4d$ impurities embedded in prototypical topological insulators,"Topological insulators are insulating bulk materials hosting conducting
+surface states. Their magnetic doping breaks time-reversal symmetry and
+generates numerous interesting effects such as dissipationless transport.
+Nonetheless, their dynamical properties are still poorly understood. Here, we
+perform a systematic investigation of transverse spin excitations of $3d$ and
+$4d$ single impurities embedded in two prototypical topological insulators
+(Bi$_2$Te$_3$ and Bi$_2$Se$_3$). The impurity-induced states within the bulk
+gap of the topological insulators are found to have a drastic impact on the
+spin excitation spectra, resulting in very high lifetimes reaching up to
+${microseconds}$. An intuitive picture of the spin dynamics is obtained by
+mapping onto a generalized Landau-Lifshitz-Gilbert phenomenological model. The
+first quantity extracted from this mapping procedure is the magnetic anisotropy
+energy, which is then compared to the one provided by the magnetic force
+theorem. This uncovers some difficulties encountered with the latter, which can
+provide erroneous results for impurities with a high density of states at the
+Fermi energy. Moreover, the Gilbert damping and nutation tensors are obtained.
+The nutation effects can lead to a non-negligible shift in the spin excitation
+resonance in the high-frequency regime. Finally, we study the impact of the
+surface state on the spin dynamics, which may be severely altered due to the
+repositioning of the impurity-induced state in comparison to the bulk case. Our
+systematic investigation of this series of magnetic impurities sheds light on
+their spin dynamics within topological insulators, with implications for
+available and future experimental studies as, for instance, on the viability of
+using such impurities for solid-state qubits.",1812.09596v1
+2019-09-23,"Coherent spin dynamics of solitons in the organic spin chain compounds ($o$-DMTTF)$_2X$ ($X$ = Cl, Br)","We studied the magnetic properties, in particular dynamics, of the correlated
+spins associated with natural defects in the organic spin chain compounds
+($o$-DMTTF)$_2X$ ($X$ = Br, Cl) by means of electron spin resonance (ESR)
+spectroscopy. Both materials exhibit spin-Peierls transitions at temperatures
+around 50 K [P. Foury-Leylekian et al. Phys. Rev. B 84, 195134 (2011)], which
+allow a separation of the properties of defects inside the chains from the
+magnetic response of the spin chains. Indeed, continuous wave ESR measurements
+performed over a wide temperature range evidence the evolution of the spin
+dynamics from being governed by the spins in the chains at elevated
+temperatures to a low-temperature regime which is dominated by defects within
+the spin-dimerized chains. Such defects polarize the antiferromagnetically
+coupled spins in their vicinity, thereby leading to a finite local alternating
+magnetization around the defect site which can be described in terms of a
+soliton, i.e. a spin 1/2 quasiparticle built of many correlated spins, pinned
+to the defect. In addition, contributions of triplon excitations of the
+spin-dimerized state to the ESR response below the transition temperature were
+observed which provides a spectroscopic estimate for the spin-gap of the
+studied systems. Moreover, details of spin dynamics deep in the spin-Peierls
+phase were investigated by pulse ESR experiments which revealed
+Rabi-oscillations as signatures of coherent spin dynamics. From a comparison of
+the characteristic damping times of the Rabi oscillations with measurements of
+the spin relaxation times by means of primary-echo decay and CPMG methods it
+becomes evident that inhomogeneities in local magnetic fields strongly
+contribute to the soliton decoherence.",1909.10301v2
+2021-08-16,Relaxation of antiferromagnetic order and growth of Rényi entropy in a generalized Heisenberg star,"Interacting central spin systems, in which a central spin is coupled to a
+strongly correlated spin bath with intrabath interaction, consist of an
+important class of spin systems beyond the usual Gaudin magnet. These systems
+are relevant to several realistic setups and serve as an interesting platform
+to study interaction controlled decoherence and frustration induced instability
+of magnetic order. Using an equations-of-motion method based on analytical
+representations of spin-operator matrix elements in the XX chain, we obtain
+exact long-time dynamics of a generalized Heisenberg star consisting of a
+spin-$S$ central spin and an inhomogeneously coupled XXZ chain of $N\leq 16$
+bath spins. In contrast to previous studies where the central spin dynamics is
+mainly concerned, we focus on the influence of the central spin on the dynamics
+of magnetic orders within the spin bath. By preparing the XXZ bath in a N\'eel
+state, we find that in the gapless phase of the bath even weak system-bath
+coupling could lead to nearly perfect relaxation of the antiferromagnetic
+order. In the gapped phase, the staggered magnetization decays rapidly and
+approaches a steady value that increases with increasing anisotropy parameter.
+These findings suggest the possibility of controlling internal dynamics of
+strongly correlated many-spin systems by certain coupled auxiliary systems of
+even few degrees of freedom. We also study the dynamics of the R\'enyi
+entanglement entropy of the central spin when the bath is prepared in the
+ground state. Both the overall profile and initial growth rate of the R\'enyi
+entropy are found to exhibit minima at the critical point of the XXZ bath.",2108.07055v3
+2022-11-02,Relaxation dynamics in a long-range system with mixed Hamiltonian and non-Hamiltonian interactions,"Sometimes the dynamics of a physical system is described by non-Hamiltonian
+equations of motion, and additionally, the system is characterized by
+long-range interactions. A concrete example is that of particles interacting
+with light as encountered in free-electron laser and cold-atom experiments. In
+this work, we study the relaxation dynamics to non-Hamiltonian systems, more
+precisely, to systems with interactions of both Hamiltonian and non-Hamiltonian
+origin. Our model consists of $N$ globally-coupled particles moving on a circle
+of unit radius; the model is one-dimensional. We show that in the infinite-size
+limit, the dynamics, similarly to the Hamiltonian case, is described by the
+Vlasov equation. In the Hamiltonian case, the system eventually reaches an
+equilibrium state, even though one has to wait for a long time diverging with
+$N$ for this to happen. By contrast, in the non-Hamiltonian case, there is no
+equilibrium state that the system is expected to reach eventually. We
+characterize this state with its average magnetization. We find that the
+relaxation dynamics depends strongly on the relative weight of the Hamiltonian
+and non-Hamiltonian contributions to the interaction. When the non-Hamiltonian
+part is predominant, the magnetization attains a vanishing value, suggesting
+that the system does not sustain states with constant magnetization, either
+stationary or rotating. On the other hand, when the Hamiltonian part is
+predominant, the magnetization presents long-lived strong oscillations, for
+which we provide a heuristic explanation. Furthermore, we find that the
+finite-size corrections are much more pronounced than those in the Hamiltonian
+case; we justify this by showing that the Lenard-Balescu equation, which gives
+leading-order corrections to the Vlasov equation, does not vanish, contrary to
+what occurs in one-dimensional Hamiltonian long-range systems.",2211.01018v1
+2023-07-06,Finding the Dynamics of an Integrable Quantum Many-Body System via Machine Learning,"We study the dynamics of the Gaudin magnet (""central-spin model"") using
+machine-learning methods. This model is of practical importance, e.g., for
+studying non-Markovian decoherence dynamics of a central spin interacting with
+a large bath of environmental spins and for studies of nonequilibrium
+superconductivity. The Gaudin magnet is also integrable, admitting many
+conserved quantities: For $N$ spins, the model Hamiltonian can be written as
+the sum of $N$ independent commuting operators. Despite this high degree of
+symmetry, a general closed-form analytic solution for the dynamics of this
+many-body problem remains elusive. Machine-learning methods may be well suited
+to exploiting the high degree of symmetry in integrable problems, even when an
+explicit analytic solution is not obvious. Motivated in part by this intuition,
+we use a neural-network representation (restricted Boltzmann machine) for each
+variational eigenstate of the model Hamiltonian. We then obtain accurate
+representations of the ground state and of the low-lying excited states of the
+Gaudin-magnet Hamiltonian through a variational Monte Carlo calculation. From
+the low-lying eigenstates, we find the non-perturbative dynamic transverse spin
+susceptibility, describing the linear response of a central spin to a
+time-varying transverse magnetic field in the presence of a spin bath. Having
+an efficient description of this susceptibility opens the door to improved
+characterization and quantum control procedures for qubits interacting with an
+environment of quantum two-level systems. These systems include electron-spin
+and hole-spin qubits interacting with environmental nuclear spins via hyperfine
+interactions or qubits with charge or flux degrees of freedom interacting with
+coherent charge or paramagnetic impurities.",2307.03310v2
+1994-11-09,Does a Non-Magnetic Solar Chromosphere Exist?,"Enhanced chromospheric emission which corresponds to an outwardly increasing
+semiempirical temperature structure can be produced by wave motion without any
+increase in the mean gas temperture. Hence, the sun may not have a classical
+chromosphere in magnetic field free internetwork regions. Other significant
+differences between the properties of dynamic and static atmospheres should be
+considered when analyzing chromospheric observations.",9411036v1
+1997-09-26,Generation of Pulsar Glitches: A Superfluid Core Model,"We show that the neutron star's crust-core interface acts as a potential
+barrier on the peripheral neutron vortices approaching this interface and thus
+prevents their continuous decay on it in the course of equilibrium state
+deceleration. The barrier arises due to the interaction of vortex magnetic flux
+with the Meissner currents set up by the crustal magnetic field at the
+interface. When the non-balanced part of the Magnus force reaches the value at
+which the vortices are able to annihilate at the interface, the rapid transfer
+of angular momentum from the superfluid spins-up the observable crust on short
+dynamical coupling times.",9709277v2
+1998-08-19,Magnetic Field Effects on the Structure of Radiatively Cooling Protostellar Jets,"In the present work, with the help of fully 3-D smooth particle
+magnetohydodynamic (SPMHD) simulations, we explore the nonlinear effects of
+magnetic fields (in close equipartition with the gas) in the structure of
+radiatively cooling, overdense jets and test their importance on the dynamics
+of protostellar jets.",9808194v1
+1999-12-14,Kick asymmetry along a strong magnetic field in the process of neutrino scattering on nucleons,"The neutrino-nucleon scattering in a collapsing star envelope with a strong
+magnetic field is investigated. The transferred by neutrinos momentum asymmetry
+along the field direction is obtained. It is shown that the neutrino-nucleon
+scattering gives a contribution to the asymmetry comparable with direct URCA
+processes. Hence, the neutrino-nucleon scattering should be taken into account
+in estimations of a possible influence of neutrino reemission processes on a
+collapsing star envelope dynamics.",9912287v1
+2000-06-23,Outflow from YSO and Angular Momentum Transfer,"Dynamical contraction of a slowly-rotating magnetized cloud is studied using
+the magnetohydrodynamical (MHD) simulations. In the isothermal stage ($n \la
+n_{\rm A} \sim 10^{10}{\rm cm}^{-3}$), the cloud evolves similarly to that
+expected from Larson-Penston self-similar solution and experiences the run-away
+collapse. However, after the central density exceeds $\sim n_{\rm A}$, an
+accretion disk is formed around the adiabatic core. Just outside the core,
+outflow is ejected by the effect of magnetic torque (magnetocentrifugal wind).
+Since $\sim$ 10% of the mass is ejected with almost all the angular momentum,
+the specific angular momentum of the protostellar core reduces to that observed
+in main-sequence stars.",0006329v1
+2000-10-12,Modeling Observational Signatures of Disk-Driven Outflows,"We present a self-consistent, semi-analytical dynamical model of disk driven
+outflows in AGNs that are accelerated by a combination of magnetic stresses and
+radiation pressure. This model will make it possible to examine scenarios in
+which the wind is homogeneous as well as cases where it consists of dense
+clouds embedded in a more tenuous, magnetized medium. The various ingredients
+of this model will be tested through quantitative predictions from both
+multiwavelength spectral observations and reverberation mapping of AGNs.",0010246v1
+2001-09-20,Pulsar Spin-Down Induced Phenomena: Heating; Magnetic Field Evolution; Glitches; Pulse-Period Modulations,"Modeling the dynamics of the quantum fluids within a spinning-down neutron
+star gives a description consistent with observed pulsar magnetic field
+evolution and spin-period ""glitches."" The long-standing problem of large
+predicted excesses in spin-down sustained pulsar heating from such models now
+see ms resolvable. However, the origin of some pulsar spin-period and
+pulse-shape modulations which have been interpreted as manifestations of very
+long period (~year) stellar precession is a crucial challenge to canonical
+neutron star models.",0109353v1
+2001-09-28,The Evolution of Magnetic Fields in Galaxy Clusters,"Cosmological simulations of magnetic fields in galaxy clusters show that
+remarkable agreement between simulations and observations of Faraday rotation
+and radio haloes can be achieved assuming that seed fields of 10^{-9} G were
+present at redshifts 15-20. The structure of the seed field is irrelevant for
+the final intracluster field. On average, the field grows exponentially with
+decreasing cluster redshift, but merger events cause steep transient increases
+in the field strength. Typical field-reversal scales are of order 50 kpc/h. In
+most cases, the intracluster fields are dynamically unimportant. Assuming
+secondary electron models, the average structure of cluster radio haloes can
+naturally be reproduced.",0109541v1
+2002-07-18,Solar and stellar dynamos -- latest developments,"Recent progress in the theory of solar and stellar dynamos is reviewed.
+Particular emphasis is placed on the mean-field theory which tries to describe
+the collective behavior of the magnetic field. In order to understand solar and
+stellar activity, a quantitatively reliable theory is necessary. Much of the
+new developments center around magnetic helicity conservation which is seen to
+be important in numerical simulations. Only a dynamical, explicitly time
+dependent theory of alpha-quenching is able to describe this behavior
+correctly.",0207393v1
+2002-12-16,"Magnetogenesis, variation of gauge couplings and inflation","The interplay among the possible variation of gauge coupling and the
+inflationary dynamics is investigated in a simplified toy model. Depending upon
+various parameters (scalar mass, curvature scale at the end of inflation and at
+the onset of the radiation epoch), the two-point function of the magnetic
+inhomogeneities grows during the de Sitter stage of expansion and,
+consequently, large scale magnetic fields are generated. The requirements
+coming from inflationary magnetogenesis are examined together with the
+theoretical constraints stemming from the explicit model of the evolution of
+the gauge coupling.",0212346v1
+2003-05-06,Electron acceleration and heating in collisionless magnetic reconnection,"We discuss electron acceleration and heating during collisionless magnetic
+reconnection by using the results of implicit kinetic simulations of Harris
+current sheets. We consider and compare electron dynamics in plasmas with
+different \beta values and perform simulations up to the physical mass ratio.
+We analyze the typical trajectory of electrons passing through the reconnection
+region, we study the electron velocity, focusing on the out-of-plane velocity,
+and we discuss the electron heating along the in-plane and out-of-plane
+directions.",0305081v1
+2004-09-03,Fermion Scattering off a CP-violating Bubble Wall in the Background of a Uniform Magnetic Field,"In the scenario of the electroweak baryogenesis we consider the dynamics of
+fermions with a spatially varying mass in presence of a CP-violating bubble
+wall and a uniform magnetic field perpendicular to the wall. The relevant
+quantity for baryogenesis, $R_{R \to L} - R_{L \to R}$, is studied ($R_{R \to
+L}$ and $R_{L \to R}$ being the reflection coefficients for right-handed and
+left-handed chiral fermions, respectively).",0409077v1
+2004-09-20,Magnetic fields in GRBs,"We discuss the dynamical role of magnetic fields in GRB explosions in the
+framework of the fireball and electromagnetic models. We contrast the
+observational predictions of the two models and argue that only the very early
+afterglow observations, almost coincident with the prompt phase, can be used as
+decisive tests of the ejecta content.",0409489v2
+2005-07-06,Chiral Properties of QCD Vacuum in Magnetars- A Nambu-Jona-Lasinio Model with Semi-Classical Approximation,"The breaking of chiral symmetry of light quarks at zero temperature in
+presence of strong quantizing magnetic fiels is studied using
+Nambu-Jona-Lasinio (NJL) model with Thomas-Fermi type semi-classical formalism.
+It is found that the dynamically generated light quark mass can never become
+zero if the Landau levels are populated and the mass increases with the
+increase of magnetic field strength.",0507127v1
+2006-06-20,Experimental evidence for magnetorotational instability in a helical magnetic field,"A recent paper [R. Hollerbach and G. Rudiger, Phys. Rev. Lett. 95, 124501
+(2005)] has shown that the threshold for the onset of the magnetorotational
+instability (MRI) in a Taylor-Couette flow is dramatically reduced if both
+axial and azimuthal magnetic fields are imposed. In agreement with this
+prediction, we present results of a Taylor-Couette experiment with the liquid
+metal alloy GaInSn, showing evidence for the existence of the MRI at Reynolds
+numbers of order 1000 and Hartmann numbers of order 10.",0606473v1
+2006-12-22,Magnetized electron-positron plasmas,"Electrostatic oscillations in cold electron-positron plasmas can be coupled
+to a propagating electromagnetic mode if the background magnetic field is
+inhomogeneous. Previous work considered this coupling in the quasi-linear
+regime, successfully simulating the electromagnetic mode. Here we present a
+stability analysis of the non-linear problem, perturbed from dynamical
+equilibrium, in order to gain some insight into the modes present in the
+system.",0612679v1
+1993-11-16,Quantum Phases of the Shraiman-Siggia Model,"We examine phases of the Shraiman-Siggia model of lightly-doped, square
+lattice quantum antiferromagnets in a self-consistent, two-loop, interacting
+magnon analysis. We find magnetically-ordered and quantum-disordered phases
+both with and without incommensurate spin correlations. The quantum disordered
+phases have a pseudo-gap in the spin excitation spectrum. The quantum
+transition between the magnetically ordered and commensurate quantum-disordered
+phases is argued to have the dynamic critical exponent $z=1$ and the same
+leading critical behavior as the disordering transition in the pure $O(3)$
+sigma model. The relationship to experiments on the doped cuprates is
+discussed.",9311037v1
+1994-03-03,Quantum Hall Fluid of Vortices in a Two Dimensional Array of Josephson Junctions,"A two dimensional array of Josephson junctions in a magnetic field is
+considered. It is shown that the dynamics of the vortices in the array
+resembles that of electrons on a two--dimensional lattice put in a magnetic
+field perpendicular to the lattice. Under appropriate conditions, this
+resemblance results in the formation of a quantum Hall fluid of vortices. The
+bosonic nature of vortices and their long range logarithmic interaction make
+some of the properties of the vortices' quantum Hall fluid different from those
+of the electronic one. Some of these differences are studied in detail.
+Finally, it is shown that a quantum Hall fluid of vortices manifests itself in
+a quantized Hall electronic transport in the array.",9403017v1
+1995-03-06,Quantum critical phenomena in ladders of Josephson junctions in a magnetic field,"A model of a ladder of Josephson junctions in a magnetic field is considered.
+The topological features of the zero-temperature phase diagram, as a function
+of charging energy and small deviations from commensurability of the vortex
+lattice, are strongly dependent on the field. In addition to
+superconductor-insulator transitions, commensurate-incommensurate transitions
+and depinning by quantum fluctuations of the vortex-lattice are also possible.
+the critical behavior of the superconductor-insulator transition at f = 1/2 is
+found to depend on the ratio between interchain and intrachain Josephson
+couplings and is in the universality of the classical XY-Ising model.",9503025v1
+1995-05-04,"Berry phase, hyperorbits, and the Hofstadter spectrum","We develop a semiclassical theory for the dynamics of electrons in a magnetic
+Bloch band, where the Berry phase plays an important role. This theory,
+together with the Boltzmann equation, provides a framework for studying
+transport problems in high magnetic fields. We also derive an Onsager-like
+formula for the quantization of cyclotron orbits, and we find a connection
+between the number of orbits and Hall conductivity. This connection is employed
+to explain the clustering structure of the Hofstadter spectrum. The advantage
+of this theory is its generality and conceptual simplicity.",9505021v1
+1995-07-06,Phases of Josephson Junction Ladders,"We study a Josephson junction ladder in a magnetic field in the absence of
+charging effects via a transfer matrix formalism. The eigenvalues of the
+transfer matrix are found numerically, giving a determination of the different
+phases of the ladder. The spatial periodicity of the ground state exhibits a
+devil's staircase as a function of the magnetic flux filling factor $f$. If the
+transverse Josephson coupling is varied a continuous superconducting-normal
+transition in the transverse direction is observed, analogous to the breakdown
+of the KAM trajectories in dynamical systems.",9507015v1
+1995-10-15,Pair breaking by impurities in the two-dimensional t-J model,"Pair breaking mechanisms by impurities are investigated in the
+two-dimensional t-J model by exact diagonalization techniques. Analysis of
+binding energies, pairing correlations, dynamical spin and pair
+susceptibilities shows that non-magnetic impurities are more effective in
+suppressing pairing than magnetic ones in agreement with experimental studies
+of Zn- and Ni- substituted High-Tc superconductors.",9510028v2
+1995-10-18,Antiferromagnetic Excitations and Van Hove Singularities in YBa$_2$Cu$_3$O$_{6+x}$,"We show that in quasi-two-dimensional $d$-wave superconductors Van Hove
+singularities close to the Fermi surface lead to novel magnetic quasi-particle
+excitations. We calculate the temperature and doping dependence of dynamical
+magnetic susceptibility for YBCO and show that the proposed excitations are in
+agreement with inelastic neutron scattering experiments. In addition, the
+values of the gap parameter and in-plane antiferromagnetic coupling are much
+smaller than usually believed.",9510100v1
+1995-11-03,Quantum Coherence in Magnetic Grains,"We consider a model of the dynamics of a magnetic grain, incorporating
+interactions with nuclear and paramagnetic spins, conduction electrons, and
+phonons. Decoherence comes both from the spins and the electrons, although
+electron effects can be neglected if the substrate is insulating, and the grain
+has spin $S \le 10^5$. A successful experiment will require both isotopic and
+chemical purification, if coherence is to be seen; we suggest a ""spin echo""
+arrangement to do this.",9511015v1
+1996-03-28,Intrinsic mechanism of phase locking in two-dimensional Josephson junction networks in presence of an external magnetic field,"We present numerical simulations of the dynamics of two-dimensional Josephson
+junction arrays to study the mechanism of mutual phase locking. We show that in
+the presence of an external magnetic field two mechanisms are playing a role in
+phase locking: feedback through the external load and internal coupling between
+rows due to microwave currents induced by the field. We have found the
+parameter values (junction capacitance, cell loop inductance, impedance of the
+external load) for which the interplay of both these mechanisms leads to the
+in-phase solution. The case of unshunted arrays is discussed as well.",9603183v1
+1996-06-20,Low Temperature Magnetic Properties of the Double Exchange Model,"We study the {\it ferromagnetic} (FM) Kondo lattice model in the strong
+coupling limit (double exchange (DE) model). The DE mechanism proposed by Zener
+to explain ferromagnetism has unexpected properties when there is more than one
+itinerant electron. We find that, in general, the many-body ground state of the
+DE model is {\it not} globally FM ordered (except for special filled-shell
+cases). Also, the low energy excitations of this model are distinct from spin
+wave excitations in usual Heisenberg ferromagnets, which will result in unusual
+dynamic magnetic properties.",9606148v1
+1996-11-13,"Impact of Charge Ordering on Magnetic Correlations in Perovskite (Bi,Ca)MnO_3","Single crystalline (Bi,Ca)MnO3 (74< %Ca <82) were studied with neutron
+scattering, electron diffraction and bulk magnetic measurement. We discovered
+dynamic ferromagnetic spin correlations at high temperatures, which are
+replaced by antiferromagnetic spin fluctuations at a concomitant charge
+ordering and structural transition. Our results indicate that thermal-activated
+hopping of the Jahn-Teller active e_g electrons in these insulating materials,
+nevertheless, induce ferromagnetic interaction through double-exchange
+mechanism. It is the ordering of these charges competing with the
+double-exchange ferromagnetic metallic state.",9611110v1
+1996-11-15,Magnetic Dynamics in Underdoped YBCO: Direct Observation of a Superconducting Gap,"Polarized and unpolarized triple-axis spectrometry has been used to study an
+underdoped YBa_2Cu3O6.6. Our results indicate that spin excitations in the
+superconducting state are essentially the same as those in the fully doped
+material except that the unusual 41 meV resonance is observed at 34.8 meV. The
+normal state spin excitations are characterized by a weakly energy-dependent
+continuum whose temperature dependence shows the clear signature of a
+superconducting gap at Tc. The enhancement at the resonance is accompanied by a
+suppression of magnetic fluctuations at both higher and lower energies.",9611123v1
+1997-01-23,Magnetic Excitations in the Spin-Peierls System $CuGeO_3$,"We have calculated the magnetic excitation spectrum in frustrated and
+dimerized spin 1/2 Heisenberg chains for model parameters which describe the
+thermodynamics and low frequency spin dynamics in the spin--Peierls system
+$CuGeO_{3}$. As a test the chosen model is found to reproduce the lowest Raman
+excitation energy near $30 cm^{-1}$ in the dimerized phase. We establish the
+elementary triplet and singlet excitation branches below the continuum and
+estimate the interchain coupling effects on the dimerization parameter.",9701176v1
+1997-08-27,Semi-classical spectrum of integrable systems in a magnetic field,"The quantum dynamics of an electron in a uniform magnetic field is studied
+for geometries corresponding to integrable cases. We obtain the uniform
+asymptotic approximation of the WKB energies and wavefunctions for the
+semi-infinite plane and the disc. These analytical solutions are shown to be in
+excellent agreement with the numerical results obtained from the Schrodinger
+equations even for the lowest energy states. The classically exact notions of
+bulk and edge states are followed to their semi-classical limit, when the
+uniform approximation provides the connection between bulk and edge.",9708206v1
+1997-09-24,Supersymmetry and Theory of Heavy-Fermions,"We propose a new approach to the Kondo lattice in order to describe
+simultaneously the Kondo effect and the local magnetism. This approach relies
+on an original representation of the $S=1/2$ impurity spin in which the
+different degrees of freedom are represented by fermionic as well as bosonic
+variables. The magnetic instability is found at $J_c/D =0.67$ in definite
+improvement compared to usual fermionic mean- field theories. The dynamical
+susceptibility contains an inelastic peak in addition to the standard
+Lindhard-type Fermi liquid contribution. The Fermi surface sum rule includes
+$n_c+1$ states corresponding to large Fermi surfaces.",9709256v1
+1997-11-06,Commensurability in One Dimension and the Josephson Junction Ladder,"We study a Josephson junction ladder in a magnetic field in the absence of
+charging effects via a transfer matrix formalism. The eigenvalues of the
+transfer matrix are found numerically, giving a determination of the different
+phases of the ladder. The spatial periodicity of the ground state exhibits a
+devil's staircase as a function of the magnetic flux filling factor f. If the
+transverse Josephson coupling is varied a continuous superconducting-normal
+transition in the transverse direction is observed, analogous to the breakdown
+of the KAM trajectories in dynamical systems. We also examine how these
+properties may be affected by a current injected along the ladder.",9711049v1
+1997-12-29,Pseudogap and incommensurate magnetic fluctuations in YBa_2Cu_3O_{6. 6},"Unpolarized inelastic neutron scattering is used to study the temperature and
+wave vector dependence of the dynamical magnetic susceptibility,
+$\chi''(q,\omega)$, of a well characterized single crystal $YBa_2Cu_3O_{6.6}$
+($T_c=62.7$ K). We find that a pseudogap opens in the spin fluctuation spectrum
+at temperatures well above $T_c$. We speculate that the appearance of the low
+frequency incommensurate fluctuations is associated with the opening of the
+pseudogap. To within the error of the measurements, a gap in the spin
+fluctuation spectrum is found in the superconducting state.",9712311v1
+1998-02-23,Magnetic Structure and NMR signal of Spin Peierls Solitons,"We compute the magnetic profile of spin Peierls solitons in a simple
+Heisenberg model with magneto elastic couplings, using independently the DMRG
+method and the Hartree Fock approximation. Our results agree qualitatively with
+published NMR data provided we average over the spin profiles. We conclude that
+he dynamics of the spin plus lattice system must be included in a more detailed
+theory of the spin Peierls transition in CuGeO.",9802245v1
+1998-06-05,Aharonov-Bohm cages in two-dimensional structures,"We present an extreme localization mechanism induced by a magnetic field for
+tight-binding electrons in two-dimensional structures. This spectacular
+phenomenon is investigated for a large class of tilings (periodic,
+quasiperiodic, or random). We are led to introduce the Aharonov-Bohm cages
+defined as the set of sites eventually visited by a wavepacket that can, for
+particular values of the magnetic flux, be bounded. We finally discuss the
+quantum dynamics which exhibits an original pulsating behaviour.",9806068v1
+1998-09-27,Magnetic Incommensurability in Doped Mott Insulator,"In this paper we explore the incommensurate spatial modulation of spin-spin
+correlations as the intrinsic property of the doped Mott insulator, described
+by the $t-J$ model. We show that such an incommensurability is a direct
+manifestation of the phase string effect introduced by doped holes in both one-
+and two-dimensional cases. The magnetic incommensurate peaks of dynamic spin
+susceptibility in momentum space are in agreement with the neutron-scattering
+measurement of cuprate superconductors in both position and doping dependence.
+In particular, this incommensurate structure can naturally reconcile the
+neutron-scattering and NMR experiments of cuprates.",9809363v1
+1998-10-26,"Quantum Environments: Spin Baths, Oscillator Baths, and applications to Quantum Magnetism","The low-energy physics of systems coupled to their surroundings is understood
+by truncating to effective Hamiltonians; these tend to reduce to a few
+canonical forms, involving coupling to ""baths"" of oscillators or spins. The
+method for doing this is demonstrated using examples from magnetism,
+superconductivity, and measurement theory, as is the way one then solves for
+the low-energy dynamics. Finally, detailed application is given to the exciting
+recent Quantum relaxation and tunneling work in naomagnets.",9810353v1
+1998-11-26,Supersymmetric Approach to Heavy-Fermion Systems,"We present a new supersymmetric approach to the Kondo lattice model in order
+to describe simultaneously the quasiparticle excitations and the low-energy
+magnetic fluctuations in heavy-Fermion systems. This approach mixes the
+fermionic and the bosonic representation of the spin following the standard
+rules of superalgebra. Our results show the formation of a bosonic band within
+the hybridization gap reflecting the spin collective modes. The density of
+states at the Fermi level is strongly renormalized while the Fermi surface sum
+rule includes $n_{c}+1$ states. The dynamical susceptibility is made of a Fermi
+liquid superimposed on a localized magnetism contribution.",9811380v1
+1998-12-21,Lifetimes of impurity states in crossed magnetic and electric fields,"We study the quantum dynamics of localized impurity states created by a point
+interaction for an electron moving in two dimensions under the influence of a
+perpendicular magnetic field and an in-plane weak electric field. All impurity
+states are unstable in presence of the electric field. Their lifetimes are
+computed and shown to grow in a Gaussian way as the electric field tends to
+zero.",9812340v1
+1999-04-17,Dynamical response of a weakly pinned two-dimensional Wigner crystal,"Motivated by puzzling results of recent experiments, we re-examine the
+response of a weakly pinned two-dimensional Wigner crystal to a uniform AC
+electric field. We confirm that at some disorder and magnetic field dependent
+frequency $\omega_p$, an inhomogeneously broadened absorption line emerges.
+Although the line is conventionally broad in zero magnetic field, in strong
+fields it appears as a sharp resonance whose width is related to the density of
+states in the low-frequency tail of the zero-field phonon spectrum. This
+behavior originates due to the long-range Coulomb interactions.",9904245v2
+1999-04-20,Random quantum magnets with long-range correlated disorder: Enhancement of critical and Griffiths-McCoy singularities,"We study the effect of spatial correlations in the quenched disorder on
+random quantum magnets at and near a quantum critical point. In the random
+transverse field Ising systems disorder correlations that decay algebraically
+with an exponent rho change the universality class of the transition for small
+enough rho and the off-critical Griffiths-McCoy singularities are enhanced. We
+present exact results for 1d utilizing a mapping to fractional Brownian motion
+and generalize the predictions for the critical exponents and the generalized
+dynamical exponent in the Griffiths phase to d>=2.",9904280v2
+1999-04-20,Interchain interactions and magnetic properties of Li2CuO2,"An effective Hamiltonian is constructed for an insulating cuprate with
+edge-sharing chains Li2CuO2.The Hamiltonian contains the nearest and
+next-nearest neighboring intrachain and zigzag-type interchain interactions.The
+values of the interactions are obtained from the analysis of the magnetic
+susceptibility, and this system is found to be described as coupled frustrated
+chains.We calculate the dynamical spin correlation function S(q,\omega) by
+using the exact diagonalization method, and show that the spectra of
+S(q,\omega) are characterized by the zigzag-type interchain interactions. The
+results of the recent inelastic neutron scattering experiment are discussed in
+the light of the calculated spectra.",9904283v2
+1999-04-23,Evidence for incommensurate spin fluctuations in Sr_2RuO_4,"We report first inelastic neutron scattering measurements in the normal state
+of Sr_2RuO_4 that reveal the existence of incommensurate magnetic spin
+fluctuations located at ${\bf q}_0=(\pm 0.6\pi/a, \pm 0.6\pi/a, 0)$. This
+finding confirms recent band structure calculations that have predicted
+incommensurate magnetic responses related to dynamical nesting properties of
+its Fermi surface.",9904348v1
+1999-06-03,Microwave Absorption Peaks : Signatures of Spin Dynamics in Cuprates,"We show that a common feature of temperature-dependent microwave absorption
+is the presence of absorption peaks. $ac$ loss peaks can arise when the
+internal $T$-dependent magnetic relaxation time crosses the measurement
+frequency. These features are observed in the \QTR{em}{insulating}
+($Sr_{x}Ca_{14-x}Cu_{24}O_{41}$, $La_{5/3}Sr_{1/3}NiO_{4}$ and
+$YBa_{2}Cu_{3}O_{6.0}$), \QTR{em}{pseudo-gap} ($T>T_{c}$ in underdoped
+$YBa_{2}Cu_{3}O_{7-\delta}$, $Hg:1223$ and $Hg:1201$) and
+\QTR{em}{superconducting} ($T<T_{c}$) states of the oxides. The commonality of
+these features suggests a magnetic (spin) mechanism, rather than a
+quasiparticle origin, for the so-called ``conductivity'' peaks observed in the
+cuprate superconductors.",9906053v2
+1999-06-04,Driving-Induced Symmetry Breaking in the Spin-Boson System,"A symmetric dissipative two-state system is asymptotically completely
+delocalized independent of the initial state. We show that driving-induced
+localization at long times can take place when both the bias and tunneling
+coupling energy are harmonically modulated. Dynamical symmetry breaking on
+average occurs when the driving frequencies are odd multiples of some reference
+frequency. This effect is universal, as it is independent of the dissipative
+mechanism. Possible candidates for an experimental observation are flux
+tunneling in the variable barrier rf SQUID and magnetization tunneling in
+magnetic molecular clusters.",9906062v1
+1999-10-05,Local Non-Fermi Liquid Theory of Magnetic Impurity Effects in Carbon Nanotubes,"Magnetic impurity effects in carbon nanotubes are studied theoretically. The
+multi channel Kondo effect is investigated with the band structure of the
+metallic nanotubes. The local non-Fermi liquid behavior is realized at
+temperatures lower than the Kondo temperature T_K. The density of states of
+localized electron has a singularity |omega|^1/2 which gives rise to a pseudo
+gap at the Kondo resonance in low temperatures. The temperature dependence of
+the electronic resistivity is predicted as T^1/2, and the imaginary part of
+dynamical susceptibilities has the |omega|^1/2 dependence.",9910053v1
+2000-03-23,Bifurcations and a chaos strip in states of long Josephson junctions,"Stationary and nonstationary, in particular, chaotic states in long Josephson
+junctions are investigated. Bifurcation lines on the parametric bias
+current-external magnetic field plane are calculated. The chaos strip along the
+bifurcation line is observed. It is shown that transitions between stationary
+states are the transitions from metastable to stable states and that the
+thermodynamical Gibbs potential of these stable states may be larger than for
+some metastable states. The definition of a dynamical critical magnetic field
+characterizing the stability of the stationary",0003375v1
+2000-05-03,Macroscopic resonant tunneling of magnetic flux,"We have developed a quantitative theory of resonant tunneling of magnetic
+flux between discrete macroscopically distinct quantum states in SQUID systems.
+The theory is based on the standard density-matrix approach. Its new elements
+include the discussion of the two different relaxation mechanisms that exist
+for the double-well potential, and description of the ``photon-assisted''
+tunneling driven by external rf radiation. It is shown that in the case of
+coherent flux dynamics, rf radiation should lead to splitting of the peaks of
+resonant flux tunneling, indicating that the resonant tunneling is a convenient
+tool for studying macroscopic quantum coherence of flux.",0005081v1
+2000-05-12,Interaction induced delocalisation for two particles in a periodic potential,"We consider two interacting particles evolving in a one-dimensional periodic
+structure embedded in a magnetic field. We show that the strong localization
+induced by the magnetic field for particular values of the flux per unit cell
+is destroyed as soon as the particles interact. We study the spectral and the
+dynamical aspects of this transition.",0005215v2
+2000-06-01,Yang-Lee and Fisher Zeros of Multisite Interaction Ising Models on the Cayley-type Lattices,"A general analytical formula for recurrence relations of multisite
+interaction Ising models in an external magnetic field on the Cayley-type
+lattices is derived. Using the theory of complex analytical dynamics on the
+Riemann sphere, a numerical algorithm to obtain Yang-Lee and Fisher zeros of
+the models is developed. It is shown that the sets of Yang-Lee and Fisher zeros
+are almost always fractals, that could be associated with Mandelbrot-like sets
+on the complex magnetic field and temperature planes respectively.",0006014v2
+2000-06-13,Theory of Transition Temperature of Magnetic Double Perovskites,"We formulate a theory of double perovskite coumpounds such as Sr$_2$FeReO$_6$
+and Sr$_2$FeMoO$_6$ which have attracted recent attention for their possible
+uses as spin valves and sources of spin polarized electrons. We solve the
+theory in the dynamical mean field approximation to find the magnetic
+transition temperature $T_c$. We find that $T_c$ is determined by a subtle
+interplay between carrier density and the Fe-Mo/Re site energy difference, and
+that the non-Fe same-sublattice hopping acts to reduce $T_c$. Our results
+suggest that presently existing materials do not optimize $T_c$.",0006208v1
+2000-07-04,Spin dynamics and ordering of a cuprate stripe-antiferromagnet,"In La1.48Nd0.4Sr0.12CuO4 the 139La and 63Cu NQR relaxation rates and signal
+wipe-out upon lowering temperature are shown to be due to purely magnetic
+fluctuations. They follow the same renormalized classical behavior as seen in
+neutron data, when the electronic spins order in stripes, with a small spread
+in spin stiffness (15% spread in activation energy). The La signal, which
+reappears at low temperatures, is magnetically broadened and experiences
+additional wipe-out due to slowing down of the Nd fluctuations.",0007057v2
+2000-09-08,Incipient nodal pairing in planar d-wave superconductors,"The possibility of a second pairing transition $d\to d+is$ ($d+id^\prime$) in
+planar $d$-wave superconductors which occurs in the absence of external
+magnetic field, magnetic impurities or boundaries is established in the
+framework of the non-perturbative phenomenon of dynamical chiral symmetry
+breaking in the system of $2+1$-dimensional Dirac-like nodal quasiparticles. We
+determine the critical exponents and quasiparticle spectral functions that
+characterize the corresponding quantum critical behavior and discuss some of
+its potentially observable spectral and transport features.",0009117v3
+2000-09-30,Hysteretic depinning and dynamical melting for magnetically interacting vortices in disordered layered superconductors,"We examine the depinning transitions and the temperature versus driving force
+phase diagram for magnetically interacting pancake vortices in layered
+superconductors. For strong disorder the initial depinning is plastic followed
+by a sharp hysteretic transition to a 3D ordered state for increasing driving
+force. Our results are in good agreement with theoretical predictions for
+driven anisotropic charge density wave systems. We also show that a temperature
+induced peak effect in the critical current occurs due to the onset of
+plasticity between the layers.",0010002v1
+2000-12-24,Microcantilever Studies of Angular Field Dependence of Vortex Dynamics in BSCCO,"Using a nanogram-sized single crystal of BSCCO attached to a microcantilever
+we demonstrate in a direct way that in magnetic fields nearly parallel to the
+{\it ab} plane the magnetic field penetrates the sample in the form of
+Josephson vortices rather than in the form of a tilted vortex lattice. We
+further investigate the relation between the Josephson vortices and the pancake
+vortices generated by the perpendicular field component.",0012453v1
+2001-01-10,Mechanical effects in quantum dots in magnetic and electric fields,"The mechanical effects in finite two-dimensional electron systems (quantum
+dots or droplets) in a strong perpendicular magnetic field are studied. It is
+shown that, due to asymmetry of the cyclotron dynamics, an additional in-plane
+electric field causes a ground state transition accompanied by a change in the
+average total angular momentum of the system, unless the lateral confining
+potential is exactly parabolic. A precise mechanical experiment is proposed in
+which a macroscopic angular momentum of a dense matrix of quantum dots could be
+measured and used to detect and estimate anharmonicity of the confinement.",0101133v1
+2001-01-11,Theoretical and Experimental Approach to Spin Dynamics in Thin Magnetic Films,"The Landau-Lifshitz (L-L) equation describing the time dependence of the
+magnetisation vector is numerically integrated fully without any simplifying
+assumptions in the time domain and the magnetisation time series obtained is
+Fourier transformed (FFT) to yield the permeability spectrum up to 10 GHz. The
+non linear results are compared to the experimental results obtained on
+magnetic amorphous thin films of Co-Zr, Co-Zr-Re. We analyse our results with
+the frequency response obtained directly from the Landau-Lifshitz equation as
+well as with the second order Gilbert frequency response.",0101154v1
+2001-01-18,C-axis Optical Sum Rule in Josephson Coupled Vortex State,"Observed violations of the $c$-axis optical sum rule can give important
+information on deviations from in-plane Fermi liquid behavior and on the nature
+of interlayer coupling between adjacent copper oxide planes. Application of a
+magnetic field perpendicular to these planes is another way to probe in-plane
+dynamics. We find that the optical sum rule is considerably modified in the
+presence of the $c$-axis magnetic field. Interlayer correlation of pancake
+vortices is involved in the sum rule modification; however, details of the
+vortex distribution in the plane are less important.",0101288v2
+2001-02-13,Nuclear spin driven quantum relaxation in LiY_0.998Ho_0.002F_4,"Staircase hysteresis loops of the magnetization of a LiY_0.998Ho_0.002F_4
+single crystal are observed at subkelvin temperatures and low field sweep
+rates. This behavior results from quantum dynamics at avoided level crossings
+of the energy spectrum of single Ho^{3+} ions in the presence of hyperfine
+interactions. Enhanced quantum relaxation in constant transverse fields allows
+the study of the relative magnitude of tunnel splittings. At faster sweep
+rates, non-equilibrated spin-phonon and spin-spin transitions, mediated by weak
+dipolar interactions, lead to magnetization oscillations and additional steps.",0102231v2
+2001-03-16,Perfectly Translating Lattices on a Cylinder,"We perform molecular dynamics simulations on an interacting electron gas
+confined to a cylindrical surface and subject to a radial magnetic field and
+the field of the positive background. In order to study the system at lowest
+energy states that still carry a current, initial configurations are obtained
+by a special quenching procedure. We observe the formation of a steady state in
+which the entire electron-lattice cycles with a common uniform velocity.
+Certain runs show an intermediate instability leading to lattice
+rearrangements. A Hall resistance can be defined and depends linearly on the
+magnetic field with an anomalous coefficient reflecting the manybody
+contributions peculiar to two dimensions.",0103353v1
+2001-05-26,Time-resolved ferromagnetic resonance in epitaxial Fe1-xCox films,"Magnetodynamics in epitaxial Fe1-xCox films on GaAs (100) are studied using
+time-resolved ferromagnetic resonance, in which the free precession of the
+magnetization after an impulsive excitation is measured using the polar Kerr
+effect. The sample is rotated with respect to the static and pulsed field
+directions, providing a complete mapping of the free energy surface and
+characteristic relaxation times. The magnetic response can be simulated with a
+simple coherent rotation model except in the immediate vicinity of switching
+fields. Bulk and surface anisotropies are identified, and unusual dynamics
+associated with the coexistence of cubic and uniaxial anisotropies are
+observed.",0105513v1
+2001-06-06,On the power spectrum of magnetization noise,"Understanding the power spectrum of the magnetization noise is a long
+standing problem. While earlier work considered superposition of 'elementary'
+jumps, without reference to the underlying physics, recent approaches relate
+the properties of the noise with the critical dynamics of domain walls. In
+particular, a new derivation of the power spectrum exponent has been proposed
+for the random-field Ising model. We apply this approach to experimental data,
+showing its validity and limitations.",0106113v1
+2001-08-23,Critical Behaviour of Non-Equilibrium Phase Transitions to Magnetically Ordered States,"We describe non-equilibrium phase transitions in arrays of dynamical systems
+with cubic nonlinearity driven by multiplicative Gaussian white noise.
+Depending on the sign of the spatial coupling we observe transitions to
+ferromagnetic or antiferromagnetic ordered states. We discuss the phase
+diagram, the order of the transitions, and the critical behaviour. For global
+coupling we show analytically that the critical exponent of the magnetization
+exhibits a transition from the value 1/2 to a non-universal behaviour depending
+on the ratio of noise strength to the magnitude of the spatial coupling.",0108379v1
+2001-09-21,Spin waves in a Bose-condensed atomic spin chain,"The spin dynamics of atomic Bose-Einstein condensates confined in a
+one-dimensional optical lattice is studied. The condensates at each lattice
+site behave like spin magnets that can interact with each other through both
+the light-induced dipole-dipole interaction and the static magnetic
+dipole-dipole interaction. We show how these site-to-site dipolar interactions
+can distort the ground state spin orientations and lead to the excitation of
+spin waves. The dispersion relation of the spin waves is studied and possible
+detection schemes are proposed.",0109415v1
+2001-10-07,Anomalous Spin Excitation Spectrum of the Heisenberg Model in a Magnetic Field,"Making the assumption that high energy fermions exist in the two dimensional
+spin-1/2 Heisenberg antiferromagnet we present predictions based on the pi-flux
+ansatz for the dynamic structure factor when the antiferromagnet is subject to
+a uniform magnetic field. The main result is the presence of gapped excitations
+in a momentum region near (pi,pi) with energy lower than that at (pi,pi). This
+is qualitatively different from spin wave theory predictions and may be tested
+by experiments or by quantum Monte Carlo.",0110133v2
+2001-12-17,Vortices in superconducting strips: interplay between surface effects and the pinning landscape,"Vortices in a narrow superconducting strip with a square array of pinning
+sites are studied. The interactions of vortices with other vortices and with
+external sources (applied magnetic field and transport current) are calculated
+via a screened Coulomb model. The edge barrier is taken into account and shown
+to have an important role on the system dynamics. Numerical simulations in this
+approach show that the field dependent magnetic moment presents peaks
+corresponding to history dependent configurations of the vortex lattice. Some
+effects of the edge barrier on the I-V characteristics are also reported.",0112313v1
+2002-01-02,Level Spectroscopy: Physical Meaning and Application to the Magnetization Plateau Problems,"We review the level spectroscopy, which is a powerful method of analyzing the
+numerical data with respect to the Berezinskii-Kosterlitz-Thouless quantum
+phase transition in one dimension. We focus on its physical meaning and also
+its application to the magnetization plateau problems.",0201013v2
+2002-01-10,Magnetism and Phase Separation in the Ground State of the Hubbard Model,"We discuss the ground state magnetic phase diagram of the Hubbard model off
+half filling within the dynamical mean-field theory. The effective
+single-impurity Anderson model is solved by Wilson's numerical renormalization
+group calculations, adapted to symmetry broken phases. We find a phase
+separated, antiferromagnetic state up to a critical doping for small and
+intermediate values of U, but could not stabilise a Neel state for large U and
+finite doping. At very large U, the phase diagram exhibits an island with a
+ferromagnetic ground state. Spectral properties in the ordered phases are
+discussed.",0201145v1
+2002-02-10,Response functions of gapped spin systems in high magnetic field,"We study the dynamical structure factor of gapped one-dimensional spin
+systems in the critical phase in high magnetic field. It is shown that the
+presence of a ``condensate'' in the ground state in the high-field phase leads
+to interesting signatures in the response functions.",0202171v1
+2002-03-01,Two-dimensional electron liquid with disorder in a weak magnetic field,"We present the effective theory for low energy dynamics of a two-dimensional
+interacting electrons in the presence of a weak short-range disorder and a weak
+perpendicular magnetic field, the filling factor $\nu \gg 1$. We investigate
+the exchange enhancement of the $g$-factor, the effective mass and the decay
+rate of the simplest spin wave excitations at $\nu = 2 N + 1$. We obtain the
+enhancement of the field-induced gap in the tunneling density of states and
+dependence of the tunneling conductivity on the applied bias.",0203022v2
+2002-04-25,Electronic structure and magnetic properties of correlated metals: A local self-consistent perturbation scheme,"In the framework of ab initio dynamical mean field theory for realistic
+electronic structure calculations a new perturbation scheme which combine the
+T-matrix and fluctuating exchange approximations has been proposed. This method
+is less computationally expensive than numerically exact quantum Monte Carlo
+technics and give an adequate description of the electronic structure and
+exchange interactions for magnetic metals. We discuss a simple expression for
+the exchange interactions corresponding to the neglecting of the vertex
+corrections which becomes exact for the spin-wave stiffness in the local
+approximation. Electronic structure, correlation effects and exchange
+interactions for ferromagnetic nickel have been discussed.",0204564v1
+2002-07-22,Thickness dependence of critical currents in thin superconductors,"Mechanisms of vortex dynamics and pinning and self-field effects which could
+account for the thickness dependence of the critical current density J_c of
+superconducting films are addressed. It is shown that at low magnetic fields B,
+the 2D single-vortex pinning and thermal fluctuations yield J_c proportional to
+(1/sqrt{d})exp[-(d_m/d)^{1/2}], if the film thickness d is smaller than the
+pinning correlation length along B. The model describes the dependence of J_c
+on d observed on YBa_2Cu_3O_7 coated conductors for d < 2(mu)m. Measurements of
+J_c(d) in strong magnetic fields are proposed to probe whether the dependence
+of J_c on d is mostly determined by the 2D pinning or changes in the material
+microstructure as the film gets thicker.",0207526v1
+2002-08-16,Supported magnetic nanoclusters: Softlanding of Pd clusters on a MgO surface,"Low-energy deposition of neutral Pd_N clusters (N=2-7 and 13) on a MgO(001)
+surface F-center (FC) was studied by spin-density-functional molecular dynamics
+simulations. The incident clusters are steered by an attractive ""funnel""
+created by the FC, resulting in adsorption of the cluster, with one of its
+atoms bonded atop of the FC. The deposited Pd_2-Pd_6 clusters retain their
+gas-phase structures, while for N>6 surface-commensurate isomers are
+energetically more favorable. Adsorbed clusters with N > 3 are found to remain
+magnetic at the surface.",0208321v1
+2002-09-17,Magnetic Order and Dynamics in an Orbitally Degenerate Ferromagnetic Insulator,"Neutron scattering was used to determine the spin structure and the magnon
+spectrum of the Mott--Hubbard insulator YTiO$_3$. The magnetic structure is
+complex, comprising substantial G-type and A-type antiferromagnetic components
+in addition to the predominant ferromagnetic component. The magnon spectrum, on
+the other hand, is gapless and nearly isotropic. We show that these findings
+are inconsistent with the orbitally ordered states thus far proposed for
+YTiO$_3$ and discuss general implications for a theoretical description of
+exchange interactions in orbitally degenerate systems.",0209400v1
+2002-12-11,Spectrum and correlation functions of a quasi-one-dimensional quantum Ising model,"We consider a model of weakly coupled quantum Ising chains. We describe the
+phase diagram of such a model and study the dynamical magnetic susceptibility
+by means of Bethe ansatz and the Random Phase Approximation applied to the
+inter-chain exchange. We argue that some of the beautiful physics of the
+quantum Ising chain in a magnetic field survives in the ordered state of the
+quasi-one-dimensional model and can be observed experimentally by means of
+neutron scattering.",0212248v2
+2003-01-07,Subharmonics and Aperiodicity in Hysteresis Loops,"We show that it is possible to have hysteretic behavior for magnets that does
+not form simple closed loops in steady state, but must cycle multiple times
+before returning to its initial state. We show this by studying the
+zero-temperature dynamics of the 3d Edwards Anderson spin glass. The specific
+multiple varies from system to system and is often quite large and increases
+with system size. The last result suggests that the magnetization could be
+aperiodic in the large system limit for some realizations of randomness. It
+should be possible to observe this phenomena in low-temperature experiments.",0301083v1
+2003-01-13,Spin freezing and magnetic inhomogeneities in bilayer manganites,"We have performed a muon spin rotation study on polycrystalline samples of
+electron-doped layered manganites, La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (0.4<
+x<1), in order to investigate the local magnetic structure and spin dynamics.
+Our results provide evidence for phase separation into A-type antiferromagnetic
+and charge-ordered phases for x=0.52 and spin freezing at low temperatures
+(T<100K) for 0.52<x<0.75. A new phase diagram which includes this spin freezing
+region is proposed.",0301177v1
+2003-01-21,Hole-Doping Effects on a Two-dimensional Kondo Insulator,"We study the effects of hole doping on the two-dimensional Heisenberg-Kondo
+model around the quantum critical point, where the spin liquid phase (Kondo
+insulator) and the magnetically ordered phase are separated via a second-order
+phase transition. By means of the self-consistent Born approximation within the
+bond operator formalism as well as the standard spin wave theory, we discuss
+dynamical properties of a doped hole. It is clarified that a quasi-particle
+state stabilized in the spin liquid phase is gradually obscured as the system
+approaches the quantum critical point. This is also the case for the
+magnetically ordered phase. We argue the similarity and the difference between
+these two cases.",0301401v1
+2003-03-26,Chern Numbers for Spin Models of Transition Metal Nanomagnets,"We argue that ferromagnetic transition metal nanoparticles with fewer than
+approximately 100 atoms can be described by an effective Hamiltonian with a
+single giant spin degree of freedom. The total spin $S$ of the effective
+Hamiltonian is specified by a Berry curvature Chern number that characterizes
+the topologically non-trivial dependence of a nanoparticle's many-electron
+wavefunction on magnetization orientation. The Berry curvatures and associated
+Chern numbers have a complex dependence on spin-orbit coupling in the
+nanoparticle and influence the semiclassical Landau-Liftshitz equations that
+describe magnetization orientation dynamics.",0303555v1
+2003-04-02,Magnetic orderings in Al nanowires suspended between electrodes,"A theoretical analysis of a relation between atomic and spin-electronic
+structures for the ground state of single-row aluminum nanowires suspended
+between Al(001) electrodes is demonstrated using first-principles
+molecular-dynamics simulations. We obtain a unusual result that a
+3-aluminum-atom nanowire sandwiched between the electrodes does not manifest
+magnetic ordering although an isolated aluminum trimer molecule in a straight
+line is spin-polarized. On the other hand, a 5-atom nanowire exhibits
+ferromagnetic ordering, where three central atoms form a spin-polarized trimer.
+Moreover, in the case of an 8-atom nanowire, the middle atoms in the nanowire
+form two spin-polarized trimers with antiferromagnetic ordering.",0304060v1
+2003-04-10,Dynamical Structure Factor in Cu Benzoate and other spin-1/2 antiferromagnetic chains,"Recent experiments of the quasi-one-dimensional spin-1/2 antiferromagnet
+Copper Benzoate established the existence of a magnetic field induced gap. The
+observed neutron scattering intensity exhibits resolution limited peaks at both
+the antiferromagnetic wave number and at incommensurate wave numbers related to
+the applied magnetic field. We determine the ratio of spectral weights of these
+peaks within the framework of a low-energy effective field theory description
+of the problem.",0304244v1
+2003-04-11,Photon-assisted tunneling in a Fe8 Single-Molecule Magnet,"The low temperature spin dynamics of a Fe8 Single-Molecule Magnet was studied
+under circularly polarized electromagnetic radiation allowing us to establish
+clearly photon-assisted tunneling. This effect, while linear at low power,
+becomes highly non-linear above a relatively low power threshold. This
+non-linearity is attributed to the nature of the coupling of the sample to the
+thermostat.These results are of great importance if such systems are to be used
+as quantum computers.",0304274v1
+2003-06-20,Quantum dynamics of tunneling between ferromagnets,"We study the Josephson-like spin currents between two ferromagnetic metals by
+deriving the effective action of the junction. A DC spin Josephson current with
+the full O(3) symmetry is obtained. By the analogy to the superconducting
+junctions, we have shown that a time-independent uniform magnetic field can
+serve as the source of the AC spin Josephson effect. That is, the spin current
+becomes a periodic function of the time with the period proportional to the
+inverse of the magnitude of the external magnetic field.",0306518v2
+2003-07-18,An extension of the Kac ring model,"We introduce a unitary dynamics for quantum spins which is an extension of a
+model introduced by Mark Kac to clarify the phenomenon of relaxation to
+equilibrium. When the number of spins gets very large, the magnetization
+satisfies an autonomous equation as function of time with exponentially fast
+relaxation to the equilibrium magnetization as determined by the microcanonical
+ensemble. This is proven as a law of large numbers with respect to a class of
+initial data. The corresponding Gibbs-von Neumann entropy is also computed and
+its monotonicity in time discussed.",0307460v3
+2003-08-23,Theory of Current-Driven Domain Wall Motion: A Poorman's Approach,"A self-contained theory of the domain wall dynamics in ferromagnets under
+finite electric current is presented.
+  The current is shown to have two effects; one is momentum transfer, which is
+proportional to the charge current and wall resistivity ($\rhow$), and the
+other is spin transfer, proportional to spin current.
+  For thick walls, as in metallic wires, the latter dominates and the threshold
+current for wall motion is determined by the hard-axis magnetic anisotropy,
+except for the case of very strong pinning.
+  For thin walls, as in nanocontacts and magnetic semiconductors, the
+momentum-transfer effect dominates, and the threshold current is proportional
+to $\Vz/\rhow$, $\Vz$ being the pinning potential.",0308464v1
+2003-08-24,Nuclear spin qubits in a pseudo-spin quantum chain,"We analyze a quantum computer (QC) design based on nuclear spin qubits in a
+quasi-one-dimensional (1D) chain of non-Kramers doublet atoms. We explore the
+use of spatial symmetry breaking to obtain control over the local dynamics of a
+qubit. We also study the decoherence mechanisms at the single qubit level and
+the interactions mediated by the magnetic media. The design can be realized in
+$\textrm{PrBr}_{\textrm{3}-x}\textrm{F}_{x}$ with nuclear magnetic resonance
+(NMR) techniques.",0308475v2
+2003-09-08,Interplay between Freezing and Superconductivity in the Optimally Doped LaEu0.20Sr0.15CuO4 under Hydrostatic Pressure,"We study the electronic properties of a LaEu0.20Sr0.15CuO4 single crystal
+under hydrostatic pressure up to 2.9 GPa. Both the freezing of the Cu 3d
+moments and the structural transition from the orthorhombic (LTO) to the
+tetragonal (LTT) phase are observed via the relaxation of the nuclear
+magnetization of La nuclei. Resistivity and magnetic susceptibility
+measurements have been carried out under pressure on the same sample. The
+combination of all data reveals the connection between glassy dynamics, charge
+localization and the disappearance of superconductivity in the LTT phase.",0309193v1
+2003-10-24,Spin-Charge Separation in Two-dimensional Frustrated Quantum Magnets,"The dynamics of a mobile hole in two-dimensional frustrated quantum magnets
+is investigated by exact diagonalization techniques. Our results provide
+evidence for spin-charge separation upon doping the kagome lattice, a prototype
+of a spin liquid. In contrast, in the checkerboard lattice, a symmetry broken
+Valence Bond Crystal, a small quasi-particle peak is seen for some crystal
+momenta, a finding interpreted as a restoration of weak holon-spinon
+confinement.",0310597v2
+2003-10-30,Distribution of exchange energy in a bond-alternating S=1 quantum spin chain,"The quasi-one-dimensional bond-alternating S=1 quantum antiferromagnet NTENP
+is studied by single crystal inelastic neutron scattering. Parameters of the
+measured dispersion relation for magnetic excitations are compared to existing
+numerical results and used to determine the magnitude of bond-strength
+alternation. The measured neutron scattering intensities are also analyzed
+using the 1st-moment sum rules for the magnetic dynamic structure factor, to
+directly determine the modulation of ground state exchange energies. These
+independently determined modulation parameters characterize the level of spin
+dimerization in NTENP. First-principle DMRG calculations are used to study the
+relation between these two quantities.",0310741v1
+2003-12-16,Interplay between the magnetic fluctuations and superconductivity in the lanthanum cuprates,"We report the analysis of the magnetic fluctuations in the superconducing
+La_{2-x}Sr_xCuO_4 and the related lanthanum cuprates having the different
+symmetry of the low temperature structure. The NMR and ESR investigations
+revealed the dynamical coexistence of the superconductivity and the
+antiferromagnetic correlations in the large part of superconductivity region of
+the phase diagram. We show that for all compounds, independent on their low
+temperature symmetry and on their superconducting properties, the enhancement
+of the spin stiffness near 1/8 doping takes place.",0312393v1
+2003-12-24,Signature of entangled eigenstates in the magnetic response of two coupled flux qubits,"We study dissipative dynamics and a magnetic response of two coupled flux
+qubits interacting with a high quality tank in the framework of the impedance
+measurement technique (IMT). It is shown that the observation of the difference
+between a sum of IMT signals from separated qubits and the signal from the
+system when both qubits are in the degeneracy point (IMT deficit) implies
+immediately a formation of the entangled two-qubit eigenstates.",0312635v1
+2004-01-12,Dynamical localization for Bloch electrons in Magnetic and Electric Fields,"We study the time evolution of wave packets of noninteracting electrons in a
+two-dimensional periodic system in the presence of magnetic and electric
+fields. The model includes consistently the coupling between Landau levels as
+well as the periodic and external field contributions. It is shown that the
+electric field produces localization along its longitudinal direction, this
+effect is a physical consequence of the quantization of the energy levels with
+respect to the longitudinal quasi-momentum. For incommensurate orientations of
+$\mathbf{E}$ relative to the lattice the wave packet becomes localized in both
+directions.",0401198v1
+2004-01-31,Resonant magnetic mode in superconducting 2-leg ladders,"The spin dynamics of a doped 2-leg spin ladder is investigated by numerical
+techniques. We show that a hole pair-magnon boundstate evolves at finite hole
+doping into a sharp magnetic excitation below the two-particle continuum. This
+is supported by a field theory argument based on a SO(6)-symmetric ladder.
+Similarities and differences with the resonant mode of the high-T$_c$ cuprates
+are discussed.",0402011v1
+2004-02-09,Phase diagram and critical exponents of a dissipative Ising spin chain in a transverse magnetic field,"We consider a one-dimensional Ising model in a transverse magnetic field
+coupled to a dissipative heat bath. The phase diagram and the critical
+exponents are determined from extensive Monte Carlo simulations. It is shown
+that the character of the quantum phase transition is radically altered from
+the corresponding non-dissipative model and the double-well coupled to a
+dissipative heat bath with linear friction. Spatial couplings and the
+dissipative dynamics combine to form a new quantum criticality.",0402224v2
+2004-02-20,Low-frequency incommensurate magnetic response in strongly correlated systems,"It is shown that in the t-J model of Cu-O planes at low frequencies the
+dynamic spin structure factor is peaked at incommensurate wave vectors
+(1/2+-delta,1/2)$, (1/2,1/2+-delta). The incommensurability is connected with
+the momentum dependencies of the magnon frequency and damping near the
+antiferromagnetic wave vector. The behavior of the incommensurate peaks is
+similar to that observed in La_{2-x}(Ba,Sr)_xCuO_{4+y} and YBa_2Cu_3O_{7-y}:
+for hole concentrations 0.02<x<=0.12 we find that delta is nearly proportional
+to x, while for x>0.12 it tends to saturation. The incommensurability
+disappears with increasing temperature. Generally the incommensurate magnetic
+response is not accompanied by an inhomogeneity of the carrier density.",0402512v1
+2004-03-03,Off-equilibrium fluctuation-dissipation relation in a spin glass,"We report new experimental results obtained onthe insulating spin glass
+CdCrInS_4. Our experimental setup allows a quantitative comparison between
+thethermo-remanent magnetization and the autocorrelation of spontaneous
+fluctuations of magnetization, yielding acomplete determination of the
+fluctuation-dissipationrelation. The dynamics can be studied both in
+thequasi-equilibrium regime, where the fluctuation-dissipation theorem holds,
+and in the deeply aging regime. The limit of separation of time-scales, as used
+in analytical calculations, can be approached by use of a scaling procedure.",0403112v2
+2004-04-04,Nonequilibrium steady states of the isotropic classical magnet,"We drive a d-dimensional Heisenberg magnet using a spatially anisotropic
+current of mobile particles or heat. The continuum Langevin equation is
+analyzed using a dynamical renormalization group, stability analysis and
+numerical simulations. We discover a rich steady-state phase diagram, including
+a critical point in a new nonequilibrium universality class, and a
+spatiotemporally chaotic phase. The latter may be `controlled' in a robust
+manner to target spatially periodic steady states with helical order. We
+discuss several physical realizations of this model and make definite
+predictions which could be tested in experimental or model lattice systems.",0404071v1
+2004-06-04,Competition between Spin-Orbit Interaction and Zeeman Coupling in Rashba 2DEGs,"We investigate systematically how the interplay between Rashba spin-orbit
+interaction and Zeeman coupling affects the electron transport and the spin
+dynamics in InGaAs-based 2D electron gases. From the quantitative analysis of
+the magnetoconductance, measured in the presence of an in-plane magnetic field,
+we conclude that this interplay results in a spin-induced breaking of time
+reversal symmetry and in an enhancement of the spin relaxation time. Both
+effects, due to a partial alignment of the electron spin along the applied
+magnetic field, are found to be in excellent agreement with recent theoretical
+predictions.",0406106v1
+2004-08-13,Finite lattice size effect in the ground state phase diagram of quasi-two-dimensional magnetic dipolar dots array with perpendicular anisotropy,"A prototype Hamiltonian for the generic patterned magnetic structures, of
+dipolar interaction with perpendicular anisotropy, is investigated within the
+finite-size framework by Landau-Lifshift-Gilbert classical spin dynamics.
+Modifications on the ground state phase diagram are discussed with an emphasis
+on the disappearance of continuous degeneracy in the ground state of in-plane
+phase due to the finite lattice size effect. The symmetry-governed ground state
+evolution upon the lattice size increase provides a critical insight into the
+systematic transition to the infinite extreme.",0408324v1
+2004-10-19,Haldane-gap chains in a magnetic field,"We consider quasi one dimensional spin-1 Heisenberg chains with crystal field
+anisotropy in a uniform magnetic field. We determine the dynamical structure
+factor in various limits and obtain a fairly complete qualitative picture of
+how it changes with the applied field. In particular, we discuss how the width
+of the higher energy single magnon modes depends on the field. We consider the
+effects of a weak interchain coupling. We discuss the relevance of our results
+for recent neutron scattering experiments on the quasi-1D Haldane-gap compound
+NDMAP.",0410487v1
+2004-10-29,How many electrons are needed to flip a local spin?,"Considering the spin of a local magnetic atom as a quantum mechanical
+operator, we illustrate the dynamics of a local spin interacting with a
+ballistic electron represented by a wave packet. This approach improves the
+semi-classical approximation and provides a complete quantum mechanical
+understanding for spin transfer phenomena. Sending spin-polarized electrons
+towards a local magnetic atom one after another, we estimate the minimum number
+of electrons needed to flip a local spin.",0410775v1
+2004-11-10,Dynamic roughening of the magnetic flux landscape in YBa$_2$Cu$_3$O$_{7-x}$,"We study the magnetic flux landscape in YBa$_2$Cu$_3$O$_{7-x}$ thin films as
+a two dimensional rough surface. The vortex density in the superconductor forms
+a self-affine structure in both space and time. This is characterized by a
+roughness exponent $\alpha = 0.76(3)$ and a growth exponent $\beta = 0.57(6)$.
+This is due to the structure and distribution of flux avalanches in the
+self-organized critical state, which is formed in the superconductor. We also
+discuss our results in the context of other roughening systems in the presence
+of quenched disorder.",0411260v1
+2005-01-21,Perspectives of Ultra Cold Atoms Trapped in Magnetic Micro Potentials,"Recent work on magnetic micro traps for ultracold atoms is briefly reviewed.
+The basic principles of operation are described together with the loading
+methods and some of the realized trap geometries. Experiments are discussed
+that study the interaction between atoms and the surface of micro traps as well
+as the dynamics of ultracold gases in wave guides are discussed. The results
+allow for an outlook towards future directions of research.",0501528v1
+2005-01-26,High-field optically detected nuclear magnetic resonance in GaAs,"A method for high-field optically detected nuclear magnetic resonance (ODNMR)
+is developed sensitive to 10**8 nuclei. Nuclear spin transitions are induced
+using a radio frequency coil and detected through Faraday rotation
+spectroscopy. Unlike conventional ODNMR, which is limited to low fields and
+relies on the measurement of time-averaged luminescence polarization, this
+technique monitors nuclear polarization through time-resolved measurements of
+electron spin dynamics. Measurements in a (110) GaAs quantum well reveal Ga-69,
+Ga-71, and As-75 resonances and their quadrupolar splittings while resolving
+changes in nuclear polarization of 0.02%.",0501652v1
+2005-01-31,Laser-controlled local magnetic field with semiconductor quantum rings,"We analize theoretically the dynamics of N electrons localized in a
+semiconductor quantum ring under a train of phase-locked infrared laser pulses.
+The pulse sequence is designed to control the total angular momentum of the
+electrons. The quantum ring can be put in states characterized by strong
+currents. The local magnetic field created by these currents can be used for a
+selective quantum control of single spins in semiconductor systems.",0502001v1
+2005-07-30,"Multiferroic behavior in CdCr2X4 (X = S, Se)","The recently discovered multiferroic material CdCr2S4 shows a coexistence of
+ferromagnetism and relaxor ferroelectricity together with a colossal
+magnetocapacitive effect. The complex dielectric permittivity of this compound
+and of the structurally related CdCr2Se4 was studied by means of broadband
+dielectric spectroscopy using different electrode materials. The observed
+magnetocapacitive coupling at the magnetic transition is driven by enormous
+changes of the relaxation dynamics induced by the development of magnetic
+order.",0508014v1
+2005-08-09,Percolation quantum phase transitions in diluted magnets,"We show that the interplay of geometric criticality and quantum fluctuations
+leads to a novel universality class for the percolation quantum phase
+transition in diluted magnets. All critical exponents involving dynamical
+correlations are different from the classical percolation values, but in two
+dimensions they can nonetheless be determined exactly. We develop a complete
+scaling theory of this transition, and we relate it to recent experiments in
+La$_{2}$Cu$_{1-p}$(Zn,Mg)$_{p}$O$_{4}$. Our results are also relevant for
+disordered interacting boson systems.",0508211v2
+2005-08-15,The Structure of the Pairing Interaction in the 2D Hubbard Model,"Dynamic cluster Monte Carlo calculations for the doped two-dimensional
+Hubbard model are used to study the irreducible particle-particle vertex
+responsible for $d_{x^2-y^2}$ pairing in this model. This vertex increases with
+increasing momentum transfer and decreases when the energy transfer exceeds a
+scale associated with the $Q=(\pi, \pi)$ spin susceptibility. Using an exact
+decomposition of this vertex into a fully irreducible two-fermion vertex and
+charge and magnetic exchange channels, the dominant part of the effective
+pairing interaction is found to come from the magnetic, spin S=1 exchange
+channel.",0508361v2
+2005-08-25,Current-induced Vortex Motion by Spin-Transfer Torque,"We investigate the dynamics of a magnetic vortex driven by spin-transfer
+torque due to spin current in the adiabatic case. The vortex core represented
+by collective coordinate experiences a transverse force proportional to the
+product of spin current and gyrovector, which can be interpreted as the
+geometric force determined by topological charges. We show that this force is
+just a reaction force of Lorentz-type force from the spin current of conduction
+electrons. Based on our analyses, we propose analytically and numerically a
+possible experiment to check the vortex displacement by spin current in the
+case of single magnetic nanodot.",0508599v1
+2005-10-14,Suppression of quantum chaos in a quantum computer hardware,"We present numerical and analytical studies of a quantum computer proposed by
+the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and
+quantum chaos regimes in the quantum computer hardware are identified as a
+function of magnetic field gradient and dipole-dipole couplings between qubits
+on a square lattice. It is shown that a strong magnetic field gradient leads to
+suppression of quantum chaos.",0510392v1
+2005-10-28,Antiferromagnetic Metal Spintronics,"Spintronics in ferromagnetic metals is built on a complementary set of
+phenomena in which magnetic configurations influence transport coefficients and
+transport currents alter magnetic configurations. In this Letter we propose
+that corresponding effects occur in circuits containing antiferromagnetic
+metals. The critical current for switching can be smaller in the
+antiferromagnetic case because of the absence of shape anisotropy and because
+spin torques act through the entire volume of an antiferromagnet. Our findings
+suggest that current-induced order parameter dynamics can be used to coarsen
+the microstructure of antiferromagnetic thin films.",0510797v1
+2005-12-09,Experimental determination of the non-extensive entropic parameter $q$,"We show how to extract the $q$ parameter from experimental data, considering
+an inhomogeneous magnetic system composed by many Maxwell-Boltzmann homogeneous
+parts, which after integration over the whole system recover the Tsallis
+non-extensivity. Analyzing the cluster distribution of
+La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ manganite, obtained through scanning tunnelling
+spectroscopy, we measure the $q$ parameter and predict the bulk magnetization
+with good accuracy. The connection between the Griffiths phase and
+non-extensivity is also considered. We conclude that the entropic parameter
+embodies information about the dynamics, the key role to describe complex
+systems.",0512208v1
+2005-12-13,Knight Field Enabled Nuclear Spin Polarization in Single Quantum Dots,"We demonstrate dynamical nuclear spin polarization in the absence of an
+external magnetic field, by resonant circularly polarized optical excitation of
+a single electron or hole charged quantum dot. Optical pumping of the electron
+spin induces an effective inhomogeneous magnetic (Knight) field that determines
+the direction along which nuclear spins could polarize and enables nuclear-spin
+cooling by suppressing depolarization induced by nuclear dipole-dipole
+interactions. Our observations suggest a new mechanism for spin-polarization
+where spin exchange with an electron reservoir plays a crucial role. These
+experiments constitute a first step towards quantum measurement of the
+Overhauser field.",0512269v1
+2006-01-25,Critical Temperatures of a Two-Band Model for Diluted Magnetic Semiconductors,"Using Dynamical Mean Field Theory (DMFT) and Monte Carlo (MC) simulations, we
+study the ferromagnetic transition temperature Tc of a two-band model for
+Diluted Magnetic Semiconductors (DMS), varying coupling constants, hopping
+parameters, and carrier densities. We found that Tc is optimized at all
+fillings p when both impurity bands (IB) fully overlap in the same energy
+range, namely when the exchange couplings J and bandwidths are identical. The
+optimal Tc is found to be about twice larger than the maximum value obtained in
+the one-band model, showing the importance of multiband descriptions of DMS at
+intermediate J's.",0601593v1
+2006-02-20,Spin liquid correlations in Nd-langasite anisotropic Kagomé antiferromagnet,"Dynamical magnetic correlations in the geometrically frustrated
+Nd$\_3$Ga$\_5$SiO$\_{14}$ compound were probed by inelastic neutron scattering
+on a single crystal. A scattering signal with a ring shape distribution in
+reciprocal space and unprecedented dispersive features was discovered.
+Comparison with calculated static magnetic scattering from models of correlated
+spins suggests that the observed phase is a spin liquid inherent to an
+antiferromagnetic kagom\'e-like lattice of anisotropic Nd moments.",0602457v2
+2006-02-24,Probability distributions of the work in the 2D-Ising model,"Probability distributions of the magnetic work are computed for the 2D Ising
+model by means of Monte Carlo simulations. The system is first prepared at
+equilibrium for three temperatures below, at and above the critical point. A
+magnetic field is then applied and grown linearly at different rates.
+Probability distributions of the work are stored and free energy differences
+computed using the Jarzynski equality. Consistency is checked and the dynamics
+of the system is analyzed. Free energies and dissipated works are reproduced
+with simple models. The critical exponent $\delta$ is estimated in an usual
+manner.",0602580v1
+2006-03-09,"Formation kinetics of magnetic chains, rings, X's, and Y's","The kinetics of aggregation in a monolayer of magnetic particles are studied
+using stochastic dynamics computer simulations. At low densities (<8% coverage)
+the equilibrium structure is made up of chains and rings; the primary
+mechanisms by which these motifs form are described. At higher densities (>15%
+coverage), we observe large transient concentrations of Y-shaped and X-shaped
+defects that ultimately give way to an extended, labyrinthine network. Our
+results suggest that a defect mechanism -- such as that proposed by Tlusty and
+Safran, Science 290, 1328 (2000) -- could drive a metastable phase separation
+in two dimensions.",0603268v1
+2006-03-27,Nonadiabatic production of spinor condensates with a QUIC trap,"Motivated by the recent experimental observation of multi-component spinor
+condensates via a time-dependent quadrupole-Ioffe-configuration trap (QUIC
+trap), we provide a general framework for the investigation of nonadiabatic
+Landau-Zener dynamics of a hyperfine spin, e.g., from an atomic magnetic dipole
+moment coupled to a weak time-dependent magnetic (B-) field. The spin flipped
+population distribution, or the so-called Majorona formula is expressed in
+terms of system parameters and experimental observables; thus, provides much
+needed insight into the underlying mechanism for the production of spinor
+condensates due to nonadiabatic level crossings.",0603686v1
+2006-04-26,Time-domain measurement of driven ferromagnetic resonance,"We present a time-resolved measurement of magnetization dynamics during
+ferromagnetic resonance (FMR) in a single layer of Ni81Fe19. Small-angle (<1
+deg.) precession of elemental Ni, Fe moments could be measured directly and
+quantitatively using time-resolved x-ray magnetic circular dichroism (XMCD) in
+transmission. The high temporal and rotational sensitivity of of this technique
+has allowed characterization of the phase and amplitude of driven FMR motion at
+2.3 GHz, verifying basic expectations for a driven resonance.",0604610v1
+2006-05-11,Power dissipation in spintronic devices out of thermodynamic equilibrium,"Quantum limits of power dissipation in spintronic computing are estimated. A
+computing element composed of a single electron in a quantum dot is considered.
+Dynamics of its spin due to external magnetic field and interaction with
+adjacent dots is described via the Bloch equations. Spin relaxation due to
+magnetic noise from various sources is described as coupling to a reservoir.
+Resulting dissipation of energy is calculated and is shown to be much less than
+the thermal limit, ~kT per bit, if the rate of spin relaxation is much slower
+than the switching rate. Clues on how to engineer an energy efficient
+spintronic device are provided.",0605298v1
+2006-05-15,Levitation of Bose-Einstein condensates induced by macroscopic non-adiabatic quantum tunneling,"We study the dynamics of two-component Bose-Einstein condensates trapped in
+different vertical positions in the presence of an oscillating magnetic field.
+It is shown here how tuning appropriately the oscillation frequency of the
+magnetic field leads to the levitation of the system against gravity. This
+phenomenon is a manifestation of a macroscopic non-adiabatic tunneling in a
+system with internal degrees of freedom.",0605385v1
+2006-06-06,Resistance noise in spin valves,"Fluctuations of the magnetization in spin valves are shown to cause
+resistance noise that strongly depends on the magnetic configuration. Due to
+the applied external field and the dynamic exchange interaction through the
+normal metal spacer, the electrical noise level of the antiparallel
+configuration can exceed that of the parallel one by an order of magnitude, in
+agreement with recent experimental results.",0606131v1
+2006-06-20,Conductivity in glass phases of disordered granular superconductors in magnetic fields,"The electric conductivities in glass phases of three-dimensional (3D)
+granular superconductors in magnetic fields are examined based on a quantum
+disordered Josephson-junction array. A correct inclusion of the Ohmic
+dissipative dynamics leads to glass phases with divergent dc conductivity. In
+contrast, with no dissipative term, a metallic response in a glass phase is
+obtained irrespective of the range of correlation of quenched disorder, i.e.,
+even in the so-called Bose-glass phase with experimentally vanishing
+resistivity.",0606522v5
+2006-07-05,A simple model for thermomagnetic instability of critical state dynamics in superconductive films,"An one-dimensional model of magnetic flux penetration into thin strip-like
+superconductive film is subject to numerical analysis which combines explicit
+account for specific oblate geometry of magnetic field lines around the film
+and a simplest phenomenology of the flux flow resistance under rigid pinning of
+vortices with temperature-dependent critical current.",0607143v1
+2006-08-02,Nuclear spin effects in negatively charged InP quantum dots,"Effects of both the dynamic nuclear polarization (DNP) created by circularly
+polarized light and the fluctuations of average nuclear spin in a quantum dot
+(QD) on the electron spin orientation are studied for singly negatively charged
+InP QDs. From the dependence of the negative circular polarization of
+photoluminescence on the applied longitudinal magnetic field, the hyperfine
+field B_N of a few mT appearing due to DNP and the effective magnetic field B_f
+of a few tens of mT arising from nuclear spin fluctuations (NSF) are estimated.
+A lifetime of about 1 microsecond is estimated for NSF.",0608043v1
+2006-08-04,"An electron spin injection driven, paramagnetic solid-state MASER device","In response to an external, microwave-frequency magnetic field, a
+paramagnetic medium will absorb energy from the field that drives the
+magnetization dynamics. Here we describe a new process by which an external
+spin injection source, when combined with the microwave field spin-pumping, can
+drive the paramagnetic medium from one that absorbs microwave energy to one
+that emits microwave energy. We derive a simple condition for the crossover
+from absorptive to emissive behavior. Based on this process, we propose a spin
+injection-driven paramagnetic MASER device.",0608111v1
+2006-10-10,Nanofabrication of spin-transfer torque devices by a PMMA mask one step process: GMR versus single layer devices,"We present a method to prepare magnetic spin torque devices of low specific
+resistance in a one step lithography process. The quality of the pillar devices
+is demonstrated for a standard magnetic double layer device. For single layer
+devices, we found hysteretic switching and a more complex dynamical excitation
+pattern in higher fields. A simple model to explain the resistance spikes is
+presented.",0610277v1
+2006-10-12,Theory of integer quantum Hall effect in graphene,"The observed quantization of the Hall conductivity in graphene at high
+magnetic fields is explained as being due to the dynamically generated spatial
+modulation of either the electron spin or the density, as decided by the
+details of Coulomb interaction on the scale of lattice constant. It is
+predicted that at a large in-plane component of the magnetic field such
+ordering will be present only at the filling factor |f|=1, and absent
+otherwise. Other experimental consequences of the theory are outlined.",0610349v3
+2006-12-19,Effect of spin-orbit coupling on the excitation spectrum of Andreev billiards,"We consider the effect of spin-orbit coupling on the low energy excitation
+spectrum of an Andreev billiard (a quantum dot weakly coupled to a
+superconductor), using a dynamical numerical model (the spin Andreev map).
+Three effects of spin-orbit coupling are obtained in our simulations: In zero
+magnetic field: (1) the narrowing of the distribution of the excitation gap;
+(2) the appearance of oscillations in the average density of states. In strong
+magnetic field: (3) the appearance of a peak in the average density of states
+at zero energy. All three effects have been predicted by random-matrix theory.",0612501v1
+2007-01-23,Observation of Spin Wave Soliton Fractals in Magnetic Film Active Feedback Rings,"The manifestation of fractals in soliton dynamics has been observed for the
+first time. The experiment utilized self-generated spin wave envelope solitons
+in a magnetic film based active feedback ring. At high ring gain, the soliton
+that circulates in the ring breathes in a fractal pattern. The corresponding
+power frequency spectrum shows a comb structure, with each peak in the comb
+having its own comb, and so on, to finer and finer scales.",0701537v1
+2007-02-01,Interacting Antiferromagnetic Droplets in Quantum Critical CeCoIn_5,"The heavy fermion superconductor CeCoIn_5 can be tuned between
+superconducting and antiferromagnetic ground states by hole doping with Cd.
+Nuclear magnetic resonance (NMR) data indicate that these two orders coexist
+microscopically with an ordered moment ~0.7 \mu_B. As the ground state evolves,
+there is no change in the low frequency spin dynamics in the disordered state.
+These results suggest that the magnetism emerges locally in the vicinity of the
+Cd dopants.",0702008v2
+2007-02-22,Radio-frequency magnetic response of vortex lattices undergoing structural transformations,"We report a clear anomaly in the rf response of a tunnel-diode resonator
+measured in borocarbide crystals in dc fields along the $c-$axis. We associate
+the anomaly in the dynamic magnetic susceptibility, $\chi$, with a structural
+transition in the vortex lattice. $\chi$ is sensitive to the Campbell
+penetration depth $\lambda_{C}$ of the rf perturbation into the mixed state.
+$\lambda_{C}$ depends on the vortex lattice elastic moduli, which in turn
+depend on the vortex lattice structure. The high-field transition line is
+clearly mapped and shown to behave in agreement with theory.",0702509v1
+2007-02-26,Measurement of mesoscopic High-$T_c$ superconductors using Si mechanical micro-oscillators,"In a superconducting mesoscopic sample, with dimensions comparable to the
+London penetration depth, some properties are qualitatively different to those
+found in the bulk material. These properties include magnetization, vortex
+dynamics and ordering of the vortex lattice. In order to detect the small
+signals produced by this kind of samples, new instruments designed for the
+microscale are needed. In this work we use micromechanical oscillators to study
+the magnetic properties of a Bi$_2$Sr$_2$CaCu$_2$O$_{8 + \delta}$ disk with a
+diameter of 13.5 microns and a thickness of 2.5 microns. The discussion of our
+results is based on the existence and contribution of inter and intra layer
+currents.",0702597v1
+2007-03-20,Magnetic focusing in normal-superconductor hybrid systems: a semiclassical analysis,"We study a transverse electron-hole focusing effect in a
+normal-superconductor system. The spectrum of the quasiparticles is calculated
+both quantum mechanically and in semiclassical approximation, showing an
+excellent agreement. A semiclassical conductance formula is derived which takes
+into account the effect of electron-like as well as hole-like quasiparticles.
+At low magnetic field the semiclassical conductance shows characteristic
+oscillations due to the Andreev reflection, while at higher fields it goes to
+zero. These findigs are in line with the results of previous quantum
+calculations and with the expectations based on the classical dynamics of the
+quasiparticles.",0703529v1
+1999-11-30,Experimental test for 5th dimension in Kaluza-Klein gravity,"Several electric/magnetic charged solutions (dyons) to 5D Kaluza-Klein
+gravity on the principal bundle are reviewed. Here we examine the possibility
+that these solutions can act as quantum virtual wormholes in spacetime foam
+models. By applying a sufficently large, external electric and/or magnetic
+field it may be possible to ``inflate'' these solutions from a quantum to a
+classical state. This effect could lead to a possible experimental signal for
+higher dimensions in multidimensional gravity.",9911120v1
+2005-05-23,Dynamical SU(2) magnetic monopoles,"In our paper Phys. Rev. Lett. 92, 151801 (2004), the oscillations of strongly
+deformed Bogomolny-Prasad-Sommerfield magnetic monopoles have been studied on a
+fixed Minkowski background. The purpose of the present article is to provide a
+more detailed account on the results yielded by our numerical simulations. In
+particular, an analysis on the dependence on the strength of the initial
+excitation is carried out in order to distinguish features which are already
+present for small perturbations from those which are consequences of the
+nonlinearity of the system.",0505117v1
+2006-10-09,On the geometrization of the electro-magnetic interaction for a spinning particle,"We outline that, in a Kaluza-Klein framework, not only the electro-magnetic
+field can be geometrized, but also the dynamics of a charged spinning particle
+can be inferred from the motion in a 5-dimensional space-time. This result is
+achieved by the dimensional splitting of Papapetrou equations and by proper
+identifications of 4-dimensional quantities.",0610036v2
+2004-06-01,Leading Quenching Effects in the Proton Magnetic Moment,"We present the first investigation of the extrapolation of quenched nucleon
+magnetic moments in quenched chiral effective field theory. We utilize
+established techniques in finite-range regularisation and compare with standard
+dimensional regularisation methods. Finite-volume corrections to the relevant
+loop integrals are also addressed. Finally, the contributions of dynamical sea
+quarks to the proton moment are estimated using a recently discovered
+phenomenological link between quenched and physical QCD.",0406001v2
+1998-03-18,Phase transition induced by a magnetic field,"The magnetic catalysis of discrete chiral symmetry breaking in the 2+1
+dimensional Nambu-Jona-Lasinio model is analyzed. A particular attention is
+paid to a possible application of the effect in solid state physics. The
+fermion contribution to the thermal conductivity as a function of the dynamical
+mass (energy gap in the spectrum) is estimated and is shown to be suppressed
+when a non-zero order parameter develops.",9803371v2
+1998-07-24,Electron Self-Energy in Strong Magnetic Field: Summation of Double Logarithmic Terms,"We study the electron self--energy in a strong magnetic field when the
+parameter \eta\equiv (\alpha/2\pi) \ln^2 (eB/m^2_0) \sim 1 and explore the
+transition between the perturbative regime \eta<<1 and the nonperturbative
+massless QED regime \eta>>1 where chiral symmetry is broken spontaneously and
+electrons acquire the dynamically induced mass.",9807486v1
+1999-08-10,Theory of the Magnetic Catalysis of Chiral Symmetry Breaking in QED,"The theory of the magnetic catalysis of chiral symmetry breaking in QED is
+developed. An approximation for the Schwinger-Dyson equations describing
+reliably this phenomenon is established, i.e., it is shown that there exists a
+consistent truncation of those equations in this problem. The equations are
+solved both analytically and numerically, and the dynamical mass of fermions is
+determined.",9908320v1
+2004-10-01,The Dynamical Mixing of Light and Pseudoscalar Fields,"We solve the general problem of mixing of electromagnetic and scalar or
+pseudoscalar fields coupled by axion-type interactions ${\cal L}_{int}
+=g_{\phi} \phi \epsilon_{\mu \nu \a \b}F^{\mu \nu}F^{\a \b} $. The problem
+depends on several dimensionful scales, including the magnitude and direction
+of background magnetic field, the pseudoscalar mass, plasma frequency,
+propagation frequency, wave number, and finally the pseudoscalar coupling. We
+apply the results to the first consistent calculations of the mixing of light
+propagating in a background magnetic field of varying direction, which shows a
+great variety of fascinating resonant and polarization effects.",0410006v1
+1994-02-16,Spontaneous Breakdown of the Lorentz Invariance,"We re-examine three-dimensional gauge theory with a Chern-Simons term in
+which the Lorentz invariance is spontaneously broken by dynamical generation of
+a magnetic field. A non-vanishing magnetic field leads, through the
+Nambu-Goldstone theorem, to the decrease of zero-point energies of photons,
+which accounts for a major part of the mechanism. The asymmetric spectral flow
+plays an important role. The instability in pure Chern-Simons theory is also
+noted.",9402096v1
+1995-04-17,Primordial Magnetic Fields From String Cosmology,"Sufficiently large seeds for generating the observed (inter)galactic magnetic
+fields emerge naturally in string cosmology from the amplification of
+electromagnetic vacuum fluctuations due to a dynamical dilaton background. The
+success of the mechanism depends crucially on two features of the so-called
+pre-big-bang scenario, an early epoch of dilaton-driven inflation at very small
+coupling, and a sufficiently long intermediate stringy era preceding the
+standard radiation-dominated evolution.",9504083v1
+1995-05-18,Spontaneous Magnetization in Lorentz Invariant Theories,"In a class of three-dimensional Abelian gauge theories with both light and
+heavy fermions, heavy chiral fermions can trigger dynamical generation of a
+magnetic field, leading to the spontaneous breaking of the Lorentz invaiance.
+Finite masses of light fermions tend to restore the Lorentz invariance.",9505113v2
+1996-05-01,Magnetic Charge in a Nonassociative Field Theory,"The violation of the Jacobi identity by the presence of magnetic charge is
+accomodated by using an explicitly nonassociative theory of octonionic fields.
+It is found that the dynamics of this theory is simplified if the Lagrangian
+contains only dyonic charges, but certain problems in the constrained
+quantisation remain. The extension of these concepts to string theory may
+however resolve these difficulties.",9604201v1
+1997-02-27,BPS Monopoles and Electromagnetic Duality,"We review our recent work on the BPS magnetic monopoles and its relation to
+the electromagnetic duality in the N=4 supersymmetric Yang-Mills systems with
+an arbitrary gauge group. The gauge group can be maximally or partially broken.
+The low energy dynamics of the massive and massless magnetic monopoles are
+approximated by the moduli space metric. We emphasize the possible connection
+between the nature of the monopole moduli space with unbroken gauge group and
+the physics of mesons and baryons in QCD.",9702200v1
+1997-11-17,Chiral symmetry breaking in a uniform external magnetic field II. Symmetry restoration at high temperatures and chemical potentials,"Chiral symmetry is dynamically broken in quenched, ladder QED at weak gauge
+couplings when an external magnetic field is present. In this paper, we show
+that chiral symmetry is restored above a critical chemical potential and the
+corresponding phase transition is of first order. In contrast, the chiral
+symmetry restoration at high temperatures (and at zero chemical potential) is a
+second order phase transition.",9711126v1
+1998-03-09,Magnetic catalysis of chiral symmetry breaking and the Pauli problem,"The non-perturbative Schwinger-Dyson equation is used to show that chiral
+symmetry is dynamically broken in QED at weak gauge couplings when an external
+uniform magnetic field is present. A complete analysis of this phenomenon may
+shed light on the Pauli problem, namely, why $\alpha$ = 1/137.",9803074v1
+2001-05-28,Compactification with U(1) magnetic field within Dirac supersymmetry,"We consider Dirac-supersymmetric interactions, which produce CP-conserving
+separation of positive and negative energy solutions in the Dirac equation in
+order to investigate an alternative to the Kaluza-Klein mechanism. We review
+conditions under which separation is possible into free particle and
+compactified behaviors in different dimensions, with attention to spin degrees
+of freedom. We show a U(1) constant magnetic field produces such kind of
+behavior; an explicit treatment is given to the 6-d to 4-d and 4-d to 2-d
+breaking cases and the spectrum is obtained. A dynamical mass-creation
+mechanism is suggested from the procedure.",0105280v1
+2004-12-13,The Klein-Gordon and the Dirac oscillators in a noncommutative space,"We study the Dirac and the klein-Gordon oscillators in a noncommutative
+space. It is shown that the Klein-Gordon oscillator in a noncommutative space
+has a similar behaviour to the dynamics of a particle in a commutative space
+and in a constant magnetic field. The Dirac oscillator in a noncommutative
+space has a similar equation to the equation of motion for a relativistic
+fermion in a commutative space and in a magnetic field, however a new exotic
+term appears, which implies that a charged fermion in a noncommutative space
+has an electric dipole moment.",0412122v1
+2005-01-18,Chiral Symmetry Breaking and Point-Splitting Procedure in Light-Cone Quantized QED in a Magnetic Field,"The summation of all rainbow diagrams in QED in a strong magnetic field leads
+to a dynamical electron mass on the light-cone. Further contributions to this
+summation however can cause problems with light-cone singularities. It is shown
+that these problems are generally avoided by applying the point-splitting
+regularization to every diagram. The possibility of implementing this procedure
+into the Lagrangian of the theory is discussed.",0501133v2
+2005-05-11,Photon emission in a constant magnetic field in 2+1 dimensional space-time,"We calculate by the proper-time method the amplitude of the two-photon
+emission by a charged fermion in a constant magnetic field in (2+1)-dimensional
+space-time. The relevant dynamics reduces to that of a supesymmetric
+quantum-mechanical system with one bosonic and one fermionic degrees of
+freedom.",0505102v2
+2005-12-26,Landau Quantization of Neutral Particles in an External Field,"The quantum dynamics of an induced electric dipole in the presence of a
+configuration of crossed electric and magnetic fields is analyzed. This field
+configuration confines the dipole in a plane and produces a coupling similar to
+the coupling of a charged particle in the presence of external magnetic field.
+In this work we investigate the analog of Landau levels in induced electric
+dipoles in a sistem of neutral particles. The energy levels and eigenfunctions
+are obtained exactly.",0512309v1
+2005-09-15,Variational approach to nonlinear gravity-driven instabilities in a MHD setting,"We establish a variational framework for nonlinear instabilities in a setting
+of the ideal magnetohydrodynamic (MHD) equations. We apply a variational method
+to various kind of smooth steady states which are shown to be nonlinearly
+unstable for both incompressible and compressible ideal MHD equations.
+Destabilizing effect of compressibility is justified as well as stabilizing
+effect of magnetic field lines arising in MHD dynamics, which distinguishes
+from the Rayleigh-Taylor instability in the absence of magnetic field lines.",0509364v1
+2005-09-19,Smoothing - Strichartz Estimates for the Schrodinger Equation with small Magnetic Potential,"The work treats smoothing and dispersive properties of solutions to the
+Schrodinger equation with magnetic potential. Under suitable smallness
+assumption on the potential involving scale invariant norms we prove smoothing
+- Strichartz estimate for the corresponding Cauchy problem. An application that
+guarantees absence of pure point spectrum of the corresponding perturbed
+Laplace operator is discussed too.",0509416v2
+2006-01-26,Further Results on Active Magnetic Bearing Control with Input Saturation,"We study the low-bias stabilization of active magnetic bearings (AMBs)
+subject to voltage saturation based on a recently proposed model for the AMB
+switching mode of operation. Using a forwarding-like approach, we construct a
+stabilizing controller of arbitrarily small amplitude and a control-Lyapunov
+function for the AMB dynamics. We illustrate our construction using a numerical
+example.",0601650v1
+2000-10-25,Avoided crossings in mesoscopic systems: electron propagation on a non-uniform magnetic cylinder,"We consider an electron constrained to move on a surface with revolution
+symmetry in the presence of a constant magnetic field $B$ parallel to the
+surface axis. Depending on $B$ and the surface geometry the transverse part of
+the spectrum typically exhibits many crossings which change to avoided
+crossings if a weak symmetry breaking interaction is introduced. We study the
+effect of such perturbations on the quantum propagation. This problem admits a
+natural reformulation to which tools from molecular dynamics can be applied. In
+turn, this leads to the study of a perturbation theory for the time dependent
+Born-Oppenheimer approximation.",0010042v1
+2004-10-19,Plasma equilibrium equations in coordinates connected with magnetic surfaces. Exact equilibrium solutions,"A representation of the static MHD equilibrium system in coordinates
+connected with magnetic surfaces is suggested. It is used for producing
+families of non-trivial 3D exact solutions of isotropic and anisotropic plasma
+equilibria in different geometries, with and without dynamics, and often
+without geometrical symmetries. The ways of finding coordinates in which exact
+equilibria can be constructed are discussed; examples and their applications as
+physical models are presented.",0410045v1
+2006-01-26,On the ground state energy for a magnetic Shcrödinger operator and the effect of the De Gennes Boundary condition,"Motivated by the Ginzburg-Landau theory of superconductivity, we estimate in
+the semi-classical limit the ground state energy of a magnetic Schr\""odinger
+operator with De Gennes boundary condition and we study the localization of the
+ground state. We exhibit cases when the De Gennes boundary condition has strong
+effects on this localization.",0601057v2
+2004-04-29,Diffusion in a stochastic magnetic field,"We consider a stochastic differential equation for a charged particle in a
+stochastic magnetic field, known as A-Langevin equation. The solution of the
+equation is found, and the Lagrange velocity correlation function is calculated
+in Corrsin approximation. A corresponding diffusion constant is estimated. We
+observe different transport regimes, such as quasilinear- or Bohm-type
+diffusion, depending on the parameters of plasma.",0404056v3
+2006-07-30,Semiclassical Theory for Parametric Correlation of Energy Levels,"Parametric energy-level correlation describes the response of the
+energy-level statistics to an external parameter such as the magnetic field.
+Using semiclassical periodic-orbit theory for a chaotic system, we evaluate the
+parametric energy-level correlation depending on the magnetic field difference.
+The small-time expansion of the spectral form factor $K(\tau)$ is shown to be
+in agreement with the prediction of parameter dependent random-matrix theory to
+all orders in $\tau$.",0607070v1
+2004-07-02,Covariant baryon charge radii and magnetic moments in a chiral constituent quark model,"The charge radii and magnetic moments of all the light and strange baryons
+are investigated within the framework of a constituent quark model based on
+Goldstone-boson-exchange dynamics. Following the point-form approach to
+relativistic quantum mechanics, the calculations are performed in a manifestly
+covariant manner. Relativistic (boost) effects have a sizeable influence on the
+results. The direct predictions of the constituent quark model are found to
+fall remarkably close to the available experimental data.",0407009v1
+1998-09-21,Quantum theory of magnetic quadrupole lenses for spin-1/2 particles,"General guidelines for constructing a quantum theory of charged-particle beam
+optics starting ab initio from the basic equations of quantum mechanics,
+appropriate to the situation under study. In the context of spin-1/2 particles,
+these guidelines are used starting with the Dirac equation. The spinor theory
+just constructed is used to obtain the transfer maps for normal and skew
+magnetic quadrupoles respectively. As expected the traditional transfer maps
+get modified by the quantum contributions. The classical limit of the quantum
+formalism presented, reproduces the well-known Lie algebraic formalism of
+charged-particle beam optics.",9809032v1
+1999-06-30,Identifying nonlinear wave interactions in plasmas using two-point measurements: a case study of Short Large Amplitude Magnetic Structures (SLAMS),"A framework is described for estimating Linear growth rates and spectral
+energy transfers in turbulent wave-fields using two-point measurements. This
+approach, which is based on Volterra series, is applied to dual satellite data
+gathered in the vicinity of the Earth's bow shock, where Short Large Amplitude
+Magnetic Structures (SLAMS) supposedly play a leading role. The analysis
+attests the dynamic evolution of the SLAMS and reveals an energy cascade toward
+high-frequency waves.",9906065v1
+1999-12-13,Detection of a flow induced magnetic field eigenmode in the Riga dynamo facility,"In an experiment at the Riga sodium dynamo facility, a slowly growing
+magnetic field eigenmode has been detected over a period of about 15 seconds.
+For a slightly decreased propeller rotation rate, additional measurements
+showed a slow decay of this mode. The measured results correspond satisfactory
+with numerical predictions for the growth rates and frequencies.",9912026v1
+2002-08-02,"Dynamics of a magnetic monopole in matter, Maxwell equations in dyonic matter and detection of electric dipole moments","For a monopole, the analogue of the Lorentz equation in matter is shown to be
+f = g (H - v cross D). Dual-symmetric Maxwell equations, for matter containing
+hidden magnetic charges in addition to electric ones, are given. They apply as
+well to ordinary matter if the particles possess T-violating electric dipole
+moments. Two schemes of experiments for the detection of such moments in
+macroscopic pieces of matter are proposed.",0208007v1
+2003-06-04,Observation of Caustics in the Trajectories of Cold Atoms in a Linear Magnetic Potential,"We have studied the spatial and temporal dynamics of a cold atom cloud in the
+conservative force field of a ferromagnetic guide, after laser cooling has been
+switched off suddenly. We observe outgoing 'waves' that correspond to caustics
+of individual trajectories of trapped atoms. This provides detailed information
+on the magnetic field, the energy distribution and the spin states.",0306040v1
+2004-05-05,Radiation Chemistry of Organic Liquids: Saturated Hydrocarbons,"In this review (124 refs), several problems in radiolysis of saturated
+hydrocarbons are examined. Special attention is paid to the chemistry of
+radical cations, high-mobility holes, excited state and spur dynamics, magnetic
+field and spin effects, and optically detected magnetic resonance spectroscopy.",0405014v1
+2004-06-26,Two-fluid magnetic island dynamics in slab geometry: I - Isolated islands,"A set of reduced, 2-D, two-fluid, drift-MHD equations is derived. Using these
+equations, a complete and fully self-consistent solution is obtained for an
+isolated magnetic island propagating through a slab plasma with uniform but
+different ion and electron fluid velocities. The ion and electron fluid flow
+profiles around the island are uniquely determined, and are everywhere
+continuous. Moreover, the island phase-velocity is uniquely specified by the
+condition that there be zero net electromagnetic force acting on the island.
+Finally, the ion polarization current correction to the Rutherford island width
+evolution equation is evaluated, and found to be stabilizing provided that the
+anomalous perpendicular ion viscosity significantly exceeds the anomalous
+perpendicular electron viscosity.",0406132v1
+2005-12-20,Cylindrical Korteweg-de Vries solitons on a ferrofluid surface,"Linear and non-linear surface waves on a ferrofluid cylinder surrounding a
+current-carrying wire are investigated. Suppressing the Rayleigh-Plateau
+instability of the fluid column by the magnetic field of a sufficiently large
+current in the wire axis-symmetric surface deformations are shown to propagate
+without dispersion in the long wavelength limit. Using multiple scale
+perturbation theory the weakly non-linear regime may be described by a
+Korteweg-de Vries equation with coefficients depending on the magnetic field
+strength. For different values for the current in the wire hence different
+solutions such as hump or hole solitons may be generated. The possibility to
+observe these structures in experiments is also elucidated.",0512185v2
+2006-06-02,Controlling electronic spin relaxation of cold molecules with electric fields,"We present a theoretical study of atom - molecule collisions in superimposed
+electric and magnetic fields and show that dynamics of electronic spin
+relaxation in molecules at temperatures below 0.5 K can be manipulated by
+varying the strength and the relative orientation of the applied fields. The
+mechanism of electric field control of Zeeman transitions is based on an
+intricate interplay between intramolecular spin-rotation couplings and
+molecule-field interactions. We suggest that electric fields may affect
+chemical reactions through inducing nonadiabatic spin transitions and
+facilitate evaporative cooling of molecules in a magnetic trap.",0606027v2
+2006-10-02,Hydrogen atom in crossed electric and magnetic fields: Phase space topology and torus quantization via periodic orbits,"A hierarchical ordering is demonstrated for the periodic orbits in a strongly
+coupled multidimensional Hamiltonian system, namely the hydrogen atom in
+crossed electric and magnetic fields. It mirrors the hierarchy of broken
+resonant tori and thereby allows one to characterize the periodic orbits by a
+set of winding numbers. With this knowledge, we construct the action variables
+as functions of the frequency ratios and carry out a semiclassical torus
+quantization. The semiclassical energy levels thus obtained agree well with
+exact quantum calculations.",0610013v1
+2007-02-26,Spherical Couette flow in a dipolar magnetic field,"We consider numerically the flow of an electrically conducting fluid in a
+differentially rotating spherical shell, in a dipolar magnetic field. For
+infinitesimal differential rotation the flow consists of a super-rotating
+region, concentrated on the particular field line C just touching the outer
+sphere, in agreement with previous results. Finite differential rotation
+suppresses this super-rotation, and pushes it inward, toward the equator of the
+inner sphere. For sufficiently strong differential rotation the outer boundary
+layer becomes unstable, yielding time-dependent solutions. Adding an overall
+rotation suppresses these instabilities again. The results are in qualitative
+agreement with the DTS liquid sodium experiment.",0702228v1
+2007-03-23,Parametric instability of the helical dynamo,"We study the dynamo threshold of a helical flow made of a mean (stationary)
+plus a fluctuating part. Two flow geometries are studied, either (i) solid body
+or (ii) smooth. Two well-known resonant dynamo conditions, elaborated for
+stationary helical flows in the limit of large magnetic Reynolds numbers, are
+tested against lower magnetic Reynolds numbers and for fluctuating flows (zero
+mean). For a flow made of a mean plus a fluctuating part the dynamo threshold
+depends on the frequency and the strength of the fluctuation. The resonant
+dynamo conditions applied on the fluctuating (resp. mean) part seems to be a
+good diagnostic to predict the existence of a dynamo threshold when the
+fluctuation level is high (resp. low).",0703216v1
+1999-09-30,Noncyclic geometric phase and its non-Abelian generalization,"We use the theory of dynamical invariants to yield a simple derivation of
+noncyclic analogues of the Abelian and non-Abelian geometric phases. This
+derivation relies only on the principle of gauge invariance and elucidates the
+existing definitions of the Abelian noncyclic geometric phase. We also discuss
+the adiabatic limit of the noncyclic geometric phase and compute the adiabatic
+non-Abelian noncyclic geometric phase for a spin 1 magnetic (or electric)
+quadrupole interacting with a precessing magnetic (electric) field.",9909093v1
+2000-03-22,Quantum Fluctuations of a Single Trapped Atom: Transient Rabi Oscillations and Magnetic Bistability,"Isolation of a single atomic particle and monitoring its resonance
+fluorescence is a powerful tool for studies of quantum effects in
+radiation-matter interaction. Here we present observations of quantum dynamics
+of an isolated neutral atom stored in a magneto-optical trap. By means of
+photon correlations in the atom's resonance fluorescence we demonstrate the
+well-known phenomenon of photon antibunching which corresponds to transient
+Rabi oscillations in the atom. Through polarization-sensitive photon
+correlations we show a novel example of resolved quantum fluctuations:
+spontaneous magnetic orientation of an atom. These effects can only be observed
+with a single atom.",0003105v1
+2000-07-12,Loading a continuous-wave atom laser by optical pumping techniques,"Demonstrating that despite loss processes, Bose-Einstein condensates can be
+formed in steady state is a prerequisite for obtaining a coherent beam of atoms
+in a continuous-wave atom laser. In this paper we propose a method for loading
+atoms into the thermal component of a Bose condensed cloud confined in a
+magnetic trap. This method is aimed at allowing steady state dynamics to be
+achieved. The proposed scheme involves loading atoms into the conservative
+magnetic potential using the spontaneous emission of photons. We show that the
+probability for the reabsorption of these photons may be small .",0007039v1
+2002-03-21,The Landau-Zener Model with Decoherence: The case S=1/2,"We study the dynamics of a spin coupled to an oscillating magnetic field, in
+the presence of decoherence and dissipation. In this context we solve the
+master equation for the Landau-Zener problem, both in the unitary and in the
+irreversible case. We show that a single spin can be ""magnetized"" in the
+direction parallel to the oscillating bias. When decay from upper to lower
+level is taken into account, hysteretic behavior is obtained.",0203110v1
+2002-10-01,Transient Dynamics in Magnetic Force Microscopy for a Single-Spin Measurement,"We analyze a single-spin measurement using a transient process in magnetic
+force microscopy (MFM) which could increase the maximum operating temperature
+by a factor of Q (the quality factor of the cantilever) in comparison with the
+static Stern-Gerlach effect. We obtain an exact solution of the master
+equation, which confirms this result. We also discuss the conditions required
+to create a macroscopic Schrodinger cat state in the cantilever.",0210006v1
+2002-12-02,The hydrogen atom in electric and magnetic fields : Pauli's 1926 article,"The results obtained by Pauli, in his 1926 article on the hydrogen atom, made
+essential use of the dynamical so(4) symmetry of the bound states. Pauli used
+this symmetry to compute the perturbed energy levels of an hydrogen atom in a
+uniform electric field (Stark effect) and in uniform electric and magnetic
+fields. Although the experimental check of the single Stark effect on the
+hydrogen atom has been studied experimentally, Pauli's results in mixed fields
+have been studied only for Rydberg states of rubidium atoms in crossedfields
+and lithium atoms in parallel fields.",0212010v2
+2003-06-17,Trapping and manipulating neutral atoms with electrostatic fields,"We report on experiments with cold thermal $^7$Li atoms confined in combined
+magnetic and electric potentials. A novel type of three-dimensional trap was
+formed by modulating a magnetic guide using electrostatic fields. We observed
+atoms trapped in a string of up to six individual such traps, a controlled
+transport of an atomic cloud over a distance of 400$\mu$m, and a dynamic
+splitting of a single trap into a double well potential. Applications for
+quantum information processing are discussed.",0306111v1
+2004-05-22,Spatial weak-light solitons in an electro-magnetically induced nonlinear waveguide,"We show that a weak probe light beam can form spatial solitons in an
+electro-magnetically induced transparency (EIT) medium composed of four-level
+atoms and a coupling light field. We find that the coupling light beam can
+induce a highly controllable nonlinear waveguide and exert very strong effects
+on the dynamical behavior of the solitons. Hence, in the EIT medium, it is not
+only possible to produce spatial solitons at very low light intensities but
+also simultaneously control these solitons by using the coupling-light-induced
+nonlinear waveguide.",0405132v1
+2005-11-02,Theory of dark-state polariton collapses and revivals,"We investigate the dynamics of dark-state polaritons in an atomic ensemble
+with ground-state degeneracy. A signal light pulse may be stored and retrieved
+from the atomic sample by adiabatic variation of the amplitude of a control
+field. During the storage process, a magnetic field causes rotation of the
+atomic hyperfine coherences, leading to collapses and revivals of the
+dark-state polariton number. These collapses and revivals should be observable
+in measurements of the retrieved signal field, as a function of storage time
+and magnetic field orientation.",0511017v1
+2007-05-19,A self-sustaining nonlinear dynamo process in Keplerian shear flows,"A three-dimensional nonlinear dynamo process is identified in rotating plane
+Couette flow in the Keplerian regime. It is analogous to the hydrodynamic
+self-sustaining process in non-rotating shear flows and relies on the
+magneto-rotational instability of a toroidal magnetic field. Steady nonlinear
+solutions are computed numerically for a wide range of magnetic Reynolds
+numbers but are restricted to low Reynolds numbers. This process may be
+important to explain the sustenance of coherent fields and turbulent motions in
+Keplerian accretion disks, where all its basic ingredients are present.",0705.2814v1
+2007-06-01,Particle-in-cell simulations of fast collisionless reconnection in gamma-ray burst outflows,"We present preliminary results of particle-in-cell simulations of
+collisionless magnetic reconnection for conditions that apply to magnetically
+dominated pair plasma jets such as those in gamma-ray bursts. We find similar
+behaviour to previous authors but with reduced reconnection efficiency. This
+results because we include the full electromagnetic field dynamically and allow
+electric field fluctuations to grow. Although weak, these fluctuations impede
+early x-point formation by periodically decelerating and even reversing the
+inflow.",0706.0193v1
+2007-06-06,Bound States and Many-Body Effects in H-Shaped Quantum Wires,"In this paper, bound states energies and corresponding wave functions of
+H-shaped quantum wires are calculated numerically in the presence of external
+magnetic and electric fields and within the Landau gauge. With a suitable
+definition of external confinement potential, we present a numerical algorithm
+to calculate the profile of probability distribution of charge carriers. Our
+analysis shows that in the presence of external electric and magnetic fields,
+bound state properties of carriers are sensitive functions of an asymmetric
+parameter $a=\frac{W_{x}}{W_{y}}$ which measures the relative width of the well
+in two directions. We also study many body effect of bandgap renormalization in
+this quasi one dimensional system within dynamical random phase approximation.",0706.0777v1
+2007-06-30,Zooming into the coexisting regime of ferromagnetism and superconductivity in ErRh4B4 single crystals,"High resolution measurements of the dynamic magnetic susceptibility are
+reported for ferromagnetic re-entrant superconductor, ErRh$_{4}$B$_{4}$.
+Detailed investigation of the coexisting regime reveals unusual
+temperature-asymmetric and magnetically anisotropic behavior. The
+superconducting phase appears via a series of discontinuous steps upon warming
+from the ferromagnetic normal phase, whereas the ferromagnetic phase develops
+via a gradual transition. A model based on local field inhomogeneity is
+proposed to explain the observations.",0707.0029v1
+2007-08-27,Magnetometry Based on Nonlinear Magneto-Optical Rotation with Amplitude-Modulated Light,"We report on an all-optical magnetometric technique based on nonlinear
+magneto-optical rotation with amplitude-modulated light. The method enables
+sensitive magnetic-field measurements in a broad dynamic range. We demonstrate
+the sensitivity of $4.3\times10^{-9}$ G/$\sqrt{\text{Hz}}$ at 10 mG and the
+magnetic field tracking in a range of 40 mG. The fundamental limits of the
+method sensitivity and factors determining current performance of the
+magnetometer are discussed.",0708.3488v2
+2007-08-28,Nonadiabatic factor accompanying magnetic translation of a charged particle,"The quantum adiabatic theorem incorporating the Berry phase phenomenon can be
+characterized as a factorization of the time evolution operator into a
+path-dependent geometric factor, a usual dynamical factor and a non-adiabatic
+factor that approaches the identity in the adiabatic limit. We study a case
+where all these three factors can be constructed explicitly and where the
+instantaneous Hamiltonian has infinitely degenerate energy eigenstates
+associated with magnetic translation symmetry. Significance of the
+non-adiabatic factor in terms of transition probabilities is discussed.",0708.3726v2
+2007-09-25,Coexisting stochastic and coherence resonance in a mean-field dynamo model for Earth's magnetic field reversals,"Using a spherical symmetric mean field alpha^2-dynamo model for Earth's
+magnetic field reversals, we show the coexistence of the noise-induced
+phenomena coherence resonance and stochastic resonance. Stochastic resonance
+has been recently invoked to explain the 100 kyr periodicity in the
+distribution of the residence time between reversals. The comparison of the
+resulting residence time distribution with the paleomagnetic one allows for
+some estimate of the effective diffusion time of the Earth's core which may be
+100 kyr or slightly below rather than 200 kyr as it would result from the
+molecular resistivity.",0709.3932v1
+2007-09-26,Spin-polarized Current-induced Instability in Spin-Valve with Antiferromagnetic Layer,"In the framework of phenomenological model we consider dynamics of a
+compensated collinear antiferromagnet (AFM) in the presence of spin-polarised
+current. The model is based on the assumption that AFM spins are localised and
+spin torque is transferred to each magnetic sublattice independently. It is
+shown that in AFM spin current i) can be a source of the ""negative friction"";
+and ii) modifies spin-wave frequencies. Equilibrium state of AFM can be
+destabilized by the current polarized in parallel to AFM vector. Threshold
+current at which the loss of stability takes place depends upon the magnetic
+anisotropy of AFM.",0709.4172v1
+2007-09-27,Flux Distribution in Superconducting Films with Holes,"Flux penetration into type-II superconducing films is simulated for
+transverse applied magnetic field and flux creep dynamics. The films contain
+macroscopic, non-conducting holes and we suggest a new method to introduce the
+holes in the simulation formalism. The method implies reconstruction of the
+magnetic field change inside the hole. We find that in the region between the
+hole and the edge the current density is compressed so that the flux density is
+slightly reduced, but the traffic of flux is significantly increased. The
+results are in good agreement with magneto-optical studies of flux
+distributions in YBCO films.",0709.4346v1
+2007-10-12,Coherent Spin Manipulations of a Polarized Beam With a Localized RF Magnetic Field,"The coherent manipulation of spin observables in storage rings provides
+opportunities to test the application of some fundamental dynamical principles.
+In this context, it is possible to confirm, using gauge invariance and Lorentz
+invariance, a conjecture framed by A. M. Kondratenko concerning the ""natural""
+or ""intrinsic"" resonance strength applicable to a spin rotation from a
+controlled Froissart-Stora sweep with an RF dipole magnet. The discussion
+includes a brief treatment of the ""forced"" component of the resonance strength
+associated with the effect of the betatron oscillations induced by the
+operation of the RF diple and a discussion of the effective resonance strength
+as a function of betatron tunes.",0710.2566v1
+2007-10-15,Ferromagnetic resonance study of polycrystalline Fe_{1-x}V_x alloy thin films,"Ferromagnetic resonance has been used to study the magnetic properties and
+magnetization dynamics of polycrystalline Fe$_{1-x}$V$_{x}$ alloy films with
+$0\leq x < 0.7$. Films were produced by co-sputtering from separate Fe and V
+targets, leading to a composition gradient across a Si substrate. FMR studies
+were conducted at room temperature with a broadband coplanar waveguide at
+frequencies up to 50 GHz using the flip-chip method. The effective
+demagnetization field $4 \pi M_{\mathrm{eff}}$ and the Gilbert damping
+parameter $\alpha$ have been determined as a function of V concentration. The
+results are compared to those of epitaxial FeV films.",0710.2826v2
+2007-10-24,Nonlinear theory of mirror instability near threshold,"An asymptotic model based on a reductive perturbative expansion of the drift
+kinetic and the Maxwell equations is used to demonstrate that, near the
+instability threshold, the nonlinear dynamics of mirror modes in a magnetized
+plasma with anisotropic ion temperatures involves a subcritical
+bifurcation,leading to the formation of small-scale structures with amplitudes
+comparable with the ambient magnetic field.",0710.4428v1
+2007-11-27,X-Ray Jet Dynamics in a Polar Coronal Hole Region,"New XRT observations of the north polar region taken from the X-ray Telescope
+(XRT) of the Hinode (Solar-B) spacecraft are used to analyze several time
+sequences showing small loop brightenings with a long ray above. We focus on
+the recorded transverse displacement of the jet and discuss scenarios to
+explain the main features of the events: the relationship with the expected
+surface magnetism, the rapid and sudden radial motion, and possibly the
+heating, based on the assumption that the jet occurs above a null point of the
+coronal magnetic field. We conclude that 3-D reconnection models are needed to
+explain the observational details of these events.",0711.4320v1
+2007-12-28,Entanglement propagation through spin chains in the presence of a staggered magnetic field,"We study the dynamics of entanglement in the XY spin chain subject to a
+staggered magnetic field and contrast it to the previously studied uniform
+field case. We find that, depending on parameter values, a staggered field can
+provide better conditions for a perfect entanglement transfer, while even a
+modest amount of exchange anisotropy appears to have a strong detrimental
+effect. We also study interactions between different waves of entanglement and
+assess the possibility of simultaneous transmission of multiple bits of quantum
+information.",0712.4349v1
+2008-01-01,Ion collection by oblique surfaces of an object in a transversely-flowing strongly-magnetized plasma,"The equations governing a collisionless obliquely-flowing plasma around an
+ion-absorbing object in a strong magnetic field are shown to have an exact
+analytic solution even for arbitrary (two-dimensional) object-shape, when
+temperature is uniform, and diffusive transport can be ignored. The solution
+has an extremely simple geometric embodiment. It shows that the ion collection
+flux density to a convex body's surface depends only upon the orientation of
+the surface, and provides the theoretical justification and calibration of
+oblique `Mach-probes'. The exponential form of this exact solution helps
+explain the approximate fit of this function to previous numerical solutions.",0801.0309v1
+2008-01-30,Polaronic signatures in the optical properties of Nd$_{2-x}$Ce$_x$CuO$_4$,"We investigate the temperature and doping dependence of the optical
+conductivity $\sigma(\omega)$ of Nd$_{2-x}$Ce$_x$CuO$_4$ in terms of
+magnetic/lattice polaron formation. We employ dynamical mean-field theory in
+the context of the Holstein-t-J model where an exact analytical solution is
+available in the limit of infinite connectivity. We show that the pseudogap
+features in the optical conductivity of this compound can be associated to the
+formation of lattice polarons assisted by the magnetic interaction.",0801.4691v1
+2008-02-18,Dynamical reentrance and geometry imposed quantization effects in Nb-AlOx-Nb Josephson junction arrays,"In this paper, we report on different phenomena related to the magnetic
+properties of artificially prepared highly ordered (periodic) two-dimensional
+Josephson junction arrays (2D-JJA) of both shunted and unshunted Nb-AlOx-Nb
+tunnel junctions. By employing mutual-inductance measurements and using a
+high-sensitive bridge, we have thoroughly investigated (both experimentally and
+theoretically) the temperature and magnetic field dependence of complex AC
+susceptibility of 2D-JJA. We also demonstrate the use of the scanning SQUID
+microscope for imaging the local flux distribution within our unshunted arrays.",0802.2485v2
+2008-02-21,Out-of-Plane Cmos Compatible Magnetometers,"Three-dimensional MEMS magnetometers with use of residual stresses in thin
+multilayers cantilevers are presented. Half-loop cantilevers based on
+Lorentz-force deflection convert magnetic flux in changes, thanks to
+piezoresistive transducers mounted in Wheatstone bridge. Magnetic field in the
+order of 10 Gauss was measured with a sensitivity of 0.015 mV/Gauss. A Finite
+Element Model of the device has been developed with Ansys for static and
+dynamic simulations. Novel out-of-plane ferromagnetic nickel plate magnetometer
+is also presented.",0802.3077v1
+2008-03-19,Transmutation of momentum into position in magnetic vortices,"We show that transmutation of linear momentum into position may occur in a
+system of three magnetic vortices thanks to a direct link between topology and
+dynamics in a ferromagnet. This happens via exchange between the linear
+momentum of a vortex-antivortex pair and the position of a single vortex during
+a semi-elastic scattering process. Vortex polarity switching occurs in the case
+of inelastic collisions.",0803.2811v1
+2008-03-20,Response of a ferrofluid to traveling-stripe forcing,"We observe the dynamics of waves propagating on the surface of a ferrofluid
+under the influence of a spatially and temporarily modulated field. In
+particular, we excite plane waves by a travelling lamellar modulation of the
+magnetization. By this external driving both the wavelength and the propagation
+velocity of the waves can be controlled. The amplitude of the excited waves
+exhibits a resonance phenomenon similar to that of a forced harmonic
+oscillator. Its analysis reveals the dispersion relation of the free surface
+waves, from which the critical magnetic field for the onset of the Rosensweig
+instability can be extrapolated.",0803.3038v1
+2008-04-07,Ferromagnetic Josephson junction with precessing magnetization,"The Josephson current in a diffusive
+superconductor/ferromagnet/superconductor junction with precessing
+magnetization is calculated within the quasiclassical theory of
+superconductivity. When the junction is phase-biased, a stationary current
+(without a.c. component) can flow through it despite the non-equilibrium
+condition. A large critical current is predicted due to a dynamically induced
+long range triplet proximity effect. Such effect could be observed in a
+conventional hybrid device close to the ferromagnetic resonance.",0804.1050v1
+2008-04-09,Chiral transition in a strong magnetic background,"The presence of a strong magnetic background can modify the nature and the
+dynamics of the chiral phase transition at finite temperature. We compute the
+modified effective potential in the linear sigma model with quarks to one loop
+in the $\bar{MS}$ scheme for $N_{f}=2$. For fields $eB\sim 5 m_{\pi}^{2}$ and
+larger a crossover is turned into a weak first-order transition. We discuss
+possible implications for non-central heavy ion collisions at RHIC and LHC, and
+for the primordial QCD transition.",0804.1452v1
+2008-04-17,Topological Disorder in Spin Models on Hierarchical Lattices,"A general approach for the description of spin systems on hierarchial
+lattices with coordination number $q$ as a dynamical variable is proposed. The
+ferromagnetic Ising model on the Bethe lattice was studied as a simple example
+demonstrating our method. The annealed and partly annealed versions of disorder
+concerned with the lattice coordination number are invented and discussed.
+Recurrent relations are obtained for the evaluation of magnetization. The
+magnetization is calculated for the particular disorder choices, $q=2,3$ and
+$q=3,4$. A nontrivial localization of critical point is revealed.",0804.2746v1
+2008-05-12,Electronic coherence in $δ$-Pu: A DMFT study,"A combination of Density Functional Theory and the Dynamical Mean Field
+theory (DMFT) is used to calculate the magnetic susceptibility, heat capacity,
+and the temperature dependence of the valence band photoemission spectra. The
+continuous-time hybridization expansion quantum Monte-Carlo is utilized to
+provide the first approximation-free DMFT solution of \emph{fcc} $\delta$-Pu
+which includes the full rotationally-invariant exchange interaction. We predict
+that $\delta$-Pu has a Pauli-like magnetic susceptibility near ambient
+temperature, as in experiment, indicating that electronic coherence causes the
+absence of local moments. Additionally, We show that volume expansion causes a
+crossover from incoherent to coherent electronic behavior at increasingly lower
+temperatures.",0805.1604v1
+2008-05-12,On the peculiar nature of turbulence in planetary dynamos,"Under the combined constraints of rapid rotation, sphericity, and magnetic
+field, motions in planetary cores get organized in a peculiar way. Classical
+hydrodynamic turbulence is not present, but turbulent motions can take place
+under the action of the buoyancy and Laplace forces. Laboratory experiments,
+such as the rotating spherical magnetic Couette DTS experiment in Grenoble,
+help us understand what motions take place in planetary core conditions.",0805.1725v2
+2008-05-28,Probing Fermionic Condensates by Fast-Sweep Projection onto Feshbach Molecules,"Fast sweep projection onto Feshbach molecules has been widely used as a probe
+of fermionic condensates. By determining the exact dynamics of a pair of atoms
+in time varying magnetic fields, we calculate the number of condensed and
+noncondensed molecules created after fast magnetic field sweeps from the BCS to
+the BEC side of the resonances in $^{40}$K and $^{6}$Li, for different sweep
+rates and a range of initial and final fields. We discuss the relation between
+the initial fermionic condensate fraction and the molecular condensate fraction
+measured after the sweep.",0805.4295v2
+2008-06-12,The Challenge of Sub-Keplerian Rotation for Disk Winds,"Strong magnetization makes the disks surrounding young stellar objects rotate
+at rates that are too sub-Keplerian to enable the thermal launching of disk
+winds from their surfaces unless the rate of gas diffusion across field lines
+is dynamically fast. This under-appreciated implication of disk magnetization
+poses a considerable challenge for disk-wind theory.",0806.2137v1
+2008-06-30,On the existence of canonical gyrokinetic variables for chaotic magnetic fields,"The gyrokinetic description of particle dynamics faces a basic difficulty
+when a special type of canonical variables is sought, i.e., the so-called
+\textit{gyrokinetic canonical variables}. These are defined in such a way that
+two of them are respectively identified with the gyrophase-angle, describing
+the fast particle gyration motion around magnetic field lines, and its
+canonically conjugate momentum. In this paper we intend to discuss the
+conditions of existence for these variables.",0806.4819v1
+2008-07-29,On the cohomological equation of magnetic flows,"We consider a magnetic flow without conjugate points on a closed manifold $M$
+with generating vector field $\G$. Let $h\in C^{\infty}(M)$ and let $\theta$ be
+a smooth 1-form on $M$. We show that the cohomological equation \[\G(u)=h\circ
+\pi+\theta\] has a solution $u\in C^{\infty}(SM)$ only if $h=0$ and $\theta$ is
+closed. This result was proved in \cite{DP2} under the assumption that the flow
+of $\G$ is Anosov.",0807.4602v1
+2008-07-31,Energy transfers in shell models for MHD turbulence,"A systematic procedure to derive shell models for MHD turbulence is proposed.
+It takes into account the conservation of ideal quadratic invariants such as
+the total energy, the cross-helicity and the magnetic helicity as well as the
+conservation of the magnetic energy by the advection term in the induction
+equation. This approach also leads to simple expressions for the energy
+exchanges as well as to unambiguous definitions for the energy fluxes. When
+applied to the existing shell models with nonlinear interactions limited to the
+nearest neighbour shells, this procedure reproduces well known models but
+suggests a reinterpretation of the energy fluxes.",0807.5076v1
+2008-09-16,Magic frequencies for cesium primary frequency standard,"We consider microwave hyperfine transitions in the ground state of cesium and
+rubidium atoms which are presently used as the primary and the secondary
+frequency standards. The atoms are confined in an optical lattice generated by
+a circularly polarized laser field. We demonstrate that applying an external
+magnetic field with appropriately chosen direction may cancel dynamic Stark
+frequency shift making the frequency of the clock transition insensitive to the
+strengths of both the laser and the magnetic fields. This can be attained for
+practically any laser frequency which is sufficiently distant from a resonance.",0809.2825v1
+2008-09-19,Dynamical Spin II,"The possibility of building all particles from spinless constituents is
+explored. Composite fermions are formed from bosonic carriers of electric and
+magnetic charge of a composite abelian gauge field. Internal attributes are
+accounted for by dimensional reduction from a higher-dimensional space-time in
+which the abelian gauge field is replaced by a composite higher-rank
+antisymmetric tensor field. The problem of building magnetically neutral
+fermions is considered.",0809.3464v1
+2008-10-19,Rashba coupling in quantum dots in the presence of magnetic field,"We present an analytical solution to the Schr\""odinger equation for electron
+in a two-dimensional circular quantum dot in the presence of both external
+magnetic field and the Rashba spin-orbit interaction. The confinement is
+described by the realistic potential well of finite depth.",0810.3394v2
+2008-11-10,Ultra-fast quenching of binary colloidal suspensions in an external magnetic field,"An ultra-fast quench is applied to binary mixtures of superparamagnetic
+colloidal particles confined at a two-dimensional water-air interface by a
+sudden increase of an external magnetic field. This quench realizes a virtually
+instantaneous cooling which is impossible in molecular systems. Using
+real-space experiments, the relaxation behavior after the quench is explored.
+Local crystallites with triangular and square symmetry are formed on different
+time scales and the correlation peak amplitude of the small particles evolves
+nonmonotonically in time in agreement with Brownian dynamics computer
+simulations.",0811.1498v2
+2008-11-25,Non-Fermi-liquid effect in magnetic susceptibility,"Taking into account the anomalous self-energy for quarks due to the dynamic
+screening effect for the transverse gluon propagator, we study the temperature
+dependence of the magnetic susceptibility in detail. It is shown that there
+does not exist the $T\ln T$ term in the susceptibility, different from the
+specific heat, but an anomalous $T^2\ln T$ term arises instead as a novel
+non-Fermi-liquid effect.",0811.4037v1
+2008-11-25,Adiabatic Magnetization of Superconductors as a High-Performance Cooling Mechanism,"The adiabatic magnetization of a superconductor is a cooling principle
+proposed in the 30s, which has never been exploited up to now. Here we present
+a detailed dynamic description of the effect, computing the achievable final
+temperatures as well as the process timescales for different superconductors in
+various regimes. We show that, although in the experimental conditions explored
+so far the method is in fact inefficient, a suitable choice of initial
+temperatures and metals can lead to unexpectedly large cooling effect, even in
+the presence of dissipative phenomena. Our results suggest that this principle
+can be re-envisaged today as a performing refrigeration method to access the
+microK regime in nanodevices.",0811.4127v1
+2009-01-23,Effect of hybridization on the magnetic properties of correlated two-band metals,"The magnetic properties of transition-like metals are discussed within the
+single site approximation, which is a picture to take into account electron
+correlations. The metal is described by two hybridized bands one of which
+includes Coulomb correlation. The presented results indicate that
+ferromagnetism arises for adequate values of hybridization (V), correlation (U)
+and occupation number($n_{\sigma}$). Some similarities with Dynamical
+Mean-Field Theory (DMFT) are indicated.",0901.3705v2